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>[,[<connector>:]<file>]
934 Broken monitors, graphic adapters, KVMs and EDIDless
935 panels may send no or incorrect EDID data sets.
936 This parameter allows to specify an EDID data sets
937 in the /lib/firmware directory that are 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
946 name. Each connector may use a unique EDID data
947 set by separating the files with a comma. An EDID
948 data set with no connector name will be used for
949 any connectors not explicitly specified.
953 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
954 module.dyndbg[="val"]
955 Enable debug messages at boot time. See
956 Documentation/dynamic-debug-howto.txt for details.
958 nompx [X86] Disables Intel Memory Protection Extensions.
959 See Documentation/x86/intel_mpx.txt for more
960 information about the feature.
963 on enable eager fpu restore
964 off disable eager fpu restore
965 auto selects the default scheme, which automatically
966 enables eagerfpu restore for xsaveopt.
968 module.async_probe [KNL]
969 Enable asynchronous probe on this module.
971 early_ioremap_debug [KNL]
972 Enable debug messages in early_ioremap support. This
973 is useful for tracking down temporary early mappings
974 which are not unmapped.
976 earlycon= [KNL] Output early console device and options.
979 Start an early, polled-mode console on a cadence serial
980 port at the specified address. The cadence serial port
981 must already be setup and configured. Options are not
984 uart[8250],io,<addr>[,options]
985 uart[8250],mmio,<addr>[,options]
986 uart[8250],mmio32,<addr>[,options]
987 uart[8250],mmio32be,<addr>[,options]
988 uart[8250],0x<addr>[,options]
989 Start an early, polled-mode console on the 8250/16550
990 UART at the specified I/O port or MMIO address.
991 MMIO inter-register address stride is either 8-bit
992 (mmio) or 32-bit (mmio32 or mmio32be).
993 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
994 to be equivalent to 'mmio'. 'options' are specified
995 in the same format described for "console=ttyS<n>"; if
996 unspecified, the h/w is not initialized.
999 Start an early, polled-mode console on a pl011 serial
1000 port at the specified address. The pl011 serial port
1001 must already be setup and configured. Options are not
1005 Start an early, polled-mode console on an msm serial
1006 port at the specified address. The serial port
1007 must already be setup and configured. Options are not
1010 msm_serial_dm,<addr>
1011 Start an early, polled-mode console on an msm serial
1012 dm port at the specified address. The serial port
1013 must already be setup and configured. Options are not
1016 smh Use ARM semihosting calls for early console.
1024 Use early console provided by serial driver available
1025 on Samsung SoCs, requires selecting proper type and
1026 a correct base address of the selected UART port. The
1027 serial port must already be setup and configured.
1028 Options are not yet supported.
1030 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1034 earlyprintk=serial[,ttySn[,baudrate]]
1035 earlyprintk=serial[,0x...[,baudrate]]
1036 earlyprintk=ttySn[,baudrate]
1037 earlyprintk=dbgp[debugController#]
1038 earlyprintk=pciserial,bus:device.function[,baudrate]
1040 earlyprintk is useful when the kernel crashes before
1041 the normal console is initialized. It is not enabled by
1042 default because it has some cosmetic problems.
1044 Append ",keep" to not disable it when the real console
1047 Only one of vga, efi, serial, or usb debug port can
1050 Currently only ttyS0 and ttyS1 may be specified by
1051 name. Other I/O ports may be explicitly specified
1052 on some architectures (x86 and arm at least) by
1053 replacing ttySn with an I/O port address, like this:
1054 earlyprintk=serial,0x1008,115200
1055 You can find the port for a given device in
1056 /proc/tty/driver/serial:
1057 2: uart:ST16650V2 port:00001008 irq:18 ...
1059 Interaction with the standard serial driver is not
1062 The VGA and EFI output is eventually overwritten by
1065 The xen output can only be used by Xen PV guests.
1067 edac_report= [HW,EDAC] Control how to report EDAC event
1068 Format: {"on" | "off" | "force"}
1069 on: enable EDAC to report H/W event. May be overridden
1070 by other higher priority error reporting module.
1071 off: disable H/W event reporting through EDAC.
1072 force: enforce the use of EDAC to report H/W event.
1075 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1078 This is designed to be used in conjunction with
1079 the boot argument: earlyprintk=vga
1082 Format: {"off" | "on" | "skip[mbr]"}
1085 Format: { "old_map", "nochunk", "noruntime", "debug" }
1086 old_map [X86-64]: switch to the old ioremap-based EFI
1087 runtime services mapping. 32-bit still uses this one by
1089 nochunk: disable reading files in "chunks" in the EFI
1090 boot stub, as chunking can cause problems with some
1091 firmware implementations.
1092 noruntime : disable EFI runtime services support
1093 debug: enable misc debug output
1095 efi_no_storage_paranoia [EFI; X86]
1096 Using this parameter you can use more than 50% of
1097 your efi variable storage. Use this parameter only if
1098 you are really sure that your UEFI does sane gc and
1099 fulfills the spec otherwise your board may brick.
1101 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1102 Add arbitrary attribute to specific memory range by
1103 updating original EFI memory map.
1104 Region of memory which aa attribute is added to is
1106 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1107 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1108 attribute is added to range 0x100000000-0x180000000 and
1109 0x10a0000000-0x1120000000.
1111 Using this parameter you can do debugging of EFI memmap
1112 related feature. For example, you can do debugging of
1113 Address Range Mirroring feature even if your box
1116 eisa_irq_edge= [PARISC,HW]
1117 See header of drivers/parisc/eisa.c.
1120 See comment before function elanfreq_setup() in
1121 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1124 Format: {"cfq" | "deadline" | "noop"}
1125 See Documentation/block/cfq-iosched.txt and
1126 Documentation/block/deadline-iosched.txt for details.
1128 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1129 Specifies physical address of start of kernel core
1130 image elf header and optionally the size. Generally
1131 kexec loader will pass this option to capture kernel.
1132 See Documentation/kdump/kdump.txt for details.
1134 enable_mtrr_cleanup [X86]
1135 The kernel tries to adjust MTRR layout from continuous
1136 to discrete, to make X server driver able to add WB
1137 entry later. This parameter enables that.
1139 enable_timer_pin_1 [X86]
1140 Enable PIN 1 of APIC timer
1141 Can be useful to work around chipset bugs
1142 (in particular on some ATI chipsets).
1143 The kernel tries to set a reasonable default.
1145 enforcing [SELINUX] Set initial enforcing status.
1147 See security/selinux/Kconfig help text.
1148 0 -- permissive (log only, no denials).
1149 1 -- enforcing (deny and log).
1151 Value can be changed at runtime via /selinux/enforce.
1154 Disable Error Record Serialization Table (ERST)
1157 ether= [HW,NET] Ethernet cards parameters
1158 This option is obsoleted by the "netdev=" option, which
1159 has equivalent usage. See its documentation for details.
1163 Permit 'security.evm' to be updated regardless of
1164 current integrity status.
1168 fail_make_request=[KNL]
1169 General fault injection mechanism.
1170 Format: <interval>,<probability>,<space>,<times>
1171 See also Documentation/fault-injection/.
1174 See Documentation/blockdev/floppy.txt.
1176 force_pal_cache_flush
1177 [IA-64] Avoid check_sal_cache_flush which may hang on
1178 buggy SAL_CACHE_FLUSH implementations. Using this
1179 parameter will force ia64_sal_cache_flush to call
1180 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1183 Forcefully enable Physical Address Extension (PAE).
1184 Many Pentium M systems disable PAE but may have a
1185 functionally usable PAE implementation.
1186 Warning: use of this parameter will taint the kernel
1187 and may cause unknown problems.
1190 [FTRACE] will set and start the specified tracer
1191 as early as possible in order to facilitate early
1194 ftrace_dump_on_oops[=orig_cpu]
1195 [FTRACE] will dump the trace buffers on oops.
1196 If no parameter is passed, ftrace will dump
1197 buffers of all CPUs, but if you pass orig_cpu, it will
1198 dump only the buffer of the CPU that triggered the
1201 ftrace_filter=[function-list]
1202 [FTRACE] Limit the functions traced by the function
1203 tracer at boot up. function-list is a comma separated
1204 list of functions. This list can be changed at run
1205 time by the set_ftrace_filter file in the debugfs
1208 ftrace_notrace=[function-list]
1209 [FTRACE] Do not trace the functions specified in
1210 function-list. This list can be changed at run time
1211 by the set_ftrace_notrace file in the debugfs
1214 ftrace_graph_filter=[function-list]
1215 [FTRACE] Limit the top level callers functions traced
1216 by the function graph tracer at boot up.
1217 function-list is a comma separated list of functions
1218 that can be changed at run time by the
1219 set_graph_function file in the debugfs tracing directory.
1221 ftrace_graph_notrace=[function-list]
1222 [FTRACE] Do not trace from the functions specified in
1223 function-list. This list is a comma separated list of
1224 functions that can be changed at run time by the
1225 set_graph_notrace file in the debugfs tracing directory.
1228 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1229 support via parallel port (up to 5 devices per port)
1230 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1231 See also Documentation/input/joystick-parport.txt
1235 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1239 gcov_persist= [GCOV] When non-zero (default), profiling data for
1240 kernel modules is saved and remains accessible via
1241 debugfs, even when the module is unloaded/reloaded.
1242 When zero, profiling data is discarded and associated
1243 debugfs files are removed at module unload time.
1245 gpt [EFI] Forces disk with valid GPT signature but
1246 invalid Protective MBR to be treated as GPT. If the
1247 primary GPT is corrupted, it enables the backup/alternate
1248 GPT to be used instead.
1250 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1251 the "Enable 0" bit of the configuration register.
1254 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1255 the "Enable 0" bit of the configuration register.
1258 grcan.select= [HW] Select which physical interface to use.
1261 grcan.txsize= [HW] Sets the size of the tx buffer.
1262 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1264 grcan.rxsize= [HW] Sets the size of the rx buffer.
1265 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1268 hashdist= [KNL,NUMA] Large hashes allocated during boot
1269 are distributed across NUMA nodes. Defaults on
1270 for 64-bit NUMA, off otherwise.
1271 Format: 0 | 1 (for off | on)
1273 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1275 hd= [EIDE] (E)IDE hard drive subsystem geometry
1276 Format: <cyl>,<head>,<sect>
1279 Disable Hardware Error Source Table (HEST) support;
1280 corresponding firmware-first mode error processing
1281 logic will be disabled.
1283 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1284 size of <nn>. This works even on boxes that have no
1285 highmem otherwise. This also works to reduce highmem
1286 size on bigger boxes.
1288 highres= [KNL] Enable/disable high resolution timer mode.
1289 Valid parameters: "on", "off"
1293 See Documentation/isdn/README.HiSax.
1297 hpet= [X86-32,HPET] option to control HPET usage
1298 Format: { enable (default) | disable | force |
1300 disable: disable HPET and use PIT instead
1301 force: allow force enabled of undocumented chips (ICH4,
1303 verbose: show contents of HPET registers during setup
1305 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1306 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1308 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1309 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1310 On x86-64 and powerpc, this option can be specified
1311 multiple times interleaved with hugepages= to reserve
1312 huge pages of different sizes. Valid pages sizes on
1313 x86-64 are 2M (when the CPU supports "pse") and 1G
1314 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1316 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1317 terminal devices. Valid values: 0..8
1318 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1319 If specified, z/VM IUCV HVC accepts connections
1320 from listed z/VM user IDs only.
1322 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1323 hardware thread id mappings.
1324 Format: <cpu>:<hwthread>
1327 Do not unregister boot console at start. This is only
1328 useful for debugging when something happens in the window
1329 between unregistering the boot console and initializing
1332 i2c_bus= [HW] Override the default board specific I2C bus speed
1333 or register an additional I2C bus that is not
1334 registered from board initialization code.
1338 i8042.debug [HW] Toggle i8042 debug mode
1339 i8042.unmask_kbd_data
1340 [HW] Enable printing of interrupt data from the KBD port
1341 (disabled by default, and as a pre-condition
1342 requires that i8042.debug=1 be enabled)
1343 i8042.direct [HW] Put keyboard port into non-translated mode
1344 i8042.dumbkbd [HW] Pretend that controller can only read data from
1345 keyboard and cannot control its state
1346 (Don't attempt to blink the leds)
1347 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1348 i8042.nokbd [HW] Don't check/create keyboard port
1349 i8042.noloop [HW] Disable the AUX Loopback command while probing
1351 i8042.nomux [HW] Don't check presence of an active multiplexing
1353 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1355 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1356 i8042.reset [HW] Reset the controller during init and cleanup
1357 i8042.unlock [HW] Unlock (ignore) the keylock
1358 i8042.kbdreset [HW] Reset device connected to KBD port
1362 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1363 indicates that the driver is running on unsupported
1365 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1366 does not match list of supported models.
