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>[,[<connector>:]<file>]
936 Broken monitors, graphic adapters, KVMs and EDIDless
937 panels may send no or incorrect EDID data sets.
938 This parameter allows to specify an EDID data sets
939 in the /lib/firmware directory that are 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
948 name. Each connector may use a unique EDID data
949 set by separating the files with a comma. An EDID
950 data set with no connector name will be used for
951 any connectors not explicitly specified.
955 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
956 module.dyndbg[="val"]
957 Enable debug messages at boot time. See
958 Documentation/dynamic-debug-howto.txt for details.
960 nompx [X86] Disables Intel Memory Protection Extensions.
961 See Documentation/x86/intel_mpx.txt for more
962 information about the feature.
965 on enable eager fpu restore
966 off disable eager fpu restore
967 auto selects the default scheme, which automatically
968 enables eagerfpu restore for xsaveopt.
970 module.async_probe [KNL]
971 Enable asynchronous probe on this module.
973 early_ioremap_debug [KNL]
974 Enable debug messages in early_ioremap support. This
975 is useful for tracking down temporary early mappings
976 which are not unmapped.
978 earlycon= [KNL] Output early console device and options.
980 When used with no options, the early console is
981 determined by the stdout-path property in device
985 Start an early, polled-mode console on a cadence serial
986 port at the specified address. The cadence serial port
987 must already be setup and configured. Options are not
990 uart[8250],io,<addr>[,options]
991 uart[8250],mmio,<addr>[,options]
992 uart[8250],mmio32,<addr>[,options]
993 uart[8250],mmio32be,<addr>[,options]
994 uart[8250],0x<addr>[,options]
995 Start an early, polled-mode console on the 8250/16550
996 UART at the specified I/O port or MMIO address.
997 MMIO inter-register address stride is either 8-bit
998 (mmio) or 32-bit (mmio32 or mmio32be).
999 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1000 to be equivalent to 'mmio'. 'options' are specified
1001 in the same format described for "console=ttyS<n>"; if
1002 unspecified, the h/w is not initialized.
1005 Start an early, polled-mode console on a pl011 serial
1006 port at the specified address. The pl011 serial port
1007 must already be setup and configured. Options are not
1011 Start an early, polled-mode console on an msm serial
1012 port at the specified address. The serial port
1013 must already be setup and configured. Options are not
1016 msm_serial_dm,<addr>
1017 Start an early, polled-mode console on an msm serial
1018 dm port at the specified address. The serial port
1019 must already be setup and configured. Options are not
1022 smh Use ARM semihosting calls for early console.
1030 Use early console provided by serial driver available
1031 on Samsung SoCs, requires selecting proper type and
1032 a correct base address of the selected UART port. The
1033 serial port must already be setup and configured.
1034 Options are not yet supported.
1036 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1040 earlyprintk=serial[,ttySn[,baudrate]]
1041 earlyprintk=serial[,0x...[,baudrate]]
1042 earlyprintk=ttySn[,baudrate]
1043 earlyprintk=dbgp[debugController#]
1044 earlyprintk=pciserial,bus:device.function[,baudrate]
1046 earlyprintk is useful when the kernel crashes before
1047 the normal console is initialized. It is not enabled by
1048 default because it has some cosmetic problems.
1050 Append ",keep" to not disable it when the real console
1053 Only one of vga, efi, serial, or usb debug port can
1056 Currently only ttyS0 and ttyS1 may be specified by
1057 name. Other I/O ports may be explicitly specified
1058 on some architectures (x86 and arm at least) by
1059 replacing ttySn with an I/O port address, like this:
1060 earlyprintk=serial,0x1008,115200
1061 You can find the port for a given device in
1062 /proc/tty/driver/serial:
1063 2: uart:ST16650V2 port:00001008 irq:18 ...
1065 Interaction with the standard serial driver is not
1068 The VGA and EFI output is eventually overwritten by
1071 The xen output can only be used by Xen PV guests.
1073 edac_report= [HW,EDAC] Control how to report EDAC event
1074 Format: {"on" | "off" | "force"}
1075 on: enable EDAC to report H/W event. May be overridden
1076 by other higher priority error reporting module.
1077 off: disable H/W event reporting through EDAC.
1078 force: enforce the use of EDAC to report H/W event.
1081 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1084 This is designed to be used in conjunction with
1085 the boot argument: earlyprintk=vga
1088 Format: {"off" | "on" | "skip[mbr]"}
1091 Format: { "old_map", "nochunk", "noruntime", "debug" }
1092 old_map [X86-64]: switch to the old ioremap-based EFI
1093 runtime services mapping. 32-bit still uses this one by
1095 nochunk: disable reading files in "chunks" in the EFI
1096 boot stub, as chunking can cause problems with some
1097 firmware implementations.
1098 noruntime : disable EFI runtime services support
1099 debug: enable misc debug output
1101 efi_no_storage_paranoia [EFI; X86]
1102 Using this parameter you can use more than 50% of
1103 your efi variable storage. Use this parameter only if
1104 you are really sure that your UEFI does sane gc and
1105 fulfills the spec otherwise your board may brick.
1107 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1108 Add arbitrary attribute to specific memory range by
1109 updating original EFI memory map.
1110 Region of memory which aa attribute is added to is
1112 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1113 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1114 attribute is added to range 0x100000000-0x180000000 and
1115 0x10a0000000-0x1120000000.
1117 Using this parameter you can do debugging of EFI memmap
1118 related feature. For example, you can do debugging of
1119 Address Range Mirroring feature even if your box
1122 eisa_irq_edge= [PARISC,HW]
1123 See header of drivers/parisc/eisa.c.
1126 See comment before function elanfreq_setup() in
1127 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1130 Format: {"cfq" | "deadline" | "noop"}
1131 See Documentation/block/cfq-iosched.txt and
1132 Documentation/block/deadline-iosched.txt for details.
1134 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1135 Specifies physical address of start of kernel core
1136 image elf header and optionally the size. Generally
1137 kexec loader will pass this option to capture kernel.
1138 See Documentation/kdump/kdump.txt for details.
1140 enable_mtrr_cleanup [X86]
1141 The kernel tries to adjust MTRR layout from continuous
1142 to discrete, to make X server driver able to add WB
1143 entry later. This parameter enables that.
1145 enable_timer_pin_1 [X86]
1146 Enable PIN 1 of APIC timer
1147 Can be useful to work around chipset bugs
1148 (in particular on some ATI chipsets).
1149 The kernel tries to set a reasonable default.
1151 enforcing [SELINUX] Set initial enforcing status.
1153 See security/selinux/Kconfig help text.
1154 0 -- permissive (log only, no denials).
1155 1 -- enforcing (deny and log).
1157 Value can be changed at runtime via /selinux/enforce.
1160 Disable Error Record Serialization Table (ERST)
1163 ether= [HW,NET] Ethernet cards parameters
1164 This option is obsoleted by the "netdev=" option, which
1165 has equivalent usage. See its documentation for details.
1169 Permit 'security.evm' to be updated regardless of
1170 current integrity status.
1174 fail_make_request=[KNL]
1175 General fault injection mechanism.
1176 Format: <interval>,<probability>,<space>,<times>
1177 See also Documentation/fault-injection/.
1180 See Documentation/blockdev/floppy.txt.
1182 force_pal_cache_flush
1183 [IA-64] Avoid check_sal_cache_flush which may hang on
1184 buggy SAL_CACHE_FLUSH implementations. Using this
1185 parameter will force ia64_sal_cache_flush to call
1186 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1189 Forcefully enable Physical Address Extension (PAE).
1190 Many Pentium M systems disable PAE but may have a
1191 functionally usable PAE implementation.
1192 Warning: use of this parameter will taint the kernel
1193 and may cause unknown problems.
1196 [FTRACE] will set and start the specified tracer
1197 as early as possible in order to facilitate early
1200 ftrace_dump_on_oops[=orig_cpu]
1201 [FTRACE] will dump the trace buffers on oops.
1202 If no parameter is passed, ftrace will dump
1203 buffers of all CPUs, but if you pass orig_cpu, it will
1204 dump only the buffer of the CPU that triggered the
1207 ftrace_filter=[function-list]
1208 [FTRACE] Limit the functions traced by the function
1209 tracer at boot up. function-list is a comma separated
1210 list of functions. This list can be changed at run
1211 time by the set_ftrace_filter file in the debugfs
1214 ftrace_notrace=[function-list]
1215 [FTRACE] Do not trace the functions specified in
1216 function-list. This list can be changed at run time
1217 by the set_ftrace_notrace file in the debugfs
1220 ftrace_graph_filter=[function-list]
1221 [FTRACE] Limit the top level callers functions traced
1222 by the function graph tracer at boot up.
1223 function-list is a comma separated list of functions
1224 that can be changed at run time by the
1225 set_graph_function file in the debugfs tracing directory.
1227 ftrace_graph_notrace=[function-list]
1228 [FTRACE] Do not trace from the functions specified in
1229 function-list. This list is a comma separated list of
1230 functions that can be changed at run time by the
1231 set_graph_notrace file in the debugfs tracing directory.
1234 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1235 support via parallel port (up to 5 devices per port)
1236 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1237 See also Documentation/input/joystick-parport.txt
1241 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1245 gcov_persist= [GCOV] When non-zero (default), profiling data for
1246 kernel modules is saved and remains accessible via
1247 debugfs, even when the module is unloaded/reloaded.
1248 When zero, profiling data is discarded and associated
1249 debugfs files are removed at module unload time.
1251 gpt [EFI] Forces disk with valid GPT signature but
1252 invalid Protective MBR to be treated as GPT. If the
1253 primary GPT is corrupted, it enables the backup/alternate
1254 GPT to be used instead.
1256 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1257 the "Enable 0" bit of the configuration register.
1260 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1261 the "Enable 0" bit of the configuration register.
1264 grcan.select= [HW] Select which physical interface to use.
1267 grcan.txsize= [HW] Sets the size of the tx buffer.
1268 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1270 grcan.rxsize= [HW] Sets the size of the rx buffer.
1271 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1274 hashdist= [KNL,NUMA] Large hashes allocated during boot
1275 are distributed across NUMA nodes. Defaults on
1276 for 64-bit NUMA, off otherwise.
1277 Format: 0 | 1 (for off | on)
1279 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1281 hd= [EIDE] (E)IDE hard drive subsystem geometry
1282 Format: <cyl>,<head>,<sect>
1285 Disable Hardware Error Source Table (HEST) support;
1286 corresponding firmware-first mode error processing
1287 logic will be disabled.
1289 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1290 size of <nn>. This works even on boxes that have no
1291 highmem otherwise. This also works to reduce highmem
1292 size on bigger boxes.
1294 highres= [KNL] Enable/disable high resolution timer mode.
1295 Valid parameters: "on", "off"
1299 See Documentation/isdn/README.HiSax.
1303 hpet= [X86-32,HPET] option to control HPET usage
1304 Format: { enable (default) | disable | force |
1306 disable: disable HPET and use PIT instead
1307 force: allow force enabled of undocumented chips (ICH4,
1309 verbose: show contents of HPET registers during setup
1311 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1312 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1314 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1315 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1316 On x86-64 and powerpc, this option can be specified
1317 multiple times interleaved with hugepages= to reserve
1318 huge pages of different sizes. Valid pages sizes on
1319 x86-64 are 2M (when the CPU supports "pse") and 1G
1320 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1322 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1323 terminal devices. Valid values: 0..8
1324 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1325 If specified, z/VM IUCV HVC accepts connections
1326 from listed z/VM user IDs only.
1328 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1329 hardware thread id mappings.
1330 Format: <cpu>:<hwthread>
1333 Do not unregister boot console at start. This is only
1334 useful for debugging when something happens in the window
1335 between unregistering the boot console and initializing
1338 i2c_bus= [HW] Override the default board specific I2C bus speed
1339 or register an additional I2C bus that is not
1340 registered from board initialization code.
1344 i8042.debug [HW] Toggle i8042 debug mode
1345 i8042.unmask_kbd_data
1346 [HW] Enable printing of interrupt data from the KBD port
1347 (disabled by default, and as a pre-condition
1348 requires that i8042.debug=1 be enabled)
1349 i8042.direct [HW] Put keyboard port into non-translated mode
1350 i8042.dumbkbd [HW] Pretend that controller can only read data from
1351 keyboard and cannot control its state
1352 (Don't attempt to blink the leds)
1353 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1354 i8042.nokbd [HW] Don't check/create keyboard port
1355 i8042.noloop [HW] Disable the AUX Loopback command while probing
1357 i8042.nomux [HW] Don't check presence of an active multiplexing
1359 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1361 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1362 i8042.reset [HW] Reset the controller during init and cleanup
1363 i8042.unlock [HW] Unlock (ignore) the keylock
1364 i8042.kbdreset [HW] Reset device connected to KBD port
1368 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1369 indicates that the driver is running on unsupported
1371 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1372 does not match list of supported models.
