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 |
172 force -- enable ACPI if default was off
173 off -- disable ACPI if default was on
174 noirq -- do not use ACPI for IRQ routing
175 strict -- Be less tolerant of platforms that are not
176 strictly ACPI specification compliant.
177 rsdt -- prefer RSDT over (default) XSDT
178 copy_dsdt -- copy DSDT to memory
179 For ARM64, ONLY "acpi=off" or "acpi=force" are available
181 See also Documentation/power/runtime_pm.txt, pci=noacpi
183 acpi_apic_instance= [ACPI, IOAPIC]
185 2: use 2nd APIC table, if available
186 1,0: use 1st APIC table
189 acpi_backlight= [HW,ACPI]
190 acpi_backlight=vendor
192 If set to vendor, prefer vendor specific driver
193 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
194 of the ACPI video.ko driver.
196 acpica_no_return_repair [HW, ACPI]
197 Disable AML predefined validation mechanism
198 This mechanism can repair the evaluation result to make
199 the return objects more ACPI specification compliant.
200 This option is useful for developers to identify the
201 root cause of an AML interpreter issue when the issue
202 has something to do with the repair mechanism.
204 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
205 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
207 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
208 debug output. Bits in debug_layer correspond to a
209 _COMPONENT in an ACPI source file, e.g.,
210 #define _COMPONENT ACPI_PCI_COMPONENT
211 Bits in debug_level correspond to a level in
212 ACPI_DEBUG_PRINT statements, e.g.,
213 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
214 The debug_level mask defaults to "info". See
215 Documentation/acpi/debug.txt for more information about
216 debug layers and levels.
218 Enable processor driver info messages:
219 acpi.debug_layer=0x20000000
220 Enable PCI/PCI interrupt routing info messages:
221 acpi.debug_layer=0x400000
222 Enable AML "Debug" output, i.e., stores to the Debug
223 object while interpreting AML:
224 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
225 Enable all messages related to ACPI hardware:
226 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
228 Some values produce so much output that the system is
229 unusable. The "log_buf_len" parameter may be useful
230 if you need to capture more output.
232 acpi_enforce_resources= [ACPI]
233 { strict | lax | no }
234 Check for resource conflicts between native drivers
235 and ACPI OperationRegions (SystemIO and SystemMemory
236 only). IO ports and memory declared in ACPI might be
237 used by the ACPI subsystem in arbitrary AML code and
238 can interfere with legacy drivers.
239 strict (default): access to resources claimed by ACPI
240 is denied; legacy drivers trying to access reserved
241 resources will fail to bind to device using them.
242 lax: access to resources claimed by ACPI is allowed;
243 legacy drivers trying to access reserved resources
244 will bind successfully but a warning message is logged.
245 no: ACPI OperationRegions are not marked as reserved,
246 no further checks are performed.
248 acpi_force_table_verification [HW,ACPI]
249 Enable table checksum verification during early stage.
250 By default, this is disabled due to x86 early mapping
253 acpi_irq_balance [HW,ACPI]
254 ACPI will balance active IRQs
257 acpi_irq_nobalance [HW,ACPI]
258 ACPI will not move active IRQs (default)
261 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
262 Format: <irq>,<irq>...
264 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
266 Format: <irq>,<irq>...
268 acpi_no_auto_serialize [HW,ACPI]
269 Disable auto-serialization of AML methods
270 AML control methods that contain the opcodes to create
271 named objects will be marked as "Serialized" by the
272 auto-serialization feature.
273 This feature is enabled by default.
274 This option allows to turn off the feature.
276 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
279 acpi_no_static_ssdt [HW,ACPI]
280 Disable installation of static SSDTs at early boot time
281 By default, SSDTs contained in the RSDT/XSDT will be
282 installed automatically and they will appear under
283 /sys/firmware/acpi/tables.
284 This option turns off this feature.
285 Note that specifying this option does not affect
286 dynamic table installation which will install SSDT
287 tables to /sys/firmware/acpi/tables/dynamic.
289 acpi_rsdp= [ACPI,EFI,KEXEC]
290 Pass the RSDP address to the kernel, mostly used
291 on machines running EFI runtime service to boot the
292 second kernel for kdump.
294 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
295 Format: To spoof as Windows 98: ="Microsoft Windows"
297 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
298 of 2 which is mandated by ACPI 6) as the supported ACPI
299 specification revision (when using this switch, it may
300 be necessary to carry out a cold reboot _twice_ in a
301 row to make it take effect on the platform firmware).
303 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
304 acpi_osi="string1" # add string1
305 acpi_osi="!string2" # remove string2
306 acpi_osi=!* # remove all strings
307 acpi_osi=! # disable all built-in OS vendor
309 acpi_osi= # disable all strings
311 'acpi_osi=!' can be used in combination with single or
312 multiple 'acpi_osi="string1"' to support specific OS
313 vendor string(s). Note that such command can only
314 affect the default state of the OS vendor strings, thus
315 it cannot affect the default state of the feature group
316 strings and the current state of the OS vendor strings,
317 specifying it multiple times through kernel command line
318 is meaningless. This command is useful when one do not
319 care about the state of the feature group strings which
320 should be controlled by the OSPM.
322 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
323 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
324 can make '_OSI("Windows 2000")' TRUE.
326 'acpi_osi=' cannot be used in combination with other
327 'acpi_osi=' command lines, the _OSI method will not
328 exist in the ACPI namespace. NOTE that such command can
329 only affect the _OSI support state, thus specifying it
330 multiple times through kernel command line is also
333 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
336 'acpi_osi=!*' can be used in combination with single or
337 multiple 'acpi_osi="string1"' to support specific
338 string(s). Note that such command can affect the
339 current state of both the OS vendor strings and the
340 feature group strings, thus specifying it multiple times
341 through kernel command line is meaningful. But it may
342 still not able to affect the final state of a string if
343 there are quirks related to this string. This command
344 is useful when one want to control the state of the
345 feature group strings to debug BIOS issues related to
348 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
349 '_OSI("Module Device")' FALSE.
350 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
351 '_OSI("Module Device")' TRUE.
352 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
354 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
356 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
357 they all will make '_OSI("Windows 2000")' TRUE.
360 Override the pmtimer bug detection: force the kernel
361 to assume that this machine's pmtimer latches its value
362 and always returns good values.
364 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
365 Format: { level | edge | high | low }
367 acpi_skip_timer_override [HW,ACPI]
368 Recognize and ignore IRQ0/pin2 Interrupt Override.
369 For broken nForce2 BIOS resulting in XT-PIC timer.
371 acpi_sleep= [HW,ACPI] Sleep options
372 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
373 old_ordering, nonvs, sci_force_enable }
374 See Documentation/power/video.txt for information on
376 s3_beep is for debugging; it makes the PC's speaker beep
377 as soon as the kernel's real-mode entry point is called.
378 s4_nohwsig prevents ACPI hardware signature from being
379 used during resume from hibernation.
380 old_ordering causes the ACPI 1.0 ordering of the _PTS
381 control method, with respect to putting devices into
382 low power states, to be enforced (the ACPI 2.0 ordering
383 of _PTS is used by default).
384 nonvs prevents the kernel from saving/restoring the
385 ACPI NVS memory during suspend/hibernation and resume.
386 sci_force_enable causes the kernel to set SCI_EN directly
387 on resume from S1/S3 (which is against the ACPI spec,
388 but some broken systems don't work without it).
390 acpi_use_timer_override [HW,ACPI]
391 Use timer override. For some broken Nvidia NF5 boards
392 that require a timer override, but don't have HPET
394 add_efi_memmap [EFI; X86] Include EFI memory map in
395 kernel's map of available physical RAM.
398 { off | try_unsupported }
399 off: disable AGP support
400 try_unsupported: try to drive unsupported chipsets
401 (may crash computer or cause data corruption)
404 See Documentation/sound/alsa/alsa-parameters.txt
407 Allow the default userspace alignment fault handler
408 behaviour to be specified. Bit 0 enables warnings,
409 bit 1 enables fixups, and bit 2 sends a segfault.
411 align_va_addr= [X86-64]
412 Align virtual addresses by clearing slice [14:12] when
413 allocating a VMA at process creation time. This option
414 gives you up to 3% performance improvement on AMD F15h
415 machines (where it is enabled by default) for a
416 CPU-intensive style benchmark, and it can vary highly in
417 a microbenchmark depending on workload and compiler.
419 32: only for 32-bit processes
420 64: only for 64-bit processes
421 on: enable for both 32- and 64-bit processes
422 off: disable for both 32- and 64-bit processes
424 alloc_snapshot [FTRACE]
425 Allocate the ftrace snapshot buffer on boot up when the
426 main buffer is allocated. This is handy if debugging
427 and you need to use tracing_snapshot() on boot up, and
428 do not want to use tracing_snapshot_alloc() as it needs
429 to be done where GFP_KERNEL allocations are allowed.
431 amd_iommu= [HW,X86-64]
432 Pass parameters to the AMD IOMMU driver in the system.
434 fullflush - enable flushing of IO/TLB entries when
435 they are unmapped. Otherwise they are
436 flushed before they will be reused, which
438 off - do not initialize any AMD IOMMU found in
440 force_isolation - Force device isolation for all
441 devices. The IOMMU driver is not
442 allowed anymore to lift isolation
443 requirements as needed. This option
444 does not override iommu=pt
446 amd_iommu_dump= [HW,X86-64]
447 Enable AMD IOMMU driver option to dump the ACPI table
448 for AMD IOMMU. With this option enabled, AMD IOMMU
449 driver will print ACPI tables for AMD IOMMU during
450 IOMMU initialization.
452 amijoy.map= [HW,JOY] Amiga joystick support
453 Map of devices attached to JOY0DAT and JOY1DAT
455 See also Documentation/input/joystick.txt
457 analog.map= [HW,JOY] Analog joystick and gamepad support
458 Specifies type or capabilities of an analog joystick
459 connected to one of 16 gameports
460 Format: <type1>,<type2>,..<type16>
463 Power management functions (SPARCstation-4/5 + deriv.)
465 Disable APC CPU standby support. SPARCstation-Fox does
466 not play well with APC CPU idle - disable it if you have
467 APC and your system crashes randomly.
469 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
470 Change the output verbosity whilst booting
471 Format: { quiet (default) | verbose | debug }
472 Change the amount of debugging information output
473 when initialising the APIC and IO-APIC components.
476 See Documentation/networking/ipv6.txt.
478 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
479 Limit apic dumping. The parameter defines the maximal
480 number of local apics being dumped. Also it is possible
481 to set it to "all" by meaning -- no limit here.
482 Format: { 1 (default) | 2 | ... | all }.
483 The parameter valid if only apic=debug or
484 apic=verbose is specified.
485 Example: apic=debug show_lapic=all
487 apm= [APM] Advanced Power Management
488 See header of arch/x86/kernel/apm_32.c.
490 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
491 Format: <io>,<irq>,<nodeID>
495 atarimouse= [HW,MOUSE] Atari Mouse
497 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
498 EzKey and similar keyboards
500 atkbd.reset= [HW] Reset keyboard during initialization
502 atkbd.set= [HW] Select keyboard code set
503 Format: <int> (2 = AT (default), 3 = PS/2)
505 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
508 atkbd.softraw= [HW] Choose between synthetic and real raw mode
509 Format: <bool> (0 = real, 1 = synthetic (default))
511 atkbd.softrepeat= [HW]
512 Use software keyboard repeat
514 audit= [KNL] Enable the audit sub-system
515 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
516 0 - kernel audit is disabled and can not be enabled
517 until the next reboot
518 unset - kernel audit is initialized but disabled and
519 will be fully enabled by the userspace auditd.
520 1 - kernel audit is initialized and partially enabled,
521 storing at most audit_backlog_limit messages in
522 RAM until it is fully enabled by the userspace
526 audit_backlog_limit= [KNL] Set the audit queue size limit.
527 Format: <int> (must be >=0)
530 baycom_epp= [HW,AX25]
533 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
535 See header of drivers/net/hamradio/baycom_par.c.
537 baycom_ser_fdx= [HW,AX25]
538 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
539 Format: <io>,<irq>,<mode>[,<baud>]
540 See header of drivers/net/hamradio/baycom_ser_fdx.c.
542 baycom_ser_hdx= [HW,AX25]
543 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
544 Format: <io>,<irq>,<mode>
545 See header of drivers/net/hamradio/baycom_ser_hdx.c.
547 blkdevparts= Manual partition parsing of block device(s) for
548 embedded devices based on command line input.
549 See Documentation/block/cmdline-partition.txt
551 boot_delay= Milliseconds to delay each printk during boot.
552 Values larger than 10 seconds (10000) are changed to
556 bootmem_debug [KNL] Enable bootmem allocator debug messages.
558 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
559 bttv.radio= Most important insmod options are available as
561 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
564 bulk_remove=off [PPC] This parameter disables the use of the pSeries
565 firmware feature for flushing multiple hpte entries
568 c101= [NET] Moxa C101 synchronous serial card
570 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
571 Sometimes CPU hardware bugs make them report the cache
572 size incorrectly. The kernel will attempt work arounds
573 to fix known problems, but for some CPUs it is not
574 possible to determine what the correct size should be.
575 This option provides an override for these situations.
577 ca_keys= [KEYS] This parameter identifies a specific key(s) on
578 the system trusted keyring to be used for certificate
580 format: { id:<keyid> | builtin }
582 cca= [MIPS] Override the kernel pages' cache coherency
583 algorithm. Accepted values range from 0 to 7
584 inclusive. See arch/mips/include/asm/pgtable-bits.h
585 for platform specific values (SB1, Loongson3 and
588 ccw_timeout_log [S390]
589 See Documentation/s390/CommonIO for details.
591 cgroup_disable= [KNL] Disable a particular controller
592 Format: {name of the controller(s) to disable}
593 The effects of cgroup_disable=foo are:
594 - foo isn't auto-mounted if you mount all cgroups in
596 - foo isn't visible as an individually mountable
598 {Currently only "memory" controller deal with this and
599 cut the overhead, others just disable the usage. So
600 only cgroup_disable=memory is actually worthy}
602 checkreqprot [SELINUX] Set initial checkreqprot flag value.
603 Format: { "0" | "1" }
604 See security/selinux/Kconfig help text.
605 0 -- check protection applied by kernel (includes
606 any implied execute protection).
607 1 -- check protection requested by application.
608 Default value is set via a kernel config option.
609 Value can be changed at runtime via
610 /selinux/checkreqprot.
613 See Documentation/s390/CommonIO for details.
616 Prevents the clock framework from automatically gating
617 clocks that have not been explicitly enabled by a Linux
618 device driver but are enabled in hardware at reset or
619 by the bootloader/firmware. Note that this does not
620 force such clocks to be always-on nor does it reserve
621 those clocks in any way. This parameter is useful for
622 debug and development, but should not be needed on a
623 platform with proper driver support. For more
624 information, see Documentation/clk.txt.
626 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
628 Forces specified clocksource (if available) to be used
629 when calculating gettimeofday(). If specified
630 clocksource is not available, it defaults to PIT.
631 Format: { pit | tsc | cyclone | pmtmr }
633 clocksource= Override the default clocksource
635 Override the default clocksource and use the clocksource
636 with the name specified.
637 Some clocksource names to choose from, depending on
639 [all] jiffies (this is the base, fallback clocksource)
641 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
642 pxa_timer,timer3,32k_counter,timer0_1
644 [X86-32] pit,hpet,tsc;
645 scx200_hrt on Geode; cyclone on IBM x440
653 clearcpuid=BITNUM [X86]
654 Disable CPUID feature X for the kernel. See
655 arch/x86/include/asm/cpufeature.h for the valid bit
656 numbers. Note the Linux specific bits are not necessarily
657 stable over kernel options, but the vendor specific
659 Also note that user programs calling CPUID directly
660 or using the feature without checking anything
661 will still see it. This just prevents it from
662 being used by the kernel or shown in /proc/cpuinfo.
