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.
1038 Use early console provided by Freescale LP UART driver
1039 found on Freescale Vybrid and QorIQ LS1021A processors.
1040 A valid base address must be provided, and the serial
1041 port must already be setup and configured.
1043 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1047 earlyprintk=serial[,ttySn[,baudrate]]
1048 earlyprintk=serial[,0x...[,baudrate]]
1049 earlyprintk=ttySn[,baudrate]
1050 earlyprintk=dbgp[debugController#]
1051 earlyprintk=pciserial,bus:device.function[,baudrate]
1053 earlyprintk is useful when the kernel crashes before
1054 the normal console is initialized. It is not enabled by
1055 default because it has some cosmetic problems.
1057 Append ",keep" to not disable it when the real console
1060 Only one of vga, efi, serial, or usb debug port can
1063 Currently only ttyS0 and ttyS1 may be specified by
1064 name. Other I/O ports may be explicitly specified
1065 on some architectures (x86 and arm at least) by
1066 replacing ttySn with an I/O port address, like this:
1067 earlyprintk=serial,0x1008,115200
1068 You can find the port for a given device in
1069 /proc/tty/driver/serial:
1070 2: uart:ST16650V2 port:00001008 irq:18 ...
1072 Interaction with the standard serial driver is not
1075 The VGA and EFI output is eventually overwritten by
1078 The xen output can only be used by Xen PV guests.
1080 edac_report= [HW,EDAC] Control how to report EDAC event
1081 Format: {"on" | "off" | "force"}
1082 on: enable EDAC to report H/W event. May be overridden
1083 by other higher priority error reporting module.
1084 off: disable H/W event reporting through EDAC.
1085 force: enforce the use of EDAC to report H/W event.
1088 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1091 This is designed to be used in conjunction with
1092 the boot argument: earlyprintk=vga
1095 Format: {"off" | "on" | "skip[mbr]"}
1098 Format: { "old_map", "nochunk", "noruntime", "debug" }
1099 old_map [X86-64]: switch to the old ioremap-based EFI
1100 runtime services mapping. 32-bit still uses this one by
1102 nochunk: disable reading files in "chunks" in the EFI
1103 boot stub, as chunking can cause problems with some
1104 firmware implementations.
1105 noruntime : disable EFI runtime services support
1106 debug: enable misc debug output
1108 efi_no_storage_paranoia [EFI; X86]
1109 Using this parameter you can use more than 50% of
1110 your efi variable storage. Use this parameter only if
1111 you are really sure that your UEFI does sane gc and
1112 fulfills the spec otherwise your board may brick.
1114 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1115 Add arbitrary attribute to specific memory range by
1116 updating original EFI memory map.
1117 Region of memory which aa attribute is added to is
1119 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1120 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1121 attribute is added to range 0x100000000-0x180000000 and
1122 0x10a0000000-0x1120000000.
1124 Using this parameter you can do debugging of EFI memmap
1125 related feature. For example, you can do debugging of
1126 Address Range Mirroring feature even if your box
1129 eisa_irq_edge= [PARISC,HW]
1130 See header of drivers/parisc/eisa.c.
1133 See comment before function elanfreq_setup() in
1134 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1137 Format: {"cfq" | "deadline" | "noop"}
1138 See Documentation/block/cfq-iosched.txt and
1139 Documentation/block/deadline-iosched.txt for details.
1141 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1142 Specifies physical address of start of kernel core
1143 image elf header and optionally the size. Generally
1144 kexec loader will pass this option to capture kernel.
1145 See Documentation/kdump/kdump.txt for details.
1147 enable_mtrr_cleanup [X86]
1148 The kernel tries to adjust MTRR layout from continuous
1149 to discrete, to make X server driver able to add WB
1150 entry later. This parameter enables that.
1152 enable_timer_pin_1 [X86]
1153 Enable PIN 1 of APIC timer
1154 Can be useful to work around chipset bugs
1155 (in particular on some ATI chipsets).
1156 The kernel tries to set a reasonable default.
1158 enforcing [SELINUX] Set initial enforcing status.
1160 See security/selinux/Kconfig help text.
1161 0 -- permissive (log only, no denials).
1162 1 -- enforcing (deny and log).
1164 Value can be changed at runtime via /selinux/enforce.
1167 Disable Error Record Serialization Table (ERST)
1170 ether= [HW,NET] Ethernet cards parameters
1171 This option is obsoleted by the "netdev=" option, which
1172 has equivalent usage. See its documentation for details.
1176 Permit 'security.evm' to be updated regardless of
1177 current integrity status.
1181 fail_make_request=[KNL]
1182 General fault injection mechanism.
1183 Format: <interval>,<probability>,<space>,<times>
1184 See also Documentation/fault-injection/.
1187 See Documentation/blockdev/floppy.txt.
1189 force_pal_cache_flush
1190 [IA-64] Avoid check_sal_cache_flush which may hang on
1191 buggy SAL_CACHE_FLUSH implementations. Using this
1192 parameter will force ia64_sal_cache_flush to call
1193 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1196 Forcefully enable Physical Address Extension (PAE).
1197 Many Pentium M systems disable PAE but may have a
1198 functionally usable PAE implementation.
1199 Warning: use of this parameter will taint the kernel
1200 and may cause unknown problems.
1203 [FTRACE] will set and start the specified tracer
1204 as early as possible in order to facilitate early
1207 ftrace_dump_on_oops[=orig_cpu]
1208 [FTRACE] will dump the trace buffers on oops.
1209 If no parameter is passed, ftrace will dump
1210 buffers of all CPUs, but if you pass orig_cpu, it will
1211 dump only the buffer of the CPU that triggered the
1214 ftrace_filter=[function-list]
1215 [FTRACE] Limit the functions traced by the function
1216 tracer at boot up. function-list is a comma separated
1217 list of functions. This list can be changed at run
1218 time by the set_ftrace_filter file in the debugfs
1221 ftrace_notrace=[function-list]
1222 [FTRACE] Do not trace the functions specified in
1223 function-list. This list can be changed at run time
1224 by the set_ftrace_notrace file in the debugfs
1227 ftrace_graph_filter=[function-list]
1228 [FTRACE] Limit the top level callers functions traced
1229 by the function graph tracer at boot up.
1230 function-list is a comma separated list of functions
1231 that can be changed at run time by the
1232 set_graph_function file in the debugfs tracing directory.
1234 ftrace_graph_notrace=[function-list]
1235 [FTRACE] Do not trace from the functions specified in
1236 function-list. This list is a comma separated list of
1237 functions that can be changed at run time by the
1238 set_graph_notrace file in the debugfs tracing directory.
1241 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1242 support via parallel port (up to 5 devices per port)
1243 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1244 See also Documentation/input/joystick-parport.txt
1248 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1252 gcov_persist= [GCOV] When non-zero (default), profiling data for
1253 kernel modules is saved and remains accessible via
1254 debugfs, even when the module is unloaded/reloaded.
1255 When zero, profiling data is discarded and associated
1256 debugfs files are removed at module unload time.
1258 gpt [EFI] Forces disk with valid GPT signature but
1259 invalid Protective MBR to be treated as GPT. If the
1260 primary GPT is corrupted, it enables the backup/alternate
1261 GPT to be used instead.
1263 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1264 the "Enable 0" bit of the configuration register.
1267 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1268 the "Enable 0" bit of the configuration register.
1271 grcan.select= [HW] Select which physical interface to use.
1274 grcan.txsize= [HW] Sets the size of the tx buffer.
1275 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1277 grcan.rxsize= [HW] Sets the size of the rx buffer.
1278 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1281 hardlockup_all_cpu_backtrace=
1282 [KNL] Should the hard-lockup detector generate
1283 backtraces on all cpus.
1286 hashdist= [KNL,NUMA] Large hashes allocated during boot
1287 are distributed across NUMA nodes. Defaults on
1288 for 64-bit NUMA, off otherwise.
1289 Format: 0 | 1 (for off | on)
1291 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1293 hd= [EIDE] (E)IDE hard drive subsystem geometry
1294 Format: <cyl>,<head>,<sect>
1297 Disable Hardware Error Source Table (HEST) support;
1298 corresponding firmware-first mode error processing
1299 logic will be disabled.
1301 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1302 size of <nn>. This works even on boxes that have no
1303 highmem otherwise. This also works to reduce highmem
1304 size on bigger boxes.
1306 highres= [KNL] Enable/disable high resolution timer mode.
1307 Valid parameters: "on", "off"
1311 See Documentation/isdn/README.HiSax.
1315 hpet= [X86-32,HPET] option to control HPET usage
1316 Format: { enable (default) | disable | force |
1318 disable: disable HPET and use PIT instead
1319 force: allow force enabled of undocumented chips (ICH4,
1321 verbose: show contents of HPET registers during setup
1323 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1324 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1326 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1327 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1328 On x86-64 and powerpc, this option can be specified
1329 multiple times interleaved with hugepages= to reserve
1330 huge pages of different sizes. Valid pages sizes on
1331 x86-64 are 2M (when the CPU supports "pse") and 1G
1332 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1334 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1335 terminal devices. Valid values: 0..8
1336 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1337 If specified, z/VM IUCV HVC accepts connections
1338 from listed z/VM user IDs only.
1340 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1341 hardware thread id mappings.
1342 Format: <cpu>:<hwthread>
1345 Do not unregister boot console at start. This is only
1346 useful for debugging when something happens in the window
1347 between unregistering the boot console and initializing
1350 i2c_bus= [HW] Override the default board specific I2C bus speed
1351 or register an additional I2C bus that is not
1352 registered from board initialization code.
1356 i8042.debug [HW] Toggle i8042 debug mode
1357 i8042.unmask_kbd_data
1358 [HW] Enable printing of interrupt data from the KBD port
1359 (disabled by default, and as a pre-condition
1360 requires that i8042.debug=1 be enabled)
1361 i8042.direct [HW] Put keyboard port into non-translated mode
1362 i8042.dumbkbd [HW] Pretend that controller can only read data from
1363 keyboard and cannot control its state
1364 (Don't attempt to blink the leds)
1365 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1366 i8042.nokbd [HW] Don't check/create keyboard port
1367 i8042.noloop [HW] Disable the AUX Loopback command while probing
1369 i8042.nomux [HW] Don't check presence of an active multiplexing
1371 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1373 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1374 i8042.reset [HW] Reset the controller during init, cleanup and
1375 suspend-to-ram transitions, only during s2r
1376 transitions, or never reset
1377 Format: { 1 | Y | y | 0 | N | n }
1378 1, Y, y: always reset controller
1379 0, N, n: don't ever reset controller
1380 Default: only on s2r transitions on x86; most other
1381 architectures force reset to be always executed
1382 i8042.unlock [HW] Unlock (ignore) the keylock
1383 i8042.kbdreset [HW] Reset device connected to KBD port
1387 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1388 indicates that the driver is running on unsupported
1390 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1391 does not match list of supported models.
1393 [HW] Report power status in /proc/i8k
1394 (disabled by default)
1395 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1398 i915.invert_brightness=
1399 [DRM] Invert the sense of the variable that is used to
1400 set the brightness of the panel backlight. Normally a
1401 brightness value of 0 indicates backlight switched off,
1402 and the maximum of the brightness value sets the backlight
1403 to maximum brightness. If this parameter is set to 0
1404 (default) and the machine requires it, or this parameter
1405 is set to 1, a brightness value of 0 sets the backlight
1406 to maximum brightness, and the maximum of the brightness
1407 value switches the backlight off.
1408 -1 -- never invert brightness
1409 0 -- machine default
1410 1 -- force brightness inversion
1413 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1415 ide-core.nodma= [HW] (E)IDE subsystem
1416 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1417 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1418 .cdrom .chs .ignore_cable are additional options
1419 See Documentation/ide/ide.txt.
1421 ide-generic.probe-mask= [HW] (E)IDE subsystem
1423 Probe mask for legacy ISA IDE ports. Depending on
1424 platform up to 6 ports are supported, enabled by
1425 setting corresponding bits in the mask to 1. The
1426 default value is 0x0, which has a special meaning.
1427 On systems that have PCI, it triggers scanning the
1428 PCI bus for the first and the second port, which
1429 are then probed. On systems without PCI the value
1430 of 0x0 enables probing the two first ports as if it
1433 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1434 Claim all unknown PCI IDE storage controllers.
1437 Format: idle=poll, idle=halt, idle=nomwait
1438 Poll forces a polling idle loop that can slightly
1439 improve the performance of waking up a idle CPU, but
1440 will use a lot of power and make the system run hot.
1442 idle=halt: Halt is forced to be used for CPU idle.
