4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
168 acpi= [HW,ACPI,X86,ARM64]
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt |
172 force -- enable ACPI if default was off
173 off -- disable ACPI if default was on
174 noirq -- do not use ACPI for IRQ routing
175 strict -- Be less tolerant of platforms that are not
176 strictly ACPI specification compliant.
177 rsdt -- prefer RSDT over (default) XSDT
178 copy_dsdt -- copy DSDT to memory
179 For ARM64, ONLY "acpi=off" or "acpi=force" are available
181 See also Documentation/power/runtime_pm.txt, pci=noacpi
183 acpi_apic_instance= [ACPI, IOAPIC]
185 2: use 2nd APIC table, if available
186 1,0: use 1st APIC table
189 acpi_backlight= [HW,ACPI]
190 acpi_backlight=vendor
192 If set to vendor, prefer vendor specific driver
193 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
194 of the ACPI video.ko driver.
196 acpica_no_return_repair [HW, ACPI]
197 Disable AML predefined validation mechanism
198 This mechanism can repair the evaluation result to make
199 the return objects more ACPI specification compliant.
200 This option is useful for developers to identify the
201 root cause of an AML interpreter issue when the issue
202 has something to do with the repair mechanism.
204 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
205 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
207 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
208 debug output. Bits in debug_layer correspond to a
209 _COMPONENT in an ACPI source file, e.g.,
210 #define _COMPONENT ACPI_PCI_COMPONENT
211 Bits in debug_level correspond to a level in
212 ACPI_DEBUG_PRINT statements, e.g.,
213 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
214 The debug_level mask defaults to "info". See
215 Documentation/acpi/debug.txt for more information about
216 debug layers and levels.
218 Enable processor driver info messages:
219 acpi.debug_layer=0x20000000
220 Enable PCI/PCI interrupt routing info messages:
221 acpi.debug_layer=0x400000
222 Enable AML "Debug" output, i.e., stores to the Debug
223 object while interpreting AML:
224 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
225 Enable all messages related to ACPI hardware:
226 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
228 Some values produce so much output that the system is
229 unusable. The "log_buf_len" parameter may be useful
230 if you need to capture more output.
232 acpi_enforce_resources= [ACPI]
233 { strict | lax | no }
234 Check for resource conflicts between native drivers
235 and ACPI OperationRegions (SystemIO and SystemMemory
236 only). IO ports and memory declared in ACPI might be
237 used by the ACPI subsystem in arbitrary AML code and
238 can interfere with legacy drivers.
239 strict (default): access to resources claimed by ACPI
240 is denied; legacy drivers trying to access reserved
241 resources will fail to bind to device using them.
242 lax: access to resources claimed by ACPI is allowed;
243 legacy drivers trying to access reserved resources
244 will bind successfully but a warning message is logged.
245 no: ACPI OperationRegions are not marked as reserved,
246 no further checks are performed.
248 acpi_force_table_verification [HW,ACPI]
249 Enable table checksum verification during early stage.
250 By default, this is disabled due to x86 early mapping
253 acpi_irq_balance [HW,ACPI]
254 ACPI will balance active IRQs
257 acpi_irq_nobalance [HW,ACPI]
258 ACPI will not move active IRQs (default)
261 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
262 Format: <irq>,<irq>...
264 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
266 Format: <irq>,<irq>...
268 acpi_no_auto_serialize [HW,ACPI]
269 Disable auto-serialization of AML methods
270 AML control methods that contain the opcodes to create
271 named objects will be marked as "Serialized" by the
272 auto-serialization feature.
273 This feature is enabled by default.
274 This option allows to turn off the feature.
276 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
279 acpi_no_static_ssdt [HW,ACPI]
280 Disable installation of static SSDTs at early boot time
281 By default, SSDTs contained in the RSDT/XSDT will be
282 installed automatically and they will appear under
283 /sys/firmware/acpi/tables.
284 This option turns off this feature.
285 Note that specifying this option does not affect
286 dynamic table installation which will install SSDT
287 tables to /sys/firmware/acpi/tables/dynamic.
289 acpi_rsdp= [ACPI,EFI,KEXEC]
290 Pass the RSDP address to the kernel, mostly used
291 on machines running EFI runtime service to boot the
292 second kernel for kdump.
294 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
295 Format: To spoof as Windows 98: ="Microsoft Windows"
297 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
298 of 2 which is mandated by ACPI 6) as the supported ACPI
299 specification revision (when using this switch, it may
300 be necessary to carry out a cold reboot _twice_ in a
301 row to make it take effect on the platform firmware).
303 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
304 acpi_osi="string1" # add string1
305 acpi_osi="!string2" # remove string2
306 acpi_osi=!* # remove all strings
307 acpi_osi=! # disable all built-in OS vendor
309 acpi_osi= # disable all strings
311 'acpi_osi=!' can be used in combination with single or
312 multiple 'acpi_osi="string1"' to support specific OS
313 vendor string(s). Note that such command can only
314 affect the default state of the OS vendor strings, thus
315 it cannot affect the default state of the feature group
316 strings and the current state of the OS vendor strings,
317 specifying it multiple times through kernel command line
318 is meaningless. This command is useful when one do not
319 care about the state of the feature group strings which
320 should be controlled by the OSPM.
322 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
323 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
324 can make '_OSI("Windows 2000")' TRUE.
326 'acpi_osi=' cannot be used in combination with other
327 'acpi_osi=' command lines, the _OSI method will not
328 exist in the ACPI namespace. NOTE that such command can
329 only affect the _OSI support state, thus specifying it
330 multiple times through kernel command line is also
333 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
336 'acpi_osi=!*' can be used in combination with single or
337 multiple 'acpi_osi="string1"' to support specific
338 string(s). Note that such command can affect the
339 current state of both the OS vendor strings and the
340 feature group strings, thus specifying it multiple times
341 through kernel command line is meaningful. But it may
342 still not able to affect the final state of a string if
343 there are quirks related to this string. This command
344 is useful when one want to control the state of the
345 feature group strings to debug BIOS issues related to
348 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
349 '_OSI("Module Device")' FALSE.
350 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
351 '_OSI("Module Device")' TRUE.
352 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
354 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
356 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
357 they all will make '_OSI("Windows 2000")' TRUE.
360 Override the pmtimer bug detection: force the kernel
361 to assume that this machine's pmtimer latches its value
362 and always returns good values.
364 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
365 Format: { level | edge | high | low }
367 acpi_skip_timer_override [HW,ACPI]
368 Recognize and ignore IRQ0/pin2 Interrupt Override.
369 For broken nForce2 BIOS resulting in XT-PIC timer.
371 acpi_sleep= [HW,ACPI] Sleep options
372 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
373 old_ordering, nonvs, sci_force_enable }
374 See Documentation/power/video.txt for information on
376 s3_beep is for debugging; it makes the PC's speaker beep
377 as soon as the kernel's real-mode entry point is called.
378 s4_nohwsig prevents ACPI hardware signature from being
379 used during resume from hibernation.
380 old_ordering causes the ACPI 1.0 ordering of the _PTS
381 control method, with respect to putting devices into
382 low power states, to be enforced (the ACPI 2.0 ordering
383 of _PTS is used by default).
384 nonvs prevents the kernel from saving/restoring the
385 ACPI NVS memory during suspend/hibernation and resume.
386 sci_force_enable causes the kernel to set SCI_EN directly
387 on resume from S1/S3 (which is against the ACPI spec,
388 but some broken systems don't work without it).
390 acpi_use_timer_override [HW,ACPI]
391 Use timer override. For some broken Nvidia NF5 boards
392 that require a timer override, but don't have HPET
394 add_efi_memmap [EFI; X86] Include EFI memory map in
395 kernel's map of available physical RAM.
398 { off | try_unsupported }
399 off: disable AGP support
400 try_unsupported: try to drive unsupported chipsets
401 (may crash computer or cause data corruption)
404 See Documentation/sound/alsa/alsa-parameters.txt
407 Allow the default userspace alignment fault handler
408 behaviour to be specified. Bit 0 enables warnings,
409 bit 1 enables fixups, and bit 2 sends a segfault.
411 align_va_addr= [X86-64]
412 Align virtual addresses by clearing slice [14:12] when
413 allocating a VMA at process creation time. This option
414 gives you up to 3% performance improvement on AMD F15h
415 machines (where it is enabled by default) for a
416 CPU-intensive style benchmark, and it can vary highly in
417 a microbenchmark depending on workload and compiler.
419 32: only for 32-bit processes
420 64: only for 64-bit processes
421 on: enable for both 32- and 64-bit processes
422 off: disable for both 32- and 64-bit processes
424 alloc_snapshot [FTRACE]
425 Allocate the ftrace snapshot buffer on boot up when the
426 main buffer is allocated. This is handy if debugging
427 and you need to use tracing_snapshot() on boot up, and
428 do not want to use tracing_snapshot_alloc() as it needs
429 to be done where GFP_KERNEL allocations are allowed.
431 amd_iommu= [HW,X86-64]
432 Pass parameters to the AMD IOMMU driver in the system.
434 fullflush - enable flushing of IO/TLB entries when
435 they are unmapped. Otherwise they are
436 flushed before they will be reused, which
438 off - do not initialize any AMD IOMMU found in
440 force_isolation - Force device isolation for all
441 devices. The IOMMU driver is not
442 allowed anymore to lift isolation
443 requirements as needed. This option
444 does not override iommu=pt
446 amd_iommu_dump= [HW,X86-64]
447 Enable AMD IOMMU driver option to dump the ACPI table
448 for AMD IOMMU. With this option enabled, AMD IOMMU
449 driver will print ACPI tables for AMD IOMMU during
450 IOMMU initialization.
452 amijoy.map= [HW,JOY] Amiga joystick support
453 Map of devices attached to JOY0DAT and JOY1DAT
455 See also Documentation/input/joystick.txt
457 analog.map= [HW,JOY] Analog joystick and gamepad support
458 Specifies type or capabilities of an analog joystick
459 connected to one of 16 gameports
460 Format: <type1>,<type2>,..<type16>
463 Power management functions (SPARCstation-4/5 + deriv.)
465 Disable APC CPU standby support. SPARCstation-Fox does
466 not play well with APC CPU idle - disable it if you have
467 APC and your system crashes randomly.
469 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
470 Change the output verbosity whilst booting
471 Format: { quiet (default) | verbose | debug }
472 Change the amount of debugging information output
473 when initialising the APIC and IO-APIC components.
476 See Documentation/networking/ipv6.txt.
478 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
479 Limit apic dumping. The parameter defines the maximal
480 number of local apics being dumped. Also it is possible
481 to set it to "all" by meaning -- no limit here.
482 Format: { 1 (default) | 2 | ... | all }.
483 The parameter valid if only apic=debug or
484 apic=verbose is specified.
485 Example: apic=debug show_lapic=all
487 apm= [APM] Advanced Power Management
488 See header of arch/x86/kernel/apm_32.c.
490 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
491 Format: <io>,<irq>,<nodeID>
495 atarimouse= [HW,MOUSE] Atari Mouse
497 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
498 EzKey and similar keyboards
500 atkbd.reset= [HW] Reset keyboard during initialization
502 atkbd.set= [HW] Select keyboard code set
503 Format: <int> (2 = AT (default), 3 = PS/2)
505 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
508 atkbd.softraw= [HW] Choose between synthetic and real raw mode
509 Format: <bool> (0 = real, 1 = synthetic (default))
511 atkbd.softrepeat= [HW]
512 Use software keyboard repeat
514 audit= [KNL] Enable the audit sub-system
515 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
516 0 - kernel audit is disabled and can not be enabled
517 until the next reboot
518 unset - kernel audit is initialized but disabled and
519 will be fully enabled by the userspace auditd.
520 1 - kernel audit is initialized and partially enabled,
521 storing at most audit_backlog_limit messages in
522 RAM until it is fully enabled by the userspace
526 audit_backlog_limit= [KNL] Set the audit queue size limit.
527 Format: <int> (must be >=0)
530 baycom_epp= [HW,AX25]
533 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
535 See header of drivers/net/hamradio/baycom_par.c.
537 baycom_ser_fdx= [HW,AX25]
538 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
539 Format: <io>,<irq>,<mode>[,<baud>]
540 See header of drivers/net/hamradio/baycom_ser_fdx.c.
542 baycom_ser_hdx= [HW,AX25]
543 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
544 Format: <io>,<irq>,<mode>
545 See header of drivers/net/hamradio/baycom_ser_hdx.c.
547 blkdevparts= Manual partition parsing of block device(s) for
548 embedded devices based on command line input.
549 See Documentation/block/cmdline-partition.txt
551 boot_delay= Milliseconds to delay each printk during boot.
552 Values larger than 10 seconds (10000) are changed to
556 bootmem_debug [KNL] Enable bootmem allocator debug messages.
558 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
559 bttv.radio= Most important insmod options are available as
561 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
564 bulk_remove=off [PPC] This parameter disables the use of the pSeries
565 firmware feature for flushing multiple hpte entries
568 c101= [NET] Moxa C101 synchronous serial card
570 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
571 Sometimes CPU hardware bugs make them report the cache
572 size incorrectly. The kernel will attempt work arounds
573 to fix known problems, but for some CPUs it is not
574 possible to determine what the correct size should be.
575 This option provides an override for these situations.
577 ca_keys= [KEYS] This parameter identifies a specific key(s) on
578 the system trusted keyring to be used for certificate
580 format: { id:<keyid> | builtin }
582 cca= [MIPS] Override the kernel pages' cache coherency
583 algorithm. Accepted values range from 0 to 7
584 inclusive. See arch/mips/include/asm/pgtable-bits.h
585 for platform specific values (SB1, Loongson3 and
588 ccw_timeout_log [S390]
589 See Documentation/s390/CommonIO for details.
591 cgroup_disable= [KNL] Disable a particular controller
592 Format: {name of the controller(s) to disable}
593 The effects of cgroup_disable=foo are:
594 - foo isn't auto-mounted if you mount all cgroups in
596 - foo isn't visible as an individually mountable
598 {Currently only "memory" controller deal with this and
599 cut the overhead, others just disable the usage. So
600 only cgroup_disable=memory is actually worthy}
602 checkreqprot [SELINUX] Set initial checkreqprot flag value.
603 Format: { "0" | "1" }
604 See security/selinux/Kconfig help text.
605 0 -- check protection applied by kernel (includes
606 any implied execute protection).
607 1 -- check protection requested by application.
608 Default value is set via a kernel config option.
609 Value can be changed at runtime via
610 /selinux/checkreqprot.
613 See Documentation/s390/CommonIO for details.
616 Prevents the clock framework from automatically gating
617 clocks that have not been explicitly enabled by a Linux
618 device driver but are enabled in hardware at reset or
619 by the bootloader/firmware. Note that this does not
620 force such clocks to be always-on nor does it reserve
621 those clocks in any way. This parameter is useful for
622 debug and development, but should not be needed on a
623 platform with proper driver support. For more
624 information, see Documentation/clk.txt.
626 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
628 Forces specified clocksource (if available) to be used
629 when calculating gettimeofday(). If specified
630 clocksource is not available, it defaults to PIT.
631 Format: { pit | tsc | cyclone | pmtmr }
633 clocksource= Override the default clocksource
635 Override the default clocksource and use the clocksource
636 with the name specified.
637 Some clocksource names to choose from, depending on
639 [all] jiffies (this is the base, fallback clocksource)
641 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
642 pxa_timer,timer3,32k_counter,timer0_1
644 [X86-32] pit,hpet,tsc;
645 scx200_hrt on Geode; cyclone on IBM x440
653 clearcpuid=BITNUM [X86]
654 Disable CPUID feature X for the kernel. See
655 arch/x86/include/asm/cpufeature.h for the valid bit
656 numbers. Note the Linux specific bits are not necessarily
657 stable over kernel options, but the vendor specific
659 Also note that user programs calling CPUID directly
660 or using the feature without checking anything
661 will still see it. This just prevents it from
662 being used by the kernel or shown in /proc/cpuinfo.