1368 [HW] Report power status in /proc/i8k
1369 (disabled by default)
1370 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1373 i915.invert_brightness=
1374 [DRM] Invert the sense of the variable that is used to
1375 set the brightness of the panel backlight. Normally a
1376 brightness value of 0 indicates backlight switched off,
1377 and the maximum of the brightness value sets the backlight
1378 to maximum brightness. If this parameter is set to 0
1379 (default) and the machine requires it, or this parameter
1380 is set to 1, a brightness value of 0 sets the backlight
1381 to maximum brightness, and the maximum of the brightness
1382 value switches the backlight off.
1383 -1 -- never invert brightness
1384 0 -- machine default
1385 1 -- force brightness inversion
1388 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1390 ide-core.nodma= [HW] (E)IDE subsystem
1391 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1392 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1393 .cdrom .chs .ignore_cable are additional options
1394 See Documentation/ide/ide.txt.
1396 ide-generic.probe-mask= [HW] (E)IDE subsystem
1398 Probe mask for legacy ISA IDE ports. Depending on
1399 platform up to 6 ports are supported, enabled by
1400 setting corresponding bits in the mask to 1. The
1401 default value is 0x0, which has a special meaning.
1402 On systems that have PCI, it triggers scanning the
1403 PCI bus for the first and the second port, which
1404 are then probed. On systems without PCI the value
1405 of 0x0 enables probing the two first ports as if it
1408 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1409 Claim all unknown PCI IDE storage controllers.
1412 Format: idle=poll, idle=halt, idle=nomwait
1413 Poll forces a polling idle loop that can slightly
1414 improve the performance of waking up a idle CPU, but
1415 will use a lot of power and make the system run hot.
1417 idle=halt: Halt is forced to be used for CPU idle.
1418 In such case C2/C3 won't be used again.
1419 idle=nomwait: Disable mwait for CPU C-states
1421 ignore_loglevel [KNL]
1422 Ignore loglevel setting - this will print /all/
1423 kernel messages to the console. Useful for debugging.
1424 We also add it as printk module parameter, so users
1425 could change it dynamically, usually by
1426 /sys/module/printk/parameters/ignore_loglevel.
1428 ihash_entries= [KNL]
1429 Set number of hash buckets for inode cache.
1431 ima_appraise= [IMA] appraise integrity measurements
1432 Format: { "off" | "enforce" | "fix" | "log" }
1435 ima_appraise_tcb [IMA]
1436 The builtin appraise policy appraises all files
1440 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1444 The list of supported hash algorithms is defined
1445 in crypto/hash_info.h.
1448 The builtin measurement policy to load during IMA
1449 setup. Specyfing "tcb" as the value, measures all
1450 programs exec'd, files mmap'd for exec, and all files
1451 opened with the read mode bit set by either the
1452 effective uid (euid=0) or uid=0.
1455 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1456 Load a policy which meets the needs of the Trusted
1457 Computing Base. This means IMA will measure all
1458 programs exec'd, files mmap'd for exec, and all files
1459 opened for read by uid=0.
1462 Select one of defined IMA measurements template formats.
1463 Formats: { "ima" | "ima-ng" | "ima-sig" }
1467 [IMA] Define a custom template format.
1468 Format: { "field1|...|fieldN" }
1470 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1471 Format: <min_file_size>
1472 Set the minimal file size for using asynchronous hash.
1473 If left unspecified, ahash usage is disabled.
1475 ahash performance varies for different data sizes on
1476 different crypto accelerators. This option can be used
1477 to achieve the best performance for a particular HW.
1479 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1481 Set hashing buffer size. Default: 4k.
1483 ahash performance varies for different chunk sizes on
1484 different crypto accelerators. This option can be used
1485 to achieve best performance for particular HW.
1489 Run specified binary instead of /sbin/init as init
1492 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1493 for working out where the kernel is dying during
1496 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1497 initcall functions. Useful for debugging built-in
1498 modules and initcalls.
1500 initrd= [BOOT] Specify the location of the initial ramdisk
1502 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1505 int_pln_enable [x86] Enable power limit notification interrupt
1507 integrity_audit=[IMA]
1508 Format: { "0" | "1" }
1509 0 -- basic integrity auditing messages. (Default)
1510 1 -- additional integrity auditing messages.
1512 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1514 Enable intel iommu driver.
1516 Disable intel iommu driver.
1517 igfx_off [Default Off]
1518 By default, gfx is mapped as normal device. If a gfx
1519 device has a dedicated DMAR unit, the DMAR unit is
1520 bypassed by not enabling DMAR with this option. In
1521 this case, gfx device will use physical address for
1524 With this option iommu will not optimize to look
1525 for io virtual address below 32-bit forcing dual
1526 address cycle on pci bus for cards supporting greater
1527 than 32-bit addressing. The default is to look
1528 for translation below 32-bit and if not available
1529 then look in the higher range.
1530 strict [Default Off]
1531 With this option on every unmap_single operation will
1532 result in a hardware IOTLB flush operation as opposed
1533 to batching them for performance.
1534 sp_off [Default Off]
1535 By default, super page will be supported if Intel IOMMU
1536 has the capability. With this option, super page will
1538 ecs_off [Default Off]
1539 By default, extended context tables will be supported if
1540 the hardware advertises that it has support both for the
1541 extended tables themselves, and also PASID support. With
1542 this option set, extended tables will not be used even
1543 on hardware which claims to support them.
1545 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1546 0 disables intel_idle and fall back on acpi_idle.
1547 1 to 6 specify maximum depth of C-state.
1551 Do not enable intel_pstate as the default
1552 scaling driver for the supported processors
1554 Enable intel_pstate on systems that prohibit it by default
1555 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1556 instead of acpi-cpufreq may disable platform features, such
1557 as thermal controls and power capping, that rely on ACPI
1558 P-States information being indicated to OSPM and therefore
1559 should be used with caution. This option does not work with
1560 processors that aren't supported by the intel_pstate driver
1561 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1563 Do not enable hardware P state control (HWP)
1566 Only load intel_pstate on systems which support
1567 hardware P state control (HWP) if available.
1569 Don't use ACPI processor performance control objects
1570 _PSS and _PPC specified limits.
1572 intremap= [X86-64, Intel-IOMMU]
1573 on enable Interrupt Remapping (default)
1574 off disable Interrupt Remapping
1575 nosid disable Source ID checking
1577 BIOS x2APIC opt-out request will be ignored
1579 iomem= Disable strict checking of access to MMIO memory
1580 strict regions from userspace.
1595 nobypass [PPC/POWERNV]
1596 Disable IOMMU bypass, using IOMMU for PCI devices.
1599 io7= [HW] IO7 for Marvel based alpha systems
1600 See comment before marvel_specify_io7 in
1601 arch/alpha/kernel/core_marvel.c.
1603 io_delay= [X86] I/O delay method
1605 Standard port 0x80 based delay
1607 Alternate port 0xed based delay (needed on some systems)
1609 Simple two microseconds delay
1614 See Documentation/filesystems/nfs/nfsroot.txt.
1617 When an interrupt is not handled search all handlers
1618 for it. Intended to get systems with badly broken
1622 When an interrupt is not handled search all handlers
1623 for it. Also check all handlers each timer
1624 interrupt. Intended to get systems with badly broken
1628 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1630 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1632 <cpu number>,...,<cpu number>
1634 <cpu number>-<cpu number>
1635 (must be a positive range in ascending order)
1637 <cpu number>,...,<cpu number>-<cpu number>
1639 This option can be used to specify one or more CPUs
1640 to isolate from the general SMP balancing and scheduling
1641 algorithms. You can move a process onto or off an
1642 "isolated" CPU via the CPU affinity syscalls or cpuset.
1643 <cpu number> begins at 0 and the maximum value is
1644 "number of CPUs in system - 1".
1646 This option is the preferred way to isolate CPUs. The
1647 alternative -- manually setting the CPU mask of all
1648 tasks in the system -- can cause problems and
1649 suboptimal load balancer performance.
1653 ivrs_ioapic [HW,X86_64]
1654 Provide an override to the IOAPIC-ID<->DEVICE-ID
1655 mapping provided in the IVRS ACPI table. For
1656 example, to map IOAPIC-ID decimal 10 to
1657 PCI device 00:14.0 write the parameter as:
1658 ivrs_ioapic[10]=00:14.0
1660 ivrs_hpet [HW,X86_64]
1661 Provide an override to the HPET-ID<->DEVICE-ID
1662 mapping provided in the IVRS ACPI table. For
1663 example, to map HPET-ID decimal 0 to
1664 PCI device 00:14.0 write the parameter as:
1665 ivrs_hpet[0]=00:14.0
1667 js= [HW,JOY] Analog joystick
1668 See Documentation/input/joystick.txt.
1671 Enable/disable kernel and module base offset ASLR
1672 (Address Space Layout Randomization) if built into
1673 the kernel. When CONFIG_HIBERNATION is selected,
1674 kASLR is disabled by default. When kASLR is enabled,
1675 hibernation will be disabled.
1679 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1680 specifies the amount of memory usable by the kernel
1681 for non-movable allocations. The requested amount is
1682 spread evenly throughout all nodes in the system. The
1683 remaining memory in each node is used for Movable
1684 pages. In the event, a node is too small to have both
1685 kernelcore and Movable pages, kernelcore pages will
1686 take priority and other nodes will have a larger number
1687 of Movable pages. The Movable zone is used for the
1688 allocation of pages that may be reclaimed or moved
1689 by the page migration subsystem. This means that
1690 HugeTLB pages may not be allocated from this zone.
1691 Note that allocations like PTEs-from-HighMem still
1692 use the HighMem zone if it exists, and the Normal
1693 zone if it does not.
1695 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1696 Format: <Controller#>[,poll interval]
1697 The controller # is the number of the ehci usb debug
1698 port as it is probed via PCI. The poll interval is
1699 optional and is the number seconds in between
1700 each poll cycle to the debug port in case you need
1701 the functionality for interrupting the kernel with
1702 gdb or control-c on the dbgp connection. When
1703 not using this parameter you use sysrq-g to break into
1704 the kernel debugger.
1706 kgdboc= [KGDB,HW] kgdb over consoles.
1707 Requires a tty driver that supports console polling,
1708 or a supported polling keyboard driver (non-usb).
1709 Serial only format: <serial_device>[,baud]
1710 keyboard only format: kbd
1711 keyboard and serial format: kbd,<serial_device>[,baud]
1712 Optional Kernel mode setting:
1713 kms, kbd format: kms,kbd
1714 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1716 kgdbwait [KGDB] Stop kernel execution and enter the
1717 kernel debugger at the earliest opportunity.
1719 kmac= [MIPS] korina ethernet MAC address.
1720 Configure the RouterBoard 532 series on-chip
1721 Ethernet adapter MAC address.
1723 kmemleak= [KNL] Boot-time kmemleak enable/disable
1724 Valid arguments: on, off
1726 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1729 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1730 Valid arguments: 0, 1, 2
1731 kmemcheck=0 (disabled)
1732 kmemcheck=1 (enabled)
1733 kmemcheck=2 (one-shot mode)
1734 Default: 2 (one-shot mode)
1736 kstack=N [X86] Print N words from the kernel stack
1739 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1740 Default is 0 (don't ignore, but inject #GP)
1742 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1746 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1747 Default is 1 (enabled)
1749 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1751 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1753 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1754 (virtualized MMU) support on capable Intel chips.
1755 Default is 1 (enabled)
1757 kvm-intel.emulate_invalid_guest_state=
1758 [KVM,Intel] Enable emulation of invalid guest states
1759 Default is 0 (disabled)
1761 kvm-intel.flexpriority=
1762 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1763 Default is 1 (enabled)
1766 [KVM,Intel] Enable VMX nesting (nVMX).
1767 Default is 0 (disabled)
1769 kvm-intel.unrestricted_guest=
1770 [KVM,Intel] Disable unrestricted guest feature
1771 (virtualized real and unpaged mode) on capable
1772 Intel chips. Default is 1 (enabled)
1774 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1775 feature (tagged TLBs) on capable Intel chips.
1776 Default is 1 (enabled)
1782 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1785 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1786 value for LAPIC timer one-shot implementation. Default
1787 back to the programmable timer unit in the LAPIC.
1789 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1792 libata.dma= [LIBATA] DMA control
1793 libata.dma=0 Disable all PATA and SATA DMA
1794 libata.dma=1 PATA and SATA Disk DMA only
1795 libata.dma=2 ATAPI (CDROM) DMA only
1796 libata.dma=4 Compact Flash DMA only
1797 Combinations also work, so libata.dma=3 enables DMA
1798 for disks and CDROMs, but not CFs.
