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, also enough extra
794 low memory is needed to make sure DMA buffers for 32-bit
795 devices won't run out. Kernel would try to allocate at
796 at least 256M below 4G automatically.
797 This one let user to specify own low range under 4G
798 for second kernel instead.
799 0: to disable low allocation.
800 It will be ignored when crashkernel=X,high is not used
801 or memory reserved is below 4G.
806 cs89x0_media= [HW,NET]
807 Format: { rj45 | aui | bnc }
810 See header of drivers/s390/block/dasd_devmap.c.
812 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
813 (one device per port)
814 Format: <port#>,<type>
815 See also Documentation/input/joystick-parport.txt
817 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
818 time. See Documentation/dynamic-debug-howto.txt for
819 details. Deprecated, see dyndbg.
821 debug [KNL] Enable kernel debugging (events log level).
824 [KNL] verbose self-tests
826 Print debugging info while doing the locking API
828 We default to 0 (no extra messages), setting it to
829 1 will print _a lot_ more information - normally
830 only useful to kernel developers.
832 debug_objects [KNL] Enable object debugging
835 [KNL] Disable object debugging
837 debug_guardpage_minorder=
838 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
839 parameter allows control of the order of pages that will
840 be intentionally kept free (and hence protected) by the
841 buddy allocator. Bigger value increase the probability
842 of catching random memory corruption, but reduce the
843 amount of memory for normal system use. The maximum
844 possible value is MAX_ORDER/2. Setting this parameter
845 to 1 or 2 should be enough to identify most random
846 memory corruption problems caused by bugs in kernel or
847 driver code when a CPU writes to (or reads from) a
848 random memory location. Note that there exists a class
849 of memory corruptions problems caused by buggy H/W or
850 F/W or by drivers badly programing DMA (basically when
851 memory is written at bus level and the CPU MMU is
852 bypassed) which are not detectable by
853 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
854 tracking down these problems.
857 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
858 parameter enables the feature at boot time. In
859 default, it is disabled. We can avoid allocating huge
860 chunk of memory for debug pagealloc if we don't enable
861 it at boot time and the system will work mostly same
862 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
863 on: enable the feature
865 debugpat [X86] Enable PAT debugging
867 decnet.addr= [HW,NET]
868 Format: <area>[,<node>]
869 See also Documentation/networking/decnet.txt.
872 [same as hugepagesz=] The size of the default
873 HugeTLB page size. This is the size represented by
874 the legacy /proc/ hugepages APIs, used for SHM, and
875 default size when mounting hugetlbfs filesystems.
876 Defaults to the default architecture's huge page size
880 Set number of hash buckets for dentry cache.
883 See Documentation/networking/ipv6.txt.
885 disable_cpu_apicid= [X86,APIC,SMP]
887 The number of initial APIC ID for the
888 corresponding CPU to be disabled at boot,
889 mostly used for the kdump 2nd kernel to
890 disable BSP to wake up multiple CPUs without
891 causing system reset or hang due to sending
894 disable_ddw [PPC/PSERIES]
895 Disable Dynamic DMA Window support. Use this if
896 to workaround buggy firmware.
899 See Documentation/networking/ipv6.txt.
901 disable_mtrr_cleanup [X86]
902 The kernel tries to adjust MTRR layout from continuous
903 to discrete, to make X server driver able to add WB
904 entry later. This parameter disables that.
906 disable_mtrr_trim [X86, Intel and AMD only]
907 By default the kernel will trim any uncacheable
908 memory out of your available memory pool based on
909 MTRR settings. This parameter disables that behavior,
910 possibly causing your machine to run very slowly.
912 disable_timer_pin_1 [X86]
913 Disable PIN 1 of APIC timer
914 Can be useful to work around chipset bugs.
916 dis_ucode_ldr [X86] Disable the microcode loader.
918 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
919 this option disables the debugging code at boot.
921 dma_debug_entries=<number>
922 This option allows to tune the number of preallocated
923 entries for DMA-API debugging code. One entry is
924 required per DMA-API allocation. Use this if the
925 DMA-API debugging code disables itself because the
926 architectural default is too low.
928 dma_debug_driver=<driver_name>
929 With this option the DMA-API debugging driver
930 filter feature can be enabled at boot time. Just
931 pass the driver to filter for as the parameter.
932 The filter can be disabled or changed to another
933 driver later using sysfs.
935 drm_kms_helper.edid_firmware=[<connector>:]<file>
936 Broken monitors, graphic adapters and KVMs may
937 send no or incorrect EDID data sets. This parameter
938 allows to specify an EDID data set in the
939 /lib/firmware directory that is used instead.
940 Generic built-in EDID data sets are used, if one of
941 edid/1024x768.bin, edid/1280x1024.bin,
942 edid/1680x1050.bin, or edid/1920x1080.bin is given
943 and no file with the same name exists. Details and
944 instructions how to build your own EDID data are
945 available in Documentation/EDID/HOWTO.txt. An EDID
946 data set will only be used for a particular connector,
947 if its name and a colon are prepended to the EDID
952 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
953 module.dyndbg[="val"]
954 Enable debug messages at boot time. See
955 Documentation/dynamic-debug-howto.txt for details.
957 nompx [X86] Disables Intel Memory Protection Extensions.
958 See Documentation/x86/intel_mpx.txt for more
959 information about the feature.
962 on enable eager fpu restore
963 off disable eager fpu restore
964 auto selects the default scheme, which automatically
965 enables eagerfpu restore for xsaveopt.
967 module.async_probe [KNL]
968 Enable asynchronous probe on this module.
970 early_ioremap_debug [KNL]
971 Enable debug messages in early_ioremap support. This
972 is useful for tracking down temporary early mappings
973 which are not unmapped.
975 earlycon= [KNL] Output early console device and options.
977 When used with no options, the early console is
978 determined by the stdout-path property in device
982 Start an early, polled-mode console on a cadence serial
983 port at the specified address. The cadence serial port
984 must already be setup and configured. Options are not
987 uart[8250],io,<addr>[,options]
988 uart[8250],mmio,<addr>[,options]
989 uart[8250],mmio32,<addr>[,options]
990 uart[8250],mmio32be,<addr>[,options]
991 uart[8250],0x<addr>[,options]
992 Start an early, polled-mode console on the 8250/16550
993 UART at the specified I/O port or MMIO address.
994 MMIO inter-register address stride is either 8-bit
995 (mmio) or 32-bit (mmio32 or mmio32be).
996 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
997 to be equivalent to 'mmio'. 'options' are specified
998 in the same format described for "console=ttyS<n>"; if
999 unspecified, the h/w is not initialized.
1002 Start an early, polled-mode console on a pl011 serial
1003 port at the specified address. The pl011 serial port
1004 must already be setup and configured. Options are not
1008 Start an early, polled-mode console on an msm serial
1009 port at the specified address. The serial port
1010 must already be setup and configured. Options are not
1013 msm_serial_dm,<addr>
1014 Start an early, polled-mode console on an msm serial
1015 dm port at the specified address. The serial port
1016 must already be setup and configured. Options are not
1019 smh Use ARM semihosting calls for early console.
1027 Use early console provided by serial driver available
1028 on Samsung SoCs, requires selecting proper type and
1029 a correct base address of the selected UART port. The
1030 serial port must already be setup and configured.
1031 Options are not yet supported.
1035 Use early console provided by Freescale LP UART driver
1036 found on Freescale Vybrid and QorIQ LS1021A processors.
1037 A valid base address must be provided, and the serial
1038 port must already be setup and configured.
1040 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1044 earlyprintk=serial[,ttySn[,baudrate]]
1045 earlyprintk=serial[,0x...[,baudrate]]
1046 earlyprintk=ttySn[,baudrate]
1047 earlyprintk=dbgp[debugController#]
1048 earlyprintk=pciserial,bus:device.function[,baudrate]
1050 earlyprintk is useful when the kernel crashes before
1051 the normal console is initialized. It is not enabled by
1052 default because it has some cosmetic problems.
1054 Append ",keep" to not disable it when the real console
1057 Only one of vga, efi, serial, or usb debug port can
1060 Currently only ttyS0 and ttyS1 may be specified by
1061 name. Other I/O ports may be explicitly specified
1062 on some architectures (x86 and arm at least) by
1063 replacing ttySn with an I/O port address, like this:
1064 earlyprintk=serial,0x1008,115200
1065 You can find the port for a given device in
1066 /proc/tty/driver/serial:
1067 2: uart:ST16650V2 port:00001008 irq:18 ...
1069 Interaction with the standard serial driver is not
1072 The VGA and EFI output is eventually overwritten by
1075 The xen output can only be used by Xen PV guests.
1077 edac_report= [HW,EDAC] Control how to report EDAC event
1078 Format: {"on" | "off" | "force"}
1079 on: enable EDAC to report H/W event. May be overridden
1080 by other higher priority error reporting module.
1081 off: disable H/W event reporting through EDAC.
1082 force: enforce the use of EDAC to report H/W event.
1085 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1088 This is designed to be used in conjunction with
1089 the boot argument: earlyprintk=vga
1092 Format: {"off" | "on" | "skip[mbr]"}
1095 Format: { "old_map", "nochunk", "noruntime", "debug" }
1096 old_map [X86-64]: switch to the old ioremap-based EFI
1097 runtime services mapping. 32-bit still uses this one by
1099 nochunk: disable reading files in "chunks" in the EFI
1100 boot stub, as chunking can cause problems with some
1101 firmware implementations.
1102 noruntime : disable EFI runtime services support
1103 debug: enable misc debug output
1105 efi_no_storage_paranoia [EFI; X86]
1106 Using this parameter you can use more than 50% of
1107 your efi variable storage. Use this parameter only if
1108 you are really sure that your UEFI does sane gc and
1109 fulfills the spec otherwise your board may brick.
1111 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1112 Add arbitrary attribute to specific memory range by
1113 updating original EFI memory map.
1114 Region of memory which aa attribute is added to is
1116 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1117 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1118 attribute is added to range 0x100000000-0x180000000 and
1119 0x10a0000000-0x1120000000.
1121 Using this parameter you can do debugging of EFI memmap
1122 related feature. For example, you can do debugging of
1123 Address Range Mirroring feature even if your box
1126 eisa_irq_edge= [PARISC,HW]
1127 See header of drivers/parisc/eisa.c.
1130 See comment before function elanfreq_setup() in
1131 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1134 Format: {"cfq" | "deadline" | "noop"}
1135 See Documentation/block/cfq-iosched.txt and
1136 Documentation/block/deadline-iosched.txt for details.
1138 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1139 Specifies physical address of start of kernel core
1140 image elf header and optionally the size. Generally
1141 kexec loader will pass this option to capture kernel.
1142 See Documentation/kdump/kdump.txt for details.
1144 enable_mtrr_cleanup [X86]
1145 The kernel tries to adjust MTRR layout from continuous
1146 to discrete, to make X server driver able to add WB
1147 entry later. This parameter enables that.
1149 enable_timer_pin_1 [X86]
1150 Enable PIN 1 of APIC timer
1151 Can be useful to work around chipset bugs
1152 (in particular on some ATI chipsets).
1153 The kernel tries to set a reasonable default.
1155 enforcing [SELINUX] Set initial enforcing status.
1157 See security/selinux/Kconfig help text.
1158 0 -- permissive (log only, no denials).
1159 1 -- enforcing (deny and log).
1161 Value can be changed at runtime via /selinux/enforce.
1164 Disable Error Record Serialization Table (ERST)
1167 ether= [HW,NET] Ethernet cards parameters
1168 This option is obsoleted by the "netdev=" option, which
1169 has equivalent usage. See its documentation for details.
1173 Permit 'security.evm' to be updated regardless of
1174 current integrity status.
1178 fail_make_request=[KNL]
1179 General fault injection mechanism.
1180 Format: <interval>,<probability>,<space>,<times>
1181 See also Documentation/fault-injection/.
1184 See Documentation/blockdev/floppy.txt.
1186 force_pal_cache_flush
1187 [IA-64] Avoid check_sal_cache_flush which may hang on
1188 buggy SAL_CACHE_FLUSH implementations. Using this
1189 parameter will force ia64_sal_cache_flush to call
1190 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1193 Forcefully enable Physical Address Extension (PAE).
1194 Many Pentium M systems disable PAE but may have a
1195 functionally usable PAE implementation.
1196 Warning: use of this parameter will taint the kernel
1197 and may cause unknown problems.
1200 [FTRACE] will set and start the specified tracer
1201 as early as possible in order to facilitate early
1204 ftrace_dump_on_oops[=orig_cpu]
1205 [FTRACE] will dump the trace buffers on oops.
1206 If no parameter is passed, ftrace will dump
1207 buffers of all CPUs, but if you pass orig_cpu, it will
1208 dump only the buffer of the CPU that triggered the
1211 ftrace_filter=[function-list]
1212 [FTRACE] Limit the functions traced by the function
1213 tracer at boot up. function-list is a comma separated
1214 list of functions. This list can be changed at run
1215 time by the set_ftrace_filter file in the debugfs
1218 ftrace_notrace=[function-list]
1219 [FTRACE] Do not trace the functions specified in
1220 function-list. This list can be changed at run time
1221 by the set_ftrace_notrace file in the debugfs
1224 ftrace_graph_filter=[function-list]
1225 [FTRACE] Limit the top level callers functions traced
1226 by the function graph tracer at boot up.
1227 function-list is a comma separated list of functions
1228 that can be changed at run time by the
1229 set_graph_function file in the debugfs tracing directory.