1443 In such case C2/C3 won't be used again.
1444 idle=nomwait: Disable mwait for CPU C-states
1446 ignore_loglevel [KNL]
1447 Ignore loglevel setting - this will print /all/
1448 kernel messages to the console. Useful for debugging.
1449 We also add it as printk module parameter, so users
1450 could change it dynamically, usually by
1451 /sys/module/printk/parameters/ignore_loglevel.
1453 ihash_entries= [KNL]
1454 Set number of hash buckets for inode cache.
1456 ima_appraise= [IMA] appraise integrity measurements
1457 Format: { "off" | "enforce" | "fix" | "log" }
1460 ima_appraise_tcb [IMA]
1461 The builtin appraise policy appraises all files
1465 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1469 The list of supported hash algorithms is defined
1470 in crypto/hash_info.h.
1473 The builtin measurement policy to load during IMA
1474 setup. Specyfing "tcb" as the value, measures all
1475 programs exec'd, files mmap'd for exec, and all files
1476 opened with the read mode bit set by either the
1477 effective uid (euid=0) or uid=0.
1480 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1481 Load a policy which meets the needs of the Trusted
1482 Computing Base. This means IMA will measure all
1483 programs exec'd, files mmap'd for exec, and all files
1484 opened for read by uid=0.
1487 Select one of defined IMA measurements template formats.
1488 Formats: { "ima" | "ima-ng" | "ima-sig" }
1492 [IMA] Define a custom template format.
1493 Format: { "field1|...|fieldN" }
1495 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1496 Format: <min_file_size>
1497 Set the minimal file size for using asynchronous hash.
1498 If left unspecified, ahash usage is disabled.
1500 ahash performance varies for different data sizes on
1501 different crypto accelerators. This option can be used
1502 to achieve the best performance for a particular HW.
1504 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1506 Set hashing buffer size. Default: 4k.
1508 ahash performance varies for different chunk sizes on
1509 different crypto accelerators. This option can be used
1510 to achieve best performance for particular HW.
1514 Run specified binary instead of /sbin/init as init
1517 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1518 for working out where the kernel is dying during
1521 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1522 initcall functions. Useful for debugging built-in
1523 modules and initcalls.
1525 initrd= [BOOT] Specify the location of the initial ramdisk
1527 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1530 int_pln_enable [x86] Enable power limit notification interrupt
1532 integrity_audit=[IMA]
1533 Format: { "0" | "1" }
1534 0 -- basic integrity auditing messages. (Default)
1535 1 -- additional integrity auditing messages.
1537 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1539 Enable intel iommu driver.
1541 Disable intel iommu driver.
1542 igfx_off [Default Off]
1543 By default, gfx is mapped as normal device. If a gfx
1544 device has a dedicated DMAR unit, the DMAR unit is
1545 bypassed by not enabling DMAR with this option. In
1546 this case, gfx device will use physical address for
1549 With this option iommu will not optimize to look
1550 for io virtual address below 32-bit forcing dual
1551 address cycle on pci bus for cards supporting greater
1552 than 32-bit addressing. The default is to look
1553 for translation below 32-bit and if not available
1554 then look in the higher range.
1555 strict [Default Off]
1556 With this option on every unmap_single operation will
1557 result in a hardware IOTLB flush operation as opposed
1558 to batching them for performance.
1559 sp_off [Default Off]
1560 By default, super page will be supported if Intel IOMMU
1561 has the capability. With this option, super page will
1563 ecs_off [Default Off]
1564 By default, extended context tables will be supported if
1565 the hardware advertises that it has support both for the
1566 extended tables themselves, and also PASID support. With
1567 this option set, extended tables will not be used even
1568 on hardware which claims to support them.
1570 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1571 0 disables intel_idle and fall back on acpi_idle.
1572 1 to 6 specify maximum depth of C-state.
1576 Do not enable intel_pstate as the default
1577 scaling driver for the supported processors
1579 Enable intel_pstate on systems that prohibit it by default
1580 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1581 instead of acpi-cpufreq may disable platform features, such
1582 as thermal controls and power capping, that rely on ACPI
1583 P-States information being indicated to OSPM and therefore
1584 should be used with caution. This option does not work with
1585 processors that aren't supported by the intel_pstate driver
1586 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1588 Do not enable hardware P state control (HWP)
1591 Only load intel_pstate on systems which support
1592 hardware P state control (HWP) if available.
1594 intremap= [X86-64, Intel-IOMMU]
1595 on enable Interrupt Remapping (default)
1596 off disable Interrupt Remapping
1597 nosid disable Source ID checking
1599 BIOS x2APIC opt-out request will be ignored
1600 nopost disable Interrupt Posting
1602 iomem= Disable strict checking of access to MMIO memory
1603 strict regions from userspace.
1618 nobypass [PPC/POWERNV]
1619 Disable IOMMU bypass, using IOMMU for PCI devices.
1622 io7= [HW] IO7 for Marvel based alpha systems
1623 See comment before marvel_specify_io7 in
1624 arch/alpha/kernel/core_marvel.c.
1626 io_delay= [X86] I/O delay method
1628 Standard port 0x80 based delay
1630 Alternate port 0xed based delay (needed on some systems)
1632 Simple two microseconds delay
1637 See Documentation/filesystems/nfs/nfsroot.txt.
1640 When an interrupt is not handled search all handlers
1641 for it. Intended to get systems with badly broken
1645 When an interrupt is not handled search all handlers
1646 for it. Also check all handlers each timer
1647 interrupt. Intended to get systems with badly broken
1651 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1653 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1655 <cpu number>,...,<cpu number>
1657 <cpu number>-<cpu number>
1658 (must be a positive range in ascending order)
1660 <cpu number>,...,<cpu number>-<cpu number>
1662 This option can be used to specify one or more CPUs
1663 to isolate from the general SMP balancing and scheduling
1664 algorithms. You can move a process onto or off an
1665 "isolated" CPU via the CPU affinity syscalls or cpuset.
1666 <cpu number> begins at 0 and the maximum value is
1667 "number of CPUs in system - 1".
1669 This option is the preferred way to isolate CPUs. The
1670 alternative -- manually setting the CPU mask of all
1671 tasks in the system -- can cause problems and
1672 suboptimal load balancer performance.
1676 ivrs_ioapic [HW,X86_64]
1677 Provide an override to the IOAPIC-ID<->DEVICE-ID
1678 mapping provided in the IVRS ACPI table. For
1679 example, to map IOAPIC-ID decimal 10 to
1680 PCI device 00:14.0 write the parameter as:
1681 ivrs_ioapic[10]=00:14.0
1683 ivrs_hpet [HW,X86_64]
1684 Provide an override to the HPET-ID<->DEVICE-ID
1685 mapping provided in the IVRS ACPI table. For
1686 example, to map HPET-ID decimal 0 to
1687 PCI device 00:14.0 write the parameter as:
1688 ivrs_hpet[0]=00:14.0
1690 js= [HW,JOY] Analog joystick
1691 See Documentation/input/joystick.txt.
1694 Enable/disable kernel and module base offset ASLR
1695 (Address Space Layout Randomization) if built into
1696 the kernel. When CONFIG_HIBERNATION is selected,
1697 kASLR is disabled by default. When kASLR is enabled,
1698 hibernation will be disabled.
1702 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1703 specifies the amount of memory usable by the kernel
1704 for non-movable allocations. The requested amount is
1705 spread evenly throughout all nodes in the system. The
1706 remaining memory in each node is used for Movable
1707 pages. In the event, a node is too small to have both
1708 kernelcore and Movable pages, kernelcore pages will
1709 take priority and other nodes will have a larger number
1710 of Movable pages. The Movable zone is used for the
1711 allocation of pages that may be reclaimed or moved
1712 by the page migration subsystem. This means that
1713 HugeTLB pages may not be allocated from this zone.
1714 Note that allocations like PTEs-from-HighMem still
1715 use the HighMem zone if it exists, and the Normal
1716 zone if it does not.
1718 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1719 Format: <Controller#>[,poll interval]
1720 The controller # is the number of the ehci usb debug
1721 port as it is probed via PCI. The poll interval is
1722 optional and is the number seconds in between
1723 each poll cycle to the debug port in case you need
1724 the functionality for interrupting the kernel with
1725 gdb or control-c on the dbgp connection. When
1726 not using this parameter you use sysrq-g to break into
1727 the kernel debugger.
1729 kgdboc= [KGDB,HW] kgdb over consoles.
1730 Requires a tty driver that supports console polling,
1731 or a supported polling keyboard driver (non-usb).
1732 Serial only format: <serial_device>[,baud]
1733 keyboard only format: kbd
1734 keyboard and serial format: kbd,<serial_device>[,baud]
1735 Optional Kernel mode setting:
1736 kms, kbd format: kms,kbd
1737 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1739 kgdbwait [KGDB] Stop kernel execution and enter the
1740 kernel debugger at the earliest opportunity.
1742 kmac= [MIPS] korina ethernet MAC address.
1743 Configure the RouterBoard 532 series on-chip
1744 Ethernet adapter MAC address.
1746 kmemleak= [KNL] Boot-time kmemleak enable/disable
1747 Valid arguments: on, off
1749 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1752 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1753 Valid arguments: 0, 1, 2
1754 kmemcheck=0 (disabled)
1755 kmemcheck=1 (enabled)
1756 kmemcheck=2 (one-shot mode)
1757 Default: 2 (one-shot mode)
1759 kstack=N [X86] Print N words from the kernel stack
1762 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1763 Default is 0 (don't ignore, but inject #GP)
1765 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1769 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1770 Default is 1 (enabled)
1772 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1774 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1776 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1777 (virtualized MMU) support on capable Intel chips.
1778 Default is 1 (enabled)
1780 kvm-intel.emulate_invalid_guest_state=
1781 [KVM,Intel] Enable emulation of invalid guest states
1782 Default is 0 (disabled)
1784 kvm-intel.flexpriority=
1785 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1786 Default is 1 (enabled)
1789 [KVM,Intel] Enable VMX nesting (nVMX).
1790 Default is 0 (disabled)
1792 kvm-intel.unrestricted_guest=
1793 [KVM,Intel] Disable unrestricted guest feature
1794 (virtualized real and unpaged mode) on capable
1795 Intel chips. Default is 1 (enabled)
1797 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1798 feature (tagged TLBs) on capable Intel chips.
1799 Default is 1 (enabled)
1805 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1808 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1809 value for LAPIC timer one-shot implementation. Default
1810 back to the programmable timer unit in the LAPIC.
1812 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1815 libata.dma= [LIBATA] DMA control
1816 libata.dma=0 Disable all PATA and SATA DMA
1817 libata.dma=1 PATA and SATA Disk DMA only
1818 libata.dma=2 ATAPI (CDROM) DMA only
1819 libata.dma=4 Compact Flash DMA only
1820 Combinations also work, so libata.dma=3 enables DMA
1821 for disks and CDROMs, but not CFs.
1823 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1824 libata.ignore_hpa=0 keep BIOS limits (default)
1825 libata.ignore_hpa=1 ignore limits, using full disk
1827 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1831 libata.force= [LIBATA] Force configurations. The format is comma
1832 separated list of "[ID:]VAL" where ID is
1833 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1834 matching port, link or device. Basically, it matches
1835 the ATA ID string printed on console by libata. If
1836 the whole ID part is omitted, the last PORT and DEVICE
1837 values are used. If ID hasn't been specified yet, the
1838 configuration applies to all ports, links and devices.
1840 If only DEVICE is omitted, the parameter applies to
1841 the port and all links and devices behind it. DEVICE
1842 number of 0 either selects the first device or the
1843 first fan-out link behind PMP device. It does not
1844 select the host link. DEVICE number of 15 selects the
1845 host link and device attached to it.
1847 The VAL specifies the configuration to force. As long
1848 as there's no ambiguity shortcut notation is allowed.
1849 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1850 The following configurations can be forced.
1852 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1853 Any ID with matching PORT is used.
1855 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1857 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1858 udma[/][16,25,33,44,66,100,133] notation is also
1861 * [no]ncq: Turn on or off NCQ.
1863 * [no]ncqtrim: Turn off queued DSM TRIM.
1865 * nohrst, nosrst, norst: suppress hard, soft
1868 * rstonce: only attempt one reset during
1869 hot-unplug link recovery
1871 * dump_id: dump IDENTIFY data.
1873 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1875 * disable: Disable this device.
1877 If there are multiple matching configurations changing
1878 the same attribute, the last one is used.
1880 memblock=debug [KNL] Enable memblock debug messages.
1882 load_ramdisk= [RAM] List of ramdisks to load from floppy
1883 See Documentation/blockdev/ramdisk.txt.
1885 lockd.nlm_grace_period=P [NFS] Assign grace period.
