4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
168 acpi= [HW,ACPI,X86,ARM64]
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt |
172 force -- enable ACPI if default was off
173 off -- disable ACPI if default was on
174 noirq -- do not use ACPI for IRQ routing
175 strict -- Be less tolerant of platforms that are not
176 strictly ACPI specification compliant.
177 rsdt -- prefer RSDT over (default) XSDT
178 copy_dsdt -- copy DSDT to memory
179 For ARM64, ONLY "acpi=off" or "acpi=force" are available
181 See also Documentation/power/runtime_pm.txt, pci=noacpi
183 acpi_apic_instance= [ACPI, IOAPIC]
185 2: use 2nd APIC table, if available
186 1,0: use 1st APIC table
189 acpi_backlight= [HW,ACPI]
190 acpi_backlight=vendor
192 If set to vendor, prefer vendor specific driver
193 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
194 of the ACPI video.ko driver.
196 acpica_no_return_repair [HW, ACPI]
197 Disable AML predefined validation mechanism
198 This mechanism can repair the evaluation result to make
199 the return objects more ACPI specification compliant.
200 This option is useful for developers to identify the
201 root cause of an AML interpreter issue when the issue
202 has something to do with the repair mechanism.
204 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
205 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
207 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
208 debug output. Bits in debug_layer correspond to a
209 _COMPONENT in an ACPI source file, e.g.,
210 #define _COMPONENT ACPI_PCI_COMPONENT
211 Bits in debug_level correspond to a level in
212 ACPI_DEBUG_PRINT statements, e.g.,
213 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
214 The debug_level mask defaults to "info". See
215 Documentation/acpi/debug.txt for more information about
216 debug layers and levels.
218 Enable processor driver info messages:
219 acpi.debug_layer=0x20000000
220 Enable PCI/PCI interrupt routing info messages:
221 acpi.debug_layer=0x400000
222 Enable AML "Debug" output, i.e., stores to the Debug
223 object while interpreting AML:
224 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
225 Enable all messages related to ACPI hardware:
226 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
228 Some values produce so much output that the system is
229 unusable. The "log_buf_len" parameter may be useful
230 if you need to capture more output.
232 acpi_enforce_resources= [ACPI]
233 { strict | lax | no }
234 Check for resource conflicts between native drivers
235 and ACPI OperationRegions (SystemIO and SystemMemory
236 only). IO ports and memory declared in ACPI might be
237 used by the ACPI subsystem in arbitrary AML code and
238 can interfere with legacy drivers.
239 strict (default): access to resources claimed by ACPI
240 is denied; legacy drivers trying to access reserved
241 resources will fail to bind to device using them.
242 lax: access to resources claimed by ACPI is allowed;
243 legacy drivers trying to access reserved resources
244 will bind successfully but a warning message is logged.
245 no: ACPI OperationRegions are not marked as reserved,
246 no further checks are performed.
248 acpi_force_table_verification [HW,ACPI]
249 Enable table checksum verification during early stage.
250 By default, this is disabled due to x86 early mapping
253 acpi_irq_balance [HW,ACPI]
254 ACPI will balance active IRQs
257 acpi_irq_nobalance [HW,ACPI]
258 ACPI will not move active IRQs (default)
261 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
262 Format: <irq>,<irq>...
264 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
266 Format: <irq>,<irq>...
268 acpi_no_auto_serialize [HW,ACPI]
269 Disable auto-serialization of AML methods
270 AML control methods that contain the opcodes to create
271 named objects will be marked as "Serialized" by the
272 auto-serialization feature.
273 This feature is enabled by default.
274 This option allows to turn off the feature.
276 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
279 acpi_no_static_ssdt [HW,ACPI]
280 Disable installation of static SSDTs at early boot time
281 By default, SSDTs contained in the RSDT/XSDT will be
282 installed automatically and they will appear under
283 /sys/firmware/acpi/tables.
284 This option turns off this feature.
285 Note that specifying this option does not affect
286 dynamic table installation which will install SSDT
287 tables to /sys/firmware/acpi/tables/dynamic.
289 acpi_rsdp= [ACPI,EFI,KEXEC]
290 Pass the RSDP address to the kernel, mostly used
291 on machines running EFI runtime service to boot the
292 second kernel for kdump.
294 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
295 Format: To spoof as Windows 98: ="Microsoft Windows"
297 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
298 of 2 which is mandated by ACPI 6) as the supported ACPI
299 specification revision (when using this switch, it may
300 be necessary to carry out a cold reboot _twice_ in a
301 row to make it take effect on the platform firmware).
303 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
304 acpi_osi="string1" # add string1
305 acpi_osi="!string2" # remove string2
306 acpi_osi=!* # remove all strings
307 acpi_osi=! # disable all built-in OS vendor
309 acpi_osi= # disable all strings
311 'acpi_osi=!' can be used in combination with single or
312 multiple 'acpi_osi="string1"' to support specific OS
313 vendor string(s). Note that such command can only
314 affect the default state of the OS vendor strings, thus
315 it cannot affect the default state of the feature group
316 strings and the current state of the OS vendor strings,
317 specifying it multiple times through kernel command line
318 is meaningless. This command is useful when one do not
319 care about the state of the feature group strings which
320 should be controlled by the OSPM.
322 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
323 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
324 can make '_OSI("Windows 2000")' TRUE.
326 'acpi_osi=' cannot be used in combination with other
327 'acpi_osi=' command lines, the _OSI method will not
328 exist in the ACPI namespace. NOTE that such command can
329 only affect the _OSI support state, thus specifying it
330 multiple times through kernel command line is also
333 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
336 'acpi_osi=!*' can be used in combination with single or
337 multiple 'acpi_osi="string1"' to support specific
338 string(s). Note that such command can affect the
339 current state of both the OS vendor strings and the
340 feature group strings, thus specifying it multiple times
341 through kernel command line is meaningful. But it may
342 still not able to affect the final state of a string if
343 there are quirks related to this string. This command
344 is useful when one want to control the state of the
345 feature group strings to debug BIOS issues related to
348 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
349 '_OSI("Module Device")' FALSE.
350 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
351 '_OSI("Module Device")' TRUE.
352 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
354 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
356 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
357 they all will make '_OSI("Windows 2000")' TRUE.
360 Override the pmtimer bug detection: force the kernel
361 to assume that this machine's pmtimer latches its value
362 and always returns good values.
364 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
365 Format: { level | edge | high | low }
367 acpi_skip_timer_override [HW,ACPI]
368 Recognize and ignore IRQ0/pin2 Interrupt Override.
369 For broken nForce2 BIOS resulting in XT-PIC timer.
371 acpi_sleep= [HW,ACPI] Sleep options
372 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
373 old_ordering, nonvs, sci_force_enable }
374 See Documentation/power/video.txt for information on
376 s3_beep is for debugging; it makes the PC's speaker beep
377 as soon as the kernel's real-mode entry point is called.
378 s4_nohwsig prevents ACPI hardware signature from being
379 used during resume from hibernation.
380 old_ordering causes the ACPI 1.0 ordering of the _PTS
381 control method, with respect to putting devices into
382 low power states, to be enforced (the ACPI 2.0 ordering
383 of _PTS is used by default).
384 nonvs prevents the kernel from saving/restoring the
385 ACPI NVS memory during suspend/hibernation and resume.
386 sci_force_enable causes the kernel to set SCI_EN directly
387 on resume from S1/S3 (which is against the ACPI spec,
388 but some broken systems don't work without it).
390 acpi_use_timer_override [HW,ACPI]
391 Use timer override. For some broken Nvidia NF5 boards
392 that require a timer override, but don't have HPET
394 add_efi_memmap [EFI; X86] Include EFI memory map in
395 kernel's map of available physical RAM.
398 { off | try_unsupported }
399 off: disable AGP support
400 try_unsupported: try to drive unsupported chipsets
401 (may crash computer or cause data corruption)
404 See Documentation/sound/alsa/alsa-parameters.txt
407 Allow the default userspace alignment fault handler
408 behaviour to be specified. Bit 0 enables warnings,
409 bit 1 enables fixups, and bit 2 sends a segfault.
411 align_va_addr= [X86-64]
412 Align virtual addresses by clearing slice [14:12] when
413 allocating a VMA at process creation time. This option
414 gives you up to 3% performance improvement on AMD F15h
415 machines (where it is enabled by default) for a
416 CPU-intensive style benchmark, and it can vary highly in
417 a microbenchmark depending on workload and compiler.
419 32: only for 32-bit processes
420 64: only for 64-bit processes
421 on: enable for both 32- and 64-bit processes
422 off: disable for both 32- and 64-bit processes
424 alloc_snapshot [FTRACE]
425 Allocate the ftrace snapshot buffer on boot up when the
426 main buffer is allocated. This is handy if debugging
427 and you need to use tracing_snapshot() on boot up, and
428 do not want to use tracing_snapshot_alloc() as it needs
429 to be done where GFP_KERNEL allocations are allowed.
431 amd_iommu= [HW,X86-64]
432 Pass parameters to the AMD IOMMU driver in the system.
434 fullflush - enable flushing of IO/TLB entries when
435 they are unmapped. Otherwise they are
436 flushed before they will be reused, which
438 off - do not initialize any AMD IOMMU found in
440 force_isolation - Force device isolation for all
441 devices. The IOMMU driver is not
442 allowed anymore to lift isolation
443 requirements as needed. This option
444 does not override iommu=pt
446 amd_iommu_dump= [HW,X86-64]
447 Enable AMD IOMMU driver option to dump the ACPI table
448 for AMD IOMMU. With this option enabled, AMD IOMMU
449 driver will print ACPI tables for AMD IOMMU during
450 IOMMU initialization.
452 amijoy.map= [HW,JOY] Amiga joystick support
453 Map of devices attached to JOY0DAT and JOY1DAT
455 See also Documentation/input/joystick.txt
457 analog.map= [HW,JOY] Analog joystick and gamepad support
458 Specifies type or capabilities of an analog joystick
459 connected to one of 16 gameports
460 Format: <type1>,<type2>,..<type16>
463 Power management functions (SPARCstation-4/5 + deriv.)
465 Disable APC CPU standby support. SPARCstation-Fox does
466 not play well with APC CPU idle - disable it if you have
467 APC and your system crashes randomly.
469 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
470 Change the output verbosity whilst booting
471 Format: { quiet (default) | verbose | debug }
472 Change the amount of debugging information output
473 when initialising the APIC and IO-APIC components.
476 See Documentation/networking/ipv6.txt.
478 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
479 Limit apic dumping. The parameter defines the maximal
480 number of local apics being dumped. Also it is possible
481 to set it to "all" by meaning -- no limit here.
482 Format: { 1 (default) | 2 | ... | all }.
483 The parameter valid if only apic=debug or
484 apic=verbose is specified.
485 Example: apic=debug show_lapic=all
487 apm= [APM] Advanced Power Management
488 See header of arch/x86/kernel/apm_32.c.
490 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
491 Format: <io>,<irq>,<nodeID>
495 atarimouse= [HW,MOUSE] Atari Mouse
497 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
498 EzKey and similar keyboards
500 atkbd.reset= [HW] Reset keyboard during initialization
502 atkbd.set= [HW] Select keyboard code set
503 Format: <int> (2 = AT (default), 3 = PS/2)
505 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
508 atkbd.softraw= [HW] Choose between synthetic and real raw mode
509 Format: <bool> (0 = real, 1 = synthetic (default))
511 atkbd.softrepeat= [HW]
512 Use software keyboard repeat
514 audit= [KNL] Enable the audit sub-system
515 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
516 0 - kernel audit is disabled and can not be enabled
517 until the next reboot
518 unset - kernel audit is initialized but disabled and
519 will be fully enabled by the userspace auditd.
520 1 - kernel audit is initialized and partially enabled,
521 storing at most audit_backlog_limit messages in
522 RAM until it is fully enabled by the userspace
526 audit_backlog_limit= [KNL] Set the audit queue size limit.
527 Format: <int> (must be >=0)
530 baycom_epp= [HW,AX25]
533 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
535 See header of drivers/net/hamradio/baycom_par.c.
537 baycom_ser_fdx= [HW,AX25]
538 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
539 Format: <io>,<irq>,<mode>[,<baud>]
540 See header of drivers/net/hamradio/baycom_ser_fdx.c.
542 baycom_ser_hdx= [HW,AX25]
543 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
544 Format: <io>,<irq>,<mode>
545 See header of drivers/net/hamradio/baycom_ser_hdx.c.
547 blkdevparts= Manual partition parsing of block device(s) for
548 embedded devices based on command line input.
549 See Documentation/block/cmdline-partition.txt
551 boot_delay= Milliseconds to delay each printk during boot.
552 Values larger than 10 seconds (10000) are changed to
556 bootmem_debug [KNL] Enable bootmem allocator debug messages.
