Commit | Line | Data |
---|---|---|
e53dd083 MCC |
1 | Kernel Parameters |
2 | ~~~~~~~~~~~~~~~~~ | |
1da177e4 | 3 | |
5888bcc5 RR |
4 | The following is a consolidated list of the kernel parameters as |
5 | implemented by the __setup(), core_param() and module_param() macros | |
6 | and sorted into English Dictionary order (defined as ignoring all | |
7 | punctuation and sorting digits before letters in a case insensitive | |
8 | manner), and with descriptions where known. | |
9 | ||
10 | The kernel parses parameters from the kernel command line up to "--"; | |
11 | if it doesn't recognize a parameter and it doesn't contain a '.', the | |
12 | parameter gets passed to init: parameters with '=' go into init's | |
13 | environment, others are passed as command line arguments to init. | |
14 | Everything after "--" is passed as an argument to init. | |
15 | ||
16 | Module parameters can be specified in two ways: via the kernel command | |
17 | line with a module name prefix, or via modprobe, e.g.: | |
18 | ||
19 | (kernel command line) usbcore.blinkenlights=1 | |
20 | (modprobe command line) modprobe usbcore blinkenlights=1 | |
21 | ||
22 | Parameters for modules which are built into the kernel need to be | |
23 | specified on the kernel command line. modprobe looks through the | |
24 | kernel command line (/proc/cmdline) and collects module parameters | |
25 | when it loads a module, so the kernel command line can be used for | |
26 | loadable modules too. | |
1da177e4 | 27 | |
ca1eda2d RD |
28 | Hyphens (dashes) and underscores are equivalent in parameter names, so |
29 | log_buf_len=1M print-fatal-signals=1 | |
30 | can also be entered as | |
31 | log-buf-len=1M print_fatal_signals=1 | |
32 | ||
5888bcc5 RR |
33 | Double-quotes can be used to protect spaces in values, e.g.: |
34 | param="spaces in here" | |
ca1eda2d | 35 | |
a901ebb9 SR |
36 | This document may not be entirely up to date and comprehensive. The command |
37 | "modinfo -p ${modulename}" shows a current list of all parameters of a loadable | |
38 | module. Loadable modules, after being loaded into the running kernel, also | |
39 | reveal their parameters in /sys/module/${modulename}/parameters/. Some of these | |
40 | parameters may be changed at runtime by the command | |
41 | "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}". | |
42 | ||
6585fa8a SR |
43 | The parameters listed below are only valid if certain kernel build options were |
44 | enabled and if respective hardware is present. The text in square brackets at | |
45 | the beginning of each description states the restrictions within which a | |
46 | parameter is applicable: | |
1da177e4 LT |
47 | |
48 | ACPI ACPI support is enabled. | |
c99c108a | 49 | AGP AGP (Accelerated Graphics Port) is enabled. |
1da177e4 LT |
50 | ALSA ALSA sound support is enabled. |
51 | APIC APIC support is enabled. | |
52 | APM Advanced Power Management support is enabled. | |
16290246 | 53 | ARM ARM architecture is enabled. |
e7ba176b | 54 | AVR32 AVR32 architecture is enabled. |
1da177e4 | 55 | AX25 Appropriate AX.25 support is enabled. |
0ae53640 | 56 | BLACKFIN Blackfin architecture is enabled. |
1e435256 | 57 | CLK Common clock infrastructure is enabled. |
5c71d618 | 58 | CMA Contiguous Memory Area support is enabled. |
9cfe268e AC |
59 | DRM Direct Rendering Management support is enabled. |
60 | DYNAMIC_DEBUG Build in debug messages and enable them at runtime | |
1da177e4 LT |
61 | EDD BIOS Enhanced Disk Drive Services (EDD) is enabled |
62 | EFI EFI Partitioning (GPT) is enabled | |
63 | EIDE EIDE/ATAPI support is enabled. | |
7102ebcd | 64 | EVM Extended Verification Module |
1da177e4 | 65 | FB The frame buffer device is enabled. |
16290246 | 66 | FTRACE Function tracing enabled. |
2521f2c2 | 67 | GCOV GCOV profiling is enabled. |
1da177e4 | 68 | HW Appropriate hardware is enabled. |
1da177e4 | 69 | IA-64 IA-64 architecture is enabled. |
6146f0d5 | 70 | IMA Integrity measurement architecture is enabled. |
1da177e4 | 71 | IOSCHED More than one I/O scheduler is enabled. |
41e2e8be | 72 | IP_PNP IP DHCP, BOOTP, or RARP is enabled. |
b0f83b28 | 73 | IPV6 IPv6 support is enabled. |
1da177e4 LT |
74 | ISAPNP ISA PnP code is enabled. |
75 | ISDN Appropriate ISDN support is enabled. | |
76 | JOY Appropriate joystick support is enabled. | |
84c08fd6 | 77 | KGDB Kernel debugger support is enabled. |
fef07aae | 78 | KVM Kernel Virtual Machine support is enabled. |
11ef697b | 79 | LIBATA Libata driver is enabled |
1da177e4 LT |
80 | LP Printer support is enabled. |
81 | LOOP Loopback device support is enabled. | |
82 | M68k M68k architecture is enabled. | |
83 | These options have more detailed description inside of | |
84 | Documentation/m68k/kernel-options.txt. | |
1da177e4 | 85 | MDA MDA console support is enabled. |
16290246 | 86 | MIPS MIPS architecture is enabled. |
1da177e4 | 87 | MOUSE Appropriate mouse support is enabled. |
309e57df | 88 | MSI Message Signaled Interrupts (PCI). |
c8facbb6 | 89 | MTD MTD (Memory Technology Device) support is enabled. |
1da177e4 LT |
90 | NET Appropriate network support is enabled. |
91 | NUMA NUMA support is enabled. | |
92 | NFS Appropriate NFS support is enabled. | |
93 | OSS OSS sound support is enabled. | |
c8facbb6 RD |
94 | PV_OPS A paravirtualized kernel is enabled. |
95 | PARIDE The ParIDE (parallel port IDE) subsystem is enabled. | |
1da177e4 LT |
96 | PARISC The PA-RISC architecture is enabled. |
97 | PCI PCI bus support is enabled. | |
7f785763 | 98 | PCIE PCI Express support is enabled. |
1da177e4 LT |
99 | PCMCIA The PCMCIA subsystem is enabled. |
100 | PNP Plug & Play support is enabled. | |
101 | PPC PowerPC architecture is enabled. | |
102 | PPT Parallel port support is enabled. | |
103 | PS2 Appropriate PS/2 support is enabled. | |
104 | RAM RAM disk support is enabled. | |
105 | S390 S390 architecture is enabled. | |
106 | SCSI Appropriate SCSI support is enabled. | |
163475fb RD |
107 | A lot of drivers have their options described inside |
108 | the Documentation/scsi/ sub-directory. | |
20510f2f | 109 | SECURITY Different security models are enabled. |
1da177e4 | 110 | SELINUX SELinux support is enabled. |
c1c124e9 | 111 | APPARMOR AppArmor support is enabled. |
1da177e4 | 112 | SERIAL Serial support is enabled. |
e523d93c | 113 | SH SuperH architecture is enabled. |
1da177e4 LT |
114 | SMP The kernel is an SMP kernel. |
115 | SPARC Sparc architecture is enabled. | |
77437fd4 DB |
116 | SWSUSP Software suspend (hibernation) is enabled. |
117 | SUSPEND System suspend states are enabled. | |
225a9be2 | 118 | TPM TPM drivers are enabled. |
1da177e4 | 119 | TS Appropriate touchscreen support is enabled. |
d4f373e5 | 120 | UMS USB Mass Storage support is enabled. |
1da177e4 LT |
121 | USB USB support is enabled. |
122 | USBHID USB Human Interface Device support is enabled. | |
123 | V4L Video For Linux support is enabled. | |
81a054ce | 124 | VMMIO Driver for memory mapped virtio devices is enabled. |
1da177e4 LT |
125 | VGA The VGA console has been enabled. |
126 | VT Virtual terminal support is enabled. | |
127 | WDT Watchdog support is enabled. | |
128 | XT IBM PC/XT MFM hard disk support is enabled. | |
cd4f0ef7 | 129 | X86-32 X86-32, aka i386 architecture is enabled. |
1da177e4 LT |
130 | X86-64 X86-64 architecture is enabled. |
131 | More X86-64 boot options can be found in | |
71cced6e | 132 | Documentation/x86/x86_64/boot-options.txt . |
16290246 | 133 | X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64) |
1c532e00 | 134 | X86_UV SGI UV support is enabled. |
c1c5413a | 135 | XEN Xen support is enabled |
1da177e4 LT |
136 | |
137 | In addition, the following text indicates that the option: | |
138 | ||
139 | BUGS= Relates to possible processor bugs on the said processor. | |
140 | KNL Is a kernel start-up parameter. | |
141 | BOOT Is a boot loader parameter. | |
142 | ||
143 | Parameters denoted with BOOT are actually interpreted by the boot | |
144 | loader, and have no meaning to the kernel directly. | |
145 | Do not modify the syntax of boot loader parameters without extreme | |
954a8b81 | 146 | need or coordination with <Documentation/x86/boot.txt>. |
1da177e4 | 147 | |
5558870b | 148 | There are also arch-specific kernel-parameters not documented here. |
71cced6e | 149 | See for example <Documentation/x86/x86_64/boot-options.txt>. |
5558870b | 150 | |
1da177e4 LT |
151 | Note that ALL kernel parameters listed below are CASE SENSITIVE, and that |
152 | a trailing = on the name of any parameter states that that parameter will | |
153 | be entered as an environment variable, whereas its absence indicates that | |
154 | it will appear as a kernel argument readable via /proc/cmdline by programs | |
155 | running once the system is up. | |
156 | ||
9c4751fd | 157 | The number of kernel parameters is not limited, but the length of the |
158 | complete command line (parameters including spaces etc.) is limited to | |
159 | a fixed number of characters. This limit depends on the architecture | |
160 | and is between 256 and 4096 characters. It is defined in the file | |
161 | ./include/asm/setup.h as COMMAND_LINE_SIZE. | |
162 | ||
7a19a237 AD |
163 | Finally, the [KMG] suffix is commonly described after a number of kernel |
164 | parameter values. These 'K', 'M', and 'G' letters represent the _binary_ | |
165 | multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30 | |
166 | bytes respectively. Such letter suffixes can also be entirely omitted. | |
167 | ||
9c4751fd | 168 | |
b10d79f7 | 169 | acpi= [HW,ACPI,X86,ARM64] |
03d926f8 | 170 | Advanced Configuration and Power Interface |
6a1f5471 | 171 | Format: { force | on | off | strict | noirq | rsdt | |
e58d154b | 172 | copy_dsdt } |
1da177e4 | 173 | force -- enable ACPI if default was off |
6a1f5471 | 174 | on -- enable ACPI but allow fallback to DT [arm64] |
1da177e4 LT |
175 | off -- disable ACPI if default was on |
176 | noirq -- do not use ACPI for IRQ routing | |
a9913044 | 177 | strict -- Be less tolerant of platforms that are not |
1da177e4 | 178 | strictly ACPI specification compliant. |
237889bf | 179 | rsdt -- prefer RSDT over (default) XSDT |
aa2110cb | 180 | copy_dsdt -- copy DSDT to memory |
6a1f5471 AB |
181 | For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force" |
182 | are available | |
1da177e4 | 183 | |
395cf969 | 184 | See also Documentation/power/runtime_pm.txt, pci=noacpi |
1da177e4 | 185 | |
a1fdcc0d LB |
186 | acpi_apic_instance= [ACPI, IOAPIC] |
187 | Format: <int> | |
188 | 2: use 2nd APIC table, if available | |
189 | 1,0: use 1st APIC table | |
4e381a4f | 190 | default: 0 |
a1fdcc0d | 191 | |
c3d6de69 TR |
192 | acpi_backlight= [HW,ACPI] |
193 | acpi_backlight=vendor | |
194 | acpi_backlight=video | |
195 | If set to vendor, prefer vendor specific driver | |
196 | (e.g. thinkpad_acpi, sony_acpi, etc.) instead | |
197 | of the ACPI video.ko driver. | |
198 | ||
b2ca5dae CIK |
199 | acpi_force_32bit_fadt_addr |
200 | force FADT to use 32 bit addresses rather than the | |
201 | 64 bit X_* addresses. Some firmware have broken 64 | |
202 | bit addresses for force ACPI ignore these and use | |
203 | the older legacy 32 bit addresses. | |
204 | ||
ef69449b DB |
205 | acpica_no_return_repair [HW, ACPI] |
206 | Disable AML predefined validation mechanism | |
207 | This mechanism can repair the evaluation result to make | |
208 | the return objects more ACPI specification compliant. | |
209 | This option is useful for developers to identify the | |
210 | root cause of an AML interpreter issue when the issue | |
211 | has something to do with the repair mechanism. | |
212 | ||
a0d84a92 BH |
213 | acpi.debug_layer= [HW,ACPI,ACPI_DEBUG] |
214 | acpi.debug_level= [HW,ACPI,ACPI_DEBUG] | |
1da177e4 | 215 | Format: <int> |
a0d84a92 BH |
216 | CONFIG_ACPI_DEBUG must be enabled to produce any ACPI |
217 | debug output. Bits in debug_layer correspond to a | |
218 | _COMPONENT in an ACPI source file, e.g., | |
219 | #define _COMPONENT ACPI_PCI_COMPONENT | |
220 | Bits in debug_level correspond to a level in | |
221 | ACPI_DEBUG_PRINT statements, e.g., | |
222 | ACPI_DEBUG_PRINT((ACPI_DB_INFO, ... | |
e76f4276 BH |
223 | The debug_level mask defaults to "info". See |
224 | Documentation/acpi/debug.txt for more information about | |
225 | debug layers and levels. | |
a0d84a92 | 226 | |
e76f4276 BH |
227 | Enable processor driver info messages: |
228 | acpi.debug_layer=0x20000000 | |
229 | Enable PCI/PCI interrupt routing info messages: | |
230 | acpi.debug_layer=0x400000 | |
a0d84a92 BH |
231 | Enable AML "Debug" output, i.e., stores to the Debug |
232 | object while interpreting AML: | |
233 | acpi.debug_layer=0xffffffff acpi.debug_level=0x2 | |
a0d84a92 BH |
234 | Enable all messages related to ACPI hardware: |
235 | acpi.debug_layer=0x2 acpi.debug_level=0xffffffff | |
236 | ||
237 | Some values produce so much output that the system is | |
238 | unusable. The "log_buf_len" parameter may be useful | |
239 | if you need to capture more output. | |
f989106c | 240 | |
ef69449b DB |
241 | acpi_enforce_resources= [ACPI] |
242 | { strict | lax | no } | |
243 | Check for resource conflicts between native drivers | |
244 | and ACPI OperationRegions (SystemIO and SystemMemory | |
245 | only). IO ports and memory declared in ACPI might be | |
246 | used by the ACPI subsystem in arbitrary AML code and | |
247 | can interfere with legacy drivers. | |
248 | strict (default): access to resources claimed by ACPI | |
249 | is denied; legacy drivers trying to access reserved | |
250 | resources will fail to bind to device using them. | |
251 | lax: access to resources claimed by ACPI is allowed; | |
252 | legacy drivers trying to access reserved resources | |
253 | will bind successfully but a warning message is logged. | |
254 | no: ACPI OperationRegions are not marked as reserved, | |
255 | no further checks are performed. | |
256 | ||
4fc0a7e8 LZ |
257 | acpi_force_table_verification [HW,ACPI] |
258 | Enable table checksum verification during early stage. | |
259 | By default, this is disabled due to x86 early mapping | |
260 | size limitation. | |
261 | ||
0cb55ad2 RD |
262 | acpi_irq_balance [HW,ACPI] |
263 | ACPI will balance active IRQs | |
264 | default in APIC mode | |
265 | ||
266 | acpi_irq_nobalance [HW,ACPI] | |
267 | ACPI will not move active IRQs (default) | |
268 | default in PIC mode | |
269 | ||
270 | acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA | |
271 | Format: <irq>,<irq>... | |
272 | ||
273 | acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for | |
274 | use by PCI | |
275 | Format: <irq>,<irq>... | |
276 | ||
08e1d7c0 LZ |
277 | acpi_no_auto_serialize [HW,ACPI] |
278 | Disable auto-serialization of AML methods | |
22b5afce BM |
279 | AML control methods that contain the opcodes to create |
280 | named objects will be marked as "Serialized" by the | |
281 | auto-serialization feature. | |
08e1d7c0 LZ |
282 | This feature is enabled by default. |
283 | This option allows to turn off the feature. | |
22b5afce | 284 | |
ef69449b DB |
285 | acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump |
286 | kernels. | |
287 | ||
a94e88cd LZ |
288 | acpi_no_static_ssdt [HW,ACPI] |
289 | Disable installation of static SSDTs at early boot time | |
290 | By default, SSDTs contained in the RSDT/XSDT will be | |
291 | installed automatically and they will appear under | |
292 | /sys/firmware/acpi/tables. | |
293 | This option turns off this feature. | |
294 | Note that specifying this option does not affect | |
295 | dynamic table installation which will install SSDT | |
296 | tables to /sys/firmware/acpi/tables/dynamic. | |
0cb55ad2 | 297 | |
ef69449b DB |
298 | acpi_rsdp= [ACPI,EFI,KEXEC] |
299 | Pass the RSDP address to the kernel, mostly used | |
300 | on machines running EFI runtime service to boot the | |
301 | second kernel for kdump. | |
4dde507f | 302 | |
0cb55ad2 RD |
303 | acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS |
304 | Format: To spoof as Windows 98: ="Microsoft Windows" | |
305 | ||
18d78b64 RW |
306 | acpi_rev_override [ACPI] Override the _REV object to return 5 (instead |
307 | of 2 which is mandated by ACPI 6) as the supported ACPI | |
308 | specification revision (when using this switch, it may | |
309 | be necessary to carry out a cold reboot _twice_ in a | |
310 | row to make it take effect on the platform firmware). | |
311 | ||
0cb55ad2 | 312 | acpi_osi= [HW,ACPI] Modify list of supported OS interface strings |
5dc17986 LZ |
313 | acpi_osi="string1" # add string1 |
314 | acpi_osi="!string2" # remove string2 | |
741d8128 | 315 | acpi_osi=!* # remove all strings |
5dc17986 LZ |
316 | acpi_osi=! # disable all built-in OS vendor |
317 | strings | |
a707edeb LZ |
318 | acpi_osi=!! # enable all built-in OS vendor |
319 | strings | |
0cb55ad2 RD |
320 | acpi_osi= # disable all strings |
321 | ||
5dc17986 LZ |
322 | 'acpi_osi=!' can be used in combination with single or |
323 | multiple 'acpi_osi="string1"' to support specific OS | |
324 | vendor string(s). Note that such command can only | |
325 | affect the default state of the OS vendor strings, thus | |
326 | it cannot affect the default state of the feature group | |
327 | strings and the current state of the OS vendor strings, | |
328 | specifying it multiple times through kernel command line | |
741d8128 LZ |
329 | is meaningless. This command is useful when one do not |
330 | care about the state of the feature group strings which | |
331 | should be controlled by the OSPM. | |
5dc17986 LZ |
332 | Examples: |
333 | 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent | |
334 | to 'acpi_osi="Windows 2000" acpi_osi=!', they all | |
335 | can make '_OSI("Windows 2000")' TRUE. | |
336 | ||
337 | 'acpi_osi=' cannot be used in combination with other | |
338 | 'acpi_osi=' command lines, the _OSI method will not | |
339 | exist in the ACPI namespace. NOTE that such command can | |
340 | only affect the _OSI support state, thus specifying it | |
341 | multiple times through kernel command line is also | |
342 | meaningless. | |
343 | Examples: | |
344 | 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)' | |
345 | FALSE. | |
346 | ||
741d8128 LZ |
347 | 'acpi_osi=!*' can be used in combination with single or |
348 | multiple 'acpi_osi="string1"' to support specific | |
349 | string(s). Note that such command can affect the | |
350 | current state of both the OS vendor strings and the | |
351 | feature group strings, thus specifying it multiple times | |
352 | through kernel command line is meaningful. But it may | |
353 | still not able to affect the final state of a string if | |
354 | there are quirks related to this string. This command | |
355 | is useful when one want to control the state of the | |
356 | feature group strings to debug BIOS issues related to | |
357 | the OSPM features. | |
358 | Examples: | |
359 | 1. 'acpi_osi="Module Device" acpi_osi=!*' can make | |
360 | '_OSI("Module Device")' FALSE. | |
361 | 2. 'acpi_osi=!* acpi_osi="Module Device"' can make | |
362 | '_OSI("Module Device")' TRUE. | |
363 | 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is | |
364 | equivalent to | |
365 | 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"' | |
366 | and | |
367 | 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!', | |
368 | they all will make '_OSI("Windows 2000")' TRUE. | |
369 | ||
6cececfc | 370 | acpi_pm_good [X86] |
0cb55ad2 RD |
371 | Override the pmtimer bug detection: force the kernel |
372 | to assume that this machine's pmtimer latches its value | |
373 | and always returns good values. | |
374 | ||
4af94f39 RD |
375 | acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode |
376 | Format: { level | edge | high | low } | |
377 | ||
4af94f39 RD |
378 | acpi_skip_timer_override [HW,ACPI] |
379 | Recognize and ignore IRQ0/pin2 Interrupt Override. | |
380 | For broken nForce2 BIOS resulting in XT-PIC timer. | |
381 | ||
382 | acpi_sleep= [HW,ACPI] Sleep options | |
383 | Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, | |
c3b0795c | 384 | old_ordering, nonvs, sci_force_enable } |
4af94f39 RD |
385 | See Documentation/power/video.txt for information on |
386 | s3_bios and s3_mode. | |
387 | s3_beep is for debugging; it makes the PC's speaker beep | |
388 | as soon as the kernel's real-mode entry point is called. | |
389 | s4_nohwsig prevents ACPI hardware signature from being | |
390 | used during resume from hibernation. | |
391 | old_ordering causes the ACPI 1.0 ordering of the _PTS | |
392 | control method, with respect to putting devices into | |
393 | low power states, to be enforced (the ACPI 2.0 ordering | |
394 | of _PTS is used by default). | |
72ad5d77 RW |
395 | nonvs prevents the kernel from saving/restoring the |
396 | ACPI NVS memory during suspend/hibernation and resume. | |
d7f0eea9 ZR |
397 | sci_force_enable causes the kernel to set SCI_EN directly |
398 | on resume from S1/S3 (which is against the ACPI spec, | |
399 | but some broken systems don't work without it). | |
4af94f39 RD |
400 | |
401 | acpi_use_timer_override [HW,ACPI] | |
402 | Use timer override. For some broken Nvidia NF5 boards | |
403 | that require a timer override, but don't have HPET | |
404 | ||
4af94f39 RD |
405 | add_efi_memmap [EFI; X86] Include EFI memory map in |
406 | kernel's map of available physical RAM. | |
407 | ||
0cb55ad2 RD |
408 | agp= [AGP] |
409 | { off | try_unsupported } | |
410 | off: disable AGP support | |
411 | try_unsupported: try to drive unsupported chipsets | |
412 | (may crash computer or cause data corruption) | |
413 | ||
bcfde334 RD |
414 | ALSA [HW,ALSA] |
415 | See Documentation/sound/alsa/alsa-parameters.txt | |
416 | ||
d944d549 RK |
417 | alignment= [KNL,ARM] |
418 | Allow the default userspace alignment fault handler | |
419 | behaviour to be specified. Bit 0 enables warnings, | |
420 | bit 1 enables fixups, and bit 2 sends a segfault. | |
421 | ||
dfb09f9b BP |
422 | align_va_addr= [X86-64] |
423 | Align virtual addresses by clearing slice [14:12] when | |
424 | allocating a VMA at process creation time. This option | |
425 | gives you up to 3% performance improvement on AMD F15h | |
426 | machines (where it is enabled by default) for a | |
427 | CPU-intensive style benchmark, and it can vary highly in | |
428 | a microbenchmark depending on workload and compiler. | |
429 | ||
8360ee2f BP |
430 | 32: only for 32-bit processes |
431 | 64: only for 64-bit processes | |
dfb09f9b BP |
432 | on: enable for both 32- and 64-bit processes |
433 | off: disable for both 32- and 64-bit processes | |
434 | ||
55034cd6 SRRH |
435 | alloc_snapshot [FTRACE] |
436 | Allocate the ftrace snapshot buffer on boot up when the | |
437 | main buffer is allocated. This is handy if debugging | |
438 | and you need to use tracing_snapshot() on boot up, and | |
439 | do not want to use tracing_snapshot_alloc() as it needs | |
440 | to be done where GFP_KERNEL allocations are allowed. | |
441 | ||
89e0b9a3 | 442 | amd_iommu= [HW,X86-64] |
54b4cbd2 JR |
443 | Pass parameters to the AMD IOMMU driver in the system. |
444 | Possible values are: | |
afa9fdc2 FT |
445 | fullflush - enable flushing of IO/TLB entries when |
446 | they are unmapped. Otherwise they are | |
447 | flushed before they will be reused, which | |
448 | is a lot of faster | |
a5235725 JR |
449 | off - do not initialize any AMD IOMMU found in |
450 | the system | |
5abcdba4 JR |
451 | force_isolation - Force device isolation for all |
452 | devices. The IOMMU driver is not | |
453 | allowed anymore to lift isolation | |
454 | requirements as needed. This option | |
455 | does not override iommu=pt | |
afa9fdc2 | 456 | |
c099cf17 SK |
457 | amd_iommu_dump= [HW,X86-64] |
458 | Enable AMD IOMMU driver option to dump the ACPI table | |
459 | for AMD IOMMU. With this option enabled, AMD IOMMU | |
460 | driver will print ACPI tables for AMD IOMMU during | |
461 | IOMMU initialization. | |
462 | ||
1da177e4 LT |
463 | amijoy.map= [HW,JOY] Amiga joystick support |
464 | Map of devices attached to JOY0DAT and JOY1DAT | |
465 | Format: <a>,<b> | |
395cf969 | 466 | See also Documentation/input/joystick.txt |
1da177e4 LT |
467 | |
468 | analog.map= [HW,JOY] Analog joystick and gamepad support | |
469 | Specifies type or capabilities of an analog joystick | |
470 | connected to one of 16 gameports | |
471 | Format: <type1>,<type2>,..<type16> | |
472 | ||
a9913044 RD |
473 | apc= [HW,SPARC] |
474 | Power management functions (SPARCstation-4/5 + deriv.) | |
1da177e4 LT |
475 | Format: noidle |
476 | Disable APC CPU standby support. SPARCstation-Fox does | |
477 | not play well with APC CPU idle - disable it if you have | |
478 | APC and your system crashes randomly. | |
479 | ||
ca1eda2d | 480 | apic= [APIC,X86-32] Advanced Programmable Interrupt Controller |
c8facbb6 | 481 | Change the output verbosity whilst booting |
1da177e4 LT |
482 | Format: { quiet (default) | verbose | debug } |
483 | Change the amount of debugging information output | |
484 | when initialising the APIC and IO-APIC components. | |
a9913044 | 485 | |
b7c4948e HK |
486 | apic_extnmi= [APIC,X86] External NMI delivery setting |
487 | Format: { bsp (default) | all | none } | |
488 | bsp: External NMI is delivered only to CPU 0 | |
489 | all: External NMIs are broadcast to all CPUs as a | |
490 | backup of CPU 0 | |
491 | none: External NMI is masked for all CPUs. This is | |
492 | useful so that a dump capture kernel won't be | |
493 | shot down by NMI | |
494 | ||
b0f83b28 BH |
495 | autoconf= [IPV6] |
496 | See Documentation/networking/ipv6.txt. | |
497 | ||
9636bc05 CG |
498 | show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller |
499 | Limit apic dumping. The parameter defines the maximal | |
500 | number of local apics being dumped. Also it is possible | |
501 | to set it to "all" by meaning -- no limit here. | |
502 | Format: { 1 (default) | 2 | ... | all }. | |
503 | The parameter valid if only apic=debug or | |
504 | apic=verbose is specified. | |
505 | Example: apic=debug show_lapic=all | |
506 | ||
1da177e4 | 507 | apm= [APM] Advanced Power Management |
71f77055 | 508 | See header of arch/x86/kernel/apm_32.c. |
1da177e4 | 509 | |
1da177e4 LT |
510 | arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards |
511 | Format: <io>,<irq>,<nodeID> | |
512 | ||
513 | ataflop= [HW,M68k] | |
514 | ||
515 | atarimouse= [HW,MOUSE] Atari Mouse | |
516 | ||
1da177e4 LT |
517 | atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, |
