[S390] vdso: compile fix
[linux-block.git] / Documentation / kernel-parameters.txt
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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
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3
4The following is a consolidated list of the kernel parameters as implemented
5(mostly) by the __setup() macro and sorted into English Dictionary order
6(defined as ignoring all punctuation and sorting digits before letters in a
7case insensitive manner), and with descriptions where known.
8
9Module parameters for loadable modules are specified only as the
10parameter name with optional '=' and value as appropriate, such as:
11
12 modprobe usbcore blinkenlights=1
13
14Module parameters for modules that are built into the kernel image
15are specified on the kernel command line with the module name plus
16'.' plus parameter name, with '=' and value if appropriate, such as:
17
18 usbcore.blinkenlights=1
19
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20This document may not be entirely up to date and comprehensive. The command
21"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22module. Loadable modules, after being loaded into the running kernel, also
23reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24parameters may be changed at runtime by the command
25"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
26
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27The parameters listed below are only valid if certain kernel build options were
28enabled and if respective hardware is present. The text in square brackets at
29the beginning of each description states the restrictions within which a
30parameter is applicable:
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31
32 ACPI ACPI support is enabled.
c99c108a 33 AGP AGP (Accelerated Graphics Port) is enabled.
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34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
e7ba176b 37 AVR32 AVR32 architecture is enabled.
1da177e4 38 AX25 Appropriate AX.25 support is enabled.
0ae53640 39 BLACKFIN Blackfin architecture is enabled.
a9913044 40 DRM Direct Rendering Management support is enabled.
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41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
42 EFI EFI Partitioning (GPT) is enabled
43 EIDE EIDE/ATAPI support is enabled.
44 FB The frame buffer device is enabled.
45 HW Appropriate hardware is enabled.
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46 IA-64 IA-64 architecture is enabled.
47 IOSCHED More than one I/O scheduler is enabled.
41e2e8be 48 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
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49 ISAPNP ISA PnP code is enabled.
50 ISDN Appropriate ISDN support is enabled.
51 JOY Appropriate joystick support is enabled.
11ef697b 52 LIBATA Libata driver is enabled
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53 LP Printer support is enabled.
54 LOOP Loopback device support is enabled.
55 M68k M68k architecture is enabled.
56 These options have more detailed description inside of
57 Documentation/m68k/kernel-options.txt.
58 MCA MCA bus support is enabled.
59 MDA MDA console support is enabled.
60 MOUSE Appropriate mouse support is enabled.
309e57df 61 MSI Message Signaled Interrupts (PCI).
c8facbb6 62 MTD MTD (Memory Technology Device) support is enabled.
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63 NET Appropriate network support is enabled.
64 NUMA NUMA support is enabled.
734efb46 65 GENERIC_TIME The generic timeofday code is enabled.
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66 NFS Appropriate NFS support is enabled.
67 OSS OSS sound support is enabled.
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68 PV_OPS A paravirtualized kernel is enabled.
69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
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70 PARISC The PA-RISC architecture is enabled.
71 PCI PCI bus support is enabled.
7f785763 72 PCIE PCI Express support is enabled.
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73 PCMCIA The PCMCIA subsystem is enabled.
74 PNP Plug & Play support is enabled.
75 PPC PowerPC architecture is enabled.
76 PPT Parallel port support is enabled.
77 PS2 Appropriate PS/2 support is enabled.
78 RAM RAM disk support is enabled.
20510f2f 79 ROOTPLUG The example Root Plug LSM is enabled.
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80 S390 S390 architecture is enabled.
81 SCSI Appropriate SCSI support is enabled.
82 A lot of drivers has their options described inside of
83 Documentation/scsi/.
20510f2f 84 SECURITY Different security models are enabled.
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85 SELINUX SELinux support is enabled.
86 SERIAL Serial support is enabled.
e523d93c 87 SH SuperH architecture is enabled.
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88 SMP The kernel is an SMP kernel.
89 SPARC Sparc architecture is enabled.
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90 SWSUSP Software suspend (hibernation) is enabled.
91 SUSPEND System suspend states are enabled.
f38f1d2a 92 FTRACE Function tracing enabled.
1da177e4 93 TS Appropriate touchscreen support is enabled.
d4f373e5 94 UMS USB Mass Storage support is enabled.
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95 USB USB support is enabled.
96 USBHID USB Human Interface Device support is enabled.
97 V4L Video For Linux support is enabled.
98 VGA The VGA console has been enabled.
99 VT Virtual terminal support is enabled.
100 WDT Watchdog support is enabled.
101 XT IBM PC/XT MFM hard disk support is enabled.
cd4f0ef7 102 X86-32 X86-32, aka i386 architecture is enabled.
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103 X86-64 X86-64 architecture is enabled.
104 More X86-64 boot options can be found in
71cced6e 105 Documentation/x86/x86_64/boot-options.txt .
c0115606 106 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
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107
108In addition, the following text indicates that the option:
109
110 BUGS= Relates to possible processor bugs on the said processor.
111 KNL Is a kernel start-up parameter.
112 BOOT Is a boot loader parameter.
113
114Parameters denoted with BOOT are actually interpreted by the boot
115loader, and have no meaning to the kernel directly.
116Do not modify the syntax of boot loader parameters without extreme
71cced6e 117need or coordination with <Documentation/x86/i386/boot.txt>.
1da177e4 118
5558870b 119There are also arch-specific kernel-parameters not documented here.
71cced6e 120See for example <Documentation/x86/x86_64/boot-options.txt>.
5558870b 121
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122Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
123a trailing = on the name of any parameter states that that parameter will
124be entered as an environment variable, whereas its absence indicates that
125it will appear as a kernel argument readable via /proc/cmdline by programs
126running once the system is up.
127
9c4751fd 128The number of kernel parameters is not limited, but the length of the
129complete command line (parameters including spaces etc.) is limited to
130a fixed number of characters. This limit depends on the architecture
131and is between 256 and 4096 characters. It is defined in the file
132./include/asm/setup.h as COMMAND_LINE_SIZE.
133
134
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135 acpi= [HW,ACPI,X86-64,i386]
136 Advanced Configuration and Power Interface
a9913044 137 Format: { force | off | ht | strict | noirq }
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138 force -- enable ACPI if default was off
139 off -- disable ACPI if default was on
140 noirq -- do not use ACPI for IRQ routing
141 ht -- run only enough ACPI to enable Hyper Threading
a9913044 142 strict -- Be less tolerant of platforms that are not
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143 strictly ACPI specification compliant.
144
53471121 145 See also Documentation/power/pm.txt, pci=noacpi
1da177e4 146
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147 acpi_apic_instance= [ACPI, IOAPIC]
148 Format: <int>
149 2: use 2nd APIC table, if available
150 1,0: use 1st APIC table
4e381a4f 151 default: 0
a1fdcc0d 152
1da177e4 153 acpi_sleep= [HW,ACPI] Sleep options
bdfe6b7c 154 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, old_ordering }
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155 See Documentation/power/video.txt for s3_bios and s3_mode.
156 s3_beep is for debugging; it makes the PC's speaker beep
157 as soon as the kernel's real-mode entry point is called.
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158 s4_nohwsig prevents ACPI hardware signature from being
159 used during resume from hibernation.
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160 old_ordering causes the ACPI 1.0 ordering of the _PTS
161 control method, wrt putting devices into low power
162 states, to be enforced (the ACPI 2.0 ordering of _PTS is
163 used by default).
a9913044 164
1da177e4 165 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
a9913044 166 Format: { level | edge | high | low }
1da177e4 167
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168 acpi_irq_balance [HW,ACPI]
169 ACPI will balance active IRQs
170 default in APIC mode
1da177e4 171
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172 acpi_irq_nobalance [HW,ACPI]
173 ACPI will not move active IRQs (default)
174 default in PIC mode
1da177e4 175
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176 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
177 use by PCI
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178 Format: <irq>,<irq>...
179
a9913044 180 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
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181 Format: <irq>,<irq>...
182
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183 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
184
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185 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
186 Format: To spoof as Windows 98: ="Microsoft Windows"
187
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188 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
189 acpi_osi="string1" # add string1 -- only one string
190 acpi_osi="!string2" # remove built-in string2
191 acpi_osi= # disable all strings
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192
193 acpi_serialize [HW,ACPI] force serialization of AML methods
194
195 acpi_skip_timer_override [HW,ACPI]
196 Recognize and ignore IRQ0/pin2 Interrupt Override.
197 For broken nForce2 BIOS resulting in XT-PIC timer.
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198 acpi_use_timer_override [HW,ACPI}
199 Use timer override. For some broken Nvidia NF5 boards
200 that require a timer override, but don't have
201 HPET
1da177e4 202
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203 acpi_backlight= [HW,ACPI]
204 acpi_backlight=vendor
205 acpi_backlight=video
206 If set to vendor, prefer vendor specific driver
207 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
208 of the ACPI video.ko driver.
209
210 acpi_display_output= [HW,ACPI]
211 acpi_display_output=vendor
212 acpi_display_output=video
213 See above.
214
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215 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
216 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
1da177e4 217 Format: <int>
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218 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
219 debug output. Bits in debug_layer correspond to a
220 _COMPONENT in an ACPI source file, e.g.,
221 #define _COMPONENT ACPI_PCI_COMPONENT
222 Bits in debug_level correspond to a level in
223 ACPI_DEBUG_PRINT statements, e.g.,
224 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
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225 The debug_level mask defaults to "info". See
226 Documentation/acpi/debug.txt for more information about
227 debug layers and levels.
a0d84a92 228
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229 Enable processor driver info messages:
230 acpi.debug_layer=0x20000000
231 Enable PCI/PCI interrupt routing info messages:
232 acpi.debug_layer=0x400000
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233 Enable AML "Debug" output, i.e., stores to the Debug
234 object while interpreting AML:
235 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
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236 Enable all messages related to ACPI hardware:
237 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
238
239 Some values produce so much output that the system is
240 unusable. The "log_buf_len" parameter may be useful
241 if you need to capture more output.
f989106c 242
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243 acpi.power_nocheck= [HW,ACPI]
244 Format: 1/0 enable/disable the check of power state.
245 On some bogus BIOS the _PSC object/_STA object of
246 power resource can't return the correct device power
247 state. In such case it is unneccessary to check its
248 power state again in power transition.
249 1 : disable the power state check
250
cd4f0ef7 251 acpi_pm_good [X86-32,X86-64]
5d0cf410 252 Override the pmtimer bug detection: force the kernel
253 to assume that this machine's pmtimer latches its value
254 and always returns good values.
255
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256 agp= [AGP]
257 { off | try_unsupported }
258 off: disable AGP support
259 try_unsupported: try to drive unsupported chipsets
260 (may crash computer or cause data corruption)
261
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262 enable_timer_pin_1 [i386,x86-64]
263 Enable PIN 1 of APIC timer
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264 Can be useful to work around chipset bugs
265 (in particular on some ATI chipsets).
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266 The kernel tries to set a reasonable default.