1374 [HW] Report power status in /proc/i8k
1375 (disabled by default)
1376 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1379 i915.invert_brightness=
1380 [DRM] Invert the sense of the variable that is used to
1381 set the brightness of the panel backlight. Normally a
1382 brightness value of 0 indicates backlight switched off,
1383 and the maximum of the brightness value sets the backlight
1384 to maximum brightness. If this parameter is set to 0
1385 (default) and the machine requires it, or this parameter
1386 is set to 1, a brightness value of 0 sets the backlight
1387 to maximum brightness, and the maximum of the brightness
1388 value switches the backlight off.
1389 -1 -- never invert brightness
1390 0 -- machine default
1391 1 -- force brightness inversion
1394 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1396 ide-core.nodma= [HW] (E)IDE subsystem
1397 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1398 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1399 .cdrom .chs .ignore_cable are additional options
1400 See Documentation/ide/ide.txt.
1402 ide-generic.probe-mask= [HW] (E)IDE subsystem
1404 Probe mask for legacy ISA IDE ports. Depending on
1405 platform up to 6 ports are supported, enabled by
1406 setting corresponding bits in the mask to 1. The
1407 default value is 0x0, which has a special meaning.
1408 On systems that have PCI, it triggers scanning the
1409 PCI bus for the first and the second port, which
1410 are then probed. On systems without PCI the value
1411 of 0x0 enables probing the two first ports as if it
1414 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1415 Claim all unknown PCI IDE storage controllers.
1418 Format: idle=poll, idle=halt, idle=nomwait
1419 Poll forces a polling idle loop that can slightly
1420 improve the performance of waking up a idle CPU, but
1421 will use a lot of power and make the system run hot.
1423 idle=halt: Halt is forced to be used for CPU idle.
1424 In such case C2/C3 won't be used again.
1425 idle=nomwait: Disable mwait for CPU C-states
1427 ignore_loglevel [KNL]
1428 Ignore loglevel setting - this will print /all/
1429 kernel messages to the console. Useful for debugging.
1430 We also add it as printk module parameter, so users
1431 could change it dynamically, usually by
1432 /sys/module/printk/parameters/ignore_loglevel.
1434 ihash_entries= [KNL]
1435 Set number of hash buckets for inode cache.
1437 ima_appraise= [IMA] appraise integrity measurements
1438 Format: { "off" | "enforce" | "fix" | "log" }
1441 ima_appraise_tcb [IMA]
1442 The builtin appraise policy appraises all files
1446 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1450 The list of supported hash algorithms is defined
1451 in crypto/hash_info.h.
1454 The builtin measurement policy to load during IMA
1455 setup. Specyfing "tcb" as the value, measures all
1456 programs exec'd, files mmap'd for exec, and all files
1457 opened with the read mode bit set by either the
1458 effective uid (euid=0) or uid=0.
1461 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1462 Load a policy which meets the needs of the Trusted
1463 Computing Base. This means IMA will measure all
1464 programs exec'd, files mmap'd for exec, and all files
1465 opened for read by uid=0.
1468 Select one of defined IMA measurements template formats.
1469 Formats: { "ima" | "ima-ng" | "ima-sig" }
1473 [IMA] Define a custom template format.
1474 Format: { "field1|...|fieldN" }
1476 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1477 Format: <min_file_size>
1478 Set the minimal file size for using asynchronous hash.
1479 If left unspecified, ahash usage is disabled.
1481 ahash performance varies for different data sizes on
1482 different crypto accelerators. This option can be used
1483 to achieve the best performance for a particular HW.
1485 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1487 Set hashing buffer size. Default: 4k.
1489 ahash performance varies for different chunk sizes on
1490 different crypto accelerators. This option can be used
1491 to achieve best performance for particular HW.
1495 Run specified binary instead of /sbin/init as init
1498 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1499 for working out where the kernel is dying during
1502 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1503 initcall functions. Useful for debugging built-in
1504 modules and initcalls.
1506 initrd= [BOOT] Specify the location of the initial ramdisk
1508 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1511 int_pln_enable [x86] Enable power limit notification interrupt
1513 integrity_audit=[IMA]
1514 Format: { "0" | "1" }
1515 0 -- basic integrity auditing messages. (Default)
1516 1 -- additional integrity auditing messages.
1518 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1520 Enable intel iommu driver.
1522 Disable intel iommu driver.
1523 igfx_off [Default Off]
1524 By default, gfx is mapped as normal device. If a gfx
1525 device has a dedicated DMAR unit, the DMAR unit is
1526 bypassed by not enabling DMAR with this option. In
1527 this case, gfx device will use physical address for
1530 With this option iommu will not optimize to look
1531 for io virtual address below 32-bit forcing dual
1532 address cycle on pci bus for cards supporting greater
1533 than 32-bit addressing. The default is to look
1534 for translation below 32-bit and if not available
1535 then look in the higher range.
1536 strict [Default Off]
1537 With this option on every unmap_single operation will
1538 result in a hardware IOTLB flush operation as opposed
1539 to batching them for performance.
1540 sp_off [Default Off]
1541 By default, super page will be supported if Intel IOMMU
1542 has the capability. With this option, super page will
1544 ecs_off [Default Off]
1545 By default, extended context tables will be supported if
1546 the hardware advertises that it has support both for the
1547 extended tables themselves, and also PASID support. With
1548 this option set, extended tables will not be used even
1549 on hardware which claims to support them.
1551 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1552 0 disables intel_idle and fall back on acpi_idle.
1553 1 to 6 specify maximum depth of C-state.
1557 Do not enable intel_pstate as the default
1558 scaling driver for the supported processors
1560 Enable intel_pstate on systems that prohibit it by default
1561 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1562 instead of acpi-cpufreq may disable platform features, such
1563 as thermal controls and power capping, that rely on ACPI
1564 P-States information being indicated to OSPM and therefore
1565 should be used with caution. This option does not work with
1566 processors that aren't supported by the intel_pstate driver
1567 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1569 Do not enable hardware P state control (HWP)
1572 Only load intel_pstate on systems which support
1573 hardware P state control (HWP) if available.
1575 Don't use ACPI processor performance control objects
1576 _PSS and _PPC specified limits.
1578 intremap= [X86-64, Intel-IOMMU]
1579 on enable Interrupt Remapping (default)
1580 off disable Interrupt Remapping
1581 nosid disable Source ID checking
1583 BIOS x2APIC opt-out request will be ignored
1585 iomem= Disable strict checking of access to MMIO memory
1586 strict regions from userspace.
1601 nobypass [PPC/POWERNV]
1602 Disable IOMMU bypass, using IOMMU for PCI devices.
1605 io7= [HW] IO7 for Marvel based alpha systems
1606 See comment before marvel_specify_io7 in
1607 arch/alpha/kernel/core_marvel.c.
1609 io_delay= [X86] I/O delay method
1611 Standard port 0x80 based delay
1613 Alternate port 0xed based delay (needed on some systems)
1615 Simple two microseconds delay
1620 See Documentation/filesystems/nfs/nfsroot.txt.
1623 When an interrupt is not handled search all handlers
1624 for it. Intended to get systems with badly broken
1628 When an interrupt is not handled search all handlers
1629 for it. Also check all handlers each timer
1630 interrupt. Intended to get systems with badly broken
1634 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1636 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1638 <cpu number>,...,<cpu number>
1640 <cpu number>-<cpu number>
1641 (must be a positive range in ascending order)
1643 <cpu number>,...,<cpu number>-<cpu number>
1645 This option can be used to specify one or more CPUs
1646 to isolate from the general SMP balancing and scheduling
1647 algorithms. You can move a process onto or off an
1648 "isolated" CPU via the CPU affinity syscalls or cpuset.
1649 <cpu number> begins at 0 and the maximum value is
1650 "number of CPUs in system - 1".
1652 This option is the preferred way to isolate CPUs. The
1653 alternative -- manually setting the CPU mask of all
1654 tasks in the system -- can cause problems and
1655 suboptimal load balancer performance.
1659 ivrs_ioapic [HW,X86_64]
1660 Provide an override to the IOAPIC-ID<->DEVICE-ID
1661 mapping provided in the IVRS ACPI table. For
1662 example, to map IOAPIC-ID decimal 10 to
1663 PCI device 00:14.0 write the parameter as:
1664 ivrs_ioapic[10]=00:14.0
1666 ivrs_hpet [HW,X86_64]
1667 Provide an override to the HPET-ID<->DEVICE-ID
1668 mapping provided in the IVRS ACPI table. For
1669 example, to map HPET-ID decimal 0 to
1670 PCI device 00:14.0 write the parameter as:
1671 ivrs_hpet[0]=00:14.0
1673 js= [HW,JOY] Analog joystick
1674 See Documentation/input/joystick.txt.
1677 Enable/disable kernel and module base offset ASLR
1678 (Address Space Layout Randomization) if built into
1679 the kernel. When CONFIG_HIBERNATION is selected,
1680 kASLR is disabled by default. When kASLR is enabled,
1681 hibernation will be disabled.
1685 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1686 specifies the amount of memory usable by the kernel
1687 for non-movable allocations. The requested amount is
1688 spread evenly throughout all nodes in the system. The
1689 remaining memory in each node is used for Movable
1690 pages. In the event, a node is too small to have both
1691 kernelcore and Movable pages, kernelcore pages will
1692 take priority and other nodes will have a larger number
1693 of Movable pages. The Movable zone is used for the
1694 allocation of pages that may be reclaimed or moved
1695 by the page migration subsystem. This means that
1696 HugeTLB pages may not be allocated from this zone.
1697 Note that allocations like PTEs-from-HighMem still
1698 use the HighMem zone if it exists, and the Normal
1699 zone if it does not.
1701 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1702 Format: <Controller#>[,poll interval]
1703 The controller # is the number of the ehci usb debug
1704 port as it is probed via PCI. The poll interval is
1705 optional and is the number seconds in between
1706 each poll cycle to the debug port in case you need
1707 the functionality for interrupting the kernel with
1708 gdb or control-c on the dbgp connection. When
1709 not using this parameter you use sysrq-g to break into
1710 the kernel debugger.
1712 kgdboc= [KGDB,HW] kgdb over consoles.
1713 Requires a tty driver that supports console polling,
1714 or a supported polling keyboard driver (non-usb).
1715 Serial only format: <serial_device>[,baud]
1716 keyboard only format: kbd
1717 keyboard and serial format: kbd,<serial_device>[,baud]
1718 Optional Kernel mode setting:
1719 kms, kbd format: kms,kbd
1720 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1722 kgdbwait [KGDB] Stop kernel execution and enter the
1723 kernel debugger at the earliest opportunity.
1725 kmac= [MIPS] korina ethernet MAC address.
1726 Configure the RouterBoard 532 series on-chip
1727 Ethernet adapter MAC address.
1729 kmemleak= [KNL] Boot-time kmemleak enable/disable
1730 Valid arguments: on, off
1732 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1735 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1736 Valid arguments: 0, 1, 2
1737 kmemcheck=0 (disabled)
1738 kmemcheck=1 (enabled)
1739 kmemcheck=2 (one-shot mode)
1740 Default: 2 (one-shot mode)
1742 kstack=N [X86] Print N words from the kernel stack
1745 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1746 Default is 0 (don't ignore, but inject #GP)
1748 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1752 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1753 Default is 1 (enabled)
1755 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1757 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1759 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1760 (virtualized MMU) support on capable Intel chips.
1761 Default is 1 (enabled)
1763 kvm-intel.emulate_invalid_guest_state=
1764 [KVM,Intel] Enable emulation of invalid guest states
1765 Default is 0 (disabled)
1767 kvm-intel.flexpriority=
1768 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1769 Default is 1 (enabled)
1772 [KVM,Intel] Enable VMX nesting (nVMX).
1773 Default is 0 (disabled)
1775 kvm-intel.unrestricted_guest=
1776 [KVM,Intel] Disable unrestricted guest feature
1777 (virtualized real and unpaged mode) on capable
1778 Intel chips. Default is 1 (enabled)
1780 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1781 feature (tagged TLBs) on capable Intel chips.
1782 Default is 1 (enabled)
1788 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1791 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1792 value for LAPIC timer one-shot implementation. Default
1793 back to the programmable timer unit in the LAPIC.
1795 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1798 libata.dma= [LIBATA] DMA control
1799 libata.dma=0 Disable all PATA and SATA DMA
1800 libata.dma=1 PATA and SATA Disk DMA only
1801 libata.dma=2 ATAPI (CDROM) DMA only
1802 libata.dma=4 Compact Flash DMA only
1803 Combinations also work, so libata.dma=3 enables DMA
1804 for disks and CDROMs, but not CFs.