518 | EzKey and similar keyboards | |
519 | ||
520 | atkbd.reset= [HW] Reset keyboard during initialization | |
521 | ||
a9913044 RD |
522 | atkbd.set= [HW] Select keyboard code set |
523 | Format: <int> (2 = AT (default), 3 = PS/2) | |
1da177e4 LT |
524 | |
525 | atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar | |
526 | keyboards | |
527 | ||
528 | atkbd.softraw= [HW] Choose between synthetic and real raw mode | |
529 | Format: <bool> (0 = real, 1 = synthetic (default)) | |
a9913044 RD |
530 | |
531 | atkbd.softrepeat= [HW] | |
532 | Use software keyboard repeat | |
1da177e4 | 533 | |
a106fb0c RGB |
534 | audit= [KNL] Enable the audit sub-system |
535 | Format: { "0" | "1" } (0 = disabled, 1 = enabled) | |
d7961148 EP |
536 | 0 - kernel audit is disabled and can not be enabled |
537 | until the next reboot | |
538 | unset - kernel audit is initialized but disabled and | |
539 | will be fully enabled by the userspace auditd. | |
540 | 1 - kernel audit is initialized and partially enabled, | |
541 | storing at most audit_backlog_limit messages in | |
542 | RAM until it is fully enabled by the userspace | |
543 | auditd. | |
a106fb0c | 544 | Default: unset |
f3411cb2 | 545 | |
f910fde7 RGB |
546 | audit_backlog_limit= [KNL] Set the audit queue size limit. |
547 | Format: <int> (must be >=0) | |
548 | Default: 64 | |
549 | ||
1c532e00 AT |
550 | bau= [X86_UV] Enable the BAU on SGI UV. The default |
551 | behavior is to disable the BAU (i.e. bau=0). | |
552 | Format: { "0" | "1" } | |
553 | 0 - Disable the BAU. | |
554 | 1 - Enable the BAU. | |
555 | unset - Disable the BAU. | |
556 | ||
1da177e4 LT |
557 | baycom_epp= [HW,AX25] |
558 | Format: <io>,<mode> | |
a9913044 | 559 | |
1da177e4 LT |
560 | baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem |
561 | Format: <io>,<mode> | |
562 | See header of drivers/net/hamradio/baycom_par.c. | |
563 | ||
a9913044 RD |
564 | baycom_ser_fdx= [HW,AX25] |
565 | BayCom Serial Port AX.25 Modem (Full Duplex Mode) | |
1da177e4 LT |
566 | Format: <io>,<irq>,<mode>[,<baud>] |
567 | See header of drivers/net/hamradio/baycom_ser_fdx.c. | |
568 | ||
a9913044 RD |
569 | baycom_ser_hdx= [HW,AX25] |
570 | BayCom Serial Port AX.25 Modem (Half Duplex Mode) | |
1da177e4 LT |
571 | Format: <io>,<irq>,<mode> |
572 | See header of drivers/net/hamradio/baycom_ser_hdx.c. | |
573 | ||
080506ad PG |
574 | blkdevparts= Manual partition parsing of block device(s) for |
575 | embedded devices based on command line input. | |
576 | See Documentation/block/cmdline-partition.txt | |
577 | ||
bfe8df3d RD |
578 | boot_delay= Milliseconds to delay each printk during boot. |
579 | Values larger than 10 seconds (10000) are changed to | |
580 | no delay (0). | |
581 | Format: integer | |
582 | ||
35fc908d AH |
583 | bootmem_debug [KNL] Enable bootmem allocator debug messages. |
584 | ||
a3e2acc5 HY |
585 | bert_disable [ACPI] |
586 | Disable BERT OS support on buggy BIOSes. | |
587 | ||
1da177e4 | 588 | bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) |
a9913044 RD |
589 | bttv.radio= Most important insmod options are available as |
590 | kernel args too. | |
1da177e4 | 591 | bttv.pll= See Documentation/video4linux/bttv/Insmod-options |
395cf969 | 592 | bttv.tuner= |
1da177e4 | 593 | |
4e89a2d8 WS |
594 | bulk_remove=off [PPC] This parameter disables the use of the pSeries |
595 | firmware feature for flushing multiple hpte entries | |
596 | at a time. | |
597 | ||
1da177e4 LT |
598 | c101= [NET] Moxa C101 synchronous serial card |
599 | ||
cd4f0ef7 | 600 | cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. |
1da177e4 LT |
601 | Sometimes CPU hardware bugs make them report the cache |
602 | size incorrectly. The kernel will attempt work arounds | |
603 | to fix known problems, but for some CPUs it is not | |
604 | possible to determine what the correct size should be. | |
605 | This option provides an override for these situations. | |
606 | ||
ffb70f61 DK |
607 | ca_keys= [KEYS] This parameter identifies a specific key(s) on |
608 | the system trusted keyring to be used for certificate | |
609 | trust validation. | |
32c4741c | 610 | format: { id:<keyid> | builtin } |
ffb70f61 | 611 | |
fd1bb4c9 FF |
612 | cca= [MIPS] Override the kernel pages' cache coherency |
613 | algorithm. Accepted values range from 0 to 7 | |
614 | inclusive. See arch/mips/include/asm/pgtable-bits.h | |
615 | for platform specific values (SB1, Loongson3 and | |
616 | others). | |
617 | ||
14ff56bb SO |
618 | ccw_timeout_log [S390] |
619 | See Documentation/s390/CommonIO for details. | |
1da177e4 | 620 | |
8bab8dde PM |
621 | cgroup_disable= [KNL] Disable a particular controller |
622 | Format: {name of the controller(s) to disable} | |
ca0bdbb5 QH |
623 | The effects of cgroup_disable=foo are: |
624 | - foo isn't auto-mounted if you mount all cgroups in | |
625 | a single hierarchy | |
626 | - foo isn't visible as an individually mountable | |
627 | subsystem | |
628 | {Currently only "memory" controller deal with this and | |
629 | cut the overhead, others just disable the usage. So | |
630 | only cgroup_disable=memory is actually worthy} | |
8bab8dde | 631 | |
1619b6d4 JW |
632 | cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1 |
633 | Format: { controller[,controller...] | "all" } | |
634 | Like cgroup_disable, but only applies to cgroup v1; | |
635 | the blacklisted controllers remain available in cgroup2. | |
636 | ||
f7e1cb6e JW |
637 | cgroup.memory= [KNL] Pass options to the cgroup memory controller. |
638 | Format: <string> | |
639 | nosocket -- Disable socket memory accounting. | |
04823c83 | 640 | nokmem -- Disable kernel memory accounting. |
f7e1cb6e | 641 | |
1da177e4 LT |
642 | checkreqprot [SELINUX] Set initial checkreqprot flag value. |
643 | Format: { "0" | "1" } | |
644 | See security/selinux/Kconfig help text. | |
a9913044 RD |
645 | 0 -- check protection applied by kernel (includes |
646 | any implied execute protection). | |
1da177e4 LT |
647 | 1 -- check protection requested by application. |
648 | Default value is set via a kernel config option. | |
a9913044 RD |
649 | Value can be changed at runtime via |
650 | /selinux/checkreqprot. | |
651 | ||
661ca0da SO |
652 | cio_ignore= [S390] |
653 | See Documentation/s390/CommonIO for details. | |
1e435256 OJ |
654 | clk_ignore_unused |
655 | [CLK] | |
e156ee56 MT |
656 | Prevents the clock framework from automatically gating |
657 | clocks that have not been explicitly enabled by a Linux | |
658 | device driver but are enabled in hardware at reset or | |
659 | by the bootloader/firmware. Note that this does not | |
660 | force such clocks to be always-on nor does it reserve | |
661 | those clocks in any way. This parameter is useful for | |
662 | debug and development, but should not be needed on a | |
663 | platform with proper driver support. For more | |
664 | information, see Documentation/clk.txt. | |
661ca0da | 665 | |
cd4f0ef7 | 666 | clock= [BUGS=X86-32, HW] gettimeofday clocksource override. |
734efb46 | 667 | [Deprecated] |
3f6dee9b | 668 | Forces specified clocksource (if available) to be used |
734efb46 | 669 | when calculating gettimeofday(). If specified |
3f6dee9b | 670 | clocksource is not available, it defaults to PIT. |
1da177e4 LT |
671 | Format: { pit | tsc | cyclone | pmtmr } |
672 | ||
592913ec | 673 | clocksource= Override the default clocksource |
3d6ac984 RD |
674 | Format: <string> |
675 | Override the default clocksource and use the clocksource | |
676 | with the name specified. | |
677 | Some clocksource names to choose from, depending on | |
678 | the platform: | |
679 | [all] jiffies (this is the base, fallback clocksource) | |
680 | [ACPI] acpi_pm | |
681 | [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, | |
682 | pxa_timer,timer3,32k_counter,timer0_1 | |
683 | [AVR32] avr32 | |
9863c90f | 684 | [X86-32] pit,hpet,tsc; |
3d6ac984 RD |
685 | scx200_hrt on Geode; cyclone on IBM x440 |
686 | [MIPS] MIPS | |
687 | [PARISC] cr16 | |
688 | [S390] tod | |
689 | [SH] SuperH | |
690 | [SPARC64] tick | |
691 | [X86-64] hpet,tsc | |
692 | ||
46fd5c6b WD |
693 | clocksource.arm_arch_timer.evtstrm= |
694 | [ARM,ARM64] | |
695 | Format: <bool> | |
696 | Enable/disable the eventstream feature of the ARM | |
697 | architected timer so that code using WFE-based polling | |
698 | loops can be debugged more effectively on production | |
699 | systems. | |
700 | ||
ac72e788 AK |
701 | clearcpuid=BITNUM [X86] |
702 | Disable CPUID feature X for the kernel. See | |
cd4d09ec | 703 | arch/x86/include/asm/cpufeatures.h for the valid bit |
07983f0e | 704 | numbers. Note the Linux specific bits are not necessarily |
ac72e788 AK |
705 | stable over kernel options, but the vendor specific |
706 | ones should be. | |
707 | Also note that user programs calling CPUID directly | |
708 | or using the feature without checking anything | |
709 | will still see it. This just prevents it from | |
710 | being used by the kernel or shown in /proc/cpuinfo. | |
711 | Also note the kernel might malfunction if you disable | |
712 | some critical bits. | |
713 | ||
5ea3b1b2 AM |
714 | cma=nn[MG]@[start[MG][-end[MG]]] |
715 | [ARM,X86,KNL] | |
716 | Sets the size of kernel global memory area for | |
717 | contiguous memory allocations and optionally the | |
718 | placement constraint by the physical address range of | |
f0d6d1f6 JD |
719 | memory allocations. A value of 0 disables CMA |
720 | altogether. For more information, see | |
c64be2bb MS |
721 | include/linux/dma-contiguous.h |
722 | ||
14f966e7 RJ |
723 | cmo_free_hint= [PPC] Format: { yes | no } |
724 | Specify whether pages are marked as being inactive | |
725 | when they are freed. This is used in CMO environments | |
726 | to determine OS memory pressure for page stealing by | |
727 | a hypervisor. | |
728 | Default: yes | |
729 | ||
c7909509 MS |
730 | coherent_pool=nn[KMG] [ARM,KNL] |
731 | Sets the size of memory pool for coherent, atomic dma | |
e9da6e99 | 732 | allocations, by default set to 256K. |
c7909509 | 733 | |
6cececfc | 734 | code_bytes [X86] How many bytes of object code to print |
a25bd949 | 735 | in an oops report. |
86c41837 CE |
736 | Range: 0 - 8192 |
737 | Default: 64 | |
738 | ||
1da177e4 | 739 | com20020= [HW,NET] ARCnet - COM20020 chipset |
a9913044 RD |
740 | Format: |
741 | <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] | |
1da177e4 LT |
742 | |
743 | com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) | |
744 | Format: <io>[,<irq>] | |
745 | ||
a9913044 RD |
746 | com90xx= [HW,NET] |
747 | ARCnet - COM90xx chipset (memory-mapped buffers) | |
1da177e4 LT |
748 | Format: <io>[,<irq>[,<memstart>]] |
749 | ||
750 | condev= [HW,S390] console device | |
751 | conmode= | |
a9913044 | 752 | |
1da177e4 LT |
753 | console= [KNL] Output console device and options. |
754 | ||
755 | tty<n> Use the virtual console device <n>. | |
756 | ||
757 | ttyS<n>[,options] | |
f1a1c2dc | 758 | ttyUSB0[,options] |
1da177e4 | 759 | Use the specified serial port. The options are of |
f1a1c2dc RD |
760 | the form "bbbbpnf", where "bbbb" is the baud rate, |
761 | "p" is parity ("n", "o", or "e"), "n" is number of | |
762 | bits, and "f" is flow control ("r" for RTS or | |
763 | omit it). Default is "9600n8". | |
764 | ||
765 | See Documentation/serial-console.txt for more | |
766 | information. See | |
767 | Documentation/networking/netconsole.txt for an | |
768 | alternative. | |
1da177e4 | 769 | |
18a8bd94 YL |
770 | uart[8250],io,<addr>[,options] |
771 | uart[8250],mmio,<addr>[,options] | |
bd94c407 | 772 | uart[8250],mmio16,<addr>[,options] |
ca782f16 PH |
773 | uart[8250],mmio32,<addr>[,options] |
774 | uart[8250],0x<addr>[,options] | |
1da177e4 LT |
775 | Start an early, polled-mode console on the 8250/16550 |
776 | UART at the specified I/O port or MMIO address, | |
ca782f16 PH |
777 | switching to the matching ttyS device later. |
778 | MMIO inter-register address stride is either 8-bit | |
bd94c407 MY |
779 | (mmio), 16-bit (mmio16), or 32-bit (mmio32). |
780 | If none of [io|mmio|mmio16|mmio32], <addr> is assumed | |
781 | to be equivalent to 'mmio'. 'options' are specified in | |
782 | the same format described for ttyS above; if unspecified, | |
ca782f16 PH |
783 | the h/w is not re-initialized. |
784 | ||
a2fd6419 KRW |
785 | hvc<n> Use the hypervisor console device <n>. This is for |
786 | both Xen and PowerPC hypervisors. | |
1da177e4 | 787 | |
f7511d5f ST |
788 | If the device connected to the port is not a TTY but a braille |
789 | device, prepend "brl," before the device type, for instance | |
790 | console=brl,ttyS0 | |
791 | For now, only VisioBraille is supported. | |
792 | ||
f324edc8 DM |
793 | consoleblank= [KNL] The console blank (screen saver) timeout in |
794 | seconds. Defaults to 10*60 = 10mins. A value of 0 | |
795 | disables the blank timer. | |
796 | ||
4cb0e11b HK |
797 | coredump_filter= |
798 | [KNL] Change the default value for | |
799 | /proc/<pid>/coredump_filter. | |
800 | See also Documentation/filesystems/proc.txt. | |
801 | ||
62027aea LB |
802 | cpuidle.off=1 [CPU_IDLE] |
803 | disable the cpuidle sub-system | |
804 | ||
d68921f9 LB |
805 | cpu_init_udelay=N |
806 | [X86] Delay for N microsec between assert and de-assert | |
807 | of APIC INIT to start processors. This delay occurs | |
808 | on every CPU online, such as boot, and resume from suspend. | |
809 | Default: 10000 | |
810 | ||
1da177e4 | 811 | cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver |
a9913044 RD |
812 | Format: |
813 | <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] | |
1da177e4 | 814 | |
6f21e646 AD |
815 | crashkernel=size[KMG][@offset[KMG]] |
816 | [KNL] Using kexec, Linux can switch to a 'crash kernel' | |
817 | upon panic. This parameter reserves the physical | |
818 | memory region [offset, offset + size] for that kernel | |
819 | image. If '@offset' is omitted, then a suitable offset | |
820 | is selected automatically. Check | |
821 | Documentation/kdump/kdump.txt for further details. | |
dc009d92 | 822 | |
fb391599 BW |
823 | crashkernel=range1:size1[,range2:size2,...][@offset] |
824 | [KNL] Same as above, but depends on the memory | |
825 | in the running system. The syntax of range is | |
826 | start-[end] where start and end are both | |
827 | a memory unit (amount[KMG]). See also | |
6f21e646 | 828 | Documentation/kdump/kdump.txt for an example. |
fb391599 | 829 | |
adbc742b | 830 | crashkernel=size[KMG],high |
55a20ee7 YL |
831 | [KNL, x86_64] range could be above 4G. Allow kernel |
832 | to allocate physical memory region from top, so could | |
833 | be above 4G if system have more than 4G ram installed. | |
834 | Otherwise memory region will be allocated below 4G, if | |
835 | available. | |
836 | It will be ignored if crashkernel=X is specified. | |
adbc742b YL |
837 | crashkernel=size[KMG],low |
838 | [KNL, x86_64] range under 4G. When crashkernel=X,high | |
839 | is passed, kernel could allocate physical memory region | |
c729de8f YL |
840 | above 4G, that cause second kernel crash on system |
841 | that require some amount of low memory, e.g. swiotlb | |
c6045031 BH |
842 | requires at least 64M+32K low memory, also enough extra |
843 | low memory is needed to make sure DMA buffers for 32-bit | |
844 | devices won't run out. Kernel would try to allocate at | |
845 | at least 256M below 4G automatically. | |
c729de8f YL |
846 | This one let user to specify own low range under 4G |
847 | for second kernel instead. | |
848 | 0: to disable low allocation. | |
adbc742b | 849 | It will be ignored when crashkernel=X,high is not used |
55a20ee7 | 850 | or memory reserved is below 4G. |
c729de8f | 851 | |
9e5c9fe4 RJ |
852 | cryptomgr.notests |
853 | [KNL] Disable crypto self-tests | |
854 | ||
1da177e4 LT |
855 | cs89x0_dma= [HW,NET] |
856 | Format: <dma> | |
857 | ||
858 | cs89x0_media= [HW,NET] | |
859 | Format: { rj45 | aui | bnc } | |
a9913044 | 860 | |
a9913044 | 861 | dasd= [HW,NET] |
1da177e4 LT |
862 | See header of drivers/s390/block/dasd_devmap.c. |
863 | ||
864 | db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port | |
865 | (one device per port) | |
866 | Format: <port#>,<type> | |
867 | See also Documentation/input/joystick-parport.txt | |
868 | ||
a648ec05 TR |
869 | ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot |
870 | time. See Documentation/dynamic-debug-howto.txt for | |
29e36c9f | 871 | details. Deprecated, see dyndbg. |
a648ec05 | 872 | |
1da177e4 LT |
873 | debug [KNL] Enable kernel debugging (events log level). |
874 | ||
cae2ed9a IM |
875 | debug_locks_verbose= |
876 | [KNL] verbose self-tests | |
877 | Format=<0|1> | |
878 | Print debugging info while doing the locking API | |
879 | self-tests. | |
880 | We default to 0 (no extra messages), setting it to | |
881 | 1 will print _a lot_ more information - normally | |
882 | only useful to kernel developers. | |
883 | ||
3ac7fe5a TG |
884 | debug_objects [KNL] Enable object debugging |
885 | ||
3e8ebb5c KM |
886 | no_debug_objects |
887 | [KNL] Disable object debugging | |
888 | ||
c0a32fc5 SG |
889 | debug_guardpage_minorder= |
890 | [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this | |
891 | parameter allows control of the order of pages that will | |
892 | be intentionally kept free (and hence protected) by the | |
893 | buddy allocator. Bigger value increase the probability | |
894 | of catching random memory corruption, but reduce the | |
895 | amount of memory for normal system use. The maximum | |
896 | possible value is MAX_ORDER/2. Setting this parameter | |
897 | to 1 or 2 should be enough to identify most random | |
898 | memory corruption problems caused by bugs in kernel or | |
899 | driver code when a CPU writes to (or reads from) a | |
900 | random memory location. Note that there exists a class | |
901 | of memory corruptions problems caused by buggy H/W or | |
902 | F/W or by drivers badly programing DMA (basically when | |
903 | memory is written at bus level and the CPU MMU is | |
904 | bypassed) which are not detectable by | |
905 | CONFIG_DEBUG_PAGEALLOC, hence this option will not help | |
906 | tracking down these problems. | |
907 | ||
031bc574 JK |
908 | debug_pagealloc= |
909 | [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this | |
910 | parameter enables the feature at boot time. In | |
911 | default, it is disabled. We can avoid allocating huge | |
912 | chunk of memory for debug pagealloc if we don't enable | |
913 | it at boot time and the system will work mostly same | |
914 | with the kernel built without CONFIG_DEBUG_PAGEALLOC. | |
915 | on: enable the feature | |
916 | ||
d3af01f1 TG |
917 | debugpat [X86] Enable PAT debugging |
918 | ||
2d27a966 | 919 | decnet.addr= [HW,NET] |
1da177e4 LT |
920 | Format: <area>[,<node>] |
921 | See also Documentation/networking/decnet.txt. | |
922 | ||
0cb55ad2 RD |
923 | default_hugepagesz= |
924 | [same as hugepagesz=] The size of the default | |
925 | HugeTLB page size. This is the size represented by | |
926 | the legacy /proc/ hugepages APIs, used for SHM, and | |
927 | default size when mounting hugetlbfs filesystems. | |
928 | Defaults to the default architecture's huge page size | |
929 | if not specified. | |
55ff9780 | 930 | |
1da177e4 LT |
931 | dhash_entries= [KNL] |
932 | Set number of hash buckets for dentry cache. | |
a9913044 | 933 | |
faf78829 OH |
934 | disable_1tb_segments [PPC] |
935 | Disables the use of 1TB hash page table segments. This | |
936 | causes the kernel to fall back to 256MB segments which | |
937 | can be useful when debugging issues that require an SLB | |
938 | miss to occur. | |
939 | ||
b0f83b28 BH |
940 | disable= [IPV6] |
941 | See Documentation/networking/ipv6.txt. | |
942 | ||
b275bfb2 AK |
943 | disable_radix [PPC] |
944 | Disable RADIX MMU mode on POWER9 | |
945 | ||
151e0c7d HD |
946 | disable_cpu_apicid= [X86,APIC,SMP] |
947 | Format: <int> | |
948 | The number of initial APIC ID for the | |
949 | corresponding CPU to be disabled at boot, | |
950 | mostly used for the kdump 2nd kernel to | |
951 | disable BSP to wake up multiple CPUs without | |
952 | causing system reset or hang due to sending | |
953 | INIT from AP to BSP. | |
954 | ||
4e8b0cf4 NA |
955 | disable_ddw [PPC/PSERIES] |
956 | Disable Dynamic DMA Window support. Use this if | |
957 | to workaround buggy firmware. | |
958 | ||
b0f83b28 BH |
959 | disable_ipv6= [IPV6] |
960 | See Documentation/networking/ipv6.txt. | |
961 | ||
95ffa243 | 962 | disable_mtrr_cleanup [X86] |
95ffa243 YL |
963 | The kernel tries to adjust MTRR layout from continuous |
964 | to discrete, to make X server driver able to add WB | |
0cb55ad2 | 965 | entry later. This parameter disables that. |
95ffa243 | 966 | |
093af8d7 | 967 | disable_mtrr_trim [X86, Intel and AMD only] |
99fc8d42 JB |
968 | By default the kernel will trim any uncacheable |
969 | memory out of your available memory pool based on | |
970 | MTRR settings. This parameter disables that behavior, | |
971 | possibly causing your machine to run very slowly. | |
972 | ||
6cececfc | 973 | disable_timer_pin_1 [X86] |
0cb55ad2 RD |
974 | Disable PIN 1 of APIC timer |
975 | Can be useful to work around chipset bugs. | |
976 | ||
ce14c583 PB |
977 | dis_ucode_ldr [X86] Disable the microcode loader. |
978 | ||
0cb55ad2 RD |
979 | dma_debug=off If the kernel is compiled with DMA_API_DEBUG support, |
980 | this option disables the debugging code at boot. | |
981 | ||
982 | dma_debug_entries=<number> | |
983 | This option allows to tune the number of preallocated | |
984 | entries for DMA-API debugging code. One entry is | |
985 | required per DMA-API allocation. Use this if the | |
986 | DMA-API debugging code disables itself because the | |
987 | architectural default is too low. | |
988 | ||
1745de5e JR |
989 | dma_debug_driver=<driver_name> |
990 | With this option the DMA-API debugging driver | |
991 | filter feature can be enabled at boot time. Just | |
992 | pass the driver to filter for as the parameter. | |
993 | The filter can be disabled or changed to another | |
994 | driver later using sysfs. | |
995 | ||
96206e29 BP |
996 | drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>] |
997 | Broken monitors, graphic adapters, KVMs and EDIDless | |
998 | panels may send no or incorrect EDID data sets. | |
999 | This parameter allows to specify an EDID data sets | |
1000 | in the /lib/firmware directory that are used instead. | |
da0df92b CE |
1001 | Generic built-in EDID data sets are used, if one of |
1002 | edid/1024x768.bin, edid/1280x1024.bin, | |
1003 | edid/1680x1050.bin, or edid/1920x1080.bin is given | |
1004 | and no file with the same name exists. Details and | |
1005 | instructions how to build your own EDID data are | |
1006 | available in Documentation/EDID/HOWTO.txt. An EDID | |
1007 | data set will only be used for a particular connector, | |
1008 | if its name and a colon are prepended to the EDID | |
96206e29 BP |
1009 | name. Each connector may use a unique EDID data |
1010 | set by separating the files with a comma. An EDID | |
1011 | data set with no connector name will be used for | |
1012 | any connectors not explicitly specified. | |
da0df92b | 1013 | |
1da177e4 LT |
1014 | dscc4.setup= [NET] |
1015 | ||
29e36c9f JC |
1016 | dyndbg[="val"] [KNL,DYNAMIC_DEBUG] |
1017 | module.dyndbg[="val"] | |
1018 | Enable debug messages at boot time. See | |
1019 | Documentation/dynamic-debug-howto.txt for details. | |
1020 | ||
8c3641e9 DH |
1021 | nompx [X86] Disables Intel Memory Protection Extensions. |
1022 | See Documentation/x86/intel_mpx.txt for more | |
1023 | information about the feature. | |
1024 | ||
06976945 DH |
1025 | nopku [X86] Disable Memory Protection Keys CPU feature found |
1026 | in some Intel CPUs. | |
1027 | ||
f29ba61d BP |
1028 | eagerfpu= [X86] |
1029 | on enable eager fpu restore | |
1030 | off disable eager fpu restore | |
1031 | auto selects the default scheme, which automatically | |
1032 | enables eagerfpu restore for xsaveopt. | |
1033 | ||
f2411da7 LR |
1034 | module.async_probe [KNL] |
1035 | Enable asynchronous probe on this module. | |
1036 | ||
56aeeba8 MS |
1037 | early_ioremap_debug [KNL] |
1038 | Enable debug messages in early_ioremap support. This | |
1039 | is useful for tracking down temporary early mappings | |
1040 | which are not unmapped. | |
1041 | ||
0cb55ad2 | 1042 | earlycon= [KNL] Output early console device and options. |
0d3c673e | 1043 | |
5664f764 SW |
1044 | When used with no options, the early console is |
1045 | determined by the stdout-path property in device | |
1046 | tree's chosen node. | |
1047 | ||
6fa62fc4 MS |
1048 | cdns,<addr> |
1049 | Start an early, polled-mode console on a cadence serial | |
1050 | port at the specified address. The cadence serial port | |
1051 | must already be setup and configured. Options are not | |
1052 | yet supported. | |
1053 | ||
0cb55ad2 RD |
1054 | uart[8250],io,<addr>[,options] |
1055 | uart[8250],mmio,<addr>[,options] | |
1917ac76 | 1056 | uart[8250],mmio32,<addr>[,options] |
6e63be3f | 1057 | uart[8250],mmio32be,<addr>[,options] |
ca782f16 | 1058 | uart[8250],0x<addr>[,options] |
0cb55ad2 RD |
1059 | Start an early, polled-mode console on the 8250/16550 |
1060 | UART at the specified I/O port or MMIO address. | |
16290246 | 1061 | MMIO inter-register address stride is either 8-bit |
6e63be3f NC |
1062 | (mmio) or 32-bit (mmio32 or mmio32be). |
1063 | If none of [io|mmio|mmio32|mmio32be], <addr> is assumed | |
1064 | to be equivalent to 'mmio'. 'options' are specified | |
1065 | in the same format described for "console=ttyS<n>"; if | |
ca782f16 | 1066 | unspecified, the h/w is not initialized. |
0cb55ad2 | 1067 | |
0d3c673e | 1068 | pl011,<addr> |
3b78fae7 | 1069 | pl011,mmio32,<addr> |
0d3c673e RH |
1070 | Start an early, polled-mode console on a pl011 serial |
1071 | port at the specified address. The pl011 serial port | |
1072 | must already be setup and configured. Options are not | |
3b78fae7 TT |
1073 | yet supported. If 'mmio32' is specified, then only |
1074 | the driver will use only 32-bit accessors to read/write | |
1075 | the device registers. | |
0d3c673e | 1076 | |
736d5538 AF |
1077 | meson,<addr> |
1078 | Start an early, polled-mode console on a meson serial | |
1079 | port at the specified address. The serial port must | |
1080 | already be setup and configured. Options are not yet | |
1081 | supported. | |
1082 | ||
0efe7296 SB |
1083 | msm_serial,<addr> |
1084 | Start an early, polled-mode console on an msm serial | |