1888 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1891 lockd.nlm_timeout=T [NFS] Assign timeout value.
1894 lockd.nlm_udpport=M [NFS] Assign UDP port.
1897 locktorture.nreaders_stress= [KNL]
1898 Set the number of locking read-acquisition kthreads.
1899 Defaults to being automatically set based on the
1900 number of online CPUs.
1902 locktorture.nwriters_stress= [KNL]
1903 Set the number of locking write-acquisition kthreads.
1905 locktorture.onoff_holdoff= [KNL]
1906 Set time (s) after boot for CPU-hotplug testing.
1908 locktorture.onoff_interval= [KNL]
1909 Set time (s) between CPU-hotplug operations, or
1910 zero to disable CPU-hotplug testing.
1912 locktorture.shuffle_interval= [KNL]
1913 Set task-shuffle interval (jiffies). Shuffling
1914 tasks allows some CPUs to go into dyntick-idle
1915 mode during the locktorture test.
1917 locktorture.shutdown_secs= [KNL]
1918 Set time (s) after boot system shutdown. This
1919 is useful for hands-off automated testing.
1921 locktorture.stat_interval= [KNL]
1922 Time (s) between statistics printk()s.
1924 locktorture.stutter= [KNL]
1925 Time (s) to stutter testing, for example,
1926 specifying five seconds causes the test to run for
1927 five seconds, wait for five seconds, and so on.
1928 This tests the locking primitive's ability to
1929 transition abruptly to and from idle.
1931 locktorture.torture_runnable= [BOOT]
1932 Start locktorture running at boot time.
1934 locktorture.torture_type= [KNL]
1935 Specify the locking implementation to test.
1937 locktorture.verbose= [KNL]
1938 Enable additional printk() statements.
1940 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1943 loglevel= All Kernel Messages with a loglevel smaller than the
1944 console loglevel will be printed to the console. It can
1945 also be changed with klogd or other programs. The
1946 loglevels are defined as follows:
1948 0 (KERN_EMERG) system is unusable
1949 1 (KERN_ALERT) action must be taken immediately
1950 2 (KERN_CRIT) critical conditions
1951 3 (KERN_ERR) error conditions
1952 4 (KERN_WARNING) warning conditions
1953 5 (KERN_NOTICE) normal but significant condition
1954 6 (KERN_INFO) informational
1955 7 (KERN_DEBUG) debug-level messages
1957 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1958 in bytes. n must be a power of two and greater
1959 than the minimal size. The minimal size is defined
1960 by LOG_BUF_SHIFT kernel config parameter. There is
1961 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1962 that allows to increase the default size depending on
1963 the number of CPUs. See init/Kconfig for more details.
1965 logo.nologo [FB] Disables display of the built-in Linux logo.
1966 This may be used to provide more screen space for
1967 kernel log messages and is useful when debugging
1968 kernel boot problems.
1970 lp=0 [LP] Specify parallel ports to use, e.g,
1971 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1972 lp=reset first parallel port). 'lp=0' disables the
1973 lp=auto printer driver. 'lp=reset' (which can be
1974 specified in addition to the ports) causes
1975 attached printers to be reset. Using
1976 lp=port1,port2,... specifies the parallel ports
1977 to associate lp devices with, starting with
1978 lp0. A port specification may be 'none' to skip
1979 that lp device, or a parport name such as
1980 'parport0'. Specifying 'lp=auto' instead of a
1981 port specification list means that device IDs
1982 from each port should be examined, to see if
1983 an IEEE 1284-compliant printer is attached; if
1984 so, the driver will manage that printer.
1985 See also header of drivers/char/lp.c.
1988 Sets loops_per_jiffy to given constant, thus avoiding
1989 time-consuming boot-time autodetection (up to 250 ms per
1990 CPU). 0 enables autodetection (default). To determine
1991 the correct value for your kernel, boot with normal
1992 autodetection and see what value is printed. Note that
1993 on SMP systems the preset will be applied to all CPUs,
1994 which is likely to cause problems if your CPUs need
1995 significantly divergent settings. An incorrect value
1996 will cause delays in the kernel to be wrong, leading to
1997 unpredictable I/O errors and other breakage. Although
1998 unlikely, in the extreme case this might damage your
2002 Format: <io>,<irq>,<dma>
2004 machvec= [IA-64] Force the use of a particular machine-vector
2005 (machvec) in a generic kernel.
2006 Example: machvec=hpzx1_swiotlb
2008 machtype= [Loongson] Share the same kernel image file between different
2010 Example: machtype=lemote-yeeloong-2f-7inch
2012 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2013 than or equal to this physical address is ignored.
2015 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2016 should make use of. maxcpus=n : n >= 0 limits the
2017 kernel to using 'n' processors. n=0 is a special case,
2018 it is equivalent to "nosmp", which also disables
2021 max_loop= [LOOP] The number of loop block devices that get
2022 (loop.max_loop) unconditionally pre-created at init time. The default
2023 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2024 of statically allocating a predefined number, loop
2025 devices can be requested on-demand with the
2026 /dev/loop-control interface.
2028 mce [X86-32] Machine Check Exception
2030 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2032 md= [HW] RAID subsystems devices and level
2033 See Documentation/md.txt.
2036 Format: <first>,<last>
2037 Specifies range of consoles to be captured by the MDA.
2039 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2040 Amount of memory to be used when the kernel is not able
2041 to see the whole system memory or for test.
2042 [X86] Work as limiting max address. Use together
2043 with memmap= to avoid physical address space collisions.
2044 Without memmap= PCI devices could be placed at addresses
2045 belonging to unused RAM.
2047 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2051 [KNL,SH] Allow user to override the default size for
2052 per-device physically contiguous DMA buffers.
2054 memmap=exactmap [KNL,X86] Enable setting of an exact
2055 E820 memory map, as specified by the user.
2056 Such memmap=exactmap lines can be constructed based on
2057 BIOS output or other requirements. See the memmap=nn@ss
2060 memmap=nn[KMG]@ss[KMG]
2061 [KNL] Force usage of a specific region of memory.
2062 Region of memory to be used is from ss to ss+nn.
2064 memmap=nn[KMG]#ss[KMG]
2065 [KNL,ACPI] Mark specific memory as ACPI data.
2066 Region of memory to be marked is from ss to ss+nn.
2068 memmap=nn[KMG]$ss[KMG]
2069 [KNL,ACPI] Mark specific memory as reserved.
2070 Region of memory to be reserved is from ss to ss+nn.
2071 Example: Exclude memory from 0x18690000-0x1869ffff
2072 memmap=64K$0x18690000
2074 memmap=0x10000$0x18690000
2076 memmap=nn[KMG]!ss[KMG]
2077 [KNL,X86] Mark specific memory as protected.
2078 Region of memory to be used, from ss to ss+nn.
2079 The memory region may be marked as e820 type 12 (0xc)
2080 and is NVDIMM or ADR memory.
2082 memory_corruption_check=0/1 [X86]
2083 Some BIOSes seem to corrupt the first 64k of
2084 memory when doing things like suspend/resume.
2085 Setting this option will scan the memory
2086 looking for corruption. Enabling this will
2087 both detect corruption and prevent the kernel
2088 from using the memory being corrupted.
2089 However, its intended as a diagnostic tool; if
2090 repeatable BIOS-originated corruption always
2091 affects the same memory, you can use memmap=
2092 to prevent the kernel from using that memory.
2094 memory_corruption_check_size=size [X86]
2095 By default it checks for corruption in the low
2096 64k, making this memory unavailable for normal
2097 use. Use this parameter to scan for
2098 corruption in more or less memory.
2100 memory_corruption_check_period=seconds [X86]
2101 By default it checks for corruption every 60
2102 seconds. Use this parameter to check at some
2103 other rate. 0 disables periodic checking.
2105 memtest= [KNL,X86,ARM] Enable memtest
2107 default : 0 <disable>
2108 Specifies the number of memtest passes to be
2109 performed. Each pass selects another test
2110 pattern from a given set of patterns. Memtest
2111 fills the memory with this pattern, validates
2112 memory contents and reserves bad memory
2113 regions that are detected.
2115 meye.*= [HW] Set MotionEye Camera parameters
2116 See Documentation/video4linux/meye.txt.
2118 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2119 Multi-Function General Purpose Timers on AMD Geode
2122 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2123 the BIOS has incorrectly applied a workaround. TinyBIOS
2124 version 0.98 is known to be affected, 0.99 fixes the
2125 problem by letting the user disable the workaround.
2129 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2130 physical address is ignored.
2132 mini2440= [ARM,HW,KNL]
2133 Format:[0..2][b][c][t]
2135 MINI2440 configuration specification:
2136 0 - The attached screen is the 3.5" TFT
2137 1 - The attached screen is the 7" TFT
2138 2 - The VGA Shield is attached (1024x768)
2139 Leaving out the screen size parameter will not load
2140 the TFT driver, and the framebuffer will be left
2142 b - Enable backlight. The TFT backlight pin will be
2143 linked to the kernel VESA blanking code and a GPIO
2144 LED. This parameter is not necessary when using the
2146 c - Enable the s3c camera interface.
2147 t - Reserved for enabling touchscreen support. The
2148 touchscreen support is not enabled in the mainstream
2149 kernel as of 2.6.30, a preliminary port can be found
2150 in the "bleeding edge" mini2440 support kernel at
2151 http://repo.or.cz/w/linux-2.6/mini2440.git
2154 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2155 parameter allows control of the logging verbosity for
2156 the additional memory initialisation checks. A value
2157 of 0 disables mminit logging and a level of 4 will
2158 log everything. Information is printed at KERN_DEBUG
2159 so loglevel=8 may also need to be specified.
2162 [KNL] When CONFIG_MODULE_SIG is set, this means that
2163 modules without (valid) signatures will fail to load.
2164 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2165 is always true, so this option does nothing.
2168 [MOUSE] Maximum time between finger touching and
2169 leaving touchpad surface for touch to be considered
2170 a tap and be reported as a left button click (for
2171 touchpads working in absolute mode only).
2173 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2174 reporting absolute coordinates, such as tablets
2175 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2176 reporting absolute coordinates, such as tablets
2178 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2179 is similar to kernelcore except it specifies the
2180 amount of memory used for migratable allocations.
2181 If both kernelcore and movablecore is specified,
2182 then kernelcore will be at *least* the specified
2183 value but may be more. If movablecore on its own
2184 is specified, the administrator must be careful
2185 that the amount of memory usable for all allocations
2188 movable_node [KNL,X86] Boot-time switch to enable the effects
2189 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2191 MTD_Partition= [MTD]
2192 Format: <name>,<region-number>,<size>,<offset>
2194 MTD_Region= [MTD] Format:
2195 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2198 See drivers/mtd/cmdlinepart.c.
2200 multitce=off [PPC] This parameter disables the use of the pSeries
2201 firmware feature for updating multiple TCE entries
2204 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2206 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2208 boundary - index of last SLC block on Flex-OneNAND.
2209 The remaining blocks are configured as MLC blocks.
2210 lock - Configure if Flex-OneNAND boundary should be locked.
2211 Once locked, the boundary cannot be changed.
2212 1 indicates lock status, 0 indicates unlock status.
2215 ARM/S3C2412 JIVE boot control
2217 See arch/arm/mach-s3c2412/mach-jive.c
2219 mtouchusb.raw_coordinates=
2220 [HW] Make the MicroTouch USB driver use raw coordinates
2221 ('y', default) or cooked coordinates ('n')
2223 mtrr_chunk_size=nn[KMG] [X86]
2224 used for mtrr cleanup. It is largest continuous chunk
2225 that could hold holes aka. UC entries.
2227 mtrr_gran_size=nn[KMG] [X86]
2228 Used for mtrr cleanup. It is granularity of mtrr block.
2230 Large value could prevent small alignment from
2233 mtrr_spare_reg_nr=n [X86]
2235 Range: 0,7 : spare reg number
2237 Used for mtrr cleanup. It is spare mtrr entries number.
2238 Set to 2 or more if your graphical card needs more.
2240 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2242 netdev= [NET] Network devices parameters
2243 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2244 Note that mem_start is often overloaded to mean
2245 something different and driver-specific.
2246 This usage is only documented in each driver source
2250 [NETFILTER] Enable connection tracking flow accounting
2251 0 to disable accounting
2252 1 to enable accounting
2255 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2256 See Documentation/filesystems/nfs/nfsroot.txt.
2258 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2259 See Documentation/filesystems/nfs/nfsroot.txt.
2261 nfsrootdebug [NFS] enable nfsroot debugging messages.
