4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
168 acpi= [HW,ACPI,X86,ARM64]
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt |
172 force -- enable ACPI if default was off
173 off -- disable ACPI if default was on
174 noirq -- do not use ACPI for IRQ routing
175 strict -- Be less tolerant of platforms that are not
176 strictly ACPI specification compliant.
177 rsdt -- prefer RSDT over (default) XSDT
178 copy_dsdt -- copy DSDT to memory
179 For ARM64, ONLY "acpi=off" or "acpi=force" are available
181 See also Documentation/power/runtime_pm.txt, pci=noacpi
183 acpi_apic_instance= [ACPI, IOAPIC]
185 2: use 2nd APIC table, if available
186 1,0: use 1st APIC table
189 acpi_backlight= [HW,ACPI]
190 acpi_backlight=vendor
192 If set to vendor, prefer vendor specific driver
193 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
194 of the ACPI video.ko driver.
196 acpica_no_return_repair [HW, ACPI]
197 Disable AML predefined validation mechanism
198 This mechanism can repair the evaluation result to make
199 the return objects more ACPI specification compliant.
200 This option is useful for developers to identify the
201 root cause of an AML interpreter issue when the issue
202 has something to do with the repair mechanism.
204 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
205 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
207 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
208 debug output. Bits in debug_layer correspond to a
209 _COMPONENT in an ACPI source file, e.g.,
210 #define _COMPONENT ACPI_PCI_COMPONENT
211 Bits in debug_level correspond to a level in
212 ACPI_DEBUG_PRINT statements, e.g.,
213 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
214 The debug_level mask defaults to "info". See
215 Documentation/acpi/debug.txt for more information about
216 debug layers and levels.
218 Enable processor driver info messages:
219 acpi.debug_layer=0x20000000
220 Enable PCI/PCI interrupt routing info messages:
221 acpi.debug_layer=0x400000
222 Enable AML "Debug" output, i.e., stores to the Debug
223 object while interpreting AML:
224 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
225 Enable all messages related to ACPI hardware:
226 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
228 Some values produce so much output that the system is
229 unusable. The "log_buf_len" parameter may be useful
230 if you need to capture more output.
232 acpi_enforce_resources= [ACPI]
233 { strict | lax | no }
234 Check for resource conflicts between native drivers
235 and ACPI OperationRegions (SystemIO and SystemMemory
236 only). IO ports and memory declared in ACPI might be
237 used by the ACPI subsystem in arbitrary AML code and
238 can interfere with legacy drivers.
239 strict (default): access to resources claimed by ACPI
240 is denied; legacy drivers trying to access reserved
241 resources will fail to bind to device using them.
242 lax: access to resources claimed by ACPI is allowed;
243 legacy drivers trying to access reserved resources
244 will bind successfully but a warning message is logged.
245 no: ACPI OperationRegions are not marked as reserved,
246 no further checks are performed.
248 acpi_force_table_verification [HW,ACPI]
249 Enable table checksum verification during early stage.
250 By default, this is disabled due to x86 early mapping
253 acpi_irq_balance [HW,ACPI]
254 ACPI will balance active IRQs
257 acpi_irq_nobalance [HW,ACPI]
258 ACPI will not move active IRQs (default)
261 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
262 Format: <irq>,<irq>...
264 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
266 Format: <irq>,<irq>...
268 acpi_no_auto_serialize [HW,ACPI]
269 Disable auto-serialization of AML methods
270 AML control methods that contain the opcodes to create
271 named objects will be marked as "Serialized" by the
272 auto-serialization feature.
273 This feature is enabled by default.
274 This option allows to turn off the feature.
276 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
279 acpi_no_static_ssdt [HW,ACPI]
280 Disable installation of static SSDTs at early boot time
281 By default, SSDTs contained in the RSDT/XSDT will be
282 installed automatically and they will appear under
283 /sys/firmware/acpi/tables.
284 This option turns off this feature.
285 Note that specifying this option does not affect
286 dynamic table installation which will install SSDT
287 tables to /sys/firmware/acpi/tables/dynamic.
289 acpi_rsdp= [ACPI,EFI,KEXEC]
290 Pass the RSDP address to the kernel, mostly used
291 on machines running EFI runtime service to boot the
292 second kernel for kdump.
294 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
295 Format: To spoof as Windows 98: ="Microsoft Windows"
297 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
298 of 2 which is mandated by ACPI 6) as the supported ACPI
299 specification revision (when using this switch, it may
300 be necessary to carry out a cold reboot _twice_ in a
301 row to make it take effect on the platform firmware).
303 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
304 acpi_osi="string1" # add string1
305 acpi_osi="!string2" # remove string2
306 acpi_osi=!* # remove all strings
307 acpi_osi=! # disable all built-in OS vendor
309 acpi_osi= # disable all strings
311 'acpi_osi=!' can be used in combination with single or
312 multiple 'acpi_osi="string1"' to support specific OS
313 vendor string(s). Note that such command can only
314 affect the default state of the OS vendor strings, thus
315 it cannot affect the default state of the feature group
316 strings and the current state of the OS vendor strings,
317 specifying it multiple times through kernel command line
318 is meaningless. This command is useful when one do not
319 care about the state of the feature group strings which
320 should be controlled by the OSPM.
322 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
323 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
324 can make '_OSI("Windows 2000")' TRUE.
326 'acpi_osi=' cannot be used in combination with other
327 'acpi_osi=' command lines, the _OSI method will not
328 exist in the ACPI namespace. NOTE that such command can
329 only affect the _OSI support state, thus specifying it
330 multiple times through kernel command line is also
333 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
336 'acpi_osi=!*' can be used in combination with single or
337 multiple 'acpi_osi="string1"' to support specific
338 string(s). Note that such command can affect the
339 current state of both the OS vendor strings and the
340 feature group strings, thus specifying it multiple times
341 through kernel command line is meaningful. But it may
342 still not able to affect the final state of a string if
343 there are quirks related to this string. This command
344 is useful when one want to control the state of the
345 feature group strings to debug BIOS issues related to
348 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
349 '_OSI("Module Device")' FALSE.
350 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
351 '_OSI("Module Device")' TRUE.
352 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
354 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
356 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
357 they all will make '_OSI("Windows 2000")' TRUE.
360 Override the pmtimer bug detection: force the kernel
361 to assume that this machine's pmtimer latches its value
362 and always returns good values.
364 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
365 Format: { level | edge | high | low }
367 acpi_skip_timer_override [HW,ACPI]
368 Recognize and ignore IRQ0/pin2 Interrupt Override.
369 For broken nForce2 BIOS resulting in XT-PIC timer.
371 acpi_sleep= [HW,ACPI] Sleep options
372 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
373 old_ordering, nonvs, sci_force_enable }
374 See Documentation/power/video.txt for information on
376 s3_beep is for debugging; it makes the PC's speaker beep
377 as soon as the kernel's real-mode entry point is called.
378 s4_nohwsig prevents ACPI hardware signature from being
379 used during resume from hibernation.
380 old_ordering causes the ACPI 1.0 ordering of the _PTS
381 control method, with respect to putting devices into
382 low power states, to be enforced (the ACPI 2.0 ordering
383 of _PTS is used by default).
384 nonvs prevents the kernel from saving/restoring the
385 ACPI NVS memory during suspend/hibernation and resume.
386 sci_force_enable causes the kernel to set SCI_EN directly
387 on resume from S1/S3 (which is against the ACPI spec,
388 but some broken systems don't work without it).
390 acpi_use_timer_override [HW,ACPI]
391 Use timer override. For some broken Nvidia NF5 boards
392 that require a timer override, but don't have HPET
394 add_efi_memmap [EFI; X86] Include EFI memory map in
395 kernel's map of available physical RAM.
398 { off | try_unsupported }
399 off: disable AGP support
400 try_unsupported: try to drive unsupported chipsets
401 (may crash computer or cause data corruption)
404 See Documentation/sound/alsa/alsa-parameters.txt
407 Allow the default userspace alignment fault handler
408 behaviour to be specified. Bit 0 enables warnings,
409 bit 1 enables fixups, and bit 2 sends a segfault.
411 align_va_addr= [X86-64]
412 Align virtual addresses by clearing slice [14:12] when
413 allocating a VMA at process creation time. This option
414 gives you up to 3% performance improvement on AMD F15h
415 machines (where it is enabled by default) for a
416 CPU-intensive style benchmark, and it can vary highly in
417 a microbenchmark depending on workload and compiler.
419 32: only for 32-bit processes
420 64: only for 64-bit processes
421 on: enable for both 32- and 64-bit processes
422 off: disable for both 32- and 64-bit processes
424 alloc_snapshot [FTRACE]
425 Allocate the ftrace snapshot buffer on boot up when the
426 main buffer is allocated. This is handy if debugging
427 and you need to use tracing_snapshot() on boot up, and
428 do not want to use tracing_snapshot_alloc() as it needs
429 to be done where GFP_KERNEL allocations are allowed.
431 amd_iommu= [HW,X86-64]
432 Pass parameters to the AMD IOMMU driver in the system.
434 fullflush - enable flushing of IO/TLB entries when
435 they are unmapped. Otherwise they are
436 flushed before they will be reused, which
438 off - do not initialize any AMD IOMMU found in
440 force_isolation - Force device isolation for all
441 devices. The IOMMU driver is not
442 allowed anymore to lift isolation
443 requirements as needed. This option
444 does not override iommu=pt
446 amd_iommu_dump= [HW,X86-64]
447 Enable AMD IOMMU driver option to dump the ACPI table
448 for AMD IOMMU. With this option enabled, AMD IOMMU
449 driver will print ACPI tables for AMD IOMMU during
450 IOMMU initialization.
452 amijoy.map= [HW,JOY] Amiga joystick support
453 Map of devices attached to JOY0DAT and JOY1DAT
455 See also Documentation/input/joystick.txt
457 analog.map= [HW,JOY] Analog joystick and gamepad support
458 Specifies type or capabilities of an analog joystick
459 connected to one of 16 gameports
460 Format: <type1>,<type2>,..<type16>
463 Power management functions (SPARCstation-4/5 + deriv.)
465 Disable APC CPU standby support. SPARCstation-Fox does
466 not play well with APC CPU idle - disable it if you have
467 APC and your system crashes randomly.
469 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
470 Change the output verbosity whilst booting
471 Format: { quiet (default) | verbose | debug }
472 Change the amount of debugging information output
473 when initialising the APIC and IO-APIC components.
476 See Documentation/networking/ipv6.txt.
478 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
479 Limit apic dumping. The parameter defines the maximal
480 number of local apics being dumped. Also it is possible
481 to set it to "all" by meaning -- no limit here.
482 Format: { 1 (default) | 2 | ... | all }.
483 The parameter valid if only apic=debug or
484 apic=verbose is specified.
485 Example: apic=debug show_lapic=all
487 apm= [APM] Advanced Power Management
488 See header of arch/x86/kernel/apm_32.c.
490 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
491 Format: <io>,<irq>,<nodeID>
495 atarimouse= [HW,MOUSE] Atari Mouse
497 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
498 EzKey and similar keyboards
500 atkbd.reset= [HW] Reset keyboard during initialization
502 atkbd.set= [HW] Select keyboard code set
503 Format: <int> (2 = AT (default), 3 = PS/2)
505 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
508 atkbd.softraw= [HW] Choose between synthetic and real raw mode
509 Format: <bool> (0 = real, 1 = synthetic (default))
511 atkbd.softrepeat= [HW]
512 Use software keyboard repeat
514 audit= [KNL] Enable the audit sub-system
515 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
516 0 - kernel audit is disabled and can not be enabled
517 until the next reboot
518 unset - kernel audit is initialized but disabled and
519 will be fully enabled by the userspace auditd.
520 1 - kernel audit is initialized and partially enabled,
521 storing at most audit_backlog_limit messages in
522 RAM until it is fully enabled by the userspace
526 audit_backlog_limit= [KNL] Set the audit queue size limit.
527 Format: <int> (must be >=0)
530 baycom_epp= [HW,AX25]
533 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
535 See header of drivers/net/hamradio/baycom_par.c.
537 baycom_ser_fdx= [HW,AX25]
538 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
539 Format: <io>,<irq>,<mode>[,<baud>]
540 See header of drivers/net/hamradio/baycom_ser_fdx.c.
542 baycom_ser_hdx= [HW,AX25]
543 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
544 Format: <io>,<irq>,<mode>
545 See header of drivers/net/hamradio/baycom_ser_hdx.c.
547 blkdevparts= Manual partition parsing of block device(s) for
548 embedded devices based on command line input.
549 See Documentation/block/cmdline-partition.txt
551 boot_delay= Milliseconds to delay each printk during boot.
552 Values larger than 10 seconds (10000) are changed to
556 bootmem_debug [KNL] Enable bootmem allocator debug messages.
558 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
559 bttv.radio= Most important insmod options are available as
561 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
564 bulk_remove=off [PPC] This parameter disables the use of the pSeries
565 firmware feature for flushing multiple hpte entries
568 c101= [NET] Moxa C101 synchronous serial card
570 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
571 Sometimes CPU hardware bugs make them report the cache
572 size incorrectly. The kernel will attempt work arounds
573 to fix known problems, but for some CPUs it is not
574 possible to determine what the correct size should be.
575 This option provides an override for these situations.
577 ca_keys= [KEYS] This parameter identifies a specific key(s) on
578 the system trusted keyring to be used for certificate
580 format: { id:<keyid> | builtin }
582 cca= [MIPS] Override the kernel pages' cache coherency
583 algorithm. Accepted values range from 0 to 7
584 inclusive. See arch/mips/include/asm/pgtable-bits.h
585 for platform specific values (SB1, Loongson3 and
588 ccw_timeout_log [S390]
589 See Documentation/s390/CommonIO for details.
591 cgroup_disable= [KNL] Disable a particular controller
592 Format: {name of the controller(s) to disable}
593 The effects of cgroup_disable=foo are:
594 - foo isn't auto-mounted if you mount all cgroups in
596 - foo isn't visible as an individually mountable
598 {Currently only "memory" controller deal with this and
599 cut the overhead, others just disable the usage. So
600 only cgroup_disable=memory is actually worthy}
602 checkreqprot [SELINUX] Set initial checkreqprot flag value.
603 Format: { "0" | "1" }
604 See security/selinux/Kconfig help text.
605 0 -- check protection applied by kernel (includes
606 any implied execute protection).
607 1 -- check protection requested by application.
608 Default value is set via a kernel config option.
609 Value can be changed at runtime via
610 /selinux/checkreqprot.
613 See Documentation/s390/CommonIO for details.
616 Prevents the clock framework from automatically gating
617 clocks that have not been explicitly enabled by a Linux
618 device driver but are enabled in hardware at reset or
619 by the bootloader/firmware. Note that this does not
620 force such clocks to be always-on nor does it reserve
621 those clocks in any way. This parameter is useful for
622 debug and development, but should not be needed on a
623 platform with proper driver support. For more
624 information, see Documentation/clk.txt.
626 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
628 Forces specified clocksource (if available) to be used
629 when calculating gettimeofday(). If specified
630 clocksource is not available, it defaults to PIT.
631 Format: { pit | tsc | cyclone | pmtmr }
633 clocksource= Override the default clocksource
635 Override the default clocksource and use the clocksource
636 with the name specified.
637 Some clocksource names to choose from, depending on
639 [all] jiffies (this is the base, fallback clocksource)
641 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
642 pxa_timer,timer3,32k_counter,timer0_1
644 [X86-32] pit,hpet,tsc;
645 scx200_hrt on Geode; cyclone on IBM x440
653 clearcpuid=BITNUM [X86]
654 Disable CPUID feature X for the kernel. See
655 arch/x86/include/asm/cpufeature.h for the valid bit
656 numbers. Note the Linux specific bits are not necessarily
657 stable over kernel options, but the vendor specific
659 Also note that user programs calling CPUID directly
660 or using the feature without checking anything
661 will still see it. This just prevents it from
662 being used by the kernel or shown in /proc/cpuinfo.