1231 ftrace_graph_notrace=[function-list]
1232 [FTRACE] Do not trace from the functions specified in
1233 function-list. This list is a comma separated list of
1234 functions that can be changed at run time by the
1235 set_graph_notrace file in the debugfs tracing directory.
1238 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1239 support via parallel port (up to 5 devices per port)
1240 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1241 See also Documentation/input/joystick-parport.txt
1245 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1249 gcov_persist= [GCOV] When non-zero (default), profiling data for
1250 kernel modules is saved and remains accessible via
1251 debugfs, even when the module is unloaded/reloaded.
1252 When zero, profiling data is discarded and associated
1253 debugfs files are removed at module unload time.
1255 gpt [EFI] Forces disk with valid GPT signature but
1256 invalid Protective MBR to be treated as GPT. If the
1257 primary GPT is corrupted, it enables the backup/alternate
1258 GPT to be used instead.
1260 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1261 the "Enable 0" bit of the configuration register.
1264 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1265 the "Enable 0" bit of the configuration register.
1268 grcan.select= [HW] Select which physical interface to use.
1271 grcan.txsize= [HW] Sets the size of the tx buffer.
1272 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1274 grcan.rxsize= [HW] Sets the size of the rx buffer.
1275 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1278 hashdist= [KNL,NUMA] Large hashes allocated during boot
1279 are distributed across NUMA nodes. Defaults on
1280 for 64-bit NUMA, off otherwise.
1281 Format: 0 | 1 (for off | on)
1283 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1285 hd= [EIDE] (E)IDE hard drive subsystem geometry
1286 Format: <cyl>,<head>,<sect>
1289 Disable Hardware Error Source Table (HEST) support;
1290 corresponding firmware-first mode error processing
1291 logic will be disabled.
1293 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1294 size of <nn>. This works even on boxes that have no
1295 highmem otherwise. This also works to reduce highmem
1296 size on bigger boxes.
1298 highres= [KNL] Enable/disable high resolution timer mode.
1299 Valid parameters: "on", "off"
1303 See Documentation/isdn/README.HiSax.
1307 hpet= [X86-32,HPET] option to control HPET usage
1308 Format: { enable (default) | disable | force |
1310 disable: disable HPET and use PIT instead
1311 force: allow force enabled of undocumented chips (ICH4,
1313 verbose: show contents of HPET registers during setup
1315 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1316 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1318 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1319 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1320 On x86-64 and powerpc, this option can be specified
1321 multiple times interleaved with hugepages= to reserve
1322 huge pages of different sizes. Valid pages sizes on
1323 x86-64 are 2M (when the CPU supports "pse") and 1G
1324 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1326 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1327 terminal devices. Valid values: 0..8
1328 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1329 If specified, z/VM IUCV HVC accepts connections
1330 from listed z/VM user IDs only.
1332 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1333 hardware thread id mappings.
1334 Format: <cpu>:<hwthread>
1337 Do not unregister boot console at start. This is only
1338 useful for debugging when something happens in the window
1339 between unregistering the boot console and initializing
1342 i2c_bus= [HW] Override the default board specific I2C bus speed
1343 or register an additional I2C bus that is not
1344 registered from board initialization code.
1348 i8042.debug [HW] Toggle i8042 debug mode
1349 i8042.unmask_kbd_data
1350 [HW] Enable printing of interrupt data from the KBD port
1351 (disabled by default, and as a pre-condition
1352 requires that i8042.debug=1 be enabled)
1353 i8042.direct [HW] Put keyboard port into non-translated mode
1354 i8042.dumbkbd [HW] Pretend that controller can only read data from
1355 keyboard and cannot control its state
1356 (Don't attempt to blink the leds)
1357 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1358 i8042.nokbd [HW] Don't check/create keyboard port
1359 i8042.noloop [HW] Disable the AUX Loopback command while probing
1361 i8042.nomux [HW] Don't check presence of an active multiplexing
1363 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1365 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1366 i8042.reset [HW] Reset the controller during init and cleanup
1367 i8042.unlock [HW] Unlock (ignore) the keylock
1368 i8042.kbdreset [HW] Reset device connected to KBD port
1372 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1373 indicates that the driver is running on unsupported
1375 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1376 does not match list of supported models.
1378 [HW] Report power status in /proc/i8k
1379 (disabled by default)
1380 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1383 i915.invert_brightness=
1384 [DRM] Invert the sense of the variable that is used to
1385 set the brightness of the panel backlight. Normally a
1386 brightness value of 0 indicates backlight switched off,
1387 and the maximum of the brightness value sets the backlight
1388 to maximum brightness. If this parameter is set to 0
1389 (default) and the machine requires it, or this parameter
1390 is set to 1, a brightness value of 0 sets the backlight
1391 to maximum brightness, and the maximum of the brightness
1392 value switches the backlight off.
1393 -1 -- never invert brightness
1394 0 -- machine default
1395 1 -- force brightness inversion
1398 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1400 ide-core.nodma= [HW] (E)IDE subsystem
1401 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1402 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1403 .cdrom .chs .ignore_cable are additional options
1404 See Documentation/ide/ide.txt.
1406 ide-generic.probe-mask= [HW] (E)IDE subsystem
1408 Probe mask for legacy ISA IDE ports. Depending on
1409 platform up to 6 ports are supported, enabled by
1410 setting corresponding bits in the mask to 1. The
1411 default value is 0x0, which has a special meaning.
1412 On systems that have PCI, it triggers scanning the
1413 PCI bus for the first and the second port, which
1414 are then probed. On systems without PCI the value
1415 of 0x0 enables probing the two first ports as if it
1418 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1419 Claim all unknown PCI IDE storage controllers.
1422 Format: idle=poll, idle=halt, idle=nomwait
1423 Poll forces a polling idle loop that can slightly
1424 improve the performance of waking up a idle CPU, but
1425 will use a lot of power and make the system run hot.
1427 idle=halt: Halt is forced to be used for CPU idle.
1428 In such case C2/C3 won't be used again.
1429 idle=nomwait: Disable mwait for CPU C-states
1431 ignore_loglevel [KNL]
1432 Ignore loglevel setting - this will print /all/
1433 kernel messages to the console. Useful for debugging.
1434 We also add it as printk module parameter, so users
1435 could change it dynamically, usually by
1436 /sys/module/printk/parameters/ignore_loglevel.
1438 ihash_entries= [KNL]
1439 Set number of hash buckets for inode cache.
1441 ima_appraise= [IMA] appraise integrity measurements
1442 Format: { "off" | "enforce" | "fix" | "log" }
1445 ima_appraise_tcb [IMA]
1446 The builtin appraise policy appraises all files
1450 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1454 The list of supported hash algorithms is defined
1455 in crypto/hash_info.h.
1458 The builtin measurement policy to load during IMA
1459 setup. Specyfing "tcb" as the value, measures all
1460 programs exec'd, files mmap'd for exec, and all files
1461 opened with the read mode bit set by either the
1462 effective uid (euid=0) or uid=0.
1465 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1466 Load a policy which meets the needs of the Trusted
1467 Computing Base. This means IMA will measure all
1468 programs exec'd, files mmap'd for exec, and all files
1469 opened for read by uid=0.
1472 Select one of defined IMA measurements template formats.
1473 Formats: { "ima" | "ima-ng" | "ima-sig" }
1477 [IMA] Define a custom template format.
1478 Format: { "field1|...|fieldN" }
1480 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1481 Format: <min_file_size>
1482 Set the minimal file size for using asynchronous hash.
1483 If left unspecified, ahash usage is disabled.
1485 ahash performance varies for different data sizes on
1486 different crypto accelerators. This option can be used
1487 to achieve the best performance for a particular HW.
1489 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1491 Set hashing buffer size. Default: 4k.
1493 ahash performance varies for different chunk sizes on
1494 different crypto accelerators. This option can be used
1495 to achieve best performance for particular HW.
1499 Run specified binary instead of /sbin/init as init
1502 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1503 for working out where the kernel is dying during
1506 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1507 initcall functions. Useful for debugging built-in
1508 modules and initcalls.
1510 initrd= [BOOT] Specify the location of the initial ramdisk
1512 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1515 int_pln_enable [x86] Enable power limit notification interrupt
1517 integrity_audit=[IMA]
1518 Format: { "0" | "1" }
1519 0 -- basic integrity auditing messages. (Default)
1520 1 -- additional integrity auditing messages.
1522 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1524 Enable intel iommu driver.
1526 Disable intel iommu driver.
1527 igfx_off [Default Off]
1528 By default, gfx is mapped as normal device. If a gfx
1529 device has a dedicated DMAR unit, the DMAR unit is
1530 bypassed by not enabling DMAR with this option. In
1531 this case, gfx device will use physical address for
1534 With this option iommu will not optimize to look
1535 for io virtual address below 32-bit forcing dual
1536 address cycle on pci bus for cards supporting greater
1537 than 32-bit addressing. The default is to look
1538 for translation below 32-bit and if not available
1539 then look in the higher range.
1540 strict [Default Off]
1541 With this option on every unmap_single operation will
1542 result in a hardware IOTLB flush operation as opposed
1543 to batching them for performance.
1544 sp_off [Default Off]
1545 By default, super page will be supported if Intel IOMMU
1546 has the capability. With this option, super page will
1548 ecs_off [Default Off]
1549 By default, extended context tables will be supported if
1550 the hardware advertises that it has support both for the
1551 extended tables themselves, and also PASID support. With
1552 this option set, extended tables will not be used even
1553 on hardware which claims to support them.
1555 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1556 0 disables intel_idle and fall back on acpi_idle.
1557 1 to 6 specify maximum depth of C-state.
1561 Do not enable intel_pstate as the default
1562 scaling driver for the supported processors
1564 Enable intel_pstate on systems that prohibit it by default
1565 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1566 instead of acpi-cpufreq may disable platform features, such
1567 as thermal controls and power capping, that rely on ACPI
1568 P-States information being indicated to OSPM and therefore
1569 should be used with caution. This option does not work with
1570 processors that aren't supported by the intel_pstate driver
1571 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1573 Do not enable hardware P state control (HWP)
1576 Only load intel_pstate on systems which support
1577 hardware P state control (HWP) if available.
1579 Don't use ACPI processor performance control objects
1580 _PSS and _PPC specified limits.
1582 intremap= [X86-64, Intel-IOMMU]
1583 on enable Interrupt Remapping (default)
1584 off disable Interrupt Remapping
1585 nosid disable Source ID checking
1587 BIOS x2APIC opt-out request will be ignored
1589 iomem= Disable strict checking of access to MMIO memory
1590 strict regions from userspace.
1605 nobypass [PPC/POWERNV]
1606 Disable IOMMU bypass, using IOMMU for PCI devices.
1609 io7= [HW] IO7 for Marvel based alpha systems
1610 See comment before marvel_specify_io7 in
1611 arch/alpha/kernel/core_marvel.c.
1613 io_delay= [X86] I/O delay method
1615 Standard port 0x80 based delay
1617 Alternate port 0xed based delay (needed on some systems)
1619 Simple two microseconds delay
1624 See Documentation/filesystems/nfs/nfsroot.txt.
1627 When an interrupt is not handled search all handlers
1628 for it. Intended to get systems with badly broken
1632 When an interrupt is not handled search all handlers
1633 for it. Also check all handlers each timer
1634 interrupt. Intended to get systems with badly broken
1638 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1640 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1642 <cpu number>,...,<cpu number>
1644 <cpu number>-<cpu number>
1645 (must be a positive range in ascending order)
1647 <cpu number>,...,<cpu number>-<cpu number>
1649 This option can be used to specify one or more CPUs
1650 to isolate from the general SMP balancing and scheduling
1651 algorithms. You can move a process onto or off an
1652 "isolated" CPU via the CPU affinity syscalls or cpuset.
1653 <cpu number> begins at 0 and the maximum value is
1654 "number of CPUs in system - 1".
1656 This option is the preferred way to isolate CPUs. The
1657 alternative -- manually setting the CPU mask of all
1658 tasks in the system -- can cause problems and
1659 suboptimal load balancer performance.
1663 ivrs_ioapic [HW,X86_64]
1664 Provide an override to the IOAPIC-ID<->DEVICE-ID
1665 mapping provided in the IVRS ACPI table. For
1666 example, to map IOAPIC-ID decimal 10 to
1667 PCI device 00:14.0 write the parameter as:
1668 ivrs_ioapic[10]=00:14.0
1670 ivrs_hpet [HW,X86_64]
1671 Provide an override to the HPET-ID<->DEVICE-ID
1672 mapping provided in the IVRS ACPI table. For
1673 example, to map HPET-ID decimal 0 to
1674 PCI device 00:14.0 write the parameter as:
1675 ivrs_hpet[0]=00:14.0
1677 js= [HW,JOY] Analog joystick
1678 See Documentation/input/joystick.txt.
1681 Enable/disable kernel and module base offset ASLR
1682 (Address Space Layout Randomization) if built into
1683 the kernel. When CONFIG_HIBERNATION is selected,
1684 kASLR is disabled by default. When kASLR is enabled,
1685 hibernation will be disabled.
1689 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1690 specifies the amount of memory usable by the kernel
1691 for non-movable allocations. The requested amount is
1692 spread evenly throughout all nodes in the system. The
1693 remaining memory in each node is used for Movable
1694 pages. In the event, a node is too small to have both
1695 kernelcore and Movable pages, kernelcore pages will
1696 take priority and other nodes will have a larger number
1697 of Movable pages. The Movable zone is used for the
1698 allocation of pages that may be reclaimed or moved
1699 by the page migration subsystem. This means that
1700 HugeTLB pages may not be allocated from this zone.
1701 Note that allocations like PTEs-from-HighMem still
1702 use the HighMem zone if it exists, and the Normal
1703 zone if it does not.