663 Also note the kernel might malfunction if you disable
666 cma=nn[MG]@[start[MG][-end[MG]]]
668 Sets the size of kernel global memory area for
669 contiguous memory allocations and optionally the
670 placement constraint by the physical address range of
671 memory allocations. A value of 0 disables CMA
672 altogether. For more information, see
673 include/linux/dma-contiguous.h
675 cmo_free_hint= [PPC] Format: { yes | no }
676 Specify whether pages are marked as being inactive
677 when they are freed. This is used in CMO environments
678 to determine OS memory pressure for page stealing by
682 coherent_pool=nn[KMG] [ARM,KNL]
683 Sets the size of memory pool for coherent, atomic dma
684 allocations, by default set to 256K.
686 code_bytes [X86] How many bytes of object code to print
691 com20020= [HW,NET] ARCnet - COM20020 chipset
693 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
695 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
699 ARCnet - COM90xx chipset (memory-mapped buffers)
700 Format: <io>[,<irq>[,<memstart>]]
702 condev= [HW,S390] console device
705 console= [KNL] Output console device and options.
707 tty<n> Use the virtual console device <n>.
711 Use the specified serial port. The options are of
712 the form "bbbbpnf", where "bbbb" is the baud rate,
713 "p" is parity ("n", "o", or "e"), "n" is number of
714 bits, and "f" is flow control ("r" for RTS or
715 omit it). Default is "9600n8".
717 See Documentation/serial-console.txt for more
719 Documentation/networking/netconsole.txt for an
722 uart[8250],io,<addr>[,options]
723 uart[8250],mmio,<addr>[,options]
724 uart[8250],mmio32,<addr>[,options]
725 uart[8250],0x<addr>[,options]
726 Start an early, polled-mode console on the 8250/16550
727 UART at the specified I/O port or MMIO address,
728 switching to the matching ttyS device later.
729 MMIO inter-register address stride is either 8-bit
730 (mmio) or 32-bit (mmio32).
731 If none of [io|mmio|mmio32], <addr> is assumed to be
732 equivalent to 'mmio'. 'options' are specified in the
733 same format described for ttyS above; if unspecified,
734 the h/w is not re-initialized.
736 hvc<n> Use the hypervisor console device <n>. This is for
737 both Xen and PowerPC hypervisors.
739 If the device connected to the port is not a TTY but a braille
740 device, prepend "brl," before the device type, for instance
742 For now, only VisioBraille is supported.
744 consoleblank= [KNL] The console blank (screen saver) timeout in
745 seconds. Defaults to 10*60 = 10mins. A value of 0
746 disables the blank timer.
749 [KNL] Change the default value for
750 /proc/<pid>/coredump_filter.
751 See also Documentation/filesystems/proc.txt.
753 cpuidle.off=1 [CPU_IDLE]
754 disable the cpuidle sub-system
757 [X86] Delay for N microsec between assert and de-assert
758 of APIC INIT to start processors. This delay occurs
759 on every CPU online, such as boot, and resume from suspend.
762 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
764 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
766 crashkernel=size[KMG][@offset[KMG]]
767 [KNL] Using kexec, Linux can switch to a 'crash kernel'
768 upon panic. This parameter reserves the physical
769 memory region [offset, offset + size] for that kernel
770 image. If '@offset' is omitted, then a suitable offset
771 is selected automatically. Check
772 Documentation/kdump/kdump.txt for further details.
774 crashkernel=range1:size1[,range2:size2,...][@offset]
775 [KNL] Same as above, but depends on the memory
776 in the running system. The syntax of range is
777 start-[end] where start and end are both
778 a memory unit (amount[KMG]). See also
779 Documentation/kdump/kdump.txt for an example.
781 crashkernel=size[KMG],high
782 [KNL, x86_64] range could be above 4G. Allow kernel
783 to allocate physical memory region from top, so could
784 be above 4G if system have more than 4G ram installed.
785 Otherwise memory region will be allocated below 4G, if
787 It will be ignored if crashkernel=X is specified.
788 crashkernel=size[KMG],low
789 [KNL, x86_64] range under 4G. When crashkernel=X,high
790 is passed, kernel could allocate physical memory region
791 above 4G, that cause second kernel crash on system
792 that require some amount of low memory, e.g. swiotlb
793 requires at least 64M+32K low memory. Kernel would
794 try to allocate 72M below 4G automatically.
795 This one let user to specify own low range under 4G
796 for second kernel instead.
797 0: to disable low allocation.
798 It will be ignored when crashkernel=X,high is not used
799 or memory reserved is below 4G.
804 cs89x0_media= [HW,NET]
805 Format: { rj45 | aui | bnc }
808 See header of drivers/s390/block/dasd_devmap.c.
810 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
811 (one device per port)
812 Format: <port#>,<type>
813 See also Documentation/input/joystick-parport.txt
815 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
816 time. See Documentation/dynamic-debug-howto.txt for
817 details. Deprecated, see dyndbg.
819 debug [KNL] Enable kernel debugging (events log level).
822 [KNL] verbose self-tests
824 Print debugging info while doing the locking API
826 We default to 0 (no extra messages), setting it to
827 1 will print _a lot_ more information - normally
828 only useful to kernel developers.
830 debug_objects [KNL] Enable object debugging
833 [KNL] Disable object debugging
835 debug_guardpage_minorder=
836 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
837 parameter allows control of the order of pages that will
838 be intentionally kept free (and hence protected) by the
839 buddy allocator. Bigger value increase the probability
840 of catching random memory corruption, but reduce the
841 amount of memory for normal system use. The maximum
842 possible value is MAX_ORDER/2. Setting this parameter
843 to 1 or 2 should be enough to identify most random
844 memory corruption problems caused by bugs in kernel or
845 driver code when a CPU writes to (or reads from) a
846 random memory location. Note that there exists a class
847 of memory corruptions problems caused by buggy H/W or
848 F/W or by drivers badly programing DMA (basically when
849 memory is written at bus level and the CPU MMU is
850 bypassed) which are not detectable by
851 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
852 tracking down these problems.
855 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
856 parameter enables the feature at boot time. In
857 default, it is disabled. We can avoid allocating huge
858 chunk of memory for debug pagealloc if we don't enable
859 it at boot time and the system will work mostly same
860 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
861 on: enable the feature
863 debugpat [X86] Enable PAT debugging
865 decnet.addr= [HW,NET]
866 Format: <area>[,<node>]
867 See also Documentation/networking/decnet.txt.
870 [same as hugepagesz=] The size of the default
871 HugeTLB page size. This is the size represented by
872 the legacy /proc/ hugepages APIs, used for SHM, and
873 default size when mounting hugetlbfs filesystems.
874 Defaults to the default architecture's huge page size
878 Set number of hash buckets for dentry cache.
881 See Documentation/networking/ipv6.txt.
883 disable_cpu_apicid= [X86,APIC,SMP]
885 The number of initial APIC ID for the
886 corresponding CPU to be disabled at boot,
887 mostly used for the kdump 2nd kernel to
888 disable BSP to wake up multiple CPUs without
889 causing system reset or hang due to sending
892 disable_ddw [PPC/PSERIES]
893 Disable Dynamic DMA Window support. Use this if
894 to workaround buggy firmware.
897 See Documentation/networking/ipv6.txt.
899 disable_mtrr_cleanup [X86]
900 The kernel tries to adjust MTRR layout from continuous
901 to discrete, to make X server driver able to add WB
902 entry later. This parameter disables that.
904 disable_mtrr_trim [X86, Intel and AMD only]
905 By default the kernel will trim any uncacheable
906 memory out of your available memory pool based on
907 MTRR settings. This parameter disables that behavior,
908 possibly causing your machine to run very slowly.
910 disable_timer_pin_1 [X86]
911 Disable PIN 1 of APIC timer
912 Can be useful to work around chipset bugs.
914 dis_ucode_ldr [X86] Disable the microcode loader.
916 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
917 this option disables the debugging code at boot.
919 dma_debug_entries=<number>
920 This option allows to tune the number of preallocated
921 entries for DMA-API debugging code. One entry is
922 required per DMA-API allocation. Use this if the
923 DMA-API debugging code disables itself because the
924 architectural default is too low.
926 dma_debug_driver=<driver_name>
927 With this option the DMA-API debugging driver
928 filter feature can be enabled at boot time. Just
929 pass the driver to filter for as the parameter.
930 The filter can be disabled or changed to another
931 driver later using sysfs.
933 drm_kms_helper.edid_firmware=[<connector>:]<file>
934 Broken monitors, graphic adapters and KVMs may
935 send no or incorrect EDID data sets. This parameter
936 allows to specify an EDID data set in the
937 /lib/firmware directory that is used instead.
938 Generic built-in EDID data sets are used, if one of
939 edid/1024x768.bin, edid/1280x1024.bin,
940 edid/1680x1050.bin, or edid/1920x1080.bin is given
941 and no file with the same name exists. Details and
942 instructions how to build your own EDID data are
943 available in Documentation/EDID/HOWTO.txt. An EDID
944 data set will only be used for a particular connector,
945 if its name and a colon are prepended to the EDID
950 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
951 module.dyndbg[="val"]
952 Enable debug messages at boot time. See
953 Documentation/dynamic-debug-howto.txt for details.
955 nompx [X86] Disables Intel Memory Protection Extensions.
956 See Documentation/x86/intel_mpx.txt for more
957 information about the feature.
960 on enable eager fpu restore
961 off disable eager fpu restore
962 auto selects the default scheme, which automatically
963 enables eagerfpu restore for xsaveopt.
965 module.async_probe [KNL]
966 Enable asynchronous probe on this module.
968 early_ioremap_debug [KNL]
969 Enable debug messages in early_ioremap support. This
970 is useful for tracking down temporary early mappings
971 which are not unmapped.
973 earlycon= [KNL] Output early console device and options.
976 Start an early, polled-mode console on a cadence serial
977 port at the specified address. The cadence serial port
978 must already be setup and configured. Options are not
981 uart[8250],io,<addr>[,options]
982 uart[8250],mmio,<addr>[,options]
983 uart[8250],mmio32,<addr>[,options]
984 uart[8250],mmio32be,<addr>[,options]
985 uart[8250],0x<addr>[,options]
986 Start an early, polled-mode console on the 8250/16550
987 UART at the specified I/O port or MMIO address.
988 MMIO inter-register address stride is either 8-bit
989 (mmio) or 32-bit (mmio32 or mmio32be).
990 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
991 to be equivalent to 'mmio'. 'options' are specified
992 in the same format described for "console=ttyS<n>"; if
993 unspecified, the h/w is not initialized.
996 Start an early, polled-mode console on a pl011 serial
997 port at the specified address. The pl011 serial port
998 must already be setup and configured. Options are not
1002 Start an early, polled-mode console on an msm serial
1003 port at the specified address. The serial port
1004 must already be setup and configured. Options are not
1007 msm_serial_dm,<addr>
1008 Start an early, polled-mode console on an msm serial
1009 dm port at the specified address. The serial port
1010 must already be setup and configured. Options are not
1013 smh Use ARM semihosting calls for early console.
1021 Use early console provided by serial driver available
1022 on Samsung SoCs, requires selecting proper type and
1023 a correct base address of the selected UART port. The
1024 serial port must already be setup and configured.
1025 Options are not yet supported.
1027 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1031 earlyprintk=serial[,ttySn[,baudrate]]
1032 earlyprintk=serial[,0x...[,baudrate]]
1033 earlyprintk=ttySn[,baudrate]
1034 earlyprintk=dbgp[debugController#]
1035 earlyprintk=pciserial,bus:device.function[,baudrate]
1037 earlyprintk is useful when the kernel crashes before
1038 the normal console is initialized. It is not enabled by
1039 default because it has some cosmetic problems.
1041 Append ",keep" to not disable it when the real console
1044 Only one of vga, efi, serial, or usb debug port can
1047 Currently only ttyS0 and ttyS1 may be specified by
1048 name. Other I/O ports may be explicitly specified
1049 on some architectures (x86 and arm at least) by
1050 replacing ttySn with an I/O port address, like this:
1051 earlyprintk=serial,0x1008,115200
1052 You can find the port for a given device in
1053 /proc/tty/driver/serial:
1054 2: uart:ST16650V2 port:00001008 irq:18 ...
1056 Interaction with the standard serial driver is not
1059 The VGA and EFI output is eventually overwritten by
1062 The xen output can only be used by Xen PV guests.
1064 edac_report= [HW,EDAC] Control how to report EDAC event
1065 Format: {"on" | "off" | "force"}
1066 on: enable EDAC to report H/W event. May be overridden
1067 by other higher priority error reporting module.
1068 off: disable H/W event reporting through EDAC.
1069 force: enforce the use of EDAC to report H/W event.
1072 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1075 This is designed to be used in conjunction with
1076 the boot argument: earlyprintk=vga
1079 Format: {"off" | "on" | "skip[mbr]"}
1082 Format: { "old_map", "nochunk", "noruntime", "debug" }
1083 old_map [X86-64]: switch to the old ioremap-based EFI
1084 runtime services mapping. 32-bit still uses this one by
1086 nochunk: disable reading files in "chunks" in the EFI
1087 boot stub, as chunking can cause problems with some
1088 firmware implementations.
1089 noruntime : disable EFI runtime services support
1090 debug: enable misc debug output
1092 efi_no_storage_paranoia [EFI; X86]
1093 Using this parameter you can use more than 50% of
1094 your efi variable storage. Use this parameter only if
1095 you are really sure that your UEFI does sane gc and
1096 fulfills the spec otherwise your board may brick.
1098 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1099 Add arbitrary attribute to specific memory range by
1100 updating original EFI memory map.
1101 Region of memory which aa attribute is added to is
1103 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1104 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1105 attribute is added to range 0x100000000-0x180000000 and
1106 0x10a0000000-0x1120000000.
1108 Using this parameter you can do debugging of EFI memmap
1109 related feature. For example, you can do debugging of
1110 Address Range Mirroring feature even if your box
1113 eisa_irq_edge= [PARISC,HW]
1114 See header of drivers/parisc/eisa.c.
1117 See comment before function elanfreq_setup() in
1118 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1121 Format: {"cfq" | "deadline" | "noop"}
1122 See Documentation/block/cfq-iosched.txt and
1123 Documentation/block/deadline-iosched.txt for details.
1125 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1126 Specifies physical address of start of kernel core
1127 image elf header and optionally the size. Generally
1128 kexec loader will pass this option to capture kernel.
1129 See Documentation/kdump/kdump.txt for details.
1131 enable_mtrr_cleanup [X86]
1132 The kernel tries to adjust MTRR layout from continuous
1133 to discrete, to make X server driver able to add WB
1134 entry later. This parameter enables that.
1136 enable_timer_pin_1 [X86]
1137 Enable PIN 1 of APIC timer
1138 Can be useful to work around chipset bugs
1139 (in particular on some ATI chipsets).
1140 The kernel tries to set a reasonable default.
1142 enforcing [SELINUX] Set initial enforcing status.
1144 See security/selinux/Kconfig help text.
1145 0 -- permissive (log only, no denials).
1146 1 -- enforcing (deny and log).
1148 Value can be changed at runtime via /selinux/enforce.
1151 Disable Error Record Serialization Table (ERST)
1154 ether= [HW,NET] Ethernet cards parameters
1155 This option is obsoleted by the "netdev=" option, which
1156 has equivalent usage. See its documentation for details.
1160 Permit 'security.evm' to be updated regardless of
1161 current integrity status.
1165 fail_make_request=[KNL]
1166 General fault injection mechanism.
1167 Format: <interval>,<probability>,<space>,<times>
1168 See also Documentation/fault-injection/.
1171 See Documentation/blockdev/floppy.txt.
1173 force_pal_cache_flush
1174 [IA-64] Avoid check_sal_cache_flush which may hang on
1175 buggy SAL_CACHE_FLUSH implementations. Using this
1176 parameter will force ia64_sal_cache_flush to call
1177 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1180 Forcefully enable Physical Address Extension (PAE).