663 Also note the kernel might malfunction if you disable
666 cma=nn[MG]@[start[MG][-end[MG]]]
668 Sets the size of kernel global memory area for
669 contiguous memory allocations and optionally the
670 placement constraint by the physical address range of
671 memory allocations. A value of 0 disables CMA
672 altogether. For more information, see
673 include/linux/dma-contiguous.h
675 cmo_free_hint= [PPC] Format: { yes | no }
676 Specify whether pages are marked as being inactive
677 when they are freed. This is used in CMO environments
678 to determine OS memory pressure for page stealing by
682 coherent_pool=nn[KMG] [ARM,KNL]
683 Sets the size of memory pool for coherent, atomic dma
684 allocations, by default set to 256K.
686 code_bytes [X86] How many bytes of object code to print
691 com20020= [HW,NET] ARCnet - COM20020 chipset
693 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
695 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
699 ARCnet - COM90xx chipset (memory-mapped buffers)
700 Format: <io>[,<irq>[,<memstart>]]
702 condev= [HW,S390] console device
705 console= [KNL] Output console device and options.
707 tty<n> Use the virtual console device <n>.
711 Use the specified serial port. The options are of
712 the form "bbbbpnf", where "bbbb" is the baud rate,
713 "p" is parity ("n", "o", or "e"), "n" is number of
714 bits, and "f" is flow control ("r" for RTS or
715 omit it). Default is "9600n8".
717 See Documentation/serial-console.txt for more
719 Documentation/networking/netconsole.txt for an
722 uart[8250],io,<addr>[,options]
723 uart[8250],mmio,<addr>[,options]
724 uart[8250],mmio32,<addr>[,options]
725 uart[8250],0x<addr>[,options]
726 Start an early, polled-mode console on the 8250/16550
727 UART at the specified I/O port or MMIO address,
728 switching to the matching ttyS device later.
729 MMIO inter-register address stride is either 8-bit
730 (mmio) or 32-bit (mmio32).
731 If none of [io|mmio|mmio32], <addr> is assumed to be
732 equivalent to 'mmio'. 'options' are specified in the
733 same format described for ttyS above; if unspecified,
734 the h/w is not re-initialized.
736 hvc<n> Use the hypervisor console device <n>. This is for
737 both Xen and PowerPC hypervisors.
739 If the device connected to the port is not a TTY but a braille
740 device, prepend "brl," before the device type, for instance
742 For now, only VisioBraille is supported.
744 consoleblank= [KNL] The console blank (screen saver) timeout in
745 seconds. Defaults to 10*60 = 10mins. A value of 0
746 disables the blank timer.
749 [KNL] Change the default value for
750 /proc/<pid>/coredump_filter.
751 See also Documentation/filesystems/proc.txt.
753 cpuidle.off=1 [CPU_IDLE]
754 disable the cpuidle sub-system
757 [X86] Delay for N microsec between assert and de-assert
758 of APIC INIT to start processors. This delay occurs
759 on every CPU online, such as boot, and resume from suspend.
762 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
764 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
766 crashkernel=size[KMG][@offset[KMG]]
767 [KNL] Using kexec, Linux can switch to a 'crash kernel'
768 upon panic. This parameter reserves the physical
769 memory region [offset, offset + size] for that kernel
770 image. If '@offset' is omitted, then a suitable offset
771 is selected automatically. Check
772 Documentation/kdump/kdump.txt for further details.
774 crashkernel=range1:size1[,range2:size2,...][@offset]
775 [KNL] Same as above, but depends on the memory
776 in the running system. The syntax of range is
777 start-[end] where start and end are both
778 a memory unit (amount[KMG]). See also
779 Documentation/kdump/kdump.txt for an example.
781 crashkernel=size[KMG],high
782 [KNL, x86_64] range could be above 4G. Allow kernel
783 to allocate physical memory region from top, so could
784 be above 4G if system have more than 4G ram installed.
785 Otherwise memory region will be allocated below 4G, if
787 It will be ignored if crashkernel=X is specified.
788 crashkernel=size[KMG],low
789 [KNL, x86_64] range under 4G. When crashkernel=X,high
790 is passed, kernel could allocate physical memory region
791 above 4G, that cause second kernel crash on system
792 that require some amount of low memory, e.g. swiotlb
793 requires at least 64M+32K low memory. Kernel would
794 try to allocate 72M below 4G automatically.
795 This one let user to specify own low range under 4G
796 for second kernel instead.
797 0: to disable low allocation.
798 It will be ignored when crashkernel=X,high is not used
799 or memory reserved is below 4G.
804 cs89x0_media= [HW,NET]
805 Format: { rj45 | aui | bnc }
808 See header of drivers/s390/block/dasd_devmap.c.
810 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
811 (one device per port)
812 Format: <port#>,<type>
813 See also Documentation/input/joystick-parport.txt
815 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
816 time. See Documentation/dynamic-debug-howto.txt for
817 details. Deprecated, see dyndbg.
819 debug [KNL] Enable kernel debugging (events log level).
822 [KNL] verbose self-tests
824 Print debugging info while doing the locking API
826 We default to 0 (no extra messages), setting it to
827 1 will print _a lot_ more information - normally
828 only useful to kernel developers.
830 debug_objects [KNL] Enable object debugging
833 [KNL] Disable object debugging
835 debug_guardpage_minorder=
836 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
837 parameter allows control of the order of pages that will
838 be intentionally kept free (and hence protected) by the
839 buddy allocator. Bigger value increase the probability
840 of catching random memory corruption, but reduce the
841 amount of memory for normal system use. The maximum
842 possible value is MAX_ORDER/2. Setting this parameter
843 to 1 or 2 should be enough to identify most random
844 memory corruption problems caused by bugs in kernel or
845 driver code when a CPU writes to (or reads from) a
846 random memory location. Note that there exists a class
847 of memory corruptions problems caused by buggy H/W or
848 F/W or by drivers badly programing DMA (basically when
849 memory is written at bus level and the CPU MMU is
850 bypassed) which are not detectable by
851 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
852 tracking down these problems.
855 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
856 parameter enables the feature at boot time. In
857 default, it is disabled. We can avoid allocating huge
858 chunk of memory for debug pagealloc if we don't enable
859 it at boot time and the system will work mostly same
860 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
861 on: enable the feature
863 debugpat [X86] Enable PAT debugging
865 decnet.addr= [HW,NET]
866 Format: <area>[,<node>]
867 See also Documentation/networking/decnet.txt.
870 [same as hugepagesz=] The size of the default
871 HugeTLB page size. This is the size represented by
872 the legacy /proc/ hugepages APIs, used for SHM, and
873 default size when mounting hugetlbfs filesystems.
874 Defaults to the default architecture's huge page size
878 Set number of hash buckets for dentry cache.
881 See Documentation/networking/ipv6.txt.
883 disable_cpu_apicid= [X86,APIC,SMP]
885 The number of initial APIC ID for the
886 corresponding CPU to be disabled at boot,
887 mostly used for the kdump 2nd kernel to
888 disable BSP to wake up multiple CPUs without
889 causing system reset or hang due to sending
892 disable_ddw [PPC/PSERIES]
893 Disable Dynamic DMA Window support. Use this if
894 to workaround buggy firmware.
897 See Documentation/networking/ipv6.txt.
899 disable_mtrr_cleanup [X86]
900 The kernel tries to adjust MTRR layout from continuous
901 to discrete, to make X server driver able to add WB
902 entry later. This parameter disables that.
904 disable_mtrr_trim [X86, Intel and AMD only]
905 By default the kernel will trim any uncacheable
906 memory out of your available memory pool based on
907 MTRR settings. This parameter disables that behavior,
908 possibly causing your machine to run very slowly.
910 disable_timer_pin_1 [X86]
911 Disable PIN 1 of APIC timer
912 Can be useful to work around chipset bugs.
914 dis_ucode_ldr [X86] Disable the microcode loader.
916 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
917 this option disables the debugging code at boot.
919 dma_debug_entries=<number>
920 This option allows to tune the number of preallocated
921 entries for DMA-API debugging code. One entry is
922 required per DMA-API allocation. Use this if the
923 DMA-API debugging code disables itself because the
924 architectural default is too low.
926 dma_debug_driver=<driver_name>
927 With this option the DMA-API debugging driver
928 filter feature can be enabled at boot time. Just
929 pass the driver to filter for as the parameter.
930 The filter can be disabled or changed to another
931 driver later using sysfs.
933 drm_kms_helper.edid_firmware=[<connector>:]<file>
934 Broken monitors, graphic adapters and KVMs may
935 send no or incorrect EDID data sets. This parameter
936 allows to specify an EDID data set in the
937 /lib/firmware directory that is used instead.
938 Generic built-in EDID data sets are used, if one of
939 edid/1024x768.bin, edid/1280x1024.bin,
940 edid/1680x1050.bin, or edid/1920x1080.bin is given
941 and no file with the same name exists. Details and
942 instructions how to build your own EDID data are
943 available in Documentation/EDID/HOWTO.txt. An EDID
944 data set will only be used for a particular connector,
945 if its name and a colon are prepended to the EDID
950 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
951 module.dyndbg[="val"]
952 Enable debug messages at boot time. See
953 Documentation/dynamic-debug-howto.txt for details.
955 nompx [X86] Disables Intel Memory Protection Extensions.
956 See Documentation/x86/intel_mpx.txt for more
957 information about the feature.
960 on enable eager fpu restore
961 off disable eager fpu restore
962 auto selects the default scheme, which automatically
963 enables eagerfpu restore for xsaveopt.
965 module.async_probe [KNL]
966 Enable asynchronous probe on this module.
968 early_ioremap_debug [KNL]
969 Enable debug messages in early_ioremap support. This
970 is useful for tracking down temporary early mappings
971 which are not unmapped.
973 earlycon= [KNL] Output early console device and options.
976 Start an early, polled-mode console on a cadence serial
977 port at the specified address. The cadence serial port
978 must already be setup and configured. Options are not
981 uart[8250],io,<addr>[,options]
982 uart[8250],mmio,<addr>[,options]
983 uart[8250],mmio32,<addr>[,options]
984 uart[8250],mmio32be,<addr>[,options]
985 uart[8250],0x<addr>[,options]
986 Start an early, polled-mode console on the 8250/16550
987 UART at the specified I/O port or MMIO address.
988 MMIO inter-register address stride is either 8-bit
989 (mmio) or 32-bit (mmio32 or mmio32be).
990 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
991 to be equivalent to 'mmio'. 'options' are specified
992 in the same format described for "console=ttyS<n>"; if
993 unspecified, the h/w is not initialized.
996 Start an early, polled-mode console on a pl011 serial
997 port at the specified address. The pl011 serial port
998 must already be setup and configured. Options are not
1002 Start an early, polled-mode console on an msm serial
1003 port at the specified address. The serial port
1004 must already be setup and configured. Options are not
1007 msm_serial_dm,<addr>
1008 Start an early, polled-mode console on an msm serial
1009 dm port at the specified address. The serial port
1010 must already be setup and configured. Options are not
1013 smh Use ARM semihosting calls for early console.
1021 Use early console provided by serial driver available
1022 on Samsung SoCs, requires selecting proper type and
1023 a correct base address of the selected UART port. The
1024 serial port must already be setup and configured.
1025 Options are not yet supported.
1027 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1031 earlyprintk=serial[,ttySn[,baudrate]]
1032 earlyprintk=serial[,0x...[,baudrate]]
1033 earlyprintk=ttySn[,baudrate]
1034 earlyprintk=dbgp[debugController#]
1035 earlyprintk=pciserial,bus:device.function[,baudrate]
1037 earlyprintk is useful when the kernel crashes before
1038 the normal console is initialized. It is not enabled by
1039 default because it has some cosmetic problems.
1041 Append ",keep" to not disable it when the real console
1044 Only one of vga, efi, serial, or usb debug port can
1047 Currently only ttyS0 and ttyS1 may be specified by
1048 name. Other I/O ports may be explicitly specified
1049 on some architectures (x86 and arm at least) by
1050 replacing ttySn with an I/O port address, like this:
1051 earlyprintk=serial,0x1008,115200
1052 You can find the port for a given device in
1053 /proc/tty/driver/serial:
1054 2: uart:ST16650V2 port:00001008 irq:18 ...
1056 Interaction with the standard serial driver is not
1059 The VGA and EFI output is eventually overwritten by
1062 The xen output can only be used by Xen PV guests.
1064 edac_report= [HW,EDAC] Control how to report EDAC event
1065 Format: {"on" | "off" | "force"}
1066 on: enable EDAC to report H/W event. May be overridden
1067 by other higher priority error reporting module.
1068 off: disable H/W event reporting through EDAC.
1069 force: enforce the use of EDAC to report H/W event.
1072 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1075 This is designed to be used in conjunction with
1076 the boot argument: earlyprintk=vga
1079 Format: {"off" | "on" | "skip[mbr]"}
1082 Format: { "old_map", "nochunk", "noruntime", "debug" }
1083 old_map [X86-64]: switch to the old ioremap-based EFI
1084 runtime services mapping. 32-bit still uses this one by
1086 nochunk: disable reading files in "chunks" in the EFI
1087 boot stub, as chunking can cause problems with some
1088 firmware implementations.
1089 noruntime : disable EFI runtime services support
1090 debug: enable misc debug output
1092 efi_no_storage_paranoia [EFI; X86]
1093 Using this parameter you can use more than 50% of
1094 your efi variable storage. Use this parameter only if
1095 you are really sure that your UEFI does sane gc and
1096 fulfills the spec otherwise your board may brick.
1098 eisa_irq_edge= [PARISC,HW]
1099 See header of drivers/parisc/eisa.c.
1102 See comment before function elanfreq_setup() in
1103 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1106 Format: {"cfq" | "deadline" | "noop"}
1107 See Documentation/block/cfq-iosched.txt and
1108 Documentation/block/deadline-iosched.txt for details.
1110 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1111 Specifies physical address of start of kernel core
1112 image elf header and optionally the size. Generally
1113 kexec loader will pass this option to capture kernel.
1114 See Documentation/kdump/kdump.txt for details.
1116 enable_mtrr_cleanup [X86]
1117 The kernel tries to adjust MTRR layout from continuous
1118 to discrete, to make X server driver able to add WB
1119 entry later. This parameter enables that.
1121 enable_timer_pin_1 [X86]
1122 Enable PIN 1 of APIC timer
1123 Can be useful to work around chipset bugs
1124 (in particular on some ATI chipsets).
1125 The kernel tries to set a reasonable default.
1127 enforcing [SELINUX] Set initial enforcing status.
1129 See security/selinux/Kconfig help text.
1130 0 -- permissive (log only, no denials).
1131 1 -- enforcing (deny and log).
1133 Value can be changed at runtime via /selinux/enforce.
1136 Disable Error Record Serialization Table (ERST)
1139 ether= [HW,NET] Ethernet cards parameters
1140 This option is obsoleted by the "netdev=" option, which
1141 has equivalent usage. See its documentation for details.
1145 Permit 'security.evm' to be updated regardless of
1146 current integrity status.
1150 fail_make_request=[KNL]
1151 General fault injection mechanism.
1152 Format: <interval>,<probability>,<space>,<times>
1153 See also Documentation/fault-injection/.
1156 See Documentation/blockdev/floppy.txt.
1158 force_pal_cache_flush
1159 [IA-64] Avoid check_sal_cache_flush which may hang on
1160 buggy SAL_CACHE_FLUSH implementations. Using this
1161 parameter will force ia64_sal_cache_flush to call
1162 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1165 Forcefully enable Physical Address Extension (PAE).
1166 Many Pentium M systems disable PAE but may have a
1167 functionally usable PAE implementation.
