4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
168 acpi= [HW,ACPI,X86,ARM64]
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt }
171 force -- enable ACPI if default was off
172 off -- disable ACPI if default was on
173 noirq -- do not use ACPI for IRQ routing
174 strict -- Be less tolerant of platforms that are not
175 strictly ACPI specification compliant.
176 rsdt -- prefer RSDT over (default) XSDT
177 copy_dsdt -- copy DSDT to memory
178 For ARM64, ONLY "acpi=off" or "acpi=force" are available
180 See also Documentation/power/runtime_pm.txt, pci=noacpi
182 acpi_apic_instance= [ACPI, IOAPIC]
184 2: use 2nd APIC table, if available
185 1,0: use 1st APIC table
188 acpi_backlight= [HW,ACPI]
189 acpi_backlight=vendor
191 If set to vendor, prefer vendor specific driver
192 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
193 of the ACPI video.ko driver.
195 acpica_no_return_repair [HW, ACPI]
196 Disable AML predefined validation mechanism
197 This mechanism can repair the evaluation result to make
198 the return objects more ACPI specification compliant.
199 This option is useful for developers to identify the
200 root cause of an AML interpreter issue when the issue
201 has something to do with the repair mechanism.
203 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
204 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
206 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
207 debug output. Bits in debug_layer correspond to a
208 _COMPONENT in an ACPI source file, e.g.,
209 #define _COMPONENT ACPI_PCI_COMPONENT
210 Bits in debug_level correspond to a level in
211 ACPI_DEBUG_PRINT statements, e.g.,
212 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
213 The debug_level mask defaults to "info". See
214 Documentation/acpi/debug.txt for more information about
215 debug layers and levels.
217 Enable processor driver info messages:
218 acpi.debug_layer=0x20000000
219 Enable PCI/PCI interrupt routing info messages:
220 acpi.debug_layer=0x400000
221 Enable AML "Debug" output, i.e., stores to the Debug
222 object while interpreting AML:
223 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
224 Enable all messages related to ACPI hardware:
225 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
227 Some values produce so much output that the system is
228 unusable. The "log_buf_len" parameter may be useful
229 if you need to capture more output.
231 acpi_enforce_resources= [ACPI]
232 { strict | lax | no }
233 Check for resource conflicts between native drivers
234 and ACPI OperationRegions (SystemIO and SystemMemory
235 only). IO ports and memory declared in ACPI might be
236 used by the ACPI subsystem in arbitrary AML code and
237 can interfere with legacy drivers.
238 strict (default): access to resources claimed by ACPI
239 is denied; legacy drivers trying to access reserved
240 resources will fail to bind to device using them.
241 lax: access to resources claimed by ACPI is allowed;
242 legacy drivers trying to access reserved resources
243 will bind successfully but a warning message is logged.
244 no: ACPI OperationRegions are not marked as reserved,
245 no further checks are performed.
247 acpi_force_table_verification [HW,ACPI]
248 Enable table checksum verification during early stage.
249 By default, this is disabled due to x86 early mapping
252 acpi_irq_balance [HW,ACPI]
253 ACPI will balance active IRQs
256 acpi_irq_nobalance [HW,ACPI]
257 ACPI will not move active IRQs (default)
260 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
261 Format: <irq>,<irq>...
263 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
265 Format: <irq>,<irq>...
267 acpi_no_auto_serialize [HW,ACPI]
268 Disable auto-serialization of AML methods
269 AML control methods that contain the opcodes to create
270 named objects will be marked as "Serialized" by the
271 auto-serialization feature.
272 This feature is enabled by default.
273 This option allows to turn off the feature.
275 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
278 acpi_no_static_ssdt [HW,ACPI]
279 Disable installation of static SSDTs at early boot time
280 By default, SSDTs contained in the RSDT/XSDT will be
281 installed automatically and they will appear under
282 /sys/firmware/acpi/tables.
283 This option turns off this feature.
284 Note that specifying this option does not affect
285 dynamic table installation which will install SSDT
286 tables to /sys/firmware/acpi/tables/dynamic.
288 acpi_rsdp= [ACPI,EFI,KEXEC]
289 Pass the RSDP address to the kernel, mostly used
290 on machines running EFI runtime service to boot the
291 second kernel for kdump.
293 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
294 Format: To spoof as Windows 98: ="Microsoft Windows"
296 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
297 of 2 which is mandated by ACPI 6) as the supported ACPI
298 specification revision (when using this switch, it may
299 be necessary to carry out a cold reboot _twice_ in a
300 row to make it take effect on the platform firmware).
302 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
303 acpi_osi="string1" # add string1
304 acpi_osi="!string2" # remove string2
305 acpi_osi=!* # remove all strings
306 acpi_osi=! # disable all built-in OS vendor
308 acpi_osi= # disable all strings
310 'acpi_osi=!' can be used in combination with single or
311 multiple 'acpi_osi="string1"' to support specific OS
312 vendor string(s). Note that such command can only
313 affect the default state of the OS vendor strings, thus
314 it cannot affect the default state of the feature group
315 strings and the current state of the OS vendor strings,
316 specifying it multiple times through kernel command line
317 is meaningless. This command is useful when one do not
318 care about the state of the feature group strings which
319 should be controlled by the OSPM.
321 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
322 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
323 can make '_OSI("Windows 2000")' TRUE.
325 'acpi_osi=' cannot be used in combination with other
326 'acpi_osi=' command lines, the _OSI method will not
327 exist in the ACPI namespace. NOTE that such command can
328 only affect the _OSI support state, thus specifying it
329 multiple times through kernel command line is also
332 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
335 'acpi_osi=!*' can be used in combination with single or
336 multiple 'acpi_osi="string1"' to support specific
337 string(s). Note that such command can affect the
338 current state of both the OS vendor strings and the
339 feature group strings, thus specifying it multiple times
340 through kernel command line is meaningful. But it may
341 still not able to affect the final state of a string if
342 there are quirks related to this string. This command
343 is useful when one want to control the state of the
344 feature group strings to debug BIOS issues related to
347 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
348 '_OSI("Module Device")' FALSE.
349 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
350 '_OSI("Module Device")' TRUE.
351 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
353 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
355 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
356 they all will make '_OSI("Windows 2000")' TRUE.
359 Override the pmtimer bug detection: force the kernel
360 to assume that this machine's pmtimer latches its value
361 and always returns good values.
363 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
364 Format: { level | edge | high | low }
366 acpi_skip_timer_override [HW,ACPI]
367 Recognize and ignore IRQ0/pin2 Interrupt Override.
368 For broken nForce2 BIOS resulting in XT-PIC timer.
370 acpi_sleep= [HW,ACPI] Sleep options
371 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
372 old_ordering, nonvs, sci_force_enable }
373 See Documentation/power/video.txt for information on
375 s3_beep is for debugging; it makes the PC's speaker beep
376 as soon as the kernel's real-mode entry point is called.
377 s4_nohwsig prevents ACPI hardware signature from being
378 used during resume from hibernation.
379 old_ordering causes the ACPI 1.0 ordering of the _PTS
380 control method, with respect to putting devices into
381 low power states, to be enforced (the ACPI 2.0 ordering
382 of _PTS is used by default).
383 nonvs prevents the kernel from saving/restoring the
384 ACPI NVS memory during suspend/hibernation and resume.
385 sci_force_enable causes the kernel to set SCI_EN directly
386 on resume from S1/S3 (which is against the ACPI spec,
387 but some broken systems don't work without it).
389 acpi_use_timer_override [HW,ACPI]
390 Use timer override. For some broken Nvidia NF5 boards
391 that require a timer override, but don't have HPET
393 add_efi_memmap [EFI; X86] Include EFI memory map in
394 kernel's map of available physical RAM.
397 { off | try_unsupported }
398 off: disable AGP support
399 try_unsupported: try to drive unsupported chipsets
400 (may crash computer or cause data corruption)
403 See Documentation/sound/alsa/alsa-parameters.txt
406 Allow the default userspace alignment fault handler
407 behaviour to be specified. Bit 0 enables warnings,
408 bit 1 enables fixups, and bit 2 sends a segfault.
410 align_va_addr= [X86-64]
411 Align virtual addresses by clearing slice [14:12] when
412 allocating a VMA at process creation time. This option
413 gives you up to 3% performance improvement on AMD F15h
414 machines (where it is enabled by default) for a
415 CPU-intensive style benchmark, and it can vary highly in
416 a microbenchmark depending on workload and compiler.
418 32: only for 32-bit processes
419 64: only for 64-bit processes
420 on: enable for both 32- and 64-bit processes
421 off: disable for both 32- and 64-bit processes
423 alloc_snapshot [FTRACE]
424 Allocate the ftrace snapshot buffer on boot up when the
425 main buffer is allocated. This is handy if debugging
426 and you need to use tracing_snapshot() on boot up, and
427 do not want to use tracing_snapshot_alloc() as it needs
428 to be done where GFP_KERNEL allocations are allowed.
430 amd_iommu= [HW,X86-64]
431 Pass parameters to the AMD IOMMU driver in the system.
433 fullflush - enable flushing of IO/TLB entries when
434 they are unmapped. Otherwise they are
435 flushed before they will be reused, which
437 off - do not initialize any AMD IOMMU found in
439 force_isolation - Force device isolation for all
440 devices. The IOMMU driver is not
441 allowed anymore to lift isolation
442 requirements as needed. This option
443 does not override iommu=pt
445 amd_iommu_dump= [HW,X86-64]
446 Enable AMD IOMMU driver option to dump the ACPI table
447 for AMD IOMMU. With this option enabled, AMD IOMMU
448 driver will print ACPI tables for AMD IOMMU during
449 IOMMU initialization.
451 amijoy.map= [HW,JOY] Amiga joystick support
452 Map of devices attached to JOY0DAT and JOY1DAT
454 See also Documentation/input/joystick.txt
456 analog.map= [HW,JOY] Analog joystick and gamepad support
457 Specifies type or capabilities of an analog joystick
458 connected to one of 16 gameports
459 Format: <type1>,<type2>,..<type16>
462 Power management functions (SPARCstation-4/5 + deriv.)
464 Disable APC CPU standby support. SPARCstation-Fox does
465 not play well with APC CPU idle - disable it if you have
466 APC and your system crashes randomly.
468 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
469 Change the output verbosity whilst booting
470 Format: { quiet (default) | verbose | debug }
471 Change the amount of debugging information output
472 when initialising the APIC and IO-APIC components.
475 See Documentation/networking/ipv6.txt.
477 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
478 Limit apic dumping. The parameter defines the maximal
479 number of local apics being dumped. Also it is possible
480 to set it to "all" by meaning -- no limit here.
481 Format: { 1 (default) | 2 | ... | all }.
482 The parameter valid if only apic=debug or
483 apic=verbose is specified.
484 Example: apic=debug show_lapic=all
486 apm= [APM] Advanced Power Management
487 See header of arch/x86/kernel/apm_32.c.
489 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
490 Format: <io>,<irq>,<nodeID>
494 atarimouse= [HW,MOUSE] Atari Mouse
496 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
497 EzKey and similar keyboards
499 atkbd.reset= [HW] Reset keyboard during initialization
501 atkbd.set= [HW] Select keyboard code set
502 Format: <int> (2 = AT (default), 3 = PS/2)
504 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
507 atkbd.softraw= [HW] Choose between synthetic and real raw mode
508 Format: <bool> (0 = real, 1 = synthetic (default))
510 atkbd.softrepeat= [HW]
511 Use software keyboard repeat
513 audit= [KNL] Enable the audit sub-system
514 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
515 0 - kernel audit is disabled and can not be enabled
516 until the next reboot
517 unset - kernel audit is initialized but disabled and
518 will be fully enabled by the userspace auditd.
519 1 - kernel audit is initialized and partially enabled,
520 storing at most audit_backlog_limit messages in
521 RAM until it is fully enabled by the userspace
525 audit_backlog_limit= [KNL] Set the audit queue size limit.
526 Format: <int> (must be >=0)
529 baycom_epp= [HW,AX25]
532 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
534 See header of drivers/net/hamradio/baycom_par.c.
536 baycom_ser_fdx= [HW,AX25]
537 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
538 Format: <io>,<irq>,<mode>[,<baud>]
539 See header of drivers/net/hamradio/baycom_ser_fdx.c.
541 baycom_ser_hdx= [HW,AX25]
542 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
543 Format: <io>,<irq>,<mode>
544 See header of drivers/net/hamradio/baycom_ser_hdx.c.
546 blkdevparts= Manual partition parsing of block device(s) for
547 embedded devices based on command line input.
548 See Documentation/block/cmdline-partition.txt
550 boot_delay= Milliseconds to delay each printk during boot.
551 Values larger than 10 seconds (10000) are changed to
555 bootmem_debug [KNL] Enable bootmem allocator debug messages.
557 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
558 bttv.radio= Most important insmod options are available as
560 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
563 bulk_remove=off [PPC] This parameter disables the use of the pSeries
564 firmware feature for flushing multiple hpte entries
567 c101= [NET] Moxa C101 synchronous serial card
569 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
570 Sometimes CPU hardware bugs make them report the cache
571 size incorrectly. The kernel will attempt work arounds
572 to fix known problems, but for some CPUs it is not
573 possible to determine what the correct size should be.
574 This option provides an override for these situations.
576 ca_keys= [KEYS] This parameter identifies a specific key(s) on
577 the system trusted keyring to be used for certificate
579 format: { id:<keyid> | builtin }
581 cca= [MIPS] Override the kernel pages' cache coherency
582 algorithm. Accepted values range from 0 to 7
583 inclusive. See arch/mips/include/asm/pgtable-bits.h
584 for platform specific values (SB1, Loongson3 and
587 ccw_timeout_log [S390]
588 See Documentation/s390/CommonIO for details.
590 cgroup_disable= [KNL] Disable a particular controller
591 Format: {name of the controller(s) to disable}
592 The effects of cgroup_disable=foo are:
593 - foo isn't auto-mounted if you mount all cgroups in
595 - foo isn't visible as an individually mountable
597 {Currently only "memory" controller deal with this and
598 cut the overhead, others just disable the usage. So
599 only cgroup_disable=memory is actually worthy}
601 checkreqprot [SELINUX] Set initial checkreqprot flag value.
602 Format: { "0" | "1" }
603 See security/selinux/Kconfig help text.
604 0 -- check protection applied by kernel (includes
605 any implied execute protection).
606 1 -- check protection requested by application.
607 Default value is set via a kernel config option.
608 Value can be changed at runtime via
609 /selinux/checkreqprot.
612 See Documentation/s390/CommonIO for details.
615 Prevents the clock framework from automatically gating
616 clocks that have not been explicitly enabled by a Linux
617 device driver but are enabled in hardware at reset or
618 by the bootloader/firmware. Note that this does not
619 force such clocks to be always-on nor does it reserve
620 those clocks in any way. This parameter is useful for
621 debug and development, but should not be needed on a
622 platform with proper driver support. For more
623 information, see Documentation/clk.txt.
625 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
627 Forces specified clocksource (if available) to be used
628 when calculating gettimeofday(). If specified
629 clocksource is not available, it defaults to PIT.
630 Format: { pit | tsc | cyclone | pmtmr }
632 clocksource= Override the default clocksource
634 Override the default clocksource and use the clocksource
635 with the name specified.
636 Some clocksource names to choose from, depending on
638 [all] jiffies (this is the base, fallback clocksource)
640 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
641 pxa_timer,timer3,32k_counter,timer0_1
643 [X86-32] pit,hpet,tsc;
644 scx200_hrt on Geode; cyclone on IBM x440
652 clearcpuid=BITNUM [X86]
653 Disable CPUID feature X for the kernel. See
654 arch/x86/include/asm/cpufeature.h for the valid bit
655 numbers. Note the Linux specific bits are not necessarily
656 stable over kernel options, but the vendor specific
658 Also note that user programs calling CPUID directly
659 or using the feature without checking anything
660 will still see it. This just prevents it from
661 being used by the kernel or shown in /proc/cpuinfo.