2262 See Documentation/filesystems/nfs/nfsroot.txt.
2264 nfs.callback_tcpport=
2265 [NFS] set the TCP port on which the NFSv4 callback
2266 channel should listen.
2269 [NFS] sets the pathname to the program which is used
2270 to update the NFS client cache entries.
2272 nfs.cache_getent_timeout=
2273 [NFS] sets the timeout after which an attempt to
2274 update a cache entry is deemed to have failed.
2276 nfs.idmap_cache_timeout=
2277 [NFS] set the maximum lifetime for idmapper cache
2281 [NFS] enable 64-bit inode numbers.
2282 If zero, the NFS client will fake up a 32-bit inode
2283 number for the readdir() and stat() syscalls instead
2284 of returning the full 64-bit number.
2285 The default is to return 64-bit inode numbers.
2287 nfs.max_session_slots=
2288 [NFSv4.1] Sets the maximum number of session slots
2289 the client will attempt to negotiate with the server.
2290 This limits the number of simultaneous RPC requests
2291 that the client can send to the NFSv4.1 server.
2292 Note that there is little point in setting this
2293 value higher than the max_tcp_slot_table_limit.
2295 nfs.nfs4_disable_idmapping=
2296 [NFSv4] When set to the default of '1', this option
2297 ensures that both the RPC level authentication
2298 scheme and the NFS level operations agree to use
2299 numeric uids/gids if the mount is using the
2300 'sec=sys' security flavour. In effect it is
2301 disabling idmapping, which can make migration from
2302 legacy NFSv2/v3 systems to NFSv4 easier.
2303 Servers that do not support this mode of operation
2304 will be autodetected by the client, and it will fall
2305 back to using the idmapper.
2306 To turn off this behaviour, set the value to '0'.
2308 [NFS4] Specify an additional fixed unique ident-
2309 ification string that NFSv4 clients can insert into
2310 their nfs_client_id4 string. This is typically a
2311 UUID that is generated at system install time.
2313 nfs.send_implementation_id =
2314 [NFSv4.1] Send client implementation identification
2315 information in exchange_id requests.
2316 If zero, no implementation identification information
2318 The default is to send the implementation identification
2321 nfs.recover_lost_locks =
2322 [NFSv4] Attempt to recover locks that were lost due
2323 to a lease timeout on the server. Please note that
2324 doing this risks data corruption, since there are
2325 no guarantees that the file will remain unchanged
2326 after the locks are lost.
2327 If you want to enable the kernel legacy behaviour of
2328 attempting to recover these locks, then set this
2330 The default parameter value of '0' causes the kernel
2331 not to attempt recovery of lost locks.
2333 nfs4.layoutstats_timer =
2334 [NFSv4.2] Change the rate at which the kernel sends
2335 layoutstats to the pNFS metadata server.
2337 Setting this to value to 0 causes the kernel to use
2338 whatever value is the default set by the layout
2339 driver. A non-zero value sets the minimum interval
2340 in seconds between layoutstats transmissions.
2342 nfsd.nfs4_disable_idmapping=
2343 [NFSv4] When set to the default of '1', the NFSv4
2344 server will return only numeric uids and gids to
2345 clients using auth_sys, and will accept numeric uids
2346 and gids from such clients. This is intended to ease
2347 migration from NFSv2/v3.
2349 objlayoutdriver.osd_login_prog=
2350 [NFS] [OBJLAYOUT] sets the pathname to the program which
2351 is used to automatically discover and login into new
2352 osd-targets. Please see:
2353 Documentation/filesystems/pnfs.txt for more explanations
2355 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2356 when a NMI is triggered.
2357 Format: [state][,regs][,debounce][,die]
2359 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2360 Format: [panic,][nopanic,][num]
2362 0 - turn hardlockup detector in nmi_watchdog off
2363 1 - turn hardlockup detector in nmi_watchdog on
2364 When panic is specified, panic when an NMI watchdog
2365 timeout occurs (or 'nopanic' to override the opposite
2366 default). To disable both hard and soft lockup detectors,
2367 please see 'nowatchdog'.
2368 This is useful when you use a panic=... timeout and
2369 need the box quickly up again.
2371 netpoll.carrier_timeout=
2372 [NET] Specifies amount of time (in seconds) that
2373 netpoll should wait for a carrier. By default netpoll
2376 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2377 emulation library even if a 387 maths coprocessor
2381 [HW] Never suspend the console
2382 Disable suspending of consoles during suspend and
2383 hibernate operations. Once disabled, debugging
2384 messages can reach various consoles while the rest
2385 of the system is being put to sleep (ie, while
2386 debugging driver suspend/resume hooks). This may
2387 not work reliably with all consoles, but is known
2388 to work with serial and VGA consoles.
2389 To facilitate more flexible debugging, we also add
2390 console_suspend, a printk module parameter to control
2391 it. Users could use console_suspend (usually
2392 /sys/module/printk/parameters/console_suspend) to
2393 turn on/off it dynamically.
2395 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2396 caches in the slab allocator. Saves per-node memory,
2397 but will impact performance.
2401 noapic [SMP,APIC] Tells the kernel to not make use of any
2402 IOAPICs that may be present in the system.
2404 noautogroup Disable scheduler automatic task group creation.
2406 nobats [PPC] Do not use BATs for mapping kernel lowmem
2407 on "Classic" PPC cores.
2411 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2413 nodelayacct [KNL] Disable per-task delay accounting
2415 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2417 nodsp [SH] Disable hardware DSP at boot time.
2419 noefi Disable EFI runtime services support.
2424 On X86-32 available only on PAE configured kernels.
2425 noexec=on: enable non-executable mappings (default)
2426 noexec=off: disable non-executable mappings
2429 Disable SMAP (Supervisor Mode Access Prevention)
2430 even if it is supported by processor.
2433 Disable SMEP (Supervisor Mode Execution Prevention)
2434 even if it is supported by processor.
2437 This affects only 32-bit executables.
2438 noexec32=on: enable non-executable mappings (default)
2439 read doesn't imply executable mappings
2440 noexec32=off: disable non-executable mappings
2441 read implies executable mappings
2443 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2445 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2446 register save and restore. The kernel will only save
2447 legacy floating-point registers on task switch.
2449 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2451 noxsave [BUGS=X86] Disables x86 extended register state save
2452 and restore using xsave. The kernel will fallback to
2453 enabling legacy floating-point and sse state.
2455 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2456 register states. The kernel will fall back to use
2457 xsave to save the states. By using this parameter,
2458 performance of saving the states is degraded because
2459 xsave doesn't support modified optimization while
2460 xsaveopt supports it on xsaveopt enabled systems.
2462 noxsaves [X86] Disables xsaves and xrstors used in saving and
2463 restoring x86 extended register state in compacted
2464 form of xsave area. The kernel will fall back to use
2465 xsaveopt and xrstor to save and restore the states
2466 in standard form of xsave area. By using this
2467 parameter, xsave area per process might occupy more
2468 memory on xsaves enabled systems.
2470 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2471 wfi(ARM) instruction doesn't work correctly and not to
2472 use it. This is also useful when using JTAG debugger.
2474 no_file_caps Tells the kernel not to honor file capabilities. The
2475 only way then for a file to be executed with privilege
2476 is to be setuid root or executed by root.
2478 nohalt [IA-64] Tells the kernel not to use the power saving
2479 function PAL_HALT_LIGHT when idle. This increases
2480 power-consumption. On the positive side, it reduces
2481 interrupt wake-up latency, which may improve performance
2482 in certain environments such as networked servers or
2485 nohibernate [HIBERNATION] Disable hibernation and resume.
2487 nohz= [KNL] Boottime enable/disable dynamic ticks
2488 Valid arguments: on, off
2491 nohz_full= [KNL,BOOT]
2492 In kernels built with CONFIG_NO_HZ_FULL=y, set
2493 the specified list of CPUs whose tick will be stopped
2494 whenever possible. The boot CPU will be forced outside
2495 the range to maintain the timekeeping.
2496 The CPUs in this range must also be included in the
2499 noiotrap [SH] Disables trapped I/O port accesses.
2501 noirqdebug [X86-32] Disables the code which attempts to detect and
2502 disable unhandled interrupt sources.
2504 no_timer_check [X86,APIC] Disables the code which tests for
2505 broken timer IRQ sources.
2507 noisapnp [ISAPNP] Disables ISA PnP code.
2509 noinitrd [RAM] Tells the kernel not to load any configured
2512 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2514 [Deprecated - use intremap=off]
2518 nojitter [IA-64] Disables jitter checking for ITC timers.
2520 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2522 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2525 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2526 steal time is computed, but won't influence scheduler
2529 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2531 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2533 noltlbs [PPC] Do not use large page/tlb entries for kernel
2534 lowmem mapping on PPC40x.
2536 nomca [IA-64] Disable machine check abort handling
2538 nomce [X86-32] Disable Machine Check Exception
2540 nomfgpt [X86-32] Disable Multi-Function General Purpose
2541 Timer usage (for AMD Geode machines).
2543 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2544 shutdown the other cpus. Instead use the REBOOT_VECTOR
2547 nomodule Disable module load
2549 nopat [X86] Disable PAT (page attribute table extension of
2550 pagetables) support.
2552 norandmaps Don't use address space randomization. Equivalent to
2553 echo 0 > /proc/sys/kernel/randomize_va_space
2555 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2557 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2558 with UP alternatives
2560 nordrand [X86] Disable kernel use of the RDRAND and
2561 RDSEED instructions even if they are supported
2562 by the processor. RDRAND and RDSEED are still
2563 available to user space applications.
2565 noresume [SWSUSP] Disables resume and restores original swap
2568 no-scroll [VGA] Disables scrollback.
2569 This is required for the Braillex ib80-piezo Braille
2570 reader made by F.H. Papenmeier (Germany).
2574 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2576 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2577 and disable the IO APIC. legacy for "maxcpus=0".
2579 nosoftlockup [KNL] Disable the soft-lockup detector.
2581 nosync [HW,M68K] Disables sync negotiation for all devices.
2583 notsc [BUGS=X86-32] Disable Time Stamp Counter
2585 nousb [USB] Disable the USB subsystem
2587 nowatchdog [KNL] Disable both lockup detectors, i.e.
2588 soft-lockup and NMI watchdog (hard-lockup).
2592 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2594 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2595 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2596 Some features depend on CPU0. Known dependencies are:
2597 1. Resume from suspend/hibernate depends on CPU0.
2598 Suspend/hibernate will fail if CPU0 is offline and you
2599 need to online CPU0 before suspend/hibernate.
2600 2. PIC interrupts also depend on CPU0. CPU0 can't be
2601 removed if a PIC interrupt is detected.
2602 It's said poweroff/reboot may depend on CPU0 on some
2603 machines although I haven't seen such issues so far
2604 after CPU0 is offline on a few tested machines.
2605 If the dependencies are under your control, you can
2606 turn on cpu0_hotplug.
2608 nptcg= [IA-64] Override max number of concurrent global TLB
2609 purges which is reported from either PAL_VM_SUMMARY or
2612 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2613 could support. nr_cpus=n : n >= 1 limits the kernel to
2614 supporting 'n' processors. Later in runtime you can not
2615 use hotplug cpu feature to put more cpu back to online.
2616 just like you compile the kernel NR_CPUS=n
2618 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2620 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2621 Allowed values are enable and disable
2623 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2624 one of ['zone', 'node', 'default'] can be specified
2625 This can be set from sysctl after boot.
2626 See Documentation/sysctl/vm.txt for details.
2628 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2629 See Documentation/debugging-via-ohci1394.txt for more
2632 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2633 Rather than timing out after 20 ms if an EC
2634 command is not properly ACKed, override the length
2635 of the timeout. We have interrupts disabled while
2636 waiting for the ACK, so if this is set too high
2637 interrupts *may* be lost!
2639 omap_mux= [OMAP] Override bootloader pin multiplexing.
2640 Format: <mux_mode0.mode_name=value>...
2641 For example, to override I2C bus2:
2642 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2644 oprofile.timer= [HW]
2645 Use timer interrupt instead of performance counters
2647 oprofile.cpu_type= Force an oprofile cpu type
2648 This might be useful if you have an older oprofile
2649 userland or if you want common events.
2650 Format: { arch_perfmon }
2651 arch_perfmon: [X86] Force use of architectural
2652 perfmon on Intel CPUs instead of the
2653 CPU specific event set.
2654 timer: [X86] Force use of architectural NMI
2655 timer mode (see also oprofile.timer
2656 for generic hr timer mode)
2657 [s390] Force legacy basic mode sampling
2658 (report cpu_type "timer")
2660 oops=panic Always panic on oopses. Default is to just kill the
2661 process, but there is a small probability of
2662 deadlocking the machine.
