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.
1029 Use early console provided by Freescale LP UART driver
1030 found on Freescale Vybrid and QorIQ LS1021A processors.
1031 A valid base address must be provided, and the serial
1032 port must already be setup and configured.
1034 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1038 earlyprintk=serial[,ttySn[,baudrate]]
1039 earlyprintk=serial[,0x...[,baudrate]]
1040 earlyprintk=ttySn[,baudrate]
1041 earlyprintk=dbgp[debugController#]
1042 earlyprintk=pciserial,bus:device.function[,baudrate]
1044 earlyprintk is useful when the kernel crashes before
1045 the normal console is initialized. It is not enabled by
1046 default because it has some cosmetic problems.
1048 Append ",keep" to not disable it when the real console
1051 Only one of vga, efi, serial, or usb debug port can
1054 Currently only ttyS0 and ttyS1 may be specified by
1055 name. Other I/O ports may be explicitly specified
1056 on some architectures (x86 and arm at least) by
1057 replacing ttySn with an I/O port address, like this:
1058 earlyprintk=serial,0x1008,115200
1059 You can find the port for a given device in
1060 /proc/tty/driver/serial:
1061 2: uart:ST16650V2 port:00001008 irq:18 ...
1063 Interaction with the standard serial driver is not
1066 The VGA and EFI output is eventually overwritten by
1069 The xen output can only be used by Xen PV guests.
1071 edac_report= [HW,EDAC] Control how to report EDAC event
1072 Format: {"on" | "off" | "force"}
1073 on: enable EDAC to report H/W event. May be overridden
1074 by other higher priority error reporting module.
1075 off: disable H/W event reporting through EDAC.
1076 force: enforce the use of EDAC to report H/W event.
1079 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1082 This is designed to be used in conjunction with
1083 the boot argument: earlyprintk=vga
1086 Format: {"off" | "on" | "skip[mbr]"}
1089 Format: { "old_map", "nochunk", "noruntime", "debug" }
1090 old_map [X86-64]: switch to the old ioremap-based EFI
1091 runtime services mapping. 32-bit still uses this one by
1093 nochunk: disable reading files in "chunks" in the EFI
1094 boot stub, as chunking can cause problems with some
1095 firmware implementations.
1096 noruntime : disable EFI runtime services support
1097 debug: enable misc debug output
1099 efi_no_storage_paranoia [EFI; X86]
1100 Using this parameter you can use more than 50% of
1101 your efi variable storage. Use this parameter only if
1102 you are really sure that your UEFI does sane gc and
1103 fulfills the spec otherwise your board may brick.
1105 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1106 Add arbitrary attribute to specific memory range by
1107 updating original EFI memory map.
1108 Region of memory which aa attribute is added to is
1110 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1111 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1112 attribute is added to range 0x100000000-0x180000000 and
1113 0x10a0000000-0x1120000000.
1115 Using this parameter you can do debugging of EFI memmap
1116 related feature. For example, you can do debugging of
1117 Address Range Mirroring feature even if your box
1120 eisa_irq_edge= [PARISC,HW]
1121 See header of drivers/parisc/eisa.c.
1124 See comment before function elanfreq_setup() in
1125 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1128 Format: {"cfq" | "deadline" | "noop"}
1129 See Documentation/block/cfq-iosched.txt and
1130 Documentation/block/deadline-iosched.txt for details.
1132 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1133 Specifies physical address of start of kernel core
1134 image elf header and optionally the size. Generally
1135 kexec loader will pass this option to capture kernel.
1136 See Documentation/kdump/kdump.txt for details.
1138 enable_mtrr_cleanup [X86]
1139 The kernel tries to adjust MTRR layout from continuous
1140 to discrete, to make X server driver able to add WB
1141 entry later. This parameter enables that.
1143 enable_timer_pin_1 [X86]
1144 Enable PIN 1 of APIC timer
1145 Can be useful to work around chipset bugs
1146 (in particular on some ATI chipsets).
1147 The kernel tries to set a reasonable default.
1149 enforcing [SELINUX] Set initial enforcing status.
1151 See security/selinux/Kconfig help text.
1152 0 -- permissive (log only, no denials).
1153 1 -- enforcing (deny and log).
1155 Value can be changed at runtime via /selinux/enforce.
1158 Disable Error Record Serialization Table (ERST)
1161 ether= [HW,NET] Ethernet cards parameters
1162 This option is obsoleted by the "netdev=" option, which
1163 has equivalent usage. See its documentation for details.
1167 Permit 'security.evm' to be updated regardless of
1168 current integrity status.
1172 fail_make_request=[KNL]
1173 General fault injection mechanism.
1174 Format: <interval>,<probability>,<space>,<times>
1175 See also Documentation/fault-injection/.
1178 See Documentation/blockdev/floppy.txt.
1180 force_pal_cache_flush
1181 [IA-64] Avoid check_sal_cache_flush which may hang on
1182 buggy SAL_CACHE_FLUSH implementations. Using this
1183 parameter will force ia64_sal_cache_flush to call
1184 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1187 Forcefully enable Physical Address Extension (PAE).
1188 Many Pentium M systems disable PAE but may have a
1189 functionally usable PAE implementation.
1190 Warning: use of this parameter will taint the kernel
1191 and may cause unknown problems.
1194 [FTRACE] will set and start the specified tracer
1195 as early as possible in order to facilitate early
1198 ftrace_dump_on_oops[=orig_cpu]
1199 [FTRACE] will dump the trace buffers on oops.
1200 If no parameter is passed, ftrace will dump
1201 buffers of all CPUs, but if you pass orig_cpu, it will
1202 dump only the buffer of the CPU that triggered the
1205 ftrace_filter=[function-list]
1206 [FTRACE] Limit the functions traced by the function
1207 tracer at boot up. function-list is a comma separated
1208 list of functions. This list can be changed at run
1209 time by the set_ftrace_filter file in the debugfs
1212 ftrace_notrace=[function-list]
1213 [FTRACE] Do not trace the functions specified in
1214 function-list. This list can be changed at run time
1215 by the set_ftrace_notrace file in the debugfs
1218 ftrace_graph_filter=[function-list]
1219 [FTRACE] Limit the top level callers functions traced
1220 by the function graph tracer at boot up.
1221 function-list is a comma separated list of functions
1222 that can be changed at run time by the
1223 set_graph_function file in the debugfs tracing directory.
1225 ftrace_graph_notrace=[function-list]
1226 [FTRACE] Do not trace from the functions specified in
1227 function-list. This list is a comma separated list of
1228 functions that can be changed at run time by the
1229 set_graph_notrace file in the debugfs tracing directory.
1232 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1233 support via parallel port (up to 5 devices per port)
1234 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1235 See also Documentation/input/joystick-parport.txt
1239 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1243 gcov_persist= [GCOV] When non-zero (default), profiling data for
1244 kernel modules is saved and remains accessible via
1245 debugfs, even when the module is unloaded/reloaded.
1246 When zero, profiling data is discarded and associated
1247 debugfs files are removed at module unload time.
1249 gpt [EFI] Forces disk with valid GPT signature but
1250 invalid Protective MBR to be treated as GPT. If the
1251 primary GPT is corrupted, it enables the backup/alternate
1252 GPT to be used instead.
1254 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1255 the "Enable 0" bit of the configuration register.
1258 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1259 the "Enable 0" bit of the configuration register.
1262 grcan.select= [HW] Select which physical interface to use.
1265 grcan.txsize= [HW] Sets the size of the tx buffer.
1266 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1268 grcan.rxsize= [HW] Sets the size of the rx buffer.
1269 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1272 hashdist= [KNL,NUMA] Large hashes allocated during boot
1273 are distributed across NUMA nodes. Defaults on
1274 for 64-bit NUMA, off otherwise.
1275 Format: 0 | 1 (for off | on)
1277 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1279 hd= [EIDE] (E)IDE hard drive subsystem geometry
1280 Format: <cyl>,<head>,<sect>
1283 Disable Hardware Error Source Table (HEST) support;
1284 corresponding firmware-first mode error processing
1285 logic will be disabled.
1287 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1288 size of <nn>. This works even on boxes that have no
1289 highmem otherwise. This also works to reduce highmem
1290 size on bigger boxes.
1292 highres= [KNL] Enable/disable high resolution timer mode.
1293 Valid parameters: "on", "off"
1297 See Documentation/isdn/README.HiSax.
1301 hpet= [X86-32,HPET] option to control HPET usage
1302 Format: { enable (default) | disable | force |
1304 disable: disable HPET and use PIT instead
1305 force: allow force enabled of undocumented chips (ICH4,
1307 verbose: show contents of HPET registers during setup
1309 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1310 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1312 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1313 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1314 On x86-64 and powerpc, this option can be specified
1315 multiple times interleaved with hugepages= to reserve
1316 huge pages of different sizes. Valid pages sizes on
1317 x86-64 are 2M (when the CPU supports "pse") and 1G
1318 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1320 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1321 terminal devices. Valid values: 0..8
1322 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1323 If specified, z/VM IUCV HVC accepts connections
1324 from listed z/VM user IDs only.
1326 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1327 hardware thread id mappings.
1328 Format: <cpu>:<hwthread>
1331 Do not unregister boot console at start. This is only
1332 useful for debugging when something happens in the window
1333 between unregistering the boot console and initializing
1336 i2c_bus= [HW] Override the default board specific I2C bus speed
1337 or register an additional I2C bus that is not
1338 registered from board initialization code.
1342 i8042.debug [HW] Toggle i8042 debug mode
1343 i8042.unmask_kbd_data
1344 [HW] Enable printing of interrupt data from the KBD port
1345 (disabled by default, and as a pre-condition
1346 requires that i8042.debug=1 be enabled)
1347 i8042.direct [HW] Put keyboard port into non-translated mode
1348 i8042.dumbkbd [HW] Pretend that controller can only read data from
1349 keyboard and cannot control its state
1350 (Don't attempt to blink the leds)
1351 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1352 i8042.nokbd [HW] Don't check/create keyboard port
1353 i8042.noloop [HW] Disable the AUX Loopback command while probing
1355 i8042.nomux [HW] Don't check presence of an active multiplexing
1357 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1359 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1360 i8042.reset [HW] Reset the controller during init and cleanup
1361 i8042.unlock [HW] Unlock (ignore) the keylock
1362 i8042.kbdreset [HW] Reset device connected to KBD port
1366 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1367 indicates that the driver is running on unsupported
1369 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1370 does not match list of supported models.
1372 [HW] Report power status in /proc/i8k
1373 (disabled by default)
1374 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1377 i915.invert_brightness=
1378 [DRM] Invert the sense of the variable that is used to
1379 set the brightness of the panel backlight. Normally a
1380 brightness value of 0 indicates backlight switched off,
1381 and the maximum of the brightness value sets the backlight
1382 to maximum brightness. If this parameter is set to 0
1383 (default) and the machine requires it, or this parameter
1384 is set to 1, a brightness value of 0 sets the backlight
1385 to maximum brightness, and the maximum of the brightness
1386 value switches the backlight off.
1387 -1 -- never invert brightness
1388 0 -- machine default
1389 1 -- force brightness inversion
1392 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1394 ide-core.nodma= [HW] (E)IDE subsystem
1395 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1396 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1397 .cdrom .chs .ignore_cable are additional options
1398 See Documentation/ide/ide.txt.
1400 ide-generic.probe-mask= [HW] (E)IDE subsystem
1402 Probe mask for legacy ISA IDE ports. Depending on
1403 platform up to 6 ports are supported, enabled by
1404 setting corresponding bits in the mask to 1. The
1405 default value is 0x0, which has a special meaning.
1406 On systems that have PCI, it triggers scanning the
1407 PCI bus for the first and the second port, which
1408 are then probed. On systems without PCI the value
1409 of 0x0 enables probing the two first ports as if it
1412 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1413 Claim all unknown PCI IDE storage controllers.
1416 Format: idle=poll, idle=halt, idle=nomwait
1417 Poll forces a polling idle loop that can slightly
1418 improve the performance of waking up a idle CPU, but
1419 will use a lot of power and make the system run hot.
1421 idle=halt: Halt is forced to be used for CPU idle.
1422 In such case C2/C3 won't be used again.
1423 idle=nomwait: Disable mwait for CPU C-states
1425 ignore_loglevel [KNL]
1426 Ignore loglevel setting - this will print /all/
1427 kernel messages to the console. Useful for debugging.
1428 We also add it as printk module parameter, so users
1429 could change it dynamically, usually by
1430 /sys/module/printk/parameters/ignore_loglevel.