1800 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1801 libata.ignore_hpa=0 keep BIOS limits (default)
1802 libata.ignore_hpa=1 ignore limits, using full disk
1804 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1808 libata.force= [LIBATA] Force configurations. The format is comma
1809 separated list of "[ID:]VAL" where ID is
1810 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1811 matching port, link or device. Basically, it matches
1812 the ATA ID string printed on console by libata. If
1813 the whole ID part is omitted, the last PORT and DEVICE
1814 values are used. If ID hasn't been specified yet, the
1815 configuration applies to all ports, links and devices.
1817 If only DEVICE is omitted, the parameter applies to
1818 the port and all links and devices behind it. DEVICE
1819 number of 0 either selects the first device or the
1820 first fan-out link behind PMP device. It does not
1821 select the host link. DEVICE number of 15 selects the
1822 host link and device attached to it.
1824 The VAL specifies the configuration to force. As long
1825 as there's no ambiguity shortcut notation is allowed.
1826 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1827 The following configurations can be forced.
1829 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1830 Any ID with matching PORT is used.
1832 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1834 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1835 udma[/][16,25,33,44,66,100,133] notation is also
1838 * [no]ncq: Turn on or off NCQ.
1840 * [no]ncqtrim: Turn off queued DSM TRIM.
1842 * nohrst, nosrst, norst: suppress hard, soft
1845 * rstonce: only attempt one reset during
1846 hot-unplug link recovery
1848 * dump_id: dump IDENTIFY data.
1850 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1852 * disable: Disable this device.
1854 If there are multiple matching configurations changing
1855 the same attribute, the last one is used.
1857 memblock=debug [KNL] Enable memblock debug messages.
1859 load_ramdisk= [RAM] List of ramdisks to load from floppy
1860 See Documentation/blockdev/ramdisk.txt.
1862 lockd.nlm_grace_period=P [NFS] Assign grace period.
1865 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1868 lockd.nlm_timeout=T [NFS] Assign timeout value.
1871 lockd.nlm_udpport=M [NFS] Assign UDP port.
1874 locktorture.nreaders_stress= [KNL]
1875 Set the number of locking read-acquisition kthreads.
1876 Defaults to being automatically set based on the
1877 number of online CPUs.
1879 locktorture.nwriters_stress= [KNL]
1880 Set the number of locking write-acquisition kthreads.
1882 locktorture.onoff_holdoff= [KNL]
1883 Set time (s) after boot for CPU-hotplug testing.
1885 locktorture.onoff_interval= [KNL]
1886 Set time (s) between CPU-hotplug operations, or
1887 zero to disable CPU-hotplug testing.
1889 locktorture.shuffle_interval= [KNL]
1890 Set task-shuffle interval (jiffies). Shuffling
1891 tasks allows some CPUs to go into dyntick-idle
1892 mode during the locktorture test.
1894 locktorture.shutdown_secs= [KNL]
1895 Set time (s) after boot system shutdown. This
1896 is useful for hands-off automated testing.
1898 locktorture.stat_interval= [KNL]
1899 Time (s) between statistics printk()s.
1901 locktorture.stutter= [KNL]
1902 Time (s) to stutter testing, for example,
1903 specifying five seconds causes the test to run for
1904 five seconds, wait for five seconds, and so on.
1905 This tests the locking primitive's ability to
1906 transition abruptly to and from idle.
1908 locktorture.torture_runnable= [BOOT]
1909 Start locktorture running at boot time.
1911 locktorture.torture_type= [KNL]
1912 Specify the locking implementation to test.
1914 locktorture.verbose= [KNL]
1915 Enable additional printk() statements.
1917 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1920 loglevel= All Kernel Messages with a loglevel smaller than the
1921 console loglevel will be printed to the console. It can
1922 also be changed with klogd or other programs. The
1923 loglevels are defined as follows:
1925 0 (KERN_EMERG) system is unusable
1926 1 (KERN_ALERT) action must be taken immediately
1927 2 (KERN_CRIT) critical conditions
1928 3 (KERN_ERR) error conditions
1929 4 (KERN_WARNING) warning conditions
1930 5 (KERN_NOTICE) normal but significant condition
1931 6 (KERN_INFO) informational
1932 7 (KERN_DEBUG) debug-level messages
1934 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1935 in bytes. n must be a power of two and greater
1936 than the minimal size. The minimal size is defined
1937 by LOG_BUF_SHIFT kernel config parameter. There is
1938 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1939 that allows to increase the default size depending on
1940 the number of CPUs. See init/Kconfig for more details.
1942 logo.nologo [FB] Disables display of the built-in Linux logo.
1943 This may be used to provide more screen space for
1944 kernel log messages and is useful when debugging
1945 kernel boot problems.
1947 lp=0 [LP] Specify parallel ports to use, e.g,
1948 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1949 lp=reset first parallel port). 'lp=0' disables the
1950 lp=auto printer driver. 'lp=reset' (which can be
1951 specified in addition to the ports) causes
1952 attached printers to be reset. Using
1953 lp=port1,port2,... specifies the parallel ports
1954 to associate lp devices with, starting with
1955 lp0. A port specification may be 'none' to skip
1956 that lp device, or a parport name such as
1957 'parport0'. Specifying 'lp=auto' instead of a
1958 port specification list means that device IDs
1959 from each port should be examined, to see if
1960 an IEEE 1284-compliant printer is attached; if
1961 so, the driver will manage that printer.
1962 See also header of drivers/char/lp.c.
1965 Sets loops_per_jiffy to given constant, thus avoiding
1966 time-consuming boot-time autodetection (up to 250 ms per
1967 CPU). 0 enables autodetection (default). To determine
1968 the correct value for your kernel, boot with normal
1969 autodetection and see what value is printed. Note that
1970 on SMP systems the preset will be applied to all CPUs,
1971 which is likely to cause problems if your CPUs need
1972 significantly divergent settings. An incorrect value
1973 will cause delays in the kernel to be wrong, leading to
1974 unpredictable I/O errors and other breakage. Although
1975 unlikely, in the extreme case this might damage your
1979 Format: <io>,<irq>,<dma>
1981 machvec= [IA-64] Force the use of a particular machine-vector
1982 (machvec) in a generic kernel.
1983 Example: machvec=hpzx1_swiotlb
1985 machtype= [Loongson] Share the same kernel image file between different
1987 Example: machtype=lemote-yeeloong-2f-7inch
1989 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1990 than or equal to this physical address is ignored.
1992 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1993 should make use of. maxcpus=n : n >= 0 limits the
1994 kernel to using 'n' processors. n=0 is a special case,
1995 it is equivalent to "nosmp", which also disables
1998 max_loop= [LOOP] The number of loop block devices that get
1999 (loop.max_loop) unconditionally pre-created at init time. The default
2000 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2001 of statically allocating a predefined number, loop
2002 devices can be requested on-demand with the
2003 /dev/loop-control interface.
2005 mce [X86-32] Machine Check Exception
2007 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2009 md= [HW] RAID subsystems devices and level
2010 See Documentation/md.txt.
2013 Format: <first>,<last>
2014 Specifies range of consoles to be captured by the MDA.
2016 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2017 Amount of memory to be used when the kernel is not able
2018 to see the whole system memory or for test.
2019 [X86] Work as limiting max address. Use together
2020 with memmap= to avoid physical address space collisions.
2021 Without memmap= PCI devices could be placed at addresses
2022 belonging to unused RAM.
2024 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2028 [KNL,SH] Allow user to override the default size for
2029 per-device physically contiguous DMA buffers.
2031 memmap=exactmap [KNL,X86] Enable setting of an exact
2032 E820 memory map, as specified by the user.
2033 Such memmap=exactmap lines can be constructed based on
2034 BIOS output or other requirements. See the memmap=nn@ss
2037 memmap=nn[KMG]@ss[KMG]
2038 [KNL] Force usage of a specific region of memory.
2039 Region of memory to be used is from ss to ss+nn.
2041 memmap=nn[KMG]#ss[KMG]
2042 [KNL,ACPI] Mark specific memory as ACPI data.
2043 Region of memory to be marked is from ss to ss+nn.
2045 memmap=nn[KMG]$ss[KMG]
2046 [KNL,ACPI] Mark specific memory as reserved.
2047 Region of memory to be reserved is from ss to ss+nn.
2048 Example: Exclude memory from 0x18690000-0x1869ffff
2049 memmap=64K$0x18690000
2051 memmap=0x10000$0x18690000
2053 memmap=nn[KMG]!ss[KMG]
2054 [KNL,X86] Mark specific memory as protected.
2055 Region of memory to be used, from ss to ss+nn.
2056 The memory region may be marked as e820 type 12 (0xc)
2057 and is NVDIMM or ADR memory.
2059 memory_corruption_check=0/1 [X86]
2060 Some BIOSes seem to corrupt the first 64k of
2061 memory when doing things like suspend/resume.
2062 Setting this option will scan the memory
2063 looking for corruption. Enabling this will
2064 both detect corruption and prevent the kernel
2065 from using the memory being corrupted.
2066 However, its intended as a diagnostic tool; if
2067 repeatable BIOS-originated corruption always
2068 affects the same memory, you can use memmap=
2069 to prevent the kernel from using that memory.
2071 memory_corruption_check_size=size [X86]
2072 By default it checks for corruption in the low
2073 64k, making this memory unavailable for normal
2074 use. Use this parameter to scan for
2075 corruption in more or less memory.
2077 memory_corruption_check_period=seconds [X86]
2078 By default it checks for corruption every 60
2079 seconds. Use this parameter to check at some
2080 other rate. 0 disables periodic checking.
2082 memtest= [KNL,X86,ARM] Enable memtest
2084 default : 0 <disable>
2085 Specifies the number of memtest passes to be
2086 performed. Each pass selects another test
2087 pattern from a given set of patterns. Memtest
2088 fills the memory with this pattern, validates
2089 memory contents and reserves bad memory
2090 regions that are detected.
2092 meye.*= [HW] Set MotionEye Camera parameters
2093 See Documentation/video4linux/meye.txt.
2095 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2096 Multi-Function General Purpose Timers on AMD Geode
2099 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2100 the BIOS has incorrectly applied a workaround. TinyBIOS
2101 version 0.98 is known to be affected, 0.99 fixes the
2102 problem by letting the user disable the workaround.
2106 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2107 physical address is ignored.
2109 mini2440= [ARM,HW,KNL]
2110 Format:[0..2][b][c][t]
2112 MINI2440 configuration specification:
2113 0 - The attached screen is the 3.5" TFT
2114 1 - The attached screen is the 7" TFT
2115 2 - The VGA Shield is attached (1024x768)
2116 Leaving out the screen size parameter will not load
2117 the TFT driver, and the framebuffer will be left
2119 b - Enable backlight. The TFT backlight pin will be
2120 linked to the kernel VESA blanking code and a GPIO
2121 LED. This parameter is not necessary when using the
2123 c - Enable the s3c camera interface.
2124 t - Reserved for enabling touchscreen support. The
2125 touchscreen support is not enabled in the mainstream
2126 kernel as of 2.6.30, a preliminary port can be found
2127 in the "bleeding edge" mini2440 support kernel at
2128 http://repo.or.cz/w/linux-2.6/mini2440.git
2131 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2132 parameter allows control of the logging verbosity for
2133 the additional memory initialisation checks. A value
2134 of 0 disables mminit logging and a level of 4 will
2135 log everything. Information is printed at KERN_DEBUG
2136 so loglevel=8 may also need to be specified.
2139 [KNL] When CONFIG_MODULE_SIG is set, this means that
2140 modules without (valid) signatures will fail to load.
2141 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2142 is always true, so this option does nothing.
2145 [MOUSE] Maximum time between finger touching and
2146 leaving touchpad surface for touch to be considered
2147 a tap and be reported as a left button click (for
2148 touchpads working in absolute mode only).
2150 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2151 reporting absolute coordinates, such as tablets
2152 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2153 reporting absolute coordinates, such as tablets
2155 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2156 is similar to kernelcore except it specifies the
2157 amount of memory used for migratable allocations.
2158 If both kernelcore and movablecore is specified,
2159 then kernelcore will be at *least* the specified
2160 value but may be more. If movablecore on its own
2161 is specified, the administrator must be careful
2162 that the amount of memory usable for all allocations
2165 movable_node [KNL,X86] Boot-time switch to enable the effects
2166 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2168 MTD_Partition= [MTD]
2169 Format: <name>,<region-number>,<size>,<offset>
2171 MTD_Region= [MTD] Format:
2172 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2175 See drivers/mtd/cmdlinepart.c.
2177 multitce=off [PPC] This parameter disables the use of the pSeries
2178 firmware feature for updating multiple TCE entries
2181 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2183 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2185 boundary - index of last SLC block on Flex-OneNAND.
2186 The remaining blocks are configured as MLC blocks.
2187 lock - Configure if Flex-OneNAND boundary should be locked.
2188 Once locked, the boundary cannot be changed.
2189 1 indicates lock status, 0 indicates unlock status.