1705 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1706 Format: <Controller#>[,poll interval]
1707 The controller # is the number of the ehci usb debug
1708 port as it is probed via PCI. The poll interval is
1709 optional and is the number seconds in between
1710 each poll cycle to the debug port in case you need
1711 the functionality for interrupting the kernel with
1712 gdb or control-c on the dbgp connection. When
1713 not using this parameter you use sysrq-g to break into
1714 the kernel debugger.
1716 kgdboc= [KGDB,HW] kgdb over consoles.
1717 Requires a tty driver that supports console polling,
1718 or a supported polling keyboard driver (non-usb).
1719 Serial only format: <serial_device>[,baud]
1720 keyboard only format: kbd
1721 keyboard and serial format: kbd,<serial_device>[,baud]
1722 Optional Kernel mode setting:
1723 kms, kbd format: kms,kbd
1724 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1726 kgdbwait [KGDB] Stop kernel execution and enter the
1727 kernel debugger at the earliest opportunity.
1729 kmac= [MIPS] korina ethernet MAC address.
1730 Configure the RouterBoard 532 series on-chip
1731 Ethernet adapter MAC address.
1733 kmemleak= [KNL] Boot-time kmemleak enable/disable
1734 Valid arguments: on, off
1736 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1739 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1740 Valid arguments: 0, 1, 2
1741 kmemcheck=0 (disabled)
1742 kmemcheck=1 (enabled)
1743 kmemcheck=2 (one-shot mode)
1744 Default: 2 (one-shot mode)
1746 kstack=N [X86] Print N words from the kernel stack
1749 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1750 Default is 0 (don't ignore, but inject #GP)
1752 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1756 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1757 Default is 1 (enabled)
1759 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1761 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1763 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1764 (virtualized MMU) support on capable Intel chips.
1765 Default is 1 (enabled)
1767 kvm-intel.emulate_invalid_guest_state=
1768 [KVM,Intel] Enable emulation of invalid guest states
1769 Default is 0 (disabled)
1771 kvm-intel.flexpriority=
1772 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1773 Default is 1 (enabled)
1776 [KVM,Intel] Enable VMX nesting (nVMX).
1777 Default is 0 (disabled)
1779 kvm-intel.unrestricted_guest=
1780 [KVM,Intel] Disable unrestricted guest feature
1781 (virtualized real and unpaged mode) on capable
1782 Intel chips. Default is 1 (enabled)
1784 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1785 feature (tagged TLBs) on capable Intel chips.
1786 Default is 1 (enabled)
1792 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1795 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1796 value for LAPIC timer one-shot implementation. Default
1797 back to the programmable timer unit in the LAPIC.
1799 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1802 libata.dma= [LIBATA] DMA control
1803 libata.dma=0 Disable all PATA and SATA DMA
1804 libata.dma=1 PATA and SATA Disk DMA only
1805 libata.dma=2 ATAPI (CDROM) DMA only
1806 libata.dma=4 Compact Flash DMA only
1807 Combinations also work, so libata.dma=3 enables DMA
1808 for disks and CDROMs, but not CFs.
1810 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1811 libata.ignore_hpa=0 keep BIOS limits (default)
1812 libata.ignore_hpa=1 ignore limits, using full disk
1814 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1818 libata.force= [LIBATA] Force configurations. The format is comma
1819 separated list of "[ID:]VAL" where ID is
1820 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1821 matching port, link or device. Basically, it matches
1822 the ATA ID string printed on console by libata. If
1823 the whole ID part is omitted, the last PORT and DEVICE
1824 values are used. If ID hasn't been specified yet, the
1825 configuration applies to all ports, links and devices.
1827 If only DEVICE is omitted, the parameter applies to
1828 the port and all links and devices behind it. DEVICE
1829 number of 0 either selects the first device or the
1830 first fan-out link behind PMP device. It does not
1831 select the host link. DEVICE number of 15 selects the
1832 host link and device attached to it.
1834 The VAL specifies the configuration to force. As long
1835 as there's no ambiguity shortcut notation is allowed.
1836 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1837 The following configurations can be forced.
1839 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1840 Any ID with matching PORT is used.
1842 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1844 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1845 udma[/][16,25,33,44,66,100,133] notation is also
1848 * [no]ncq: Turn on or off NCQ.
1850 * [no]ncqtrim: Turn off queued DSM TRIM.
1852 * nohrst, nosrst, norst: suppress hard, soft
1855 * rstonce: only attempt one reset during
1856 hot-unplug link recovery
1858 * dump_id: dump IDENTIFY data.
1860 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1862 * disable: Disable this device.
1864 If there are multiple matching configurations changing
1865 the same attribute, the last one is used.
1867 memblock=debug [KNL] Enable memblock debug messages.
1869 load_ramdisk= [RAM] List of ramdisks to load from floppy
1870 See Documentation/blockdev/ramdisk.txt.
1872 lockd.nlm_grace_period=P [NFS] Assign grace period.
1875 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1878 lockd.nlm_timeout=T [NFS] Assign timeout value.
1881 lockd.nlm_udpport=M [NFS] Assign UDP port.
1884 locktorture.nreaders_stress= [KNL]
1885 Set the number of locking read-acquisition kthreads.
1886 Defaults to being automatically set based on the
1887 number of online CPUs.
1889 locktorture.nwriters_stress= [KNL]
1890 Set the number of locking write-acquisition kthreads.
1892 locktorture.onoff_holdoff= [KNL]
1893 Set time (s) after boot for CPU-hotplug testing.
1895 locktorture.onoff_interval= [KNL]
1896 Set time (s) between CPU-hotplug operations, or
1897 zero to disable CPU-hotplug testing.
1899 locktorture.shuffle_interval= [KNL]
1900 Set task-shuffle interval (jiffies). Shuffling
1901 tasks allows some CPUs to go into dyntick-idle
1902 mode during the locktorture test.
1904 locktorture.shutdown_secs= [KNL]
1905 Set time (s) after boot system shutdown. This
1906 is useful for hands-off automated testing.
1908 locktorture.stat_interval= [KNL]
1909 Time (s) between statistics printk()s.
1911 locktorture.stutter= [KNL]
1912 Time (s) to stutter testing, for example,
1913 specifying five seconds causes the test to run for
1914 five seconds, wait for five seconds, and so on.
1915 This tests the locking primitive's ability to
1916 transition abruptly to and from idle.
1918 locktorture.torture_runnable= [BOOT]
1919 Start locktorture running at boot time.
1921 locktorture.torture_type= [KNL]
1922 Specify the locking implementation to test.
1924 locktorture.verbose= [KNL]
1925 Enable additional printk() statements.
1927 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1930 loglevel= All Kernel Messages with a loglevel smaller than the
1931 console loglevel will be printed to the console. It can
1932 also be changed with klogd or other programs. The
1933 loglevels are defined as follows:
1935 0 (KERN_EMERG) system is unusable
1936 1 (KERN_ALERT) action must be taken immediately
1937 2 (KERN_CRIT) critical conditions
1938 3 (KERN_ERR) error conditions
1939 4 (KERN_WARNING) warning conditions
1940 5 (KERN_NOTICE) normal but significant condition
1941 6 (KERN_INFO) informational
1942 7 (KERN_DEBUG) debug-level messages
1944 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1945 in bytes. n must be a power of two and greater
1946 than the minimal size. The minimal size is defined
1947 by LOG_BUF_SHIFT kernel config parameter. There is
1948 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1949 that allows to increase the default size depending on
1950 the number of CPUs. See init/Kconfig for more details.
1952 logo.nologo [FB] Disables display of the built-in Linux logo.
1953 This may be used to provide more screen space for
1954 kernel log messages and is useful when debugging
1955 kernel boot problems.
1957 lp=0 [LP] Specify parallel ports to use, e.g,
1958 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1959 lp=reset first parallel port). 'lp=0' disables the
1960 lp=auto printer driver. 'lp=reset' (which can be
1961 specified in addition to the ports) causes
1962 attached printers to be reset. Using
1963 lp=port1,port2,... specifies the parallel ports
1964 to associate lp devices with, starting with
1965 lp0. A port specification may be 'none' to skip
1966 that lp device, or a parport name such as
1967 'parport0'. Specifying 'lp=auto' instead of a
1968 port specification list means that device IDs
1969 from each port should be examined, to see if
1970 an IEEE 1284-compliant printer is attached; if
1971 so, the driver will manage that printer.
1972 See also header of drivers/char/lp.c.
1975 Sets loops_per_jiffy to given constant, thus avoiding
1976 time-consuming boot-time autodetection (up to 250 ms per
1977 CPU). 0 enables autodetection (default). To determine
1978 the correct value for your kernel, boot with normal
1979 autodetection and see what value is printed. Note that
1980 on SMP systems the preset will be applied to all CPUs,
1981 which is likely to cause problems if your CPUs need
1982 significantly divergent settings. An incorrect value
1983 will cause delays in the kernel to be wrong, leading to
1984 unpredictable I/O errors and other breakage. Although
1985 unlikely, in the extreme case this might damage your
1989 Format: <io>,<irq>,<dma>
1991 machvec= [IA-64] Force the use of a particular machine-vector
1992 (machvec) in a generic kernel.
1993 Example: machvec=hpzx1_swiotlb
1995 machtype= [Loongson] Share the same kernel image file between different
1997 Example: machtype=lemote-yeeloong-2f-7inch
1999 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2000 than or equal to this physical address is ignored.
2002 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2003 should make use of. maxcpus=n : n >= 0 limits the
2004 kernel to using 'n' processors. n=0 is a special case,
2005 it is equivalent to "nosmp", which also disables
2008 max_loop= [LOOP] The number of loop block devices that get
2009 (loop.max_loop) unconditionally pre-created at init time. The default
2010 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2011 of statically allocating a predefined number, loop
2012 devices can be requested on-demand with the
2013 /dev/loop-control interface.
2015 mce [X86-32] Machine Check Exception
2017 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2019 md= [HW] RAID subsystems devices and level
2020 See Documentation/md.txt.
2023 Format: <first>,<last>
2024 Specifies range of consoles to be captured by the MDA.
2026 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2027 Amount of memory to be used when the kernel is not able
2028 to see the whole system memory or for test.
2029 [X86] Work as limiting max address. Use together
2030 with memmap= to avoid physical address space collisions.
2031 Without memmap= PCI devices could be placed at addresses
2032 belonging to unused RAM.
2034 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2038 [KNL,SH] Allow user to override the default size for
2039 per-device physically contiguous DMA buffers.
2041 memmap=exactmap [KNL,X86] Enable setting of an exact
2042 E820 memory map, as specified by the user.
2043 Such memmap=exactmap lines can be constructed based on
2044 BIOS output or other requirements. See the memmap=nn@ss
2047 memmap=nn[KMG]@ss[KMG]
2048 [KNL] Force usage of a specific region of memory.
2049 Region of memory to be used is from ss to ss+nn.
2051 memmap=nn[KMG]#ss[KMG]
2052 [KNL,ACPI] Mark specific memory as ACPI data.
2053 Region of memory to be marked is from ss to ss+nn.
2055 memmap=nn[KMG]$ss[KMG]
2056 [KNL,ACPI] Mark specific memory as reserved.
2057 Region of memory to be reserved is from ss to ss+nn.
2058 Example: Exclude memory from 0x18690000-0x1869ffff
2059 memmap=64K$0x18690000
2061 memmap=0x10000$0x18690000
2063 memmap=nn[KMG]!ss[KMG]
2064 [KNL,X86] Mark specific memory as protected.
2065 Region of memory to be used, from ss to ss+nn.
2066 The memory region may be marked as e820 type 12 (0xc)
2067 and is NVDIMM or ADR memory.
2069 memory_corruption_check=0/1 [X86]
2070 Some BIOSes seem to corrupt the first 64k of
2071 memory when doing things like suspend/resume.
2072 Setting this option will scan the memory
2073 looking for corruption. Enabling this will
2074 both detect corruption and prevent the kernel
2075 from using the memory being corrupted.
2076 However, its intended as a diagnostic tool; if
2077 repeatable BIOS-originated corruption always
2078 affects the same memory, you can use memmap=
2079 to prevent the kernel from using that memory.
2081 memory_corruption_check_size=size [X86]
2082 By default it checks for corruption in the low
2083 64k, making this memory unavailable for normal
2084 use. Use this parameter to scan for
2085 corruption in more or less memory.
2087 memory_corruption_check_period=seconds [X86]
2088 By default it checks for corruption every 60
2089 seconds. Use this parameter to check at some
2090 other rate. 0 disables periodic checking.
2092 memtest= [KNL,X86,ARM] Enable memtest
2094 default : 0 <disable>
2095 Specifies the number of memtest passes to be
2096 performed. Each pass selects another test
2097 pattern from a given set of patterns. Memtest
2098 fills the memory with this pattern, validates
2099 memory contents and reserves bad memory
2100 regions that are detected.
2102 meye.*= [HW] Set MotionEye Camera parameters
2103 See Documentation/video4linux/meye.txt.
2105 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2106 Multi-Function General Purpose Timers on AMD Geode
2109 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2110 the BIOS has incorrectly applied a workaround. TinyBIOS
2111 version 0.98 is known to be affected, 0.99 fixes the
2112 problem by letting the user disable the workaround.