1085 | port at the specified address. The serial port | |
1086 | must already be setup and configured. Options are not | |
1087 | yet supported. | |
1088 | ||
1089 | msm_serial_dm,<addr> | |
1090 | Start an early, polled-mode console on an msm serial | |
1091 | dm port at the specified address. The serial port | |
1092 | must already be setup and configured. Options are not | |
1093 | yet supported. | |
1094 | ||
d50d7269 RH |
1095 | smh Use ARM semihosting calls for early console. |
1096 | ||
b94ba032 TF |
1097 | s3c2410,<addr> |
1098 | s3c2412,<addr> | |
1099 | s3c2440,<addr> | |
1100 | s3c6400,<addr> | |
1101 | s5pv210,<addr> | |
1102 | exynos4210,<addr> | |
1103 | Use early console provided by serial driver available | |
1104 | on Samsung SoCs, requires selecting proper type and | |
1105 | a correct base address of the selected UART port. The | |
1106 | serial port must already be setup and configured. | |
1107 | Options are not yet supported. | |
1108 | ||
1d59b382 SA |
1109 | lpuart,<addr> |
1110 | lpuart32,<addr> | |
1111 | Use early console provided by Freescale LP UART driver | |
1112 | found on Freescale Vybrid and QorIQ LS1021A processors. | |
1113 | A valid base address must be provided, and the serial | |
1114 | port must already be setup and configured. | |
1115 | ||
30530791 WD |
1116 | armada3700_uart,<addr> |
1117 | Start an early, polled-mode console on the | |
1118 | Armada 3700 serial port at the specified | |
1119 | address. The serial port must already be setup | |
1120 | and configured. Options are not yet supported. | |
1121 | ||
7913ad1a | 1122 | earlyprintk= [X86,SH,BLACKFIN,ARM,M68k] |
1da177e4 | 1123 | earlyprintk=vga |
72548e83 | 1124 | earlyprintk=efi |
2482a92e | 1125 | earlyprintk=xen |
1da177e4 | 1126 | earlyprintk=serial[,ttySn[,baudrate]] |
147ea091 | 1127 | earlyprintk=serial[,0x...[,baudrate]] |
ea3acb19 | 1128 | earlyprintk=ttySn[,baudrate] |
9780bc41 | 1129 | earlyprintk=dbgp[debugController#] |
c43088e3 | 1130 | earlyprintk=pciserial,bus:device.function[,baudrate] |
1da177e4 | 1131 | |
147ea091 DH |
1132 | earlyprintk is useful when the kernel crashes before |
1133 | the normal console is initialized. It is not enabled by | |
1134 | default because it has some cosmetic problems. | |
1135 | ||
a9913044 | 1136 | Append ",keep" to not disable it when the real console |
1da177e4 LT |
1137 | takes over. |
1138 | ||
72548e83 MF |
1139 | Only one of vga, efi, serial, or usb debug port can |
1140 | be used at a time. | |
1da177e4 | 1141 | |
147ea091 DH |
1142 | Currently only ttyS0 and ttyS1 may be specified by |
1143 | name. Other I/O ports may be explicitly specified | |
1144 | on some architectures (x86 and arm at least) by | |
1145 | replacing ttySn with an I/O port address, like this: | |
1146 | earlyprintk=serial,0x1008,115200 | |
1147 | You can find the port for a given device in | |
1148 | /proc/tty/driver/serial: | |
1149 | 2: uart:ST16650V2 port:00001008 irq:18 ... | |
1da177e4 LT |
1150 | |
1151 | Interaction with the standard serial driver is not | |
1152 | very good. | |
1153 | ||
72548e83 MF |
1154 | The VGA and EFI output is eventually overwritten by |
1155 | the real console. | |
1da177e4 | 1156 | |
2482a92e KRW |
1157 | The xen output can only be used by Xen PV guests. |
1158 | ||
c700f013 CG |
1159 | edac_report= [HW,EDAC] Control how to report EDAC event |
1160 | Format: {"on" | "off" | "force"} | |
1161 | on: enable EDAC to report H/W event. May be overridden | |
1162 | by other higher priority error reporting module. | |
1163 | off: disable H/W event reporting through EDAC. | |
1164 | force: enforce the use of EDAC to report H/W event. | |
1165 | default: on. | |
1166 | ||
9731191f JW |
1167 | ekgdboc= [X86,KGDB] Allow early kernel console debugging |
1168 | ekgdboc=kbd | |
1169 | ||
25985edc | 1170 | This is designed to be used in conjunction with |
9731191f JW |
1171 | the boot argument: earlyprintk=vga |
1172 | ||
1da177e4 | 1173 | edd= [EDD] |
8c4dd606 | 1174 | Format: {"off" | "on" | "skip[mbr]"} |
1da177e4 | 1175 | |
d2f7cbe7 | 1176 | efi= [EFI] |
fed6cefe | 1177 | Format: { "old_map", "nochunk", "noruntime", "debug" } |
d2f7cbe7 BP |
1178 | old_map [X86-64]: switch to the old ioremap-based EFI |
1179 | runtime services mapping. 32-bit still uses this one by | |
1180 | default. | |
5a17dae4 MF |
1181 | nochunk: disable reading files in "chunks" in the EFI |
1182 | boot stub, as chunking can cause problems with some | |
1183 | firmware implementations. | |
5ae3683c | 1184 | noruntime : disable EFI runtime services support |
fed6cefe | 1185 | debug: enable misc debug output |
d2f7cbe7 | 1186 | |
8c58bf3e RW |
1187 | efi_no_storage_paranoia [EFI; X86] |
1188 | Using this parameter you can use more than 50% of | |
1189 | your efi variable storage. Use this parameter only if | |
1190 | you are really sure that your UEFI does sane gc and | |
1191 | fulfills the spec otherwise your board may brick. | |
1192 | ||
0f96a99d TI |
1193 | efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86] |
1194 | Add arbitrary attribute to specific memory range by | |
1195 | updating original EFI memory map. | |
1196 | Region of memory which aa attribute is added to is | |
1197 | from ss to ss+nn. | |
1198 | If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000 | |
1199 | is specified, EFI_MEMORY_MORE_RELIABLE(0x10000) | |
1200 | attribute is added to range 0x100000000-0x180000000 and | |
1201 | 0x10a0000000-0x1120000000. | |
1202 | ||
1203 | Using this parameter you can do debugging of EFI memmap | |
1204 | related feature. For example, you can do debugging of | |
1205 | Address Range Mirroring feature even if your box | |
1206 | doesn't support it. | |
1207 | ||
475fb4e8 OP |
1208 | efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT |
1209 | that is to be dynamically loaded by Linux. If there are | |
1210 | multiple variables with the same name but with different | |
1211 | vendor GUIDs, all of them will be loaded. See | |
1212 | Documentation/acpi/ssdt-overlays.txt for details. | |
1213 | ||
1214 | ||
1da177e4 LT |
1215 | eisa_irq_edge= [PARISC,HW] |
1216 | See header of drivers/parisc/eisa.c. | |
1217 | ||
cd4f0ef7 | 1218 | elanfreq= [X86-32] |
1da177e4 | 1219 | See comment before function elanfreq_setup() in |
71f77055 | 1220 | arch/x86/kernel/cpu/cpufreq/elanfreq.c. |
1da177e4 LT |
1221 | |
1222 | elevator= [IOSCHED] | |
17a9e7bb | 1223 | Format: {"cfq" | "deadline" | "noop"} |
395cf969 | 1224 | See Documentation/block/cfq-iosched.txt and |
a9913044 RD |
1225 | Documentation/block/deadline-iosched.txt for details. |
1226 | ||
d3bf3795 | 1227 | elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390] |
a9913044 | 1228 | Specifies physical address of start of kernel core |
d3bf3795 MH |
1229 | image elf header and optionally the size. Generally |
1230 | kexec loader will pass this option to capture kernel. | |
aac04b32 | 1231 | See Documentation/kdump/kdump.txt for details. |
1da177e4 | 1232 | |
0cb55ad2 RD |
1233 | enable_mtrr_cleanup [X86] |
1234 | The kernel tries to adjust MTRR layout from continuous | |
1235 | to discrete, to make X server driver able to add WB | |
1236 | entry later. This parameter enables that. | |
1237 | ||
ca1eda2d | 1238 | enable_timer_pin_1 [X86] |
0cb55ad2 RD |
1239 | Enable PIN 1 of APIC timer |
1240 | Can be useful to work around chipset bugs | |
1241 | (in particular on some ATI chipsets). | |
1242 | The kernel tries to set a reasonable default. | |
1243 | ||
1da177e4 LT |
1244 | enforcing [SELINUX] Set initial enforcing status. |
1245 | Format: {"0" | "1"} | |
1246 | See security/selinux/Kconfig help text. | |
1247 | 0 -- permissive (log only, no denials). | |
1248 | 1 -- enforcing (deny and log). | |
1249 | Default value is 0. | |
1250 | Value can be changed at runtime via /selinux/enforce. | |
1251 | ||
a08f82d0 HY |
1252 | erst_disable [ACPI] |
1253 | Disable Error Record Serialization Table (ERST) | |
1254 | support. | |
1255 | ||
1da177e4 LT |
1256 | ether= [HW,NET] Ethernet cards parameters |
1257 | This option is obsoleted by the "netdev=" option, which | |
1258 | has equivalent usage. See its documentation for details. | |
1259 | ||
7102ebcd MZ |
1260 | evm= [EVM] |
1261 | Format: { "fix" } | |
1262 | Permit 'security.evm' to be updated regardless of | |
1263 | current integrity status. | |
1264 | ||
de1ba09b AM |
1265 | failslab= |
1266 | fail_page_alloc= | |
1267 | fail_make_request=[KNL] | |
1268 | General fault injection mechanism. | |
1269 | Format: <interval>,<probability>,<space>,<times> | |
395cf969 | 1270 | See also Documentation/fault-injection/. |
de1ba09b | 1271 | |
1da177e4 | 1272 | floppy= [HW] |
31c00fc1 | 1273 | See Documentation/blockdev/floppy.txt. |
1da177e4 | 1274 | |
f13ae30e AC |
1275 | force_pal_cache_flush |
1276 | [IA-64] Avoid check_sal_cache_flush which may hang on | |
1277 | buggy SAL_CACHE_FLUSH implementations. Using this | |
1278 | parameter will force ia64_sal_cache_flush to call | |
1279 | ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. | |
1280 | ||
69f2366c CB |
1281 | forcepae [X86-32] |
1282 | Forcefully enable Physical Address Extension (PAE). | |
1283 | Many Pentium M systems disable PAE but may have a | |
1284 | functionally usable PAE implementation. | |
1285 | Warning: use of this parameter will taint the kernel | |
1286 | and may cause unknown problems. | |
1287 | ||
d9e54076 | 1288 | ftrace=[tracer] |
2af15d6a | 1289 | [FTRACE] will set and start the specified tracer |
d9e54076 PZ |
1290 | as early as possible in order to facilitate early |
1291 | boot debugging. | |
1292 | ||
cecbca96 | 1293 | ftrace_dump_on_oops[=orig_cpu] |
2af15d6a | 1294 | [FTRACE] will dump the trace buffers on oops. |
cecbca96 FW |
1295 | If no parameter is passed, ftrace will dump |
1296 | buffers of all CPUs, but if you pass orig_cpu, it will | |
1297 | dump only the buffer of the CPU that triggered the | |
1298 | oops. | |
2af15d6a SR |
1299 | |
1300 | ftrace_filter=[function-list] | |
1301 | [FTRACE] Limit the functions traced by the function | |
1302 | tracer at boot up. function-list is a comma separated | |
1303 | list of functions. This list can be changed at run | |
1304 | time by the set_ftrace_filter file in the debugfs | |
16290246 | 1305 | tracing directory. |
2af15d6a SR |
1306 | |
1307 | ftrace_notrace=[function-list] | |
1308 | [FTRACE] Do not trace the functions specified in | |
1309 | function-list. This list can be changed at run time | |
1310 | by the set_ftrace_notrace file in the debugfs | |
1311 | tracing directory. | |
d9e54076 | 1312 | |
369bc18f SA |
1313 | ftrace_graph_filter=[function-list] |
1314 | [FTRACE] Limit the top level callers functions traced | |
1315 | by the function graph tracer at boot up. | |
1316 | function-list is a comma separated list of functions | |
1317 | that can be changed at run time by the | |
1318 | set_graph_function file in the debugfs tracing directory. | |
1319 | ||
0d7d9a16 NK |
1320 | ftrace_graph_notrace=[function-list] |
1321 | [FTRACE] Do not trace from the functions specified in | |
1322 | function-list. This list is a comma separated list of | |
1323 | functions that can be changed at run time by the | |
1324 | set_graph_notrace file in the debugfs tracing directory. | |
1325 | ||
1da177e4 LT |
1326 | gamecon.map[2|3]= |
1327 | [HW,JOY] Multisystem joystick and NES/SNES/PSX pad | |
1328 | support via parallel port (up to 5 devices per port) | |
1329 | Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> | |
1330 | See also Documentation/input/joystick-parport.txt | |
1331 | ||
1332 | gamma= [HW,DRM] | |
1333 | ||
aaf23042 YL |
1334 | gart_fix_e820= [X86_64] disable the fix e820 for K8 GART |
1335 | Format: off | on | |
1336 | default: on | |
1337 | ||
2521f2c2 PO |
1338 | gcov_persist= [GCOV] When non-zero (default), profiling data for |
1339 | kernel modules is saved and remains accessible via | |
1340 | debugfs, even when the module is unloaded/reloaded. | |
1341 | When zero, profiling data is discarded and associated | |
1342 | debugfs files are removed at module unload time. | |
1343 | ||
1da177e4 | 1344 | gpt [EFI] Forces disk with valid GPT signature but |
6c5de79b DB |
1345 | invalid Protective MBR to be treated as GPT. If the |
1346 | primary GPT is corrupted, it enables the backup/alternate | |
1347 | GPT to be used instead. | |
1da177e4 | 1348 | |
6cec9b07 AL |
1349 | grcan.enable0= [HW] Configuration of physical interface 0. Determines |
1350 | the "Enable 0" bit of the configuration register. | |
1351 | Format: 0 | 1 | |
1352 | Default: 0 | |
1353 | grcan.enable1= [HW] Configuration of physical interface 1. Determines | |
1354 | the "Enable 0" bit of the configuration register. | |
1355 | Format: 0 | 1 | |
1356 | Default: 0 | |
1357 | grcan.select= [HW] Select which physical interface to use. | |
1358 | Format: 0 | 1 | |
1359 | Default: 0 | |
1360 | grcan.txsize= [HW] Sets the size of the tx buffer. | |
1361 | Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0. | |
1362 | Default: 1024 | |
1363 | grcan.rxsize= [HW] Sets the size of the rx buffer. | |
1364 | Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0. | |
1365 | Default: 1024 | |
1366 | ||
55537871 JK |
1367 | hardlockup_all_cpu_backtrace= |
1368 | [KNL] Should the hard-lockup detector generate | |
1369 | backtraces on all cpus. | |
1370 | Format: <integer> | |
1371 | ||
1da177e4 LT |
1372 | hashdist= [KNL,NUMA] Large hashes allocated during boot |
1373 | are distributed across NUMA nodes. Defaults on | |
16290246 | 1374 | for 64-bit NUMA, off otherwise. |
a9913044 | 1375 | Format: 0 | 1 (for off | on) |
1da177e4 LT |
1376 | |
1377 | hcl= [IA-64] SGI's Hardware Graph compatibility layer | |
1378 | ||
1379 | hd= [EIDE] (E)IDE hard drive subsystem geometry | |
1380 | Format: <cyl>,<head>,<sect> | |
1381 | ||
ea8c071c HY |
1382 | hest_disable [ACPI] |
1383 | Disable Hardware Error Source Table (HEST) support; | |
1384 | corresponding firmware-first mode error processing | |
1385 | logic will be disabled. | |
1386 | ||
1da177e4 LT |
1387 | highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact |
1388 | size of <nn>. This works even on boxes that have no | |
1389 | highmem otherwise. This also works to reduce highmem | |
1390 | size on bigger boxes. | |
1391 | ||
54cdfdb4 TG |
1392 | highres= [KNL] Enable/disable high resolution timer mode. |
1393 | Valid parameters: "on", "off" | |
1394 | Default: "on" | |
1395 | ||
1da177e4 LT |
1396 | hisax= [HW,ISDN] |
1397 | See Documentation/isdn/README.HiSax. | |
1398 | ||
0cb55ad2 RD |
1399 | hlt [BUGS=ARM,SH] |
1400 | ||
1401 | hpet= [X86-32,HPET] option to control HPET usage | |
1402 | Format: { enable (default) | disable | force | | |
1403 | verbose } | |
1404 | disable: disable HPET and use PIT instead | |
1405 | force: allow force enabled of undocumented chips (ICH4, | |
1406 | VIA, nVidia) | |
1407 | verbose: show contents of HPET registers during setup | |
1408 | ||
3d035f58 PB |
1409 | hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET |
1410 | registers. Default set by CONFIG_HPET_MMAP_DEFAULT. | |
1411 | ||
b4718e62 AK |
1412 | hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot. |
1413 | hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages. | |
0d9ea754 JT |
1414 | On x86-64 and powerpc, this option can be specified |
1415 | multiple times interleaved with hugepages= to reserve | |
1416 | huge pages of different sizes. Valid pages sizes on | |
1417 | x86-64 are 2M (when the CPU supports "pse") and 1G | |
27ec26ec | 1418 | (when the CPU supports the "pdpe1gb" cpuinfo flag). |
6902aa84 | 1419 | |
555d61d6 HB |
1420 | hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) |
1421 | terminal devices. Valid values: 0..8 | |
431429ff HB |
1422 | hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. |
1423 | If specified, z/VM IUCV HVC accepts connections | |
1424 | from listed z/VM user IDs only. | |
cef7125d | 1425 | |
fdabf525 JH |
1426 | hwthread_map= [METAG] Comma-separated list of Linux cpu id to |
1427 | hardware thread id mappings. | |
1428 | Format: <cpu>:<hwthread> | |
1429 | ||
7bf69395 FDN |
1430 | keep_bootcon [KNL] |
1431 | Do not unregister boot console at start. This is only | |
1432 | useful for debugging when something happens in the window | |
1433 | between unregistering the boot console and initializing | |
1434 | the real console. | |
1435 | ||
3a853fb9 | 1436 | i2c_bus= [HW] Override the default board specific I2C bus speed |
7954763b JN |
1437 | or register an additional I2C bus that is not |
1438 | registered from board initialization code. | |
3a853fb9 JN |
1439 | Format: |
1440 | <bus_id>,<clkrate> | |
1441 | ||
36d95739 | 1442 | i8042.debug [HW] Toggle i8042 debug mode |
e1443d28 SCP |
1443 | i8042.unmask_kbd_data |
1444 | [HW] Enable printing of interrupt data from the KBD port | |
1445 | (disabled by default, and as a pre-condition | |
1446 | requires that i8042.debug=1 be enabled) | |
1da177e4 | 1447 | i8042.direct [HW] Put keyboard port into non-translated mode |
84eb8d06 ML |
1448 | i8042.dumbkbd [HW] Pretend that controller can only read data from |
1449 | keyboard and cannot control its state | |
1da177e4 LT |
1450 | (Don't attempt to blink the leds) |
1451 | i8042.noaux [HW] Don't check for auxiliary (== mouse) port | |
945ef0d4 | 1452 | i8042.nokbd [HW] Don't check/create keyboard port |
75d08c78 JK |
1453 | i8042.noloop [HW] Disable the AUX Loopback command while probing |
1454 | for the AUX port | |
1da177e4 | 1455 | i8042.nomux [HW] Don't check presence of an active multiplexing |
e55a3366 | 1456 | controller |
1da177e4 LT |
1457 | i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX |
1458 | controllers | |
24775d65 | 1459 | i8042.notimeout [HW] Ignore timeout condition signalled by controller |
1da177e4 LT |
1460 | i8042.reset [HW] Reset the controller during init and cleanup |
1461 | i8042.unlock [HW] Unlock (ignore) the keylock | |
148e9a71 | 1462 | i8042.kbdreset [HW] Reset device connected to KBD port |
1da177e4 LT |
1463 | |
1464 | i810= [HW,DRM] | |
1465 | ||
e70c9d5e DT |
1466 | i8k.ignore_dmi [HW] Continue probing hardware even if DMI data |
1467 | indicates that the driver is running on unsupported | |
1468 | hardware. | |
1da177e4 LT |
1469 | i8k.force [HW] Activate i8k driver even if SMM BIOS signature |
1470 | does not match list of supported models. | |
1471 | i8k.power_status | |
1472 | [HW] Report power status in /proc/i8k | |
1473 | (disabled by default) | |
1474 | i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN | |
1475 | capability is set. | |
1476 | ||
4dca20ef | 1477 | i915.invert_brightness= |
7bd90909 CE |
1478 | [DRM] Invert the sense of the variable that is used to |
1479 | set the brightness of the panel backlight. Normally a | |
4dca20ef CE |
1480 | brightness value of 0 indicates backlight switched off, |
1481 | and the maximum of the brightness value sets the backlight | |
1482 | to maximum brightness. If this parameter is set to 0 | |
1483 | (default) and the machine requires it, or this parameter | |
1484 | is set to 1, a brightness value of 0 sets the backlight | |
1485 | to maximum brightness, and the maximum of the brightness | |
1486 | value switches the backlight off. | |
1487 | -1 -- never invert brightness | |
1488 | 0 -- machine default | |
1489 | 1 -- force brightness inversion | |
7bd90909 | 1490 | |
1da177e4 LT |
1491 | icn= [HW,ISDN] |
1492 | Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] | |
1493 | ||
0af80c04 DF |
1494 | ide-core.nodma= [HW] (E)IDE subsystem |
1495 | Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc | |
075affcb BZ |
1496 | .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr |
1497 | .cdrom .chs .ignore_cable are additional options | |
1c10e938 | 1498 | See Documentation/ide/ide.txt. |
1da177e4 | 1499 | |
0f8b7f5d MR |
1500 | ide-generic.probe-mask= [HW] (E)IDE subsystem |
1501 | Format: <int> | |
1502 | Probe mask for legacy ISA IDE ports. Depending on | |
1503 | platform up to 6 ports are supported, enabled by | |
1504 | setting corresponding bits in the mask to 1. The | |
1505 | default value is 0x0, which has a special meaning. | |
1506 | On systems that have PCI, it triggers scanning the | |
1507 | PCI bus for the first and the second port, which | |
1508 | are then probed. On systems without PCI the value | |
1509 | of 0x0 enables probing the two first ports as if it | |
1510 | was 0x3. | |
1511 | ||
0cb55ad2 RD |
1512 | ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem |
1513 | Claim all unknown PCI IDE storage controllers. | |
1514 | ||
f039b754 | 1515 | idle= [X86] |
69fb3676 | 1516 | Format: idle=poll, idle=halt, idle=nomwait |
ada9cfdd RD |
1517 | Poll forces a polling idle loop that can slightly |
1518 | improve the performance of waking up a idle CPU, but | |
1519 | will use a lot of power and make the system run hot. | |
1520 | Not recommended. | |
ada9cfdd | 1521 | idle=halt: Halt is forced to be used for CPU idle. |
c1e3b377 | 1522 | In such case C2/C3 won't be used again. |
ada9cfdd | 1523 | idle=nomwait: Disable mwait for CPU C-states |
a9913044 | 1524 | |
503943e0 MR |
1525 | ieee754= [MIPS] Select IEEE Std 754 conformance mode |
1526 | Format: { strict | legacy | 2008 | relaxed } | |
1527 | Default: strict | |
1528 | ||
1529 | Choose which programs will be accepted for execution | |
1530 | based on the IEEE 754 NaN encoding(s) supported by | |
1531 | the FPU and the NaN encoding requested with the value | |
1532 | of an ELF file header flag individually set by each | |
1533 | binary. Hardware implementations are permitted to | |
1534 | support either or both of the legacy and the 2008 NaN | |
1535 | encoding mode. | |
1536 | ||
1537 | Available settings are as follows: | |
1538 | strict accept binaries that request a NaN encoding | |
1539 | supported by the FPU | |
1540 | legacy only accept legacy-NaN binaries, if supported | |
1541 | by the FPU | |
1542 | 2008 only accept 2008-NaN binaries, if supported | |
1543 | by the FPU | |
1544 | relaxed accept any binaries regardless of whether | |
1545 | supported by the FPU | |
1546 | ||
1547 | The FPU emulator is always able to support both NaN | |
1548 | encodings, so if no FPU hardware is present or it has | |
1549 | been disabled with 'nofpu', then the settings of | |
1550 | 'legacy' and '2008' strap the emulator accordingly, | |
1551 | 'relaxed' straps the emulator for both legacy-NaN and | |
1552 | 2008-NaN, whereas 'strict' enables legacy-NaN only on | |
1553 | legacy processors and both NaN encodings on MIPS32 or | |
1554 | MIPS64 CPUs. | |
1555 | ||
1556 | The setting for ABS.fmt/NEG.fmt instruction execution | |
1557 | mode generally follows that for the NaN encoding, | |
1558 | except where unsupported by hardware. | |
1559 | ||
79290822 IM |
1560 | ignore_loglevel [KNL] |
1561 | Ignore loglevel setting - this will print /all/ | |
1562 | kernel messages to the console. Useful for debugging. | |
0eca6b7c YZ |
1563 | We also add it as printk module parameter, so users |
1564 | could change it dynamically, usually by | |
1565 | /sys/module/printk/parameters/ignore_loglevel. | |
79290822 | 1566 | |
d977d56c KK |
1567 | ignore_rlimit_data |
1568 | Ignore RLIMIT_DATA setting for data mappings, | |
1569 | print warning at first misuse. Can be changed via | |
1570 | /sys/module/kernel/parameters/ignore_rlimit_data. | |
1571 | ||
1da177e4 LT |
1572 | ihash_entries= [KNL] |
1573 | Set number of hash buckets for inode cache. | |
1574 | ||
2fe5d6de | 1575 | ima_appraise= [IMA] appraise integrity measurements |
2faa6ef3 | 1576 | Format: { "off" | "enforce" | "fix" | "log" } |
2fe5d6de MZ |
1577 | default: "enforce" |
1578 | ||
07f6a794 MZ |
1579 | ima_appraise_tcb [IMA] |
1580 | The builtin appraise policy appraises all files | |
1581 | owned by uid=0. | |
1582 | ||
3323eec9 | 1583 | ima_hash= [IMA] |
e7a2ad7e MZ |
1584 | Format: { md5 | sha1 | rmd160 | sha256 | sha384 |
1585 | | sha512 | ... } | |
3323eec9 MZ |
1586 | default: "sha1" |
1587 | ||
e7a2ad7e MZ |
1588 | The list of supported hash algorithms is defined |
1589 | in crypto/hash_info.h. | |
1590 | ||
24fd03c8 MZ |
1591 | ima_policy= [IMA] |
1592 | The builtin measurement policy to load during IMA | |
1593 | setup. Specyfing "tcb" as the value, measures all | |
1594 | programs exec'd, files mmap'd for exec, and all files | |
1595 | opened with the read mode bit set by either the | |
1596 | effective uid (euid=0) or uid=0. | |
1597 | Format: "tcb" | |
1598 | ||
1599 | ima_tcb [IMA] Deprecated. Use ima_policy= instead. | |
5789ba3b EP |
1600 | Load a policy which meets the needs of the Trusted |
1601 | Computing Base. This means IMA will measure all | |
1602 | programs exec'd, files mmap'd for exec, and all files | |
1603 | opened for read by uid=0. | |
1604 | ||
9b9d4ce5 RS |
1605 | ima_template= [IMA] |
1606 | Select one of defined IMA measurements template formats. | |
8265a2f8 | 1607 | Formats: { "ima" | "ima-ng" | "ima-sig" } |
9b9d4ce5 RS |
1608 | Default: "ima-ng" |
1609 | ||
c2426d2a RS |
1610 | ima_template_fmt= |
1611 | [IMA] Define a custom template format. | |
1612 | Format: { "field1|...|fieldN" } | |
1613 | ||
3bcced39 DK |
1614 | ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage |
1615 | Format: <min_file_size> | |
1616 | Set the minimal file size for using asynchronous hash. | |
1617 | If left unspecified, ahash usage is disabled. | |
1618 | ||
1619 | ahash performance varies for different data sizes on | |
1620 | different crypto accelerators. This option can be used | |
1621 | to achieve the best performance for a particular HW. | |
1622 | ||
6edf7a89 DK |
1623 | ima.ahash_bufsize= [IMA] Asynchronous hash buffer size |
1624 | Format: <bufsize> | |
1625 | Set hashing buffer size. Default: 4k. | |
1626 | ||
1627 | ahash performance varies for different chunk sizes on | |
1628 | different crypto accelerators. This option can be used | |
1629 | to achieve best performance for particular HW. | |
1630 | ||
1da177e4 LT |
1631 | init= [KNL] |
1632 | Format: <full_path> | |
1633 | Run specified binary instead of /sbin/init as init | |
1634 | process. | |
1635 | ||
1636 | initcall_debug [KNL] Trace initcalls as they are executed. Useful | |
1637 | for working out where the kernel is dying during | |
1638 | startup. | |
1639 | ||
7b0b73d7 PB |
1640 | initcall_blacklist= [KNL] Do not execute a comma-separated list of |
1641 | initcall functions. Useful for debugging built-in | |
1642 | modules and initcalls. | |
1643 | ||
1da177e4 LT |
1644 | initrd= [BOOT] Specify the location of the initial ramdisk |