1181 Many Pentium M systems disable PAE but may have a
1182 functionally usable PAE implementation.
1183 Warning: use of this parameter will taint the kernel
1184 and may cause unknown problems.
1187 [FTRACE] will set and start the specified tracer
1188 as early as possible in order to facilitate early
1191 ftrace_dump_on_oops[=orig_cpu]
1192 [FTRACE] will dump the trace buffers on oops.
1193 If no parameter is passed, ftrace will dump
1194 buffers of all CPUs, but if you pass orig_cpu, it will
1195 dump only the buffer of the CPU that triggered the
1198 ftrace_filter=[function-list]
1199 [FTRACE] Limit the functions traced by the function
1200 tracer at boot up. function-list is a comma separated
1201 list of functions. This list can be changed at run
1202 time by the set_ftrace_filter file in the debugfs
1205 ftrace_notrace=[function-list]
1206 [FTRACE] Do not trace the functions specified in
1207 function-list. This list can be changed at run time
1208 by the set_ftrace_notrace file in the debugfs
1211 ftrace_graph_filter=[function-list]
1212 [FTRACE] Limit the top level callers functions traced
1213 by the function graph tracer at boot up.
1214 function-list is a comma separated list of functions
1215 that can be changed at run time by the
1216 set_graph_function file in the debugfs tracing directory.
1218 ftrace_graph_notrace=[function-list]
1219 [FTRACE] Do not trace from the functions specified in
1220 function-list. This list is a comma separated list of
1221 functions that can be changed at run time by the
1222 set_graph_notrace file in the debugfs tracing directory.
1225 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1226 support via parallel port (up to 5 devices per port)
1227 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1228 See also Documentation/input/joystick-parport.txt
1232 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1236 gcov_persist= [GCOV] When non-zero (default), profiling data for
1237 kernel modules is saved and remains accessible via
1238 debugfs, even when the module is unloaded/reloaded.
1239 When zero, profiling data is discarded and associated
1240 debugfs files are removed at module unload time.
1242 gpt [EFI] Forces disk with valid GPT signature but
1243 invalid Protective MBR to be treated as GPT. If the
1244 primary GPT is corrupted, it enables the backup/alternate
1245 GPT to be used instead.
1247 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1248 the "Enable 0" bit of the configuration register.
1251 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1252 the "Enable 0" bit of the configuration register.
1255 grcan.select= [HW] Select which physical interface to use.
1258 grcan.txsize= [HW] Sets the size of the tx buffer.
1259 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1261 grcan.rxsize= [HW] Sets the size of the rx buffer.
1262 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1265 hashdist= [KNL,NUMA] Large hashes allocated during boot
1266 are distributed across NUMA nodes. Defaults on
1267 for 64-bit NUMA, off otherwise.
1268 Format: 0 | 1 (for off | on)
1270 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1272 hd= [EIDE] (E)IDE hard drive subsystem geometry
1273 Format: <cyl>,<head>,<sect>
1276 Disable Hardware Error Source Table (HEST) support;
1277 corresponding firmware-first mode error processing
1278 logic will be disabled.
1280 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1281 size of <nn>. This works even on boxes that have no
1282 highmem otherwise. This also works to reduce highmem
1283 size on bigger boxes.
1285 highres= [KNL] Enable/disable high resolution timer mode.
1286 Valid parameters: "on", "off"
1290 See Documentation/isdn/README.HiSax.
1294 hpet= [X86-32,HPET] option to control HPET usage
1295 Format: { enable (default) | disable | force |
1297 disable: disable HPET and use PIT instead
1298 force: allow force enabled of undocumented chips (ICH4,
1300 verbose: show contents of HPET registers during setup
1302 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1303 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1305 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1306 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1307 On x86-64 and powerpc, this option can be specified
1308 multiple times interleaved with hugepages= to reserve
1309 huge pages of different sizes. Valid pages sizes on
1310 x86-64 are 2M (when the CPU supports "pse") and 1G
1311 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1313 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1314 terminal devices. Valid values: 0..8
1315 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1316 If specified, z/VM IUCV HVC accepts connections
1317 from listed z/VM user IDs only.
1319 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1320 hardware thread id mappings.
1321 Format: <cpu>:<hwthread>
1324 Do not unregister boot console at start. This is only
1325 useful for debugging when something happens in the window
1326 between unregistering the boot console and initializing
1329 i2c_bus= [HW] Override the default board specific I2C bus speed
1330 or register an additional I2C bus that is not
1331 registered from board initialization code.
1335 i8042.debug [HW] Toggle i8042 debug mode
1336 i8042.unmask_kbd_data
1337 [HW] Enable printing of interrupt data from the KBD port
1338 (disabled by default, and as a pre-condition
1339 requires that i8042.debug=1 be enabled)
1340 i8042.direct [HW] Put keyboard port into non-translated mode
1341 i8042.dumbkbd [HW] Pretend that controller can only read data from
1342 keyboard and cannot control its state
1343 (Don't attempt to blink the leds)
1344 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1345 i8042.nokbd [HW] Don't check/create keyboard port
1346 i8042.noloop [HW] Disable the AUX Loopback command while probing
1348 i8042.nomux [HW] Don't check presence of an active multiplexing
1350 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1352 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1353 i8042.reset [HW] Reset the controller during init and cleanup
1354 i8042.unlock [HW] Unlock (ignore) the keylock
1355 i8042.kbdreset [HW] Reset device connected to KBD port
1359 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1360 indicates that the driver is running on unsupported
1362 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1363 does not match list of supported models.
1365 [HW] Report power status in /proc/i8k
1366 (disabled by default)
1367 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1370 i915.invert_brightness=
1371 [DRM] Invert the sense of the variable that is used to
1372 set the brightness of the panel backlight. Normally a
1373 brightness value of 0 indicates backlight switched off,
1374 and the maximum of the brightness value sets the backlight
1375 to maximum brightness. If this parameter is set to 0
1376 (default) and the machine requires it, or this parameter
1377 is set to 1, a brightness value of 0 sets the backlight
1378 to maximum brightness, and the maximum of the brightness
1379 value switches the backlight off.
1380 -1 -- never invert brightness
1381 0 -- machine default
1382 1 -- force brightness inversion
1385 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1387 ide-core.nodma= [HW] (E)IDE subsystem
1388 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1389 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1390 .cdrom .chs .ignore_cable are additional options
1391 See Documentation/ide/ide.txt.
1393 ide-generic.probe-mask= [HW] (E)IDE subsystem
1395 Probe mask for legacy ISA IDE ports. Depending on
1396 platform up to 6 ports are supported, enabled by
1397 setting corresponding bits in the mask to 1. The
1398 default value is 0x0, which has a special meaning.
1399 On systems that have PCI, it triggers scanning the
1400 PCI bus for the first and the second port, which
1401 are then probed. On systems without PCI the value
1402 of 0x0 enables probing the two first ports as if it
1405 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1406 Claim all unknown PCI IDE storage controllers.
1409 Format: idle=poll, idle=halt, idle=nomwait
1410 Poll forces a polling idle loop that can slightly
1411 improve the performance of waking up a idle CPU, but
1412 will use a lot of power and make the system run hot.
1414 idle=halt: Halt is forced to be used for CPU idle.
1415 In such case C2/C3 won't be used again.
1416 idle=nomwait: Disable mwait for CPU C-states
1418 ignore_loglevel [KNL]
1419 Ignore loglevel setting - this will print /all/
1420 kernel messages to the console. Useful for debugging.
1421 We also add it as printk module parameter, so users
1422 could change it dynamically, usually by
1423 /sys/module/printk/parameters/ignore_loglevel.
1425 ihash_entries= [KNL]
1426 Set number of hash buckets for inode cache.
1428 ima_appraise= [IMA] appraise integrity measurements
1429 Format: { "off" | "enforce" | "fix" | "log" }
1432 ima_appraise_tcb [IMA]
1433 The builtin appraise policy appraises all files
1437 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1441 The list of supported hash algorithms is defined
1442 in crypto/hash_info.h.
1445 The builtin measurement policy to load during IMA
1446 setup. Specyfing "tcb" as the value, measures all
1447 programs exec'd, files mmap'd for exec, and all files
1448 opened with the read mode bit set by either the
1449 effective uid (euid=0) or uid=0.
1452 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1453 Load a policy which meets the needs of the Trusted
1454 Computing Base. This means IMA will measure all
1455 programs exec'd, files mmap'd for exec, and all files
1456 opened for read by uid=0.
1459 Select one of defined IMA measurements template formats.
1460 Formats: { "ima" | "ima-ng" | "ima-sig" }
1464 [IMA] Define a custom template format.
1465 Format: { "field1|...|fieldN" }
1467 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1468 Format: <min_file_size>
1469 Set the minimal file size for using asynchronous hash.
1470 If left unspecified, ahash usage is disabled.
1472 ahash performance varies for different data sizes on
1473 different crypto accelerators. This option can be used
1474 to achieve the best performance for a particular HW.
1476 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1478 Set hashing buffer size. Default: 4k.
1480 ahash performance varies for different chunk sizes on
1481 different crypto accelerators. This option can be used
1482 to achieve best performance for particular HW.
1486 Run specified binary instead of /sbin/init as init
1489 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1490 for working out where the kernel is dying during
1493 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1494 initcall functions. Useful for debugging built-in
1495 modules and initcalls.
1497 initrd= [BOOT] Specify the location of the initial ramdisk
1499 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1502 int_pln_enable [x86] Enable power limit notification interrupt
1504 integrity_audit=[IMA]
1505 Format: { "0" | "1" }
1506 0 -- basic integrity auditing messages. (Default)
1507 1 -- additional integrity auditing messages.
1509 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1511 Enable intel iommu driver.
1513 Disable intel iommu driver.
1514 igfx_off [Default Off]
1515 By default, gfx is mapped as normal device. If a gfx
1516 device has a dedicated DMAR unit, the DMAR unit is
1517 bypassed by not enabling DMAR with this option. In
1518 this case, gfx device will use physical address for
1521 With this option iommu will not optimize to look
1522 for io virtual address below 32-bit forcing dual
1523 address cycle on pci bus for cards supporting greater
1524 than 32-bit addressing. The default is to look
1525 for translation below 32-bit and if not available
1526 then look in the higher range.
1527 strict [Default Off]
1528 With this option on every unmap_single operation will
1529 result in a hardware IOTLB flush operation as opposed
1530 to batching them for performance.
1531 sp_off [Default Off]
1532 By default, super page will be supported if Intel IOMMU
1533 has the capability. With this option, super page will
1535 ecs_off [Default Off]
1536 By default, extended context tables will be supported if
1537 the hardware advertises that it has support both for the
1538 extended tables themselves, and also PASID support. With
1539 this option set, extended tables will not be used even
1540 on hardware which claims to support them.
1542 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1543 0 disables intel_idle and fall back on acpi_idle.
1544 1 to 6 specify maximum depth of C-state.
1548 Do not enable intel_pstate as the default
1549 scaling driver for the supported processors
1551 Enable intel_pstate on systems that prohibit it by default
1552 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1553 instead of acpi-cpufreq may disable platform features, such
1554 as thermal controls and power capping, that rely on ACPI
1555 P-States information being indicated to OSPM and therefore
1556 should be used with caution. This option does not work with
1557 processors that aren't supported by the intel_pstate driver
1558 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1560 Do not enable hardware P state control (HWP)
1563 Only load intel_pstate on systems which support
1564 hardware P state control (HWP) if available.
1566 Don't use ACPI processor performance control objects
1567 _PSS and _PPC specified limits.
1569 intremap= [X86-64, Intel-IOMMU]
1570 on enable Interrupt Remapping (default)
1571 off disable Interrupt Remapping
1572 nosid disable Source ID checking
1574 BIOS x2APIC opt-out request will be ignored
1576 iomem= Disable strict checking of access to MMIO memory
1577 strict regions from userspace.
1592 nobypass [PPC/POWERNV]
1593 Disable IOMMU bypass, using IOMMU for PCI devices.
1596 io7= [HW] IO7 for Marvel based alpha systems
1597 See comment before marvel_specify_io7 in
1598 arch/alpha/kernel/core_marvel.c.
1600 io_delay= [X86] I/O delay method
1602 Standard port 0x80 based delay
1604 Alternate port 0xed based delay (needed on some systems)
1606 Simple two microseconds delay
1611 See Documentation/filesystems/nfs/nfsroot.txt.
1614 When an interrupt is not handled search all handlers
1615 for it. Intended to get systems with badly broken
1619 When an interrupt is not handled search all handlers
1620 for it. Also check all handlers each timer
1621 interrupt. Intended to get systems with badly broken
1625 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1627 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1629 <cpu number>,...,<cpu number>
1631 <cpu number>-<cpu number>
1632 (must be a positive range in ascending order)
1634 <cpu number>,...,<cpu number>-<cpu number>
1636 This option can be used to specify one or more CPUs
1637 to isolate from the general SMP balancing and scheduling
1638 algorithms. You can move a process onto or off an
1639 "isolated" CPU via the CPU affinity syscalls or cpuset.
1640 <cpu number> begins at 0 and the maximum value is
1641 "number of CPUs in system - 1".
1643 This option is the preferred way to isolate CPUs. The
1644 alternative -- manually setting the CPU mask of all
1645 tasks in the system -- can cause problems and
1646 suboptimal load balancer performance.
1650 ivrs_ioapic [HW,X86_64]
1651 Provide an override to the IOAPIC-ID<->DEVICE-ID
1652 mapping provided in the IVRS ACPI table. For
1653 example, to map IOAPIC-ID decimal 10 to
1654 PCI device 00:14.0 write the parameter as:
1655 ivrs_ioapic[10]=00:14.0
1657 ivrs_hpet [HW,X86_64]
1658 Provide an override to the HPET-ID<->DEVICE-ID
1659 mapping provided in the IVRS ACPI table. For
1660 example, to map HPET-ID decimal 0 to
1661 PCI device 00:14.0 write the parameter as:
1662 ivrs_hpet[0]=00:14.0
1664 js= [HW,JOY] Analog joystick
1665 See Documentation/input/joystick.txt.
1668 Enable/disable kernel and module base offset ASLR
1669 (Address Space Layout Randomization) if built into
1670 the kernel. When CONFIG_HIBERNATION is selected,
1671 kASLR is disabled by default. When kASLR is enabled,
1672 hibernation will be disabled.
1676 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1677 specifies the amount of memory usable by the kernel
1678 for non-movable allocations. The requested amount is
1679 spread evenly throughout all nodes in the system. The
1680 remaining memory in each node is used for Movable
1681 pages. In the event, a node is too small to have both
1682 kernelcore and Movable pages, kernelcore pages will
1683 take priority and other nodes will have a larger number
1684 of Movable pages. The Movable zone is used for the
1685 allocation of pages that may be reclaimed or moved
1686 by the page migration subsystem. This means that
1687 HugeTLB pages may not be allocated from this zone.
1688 Note that allocations like PTEs-from-HighMem still
1689 use the HighMem zone if it exists, and the Normal
1690 zone if it does not.
1692 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1693 Format: <Controller#>[,poll interval]
1694 The controller # is the number of the ehci usb debug
1695 port as it is probed via PCI. The poll interval is
1696 optional and is the number seconds in between
1697 each poll cycle to the debug port in case you need
1698 the functionality for interrupting the kernel with
1699 gdb or control-c on the dbgp connection. When
1700 not using this parameter you use sysrq-g to break into
1701 the kernel debugger.
1703 kgdboc= [KGDB,HW] kgdb over consoles.
1704 Requires a tty driver that supports console polling,
1705 or a supported polling keyboard driver (non-usb).