663 Also note the kernel might malfunction if you disable
666 cma=nn[MG]@[start[MG][-end[MG]]]
668 Sets the size of kernel global memory area for
669 contiguous memory allocations and optionally the
670 placement constraint by the physical address range of
671 memory allocations. A value of 0 disables CMA
672 altogether. For more information, see
673 include/linux/dma-contiguous.h
675 cmo_free_hint= [PPC] Format: { yes | no }
676 Specify whether pages are marked as being inactive
677 when they are freed. This is used in CMO environments
678 to determine OS memory pressure for page stealing by
682 coherent_pool=nn[KMG] [ARM,KNL]
683 Sets the size of memory pool for coherent, atomic dma
684 allocations, by default set to 256K.
686 code_bytes [X86] How many bytes of object code to print
691 com20020= [HW,NET] ARCnet - COM20020 chipset
693 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
695 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
699 ARCnet - COM90xx chipset (memory-mapped buffers)
700 Format: <io>[,<irq>[,<memstart>]]
702 condev= [HW,S390] console device
705 console= [KNL] Output console device and options.
707 tty<n> Use the virtual console device <n>.
711 Use the specified serial port. The options are of
712 the form "bbbbpnf", where "bbbb" is the baud rate,
713 "p" is parity ("n", "o", or "e"), "n" is number of
714 bits, and "f" is flow control ("r" for RTS or
715 omit it). Default is "9600n8".
717 See Documentation/serial-console.txt for more
719 Documentation/networking/netconsole.txt for an
722 uart[8250],io,<addr>[,options]
723 uart[8250],mmio,<addr>[,options]
724 uart[8250],mmio32,<addr>[,options]
725 uart[8250],0x<addr>[,options]
726 Start an early, polled-mode console on the 8250/16550
727 UART at the specified I/O port or MMIO address,
728 switching to the matching ttyS device later.
729 MMIO inter-register address stride is either 8-bit
730 (mmio) or 32-bit (mmio32).
731 If none of [io|mmio|mmio32], <addr> is assumed to be
732 equivalent to 'mmio'. 'options' are specified in the
733 same format described for ttyS above; if unspecified,
734 the h/w is not re-initialized.
736 hvc<n> Use the hypervisor console device <n>. This is for
737 both Xen and PowerPC hypervisors.
739 If the device connected to the port is not a TTY but a braille
740 device, prepend "brl," before the device type, for instance
742 For now, only VisioBraille is supported.
744 consoleblank= [KNL] The console blank (screen saver) timeout in
745 seconds. Defaults to 10*60 = 10mins. A value of 0
746 disables the blank timer.
749 [KNL] Change the default value for
750 /proc/<pid>/coredump_filter.
751 See also Documentation/filesystems/proc.txt.
753 cpuidle.off=1 [CPU_IDLE]
754 disable the cpuidle sub-system
757 [X86] Delay for N microsec between assert and de-assert
758 of APIC INIT to start processors. This delay occurs
759 on every CPU online, such as boot, and resume from suspend.
762 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
764 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
766 crashkernel=size[KMG][@offset[KMG]]
767 [KNL] Using kexec, Linux can switch to a 'crash kernel'
768 upon panic. This parameter reserves the physical
769 memory region [offset, offset + size] for that kernel
770 image. If '@offset' is omitted, then a suitable offset
771 is selected automatically. Check
772 Documentation/kdump/kdump.txt for further details.
774 crashkernel=range1:size1[,range2:size2,...][@offset]
775 [KNL] Same as above, but depends on the memory
776 in the running system. The syntax of range is
777 start-[end] where start and end are both
778 a memory unit (amount[KMG]). See also
779 Documentation/kdump/kdump.txt for an example.
781 crashkernel=size[KMG],high
782 [KNL, x86_64] range could be above 4G. Allow kernel
783 to allocate physical memory region from top, so could
784 be above 4G if system have more than 4G ram installed.
785 Otherwise memory region will be allocated below 4G, if
787 It will be ignored if crashkernel=X is specified.
788 crashkernel=size[KMG],low
789 [KNL, x86_64] range under 4G. When crashkernel=X,high
790 is passed, kernel could allocate physical memory region
791 above 4G, that cause second kernel crash on system
792 that require some amount of low memory, e.g. swiotlb
793 requires at least 64M+32K low memory. Kernel would
794 try to allocate 72M below 4G automatically.
795 This one let user to specify own low range under 4G
796 for second kernel instead.
797 0: to disable low allocation.
798 It will be ignored when crashkernel=X,high is not used
799 or memory reserved is below 4G.
804 cs89x0_media= [HW,NET]
805 Format: { rj45 | aui | bnc }
808 See header of drivers/s390/block/dasd_devmap.c.
810 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
811 (one device per port)
812 Format: <port#>,<type>
813 See also Documentation/input/joystick-parport.txt
815 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
816 time. See Documentation/dynamic-debug-howto.txt for
817 details. Deprecated, see dyndbg.
819 debug [KNL] Enable kernel debugging (events log level).
822 [KNL] verbose self-tests
824 Print debugging info while doing the locking API
826 We default to 0 (no extra messages), setting it to
827 1 will print _a lot_ more information - normally
828 only useful to kernel developers.
830 debug_objects [KNL] Enable object debugging
833 [KNL] Disable object debugging
835 debug_guardpage_minorder=
836 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
837 parameter allows control of the order of pages that will
838 be intentionally kept free (and hence protected) by the
839 buddy allocator. Bigger value increase the probability
840 of catching random memory corruption, but reduce the
841 amount of memory for normal system use. The maximum
842 possible value is MAX_ORDER/2. Setting this parameter
843 to 1 or 2 should be enough to identify most random
844 memory corruption problems caused by bugs in kernel or
845 driver code when a CPU writes to (or reads from) a
846 random memory location. Note that there exists a class
847 of memory corruptions problems caused by buggy H/W or
848 F/W or by drivers badly programing DMA (basically when
849 memory is written at bus level and the CPU MMU is
850 bypassed) which are not detectable by
851 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
852 tracking down these problems.
855 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
856 parameter enables the feature at boot time. In
857 default, it is disabled. We can avoid allocating huge
858 chunk of memory for debug pagealloc if we don't enable
859 it at boot time and the system will work mostly same
860 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
861 on: enable the feature
863 debugpat [X86] Enable PAT debugging
865 decnet.addr= [HW,NET]
866 Format: <area>[,<node>]
867 See also Documentation/networking/decnet.txt.
870 [same as hugepagesz=] The size of the default
871 HugeTLB page size. This is the size represented by
872 the legacy /proc/ hugepages APIs, used for SHM, and
873 default size when mounting hugetlbfs filesystems.
874 Defaults to the default architecture's huge page size
878 Set number of hash buckets for dentry cache.
881 See Documentation/networking/ipv6.txt.
883 disable_cpu_apicid= [X86,APIC,SMP]
885 The number of initial APIC ID for the
886 corresponding CPU to be disabled at boot,
887 mostly used for the kdump 2nd kernel to
888 disable BSP to wake up multiple CPUs without
889 causing system reset or hang due to sending
892 disable_ddw [PPC/PSERIES]
893 Disable Dynamic DMA Window support. Use this if
894 to workaround buggy firmware.
897 See Documentation/networking/ipv6.txt.
899 disable_mtrr_cleanup [X86]
900 The kernel tries to adjust MTRR layout from continuous
901 to discrete, to make X server driver able to add WB
902 entry later. This parameter disables that.
904 disable_mtrr_trim [X86, Intel and AMD only]
905 By default the kernel will trim any uncacheable
906 memory out of your available memory pool based on
907 MTRR settings. This parameter disables that behavior,
908 possibly causing your machine to run very slowly.
910 disable_timer_pin_1 [X86]
911 Disable PIN 1 of APIC timer
912 Can be useful to work around chipset bugs.
914 dis_ucode_ldr [X86] Disable the microcode loader.
916 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
917 this option disables the debugging code at boot.
919 dma_debug_entries=<number>
920 This option allows to tune the number of preallocated
921 entries for DMA-API debugging code. One entry is
922 required per DMA-API allocation. Use this if the
923 DMA-API debugging code disables itself because the
924 architectural default is too low.
926 dma_debug_driver=<driver_name>
927 With this option the DMA-API debugging driver
928 filter feature can be enabled at boot time. Just
929 pass the driver to filter for as the parameter.
930 The filter can be disabled or changed to another
931 driver later using sysfs.
933 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
934 Broken monitors, graphic adapters, KVMs and EDIDless
935 panels may send no or incorrect EDID data sets.
936 This parameter allows to specify an EDID data sets
937 in the /lib/firmware directory that are used instead.
938 Generic built-in EDID data sets are used, if one of
939 edid/1024x768.bin, edid/1280x1024.bin,
940 edid/1680x1050.bin, or edid/1920x1080.bin is given
941 and no file with the same name exists. Details and
942 instructions how to build your own EDID data are
943 available in Documentation/EDID/HOWTO.txt. An EDID
944 data set will only be used for a particular connector,
945 if its name and a colon are prepended to the EDID
946 name. Each connector may use a unique EDID data
947 set by separating the files with a comma. An EDID
948 data set with no connector name will be used for
949 any connectors not explicitly specified.
953 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
954 module.dyndbg[="val"]
955 Enable debug messages at boot time. See
956 Documentation/dynamic-debug-howto.txt for details.
958 nompx [X86] Disables Intel Memory Protection Extensions.
959 See Documentation/x86/intel_mpx.txt for more
960 information about the feature.
963 on enable eager fpu restore
964 off disable eager fpu restore
965 auto selects the default scheme, which automatically
966 enables eagerfpu restore for xsaveopt.
968 module.async_probe [KNL]
969 Enable asynchronous probe on this module.
971 early_ioremap_debug [KNL]
972 Enable debug messages in early_ioremap support. This
973 is useful for tracking down temporary early mappings
974 which are not unmapped.
976 earlycon= [KNL] Output early console device and options.
979 Start an early, polled-mode console on a cadence serial
980 port at the specified address. The cadence serial port
981 must already be setup and configured. Options are not
984 uart[8250],io,<addr>[,options]
985 uart[8250],mmio,<addr>[,options]
986 uart[8250],mmio32,<addr>[,options]
987 uart[8250],mmio32be,<addr>[,options]
988 uart[8250],0x<addr>[,options]
989 Start an early, polled-mode console on the 8250/16550
990 UART at the specified I/O port or MMIO address.
991 MMIO inter-register address stride is either 8-bit
992 (mmio) or 32-bit (mmio32 or mmio32be).
993 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
994 to be equivalent to 'mmio'. 'options' are specified
995 in the same format described for "console=ttyS<n>"; if
996 unspecified, the h/w is not initialized.
999 Start an early, polled-mode console on a pl011 serial
1000 port at the specified address. The pl011 serial port
1001 must already be setup and configured. Options are not
1005 Start an early, polled-mode console on an msm serial
1006 port at the specified address. The serial port
1007 must already be setup and configured. Options are not
1010 msm_serial_dm,<addr>
1011 Start an early, polled-mode console on an msm serial
1012 dm port at the specified address. The serial port
1013 must already be setup and configured. Options are not
1016 smh Use ARM semihosting calls for early console.
1024 Use early console provided by serial driver available
1025 on Samsung SoCs, requires selecting proper type and
1026 a correct base address of the selected UART port. The
1027 serial port must already be setup and configured.
1028 Options are not yet supported.
1030 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1034 earlyprintk=serial[,ttySn[,baudrate]]
1035 earlyprintk=serial[,0x...[,baudrate]]
1036 earlyprintk=ttySn[,baudrate]
1037 earlyprintk=dbgp[debugController#]
1038 earlyprintk=pciserial,bus:device.function[,baudrate]
1040 earlyprintk is useful when the kernel crashes before
1041 the normal console is initialized. It is not enabled by
1042 default because it has some cosmetic problems.
1044 Append ",keep" to not disable it when the real console
1047 Only one of vga, efi, serial, or usb debug port can
1050 Currently only ttyS0 and ttyS1 may be specified by
1051 name. Other I/O ports may be explicitly specified
1052 on some architectures (x86 and arm at least) by
1053 replacing ttySn with an I/O port address, like this:
1054 earlyprintk=serial,0x1008,115200
1055 You can find the port for a given device in
1056 /proc/tty/driver/serial:
1057 2: uart:ST16650V2 port:00001008 irq:18 ...
1059 Interaction with the standard serial driver is not
1062 The VGA and EFI output is eventually overwritten by
1065 The xen output can only be used by Xen PV guests.
1067 edac_report= [HW,EDAC] Control how to report EDAC event
1068 Format: {"on" | "off" | "force"}
1069 on: enable EDAC to report H/W event. May be overridden
1070 by other higher priority error reporting module.
1071 off: disable H/W event reporting through EDAC.
1072 force: enforce the use of EDAC to report H/W event.
1075 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1078 This is designed to be used in conjunction with
1079 the boot argument: earlyprintk=vga
1082 Format: {"off" | "on" | "skip[mbr]"}
1085 Format: { "old_map", "nochunk", "noruntime", "debug" }
1086 old_map [X86-64]: switch to the old ioremap-based EFI
1087 runtime services mapping. 32-bit still uses this one by
1089 nochunk: disable reading files in "chunks" in the EFI
1090 boot stub, as chunking can cause problems with some
1091 firmware implementations.
1092 noruntime : disable EFI runtime services support
1093 debug: enable misc debug output
1095 efi_no_storage_paranoia [EFI; X86]
1096 Using this parameter you can use more than 50% of
1097 your efi variable storage. Use this parameter only if
1098 you are really sure that your UEFI does sane gc and
1099 fulfills the spec otherwise your board may brick.
1101 eisa_irq_edge= [PARISC,HW]
1102 See header of drivers/parisc/eisa.c.
1105 See comment before function elanfreq_setup() in
1106 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1109 Format: {"cfq" | "deadline" | "noop"}
1110 See Documentation/block/cfq-iosched.txt and
1111 Documentation/block/deadline-iosched.txt for details.
1113 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1114 Specifies physical address of start of kernel core
1115 image elf header and optionally the size. Generally
1116 kexec loader will pass this option to capture kernel.
1117 See Documentation/kdump/kdump.txt for details.
1119 enable_mtrr_cleanup [X86]
1120 The kernel tries to adjust MTRR layout from continuous
1121 to discrete, to make X server driver able to add WB
1122 entry later. This parameter enables that.
1124 enable_timer_pin_1 [X86]
1125 Enable PIN 1 of APIC timer
1126 Can be useful to work around chipset bugs
1127 (in particular on some ATI chipsets).
1128 The kernel tries to set a reasonable default.
1130 enforcing [SELINUX] Set initial enforcing status.
1132 See security/selinux/Kconfig help text.
1133 0 -- permissive (log only, no denials).
1134 1 -- enforcing (deny and log).
1136 Value can be changed at runtime via /selinux/enforce.
1139 Disable Error Record Serialization Table (ERST)
1142 ether= [HW,NET] Ethernet cards parameters
1143 This option is obsoleted by the "netdev=" option, which
1144 has equivalent usage. See its documentation for details.
1148 Permit 'security.evm' to be updated regardless of
1149 current integrity status.
1153 fail_make_request=[KNL]
1154 General fault injection mechanism.
1155 Format: <interval>,<probability>,<space>,<times>
1156 See also Documentation/fault-injection/.
1159 See Documentation/blockdev/floppy.txt.
1161 force_pal_cache_flush
1162 [IA-64] Avoid check_sal_cache_flush which may hang on
1163 buggy SAL_CACHE_FLUSH implementations. Using this
1164 parameter will force ia64_sal_cache_flush to call
1165 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1168 Forcefully enable Physical Address Extension (PAE).