662 Also note the kernel might malfunction if you disable
665 cma=nn[MG]@[start[MG][-end[MG]]]
667 Sets the size of kernel global memory area for
668 contiguous memory allocations and optionally the
669 placement constraint by the physical address range of
670 memory allocations. A value of 0 disables CMA
671 altogether. For more information, see
672 include/linux/dma-contiguous.h
674 cmo_free_hint= [PPC] Format: { yes | no }
675 Specify whether pages are marked as being inactive
676 when they are freed. This is used in CMO environments
677 to determine OS memory pressure for page stealing by
681 coherent_pool=nn[KMG] [ARM,KNL]
682 Sets the size of memory pool for coherent, atomic dma
683 allocations, by default set to 256K.
685 code_bytes [X86] How many bytes of object code to print
690 com20020= [HW,NET] ARCnet - COM20020 chipset
692 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
694 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
698 ARCnet - COM90xx chipset (memory-mapped buffers)
699 Format: <io>[,<irq>[,<memstart>]]
701 condev= [HW,S390] console device
704 console= [KNL] Output console device and options.
706 tty<n> Use the virtual console device <n>.
710 Use the specified serial port. The options are of
711 the form "bbbbpnf", where "bbbb" is the baud rate,
712 "p" is parity ("n", "o", or "e"), "n" is number of
713 bits, and "f" is flow control ("r" for RTS or
714 omit it). Default is "9600n8".
716 See Documentation/serial-console.txt for more
718 Documentation/networking/netconsole.txt for an
721 uart[8250],io,<addr>[,options]
722 uart[8250],mmio,<addr>[,options]
723 uart[8250],mmio32,<addr>[,options]
724 uart[8250],0x<addr>[,options]
725 Start an early, polled-mode console on the 8250/16550
726 UART at the specified I/O port or MMIO address,
727 switching to the matching ttyS device later.
728 MMIO inter-register address stride is either 8-bit
729 (mmio) or 32-bit (mmio32).
730 If none of [io|mmio|mmio32], <addr> is assumed to be
731 equivalent to 'mmio'. 'options' are specified in the
732 same format described for ttyS above; if unspecified,
733 the h/w is not re-initialized.
735 hvc<n> Use the hypervisor console device <n>. This is for
736 both Xen and PowerPC hypervisors.
738 If the device connected to the port is not a TTY but a braille
739 device, prepend "brl," before the device type, for instance
741 For now, only VisioBraille is supported.
743 consoleblank= [KNL] The console blank (screen saver) timeout in
744 seconds. Defaults to 10*60 = 10mins. A value of 0
745 disables the blank timer.
748 [KNL] Change the default value for
749 /proc/<pid>/coredump_filter.
750 See also Documentation/filesystems/proc.txt.
752 cpuidle.off=1 [CPU_IDLE]
753 disable the cpuidle sub-system
756 [X86] Delay for N microsec between assert and de-assert
757 of APIC INIT to start processors. This delay occurs
758 on every CPU online, such as boot, and resume from suspend.
761 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
763 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
765 crashkernel=size[KMG][@offset[KMG]]
766 [KNL] Using kexec, Linux can switch to a 'crash kernel'
767 upon panic. This parameter reserves the physical
768 memory region [offset, offset + size] for that kernel
769 image. If '@offset' is omitted, then a suitable offset
770 is selected automatically. Check
771 Documentation/kdump/kdump.txt for further details.
773 crashkernel=range1:size1[,range2:size2,...][@offset]
774 [KNL] Same as above, but depends on the memory
775 in the running system. The syntax of range is
776 start-[end] where start and end are both
777 a memory unit (amount[KMG]). See also
778 Documentation/kdump/kdump.txt for an example.
780 crashkernel=size[KMG],high
781 [KNL, x86_64] range could be above 4G. Allow kernel
782 to allocate physical memory region from top, so could
783 be above 4G if system have more than 4G ram installed.
784 Otherwise memory region will be allocated below 4G, if
786 It will be ignored if crashkernel=X is specified.
787 crashkernel=size[KMG],low
788 [KNL, x86_64] range under 4G. When crashkernel=X,high
789 is passed, kernel could allocate physical memory region
790 above 4G, that cause second kernel crash on system
791 that require some amount of low memory, e.g. swiotlb
792 requires at least 64M+32K low memory. Kernel would
793 try to allocate 72M below 4G automatically.
794 This one let user to specify own low range under 4G
795 for second kernel instead.
796 0: to disable low allocation.
797 It will be ignored when crashkernel=X,high is not used
798 or memory reserved is below 4G.
803 cs89x0_media= [HW,NET]
804 Format: { rj45 | aui | bnc }
807 See header of drivers/s390/block/dasd_devmap.c.
809 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
810 (one device per port)
811 Format: <port#>,<type>
812 See also Documentation/input/joystick-parport.txt
814 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
815 time. See Documentation/dynamic-debug-howto.txt for
816 details. Deprecated, see dyndbg.
818 debug [KNL] Enable kernel debugging (events log level).
821 [KNL] verbose self-tests
823 Print debugging info while doing the locking API
825 We default to 0 (no extra messages), setting it to
826 1 will print _a lot_ more information - normally
827 only useful to kernel developers.
829 debug_objects [KNL] Enable object debugging
832 [KNL] Disable object debugging
834 debug_guardpage_minorder=
835 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
836 parameter allows control of the order of pages that will
837 be intentionally kept free (and hence protected) by the
838 buddy allocator. Bigger value increase the probability
839 of catching random memory corruption, but reduce the
840 amount of memory for normal system use. The maximum
841 possible value is MAX_ORDER/2. Setting this parameter
842 to 1 or 2 should be enough to identify most random
843 memory corruption problems caused by bugs in kernel or
844 driver code when a CPU writes to (or reads from) a
845 random memory location. Note that there exists a class
846 of memory corruptions problems caused by buggy H/W or
847 F/W or by drivers badly programing DMA (basically when
848 memory is written at bus level and the CPU MMU is
849 bypassed) which are not detectable by
850 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
851 tracking down these problems.
854 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
855 parameter enables the feature at boot time. In
856 default, it is disabled. We can avoid allocating huge
857 chunk of memory for debug pagealloc if we don't enable
858 it at boot time and the system will work mostly same
859 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
860 on: enable the feature
862 debugpat [X86] Enable PAT debugging
864 decnet.addr= [HW,NET]
865 Format: <area>[,<node>]
866 See also Documentation/networking/decnet.txt.
869 [same as hugepagesz=] The size of the default
870 HugeTLB page size. This is the size represented by
871 the legacy /proc/ hugepages APIs, used for SHM, and
872 default size when mounting hugetlbfs filesystems.
873 Defaults to the default architecture's huge page size
877 Set number of hash buckets for dentry cache.
880 See Documentation/networking/ipv6.txt.
882 disable_cpu_apicid= [X86,APIC,SMP]
884 The number of initial APIC ID for the
885 corresponding CPU to be disabled at boot,
886 mostly used for the kdump 2nd kernel to
887 disable BSP to wake up multiple CPUs without
888 causing system reset or hang due to sending
891 disable_ddw [PPC/PSERIES]
892 Disable Dynamic DMA Window support. Use this if
893 to workaround buggy firmware.
896 See Documentation/networking/ipv6.txt.
898 disable_mtrr_cleanup [X86]
899 The kernel tries to adjust MTRR layout from continuous
900 to discrete, to make X server driver able to add WB
901 entry later. This parameter disables that.
903 disable_mtrr_trim [X86, Intel and AMD only]
904 By default the kernel will trim any uncacheable
905 memory out of your available memory pool based on
906 MTRR settings. This parameter disables that behavior,
907 possibly causing your machine to run very slowly.
909 disable_timer_pin_1 [X86]
910 Disable PIN 1 of APIC timer
911 Can be useful to work around chipset bugs.
913 dis_ucode_ldr [X86] Disable the microcode loader.
915 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
916 this option disables the debugging code at boot.
918 dma_debug_entries=<number>
919 This option allows to tune the number of preallocated
920 entries for DMA-API debugging code. One entry is
921 required per DMA-API allocation. Use this if the
922 DMA-API debugging code disables itself because the
923 architectural default is too low.
925 dma_debug_driver=<driver_name>
926 With this option the DMA-API debugging driver
927 filter feature can be enabled at boot time. Just
928 pass the driver to filter for as the parameter.
929 The filter can be disabled or changed to another
930 driver later using sysfs.
932 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
933 Broken monitors, graphic adapters, KVMs and EDIDless
934 panels may send no or incorrect EDID data sets.
935 This parameter allows to specify an EDID data sets
936 in the /lib/firmware directory that are used instead.
937 Generic built-in EDID data sets are used, if one of
938 edid/1024x768.bin, edid/1280x1024.bin,
939 edid/1680x1050.bin, or edid/1920x1080.bin is given
940 and no file with the same name exists. Details and
941 instructions how to build your own EDID data are
942 available in Documentation/EDID/HOWTO.txt. An EDID
943 data set will only be used for a particular connector,
944 if its name and a colon are prepended to the EDID
945 name. Each connector may use a unique EDID data
946 set by separating the files with a comma. An EDID
947 data set with no connector name will be used for
948 any connectors not explicitly specified.
952 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
953 module.dyndbg[="val"]
954 Enable debug messages at boot time. See
955 Documentation/dynamic-debug-howto.txt for details.
957 nompx [X86] Disables Intel Memory Protection Extensions.
958 See Documentation/x86/intel_mpx.txt for more
959 information about the feature.
962 on enable eager fpu restore
963 off disable eager fpu restore
964 auto selects the default scheme, which automatically
965 enables eagerfpu restore for xsaveopt.
967 module.async_probe [KNL]
968 Enable asynchronous probe on this module.
970 early_ioremap_debug [KNL]
971 Enable debug messages in early_ioremap support. This
972 is useful for tracking down temporary early mappings
973 which are not unmapped.
975 earlycon= [KNL] Output early console device and options.
978 Start an early, polled-mode console on a cadence serial
979 port at the specified address. The cadence serial port
980 must already be setup and configured. Options are not
983 uart[8250],io,<addr>[,options]
984 uart[8250],mmio,<addr>[,options]
985 uart[8250],mmio32,<addr>[,options]
986 uart[8250],mmio32be,<addr>[,options]
987 uart[8250],0x<addr>[,options]
988 Start an early, polled-mode console on the 8250/16550
989 UART at the specified I/O port or MMIO address.
990 MMIO inter-register address stride is either 8-bit
991 (mmio) or 32-bit (mmio32 or mmio32be).
992 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
993 to be equivalent to 'mmio'. 'options' are specified
994 in the same format described for "console=ttyS<n>"; if
995 unspecified, the h/w is not initialized.
998 Start an early, polled-mode console on a pl011 serial
999 port at the specified address. The pl011 serial port
1000 must already be setup and configured. Options are not
1004 Start an early, polled-mode console on an msm serial
1005 port at the specified address. The serial port
1006 must already be setup and configured. Options are not
1009 msm_serial_dm,<addr>
1010 Start an early, polled-mode console on an msm serial
1011 dm port at the specified address. The serial port
1012 must already be setup and configured. Options are not
1015 smh Use ARM semihosting calls for early console.
1023 Use early console provided by serial driver available
1024 on Samsung SoCs, requires selecting proper type and
1025 a correct base address of the selected UART port. The
1026 serial port must already be setup and configured.
1027 Options are not yet supported.
1029 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1033 earlyprintk=serial[,ttySn[,baudrate]]
1034 earlyprintk=serial[,0x...[,baudrate]]
1035 earlyprintk=ttySn[,baudrate]
1036 earlyprintk=dbgp[debugController#]
1037 earlyprintk=pciserial,bus:device.function[,baudrate]
1039 earlyprintk is useful when the kernel crashes before
1040 the normal console is initialized. It is not enabled by
1041 default because it has some cosmetic problems.
1043 Append ",keep" to not disable it when the real console
1046 Only one of vga, efi, serial, or usb debug port can
1049 Currently only ttyS0 and ttyS1 may be specified by
1050 name. Other I/O ports may be explicitly specified
1051 on some architectures (x86 and arm at least) by
1052 replacing ttySn with an I/O port address, like this:
1053 earlyprintk=serial,0x1008,115200
1054 You can find the port for a given device in
1055 /proc/tty/driver/serial:
1056 2: uart:ST16650V2 port:00001008 irq:18 ...
1058 Interaction with the standard serial driver is not
1061 The VGA and EFI output is eventually overwritten by
1064 The xen output can only be used by Xen PV guests.
1066 edac_report= [HW,EDAC] Control how to report EDAC event
1067 Format: {"on" | "off" | "force"}
1068 on: enable EDAC to report H/W event. May be overridden
1069 by other higher priority error reporting module.
1070 off: disable H/W event reporting through EDAC.
1071 force: enforce the use of EDAC to report H/W event.
1074 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1077 This is designed to be used in conjunction with
1078 the boot argument: earlyprintk=vga
1081 Format: {"off" | "on" | "skip[mbr]"}
1084 Format: { "old_map", "nochunk", "noruntime", "debug" }
1085 old_map [X86-64]: switch to the old ioremap-based EFI
1086 runtime services mapping. 32-bit still uses this one by
1088 nochunk: disable reading files in "chunks" in the EFI
1089 boot stub, as chunking can cause problems with some
1090 firmware implementations.
1091 noruntime : disable EFI runtime services support
1092 debug: enable misc debug output
1094 efi_no_storage_paranoia [EFI; X86]
1095 Using this parameter you can use more than 50% of
1096 your efi variable storage. Use this parameter only if
1097 you are really sure that your UEFI does sane gc and
1098 fulfills the spec otherwise your board may brick.
1100 eisa_irq_edge= [PARISC,HW]
1101 See header of drivers/parisc/eisa.c.
1104 See comment before function elanfreq_setup() in
1105 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1108 Format: {"cfq" | "deadline" | "noop"}
1109 See Documentation/block/cfq-iosched.txt and
1110 Documentation/block/deadline-iosched.txt for details.
1112 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1113 Specifies physical address of start of kernel core
1114 image elf header and optionally the size. Generally
1115 kexec loader will pass this option to capture kernel.
1116 See Documentation/kdump/kdump.txt for details.
1118 enable_mtrr_cleanup [X86]
1119 The kernel tries to adjust MTRR layout from continuous
1120 to discrete, to make X server driver able to add WB
1121 entry later. This parameter enables that.
1123 enable_timer_pin_1 [X86]
1124 Enable PIN 1 of APIC timer
1125 Can be useful to work around chipset bugs
1126 (in particular on some ATI chipsets).
1127 The kernel tries to set a reasonable default.
1129 enforcing [SELINUX] Set initial enforcing status.
1131 See security/selinux/Kconfig help text.
1132 0 -- permissive (log only, no denials).
1133 1 -- enforcing (deny and log).
1135 Value can be changed at runtime via /selinux/enforce.
1138 Disable Error Record Serialization Table (ERST)
1141 ether= [HW,NET] Ethernet cards parameters
1142 This option is obsoleted by the "netdev=" option, which
1143 has equivalent usage. See its documentation for details.
1147 Permit 'security.evm' to be updated regardless of
1148 current integrity status.
1152 fail_make_request=[KNL]
1153 General fault injection mechanism.
1154 Format: <interval>,<probability>,<space>,<times>
1155 See also Documentation/fault-injection/.
1158 See Documentation/blockdev/floppy.txt.
1160 force_pal_cache_flush
1161 [IA-64] Avoid check_sal_cache_flush which may hang on
1162 buggy SAL_CACHE_FLUSH implementations. Using this
1163 parameter will force ia64_sal_cache_flush to call
1164 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1167 Forcefully enable Physical Address Extension (PAE).