1168 Warning: use of this parameter will taint the kernel
1169 and may cause unknown problems.
1172 [FTRACE] will set and start the specified tracer
1173 as early as possible in order to facilitate early
1176 ftrace_dump_on_oops[=orig_cpu]
1177 [FTRACE] will dump the trace buffers on oops.
1178 If no parameter is passed, ftrace will dump
1179 buffers of all CPUs, but if you pass orig_cpu, it will
1180 dump only the buffer of the CPU that triggered the
1183 ftrace_filter=[function-list]
1184 [FTRACE] Limit the functions traced by the function
1185 tracer at boot up. function-list is a comma separated
1186 list of functions. This list can be changed at run
1187 time by the set_ftrace_filter file in the debugfs
1190 ftrace_notrace=[function-list]
1191 [FTRACE] Do not trace the functions specified in
1192 function-list. This list can be changed at run time
1193 by the set_ftrace_notrace file in the debugfs
1196 ftrace_graph_filter=[function-list]
1197 [FTRACE] Limit the top level callers functions traced
1198 by the function graph tracer at boot up.
1199 function-list is a comma separated list of functions
1200 that can be changed at run time by the
1201 set_graph_function file in the debugfs tracing directory.
1203 ftrace_graph_notrace=[function-list]
1204 [FTRACE] Do not trace from the functions specified in
1205 function-list. This list is a comma separated list of
1206 functions that can be changed at run time by the
1207 set_graph_notrace file in the debugfs tracing directory.
1210 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1211 support via parallel port (up to 5 devices per port)
1212 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1213 See also Documentation/input/joystick-parport.txt
1217 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1221 gcov_persist= [GCOV] When non-zero (default), profiling data for
1222 kernel modules is saved and remains accessible via
1223 debugfs, even when the module is unloaded/reloaded.
1224 When zero, profiling data is discarded and associated
1225 debugfs files are removed at module unload time.
1227 gpt [EFI] Forces disk with valid GPT signature but
1228 invalid Protective MBR to be treated as GPT. If the
1229 primary GPT is corrupted, it enables the backup/alternate
1230 GPT to be used instead.
1232 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1233 the "Enable 0" bit of the configuration register.
1236 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1237 the "Enable 0" bit of the configuration register.
1240 grcan.select= [HW] Select which physical interface to use.
1243 grcan.txsize= [HW] Sets the size of the tx buffer.
1244 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1246 grcan.rxsize= [HW] Sets the size of the rx buffer.
1247 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1250 hashdist= [KNL,NUMA] Large hashes allocated during boot
1251 are distributed across NUMA nodes. Defaults on
1252 for 64-bit NUMA, off otherwise.
1253 Format: 0 | 1 (for off | on)
1255 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1257 hd= [EIDE] (E)IDE hard drive subsystem geometry
1258 Format: <cyl>,<head>,<sect>
1261 Disable Hardware Error Source Table (HEST) support;
1262 corresponding firmware-first mode error processing
1263 logic will be disabled.
1265 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1266 size of <nn>. This works even on boxes that have no
1267 highmem otherwise. This also works to reduce highmem
1268 size on bigger boxes.
1270 highres= [KNL] Enable/disable high resolution timer mode.
1271 Valid parameters: "on", "off"
1275 See Documentation/isdn/README.HiSax.
1279 hpet= [X86-32,HPET] option to control HPET usage
1280 Format: { enable (default) | disable | force |
1282 disable: disable HPET and use PIT instead
1283 force: allow force enabled of undocumented chips (ICH4,
1285 verbose: show contents of HPET registers during setup
1287 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1288 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1290 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1291 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1292 On x86-64 and powerpc, this option can be specified
1293 multiple times interleaved with hugepages= to reserve
1294 huge pages of different sizes. Valid pages sizes on
1295 x86-64 are 2M (when the CPU supports "pse") and 1G
1296 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1298 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1299 terminal devices. Valid values: 0..8
1300 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1301 If specified, z/VM IUCV HVC accepts connections
1302 from listed z/VM user IDs only.
1304 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1305 hardware thread id mappings.
1306 Format: <cpu>:<hwthread>
1309 Do not unregister boot console at start. This is only
1310 useful for debugging when something happens in the window
1311 between unregistering the boot console and initializing
1314 i2c_bus= [HW] Override the default board specific I2C bus speed
1315 or register an additional I2C bus that is not
1316 registered from board initialization code.
1320 i8042.debug [HW] Toggle i8042 debug mode
1321 i8042.unmask_kbd_data
1322 [HW] Enable printing of interrupt data from the KBD port
1323 (disabled by default, and as a pre-condition
1324 requires that i8042.debug=1 be enabled)
1325 i8042.direct [HW] Put keyboard port into non-translated mode
1326 i8042.dumbkbd [HW] Pretend that controller can only read data from
1327 keyboard and cannot control its state
1328 (Don't attempt to blink the leds)
1329 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1330 i8042.nokbd [HW] Don't check/create keyboard port
1331 i8042.noloop [HW] Disable the AUX Loopback command while probing
1333 i8042.nomux [HW] Don't check presence of an active multiplexing
1335 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1337 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1338 i8042.reset [HW] Reset the controller during init and cleanup
1339 i8042.unlock [HW] Unlock (ignore) the keylock
1340 i8042.kbdreset [HW] Reset device connected to KBD port
1344 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1345 indicates that the driver is running on unsupported
1347 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1348 does not match list of supported models.
1350 [HW] Report power status in /proc/i8k
1351 (disabled by default)
1352 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1355 i915.invert_brightness=
1356 [DRM] Invert the sense of the variable that is used to
1357 set the brightness of the panel backlight. Normally a
1358 brightness value of 0 indicates backlight switched off,
1359 and the maximum of the brightness value sets the backlight
1360 to maximum brightness. If this parameter is set to 0
1361 (default) and the machine requires it, or this parameter
1362 is set to 1, a brightness value of 0 sets the backlight
1363 to maximum brightness, and the maximum of the brightness
1364 value switches the backlight off.
1365 -1 -- never invert brightness
1366 0 -- machine default
1367 1 -- force brightness inversion
1370 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1372 ide-core.nodma= [HW] (E)IDE subsystem
1373 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1374 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1375 .cdrom .chs .ignore_cable are additional options
1376 See Documentation/ide/ide.txt.
1378 ide-generic.probe-mask= [HW] (E)IDE subsystem
1380 Probe mask for legacy ISA IDE ports. Depending on
1381 platform up to 6 ports are supported, enabled by
1382 setting corresponding bits in the mask to 1. The
1383 default value is 0x0, which has a special meaning.
1384 On systems that have PCI, it triggers scanning the
1385 PCI bus for the first and the second port, which
1386 are then probed. On systems without PCI the value
1387 of 0x0 enables probing the two first ports as if it
1390 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1391 Claim all unknown PCI IDE storage controllers.
1394 Format: idle=poll, idle=halt, idle=nomwait
1395 Poll forces a polling idle loop that can slightly
1396 improve the performance of waking up a idle CPU, but
1397 will use a lot of power and make the system run hot.
1399 idle=halt: Halt is forced to be used for CPU idle.
1400 In such case C2/C3 won't be used again.
1401 idle=nomwait: Disable mwait for CPU C-states
1403 ignore_loglevel [KNL]
1404 Ignore loglevel setting - this will print /all/
1405 kernel messages to the console. Useful for debugging.
1406 We also add it as printk module parameter, so users
1407 could change it dynamically, usually by
1408 /sys/module/printk/parameters/ignore_loglevel.
1410 ihash_entries= [KNL]
1411 Set number of hash buckets for inode cache.
1413 ima_appraise= [IMA] appraise integrity measurements
1414 Format: { "off" | "enforce" | "fix" | "log" }
1417 ima_appraise_tcb [IMA]
1418 The builtin appraise policy appraises all files
1422 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1426 The list of supported hash algorithms is defined
1427 in crypto/hash_info.h.
1430 The builtin measurement policy to load during IMA
1431 setup. Specyfing "tcb" as the value, measures all
1432 programs exec'd, files mmap'd for exec, and all files
1433 opened with the read mode bit set by either the
1434 effective uid (euid=0) or uid=0.
1437 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1438 Load a policy which meets the needs of the Trusted
1439 Computing Base. This means IMA will measure all
1440 programs exec'd, files mmap'd for exec, and all files
1441 opened for read by uid=0.
1444 Select one of defined IMA measurements template formats.
1445 Formats: { "ima" | "ima-ng" | "ima-sig" }
1449 [IMA] Define a custom template format.
1450 Format: { "field1|...|fieldN" }
1452 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1453 Format: <min_file_size>
1454 Set the minimal file size for using asynchronous hash.
1455 If left unspecified, ahash usage is disabled.
1457 ahash performance varies for different data sizes on
1458 different crypto accelerators. This option can be used
1459 to achieve the best performance for a particular HW.
1461 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1463 Set hashing buffer size. Default: 4k.
1465 ahash performance varies for different chunk sizes on
1466 different crypto accelerators. This option can be used
1467 to achieve best performance for particular HW.
1471 Run specified binary instead of /sbin/init as init
1474 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1475 for working out where the kernel is dying during
1478 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1479 initcall functions. Useful for debugging built-in
1480 modules and initcalls.
1482 initrd= [BOOT] Specify the location of the initial ramdisk
1484 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1487 int_pln_enable [x86] Enable power limit notification interrupt
1489 integrity_audit=[IMA]
1490 Format: { "0" | "1" }
1491 0 -- basic integrity auditing messages. (Default)
1492 1 -- additional integrity auditing messages.
1494 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1496 Enable intel iommu driver.
1498 Disable intel iommu driver.
1499 igfx_off [Default Off]
1500 By default, gfx is mapped as normal device. If a gfx
1501 device has a dedicated DMAR unit, the DMAR unit is
1502 bypassed by not enabling DMAR with this option. In
1503 this case, gfx device will use physical address for
1506 With this option iommu will not optimize to look
1507 for io virtual address below 32-bit forcing dual
1508 address cycle on pci bus for cards supporting greater
1509 than 32-bit addressing. The default is to look
1510 for translation below 32-bit and if not available
1511 then look in the higher range.
1512 strict [Default Off]
1513 With this option on every unmap_single operation will
1514 result in a hardware IOTLB flush operation as opposed
1515 to batching them for performance.
1516 sp_off [Default Off]
1517 By default, super page will be supported if Intel IOMMU
1518 has the capability. With this option, super page will
1520 ecs_off [Default Off]
1521 By default, extended context tables will be supported if
1522 the hardware advertises that it has support both for the
1523 extended tables themselves, and also PASID support. With
1524 this option set, extended tables will not be used even
1525 on hardware which claims to support them.
1527 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1528 0 disables intel_idle and fall back on acpi_idle.
1529 1 to 6 specify maximum depth of C-state.
1533 Do not enable intel_pstate as the default
1534 scaling driver for the supported processors
1536 Enable intel_pstate on systems that prohibit it by default
1537 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1538 instead of acpi-cpufreq may disable platform features, such
1539 as thermal controls and power capping, that rely on ACPI
1540 P-States information being indicated to OSPM and therefore
1541 should be used with caution. This option does not work with
1542 processors that aren't supported by the intel_pstate driver
1543 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1545 Do not enable hardware P state control (HWP)
1548 Only load intel_pstate on systems which support
1549 hardware P state control (HWP) if available.
1551 Don't use ACPI processor performance control objects
1552 _PSS and _PPC specified limits.
1554 intremap= [X86-64, Intel-IOMMU]
1555 on enable Interrupt Remapping (default)
1556 off disable Interrupt Remapping
1557 nosid disable Source ID checking
1559 BIOS x2APIC opt-out request will be ignored
1561 iomem= Disable strict checking of access to MMIO memory
1562 strict regions from userspace.
1577 nobypass [PPC/POWERNV]
1578 Disable IOMMU bypass, using IOMMU for PCI devices.
1581 io7= [HW] IO7 for Marvel based alpha systems
1582 See comment before marvel_specify_io7 in
1583 arch/alpha/kernel/core_marvel.c.
1585 io_delay= [X86] I/O delay method
1587 Standard port 0x80 based delay
1589 Alternate port 0xed based delay (needed on some systems)
1591 Simple two microseconds delay
1596 See Documentation/filesystems/nfs/nfsroot.txt.
1599 When an interrupt is not handled search all handlers
1600 for it. Intended to get systems with badly broken
1604 When an interrupt is not handled search all handlers
1605 for it. Also check all handlers each timer
1606 interrupt. Intended to get systems with badly broken
1610 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1612 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1614 <cpu number>,...,<cpu number>
1616 <cpu number>-<cpu number>
1617 (must be a positive range in ascending order)
1619 <cpu number>,...,<cpu number>-<cpu number>
1621 This option can be used to specify one or more CPUs
1622 to isolate from the general SMP balancing and scheduling
1623 algorithms. You can move a process onto or off an
1624 "isolated" CPU via the CPU affinity syscalls or cpuset.
1625 <cpu number> begins at 0 and the maximum value is
1626 "number of CPUs in system - 1".
1628 This option is the preferred way to isolate CPUs. The
1629 alternative -- manually setting the CPU mask of all
1630 tasks in the system -- can cause problems and
1631 suboptimal load balancer performance.
1635 ivrs_ioapic [HW,X86_64]
1636 Provide an override to the IOAPIC-ID<->DEVICE-ID
1637 mapping provided in the IVRS ACPI table. For
1638 example, to map IOAPIC-ID decimal 10 to
1639 PCI device 00:14.0 write the parameter as:
1640 ivrs_ioapic[10]=00:14.0
1642 ivrs_hpet [HW,X86_64]
1643 Provide an override to the HPET-ID<->DEVICE-ID
1644 mapping provided in the IVRS ACPI table. For
1645 example, to map HPET-ID decimal 0 to
1646 PCI device 00:14.0 write the parameter as:
1647 ivrs_hpet[0]=00:14.0
1649 js= [HW,JOY] Analog joystick
1650 See Documentation/input/joystick.txt.
1653 Enable/disable kernel and module base offset ASLR
1654 (Address Space Layout Randomization) if built into
1655 the kernel. When CONFIG_HIBERNATION is selected,
1656 kASLR is disabled by default. When kASLR is enabled,
1657 hibernation will be disabled.
1661 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1662 specifies the amount of memory usable by the kernel
1663 for non-movable allocations. The requested amount is
1664 spread evenly throughout all nodes in the system. The
1665 remaining memory in each node is used for Movable
1666 pages. In the event, a node is too small to have both
1667 kernelcore and Movable pages, kernelcore pages will
1668 take priority and other nodes will have a larger number
1669 of Movable pages. The Movable zone is used for the
1670 allocation of pages that may be reclaimed or moved
1671 by the page migration subsystem. This means that
1672 HugeTLB pages may not be allocated from this zone.
1673 Note that allocations like PTEs-from-HighMem still
1674 use the HighMem zone if it exists, and the Normal
1675 zone if it does not.
1677 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1678 Format: <Controller#>[,poll interval]
1679 The controller # is the number of the ehci usb debug
1680 port as it is probed via PCI. The poll interval is
1681 optional and is the number seconds in between
1682 each poll cycle to the debug port in case you need
1683 the functionality for interrupting the kernel with
1684 gdb or control-c on the dbgp connection. When
1685 not using this parameter you use sysrq-g to break into
1686 the kernel debugger.
1688 kgdboc= [KGDB,HW] kgdb over consoles.
1689 Requires a tty driver that supports console polling,
1690 or a supported polling keyboard driver (non-usb).
1691 Serial only format: <serial_device>[,baud]
1692 keyboard only format: kbd
1693 keyboard and serial format: kbd,<serial_device>[,baud]
1694 Optional Kernel mode setting:
1695 kms, kbd format: kms,kbd
1696 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1698 kgdbwait [KGDB] Stop kernel execution and enter the
1699 kernel debugger at the earliest opportunity.