1645 | ||
acd547b2 DH |
1646 | init_pkru= [x86] Specify the default memory protection keys rights |
1647 | register contents for all processes. 0x55555554 by | |
1648 | default (disallow access to all but pkey 0). Can | |
1649 | override in debugfs after boot. | |
1650 | ||
1da177e4 LT |
1651 | inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver |
1652 | Format: <irq> | |
1653 | ||
6bb2ff84 FY |
1654 | int_pln_enable [x86] Enable power limit notification interrupt |
1655 | ||
d726d8d7 MZ |
1656 | integrity_audit=[IMA] |
1657 | Format: { "0" | "1" } | |
1658 | 0 -- basic integrity auditing messages. (Default) | |
1659 | 1 -- additional integrity auditing messages. | |
1660 | ||
ba395927 | 1661 | intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option |
0cd5c3c8 KM |
1662 | on |
1663 | Enable intel iommu driver. | |
ba395927 KA |
1664 | off |
1665 | Disable intel iommu driver. | |
1666 | igfx_off [Default Off] | |
1667 | By default, gfx is mapped as normal device. If a gfx | |
1668 | device has a dedicated DMAR unit, the DMAR unit is | |
1669 | bypassed by not enabling DMAR with this option. In | |
1670 | this case, gfx device will use physical address for | |
1671 | DMA. | |
7d3b03ce KA |
1672 | forcedac [x86_64] |
1673 | With this option iommu will not optimize to look | |
16290246 | 1674 | for io virtual address below 32-bit forcing dual |
7d3b03ce | 1675 | address cycle on pci bus for cards supporting greater |
16290246 RD |
1676 | than 32-bit addressing. The default is to look |
1677 | for translation below 32-bit and if not available | |
7d3b03ce | 1678 | then look in the higher range. |
5e0d2a6f | 1679 | strict [Default Off] |
1680 | With this option on every unmap_single operation will | |
1681 | result in a hardware IOTLB flush operation as opposed | |
1682 | to batching them for performance. | |
6dd9a7c7 YS |
1683 | sp_off [Default Off] |
1684 | By default, super page will be supported if Intel IOMMU | |
1685 | has the capability. With this option, super page will | |
1686 | not be supported. | |
c83b2f20 DW |
1687 | ecs_off [Default Off] |
1688 | By default, extended context tables will be supported if | |
1689 | the hardware advertises that it has support both for the | |
1690 | extended tables themselves, and also PASID support. With | |
1691 | this option set, extended tables will not be used even | |
1692 | on hardware which claims to support them. | |
2e92c7ad MI |
1693 | |
1694 | intel_idle.max_cstate= [KNL,HW,ACPI,X86] | |
1695 | 0 disables intel_idle and fall back on acpi_idle. | |
1696 | 1 to 6 specify maximum depth of C-state. | |
1697 | ||
6be26498 DB |
1698 | intel_pstate= [X86] |
1699 | disable | |
1700 | Do not enable intel_pstate as the default | |
1701 | scaling driver for the supported processors | |
aa4ea34d EZ |
1702 | force |
1703 | Enable intel_pstate on systems that prohibit it by default | |
1704 | in favor of acpi-cpufreq. Forcing the intel_pstate driver | |
1705 | instead of acpi-cpufreq may disable platform features, such | |
1706 | as thermal controls and power capping, that rely on ACPI | |
1707 | P-States information being indicated to OSPM and therefore | |
1708 | should be used with caution. This option does not work with | |
1709 | processors that aren't supported by the intel_pstate driver | |
1710 | or on platforms that use pcc-cpufreq instead of acpi-cpufreq. | |
2f86dc4c DB |
1711 | no_hwp |
1712 | Do not enable hardware P state control (HWP) | |
1713 | if available. | |
d64c3b0b KCA |
1714 | hwp_only |
1715 | Only load intel_pstate on systems which support | |
1716 | hardware P state control (HWP) if available. | |
9522a2ff | 1717 | support_acpi_ppc |
2b3ec765 SP |
1718 | Enforce ACPI _PPC performance limits. If the Fixed ACPI |
1719 | Description Table, specifies preferred power management | |
1720 | profile as "Enterprise Server" or "Performance Server", | |
1721 | then this feature is turned on by default. | |
6be26498 | 1722 | |
d1423d56 | 1723 | intremap= [X86-64, Intel-IOMMU] |
d1423d56 CW |
1724 | on enable Interrupt Remapping (default) |
1725 | off disable Interrupt Remapping | |
1726 | nosid disable Source ID checking | |
41750d31 SS |
1727 | no_x2apic_optout |
1728 | BIOS x2APIC opt-out request will be ignored | |
b7d20631 | 1729 | nopost disable Interrupt Posting |
d1423d56 | 1730 | |
0cb55ad2 RD |
1731 | iomem= Disable strict checking of access to MMIO memory |
1732 | strict regions from userspace. | |
1733 | relaxed | |
1734 | ||
1735 | iommu= [x86] | |
1736 | off | |
1737 | force | |
1738 | noforce | |
1739 | biomerge | |
1740 | panic | |
1741 | nopanic | |
1742 | merge | |
1743 | nomerge | |
1744 | forcesac | |
1745 | soft | |
bcb71abe | 1746 | pt [x86, IA-64] |
4e287840 TLSC |
1747 | nobypass [PPC/POWERNV] |
1748 | Disable IOMMU bypass, using IOMMU for PCI devices. | |
bcb71abe | 1749 | |
0cb55ad2 RD |
1750 | |
1751 | io7= [HW] IO7 for Marvel based alpha systems | |
1752 | See comment before marvel_specify_io7 in | |
1753 | arch/alpha/kernel/core_marvel.c. | |
1754 | ||
6cececfc | 1755 | io_delay= [X86] I/O delay method |
6e7c4025 IM |
1756 | 0x80 |
1757 | Standard port 0x80 based delay | |
1758 | 0xed | |
1759 | Alternate port 0xed based delay (needed on some systems) | |
b02aae9c | 1760 | udelay |
6e7c4025 IM |
1761 | Simple two microseconds delay |
1762 | none | |
1763 | No delay | |
b02aae9c | 1764 | |
1da177e4 | 1765 | ip= [IP_PNP] |
dc7a0816 | 1766 | See Documentation/filesystems/nfs/nfsroot.txt. |
1da177e4 | 1767 | |
fbf19803 TG |
1768 | irqaffinity= [SMP] Set the default irq affinity mask |
1769 | Format: | |
1770 | <cpu number>,...,<cpu number> | |
1771 | or | |
1772 | <cpu number>-<cpu number> | |
1773 | (must be a positive range in ascending order) | |
1774 | or a mixture | |
1775 | <cpu number>,...,<cpu number>-<cpu number> | |
1776 | ||
200803df AC |
1777 | irqfixup [HW] |
1778 | When an interrupt is not handled search all handlers | |
1779 | for it. Intended to get systems with badly broken | |
1780 | firmware running. | |
1781 | ||
1782 | irqpoll [HW] | |
1783 | When an interrupt is not handled search all handlers | |
1784 | for it. Also check all handlers each timer | |
1785 | interrupt. Intended to get systems with badly broken | |
1786 | firmware running. | |
1787 | ||
1da177e4 | 1788 | isapnp= [ISAPNP] |
a9913044 | 1789 | Format: <RDP>,<reset>,<pci_scan>,<verbosity> |
1da177e4 LT |
1790 | |
1791 | isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler. | |
22f2e280 DF |
1792 | Format: |
1793 | <cpu number>,...,<cpu number> | |
1794 | or | |
b225d44e LZ |
1795 | <cpu number>-<cpu number> |
1796 | (must be a positive range in ascending order) | |
22f2e280 DF |
1797 | or a mixture |
1798 | <cpu number>,...,<cpu number>-<cpu number> | |
b225d44e | 1799 | |
1da177e4 LT |
1800 | This option can be used to specify one or more CPUs |
1801 | to isolate from the general SMP balancing and scheduling | |
b225d44e LZ |
1802 | algorithms. You can move a process onto or off an |
1803 | "isolated" CPU via the CPU affinity syscalls or cpuset. | |
1da177e4 LT |
1804 | <cpu number> begins at 0 and the maximum value is |
1805 | "number of CPUs in system - 1". | |
1806 | ||
1807 | This option is the preferred way to isolate CPUs. The | |
a9913044 RD |
1808 | alternative -- manually setting the CPU mask of all |
1809 | tasks in the system -- can cause problems and | |
1810 | suboptimal load balancer performance. | |
1da177e4 | 1811 | |
a9913044 | 1812 | iucv= [HW,NET] |
1da177e4 | 1813 | |
7d8bfa26 JR |
1814 | ivrs_ioapic [HW,X86_64] |
1815 | Provide an override to the IOAPIC-ID<->DEVICE-ID | |
1816 | mapping provided in the IVRS ACPI table. For | |
1817 | example, to map IOAPIC-ID decimal 10 to | |
1818 | PCI device 00:14.0 write the parameter as: | |
1819 | ivrs_ioapic[10]=00:14.0 | |
1820 | ||
1821 | ivrs_hpet [HW,X86_64] | |
1822 | Provide an override to the HPET-ID<->DEVICE-ID | |
1823 | mapping provided in the IVRS ACPI table. For | |
1824 | example, to map HPET-ID decimal 0 to | |
1825 | PCI device 00:14.0 write the parameter as: | |
1826 | ivrs_hpet[0]=00:14.0 | |
1827 | ||
ca3bf5d4 SS |
1828 | ivrs_acpihid [HW,X86_64] |
1829 | Provide an override to the ACPI-HID:UID<->DEVICE-ID | |
1830 | mapping provided in the IVRS ACPI table. For | |
1831 | example, to map UART-HID:UID AMD0020:0 to | |
1832 | PCI device 00:14.5 write the parameter as: | |
1833 | ivrs_acpihid[00:14.5]=AMD0020:0 | |
1834 | ||
1da177e4 LT |
1835 | js= [HW,JOY] Analog joystick |
1836 | See Documentation/input/joystick.txt. | |
1837 | ||
65fe935d KC |
1838 | nokaslr [KNL] |
1839 | When CONFIG_RANDOMIZE_BASE is set, this disables | |
1840 | kernel and module base offset ASLR (Address Space | |
1841 | Layout Randomization). | |
24f2e027 | 1842 | |
0cb55ad2 RD |
1843 | keepinitrd [HW,ARM] |
1844 | ||
342332e6 TI |
1845 | kernelcore= [KNL,X86,IA-64,PPC] |
1846 | Format: nn[KMGTPE] | "mirror" | |
1847 | This parameter | |
ed7ed365 MG |
1848 | specifies the amount of memory usable by the kernel |
1849 | for non-movable allocations. The requested amount is | |
1850 | spread evenly throughout all nodes in the system. The | |
1851 | remaining memory in each node is used for Movable | |
1852 | pages. In the event, a node is too small to have both | |
1853 | kernelcore and Movable pages, kernelcore pages will | |
1854 | take priority and other nodes will have a larger number | |
675217fd | 1855 | of Movable pages. The Movable zone is used for the |
ed7ed365 MG |
1856 | allocation of pages that may be reclaimed or moved |
1857 | by the page migration subsystem. This means that | |
1858 | HugeTLB pages may not be allocated from this zone. | |
1859 | Note that allocations like PTEs-from-HighMem still | |
1860 | use the HighMem zone if it exists, and the Normal | |
1861 | zone if it does not. | |
1862 | ||
342332e6 TI |
1863 | Instead of specifying the amount of memory (nn[KMGTPE]), |
1864 | you can specify "mirror" option. In case "mirror" | |
1865 | option is specified, mirrored (reliable) memory is used | |
1866 | for non-movable allocations and remaining memory is used | |
1867 | for Movable pages. nn[KMGTPE] and "mirror" are exclusive, | |
1868 | so you can NOT specify nn[KMGTPE] and "mirror" at the same | |
1869 | time. | |
ed7ed365 | 1870 | |
4fe1da4e JW |
1871 | kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port. |
1872 | Format: <Controller#>[,poll interval] | |
1873 | The controller # is the number of the ehci usb debug | |
1874 | port as it is probed via PCI. The poll interval is | |
1875 | optional and is the number seconds in between | |
1876 | each poll cycle to the debug port in case you need | |
1877 | the functionality for interrupting the kernel with | |
1878 | gdb or control-c on the dbgp connection. When | |
1879 | not using this parameter you use sysrq-g to break into | |
1880 | the kernel debugger. | |
1881 | ||
84c08fd6 | 1882 | kgdboc= [KGDB,HW] kgdb over consoles. |
ada64e4c JW |
1883 | Requires a tty driver that supports console polling, |
1884 | or a supported polling keyboard driver (non-usb). | |
65b5ac14 JW |
1885 | Serial only format: <serial_device>[,baud] |
1886 | keyboard only format: kbd | |
1887 | keyboard and serial format: kbd,<serial_device>[,baud] | |
1888 | Optional Kernel mode setting: | |
1889 | kms, kbd format: kms,kbd | |
1890 | kms, kbd and serial format: kms,kbd,<ser_dev>[,baud] | |
6cdf6e06 | 1891 | |
84c08fd6 JW |
1892 | kgdbwait [KGDB] Stop kernel execution and enter the |
1893 | kernel debugger at the earliest opportunity. | |
1894 | ||
9bed90c6 FF |
1895 | kmac= [MIPS] korina ethernet MAC address. |
1896 | Configure the RouterBoard 532 series on-chip | |
1897 | Ethernet adapter MAC address. | |
1898 | ||
04f70336 CM |
1899 | kmemleak= [KNL] Boot-time kmemleak enable/disable |
1900 | Valid arguments: on, off | |
1901 | Default: on | |
47aeeddc MI |
1902 | Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y, |
1903 | the default is off. | |
04f70336 | 1904 | |
c3ac14b2 XQ |
1905 | kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode |
1906 | Valid arguments: 0, 1, 2 | |
1907 | kmemcheck=0 (disabled) | |
1908 | kmemcheck=1 (enabled) | |
1909 | kmemcheck=2 (one-shot mode) | |
1910 | Default: 2 (one-shot mode) | |
1911 | ||
6cececfc | 1912 | kstack=N [X86] Print N words from the kernel stack |
0cb55ad2 RD |
1913 | in oops dumps. |
1914 | ||
fef07aae AP |
1915 | kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. |
1916 | Default is 0 (don't ignore, but inject #GP) | |
1917 | ||
a182d873 XG |
1918 | kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit |
1919 | KVM MMU at runtime. | |
fef07aae AP |
1920 | Default is 0 (off) |
1921 | ||
fef07aae | 1922 | kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. |
8475f94a | 1923 | Default is 1 (enabled) |
fef07aae AP |
1924 | |
1925 | kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU) | |
1926 | for all guests. | |
16290246 | 1927 | Default is 1 (enabled) if in 64-bit or 32-bit PAE mode. |
fef07aae | 1928 | |
fef07aae AP |
1929 | kvm-intel.ept= [KVM,Intel] Disable extended page tables |
1930 | (virtualized MMU) support on capable Intel chips. | |
1931 | Default is 1 (enabled) | |
1932 | ||
1933 | kvm-intel.emulate_invalid_guest_state= | |
1934 | [KVM,Intel] Enable emulation of invalid guest states | |
1935 | Default is 0 (disabled) | |
1936 | ||
1937 | kvm-intel.flexpriority= | |
1938 | [KVM,Intel] Disable FlexPriority feature (TPR shadow). | |
1939 | Default is 1 (enabled) | |
1940 | ||
e1a72ae2 SL |
1941 | kvm-intel.nested= |
1942 | [KVM,Intel] Enable VMX nesting (nVMX). | |
1943 | Default is 0 (disabled) | |
1944 | ||
fef07aae AP |
1945 | kvm-intel.unrestricted_guest= |
1946 | [KVM,Intel] Disable unrestricted guest feature | |
1947 | (virtualized real and unpaged mode) on capable | |
1948 | Intel chips. Default is 1 (enabled) | |
1949 | ||
1950 | kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification | |
1951 | feature (tagged TLBs) on capable Intel chips. | |
1952 | Default is 1 (enabled) | |
1953 | ||
1da177e4 LT |
1954 | l2cr= [PPC] |
1955 | ||
a78bfbfc RB |
1956 | l3cr= [PPC] |
1957 | ||
cd4f0ef7 | 1958 | lapic [X86-32,APIC] Enable the local APIC even if BIOS |
a9913044 | 1959 | disabled it. |
1da177e4 | 1960 | |
279f1461 SS |
1961 | lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline |
1962 | value for LAPIC timer one-shot implementation. Default | |
1963 | back to the programmable timer unit in the LAPIC. | |
1964 | ||
6cececfc | 1965 | lapic_timer_c2_ok [X86,APIC] trust the local apic timer |
ada9cfdd | 1966 | in C2 power state. |
e585bef8 | 1967 | |
fcb71f6f FC |
1968 | libata.dma= [LIBATA] DMA control |
1969 | libata.dma=0 Disable all PATA and SATA DMA | |
1970 | libata.dma=1 PATA and SATA Disk DMA only | |
1971 | libata.dma=2 ATAPI (CDROM) DMA only | |
16290246 | 1972 | libata.dma=4 Compact Flash DMA only |
fcb71f6f FC |
1973 | Combinations also work, so libata.dma=3 enables DMA |
1974 | for disks and CDROMs, but not CFs. | |
16290246 | 1975 | |
20308871 MP |
1976 | libata.ignore_hpa= [LIBATA] Ignore HPA limit |
1977 | libata.ignore_hpa=0 keep BIOS limits (default) | |
1978 | libata.ignore_hpa=1 ignore limits, using full disk | |
fcb71f6f | 1979 | |
78e70c23 DJ |
1980 | libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume |
1981 | when set. | |
1982 | Format: <int> | |
1983 | ||
33267325 TH |
1984 | libata.force= [LIBATA] Force configurations. The format is comma |
1985 | separated list of "[ID:]VAL" where ID is | |
4c44f309 | 1986 | PORT[.DEVICE]. PORT and DEVICE are decimal numbers |
33267325 TH |
1987 | matching port, link or device. Basically, it matches |
1988 | the ATA ID string printed on console by libata. If | |
1989 | the whole ID part is omitted, the last PORT and DEVICE | |
1990 | values are used. If ID hasn't been specified yet, the | |
1991 | configuration applies to all ports, links and devices. | |
1992 | ||
1993 | If only DEVICE is omitted, the parameter applies to | |
1994 | the port and all links and devices behind it. DEVICE | |
1995 | number of 0 either selects the first device or the | |
1996 | first fan-out link behind PMP device. It does not | |
1997 | select the host link. DEVICE number of 15 selects the | |
1998 | host link and device attached to it. | |
1999 | ||
2000 | The VAL specifies the configuration to force. As long | |
2001 | as there's no ambiguity shortcut notation is allowed. | |
2002 | For example, both 1.5 and 1.5G would work for 1.5Gbps. | |
2003 | The following configurations can be forced. | |
2004 | ||
2005 | * Cable type: 40c, 80c, short40c, unk, ign or sata. | |
2006 | Any ID with matching PORT is used. | |
2007 | ||
2008 | * SATA link speed limit: 1.5Gbps or 3.0Gbps. | |
2009 | ||
2010 | * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. | |
2011 | udma[/][16,25,33,44,66,100,133] notation is also | |
2012 | allowed. | |
2013 | ||
2014 | * [no]ncq: Turn on or off NCQ. | |
2015 | ||
d7b16e4f MP |
2016 | * [no]ncqtrim: Turn off queued DSM TRIM. |
2017 | ||
05944bdf TH |
2018 | * nohrst, nosrst, norst: suppress hard, soft |
2019 | and both resets. | |
2020 | ||
ca6d43b0 DW |
2021 | * rstonce: only attempt one reset during |
2022 | hot-unplug link recovery | |
2023 | ||
43c9c591 TH |
2024 | * dump_id: dump IDENTIFY data. |
2025 | ||
966fbe19 VP |
2026 | * atapi_dmadir: Enable ATAPI DMADIR bridge support |
2027 | ||
b8bd6dc3 RJ |
2028 | * disable: Disable this device. |
2029 | ||
33267325 TH |
2030 | If there are multiple matching configurations changing |
2031 | the same attribute, the last one is used. | |
2032 | ||
95f72d1e | 2033 | memblock=debug [KNL] Enable memblock debug messages. |
7c4be253 | 2034 | |
1da177e4 | 2035 | load_ramdisk= [RAM] List of ramdisks to load from floppy |
31c00fc1 | 2036 | See Documentation/blockdev/ramdisk.txt. |
1da177e4 | 2037 | |
a6b25b67 RD |
2038 | lockd.nlm_grace_period=P [NFS] Assign grace period. |
2039 | Format: <integer> | |
1da177e4 | 2040 | |
a6b25b67 RD |
2041 | lockd.nlm_tcpport=N [NFS] Assign TCP port. |
2042 | Format: <integer> | |
2043 | ||
2044 | lockd.nlm_timeout=T [NFS] Assign timeout value. | |
2045 | Format: <integer> | |
2046 | ||
2047 | lockd.nlm_udpport=M [NFS] Assign UDP port. | |
2048 | Format: <integer> | |
1da177e4 | 2049 | |
ec4518aa PM |
2050 | locktorture.nreaders_stress= [KNL] |
2051 | Set the number of locking read-acquisition kthreads. | |
2052 | Defaults to being automatically set based on the | |
2053 | number of online CPUs. | |
2054 | ||
2055 | locktorture.nwriters_stress= [KNL] | |
2056 | Set the number of locking write-acquisition kthreads. | |
2057 | ||
2058 | locktorture.onoff_holdoff= [KNL] | |
2059 | Set time (s) after boot for CPU-hotplug testing. | |
2060 | ||
2061 | locktorture.onoff_interval= [KNL] | |
2062 | Set time (s) between CPU-hotplug operations, or | |
2063 | zero to disable CPU-hotplug testing. | |
2064 | ||
2065 | locktorture.shuffle_interval= [KNL] | |
2066 | Set task-shuffle interval (jiffies). Shuffling | |
2067 | tasks allows some CPUs to go into dyntick-idle | |
2068 | mode during the locktorture test. | |
2069 | ||
2070 | locktorture.shutdown_secs= [KNL] | |
2071 | Set time (s) after boot system shutdown. This | |
2072 | is useful for hands-off automated testing. | |
2073 | ||
2074 | locktorture.stat_interval= [KNL] | |
2075 | Time (s) between statistics printk()s. | |
2076 | ||
2077 | locktorture.stutter= [KNL] | |
2078 | Time (s) to stutter testing, for example, | |
2079 | specifying five seconds causes the test to run for | |
2080 | five seconds, wait for five seconds, and so on. | |
2081 | This tests the locking primitive's ability to | |
2082 | transition abruptly to and from idle. | |
2083 | ||
2084 | locktorture.torture_runnable= [BOOT] | |
2085 | Start locktorture running at boot time. | |
2086 | ||
2087 | locktorture.torture_type= [KNL] | |
2088 | Specify the locking implementation to test. | |
2089 | ||
2090 | locktorture.verbose= [KNL] | |
2091 | Enable additional printk() statements. | |
2092 | ||
1da177e4 LT |
2093 | logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver |
2094 | Format: <irq> | |
2095 | ||
2096 | loglevel= All Kernel Messages with a loglevel smaller than the | |
2097 | console loglevel will be printed to the console. It can | |
2098 | also be changed with klogd or other programs. The | |
2099 | loglevels are defined as follows: | |
2100 | ||
2101 | 0 (KERN_EMERG) system is unusable | |
2102 | 1 (KERN_ALERT) action must be taken immediately | |
2103 | 2 (KERN_CRIT) critical conditions | |
2104 | 3 (KERN_ERR) error conditions | |
2105 | 4 (KERN_WARNING) warning conditions | |
2106 | 5 (KERN_NOTICE) normal but significant condition | |
2107 | 6 (KERN_INFO) informational | |
2108 | 7 (KERN_DEBUG) debug-level messages | |
2109 | ||
c756d08a | 2110 | log_buf_len=n[KMG] Sets the size of the printk ring buffer, |
23b2899f LR |
2111 | in bytes. n must be a power of two and greater |
2112 | than the minimal size. The minimal size is defined | |
2113 | by LOG_BUF_SHIFT kernel config parameter. There is | |
2114 | also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter | |
2115 | that allows to increase the default size depending on | |
2116 | the number of CPUs. See init/Kconfig for more details. | |
1da177e4 | 2117 | |
accaa24c RD |
2118 | logo.nologo [FB] Disables display of the built-in Linux logo. |
2119 | This may be used to provide more screen space for | |
2120 | kernel log messages and is useful when debugging | |
2121 | kernel boot problems. | |
2122 | ||
1da177e4 LT |
2123 | lp=0 [LP] Specify parallel ports to use, e.g, |
2124 | lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses | |
2125 | lp=reset first parallel port). 'lp=0' disables the | |
2126 | lp=auto printer driver. 'lp=reset' (which can be | |
2127 | specified in addition to the ports) causes | |
2128 | attached printers to be reset. Using | |
2129 | lp=port1,port2,... specifies the parallel ports | |
2130 | to associate lp devices with, starting with | |
2131 | lp0. A port specification may be 'none' to skip | |
2132 | that lp device, or a parport name such as | |
2133 | 'parport0'. Specifying 'lp=auto' instead of a | |
2134 | port specification list means that device IDs | |
2135 | from each port should be examined, to see if | |
2136 | an IEEE 1284-compliant printer is attached; if | |
2137 | so, the driver will manage that printer. | |
2138 | See also header of drivers/char/lp.c. | |
2139 | ||
2140 | lpj=n [KNL] | |
2141 | Sets loops_per_jiffy to given constant, thus avoiding | |
2142 | time-consuming boot-time autodetection (up to 250 ms per | |
2143 | CPU). 0 enables autodetection (default). To determine | |
2144 | the correct value for your kernel, boot with normal | |
2145 | autodetection and see what value is printed. Note that | |
2146 | on SMP systems the preset will be applied to all CPUs, | |
2147 | which is likely to cause problems if your CPUs need | |
2148 | significantly divergent settings. An incorrect value | |
2149 | will cause delays in the kernel to be wrong, leading to | |
2150 | unpredictable I/O errors and other breakage. Although | |
2151 | unlikely, in the extreme case this might damage your | |
2152 | hardware. | |
2153 | ||
2154 | ltpc= [NET] | |
2155 | Format: <io>,<irq>,<dma> | |
2156 | ||
16290246 | 2157 | machvec= [IA-64] Force the use of a particular machine-vector |
a9913044 RD |
2158 | (machvec) in a generic kernel. |
2159 | Example: machvec=hpzx1_swiotlb | |
1da177e4 | 2160 | |
3209e70e WZ |
2161 | machtype= [Loongson] Share the same kernel image file between different |
2162 | yeeloong laptop. | |
2163 | Example: machtype=lemote-yeeloong-2f-7inch | |
2164 | ||
0cb55ad2 RD |
2165 | max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater |
2166 | than or equal to this physical address is ignored. | |
1da177e4 LT |
2167 | |
2168 | maxcpus= [SMP] Maximum number of processors that an SMP kernel | |
61ec7567 LB |
2169 | should make use of. maxcpus=n : n >= 0 limits the |
2170 | kernel to using 'n' processors. n=0 is a special case, | |
2171 | it is equivalent to "nosmp", which also disables | |
2172 | the IO APIC. | |
1da177e4 | 2173 | |
d134b00b KS |
2174 | max_loop= [LOOP] The number of loop block devices that get |
2175 | (loop.max_loop) unconditionally pre-created at init time. The default | |
2176 | number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead | |
2177 | of statically allocating a predefined number, loop | |
2178 | devices can be requested on-demand with the | |
2179 | /dev/loop-control interface. | |
2b2c3750 | 2180 | |
cd4f0ef7 | 2181 | mce [X86-32] Machine Check Exception |
1da177e4 | 2182 | |
71cced6e | 2183 | mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt |
909dd324 | 2184 | |
1da177e4 LT |
2185 | md= [HW] RAID subsystems devices and level |
2186 | See Documentation/md.txt. | |
a9913044 | 2187 | |
1da177e4 LT |
2188 | mdacon= [MDA] |
2189 | Format: <first>,<last> | |
2190 | Specifies range of consoles to be captured by the MDA. | |
a9913044 | 2191 | |
1da177e4 LT |
2192 | mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory |
2193 | Amount of memory to be used when the kernel is not able | |
2194 | to see the whole system memory or for test. | |
fbb97d87 WC |
2195 | [X86] Work as limiting max address. Use together |
2196 | with memmap= to avoid physical address space collisions. | |
2197 | Without memmap= PCI devices could be placed at addresses | |
2198 | belonging to unused RAM. | |
1da177e4 | 2199 | |
cd4f0ef7 | 2200 | mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel |
1da177e4 LT |
2201 | memory. |
2202 | ||
6902aa84 PM |
2203 | memchunk=nn[KMG] |
2204 | [KNL,SH] Allow user to override the default size for | |
2205 | per-device physically contiguous DMA buffers. | |
2206 | ||
86dd995d VK |
2207 | memhp_default_state=online/offline |
2208 | [KNL] Set the initial state for the memory hotplug | |
2209 | onlining policy. If not specified, the default value is | |
2210 | set according to the | |
2211 | CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config | |
2212 | option. | |
2213 | See Documentation/memory-hotplug.txt. | |
2214 | ||
6cececfc | 2215 | memmap=exactmap [KNL,X86] Enable setting of an exact |
1da177e4 LT |
2216 | E820 memory map, as specified by the user. |
2217 | Such memmap=exactmap lines can be constructed based on | |
2218 | BIOS output or other requirements. See the memmap=nn@ss | |
2219 | option description. | |
2220 | ||
2221 | memmap=nn[KMG]@ss[KMG] | |
277cba1d RD |