1169 Many Pentium M systems disable PAE but may have a
1170 functionally usable PAE implementation.
1171 Warning: use of this parameter will taint the kernel
1172 and may cause unknown problems.
1175 [FTRACE] will set and start the specified tracer
1176 as early as possible in order to facilitate early
1179 ftrace_dump_on_oops[=orig_cpu]
1180 [FTRACE] will dump the trace buffers on oops.
1181 If no parameter is passed, ftrace will dump
1182 buffers of all CPUs, but if you pass orig_cpu, it will
1183 dump only the buffer of the CPU that triggered the
1186 ftrace_filter=[function-list]
1187 [FTRACE] Limit the functions traced by the function
1188 tracer at boot up. function-list is a comma separated
1189 list of functions. This list can be changed at run
1190 time by the set_ftrace_filter file in the debugfs
1193 ftrace_notrace=[function-list]
1194 [FTRACE] Do not trace the functions specified in
1195 function-list. This list can be changed at run time
1196 by the set_ftrace_notrace file in the debugfs
1199 ftrace_graph_filter=[function-list]
1200 [FTRACE] Limit the top level callers functions traced
1201 by the function graph tracer at boot up.
1202 function-list is a comma separated list of functions
1203 that can be changed at run time by the
1204 set_graph_function file in the debugfs tracing directory.
1206 ftrace_graph_notrace=[function-list]
1207 [FTRACE] Do not trace from the functions specified in
1208 function-list. This list is a comma separated list of
1209 functions that can be changed at run time by the
1210 set_graph_notrace file in the debugfs tracing directory.
1213 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1214 support via parallel port (up to 5 devices per port)
1215 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1216 See also Documentation/input/joystick-parport.txt
1220 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1224 gcov_persist= [GCOV] When non-zero (default), profiling data for
1225 kernel modules is saved and remains accessible via
1226 debugfs, even when the module is unloaded/reloaded.
1227 When zero, profiling data is discarded and associated
1228 debugfs files are removed at module unload time.
1230 gpt [EFI] Forces disk with valid GPT signature but
1231 invalid Protective MBR to be treated as GPT. If the
1232 primary GPT is corrupted, it enables the backup/alternate
1233 GPT to be used instead.
1235 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1236 the "Enable 0" bit of the configuration register.
1239 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1240 the "Enable 0" bit of the configuration register.
1243 grcan.select= [HW] Select which physical interface to use.
1246 grcan.txsize= [HW] Sets the size of the tx buffer.
1247 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1249 grcan.rxsize= [HW] Sets the size of the rx buffer.
1250 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1253 hashdist= [KNL,NUMA] Large hashes allocated during boot
1254 are distributed across NUMA nodes. Defaults on
1255 for 64-bit NUMA, off otherwise.
1256 Format: 0 | 1 (for off | on)
1258 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1260 hd= [EIDE] (E)IDE hard drive subsystem geometry
1261 Format: <cyl>,<head>,<sect>
1264 Disable Hardware Error Source Table (HEST) support;
1265 corresponding firmware-first mode error processing
1266 logic will be disabled.
1268 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1269 size of <nn>. This works even on boxes that have no
1270 highmem otherwise. This also works to reduce highmem
1271 size on bigger boxes.
1273 highres= [KNL] Enable/disable high resolution timer mode.
1274 Valid parameters: "on", "off"
1278 See Documentation/isdn/README.HiSax.
1282 hpet= [X86-32,HPET] option to control HPET usage
1283 Format: { enable (default) | disable | force |
1285 disable: disable HPET and use PIT instead
1286 force: allow force enabled of undocumented chips (ICH4,
1288 verbose: show contents of HPET registers during setup
1290 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1291 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1293 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1294 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1295 On x86-64 and powerpc, this option can be specified
1296 multiple times interleaved with hugepages= to reserve
1297 huge pages of different sizes. Valid pages sizes on
1298 x86-64 are 2M (when the CPU supports "pse") and 1G
1299 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1301 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1302 terminal devices. Valid values: 0..8
1303 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1304 If specified, z/VM IUCV HVC accepts connections
1305 from listed z/VM user IDs only.
1307 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1308 hardware thread id mappings.
1309 Format: <cpu>:<hwthread>
1312 Do not unregister boot console at start. This is only
1313 useful for debugging when something happens in the window
1314 between unregistering the boot console and initializing
1317 i2c_bus= [HW] Override the default board specific I2C bus speed
1318 or register an additional I2C bus that is not
1319 registered from board initialization code.
1323 i8042.debug [HW] Toggle i8042 debug mode
1324 i8042.unmask_kbd_data
1325 [HW] Enable printing of interrupt data from the KBD port
1326 (disabled by default, and as a pre-condition
1327 requires that i8042.debug=1 be enabled)
1328 i8042.direct [HW] Put keyboard port into non-translated mode
1329 i8042.dumbkbd [HW] Pretend that controller can only read data from
1330 keyboard and cannot control its state
1331 (Don't attempt to blink the leds)
1332 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1333 i8042.nokbd [HW] Don't check/create keyboard port
1334 i8042.noloop [HW] Disable the AUX Loopback command while probing
1336 i8042.nomux [HW] Don't check presence of an active multiplexing
1338 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1340 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1341 i8042.reset [HW] Reset the controller during init and cleanup
1342 i8042.unlock [HW] Unlock (ignore) the keylock
1343 i8042.kbdreset [HW] Reset device connected to KBD port
1347 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1348 indicates that the driver is running on unsupported
1350 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1351 does not match list of supported models.
1353 [HW] Report power status in /proc/i8k
1354 (disabled by default)
1355 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1358 i915.invert_brightness=
1359 [DRM] Invert the sense of the variable that is used to
1360 set the brightness of the panel backlight. Normally a
1361 brightness value of 0 indicates backlight switched off,
1362 and the maximum of the brightness value sets the backlight
1363 to maximum brightness. If this parameter is set to 0
1364 (default) and the machine requires it, or this parameter
1365 is set to 1, a brightness value of 0 sets the backlight
1366 to maximum brightness, and the maximum of the brightness
1367 value switches the backlight off.
1368 -1 -- never invert brightness
1369 0 -- machine default
1370 1 -- force brightness inversion
1373 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1375 ide-core.nodma= [HW] (E)IDE subsystem
1376 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1377 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1378 .cdrom .chs .ignore_cable are additional options
1379 See Documentation/ide/ide.txt.
1381 ide-generic.probe-mask= [HW] (E)IDE subsystem
1383 Probe mask for legacy ISA IDE ports. Depending on
1384 platform up to 6 ports are supported, enabled by
1385 setting corresponding bits in the mask to 1. The
1386 default value is 0x0, which has a special meaning.
1387 On systems that have PCI, it triggers scanning the
1388 PCI bus for the first and the second port, which
1389 are then probed. On systems without PCI the value
1390 of 0x0 enables probing the two first ports as if it
1393 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1394 Claim all unknown PCI IDE storage controllers.
1397 Format: idle=poll, idle=halt, idle=nomwait
1398 Poll forces a polling idle loop that can slightly
1399 improve the performance of waking up a idle CPU, but
1400 will use a lot of power and make the system run hot.
1402 idle=halt: Halt is forced to be used for CPU idle.
1403 In such case C2/C3 won't be used again.
1404 idle=nomwait: Disable mwait for CPU C-states
1406 ignore_loglevel [KNL]
1407 Ignore loglevel setting - this will print /all/
1408 kernel messages to the console. Useful for debugging.
1409 We also add it as printk module parameter, so users
1410 could change it dynamically, usually by
1411 /sys/module/printk/parameters/ignore_loglevel.
1413 ihash_entries= [KNL]
1414 Set number of hash buckets for inode cache.
1416 ima_appraise= [IMA] appraise integrity measurements
1417 Format: { "off" | "enforce" | "fix" | "log" }
1420 ima_appraise_tcb [IMA]
1421 The builtin appraise policy appraises all files
1425 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1429 The list of supported hash algorithms is defined
1430 in crypto/hash_info.h.
1433 The builtin measurement policy to load during IMA
1434 setup. Specyfing "tcb" as the value, measures all
1435 programs exec'd, files mmap'd for exec, and all files
1436 opened with the read mode bit set by either the
1437 effective uid (euid=0) or uid=0.
1440 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1441 Load a policy which meets the needs of the Trusted
1442 Computing Base. This means IMA will measure all
1443 programs exec'd, files mmap'd for exec, and all files
1444 opened for read by uid=0.
1447 Select one of defined IMA measurements template formats.
1448 Formats: { "ima" | "ima-ng" | "ima-sig" }
1452 [IMA] Define a custom template format.
1453 Format: { "field1|...|fieldN" }
1455 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1456 Format: <min_file_size>
1457 Set the minimal file size for using asynchronous hash.
1458 If left unspecified, ahash usage is disabled.
1460 ahash performance varies for different data sizes on
1461 different crypto accelerators. This option can be used
1462 to achieve the best performance for a particular HW.
1464 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1466 Set hashing buffer size. Default: 4k.
1468 ahash performance varies for different chunk sizes on
1469 different crypto accelerators. This option can be used
1470 to achieve best performance for particular HW.
1474 Run specified binary instead of /sbin/init as init
1477 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1478 for working out where the kernel is dying during
1481 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1482 initcall functions. Useful for debugging built-in
1483 modules and initcalls.
1485 initrd= [BOOT] Specify the location of the initial ramdisk
1487 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1490 int_pln_enable [x86] Enable power limit notification interrupt
1492 integrity_audit=[IMA]
1493 Format: { "0" | "1" }
1494 0 -- basic integrity auditing messages. (Default)
1495 1 -- additional integrity auditing messages.
1497 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1499 Enable intel iommu driver.
1501 Disable intel iommu driver.
1502 igfx_off [Default Off]
1503 By default, gfx is mapped as normal device. If a gfx
1504 device has a dedicated DMAR unit, the DMAR unit is
1505 bypassed by not enabling DMAR with this option. In
1506 this case, gfx device will use physical address for
1509 With this option iommu will not optimize to look
1510 for io virtual address below 32-bit forcing dual
1511 address cycle on pci bus for cards supporting greater
1512 than 32-bit addressing. The default is to look
1513 for translation below 32-bit and if not available
1514 then look in the higher range.
1515 strict [Default Off]
1516 With this option on every unmap_single operation will
1517 result in a hardware IOTLB flush operation as opposed
1518 to batching them for performance.
1519 sp_off [Default Off]
1520 By default, super page will be supported if Intel IOMMU
1521 has the capability. With this option, super page will
1523 ecs_off [Default Off]
1524 By default, extended context tables will be supported if
1525 the hardware advertises that it has support both for the
1526 extended tables themselves, and also PASID support. With
1527 this option set, extended tables will not be used even
1528 on hardware which claims to support them.
1530 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1531 0 disables intel_idle and fall back on acpi_idle.
1532 1 to 6 specify maximum depth of C-state.
1536 Do not enable intel_pstate as the default
1537 scaling driver for the supported processors
1539 Enable intel_pstate on systems that prohibit it by default
1540 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1541 instead of acpi-cpufreq may disable platform features, such
1542 as thermal controls and power capping, that rely on ACPI
1543 P-States information being indicated to OSPM and therefore
1544 should be used with caution. This option does not work with
1545 processors that aren't supported by the intel_pstate driver
1546 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1548 Do not enable hardware P state control (HWP)
1551 Only load intel_pstate on systems which support
1552 hardware P state control (HWP) if available.
1554 Don't use ACPI processor performance control objects
1555 _PSS and _PPC specified limits.
1557 intremap= [X86-64, Intel-IOMMU]
1558 on enable Interrupt Remapping (default)
1559 off disable Interrupt Remapping
1560 nosid disable Source ID checking
1562 BIOS x2APIC opt-out request will be ignored
1564 iomem= Disable strict checking of access to MMIO memory
1565 strict regions from userspace.
1580 nobypass [PPC/POWERNV]
1581 Disable IOMMU bypass, using IOMMU for PCI devices.
1584 io7= [HW] IO7 for Marvel based alpha systems
1585 See comment before marvel_specify_io7 in
1586 arch/alpha/kernel/core_marvel.c.
1588 io_delay= [X86] I/O delay method
1590 Standard port 0x80 based delay
1592 Alternate port 0xed based delay (needed on some systems)
1594 Simple two microseconds delay
1599 See Documentation/filesystems/nfs/nfsroot.txt.
1602 When an interrupt is not handled search all handlers
1603 for it. Intended to get systems with badly broken
1607 When an interrupt is not handled search all handlers
1608 for it. Also check all handlers each timer
1609 interrupt. Intended to get systems with badly broken
1613 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1615 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1617 <cpu number>,...,<cpu number>
1619 <cpu number>-<cpu number>
1620 (must be a positive range in ascending order)
1622 <cpu number>,...,<cpu number>-<cpu number>
1624 This option can be used to specify one or more CPUs
1625 to isolate from the general SMP balancing and scheduling
1626 algorithms. You can move a process onto or off an
1627 "isolated" CPU via the CPU affinity syscalls or cpuset.
1628 <cpu number> begins at 0 and the maximum value is
1629 "number of CPUs in system - 1".
1631 This option is the preferred way to isolate CPUs. The
1632 alternative -- manually setting the CPU mask of all
1633 tasks in the system -- can cause problems and
1634 suboptimal load balancer performance.
1638 ivrs_ioapic [HW,X86_64]
1639 Provide an override to the IOAPIC-ID<->DEVICE-ID
1640 mapping provided in the IVRS ACPI table. For
1641 example, to map IOAPIC-ID decimal 10 to
1642 PCI device 00:14.0 write the parameter as:
1643 ivrs_ioapic[10]=00:14.0
1645 ivrs_hpet [HW,X86_64]
1646 Provide an override to the HPET-ID<->DEVICE-ID
1647 mapping provided in the IVRS ACPI table. For
1648 example, to map HPET-ID decimal 0 to
1649 PCI device 00:14.0 write the parameter as:
1650 ivrs_hpet[0]=00:14.0
1652 js= [HW,JOY] Analog joystick
1653 See Documentation/input/joystick.txt.
1656 Enable/disable kernel and module base offset ASLR
1657 (Address Space Layout Randomization) if built into
1658 the kernel. When CONFIG_HIBERNATION is selected,
1659 kASLR is disabled by default. When kASLR is enabled,
1660 hibernation will be disabled.
1664 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1665 specifies the amount of memory usable by the kernel
1666 for non-movable allocations. The requested amount is
1667 spread evenly throughout all nodes in the system. The
1668 remaining memory in each node is used for Movable
1669 pages. In the event, a node is too small to have both
1670 kernelcore and Movable pages, kernelcore pages will
1671 take priority and other nodes will have a larger number
1672 of Movable pages. The Movable zone is used for the
1673 allocation of pages that may be reclaimed or moved
1674 by the page migration subsystem. This means that
1675 HugeTLB pages may not be allocated from this zone.
1676 Note that allocations like PTEs-from-HighMem still
1677 use the HighMem zone if it exists, and the Normal
1678 zone if it does not.
1680 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1681 Format: <Controller#>[,poll interval]
1682 The controller # is the number of the ehci usb debug
1683 port as it is probed via PCI. The poll interval is
1684 optional and is the number seconds in between
1685 each poll cycle to the debug port in case you need
1686 the functionality for interrupting the kernel with
1687 gdb or control-c on the dbgp connection. When
1688 not using this parameter you use sysrq-g to break into
1689 the kernel debugger.
1691 kgdboc= [KGDB,HW] kgdb over consoles.
1692 Requires a tty driver that supports console polling,
1693 or a supported polling keyboard driver (non-usb).
1694 Serial only format: <serial_device>[,baud]
1695 keyboard only format: kbd
1696 keyboard and serial format: kbd,<serial_device>[,baud]
1697 Optional Kernel mode setting:
1698 kms, kbd format: kms,kbd
1699 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1701 kgdbwait [KGDB] Stop kernel execution and enter the
1702 kernel debugger at the earliest opportunity.
