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>
934 Broken monitors, graphic adapters and KVMs may
935 send no or incorrect EDID data sets. This parameter
936 allows to specify an EDID data set in the
937 /lib/firmware directory that is 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
950 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
951 module.dyndbg[="val"]
952 Enable debug messages at boot time. See
953 Documentation/dynamic-debug-howto.txt for details.
955 nompx [X86] Disables Intel Memory Protection Extensions.
956 See Documentation/x86/intel_mpx.txt for more
957 information about the feature.
960 on enable eager fpu restore
961 off disable eager fpu restore
962 auto selects the default scheme, which automatically
963 enables eagerfpu restore for xsaveopt.
965 module.async_probe [KNL]
966 Enable asynchronous probe on this module.
968 early_ioremap_debug [KNL]
969 Enable debug messages in early_ioremap support. This
970 is useful for tracking down temporary early mappings
971 which are not unmapped.
973 earlycon= [KNL] Output early console device and options.
976 Start an early, polled-mode console on a cadence serial
977 port at the specified address. The cadence serial port
978 must already be setup and configured. Options are not
981 uart[8250],io,<addr>[,options]
982 uart[8250],mmio,<addr>[,options]
983 uart[8250],mmio32,<addr>[,options]
984 uart[8250],mmio32be,<addr>[,options]
985 uart[8250],0x<addr>[,options]
986 Start an early, polled-mode console on the 8250/16550
987 UART at the specified I/O port or MMIO address.
988 MMIO inter-register address stride is either 8-bit
989 (mmio) or 32-bit (mmio32 or mmio32be).
990 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
991 to be equivalent to 'mmio'. 'options' are specified
992 in the same format described for "console=ttyS<n>"; if
993 unspecified, the h/w is not initialized.
996 Start an early, polled-mode console on a pl011 serial
997 port at the specified address. The pl011 serial port
998 must already be setup and configured. Options are not
1002 Start an early, polled-mode console on an msm serial
1003 port at the specified address. The serial port
1004 must already be setup and configured. Options are not
1007 msm_serial_dm,<addr>
1008 Start an early, polled-mode console on an msm serial
1009 dm port at the specified address. The serial port
1010 must already be setup and configured. Options are not
1013 smh Use ARM semihosting calls for early console.
1021 Use early console provided by serial driver available
1022 on Samsung SoCs, requires selecting proper type and
1023 a correct base address of the selected UART port. The
1024 serial port must already be setup and configured.
1025 Options are not yet supported.
1027 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1031 earlyprintk=serial[,ttySn[,baudrate]]
1032 earlyprintk=serial[,0x...[,baudrate]]
1033 earlyprintk=ttySn[,baudrate]
1034 earlyprintk=dbgp[debugController#]
1035 earlyprintk=pciserial,bus:device.function[,baudrate]
1037 earlyprintk is useful when the kernel crashes before
1038 the normal console is initialized. It is not enabled by
1039 default because it has some cosmetic problems.
1041 Append ",keep" to not disable it when the real console
1044 Only one of vga, efi, serial, or usb debug port can
1047 Currently only ttyS0 and ttyS1 may be specified by
1048 name. Other I/O ports may be explicitly specified
1049 on some architectures (x86 and arm at least) by
1050 replacing ttySn with an I/O port address, like this:
1051 earlyprintk=serial,0x1008,115200
1052 You can find the port for a given device in
1053 /proc/tty/driver/serial:
1054 2: uart:ST16650V2 port:00001008 irq:18 ...
1056 Interaction with the standard serial driver is not
1059 The VGA and EFI output is eventually overwritten by
1062 The xen output can only be used by Xen PV guests.
1064 edac_report= [HW,EDAC] Control how to report EDAC event
1065 Format: {"on" | "off" | "force"}
1066 on: enable EDAC to report H/W event. May be overridden
1067 by other higher priority error reporting module.
1068 off: disable H/W event reporting through EDAC.
1069 force: enforce the use of EDAC to report H/W event.
1072 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1075 This is designed to be used in conjunction with
1076 the boot argument: earlyprintk=vga
1079 Format: {"off" | "on" | "skip[mbr]"}
1082 Format: { "old_map", "nochunk", "noruntime", "debug" }
1083 old_map [X86-64]: switch to the old ioremap-based EFI
1084 runtime services mapping. 32-bit still uses this one by
1086 nochunk: disable reading files in "chunks" in the EFI
1087 boot stub, as chunking can cause problems with some
1088 firmware implementations.
1089 noruntime : disable EFI runtime services support
1090 debug: enable misc debug output
1092 efi_no_storage_paranoia [EFI; X86]
1093 Using this parameter you can use more than 50% of
1094 your efi variable storage. Use this parameter only if
1095 you are really sure that your UEFI does sane gc and
1096 fulfills the spec otherwise your board may brick.
1098 eisa_irq_edge= [PARISC,HW]
1099 See header of drivers/parisc/eisa.c.
1102 See comment before function elanfreq_setup() in
1103 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1106 Format: {"cfq" | "deadline" | "noop"}
1107 See Documentation/block/cfq-iosched.txt and
1108 Documentation/block/deadline-iosched.txt for details.
1110 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1111 Specifies physical address of start of kernel core
1112 image elf header and optionally the size. Generally
1113 kexec loader will pass this option to capture kernel.
1114 See Documentation/kdump/kdump.txt for details.
1116 enable_mtrr_cleanup [X86]
1117 The kernel tries to adjust MTRR layout from continuous
1118 to discrete, to make X server driver able to add WB
1119 entry later. This parameter enables that.
1121 enable_timer_pin_1 [X86]
1122 Enable PIN 1 of APIC timer
1123 Can be useful to work around chipset bugs
1124 (in particular on some ATI chipsets).
1125 The kernel tries to set a reasonable default.
1127 enforcing [SELINUX] Set initial enforcing status.
1129 See security/selinux/Kconfig help text.
1130 0 -- permissive (log only, no denials).
1131 1 -- enforcing (deny and log).
1133 Value can be changed at runtime via /selinux/enforce.
1136 Disable Error Record Serialization Table (ERST)
1139 ether= [HW,NET] Ethernet cards parameters
1140 This option is obsoleted by the "netdev=" option, which
1141 has equivalent usage. See its documentation for details.
1145 Permit 'security.evm' to be updated regardless of
1146 current integrity status.
1150 fail_make_request=[KNL]
1151 General fault injection mechanism.
1152 Format: <interval>,<probability>,<space>,<times>
1153 See also Documentation/fault-injection/.
1156 See Documentation/blockdev/floppy.txt.
1158 force_pal_cache_flush
1159 [IA-64] Avoid check_sal_cache_flush which may hang on
1160 buggy SAL_CACHE_FLUSH implementations. Using this
1161 parameter will force ia64_sal_cache_flush to call
1162 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1165 Forcefully enable Physical Address Extension (PAE).
1166 Many Pentium M systems disable PAE but may have a
1167 functionally usable PAE implementation.
1168 Warning: use of this parameter will taint the kernel
1169 and may cause unknown problems.
1172 [FTRACE] will set and start the specified tracer
1173 as early as possible in order to facilitate early
1176 ftrace_dump_on_oops[=orig_cpu]
1177 [FTRACE] will dump the trace buffers on oops.
1178 If no parameter is passed, ftrace will dump
1179 buffers of all CPUs, but if you pass orig_cpu, it will
1180 dump only the buffer of the CPU that triggered the
1183 ftrace_filter=[function-list]
1184 [FTRACE] Limit the functions traced by the function
1185 tracer at boot up. function-list is a comma separated
1186 list of functions. This list can be changed at run
1187 time by the set_ftrace_filter file in the debugfs
1190 ftrace_notrace=[function-list]
1191 [FTRACE] Do not trace the functions specified in
1192 function-list. This list can be changed at run time
1193 by the set_ftrace_notrace file in the debugfs
1196 ftrace_graph_filter=[function-list]
1197 [FTRACE] Limit the top level callers functions traced
1198 by the function graph tracer at boot up.
1199 function-list is a comma separated list of functions
1200 that can be changed at run time by the
1201 set_graph_function file in the debugfs tracing directory.
1203 ftrace_graph_notrace=[function-list]
1204 [FTRACE] Do not trace from the functions specified in
1205 function-list. This list is a comma separated list of
1206 functions that can be changed at run time by the
1207 set_graph_notrace file in the debugfs tracing directory.
1210 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1211 support via parallel port (up to 5 devices per port)
1212 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1213 See also Documentation/input/joystick-parport.txt
1217 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1221 gcov_persist= [GCOV] When non-zero (default), profiling data for
1222 kernel modules is saved and remains accessible via
1223 debugfs, even when the module is unloaded/reloaded.
1224 When zero, profiling data is discarded and associated
1225 debugfs files are removed at module unload time.
1227 gpt [EFI] Forces disk with valid GPT signature but
1228 invalid Protective MBR to be treated as GPT. If the
1229 primary GPT is corrupted, it enables the backup/alternate
1230 GPT to be used instead.
1232 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1233 the "Enable 0" bit of the configuration register.
1236 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1237 the "Enable 0" bit of the configuration register.
1240 grcan.select= [HW] Select which physical interface to use.
1243 grcan.txsize= [HW] Sets the size of the tx buffer.
1244 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1246 grcan.rxsize= [HW] Sets the size of the rx buffer.
1247 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1250 hashdist= [KNL,NUMA] Large hashes allocated during boot
1251 are distributed across NUMA nodes. Defaults on
1252 for 64-bit NUMA, off otherwise.
1253 Format: 0 | 1 (for off | on)
1255 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1257 hd= [EIDE] (E)IDE hard drive subsystem geometry
1258 Format: <cyl>,<head>,<sect>
1261 Disable Hardware Error Source Table (HEST) support;
1262 corresponding firmware-first mode error processing
1263 logic will be disabled.
1265 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1266 size of <nn>. This works even on boxes that have no
1267 highmem otherwise. This also works to reduce highmem
1268 size on bigger boxes.
1270 highres= [KNL] Enable/disable high resolution timer mode.
1271 Valid parameters: "on", "off"
1275 See Documentation/isdn/README.HiSax.
1279 hpet= [X86-32,HPET] option to control HPET usage
1280 Format: { enable (default) | disable | force |
1282 disable: disable HPET and use PIT instead
1283 force: allow force enabled of undocumented chips (ICH4,
1285 verbose: show contents of HPET registers during setup
1287 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1288 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1290 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1291 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1292 On x86-64 and powerpc, this option can be specified
1293 multiple times interleaved with hugepages= to reserve
1294 huge pages of different sizes. Valid pages sizes on
1295 x86-64 are 2M (when the CPU supports "pse") and 1G
1296 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1298 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1299 terminal devices. Valid values: 0..8
1300 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1301 If specified, z/VM IUCV HVC accepts connections
1302 from listed z/VM user IDs only.
1304 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1305 hardware thread id mappings.
1306 Format: <cpu>:<hwthread>
1309 Do not unregister boot console at start. This is only
1310 useful for debugging when something happens in the window
1311 between unregistering the boot console and initializing
1314 i2c_bus= [HW] Override the default board specific I2C bus speed
1315 or register an additional I2C bus that is not
1316 registered from board initialization code.
1320 i8042.debug [HW] Toggle i8042 debug mode
1321 i8042.unmask_kbd_data
1322 [HW] Enable printing of interrupt data from the KBD port
1323 (disabled by default, and as a pre-condition
1324 requires that i8042.debug=1 be enabled)
1325 i8042.direct [HW] Put keyboard port into non-translated mode
1326 i8042.dumbkbd [HW] Pretend that controller can only read data from
1327 keyboard and cannot control its state
1328 (Don't attempt to blink the leds)
1329 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1330 i8042.nokbd [HW] Don't check/create keyboard port
1331 i8042.noloop [HW] Disable the AUX Loopback command while probing
1333 i8042.nomux [HW] Don't check presence of an active multiplexing
1335 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1337 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1338 i8042.reset [HW] Reset the controller during init and cleanup
1339 i8042.unlock [HW] Unlock (ignore) the keylock
1340 i8042.kbdreset [HW] Reset device connected to KBD port
1344 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1345 indicates that the driver is running on unsupported
1347 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1348 does not match list of supported models.
1350 [HW] Report power status in /proc/i8k
1351 (disabled by default)
1352 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1355 i915.invert_brightness=
1356 [DRM] Invert the sense of the variable that is used to
1357 set the brightness of the panel backlight. Normally a
1358 brightness value of 0 indicates backlight switched off,
1359 and the maximum of the brightness value sets the backlight
1360 to maximum brightness. If this parameter is set to 0
1361 (default) and the machine requires it, or this parameter
1362 is set to 1, a brightness value of 0 sets the backlight
1363 to maximum brightness, and the maximum of the brightness
1364 value switches the backlight off.