2222 | [KNL] Force usage of a specific region of memory. |
2223 | Region of memory to be used is from ss to ss+nn. | |
1da177e4 LT |
2224 | |
2225 | memmap=nn[KMG]#ss[KMG] | |
2226 | [KNL,ACPI] Mark specific memory as ACPI data. | |
277cba1d | 2227 | Region of memory to be marked is from ss to ss+nn. |
1da177e4 LT |
2228 | |
2229 | memmap=nn[KMG]$ss[KMG] | |
2230 | [KNL,ACPI] Mark specific memory as reserved. | |
277cba1d | 2231 | Region of memory to be reserved is from ss to ss+nn. |
1312848e PM |
2232 | Example: Exclude memory from 0x18690000-0x1869ffff |
2233 | memmap=64K$0x18690000 | |
2234 | or | |
2235 | memmap=0x10000$0x18690000 | |
1da177e4 | 2236 | |
ec776ef6 CH |
2237 | memmap=nn[KMG]!ss[KMG] |
2238 | [KNL,X86] Mark specific memory as protected. | |
2239 | Region of memory to be used, from ss to ss+nn. | |
2240 | The memory region may be marked as e820 type 12 (0xc) | |
2241 | and is NVDIMM or ADR memory. | |
2242 | ||
9f077871 JF |
2243 | memory_corruption_check=0/1 [X86] |
2244 | Some BIOSes seem to corrupt the first 64k of | |
2245 | memory when doing things like suspend/resume. | |
2246 | Setting this option will scan the memory | |
2247 | looking for corruption. Enabling this will | |
2248 | both detect corruption and prevent the kernel | |
2249 | from using the memory being corrupted. | |
2250 | However, its intended as a diagnostic tool; if | |
2251 | repeatable BIOS-originated corruption always | |
2252 | affects the same memory, you can use memmap= | |
2253 | to prevent the kernel from using that memory. | |
2254 | ||
2255 | memory_corruption_check_size=size [X86] | |
2256 | By default it checks for corruption in the low | |
2257 | 64k, making this memory unavailable for normal | |
2258 | use. Use this parameter to scan for | |
2259 | corruption in more or less memory. | |
2260 | ||
2261 | memory_corruption_check_period=seconds [X86] | |
2262 | By default it checks for corruption every 60 | |
2263 | seconds. Use this parameter to check at some | |
2264 | other rate. 0 disables periodic checking. | |
2265 | ||
e4b0db72 | 2266 | memtest= [KNL,X86,ARM] Enable memtest |
c64df707 | 2267 | Format: <integer> |
c64df707 | 2268 | default : 0 <disable> |
9e5f6cf5 AH |
2269 | Specifies the number of memtest passes to be |
2270 | performed. Each pass selects another test | |
2271 | pattern from a given set of patterns. Memtest | |
2272 | fills the memory with this pattern, validates | |
2273 | memory contents and reserves bad memory | |
2274 | regions that are detected. | |
c64df707 | 2275 | |
1da177e4 LT |
2276 | meye.*= [HW] Set MotionEye Camera parameters |
2277 | See Documentation/video4linux/meye.txt. | |
2278 | ||
8f36881b AS |
2279 | mfgpt_irq= [IA-32] Specify the IRQ to use for the |
2280 | Multi-Function General Purpose Timers on AMD Geode | |
2281 | platforms. | |
2282 | ||
e6c4dc6c WT |
2283 | mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when |
2284 | the BIOS has incorrectly applied a workaround. TinyBIOS | |
2285 | version 0.98 is known to be affected, 0.99 fixes the | |
2286 | problem by letting the user disable the workaround. | |
2287 | ||
1da177e4 LT |
2288 | mga= [HW,DRM] |
2289 | ||
1c207f95 RD |
2290 | min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this |
2291 | physical address is ignored. | |
2292 | ||
39f45d7b MP |
2293 | mini2440= [ARM,HW,KNL] |
2294 | Format:[0..2][b][c][t] | |
2295 | Default: "0tb" | |
2296 | MINI2440 configuration specification: | |
2297 | 0 - The attached screen is the 3.5" TFT | |
2298 | 1 - The attached screen is the 7" TFT | |
2299 | 2 - The VGA Shield is attached (1024x768) | |
2300 | Leaving out the screen size parameter will not load | |
2301 | the TFT driver, and the framebuffer will be left | |
2302 | unconfigured. | |
2303 | b - Enable backlight. The TFT backlight pin will be | |
2304 | linked to the kernel VESA blanking code and a GPIO | |
2305 | LED. This parameter is not necessary when using the | |
2306 | VGA shield. | |
2307 | c - Enable the s3c camera interface. | |
2308 | t - Reserved for enabling touchscreen support. The | |
2309 | touchscreen support is not enabled in the mainstream | |
2310 | kernel as of 2.6.30, a preliminary port can be found | |
2311 | in the "bleeding edge" mini2440 support kernel at | |
2312 | http://repo.or.cz/w/linux-2.6/mini2440.git | |
2313 | ||
6b74ab97 MG |
2314 | mminit_loglevel= |
2315 | [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this | |
2316 | parameter allows control of the logging verbosity for | |
2317 | the additional memory initialisation checks. A value | |
2318 | of 0 disables mminit logging and a level of 4 will | |
2319 | log everything. Information is printed at KERN_DEBUG | |
2320 | so loglevel=8 may also need to be specified. | |
2321 | ||
106a4ee2 RR |
2322 | module.sig_enforce |
2323 | [KNL] When CONFIG_MODULE_SIG is set, this means that | |
2324 | modules without (valid) signatures will fail to load. | |
2a039be7 | 2325 | Note that if CONFIG_MODULE_SIG_FORCE is set, that |
106a4ee2 RR |
2326 | is always true, so this option does nothing. |
2327 | ||
be7de5f9 PB |
2328 | module_blacklist= [KNL] Do not load a comma-separated list of |
2329 | modules. Useful for debugging problem modules. | |
2330 | ||
1da177e4 LT |
2331 | mousedev.tap_time= |
2332 | [MOUSE] Maximum time between finger touching and | |
2333 | leaving touchpad surface for touch to be considered | |
2334 | a tap and be reported as a left button click (for | |
2335 | touchpads working in absolute mode only). | |
2336 | Format: <msecs> | |
2337 | mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices | |
2338 | reporting absolute coordinates, such as tablets | |
2339 | mousedev.yres= [MOUSE] Vertical screen resolution, used for devices | |
2340 | reporting absolute coordinates, such as tablets | |
2341 | ||
6cececfc | 2342 | movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter |
0cb55ad2 RD |
2343 | is similar to kernelcore except it specifies the |
2344 | amount of memory used for migratable allocations. | |
2345 | If both kernelcore and movablecore is specified, | |
2346 | then kernelcore will be at *least* the specified | |
2347 | value but may be more. If movablecore on its own | |
2348 | is specified, the administrator must be careful | |
2349 | that the amount of memory usable for all allocations | |
2350 | is not too small. | |
2351 | ||
c5320926 TC |
2352 | movable_node [KNL,X86] Boot-time switch to enable the effects |
2353 | of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details. | |
2354 | ||
1da177e4 LT |
2355 | MTD_Partition= [MTD] |
2356 | Format: <name>,<region-number>,<size>,<offset> | |
2357 | ||
a9913044 RD |
2358 | MTD_Region= [MTD] Format: |
2359 | <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] | |
1da177e4 LT |
2360 | |
2361 | mtdparts= [MTD] | |
c8facbb6 | 2362 | See drivers/mtd/cmdlinepart.c. |
1da177e4 | 2363 | |
4e89a2d8 WS |
2364 | multitce=off [PPC] This parameter disables the use of the pSeries |
2365 | firmware feature for updating multiple TCE entries | |
2366 | at a time. | |
2367 | ||
5988af23 RH |
2368 | onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration |
2369 | ||
2370 | Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] | |
2371 | ||
2372 | boundary - index of last SLC block on Flex-OneNAND. | |
2373 | The remaining blocks are configured as MLC blocks. | |
2374 | lock - Configure if Flex-OneNAND boundary should be locked. | |
2375 | Once locked, the boundary cannot be changed. | |
2376 | 1 indicates lock status, 0 indicates unlock status. | |
2377 | ||
9db829f4 BD |
2378 | mtdset= [ARM] |
2379 | ARM/S3C2412 JIVE boot control | |
2380 | ||
2381 | See arch/arm/mach-s3c2412/mach-jive.c | |
2382 | ||
1da177e4 | 2383 | mtouchusb.raw_coordinates= |
a9913044 RD |
2384 | [HW] Make the MicroTouch USB driver use raw coordinates |
2385 | ('y', default) or cooked coordinates ('n') | |
1da177e4 | 2386 | |
0cb55ad2 | 2387 | mtrr_chunk_size=nn[KMG] [X86] |
19f59460 | 2388 | used for mtrr cleanup. It is largest continuous chunk |
0cb55ad2 RD |
2389 | that could hold holes aka. UC entries. |
2390 | ||
2391 | mtrr_gran_size=nn[KMG] [X86] | |
2392 | Used for mtrr cleanup. It is granularity of mtrr block. | |
2393 | Default is 1. | |
2394 | Large value could prevent small alignment from | |
2395 | using up MTRRs. | |
2396 | ||
2397 | mtrr_spare_reg_nr=n [X86] | |
2398 | Format: <integer> | |
2399 | Range: 0,7 : spare reg number | |
2400 | Default : 1 | |
2401 | Used for mtrr cleanup. It is spare mtrr entries number. | |
2402 | Set to 2 or more if your graphical card needs more. | |
2403 | ||
1da177e4 LT |
2404 | n2= [NET] SDL Inc. RISCom/N2 synchronous serial card |
2405 | ||
1da177e4 LT |
2406 | netdev= [NET] Network devices parameters |
2407 | Format: <irq>,<io>,<mem_start>,<mem_end>,<name> | |
2408 | Note that mem_start is often overloaded to mean | |
2409 | something different and driver-specific. | |
a9913044 RD |
2410 | This usage is only documented in each driver source |
2411 | file if at all. | |
2412 | ||
58401572 KPO |
2413 | nf_conntrack.acct= |
2414 | [NETFILTER] Enable connection tracking flow accounting | |
2415 | 0 to disable accounting | |
2416 | 1 to enable accounting | |
d70a011d | 2417 | Default value is 0. |
58401572 | 2418 | |
306a0753 | 2419 | nfsaddrs= [NFS] Deprecated. Use ip= instead. |
dc7a0816 | 2420 | See Documentation/filesystems/nfs/nfsroot.txt. |
1da177e4 LT |
2421 | |
2422 | nfsroot= [NFS] nfs root filesystem for disk-less boxes. | |
dc7a0816 | 2423 | See Documentation/filesystems/nfs/nfsroot.txt. |
1da177e4 | 2424 | |
306a0753 CL |
2425 | nfsrootdebug [NFS] enable nfsroot debugging messages. |
2426 | See Documentation/filesystems/nfs/nfsroot.txt. | |
2427 | ||
a72b4422 TM |
2428 | nfs.callback_tcpport= |
2429 | [NFS] set the TCP port on which the NFSv4 callback | |
2430 | channel should listen. | |
2431 | ||
e571cbf1 TM |
2432 | nfs.cache_getent= |
2433 | [NFS] sets the pathname to the program which is used | |
2434 | to update the NFS client cache entries. | |
2435 | ||
2436 | nfs.cache_getent_timeout= | |
2437 | [NFS] sets the timeout after which an attempt to | |
2438 | update a cache entry is deemed to have failed. | |
2439 | ||
58df095b TM |
2440 | nfs.idmap_cache_timeout= |
2441 | [NFS] set the maximum lifetime for idmapper cache | |
2442 | entries. | |
2443 | ||
f43bf0be TM |
2444 | nfs.enable_ino64= |
2445 | [NFS] enable 64-bit inode numbers. | |
2446 | If zero, the NFS client will fake up a 32-bit inode | |
2447 | number for the readdir() and stat() syscalls instead | |
2448 | of returning the full 64-bit number. | |
2449 | The default is to return 64-bit inode numbers. | |
2450 | ||
ef159e91 TM |
2451 | nfs.max_session_slots= |
2452 | [NFSv4.1] Sets the maximum number of session slots | |
2453 | the client will attempt to negotiate with the server. | |
2454 | This limits the number of simultaneous RPC requests | |
2455 | that the client can send to the NFSv4.1 server. | |
2456 | Note that there is little point in setting this | |
2457 | value higher than the max_tcp_slot_table_limit. | |
2458 | ||
b064eca2 | 2459 | nfs.nfs4_disable_idmapping= |
074b1d12 TM |
2460 | [NFSv4] When set to the default of '1', this option |
2461 | ensures that both the RPC level authentication | |
2462 | scheme and the NFS level operations agree to use | |
2463 | numeric uids/gids if the mount is using the | |
2464 | 'sec=sys' security flavour. In effect it is | |
2465 | disabling idmapping, which can make migration from | |
2466 | legacy NFSv2/v3 systems to NFSv4 easier. | |
2467 | Servers that do not support this mode of operation | |
2468 | will be autodetected by the client, and it will fall | |
2469 | back to using the idmapper. | |
2470 | To turn off this behaviour, set the value to '0'. | |
6f2ea7f2 CL |
2471 | nfs.nfs4_unique_id= |
2472 | [NFS4] Specify an additional fixed unique ident- | |
2473 | ification string that NFSv4 clients can insert into | |
2474 | their nfs_client_id4 string. This is typically a | |
2475 | UUID that is generated at system install time. | |
b064eca2 | 2476 | |
db8ac8ba WAA |
2477 | nfs.send_implementation_id = |
2478 | [NFSv4.1] Send client implementation identification | |
2479 | information in exchange_id requests. | |
2480 | If zero, no implementation identification information | |
2481 | will be sent. | |
2482 | The default is to send the implementation identification | |
2483 | information. | |
f6de7a39 TM |
2484 | |
2485 | nfs.recover_lost_locks = | |
2486 | [NFSv4] Attempt to recover locks that were lost due | |
2487 | to a lease timeout on the server. Please note that | |
2488 | doing this risks data corruption, since there are | |
2489 | no guarantees that the file will remain unchanged | |
2490 | after the locks are lost. | |
2491 | If you want to enable the kernel legacy behaviour of | |
2492 | attempting to recover these locks, then set this | |
2493 | parameter to '1'. | |
2494 | The default parameter value of '0' causes the kernel | |
2495 | not to attempt recovery of lost locks. | |
db8ac8ba | 2496 | |
bbf58bf3 TM |
2497 | nfs4.layoutstats_timer = |
2498 | [NFSv4.2] Change the rate at which the kernel sends | |
2499 | layoutstats to the pNFS metadata server. | |
2500 | ||
2501 | Setting this to value to 0 causes the kernel to use | |
2502 | whatever value is the default set by the layout | |
2503 | driver. A non-zero value sets the minimum interval | |
2504 | in seconds between layoutstats transmissions. | |
2505 | ||
e9541ce8 BF |
2506 | nfsd.nfs4_disable_idmapping= |
2507 | [NFSv4] When set to the default of '1', the NFSv4 | |
2508 | server will return only numeric uids and gids to | |
2509 | clients using auth_sys, and will accept numeric uids | |
2510 | and gids from such clients. This is intended to ease | |
2511 | migration from NFSv2/v3. | |
db8ac8ba | 2512 | |
18d98f6c SB |
2513 | objlayoutdriver.osd_login_prog= |
2514 | [NFS] [OBJLAYOUT] sets the pathname to the program which | |
2515 | is used to automatically discover and login into new | |
2516 | osd-targets. Please see: | |
2517 | Documentation/filesystems/pnfs.txt for more explanations | |
2518 | ||
1e1030dc | 2519 | nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take |
e7ba176b HS |
2520 | when a NMI is triggered. |
2521 | Format: [state][,regs][,debounce][,die] | |
2522 | ||
6cececfc | 2523 | nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels |
fef2c9bc | 2524 | Format: [panic,][nopanic,][num] |
195daf66 | 2525 | Valid num: 0 or 1 |
334bb79c PK |
2526 | 0 - turn hardlockup detector in nmi_watchdog off |
2527 | 1 - turn hardlockup detector in nmi_watchdog on | |
0cb55ad2 | 2528 | When panic is specified, panic when an NMI watchdog |
fef2c9bc | 2529 | timeout occurs (or 'nopanic' to override the opposite |
334bb79c PK |
2530 | default). To disable both hard and soft lockup detectors, |
2531 | please see 'nowatchdog'. | |
0cb55ad2 RD |
2532 | This is useful when you use a panic=... timeout and |
2533 | need the box quickly up again. | |
1da177e4 | 2534 | |
bff38771 AV |
2535 | netpoll.carrier_timeout= |
2536 | [NET] Specifies amount of time (in seconds) that | |
2537 | netpoll should wait for a carrier. By default netpoll | |
2538 | waits 4 seconds. | |
2539 | ||
cd4f0ef7 | 2540 | no387 [BUGS=X86-32] Tells the kernel to use the 387 maths |
1da177e4 LT |
2541 | emulation library even if a 387 maths coprocessor |
2542 | is present. | |
2543 | ||
0cb55ad2 RD |
2544 | no_console_suspend |
2545 | [HW] Never suspend the console | |
2546 | Disable suspending of consoles during suspend and | |
2547 | hibernate operations. Once disabled, debugging | |
2548 | messages can reach various consoles while the rest | |
2549 | of the system is being put to sleep (ie, while | |
2550 | debugging driver suspend/resume hooks). This may | |
2551 | not work reliably with all consoles, but is known | |
2552 | to work with serial and VGA consoles. | |
134620f7 YZ |
2553 | To facilitate more flexible debugging, we also add |
2554 | console_suspend, a printk module parameter to control | |
2555 | it. Users could use console_suspend (usually | |
2556 | /sys/module/printk/parameters/console_suspend) to | |
2557 | turn on/off it dynamically. | |
0cb55ad2 | 2558 | |
c1aee215 CL |
2559 | noaliencache [MM, NUMA, SLAB] Disables the allocation of alien |
2560 | caches in the slab allocator. Saves per-node memory, | |
2561 | but will impact performance. | |
3395ee05 | 2562 | |
a9913044 RD |
2563 | noalign [KNL,ARM] |
2564 | ||
1da177e4 LT |
2565 | noapic [SMP,APIC] Tells the kernel to not make use of any |
2566 | IOAPICs that may be present in the system. | |
2567 | ||
5091faa4 MG |
2568 | noautogroup Disable scheduler automatic task group creation. |
2569 | ||
1da177e4 LT |
2570 | nobats [PPC] Do not use BATs for mapping kernel lowmem |
2571 | on "Classic" PPC cores. | |
2572 | ||
2573 | nocache [ARM] | |
a9913044 | 2574 | |
0cb55ad2 RD |
2575 | noclflush [BUGS=X86] Don't use the CLFLUSH instruction |
2576 | ||
163ecdff SN |
2577 | nodelayacct [KNL] Disable per-task delay accounting |
2578 | ||
1da177e4 LT |
2579 | nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects. |
2580 | ||
6902aa84 PM |
2581 | nodsp [SH] Disable hardware DSP at boot time. |
2582 | ||
b2e0a54a | 2583 | noefi Disable EFI runtime services support. |
8b2cb7a8 | 2584 | |
1da177e4 LT |
2585 | noexec [IA-64] |
2586 | ||
6cececfc | 2587 | noexec [X86] |
f5a1b191 | 2588 | On X86-32 available only on PAE configured kernels. |
1da177e4 | 2589 | noexec=on: enable non-executable mappings (default) |
f5a1b191 JS |
2590 | noexec=off: disable non-executable mappings |
2591 | ||
52b6179a PA |
2592 | nosmap [X86] |
2593 | Disable SMAP (Supervisor Mode Access Prevention) | |
2594 | even if it is supported by processor. | |
2595 | ||
de5397ad | 2596 | nosmep [X86] |
52b6179a | 2597 | Disable SMEP (Supervisor Mode Execution Prevention) |
de5397ad FY |
2598 | even if it is supported by processor. |
2599 | ||
f5a1b191 JS |
2600 | noexec32 [X86-64] |
2601 | This affects only 32-bit executables. | |
2602 | noexec32=on: enable non-executable mappings (default) | |
2603 | read doesn't imply executable mappings | |
2604 | noexec32=off: disable non-executable mappings | |
2605 | read implies executable mappings | |
1da177e4 | 2606 | |
fab43ef4 | 2607 | nofpu [MIPS,SH] Disable hardware FPU at boot time. |
6902aa84 | 2608 | |
cd4f0ef7 | 2609 | nofxsr [BUGS=X86-32] Disables x86 floating point extended |
4f886511 CE |
2610 | register save and restore. The kernel will only save |
2611 | legacy floating-point registers on task switch. | |
1da177e4 | 2612 | |
0ddab1d2 TK |
2613 | nohugeiomap [KNL,x86] Disable kernel huge I/O mappings. |
2614 | ||
52c48c51 SS |
2615 | nosmt [KNL,S390] Disable symmetric multithreading (SMT). |
2616 | Equivalent to smt=1. | |
2617 | ||
0c752a93 SS |
2618 | noxsave [BUGS=X86] Disables x86 extended register state save |
2619 | and restore using xsave. The kernel will fallback to | |
2620 | enabling legacy floating-point and sse state. | |
2621 | ||
b6f42a4a FY |
2622 | noxsaveopt [X86] Disables xsaveopt used in saving x86 extended |
2623 | register states. The kernel will fall back to use | |
2624 | xsave to save the states. By using this parameter, | |
2625 | performance of saving the states is degraded because | |
2626 | xsave doesn't support modified optimization while | |
2627 | xsaveopt supports it on xsaveopt enabled systems. | |
2628 | ||
2629 | noxsaves [X86] Disables xsaves and xrstors used in saving and | |
2630 | restoring x86 extended register state in compacted | |
2631 | form of xsave area. The kernel will fall back to use | |
2632 | xsaveopt and xrstor to save and restore the states | |
2633 | in standard form of xsave area. By using this | |
2634 | parameter, xsave area per process might occupy more | |
2635 | memory on xsaves enabled systems. | |
2636 | ||
01a24d2b PZ |
2637 | nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or |
2638 | wfi(ARM) instruction doesn't work correctly and not to | |
2639 | use it. This is also useful when using JTAG debugger. | |
a9913044 | 2640 | |
1f29fae2 SH |
2641 | no_file_caps Tells the kernel not to honor file capabilities. The |
2642 | only way then for a file to be executed with privilege | |
2643 | is to be setuid root or executed by root. | |
2644 | ||
1da177e4 LT |
2645 | nohalt [IA-64] Tells the kernel not to use the power saving |
2646 | function PAL_HALT_LIGHT when idle. This increases | |
2647 | power-consumption. On the positive side, it reduces | |
2648 | interrupt wake-up latency, which may improve performance | |
2649 | in certain environments such as networked servers or | |
2650 | real-time systems. | |
2651 | ||
a6e15a39 KC |
2652 | nohibernate [HIBERNATION] Disable hibernation and resume. |
2653 | ||
79bf2bb3 TG |
2654 | nohz= [KNL] Boottime enable/disable dynamic ticks |
2655 | Valid arguments: on, off | |
2656 | Default: on | |
2657 | ||
c5bfece2 FW |
2658 | nohz_full= [KNL,BOOT] |
2659 | In kernels built with CONFIG_NO_HZ_FULL=y, set | |
a831881b | 2660 | the specified list of CPUs whose tick will be stopped |
0453b435 FW |
2661 | whenever possible. The boot CPU will be forced outside |
2662 | the range to maintain the timekeeping. | |
d1e43fa5 FW |
2663 | The CPUs in this range must also be included in the |
2664 | rcu_nocbs= set. | |
a831881b | 2665 | |
eeee7853 PM |
2666 | noiotrap [SH] Disables trapped I/O port accesses. |
2667 | ||
cd4f0ef7 | 2668 | noirqdebug [X86-32] Disables the code which attempts to detect and |
1da177e4 LT |
2669 | disable unhandled interrupt sources. |
2670 | ||
6cececfc | 2671 | no_timer_check [X86,APIC] Disables the code which tests for |
8542b200 ZA |
2672 | broken timer IRQ sources. |
2673 | ||
1da177e4 LT |
2674 | noisapnp [ISAPNP] Disables ISA PnP code. |
2675 | ||
2676 | noinitrd [RAM] Tells the kernel not to load any configured | |
2677 | initial RAM disk. | |
2678 | ||
03ea8155 WH |
2679 | nointremap [X86-64, Intel-IOMMU] Do not enable interrupt |
2680 | remapping. | |
d1423d56 | 2681 | [Deprecated - use intremap=off] |
03ea8155 | 2682 | |
1da177e4 LT |
2683 | nointroute [IA-64] |
2684 | ||
d12a72b8 AL |
2685 | noinvpcid [X86] Disable the INVPCID cpu feature. |
2686 | ||
16290246 | 2687 | nojitter [IA-64] Disables jitter checking for ITC timers. |
0aa366f3 | 2688 | |
9cf4c4fc JK |
2689 | no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver |
2690 | ||
fd10cde9 GN |
2691 | no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page |
2692 | fault handling. | |
2693 | ||
d910f5c1 GC |
2694 | no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting. |
2695 | steal time is computed, but won't influence scheduler | |
2696 | behaviour | |
2697 | ||
cd4f0ef7 | 2698 | nolapic [X86-32,APIC] Do not enable or use the local APIC. |
1da177e4 | 2699 | |
cd4f0ef7 | 2700 | nolapic_timer [X86-32,APIC] Do not use the local APIC timer. |
ad62ca2b | 2701 | |
1da177e4 | 2702 | noltlbs [PPC] Do not use large page/tlb entries for kernel |
f15eea66 | 2703 | lowmem mapping on PPC40x and PPC8xx |
1da177e4 | 2704 | |
312f1f01 H |
2705 | nomca [IA-64] Disable machine check abort handling |
2706 | ||
13696e0a | 2707 | nomce [X86-32] Disable Machine Check Exception |
abe37e5a | 2708 | |
83d7384f AS |
2709 | nomfgpt [X86-32] Disable Multi-Function General Purpose |
2710 | Timer usage (for AMD Geode machines). | |
2711 | ||
bda62633 DZ |
2712 | nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to |
2713 | shutdown the other cpus. Instead use the REBOOT_VECTOR | |
2714 | irq. | |
2715 | ||
02608bef DY |
2716 | nomodule Disable module load |
2717 | ||
016ddd9b JK |
2718 | nopat [X86] Disable PAT (page attribute table extension of |
2719 | pagetables) support. | |
2720 | ||
0cb55ad2 RD |
2721 | norandmaps Don't use address space randomization. Equivalent to |
2722 | echo 0 > /proc/sys/kernel/randomize_va_space | |
2723 | ||
bbff2168 | 2724 | noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops |
959b4fdf | 2725 | |
cd4f0ef7 | 2726 | noreplace-smp [X86-32,SMP] Don't replace SMP instructions |
b7fb4af0 JF |
2727 | with UP alternatives |
2728 | ||
7a5091d5 PA |
2729 | nordrand [X86] Disable kernel use of the RDRAND and |
2730 | RDSEED instructions even if they are supported | |
2731 | by the processor. RDRAND and RDSEED are still | |
2732 | available to user space applications. | |
49d859d7 | 2733 | |
a9913044 RD |
2734 | noresume [SWSUSP] Disables resume and restores original swap |
2735 | space. | |
2736 | ||
1da177e4 LT |
2737 | no-scroll [VGA] Disables scrollback. |
2738 | This is required for the Braillex ib80-piezo Braille | |
2739 | reader made by F.H. Papenmeier (Germany). | |
2740 | ||
2741 | nosbagart [IA-64] | |
2742 | ||
cd4f0ef7 | 2743 | nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support. |
4f886511 | 2744 | |
61ec7567 LB |
2745 | nosmp [SMP] Tells an SMP kernel to act as a UP kernel, |
2746 | and disable the IO APIC. legacy for "maxcpus=0". | |
1da177e4 | 2747 | |
97842216 DJ |
2748 | nosoftlockup [KNL] Disable the soft-lockup detector. |
2749 | ||
1da177e4 LT |
2750 | nosync [HW,M68K] Disables sync negotiation for all devices. |
2751 | ||
cd4f0ef7 | 2752 | notsc [BUGS=X86-32] Disable Time Stamp Counter |
1da177e4 | 2753 | |
195daf66 UO |
2754 | nowatchdog [KNL] Disable both lockup detectors, i.e. |
2755 | soft-lockup and NMI watchdog (hard-lockup). | |
58687acb | 2756 | |
1da177e4 | 2757 | nowb [ARM] |
a9913044 | 2758 | |
2b2fd87a WH |
2759 | nox2apic [X86-64,APIC] Do not enable x2APIC mode. |
2760 | ||
f78cff48 FY |
2761 | cpu0_hotplug [X86] Turn on CPU0 hotplug feature when |
2762 | CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off. | |
2763 | Some features depend on CPU0. Known dependencies are: | |
2764 | 1. Resume from suspend/hibernate depends on CPU0. | |
2765 | Suspend/hibernate will fail if CPU0 is offline and you | |
2766 | need to online CPU0 before suspend/hibernate. | |
2767 | 2. PIC interrupts also depend on CPU0. CPU0 can't be | |
2768 | removed if a PIC interrupt is detected. | |
2769 | It's said poweroff/reboot may depend on CPU0 on some | |
2770 | machines although I haven't seen such issues so far | |
2771 | after CPU0 is offline on a few tested machines. | |
2772 | If the dependencies are under your control, you can | |
2773 | turn on cpu0_hotplug. | |
2774 | ||
16290246 | 2775 | nptcg= [IA-64] Override max number of concurrent global TLB |
a6c75b86 FY |
2776 | purges which is reported from either PAL_VM_SUMMARY or |
2777 | SAL PALO. | |
2778 | ||
2b633e3f YL |