1704 kmac= [MIPS] korina ethernet MAC address.
1705 Configure the RouterBoard 532 series on-chip
1706 Ethernet adapter MAC address.
1708 kmemleak= [KNL] Boot-time kmemleak enable/disable
1709 Valid arguments: on, off
1711 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1714 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1715 Valid arguments: 0, 1, 2
1716 kmemcheck=0 (disabled)
1717 kmemcheck=1 (enabled)
1718 kmemcheck=2 (one-shot mode)
1719 Default: 2 (one-shot mode)
1721 kstack=N [X86] Print N words from the kernel stack
1724 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1725 Default is 0 (don't ignore, but inject #GP)
1727 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1731 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1732 Default is 1 (enabled)
1734 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1736 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1738 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1739 (virtualized MMU) support on capable Intel chips.
1740 Default is 1 (enabled)
1742 kvm-intel.emulate_invalid_guest_state=
1743 [KVM,Intel] Enable emulation of invalid guest states
1744 Default is 0 (disabled)
1746 kvm-intel.flexpriority=
1747 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1748 Default is 1 (enabled)
1751 [KVM,Intel] Enable VMX nesting (nVMX).
1752 Default is 0 (disabled)
1754 kvm-intel.unrestricted_guest=
1755 [KVM,Intel] Disable unrestricted guest feature
1756 (virtualized real and unpaged mode) on capable
1757 Intel chips. Default is 1 (enabled)
1759 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1760 feature (tagged TLBs) on capable Intel chips.
1761 Default is 1 (enabled)
1767 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1770 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1771 value for LAPIC timer one-shot implementation. Default
1772 back to the programmable timer unit in the LAPIC.
1774 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1777 libata.dma= [LIBATA] DMA control
1778 libata.dma=0 Disable all PATA and SATA DMA
1779 libata.dma=1 PATA and SATA Disk DMA only
1780 libata.dma=2 ATAPI (CDROM) DMA only
1781 libata.dma=4 Compact Flash DMA only
1782 Combinations also work, so libata.dma=3 enables DMA
1783 for disks and CDROMs, but not CFs.
1785 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1786 libata.ignore_hpa=0 keep BIOS limits (default)
1787 libata.ignore_hpa=1 ignore limits, using full disk
1789 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1793 libata.force= [LIBATA] Force configurations. The format is comma
1794 separated list of "[ID:]VAL" where ID is
1795 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1796 matching port, link or device. Basically, it matches
1797 the ATA ID string printed on console by libata. If
1798 the whole ID part is omitted, the last PORT and DEVICE
1799 values are used. If ID hasn't been specified yet, the
1800 configuration applies to all ports, links and devices.
1802 If only DEVICE is omitted, the parameter applies to
1803 the port and all links and devices behind it. DEVICE
1804 number of 0 either selects the first device or the
1805 first fan-out link behind PMP device. It does not
1806 select the host link. DEVICE number of 15 selects the
1807 host link and device attached to it.
1809 The VAL specifies the configuration to force. As long
1810 as there's no ambiguity shortcut notation is allowed.
1811 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1812 The following configurations can be forced.
1814 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1815 Any ID with matching PORT is used.
1817 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1819 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1820 udma[/][16,25,33,44,66,100,133] notation is also
1823 * [no]ncq: Turn on or off NCQ.
1825 * [no]ncqtrim: Turn off queued DSM TRIM.
1827 * nohrst, nosrst, norst: suppress hard, soft
1830 * rstonce: only attempt one reset during
1831 hot-unplug link recovery
1833 * dump_id: dump IDENTIFY data.
1835 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1837 * disable: Disable this device.
1839 If there are multiple matching configurations changing
1840 the same attribute, the last one is used.
1842 memblock=debug [KNL] Enable memblock debug messages.
1844 load_ramdisk= [RAM] List of ramdisks to load from floppy
1845 See Documentation/blockdev/ramdisk.txt.
1847 lockd.nlm_grace_period=P [NFS] Assign grace period.
1850 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1853 lockd.nlm_timeout=T [NFS] Assign timeout value.
1856 lockd.nlm_udpport=M [NFS] Assign UDP port.
1859 locktorture.nreaders_stress= [KNL]
1860 Set the number of locking read-acquisition kthreads.
1861 Defaults to being automatically set based on the
1862 number of online CPUs.
1864 locktorture.nwriters_stress= [KNL]
1865 Set the number of locking write-acquisition kthreads.
1867 locktorture.onoff_holdoff= [KNL]
1868 Set time (s) after boot for CPU-hotplug testing.
1870 locktorture.onoff_interval= [KNL]
1871 Set time (s) between CPU-hotplug operations, or
1872 zero to disable CPU-hotplug testing.
1874 locktorture.shuffle_interval= [KNL]
1875 Set task-shuffle interval (jiffies). Shuffling
1876 tasks allows some CPUs to go into dyntick-idle
1877 mode during the locktorture test.
1879 locktorture.shutdown_secs= [KNL]
1880 Set time (s) after boot system shutdown. This
1881 is useful for hands-off automated testing.
1883 locktorture.stat_interval= [KNL]
1884 Time (s) between statistics printk()s.
1886 locktorture.stutter= [KNL]
1887 Time (s) to stutter testing, for example,
1888 specifying five seconds causes the test to run for
1889 five seconds, wait for five seconds, and so on.
1890 This tests the locking primitive's ability to
1891 transition abruptly to and from idle.
1893 locktorture.torture_runnable= [BOOT]
1894 Start locktorture running at boot time.
1896 locktorture.torture_type= [KNL]
1897 Specify the locking implementation to test.
1899 locktorture.verbose= [KNL]
1900 Enable additional printk() statements.
1902 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1905 loglevel= All Kernel Messages with a loglevel smaller than the
1906 console loglevel will be printed to the console. It can
1907 also be changed with klogd or other programs. The
1908 loglevels are defined as follows:
1910 0 (KERN_EMERG) system is unusable
1911 1 (KERN_ALERT) action must be taken immediately
1912 2 (KERN_CRIT) critical conditions
1913 3 (KERN_ERR) error conditions
1914 4 (KERN_WARNING) warning conditions
1915 5 (KERN_NOTICE) normal but significant condition
1916 6 (KERN_INFO) informational
1917 7 (KERN_DEBUG) debug-level messages
1919 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1920 in bytes. n must be a power of two and greater
1921 than the minimal size. The minimal size is defined
1922 by LOG_BUF_SHIFT kernel config parameter. There is
1923 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1924 that allows to increase the default size depending on
1925 the number of CPUs. See init/Kconfig for more details.
1927 logo.nologo [FB] Disables display of the built-in Linux logo.
1928 This may be used to provide more screen space for
1929 kernel log messages and is useful when debugging
1930 kernel boot problems.
1932 lp=0 [LP] Specify parallel ports to use, e.g,
1933 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1934 lp=reset first parallel port). 'lp=0' disables the
1935 lp=auto printer driver. 'lp=reset' (which can be
1936 specified in addition to the ports) causes
1937 attached printers to be reset. Using
1938 lp=port1,port2,... specifies the parallel ports
1939 to associate lp devices with, starting with
1940 lp0. A port specification may be 'none' to skip
1941 that lp device, or a parport name such as
1942 'parport0'. Specifying 'lp=auto' instead of a
1943 port specification list means that device IDs
1944 from each port should be examined, to see if
1945 an IEEE 1284-compliant printer is attached; if
1946 so, the driver will manage that printer.
1947 See also header of drivers/char/lp.c.
1950 Sets loops_per_jiffy to given constant, thus avoiding
1951 time-consuming boot-time autodetection (up to 250 ms per
1952 CPU). 0 enables autodetection (default). To determine
1953 the correct value for your kernel, boot with normal
1954 autodetection and see what value is printed. Note that
1955 on SMP systems the preset will be applied to all CPUs,
1956 which is likely to cause problems if your CPUs need
1957 significantly divergent settings. An incorrect value
1958 will cause delays in the kernel to be wrong, leading to
1959 unpredictable I/O errors and other breakage. Although
1960 unlikely, in the extreme case this might damage your
1964 Format: <io>,<irq>,<dma>
1966 machvec= [IA-64] Force the use of a particular machine-vector
1967 (machvec) in a generic kernel.
1968 Example: machvec=hpzx1_swiotlb
1970 machtype= [Loongson] Share the same kernel image file between different
1972 Example: machtype=lemote-yeeloong-2f-7inch
1974 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1975 than or equal to this physical address is ignored.
1977 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1978 should make use of. maxcpus=n : n >= 0 limits the
1979 kernel to using 'n' processors. n=0 is a special case,
1980 it is equivalent to "nosmp", which also disables
1983 max_loop= [LOOP] The number of loop block devices that get
1984 (loop.max_loop) unconditionally pre-created at init time. The default
1985 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1986 of statically allocating a predefined number, loop
1987 devices can be requested on-demand with the
1988 /dev/loop-control interface.
1990 mce [X86-32] Machine Check Exception
1992 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1994 md= [HW] RAID subsystems devices and level
1995 See Documentation/md.txt.
1998 Format: <first>,<last>
1999 Specifies range of consoles to be captured by the MDA.
2001 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2002 Amount of memory to be used when the kernel is not able
2003 to see the whole system memory or for test.
2004 [X86] Work as limiting max address. Use together
2005 with memmap= to avoid physical address space collisions.
2006 Without memmap= PCI devices could be placed at addresses
2007 belonging to unused RAM.
2009 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2013 [KNL,SH] Allow user to override the default size for
2014 per-device physically contiguous DMA buffers.
2016 memmap=exactmap [KNL,X86] Enable setting of an exact
2017 E820 memory map, as specified by the user.
2018 Such memmap=exactmap lines can be constructed based on
2019 BIOS output or other requirements. See the memmap=nn@ss
2022 memmap=nn[KMG]@ss[KMG]
2023 [KNL] Force usage of a specific region of memory.
2024 Region of memory to be used is from ss to ss+nn.
2026 memmap=nn[KMG]#ss[KMG]
2027 [KNL,ACPI] Mark specific memory as ACPI data.
2028 Region of memory to be marked is from ss to ss+nn.
2030 memmap=nn[KMG]$ss[KMG]
2031 [KNL,ACPI] Mark specific memory as reserved.
2032 Region of memory to be reserved is from ss to ss+nn.
2033 Example: Exclude memory from 0x18690000-0x1869ffff
2034 memmap=64K$0x18690000
2036 memmap=0x10000$0x18690000
2038 memmap=nn[KMG]!ss[KMG]
2039 [KNL,X86] Mark specific memory as protected.
2040 Region of memory to be used, from ss to ss+nn.
2041 The memory region may be marked as e820 type 12 (0xc)
2042 and is NVDIMM or ADR memory.
2044 memory_corruption_check=0/1 [X86]
2045 Some BIOSes seem to corrupt the first 64k of
2046 memory when doing things like suspend/resume.
2047 Setting this option will scan the memory
2048 looking for corruption. Enabling this will
2049 both detect corruption and prevent the kernel
2050 from using the memory being corrupted.
2051 However, its intended as a diagnostic tool; if
2052 repeatable BIOS-originated corruption always
2053 affects the same memory, you can use memmap=
2054 to prevent the kernel from using that memory.
2056 memory_corruption_check_size=size [X86]
2057 By default it checks for corruption in the low
2058 64k, making this memory unavailable for normal
2059 use. Use this parameter to scan for
2060 corruption in more or less memory.
2062 memory_corruption_check_period=seconds [X86]
2063 By default it checks for corruption every 60
2064 seconds. Use this parameter to check at some
2065 other rate. 0 disables periodic checking.
2067 memtest= [KNL,X86,ARM] Enable memtest
2069 default : 0 <disable>
2070 Specifies the number of memtest passes to be
2071 performed. Each pass selects another test
2072 pattern from a given set of patterns. Memtest
2073 fills the memory with this pattern, validates
2074 memory contents and reserves bad memory
2075 regions that are detected.
2077 meye.*= [HW] Set MotionEye Camera parameters
2078 See Documentation/video4linux/meye.txt.
2080 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2081 Multi-Function General Purpose Timers on AMD Geode
2084 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2085 the BIOS has incorrectly applied a workaround. TinyBIOS
2086 version 0.98 is known to be affected, 0.99 fixes the
2087 problem by letting the user disable the workaround.
2091 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2092 physical address is ignored.
2094 mini2440= [ARM,HW,KNL]
2095 Format:[0..2][b][c][t]
2097 MINI2440 configuration specification:
2098 0 - The attached screen is the 3.5" TFT
2099 1 - The attached screen is the 7" TFT
2100 2 - The VGA Shield is attached (1024x768)
2101 Leaving out the screen size parameter will not load
2102 the TFT driver, and the framebuffer will be left
2104 b - Enable backlight. The TFT backlight pin will be
2105 linked to the kernel VESA blanking code and a GPIO
2106 LED. This parameter is not necessary when using the
2108 c - Enable the s3c camera interface.
2109 t - Reserved for enabling touchscreen support. The
2110 touchscreen support is not enabled in the mainstream
2111 kernel as of 2.6.30, a preliminary port can be found
2112 in the "bleeding edge" mini2440 support kernel at
2113 http://repo.or.cz/w/linux-2.6/mini2440.git
2116 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2117 parameter allows control of the logging verbosity for
2118 the additional memory initialisation checks. A value
2119 of 0 disables mminit logging and a level of 4 will
2120 log everything. Information is printed at KERN_DEBUG
2121 so loglevel=8 may also need to be specified.
2124 [KNL] When CONFIG_MODULE_SIG is set, this means that
2125 modules without (valid) signatures will fail to load.
2126 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2127 is always true, so this option does nothing.
2130 [MOUSE] Maximum time between finger touching and
2131 leaving touchpad surface for touch to be considered
2132 a tap and be reported as a left button click (for
2133 touchpads working in absolute mode only).
2135 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2136 reporting absolute coordinates, such as tablets
2137 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2138 reporting absolute coordinates, such as tablets
2140 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2141 is similar to kernelcore except it specifies the
2142 amount of memory used for migratable allocations.
2143 If both kernelcore and movablecore is specified,
2144 then kernelcore will be at *least* the specified
2145 value but may be more. If movablecore on its own
2146 is specified, the administrator must be careful
2147 that the amount of memory usable for all allocations
2150 movable_node [KNL,X86] Boot-time switch to enable the effects
2151 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2153 MTD_Partition= [MTD]
2154 Format: <name>,<region-number>,<size>,<offset>
2156 MTD_Region= [MTD] Format:
2157 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2160 See drivers/mtd/cmdlinepart.c.
2162 multitce=off [PPC] This parameter disables the use of the pSeries
2163 firmware feature for updating multiple TCE entries
2166 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2168 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2170 boundary - index of last SLC block on Flex-OneNAND.
2171 The remaining blocks are configured as MLC blocks.
2172 lock - Configure if Flex-OneNAND boundary should be locked.
2173 Once locked, the boundary cannot be changed.
2174 1 indicates lock status, 0 indicates unlock status.
2177 ARM/S3C2412 JIVE boot control
2179 See arch/arm/mach-s3c2412/mach-jive.c
2181 mtouchusb.raw_coordinates=
2182 [HW] Make the MicroTouch USB driver use raw coordinates
2183 ('y', default) or cooked coordinates ('n')
2185 mtrr_chunk_size=nn[KMG] [X86]
2186 used for mtrr cleanup. It is largest continuous chunk
2187 that could hold holes aka. UC entries.