2116 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2117 physical address is ignored.
2119 mini2440= [ARM,HW,KNL]
2120 Format:[0..2][b][c][t]
2122 MINI2440 configuration specification:
2123 0 - The attached screen is the 3.5" TFT
2124 1 - The attached screen is the 7" TFT
2125 2 - The VGA Shield is attached (1024x768)
2126 Leaving out the screen size parameter will not load
2127 the TFT driver, and the framebuffer will be left
2129 b - Enable backlight. The TFT backlight pin will be
2130 linked to the kernel VESA blanking code and a GPIO
2131 LED. This parameter is not necessary when using the
2133 c - Enable the s3c camera interface.
2134 t - Reserved for enabling touchscreen support. The
2135 touchscreen support is not enabled in the mainstream
2136 kernel as of 2.6.30, a preliminary port can be found
2137 in the "bleeding edge" mini2440 support kernel at
2138 http://repo.or.cz/w/linux-2.6/mini2440.git
2141 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2142 parameter allows control of the logging verbosity for
2143 the additional memory initialisation checks. A value
2144 of 0 disables mminit logging and a level of 4 will
2145 log everything. Information is printed at KERN_DEBUG
2146 so loglevel=8 may also need to be specified.
2149 [KNL] When CONFIG_MODULE_SIG is set, this means that
2150 modules without (valid) signatures will fail to load.
2151 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2152 is always true, so this option does nothing.
2155 [MOUSE] Maximum time between finger touching and
2156 leaving touchpad surface for touch to be considered
2157 a tap and be reported as a left button click (for
2158 touchpads working in absolute mode only).
2160 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2161 reporting absolute coordinates, such as tablets
2162 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2163 reporting absolute coordinates, such as tablets
2165 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2166 is similar to kernelcore except it specifies the
2167 amount of memory used for migratable allocations.
2168 If both kernelcore and movablecore is specified,
2169 then kernelcore will be at *least* the specified
2170 value but may be more. If movablecore on its own
2171 is specified, the administrator must be careful
2172 that the amount of memory usable for all allocations
2175 movable_node [KNL,X86] Boot-time switch to enable the effects
2176 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2178 MTD_Partition= [MTD]
2179 Format: <name>,<region-number>,<size>,<offset>
2181 MTD_Region= [MTD] Format:
2182 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2185 See drivers/mtd/cmdlinepart.c.
2187 multitce=off [PPC] This parameter disables the use of the pSeries
2188 firmware feature for updating multiple TCE entries
2191 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2193 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2195 boundary - index of last SLC block on Flex-OneNAND.
2196 The remaining blocks are configured as MLC blocks.
2197 lock - Configure if Flex-OneNAND boundary should be locked.
2198 Once locked, the boundary cannot be changed.
2199 1 indicates lock status, 0 indicates unlock status.
2202 ARM/S3C2412 JIVE boot control
2204 See arch/arm/mach-s3c2412/mach-jive.c
2206 mtouchusb.raw_coordinates=
2207 [HW] Make the MicroTouch USB driver use raw coordinates
2208 ('y', default) or cooked coordinates ('n')
2210 mtrr_chunk_size=nn[KMG] [X86]
2211 used for mtrr cleanup. It is largest continuous chunk
2212 that could hold holes aka. UC entries.
2214 mtrr_gran_size=nn[KMG] [X86]
2215 Used for mtrr cleanup. It is granularity of mtrr block.
2217 Large value could prevent small alignment from
2220 mtrr_spare_reg_nr=n [X86]
2222 Range: 0,7 : spare reg number
2224 Used for mtrr cleanup. It is spare mtrr entries number.
2225 Set to 2 or more if your graphical card needs more.
2227 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2229 netdev= [NET] Network devices parameters
2230 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2231 Note that mem_start is often overloaded to mean
2232 something different and driver-specific.
2233 This usage is only documented in each driver source
2237 [NETFILTER] Enable connection tracking flow accounting
2238 0 to disable accounting
2239 1 to enable accounting
2242 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2243 See Documentation/filesystems/nfs/nfsroot.txt.
2245 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2246 See Documentation/filesystems/nfs/nfsroot.txt.
2248 nfsrootdebug [NFS] enable nfsroot debugging messages.
2249 See Documentation/filesystems/nfs/nfsroot.txt.
2251 nfs.callback_tcpport=
2252 [NFS] set the TCP port on which the NFSv4 callback
2253 channel should listen.
2256 [NFS] sets the pathname to the program which is used
2257 to update the NFS client cache entries.
2259 nfs.cache_getent_timeout=
2260 [NFS] sets the timeout after which an attempt to
2261 update a cache entry is deemed to have failed.
2263 nfs.idmap_cache_timeout=
2264 [NFS] set the maximum lifetime for idmapper cache
2268 [NFS] enable 64-bit inode numbers.
2269 If zero, the NFS client will fake up a 32-bit inode
2270 number for the readdir() and stat() syscalls instead
2271 of returning the full 64-bit number.
2272 The default is to return 64-bit inode numbers.
2274 nfs.max_session_slots=
2275 [NFSv4.1] Sets the maximum number of session slots
2276 the client will attempt to negotiate with the server.
2277 This limits the number of simultaneous RPC requests
2278 that the client can send to the NFSv4.1 server.
2279 Note that there is little point in setting this
2280 value higher than the max_tcp_slot_table_limit.
2282 nfs.nfs4_disable_idmapping=
2283 [NFSv4] When set to the default of '1', this option
2284 ensures that both the RPC level authentication
2285 scheme and the NFS level operations agree to use
2286 numeric uids/gids if the mount is using the
2287 'sec=sys' security flavour. In effect it is
2288 disabling idmapping, which can make migration from
2289 legacy NFSv2/v3 systems to NFSv4 easier.
2290 Servers that do not support this mode of operation
2291 will be autodetected by the client, and it will fall
2292 back to using the idmapper.
2293 To turn off this behaviour, set the value to '0'.
2295 [NFS4] Specify an additional fixed unique ident-
2296 ification string that NFSv4 clients can insert into
2297 their nfs_client_id4 string. This is typically a
2298 UUID that is generated at system install time.
2300 nfs.send_implementation_id =
2301 [NFSv4.1] Send client implementation identification
2302 information in exchange_id requests.
2303 If zero, no implementation identification information
2305 The default is to send the implementation identification
2308 nfs.recover_lost_locks =
2309 [NFSv4] Attempt to recover locks that were lost due
2310 to a lease timeout on the server. Please note that
2311 doing this risks data corruption, since there are
2312 no guarantees that the file will remain unchanged
2313 after the locks are lost.
2314 If you want to enable the kernel legacy behaviour of
2315 attempting to recover these locks, then set this
2317 The default parameter value of '0' causes the kernel
2318 not to attempt recovery of lost locks.
2320 nfs4.layoutstats_timer =
2321 [NFSv4.2] Change the rate at which the kernel sends
2322 layoutstats to the pNFS metadata server.
2324 Setting this to value to 0 causes the kernel to use
2325 whatever value is the default set by the layout
2326 driver. A non-zero value sets the minimum interval
2327 in seconds between layoutstats transmissions.
2329 nfsd.nfs4_disable_idmapping=
2330 [NFSv4] When set to the default of '1', the NFSv4
2331 server will return only numeric uids and gids to
2332 clients using auth_sys, and will accept numeric uids
2333 and gids from such clients. This is intended to ease
2334 migration from NFSv2/v3.
2336 objlayoutdriver.osd_login_prog=
2337 [NFS] [OBJLAYOUT] sets the pathname to the program which
2338 is used to automatically discover and login into new
2339 osd-targets. Please see:
2340 Documentation/filesystems/pnfs.txt for more explanations
2342 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2343 when a NMI is triggered.
2344 Format: [state][,regs][,debounce][,die]
2346 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2347 Format: [panic,][nopanic,][num]
2349 0 - turn hardlockup detector in nmi_watchdog off
2350 1 - turn hardlockup detector in nmi_watchdog on
2351 When panic is specified, panic when an NMI watchdog
2352 timeout occurs (or 'nopanic' to override the opposite
2353 default). To disable both hard and soft lockup detectors,
2354 please see 'nowatchdog'.
2355 This is useful when you use a panic=... timeout and
2356 need the box quickly up again.
2358 netpoll.carrier_timeout=
2359 [NET] Specifies amount of time (in seconds) that
2360 netpoll should wait for a carrier. By default netpoll
2363 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2364 emulation library even if a 387 maths coprocessor
2368 [HW] Never suspend the console
2369 Disable suspending of consoles during suspend and
2370 hibernate operations. Once disabled, debugging
2371 messages can reach various consoles while the rest
2372 of the system is being put to sleep (ie, while
2373 debugging driver suspend/resume hooks). This may
2374 not work reliably with all consoles, but is known
2375 to work with serial and VGA consoles.
2376 To facilitate more flexible debugging, we also add
2377 console_suspend, a printk module parameter to control
2378 it. Users could use console_suspend (usually
2379 /sys/module/printk/parameters/console_suspend) to
2380 turn on/off it dynamically.
2382 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2383 caches in the slab allocator. Saves per-node memory,
2384 but will impact performance.
2388 noapic [SMP,APIC] Tells the kernel to not make use of any
2389 IOAPICs that may be present in the system.
2391 noautogroup Disable scheduler automatic task group creation.
2393 nobats [PPC] Do not use BATs for mapping kernel lowmem
2394 on "Classic" PPC cores.
2398 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2400 nodelayacct [KNL] Disable per-task delay accounting
2402 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2404 nodsp [SH] Disable hardware DSP at boot time.
2406 noefi Disable EFI runtime services support.
2411 On X86-32 available only on PAE configured kernels.
2412 noexec=on: enable non-executable mappings (default)
2413 noexec=off: disable non-executable mappings
2416 Disable SMAP (Supervisor Mode Access Prevention)
2417 even if it is supported by processor.
2420 Disable SMEP (Supervisor Mode Execution Prevention)
2421 even if it is supported by processor.
2424 This affects only 32-bit executables.
2425 noexec32=on: enable non-executable mappings (default)
2426 read doesn't imply executable mappings
2427 noexec32=off: disable non-executable mappings
2428 read implies executable mappings
2430 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2432 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2433 register save and restore. The kernel will only save
2434 legacy floating-point registers on task switch.
2436 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2438 noxsave [BUGS=X86] Disables x86 extended register state save
2439 and restore using xsave. The kernel will fallback to
2440 enabling legacy floating-point and sse state.
2442 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2443 register states. The kernel will fall back to use
2444 xsave to save the states. By using this parameter,
2445 performance of saving the states is degraded because
2446 xsave doesn't support modified optimization while
2447 xsaveopt supports it on xsaveopt enabled systems.
2449 noxsaves [X86] Disables xsaves and xrstors used in saving and
2450 restoring x86 extended register state in compacted
2451 form of xsave area. The kernel will fall back to use
2452 xsaveopt and xrstor to save and restore the states
2453 in standard form of xsave area. By using this
2454 parameter, xsave area per process might occupy more
2455 memory on xsaves enabled systems.
2457 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2458 wfi(ARM) instruction doesn't work correctly and not to
2459 use it. This is also useful when using JTAG debugger.
2461 no_file_caps Tells the kernel not to honor file capabilities. The
2462 only way then for a file to be executed with privilege
2463 is to be setuid root or executed by root.
2465 nohalt [IA-64] Tells the kernel not to use the power saving
2466 function PAL_HALT_LIGHT when idle. This increases
2467 power-consumption. On the positive side, it reduces
2468 interrupt wake-up latency, which may improve performance
2469 in certain environments such as networked servers or
2472 nohibernate [HIBERNATION] Disable hibernation and resume.
2474 nohz= [KNL] Boottime enable/disable dynamic ticks
2475 Valid arguments: on, off
2478 nohz_full= [KNL,BOOT]
2479 In kernels built with CONFIG_NO_HZ_FULL=y, set
2480 the specified list of CPUs whose tick will be stopped
2481 whenever possible. The boot CPU will be forced outside
2482 the range to maintain the timekeeping.
2483 The CPUs in this range must also be included in the
2486 noiotrap [SH] Disables trapped I/O port accesses.
2488 noirqdebug [X86-32] Disables the code which attempts to detect and
2489 disable unhandled interrupt sources.
2491 no_timer_check [X86,APIC] Disables the code which tests for
2492 broken timer IRQ sources.
2494 noisapnp [ISAPNP] Disables ISA PnP code.
2496 noinitrd [RAM] Tells the kernel not to load any configured
2499 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2501 [Deprecated - use intremap=off]
2505 nojitter [IA-64] Disables jitter checking for ITC timers.
2507 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2509 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2512 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2513 steal time is computed, but won't influence scheduler
2516 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2518 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2520 noltlbs [PPC] Do not use large page/tlb entries for kernel
2521 lowmem mapping on PPC40x.
2523 nomca [IA-64] Disable machine check abort handling
2525 nomce [X86-32] Disable Machine Check Exception
2527 nomfgpt [X86-32] Disable Multi-Function General Purpose
2528 Timer usage (for AMD Geode machines).
2530 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2531 shutdown the other cpus. Instead use the REBOOT_VECTOR
2534 nomodule Disable module load
2536 nopat [X86] Disable PAT (page attribute table extension of
2537 pagetables) support.