1365 -1 -- never invert brightness
1366 0 -- machine default
1367 1 -- force brightness inversion
1370 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1372 ide-core.nodma= [HW] (E)IDE subsystem
1373 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1374 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1375 .cdrom .chs .ignore_cable are additional options
1376 See Documentation/ide/ide.txt.
1378 ide-generic.probe-mask= [HW] (E)IDE subsystem
1380 Probe mask for legacy ISA IDE ports. Depending on
1381 platform up to 6 ports are supported, enabled by
1382 setting corresponding bits in the mask to 1. The
1383 default value is 0x0, which has a special meaning.
1384 On systems that have PCI, it triggers scanning the
1385 PCI bus for the first and the second port, which
1386 are then probed. On systems without PCI the value
1387 of 0x0 enables probing the two first ports as if it
1390 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1391 Claim all unknown PCI IDE storage controllers.
1394 Format: idle=poll, idle=halt, idle=nomwait
1395 Poll forces a polling idle loop that can slightly
1396 improve the performance of waking up a idle CPU, but
1397 will use a lot of power and make the system run hot.
1399 idle=halt: Halt is forced to be used for CPU idle.
1400 In such case C2/C3 won't be used again.
1401 idle=nomwait: Disable mwait for CPU C-states
1403 ignore_loglevel [KNL]
1404 Ignore loglevel setting - this will print /all/
1405 kernel messages to the console. Useful for debugging.
1406 We also add it as printk module parameter, so users
1407 could change it dynamically, usually by
1408 /sys/module/printk/parameters/ignore_loglevel.
1410 ihash_entries= [KNL]
1411 Set number of hash buckets for inode cache.
1413 ima_appraise= [IMA] appraise integrity measurements
1414 Format: { "off" | "enforce" | "fix" | "log" }
1417 ima_appraise_tcb [IMA]
1418 The builtin appraise policy appraises all files
1422 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1426 The list of supported hash algorithms is defined
1427 in crypto/hash_info.h.
1430 The builtin measurement policy to load during IMA
1431 setup. Specyfing "tcb" as the value, measures all
1432 programs exec'd, files mmap'd for exec, and all files
1433 opened with the read mode bit set by either the
1434 effective uid (euid=0) or uid=0.
1437 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1438 Load a policy which meets the needs of the Trusted
1439 Computing Base. This means IMA will measure all
1440 programs exec'd, files mmap'd for exec, and all files
1441 opened for read by uid=0.
1444 Select one of defined IMA measurements template formats.
1445 Formats: { "ima" | "ima-ng" | "ima-sig" }
1449 [IMA] Define a custom template format.
1450 Format: { "field1|...|fieldN" }
1452 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1453 Format: <min_file_size>
1454 Set the minimal file size for using asynchronous hash.
1455 If left unspecified, ahash usage is disabled.
1457 ahash performance varies for different data sizes on
1458 different crypto accelerators. This option can be used
1459 to achieve the best performance for a particular HW.
1461 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1463 Set hashing buffer size. Default: 4k.
1465 ahash performance varies for different chunk sizes on
1466 different crypto accelerators. This option can be used
1467 to achieve best performance for particular HW.
1471 Run specified binary instead of /sbin/init as init
1474 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1475 for working out where the kernel is dying during
1478 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1479 initcall functions. Useful for debugging built-in
1480 modules and initcalls.
1482 initrd= [BOOT] Specify the location of the initial ramdisk
1484 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1487 int_pln_enable [x86] Enable power limit notification interrupt
1489 integrity_audit=[IMA]
1490 Format: { "0" | "1" }
1491 0 -- basic integrity auditing messages. (Default)
1492 1 -- additional integrity auditing messages.
1494 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1496 Enable intel iommu driver.
1498 Disable intel iommu driver.
1499 igfx_off [Default Off]
1500 By default, gfx is mapped as normal device. If a gfx
1501 device has a dedicated DMAR unit, the DMAR unit is
1502 bypassed by not enabling DMAR with this option. In
1503 this case, gfx device will use physical address for
1506 With this option iommu will not optimize to look
1507 for io virtual address below 32-bit forcing dual
1508 address cycle on pci bus for cards supporting greater
1509 than 32-bit addressing. The default is to look
1510 for translation below 32-bit and if not available
1511 then look in the higher range.
1512 strict [Default Off]
1513 With this option on every unmap_single operation will
1514 result in a hardware IOTLB flush operation as opposed
1515 to batching them for performance.
1516 sp_off [Default Off]
1517 By default, super page will be supported if Intel IOMMU
1518 has the capability. With this option, super page will
1520 ecs_off [Default Off]
1521 By default, extended context tables will be supported if
1522 the hardware advertises that it has support both for the
1523 extended tables themselves, and also PASID support. With
1524 this option set, extended tables will not be used even
1525 on hardware which claims to support them.
1527 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1528 0 disables intel_idle and fall back on acpi_idle.
1529 1 to 6 specify maximum depth of C-state.
1533 Do not enable intel_pstate as the default
1534 scaling driver for the supported processors
1536 Enable intel_pstate on systems that prohibit it by default
1537 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1538 instead of acpi-cpufreq may disable platform features, such
1539 as thermal controls and power capping, that rely on ACPI
1540 P-States information being indicated to OSPM and therefore
1541 should be used with caution. This option does not work with
1542 processors that aren't supported by the intel_pstate driver
1543 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1545 Do not enable hardware P state control (HWP)
1548 Only load intel_pstate on systems which support
1549 hardware P state control (HWP) if available.
1551 intremap= [X86-64, Intel-IOMMU]
1552 on enable Interrupt Remapping (default)
1553 off disable Interrupt Remapping
1554 nosid disable Source ID checking
1556 BIOS x2APIC opt-out request will be ignored
1558 iomem= Disable strict checking of access to MMIO memory
1559 strict regions from userspace.
1574 nobypass [PPC/POWERNV]
1575 Disable IOMMU bypass, using IOMMU for PCI devices.
1578 io7= [HW] IO7 for Marvel based alpha systems
1579 See comment before marvel_specify_io7 in
1580 arch/alpha/kernel/core_marvel.c.
1582 io_delay= [X86] I/O delay method
1584 Standard port 0x80 based delay
1586 Alternate port 0xed based delay (needed on some systems)
1588 Simple two microseconds delay
1593 See Documentation/filesystems/nfs/nfsroot.txt.
1596 When an interrupt is not handled search all handlers
1597 for it. Intended to get systems with badly broken
1601 When an interrupt is not handled search all handlers
1602 for it. Also check all handlers each timer
1603 interrupt. Intended to get systems with badly broken
1607 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1609 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1611 <cpu number>,...,<cpu number>
1613 <cpu number>-<cpu number>
1614 (must be a positive range in ascending order)
1616 <cpu number>,...,<cpu number>-<cpu number>
1618 This option can be used to specify one or more CPUs
1619 to isolate from the general SMP balancing and scheduling
1620 algorithms. You can move a process onto or off an
1621 "isolated" CPU via the CPU affinity syscalls or cpuset.
1622 <cpu number> begins at 0 and the maximum value is
1623 "number of CPUs in system - 1".
1625 This option is the preferred way to isolate CPUs. The
1626 alternative -- manually setting the CPU mask of all
1627 tasks in the system -- can cause problems and
1628 suboptimal load balancer performance.
1632 ivrs_ioapic [HW,X86_64]
1633 Provide an override to the IOAPIC-ID<->DEVICE-ID
1634 mapping provided in the IVRS ACPI table. For
1635 example, to map IOAPIC-ID decimal 10 to
1636 PCI device 00:14.0 write the parameter as:
1637 ivrs_ioapic[10]=00:14.0
1639 ivrs_hpet [HW,X86_64]
1640 Provide an override to the HPET-ID<->DEVICE-ID
1641 mapping provided in the IVRS ACPI table. For
1642 example, to map HPET-ID decimal 0 to
1643 PCI device 00:14.0 write the parameter as:
1644 ivrs_hpet[0]=00:14.0
1646 js= [HW,JOY] Analog joystick
1647 See Documentation/input/joystick.txt.
1650 Enable/disable kernel and module base offset ASLR
1651 (Address Space Layout Randomization) if built into
1652 the kernel. When CONFIG_HIBERNATION is selected,
1653 kASLR is disabled by default. When kASLR is enabled,
1654 hibernation will be disabled.
1658 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1659 specifies the amount of memory usable by the kernel
1660 for non-movable allocations. The requested amount is
1661 spread evenly throughout all nodes in the system. The
1662 remaining memory in each node is used for Movable
1663 pages. In the event, a node is too small to have both
1664 kernelcore and Movable pages, kernelcore pages will
1665 take priority and other nodes will have a larger number
1666 of Movable pages. The Movable zone is used for the
1667 allocation of pages that may be reclaimed or moved
1668 by the page migration subsystem. This means that
1669 HugeTLB pages may not be allocated from this zone.
1670 Note that allocations like PTEs-from-HighMem still
1671 use the HighMem zone if it exists, and the Normal
1672 zone if it does not.
1674 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1675 Format: <Controller#>[,poll interval]
1676 The controller # is the number of the ehci usb debug
1677 port as it is probed via PCI. The poll interval is
1678 optional and is the number seconds in between
1679 each poll cycle to the debug port in case you need
1680 the functionality for interrupting the kernel with
1681 gdb or control-c on the dbgp connection. When
1682 not using this parameter you use sysrq-g to break into
1683 the kernel debugger.
1685 kgdboc= [KGDB,HW] kgdb over consoles.
1686 Requires a tty driver that supports console polling,
1687 or a supported polling keyboard driver (non-usb).
1688 Serial only format: <serial_device>[,baud]
1689 keyboard only format: kbd
1690 keyboard and serial format: kbd,<serial_device>[,baud]
1691 Optional Kernel mode setting:
1692 kms, kbd format: kms,kbd
1693 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1695 kgdbwait [KGDB] Stop kernel execution and enter the
1696 kernel debugger at the earliest opportunity.
1698 kmac= [MIPS] korina ethernet MAC address.
1699 Configure the RouterBoard 532 series on-chip
1700 Ethernet adapter MAC address.
1702 kmemleak= [KNL] Boot-time kmemleak enable/disable
1703 Valid arguments: on, off
1705 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1708 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1709 Valid arguments: 0, 1, 2
1710 kmemcheck=0 (disabled)
1711 kmemcheck=1 (enabled)
1712 kmemcheck=2 (one-shot mode)
1713 Default: 2 (one-shot mode)
1715 kstack=N [X86] Print N words from the kernel stack
1718 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1719 Default is 0 (don't ignore, but inject #GP)
1721 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1725 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1726 Default is 1 (enabled)
1728 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1730 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1732 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1733 (virtualized MMU) support on capable Intel chips.
1734 Default is 1 (enabled)
1736 kvm-intel.emulate_invalid_guest_state=
1737 [KVM,Intel] Enable emulation of invalid guest states
1738 Default is 0 (disabled)
1740 kvm-intel.flexpriority=
1741 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1742 Default is 1 (enabled)
1745 [KVM,Intel] Enable VMX nesting (nVMX).
1746 Default is 0 (disabled)
1748 kvm-intel.unrestricted_guest=
1749 [KVM,Intel] Disable unrestricted guest feature
1750 (virtualized real and unpaged mode) on capable
1751 Intel chips. Default is 1 (enabled)
1753 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1754 feature (tagged TLBs) on capable Intel chips.
1755 Default is 1 (enabled)
1761 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1764 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1765 value for LAPIC timer one-shot implementation. Default
1766 back to the programmable timer unit in the LAPIC.
1768 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1771 libata.dma= [LIBATA] DMA control
1772 libata.dma=0 Disable all PATA and SATA DMA
1773 libata.dma=1 PATA and SATA Disk DMA only
1774 libata.dma=2 ATAPI (CDROM) DMA only
1775 libata.dma=4 Compact Flash DMA only
1776 Combinations also work, so libata.dma=3 enables DMA
1777 for disks and CDROMs, but not CFs.
1779 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1780 libata.ignore_hpa=0 keep BIOS limits (default)
1781 libata.ignore_hpa=1 ignore limits, using full disk
1783 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1787 libata.force= [LIBATA] Force configurations. The format is comma
1788 separated list of "[ID:]VAL" where ID is
1789 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1790 matching port, link or device. Basically, it matches
1791 the ATA ID string printed on console by libata. If
1792 the whole ID part is omitted, the last PORT and DEVICE
1793 values are used. If ID hasn't been specified yet, the
1794 configuration applies to all ports, links and devices.
1796 If only DEVICE is omitted, the parameter applies to
1797 the port and all links and devices behind it. DEVICE
1798 number of 0 either selects the first device or the
1799 first fan-out link behind PMP device. It does not
1800 select the host link. DEVICE number of 15 selects the
1801 host link and device attached to it.