1806 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1807 libata.ignore_hpa=0 keep BIOS limits (default)
1808 libata.ignore_hpa=1 ignore limits, using full disk
1810 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1814 libata.force= [LIBATA] Force configurations. The format is comma
1815 separated list of "[ID:]VAL" where ID is
1816 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1817 matching port, link or device. Basically, it matches
1818 the ATA ID string printed on console by libata. If
1819 the whole ID part is omitted, the last PORT and DEVICE
1820 values are used. If ID hasn't been specified yet, the
1821 configuration applies to all ports, links and devices.
1823 If only DEVICE is omitted, the parameter applies to
1824 the port and all links and devices behind it. DEVICE
1825 number of 0 either selects the first device or the
1826 first fan-out link behind PMP device. It does not
1827 select the host link. DEVICE number of 15 selects the
1828 host link and device attached to it.
1830 The VAL specifies the configuration to force. As long
1831 as there's no ambiguity shortcut notation is allowed.
1832 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1833 The following configurations can be forced.
1835 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1836 Any ID with matching PORT is used.
1838 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1840 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1841 udma[/][16,25,33,44,66,100,133] notation is also
1844 * [no]ncq: Turn on or off NCQ.
1846 * [no]ncqtrim: Turn off queued DSM TRIM.
1848 * nohrst, nosrst, norst: suppress hard, soft
1851 * rstonce: only attempt one reset during
1852 hot-unplug link recovery
1854 * dump_id: dump IDENTIFY data.
1856 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1858 * disable: Disable this device.
1860 If there are multiple matching configurations changing
1861 the same attribute, the last one is used.
1863 memblock=debug [KNL] Enable memblock debug messages.
1865 load_ramdisk= [RAM] List of ramdisks to load from floppy
1866 See Documentation/blockdev/ramdisk.txt.
1868 lockd.nlm_grace_period=P [NFS] Assign grace period.
1871 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1874 lockd.nlm_timeout=T [NFS] Assign timeout value.
1877 lockd.nlm_udpport=M [NFS] Assign UDP port.
1880 locktorture.nreaders_stress= [KNL]
1881 Set the number of locking read-acquisition kthreads.
1882 Defaults to being automatically set based on the
1883 number of online CPUs.
1885 locktorture.nwriters_stress= [KNL]
1886 Set the number of locking write-acquisition kthreads.
1888 locktorture.onoff_holdoff= [KNL]
1889 Set time (s) after boot for CPU-hotplug testing.
1891 locktorture.onoff_interval= [KNL]
1892 Set time (s) between CPU-hotplug operations, or
1893 zero to disable CPU-hotplug testing.
1895 locktorture.shuffle_interval= [KNL]
1896 Set task-shuffle interval (jiffies). Shuffling
1897 tasks allows some CPUs to go into dyntick-idle
1898 mode during the locktorture test.
1900 locktorture.shutdown_secs= [KNL]
1901 Set time (s) after boot system shutdown. This
1902 is useful for hands-off automated testing.
1904 locktorture.stat_interval= [KNL]
1905 Time (s) between statistics printk()s.
1907 locktorture.stutter= [KNL]
1908 Time (s) to stutter testing, for example,
1909 specifying five seconds causes the test to run for
1910 five seconds, wait for five seconds, and so on.
1911 This tests the locking primitive's ability to
1912 transition abruptly to and from idle.
1914 locktorture.torture_runnable= [BOOT]
1915 Start locktorture running at boot time.
1917 locktorture.torture_type= [KNL]
1918 Specify the locking implementation to test.
1920 locktorture.verbose= [KNL]
1921 Enable additional printk() statements.
1923 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1926 loglevel= All Kernel Messages with a loglevel smaller than the
1927 console loglevel will be printed to the console. It can
1928 also be changed with klogd or other programs. The
1929 loglevels are defined as follows:
1931 0 (KERN_EMERG) system is unusable
1932 1 (KERN_ALERT) action must be taken immediately
1933 2 (KERN_CRIT) critical conditions
1934 3 (KERN_ERR) error conditions
1935 4 (KERN_WARNING) warning conditions
1936 5 (KERN_NOTICE) normal but significant condition
1937 6 (KERN_INFO) informational
1938 7 (KERN_DEBUG) debug-level messages
1940 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1941 in bytes. n must be a power of two and greater
1942 than the minimal size. The minimal size is defined
1943 by LOG_BUF_SHIFT kernel config parameter. There is
1944 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1945 that allows to increase the default size depending on
1946 the number of CPUs. See init/Kconfig for more details.
1948 logo.nologo [FB] Disables display of the built-in Linux logo.
1949 This may be used to provide more screen space for
1950 kernel log messages and is useful when debugging
1951 kernel boot problems.
1953 lp=0 [LP] Specify parallel ports to use, e.g,
1954 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1955 lp=reset first parallel port). 'lp=0' disables the
1956 lp=auto printer driver. 'lp=reset' (which can be
1957 specified in addition to the ports) causes
1958 attached printers to be reset. Using
1959 lp=port1,port2,... specifies the parallel ports
1960 to associate lp devices with, starting with
1961 lp0. A port specification may be 'none' to skip
1962 that lp device, or a parport name such as
1963 'parport0'. Specifying 'lp=auto' instead of a
1964 port specification list means that device IDs
1965 from each port should be examined, to see if
1966 an IEEE 1284-compliant printer is attached; if
1967 so, the driver will manage that printer.
1968 See also header of drivers/char/lp.c.
1971 Sets loops_per_jiffy to given constant, thus avoiding
1972 time-consuming boot-time autodetection (up to 250 ms per
1973 CPU). 0 enables autodetection (default). To determine
1974 the correct value for your kernel, boot with normal
1975 autodetection and see what value is printed. Note that
1976 on SMP systems the preset will be applied to all CPUs,
1977 which is likely to cause problems if your CPUs need
1978 significantly divergent settings. An incorrect value
1979 will cause delays in the kernel to be wrong, leading to
1980 unpredictable I/O errors and other breakage. Although
1981 unlikely, in the extreme case this might damage your
1985 Format: <io>,<irq>,<dma>
1987 machvec= [IA-64] Force the use of a particular machine-vector
1988 (machvec) in a generic kernel.
1989 Example: machvec=hpzx1_swiotlb
1991 machtype= [Loongson] Share the same kernel image file between different
1993 Example: machtype=lemote-yeeloong-2f-7inch
1995 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1996 than or equal to this physical address is ignored.
1998 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1999 should make use of. maxcpus=n : n >= 0 limits the
2000 kernel to using 'n' processors. n=0 is a special case,
2001 it is equivalent to "nosmp", which also disables
2004 max_loop= [LOOP] The number of loop block devices that get
2005 (loop.max_loop) unconditionally pre-created at init time. The default
2006 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2007 of statically allocating a predefined number, loop
2008 devices can be requested on-demand with the
2009 /dev/loop-control interface.
2011 mce [X86-32] Machine Check Exception
2013 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2015 md= [HW] RAID subsystems devices and level
2016 See Documentation/md.txt.
2019 Format: <first>,<last>
2020 Specifies range of consoles to be captured by the MDA.
2022 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2023 Amount of memory to be used when the kernel is not able
2024 to see the whole system memory or for test.
2025 [X86] Work as limiting max address. Use together
2026 with memmap= to avoid physical address space collisions.
2027 Without memmap= PCI devices could be placed at addresses
2028 belonging to unused RAM.
2030 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2034 [KNL,SH] Allow user to override the default size for
2035 per-device physically contiguous DMA buffers.
2037 memmap=exactmap [KNL,X86] Enable setting of an exact
2038 E820 memory map, as specified by the user.
2039 Such memmap=exactmap lines can be constructed based on
2040 BIOS output or other requirements. See the memmap=nn@ss
2043 memmap=nn[KMG]@ss[KMG]
2044 [KNL] Force usage of a specific region of memory.
2045 Region of memory to be used is from ss to ss+nn.
2047 memmap=nn[KMG]#ss[KMG]
2048 [KNL,ACPI] Mark specific memory as ACPI data.
2049 Region of memory to be marked is from ss to ss+nn.
2051 memmap=nn[KMG]$ss[KMG]
2052 [KNL,ACPI] Mark specific memory as reserved.
2053 Region of memory to be reserved is from ss to ss+nn.
2054 Example: Exclude memory from 0x18690000-0x1869ffff
2055 memmap=64K$0x18690000
2057 memmap=0x10000$0x18690000
2059 memmap=nn[KMG]!ss[KMG]
2060 [KNL,X86] Mark specific memory as protected.
2061 Region of memory to be used, from ss to ss+nn.
2062 The memory region may be marked as e820 type 12 (0xc)
2063 and is NVDIMM or ADR memory.
2065 memory_corruption_check=0/1 [X86]
2066 Some BIOSes seem to corrupt the first 64k of
2067 memory when doing things like suspend/resume.
2068 Setting this option will scan the memory
2069 looking for corruption. Enabling this will
2070 both detect corruption and prevent the kernel
2071 from using the memory being corrupted.
2072 However, its intended as a diagnostic tool; if
2073 repeatable BIOS-originated corruption always
2074 affects the same memory, you can use memmap=
2075 to prevent the kernel from using that memory.
2077 memory_corruption_check_size=size [X86]
2078 By default it checks for corruption in the low
2079 64k, making this memory unavailable for normal
2080 use. Use this parameter to scan for
2081 corruption in more or less memory.
2083 memory_corruption_check_period=seconds [X86]
2084 By default it checks for corruption every 60
2085 seconds. Use this parameter to check at some
2086 other rate. 0 disables periodic checking.
2088 memtest= [KNL,X86,ARM] Enable memtest
2090 default : 0 <disable>
2091 Specifies the number of memtest passes to be
2092 performed. Each pass selects another test
2093 pattern from a given set of patterns. Memtest
2094 fills the memory with this pattern, validates
2095 memory contents and reserves bad memory
2096 regions that are detected.
2098 meye.*= [HW] Set MotionEye Camera parameters
2099 See Documentation/video4linux/meye.txt.
2101 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2102 Multi-Function General Purpose Timers on AMD Geode
2105 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2106 the BIOS has incorrectly applied a workaround. TinyBIOS
2107 version 0.98 is known to be affected, 0.99 fixes the
2108 problem by letting the user disable the workaround.
2112 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2113 physical address is ignored.
2115 mini2440= [ARM,HW,KNL]
2116 Format:[0..2][b][c][t]
2118 MINI2440 configuration specification:
2119 0 - The attached screen is the 3.5" TFT
2120 1 - The attached screen is the 7" TFT
2121 2 - The VGA Shield is attached (1024x768)
2122 Leaving out the screen size parameter will not load
2123 the TFT driver, and the framebuffer will be left
2125 b - Enable backlight. The TFT backlight pin will be
2126 linked to the kernel VESA blanking code and a GPIO
2127 LED. This parameter is not necessary when using the
2129 c - Enable the s3c camera interface.
2130 t - Reserved for enabling touchscreen support. The
2131 touchscreen support is not enabled in the mainstream
2132 kernel as of 2.6.30, a preliminary port can be found
2133 in the "bleeding edge" mini2440 support kernel at
2134 http://repo.or.cz/w/linux-2.6/mini2440.git
2137 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2138 parameter allows control of the logging verbosity for
2139 the additional memory initialisation checks. A value
2140 of 0 disables mminit logging and a level of 4 will
2141 log everything. Information is printed at KERN_DEBUG
2142 so loglevel=8 may also need to be specified.
2145 [KNL] When CONFIG_MODULE_SIG is set, this means that
2146 modules without (valid) signatures will fail to load.
2147 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2148 is always true, so this option does nothing.
2151 [MOUSE] Maximum time between finger touching and
2152 leaving touchpad surface for touch to be considered
2153 a tap and be reported as a left button click (for
2154 touchpads working in absolute mode only).
2156 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2157 reporting absolute coordinates, such as tablets
2158 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2159 reporting absolute coordinates, such as tablets
2161 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2162 is similar to kernelcore except it specifies the
2163 amount of memory used for migratable allocations.
2164 If both kernelcore and movablecore is specified,
2165 then kernelcore will be at *least* the specified
2166 value but may be more. If movablecore on its own
2167 is specified, the administrator must be careful
2168 that the amount of memory usable for all allocations
2171 movable_node [KNL,X86] Boot-time switch to enable the effects
2172 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2174 MTD_Partition= [MTD]
2175 Format: <name>,<region-number>,<size>,<offset>
2177 MTD_Region= [MTD] Format:
2178 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2181 See drivers/mtd/cmdlinepart.c.
2183 multitce=off [PPC] This parameter disables the use of the pSeries
2184 firmware feature for updating multiple TCE entries
2187 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2189 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2191 boundary - index of last SLC block on Flex-OneNAND.
2192 The remaining blocks are configured as MLC blocks.
2193 lock - Configure if Flex-OneNAND boundary should be locked.
2194 Once locked, the boundary cannot be changed.
2195 1 indicates lock status, 0 indicates unlock status.