1706 Serial only format: <serial_device>[,baud]
1707 keyboard only format: kbd
1708 keyboard and serial format: kbd,<serial_device>[,baud]
1709 Optional Kernel mode setting:
1710 kms, kbd format: kms,kbd
1711 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1713 kgdbwait [KGDB] Stop kernel execution and enter the
1714 kernel debugger at the earliest opportunity.
1716 kmac= [MIPS] korina ethernet MAC address.
1717 Configure the RouterBoard 532 series on-chip
1718 Ethernet adapter MAC address.
1720 kmemleak= [KNL] Boot-time kmemleak enable/disable
1721 Valid arguments: on, off
1723 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1726 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1727 Valid arguments: 0, 1, 2
1728 kmemcheck=0 (disabled)
1729 kmemcheck=1 (enabled)
1730 kmemcheck=2 (one-shot mode)
1731 Default: 2 (one-shot mode)
1733 kstack=N [X86] Print N words from the kernel stack
1736 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1737 Default is 0 (don't ignore, but inject #GP)
1739 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1743 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1744 Default is 1 (enabled)
1746 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1748 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1750 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1751 (virtualized MMU) support on capable Intel chips.
1752 Default is 1 (enabled)
1754 kvm-intel.emulate_invalid_guest_state=
1755 [KVM,Intel] Enable emulation of invalid guest states
1756 Default is 0 (disabled)
1758 kvm-intel.flexpriority=
1759 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1760 Default is 1 (enabled)
1763 [KVM,Intel] Enable VMX nesting (nVMX).
1764 Default is 0 (disabled)
1766 kvm-intel.unrestricted_guest=
1767 [KVM,Intel] Disable unrestricted guest feature
1768 (virtualized real and unpaged mode) on capable
1769 Intel chips. Default is 1 (enabled)
1771 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1772 feature (tagged TLBs) on capable Intel chips.
1773 Default is 1 (enabled)
1779 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1782 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1783 value for LAPIC timer one-shot implementation. Default
1784 back to the programmable timer unit in the LAPIC.
1786 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1789 libata.dma= [LIBATA] DMA control
1790 libata.dma=0 Disable all PATA and SATA DMA
1791 libata.dma=1 PATA and SATA Disk DMA only
1792 libata.dma=2 ATAPI (CDROM) DMA only
1793 libata.dma=4 Compact Flash DMA only
1794 Combinations also work, so libata.dma=3 enables DMA
1795 for disks and CDROMs, but not CFs.
1797 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1798 libata.ignore_hpa=0 keep BIOS limits (default)
1799 libata.ignore_hpa=1 ignore limits, using full disk
1801 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1805 libata.force= [LIBATA] Force configurations. The format is comma
1806 separated list of "[ID:]VAL" where ID is
1807 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1808 matching port, link or device. Basically, it matches
1809 the ATA ID string printed on console by libata. If
1810 the whole ID part is omitted, the last PORT and DEVICE
1811 values are used. If ID hasn't been specified yet, the
1812 configuration applies to all ports, links and devices.
1814 If only DEVICE is omitted, the parameter applies to
1815 the port and all links and devices behind it. DEVICE
1816 number of 0 either selects the first device or the
1817 first fan-out link behind PMP device. It does not
1818 select the host link. DEVICE number of 15 selects the
1819 host link and device attached to it.
1821 The VAL specifies the configuration to force. As long
1822 as there's no ambiguity shortcut notation is allowed.
1823 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1824 The following configurations can be forced.
1826 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1827 Any ID with matching PORT is used.
1829 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1831 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1832 udma[/][16,25,33,44,66,100,133] notation is also
1835 * [no]ncq: Turn on or off NCQ.
1837 * [no]ncqtrim: Turn off queued DSM TRIM.
1839 * nohrst, nosrst, norst: suppress hard, soft
1842 * rstonce: only attempt one reset during
1843 hot-unplug link recovery
1845 * dump_id: dump IDENTIFY data.
1847 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1849 * disable: Disable this device.
1851 If there are multiple matching configurations changing
1852 the same attribute, the last one is used.
1854 memblock=debug [KNL] Enable memblock debug messages.
1856 load_ramdisk= [RAM] List of ramdisks to load from floppy
1857 See Documentation/blockdev/ramdisk.txt.
1859 lockd.nlm_grace_period=P [NFS] Assign grace period.
1862 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1865 lockd.nlm_timeout=T [NFS] Assign timeout value.
1868 lockd.nlm_udpport=M [NFS] Assign UDP port.
1871 locktorture.nreaders_stress= [KNL]
1872 Set the number of locking read-acquisition kthreads.
1873 Defaults to being automatically set based on the
1874 number of online CPUs.
1876 locktorture.nwriters_stress= [KNL]
1877 Set the number of locking write-acquisition kthreads.
1879 locktorture.onoff_holdoff= [KNL]
1880 Set time (s) after boot for CPU-hotplug testing.
1882 locktorture.onoff_interval= [KNL]
1883 Set time (s) between CPU-hotplug operations, or
1884 zero to disable CPU-hotplug testing.
1886 locktorture.shuffle_interval= [KNL]
1887 Set task-shuffle interval (jiffies). Shuffling
1888 tasks allows some CPUs to go into dyntick-idle
1889 mode during the locktorture test.
1891 locktorture.shutdown_secs= [KNL]
1892 Set time (s) after boot system shutdown. This
1893 is useful for hands-off automated testing.
1895 locktorture.stat_interval= [KNL]
1896 Time (s) between statistics printk()s.
1898 locktorture.stutter= [KNL]
1899 Time (s) to stutter testing, for example,
1900 specifying five seconds causes the test to run for
1901 five seconds, wait for five seconds, and so on.
1902 This tests the locking primitive's ability to
1903 transition abruptly to and from idle.
1905 locktorture.torture_runnable= [BOOT]
1906 Start locktorture running at boot time.
1908 locktorture.torture_type= [KNL]
1909 Specify the locking implementation to test.
1911 locktorture.verbose= [KNL]
1912 Enable additional printk() statements.
1914 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1917 loglevel= All Kernel Messages with a loglevel smaller than the
1918 console loglevel will be printed to the console. It can
1919 also be changed with klogd or other programs. The
1920 loglevels are defined as follows:
1922 0 (KERN_EMERG) system is unusable
1923 1 (KERN_ALERT) action must be taken immediately
1924 2 (KERN_CRIT) critical conditions
1925 3 (KERN_ERR) error conditions
1926 4 (KERN_WARNING) warning conditions
1927 5 (KERN_NOTICE) normal but significant condition
1928 6 (KERN_INFO) informational
1929 7 (KERN_DEBUG) debug-level messages
1931 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1932 in bytes. n must be a power of two and greater
1933 than the minimal size. The minimal size is defined
1934 by LOG_BUF_SHIFT kernel config parameter. There is
1935 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1936 that allows to increase the default size depending on
1937 the number of CPUs. See init/Kconfig for more details.
1939 logo.nologo [FB] Disables display of the built-in Linux logo.
1940 This may be used to provide more screen space for
1941 kernel log messages and is useful when debugging
1942 kernel boot problems.
1944 lp=0 [LP] Specify parallel ports to use, e.g,
1945 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1946 lp=reset first parallel port). 'lp=0' disables the
1947 lp=auto printer driver. 'lp=reset' (which can be
1948 specified in addition to the ports) causes
1949 attached printers to be reset. Using
1950 lp=port1,port2,... specifies the parallel ports
1951 to associate lp devices with, starting with
1952 lp0. A port specification may be 'none' to skip
1953 that lp device, or a parport name such as
1954 'parport0'. Specifying 'lp=auto' instead of a
1955 port specification list means that device IDs
1956 from each port should be examined, to see if
1957 an IEEE 1284-compliant printer is attached; if
1958 so, the driver will manage that printer.
1959 See also header of drivers/char/lp.c.
1962 Sets loops_per_jiffy to given constant, thus avoiding
1963 time-consuming boot-time autodetection (up to 250 ms per
1964 CPU). 0 enables autodetection (default). To determine
1965 the correct value for your kernel, boot with normal
1966 autodetection and see what value is printed. Note that
1967 on SMP systems the preset will be applied to all CPUs,
1968 which is likely to cause problems if your CPUs need
1969 significantly divergent settings. An incorrect value
1970 will cause delays in the kernel to be wrong, leading to
1971 unpredictable I/O errors and other breakage. Although
1972 unlikely, in the extreme case this might damage your
1976 Format: <io>,<irq>,<dma>
1978 machvec= [IA-64] Force the use of a particular machine-vector
1979 (machvec) in a generic kernel.
1980 Example: machvec=hpzx1_swiotlb
1982 machtype= [Loongson] Share the same kernel image file between different
1984 Example: machtype=lemote-yeeloong-2f-7inch
1986 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1987 than or equal to this physical address is ignored.
1989 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1990 should make use of. maxcpus=n : n >= 0 limits the
1991 kernel to using 'n' processors. n=0 is a special case,
1992 it is equivalent to "nosmp", which also disables
1995 max_loop= [LOOP] The number of loop block devices that get
1996 (loop.max_loop) unconditionally pre-created at init time. The default
1997 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1998 of statically allocating a predefined number, loop
1999 devices can be requested on-demand with the
2000 /dev/loop-control interface.
2002 mce [X86-32] Machine Check Exception
2004 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2006 md= [HW] RAID subsystems devices and level
2007 See Documentation/md.txt.
2010 Format: <first>,<last>
2011 Specifies range of consoles to be captured by the MDA.
2013 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2014 Amount of memory to be used when the kernel is not able
2015 to see the whole system memory or for test.
2016 [X86] Work as limiting max address. Use together
2017 with memmap= to avoid physical address space collisions.
2018 Without memmap= PCI devices could be placed at addresses
2019 belonging to unused RAM.
2021 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2025 [KNL,SH] Allow user to override the default size for
2026 per-device physically contiguous DMA buffers.
2028 memmap=exactmap [KNL,X86] Enable setting of an exact
2029 E820 memory map, as specified by the user.
2030 Such memmap=exactmap lines can be constructed based on
2031 BIOS output or other requirements. See the memmap=nn@ss
2034 memmap=nn[KMG]@ss[KMG]
2035 [KNL] Force usage of a specific region of memory.
2036 Region of memory to be used is from ss to ss+nn.
2038 memmap=nn[KMG]#ss[KMG]
2039 [KNL,ACPI] Mark specific memory as ACPI data.
2040 Region of memory to be marked is from ss to ss+nn.
2042 memmap=nn[KMG]$ss[KMG]
2043 [KNL,ACPI] Mark specific memory as reserved.
2044 Region of memory to be reserved is from ss to ss+nn.
2045 Example: Exclude memory from 0x18690000-0x1869ffff
2046 memmap=64K$0x18690000
2048 memmap=0x10000$0x18690000
2050 memmap=nn[KMG]!ss[KMG]
2051 [KNL,X86] Mark specific memory as protected.
2052 Region of memory to be used, from ss to ss+nn.
2053 The memory region may be marked as e820 type 12 (0xc)
2054 and is NVDIMM or ADR memory.
2056 memory_corruption_check=0/1 [X86]
2057 Some BIOSes seem to corrupt the first 64k of
2058 memory when doing things like suspend/resume.
2059 Setting this option will scan the memory
2060 looking for corruption. Enabling this will
2061 both detect corruption and prevent the kernel
2062 from using the memory being corrupted.
2063 However, its intended as a diagnostic tool; if
2064 repeatable BIOS-originated corruption always
2065 affects the same memory, you can use memmap=
2066 to prevent the kernel from using that memory.
2068 memory_corruption_check_size=size [X86]
2069 By default it checks for corruption in the low
2070 64k, making this memory unavailable for normal
2071 use. Use this parameter to scan for
2072 corruption in more or less memory.
2074 memory_corruption_check_period=seconds [X86]
2075 By default it checks for corruption every 60
2076 seconds. Use this parameter to check at some
2077 other rate. 0 disables periodic checking.
2079 memtest= [KNL,X86,ARM] Enable memtest
2081 default : 0 <disable>
2082 Specifies the number of memtest passes to be
2083 performed. Each pass selects another test
2084 pattern from a given set of patterns. Memtest
2085 fills the memory with this pattern, validates
2086 memory contents and reserves bad memory
2087 regions that are detected.
2089 meye.*= [HW] Set MotionEye Camera parameters
2090 See Documentation/video4linux/meye.txt.
2092 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2093 Multi-Function General Purpose Timers on AMD Geode
2096 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2097 the BIOS has incorrectly applied a workaround. TinyBIOS
2098 version 0.98 is known to be affected, 0.99 fixes the
2099 problem by letting the user disable the workaround.
2103 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2104 physical address is ignored.
2106 mini2440= [ARM,HW,KNL]
2107 Format:[0..2][b][c][t]
2109 MINI2440 configuration specification:
2110 0 - The attached screen is the 3.5" TFT
2111 1 - The attached screen is the 7" TFT
2112 2 - The VGA Shield is attached (1024x768)
2113 Leaving out the screen size parameter will not load
2114 the TFT driver, and the framebuffer will be left
2116 b - Enable backlight. The TFT backlight pin will be
2117 linked to the kernel VESA blanking code and a GPIO
2118 LED. This parameter is not necessary when using the
2120 c - Enable the s3c camera interface.
2121 t - Reserved for enabling touchscreen support. The
2122 touchscreen support is not enabled in the mainstream
2123 kernel as of 2.6.30, a preliminary port can be found
2124 in the "bleeding edge" mini2440 support kernel at
2125 http://repo.or.cz/w/linux-2.6/mini2440.git
2128 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2129 parameter allows control of the logging verbosity for
2130 the additional memory initialisation checks. A value
2131 of 0 disables mminit logging and a level of 4 will
2132 log everything. Information is printed at KERN_DEBUG
2133 so loglevel=8 may also need to be specified.
2136 [KNL] When CONFIG_MODULE_SIG is set, this means that
2137 modules without (valid) signatures will fail to load.
2138 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2139 is always true, so this option does nothing.
2142 [MOUSE] Maximum time between finger touching and
2143 leaving touchpad surface for touch to be considered
2144 a tap and be reported as a left button click (for
2145 touchpads working in absolute mode only).
2147 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2148 reporting absolute coordinates, such as tablets
2149 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2150 reporting absolute coordinates, such as tablets
2152 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2153 is similar to kernelcore except it specifies the
2154 amount of memory used for migratable allocations.
2155 If both kernelcore and movablecore is specified,
2156 then kernelcore will be at *least* the specified
2157 value but may be more. If movablecore on its own
2158 is specified, the administrator must be careful
2159 that the amount of memory usable for all allocations
2162 movable_node [KNL,X86] Boot-time switch to enable the effects
2163 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2165 MTD_Partition= [MTD]
2166 Format: <name>,<region-number>,<size>,<offset>
2168 MTD_Region= [MTD] Format:
2169 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2172 See drivers/mtd/cmdlinepart.c.
2174 multitce=off [PPC] This parameter disables the use of the pSeries
2175 firmware feature for updating multiple TCE entries
2178 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2180 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2182 boundary - index of last SLC block on Flex-OneNAND.
2183 The remaining blocks are configured as MLC blocks.
2184 lock - Configure if Flex-OneNAND boundary should be locked.
2185 Once locked, the boundary cannot be changed.
2186 1 indicates lock status, 0 indicates unlock status.
2189 ARM/S3C2412 JIVE boot control
2191 See arch/arm/mach-s3c2412/mach-jive.c
2193 mtouchusb.raw_coordinates=
2194 [HW] Make the MicroTouch USB driver use raw coordinates
2195 ('y', default) or cooked coordinates ('n')
2197 mtrr_chunk_size=nn[KMG] [X86]
2198 used for mtrr cleanup. It is largest continuous chunk
2199 that could hold holes aka. UC entries.