1803 The VAL specifies the configuration to force. As long
1804 as there's no ambiguity shortcut notation is allowed.
1805 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1806 The following configurations can be forced.
1808 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1809 Any ID with matching PORT is used.
1811 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1813 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1814 udma[/][16,25,33,44,66,100,133] notation is also
1817 * [no]ncq: Turn on or off NCQ.
1819 * [no]ncqtrim: Turn off queued DSM TRIM.
1821 * nohrst, nosrst, norst: suppress hard, soft
1824 * rstonce: only attempt one reset during
1825 hot-unplug link recovery
1827 * dump_id: dump IDENTIFY data.
1829 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1831 * disable: Disable this device.
1833 If there are multiple matching configurations changing
1834 the same attribute, the last one is used.
1836 memblock=debug [KNL] Enable memblock debug messages.
1838 load_ramdisk= [RAM] List of ramdisks to load from floppy
1839 See Documentation/blockdev/ramdisk.txt.
1841 lockd.nlm_grace_period=P [NFS] Assign grace period.
1844 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1847 lockd.nlm_timeout=T [NFS] Assign timeout value.
1850 lockd.nlm_udpport=M [NFS] Assign UDP port.
1853 locktorture.nreaders_stress= [KNL]
1854 Set the number of locking read-acquisition kthreads.
1855 Defaults to being automatically set based on the
1856 number of online CPUs.
1858 locktorture.nwriters_stress= [KNL]
1859 Set the number of locking write-acquisition kthreads.
1861 locktorture.onoff_holdoff= [KNL]
1862 Set time (s) after boot for CPU-hotplug testing.
1864 locktorture.onoff_interval= [KNL]
1865 Set time (s) between CPU-hotplug operations, or
1866 zero to disable CPU-hotplug testing.
1868 locktorture.shuffle_interval= [KNL]
1869 Set task-shuffle interval (jiffies). Shuffling
1870 tasks allows some CPUs to go into dyntick-idle
1871 mode during the locktorture test.
1873 locktorture.shutdown_secs= [KNL]
1874 Set time (s) after boot system shutdown. This
1875 is useful for hands-off automated testing.
1877 locktorture.stat_interval= [KNL]
1878 Time (s) between statistics printk()s.
1880 locktorture.stutter= [KNL]
1881 Time (s) to stutter testing, for example,
1882 specifying five seconds causes the test to run for
1883 five seconds, wait for five seconds, and so on.
1884 This tests the locking primitive's ability to
1885 transition abruptly to and from idle.
1887 locktorture.torture_runnable= [BOOT]
1888 Start locktorture running at boot time.
1890 locktorture.torture_type= [KNL]
1891 Specify the locking implementation to test.
1893 locktorture.verbose= [KNL]
1894 Enable additional printk() statements.
1896 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1899 loglevel= All Kernel Messages with a loglevel smaller than the
1900 console loglevel will be printed to the console. It can
1901 also be changed with klogd or other programs. The
1902 loglevels are defined as follows:
1904 0 (KERN_EMERG) system is unusable
1905 1 (KERN_ALERT) action must be taken immediately
1906 2 (KERN_CRIT) critical conditions
1907 3 (KERN_ERR) error conditions
1908 4 (KERN_WARNING) warning conditions
1909 5 (KERN_NOTICE) normal but significant condition
1910 6 (KERN_INFO) informational
1911 7 (KERN_DEBUG) debug-level messages
1913 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1914 in bytes. n must be a power of two and greater
1915 than the minimal size. The minimal size is defined
1916 by LOG_BUF_SHIFT kernel config parameter. There is
1917 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1918 that allows to increase the default size depending on
1919 the number of CPUs. See init/Kconfig for more details.
1921 logo.nologo [FB] Disables display of the built-in Linux logo.
1922 This may be used to provide more screen space for
1923 kernel log messages and is useful when debugging
1924 kernel boot problems.
1926 lp=0 [LP] Specify parallel ports to use, e.g,
1927 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1928 lp=reset first parallel port). 'lp=0' disables the
1929 lp=auto printer driver. 'lp=reset' (which can be
1930 specified in addition to the ports) causes
1931 attached printers to be reset. Using
1932 lp=port1,port2,... specifies the parallel ports
1933 to associate lp devices with, starting with
1934 lp0. A port specification may be 'none' to skip
1935 that lp device, or a parport name such as
1936 'parport0'. Specifying 'lp=auto' instead of a
1937 port specification list means that device IDs
1938 from each port should be examined, to see if
1939 an IEEE 1284-compliant printer is attached; if
1940 so, the driver will manage that printer.
1941 See also header of drivers/char/lp.c.
1944 Sets loops_per_jiffy to given constant, thus avoiding
1945 time-consuming boot-time autodetection (up to 250 ms per
1946 CPU). 0 enables autodetection (default). To determine
1947 the correct value for your kernel, boot with normal
1948 autodetection and see what value is printed. Note that
1949 on SMP systems the preset will be applied to all CPUs,
1950 which is likely to cause problems if your CPUs need
1951 significantly divergent settings. An incorrect value
1952 will cause delays in the kernel to be wrong, leading to
1953 unpredictable I/O errors and other breakage. Although
1954 unlikely, in the extreme case this might damage your
1958 Format: <io>,<irq>,<dma>
1960 machvec= [IA-64] Force the use of a particular machine-vector
1961 (machvec) in a generic kernel.
1962 Example: machvec=hpzx1_swiotlb
1964 machtype= [Loongson] Share the same kernel image file between different
1966 Example: machtype=lemote-yeeloong-2f-7inch
1968 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1969 than or equal to this physical address is ignored.
1971 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1972 should make use of. maxcpus=n : n >= 0 limits the
1973 kernel to using 'n' processors. n=0 is a special case,
1974 it is equivalent to "nosmp", which also disables
1977 max_loop= [LOOP] The number of loop block devices that get
1978 (loop.max_loop) unconditionally pre-created at init time. The default
1979 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1980 of statically allocating a predefined number, loop
1981 devices can be requested on-demand with the
1982 /dev/loop-control interface.
1984 mce [X86-32] Machine Check Exception
1986 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1988 md= [HW] RAID subsystems devices and level
1989 See Documentation/md.txt.
1992 Format: <first>,<last>
1993 Specifies range of consoles to be captured by the MDA.
1995 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1996 Amount of memory to be used when the kernel is not able
1997 to see the whole system memory or for test.
1998 [X86] Work as limiting max address. Use together
1999 with memmap= to avoid physical address space collisions.
2000 Without memmap= PCI devices could be placed at addresses
2001 belonging to unused RAM.
2003 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2007 [KNL,SH] Allow user to override the default size for
2008 per-device physically contiguous DMA buffers.
2010 memmap=exactmap [KNL,X86] Enable setting of an exact
2011 E820 memory map, as specified by the user.
2012 Such memmap=exactmap lines can be constructed based on
2013 BIOS output or other requirements. See the memmap=nn@ss
2016 memmap=nn[KMG]@ss[KMG]
2017 [KNL] Force usage of a specific region of memory.
2018 Region of memory to be used is from ss to ss+nn.
2020 memmap=nn[KMG]#ss[KMG]
2021 [KNL,ACPI] Mark specific memory as ACPI data.
2022 Region of memory to be marked is from ss to ss+nn.
2024 memmap=nn[KMG]$ss[KMG]
2025 [KNL,ACPI] Mark specific memory as reserved.
2026 Region of memory to be reserved is from ss to ss+nn.
2027 Example: Exclude memory from 0x18690000-0x1869ffff
2028 memmap=64K$0x18690000
2030 memmap=0x10000$0x18690000
2032 memmap=nn[KMG]!ss[KMG]
2033 [KNL,X86] Mark specific memory as protected.
2034 Region of memory to be used, from ss to ss+nn.
2035 The memory region may be marked as e820 type 12 (0xc)
2036 and is NVDIMM or ADR memory.
2038 memory_corruption_check=0/1 [X86]
2039 Some BIOSes seem to corrupt the first 64k of
2040 memory when doing things like suspend/resume.
2041 Setting this option will scan the memory
2042 looking for corruption. Enabling this will
2043 both detect corruption and prevent the kernel
2044 from using the memory being corrupted.
2045 However, its intended as a diagnostic tool; if
2046 repeatable BIOS-originated corruption always
2047 affects the same memory, you can use memmap=
2048 to prevent the kernel from using that memory.
2050 memory_corruption_check_size=size [X86]
2051 By default it checks for corruption in the low
2052 64k, making this memory unavailable for normal
2053 use. Use this parameter to scan for
2054 corruption in more or less memory.
2056 memory_corruption_check_period=seconds [X86]
2057 By default it checks for corruption every 60
2058 seconds. Use this parameter to check at some
2059 other rate. 0 disables periodic checking.
2061 memtest= [KNL,X86,ARM] Enable memtest
2063 default : 0 <disable>
2064 Specifies the number of memtest passes to be
2065 performed. Each pass selects another test
2066 pattern from a given set of patterns. Memtest
2067 fills the memory with this pattern, validates
2068 memory contents and reserves bad memory
2069 regions that are detected.
2071 meye.*= [HW] Set MotionEye Camera parameters
2072 See Documentation/video4linux/meye.txt.
2074 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2075 Multi-Function General Purpose Timers on AMD Geode
2078 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2079 the BIOS has incorrectly applied a workaround. TinyBIOS
2080 version 0.98 is known to be affected, 0.99 fixes the
2081 problem by letting the user disable the workaround.
2085 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2086 physical address is ignored.
2088 mini2440= [ARM,HW,KNL]
2089 Format:[0..2][b][c][t]
2091 MINI2440 configuration specification:
2092 0 - The attached screen is the 3.5" TFT
2093 1 - The attached screen is the 7" TFT
2094 2 - The VGA Shield is attached (1024x768)
2095 Leaving out the screen size parameter will not load
2096 the TFT driver, and the framebuffer will be left
2098 b - Enable backlight. The TFT backlight pin will be
2099 linked to the kernel VESA blanking code and a GPIO
2100 LED. This parameter is not necessary when using the
2102 c - Enable the s3c camera interface.
2103 t - Reserved for enabling touchscreen support. The
2104 touchscreen support is not enabled in the mainstream
2105 kernel as of 2.6.30, a preliminary port can be found
2106 in the "bleeding edge" mini2440 support kernel at
2107 http://repo.or.cz/w/linux-2.6/mini2440.git
2110 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2111 parameter allows control of the logging verbosity for
2112 the additional memory initialisation checks. A value
2113 of 0 disables mminit logging and a level of 4 will
2114 log everything. Information is printed at KERN_DEBUG
2115 so loglevel=8 may also need to be specified.
2118 [KNL] When CONFIG_MODULE_SIG is set, this means that
2119 modules without (valid) signatures will fail to load.
2120 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2121 is always true, so this option does nothing.
2124 [MOUSE] Maximum time between finger touching and
2125 leaving touchpad surface for touch to be considered
2126 a tap and be reported as a left button click (for
2127 touchpads working in absolute mode only).
2129 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2130 reporting absolute coordinates, such as tablets
2131 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2132 reporting absolute coordinates, such as tablets
2134 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2135 is similar to kernelcore except it specifies the
2136 amount of memory used for migratable allocations.
2137 If both kernelcore and movablecore is specified,
2138 then kernelcore will be at *least* the specified
2139 value but may be more. If movablecore on its own
2140 is specified, the administrator must be careful
2141 that the amount of memory usable for all allocations
2144 movable_node [KNL,X86] Boot-time switch to enable the effects
2145 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2147 MTD_Partition= [MTD]
2148 Format: <name>,<region-number>,<size>,<offset>
2150 MTD_Region= [MTD] Format:
2151 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2154 See drivers/mtd/cmdlinepart.c.
2156 multitce=off [PPC] This parameter disables the use of the pSeries
2157 firmware feature for updating multiple TCE entries
2160 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2162 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2164 boundary - index of last SLC block on Flex-OneNAND.
2165 The remaining blocks are configured as MLC blocks.
2166 lock - Configure if Flex-OneNAND boundary should be locked.
2167 Once locked, the boundary cannot be changed.
2168 1 indicates lock status, 0 indicates unlock status.
2171 ARM/S3C2412 JIVE boot control
2173 See arch/arm/mach-s3c2412/mach-jive.c
2175 mtouchusb.raw_coordinates=
2176 [HW] Make the MicroTouch USB driver use raw coordinates
2177 ('y', default) or cooked coordinates ('n')
2179 mtrr_chunk_size=nn[KMG] [X86]
2180 used for mtrr cleanup. It is largest continuous chunk
2181 that could hold holes aka. UC entries.