2663 This will also cause panics on machine check exceptions.
2664 Useful together with panic=30 to trigger a reboot.
2667 See Documentation/sound/oss/oss-parameters.txt
2669 page_owner= [KNL] Boot-time page_owner enabling option.
2670 Storage of the information about who allocated
2671 each page is disabled in default. With this switch,
2673 on: enable the feature
2675 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2676 timeout > 0: seconds before rebooting
2677 timeout = 0: wait forever
2678 timeout < 0: reboot immediately
2681 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2684 crash_kexec_post_notifiers
2685 Run kdump after running panic-notifiers and dumping
2686 kmsg. This only for the users who doubt kdump always
2687 succeeds in any situation.
2688 Note that this also increases risks of kdump failure,
2689 because some panic notifiers can make the crashed
2690 kernel more unstable.
2692 parkbd.port= [HW] Parallel port number the keyboard adapter is
2693 connected to, default is 0.
2695 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2696 0 for XT, 1 for AT (default is AT).
2699 parport= [HW,PPT] Specify parallel ports. 0 disables.
2700 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2701 Use 'auto' to force the driver to use any
2702 IRQ/DMA settings detected (the default is to
2703 ignore detected IRQ/DMA settings because of
2704 possible conflicts). You can specify the base
2705 address, IRQ, and DMA settings; IRQ and DMA
2706 should be numbers, or 'auto' (for using detected
2707 settings on that particular port), or 'nofifo'
2708 (to avoid using a FIFO even if it is detected).
2709 Parallel ports are assigned in the order they
2710 are specified on the command line, starting
2713 parport_init_mode= [HW,PPT]
2714 Configure VIA parallel port to operate in
2715 a specific mode. This is necessary on Pegasos
2716 computer where firmware has no options for setting
2717 up parallel port mode and sets it to spp.
2718 Currently this function knows 686a and 8231 chips.
2719 Format: [spp|ps2|epp|ecp|ecpepp]
2722 Halt all CPUs after the first oops has been printed for
2723 the specified number of seconds. This is to be used if
2724 your oopses keep scrolling off the screen.
2729 See header of drivers/block/paride/pcd.c.
2730 See also Documentation/blockdev/paride.txt.
2732 pci=option[,option...] [PCI] various PCI subsystem options:
2733 earlydump [X86] dump PCI config space before the kernel
2735 off [X86] don't probe for the PCI bus
2736 bios [X86-32] force use of PCI BIOS, don't access
2737 the hardware directly. Use this if your machine
2738 has a non-standard PCI host bridge.
2739 nobios [X86-32] disallow use of PCI BIOS, only direct
2740 hardware access methods are allowed. Use this
2741 if you experience crashes upon bootup and you
2742 suspect they are caused by the BIOS.
2743 conf1 [X86] Force use of PCI Configuration
2745 conf2 [X86] Force use of PCI Configuration
2747 noaer [PCIE] If the PCIEAER kernel config parameter is
2748 enabled, this kernel boot option can be used to
2749 disable the use of PCIE advanced error reporting.
2750 nodomains [PCI] Disable support for multiple PCI
2751 root domains (aka PCI segments, in ACPI-speak).
2752 nommconf [X86] Disable use of MMCONFIG for PCI
2754 check_enable_amd_mmconf [X86] check for and enable
2755 properly configured MMIO access to PCI
2756 config space on AMD family 10h CPU
2757 nomsi [MSI] If the PCI_MSI kernel config parameter is
2758 enabled, this kernel boot option can be used to
2759 disable the use of MSI interrupts system-wide.
2760 noioapicquirk [APIC] Disable all boot interrupt quirks.
2761 Safety option to keep boot IRQs enabled. This
2762 should never be necessary.
2763 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2764 primary IO-APIC for bridges that cannot disable
2765 boot IRQs. This fixes a source of spurious IRQs
2766 when the system masks IRQs.
2767 noioapicreroute [APIC] Disable workaround that uses the
2768 boot IRQ equivalent of an IRQ that connects to
2769 a chipset where boot IRQs cannot be disabled.
2770 The opposite of ioapicreroute.
2771 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2772 routing table. These calls are known to be buggy
2773 on several machines and they hang the machine
2774 when used, but on other computers it's the only
2775 way to get the interrupt routing table. Try
2776 this option if the kernel is unable to allocate
2777 IRQs or discover secondary PCI buses on your
2779 rom [X86] Assign address space to expansion ROMs.
2780 Use with caution as certain devices share
2781 address decoders between ROMs and other
2783 norom [X86] Do not assign address space to
2784 expansion ROMs that do not already have
2785 BIOS assigned address ranges.
2786 nobar [X86] Do not assign address space to the
2787 BARs that weren't assigned by the BIOS.
2788 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2789 assigned automatically to PCI devices. You can
2790 make the kernel exclude IRQs of your ISA cards
2792 pirqaddr=0xAAAAA [X86] Specify the physical address
2793 of the PIRQ table (normally generated
2794 by the BIOS) if it is outside the
2795 F0000h-100000h range.
2796 lastbus=N [X86] Scan all buses thru bus #N. Can be
2797 useful if the kernel is unable to find your
2798 secondary buses and you want to tell it
2799 explicitly which ones they are.
2800 assign-busses [X86] Always assign all PCI bus
2801 numbers ourselves, overriding
2802 whatever the firmware may have done.
2803 usepirqmask [X86] Honor the possible IRQ mask stored
2804 in the BIOS $PIR table. This is needed on
2805 some systems with broken BIOSes, notably
2806 some HP Pavilion N5400 and Omnibook XE3
2807 notebooks. This will have no effect if ACPI
2808 IRQ routing is enabled.
2809 noacpi [X86] Do not use ACPI for IRQ routing
2810 or for PCI scanning.
2811 use_crs [X86] Use PCI host bridge window information
2812 from ACPI. On BIOSes from 2008 or later, this
2813 is enabled by default. If you need to use this,
2814 please report a bug.
2815 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2816 If you need to use this, please report a bug.
2817 routeirq Do IRQ routing for all PCI devices.
2818 This is normally done in pci_enable_device(),
2819 so this option is a temporary workaround
2820 for broken drivers that don't call it.
2821 skip_isa_align [X86] do not align io start addr, so can
2822 handle more pci cards
2823 firmware [ARM] Do not re-enumerate the bus but instead
2824 just use the configuration from the
2825 bootloader. This is currently used on
2826 IXP2000 systems where the bus has to be
2827 configured a certain way for adjunct CPUs.
2828 noearly [X86] Don't do any early type 1 scanning.
2829 This might help on some broken boards which
2830 machine check when some devices' config space
2831 is read. But various workarounds are disabled
2832 and some IOMMU drivers will not work.
2833 bfsort Sort PCI devices into breadth-first order.
2834 This sorting is done to get a device
2835 order compatible with older (<= 2.4) kernels.
2836 nobfsort Don't sort PCI devices into breadth-first order.
2837 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2838 tuning and use the BIOS-configured MPS defaults.
2839 pcie_bus_safe Set every device's MPS to the largest value
2840 supported by all devices below the root complex.
2841 pcie_bus_perf Set device MPS to the largest allowable MPS
2842 based on its parent bus. Also set MRRS (Max
2843 Read Request Size) to the largest supported
2844 value (no larger than the MPS that the device
2845 or bus can support) for best performance.
2846 pcie_bus_peer2peer Set every device's MPS to 128B, which
2847 every device is guaranteed to support. This
2848 configuration allows peer-to-peer DMA between
2849 any pair of devices, possibly at the cost of
2850 reduced performance. This also guarantees
2851 that hot-added devices will work.
2852 cbiosize=nn[KMG] The fixed amount of bus space which is
2853 reserved for the CardBus bridge's IO window.
2854 The default value is 256 bytes.
2855 cbmemsize=nn[KMG] The fixed amount of bus space which is
2856 reserved for the CardBus bridge's memory
2857 window. The default value is 64 megabytes.
2860 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2861 Specifies alignment and device to reassign
2862 aligned memory resources.
2863 If <order of align> is not specified,
2864 PAGE_SIZE is used as alignment.
2865 PCI-PCI bridge can be specified, if resource
2866 windows need to be expanded.
2867 ecrc= Enable/disable PCIe ECRC (transaction layer
2868 end-to-end CRC checking).
2869 bios: Use BIOS/firmware settings. This is the
2873 hpiosize=nn[KMG] The fixed amount of bus space which is
2874 reserved for hotplug bridge's IO window.
2875 Default size is 256 bytes.
2876 hpmemsize=nn[KMG] The fixed amount of bus space which is
2877 reserved for hotplug bridge's memory window.
2878 Default size is 2 megabytes.
2879 realloc= Enable/disable reallocating PCI bridge resources
2880 if allocations done by BIOS are too small to
2881 accommodate resources required by all child
2883 off: Turn realloc off
2885 realloc same as realloc=on
2886 noari do not use PCIe ARI.
2887 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2888 only look for one device below a PCIe downstream
2891 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2894 force Enable ASPM even on devices that claim not to support it.
2895 WARNING: Forcing ASPM on may cause system lockups.
2897 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2898 nomsi Do not use MSI for PCI Express Native Hotplug (this
2899 makes all PCIe ports use INTx for hotplug services).
2901 pcie_ports= [PCIE] PCIe ports handling:
2902 auto Ask the BIOS whether or not to use native PCIe services
2903 associated with PCIe ports (PME, hot-plug, AER). Use
2904 them only if that is allowed by the BIOS.
2905 native Use native PCIe services associated with PCIe ports
2907 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2910 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2911 nomsi Do not use MSI for native PCIe PME signaling (this makes
2912 all PCIe root ports use INTx for all services).
2914 pcmv= [HW,PCMCIA] BadgePAD 4
2918 Keep all power-domains already enabled by bootloader on,
2919 even if no driver has claimed them. This is useful
2920 for debug and development, but should not be
2921 needed on a platform with proper driver support.
2924 See Documentation/blockdev/paride.txt.
2926 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2929 See arch/parisc/kernel/pdc_chassis.c
2931 percpu_alloc= Select which percpu first chunk allocator to use.
2932 Currently supported values are "embed" and "page".
2933 Archs may support subset or none of the selections.
2934 See comments in mm/percpu.c for details on each
2935 allocator. This parameter is primarily for debugging
2936 and performance comparison.
2939 See Documentation/blockdev/paride.txt.
2942 See Documentation/blockdev/paride.txt.
2944 pirq= [SMP,APIC] Manual mp-table setup
2945 See Documentation/x86/i386/IO-APIC.txt.
2947 plip= [PPT,NET] Parallel port network link
2948 Format: { parport<nr> | timid | 0 }
2949 See also Documentation/parport.txt.
2951 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2952 Override pmtimer IOPort with a hex value.
2956 Enable PNP debug messages (depends on the
2957 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2958 via /sys/module/pnp/parameters/debug. We always show
2959 current resource usage; turning this on also shows
2960 possible settings and some assignment information.
2966 { on | off | curr | res | no-curr | no-res }
2969 [ISAPNP] Exclude IRQs for the autoconfiguration
2972 [ISAPNP] Exclude DMAs for the autoconfiguration
2974 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2975 Ranges are in pairs (I/O port base and size).
2978 [ISAPNP] Exclude memory regions for the
2980 Ranges are in pairs (memory base and size).
2982 ports= [IP_VS_FTP] IPVS ftp helper module
2984 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2986 Format: <port>,<port>....
2988 print-fatal-signals=
2989 [KNL] debug: print fatal signals
2991 If enabled, warn about various signal handling
2992 related application anomalies: too many signals,
2993 too many POSIX.1 timers, fatal signals causing a
2996 If you hit the warning due to signal overflow,
2997 you might want to try "ulimit -i unlimited".
3001 printk.always_kmsg_dump=
3002 Trigger kmsg_dump for cases other than kernel oops or
3004 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3007 printk.time= Show timing data prefixed to each printk message line
3008 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3010 processor.max_cstate= [HW,ACPI]
3011 Limit processor to maximum C-state
3012 max_cstate=9 overrides any DMI blacklist limit.
3014 processor.nocst [HW,ACPI]
3015 Ignore the _CST method to determine C-states,
3016 instead using the legacy FADT method
3018 profile= [KNL] Enable kernel profiling via /proc/profile
3019 Format: [schedule,]<number>
3020 Param: "schedule" - profile schedule points.
3021 Param: <number> - step/bucket size as a power of 2 for
3022 statistical time based profiling.
3023 Param: "sleep" - profile D-state sleeping (millisecs).
3024 Requires CONFIG_SCHEDSTATS
3025 Param: "kvm" - profile VM exits.
3027 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3029 See Documentation/blockdev/ramdisk.txt.