1432 ihash_entries= [KNL]
1433 Set number of hash buckets for inode cache.
1435 ima_appraise= [IMA] appraise integrity measurements
1436 Format: { "off" | "enforce" | "fix" | "log" }
1439 ima_appraise_tcb [IMA]
1440 The builtin appraise policy appraises all files
1444 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1448 The list of supported hash algorithms is defined
1449 in crypto/hash_info.h.
1452 The builtin measurement policy to load during IMA
1453 setup. Specyfing "tcb" as the value, measures all
1454 programs exec'd, files mmap'd for exec, and all files
1455 opened with the read mode bit set by either the
1456 effective uid (euid=0) or uid=0.
1459 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1460 Load a policy which meets the needs of the Trusted
1461 Computing Base. This means IMA will measure all
1462 programs exec'd, files mmap'd for exec, and all files
1463 opened for read by uid=0.
1466 Select one of defined IMA measurements template formats.
1467 Formats: { "ima" | "ima-ng" | "ima-sig" }
1471 [IMA] Define a custom template format.
1472 Format: { "field1|...|fieldN" }
1474 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1475 Format: <min_file_size>
1476 Set the minimal file size for using asynchronous hash.
1477 If left unspecified, ahash usage is disabled.
1479 ahash performance varies for different data sizes on
1480 different crypto accelerators. This option can be used
1481 to achieve the best performance for a particular HW.
1483 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1485 Set hashing buffer size. Default: 4k.
1487 ahash performance varies for different chunk sizes on
1488 different crypto accelerators. This option can be used
1489 to achieve best performance for particular HW.
1493 Run specified binary instead of /sbin/init as init
1496 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1497 for working out where the kernel is dying during
1500 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1501 initcall functions. Useful for debugging built-in
1502 modules and initcalls.
1504 initrd= [BOOT] Specify the location of the initial ramdisk
1506 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1509 int_pln_enable [x86] Enable power limit notification interrupt
1511 integrity_audit=[IMA]
1512 Format: { "0" | "1" }
1513 0 -- basic integrity auditing messages. (Default)
1514 1 -- additional integrity auditing messages.
1516 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1518 Enable intel iommu driver.
1520 Disable intel iommu driver.
1521 igfx_off [Default Off]
1522 By default, gfx is mapped as normal device. If a gfx
1523 device has a dedicated DMAR unit, the DMAR unit is
1524 bypassed by not enabling DMAR with this option. In
1525 this case, gfx device will use physical address for
1528 With this option iommu will not optimize to look
1529 for io virtual address below 32-bit forcing dual
1530 address cycle on pci bus for cards supporting greater
1531 than 32-bit addressing. The default is to look
1532 for translation below 32-bit and if not available
1533 then look in the higher range.
1534 strict [Default Off]
1535 With this option on every unmap_single operation will
1536 result in a hardware IOTLB flush operation as opposed
1537 to batching them for performance.
1538 sp_off [Default Off]
1539 By default, super page will be supported if Intel IOMMU
1540 has the capability. With this option, super page will
1542 ecs_off [Default Off]
1543 By default, extended context tables will be supported if
1544 the hardware advertises that it has support both for the
1545 extended tables themselves, and also PASID support. With
1546 this option set, extended tables will not be used even
1547 on hardware which claims to support them.
1549 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1550 0 disables intel_idle and fall back on acpi_idle.
1551 1 to 6 specify maximum depth of C-state.
1555 Do not enable intel_pstate as the default
1556 scaling driver for the supported processors
1558 Enable intel_pstate on systems that prohibit it by default
1559 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1560 instead of acpi-cpufreq may disable platform features, such
1561 as thermal controls and power capping, that rely on ACPI
1562 P-States information being indicated to OSPM and therefore
1563 should be used with caution. This option does not work with
1564 processors that aren't supported by the intel_pstate driver
1565 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1567 Do not enable hardware P state control (HWP)
1570 Only load intel_pstate on systems which support
1571 hardware P state control (HWP) if available.
1573 Don't use ACPI processor performance control objects
1574 _PSS and _PPC specified limits.
1576 intremap= [X86-64, Intel-IOMMU]
1577 on enable Interrupt Remapping (default)
1578 off disable Interrupt Remapping
1579 nosid disable Source ID checking
1581 BIOS x2APIC opt-out request will be ignored
1583 iomem= Disable strict checking of access to MMIO memory
1584 strict regions from userspace.
1599 nobypass [PPC/POWERNV]
1600 Disable IOMMU bypass, using IOMMU for PCI devices.
1603 io7= [HW] IO7 for Marvel based alpha systems
1604 See comment before marvel_specify_io7 in
1605 arch/alpha/kernel/core_marvel.c.
1607 io_delay= [X86] I/O delay method
1609 Standard port 0x80 based delay
1611 Alternate port 0xed based delay (needed on some systems)
1613 Simple two microseconds delay
1618 See Documentation/filesystems/nfs/nfsroot.txt.
1621 When an interrupt is not handled search all handlers
1622 for it. Intended to get systems with badly broken
1626 When an interrupt is not handled search all handlers
1627 for it. Also check all handlers each timer
1628 interrupt. Intended to get systems with badly broken
1632 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1634 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1636 <cpu number>,...,<cpu number>
1638 <cpu number>-<cpu number>
1639 (must be a positive range in ascending order)
1641 <cpu number>,...,<cpu number>-<cpu number>
1643 This option can be used to specify one or more CPUs
1644 to isolate from the general SMP balancing and scheduling
1645 algorithms. You can move a process onto or off an
1646 "isolated" CPU via the CPU affinity syscalls or cpuset.
1647 <cpu number> begins at 0 and the maximum value is
1648 "number of CPUs in system - 1".
1650 This option is the preferred way to isolate CPUs. The
1651 alternative -- manually setting the CPU mask of all
1652 tasks in the system -- can cause problems and
1653 suboptimal load balancer performance.
1657 ivrs_ioapic [HW,X86_64]
1658 Provide an override to the IOAPIC-ID<->DEVICE-ID
1659 mapping provided in the IVRS ACPI table. For
1660 example, to map IOAPIC-ID decimal 10 to
1661 PCI device 00:14.0 write the parameter as:
1662 ivrs_ioapic[10]=00:14.0
1664 ivrs_hpet [HW,X86_64]
1665 Provide an override to the HPET-ID<->DEVICE-ID
1666 mapping provided in the IVRS ACPI table. For
1667 example, to map HPET-ID decimal 0 to
1668 PCI device 00:14.0 write the parameter as:
1669 ivrs_hpet[0]=00:14.0
1671 js= [HW,JOY] Analog joystick
1672 See Documentation/input/joystick.txt.
1675 Enable/disable kernel and module base offset ASLR
1676 (Address Space Layout Randomization) if built into
1677 the kernel. When CONFIG_HIBERNATION is selected,
1678 kASLR is disabled by default. When kASLR is enabled,
1679 hibernation will be disabled.
1683 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1684 specifies the amount of memory usable by the kernel
1685 for non-movable allocations. The requested amount is
1686 spread evenly throughout all nodes in the system. The
1687 remaining memory in each node is used for Movable
1688 pages. In the event, a node is too small to have both
1689 kernelcore and Movable pages, kernelcore pages will
1690 take priority and other nodes will have a larger number
1691 of Movable pages. The Movable zone is used for the
1692 allocation of pages that may be reclaimed or moved
1693 by the page migration subsystem. This means that
1694 HugeTLB pages may not be allocated from this zone.
1695 Note that allocations like PTEs-from-HighMem still
1696 use the HighMem zone if it exists, and the Normal
1697 zone if it does not.
1699 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1700 Format: <Controller#>[,poll interval]
1701 The controller # is the number of the ehci usb debug
1702 port as it is probed via PCI. The poll interval is
1703 optional and is the number seconds in between
1704 each poll cycle to the debug port in case you need
1705 the functionality for interrupting the kernel with
1706 gdb or control-c on the dbgp connection. When
1707 not using this parameter you use sysrq-g to break into
1708 the kernel debugger.
1710 kgdboc= [KGDB,HW] kgdb over consoles.
1711 Requires a tty driver that supports console polling,
1712 or a supported polling keyboard driver (non-usb).
1713 Serial only format: <serial_device>[,baud]
1714 keyboard only format: kbd
1715 keyboard and serial format: kbd,<serial_device>[,baud]
1716 Optional Kernel mode setting:
1717 kms, kbd format: kms,kbd
1718 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1720 kgdbwait [KGDB] Stop kernel execution and enter the
1721 kernel debugger at the earliest opportunity.
1723 kmac= [MIPS] korina ethernet MAC address.
1724 Configure the RouterBoard 532 series on-chip
1725 Ethernet adapter MAC address.
1727 kmemleak= [KNL] Boot-time kmemleak enable/disable
1728 Valid arguments: on, off
1730 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1733 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1734 Valid arguments: 0, 1, 2
1735 kmemcheck=0 (disabled)
1736 kmemcheck=1 (enabled)
1737 kmemcheck=2 (one-shot mode)
1738 Default: 2 (one-shot mode)
1740 kstack=N [X86] Print N words from the kernel stack
1743 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1744 Default is 0 (don't ignore, but inject #GP)
1746 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1750 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1751 Default is 1 (enabled)
1753 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1755 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1757 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1758 (virtualized MMU) support on capable Intel chips.
1759 Default is 1 (enabled)
1761 kvm-intel.emulate_invalid_guest_state=
1762 [KVM,Intel] Enable emulation of invalid guest states
1763 Default is 0 (disabled)
1765 kvm-intel.flexpriority=
1766 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1767 Default is 1 (enabled)
1770 [KVM,Intel] Enable VMX nesting (nVMX).
1771 Default is 0 (disabled)
1773 kvm-intel.unrestricted_guest=
1774 [KVM,Intel] Disable unrestricted guest feature
1775 (virtualized real and unpaged mode) on capable
1776 Intel chips. Default is 1 (enabled)
1778 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1779 feature (tagged TLBs) on capable Intel chips.
1780 Default is 1 (enabled)
1786 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1789 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1790 value for LAPIC timer one-shot implementation. Default
1791 back to the programmable timer unit in the LAPIC.
1793 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1796 libata.dma= [LIBATA] DMA control
1797 libata.dma=0 Disable all PATA and SATA DMA
1798 libata.dma=1 PATA and SATA Disk DMA only
1799 libata.dma=2 ATAPI (CDROM) DMA only
1800 libata.dma=4 Compact Flash DMA only
1801 Combinations also work, so libata.dma=3 enables DMA
1802 for disks and CDROMs, but not CFs.
1804 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1805 libata.ignore_hpa=0 keep BIOS limits (default)
1806 libata.ignore_hpa=1 ignore limits, using full disk
1808 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1812 libata.force= [LIBATA] Force configurations. The format is comma
1813 separated list of "[ID:]VAL" where ID is
1814 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1815 matching port, link or device. Basically, it matches
1816 the ATA ID string printed on console by libata. If
1817 the whole ID part is omitted, the last PORT and DEVICE
1818 values are used. If ID hasn't been specified yet, the
1819 configuration applies to all ports, links and devices.
1821 If only DEVICE is omitted, the parameter applies to
1822 the port and all links and devices behind it. DEVICE
1823 number of 0 either selects the first device or the
1824 first fan-out link behind PMP device. It does not
1825 select the host link. DEVICE number of 15 selects the
1826 host link and device attached to it.
1828 The VAL specifies the configuration to force. As long
1829 as there's no ambiguity shortcut notation is allowed.
1830 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1831 The following configurations can be forced.
1833 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1834 Any ID with matching PORT is used.
1836 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1838 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1839 udma[/][16,25,33,44,66,100,133] notation is also
1842 * [no]ncq: Turn on or off NCQ.
1844 * [no]ncqtrim: Turn off queued DSM TRIM.
1846 * nohrst, nosrst, norst: suppress hard, soft
1849 * rstonce: only attempt one reset during
1850 hot-unplug link recovery
1852 * dump_id: dump IDENTIFY data.
1854 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1856 * disable: Disable this device.
1858 If there are multiple matching configurations changing
1859 the same attribute, the last one is used.
1861 memblock=debug [KNL] Enable memblock debug messages.
1863 load_ramdisk= [RAM] List of ramdisks to load from floppy
1864 See Documentation/blockdev/ramdisk.txt.
1866 lockd.nlm_grace_period=P [NFS] Assign grace period.
1869 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1872 lockd.nlm_timeout=T [NFS] Assign timeout value.
1875 lockd.nlm_udpport=M [NFS] Assign UDP port.