2198 ARM/S3C2412 JIVE boot control
2200 See arch/arm/mach-s3c2412/mach-jive.c
2202 mtouchusb.raw_coordinates=
2203 [HW] Make the MicroTouch USB driver use raw coordinates
2204 ('y', default) or cooked coordinates ('n')
2206 mtrr_chunk_size=nn[KMG] [X86]
2207 used for mtrr cleanup. It is largest continuous chunk
2208 that could hold holes aka. UC entries.
2210 mtrr_gran_size=nn[KMG] [X86]
2211 Used for mtrr cleanup. It is granularity of mtrr block.
2213 Large value could prevent small alignment from
2216 mtrr_spare_reg_nr=n [X86]
2218 Range: 0,7 : spare reg number
2220 Used for mtrr cleanup. It is spare mtrr entries number.
2221 Set to 2 or more if your graphical card needs more.
2223 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2225 netdev= [NET] Network devices parameters
2226 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2227 Note that mem_start is often overloaded to mean
2228 something different and driver-specific.
2229 This usage is only documented in each driver source
2233 [NETFILTER] Enable connection tracking flow accounting
2234 0 to disable accounting
2235 1 to enable accounting
2238 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2239 See Documentation/filesystems/nfs/nfsroot.txt.
2241 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2242 See Documentation/filesystems/nfs/nfsroot.txt.
2244 nfsrootdebug [NFS] enable nfsroot debugging messages.
2245 See Documentation/filesystems/nfs/nfsroot.txt.
2247 nfs.callback_tcpport=
2248 [NFS] set the TCP port on which the NFSv4 callback
2249 channel should listen.
2252 [NFS] sets the pathname to the program which is used
2253 to update the NFS client cache entries.
2255 nfs.cache_getent_timeout=
2256 [NFS] sets the timeout after which an attempt to
2257 update a cache entry is deemed to have failed.
2259 nfs.idmap_cache_timeout=
2260 [NFS] set the maximum lifetime for idmapper cache
2264 [NFS] enable 64-bit inode numbers.
2265 If zero, the NFS client will fake up a 32-bit inode
2266 number for the readdir() and stat() syscalls instead
2267 of returning the full 64-bit number.
2268 The default is to return 64-bit inode numbers.
2270 nfs.max_session_slots=
2271 [NFSv4.1] Sets the maximum number of session slots
2272 the client will attempt to negotiate with the server.
2273 This limits the number of simultaneous RPC requests
2274 that the client can send to the NFSv4.1 server.
2275 Note that there is little point in setting this
2276 value higher than the max_tcp_slot_table_limit.
2278 nfs.nfs4_disable_idmapping=
2279 [NFSv4] When set to the default of '1', this option
2280 ensures that both the RPC level authentication
2281 scheme and the NFS level operations agree to use
2282 numeric uids/gids if the mount is using the
2283 'sec=sys' security flavour. In effect it is
2284 disabling idmapping, which can make migration from
2285 legacy NFSv2/v3 systems to NFSv4 easier.
2286 Servers that do not support this mode of operation
2287 will be autodetected by the client, and it will fall
2288 back to using the idmapper.
2289 To turn off this behaviour, set the value to '0'.
2291 [NFS4] Specify an additional fixed unique ident-
2292 ification string that NFSv4 clients can insert into
2293 their nfs_client_id4 string. This is typically a
2294 UUID that is generated at system install time.
2296 nfs.send_implementation_id =
2297 [NFSv4.1] Send client implementation identification
2298 information in exchange_id requests.
2299 If zero, no implementation identification information
2301 The default is to send the implementation identification
2304 nfs.recover_lost_locks =
2305 [NFSv4] Attempt to recover locks that were lost due
2306 to a lease timeout on the server. Please note that
2307 doing this risks data corruption, since there are
2308 no guarantees that the file will remain unchanged
2309 after the locks are lost.
2310 If you want to enable the kernel legacy behaviour of
2311 attempting to recover these locks, then set this
2313 The default parameter value of '0' causes the kernel
2314 not to attempt recovery of lost locks.
2316 nfs4.layoutstats_timer =
2317 [NFSv4.2] Change the rate at which the kernel sends
2318 layoutstats to the pNFS metadata server.
2320 Setting this to value to 0 causes the kernel to use
2321 whatever value is the default set by the layout
2322 driver. A non-zero value sets the minimum interval
2323 in seconds between layoutstats transmissions.
2325 nfsd.nfs4_disable_idmapping=
2326 [NFSv4] When set to the default of '1', the NFSv4
2327 server will return only numeric uids and gids to
2328 clients using auth_sys, and will accept numeric uids
2329 and gids from such clients. This is intended to ease
2330 migration from NFSv2/v3.
2332 objlayoutdriver.osd_login_prog=
2333 [NFS] [OBJLAYOUT] sets the pathname to the program which
2334 is used to automatically discover and login into new
2335 osd-targets. Please see:
2336 Documentation/filesystems/pnfs.txt for more explanations
2338 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2339 when a NMI is triggered.
2340 Format: [state][,regs][,debounce][,die]
2342 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2343 Format: [panic,][nopanic,][num]
2345 0 - turn hardlockup detector in nmi_watchdog off
2346 1 - turn hardlockup detector in nmi_watchdog on
2347 When panic is specified, panic when an NMI watchdog
2348 timeout occurs (or 'nopanic' to override the opposite
2349 default). To disable both hard and soft lockup detectors,
2350 please see 'nowatchdog'.
2351 This is useful when you use a panic=... timeout and
2352 need the box quickly up again.
2354 netpoll.carrier_timeout=
2355 [NET] Specifies amount of time (in seconds) that
2356 netpoll should wait for a carrier. By default netpoll
2359 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2360 emulation library even if a 387 maths coprocessor
2364 [HW] Never suspend the console
2365 Disable suspending of consoles during suspend and
2366 hibernate operations. Once disabled, debugging
2367 messages can reach various consoles while the rest
2368 of the system is being put to sleep (ie, while
2369 debugging driver suspend/resume hooks). This may
2370 not work reliably with all consoles, but is known
2371 to work with serial and VGA consoles.
2372 To facilitate more flexible debugging, we also add
2373 console_suspend, a printk module parameter to control
2374 it. Users could use console_suspend (usually
2375 /sys/module/printk/parameters/console_suspend) to
2376 turn on/off it dynamically.
2378 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2379 caches in the slab allocator. Saves per-node memory,
2380 but will impact performance.
2384 noapic [SMP,APIC] Tells the kernel to not make use of any
2385 IOAPICs that may be present in the system.
2387 noautogroup Disable scheduler automatic task group creation.
2389 nobats [PPC] Do not use BATs for mapping kernel lowmem
2390 on "Classic" PPC cores.
2394 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2396 nodelayacct [KNL] Disable per-task delay accounting
2398 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2400 nodsp [SH] Disable hardware DSP at boot time.
2402 noefi Disable EFI runtime services support.
2407 On X86-32 available only on PAE configured kernels.
2408 noexec=on: enable non-executable mappings (default)
2409 noexec=off: disable non-executable mappings
2412 Disable SMAP (Supervisor Mode Access Prevention)
2413 even if it is supported by processor.
2416 Disable SMEP (Supervisor Mode Execution Prevention)
2417 even if it is supported by processor.
2420 This affects only 32-bit executables.
2421 noexec32=on: enable non-executable mappings (default)
2422 read doesn't imply executable mappings
2423 noexec32=off: disable non-executable mappings
2424 read implies executable mappings
2426 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2428 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2429 register save and restore. The kernel will only save
2430 legacy floating-point registers on task switch.
2432 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2434 noxsave [BUGS=X86] Disables x86 extended register state save
2435 and restore using xsave. The kernel will fallback to
2436 enabling legacy floating-point and sse state.
2438 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2439 register states. The kernel will fall back to use
2440 xsave to save the states. By using this parameter,
2441 performance of saving the states is degraded because
2442 xsave doesn't support modified optimization while
2443 xsaveopt supports it on xsaveopt enabled systems.
2445 noxsaves [X86] Disables xsaves and xrstors used in saving and
2446 restoring x86 extended register state in compacted
2447 form of xsave area. The kernel will fall back to use
2448 xsaveopt and xrstor to save and restore the states
2449 in standard form of xsave area. By using this
2450 parameter, xsave area per process might occupy more
2451 memory on xsaves enabled systems.
2453 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2454 wfi(ARM) instruction doesn't work correctly and not to
2455 use it. This is also useful when using JTAG debugger.
2457 no_file_caps Tells the kernel not to honor file capabilities. The
2458 only way then for a file to be executed with privilege
2459 is to be setuid root or executed by root.
2461 nohalt [IA-64] Tells the kernel not to use the power saving
2462 function PAL_HALT_LIGHT when idle. This increases
2463 power-consumption. On the positive side, it reduces
2464 interrupt wake-up latency, which may improve performance
2465 in certain environments such as networked servers or
2468 nohibernate [HIBERNATION] Disable hibernation and resume.
2470 nohz= [KNL] Boottime enable/disable dynamic ticks
2471 Valid arguments: on, off
2474 nohz_full= [KNL,BOOT]
2475 In kernels built with CONFIG_NO_HZ_FULL=y, set
2476 the specified list of CPUs whose tick will be stopped
2477 whenever possible. The boot CPU will be forced outside
2478 the range to maintain the timekeeping.
2479 The CPUs in this range must also be included in the
2482 noiotrap [SH] Disables trapped I/O port accesses.
2484 noirqdebug [X86-32] Disables the code which attempts to detect and
2485 disable unhandled interrupt sources.
2487 no_timer_check [X86,APIC] Disables the code which tests for
2488 broken timer IRQ sources.
2490 noisapnp [ISAPNP] Disables ISA PnP code.
2492 noinitrd [RAM] Tells the kernel not to load any configured
2495 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2497 [Deprecated - use intremap=off]
2501 nojitter [IA-64] Disables jitter checking for ITC timers.
2503 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2505 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2508 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2509 steal time is computed, but won't influence scheduler
2512 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2514 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2516 noltlbs [PPC] Do not use large page/tlb entries for kernel
2517 lowmem mapping on PPC40x.
2519 nomca [IA-64] Disable machine check abort handling
2521 nomce [X86-32] Disable Machine Check Exception
2523 nomfgpt [X86-32] Disable Multi-Function General Purpose
2524 Timer usage (for AMD Geode machines).
2526 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2527 shutdown the other cpus. Instead use the REBOOT_VECTOR
2530 nomodule Disable module load
2532 nopat [X86] Disable PAT (page attribute table extension of
2533 pagetables) support.
2535 norandmaps Don't use address space randomization. Equivalent to
2536 echo 0 > /proc/sys/kernel/randomize_va_space
2538 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2540 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2541 with UP alternatives
2543 nordrand [X86] Disable kernel use of the RDRAND and
2544 RDSEED instructions even if they are supported
2545 by the processor. RDRAND and RDSEED are still
2546 available to user space applications.
2548 noresume [SWSUSP] Disables resume and restores original swap
2551 no-scroll [VGA] Disables scrollback.
2552 This is required for the Braillex ib80-piezo Braille
2553 reader made by F.H. Papenmeier (Germany).
2557 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2559 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2560 and disable the IO APIC. legacy for "maxcpus=0".
2562 nosoftlockup [KNL] Disable the soft-lockup detector.
2564 nosync [HW,M68K] Disables sync negotiation for all devices.
2566 notsc [BUGS=X86-32] Disable Time Stamp Counter
2568 nousb [USB] Disable the USB subsystem
2570 nowatchdog [KNL] Disable both lockup detectors, i.e.
2571 soft-lockup and NMI watchdog (hard-lockup).
2575 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2577 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2578 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2579 Some features depend on CPU0. Known dependencies are:
2580 1. Resume from suspend/hibernate depends on CPU0.
2581 Suspend/hibernate will fail if CPU0 is offline and you
2582 need to online CPU0 before suspend/hibernate.
2583 2. PIC interrupts also depend on CPU0. CPU0 can't be
2584 removed if a PIC interrupt is detected.
2585 It's said poweroff/reboot may depend on CPU0 on some
2586 machines although I haven't seen such issues so far
2587 after CPU0 is offline on a few tested machines.
2588 If the dependencies are under your control, you can
2589 turn on cpu0_hotplug.
2591 nptcg= [IA-64] Override max number of concurrent global TLB
2592 purges which is reported from either PAL_VM_SUMMARY or
2595 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2596 could support. nr_cpus=n : n >= 1 limits the kernel to
2597 supporting 'n' processors. Later in runtime you can not
2598 use hotplug cpu feature to put more cpu back to online.
2599 just like you compile the kernel NR_CPUS=n
2601 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2603 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2604 Allowed values are enable and disable
2606 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2607 one of ['zone', 'node', 'default'] can be specified
2608 This can be set from sysctl after boot.
2609 See Documentation/sysctl/vm.txt for details.
2611 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2612 See Documentation/debugging-via-ohci1394.txt for more
2615 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2616 Rather than timing out after 20 ms if an EC
2617 command is not properly ACKed, override the length
2618 of the timeout. We have interrupts disabled while
2619 waiting for the ACK, so if this is set too high
2620 interrupts *may* be lost!