3031 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3032 probe for; one of (bare|imps|exps|lifebook|any).
3033 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3035 psmouse.resetafter= [HW,MOUSE]
3036 Try to reset the device after so many bad packets
3039 [HW,MOUSE] Set desired mouse resolution, in dpi.
3040 psmouse.smartscroll=
3041 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3042 0 = disabled, 1 = enabled (default).
3044 pstore.backend= Specify the name of the pstore backend to use
3047 See Documentation/blockdev/paride.txt.
3050 [KNL] Number of legacy pty's. Overwrites compiled-in
3053 quiet [KNL] Disable most log messages
3058 See Documentation/md.txt.
3060 ramdisk_blocksize= [RAM]
3061 See Documentation/blockdev/ramdisk.txt.
3063 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3064 See Documentation/blockdev/ramdisk.txt.
3067 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3068 the specified list of CPUs to be no-callback CPUs.
3069 Invocation of these CPUs' RCU callbacks will
3070 be offloaded to "rcuox/N" kthreads created for
3071 that purpose, where "x" is "b" for RCU-bh, "p"
3072 for RCU-preempt, and "s" for RCU-sched, and "N"
3073 is the CPU number. This reduces OS jitter on the
3074 offloaded CPUs, which can be useful for HPC and
3075 real-time workloads. It can also improve energy
3076 efficiency for asymmetric multiprocessors.
3079 Rather than requiring that offloaded CPUs
3080 (specified by rcu_nocbs= above) explicitly
3081 awaken the corresponding "rcuoN" kthreads,
3082 make these kthreads poll for callbacks.
3083 This improves the real-time response for the
3084 offloaded CPUs by relieving them of the need to
3085 wake up the corresponding kthread, but degrades
3086 energy efficiency by requiring that the kthreads
3087 periodically wake up to do the polling.
3089 rcutree.blimit= [KNL]
3090 Set maximum number of finished RCU callbacks to
3091 process in one batch.
3093 rcutree.dump_tree= [KNL]
3094 Dump the structure of the rcu_node combining tree
3095 out at early boot. This is used for diagnostic
3096 purposes, to verify correct tree setup.
3098 rcutree.gp_cleanup_delay= [KNL]
3099 Set the number of jiffies to delay each step of
3100 RCU grace-period cleanup. This only has effect
3101 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3103 rcutree.gp_init_delay= [KNL]
3104 Set the number of jiffies to delay each step of
3105 RCU grace-period initialization. This only has
3106 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3109 rcutree.gp_preinit_delay= [KNL]
3110 Set the number of jiffies to delay each step of
3111 RCU grace-period pre-initialization, that is,
3112 the propagation of recent CPU-hotplug changes up
3113 the rcu_node combining tree. This only has effect
3114 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3116 rcutree.rcu_fanout_exact= [KNL]
3117 Disable autobalancing of the rcu_node combining
3118 tree. This is used by rcutorture, and might
3119 possibly be useful for architectures having high
3120 cache-to-cache transfer latencies.
3122 rcutree.rcu_fanout_leaf= [KNL]
3123 Change the number of CPUs assigned to each
3124 leaf rcu_node structure. Useful for very
3125 large systems, which will choose the value 64,
3126 and for NUMA systems with large remote-access
3127 latencies, which will choose a value aligned
3128 with the appropriate hardware boundaries.
3130 rcutree.jiffies_till_sched_qs= [KNL]
3131 Set required age in jiffies for a
3132 given grace period before RCU starts
3133 soliciting quiescent-state help from
3134 rcu_note_context_switch().
3136 rcutree.jiffies_till_first_fqs= [KNL]
3137 Set delay from grace-period initialization to
3138 first attempt to force quiescent states.
3139 Units are jiffies, minimum value is zero,
3140 and maximum value is HZ.
3142 rcutree.jiffies_till_next_fqs= [KNL]
3143 Set delay between subsequent attempts to force
3144 quiescent states. Units are jiffies, minimum
3145 value is one, and maximum value is HZ.
3147 rcutree.kthread_prio= [KNL,BOOT]
3148 Set the SCHED_FIFO priority of the RCU per-CPU
3149 kthreads (rcuc/N). This value is also used for
3150 the priority of the RCU boost threads (rcub/N)
3151 and for the RCU grace-period kthreads (rcu_bh,
3152 rcu_preempt, and rcu_sched). If RCU_BOOST is
3153 set, valid values are 1-99 and the default is 1
3154 (the least-favored priority). Otherwise, when
3155 RCU_BOOST is not set, valid values are 0-99 and
3156 the default is zero (non-realtime operation).
3158 rcutree.rcu_nocb_leader_stride= [KNL]
3159 Set the number of NOCB kthread groups, which
3160 defaults to the square root of the number of
3161 CPUs. Larger numbers reduces the wakeup overhead
3162 on the per-CPU grace-period kthreads, but increases
3163 that same overhead on each group's leader.
3165 rcutree.qhimark= [KNL]
3166 Set threshold of queued RCU callbacks beyond which
3167 batch limiting is disabled.
3169 rcutree.qlowmark= [KNL]
3170 Set threshold of queued RCU callbacks below which
3171 batch limiting is re-enabled.
3173 rcutree.rcu_idle_gp_delay= [KNL]
3174 Set wakeup interval for idle CPUs that have
3175 RCU callbacks (RCU_FAST_NO_HZ=y).
3177 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3178 Set wakeup interval for idle CPUs that have
3179 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3180 Lazy RCU callbacks are those which RCU can
3181 prove do nothing more than free memory.
3183 rcutorture.cbflood_inter_holdoff= [KNL]
3184 Set holdoff time (jiffies) between successive
3185 callback-flood tests.
3187 rcutorture.cbflood_intra_holdoff= [KNL]
3188 Set holdoff time (jiffies) between successive
3189 bursts of callbacks within a given callback-flood
3192 rcutorture.cbflood_n_burst= [KNL]
3193 Set the number of bursts making up a given
3194 callback-flood test. Set this to zero to
3195 disable callback-flood testing.
3197 rcutorture.cbflood_n_per_burst= [KNL]
3198 Set the number of callbacks to be registered
3199 in a given burst of a callback-flood test.
3201 rcutorture.fqs_duration= [KNL]
3202 Set duration of force_quiescent_state bursts
3205 rcutorture.fqs_holdoff= [KNL]
3206 Set holdoff time within force_quiescent_state bursts
3209 rcutorture.fqs_stutter= [KNL]
3210 Set wait time between force_quiescent_state bursts
3213 rcutorture.gp_cond= [KNL]
3214 Use conditional/asynchronous update-side
3215 primitives, if available.
3217 rcutorture.gp_exp= [KNL]
3218 Use expedited update-side primitives, if available.
3220 rcutorture.gp_normal= [KNL]
3221 Use normal (non-expedited) asynchronous
3222 update-side primitives, if available.
3224 rcutorture.gp_sync= [KNL]
3225 Use normal (non-expedited) synchronous
3226 update-side primitives, if available. If all
3227 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3228 rcutorture.gp_normal=, and rcutorture.gp_sync=
3229 are zero, rcutorture acts as if is interpreted
3230 they are all non-zero.
3232 rcutorture.n_barrier_cbs= [KNL]
3233 Set callbacks/threads for rcu_barrier() testing.
3235 rcutorture.nfakewriters= [KNL]
3236 Set number of concurrent RCU writers. These just
3237 stress RCU, they don't participate in the actual
3238 test, hence the "fake".
3240 rcutorture.nreaders= [KNL]
3241 Set number of RCU readers. The value -1 selects
3242 N-1, where N is the number of CPUs. A value
3243 "n" less than -1 selects N-n-2, where N is again
3244 the number of CPUs. For example, -2 selects N
3245 (the number of CPUs), -3 selects N+1, and so on.
3247 rcutorture.object_debug= [KNL]
3248 Enable debug-object double-call_rcu() testing.
3250 rcutorture.onoff_holdoff= [KNL]
3251 Set time (s) after boot for CPU-hotplug testing.
3253 rcutorture.onoff_interval= [KNL]
3254 Set time (s) between CPU-hotplug operations, or
3255 zero to disable CPU-hotplug testing.
3257 rcutorture.shuffle_interval= [KNL]
3258 Set task-shuffle interval (s). Shuffling tasks
3259 allows some CPUs to go into dyntick-idle mode
3260 during the rcutorture test.
3262 rcutorture.shutdown_secs= [KNL]
3263 Set time (s) after boot system shutdown. This
3264 is useful for hands-off automated testing.
3266 rcutorture.stall_cpu= [KNL]
3267 Duration of CPU stall (s) to test RCU CPU stall
3268 warnings, zero to disable.
3270 rcutorture.stall_cpu_holdoff= [KNL]
3271 Time to wait (s) after boot before inducing stall.
3273 rcutorture.stat_interval= [KNL]
3274 Time (s) between statistics printk()s.
3276 rcutorture.stutter= [KNL]
3277 Time (s) to stutter testing, for example, specifying
3278 five seconds causes the test to run for five seconds,
3279 wait for five seconds, and so on. This tests RCU's
3280 ability to transition abruptly to and from idle.
3282 rcutorture.test_boost= [KNL]
3283 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3284 "Maybe" means test if the RCU implementation
3285 under test support RCU priority boosting.
3287 rcutorture.test_boost_duration= [KNL]
3288 Duration (s) of each individual boost test.
3290 rcutorture.test_boost_interval= [KNL]
3291 Interval (s) between each boost test.
3293 rcutorture.test_no_idle_hz= [KNL]
3294 Test RCU's dyntick-idle handling. See also the
3295 rcutorture.shuffle_interval parameter.
3297 rcutorture.torture_runnable= [BOOT]
3298 Start rcutorture running at boot time.
3300 rcutorture.torture_type= [KNL]
3301 Specify the RCU implementation to test.
3303 rcutorture.verbose= [KNL]
3304 Enable additional printk() statements.
3306 rcupdate.rcu_expedited= [KNL]
3307 Use expedited grace-period primitives, for
3308 example, synchronize_rcu_expedited() instead
3309 of synchronize_rcu(). This reduces latency,
3310 but can increase CPU utilization, degrade
3311 real-time latency, and degrade energy efficiency.
3313 rcupdate.rcu_cpu_stall_suppress= [KNL]
3314 Suppress RCU CPU stall warning messages.
3316 rcupdate.rcu_cpu_stall_timeout= [KNL]
3317 Set timeout for RCU CPU stall warning messages.
3319 rcupdate.rcu_task_stall_timeout= [KNL]
3320 Set timeout in jiffies for RCU task stall warning
3321 messages. Disable with a value less than or equal
3324 rcupdate.rcu_self_test= [KNL]
3325 Run the RCU early boot self tests
3327 rcupdate.rcu_self_test_bh= [KNL]
3328 Run the RCU bh early boot self tests
3330 rcupdate.rcu_self_test_sched= [KNL]
3331 Run the RCU sched early boot self tests
3335 Run specified binary instead of /init from the ramdisk,
3336 used for early userspace startup. See initrd.
3339 Format (x86 or x86_64):
3340 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3342 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3344 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3345 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3346 reboot_force is either force or not specified,
3347 reboot_cpu is s[mp]#### with #### being the processor
3348 to be used for rebooting.
3351 [KNL, SMP] Set scheduler's default relax_domain_level.
3352 See Documentation/cgroups/cpusets.txt.
3354 relative_sleep_states=
3355 [SUSPEND] Use sleep state labeling where the deepest
3356 state available other than hibernation is always "mem".
3357 Format: { "0" | "1" }
3358 0 -- Traditional sleep state labels.
3359 1 -- Relative sleep state labels.
3361 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3363 reservetop= [X86-32]
3365 Reserves a hole at the top of the kernel virtual
3370 Set the amount of memory to reserve for BIOS at
3371 the bottom of the address space.
3373 reset_devices [KNL] Force drivers to reset the underlying device
3374 during initialization.
3377 Specify the partition device for software suspend
3379 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3381 resume_offset= [SWSUSP]
3382 Specify the offset from the beginning of the partition
3383 given by "resume=" at which the swap header is located,
3384 in <PAGE_SIZE> units (needed only for swap files).
3385 See Documentation/power/swsusp-and-swap-files.txt
3387 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3388 read the resume files
3390 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3391 Useful for devices that are detected asynchronously
3392 (e.g. USB and MMC devices).
3394 hibernate= [HIBERNATION]
3395 noresume Don't check if there's a hibernation image
3396 present during boot.
3397 nocompress Don't compress/decompress hibernation images.