558 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
559 bttv.radio= Most important insmod options are available as
561 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
564 bulk_remove=off [PPC] This parameter disables the use of the pSeries
565 firmware feature for flushing multiple hpte entries
568 c101= [NET] Moxa C101 synchronous serial card
570 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
571 Sometimes CPU hardware bugs make them report the cache
572 size incorrectly. The kernel will attempt work arounds
573 to fix known problems, but for some CPUs it is not
574 possible to determine what the correct size should be.
575 This option provides an override for these situations.
577 ca_keys= [KEYS] This parameter identifies a specific key(s) on
578 the system trusted keyring to be used for certificate
580 format: { id:<keyid> | builtin }
582 cca= [MIPS] Override the kernel pages' cache coherency
583 algorithm. Accepted values range from 0 to 7
584 inclusive. See arch/mips/include/asm/pgtable-bits.h
585 for platform specific values (SB1, Loongson3 and
588 ccw_timeout_log [S390]
589 See Documentation/s390/CommonIO for details.
591 cgroup_disable= [KNL] Disable a particular controller
592 Format: {name of the controller(s) to disable}
593 The effects of cgroup_disable=foo are:
594 - foo isn't auto-mounted if you mount all cgroups in
596 - foo isn't visible as an individually mountable
598 {Currently only "memory" controller deal with this and
599 cut the overhead, others just disable the usage. So
600 only cgroup_disable=memory is actually worthy}
602 checkreqprot [SELINUX] Set initial checkreqprot flag value.
603 Format: { "0" | "1" }
604 See security/selinux/Kconfig help text.
605 0 -- check protection applied by kernel (includes
606 any implied execute protection).
607 1 -- check protection requested by application.
608 Default value is set via a kernel config option.
609 Value can be changed at runtime via
610 /selinux/checkreqprot.
613 See Documentation/s390/CommonIO for details.
616 Prevents the clock framework from automatically gating
617 clocks that have not been explicitly enabled by a Linux
618 device driver but are enabled in hardware at reset or
619 by the bootloader/firmware. Note that this does not
620 force such clocks to be always-on nor does it reserve
621 those clocks in any way. This parameter is useful for
622 debug and development, but should not be needed on a
623 platform with proper driver support. For more
624 information, see Documentation/clk.txt.
626 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
628 Forces specified clocksource (if available) to be used
629 when calculating gettimeofday(). If specified
630 clocksource is not available, it defaults to PIT.
631 Format: { pit | tsc | cyclone | pmtmr }
633 clocksource= Override the default clocksource
635 Override the default clocksource and use the clocksource
636 with the name specified.
637 Some clocksource names to choose from, depending on
639 [all] jiffies (this is the base, fallback clocksource)
641 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
642 pxa_timer,timer3,32k_counter,timer0_1
644 [X86-32] pit,hpet,tsc;
645 scx200_hrt on Geode; cyclone on IBM x440
653 clearcpuid=BITNUM [X86]
654 Disable CPUID feature X for the kernel. See
655 arch/x86/include/asm/cpufeature.h for the valid bit
656 numbers. Note the Linux specific bits are not necessarily
657 stable over kernel options, but the vendor specific
659 Also note that user programs calling CPUID directly
660 or using the feature without checking anything
661 will still see it. This just prevents it from
662 being used by the kernel or shown in /proc/cpuinfo.
663 Also note the kernel might malfunction if you disable
666 cma=nn[MG]@[start[MG][-end[MG]]]
668 Sets the size of kernel global memory area for
669 contiguous memory allocations and optionally the
670 placement constraint by the physical address range of
671 memory allocations. A value of 0 disables CMA
672 altogether. For more information, see
673 include/linux/dma-contiguous.h
675 cmo_free_hint= [PPC] Format: { yes | no }
676 Specify whether pages are marked as being inactive
677 when they are freed. This is used in CMO environments
678 to determine OS memory pressure for page stealing by
682 coherent_pool=nn[KMG] [ARM,KNL]
683 Sets the size of memory pool for coherent, atomic dma
684 allocations, by default set to 256K.
686 code_bytes [X86] How many bytes of object code to print
691 com20020= [HW,NET] ARCnet - COM20020 chipset
693 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
695 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
699 ARCnet - COM90xx chipset (memory-mapped buffers)
700 Format: <io>[,<irq>[,<memstart>]]
702 condev= [HW,S390] console device
705 console= [KNL] Output console device and options.
707 tty<n> Use the virtual console device <n>.
711 Use the specified serial port. The options are of
712 the form "bbbbpnf", where "bbbb" is the baud rate,
713 "p" is parity ("n", "o", or "e"), "n" is number of
714 bits, and "f" is flow control ("r" for RTS or
715 omit it). Default is "9600n8".
717 See Documentation/serial-console.txt for more
719 Documentation/networking/netconsole.txt for an
722 uart[8250],io,<addr>[,options]
723 uart[8250],mmio,<addr>[,options]
724 uart[8250],mmio32,<addr>[,options]
725 uart[8250],0x<addr>[,options]
726 Start an early, polled-mode console on the 8250/16550
727 UART at the specified I/O port or MMIO address,
728 switching to the matching ttyS device later.
729 MMIO inter-register address stride is either 8-bit
730 (mmio) or 32-bit (mmio32).
731 If none of [io|mmio|mmio32], <addr> is assumed to be
732 equivalent to 'mmio'. 'options' are specified in the
733 same format described for ttyS above; if unspecified,
734 the h/w is not re-initialized.
736 hvc<n> Use the hypervisor console device <n>. This is for
737 both Xen and PowerPC hypervisors.
739 If the device connected to the port is not a TTY but a braille
740 device, prepend "brl," before the device type, for instance
742 For now, only VisioBraille is supported.
744 consoleblank= [KNL] The console blank (screen saver) timeout in
745 seconds. Defaults to 10*60 = 10mins. A value of 0
746 disables the blank timer.
749 [KNL] Change the default value for
750 /proc/<pid>/coredump_filter.
751 See also Documentation/filesystems/proc.txt.
753 cpuidle.off=1 [CPU_IDLE]
754 disable the cpuidle sub-system
757 [X86] Delay for N microsec between assert and de-assert
758 of APIC INIT to start processors. This delay occurs
759 on every CPU online, such as boot, and resume from suspend.
762 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
764 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
766 crashkernel=size[KMG][@offset[KMG]]
767 [KNL] Using kexec, Linux can switch to a 'crash kernel'
768 upon panic. This parameter reserves the physical
769 memory region [offset, offset + size] for that kernel
770 image. If '@offset' is omitted, then a suitable offset
771 is selected automatically. Check
772 Documentation/kdump/kdump.txt for further details.
774 crashkernel=range1:size1[,range2:size2,...][@offset]
775 [KNL] Same as above, but depends on the memory
776 in the running system. The syntax of range is
777 start-[end] where start and end are both
778 a memory unit (amount[KMG]). See also
779 Documentation/kdump/kdump.txt for an example.
781 crashkernel=size[KMG],high
782 [KNL, x86_64] range could be above 4G. Allow kernel
783 to allocate physical memory region from top, so could
784 be above 4G if system have more than 4G ram installed.
785 Otherwise memory region will be allocated below 4G, if
787 It will be ignored if crashkernel=X is specified.
788 crashkernel=size[KMG],low
789 [KNL, x86_64] range under 4G. When crashkernel=X,high
790 is passed, kernel could allocate physical memory region
791 above 4G, that cause second kernel crash on system
792 that require some amount of low memory, e.g. swiotlb
793 requires at least 64M+32K low memory, also enough extra
794 low memory is needed to make sure DMA buffers for 32-bit
795 devices won't run out. Kernel would try to allocate at
796 at least 256M below 4G automatically.
797 This one let user to specify own low range under 4G
798 for second kernel instead.
799 0: to disable low allocation.
800 It will be ignored when crashkernel=X,high is not used
801 or memory reserved is below 4G.
806 cs89x0_media= [HW,NET]
807 Format: { rj45 | aui | bnc }
810 See header of drivers/s390/block/dasd_devmap.c.
812 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
813 (one device per port)
814 Format: <port#>,<type>
815 See also Documentation/input/joystick-parport.txt
817 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
818 time. See Documentation/dynamic-debug-howto.txt for
819 details. Deprecated, see dyndbg.
821 debug [KNL] Enable kernel debugging (events log level).
824 [KNL] verbose self-tests
826 Print debugging info while doing the locking API
828 We default to 0 (no extra messages), setting it to
829 1 will print _a lot_ more information - normally
830 only useful to kernel developers.
832 debug_objects [KNL] Enable object debugging
835 [KNL] Disable object debugging
837 debug_guardpage_minorder=
838 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
839 parameter allows control of the order of pages that will
840 be intentionally kept free (and hence protected) by the
841 buddy allocator. Bigger value increase the probability
842 of catching random memory corruption, but reduce the
843 amount of memory for normal system use. The maximum
844 possible value is MAX_ORDER/2. Setting this parameter
845 to 1 or 2 should be enough to identify most random
846 memory corruption problems caused by bugs in kernel or
847 driver code when a CPU writes to (or reads from) a
848 random memory location. Note that there exists a class
849 of memory corruptions problems caused by buggy H/W or
850 F/W or by drivers badly programing DMA (basically when
851 memory is written at bus level and the CPU MMU is
852 bypassed) which are not detectable by
853 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
854 tracking down these problems.
857 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
858 parameter enables the feature at boot time. In
859 default, it is disabled. We can avoid allocating huge
860 chunk of memory for debug pagealloc if we don't enable
861 it at boot time and the system will work mostly same
862 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
863 on: enable the feature
865 debugpat [X86] Enable PAT debugging
867 decnet.addr= [HW,NET]
868 Format: <area>[,<node>]
869 See also Documentation/networking/decnet.txt.
872 [same as hugepagesz=] The size of the default
873 HugeTLB page size. This is the size represented by
874 the legacy /proc/ hugepages APIs, used for SHM, and
875 default size when mounting hugetlbfs filesystems.
876 Defaults to the default architecture's huge page size
880 Set number of hash buckets for dentry cache.
883 See Documentation/networking/ipv6.txt.
885 disable_cpu_apicid= [X86,APIC,SMP]
887 The number of initial APIC ID for the
888 corresponding CPU to be disabled at boot,
889 mostly used for the kdump 2nd kernel to
890 disable BSP to wake up multiple CPUs without
891 causing system reset or hang due to sending
894 disable_ddw [PPC/PSERIES]
895 Disable Dynamic DMA Window support. Use this if
896 to workaround buggy firmware.
899 See Documentation/networking/ipv6.txt.
901 disable_mtrr_cleanup [X86]
902 The kernel tries to adjust MTRR layout from continuous
903 to discrete, to make X server driver able to add WB
904 entry later. This parameter disables that.
906 disable_mtrr_trim [X86, Intel and AMD only]
907 By default the kernel will trim any uncacheable
908 memory out of your available memory pool based on
909 MTRR settings. This parameter disables that behavior,
910 possibly causing your machine to run very slowly.
912 disable_timer_pin_1 [X86]
913 Disable PIN 1 of APIC timer
914 Can be useful to work around chipset bugs.
916 dis_ucode_ldr [X86] Disable the microcode loader.
918 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
919 this option disables the debugging code at boot.
921 dma_debug_entries=<number>
922 This option allows to tune the number of preallocated
923 entries for DMA-API debugging code. One entry is
924 required per DMA-API allocation. Use this if the
925 DMA-API debugging code disables itself because the
926 architectural default is too low.
928 dma_debug_driver=<driver_name>
929 With this option the DMA-API debugging driver
930 filter feature can be enabled at boot time. Just
931 pass the driver to filter for as the parameter.
932 The filter can be disabled or changed to another
933 driver later using sysfs.
935 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
936 Broken monitors, graphic adapters, KVMs and EDIDless
937 panels may send no or incorrect EDID data sets.
938 This parameter allows to specify an EDID data sets
939 in the /lib/firmware directory that are used instead.
940 Generic built-in EDID data sets are used, if one of
941 edid/1024x768.bin, edid/1280x1024.bin,
942 edid/1680x1050.bin, or edid/1920x1080.bin is given
943 and no file with the same name exists. Details and
944 instructions how to build your own EDID data are
945 available in Documentation/EDID/HOWTO.txt. An EDID
946 data set will only be used for a particular connector,
947 if its name and a colon are prepended to the EDID
948 name. Each connector may use a unique EDID data
949 set by separating the files with a comma. An EDID
950 data set with no connector name will be used for
951 any connectors not explicitly specified.
955 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
956 module.dyndbg[="val"]
957 Enable debug messages at boot time. See
958 Documentation/dynamic-debug-howto.txt for details.
960 nompx [X86] Disables Intel Memory Protection Extensions.
961 See Documentation/x86/intel_mpx.txt for more
962 information about the feature.
965 on enable eager fpu restore
966 off disable eager fpu restore
967 auto selects the default scheme, which automatically
968 enables eagerfpu restore for xsaveopt.