1701 kmac= [MIPS] korina ethernet MAC address.
1702 Configure the RouterBoard 532 series on-chip
1703 Ethernet adapter MAC address.
1705 kmemleak= [KNL] Boot-time kmemleak enable/disable
1706 Valid arguments: on, off
1708 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1711 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1712 Valid arguments: 0, 1, 2
1713 kmemcheck=0 (disabled)
1714 kmemcheck=1 (enabled)
1715 kmemcheck=2 (one-shot mode)
1716 Default: 2 (one-shot mode)
1718 kstack=N [X86] Print N words from the kernel stack
1721 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1722 Default is 0 (don't ignore, but inject #GP)
1724 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1728 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1729 Default is 1 (enabled)
1731 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1733 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1735 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1736 (virtualized MMU) support on capable Intel chips.
1737 Default is 1 (enabled)
1739 kvm-intel.emulate_invalid_guest_state=
1740 [KVM,Intel] Enable emulation of invalid guest states
1741 Default is 0 (disabled)
1743 kvm-intel.flexpriority=
1744 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1745 Default is 1 (enabled)
1748 [KVM,Intel] Enable VMX nesting (nVMX).
1749 Default is 0 (disabled)
1751 kvm-intel.unrestricted_guest=
1752 [KVM,Intel] Disable unrestricted guest feature
1753 (virtualized real and unpaged mode) on capable
1754 Intel chips. Default is 1 (enabled)
1756 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1757 feature (tagged TLBs) on capable Intel chips.
1758 Default is 1 (enabled)
1764 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1767 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1768 value for LAPIC timer one-shot implementation. Default
1769 back to the programmable timer unit in the LAPIC.
1771 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1774 libata.dma= [LIBATA] DMA control
1775 libata.dma=0 Disable all PATA and SATA DMA
1776 libata.dma=1 PATA and SATA Disk DMA only
1777 libata.dma=2 ATAPI (CDROM) DMA only
1778 libata.dma=4 Compact Flash DMA only
1779 Combinations also work, so libata.dma=3 enables DMA
1780 for disks and CDROMs, but not CFs.
1782 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1783 libata.ignore_hpa=0 keep BIOS limits (default)
1784 libata.ignore_hpa=1 ignore limits, using full disk
1786 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1790 libata.force= [LIBATA] Force configurations. The format is comma
1791 separated list of "[ID:]VAL" where ID is
1792 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1793 matching port, link or device. Basically, it matches
1794 the ATA ID string printed on console by libata. If
1795 the whole ID part is omitted, the last PORT and DEVICE
1796 values are used. If ID hasn't been specified yet, the
1797 configuration applies to all ports, links and devices.
1799 If only DEVICE is omitted, the parameter applies to
1800 the port and all links and devices behind it. DEVICE
1801 number of 0 either selects the first device or the
1802 first fan-out link behind PMP device. It does not
1803 select the host link. DEVICE number of 15 selects the
1804 host link and device attached to it.
1806 The VAL specifies the configuration to force. As long
1807 as there's no ambiguity shortcut notation is allowed.
1808 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1809 The following configurations can be forced.
1811 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1812 Any ID with matching PORT is used.
1814 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1816 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1817 udma[/][16,25,33,44,66,100,133] notation is also
1820 * [no]ncq: Turn on or off NCQ.
1822 * [no]ncqtrim: Turn off queued DSM TRIM.
1824 * nohrst, nosrst, norst: suppress hard, soft
1827 * rstonce: only attempt one reset during
1828 hot-unplug link recovery
1830 * dump_id: dump IDENTIFY data.
1832 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1834 * disable: Disable this device.
1836 If there are multiple matching configurations changing
1837 the same attribute, the last one is used.
1839 memblock=debug [KNL] Enable memblock debug messages.
1841 load_ramdisk= [RAM] List of ramdisks to load from floppy
1842 See Documentation/blockdev/ramdisk.txt.
1844 lockd.nlm_grace_period=P [NFS] Assign grace period.
1847 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1850 lockd.nlm_timeout=T [NFS] Assign timeout value.
1853 lockd.nlm_udpport=M [NFS] Assign UDP port.
1856 locktorture.nreaders_stress= [KNL]
1857 Set the number of locking read-acquisition kthreads.
1858 Defaults to being automatically set based on the
1859 number of online CPUs.
1861 locktorture.nwriters_stress= [KNL]
1862 Set the number of locking write-acquisition kthreads.
1864 locktorture.onoff_holdoff= [KNL]
1865 Set time (s) after boot for CPU-hotplug testing.
1867 locktorture.onoff_interval= [KNL]
1868 Set time (s) between CPU-hotplug operations, or
1869 zero to disable CPU-hotplug testing.
1871 locktorture.shuffle_interval= [KNL]
1872 Set task-shuffle interval (jiffies). Shuffling
1873 tasks allows some CPUs to go into dyntick-idle
1874 mode during the locktorture test.
1876 locktorture.shutdown_secs= [KNL]
1877 Set time (s) after boot system shutdown. This
1878 is useful for hands-off automated testing.
1880 locktorture.stat_interval= [KNL]
1881 Time (s) between statistics printk()s.
1883 locktorture.stutter= [KNL]
1884 Time (s) to stutter testing, for example,
1885 specifying five seconds causes the test to run for
1886 five seconds, wait for five seconds, and so on.
1887 This tests the locking primitive's ability to
1888 transition abruptly to and from idle.
1890 locktorture.torture_runnable= [BOOT]
1891 Start locktorture running at boot time.
1893 locktorture.torture_type= [KNL]
1894 Specify the locking implementation to test.
1896 locktorture.verbose= [KNL]
1897 Enable additional printk() statements.
1899 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1902 loglevel= All Kernel Messages with a loglevel smaller than the
1903 console loglevel will be printed to the console. It can
1904 also be changed with klogd or other programs. The
1905 loglevels are defined as follows:
1907 0 (KERN_EMERG) system is unusable
1908 1 (KERN_ALERT) action must be taken immediately
1909 2 (KERN_CRIT) critical conditions
1910 3 (KERN_ERR) error conditions
1911 4 (KERN_WARNING) warning conditions
1912 5 (KERN_NOTICE) normal but significant condition
1913 6 (KERN_INFO) informational
1914 7 (KERN_DEBUG) debug-level messages
1916 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1917 in bytes. n must be a power of two and greater
1918 than the minimal size. The minimal size is defined
1919 by LOG_BUF_SHIFT kernel config parameter. There is
1920 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1921 that allows to increase the default size depending on
1922 the number of CPUs. See init/Kconfig for more details.
1924 logo.nologo [FB] Disables display of the built-in Linux logo.
1925 This may be used to provide more screen space for
1926 kernel log messages and is useful when debugging
1927 kernel boot problems.
1929 lp=0 [LP] Specify parallel ports to use, e.g,
1930 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1931 lp=reset first parallel port). 'lp=0' disables the
1932 lp=auto printer driver. 'lp=reset' (which can be
1933 specified in addition to the ports) causes
1934 attached printers to be reset. Using
1935 lp=port1,port2,... specifies the parallel ports
1936 to associate lp devices with, starting with
1937 lp0. A port specification may be 'none' to skip
1938 that lp device, or a parport name such as
1939 'parport0'. Specifying 'lp=auto' instead of a
1940 port specification list means that device IDs
1941 from each port should be examined, to see if
1942 an IEEE 1284-compliant printer is attached; if
1943 so, the driver will manage that printer.
1944 See also header of drivers/char/lp.c.
1947 Sets loops_per_jiffy to given constant, thus avoiding
1948 time-consuming boot-time autodetection (up to 250 ms per
1949 CPU). 0 enables autodetection (default). To determine
1950 the correct value for your kernel, boot with normal
1951 autodetection and see what value is printed. Note that
1952 on SMP systems the preset will be applied to all CPUs,
1953 which is likely to cause problems if your CPUs need
1954 significantly divergent settings. An incorrect value
1955 will cause delays in the kernel to be wrong, leading to
1956 unpredictable I/O errors and other breakage. Although
1957 unlikely, in the extreme case this might damage your
1961 Format: <io>,<irq>,<dma>
1963 machvec= [IA-64] Force the use of a particular machine-vector
1964 (machvec) in a generic kernel.
1965 Example: machvec=hpzx1_swiotlb
1967 machtype= [Loongson] Share the same kernel image file between different
1969 Example: machtype=lemote-yeeloong-2f-7inch
1971 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1972 than or equal to this physical address is ignored.
1974 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1975 should make use of. maxcpus=n : n >= 0 limits the
1976 kernel to using 'n' processors. n=0 is a special case,
1977 it is equivalent to "nosmp", which also disables
1980 max_loop= [LOOP] The number of loop block devices that get
1981 (loop.max_loop) unconditionally pre-created at init time. The default
1982 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1983 of statically allocating a predefined number, loop
1984 devices can be requested on-demand with the
1985 /dev/loop-control interface.
1987 mce [X86-32] Machine Check Exception
1989 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1991 md= [HW] RAID subsystems devices and level
1992 See Documentation/md.txt.
1995 Format: <first>,<last>
1996 Specifies range of consoles to be captured by the MDA.
1998 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1999 Amount of memory to be used when the kernel is not able
2000 to see the whole system memory or for test.
2001 [X86] Work as limiting max address. Use together
2002 with memmap= to avoid physical address space collisions.
2003 Without memmap= PCI devices could be placed at addresses
2004 belonging to unused RAM.
2006 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2010 [KNL,SH] Allow user to override the default size for
2011 per-device physically contiguous DMA buffers.
2013 memmap=exactmap [KNL,X86] Enable setting of an exact
2014 E820 memory map, as specified by the user.
2015 Such memmap=exactmap lines can be constructed based on
2016 BIOS output or other requirements. See the memmap=nn@ss
2019 memmap=nn[KMG]@ss[KMG]
2020 [KNL] Force usage of a specific region of memory.
2021 Region of memory to be used is from ss to ss+nn.
2023 memmap=nn[KMG]#ss[KMG]
2024 [KNL,ACPI] Mark specific memory as ACPI data.
2025 Region of memory to be marked is from ss to ss+nn.
2027 memmap=nn[KMG]$ss[KMG]
2028 [KNL,ACPI] Mark specific memory as reserved.
2029 Region of memory to be reserved is from ss to ss+nn.
2030 Example: Exclude memory from 0x18690000-0x1869ffff
2031 memmap=64K$0x18690000
2033 memmap=0x10000$0x18690000
2035 memmap=nn[KMG]!ss[KMG]
2036 [KNL,X86] Mark specific memory as protected.
2037 Region of memory to be used, from ss to ss+nn.
2038 The memory region may be marked as e820 type 12 (0xc)
2039 and is NVDIMM or ADR memory.
2041 memory_corruption_check=0/1 [X86]
2042 Some BIOSes seem to corrupt the first 64k of
2043 memory when doing things like suspend/resume.
2044 Setting this option will scan the memory
2045 looking for corruption. Enabling this will
2046 both detect corruption and prevent the kernel
2047 from using the memory being corrupted.
2048 However, its intended as a diagnostic tool; if
2049 repeatable BIOS-originated corruption always
2050 affects the same memory, you can use memmap=
2051 to prevent the kernel from using that memory.
2053 memory_corruption_check_size=size [X86]
2054 By default it checks for corruption in the low
2055 64k, making this memory unavailable for normal
2056 use. Use this parameter to scan for
2057 corruption in more or less memory.
2059 memory_corruption_check_period=seconds [X86]
2060 By default it checks for corruption every 60
2061 seconds. Use this parameter to check at some
2062 other rate. 0 disables periodic checking.
2064 memtest= [KNL,X86,ARM] Enable memtest
2066 default : 0 <disable>
2067 Specifies the number of memtest passes to be
2068 performed. Each pass selects another test
2069 pattern from a given set of patterns. Memtest
2070 fills the memory with this pattern, validates
2071 memory contents and reserves bad memory
2072 regions that are detected.
2074 meye.*= [HW] Set MotionEye Camera parameters
2075 See Documentation/video4linux/meye.txt.
2077 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2078 Multi-Function General Purpose Timers on AMD Geode
2081 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2082 the BIOS has incorrectly applied a workaround. TinyBIOS
2083 version 0.98 is known to be affected, 0.99 fixes the
2084 problem by letting the user disable the workaround.
2088 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2089 physical address is ignored.
2091 mini2440= [ARM,HW,KNL]
2092 Format:[0..2][b][c][t]
2094 MINI2440 configuration specification:
2095 0 - The attached screen is the 3.5" TFT
2096 1 - The attached screen is the 7" TFT
2097 2 - The VGA Shield is attached (1024x768)
2098 Leaving out the screen size parameter will not load
2099 the TFT driver, and the framebuffer will be left
2101 b - Enable backlight. The TFT backlight pin will be
2102 linked to the kernel VESA blanking code and a GPIO
2103 LED. This parameter is not necessary when using the
2105 c - Enable the s3c camera interface.
2106 t - Reserved for enabling touchscreen support. The
2107 touchscreen support is not enabled in the mainstream
2108 kernel as of 2.6.30, a preliminary port can be found
2109 in the "bleeding edge" mini2440 support kernel at
2110 http://repo.or.cz/w/linux-2.6/mini2440.git
2113 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2114 parameter allows control of the logging verbosity for
2115 the additional memory initialisation checks. A value
2116 of 0 disables mminit logging and a level of 4 will
2117 log everything. Information is printed at KERN_DEBUG
2118 so loglevel=8 may also need to be specified.
2121 [KNL] When CONFIG_MODULE_SIG is set, this means that
2122 modules without (valid) signatures will fail to load.
2123 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2124 is always true, so this option does nothing.
2127 [MOUSE] Maximum time between finger touching and
2128 leaving touchpad surface for touch to be considered
2129 a tap and be reported as a left button click (for
2130 touchpads working in absolute mode only).
2132 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2133 reporting absolute coordinates, such as tablets
2134 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2135 reporting absolute coordinates, such as tablets
2137 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2138 is similar to kernelcore except it specifies the
2139 amount of memory used for migratable allocations.
2140 If both kernelcore and movablecore is specified,
2141 then kernelcore will be at *least* the specified
2142 value but may be more. If movablecore on its own
2143 is specified, the administrator must be careful
2144 that the amount of memory usable for all allocations
2147 movable_node [KNL,X86] Boot-time switch to enable the effects
2148 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2150 MTD_Partition= [MTD]
2151 Format: <name>,<region-number>,<size>,<offset>
2153 MTD_Region= [MTD] Format:
2154 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2157 See drivers/mtd/cmdlinepart.c.
2159 multitce=off [PPC] This parameter disables the use of the pSeries
2160 firmware feature for updating multiple TCE entries
2163 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2165 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2167 boundary - index of last SLC block on Flex-OneNAND.
2168 The remaining blocks are configured as MLC blocks.
2169 lock - Configure if Flex-OneNAND boundary should be locked.
2170 Once locked, the boundary cannot be changed.
2171 1 indicates lock status, 0 indicates unlock status.
2174 ARM/S3C2412 JIVE boot control
2176 See arch/arm/mach-s3c2412/mach-jive.c
2178 mtouchusb.raw_coordinates=
2179 [HW] Make the MicroTouch USB driver use raw coordinates
2180 ('y', default) or cooked coordinates ('n')
2182 mtrr_chunk_size=nn[KMG] [X86]
2183 used for mtrr cleanup. It is largest continuous chunk
2184 that could hold holes aka. UC entries.
2186 mtrr_gran_size=nn[KMG] [X86]
2187 Used for mtrr cleanup. It is granularity of mtrr block.
2189 Large value could prevent small alignment from
2192 mtrr_spare_reg_nr=n [X86]
2194 Range: 0,7 : spare reg number
2196 Used for mtrr cleanup. It is spare mtrr entries number.
2197 Set to 2 or more if your graphical card needs more.
2199 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2201 netdev= [NET] Network devices parameters
2202 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2203 Note that mem_start is often overloaded to mean
2204 something different and driver-specific.