2779 | nr_cpus= [SMP] Maximum number of processors that an SMP kernel |
2780 | could support. nr_cpus=n : n >= 1 limits the kernel to | |
2781 | supporting 'n' processors. Later in runtime you can not | |
2782 | use hotplug cpu feature to put more cpu back to online. | |
2783 | just like you compile the kernel NR_CPUS=n | |
2784 | ||
0cb55ad2 RD |
2785 | nr_uarts= [SERIAL] maximum number of UARTs to be registered. |
2786 | ||
1a687c2e MG |
2787 | numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing. |
2788 | Allowed values are enable and disable | |
2789 | ||
f0c0b2b8 KH |
2790 | numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. |
2791 | one of ['zone', 'node', 'default'] can be specified | |
2792 | This can be set from sysctl after boot. | |
2793 | See Documentation/sysctl/vm.txt for details. | |
2794 | ||
7c4be253 RD |
2795 | ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. |
2796 | See Documentation/debugging-via-ohci1394.txt for more | |
2797 | info. | |
2798 | ||
3ef0e1f8 AS |
2799 | olpc_ec_timeout= [OLPC] ms delay when issuing EC commands |
2800 | Rather than timing out after 20 ms if an EC | |
2801 | command is not properly ACKed, override the length | |
2802 | of the timeout. We have interrupts disabled while | |
2803 | waiting for the ACK, so if this is set too high | |
2804 | interrupts *may* be lost! | |
2805 | ||
15ac7afe TL |
2806 | omap_mux= [OMAP] Override bootloader pin multiplexing. |
2807 | Format: <mux_mode0.mode_name=value>... | |
2808 | For example, to override I2C bus2: | |
2809 | omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 | |
2810 | ||
1da177e4 LT |
2811 | oprofile.timer= [HW] |
2812 | Use timer interrupt instead of performance counters | |
2813 | ||
7e4e0bd5 RR |
2814 | oprofile.cpu_type= Force an oprofile cpu type |
2815 | This might be useful if you have an older oprofile | |
2816 | userland or if you want common events. | |
8d7ff4f2 RR |
2817 | Format: { arch_perfmon } |
2818 | arch_perfmon: [X86] Force use of architectural | |
7e4e0bd5 RR |
2819 | perfmon on Intel CPUs instead of the |
2820 | CPU specific event set. | |
159a80b2 RR |
2821 | timer: [X86] Force use of architectural NMI |
2822 | timer mode (see also oprofile.timer | |
2823 | for generic hr timer mode) | |
1dcdb5a9 | 2824 | |
44a4dcf7 RD |
2825 | oops=panic Always panic on oopses. Default is to just kill the |
2826 | process, but there is a small probability of | |
2827 | deadlocking the machine. | |
d404ab0a OH |
2828 | This will also cause panics on machine check exceptions. |
2829 | Useful together with panic=30 to trigger a reboot. | |
2830 | ||
bcfde334 RD |
2831 | OSS [HW,OSS] |
2832 | See Documentation/sound/oss/oss-parameters.txt | |
2833 | ||
48c96a36 JK |
2834 | page_owner= [KNL] Boot-time page_owner enabling option. |
2835 | Storage of the information about who allocated | |
2836 | each page is disabled in default. With this switch, | |
2837 | we can turn it on. | |
2838 | on: enable the feature | |
2839 | ||
8823b1db LA |
2840 | page_poison= [KNL] Boot-time parameter changing the state of |
2841 | poisoning on the buddy allocator. | |
2842 | off: turn off poisoning | |
2843 | on: turn on poisoning | |
2844 | ||
44a4dcf7 | 2845 | panic= [KNL] Kernel behaviour on panic: delay <timeout> |
4302fbc8 HD |
2846 | timeout > 0: seconds before rebooting |
2847 | timeout = 0: wait forever | |
2848 | timeout < 0: reboot immediately | |
1da177e4 LT |
2849 | Format: <timeout> |
2850 | ||
9e3961a0 PB |
2851 | panic_on_warn panic() instead of WARN(). Useful to cause kdump |
2852 | on a WARN(). | |
2853 | ||
f06e5153 MH |
2854 | crash_kexec_post_notifiers |
2855 | Run kdump after running panic-notifiers and dumping | |
2856 | kmsg. This only for the users who doubt kdump always | |
2857 | succeeds in any situation. | |
2858 | Note that this also increases risks of kdump failure, | |
2859 | because some panic notifiers can make the crashed | |
2860 | kernel more unstable. | |
2861 | ||
1da177e4 LT |
2862 | parkbd.port= [HW] Parallel port number the keyboard adapter is |
2863 | connected to, default is 0. | |
2864 | Format: <parport#> | |
2865 | parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, | |
2866 | 0 for XT, 1 for AT (default is AT). | |
a9913044 RD |
2867 | Format: <mode> |
2868 | ||
2869 | parport= [HW,PPT] Specify parallel ports. 0 disables. | |
2870 | Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } | |
2871 | Use 'auto' to force the driver to use any | |
2872 | IRQ/DMA settings detected (the default is to | |
2873 | ignore detected IRQ/DMA settings because of | |
2874 | possible conflicts). You can specify the base | |
2875 | address, IRQ, and DMA settings; IRQ and DMA | |
2876 | should be numbers, or 'auto' (for using detected | |
2877 | settings on that particular port), or 'nofifo' | |
2878 | (to avoid using a FIFO even if it is detected). | |
2879 | Parallel ports are assigned in the order they | |
2880 | are specified on the command line, starting | |
2881 | with parport0. | |
2882 | ||
2883 | parport_init_mode= [HW,PPT] | |
2884 | Configure VIA parallel port to operate in | |
2885 | a specific mode. This is necessary on Pegasos | |
2886 | computer where firmware has no options for setting | |
2887 | up parallel port mode and sets it to spp. | |
2888 | Currently this function knows 686a and 8231 chips. | |
1da177e4 LT |
2889 | Format: [spp|ps2|epp|ecp|ecpepp] |
2890 | ||
dd287796 AM |
2891 | pause_on_oops= |
2892 | Halt all CPUs after the first oops has been printed for | |
2893 | the specified number of seconds. This is to be used if | |
2894 | your oopses keep scrolling off the screen. | |
2895 | ||
1da177e4 LT |
2896 | pcbit= [HW,ISDN] |
2897 | ||
2898 | pcd. [PARIDE] | |
2899 | See header of drivers/block/paride/pcd.c. | |
31c00fc1 | 2900 | See also Documentation/blockdev/paride.txt. |
1da177e4 | 2901 | |
a9913044 | 2902 | pci=option[,option...] [PCI] various PCI subsystem options: |
1cc0ca26 BH |
2903 | earlydump [X86] dump PCI config space before the kernel |
2904 | changes anything | |
c0115606 | 2905 | off [X86] don't probe for the PCI bus |
cd4f0ef7 | 2906 | bios [X86-32] force use of PCI BIOS, don't access |
a9913044 RD |
2907 | the hardware directly. Use this if your machine |
2908 | has a non-standard PCI host bridge. | |
cd4f0ef7 | 2909 | nobios [X86-32] disallow use of PCI BIOS, only direct |
a9913044 RD |
2910 | hardware access methods are allowed. Use this |
2911 | if you experience crashes upon bootup and you | |
2912 | suspect they are caused by the BIOS. | |
afd8c084 BP |
2913 | conf1 [X86] Force use of PCI Configuration Access |
2914 | Mechanism 1 (config address in IO port 0xCF8, | |
2915 | data in IO port 0xCFC, both 32-bit). | |
2916 | conf2 [X86] Force use of PCI Configuration Access | |
2917 | Mechanism 2 (IO port 0xCF8 is an 8-bit port for | |
2918 | the function, IO port 0xCFA, also 8-bit, sets | |
2919 | bus number. The config space is then accessed | |
2920 | through ports 0xC000-0xCFFF). | |
2921 | See http://wiki.osdev.org/PCI for more info | |
2922 | on the configuration access mechanisms. | |
7f785763 RD |
2923 | noaer [PCIE] If the PCIEAER kernel config parameter is |
2924 | enabled, this kernel boot option can be used to | |
2925 | disable the use of PCIE advanced error reporting. | |
32a2eea7 JG |
2926 | nodomains [PCI] Disable support for multiple PCI |
2927 | root domains (aka PCI segments, in ACPI-speak). | |
6cececfc | 2928 | nommconf [X86] Disable use of MMCONFIG for PCI |
61be6d66 | 2929 | Configuration |
12983077 AH |
2930 | check_enable_amd_mmconf [X86] check for and enable |
2931 | properly configured MMIO access to PCI | |
2932 | config space on AMD family 10h CPU | |
309e57df MW |
2933 | nomsi [MSI] If the PCI_MSI kernel config parameter is |
2934 | enabled, this kernel boot option can be used to | |
2935 | disable the use of MSI interrupts system-wide. | |
a9322f64 SA |
2936 | noioapicquirk [APIC] Disable all boot interrupt quirks. |
2937 | Safety option to keep boot IRQs enabled. This | |
2938 | should never be necessary. | |
9197979b SA |
2939 | ioapicreroute [APIC] Enable rerouting of boot IRQs to the |
2940 | primary IO-APIC for bridges that cannot disable | |
2941 | boot IRQs. This fixes a source of spurious IRQs | |
2942 | when the system masks IRQs. | |
41b9eb26 SA |
2943 | noioapicreroute [APIC] Disable workaround that uses the |
2944 | boot IRQ equivalent of an IRQ that connects to | |
2945 | a chipset where boot IRQs cannot be disabled. | |
2946 | The opposite of ioapicreroute. | |
cd4f0ef7 | 2947 | biosirq [X86-32] Use PCI BIOS calls to get the interrupt |
a9913044 RD |
2948 | routing table. These calls are known to be buggy |
2949 | on several machines and they hang the machine | |
2950 | when used, but on other computers it's the only | |
2951 | way to get the interrupt routing table. Try | |
2952 | this option if the kernel is unable to allocate | |
2953 | IRQs or discover secondary PCI buses on your | |
2954 | motherboard. | |
c0115606 | 2955 | rom [X86] Assign address space to expansion ROMs. |
a9913044 RD |
2956 | Use with caution as certain devices share |
2957 | address decoders between ROMs and other | |
2958 | resources. | |
c0115606 | 2959 | norom [X86] Do not assign address space to |
bb71ad88 GH |
2960 | expansion ROMs that do not already have |
2961 | BIOS assigned address ranges. | |
7bd1c365 MH |
2962 | nobar [X86] Do not assign address space to the |
2963 | BARs that weren't assigned by the BIOS. | |
c0115606 | 2964 | irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be |
a9913044 RD |
2965 | assigned automatically to PCI devices. You can |
2966 | make the kernel exclude IRQs of your ISA cards | |
2967 | this way. | |
c0115606 | 2968 | pirqaddr=0xAAAAA [X86] Specify the physical address |
a9913044 RD |
2969 | of the PIRQ table (normally generated |
2970 | by the BIOS) if it is outside the | |
2971 | F0000h-100000h range. | |
c0115606 | 2972 | lastbus=N [X86] Scan all buses thru bus #N. Can be |
a9913044 RD |
2973 | useful if the kernel is unable to find your |
2974 | secondary buses and you want to tell it | |
2975 | explicitly which ones they are. | |
c0115606 | 2976 | assign-busses [X86] Always assign all PCI bus |
a9913044 RD |
2977 | numbers ourselves, overriding |
2978 | whatever the firmware may have done. | |
c0115606 | 2979 | usepirqmask [X86] Honor the possible IRQ mask stored |
a9913044 RD |
2980 | in the BIOS $PIR table. This is needed on |
2981 | some systems with broken BIOSes, notably | |
2982 | some HP Pavilion N5400 and Omnibook XE3 | |
2983 | notebooks. This will have no effect if ACPI | |
2984 | IRQ routing is enabled. | |
c0115606 | 2985 | noacpi [X86] Do not use ACPI for IRQ routing |
a9913044 | 2986 | or for PCI scanning. |
7bc5e3f2 BH |
2987 | use_crs [X86] Use PCI host bridge window information |
2988 | from ACPI. On BIOSes from 2008 or later, this | |
2989 | is enabled by default. If you need to use this, | |
2990 | please report a bug. | |
2991 | nocrs [X86] Ignore PCI host bridge windows from ACPI. | |
2992 | If you need to use this, please report a bug. | |
a9913044 RD |
2993 | routeirq Do IRQ routing for all PCI devices. |
2994 | This is normally done in pci_enable_device(), | |
2995 | so this option is a temporary workaround | |
2996 | for broken drivers that don't call it. | |
13a6ddb0 YL |
2997 | skip_isa_align [X86] do not align io start addr, so can |
2998 | handle more pci cards | |
0637a70a AK |
2999 | noearly [X86] Don't do any early type 1 scanning. |
3000 | This might help on some broken boards which | |
3001 | machine check when some devices' config space | |
3002 | is read. But various workarounds are disabled | |
3003 | and some IOMMU drivers will not work. | |
6b4b78fe MD |
3004 | bfsort Sort PCI devices into breadth-first order. |
3005 | This sorting is done to get a device | |
3006 | order compatible with older (<= 2.4) kernels. | |
3007 | nobfsort Don't sort PCI devices into breadth-first order. | |
fa238712 YW |
3008 | pcie_bus_tune_off Disable PCIe MPS (Max Payload Size) |
3009 | tuning and use the BIOS-configured MPS defaults. | |
3010 | pcie_bus_safe Set every device's MPS to the largest value | |
3011 | supported by all devices below the root complex. | |
3012 | pcie_bus_perf Set device MPS to the largest allowable MPS | |
3013 | based on its parent bus. Also set MRRS (Max | |
3014 | Read Request Size) to the largest supported | |
3015 | value (no larger than the MPS that the device | |
3016 | or bus can support) for best performance. | |
3017 | pcie_bus_peer2peer Set every device's MPS to 128B, which | |
3018 | every device is guaranteed to support. This | |
3019 | configuration allows peer-to-peer DMA between | |
3020 | any pair of devices, possibly at the cost of | |
3021 | reduced performance. This also guarantees | |
3022 | that hot-added devices will work. | |
4516a618 AN |
3023 | cbiosize=nn[KMG] The fixed amount of bus space which is |
3024 | reserved for the CardBus bridge's IO window. | |
3025 | The default value is 256 bytes. | |
3026 | cbmemsize=nn[KMG] The fixed amount of bus space which is | |
3027 | reserved for the CardBus bridge's memory | |
3028 | window. The default value is 64 megabytes. | |
32a9a682 YS |
3029 | resource_alignment= |
3030 | Format: | |
3031 | [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...] | |
644a544f KMEE |
3032 | [<order of align>@]pci:<vendor>:<device>\ |
3033 | [:<subvendor>:<subdevice>][; ...] | |
32a9a682 YS |
3034 | Specifies alignment and device to reassign |
3035 | aligned memory resources. | |
3036 | If <order of align> is not specified, | |
3037 | PAGE_SIZE is used as alignment. | |
3038 | PCI-PCI bridge can be specified, if resource | |
3039 | windows need to be expanded. | |
8b078c60 MK |
3040 | To specify the alignment for several |
3041 | instances of a device, the PCI vendor, | |
3042 | device, subvendor, and subdevice may be | |
3043 | specified, e.g., 4096@pci:8086:9c22:103c:198f | |
43c16408 AP |
3044 | ecrc= Enable/disable PCIe ECRC (transaction layer |
3045 | end-to-end CRC checking). | |
3046 | bios: Use BIOS/firmware settings. This is the | |
3047 | the default. | |
3048 | off: Turn ECRC off | |
3049 | on: Turn ECRC on. | |
8c8803c5 YW |
3050 | hpiosize=nn[KMG] The fixed amount of bus space which is |
3051 | reserved for hotplug bridge's IO window. | |
3052 | Default size is 256 bytes. | |
3053 | hpmemsize=nn[KMG] The fixed amount of bus space which is | |
3054 | reserved for hotplug bridge's memory window. | |
3055 | Default size is 2 megabytes. | |
e16b4660 KB |
3056 | hpbussize=nn The minimum amount of additional bus numbers |
3057 | reserved for buses below a hotplug bridge. | |
3058 | Default is 1. | |
b55438fd YL |
3059 | realloc= Enable/disable reallocating PCI bridge resources |
3060 | if allocations done by BIOS are too small to | |
3061 | accommodate resources required by all child | |
3062 | devices. | |
3063 | off: Turn realloc off | |
3064 | on: Turn realloc on | |
3065 | realloc same as realloc=on | |
6748dcc2 | 3066 | noari do not use PCIe ARI. |
284f5f9d BH |
3067 | pcie_scan_all Scan all possible PCIe devices. Otherwise we |
3068 | only look for one device below a PCIe downstream | |
3069 | port. | |
6b4b78fe | 3070 | |
e5665a45 CE |
3071 | pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power |
3072 | Management. | |
3073 | off Disable ASPM. | |
3074 | force Enable ASPM even on devices that claim not to support it. | |
3075 | WARNING: Forcing ASPM on may cause system lockups. | |
3076 | ||
7570a333 MT |
3077 | pcie_hp= [PCIE] PCI Express Hotplug driver options: |
3078 | nomsi Do not use MSI for PCI Express Native Hotplug (this | |
3079 | makes all PCIe ports use INTx for hotplug services). | |
3080 | ||
79dd9182 | 3081 | pcie_ports= [PCIE] PCIe ports handling: |
28eb5f27 RW |
3082 | auto Ask the BIOS whether or not to use native PCIe services |
3083 | associated with PCIe ports (PME, hot-plug, AER). Use | |
3084 | them only if that is allowed by the BIOS. | |
3085 | native Use native PCIe services associated with PCIe ports | |
3086 | unconditionally. | |
79dd9182 RW |
3087 | compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe |
3088 | ports driver. | |
3089 | ||
9d26d3a8 MW |
3090 | pcie_port_pm= [PCIE] PCIe port power management handling: |
3091 | off Disable power management of all PCIe ports | |
3092 | force Forcibly enable power management of all PCIe ports | |
3093 | ||
c7f48656 | 3094 | pcie_pme= [PCIE,PM] Native PCIe PME signaling options: |
c39fae14 | 3095 | nomsi Do not use MSI for native PCIe PME signaling (this makes |
28eb5f27 | 3096 | all PCIe root ports use INTx for all services). |
c7f48656 | 3097 | |
1da177e4 LT |
3098 | pcmv= [HW,PCMCIA] BadgePAD 4 |
3099 | ||
39ac5ba5 TB |
3100 | pd_ignore_unused |
3101 | [PM] | |
3102 | Keep all power-domains already enabled by bootloader on, | |
3103 | even if no driver has claimed them. This is useful | |
3104 | for debug and development, but should not be | |
3105 | needed on a platform with proper driver support. | |
3106 | ||
1da177e4 | 3107 | pd. [PARIDE] |
31c00fc1 | 3108 | See Documentation/blockdev/paride.txt. |
1da177e4 LT |
3109 | |
3110 | pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at | |
3111 | boot time. | |
3112 | Format: { 0 | 1 } | |
3113 | See arch/parisc/kernel/pdc_chassis.c | |
3114 | ||
f58dc01b | 3115 | percpu_alloc= Select which percpu first chunk allocator to use. |
e933a73f TH |
3116 | Currently supported values are "embed" and "page". |
3117 | Archs may support subset or none of the selections. | |
3118 | See comments in mm/percpu.c for details on each | |
3119 | allocator. This parameter is primarily for debugging | |
3120 | and performance comparison. | |
fa8a7094 | 3121 | |
1da177e4 | 3122 | pf. [PARIDE] |
31c00fc1 | 3123 | See Documentation/blockdev/paride.txt. |
1da177e4 LT |
3124 | |
3125 | pg. [PARIDE] | |
31c00fc1 | 3126 | See Documentation/blockdev/paride.txt. |
1da177e4 LT |
3127 | |
3128 | pirq= [SMP,APIC] Manual mp-table setup | |
71cced6e | 3129 | See Documentation/x86/i386/IO-APIC.txt. |
1da177e4 LT |
3130 | |
3131 | plip= [PPT,NET] Parallel port network link | |
3132 | Format: { parport<nr> | timid | 0 } | |
3133 | See also Documentation/parport.txt. | |
3134 | ||
16290246 | 3135 | pmtmr= [X86] Manual setup of pmtmr I/O Port. |
de32a243 TG |
3136 | Override pmtimer IOPort with a hex value. |
3137 | e.g. pmtmr=0x508 | |
3138 | ||
96242116 BH |
3139 | pnp.debug=1 [PNP] |
3140 | Enable PNP debug messages (depends on the | |
3141 | CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time | |
3142 | via /sys/module/pnp/parameters/debug. We always show | |
3143 | current resource usage; turning this on also shows | |
3144 | possible settings and some assignment information. | |
97ef062b | 3145 | |
1da177e4 LT |
3146 | pnpacpi= [ACPI] |
3147 | { off } | |
3148 | ||
3149 | pnpbios= [ISAPNP] | |
3150 | { on | off | curr | res | no-curr | no-res } | |
3151 | ||
3152 | pnp_reserve_irq= | |
3153 | [ISAPNP] Exclude IRQs for the autoconfiguration | |
3154 | ||
3155 | pnp_reserve_dma= | |
3156 | [ISAPNP] Exclude DMAs for the autoconfiguration | |
3157 | ||
3158 | pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration | |
a9913044 | 3159 | Ranges are in pairs (I/O port base and size). |
1da177e4 LT |
3160 | |
3161 | pnp_reserve_mem= | |
a9913044 RD |
3162 | [ISAPNP] Exclude memory regions for the |
3163 | autoconfiguration. | |
1da177e4 LT |
3164 | Ranges are in pairs (memory base and size). |
3165 | ||
4af94f39 RD |
3166 | ports= [IP_VS_FTP] IPVS ftp helper module |
3167 | Default is 21. | |
3168 | Up to 8 (IP_VS_APP_MAX_PORTS) ports | |
3169 | may be specified. | |
3170 | Format: <port>,<port>.... | |
3171 | ||
3eb5d588 AB |
3172 | ppc_strict_facility_enable |
3173 | [PPC] This option catches any kernel floating point, | |
3174 | Altivec, VSX and SPE outside of regions specifically | |
3175 | allowed (eg kernel_enable_fpu()/kernel_disable_fpu()). | |
3176 | There is some performance impact when enabling this. | |
3177 | ||
45807a1d IM |
3178 | print-fatal-signals= |
3179 | [KNL] debug: print fatal signals | |
f84d49b2 NO |
3180 | |
3181 | If enabled, warn about various signal handling | |
3182 | related application anomalies: too many signals, | |
3183 | too many POSIX.1 timers, fatal signals causing a | |
3184 | coredump - etc. | |
3185 | ||
3186 | If you hit the warning due to signal overflow, | |
3187 | you might want to try "ulimit -i unlimited". | |
3188 | ||
45807a1d IM |
3189 | default: off. |
3190 | ||
c22ab332 MG |
3191 | printk.always_kmsg_dump= |
3192 | Trigger kmsg_dump for cases other than kernel oops or | |
3193 | panics | |
3194 | Format: <bool> (1/Y/y=enable, 0/N/n=disable) | |
3195 | default: disabled | |
3196 | ||
750afe7b BP |
3197 | printk.devkmsg={on,off,ratelimit} |
3198 | Control writing to /dev/kmsg. | |
3199 | on - unlimited logging to /dev/kmsg from userspace | |
3200 | off - logging to /dev/kmsg disabled | |
3201 | ratelimit - ratelimit the logging | |
3202 | Default: ratelimit | |
3203 | ||
e84845c4 RD |
3204 | printk.time= Show timing data prefixed to each printk message line |
3205 | Format: <bool> (1/Y/y=enable, 0/N/n=disable) | |
3206 | ||
0cb55ad2 RD |
3207 | processor.max_cstate= [HW,ACPI] |
3208 | Limit processor to maximum C-state | |
3209 | max_cstate=9 overrides any DMI blacklist limit. | |
3210 | ||
3211 | processor.nocst [HW,ACPI] | |
3212 | Ignore the _CST method to determine C-states, | |
3213 | instead using the legacy FADT method | |
3214 | ||
1da177e4 | 3215 | profile= [KNL] Enable kernel profiling via /proc/profile |
a9913044 RD |
3216 | Format: [schedule,]<number> |
3217 | Param: "schedule" - profile schedule points. | |
3218 | Param: <number> - step/bucket size as a power of 2 for | |
3219 | statistical time based profiling. | |
b3da2a73 MG |
3220 | Param: "sleep" - profile D-state sleeping (millisecs). |
3221 | Requires CONFIG_SCHEDSTATS | |
c0fe2e69 | 3222 | Param: "kvm" - profile VM exits. |
1da177e4 | 3223 | |
1da177e4 LT |
3224 | prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk |
3225 | before loading. | |
31c00fc1 | 3226 | See Documentation/blockdev/ramdisk.txt. |
1da177e4 | 3227 | |
a9913044 RD |
3228 | psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to |
3229 | probe for; one of (bare|imps|exps|lifebook|any). | |
1da177e4 LT |
3230 | psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports |
3231 | per second. | |
a9913044 RD |
3232 | psmouse.resetafter= [HW,MOUSE] |
3233 | Try to reset the device after so many bad packets | |
1da177e4 LT |
3234 | (0 = never). |
3235 | psmouse.resolution= | |
3236 | [HW,MOUSE] Set desired mouse resolution, in dpi. | |
3237 | psmouse.smartscroll= | |
a9913044 | 3238 | [HW,MOUSE] Controls Logitech smartscroll autorepeat. |
1da177e4 LT |
3239 | 0 = disabled, 1 = enabled (default). |
3240 | ||
dee28e72 MG |
3241 | pstore.backend= Specify the name of the pstore backend to use |
3242 | ||
1da177e4 | 3243 | pt. [PARIDE] |
31c00fc1 | 3244 | See Documentation/blockdev/paride.txt. |
1da177e4 | 3245 | |
dc8c8587 KS |
3246 | pty.legacy_count= |
3247 | [KNL] Number of legacy pty's. Overwrites compiled-in | |
3248 | default number. | |
3249 | ||
7d2c502f | 3250 | quiet [KNL] Disable most log messages |
a9913044 | 3251 | |
1da177e4 LT |
3252 | r128= [HW,DRM] |
3253 | ||
3254 | raid= [HW,RAID] | |
3255 | See Documentation/md.txt. | |
3256 | ||
1da177e4 | 3257 | ramdisk_size= [RAM] Sizes of RAM disks in kilobytes |
31c00fc1 | 3258 | See Documentation/blockdev/ramdisk.txt. |
1da177e4 | 3259 | |
4102adab | 3260 | rcu_nocbs= [KNL] |
3fbfbf7a PM |
3261 | In kernels built with CONFIG_RCU_NOCB_CPU=y, set |
3262 | the specified list of CPUs to be no-callback CPUs. | |
3263 | Invocation of these CPUs' RCU callbacks will | |
a4889858 PM |
3264 | be offloaded to "rcuox/N" kthreads created for |
3265 | that purpose, where "x" is "b" for RCU-bh, "p" | |
3266 | for RCU-preempt, and "s" for RCU-sched, and "N" | |
3267 | is the CPU number. This reduces OS jitter on the | |
3fbfbf7a PM |
3268 | offloaded CPUs, which can be useful for HPC and |
3269 | real-time workloads. It can also improve energy | |
3270 | efficiency for asymmetric multiprocessors. | |
3271 | ||
4102adab | 3272 | rcu_nocb_poll [KNL] |
3fbfbf7a PM |
3273 | Rather than requiring that offloaded CPUs |
3274 | (specified by rcu_nocbs= above) explicitly | |
3275 | awaken the corresponding "rcuoN" kthreads, | |
3276 | make these kthreads poll for callbacks. | |
3277 | This improves the real-time response for the | |
3278 | offloaded CPUs by relieving them of the need to | |
3279 | wake up the corresponding kthread, but degrades | |
3280 | energy efficiency by requiring that the kthreads | |
3281 | periodically wake up to do the polling. | |
3282 | ||
4102adab | 3283 | rcutree.blimit= [KNL] |
97e63f0c PM |
3284 | Set maximum number of finished RCU callbacks to |
3285 | process in one batch. | |
21a1ea9e | 3286 | |
a3dc2948 PM |
3287 | rcutree.dump_tree= [KNL] |
3288 | Dump the structure of the rcu_node combining tree | |
3289 | out at early boot. This is used for diagnostic | |
3290 | purposes, to verify correct tree setup. | |
3291 | ||
0f41c0dd PM |
3292 | rcutree.gp_cleanup_delay= [KNL] |
3293 | Set the number of jiffies to delay each step of | |
3294 | RCU grace-period cleanup. This only has effect | |
3295 | when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set. | |
3296 | ||
37745d28 PM |
3297 | rcutree.gp_init_delay= [KNL] |
3298 | Set the number of jiffies to delay each step of | |
3299 | RCU grace-period initialization. This only has | |
0f41c0dd PM |
3300 | effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT |
3301 | is set. | |
3302 | ||
3303 | rcutree.gp_preinit_delay= [KNL] | |
3304 | Set the number of jiffies to delay each step of | |
3305 | RCU grace-period pre-initialization, that is, | |
3306 | the propagation of recent CPU-hotplug changes up | |
3307 | the rcu_node combining tree. This only has effect | |
3308 | when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set. | |
37745d28 | 3309 | |
7fa27001 PM |
3310 | rcutree.rcu_fanout_exact= [KNL] |
3311 | Disable autobalancing of the rcu_node combining | |
3312 | tree. This is used by rcutorture, and might | |
3313 | possibly be useful for architectures having high | |
3314 | cache-to-cache transfer latencies. | |
37745d28 | 3315 | |
4102adab | 3316 | rcutree.rcu_fanout_leaf= [KNL] |
ee968ac6 PM |
3317 | Change the number of CPUs assigned to each |
3318 | leaf rcu_node structure. Useful for very | |