2183 mtrr_gran_size=nn[KMG] [X86]
2184 Used for mtrr cleanup. It is granularity of mtrr block.
2186 Large value could prevent small alignment from
2189 mtrr_spare_reg_nr=n [X86]
2191 Range: 0,7 : spare reg number
2193 Used for mtrr cleanup. It is spare mtrr entries number.
2194 Set to 2 or more if your graphical card needs more.
2196 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2198 netdev= [NET] Network devices parameters
2199 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2200 Note that mem_start is often overloaded to mean
2201 something different and driver-specific.
2202 This usage is only documented in each driver source
2206 [NETFILTER] Enable connection tracking flow accounting
2207 0 to disable accounting
2208 1 to enable accounting
2211 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2212 See Documentation/filesystems/nfs/nfsroot.txt.
2214 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2215 See Documentation/filesystems/nfs/nfsroot.txt.
2217 nfsrootdebug [NFS] enable nfsroot debugging messages.
2218 See Documentation/filesystems/nfs/nfsroot.txt.
2220 nfs.callback_tcpport=
2221 [NFS] set the TCP port on which the NFSv4 callback
2222 channel should listen.
2225 [NFS] sets the pathname to the program which is used
2226 to update the NFS client cache entries.
2228 nfs.cache_getent_timeout=
2229 [NFS] sets the timeout after which an attempt to
2230 update a cache entry is deemed to have failed.
2232 nfs.idmap_cache_timeout=
2233 [NFS] set the maximum lifetime for idmapper cache
2237 [NFS] enable 64-bit inode numbers.
2238 If zero, the NFS client will fake up a 32-bit inode
2239 number for the readdir() and stat() syscalls instead
2240 of returning the full 64-bit number.
2241 The default is to return 64-bit inode numbers.
2243 nfs.max_session_slots=
2244 [NFSv4.1] Sets the maximum number of session slots
2245 the client will attempt to negotiate with the server.
2246 This limits the number of simultaneous RPC requests
2247 that the client can send to the NFSv4.1 server.
2248 Note that there is little point in setting this
2249 value higher than the max_tcp_slot_table_limit.
2251 nfs.nfs4_disable_idmapping=
2252 [NFSv4] When set to the default of '1', this option
2253 ensures that both the RPC level authentication
2254 scheme and the NFS level operations agree to use
2255 numeric uids/gids if the mount is using the
2256 'sec=sys' security flavour. In effect it is
2257 disabling idmapping, which can make migration from
2258 legacy NFSv2/v3 systems to NFSv4 easier.
2259 Servers that do not support this mode of operation
2260 will be autodetected by the client, and it will fall
2261 back to using the idmapper.
2262 To turn off this behaviour, set the value to '0'.
2264 [NFS4] Specify an additional fixed unique ident-
2265 ification string that NFSv4 clients can insert into
2266 their nfs_client_id4 string. This is typically a
2267 UUID that is generated at system install time.
2269 nfs.send_implementation_id =
2270 [NFSv4.1] Send client implementation identification
2271 information in exchange_id requests.
2272 If zero, no implementation identification information
2274 The default is to send the implementation identification
2277 nfs.recover_lost_locks =
2278 [NFSv4] Attempt to recover locks that were lost due
2279 to a lease timeout on the server. Please note that
2280 doing this risks data corruption, since there are
2281 no guarantees that the file will remain unchanged
2282 after the locks are lost.
2283 If you want to enable the kernel legacy behaviour of
2284 attempting to recover these locks, then set this
2286 The default parameter value of '0' causes the kernel
2287 not to attempt recovery of lost locks.
2289 nfs4.layoutstats_timer =
2290 [NFSv4.2] Change the rate at which the kernel sends
2291 layoutstats to the pNFS metadata server.
2293 Setting this to value to 0 causes the kernel to use
2294 whatever value is the default set by the layout
2295 driver. A non-zero value sets the minimum interval
2296 in seconds between layoutstats transmissions.
2298 nfsd.nfs4_disable_idmapping=
2299 [NFSv4] When set to the default of '1', the NFSv4
2300 server will return only numeric uids and gids to
2301 clients using auth_sys, and will accept numeric uids
2302 and gids from such clients. This is intended to ease
2303 migration from NFSv2/v3.
2305 objlayoutdriver.osd_login_prog=
2306 [NFS] [OBJLAYOUT] sets the pathname to the program which
2307 is used to automatically discover and login into new
2308 osd-targets. Please see:
2309 Documentation/filesystems/pnfs.txt for more explanations
2311 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2312 when a NMI is triggered.
2313 Format: [state][,regs][,debounce][,die]
2315 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2316 Format: [panic,][nopanic,][num]
2318 0 - turn nmi_watchdog off
2319 1 - turn nmi_watchdog on
2320 When panic is specified, panic when an NMI watchdog
2321 timeout occurs (or 'nopanic' to override the opposite
2323 This is useful when you use a panic=... timeout and
2324 need the box quickly up again.
2326 netpoll.carrier_timeout=
2327 [NET] Specifies amount of time (in seconds) that
2328 netpoll should wait for a carrier. By default netpoll
2331 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2332 emulation library even if a 387 maths coprocessor
2336 [HW] Never suspend the console
2337 Disable suspending of consoles during suspend and
2338 hibernate operations. Once disabled, debugging
2339 messages can reach various consoles while the rest
2340 of the system is being put to sleep (ie, while
2341 debugging driver suspend/resume hooks). This may
2342 not work reliably with all consoles, but is known
2343 to work with serial and VGA consoles.
2344 To facilitate more flexible debugging, we also add
2345 console_suspend, a printk module parameter to control
2346 it. Users could use console_suspend (usually
2347 /sys/module/printk/parameters/console_suspend) to
2348 turn on/off it dynamically.
2350 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2351 caches in the slab allocator. Saves per-node memory,
2352 but will impact performance.
2356 noapic [SMP,APIC] Tells the kernel to not make use of any
2357 IOAPICs that may be present in the system.
2359 noautogroup Disable scheduler automatic task group creation.
2361 nobats [PPC] Do not use BATs for mapping kernel lowmem
2362 on "Classic" PPC cores.
2366 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2368 nodelayacct [KNL] Disable per-task delay accounting
2370 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2372 nodsp [SH] Disable hardware DSP at boot time.
2374 noefi Disable EFI runtime services support.
2379 On X86-32 available only on PAE configured kernels.
2380 noexec=on: enable non-executable mappings (default)
2381 noexec=off: disable non-executable mappings
2384 Disable SMAP (Supervisor Mode Access Prevention)
2385 even if it is supported by processor.
2388 Disable SMEP (Supervisor Mode Execution Prevention)
2389 even if it is supported by processor.
2392 This affects only 32-bit executables.
2393 noexec32=on: enable non-executable mappings (default)
2394 read doesn't imply executable mappings
2395 noexec32=off: disable non-executable mappings
2396 read implies executable mappings
2398 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2400 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2401 register save and restore. The kernel will only save
2402 legacy floating-point registers on task switch.
2404 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2406 noxsave [BUGS=X86] Disables x86 extended register state save
2407 and restore using xsave. The kernel will fallback to
2408 enabling legacy floating-point and sse state.
2410 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2411 register states. The kernel will fall back to use
2412 xsave to save the states. By using this parameter,
2413 performance of saving the states is degraded because
2414 xsave doesn't support modified optimization while
2415 xsaveopt supports it on xsaveopt enabled systems.
2417 noxsaves [X86] Disables xsaves and xrstors used in saving and
2418 restoring x86 extended register state in compacted
2419 form of xsave area. The kernel will fall back to use
2420 xsaveopt and xrstor to save and restore the states
2421 in standard form of xsave area. By using this
2422 parameter, xsave area per process might occupy more
2423 memory on xsaves enabled systems.
2425 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2426 wfi(ARM) instruction doesn't work correctly and not to
2427 use it. This is also useful when using JTAG debugger.
2429 no_file_caps Tells the kernel not to honor file capabilities. The
2430 only way then for a file to be executed with privilege
2431 is to be setuid root or executed by root.
2433 nohalt [IA-64] Tells the kernel not to use the power saving
2434 function PAL_HALT_LIGHT when idle. This increases
2435 power-consumption. On the positive side, it reduces
2436 interrupt wake-up latency, which may improve performance
2437 in certain environments such as networked servers or
2440 nohibernate [HIBERNATION] Disable hibernation and resume.
2442 nohz= [KNL] Boottime enable/disable dynamic ticks
2443 Valid arguments: on, off
2446 nohz_full= [KNL,BOOT]
2447 In kernels built with CONFIG_NO_HZ_FULL=y, set
2448 the specified list of CPUs whose tick will be stopped
2449 whenever possible. The boot CPU will be forced outside
2450 the range to maintain the timekeeping.
2451 The CPUs in this range must also be included in the
2454 noiotrap [SH] Disables trapped I/O port accesses.
2456 noirqdebug [X86-32] Disables the code which attempts to detect and
2457 disable unhandled interrupt sources.
2459 no_timer_check [X86,APIC] Disables the code which tests for
2460 broken timer IRQ sources.
2462 noisapnp [ISAPNP] Disables ISA PnP code.
2464 noinitrd [RAM] Tells the kernel not to load any configured
2467 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2469 [Deprecated - use intremap=off]
2473 nojitter [IA-64] Disables jitter checking for ITC timers.
2475 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2477 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2480 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2481 steal time is computed, but won't influence scheduler
2484 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2486 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2488 noltlbs [PPC] Do not use large page/tlb entries for kernel
2489 lowmem mapping on PPC40x.
2491 nomca [IA-64] Disable machine check abort handling
2493 nomce [X86-32] Disable Machine Check Exception
2495 nomfgpt [X86-32] Disable Multi-Function General Purpose
2496 Timer usage (for AMD Geode machines).
2498 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2499 shutdown the other cpus. Instead use the REBOOT_VECTOR
2502 nomodule Disable module load
2504 nopat [X86] Disable PAT (page attribute table extension of
2505 pagetables) support.
2507 norandmaps Don't use address space randomization. Equivalent to
2508 echo 0 > /proc/sys/kernel/randomize_va_space
2510 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2512 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2513 with UP alternatives
2515 nordrand [X86] Disable kernel use of the RDRAND and
2516 RDSEED instructions even if they are supported
2517 by the processor. RDRAND and RDSEED are still
2518 available to user space applications.
2520 noresume [SWSUSP] Disables resume and restores original swap
2523 no-scroll [VGA] Disables scrollback.
2524 This is required for the Braillex ib80-piezo Braille
2525 reader made by F.H. Papenmeier (Germany).
2529 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2531 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2532 and disable the IO APIC. legacy for "maxcpus=0".
2534 nosoftlockup [KNL] Disable the soft-lockup detector.
2536 nosync [HW,M68K] Disables sync negotiation for all devices.
2538 notsc [BUGS=X86-32] Disable Time Stamp Counter
2540 nousb [USB] Disable the USB subsystem
2542 nowatchdog [KNL] Disable both lockup detectors, i.e.
2543 soft-lockup and NMI watchdog (hard-lockup).
2547 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2549 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2550 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2551 Some features depend on CPU0. Known dependencies are:
2552 1. Resume from suspend/hibernate depends on CPU0.
2553 Suspend/hibernate will fail if CPU0 is offline and you
2554 need to online CPU0 before suspend/hibernate.
2555 2. PIC interrupts also depend on CPU0. CPU0 can't be
2556 removed if a PIC interrupt is detected.
2557 It's said poweroff/reboot may depend on CPU0 on some
2558 machines although I haven't seen such issues so far
2559 after CPU0 is offline on a few tested machines.
2560 If the dependencies are under your control, you can
2561 turn on cpu0_hotplug.
2563 nptcg= [IA-64] Override max number of concurrent global TLB
2564 purges which is reported from either PAL_VM_SUMMARY or
2567 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2568 could support. nr_cpus=n : n >= 1 limits the kernel to
2569 supporting 'n' processors. Later in runtime you can not
2570 use hotplug cpu feature to put more cpu back to online.
2571 just like you compile the kernel NR_CPUS=n
2573 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2575 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2576 Allowed values are enable and disable
2578 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2579 one of ['zone', 'node', 'default'] can be specified
2580 This can be set from sysctl after boot.
2581 See Documentation/sysctl/vm.txt for details.
2583 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2584 See Documentation/debugging-via-ohci1394.txt for more
2587 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2588 Rather than timing out after 20 ms if an EC
2589 command is not properly ACKed, override the length
2590 of the timeout. We have interrupts disabled while
2591 waiting for the ACK, so if this is set too high
2592 interrupts *may* be lost!
2594 omap_mux= [OMAP] Override bootloader pin multiplexing.