2622 omap_mux= [OMAP] Override bootloader pin multiplexing.
2623 Format: <mux_mode0.mode_name=value>...
2624 For example, to override I2C bus2:
2625 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2627 oprofile.timer= [HW]
2628 Use timer interrupt instead of performance counters
2630 oprofile.cpu_type= Force an oprofile cpu type
2631 This might be useful if you have an older oprofile
2632 userland or if you want common events.
2633 Format: { arch_perfmon }
2634 arch_perfmon: [X86] Force use of architectural
2635 perfmon on Intel CPUs instead of the
2636 CPU specific event set.
2637 timer: [X86] Force use of architectural NMI
2638 timer mode (see also oprofile.timer
2639 for generic hr timer mode)
2640 [s390] Force legacy basic mode sampling
2641 (report cpu_type "timer")
2643 oops=panic Always panic on oopses. Default is to just kill the
2644 process, but there is a small probability of
2645 deadlocking the machine.
2646 This will also cause panics on machine check exceptions.
2647 Useful together with panic=30 to trigger a reboot.
2650 See Documentation/sound/oss/oss-parameters.txt
2652 page_owner= [KNL] Boot-time page_owner enabling option.
2653 Storage of the information about who allocated
2654 each page is disabled in default. With this switch,
2656 on: enable the feature
2658 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2659 timeout > 0: seconds before rebooting
2660 timeout = 0: wait forever
2661 timeout < 0: reboot immediately
2664 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2667 crash_kexec_post_notifiers
2668 Run kdump after running panic-notifiers and dumping
2669 kmsg. This only for the users who doubt kdump always
2670 succeeds in any situation.
2671 Note that this also increases risks of kdump failure,
2672 because some panic notifiers can make the crashed
2673 kernel more unstable.
2675 parkbd.port= [HW] Parallel port number the keyboard adapter is
2676 connected to, default is 0.
2678 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2679 0 for XT, 1 for AT (default is AT).
2682 parport= [HW,PPT] Specify parallel ports. 0 disables.
2683 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2684 Use 'auto' to force the driver to use any
2685 IRQ/DMA settings detected (the default is to
2686 ignore detected IRQ/DMA settings because of
2687 possible conflicts). You can specify the base
2688 address, IRQ, and DMA settings; IRQ and DMA
2689 should be numbers, or 'auto' (for using detected
2690 settings on that particular port), or 'nofifo'
2691 (to avoid using a FIFO even if it is detected).
2692 Parallel ports are assigned in the order they
2693 are specified on the command line, starting
2696 parport_init_mode= [HW,PPT]
2697 Configure VIA parallel port to operate in
2698 a specific mode. This is necessary on Pegasos
2699 computer where firmware has no options for setting
2700 up parallel port mode and sets it to spp.
2701 Currently this function knows 686a and 8231 chips.
2702 Format: [spp|ps2|epp|ecp|ecpepp]
2705 Halt all CPUs after the first oops has been printed for
2706 the specified number of seconds. This is to be used if
2707 your oopses keep scrolling off the screen.
2712 See header of drivers/block/paride/pcd.c.
2713 See also Documentation/blockdev/paride.txt.
2715 pci=option[,option...] [PCI] various PCI subsystem options:
2716 earlydump [X86] dump PCI config space before the kernel
2718 off [X86] don't probe for the PCI bus
2719 bios [X86-32] force use of PCI BIOS, don't access
2720 the hardware directly. Use this if your machine
2721 has a non-standard PCI host bridge.
2722 nobios [X86-32] disallow use of PCI BIOS, only direct
2723 hardware access methods are allowed. Use this
2724 if you experience crashes upon bootup and you
2725 suspect they are caused by the BIOS.
2726 conf1 [X86] Force use of PCI Configuration
2728 conf2 [X86] Force use of PCI Configuration
2730 noaer [PCIE] If the PCIEAER kernel config parameter is
2731 enabled, this kernel boot option can be used to
2732 disable the use of PCIE advanced error reporting.
2733 nodomains [PCI] Disable support for multiple PCI
2734 root domains (aka PCI segments, in ACPI-speak).
2735 nommconf [X86] Disable use of MMCONFIG for PCI
2737 check_enable_amd_mmconf [X86] check for and enable
2738 properly configured MMIO access to PCI
2739 config space on AMD family 10h CPU
2740 nomsi [MSI] If the PCI_MSI kernel config parameter is
2741 enabled, this kernel boot option can be used to
2742 disable the use of MSI interrupts system-wide.
2743 noioapicquirk [APIC] Disable all boot interrupt quirks.
2744 Safety option to keep boot IRQs enabled. This
2745 should never be necessary.
2746 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2747 primary IO-APIC for bridges that cannot disable
2748 boot IRQs. This fixes a source of spurious IRQs
2749 when the system masks IRQs.
2750 noioapicreroute [APIC] Disable workaround that uses the
2751 boot IRQ equivalent of an IRQ that connects to
2752 a chipset where boot IRQs cannot be disabled.
2753 The opposite of ioapicreroute.
2754 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2755 routing table. These calls are known to be buggy
2756 on several machines and they hang the machine
2757 when used, but on other computers it's the only
2758 way to get the interrupt routing table. Try
2759 this option if the kernel is unable to allocate
2760 IRQs or discover secondary PCI buses on your
2762 rom [X86] Assign address space to expansion ROMs.
2763 Use with caution as certain devices share
2764 address decoders between ROMs and other
2766 norom [X86] Do not assign address space to
2767 expansion ROMs that do not already have
2768 BIOS assigned address ranges.
2769 nobar [X86] Do not assign address space to the
2770 BARs that weren't assigned by the BIOS.
2771 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2772 assigned automatically to PCI devices. You can
2773 make the kernel exclude IRQs of your ISA cards
2775 pirqaddr=0xAAAAA [X86] Specify the physical address
2776 of the PIRQ table (normally generated
2777 by the BIOS) if it is outside the
2778 F0000h-100000h range.
2779 lastbus=N [X86] Scan all buses thru bus #N. Can be
2780 useful if the kernel is unable to find your
2781 secondary buses and you want to tell it
2782 explicitly which ones they are.
2783 assign-busses [X86] Always assign all PCI bus
2784 numbers ourselves, overriding
2785 whatever the firmware may have done.
2786 usepirqmask [X86] Honor the possible IRQ mask stored
2787 in the BIOS $PIR table. This is needed on
2788 some systems with broken BIOSes, notably
2789 some HP Pavilion N5400 and Omnibook XE3
2790 notebooks. This will have no effect if ACPI
2791 IRQ routing is enabled.
2792 noacpi [X86] Do not use ACPI for IRQ routing
2793 or for PCI scanning.
2794 use_crs [X86] Use PCI host bridge window information
2795 from ACPI. On BIOSes from 2008 or later, this
2796 is enabled by default. If you need to use this,
2797 please report a bug.
2798 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2799 If you need to use this, please report a bug.
2800 routeirq Do IRQ routing for all PCI devices.
2801 This is normally done in pci_enable_device(),
2802 so this option is a temporary workaround
2803 for broken drivers that don't call it.
2804 skip_isa_align [X86] do not align io start addr, so can
2805 handle more pci cards
2806 firmware [ARM] Do not re-enumerate the bus but instead
2807 just use the configuration from the
2808 bootloader. This is currently used on
2809 IXP2000 systems where the bus has to be
2810 configured a certain way for adjunct CPUs.
2811 noearly [X86] Don't do any early type 1 scanning.
2812 This might help on some broken boards which
2813 machine check when some devices' config space
2814 is read. But various workarounds are disabled
2815 and some IOMMU drivers will not work.
2816 bfsort Sort PCI devices into breadth-first order.
2817 This sorting is done to get a device
2818 order compatible with older (<= 2.4) kernels.
2819 nobfsort Don't sort PCI devices into breadth-first order.
2820 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2821 tuning and use the BIOS-configured MPS defaults.
2822 pcie_bus_safe Set every device's MPS to the largest value
2823 supported by all devices below the root complex.
2824 pcie_bus_perf Set device MPS to the largest allowable MPS
2825 based on its parent bus. Also set MRRS (Max
2826 Read Request Size) to the largest supported
2827 value (no larger than the MPS that the device
2828 or bus can support) for best performance.
2829 pcie_bus_peer2peer Set every device's MPS to 128B, which
2830 every device is guaranteed to support. This
2831 configuration allows peer-to-peer DMA between
2832 any pair of devices, possibly at the cost of
2833 reduced performance. This also guarantees
2834 that hot-added devices will work.
2835 cbiosize=nn[KMG] The fixed amount of bus space which is
2836 reserved for the CardBus bridge's IO window.
2837 The default value is 256 bytes.
2838 cbmemsize=nn[KMG] The fixed amount of bus space which is
2839 reserved for the CardBus bridge's memory
2840 window. The default value is 64 megabytes.
2843 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2844 Specifies alignment and device to reassign
2845 aligned memory resources.
2846 If <order of align> is not specified,
2847 PAGE_SIZE is used as alignment.
2848 PCI-PCI bridge can be specified, if resource
2849 windows need to be expanded.
2850 ecrc= Enable/disable PCIe ECRC (transaction layer
2851 end-to-end CRC checking).
2852 bios: Use BIOS/firmware settings. This is the
2856 hpiosize=nn[KMG] The fixed amount of bus space which is
2857 reserved for hotplug bridge's IO window.
2858 Default size is 256 bytes.
2859 hpmemsize=nn[KMG] The fixed amount of bus space which is
2860 reserved for hotplug bridge's memory window.
2861 Default size is 2 megabytes.
2862 realloc= Enable/disable reallocating PCI bridge resources
2863 if allocations done by BIOS are too small to
2864 accommodate resources required by all child
2866 off: Turn realloc off
2868 realloc same as realloc=on
2869 noari do not use PCIe ARI.
2870 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2871 only look for one device below a PCIe downstream
2874 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2877 force Enable ASPM even on devices that claim not to support it.
2878 WARNING: Forcing ASPM on may cause system lockups.
2880 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2881 nomsi Do not use MSI for PCI Express Native Hotplug (this
2882 makes all PCIe ports use INTx for hotplug services).
2884 pcie_ports= [PCIE] PCIe ports handling:
2885 auto Ask the BIOS whether or not to use native PCIe services
2886 associated with PCIe ports (PME, hot-plug, AER). Use
2887 them only if that is allowed by the BIOS.
2888 native Use native PCIe services associated with PCIe ports
2890 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2893 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2894 nomsi Do not use MSI for native PCIe PME signaling (this makes
2895 all PCIe root ports use INTx for all services).
2897 pcmv= [HW,PCMCIA] BadgePAD 4
2901 Keep all power-domains already enabled by bootloader on,
2902 even if no driver has claimed them. This is useful
2903 for debug and development, but should not be
2904 needed on a platform with proper driver support.
2907 See Documentation/blockdev/paride.txt.
2909 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2912 See arch/parisc/kernel/pdc_chassis.c
2914 percpu_alloc= Select which percpu first chunk allocator to use.
2915 Currently supported values are "embed" and "page".
2916 Archs may support subset or none of the selections.
2917 See comments in mm/percpu.c for details on each
2918 allocator. This parameter is primarily for debugging
2919 and performance comparison.
2922 See Documentation/blockdev/paride.txt.
2925 See Documentation/blockdev/paride.txt.
2927 pirq= [SMP,APIC] Manual mp-table setup
2928 See Documentation/x86/i386/IO-APIC.txt.
2930 plip= [PPT,NET] Parallel port network link
2931 Format: { parport<nr> | timid | 0 }
2932 See also Documentation/parport.txt.
2934 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2935 Override pmtimer IOPort with a hex value.
2939 Enable PNP debug messages (depends on the
2940 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2941 via /sys/module/pnp/parameters/debug. We always show
2942 current resource usage; turning this on also shows
2943 possible settings and some assignment information.
2949 { on | off | curr | res | no-curr | no-res }
2952 [ISAPNP] Exclude IRQs for the autoconfiguration
2955 [ISAPNP] Exclude DMAs for the autoconfiguration
2957 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2958 Ranges are in pairs (I/O port base and size).
2961 [ISAPNP] Exclude memory regions for the
2963 Ranges are in pairs (memory base and size).
2965 ports= [IP_VS_FTP] IPVS ftp helper module
2967 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2969 Format: <port>,<port>....
2971 print-fatal-signals=
2972 [KNL] debug: print fatal signals
2974 If enabled, warn about various signal handling
2975 related application anomalies: too many signals,
2976 too many POSIX.1 timers, fatal signals causing a
2979 If you hit the warning due to signal overflow,
2980 you might want to try "ulimit -i unlimited".