3319 | large systems, which will choose the value 64, | |
3320 | and for NUMA systems with large remote-access | |
3321 | latencies, which will choose a value aligned | |
3322 | with the appropriate hardware boundaries. | |
f885b7f2 | 3323 | |
4a81e832 PM |
3324 | rcutree.jiffies_till_sched_qs= [KNL] |
3325 | Set required age in jiffies for a | |
3326 | given grace period before RCU starts | |
3327 | soliciting quiescent-state help from | |
3328 | rcu_note_context_switch(). | |
3329 | ||
4102adab | 3330 | rcutree.jiffies_till_first_fqs= [KNL] |
c0f4dfd4 PM |
3331 | Set delay from grace-period initialization to |
3332 | first attempt to force quiescent states. | |
3333 | Units are jiffies, minimum value is zero, | |
3334 | and maximum value is HZ. | |
3335 | ||
4102adab | 3336 | rcutree.jiffies_till_next_fqs= [KNL] |
c0f4dfd4 PM |
3337 | Set delay between subsequent attempts to force |
3338 | quiescent states. Units are jiffies, minimum | |
3339 | value is one, and maximum value is HZ. | |
3340 | ||
21871d7e | 3341 | rcutree.kthread_prio= [KNL,BOOT] |
d2af1ad7 PM |
3342 | Set the SCHED_FIFO priority of the RCU per-CPU |
3343 | kthreads (rcuc/N). This value is also used for | |
3344 | the priority of the RCU boost threads (rcub/N) | |
3345 | and for the RCU grace-period kthreads (rcu_bh, | |
3346 | rcu_preempt, and rcu_sched). If RCU_BOOST is | |
3347 | set, valid values are 1-99 and the default is 1 | |
3348 | (the least-favored priority). Otherwise, when | |
3349 | RCU_BOOST is not set, valid values are 0-99 and | |
3350 | the default is zero (non-realtime operation). | |
21871d7e | 3351 | |
fbce7497 PM |
3352 | rcutree.rcu_nocb_leader_stride= [KNL] |
3353 | Set the number of NOCB kthread groups, which | |
3354 | defaults to the square root of the number of | |
3355 | CPUs. Larger numbers reduces the wakeup overhead | |
3356 | on the per-CPU grace-period kthreads, but increases | |
3357 | that same overhead on each group's leader. | |
3358 | ||
4102adab | 3359 | rcutree.qhimark= [KNL] |
97e63f0c PM |
3360 | Set threshold of queued RCU callbacks beyond which |
3361 | batch limiting is disabled. | |
21a1ea9e | 3362 | |
4102adab | 3363 | rcutree.qlowmark= [KNL] |
24aaef8d RD |
3364 | Set threshold of queued RCU callbacks below which |
3365 | batch limiting is re-enabled. | |
21a1ea9e | 3366 | |
4102adab | 3367 | rcutree.rcu_idle_gp_delay= [KNL] |
c0f4dfd4 PM |
3368 | Set wakeup interval for idle CPUs that have |
3369 | RCU callbacks (RCU_FAST_NO_HZ=y). | |
d40011f6 | 3370 | |
4102adab | 3371 | rcutree.rcu_idle_lazy_gp_delay= [KNL] |
c0f4dfd4 PM |
3372 | Set wakeup interval for idle CPUs that have |
3373 | only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y). | |
3374 | Lazy RCU callbacks are those which RCU can | |
3375 | prove do nothing more than free memory. | |
d40011f6 | 3376 | |
bdea9e34 PM |
3377 | rcuperf.gp_exp= [KNL] |
3378 | Measure performance of expedited synchronous | |
3379 | grace-period primitives. | |
3380 | ||
df37e66b PM |
3381 | rcuperf.holdoff= [KNL] |
3382 | Set test-start holdoff period. The purpose of | |
3383 | this parameter is to delay the start of the | |
3384 | test until boot completes in order to avoid | |
3385 | interference. | |
3386 | ||
bdea9e34 PM |
3387 | rcuperf.nreaders= [KNL] |
3388 | Set number of RCU readers. The value -1 selects | |
3389 | N, where N is the number of CPUs. A value | |
3390 | "n" less than -1 selects N-n+1, where N is again | |
3391 | the number of CPUs. For example, -2 selects N | |
3392 | (the number of CPUs), -3 selects N+1, and so on. | |
3393 | A value of "n" less than or equal to -N selects | |
3394 | a single reader. | |
3395 | ||
3396 | rcuperf.nwriters= [KNL] | |
3397 | Set number of RCU writers. The values operate | |
3398 | the same as for rcuperf.nreaders. | |
3399 | N, where N is the number of CPUs | |
3400 | ||
3401 | rcuperf.perf_runnable= [BOOT] | |
3402 | Start rcuperf running at boot time. | |
3403 | ||
3404 | rcuperf.shutdown= [KNL] | |
3405 | Shut the system down after performance tests | |
3406 | complete. This is useful for hands-off automated | |
3407 | testing. | |
3408 | ||
3409 | rcuperf.perf_type= [KNL] | |
3410 | Specify the RCU implementation to test. | |
3411 | ||
3412 | rcuperf.verbose= [KNL] | |
3413 | Enable additional printk() statements. | |
3414 | ||
38706bc5 PM |
3415 | rcutorture.cbflood_inter_holdoff= [KNL] |
3416 | Set holdoff time (jiffies) between successive | |
3417 | callback-flood tests. | |
3418 | ||
3419 | rcutorture.cbflood_intra_holdoff= [KNL] | |
3420 | Set holdoff time (jiffies) between successive | |
3421 | bursts of callbacks within a given callback-flood | |
3422 | test. | |
3423 | ||
3424 | rcutorture.cbflood_n_burst= [KNL] | |
3425 | Set the number of bursts making up a given | |
3426 | callback-flood test. Set this to zero to | |
3427 | disable callback-flood testing. | |
3428 | ||
3429 | rcutorture.cbflood_n_per_burst= [KNL] | |
3430 | Set the number of callbacks to be registered | |
3431 | in a given burst of a callback-flood test. | |
3432 | ||
4102adab | 3433 | rcutorture.fqs_duration= [KNL] |
21b05de4 PM |
3434 | Set duration of force_quiescent_state bursts |
3435 | in microseconds. | |
dabb8aa9 | 3436 | |
4102adab | 3437 | rcutorture.fqs_holdoff= [KNL] |
21b05de4 PM |
3438 | Set holdoff time within force_quiescent_state bursts |
3439 | in microseconds. | |
dabb8aa9 | 3440 | |
4102adab | 3441 | rcutorture.fqs_stutter= [KNL] |
21b05de4 PM |
3442 | Set wait time between force_quiescent_state bursts |
3443 | in seconds. | |
3444 | ||
3445 | rcutorture.gp_cond= [KNL] | |
3446 | Use conditional/asynchronous update-side | |
3447 | primitives, if available. | |
dabb8aa9 | 3448 | |
4102adab | 3449 | rcutorture.gp_exp= [KNL] |
21b05de4 | 3450 | Use expedited update-side primitives, if available. |
4102adab PM |
3451 | |
3452 | rcutorture.gp_normal= [KNL] | |
21b05de4 PM |
3453 | Use normal (non-expedited) asynchronous |
3454 | update-side primitives, if available. | |
3455 | ||
3456 | rcutorture.gp_sync= [KNL] | |
3457 | Use normal (non-expedited) synchronous | |
3458 | update-side primitives, if available. If all | |
3459 | of rcutorture.gp_cond=, rcutorture.gp_exp=, | |
3460 | rcutorture.gp_normal=, and rcutorture.gp_sync= | |
3461 | are zero, rcutorture acts as if is interpreted | |
3462 | they are all non-zero. | |
dabb8aa9 | 3463 | |
4102adab | 3464 | rcutorture.n_barrier_cbs= [KNL] |
dabb8aa9 PM |
3465 | Set callbacks/threads for rcu_barrier() testing. |
3466 | ||
4102adab | 3467 | rcutorture.nfakewriters= [KNL] |
dabb8aa9 PM |
3468 | Set number of concurrent RCU writers. These just |
3469 | stress RCU, they don't participate in the actual | |
3470 | test, hence the "fake". | |
3471 | ||
4102adab | 3472 | rcutorture.nreaders= [KNL] |
3838cc18 PM |
3473 | Set number of RCU readers. The value -1 selects |
3474 | N-1, where N is the number of CPUs. A value | |
3475 | "n" less than -1 selects N-n-2, where N is again | |
3476 | the number of CPUs. For example, -2 selects N | |
3477 | (the number of CPUs), -3 selects N+1, and so on. | |
dabb8aa9 | 3478 | |
4102adab PM |
3479 | rcutorture.object_debug= [KNL] |
3480 | Enable debug-object double-call_rcu() testing. | |
3481 | ||
3482 | rcutorture.onoff_holdoff= [KNL] | |
dabb8aa9 PM |
3483 | Set time (s) after boot for CPU-hotplug testing. |
3484 | ||
4102adab | 3485 | rcutorture.onoff_interval= [KNL] |
dabb8aa9 PM |
3486 | Set time (s) between CPU-hotplug operations, or |
3487 | zero to disable CPU-hotplug testing. | |
3488 | ||
4102adab | 3489 | rcutorture.shuffle_interval= [KNL] |
dabb8aa9 PM |
3490 | Set task-shuffle interval (s). Shuffling tasks |
3491 | allows some CPUs to go into dyntick-idle mode | |
3492 | during the rcutorture test. | |
3493 | ||
4102adab | 3494 | rcutorture.shutdown_secs= [KNL] |
dabb8aa9 PM |
3495 | Set time (s) after boot system shutdown. This |
3496 | is useful for hands-off automated testing. | |
3497 | ||
4102adab | 3498 | rcutorture.stall_cpu= [KNL] |
dabb8aa9 PM |
3499 | Duration of CPU stall (s) to test RCU CPU stall |
3500 | warnings, zero to disable. | |
3501 | ||
4102adab | 3502 | rcutorture.stall_cpu_holdoff= [KNL] |
dabb8aa9 PM |
3503 | Time to wait (s) after boot before inducing stall. |
3504 | ||
4102adab | 3505 | rcutorture.stat_interval= [KNL] |
dabb8aa9 PM |
3506 | Time (s) between statistics printk()s. |
3507 | ||
4102adab | 3508 | rcutorture.stutter= [KNL] |
dabb8aa9 PM |
3509 | Time (s) to stutter testing, for example, specifying |
3510 | five seconds causes the test to run for five seconds, | |
3511 | wait for five seconds, and so on. This tests RCU's | |
3512 | ability to transition abruptly to and from idle. | |
3513 | ||
4102adab | 3514 | rcutorture.test_boost= [KNL] |
dabb8aa9 PM |
3515 | Test RCU priority boosting? 0=no, 1=maybe, 2=yes. |
3516 | "Maybe" means test if the RCU implementation | |
3517 | under test support RCU priority boosting. | |
3518 | ||
4102adab | 3519 | rcutorture.test_boost_duration= [KNL] |
dabb8aa9 PM |
3520 | Duration (s) of each individual boost test. |
3521 | ||
4102adab | 3522 | rcutorture.test_boost_interval= [KNL] |
dabb8aa9 PM |
3523 | Interval (s) between each boost test. |
3524 | ||
4102adab | 3525 | rcutorture.test_no_idle_hz= [KNL] |
dabb8aa9 PM |
3526 | Test RCU's dyntick-idle handling. See also the |
3527 | rcutorture.shuffle_interval parameter. | |
3528 | ||
21b05de4 PM |
3529 | rcutorture.torture_runnable= [BOOT] |
3530 | Start rcutorture running at boot time. | |
3531 | ||
4102adab | 3532 | rcutorture.torture_type= [KNL] |
dabb8aa9 PM |
3533 | Specify the RCU implementation to test. |
3534 | ||
4102adab | 3535 | rcutorture.verbose= [KNL] |
dabb8aa9 PM |
3536 | Enable additional printk() statements. |
3537 | ||
5a9be7c6 PM |
3538 | rcupdate.rcu_cpu_stall_suppress= [KNL] |
3539 | Suppress RCU CPU stall warning messages. | |
3540 | ||
3541 | rcupdate.rcu_cpu_stall_timeout= [KNL] | |
3542 | Set timeout for RCU CPU stall warning messages. | |
3543 | ||
4102adab PM |
3544 | rcupdate.rcu_expedited= [KNL] |
3545 | Use expedited grace-period primitives, for | |
3546 | example, synchronize_rcu_expedited() instead | |
3547 | of synchronize_rcu(). This reduces latency, | |
3548 | but can increase CPU utilization, degrade | |
3549 | real-time latency, and degrade energy efficiency. | |
79cfea02 | 3550 | No effect on CONFIG_TINY_RCU kernels. |
4102adab | 3551 | |
5a9be7c6 PM |
3552 | rcupdate.rcu_normal= [KNL] |
3553 | Use only normal grace-period primitives, | |
3554 | for example, synchronize_rcu() instead of | |
3555 | synchronize_rcu_expedited(). This improves | |
79cfea02 PM |
3556 | real-time latency, CPU utilization, and |
3557 | energy efficiency, but can expose users to | |
3558 | increased grace-period latency. This parameter | |
3559 | overrides rcupdate.rcu_expedited. No effect on | |
3560 | CONFIG_TINY_RCU kernels. | |
4102adab | 3561 | |
3e42ec1a PM |
3562 | rcupdate.rcu_normal_after_boot= [KNL] |
3563 | Once boot has completed (that is, after | |
3564 | rcu_end_inkernel_boot() has been invoked), use | |
79cfea02 PM |
3565 | only normal grace-period primitives. No effect |
3566 | on CONFIG_TINY_RCU kernels. | |
3e42ec1a | 3567 | |
52db30ab PM |
3568 | rcupdate.rcu_task_stall_timeout= [KNL] |
3569 | Set timeout in jiffies for RCU task stall warning | |
3570 | messages. Disable with a value less than or equal | |
3571 | to zero. | |
3572 | ||
74860fee PK |
3573 | rcupdate.rcu_self_test= [KNL] |
3574 | Run the RCU early boot self tests | |
3575 | ||
3576 | rcupdate.rcu_self_test_bh= [KNL] | |
3577 | Run the RCU bh early boot self tests | |
3578 | ||
3579 | rcupdate.rcu_self_test_sched= [KNL] | |
3580 | Run the RCU sched early boot self tests | |
3581 | ||
ffdfc409 OJ |
3582 | rdinit= [KNL] |
3583 | Format: <full_path> | |
3584 | Run specified binary instead of /init from the ramdisk, | |
3585 | used for early userspace startup. See initrd. | |
3586 | ||
1b3a5d02 RH |
3587 | reboot= [KNL] |
3588 | Format (x86 or x86_64): | |
3589 | [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \ | |
3590 | [[,]s[mp]#### \ | |
3591 | [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \ | |
3592 | [[,]f[orce] | |
3593 | Where reboot_mode is one of warm (soft) or cold (hard) or gpio, | |
3594 | reboot_type is one of bios, acpi, kbd, triple, efi, or pci, | |
3595 | reboot_force is either force or not specified, | |
3596 | reboot_cpu is s[mp]#### with #### being the processor | |
3597 | to be used for rebooting. | |
1da177e4 | 3598 | |
46b6d94e PJ |
3599 | relax_domain_level= |
3600 | [KNL, SMP] Set scheduler's default relax_domain_level. | |
09c3bcce | 3601 | See Documentation/cgroup-v1/cpusets.txt. |
46b6d94e | 3602 | |
0399d4db RW |
3603 | relative_sleep_states= |
3604 | [SUSPEND] Use sleep state labeling where the deepest | |
3605 | state available other than hibernation is always "mem". | |
3606 | Format: { "0" | "1" } | |
3607 | 0 -- Traditional sleep state labels. | |
3608 | 1 -- Relative sleep state labels. | |
3609 | ||
1da177e4 LT |
3610 | reserve= [KNL,BUGS] Force the kernel to ignore some iomem area |
3611 | ||
cd4f0ef7 | 3612 | reservetop= [X86-32] |
461a9aff ZA |
3613 | Format: nn[KMG] |
3614 | Reserves a hole at the top of the kernel virtual | |
3615 | address space. | |
3616 | ||
9ea77bdb PA |
3617 | reservelow= [X86] |
3618 | Format: nn[K] | |
3619 | Set the amount of memory to reserve for BIOS at | |
3620 | the bottom of the address space. | |
3621 | ||
7e96287d VG |
3622 | reset_devices [KNL] Force drivers to reset the underlying device |
3623 | during initialization. | |
3624 | ||
a9913044 RD |
3625 | resume= [SWSUSP] |
3626 | Specify the partition device for software suspend | |
2df83fa4 MB |
3627 | Format: |
3628 | {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>} | |
1da177e4 | 3629 | |
ecbd0da1 RW |
3630 | resume_offset= [SWSUSP] |
3631 | Specify the offset from the beginning of the partition | |
3632 | given by "resume=" at which the swap header is located, | |
3633 | in <PAGE_SIZE> units (needed only for swap files). | |
3634 | See Documentation/power/swsusp-and-swap-files.txt | |
3635 | ||
f126f733 BS |
3636 | resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to |
3637 | read the resume files | |
3638 | ||
6f8d7022 BS |
3639 | resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up. |
3640 | Useful for devices that are detected asynchronously | |
3641 | (e.g. USB and MMC devices). | |
3642 | ||
f996fc96 BS |
3643 | hibernate= [HIBERNATION] |
3644 | noresume Don't check if there's a hibernation image | |
3645 | present during boot. | |
3646 | nocompress Don't compress/decompress hibernation images. | |
a6e15a39 | 3647 | no Disable hibernation and resume. |
4c0b6c10 RW |
3648 | protect_image Turn on image protection during restoration |
3649 | (that will set all pages holding image data | |
3650 | during restoration read-only). | |
f996fc96 | 3651 | |
0a7b35cb MN |
3652 | retain_initrd [RAM] Keep initrd memory after extraction |
3653 | ||
0efbb786 AC |
3654 | rfkill.default_state= |
3655 | 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm, | |
3656 | etc. communication is blocked by default. | |
3657 | 1 Unblocked. | |
3658 | ||
3659 | rfkill.master_switch_mode= | |
3660 | 0 The "airplane mode" button does nothing. | |
3661 | 1 The "airplane mode" button toggles between everything | |
3662 | blocked and the previous configuration. | |
3663 | 2 The "airplane mode" button toggles between everything | |
3664 | blocked and everything unblocked. | |
3665 | ||
1da177e4 LT |
3666 | rhash_entries= [KNL,NET] |
3667 | Set number of hash buckets for route cache | |
3668 | ||
1da177e4 LT |
3669 | ro [KNL] Mount root device read-only on boot |
3670 | ||
d2aa1aca KC |
3671 | rodata= [KNL] |
3672 | on Mark read-only kernel memory as read-only (default). | |
3673 | off Leave read-only kernel memory writable for debugging. | |
3674 | ||
605df8af HS |
3675 | rockchip.usb_uart |
3676 | Enable the uart passthrough on the designated usb port | |
3677 | on Rockchip SoCs. When active, the signals of the | |
3678 | debug-uart get routed to the D+ and D- pins of the usb | |
3679 | port and the regular usb controller gets disabled. | |
3680 | ||
1da177e4 | 3681 | root= [KNL] Root filesystem |
f2d34fd9 | 3682 | See name_to_dev_t comment in init/do_mounts.c. |
1da177e4 LT |
3683 | |
3684 | rootdelay= [KNL] Delay (in seconds) to pause before attempting to | |
3685 | mount the root filesystem | |
3686 | ||
3687 | rootflags= [KNL] Set root filesystem mount option string | |
3688 | ||
3689 | rootfstype= [KNL] Set root filesystem type | |
3690 | ||
cc1ed754 PO |
3691 | rootwait [KNL] Wait (indefinitely) for root device to show up. |
3692 | Useful for devices that are detected asynchronously | |
3693 | (e.g. USB and MMC devices). | |
3694 | ||
5c71d618 RT |
3695 | rproc_mem=nn[KMG][@address] |
3696 | [KNL,ARM,CMA] Remoteproc physical memory block. | |
3697 | Memory area to be used by remote processor image, | |
3698 | managed by CMA. | |
3699 | ||
1da177e4 LT |
3700 | rw [KNL] Mount root device read-write on boot |
3701 | ||
3702 | S [KNL] Run init in single mode | |
3703 | ||
c60d1ae4 GS |
3704 | s390_iommu= [HW,S390] |
3705 | Set s390 IOTLB flushing mode | |
3706 | strict | |
3707 | With strict flushing every unmap operation will result in | |
3708 | an IOTLB flush. Default is lazy flushing before reuse, | |
3709 | which is faster. | |
3710 | ||
1da177e4 LT |
3711 | sa1100ir [NET] |
3712 | See drivers/net/irda/sa1100_ir.c. | |
3713 | ||
1da177e4 | 3714 | sbni= [NET] Granch SBNI12 leased line adapter |
a9913044 | 3715 | |
f6630114 MT |
3716 | sched_debug [KNL] Enables verbose scheduler debug messages. |
3717 | ||
cb251765 MG |
3718 | schedstats= [KNL,X86] Enable or disable scheduled statistics. |
3719 | Allowed values are enable and disable. This feature | |
3720 | incurs a small amount of overhead in the scheduler | |
3721 | but is useful for debugging and performance tuning. | |
f6630114 | 3722 | |
5307c955 MG |
3723 | skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate |
3724 | xtime_lock contention on larger systems, and/or RCU lock | |
3725 | contention on all systems with CONFIG_MAXSMP set. | |
3726 | Format: { "0" | "1" } | |
3727 | 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1" | |
3728 | 1 -- enable. | |
3729 | Note: increases power consumption, thus should only be | |
3730 | enabled if running jitter sensitive (HPC/RT) workloads. | |
3731 | ||
0cb55ad2 RD |
3732 | security= [SECURITY] Choose a security module to enable at boot. |
3733 | If this boot parameter is not specified, only the first | |
3734 | security module asking for security registration will be | |
3735 | loaded. An invalid security module name will be treated | |
3736 | as if no module has been chosen. | |
3737 | ||
3738 | selinux= [SELINUX] Disable or enable SELinux at boot time. | |
1da177e4 LT |
3739 | Format: { "0" | "1" } |
3740 | See security/selinux/Kconfig help text. | |
3741 | 0 -- disable. | |
3742 | 1 -- enable. | |
3743 | Default value is set via kernel config option. | |
3744 | If enabled at boot time, /selinux/disable can be used | |
3745 | later to disable prior to initial policy load. | |
3746 | ||
c1c124e9 JJ |
3747 | apparmor= [APPARMOR] Disable or enable AppArmor at boot time |
3748 | Format: { "0" | "1" } | |
3749 | See security/apparmor/Kconfig help text | |
3750 | 0 -- disable. | |
3751 | 1 -- enable. | |
3752 | Default value is set via kernel config option. | |
3753 | ||
cd4f0ef7 | 3754 | serialnumber [BUGS=X86-32] |
1da177e4 | 3755 | |
1da177e4 LT |
3756 | shapers= [NET] |
3757 | Maximal number of shapers. | |
a9913044 | 3758 | |
b05f78f5 YL |
3759 | show_msr= [x86] show boot-time MSR settings |
3760 | Format: { <integer> } | |
3761 | Show boot-time (BIOS-initialized) MSR settings. | |
3762 | The parameter means the number of CPUs to show, | |
3763 | for example 1 means boot CPU only. | |
3764 | ||
1da177e4 LT |
3765 | simeth= [IA-64] |
3766 | simscsi= | |
a9913044 | 3767 | |
1da177e4 LT |
3768 | slram= [HW,MTD] |
3769 | ||
423c929c JK |
3770 | slab_nomerge [MM] |
3771 | Disable merging of slabs with similar size. May be | |
3772 | necessary if there is some reason to distinguish | |
3773 | allocs to different slabs. Debug options disable | |
3774 | merging on their own. | |
3775 | For more information see Documentation/vm/slub.txt. | |
3776 | ||
3df1cccd DR |
3777 | slab_max_order= [MM, SLAB] |
3778 | Determines the maximum allowed order for slabs. | |
3779 | A high setting may cause OOMs due to memory | |
3780 | fragmentation. Defaults to 1 for systems with | |
3781 | more than 32MB of RAM, 0 otherwise. | |
3782 | ||
f0630fff CL |
3783 | slub_debug[=options[,slabs]] [MM, SLUB] |
3784 | Enabling slub_debug allows one to determine the | |
3785 | culprit if slab objects become corrupted. Enabling | |
3786 | slub_debug can create guard zones around objects and | |
3787 | may poison objects when not in use. Also tracks the | |
3788 | last alloc / free. For more information see | |
3789 | Documentation/vm/slub.txt. | |
c1aee215 CL |
3790 | |
3791 | slub_max_order= [MM, SLUB] | |
f0630fff CL |
3792 | Determines the maximum allowed order for slabs. |
3793 | A high setting may cause OOMs due to memory | |
3794 | fragmentation. For more information see | |
3795 | Documentation/vm/slub.txt. | |
c1aee215 CL |
3796 | |
3797 | slub_min_objects= [MM, SLUB] | |
f0630fff CL |
3798 | The minimum number of objects per slab. SLUB will |
3799 | increase the slab order up to slub_max_order to | |
3800 | generate a sufficiently large slab able to contain | |
3801 | the number of objects indicated. The higher the number | |
3802 | of objects the smaller the overhead of tracking slabs | |
3803 | and the less frequently locks need to be acquired. | |
c1aee215 CL |
3804 | For more information see Documentation/vm/slub.txt. |
3805 | ||
3806 | slub_min_order= [MM, SLUB] | |
24775d65 | 3807 | Determines the minimum page order for slabs. Must be |
f0630fff | 3808 | lower than slub_max_order. |
c1aee215 CL |
3809 | For more information see Documentation/vm/slub.txt. |
3810 | ||
3811 | slub_nomerge [MM, SLUB] | |
423c929c JK |
3812 | Same with slab_nomerge. This is supported for legacy. |
3813 | See slab_nomerge for more information. | |
c1aee215 | 3814 | |
1da177e4 LT |
3815 | smart2= [HW] |
3816 | Format: <io1>[,<io2>[,...,<io8>]] | |
3817 | ||
d0d4f69b BH |
3818 | smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices |
3819 | smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port | |
3820 | smsc-ircc2.ircc_sir= [HW] SIR base I/O port | |
3821 | smsc-ircc2.ircc_fir= [HW] FIR base I/O port | |
3822 | smsc-ircc2.ircc_irq= [HW] IRQ line | |
3823 | smsc-ircc2.ircc_dma= [HW] DMA channel | |
3824 | smsc-ircc2.ircc_transceiver= [HW] Transceiver type: | |
3825 | 0: Toshiba Satellite 1800 (GP data pin select) | |
3826 | 1: Fast pin select (default) | |
3827 | 2: ATC IRMode | |
3828 | ||
52c48c51 SS |
3829 | smt [KNL,S390] Set the maximum number of threads (logical |
3830 | CPUs) to use per physical CPU on systems capable of | |
3831 | symmetric multithreading (SMT). Will be capped to the | |
3832 | actual hardware limit. | |
3833 | Format: <integer> | |
3834 | Default: -1 (no limit) | |
3835 | ||
9c44bc03 IM |
3836 | softlockup_panic= |
3837 | [KNL] Should the soft-lockup detector generate panics. | |
44a4dcf7 | 3838 | Format: <integer> |
9c44bc03 | 3839 | |
ed235875 AT |
3840 | softlockup_all_cpu_backtrace= |
3841 | [KNL] Should the soft-lockup detector generate | |
3842 | backtraces on all cpus. | |
3843 | Format: <integer> | |
3844 | ||
1da177e4 | 3845 | sonypi.*= [HW] Sony Programmable I/O Control Device driver |
395cf969 | 3846 | See Documentation/laptops/sonypi.txt |
1da177e4 | 3847 | |
1da177e4 LT |
3848 | spia_io_base= [HW,MTD] |
3849 | spia_fio_base= | |
3850 | spia_pedr= | |
3851 | spia_peddr= | |
3852 | ||
f38f1d2a SR |
3853 | stacktrace [FTRACE] |
3854 | Enabled the stack tracer on boot up. | |
3855 | ||
762e1207 SR |
3856 | stacktrace_filter=[function-list] |
3857 | [FTRACE] Limit the functions that the stack tracer | |
3858 | will trace at boot up. function-list is a comma separated | |
3859 | list of functions. This list can be changed at run | |
3860 | time by the stack_trace_filter file in the debugfs | |
3861 | tracing directory. Note, this enables stack tracing | |
3862 | and the stacktrace above is not needed. | |
3863 | ||
1da177e4 LT |
3864 | sti= [PARISC,HW] |
3865 | Format: <num> | |
3866 | Set the STI (builtin display/keyboard on the HP-PARISC | |
3867 | machines) console (graphic card) which should be used | |
3868 | as the initial boot-console. | |
3869 | See also comment in drivers/video/console/sticore.c. | |
3870 | ||
3871 | sti_font= [HW] | |
3872 | See comment in drivers/video/console/sticore.c. | |
3873 | ||
3874 | stifb= [HW] | |
3875 | Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] | |
3876 | ||
cbf11071 TM |
3877 | sunrpc.min_resvport= |
3878 | sunrpc.max_resvport= | |
3879 | [NFS,SUNRPC] | |
3880 | SunRPC servers often require that client requests | |
3881 | originate from a privileged port (i.e. a port in the | |
3882 | range 0 < portnr < 1024). | |
3883 | An administrator who wishes to reserve some of these | |
3884 | ports for other uses may adjust the range that the | |
3885 | kernel's sunrpc client considers to be privileged | |
3886 | using these two parameters to set the minimum and | |
3887 | maximum port values. | |
3888 | ||
ff3ac5c3 TM |
3889 | sunrpc.svc_rpc_per_connection_limit= |
3890 | [NFS,SUNRPC] | |
3891 | Limit the number of requests that the server will | |
3892 | process in parallel from a single connection. | |
3893 | The default value is 0 (no limit). | |
3894 | ||
42a7fc4a GB |
3895 | sunrpc.pool_mode= |
3896 | [NFS] | |
3897 | Control how the NFS server code allocates CPUs to | |
3898 | service thread pools. Depending on how many NICs | |
3899 | you have and where their interrupts are bound, this | |
3900 | option will affect which CPUs will do NFS serving. | |
3901 | Note: this parameter cannot be changed while the | |
3902 | NFS server is running. | |
3903 | ||
3904 | auto the server chooses an appropriate mode | |
3905 | automatically using heuristics | |
3906 | global a single global pool contains all CPUs | |
3907 | percpu one pool for each CPU | |
3908 | pernode one pool for each NUMA node (equivalent | |
3909 | to global on non-NUMA machines) | |
3910 | ||
cbf11071 TM |
3911 | sunrpc.tcp_slot_table_entries= |
3912 | sunrpc.udp_slot_table_entries= | |