1168 Many Pentium M systems disable PAE but may have a
1169 functionally usable PAE implementation.
1170 Warning: use of this parameter will taint the kernel
1171 and may cause unknown problems.
1174 [FTRACE] will set and start the specified tracer
1175 as early as possible in order to facilitate early
1178 ftrace_dump_on_oops[=orig_cpu]
1179 [FTRACE] will dump the trace buffers on oops.
1180 If no parameter is passed, ftrace will dump
1181 buffers of all CPUs, but if you pass orig_cpu, it will
1182 dump only the buffer of the CPU that triggered the
1185 ftrace_filter=[function-list]
1186 [FTRACE] Limit the functions traced by the function
1187 tracer at boot up. function-list is a comma separated
1188 list of functions. This list can be changed at run
1189 time by the set_ftrace_filter file in the debugfs
1192 ftrace_notrace=[function-list]
1193 [FTRACE] Do not trace the functions specified in
1194 function-list. This list can be changed at run time
1195 by the set_ftrace_notrace file in the debugfs
1198 ftrace_graph_filter=[function-list]
1199 [FTRACE] Limit the top level callers functions traced
1200 by the function graph tracer at boot up.
1201 function-list is a comma separated list of functions
1202 that can be changed at run time by the
1203 set_graph_function file in the debugfs tracing directory.
1205 ftrace_graph_notrace=[function-list]
1206 [FTRACE] Do not trace from the functions specified in
1207 function-list. This list is a comma separated list of
1208 functions that can be changed at run time by the
1209 set_graph_notrace file in the debugfs tracing directory.
1212 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1213 support via parallel port (up to 5 devices per port)
1214 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1215 See also Documentation/input/joystick-parport.txt
1219 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1223 gcov_persist= [GCOV] When non-zero (default), profiling data for
1224 kernel modules is saved and remains accessible via
1225 debugfs, even when the module is unloaded/reloaded.
1226 When zero, profiling data is discarded and associated
1227 debugfs files are removed at module unload time.
1229 gpt [EFI] Forces disk with valid GPT signature but
1230 invalid Protective MBR to be treated as GPT. If the
1231 primary GPT is corrupted, it enables the backup/alternate
1232 GPT to be used instead.
1234 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1235 the "Enable 0" bit of the configuration register.
1238 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1239 the "Enable 0" bit of the configuration register.
1242 grcan.select= [HW] Select which physical interface to use.
1245 grcan.txsize= [HW] Sets the size of the tx buffer.
1246 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1248 grcan.rxsize= [HW] Sets the size of the rx buffer.
1249 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1252 hashdist= [KNL,NUMA] Large hashes allocated during boot
1253 are distributed across NUMA nodes. Defaults on
1254 for 64-bit NUMA, off otherwise.
1255 Format: 0 | 1 (for off | on)
1257 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1259 hd= [EIDE] (E)IDE hard drive subsystem geometry
1260 Format: <cyl>,<head>,<sect>
1263 Disable Hardware Error Source Table (HEST) support;
1264 corresponding firmware-first mode error processing
1265 logic will be disabled.
1267 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1268 size of <nn>. This works even on boxes that have no
1269 highmem otherwise. This also works to reduce highmem
1270 size on bigger boxes.
1272 highres= [KNL] Enable/disable high resolution timer mode.
1273 Valid parameters: "on", "off"
1277 See Documentation/isdn/README.HiSax.
1281 hpet= [X86-32,HPET] option to control HPET usage
1282 Format: { enable (default) | disable | force |
1284 disable: disable HPET and use PIT instead
1285 force: allow force enabled of undocumented chips (ICH4,
1287 verbose: show contents of HPET registers during setup
1289 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1290 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1292 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1293 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1294 On x86-64 and powerpc, this option can be specified
1295 multiple times interleaved with hugepages= to reserve
1296 huge pages of different sizes. Valid pages sizes on
1297 x86-64 are 2M (when the CPU supports "pse") and 1G
1298 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1300 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1301 terminal devices. Valid values: 0..8
1302 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1303 If specified, z/VM IUCV HVC accepts connections
1304 from listed z/VM user IDs only.
1306 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1307 hardware thread id mappings.
1308 Format: <cpu>:<hwthread>
1311 Do not unregister boot console at start. This is only
1312 useful for debugging when something happens in the window
1313 between unregistering the boot console and initializing
1316 i2c_bus= [HW] Override the default board specific I2C bus speed
1317 or register an additional I2C bus that is not
1318 registered from board initialization code.
1322 i8042.debug [HW] Toggle i8042 debug mode
1323 i8042.unmask_kbd_data
1324 [HW] Enable printing of interrupt data from the KBD port
1325 (disabled by default, and as a pre-condition
1326 requires that i8042.debug=1 be enabled)
1327 i8042.direct [HW] Put keyboard port into non-translated mode
1328 i8042.dumbkbd [HW] Pretend that controller can only read data from
1329 keyboard and cannot control its state
1330 (Don't attempt to blink the leds)
1331 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1332 i8042.nokbd [HW] Don't check/create keyboard port
1333 i8042.noloop [HW] Disable the AUX Loopback command while probing
1335 i8042.nomux [HW] Don't check presence of an active multiplexing
1337 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1339 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1340 i8042.reset [HW] Reset the controller during init and cleanup
1341 i8042.unlock [HW] Unlock (ignore) the keylock
1342 i8042.kbdreset [HW] Reset device connected to KBD port
1346 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1347 indicates that the driver is running on unsupported
1349 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1350 does not match list of supported models.
1352 [HW] Report power status in /proc/i8k
1353 (disabled by default)
1354 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1357 i915.invert_brightness=
1358 [DRM] Invert the sense of the variable that is used to
1359 set the brightness of the panel backlight. Normally a
1360 brightness value of 0 indicates backlight switched off,
1361 and the maximum of the brightness value sets the backlight
1362 to maximum brightness. If this parameter is set to 0
1363 (default) and the machine requires it, or this parameter
1364 is set to 1, a brightness value of 0 sets the backlight
1365 to maximum brightness, and the maximum of the brightness
1366 value switches the backlight off.
1367 -1 -- never invert brightness
1368 0 -- machine default
1369 1 -- force brightness inversion
1372 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1374 ide-core.nodma= [HW] (E)IDE subsystem
1375 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1376 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1377 .cdrom .chs .ignore_cable are additional options
1378 See Documentation/ide/ide.txt.
1380 ide-generic.probe-mask= [HW] (E)IDE subsystem
1382 Probe mask for legacy ISA IDE ports. Depending on
1383 platform up to 6 ports are supported, enabled by
1384 setting corresponding bits in the mask to 1. The
1385 default value is 0x0, which has a special meaning.
1386 On systems that have PCI, it triggers scanning the
1387 PCI bus for the first and the second port, which
1388 are then probed. On systems without PCI the value
1389 of 0x0 enables probing the two first ports as if it
1392 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1393 Claim all unknown PCI IDE storage controllers.
1396 Format: idle=poll, idle=halt, idle=nomwait
1397 Poll forces a polling idle loop that can slightly
1398 improve the performance of waking up a idle CPU, but
1399 will use a lot of power and make the system run hot.
1401 idle=halt: Halt is forced to be used for CPU idle.
1402 In such case C2/C3 won't be used again.
1403 idle=nomwait: Disable mwait for CPU C-states
1405 ignore_loglevel [KNL]
1406 Ignore loglevel setting - this will print /all/
1407 kernel messages to the console. Useful for debugging.
1408 We also add it as printk module parameter, so users
1409 could change it dynamically, usually by
1410 /sys/module/printk/parameters/ignore_loglevel.
1412 ihash_entries= [KNL]
1413 Set number of hash buckets for inode cache.
1415 ima_appraise= [IMA] appraise integrity measurements
1416 Format: { "off" | "enforce" | "fix" | "log" }
1419 ima_appraise_tcb [IMA]
1420 The builtin appraise policy appraises all files
1424 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1428 The list of supported hash algorithms is defined
1429 in crypto/hash_info.h.
1432 The builtin measurement policy to load during IMA
1433 setup. Specyfing "tcb" as the value, measures all
1434 programs exec'd, files mmap'd for exec, and all files
1435 opened with the read mode bit set by either the
1436 effective uid (euid=0) or uid=0.
1439 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1440 Load a policy which meets the needs of the Trusted
1441 Computing Base. This means IMA will measure all
1442 programs exec'd, files mmap'd for exec, and all files
1443 opened for read by uid=0.
1446 Select one of defined IMA measurements template formats.
1447 Formats: { "ima" | "ima-ng" | "ima-sig" }
1451 [IMA] Define a custom template format.
1452 Format: { "field1|...|fieldN" }
1454 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1455 Format: <min_file_size>
1456 Set the minimal file size for using asynchronous hash.
1457 If left unspecified, ahash usage is disabled.
1459 ahash performance varies for different data sizes on
1460 different crypto accelerators. This option can be used
1461 to achieve the best performance for a particular HW.
1463 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1465 Set hashing buffer size. Default: 4k.
1467 ahash performance varies for different chunk sizes on
1468 different crypto accelerators. This option can be used
1469 to achieve best performance for particular HW.
1473 Run specified binary instead of /sbin/init as init
1476 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1477 for working out where the kernel is dying during
1480 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1481 initcall functions. Useful for debugging built-in
1482 modules and initcalls.
1484 initrd= [BOOT] Specify the location of the initial ramdisk
1486 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1489 int_pln_enable [x86] Enable power limit notification interrupt
1491 integrity_audit=[IMA]
1492 Format: { "0" | "1" }
1493 0 -- basic integrity auditing messages. (Default)
1494 1 -- additional integrity auditing messages.
1496 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1498 Enable intel iommu driver.
1500 Disable intel iommu driver.
1501 igfx_off [Default Off]
1502 By default, gfx is mapped as normal device. If a gfx
1503 device has a dedicated DMAR unit, the DMAR unit is
1504 bypassed by not enabling DMAR with this option. In
1505 this case, gfx device will use physical address for
1508 With this option iommu will not optimize to look
1509 for io virtual address below 32-bit forcing dual
1510 address cycle on pci bus for cards supporting greater
1511 than 32-bit addressing. The default is to look
1512 for translation below 32-bit and if not available
1513 then look in the higher range.
1514 strict [Default Off]
1515 With this option on every unmap_single operation will
1516 result in a hardware IOTLB flush operation as opposed
1517 to batching them for performance.
1518 sp_off [Default Off]
1519 By default, super page will be supported if Intel IOMMU
1520 has the capability. With this option, super page will
1522 ecs_off [Default Off]
1523 By default, extended context tables will be supported if
1524 the hardware advertises that it has support both for the
1525 extended tables themselves, and also PASID support. With
1526 this option set, extended tables will not be used even
1527 on hardware which claims to support them.
1529 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1530 0 disables intel_idle and fall back on acpi_idle.
1531 1 to 6 specify maximum depth of C-state.
1535 Do not enable intel_pstate as the default
1536 scaling driver for the supported processors
1538 Enable intel_pstate on systems that prohibit it by default
1539 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1540 instead of acpi-cpufreq may disable platform features, such
1541 as thermal controls and power capping, that rely on ACPI
1542 P-States information being indicated to OSPM and therefore
1543 should be used with caution. This option does not work with
1544 processors that aren't supported by the intel_pstate driver
1545 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1547 Do not enable hardware P state control (HWP)
1550 Only load intel_pstate on systems which support
1551 hardware P state control (HWP) if available.
1553 intremap= [X86-64, Intel-IOMMU]
1554 on enable Interrupt Remapping (default)
1555 off disable Interrupt Remapping
1556 nosid disable Source ID checking
1558 BIOS x2APIC opt-out request will be ignored
1560 iomem= Disable strict checking of access to MMIO memory
1561 strict regions from userspace.
1576 nobypass [PPC/POWERNV]
1577 Disable IOMMU bypass, using IOMMU for PCI devices.
1580 io7= [HW] IO7 for Marvel based alpha systems
1581 See comment before marvel_specify_io7 in
1582 arch/alpha/kernel/core_marvel.c.
1584 io_delay= [X86] I/O delay method
1586 Standard port 0x80 based delay
1588 Alternate port 0xed based delay (needed on some systems)
1590 Simple two microseconds delay
1595 See Documentation/filesystems/nfs/nfsroot.txt.
1598 When an interrupt is not handled search all handlers
1599 for it. Intended to get systems with badly broken
1603 When an interrupt is not handled search all handlers
1604 for it. Also check all handlers each timer
1605 interrupt. Intended to get systems with badly broken
1609 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1611 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1613 <cpu number>,...,<cpu number>
1615 <cpu number>-<cpu number>
1616 (must be a positive range in ascending order)
1618 <cpu number>,...,<cpu number>-<cpu number>
1620 This option can be used to specify one or more CPUs
1621 to isolate from the general SMP balancing and scheduling
1622 algorithms. You can move a process onto or off an
1623 "isolated" CPU via the CPU affinity syscalls or cpuset.
1624 <cpu number> begins at 0 and the maximum value is
1625 "number of CPUs in system - 1".
1627 This option is the preferred way to isolate CPUs. The
1628 alternative -- manually setting the CPU mask of all
1629 tasks in the system -- can cause problems and
1630 suboptimal load balancer performance.
1634 ivrs_ioapic [HW,X86_64]
1635 Provide an override to the IOAPIC-ID<->DEVICE-ID
1636 mapping provided in the IVRS ACPI table. For
1637 example, to map IOAPIC-ID decimal 10 to
1638 PCI device 00:14.0 write the parameter as:
1639 ivrs_ioapic[10]=00:14.0
1641 ivrs_hpet [HW,X86_64]
1642 Provide an override to the HPET-ID<->DEVICE-ID
1643 mapping provided in the IVRS ACPI table. For
1644 example, to map HPET-ID decimal 0 to
1645 PCI device 00:14.0 write the parameter as:
1646 ivrs_hpet[0]=00:14.0
1648 js= [HW,JOY] Analog joystick
1649 See Documentation/input/joystick.txt.
1652 Enable/disable kernel and module base offset ASLR
1653 (Address Space Layout Randomization) if built into
1654 the kernel. When CONFIG_HIBERNATION is selected,
1655 kASLR is disabled by default. When kASLR is enabled,
1656 hibernation will be disabled.
1660 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1661 specifies the amount of memory usable by the kernel
1662 for non-movable allocations. The requested amount is
1663 spread evenly throughout all nodes in the system. The
1664 remaining memory in each node is used for Movable
1665 pages. In the event, a node is too small to have both
1666 kernelcore and Movable pages, kernelcore pages will
1667 take priority and other nodes will have a larger number
1668 of Movable pages. The Movable zone is used for the
1669 allocation of pages that may be reclaimed or moved
1670 by the page migration subsystem. This means that
1671 HugeTLB pages may not be allocated from this zone.
1672 Note that allocations like PTEs-from-HighMem still
1673 use the HighMem zone if it exists, and the Normal
1674 zone if it does not.
1676 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1677 Format: <Controller#>[,poll interval]
1678 The controller # is the number of the ehci usb debug
1679 port as it is probed via PCI. The poll interval is
1680 optional and is the number seconds in between
1681 each poll cycle to the debug port in case you need
1682 the functionality for interrupting the kernel with
1683 gdb or control-c on the dbgp connection. When
1684 not using this parameter you use sysrq-g to break into
1685 the kernel debugger.
1687 kgdboc= [KGDB,HW] kgdb over consoles.
1688 Requires a tty driver that supports console polling,
1689 or a supported polling keyboard driver (non-usb).
1690 Serial only format: <serial_device>[,baud]
1691 keyboard only format: kbd
1692 keyboard and serial format: kbd,<serial_device>[,baud]
1693 Optional Kernel mode setting:
1694 kms, kbd format: kms,kbd
1695 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1697 kgdbwait [KGDB] Stop kernel execution and enter the
1698 kernel debugger at the earliest opportunity.