2189 mtrr_gran_size=nn[KMG] [X86]
2190 Used for mtrr cleanup. It is granularity of mtrr block.
2192 Large value could prevent small alignment from
2195 mtrr_spare_reg_nr=n [X86]
2197 Range: 0,7 : spare reg number
2199 Used for mtrr cleanup. It is spare mtrr entries number.
2200 Set to 2 or more if your graphical card needs more.
2202 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2204 netdev= [NET] Network devices parameters
2205 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2206 Note that mem_start is often overloaded to mean
2207 something different and driver-specific.
2208 This usage is only documented in each driver source
2212 [NETFILTER] Enable connection tracking flow accounting
2213 0 to disable accounting
2214 1 to enable accounting
2217 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2218 See Documentation/filesystems/nfs/nfsroot.txt.
2220 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2221 See Documentation/filesystems/nfs/nfsroot.txt.
2223 nfsrootdebug [NFS] enable nfsroot debugging messages.
2224 See Documentation/filesystems/nfs/nfsroot.txt.
2226 nfs.callback_tcpport=
2227 [NFS] set the TCP port on which the NFSv4 callback
2228 channel should listen.
2231 [NFS] sets the pathname to the program which is used
2232 to update the NFS client cache entries.
2234 nfs.cache_getent_timeout=
2235 [NFS] sets the timeout after which an attempt to
2236 update a cache entry is deemed to have failed.
2238 nfs.idmap_cache_timeout=
2239 [NFS] set the maximum lifetime for idmapper cache
2243 [NFS] enable 64-bit inode numbers.
2244 If zero, the NFS client will fake up a 32-bit inode
2245 number for the readdir() and stat() syscalls instead
2246 of returning the full 64-bit number.
2247 The default is to return 64-bit inode numbers.
2249 nfs.max_session_slots=
2250 [NFSv4.1] Sets the maximum number of session slots
2251 the client will attempt to negotiate with the server.
2252 This limits the number of simultaneous RPC requests
2253 that the client can send to the NFSv4.1 server.
2254 Note that there is little point in setting this
2255 value higher than the max_tcp_slot_table_limit.
2257 nfs.nfs4_disable_idmapping=
2258 [NFSv4] When set to the default of '1', this option
2259 ensures that both the RPC level authentication
2260 scheme and the NFS level operations agree to use
2261 numeric uids/gids if the mount is using the
2262 'sec=sys' security flavour. In effect it is
2263 disabling idmapping, which can make migration from
2264 legacy NFSv2/v3 systems to NFSv4 easier.
2265 Servers that do not support this mode of operation
2266 will be autodetected by the client, and it will fall
2267 back to using the idmapper.
2268 To turn off this behaviour, set the value to '0'.
2270 [NFS4] Specify an additional fixed unique ident-
2271 ification string that NFSv4 clients can insert into
2272 their nfs_client_id4 string. This is typically a
2273 UUID that is generated at system install time.
2275 nfs.send_implementation_id =
2276 [NFSv4.1] Send client implementation identification
2277 information in exchange_id requests.
2278 If zero, no implementation identification information
2280 The default is to send the implementation identification
2283 nfs.recover_lost_locks =
2284 [NFSv4] Attempt to recover locks that were lost due
2285 to a lease timeout on the server. Please note that
2286 doing this risks data corruption, since there are
2287 no guarantees that the file will remain unchanged
2288 after the locks are lost.
2289 If you want to enable the kernel legacy behaviour of
2290 attempting to recover these locks, then set this
2292 The default parameter value of '0' causes the kernel
2293 not to attempt recovery of lost locks.
2295 nfs4.layoutstats_timer =
2296 [NFSv4.2] Change the rate at which the kernel sends
2297 layoutstats to the pNFS metadata server.
2299 Setting this to value to 0 causes the kernel to use
2300 whatever value is the default set by the layout
2301 driver. A non-zero value sets the minimum interval
2302 in seconds between layoutstats transmissions.
2304 nfsd.nfs4_disable_idmapping=
2305 [NFSv4] When set to the default of '1', the NFSv4
2306 server will return only numeric uids and gids to
2307 clients using auth_sys, and will accept numeric uids
2308 and gids from such clients. This is intended to ease
2309 migration from NFSv2/v3.
2311 objlayoutdriver.osd_login_prog=
2312 [NFS] [OBJLAYOUT] sets the pathname to the program which
2313 is used to automatically discover and login into new
2314 osd-targets. Please see:
2315 Documentation/filesystems/pnfs.txt for more explanations
2317 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2318 when a NMI is triggered.
2319 Format: [state][,regs][,debounce][,die]
2321 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2322 Format: [panic,][nopanic,][num]
2324 0 - turn nmi_watchdog off
2325 1 - turn nmi_watchdog on
2326 When panic is specified, panic when an NMI watchdog
2327 timeout occurs (or 'nopanic' to override the opposite
2329 This is useful when you use a panic=... timeout and
2330 need the box quickly up again.
2332 netpoll.carrier_timeout=
2333 [NET] Specifies amount of time (in seconds) that
2334 netpoll should wait for a carrier. By default netpoll
2337 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2338 emulation library even if a 387 maths coprocessor
2342 [HW] Never suspend the console
2343 Disable suspending of consoles during suspend and
2344 hibernate operations. Once disabled, debugging
2345 messages can reach various consoles while the rest
2346 of the system is being put to sleep (ie, while
2347 debugging driver suspend/resume hooks). This may
2348 not work reliably with all consoles, but is known
2349 to work with serial and VGA consoles.
2350 To facilitate more flexible debugging, we also add
2351 console_suspend, a printk module parameter to control
2352 it. Users could use console_suspend (usually
2353 /sys/module/printk/parameters/console_suspend) to
2354 turn on/off it dynamically.
2356 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2357 caches in the slab allocator. Saves per-node memory,
2358 but will impact performance.
2362 noapic [SMP,APIC] Tells the kernel to not make use of any
2363 IOAPICs that may be present in the system.
2365 noautogroup Disable scheduler automatic task group creation.
2367 nobats [PPC] Do not use BATs for mapping kernel lowmem
2368 on "Classic" PPC cores.
2372 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2374 nodelayacct [KNL] Disable per-task delay accounting
2376 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2378 nodsp [SH] Disable hardware DSP at boot time.
2380 noefi Disable EFI runtime services support.
2385 On X86-32 available only on PAE configured kernels.
2386 noexec=on: enable non-executable mappings (default)
2387 noexec=off: disable non-executable mappings
2390 Disable SMAP (Supervisor Mode Access Prevention)
2391 even if it is supported by processor.
2394 Disable SMEP (Supervisor Mode Execution Prevention)
2395 even if it is supported by processor.
2398 This affects only 32-bit executables.
2399 noexec32=on: enable non-executable mappings (default)
2400 read doesn't imply executable mappings
2401 noexec32=off: disable non-executable mappings
2402 read implies executable mappings
2404 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2406 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2407 register save and restore. The kernel will only save
2408 legacy floating-point registers on task switch.
2410 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2412 noxsave [BUGS=X86] Disables x86 extended register state save
2413 and restore using xsave. The kernel will fallback to
2414 enabling legacy floating-point and sse state.
2416 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2417 register states. The kernel will fall back to use
2418 xsave to save the states. By using this parameter,
2419 performance of saving the states is degraded because
2420 xsave doesn't support modified optimization while
2421 xsaveopt supports it on xsaveopt enabled systems.
2423 noxsaves [X86] Disables xsaves and xrstors used in saving and
2424 restoring x86 extended register state in compacted
2425 form of xsave area. The kernel will fall back to use
2426 xsaveopt and xrstor to save and restore the states
2427 in standard form of xsave area. By using this
2428 parameter, xsave area per process might occupy more
2429 memory on xsaves enabled systems.
2431 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2432 wfi(ARM) instruction doesn't work correctly and not to
2433 use it. This is also useful when using JTAG debugger.
2435 no_file_caps Tells the kernel not to honor file capabilities. The
2436 only way then for a file to be executed with privilege
2437 is to be setuid root or executed by root.
2439 nohalt [IA-64] Tells the kernel not to use the power saving
2440 function PAL_HALT_LIGHT when idle. This increases
2441 power-consumption. On the positive side, it reduces
2442 interrupt wake-up latency, which may improve performance
2443 in certain environments such as networked servers or
2446 nohibernate [HIBERNATION] Disable hibernation and resume.
2448 nohz= [KNL] Boottime enable/disable dynamic ticks
2449 Valid arguments: on, off
2452 nohz_full= [KNL,BOOT]
2453 In kernels built with CONFIG_NO_HZ_FULL=y, set
2454 the specified list of CPUs whose tick will be stopped
2455 whenever possible. The boot CPU will be forced outside
2456 the range to maintain the timekeeping.
2457 The CPUs in this range must also be included in the
2460 noiotrap [SH] Disables trapped I/O port accesses.
2462 noirqdebug [X86-32] Disables the code which attempts to detect and
2463 disable unhandled interrupt sources.
2465 no_timer_check [X86,APIC] Disables the code which tests for
2466 broken timer IRQ sources.
2468 noisapnp [ISAPNP] Disables ISA PnP code.
2470 noinitrd [RAM] Tells the kernel not to load any configured
2473 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2475 [Deprecated - use intremap=off]
2479 nojitter [IA-64] Disables jitter checking for ITC timers.
2481 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2483 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2486 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2487 steal time is computed, but won't influence scheduler
2490 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2492 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2494 noltlbs [PPC] Do not use large page/tlb entries for kernel
2495 lowmem mapping on PPC40x.
2497 nomca [IA-64] Disable machine check abort handling
2499 nomce [X86-32] Disable Machine Check Exception
2501 nomfgpt [X86-32] Disable Multi-Function General Purpose
2502 Timer usage (for AMD Geode machines).
2504 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2505 shutdown the other cpus. Instead use the REBOOT_VECTOR
2508 nomodule Disable module load
2510 nopat [X86] Disable PAT (page attribute table extension of
2511 pagetables) support.
2513 norandmaps Don't use address space randomization. Equivalent to
2514 echo 0 > /proc/sys/kernel/randomize_va_space
2516 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2518 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2519 with UP alternatives
2521 nordrand [X86] Disable kernel use of the RDRAND and
2522 RDSEED instructions even if they are supported
2523 by the processor. RDRAND and RDSEED are still
2524 available to user space applications.
2526 noresume [SWSUSP] Disables resume and restores original swap
2529 no-scroll [VGA] Disables scrollback.
2530 This is required for the Braillex ib80-piezo Braille
2531 reader made by F.H. Papenmeier (Germany).
2535 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2537 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2538 and disable the IO APIC. legacy for "maxcpus=0".
2540 nosoftlockup [KNL] Disable the soft-lockup detector.
2542 nosync [HW,M68K] Disables sync negotiation for all devices.
2544 notsc [BUGS=X86-32] Disable Time Stamp Counter
2546 nousb [USB] Disable the USB subsystem
2548 nowatchdog [KNL] Disable both lockup detectors, i.e.
2549 soft-lockup and NMI watchdog (hard-lockup).
2553 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2555 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2556 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2557 Some features depend on CPU0. Known dependencies are:
2558 1. Resume from suspend/hibernate depends on CPU0.
2559 Suspend/hibernate will fail if CPU0 is offline and you
2560 need to online CPU0 before suspend/hibernate.
2561 2. PIC interrupts also depend on CPU0. CPU0 can't be
2562 removed if a PIC interrupt is detected.
2563 It's said poweroff/reboot may depend on CPU0 on some
2564 machines although I haven't seen such issues so far
2565 after CPU0 is offline on a few tested machines.
2566 If the dependencies are under your control, you can
2567 turn on cpu0_hotplug.
2569 nptcg= [IA-64] Override max number of concurrent global TLB
2570 purges which is reported from either PAL_VM_SUMMARY or
2573 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2574 could support. nr_cpus=n : n >= 1 limits the kernel to
2575 supporting 'n' processors. Later in runtime you can not
2576 use hotplug cpu feature to put more cpu back to online.
2577 just like you compile the kernel NR_CPUS=n
2579 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2581 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2582 Allowed values are enable and disable
2584 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2585 one of ['zone', 'node', 'default'] can be specified
2586 This can be set from sysctl after boot.
2587 See Documentation/sysctl/vm.txt for details.
2589 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2590 See Documentation/debugging-via-ohci1394.txt for more
2593 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2594 Rather than timing out after 20 ms if an EC
2595 command is not properly ACKed, override the length
2596 of the timeout. We have interrupts disabled while
2597 waiting for the ACK, so if this is set too high
2598 interrupts *may* be lost!
2600 omap_mux= [OMAP] Override bootloader pin multiplexing.
2601 Format: <mux_mode0.mode_name=value>...
2602 For example, to override I2C bus2:
2603 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2605 oprofile.timer= [HW]
2606 Use timer interrupt instead of performance counters
2608 oprofile.cpu_type= Force an oprofile cpu type
2609 This might be useful if you have an older oprofile
2610 userland or if you want common events.
2611 Format: { arch_perfmon }
2612 arch_perfmon: [X86] Force use of architectural
2613 perfmon on Intel CPUs instead of the
2614 CPU specific event set.
2615 timer: [X86] Force use of architectural NMI
2616 timer mode (see also oprofile.timer
2617 for generic hr timer mode)
2618 [s390] Force legacy basic mode sampling
2619 (report cpu_type "timer")
2621 oops=panic Always panic on oopses. Default is to just kill the
2622 process, but there is a small probability of
2623 deadlocking the machine.
2624 This will also cause panics on machine check exceptions.
2625 Useful together with panic=30 to trigger a reboot.
2628 See Documentation/sound/oss/oss-parameters.txt
2630 page_owner= [KNL] Boot-time page_owner enabling option.
2631 Storage of the information about who allocated
2632 each page is disabled in default. With this switch,
2634 on: enable the feature
2636 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2637 timeout > 0: seconds before rebooting
2638 timeout = 0: wait forever
2639 timeout < 0: reboot immediately
2642 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2645 crash_kexec_post_notifiers
2646 Run kdump after running panic-notifiers and dumping
2647 kmsg. This only for the users who doubt kdump always
2648 succeeds in any situation.
2649 Note that this also increases risks of kdump failure,
2650 because some panic notifiers can make the crashed
2651 kernel more unstable.
2653 parkbd.port= [HW] Parallel port number the keyboard adapter is
2654 connected to, default is 0.
2656 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2657 0 for XT, 1 for AT (default is AT).
2660 parport= [HW,PPT] Specify parallel ports. 0 disables.
2661 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2662 Use 'auto' to force the driver to use any
2663 IRQ/DMA settings detected (the default is to
2664 ignore detected IRQ/DMA settings because of
2665 possible conflicts). You can specify the base
2666 address, IRQ, and DMA settings; IRQ and DMA
2667 should be numbers, or 'auto' (for using detected
2668 settings on that particular port), or 'nofifo'
2669 (to avoid using a FIFO even if it is detected).
2670 Parallel ports are assigned in the order they
2671 are specified on the command line, starting
2674 parport_init_mode= [HW,PPT]
2675 Configure VIA parallel port to operate in
2676 a specific mode. This is necessary on Pegasos
2677 computer where firmware has no options for setting
2678 up parallel port mode and sets it to spp.
2679 Currently this function knows 686a and 8231 chips.
2680 Format: [spp|ps2|epp|ecp|ecpepp]
2683 Halt all CPUs after the first oops has been printed for
2684 the specified number of seconds. This is to be used if
2685 your oopses keep scrolling off the screen.
2690 See header of drivers/block/paride/pcd.c.
2691 See also Documentation/blockdev/paride.txt.
2693 pci=option[,option...] [PCI] various PCI subsystem options:
2694 earlydump [X86] dump PCI config space before the kernel
2696 off [X86] don't probe for the PCI bus
2697 bios [X86-32] force use of PCI BIOS, don't access
2698 the hardware directly. Use this if your machine
2699 has a non-standard PCI host bridge.
2700 nobios [X86-32] disallow use of PCI BIOS, only direct
2701 hardware access methods are allowed. Use this
2702 if you experience crashes upon bootup and you
2703 suspect they are caused by the BIOS.