267
268 disable_timer_pin_1 [i386,x86-64]
269 Disable PIN 1 of APIC timer
270 Can be useful to work around chipset bugs.
271
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272 ad1848= [HW,OSS]
273 Format: <io>,<irq>,<dma>,<dma2>,<type>
274
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275 advansys= [HW,SCSI]
276 See header of drivers/scsi/advansys.c.
277
278 advwdt= [HW,WDT] Advantech WDT
279 Format: <iostart>,<iostop>
280
281 aedsp16= [HW,OSS] Audio Excel DSP 16
282 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
283 See also header of sound/oss/aedsp16.c.
a9913044 284
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285 aha152x= [HW,SCSI]
286 See Documentation/scsi/aha152x.txt.
287
288 aha1542= [HW,SCSI]
289 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
290
291 aic7xxx= [HW,SCSI]
292 See Documentation/scsi/aic7xxx.txt.
293
294 aic79xx= [HW,SCSI]
295 See Documentation/scsi/aic79xx.txt.
296
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297 amd_iommu= [HW,X86-84]
298 Pass parameters to the AMD IOMMU driver in the system.
299 Possible values are:
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300 isolate - enable device isolation (each device, as far
301 as possible, will get its own protection
3ce1f93c 302 domain) [default]
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303 share - put every device behind one IOMMU into the
304 same protection domain
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305 fullflush - enable flushing of IO/TLB entries when
306 they are unmapped. Otherwise they are
307 flushed before they will be reused, which
308 is a lot of faster
309
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310 amd_iommu_size= [HW,X86-64]
311 Define the size of the aperture for the AMD IOMMU
312 driver. Possible values are:
313 '32M', '64M' (default), '128M', '256M', '512M', '1G'
314
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315 amijoy.map= [HW,JOY] Amiga joystick support
316 Map of devices attached to JOY0DAT and JOY1DAT
317 Format: <a>,<b>
318 See also Documentation/kernel/input/joystick.txt
319
320 analog.map= [HW,JOY] Analog joystick and gamepad support
321 Specifies type or capabilities of an analog joystick
322 connected to one of 16 gameports
323 Format: <type1>,<type2>,..<type16>
324
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325 apc= [HW,SPARC]
326 Power management functions (SPARCstation-4/5 + deriv.)
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327 Format: noidle
328 Disable APC CPU standby support. SPARCstation-Fox does
329 not play well with APC CPU idle - disable it if you have
330 APC and your system crashes randomly.
331
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332 apic= [APIC,i386] Advanced Programmable Interrupt Controller
333 Change the output verbosity whilst booting
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334 Format: { quiet (default) | verbose | debug }
335 Change the amount of debugging information output
336 when initialising the APIC and IO-APIC components.
a9913044 337
1da177e4 338 apm= [APM] Advanced Power Management
71f77055 339 See header of arch/x86/kernel/apm_32.c.
1da177e4 340
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341 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
342 Format: <io>,<irq>,<nodeID>
343
344 ataflop= [HW,M68k]
345
346 atarimouse= [HW,MOUSE] Atari Mouse
347
348 atascsi= [HW,SCSI] Atari SCSI
349
350 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
351 EzKey and similar keyboards
352
353 atkbd.reset= [HW] Reset keyboard during initialization
354
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355 atkbd.set= [HW] Select keyboard code set
356 Format: <int> (2 = AT (default), 3 = PS/2)
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357
358 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
359 keyboards
360
361 atkbd.softraw= [HW] Choose between synthetic and real raw mode
362 Format: <bool> (0 = real, 1 = synthetic (default))
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363
364 atkbd.softrepeat= [HW]
365 Use software keyboard repeat
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366
367 autotest [IA64]
368
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369 baycom_epp= [HW,AX25]
370 Format: <io>,<mode>
a9913044 371
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372 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
373 Format: <io>,<mode>
374 See header of drivers/net/hamradio/baycom_par.c.
375
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376 baycom_ser_fdx= [HW,AX25]
377 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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378 Format: <io>,<irq>,<mode>[,<baud>]
379 See header of drivers/net/hamradio/baycom_ser_fdx.c.
380
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381 baycom_ser_hdx= [HW,AX25]
382 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
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383 Format: <io>,<irq>,<mode>
384 See header of drivers/net/hamradio/baycom_ser_hdx.c.
385
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386 boot_delay= Milliseconds to delay each printk during boot.
387 Values larger than 10 seconds (10000) are changed to
388 no delay (0).
389 Format: integer
390
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391 bootmem_debug [KNL] Enable bootmem allocator debug messages.
392
1da177e4 393 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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394 bttv.radio= Most important insmod options are available as
395 kernel args too.
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396 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
397 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
398
399 BusLogic= [HW,SCSI]
400 See drivers/scsi/BusLogic.c, comment before function
401 BusLogic_ParseDriverOptions().
402
403 c101= [NET] Moxa C101 synchronous serial card
404
cd4f0ef7 405 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
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406 Sometimes CPU hardware bugs make them report the cache
407 size incorrectly. The kernel will attempt work arounds
408 to fix known problems, but for some CPUs it is not
409 possible to determine what the correct size should be.
410 This option provides an override for these situations.
411
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412 security= [SECURITY] Choose a security module to enable at boot.
413 If this boot parameter is not specified, only the first
414 security module asking for security registration will be
415 loaded. An invalid security module name will be treated
416 as if no module has been chosen.
417
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418 capability.disable=
419 [SECURITY] Disable capabilities. This would normally
420 be used only if an alternative security model is to be
421 configured. Potentially dangerous and should only be
422 used if you are entirely sure of the consequences.
423
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424 ccw_timeout_log [S390]
425 See Documentation/s390/CommonIO for details.
1da177e4 426
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427 cgroup_disable= [KNL] Disable a particular controller
428 Format: {name of the controller(s) to disable}
429 {Currently supported controllers - "memory"}
430
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431 checkreqprot [SELINUX] Set initial checkreqprot flag value.
432 Format: { "0" | "1" }
433 See security/selinux/Kconfig help text.
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434 0 -- check protection applied by kernel (includes
435 any implied execute protection).
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436 1 -- check protection requested by application.
437 Default value is set via a kernel config option.
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438 Value can be changed at runtime via
439 /selinux/checkreqprot.
440
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441 cio_ignore= [S390]
442 See Documentation/s390/CommonIO for details.
443
cd4f0ef7 444 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 445 [Deprecated]
3f6dee9b 446 Forces specified clocksource (if available) to be used
734efb46 447 when calculating gettimeofday(). If specified
3f6dee9b 448 clocksource is not available, it defaults to PIT.
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449 Format: { pit | tsc | cyclone | pmtmr }
450
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451 clocksource= [GENERIC_TIME] Override the default clocksource
452 Format: <string>
453 Override the default clocksource and use the clocksource
454 with the name specified.
455 Some clocksource names to choose from, depending on
456 the platform:
457 [all] jiffies (this is the base, fallback clocksource)
458 [ACPI] acpi_pm
459 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
460 pxa_timer,timer3,32k_counter,timer0_1
461 [AVR32] avr32
cd4f0ef7 462 [X86-32] pit,hpet,tsc,vmi-timer;
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463 scx200_hrt on Geode; cyclone on IBM x440
464 [MIPS] MIPS
465 [PARISC] cr16
466 [S390] tod
467 [SH] SuperH
468 [SPARC64] tick
469 [X86-64] hpet,tsc
470
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471 clearcpuid=BITNUM [X86]
472 Disable CPUID feature X for the kernel. See
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473 arch/x86/include/asm/cpufeature.h for the valid bit
474 numbers. Note the Linux specific bits are not necessarily
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475 stable over kernel options, but the vendor specific
476 ones should be.
477 Also note that user programs calling CPUID directly
478 or using the feature without checking anything
479 will still see it. This just prevents it from
480 being used by the kernel or shown in /proc/cpuinfo.
481 Also note the kernel might malfunction if you disable
482 some critical bits.
483
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484 code_bytes [IA32/X86_64] How many bytes of object code to print
485 in an oops report.
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486 Range: 0 - 8192
487 Default: 64
488
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489 hpet= [X86-32,HPET] option to control HPET usage
490 Format: { enable (default) | disable | force }
491 disable: disable HPET and use PIT instead
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492 force: allow force enabled of undocumented chips (ICH4,
493 VIA, nVidia)
1da177e4 494
1da177e4 495 com20020= [HW,NET] ARCnet - COM20020 chipset
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496 Format:
497 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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498
499 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
500 Format: <io>[,<irq>]
501
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502 com90xx= [HW,NET]
503 ARCnet - COM90xx chipset (memory-mapped buffers)
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504 Format: <io>[,<irq>[,<memstart>]]
505
506 condev= [HW,S390] console device
507 conmode=
a9913044 508
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509 console= [KNL] Output console device and options.
510
511 tty<n> Use the virtual console device <n>.
512
513 ttyS<n>[,options]
f1a1c2dc 514 ttyUSB0[,options]
1da177e4 515 Use the specified serial port. The options are of
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516 the form "bbbbpnf", where "bbbb" is the baud rate,
517 "p" is parity ("n", "o", or "e"), "n" is number of
518 bits, and "f" is flow control ("r" for RTS or
519 omit it). Default is "9600n8".
520
521 See Documentation/serial-console.txt for more
522 information. See
523 Documentation/networking/netconsole.txt for an
524 alternative.
1da177e4 525
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526 uart[8250],io,<addr>[,options]
527 uart[8250],mmio,<addr>[,options]
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528 Start an early, polled-mode console on the 8250/16550
529 UART at the specified I/O port or MMIO address,
530 switching to the matching ttyS device later. The
531 options are the same as for ttyS, above.
532
f7511d5f
ST
533 If the device connected to the port is not a TTY but a braille
534 device, prepend "brl," before the device type, for instance
535 console=brl,ttyS0
536 For now, only VisioBraille is supported.
537
18a8bd94
YL
538 earlycon= [KNL] Output early console device and options.
539 uart[8250],io,<addr>[,options]
540 uart[8250],mmio,<addr>[,options]
541 Start an early, polled-mode console on the 8250/16550
542 UART at the specified I/O port or MMIO address.
543 The options are the same as for ttyS, above.
544
8f4ce8c3
AS
545 no_console_suspend
546 [HW] Never suspend the console
547 Disable suspending of consoles during suspend and
548 hibernate operations. Once disabled, debugging
549 messages can reach various consoles while the rest
550 of the system is being put to sleep (ie, while
551 debugging driver suspend/resume hooks). This may
552 not work reliably with all consoles, but is known
553 to work with serial and VGA consoles.
554
4cb0e11b
HK
555 coredump_filter=
556 [KNL] Change the default value for
557 /proc/<pid>/coredump_filter.
558 See also Documentation/filesystems/proc.txt.
559
1da177e4 560 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
a9913044
RD
561 Format:
562 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 563
dc009d92
EB
564 crashkernel=nn[KMG]@ss[KMG]
565 [KNL] Reserve a chunk of physical memory to
566 hold a kernel to switch to with kexec on panic.
567
fb391599
BW
568 crashkernel=range1:size1[,range2:size2,...][@offset]
569 [KNL] Same as above, but depends on the memory
570 in the running system. The syntax of range is
571 start-[end] where start and end are both
572 a memory unit (amount[KMG]). See also
573 Documentation/kdump/kdump.txt for a example.
574
1da177e4
LT
575 cs4232= [HW,OSS]
576 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
577
578 cs89x0_dma= [HW,NET]
579 Format: <dma>
580
581 cs89x0_media= [HW,NET]
582 Format: { rj45 | aui | bnc }
a9913044 583
a9913044 584 dasd= [HW,NET]
1da177e4
LT
585 See header of drivers/s390/block/dasd_devmap.c.
586
587 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
588 (one device per port)
589 Format: <port#>,<type>
590 See also Documentation/input/joystick-parport.txt
591
592 debug [KNL] Enable kernel debugging (events log level).
593
cae2ed9a
IM
594 debug_locks_verbose=
595 [KNL] verbose self-tests
596 Format=<0|1>
597 Print debugging info while doing the locking API
598 self-tests.
599 We default to 0 (no extra messages), setting it to
600 1 will print _a lot_ more information - normally
601 only useful to kernel developers.
602
3ac7fe5a
TG
603 debug_objects [KNL] Enable object debugging
604
d3af01f1
TG
605 debugpat [X86] Enable PAT debugging
606
2d27a966 607 decnet.addr= [HW,NET]
1da177e4
LT
608 Format: <area>[,<node>]
609 See also Documentation/networking/decnet.txt.
610
ecb77fa9 611 vt.default_blu= [VT]
55ff9780
AD
612 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
613 Change the default blue palette of the console.
614 This is a 16-member array composed of values
615 ranging from 0-255.
616
ecb77fa9 617 vt.default_grn= [VT]
55ff9780
AD
618 Format: <green0>,<green1>,<green2>,...,<green15>
619 Change the default green palette of the console.
620 This is a 16-member array composed of values
621 ranging from 0-255.