1700 kmac= [MIPS] korina ethernet MAC address.
1701 Configure the RouterBoard 532 series on-chip
1702 Ethernet adapter MAC address.
1704 kmemleak= [KNL] Boot-time kmemleak enable/disable
1705 Valid arguments: on, off
1707 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1710 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1711 Valid arguments: 0, 1, 2
1712 kmemcheck=0 (disabled)
1713 kmemcheck=1 (enabled)
1714 kmemcheck=2 (one-shot mode)
1715 Default: 2 (one-shot mode)
1717 kstack=N [X86] Print N words from the kernel stack
1720 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1721 Default is 0 (don't ignore, but inject #GP)
1723 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1727 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1728 Default is 1 (enabled)
1730 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1732 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1734 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1735 (virtualized MMU) support on capable Intel chips.
1736 Default is 1 (enabled)
1738 kvm-intel.emulate_invalid_guest_state=
1739 [KVM,Intel] Enable emulation of invalid guest states
1740 Default is 0 (disabled)
1742 kvm-intel.flexpriority=
1743 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1744 Default is 1 (enabled)
1747 [KVM,Intel] Enable VMX nesting (nVMX).
1748 Default is 0 (disabled)
1750 kvm-intel.unrestricted_guest=
1751 [KVM,Intel] Disable unrestricted guest feature
1752 (virtualized real and unpaged mode) on capable
1753 Intel chips. Default is 1 (enabled)
1755 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1756 feature (tagged TLBs) on capable Intel chips.
1757 Default is 1 (enabled)
1763 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1766 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1767 value for LAPIC timer one-shot implementation. Default
1768 back to the programmable timer unit in the LAPIC.
1770 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1773 libata.dma= [LIBATA] DMA control
1774 libata.dma=0 Disable all PATA and SATA DMA
1775 libata.dma=1 PATA and SATA Disk DMA only
1776 libata.dma=2 ATAPI (CDROM) DMA only
1777 libata.dma=4 Compact Flash DMA only
1778 Combinations also work, so libata.dma=3 enables DMA
1779 for disks and CDROMs, but not CFs.
1781 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1782 libata.ignore_hpa=0 keep BIOS limits (default)
1783 libata.ignore_hpa=1 ignore limits, using full disk
1785 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1789 libata.force= [LIBATA] Force configurations. The format is comma
1790 separated list of "[ID:]VAL" where ID is
1791 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1792 matching port, link or device. Basically, it matches
1793 the ATA ID string printed on console by libata. If
1794 the whole ID part is omitted, the last PORT and DEVICE
1795 values are used. If ID hasn't been specified yet, the
1796 configuration applies to all ports, links and devices.
1798 If only DEVICE is omitted, the parameter applies to
1799 the port and all links and devices behind it. DEVICE
1800 number of 0 either selects the first device or the
1801 first fan-out link behind PMP device. It does not
1802 select the host link. DEVICE number of 15 selects the
1803 host link and device attached to it.
1805 The VAL specifies the configuration to force. As long
1806 as there's no ambiguity shortcut notation is allowed.
1807 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1808 The following configurations can be forced.
1810 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1811 Any ID with matching PORT is used.
1813 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1815 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1816 udma[/][16,25,33,44,66,100,133] notation is also
1819 * [no]ncq: Turn on or off NCQ.
1821 * [no]ncqtrim: Turn off queued DSM TRIM.
1823 * nohrst, nosrst, norst: suppress hard, soft
1826 * rstonce: only attempt one reset during
1827 hot-unplug link recovery
1829 * dump_id: dump IDENTIFY data.
1831 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1833 * disable: Disable this device.
1835 If there are multiple matching configurations changing
1836 the same attribute, the last one is used.
1838 memblock=debug [KNL] Enable memblock debug messages.
1840 load_ramdisk= [RAM] List of ramdisks to load from floppy
1841 See Documentation/blockdev/ramdisk.txt.
1843 lockd.nlm_grace_period=P [NFS] Assign grace period.
1846 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1849 lockd.nlm_timeout=T [NFS] Assign timeout value.
1852 lockd.nlm_udpport=M [NFS] Assign UDP port.
1855 locktorture.nreaders_stress= [KNL]
1856 Set the number of locking read-acquisition kthreads.
1857 Defaults to being automatically set based on the
1858 number of online CPUs.
1860 locktorture.nwriters_stress= [KNL]
1861 Set the number of locking write-acquisition kthreads.
1863 locktorture.onoff_holdoff= [KNL]
1864 Set time (s) after boot for CPU-hotplug testing.
1866 locktorture.onoff_interval= [KNL]
1867 Set time (s) between CPU-hotplug operations, or
1868 zero to disable CPU-hotplug testing.
1870 locktorture.shuffle_interval= [KNL]
1871 Set task-shuffle interval (jiffies). Shuffling
1872 tasks allows some CPUs to go into dyntick-idle
1873 mode during the locktorture test.
1875 locktorture.shutdown_secs= [KNL]
1876 Set time (s) after boot system shutdown. This
1877 is useful for hands-off automated testing.
1879 locktorture.stat_interval= [KNL]
1880 Time (s) between statistics printk()s.
1882 locktorture.stutter= [KNL]
1883 Time (s) to stutter testing, for example,
1884 specifying five seconds causes the test to run for
1885 five seconds, wait for five seconds, and so on.
1886 This tests the locking primitive's ability to
1887 transition abruptly to and from idle.
1889 locktorture.torture_runnable= [BOOT]
1890 Start locktorture running at boot time.
1892 locktorture.torture_type= [KNL]
1893 Specify the locking implementation to test.
1895 locktorture.verbose= [KNL]
1896 Enable additional printk() statements.
1898 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1901 loglevel= All Kernel Messages with a loglevel smaller than the
1902 console loglevel will be printed to the console. It can
1903 also be changed with klogd or other programs. The
1904 loglevels are defined as follows:
1906 0 (KERN_EMERG) system is unusable
1907 1 (KERN_ALERT) action must be taken immediately
1908 2 (KERN_CRIT) critical conditions
1909 3 (KERN_ERR) error conditions
1910 4 (KERN_WARNING) warning conditions
1911 5 (KERN_NOTICE) normal but significant condition
1912 6 (KERN_INFO) informational
1913 7 (KERN_DEBUG) debug-level messages
1915 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1916 in bytes. n must be a power of two and greater
1917 than the minimal size. The minimal size is defined
1918 by LOG_BUF_SHIFT kernel config parameter. There is
1919 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1920 that allows to increase the default size depending on
1921 the number of CPUs. See init/Kconfig for more details.
1923 logo.nologo [FB] Disables display of the built-in Linux logo.
1924 This may be used to provide more screen space for
1925 kernel log messages and is useful when debugging
1926 kernel boot problems.
1928 lp=0 [LP] Specify parallel ports to use, e.g,
1929 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1930 lp=reset first parallel port). 'lp=0' disables the
1931 lp=auto printer driver. 'lp=reset' (which can be
1932 specified in addition to the ports) causes
1933 attached printers to be reset. Using
1934 lp=port1,port2,... specifies the parallel ports
1935 to associate lp devices with, starting with
1936 lp0. A port specification may be 'none' to skip
1937 that lp device, or a parport name such as
1938 'parport0'. Specifying 'lp=auto' instead of a
1939 port specification list means that device IDs
1940 from each port should be examined, to see if
1941 an IEEE 1284-compliant printer is attached; if
1942 so, the driver will manage that printer.
1943 See also header of drivers/char/lp.c.
1946 Sets loops_per_jiffy to given constant, thus avoiding
1947 time-consuming boot-time autodetection (up to 250 ms per
1948 CPU). 0 enables autodetection (default). To determine
1949 the correct value for your kernel, boot with normal
1950 autodetection and see what value is printed. Note that
1951 on SMP systems the preset will be applied to all CPUs,
1952 which is likely to cause problems if your CPUs need
1953 significantly divergent settings. An incorrect value
1954 will cause delays in the kernel to be wrong, leading to
1955 unpredictable I/O errors and other breakage. Although
1956 unlikely, in the extreme case this might damage your
1960 Format: <io>,<irq>,<dma>
1962 machvec= [IA-64] Force the use of a particular machine-vector
1963 (machvec) in a generic kernel.
1964 Example: machvec=hpzx1_swiotlb
1966 machtype= [Loongson] Share the same kernel image file between different
1968 Example: machtype=lemote-yeeloong-2f-7inch
1970 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1971 than or equal to this physical address is ignored.
1973 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1974 should make use of. maxcpus=n : n >= 0 limits the
1975 kernel to using 'n' processors. n=0 is a special case,
1976 it is equivalent to "nosmp", which also disables
1979 max_loop= [LOOP] The number of loop block devices that get
1980 (loop.max_loop) unconditionally pre-created at init time. The default
1981 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1982 of statically allocating a predefined number, loop
1983 devices can be requested on-demand with the
1984 /dev/loop-control interface.
1986 mce [X86-32] Machine Check Exception
1988 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1990 md= [HW] RAID subsystems devices and level
1991 See Documentation/md.txt.
1994 Format: <first>,<last>
1995 Specifies range of consoles to be captured by the MDA.
1997 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1998 Amount of memory to be used when the kernel is not able
1999 to see the whole system memory or for test.
2000 [X86] Work as limiting max address. Use together
2001 with memmap= to avoid physical address space collisions.
2002 Without memmap= PCI devices could be placed at addresses
2003 belonging to unused RAM.
2005 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2009 [KNL,SH] Allow user to override the default size for
2010 per-device physically contiguous DMA buffers.
2012 memmap=exactmap [KNL,X86] Enable setting of an exact
2013 E820 memory map, as specified by the user.
2014 Such memmap=exactmap lines can be constructed based on
2015 BIOS output or other requirements. See the memmap=nn@ss
2018 memmap=nn[KMG]@ss[KMG]
2019 [KNL] Force usage of a specific region of memory.
2020 Region of memory to be used is from ss to ss+nn.
2022 memmap=nn[KMG]#ss[KMG]
2023 [KNL,ACPI] Mark specific memory as ACPI data.
2024 Region of memory to be marked is from ss to ss+nn.
2026 memmap=nn[KMG]$ss[KMG]
2027 [KNL,ACPI] Mark specific memory as reserved.
2028 Region of memory to be reserved is from ss to ss+nn.
2029 Example: Exclude memory from 0x18690000-0x1869ffff
2030 memmap=64K$0x18690000
2032 memmap=0x10000$0x18690000
2034 memmap=nn[KMG]!ss[KMG]
2035 [KNL,X86] Mark specific memory as protected.
2036 Region of memory to be used, from ss to ss+nn.
2037 The memory region may be marked as e820 type 12 (0xc)
2038 and is NVDIMM or ADR memory.
2040 memory_corruption_check=0/1 [X86]
2041 Some BIOSes seem to corrupt the first 64k of
2042 memory when doing things like suspend/resume.
2043 Setting this option will scan the memory
2044 looking for corruption. Enabling this will
2045 both detect corruption and prevent the kernel
2046 from using the memory being corrupted.
2047 However, its intended as a diagnostic tool; if
2048 repeatable BIOS-originated corruption always
2049 affects the same memory, you can use memmap=
2050 to prevent the kernel from using that memory.
2052 memory_corruption_check_size=size [X86]
2053 By default it checks for corruption in the low
2054 64k, making this memory unavailable for normal
2055 use. Use this parameter to scan for
2056 corruption in more or less memory.
2058 memory_corruption_check_period=seconds [X86]
2059 By default it checks for corruption every 60
2060 seconds. Use this parameter to check at some
2061 other rate. 0 disables periodic checking.
2063 memtest= [KNL,X86,ARM] Enable memtest
2065 default : 0 <disable>
2066 Specifies the number of memtest passes to be
2067 performed. Each pass selects another test
2068 pattern from a given set of patterns. Memtest
2069 fills the memory with this pattern, validates
2070 memory contents and reserves bad memory
2071 regions that are detected.
2073 meye.*= [HW] Set MotionEye Camera parameters
2074 See Documentation/video4linux/meye.txt.
2076 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2077 Multi-Function General Purpose Timers on AMD Geode
2080 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2081 the BIOS has incorrectly applied a workaround. TinyBIOS
2082 version 0.98 is known to be affected, 0.99 fixes the
2083 problem by letting the user disable the workaround.
2087 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2088 physical address is ignored.
2090 mini2440= [ARM,HW,KNL]
2091 Format:[0..2][b][c][t]
2093 MINI2440 configuration specification:
2094 0 - The attached screen is the 3.5" TFT
2095 1 - The attached screen is the 7" TFT
2096 2 - The VGA Shield is attached (1024x768)
2097 Leaving out the screen size parameter will not load
2098 the TFT driver, and the framebuffer will be left
2100 b - Enable backlight. The TFT backlight pin will be
2101 linked to the kernel VESA blanking code and a GPIO
2102 LED. This parameter is not necessary when using the
2104 c - Enable the s3c camera interface.
2105 t - Reserved for enabling touchscreen support. The
2106 touchscreen support is not enabled in the mainstream
2107 kernel as of 2.6.30, a preliminary port can be found
2108 in the "bleeding edge" mini2440 support kernel at
2109 http://repo.or.cz/w/linux-2.6/mini2440.git
2112 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2113 parameter allows control of the logging verbosity for
2114 the additional memory initialisation checks. A value
2115 of 0 disables mminit logging and a level of 4 will
2116 log everything. Information is printed at KERN_DEBUG
2117 so loglevel=8 may also need to be specified.
2120 [KNL] When CONFIG_MODULE_SIG is set, this means that
2121 modules without (valid) signatures will fail to load.
2122 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2123 is always true, so this option does nothing.
2126 [MOUSE] Maximum time between finger touching and
2127 leaving touchpad surface for touch to be considered
2128 a tap and be reported as a left button click (for
2129 touchpads working in absolute mode only).
2131 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2132 reporting absolute coordinates, such as tablets
2133 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2134 reporting absolute coordinates, such as tablets
2136 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2137 is similar to kernelcore except it specifies the
2138 amount of memory used for migratable allocations.
2139 If both kernelcore and movablecore is specified,
2140 then kernelcore will be at *least* the specified
2141 value but may be more. If movablecore on its own
2142 is specified, the administrator must be careful
2143 that the amount of memory usable for all allocations
2146 movable_node [KNL,X86] Boot-time switch to enable the effects
2147 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2149 MTD_Partition= [MTD]
2150 Format: <name>,<region-number>,<size>,<offset>
2152 MTD_Region= [MTD] Format:
2153 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2156 See drivers/mtd/cmdlinepart.c.
2158 multitce=off [PPC] This parameter disables the use of the pSeries
2159 firmware feature for updating multiple TCE entries
2162 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2164 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2166 boundary - index of last SLC block on Flex-OneNAND.
2167 The remaining blocks are configured as MLC blocks.
2168 lock - Configure if Flex-OneNAND boundary should be locked.
2169 Once locked, the boundary cannot be changed.
2170 1 indicates lock status, 0 indicates unlock status.
2173 ARM/S3C2412 JIVE boot control
2175 See arch/arm/mach-s3c2412/mach-jive.c
2177 mtouchusb.raw_coordinates=
2178 [HW] Make the MicroTouch USB driver use raw coordinates
2179 ('y', default) or cooked coordinates ('n')
2181 mtrr_chunk_size=nn[KMG] [X86]
2182 used for mtrr cleanup. It is largest continuous chunk
2183 that could hold holes aka. UC entries.
2185 mtrr_gran_size=nn[KMG] [X86]
2186 Used for mtrr cleanup. It is granularity of mtrr block.
2188 Large value could prevent small alignment from
2191 mtrr_spare_reg_nr=n [X86]
2193 Range: 0,7 : spare reg number
2195 Used for mtrr cleanup. It is spare mtrr entries number.
2196 Set to 2 or more if your graphical card needs more.
2198 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2200 netdev= [NET] Network devices parameters
2201 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2202 Note that mem_start is often overloaded to mean
2203 something different and driver-specific.