2539 norandmaps Don't use address space randomization. Equivalent to
2540 echo 0 > /proc/sys/kernel/randomize_va_space
2542 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2544 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2545 with UP alternatives
2547 nordrand [X86] Disable kernel use of the RDRAND and
2548 RDSEED instructions even if they are supported
2549 by the processor. RDRAND and RDSEED are still
2550 available to user space applications.
2552 noresume [SWSUSP] Disables resume and restores original swap
2555 no-scroll [VGA] Disables scrollback.
2556 This is required for the Braillex ib80-piezo Braille
2557 reader made by F.H. Papenmeier (Germany).
2561 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2563 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2564 and disable the IO APIC. legacy for "maxcpus=0".
2566 nosoftlockup [KNL] Disable the soft-lockup detector.
2568 nosync [HW,M68K] Disables sync negotiation for all devices.
2570 notsc [BUGS=X86-32] Disable Time Stamp Counter
2572 nousb [USB] Disable the USB subsystem
2574 nowatchdog [KNL] Disable both lockup detectors, i.e.
2575 soft-lockup and NMI watchdog (hard-lockup).
2579 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2581 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2582 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2583 Some features depend on CPU0. Known dependencies are:
2584 1. Resume from suspend/hibernate depends on CPU0.
2585 Suspend/hibernate will fail if CPU0 is offline and you
2586 need to online CPU0 before suspend/hibernate.
2587 2. PIC interrupts also depend on CPU0. CPU0 can't be
2588 removed if a PIC interrupt is detected.
2589 It's said poweroff/reboot may depend on CPU0 on some
2590 machines although I haven't seen such issues so far
2591 after CPU0 is offline on a few tested machines.
2592 If the dependencies are under your control, you can
2593 turn on cpu0_hotplug.
2595 nptcg= [IA-64] Override max number of concurrent global TLB
2596 purges which is reported from either PAL_VM_SUMMARY or
2599 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2600 could support. nr_cpus=n : n >= 1 limits the kernel to
2601 supporting 'n' processors. Later in runtime you can not
2602 use hotplug cpu feature to put more cpu back to online.
2603 just like you compile the kernel NR_CPUS=n
2605 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2607 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2608 Allowed values are enable and disable
2610 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2611 one of ['zone', 'node', 'default'] can be specified
2612 This can be set from sysctl after boot.
2613 See Documentation/sysctl/vm.txt for details.
2615 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2616 See Documentation/debugging-via-ohci1394.txt for more
2619 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2620 Rather than timing out after 20 ms if an EC
2621 command is not properly ACKed, override the length
2622 of the timeout. We have interrupts disabled while
2623 waiting for the ACK, so if this is set too high
2624 interrupts *may* be lost!
2626 omap_mux= [OMAP] Override bootloader pin multiplexing.
2627 Format: <mux_mode0.mode_name=value>...
2628 For example, to override I2C bus2:
2629 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2631 oprofile.timer= [HW]
2632 Use timer interrupt instead of performance counters
2634 oprofile.cpu_type= Force an oprofile cpu type
2635 This might be useful if you have an older oprofile
2636 userland or if you want common events.
2637 Format: { arch_perfmon }
2638 arch_perfmon: [X86] Force use of architectural
2639 perfmon on Intel CPUs instead of the
2640 CPU specific event set.
2641 timer: [X86] Force use of architectural NMI
2642 timer mode (see also oprofile.timer
2643 for generic hr timer mode)
2644 [s390] Force legacy basic mode sampling
2645 (report cpu_type "timer")
2647 oops=panic Always panic on oopses. Default is to just kill the
2648 process, but there is a small probability of
2649 deadlocking the machine.
2650 This will also cause panics on machine check exceptions.
2651 Useful together with panic=30 to trigger a reboot.
2654 See Documentation/sound/oss/oss-parameters.txt
2656 page_owner= [KNL] Boot-time page_owner enabling option.
2657 Storage of the information about who allocated
2658 each page is disabled in default. With this switch,
2660 on: enable the feature
2662 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2663 timeout > 0: seconds before rebooting
2664 timeout = 0: wait forever
2665 timeout < 0: reboot immediately
2668 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2671 crash_kexec_post_notifiers
2672 Run kdump after running panic-notifiers and dumping
2673 kmsg. This only for the users who doubt kdump always
2674 succeeds in any situation.
2675 Note that this also increases risks of kdump failure,
2676 because some panic notifiers can make the crashed
2677 kernel more unstable.
2679 parkbd.port= [HW] Parallel port number the keyboard adapter is
2680 connected to, default is 0.
2682 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2683 0 for XT, 1 for AT (default is AT).
2686 parport= [HW,PPT] Specify parallel ports. 0 disables.
2687 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2688 Use 'auto' to force the driver to use any
2689 IRQ/DMA settings detected (the default is to
2690 ignore detected IRQ/DMA settings because of
2691 possible conflicts). You can specify the base
2692 address, IRQ, and DMA settings; IRQ and DMA
2693 should be numbers, or 'auto' (for using detected
2694 settings on that particular port), or 'nofifo'
2695 (to avoid using a FIFO even if it is detected).
2696 Parallel ports are assigned in the order they
2697 are specified on the command line, starting
2700 parport_init_mode= [HW,PPT]
2701 Configure VIA parallel port to operate in
2702 a specific mode. This is necessary on Pegasos
2703 computer where firmware has no options for setting
2704 up parallel port mode and sets it to spp.
2705 Currently this function knows 686a and 8231 chips.
2706 Format: [spp|ps2|epp|ecp|ecpepp]
2709 Halt all CPUs after the first oops has been printed for
2710 the specified number of seconds. This is to be used if
2711 your oopses keep scrolling off the screen.
2716 See header of drivers/block/paride/pcd.c.
2717 See also Documentation/blockdev/paride.txt.
2719 pci=option[,option...] [PCI] various PCI subsystem options:
2720 earlydump [X86] dump PCI config space before the kernel
2722 off [X86] don't probe for the PCI bus
2723 bios [X86-32] force use of PCI BIOS, don't access
2724 the hardware directly. Use this if your machine
2725 has a non-standard PCI host bridge.
2726 nobios [X86-32] disallow use of PCI BIOS, only direct
2727 hardware access methods are allowed. Use this
2728 if you experience crashes upon bootup and you
2729 suspect they are caused by the BIOS.
2730 conf1 [X86] Force use of PCI Configuration
2732 conf2 [X86] Force use of PCI Configuration
2734 noaer [PCIE] If the PCIEAER kernel config parameter is
2735 enabled, this kernel boot option can be used to
2736 disable the use of PCIE advanced error reporting.
2737 nodomains [PCI] Disable support for multiple PCI
2738 root domains (aka PCI segments, in ACPI-speak).
2739 nommconf [X86] Disable use of MMCONFIG for PCI
2741 check_enable_amd_mmconf [X86] check for and enable
2742 properly configured MMIO access to PCI
2743 config space on AMD family 10h CPU
2744 nomsi [MSI] If the PCI_MSI kernel config parameter is
2745 enabled, this kernel boot option can be used to
2746 disable the use of MSI interrupts system-wide.
2747 noioapicquirk [APIC] Disable all boot interrupt quirks.
2748 Safety option to keep boot IRQs enabled. This
2749 should never be necessary.
2750 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2751 primary IO-APIC for bridges that cannot disable
2752 boot IRQs. This fixes a source of spurious IRQs
2753 when the system masks IRQs.
2754 noioapicreroute [APIC] Disable workaround that uses the
2755 boot IRQ equivalent of an IRQ that connects to
2756 a chipset where boot IRQs cannot be disabled.
2757 The opposite of ioapicreroute.
2758 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2759 routing table. These calls are known to be buggy
2760 on several machines and they hang the machine
2761 when used, but on other computers it's the only
2762 way to get the interrupt routing table. Try
2763 this option if the kernel is unable to allocate
2764 IRQs or discover secondary PCI buses on your
2766 rom [X86] Assign address space to expansion ROMs.
2767 Use with caution as certain devices share
2768 address decoders between ROMs and other
2770 norom [X86] Do not assign address space to
2771 expansion ROMs that do not already have
2772 BIOS assigned address ranges.
2773 nobar [X86] Do not assign address space to the
2774 BARs that weren't assigned by the BIOS.
2775 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2776 assigned automatically to PCI devices. You can
2777 make the kernel exclude IRQs of your ISA cards
2779 pirqaddr=0xAAAAA [X86] Specify the physical address
2780 of the PIRQ table (normally generated
2781 by the BIOS) if it is outside the
2782 F0000h-100000h range.
2783 lastbus=N [X86] Scan all buses thru bus #N. Can be
2784 useful if the kernel is unable to find your
2785 secondary buses and you want to tell it
2786 explicitly which ones they are.
2787 assign-busses [X86] Always assign all PCI bus
2788 numbers ourselves, overriding
2789 whatever the firmware may have done.
2790 usepirqmask [X86] Honor the possible IRQ mask stored
2791 in the BIOS $PIR table. This is needed on
2792 some systems with broken BIOSes, notably
2793 some HP Pavilion N5400 and Omnibook XE3
2794 notebooks. This will have no effect if ACPI
2795 IRQ routing is enabled.
2796 noacpi [X86] Do not use ACPI for IRQ routing
2797 or for PCI scanning.
2798 use_crs [X86] Use PCI host bridge window information
2799 from ACPI. On BIOSes from 2008 or later, this
2800 is enabled by default. If you need to use this,
2801 please report a bug.
2802 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2803 If you need to use this, please report a bug.
2804 routeirq Do IRQ routing for all PCI devices.
2805 This is normally done in pci_enable_device(),
2806 so this option is a temporary workaround
2807 for broken drivers that don't call it.
2808 skip_isa_align [X86] do not align io start addr, so can
2809 handle more pci cards
2810 firmware [ARM] Do not re-enumerate the bus but instead
2811 just use the configuration from the
2812 bootloader. This is currently used on
2813 IXP2000 systems where the bus has to be
2814 configured a certain way for adjunct CPUs.
2815 noearly [X86] Don't do any early type 1 scanning.
2816 This might help on some broken boards which
2817 machine check when some devices' config space
2818 is read. But various workarounds are disabled
2819 and some IOMMU drivers will not work.
2820 bfsort Sort PCI devices into breadth-first order.
2821 This sorting is done to get a device
2822 order compatible with older (<= 2.4) kernels.
2823 nobfsort Don't sort PCI devices into breadth-first order.
2824 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2825 tuning and use the BIOS-configured MPS defaults.
2826 pcie_bus_safe Set every device's MPS to the largest value
2827 supported by all devices below the root complex.
2828 pcie_bus_perf Set device MPS to the largest allowable MPS
2829 based on its parent bus. Also set MRRS (Max
2830 Read Request Size) to the largest supported
2831 value (no larger than the MPS that the device
2832 or bus can support) for best performance.
2833 pcie_bus_peer2peer Set every device's MPS to 128B, which
2834 every device is guaranteed to support. This
2835 configuration allows peer-to-peer DMA between
2836 any pair of devices, possibly at the cost of
2837 reduced performance. This also guarantees
2838 that hot-added devices will work.
2839 cbiosize=nn[KMG] The fixed amount of bus space which is
2840 reserved for the CardBus bridge's IO window.
2841 The default value is 256 bytes.
2842 cbmemsize=nn[KMG] The fixed amount of bus space which is
2843 reserved for the CardBus bridge's memory
2844 window. The default value is 64 megabytes.
2847 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2848 Specifies alignment and device to reassign
2849 aligned memory resources.
2850 If <order of align> is not specified,
2851 PAGE_SIZE is used as alignment.
2852 PCI-PCI bridge can be specified, if resource
2853 windows need to be expanded.
2854 ecrc= Enable/disable PCIe ECRC (transaction layer
2855 end-to-end CRC checking).
2856 bios: Use BIOS/firmware settings. This is the
2860 hpiosize=nn[KMG] The fixed amount of bus space which is
2861 reserved for hotplug bridge's IO window.
2862 Default size is 256 bytes.
2863 hpmemsize=nn[KMG] The fixed amount of bus space which is
2864 reserved for hotplug bridge's memory window.
2865 Default size is 2 megabytes.
2866 realloc= Enable/disable reallocating PCI bridge resources
2867 if allocations done by BIOS are too small to
2868 accommodate resources required by all child
2870 off: Turn realloc off
2872 realloc same as realloc=on
2873 noari do not use PCIe ARI.
2874 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2875 only look for one device below a PCIe downstream
2878 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2881 force Enable ASPM even on devices that claim not to support it.
2882 WARNING: Forcing ASPM on may cause system lockups.
2884 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2885 nomsi Do not use MSI for PCI Express Native Hotplug (this
2886 makes all PCIe ports use INTx for hotplug services).
2888 pcie_ports= [PCIE] PCIe ports handling:
2889 auto Ask the BIOS whether or not to use native PCIe services
2890 associated with PCIe ports (PME, hot-plug, AER). Use
2891 them only if that is allowed by the BIOS.
2892 native Use native PCIe services associated with PCIe ports
2894 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2897 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2898 nomsi Do not use MSI for native PCIe PME signaling (this makes
2899 all PCIe root ports use INTx for all services).
2901 pcmv= [HW,PCMCIA] BadgePAD 4
2905 Keep all power-domains already enabled by bootloader on,
2906 even if no driver has claimed them. This is useful
2907 for debug and development, but should not be
2908 needed on a platform with proper driver support.
2911 See Documentation/blockdev/paride.txt.
2913 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2916 See arch/parisc/kernel/pdc_chassis.c
2918 percpu_alloc= Select which percpu first chunk allocator to use.