1878 locktorture.nreaders_stress= [KNL]
1879 Set the number of locking read-acquisition kthreads.
1880 Defaults to being automatically set based on the
1881 number of online CPUs.
1883 locktorture.nwriters_stress= [KNL]
1884 Set the number of locking write-acquisition kthreads.
1886 locktorture.onoff_holdoff= [KNL]
1887 Set time (s) after boot for CPU-hotplug testing.
1889 locktorture.onoff_interval= [KNL]
1890 Set time (s) between CPU-hotplug operations, or
1891 zero to disable CPU-hotplug testing.
1893 locktorture.shuffle_interval= [KNL]
1894 Set task-shuffle interval (jiffies). Shuffling
1895 tasks allows some CPUs to go into dyntick-idle
1896 mode during the locktorture test.
1898 locktorture.shutdown_secs= [KNL]
1899 Set time (s) after boot system shutdown. This
1900 is useful for hands-off automated testing.
1902 locktorture.stat_interval= [KNL]
1903 Time (s) between statistics printk()s.
1905 locktorture.stutter= [KNL]
1906 Time (s) to stutter testing, for example,
1907 specifying five seconds causes the test to run for
1908 five seconds, wait for five seconds, and so on.
1909 This tests the locking primitive's ability to
1910 transition abruptly to and from idle.
1912 locktorture.torture_runnable= [BOOT]
1913 Start locktorture running at boot time.
1915 locktorture.torture_type= [KNL]
1916 Specify the locking implementation to test.
1918 locktorture.verbose= [KNL]
1919 Enable additional printk() statements.
1921 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1924 loglevel= All Kernel Messages with a loglevel smaller than the
1925 console loglevel will be printed to the console. It can
1926 also be changed with klogd or other programs. The
1927 loglevels are defined as follows:
1929 0 (KERN_EMERG) system is unusable
1930 1 (KERN_ALERT) action must be taken immediately
1931 2 (KERN_CRIT) critical conditions
1932 3 (KERN_ERR) error conditions
1933 4 (KERN_WARNING) warning conditions
1934 5 (KERN_NOTICE) normal but significant condition
1935 6 (KERN_INFO) informational
1936 7 (KERN_DEBUG) debug-level messages
1938 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1939 in bytes. n must be a power of two and greater
1940 than the minimal size. The minimal size is defined
1941 by LOG_BUF_SHIFT kernel config parameter. There is
1942 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1943 that allows to increase the default size depending on
1944 the number of CPUs. See init/Kconfig for more details.
1946 logo.nologo [FB] Disables display of the built-in Linux logo.
1947 This may be used to provide more screen space for
1948 kernel log messages and is useful when debugging
1949 kernel boot problems.
1951 lp=0 [LP] Specify parallel ports to use, e.g,
1952 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1953 lp=reset first parallel port). 'lp=0' disables the
1954 lp=auto printer driver. 'lp=reset' (which can be
1955 specified in addition to the ports) causes
1956 attached printers to be reset. Using
1957 lp=port1,port2,... specifies the parallel ports
1958 to associate lp devices with, starting with
1959 lp0. A port specification may be 'none' to skip
1960 that lp device, or a parport name such as
1961 'parport0'. Specifying 'lp=auto' instead of a
1962 port specification list means that device IDs
1963 from each port should be examined, to see if
1964 an IEEE 1284-compliant printer is attached; if
1965 so, the driver will manage that printer.
1966 See also header of drivers/char/lp.c.
1969 Sets loops_per_jiffy to given constant, thus avoiding
1970 time-consuming boot-time autodetection (up to 250 ms per
1971 CPU). 0 enables autodetection (default). To determine
1972 the correct value for your kernel, boot with normal
1973 autodetection and see what value is printed. Note that
1974 on SMP systems the preset will be applied to all CPUs,
1975 which is likely to cause problems if your CPUs need
1976 significantly divergent settings. An incorrect value
1977 will cause delays in the kernel to be wrong, leading to
1978 unpredictable I/O errors and other breakage. Although
1979 unlikely, in the extreme case this might damage your
1983 Format: <io>,<irq>,<dma>
1985 machvec= [IA-64] Force the use of a particular machine-vector
1986 (machvec) in a generic kernel.
1987 Example: machvec=hpzx1_swiotlb
1989 machtype= [Loongson] Share the same kernel image file between different
1991 Example: machtype=lemote-yeeloong-2f-7inch
1993 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1994 than or equal to this physical address is ignored.
1996 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1997 should make use of. maxcpus=n : n >= 0 limits the
1998 kernel to using 'n' processors. n=0 is a special case,
1999 it is equivalent to "nosmp", which also disables
2002 max_loop= [LOOP] The number of loop block devices that get
2003 (loop.max_loop) unconditionally pre-created at init time. The default
2004 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2005 of statically allocating a predefined number, loop
2006 devices can be requested on-demand with the
2007 /dev/loop-control interface.
2009 mce [X86-32] Machine Check Exception
2011 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2013 md= [HW] RAID subsystems devices and level
2014 See Documentation/md.txt.
2017 Format: <first>,<last>
2018 Specifies range of consoles to be captured by the MDA.
2020 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2021 Amount of memory to be used when the kernel is not able
2022 to see the whole system memory or for test.
2023 [X86] Work as limiting max address. Use together
2024 with memmap= to avoid physical address space collisions.
2025 Without memmap= PCI devices could be placed at addresses
2026 belonging to unused RAM.
2028 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2032 [KNL,SH] Allow user to override the default size for
2033 per-device physically contiguous DMA buffers.
2035 memmap=exactmap [KNL,X86] Enable setting of an exact
2036 E820 memory map, as specified by the user.
2037 Such memmap=exactmap lines can be constructed based on
2038 BIOS output or other requirements. See the memmap=nn@ss
2041 memmap=nn[KMG]@ss[KMG]
2042 [KNL] Force usage of a specific region of memory.
2043 Region of memory to be used is from ss to ss+nn.
2045 memmap=nn[KMG]#ss[KMG]
2046 [KNL,ACPI] Mark specific memory as ACPI data.
2047 Region of memory to be marked is from ss to ss+nn.
2049 memmap=nn[KMG]$ss[KMG]
2050 [KNL,ACPI] Mark specific memory as reserved.
2051 Region of memory to be reserved is from ss to ss+nn.
2052 Example: Exclude memory from 0x18690000-0x1869ffff
2053 memmap=64K$0x18690000
2055 memmap=0x10000$0x18690000
2057 memmap=nn[KMG]!ss[KMG]
2058 [KNL,X86] Mark specific memory as protected.
2059 Region of memory to be used, from ss to ss+nn.
2060 The memory region may be marked as e820 type 12 (0xc)
2061 and is NVDIMM or ADR memory.
2063 memory_corruption_check=0/1 [X86]
2064 Some BIOSes seem to corrupt the first 64k of
2065 memory when doing things like suspend/resume.
2066 Setting this option will scan the memory
2067 looking for corruption. Enabling this will
2068 both detect corruption and prevent the kernel
2069 from using the memory being corrupted.
2070 However, its intended as a diagnostic tool; if
2071 repeatable BIOS-originated corruption always
2072 affects the same memory, you can use memmap=
2073 to prevent the kernel from using that memory.
2075 memory_corruption_check_size=size [X86]
2076 By default it checks for corruption in the low
2077 64k, making this memory unavailable for normal
2078 use. Use this parameter to scan for
2079 corruption in more or less memory.
2081 memory_corruption_check_period=seconds [X86]
2082 By default it checks for corruption every 60
2083 seconds. Use this parameter to check at some
2084 other rate. 0 disables periodic checking.
2086 memtest= [KNL,X86,ARM] Enable memtest
2088 default : 0 <disable>
2089 Specifies the number of memtest passes to be
2090 performed. Each pass selects another test
2091 pattern from a given set of patterns. Memtest
2092 fills the memory with this pattern, validates
2093 memory contents and reserves bad memory
2094 regions that are detected.
2096 meye.*= [HW] Set MotionEye Camera parameters
2097 See Documentation/video4linux/meye.txt.
2099 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2100 Multi-Function General Purpose Timers on AMD Geode
2103 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2104 the BIOS has incorrectly applied a workaround. TinyBIOS
2105 version 0.98 is known to be affected, 0.99 fixes the
2106 problem by letting the user disable the workaround.
2110 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2111 physical address is ignored.
2113 mini2440= [ARM,HW,KNL]
2114 Format:[0..2][b][c][t]
2116 MINI2440 configuration specification:
2117 0 - The attached screen is the 3.5" TFT
2118 1 - The attached screen is the 7" TFT
2119 2 - The VGA Shield is attached (1024x768)
2120 Leaving out the screen size parameter will not load
2121 the TFT driver, and the framebuffer will be left
2123 b - Enable backlight. The TFT backlight pin will be
2124 linked to the kernel VESA blanking code and a GPIO
2125 LED. This parameter is not necessary when using the
2127 c - Enable the s3c camera interface.
2128 t - Reserved for enabling touchscreen support. The
2129 touchscreen support is not enabled in the mainstream
2130 kernel as of 2.6.30, a preliminary port can be found
2131 in the "bleeding edge" mini2440 support kernel at
2132 http://repo.or.cz/w/linux-2.6/mini2440.git
2135 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2136 parameter allows control of the logging verbosity for
2137 the additional memory initialisation checks. A value
2138 of 0 disables mminit logging and a level of 4 will
2139 log everything. Information is printed at KERN_DEBUG
2140 so loglevel=8 may also need to be specified.
2143 [KNL] When CONFIG_MODULE_SIG is set, this means that
2144 modules without (valid) signatures will fail to load.
2145 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2146 is always true, so this option does nothing.
2149 [MOUSE] Maximum time between finger touching and
2150 leaving touchpad surface for touch to be considered
2151 a tap and be reported as a left button click (for
2152 touchpads working in absolute mode only).
2154 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2155 reporting absolute coordinates, such as tablets
2156 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2157 reporting absolute coordinates, such as tablets
2159 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2160 is similar to kernelcore except it specifies the
2161 amount of memory used for migratable allocations.
2162 If both kernelcore and movablecore is specified,
2163 then kernelcore will be at *least* the specified
2164 value but may be more. If movablecore on its own
2165 is specified, the administrator must be careful
2166 that the amount of memory usable for all allocations
2169 movable_node [KNL,X86] Boot-time switch to enable the effects
2170 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2172 MTD_Partition= [MTD]
2173 Format: <name>,<region-number>,<size>,<offset>
2175 MTD_Region= [MTD] Format:
2176 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2179 See drivers/mtd/cmdlinepart.c.
2181 multitce=off [PPC] This parameter disables the use of the pSeries
2182 firmware feature for updating multiple TCE entries
2185 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2187 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2189 boundary - index of last SLC block on Flex-OneNAND.
2190 The remaining blocks are configured as MLC blocks.
2191 lock - Configure if Flex-OneNAND boundary should be locked.
2192 Once locked, the boundary cannot be changed.
2193 1 indicates lock status, 0 indicates unlock status.
2196 ARM/S3C2412 JIVE boot control
2198 See arch/arm/mach-s3c2412/mach-jive.c
2200 mtouchusb.raw_coordinates=
2201 [HW] Make the MicroTouch USB driver use raw coordinates
2202 ('y', default) or cooked coordinates ('n')
2204 mtrr_chunk_size=nn[KMG] [X86]
2205 used for mtrr cleanup. It is largest continuous chunk
2206 that could hold holes aka. UC entries.
2208 mtrr_gran_size=nn[KMG] [X86]
2209 Used for mtrr cleanup. It is granularity of mtrr block.
2211 Large value could prevent small alignment from
2214 mtrr_spare_reg_nr=n [X86]
2216 Range: 0,7 : spare reg number
2218 Used for mtrr cleanup. It is spare mtrr entries number.
2219 Set to 2 or more if your graphical card needs more.
2221 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2223 netdev= [NET] Network devices parameters
2224 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2225 Note that mem_start is often overloaded to mean
2226 something different and driver-specific.
2227 This usage is only documented in each driver source
2231 [NETFILTER] Enable connection tracking flow accounting
2232 0 to disable accounting
2233 1 to enable accounting
2236 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2237 See Documentation/filesystems/nfs/nfsroot.txt.
2239 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2240 See Documentation/filesystems/nfs/nfsroot.txt.
2242 nfsrootdebug [NFS] enable nfsroot debugging messages.
2243 See Documentation/filesystems/nfs/nfsroot.txt.
2245 nfs.callback_tcpport=
2246 [NFS] set the TCP port on which the NFSv4 callback
2247 channel should listen.