2201 mtrr_gran_size=nn[KMG] [X86]
2202 Used for mtrr cleanup. It is granularity of mtrr block.
2204 Large value could prevent small alignment from
2207 mtrr_spare_reg_nr=n [X86]
2209 Range: 0,7 : spare reg number
2211 Used for mtrr cleanup. It is spare mtrr entries number.
2212 Set to 2 or more if your graphical card needs more.
2214 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2216 netdev= [NET] Network devices parameters
2217 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2218 Note that mem_start is often overloaded to mean
2219 something different and driver-specific.
2220 This usage is only documented in each driver source
2224 [NETFILTER] Enable connection tracking flow accounting
2225 0 to disable accounting
2226 1 to enable accounting
2229 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2230 See Documentation/filesystems/nfs/nfsroot.txt.
2232 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2233 See Documentation/filesystems/nfs/nfsroot.txt.
2235 nfsrootdebug [NFS] enable nfsroot debugging messages.
2236 See Documentation/filesystems/nfs/nfsroot.txt.
2238 nfs.callback_tcpport=
2239 [NFS] set the TCP port on which the NFSv4 callback
2240 channel should listen.
2243 [NFS] sets the pathname to the program which is used
2244 to update the NFS client cache entries.
2246 nfs.cache_getent_timeout=
2247 [NFS] sets the timeout after which an attempt to
2248 update a cache entry is deemed to have failed.
2250 nfs.idmap_cache_timeout=
2251 [NFS] set the maximum lifetime for idmapper cache
2255 [NFS] enable 64-bit inode numbers.
2256 If zero, the NFS client will fake up a 32-bit inode
2257 number for the readdir() and stat() syscalls instead
2258 of returning the full 64-bit number.
2259 The default is to return 64-bit inode numbers.
2261 nfs.max_session_slots=
2262 [NFSv4.1] Sets the maximum number of session slots
2263 the client will attempt to negotiate with the server.
2264 This limits the number of simultaneous RPC requests
2265 that the client can send to the NFSv4.1 server.
2266 Note that there is little point in setting this
2267 value higher than the max_tcp_slot_table_limit.
2269 nfs.nfs4_disable_idmapping=
2270 [NFSv4] When set to the default of '1', this option
2271 ensures that both the RPC level authentication
2272 scheme and the NFS level operations agree to use
2273 numeric uids/gids if the mount is using the
2274 'sec=sys' security flavour. In effect it is
2275 disabling idmapping, which can make migration from
2276 legacy NFSv2/v3 systems to NFSv4 easier.
2277 Servers that do not support this mode of operation
2278 will be autodetected by the client, and it will fall
2279 back to using the idmapper.
2280 To turn off this behaviour, set the value to '0'.
2282 [NFS4] Specify an additional fixed unique ident-
2283 ification string that NFSv4 clients can insert into
2284 their nfs_client_id4 string. This is typically a
2285 UUID that is generated at system install time.
2287 nfs.send_implementation_id =
2288 [NFSv4.1] Send client implementation identification
2289 information in exchange_id requests.
2290 If zero, no implementation identification information
2292 The default is to send the implementation identification
2295 nfs.recover_lost_locks =
2296 [NFSv4] Attempt to recover locks that were lost due
2297 to a lease timeout on the server. Please note that
2298 doing this risks data corruption, since there are
2299 no guarantees that the file will remain unchanged
2300 after the locks are lost.
2301 If you want to enable the kernel legacy behaviour of
2302 attempting to recover these locks, then set this
2304 The default parameter value of '0' causes the kernel
2305 not to attempt recovery of lost locks.
2307 nfs4.layoutstats_timer =
2308 [NFSv4.2] Change the rate at which the kernel sends
2309 layoutstats to the pNFS metadata server.
2311 Setting this to value to 0 causes the kernel to use
2312 whatever value is the default set by the layout
2313 driver. A non-zero value sets the minimum interval
2314 in seconds between layoutstats transmissions.
2316 nfsd.nfs4_disable_idmapping=
2317 [NFSv4] When set to the default of '1', the NFSv4
2318 server will return only numeric uids and gids to
2319 clients using auth_sys, and will accept numeric uids
2320 and gids from such clients. This is intended to ease
2321 migration from NFSv2/v3.
2323 objlayoutdriver.osd_login_prog=
2324 [NFS] [OBJLAYOUT] sets the pathname to the program which
2325 is used to automatically discover and login into new
2326 osd-targets. Please see:
2327 Documentation/filesystems/pnfs.txt for more explanations
2329 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2330 when a NMI is triggered.
2331 Format: [state][,regs][,debounce][,die]
2333 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2334 Format: [panic,][nopanic,][num]
2336 0 - turn nmi_watchdog off
2337 1 - turn nmi_watchdog on
2338 When panic is specified, panic when an NMI watchdog
2339 timeout occurs (or 'nopanic' to override the opposite
2341 This is useful when you use a panic=... timeout and
2342 need the box quickly up again.
2344 netpoll.carrier_timeout=
2345 [NET] Specifies amount of time (in seconds) that
2346 netpoll should wait for a carrier. By default netpoll
2349 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2350 emulation library even if a 387 maths coprocessor
2354 [HW] Never suspend the console
2355 Disable suspending of consoles during suspend and
2356 hibernate operations. Once disabled, debugging
2357 messages can reach various consoles while the rest
2358 of the system is being put to sleep (ie, while
2359 debugging driver suspend/resume hooks). This may
2360 not work reliably with all consoles, but is known
2361 to work with serial and VGA consoles.
2362 To facilitate more flexible debugging, we also add
2363 console_suspend, a printk module parameter to control
2364 it. Users could use console_suspend (usually
2365 /sys/module/printk/parameters/console_suspend) to
2366 turn on/off it dynamically.
2368 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2369 caches in the slab allocator. Saves per-node memory,
2370 but will impact performance.
2374 noapic [SMP,APIC] Tells the kernel to not make use of any
2375 IOAPICs that may be present in the system.
2377 noautogroup Disable scheduler automatic task group creation.
2379 nobats [PPC] Do not use BATs for mapping kernel lowmem
2380 on "Classic" PPC cores.
2384 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2386 nodelayacct [KNL] Disable per-task delay accounting
2388 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2390 nodsp [SH] Disable hardware DSP at boot time.
2392 noefi Disable EFI runtime services support.
2397 On X86-32 available only on PAE configured kernels.
2398 noexec=on: enable non-executable mappings (default)
2399 noexec=off: disable non-executable mappings
2402 Disable SMAP (Supervisor Mode Access Prevention)
2403 even if it is supported by processor.
2406 Disable SMEP (Supervisor Mode Execution Prevention)
2407 even if it is supported by processor.
2410 This affects only 32-bit executables.
2411 noexec32=on: enable non-executable mappings (default)
2412 read doesn't imply executable mappings
2413 noexec32=off: disable non-executable mappings
2414 read implies executable mappings
2416 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2418 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2419 register save and restore. The kernel will only save
2420 legacy floating-point registers on task switch.
2422 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2424 noxsave [BUGS=X86] Disables x86 extended register state save
2425 and restore using xsave. The kernel will fallback to
2426 enabling legacy floating-point and sse state.
2428 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2429 register states. The kernel will fall back to use
2430 xsave to save the states. By using this parameter,
2431 performance of saving the states is degraded because
2432 xsave doesn't support modified optimization while
2433 xsaveopt supports it on xsaveopt enabled systems.
2435 noxsaves [X86] Disables xsaves and xrstors used in saving and
2436 restoring x86 extended register state in compacted
2437 form of xsave area. The kernel will fall back to use
2438 xsaveopt and xrstor to save and restore the states
2439 in standard form of xsave area. By using this
2440 parameter, xsave area per process might occupy more
2441 memory on xsaves enabled systems.
2443 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2444 wfi(ARM) instruction doesn't work correctly and not to
2445 use it. This is also useful when using JTAG debugger.
2447 no_file_caps Tells the kernel not to honor file capabilities. The
2448 only way then for a file to be executed with privilege
2449 is to be setuid root or executed by root.
2451 nohalt [IA-64] Tells the kernel not to use the power saving
2452 function PAL_HALT_LIGHT when idle. This increases
2453 power-consumption. On the positive side, it reduces
2454 interrupt wake-up latency, which may improve performance
2455 in certain environments such as networked servers or
2458 nohibernate [HIBERNATION] Disable hibernation and resume.
2460 nohz= [KNL] Boottime enable/disable dynamic ticks
2461 Valid arguments: on, off
2464 nohz_full= [KNL,BOOT]
2465 In kernels built with CONFIG_NO_HZ_FULL=y, set
2466 the specified list of CPUs whose tick will be stopped
2467 whenever possible. The boot CPU will be forced outside
2468 the range to maintain the timekeeping.
2469 The CPUs in this range must also be included in the
2472 noiotrap [SH] Disables trapped I/O port accesses.
2474 noirqdebug [X86-32] Disables the code which attempts to detect and
2475 disable unhandled interrupt sources.
2477 no_timer_check [X86,APIC] Disables the code which tests for
2478 broken timer IRQ sources.
2480 noisapnp [ISAPNP] Disables ISA PnP code.
2482 noinitrd [RAM] Tells the kernel not to load any configured
2485 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2487 [Deprecated - use intremap=off]
2491 nojitter [IA-64] Disables jitter checking for ITC timers.
2493 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2495 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2498 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2499 steal time is computed, but won't influence scheduler
2502 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2504 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2506 noltlbs [PPC] Do not use large page/tlb entries for kernel
2507 lowmem mapping on PPC40x.
2509 nomca [IA-64] Disable machine check abort handling
2511 nomce [X86-32] Disable Machine Check Exception
2513 nomfgpt [X86-32] Disable Multi-Function General Purpose
2514 Timer usage (for AMD Geode machines).
2516 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2517 shutdown the other cpus. Instead use the REBOOT_VECTOR
2520 nomodule Disable module load
2522 nopat [X86] Disable PAT (page attribute table extension of
2523 pagetables) support.
2525 norandmaps Don't use address space randomization. Equivalent to
2526 echo 0 > /proc/sys/kernel/randomize_va_space
2528 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2530 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2531 with UP alternatives
2533 nordrand [X86] Disable kernel use of the RDRAND and
2534 RDSEED instructions even if they are supported
2535 by the processor. RDRAND and RDSEED are still
2536 available to user space applications.
2538 noresume [SWSUSP] Disables resume and restores original swap
2541 no-scroll [VGA] Disables scrollback.
2542 This is required for the Braillex ib80-piezo Braille
2543 reader made by F.H. Papenmeier (Germany).
2547 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2549 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2550 and disable the IO APIC. legacy for "maxcpus=0".
2552 nosoftlockup [KNL] Disable the soft-lockup detector.
2554 nosync [HW,M68K] Disables sync negotiation for all devices.
2556 notsc [BUGS=X86-32] Disable Time Stamp Counter
2558 nousb [USB] Disable the USB subsystem
2560 nowatchdog [KNL] Disable both lockup detectors, i.e.
2561 soft-lockup and NMI watchdog (hard-lockup).
2565 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2567 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2568 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2569 Some features depend on CPU0. Known dependencies are:
2570 1. Resume from suspend/hibernate depends on CPU0.
2571 Suspend/hibernate will fail if CPU0 is offline and you
2572 need to online CPU0 before suspend/hibernate.
2573 2. PIC interrupts also depend on CPU0. CPU0 can't be
2574 removed if a PIC interrupt is detected.
2575 It's said poweroff/reboot may depend on CPU0 on some
2576 machines although I haven't seen such issues so far
2577 after CPU0 is offline on a few tested machines.
2578 If the dependencies are under your control, you can
2579 turn on cpu0_hotplug.
2581 nptcg= [IA-64] Override max number of concurrent global TLB
2582 purges which is reported from either PAL_VM_SUMMARY or
2585 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2586 could support. nr_cpus=n : n >= 1 limits the kernel to
2587 supporting 'n' processors. Later in runtime you can not
2588 use hotplug cpu feature to put more cpu back to online.
2589 just like you compile the kernel NR_CPUS=n
2591 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2593 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2594 Allowed values are enable and disable
2596 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2597 one of ['zone', 'node', 'default'] can be specified
2598 This can be set from sysctl after boot.
2599 See Documentation/sysctl/vm.txt for details.
2601 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2602 See Documentation/debugging-via-ohci1394.txt for more
2605 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2606 Rather than timing out after 20 ms if an EC
2607 command is not properly ACKed, override the length
2608 of the timeout. We have interrupts disabled while
2609 waiting for the ACK, so if this is set too high
2610 interrupts *may* be lost!
2612 omap_mux= [OMAP] Override bootloader pin multiplexing.
2613 Format: <mux_mode0.mode_name=value>...
2614 For example, to override I2C bus2:
2615 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2617 oprofile.timer= [HW]
2618 Use timer interrupt instead of performance counters
2620 oprofile.cpu_type= Force an oprofile cpu type
2621 This might be useful if you have an older oprofile
2622 userland or if you want common events.
2623 Format: { arch_perfmon }
2624 arch_perfmon: [X86] Force use of architectural
2625 perfmon on Intel CPUs instead of the
2626 CPU specific event set.
2627 timer: [X86] Force use of architectural NMI
2628 timer mode (see also oprofile.timer
2629 for generic hr timer mode)
2630 [s390] Force legacy basic mode sampling
2631 (report cpu_type "timer")
2633 oops=panic Always panic on oopses. Default is to just kill the
2634 process, but there is a small probability of
2635 deadlocking the machine.
2636 This will also cause panics on machine check exceptions.
2637 Useful together with panic=30 to trigger a reboot.
2640 See Documentation/sound/oss/oss-parameters.txt
2642 page_owner= [KNL] Boot-time page_owner enabling option.
2643 Storage of the information about who allocated
2644 each page is disabled in default. With this switch,
2646 on: enable the feature
2648 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2649 timeout > 0: seconds before rebooting
2650 timeout = 0: wait forever
2651 timeout < 0: reboot immediately
2654 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2657 crash_kexec_post_notifiers
2658 Run kdump after running panic-notifiers and dumping
2659 kmsg. This only for the users who doubt kdump always
2660 succeeds in any situation.
2661 Note that this also increases risks of kdump failure,
2662 because some panic notifiers can make the crashed
2663 kernel more unstable.
2665 parkbd.port= [HW] Parallel port number the keyboard adapter is
2666 connected to, default is 0.
2668 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2669 0 for XT, 1 for AT (default is AT).
2672 parport= [HW,PPT] Specify parallel ports. 0 disables.
2673 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2674 Use 'auto' to force the driver to use any
2675 IRQ/DMA settings detected (the default is to
2676 ignore detected IRQ/DMA settings because of
2677 possible conflicts). You can specify the base
2678 address, IRQ, and DMA settings; IRQ and DMA
2679 should be numbers, or 'auto' (for using detected
2680 settings on that particular port), or 'nofifo'
2681 (to avoid using a FIFO even if it is detected).
2682 Parallel ports are assigned in the order they
2683 are specified on the command line, starting
2686 parport_init_mode= [HW,PPT]
2687 Configure VIA parallel port to operate in
2688 a specific mode. This is necessary on Pegasos
2689 computer where firmware has no options for setting
2690 up parallel port mode and sets it to spp.
2691 Currently this function knows 686a and 8231 chips.
2692 Format: [spp|ps2|epp|ecp|ecpepp]
2695 Halt all CPUs after the first oops has been printed for
2696 the specified number of seconds. This is to be used if
2697 your oopses keep scrolling off the screen.
2702 See header of drivers/block/paride/pcd.c.
2703 See also Documentation/blockdev/paride.txt.
2705 pci=option[,option...] [PCI] various PCI subsystem options:
2706 earlydump [X86] dump PCI config space before the kernel
2708 off [X86] don't probe for the PCI bus
2709 bios [X86-32] force use of PCI BIOS, don't access
2710 the hardware directly. Use this if your machine
2711 has a non-standard PCI host bridge.
2712 nobios [X86-32] disallow use of PCI BIOS, only direct
2713 hardware access methods are allowed. Use this
2714 if you experience crashes upon bootup and you
2715 suspect they are caused by the BIOS.