2192 ARM/S3C2412 JIVE boot control
2194 See arch/arm/mach-s3c2412/mach-jive.c
2196 mtouchusb.raw_coordinates=
2197 [HW] Make the MicroTouch USB driver use raw coordinates
2198 ('y', default) or cooked coordinates ('n')
2200 mtrr_chunk_size=nn[KMG] [X86]
2201 used for mtrr cleanup. It is largest continuous chunk
2202 that could hold holes aka. UC entries.
2204 mtrr_gran_size=nn[KMG] [X86]
2205 Used for mtrr cleanup. It is granularity of mtrr block.
2207 Large value could prevent small alignment from
2210 mtrr_spare_reg_nr=n [X86]
2212 Range: 0,7 : spare reg number
2214 Used for mtrr cleanup. It is spare mtrr entries number.
2215 Set to 2 or more if your graphical card needs more.
2217 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2219 netdev= [NET] Network devices parameters
2220 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2221 Note that mem_start is often overloaded to mean
2222 something different and driver-specific.
2223 This usage is only documented in each driver source
2227 [NETFILTER] Enable connection tracking flow accounting
2228 0 to disable accounting
2229 1 to enable accounting
2232 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2233 See Documentation/filesystems/nfs/nfsroot.txt.
2235 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2236 See Documentation/filesystems/nfs/nfsroot.txt.
2238 nfsrootdebug [NFS] enable nfsroot debugging messages.
2239 See Documentation/filesystems/nfs/nfsroot.txt.
2241 nfs.callback_tcpport=
2242 [NFS] set the TCP port on which the NFSv4 callback
2243 channel should listen.
2246 [NFS] sets the pathname to the program which is used
2247 to update the NFS client cache entries.
2249 nfs.cache_getent_timeout=
2250 [NFS] sets the timeout after which an attempt to
2251 update a cache entry is deemed to have failed.
2253 nfs.idmap_cache_timeout=
2254 [NFS] set the maximum lifetime for idmapper cache
2258 [NFS] enable 64-bit inode numbers.
2259 If zero, the NFS client will fake up a 32-bit inode
2260 number for the readdir() and stat() syscalls instead
2261 of returning the full 64-bit number.
2262 The default is to return 64-bit inode numbers.
2264 nfs.max_session_slots=
2265 [NFSv4.1] Sets the maximum number of session slots
2266 the client will attempt to negotiate with the server.
2267 This limits the number of simultaneous RPC requests
2268 that the client can send to the NFSv4.1 server.
2269 Note that there is little point in setting this
2270 value higher than the max_tcp_slot_table_limit.
2272 nfs.nfs4_disable_idmapping=
2273 [NFSv4] When set to the default of '1', this option
2274 ensures that both the RPC level authentication
2275 scheme and the NFS level operations agree to use
2276 numeric uids/gids if the mount is using the
2277 'sec=sys' security flavour. In effect it is
2278 disabling idmapping, which can make migration from
2279 legacy NFSv2/v3 systems to NFSv4 easier.
2280 Servers that do not support this mode of operation
2281 will be autodetected by the client, and it will fall
2282 back to using the idmapper.
2283 To turn off this behaviour, set the value to '0'.
2285 [NFS4] Specify an additional fixed unique ident-
2286 ification string that NFSv4 clients can insert into
2287 their nfs_client_id4 string. This is typically a
2288 UUID that is generated at system install time.
2290 nfs.send_implementation_id =
2291 [NFSv4.1] Send client implementation identification
2292 information in exchange_id requests.
2293 If zero, no implementation identification information
2295 The default is to send the implementation identification
2298 nfs.recover_lost_locks =
2299 [NFSv4] Attempt to recover locks that were lost due
2300 to a lease timeout on the server. Please note that
2301 doing this risks data corruption, since there are
2302 no guarantees that the file will remain unchanged
2303 after the locks are lost.
2304 If you want to enable the kernel legacy behaviour of
2305 attempting to recover these locks, then set this
2307 The default parameter value of '0' causes the kernel
2308 not to attempt recovery of lost locks.
2310 nfs4.layoutstats_timer =
2311 [NFSv4.2] Change the rate at which the kernel sends
2312 layoutstats to the pNFS metadata server.
2314 Setting this to value to 0 causes the kernel to use
2315 whatever value is the default set by the layout
2316 driver. A non-zero value sets the minimum interval
2317 in seconds between layoutstats transmissions.
2319 nfsd.nfs4_disable_idmapping=
2320 [NFSv4] When set to the default of '1', the NFSv4
2321 server will return only numeric uids and gids to
2322 clients using auth_sys, and will accept numeric uids
2323 and gids from such clients. This is intended to ease
2324 migration from NFSv2/v3.
2326 objlayoutdriver.osd_login_prog=
2327 [NFS] [OBJLAYOUT] sets the pathname to the program which
2328 is used to automatically discover and login into new
2329 osd-targets. Please see:
2330 Documentation/filesystems/pnfs.txt for more explanations
2332 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2333 when a NMI is triggered.
2334 Format: [state][,regs][,debounce][,die]
2336 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2337 Format: [panic,][nopanic,][num]
2339 0 - turn nmi_watchdog off
2340 1 - turn nmi_watchdog on
2341 When panic is specified, panic when an NMI watchdog
2342 timeout occurs (or 'nopanic' to override the opposite
2344 This is useful when you use a panic=... timeout and
2345 need the box quickly up again.
2347 netpoll.carrier_timeout=
2348 [NET] Specifies amount of time (in seconds) that
2349 netpoll should wait for a carrier. By default netpoll
2352 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2353 emulation library even if a 387 maths coprocessor
2357 [HW] Never suspend the console
2358 Disable suspending of consoles during suspend and
2359 hibernate operations. Once disabled, debugging
2360 messages can reach various consoles while the rest
2361 of the system is being put to sleep (ie, while
2362 debugging driver suspend/resume hooks). This may
2363 not work reliably with all consoles, but is known
2364 to work with serial and VGA consoles.
2365 To facilitate more flexible debugging, we also add
2366 console_suspend, a printk module parameter to control
2367 it. Users could use console_suspend (usually
2368 /sys/module/printk/parameters/console_suspend) to
2369 turn on/off it dynamically.
2371 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2372 caches in the slab allocator. Saves per-node memory,
2373 but will impact performance.
2377 noapic [SMP,APIC] Tells the kernel to not make use of any
2378 IOAPICs that may be present in the system.
2380 noautogroup Disable scheduler automatic task group creation.
2382 nobats [PPC] Do not use BATs for mapping kernel lowmem
2383 on "Classic" PPC cores.
2387 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2389 nodelayacct [KNL] Disable per-task delay accounting
2391 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2393 nodsp [SH] Disable hardware DSP at boot time.
2395 noefi Disable EFI runtime services support.
2400 On X86-32 available only on PAE configured kernels.
2401 noexec=on: enable non-executable mappings (default)
2402 noexec=off: disable non-executable mappings
2405 Disable SMAP (Supervisor Mode Access Prevention)
2406 even if it is supported by processor.
2409 Disable SMEP (Supervisor Mode Execution Prevention)
2410 even if it is supported by processor.
2413 This affects only 32-bit executables.
2414 noexec32=on: enable non-executable mappings (default)
2415 read doesn't imply executable mappings
2416 noexec32=off: disable non-executable mappings
2417 read implies executable mappings
2419 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2421 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2422 register save and restore. The kernel will only save
2423 legacy floating-point registers on task switch.
2425 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2427 noxsave [BUGS=X86] Disables x86 extended register state save
2428 and restore using xsave. The kernel will fallback to
2429 enabling legacy floating-point and sse state.
2431 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2432 register states. The kernel will fall back to use
2433 xsave to save the states. By using this parameter,
2434 performance of saving the states is degraded because
2435 xsave doesn't support modified optimization while
2436 xsaveopt supports it on xsaveopt enabled systems.
2438 noxsaves [X86] Disables xsaves and xrstors used in saving and
2439 restoring x86 extended register state in compacted
2440 form of xsave area. The kernel will fall back to use
2441 xsaveopt and xrstor to save and restore the states
2442 in standard form of xsave area. By using this
2443 parameter, xsave area per process might occupy more
2444 memory on xsaves enabled systems.
2446 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2447 wfi(ARM) instruction doesn't work correctly and not to
2448 use it. This is also useful when using JTAG debugger.
2450 no_file_caps Tells the kernel not to honor file capabilities. The
2451 only way then for a file to be executed with privilege
2452 is to be setuid root or executed by root.
2454 nohalt [IA-64] Tells the kernel not to use the power saving
2455 function PAL_HALT_LIGHT when idle. This increases
2456 power-consumption. On the positive side, it reduces
2457 interrupt wake-up latency, which may improve performance
2458 in certain environments such as networked servers or
2461 nohibernate [HIBERNATION] Disable hibernation and resume.
2463 nohz= [KNL] Boottime enable/disable dynamic ticks
2464 Valid arguments: on, off
2467 nohz_full= [KNL,BOOT]
2468 In kernels built with CONFIG_NO_HZ_FULL=y, set
2469 the specified list of CPUs whose tick will be stopped
2470 whenever possible. The boot CPU will be forced outside
2471 the range to maintain the timekeeping.
2472 The CPUs in this range must also be included in the
2475 noiotrap [SH] Disables trapped I/O port accesses.
2477 noirqdebug [X86-32] Disables the code which attempts to detect and
2478 disable unhandled interrupt sources.
2480 no_timer_check [X86,APIC] Disables the code which tests for
2481 broken timer IRQ sources.
2483 noisapnp [ISAPNP] Disables ISA PnP code.
2485 noinitrd [RAM] Tells the kernel not to load any configured
2488 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2490 [Deprecated - use intremap=off]
2494 nojitter [IA-64] Disables jitter checking for ITC timers.
2496 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2498 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2501 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2502 steal time is computed, but won't influence scheduler
2505 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2507 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2509 noltlbs [PPC] Do not use large page/tlb entries for kernel
2510 lowmem mapping on PPC40x.
2512 nomca [IA-64] Disable machine check abort handling
2514 nomce [X86-32] Disable Machine Check Exception
2516 nomfgpt [X86-32] Disable Multi-Function General Purpose
2517 Timer usage (for AMD Geode machines).
2519 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2520 shutdown the other cpus. Instead use the REBOOT_VECTOR
2523 nomodule Disable module load
2525 nopat [X86] Disable PAT (page attribute table extension of
2526 pagetables) support.
2528 norandmaps Don't use address space randomization. Equivalent to
2529 echo 0 > /proc/sys/kernel/randomize_va_space
2531 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2533 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2534 with UP alternatives
2536 nordrand [X86] Disable kernel use of the RDRAND and
2537 RDSEED instructions even if they are supported
2538 by the processor. RDRAND and RDSEED are still
2539 available to user space applications.
2541 noresume [SWSUSP] Disables resume and restores original swap
2544 no-scroll [VGA] Disables scrollback.
2545 This is required for the Braillex ib80-piezo Braille
2546 reader made by F.H. Papenmeier (Germany).
2550 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2552 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2553 and disable the IO APIC. legacy for "maxcpus=0".
2555 nosoftlockup [KNL] Disable the soft-lockup detector.
2557 nosync [HW,M68K] Disables sync negotiation for all devices.
2559 notsc [BUGS=X86-32] Disable Time Stamp Counter
2561 nousb [USB] Disable the USB subsystem
2563 nowatchdog [KNL] Disable both lockup detectors, i.e.
2564 soft-lockup and NMI watchdog (hard-lockup).
2568 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2570 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2571 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2572 Some features depend on CPU0. Known dependencies are:
2573 1. Resume from suspend/hibernate depends on CPU0.
2574 Suspend/hibernate will fail if CPU0 is offline and you
2575 need to online CPU0 before suspend/hibernate.
2576 2. PIC interrupts also depend on CPU0. CPU0 can't be
2577 removed if a PIC interrupt is detected.
2578 It's said poweroff/reboot may depend on CPU0 on some
2579 machines although I haven't seen such issues so far
2580 after CPU0 is offline on a few tested machines.
2581 If the dependencies are under your control, you can
2582 turn on cpu0_hotplug.
2584 nptcg= [IA-64] Override max number of concurrent global TLB
2585 purges which is reported from either PAL_VM_SUMMARY or
2588 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2589 could support. nr_cpus=n : n >= 1 limits the kernel to
2590 supporting 'n' processors. Later in runtime you can not
2591 use hotplug cpu feature to put more cpu back to online.
2592 just like you compile the kernel NR_CPUS=n
2594 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2596 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2597 Allowed values are enable and disable
2599 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2600 one of ['zone', 'node', 'default'] can be specified
2601 This can be set from sysctl after boot.
2602 See Documentation/sysctl/vm.txt for details.
2604 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2605 See Documentation/debugging-via-ohci1394.txt for more
2608 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2609 Rather than timing out after 20 ms if an EC
2610 command is not properly ACKed, override the length
2611 of the timeout. We have interrupts disabled while
2612 waiting for the ACK, so if this is set too high
2613 interrupts *may* be lost!