970 module.async_probe [KNL]
971 Enable asynchronous probe on this module.
973 early_ioremap_debug [KNL]
974 Enable debug messages in early_ioremap support. This
975 is useful for tracking down temporary early mappings
976 which are not unmapped.
978 earlycon= [KNL] Output early console device and options.
980 When used with no options, the early console is
981 determined by the stdout-path property in device
985 Start an early, polled-mode console on a cadence serial
986 port at the specified address. The cadence serial port
987 must already be setup and configured. Options are not
990 uart[8250],io,<addr>[,options]
991 uart[8250],mmio,<addr>[,options]
992 uart[8250],mmio32,<addr>[,options]
993 uart[8250],mmio32be,<addr>[,options]
994 uart[8250],0x<addr>[,options]
995 Start an early, polled-mode console on the 8250/16550
996 UART at the specified I/O port or MMIO address.
997 MMIO inter-register address stride is either 8-bit
998 (mmio) or 32-bit (mmio32 or mmio32be).
999 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1000 to be equivalent to 'mmio'. 'options' are specified
1001 in the same format described for "console=ttyS<n>"; if
1002 unspecified, the h/w is not initialized.
1005 Start an early, polled-mode console on a pl011 serial
1006 port at the specified address. The pl011 serial port
1007 must already be setup and configured. Options are not
1011 Start an early, polled-mode console on an msm serial
1012 port at the specified address. The serial port
1013 must already be setup and configured. Options are not
1016 msm_serial_dm,<addr>
1017 Start an early, polled-mode console on an msm serial
1018 dm port at the specified address. The serial port
1019 must already be setup and configured. Options are not
1022 smh Use ARM semihosting calls for early console.
1030 Use early console provided by serial driver available
1031 on Samsung SoCs, requires selecting proper type and
1032 a correct base address of the selected UART port. The
1033 serial port must already be setup and configured.
1034 Options are not yet supported.
1036 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1040 earlyprintk=serial[,ttySn[,baudrate]]
1041 earlyprintk=serial[,0x...[,baudrate]]
1042 earlyprintk=ttySn[,baudrate]
1043 earlyprintk=dbgp[debugController#]
1044 earlyprintk=pciserial,bus:device.function[,baudrate]
1046 earlyprintk is useful when the kernel crashes before
1047 the normal console is initialized. It is not enabled by
1048 default because it has some cosmetic problems.
1050 Append ",keep" to not disable it when the real console
1053 Only one of vga, efi, serial, or usb debug port can
1056 Currently only ttyS0 and ttyS1 may be specified by
1057 name. Other I/O ports may be explicitly specified
1058 on some architectures (x86 and arm at least) by
1059 replacing ttySn with an I/O port address, like this:
1060 earlyprintk=serial,0x1008,115200
1061 You can find the port for a given device in
1062 /proc/tty/driver/serial:
1063 2: uart:ST16650V2 port:00001008 irq:18 ...
1065 Interaction with the standard serial driver is not
1068 The VGA and EFI output is eventually overwritten by
1071 The xen output can only be used by Xen PV guests.
1073 edac_report= [HW,EDAC] Control how to report EDAC event
1074 Format: {"on" | "off" | "force"}
1075 on: enable EDAC to report H/W event. May be overridden
1076 by other higher priority error reporting module.
1077 off: disable H/W event reporting through EDAC.
1078 force: enforce the use of EDAC to report H/W event.
1081 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1084 This is designed to be used in conjunction with
1085 the boot argument: earlyprintk=vga
1088 Format: {"off" | "on" | "skip[mbr]"}
1091 Format: { "old_map", "nochunk", "noruntime", "debug" }
1092 old_map [X86-64]: switch to the old ioremap-based EFI
1093 runtime services mapping. 32-bit still uses this one by
1095 nochunk: disable reading files in "chunks" in the EFI
1096 boot stub, as chunking can cause problems with some
1097 firmware implementations.
1098 noruntime : disable EFI runtime services support
1099 debug: enable misc debug output
1101 efi_no_storage_paranoia [EFI; X86]
1102 Using this parameter you can use more than 50% of
1103 your efi variable storage. Use this parameter only if
1104 you are really sure that your UEFI does sane gc and
1105 fulfills the spec otherwise your board may brick.
1107 eisa_irq_edge= [PARISC,HW]
1108 See header of drivers/parisc/eisa.c.
1111 See comment before function elanfreq_setup() in
1112 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1115 Format: {"cfq" | "deadline" | "noop"}
1116 See Documentation/block/cfq-iosched.txt and
1117 Documentation/block/deadline-iosched.txt for details.
1119 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1120 Specifies physical address of start of kernel core
1121 image elf header and optionally the size. Generally
1122 kexec loader will pass this option to capture kernel.
1123 See Documentation/kdump/kdump.txt for details.
1125 enable_mtrr_cleanup [X86]
1126 The kernel tries to adjust MTRR layout from continuous
1127 to discrete, to make X server driver able to add WB
1128 entry later. This parameter enables that.
1130 enable_timer_pin_1 [X86]
1131 Enable PIN 1 of APIC timer
1132 Can be useful to work around chipset bugs
1133 (in particular on some ATI chipsets).
1134 The kernel tries to set a reasonable default.
1136 enforcing [SELINUX] Set initial enforcing status.
1138 See security/selinux/Kconfig help text.
1139 0 -- permissive (log only, no denials).
1140 1 -- enforcing (deny and log).
1142 Value can be changed at runtime via /selinux/enforce.
1145 Disable Error Record Serialization Table (ERST)
1148 ether= [HW,NET] Ethernet cards parameters
1149 This option is obsoleted by the "netdev=" option, which
1150 has equivalent usage. See its documentation for details.
1154 Permit 'security.evm' to be updated regardless of
1155 current integrity status.
1159 fail_make_request=[KNL]
1160 General fault injection mechanism.
1161 Format: <interval>,<probability>,<space>,<times>
1162 See also Documentation/fault-injection/.
1165 See Documentation/blockdev/floppy.txt.
1167 force_pal_cache_flush
1168 [IA-64] Avoid check_sal_cache_flush which may hang on
1169 buggy SAL_CACHE_FLUSH implementations. Using this
1170 parameter will force ia64_sal_cache_flush to call
1171 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1174 Forcefully enable Physical Address Extension (PAE).
1175 Many Pentium M systems disable PAE but may have a
1176 functionally usable PAE implementation.
1177 Warning: use of this parameter will taint the kernel
1178 and may cause unknown problems.
1181 [FTRACE] will set and start the specified tracer
1182 as early as possible in order to facilitate early
1185 ftrace_dump_on_oops[=orig_cpu]
1186 [FTRACE] will dump the trace buffers on oops.
1187 If no parameter is passed, ftrace will dump
1188 buffers of all CPUs, but if you pass orig_cpu, it will
1189 dump only the buffer of the CPU that triggered the
1192 ftrace_filter=[function-list]
1193 [FTRACE] Limit the functions traced by the function
1194 tracer at boot up. function-list is a comma separated
1195 list of functions. This list can be changed at run
1196 time by the set_ftrace_filter file in the debugfs
1199 ftrace_notrace=[function-list]
1200 [FTRACE] Do not trace the functions specified in
1201 function-list. This list can be changed at run time
1202 by the set_ftrace_notrace file in the debugfs
1205 ftrace_graph_filter=[function-list]
1206 [FTRACE] Limit the top level callers functions traced
1207 by the function graph tracer at boot up.
1208 function-list is a comma separated list of functions
1209 that can be changed at run time by the
1210 set_graph_function file in the debugfs tracing directory.
1212 ftrace_graph_notrace=[function-list]
1213 [FTRACE] Do not trace from the functions specified in
1214 function-list. This list is a comma separated list of
1215 functions that can be changed at run time by the
1216 set_graph_notrace file in the debugfs tracing directory.
1219 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1220 support via parallel port (up to 5 devices per port)
1221 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1222 See also Documentation/input/joystick-parport.txt
1226 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1230 gcov_persist= [GCOV] When non-zero (default), profiling data for
1231 kernel modules is saved and remains accessible via
1232 debugfs, even when the module is unloaded/reloaded.
1233 When zero, profiling data is discarded and associated
1234 debugfs files are removed at module unload time.
1236 gpt [EFI] Forces disk with valid GPT signature but
1237 invalid Protective MBR to be treated as GPT. If the
1238 primary GPT is corrupted, it enables the backup/alternate
1239 GPT to be used instead.
1241 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1242 the "Enable 0" bit of the configuration register.
1245 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1246 the "Enable 0" bit of the configuration register.
1249 grcan.select= [HW] Select which physical interface to use.
1252 grcan.txsize= [HW] Sets the size of the tx buffer.
1253 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1255 grcan.rxsize= [HW] Sets the size of the rx buffer.
1256 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1259 hashdist= [KNL,NUMA] Large hashes allocated during boot
1260 are distributed across NUMA nodes. Defaults on
1261 for 64-bit NUMA, off otherwise.
1262 Format: 0 | 1 (for off | on)
1264 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1266 hd= [EIDE] (E)IDE hard drive subsystem geometry
1267 Format: <cyl>,<head>,<sect>
1270 Disable Hardware Error Source Table (HEST) support;
1271 corresponding firmware-first mode error processing
1272 logic will be disabled.
1274 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1275 size of <nn>. This works even on boxes that have no
1276 highmem otherwise. This also works to reduce highmem
1277 size on bigger boxes.
1279 highres= [KNL] Enable/disable high resolution timer mode.
1280 Valid parameters: "on", "off"
1284 See Documentation/isdn/README.HiSax.
1288 hpet= [X86-32,HPET] option to control HPET usage
1289 Format: { enable (default) | disable | force |
1291 disable: disable HPET and use PIT instead
1292 force: allow force enabled of undocumented chips (ICH4,
1294 verbose: show contents of HPET registers during setup
1296 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1297 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1299 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1300 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1301 On x86-64 and powerpc, this option can be specified
1302 multiple times interleaved with hugepages= to reserve
1303 huge pages of different sizes. Valid pages sizes on
1304 x86-64 are 2M (when the CPU supports "pse") and 1G
1305 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1307 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1308 terminal devices. Valid values: 0..8
1309 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1310 If specified, z/VM IUCV HVC accepts connections
1311 from listed z/VM user IDs only.
1313 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1314 hardware thread id mappings.
1315 Format: <cpu>:<hwthread>
1318 Do not unregister boot console at start. This is only
1319 useful for debugging when something happens in the window
1320 between unregistering the boot console and initializing
1323 i2c_bus= [HW] Override the default board specific I2C bus speed
1324 or register an additional I2C bus that is not
1325 registered from board initialization code.
1329 i8042.debug [HW] Toggle i8042 debug mode
1330 i8042.unmask_kbd_data
1331 [HW] Enable printing of interrupt data from the KBD port
1332 (disabled by default, and as a pre-condition
1333 requires that i8042.debug=1 be enabled)
1334 i8042.direct [HW] Put keyboard port into non-translated mode
1335 i8042.dumbkbd [HW] Pretend that controller can only read data from
1336 keyboard and cannot control its state
1337 (Don't attempt to blink the leds)
1338 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1339 i8042.nokbd [HW] Don't check/create keyboard port
1340 i8042.noloop [HW] Disable the AUX Loopback command while probing
1342 i8042.nomux [HW] Don't check presence of an active multiplexing
1344 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1346 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1347 i8042.reset [HW] Reset the controller during init and cleanup
1348 i8042.unlock [HW] Unlock (ignore) the keylock
1349 i8042.kbdreset [HW] Reset device connected to KBD port
1353 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1354 indicates that the driver is running on unsupported
1356 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1357 does not match list of supported models.
1359 [HW] Report power status in /proc/i8k
1360 (disabled by default)
1361 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1364 i915.invert_brightness=
1365 [DRM] Invert the sense of the variable that is used to
1366 set the brightness of the panel backlight. Normally a
1367 brightness value of 0 indicates backlight switched off,
1368 and the maximum of the brightness value sets the backlight
1369 to maximum brightness. If this parameter is set to 0
1370 (default) and the machine requires it, or this parameter
1371 is set to 1, a brightness value of 0 sets the backlight
1372 to maximum brightness, and the maximum of the brightness
1373 value switches the backlight off.
1374 -1 -- never invert brightness
1375 0 -- machine default
1376 1 -- force brightness inversion
1379 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1381 ide-core.nodma= [HW] (E)IDE subsystem
1382 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1383 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1384 .cdrom .chs .ignore_cable are additional options
1385 See Documentation/ide/ide.txt.
1387 ide-generic.probe-mask= [HW] (E)IDE subsystem
1389 Probe mask for legacy ISA IDE ports. Depending on
1390 platform up to 6 ports are supported, enabled by
1391 setting corresponding bits in the mask to 1. The
1392 default value is 0x0, which has a special meaning.
1393 On systems that have PCI, it triggers scanning the
1394 PCI bus for the first and the second port, which
1395 are then probed. On systems without PCI the value
1396 of 0x0 enables probing the two first ports as if it
1399 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1400 Claim all unknown PCI IDE storage controllers.