622
ecb77fa9 623 vt.default_red= [VT]
55ff9780
AD
624 Format: <red0>,<red1>,<red2>,...,<red15>
625 Change the default red palette of the console.
626 This is a 16-member array composed of values
627 ranging from 0-255.
628
ecb77fa9
ST
629 vt.default_utf8=
630 [VT]
55ff9780
AD
631 Format=<0|1>
632 Set system-wide default UTF-8 mode for all tty's.
ecb77fa9
ST
633 Default is 1, i.e. UTF-8 mode is enabled for all
634 newly opened terminals.
55ff9780 635
1da177e4
LT
636 dhash_entries= [KNL]
637 Set number of hash buckets for dentry cache.
a9913044 638
1da177e4
LT
639 digi= [HW,SERIAL]
640 IO parameters + enable/disable command.
641
642 digiepca= [HW,SERIAL]
643 See drivers/char/README.epca and
31c00fc1 644 Documentation/serial/digiepca.txt.
1da177e4 645
95ffa243
YL
646 disable_mtrr_cleanup [X86]
647 enable_mtrr_cleanup [X86]
648 The kernel tries to adjust MTRR layout from continuous
649 to discrete, to make X server driver able to add WB
650 entry later. This parameter enables/disables that.
651
652 mtrr_chunk_size=nn[KMG] [X86]
653 used for mtrr cleanup. It is largest continous chunk
654 that could hold holes aka. UC entries.
655
656 mtrr_gran_size=nn[KMG] [X86]
12031a62
YL
657 Used for mtrr cleanup. It is granularity of mtrr block.
658 Default is 1.
659 Large value could prevent small alignment from
660 using up MTRRs.
661
662 mtrr_spare_reg_nr=n [X86]
663 Format: <integer>
664 Range: 0,7 : spare reg number
665 Default : 1
666 Used for mtrr cleanup. It is spare mtrr entries number.
667 Set to 2 or more if your graphical card needs more.
95ffa243 668
093af8d7 669 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
670 By default the kernel will trim any uncacheable
671 memory out of your available memory pool based on
672 MTRR settings. This parameter disables that behavior,
673 possibly causing your machine to run very slowly.
674
1da177e4
LT
675 dmasound= [HW,OSS] Sound subsystem buffers
676
677 dscc4.setup= [NET]
678
679 dtc3181e= [HW,SCSI]
680
0ae53640 681 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
1da177e4
LT
682 earlyprintk=vga
683 earlyprintk=serial[,ttySn[,baudrate]]
5c05917e 684 earlyprintk=dbgp
1da177e4 685
a9913044 686 Append ",keep" to not disable it when the real console
1da177e4
LT
687 takes over.
688
5c05917e 689 Only vga or serial or usb debug port at a time.
1da177e4
LT
690
691 Currently only ttyS0 and ttyS1 are supported.
692
693 Interaction with the standard serial driver is not
694 very good.
695
696 The VGA output is eventually overwritten by the real
697 console.
698
699 eata= [HW,SCSI]
700
1da177e4 701 edd= [EDD]
8c4dd606 702 Format: {"off" | "on" | "skip[mbr]"}
1da177e4 703
1da177e4
LT
704 eisa_irq_edge= [PARISC,HW]
705 See header of drivers/parisc/eisa.c.
706
cd4f0ef7 707 elanfreq= [X86-32]
1da177e4 708 See comment before function elanfreq_setup() in
71f77055 709 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1da177e4
LT
710
711 elevator= [IOSCHED]
16ab3adf 712 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
713 See Documentation/block/as-iosched.txt and
714 Documentation/block/deadline-iosched.txt for details.
715
e515a0d6 716 elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
a9913044 717 Specifies physical address of start of kernel core
aac04b32
VG
718 image elf header. Generally kexec loader will
719 pass this option to capture kernel.
720 See Documentation/kdump/kdump.txt for details.
1da177e4
LT
721
722 enforcing [SELINUX] Set initial enforcing status.
723 Format: {"0" | "1"}
724 See security/selinux/Kconfig help text.
725 0 -- permissive (log only, no denials).
726 1 -- enforcing (deny and log).
727 Default value is 0.
728 Value can be changed at runtime via /selinux/enforce.
729
1da177e4
LT
730 es1371= [HW,OSS]
731 Format: <spdif>,[<nomix>,[<amplifier>]]
732 See also header of sound/oss/es1371.c.
a9913044 733
1da177e4
LT
734 ether= [HW,NET] Ethernet cards parameters
735 This option is obsoleted by the "netdev=" option, which
736 has equivalent usage. See its documentation for details.
737
738 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
739 Format: <io>[,<irq>]
740
de1ba09b
AM
741 failslab=
742 fail_page_alloc=
743 fail_make_request=[KNL]
744 General fault injection mechanism.
745 Format: <interval>,<probability>,<space>,<times>
746 See also /Documentation/fault-injection/.
747
1da177e4
LT
748 fd_mcs= [HW,SCSI]
749 See header of drivers/scsi/fd_mcs.c.
750
751 fdomain= [HW,SCSI]
752 See header of drivers/scsi/fdomain.c.
753
754 floppy= [HW]
31c00fc1 755 See Documentation/blockdev/floppy.txt.
1da177e4 756
f13ae30e
AC
757 force_pal_cache_flush
758 [IA-64] Avoid check_sal_cache_flush which may hang on
759 buggy SAL_CACHE_FLUSH implementations. Using this
760 parameter will force ia64_sal_cache_flush to call
761 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
762
d9e54076
PZ
763 ftrace=[tracer]
764 [ftrace] will set and start the specified tracer
765 as early as possible in order to facilitate early
766 boot debugging.
767
768 ftrace_dump_on_oops
769 [ftrace] will dump the trace buffers on oops.
770
1da177e4
LT
771 gamecon.map[2|3]=
772 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
773 support via parallel port (up to 5 devices per port)
774 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
775 See also Documentation/input/joystick-parport.txt
776
777 gamma= [HW,DRM]
778
aaf23042
YL
779 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
780 Format: off | on
781 default: on
782
1da177e4
LT
783 gdth= [HW,SCSI]
784 See header of drivers/scsi/gdth.c.
785
786 gpt [EFI] Forces disk with valid GPT signature but
787 invalid Protective MBR to be treated as GPT.
788
1da177e4
LT
789 gvp11= [HW,SCSI]
790
791 hashdist= [KNL,NUMA] Large hashes allocated during boot
792 are distributed across NUMA nodes. Defaults on
793 for IA-64, off otherwise.
a9913044 794 Format: 0 | 1 (for off | on)
1da177e4
LT
795
796 hcl= [IA-64] SGI's Hardware Graph compatibility layer
797
798 hd= [EIDE] (E)IDE hard drive subsystem geometry
799 Format: <cyl>,<head>,<sect>
800
1da177e4
LT
801 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
802 size of <nn>. This works even on boxes that have no
803 highmem otherwise. This also works to reduce highmem
804 size on bigger boxes.
805
54cdfdb4
TG
806 highres= [KNL] Enable/disable high resolution timer mode.
807 Valid parameters: "on", "off"
808 Default: "on"
809
1da177e4
LT
810 hisax= [HW,ISDN]
811 See Documentation/isdn/README.HiSax.
812
b4718e62
AK
813 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
814 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
0d9ea754
JT
815 On x86-64 and powerpc, this option can be specified
816 multiple times interleaved with hugepages= to reserve
817 huge pages of different sizes. Valid pages sizes on
818 x86-64 are 2M (when the CPU supports "pse") and 1G
819 (when the CPU supports the "pdpe1gb" cpuinfo flag)
b4718e62
AK
820 Note that 1GB pages can only be allocated at boot time
821 using hugepages= and not freed afterwards.
e11bfbfc
NP
822 default_hugepagesz=
823 [same as hugepagesz=] The size of the default
824 HugeTLB page size. This is the size represented by
825 the legacy /proc/ hugepages APIs, used for SHM, and
826 default size when mounting hugetlbfs filesystems.
827 Defaults to the default architecture's huge page size
828 if not specified.
1da177e4 829
6902aa84
PM
830 hlt [BUGS=ARM,SH]
831
cef7125d
HB
832 hvc_iucv= [S390] Number of z/VM IUCV Hypervisor console (HVC)
833 back-ends. Valid parameters: 0..8
834
36d95739 835 i8042.debug [HW] Toggle i8042 debug mode
1da177e4 836 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
837 i8042.dumbkbd [HW] Pretend that controller can only read data from
838 keyboard and cannot control its state
1da177e4
LT
839 (Don't attempt to blink the leds)
840 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 841 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
842 i8042.noloop [HW] Disable the AUX Loopback command while probing
843 for the AUX port
1da177e4
LT
844 i8042.nomux [HW] Don't check presence of an active multiplexing
845 controller
846 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
847 controllers
848 i8042.panicblink=
849 [HW] Frequency with which keyboard LEDs should blink
850 when kernel panics (default is 0.5 sec)
851 i8042.reset [HW] Reset the controller during init and cleanup
852 i8042.unlock [HW] Unlock (ignore) the keylock
853
854 i810= [HW,DRM]
855
e70c9d5e
DT
856 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
857 indicates that the driver is running on unsupported
858 hardware.
1da177e4
LT
859 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
860 does not match list of supported models.
861 i8k.power_status
862 [HW] Report power status in /proc/i8k
863 (disabled by default)
864 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
865 capability is set.
866
867 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
868 See Documentation/mca.txt.
869
870 icn= [HW,ISDN]
871 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
872
873 ide= [HW] (E)IDE subsystem
a594eeb1 874 Format: ide=nodma or ide=doubler
1c10e938 875 See Documentation/ide/ide.txt.
1da177e4 876
1da177e4 877 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
1c10e938 878 See Documentation/ide/ide.txt.
1da177e4 879
f039b754 880 idle= [X86]
da5e09a1 881 Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
f039b754
AK
882 Poll forces a polling idle loop that can slightly improves the performance
883 of waking up a idle CPU, but will use a lot of power and make the system
884 run hot. Not recommended.
885 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
886 to not use it because it doesn't save as much power as a normal idle
887 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
888 as idle=poll.
c1e3b377
ZY
889 idle=halt. Halt is forced to be used for CPU idle.
890 In such case C2/C3 won't be used again.
da5e09a1 891 idle=nomwait. Disable mwait for CPU C-states
a9913044 892
594765a7
DC
893 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
894 Claim all unknown PCI IDE storage controllers.
895
79290822
IM
896 ignore_loglevel [KNL]
897 Ignore loglevel setting - this will print /all/
898 kernel messages to the console. Useful for debugging.
899
1da177e4
LT
900 ihash_entries= [KNL]
901 Set number of hash buckets for inode cache.
902
903 in2000= [HW,SCSI]
904 See header of drivers/scsi/in2000.c.
905
906 init= [KNL]
907 Format: <full_path>
908 Run specified binary instead of /sbin/init as init
909 process.
910
911 initcall_debug [KNL] Trace initcalls as they are executed. Useful
912 for working out where the kernel is dying during
913 startup.
914
915 initrd= [BOOT] Specify the location of the initial ramdisk
916
917 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
918 Format: <irq>
919
920 inttest= [IA64]
921
e8de1481
AV
922 iomem= Disable strict checking of access to MMIO memory
923 strict regions from userspace.
924 relaxed
925
b552da87
PM
926 iommu= [x86]
927 off
928 force
929 noforce
930 biomerge
931 panic
932 nopanic
933 merge
934 nomerge
935 forcesac
936 soft
937
938
ba395927
KA
939 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
940 off
941 Disable intel iommu driver.
942 igfx_off [Default Off]
943 By default, gfx is mapped as normal device. If a gfx
944 device has a dedicated DMAR unit, the DMAR unit is
945 bypassed by not enabling DMAR with this option. In
946 this case, gfx device will use physical address for
947 DMA.
7d3b03ce
KA
948 forcedac [x86_64]
949 With this option iommu will not optimize to look
950 for io virtual address below 32 bit forcing dual
951 address cycle on pci bus for cards supporting greater
952 than 32 bit addressing. The default is to look
953 for translation below 32 bit and if not available
954 then look in the higher range.