3398 no Disable hibernation and resume.
3400 retain_initrd [RAM] Keep initrd memory after extraction
3402 rfkill.default_state=
3403 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3404 etc. communication is blocked by default.
3407 rfkill.master_switch_mode=
3408 0 The "airplane mode" button does nothing.
3409 1 The "airplane mode" button toggles between everything
3410 blocked and the previous configuration.
3411 2 The "airplane mode" button toggles between everything
3412 blocked and everything unblocked.
3414 rhash_entries= [KNL,NET]
3415 Set number of hash buckets for route cache
3417 ro [KNL] Mount root device read-only on boot
3419 root= [KNL] Root filesystem
3420 See name_to_dev_t comment in init/do_mounts.c.
3422 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3423 mount the root filesystem
3425 rootflags= [KNL] Set root filesystem mount option string
3427 rootfstype= [KNL] Set root filesystem type
3429 rootwait [KNL] Wait (indefinitely) for root device to show up.
3430 Useful for devices that are detected asynchronously
3431 (e.g. USB and MMC devices).
3433 rproc_mem=nn[KMG][@address]
3434 [KNL,ARM,CMA] Remoteproc physical memory block.
3435 Memory area to be used by remote processor image,
3438 rw [KNL] Mount root device read-write on boot
3440 S [KNL] Run init in single mode
3442 s390_iommu= [HW,S390]
3443 Set s390 IOTLB flushing mode
3445 With strict flushing every unmap operation will result in
3446 an IOTLB flush. Default is lazy flushing before reuse,
3450 See drivers/net/irda/sa1100_ir.c.
3452 sbni= [NET] Granch SBNI12 leased line adapter
3454 sched_debug [KNL] Enables verbose scheduler debug messages.
3456 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3457 xtime_lock contention on larger systems, and/or RCU lock
3458 contention on all systems with CONFIG_MAXSMP set.
3459 Format: { "0" | "1" }
3460 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3462 Note: increases power consumption, thus should only be
3463 enabled if running jitter sensitive (HPC/RT) workloads.
3465 security= [SECURITY] Choose a security module to enable at boot.
3466 If this boot parameter is not specified, only the first
3467 security module asking for security registration will be
3468 loaded. An invalid security module name will be treated
3469 as if no module has been chosen.
3471 selinux= [SELINUX] Disable or enable SELinux at boot time.
3472 Format: { "0" | "1" }
3473 See security/selinux/Kconfig help text.
3476 Default value is set via kernel config option.
3477 If enabled at boot time, /selinux/disable can be used
3478 later to disable prior to initial policy load.
3480 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3481 Format: { "0" | "1" }
3482 See security/apparmor/Kconfig help text
3485 Default value is set via kernel config option.
3487 serialnumber [BUGS=X86-32]
3490 Maximal number of shapers.
3492 show_msr= [x86] show boot-time MSR settings
3493 Format: { <integer> }
3494 Show boot-time (BIOS-initialized) MSR settings.
3495 The parameter means the number of CPUs to show,
3496 for example 1 means boot CPU only.
3504 Disable merging of slabs with similar size. May be
3505 necessary if there is some reason to distinguish
3506 allocs to different slabs. Debug options disable
3507 merging on their own.
3508 For more information see Documentation/vm/slub.txt.
3510 slab_max_order= [MM, SLAB]
3511 Determines the maximum allowed order for slabs.
3512 A high setting may cause OOMs due to memory
3513 fragmentation. Defaults to 1 for systems with
3514 more than 32MB of RAM, 0 otherwise.
3516 slub_debug[=options[,slabs]] [MM, SLUB]
3517 Enabling slub_debug allows one to determine the
3518 culprit if slab objects become corrupted. Enabling
3519 slub_debug can create guard zones around objects and
3520 may poison objects when not in use. Also tracks the
3521 last alloc / free. For more information see
3522 Documentation/vm/slub.txt.
3524 slub_max_order= [MM, SLUB]
3525 Determines the maximum allowed order for slabs.
3526 A high setting may cause OOMs due to memory
3527 fragmentation. For more information see
3528 Documentation/vm/slub.txt.
3530 slub_min_objects= [MM, SLUB]
3531 The minimum number of objects per slab. SLUB will
3532 increase the slab order up to slub_max_order to
3533 generate a sufficiently large slab able to contain
3534 the number of objects indicated. The higher the number
3535 of objects the smaller the overhead of tracking slabs
3536 and the less frequently locks need to be acquired.
3537 For more information see Documentation/vm/slub.txt.
3539 slub_min_order= [MM, SLUB]
3540 Determines the minimum page order for slabs. Must be
3541 lower than slub_max_order.
3542 For more information see Documentation/vm/slub.txt.
3544 slub_nomerge [MM, SLUB]
3545 Same with slab_nomerge. This is supported for legacy.
3546 See slab_nomerge for more information.
3549 Format: <io1>[,<io2>[,...,<io8>]]
3551 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3552 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3553 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3554 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3555 smsc-ircc2.ircc_irq= [HW] IRQ line
3556 smsc-ircc2.ircc_dma= [HW] DMA channel
3557 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3558 0: Toshiba Satellite 1800 (GP data pin select)
3559 1: Fast pin select (default)
3563 [KNL] Should the soft-lockup detector generate panics.
3566 softlockup_all_cpu_backtrace=
3567 [KNL] Should the soft-lockup detector generate
3568 backtraces on all cpus.
3571 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3572 See Documentation/laptops/sonypi.txt
3574 spia_io_base= [HW,MTD]
3580 Enabled the stack tracer on boot up.
3582 stacktrace_filter=[function-list]
3583 [FTRACE] Limit the functions that the stack tracer
3584 will trace at boot up. function-list is a comma separated
3585 list of functions. This list can be changed at run
3586 time by the stack_trace_filter file in the debugfs
3587 tracing directory. Note, this enables stack tracing
3588 and the stacktrace above is not needed.
3592 Set the STI (builtin display/keyboard on the HP-PARISC
3593 machines) console (graphic card) which should be used
3594 as the initial boot-console.
3595 See also comment in drivers/video/console/sticore.c.
3598 See comment in drivers/video/console/sticore.c.
3601 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3603 sunrpc.min_resvport=
3604 sunrpc.max_resvport=
3606 SunRPC servers often require that client requests
3607 originate from a privileged port (i.e. a port in the
3608 range 0 < portnr < 1024).
3609 An administrator who wishes to reserve some of these
3610 ports for other uses may adjust the range that the
3611 kernel's sunrpc client considers to be privileged
3612 using these two parameters to set the minimum and
3613 maximum port values.
3617 Control how the NFS server code allocates CPUs to
3618 service thread pools. Depending on how many NICs
3619 you have and where their interrupts are bound, this
3620 option will affect which CPUs will do NFS serving.
3621 Note: this parameter cannot be changed while the
3622 NFS server is running.
3624 auto the server chooses an appropriate mode
3625 automatically using heuristics
3626 global a single global pool contains all CPUs
3627 percpu one pool for each CPU
3628 pernode one pool for each NUMA node (equivalent
3629 to global on non-NUMA machines)
3631 sunrpc.tcp_slot_table_entries=
3632 sunrpc.udp_slot_table_entries=
3634 Sets the upper limit on the number of simultaneous
3635 RPC calls that can be sent from the client to a
3636 server. Increasing these values may allow you to
3637 improve throughput, but will also increase the
3638 amount of memory reserved for use by the client.
3640 suspend.pm_test_delay=
3642 Sets the number of seconds to remain in a suspend test
3643 mode before resuming the system (see
3644 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3645 is set. Default value is 5.
3648 [KNL] Enable accounting of swap in memory resource
3649 controller if no parameter or 1 is given or disable
3650 it if 0 is given (See Documentation/cgroups/memory.txt)
3652 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3653 Format: { <int> | force }
3654 <int> -- Number of I/O TLB slabs
3655 force -- force using of bounce buffers even if they
3656 wouldn't be automatically used by the kernel
3660 sysfs.deprecated=0|1 [KNL]
3661 Enable/disable old style sysfs layout for old udev
3662 on older distributions. When this option is enabled
3663 very new udev will not work anymore. When this option
3664 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3665 in older udev will not work anymore.
3666 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3667 the kernel configuration.
3669 sysrq_always_enabled
3671 Ignore sysrq setting - this boot parameter will
3672 neutralize any effect of /proc/sys/kernel/sysrq.
3673 Useful for debugging.
3675 tcpmhash_entries= [KNL,NET]
3676 Set the number of tcp_metrics_hash slots.
3677 Default value is 8192 or 16384 depending on total
3678 ram pages. This is used to specify the TCP metrics
3679 cache size. See Documentation/networking/ip-sysctl.txt
3680 "tcp_no_metrics_save" section for more details.
3684 test_suspend= [SUSPEND][,N]
3685 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3686 standby suspend) or "freeze" (for suspend type freeze)
3687 as the system sleep state during system startup with
3688 the optional capability to repeat N number of times.
3689 The system is woken from this state using a
3690 wakeup-capable RTC alarm.
3692 thash_entries= [KNL,NET]
3693 Set number of hash buckets for TCP connection
3695 thermal.act= [HW,ACPI]
3696 -1: disable all active trip points in all thermal zones
3697 <degrees C>: override all lowest active trip points
3699 thermal.crt= [HW,ACPI]
3700 -1: disable all critical trip points in all thermal zones
3701 <degrees C>: override all critical trip points
3703 thermal.nocrt= [HW,ACPI]
3704 Set to disable actions on ACPI thermal zone
3705 critical and hot trip points.
3707 thermal.off= [HW,ACPI]
3708 1: disable ACPI thermal control
3710 thermal.psv= [HW,ACPI]
3711 -1: disable all passive trip points
3712 <degrees C>: override all passive trip points to this
3715 thermal.tzp= [HW,ACPI]
3716 Specify global default ACPI thermal zone polling rate
3717 <deci-seconds>: poll all this frequency
3718 0: no polling (default)
3721 Force threading of all interrupt handlers except those
3722 marked explicitly IRQF_NO_THREAD.
3725 Enable the Transcendent memory driver if built-in.
3727 tmem.cleancache=0|1 [KNL, XEN]
3728 Default is on (1). Disable the usage of the cleancache
3729 API to send anonymous pages to the hypervisor.
3731 tmem.frontswap=0|1 [KNL, XEN]
3732 Default is on (1). Disable the usage of the frontswap
3733 API to send swap pages to the hypervisor. If disabled
3734 the selfballooning and selfshrinking are force disabled.
3736 tmem.selfballooning=0|1 [KNL, XEN]
3737 Default is on (1). Disable the driving of swap pages
3740 tmem.selfshrinking=0|1 [KNL, XEN]
3741 Default is on (1). Partial swapoff that immediately
3742 transfers pages from Xen hypervisor back to the
3743 kernel based on different criteria.
3747 Specify if the kernel should make use of the cpu
3748 topology information if the hardware supports this.
3749 The scheduler will make use of this information and
3750 e.g. base its process migration decisions on it.
3753 topology_updates= [KNL, PPC, NUMA]
3755 Specify if the kernel should ignore (off)
3756 topology updates sent by the hypervisor to this
3761 tpm_suspend_pcr=[HW,TPM]
3762 Format: integer pcr id
3763 Specify that at suspend time, the tpm driver
3764 should extend the specified pcr with zeros,
3765 as a workaround for some chips which fail to
3766 flush the last written pcr on TPM_SaveState.
3767 This will guarantee that all the other pcrs
3770 trace_buf_size=nn[KMG]
3771 [FTRACE] will set tracing buffer size on each cpu.
3773 trace_event=[event-list]
3774 [FTRACE] Set and start specified trace events in order
3775 to facilitate early boot debugging.
3776 See also Documentation/trace/events.txt
3778 trace_options=[option-list]
3779 [FTRACE] Enable or disable tracer options at boot.
3780 The option-list is a comma delimited list of options
3781 that can be enabled or disabled just as if you were
3782 to echo the option name into
3784 /sys/kernel/debug/tracing/trace_options
3786 For example, to enable stacktrace option (to dump the
3787 stack trace of each event), add to the command line:
3789 trace_options=stacktrace
3791 See also Documentation/trace/ftrace.txt "trace options"
3795 Have the tracepoints sent to printk as well as the
3796 tracing ring buffer. This is useful for early boot up
3797 where the system hangs or reboots and does not give the
3798 option for reading the tracing buffer or performing a
3799 ftrace_dump_on_oops.
3801 To turn off having tracepoints sent to printk,
3802 echo 0 > /proc/sys/kernel/tracepoint_printk
3803 Note, echoing 1 into this file without the
3804 tracepoint_printk kernel cmdline option has no effect.