1403 Format: idle=poll, idle=halt, idle=nomwait
1404 Poll forces a polling idle loop that can slightly
1405 improve the performance of waking up a idle CPU, but
1406 will use a lot of power and make the system run hot.
1408 idle=halt: Halt is forced to be used for CPU idle.
1409 In such case C2/C3 won't be used again.
1410 idle=nomwait: Disable mwait for CPU C-states
1412 ignore_loglevel [KNL]
1413 Ignore loglevel setting - this will print /all/
1414 kernel messages to the console. Useful for debugging.
1415 We also add it as printk module parameter, so users
1416 could change it dynamically, usually by
1417 /sys/module/printk/parameters/ignore_loglevel.
1419 ihash_entries= [KNL]
1420 Set number of hash buckets for inode cache.
1422 ima_appraise= [IMA] appraise integrity measurements
1423 Format: { "off" | "enforce" | "fix" | "log" }
1426 ima_appraise_tcb [IMA]
1427 The builtin appraise policy appraises all files
1431 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1435 The list of supported hash algorithms is defined
1436 in crypto/hash_info.h.
1439 The builtin measurement policy to load during IMA
1440 setup. Specyfing "tcb" as the value, measures all
1441 programs exec'd, files mmap'd for exec, and all files
1442 opened with the read mode bit set by either the
1443 effective uid (euid=0) or uid=0.
1446 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1447 Load a policy which meets the needs of the Trusted
1448 Computing Base. This means IMA will measure all
1449 programs exec'd, files mmap'd for exec, and all files
1450 opened for read by uid=0.
1453 Select one of defined IMA measurements template formats.
1454 Formats: { "ima" | "ima-ng" | "ima-sig" }
1458 [IMA] Define a custom template format.
1459 Format: { "field1|...|fieldN" }
1461 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1462 Format: <min_file_size>
1463 Set the minimal file size for using asynchronous hash.
1464 If left unspecified, ahash usage is disabled.
1466 ahash performance varies for different data sizes on
1467 different crypto accelerators. This option can be used
1468 to achieve the best performance for a particular HW.
1470 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1472 Set hashing buffer size. Default: 4k.
1474 ahash performance varies for different chunk sizes on
1475 different crypto accelerators. This option can be used
1476 to achieve best performance for particular HW.
1480 Run specified binary instead of /sbin/init as init
1483 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1484 for working out where the kernel is dying during
1487 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1488 initcall functions. Useful for debugging built-in
1489 modules and initcalls.
1491 initrd= [BOOT] Specify the location of the initial ramdisk
1493 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1496 int_pln_enable [x86] Enable power limit notification interrupt
1498 integrity_audit=[IMA]
1499 Format: { "0" | "1" }
1500 0 -- basic integrity auditing messages. (Default)
1501 1 -- additional integrity auditing messages.
1503 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1505 Enable intel iommu driver.
1507 Disable intel iommu driver.
1508 igfx_off [Default Off]
1509 By default, gfx is mapped as normal device. If a gfx
1510 device has a dedicated DMAR unit, the DMAR unit is
1511 bypassed by not enabling DMAR with this option. In
1512 this case, gfx device will use physical address for
1515 With this option iommu will not optimize to look
1516 for io virtual address below 32-bit forcing dual
1517 address cycle on pci bus for cards supporting greater
1518 than 32-bit addressing. The default is to look
1519 for translation below 32-bit and if not available
1520 then look in the higher range.
1521 strict [Default Off]
1522 With this option on every unmap_single operation will
1523 result in a hardware IOTLB flush operation as opposed
1524 to batching them for performance.
1525 sp_off [Default Off]
1526 By default, super page will be supported if Intel IOMMU
1527 has the capability. With this option, super page will
1529 ecs_off [Default Off]
1530 By default, extended context tables will be supported if
1531 the hardware advertises that it has support both for the
1532 extended tables themselves, and also PASID support. With
1533 this option set, extended tables will not be used even
1534 on hardware which claims to support them.
1536 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1537 0 disables intel_idle and fall back on acpi_idle.
1538 1 to 6 specify maximum depth of C-state.
1542 Do not enable intel_pstate as the default
1543 scaling driver for the supported processors
1545 Enable intel_pstate on systems that prohibit it by default
1546 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1547 instead of acpi-cpufreq may disable platform features, such
1548 as thermal controls and power capping, that rely on ACPI
1549 P-States information being indicated to OSPM and therefore
1550 should be used with caution. This option does not work with
1551 processors that aren't supported by the intel_pstate driver
1552 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1554 Do not enable hardware P state control (HWP)
1557 Only load intel_pstate on systems which support
1558 hardware P state control (HWP) if available.
1560 Don't use ACPI processor performance control objects
1561 _PSS and _PPC specified limits.
1563 intremap= [X86-64, Intel-IOMMU]
1564 on enable Interrupt Remapping (default)
1565 off disable Interrupt Remapping
1566 nosid disable Source ID checking
1568 BIOS x2APIC opt-out request will be ignored
1570 iomem= Disable strict checking of access to MMIO memory
1571 strict regions from userspace.
1586 nobypass [PPC/POWERNV]
1587 Disable IOMMU bypass, using IOMMU for PCI devices.
1590 io7= [HW] IO7 for Marvel based alpha systems
1591 See comment before marvel_specify_io7 in
1592 arch/alpha/kernel/core_marvel.c.
1594 io_delay= [X86] I/O delay method
1596 Standard port 0x80 based delay
1598 Alternate port 0xed based delay (needed on some systems)
1600 Simple two microseconds delay
1605 See Documentation/filesystems/nfs/nfsroot.txt.
1608 When an interrupt is not handled search all handlers
1609 for it. Intended to get systems with badly broken
1613 When an interrupt is not handled search all handlers
1614 for it. Also check all handlers each timer
1615 interrupt. Intended to get systems with badly broken
1619 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1621 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1623 <cpu number>,...,<cpu number>
1625 <cpu number>-<cpu number>
1626 (must be a positive range in ascending order)
1628 <cpu number>,...,<cpu number>-<cpu number>
1630 This option can be used to specify one or more CPUs
1631 to isolate from the general SMP balancing and scheduling
1632 algorithms. You can move a process onto or off an
1633 "isolated" CPU via the CPU affinity syscalls or cpuset.
1634 <cpu number> begins at 0 and the maximum value is
1635 "number of CPUs in system - 1".
1637 This option is the preferred way to isolate CPUs. The
1638 alternative -- manually setting the CPU mask of all
1639 tasks in the system -- can cause problems and
1640 suboptimal load balancer performance.
1644 ivrs_ioapic [HW,X86_64]
1645 Provide an override to the IOAPIC-ID<->DEVICE-ID
1646 mapping provided in the IVRS ACPI table. For
1647 example, to map IOAPIC-ID decimal 10 to
1648 PCI device 00:14.0 write the parameter as:
1649 ivrs_ioapic[10]=00:14.0
1651 ivrs_hpet [HW,X86_64]
1652 Provide an override to the HPET-ID<->DEVICE-ID
1653 mapping provided in the IVRS ACPI table. For
1654 example, to map HPET-ID decimal 0 to
1655 PCI device 00:14.0 write the parameter as:
1656 ivrs_hpet[0]=00:14.0
1658 js= [HW,JOY] Analog joystick
1659 See Documentation/input/joystick.txt.
1662 Enable/disable kernel and module base offset ASLR
1663 (Address Space Layout Randomization) if built into
1664 the kernel. When CONFIG_HIBERNATION is selected,
1665 kASLR is disabled by default. When kASLR is enabled,
1666 hibernation will be disabled.
1670 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1671 specifies the amount of memory usable by the kernel
1672 for non-movable allocations. The requested amount is
1673 spread evenly throughout all nodes in the system. The
1674 remaining memory in each node is used for Movable
1675 pages. In the event, a node is too small to have both
1676 kernelcore and Movable pages, kernelcore pages will
1677 take priority and other nodes will have a larger number
1678 of Movable pages. The Movable zone is used for the
1679 allocation of pages that may be reclaimed or moved
1680 by the page migration subsystem. This means that
1681 HugeTLB pages may not be allocated from this zone.
1682 Note that allocations like PTEs-from-HighMem still
1683 use the HighMem zone if it exists, and the Normal
1684 zone if it does not.
1686 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1687 Format: <Controller#>[,poll interval]
1688 The controller # is the number of the ehci usb debug
1689 port as it is probed via PCI. The poll interval is
1690 optional and is the number seconds in between
1691 each poll cycle to the debug port in case you need
1692 the functionality for interrupting the kernel with
1693 gdb or control-c on the dbgp connection. When
1694 not using this parameter you use sysrq-g to break into
1695 the kernel debugger.
1697 kgdboc= [KGDB,HW] kgdb over consoles.
1698 Requires a tty driver that supports console polling,
1699 or a supported polling keyboard driver (non-usb).
1700 Serial only format: <serial_device>[,baud]
1701 keyboard only format: kbd
1702 keyboard and serial format: kbd,<serial_device>[,baud]
1703 Optional Kernel mode setting:
1704 kms, kbd format: kms,kbd
1705 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1707 kgdbwait [KGDB] Stop kernel execution and enter the
1708 kernel debugger at the earliest opportunity.
1710 kmac= [MIPS] korina ethernet MAC address.
1711 Configure the RouterBoard 532 series on-chip
1712 Ethernet adapter MAC address.
1714 kmemleak= [KNL] Boot-time kmemleak enable/disable
1715 Valid arguments: on, off
1717 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1720 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1721 Valid arguments: 0, 1, 2
1722 kmemcheck=0 (disabled)
1723 kmemcheck=1 (enabled)
1724 kmemcheck=2 (one-shot mode)
1725 Default: 2 (one-shot mode)
1727 kstack=N [X86] Print N words from the kernel stack
1730 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1731 Default is 0 (don't ignore, but inject #GP)
1733 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1737 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1738 Default is 1 (enabled)
1740 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1742 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1744 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1745 (virtualized MMU) support on capable Intel chips.
1746 Default is 1 (enabled)
1748 kvm-intel.emulate_invalid_guest_state=
1749 [KVM,Intel] Enable emulation of invalid guest states
1750 Default is 0 (disabled)
1752 kvm-intel.flexpriority=
1753 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1754 Default is 1 (enabled)
1757 [KVM,Intel] Enable VMX nesting (nVMX).
1758 Default is 0 (disabled)
1760 kvm-intel.unrestricted_guest=
1761 [KVM,Intel] Disable unrestricted guest feature
1762 (virtualized real and unpaged mode) on capable
1763 Intel chips. Default is 1 (enabled)
1765 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1766 feature (tagged TLBs) on capable Intel chips.
1767 Default is 1 (enabled)
1773 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1776 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1777 value for LAPIC timer one-shot implementation. Default
1778 back to the programmable timer unit in the LAPIC.
1780 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1783 libata.dma= [LIBATA] DMA control
1784 libata.dma=0 Disable all PATA and SATA DMA
1785 libata.dma=1 PATA and SATA Disk DMA only
1786 libata.dma=2 ATAPI (CDROM) DMA only
1787 libata.dma=4 Compact Flash DMA only
1788 Combinations also work, so libata.dma=3 enables DMA
1789 for disks and CDROMs, but not CFs.
1791 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1792 libata.ignore_hpa=0 keep BIOS limits (default)
1793 libata.ignore_hpa=1 ignore limits, using full disk
1795 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1799 libata.force= [LIBATA] Force configurations. The format is comma
1800 separated list of "[ID:]VAL" where ID is
1801 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1802 matching port, link or device. Basically, it matches
1803 the ATA ID string printed on console by libata. If
1804 the whole ID part is omitted, the last PORT and DEVICE
1805 values are used. If ID hasn't been specified yet, the
1806 configuration applies to all ports, links and devices.
1808 If only DEVICE is omitted, the parameter applies to
1809 the port and all links and devices behind it. DEVICE
1810 number of 0 either selects the first device or the
1811 first fan-out link behind PMP device. It does not
1812 select the host link. DEVICE number of 15 selects the
1813 host link and device attached to it.
1815 The VAL specifies the configuration to force. As long
1816 as there's no ambiguity shortcut notation is allowed.
1817 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1818 The following configurations can be forced.
1820 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1821 Any ID with matching PORT is used.
1823 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1825 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1826 udma[/][16,25,33,44,66,100,133] notation is also
1829 * [no]ncq: Turn on or off NCQ.
1831 * [no]ncqtrim: Turn off queued DSM TRIM.
1833 * nohrst, nosrst, norst: suppress hard, soft
1836 * rstonce: only attempt one reset during
1837 hot-unplug link recovery
1839 * dump_id: dump IDENTIFY data.
1841 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1843 * disable: Disable this device.
1845 If there are multiple matching configurations changing
1846 the same attribute, the last one is used.
1848 memblock=debug [KNL] Enable memblock debug messages.