3913 | [NFS,SUNRPC] | |
3914 | Sets the upper limit on the number of simultaneous | |
3915 | RPC calls that can be sent from the client to a | |
3916 | server. Increasing these values may allow you to | |
3917 | improve throughput, but will also increase the | |
3918 | amount of memory reserved for use by the client. | |
3919 | ||
1d4a9c17 BN |
3920 | suspend.pm_test_delay= |
3921 | [SUSPEND] | |
3922 | Sets the number of seconds to remain in a suspend test | |
3923 | mode before resuming the system (see | |
3924 | /sys/power/pm_test). Only available when CONFIG_PM_DEBUG | |
3925 | is set. Default value is 5. | |
3926 | ||
07555ac1 | 3927 | swapaccount=[0|1] |
a42c390c MH |
3928 | [KNL] Enable accounting of swap in memory resource |
3929 | controller if no parameter or 1 is given or disable | |
09c3bcce | 3930 | it if 0 is given (See Documentation/cgroup-v1/memory.txt) |
a42c390c | 3931 | |
91fec0f5 JK |
3932 | swiotlb= [ARM,IA-64,PPC,MIPS,X86] |
3933 | Format: { <int> | force } | |
3934 | <int> -- Number of I/O TLB slabs | |
3935 | force -- force using of bounce buffers even if they | |
3936 | wouldn't be automatically used by the kernel | |
a9913044 | 3937 | |
1da177e4 LT |
3938 | switches= [HW,M68k] |
3939 | ||
e52eec13 AK |
3940 | sysfs.deprecated=0|1 [KNL] |
3941 | Enable/disable old style sysfs layout for old udev | |
3942 | on older distributions. When this option is enabled | |
3943 | very new udev will not work anymore. When this option | |
3944 | is disabled (or CONFIG_SYSFS_DEPRECATED not compiled) | |
3945 | in older udev will not work anymore. | |
3946 | Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in | |
3947 | the kernel configuration. | |
3948 | ||
5d6f647f IM |
3949 | sysrq_always_enabled |
3950 | [KNL] | |
3951 | Ignore sysrq setting - this boot parameter will | |
3952 | neutralize any effect of /proc/sys/kernel/sysrq. | |
3953 | Useful for debugging. | |
3954 | ||
747029a5 FF |
3955 | tcpmhash_entries= [KNL,NET] |
3956 | Set the number of tcp_metrics_hash slots. | |
3957 | Default value is 8192 or 16384 depending on total | |
3958 | ram pages. This is used to specify the TCP metrics | |
3959 | cache size. See Documentation/networking/ip-sysctl.txt | |
3960 | "tcp_no_metrics_save" section for more details. | |
3961 | ||
1da177e4 LT |
3962 | tdfx= [HW,DRM] |
3963 | ||
acc82342 | 3964 | test_suspend= [SUSPEND][,N] |
77437fd4 | 3965 | Specify "mem" (for Suspend-to-RAM) or "standby" (for |
acc82342 SP |
3966 | standby suspend) or "freeze" (for suspend type freeze) |
3967 | as the system sleep state during system startup with | |
3968 | the optional capability to repeat N number of times. | |
3969 | The system is woken from this state using a | |
3970 | wakeup-capable RTC alarm. | |
77437fd4 | 3971 | |
1da177e4 LT |
3972 | thash_entries= [KNL,NET] |
3973 | Set number of hash buckets for TCP connection | |
3974 | ||
f8707ec9 LB |
3975 | thermal.act= [HW,ACPI] |
3976 | -1: disable all active trip points in all thermal zones | |
3977 | <degrees C>: override all lowest active trip points | |
3978 | ||
c52a7419 LB |
3979 | thermal.crt= [HW,ACPI] |
3980 | -1: disable all critical trip points in all thermal zones | |
22a94d79 | 3981 | <degrees C>: override all critical trip points |
c52a7419 | 3982 | |
f5487145 LB |
3983 | thermal.nocrt= [HW,ACPI] |
3984 | Set to disable actions on ACPI thermal zone | |
3985 | critical and hot trip points. | |
3986 | ||
72b33ef8 LB |
3987 | thermal.off= [HW,ACPI] |
3988 | 1: disable ACPI thermal control | |
3989 | ||
a70cdc52 LB |
3990 | thermal.psv= [HW,ACPI] |
3991 | -1: disable all passive trip points | |
ada9cfdd RD |
3992 | <degrees C>: override all passive trip points to this |
3993 | value | |
a70cdc52 | 3994 | |
730ff34d LB |
3995 | thermal.tzp= [HW,ACPI] |
3996 | Specify global default ACPI thermal zone polling rate | |
3997 | <deci-seconds>: poll all this frequency | |
3998 | 0: no polling (default) | |
3999 | ||
8d32a307 TG |
4000 | threadirqs [KNL] |
4001 | Force threading of all interrupt handlers except those | |
24775d65 | 4002 | marked explicitly IRQF_NO_THREAD. |
8d32a307 | 4003 | |
2ca62b04 KRW |
4004 | tmem [KNL,XEN] |
4005 | Enable the Transcendent memory driver if built-in. | |
4006 | ||
4007 | tmem.cleancache=0|1 [KNL, XEN] | |
4008 | Default is on (1). Disable the usage of the cleancache | |
4009 | API to send anonymous pages to the hypervisor. | |
4010 | ||
4011 | tmem.frontswap=0|1 [KNL, XEN] | |
4012 | Default is on (1). Disable the usage of the frontswap | |
37d46e15 KRW |
4013 | API to send swap pages to the hypervisor. If disabled |
4014 | the selfballooning and selfshrinking are force disabled. | |
2ca62b04 KRW |
4015 | |
4016 | tmem.selfballooning=0|1 [KNL, XEN] | |
4017 | Default is on (1). Disable the driving of swap pages | |
4018 | to the hypervisor. | |
4019 | ||
4020 | tmem.selfshrinking=0|1 [KNL, XEN] | |
4021 | Default is on (1). Partial swapoff that immediately | |
4022 | transfers pages from Xen hypervisor back to the | |
4023 | kernel based on different criteria. | |
4024 | ||
2b1a61f0 HC |
4025 | topology= [S390] |
4026 | Format: {off | on} | |
4027 | Specify if the kernel should make use of the cpu | |
f65e51d7 SL |
4028 | topology information if the hardware supports this. |
4029 | The scheduler will make use of this information and | |
2b1a61f0 | 4030 | e.g. base its process migration decisions on it. |
c9af3fa9 | 4031 | Default is on. |
2b1a61f0 | 4032 | |
2d73bae1 NA |
4033 | topology_updates= [KNL, PPC, NUMA] |
4034 | Format: {off} | |
4035 | Specify if the kernel should ignore (off) | |
4036 | topology updates sent by the hypervisor to this | |
4037 | LPAR. | |
4038 | ||
1da177e4 LT |
4039 | tp720= [HW,PS2] |
4040 | ||
225a9be2 RA |
4041 | tpm_suspend_pcr=[HW,TPM] |
4042 | Format: integer pcr id | |
4043 | Specify that at suspend time, the tpm driver | |
4044 | should extend the specified pcr with zeros, | |
4045 | as a workaround for some chips which fail to | |
4046 | flush the last written pcr on TPM_SaveState. | |
4047 | This will guarantee that all the other pcrs | |
4048 | are saved. | |
4049 | ||
9d612bef | 4050 | trace_buf_size=nn[KMG] |
3e6fb8e9 | 4051 | [FTRACE] will set tracing buffer size on each cpu. |
631595fb | 4052 | |
020e5f85 LZ |
4053 | trace_event=[event-list] |
4054 | [FTRACE] Set and start specified trace events in order | |
d81749ea BN |
4055 | to facilitate early boot debugging. The event-list is a |
4056 | comma separated list of trace events to enable. See | |
4057 | also Documentation/trace/events.txt | |
020e5f85 | 4058 | |
7bcfaf54 SR |
4059 | trace_options=[option-list] |
4060 | [FTRACE] Enable or disable tracer options at boot. | |
4061 | The option-list is a comma delimited list of options | |
4062 | that can be enabled or disabled just as if you were | |
4063 | to echo the option name into | |
4064 | ||
4065 | /sys/kernel/debug/tracing/trace_options | |
4066 | ||
4067 | For example, to enable stacktrace option (to dump the | |
4068 | stack trace of each event), add to the command line: | |
4069 | ||
4070 | trace_options=stacktrace | |
4071 | ||
4072 | See also Documentation/trace/ftrace.txt "trace options" | |
4073 | section. | |
4074 | ||
0daa2302 SRRH |
4075 | tp_printk[FTRACE] |
4076 | Have the tracepoints sent to printk as well as the | |
4077 | tracing ring buffer. This is useful for early boot up | |
4078 | where the system hangs or reboots and does not give the | |
4079 | option for reading the tracing buffer or performing a | |
4080 | ftrace_dump_on_oops. | |
4081 | ||
4082 | To turn off having tracepoints sent to printk, | |
4083 | echo 0 > /proc/sys/kernel/tracepoint_printk | |
4084 | Note, echoing 1 into this file without the | |
4085 | tracepoint_printk kernel cmdline option has no effect. | |
4086 | ||
4087 | ** CAUTION ** | |
4088 | ||
4089 | Having tracepoints sent to printk() and activating high | |
4090 | frequency tracepoints such as irq or sched, can cause | |
4091 | the system to live lock. | |
4092 | ||
de7edd31 SRRH |
4093 | traceoff_on_warning |
4094 | [FTRACE] enable this option to disable tracing when a | |
4095 | warning is hit. This turns off "tracing_on". Tracing can | |
4096 | be enabled again by echoing '1' into the "tracing_on" | |
4097 | file located in /sys/kernel/debug/tracing/ | |
4098 | ||
4099 | This option is useful, as it disables the trace before | |
4100 | the WARNING dump is called, which prevents the trace to | |
4101 | be filled with content caused by the warning output. | |
4102 | ||
4103 | This option can also be set at run time via the sysctl | |
4104 | option: kernel/traceoff_on_warning | |
4105 | ||
fcf4d821 JK |
4106 | transparent_hugepage= |
4107 | [KNL] | |
4108 | Format: [always|madvise|never] | |
4109 | Can be used to control the default behavior of the system | |
4110 | with respect to transparent hugepages. | |
4111 | See Documentation/vm/transhuge.txt for more details. | |
4112 | ||
d3b8f889 | 4113 | tsc= Disable clocksource stability checks for TSC. |
395628ef AK |
4114 | Format: <string> |
4115 | [x86] reliable: mark tsc clocksource as reliable, this | |
d3b8f889 | 4116 | disables clocksource verification at runtime, as well |
4117 | as the stability checks done at bootup. Used to enable | |
4118 | high-resolution timer mode on older hardware, and in | |
4119 | virtualized environment. | |
e82b8e4e VP |
4120 | [x86] noirqtime: Do not use TSC to do irq accounting. |
4121 | Used to run time disable IRQ_TIME_ACCOUNTING on any | |
4122 | platforms where RDTSC is slow and this accounting | |
4123 | can add overhead. | |
395628ef | 4124 | |
a9913044 RD |
4125 | turbografx.map[2|3]= [HW,JOY] |
4126 | TurboGraFX parallel port interface | |
4127 | Format: | |
4128 | <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> | |
1da177e4 LT |
4129 | See also Documentation/input/joystick-parport.txt |
4130 | ||
b6935f8c CK |
4131 | udbg-immortal [PPC] When debugging early kernel crashes that |
4132 | happen after console_init() and before a proper | |
4133 | console driver takes over, this boot options might | |
4134 | help "seeing" what's going on. | |
4135 | ||
f86dcc5a ED |
4136 | uhash_entries= [KNL,NET] |
4137 | Set number of hash buckets for UDP/UDP-Lite connections | |
4138 | ||
5f8364b7 AS |
4139 | uhci-hcd.ignore_oc= |
4140 | [USB] Ignore overcurrent events (default N). | |
4141 | Some badly-designed motherboards generate lots of | |
4142 | bogus events, for ports that aren't wired to | |
4143 | anything. Set this parameter to avoid log spamming. | |
4144 | Note that genuine overcurrent events won't be | |
4145 | reported either. | |
4146 | ||
e3a61b0a | 4147 | unknown_nmi_panic |
44a4dcf7 | 4148 | [X86] Cause panic on unknown NMI. |
e3a61b0a | 4149 | |
c4fc2342 CDH |
4150 | usbcore.authorized_default= |
4151 | [USB] Default USB device authorization: | |
4152 | (default -1 = authorized except for wireless USB, | |
4153 | 0 = not authorized, 1 = authorized) | |
4154 | ||
b5e795f8 AS |
4155 | usbcore.autosuspend= |
4156 | [USB] The autosuspend time delay (in seconds) used | |
4157 | for newly-detected USB devices (default 2). This | |
4158 | is the time required before an idle device will be | |
4159 | autosuspended. Devices for which the delay is set | |
eaafbc3a | 4160 | to a negative value won't be autosuspended at all. |
b5e795f8 | 4161 | |
fd7c519d JK |
4162 | usbcore.usbfs_snoop= |
4163 | [USB] Set to log all usbfs traffic (default 0 = off). | |
4164 | ||
0290cc9f AS |
4165 | usbcore.usbfs_snoop_max= |
4166 | [USB] Maximum number of bytes to snoop in each URB | |
4167 | (default = 65536). | |
4168 | ||
fd7c519d JK |
4169 | usbcore.blinkenlights= |
4170 | [USB] Set to cycle leds on hubs (default 0 = off). | |
4171 | ||
4172 | usbcore.old_scheme_first= | |
4173 | [USB] Start with the old device initialization | |
4174 | scheme (default 0 = off). | |
4175 | ||
3f5eb8d5 AS |
4176 | usbcore.usbfs_memory_mb= |
4177 | [USB] Memory limit (in MB) for buffers allocated by | |
4178 | usbfs (default = 16, 0 = max = 2047). | |
4179 | ||
fd7c519d JK |
4180 | usbcore.use_both_schemes= |
4181 | [USB] Try the other device initialization scheme | |
4182 | if the first one fails (default 1 = enabled). | |
4183 | ||
4184 | usbcore.initial_descriptor_timeout= | |
4185 | [USB] Specifies timeout for the initial 64-byte | |
4186 | USB_REQ_GET_DESCRIPTOR request in milliseconds | |
4187 | (default 5000 = 5.0 seconds). | |
4188 | ||
40d58148 ON |
4189 | usbcore.nousb [USB] Disable the USB subsystem |
4190 | ||
1da177e4 LT |
4191 | usbhid.mousepoll= |
4192 | [USBHID] The interval which mice are to be polled at. | |
a9913044 | 4193 | |
d4f373e5 AS |
4194 | usb-storage.delay_use= |
4195 | [UMS] The delay in seconds before a new device is | |
19101954 | 4196 | scanned for Logical Units (default 1). |
d4f373e5 AS |
4197 | |
4198 | usb-storage.quirks= | |
4199 | [UMS] A list of quirks entries to supplement or | |
4200 | override the built-in unusual_devs list. List | |
4201 | entries are separated by commas. Each entry has | |
4202 | the form VID:PID:Flags where VID and PID are Vendor | |
4203 | and Product ID values (4-digit hex numbers) and | |
4204 | Flags is a set of characters, each corresponding | |
4205 | to a common usb-storage quirk flag as follows: | |
c838ea46 AS |
4206 | a = SANE_SENSE (collect more than 18 bytes |
4207 | of sense data); | |
a0bb1081 AS |
4208 | b = BAD_SENSE (don't collect more than 18 |
4209 | bytes of sense data); | |
d4f373e5 AS |
4210 | c = FIX_CAPACITY (decrease the reported |
4211 | device capacity by one sector); | |
5116901d KR |
4212 | d = NO_READ_DISC_INFO (don't use |
4213 | READ_DISC_INFO command); | |
4214 | e = NO_READ_CAPACITY_16 (don't use | |
4215 | READ_CAPACITY_16 command); | |
734016b0 HG |
4216 | f = NO_REPORT_OPCODES (don't use report opcodes |
4217 | command, uas only); | |
ee136af4 HG |
4218 | g = MAX_SECTORS_240 (don't transfer more than |
4219 | 240 sectors at a time, uas only); | |
c838ea46 AS |
4220 | h = CAPACITY_HEURISTICS (decrease the |
4221 | reported device capacity by one | |
4222 | sector if the number is odd); | |
d4f373e5 AS |
4223 | i = IGNORE_DEVICE (don't bind to this |
4224 | device); | |
13630746 HG |
4225 | j = NO_REPORT_LUNS (don't use report luns |
4226 | command, uas only); | |
d4f373e5 AS |
4227 | l = NOT_LOCKABLE (don't try to lock and |
4228 | unlock ejectable media); | |
4229 | m = MAX_SECTORS_64 (don't transfer more | |
4230 | than 64 sectors = 32 KB at a time); | |
21c13a4f AS |
4231 | n = INITIAL_READ10 (force a retry of the |
4232 | initial READ(10) command); | |
c838ea46 AS |
4233 | o = CAPACITY_OK (accept the capacity |
4234 | reported by the device); | |
eaa05dfc NJ |
4235 | p = WRITE_CACHE (the device cache is ON |
4236 | by default); | |
d4f373e5 AS |
4237 | r = IGNORE_RESIDUE (the device reports |
4238 | bogus residue values); | |
4239 | s = SINGLE_LUN (the device has only one | |
4240 | Logical Unit); | |
59307852 HG |
4241 | t = NO_ATA_1X (don't allow ATA(12) and ATA(16) |
4242 | commands, uas only); | |
b6089f19 | 4243 | u = IGNORE_UAS (don't bind to the uas driver); |
d4f373e5 AS |
4244 | w = NO_WP_DETECT (don't test whether the |
4245 | medium is write-protected). | |
4246 | Example: quirks=0419:aaf5:rl,0421:0433:rc | |
4247 | ||
ac1667db SB |
4248 | user_debug= [KNL,ARM] |
4249 | Format: <int> | |
4250 | See arch/arm/Kconfig.debug help text. | |
4251 | 1 - undefined instruction events | |
4252 | 2 - system calls | |
4253 | 4 - invalid data aborts | |
4254 | 8 - SIGSEGV faults | |
4255 | 16 - SIGBUS faults | |
4256 | Example: user_debug=31 | |
4257 | ||
14315592 IC |
4258 | userpte= |
4259 | [X86] Flags controlling user PTE allocations. | |
4260 | ||
4261 | nohigh = do not allocate PTE pages in | |
4262 | HIGHMEM regardless of setting | |
4263 | of CONFIG_HIGHPTE. | |
4264 | ||
6cececfc | 4265 | vdso= [X86,SH] |
b0b49f26 AL |
4266 | On X86_32, this is an alias for vdso32=. Otherwise: |
4267 | ||
4268 | vdso=1: enable VDSO (the default) | |
e6e5494c IM |
4269 | vdso=0: disable VDSO mapping |
4270 | ||
b0b49f26 AL |
4271 | vdso32= [X86] Control the 32-bit vDSO |
4272 | vdso32=1: enable 32-bit VDSO | |
4273 | vdso32=0 or vdso32=2: disable 32-bit VDSO | |
4274 | ||
4275 | See the help text for CONFIG_COMPAT_VDSO for more | |
4276 | details. If CONFIG_COMPAT_VDSO is set, the default is | |
4277 | vdso32=0; otherwise, the default is vdso32=1. | |
4278 | ||
4279 | For compatibility with older kernels, vdso32=2 is an | |
4280 | alias for vdso32=0. | |
4281 | ||
4282 | Try vdso32=0 if you encounter an error that says: | |
4283 | dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed! | |
af65d648 | 4284 | |
d080d397 YI |
4285 | vector= [IA-64,SMP] |
4286 | vector=percpu: enable percpu vector domain | |
4287 | ||
1da177e4 LT |
4288 | video= [FB] Frame buffer configuration |
4289 | See Documentation/fb/modedb.txt. | |
4290 | ||
3afe6dab AL |
4291 | video.brightness_switch_enabled= [0,1] |
4292 | If set to 1, on receiving an ACPI notify event | |
4293 | generated by hotkey, video driver will adjust brightness | |
4294 | level and then send out the event to user space through | |
4295 | the allocated input device; If set to 0, video driver | |
4296 | will only send out the event without touching backlight | |
4297 | brightness level. | |
2843768b | 4298 | default: 1 |
3afe6dab | 4299 | |
81a054ce PM |
4300 | virtio_mmio.device= |
4301 | [VMMIO] Memory mapped virtio (platform) device. | |
4302 | ||
4303 | <size>@<baseaddr>:<irq>[:<id>] | |
4304 | where: | |
4305 | <size> := size (can use standard suffixes | |
4306 | like K, M and G) | |
4307 | <baseaddr> := physical base address | |
4308 | <irq> := interrupt number (as passed to | |
4309 | request_irq()) | |
4310 | <id> := (optional) platform device id | |
4311 | example: | |
4312 | virtio_mmio.device=1K@0x100b0000:48:7 | |
4313 | ||
4314 | Can be used multiple times for multiple devices. | |
4315 | ||
cd4f0ef7 | 4316 | vga= [BOOT,X86-32] Select a particular video mode |
954a8b81 | 4317 | See Documentation/x86/boot.txt and |
a9913044 | 4318 | Documentation/svga.txt. |
1da177e4 LT |
4319 | Use vga=ask for menu. |
4320 | This is actually a boot loader parameter; the value is | |
4321 | passed to the kernel using a special protocol. | |
4322 | ||
a9913044 | 4323 | vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact |
1da177e4 LT |
4324 | size of <nn>. This can be used to increase the |
4325 | minimum size (128MB on x86). It can also be used to | |
4326 | decrease the size and leave more room for directly | |
4327 | mapped kernel RAM. | |
4328 | ||
585c3047 PO |
4329 | vmhalt= [KNL,S390] Perform z/VM CP command after system halt. |
4330 | Format: <command> | |
1da177e4 | 4331 | |
585c3047 PO |
4332 | vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. |
4333 | Format: <command> | |
4334 | ||
4335 | vmpoff= [KNL,S390] Perform z/VM CP command after power off. | |
4336 | Format: <command> | |
a9913044 | 4337 | |
3ae36655 AL |
4338 | vsyscall= [X86-64] |
4339 | Controls the behavior of vsyscalls (i.e. calls to | |
4340 | fixed addresses of 0xffffffffff600x00 from legacy | |
4341 | code). Most statically-linked binaries and older | |
4342 | versions of glibc use these calls. Because these | |
4343 | functions are at fixed addresses, they make nice | |
4344 | targets for exploits that can control RIP. | |
4345 | ||
2e57ae05 AL |
4346 | emulate [default] Vsyscalls turn into traps and are |
4347 | emulated reasonably safely. | |
3ae36655 | 4348 | |
2e57ae05 | 4349 | native Vsyscalls are native syscall instructions. |
3ae36655 AL |
4350 | This is a little bit faster than trapping |
4351 | and makes a few dynamic recompilers work | |
4352 | better than they would in emulation mode. | |
4353 | It also makes exploits much easier to write. | |
4354 | ||
4355 | none Vsyscalls don't work at all. This makes | |
4356 | them quite hard to use for exploits but | |
4357 | might break your system. | |
4358 | ||
3855ae1c CL |
4359 | vt.color= [VT] Default text color. |
4360 | Format: 0xYX, X = foreground, Y = background. | |
4361 | Default: 0x07 = light gray on black. | |
4362 | ||
9ea9a886 CL |
4363 | vt.cur_default= [VT] Default cursor shape. |
4364 | Format: 0xCCBBAA, where AA, BB, and CC are the same as | |
4365 | the parameters of the <Esc>[?A;B;Cc escape sequence; | |
4366 | see VGA-softcursor.txt. Default: 2 = underline. | |
4367 | ||
0cb55ad2 RD |
4368 | vt.default_blu= [VT] |
4369 | Format: <blue0>,<blue1>,<blue2>,...,<blue15> | |
4370 | Change the default blue palette of the console. | |
4371 | This is a 16-member array composed of values | |
4372 | ranging from 0-255. | |
4373 | ||
4374 | vt.default_grn= [VT] | |
4375 | Format: <green0>,<green1>,<green2>,...,<green15> | |
4376 | Change the default green palette of the console. | |
4377 | This is a 16-member array composed of values | |
4378 | ranging from 0-255. | |
4379 | ||
4380 | vt.default_red= [VT] | |
4381 | Format: <red0>,<red1>,<red2>,...,<red15> | |
4382 | Change the default red palette of the console. | |
4383 | This is a 16-member array composed of values | |
4384 | ranging from 0-255. | |
4385 | ||
4386 | vt.default_utf8= | |
4387 | [VT] | |
4388 | Format=<0|1> | |
4389 | Set system-wide default UTF-8 mode for all tty's. | |
4390 | Default is 1, i.e. UTF-8 mode is enabled for all | |
4391 | newly opened terminals. | |
4392 | ||
f6c06b68 MG |
4393 | vt.global_cursor_default= |
4394 | [VT] | |
4395 | Format=<-1|0|1> | |
4396 | Set system-wide default for whether a cursor | |
4397 | is shown on new VTs. Default is -1, | |
4398 | i.e. cursors will be created by default unless | |
4399 | overridden by individual drivers. 0 will hide | |
4400 | cursors, 1 will display them. | |
4401 | ||
3855ae1c CL |
4402 | vt.italic= [VT] Default color for italic text; 0-15. |
4403 | Default: 2 = green. | |
4404 | ||
4405 | vt.underline= [VT] Default color for underlined text; 0-15. | |
4406 | Default: 3 = cyan. | |
4407 | ||
4724ba57 RD |
4408 | watchdog timers [HW,WDT] For information on watchdog timers, |
4409 | see Documentation/watchdog/watchdog-parameters.txt | |
4410 | or other driver-specific files in the | |
4411 | Documentation/watchdog/ directory. | |
1da177e4 | 4412 | |
82607adc TH |
4413 | workqueue.watchdog_thresh= |
4414 | If CONFIG_WQ_WATCHDOG is configured, workqueue can | |
4415 | warn stall conditions and dump internal state to | |
4416 | help debugging. 0 disables workqueue stall | |
4417 | detection; otherwise, it's the stall threshold | |
4418 | duration in seconds. The default value is 30 and | |
4419 | it can be updated at runtime by writing to the | |
4420 | corresponding sysfs file. | |
4421 | ||
d55262c4 TH |
4422 | workqueue.disable_numa |
4423 | By default, all work items queued to unbound | |
4424 | workqueues are affine to the NUMA nodes they're | |
4425 | issued on, which results in better behavior in | |
4426 | general. If NUMA affinity needs to be disabled for | |
4427 | whatever reason, this option can be used. Note | |
4428 | that this also can be controlled per-workqueue for | |
4429 | workqueues visible under /sys/bus/workqueue/. | |
4430 | ||
cee22a15 VK |
4431 | workqueue.power_efficient |
4432 | Per-cpu workqueues are generally preferred because | |
4433 | they show better performance thanks to cache | |
4434 | locality; unfortunately, per-cpu workqueues tend to | |
4435 | be more power hungry than unbound workqueues. | |
4436 | ||
4437 | Enabling this makes the per-cpu workqueues which | |
4438 | were observed to contribute significantly to power | |
4439 | consumption unbound, leading to measurably lower | |
4440 | power usage at the cost of small performance | |
4441 | overhead. | |
4442 | ||
4443 | The default value of this parameter is determined by | |
4444 | the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT. | |
4445 | ||
f303fccb TH |
4446 | workqueue.debug_force_rr_cpu |
4447 | Workqueue used to implicitly guarantee that work | |
4448 | items queued without explicit CPU specified are put | |
4449 | on the local CPU. This guarantee is no longer true | |
4450 | and while local CPU is still preferred work items | |
4451 | may be put on foreign CPUs. This debug option | |
4452 | forces round-robin CPU selection to flush out | |
4453 | usages which depend on the now broken guarantee. | |
4454 | When enabled, memory and cache locality will be | |
4455 | impacted. | |
4456 | ||
0cb55ad2 RD |
4457 | x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of |
4458 | default x2apic cluster mode on platforms | |
4459 | supporting x2apic. | |
4460 | ||
712b6aa8 KS |
4461 | x86_intel_mid_timer= [X86-32,APBT] |
4462 | Choose timer option for x86 Intel MID platform. | |
bb24c471 JP |
4463 | Two valid options are apbt timer only and lapic timer |
4464 | plus one apbt timer for broadcast timer. | |
712b6aa8 | 4465 | x86_intel_mid_timer=apbt_only | lapic_and_apbt |
bb24c471 | 4466 | |
c70727a5 JG |
4467 | xen_512gb_limit [KNL,X86-64,XEN] |
4468 | Restricts the kernel running paravirtualized under Xen | |
4469 | to use only up to 512 GB of RAM. The reason to do so is | |
4470 | crash analysis tools and Xen tools for doing domain | |
4471 | save/restore/migration must be enabled to handle larger | |
4472 | domains. | |
4473 | ||
c1c5413a SS |
4474 | xen_emul_unplug= [HW,X86,XEN] |
4475 | Unplug Xen emulated devices | |
4476 | Format: [unplug0,][unplug1] | |
4477 | ide-disks -- unplug primary master IDE devices | |
4478 | aux-ide-disks -- unplug non-primary-master IDE devices | |
4479 | nics -- unplug network devices | |
4480 | all -- unplug all emulated devices (NICs and IDE disks) | |
1dc7ce99 IC |
4481 | unnecessary -- unplugging emulated devices is |
4482 | unnecessary even if the host did not respond to | |
4483 | the unplug protocol | |
c93a4dfb | 4484 | never -- do not unplug even if version check succeeds |
c1c5413a | 4485 | |
15a3eac0 KRW |
4486 | xen_nopvspin [X86,XEN] |
4487 | Disables the ticketlock slowpath using Xen PV | |
4488 | optimizations. | |
4489 | ||
8d693b91 KRW |
4490 | xen_nopv [X86] |
4491 | Disables the PV optimizations forcing the HVM guest to | |
4492 | run as generic HVM guest with no PV drivers. | |
4493 | ||
1da177e4 | 4494 | xirc2ps_cs= [NET,PCMCIA] |
a9913044 RD |
4495 | Format: |
4496 | <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] | |
1da177e4 | 4497 | |
a9913044 | 4498 | ______________________________________________________________________ |
1da177e4 LT |
4499 | |
4500 | TODO: | |
4501 | ||
1da177e4 | 4502 | Add more DRM drivers. |