2205 This usage is only documented in each driver source
2209 [NETFILTER] Enable connection tracking flow accounting
2210 0 to disable accounting
2211 1 to enable accounting
2214 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2215 See Documentation/filesystems/nfs/nfsroot.txt.
2217 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2218 See Documentation/filesystems/nfs/nfsroot.txt.
2220 nfsrootdebug [NFS] enable nfsroot debugging messages.
2221 See Documentation/filesystems/nfs/nfsroot.txt.
2223 nfs.callback_tcpport=
2224 [NFS] set the TCP port on which the NFSv4 callback
2225 channel should listen.
2228 [NFS] sets the pathname to the program which is used
2229 to update the NFS client cache entries.
2231 nfs.cache_getent_timeout=
2232 [NFS] sets the timeout after which an attempt to
2233 update a cache entry is deemed to have failed.
2235 nfs.idmap_cache_timeout=
2236 [NFS] set the maximum lifetime for idmapper cache
2240 [NFS] enable 64-bit inode numbers.
2241 If zero, the NFS client will fake up a 32-bit inode
2242 number for the readdir() and stat() syscalls instead
2243 of returning the full 64-bit number.
2244 The default is to return 64-bit inode numbers.
2246 nfs.max_session_slots=
2247 [NFSv4.1] Sets the maximum number of session slots
2248 the client will attempt to negotiate with the server.
2249 This limits the number of simultaneous RPC requests
2250 that the client can send to the NFSv4.1 server.
2251 Note that there is little point in setting this
2252 value higher than the max_tcp_slot_table_limit.
2254 nfs.nfs4_disable_idmapping=
2255 [NFSv4] When set to the default of '1', this option
2256 ensures that both the RPC level authentication
2257 scheme and the NFS level operations agree to use
2258 numeric uids/gids if the mount is using the
2259 'sec=sys' security flavour. In effect it is
2260 disabling idmapping, which can make migration from
2261 legacy NFSv2/v3 systems to NFSv4 easier.
2262 Servers that do not support this mode of operation
2263 will be autodetected by the client, and it will fall
2264 back to using the idmapper.
2265 To turn off this behaviour, set the value to '0'.
2267 [NFS4] Specify an additional fixed unique ident-
2268 ification string that NFSv4 clients can insert into
2269 their nfs_client_id4 string. This is typically a
2270 UUID that is generated at system install time.
2272 nfs.send_implementation_id =
2273 [NFSv4.1] Send client implementation identification
2274 information in exchange_id requests.
2275 If zero, no implementation identification information
2277 The default is to send the implementation identification
2280 nfs.recover_lost_locks =
2281 [NFSv4] Attempt to recover locks that were lost due
2282 to a lease timeout on the server. Please note that
2283 doing this risks data corruption, since there are
2284 no guarantees that the file will remain unchanged
2285 after the locks are lost.
2286 If you want to enable the kernel legacy behaviour of
2287 attempting to recover these locks, then set this
2289 The default parameter value of '0' causes the kernel
2290 not to attempt recovery of lost locks.
2292 nfs4.layoutstats_timer =
2293 [NFSv4.2] Change the rate at which the kernel sends
2294 layoutstats to the pNFS metadata server.
2296 Setting this to value to 0 causes the kernel to use
2297 whatever value is the default set by the layout
2298 driver. A non-zero value sets the minimum interval
2299 in seconds between layoutstats transmissions.
2301 nfsd.nfs4_disable_idmapping=
2302 [NFSv4] When set to the default of '1', the NFSv4
2303 server will return only numeric uids and gids to
2304 clients using auth_sys, and will accept numeric uids
2305 and gids from such clients. This is intended to ease
2306 migration from NFSv2/v3.
2308 objlayoutdriver.osd_login_prog=
2309 [NFS] [OBJLAYOUT] sets the pathname to the program which
2310 is used to automatically discover and login into new
2311 osd-targets. Please see:
2312 Documentation/filesystems/pnfs.txt for more explanations
2314 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2315 when a NMI is triggered.
2316 Format: [state][,regs][,debounce][,die]
2318 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2319 Format: [panic,][nopanic,][num]
2321 0 - turn nmi_watchdog off
2322 1 - turn nmi_watchdog on
2323 When panic is specified, panic when an NMI watchdog
2324 timeout occurs (or 'nopanic' to override the opposite
2326 This is useful when you use a panic=... timeout and
2327 need the box quickly up again.
2329 netpoll.carrier_timeout=
2330 [NET] Specifies amount of time (in seconds) that
2331 netpoll should wait for a carrier. By default netpoll
2334 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2335 emulation library even if a 387 maths coprocessor
2339 [HW] Never suspend the console
2340 Disable suspending of consoles during suspend and
2341 hibernate operations. Once disabled, debugging
2342 messages can reach various consoles while the rest
2343 of the system is being put to sleep (ie, while
2344 debugging driver suspend/resume hooks). This may
2345 not work reliably with all consoles, but is known
2346 to work with serial and VGA consoles.
2347 To facilitate more flexible debugging, we also add
2348 console_suspend, a printk module parameter to control
2349 it. Users could use console_suspend (usually
2350 /sys/module/printk/parameters/console_suspend) to
2351 turn on/off it dynamically.
2353 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2354 caches in the slab allocator. Saves per-node memory,
2355 but will impact performance.
2359 noapic [SMP,APIC] Tells the kernel to not make use of any
2360 IOAPICs that may be present in the system.
2362 noautogroup Disable scheduler automatic task group creation.
2364 nobats [PPC] Do not use BATs for mapping kernel lowmem
2365 on "Classic" PPC cores.
2369 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2371 nodelayacct [KNL] Disable per-task delay accounting
2373 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2375 nodsp [SH] Disable hardware DSP at boot time.
2377 noefi Disable EFI runtime services support.
2382 On X86-32 available only on PAE configured kernels.
2383 noexec=on: enable non-executable mappings (default)
2384 noexec=off: disable non-executable mappings
2387 Disable SMAP (Supervisor Mode Access Prevention)
2388 even if it is supported by processor.
2391 Disable SMEP (Supervisor Mode Execution Prevention)
2392 even if it is supported by processor.
2395 This affects only 32-bit executables.
2396 noexec32=on: enable non-executable mappings (default)
2397 read doesn't imply executable mappings
2398 noexec32=off: disable non-executable mappings
2399 read implies executable mappings
2401 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2403 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2404 register save and restore. The kernel will only save
2405 legacy floating-point registers on task switch.
2407 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2409 noxsave [BUGS=X86] Disables x86 extended register state save
2410 and restore using xsave. The kernel will fallback to
2411 enabling legacy floating-point and sse state.
2413 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2414 register states. The kernel will fall back to use
2415 xsave to save the states. By using this parameter,
2416 performance of saving the states is degraded because
2417 xsave doesn't support modified optimization while
2418 xsaveopt supports it on xsaveopt enabled systems.
2420 noxsaves [X86] Disables xsaves and xrstors used in saving and
2421 restoring x86 extended register state in compacted
2422 form of xsave area. The kernel will fall back to use
2423 xsaveopt and xrstor to save and restore the states
2424 in standard form of xsave area. By using this
2425 parameter, xsave area per process might occupy more
2426 memory on xsaves enabled systems.
2428 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2429 wfi(ARM) instruction doesn't work correctly and not to
2430 use it. This is also useful when using JTAG debugger.
2432 no_file_caps Tells the kernel not to honor file capabilities. The
2433 only way then for a file to be executed with privilege
2434 is to be setuid root or executed by root.
2436 nohalt [IA-64] Tells the kernel not to use the power saving
2437 function PAL_HALT_LIGHT when idle. This increases
2438 power-consumption. On the positive side, it reduces
2439 interrupt wake-up latency, which may improve performance
2440 in certain environments such as networked servers or
2443 nohibernate [HIBERNATION] Disable hibernation and resume.
2445 nohz= [KNL] Boottime enable/disable dynamic ticks
2446 Valid arguments: on, off
2449 nohz_full= [KNL,BOOT]
2450 In kernels built with CONFIG_NO_HZ_FULL=y, set
2451 the specified list of CPUs whose tick will be stopped
2452 whenever possible. The boot CPU will be forced outside
2453 the range to maintain the timekeeping.
2454 The CPUs in this range must also be included in the
2457 noiotrap [SH] Disables trapped I/O port accesses.
2459 noirqdebug [X86-32] Disables the code which attempts to detect and
2460 disable unhandled interrupt sources.
2462 no_timer_check [X86,APIC] Disables the code which tests for
2463 broken timer IRQ sources.
2465 noisapnp [ISAPNP] Disables ISA PnP code.
2467 noinitrd [RAM] Tells the kernel not to load any configured
2470 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2472 [Deprecated - use intremap=off]
2476 nojitter [IA-64] Disables jitter checking for ITC timers.
2478 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2480 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2483 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2484 steal time is computed, but won't influence scheduler
2487 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2489 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2491 noltlbs [PPC] Do not use large page/tlb entries for kernel
2492 lowmem mapping on PPC40x.
2494 nomca [IA-64] Disable machine check abort handling
2496 nomce [X86-32] Disable Machine Check Exception
2498 nomfgpt [X86-32] Disable Multi-Function General Purpose
2499 Timer usage (for AMD Geode machines).
2501 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2502 shutdown the other cpus. Instead use the REBOOT_VECTOR
2505 nomodule Disable module load
2507 nopat [X86] Disable PAT (page attribute table extension of
2508 pagetables) support.
2510 norandmaps Don't use address space randomization. Equivalent to
2511 echo 0 > /proc/sys/kernel/randomize_va_space
2513 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2515 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2516 with UP alternatives
2518 nordrand [X86] Disable kernel use of the RDRAND and
2519 RDSEED instructions even if they are supported
2520 by the processor. RDRAND and RDSEED are still
2521 available to user space applications.
2523 noresume [SWSUSP] Disables resume and restores original swap
2526 no-scroll [VGA] Disables scrollback.
2527 This is required for the Braillex ib80-piezo Braille
2528 reader made by F.H. Papenmeier (Germany).
2532 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2534 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2535 and disable the IO APIC. legacy for "maxcpus=0".
2537 nosoftlockup [KNL] Disable the soft-lockup detector.
2539 nosync [HW,M68K] Disables sync negotiation for all devices.
2541 notsc [BUGS=X86-32] Disable Time Stamp Counter
2543 nousb [USB] Disable the USB subsystem
2545 nowatchdog [KNL] Disable both lockup detectors, i.e.
2546 soft-lockup and NMI watchdog (hard-lockup).
2550 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2552 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2553 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2554 Some features depend on CPU0. Known dependencies are:
2555 1. Resume from suspend/hibernate depends on CPU0.
2556 Suspend/hibernate will fail if CPU0 is offline and you
2557 need to online CPU0 before suspend/hibernate.
2558 2. PIC interrupts also depend on CPU0. CPU0 can't be
2559 removed if a PIC interrupt is detected.
2560 It's said poweroff/reboot may depend on CPU0 on some
2561 machines although I haven't seen such issues so far
2562 after CPU0 is offline on a few tested machines.
2563 If the dependencies are under your control, you can
2564 turn on cpu0_hotplug.
2566 nptcg= [IA-64] Override max number of concurrent global TLB
2567 purges which is reported from either PAL_VM_SUMMARY or
2570 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2571 could support. nr_cpus=n : n >= 1 limits the kernel to
2572 supporting 'n' processors. Later in runtime you can not
2573 use hotplug cpu feature to put more cpu back to online.
2574 just like you compile the kernel NR_CPUS=n
2576 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2578 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2579 Allowed values are enable and disable
2581 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2582 one of ['zone', 'node', 'default'] can be specified
2583 This can be set from sysctl after boot.
2584 See Documentation/sysctl/vm.txt for details.
2586 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2587 See Documentation/debugging-via-ohci1394.txt for more
2590 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2591 Rather than timing out after 20 ms if an EC
2592 command is not properly ACKed, override the length
2593 of the timeout. We have interrupts disabled while
2594 waiting for the ACK, so if this is set too high
2595 interrupts *may* be lost!
2597 omap_mux= [OMAP] Override bootloader pin multiplexing.
2598 Format: <mux_mode0.mode_name=value>...
2599 For example, to override I2C bus2:
2600 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2602 oprofile.timer= [HW]
2603 Use timer interrupt instead of performance counters
2605 oprofile.cpu_type= Force an oprofile cpu type
2606 This might be useful if you have an older oprofile
2607 userland or if you want common events.
2608 Format: { arch_perfmon }
2609 arch_perfmon: [X86] Force use of architectural
2610 perfmon on Intel CPUs instead of the
2611 CPU specific event set.
2612 timer: [X86] Force use of architectural NMI
2613 timer mode (see also oprofile.timer
2614 for generic hr timer mode)
2615 [s390] Force legacy basic mode sampling
2616 (report cpu_type "timer")
2618 oops=panic Always panic on oopses. Default is to just kill the
2619 process, but there is a small probability of
2620 deadlocking the machine.
2621 This will also cause panics on machine check exceptions.
2622 Useful together with panic=30 to trigger a reboot.
2625 See Documentation/sound/oss/oss-parameters.txt
2627 page_owner= [KNL] Boot-time page_owner enabling option.
2628 Storage of the information about who allocated
2629 each page is disabled in default. With this switch,
2631 on: enable the feature
2633 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2634 timeout > 0: seconds before rebooting
2635 timeout = 0: wait forever
2636 timeout < 0: reboot immediately
2639 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2642 crash_kexec_post_notifiers
2643 Run kdump after running panic-notifiers and dumping
2644 kmsg. This only for the users who doubt kdump always
2645 succeeds in any situation.
2646 Note that this also increases risks of kdump failure,
2647 because some panic notifiers can make the crashed
2648 kernel more unstable.
2650 parkbd.port= [HW] Parallel port number the keyboard adapter is
2651 connected to, default is 0.
2653 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2654 0 for XT, 1 for AT (default is AT).
2657 parport= [HW,PPT] Specify parallel ports. 0 disables.
2658 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2659 Use 'auto' to force the driver to use any
2660 IRQ/DMA settings detected (the default is to
2661 ignore detected IRQ/DMA settings because of
2662 possible conflicts). You can specify the base
2663 address, IRQ, and DMA settings; IRQ and DMA
2664 should be numbers, or 'auto' (for using detected
2665 settings on that particular port), or 'nofifo'
2666 (to avoid using a FIFO even if it is detected).
2667 Parallel ports are assigned in the order they
2668 are specified on the command line, starting
2671 parport_init_mode= [HW,PPT]
2672 Configure VIA parallel port to operate in
2673 a specific mode. This is necessary on Pegasos
2674 computer where firmware has no options for setting
2675 up parallel port mode and sets it to spp.
2676 Currently this function knows 686a and 8231 chips.
2677 Format: [spp|ps2|epp|ecp|ecpepp]
2680 Halt all CPUs after the first oops has been printed for
2681 the specified number of seconds. This is to be used if
2682 your oopses keep scrolling off the screen.
2687 See header of drivers/block/paride/pcd.c.
2688 See also Documentation/blockdev/paride.txt.
2690 pci=option[,option...] [PCI] various PCI subsystem options:
2691 earlydump [X86] dump PCI config space before the kernel
2693 off [X86] don't probe for the PCI bus
2694 bios [X86-32] force use of PCI BIOS, don't access
2695 the hardware directly. Use this if your machine
2696 has a non-standard PCI host bridge.
2697 nobios [X86-32] disallow use of PCI BIOS, only direct
2698 hardware access methods are allowed. Use this
2699 if you experience crashes upon bootup and you
2700 suspect they are caused by the BIOS.