5e0d2a6f 955 strict [Default Off]
956 With this option on every unmap_single operation will
957 result in a hardware IOTLB flush operation as opposed
958 to batching them for performance.
ba395927 959
b02aae9c 960 io_delay= [X86-32,X86-64] I/O delay method
6e7c4025
IM
961 0x80
962 Standard port 0x80 based delay
963 0xed
964 Alternate port 0xed based delay (needed on some systems)
b02aae9c 965 udelay
6e7c4025
IM
966 Simple two microseconds delay
967 none
968 No delay
b02aae9c 969
1da177e4
LT
970 io7= [HW] IO7 for Marvel based alpha systems
971 See comment before marvel_specify_io7 in
972 arch/alpha/kernel/core_marvel.c.
973
974 ip= [IP_PNP]
6ded55da 975 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
976
977 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
978 See comment before ip2_setup() in
979 drivers/char/ip2/ip2base.c.
1da177e4
LT
980
981 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
982 See header of drivers/scsi/ips.c.
983
72c4a13a
SH
984 ports= [IP_VS_FTP] IPVS ftp helper module
985 Default is 21.
986 Up to 8 (IP_VS_APP_MAX_PORTS) ports
987 may be specified.
988 Format: <port>,<port>....
989
200803df
AC
990 irqfixup [HW]
991 When an interrupt is not handled search all handlers
992 for it. Intended to get systems with badly broken
993 firmware running.
994
995 irqpoll [HW]
996 When an interrupt is not handled search all handlers
997 for it. Also check all handlers each timer
998 interrupt. Intended to get systems with badly broken
999 firmware running.
1000
1da177e4 1001 isapnp= [ISAPNP]
a9913044 1002 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
1003
1004 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
1005 Format:
1006 <cpu number>,...,<cpu number>
1007 or
b225d44e
LZ
1008 <cpu number>-<cpu number>
1009 (must be a positive range in ascending order)
22f2e280
DF
1010 or a mixture
1011 <cpu number>,...,<cpu number>-<cpu number>
b225d44e 1012
1da177e4
LT
1013 This option can be used to specify one or more CPUs
1014 to isolate from the general SMP balancing and scheduling
b225d44e
LZ
1015 algorithms. You can move a process onto or off an
1016 "isolated" CPU via the CPU affinity syscalls or cpuset.
1da177e4
LT
1017 <cpu number> begins at 0 and the maximum value is
1018 "number of CPUs in system - 1".
1019
1020 This option is the preferred way to isolate CPUs. The
a9913044
RD
1021 alternative -- manually setting the CPU mask of all
1022 tasks in the system -- can cause problems and
1023 suboptimal load balancer performance.
1da177e4 1024
a9913044 1025 iucv= [HW,NET]
1da177e4
LT
1026
1027 js= [HW,JOY] Analog joystick
1028 See Documentation/input/joystick.txt.
1029
cd4f0ef7 1030 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
ed7ed365
MG
1031 specifies the amount of memory usable by the kernel
1032 for non-movable allocations. The requested amount is
1033 spread evenly throughout all nodes in the system. The
1034 remaining memory in each node is used for Movable
1035 pages. In the event, a node is too small to have both
1036 kernelcore and Movable pages, kernelcore pages will
1037 take priority and other nodes will have a larger number
1038 of kernelcore pages. The Movable zone is used for the
1039 allocation of pages that may be reclaimed or moved
1040 by the page migration subsystem. This means that
1041 HugeTLB pages may not be allocated from this zone.
1042 Note that allocations like PTEs-from-HighMem still
1043 use the HighMem zone if it exists, and the Normal
1044 zone if it does not.
1045
cd4f0ef7 1046 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
7e63efef
MG
1047 is similar to kernelcore except it specifies the
1048 amount of memory used for migratable allocations.
1049 If both kernelcore and movablecore is specified,
1050 then kernelcore will be at *least* the specified
1051 value but may be more. If movablecore on its own
1052 is specified, the administrator must be careful
1053 that the amount of memory usable for all allocations
1054 is not too small.
1055
1da177e4
LT
1056 keepinitrd [HW,ARM]
1057
cd4f0ef7 1058 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1da177e4
LT
1059 in oops dumps.
1060
6cdf6e06
JW
1061 kgdboc= [HW] kgdb over consoles.
1062 Requires a tty driver that supports console polling.
1063 (only serial suported for now)
1064 Format: <serial_device>[,baud]
1065
9bed90c6
FF
1066 kmac= [MIPS] korina ethernet MAC address.
1067 Configure the RouterBoard 532 series on-chip
1068 Ethernet adapter MAC address.
1069
1da177e4
LT
1070 l2cr= [PPC]
1071
a78bfbfc
RB
1072 l3cr= [PPC]
1073
cd4f0ef7 1074 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 1075 disabled it.
1da177e4 1076
cd4f0ef7 1077 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
e585bef8
TG
1078 C2 power state.
1079
fcb71f6f
FC
1080 libata.dma= [LIBATA] DMA control
1081 libata.dma=0 Disable all PATA and SATA DMA
1082 libata.dma=1 PATA and SATA Disk DMA only
1083 libata.dma=2 ATAPI (CDROM) DMA only
1084 libata.dma=4 Compact Flash DMA only
1085 Combinations also work, so libata.dma=3 enables DMA
1086 for disks and CDROMs, but not CFs.
1087
78e70c23
DJ
1088 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1089 when set.
1090 Format: <int>
1091
33267325
TH
1092 libata.force= [LIBATA] Force configurations. The format is comma
1093 separated list of "[ID:]VAL" where ID is
1094 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1095 matching port, link or device. Basically, it matches
1096 the ATA ID string printed on console by libata. If
1097 the whole ID part is omitted, the last PORT and DEVICE
1098 values are used. If ID hasn't been specified yet, the
1099 configuration applies to all ports, links and devices.
1100
1101 If only DEVICE is omitted, the parameter applies to
1102 the port and all links and devices behind it. DEVICE
1103 number of 0 either selects the first device or the
1104 first fan-out link behind PMP device. It does not
1105 select the host link. DEVICE number of 15 selects the
1106 host link and device attached to it.
1107
1108 The VAL specifies the configuration to force. As long
1109 as there's no ambiguity shortcut notation is allowed.
1110 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1111 The following configurations can be forced.
1112
1113 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1114 Any ID with matching PORT is used.
1115
1116 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1117
1118 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1119 udma[/][16,25,33,44,66,100,133] notation is also
1120 allowed.
1121
1122 * [no]ncq: Turn on or off NCQ.
1123
05944bdf
TH
1124 * nohrst, nosrst, norst: suppress hard, soft
1125 and both resets.
1126
33267325
TH
1127 If there are multiple matching configurations changing
1128 the same attribute, the last one is used.
1129
7c4be253
RD
1130 lmb=debug [KNL] Enable lmb debug messages.
1131
1da177e4 1132 load_ramdisk= [RAM] List of ramdisks to load from floppy
31c00fc1 1133 See Documentation/blockdev/ramdisk.txt.
1da177e4 1134
a6b25b67
RD
1135 lockd.nlm_grace_period=P [NFS] Assign grace period.
1136 Format: <integer>
1da177e4 1137
a6b25b67
RD
1138 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1139 Format: <integer>
1140
1141 lockd.nlm_timeout=T [NFS] Assign timeout value.
1142 Format: <integer>
1143
1144 lockd.nlm_udpport=M [NFS] Assign UDP port.
1145 Format: <integer>
1da177e4
LT
1146
1147 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1148 Format: <irq>
1149
1150 loglevel= All Kernel Messages with a loglevel smaller than the
1151 console loglevel will be printed to the console. It can
1152 also be changed with klogd or other programs. The
1153 loglevels are defined as follows:
1154
1155 0 (KERN_EMERG) system is unusable
1156 1 (KERN_ALERT) action must be taken immediately
1157 2 (KERN_CRIT) critical conditions
1158 3 (KERN_ERR) error conditions
1159 4 (KERN_WARNING) warning conditions
1160 5 (KERN_NOTICE) normal but significant condition
1161 6 (KERN_INFO) informational
1162 7 (KERN_DEBUG) debug-level messages
1163
1164 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1165 Format: { n | nk | nM }
1166 n must be a power of two. The default size
1167 is set in the kernel config file.
1da177e4 1168
accaa24c
RD
1169 logo.nologo [FB] Disables display of the built-in Linux logo.
1170 This may be used to provide more screen space for
1171 kernel log messages and is useful when debugging
1172 kernel boot problems.
1173
1da177e4
LT
1174 lp=0 [LP] Specify parallel ports to use, e.g,
1175 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1176 lp=reset first parallel port). 'lp=0' disables the
1177 lp=auto printer driver. 'lp=reset' (which can be
1178 specified in addition to the ports) causes
1179 attached printers to be reset. Using
1180 lp=port1,port2,... specifies the parallel ports
1181 to associate lp devices with, starting with
1182 lp0. A port specification may be 'none' to skip
1183 that lp device, or a parport name such as
1184 'parport0'. Specifying 'lp=auto' instead of a
1185 port specification list means that device IDs
1186 from each port should be examined, to see if
1187 an IEEE 1284-compliant printer is attached; if
1188 so, the driver will manage that printer.
1189 See also header of drivers/char/lp.c.
1190
1191 lpj=n [KNL]
1192 Sets loops_per_jiffy to given constant, thus avoiding
1193 time-consuming boot-time autodetection (up to 250 ms per
1194 CPU). 0 enables autodetection (default). To determine
1195 the correct value for your kernel, boot with normal
1196 autodetection and see what value is printed. Note that
1197 on SMP systems the preset will be applied to all CPUs,
1198 which is likely to cause problems if your CPUs need
1199 significantly divergent settings. An incorrect value
1200 will cause delays in the kernel to be wrong, leading to
1201 unpredictable I/O errors and other breakage. Although
1202 unlikely, in the extreme case this might damage your
1203 hardware.
1204
1205 ltpc= [NET]
1206 Format: <io>,<irq>,<dma>
1207
a9913044
RD
1208 mac5380= [HW,SCSI] Format:
1209 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1210
a9913044
RD
1211 machvec= [IA64] Force the use of a particular machine-vector
1212 (machvec) in a generic kernel.
1213 Example: machvec=hpzx1_swiotlb
1da177e4 1214
a9913044 1215 max_loop= [LOOP] Maximum number of loopback devices that can
1da177e4
LT
1216 be mounted
1217 Format: <1-256>
1218
1219 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1220 should make use of. maxcpus=n : n >= 0 limits the
1221 kernel to using 'n' processors. n=0 is a special case,
1222 it is equivalent to "nosmp", which also disables
1223 the IO APIC.
1da177e4 1224
1c207f95
RD
1225 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater than
1226 or equal to this physical address is ignored.
2b2c3750 1227
a9913044 1228 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1229 Should be between 1 and 2^32-1.
1230
1231 max_report_luns=
a9913044 1232 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1233 Should be between 1 and 16384.
1234
1da177e4
LT
1235 mcatest= [IA-64]
1236
cd4f0ef7 1237 mce [X86-32] Machine Check Exception
1da177e4 1238
71cced6e 1239 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
909dd324 1240
1da177e4
LT
1241 md= [HW] RAID subsystems devices and level
1242 See Documentation/md.txt.
a9913044 1243
1da177e4
LT
1244 mdacon= [MDA]
1245 Format: <first>,<last>
1246 Specifies range of consoles to be captured by the MDA.
a9913044 1247
1da177e4
LT
1248 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1249 Amount of memory to be used when the kernel is not able
1250 to see the whole system memory or for test.
cd4f0ef7 1251 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1252 address space collisions. Without memmap= PCI devices
1253 could be placed at addresses belonging to unused RAM.
1254
cd4f0ef7 1255 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1256 memory.
1257
6902aa84
PM
1258 memchunk=nn[KMG]
1259 [KNL,SH] Allow user to override the default size for
1260 per-device physically contiguous DMA buffers.