2204 This usage is only documented in each driver source
2208 [NETFILTER] Enable connection tracking flow accounting
2209 0 to disable accounting
2210 1 to enable accounting
2213 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2214 See Documentation/filesystems/nfs/nfsroot.txt.
2216 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2217 See Documentation/filesystems/nfs/nfsroot.txt.
2219 nfsrootdebug [NFS] enable nfsroot debugging messages.
2220 See Documentation/filesystems/nfs/nfsroot.txt.
2222 nfs.callback_tcpport=
2223 [NFS] set the TCP port on which the NFSv4 callback
2224 channel should listen.
2227 [NFS] sets the pathname to the program which is used
2228 to update the NFS client cache entries.
2230 nfs.cache_getent_timeout=
2231 [NFS] sets the timeout after which an attempt to
2232 update a cache entry is deemed to have failed.
2234 nfs.idmap_cache_timeout=
2235 [NFS] set the maximum lifetime for idmapper cache
2239 [NFS] enable 64-bit inode numbers.
2240 If zero, the NFS client will fake up a 32-bit inode
2241 number for the readdir() and stat() syscalls instead
2242 of returning the full 64-bit number.
2243 The default is to return 64-bit inode numbers.
2245 nfs.max_session_slots=
2246 [NFSv4.1] Sets the maximum number of session slots
2247 the client will attempt to negotiate with the server.
2248 This limits the number of simultaneous RPC requests
2249 that the client can send to the NFSv4.1 server.
2250 Note that there is little point in setting this
2251 value higher than the max_tcp_slot_table_limit.
2253 nfs.nfs4_disable_idmapping=
2254 [NFSv4] When set to the default of '1', this option
2255 ensures that both the RPC level authentication
2256 scheme and the NFS level operations agree to use
2257 numeric uids/gids if the mount is using the
2258 'sec=sys' security flavour. In effect it is
2259 disabling idmapping, which can make migration from
2260 legacy NFSv2/v3 systems to NFSv4 easier.
2261 Servers that do not support this mode of operation
2262 will be autodetected by the client, and it will fall
2263 back to using the idmapper.
2264 To turn off this behaviour, set the value to '0'.
2266 [NFS4] Specify an additional fixed unique ident-
2267 ification string that NFSv4 clients can insert into
2268 their nfs_client_id4 string. This is typically a
2269 UUID that is generated at system install time.
2271 nfs.send_implementation_id =
2272 [NFSv4.1] Send client implementation identification
2273 information in exchange_id requests.
2274 If zero, no implementation identification information
2276 The default is to send the implementation identification
2279 nfs.recover_lost_locks =
2280 [NFSv4] Attempt to recover locks that were lost due
2281 to a lease timeout on the server. Please note that
2282 doing this risks data corruption, since there are
2283 no guarantees that the file will remain unchanged
2284 after the locks are lost.
2285 If you want to enable the kernel legacy behaviour of
2286 attempting to recover these locks, then set this
2288 The default parameter value of '0' causes the kernel
2289 not to attempt recovery of lost locks.
2291 nfs4.layoutstats_timer =
2292 [NFSv4.2] Change the rate at which the kernel sends
2293 layoutstats to the pNFS metadata server.
2295 Setting this to value to 0 causes the kernel to use
2296 whatever value is the default set by the layout
2297 driver. A non-zero value sets the minimum interval
2298 in seconds between layoutstats transmissions.
2300 nfsd.nfs4_disable_idmapping=
2301 [NFSv4] When set to the default of '1', the NFSv4
2302 server will return only numeric uids and gids to
2303 clients using auth_sys, and will accept numeric uids
2304 and gids from such clients. This is intended to ease
2305 migration from NFSv2/v3.
2307 objlayoutdriver.osd_login_prog=
2308 [NFS] [OBJLAYOUT] sets the pathname to the program which
2309 is used to automatically discover and login into new
2310 osd-targets. Please see:
2311 Documentation/filesystems/pnfs.txt for more explanations
2313 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2314 when a NMI is triggered.
2315 Format: [state][,regs][,debounce][,die]
2317 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2318 Format: [panic,][nopanic,][num]
2320 0 - turn nmi_watchdog off
2321 1 - turn nmi_watchdog on
2322 When panic is specified, panic when an NMI watchdog
2323 timeout occurs (or 'nopanic' to override the opposite
2325 This is useful when you use a panic=... timeout and
2326 need the box quickly up again.
2328 netpoll.carrier_timeout=
2329 [NET] Specifies amount of time (in seconds) that
2330 netpoll should wait for a carrier. By default netpoll
2333 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2334 emulation library even if a 387 maths coprocessor
2338 [HW] Never suspend the console
2339 Disable suspending of consoles during suspend and
2340 hibernate operations. Once disabled, debugging
2341 messages can reach various consoles while the rest
2342 of the system is being put to sleep (ie, while
2343 debugging driver suspend/resume hooks). This may
2344 not work reliably with all consoles, but is known
2345 to work with serial and VGA consoles.
2346 To facilitate more flexible debugging, we also add
2347 console_suspend, a printk module parameter to control
2348 it. Users could use console_suspend (usually
2349 /sys/module/printk/parameters/console_suspend) to
2350 turn on/off it dynamically.
2352 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2353 caches in the slab allocator. Saves per-node memory,
2354 but will impact performance.
2358 noapic [SMP,APIC] Tells the kernel to not make use of any
2359 IOAPICs that may be present in the system.
2361 noautogroup Disable scheduler automatic task group creation.
2363 nobats [PPC] Do not use BATs for mapping kernel lowmem
2364 on "Classic" PPC cores.
2368 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2370 nodelayacct [KNL] Disable per-task delay accounting
2372 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2374 nodsp [SH] Disable hardware DSP at boot time.
2376 noefi Disable EFI runtime services support.
2381 On X86-32 available only on PAE configured kernels.
2382 noexec=on: enable non-executable mappings (default)
2383 noexec=off: disable non-executable mappings
2386 Disable SMAP (Supervisor Mode Access Prevention)
2387 even if it is supported by processor.
2390 Disable SMEP (Supervisor Mode Execution Prevention)
2391 even if it is supported by processor.
2394 This affects only 32-bit executables.
2395 noexec32=on: enable non-executable mappings (default)
2396 read doesn't imply executable mappings
2397 noexec32=off: disable non-executable mappings
2398 read implies executable mappings
2400 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2402 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2403 register save and restore. The kernel will only save
2404 legacy floating-point registers on task switch.
2406 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2408 noxsave [BUGS=X86] Disables x86 extended register state save
2409 and restore using xsave. The kernel will fallback to
2410 enabling legacy floating-point and sse state.
2412 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2413 register states. The kernel will fall back to use
2414 xsave to save the states. By using this parameter,
2415 performance of saving the states is degraded because
2416 xsave doesn't support modified optimization while
2417 xsaveopt supports it on xsaveopt enabled systems.
2419 noxsaves [X86] Disables xsaves and xrstors used in saving and
2420 restoring x86 extended register state in compacted
2421 form of xsave area. The kernel will fall back to use
2422 xsaveopt and xrstor to save and restore the states
2423 in standard form of xsave area. By using this
2424 parameter, xsave area per process might occupy more
2425 memory on xsaves enabled systems.
2427 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2428 wfi(ARM) instruction doesn't work correctly and not to
2429 use it. This is also useful when using JTAG debugger.
2431 no_file_caps Tells the kernel not to honor file capabilities. The
2432 only way then for a file to be executed with privilege
2433 is to be setuid root or executed by root.
2435 nohalt [IA-64] Tells the kernel not to use the power saving
2436 function PAL_HALT_LIGHT when idle. This increases
2437 power-consumption. On the positive side, it reduces
2438 interrupt wake-up latency, which may improve performance
2439 in certain environments such as networked servers or
2442 nohibernate [HIBERNATION] Disable hibernation and resume.
2444 nohz= [KNL] Boottime enable/disable dynamic ticks
2445 Valid arguments: on, off
2448 nohz_full= [KNL,BOOT]
2449 In kernels built with CONFIG_NO_HZ_FULL=y, set
2450 the specified list of CPUs whose tick will be stopped
2451 whenever possible. The boot CPU will be forced outside
2452 the range to maintain the timekeeping.
2453 The CPUs in this range must also be included in the
2456 noiotrap [SH] Disables trapped I/O port accesses.
2458 noirqdebug [X86-32] Disables the code which attempts to detect and
2459 disable unhandled interrupt sources.
2461 no_timer_check [X86,APIC] Disables the code which tests for
2462 broken timer IRQ sources.
2464 noisapnp [ISAPNP] Disables ISA PnP code.
2466 noinitrd [RAM] Tells the kernel not to load any configured
2469 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2471 [Deprecated - use intremap=off]
2475 nojitter [IA-64] Disables jitter checking for ITC timers.
2477 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2479 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2482 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2483 steal time is computed, but won't influence scheduler
2486 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2488 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2490 noltlbs [PPC] Do not use large page/tlb entries for kernel
2491 lowmem mapping on PPC40x.
2493 nomca [IA-64] Disable machine check abort handling
2495 nomce [X86-32] Disable Machine Check Exception
2497 nomfgpt [X86-32] Disable Multi-Function General Purpose
2498 Timer usage (for AMD Geode machines).
2500 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2501 shutdown the other cpus. Instead use the REBOOT_VECTOR
2504 nomodule Disable module load
2506 nopat [X86] Disable PAT (page attribute table extension of
2507 pagetables) support.
2509 norandmaps Don't use address space randomization. Equivalent to
2510 echo 0 > /proc/sys/kernel/randomize_va_space
2512 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2514 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2515 with UP alternatives
2517 nordrand [X86] Disable kernel use of the RDRAND and
2518 RDSEED instructions even if they are supported
2519 by the processor. RDRAND and RDSEED are still
2520 available to user space applications.
2522 noresume [SWSUSP] Disables resume and restores original swap
2525 no-scroll [VGA] Disables scrollback.
2526 This is required for the Braillex ib80-piezo Braille
2527 reader made by F.H. Papenmeier (Germany).
2531 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2533 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2534 and disable the IO APIC. legacy for "maxcpus=0".
2536 nosoftlockup [KNL] Disable the soft-lockup detector.
2538 nosync [HW,M68K] Disables sync negotiation for all devices.
2540 notsc [BUGS=X86-32] Disable Time Stamp Counter
2542 nousb [USB] Disable the USB subsystem
2544 nowatchdog [KNL] Disable both lockup detectors, i.e.
2545 soft-lockup and NMI watchdog (hard-lockup).
2549 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2551 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2552 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2553 Some features depend on CPU0. Known dependencies are:
2554 1. Resume from suspend/hibernate depends on CPU0.
2555 Suspend/hibernate will fail if CPU0 is offline and you
2556 need to online CPU0 before suspend/hibernate.
2557 2. PIC interrupts also depend on CPU0. CPU0 can't be
2558 removed if a PIC interrupt is detected.
2559 It's said poweroff/reboot may depend on CPU0 on some
2560 machines although I haven't seen such issues so far
2561 after CPU0 is offline on a few tested machines.
2562 If the dependencies are under your control, you can
2563 turn on cpu0_hotplug.
2565 nptcg= [IA-64] Override max number of concurrent global TLB
2566 purges which is reported from either PAL_VM_SUMMARY or
2569 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2570 could support. nr_cpus=n : n >= 1 limits the kernel to
2571 supporting 'n' processors. Later in runtime you can not
2572 use hotplug cpu feature to put more cpu back to online.
2573 just like you compile the kernel NR_CPUS=n
2575 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2577 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2578 Allowed values are enable and disable
2580 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2581 one of ['zone', 'node', 'default'] can be specified
2582 This can be set from sysctl after boot.
2583 See Documentation/sysctl/vm.txt for details.
2585 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2586 See Documentation/debugging-via-ohci1394.txt for more
2589 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2590 Rather than timing out after 20 ms if an EC
2591 command is not properly ACKed, override the length
2592 of the timeout. We have interrupts disabled while
2593 waiting for the ACK, so if this is set too high
2594 interrupts *may* be lost!
2596 omap_mux= [OMAP] Override bootloader pin multiplexing.
2597 Format: <mux_mode0.mode_name=value>...
2598 For example, to override I2C bus2:
2599 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2601 oprofile.timer= [HW]
2602 Use timer interrupt instead of performance counters
2604 oprofile.cpu_type= Force an oprofile cpu type
2605 This might be useful if you have an older oprofile
2606 userland or if you want common events.
2607 Format: { arch_perfmon }
2608 arch_perfmon: [X86] Force use of architectural
2609 perfmon on Intel CPUs instead of the
2610 CPU specific event set.
2611 timer: [X86] Force use of architectural NMI
2612 timer mode (see also oprofile.timer
2613 for generic hr timer mode)
2614 [s390] Force legacy basic mode sampling
2615 (report cpu_type "timer")
2617 oops=panic Always panic on oopses. Default is to just kill the
2618 process, but there is a small probability of
2619 deadlocking the machine.
2620 This will also cause panics on machine check exceptions.
2621 Useful together with panic=30 to trigger a reboot.
2624 See Documentation/sound/oss/oss-parameters.txt
2626 page_owner= [KNL] Boot-time page_owner enabling option.
2627 Storage of the information about who allocated
2628 each page is disabled in default. With this switch,
2630 on: enable the feature
2632 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2633 timeout > 0: seconds before rebooting
2634 timeout = 0: wait forever
2635 timeout < 0: reboot immediately
2638 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2641 crash_kexec_post_notifiers
2642 Run kdump after running panic-notifiers and dumping
2643 kmsg. This only for the users who doubt kdump always
2644 succeeds in any situation.
2645 Note that this also increases risks of kdump failure,
2646 because some panic notifiers can make the crashed
2647 kernel more unstable.
2649 parkbd.port= [HW] Parallel port number the keyboard adapter is
2650 connected to, default is 0.
2652 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2653 0 for XT, 1 for AT (default is AT).
2656 parport= [HW,PPT] Specify parallel ports. 0 disables.
2657 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2658 Use 'auto' to force the driver to use any
2659 IRQ/DMA settings detected (the default is to
2660 ignore detected IRQ/DMA settings because of
2661 possible conflicts). You can specify the base
2662 address, IRQ, and DMA settings; IRQ and DMA
2663 should be numbers, or 'auto' (for using detected
2664 settings on that particular port), or 'nofifo'
2665 (to avoid using a FIFO even if it is detected).
2666 Parallel ports are assigned in the order they
2667 are specified on the command line, starting
2670 parport_init_mode= [HW,PPT]
2671 Configure VIA parallel port to operate in
2672 a specific mode. This is necessary on Pegasos
2673 computer where firmware has no options for setting
2674 up parallel port mode and sets it to spp.
2675 Currently this function knows 686a and 8231 chips.
2676 Format: [spp|ps2|epp|ecp|ecpepp]
2679 Halt all CPUs after the first oops has been printed for
2680 the specified number of seconds. This is to be used if
2681 your oopses keep scrolling off the screen.
2686 See header of drivers/block/paride/pcd.c.
2687 See also Documentation/blockdev/paride.txt.
2689 pci=option[,option...] [PCI] various PCI subsystem options:
2690 earlydump [X86] dump PCI config space before the kernel
2692 off [X86] don't probe for the PCI bus
2693 bios [X86-32] force use of PCI BIOS, don't access
2694 the hardware directly. Use this if your machine
2695 has a non-standard PCI host bridge.
2696 nobios [X86-32] disallow use of PCI BIOS, only direct
2697 hardware access methods are allowed. Use this
2698 if you experience crashes upon bootup and you
2699 suspect they are caused by the BIOS.