2701 conf1 [X86] Force use of PCI Configuration
2703 conf2 [X86] Force use of PCI Configuration
2705 noaer [PCIE] If the PCIEAER kernel config parameter is
2706 enabled, this kernel boot option can be used to
2707 disable the use of PCIE advanced error reporting.
2708 nodomains [PCI] Disable support for multiple PCI
2709 root domains (aka PCI segments, in ACPI-speak).
2710 nommconf [X86] Disable use of MMCONFIG for PCI
2712 check_enable_amd_mmconf [X86] check for and enable
2713 properly configured MMIO access to PCI
2714 config space on AMD family 10h CPU
2715 nomsi [MSI] If the PCI_MSI kernel config parameter is
2716 enabled, this kernel boot option can be used to
2717 disable the use of MSI interrupts system-wide.
2718 noioapicquirk [APIC] Disable all boot interrupt quirks.
2719 Safety option to keep boot IRQs enabled. This
2720 should never be necessary.
2721 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2722 primary IO-APIC for bridges that cannot disable
2723 boot IRQs. This fixes a source of spurious IRQs
2724 when the system masks IRQs.
2725 noioapicreroute [APIC] Disable workaround that uses the
2726 boot IRQ equivalent of an IRQ that connects to
2727 a chipset where boot IRQs cannot be disabled.
2728 The opposite of ioapicreroute.
2729 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2730 routing table. These calls are known to be buggy
2731 on several machines and they hang the machine
2732 when used, but on other computers it's the only
2733 way to get the interrupt routing table. Try
2734 this option if the kernel is unable to allocate
2735 IRQs or discover secondary PCI buses on your
2737 rom [X86] Assign address space to expansion ROMs.
2738 Use with caution as certain devices share
2739 address decoders between ROMs and other
2741 norom [X86] Do not assign address space to
2742 expansion ROMs that do not already have
2743 BIOS assigned address ranges.
2744 nobar [X86] Do not assign address space to the
2745 BARs that weren't assigned by the BIOS.
2746 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2747 assigned automatically to PCI devices. You can
2748 make the kernel exclude IRQs of your ISA cards
2750 pirqaddr=0xAAAAA [X86] Specify the physical address
2751 of the PIRQ table (normally generated
2752 by the BIOS) if it is outside the
2753 F0000h-100000h range.
2754 lastbus=N [X86] Scan all buses thru bus #N. Can be
2755 useful if the kernel is unable to find your
2756 secondary buses and you want to tell it
2757 explicitly which ones they are.
2758 assign-busses [X86] Always assign all PCI bus
2759 numbers ourselves, overriding
2760 whatever the firmware may have done.
2761 usepirqmask [X86] Honor the possible IRQ mask stored
2762 in the BIOS $PIR table. This is needed on
2763 some systems with broken BIOSes, notably
2764 some HP Pavilion N5400 and Omnibook XE3
2765 notebooks. This will have no effect if ACPI
2766 IRQ routing is enabled.
2767 noacpi [X86] Do not use ACPI for IRQ routing
2768 or for PCI scanning.
2769 use_crs [X86] Use PCI host bridge window information
2770 from ACPI. On BIOSes from 2008 or later, this
2771 is enabled by default. If you need to use this,
2772 please report a bug.
2773 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2774 If you need to use this, please report a bug.
2775 routeirq Do IRQ routing for all PCI devices.
2776 This is normally done in pci_enable_device(),
2777 so this option is a temporary workaround
2778 for broken drivers that don't call it.
2779 skip_isa_align [X86] do not align io start addr, so can
2780 handle more pci cards
2781 firmware [ARM] Do not re-enumerate the bus but instead
2782 just use the configuration from the
2783 bootloader. This is currently used on
2784 IXP2000 systems where the bus has to be
2785 configured a certain way for adjunct CPUs.
2786 noearly [X86] Don't do any early type 1 scanning.
2787 This might help on some broken boards which
2788 machine check when some devices' config space
2789 is read. But various workarounds are disabled
2790 and some IOMMU drivers will not work.
2791 bfsort Sort PCI devices into breadth-first order.
2792 This sorting is done to get a device
2793 order compatible with older (<= 2.4) kernels.
2794 nobfsort Don't sort PCI devices into breadth-first order.
2795 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2796 tuning and use the BIOS-configured MPS defaults.
2797 pcie_bus_safe Set every device's MPS to the largest value
2798 supported by all devices below the root complex.
2799 pcie_bus_perf Set device MPS to the largest allowable MPS
2800 based on its parent bus. Also set MRRS (Max
2801 Read Request Size) to the largest supported
2802 value (no larger than the MPS that the device
2803 or bus can support) for best performance.
2804 pcie_bus_peer2peer Set every device's MPS to 128B, which
2805 every device is guaranteed to support. This
2806 configuration allows peer-to-peer DMA between
2807 any pair of devices, possibly at the cost of
2808 reduced performance. This also guarantees
2809 that hot-added devices will work.
2810 cbiosize=nn[KMG] The fixed amount of bus space which is
2811 reserved for the CardBus bridge's IO window.
2812 The default value is 256 bytes.
2813 cbmemsize=nn[KMG] The fixed amount of bus space which is
2814 reserved for the CardBus bridge's memory
2815 window. The default value is 64 megabytes.
2818 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2819 Specifies alignment and device to reassign
2820 aligned memory resources.
2821 If <order of align> is not specified,
2822 PAGE_SIZE is used as alignment.
2823 PCI-PCI bridge can be specified, if resource
2824 windows need to be expanded.
2825 ecrc= Enable/disable PCIe ECRC (transaction layer
2826 end-to-end CRC checking).
2827 bios: Use BIOS/firmware settings. This is the
2831 hpiosize=nn[KMG] The fixed amount of bus space which is
2832 reserved for hotplug bridge's IO window.
2833 Default size is 256 bytes.
2834 hpmemsize=nn[KMG] The fixed amount of bus space which is
2835 reserved for hotplug bridge's memory window.
2836 Default size is 2 megabytes.
2837 realloc= Enable/disable reallocating PCI bridge resources
2838 if allocations done by BIOS are too small to
2839 accommodate resources required by all child
2841 off: Turn realloc off
2843 realloc same as realloc=on
2844 noari do not use PCIe ARI.
2845 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2846 only look for one device below a PCIe downstream
2849 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2852 force Enable ASPM even on devices that claim not to support it.
2853 WARNING: Forcing ASPM on may cause system lockups.
2855 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2856 nomsi Do not use MSI for PCI Express Native Hotplug (this
2857 makes all PCIe ports use INTx for hotplug services).
2859 pcie_ports= [PCIE] PCIe ports handling:
2860 auto Ask the BIOS whether or not to use native PCIe services
2861 associated with PCIe ports (PME, hot-plug, AER). Use
2862 them only if that is allowed by the BIOS.
2863 native Use native PCIe services associated with PCIe ports
2865 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2868 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2869 nomsi Do not use MSI for native PCIe PME signaling (this makes
2870 all PCIe root ports use INTx for all services).
2872 pcmv= [HW,PCMCIA] BadgePAD 4
2876 Keep all power-domains already enabled by bootloader on,
2877 even if no driver has claimed them. This is useful
2878 for debug and development, but should not be
2879 needed on a platform with proper driver support.
2882 See Documentation/blockdev/paride.txt.
2884 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2887 See arch/parisc/kernel/pdc_chassis.c
2889 percpu_alloc= Select which percpu first chunk allocator to use.
2890 Currently supported values are "embed" and "page".
2891 Archs may support subset or none of the selections.
2892 See comments in mm/percpu.c for details on each
2893 allocator. This parameter is primarily for debugging
2894 and performance comparison.
2897 See Documentation/blockdev/paride.txt.
2900 See Documentation/blockdev/paride.txt.
2902 pirq= [SMP,APIC] Manual mp-table setup
2903 See Documentation/x86/i386/IO-APIC.txt.
2905 plip= [PPT,NET] Parallel port network link
2906 Format: { parport<nr> | timid | 0 }
2907 See also Documentation/parport.txt.
2909 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2910 Override pmtimer IOPort with a hex value.
2914 Enable PNP debug messages (depends on the
2915 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2916 via /sys/module/pnp/parameters/debug. We always show
2917 current resource usage; turning this on also shows
2918 possible settings and some assignment information.
2924 { on | off | curr | res | no-curr | no-res }
2927 [ISAPNP] Exclude IRQs for the autoconfiguration
2930 [ISAPNP] Exclude DMAs for the autoconfiguration
2932 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2933 Ranges are in pairs (I/O port base and size).
2936 [ISAPNP] Exclude memory regions for the
2938 Ranges are in pairs (memory base and size).
2940 ports= [IP_VS_FTP] IPVS ftp helper module
2942 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2944 Format: <port>,<port>....
2946 print-fatal-signals=
2947 [KNL] debug: print fatal signals
2949 If enabled, warn about various signal handling
2950 related application anomalies: too many signals,
2951 too many POSIX.1 timers, fatal signals causing a
2954 If you hit the warning due to signal overflow,
2955 you might want to try "ulimit -i unlimited".
2959 printk.always_kmsg_dump=
2960 Trigger kmsg_dump for cases other than kernel oops or
2962 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2965 printk.time= Show timing data prefixed to each printk message line
2966 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2968 processor.max_cstate= [HW,ACPI]
2969 Limit processor to maximum C-state
2970 max_cstate=9 overrides any DMI blacklist limit.
2972 processor.nocst [HW,ACPI]
2973 Ignore the _CST method to determine C-states,
2974 instead using the legacy FADT method
2976 profile= [KNL] Enable kernel profiling via /proc/profile
2977 Format: [schedule,]<number>
2978 Param: "schedule" - profile schedule points.
2979 Param: <number> - step/bucket size as a power of 2 for
2980 statistical time based profiling.
2981 Param: "sleep" - profile D-state sleeping (millisecs).
2982 Requires CONFIG_SCHEDSTATS
2983 Param: "kvm" - profile VM exits.
2985 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2987 See Documentation/blockdev/ramdisk.txt.
2989 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2990 probe for; one of (bare|imps|exps|lifebook|any).
2991 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2993 psmouse.resetafter= [HW,MOUSE]
2994 Try to reset the device after so many bad packets
2997 [HW,MOUSE] Set desired mouse resolution, in dpi.
2998 psmouse.smartscroll=
2999 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3000 0 = disabled, 1 = enabled (default).
3002 pstore.backend= Specify the name of the pstore backend to use
3005 See Documentation/blockdev/paride.txt.
3008 [KNL] Number of legacy pty's. Overwrites compiled-in
3011 quiet [KNL] Disable most log messages
3016 See Documentation/md.txt.
3018 ramdisk_blocksize= [RAM]
3019 See Documentation/blockdev/ramdisk.txt.
3021 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3022 See Documentation/blockdev/ramdisk.txt.
3025 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3026 the specified list of CPUs to be no-callback CPUs.
3027 Invocation of these CPUs' RCU callbacks will
3028 be offloaded to "rcuox/N" kthreads created for
3029 that purpose, where "x" is "b" for RCU-bh, "p"
3030 for RCU-preempt, and "s" for RCU-sched, and "N"
3031 is the CPU number. This reduces OS jitter on the
3032 offloaded CPUs, which can be useful for HPC and
3033 real-time workloads. It can also improve energy
3034 efficiency for asymmetric multiprocessors.
3037 Rather than requiring that offloaded CPUs
3038 (specified by rcu_nocbs= above) explicitly
3039 awaken the corresponding "rcuoN" kthreads,
3040 make these kthreads poll for callbacks.
3041 This improves the real-time response for the
3042 offloaded CPUs by relieving them of the need to
3043 wake up the corresponding kthread, but degrades
3044 energy efficiency by requiring that the kthreads
3045 periodically wake up to do the polling.
3047 rcutree.blimit= [KNL]
3048 Set maximum number of finished RCU callbacks to
3049 process in one batch.
3051 rcutree.dump_tree= [KNL]
3052 Dump the structure of the rcu_node combining tree
3053 out at early boot. This is used for diagnostic
3054 purposes, to verify correct tree setup.
3056 rcutree.gp_cleanup_delay= [KNL]
3057 Set the number of jiffies to delay each step of
3058 RCU grace-period cleanup. This only has effect
3059 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3061 rcutree.gp_init_delay= [KNL]
3062 Set the number of jiffies to delay each step of
3063 RCU grace-period initialization. This only has
3064 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3067 rcutree.gp_preinit_delay= [KNL]
3068 Set the number of jiffies to delay each step of
3069 RCU grace-period pre-initialization, that is,
3070 the propagation of recent CPU-hotplug changes up
3071 the rcu_node combining tree. This only has effect
3072 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3074 rcutree.rcu_fanout_exact= [KNL]
3075 Disable autobalancing of the rcu_node combining
3076 tree. This is used by rcutorture, and might
3077 possibly be useful for architectures having high
3078 cache-to-cache transfer latencies.
3080 rcutree.rcu_fanout_leaf= [KNL]
3081 Increase the number of CPUs assigned to each
3082 leaf rcu_node structure. Useful for very large
3085 rcutree.jiffies_till_sched_qs= [KNL]
3086 Set required age in jiffies for a
3087 given grace period before RCU starts
3088 soliciting quiescent-state help from
3089 rcu_note_context_switch().
3091 rcutree.jiffies_till_first_fqs= [KNL]
3092 Set delay from grace-period initialization to
3093 first attempt to force quiescent states.
3094 Units are jiffies, minimum value is zero,
3095 and maximum value is HZ.
3097 rcutree.jiffies_till_next_fqs= [KNL]
3098 Set delay between subsequent attempts to force
3099 quiescent states. Units are jiffies, minimum
3100 value is one, and maximum value is HZ.
3102 rcutree.kthread_prio= [KNL,BOOT]
3103 Set the SCHED_FIFO priority of the RCU per-CPU
3104 kthreads (rcuc/N). This value is also used for
3105 the priority of the RCU boost threads (rcub/N)
3106 and for the RCU grace-period kthreads (rcu_bh,
3107 rcu_preempt, and rcu_sched). If RCU_BOOST is
3108 set, valid values are 1-99 and the default is 1
3109 (the least-favored priority). Otherwise, when
3110 RCU_BOOST is not set, valid values are 0-99 and
3111 the default is zero (non-realtime operation).
3113 rcutree.rcu_nocb_leader_stride= [KNL]
3114 Set the number of NOCB kthread groups, which
3115 defaults to the square root of the number of
3116 CPUs. Larger numbers reduces the wakeup overhead
3117 on the per-CPU grace-period kthreads, but increases
3118 that same overhead on each group's leader.
3120 rcutree.qhimark= [KNL]
3121 Set threshold of queued RCU callbacks beyond which
3122 batch limiting is disabled.
3124 rcutree.qlowmark= [KNL]
3125 Set threshold of queued RCU callbacks below which
3126 batch limiting is re-enabled.
3128 rcutree.rcu_idle_gp_delay= [KNL]
3129 Set wakeup interval for idle CPUs that have
3130 RCU callbacks (RCU_FAST_NO_HZ=y).
3132 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3133 Set wakeup interval for idle CPUs that have
3134 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3135 Lazy RCU callbacks are those which RCU can
3136 prove do nothing more than free memory.
3138 rcutorture.cbflood_inter_holdoff= [KNL]
3139 Set holdoff time (jiffies) between successive
3140 callback-flood tests.
3142 rcutorture.cbflood_intra_holdoff= [KNL]
3143 Set holdoff time (jiffies) between successive
3144 bursts of callbacks within a given callback-flood
3147 rcutorture.cbflood_n_burst= [KNL]
3148 Set the number of bursts making up a given
3149 callback-flood test. Set this to zero to
3150 disable callback-flood testing.