1261
cd4f0ef7 1262 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1da177e4
LT
1263 E820 memory map, as specified by the user.
1264 Such memmap=exactmap lines can be constructed based on
1265 BIOS output or other requirements. See the memmap=nn@ss
1266 option description.
1267
1268 memmap=nn[KMG]@ss[KMG]
1269 [KNL] Force usage of a specific region of memory
1270 Region of memory to be used, from ss to ss+nn.
1271
1272 memmap=nn[KMG]#ss[KMG]
1273 [KNL,ACPI] Mark specific memory as ACPI data.
1274 Region of memory to be used, from ss to ss+nn.
1275
1276 memmap=nn[KMG]$ss[KMG]
1277 [KNL,ACPI] Mark specific memory as reserved.
1278 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1279 Example: Exclude memory from 0x18690000-0x1869ffff
1280 memmap=64K$0x18690000
1281 or
1282 memmap=0x10000$0x18690000
1da177e4 1283
9f077871
JF
1284 memory_corruption_check=0/1 [X86]
1285 Some BIOSes seem to corrupt the first 64k of
1286 memory when doing things like suspend/resume.
1287 Setting this option will scan the memory
1288 looking for corruption. Enabling this will
1289 both detect corruption and prevent the kernel
1290 from using the memory being corrupted.
1291 However, its intended as a diagnostic tool; if
1292 repeatable BIOS-originated corruption always
1293 affects the same memory, you can use memmap=
1294 to prevent the kernel from using that memory.
1295
1296 memory_corruption_check_size=size [X86]
1297 By default it checks for corruption in the low
1298 64k, making this memory unavailable for normal
1299 use. Use this parameter to scan for
1300 corruption in more or less memory.
1301
1302 memory_corruption_check_period=seconds [X86]
1303 By default it checks for corruption every 60
1304 seconds. Use this parameter to check at some
1305 other rate. 0 disables periodic checking.
1306
caadbdce 1307 memtest= [KNL,X86] Enable memtest
c64df707
YL
1308 Format: <integer>
1309 range: 0,4 : pattern number
1310 default : 0 <disable>
1311
1da177e4
LT
1312 meye.*= [HW] Set MotionEye Camera parameters
1313 See Documentation/video4linux/meye.txt.
1314
8f36881b
AS
1315 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1316 Multi-Function General Purpose Timers on AMD Geode
1317 platforms.
1318
e6c4dc6c
WT
1319 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1320 the BIOS has incorrectly applied a workaround. TinyBIOS
1321 version 0.98 is known to be affected, 0.99 fixes the
1322 problem by letting the user disable the workaround.
1323
1da177e4
LT
1324 mga= [HW,DRM]
1325
1c207f95
RD
1326 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1327 physical address is ignored.
1328
6b74ab97
MG
1329 mminit_loglevel=
1330 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1331 parameter allows control of the logging verbosity for
1332 the additional memory initialisation checks. A value
1333 of 0 disables mminit logging and a level of 4 will
1334 log everything. Information is printed at KERN_DEBUG
1335 so loglevel=8 may also need to be specified.
1336
1da177e4
LT
1337 mousedev.tap_time=
1338 [MOUSE] Maximum time between finger touching and
1339 leaving touchpad surface for touch to be considered
1340 a tap and be reported as a left button click (for
1341 touchpads working in absolute mode only).
1342 Format: <msecs>
1343 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1344 reporting absolute coordinates, such as tablets
1345 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1346 reporting absolute coordinates, such as tablets
1347
1348 mpu401= [HW,OSS]
1349 Format: <io>,<irq>
1350
1351 MTD_Partition= [MTD]
1352 Format: <name>,<region-number>,<size>,<offset>
1353
a9913044
RD
1354 MTD_Region= [MTD] Format:
1355 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1356
1357 mtdparts= [MTD]
c8facbb6 1358 See drivers/mtd/cmdlinepart.c.
1da177e4 1359
9db829f4
BD
1360 mtdset= [ARM]
1361 ARM/S3C2412 JIVE boot control
1362
1363 See arch/arm/mach-s3c2412/mach-jive.c
1364
1da177e4 1365 mtouchusb.raw_coordinates=
a9913044
RD
1366 [HW] Make the MicroTouch USB driver use raw coordinates
1367 ('y', default) or cooked coordinates ('n')
1da177e4
LT
1368
1369 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1370
1371 NCR_D700= [HW,SCSI]
1372 See header of drivers/scsi/NCR_D700.c.
1373
1374 ncr5380= [HW,SCSI]
1375
1376 ncr53c400= [HW,SCSI]
1377
1378 ncr53c400a= [HW,SCSI]
1379
1380 ncr53c406a= [HW,SCSI]
1381
1382 ncr53c8xx= [HW,SCSI]
1383
1384 netdev= [NET] Network devices parameters
1385 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1386 Note that mem_start is often overloaded to mean
1387 something different and driver-specific.
a9913044
RD
1388 This usage is only documented in each driver source
1389 file if at all.
1390
58401572
KPO
1391 nf_conntrack.acct=
1392 [NETFILTER] Enable connection tracking flow accounting
1393 0 to disable accounting
1394 1 to enable accounting
1395 Default value depends on CONFIG_NF_CT_ACCT that is
1396 going to be removed in 2.6.29.
1397
1da177e4 1398 nfsaddrs= [NFS]
6ded55da 1399 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
1400
1401 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
6ded55da 1402 See Documentation/filesystems/nfsroot.txt.
1da177e4 1403
a72b4422
TM
1404 nfs.callback_tcpport=
1405 [NFS] set the TCP port on which the NFSv4 callback
1406 channel should listen.
1407
58df095b
TM
1408 nfs.idmap_cache_timeout=
1409 [NFS] set the maximum lifetime for idmapper cache
1410 entries.
1411
f43bf0be
TM
1412 nfs.enable_ino64=
1413 [NFS] enable 64-bit inode numbers.
1414 If zero, the NFS client will fake up a 32-bit inode
1415 number for the readdir() and stat() syscalls instead
1416 of returning the full 64-bit number.
1417 The default is to return 64-bit inode numbers.
1418
e7ba176b
HS
1419 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1420 when a NMI is triggered.
1421 Format: [state][,regs][,debounce][,die]
1422
5b9a0e14
CG
1423 nmi_watchdog= [KNL,BUGS=X86-32,X86-64] Debugging features for SMP kernels
1424 Format: [panic,][num]
1425 Valid num: 0,1,2
1426 0 - turn nmi_watchdog off
1427 1 - use the IO-APIC timer for the NMI watchdog
1428 2 - use the local APIC for the NMI watchdog using
1429 a performance counter. Note: This will use one performance
1430 counter and the local APIC's performance vector.
1431 When panic is specified panic when an NMI watchdog timeout occurs.
1432 This is useful when you use a panic=... timeout and need the box
1433 quickly up again.
1434 Instead of 1 and 2 it is possible to use the following
1435 symbolic names: lapic and ioapic
1436 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1da177e4 1437
cd4f0ef7 1438 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1439 emulation library even if a 387 maths coprocessor
1440 is present.
1441
c1aee215
CL
1442 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1443 caches in the slab allocator. Saves per-node memory,
1444 but will impact performance.
3395ee05 1445
a9913044
RD
1446 noalign [KNL,ARM]
1447
1da177e4
LT
1448 noapic [SMP,APIC] Tells the kernel to not make use of any
1449 IOAPICs that may be present in the system.
1450
1da177e4
LT
1451 nobats [PPC] Do not use BATs for mapping kernel lowmem
1452 on "Classic" PPC cores.
1453
1454 nocache [ARM]
a9913044 1455
163ecdff
SN
1456 nodelayacct [KNL] Disable per-task delay accounting
1457
1da177e4
LT
1458 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1459
6902aa84
PM
1460 nodsp [SH] Disable hardware DSP at boot time.
1461
8b2cb7a8
HY
1462 noefi [X86-32,X86-64] Disable EFI runtime services support.
1463
1da177e4
LT
1464 noexec [IA-64]
1465
cd4f0ef7 1466 noexec [X86-32,X86-64]
f5a1b191 1467 On X86-32 available only on PAE configured kernels.
1da177e4 1468 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
1469 noexec=off: disable non-executable mappings
1470
1471 noexec32 [X86-64]
1472 This affects only 32-bit executables.
1473 noexec32=on: enable non-executable mappings (default)
1474 read doesn't imply executable mappings
1475 noexec32=off: disable non-executable mappings
1476 read implies executable mappings
1da177e4 1477
6902aa84
PM
1478 nofpu [SH] Disable hardware FPU at boot time.
1479
cd4f0ef7 1480 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1481 register save and restore. The kernel will only save
1482 legacy floating-point registers on task switch.
1da177e4 1483
191679fd
AK
1484 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1485
6902aa84 1486 nohlt [BUGS=ARM,SH]
a9913044 1487
cd4f0ef7 1488 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1489 instruction doesn't work correctly and not to
1490 use it.
1491
1f29fae2
SH
1492 no_file_caps Tells the kernel not to honor file capabilities. The
1493 only way then for a file to be executed with privilege
1494 is to be setuid root or executed by root.
1495
1da177e4
LT
1496 nohalt [IA-64] Tells the kernel not to use the power saving
1497 function PAL_HALT_LIGHT when idle. This increases
1498 power-consumption. On the positive side, it reduces
1499 interrupt wake-up latency, which may improve performance
1500 in certain environments such as networked servers or
1501 real-time systems.
1502
79bf2bb3
TG
1503 nohz= [KNL] Boottime enable/disable dynamic ticks
1504 Valid arguments: on, off
1505 Default: on
1506
cd4f0ef7 1507 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1508 disable unhandled interrupt sources.
1509
cd4f0ef7 1510 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
8542b200
ZA
1511 broken timer IRQ sources.
1512
1da177e4
LT
1513 noisapnp [ISAPNP] Disables ISA PnP code.
1514
1515 noinitrd [RAM] Tells the kernel not to load any configured
1516 initial RAM disk.
1517
1518 nointroute [IA-64]
1519
0aa366f3
TL
1520 nojitter [IA64] Disables jitter checking for ITC timers.
1521
cd4f0ef7 1522 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1523
cd4f0ef7 1524 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1525
6e1cb38a
SS
1526 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1527
af9d1388
SS
1528 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
1529 default x2apic cluster mode on platforms
1530 supporting x2apic.
1531
1da177e4
LT
1532 noltlbs [PPC] Do not use large page/tlb entries for kernel
1533 lowmem mapping on PPC40x.
1534
312f1f01
H
1535 nomca [IA-64] Disable machine check abort handling
1536
cd4f0ef7 1537 nomce [X86-32] Machine Check Exception
abe37e5a 1538
83d7384f
AS
1539 nomfgpt [X86-32] Disable Multi-Function General Purpose
1540 Timer usage (for AMD Geode machines).
1541
cd4f0ef7 1542 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1543
cd4f0ef7 1544 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1545 with UP alternatives
1546
1da177e4
LT
1547 noresidual [PPC] Don't use residual data on PReP machines.
1548
a9913044
RD
1549 noresume [SWSUSP] Disables resume and restores original swap
1550 space.
1551
1da177e4
LT
1552 no-scroll [VGA] Disables scrollback.
1553 This is required for the Braillex ib80-piezo Braille
1554 reader made by F.H. Papenmeier (Germany).
1555
1556 nosbagart [IA-64]
1557
cd4f0ef7 1558 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1559
61ec7567
LB
1560 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1561 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1562
97842216
DJ
1563 nosoftlockup [KNL] Disable the soft-lockup detector.
1564
c077719b
KH
1565 noswapaccount [KNL] Disable accounting of swap in memory resource
1566 controller. (See Documentation/controllers/memory.txt)
1567
1da177e4
LT
1568 nosync [HW,M68K] Disables sync negotiation for all devices.