2700 conf1 [X86] Force use of PCI Configuration
2702 conf2 [X86] Force use of PCI Configuration
2704 noaer [PCIE] If the PCIEAER kernel config parameter is
2705 enabled, this kernel boot option can be used to
2706 disable the use of PCIE advanced error reporting.
2707 nodomains [PCI] Disable support for multiple PCI
2708 root domains (aka PCI segments, in ACPI-speak).
2709 nommconf [X86] Disable use of MMCONFIG for PCI
2711 check_enable_amd_mmconf [X86] check for and enable
2712 properly configured MMIO access to PCI
2713 config space on AMD family 10h CPU
2714 nomsi [MSI] If the PCI_MSI kernel config parameter is
2715 enabled, this kernel boot option can be used to
2716 disable the use of MSI interrupts system-wide.
2717 noioapicquirk [APIC] Disable all boot interrupt quirks.
2718 Safety option to keep boot IRQs enabled. This
2719 should never be necessary.
2720 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2721 primary IO-APIC for bridges that cannot disable
2722 boot IRQs. This fixes a source of spurious IRQs
2723 when the system masks IRQs.
2724 noioapicreroute [APIC] Disable workaround that uses the
2725 boot IRQ equivalent of an IRQ that connects to
2726 a chipset where boot IRQs cannot be disabled.
2727 The opposite of ioapicreroute.
2728 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2729 routing table. These calls are known to be buggy
2730 on several machines and they hang the machine
2731 when used, but on other computers it's the only
2732 way to get the interrupt routing table. Try
2733 this option if the kernel is unable to allocate
2734 IRQs or discover secondary PCI buses on your
2736 rom [X86] Assign address space to expansion ROMs.
2737 Use with caution as certain devices share
2738 address decoders between ROMs and other
2740 norom [X86] Do not assign address space to
2741 expansion ROMs that do not already have
2742 BIOS assigned address ranges.
2743 nobar [X86] Do not assign address space to the
2744 BARs that weren't assigned by the BIOS.
2745 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2746 assigned automatically to PCI devices. You can
2747 make the kernel exclude IRQs of your ISA cards
2749 pirqaddr=0xAAAAA [X86] Specify the physical address
2750 of the PIRQ table (normally generated
2751 by the BIOS) if it is outside the
2752 F0000h-100000h range.
2753 lastbus=N [X86] Scan all buses thru bus #N. Can be
2754 useful if the kernel is unable to find your
2755 secondary buses and you want to tell it
2756 explicitly which ones they are.
2757 assign-busses [X86] Always assign all PCI bus
2758 numbers ourselves, overriding
2759 whatever the firmware may have done.
2760 usepirqmask [X86] Honor the possible IRQ mask stored
2761 in the BIOS $PIR table. This is needed on
2762 some systems with broken BIOSes, notably
2763 some HP Pavilion N5400 and Omnibook XE3
2764 notebooks. This will have no effect if ACPI
2765 IRQ routing is enabled.
2766 noacpi [X86] Do not use ACPI for IRQ routing
2767 or for PCI scanning.
2768 use_crs [X86] Use PCI host bridge window information
2769 from ACPI. On BIOSes from 2008 or later, this
2770 is enabled by default. If you need to use this,
2771 please report a bug.
2772 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2773 If you need to use this, please report a bug.
2774 routeirq Do IRQ routing for all PCI devices.
2775 This is normally done in pci_enable_device(),
2776 so this option is a temporary workaround
2777 for broken drivers that don't call it.
2778 skip_isa_align [X86] do not align io start addr, so can
2779 handle more pci cards
2780 firmware [ARM] Do not re-enumerate the bus but instead
2781 just use the configuration from the
2782 bootloader. This is currently used on
2783 IXP2000 systems where the bus has to be
2784 configured a certain way for adjunct CPUs.
2785 noearly [X86] Don't do any early type 1 scanning.
2786 This might help on some broken boards which
2787 machine check when some devices' config space
2788 is read. But various workarounds are disabled
2789 and some IOMMU drivers will not work.
2790 bfsort Sort PCI devices into breadth-first order.
2791 This sorting is done to get a device
2792 order compatible with older (<= 2.4) kernels.
2793 nobfsort Don't sort PCI devices into breadth-first order.
2794 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2795 tuning and use the BIOS-configured MPS defaults.
2796 pcie_bus_safe Set every device's MPS to the largest value
2797 supported by all devices below the root complex.
2798 pcie_bus_perf Set device MPS to the largest allowable MPS
2799 based on its parent bus. Also set MRRS (Max
2800 Read Request Size) to the largest supported
2801 value (no larger than the MPS that the device
2802 or bus can support) for best performance.
2803 pcie_bus_peer2peer Set every device's MPS to 128B, which
2804 every device is guaranteed to support. This
2805 configuration allows peer-to-peer DMA between
2806 any pair of devices, possibly at the cost of
2807 reduced performance. This also guarantees
2808 that hot-added devices will work.
2809 cbiosize=nn[KMG] The fixed amount of bus space which is
2810 reserved for the CardBus bridge's IO window.
2811 The default value is 256 bytes.
2812 cbmemsize=nn[KMG] The fixed amount of bus space which is
2813 reserved for the CardBus bridge's memory
2814 window. The default value is 64 megabytes.
2817 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2818 Specifies alignment and device to reassign
2819 aligned memory resources.
2820 If <order of align> is not specified,
2821 PAGE_SIZE is used as alignment.
2822 PCI-PCI bridge can be specified, if resource
2823 windows need to be expanded.
2824 ecrc= Enable/disable PCIe ECRC (transaction layer
2825 end-to-end CRC checking).
2826 bios: Use BIOS/firmware settings. This is the
2830 hpiosize=nn[KMG] The fixed amount of bus space which is
2831 reserved for hotplug bridge's IO window.
2832 Default size is 256 bytes.
2833 hpmemsize=nn[KMG] The fixed amount of bus space which is
2834 reserved for hotplug bridge's memory window.
2835 Default size is 2 megabytes.
2836 realloc= Enable/disable reallocating PCI bridge resources
2837 if allocations done by BIOS are too small to
2838 accommodate resources required by all child
2840 off: Turn realloc off
2842 realloc same as realloc=on
2843 noari do not use PCIe ARI.
2844 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2845 only look for one device below a PCIe downstream
2848 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2851 force Enable ASPM even on devices that claim not to support it.
2852 WARNING: Forcing ASPM on may cause system lockups.
2854 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2855 nomsi Do not use MSI for PCI Express Native Hotplug (this
2856 makes all PCIe ports use INTx for hotplug services).
2858 pcie_ports= [PCIE] PCIe ports handling:
2859 auto Ask the BIOS whether or not to use native PCIe services
2860 associated with PCIe ports (PME, hot-plug, AER). Use
2861 them only if that is allowed by the BIOS.
2862 native Use native PCIe services associated with PCIe ports
2864 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2867 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2868 nomsi Do not use MSI for native PCIe PME signaling (this makes
2869 all PCIe root ports use INTx for all services).
2871 pcmv= [HW,PCMCIA] BadgePAD 4
2875 Keep all power-domains already enabled by bootloader on,
2876 even if no driver has claimed them. This is useful
2877 for debug and development, but should not be
2878 needed on a platform with proper driver support.
2881 See Documentation/blockdev/paride.txt.
2883 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2886 See arch/parisc/kernel/pdc_chassis.c
2888 percpu_alloc= Select which percpu first chunk allocator to use.
2889 Currently supported values are "embed" and "page".
2890 Archs may support subset or none of the selections.
2891 See comments in mm/percpu.c for details on each
2892 allocator. This parameter is primarily for debugging
2893 and performance comparison.
2896 See Documentation/blockdev/paride.txt.
2899 See Documentation/blockdev/paride.txt.
2901 pirq= [SMP,APIC] Manual mp-table setup
2902 See Documentation/x86/i386/IO-APIC.txt.
2904 plip= [PPT,NET] Parallel port network link
2905 Format: { parport<nr> | timid | 0 }
2906 See also Documentation/parport.txt.
2908 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2909 Override pmtimer IOPort with a hex value.
2913 Enable PNP debug messages (depends on the
2914 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2915 via /sys/module/pnp/parameters/debug. We always show
2916 current resource usage; turning this on also shows
2917 possible settings and some assignment information.
2923 { on | off | curr | res | no-curr | no-res }
2926 [ISAPNP] Exclude IRQs for the autoconfiguration
2929 [ISAPNP] Exclude DMAs for the autoconfiguration
2931 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2932 Ranges are in pairs (I/O port base and size).
2935 [ISAPNP] Exclude memory regions for the
2937 Ranges are in pairs (memory base and size).
2939 ports= [IP_VS_FTP] IPVS ftp helper module
2941 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2943 Format: <port>,<port>....
2945 print-fatal-signals=
2946 [KNL] debug: print fatal signals
2948 If enabled, warn about various signal handling
2949 related application anomalies: too many signals,
2950 too many POSIX.1 timers, fatal signals causing a
2953 If you hit the warning due to signal overflow,
2954 you might want to try "ulimit -i unlimited".
2958 printk.always_kmsg_dump=
2959 Trigger kmsg_dump for cases other than kernel oops or
2961 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2964 printk.time= Show timing data prefixed to each printk message line
2965 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2967 processor.max_cstate= [HW,ACPI]
2968 Limit processor to maximum C-state
2969 max_cstate=9 overrides any DMI blacklist limit.
2971 processor.nocst [HW,ACPI]
2972 Ignore the _CST method to determine C-states,
2973 instead using the legacy FADT method
2975 profile= [KNL] Enable kernel profiling via /proc/profile
2976 Format: [schedule,]<number>
2977 Param: "schedule" - profile schedule points.
2978 Param: <number> - step/bucket size as a power of 2 for
2979 statistical time based profiling.
2980 Param: "sleep" - profile D-state sleeping (millisecs).
2981 Requires CONFIG_SCHEDSTATS
2982 Param: "kvm" - profile VM exits.
2984 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2986 See Documentation/blockdev/ramdisk.txt.
2988 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2989 probe for; one of (bare|imps|exps|lifebook|any).
2990 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2992 psmouse.resetafter= [HW,MOUSE]
2993 Try to reset the device after so many bad packets
2996 [HW,MOUSE] Set desired mouse resolution, in dpi.
2997 psmouse.smartscroll=
2998 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2999 0 = disabled, 1 = enabled (default).
3001 pstore.backend= Specify the name of the pstore backend to use
3004 See Documentation/blockdev/paride.txt.
3007 [KNL] Number of legacy pty's. Overwrites compiled-in
3010 quiet [KNL] Disable most log messages
3015 See Documentation/md.txt.
3017 ramdisk_blocksize= [RAM]
3018 See Documentation/blockdev/ramdisk.txt.
3020 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3021 See Documentation/blockdev/ramdisk.txt.
3024 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3025 the specified list of CPUs to be no-callback CPUs.
3026 Invocation of these CPUs' RCU callbacks will
3027 be offloaded to "rcuox/N" kthreads created for
3028 that purpose, where "x" is "b" for RCU-bh, "p"
3029 for RCU-preempt, and "s" for RCU-sched, and "N"
3030 is the CPU number. This reduces OS jitter on the
3031 offloaded CPUs, which can be useful for HPC and
3032 real-time workloads. It can also improve energy
3033 efficiency for asymmetric multiprocessors.
3036 Rather than requiring that offloaded CPUs
3037 (specified by rcu_nocbs= above) explicitly
3038 awaken the corresponding "rcuoN" kthreads,
3039 make these kthreads poll for callbacks.
3040 This improves the real-time response for the
3041 offloaded CPUs by relieving them of the need to
3042 wake up the corresponding kthread, but degrades
3043 energy efficiency by requiring that the kthreads
3044 periodically wake up to do the polling.
3046 rcutree.blimit= [KNL]
3047 Set maximum number of finished RCU callbacks to
3048 process in one batch.
3050 rcutree.dump_tree= [KNL]
3051 Dump the structure of the rcu_node combining tree
3052 out at early boot. This is used for diagnostic
3053 purposes, to verify correct tree setup.
3055 rcutree.gp_cleanup_delay= [KNL]
3056 Set the number of jiffies to delay each step of
3057 RCU grace-period cleanup. This only has effect
3058 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3060 rcutree.gp_init_delay= [KNL]
3061 Set the number of jiffies to delay each step of
3062 RCU grace-period initialization. This only has
3063 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3066 rcutree.gp_preinit_delay= [KNL]
3067 Set the number of jiffies to delay each step of
3068 RCU grace-period pre-initialization, that is,
3069 the propagation of recent CPU-hotplug changes up
3070 the rcu_node combining tree. This only has effect
3071 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3073 rcutree.rcu_fanout_exact= [KNL]
3074 Disable autobalancing of the rcu_node combining
3075 tree. This is used by rcutorture, and might
3076 possibly be useful for architectures having high
3077 cache-to-cache transfer latencies.
3079 rcutree.rcu_fanout_leaf= [KNL]
3080 Increase the number of CPUs assigned to each
3081 leaf rcu_node structure. Useful for very large
3084 rcutree.jiffies_till_sched_qs= [KNL]
3085 Set required age in jiffies for a
3086 given grace period before RCU starts
3087 soliciting quiescent-state help from
3088 rcu_note_context_switch().
3090 rcutree.jiffies_till_first_fqs= [KNL]
3091 Set delay from grace-period initialization to
3092 first attempt to force quiescent states.
3093 Units are jiffies, minimum value is zero,
3094 and maximum value is HZ.
3096 rcutree.jiffies_till_next_fqs= [KNL]
3097 Set delay between subsequent attempts to force
3098 quiescent states. Units are jiffies, minimum
3099 value is one, and maximum value is HZ.
3101 rcutree.kthread_prio= [KNL,BOOT]
3102 Set the SCHED_FIFO priority of the RCU per-CPU
3103 kthreads (rcuc/N). This value is also used for
3104 the priority of the RCU boost threads (rcub/N)
3105 and for the RCU grace-period kthreads (rcu_bh,
3106 rcu_preempt, and rcu_sched). If RCU_BOOST is
3107 set, valid values are 1-99 and the default is 1
3108 (the least-favored priority). Otherwise, when
3109 RCU_BOOST is not set, valid values are 0-99 and
3110 the default is zero (non-realtime operation).
3112 rcutree.rcu_nocb_leader_stride= [KNL]
3113 Set the number of NOCB kthread groups, which
3114 defaults to the square root of the number of
3115 CPUs. Larger numbers reduces the wakeup overhead
3116 on the per-CPU grace-period kthreads, but increases
3117 that same overhead on each group's leader.
3119 rcutree.qhimark= [KNL]
3120 Set threshold of queued RCU callbacks beyond which
3121 batch limiting is disabled.
3123 rcutree.qlowmark= [KNL]
3124 Set threshold of queued RCU callbacks below which
3125 batch limiting is re-enabled.
3127 rcutree.rcu_idle_gp_delay= [KNL]
3128 Set wakeup interval for idle CPUs that have
3129 RCU callbacks (RCU_FAST_NO_HZ=y).
3131 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3132 Set wakeup interval for idle CPUs that have
3133 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3134 Lazy RCU callbacks are those which RCU can
3135 prove do nothing more than free memory.
3137 rcutorture.cbflood_inter_holdoff= [KNL]
3138 Set holdoff time (jiffies) between successive
3139 callback-flood tests.
3141 rcutorture.cbflood_intra_holdoff= [KNL]
3142 Set holdoff time (jiffies) between successive
3143 bursts of callbacks within a given callback-flood
3146 rcutorture.cbflood_n_burst= [KNL]
3147 Set the number of bursts making up a given
3148 callback-flood test. Set this to zero to
3149 disable callback-flood testing.