2716 conf1 [X86] Force use of PCI Configuration
2718 conf2 [X86] Force use of PCI Configuration
2720 noaer [PCIE] If the PCIEAER kernel config parameter is
2721 enabled, this kernel boot option can be used to
2722 disable the use of PCIE advanced error reporting.
2723 nodomains [PCI] Disable support for multiple PCI
2724 root domains (aka PCI segments, in ACPI-speak).
2725 nommconf [X86] Disable use of MMCONFIG for PCI
2727 check_enable_amd_mmconf [X86] check for and enable
2728 properly configured MMIO access to PCI
2729 config space on AMD family 10h CPU
2730 nomsi [MSI] If the PCI_MSI kernel config parameter is
2731 enabled, this kernel boot option can be used to
2732 disable the use of MSI interrupts system-wide.
2733 noioapicquirk [APIC] Disable all boot interrupt quirks.
2734 Safety option to keep boot IRQs enabled. This
2735 should never be necessary.
2736 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2737 primary IO-APIC for bridges that cannot disable
2738 boot IRQs. This fixes a source of spurious IRQs
2739 when the system masks IRQs.
2740 noioapicreroute [APIC] Disable workaround that uses the
2741 boot IRQ equivalent of an IRQ that connects to
2742 a chipset where boot IRQs cannot be disabled.
2743 The opposite of ioapicreroute.
2744 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2745 routing table. These calls are known to be buggy
2746 on several machines and they hang the machine
2747 when used, but on other computers it's the only
2748 way to get the interrupt routing table. Try
2749 this option if the kernel is unable to allocate
2750 IRQs or discover secondary PCI buses on your
2752 rom [X86] Assign address space to expansion ROMs.
2753 Use with caution as certain devices share
2754 address decoders between ROMs and other
2756 norom [X86] Do not assign address space to
2757 expansion ROMs that do not already have
2758 BIOS assigned address ranges.
2759 nobar [X86] Do not assign address space to the
2760 BARs that weren't assigned by the BIOS.
2761 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2762 assigned automatically to PCI devices. You can
2763 make the kernel exclude IRQs of your ISA cards
2765 pirqaddr=0xAAAAA [X86] Specify the physical address
2766 of the PIRQ table (normally generated
2767 by the BIOS) if it is outside the
2768 F0000h-100000h range.
2769 lastbus=N [X86] Scan all buses thru bus #N. Can be
2770 useful if the kernel is unable to find your
2771 secondary buses and you want to tell it
2772 explicitly which ones they are.
2773 assign-busses [X86] Always assign all PCI bus
2774 numbers ourselves, overriding
2775 whatever the firmware may have done.
2776 usepirqmask [X86] Honor the possible IRQ mask stored
2777 in the BIOS $PIR table. This is needed on
2778 some systems with broken BIOSes, notably
2779 some HP Pavilion N5400 and Omnibook XE3
2780 notebooks. This will have no effect if ACPI
2781 IRQ routing is enabled.
2782 noacpi [X86] Do not use ACPI for IRQ routing
2783 or for PCI scanning.
2784 use_crs [X86] Use PCI host bridge window information
2785 from ACPI. On BIOSes from 2008 or later, this
2786 is enabled by default. If you need to use this,
2787 please report a bug.
2788 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2789 If you need to use this, please report a bug.
2790 routeirq Do IRQ routing for all PCI devices.
2791 This is normally done in pci_enable_device(),
2792 so this option is a temporary workaround
2793 for broken drivers that don't call it.
2794 skip_isa_align [X86] do not align io start addr, so can
2795 handle more pci cards
2796 firmware [ARM] Do not re-enumerate the bus but instead
2797 just use the configuration from the
2798 bootloader. This is currently used on
2799 IXP2000 systems where the bus has to be
2800 configured a certain way for adjunct CPUs.
2801 noearly [X86] Don't do any early type 1 scanning.
2802 This might help on some broken boards which
2803 machine check when some devices' config space
2804 is read. But various workarounds are disabled
2805 and some IOMMU drivers will not work.
2806 bfsort Sort PCI devices into breadth-first order.
2807 This sorting is done to get a device
2808 order compatible with older (<= 2.4) kernels.
2809 nobfsort Don't sort PCI devices into breadth-first order.
2810 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2811 tuning and use the BIOS-configured MPS defaults.
2812 pcie_bus_safe Set every device's MPS to the largest value
2813 supported by all devices below the root complex.
2814 pcie_bus_perf Set device MPS to the largest allowable MPS
2815 based on its parent bus. Also set MRRS (Max
2816 Read Request Size) to the largest supported
2817 value (no larger than the MPS that the device
2818 or bus can support) for best performance.
2819 pcie_bus_peer2peer Set every device's MPS to 128B, which
2820 every device is guaranteed to support. This
2821 configuration allows peer-to-peer DMA between
2822 any pair of devices, possibly at the cost of
2823 reduced performance. This also guarantees
2824 that hot-added devices will work.
2825 cbiosize=nn[KMG] The fixed amount of bus space which is
2826 reserved for the CardBus bridge's IO window.
2827 The default value is 256 bytes.
2828 cbmemsize=nn[KMG] The fixed amount of bus space which is
2829 reserved for the CardBus bridge's memory
2830 window. The default value is 64 megabytes.
2833 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2834 Specifies alignment and device to reassign
2835 aligned memory resources.
2836 If <order of align> is not specified,
2837 PAGE_SIZE is used as alignment.
2838 PCI-PCI bridge can be specified, if resource
2839 windows need to be expanded.
2840 ecrc= Enable/disable PCIe ECRC (transaction layer
2841 end-to-end CRC checking).
2842 bios: Use BIOS/firmware settings. This is the
2846 hpiosize=nn[KMG] The fixed amount of bus space which is
2847 reserved for hotplug bridge's IO window.
2848 Default size is 256 bytes.
2849 hpmemsize=nn[KMG] The fixed amount of bus space which is
2850 reserved for hotplug bridge's memory window.
2851 Default size is 2 megabytes.
2852 realloc= Enable/disable reallocating PCI bridge resources
2853 if allocations done by BIOS are too small to
2854 accommodate resources required by all child
2856 off: Turn realloc off
2858 realloc same as realloc=on
2859 noari do not use PCIe ARI.
2860 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2861 only look for one device below a PCIe downstream
2864 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2867 force Enable ASPM even on devices that claim not to support it.
2868 WARNING: Forcing ASPM on may cause system lockups.
2870 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2871 nomsi Do not use MSI for PCI Express Native Hotplug (this
2872 makes all PCIe ports use INTx for hotplug services).
2874 pcie_ports= [PCIE] PCIe ports handling:
2875 auto Ask the BIOS whether or not to use native PCIe services
2876 associated with PCIe ports (PME, hot-plug, AER). Use
2877 them only if that is allowed by the BIOS.
2878 native Use native PCIe services associated with PCIe ports
2880 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2883 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2884 nomsi Do not use MSI for native PCIe PME signaling (this makes
2885 all PCIe root ports use INTx for all services).
2887 pcmv= [HW,PCMCIA] BadgePAD 4
2891 Keep all power-domains already enabled by bootloader on,
2892 even if no driver has claimed them. This is useful
2893 for debug and development, but should not be
2894 needed on a platform with proper driver support.
2897 See Documentation/blockdev/paride.txt.
2899 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2902 See arch/parisc/kernel/pdc_chassis.c
2904 percpu_alloc= Select which percpu first chunk allocator to use.
2905 Currently supported values are "embed" and "page".
2906 Archs may support subset or none of the selections.
2907 See comments in mm/percpu.c for details on each
2908 allocator. This parameter is primarily for debugging
2909 and performance comparison.
2912 See Documentation/blockdev/paride.txt.
2915 See Documentation/blockdev/paride.txt.
2917 pirq= [SMP,APIC] Manual mp-table setup
2918 See Documentation/x86/i386/IO-APIC.txt.
2920 plip= [PPT,NET] Parallel port network link
2921 Format: { parport<nr> | timid | 0 }
2922 See also Documentation/parport.txt.
2924 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2925 Override pmtimer IOPort with a hex value.
2929 Enable PNP debug messages (depends on the
2930 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2931 via /sys/module/pnp/parameters/debug. We always show
2932 current resource usage; turning this on also shows
2933 possible settings and some assignment information.
2939 { on | off | curr | res | no-curr | no-res }
2942 [ISAPNP] Exclude IRQs for the autoconfiguration
2945 [ISAPNP] Exclude DMAs for the autoconfiguration
2947 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2948 Ranges are in pairs (I/O port base and size).
2951 [ISAPNP] Exclude memory regions for the
2953 Ranges are in pairs (memory base and size).
2955 ports= [IP_VS_FTP] IPVS ftp helper module
2957 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2959 Format: <port>,<port>....
2961 print-fatal-signals=
2962 [KNL] debug: print fatal signals
2964 If enabled, warn about various signal handling
2965 related application anomalies: too many signals,
2966 too many POSIX.1 timers, fatal signals causing a
2969 If you hit the warning due to signal overflow,
2970 you might want to try "ulimit -i unlimited".
2974 printk.always_kmsg_dump=
2975 Trigger kmsg_dump for cases other than kernel oops or
2977 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2980 printk.time= Show timing data prefixed to each printk message line
2981 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2983 processor.max_cstate= [HW,ACPI]
2984 Limit processor to maximum C-state
2985 max_cstate=9 overrides any DMI blacklist limit.
2987 processor.nocst [HW,ACPI]
2988 Ignore the _CST method to determine C-states,
2989 instead using the legacy FADT method
2991 profile= [KNL] Enable kernel profiling via /proc/profile
2992 Format: [schedule,]<number>
2993 Param: "schedule" - profile schedule points.
2994 Param: <number> - step/bucket size as a power of 2 for
2995 statistical time based profiling.
2996 Param: "sleep" - profile D-state sleeping (millisecs).
2997 Requires CONFIG_SCHEDSTATS
2998 Param: "kvm" - profile VM exits.
3000 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3002 See Documentation/blockdev/ramdisk.txt.
3004 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3005 probe for; one of (bare|imps|exps|lifebook|any).
3006 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3008 psmouse.resetafter= [HW,MOUSE]
3009 Try to reset the device after so many bad packets
3012 [HW,MOUSE] Set desired mouse resolution, in dpi.
3013 psmouse.smartscroll=
3014 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3015 0 = disabled, 1 = enabled (default).
3017 pstore.backend= Specify the name of the pstore backend to use
3020 See Documentation/blockdev/paride.txt.
3023 [KNL] Number of legacy pty's. Overwrites compiled-in
3026 quiet [KNL] Disable most log messages
3031 See Documentation/md.txt.
3033 ramdisk_blocksize= [RAM]
3034 See Documentation/blockdev/ramdisk.txt.
3036 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3037 See Documentation/blockdev/ramdisk.txt.
3040 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3041 the specified list of CPUs to be no-callback CPUs.
3042 Invocation of these CPUs' RCU callbacks will
3043 be offloaded to "rcuox/N" kthreads created for
3044 that purpose, where "x" is "b" for RCU-bh, "p"
3045 for RCU-preempt, and "s" for RCU-sched, and "N"
3046 is the CPU number. This reduces OS jitter on the
3047 offloaded CPUs, which can be useful for HPC and
3048 real-time workloads. It can also improve energy
3049 efficiency for asymmetric multiprocessors.
3052 Rather than requiring that offloaded CPUs
3053 (specified by rcu_nocbs= above) explicitly
3054 awaken the corresponding "rcuoN" kthreads,
3055 make these kthreads poll for callbacks.
3056 This improves the real-time response for the
3057 offloaded CPUs by relieving them of the need to
3058 wake up the corresponding kthread, but degrades
3059 energy efficiency by requiring that the kthreads
3060 periodically wake up to do the polling.
3062 rcutree.blimit= [KNL]
3063 Set maximum number of finished RCU callbacks to
3064 process in one batch.
3066 rcutree.dump_tree= [KNL]
3067 Dump the structure of the rcu_node combining tree
3068 out at early boot. This is used for diagnostic
3069 purposes, to verify correct tree setup.
3071 rcutree.gp_cleanup_delay= [KNL]
3072 Set the number of jiffies to delay each step of
3073 RCU grace-period cleanup. This only has effect
3074 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3076 rcutree.gp_init_delay= [KNL]
3077 Set the number of jiffies to delay each step of
3078 RCU grace-period initialization. This only has
3079 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3082 rcutree.gp_preinit_delay= [KNL]
3083 Set the number of jiffies to delay each step of
3084 RCU grace-period pre-initialization, that is,
3085 the propagation of recent CPU-hotplug changes up
3086 the rcu_node combining tree. This only has effect
3087 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3089 rcutree.rcu_fanout_exact= [KNL]
3090 Disable autobalancing of the rcu_node combining
3091 tree. This is used by rcutorture, and might
3092 possibly be useful for architectures having high
3093 cache-to-cache transfer latencies.
3095 rcutree.rcu_fanout_leaf= [KNL]
3096 Change the number of CPUs assigned to each
3097 leaf rcu_node structure. Useful for very
3098 large systems, which will choose the value 64,
3099 and for NUMA systems with large remote-access
3100 latencies, which will choose a value aligned
3101 with the appropriate hardware boundaries.
3103 rcutree.jiffies_till_sched_qs= [KNL]
3104 Set required age in jiffies for a
3105 given grace period before RCU starts
3106 soliciting quiescent-state help from
3107 rcu_note_context_switch().
3109 rcutree.jiffies_till_first_fqs= [KNL]
3110 Set delay from grace-period initialization to
3111 first attempt to force quiescent states.
3112 Units are jiffies, minimum value is zero,
3113 and maximum value is HZ.
3115 rcutree.jiffies_till_next_fqs= [KNL]
3116 Set delay between subsequent attempts to force
3117 quiescent states. Units are jiffies, minimum
3118 value is one, and maximum value is HZ.
3120 rcutree.kthread_prio= [KNL,BOOT]
3121 Set the SCHED_FIFO priority of the RCU per-CPU
3122 kthreads (rcuc/N). This value is also used for
3123 the priority of the RCU boost threads (rcub/N)
3124 and for the RCU grace-period kthreads (rcu_bh,
3125 rcu_preempt, and rcu_sched). If RCU_BOOST is
3126 set, valid values are 1-99 and the default is 1
3127 (the least-favored priority). Otherwise, when
3128 RCU_BOOST is not set, valid values are 0-99 and
3129 the default is zero (non-realtime operation).
3131 rcutree.rcu_nocb_leader_stride= [KNL]
3132 Set the number of NOCB kthread groups, which
3133 defaults to the square root of the number of
3134 CPUs. Larger numbers reduces the wakeup overhead
3135 on the per-CPU grace-period kthreads, but increases
3136 that same overhead on each group's leader.
3138 rcutree.qhimark= [KNL]
3139 Set threshold of queued RCU callbacks beyond which
3140 batch limiting is disabled.
3142 rcutree.qlowmark= [KNL]
3143 Set threshold of queued RCU callbacks below which
3144 batch limiting is re-enabled.
3146 rcutree.rcu_idle_gp_delay= [KNL]
3147 Set wakeup interval for idle CPUs that have
3148 RCU callbacks (RCU_FAST_NO_HZ=y).
3150 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3151 Set wakeup interval for idle CPUs that have
3152 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3153 Lazy RCU callbacks are those which RCU can
3154 prove do nothing more than free memory.
3156 rcutorture.cbflood_inter_holdoff= [KNL]
3157 Set holdoff time (jiffies) between successive
3158 callback-flood tests.
3160 rcutorture.cbflood_intra_holdoff= [KNL]
3161 Set holdoff time (jiffies) between successive
3162 bursts of callbacks within a given callback-flood
3165 rcutorture.cbflood_n_burst= [KNL]
3166 Set the number of bursts making up a given
3167 callback-flood test. Set this to zero to
3168 disable callback-flood testing.