1569
cd4f0ef7 1570 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1571
1572 nousb [USB] Disable the USB subsystem
1573
1574 nowb [ARM]
a9913044 1575
a6c75b86
FY
1576 nptcg= [IA64] Override max number of concurrent global TLB
1577 purges which is reported from either PAL_VM_SUMMARY or
1578 SAL PALO.
1579
f0c0b2b8
KH
1580 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1581 one of ['zone', 'node', 'default'] can be specified
1582 This can be set from sysctl after boot.
1583 See Documentation/sysctl/vm.txt for details.
1584
a61c2d78
DJ
1585 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1586
7c4be253
RD
1587 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1588 See Documentation/debugging-via-ohci1394.txt for more
1589 info.
1590
3ef0e1f8
AS
1591 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1592 Rather than timing out after 20 ms if an EC
1593 command is not properly ACKed, override the length
1594 of the timeout. We have interrupts disabled while
1595 waiting for the ACK, so if this is set too high
1596 interrupts *may* be lost!
1597
1da177e4
LT
1598 opl3= [HW,OSS]
1599 Format: <io>
1600
1da177e4
LT
1601 oprofile.timer= [HW]
1602 Use timer interrupt instead of performance counters
1603
1da177e4
LT
1604 osst= [HW,SCSI] SCSI Tape Driver
1605 Format: <buffer_size>,<write_threshold>
1606 See also Documentation/scsi/st.txt.
1607
1608 panic= [KNL] Kernel behaviour on panic
1609 Format: <timeout>
1610
1611 parkbd.port= [HW] Parallel port number the keyboard adapter is
1612 connected to, default is 0.
1613 Format: <parport#>
1614 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1615 0 for XT, 1 for AT (default is AT).
a9913044
RD
1616 Format: <mode>
1617
1618 parport= [HW,PPT] Specify parallel ports. 0 disables.
1619 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1620 Use 'auto' to force the driver to use any
1621 IRQ/DMA settings detected (the default is to
1622 ignore detected IRQ/DMA settings because of
1623 possible conflicts). You can specify the base
1624 address, IRQ, and DMA settings; IRQ and DMA
1625 should be numbers, or 'auto' (for using detected
1626 settings on that particular port), or 'nofifo'
1627 (to avoid using a FIFO even if it is detected).
1628 Parallel ports are assigned in the order they
1629 are specified on the command line, starting
1630 with parport0.
1631
1632 parport_init_mode= [HW,PPT]
1633 Configure VIA parallel port to operate in
1634 a specific mode. This is necessary on Pegasos
1635 computer where firmware has no options for setting
1636 up parallel port mode and sets it to spp.
1637 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1638 Format: [spp|ps2|epp|ecp|ecpepp]
1639
a9913044
RD
1640 pas2= [HW,OSS] Format:
1641 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1642
1da177e4
LT
1643 pas16= [HW,SCSI]
1644 See header of drivers/scsi/pas16.c.
1645
dd287796
AM
1646 pause_on_oops=
1647 Halt all CPUs after the first oops has been printed for
1648 the specified number of seconds. This is to be used if
1649 your oopses keep scrolling off the screen.
1650
1da177e4
LT
1651 pcbit= [HW,ISDN]
1652
1653 pcd. [PARIDE]
1654 See header of drivers/block/paride/pcd.c.
31c00fc1 1655 See also Documentation/blockdev/paride.txt.
1da177e4 1656
a9913044 1657 pci=option[,option...] [PCI] various PCI subsystem options:
c0115606 1658 off [X86] don't probe for the PCI bus
cd4f0ef7 1659 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1660 the hardware directly. Use this if your machine
1661 has a non-standard PCI host bridge.
cd4f0ef7 1662 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1663 hardware access methods are allowed. Use this
1664 if you experience crashes upon bootup and you
1665 suspect they are caused by the BIOS.
c0115606 1666 conf1 [X86] Force use of PCI Configuration
a9913044 1667 Mechanism 1.
c0115606 1668 conf2 [X86] Force use of PCI Configuration
a9913044 1669 Mechanism 2.
7f785763
RD
1670 noaer [PCIE] If the PCIEAER kernel config parameter is
1671 enabled, this kernel boot option can be used to
1672 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1673 nodomains [PCI] Disable support for multiple PCI
1674 root domains (aka PCI segments, in ACPI-speak).
cd4f0ef7 1675 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
61be6d66 1676 Configuration
309e57df
MW
1677 nomsi [MSI] If the PCI_MSI kernel config parameter is
1678 enabled, this kernel boot option can be used to
1679 disable the use of MSI interrupts system-wide.
a9322f64
SA
1680 noioapicquirk [APIC] Disable all boot interrupt quirks.
1681 Safety option to keep boot IRQs enabled. This
1682 should never be necessary.
9197979b
SA
1683 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1684 primary IO-APIC for bridges that cannot disable
1685 boot IRQs. This fixes a source of spurious IRQs
1686 when the system masks IRQs.
41b9eb26
SA
1687 noioapicreroute [APIC] Disable workaround that uses the
1688 boot IRQ equivalent of an IRQ that connects to
1689 a chipset where boot IRQs cannot be disabled.
1690 The opposite of ioapicreroute.
cd4f0ef7 1691 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1692 routing table. These calls are known to be buggy
1693 on several machines and they hang the machine
1694 when used, but on other computers it's the only
1695 way to get the interrupt routing table. Try
1696 this option if the kernel is unable to allocate
1697 IRQs or discover secondary PCI buses on your
1698 motherboard.
c0115606 1699 rom [X86] Assign address space to expansion ROMs.
a9913044
RD
1700 Use with caution as certain devices share
1701 address decoders between ROMs and other
1702 resources.
c0115606 1703 norom [X86] Do not assign address space to
bb71ad88
GH
1704 expansion ROMs that do not already have
1705 BIOS assigned address ranges.
c0115606 1706 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
a9913044
RD
1707 assigned automatically to PCI devices. You can
1708 make the kernel exclude IRQs of your ISA cards
1709 this way.
c0115606 1710 pirqaddr=0xAAAAA [X86] Specify the physical address
a9913044
RD
1711 of the PIRQ table (normally generated
1712 by the BIOS) if it is outside the
1713 F0000h-100000h range.
c0115606 1714 lastbus=N [X86] Scan all buses thru bus #N. Can be
a9913044
RD
1715 useful if the kernel is unable to find your
1716 secondary buses and you want to tell it
1717 explicitly which ones they are.
c0115606 1718 assign-busses [X86] Always assign all PCI bus
a9913044
RD
1719 numbers ourselves, overriding
1720 whatever the firmware may have done.
c0115606 1721 usepirqmask [X86] Honor the possible IRQ mask stored
a9913044
RD
1722 in the BIOS $PIR table. This is needed on
1723 some systems with broken BIOSes, notably
1724 some HP Pavilion N5400 and Omnibook XE3
1725 notebooks. This will have no effect if ACPI
1726 IRQ routing is enabled.
c0115606 1727 noacpi [X86] Do not use ACPI for IRQ routing
a9913044 1728 or for PCI scanning.
c0115606 1729 use_crs [X86] Use _CRS for PCI resource
62f420f8 1730 allocation.
a9913044
RD
1731 routeirq Do IRQ routing for all PCI devices.
1732 This is normally done in pci_enable_device(),
1733 so this option is a temporary workaround
1734 for broken drivers that don't call it.
13a6ddb0
YL
1735 skip_isa_align [X86] do not align io start addr, so can
1736 handle more pci cards
a9913044
RD
1737 firmware [ARM] Do not re-enumerate the bus but instead
1738 just use the configuration from the
1739 bootloader. This is currently used on
1740 IXP2000 systems where the bus has to be
1741 configured a certain way for adjunct CPUs.
0637a70a
AK
1742 noearly [X86] Don't do any early type 1 scanning.
1743 This might help on some broken boards which
1744 machine check when some devices' config space
1745 is read. But various workarounds are disabled
1746 and some IOMMU drivers will not work.
6b4b78fe
MD
1747 bfsort Sort PCI devices into breadth-first order.
1748 This sorting is done to get a device
1749 order compatible with older (<= 2.4) kernels.
1750 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1751 cbiosize=nn[KMG] The fixed amount of bus space which is
1752 reserved for the CardBus bridge's IO window.
1753 The default value is 256 bytes.
1754 cbmemsize=nn[KMG] The fixed amount of bus space which is
1755 reserved for the CardBus bridge's memory
1756 window. The default value is 64 megabytes.
6b4b78fe 1757
e5665a45
CE
1758 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1759 Management.
1760 off Disable ASPM.
1761 force Enable ASPM even on devices that claim not to support it.
1762 WARNING: Forcing ASPM on may cause system lockups.
1763
1da177e4
LT
1764 pcmv= [HW,PCMCIA] BadgePAD 4
1765
1766 pd. [PARIDE]
31c00fc1 1767 See Documentation/blockdev/paride.txt.
1da177e4
LT
1768
1769 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1770 boot time.
1771 Format: { 0 | 1 }
1772 See arch/parisc/kernel/pdc_chassis.c
1773
1774 pf. [PARIDE]
31c00fc1 1775 See Documentation/blockdev/paride.txt.
1da177e4
LT
1776
1777 pg. [PARIDE]
31c00fc1 1778 See Documentation/blockdev/paride.txt.
1da177e4
LT
1779
1780 pirq= [SMP,APIC] Manual mp-table setup
71cced6e 1781 See Documentation/x86/i386/IO-APIC.txt.
1da177e4
LT
1782
1783 plip= [PPT,NET] Parallel port network link
1784 Format: { parport<nr> | timid | 0 }
1785 See also Documentation/parport.txt.
1786
de32a243
TG
1787 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1788 Override pmtimer IOPort with a hex value.
1789 e.g. pmtmr=0x508
1790
97ef062b
BH
1791 pnp.debug [PNP]
1792 Enable PNP debug messages. This depends on the
1793 CONFIG_PNP_DEBUG_MESSAGES option.
1794
1da177e4
LT
1795 pnpacpi= [ACPI]
1796 { off }
1797
1798 pnpbios= [ISAPNP]
1799 { on | off | curr | res | no-curr | no-res }
1800
1801 pnp_reserve_irq=
1802 [ISAPNP] Exclude IRQs for the autoconfiguration
1803
1804 pnp_reserve_dma=
1805 [ISAPNP] Exclude DMAs for the autoconfiguration
1806
1807 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1808 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1809
1810 pnp_reserve_mem=
a9913044
RD
1811 [ISAPNP] Exclude memory regions for the
1812 autoconfiguration.
1da177e4
LT
1813 Ranges are in pairs (memory base and size).
1814
ecb08d81
RD
1815 dynamic_printk Enables pr_debug()/dev_dbg() calls if
1816 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
1817 These can also be switched on/off via
1818 <debugfs>/dynamic_printk/modules
346e15be 1819
45807a1d
IM
1820 print-fatal-signals=
1821 [KNL] debug: print fatal signals
1822 print-fatal-signals=1: print segfault info to
1823 the kernel console.
1824 default: off.
1825
e84845c4
RD
1826 printk.time= Show timing data prefixed to each printk message line
1827 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1828
1da177e4 1829 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1830 Format: [schedule,]<number>
1831 Param: "schedule" - profile schedule points.
1832 Param: <number> - step/bucket size as a power of 2 for
1833 statistical time based profiling.
b3da2a73
MG
1834 Param: "sleep" - profile D-state sleeping (millisecs).
1835 Requires CONFIG_SCHEDSTATS
c0fe2e69 1836 Param: "kvm" - profile VM exits.
1da177e4 1837
a9913044 1838 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1839 Limit processor to maximum C-state
1840 max_cstate=9 overrides any DMI blacklist limit.
1841
41c0d868
LB
1842 processor.nocst [HW,ACPI]
1843 Ignore the _CST method to determine C-states,
1844 instead using the legacy FADT method
1845
1da177e4
LT
1846 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1847 before loading.
31c00fc1 1848 See Documentation/blockdev/ramdisk.txt.