2595 Format: <mux_mode0.mode_name=value>...
2596 For example, to override I2C bus2:
2597 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2599 oprofile.timer= [HW]
2600 Use timer interrupt instead of performance counters
2602 oprofile.cpu_type= Force an oprofile cpu type
2603 This might be useful if you have an older oprofile
2604 userland or if you want common events.
2605 Format: { arch_perfmon }
2606 arch_perfmon: [X86] Force use of architectural
2607 perfmon on Intel CPUs instead of the
2608 CPU specific event set.
2609 timer: [X86] Force use of architectural NMI
2610 timer mode (see also oprofile.timer
2611 for generic hr timer mode)
2612 [s390] Force legacy basic mode sampling
2613 (report cpu_type "timer")
2615 oops=panic Always panic on oopses. Default is to just kill the
2616 process, but there is a small probability of
2617 deadlocking the machine.
2618 This will also cause panics on machine check exceptions.
2619 Useful together with panic=30 to trigger a reboot.
2622 See Documentation/sound/oss/oss-parameters.txt
2624 page_owner= [KNL] Boot-time page_owner enabling option.
2625 Storage of the information about who allocated
2626 each page is disabled in default. With this switch,
2628 on: enable the feature
2630 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2631 timeout > 0: seconds before rebooting
2632 timeout = 0: wait forever
2633 timeout < 0: reboot immediately
2636 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2639 crash_kexec_post_notifiers
2640 Run kdump after running panic-notifiers and dumping
2641 kmsg. This only for the users who doubt kdump always
2642 succeeds in any situation.
2643 Note that this also increases risks of kdump failure,
2644 because some panic notifiers can make the crashed
2645 kernel more unstable.
2647 parkbd.port= [HW] Parallel port number the keyboard adapter is
2648 connected to, default is 0.
2650 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2651 0 for XT, 1 for AT (default is AT).
2654 parport= [HW,PPT] Specify parallel ports. 0 disables.
2655 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2656 Use 'auto' to force the driver to use any
2657 IRQ/DMA settings detected (the default is to
2658 ignore detected IRQ/DMA settings because of
2659 possible conflicts). You can specify the base
2660 address, IRQ, and DMA settings; IRQ and DMA
2661 should be numbers, or 'auto' (for using detected
2662 settings on that particular port), or 'nofifo'
2663 (to avoid using a FIFO even if it is detected).
2664 Parallel ports are assigned in the order they
2665 are specified on the command line, starting
2668 parport_init_mode= [HW,PPT]
2669 Configure VIA parallel port to operate in
2670 a specific mode. This is necessary on Pegasos
2671 computer where firmware has no options for setting
2672 up parallel port mode and sets it to spp.
2673 Currently this function knows 686a and 8231 chips.
2674 Format: [spp|ps2|epp|ecp|ecpepp]
2677 Halt all CPUs after the first oops has been printed for
2678 the specified number of seconds. This is to be used if
2679 your oopses keep scrolling off the screen.
2684 See header of drivers/block/paride/pcd.c.
2685 See also Documentation/blockdev/paride.txt.
2687 pci=option[,option...] [PCI] various PCI subsystem options:
2688 earlydump [X86] dump PCI config space before the kernel
2690 off [X86] don't probe for the PCI bus
2691 bios [X86-32] force use of PCI BIOS, don't access
2692 the hardware directly. Use this if your machine
2693 has a non-standard PCI host bridge.
2694 nobios [X86-32] disallow use of PCI BIOS, only direct
2695 hardware access methods are allowed. Use this
2696 if you experience crashes upon bootup and you
2697 suspect they are caused by the BIOS.
2698 conf1 [X86] Force use of PCI Configuration
2700 conf2 [X86] Force use of PCI Configuration
2702 noaer [PCIE] If the PCIEAER kernel config parameter is
2703 enabled, this kernel boot option can be used to
2704 disable the use of PCIE advanced error reporting.
2705 nodomains [PCI] Disable support for multiple PCI
2706 root domains (aka PCI segments, in ACPI-speak).
2707 nommconf [X86] Disable use of MMCONFIG for PCI
2709 check_enable_amd_mmconf [X86] check for and enable
2710 properly configured MMIO access to PCI
2711 config space on AMD family 10h CPU
2712 nomsi [MSI] If the PCI_MSI kernel config parameter is
2713 enabled, this kernel boot option can be used to
2714 disable the use of MSI interrupts system-wide.
2715 noioapicquirk [APIC] Disable all boot interrupt quirks.
2716 Safety option to keep boot IRQs enabled. This
2717 should never be necessary.
2718 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2719 primary IO-APIC for bridges that cannot disable
2720 boot IRQs. This fixes a source of spurious IRQs
2721 when the system masks IRQs.
2722 noioapicreroute [APIC] Disable workaround that uses the
2723 boot IRQ equivalent of an IRQ that connects to
2724 a chipset where boot IRQs cannot be disabled.
2725 The opposite of ioapicreroute.
2726 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2727 routing table. These calls are known to be buggy
2728 on several machines and they hang the machine
2729 when used, but on other computers it's the only
2730 way to get the interrupt routing table. Try
2731 this option if the kernel is unable to allocate
2732 IRQs or discover secondary PCI buses on your
2734 rom [X86] Assign address space to expansion ROMs.
2735 Use with caution as certain devices share
2736 address decoders between ROMs and other
2738 norom [X86] Do not assign address space to
2739 expansion ROMs that do not already have
2740 BIOS assigned address ranges.
2741 nobar [X86] Do not assign address space to the
2742 BARs that weren't assigned by the BIOS.
2743 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2744 assigned automatically to PCI devices. You can
2745 make the kernel exclude IRQs of your ISA cards
2747 pirqaddr=0xAAAAA [X86] Specify the physical address
2748 of the PIRQ table (normally generated
2749 by the BIOS) if it is outside the
2750 F0000h-100000h range.
2751 lastbus=N [X86] Scan all buses thru bus #N. Can be
2752 useful if the kernel is unable to find your
2753 secondary buses and you want to tell it
2754 explicitly which ones they are.
2755 assign-busses [X86] Always assign all PCI bus
2756 numbers ourselves, overriding
2757 whatever the firmware may have done.
2758 usepirqmask [X86] Honor the possible IRQ mask stored
2759 in the BIOS $PIR table. This is needed on
2760 some systems with broken BIOSes, notably
2761 some HP Pavilion N5400 and Omnibook XE3
2762 notebooks. This will have no effect if ACPI
2763 IRQ routing is enabled.
2764 noacpi [X86] Do not use ACPI for IRQ routing
2765 or for PCI scanning.
2766 use_crs [X86] Use PCI host bridge window information
2767 from ACPI. On BIOSes from 2008 or later, this
2768 is enabled by default. If you need to use this,
2769 please report a bug.
2770 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2771 If you need to use this, please report a bug.
2772 routeirq Do IRQ routing for all PCI devices.
2773 This is normally done in pci_enable_device(),
2774 so this option is a temporary workaround
2775 for broken drivers that don't call it.
2776 skip_isa_align [X86] do not align io start addr, so can
2777 handle more pci cards
2778 firmware [ARM] Do not re-enumerate the bus but instead
2779 just use the configuration from the
2780 bootloader. This is currently used on
2781 IXP2000 systems where the bus has to be
2782 configured a certain way for adjunct CPUs.
2783 noearly [X86] Don't do any early type 1 scanning.
2784 This might help on some broken boards which
2785 machine check when some devices' config space
2786 is read. But various workarounds are disabled
2787 and some IOMMU drivers will not work.
2788 bfsort Sort PCI devices into breadth-first order.
2789 This sorting is done to get a device
2790 order compatible with older (<= 2.4) kernels.
2791 nobfsort Don't sort PCI devices into breadth-first order.
2792 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2793 tuning and use the BIOS-configured MPS defaults.
2794 pcie_bus_safe Set every device's MPS to the largest value
2795 supported by all devices below the root complex.
2796 pcie_bus_perf Set device MPS to the largest allowable MPS
2797 based on its parent bus. Also set MRRS (Max
2798 Read Request Size) to the largest supported
2799 value (no larger than the MPS that the device
2800 or bus can support) for best performance.
2801 pcie_bus_peer2peer Set every device's MPS to 128B, which
2802 every device is guaranteed to support. This
2803 configuration allows peer-to-peer DMA between
2804 any pair of devices, possibly at the cost of
2805 reduced performance. This also guarantees
2806 that hot-added devices will work.
2807 cbiosize=nn[KMG] The fixed amount of bus space which is
2808 reserved for the CardBus bridge's IO window.
2809 The default value is 256 bytes.
2810 cbmemsize=nn[KMG] The fixed amount of bus space which is
2811 reserved for the CardBus bridge's memory
2812 window. The default value is 64 megabytes.
2815 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2816 Specifies alignment and device to reassign
2817 aligned memory resources.
2818 If <order of align> is not specified,
2819 PAGE_SIZE is used as alignment.
2820 PCI-PCI bridge can be specified, if resource
2821 windows need to be expanded.
2822 ecrc= Enable/disable PCIe ECRC (transaction layer
2823 end-to-end CRC checking).
2824 bios: Use BIOS/firmware settings. This is the
2828 hpiosize=nn[KMG] The fixed amount of bus space which is
2829 reserved for hotplug bridge's IO window.
2830 Default size is 256 bytes.
2831 hpmemsize=nn[KMG] The fixed amount of bus space which is
2832 reserved for hotplug bridge's memory window.
2833 Default size is 2 megabytes.
2834 realloc= Enable/disable reallocating PCI bridge resources
2835 if allocations done by BIOS are too small to
2836 accommodate resources required by all child
2838 off: Turn realloc off
2840 realloc same as realloc=on
2841 noari do not use PCIe ARI.
2842 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2843 only look for one device below a PCIe downstream
2846 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2849 force Enable ASPM even on devices that claim not to support it.
2850 WARNING: Forcing ASPM on may cause system lockups.
2852 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2853 nomsi Do not use MSI for PCI Express Native Hotplug (this
2854 makes all PCIe ports use INTx for hotplug services).
2856 pcie_ports= [PCIE] PCIe ports handling:
2857 auto Ask the BIOS whether or not to use native PCIe services
2858 associated with PCIe ports (PME, hot-plug, AER). Use
2859 them only if that is allowed by the BIOS.
2860 native Use native PCIe services associated with PCIe ports
2862 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2865 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2866 nomsi Do not use MSI for native PCIe PME signaling (this makes
2867 all PCIe root ports use INTx for all services).
2869 pcmv= [HW,PCMCIA] BadgePAD 4
2873 Keep all power-domains already enabled by bootloader on,
2874 even if no driver has claimed them. This is useful
2875 for debug and development, but should not be
2876 needed on a platform with proper driver support.
2879 See Documentation/blockdev/paride.txt.
2881 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2884 See arch/parisc/kernel/pdc_chassis.c
2886 percpu_alloc= Select which percpu first chunk allocator to use.
2887 Currently supported values are "embed" and "page".
2888 Archs may support subset or none of the selections.
2889 See comments in mm/percpu.c for details on each
2890 allocator. This parameter is primarily for debugging
2891 and performance comparison.
2894 See Documentation/blockdev/paride.txt.
2897 See Documentation/blockdev/paride.txt.
2899 pirq= [SMP,APIC] Manual mp-table setup
2900 See Documentation/x86/i386/IO-APIC.txt.
2902 plip= [PPT,NET] Parallel port network link
2903 Format: { parport<nr> | timid | 0 }
2904 See also Documentation/parport.txt.
2906 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2907 Override pmtimer IOPort with a hex value.
2911 Enable PNP debug messages (depends on the
2912 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2913 via /sys/module/pnp/parameters/debug. We always show
2914 current resource usage; turning this on also shows
2915 possible settings and some assignment information.
2921 { on | off | curr | res | no-curr | no-res }
2924 [ISAPNP] Exclude IRQs for the autoconfiguration
2927 [ISAPNP] Exclude DMAs for the autoconfiguration
2929 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2930 Ranges are in pairs (I/O port base and size).
2933 [ISAPNP] Exclude memory regions for the
2935 Ranges are in pairs (memory base and size).
2937 ports= [IP_VS_FTP] IPVS ftp helper module
2939 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2941 Format: <port>,<port>....
2943 print-fatal-signals=
2944 [KNL] debug: print fatal signals
2946 If enabled, warn about various signal handling
2947 related application anomalies: too many signals,
2948 too many POSIX.1 timers, fatal signals causing a
2951 If you hit the warning due to signal overflow,
2952 you might want to try "ulimit -i unlimited".
2956 printk.always_kmsg_dump=
2957 Trigger kmsg_dump for cases other than kernel oops or
2959 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2962 printk.time= Show timing data prefixed to each printk message line
2963 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2965 processor.max_cstate= [HW,ACPI]
2966 Limit processor to maximum C-state
2967 max_cstate=9 overrides any DMI blacklist limit.