1850 load_ramdisk= [RAM] List of ramdisks to load from floppy
1851 See Documentation/blockdev/ramdisk.txt.
1853 lockd.nlm_grace_period=P [NFS] Assign grace period.
1856 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1859 lockd.nlm_timeout=T [NFS] Assign timeout value.
1862 lockd.nlm_udpport=M [NFS] Assign UDP port.
1865 locktorture.nreaders_stress= [KNL]
1866 Set the number of locking read-acquisition kthreads.
1867 Defaults to being automatically set based on the
1868 number of online CPUs.
1870 locktorture.nwriters_stress= [KNL]
1871 Set the number of locking write-acquisition kthreads.
1873 locktorture.onoff_holdoff= [KNL]
1874 Set time (s) after boot for CPU-hotplug testing.
1876 locktorture.onoff_interval= [KNL]
1877 Set time (s) between CPU-hotplug operations, or
1878 zero to disable CPU-hotplug testing.
1880 locktorture.shuffle_interval= [KNL]
1881 Set task-shuffle interval (jiffies). Shuffling
1882 tasks allows some CPUs to go into dyntick-idle
1883 mode during the locktorture test.
1885 locktorture.shutdown_secs= [KNL]
1886 Set time (s) after boot system shutdown. This
1887 is useful for hands-off automated testing.
1889 locktorture.stat_interval= [KNL]
1890 Time (s) between statistics printk()s.
1892 locktorture.stutter= [KNL]
1893 Time (s) to stutter testing, for example,
1894 specifying five seconds causes the test to run for
1895 five seconds, wait for five seconds, and so on.
1896 This tests the locking primitive's ability to
1897 transition abruptly to and from idle.
1899 locktorture.torture_runnable= [BOOT]
1900 Start locktorture running at boot time.
1902 locktorture.torture_type= [KNL]
1903 Specify the locking implementation to test.
1905 locktorture.verbose= [KNL]
1906 Enable additional printk() statements.
1908 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1911 loglevel= All Kernel Messages with a loglevel smaller than the
1912 console loglevel will be printed to the console. It can
1913 also be changed with klogd or other programs. The
1914 loglevels are defined as follows:
1916 0 (KERN_EMERG) system is unusable
1917 1 (KERN_ALERT) action must be taken immediately
1918 2 (KERN_CRIT) critical conditions
1919 3 (KERN_ERR) error conditions
1920 4 (KERN_WARNING) warning conditions
1921 5 (KERN_NOTICE) normal but significant condition
1922 6 (KERN_INFO) informational
1923 7 (KERN_DEBUG) debug-level messages
1925 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1926 in bytes. n must be a power of two and greater
1927 than the minimal size. The minimal size is defined
1928 by LOG_BUF_SHIFT kernel config parameter. There is
1929 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1930 that allows to increase the default size depending on
1931 the number of CPUs. See init/Kconfig for more details.
1933 logo.nologo [FB] Disables display of the built-in Linux logo.
1934 This may be used to provide more screen space for
1935 kernel log messages and is useful when debugging
1936 kernel boot problems.
1938 lp=0 [LP] Specify parallel ports to use, e.g,
1939 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1940 lp=reset first parallel port). 'lp=0' disables the
1941 lp=auto printer driver. 'lp=reset' (which can be
1942 specified in addition to the ports) causes
1943 attached printers to be reset. Using
1944 lp=port1,port2,... specifies the parallel ports
1945 to associate lp devices with, starting with
1946 lp0. A port specification may be 'none' to skip
1947 that lp device, or a parport name such as
1948 'parport0'. Specifying 'lp=auto' instead of a
1949 port specification list means that device IDs
1950 from each port should be examined, to see if
1951 an IEEE 1284-compliant printer is attached; if
1952 so, the driver will manage that printer.
1953 See also header of drivers/char/lp.c.
1956 Sets loops_per_jiffy to given constant, thus avoiding
1957 time-consuming boot-time autodetection (up to 250 ms per
1958 CPU). 0 enables autodetection (default). To determine
1959 the correct value for your kernel, boot with normal
1960 autodetection and see what value is printed. Note that
1961 on SMP systems the preset will be applied to all CPUs,
1962 which is likely to cause problems if your CPUs need
1963 significantly divergent settings. An incorrect value
1964 will cause delays in the kernel to be wrong, leading to
1965 unpredictable I/O errors and other breakage. Although
1966 unlikely, in the extreme case this might damage your
1970 Format: <io>,<irq>,<dma>
1972 machvec= [IA-64] Force the use of a particular machine-vector
1973 (machvec) in a generic kernel.
1974 Example: machvec=hpzx1_swiotlb
1976 machtype= [Loongson] Share the same kernel image file between different
1978 Example: machtype=lemote-yeeloong-2f-7inch
1980 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1981 than or equal to this physical address is ignored.
1983 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1984 should make use of. maxcpus=n : n >= 0 limits the
1985 kernel to using 'n' processors. n=0 is a special case,
1986 it is equivalent to "nosmp", which also disables
1989 max_loop= [LOOP] The number of loop block devices that get
1990 (loop.max_loop) unconditionally pre-created at init time. The default
1991 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1992 of statically allocating a predefined number, loop
1993 devices can be requested on-demand with the
1994 /dev/loop-control interface.
1996 mce [X86-32] Machine Check Exception
1998 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2000 md= [HW] RAID subsystems devices and level
2001 See Documentation/md.txt.
2004 Format: <first>,<last>
2005 Specifies range of consoles to be captured by the MDA.
2007 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2008 Amount of memory to be used when the kernel is not able
2009 to see the whole system memory or for test.
2010 [X86] Work as limiting max address. Use together
2011 with memmap= to avoid physical address space collisions.
2012 Without memmap= PCI devices could be placed at addresses
2013 belonging to unused RAM.
2015 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2019 [KNL,SH] Allow user to override the default size for
2020 per-device physically contiguous DMA buffers.
2022 memmap=exactmap [KNL,X86] Enable setting of an exact
2023 E820 memory map, as specified by the user.
2024 Such memmap=exactmap lines can be constructed based on
2025 BIOS output or other requirements. See the memmap=nn@ss
2028 memmap=nn[KMG]@ss[KMG]
2029 [KNL] Force usage of a specific region of memory.
2030 Region of memory to be used is from ss to ss+nn.
2032 memmap=nn[KMG]#ss[KMG]
2033 [KNL,ACPI] Mark specific memory as ACPI data.
2034 Region of memory to be marked is from ss to ss+nn.
2036 memmap=nn[KMG]$ss[KMG]
2037 [KNL,ACPI] Mark specific memory as reserved.
2038 Region of memory to be reserved is from ss to ss+nn.
2039 Example: Exclude memory from 0x18690000-0x1869ffff
2040 memmap=64K$0x18690000
2042 memmap=0x10000$0x18690000
2044 memmap=nn[KMG]!ss[KMG]
2045 [KNL,X86] Mark specific memory as protected.
2046 Region of memory to be used, from ss to ss+nn.
2047 The memory region may be marked as e820 type 12 (0xc)
2048 and is NVDIMM or ADR memory.
2050 memory_corruption_check=0/1 [X86]
2051 Some BIOSes seem to corrupt the first 64k of
2052 memory when doing things like suspend/resume.
2053 Setting this option will scan the memory
2054 looking for corruption. Enabling this will
2055 both detect corruption and prevent the kernel
2056 from using the memory being corrupted.
2057 However, its intended as a diagnostic tool; if
2058 repeatable BIOS-originated corruption always
2059 affects the same memory, you can use memmap=
2060 to prevent the kernel from using that memory.
2062 memory_corruption_check_size=size [X86]
2063 By default it checks for corruption in the low
2064 64k, making this memory unavailable for normal
2065 use. Use this parameter to scan for
2066 corruption in more or less memory.
2068 memory_corruption_check_period=seconds [X86]
2069 By default it checks for corruption every 60
2070 seconds. Use this parameter to check at some
2071 other rate. 0 disables periodic checking.
2073 memtest= [KNL,X86,ARM] Enable memtest
2075 default : 0 <disable>
2076 Specifies the number of memtest passes to be
2077 performed. Each pass selects another test
2078 pattern from a given set of patterns. Memtest
2079 fills the memory with this pattern, validates
2080 memory contents and reserves bad memory
2081 regions that are detected.
2083 meye.*= [HW] Set MotionEye Camera parameters
2084 See Documentation/video4linux/meye.txt.
2086 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2087 Multi-Function General Purpose Timers on AMD Geode
2090 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2091 the BIOS has incorrectly applied a workaround. TinyBIOS
2092 version 0.98 is known to be affected, 0.99 fixes the
2093 problem by letting the user disable the workaround.
2097 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2098 physical address is ignored.
2100 mini2440= [ARM,HW,KNL]
2101 Format:[0..2][b][c][t]
2103 MINI2440 configuration specification:
2104 0 - The attached screen is the 3.5" TFT
2105 1 - The attached screen is the 7" TFT
2106 2 - The VGA Shield is attached (1024x768)
2107 Leaving out the screen size parameter will not load
2108 the TFT driver, and the framebuffer will be left
2110 b - Enable backlight. The TFT backlight pin will be
2111 linked to the kernel VESA blanking code and a GPIO
2112 LED. This parameter is not necessary when using the
2114 c - Enable the s3c camera interface.
2115 t - Reserved for enabling touchscreen support. The
2116 touchscreen support is not enabled in the mainstream
2117 kernel as of 2.6.30, a preliminary port can be found
2118 in the "bleeding edge" mini2440 support kernel at
2119 http://repo.or.cz/w/linux-2.6/mini2440.git
2122 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2123 parameter allows control of the logging verbosity for
2124 the additional memory initialisation checks. A value
2125 of 0 disables mminit logging and a level of 4 will
2126 log everything. Information is printed at KERN_DEBUG
2127 so loglevel=8 may also need to be specified.
2130 [KNL] When CONFIG_MODULE_SIG is set, this means that
2131 modules without (valid) signatures will fail to load.
2132 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2133 is always true, so this option does nothing.
2136 [MOUSE] Maximum time between finger touching and
2137 leaving touchpad surface for touch to be considered
2138 a tap and be reported as a left button click (for
2139 touchpads working in absolute mode only).
2141 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2142 reporting absolute coordinates, such as tablets
2143 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2144 reporting absolute coordinates, such as tablets
2146 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2147 is similar to kernelcore except it specifies the
2148 amount of memory used for migratable allocations.
2149 If both kernelcore and movablecore is specified,
2150 then kernelcore will be at *least* the specified
2151 value but may be more. If movablecore on its own
2152 is specified, the administrator must be careful
2153 that the amount of memory usable for all allocations
2156 movable_node [KNL,X86] Boot-time switch to enable the effects
2157 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2159 MTD_Partition= [MTD]
2160 Format: <name>,<region-number>,<size>,<offset>
2162 MTD_Region= [MTD] Format:
2163 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2166 See drivers/mtd/cmdlinepart.c.
2168 multitce=off [PPC] This parameter disables the use of the pSeries
2169 firmware feature for updating multiple TCE entries
2172 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2174 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2176 boundary - index of last SLC block on Flex-OneNAND.
2177 The remaining blocks are configured as MLC blocks.
2178 lock - Configure if Flex-OneNAND boundary should be locked.
2179 Once locked, the boundary cannot be changed.
2180 1 indicates lock status, 0 indicates unlock status.
2183 ARM/S3C2412 JIVE boot control
2185 See arch/arm/mach-s3c2412/mach-jive.c
2187 mtouchusb.raw_coordinates=
2188 [HW] Make the MicroTouch USB driver use raw coordinates
2189 ('y', default) or cooked coordinates ('n')
2191 mtrr_chunk_size=nn[KMG] [X86]
2192 used for mtrr cleanup. It is largest continuous chunk
2193 that could hold holes aka. UC entries.
2195 mtrr_gran_size=nn[KMG] [X86]
2196 Used for mtrr cleanup. It is granularity of mtrr block.
2198 Large value could prevent small alignment from
2201 mtrr_spare_reg_nr=n [X86]
2203 Range: 0,7 : spare reg number
2205 Used for mtrr cleanup. It is spare mtrr entries number.
2206 Set to 2 or more if your graphical card needs more.
2208 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2210 netdev= [NET] Network devices parameters
2211 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2212 Note that mem_start is often overloaded to mean
2213 something different and driver-specific.
2214 This usage is only documented in each driver source
2218 [NETFILTER] Enable connection tracking flow accounting
2219 0 to disable accounting
2220 1 to enable accounting
2223 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2224 See Documentation/filesystems/nfs/nfsroot.txt.
2226 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2227 See Documentation/filesystems/nfs/nfsroot.txt.
2229 nfsrootdebug [NFS] enable nfsroot debugging messages.
2230 See Documentation/filesystems/nfs/nfsroot.txt.
2232 nfs.callback_tcpport=
2233 [NFS] set the TCP port on which the NFSv4 callback
2234 channel should listen.