2250 [NFS] sets the pathname to the program which is used
2251 to update the NFS client cache entries.
2253 nfs.cache_getent_timeout=
2254 [NFS] sets the timeout after which an attempt to
2255 update a cache entry is deemed to have failed.
2257 nfs.idmap_cache_timeout=
2258 [NFS] set the maximum lifetime for idmapper cache
2262 [NFS] enable 64-bit inode numbers.
2263 If zero, the NFS client will fake up a 32-bit inode
2264 number for the readdir() and stat() syscalls instead
2265 of returning the full 64-bit number.
2266 The default is to return 64-bit inode numbers.
2268 nfs.max_session_slots=
2269 [NFSv4.1] Sets the maximum number of session slots
2270 the client will attempt to negotiate with the server.
2271 This limits the number of simultaneous RPC requests
2272 that the client can send to the NFSv4.1 server.
2273 Note that there is little point in setting this
2274 value higher than the max_tcp_slot_table_limit.
2276 nfs.nfs4_disable_idmapping=
2277 [NFSv4] When set to the default of '1', this option
2278 ensures that both the RPC level authentication
2279 scheme and the NFS level operations agree to use
2280 numeric uids/gids if the mount is using the
2281 'sec=sys' security flavour. In effect it is
2282 disabling idmapping, which can make migration from
2283 legacy NFSv2/v3 systems to NFSv4 easier.
2284 Servers that do not support this mode of operation
2285 will be autodetected by the client, and it will fall
2286 back to using the idmapper.
2287 To turn off this behaviour, set the value to '0'.
2289 [NFS4] Specify an additional fixed unique ident-
2290 ification string that NFSv4 clients can insert into
2291 their nfs_client_id4 string. This is typically a
2292 UUID that is generated at system install time.
2294 nfs.send_implementation_id =
2295 [NFSv4.1] Send client implementation identification
2296 information in exchange_id requests.
2297 If zero, no implementation identification information
2299 The default is to send the implementation identification
2302 nfs.recover_lost_locks =
2303 [NFSv4] Attempt to recover locks that were lost due
2304 to a lease timeout on the server. Please note that
2305 doing this risks data corruption, since there are
2306 no guarantees that the file will remain unchanged
2307 after the locks are lost.
2308 If you want to enable the kernel legacy behaviour of
2309 attempting to recover these locks, then set this
2311 The default parameter value of '0' causes the kernel
2312 not to attempt recovery of lost locks.
2314 nfs4.layoutstats_timer =
2315 [NFSv4.2] Change the rate at which the kernel sends
2316 layoutstats to the pNFS metadata server.
2318 Setting this to value to 0 causes the kernel to use
2319 whatever value is the default set by the layout
2320 driver. A non-zero value sets the minimum interval
2321 in seconds between layoutstats transmissions.
2323 nfsd.nfs4_disable_idmapping=
2324 [NFSv4] When set to the default of '1', the NFSv4
2325 server will return only numeric uids and gids to
2326 clients using auth_sys, and will accept numeric uids
2327 and gids from such clients. This is intended to ease
2328 migration from NFSv2/v3.
2330 objlayoutdriver.osd_login_prog=
2331 [NFS] [OBJLAYOUT] sets the pathname to the program which
2332 is used to automatically discover and login into new
2333 osd-targets. Please see:
2334 Documentation/filesystems/pnfs.txt for more explanations
2336 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2337 when a NMI is triggered.
2338 Format: [state][,regs][,debounce][,die]
2340 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2341 Format: [panic,][nopanic,][num]
2343 0 - turn nmi_watchdog off
2344 1 - turn nmi_watchdog on
2345 When panic is specified, panic when an NMI watchdog
2346 timeout occurs (or 'nopanic' to override the opposite
2348 This is useful when you use a panic=... timeout and
2349 need the box quickly up again.
2351 netpoll.carrier_timeout=
2352 [NET] Specifies amount of time (in seconds) that
2353 netpoll should wait for a carrier. By default netpoll
2356 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2357 emulation library even if a 387 maths coprocessor
2361 [HW] Never suspend the console
2362 Disable suspending of consoles during suspend and
2363 hibernate operations. Once disabled, debugging
2364 messages can reach various consoles while the rest
2365 of the system is being put to sleep (ie, while
2366 debugging driver suspend/resume hooks). This may
2367 not work reliably with all consoles, but is known
2368 to work with serial and VGA consoles.
2369 To facilitate more flexible debugging, we also add
2370 console_suspend, a printk module parameter to control
2371 it. Users could use console_suspend (usually
2372 /sys/module/printk/parameters/console_suspend) to
2373 turn on/off it dynamically.
2375 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2376 caches in the slab allocator. Saves per-node memory,
2377 but will impact performance.
2381 noapic [SMP,APIC] Tells the kernel to not make use of any
2382 IOAPICs that may be present in the system.
2384 noautogroup Disable scheduler automatic task group creation.
2386 nobats [PPC] Do not use BATs for mapping kernel lowmem
2387 on "Classic" PPC cores.
2391 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2393 nodelayacct [KNL] Disable per-task delay accounting
2395 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2397 nodsp [SH] Disable hardware DSP at boot time.
2399 noefi Disable EFI runtime services support.
2404 On X86-32 available only on PAE configured kernels.
2405 noexec=on: enable non-executable mappings (default)
2406 noexec=off: disable non-executable mappings
2409 Disable SMAP (Supervisor Mode Access Prevention)
2410 even if it is supported by processor.
2413 Disable SMEP (Supervisor Mode Execution Prevention)
2414 even if it is supported by processor.
2417 This affects only 32-bit executables.
2418 noexec32=on: enable non-executable mappings (default)
2419 read doesn't imply executable mappings
2420 noexec32=off: disable non-executable mappings
2421 read implies executable mappings
2423 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2425 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2426 register save and restore. The kernel will only save
2427 legacy floating-point registers on task switch.
2429 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2431 noxsave [BUGS=X86] Disables x86 extended register state save
2432 and restore using xsave. The kernel will fallback to
2433 enabling legacy floating-point and sse state.
2435 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2436 register states. The kernel will fall back to use
2437 xsave to save the states. By using this parameter,
2438 performance of saving the states is degraded because
2439 xsave doesn't support modified optimization while
2440 xsaveopt supports it on xsaveopt enabled systems.
2442 noxsaves [X86] Disables xsaves and xrstors used in saving and
2443 restoring x86 extended register state in compacted
2444 form of xsave area. The kernel will fall back to use
2445 xsaveopt and xrstor to save and restore the states
2446 in standard form of xsave area. By using this
2447 parameter, xsave area per process might occupy more
2448 memory on xsaves enabled systems.
2450 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2451 wfi(ARM) instruction doesn't work correctly and not to
2452 use it. This is also useful when using JTAG debugger.
2454 no_file_caps Tells the kernel not to honor file capabilities. The
2455 only way then for a file to be executed with privilege
2456 is to be setuid root or executed by root.
2458 nohalt [IA-64] Tells the kernel not to use the power saving
2459 function PAL_HALT_LIGHT when idle. This increases
2460 power-consumption. On the positive side, it reduces
2461 interrupt wake-up latency, which may improve performance
2462 in certain environments such as networked servers or
2465 nohibernate [HIBERNATION] Disable hibernation and resume.
2467 nohz= [KNL] Boottime enable/disable dynamic ticks
2468 Valid arguments: on, off
2471 nohz_full= [KNL,BOOT]
2472 In kernels built with CONFIG_NO_HZ_FULL=y, set
2473 the specified list of CPUs whose tick will be stopped
2474 whenever possible. The boot CPU will be forced outside
2475 the range to maintain the timekeeping.
2476 The CPUs in this range must also be included in the
2479 noiotrap [SH] Disables trapped I/O port accesses.
2481 noirqdebug [X86-32] Disables the code which attempts to detect and
2482 disable unhandled interrupt sources.
2484 no_timer_check [X86,APIC] Disables the code which tests for
2485 broken timer IRQ sources.
2487 noisapnp [ISAPNP] Disables ISA PnP code.
2489 noinitrd [RAM] Tells the kernel not to load any configured
2492 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2494 [Deprecated - use intremap=off]
2498 nojitter [IA-64] Disables jitter checking for ITC timers.
2500 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2502 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2505 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2506 steal time is computed, but won't influence scheduler
2509 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2511 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2513 noltlbs [PPC] Do not use large page/tlb entries for kernel
2514 lowmem mapping on PPC40x.
2516 nomca [IA-64] Disable machine check abort handling
2518 nomce [X86-32] Disable Machine Check Exception
2520 nomfgpt [X86-32] Disable Multi-Function General Purpose
2521 Timer usage (for AMD Geode machines).
2523 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2524 shutdown the other cpus. Instead use the REBOOT_VECTOR
2527 nomodule Disable module load
2529 nopat [X86] Disable PAT (page attribute table extension of
2530 pagetables) support.
2532 norandmaps Don't use address space randomization. Equivalent to
2533 echo 0 > /proc/sys/kernel/randomize_va_space
2535 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2537 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2538 with UP alternatives
2540 nordrand [X86] Disable kernel use of the RDRAND and
2541 RDSEED instructions even if they are supported
2542 by the processor. RDRAND and RDSEED are still
2543 available to user space applications.
2545 noresume [SWSUSP] Disables resume and restores original swap
2548 no-scroll [VGA] Disables scrollback.
2549 This is required for the Braillex ib80-piezo Braille
2550 reader made by F.H. Papenmeier (Germany).
2554 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2556 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2557 and disable the IO APIC. legacy for "maxcpus=0".
2559 nosoftlockup [KNL] Disable the soft-lockup detector.
2561 nosync [HW,M68K] Disables sync negotiation for all devices.
2563 notsc [BUGS=X86-32] Disable Time Stamp Counter
2565 nousb [USB] Disable the USB subsystem
2567 nowatchdog [KNL] Disable both lockup detectors, i.e.
2568 soft-lockup and NMI watchdog (hard-lockup).
2572 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2574 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2575 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2576 Some features depend on CPU0. Known dependencies are:
2577 1. Resume from suspend/hibernate depends on CPU0.
2578 Suspend/hibernate will fail if CPU0 is offline and you
2579 need to online CPU0 before suspend/hibernate.
2580 2. PIC interrupts also depend on CPU0. CPU0 can't be
2581 removed if a PIC interrupt is detected.
2582 It's said poweroff/reboot may depend on CPU0 on some
2583 machines although I haven't seen such issues so far
2584 after CPU0 is offline on a few tested machines.
2585 If the dependencies are under your control, you can
2586 turn on cpu0_hotplug.
2588 nptcg= [IA-64] Override max number of concurrent global TLB
2589 purges which is reported from either PAL_VM_SUMMARY or
2592 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2593 could support. nr_cpus=n : n >= 1 limits the kernel to
2594 supporting 'n' processors. Later in runtime you can not
2595 use hotplug cpu feature to put more cpu back to online.
2596 just like you compile the kernel NR_CPUS=n
2598 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2600 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2601 Allowed values are enable and disable
2603 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2604 one of ['zone', 'node', 'default'] can be specified
2605 This can be set from sysctl after boot.
2606 See Documentation/sysctl/vm.txt for details.
2608 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2609 See Documentation/debugging-via-ohci1394.txt for more
2612 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2613 Rather than timing out after 20 ms if an EC
2614 command is not properly ACKed, override the length
2615 of the timeout. We have interrupts disabled while
2616 waiting for the ACK, so if this is set too high
2617 interrupts *may* be lost!
2619 omap_mux= [OMAP] Override bootloader pin multiplexing.
2620 Format: <mux_mode0.mode_name=value>...
2621 For example, to override I2C bus2:
2622 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2624 oprofile.timer= [HW]
2625 Use timer interrupt instead of performance counters
2627 oprofile.cpu_type= Force an oprofile cpu type
2628 This might be useful if you have an older oprofile
2629 userland or if you want common events.
2630 Format: { arch_perfmon }
2631 arch_perfmon: [X86] Force use of architectural
2632 perfmon on Intel CPUs instead of the
2633 CPU specific event set.
2634 timer: [X86] Force use of architectural NMI
2635 timer mode (see also oprofile.timer
2636 for generic hr timer mode)
2637 [s390] Force legacy basic mode sampling
2638 (report cpu_type "timer")
2640 oops=panic Always panic on oopses. Default is to just kill the
2641 process, but there is a small probability of
2642 deadlocking the machine.
2643 This will also cause panics on machine check exceptions.
2644 Useful together with panic=30 to trigger a reboot.
2647 See Documentation/sound/oss/oss-parameters.txt
2649 page_owner= [KNL] Boot-time page_owner enabling option.