2969 processor.nocst [HW,ACPI]
2970 Ignore the _CST method to determine C-states,
2971 instead using the legacy FADT method
2973 profile= [KNL] Enable kernel profiling via /proc/profile
2974 Format: [schedule,]<number>
2975 Param: "schedule" - profile schedule points.
2976 Param: <number> - step/bucket size as a power of 2 for
2977 statistical time based profiling.
2978 Param: "sleep" - profile D-state sleeping (millisecs).
2979 Requires CONFIG_SCHEDSTATS
2980 Param: "kvm" - profile VM exits.
2982 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2984 See Documentation/blockdev/ramdisk.txt.
2986 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2987 probe for; one of (bare|imps|exps|lifebook|any).
2988 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2990 psmouse.resetafter= [HW,MOUSE]
2991 Try to reset the device after so many bad packets
2994 [HW,MOUSE] Set desired mouse resolution, in dpi.
2995 psmouse.smartscroll=
2996 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2997 0 = disabled, 1 = enabled (default).
2999 pstore.backend= Specify the name of the pstore backend to use
3002 See Documentation/blockdev/paride.txt.
3005 [KNL] Number of legacy pty's. Overwrites compiled-in
3008 quiet [KNL] Disable most log messages
3013 See Documentation/md.txt.
3015 ramdisk_blocksize= [RAM]
3016 See Documentation/blockdev/ramdisk.txt.
3018 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3019 See Documentation/blockdev/ramdisk.txt.
3022 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3023 the specified list of CPUs to be no-callback CPUs.
3024 Invocation of these CPUs' RCU callbacks will
3025 be offloaded to "rcuox/N" kthreads created for
3026 that purpose, where "x" is "b" for RCU-bh, "p"
3027 for RCU-preempt, and "s" for RCU-sched, and "N"
3028 is the CPU number. This reduces OS jitter on the
3029 offloaded CPUs, which can be useful for HPC and
3030 real-time workloads. It can also improve energy
3031 efficiency for asymmetric multiprocessors.
3034 Rather than requiring that offloaded CPUs
3035 (specified by rcu_nocbs= above) explicitly
3036 awaken the corresponding "rcuoN" kthreads,
3037 make these kthreads poll for callbacks.
3038 This improves the real-time response for the
3039 offloaded CPUs by relieving them of the need to
3040 wake up the corresponding kthread, but degrades
3041 energy efficiency by requiring that the kthreads
3042 periodically wake up to do the polling.
3044 rcutree.blimit= [KNL]
3045 Set maximum number of finished RCU callbacks to
3046 process in one batch.
3048 rcutree.dump_tree= [KNL]
3049 Dump the structure of the rcu_node combining tree
3050 out at early boot. This is used for diagnostic
3051 purposes, to verify correct tree setup.
3053 rcutree.gp_cleanup_delay= [KNL]
3054 Set the number of jiffies to delay each step of
3055 RCU grace-period cleanup. This only has effect
3056 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3058 rcutree.gp_init_delay= [KNL]
3059 Set the number of jiffies to delay each step of
3060 RCU grace-period initialization. This only has
3061 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3064 rcutree.gp_preinit_delay= [KNL]
3065 Set the number of jiffies to delay each step of
3066 RCU grace-period pre-initialization, that is,
3067 the propagation of recent CPU-hotplug changes up
3068 the rcu_node combining tree. This only has effect
3069 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3071 rcutree.rcu_fanout_exact= [KNL]
3072 Disable autobalancing of the rcu_node combining
3073 tree. This is used by rcutorture, and might
3074 possibly be useful for architectures having high
3075 cache-to-cache transfer latencies.
3077 rcutree.rcu_fanout_leaf= [KNL]
3078 Increase the number of CPUs assigned to each
3079 leaf rcu_node structure. Useful for very large
3082 rcutree.jiffies_till_sched_qs= [KNL]
3083 Set required age in jiffies for a
3084 given grace period before RCU starts
3085 soliciting quiescent-state help from
3086 rcu_note_context_switch().
3088 rcutree.jiffies_till_first_fqs= [KNL]
3089 Set delay from grace-period initialization to
3090 first attempt to force quiescent states.
3091 Units are jiffies, minimum value is zero,
3092 and maximum value is HZ.
3094 rcutree.jiffies_till_next_fqs= [KNL]
3095 Set delay between subsequent attempts to force
3096 quiescent states. Units are jiffies, minimum
3097 value is one, and maximum value is HZ.
3099 rcutree.kthread_prio= [KNL,BOOT]
3100 Set the SCHED_FIFO priority of the RCU per-CPU
3101 kthreads (rcuc/N). This value is also used for
3102 the priority of the RCU boost threads (rcub/N)
3103 and for the RCU grace-period kthreads (rcu_bh,
3104 rcu_preempt, and rcu_sched). If RCU_BOOST is
3105 set, valid values are 1-99 and the default is 1
3106 (the least-favored priority). Otherwise, when
3107 RCU_BOOST is not set, valid values are 0-99 and
3108 the default is zero (non-realtime operation).
3110 rcutree.rcu_nocb_leader_stride= [KNL]
3111 Set the number of NOCB kthread groups, which
3112 defaults to the square root of the number of
3113 CPUs. Larger numbers reduces the wakeup overhead
3114 on the per-CPU grace-period kthreads, but increases
3115 that same overhead on each group's leader.
3117 rcutree.qhimark= [KNL]
3118 Set threshold of queued RCU callbacks beyond which
3119 batch limiting is disabled.
3121 rcutree.qlowmark= [KNL]
3122 Set threshold of queued RCU callbacks below which
3123 batch limiting is re-enabled.
3125 rcutree.rcu_idle_gp_delay= [KNL]
3126 Set wakeup interval for idle CPUs that have
3127 RCU callbacks (RCU_FAST_NO_HZ=y).
3129 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3130 Set wakeup interval for idle CPUs that have
3131 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3132 Lazy RCU callbacks are those which RCU can
3133 prove do nothing more than free memory.
3135 rcutorture.cbflood_inter_holdoff= [KNL]
3136 Set holdoff time (jiffies) between successive
3137 callback-flood tests.
3139 rcutorture.cbflood_intra_holdoff= [KNL]
3140 Set holdoff time (jiffies) between successive
3141 bursts of callbacks within a given callback-flood
3144 rcutorture.cbflood_n_burst= [KNL]
3145 Set the number of bursts making up a given
3146 callback-flood test. Set this to zero to
3147 disable callback-flood testing.
3149 rcutorture.cbflood_n_per_burst= [KNL]
3150 Set the number of callbacks to be registered
3151 in a given burst of a callback-flood test.
3153 rcutorture.fqs_duration= [KNL]
3154 Set duration of force_quiescent_state bursts
3157 rcutorture.fqs_holdoff= [KNL]
3158 Set holdoff time within force_quiescent_state bursts
3161 rcutorture.fqs_stutter= [KNL]
3162 Set wait time between force_quiescent_state bursts
3165 rcutorture.gp_cond= [KNL]
3166 Use conditional/asynchronous update-side
3167 primitives, if available.
3169 rcutorture.gp_exp= [KNL]
3170 Use expedited update-side primitives, if available.
3172 rcutorture.gp_normal= [KNL]
3173 Use normal (non-expedited) asynchronous
3174 update-side primitives, if available.
3176 rcutorture.gp_sync= [KNL]
3177 Use normal (non-expedited) synchronous
3178 update-side primitives, if available. If all
3179 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3180 rcutorture.gp_normal=, and rcutorture.gp_sync=
3181 are zero, rcutorture acts as if is interpreted
3182 they are all non-zero.
3184 rcutorture.n_barrier_cbs= [KNL]
3185 Set callbacks/threads for rcu_barrier() testing.
3187 rcutorture.nfakewriters= [KNL]
3188 Set number of concurrent RCU writers. These just
3189 stress RCU, they don't participate in the actual
3190 test, hence the "fake".
3192 rcutorture.nreaders= [KNL]
3193 Set number of RCU readers. The value -1 selects
3194 N-1, where N is the number of CPUs. A value
3195 "n" less than -1 selects N-n-2, where N is again
3196 the number of CPUs. For example, -2 selects N
3197 (the number of CPUs), -3 selects N+1, and so on.
3199 rcutorture.object_debug= [KNL]
3200 Enable debug-object double-call_rcu() testing.
3202 rcutorture.onoff_holdoff= [KNL]
3203 Set time (s) after boot for CPU-hotplug testing.
3205 rcutorture.onoff_interval= [KNL]
3206 Set time (s) between CPU-hotplug operations, or
3207 zero to disable CPU-hotplug testing.
3209 rcutorture.shuffle_interval= [KNL]
3210 Set task-shuffle interval (s). Shuffling tasks
3211 allows some CPUs to go into dyntick-idle mode
3212 during the rcutorture test.
3214 rcutorture.shutdown_secs= [KNL]
3215 Set time (s) after boot system shutdown. This
3216 is useful for hands-off automated testing.
3218 rcutorture.stall_cpu= [KNL]
3219 Duration of CPU stall (s) to test RCU CPU stall
3220 warnings, zero to disable.
3222 rcutorture.stall_cpu_holdoff= [KNL]
3223 Time to wait (s) after boot before inducing stall.
3225 rcutorture.stat_interval= [KNL]
3226 Time (s) between statistics printk()s.
3228 rcutorture.stutter= [KNL]
3229 Time (s) to stutter testing, for example, specifying
3230 five seconds causes the test to run for five seconds,
3231 wait for five seconds, and so on. This tests RCU's
3232 ability to transition abruptly to and from idle.
3234 rcutorture.test_boost= [KNL]
3235 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3236 "Maybe" means test if the RCU implementation
3237 under test support RCU priority boosting.
3239 rcutorture.test_boost_duration= [KNL]
3240 Duration (s) of each individual boost test.
3242 rcutorture.test_boost_interval= [KNL]
3243 Interval (s) between each boost test.
3245 rcutorture.test_no_idle_hz= [KNL]
3246 Test RCU's dyntick-idle handling. See also the
3247 rcutorture.shuffle_interval parameter.
3249 rcutorture.torture_runnable= [BOOT]
3250 Start rcutorture running at boot time.
3252 rcutorture.torture_type= [KNL]
3253 Specify the RCU implementation to test.
3255 rcutorture.verbose= [KNL]
3256 Enable additional printk() statements.
3258 rcupdate.rcu_expedited= [KNL]
3259 Use expedited grace-period primitives, for
3260 example, synchronize_rcu_expedited() instead
3261 of synchronize_rcu(). This reduces latency,
3262 but can increase CPU utilization, degrade
3263 real-time latency, and degrade energy efficiency.
3265 rcupdate.rcu_cpu_stall_suppress= [KNL]
3266 Suppress RCU CPU stall warning messages.
3268 rcupdate.rcu_cpu_stall_timeout= [KNL]
3269 Set timeout for RCU CPU stall warning messages.
3271 rcupdate.rcu_task_stall_timeout= [KNL]
3272 Set timeout in jiffies for RCU task stall warning
3273 messages. Disable with a value less than or equal
3276 rcupdate.rcu_self_test= [KNL]
3277 Run the RCU early boot self tests
3279 rcupdate.rcu_self_test_bh= [KNL]
3280 Run the RCU bh early boot self tests
3282 rcupdate.rcu_self_test_sched= [KNL]
3283 Run the RCU sched early boot self tests
3287 Run specified binary instead of /init from the ramdisk,
3288 used for early userspace startup. See initrd.
3291 Format (x86 or x86_64):
3292 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3294 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3296 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3297 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3298 reboot_force is either force or not specified,
3299 reboot_cpu is s[mp]#### with #### being the processor
3300 to be used for rebooting.
3303 [KNL, SMP] Set scheduler's default relax_domain_level.
3304 See Documentation/cgroups/cpusets.txt.
3306 relative_sleep_states=
3307 [SUSPEND] Use sleep state labeling where the deepest
3308 state available other than hibernation is always "mem".
3309 Format: { "0" | "1" }
3310 0 -- Traditional sleep state labels.
3311 1 -- Relative sleep state labels.
3313 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3315 reservetop= [X86-32]
3317 Reserves a hole at the top of the kernel virtual
3322 Set the amount of memory to reserve for BIOS at
3323 the bottom of the address space.
3325 reset_devices [KNL] Force drivers to reset the underlying device
3326 during initialization.
3329 Specify the partition device for software suspend
3331 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3333 resume_offset= [SWSUSP]
3334 Specify the offset from the beginning of the partition
3335 given by "resume=" at which the swap header is located,
3336 in <PAGE_SIZE> units (needed only for swap files).
3337 See Documentation/power/swsusp-and-swap-files.txt
3339 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3340 read the resume files
3342 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3343 Useful for devices that are detected asynchronously
3344 (e.g. USB and MMC devices).