1da177e4 1849
a9913044
RD
1850 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1851 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1852 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1853 per second.
a9913044
RD
1854 psmouse.resetafter= [HW,MOUSE]
1855 Try to reset the device after so many bad packets
1da177e4
LT
1856 (0 = never).
1857 psmouse.resolution=
1858 [HW,MOUSE] Set desired mouse resolution, in dpi.
1859 psmouse.smartscroll=
a9913044 1860 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1861 0 = disabled, 1 = enabled (default).
1862
1863 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1864 Format:
1865 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1866
1867 pt. [PARIDE]
31c00fc1 1868 See Documentation/blockdev/paride.txt.
1da177e4 1869
dc8c8587
KS
1870 pty.legacy_count=
1871 [KNL] Number of legacy pty's. Overwrites compiled-in
1872 default number.
1873
7d2c502f 1874 quiet [KNL] Disable most log messages
a9913044 1875
1da177e4
LT
1876 r128= [HW,DRM]
1877
1878 raid= [HW,RAID]
1879 See Documentation/md.txt.
1880
a9913044 1881 ramdisk_blocksize= [RAM]
31c00fc1 1882 See Documentation/blockdev/ramdisk.txt.
a9913044 1883
1da177e4 1884 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
31c00fc1 1885 See Documentation/blockdev/ramdisk.txt.
1da177e4 1886
24aaef8d
RD
1887 rcupdate.blimit= [KNL,BOOT]
1888 Set maximum number of finished RCU callbacks to process
1889 in one batch.
21a1ea9e 1890
24aaef8d
RD
1891 rcupdate.qhimark= [KNL,BOOT]
1892 Set threshold of queued
21a1ea9e
DS
1893 RCU callbacks over which batch limiting is disabled.
1894
24aaef8d
RD
1895 rcupdate.qlowmark= [KNL,BOOT]
1896 Set threshold of queued RCU callbacks below which
1897 batch limiting is re-enabled.
21a1ea9e 1898
ffdfc409
OJ
1899 rdinit= [KNL]
1900 Format: <full_path>
1901 Run specified binary instead of /init from the ramdisk,
1902 used for early userspace startup. See initrd.
1903
cd4f0ef7 1904 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1905 Format: <reboot_mode>[,<reboot_mode2>[,...]]
ecb08d81 1906 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4 1907
46b6d94e
PJ
1908 relax_domain_level=
1909 [KNL, SMP] Set scheduler's default relax_domain_level.
1910 See Documentation/cpusets.txt.
1911
1da177e4
LT
1912 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1913
cd4f0ef7 1914 reservetop= [X86-32]
461a9aff
ZA
1915 Format: nn[KMG]
1916 Reserves a hole at the top of the kernel virtual
1917 address space.
1918
7e96287d
VG
1919 reset_devices [KNL] Force drivers to reset the underlying device
1920 during initialization.
1921
a9913044
RD
1922 resume= [SWSUSP]
1923 Specify the partition device for software suspend
1da177e4 1924
ecbd0da1
RW
1925 resume_offset= [SWSUSP]
1926 Specify the offset from the beginning of the partition
1927 given by "resume=" at which the swap header is located,
1928 in <PAGE_SIZE> units (needed only for swap files).
1929 See Documentation/power/swsusp-and-swap-files.txt
1930
0a7b35cb
MN
1931 retain_initrd [RAM] Keep initrd memory after extraction
1932
1da177e4
LT
1933 rhash_entries= [KNL,NET]
1934 Set number of hash buckets for route cache
1935
1936 riscom8= [HW,SERIAL]
1937 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1938
1939 ro [KNL] Mount root device read-only on boot
1940
1941 root= [KNL] Root filesystem
1942
1943 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1944 mount the root filesystem
1945
1946 rootflags= [KNL] Set root filesystem mount option string
1947
1948 rootfstype= [KNL] Set root filesystem type
1949
cc1ed754
PO
1950 rootwait [KNL] Wait (indefinitely) for root device to show up.
1951 Useful for devices that are detected asynchronously
1952 (e.g. USB and MMC devices).
1953
20510f2f
JM
1954 root_plug.vendor_id=
1955 [ROOTPLUG] Override the default vendor ID
1956
1957 root_plug.product_id=
1958 [ROOTPLUG] Override the default product ID
1959
1960 root_plug.debug=
1961 [ROOTPLUG] Enable debugging output
1962
1da177e4
LT
1963 rw [KNL] Mount root device read-write on boot
1964
1965 S [KNL] Run init in single mode
1966
1967 sa1100ir [NET]
1968 See drivers/net/irda/sa1100_ir.c.
1969
1da177e4 1970 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1971
1da177e4
LT
1972 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1973 Format: <io>[,<timeout>[,<isapnp>]]
1974
1975 scsi_debug_*= [SCSI]
1976 See drivers/scsi/scsi_debug.c.
1977
1978 scsi_default_dev_flags=
1979 [SCSI] SCSI default device flags
1980 Format: <integer>
1981
1982 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1983 Format: <vendor>:<model>:<flags>
1984 (flags are integer value)
1985
6af6632a
RD
1986 scsi_logging_level= [SCSI] a bit mask of logging levels
1987 See drivers/scsi/scsi_logging.h for bits. Also
1988 settable via sysctl at dev.scsi.logging_level
1989 (/proc/sys/dev/scsi/logging_level).
1990 There is also a nice 'scsi_logging_level' script in the
1991 S390-tools package, available for download at
1992 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 1993
3e082a91
MW
1994 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1995 discovered. async scans them in kernel threads,
1996 allowing boot to proceed. none ignores them, expecting
1997 user space to do the scan.
1998
1da177e4
LT
1999 selinux [SELINUX] Disable or enable SELinux at boot time.
2000 Format: { "0" | "1" }
2001 See security/selinux/Kconfig help text.
2002 0 -- disable.
2003 1 -- enable.
2004 Default value is set via kernel config option.
2005 If enabled at boot time, /selinux/disable can be used
2006 later to disable prior to initial policy load.
2007
4e5ab4cb
JM
2008 selinux_compat_net =
2009 [SELINUX] Set initial selinux_compat_net flag value.
e53dd083
MCC
2010 Format: { "0" | "1" }
2011 0 -- use new secmark-based packet controls
2012 1 -- use legacy packet controls
2013 Default value is 0 (preferred).
2014 Value can be changed at runtime via
2015 /selinux/compat_net.
4e5ab4cb 2016
cd4f0ef7 2017 serialnumber [BUGS=X86-32]
1da177e4 2018
1da177e4
LT
2019 shapers= [NET]
2020 Maximal number of shapers.
a9913044 2021
b05f78f5
YL
2022 show_msr= [x86] show boot-time MSR settings
2023 Format: { <integer> }
2024 Show boot-time (BIOS-initialized) MSR settings.
2025 The parameter means the number of CPUs to show,
2026 for example 1 means boot CPU only.
2027
1da177e4
LT
2028 sim710= [SCSI,HW]
2029 See header of drivers/scsi/sim710.c.
2030
2031 simeth= [IA-64]
2032 simscsi=
a9913044 2033
1da177e4
LT
2034 slram= [HW,MTD]
2035
f0630fff
CL
2036 slub_debug[=options[,slabs]] [MM, SLUB]
2037 Enabling slub_debug allows one to determine the
2038 culprit if slab objects become corrupted. Enabling
2039 slub_debug can create guard zones around objects and
2040 may poison objects when not in use. Also tracks the
2041 last alloc / free. For more information see
2042 Documentation/vm/slub.txt.
c1aee215
CL
2043
2044 slub_max_order= [MM, SLUB]
f0630fff
CL
2045 Determines the maximum allowed order for slabs.
2046 A high setting may cause OOMs due to memory
2047 fragmentation. For more information see
2048 Documentation/vm/slub.txt.
c1aee215
CL
2049
2050 slub_min_objects= [MM, SLUB]
f0630fff
CL
2051 The minimum number of objects per slab. SLUB will
2052 increase the slab order up to slub_max_order to
2053 generate a sufficiently large slab able to contain
2054 the number of objects indicated. The higher the number
2055 of objects the smaller the overhead of tracking slabs
2056 and the less frequently locks need to be acquired.
c1aee215
CL
2057 For more information see Documentation/vm/slub.txt.
2058
2059 slub_min_order= [MM, SLUB]
2060 Determines the mininum page order for slabs. Must be
f0630fff 2061 lower than slub_max_order.
c1aee215
CL
2062 For more information see Documentation/vm/slub.txt.
2063
2064 slub_nomerge [MM, SLUB]
f0630fff 2065 Disable merging of slabs with similar size. May be
c1aee215 2066 necessary if there is some reason to distinguish
f0630fff
CL
2067 allocs to different slabs. Debug options disable
2068 merging on their own.
c1aee215
CL
2069 For more information see Documentation/vm/slub.txt.
2070
1da177e4
LT
2071 smart2= [HW]
2072 Format: <io1>[,<io2>[,...,<io8>]]
2073
cd4f0ef7 2074 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
2075 attempt to substitute SMP alternatives once at boot.
2076
d0d4f69b
BH
2077 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2078 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2079 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2080 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2081 smsc-ircc2.ircc_irq= [HW] IRQ line
2082 smsc-ircc2.ircc_dma= [HW] DMA channel
2083 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2084 0: Toshiba Satellite 1800 (GP data pin select)
2085 1: Fast pin select (default)
2086 2: ATC IRMode
2087
1da177e4
LT
2088 snd-ad1816a= [HW,ALSA]
2089
2090 snd-ad1848= [HW,ALSA]
2091
2092 snd-ali5451= [HW,ALSA]
2093
2094 snd-als100= [HW,ALSA]
2095
2096 snd-als4000= [HW,ALSA]
2097
2098 snd-azt2320= [HW,ALSA]
2099
2100 snd-cmi8330= [HW,ALSA]
2101
2102 snd-cmipci= [HW,ALSA]
2103
2104 snd-cs4231= [HW,ALSA]
2105
2106 snd-cs4232= [HW,ALSA]
2107
2108 snd-cs4236= [HW,ALSA]
2109
2110 snd-cs4281= [HW,ALSA]
2111
2112 snd-cs46xx= [HW,ALSA]
2113
2114 snd-dt019x= [HW,ALSA]
2115
2116 snd-dummy= [HW,ALSA]
2117
2118 snd-emu10k1= [HW,ALSA]
2119
2120 snd-ens1370= [HW,ALSA]
2121
2122 snd-ens1371= [HW,ALSA]
2123
2124 snd-es968= [HW,ALSA]
2125
2126 snd-es1688= [HW,ALSA]
2127
2128 snd-es18xx= [HW,ALSA]
2129
2130 snd-es1938= [HW,ALSA]
2131
2132 snd-es1968= [HW,ALSA]
2133
2134 snd-fm801= [HW,ALSA]
2135
2136 snd-gusclassic= [HW,ALSA]
2137
2138 snd-gusextreme= [HW,ALSA]
2139
2140 snd-gusmax= [HW,ALSA]
2141
2142 snd-hdsp= [HW,ALSA]
2143
2144 snd-ice1712= [HW,ALSA]
2145
2146 snd-intel8x0= [HW,ALSA]
2147
2148 snd-interwave= [HW,ALSA]
2149
2150 snd-interwave-stb=
2151 [HW,ALSA]
2152
2153 snd-korg1212= [HW,ALSA]
2154
2155 snd-maestro3= [HW,ALSA]
2156
2157 snd-mpu401= [HW,ALSA]
2158
2159 snd-mtpav= [HW,ALSA]
2160
2161 snd-nm256= [HW,ALSA]
2162
2163 snd-opl3sa2= [HW,ALSA]
2164
2165 snd-opti92x-ad1848=
2166 [HW,ALSA]
2167
2168 snd-opti92x-cs4231=
2169 [HW,ALSA]
2170
2171 snd-opti93x= [HW,ALSA]
2172
2173 snd-pmac= [HW,ALSA]
2174
2175 snd-rme32= [HW,ALSA]
2176
2177 snd-rme96= [HW,ALSA]
2178
2179 snd-rme9652= [HW,ALSA]
2180
2181 snd-sb8= [HW,ALSA]
2182
2183 snd-sb16= [HW,ALSA]
2184
2185 snd-sbawe= [HW,ALSA]
2186
2187 snd-serial= [HW,ALSA]
2188
2189 snd-sgalaxy= [HW,ALSA]
2190
2191 snd-sonicvibes= [HW,ALSA]
2192
2193 snd-sun-amd7930=
2194 [HW,ALSA]
2195
2196 snd-sun-cs4231= [HW,ALSA]
2197
2198 snd-trident= [HW,ALSA]
2199
2200 snd-usb-audio= [HW,ALSA,USB]
2201
2202 snd-via82xx= [HW,ALSA]
2203
2204 snd-virmidi= [HW,ALSA]
2205
2206 snd-wavefront= [HW,ALSA]
2207
2208 snd-ymfpci= [HW,ALSA]
a9913044 2209
9c44bc03
IM
2210 softlockup_panic=
2211 [KNL] Should the soft-lockup detector generate panics.