2919 Currently supported values are "embed" and "page".
2920 Archs may support subset or none of the selections.
2921 See comments in mm/percpu.c for details on each
2922 allocator. This parameter is primarily for debugging
2923 and performance comparison.
2926 See Documentation/blockdev/paride.txt.
2929 See Documentation/blockdev/paride.txt.
2931 pirq= [SMP,APIC] Manual mp-table setup
2932 See Documentation/x86/i386/IO-APIC.txt.
2934 plip= [PPT,NET] Parallel port network link
2935 Format: { parport<nr> | timid | 0 }
2936 See also Documentation/parport.txt.
2938 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2939 Override pmtimer IOPort with a hex value.
2943 Enable PNP debug messages (depends on the
2944 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2945 via /sys/module/pnp/parameters/debug. We always show
2946 current resource usage; turning this on also shows
2947 possible settings and some assignment information.
2953 { on | off | curr | res | no-curr | no-res }
2956 [ISAPNP] Exclude IRQs for the autoconfiguration
2959 [ISAPNP] Exclude DMAs for the autoconfiguration
2961 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2962 Ranges are in pairs (I/O port base and size).
2965 [ISAPNP] Exclude memory regions for the
2967 Ranges are in pairs (memory base and size).
2969 ports= [IP_VS_FTP] IPVS ftp helper module
2971 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2973 Format: <port>,<port>....
2975 print-fatal-signals=
2976 [KNL] debug: print fatal signals
2978 If enabled, warn about various signal handling
2979 related application anomalies: too many signals,
2980 too many POSIX.1 timers, fatal signals causing a
2983 If you hit the warning due to signal overflow,
2984 you might want to try "ulimit -i unlimited".
2988 printk.always_kmsg_dump=
2989 Trigger kmsg_dump for cases other than kernel oops or
2991 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2994 printk.time= Show timing data prefixed to each printk message line
2995 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2997 processor.max_cstate= [HW,ACPI]
2998 Limit processor to maximum C-state
2999 max_cstate=9 overrides any DMI blacklist limit.
3001 processor.nocst [HW,ACPI]
3002 Ignore the _CST method to determine C-states,
3003 instead using the legacy FADT method
3005 profile= [KNL] Enable kernel profiling via /proc/profile
3006 Format: [schedule,]<number>
3007 Param: "schedule" - profile schedule points.
3008 Param: <number> - step/bucket size as a power of 2 for
3009 statistical time based profiling.
3010 Param: "sleep" - profile D-state sleeping (millisecs).
3011 Requires CONFIG_SCHEDSTATS
3012 Param: "kvm" - profile VM exits.
3014 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3016 See Documentation/blockdev/ramdisk.txt.
3018 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3019 probe for; one of (bare|imps|exps|lifebook|any).
3020 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3022 psmouse.resetafter= [HW,MOUSE]
3023 Try to reset the device after so many bad packets
3026 [HW,MOUSE] Set desired mouse resolution, in dpi.
3027 psmouse.smartscroll=
3028 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3029 0 = disabled, 1 = enabled (default).
3031 pstore.backend= Specify the name of the pstore backend to use
3034 See Documentation/blockdev/paride.txt.
3037 [KNL] Number of legacy pty's. Overwrites compiled-in
3040 quiet [KNL] Disable most log messages
3045 See Documentation/md.txt.
3047 ramdisk_blocksize= [RAM]
3048 See Documentation/blockdev/ramdisk.txt.
3050 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3051 See Documentation/blockdev/ramdisk.txt.
3054 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3055 the specified list of CPUs to be no-callback CPUs.
3056 Invocation of these CPUs' RCU callbacks will
3057 be offloaded to "rcuox/N" kthreads created for
3058 that purpose, where "x" is "b" for RCU-bh, "p"
3059 for RCU-preempt, and "s" for RCU-sched, and "N"
3060 is the CPU number. This reduces OS jitter on the
3061 offloaded CPUs, which can be useful for HPC and
3062 real-time workloads. It can also improve energy
3063 efficiency for asymmetric multiprocessors.
3066 Rather than requiring that offloaded CPUs
3067 (specified by rcu_nocbs= above) explicitly
3068 awaken the corresponding "rcuoN" kthreads,
3069 make these kthreads poll for callbacks.
3070 This improves the real-time response for the
3071 offloaded CPUs by relieving them of the need to
3072 wake up the corresponding kthread, but degrades
3073 energy efficiency by requiring that the kthreads
3074 periodically wake up to do the polling.
3076 rcutree.blimit= [KNL]
3077 Set maximum number of finished RCU callbacks to
3078 process in one batch.
3080 rcutree.dump_tree= [KNL]
3081 Dump the structure of the rcu_node combining tree
3082 out at early boot. This is used for diagnostic
3083 purposes, to verify correct tree setup.
3085 rcutree.gp_cleanup_delay= [KNL]
3086 Set the number of jiffies to delay each step of
3087 RCU grace-period cleanup. This only has effect
3088 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3090 rcutree.gp_init_delay= [KNL]
3091 Set the number of jiffies to delay each step of
3092 RCU grace-period initialization. This only has
3093 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3096 rcutree.gp_preinit_delay= [KNL]
3097 Set the number of jiffies to delay each step of
3098 RCU grace-period pre-initialization, that is,
3099 the propagation of recent CPU-hotplug changes up
3100 the rcu_node combining tree. This only has effect
3101 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3103 rcutree.rcu_fanout_exact= [KNL]
3104 Disable autobalancing of the rcu_node combining
3105 tree. This is used by rcutorture, and might
3106 possibly be useful for architectures having high
3107 cache-to-cache transfer latencies.
3109 rcutree.rcu_fanout_leaf= [KNL]
3110 Change the number of CPUs assigned to each
3111 leaf rcu_node structure. Useful for very
3112 large systems, which will choose the value 64,
3113 and for NUMA systems with large remote-access
3114 latencies, which will choose a value aligned
3115 with the appropriate hardware boundaries.
3117 rcutree.jiffies_till_sched_qs= [KNL]
3118 Set required age in jiffies for a
3119 given grace period before RCU starts
3120 soliciting quiescent-state help from
3121 rcu_note_context_switch().
3123 rcutree.jiffies_till_first_fqs= [KNL]
3124 Set delay from grace-period initialization to
3125 first attempt to force quiescent states.
3126 Units are jiffies, minimum value is zero,
3127 and maximum value is HZ.
3129 rcutree.jiffies_till_next_fqs= [KNL]
3130 Set delay between subsequent attempts to force
3131 quiescent states. Units are jiffies, minimum
3132 value is one, and maximum value is HZ.
3134 rcutree.kthread_prio= [KNL,BOOT]
3135 Set the SCHED_FIFO priority of the RCU per-CPU
3136 kthreads (rcuc/N). This value is also used for
3137 the priority of the RCU boost threads (rcub/N)
3138 and for the RCU grace-period kthreads (rcu_bh,
3139 rcu_preempt, and rcu_sched). If RCU_BOOST is
3140 set, valid values are 1-99 and the default is 1
3141 (the least-favored priority). Otherwise, when
3142 RCU_BOOST is not set, valid values are 0-99 and
3143 the default is zero (non-realtime operation).
3145 rcutree.rcu_nocb_leader_stride= [KNL]
3146 Set the number of NOCB kthread groups, which
3147 defaults to the square root of the number of
3148 CPUs. Larger numbers reduces the wakeup overhead
3149 on the per-CPU grace-period kthreads, but increases
3150 that same overhead on each group's leader.
3152 rcutree.qhimark= [KNL]
3153 Set threshold of queued RCU callbacks beyond which
3154 batch limiting is disabled.
3156 rcutree.qlowmark= [KNL]
3157 Set threshold of queued RCU callbacks below which
3158 batch limiting is re-enabled.
3160 rcutree.rcu_idle_gp_delay= [KNL]
3161 Set wakeup interval for idle CPUs that have
3162 RCU callbacks (RCU_FAST_NO_HZ=y).
3164 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3165 Set wakeup interval for idle CPUs that have
3166 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3167 Lazy RCU callbacks are those which RCU can
3168 prove do nothing more than free memory.
3170 rcutorture.cbflood_inter_holdoff= [KNL]
3171 Set holdoff time (jiffies) between successive
3172 callback-flood tests.
3174 rcutorture.cbflood_intra_holdoff= [KNL]
3175 Set holdoff time (jiffies) between successive
3176 bursts of callbacks within a given callback-flood
3179 rcutorture.cbflood_n_burst= [KNL]
3180 Set the number of bursts making up a given
3181 callback-flood test. Set this to zero to
3182 disable callback-flood testing.
3184 rcutorture.cbflood_n_per_burst= [KNL]
3185 Set the number of callbacks to be registered
3186 in a given burst of a callback-flood test.
3188 rcutorture.fqs_duration= [KNL]
3189 Set duration of force_quiescent_state bursts
3192 rcutorture.fqs_holdoff= [KNL]
3193 Set holdoff time within force_quiescent_state bursts
3196 rcutorture.fqs_stutter= [KNL]
3197 Set wait time between force_quiescent_state bursts
3200 rcutorture.gp_cond= [KNL]
3201 Use conditional/asynchronous update-side
3202 primitives, if available.
3204 rcutorture.gp_exp= [KNL]
3205 Use expedited update-side primitives, if available.
3207 rcutorture.gp_normal= [KNL]
3208 Use normal (non-expedited) asynchronous
3209 update-side primitives, if available.
3211 rcutorture.gp_sync= [KNL]
3212 Use normal (non-expedited) synchronous
3213 update-side primitives, if available. If all
3214 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3215 rcutorture.gp_normal=, and rcutorture.gp_sync=
3216 are zero, rcutorture acts as if is interpreted
3217 they are all non-zero.
3219 rcutorture.n_barrier_cbs= [KNL]
3220 Set callbacks/threads for rcu_barrier() testing.
3222 rcutorture.nfakewriters= [KNL]
3223 Set number of concurrent RCU writers. These just
3224 stress RCU, they don't participate in the actual
3225 test, hence the "fake".
3227 rcutorture.nreaders= [KNL]
3228 Set number of RCU readers. The value -1 selects
3229 N-1, where N is the number of CPUs. A value
3230 "n" less than -1 selects N-n-2, where N is again
3231 the number of CPUs. For example, -2 selects N
3232 (the number of CPUs), -3 selects N+1, and so on.
3234 rcutorture.object_debug= [KNL]
3235 Enable debug-object double-call_rcu() testing.
3237 rcutorture.onoff_holdoff= [KNL]
3238 Set time (s) after boot for CPU-hotplug testing.
3240 rcutorture.onoff_interval= [KNL]
3241 Set time (s) between CPU-hotplug operations, or
3242 zero to disable CPU-hotplug testing.
3244 rcutorture.shuffle_interval= [KNL]
3245 Set task-shuffle interval (s). Shuffling tasks
3246 allows some CPUs to go into dyntick-idle mode
3247 during the rcutorture test.
3249 rcutorture.shutdown_secs= [KNL]
3250 Set time (s) after boot system shutdown. This
3251 is useful for hands-off automated testing.
3253 rcutorture.stall_cpu= [KNL]
3254 Duration of CPU stall (s) to test RCU CPU stall
3255 warnings, zero to disable.
3257 rcutorture.stall_cpu_holdoff= [KNL]
3258 Time to wait (s) after boot before inducing stall.
3260 rcutorture.stat_interval= [KNL]
3261 Time (s) between statistics printk()s.
3263 rcutorture.stutter= [KNL]
3264 Time (s) to stutter testing, for example, specifying
3265 five seconds causes the test to run for five seconds,
3266 wait for five seconds, and so on. This tests RCU's
3267 ability to transition abruptly to and from idle.
3269 rcutorture.test_boost= [KNL]
3270 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3271 "Maybe" means test if the RCU implementation
3272 under test support RCU priority boosting.
3274 rcutorture.test_boost_duration= [KNL]
3275 Duration (s) of each individual boost test.
3277 rcutorture.test_boost_interval= [KNL]
3278 Interval (s) between each boost test.
3280 rcutorture.test_no_idle_hz= [KNL]
3281 Test RCU's dyntick-idle handling. See also the
3282 rcutorture.shuffle_interval parameter.
3284 rcutorture.torture_runnable= [BOOT]
3285 Start rcutorture running at boot time.
3287 rcutorture.torture_type= [KNL]
3288 Specify the RCU implementation to test.
3290 rcutorture.verbose= [KNL]
3291 Enable additional printk() statements.
3293 rcupdate.rcu_expedited= [KNL]
3294 Use expedited grace-period primitives, for
3295 example, synchronize_rcu_expedited() instead
3296 of synchronize_rcu(). This reduces latency,
3297 but can increase CPU utilization, degrade
3298 real-time latency, and degrade energy efficiency.
3300 rcupdate.rcu_cpu_stall_suppress= [KNL]
3301 Suppress RCU CPU stall warning messages.
3303 rcupdate.rcu_cpu_stall_timeout= [KNL]
3304 Set timeout for RCU CPU stall warning messages.
3306 rcupdate.rcu_task_stall_timeout= [KNL]
3307 Set timeout in jiffies for RCU task stall warning
3308 messages. Disable with a value less than or equal
3311 rcupdate.rcu_self_test= [KNL]
3312 Run the RCU early boot self tests
3314 rcupdate.rcu_self_test_bh= [KNL]
3315 Run the RCU bh early boot self tests
3317 rcupdate.rcu_self_test_sched= [KNL]
3318 Run the RCU sched early boot self tests
3322 Run specified binary instead of /init from the ramdisk,
3323 used for early userspace startup. See initrd.