2615 omap_mux= [OMAP] Override bootloader pin multiplexing.
2616 Format: <mux_mode0.mode_name=value>...
2617 For example, to override I2C bus2:
2618 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2620 oprofile.timer= [HW]
2621 Use timer interrupt instead of performance counters
2623 oprofile.cpu_type= Force an oprofile cpu type
2624 This might be useful if you have an older oprofile
2625 userland or if you want common events.
2626 Format: { arch_perfmon }
2627 arch_perfmon: [X86] Force use of architectural
2628 perfmon on Intel CPUs instead of the
2629 CPU specific event set.
2630 timer: [X86] Force use of architectural NMI
2631 timer mode (see also oprofile.timer
2632 for generic hr timer mode)
2633 [s390] Force legacy basic mode sampling
2634 (report cpu_type "timer")
2636 oops=panic Always panic on oopses. Default is to just kill the
2637 process, but there is a small probability of
2638 deadlocking the machine.
2639 This will also cause panics on machine check exceptions.
2640 Useful together with panic=30 to trigger a reboot.
2643 See Documentation/sound/oss/oss-parameters.txt
2645 page_owner= [KNL] Boot-time page_owner enabling option.
2646 Storage of the information about who allocated
2647 each page is disabled in default. With this switch,
2649 on: enable the feature
2651 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2652 timeout > 0: seconds before rebooting
2653 timeout = 0: wait forever
2654 timeout < 0: reboot immediately
2657 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2660 crash_kexec_post_notifiers
2661 Run kdump after running panic-notifiers and dumping
2662 kmsg. This only for the users who doubt kdump always
2663 succeeds in any situation.
2664 Note that this also increases risks of kdump failure,
2665 because some panic notifiers can make the crashed
2666 kernel more unstable.
2668 parkbd.port= [HW] Parallel port number the keyboard adapter is
2669 connected to, default is 0.
2671 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2672 0 for XT, 1 for AT (default is AT).
2675 parport= [HW,PPT] Specify parallel ports. 0 disables.
2676 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2677 Use 'auto' to force the driver to use any
2678 IRQ/DMA settings detected (the default is to
2679 ignore detected IRQ/DMA settings because of
2680 possible conflicts). You can specify the base
2681 address, IRQ, and DMA settings; IRQ and DMA
2682 should be numbers, or 'auto' (for using detected
2683 settings on that particular port), or 'nofifo'
2684 (to avoid using a FIFO even if it is detected).
2685 Parallel ports are assigned in the order they
2686 are specified on the command line, starting
2689 parport_init_mode= [HW,PPT]
2690 Configure VIA parallel port to operate in
2691 a specific mode. This is necessary on Pegasos
2692 computer where firmware has no options for setting
2693 up parallel port mode and sets it to spp.
2694 Currently this function knows 686a and 8231 chips.
2695 Format: [spp|ps2|epp|ecp|ecpepp]
2698 Halt all CPUs after the first oops has been printed for
2699 the specified number of seconds. This is to be used if
2700 your oopses keep scrolling off the screen.
2705 See header of drivers/block/paride/pcd.c.
2706 See also Documentation/blockdev/paride.txt.
2708 pci=option[,option...] [PCI] various PCI subsystem options:
2709 earlydump [X86] dump PCI config space before the kernel
2711 off [X86] don't probe for the PCI bus
2712 bios [X86-32] force use of PCI BIOS, don't access
2713 the hardware directly. Use this if your machine
2714 has a non-standard PCI host bridge.
2715 nobios [X86-32] disallow use of PCI BIOS, only direct
2716 hardware access methods are allowed. Use this
2717 if you experience crashes upon bootup and you
2718 suspect they are caused by the BIOS.
2719 conf1 [X86] Force use of PCI Configuration
2721 conf2 [X86] Force use of PCI Configuration
2723 noaer [PCIE] If the PCIEAER kernel config parameter is
2724 enabled, this kernel boot option can be used to
2725 disable the use of PCIE advanced error reporting.
2726 nodomains [PCI] Disable support for multiple PCI
2727 root domains (aka PCI segments, in ACPI-speak).
2728 nommconf [X86] Disable use of MMCONFIG for PCI
2730 check_enable_amd_mmconf [X86] check for and enable
2731 properly configured MMIO access to PCI
2732 config space on AMD family 10h CPU
2733 nomsi [MSI] If the PCI_MSI kernel config parameter is
2734 enabled, this kernel boot option can be used to
2735 disable the use of MSI interrupts system-wide.
2736 noioapicquirk [APIC] Disable all boot interrupt quirks.
2737 Safety option to keep boot IRQs enabled. This
2738 should never be necessary.
2739 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2740 primary IO-APIC for bridges that cannot disable
2741 boot IRQs. This fixes a source of spurious IRQs
2742 when the system masks IRQs.
2743 noioapicreroute [APIC] Disable workaround that uses the
2744 boot IRQ equivalent of an IRQ that connects to
2745 a chipset where boot IRQs cannot be disabled.
2746 The opposite of ioapicreroute.
2747 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2748 routing table. These calls are known to be buggy
2749 on several machines and they hang the machine
2750 when used, but on other computers it's the only
2751 way to get the interrupt routing table. Try
2752 this option if the kernel is unable to allocate
2753 IRQs or discover secondary PCI buses on your
2755 rom [X86] Assign address space to expansion ROMs.
2756 Use with caution as certain devices share
2757 address decoders between ROMs and other
2759 norom [X86] Do not assign address space to
2760 expansion ROMs that do not already have
2761 BIOS assigned address ranges.
2762 nobar [X86] Do not assign address space to the
2763 BARs that weren't assigned by the BIOS.
2764 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2765 assigned automatically to PCI devices. You can
2766 make the kernel exclude IRQs of your ISA cards
2768 pirqaddr=0xAAAAA [X86] Specify the physical address
2769 of the PIRQ table (normally generated
2770 by the BIOS) if it is outside the
2771 F0000h-100000h range.
2772 lastbus=N [X86] Scan all buses thru bus #N. Can be
2773 useful if the kernel is unable to find your
2774 secondary buses and you want to tell it
2775 explicitly which ones they are.
2776 assign-busses [X86] Always assign all PCI bus
2777 numbers ourselves, overriding
2778 whatever the firmware may have done.
2779 usepirqmask [X86] Honor the possible IRQ mask stored
2780 in the BIOS $PIR table. This is needed on
2781 some systems with broken BIOSes, notably
2782 some HP Pavilion N5400 and Omnibook XE3
2783 notebooks. This will have no effect if ACPI
2784 IRQ routing is enabled.
2785 noacpi [X86] Do not use ACPI for IRQ routing
2786 or for PCI scanning.
2787 use_crs [X86] Use PCI host bridge window information
2788 from ACPI. On BIOSes from 2008 or later, this
2789 is enabled by default. If you need to use this,
2790 please report a bug.
2791 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2792 If you need to use this, please report a bug.
2793 routeirq Do IRQ routing for all PCI devices.
2794 This is normally done in pci_enable_device(),
2795 so this option is a temporary workaround
2796 for broken drivers that don't call it.
2797 skip_isa_align [X86] do not align io start addr, so can
2798 handle more pci cards
2799 firmware [ARM] Do not re-enumerate the bus but instead
2800 just use the configuration from the
2801 bootloader. This is currently used on
2802 IXP2000 systems where the bus has to be
2803 configured a certain way for adjunct CPUs.
2804 noearly [X86] Don't do any early type 1 scanning.
2805 This might help on some broken boards which
2806 machine check when some devices' config space
2807 is read. But various workarounds are disabled
2808 and some IOMMU drivers will not work.
2809 bfsort Sort PCI devices into breadth-first order.
2810 This sorting is done to get a device
2811 order compatible with older (<= 2.4) kernels.
2812 nobfsort Don't sort PCI devices into breadth-first order.
2813 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2814 tuning and use the BIOS-configured MPS defaults.
2815 pcie_bus_safe Set every device's MPS to the largest value
2816 supported by all devices below the root complex.
2817 pcie_bus_perf Set device MPS to the largest allowable MPS
2818 based on its parent bus. Also set MRRS (Max
2819 Read Request Size) to the largest supported
2820 value (no larger than the MPS that the device
2821 or bus can support) for best performance.
2822 pcie_bus_peer2peer Set every device's MPS to 128B, which
2823 every device is guaranteed to support. This
2824 configuration allows peer-to-peer DMA between
2825 any pair of devices, possibly at the cost of
2826 reduced performance. This also guarantees
2827 that hot-added devices will work.
2828 cbiosize=nn[KMG] The fixed amount of bus space which is
2829 reserved for the CardBus bridge's IO window.
2830 The default value is 256 bytes.
2831 cbmemsize=nn[KMG] The fixed amount of bus space which is
2832 reserved for the CardBus bridge's memory
2833 window. The default value is 64 megabytes.
2836 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2837 Specifies alignment and device to reassign
2838 aligned memory resources.
2839 If <order of align> is not specified,
2840 PAGE_SIZE is used as alignment.
2841 PCI-PCI bridge can be specified, if resource
2842 windows need to be expanded.
2843 ecrc= Enable/disable PCIe ECRC (transaction layer
2844 end-to-end CRC checking).
2845 bios: Use BIOS/firmware settings. This is the
2849 hpiosize=nn[KMG] The fixed amount of bus space which is
2850 reserved for hotplug bridge's IO window.
2851 Default size is 256 bytes.
2852 hpmemsize=nn[KMG] The fixed amount of bus space which is
2853 reserved for hotplug bridge's memory window.
2854 Default size is 2 megabytes.
2855 realloc= Enable/disable reallocating PCI bridge resources
2856 if allocations done by BIOS are too small to
2857 accommodate resources required by all child
2859 off: Turn realloc off
2861 realloc same as realloc=on
2862 noari do not use PCIe ARI.
2863 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2864 only look for one device below a PCIe downstream
2867 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2870 force Enable ASPM even on devices that claim not to support it.
2871 WARNING: Forcing ASPM on may cause system lockups.
2873 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2874 nomsi Do not use MSI for PCI Express Native Hotplug (this
2875 makes all PCIe ports use INTx for hotplug services).
2877 pcie_ports= [PCIE] PCIe ports handling:
2878 auto Ask the BIOS whether or not to use native PCIe services
2879 associated with PCIe ports (PME, hot-plug, AER). Use
2880 them only if that is allowed by the BIOS.
2881 native Use native PCIe services associated with PCIe ports
2883 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2886 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2887 nomsi Do not use MSI for native PCIe PME signaling (this makes
2888 all PCIe root ports use INTx for all services).
2890 pcmv= [HW,PCMCIA] BadgePAD 4
2894 Keep all power-domains already enabled by bootloader on,
2895 even if no driver has claimed them. This is useful
2896 for debug and development, but should not be
2897 needed on a platform with proper driver support.
2900 See Documentation/blockdev/paride.txt.
2902 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2905 See arch/parisc/kernel/pdc_chassis.c
2907 percpu_alloc= Select which percpu first chunk allocator to use.
2908 Currently supported values are "embed" and "page".
2909 Archs may support subset or none of the selections.
2910 See comments in mm/percpu.c for details on each
2911 allocator. This parameter is primarily for debugging
2912 and performance comparison.
2915 See Documentation/blockdev/paride.txt.
2918 See Documentation/blockdev/paride.txt.
2920 pirq= [SMP,APIC] Manual mp-table setup
2921 See Documentation/x86/i386/IO-APIC.txt.
2923 plip= [PPT,NET] Parallel port network link
2924 Format: { parport<nr> | timid | 0 }
2925 See also Documentation/parport.txt.
2927 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2928 Override pmtimer IOPort with a hex value.
2932 Enable PNP debug messages (depends on the
2933 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2934 via /sys/module/pnp/parameters/debug. We always show
2935 current resource usage; turning this on also shows
2936 possible settings and some assignment information.
2942 { on | off | curr | res | no-curr | no-res }
2945 [ISAPNP] Exclude IRQs for the autoconfiguration
2948 [ISAPNP] Exclude DMAs for the autoconfiguration
2950 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2951 Ranges are in pairs (I/O port base and size).
2954 [ISAPNP] Exclude memory regions for the
2956 Ranges are in pairs (memory base and size).
2958 ports= [IP_VS_FTP] IPVS ftp helper module
2960 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2962 Format: <port>,<port>....
2964 print-fatal-signals=
2965 [KNL] debug: print fatal signals
2967 If enabled, warn about various signal handling
2968 related application anomalies: too many signals,
2969 too many POSIX.1 timers, fatal signals causing a
2972 If you hit the warning due to signal overflow,
2973 you might want to try "ulimit -i unlimited".