2984 printk.always_kmsg_dump=
2985 Trigger kmsg_dump for cases other than kernel oops or
2987 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2990 printk.time= Show timing data prefixed to each printk message line
2991 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2993 processor.max_cstate= [HW,ACPI]
2994 Limit processor to maximum C-state
2995 max_cstate=9 overrides any DMI blacklist limit.
2997 processor.nocst [HW,ACPI]
2998 Ignore the _CST method to determine C-states,
2999 instead using the legacy FADT method
3001 profile= [KNL] Enable kernel profiling via /proc/profile
3002 Format: [schedule,]<number>
3003 Param: "schedule" - profile schedule points.
3004 Param: <number> - step/bucket size as a power of 2 for
3005 statistical time based profiling.
3006 Param: "sleep" - profile D-state sleeping (millisecs).
3007 Requires CONFIG_SCHEDSTATS
3008 Param: "kvm" - profile VM exits.
3010 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3012 See Documentation/blockdev/ramdisk.txt.
3014 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3015 probe for; one of (bare|imps|exps|lifebook|any).
3016 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3018 psmouse.resetafter= [HW,MOUSE]
3019 Try to reset the device after so many bad packets
3022 [HW,MOUSE] Set desired mouse resolution, in dpi.
3023 psmouse.smartscroll=
3024 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3025 0 = disabled, 1 = enabled (default).
3027 pstore.backend= Specify the name of the pstore backend to use
3030 See Documentation/blockdev/paride.txt.
3033 [KNL] Number of legacy pty's. Overwrites compiled-in
3036 quiet [KNL] Disable most log messages
3041 See Documentation/md.txt.
3043 ramdisk_blocksize= [RAM]
3044 See Documentation/blockdev/ramdisk.txt.
3046 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3047 See Documentation/blockdev/ramdisk.txt.
3050 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3051 the specified list of CPUs to be no-callback CPUs.
3052 Invocation of these CPUs' RCU callbacks will
3053 be offloaded to "rcuox/N" kthreads created for
3054 that purpose, where "x" is "b" for RCU-bh, "p"
3055 for RCU-preempt, and "s" for RCU-sched, and "N"
3056 is the CPU number. This reduces OS jitter on the
3057 offloaded CPUs, which can be useful for HPC and
3058 real-time workloads. It can also improve energy
3059 efficiency for asymmetric multiprocessors.
3062 Rather than requiring that offloaded CPUs
3063 (specified by rcu_nocbs= above) explicitly
3064 awaken the corresponding "rcuoN" kthreads,
3065 make these kthreads poll for callbacks.
3066 This improves the real-time response for the
3067 offloaded CPUs by relieving them of the need to
3068 wake up the corresponding kthread, but degrades
3069 energy efficiency by requiring that the kthreads
3070 periodically wake up to do the polling.
3072 rcutree.blimit= [KNL]
3073 Set maximum number of finished RCU callbacks to
3074 process in one batch.
3076 rcutree.dump_tree= [KNL]
3077 Dump the structure of the rcu_node combining tree
3078 out at early boot. This is used for diagnostic
3079 purposes, to verify correct tree setup.
3081 rcutree.gp_cleanup_delay= [KNL]
3082 Set the number of jiffies to delay each step of
3083 RCU grace-period cleanup. This only has effect
3084 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3086 rcutree.gp_init_delay= [KNL]
3087 Set the number of jiffies to delay each step of
3088 RCU grace-period initialization. This only has
3089 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3092 rcutree.gp_preinit_delay= [KNL]
3093 Set the number of jiffies to delay each step of
3094 RCU grace-period pre-initialization, that is,
3095 the propagation of recent CPU-hotplug changes up
3096 the rcu_node combining tree. This only has effect
3097 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3099 rcutree.rcu_fanout_exact= [KNL]
3100 Disable autobalancing of the rcu_node combining
3101 tree. This is used by rcutorture, and might
3102 possibly be useful for architectures having high
3103 cache-to-cache transfer latencies.
3105 rcutree.rcu_fanout_leaf= [KNL]
3106 Change the number of CPUs assigned to each
3107 leaf rcu_node structure. Useful for very
3108 large systems, which will choose the value 64,
3109 and for NUMA systems with large remote-access
3110 latencies, which will choose a value aligned
3111 with the appropriate hardware boundaries.
3113 rcutree.jiffies_till_sched_qs= [KNL]
3114 Set required age in jiffies for a
3115 given grace period before RCU starts
3116 soliciting quiescent-state help from
3117 rcu_note_context_switch().
3119 rcutree.jiffies_till_first_fqs= [KNL]
3120 Set delay from grace-period initialization to
3121 first attempt to force quiescent states.
3122 Units are jiffies, minimum value is zero,
3123 and maximum value is HZ.
3125 rcutree.jiffies_till_next_fqs= [KNL]
3126 Set delay between subsequent attempts to force
3127 quiescent states. Units are jiffies, minimum
3128 value is one, and maximum value is HZ.
3130 rcutree.kthread_prio= [KNL,BOOT]
3131 Set the SCHED_FIFO priority of the RCU per-CPU
3132 kthreads (rcuc/N). This value is also used for
3133 the priority of the RCU boost threads (rcub/N)
3134 and for the RCU grace-period kthreads (rcu_bh,
3135 rcu_preempt, and rcu_sched). If RCU_BOOST is
3136 set, valid values are 1-99 and the default is 1
3137 (the least-favored priority). Otherwise, when
3138 RCU_BOOST is not set, valid values are 0-99 and
3139 the default is zero (non-realtime operation).
3141 rcutree.rcu_nocb_leader_stride= [KNL]
3142 Set the number of NOCB kthread groups, which
3143 defaults to the square root of the number of
3144 CPUs. Larger numbers reduces the wakeup overhead
3145 on the per-CPU grace-period kthreads, but increases
3146 that same overhead on each group's leader.
3148 rcutree.qhimark= [KNL]
3149 Set threshold of queued RCU callbacks beyond which
3150 batch limiting is disabled.
3152 rcutree.qlowmark= [KNL]
3153 Set threshold of queued RCU callbacks below which
3154 batch limiting is re-enabled.
3156 rcutree.rcu_idle_gp_delay= [KNL]
3157 Set wakeup interval for idle CPUs that have
3158 RCU callbacks (RCU_FAST_NO_HZ=y).
3160 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3161 Set wakeup interval for idle CPUs that have
3162 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3163 Lazy RCU callbacks are those which RCU can
3164 prove do nothing more than free memory.
3166 rcutorture.cbflood_inter_holdoff= [KNL]
3167 Set holdoff time (jiffies) between successive
3168 callback-flood tests.
3170 rcutorture.cbflood_intra_holdoff= [KNL]
3171 Set holdoff time (jiffies) between successive
3172 bursts of callbacks within a given callback-flood
3175 rcutorture.cbflood_n_burst= [KNL]
3176 Set the number of bursts making up a given
3177 callback-flood test. Set this to zero to
3178 disable callback-flood testing.
3180 rcutorture.cbflood_n_per_burst= [KNL]
3181 Set the number of callbacks to be registered
3182 in a given burst of a callback-flood test.
3184 rcutorture.fqs_duration= [KNL]
3185 Set duration of force_quiescent_state bursts
3188 rcutorture.fqs_holdoff= [KNL]
3189 Set holdoff time within force_quiescent_state bursts
3192 rcutorture.fqs_stutter= [KNL]
3193 Set wait time between force_quiescent_state bursts
3196 rcutorture.gp_cond= [KNL]
3197 Use conditional/asynchronous update-side
3198 primitives, if available.
3200 rcutorture.gp_exp= [KNL]
3201 Use expedited update-side primitives, if available.
3203 rcutorture.gp_normal= [KNL]
3204 Use normal (non-expedited) asynchronous
3205 update-side primitives, if available.
3207 rcutorture.gp_sync= [KNL]
3208 Use normal (non-expedited) synchronous
3209 update-side primitives, if available. If all
3210 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3211 rcutorture.gp_normal=, and rcutorture.gp_sync=
3212 are zero, rcutorture acts as if is interpreted
3213 they are all non-zero.
3215 rcutorture.n_barrier_cbs= [KNL]
3216 Set callbacks/threads for rcu_barrier() testing.
3218 rcutorture.nfakewriters= [KNL]
3219 Set number of concurrent RCU writers. These just
3220 stress RCU, they don't participate in the actual
3221 test, hence the "fake".
3223 rcutorture.nreaders= [KNL]
3224 Set number of RCU readers. The value -1 selects
3225 N-1, where N is the number of CPUs. A value
3226 "n" less than -1 selects N-n-2, where N is again
3227 the number of CPUs. For example, -2 selects N
3228 (the number of CPUs), -3 selects N+1, and so on.
3230 rcutorture.object_debug= [KNL]
3231 Enable debug-object double-call_rcu() testing.
3233 rcutorture.onoff_holdoff= [KNL]
3234 Set time (s) after boot for CPU-hotplug testing.
3236 rcutorture.onoff_interval= [KNL]
3237 Set time (s) between CPU-hotplug operations, or
3238 zero to disable CPU-hotplug testing.
3240 rcutorture.shuffle_interval= [KNL]
3241 Set task-shuffle interval (s). Shuffling tasks
3242 allows some CPUs to go into dyntick-idle mode
3243 during the rcutorture test.
3245 rcutorture.shutdown_secs= [KNL]
3246 Set time (s) after boot system shutdown. This
3247 is useful for hands-off automated testing.
3249 rcutorture.stall_cpu= [KNL]
3250 Duration of CPU stall (s) to test RCU CPU stall
3251 warnings, zero to disable.
3253 rcutorture.stall_cpu_holdoff= [KNL]
3254 Time to wait (s) after boot before inducing stall.
3256 rcutorture.stat_interval= [KNL]
3257 Time (s) between statistics printk()s.
3259 rcutorture.stutter= [KNL]
3260 Time (s) to stutter testing, for example, specifying
3261 five seconds causes the test to run for five seconds,
3262 wait for five seconds, and so on. This tests RCU's
3263 ability to transition abruptly to and from idle.
3265 rcutorture.test_boost= [KNL]
3266 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3267 "Maybe" means test if the RCU implementation
3268 under test support RCU priority boosting.
3270 rcutorture.test_boost_duration= [KNL]
3271 Duration (s) of each individual boost test.
3273 rcutorture.test_boost_interval= [KNL]
3274 Interval (s) between each boost test.
3276 rcutorture.test_no_idle_hz= [KNL]
3277 Test RCU's dyntick-idle handling. See also the
3278 rcutorture.shuffle_interval parameter.
3280 rcutorture.torture_runnable= [BOOT]
3281 Start rcutorture running at boot time.
3283 rcutorture.torture_type= [KNL]
3284 Specify the RCU implementation to test.
3286 rcutorture.verbose= [KNL]
3287 Enable additional printk() statements.
3289 rcupdate.rcu_expedited= [KNL]
3290 Use expedited grace-period primitives, for
3291 example, synchronize_rcu_expedited() instead
3292 of synchronize_rcu(). This reduces latency,
3293 but can increase CPU utilization, degrade
3294 real-time latency, and degrade energy efficiency.
3296 rcupdate.rcu_cpu_stall_suppress= [KNL]
3297 Suppress RCU CPU stall warning messages.
3299 rcupdate.rcu_cpu_stall_timeout= [KNL]
3300 Set timeout for RCU CPU stall warning messages.
3302 rcupdate.rcu_task_stall_timeout= [KNL]
3303 Set timeout in jiffies for RCU task stall warning
3304 messages. Disable with a value less than or equal
3307 rcupdate.rcu_self_test= [KNL]
3308 Run the RCU early boot self tests
3310 rcupdate.rcu_self_test_bh= [KNL]
3311 Run the RCU bh early boot self tests
3313 rcupdate.rcu_self_test_sched= [KNL]
3314 Run the RCU sched early boot self tests
3318 Run specified binary instead of /init from the ramdisk,
3319 used for early userspace startup. See initrd.
3322 Format (x86 or x86_64):
3323 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3325 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3327 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3328 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3329 reboot_force is either force or not specified,
3330 reboot_cpu is s[mp]#### with #### being the processor
3331 to be used for rebooting.
3334 [KNL, SMP] Set scheduler's default relax_domain_level.
3335 See Documentation/cgroups/cpusets.txt.
3337 relative_sleep_states=
3338 [SUSPEND] Use sleep state labeling where the deepest
3339 state available other than hibernation is always "mem".
3340 Format: { "0" | "1" }
3341 0 -- Traditional sleep state labels.
3342 1 -- Relative sleep state labels.
3344 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3346 reservetop= [X86-32]
3348 Reserves a hole at the top of the kernel virtual
3353 Set the amount of memory to reserve for BIOS at
3354 the bottom of the address space.
3356 reset_devices [KNL] Force drivers to reset the underlying device
3357 during initialization.