3346 hibernate= [HIBERNATION]
3347 noresume Don't check if there's a hibernation image
3348 present during boot.
3349 nocompress Don't compress/decompress hibernation images.
3350 no Disable hibernation and resume.
3352 retain_initrd [RAM] Keep initrd memory after extraction
3354 rfkill.default_state=
3355 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3356 etc. communication is blocked by default.
3359 rfkill.master_switch_mode=
3360 0 The "airplane mode" button does nothing.
3361 1 The "airplane mode" button toggles between everything
3362 blocked and the previous configuration.
3363 2 The "airplane mode" button toggles between everything
3364 blocked and everything unblocked.
3366 rhash_entries= [KNL,NET]
3367 Set number of hash buckets for route cache
3369 ro [KNL] Mount root device read-only on boot
3371 root= [KNL] Root filesystem
3372 See name_to_dev_t comment in init/do_mounts.c.
3374 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3375 mount the root filesystem
3377 rootflags= [KNL] Set root filesystem mount option string
3379 rootfstype= [KNL] Set root filesystem type
3381 rootwait [KNL] Wait (indefinitely) for root device to show up.
3382 Useful for devices that are detected asynchronously
3383 (e.g. USB and MMC devices).
3385 rproc_mem=nn[KMG][@address]
3386 [KNL,ARM,CMA] Remoteproc physical memory block.
3387 Memory area to be used by remote processor image,
3390 rw [KNL] Mount root device read-write on boot
3392 S [KNL] Run init in single mode
3394 s390_iommu= [HW,S390]
3395 Set s390 IOTLB flushing mode
3397 With strict flushing every unmap operation will result in
3398 an IOTLB flush. Default is lazy flushing before reuse,
3402 See drivers/net/irda/sa1100_ir.c.
3404 sbni= [NET] Granch SBNI12 leased line adapter
3406 sched_debug [KNL] Enables verbose scheduler debug messages.
3408 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3409 xtime_lock contention on larger systems, and/or RCU lock
3410 contention on all systems with CONFIG_MAXSMP set.
3411 Format: { "0" | "1" }
3412 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3414 Note: increases power consumption, thus should only be
3415 enabled if running jitter sensitive (HPC/RT) workloads.
3417 security= [SECURITY] Choose a security module to enable at boot.
3418 If this boot parameter is not specified, only the first
3419 security module asking for security registration will be
3420 loaded. An invalid security module name will be treated
3421 as if no module has been chosen.
3423 selinux= [SELINUX] Disable or enable SELinux at boot time.
3424 Format: { "0" | "1" }
3425 See security/selinux/Kconfig help text.
3428 Default value is set via kernel config option.
3429 If enabled at boot time, /selinux/disable can be used
3430 later to disable prior to initial policy load.
3432 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3433 Format: { "0" | "1" }
3434 See security/apparmor/Kconfig help text
3437 Default value is set via kernel config option.
3439 serialnumber [BUGS=X86-32]
3442 Maximal number of shapers.
3444 show_msr= [x86] show boot-time MSR settings
3445 Format: { <integer> }
3446 Show boot-time (BIOS-initialized) MSR settings.
3447 The parameter means the number of CPUs to show,
3448 for example 1 means boot CPU only.
3456 Disable merging of slabs with similar size. May be
3457 necessary if there is some reason to distinguish
3458 allocs to different slabs. Debug options disable
3459 merging on their own.
3460 For more information see Documentation/vm/slub.txt.
3462 slab_max_order= [MM, SLAB]
3463 Determines the maximum allowed order for slabs.
3464 A high setting may cause OOMs due to memory
3465 fragmentation. Defaults to 1 for systems with
3466 more than 32MB of RAM, 0 otherwise.
3468 slub_debug[=options[,slabs]] [MM, SLUB]
3469 Enabling slub_debug allows one to determine the
3470 culprit if slab objects become corrupted. Enabling
3471 slub_debug can create guard zones around objects and
3472 may poison objects when not in use. Also tracks the
3473 last alloc / free. For more information see
3474 Documentation/vm/slub.txt.
3476 slub_max_order= [MM, SLUB]
3477 Determines the maximum allowed order for slabs.
3478 A high setting may cause OOMs due to memory
3479 fragmentation. For more information see
3480 Documentation/vm/slub.txt.
3482 slub_min_objects= [MM, SLUB]
3483 The minimum number of objects per slab. SLUB will
3484 increase the slab order up to slub_max_order to
3485 generate a sufficiently large slab able to contain
3486 the number of objects indicated. The higher the number
3487 of objects the smaller the overhead of tracking slabs
3488 and the less frequently locks need to be acquired.
3489 For more information see Documentation/vm/slub.txt.
3491 slub_min_order= [MM, SLUB]
3492 Determines the minimum page order for slabs. Must be
3493 lower than slub_max_order.
3494 For more information see Documentation/vm/slub.txt.
3496 slub_nomerge [MM, SLUB]
3497 Same with slab_nomerge. This is supported for legacy.
3498 See slab_nomerge for more information.
3501 Format: <io1>[,<io2>[,...,<io8>]]
3503 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3504 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3505 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3506 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3507 smsc-ircc2.ircc_irq= [HW] IRQ line
3508 smsc-ircc2.ircc_dma= [HW] DMA channel
3509 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3510 0: Toshiba Satellite 1800 (GP data pin select)
3511 1: Fast pin select (default)
3515 [KNL] Should the soft-lockup detector generate panics.
3518 softlockup_all_cpu_backtrace=
3519 [KNL] Should the soft-lockup detector generate
3520 backtraces on all cpus.
3523 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3524 See Documentation/laptops/sonypi.txt
3526 spia_io_base= [HW,MTD]
3532 Enabled the stack tracer on boot up.
3534 stacktrace_filter=[function-list]
3535 [FTRACE] Limit the functions that the stack tracer
3536 will trace at boot up. function-list is a comma separated
3537 list of functions. This list can be changed at run
3538 time by the stack_trace_filter file in the debugfs
3539 tracing directory. Note, this enables stack tracing
3540 and the stacktrace above is not needed.
3544 Set the STI (builtin display/keyboard on the HP-PARISC
3545 machines) console (graphic card) which should be used
3546 as the initial boot-console.
3547 See also comment in drivers/video/console/sticore.c.
3550 See comment in drivers/video/console/sticore.c.
3553 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3555 sunrpc.min_resvport=
3556 sunrpc.max_resvport=
3558 SunRPC servers often require that client requests
3559 originate from a privileged port (i.e. a port in the
3560 range 0 < portnr < 1024).
3561 An administrator who wishes to reserve some of these
3562 ports for other uses may adjust the range that the
3563 kernel's sunrpc client considers to be privileged
3564 using these two parameters to set the minimum and
3565 maximum port values.
3569 Control how the NFS server code allocates CPUs to
3570 service thread pools. Depending on how many NICs
3571 you have and where their interrupts are bound, this
3572 option will affect which CPUs will do NFS serving.
3573 Note: this parameter cannot be changed while the
3574 NFS server is running.
3576 auto the server chooses an appropriate mode
3577 automatically using heuristics
3578 global a single global pool contains all CPUs
3579 percpu one pool for each CPU
3580 pernode one pool for each NUMA node (equivalent
3581 to global on non-NUMA machines)
3583 sunrpc.tcp_slot_table_entries=
3584 sunrpc.udp_slot_table_entries=
3586 Sets the upper limit on the number of simultaneous
3587 RPC calls that can be sent from the client to a
3588 server. Increasing these values may allow you to
3589 improve throughput, but will also increase the
3590 amount of memory reserved for use by the client.
3592 suspend.pm_test_delay=
3594 Sets the number of seconds to remain in a suspend test
3595 mode before resuming the system (see
3596 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3597 is set. Default value is 5.
3600 [KNL] Enable accounting of swap in memory resource
3601 controller if no parameter or 1 is given or disable
3602 it if 0 is given (See Documentation/cgroups/memory.txt)
3604 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3605 Format: { <int> | force }
3606 <int> -- Number of I/O TLB slabs
3607 force -- force using of bounce buffers even if they
3608 wouldn't be automatically used by the kernel
3612 sysfs.deprecated=0|1 [KNL]
3613 Enable/disable old style sysfs layout for old udev
3614 on older distributions. When this option is enabled
3615 very new udev will not work anymore. When this option
3616 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3617 in older udev will not work anymore.
3618 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3619 the kernel configuration.
3621 sysrq_always_enabled
3623 Ignore sysrq setting - this boot parameter will
3624 neutralize any effect of /proc/sys/kernel/sysrq.
3625 Useful for debugging.
3627 tcpmhash_entries= [KNL,NET]
3628 Set the number of tcp_metrics_hash slots.
3629 Default value is 8192 or 16384 depending on total
3630 ram pages. This is used to specify the TCP metrics
3631 cache size. See Documentation/networking/ip-sysctl.txt
3632 "tcp_no_metrics_save" section for more details.
3636 test_suspend= [SUSPEND][,N]
3637 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3638 standby suspend) or "freeze" (for suspend type freeze)
3639 as the system sleep state during system startup with
3640 the optional capability to repeat N number of times.
3641 The system is woken from this state using a
3642 wakeup-capable RTC alarm.
3644 thash_entries= [KNL,NET]
3645 Set number of hash buckets for TCP connection
3647 thermal.act= [HW,ACPI]
3648 -1: disable all active trip points in all thermal zones
3649 <degrees C>: override all lowest active trip points
3651 thermal.crt= [HW,ACPI]
3652 -1: disable all critical trip points in all thermal zones
3653 <degrees C>: override all critical trip points
3655 thermal.nocrt= [HW,ACPI]
3656 Set to disable actions on ACPI thermal zone
3657 critical and hot trip points.
3659 thermal.off= [HW,ACPI]
3660 1: disable ACPI thermal control
3662 thermal.psv= [HW,ACPI]
3663 -1: disable all passive trip points
3664 <degrees C>: override all passive trip points to this
3667 thermal.tzp= [HW,ACPI]
3668 Specify global default ACPI thermal zone polling rate
3669 <deci-seconds>: poll all this frequency
3670 0: no polling (default)
3673 Force threading of all interrupt handlers except those
3674 marked explicitly IRQF_NO_THREAD.
3677 Enable the Transcendent memory driver if built-in.
3679 tmem.cleancache=0|1 [KNL, XEN]
3680 Default is on (1). Disable the usage of the cleancache
3681 API to send anonymous pages to the hypervisor.
3683 tmem.frontswap=0|1 [KNL, XEN]
3684 Default is on (1). Disable the usage of the frontswap
3685 API to send swap pages to the hypervisor. If disabled
3686 the selfballooning and selfshrinking are force disabled.
3688 tmem.selfballooning=0|1 [KNL, XEN]
3689 Default is on (1). Disable the driving of swap pages
3692 tmem.selfshrinking=0|1 [KNL, XEN]
3693 Default is on (1). Partial swapoff that immediately
3694 transfers pages from Xen hypervisor back to the
3695 kernel based on different criteria.
3699 Specify if the kernel should make use of the cpu
3700 topology information if the hardware supports this.
3701 The scheduler will make use of this information and
3702 e.g. base its process migration decisions on it.
3705 topology_updates= [KNL, PPC, NUMA]
3707 Specify if the kernel should ignore (off)
3708 topology updates sent by the hypervisor to this
3713 tpm_suspend_pcr=[HW,TPM]
3714 Format: integer pcr id
3715 Specify that at suspend time, the tpm driver
3716 should extend the specified pcr with zeros,
3717 as a workaround for some chips which fail to
3718 flush the last written pcr on TPM_SaveState.
3719 This will guarantee that all the other pcrs
3722 trace_buf_size=nn[KMG]
3723 [FTRACE] will set tracing buffer size on each cpu.
3725 trace_event=[event-list]
3726 [FTRACE] Set and start specified trace events in order
3727 to facilitate early boot debugging.
3728 See also Documentation/trace/events.txt
3730 trace_options=[option-list]
3731 [FTRACE] Enable or disable tracer options at boot.
3732 The option-list is a comma delimited list of options
3733 that can be enabled or disabled just as if you were
3734 to echo the option name into
3736 /sys/kernel/debug/tracing/trace_options
3738 For example, to enable stacktrace option (to dump the
3739 stack trace of each event), add to the command line:
3741 trace_options=stacktrace
3743 See also Documentation/trace/ftrace.txt "trace options"
3747 Have the tracepoints sent to printk as well as the
3748 tracing ring buffer. This is useful for early boot up
3749 where the system hangs or reboots and does not give the
3750 option for reading the tracing buffer or performing a
3751 ftrace_dump_on_oops.