2977 printk.always_kmsg_dump=
2978 Trigger kmsg_dump for cases other than kernel oops or
2980 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2983 printk.time= Show timing data prefixed to each printk message line
2984 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2986 processor.max_cstate= [HW,ACPI]
2987 Limit processor to maximum C-state
2988 max_cstate=9 overrides any DMI blacklist limit.
2990 processor.nocst [HW,ACPI]
2991 Ignore the _CST method to determine C-states,
2992 instead using the legacy FADT method
2994 profile= [KNL] Enable kernel profiling via /proc/profile
2995 Format: [schedule,]<number>
2996 Param: "schedule" - profile schedule points.
2997 Param: <number> - step/bucket size as a power of 2 for
2998 statistical time based profiling.
2999 Param: "sleep" - profile D-state sleeping (millisecs).
3000 Requires CONFIG_SCHEDSTATS
3001 Param: "kvm" - profile VM exits.
3003 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3005 See Documentation/blockdev/ramdisk.txt.
3007 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3008 probe for; one of (bare|imps|exps|lifebook|any).
3009 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3011 psmouse.resetafter= [HW,MOUSE]
3012 Try to reset the device after so many bad packets
3015 [HW,MOUSE] Set desired mouse resolution, in dpi.
3016 psmouse.smartscroll=
3017 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3018 0 = disabled, 1 = enabled (default).
3020 pstore.backend= Specify the name of the pstore backend to use
3023 See Documentation/blockdev/paride.txt.
3026 [KNL] Number of legacy pty's. Overwrites compiled-in
3029 quiet [KNL] Disable most log messages
3034 See Documentation/md.txt.
3036 ramdisk_blocksize= [RAM]
3037 See Documentation/blockdev/ramdisk.txt.
3039 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3040 See Documentation/blockdev/ramdisk.txt.
3043 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3044 the specified list of CPUs to be no-callback CPUs.
3045 Invocation of these CPUs' RCU callbacks will
3046 be offloaded to "rcuox/N" kthreads created for
3047 that purpose, where "x" is "b" for RCU-bh, "p"
3048 for RCU-preempt, and "s" for RCU-sched, and "N"
3049 is the CPU number. This reduces OS jitter on the
3050 offloaded CPUs, which can be useful for HPC and
3051 real-time workloads. It can also improve energy
3052 efficiency for asymmetric multiprocessors.
3055 Rather than requiring that offloaded CPUs
3056 (specified by rcu_nocbs= above) explicitly
3057 awaken the corresponding "rcuoN" kthreads,
3058 make these kthreads poll for callbacks.
3059 This improves the real-time response for the
3060 offloaded CPUs by relieving them of the need to
3061 wake up the corresponding kthread, but degrades
3062 energy efficiency by requiring that the kthreads
3063 periodically wake up to do the polling.
3065 rcutree.blimit= [KNL]
3066 Set maximum number of finished RCU callbacks to
3067 process in one batch.
3069 rcutree.dump_tree= [KNL]
3070 Dump the structure of the rcu_node combining tree
3071 out at early boot. This is used for diagnostic
3072 purposes, to verify correct tree setup.
3074 rcutree.gp_cleanup_delay= [KNL]
3075 Set the number of jiffies to delay each step of
3076 RCU grace-period cleanup. This only has effect
3077 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3079 rcutree.gp_init_delay= [KNL]
3080 Set the number of jiffies to delay each step of
3081 RCU grace-period initialization. This only has
3082 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3085 rcutree.gp_preinit_delay= [KNL]
3086 Set the number of jiffies to delay each step of
3087 RCU grace-period pre-initialization, that is,
3088 the propagation of recent CPU-hotplug changes up
3089 the rcu_node combining tree. This only has effect
3090 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3092 rcutree.rcu_fanout_exact= [KNL]
3093 Disable autobalancing of the rcu_node combining
3094 tree. This is used by rcutorture, and might
3095 possibly be useful for architectures having high
3096 cache-to-cache transfer latencies.
3098 rcutree.rcu_fanout_leaf= [KNL]
3099 Change the number of CPUs assigned to each
3100 leaf rcu_node structure. Useful for very
3101 large systems, which will choose the value 64,
3102 and for NUMA systems with large remote-access
3103 latencies, which will choose a value aligned
3104 with the appropriate hardware boundaries.
3106 rcutree.jiffies_till_sched_qs= [KNL]
3107 Set required age in jiffies for a
3108 given grace period before RCU starts
3109 soliciting quiescent-state help from
3110 rcu_note_context_switch().
3112 rcutree.jiffies_till_first_fqs= [KNL]
3113 Set delay from grace-period initialization to
3114 first attempt to force quiescent states.
3115 Units are jiffies, minimum value is zero,
3116 and maximum value is HZ.
3118 rcutree.jiffies_till_next_fqs= [KNL]
3119 Set delay between subsequent attempts to force
3120 quiescent states. Units are jiffies, minimum
3121 value is one, and maximum value is HZ.
3123 rcutree.kthread_prio= [KNL,BOOT]
3124 Set the SCHED_FIFO priority of the RCU per-CPU
3125 kthreads (rcuc/N). This value is also used for
3126 the priority of the RCU boost threads (rcub/N)
3127 and for the RCU grace-period kthreads (rcu_bh,
3128 rcu_preempt, and rcu_sched). If RCU_BOOST is
3129 set, valid values are 1-99 and the default is 1
3130 (the least-favored priority). Otherwise, when
3131 RCU_BOOST is not set, valid values are 0-99 and
3132 the default is zero (non-realtime operation).
3134 rcutree.rcu_nocb_leader_stride= [KNL]
3135 Set the number of NOCB kthread groups, which
3136 defaults to the square root of the number of
3137 CPUs. Larger numbers reduces the wakeup overhead
3138 on the per-CPU grace-period kthreads, but increases
3139 that same overhead on each group's leader.
3141 rcutree.qhimark= [KNL]
3142 Set threshold of queued RCU callbacks beyond which
3143 batch limiting is disabled.
3145 rcutree.qlowmark= [KNL]
3146 Set threshold of queued RCU callbacks below which
3147 batch limiting is re-enabled.
3149 rcutree.rcu_idle_gp_delay= [KNL]
3150 Set wakeup interval for idle CPUs that have
3151 RCU callbacks (RCU_FAST_NO_HZ=y).
3153 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3154 Set wakeup interval for idle CPUs that have
3155 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3156 Lazy RCU callbacks are those which RCU can
3157 prove do nothing more than free memory.
3159 rcutorture.cbflood_inter_holdoff= [KNL]
3160 Set holdoff time (jiffies) between successive
3161 callback-flood tests.
3163 rcutorture.cbflood_intra_holdoff= [KNL]
3164 Set holdoff time (jiffies) between successive
3165 bursts of callbacks within a given callback-flood
3168 rcutorture.cbflood_n_burst= [KNL]
3169 Set the number of bursts making up a given
3170 callback-flood test. Set this to zero to
3171 disable callback-flood testing.
3173 rcutorture.cbflood_n_per_burst= [KNL]
3174 Set the number of callbacks to be registered
3175 in a given burst of a callback-flood test.
3177 rcutorture.fqs_duration= [KNL]
3178 Set duration of force_quiescent_state bursts
3181 rcutorture.fqs_holdoff= [KNL]
3182 Set holdoff time within force_quiescent_state bursts
3185 rcutorture.fqs_stutter= [KNL]
3186 Set wait time between force_quiescent_state bursts
3189 rcutorture.gp_cond= [KNL]
3190 Use conditional/asynchronous update-side
3191 primitives, if available.
3193 rcutorture.gp_exp= [KNL]
3194 Use expedited update-side primitives, if available.
3196 rcutorture.gp_normal= [KNL]
3197 Use normal (non-expedited) asynchronous
3198 update-side primitives, if available.
3200 rcutorture.gp_sync= [KNL]
3201 Use normal (non-expedited) synchronous
3202 update-side primitives, if available. If all
3203 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3204 rcutorture.gp_normal=, and rcutorture.gp_sync=
3205 are zero, rcutorture acts as if is interpreted
3206 they are all non-zero.
3208 rcutorture.n_barrier_cbs= [KNL]
3209 Set callbacks/threads for rcu_barrier() testing.
3211 rcutorture.nfakewriters= [KNL]
3212 Set number of concurrent RCU writers. These just
3213 stress RCU, they don't participate in the actual
3214 test, hence the "fake".
3216 rcutorture.nreaders= [KNL]
3217 Set number of RCU readers. The value -1 selects
3218 N-1, where N is the number of CPUs. A value
3219 "n" less than -1 selects N-n-2, where N is again
3220 the number of CPUs. For example, -2 selects N
3221 (the number of CPUs), -3 selects N+1, and so on.
3223 rcutorture.object_debug= [KNL]
3224 Enable debug-object double-call_rcu() testing.
3226 rcutorture.onoff_holdoff= [KNL]
3227 Set time (s) after boot for CPU-hotplug testing.
3229 rcutorture.onoff_interval= [KNL]
3230 Set time (s) between CPU-hotplug operations, or
3231 zero to disable CPU-hotplug testing.
3233 rcutorture.shuffle_interval= [KNL]
3234 Set task-shuffle interval (s). Shuffling tasks
3235 allows some CPUs to go into dyntick-idle mode
3236 during the rcutorture test.
3238 rcutorture.shutdown_secs= [KNL]
3239 Set time (s) after boot system shutdown. This
3240 is useful for hands-off automated testing.
3242 rcutorture.stall_cpu= [KNL]
3243 Duration of CPU stall (s) to test RCU CPU stall
3244 warnings, zero to disable.
3246 rcutorture.stall_cpu_holdoff= [KNL]
3247 Time to wait (s) after boot before inducing stall.
3249 rcutorture.stat_interval= [KNL]
3250 Time (s) between statistics printk()s.
3252 rcutorture.stutter= [KNL]
3253 Time (s) to stutter testing, for example, specifying
3254 five seconds causes the test to run for five seconds,
3255 wait for five seconds, and so on. This tests RCU's
3256 ability to transition abruptly to and from idle.
3258 rcutorture.test_boost= [KNL]
3259 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3260 "Maybe" means test if the RCU implementation
3261 under test support RCU priority boosting.
3263 rcutorture.test_boost_duration= [KNL]
3264 Duration (s) of each individual boost test.
3266 rcutorture.test_boost_interval= [KNL]
3267 Interval (s) between each boost test.
3269 rcutorture.test_no_idle_hz= [KNL]
3270 Test RCU's dyntick-idle handling. See also the
3271 rcutorture.shuffle_interval parameter.
3273 rcutorture.torture_runnable= [BOOT]
3274 Start rcutorture running at boot time.
3276 rcutorture.torture_type= [KNL]
3277 Specify the RCU implementation to test.
3279 rcutorture.verbose= [KNL]
3280 Enable additional printk() statements.
3282 rcupdate.rcu_expedited= [KNL]
3283 Use expedited grace-period primitives, for
3284 example, synchronize_rcu_expedited() instead
3285 of synchronize_rcu(). This reduces latency,
3286 but can increase CPU utilization, degrade
3287 real-time latency, and degrade energy efficiency.
3289 rcupdate.rcu_cpu_stall_suppress= [KNL]
3290 Suppress RCU CPU stall warning messages.
3292 rcupdate.rcu_cpu_stall_timeout= [KNL]
3293 Set timeout for RCU CPU stall warning messages.
3295 rcupdate.rcu_task_stall_timeout= [KNL]
3296 Set timeout in jiffies for RCU task stall warning
3297 messages. Disable with a value less than or equal
3300 rcupdate.rcu_self_test= [KNL]
3301 Run the RCU early boot self tests
3303 rcupdate.rcu_self_test_bh= [KNL]
3304 Run the RCU bh early boot self tests
3306 rcupdate.rcu_self_test_sched= [KNL]
3307 Run the RCU sched early boot self tests
3311 Run specified binary instead of /init from the ramdisk,
3312 used for early userspace startup. See initrd.
3315 Format (x86 or x86_64):
3316 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3318 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3320 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3321 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3322 reboot_force is either force or not specified,
3323 reboot_cpu is s[mp]#### with #### being the processor
3324 to be used for rebooting.
3327 [KNL, SMP] Set scheduler's default relax_domain_level.
3328 See Documentation/cgroups/cpusets.txt.
3330 relative_sleep_states=
3331 [SUSPEND] Use sleep state labeling where the deepest
3332 state available other than hibernation is always "mem".
3333 Format: { "0" | "1" }
3334 0 -- Traditional sleep state labels.
3335 1 -- Relative sleep state labels.
3337 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3339 reservetop= [X86-32]
3341 Reserves a hole at the top of the kernel virtual
3346 Set the amount of memory to reserve for BIOS at
3347 the bottom of the address space.
3349 reset_devices [KNL] Force drivers to reset the underlying device
3350 during initialization.