2704 conf1 [X86] Force use of PCI Configuration
2706 conf2 [X86] Force use of PCI Configuration
2708 noaer [PCIE] If the PCIEAER kernel config parameter is
2709 enabled, this kernel boot option can be used to
2710 disable the use of PCIE advanced error reporting.
2711 nodomains [PCI] Disable support for multiple PCI
2712 root domains (aka PCI segments, in ACPI-speak).
2713 nommconf [X86] Disable use of MMCONFIG for PCI
2715 check_enable_amd_mmconf [X86] check for and enable
2716 properly configured MMIO access to PCI
2717 config space on AMD family 10h CPU
2718 nomsi [MSI] If the PCI_MSI kernel config parameter is
2719 enabled, this kernel boot option can be used to
2720 disable the use of MSI interrupts system-wide.
2721 noioapicquirk [APIC] Disable all boot interrupt quirks.
2722 Safety option to keep boot IRQs enabled. This
2723 should never be necessary.
2724 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2725 primary IO-APIC for bridges that cannot disable
2726 boot IRQs. This fixes a source of spurious IRQs
2727 when the system masks IRQs.
2728 noioapicreroute [APIC] Disable workaround that uses the
2729 boot IRQ equivalent of an IRQ that connects to
2730 a chipset where boot IRQs cannot be disabled.
2731 The opposite of ioapicreroute.
2732 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2733 routing table. These calls are known to be buggy
2734 on several machines and they hang the machine
2735 when used, but on other computers it's the only
2736 way to get the interrupt routing table. Try
2737 this option if the kernel is unable to allocate
2738 IRQs or discover secondary PCI buses on your
2740 rom [X86] Assign address space to expansion ROMs.
2741 Use with caution as certain devices share
2742 address decoders between ROMs and other
2744 norom [X86] Do not assign address space to
2745 expansion ROMs that do not already have
2746 BIOS assigned address ranges.
2747 nobar [X86] Do not assign address space to the
2748 BARs that weren't assigned by the BIOS.
2749 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2750 assigned automatically to PCI devices. You can
2751 make the kernel exclude IRQs of your ISA cards
2753 pirqaddr=0xAAAAA [X86] Specify the physical address
2754 of the PIRQ table (normally generated
2755 by the BIOS) if it is outside the
2756 F0000h-100000h range.
2757 lastbus=N [X86] Scan all buses thru bus #N. Can be
2758 useful if the kernel is unable to find your
2759 secondary buses and you want to tell it
2760 explicitly which ones they are.
2761 assign-busses [X86] Always assign all PCI bus
2762 numbers ourselves, overriding
2763 whatever the firmware may have done.
2764 usepirqmask [X86] Honor the possible IRQ mask stored
2765 in the BIOS $PIR table. This is needed on
2766 some systems with broken BIOSes, notably
2767 some HP Pavilion N5400 and Omnibook XE3
2768 notebooks. This will have no effect if ACPI
2769 IRQ routing is enabled.
2770 noacpi [X86] Do not use ACPI for IRQ routing
2771 or for PCI scanning.
2772 use_crs [X86] Use PCI host bridge window information
2773 from ACPI. On BIOSes from 2008 or later, this
2774 is enabled by default. If you need to use this,
2775 please report a bug.
2776 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2777 If you need to use this, please report a bug.
2778 routeirq Do IRQ routing for all PCI devices.
2779 This is normally done in pci_enable_device(),
2780 so this option is a temporary workaround
2781 for broken drivers that don't call it.
2782 skip_isa_align [X86] do not align io start addr, so can
2783 handle more pci cards
2784 firmware [ARM] Do not re-enumerate the bus but instead
2785 just use the configuration from the
2786 bootloader. This is currently used on
2787 IXP2000 systems where the bus has to be
2788 configured a certain way for adjunct CPUs.
2789 noearly [X86] Don't do any early type 1 scanning.
2790 This might help on some broken boards which
2791 machine check when some devices' config space
2792 is read. But various workarounds are disabled
2793 and some IOMMU drivers will not work.
2794 bfsort Sort PCI devices into breadth-first order.
2795 This sorting is done to get a device
2796 order compatible with older (<= 2.4) kernels.
2797 nobfsort Don't sort PCI devices into breadth-first order.
2798 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2799 tuning and use the BIOS-configured MPS defaults.
2800 pcie_bus_safe Set every device's MPS to the largest value
2801 supported by all devices below the root complex.
2802 pcie_bus_perf Set device MPS to the largest allowable MPS
2803 based on its parent bus. Also set MRRS (Max
2804 Read Request Size) to the largest supported
2805 value (no larger than the MPS that the device
2806 or bus can support) for best performance.
2807 pcie_bus_peer2peer Set every device's MPS to 128B, which
2808 every device is guaranteed to support. This
2809 configuration allows peer-to-peer DMA between
2810 any pair of devices, possibly at the cost of
2811 reduced performance. This also guarantees
2812 that hot-added devices will work.
2813 cbiosize=nn[KMG] The fixed amount of bus space which is
2814 reserved for the CardBus bridge's IO window.
2815 The default value is 256 bytes.
2816 cbmemsize=nn[KMG] The fixed amount of bus space which is
2817 reserved for the CardBus bridge's memory
2818 window. The default value is 64 megabytes.
2821 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2822 Specifies alignment and device to reassign
2823 aligned memory resources.
2824 If <order of align> is not specified,
2825 PAGE_SIZE is used as alignment.
2826 PCI-PCI bridge can be specified, if resource
2827 windows need to be expanded.
2828 ecrc= Enable/disable PCIe ECRC (transaction layer
2829 end-to-end CRC checking).
2830 bios: Use BIOS/firmware settings. This is the
2834 hpiosize=nn[KMG] The fixed amount of bus space which is
2835 reserved for hotplug bridge's IO window.
2836 Default size is 256 bytes.
2837 hpmemsize=nn[KMG] The fixed amount of bus space which is
2838 reserved for hotplug bridge's memory window.
2839 Default size is 2 megabytes.
2840 realloc= Enable/disable reallocating PCI bridge resources
2841 if allocations done by BIOS are too small to
2842 accommodate resources required by all child
2844 off: Turn realloc off
2846 realloc same as realloc=on
2847 noari do not use PCIe ARI.
2848 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2849 only look for one device below a PCIe downstream
2852 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2855 force Enable ASPM even on devices that claim not to support it.
2856 WARNING: Forcing ASPM on may cause system lockups.
2858 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2859 nomsi Do not use MSI for PCI Express Native Hotplug (this
2860 makes all PCIe ports use INTx for hotplug services).
2862 pcie_ports= [PCIE] PCIe ports handling:
2863 auto Ask the BIOS whether or not to use native PCIe services
2864 associated with PCIe ports (PME, hot-plug, AER). Use
2865 them only if that is allowed by the BIOS.
2866 native Use native PCIe services associated with PCIe ports
2868 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2871 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2872 nomsi Do not use MSI for native PCIe PME signaling (this makes
2873 all PCIe root ports use INTx for all services).
2875 pcmv= [HW,PCMCIA] BadgePAD 4
2879 Keep all power-domains already enabled by bootloader on,
2880 even if no driver has claimed them. This is useful
2881 for debug and development, but should not be
2882 needed on a platform with proper driver support.
2885 See Documentation/blockdev/paride.txt.
2887 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2890 See arch/parisc/kernel/pdc_chassis.c
2892 percpu_alloc= Select which percpu first chunk allocator to use.
2893 Currently supported values are "embed" and "page".
2894 Archs may support subset or none of the selections.
2895 See comments in mm/percpu.c for details on each
2896 allocator. This parameter is primarily for debugging
2897 and performance comparison.
2900 See Documentation/blockdev/paride.txt.
2903 See Documentation/blockdev/paride.txt.
2905 pirq= [SMP,APIC] Manual mp-table setup
2906 See Documentation/x86/i386/IO-APIC.txt.
2908 plip= [PPT,NET] Parallel port network link
2909 Format: { parport<nr> | timid | 0 }
2910 See also Documentation/parport.txt.
2912 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2913 Override pmtimer IOPort with a hex value.
2917 Enable PNP debug messages (depends on the
2918 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2919 via /sys/module/pnp/parameters/debug. We always show
2920 current resource usage; turning this on also shows
2921 possible settings and some assignment information.
2927 { on | off | curr | res | no-curr | no-res }
2930 [ISAPNP] Exclude IRQs for the autoconfiguration
2933 [ISAPNP] Exclude DMAs for the autoconfiguration
2935 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2936 Ranges are in pairs (I/O port base and size).
2939 [ISAPNP] Exclude memory regions for the
2941 Ranges are in pairs (memory base and size).
2943 ports= [IP_VS_FTP] IPVS ftp helper module
2945 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2947 Format: <port>,<port>....
2949 print-fatal-signals=
2950 [KNL] debug: print fatal signals
2952 If enabled, warn about various signal handling
2953 related application anomalies: too many signals,
2954 too many POSIX.1 timers, fatal signals causing a
2957 If you hit the warning due to signal overflow,
2958 you might want to try "ulimit -i unlimited".
2962 printk.always_kmsg_dump=
2963 Trigger kmsg_dump for cases other than kernel oops or
2965 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2968 printk.time= Show timing data prefixed to each printk message line
2969 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2971 processor.max_cstate= [HW,ACPI]
2972 Limit processor to maximum C-state
2973 max_cstate=9 overrides any DMI blacklist limit.
2975 processor.nocst [HW,ACPI]
2976 Ignore the _CST method to determine C-states,
2977 instead using the legacy FADT method
2979 profile= [KNL] Enable kernel profiling via /proc/profile
2980 Format: [schedule,]<number>
2981 Param: "schedule" - profile schedule points.
2982 Param: <number> - step/bucket size as a power of 2 for
2983 statistical time based profiling.
2984 Param: "sleep" - profile D-state sleeping (millisecs).
2985 Requires CONFIG_SCHEDSTATS
2986 Param: "kvm" - profile VM exits.
2988 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2990 See Documentation/blockdev/ramdisk.txt.
2992 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2993 probe for; one of (bare|imps|exps|lifebook|any).
2994 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2996 psmouse.resetafter= [HW,MOUSE]
2997 Try to reset the device after so many bad packets
3000 [HW,MOUSE] Set desired mouse resolution, in dpi.
3001 psmouse.smartscroll=
3002 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3003 0 = disabled, 1 = enabled (default).
3005 pstore.backend= Specify the name of the pstore backend to use
3008 See Documentation/blockdev/paride.txt.
3011 [KNL] Number of legacy pty's. Overwrites compiled-in
3014 quiet [KNL] Disable most log messages
3019 See Documentation/md.txt.
3021 ramdisk_blocksize= [RAM]
3022 See Documentation/blockdev/ramdisk.txt.
3024 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3025 See Documentation/blockdev/ramdisk.txt.
3028 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3029 the specified list of CPUs to be no-callback CPUs.
3030 Invocation of these CPUs' RCU callbacks will
3031 be offloaded to "rcuox/N" kthreads created for
3032 that purpose, where "x" is "b" for RCU-bh, "p"
3033 for RCU-preempt, and "s" for RCU-sched, and "N"
3034 is the CPU number. This reduces OS jitter on the
3035 offloaded CPUs, which can be useful for HPC and
3036 real-time workloads. It can also improve energy
3037 efficiency for asymmetric multiprocessors.
3040 Rather than requiring that offloaded CPUs
3041 (specified by rcu_nocbs= above) explicitly
3042 awaken the corresponding "rcuoN" kthreads,
3043 make these kthreads poll for callbacks.
3044 This improves the real-time response for the
3045 offloaded CPUs by relieving them of the need to
3046 wake up the corresponding kthread, but degrades
3047 energy efficiency by requiring that the kthreads
3048 periodically wake up to do the polling.
3050 rcutree.blimit= [KNL]
3051 Set maximum number of finished RCU callbacks to
3052 process in one batch.
3054 rcutree.dump_tree= [KNL]
3055 Dump the structure of the rcu_node combining tree
3056 out at early boot. This is used for diagnostic
3057 purposes, to verify correct tree setup.
3059 rcutree.gp_cleanup_delay= [KNL]
3060 Set the number of jiffies to delay each step of
3061 RCU grace-period cleanup. This only has effect
3062 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3064 rcutree.gp_init_delay= [KNL]
3065 Set the number of jiffies to delay each step of
3066 RCU grace-period initialization. This only has
3067 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3070 rcutree.gp_preinit_delay= [KNL]
3071 Set the number of jiffies to delay each step of
3072 RCU grace-period pre-initialization, that is,
3073 the propagation of recent CPU-hotplug changes up
3074 the rcu_node combining tree. This only has effect
3075 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3077 rcutree.rcu_fanout_exact= [KNL]
3078 Disable autobalancing of the rcu_node combining
3079 tree. This is used by rcutorture, and might
3080 possibly be useful for architectures having high
3081 cache-to-cache transfer latencies.
3083 rcutree.rcu_fanout_leaf= [KNL]
3084 Increase the number of CPUs assigned to each
3085 leaf rcu_node structure. Useful for very large
3088 rcutree.jiffies_till_sched_qs= [KNL]
3089 Set required age in jiffies for a
3090 given grace period before RCU starts
3091 soliciting quiescent-state help from
3092 rcu_note_context_switch().
3094 rcutree.jiffies_till_first_fqs= [KNL]
3095 Set delay from grace-period initialization to
3096 first attempt to force quiescent states.
3097 Units are jiffies, minimum value is zero,
3098 and maximum value is HZ.
3100 rcutree.jiffies_till_next_fqs= [KNL]
3101 Set delay between subsequent attempts to force
3102 quiescent states. Units are jiffies, minimum
3103 value is one, and maximum value is HZ.
3105 rcutree.kthread_prio= [KNL,BOOT]
3106 Set the SCHED_FIFO priority of the RCU per-CPU
3107 kthreads (rcuc/N). This value is also used for
3108 the priority of the RCU boost threads (rcub/N)
3109 and for the RCU grace-period kthreads (rcu_bh,
3110 rcu_preempt, and rcu_sched). If RCU_BOOST is
3111 set, valid values are 1-99 and the default is 1
3112 (the least-favored priority). Otherwise, when
3113 RCU_BOOST is not set, valid values are 0-99 and
3114 the default is zero (non-realtime operation).
3116 rcutree.rcu_nocb_leader_stride= [KNL]
3117 Set the number of NOCB kthread groups, which
3118 defaults to the square root of the number of
3119 CPUs. Larger numbers reduces the wakeup overhead
3120 on the per-CPU grace-period kthreads, but increases
3121 that same overhead on each group's leader.
3123 rcutree.qhimark= [KNL]
3124 Set threshold of queued RCU callbacks beyond which
3125 batch limiting is disabled.
3127 rcutree.qlowmark= [KNL]
3128 Set threshold of queued RCU callbacks below which
3129 batch limiting is re-enabled.
3131 rcutree.rcu_idle_gp_delay= [KNL]
3132 Set wakeup interval for idle CPUs that have
3133 RCU callbacks (RCU_FAST_NO_HZ=y).
3135 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3136 Set wakeup interval for idle CPUs that have
3137 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3138 Lazy RCU callbacks are those which RCU can
3139 prove do nothing more than free memory.
3141 rcutorture.cbflood_inter_holdoff= [KNL]
3142 Set holdoff time (jiffies) between successive
3143 callback-flood tests.
3145 rcutorture.cbflood_intra_holdoff= [KNL]
3146 Set holdoff time (jiffies) between successive
3147 bursts of callbacks within a given callback-flood
3150 rcutorture.cbflood_n_burst= [KNL]
3151 Set the number of bursts making up a given
3152 callback-flood test. Set this to zero to
3153 disable callback-flood testing.