2212
1da177e4
LT
2213 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2214 See Documentation/sonypi.txt
2215
2216 specialix= [HW,SERIAL] Specialix multi-serial port adapter
31c00fc1 2217 See Documentation/serial/specialix.txt.
1da177e4
LT
2218
2219 spia_io_base= [HW,MTD]
2220 spia_fio_base=
2221 spia_pedr=
2222 spia_peddr=
2223
2224 sscape= [HW,OSS]
2225 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 2226
1da177e4
LT
2227 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2228 See Documentation/scsi/st.txt.
2229
f38f1d2a
SR
2230 stacktrace [FTRACE]
2231 Enabled the stack tracer on boot up.
2232
1da177e4
LT
2233 sti= [PARISC,HW]
2234 Format: <num>
2235 Set the STI (builtin display/keyboard on the HP-PARISC
2236 machines) console (graphic card) which should be used
2237 as the initial boot-console.
2238 See also comment in drivers/video/console/sticore.c.
2239
2240 sti_font= [HW]
2241 See comment in drivers/video/console/sticore.c.
2242
2243 stifb= [HW]
2244 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2245
42a7fc4a
GB
2246 sunrpc.pool_mode=
2247 [NFS]
2248 Control how the NFS server code allocates CPUs to
2249 service thread pools. Depending on how many NICs
2250 you have and where their interrupts are bound, this
2251 option will affect which CPUs will do NFS serving.
2252 Note: this parameter cannot be changed while the
2253 NFS server is running.
2254
2255 auto the server chooses an appropriate mode
2256 automatically using heuristics
2257 global a single global pool contains all CPUs
2258 percpu one pool for each CPU
2259 pernode one pool for each NUMA node (equivalent
2260 to global on non-NUMA machines)
2261
1da177e4 2262 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2263
1da177e4
LT
2264 switches= [HW,M68k]
2265
2266 sym53c416= [HW,SCSI]
2267 See header of drivers/scsi/sym53c416.c.
2268
5d6f647f
IM
2269 sysrq_always_enabled
2270 [KNL]
2271 Ignore sysrq setting - this boot parameter will
2272 neutralize any effect of /proc/sys/kernel/sysrq.
2273 Useful for debugging.
2274
1da177e4
LT
2275 t128= [HW,SCSI]
2276 See header of drivers/scsi/t128.c.
2277
2278 tdfx= [HW,DRM]
2279
77437fd4
DB
2280 test_suspend= [SUSPEND]
2281 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2282 standby suspend) as the system sleep state to briefly
2283 enter during system startup. The system is woken from
2284 this state using a wakeup-capable RTC alarm.
2285
1da177e4
LT
2286 thash_entries= [KNL,NET]
2287 Set number of hash buckets for TCP connection
2288
f8707ec9
LB
2289 thermal.act= [HW,ACPI]
2290 -1: disable all active trip points in all thermal zones
2291 <degrees C>: override all lowest active trip points
2292
c52a7419
LB
2293 thermal.crt= [HW,ACPI]
2294 -1: disable all critical trip points in all thermal zones
22a94d79 2295 <degrees C>: override all critical trip points
c52a7419 2296
f5487145
LB
2297 thermal.nocrt= [HW,ACPI]
2298 Set to disable actions on ACPI thermal zone
2299 critical and hot trip points.
2300
72b33ef8
LB
2301 thermal.off= [HW,ACPI]
2302 1: disable ACPI thermal control
2303
a70cdc52
LB
2304 thermal.psv= [HW,ACPI]
2305 -1: disable all passive trip points
2306 <degrees C>: override all passive trip points to this value
2307
730ff34d
LB
2308 thermal.tzp= [HW,ACPI]
2309 Specify global default ACPI thermal zone polling rate
2310 <deci-seconds>: poll all this frequency
2311 0: no polling (default)
2312
1da177e4
LT
2313 tmscsim= [HW,SCSI]
2314 See comment before function dc390_setup() in
2315 drivers/scsi/tmscsim.c.
2316
2b1a61f0
HC
2317 topology= [S390]
2318 Format: {off | on}
2319 Specify if the kernel should make use of the cpu
2320 topology informations if the hardware supports these.
2321 The scheduler will make use of these informations and
2322 e.g. base its process migration decisions on it.
2323 Default is off.
2324
1da177e4
LT
2325 tp720= [HW,PS2]
2326
2327 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2328 Format:
2329 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2330
395628ef
AK
2331 tsc= Disable clocksource-must-verify flag for TSC.
2332 Format: <string>
2333 [x86] reliable: mark tsc clocksource as reliable, this
2334 disables clocksource verification at runtime.
2335 Used to enable high-resolution timer mode on older
2336 hardware, and in virtualized environment.
2337
a9913044
RD
2338 turbografx.map[2|3]= [HW,JOY]
2339 TurboGraFX parallel port interface
2340 Format:
2341 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2342 See also Documentation/input/joystick-parport.txt
2343
2344 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2345 See header of drivers/scsi/u14-34f.c.
2346
2347 uart401= [HW,OSS]
2348 Format: <io>,<irq>
2349
2350 uart6850= [HW,OSS]
2351 Format: <io>,<irq>
2352
5f8364b7
AS
2353 uhci-hcd.ignore_oc=
2354 [USB] Ignore overcurrent events (default N).
2355 Some badly-designed motherboards generate lots of
2356 bogus events, for ports that aren't wired to
2357 anything. Set this parameter to avoid log spamming.
2358 Note that genuine overcurrent events won't be
2359 reported either.
2360
e3a61b0a
SA
2361 unknown_nmi_panic
2362 [X86-32,X86-64]
2363 Set unknown_nmi_panic=1 early on boot.
2364
b5e795f8
AS
2365 usbcore.autosuspend=
2366 [USB] The autosuspend time delay (in seconds) used
2367 for newly-detected USB devices (default 2). This
2368 is the time required before an idle device will be
2369 autosuspended. Devices for which the delay is set
eaafbc3a 2370 to a negative value won't be autosuspended at all.
b5e795f8 2371
fd7c519d
JK
2372 usbcore.usbfs_snoop=
2373 [USB] Set to log all usbfs traffic (default 0 = off).
2374
2375 usbcore.blinkenlights=
2376 [USB] Set to cycle leds on hubs (default 0 = off).
2377
2378 usbcore.old_scheme_first=
2379 [USB] Start with the old device initialization
2380 scheme (default 0 = off).
2381
2382 usbcore.use_both_schemes=
2383 [USB] Try the other device initialization scheme
2384 if the first one fails (default 1 = enabled).
2385
2386 usbcore.initial_descriptor_timeout=
2387 [USB] Specifies timeout for the initial 64-byte
2388 USB_REQ_GET_DESCRIPTOR request in milliseconds
2389 (default 5000 = 5.0 seconds).
2390
1da177e4
LT
2391 usbhid.mousepoll=
2392 [USBHID] The interval which mice are to be polled at.
a9913044 2393
d4f373e5
AS
2394 usb-storage.delay_use=
2395 [UMS] The delay in seconds before a new device is
2396 scanned for Logical Units (default 5).
2397
2398 usb-storage.quirks=
2399 [UMS] A list of quirks entries to supplement or
2400 override the built-in unusual_devs list. List
2401 entries are separated by commas. Each entry has
2402 the form VID:PID:Flags where VID and PID are Vendor
2403 and Product ID values (4-digit hex numbers) and
2404 Flags is a set of characters, each corresponding
2405 to a common usb-storage quirk flag as follows:
c838ea46
AS
2406 a = SANE_SENSE (collect more than 18 bytes
2407 of sense data);
d4f373e5
AS
2408 c = FIX_CAPACITY (decrease the reported
2409 device capacity by one sector);
c838ea46
AS
2410 h = CAPACITY_HEURISTICS (decrease the
2411 reported device capacity by one
2412 sector if the number is odd);
d4f373e5
AS
2413 i = IGNORE_DEVICE (don't bind to this
2414 device);
2415 l = NOT_LOCKABLE (don't try to lock and
2416 unlock ejectable media);
2417 m = MAX_SECTORS_64 (don't transfer more
2418 than 64 sectors = 32 KB at a time);
c838ea46
AS
2419 o = CAPACITY_OK (accept the capacity
2420 reported by the device);
d4f373e5
AS
2421 r = IGNORE_RESIDUE (the device reports
2422 bogus residue values);
2423 s = SINGLE_LUN (the device has only one
2424 Logical Unit);
2425 w = NO_WP_DETECT (don't test whether the
2426 medium is write-protected).
2427 Example: quirks=0419:aaf5:rl,0421:0433:rc
2428
200001eb
PJ
2429 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2430 kernel's map of available physical RAM.
2431
cd4f0ef7 2432 vdso= [X86-32,SH,x86-64]
1dbf527c 2433 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2434 vdso=1: enable VDSO (default)
2435 vdso=0: disable VDSO mapping
2436
af65d648
RM
2437 vdso32= [X86-32,X86-64]
2438 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2439 vdso32=1: enable 32-bit VDSO (default)
2440 vdso32=0: disable 32-bit VDSO mapping
2441
d080d397
YI
2442 vector= [IA-64,SMP]
2443 vector=percpu: enable percpu vector domain
2444
1da177e4
LT
2445 video= [FB] Frame buffer configuration
2446 See Documentation/fb/modedb.txt.
2447
cd4f0ef7 2448 vga= [BOOT,X86-32] Select a particular video mode
71cced6e 2449 See Documentation/x86/i386/boot.txt and
a9913044 2450 Documentation/svga.txt.
1da177e4
LT
2451 Use vga=ask for menu.
2452 This is actually a boot loader parameter; the value is
2453 passed to the kernel using a special protocol.
2454
a9913044 2455 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2456 size of <nn>. This can be used to increase the
2457 minimum size (128MB on x86). It can also be used to
2458 decrease the size and leave more room for directly
2459 mapped kernel RAM.
2460
585c3047
PO
2461 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2462 Format: <command>
1da177e4 2463
585c3047
PO
2464 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2465 Format: <command>
2466
2467 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2468 Format: <command>
a9913044 2469
1da177e4
LT
2470 waveartist= [HW,OSS]
2471 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2472
1da177e4
LT
2473 wd33c93= [HW,SCSI]
2474 See header of drivers/scsi/wd33c93.c.
2475
2476 wd7000= [HW,SCSI]
2477 See header of drivers/scsi/wd7000.c.
2478
2479 wdt= [WDT] Watchdog
8dfe9c21 2480 See Documentation/watchdog/wdt.txt.
1da177e4
LT
2481
2482 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2483 xd_geo= See header of drivers/block/xd.c.
2484
2485 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2486 Format:
2487 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2488
ecb08d81
RD
2489 norandmaps Don't use address space randomization. Equivalent to
2490 echo 0 > /proc/sys/kernel/randomize_va_space
a62eaf15 2491
a9913044 2492______________________________________________________________________
1da177e4
LT
2493
2494TODO:
2495
2496 Add documentation for ALSA options.
2497 Add more DRM drivers.