3151 rcutorture.cbflood_n_per_burst= [KNL]
3152 Set the number of callbacks to be registered
3153 in a given burst of a callback-flood test.
3155 rcutorture.fqs_duration= [KNL]
3156 Set duration of force_quiescent_state bursts
3159 rcutorture.fqs_holdoff= [KNL]
3160 Set holdoff time within force_quiescent_state bursts
3163 rcutorture.fqs_stutter= [KNL]
3164 Set wait time between force_quiescent_state bursts
3167 rcutorture.gp_cond= [KNL]
3168 Use conditional/asynchronous update-side
3169 primitives, if available.
3171 rcutorture.gp_exp= [KNL]
3172 Use expedited update-side primitives, if available.
3174 rcutorture.gp_normal= [KNL]
3175 Use normal (non-expedited) asynchronous
3176 update-side primitives, if available.
3178 rcutorture.gp_sync= [KNL]
3179 Use normal (non-expedited) synchronous
3180 update-side primitives, if available. If all
3181 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3182 rcutorture.gp_normal=, and rcutorture.gp_sync=
3183 are zero, rcutorture acts as if is interpreted
3184 they are all non-zero.
3186 rcutorture.n_barrier_cbs= [KNL]
3187 Set callbacks/threads for rcu_barrier() testing.
3189 rcutorture.nfakewriters= [KNL]
3190 Set number of concurrent RCU writers. These just
3191 stress RCU, they don't participate in the actual
3192 test, hence the "fake".
3194 rcutorture.nreaders= [KNL]
3195 Set number of RCU readers. The value -1 selects
3196 N-1, where N is the number of CPUs. A value
3197 "n" less than -1 selects N-n-2, where N is again
3198 the number of CPUs. For example, -2 selects N
3199 (the number of CPUs), -3 selects N+1, and so on.
3201 rcutorture.object_debug= [KNL]
3202 Enable debug-object double-call_rcu() testing.
3204 rcutorture.onoff_holdoff= [KNL]
3205 Set time (s) after boot for CPU-hotplug testing.
3207 rcutorture.onoff_interval= [KNL]
3208 Set time (s) between CPU-hotplug operations, or
3209 zero to disable CPU-hotplug testing.
3211 rcutorture.shuffle_interval= [KNL]
3212 Set task-shuffle interval (s). Shuffling tasks
3213 allows some CPUs to go into dyntick-idle mode
3214 during the rcutorture test.
3216 rcutorture.shutdown_secs= [KNL]
3217 Set time (s) after boot system shutdown. This
3218 is useful for hands-off automated testing.
3220 rcutorture.stall_cpu= [KNL]
3221 Duration of CPU stall (s) to test RCU CPU stall
3222 warnings, zero to disable.
3224 rcutorture.stall_cpu_holdoff= [KNL]
3225 Time to wait (s) after boot before inducing stall.
3227 rcutorture.stat_interval= [KNL]
3228 Time (s) between statistics printk()s.
3230 rcutorture.stutter= [KNL]
3231 Time (s) to stutter testing, for example, specifying
3232 five seconds causes the test to run for five seconds,
3233 wait for five seconds, and so on. This tests RCU's
3234 ability to transition abruptly to and from idle.
3236 rcutorture.test_boost= [KNL]
3237 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3238 "Maybe" means test if the RCU implementation
3239 under test support RCU priority boosting.
3241 rcutorture.test_boost_duration= [KNL]
3242 Duration (s) of each individual boost test.
3244 rcutorture.test_boost_interval= [KNL]
3245 Interval (s) between each boost test.
3247 rcutorture.test_no_idle_hz= [KNL]
3248 Test RCU's dyntick-idle handling. See also the
3249 rcutorture.shuffle_interval parameter.
3251 rcutorture.torture_runnable= [BOOT]
3252 Start rcutorture running at boot time.
3254 rcutorture.torture_type= [KNL]
3255 Specify the RCU implementation to test.
3257 rcutorture.verbose= [KNL]
3258 Enable additional printk() statements.
3260 rcupdate.rcu_expedited= [KNL]
3261 Use expedited grace-period primitives, for
3262 example, synchronize_rcu_expedited() instead
3263 of synchronize_rcu(). This reduces latency,
3264 but can increase CPU utilization, degrade
3265 real-time latency, and degrade energy efficiency.
3267 rcupdate.rcu_cpu_stall_suppress= [KNL]
3268 Suppress RCU CPU stall warning messages.
3270 rcupdate.rcu_cpu_stall_timeout= [KNL]
3271 Set timeout for RCU CPU stall warning messages.
3273 rcupdate.rcu_task_stall_timeout= [KNL]
3274 Set timeout in jiffies for RCU task stall warning
3275 messages. Disable with a value less than or equal
3278 rcupdate.rcu_self_test= [KNL]
3279 Run the RCU early boot self tests
3281 rcupdate.rcu_self_test_bh= [KNL]
3282 Run the RCU bh early boot self tests
3284 rcupdate.rcu_self_test_sched= [KNL]
3285 Run the RCU sched early boot self tests
3289 Run specified binary instead of /init from the ramdisk,
3290 used for early userspace startup. See initrd.
3293 Format (x86 or x86_64):
3294 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3296 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3298 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3299 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3300 reboot_force is either force or not specified,
3301 reboot_cpu is s[mp]#### with #### being the processor
3302 to be used for rebooting.
3305 [KNL, SMP] Set scheduler's default relax_domain_level.
3306 See Documentation/cgroups/cpusets.txt.
3308 relative_sleep_states=
3309 [SUSPEND] Use sleep state labeling where the deepest
3310 state available other than hibernation is always "mem".
3311 Format: { "0" | "1" }
3312 0 -- Traditional sleep state labels.
3313 1 -- Relative sleep state labels.
3315 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3317 reservetop= [X86-32]
3319 Reserves a hole at the top of the kernel virtual
3324 Set the amount of memory to reserve for BIOS at
3325 the bottom of the address space.
3327 reset_devices [KNL] Force drivers to reset the underlying device
3328 during initialization.
3331 Specify the partition device for software suspend
3333 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3335 resume_offset= [SWSUSP]
3336 Specify the offset from the beginning of the partition
3337 given by "resume=" at which the swap header is located,
3338 in <PAGE_SIZE> units (needed only for swap files).
3339 See Documentation/power/swsusp-and-swap-files.txt
3341 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3342 read the resume files
3344 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3345 Useful for devices that are detected asynchronously
3346 (e.g. USB and MMC devices).
3348 hibernate= [HIBERNATION]
3349 noresume Don't check if there's a hibernation image
3350 present during boot.
3351 nocompress Don't compress/decompress hibernation images.
3352 no Disable hibernation and resume.
3354 retain_initrd [RAM] Keep initrd memory after extraction
3356 rfkill.default_state=
3357 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3358 etc. communication is blocked by default.
3361 rfkill.master_switch_mode=
3362 0 The "airplane mode" button does nothing.
3363 1 The "airplane mode" button toggles between everything
3364 blocked and the previous configuration.
3365 2 The "airplane mode" button toggles between everything
3366 blocked and everything unblocked.
3368 rhash_entries= [KNL,NET]
3369 Set number of hash buckets for route cache
3371 ro [KNL] Mount root device read-only on boot
3373 root= [KNL] Root filesystem
3374 See name_to_dev_t comment in init/do_mounts.c.
3376 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3377 mount the root filesystem
3379 rootflags= [KNL] Set root filesystem mount option string
3381 rootfstype= [KNL] Set root filesystem type
3383 rootwait [KNL] Wait (indefinitely) for root device to show up.
3384 Useful for devices that are detected asynchronously
3385 (e.g. USB and MMC devices).
3387 rproc_mem=nn[KMG][@address]
3388 [KNL,ARM,CMA] Remoteproc physical memory block.
3389 Memory area to be used by remote processor image,
3392 rw [KNL] Mount root device read-write on boot
3394 S [KNL] Run init in single mode
3396 s390_iommu= [HW,S390]
3397 Set s390 IOTLB flushing mode
3399 With strict flushing every unmap operation will result in
3400 an IOTLB flush. Default is lazy flushing before reuse,
3404 See drivers/net/irda/sa1100_ir.c.
3406 sbni= [NET] Granch SBNI12 leased line adapter
3408 sched_debug [KNL] Enables verbose scheduler debug messages.
3410 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3411 xtime_lock contention on larger systems, and/or RCU lock
3412 contention on all systems with CONFIG_MAXSMP set.
3413 Format: { "0" | "1" }
3414 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3416 Note: increases power consumption, thus should only be
3417 enabled if running jitter sensitive (HPC/RT) workloads.
3419 security= [SECURITY] Choose a security module to enable at boot.
3420 If this boot parameter is not specified, only the first
3421 security module asking for security registration will be
3422 loaded. An invalid security module name will be treated
3423 as if no module has been chosen.
3425 selinux= [SELINUX] Disable or enable SELinux at boot time.
3426 Format: { "0" | "1" }
3427 See security/selinux/Kconfig help text.
3430 Default value is set via kernel config option.
3431 If enabled at boot time, /selinux/disable can be used
3432 later to disable prior to initial policy load.
3434 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3435 Format: { "0" | "1" }
3436 See security/apparmor/Kconfig help text
3439 Default value is set via kernel config option.
3441 serialnumber [BUGS=X86-32]
3444 Maximal number of shapers.
3446 show_msr= [x86] show boot-time MSR settings
3447 Format: { <integer> }
3448 Show boot-time (BIOS-initialized) MSR settings.
3449 The parameter means the number of CPUs to show,
3450 for example 1 means boot CPU only.
3458 Disable merging of slabs with similar size. May be
3459 necessary if there is some reason to distinguish
3460 allocs to different slabs. Debug options disable
3461 merging on their own.
3462 For more information see Documentation/vm/slub.txt.
3464 slab_max_order= [MM, SLAB]
3465 Determines the maximum allowed order for slabs.
3466 A high setting may cause OOMs due to memory
3467 fragmentation. Defaults to 1 for systems with
3468 more than 32MB of RAM, 0 otherwise.
3470 slub_debug[=options[,slabs]] [MM, SLUB]
3471 Enabling slub_debug allows one to determine the
3472 culprit if slab objects become corrupted. Enabling
3473 slub_debug can create guard zones around objects and
3474 may poison objects when not in use. Also tracks the
3475 last alloc / free. For more information see
3476 Documentation/vm/slub.txt.
3478 slub_max_order= [MM, SLUB]
3479 Determines the maximum allowed order for slabs.
3480 A high setting may cause OOMs due to memory
3481 fragmentation. For more information see
3482 Documentation/vm/slub.txt.
3484 slub_min_objects= [MM, SLUB]
3485 The minimum number of objects per slab. SLUB will
3486 increase the slab order up to slub_max_order to
3487 generate a sufficiently large slab able to contain
3488 the number of objects indicated. The higher the number
3489 of objects the smaller the overhead of tracking slabs
3490 and the less frequently locks need to be acquired.
3491 For more information see Documentation/vm/slub.txt.
3493 slub_min_order= [MM, SLUB]
3494 Determines the minimum page order for slabs. Must be
3495 lower than slub_max_order.
3496 For more information see Documentation/vm/slub.txt.
3498 slub_nomerge [MM, SLUB]
3499 Same with slab_nomerge. This is supported for legacy.
3500 See slab_nomerge for more information.
3503 Format: <io1>[,<io2>[,...,<io8>]]
3505 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3506 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3507 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3508 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3509 smsc-ircc2.ircc_irq= [HW] IRQ line
3510 smsc-ircc2.ircc_dma= [HW] DMA channel
3511 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3512 0: Toshiba Satellite 1800 (GP data pin select)
3513 1: Fast pin select (default)
3517 [KNL] Should the soft-lockup detector generate panics.
3520 softlockup_all_cpu_backtrace=
3521 [KNL] Should the soft-lockup detector generate
3522 backtraces on all cpus.
3525 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3526 See Documentation/laptops/sonypi.txt
3528 spia_io_base= [HW,MTD]
3534 Enabled the stack tracer on boot up.
3536 stacktrace_filter=[function-list]
3537 [FTRACE] Limit the functions that the stack tracer
3538 will trace at boot up. function-list is a comma separated
3539 list of functions. This list can be changed at run
3540 time by the stack_trace_filter file in the debugfs
3541 tracing directory. Note, this enables stack tracing
3542 and the stacktrace above is not needed.
3546 Set the STI (builtin display/keyboard on the HP-PARISC
3547 machines) console (graphic card) which should be used
3548 as the initial boot-console.
3549 See also comment in drivers/video/console/sticore.c.
3552 See comment in drivers/video/console/sticore.c.
3555 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3557 sunrpc.min_resvport=
3558 sunrpc.max_resvport=
3560 SunRPC servers often require that client requests
3561 originate from a privileged port (i.e. a port in the
3562 range 0 < portnr < 1024).
3563 An administrator who wishes to reserve some of these
3564 ports for other uses may adjust the range that the
3565 kernel's sunrpc client considers to be privileged
3566 using these two parameters to set the minimum and
3567 maximum port values.
3571 Control how the NFS server code allocates CPUs to
3572 service thread pools. Depending on how many NICs
3573 you have and where their interrupts are bound, this
3574 option will affect which CPUs will do NFS serving.
3575 Note: this parameter cannot be changed while the
3576 NFS server is running.
3578 auto the server chooses an appropriate mode
3579 automatically using heuristics
3580 global a single global pool contains all CPUs
3581 percpu one pool for each CPU
3582 pernode one pool for each NUMA node (equivalent
3583 to global on non-NUMA machines)
3585 sunrpc.tcp_slot_table_entries=
3586 sunrpc.udp_slot_table_entries=
3588 Sets the upper limit on the number of simultaneous
3589 RPC calls that can be sent from the client to a
3590 server. Increasing these values may allow you to
3591 improve throughput, but will also increase the
3592 amount of memory reserved for use by the client.
3594 suspend.pm_test_delay=
3596 Sets the number of seconds to remain in a suspend test
3597 mode before resuming the system (see
3598 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3599 is set. Default value is 5.
3602 [KNL] Enable accounting of swap in memory resource
3603 controller if no parameter or 1 is given or disable
3604 it if 0 is given (See Documentation/cgroups/memory.txt)
3606 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3607 Format: { <int> | force }
3608 <int> -- Number of I/O TLB slabs
3609 force -- force using of bounce buffers even if they
3610 wouldn't be automatically used by the kernel
3614 sysfs.deprecated=0|1 [KNL]
3615 Enable/disable old style sysfs layout for old udev
3616 on older distributions. When this option is enabled
3617 very new udev will not work anymore. When this option
3618 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3619 in older udev will not work anymore.
3620 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3621 the kernel configuration.
3623 sysrq_always_enabled
3625 Ignore sysrq setting - this boot parameter will
3626 neutralize any effect of /proc/sys/kernel/sysrq.
3627 Useful for debugging.
3629 tcpmhash_entries= [KNL,NET]
3630 Set the number of tcp_metrics_hash slots.
3631 Default value is 8192 or 16384 depending on total
3632 ram pages. This is used to specify the TCP metrics
3633 cache size. See Documentation/networking/ip-sysctl.txt
3634 "tcp_no_metrics_save" section for more details.
3638 test_suspend= [SUSPEND][,N]
3639 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3640 standby suspend) or "freeze" (for suspend type freeze)
3641 as the system sleep state during system startup with
3642 the optional capability to repeat N number of times.
3643 The system is woken from this state using a
3644 wakeup-capable RTC alarm.
3646 thash_entries= [KNL,NET]
3647 Set number of hash buckets for TCP connection
3649 thermal.act= [HW,ACPI]
3650 -1: disable all active trip points in all thermal zones
3651 <degrees C>: override all lowest active trip points
3653 thermal.crt= [HW,ACPI]
3654 -1: disable all critical trip points in all thermal zones
3655 <degrees C>: override all critical trip points
3657 thermal.nocrt= [HW,ACPI]
3658 Set to disable actions on ACPI thermal zone
3659 critical and hot trip points.