3152 rcutorture.cbflood_n_per_burst= [KNL]
3153 Set the number of callbacks to be registered
3154 in a given burst of a callback-flood test.
3156 rcutorture.fqs_duration= [KNL]
3157 Set duration of force_quiescent_state bursts
3160 rcutorture.fqs_holdoff= [KNL]
3161 Set holdoff time within force_quiescent_state bursts
3164 rcutorture.fqs_stutter= [KNL]
3165 Set wait time between force_quiescent_state bursts
3168 rcutorture.gp_cond= [KNL]
3169 Use conditional/asynchronous update-side
3170 primitives, if available.
3172 rcutorture.gp_exp= [KNL]
3173 Use expedited update-side primitives, if available.
3175 rcutorture.gp_normal= [KNL]
3176 Use normal (non-expedited) asynchronous
3177 update-side primitives, if available.
3179 rcutorture.gp_sync= [KNL]
3180 Use normal (non-expedited) synchronous
3181 update-side primitives, if available. If all
3182 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3183 rcutorture.gp_normal=, and rcutorture.gp_sync=
3184 are zero, rcutorture acts as if is interpreted
3185 they are all non-zero.
3187 rcutorture.n_barrier_cbs= [KNL]
3188 Set callbacks/threads for rcu_barrier() testing.
3190 rcutorture.nfakewriters= [KNL]
3191 Set number of concurrent RCU writers. These just
3192 stress RCU, they don't participate in the actual
3193 test, hence the "fake".
3195 rcutorture.nreaders= [KNL]
3196 Set number of RCU readers. The value -1 selects
3197 N-1, where N is the number of CPUs. A value
3198 "n" less than -1 selects N-n-2, where N is again
3199 the number of CPUs. For example, -2 selects N
3200 (the number of CPUs), -3 selects N+1, and so on.
3202 rcutorture.object_debug= [KNL]
3203 Enable debug-object double-call_rcu() testing.
3205 rcutorture.onoff_holdoff= [KNL]
3206 Set time (s) after boot for CPU-hotplug testing.
3208 rcutorture.onoff_interval= [KNL]
3209 Set time (s) between CPU-hotplug operations, or
3210 zero to disable CPU-hotplug testing.
3212 rcutorture.shuffle_interval= [KNL]
3213 Set task-shuffle interval (s). Shuffling tasks
3214 allows some CPUs to go into dyntick-idle mode
3215 during the rcutorture test.
3217 rcutorture.shutdown_secs= [KNL]
3218 Set time (s) after boot system shutdown. This
3219 is useful for hands-off automated testing.
3221 rcutorture.stall_cpu= [KNL]
3222 Duration of CPU stall (s) to test RCU CPU stall
3223 warnings, zero to disable.
3225 rcutorture.stall_cpu_holdoff= [KNL]
3226 Time to wait (s) after boot before inducing stall.
3228 rcutorture.stat_interval= [KNL]
3229 Time (s) between statistics printk()s.
3231 rcutorture.stutter= [KNL]
3232 Time (s) to stutter testing, for example, specifying
3233 five seconds causes the test to run for five seconds,
3234 wait for five seconds, and so on. This tests RCU's
3235 ability to transition abruptly to and from idle.
3237 rcutorture.test_boost= [KNL]
3238 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3239 "Maybe" means test if the RCU implementation
3240 under test support RCU priority boosting.
3242 rcutorture.test_boost_duration= [KNL]
3243 Duration (s) of each individual boost test.
3245 rcutorture.test_boost_interval= [KNL]
3246 Interval (s) between each boost test.
3248 rcutorture.test_no_idle_hz= [KNL]
3249 Test RCU's dyntick-idle handling. See also the
3250 rcutorture.shuffle_interval parameter.
3252 rcutorture.torture_runnable= [BOOT]
3253 Start rcutorture running at boot time.
3255 rcutorture.torture_type= [KNL]
3256 Specify the RCU implementation to test.
3258 rcutorture.verbose= [KNL]
3259 Enable additional printk() statements.
3261 rcupdate.rcu_expedited= [KNL]
3262 Use expedited grace-period primitives, for
3263 example, synchronize_rcu_expedited() instead
3264 of synchronize_rcu(). This reduces latency,
3265 but can increase CPU utilization, degrade
3266 real-time latency, and degrade energy efficiency.
3268 rcupdate.rcu_cpu_stall_suppress= [KNL]
3269 Suppress RCU CPU stall warning messages.
3271 rcupdate.rcu_cpu_stall_timeout= [KNL]
3272 Set timeout for RCU CPU stall warning messages.
3274 rcupdate.rcu_task_stall_timeout= [KNL]
3275 Set timeout in jiffies for RCU task stall warning
3276 messages. Disable with a value less than or equal
3279 rcupdate.rcu_self_test= [KNL]
3280 Run the RCU early boot self tests
3282 rcupdate.rcu_self_test_bh= [KNL]
3283 Run the RCU bh early boot self tests
3285 rcupdate.rcu_self_test_sched= [KNL]
3286 Run the RCU sched early boot self tests
3290 Run specified binary instead of /init from the ramdisk,
3291 used for early userspace startup. See initrd.
3294 Format (x86 or x86_64):
3295 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3297 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3299 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3300 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3301 reboot_force is either force or not specified,
3302 reboot_cpu is s[mp]#### with #### being the processor
3303 to be used for rebooting.
3306 [KNL, SMP] Set scheduler's default relax_domain_level.
3307 See Documentation/cgroups/cpusets.txt.
3309 relative_sleep_states=
3310 [SUSPEND] Use sleep state labeling where the deepest
3311 state available other than hibernation is always "mem".
3312 Format: { "0" | "1" }
3313 0 -- Traditional sleep state labels.
3314 1 -- Relative sleep state labels.
3316 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3318 reservetop= [X86-32]
3320 Reserves a hole at the top of the kernel virtual
3325 Set the amount of memory to reserve for BIOS at
3326 the bottom of the address space.
3328 reset_devices [KNL] Force drivers to reset the underlying device
3329 during initialization.
3332 Specify the partition device for software suspend
3334 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3336 resume_offset= [SWSUSP]
3337 Specify the offset from the beginning of the partition
3338 given by "resume=" at which the swap header is located,
3339 in <PAGE_SIZE> units (needed only for swap files).
3340 See Documentation/power/swsusp-and-swap-files.txt
3342 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3343 read the resume files
3345 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3346 Useful for devices that are detected asynchronously
3347 (e.g. USB and MMC devices).
3349 hibernate= [HIBERNATION]
3350 noresume Don't check if there's a hibernation image
3351 present during boot.
3352 nocompress Don't compress/decompress hibernation images.
3353 no Disable hibernation and resume.
3355 retain_initrd [RAM] Keep initrd memory after extraction
3357 rfkill.default_state=
3358 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3359 etc. communication is blocked by default.
3362 rfkill.master_switch_mode=
3363 0 The "airplane mode" button does nothing.
3364 1 The "airplane mode" button toggles between everything
3365 blocked and the previous configuration.
3366 2 The "airplane mode" button toggles between everything
3367 blocked and everything unblocked.
3369 rhash_entries= [KNL,NET]
3370 Set number of hash buckets for route cache
3372 ro [KNL] Mount root device read-only on boot
3374 root= [KNL] Root filesystem
3375 See name_to_dev_t comment in init/do_mounts.c.
3377 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3378 mount the root filesystem
3380 rootflags= [KNL] Set root filesystem mount option string
3382 rootfstype= [KNL] Set root filesystem type
3384 rootwait [KNL] Wait (indefinitely) for root device to show up.
3385 Useful for devices that are detected asynchronously
3386 (e.g. USB and MMC devices).
3388 rproc_mem=nn[KMG][@address]
3389 [KNL,ARM,CMA] Remoteproc physical memory block.
3390 Memory area to be used by remote processor image,
3393 rw [KNL] Mount root device read-write on boot
3395 S [KNL] Run init in single mode
3397 s390_iommu= [HW,S390]
3398 Set s390 IOTLB flushing mode
3400 With strict flushing every unmap operation will result in
3401 an IOTLB flush. Default is lazy flushing before reuse,
3405 See drivers/net/irda/sa1100_ir.c.
3407 sbni= [NET] Granch SBNI12 leased line adapter
3409 sched_debug [KNL] Enables verbose scheduler debug messages.
3411 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3412 xtime_lock contention on larger systems, and/or RCU lock
3413 contention on all systems with CONFIG_MAXSMP set.
3414 Format: { "0" | "1" }
3415 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3417 Note: increases power consumption, thus should only be
3418 enabled if running jitter sensitive (HPC/RT) workloads.
3420 security= [SECURITY] Choose a security module to enable at boot.
3421 If this boot parameter is not specified, only the first
3422 security module asking for security registration will be
3423 loaded. An invalid security module name will be treated
3424 as if no module has been chosen.
3426 selinux= [SELINUX] Disable or enable SELinux at boot time.
3427 Format: { "0" | "1" }
3428 See security/selinux/Kconfig help text.
3431 Default value is set via kernel config option.
3432 If enabled at boot time, /selinux/disable can be used
3433 later to disable prior to initial policy load.
3435 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3436 Format: { "0" | "1" }
3437 See security/apparmor/Kconfig help text
3440 Default value is set via kernel config option.
3442 serialnumber [BUGS=X86-32]
3445 Maximal number of shapers.
3447 show_msr= [x86] show boot-time MSR settings
3448 Format: { <integer> }
3449 Show boot-time (BIOS-initialized) MSR settings.
3450 The parameter means the number of CPUs to show,
3451 for example 1 means boot CPU only.
3459 Disable merging of slabs with similar size. May be
3460 necessary if there is some reason to distinguish
3461 allocs to different slabs. Debug options disable
3462 merging on their own.
3463 For more information see Documentation/vm/slub.txt.
3465 slab_max_order= [MM, SLAB]
3466 Determines the maximum allowed order for slabs.
3467 A high setting may cause OOMs due to memory
3468 fragmentation. Defaults to 1 for systems with
3469 more than 32MB of RAM, 0 otherwise.
3471 slub_debug[=options[,slabs]] [MM, SLUB]
3472 Enabling slub_debug allows one to determine the
3473 culprit if slab objects become corrupted. Enabling
3474 slub_debug can create guard zones around objects and
3475 may poison objects when not in use. Also tracks the
3476 last alloc / free. For more information see
3477 Documentation/vm/slub.txt.
3479 slub_max_order= [MM, SLUB]
3480 Determines the maximum allowed order for slabs.
3481 A high setting may cause OOMs due to memory
3482 fragmentation. For more information see
3483 Documentation/vm/slub.txt.
3485 slub_min_objects= [MM, SLUB]
3486 The minimum number of objects per slab. SLUB will
3487 increase the slab order up to slub_max_order to
3488 generate a sufficiently large slab able to contain
3489 the number of objects indicated. The higher the number
3490 of objects the smaller the overhead of tracking slabs
3491 and the less frequently locks need to be acquired.
3492 For more information see Documentation/vm/slub.txt.
3494 slub_min_order= [MM, SLUB]
3495 Determines the minimum page order for slabs. Must be
3496 lower than slub_max_order.
3497 For more information see Documentation/vm/slub.txt.
3499 slub_nomerge [MM, SLUB]
3500 Same with slab_nomerge. This is supported for legacy.
3501 See slab_nomerge for more information.
3504 Format: <io1>[,<io2>[,...,<io8>]]
3506 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3507 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3508 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3509 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3510 smsc-ircc2.ircc_irq= [HW] IRQ line
3511 smsc-ircc2.ircc_dma= [HW] DMA channel
3512 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3513 0: Toshiba Satellite 1800 (GP data pin select)
3514 1: Fast pin select (default)
3518 [KNL] Should the soft-lockup detector generate panics.
3521 softlockup_all_cpu_backtrace=
3522 [KNL] Should the soft-lockup detector generate
3523 backtraces on all cpus.
3526 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3527 See Documentation/laptops/sonypi.txt
3529 spia_io_base= [HW,MTD]
3535 Enabled the stack tracer on boot up.
3537 stacktrace_filter=[function-list]
3538 [FTRACE] Limit the functions that the stack tracer
3539 will trace at boot up. function-list is a comma separated
3540 list of functions. This list can be changed at run
3541 time by the stack_trace_filter file in the debugfs
3542 tracing directory. Note, this enables stack tracing
3543 and the stacktrace above is not needed.
3547 Set the STI (builtin display/keyboard on the HP-PARISC
3548 machines) console (graphic card) which should be used
3549 as the initial boot-console.
3550 See also comment in drivers/video/console/sticore.c.
3553 See comment in drivers/video/console/sticore.c.
3556 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3558 sunrpc.min_resvport=
3559 sunrpc.max_resvport=
3561 SunRPC servers often require that client requests
3562 originate from a privileged port (i.e. a port in the
3563 range 0 < portnr < 1024).
3564 An administrator who wishes to reserve some of these
3565 ports for other uses may adjust the range that the
3566 kernel's sunrpc client considers to be privileged
3567 using these two parameters to set the minimum and
3568 maximum port values.
3572 Control how the NFS server code allocates CPUs to
3573 service thread pools. Depending on how many NICs
3574 you have and where their interrupts are bound, this
3575 option will affect which CPUs will do NFS serving.
3576 Note: this parameter cannot be changed while the
3577 NFS server is running.
3579 auto the server chooses an appropriate mode
3580 automatically using heuristics
3581 global a single global pool contains all CPUs
3582 percpu one pool for each CPU
3583 pernode one pool for each NUMA node (equivalent
3584 to global on non-NUMA machines)
3586 sunrpc.tcp_slot_table_entries=
3587 sunrpc.udp_slot_table_entries=
3589 Sets the upper limit on the number of simultaneous
3590 RPC calls that can be sent from the client to a
3591 server. Increasing these values may allow you to
3592 improve throughput, but will also increase the
3593 amount of memory reserved for use by the client.
3595 suspend.pm_test_delay=
3597 Sets the number of seconds to remain in a suspend test
3598 mode before resuming the system (see
3599 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3600 is set. Default value is 5.
3603 [KNL] Enable accounting of swap in memory resource
3604 controller if no parameter or 1 is given or disable
3605 it if 0 is given (See Documentation/cgroups/memory.txt)
3607 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3608 Format: { <int> | force }
3609 <int> -- Number of I/O TLB slabs
3610 force -- force using of bounce buffers even if they
3611 wouldn't be automatically used by the kernel
3615 sysfs.deprecated=0|1 [KNL]
3616 Enable/disable old style sysfs layout for old udev
3617 on older distributions. When this option is enabled
3618 very new udev will not work anymore. When this option
3619 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3620 in older udev will not work anymore.
3621 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3622 the kernel configuration.
3624 sysrq_always_enabled
3626 Ignore sysrq setting - this boot parameter will
3627 neutralize any effect of /proc/sys/kernel/sysrq.
3628 Useful for debugging.
3630 tcpmhash_entries= [KNL,NET]
3631 Set the number of tcp_metrics_hash slots.
3632 Default value is 8192 or 16384 depending on total
3633 ram pages. This is used to specify the TCP metrics
3634 cache size. See Documentation/networking/ip-sysctl.txt
3635 "tcp_no_metrics_save" section for more details.
3639 test_suspend= [SUSPEND][,N]
3640 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3641 standby suspend) or "freeze" (for suspend type freeze)
3642 as the system sleep state during system startup with
3643 the optional capability to repeat N number of times.
3644 The system is woken from this state using a
3645 wakeup-capable RTC alarm.
3647 thash_entries= [KNL,NET]
3648 Set number of hash buckets for TCP connection
3650 thermal.act= [HW,ACPI]
3651 -1: disable all active trip points in all thermal zones
3652 <degrees C>: override all lowest active trip points
3654 thermal.crt= [HW,ACPI]
3655 -1: disable all critical trip points in all thermal zones
3656 <degrees C>: override all critical trip points
3658 thermal.nocrt= [HW,ACPI]
3659 Set to disable actions on ACPI thermal zone
3660 critical and hot trip points.