3360 Specify the partition device for software suspend
3362 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3364 resume_offset= [SWSUSP]
3365 Specify the offset from the beginning of the partition
3366 given by "resume=" at which the swap header is located,
3367 in <PAGE_SIZE> units (needed only for swap files).
3368 See Documentation/power/swsusp-and-swap-files.txt
3370 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3371 read the resume files
3373 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3374 Useful for devices that are detected asynchronously
3375 (e.g. USB and MMC devices).
3377 hibernate= [HIBERNATION]
3378 noresume Don't check if there's a hibernation image
3379 present during boot.
3380 nocompress Don't compress/decompress hibernation images.
3381 no Disable hibernation and resume.
3383 retain_initrd [RAM] Keep initrd memory after extraction
3385 rfkill.default_state=
3386 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3387 etc. communication is blocked by default.
3390 rfkill.master_switch_mode=
3391 0 The "airplane mode" button does nothing.
3392 1 The "airplane mode" button toggles between everything
3393 blocked and the previous configuration.
3394 2 The "airplane mode" button toggles between everything
3395 blocked and everything unblocked.
3397 rhash_entries= [KNL,NET]
3398 Set number of hash buckets for route cache
3400 ro [KNL] Mount root device read-only on boot
3402 root= [KNL] Root filesystem
3403 See name_to_dev_t comment in init/do_mounts.c.
3405 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3406 mount the root filesystem
3408 rootflags= [KNL] Set root filesystem mount option string
3410 rootfstype= [KNL] Set root filesystem type
3412 rootwait [KNL] Wait (indefinitely) for root device to show up.
3413 Useful for devices that are detected asynchronously
3414 (e.g. USB and MMC devices).
3416 rproc_mem=nn[KMG][@address]
3417 [KNL,ARM,CMA] Remoteproc physical memory block.
3418 Memory area to be used by remote processor image,
3421 rw [KNL] Mount root device read-write on boot
3423 S [KNL] Run init in single mode
3425 s390_iommu= [HW,S390]
3426 Set s390 IOTLB flushing mode
3428 With strict flushing every unmap operation will result in
3429 an IOTLB flush. Default is lazy flushing before reuse,
3433 See drivers/net/irda/sa1100_ir.c.
3435 sbni= [NET] Granch SBNI12 leased line adapter
3437 sched_debug [KNL] Enables verbose scheduler debug messages.
3439 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3440 xtime_lock contention on larger systems, and/or RCU lock
3441 contention on all systems with CONFIG_MAXSMP set.
3442 Format: { "0" | "1" }
3443 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3445 Note: increases power consumption, thus should only be
3446 enabled if running jitter sensitive (HPC/RT) workloads.
3448 security= [SECURITY] Choose a security module to enable at boot.
3449 If this boot parameter is not specified, only the first
3450 security module asking for security registration will be
3451 loaded. An invalid security module name will be treated
3452 as if no module has been chosen.
3454 selinux= [SELINUX] Disable or enable SELinux at boot time.
3455 Format: { "0" | "1" }
3456 See security/selinux/Kconfig help text.
3459 Default value is set via kernel config option.
3460 If enabled at boot time, /selinux/disable can be used
3461 later to disable prior to initial policy load.
3463 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3464 Format: { "0" | "1" }
3465 See security/apparmor/Kconfig help text
3468 Default value is set via kernel config option.
3470 serialnumber [BUGS=X86-32]
3473 Maximal number of shapers.
3475 show_msr= [x86] show boot-time MSR settings
3476 Format: { <integer> }
3477 Show boot-time (BIOS-initialized) MSR settings.
3478 The parameter means the number of CPUs to show,
3479 for example 1 means boot CPU only.
3487 Disable merging of slabs with similar size. May be
3488 necessary if there is some reason to distinguish
3489 allocs to different slabs. Debug options disable
3490 merging on their own.
3491 For more information see Documentation/vm/slub.txt.
3493 slab_max_order= [MM, SLAB]
3494 Determines the maximum allowed order for slabs.
3495 A high setting may cause OOMs due to memory
3496 fragmentation. Defaults to 1 for systems with
3497 more than 32MB of RAM, 0 otherwise.
3499 slub_debug[=options[,slabs]] [MM, SLUB]
3500 Enabling slub_debug allows one to determine the
3501 culprit if slab objects become corrupted. Enabling
3502 slub_debug can create guard zones around objects and
3503 may poison objects when not in use. Also tracks the
3504 last alloc / free. For more information see
3505 Documentation/vm/slub.txt.
3507 slub_max_order= [MM, SLUB]
3508 Determines the maximum allowed order for slabs.
3509 A high setting may cause OOMs due to memory
3510 fragmentation. For more information see
3511 Documentation/vm/slub.txt.
3513 slub_min_objects= [MM, SLUB]
3514 The minimum number of objects per slab. SLUB will
3515 increase the slab order up to slub_max_order to
3516 generate a sufficiently large slab able to contain
3517 the number of objects indicated. The higher the number
3518 of objects the smaller the overhead of tracking slabs
3519 and the less frequently locks need to be acquired.
3520 For more information see Documentation/vm/slub.txt.
3522 slub_min_order= [MM, SLUB]
3523 Determines the minimum page order for slabs. Must be
3524 lower than slub_max_order.
3525 For more information see Documentation/vm/slub.txt.
3527 slub_nomerge [MM, SLUB]
3528 Same with slab_nomerge. This is supported for legacy.
3529 See slab_nomerge for more information.
3532 Format: <io1>[,<io2>[,...,<io8>]]
3534 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3535 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3536 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3537 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3538 smsc-ircc2.ircc_irq= [HW] IRQ line
3539 smsc-ircc2.ircc_dma= [HW] DMA channel
3540 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3541 0: Toshiba Satellite 1800 (GP data pin select)
3542 1: Fast pin select (default)
3546 [KNL] Should the soft-lockup detector generate panics.
3549 softlockup_all_cpu_backtrace=
3550 [KNL] Should the soft-lockup detector generate
3551 backtraces on all cpus.
3554 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3555 See Documentation/laptops/sonypi.txt
3557 spia_io_base= [HW,MTD]
3563 Enabled the stack tracer on boot up.
3565 stacktrace_filter=[function-list]
3566 [FTRACE] Limit the functions that the stack tracer
3567 will trace at boot up. function-list is a comma separated
3568 list of functions. This list can be changed at run
3569 time by the stack_trace_filter file in the debugfs
3570 tracing directory. Note, this enables stack tracing
3571 and the stacktrace above is not needed.
3575 Set the STI (builtin display/keyboard on the HP-PARISC
3576 machines) console (graphic card) which should be used
3577 as the initial boot-console.
3578 See also comment in drivers/video/console/sticore.c.
3581 See comment in drivers/video/console/sticore.c.
3584 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3586 sunrpc.min_resvport=
3587 sunrpc.max_resvport=
3589 SunRPC servers often require that client requests
3590 originate from a privileged port (i.e. a port in the
3591 range 0 < portnr < 1024).
3592 An administrator who wishes to reserve some of these
3593 ports for other uses may adjust the range that the
3594 kernel's sunrpc client considers to be privileged
3595 using these two parameters to set the minimum and
3596 maximum port values.
3600 Control how the NFS server code allocates CPUs to
3601 service thread pools. Depending on how many NICs
3602 you have and where their interrupts are bound, this
3603 option will affect which CPUs will do NFS serving.
3604 Note: this parameter cannot be changed while the
3605 NFS server is running.
3607 auto the server chooses an appropriate mode
3608 automatically using heuristics
3609 global a single global pool contains all CPUs
3610 percpu one pool for each CPU
3611 pernode one pool for each NUMA node (equivalent
3612 to global on non-NUMA machines)
3614 sunrpc.tcp_slot_table_entries=
3615 sunrpc.udp_slot_table_entries=
3617 Sets the upper limit on the number of simultaneous
3618 RPC calls that can be sent from the client to a
3619 server. Increasing these values may allow you to
3620 improve throughput, but will also increase the
3621 amount of memory reserved for use by the client.
3623 suspend.pm_test_delay=
3625 Sets the number of seconds to remain in a suspend test
3626 mode before resuming the system (see
3627 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3628 is set. Default value is 5.
3631 [KNL] Enable accounting of swap in memory resource
3632 controller if no parameter or 1 is given or disable
3633 it if 0 is given (See Documentation/cgroups/memory.txt)
3635 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3636 Format: { <int> | force }
3637 <int> -- Number of I/O TLB slabs
3638 force -- force using of bounce buffers even if they
3639 wouldn't be automatically used by the kernel
3643 sysfs.deprecated=0|1 [KNL]
3644 Enable/disable old style sysfs layout for old udev
3645 on older distributions. When this option is enabled
3646 very new udev will not work anymore. When this option
3647 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3648 in older udev will not work anymore.
3649 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3650 the kernel configuration.
3652 sysrq_always_enabled
3654 Ignore sysrq setting - this boot parameter will
3655 neutralize any effect of /proc/sys/kernel/sysrq.
3656 Useful for debugging.
3658 tcpmhash_entries= [KNL,NET]
3659 Set the number of tcp_metrics_hash slots.
3660 Default value is 8192 or 16384 depending on total
3661 ram pages. This is used to specify the TCP metrics
3662 cache size. See Documentation/networking/ip-sysctl.txt
3663 "tcp_no_metrics_save" section for more details.
3667 test_suspend= [SUSPEND][,N]
3668 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3669 standby suspend) or "freeze" (for suspend type freeze)
3670 as the system sleep state during system startup with
3671 the optional capability to repeat N number of times.
3672 The system is woken from this state using a
3673 wakeup-capable RTC alarm.
3675 thash_entries= [KNL,NET]
3676 Set number of hash buckets for TCP connection
3678 thermal.act= [HW,ACPI]
3679 -1: disable all active trip points in all thermal zones
3680 <degrees C>: override all lowest active trip points
3682 thermal.crt= [HW,ACPI]
3683 -1: disable all critical trip points in all thermal zones
3684 <degrees C>: override all critical trip points
3686 thermal.nocrt= [HW,ACPI]
3687 Set to disable actions on ACPI thermal zone
3688 critical and hot trip points.
3690 thermal.off= [HW,ACPI]
3691 1: disable ACPI thermal control
3693 thermal.psv= [HW,ACPI]
3694 -1: disable all passive trip points
3695 <degrees C>: override all passive trip points to this
3698 thermal.tzp= [HW,ACPI]
3699 Specify global default ACPI thermal zone polling rate
3700 <deci-seconds>: poll all this frequency
3701 0: no polling (default)
3704 Force threading of all interrupt handlers except those
3705 marked explicitly IRQF_NO_THREAD.
3708 Enable the Transcendent memory driver if built-in.
3710 tmem.cleancache=0|1 [KNL, XEN]
3711 Default is on (1). Disable the usage of the cleancache
3712 API to send anonymous pages to the hypervisor.
3714 tmem.frontswap=0|1 [KNL, XEN]
3715 Default is on (1). Disable the usage of the frontswap
3716 API to send swap pages to the hypervisor. If disabled
3717 the selfballooning and selfshrinking are force disabled.
3719 tmem.selfballooning=0|1 [KNL, XEN]
3720 Default is on (1). Disable the driving of swap pages
3723 tmem.selfshrinking=0|1 [KNL, XEN]
3724 Default is on (1). Partial swapoff that immediately
3725 transfers pages from Xen hypervisor back to the
3726 kernel based on different criteria.
3730 Specify if the kernel should make use of the cpu
3731 topology information if the hardware supports this.
3732 The scheduler will make use of this information and
3733 e.g. base its process migration decisions on it.
3736 topology_updates= [KNL, PPC, NUMA]
3738 Specify if the kernel should ignore (off)
3739 topology updates sent by the hypervisor to this
3744 tpm_suspend_pcr=[HW,TPM]
3745 Format: integer pcr id
3746 Specify that at suspend time, the tpm driver
3747 should extend the specified pcr with zeros,
3748 as a workaround for some chips which fail to
3749 flush the last written pcr on TPM_SaveState.
3750 This will guarantee that all the other pcrs
3753 trace_buf_size=nn[KMG]
3754 [FTRACE] will set tracing buffer size on each cpu.
3756 trace_event=[event-list]
3757 [FTRACE] Set and start specified trace events in order
3758 to facilitate early boot debugging.
3759 See also Documentation/trace/events.txt
3761 trace_options=[option-list]
3762 [FTRACE] Enable or disable tracer options at boot.
3763 The option-list is a comma delimited list of options
3764 that can be enabled or disabled just as if you were
3765 to echo the option name into
3767 /sys/kernel/debug/tracing/trace_options
3769 For example, to enable stacktrace option (to dump the
3770 stack trace of each event), add to the command line:
3772 trace_options=stacktrace
3774 See also Documentation/trace/ftrace.txt "trace options"
3778 Have the tracepoints sent to printk as well as the
3779 tracing ring buffer. This is useful for early boot up
3780 where the system hangs or reboots and does not give the
3781 option for reading the tracing buffer or performing a
3782 ftrace_dump_on_oops.