3661 thermal.off= [HW,ACPI]
3662 1: disable ACPI thermal control
3664 thermal.psv= [HW,ACPI]
3665 -1: disable all passive trip points
3666 <degrees C>: override all passive trip points to this
3669 thermal.tzp= [HW,ACPI]
3670 Specify global default ACPI thermal zone polling rate
3671 <deci-seconds>: poll all this frequency
3672 0: no polling (default)
3675 Force threading of all interrupt handlers except those
3676 marked explicitly IRQF_NO_THREAD.
3679 Enable the Transcendent memory driver if built-in.
3681 tmem.cleancache=0|1 [KNL, XEN]
3682 Default is on (1). Disable the usage of the cleancache
3683 API to send anonymous pages to the hypervisor.
3685 tmem.frontswap=0|1 [KNL, XEN]
3686 Default is on (1). Disable the usage of the frontswap
3687 API to send swap pages to the hypervisor. If disabled
3688 the selfballooning and selfshrinking are force disabled.
3690 tmem.selfballooning=0|1 [KNL, XEN]
3691 Default is on (1). Disable the driving of swap pages
3694 tmem.selfshrinking=0|1 [KNL, XEN]
3695 Default is on (1). Partial swapoff that immediately
3696 transfers pages from Xen hypervisor back to the
3697 kernel based on different criteria.
3701 Specify if the kernel should make use of the cpu
3702 topology information if the hardware supports this.
3703 The scheduler will make use of this information and
3704 e.g. base its process migration decisions on it.
3707 topology_updates= [KNL, PPC, NUMA]
3709 Specify if the kernel should ignore (off)
3710 topology updates sent by the hypervisor to this
3715 tpm_suspend_pcr=[HW,TPM]
3716 Format: integer pcr id
3717 Specify that at suspend time, the tpm driver
3718 should extend the specified pcr with zeros,
3719 as a workaround for some chips which fail to
3720 flush the last written pcr on TPM_SaveState.
3721 This will guarantee that all the other pcrs
3724 trace_buf_size=nn[KMG]
3725 [FTRACE] will set tracing buffer size on each cpu.
3727 trace_event=[event-list]
3728 [FTRACE] Set and start specified trace events in order
3729 to facilitate early boot debugging.
3730 See also Documentation/trace/events.txt
3732 trace_options=[option-list]
3733 [FTRACE] Enable or disable tracer options at boot.
3734 The option-list is a comma delimited list of options
3735 that can be enabled or disabled just as if you were
3736 to echo the option name into
3738 /sys/kernel/debug/tracing/trace_options
3740 For example, to enable stacktrace option (to dump the
3741 stack trace of each event), add to the command line:
3743 trace_options=stacktrace
3745 See also Documentation/trace/ftrace.txt "trace options"
3749 Have the tracepoints sent to printk as well as the
3750 tracing ring buffer. This is useful for early boot up
3751 where the system hangs or reboots and does not give the
3752 option for reading the tracing buffer or performing a
3753 ftrace_dump_on_oops.
3755 To turn off having tracepoints sent to printk,
3756 echo 0 > /proc/sys/kernel/tracepoint_printk
3757 Note, echoing 1 into this file without the
3758 tracepoint_printk kernel cmdline option has no effect.
3762 Having tracepoints sent to printk() and activating high
3763 frequency tracepoints such as irq or sched, can cause
3764 the system to live lock.
3767 [FTRACE] enable this option to disable tracing when a
3768 warning is hit. This turns off "tracing_on". Tracing can
3769 be enabled again by echoing '1' into the "tracing_on"
3770 file located in /sys/kernel/debug/tracing/
3772 This option is useful, as it disables the trace before
3773 the WARNING dump is called, which prevents the trace to
3774 be filled with content caused by the warning output.
3776 This option can also be set at run time via the sysctl
3777 option: kernel/traceoff_on_warning
3779 transparent_hugepage=
3781 Format: [always|madvise|never]
3782 Can be used to control the default behavior of the system
3783 with respect to transparent hugepages.
3784 See Documentation/vm/transhuge.txt for more details.
3786 tsc= Disable clocksource stability checks for TSC.
3788 [x86] reliable: mark tsc clocksource as reliable, this
3789 disables clocksource verification at runtime, as well
3790 as the stability checks done at bootup. Used to enable
3791 high-resolution timer mode on older hardware, and in
3792 virtualized environment.
3793 [x86] noirqtime: Do not use TSC to do irq accounting.
3794 Used to run time disable IRQ_TIME_ACCOUNTING on any
3795 platforms where RDTSC is slow and this accounting
3798 turbografx.map[2|3]= [HW,JOY]
3799 TurboGraFX parallel port interface
3801 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3802 See also Documentation/input/joystick-parport.txt
3804 udbg-immortal [PPC] When debugging early kernel crashes that
3805 happen after console_init() and before a proper
3806 console driver takes over, this boot options might
3807 help "seeing" what's going on.
3809 uhash_entries= [KNL,NET]
3810 Set number of hash buckets for UDP/UDP-Lite connections
3813 [USB] Ignore overcurrent events (default N).
3814 Some badly-designed motherboards generate lots of
3815 bogus events, for ports that aren't wired to
3816 anything. Set this parameter to avoid log spamming.
3817 Note that genuine overcurrent events won't be
3821 [X86] Cause panic on unknown NMI.
3823 usbcore.authorized_default=
3824 [USB] Default USB device authorization:
3825 (default -1 = authorized except for wireless USB,
3826 0 = not authorized, 1 = authorized)
3828 usbcore.autosuspend=
3829 [USB] The autosuspend time delay (in seconds) used
3830 for newly-detected USB devices (default 2). This
3831 is the time required before an idle device will be
3832 autosuspended. Devices for which the delay is set
3833 to a negative value won't be autosuspended at all.
3835 usbcore.usbfs_snoop=
3836 [USB] Set to log all usbfs traffic (default 0 = off).
3838 usbcore.blinkenlights=
3839 [USB] Set to cycle leds on hubs (default 0 = off).
3841 usbcore.old_scheme_first=
3842 [USB] Start with the old device initialization
3843 scheme (default 0 = off).
3845 usbcore.usbfs_memory_mb=
3846 [USB] Memory limit (in MB) for buffers allocated by
3847 usbfs (default = 16, 0 = max = 2047).
3849 usbcore.use_both_schemes=
3850 [USB] Try the other device initialization scheme
3851 if the first one fails (default 1 = enabled).
3853 usbcore.initial_descriptor_timeout=
3854 [USB] Specifies timeout for the initial 64-byte
3855 USB_REQ_GET_DESCRIPTOR request in milliseconds
3856 (default 5000 = 5.0 seconds).
3859 [USBHID] The interval which mice are to be polled at.
3861 usb-storage.delay_use=
3862 [UMS] The delay in seconds before a new device is
3863 scanned for Logical Units (default 1).
3866 [UMS] A list of quirks entries to supplement or
3867 override the built-in unusual_devs list. List
3868 entries are separated by commas. Each entry has
3869 the form VID:PID:Flags where VID and PID are Vendor
3870 and Product ID values (4-digit hex numbers) and
3871 Flags is a set of characters, each corresponding
3872 to a common usb-storage quirk flag as follows:
3873 a = SANE_SENSE (collect more than 18 bytes
3875 b = BAD_SENSE (don't collect more than 18
3876 bytes of sense data);
3877 c = FIX_CAPACITY (decrease the reported
3878 device capacity by one sector);
3879 d = NO_READ_DISC_INFO (don't use
3880 READ_DISC_INFO command);
3881 e = NO_READ_CAPACITY_16 (don't use
3882 READ_CAPACITY_16 command);
3883 f = NO_REPORT_OPCODES (don't use report opcodes
3885 g = MAX_SECTORS_240 (don't transfer more than
3886 240 sectors at a time, uas only);
3887 h = CAPACITY_HEURISTICS (decrease the
3888 reported device capacity by one
3889 sector if the number is odd);
3890 i = IGNORE_DEVICE (don't bind to this
3892 l = NOT_LOCKABLE (don't try to lock and
3893 unlock ejectable media);
3894 m = MAX_SECTORS_64 (don't transfer more
3895 than 64 sectors = 32 KB at a time);
3896 n = INITIAL_READ10 (force a retry of the
3897 initial READ(10) command);
3898 o = CAPACITY_OK (accept the capacity
3899 reported by the device);
3900 p = WRITE_CACHE (the device cache is ON
3902 r = IGNORE_RESIDUE (the device reports
3903 bogus residue values);
3904 s = SINGLE_LUN (the device has only one
3906 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3907 commands, uas only);
3908 u = IGNORE_UAS (don't bind to the uas driver);
3909 w = NO_WP_DETECT (don't test whether the
3910 medium is write-protected).
3911 Example: quirks=0419:aaf5:rl,0421:0433:rc
3913 user_debug= [KNL,ARM]
3915 See arch/arm/Kconfig.debug help text.
3916 1 - undefined instruction events
3918 4 - invalid data aborts
3921 Example: user_debug=31
3924 [X86] Flags controlling user PTE allocations.
3926 nohigh = do not allocate PTE pages in
3927 HIGHMEM regardless of setting
3931 On X86_32, this is an alias for vdso32=. Otherwise:
3933 vdso=1: enable VDSO (the default)
3934 vdso=0: disable VDSO mapping
3936 vdso32= [X86] Control the 32-bit vDSO
3937 vdso32=1: enable 32-bit VDSO
3938 vdso32=0 or vdso32=2: disable 32-bit VDSO
3940 See the help text for CONFIG_COMPAT_VDSO for more
3941 details. If CONFIG_COMPAT_VDSO is set, the default is
3942 vdso32=0; otherwise, the default is vdso32=1.
3944 For compatibility with older kernels, vdso32=2 is an
3947 Try vdso32=0 if you encounter an error that says:
3948 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3951 vector=percpu: enable percpu vector domain
3953 video= [FB] Frame buffer configuration
3954 See Documentation/fb/modedb.txt.
3956 video.brightness_switch_enabled= [0,1]
3957 If set to 1, on receiving an ACPI notify event
3958 generated by hotkey, video driver will adjust brightness
3959 level and then send out the event to user space through
3960 the allocated input device; If set to 0, video driver
3961 will only send out the event without touching backlight
3966 [VMMIO] Memory mapped virtio (platform) device.
3968 <size>@<baseaddr>:<irq>[:<id>]
3970 <size> := size (can use standard suffixes
3972 <baseaddr> := physical base address
3973 <irq> := interrupt number (as passed to
3975 <id> := (optional) platform device id
3977 virtio_mmio.device=1K@0x100b0000:48:7
3979 Can be used multiple times for multiple devices.
3981 vga= [BOOT,X86-32] Select a particular video mode
3982 See Documentation/x86/boot.txt and
3983 Documentation/svga.txt.
3984 Use vga=ask for menu.
3985 This is actually a boot loader parameter; the value is
3986 passed to the kernel using a special protocol.
3988 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3989 size of <nn>. This can be used to increase the
3990 minimum size (128MB on x86). It can also be used to
3991 decrease the size and leave more room for directly
3994 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3997 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4000 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4004 Controls the behavior of vsyscalls (i.e. calls to
4005 fixed addresses of 0xffffffffff600x00 from legacy
4006 code). Most statically-linked binaries and older
4007 versions of glibc use these calls. Because these
4008 functions are at fixed addresses, they make nice
4009 targets for exploits that can control RIP.
4011 emulate [default] Vsyscalls turn into traps and are
4012 emulated reasonably safely.
4014 native Vsyscalls are native syscall instructions.
4015 This is a little bit faster than trapping
4016 and makes a few dynamic recompilers work
4017 better than they would in emulation mode.
4018 It also makes exploits much easier to write.
4020 none Vsyscalls don't work at all. This makes
4021 them quite hard to use for exploits but
4022 might break your system.
4024 vt.color= [VT] Default text color.
4025 Format: 0xYX, X = foreground, Y = background.
4026 Default: 0x07 = light gray on black.
4028 vt.cur_default= [VT] Default cursor shape.
4029 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4030 the parameters of the <Esc>[?A;B;Cc escape sequence;
4031 see VGA-softcursor.txt. Default: 2 = underline.
4033 vt.default_blu= [VT]
4034 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4035 Change the default blue palette of the console.
4036 This is a 16-member array composed of values
4039 vt.default_grn= [VT]
4040 Format: <green0>,<green1>,<green2>,...,<green15>
4041 Change the default green palette of the console.
4042 This is a 16-member array composed of values
4045 vt.default_red= [VT]
4046 Format: <red0>,<red1>,<red2>,...,<red15>
4047 Change the default red palette of the console.
4048 This is a 16-member array composed of values
4054 Set system-wide default UTF-8 mode for all tty's.
4055 Default is 1, i.e. UTF-8 mode is enabled for all
4056 newly opened terminals.
4058 vt.global_cursor_default=
4061 Set system-wide default for whether a cursor
4062 is shown on new VTs. Default is -1,
4063 i.e. cursors will be created by default unless
4064 overridden by individual drivers. 0 will hide
4065 cursors, 1 will display them.
4067 vt.italic= [VT] Default color for italic text; 0-15.
4070 vt.underline= [VT] Default color for underlined text; 0-15.
4073 watchdog timers [HW,WDT] For information on watchdog timers,
4074 see Documentation/watchdog/watchdog-parameters.txt
4075 or other driver-specific files in the
4076 Documentation/watchdog/ directory.
4078 workqueue.disable_numa
4079 By default, all work items queued to unbound
4080 workqueues are affine to the NUMA nodes they're
4081 issued on, which results in better behavior in
4082 general. If NUMA affinity needs to be disabled for
4083 whatever reason, this option can be used. Note
4084 that this also can be controlled per-workqueue for
4085 workqueues visible under /sys/bus/workqueue/.
4087 workqueue.power_efficient
4088 Per-cpu workqueues are generally preferred because
4089 they show better performance thanks to cache
4090 locality; unfortunately, per-cpu workqueues tend to
4091 be more power hungry than unbound workqueues.
4093 Enabling this makes the per-cpu workqueues which
4094 were observed to contribute significantly to power
4095 consumption unbound, leading to measurably lower
4096 power usage at the cost of small performance
4099 The default value of this parameter is determined by
4100 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4102 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4103 default x2apic cluster mode on platforms
4106 x86_intel_mid_timer= [X86-32,APBT]
4107 Choose timer option for x86 Intel MID platform.
4108 Two valid options are apbt timer only and lapic timer
4109 plus one apbt timer for broadcast timer.
4110 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4112 xen_512gb_limit [KNL,X86-64,XEN]
4113 Restricts the kernel running paravirtualized under Xen
4114 to use only up to 512 GB of RAM. The reason to do so is
4115 crash analysis tools and Xen tools for doing domain
4116 save/restore/migration must be enabled to handle larger
4119 xen_emul_unplug= [HW,X86,XEN]
4120 Unplug Xen emulated devices
4121 Format: [unplug0,][unplug1]
4122 ide-disks -- unplug primary master IDE devices
4123 aux-ide-disks -- unplug non-primary-master IDE devices
4124 nics -- unplug network devices
4125 all -- unplug all emulated devices (NICs and IDE disks)
4126 unnecessary -- unplugging emulated devices is
4127 unnecessary even if the host did not respond to
4129 never -- do not unplug even if version check succeeds
4131 xen_nopvspin [X86,XEN]
4132 Disables the ticketlock slowpath using Xen PV
4136 Disables the PV optimizations forcing the HVM guest to
4137 run as generic HVM guest with no PV drivers.
4139 xirc2ps_cs= [NET,PCMCIA]
4141 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4143 ______________________________________________________________________
4147 Add more DRM drivers.
projects / linux-2.6-block.git / blob