2650 Storage of the information about who allocated
2651 each page is disabled in default. With this switch,
2653 on: enable the feature
2655 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2656 timeout > 0: seconds before rebooting
2657 timeout = 0: wait forever
2658 timeout < 0: reboot immediately
2661 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2664 crash_kexec_post_notifiers
2665 Run kdump after running panic-notifiers and dumping
2666 kmsg. This only for the users who doubt kdump always
2667 succeeds in any situation.
2668 Note that this also increases risks of kdump failure,
2669 because some panic notifiers can make the crashed
2670 kernel more unstable.
2672 parkbd.port= [HW] Parallel port number the keyboard adapter is
2673 connected to, default is 0.
2675 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2676 0 for XT, 1 for AT (default is AT).
2679 parport= [HW,PPT] Specify parallel ports. 0 disables.
2680 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2681 Use 'auto' to force the driver to use any
2682 IRQ/DMA settings detected (the default is to
2683 ignore detected IRQ/DMA settings because of
2684 possible conflicts). You can specify the base
2685 address, IRQ, and DMA settings; IRQ and DMA
2686 should be numbers, or 'auto' (for using detected
2687 settings on that particular port), or 'nofifo'
2688 (to avoid using a FIFO even if it is detected).
2689 Parallel ports are assigned in the order they
2690 are specified on the command line, starting
2693 parport_init_mode= [HW,PPT]
2694 Configure VIA parallel port to operate in
2695 a specific mode. This is necessary on Pegasos
2696 computer where firmware has no options for setting
2697 up parallel port mode and sets it to spp.
2698 Currently this function knows 686a and 8231 chips.
2699 Format: [spp|ps2|epp|ecp|ecpepp]
2702 Halt all CPUs after the first oops has been printed for
2703 the specified number of seconds. This is to be used if
2704 your oopses keep scrolling off the screen.
2709 See header of drivers/block/paride/pcd.c.
2710 See also Documentation/blockdev/paride.txt.
2712 pci=option[,option...] [PCI] various PCI subsystem options:
2713 earlydump [X86] dump PCI config space before the kernel
2715 off [X86] don't probe for the PCI bus
2716 bios [X86-32] force use of PCI BIOS, don't access
2717 the hardware directly. Use this if your machine
2718 has a non-standard PCI host bridge.
2719 nobios [X86-32] disallow use of PCI BIOS, only direct
2720 hardware access methods are allowed. Use this
2721 if you experience crashes upon bootup and you
2722 suspect they are caused by the BIOS.
2723 conf1 [X86] Force use of PCI Configuration
2725 conf2 [X86] Force use of PCI Configuration
2727 noaer [PCIE] If the PCIEAER kernel config parameter is
2728 enabled, this kernel boot option can be used to
2729 disable the use of PCIE advanced error reporting.
2730 nodomains [PCI] Disable support for multiple PCI
2731 root domains (aka PCI segments, in ACPI-speak).
2732 nommconf [X86] Disable use of MMCONFIG for PCI
2734 check_enable_amd_mmconf [X86] check for and enable
2735 properly configured MMIO access to PCI
2736 config space on AMD family 10h CPU
2737 nomsi [MSI] If the PCI_MSI kernel config parameter is
2738 enabled, this kernel boot option can be used to
2739 disable the use of MSI interrupts system-wide.
2740 noioapicquirk [APIC] Disable all boot interrupt quirks.
2741 Safety option to keep boot IRQs enabled. This
2742 should never be necessary.
2743 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2744 primary IO-APIC for bridges that cannot disable
2745 boot IRQs. This fixes a source of spurious IRQs
2746 when the system masks IRQs.
2747 noioapicreroute [APIC] Disable workaround that uses the
2748 boot IRQ equivalent of an IRQ that connects to
2749 a chipset where boot IRQs cannot be disabled.
2750 The opposite of ioapicreroute.
2751 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2752 routing table. These calls are known to be buggy
2753 on several machines and they hang the machine
2754 when used, but on other computers it's the only
2755 way to get the interrupt routing table. Try
2756 this option if the kernel is unable to allocate
2757 IRQs or discover secondary PCI buses on your
2759 rom [X86] Assign address space to expansion ROMs.
2760 Use with caution as certain devices share
2761 address decoders between ROMs and other
2763 norom [X86] Do not assign address space to
2764 expansion ROMs that do not already have
2765 BIOS assigned address ranges.
2766 nobar [X86] Do not assign address space to the
2767 BARs that weren't assigned by the BIOS.
2768 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2769 assigned automatically to PCI devices. You can
2770 make the kernel exclude IRQs of your ISA cards
2772 pirqaddr=0xAAAAA [X86] Specify the physical address
2773 of the PIRQ table (normally generated
2774 by the BIOS) if it is outside the
2775 F0000h-100000h range.
2776 lastbus=N [X86] Scan all buses thru bus #N. Can be
2777 useful if the kernel is unable to find your
2778 secondary buses and you want to tell it
2779 explicitly which ones they are.
2780 assign-busses [X86] Always assign all PCI bus
2781 numbers ourselves, overriding
2782 whatever the firmware may have done.
2783 usepirqmask [X86] Honor the possible IRQ mask stored
2784 in the BIOS $PIR table. This is needed on
2785 some systems with broken BIOSes, notably
2786 some HP Pavilion N5400 and Omnibook XE3
2787 notebooks. This will have no effect if ACPI
2788 IRQ routing is enabled.
2789 noacpi [X86] Do not use ACPI for IRQ routing
2790 or for PCI scanning.
2791 use_crs [X86] Use PCI host bridge window information
2792 from ACPI. On BIOSes from 2008 or later, this
2793 is enabled by default. If you need to use this,
2794 please report a bug.
2795 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2796 If you need to use this, please report a bug.
2797 routeirq Do IRQ routing for all PCI devices.
2798 This is normally done in pci_enable_device(),
2799 so this option is a temporary workaround
2800 for broken drivers that don't call it.
2801 skip_isa_align [X86] do not align io start addr, so can
2802 handle more pci cards
2803 firmware [ARM] Do not re-enumerate the bus but instead
2804 just use the configuration from the
2805 bootloader. This is currently used on
2806 IXP2000 systems where the bus has to be
2807 configured a certain way for adjunct CPUs.
2808 noearly [X86] Don't do any early type 1 scanning.
2809 This might help on some broken boards which
2810 machine check when some devices' config space
2811 is read. But various workarounds are disabled
2812 and some IOMMU drivers will not work.
2813 bfsort Sort PCI devices into breadth-first order.
2814 This sorting is done to get a device
2815 order compatible with older (<= 2.4) kernels.
2816 nobfsort Don't sort PCI devices into breadth-first order.
2817 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2818 tuning and use the BIOS-configured MPS defaults.
2819 pcie_bus_safe Set every device's MPS to the largest value
2820 supported by all devices below the root complex.
2821 pcie_bus_perf Set device MPS to the largest allowable MPS
2822 based on its parent bus. Also set MRRS (Max
2823 Read Request Size) to the largest supported
2824 value (no larger than the MPS that the device
2825 or bus can support) for best performance.
2826 pcie_bus_peer2peer Set every device's MPS to 128B, which
2827 every device is guaranteed to support. This
2828 configuration allows peer-to-peer DMA between
2829 any pair of devices, possibly at the cost of
2830 reduced performance. This also guarantees
2831 that hot-added devices will work.
2832 cbiosize=nn[KMG] The fixed amount of bus space which is
2833 reserved for the CardBus bridge's IO window.
2834 The default value is 256 bytes.
2835 cbmemsize=nn[KMG] The fixed amount of bus space which is
2836 reserved for the CardBus bridge's memory
2837 window. The default value is 64 megabytes.
2840 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2841 Specifies alignment and device to reassign
2842 aligned memory resources.
2843 If <order of align> is not specified,
2844 PAGE_SIZE is used as alignment.
2845 PCI-PCI bridge can be specified, if resource
2846 windows need to be expanded.
2847 ecrc= Enable/disable PCIe ECRC (transaction layer
2848 end-to-end CRC checking).
2849 bios: Use BIOS/firmware settings. This is the
2853 hpiosize=nn[KMG] The fixed amount of bus space which is
2854 reserved for hotplug bridge's IO window.
2855 Default size is 256 bytes.
2856 hpmemsize=nn[KMG] The fixed amount of bus space which is
2857 reserved for hotplug bridge's memory window.
2858 Default size is 2 megabytes.
2859 realloc= Enable/disable reallocating PCI bridge resources
2860 if allocations done by BIOS are too small to
2861 accommodate resources required by all child
2863 off: Turn realloc off
2865 realloc same as realloc=on
2866 noari do not use PCIe ARI.
2867 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2868 only look for one device below a PCIe downstream
2871 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2874 force Enable ASPM even on devices that claim not to support it.
2875 WARNING: Forcing ASPM on may cause system lockups.
2877 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2878 nomsi Do not use MSI for PCI Express Native Hotplug (this
2879 makes all PCIe ports use INTx for hotplug services).
2881 pcie_ports= [PCIE] PCIe ports handling:
2882 auto Ask the BIOS whether or not to use native PCIe services
2883 associated with PCIe ports (PME, hot-plug, AER). Use
2884 them only if that is allowed by the BIOS.
2885 native Use native PCIe services associated with PCIe ports
2887 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2890 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2891 nomsi Do not use MSI for native PCIe PME signaling (this makes
2892 all PCIe root ports use INTx for all services).
2894 pcmv= [HW,PCMCIA] BadgePAD 4
2898 Keep all power-domains already enabled by bootloader on,
2899 even if no driver has claimed them. This is useful
2900 for debug and development, but should not be
2901 needed on a platform with proper driver support.
2904 See Documentation/blockdev/paride.txt.
2906 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2909 See arch/parisc/kernel/pdc_chassis.c
2911 percpu_alloc= Select which percpu first chunk allocator to use.
2912 Currently supported values are "embed" and "page".
2913 Archs may support subset or none of the selections.
2914 See comments in mm/percpu.c for details on each
2915 allocator. This parameter is primarily for debugging
2916 and performance comparison.
2919 See Documentation/blockdev/paride.txt.
2922 See Documentation/blockdev/paride.txt.
2924 pirq= [SMP,APIC] Manual mp-table setup
2925 See Documentation/x86/i386/IO-APIC.txt.
2927 plip= [PPT,NET] Parallel port network link
2928 Format: { parport<nr> | timid | 0 }
2929 See also Documentation/parport.txt.
2931 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2932 Override pmtimer IOPort with a hex value.
2936 Enable PNP debug messages (depends on the
2937 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2938 via /sys/module/pnp/parameters/debug. We always show
2939 current resource usage; turning this on also shows
2940 possible settings and some assignment information.
2946 { on | off | curr | res | no-curr | no-res }
2949 [ISAPNP] Exclude IRQs for the autoconfiguration
2952 [ISAPNP] Exclude DMAs for the autoconfiguration
2954 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2955 Ranges are in pairs (I/O port base and size).
2958 [ISAPNP] Exclude memory regions for the
2960 Ranges are in pairs (memory base and size).
2962 ports= [IP_VS_FTP] IPVS ftp helper module
2964 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2966 Format: <port>,<port>....
2968 print-fatal-signals=
2969 [KNL] debug: print fatal signals
2971 If enabled, warn about various signal handling
2972 related application anomalies: too many signals,
2973 too many POSIX.1 timers, fatal signals causing a
2976 If you hit the warning due to signal overflow,
2977 you might want to try "ulimit -i unlimited".
2981 printk.always_kmsg_dump=
2982 Trigger kmsg_dump for cases other than kernel oops or
2984 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2987 printk.time= Show timing data prefixed to each printk message line
2988 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2990 processor.max_cstate= [HW,ACPI]
2991 Limit processor to maximum C-state
2992 max_cstate=9 overrides any DMI blacklist limit.
2994 processor.nocst [HW,ACPI]
2995 Ignore the _CST method to determine C-states,
2996 instead using the legacy FADT method
2998 profile= [KNL] Enable kernel profiling via /proc/profile
2999 Format: [schedule,]<number>
3000 Param: "schedule" - profile schedule points.
3001 Param: <number> - step/bucket size as a power of 2 for
3002 statistical time based profiling.
3003 Param: "sleep" - profile D-state sleeping (millisecs).
3004 Requires CONFIG_SCHEDSTATS
3005 Param: "kvm" - profile VM exits.
3007 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3009 See Documentation/blockdev/ramdisk.txt.
3011 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3012 probe for; one of (bare|imps|exps|lifebook|any).