3326 Format (x86 or x86_64):
3327 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3329 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3331 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3332 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3333 reboot_force is either force or not specified,
3334 reboot_cpu is s[mp]#### with #### being the processor
3335 to be used for rebooting.
3338 [KNL, SMP] Set scheduler's default relax_domain_level.
3339 See Documentation/cgroups/cpusets.txt.
3341 relative_sleep_states=
3342 [SUSPEND] Use sleep state labeling where the deepest
3343 state available other than hibernation is always "mem".
3344 Format: { "0" | "1" }
3345 0 -- Traditional sleep state labels.
3346 1 -- Relative sleep state labels.
3348 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3350 reservetop= [X86-32]
3352 Reserves a hole at the top of the kernel virtual
3357 Set the amount of memory to reserve for BIOS at
3358 the bottom of the address space.
3360 reset_devices [KNL] Force drivers to reset the underlying device
3361 during initialization.
3364 Specify the partition device for software suspend
3366 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3368 resume_offset= [SWSUSP]
3369 Specify the offset from the beginning of the partition
3370 given by "resume=" at which the swap header is located,
3371 in <PAGE_SIZE> units (needed only for swap files).
3372 See Documentation/power/swsusp-and-swap-files.txt
3374 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3375 read the resume files
3377 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3378 Useful for devices that are detected asynchronously
3379 (e.g. USB and MMC devices).
3381 hibernate= [HIBERNATION]
3382 noresume Don't check if there's a hibernation image
3383 present during boot.
3384 nocompress Don't compress/decompress hibernation images.
3385 no Disable hibernation and resume.
3387 retain_initrd [RAM] Keep initrd memory after extraction
3389 rfkill.default_state=
3390 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3391 etc. communication is blocked by default.
3394 rfkill.master_switch_mode=
3395 0 The "airplane mode" button does nothing.
3396 1 The "airplane mode" button toggles between everything
3397 blocked and the previous configuration.
3398 2 The "airplane mode" button toggles between everything
3399 blocked and everything unblocked.
3401 rhash_entries= [KNL,NET]
3402 Set number of hash buckets for route cache
3404 ro [KNL] Mount root device read-only on boot
3406 root= [KNL] Root filesystem
3407 See name_to_dev_t comment in init/do_mounts.c.
3409 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3410 mount the root filesystem
3412 rootflags= [KNL] Set root filesystem mount option string
3414 rootfstype= [KNL] Set root filesystem type
3416 rootwait [KNL] Wait (indefinitely) for root device to show up.
3417 Useful for devices that are detected asynchronously
3418 (e.g. USB and MMC devices).
3420 rproc_mem=nn[KMG][@address]
3421 [KNL,ARM,CMA] Remoteproc physical memory block.
3422 Memory area to be used by remote processor image,
3425 rw [KNL] Mount root device read-write on boot
3427 S [KNL] Run init in single mode
3429 s390_iommu= [HW,S390]
3430 Set s390 IOTLB flushing mode
3432 With strict flushing every unmap operation will result in
3433 an IOTLB flush. Default is lazy flushing before reuse,
3437 See drivers/net/irda/sa1100_ir.c.
3439 sbni= [NET] Granch SBNI12 leased line adapter
3441 sched_debug [KNL] Enables verbose scheduler debug messages.
3443 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3444 xtime_lock contention on larger systems, and/or RCU lock
3445 contention on all systems with CONFIG_MAXSMP set.
3446 Format: { "0" | "1" }
3447 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3449 Note: increases power consumption, thus should only be
3450 enabled if running jitter sensitive (HPC/RT) workloads.
3452 security= [SECURITY] Choose a security module to enable at boot.
3453 If this boot parameter is not specified, only the first
3454 security module asking for security registration will be
3455 loaded. An invalid security module name will be treated
3456 as if no module has been chosen.
3458 selinux= [SELINUX] Disable or enable SELinux at boot time.
3459 Format: { "0" | "1" }
3460 See security/selinux/Kconfig help text.
3463 Default value is set via kernel config option.
3464 If enabled at boot time, /selinux/disable can be used
3465 later to disable prior to initial policy load.
3467 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3468 Format: { "0" | "1" }
3469 See security/apparmor/Kconfig help text
3472 Default value is set via kernel config option.
3474 serialnumber [BUGS=X86-32]
3477 Maximal number of shapers.
3479 show_msr= [x86] show boot-time MSR settings
3480 Format: { <integer> }
3481 Show boot-time (BIOS-initialized) MSR settings.
3482 The parameter means the number of CPUs to show,
3483 for example 1 means boot CPU only.
3491 Disable merging of slabs with similar size. May be
3492 necessary if there is some reason to distinguish
3493 allocs to different slabs. Debug options disable
3494 merging on their own.
3495 For more information see Documentation/vm/slub.txt.
3497 slab_max_order= [MM, SLAB]
3498 Determines the maximum allowed order for slabs.
3499 A high setting may cause OOMs due to memory
3500 fragmentation. Defaults to 1 for systems with
3501 more than 32MB of RAM, 0 otherwise.
3503 slub_debug[=options[,slabs]] [MM, SLUB]
3504 Enabling slub_debug allows one to determine the
3505 culprit if slab objects become corrupted. Enabling
3506 slub_debug can create guard zones around objects and
3507 may poison objects when not in use. Also tracks the
3508 last alloc / free. For more information see
3509 Documentation/vm/slub.txt.
3511 slub_max_order= [MM, SLUB]
3512 Determines the maximum allowed order for slabs.
3513 A high setting may cause OOMs due to memory
3514 fragmentation. For more information see
3515 Documentation/vm/slub.txt.
3517 slub_min_objects= [MM, SLUB]
3518 The minimum number of objects per slab. SLUB will
3519 increase the slab order up to slub_max_order to
3520 generate a sufficiently large slab able to contain
3521 the number of objects indicated. The higher the number
3522 of objects the smaller the overhead of tracking slabs
3523 and the less frequently locks need to be acquired.
3524 For more information see Documentation/vm/slub.txt.
3526 slub_min_order= [MM, SLUB]
3527 Determines the minimum page order for slabs. Must be
3528 lower than slub_max_order.
3529 For more information see Documentation/vm/slub.txt.
3531 slub_nomerge [MM, SLUB]
3532 Same with slab_nomerge. This is supported for legacy.
3533 See slab_nomerge for more information.
3536 Format: <io1>[,<io2>[,...,<io8>]]
3538 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3539 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3540 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3541 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3542 smsc-ircc2.ircc_irq= [HW] IRQ line
3543 smsc-ircc2.ircc_dma= [HW] DMA channel
3544 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3545 0: Toshiba Satellite 1800 (GP data pin select)
3546 1: Fast pin select (default)
3550 [KNL] Should the soft-lockup detector generate panics.
3553 softlockup_all_cpu_backtrace=
3554 [KNL] Should the soft-lockup detector generate
3555 backtraces on all cpus.
3558 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3559 See Documentation/laptops/sonypi.txt
3561 spia_io_base= [HW,MTD]
3567 Enabled the stack tracer on boot up.
3569 stacktrace_filter=[function-list]
3570 [FTRACE] Limit the functions that the stack tracer
3571 will trace at boot up. function-list is a comma separated
3572 list of functions. This list can be changed at run
3573 time by the stack_trace_filter file in the debugfs
3574 tracing directory. Note, this enables stack tracing
3575 and the stacktrace above is not needed.
3579 Set the STI (builtin display/keyboard on the HP-PARISC
3580 machines) console (graphic card) which should be used
3581 as the initial boot-console.
3582 See also comment in drivers/video/console/sticore.c.
3585 See comment in drivers/video/console/sticore.c.
3588 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3590 sunrpc.min_resvport=
3591 sunrpc.max_resvport=
3593 SunRPC servers often require that client requests
3594 originate from a privileged port (i.e. a port in the
3595 range 0 < portnr < 1024).
3596 An administrator who wishes to reserve some of these
3597 ports for other uses may adjust the range that the
3598 kernel's sunrpc client considers to be privileged
3599 using these two parameters to set the minimum and
3600 maximum port values.
3604 Control how the NFS server code allocates CPUs to
3605 service thread pools. Depending on how many NICs
3606 you have and where their interrupts are bound, this
3607 option will affect which CPUs will do NFS serving.
3608 Note: this parameter cannot be changed while the
3609 NFS server is running.
3611 auto the server chooses an appropriate mode
3612 automatically using heuristics
3613 global a single global pool contains all CPUs
3614 percpu one pool for each CPU
3615 pernode one pool for each NUMA node (equivalent
3616 to global on non-NUMA machines)
3618 sunrpc.tcp_slot_table_entries=
3619 sunrpc.udp_slot_table_entries=
3621 Sets the upper limit on the number of simultaneous
3622 RPC calls that can be sent from the client to a
3623 server. Increasing these values may allow you to
3624 improve throughput, but will also increase the
3625 amount of memory reserved for use by the client.
3627 suspend.pm_test_delay=
3629 Sets the number of seconds to remain in a suspend test
3630 mode before resuming the system (see
3631 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3632 is set. Default value is 5.
3635 [KNL] Enable accounting of swap in memory resource
3636 controller if no parameter or 1 is given or disable
3637 it if 0 is given (See Documentation/cgroups/memory.txt)
3639 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3640 Format: { <int> | force }
3641 <int> -- Number of I/O TLB slabs
3642 force -- force using of bounce buffers even if they
3643 wouldn't be automatically used by the kernel
3647 sysfs.deprecated=0|1 [KNL]
3648 Enable/disable old style sysfs layout for old udev
3649 on older distributions. When this option is enabled
3650 very new udev will not work anymore. When this option
3651 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3652 in older udev will not work anymore.
3653 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3654 the kernel configuration.
3656 sysrq_always_enabled
3658 Ignore sysrq setting - this boot parameter will
3659 neutralize any effect of /proc/sys/kernel/sysrq.
3660 Useful for debugging.
3662 tcpmhash_entries= [KNL,NET]
3663 Set the number of tcp_metrics_hash slots.
3664 Default value is 8192 or 16384 depending on total
3665 ram pages. This is used to specify the TCP metrics
3666 cache size. See Documentation/networking/ip-sysctl.txt
3667 "tcp_no_metrics_save" section for more details.
3671 test_suspend= [SUSPEND][,N]
3672 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3673 standby suspend) or "freeze" (for suspend type freeze)
3674 as the system sleep state during system startup with
3675 the optional capability to repeat N number of times.
3676 The system is woken from this state using a
3677 wakeup-capable RTC alarm.
3679 thash_entries= [KNL,NET]
3680 Set number of hash buckets for TCP connection
3682 thermal.act= [HW,ACPI]
3683 -1: disable all active trip points in all thermal zones
3684 <degrees C>: override all lowest active trip points
3686 thermal.crt= [HW,ACPI]
3687 -1: disable all critical trip points in all thermal zones
3688 <degrees C>: override all critical trip points
3690 thermal.nocrt= [HW,ACPI]
3691 Set to disable actions on ACPI thermal zone
3692 critical and hot trip points.
3694 thermal.off= [HW,ACPI]
3695 1: disable ACPI thermal control
3697 thermal.psv= [HW,ACPI]
3698 -1: disable all passive trip points
3699 <degrees C>: override all passive trip points to this
3702 thermal.tzp= [HW,ACPI]
3703 Specify global default ACPI thermal zone polling rate
3704 <deci-seconds>: poll all this frequency
3705 0: no polling (default)
3708 Force threading of all interrupt handlers except those
3709 marked explicitly IRQF_NO_THREAD.
3712 Enable the Transcendent memory driver if built-in.
3714 tmem.cleancache=0|1 [KNL, XEN]
3715 Default is on (1). Disable the usage of the cleancache
3716 API to send anonymous pages to the hypervisor.
3718 tmem.frontswap=0|1 [KNL, XEN]
3719 Default is on (1). Disable the usage of the frontswap
3720 API to send swap pages to the hypervisor. If disabled
3721 the selfballooning and selfshrinking are force disabled.
3723 tmem.selfballooning=0|1 [KNL, XEN]
3724 Default is on (1). Disable the driving of swap pages
3727 tmem.selfshrinking=0|1 [KNL, XEN]
3728 Default is on (1). Partial swapoff that immediately
3729 transfers pages from Xen hypervisor back to the
3730 kernel based on different criteria.
3734 Specify if the kernel should make use of the cpu
3735 topology information if the hardware supports this.
3736 The scheduler will make use of this information and
3737 e.g. base its process migration decisions on it.
3740 topology_updates= [KNL, PPC, NUMA]
3742 Specify if the kernel should ignore (off)
3743 topology updates sent by the hypervisor to this
3748 tpm_suspend_pcr=[HW,TPM]
3749 Format: integer pcr id
3750 Specify that at suspend time, the tpm driver
3751 should extend the specified pcr with zeros,
3752 as a workaround for some chips which fail to
3753 flush the last written pcr on TPM_SaveState.
3754 This will guarantee that all the other pcrs
3757 trace_buf_size=nn[KMG]
3758 [FTRACE] will set tracing buffer size on each cpu.
3760 trace_event=[event-list]
3761 [FTRACE] Set and start specified trace events in order
3762 to facilitate early boot debugging.
3763 See also Documentation/trace/events.txt
3765 trace_options=[option-list]
3766 [FTRACE] Enable or disable tracer options at boot.