2237 [NFS] sets the pathname to the program which is used
2238 to update the NFS client cache entries.
2240 nfs.cache_getent_timeout=
2241 [NFS] sets the timeout after which an attempt to
2242 update a cache entry is deemed to have failed.
2244 nfs.idmap_cache_timeout=
2245 [NFS] set the maximum lifetime for idmapper cache
2249 [NFS] enable 64-bit inode numbers.
2250 If zero, the NFS client will fake up a 32-bit inode
2251 number for the readdir() and stat() syscalls instead
2252 of returning the full 64-bit number.
2253 The default is to return 64-bit inode numbers.
2255 nfs.max_session_slots=
2256 [NFSv4.1] Sets the maximum number of session slots
2257 the client will attempt to negotiate with the server.
2258 This limits the number of simultaneous RPC requests
2259 that the client can send to the NFSv4.1 server.
2260 Note that there is little point in setting this
2261 value higher than the max_tcp_slot_table_limit.
2263 nfs.nfs4_disable_idmapping=
2264 [NFSv4] When set to the default of '1', this option
2265 ensures that both the RPC level authentication
2266 scheme and the NFS level operations agree to use
2267 numeric uids/gids if the mount is using the
2268 'sec=sys' security flavour. In effect it is
2269 disabling idmapping, which can make migration from
2270 legacy NFSv2/v3 systems to NFSv4 easier.
2271 Servers that do not support this mode of operation
2272 will be autodetected by the client, and it will fall
2273 back to using the idmapper.
2274 To turn off this behaviour, set the value to '0'.
2276 [NFS4] Specify an additional fixed unique ident-
2277 ification string that NFSv4 clients can insert into
2278 their nfs_client_id4 string. This is typically a
2279 UUID that is generated at system install time.
2281 nfs.send_implementation_id =
2282 [NFSv4.1] Send client implementation identification
2283 information in exchange_id requests.
2284 If zero, no implementation identification information
2286 The default is to send the implementation identification
2289 nfs.recover_lost_locks =
2290 [NFSv4] Attempt to recover locks that were lost due
2291 to a lease timeout on the server. Please note that
2292 doing this risks data corruption, since there are
2293 no guarantees that the file will remain unchanged
2294 after the locks are lost.
2295 If you want to enable the kernel legacy behaviour of
2296 attempting to recover these locks, then set this
2298 The default parameter value of '0' causes the kernel
2299 not to attempt recovery of lost locks.
2301 nfs4.layoutstats_timer =
2302 [NFSv4.2] Change the rate at which the kernel sends
2303 layoutstats to the pNFS metadata server.
2305 Setting this to value to 0 causes the kernel to use
2306 whatever value is the default set by the layout
2307 driver. A non-zero value sets the minimum interval
2308 in seconds between layoutstats transmissions.
2310 nfsd.nfs4_disable_idmapping=
2311 [NFSv4] When set to the default of '1', the NFSv4
2312 server will return only numeric uids and gids to
2313 clients using auth_sys, and will accept numeric uids
2314 and gids from such clients. This is intended to ease
2315 migration from NFSv2/v3.
2317 objlayoutdriver.osd_login_prog=
2318 [NFS] [OBJLAYOUT] sets the pathname to the program which
2319 is used to automatically discover and login into new
2320 osd-targets. Please see:
2321 Documentation/filesystems/pnfs.txt for more explanations
2323 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2324 when a NMI is triggered.
2325 Format: [state][,regs][,debounce][,die]
2327 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2328 Format: [panic,][nopanic,][num]
2330 0 - turn hardlockup detector in nmi_watchdog off
2331 1 - turn hardlockup detector in nmi_watchdog on
2332 When panic is specified, panic when an NMI watchdog
2333 timeout occurs (or 'nopanic' to override the opposite
2334 default). To disable both hard and soft lockup detectors,
2335 please see 'nowatchdog'.
2336 This is useful when you use a panic=... timeout and
2337 need the box quickly up again.
2339 netpoll.carrier_timeout=
2340 [NET] Specifies amount of time (in seconds) that
2341 netpoll should wait for a carrier. By default netpoll
2344 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2345 emulation library even if a 387 maths coprocessor
2349 [HW] Never suspend the console
2350 Disable suspending of consoles during suspend and
2351 hibernate operations. Once disabled, debugging
2352 messages can reach various consoles while the rest
2353 of the system is being put to sleep (ie, while
2354 debugging driver suspend/resume hooks). This may
2355 not work reliably with all consoles, but is known
2356 to work with serial and VGA consoles.
2357 To facilitate more flexible debugging, we also add
2358 console_suspend, a printk module parameter to control
2359 it. Users could use console_suspend (usually
2360 /sys/module/printk/parameters/console_suspend) to
2361 turn on/off it dynamically.
2363 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2364 caches in the slab allocator. Saves per-node memory,
2365 but will impact performance.
2369 noapic [SMP,APIC] Tells the kernel to not make use of any
2370 IOAPICs that may be present in the system.
2372 noautogroup Disable scheduler automatic task group creation.
2374 nobats [PPC] Do not use BATs for mapping kernel lowmem
2375 on "Classic" PPC cores.
2379 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2381 nodelayacct [KNL] Disable per-task delay accounting
2383 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2385 nodsp [SH] Disable hardware DSP at boot time.
2387 noefi Disable EFI runtime services support.
2392 On X86-32 available only on PAE configured kernels.
2393 noexec=on: enable non-executable mappings (default)
2394 noexec=off: disable non-executable mappings
2397 Disable SMAP (Supervisor Mode Access Prevention)
2398 even if it is supported by processor.
2401 Disable SMEP (Supervisor Mode Execution Prevention)
2402 even if it is supported by processor.
2405 This affects only 32-bit executables.
2406 noexec32=on: enable non-executable mappings (default)
2407 read doesn't imply executable mappings
2408 noexec32=off: disable non-executable mappings
2409 read implies executable mappings
2411 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2413 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2414 register save and restore. The kernel will only save
2415 legacy floating-point registers on task switch.
2417 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2419 noxsave [BUGS=X86] Disables x86 extended register state save
2420 and restore using xsave. The kernel will fallback to
2421 enabling legacy floating-point and sse state.
2423 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2424 register states. The kernel will fall back to use
2425 xsave to save the states. By using this parameter,
2426 performance of saving the states is degraded because
2427 xsave doesn't support modified optimization while
2428 xsaveopt supports it on xsaveopt enabled systems.
2430 noxsaves [X86] Disables xsaves and xrstors used in saving and
2431 restoring x86 extended register state in compacted
2432 form of xsave area. The kernel will fall back to use
2433 xsaveopt and xrstor to save and restore the states
2434 in standard form of xsave area. By using this
2435 parameter, xsave area per process might occupy more
2436 memory on xsaves enabled systems.
2438 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2439 wfi(ARM) instruction doesn't work correctly and not to
2440 use it. This is also useful when using JTAG debugger.
2442 no_file_caps Tells the kernel not to honor file capabilities. The
2443 only way then for a file to be executed with privilege
2444 is to be setuid root or executed by root.
2446 nohalt [IA-64] Tells the kernel not to use the power saving
2447 function PAL_HALT_LIGHT when idle. This increases
2448 power-consumption. On the positive side, it reduces
2449 interrupt wake-up latency, which may improve performance
2450 in certain environments such as networked servers or
2453 nohibernate [HIBERNATION] Disable hibernation and resume.
2455 nohz= [KNL] Boottime enable/disable dynamic ticks
2456 Valid arguments: on, off
2459 nohz_full= [KNL,BOOT]
2460 In kernels built with CONFIG_NO_HZ_FULL=y, set
2461 the specified list of CPUs whose tick will be stopped
2462 whenever possible. The boot CPU will be forced outside
2463 the range to maintain the timekeeping.
2464 The CPUs in this range must also be included in the
2467 noiotrap [SH] Disables trapped I/O port accesses.
2469 noirqdebug [X86-32] Disables the code which attempts to detect and
2470 disable unhandled interrupt sources.
2472 no_timer_check [X86,APIC] Disables the code which tests for
2473 broken timer IRQ sources.
2475 noisapnp [ISAPNP] Disables ISA PnP code.
2477 noinitrd [RAM] Tells the kernel not to load any configured
2480 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2482 [Deprecated - use intremap=off]
2486 nojitter [IA-64] Disables jitter checking for ITC timers.
2488 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2490 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2493 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2494 steal time is computed, but won't influence scheduler
2497 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2499 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2501 noltlbs [PPC] Do not use large page/tlb entries for kernel
2502 lowmem mapping on PPC40x.
2504 nomca [IA-64] Disable machine check abort handling
2506 nomce [X86-32] Disable Machine Check Exception
2508 nomfgpt [X86-32] Disable Multi-Function General Purpose
2509 Timer usage (for AMD Geode machines).
2511 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2512 shutdown the other cpus. Instead use the REBOOT_VECTOR
2515 nomodule Disable module load
2517 nopat [X86] Disable PAT (page attribute table extension of
2518 pagetables) support.
2520 norandmaps Don't use address space randomization. Equivalent to
2521 echo 0 > /proc/sys/kernel/randomize_va_space
2523 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2525 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2526 with UP alternatives
2528 nordrand [X86] Disable kernel use of the RDRAND and
2529 RDSEED instructions even if they are supported
2530 by the processor. RDRAND and RDSEED are still
2531 available to user space applications.
2533 noresume [SWSUSP] Disables resume and restores original swap
2536 no-scroll [VGA] Disables scrollback.
2537 This is required for the Braillex ib80-piezo Braille
2538 reader made by F.H. Papenmeier (Germany).
2542 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2544 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2545 and disable the IO APIC. legacy for "maxcpus=0".
2547 nosoftlockup [KNL] Disable the soft-lockup detector.
2549 nosync [HW,M68K] Disables sync negotiation for all devices.
2551 notsc [BUGS=X86-32] Disable Time Stamp Counter
2553 nousb [USB] Disable the USB subsystem
2555 nowatchdog [KNL] Disable both lockup detectors, i.e.
2556 soft-lockup and NMI watchdog (hard-lockup).
2560 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2562 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2563 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2564 Some features depend on CPU0. Known dependencies are:
2565 1. Resume from suspend/hibernate depends on CPU0.
2566 Suspend/hibernate will fail if CPU0 is offline and you
2567 need to online CPU0 before suspend/hibernate.
2568 2. PIC interrupts also depend on CPU0. CPU0 can't be
2569 removed if a PIC interrupt is detected.
2570 It's said poweroff/reboot may depend on CPU0 on some
2571 machines although I haven't seen such issues so far
2572 after CPU0 is offline on a few tested machines.
2573 If the dependencies are under your control, you can
2574 turn on cpu0_hotplug.
2576 nptcg= [IA-64] Override max number of concurrent global TLB
2577 purges which is reported from either PAL_VM_SUMMARY or
2580 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2581 could support. nr_cpus=n : n >= 1 limits the kernel to
2582 supporting 'n' processors. Later in runtime you can not
2583 use hotplug cpu feature to put more cpu back to online.
2584 just like you compile the kernel NR_CPUS=n
2586 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2588 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2589 Allowed values are enable and disable
2591 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2592 one of ['zone', 'node', 'default'] can be specified
2593 This can be set from sysctl after boot.
2594 See Documentation/sysctl/vm.txt for details.
2596 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2597 See Documentation/debugging-via-ohci1394.txt for more
2600 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2601 Rather than timing out after 20 ms if an EC
2602 command is not properly ACKed, override the length
2603 of the timeout. We have interrupts disabled while
2604 waiting for the ACK, so if this is set too high
2605 interrupts *may* be lost!
2607 omap_mux= [OMAP] Override bootloader pin multiplexing.
2608 Format: <mux_mode0.mode_name=value>...
2609 For example, to override I2C bus2:
2610 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2612 oprofile.timer= [HW]
2613 Use timer interrupt instead of performance counters
2615 oprofile.cpu_type= Force an oprofile cpu type
2616 This might be useful if you have an older oprofile
2617 userland or if you want common events.
2618 Format: { arch_perfmon }
2619 arch_perfmon: [X86] Force use of architectural
2620 perfmon on Intel CPUs instead of the
2621 CPU specific event set.
2622 timer: [X86] Force use of architectural NMI
2623 timer mode (see also oprofile.timer
2624 for generic hr timer mode)
2625 [s390] Force legacy basic mode sampling
2626 (report cpu_type "timer")
2628 oops=panic Always panic on oopses. Default is to just kill the
2629 process, but there is a small probability of
2630 deadlocking the machine.
2631 This will also cause panics on machine check exceptions.
2632 Useful together with panic=30 to trigger a reboot.
2635 See Documentation/sound/oss/oss-parameters.txt
2637 page_owner= [KNL] Boot-time page_owner enabling option.