3784 To turn off having tracepoints sent to printk,
3785 echo 0 > /proc/sys/kernel/tracepoint_printk
3786 Note, echoing 1 into this file without the
3787 tracepoint_printk kernel cmdline option has no effect.
3791 Having tracepoints sent to printk() and activating high
3792 frequency tracepoints such as irq or sched, can cause
3793 the system to live lock.
3796 [FTRACE] enable this option to disable tracing when a
3797 warning is hit. This turns off "tracing_on". Tracing can
3798 be enabled again by echoing '1' into the "tracing_on"
3799 file located in /sys/kernel/debug/tracing/
3801 This option is useful, as it disables the trace before
3802 the WARNING dump is called, which prevents the trace to
3803 be filled with content caused by the warning output.
3805 This option can also be set at run time via the sysctl
3806 option: kernel/traceoff_on_warning
3808 transparent_hugepage=
3810 Format: [always|madvise|never]
3811 Can be used to control the default behavior of the system
3812 with respect to transparent hugepages.
3813 See Documentation/vm/transhuge.txt for more details.
3815 tsc= Disable clocksource stability checks for TSC.
3817 [x86] reliable: mark tsc clocksource as reliable, this
3818 disables clocksource verification at runtime, as well
3819 as the stability checks done at bootup. Used to enable
3820 high-resolution timer mode on older hardware, and in
3821 virtualized environment.
3822 [x86] noirqtime: Do not use TSC to do irq accounting.
3823 Used to run time disable IRQ_TIME_ACCOUNTING on any
3824 platforms where RDTSC is slow and this accounting
3827 turbografx.map[2|3]= [HW,JOY]
3828 TurboGraFX parallel port interface
3830 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3831 See also Documentation/input/joystick-parport.txt
3833 udbg-immortal [PPC] When debugging early kernel crashes that
3834 happen after console_init() and before a proper
3835 console driver takes over, this boot options might
3836 help "seeing" what's going on.
3838 uhash_entries= [KNL,NET]
3839 Set number of hash buckets for UDP/UDP-Lite connections
3842 [USB] Ignore overcurrent events (default N).
3843 Some badly-designed motherboards generate lots of
3844 bogus events, for ports that aren't wired to
3845 anything. Set this parameter to avoid log spamming.
3846 Note that genuine overcurrent events won't be
3850 [X86] Cause panic on unknown NMI.
3852 usbcore.authorized_default=
3853 [USB] Default USB device authorization:
3854 (default -1 = authorized except for wireless USB,
3855 0 = not authorized, 1 = authorized)
3857 usbcore.autosuspend=
3858 [USB] The autosuspend time delay (in seconds) used
3859 for newly-detected USB devices (default 2). This
3860 is the time required before an idle device will be
3861 autosuspended. Devices for which the delay is set
3862 to a negative value won't be autosuspended at all.
3864 usbcore.usbfs_snoop=
3865 [USB] Set to log all usbfs traffic (default 0 = off).
3867 usbcore.blinkenlights=
3868 [USB] Set to cycle leds on hubs (default 0 = off).
3870 usbcore.old_scheme_first=
3871 [USB] Start with the old device initialization
3872 scheme (default 0 = off).
3874 usbcore.usbfs_memory_mb=
3875 [USB] Memory limit (in MB) for buffers allocated by
3876 usbfs (default = 16, 0 = max = 2047).
3878 usbcore.use_both_schemes=
3879 [USB] Try the other device initialization scheme
3880 if the first one fails (default 1 = enabled).
3882 usbcore.initial_descriptor_timeout=
3883 [USB] Specifies timeout for the initial 64-byte
3884 USB_REQ_GET_DESCRIPTOR request in milliseconds
3885 (default 5000 = 5.0 seconds).
3888 [USBHID] The interval which mice are to be polled at.
3890 usb-storage.delay_use=
3891 [UMS] The delay in seconds before a new device is
3892 scanned for Logical Units (default 1).
3895 [UMS] A list of quirks entries to supplement or
3896 override the built-in unusual_devs list. List
3897 entries are separated by commas. Each entry has
3898 the form VID:PID:Flags where VID and PID are Vendor
3899 and Product ID values (4-digit hex numbers) and
3900 Flags is a set of characters, each corresponding
3901 to a common usb-storage quirk flag as follows:
3902 a = SANE_SENSE (collect more than 18 bytes
3904 b = BAD_SENSE (don't collect more than 18
3905 bytes of sense data);
3906 c = FIX_CAPACITY (decrease the reported
3907 device capacity by one sector);
3908 d = NO_READ_DISC_INFO (don't use
3909 READ_DISC_INFO command);
3910 e = NO_READ_CAPACITY_16 (don't use
3911 READ_CAPACITY_16 command);
3912 f = NO_REPORT_OPCODES (don't use report opcodes
3914 g = MAX_SECTORS_240 (don't transfer more than
3915 240 sectors at a time, uas only);
3916 h = CAPACITY_HEURISTICS (decrease the
3917 reported device capacity by one
3918 sector if the number is odd);
3919 i = IGNORE_DEVICE (don't bind to this
3921 l = NOT_LOCKABLE (don't try to lock and
3922 unlock ejectable media);
3923 m = MAX_SECTORS_64 (don't transfer more
3924 than 64 sectors = 32 KB at a time);
3925 n = INITIAL_READ10 (force a retry of the
3926 initial READ(10) command);
3927 o = CAPACITY_OK (accept the capacity
3928 reported by the device);
3929 p = WRITE_CACHE (the device cache is ON
3931 r = IGNORE_RESIDUE (the device reports
3932 bogus residue values);
3933 s = SINGLE_LUN (the device has only one
3935 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3936 commands, uas only);
3937 u = IGNORE_UAS (don't bind to the uas driver);
3938 w = NO_WP_DETECT (don't test whether the
3939 medium is write-protected).
3940 Example: quirks=0419:aaf5:rl,0421:0433:rc
3942 user_debug= [KNL,ARM]
3944 See arch/arm/Kconfig.debug help text.
3945 1 - undefined instruction events
3947 4 - invalid data aborts
3950 Example: user_debug=31
3953 [X86] Flags controlling user PTE allocations.
3955 nohigh = do not allocate PTE pages in
3956 HIGHMEM regardless of setting
3960 On X86_32, this is an alias for vdso32=. Otherwise:
3962 vdso=1: enable VDSO (the default)
3963 vdso=0: disable VDSO mapping
3965 vdso32= [X86] Control the 32-bit vDSO
3966 vdso32=1: enable 32-bit VDSO
3967 vdso32=0 or vdso32=2: disable 32-bit VDSO
3969 See the help text for CONFIG_COMPAT_VDSO for more
3970 details. If CONFIG_COMPAT_VDSO is set, the default is
3971 vdso32=0; otherwise, the default is vdso32=1.
3973 For compatibility with older kernels, vdso32=2 is an
3976 Try vdso32=0 if you encounter an error that says:
3977 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3980 vector=percpu: enable percpu vector domain
3982 video= [FB] Frame buffer configuration
3983 See Documentation/fb/modedb.txt.
3985 video.brightness_switch_enabled= [0,1]
3986 If set to 1, on receiving an ACPI notify event
3987 generated by hotkey, video driver will adjust brightness
3988 level and then send out the event to user space through
3989 the allocated input device; If set to 0, video driver
3990 will only send out the event without touching backlight
3995 [VMMIO] Memory mapped virtio (platform) device.
3997 <size>@<baseaddr>:<irq>[:<id>]
3999 <size> := size (can use standard suffixes
4001 <baseaddr> := physical base address
4002 <irq> := interrupt number (as passed to
4004 <id> := (optional) platform device id
4006 virtio_mmio.device=1K@0x100b0000:48:7
4008 Can be used multiple times for multiple devices.
4010 vga= [BOOT,X86-32] Select a particular video mode
4011 See Documentation/x86/boot.txt and
4012 Documentation/svga.txt.
4013 Use vga=ask for menu.
4014 This is actually a boot loader parameter; the value is
4015 passed to the kernel using a special protocol.
4017 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4018 size of <nn>. This can be used to increase the
4019 minimum size (128MB on x86). It can also be used to
4020 decrease the size and leave more room for directly
4023 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4026 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4029 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4033 Controls the behavior of vsyscalls (i.e. calls to
4034 fixed addresses of 0xffffffffff600x00 from legacy
4035 code). Most statically-linked binaries and older
4036 versions of glibc use these calls. Because these
4037 functions are at fixed addresses, they make nice
4038 targets for exploits that can control RIP.
4040 emulate [default] Vsyscalls turn into traps and are
4041 emulated reasonably safely.
4043 native Vsyscalls are native syscall instructions.
4044 This is a little bit faster than trapping
4045 and makes a few dynamic recompilers work
4046 better than they would in emulation mode.
4047 It also makes exploits much easier to write.
4049 none Vsyscalls don't work at all. This makes
4050 them quite hard to use for exploits but
4051 might break your system.
4053 vt.color= [VT] Default text color.
4054 Format: 0xYX, X = foreground, Y = background.
4055 Default: 0x07 = light gray on black.
4057 vt.cur_default= [VT] Default cursor shape.
4058 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4059 the parameters of the <Esc>[?A;B;Cc escape sequence;
4060 see VGA-softcursor.txt. Default: 2 = underline.
4062 vt.default_blu= [VT]
4063 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4064 Change the default blue palette of the console.
4065 This is a 16-member array composed of values
4068 vt.default_grn= [VT]
4069 Format: <green0>,<green1>,<green2>,...,<green15>
4070 Change the default green palette of the console.
4071 This is a 16-member array composed of values
4074 vt.default_red= [VT]
4075 Format: <red0>,<red1>,<red2>,...,<red15>
4076 Change the default red palette of the console.
4077 This is a 16-member array composed of values
4083 Set system-wide default UTF-8 mode for all tty's.
4084 Default is 1, i.e. UTF-8 mode is enabled for all
4085 newly opened terminals.
4087 vt.global_cursor_default=
4090 Set system-wide default for whether a cursor
4091 is shown on new VTs. Default is -1,
4092 i.e. cursors will be created by default unless
4093 overridden by individual drivers. 0 will hide
4094 cursors, 1 will display them.
4096 vt.italic= [VT] Default color for italic text; 0-15.
4099 vt.underline= [VT] Default color for underlined text; 0-15.
4102 watchdog timers [HW,WDT] For information on watchdog timers,
4103 see Documentation/watchdog/watchdog-parameters.txt
4104 or other driver-specific files in the
4105 Documentation/watchdog/ directory.
4107 workqueue.disable_numa
4108 By default, all work items queued to unbound
4109 workqueues are affine to the NUMA nodes they're
4110 issued on, which results in better behavior in
4111 general. If NUMA affinity needs to be disabled for
4112 whatever reason, this option can be used. Note
4113 that this also can be controlled per-workqueue for
4114 workqueues visible under /sys/bus/workqueue/.
4116 workqueue.power_efficient
4117 Per-cpu workqueues are generally preferred because
4118 they show better performance thanks to cache
4119 locality; unfortunately, per-cpu workqueues tend to
4120 be more power hungry than unbound workqueues.
4122 Enabling this makes the per-cpu workqueues which
4123 were observed to contribute significantly to power
4124 consumption unbound, leading to measurably lower
4125 power usage at the cost of small performance
4128 The default value of this parameter is determined by
4129 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4131 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4132 default x2apic cluster mode on platforms
4135 x86_intel_mid_timer= [X86-32,APBT]
4136 Choose timer option for x86 Intel MID platform.
4137 Two valid options are apbt timer only and lapic timer
4138 plus one apbt timer for broadcast timer.
4139 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4141 xen_512gb_limit [KNL,X86-64,XEN]
4142 Restricts the kernel running paravirtualized under Xen
4143 to use only up to 512 GB of RAM. The reason to do so is
4144 crash analysis tools and Xen tools for doing domain
4145 save/restore/migration must be enabled to handle larger
4148 xen_emul_unplug= [HW,X86,XEN]
4149 Unplug Xen emulated devices
4150 Format: [unplug0,][unplug1]
4151 ide-disks -- unplug primary master IDE devices
4152 aux-ide-disks -- unplug non-primary-master IDE devices
4153 nics -- unplug network devices
4154 all -- unplug all emulated devices (NICs and IDE disks)
4155 unnecessary -- unplugging emulated devices is
4156 unnecessary even if the host did not respond to
4158 never -- do not unplug even if version check succeeds
4160 xen_nopvspin [X86,XEN]
4161 Disables the ticketlock slowpath using Xen PV
4165 Disables the PV optimizations forcing the HVM guest to
4166 run as generic HVM guest with no PV drivers.
4168 xirc2ps_cs= [NET,PCMCIA]
4170 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4172 ______________________________________________________________________
4176 Add more DRM drivers.
projects / karo-tx-linux.git / blob