3767 The option-list is a comma delimited list of options
3768 that can be enabled or disabled just as if you were
3769 to echo the option name into
3771 /sys/kernel/debug/tracing/trace_options
3773 For example, to enable stacktrace option (to dump the
3774 stack trace of each event), add to the command line:
3776 trace_options=stacktrace
3778 See also Documentation/trace/ftrace.txt "trace options"
3782 Have the tracepoints sent to printk as well as the
3783 tracing ring buffer. This is useful for early boot up
3784 where the system hangs or reboots and does not give the
3785 option for reading the tracing buffer or performing a
3786 ftrace_dump_on_oops.
3788 To turn off having tracepoints sent to printk,
3789 echo 0 > /proc/sys/kernel/tracepoint_printk
3790 Note, echoing 1 into this file without the
3791 tracepoint_printk kernel cmdline option has no effect.
3795 Having tracepoints sent to printk() and activating high
3796 frequency tracepoints such as irq or sched, can cause
3797 the system to live lock.
3800 [FTRACE] enable this option to disable tracing when a
3801 warning is hit. This turns off "tracing_on". Tracing can
3802 be enabled again by echoing '1' into the "tracing_on"
3803 file located in /sys/kernel/debug/tracing/
3805 This option is useful, as it disables the trace before
3806 the WARNING dump is called, which prevents the trace to
3807 be filled with content caused by the warning output.
3809 This option can also be set at run time via the sysctl
3810 option: kernel/traceoff_on_warning
3812 transparent_hugepage=
3814 Format: [always|madvise|never]
3815 Can be used to control the default behavior of the system
3816 with respect to transparent hugepages.
3817 See Documentation/vm/transhuge.txt for more details.
3819 tsc= Disable clocksource stability checks for TSC.
3821 [x86] reliable: mark tsc clocksource as reliable, this
3822 disables clocksource verification at runtime, as well
3823 as the stability checks done at bootup. Used to enable
3824 high-resolution timer mode on older hardware, and in
3825 virtualized environment.
3826 [x86] noirqtime: Do not use TSC to do irq accounting.
3827 Used to run time disable IRQ_TIME_ACCOUNTING on any
3828 platforms where RDTSC is slow and this accounting
3831 turbografx.map[2|3]= [HW,JOY]
3832 TurboGraFX parallel port interface
3834 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3835 See also Documentation/input/joystick-parport.txt
3837 udbg-immortal [PPC] When debugging early kernel crashes that
3838 happen after console_init() and before a proper
3839 console driver takes over, this boot options might
3840 help "seeing" what's going on.
3842 uhash_entries= [KNL,NET]
3843 Set number of hash buckets for UDP/UDP-Lite connections
3846 [USB] Ignore overcurrent events (default N).
3847 Some badly-designed motherboards generate lots of
3848 bogus events, for ports that aren't wired to
3849 anything. Set this parameter to avoid log spamming.
3850 Note that genuine overcurrent events won't be
3854 [X86] Cause panic on unknown NMI.
3856 usbcore.authorized_default=
3857 [USB] Default USB device authorization:
3858 (default -1 = authorized except for wireless USB,
3859 0 = not authorized, 1 = authorized)
3861 usbcore.autosuspend=
3862 [USB] The autosuspend time delay (in seconds) used
3863 for newly-detected USB devices (default 2). This
3864 is the time required before an idle device will be
3865 autosuspended. Devices for which the delay is set
3866 to a negative value won't be autosuspended at all.
3868 usbcore.usbfs_snoop=
3869 [USB] Set to log all usbfs traffic (default 0 = off).
3871 usbcore.blinkenlights=
3872 [USB] Set to cycle leds on hubs (default 0 = off).
3874 usbcore.old_scheme_first=
3875 [USB] Start with the old device initialization
3876 scheme (default 0 = off).
3878 usbcore.usbfs_memory_mb=
3879 [USB] Memory limit (in MB) for buffers allocated by
3880 usbfs (default = 16, 0 = max = 2047).
3882 usbcore.use_both_schemes=
3883 [USB] Try the other device initialization scheme
3884 if the first one fails (default 1 = enabled).
3886 usbcore.initial_descriptor_timeout=
3887 [USB] Specifies timeout for the initial 64-byte
3888 USB_REQ_GET_DESCRIPTOR request in milliseconds
3889 (default 5000 = 5.0 seconds).
3892 [USBHID] The interval which mice are to be polled at.
3894 usb-storage.delay_use=
3895 [UMS] The delay in seconds before a new device is
3896 scanned for Logical Units (default 1).
3899 [UMS] A list of quirks entries to supplement or
3900 override the built-in unusual_devs list. List
3901 entries are separated by commas. Each entry has
3902 the form VID:PID:Flags where VID and PID are Vendor
3903 and Product ID values (4-digit hex numbers) and
3904 Flags is a set of characters, each corresponding
3905 to a common usb-storage quirk flag as follows:
3906 a = SANE_SENSE (collect more than 18 bytes
3908 b = BAD_SENSE (don't collect more than 18
3909 bytes of sense data);
3910 c = FIX_CAPACITY (decrease the reported
3911 device capacity by one sector);
3912 d = NO_READ_DISC_INFO (don't use
3913 READ_DISC_INFO command);
3914 e = NO_READ_CAPACITY_16 (don't use
3915 READ_CAPACITY_16 command);
3916 f = NO_REPORT_OPCODES (don't use report opcodes
3918 g = MAX_SECTORS_240 (don't transfer more than
3919 240 sectors at a time, uas only);
3920 h = CAPACITY_HEURISTICS (decrease the
3921 reported device capacity by one
3922 sector if the number is odd);
3923 i = IGNORE_DEVICE (don't bind to this
3925 l = NOT_LOCKABLE (don't try to lock and
3926 unlock ejectable media);
3927 m = MAX_SECTORS_64 (don't transfer more
3928 than 64 sectors = 32 KB at a time);
3929 n = INITIAL_READ10 (force a retry of the
3930 initial READ(10) command);
3931 o = CAPACITY_OK (accept the capacity
3932 reported by the device);
3933 p = WRITE_CACHE (the device cache is ON
3935 r = IGNORE_RESIDUE (the device reports
3936 bogus residue values);
3937 s = SINGLE_LUN (the device has only one
3939 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3940 commands, uas only);
3941 u = IGNORE_UAS (don't bind to the uas driver);
3942 w = NO_WP_DETECT (don't test whether the
3943 medium is write-protected).
3944 Example: quirks=0419:aaf5:rl,0421:0433:rc
3946 user_debug= [KNL,ARM]
3948 See arch/arm/Kconfig.debug help text.
3949 1 - undefined instruction events
3951 4 - invalid data aborts
3954 Example: user_debug=31
3957 [X86] Flags controlling user PTE allocations.
3959 nohigh = do not allocate PTE pages in
3960 HIGHMEM regardless of setting
3964 On X86_32, this is an alias for vdso32=. Otherwise:
3966 vdso=1: enable VDSO (the default)
3967 vdso=0: disable VDSO mapping
3969 vdso32= [X86] Control the 32-bit vDSO
3970 vdso32=1: enable 32-bit VDSO
3971 vdso32=0 or vdso32=2: disable 32-bit VDSO
3973 See the help text for CONFIG_COMPAT_VDSO for more
3974 details. If CONFIG_COMPAT_VDSO is set, the default is
3975 vdso32=0; otherwise, the default is vdso32=1.
3977 For compatibility with older kernels, vdso32=2 is an
3980 Try vdso32=0 if you encounter an error that says:
3981 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3984 vector=percpu: enable percpu vector domain
3986 video= [FB] Frame buffer configuration
3987 See Documentation/fb/modedb.txt.
3989 video.brightness_switch_enabled= [0,1]
3990 If set to 1, on receiving an ACPI notify event
3991 generated by hotkey, video driver will adjust brightness
3992 level and then send out the event to user space through
3993 the allocated input device; If set to 0, video driver
3994 will only send out the event without touching backlight
3999 [VMMIO] Memory mapped virtio (platform) device.
4001 <size>@<baseaddr>:<irq>[:<id>]
4003 <size> := size (can use standard suffixes
4005 <baseaddr> := physical base address
4006 <irq> := interrupt number (as passed to
4008 <id> := (optional) platform device id
4010 virtio_mmio.device=1K@0x100b0000:48:7
4012 Can be used multiple times for multiple devices.
4014 vga= [BOOT,X86-32] Select a particular video mode
4015 See Documentation/x86/boot.txt and
4016 Documentation/svga.txt.
4017 Use vga=ask for menu.
4018 This is actually a boot loader parameter; the value is
4019 passed to the kernel using a special protocol.
4021 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4022 size of <nn>. This can be used to increase the
4023 minimum size (128MB on x86). It can also be used to
4024 decrease the size and leave more room for directly
4027 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4030 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4033 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4037 Controls the behavior of vsyscalls (i.e. calls to
4038 fixed addresses of 0xffffffffff600x00 from legacy
4039 code). Most statically-linked binaries and older
4040 versions of glibc use these calls. Because these
4041 functions are at fixed addresses, they make nice
4042 targets for exploits that can control RIP.
4044 emulate [default] Vsyscalls turn into traps and are
4045 emulated reasonably safely.
4047 native Vsyscalls are native syscall instructions.
4048 This is a little bit faster than trapping
4049 and makes a few dynamic recompilers work
4050 better than they would in emulation mode.
4051 It also makes exploits much easier to write.
4053 none Vsyscalls don't work at all. This makes
4054 them quite hard to use for exploits but
4055 might break your system.
4057 vt.color= [VT] Default text color.
4058 Format: 0xYX, X = foreground, Y = background.
4059 Default: 0x07 = light gray on black.
4061 vt.cur_default= [VT] Default cursor shape.
4062 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4063 the parameters of the <Esc>[?A;B;Cc escape sequence;
4064 see VGA-softcursor.txt. Default: 2 = underline.
4066 vt.default_blu= [VT]
4067 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4068 Change the default blue palette of the console.
4069 This is a 16-member array composed of values
4072 vt.default_grn= [VT]
4073 Format: <green0>,<green1>,<green2>,...,<green15>
4074 Change the default green palette of the console.
4075 This is a 16-member array composed of values
4078 vt.default_red= [VT]
4079 Format: <red0>,<red1>,<red2>,...,<red15>
4080 Change the default red palette of the console.
4081 This is a 16-member array composed of values
4087 Set system-wide default UTF-8 mode for all tty's.
4088 Default is 1, i.e. UTF-8 mode is enabled for all
4089 newly opened terminals.
4091 vt.global_cursor_default=
4094 Set system-wide default for whether a cursor
4095 is shown on new VTs. Default is -1,
4096 i.e. cursors will be created by default unless
4097 overridden by individual drivers. 0 will hide
4098 cursors, 1 will display them.
4100 vt.italic= [VT] Default color for italic text; 0-15.
4103 vt.underline= [VT] Default color for underlined text; 0-15.
4106 watchdog timers [HW,WDT] For information on watchdog timers,
4107 see Documentation/watchdog/watchdog-parameters.txt
4108 or other driver-specific files in the
4109 Documentation/watchdog/ directory.
4111 workqueue.disable_numa
4112 By default, all work items queued to unbound
4113 workqueues are affine to the NUMA nodes they're
4114 issued on, which results in better behavior in
4115 general. If NUMA affinity needs to be disabled for
4116 whatever reason, this option can be used. Note
4117 that this also can be controlled per-workqueue for
4118 workqueues visible under /sys/bus/workqueue/.
4120 workqueue.power_efficient
4121 Per-cpu workqueues are generally preferred because
4122 they show better performance thanks to cache
4123 locality; unfortunately, per-cpu workqueues tend to
4124 be more power hungry than unbound workqueues.
4126 Enabling this makes the per-cpu workqueues which
4127 were observed to contribute significantly to power
4128 consumption unbound, leading to measurably lower
4129 power usage at the cost of small performance
4132 The default value of this parameter is determined by
4133 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4135 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4136 default x2apic cluster mode on platforms
4139 x86_intel_mid_timer= [X86-32,APBT]
4140 Choose timer option for x86 Intel MID platform.
4141 Two valid options are apbt timer only and lapic timer
4142 plus one apbt timer for broadcast timer.
4143 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4145 xen_512gb_limit [KNL,X86-64,XEN]
4146 Restricts the kernel running paravirtualized under Xen
4147 to use only up to 512 GB of RAM. The reason to do so is
4148 crash analysis tools and Xen tools for doing domain
4149 save/restore/migration must be enabled to handle larger
4152 xen_emul_unplug= [HW,X86,XEN]
4153 Unplug Xen emulated devices
4154 Format: [unplug0,][unplug1]
4155 ide-disks -- unplug primary master IDE devices
4156 aux-ide-disks -- unplug non-primary-master IDE devices
4157 nics -- unplug network devices
4158 all -- unplug all emulated devices (NICs and IDE disks)
4159 unnecessary -- unplugging emulated devices is
4160 unnecessary even if the host did not respond to
4162 never -- do not unplug even if version check succeeds
4164 xen_nopvspin [X86,XEN]
4165 Disables the ticketlock slowpath using Xen PV
4169 Disables the PV optimizations forcing the HVM guest to
4170 run as generic HVM guest with no PV drivers.
4172 xirc2ps_cs= [NET,PCMCIA]
4174 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4176 ______________________________________________________________________
4180 Add more DRM drivers.
projects / firefly-linux-kernel-4.4.55.git / blob