3353 Specify the partition device for software suspend
3355 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3357 resume_offset= [SWSUSP]
3358 Specify the offset from the beginning of the partition
3359 given by "resume=" at which the swap header is located,
3360 in <PAGE_SIZE> units (needed only for swap files).
3361 See Documentation/power/swsusp-and-swap-files.txt
3363 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3364 read the resume files
3366 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3367 Useful for devices that are detected asynchronously
3368 (e.g. USB and MMC devices).
3370 hibernate= [HIBERNATION]
3371 noresume Don't check if there's a hibernation image
3372 present during boot.
3373 nocompress Don't compress/decompress hibernation images.
3374 no Disable hibernation and resume.
3376 retain_initrd [RAM] Keep initrd memory after extraction
3378 rfkill.default_state=
3379 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3380 etc. communication is blocked by default.
3383 rfkill.master_switch_mode=
3384 0 The "airplane mode" button does nothing.
3385 1 The "airplane mode" button toggles between everything
3386 blocked and the previous configuration.
3387 2 The "airplane mode" button toggles between everything
3388 blocked and everything unblocked.
3390 rhash_entries= [KNL,NET]
3391 Set number of hash buckets for route cache
3393 ro [KNL] Mount root device read-only on boot
3395 root= [KNL] Root filesystem
3396 See name_to_dev_t comment in init/do_mounts.c.
3398 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3399 mount the root filesystem
3401 rootflags= [KNL] Set root filesystem mount option string
3403 rootfstype= [KNL] Set root filesystem type
3405 rootwait [KNL] Wait (indefinitely) for root device to show up.
3406 Useful for devices that are detected asynchronously
3407 (e.g. USB and MMC devices).
3409 rproc_mem=nn[KMG][@address]
3410 [KNL,ARM,CMA] Remoteproc physical memory block.
3411 Memory area to be used by remote processor image,
3414 rw [KNL] Mount root device read-write on boot
3416 S [KNL] Run init in single mode
3418 s390_iommu= [HW,S390]
3419 Set s390 IOTLB flushing mode
3421 With strict flushing every unmap operation will result in
3422 an IOTLB flush. Default is lazy flushing before reuse,
3426 See drivers/net/irda/sa1100_ir.c.
3428 sbni= [NET] Granch SBNI12 leased line adapter
3430 sched_debug [KNL] Enables verbose scheduler debug messages.
3432 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3433 xtime_lock contention on larger systems, and/or RCU lock
3434 contention on all systems with CONFIG_MAXSMP set.
3435 Format: { "0" | "1" }
3436 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3438 Note: increases power consumption, thus should only be
3439 enabled if running jitter sensitive (HPC/RT) workloads.
3441 security= [SECURITY] Choose a security module to enable at boot.
3442 If this boot parameter is not specified, only the first
3443 security module asking for security registration will be
3444 loaded. An invalid security module name will be treated
3445 as if no module has been chosen.
3447 selinux= [SELINUX] Disable or enable SELinux at boot time.
3448 Format: { "0" | "1" }
3449 See security/selinux/Kconfig help text.
3452 Default value is set via kernel config option.
3453 If enabled at boot time, /selinux/disable can be used
3454 later to disable prior to initial policy load.
3456 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3457 Format: { "0" | "1" }
3458 See security/apparmor/Kconfig help text
3461 Default value is set via kernel config option.
3463 serialnumber [BUGS=X86-32]
3466 Maximal number of shapers.
3468 show_msr= [x86] show boot-time MSR settings
3469 Format: { <integer> }
3470 Show boot-time (BIOS-initialized) MSR settings.
3471 The parameter means the number of CPUs to show,
3472 for example 1 means boot CPU only.
3480 Disable merging of slabs with similar size. May be
3481 necessary if there is some reason to distinguish
3482 allocs to different slabs. Debug options disable
3483 merging on their own.
3484 For more information see Documentation/vm/slub.txt.
3486 slab_max_order= [MM, SLAB]
3487 Determines the maximum allowed order for slabs.
3488 A high setting may cause OOMs due to memory
3489 fragmentation. Defaults to 1 for systems with
3490 more than 32MB of RAM, 0 otherwise.
3492 slub_debug[=options[,slabs]] [MM, SLUB]
3493 Enabling slub_debug allows one to determine the
3494 culprit if slab objects become corrupted. Enabling
3495 slub_debug can create guard zones around objects and
3496 may poison objects when not in use. Also tracks the
3497 last alloc / free. For more information see
3498 Documentation/vm/slub.txt.
3500 slub_max_order= [MM, SLUB]
3501 Determines the maximum allowed order for slabs.
3502 A high setting may cause OOMs due to memory
3503 fragmentation. For more information see
3504 Documentation/vm/slub.txt.
3506 slub_min_objects= [MM, SLUB]
3507 The minimum number of objects per slab. SLUB will
3508 increase the slab order up to slub_max_order to
3509 generate a sufficiently large slab able to contain
3510 the number of objects indicated. The higher the number
3511 of objects the smaller the overhead of tracking slabs
3512 and the less frequently locks need to be acquired.
3513 For more information see Documentation/vm/slub.txt.
3515 slub_min_order= [MM, SLUB]
3516 Determines the minimum page order for slabs. Must be
3517 lower than slub_max_order.
3518 For more information see Documentation/vm/slub.txt.
3520 slub_nomerge [MM, SLUB]
3521 Same with slab_nomerge. This is supported for legacy.
3522 See slab_nomerge for more information.
3525 Format: <io1>[,<io2>[,...,<io8>]]
3527 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3528 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3529 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3530 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3531 smsc-ircc2.ircc_irq= [HW] IRQ line
3532 smsc-ircc2.ircc_dma= [HW] DMA channel
3533 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3534 0: Toshiba Satellite 1800 (GP data pin select)
3535 1: Fast pin select (default)
3539 [KNL] Should the soft-lockup detector generate panics.
3542 softlockup_all_cpu_backtrace=
3543 [KNL] Should the soft-lockup detector generate
3544 backtraces on all cpus.
3547 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3548 See Documentation/laptops/sonypi.txt
3550 spia_io_base= [HW,MTD]
3556 Enabled the stack tracer on boot up.
3558 stacktrace_filter=[function-list]
3559 [FTRACE] Limit the functions that the stack tracer
3560 will trace at boot up. function-list is a comma separated
3561 list of functions. This list can be changed at run
3562 time by the stack_trace_filter file in the debugfs
3563 tracing directory. Note, this enables stack tracing
3564 and the stacktrace above is not needed.
3568 Set the STI (builtin display/keyboard on the HP-PARISC
3569 machines) console (graphic card) which should be used
3570 as the initial boot-console.
3571 See also comment in drivers/video/console/sticore.c.
3574 See comment in drivers/video/console/sticore.c.
3577 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3579 sunrpc.min_resvport=
3580 sunrpc.max_resvport=
3582 SunRPC servers often require that client requests
3583 originate from a privileged port (i.e. a port in the
3584 range 0 < portnr < 1024).
3585 An administrator who wishes to reserve some of these
3586 ports for other uses may adjust the range that the
3587 kernel's sunrpc client considers to be privileged
3588 using these two parameters to set the minimum and
3589 maximum port values.
3593 Control how the NFS server code allocates CPUs to
3594 service thread pools. Depending on how many NICs
3595 you have and where their interrupts are bound, this
3596 option will affect which CPUs will do NFS serving.
3597 Note: this parameter cannot be changed while the
3598 NFS server is running.
3600 auto the server chooses an appropriate mode
3601 automatically using heuristics
3602 global a single global pool contains all CPUs
3603 percpu one pool for each CPU
3604 pernode one pool for each NUMA node (equivalent
3605 to global on non-NUMA machines)
3607 sunrpc.tcp_slot_table_entries=
3608 sunrpc.udp_slot_table_entries=
3610 Sets the upper limit on the number of simultaneous
3611 RPC calls that can be sent from the client to a
3612 server. Increasing these values may allow you to
3613 improve throughput, but will also increase the
3614 amount of memory reserved for use by the client.
3616 suspend.pm_test_delay=
3618 Sets the number of seconds to remain in a suspend test
3619 mode before resuming the system (see
3620 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3621 is set. Default value is 5.
3624 [KNL] Enable accounting of swap in memory resource
3625 controller if no parameter or 1 is given or disable
3626 it if 0 is given (See Documentation/cgroups/memory.txt)
3628 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3629 Format: { <int> | force }
3630 <int> -- Number of I/O TLB slabs
3631 force -- force using of bounce buffers even if they
3632 wouldn't be automatically used by the kernel
3636 sysfs.deprecated=0|1 [KNL]
3637 Enable/disable old style sysfs layout for old udev
3638 on older distributions. When this option is enabled
3639 very new udev will not work anymore. When this option
3640 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3641 in older udev will not work anymore.
3642 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3643 the kernel configuration.
3645 sysrq_always_enabled
3647 Ignore sysrq setting - this boot parameter will
3648 neutralize any effect of /proc/sys/kernel/sysrq.
3649 Useful for debugging.
3651 tcpmhash_entries= [KNL,NET]
3652 Set the number of tcp_metrics_hash slots.
3653 Default value is 8192 or 16384 depending on total
3654 ram pages. This is used to specify the TCP metrics
3655 cache size. See Documentation/networking/ip-sysctl.txt
3656 "tcp_no_metrics_save" section for more details.
3660 test_suspend= [SUSPEND][,N]
3661 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3662 standby suspend) or "freeze" (for suspend type freeze)
3663 as the system sleep state during system startup with
3664 the optional capability to repeat N number of times.
3665 The system is woken from this state using a
3666 wakeup-capable RTC alarm.
3668 thash_entries= [KNL,NET]
3669 Set number of hash buckets for TCP connection
3671 thermal.act= [HW,ACPI]
3672 -1: disable all active trip points in all thermal zones
3673 <degrees C>: override all lowest active trip points
3675 thermal.crt= [HW,ACPI]
3676 -1: disable all critical trip points in all thermal zones
3677 <degrees C>: override all critical trip points
3679 thermal.nocrt= [HW,ACPI]
3680 Set to disable actions on ACPI thermal zone
3681 critical and hot trip points.
3683 thermal.off= [HW,ACPI]
3684 1: disable ACPI thermal control
3686 thermal.psv= [HW,ACPI]
3687 -1: disable all passive trip points
3688 <degrees C>: override all passive trip points to this
3691 thermal.tzp= [HW,ACPI]
3692 Specify global default ACPI thermal zone polling rate
3693 <deci-seconds>: poll all this frequency
3694 0: no polling (default)
3697 Force threading of all interrupt handlers except those
3698 marked explicitly IRQF_NO_THREAD.
3701 Enable the Transcendent memory driver if built-in.
3703 tmem.cleancache=0|1 [KNL, XEN]
3704 Default is on (1). Disable the usage of the cleancache
3705 API to send anonymous pages to the hypervisor.
3707 tmem.frontswap=0|1 [KNL, XEN]
3708 Default is on (1). Disable the usage of the frontswap
3709 API to send swap pages to the hypervisor. If disabled
3710 the selfballooning and selfshrinking are force disabled.
3712 tmem.selfballooning=0|1 [KNL, XEN]
3713 Default is on (1). Disable the driving of swap pages
3716 tmem.selfshrinking=0|1 [KNL, XEN]
3717 Default is on (1). Partial swapoff that immediately
3718 transfers pages from Xen hypervisor back to the
3719 kernel based on different criteria.
3723 Specify if the kernel should make use of the cpu
3724 topology information if the hardware supports this.
3725 The scheduler will make use of this information and
3726 e.g. base its process migration decisions on it.
3729 topology_updates= [KNL, PPC, NUMA]
3731 Specify if the kernel should ignore (off)
3732 topology updates sent by the hypervisor to this
3737 tpm_suspend_pcr=[HW,TPM]
3738 Format: integer pcr id
3739 Specify that at suspend time, the tpm driver
3740 should extend the specified pcr with zeros,
3741 as a workaround for some chips which fail to
3742 flush the last written pcr on TPM_SaveState.
3743 This will guarantee that all the other pcrs
3746 trace_buf_size=nn[KMG]
3747 [FTRACE] will set tracing buffer size on each cpu.
3749 trace_event=[event-list]
3750 [FTRACE] Set and start specified trace events in order
3751 to facilitate early boot debugging.
3752 See also Documentation/trace/events.txt
3754 trace_options=[option-list]
3755 [FTRACE] Enable or disable tracer options at boot.
3756 The option-list is a comma delimited list of options
3757 that can be enabled or disabled just as if you were
3758 to echo the option name into
3760 /sys/kernel/debug/tracing/trace_options
3762 For example, to enable stacktrace option (to dump the
3763 stack trace of each event), add to the command line:
3765 trace_options=stacktrace
3767 See also Documentation/trace/ftrace.txt "trace options"
3771 Have the tracepoints sent to printk as well as the
3772 tracing ring buffer. This is useful for early boot up
3773 where the system hangs or reboots and does not give the
3774 option for reading the tracing buffer or performing a
3775 ftrace_dump_on_oops.