2638 Storage of the information about who allocated
2639 each page is disabled in default. With this switch,
2641 on: enable the feature
2643 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2644 timeout > 0: seconds before rebooting
2645 timeout = 0: wait forever
2646 timeout < 0: reboot immediately
2649 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2652 crash_kexec_post_notifiers
2653 Run kdump after running panic-notifiers and dumping
2654 kmsg. This only for the users who doubt kdump always
2655 succeeds in any situation.
2656 Note that this also increases risks of kdump failure,
2657 because some panic notifiers can make the crashed
2658 kernel more unstable.
2660 parkbd.port= [HW] Parallel port number the keyboard adapter is
2661 connected to, default is 0.
2663 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2664 0 for XT, 1 for AT (default is AT).
2667 parport= [HW,PPT] Specify parallel ports. 0 disables.
2668 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2669 Use 'auto' to force the driver to use any
2670 IRQ/DMA settings detected (the default is to
2671 ignore detected IRQ/DMA settings because of
2672 possible conflicts). You can specify the base
2673 address, IRQ, and DMA settings; IRQ and DMA
2674 should be numbers, or 'auto' (for using detected
2675 settings on that particular port), or 'nofifo'
2676 (to avoid using a FIFO even if it is detected).
2677 Parallel ports are assigned in the order they
2678 are specified on the command line, starting
2681 parport_init_mode= [HW,PPT]
2682 Configure VIA parallel port to operate in
2683 a specific mode. This is necessary on Pegasos
2684 computer where firmware has no options for setting
2685 up parallel port mode and sets it to spp.
2686 Currently this function knows 686a and 8231 chips.
2687 Format: [spp|ps2|epp|ecp|ecpepp]
2690 Halt all CPUs after the first oops has been printed for
2691 the specified number of seconds. This is to be used if
2692 your oopses keep scrolling off the screen.
2697 See header of drivers/block/paride/pcd.c.
2698 See also Documentation/blockdev/paride.txt.
2700 pci=option[,option...] [PCI] various PCI subsystem options:
2701 earlydump [X86] dump PCI config space before the kernel
2703 off [X86] don't probe for the PCI bus
2704 bios [X86-32] force use of PCI BIOS, don't access
2705 the hardware directly. Use this if your machine
2706 has a non-standard PCI host bridge.
2707 nobios [X86-32] disallow use of PCI BIOS, only direct
2708 hardware access methods are allowed. Use this
2709 if you experience crashes upon bootup and you
2710 suspect they are caused by the BIOS.
2711 conf1 [X86] Force use of PCI Configuration
2713 conf2 [X86] Force use of PCI Configuration
2715 noaer [PCIE] If the PCIEAER kernel config parameter is
2716 enabled, this kernel boot option can be used to
2717 disable the use of PCIE advanced error reporting.
2718 nodomains [PCI] Disable support for multiple PCI
2719 root domains (aka PCI segments, in ACPI-speak).
2720 nommconf [X86] Disable use of MMCONFIG for PCI
2722 check_enable_amd_mmconf [X86] check for and enable
2723 properly configured MMIO access to PCI
2724 config space on AMD family 10h CPU
2725 nomsi [MSI] If the PCI_MSI kernel config parameter is
2726 enabled, this kernel boot option can be used to
2727 disable the use of MSI interrupts system-wide.
2728 noioapicquirk [APIC] Disable all boot interrupt quirks.
2729 Safety option to keep boot IRQs enabled. This
2730 should never be necessary.
2731 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2732 primary IO-APIC for bridges that cannot disable
2733 boot IRQs. This fixes a source of spurious IRQs
2734 when the system masks IRQs.
2735 noioapicreroute [APIC] Disable workaround that uses the
2736 boot IRQ equivalent of an IRQ that connects to
2737 a chipset where boot IRQs cannot be disabled.
2738 The opposite of ioapicreroute.
2739 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2740 routing table. These calls are known to be buggy
2741 on several machines and they hang the machine
2742 when used, but on other computers it's the only
2743 way to get the interrupt routing table. Try
2744 this option if the kernel is unable to allocate
2745 IRQs or discover secondary PCI buses on your
2747 rom [X86] Assign address space to expansion ROMs.
2748 Use with caution as certain devices share
2749 address decoders between ROMs and other
2751 norom [X86] Do not assign address space to
2752 expansion ROMs that do not already have
2753 BIOS assigned address ranges.
2754 nobar [X86] Do not assign address space to the
2755 BARs that weren't assigned by the BIOS.
2756 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2757 assigned automatically to PCI devices. You can
2758 make the kernel exclude IRQs of your ISA cards
2760 pirqaddr=0xAAAAA [X86] Specify the physical address
2761 of the PIRQ table (normally generated
2762 by the BIOS) if it is outside the
2763 F0000h-100000h range.
2764 lastbus=N [X86] Scan all buses thru bus #N. Can be
2765 useful if the kernel is unable to find your
2766 secondary buses and you want to tell it
2767 explicitly which ones they are.
2768 assign-busses [X86] Always assign all PCI bus
2769 numbers ourselves, overriding
2770 whatever the firmware may have done.
2771 usepirqmask [X86] Honor the possible IRQ mask stored
2772 in the BIOS $PIR table. This is needed on
2773 some systems with broken BIOSes, notably
2774 some HP Pavilion N5400 and Omnibook XE3
2775 notebooks. This will have no effect if ACPI
2776 IRQ routing is enabled.
2777 noacpi [X86] Do not use ACPI for IRQ routing
2778 or for PCI scanning.
2779 use_crs [X86] Use PCI host bridge window information
2780 from ACPI. On BIOSes from 2008 or later, this
2781 is enabled by default. If you need to use this,
2782 please report a bug.
2783 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2784 If you need to use this, please report a bug.
2785 routeirq Do IRQ routing for all PCI devices.
2786 This is normally done in pci_enable_device(),
2787 so this option is a temporary workaround
2788 for broken drivers that don't call it.
2789 skip_isa_align [X86] do not align io start addr, so can
2790 handle more pci cards
2791 firmware [ARM] Do not re-enumerate the bus but instead
2792 just use the configuration from the
2793 bootloader. This is currently used on
2794 IXP2000 systems where the bus has to be
2795 configured a certain way for adjunct CPUs.
2796 noearly [X86] Don't do any early type 1 scanning.
2797 This might help on some broken boards which
2798 machine check when some devices' config space
2799 is read. But various workarounds are disabled
2800 and some IOMMU drivers will not work.
2801 bfsort Sort PCI devices into breadth-first order.
2802 This sorting is done to get a device
2803 order compatible with older (<= 2.4) kernels.
2804 nobfsort Don't sort PCI devices into breadth-first order.
2805 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2806 tuning and use the BIOS-configured MPS defaults.
2807 pcie_bus_safe Set every device's MPS to the largest value
2808 supported by all devices below the root complex.
2809 pcie_bus_perf Set device MPS to the largest allowable MPS
2810 based on its parent bus. Also set MRRS (Max
2811 Read Request Size) to the largest supported
2812 value (no larger than the MPS that the device
2813 or bus can support) for best performance.
2814 pcie_bus_peer2peer Set every device's MPS to 128B, which
2815 every device is guaranteed to support. This
2816 configuration allows peer-to-peer DMA between
2817 any pair of devices, possibly at the cost of
2818 reduced performance. This also guarantees
2819 that hot-added devices will work.
2820 cbiosize=nn[KMG] The fixed amount of bus space which is
2821 reserved for the CardBus bridge's IO window.
2822 The default value is 256 bytes.
2823 cbmemsize=nn[KMG] The fixed amount of bus space which is
2824 reserved for the CardBus bridge's memory
2825 window. The default value is 64 megabytes.
2828 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2829 Specifies alignment and device to reassign
2830 aligned memory resources.
2831 If <order of align> is not specified,
2832 PAGE_SIZE is used as alignment.
2833 PCI-PCI bridge can be specified, if resource
2834 windows need to be expanded.
2835 ecrc= Enable/disable PCIe ECRC (transaction layer
2836 end-to-end CRC checking).
2837 bios: Use BIOS/firmware settings. This is the
2841 hpiosize=nn[KMG] The fixed amount of bus space which is
2842 reserved for hotplug bridge's IO window.
2843 Default size is 256 bytes.
2844 hpmemsize=nn[KMG] The fixed amount of bus space which is
2845 reserved for hotplug bridge's memory window.
2846 Default size is 2 megabytes.
2847 realloc= Enable/disable reallocating PCI bridge resources
2848 if allocations done by BIOS are too small to
2849 accommodate resources required by all child
2851 off: Turn realloc off
2853 realloc same as realloc=on
2854 noari do not use PCIe ARI.
2855 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2856 only look for one device below a PCIe downstream
2859 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2862 force Enable ASPM even on devices that claim not to support it.
2863 WARNING: Forcing ASPM on may cause system lockups.
2865 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2866 nomsi Do not use MSI for PCI Express Native Hotplug (this
2867 makes all PCIe ports use INTx for hotplug services).
2869 pcie_ports= [PCIE] PCIe ports handling:
2870 auto Ask the BIOS whether or not to use native PCIe services
2871 associated with PCIe ports (PME, hot-plug, AER). Use
2872 them only if that is allowed by the BIOS.
2873 native Use native PCIe services associated with PCIe ports
2875 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2878 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2879 nomsi Do not use MSI for native PCIe PME signaling (this makes
2880 all PCIe root ports use INTx for all services).
2882 pcmv= [HW,PCMCIA] BadgePAD 4
2886 Keep all power-domains already enabled by bootloader on,
2887 even if no driver has claimed them. This is useful
2888 for debug and development, but should not be
2889 needed on a platform with proper driver support.
2892 See Documentation/blockdev/paride.txt.
2894 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2897 See arch/parisc/kernel/pdc_chassis.c
2899 percpu_alloc= Select which percpu first chunk allocator to use.
2900 Currently supported values are "embed" and "page".
2901 Archs may support subset or none of the selections.
2902 See comments in mm/percpu.c for details on each
2903 allocator. This parameter is primarily for debugging
2904 and performance comparison.
2907 See Documentation/blockdev/paride.txt.
2910 See Documentation/blockdev/paride.txt.
2912 pirq= [SMP,APIC] Manual mp-table setup
2913 See Documentation/x86/i386/IO-APIC.txt.
2915 plip= [PPT,NET] Parallel port network link
2916 Format: { parport<nr> | timid | 0 }
2917 See also Documentation/parport.txt.
2919 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2920 Override pmtimer IOPort with a hex value.
2924 Enable PNP debug messages (depends on the
2925 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2926 via /sys/module/pnp/parameters/debug. We always show
2927 current resource usage; turning this on also shows
2928 possible settings and some assignment information.
2934 { on | off | curr | res | no-curr | no-res }
2937 [ISAPNP] Exclude IRQs for the autoconfiguration
2940 [ISAPNP] Exclude DMAs for the autoconfiguration
2942 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2943 Ranges are in pairs (I/O port base and size).
2946 [ISAPNP] Exclude memory regions for the
2948 Ranges are in pairs (memory base and size).
2950 ports= [IP_VS_FTP] IPVS ftp helper module
2952 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2954 Format: <port>,<port>....
2956 print-fatal-signals=
2957 [KNL] debug: print fatal signals
2959 If enabled, warn about various signal handling
2960 related application anomalies: too many signals,
2961 too many POSIX.1 timers, fatal signals causing a
2964 If you hit the warning due to signal overflow,
2965 you might want to try "ulimit -i unlimited".
2969 printk.always_kmsg_dump=
2970 Trigger kmsg_dump for cases other than kernel oops or
2972 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2975 printk.time= Show timing data prefixed to each printk message line
2976 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2978 processor.max_cstate= [HW,ACPI]
2979 Limit processor to maximum C-state
2980 max_cstate=9 overrides any DMI blacklist limit.
2982 processor.nocst [HW,ACPI]
2983 Ignore the _CST method to determine C-states,
2984 instead using the legacy FADT method
2986 profile= [KNL] Enable kernel profiling via /proc/profile
2987 Format: [schedule,]<number>
2988 Param: "schedule" - profile schedule points.
2989 Param: <number> - step/bucket size as a power of 2 for
2990 statistical time based profiling.
2991 Param: "sleep" - profile D-state sleeping (millisecs).
2992 Requires CONFIG_SCHEDSTATS
2993 Param: "kvm" - profile VM exits.
2995 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2997 See Documentation/blockdev/ramdisk.txt.
2999 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3000 probe for; one of (bare|imps|exps|lifebook|any).
3001 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3003 psmouse.resetafter= [HW,MOUSE]
3004 Try to reset the device after so many bad packets
3007 [HW,MOUSE] Set desired mouse resolution, in dpi.
3008 psmouse.smartscroll=
3009 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3010 0 = disabled, 1 = enabled (default).
3012 pstore.backend= Specify the name of the pstore backend to use
3015 See Documentation/blockdev/paride.txt.
3018 [KNL] Number of legacy pty's. Overwrites compiled-in
3021 quiet [KNL] Disable most log messages
3026 See Documentation/md.txt.
3028 ramdisk_blocksize= [RAM]
3029 See Documentation/blockdev/ramdisk.txt.
3031 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3032 See Documentation/blockdev/ramdisk.txt.