3662 thermal.off= [HW,ACPI]
3663 1: disable ACPI thermal control
3665 thermal.psv= [HW,ACPI]
3666 -1: disable all passive trip points
3667 <degrees C>: override all passive trip points to this
3670 thermal.tzp= [HW,ACPI]
3671 Specify global default ACPI thermal zone polling rate
3672 <deci-seconds>: poll all this frequency
3673 0: no polling (default)
3676 Force threading of all interrupt handlers except those
3677 marked explicitly IRQF_NO_THREAD.
3680 Enable the Transcendent memory driver if built-in.
3682 tmem.cleancache=0|1 [KNL, XEN]
3683 Default is on (1). Disable the usage of the cleancache
3684 API to send anonymous pages to the hypervisor.
3686 tmem.frontswap=0|1 [KNL, XEN]
3687 Default is on (1). Disable the usage of the frontswap
3688 API to send swap pages to the hypervisor. If disabled
3689 the selfballooning and selfshrinking are force disabled.
3691 tmem.selfballooning=0|1 [KNL, XEN]
3692 Default is on (1). Disable the driving of swap pages
3695 tmem.selfshrinking=0|1 [KNL, XEN]
3696 Default is on (1). Partial swapoff that immediately
3697 transfers pages from Xen hypervisor back to the
3698 kernel based on different criteria.
3702 Specify if the kernel should make use of the cpu
3703 topology information if the hardware supports this.
3704 The scheduler will make use of this information and
3705 e.g. base its process migration decisions on it.
3708 topology_updates= [KNL, PPC, NUMA]
3710 Specify if the kernel should ignore (off)
3711 topology updates sent by the hypervisor to this
3716 tpm_suspend_pcr=[HW,TPM]
3717 Format: integer pcr id
3718 Specify that at suspend time, the tpm driver
3719 should extend the specified pcr with zeros,
3720 as a workaround for some chips which fail to
3721 flush the last written pcr on TPM_SaveState.
3722 This will guarantee that all the other pcrs
3725 trace_buf_size=nn[KMG]
3726 [FTRACE] will set tracing buffer size on each cpu.
3728 trace_event=[event-list]
3729 [FTRACE] Set and start specified trace events in order
3730 to facilitate early boot debugging.
3731 See also Documentation/trace/events.txt
3733 trace_options=[option-list]
3734 [FTRACE] Enable or disable tracer options at boot.
3735 The option-list is a comma delimited list of options
3736 that can be enabled or disabled just as if you were
3737 to echo the option name into
3739 /sys/kernel/debug/tracing/trace_options
3741 For example, to enable stacktrace option (to dump the
3742 stack trace of each event), add to the command line:
3744 trace_options=stacktrace
3746 See also Documentation/trace/ftrace.txt "trace options"
3750 Have the tracepoints sent to printk as well as the
3751 tracing ring buffer. This is useful for early boot up
3752 where the system hangs or reboots and does not give the
3753 option for reading the tracing buffer or performing a
3754 ftrace_dump_on_oops.
3756 To turn off having tracepoints sent to printk,
3757 echo 0 > /proc/sys/kernel/tracepoint_printk
3758 Note, echoing 1 into this file without the
3759 tracepoint_printk kernel cmdline option has no effect.
3763 Having tracepoints sent to printk() and activating high
3764 frequency tracepoints such as irq or sched, can cause
3765 the system to live lock.
3768 [FTRACE] enable this option to disable tracing when a
3769 warning is hit. This turns off "tracing_on". Tracing can
3770 be enabled again by echoing '1' into the "tracing_on"
3771 file located in /sys/kernel/debug/tracing/
3773 This option is useful, as it disables the trace before
3774 the WARNING dump is called, which prevents the trace to
3775 be filled with content caused by the warning output.
3777 This option can also be set at run time via the sysctl
3778 option: kernel/traceoff_on_warning
3780 transparent_hugepage=
3782 Format: [always|madvise|never]
3783 Can be used to control the default behavior of the system
3784 with respect to transparent hugepages.
3785 See Documentation/vm/transhuge.txt for more details.
3787 tsc= Disable clocksource stability checks for TSC.
3789 [x86] reliable: mark tsc clocksource as reliable, this
3790 disables clocksource verification at runtime, as well
3791 as the stability checks done at bootup. Used to enable
3792 high-resolution timer mode on older hardware, and in
3793 virtualized environment.
3794 [x86] noirqtime: Do not use TSC to do irq accounting.
3795 Used to run time disable IRQ_TIME_ACCOUNTING on any
3796 platforms where RDTSC is slow and this accounting
3799 turbografx.map[2|3]= [HW,JOY]
3800 TurboGraFX parallel port interface
3802 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3803 See also Documentation/input/joystick-parport.txt
3805 udbg-immortal [PPC] When debugging early kernel crashes that
3806 happen after console_init() and before a proper
3807 console driver takes over, this boot options might
3808 help "seeing" what's going on.
3810 uhash_entries= [KNL,NET]
3811 Set number of hash buckets for UDP/UDP-Lite connections
3814 [USB] Ignore overcurrent events (default N).
3815 Some badly-designed motherboards generate lots of
3816 bogus events, for ports that aren't wired to
3817 anything. Set this parameter to avoid log spamming.
3818 Note that genuine overcurrent events won't be
3822 [X86] Cause panic on unknown NMI.
3824 usbcore.authorized_default=
3825 [USB] Default USB device authorization:
3826 (default -1 = authorized except for wireless USB,
3827 0 = not authorized, 1 = authorized)
3829 usbcore.autosuspend=
3830 [USB] The autosuspend time delay (in seconds) used
3831 for newly-detected USB devices (default 2). This
3832 is the time required before an idle device will be
3833 autosuspended. Devices for which the delay is set
3834 to a negative value won't be autosuspended at all.
3836 usbcore.usbfs_snoop=
3837 [USB] Set to log all usbfs traffic (default 0 = off).
3839 usbcore.blinkenlights=
3840 [USB] Set to cycle leds on hubs (default 0 = off).
3842 usbcore.old_scheme_first=
3843 [USB] Start with the old device initialization
3844 scheme (default 0 = off).
3846 usbcore.usbfs_memory_mb=
3847 [USB] Memory limit (in MB) for buffers allocated by
3848 usbfs (default = 16, 0 = max = 2047).
3850 usbcore.use_both_schemes=
3851 [USB] Try the other device initialization scheme
3852 if the first one fails (default 1 = enabled).
3854 usbcore.initial_descriptor_timeout=
3855 [USB] Specifies timeout for the initial 64-byte
3856 USB_REQ_GET_DESCRIPTOR request in milliseconds
3857 (default 5000 = 5.0 seconds).
3860 [USBHID] The interval which mice are to be polled at.
3862 usb-storage.delay_use=
3863 [UMS] The delay in seconds before a new device is
3864 scanned for Logical Units (default 1).
3867 [UMS] A list of quirks entries to supplement or
3868 override the built-in unusual_devs list. List
3869 entries are separated by commas. Each entry has
3870 the form VID:PID:Flags where VID and PID are Vendor
3871 and Product ID values (4-digit hex numbers) and
3872 Flags is a set of characters, each corresponding
3873 to a common usb-storage quirk flag as follows:
3874 a = SANE_SENSE (collect more than 18 bytes
3876 b = BAD_SENSE (don't collect more than 18
3877 bytes of sense data);
3878 c = FIX_CAPACITY (decrease the reported
3879 device capacity by one sector);
3880 d = NO_READ_DISC_INFO (don't use
3881 READ_DISC_INFO command);
3882 e = NO_READ_CAPACITY_16 (don't use
3883 READ_CAPACITY_16 command);
3884 f = NO_REPORT_OPCODES (don't use report opcodes
3886 g = MAX_SECTORS_240 (don't transfer more than
3887 240 sectors at a time, uas only);
3888 h = CAPACITY_HEURISTICS (decrease the
3889 reported device capacity by one
3890 sector if the number is odd);
3891 i = IGNORE_DEVICE (don't bind to this
3893 l = NOT_LOCKABLE (don't try to lock and
3894 unlock ejectable media);
3895 m = MAX_SECTORS_64 (don't transfer more
3896 than 64 sectors = 32 KB at a time);
3897 n = INITIAL_READ10 (force a retry of the
3898 initial READ(10) command);
3899 o = CAPACITY_OK (accept the capacity
3900 reported by the device);
3901 p = WRITE_CACHE (the device cache is ON
3903 r = IGNORE_RESIDUE (the device reports
3904 bogus residue values);
3905 s = SINGLE_LUN (the device has only one
3907 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3908 commands, uas only);
3909 u = IGNORE_UAS (don't bind to the uas driver);
3910 w = NO_WP_DETECT (don't test whether the
3911 medium is write-protected).
3912 Example: quirks=0419:aaf5:rl,0421:0433:rc
3914 user_debug= [KNL,ARM]
3916 See arch/arm/Kconfig.debug help text.
3917 1 - undefined instruction events
3919 4 - invalid data aborts
3922 Example: user_debug=31
3925 [X86] Flags controlling user PTE allocations.
3927 nohigh = do not allocate PTE pages in
3928 HIGHMEM regardless of setting
3932 On X86_32, this is an alias for vdso32=. Otherwise:
3934 vdso=1: enable VDSO (the default)
3935 vdso=0: disable VDSO mapping
3937 vdso32= [X86] Control the 32-bit vDSO
3938 vdso32=1: enable 32-bit VDSO
3939 vdso32=0 or vdso32=2: disable 32-bit VDSO
3941 See the help text for CONFIG_COMPAT_VDSO for more
3942 details. If CONFIG_COMPAT_VDSO is set, the default is
3943 vdso32=0; otherwise, the default is vdso32=1.
3945 For compatibility with older kernels, vdso32=2 is an
3948 Try vdso32=0 if you encounter an error that says:
3949 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3952 vector=percpu: enable percpu vector domain
3954 video= [FB] Frame buffer configuration
3955 See Documentation/fb/modedb.txt.
3957 video.brightness_switch_enabled= [0,1]
3958 If set to 1, on receiving an ACPI notify event
3959 generated by hotkey, video driver will adjust brightness
3960 level and then send out the event to user space through
3961 the allocated input device; If set to 0, video driver
3962 will only send out the event without touching backlight
3967 [VMMIO] Memory mapped virtio (platform) device.
3969 <size>@<baseaddr>:<irq>[:<id>]
3971 <size> := size (can use standard suffixes
3973 <baseaddr> := physical base address
3974 <irq> := interrupt number (as passed to
3976 <id> := (optional) platform device id
3978 virtio_mmio.device=1K@0x100b0000:48:7
3980 Can be used multiple times for multiple devices.
3982 vga= [BOOT,X86-32] Select a particular video mode
3983 See Documentation/x86/boot.txt and
3984 Documentation/svga.txt.
3985 Use vga=ask for menu.
3986 This is actually a boot loader parameter; the value is
3987 passed to the kernel using a special protocol.
3989 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3990 size of <nn>. This can be used to increase the
3991 minimum size (128MB on x86). It can also be used to
3992 decrease the size and leave more room for directly
3995 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3998 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4001 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4005 Controls the behavior of vsyscalls (i.e. calls to
4006 fixed addresses of 0xffffffffff600x00 from legacy
4007 code). Most statically-linked binaries and older
4008 versions of glibc use these calls. Because these
4009 functions are at fixed addresses, they make nice
4010 targets for exploits that can control RIP.
4012 emulate [default] Vsyscalls turn into traps and are
4013 emulated reasonably safely.
4015 native Vsyscalls are native syscall instructions.
4016 This is a little bit faster than trapping
4017 and makes a few dynamic recompilers work
4018 better than they would in emulation mode.
4019 It also makes exploits much easier to write.
4021 none Vsyscalls don't work at all. This makes
4022 them quite hard to use for exploits but
4023 might break your system.
4025 vt.color= [VT] Default text color.
4026 Format: 0xYX, X = foreground, Y = background.
4027 Default: 0x07 = light gray on black.
4029 vt.cur_default= [VT] Default cursor shape.
4030 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4031 the parameters of the <Esc>[?A;B;Cc escape sequence;
4032 see VGA-softcursor.txt. Default: 2 = underline.
4034 vt.default_blu= [VT]
4035 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4036 Change the default blue palette of the console.
4037 This is a 16-member array composed of values
4040 vt.default_grn= [VT]
4041 Format: <green0>,<green1>,<green2>,...,<green15>
4042 Change the default green palette of the console.
4043 This is a 16-member array composed of values
4046 vt.default_red= [VT]
4047 Format: <red0>,<red1>,<red2>,...,<red15>
4048 Change the default red palette of the console.
4049 This is a 16-member array composed of values
4055 Set system-wide default UTF-8 mode for all tty's.
4056 Default is 1, i.e. UTF-8 mode is enabled for all
4057 newly opened terminals.
4059 vt.global_cursor_default=
4062 Set system-wide default for whether a cursor
4063 is shown on new VTs. Default is -1,
4064 i.e. cursors will be created by default unless
4065 overridden by individual drivers. 0 will hide
4066 cursors, 1 will display them.
4068 vt.italic= [VT] Default color for italic text; 0-15.
4071 vt.underline= [VT] Default color for underlined text; 0-15.
4074 watchdog timers [HW,WDT] For information on watchdog timers,
4075 see Documentation/watchdog/watchdog-parameters.txt
4076 or other driver-specific files in the
4077 Documentation/watchdog/ directory.
4079 workqueue.disable_numa
4080 By default, all work items queued to unbound
4081 workqueues are affine to the NUMA nodes they're
4082 issued on, which results in better behavior in
4083 general. If NUMA affinity needs to be disabled for
4084 whatever reason, this option can be used. Note
4085 that this also can be controlled per-workqueue for
4086 workqueues visible under /sys/bus/workqueue/.
4088 workqueue.power_efficient
4089 Per-cpu workqueues are generally preferred because
4090 they show better performance thanks to cache
4091 locality; unfortunately, per-cpu workqueues tend to
4092 be more power hungry than unbound workqueues.
4094 Enabling this makes the per-cpu workqueues which
4095 were observed to contribute significantly to power
4096 consumption unbound, leading to measurably lower
4097 power usage at the cost of small performance
4100 The default value of this parameter is determined by
4101 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4103 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4104 default x2apic cluster mode on platforms
4107 x86_intel_mid_timer= [X86-32,APBT]
4108 Choose timer option for x86 Intel MID platform.
4109 Two valid options are apbt timer only and lapic timer
4110 plus one apbt timer for broadcast timer.
4111 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4113 xen_512gb_limit [KNL,X86-64,XEN]
4114 Restricts the kernel running paravirtualized under Xen
4115 to use only up to 512 GB of RAM. The reason to do so is
4116 crash analysis tools and Xen tools for doing domain
4117 save/restore/migration must be enabled to handle larger
4120 xen_emul_unplug= [HW,X86,XEN]
4121 Unplug Xen emulated devices
4122 Format: [unplug0,][unplug1]
4123 ide-disks -- unplug primary master IDE devices
4124 aux-ide-disks -- unplug non-primary-master IDE devices
4125 nics -- unplug network devices
4126 all -- unplug all emulated devices (NICs and IDE disks)
4127 unnecessary -- unplugging emulated devices is
4128 unnecessary even if the host did not respond to
4130 never -- do not unplug even if version check succeeds
4132 xen_nopvspin [X86,XEN]
4133 Disables the ticketlock slowpath using Xen PV
4137 Disables the PV optimizations forcing the HVM guest to
4138 run as generic HVM guest with no PV drivers.
4140 xirc2ps_cs= [NET,PCMCIA]
4142 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4144 ______________________________________________________________________
4148 Add more DRM drivers.
projects / karo-tx-linux.git / blob