3170 rcutorture.cbflood_n_per_burst= [KNL]
3171 Set the number of callbacks to be registered
3172 in a given burst of a callback-flood test.
3174 rcutorture.fqs_duration= [KNL]
3175 Set duration of force_quiescent_state bursts
3178 rcutorture.fqs_holdoff= [KNL]
3179 Set holdoff time within force_quiescent_state bursts
3182 rcutorture.fqs_stutter= [KNL]
3183 Set wait time between force_quiescent_state bursts
3186 rcutorture.gp_cond= [KNL]
3187 Use conditional/asynchronous update-side
3188 primitives, if available.
3190 rcutorture.gp_exp= [KNL]
3191 Use expedited update-side primitives, if available.
3193 rcutorture.gp_normal= [KNL]
3194 Use normal (non-expedited) asynchronous
3195 update-side primitives, if available.
3197 rcutorture.gp_sync= [KNL]
3198 Use normal (non-expedited) synchronous
3199 update-side primitives, if available. If all
3200 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3201 rcutorture.gp_normal=, and rcutorture.gp_sync=
3202 are zero, rcutorture acts as if is interpreted
3203 they are all non-zero.
3205 rcutorture.n_barrier_cbs= [KNL]
3206 Set callbacks/threads for rcu_barrier() testing.
3208 rcutorture.nfakewriters= [KNL]
3209 Set number of concurrent RCU writers. These just
3210 stress RCU, they don't participate in the actual
3211 test, hence the "fake".
3213 rcutorture.nreaders= [KNL]
3214 Set number of RCU readers. The value -1 selects
3215 N-1, where N is the number of CPUs. A value
3216 "n" less than -1 selects N-n-2, where N is again
3217 the number of CPUs. For example, -2 selects N
3218 (the number of CPUs), -3 selects N+1, and so on.
3220 rcutorture.object_debug= [KNL]
3221 Enable debug-object double-call_rcu() testing.
3223 rcutorture.onoff_holdoff= [KNL]
3224 Set time (s) after boot for CPU-hotplug testing.
3226 rcutorture.onoff_interval= [KNL]
3227 Set time (s) between CPU-hotplug operations, or
3228 zero to disable CPU-hotplug testing.
3230 rcutorture.shuffle_interval= [KNL]
3231 Set task-shuffle interval (s). Shuffling tasks
3232 allows some CPUs to go into dyntick-idle mode
3233 during the rcutorture test.
3235 rcutorture.shutdown_secs= [KNL]
3236 Set time (s) after boot system shutdown. This
3237 is useful for hands-off automated testing.
3239 rcutorture.stall_cpu= [KNL]
3240 Duration of CPU stall (s) to test RCU CPU stall
3241 warnings, zero to disable.
3243 rcutorture.stall_cpu_holdoff= [KNL]
3244 Time to wait (s) after boot before inducing stall.
3246 rcutorture.stat_interval= [KNL]
3247 Time (s) between statistics printk()s.
3249 rcutorture.stutter= [KNL]
3250 Time (s) to stutter testing, for example, specifying
3251 five seconds causes the test to run for five seconds,
3252 wait for five seconds, and so on. This tests RCU's
3253 ability to transition abruptly to and from idle.
3255 rcutorture.test_boost= [KNL]
3256 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3257 "Maybe" means test if the RCU implementation
3258 under test support RCU priority boosting.
3260 rcutorture.test_boost_duration= [KNL]
3261 Duration (s) of each individual boost test.
3263 rcutorture.test_boost_interval= [KNL]
3264 Interval (s) between each boost test.
3266 rcutorture.test_no_idle_hz= [KNL]
3267 Test RCU's dyntick-idle handling. See also the
3268 rcutorture.shuffle_interval parameter.
3270 rcutorture.torture_runnable= [BOOT]
3271 Start rcutorture running at boot time.
3273 rcutorture.torture_type= [KNL]
3274 Specify the RCU implementation to test.
3276 rcutorture.verbose= [KNL]
3277 Enable additional printk() statements.
3279 rcupdate.rcu_expedited= [KNL]
3280 Use expedited grace-period primitives, for
3281 example, synchronize_rcu_expedited() instead
3282 of synchronize_rcu(). This reduces latency,
3283 but can increase CPU utilization, degrade
3284 real-time latency, and degrade energy efficiency.
3286 rcupdate.rcu_cpu_stall_suppress= [KNL]
3287 Suppress RCU CPU stall warning messages.
3289 rcupdate.rcu_cpu_stall_timeout= [KNL]
3290 Set timeout for RCU CPU stall warning messages.
3292 rcupdate.rcu_task_stall_timeout= [KNL]
3293 Set timeout in jiffies for RCU task stall warning
3294 messages. Disable with a value less than or equal
3297 rcupdate.rcu_self_test= [KNL]
3298 Run the RCU early boot self tests
3300 rcupdate.rcu_self_test_bh= [KNL]
3301 Run the RCU bh early boot self tests
3303 rcupdate.rcu_self_test_sched= [KNL]
3304 Run the RCU sched early boot self tests
3308 Run specified binary instead of /init from the ramdisk,
3309 used for early userspace startup. See initrd.
3312 Format (x86 or x86_64):
3313 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3315 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3317 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3318 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3319 reboot_force is either force or not specified,
3320 reboot_cpu is s[mp]#### with #### being the processor
3321 to be used for rebooting.
3324 [KNL, SMP] Set scheduler's default relax_domain_level.
3325 See Documentation/cgroups/cpusets.txt.
3327 relative_sleep_states=
3328 [SUSPEND] Use sleep state labeling where the deepest
3329 state available other than hibernation is always "mem".
3330 Format: { "0" | "1" }
3331 0 -- Traditional sleep state labels.
3332 1 -- Relative sleep state labels.
3334 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3336 reservetop= [X86-32]
3338 Reserves a hole at the top of the kernel virtual
3343 Set the amount of memory to reserve for BIOS at
3344 the bottom of the address space.
3346 reset_devices [KNL] Force drivers to reset the underlying device
3347 during initialization.
3350 Specify the partition device for software suspend
3352 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3354 resume_offset= [SWSUSP]
3355 Specify the offset from the beginning of the partition
3356 given by "resume=" at which the swap header is located,
3357 in <PAGE_SIZE> units (needed only for swap files).
3358 See Documentation/power/swsusp-and-swap-files.txt
3360 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3361 read the resume files
3363 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3364 Useful for devices that are detected asynchronously
3365 (e.g. USB and MMC devices).
3367 hibernate= [HIBERNATION]
3368 noresume Don't check if there's a hibernation image
3369 present during boot.
3370 nocompress Don't compress/decompress hibernation images.
3371 no Disable hibernation and resume.
3373 retain_initrd [RAM] Keep initrd memory after extraction
3375 rfkill.default_state=
3376 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3377 etc. communication is blocked by default.
3380 rfkill.master_switch_mode=
3381 0 The "airplane mode" button does nothing.
3382 1 The "airplane mode" button toggles between everything
3383 blocked and the previous configuration.
3384 2 The "airplane mode" button toggles between everything
3385 blocked and everything unblocked.
3387 rhash_entries= [KNL,NET]
3388 Set number of hash buckets for route cache
3390 ro [KNL] Mount root device read-only on boot
3392 root= [KNL] Root filesystem
3393 See name_to_dev_t comment in init/do_mounts.c.
3395 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3396 mount the root filesystem
3398 rootflags= [KNL] Set root filesystem mount option string
3400 rootfstype= [KNL] Set root filesystem type
3402 rootwait [KNL] Wait (indefinitely) for root device to show up.
3403 Useful for devices that are detected asynchronously
3404 (e.g. USB and MMC devices).
3406 rproc_mem=nn[KMG][@address]
3407 [KNL,ARM,CMA] Remoteproc physical memory block.
3408 Memory area to be used by remote processor image,
3411 rw [KNL] Mount root device read-write on boot
3413 S [KNL] Run init in single mode
3415 s390_iommu= [HW,S390]
3416 Set s390 IOTLB flushing mode
3418 With strict flushing every unmap operation will result in
3419 an IOTLB flush. Default is lazy flushing before reuse,
3423 See drivers/net/irda/sa1100_ir.c.
3425 sbni= [NET] Granch SBNI12 leased line adapter
3427 sched_debug [KNL] Enables verbose scheduler debug messages.
3429 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3430 xtime_lock contention on larger systems, and/or RCU lock
3431 contention on all systems with CONFIG_MAXSMP set.
3432 Format: { "0" | "1" }
3433 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3435 Note: increases power consumption, thus should only be
3436 enabled if running jitter sensitive (HPC/RT) workloads.
3438 security= [SECURITY] Choose a security module to enable at boot.
3439 If this boot parameter is not specified, only the first
3440 security module asking for security registration will be
3441 loaded. An invalid security module name will be treated
3442 as if no module has been chosen.
3444 selinux= [SELINUX] Disable or enable SELinux at boot time.
3445 Format: { "0" | "1" }
3446 See security/selinux/Kconfig help text.
3449 Default value is set via kernel config option.
3450 If enabled at boot time, /selinux/disable can be used
3451 later to disable prior to initial policy load.
3453 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3454 Format: { "0" | "1" }
3455 See security/apparmor/Kconfig help text
3458 Default value is set via kernel config option.
3460 serialnumber [BUGS=X86-32]
3463 Maximal number of shapers.
3465 show_msr= [x86] show boot-time MSR settings
3466 Format: { <integer> }
3467 Show boot-time (BIOS-initialized) MSR settings.
3468 The parameter means the number of CPUs to show,
3469 for example 1 means boot CPU only.
3477 Disable merging of slabs with similar size. May be
3478 necessary if there is some reason to distinguish
3479 allocs to different slabs. Debug options disable
3480 merging on their own.
3481 For more information see Documentation/vm/slub.txt.
3483 slab_max_order= [MM, SLAB]
3484 Determines the maximum allowed order for slabs.
3485 A high setting may cause OOMs due to memory
3486 fragmentation. Defaults to 1 for systems with
3487 more than 32MB of RAM, 0 otherwise.
3489 slub_debug[=options[,slabs]] [MM, SLUB]
3490 Enabling slub_debug allows one to determine the
3491 culprit if slab objects become corrupted. Enabling
3492 slub_debug can create guard zones around objects and
3493 may poison objects when not in use. Also tracks the
3494 last alloc / free. For more information see
3495 Documentation/vm/slub.txt.
3497 slub_max_order= [MM, SLUB]
3498 Determines the maximum allowed order for slabs.
3499 A high setting may cause OOMs due to memory
3500 fragmentation. For more information see
3501 Documentation/vm/slub.txt.
3503 slub_min_objects= [MM, SLUB]
3504 The minimum number of objects per slab. SLUB will
3505 increase the slab order up to slub_max_order to
3506 generate a sufficiently large slab able to contain
3507 the number of objects indicated. The higher the number
3508 of objects the smaller the overhead of tracking slabs
3509 and the less frequently locks need to be acquired.
3510 For more information see Documentation/vm/slub.txt.
3512 slub_min_order= [MM, SLUB]
3513 Determines the minimum page order for slabs. Must be
3514 lower than slub_max_order.
3515 For more information see Documentation/vm/slub.txt.
3517 slub_nomerge [MM, SLUB]
3518 Same with slab_nomerge. This is supported for legacy.
3519 See slab_nomerge for more information.
3522 Format: <io1>[,<io2>[,...,<io8>]]
3524 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3525 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3526 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3527 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3528 smsc-ircc2.ircc_irq= [HW] IRQ line
3529 smsc-ircc2.ircc_dma= [HW] DMA channel
3530 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3531 0: Toshiba Satellite 1800 (GP data pin select)
3532 1: Fast pin select (default)
3536 [KNL] Should the soft-lockup detector generate panics.
3539 softlockup_all_cpu_backtrace=
3540 [KNL] Should the soft-lockup detector generate
3541 backtraces on all cpus.
3544 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3545 See Documentation/laptops/sonypi.txt
3547 spia_io_base= [HW,MTD]
3553 Enabled the stack tracer on boot up.
3555 stacktrace_filter=[function-list]
3556 [FTRACE] Limit the functions that the stack tracer
3557 will trace at boot up. function-list is a comma separated
3558 list of functions. This list can be changed at run
3559 time by the stack_trace_filter file in the debugfs
3560 tracing directory. Note, this enables stack tracing
3561 and the stacktrace above is not needed.
3565 Set the STI (builtin display/keyboard on the HP-PARISC
3566 machines) console (graphic card) which should be used
3567 as the initial boot-console.
3568 See also comment in drivers/video/console/sticore.c.
3571 See comment in drivers/video/console/sticore.c.
3574 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3576 sunrpc.min_resvport=
3577 sunrpc.max_resvport=
3579 SunRPC servers often require that client requests
3580 originate from a privileged port (i.e. a port in the
3581 range 0 < portnr < 1024).
3582 An administrator who wishes to reserve some of these
3583 ports for other uses may adjust the range that the
3584 kernel's sunrpc client considers to be privileged
3585 using these two parameters to set the minimum and
3586 maximum port values.
3590 Control how the NFS server code allocates CPUs to
3591 service thread pools. Depending on how many NICs
3592 you have and where their interrupts are bound, this
3593 option will affect which CPUs will do NFS serving.
3594 Note: this parameter cannot be changed while the
3595 NFS server is running.
3597 auto the server chooses an appropriate mode
3598 automatically using heuristics
3599 global a single global pool contains all CPUs
3600 percpu one pool for each CPU
3601 pernode one pool for each NUMA node (equivalent
3602 to global on non-NUMA machines)
3604 sunrpc.tcp_slot_table_entries=
3605 sunrpc.udp_slot_table_entries=
3607 Sets the upper limit on the number of simultaneous
3608 RPC calls that can be sent from the client to a
3609 server. Increasing these values may allow you to
3610 improve throughput, but will also increase the
3611 amount of memory reserved for use by the client.
3613 suspend.pm_test_delay=
3615 Sets the number of seconds to remain in a suspend test
3616 mode before resuming the system (see
3617 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3618 is set. Default value is 5.
3621 [KNL] Enable accounting of swap in memory resource
3622 controller if no parameter or 1 is given or disable
3623 it if 0 is given (See Documentation/cgroups/memory.txt)
3625 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3626 Format: { <int> | force }
3627 <int> -- Number of I/O TLB slabs
3628 force -- force using of bounce buffers even if they
3629 wouldn't be automatically used by the kernel
3633 sysfs.deprecated=0|1 [KNL]
3634 Enable/disable old style sysfs layout for old udev
3635 on older distributions. When this option is enabled
3636 very new udev will not work anymore. When this option
3637 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3638 in older udev will not work anymore.
3639 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3640 the kernel configuration.
3642 sysrq_always_enabled
3644 Ignore sysrq setting - this boot parameter will
3645 neutralize any effect of /proc/sys/kernel/sysrq.
3646 Useful for debugging.
3648 tcpmhash_entries= [KNL,NET]
3649 Set the number of tcp_metrics_hash slots.
3650 Default value is 8192 or 16384 depending on total
3651 ram pages. This is used to specify the TCP metrics
3652 cache size. See Documentation/networking/ip-sysctl.txt
3653 "tcp_no_metrics_save" section for more details.
3657 test_suspend= [SUSPEND][,N]
3658 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3659 standby suspend) or "freeze" (for suspend type freeze)
3660 as the system sleep state during system startup with
3661 the optional capability to repeat N number of times.
3662 The system is woken from this state using a
3663 wakeup-capable RTC alarm.
3665 thash_entries= [KNL,NET]
3666 Set number of hash buckets for TCP connection
3668 thermal.act= [HW,ACPI]
3669 -1: disable all active trip points in all thermal zones
3670 <degrees C>: override all lowest active trip points
3672 thermal.crt= [HW,ACPI]
3673 -1: disable all critical trip points in all thermal zones
3674 <degrees C>: override all critical trip points
3676 thermal.nocrt= [HW,ACPI]
3677 Set to disable actions on ACPI thermal zone
3678 critical and hot trip points.