3013 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3015 psmouse.resetafter= [HW,MOUSE]
3016 Try to reset the device after so many bad packets
3019 [HW,MOUSE] Set desired mouse resolution, in dpi.
3020 psmouse.smartscroll=
3021 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3022 0 = disabled, 1 = enabled (default).
3024 pstore.backend= Specify the name of the pstore backend to use
3027 See Documentation/blockdev/paride.txt.
3030 [KNL] Number of legacy pty's. Overwrites compiled-in
3033 quiet [KNL] Disable most log messages
3038 See Documentation/md.txt.
3040 ramdisk_blocksize= [RAM]
3041 See Documentation/blockdev/ramdisk.txt.
3043 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3044 See Documentation/blockdev/ramdisk.txt.
3047 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3048 the specified list of CPUs to be no-callback CPUs.
3049 Invocation of these CPUs' RCU callbacks will
3050 be offloaded to "rcuox/N" kthreads created for
3051 that purpose, where "x" is "b" for RCU-bh, "p"
3052 for RCU-preempt, and "s" for RCU-sched, and "N"
3053 is the CPU number. This reduces OS jitter on the
3054 offloaded CPUs, which can be useful for HPC and
3055 real-time workloads. It can also improve energy
3056 efficiency for asymmetric multiprocessors.
3059 Rather than requiring that offloaded CPUs
3060 (specified by rcu_nocbs= above) explicitly
3061 awaken the corresponding "rcuoN" kthreads,
3062 make these kthreads poll for callbacks.
3063 This improves the real-time response for the
3064 offloaded CPUs by relieving them of the need to
3065 wake up the corresponding kthread, but degrades
3066 energy efficiency by requiring that the kthreads
3067 periodically wake up to do the polling.
3069 rcutree.blimit= [KNL]
3070 Set maximum number of finished RCU callbacks to
3071 process in one batch.
3073 rcutree.dump_tree= [KNL]
3074 Dump the structure of the rcu_node combining tree
3075 out at early boot. This is used for diagnostic
3076 purposes, to verify correct tree setup.
3078 rcutree.gp_cleanup_delay= [KNL]
3079 Set the number of jiffies to delay each step of
3080 RCU grace-period cleanup. This only has effect
3081 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3083 rcutree.gp_init_delay= [KNL]
3084 Set the number of jiffies to delay each step of
3085 RCU grace-period initialization. This only has
3086 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3089 rcutree.gp_preinit_delay= [KNL]
3090 Set the number of jiffies to delay each step of
3091 RCU grace-period pre-initialization, that is,
3092 the propagation of recent CPU-hotplug changes up
3093 the rcu_node combining tree. This only has effect
3094 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3096 rcutree.rcu_fanout_exact= [KNL]
3097 Disable autobalancing of the rcu_node combining
3098 tree. This is used by rcutorture, and might
3099 possibly be useful for architectures having high
3100 cache-to-cache transfer latencies.
3102 rcutree.rcu_fanout_leaf= [KNL]
3103 Change the number of CPUs assigned to each
3104 leaf rcu_node structure. Useful for very
3105 large systems, which will choose the value 64,
3106 and for NUMA systems with large remote-access
3107 latencies, which will choose a value aligned
3108 with the appropriate hardware boundaries.
3110 rcutree.jiffies_till_sched_qs= [KNL]
3111 Set required age in jiffies for a
3112 given grace period before RCU starts
3113 soliciting quiescent-state help from
3114 rcu_note_context_switch().
3116 rcutree.jiffies_till_first_fqs= [KNL]
3117 Set delay from grace-period initialization to
3118 first attempt to force quiescent states.
3119 Units are jiffies, minimum value is zero,
3120 and maximum value is HZ.
3122 rcutree.jiffies_till_next_fqs= [KNL]
3123 Set delay between subsequent attempts to force
3124 quiescent states. Units are jiffies, minimum
3125 value is one, and maximum value is HZ.
3127 rcutree.kthread_prio= [KNL,BOOT]
3128 Set the SCHED_FIFO priority of the RCU per-CPU
3129 kthreads (rcuc/N). This value is also used for
3130 the priority of the RCU boost threads (rcub/N)
3131 and for the RCU grace-period kthreads (rcu_bh,
3132 rcu_preempt, and rcu_sched). If RCU_BOOST is
3133 set, valid values are 1-99 and the default is 1
3134 (the least-favored priority). Otherwise, when
3135 RCU_BOOST is not set, valid values are 0-99 and
3136 the default is zero (non-realtime operation).
3138 rcutree.rcu_nocb_leader_stride= [KNL]
3139 Set the number of NOCB kthread groups, which
3140 defaults to the square root of the number of
3141 CPUs. Larger numbers reduces the wakeup overhead
3142 on the per-CPU grace-period kthreads, but increases
3143 that same overhead on each group's leader.
3145 rcutree.qhimark= [KNL]
3146 Set threshold of queued RCU callbacks beyond which
3147 batch limiting is disabled.
3149 rcutree.qlowmark= [KNL]
3150 Set threshold of queued RCU callbacks below which
3151 batch limiting is re-enabled.
3153 rcutree.rcu_idle_gp_delay= [KNL]
3154 Set wakeup interval for idle CPUs that have
3155 RCU callbacks (RCU_FAST_NO_HZ=y).
3157 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3158 Set wakeup interval for idle CPUs that have
3159 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3160 Lazy RCU callbacks are those which RCU can
3161 prove do nothing more than free memory.
3163 rcutorture.cbflood_inter_holdoff= [KNL]
3164 Set holdoff time (jiffies) between successive
3165 callback-flood tests.
3167 rcutorture.cbflood_intra_holdoff= [KNL]
3168 Set holdoff time (jiffies) between successive
3169 bursts of callbacks within a given callback-flood
3172 rcutorture.cbflood_n_burst= [KNL]
3173 Set the number of bursts making up a given
3174 callback-flood test. Set this to zero to
3175 disable callback-flood testing.
3177 rcutorture.cbflood_n_per_burst= [KNL]
3178 Set the number of callbacks to be registered
3179 in a given burst of a callback-flood test.
3181 rcutorture.fqs_duration= [KNL]
3182 Set duration of force_quiescent_state bursts
3185 rcutorture.fqs_holdoff= [KNL]
3186 Set holdoff time within force_quiescent_state bursts
3189 rcutorture.fqs_stutter= [KNL]
3190 Set wait time between force_quiescent_state bursts
3193 rcutorture.gp_cond= [KNL]
3194 Use conditional/asynchronous update-side
3195 primitives, if available.
3197 rcutorture.gp_exp= [KNL]
3198 Use expedited update-side primitives, if available.
3200 rcutorture.gp_normal= [KNL]
3201 Use normal (non-expedited) asynchronous
3202 update-side primitives, if available.
3204 rcutorture.gp_sync= [KNL]
3205 Use normal (non-expedited) synchronous
3206 update-side primitives, if available. If all
3207 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3208 rcutorture.gp_normal=, and rcutorture.gp_sync=
3209 are zero, rcutorture acts as if is interpreted
3210 they are all non-zero.
3212 rcutorture.n_barrier_cbs= [KNL]
3213 Set callbacks/threads for rcu_barrier() testing.
3215 rcutorture.nfakewriters= [KNL]
3216 Set number of concurrent RCU writers. These just
3217 stress RCU, they don't participate in the actual
3218 test, hence the "fake".
3220 rcutorture.nreaders= [KNL]
3221 Set number of RCU readers. The value -1 selects
3222 N-1, where N is the number of CPUs. A value
3223 "n" less than -1 selects N-n-2, where N is again
3224 the number of CPUs. For example, -2 selects N
3225 (the number of CPUs), -3 selects N+1, and so on.
3227 rcutorture.object_debug= [KNL]
3228 Enable debug-object double-call_rcu() testing.
3230 rcutorture.onoff_holdoff= [KNL]
3231 Set time (s) after boot for CPU-hotplug testing.
3233 rcutorture.onoff_interval= [KNL]
3234 Set time (s) between CPU-hotplug operations, or
3235 zero to disable CPU-hotplug testing.
3237 rcutorture.shuffle_interval= [KNL]
3238 Set task-shuffle interval (s). Shuffling tasks
3239 allows some CPUs to go into dyntick-idle mode
3240 during the rcutorture test.
3242 rcutorture.shutdown_secs= [KNL]
3243 Set time (s) after boot system shutdown. This
3244 is useful for hands-off automated testing.
3246 rcutorture.stall_cpu= [KNL]
3247 Duration of CPU stall (s) to test RCU CPU stall
3248 warnings, zero to disable.
3250 rcutorture.stall_cpu_holdoff= [KNL]
3251 Time to wait (s) after boot before inducing stall.
3253 rcutorture.stat_interval= [KNL]
3254 Time (s) between statistics printk()s.
3256 rcutorture.stutter= [KNL]
3257 Time (s) to stutter testing, for example, specifying
3258 five seconds causes the test to run for five seconds,
3259 wait for five seconds, and so on. This tests RCU's
3260 ability to transition abruptly to and from idle.
3262 rcutorture.test_boost= [KNL]
3263 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3264 "Maybe" means test if the RCU implementation
3265 under test support RCU priority boosting.
3267 rcutorture.test_boost_duration= [KNL]
3268 Duration (s) of each individual boost test.
3270 rcutorture.test_boost_interval= [KNL]
3271 Interval (s) between each boost test.
3273 rcutorture.test_no_idle_hz= [KNL]
3274 Test RCU's dyntick-idle handling. See also the
3275 rcutorture.shuffle_interval parameter.
3277 rcutorture.torture_runnable= [BOOT]
3278 Start rcutorture running at boot time.
3280 rcutorture.torture_type= [KNL]
3281 Specify the RCU implementation to test.
3283 rcutorture.verbose= [KNL]
3284 Enable additional printk() statements.
3286 rcupdate.rcu_expedited= [KNL]
3287 Use expedited grace-period primitives, for
3288 example, synchronize_rcu_expedited() instead
3289 of synchronize_rcu(). This reduces latency,
3290 but can increase CPU utilization, degrade
3291 real-time latency, and degrade energy efficiency.
3293 rcupdate.rcu_cpu_stall_suppress= [KNL]
3294 Suppress RCU CPU stall warning messages.
3296 rcupdate.rcu_cpu_stall_timeout= [KNL]
3297 Set timeout for RCU CPU stall warning messages.
3299 rcupdate.rcu_task_stall_timeout= [KNL]
3300 Set timeout in jiffies for RCU task stall warning
3301 messages. Disable with a value less than or equal
3304 rcupdate.rcu_self_test= [KNL]
3305 Run the RCU early boot self tests
3307 rcupdate.rcu_self_test_bh= [KNL]
3308 Run the RCU bh early boot self tests
3310 rcupdate.rcu_self_test_sched= [KNL]
3311 Run the RCU sched early boot self tests
3315 Run specified binary instead of /init from the ramdisk,
3316 used for early userspace startup. See initrd.
3319 Format (x86 or x86_64):
3320 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3322 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3324 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3325 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3326 reboot_force is either force or not specified,
3327 reboot_cpu is s[mp]#### with #### being the processor
3328 to be used for rebooting.
3331 [KNL, SMP] Set scheduler's default relax_domain_level.
3332 See Documentation/cgroups/cpusets.txt.
3334 relative_sleep_states=
3335 [SUSPEND] Use sleep state labeling where the deepest
3336 state available other than hibernation is always "mem".
3337 Format: { "0" | "1" }
3338 0 -- Traditional sleep state labels.
3339 1 -- Relative sleep state labels.
3341 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3343 reservetop= [X86-32]
3345 Reserves a hole at the top of the kernel virtual
3350 Set the amount of memory to reserve for BIOS at
3351 the bottom of the address space.
3353 reset_devices [KNL] Force drivers to reset the underlying device
3354 during initialization.
3357 Specify the partition device for software suspend
3359 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3361 resume_offset= [SWSUSP]
3362 Specify the offset from the beginning of the partition
3363 given by "resume=" at which the swap header is located,
3364 in <PAGE_SIZE> units (needed only for swap files).
3365 See Documentation/power/swsusp-and-swap-files.txt
3367 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3368 read the resume files
3370 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3371 Useful for devices that are detected asynchronously
3372 (e.g. USB and MMC devices).
3374 hibernate= [HIBERNATION]
3375 noresume Don't check if there's a hibernation image
3376 present during boot.
3377 nocompress Don't compress/decompress hibernation images.
3378 no Disable hibernation and resume.
3380 retain_initrd [RAM] Keep initrd memory after extraction
3382 rfkill.default_state=
3383 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3384 etc. communication is blocked by default.