3753 To turn off having tracepoints sent to printk,
3754 echo 0 > /proc/sys/kernel/tracepoint_printk
3755 Note, echoing 1 into this file without the
3756 tracepoint_printk kernel cmdline option has no effect.
3760 Having tracepoints sent to printk() and activating high
3761 frequency tracepoints such as irq or sched, can cause
3762 the system to live lock.
3765 [FTRACE] enable this option to disable tracing when a
3766 warning is hit. This turns off "tracing_on". Tracing can
3767 be enabled again by echoing '1' into the "tracing_on"
3768 file located in /sys/kernel/debug/tracing/
3770 This option is useful, as it disables the trace before
3771 the WARNING dump is called, which prevents the trace to
3772 be filled with content caused by the warning output.
3774 This option can also be set at run time via the sysctl
3775 option: kernel/traceoff_on_warning
3777 transparent_hugepage=
3779 Format: [always|madvise|never]
3780 Can be used to control the default behavior of the system
3781 with respect to transparent hugepages.
3782 See Documentation/vm/transhuge.txt for more details.
3784 tsc= Disable clocksource stability checks for TSC.
3786 [x86] reliable: mark tsc clocksource as reliable, this
3787 disables clocksource verification at runtime, as well
3788 as the stability checks done at bootup. Used to enable
3789 high-resolution timer mode on older hardware, and in
3790 virtualized environment.
3791 [x86] noirqtime: Do not use TSC to do irq accounting.
3792 Used to run time disable IRQ_TIME_ACCOUNTING on any
3793 platforms where RDTSC is slow and this accounting
3796 turbografx.map[2|3]= [HW,JOY]
3797 TurboGraFX parallel port interface
3799 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3800 See also Documentation/input/joystick-parport.txt
3802 udbg-immortal [PPC] When debugging early kernel crashes that
3803 happen after console_init() and before a proper
3804 console driver takes over, this boot options might
3805 help "seeing" what's going on.
3807 uhash_entries= [KNL,NET]
3808 Set number of hash buckets for UDP/UDP-Lite connections
3811 [USB] Ignore overcurrent events (default N).
3812 Some badly-designed motherboards generate lots of
3813 bogus events, for ports that aren't wired to
3814 anything. Set this parameter to avoid log spamming.
3815 Note that genuine overcurrent events won't be
3819 [X86] Cause panic on unknown NMI.
3821 usbcore.authorized_default=
3822 [USB] Default USB device authorization:
3823 (default -1 = authorized except for wireless USB,
3824 0 = not authorized, 1 = authorized)
3826 usbcore.autosuspend=
3827 [USB] The autosuspend time delay (in seconds) used
3828 for newly-detected USB devices (default 2). This
3829 is the time required before an idle device will be
3830 autosuspended. Devices for which the delay is set
3831 to a negative value won't be autosuspended at all.
3833 usbcore.usbfs_snoop=
3834 [USB] Set to log all usbfs traffic (default 0 = off).
3836 usbcore.blinkenlights=
3837 [USB] Set to cycle leds on hubs (default 0 = off).
3839 usbcore.old_scheme_first=
3840 [USB] Start with the old device initialization
3841 scheme (default 0 = off).
3843 usbcore.usbfs_memory_mb=
3844 [USB] Memory limit (in MB) for buffers allocated by
3845 usbfs (default = 16, 0 = max = 2047).
3847 usbcore.use_both_schemes=
3848 [USB] Try the other device initialization scheme
3849 if the first one fails (default 1 = enabled).
3851 usbcore.initial_descriptor_timeout=
3852 [USB] Specifies timeout for the initial 64-byte
3853 USB_REQ_GET_DESCRIPTOR request in milliseconds
3854 (default 5000 = 5.0 seconds).
3857 [USBHID] The interval which mice are to be polled at.
3859 usb-storage.delay_use=
3860 [UMS] The delay in seconds before a new device is
3861 scanned for Logical Units (default 1).
3864 [UMS] A list of quirks entries to supplement or
3865 override the built-in unusual_devs list. List
3866 entries are separated by commas. Each entry has
3867 the form VID:PID:Flags where VID and PID are Vendor
3868 and Product ID values (4-digit hex numbers) and
3869 Flags is a set of characters, each corresponding
3870 to a common usb-storage quirk flag as follows:
3871 a = SANE_SENSE (collect more than 18 bytes
3873 b = BAD_SENSE (don't collect more than 18
3874 bytes of sense data);
3875 c = FIX_CAPACITY (decrease the reported
3876 device capacity by one sector);
3877 d = NO_READ_DISC_INFO (don't use
3878 READ_DISC_INFO command);
3879 e = NO_READ_CAPACITY_16 (don't use
3880 READ_CAPACITY_16 command);
3881 f = NO_REPORT_OPCODES (don't use report opcodes
3883 g = MAX_SECTORS_240 (don't transfer more than
3884 240 sectors at a time, uas only);
3885 h = CAPACITY_HEURISTICS (decrease the
3886 reported device capacity by one
3887 sector if the number is odd);
3888 i = IGNORE_DEVICE (don't bind to this
3890 l = NOT_LOCKABLE (don't try to lock and
3891 unlock ejectable media);
3892 m = MAX_SECTORS_64 (don't transfer more
3893 than 64 sectors = 32 KB at a time);
3894 n = INITIAL_READ10 (force a retry of the
3895 initial READ(10) command);
3896 o = CAPACITY_OK (accept the capacity
3897 reported by the device);
3898 p = WRITE_CACHE (the device cache is ON
3900 r = IGNORE_RESIDUE (the device reports
3901 bogus residue values);
3902 s = SINGLE_LUN (the device has only one
3904 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3905 commands, uas only);
3906 u = IGNORE_UAS (don't bind to the uas driver);
3907 w = NO_WP_DETECT (don't test whether the
3908 medium is write-protected).
3909 Example: quirks=0419:aaf5:rl,0421:0433:rc
3911 user_debug= [KNL,ARM]
3913 See arch/arm/Kconfig.debug help text.
3914 1 - undefined instruction events
3916 4 - invalid data aborts
3919 Example: user_debug=31
3922 [X86] Flags controlling user PTE allocations.
3924 nohigh = do not allocate PTE pages in
3925 HIGHMEM regardless of setting
3929 On X86_32, this is an alias for vdso32=. Otherwise:
3931 vdso=1: enable VDSO (the default)
3932 vdso=0: disable VDSO mapping
3934 vdso32= [X86] Control the 32-bit vDSO
3935 vdso32=1: enable 32-bit VDSO
3936 vdso32=0 or vdso32=2: disable 32-bit VDSO
3938 See the help text for CONFIG_COMPAT_VDSO for more
3939 details. If CONFIG_COMPAT_VDSO is set, the default is
3940 vdso32=0; otherwise, the default is vdso32=1.
3942 For compatibility with older kernels, vdso32=2 is an
3945 Try vdso32=0 if you encounter an error that says:
3946 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3949 vector=percpu: enable percpu vector domain
3951 video= [FB] Frame buffer configuration
3952 See Documentation/fb/modedb.txt.
3954 video.brightness_switch_enabled= [0,1]
3955 If set to 1, on receiving an ACPI notify event
3956 generated by hotkey, video driver will adjust brightness
3957 level and then send out the event to user space through
3958 the allocated input device; If set to 0, video driver
3959 will only send out the event without touching backlight
3964 [VMMIO] Memory mapped virtio (platform) device.
3966 <size>@<baseaddr>:<irq>[:<id>]
3968 <size> := size (can use standard suffixes
3970 <baseaddr> := physical base address
3971 <irq> := interrupt number (as passed to
3973 <id> := (optional) platform device id
3975 virtio_mmio.device=1K@0x100b0000:48:7
3977 Can be used multiple times for multiple devices.
3979 vga= [BOOT,X86-32] Select a particular video mode
3980 See Documentation/x86/boot.txt and
3981 Documentation/svga.txt.
3982 Use vga=ask for menu.
3983 This is actually a boot loader parameter; the value is
3984 passed to the kernel using a special protocol.
3986 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3987 size of <nn>. This can be used to increase the
3988 minimum size (128MB on x86). It can also be used to
3989 decrease the size and leave more room for directly
3992 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3995 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3998 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4002 Controls the behavior of vsyscalls (i.e. calls to
4003 fixed addresses of 0xffffffffff600x00 from legacy
4004 code). Most statically-linked binaries and older
4005 versions of glibc use these calls. Because these
4006 functions are at fixed addresses, they make nice
4007 targets for exploits that can control RIP.
4009 emulate [default] Vsyscalls turn into traps and are
4010 emulated reasonably safely.
4012 native Vsyscalls are native syscall instructions.
4013 This is a little bit faster than trapping
4014 and makes a few dynamic recompilers work
4015 better than they would in emulation mode.
4016 It also makes exploits much easier to write.
4018 none Vsyscalls don't work at all. This makes
4019 them quite hard to use for exploits but
4020 might break your system.
4022 vt.color= [VT] Default text color.
4023 Format: 0xYX, X = foreground, Y = background.
4024 Default: 0x07 = light gray on black.
4026 vt.cur_default= [VT] Default cursor shape.
4027 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4028 the parameters of the <Esc>[?A;B;Cc escape sequence;
4029 see VGA-softcursor.txt. Default: 2 = underline.
4031 vt.default_blu= [VT]
4032 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4033 Change the default blue palette of the console.
4034 This is a 16-member array composed of values
4037 vt.default_grn= [VT]
4038 Format: <green0>,<green1>,<green2>,...,<green15>
4039 Change the default green palette of the console.
4040 This is a 16-member array composed of values
4043 vt.default_red= [VT]
4044 Format: <red0>,<red1>,<red2>,...,<red15>
4045 Change the default red palette of the console.
4046 This is a 16-member array composed of values
4052 Set system-wide default UTF-8 mode for all tty's.
4053 Default is 1, i.e. UTF-8 mode is enabled for all
4054 newly opened terminals.
4056 vt.global_cursor_default=
4059 Set system-wide default for whether a cursor
4060 is shown on new VTs. Default is -1,
4061 i.e. cursors will be created by default unless
4062 overridden by individual drivers. 0 will hide
4063 cursors, 1 will display them.
4065 vt.italic= [VT] Default color for italic text; 0-15.
4068 vt.underline= [VT] Default color for underlined text; 0-15.
4071 watchdog timers [HW,WDT] For information on watchdog timers,
4072 see Documentation/watchdog/watchdog-parameters.txt
4073 or other driver-specific files in the
4074 Documentation/watchdog/ directory.
4076 workqueue.disable_numa
4077 By default, all work items queued to unbound
4078 workqueues are affine to the NUMA nodes they're
4079 issued on, which results in better behavior in
4080 general. If NUMA affinity needs to be disabled for
4081 whatever reason, this option can be used. Note
4082 that this also can be controlled per-workqueue for
4083 workqueues visible under /sys/bus/workqueue/.
4085 workqueue.power_efficient
4086 Per-cpu workqueues are generally preferred because
4087 they show better performance thanks to cache
4088 locality; unfortunately, per-cpu workqueues tend to
4089 be more power hungry than unbound workqueues.
4091 Enabling this makes the per-cpu workqueues which
4092 were observed to contribute significantly to power
4093 consumption unbound, leading to measurably lower
4094 power usage at the cost of small performance
4097 The default value of this parameter is determined by
4098 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4100 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4101 default x2apic cluster mode on platforms
4104 x86_intel_mid_timer= [X86-32,APBT]
4105 Choose timer option for x86 Intel MID platform.
4106 Two valid options are apbt timer only and lapic timer
4107 plus one apbt timer for broadcast timer.
4108 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4110 xen_512gb_limit [KNL,X86-64,XEN]
4111 Restricts the kernel running paravirtualized under Xen
4112 to use only up to 512 GB of RAM. The reason to do so is
4113 crash analysis tools and Xen tools for doing domain
4114 save/restore/migration must be enabled to handle larger
4117 xen_emul_unplug= [HW,X86,XEN]
4118 Unplug Xen emulated devices
4119 Format: [unplug0,][unplug1]
4120 ide-disks -- unplug primary master IDE devices
4121 aux-ide-disks -- unplug non-primary-master IDE devices
4122 nics -- unplug network devices
4123 all -- unplug all emulated devices (NICs and IDE disks)
4124 unnecessary -- unplugging emulated devices is
4125 unnecessary even if the host did not respond to
4127 never -- do not unplug even if version check succeeds
4129 xen_nopvspin [X86,XEN]
4130 Disables the ticketlock slowpath using Xen PV
4134 Disables the PV optimizations forcing the HVM guest to
4135 run as generic HVM guest with no PV drivers.
4137 xirc2ps_cs= [NET,PCMCIA]
4139 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4141 ______________________________________________________________________
4145 Add more DRM drivers.
projects / karo-tx-linux.git / blob