3155 rcutorture.cbflood_n_per_burst= [KNL]
3156 Set the number of callbacks to be registered
3157 in a given burst of a callback-flood test.
3159 rcutorture.fqs_duration= [KNL]
3160 Set duration of force_quiescent_state bursts
3163 rcutorture.fqs_holdoff= [KNL]
3164 Set holdoff time within force_quiescent_state bursts
3167 rcutorture.fqs_stutter= [KNL]
3168 Set wait time between force_quiescent_state bursts
3171 rcutorture.gp_cond= [KNL]
3172 Use conditional/asynchronous update-side
3173 primitives, if available.
3175 rcutorture.gp_exp= [KNL]
3176 Use expedited update-side primitives, if available.
3178 rcutorture.gp_normal= [KNL]
3179 Use normal (non-expedited) asynchronous
3180 update-side primitives, if available.
3182 rcutorture.gp_sync= [KNL]
3183 Use normal (non-expedited) synchronous
3184 update-side primitives, if available. If all
3185 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3186 rcutorture.gp_normal=, and rcutorture.gp_sync=
3187 are zero, rcutorture acts as if is interpreted
3188 they are all non-zero.
3190 rcutorture.n_barrier_cbs= [KNL]
3191 Set callbacks/threads for rcu_barrier() testing.
3193 rcutorture.nfakewriters= [KNL]
3194 Set number of concurrent RCU writers. These just
3195 stress RCU, they don't participate in the actual
3196 test, hence the "fake".
3198 rcutorture.nreaders= [KNL]
3199 Set number of RCU readers. The value -1 selects
3200 N-1, where N is the number of CPUs. A value
3201 "n" less than -1 selects N-n-2, where N is again
3202 the number of CPUs. For example, -2 selects N
3203 (the number of CPUs), -3 selects N+1, and so on.
3205 rcutorture.object_debug= [KNL]
3206 Enable debug-object double-call_rcu() testing.
3208 rcutorture.onoff_holdoff= [KNL]
3209 Set time (s) after boot for CPU-hotplug testing.
3211 rcutorture.onoff_interval= [KNL]
3212 Set time (s) between CPU-hotplug operations, or
3213 zero to disable CPU-hotplug testing.
3215 rcutorture.shuffle_interval= [KNL]
3216 Set task-shuffle interval (s). Shuffling tasks
3217 allows some CPUs to go into dyntick-idle mode
3218 during the rcutorture test.
3220 rcutorture.shutdown_secs= [KNL]
3221 Set time (s) after boot system shutdown. This
3222 is useful for hands-off automated testing.
3224 rcutorture.stall_cpu= [KNL]
3225 Duration of CPU stall (s) to test RCU CPU stall
3226 warnings, zero to disable.
3228 rcutorture.stall_cpu_holdoff= [KNL]
3229 Time to wait (s) after boot before inducing stall.
3231 rcutorture.stat_interval= [KNL]
3232 Time (s) between statistics printk()s.
3234 rcutorture.stutter= [KNL]
3235 Time (s) to stutter testing, for example, specifying
3236 five seconds causes the test to run for five seconds,
3237 wait for five seconds, and so on. This tests RCU's
3238 ability to transition abruptly to and from idle.
3240 rcutorture.test_boost= [KNL]
3241 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3242 "Maybe" means test if the RCU implementation
3243 under test support RCU priority boosting.
3245 rcutorture.test_boost_duration= [KNL]
3246 Duration (s) of each individual boost test.
3248 rcutorture.test_boost_interval= [KNL]
3249 Interval (s) between each boost test.
3251 rcutorture.test_no_idle_hz= [KNL]
3252 Test RCU's dyntick-idle handling. See also the
3253 rcutorture.shuffle_interval parameter.
3255 rcutorture.torture_runnable= [BOOT]
3256 Start rcutorture running at boot time.
3258 rcutorture.torture_type= [KNL]
3259 Specify the RCU implementation to test.
3261 rcutorture.verbose= [KNL]
3262 Enable additional printk() statements.
3264 rcupdate.rcu_expedited= [KNL]
3265 Use expedited grace-period primitives, for
3266 example, synchronize_rcu_expedited() instead
3267 of synchronize_rcu(). This reduces latency,
3268 but can increase CPU utilization, degrade
3269 real-time latency, and degrade energy efficiency.
3271 rcupdate.rcu_cpu_stall_suppress= [KNL]
3272 Suppress RCU CPU stall warning messages.
3274 rcupdate.rcu_cpu_stall_timeout= [KNL]
3275 Set timeout for RCU CPU stall warning messages.
3277 rcupdate.rcu_task_stall_timeout= [KNL]
3278 Set timeout in jiffies for RCU task stall warning
3279 messages. Disable with a value less than or equal
3282 rcupdate.rcu_self_test= [KNL]
3283 Run the RCU early boot self tests
3285 rcupdate.rcu_self_test_bh= [KNL]
3286 Run the RCU bh early boot self tests
3288 rcupdate.rcu_self_test_sched= [KNL]
3289 Run the RCU sched early boot self tests
3293 Run specified binary instead of /init from the ramdisk,
3294 used for early userspace startup. See initrd.
3297 Format (x86 or x86_64):
3298 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3300 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3302 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3303 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3304 reboot_force is either force or not specified,
3305 reboot_cpu is s[mp]#### with #### being the processor
3306 to be used for rebooting.
3309 [KNL, SMP] Set scheduler's default relax_domain_level.
3310 See Documentation/cgroups/cpusets.txt.
3312 relative_sleep_states=
3313 [SUSPEND] Use sleep state labeling where the deepest
3314 state available other than hibernation is always "mem".
3315 Format: { "0" | "1" }
3316 0 -- Traditional sleep state labels.
3317 1 -- Relative sleep state labels.
3319 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3321 reservetop= [X86-32]
3323 Reserves a hole at the top of the kernel virtual
3328 Set the amount of memory to reserve for BIOS at
3329 the bottom of the address space.
3331 reset_devices [KNL] Force drivers to reset the underlying device
3332 during initialization.
3335 Specify the partition device for software suspend
3337 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3339 resume_offset= [SWSUSP]
3340 Specify the offset from the beginning of the partition
3341 given by "resume=" at which the swap header is located,
3342 in <PAGE_SIZE> units (needed only for swap files).
3343 See Documentation/power/swsusp-and-swap-files.txt
3345 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3346 read the resume files
3348 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3349 Useful for devices that are detected asynchronously
3350 (e.g. USB and MMC devices).
3352 hibernate= [HIBERNATION]
3353 noresume Don't check if there's a hibernation image
3354 present during boot.
3355 nocompress Don't compress/decompress hibernation images.
3356 no Disable hibernation and resume.
3358 retain_initrd [RAM] Keep initrd memory after extraction
3360 rfkill.default_state=
3361 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3362 etc. communication is blocked by default.
3365 rfkill.master_switch_mode=
3366 0 The "airplane mode" button does nothing.
3367 1 The "airplane mode" button toggles between everything
3368 blocked and the previous configuration.
3369 2 The "airplane mode" button toggles between everything
3370 blocked and everything unblocked.
3372 rhash_entries= [KNL,NET]
3373 Set number of hash buckets for route cache
3375 ro [KNL] Mount root device read-only on boot
3377 root= [KNL] Root filesystem
3378 See name_to_dev_t comment in init/do_mounts.c.
3380 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3381 mount the root filesystem
3383 rootflags= [KNL] Set root filesystem mount option string
3385 rootfstype= [KNL] Set root filesystem type
3387 rootwait [KNL] Wait (indefinitely) for root device to show up.
3388 Useful for devices that are detected asynchronously
3389 (e.g. USB and MMC devices).
3391 rproc_mem=nn[KMG][@address]
3392 [KNL,ARM,CMA] Remoteproc physical memory block.
3393 Memory area to be used by remote processor image,
3396 rw [KNL] Mount root device read-write on boot
3398 S [KNL] Run init in single mode
3400 s390_iommu= [HW,S390]
3401 Set s390 IOTLB flushing mode
3403 With strict flushing every unmap operation will result in
3404 an IOTLB flush. Default is lazy flushing before reuse,
3408 See drivers/net/irda/sa1100_ir.c.
3410 sbni= [NET] Granch SBNI12 leased line adapter
3412 sched_debug [KNL] Enables verbose scheduler debug messages.
3414 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3415 xtime_lock contention on larger systems, and/or RCU lock
3416 contention on all systems with CONFIG_MAXSMP set.
3417 Format: { "0" | "1" }
3418 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3420 Note: increases power consumption, thus should only be
3421 enabled if running jitter sensitive (HPC/RT) workloads.
3423 security= [SECURITY] Choose a security module to enable at boot.
3424 If this boot parameter is not specified, only the first
3425 security module asking for security registration will be
3426 loaded. An invalid security module name will be treated
3427 as if no module has been chosen.
3429 selinux= [SELINUX] Disable or enable SELinux at boot time.
3430 Format: { "0" | "1" }
3431 See security/selinux/Kconfig help text.
3434 Default value is set via kernel config option.
3435 If enabled at boot time, /selinux/disable can be used
3436 later to disable prior to initial policy load.
3438 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3439 Format: { "0" | "1" }
3440 See security/apparmor/Kconfig help text
3443 Default value is set via kernel config option.
3445 serialnumber [BUGS=X86-32]
3448 Maximal number of shapers.
3450 show_msr= [x86] show boot-time MSR settings
3451 Format: { <integer> }
3452 Show boot-time (BIOS-initialized) MSR settings.
3453 The parameter means the number of CPUs to show,
3454 for example 1 means boot CPU only.
3462 Disable merging of slabs with similar size. May be
3463 necessary if there is some reason to distinguish
3464 allocs to different slabs. Debug options disable
3465 merging on their own.
3466 For more information see Documentation/vm/slub.txt.
3468 slab_max_order= [MM, SLAB]
3469 Determines the maximum allowed order for slabs.
3470 A high setting may cause OOMs due to memory
3471 fragmentation. Defaults to 1 for systems with
3472 more than 32MB of RAM, 0 otherwise.
3474 slub_debug[=options[,slabs]] [MM, SLUB]
3475 Enabling slub_debug allows one to determine the
3476 culprit if slab objects become corrupted. Enabling
3477 slub_debug can create guard zones around objects and
3478 may poison objects when not in use. Also tracks the
3479 last alloc / free. For more information see
3480 Documentation/vm/slub.txt.
3482 slub_max_order= [MM, SLUB]
3483 Determines the maximum allowed order for slabs.
3484 A high setting may cause OOMs due to memory
3485 fragmentation. For more information see
3486 Documentation/vm/slub.txt.
3488 slub_min_objects= [MM, SLUB]
3489 The minimum number of objects per slab. SLUB will
3490 increase the slab order up to slub_max_order to
3491 generate a sufficiently large slab able to contain
3492 the number of objects indicated. The higher the number
3493 of objects the smaller the overhead of tracking slabs
3494 and the less frequently locks need to be acquired.
3495 For more information see Documentation/vm/slub.txt.
3497 slub_min_order= [MM, SLUB]
3498 Determines the minimum page order for slabs. Must be
3499 lower than slub_max_order.
3500 For more information see Documentation/vm/slub.txt.
3502 slub_nomerge [MM, SLUB]
3503 Same with slab_nomerge. This is supported for legacy.
3504 See slab_nomerge for more information.
3507 Format: <io1>[,<io2>[,...,<io8>]]
3509 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3510 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3511 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3512 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3513 smsc-ircc2.ircc_irq= [HW] IRQ line
3514 smsc-ircc2.ircc_dma= [HW] DMA channel
3515 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3516 0: Toshiba Satellite 1800 (GP data pin select)
3517 1: Fast pin select (default)
3521 [KNL] Should the soft-lockup detector generate panics.
3524 softlockup_all_cpu_backtrace=
3525 [KNL] Should the soft-lockup detector generate
3526 backtraces on all cpus.
3529 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3530 See Documentation/laptops/sonypi.txt
3532 spia_io_base= [HW,MTD]
3538 Enabled the stack tracer on boot up.
3540 stacktrace_filter=[function-list]
3541 [FTRACE] Limit the functions that the stack tracer
3542 will trace at boot up. function-list is a comma separated
3543 list of functions. This list can be changed at run
3544 time by the stack_trace_filter file in the debugfs
3545 tracing directory. Note, this enables stack tracing
3546 and the stacktrace above is not needed.
3550 Set the STI (builtin display/keyboard on the HP-PARISC
3551 machines) console (graphic card) which should be used
3552 as the initial boot-console.
3553 See also comment in drivers/video/console/sticore.c.
3556 See comment in drivers/video/console/sticore.c.
3559 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3561 sunrpc.min_resvport=
3562 sunrpc.max_resvport=
3564 SunRPC servers often require that client requests
3565 originate from a privileged port (i.e. a port in the
3566 range 0 < portnr < 1024).
3567 An administrator who wishes to reserve some of these
3568 ports for other uses may adjust the range that the
3569 kernel's sunrpc client considers to be privileged
3570 using these two parameters to set the minimum and
3571 maximum port values.
3575 Control how the NFS server code allocates CPUs to
3576 service thread pools. Depending on how many NICs
3577 you have and where their interrupts are bound, this
3578 option will affect which CPUs will do NFS serving.
3579 Note: this parameter cannot be changed while the
3580 NFS server is running.
3582 auto the server chooses an appropriate mode
3583 automatically using heuristics
3584 global a single global pool contains all CPUs
3585 percpu one pool for each CPU
3586 pernode one pool for each NUMA node (equivalent
3587 to global on non-NUMA machines)
3589 sunrpc.tcp_slot_table_entries=
3590 sunrpc.udp_slot_table_entries=
3592 Sets the upper limit on the number of simultaneous
3593 RPC calls that can be sent from the client to a
3594 server. Increasing these values may allow you to
3595 improve throughput, but will also increase the
3596 amount of memory reserved for use by the client.
3598 suspend.pm_test_delay=
3600 Sets the number of seconds to remain in a suspend test
3601 mode before resuming the system (see
3602 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3603 is set. Default value is 5.
3606 [KNL] Enable accounting of swap in memory resource
3607 controller if no parameter or 1 is given or disable
3608 it if 0 is given (See Documentation/cgroups/memory.txt)
3610 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3611 Format: { <int> | force }
3612 <int> -- Number of I/O TLB slabs
3613 force -- force using of bounce buffers even if they
3614 wouldn't be automatically used by the kernel
3618 sysfs.deprecated=0|1 [KNL]
3619 Enable/disable old style sysfs layout for old udev
3620 on older distributions. When this option is enabled
3621 very new udev will not work anymore. When this option
3622 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3623 in older udev will not work anymore.
3624 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3625 the kernel configuration.
3627 sysrq_always_enabled
3629 Ignore sysrq setting - this boot parameter will
3630 neutralize any effect of /proc/sys/kernel/sysrq.
3631 Useful for debugging.
3633 tcpmhash_entries= [KNL,NET]
3634 Set the number of tcp_metrics_hash slots.
3635 Default value is 8192 or 16384 depending on total
3636 ram pages. This is used to specify the TCP metrics
3637 cache size. See Documentation/networking/ip-sysctl.txt
3638 "tcp_no_metrics_save" section for more details.
3642 test_suspend= [SUSPEND][,N]
3643 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3644 standby suspend) or "freeze" (for suspend type freeze)
3645 as the system sleep state during system startup with
3646 the optional capability to repeat N number of times.
3647 The system is woken from this state using a
3648 wakeup-capable RTC alarm.
3650 thash_entries= [KNL,NET]
3651 Set number of hash buckets for TCP connection
3653 thermal.act= [HW,ACPI]
3654 -1: disable all active trip points in all thermal zones
3655 <degrees C>: override all lowest active trip points
3657 thermal.crt= [HW,ACPI]
3658 -1: disable all critical trip points in all thermal zones
3659 <degrees C>: override all critical trip points
3661 thermal.nocrt= [HW,ACPI]
3662 Set to disable actions on ACPI thermal zone
3663 critical and hot trip points.