3387 rfkill.master_switch_mode=
3388 0 The "airplane mode" button does nothing.
3389 1 The "airplane mode" button toggles between everything
3390 blocked and the previous configuration.
3391 2 The "airplane mode" button toggles between everything
3392 blocked and everything unblocked.
3394 rhash_entries= [KNL,NET]
3395 Set number of hash buckets for route cache
3397 ro [KNL] Mount root device read-only on boot
3399 root= [KNL] Root filesystem
3400 See name_to_dev_t comment in init/do_mounts.c.
3402 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3403 mount the root filesystem
3405 rootflags= [KNL] Set root filesystem mount option string
3407 rootfstype= [KNL] Set root filesystem type
3409 rootwait [KNL] Wait (indefinitely) for root device to show up.
3410 Useful for devices that are detected asynchronously
3411 (e.g. USB and MMC devices).
3413 rproc_mem=nn[KMG][@address]
3414 [KNL,ARM,CMA] Remoteproc physical memory block.
3415 Memory area to be used by remote processor image,
3418 rw [KNL] Mount root device read-write on boot
3420 S [KNL] Run init in single mode
3422 s390_iommu= [HW,S390]
3423 Set s390 IOTLB flushing mode
3425 With strict flushing every unmap operation will result in
3426 an IOTLB flush. Default is lazy flushing before reuse,
3430 See drivers/net/irda/sa1100_ir.c.
3432 sbni= [NET] Granch SBNI12 leased line adapter
3434 sched_debug [KNL] Enables verbose scheduler debug messages.
3436 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3437 xtime_lock contention on larger systems, and/or RCU lock
3438 contention on all systems with CONFIG_MAXSMP set.
3439 Format: { "0" | "1" }
3440 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3442 Note: increases power consumption, thus should only be
3443 enabled if running jitter sensitive (HPC/RT) workloads.
3445 security= [SECURITY] Choose a security module to enable at boot.
3446 If this boot parameter is not specified, only the first
3447 security module asking for security registration will be
3448 loaded. An invalid security module name will be treated
3449 as if no module has been chosen.
3451 selinux= [SELINUX] Disable or enable SELinux at boot time.
3452 Format: { "0" | "1" }
3453 See security/selinux/Kconfig help text.
3456 Default value is set via kernel config option.
3457 If enabled at boot time, /selinux/disable can be used
3458 later to disable prior to initial policy load.
3460 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3461 Format: { "0" | "1" }
3462 See security/apparmor/Kconfig help text
3465 Default value is set via kernel config option.
3467 serialnumber [BUGS=X86-32]
3470 Maximal number of shapers.
3472 show_msr= [x86] show boot-time MSR settings
3473 Format: { <integer> }
3474 Show boot-time (BIOS-initialized) MSR settings.
3475 The parameter means the number of CPUs to show,
3476 for example 1 means boot CPU only.
3484 Disable merging of slabs with similar size. May be
3485 necessary if there is some reason to distinguish
3486 allocs to different slabs. Debug options disable
3487 merging on their own.
3488 For more information see Documentation/vm/slub.txt.
3490 slab_max_order= [MM, SLAB]
3491 Determines the maximum allowed order for slabs.
3492 A high setting may cause OOMs due to memory
3493 fragmentation. Defaults to 1 for systems with
3494 more than 32MB of RAM, 0 otherwise.
3496 slub_debug[=options[,slabs]] [MM, SLUB]
3497 Enabling slub_debug allows one to determine the
3498 culprit if slab objects become corrupted. Enabling
3499 slub_debug can create guard zones around objects and
3500 may poison objects when not in use. Also tracks the
3501 last alloc / free. For more information see
3502 Documentation/vm/slub.txt.
3504 slub_max_order= [MM, SLUB]
3505 Determines the maximum allowed order for slabs.
3506 A high setting may cause OOMs due to memory
3507 fragmentation. For more information see
3508 Documentation/vm/slub.txt.
3510 slub_min_objects= [MM, SLUB]
3511 The minimum number of objects per slab. SLUB will
3512 increase the slab order up to slub_max_order to
3513 generate a sufficiently large slab able to contain
3514 the number of objects indicated. The higher the number
3515 of objects the smaller the overhead of tracking slabs
3516 and the less frequently locks need to be acquired.
3517 For more information see Documentation/vm/slub.txt.
3519 slub_min_order= [MM, SLUB]
3520 Determines the minimum page order for slabs. Must be
3521 lower than slub_max_order.
3522 For more information see Documentation/vm/slub.txt.
3524 slub_nomerge [MM, SLUB]
3525 Same with slab_nomerge. This is supported for legacy.
3526 See slab_nomerge for more information.
3529 Format: <io1>[,<io2>[,...,<io8>]]
3531 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3532 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3533 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3534 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3535 smsc-ircc2.ircc_irq= [HW] IRQ line
3536 smsc-ircc2.ircc_dma= [HW] DMA channel
3537 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3538 0: Toshiba Satellite 1800 (GP data pin select)
3539 1: Fast pin select (default)
3543 [KNL] Should the soft-lockup detector generate panics.
3546 softlockup_all_cpu_backtrace=
3547 [KNL] Should the soft-lockup detector generate
3548 backtraces on all cpus.
3551 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3552 See Documentation/laptops/sonypi.txt
3554 spia_io_base= [HW,MTD]
3560 Enabled the stack tracer on boot up.
3562 stacktrace_filter=[function-list]
3563 [FTRACE] Limit the functions that the stack tracer
3564 will trace at boot up. function-list is a comma separated
3565 list of functions. This list can be changed at run
3566 time by the stack_trace_filter file in the debugfs
3567 tracing directory. Note, this enables stack tracing
3568 and the stacktrace above is not needed.
3572 Set the STI (builtin display/keyboard on the HP-PARISC
3573 machines) console (graphic card) which should be used
3574 as the initial boot-console.
3575 See also comment in drivers/video/console/sticore.c.
3578 See comment in drivers/video/console/sticore.c.
3581 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3583 sunrpc.min_resvport=
3584 sunrpc.max_resvport=
3586 SunRPC servers often require that client requests
3587 originate from a privileged port (i.e. a port in the
3588 range 0 < portnr < 1024).
3589 An administrator who wishes to reserve some of these
3590 ports for other uses may adjust the range that the
3591 kernel's sunrpc client considers to be privileged
3592 using these two parameters to set the minimum and
3593 maximum port values.
3597 Control how the NFS server code allocates CPUs to
3598 service thread pools. Depending on how many NICs
3599 you have and where their interrupts are bound, this
3600 option will affect which CPUs will do NFS serving.
3601 Note: this parameter cannot be changed while the
3602 NFS server is running.
3604 auto the server chooses an appropriate mode
3605 automatically using heuristics
3606 global a single global pool contains all CPUs
3607 percpu one pool for each CPU
3608 pernode one pool for each NUMA node (equivalent
3609 to global on non-NUMA machines)
3611 sunrpc.tcp_slot_table_entries=
3612 sunrpc.udp_slot_table_entries=
3614 Sets the upper limit on the number of simultaneous
3615 RPC calls that can be sent from the client to a
3616 server. Increasing these values may allow you to
3617 improve throughput, but will also increase the
3618 amount of memory reserved for use by the client.
3620 suspend.pm_test_delay=
3622 Sets the number of seconds to remain in a suspend test
3623 mode before resuming the system (see
3624 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3625 is set. Default value is 5.
3628 [KNL] Enable accounting of swap in memory resource
3629 controller if no parameter or 1 is given or disable
3630 it if 0 is given (See Documentation/cgroups/memory.txt)
3632 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3633 Format: { <int> | force }
3634 <int> -- Number of I/O TLB slabs
3635 force -- force using of bounce buffers even if they
3636 wouldn't be automatically used by the kernel
3640 sysfs.deprecated=0|1 [KNL]
3641 Enable/disable old style sysfs layout for old udev
3642 on older distributions. When this option is enabled
3643 very new udev will not work anymore. When this option
3644 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3645 in older udev will not work anymore.
3646 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3647 the kernel configuration.
3649 sysrq_always_enabled
3651 Ignore sysrq setting - this boot parameter will
3652 neutralize any effect of /proc/sys/kernel/sysrq.
3653 Useful for debugging.
3655 tcpmhash_entries= [KNL,NET]
3656 Set the number of tcp_metrics_hash slots.
3657 Default value is 8192 or 16384 depending on total
3658 ram pages. This is used to specify the TCP metrics
3659 cache size. See Documentation/networking/ip-sysctl.txt
3660 "tcp_no_metrics_save" section for more details.
3664 test_suspend= [SUSPEND][,N]
3665 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3666 standby suspend) or "freeze" (for suspend type freeze)
3667 as the system sleep state during system startup with
3668 the optional capability to repeat N number of times.
3669 The system is woken from this state using a
3670 wakeup-capable RTC alarm.
3672 thash_entries= [KNL,NET]
3673 Set number of hash buckets for TCP connection
3675 thermal.act= [HW,ACPI]
3676 -1: disable all active trip points in all thermal zones
3677 <degrees C>: override all lowest active trip points
3679 thermal.crt= [HW,ACPI]
3680 -1: disable all critical trip points in all thermal zones
3681 <degrees C>: override all critical trip points
3683 thermal.nocrt= [HW,ACPI]
3684 Set to disable actions on ACPI thermal zone
3685 critical and hot trip points.
3687 thermal.off= [HW,ACPI]
3688 1: disable ACPI thermal control
3690 thermal.psv= [HW,ACPI]
3691 -1: disable all passive trip points
3692 <degrees C>: override all passive trip points to this
3695 thermal.tzp= [HW,ACPI]
3696 Specify global default ACPI thermal zone polling rate
3697 <deci-seconds>: poll all this frequency
3698 0: no polling (default)
3701 Force threading of all interrupt handlers except those
3702 marked explicitly IRQF_NO_THREAD.
3705 Enable the Transcendent memory driver if built-in.
3707 tmem.cleancache=0|1 [KNL, XEN]
3708 Default is on (1). Disable the usage of the cleancache
3709 API to send anonymous pages to the hypervisor.
3711 tmem.frontswap=0|1 [KNL, XEN]
3712 Default is on (1). Disable the usage of the frontswap
3713 API to send swap pages to the hypervisor. If disabled
3714 the selfballooning and selfshrinking are force disabled.
3716 tmem.selfballooning=0|1 [KNL, XEN]
3717 Default is on (1). Disable the driving of swap pages
3720 tmem.selfshrinking=0|1 [KNL, XEN]
3721 Default is on (1). Partial swapoff that immediately
3722 transfers pages from Xen hypervisor back to the
3723 kernel based on different criteria.
3727 Specify if the kernel should make use of the cpu
3728 topology information if the hardware supports this.
3729 The scheduler will make use of this information and
3730 e.g. base its process migration decisions on it.
3733 topology_updates= [KNL, PPC, NUMA]
3735 Specify if the kernel should ignore (off)
3736 topology updates sent by the hypervisor to this
3741 tpm_suspend_pcr=[HW,TPM]
3742 Format: integer pcr id
3743 Specify that at suspend time, the tpm driver
3744 should extend the specified pcr with zeros,
3745 as a workaround for some chips which fail to
3746 flush the last written pcr on TPM_SaveState.
3747 This will guarantee that all the other pcrs
3750 trace_buf_size=nn[KMG]
3751 [FTRACE] will set tracing buffer size on each cpu.
3753 trace_event=[event-list]
3754 [FTRACE] Set and start specified trace events in order
3755 to facilitate early boot debugging.
3756 See also Documentation/trace/events.txt
3758 trace_options=[option-list]
3759 [FTRACE] Enable or disable tracer options at boot.
3760 The option-list is a comma delimited list of options
3761 that can be enabled or disabled just as if you were
3762 to echo the option name into
3764 /sys/kernel/debug/tracing/trace_options
3766 For example, to enable stacktrace option (to dump the
3767 stack trace of each event), add to the command line:
3769 trace_options=stacktrace
3771 See also Documentation/trace/ftrace.txt "trace options"
3775 Have the tracepoints sent to printk as well as the
3776 tracing ring buffer. This is useful for early boot up
3777 where the system hangs or reboots and does not give the
3778 option for reading the tracing buffer or performing a
3779 ftrace_dump_on_oops.
3781 To turn off having tracepoints sent to printk,
3782 echo 0 > /proc/sys/kernel/tracepoint_printk
3783 Note, echoing 1 into this file without the
3784 tracepoint_printk kernel cmdline option has no effect.