3777 To turn off having tracepoints sent to printk,
3778 echo 0 > /proc/sys/kernel/tracepoint_printk
3779 Note, echoing 1 into this file without the
3780 tracepoint_printk kernel cmdline option has no effect.
3784 Having tracepoints sent to printk() and activating high
3785 frequency tracepoints such as irq or sched, can cause
3786 the system to live lock.
3789 [FTRACE] enable this option to disable tracing when a
3790 warning is hit. This turns off "tracing_on". Tracing can
3791 be enabled again by echoing '1' into the "tracing_on"
3792 file located in /sys/kernel/debug/tracing/
3794 This option is useful, as it disables the trace before
3795 the WARNING dump is called, which prevents the trace to
3796 be filled with content caused by the warning output.
3798 This option can also be set at run time via the sysctl
3799 option: kernel/traceoff_on_warning
3801 transparent_hugepage=
3803 Format: [always|madvise|never]
3804 Can be used to control the default behavior of the system
3805 with respect to transparent hugepages.
3806 See Documentation/vm/transhuge.txt for more details.
3808 tsc= Disable clocksource stability checks for TSC.
3810 [x86] reliable: mark tsc clocksource as reliable, this
3811 disables clocksource verification at runtime, as well
3812 as the stability checks done at bootup. Used to enable
3813 high-resolution timer mode on older hardware, and in
3814 virtualized environment.
3815 [x86] noirqtime: Do not use TSC to do irq accounting.
3816 Used to run time disable IRQ_TIME_ACCOUNTING on any
3817 platforms where RDTSC is slow and this accounting
3820 turbografx.map[2|3]= [HW,JOY]
3821 TurboGraFX parallel port interface
3823 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3824 See also Documentation/input/joystick-parport.txt
3826 udbg-immortal [PPC] When debugging early kernel crashes that
3827 happen after console_init() and before a proper
3828 console driver takes over, this boot options might
3829 help "seeing" what's going on.
3831 uhash_entries= [KNL,NET]
3832 Set number of hash buckets for UDP/UDP-Lite connections
3835 [USB] Ignore overcurrent events (default N).
3836 Some badly-designed motherboards generate lots of
3837 bogus events, for ports that aren't wired to
3838 anything. Set this parameter to avoid log spamming.
3839 Note that genuine overcurrent events won't be
3843 [X86] Cause panic on unknown NMI.
3845 usbcore.authorized_default=
3846 [USB] Default USB device authorization:
3847 (default -1 = authorized except for wireless USB,
3848 0 = not authorized, 1 = authorized)
3850 usbcore.autosuspend=
3851 [USB] The autosuspend time delay (in seconds) used
3852 for newly-detected USB devices (default 2). This
3853 is the time required before an idle device will be
3854 autosuspended. Devices for which the delay is set
3855 to a negative value won't be autosuspended at all.
3857 usbcore.usbfs_snoop=
3858 [USB] Set to log all usbfs traffic (default 0 = off).
3860 usbcore.blinkenlights=
3861 [USB] Set to cycle leds on hubs (default 0 = off).
3863 usbcore.old_scheme_first=
3864 [USB] Start with the old device initialization
3865 scheme (default 0 = off).
3867 usbcore.usbfs_memory_mb=
3868 [USB] Memory limit (in MB) for buffers allocated by
3869 usbfs (default = 16, 0 = max = 2047).
3871 usbcore.use_both_schemes=
3872 [USB] Try the other device initialization scheme
3873 if the first one fails (default 1 = enabled).
3875 usbcore.initial_descriptor_timeout=
3876 [USB] Specifies timeout for the initial 64-byte
3877 USB_REQ_GET_DESCRIPTOR request in milliseconds
3878 (default 5000 = 5.0 seconds).
3881 [USBHID] The interval which mice are to be polled at.
3883 usb-storage.delay_use=
3884 [UMS] The delay in seconds before a new device is
3885 scanned for Logical Units (default 1).
3888 [UMS] A list of quirks entries to supplement or
3889 override the built-in unusual_devs list. List
3890 entries are separated by commas. Each entry has
3891 the form VID:PID:Flags where VID and PID are Vendor
3892 and Product ID values (4-digit hex numbers) and
3893 Flags is a set of characters, each corresponding
3894 to a common usb-storage quirk flag as follows:
3895 a = SANE_SENSE (collect more than 18 bytes
3897 b = BAD_SENSE (don't collect more than 18
3898 bytes of sense data);
3899 c = FIX_CAPACITY (decrease the reported
3900 device capacity by one sector);
3901 d = NO_READ_DISC_INFO (don't use
3902 READ_DISC_INFO command);
3903 e = NO_READ_CAPACITY_16 (don't use
3904 READ_CAPACITY_16 command);
3905 f = NO_REPORT_OPCODES (don't use report opcodes
3907 g = MAX_SECTORS_240 (don't transfer more than
3908 240 sectors at a time, uas only);
3909 h = CAPACITY_HEURISTICS (decrease the
3910 reported device capacity by one
3911 sector if the number is odd);
3912 i = IGNORE_DEVICE (don't bind to this
3914 l = NOT_LOCKABLE (don't try to lock and
3915 unlock ejectable media);
3916 m = MAX_SECTORS_64 (don't transfer more
3917 than 64 sectors = 32 KB at a time);
3918 n = INITIAL_READ10 (force a retry of the
3919 initial READ(10) command);
3920 o = CAPACITY_OK (accept the capacity
3921 reported by the device);
3922 p = WRITE_CACHE (the device cache is ON
3924 r = IGNORE_RESIDUE (the device reports
3925 bogus residue values);
3926 s = SINGLE_LUN (the device has only one
3928 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3929 commands, uas only);
3930 u = IGNORE_UAS (don't bind to the uas driver);
3931 w = NO_WP_DETECT (don't test whether the
3932 medium is write-protected).
3933 Example: quirks=0419:aaf5:rl,0421:0433:rc
3935 user_debug= [KNL,ARM]
3937 See arch/arm/Kconfig.debug help text.
3938 1 - undefined instruction events
3940 4 - invalid data aborts
3943 Example: user_debug=31
3946 [X86] Flags controlling user PTE allocations.
3948 nohigh = do not allocate PTE pages in
3949 HIGHMEM regardless of setting
3953 On X86_32, this is an alias for vdso32=. Otherwise:
3955 vdso=1: enable VDSO (the default)
3956 vdso=0: disable VDSO mapping
3958 vdso32= [X86] Control the 32-bit vDSO
3959 vdso32=1: enable 32-bit VDSO
3960 vdso32=0 or vdso32=2: disable 32-bit VDSO
3962 See the help text for CONFIG_COMPAT_VDSO for more
3963 details. If CONFIG_COMPAT_VDSO is set, the default is
3964 vdso32=0; otherwise, the default is vdso32=1.
3966 For compatibility with older kernels, vdso32=2 is an
3969 Try vdso32=0 if you encounter an error that says:
3970 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3973 vector=percpu: enable percpu vector domain
3975 video= [FB] Frame buffer configuration
3976 See Documentation/fb/modedb.txt.
3978 video.brightness_switch_enabled= [0,1]
3979 If set to 1, on receiving an ACPI notify event
3980 generated by hotkey, video driver will adjust brightness
3981 level and then send out the event to user space through
3982 the allocated input device; If set to 0, video driver
3983 will only send out the event without touching backlight
3988 [VMMIO] Memory mapped virtio (platform) device.
3990 <size>@<baseaddr>:<irq>[:<id>]
3992 <size> := size (can use standard suffixes
3994 <baseaddr> := physical base address
3995 <irq> := interrupt number (as passed to
3997 <id> := (optional) platform device id
3999 virtio_mmio.device=1K@0x100b0000:48:7
4001 Can be used multiple times for multiple devices.
4003 vga= [BOOT,X86-32] Select a particular video mode
4004 See Documentation/x86/boot.txt and
4005 Documentation/svga.txt.
4006 Use vga=ask for menu.
4007 This is actually a boot loader parameter; the value is
4008 passed to the kernel using a special protocol.
4010 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4011 size of <nn>. This can be used to increase the
4012 minimum size (128MB on x86). It can also be used to
4013 decrease the size and leave more room for directly
4016 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4019 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4022 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4026 Controls the behavior of vsyscalls (i.e. calls to
4027 fixed addresses of 0xffffffffff600x00 from legacy
4028 code). Most statically-linked binaries and older
4029 versions of glibc use these calls. Because these
4030 functions are at fixed addresses, they make nice
4031 targets for exploits that can control RIP.
4033 emulate [default] Vsyscalls turn into traps and are
4034 emulated reasonably safely.
4036 native Vsyscalls are native syscall instructions.
4037 This is a little bit faster than trapping
4038 and makes a few dynamic recompilers work
4039 better than they would in emulation mode.
4040 It also makes exploits much easier to write.
4042 none Vsyscalls don't work at all. This makes
4043 them quite hard to use for exploits but
4044 might break your system.
4046 vt.color= [VT] Default text color.
4047 Format: 0xYX, X = foreground, Y = background.
4048 Default: 0x07 = light gray on black.
4050 vt.cur_default= [VT] Default cursor shape.
4051 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4052 the parameters of the <Esc>[?A;B;Cc escape sequence;
4053 see VGA-softcursor.txt. Default: 2 = underline.
4055 vt.default_blu= [VT]
4056 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4057 Change the default blue palette of the console.
4058 This is a 16-member array composed of values
4061 vt.default_grn= [VT]
4062 Format: <green0>,<green1>,<green2>,...,<green15>
4063 Change the default green palette of the console.
4064 This is a 16-member array composed of values
4067 vt.default_red= [VT]
4068 Format: <red0>,<red1>,<red2>,...,<red15>
4069 Change the default red palette of the console.
4070 This is a 16-member array composed of values
4076 Set system-wide default UTF-8 mode for all tty's.
4077 Default is 1, i.e. UTF-8 mode is enabled for all
4078 newly opened terminals.
4080 vt.global_cursor_default=
4083 Set system-wide default for whether a cursor
4084 is shown on new VTs. Default is -1,
4085 i.e. cursors will be created by default unless
4086 overridden by individual drivers. 0 will hide
4087 cursors, 1 will display them.
4089 vt.italic= [VT] Default color for italic text; 0-15.
4092 vt.underline= [VT] Default color for underlined text; 0-15.
4095 watchdog timers [HW,WDT] For information on watchdog timers,
4096 see Documentation/watchdog/watchdog-parameters.txt
4097 or other driver-specific files in the
4098 Documentation/watchdog/ directory.
4100 workqueue.disable_numa
4101 By default, all work items queued to unbound
4102 workqueues are affine to the NUMA nodes they're
4103 issued on, which results in better behavior in
4104 general. If NUMA affinity needs to be disabled for
4105 whatever reason, this option can be used. Note
4106 that this also can be controlled per-workqueue for
4107 workqueues visible under /sys/bus/workqueue/.
4109 workqueue.power_efficient
4110 Per-cpu workqueues are generally preferred because
4111 they show better performance thanks to cache
4112 locality; unfortunately, per-cpu workqueues tend to
4113 be more power hungry than unbound workqueues.
4115 Enabling this makes the per-cpu workqueues which
4116 were observed to contribute significantly to power
4117 consumption unbound, leading to measurably lower
4118 power usage at the cost of small performance
4121 The default value of this parameter is determined by
4122 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4124 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4125 default x2apic cluster mode on platforms
4128 x86_intel_mid_timer= [X86-32,APBT]
4129 Choose timer option for x86 Intel MID platform.
4130 Two valid options are apbt timer only and lapic timer
4131 plus one apbt timer for broadcast timer.
4132 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4134 xen_512gb_limit [KNL,X86-64,XEN]
4135 Restricts the kernel running paravirtualized under Xen
4136 to use only up to 512 GB of RAM. The reason to do so is
4137 crash analysis tools and Xen tools for doing domain
4138 save/restore/migration must be enabled to handle larger
4141 xen_emul_unplug= [HW,X86,XEN]
4142 Unplug Xen emulated devices
4143 Format: [unplug0,][unplug1]
4144 ide-disks -- unplug primary master IDE devices
4145 aux-ide-disks -- unplug non-primary-master IDE devices
4146 nics -- unplug network devices
4147 all -- unplug all emulated devices (NICs and IDE disks)
4148 unnecessary -- unplugging emulated devices is
4149 unnecessary even if the host did not respond to
4151 never -- do not unplug even if version check succeeds
4153 xen_nopvspin [X86,XEN]
4154 Disables the ticketlock slowpath using Xen PV
4158 Disables the PV optimizations forcing the HVM guest to
4159 run as generic HVM guest with no PV drivers.
4161 xirc2ps_cs= [NET,PCMCIA]
4163 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4165 ______________________________________________________________________
4169 Add more DRM drivers.