3665 thermal.off= [HW,ACPI]
3666 1: disable ACPI thermal control
3668 thermal.psv= [HW,ACPI]
3669 -1: disable all passive trip points
3670 <degrees C>: override all passive trip points to this
3673 thermal.tzp= [HW,ACPI]
3674 Specify global default ACPI thermal zone polling rate
3675 <deci-seconds>: poll all this frequency
3676 0: no polling (default)
3679 Force threading of all interrupt handlers except those
3680 marked explicitly IRQF_NO_THREAD.
3683 Enable the Transcendent memory driver if built-in.
3685 tmem.cleancache=0|1 [KNL, XEN]
3686 Default is on (1). Disable the usage of the cleancache
3687 API to send anonymous pages to the hypervisor.
3689 tmem.frontswap=0|1 [KNL, XEN]
3690 Default is on (1). Disable the usage of the frontswap
3691 API to send swap pages to the hypervisor. If disabled
3692 the selfballooning and selfshrinking are force disabled.
3694 tmem.selfballooning=0|1 [KNL, XEN]
3695 Default is on (1). Disable the driving of swap pages
3698 tmem.selfshrinking=0|1 [KNL, XEN]
3699 Default is on (1). Partial swapoff that immediately
3700 transfers pages from Xen hypervisor back to the
3701 kernel based on different criteria.
3705 Specify if the kernel should make use of the cpu
3706 topology information if the hardware supports this.
3707 The scheduler will make use of this information and
3708 e.g. base its process migration decisions on it.
3711 topology_updates= [KNL, PPC, NUMA]
3713 Specify if the kernel should ignore (off)
3714 topology updates sent by the hypervisor to this
3719 tpm_suspend_pcr=[HW,TPM]
3720 Format: integer pcr id
3721 Specify that at suspend time, the tpm driver
3722 should extend the specified pcr with zeros,
3723 as a workaround for some chips which fail to
3724 flush the last written pcr on TPM_SaveState.
3725 This will guarantee that all the other pcrs
3728 trace_buf_size=nn[KMG]
3729 [FTRACE] will set tracing buffer size on each cpu.
3731 trace_event=[event-list]
3732 [FTRACE] Set and start specified trace events in order
3733 to facilitate early boot debugging.
3734 See also Documentation/trace/events.txt
3736 trace_options=[option-list]
3737 [FTRACE] Enable or disable tracer options at boot.
3738 The option-list is a comma delimited list of options
3739 that can be enabled or disabled just as if you were
3740 to echo the option name into
3742 /sys/kernel/debug/tracing/trace_options
3744 For example, to enable stacktrace option (to dump the
3745 stack trace of each event), add to the command line:
3747 trace_options=stacktrace
3749 See also Documentation/trace/ftrace.txt "trace options"
3753 Have the tracepoints sent to printk as well as the
3754 tracing ring buffer. This is useful for early boot up
3755 where the system hangs or reboots and does not give the
3756 option for reading the tracing buffer or performing a
3757 ftrace_dump_on_oops.
3759 To turn off having tracepoints sent to printk,
3760 echo 0 > /proc/sys/kernel/tracepoint_printk
3761 Note, echoing 1 into this file without the
3762 tracepoint_printk kernel cmdline option has no effect.
3766 Having tracepoints sent to printk() and activating high
3767 frequency tracepoints such as irq or sched, can cause
3768 the system to live lock.
3771 [FTRACE] enable this option to disable tracing when a
3772 warning is hit. This turns off "tracing_on". Tracing can
3773 be enabled again by echoing '1' into the "tracing_on"
3774 file located in /sys/kernel/debug/tracing/
3776 This option is useful, as it disables the trace before
3777 the WARNING dump is called, which prevents the trace to
3778 be filled with content caused by the warning output.
3780 This option can also be set at run time via the sysctl
3781 option: kernel/traceoff_on_warning
3783 transparent_hugepage=
3785 Format: [always|madvise|never]
3786 Can be used to control the default behavior of the system
3787 with respect to transparent hugepages.
3788 See Documentation/vm/transhuge.txt for more details.
3790 tsc= Disable clocksource stability checks for TSC.
3792 [x86] reliable: mark tsc clocksource as reliable, this
3793 disables clocksource verification at runtime, as well
3794 as the stability checks done at bootup. Used to enable
3795 high-resolution timer mode on older hardware, and in
3796 virtualized environment.
3797 [x86] noirqtime: Do not use TSC to do irq accounting.
3798 Used to run time disable IRQ_TIME_ACCOUNTING on any
3799 platforms where RDTSC is slow and this accounting
3802 turbografx.map[2|3]= [HW,JOY]
3803 TurboGraFX parallel port interface
3805 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3806 See also Documentation/input/joystick-parport.txt
3808 udbg-immortal [PPC] When debugging early kernel crashes that
3809 happen after console_init() and before a proper
3810 console driver takes over, this boot options might
3811 help "seeing" what's going on.
3813 uhash_entries= [KNL,NET]
3814 Set number of hash buckets for UDP/UDP-Lite connections
3817 [USB] Ignore overcurrent events (default N).
3818 Some badly-designed motherboards generate lots of
3819 bogus events, for ports that aren't wired to
3820 anything. Set this parameter to avoid log spamming.
3821 Note that genuine overcurrent events won't be
3825 [X86] Cause panic on unknown NMI.
3827 usbcore.authorized_default=
3828 [USB] Default USB device authorization:
3829 (default -1 = authorized except for wireless USB,
3830 0 = not authorized, 1 = authorized)
3832 usbcore.autosuspend=
3833 [USB] The autosuspend time delay (in seconds) used
3834 for newly-detected USB devices (default 2). This
3835 is the time required before an idle device will be
3836 autosuspended. Devices for which the delay is set
3837 to a negative value won't be autosuspended at all.
3839 usbcore.usbfs_snoop=
3840 [USB] Set to log all usbfs traffic (default 0 = off).
3842 usbcore.blinkenlights=
3843 [USB] Set to cycle leds on hubs (default 0 = off).
3845 usbcore.old_scheme_first=
3846 [USB] Start with the old device initialization
3847 scheme (default 0 = off).
3849 usbcore.usbfs_memory_mb=
3850 [USB] Memory limit (in MB) for buffers allocated by
3851 usbfs (default = 16, 0 = max = 2047).
3853 usbcore.use_both_schemes=
3854 [USB] Try the other device initialization scheme
3855 if the first one fails (default 1 = enabled).
3857 usbcore.initial_descriptor_timeout=
3858 [USB] Specifies timeout for the initial 64-byte
3859 USB_REQ_GET_DESCRIPTOR request in milliseconds
3860 (default 5000 = 5.0 seconds).
3863 [USBHID] The interval which mice are to be polled at.
3865 usb-storage.delay_use=
3866 [UMS] The delay in seconds before a new device is
3867 scanned for Logical Units (default 1).
3870 [UMS] A list of quirks entries to supplement or
3871 override the built-in unusual_devs list. List
3872 entries are separated by commas. Each entry has
3873 the form VID:PID:Flags where VID and PID are Vendor
3874 and Product ID values (4-digit hex numbers) and
3875 Flags is a set of characters, each corresponding
3876 to a common usb-storage quirk flag as follows:
3877 a = SANE_SENSE (collect more than 18 bytes
3879 b = BAD_SENSE (don't collect more than 18
3880 bytes of sense data);
3881 c = FIX_CAPACITY (decrease the reported
3882 device capacity by one sector);
3883 d = NO_READ_DISC_INFO (don't use
3884 READ_DISC_INFO command);
3885 e = NO_READ_CAPACITY_16 (don't use
3886 READ_CAPACITY_16 command);
3887 f = NO_REPORT_OPCODES (don't use report opcodes
3889 g = MAX_SECTORS_240 (don't transfer more than
3890 240 sectors at a time, uas only);
3891 h = CAPACITY_HEURISTICS (decrease the
3892 reported device capacity by one
3893 sector if the number is odd);
3894 i = IGNORE_DEVICE (don't bind to this
3896 l = NOT_LOCKABLE (don't try to lock and
3897 unlock ejectable media);
3898 m = MAX_SECTORS_64 (don't transfer more
3899 than 64 sectors = 32 KB at a time);
3900 n = INITIAL_READ10 (force a retry of the
3901 initial READ(10) command);
3902 o = CAPACITY_OK (accept the capacity
3903 reported by the device);
3904 p = WRITE_CACHE (the device cache is ON
3906 r = IGNORE_RESIDUE (the device reports
3907 bogus residue values);
3908 s = SINGLE_LUN (the device has only one
3910 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3911 commands, uas only);
3912 u = IGNORE_UAS (don't bind to the uas driver);
3913 w = NO_WP_DETECT (don't test whether the
3914 medium is write-protected).
3915 Example: quirks=0419:aaf5:rl,0421:0433:rc
3917 user_debug= [KNL,ARM]
3919 See arch/arm/Kconfig.debug help text.
3920 1 - undefined instruction events
3922 4 - invalid data aborts
3925 Example: user_debug=31
3928 [X86] Flags controlling user PTE allocations.
3930 nohigh = do not allocate PTE pages in
3931 HIGHMEM regardless of setting
3935 On X86_32, this is an alias for vdso32=. Otherwise:
3937 vdso=1: enable VDSO (the default)
3938 vdso=0: disable VDSO mapping
3940 vdso32= [X86] Control the 32-bit vDSO
3941 vdso32=1: enable 32-bit VDSO
3942 vdso32=0 or vdso32=2: disable 32-bit VDSO
3944 See the help text for CONFIG_COMPAT_VDSO for more
3945 details. If CONFIG_COMPAT_VDSO is set, the default is
3946 vdso32=0; otherwise, the default is vdso32=1.
3948 For compatibility with older kernels, vdso32=2 is an
3951 Try vdso32=0 if you encounter an error that says:
3952 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3955 vector=percpu: enable percpu vector domain
3957 video= [FB] Frame buffer configuration
3958 See Documentation/fb/modedb.txt.
3960 video.brightness_switch_enabled= [0,1]
3961 If set to 1, on receiving an ACPI notify event
3962 generated by hotkey, video driver will adjust brightness
3963 level and then send out the event to user space through
3964 the allocated input device; If set to 0, video driver
3965 will only send out the event without touching backlight
3970 [VMMIO] Memory mapped virtio (platform) device.
3972 <size>@<baseaddr>:<irq>[:<id>]
3974 <size> := size (can use standard suffixes
3976 <baseaddr> := physical base address
3977 <irq> := interrupt number (as passed to
3979 <id> := (optional) platform device id
3981 virtio_mmio.device=1K@0x100b0000:48:7
3983 Can be used multiple times for multiple devices.
3985 vga= [BOOT,X86-32] Select a particular video mode
3986 See Documentation/x86/boot.txt and
3987 Documentation/svga.txt.
3988 Use vga=ask for menu.
3989 This is actually a boot loader parameter; the value is
3990 passed to the kernel using a special protocol.
3992 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3993 size of <nn>. This can be used to increase the
3994 minimum size (128MB on x86). It can also be used to
3995 decrease the size and leave more room for directly
3998 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4001 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4004 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4008 Controls the behavior of vsyscalls (i.e. calls to
4009 fixed addresses of 0xffffffffff600x00 from legacy
4010 code). Most statically-linked binaries and older
4011 versions of glibc use these calls. Because these
4012 functions are at fixed addresses, they make nice
4013 targets for exploits that can control RIP.
4015 emulate [default] Vsyscalls turn into traps and are
4016 emulated reasonably safely.
4018 native Vsyscalls are native syscall instructions.
4019 This is a little bit faster than trapping
4020 and makes a few dynamic recompilers work
4021 better than they would in emulation mode.
4022 It also makes exploits much easier to write.
4024 none Vsyscalls don't work at all. This makes
4025 them quite hard to use for exploits but
4026 might break your system.
4028 vt.color= [VT] Default text color.
4029 Format: 0xYX, X = foreground, Y = background.
4030 Default: 0x07 = light gray on black.
4032 vt.cur_default= [VT] Default cursor shape.
4033 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4034 the parameters of the <Esc>[?A;B;Cc escape sequence;
4035 see VGA-softcursor.txt. Default: 2 = underline.
4037 vt.default_blu= [VT]
4038 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4039 Change the default blue palette of the console.
4040 This is a 16-member array composed of values
4043 vt.default_grn= [VT]
4044 Format: <green0>,<green1>,<green2>,...,<green15>
4045 Change the default green palette of the console.
4046 This is a 16-member array composed of values
4049 vt.default_red= [VT]
4050 Format: <red0>,<red1>,<red2>,...,<red15>
4051 Change the default red palette of the console.
4052 This is a 16-member array composed of values
4058 Set system-wide default UTF-8 mode for all tty's.
4059 Default is 1, i.e. UTF-8 mode is enabled for all
4060 newly opened terminals.
4062 vt.global_cursor_default=
4065 Set system-wide default for whether a cursor
4066 is shown on new VTs. Default is -1,
4067 i.e. cursors will be created by default unless
4068 overridden by individual drivers. 0 will hide
4069 cursors, 1 will display them.
4071 vt.italic= [VT] Default color for italic text; 0-15.
4074 vt.underline= [VT] Default color for underlined text; 0-15.
4077 watchdog timers [HW,WDT] For information on watchdog timers,
4078 see Documentation/watchdog/watchdog-parameters.txt
4079 or other driver-specific files in the
4080 Documentation/watchdog/ directory.
4082 workqueue.disable_numa
4083 By default, all work items queued to unbound
4084 workqueues are affine to the NUMA nodes they're
4085 issued on, which results in better behavior in
4086 general. If NUMA affinity needs to be disabled for
4087 whatever reason, this option can be used. Note
4088 that this also can be controlled per-workqueue for
4089 workqueues visible under /sys/bus/workqueue/.
4091 workqueue.power_efficient
4092 Per-cpu workqueues are generally preferred because
4093 they show better performance thanks to cache
4094 locality; unfortunately, per-cpu workqueues tend to
4095 be more power hungry than unbound workqueues.
4097 Enabling this makes the per-cpu workqueues which
4098 were observed to contribute significantly to power
4099 consumption unbound, leading to measurably lower
4100 power usage at the cost of small performance
4103 The default value of this parameter is determined by
4104 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4106 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4107 default x2apic cluster mode on platforms
4110 x86_intel_mid_timer= [X86-32,APBT]
4111 Choose timer option for x86 Intel MID platform.
4112 Two valid options are apbt timer only and lapic timer
4113 plus one apbt timer for broadcast timer.
4114 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4116 xen_512gb_limit [KNL,X86-64,XEN]
4117 Restricts the kernel running paravirtualized under Xen
4118 to use only up to 512 GB of RAM. The reason to do so is
4119 crash analysis tools and Xen tools for doing domain
4120 save/restore/migration must be enabled to handle larger
4123 xen_emul_unplug= [HW,X86,XEN]
4124 Unplug Xen emulated devices
4125 Format: [unplug0,][unplug1]
4126 ide-disks -- unplug primary master IDE devices
4127 aux-ide-disks -- unplug non-primary-master IDE devices
4128 nics -- unplug network devices
4129 all -- unplug all emulated devices (NICs and IDE disks)
4130 unnecessary -- unplugging emulated devices is
4131 unnecessary even if the host did not respond to
4133 never -- do not unplug even if version check succeeds
4135 xen_nopvspin [X86,XEN]
4136 Disables the ticketlock slowpath using Xen PV
4140 Disables the PV optimizations forcing the HVM guest to
4141 run as generic HVM guest with no PV drivers.
4143 xirc2ps_cs= [NET,PCMCIA]
4145 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4147 ______________________________________________________________________
4151 Add more DRM drivers.