3788 Having tracepoints sent to printk() and activating high
3789 frequency tracepoints such as irq or sched, can cause
3790 the system to live lock.
3793 [FTRACE] enable this option to disable tracing when a
3794 warning is hit. This turns off "tracing_on". Tracing can
3795 be enabled again by echoing '1' into the "tracing_on"
3796 file located in /sys/kernel/debug/tracing/
3798 This option is useful, as it disables the trace before
3799 the WARNING dump is called, which prevents the trace to
3800 be filled with content caused by the warning output.
3802 This option can also be set at run time via the sysctl
3803 option: kernel/traceoff_on_warning
3805 transparent_hugepage=
3807 Format: [always|madvise|never]
3808 Can be used to control the default behavior of the system
3809 with respect to transparent hugepages.
3810 See Documentation/vm/transhuge.txt for more details.
3812 tsc= Disable clocksource stability checks for TSC.
3814 [x86] reliable: mark tsc clocksource as reliable, this
3815 disables clocksource verification at runtime, as well
3816 as the stability checks done at bootup. Used to enable
3817 high-resolution timer mode on older hardware, and in
3818 virtualized environment.
3819 [x86] noirqtime: Do not use TSC to do irq accounting.
3820 Used to run time disable IRQ_TIME_ACCOUNTING on any
3821 platforms where RDTSC is slow and this accounting
3824 turbografx.map[2|3]= [HW,JOY]
3825 TurboGraFX parallel port interface
3827 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3828 See also Documentation/input/joystick-parport.txt
3830 udbg-immortal [PPC] When debugging early kernel crashes that
3831 happen after console_init() and before a proper
3832 console driver takes over, this boot options might
3833 help "seeing" what's going on.
3835 uhash_entries= [KNL,NET]
3836 Set number of hash buckets for UDP/UDP-Lite connections
3839 [USB] Ignore overcurrent events (default N).
3840 Some badly-designed motherboards generate lots of
3841 bogus events, for ports that aren't wired to
3842 anything. Set this parameter to avoid log spamming.
3843 Note that genuine overcurrent events won't be
3847 [X86] Cause panic on unknown NMI.
3849 usbcore.authorized_default=
3850 [USB] Default USB device authorization:
3851 (default -1 = authorized except for wireless USB,
3852 0 = not authorized, 1 = authorized)
3854 usbcore.autosuspend=
3855 [USB] The autosuspend time delay (in seconds) used
3856 for newly-detected USB devices (default 2). This
3857 is the time required before an idle device will be
3858 autosuspended. Devices for which the delay is set
3859 to a negative value won't be autosuspended at all.
3861 usbcore.usbfs_snoop=
3862 [USB] Set to log all usbfs traffic (default 0 = off).
3864 usbcore.blinkenlights=
3865 [USB] Set to cycle leds on hubs (default 0 = off).
3867 usbcore.old_scheme_first=
3868 [USB] Start with the old device initialization
3869 scheme (default 0 = off).
3871 usbcore.usbfs_memory_mb=
3872 [USB] Memory limit (in MB) for buffers allocated by
3873 usbfs (default = 16, 0 = max = 2047).
3875 usbcore.use_both_schemes=
3876 [USB] Try the other device initialization scheme
3877 if the first one fails (default 1 = enabled).
3879 usbcore.initial_descriptor_timeout=
3880 [USB] Specifies timeout for the initial 64-byte
3881 USB_REQ_GET_DESCRIPTOR request in milliseconds
3882 (default 5000 = 5.0 seconds).
3885 [USBHID] The interval which mice are to be polled at.
3887 usb-storage.delay_use=
3888 [UMS] The delay in seconds before a new device is
3889 scanned for Logical Units (default 1).
3892 [UMS] A list of quirks entries to supplement or
3893 override the built-in unusual_devs list. List
3894 entries are separated by commas. Each entry has
3895 the form VID:PID:Flags where VID and PID are Vendor
3896 and Product ID values (4-digit hex numbers) and
3897 Flags is a set of characters, each corresponding
3898 to a common usb-storage quirk flag as follows:
3899 a = SANE_SENSE (collect more than 18 bytes
3901 b = BAD_SENSE (don't collect more than 18
3902 bytes of sense data);
3903 c = FIX_CAPACITY (decrease the reported
3904 device capacity by one sector);
3905 d = NO_READ_DISC_INFO (don't use
3906 READ_DISC_INFO command);
3907 e = NO_READ_CAPACITY_16 (don't use
3908 READ_CAPACITY_16 command);
3909 f = NO_REPORT_OPCODES (don't use report opcodes
3911 g = MAX_SECTORS_240 (don't transfer more than
3912 240 sectors at a time, uas only);
3913 h = CAPACITY_HEURISTICS (decrease the
3914 reported device capacity by one
3915 sector if the number is odd);
3916 i = IGNORE_DEVICE (don't bind to this
3918 l = NOT_LOCKABLE (don't try to lock and
3919 unlock ejectable media);
3920 m = MAX_SECTORS_64 (don't transfer more
3921 than 64 sectors = 32 KB at a time);
3922 n = INITIAL_READ10 (force a retry of the
3923 initial READ(10) command);
3924 o = CAPACITY_OK (accept the capacity
3925 reported by the device);
3926 p = WRITE_CACHE (the device cache is ON
3928 r = IGNORE_RESIDUE (the device reports
3929 bogus residue values);
3930 s = SINGLE_LUN (the device has only one
3932 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3933 commands, uas only);
3934 u = IGNORE_UAS (don't bind to the uas driver);
3935 w = NO_WP_DETECT (don't test whether the
3936 medium is write-protected).
3937 Example: quirks=0419:aaf5:rl,0421:0433:rc
3939 user_debug= [KNL,ARM]
3941 See arch/arm/Kconfig.debug help text.
3942 1 - undefined instruction events
3944 4 - invalid data aborts
3947 Example: user_debug=31
3950 [X86] Flags controlling user PTE allocations.
3952 nohigh = do not allocate PTE pages in
3953 HIGHMEM regardless of setting
3957 On X86_32, this is an alias for vdso32=. Otherwise:
3959 vdso=1: enable VDSO (the default)
3960 vdso=0: disable VDSO mapping
3962 vdso32= [X86] Control the 32-bit vDSO
3963 vdso32=1: enable 32-bit VDSO
3964 vdso32=0 or vdso32=2: disable 32-bit VDSO
3966 See the help text for CONFIG_COMPAT_VDSO for more
3967 details. If CONFIG_COMPAT_VDSO is set, the default is
3968 vdso32=0; otherwise, the default is vdso32=1.
3970 For compatibility with older kernels, vdso32=2 is an
3973 Try vdso32=0 if you encounter an error that says:
3974 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3977 vector=percpu: enable percpu vector domain
3979 video= [FB] Frame buffer configuration
3980 See Documentation/fb/modedb.txt.
3982 video.brightness_switch_enabled= [0,1]
3983 If set to 1, on receiving an ACPI notify event
3984 generated by hotkey, video driver will adjust brightness
3985 level and then send out the event to user space through
3986 the allocated input device; If set to 0, video driver
3987 will only send out the event without touching backlight
3992 [VMMIO] Memory mapped virtio (platform) device.
3994 <size>@<baseaddr>:<irq>[:<id>]
3996 <size> := size (can use standard suffixes
3998 <baseaddr> := physical base address
3999 <irq> := interrupt number (as passed to
4001 <id> := (optional) platform device id
4003 virtio_mmio.device=1K@0x100b0000:48:7
4005 Can be used multiple times for multiple devices.
4007 vga= [BOOT,X86-32] Select a particular video mode
4008 See Documentation/x86/boot.txt and
4009 Documentation/svga.txt.
4010 Use vga=ask for menu.
4011 This is actually a boot loader parameter; the value is
4012 passed to the kernel using a special protocol.
4014 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4015 size of <nn>. This can be used to increase the
4016 minimum size (128MB on x86). It can also be used to
4017 decrease the size and leave more room for directly
4020 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4023 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4026 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4030 Controls the behavior of vsyscalls (i.e. calls to
4031 fixed addresses of 0xffffffffff600x00 from legacy
4032 code). Most statically-linked binaries and older
4033 versions of glibc use these calls. Because these
4034 functions are at fixed addresses, they make nice
4035 targets for exploits that can control RIP.
4037 emulate [default] Vsyscalls turn into traps and are
4038 emulated reasonably safely.
4040 native Vsyscalls are native syscall instructions.
4041 This is a little bit faster than trapping
4042 and makes a few dynamic recompilers work
4043 better than they would in emulation mode.
4044 It also makes exploits much easier to write.
4046 none Vsyscalls don't work at all. This makes
4047 them quite hard to use for exploits but
4048 might break your system.
4050 vt.color= [VT] Default text color.
4051 Format: 0xYX, X = foreground, Y = background.
4052 Default: 0x07 = light gray on black.
4054 vt.cur_default= [VT] Default cursor shape.
4055 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4056 the parameters of the <Esc>[?A;B;Cc escape sequence;
4057 see VGA-softcursor.txt. Default: 2 = underline.
4059 vt.default_blu= [VT]
4060 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4061 Change the default blue palette of the console.
4062 This is a 16-member array composed of values
4065 vt.default_grn= [VT]
4066 Format: <green0>,<green1>,<green2>,...,<green15>
4067 Change the default green palette of the console.
4068 This is a 16-member array composed of values
4071 vt.default_red= [VT]
4072 Format: <red0>,<red1>,<red2>,...,<red15>
4073 Change the default red palette of the console.
4074 This is a 16-member array composed of values
4080 Set system-wide default UTF-8 mode for all tty's.
4081 Default is 1, i.e. UTF-8 mode is enabled for all
4082 newly opened terminals.
4084 vt.global_cursor_default=
4087 Set system-wide default for whether a cursor
4088 is shown on new VTs. Default is -1,
4089 i.e. cursors will be created by default unless
4090 overridden by individual drivers. 0 will hide
4091 cursors, 1 will display them.
4093 vt.italic= [VT] Default color for italic text; 0-15.
4096 vt.underline= [VT] Default color for underlined text; 0-15.
4099 watchdog timers [HW,WDT] For information on watchdog timers,
4100 see Documentation/watchdog/watchdog-parameters.txt
4101 or other driver-specific files in the
4102 Documentation/watchdog/ directory.
4104 workqueue.disable_numa
4105 By default, all work items queued to unbound
4106 workqueues are affine to the NUMA nodes they're
4107 issued on, which results in better behavior in
4108 general. If NUMA affinity needs to be disabled for
4109 whatever reason, this option can be used. Note
4110 that this also can be controlled per-workqueue for
4111 workqueues visible under /sys/bus/workqueue/.
4113 workqueue.power_efficient
4114 Per-cpu workqueues are generally preferred because
4115 they show better performance thanks to cache
4116 locality; unfortunately, per-cpu workqueues tend to
4117 be more power hungry than unbound workqueues.
4119 Enabling this makes the per-cpu workqueues which
4120 were observed to contribute significantly to power
4121 consumption unbound, leading to measurably lower
4122 power usage at the cost of small performance
4125 The default value of this parameter is determined by
4126 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4128 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4129 default x2apic cluster mode on platforms
4132 x86_intel_mid_timer= [X86-32,APBT]
4133 Choose timer option for x86 Intel MID platform.
4134 Two valid options are apbt timer only and lapic timer
4135 plus one apbt timer for broadcast timer.
4136 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4138 xen_512gb_limit [KNL,X86-64,XEN]
4139 Restricts the kernel running paravirtualized under Xen
4140 to use only up to 512 GB of RAM. The reason to do so is
4141 crash analysis tools and Xen tools for doing domain
4142 save/restore/migration must be enabled to handle larger
4145 xen_emul_unplug= [HW,X86,XEN]
4146 Unplug Xen emulated devices
4147 Format: [unplug0,][unplug1]
4148 ide-disks -- unplug primary master IDE devices
4149 aux-ide-disks -- unplug non-primary-master IDE devices
4150 nics -- unplug network devices
4151 all -- unplug all emulated devices (NICs and IDE disks)
4152 unnecessary -- unplugging emulated devices is
4153 unnecessary even if the host did not respond to
4155 never -- do not unplug even if version check succeeds
4157 xen_nopvspin [X86,XEN]
4158 Disables the ticketlock slowpath using Xen PV
4162 Disables the PV optimizations forcing the HVM guest to
4163 run as generic HVM guest with no PV drivers.
4165 xirc2ps_cs= [NET,PCMCIA]
4167 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4169 ______________________________________________________________________
4173 Add more DRM drivers.
projects / cascardo / linux.git / blob