3680 thermal.off= [HW,ACPI]
3681 1: disable ACPI thermal control
3683 thermal.psv= [HW,ACPI]
3684 -1: disable all passive trip points
3685 <degrees C>: override all passive trip points to this
3688 thermal.tzp= [HW,ACPI]
3689 Specify global default ACPI thermal zone polling rate
3690 <deci-seconds>: poll all this frequency
3691 0: no polling (default)
3694 Force threading of all interrupt handlers except those
3695 marked explicitly IRQF_NO_THREAD.
3698 Enable the Transcendent memory driver if built-in.
3700 tmem.cleancache=0|1 [KNL, XEN]
3701 Default is on (1). Disable the usage of the cleancache
3702 API to send anonymous pages to the hypervisor.
3704 tmem.frontswap=0|1 [KNL, XEN]
3705 Default is on (1). Disable the usage of the frontswap
3706 API to send swap pages to the hypervisor. If disabled
3707 the selfballooning and selfshrinking are force disabled.
3709 tmem.selfballooning=0|1 [KNL, XEN]
3710 Default is on (1). Disable the driving of swap pages
3713 tmem.selfshrinking=0|1 [KNL, XEN]
3714 Default is on (1). Partial swapoff that immediately
3715 transfers pages from Xen hypervisor back to the
3716 kernel based on different criteria.
3720 Specify if the kernel should make use of the cpu
3721 topology information if the hardware supports this.
3722 The scheduler will make use of this information and
3723 e.g. base its process migration decisions on it.
3726 topology_updates= [KNL, PPC, NUMA]
3728 Specify if the kernel should ignore (off)
3729 topology updates sent by the hypervisor to this
3734 tpm_suspend_pcr=[HW,TPM]
3735 Format: integer pcr id
3736 Specify that at suspend time, the tpm driver
3737 should extend the specified pcr with zeros,
3738 as a workaround for some chips which fail to
3739 flush the last written pcr on TPM_SaveState.
3740 This will guarantee that all the other pcrs
3743 trace_buf_size=nn[KMG]
3744 [FTRACE] will set tracing buffer size on each cpu.
3746 trace_event=[event-list]
3747 [FTRACE] Set and start specified trace events in order
3748 to facilitate early boot debugging.
3749 See also Documentation/trace/events.txt
3751 trace_options=[option-list]
3752 [FTRACE] Enable or disable tracer options at boot.
3753 The option-list is a comma delimited list of options
3754 that can be enabled or disabled just as if you were
3755 to echo the option name into
3757 /sys/kernel/debug/tracing/trace_options
3759 For example, to enable stacktrace option (to dump the
3760 stack trace of each event), add to the command line:
3762 trace_options=stacktrace
3764 See also Documentation/trace/ftrace.txt "trace options"
3768 Have the tracepoints sent to printk as well as the
3769 tracing ring buffer. This is useful for early boot up
3770 where the system hangs or reboots and does not give the
3771 option for reading the tracing buffer or performing a
3772 ftrace_dump_on_oops.
3774 To turn off having tracepoints sent to printk,
3775 echo 0 > /proc/sys/kernel/tracepoint_printk
3776 Note, echoing 1 into this file without the
3777 tracepoint_printk kernel cmdline option has no effect.
3781 Having tracepoints sent to printk() and activating high
3782 frequency tracepoints such as irq or sched, can cause
3783 the system to live lock.
3786 [FTRACE] enable this option to disable tracing when a
3787 warning is hit. This turns off "tracing_on". Tracing can
3788 be enabled again by echoing '1' into the "tracing_on"
3789 file located in /sys/kernel/debug/tracing/
3791 This option is useful, as it disables the trace before
3792 the WARNING dump is called, which prevents the trace to
3793 be filled with content caused by the warning output.
3795 This option can also be set at run time via the sysctl
3796 option: kernel/traceoff_on_warning
3798 transparent_hugepage=
3800 Format: [always|madvise|never]
3801 Can be used to control the default behavior of the system
3802 with respect to transparent hugepages.
3803 See Documentation/vm/transhuge.txt for more details.
3805 tsc= Disable clocksource stability checks for TSC.
3807 [x86] reliable: mark tsc clocksource as reliable, this
3808 disables clocksource verification at runtime, as well
3809 as the stability checks done at bootup. Used to enable
3810 high-resolution timer mode on older hardware, and in
3811 virtualized environment.
3812 [x86] noirqtime: Do not use TSC to do irq accounting.
3813 Used to run time disable IRQ_TIME_ACCOUNTING on any
3814 platforms where RDTSC is slow and this accounting
3817 turbografx.map[2|3]= [HW,JOY]
3818 TurboGraFX parallel port interface
3820 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3821 See also Documentation/input/joystick-parport.txt
3823 udbg-immortal [PPC] When debugging early kernel crashes that
3824 happen after console_init() and before a proper
3825 console driver takes over, this boot options might
3826 help "seeing" what's going on.
3828 uhash_entries= [KNL,NET]
3829 Set number of hash buckets for UDP/UDP-Lite connections
3832 [USB] Ignore overcurrent events (default N).
3833 Some badly-designed motherboards generate lots of
3834 bogus events, for ports that aren't wired to
3835 anything. Set this parameter to avoid log spamming.
3836 Note that genuine overcurrent events won't be
3840 [X86] Cause panic on unknown NMI.
3842 usbcore.authorized_default=
3843 [USB] Default USB device authorization:
3844 (default -1 = authorized except for wireless USB,
3845 0 = not authorized, 1 = authorized)
3847 usbcore.autosuspend=
3848 [USB] The autosuspend time delay (in seconds) used
3849 for newly-detected USB devices (default 2). This
3850 is the time required before an idle device will be
3851 autosuspended. Devices for which the delay is set
3852 to a negative value won't be autosuspended at all.
3854 usbcore.usbfs_snoop=
3855 [USB] Set to log all usbfs traffic (default 0 = off).
3857 usbcore.blinkenlights=
3858 [USB] Set to cycle leds on hubs (default 0 = off).
3860 usbcore.old_scheme_first=
3861 [USB] Start with the old device initialization
3862 scheme (default 0 = off).
3864 usbcore.usbfs_memory_mb=
3865 [USB] Memory limit (in MB) for buffers allocated by
3866 usbfs (default = 16, 0 = max = 2047).
3868 usbcore.use_both_schemes=
3869 [USB] Try the other device initialization scheme
3870 if the first one fails (default 1 = enabled).
3872 usbcore.initial_descriptor_timeout=
3873 [USB] Specifies timeout for the initial 64-byte
3874 USB_REQ_GET_DESCRIPTOR request in milliseconds
3875 (default 5000 = 5.0 seconds).
3878 [USBHID] The interval which mice are to be polled at.
3880 usb-storage.delay_use=
3881 [UMS] The delay in seconds before a new device is
3882 scanned for Logical Units (default 1).
3885 [UMS] A list of quirks entries to supplement or
3886 override the built-in unusual_devs list. List
3887 entries are separated by commas. Each entry has
3888 the form VID:PID:Flags where VID and PID are Vendor
3889 and Product ID values (4-digit hex numbers) and
3890 Flags is a set of characters, each corresponding
3891 to a common usb-storage quirk flag as follows:
3892 a = SANE_SENSE (collect more than 18 bytes
3894 b = BAD_SENSE (don't collect more than 18
3895 bytes of sense data);
3896 c = FIX_CAPACITY (decrease the reported
3897 device capacity by one sector);
3898 d = NO_READ_DISC_INFO (don't use
3899 READ_DISC_INFO command);
3900 e = NO_READ_CAPACITY_16 (don't use
3901 READ_CAPACITY_16 command);
3902 f = NO_REPORT_OPCODES (don't use report opcodes
3904 g = MAX_SECTORS_240 (don't transfer more than
3905 240 sectors at a time, uas only);
3906 h = CAPACITY_HEURISTICS (decrease the
3907 reported device capacity by one
3908 sector if the number is odd);
3909 i = IGNORE_DEVICE (don't bind to this
3911 l = NOT_LOCKABLE (don't try to lock and
3912 unlock ejectable media);
3913 m = MAX_SECTORS_64 (don't transfer more
3914 than 64 sectors = 32 KB at a time);
3915 n = INITIAL_READ10 (force a retry of the
3916 initial READ(10) command);
3917 o = CAPACITY_OK (accept the capacity
3918 reported by the device);
3919 p = WRITE_CACHE (the device cache is ON
3921 r = IGNORE_RESIDUE (the device reports
3922 bogus residue values);
3923 s = SINGLE_LUN (the device has only one
3925 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3926 commands, uas only);
3927 u = IGNORE_UAS (don't bind to the uas driver);
3928 w = NO_WP_DETECT (don't test whether the
3929 medium is write-protected).
3930 Example: quirks=0419:aaf5:rl,0421:0433:rc
3932 user_debug= [KNL,ARM]
3934 See arch/arm/Kconfig.debug help text.
3935 1 - undefined instruction events
3937 4 - invalid data aborts
3940 Example: user_debug=31
3943 [X86] Flags controlling user PTE allocations.
3945 nohigh = do not allocate PTE pages in
3946 HIGHMEM regardless of setting
3950 On X86_32, this is an alias for vdso32=. Otherwise:
3952 vdso=1: enable VDSO (the default)
3953 vdso=0: disable VDSO mapping
3955 vdso32= [X86] Control the 32-bit vDSO
3956 vdso32=1: enable 32-bit VDSO
3957 vdso32=0 or vdso32=2: disable 32-bit VDSO
3959 See the help text for CONFIG_COMPAT_VDSO for more
3960 details. If CONFIG_COMPAT_VDSO is set, the default is
3961 vdso32=0; otherwise, the default is vdso32=1.
3963 For compatibility with older kernels, vdso32=2 is an
3966 Try vdso32=0 if you encounter an error that says:
3967 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3970 vector=percpu: enable percpu vector domain
3972 video= [FB] Frame buffer configuration
3973 See Documentation/fb/modedb.txt.
3975 video.brightness_switch_enabled= [0,1]
3976 If set to 1, on receiving an ACPI notify event
3977 generated by hotkey, video driver will adjust brightness
3978 level and then send out the event to user space through
3979 the allocated input device; If set to 0, video driver
3980 will only send out the event without touching backlight
3985 [VMMIO] Memory mapped virtio (platform) device.
3987 <size>@<baseaddr>:<irq>[:<id>]
3989 <size> := size (can use standard suffixes
3991 <baseaddr> := physical base address
3992 <irq> := interrupt number (as passed to
3994 <id> := (optional) platform device id
3996 virtio_mmio.device=1K@0x100b0000:48:7
3998 Can be used multiple times for multiple devices.
4000 vga= [BOOT,X86-32] Select a particular video mode
4001 See Documentation/x86/boot.txt and
4002 Documentation/svga.txt.
4003 Use vga=ask for menu.
4004 This is actually a boot loader parameter; the value is
4005 passed to the kernel using a special protocol.
4007 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4008 size of <nn>. This can be used to increase the
4009 minimum size (128MB on x86). It can also be used to
4010 decrease the size and leave more room for directly
4013 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4016 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4019 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4023 Controls the behavior of vsyscalls (i.e. calls to
4024 fixed addresses of 0xffffffffff600x00 from legacy
4025 code). Most statically-linked binaries and older
4026 versions of glibc use these calls. Because these
4027 functions are at fixed addresses, they make nice
4028 targets for exploits that can control RIP.
4030 emulate [default] Vsyscalls turn into traps and are
4031 emulated reasonably safely.
4033 native Vsyscalls are native syscall instructions.
4034 This is a little bit faster than trapping
4035 and makes a few dynamic recompilers work
4036 better than they would in emulation mode.
4037 It also makes exploits much easier to write.
4039 none Vsyscalls don't work at all. This makes
4040 them quite hard to use for exploits but
4041 might break your system.
4043 vt.color= [VT] Default text color.
4044 Format: 0xYX, X = foreground, Y = background.
4045 Default: 0x07 = light gray on black.
4047 vt.cur_default= [VT] Default cursor shape.
4048 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4049 the parameters of the <Esc>[?A;B;Cc escape sequence;
4050 see VGA-softcursor.txt. Default: 2 = underline.
4052 vt.default_blu= [VT]
4053 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4054 Change the default blue palette of the console.
4055 This is a 16-member array composed of values
4058 vt.default_grn= [VT]
4059 Format: <green0>,<green1>,<green2>,...,<green15>
4060 Change the default green palette of the console.
4061 This is a 16-member array composed of values
4064 vt.default_red= [VT]
4065 Format: <red0>,<red1>,<red2>,...,<red15>
4066 Change the default red palette of the console.
4067 This is a 16-member array composed of values
4073 Set system-wide default UTF-8 mode for all tty's.
4074 Default is 1, i.e. UTF-8 mode is enabled for all
4075 newly opened terminals.
4077 vt.global_cursor_default=
4080 Set system-wide default for whether a cursor
4081 is shown on new VTs. Default is -1,
4082 i.e. cursors will be created by default unless
4083 overridden by individual drivers. 0 will hide
4084 cursors, 1 will display them.
4086 vt.italic= [VT] Default color for italic text; 0-15.
4089 vt.underline= [VT] Default color for underlined text; 0-15.
4092 watchdog timers [HW,WDT] For information on watchdog timers,
4093 see Documentation/watchdog/watchdog-parameters.txt
4094 or other driver-specific files in the
4095 Documentation/watchdog/ directory.
4097 workqueue.disable_numa
4098 By default, all work items queued to unbound
4099 workqueues are affine to the NUMA nodes they're
4100 issued on, which results in better behavior in
4101 general. If NUMA affinity needs to be disabled for
4102 whatever reason, this option can be used. Note
4103 that this also can be controlled per-workqueue for
4104 workqueues visible under /sys/bus/workqueue/.
4106 workqueue.power_efficient
4107 Per-cpu workqueues are generally preferred because
4108 they show better performance thanks to cache
4109 locality; unfortunately, per-cpu workqueues tend to
4110 be more power hungry than unbound workqueues.
4112 Enabling this makes the per-cpu workqueues which
4113 were observed to contribute significantly to power
4114 consumption unbound, leading to measurably lower
4115 power usage at the cost of small performance
4118 The default value of this parameter is determined by
4119 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4121 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4122 default x2apic cluster mode on platforms
4125 x86_intel_mid_timer= [X86-32,APBT]
4126 Choose timer option for x86 Intel MID platform.
4127 Two valid options are apbt timer only and lapic timer
4128 plus one apbt timer for broadcast timer.
4129 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4131 xen_512gb_limit [KNL,X86-64,XEN]
4132 Restricts the kernel running paravirtualized under Xen
4133 to use only up to 512 GB of RAM. The reason to do so is
4134 crash analysis tools and Xen tools for doing domain
4135 save/restore/migration must be enabled to handle larger
4138 xen_emul_unplug= [HW,X86,XEN]
4139 Unplug Xen emulated devices
4140 Format: [unplug0,][unplug1]
4141 ide-disks -- unplug primary master IDE devices
4142 aux-ide-disks -- unplug non-primary-master IDE devices
4143 nics -- unplug network devices
4144 all -- unplug all emulated devices (NICs and IDE disks)
4145 unnecessary -- unplugging emulated devices is
4146 unnecessary even if the host did not respond to
4148 never -- do not unplug even if version check succeeds
4150 xen_nopvspin [X86,XEN]
4151 Disables the ticketlock slowpath using Xen PV
4155 Disables the PV optimizations forcing the HVM guest to
4156 run as generic HVM guest with no PV drivers.
4158 xirc2ps_cs= [NET,PCMCIA]
4160 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4162 ______________________________________________________________________
4166 Add more DRM drivers.
projects / karo-tx-linux.git / blob