3808 Having tracepoints sent to printk() and activating high
3809 frequency tracepoints such as irq or sched, can cause
3810 the system to live lock.
3813 [FTRACE] enable this option to disable tracing when a
3814 warning is hit. This turns off "tracing_on". Tracing can
3815 be enabled again by echoing '1' into the "tracing_on"
3816 file located in /sys/kernel/debug/tracing/
3818 This option is useful, as it disables the trace before
3819 the WARNING dump is called, which prevents the trace to
3820 be filled with content caused by the warning output.
3822 This option can also be set at run time via the sysctl
3823 option: kernel/traceoff_on_warning
3825 transparent_hugepage=
3827 Format: [always|madvise|never]
3828 Can be used to control the default behavior of the system
3829 with respect to transparent hugepages.
3830 See Documentation/vm/transhuge.txt for more details.
3832 tsc= Disable clocksource stability checks for TSC.
3834 [x86] reliable: mark tsc clocksource as reliable, this
3835 disables clocksource verification at runtime, as well
3836 as the stability checks done at bootup. Used to enable
3837 high-resolution timer mode on older hardware, and in
3838 virtualized environment.
3839 [x86] noirqtime: Do not use TSC to do irq accounting.
3840 Used to run time disable IRQ_TIME_ACCOUNTING on any
3841 platforms where RDTSC is slow and this accounting
3844 turbografx.map[2|3]= [HW,JOY]
3845 TurboGraFX parallel port interface
3847 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3848 See also Documentation/input/joystick-parport.txt
3850 udbg-immortal [PPC] When debugging early kernel crashes that
3851 happen after console_init() and before a proper
3852 console driver takes over, this boot options might
3853 help "seeing" what's going on.
3855 uhash_entries= [KNL,NET]
3856 Set number of hash buckets for UDP/UDP-Lite connections
3859 [USB] Ignore overcurrent events (default N).
3860 Some badly-designed motherboards generate lots of
3861 bogus events, for ports that aren't wired to
3862 anything. Set this parameter to avoid log spamming.
3863 Note that genuine overcurrent events won't be
3867 [X86] Cause panic on unknown NMI.
3869 usbcore.authorized_default=
3870 [USB] Default USB device authorization:
3871 (default -1 = authorized except for wireless USB,
3872 0 = not authorized, 1 = authorized)
3874 usbcore.autosuspend=
3875 [USB] The autosuspend time delay (in seconds) used
3876 for newly-detected USB devices (default 2). This
3877 is the time required before an idle device will be
3878 autosuspended. Devices for which the delay is set
3879 to a negative value won't be autosuspended at all.
3881 usbcore.usbfs_snoop=
3882 [USB] Set to log all usbfs traffic (default 0 = off).
3884 usbcore.blinkenlights=
3885 [USB] Set to cycle leds on hubs (default 0 = off).
3887 usbcore.old_scheme_first=
3888 [USB] Start with the old device initialization
3889 scheme (default 0 = off).
3891 usbcore.usbfs_memory_mb=
3892 [USB] Memory limit (in MB) for buffers allocated by
3893 usbfs (default = 16, 0 = max = 2047).
3895 usbcore.use_both_schemes=
3896 [USB] Try the other device initialization scheme
3897 if the first one fails (default 1 = enabled).
3899 usbcore.initial_descriptor_timeout=
3900 [USB] Specifies timeout for the initial 64-byte
3901 USB_REQ_GET_DESCRIPTOR request in milliseconds
3902 (default 5000 = 5.0 seconds).
3905 [USBHID] The interval which mice are to be polled at.
3907 usb-storage.delay_use=
3908 [UMS] The delay in seconds before a new device is
3909 scanned for Logical Units (default 1).
3912 [UMS] A list of quirks entries to supplement or
3913 override the built-in unusual_devs list. List
3914 entries are separated by commas. Each entry has
3915 the form VID:PID:Flags where VID and PID are Vendor
3916 and Product ID values (4-digit hex numbers) and
3917 Flags is a set of characters, each corresponding
3918 to a common usb-storage quirk flag as follows:
3919 a = SANE_SENSE (collect more than 18 bytes
3921 b = BAD_SENSE (don't collect more than 18
3922 bytes of sense data);
3923 c = FIX_CAPACITY (decrease the reported
3924 device capacity by one sector);
3925 d = NO_READ_DISC_INFO (don't use
3926 READ_DISC_INFO command);
3927 e = NO_READ_CAPACITY_16 (don't use
3928 READ_CAPACITY_16 command);
3929 f = NO_REPORT_OPCODES (don't use report opcodes
3931 g = MAX_SECTORS_240 (don't transfer more than
3932 240 sectors at a time, uas only);
3933 h = CAPACITY_HEURISTICS (decrease the
3934 reported device capacity by one
3935 sector if the number is odd);
3936 i = IGNORE_DEVICE (don't bind to this
3938 j = NO_REPORT_LUNS (don't use report luns
3940 l = NOT_LOCKABLE (don't try to lock and
3941 unlock ejectable media);
3942 m = MAX_SECTORS_64 (don't transfer more
3943 than 64 sectors = 32 KB at a time);
3944 n = INITIAL_READ10 (force a retry of the
3945 initial READ(10) command);
3946 o = CAPACITY_OK (accept the capacity
3947 reported by the device);
3948 p = WRITE_CACHE (the device cache is ON
3950 r = IGNORE_RESIDUE (the device reports
3951 bogus residue values);
3952 s = SINGLE_LUN (the device has only one
3954 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3955 commands, uas only);
3956 u = IGNORE_UAS (don't bind to the uas driver);
3957 w = NO_WP_DETECT (don't test whether the
3958 medium is write-protected).
3959 Example: quirks=0419:aaf5:rl,0421:0433:rc
3961 user_debug= [KNL,ARM]
3963 See arch/arm/Kconfig.debug help text.
3964 1 - undefined instruction events
3966 4 - invalid data aborts
3969 Example: user_debug=31
3972 [X86] Flags controlling user PTE allocations.
3974 nohigh = do not allocate PTE pages in
3975 HIGHMEM regardless of setting
3979 On X86_32, this is an alias for vdso32=. Otherwise:
3981 vdso=1: enable VDSO (the default)
3982 vdso=0: disable VDSO mapping
3984 vdso32= [X86] Control the 32-bit vDSO
3985 vdso32=1: enable 32-bit VDSO
3986 vdso32=0 or vdso32=2: disable 32-bit VDSO
3988 See the help text for CONFIG_COMPAT_VDSO for more
3989 details. If CONFIG_COMPAT_VDSO is set, the default is
3990 vdso32=0; otherwise, the default is vdso32=1.
3992 For compatibility with older kernels, vdso32=2 is an
3995 Try vdso32=0 if you encounter an error that says:
3996 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3999 vector=percpu: enable percpu vector domain
4001 video= [FB] Frame buffer configuration
4002 See Documentation/fb/modedb.txt.
4004 video.brightness_switch_enabled= [0,1]
4005 If set to 1, on receiving an ACPI notify event
4006 generated by hotkey, video driver will adjust brightness
4007 level and then send out the event to user space through
4008 the allocated input device; If set to 0, video driver
4009 will only send out the event without touching backlight
4014 [VMMIO] Memory mapped virtio (platform) device.
4016 <size>@<baseaddr>:<irq>[:<id>]
4018 <size> := size (can use standard suffixes
4020 <baseaddr> := physical base address
4021 <irq> := interrupt number (as passed to
4023 <id> := (optional) platform device id
4025 virtio_mmio.device=1K@0x100b0000:48:7
4027 Can be used multiple times for multiple devices.
4029 vga= [BOOT,X86-32] Select a particular video mode
4030 See Documentation/x86/boot.txt and
4031 Documentation/svga.txt.
4032 Use vga=ask for menu.
4033 This is actually a boot loader parameter; the value is
4034 passed to the kernel using a special protocol.
4036 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4037 size of <nn>. This can be used to increase the
4038 minimum size (128MB on x86). It can also be used to
4039 decrease the size and leave more room for directly
4042 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4045 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4048 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4052 Controls the behavior of vsyscalls (i.e. calls to
4053 fixed addresses of 0xffffffffff600x00 from legacy
4054 code). Most statically-linked binaries and older
4055 versions of glibc use these calls. Because these
4056 functions are at fixed addresses, they make nice
4057 targets for exploits that can control RIP.
4059 emulate [default] Vsyscalls turn into traps and are
4060 emulated reasonably safely.
4062 native Vsyscalls are native syscall instructions.
4063 This is a little bit faster than trapping
4064 and makes a few dynamic recompilers work
4065 better than they would in emulation mode.
4066 It also makes exploits much easier to write.
4068 none Vsyscalls don't work at all. This makes
4069 them quite hard to use for exploits but
4070 might break your system.
4072 vt.color= [VT] Default text color.
4073 Format: 0xYX, X = foreground, Y = background.
4074 Default: 0x07 = light gray on black.
4076 vt.cur_default= [VT] Default cursor shape.
4077 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4078 the parameters of the <Esc>[?A;B;Cc escape sequence;
4079 see VGA-softcursor.txt. Default: 2 = underline.
4081 vt.default_blu= [VT]
4082 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4083 Change the default blue palette of the console.
4084 This is a 16-member array composed of values
4087 vt.default_grn= [VT]
4088 Format: <green0>,<green1>,<green2>,...,<green15>
4089 Change the default green palette of the console.
4090 This is a 16-member array composed of values
4093 vt.default_red= [VT]
4094 Format: <red0>,<red1>,<red2>,...,<red15>
4095 Change the default red palette of the console.
4096 This is a 16-member array composed of values
4102 Set system-wide default UTF-8 mode for all tty's.
4103 Default is 1, i.e. UTF-8 mode is enabled for all
4104 newly opened terminals.
4106 vt.global_cursor_default=
4109 Set system-wide default for whether a cursor
4110 is shown on new VTs. Default is -1,
4111 i.e. cursors will be created by default unless
4112 overridden by individual drivers. 0 will hide
4113 cursors, 1 will display them.
4115 vt.italic= [VT] Default color for italic text; 0-15.
4118 vt.underline= [VT] Default color for underlined text; 0-15.
4121 watchdog timers [HW,WDT] For information on watchdog timers,
4122 see Documentation/watchdog/watchdog-parameters.txt
4123 or other driver-specific files in the
4124 Documentation/watchdog/ directory.
4126 workqueue.disable_numa
4127 By default, all work items queued to unbound
4128 workqueues are affine to the NUMA nodes they're
4129 issued on, which results in better behavior in
4130 general. If NUMA affinity needs to be disabled for
4131 whatever reason, this option can be used. Note
4132 that this also can be controlled per-workqueue for
4133 workqueues visible under /sys/bus/workqueue/.
4135 workqueue.power_efficient
4136 Per-cpu workqueues are generally preferred because
4137 they show better performance thanks to cache
4138 locality; unfortunately, per-cpu workqueues tend to
4139 be more power hungry than unbound workqueues.
4141 Enabling this makes the per-cpu workqueues which
4142 were observed to contribute significantly to power
4143 consumption unbound, leading to measurably lower
4144 power usage at the cost of small performance
4147 The default value of this parameter is determined by
4148 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4150 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4151 default x2apic cluster mode on platforms
4154 x86_intel_mid_timer= [X86-32,APBT]
4155 Choose timer option for x86 Intel MID platform.
4156 Two valid options are apbt timer only and lapic timer
4157 plus one apbt timer for broadcast timer.
4158 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4160 xen_512gb_limit [KNL,X86-64,XEN]
4161 Restricts the kernel running paravirtualized under Xen
4162 to use only up to 512 GB of RAM. The reason to do so is
4163 crash analysis tools and Xen tools for doing domain
4164 save/restore/migration must be enabled to handle larger
4167 xen_emul_unplug= [HW,X86,XEN]
4168 Unplug Xen emulated devices
4169 Format: [unplug0,][unplug1]
4170 ide-disks -- unplug primary master IDE devices
4171 aux-ide-disks -- unplug non-primary-master IDE devices
4172 nics -- unplug network devices
4173 all -- unplug all emulated devices (NICs and IDE disks)
4174 unnecessary -- unplugging emulated devices is
4175 unnecessary even if the host did not respond to
4177 never -- do not unplug even if version check succeeds
4179 xen_nopvspin [X86,XEN]
4180 Disables the ticketlock slowpath using Xen PV
4184 Disables the PV optimizations forcing the HVM guest to
4185 run as generic HVM guest with no PV drivers.
4187 xirc2ps_cs= [NET,PCMCIA]
4189 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4191 ______________________________________________________________________
4195 Add more DRM drivers.
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