3035 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3036 the specified list of CPUs to be no-callback CPUs.
3037 Invocation of these CPUs' RCU callbacks will
3038 be offloaded to "rcuox/N" kthreads created for
3039 that purpose, where "x" is "b" for RCU-bh, "p"
3040 for RCU-preempt, and "s" for RCU-sched, and "N"
3041 is the CPU number. This reduces OS jitter on the
3042 offloaded CPUs, which can be useful for HPC and
3043 real-time workloads. It can also improve energy
3044 efficiency for asymmetric multiprocessors.
3047 Rather than requiring that offloaded CPUs
3048 (specified by rcu_nocbs= above) explicitly
3049 awaken the corresponding "rcuoN" kthreads,
3050 make these kthreads poll for callbacks.
3051 This improves the real-time response for the
3052 offloaded CPUs by relieving them of the need to
3053 wake up the corresponding kthread, but degrades
3054 energy efficiency by requiring that the kthreads
3055 periodically wake up to do the polling.
3057 rcutree.blimit= [KNL]
3058 Set maximum number of finished RCU callbacks to
3059 process in one batch.
3061 rcutree.dump_tree= [KNL]
3062 Dump the structure of the rcu_node combining tree
3063 out at early boot. This is used for diagnostic
3064 purposes, to verify correct tree setup.
3066 rcutree.gp_cleanup_delay= [KNL]
3067 Set the number of jiffies to delay each step of
3068 RCU grace-period cleanup. This only has effect
3069 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3071 rcutree.gp_init_delay= [KNL]
3072 Set the number of jiffies to delay each step of
3073 RCU grace-period initialization. This only has
3074 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3077 rcutree.gp_preinit_delay= [KNL]
3078 Set the number of jiffies to delay each step of
3079 RCU grace-period pre-initialization, that is,
3080 the propagation of recent CPU-hotplug changes up
3081 the rcu_node combining tree. This only has effect
3082 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3084 rcutree.rcu_fanout_exact= [KNL]
3085 Disable autobalancing of the rcu_node combining
3086 tree. This is used by rcutorture, and might
3087 possibly be useful for architectures having high
3088 cache-to-cache transfer latencies.
3090 rcutree.rcu_fanout_leaf= [KNL]
3091 Increase the number of CPUs assigned to each
3092 leaf rcu_node structure. Useful for very large
3095 rcutree.jiffies_till_sched_qs= [KNL]
3096 Set required age in jiffies for a
3097 given grace period before RCU starts
3098 soliciting quiescent-state help from
3099 rcu_note_context_switch().
3101 rcutree.jiffies_till_first_fqs= [KNL]
3102 Set delay from grace-period initialization to
3103 first attempt to force quiescent states.
3104 Units are jiffies, minimum value is zero,
3105 and maximum value is HZ.
3107 rcutree.jiffies_till_next_fqs= [KNL]
3108 Set delay between subsequent attempts to force
3109 quiescent states. Units are jiffies, minimum
3110 value is one, and maximum value is HZ.
3112 rcutree.kthread_prio= [KNL,BOOT]
3113 Set the SCHED_FIFO priority of the RCU per-CPU
3114 kthreads (rcuc/N). This value is also used for
3115 the priority of the RCU boost threads (rcub/N)
3116 and for the RCU grace-period kthreads (rcu_bh,
3117 rcu_preempt, and rcu_sched). If RCU_BOOST is
3118 set, valid values are 1-99 and the default is 1
3119 (the least-favored priority). Otherwise, when
3120 RCU_BOOST is not set, valid values are 0-99 and
3121 the default is zero (non-realtime operation).
3123 rcutree.rcu_nocb_leader_stride= [KNL]
3124 Set the number of NOCB kthread groups, which
3125 defaults to the square root of the number of
3126 CPUs. Larger numbers reduces the wakeup overhead
3127 on the per-CPU grace-period kthreads, but increases
3128 that same overhead on each group's leader.
3130 rcutree.qhimark= [KNL]
3131 Set threshold of queued RCU callbacks beyond which
3132 batch limiting is disabled.
3134 rcutree.qlowmark= [KNL]
3135 Set threshold of queued RCU callbacks below which
3136 batch limiting is re-enabled.
3138 rcutree.rcu_idle_gp_delay= [KNL]
3139 Set wakeup interval for idle CPUs that have
3140 RCU callbacks (RCU_FAST_NO_HZ=y).
3142 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3143 Set wakeup interval for idle CPUs that have
3144 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3145 Lazy RCU callbacks are those which RCU can
3146 prove do nothing more than free memory.
3148 rcutorture.cbflood_inter_holdoff= [KNL]
3149 Set holdoff time (jiffies) between successive
3150 callback-flood tests.
3152 rcutorture.cbflood_intra_holdoff= [KNL]
3153 Set holdoff time (jiffies) between successive
3154 bursts of callbacks within a given callback-flood
3157 rcutorture.cbflood_n_burst= [KNL]
3158 Set the number of bursts making up a given
3159 callback-flood test. Set this to zero to
3160 disable callback-flood testing.
3162 rcutorture.cbflood_n_per_burst= [KNL]
3163 Set the number of callbacks to be registered
3164 in a given burst of a callback-flood test.
3166 rcutorture.fqs_duration= [KNL]
3167 Set duration of force_quiescent_state bursts
3170 rcutorture.fqs_holdoff= [KNL]
3171 Set holdoff time within force_quiescent_state bursts
3174 rcutorture.fqs_stutter= [KNL]
3175 Set wait time between force_quiescent_state bursts
3178 rcutorture.gp_cond= [KNL]
3179 Use conditional/asynchronous update-side
3180 primitives, if available.
3182 rcutorture.gp_exp= [KNL]
3183 Use expedited update-side primitives, if available.
3185 rcutorture.gp_normal= [KNL]
3186 Use normal (non-expedited) asynchronous
3187 update-side primitives, if available.
3189 rcutorture.gp_sync= [KNL]
3190 Use normal (non-expedited) synchronous
3191 update-side primitives, if available. If all
3192 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3193 rcutorture.gp_normal=, and rcutorture.gp_sync=
3194 are zero, rcutorture acts as if is interpreted
3195 they are all non-zero.
3197 rcutorture.n_barrier_cbs= [KNL]
3198 Set callbacks/threads for rcu_barrier() testing.
3200 rcutorture.nfakewriters= [KNL]
3201 Set number of concurrent RCU writers. These just
3202 stress RCU, they don't participate in the actual
3203 test, hence the "fake".
3205 rcutorture.nreaders= [KNL]
3206 Set number of RCU readers. The value -1 selects
3207 N-1, where N is the number of CPUs. A value
3208 "n" less than -1 selects N-n-2, where N is again
3209 the number of CPUs. For example, -2 selects N
3210 (the number of CPUs), -3 selects N+1, and so on.
3212 rcutorture.object_debug= [KNL]
3213 Enable debug-object double-call_rcu() testing.
3215 rcutorture.onoff_holdoff= [KNL]
3216 Set time (s) after boot for CPU-hotplug testing.
3218 rcutorture.onoff_interval= [KNL]
3219 Set time (s) between CPU-hotplug operations, or
3220 zero to disable CPU-hotplug testing.
3222 rcutorture.shuffle_interval= [KNL]
3223 Set task-shuffle interval (s). Shuffling tasks
3224 allows some CPUs to go into dyntick-idle mode
3225 during the rcutorture test.
3227 rcutorture.shutdown_secs= [KNL]
3228 Set time (s) after boot system shutdown. This
3229 is useful for hands-off automated testing.
3231 rcutorture.stall_cpu= [KNL]
3232 Duration of CPU stall (s) to test RCU CPU stall
3233 warnings, zero to disable.
3235 rcutorture.stall_cpu_holdoff= [KNL]
3236 Time to wait (s) after boot before inducing stall.
3238 rcutorture.stat_interval= [KNL]
3239 Time (s) between statistics printk()s.
3241 rcutorture.stutter= [KNL]
3242 Time (s) to stutter testing, for example, specifying
3243 five seconds causes the test to run for five seconds,
3244 wait for five seconds, and so on. This tests RCU's
3245 ability to transition abruptly to and from idle.
3247 rcutorture.test_boost= [KNL]
3248 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3249 "Maybe" means test if the RCU implementation
3250 under test support RCU priority boosting.
3252 rcutorture.test_boost_duration= [KNL]
3253 Duration (s) of each individual boost test.
3255 rcutorture.test_boost_interval= [KNL]
3256 Interval (s) between each boost test.
3258 rcutorture.test_no_idle_hz= [KNL]
3259 Test RCU's dyntick-idle handling. See also the
3260 rcutorture.shuffle_interval parameter.
3262 rcutorture.torture_runnable= [BOOT]
3263 Start rcutorture running at boot time.
3265 rcutorture.torture_type= [KNL]
3266 Specify the RCU implementation to test.
3268 rcutorture.verbose= [KNL]
3269 Enable additional printk() statements.
3271 rcupdate.rcu_expedited= [KNL]
3272 Use expedited grace-period primitives, for
3273 example, synchronize_rcu_expedited() instead
3274 of synchronize_rcu(). This reduces latency,
3275 but can increase CPU utilization, degrade
3276 real-time latency, and degrade energy efficiency.
3278 rcupdate.rcu_cpu_stall_suppress= [KNL]
3279 Suppress RCU CPU stall warning messages.
3281 rcupdate.rcu_cpu_stall_timeout= [KNL]
3282 Set timeout for RCU CPU stall warning messages.
3284 rcupdate.rcu_task_stall_timeout= [KNL]
3285 Set timeout in jiffies for RCU task stall warning
3286 messages. Disable with a value less than or equal
3289 rcupdate.rcu_self_test= [KNL]
3290 Run the RCU early boot self tests
3292 rcupdate.rcu_self_test_bh= [KNL]
3293 Run the RCU bh early boot self tests
3295 rcupdate.rcu_self_test_sched= [KNL]
3296 Run the RCU sched early boot self tests
3300 Run specified binary instead of /init from the ramdisk,
3301 used for early userspace startup. See initrd.
3304 Format (x86 or x86_64):
3305 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3307 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3309 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3310 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3311 reboot_force is either force or not specified,
3312 reboot_cpu is s[mp]#### with #### being the processor
3313 to be used for rebooting.
3316 [KNL, SMP] Set scheduler's default relax_domain_level.
3317 See Documentation/cgroups/cpusets.txt.
3319 relative_sleep_states=
3320 [SUSPEND] Use sleep state labeling where the deepest
3321 state available other than hibernation is always "mem".
3322 Format: { "0" | "1" }
3323 0 -- Traditional sleep state labels.
3324 1 -- Relative sleep state labels.
3326 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3328 reservetop= [X86-32]
3330 Reserves a hole at the top of the kernel virtual
3335 Set the amount of memory to reserve for BIOS at
3336 the bottom of the address space.
3338 reset_devices [KNL] Force drivers to reset the underlying device
3339 during initialization.
3342 Specify the partition device for software suspend
3344 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3346 resume_offset= [SWSUSP]
3347 Specify the offset from the beginning of the partition
3348 given by "resume=" at which the swap header is located,
3349 in <PAGE_SIZE> units (needed only for swap files).
3350 See Documentation/power/swsusp-and-swap-files.txt
3352 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3353 read the resume files
3355 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3356 Useful for devices that are detected asynchronously
3357 (e.g. USB and MMC devices).
3359 hibernate= [HIBERNATION]
3360 noresume Don't check if there's a hibernation image
3361 present during boot.
3362 nocompress Don't compress/decompress hibernation images.
3363 no Disable hibernation and resume.
3365 retain_initrd [RAM] Keep initrd memory after extraction
3367 rfkill.default_state=
3368 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3369 etc. communication is blocked by default.
3372 rfkill.master_switch_mode=
3373 0 The "airplane mode" button does nothing.
3374 1 The "airplane mode" button toggles between everything
3375 blocked and the previous configuration.
3376 2 The "airplane mode" button toggles between everything
3377 blocked and everything unblocked.
3379 rhash_entries= [KNL,NET]
3380 Set number of hash buckets for route cache
3382 ro [KNL] Mount root device read-only on boot
3384 root= [KNL] Root filesystem
3385 See name_to_dev_t comment in init/do_mounts.c.
3387 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3388 mount the root filesystem
3390 rootflags= [KNL] Set root filesystem mount option string
3392 rootfstype= [KNL] Set root filesystem type
3394 rootwait [KNL] Wait (indefinitely) for root device to show up.
3395 Useful for devices that are detected asynchronously
3396 (e.g. USB and MMC devices).
3398 rproc_mem=nn[KMG][@address]
3399 [KNL,ARM,CMA] Remoteproc physical memory block.
3400 Memory area to be used by remote processor image,
3403 rw [KNL] Mount root device read-write on boot
3405 S [KNL] Run init in single mode
3407 s390_iommu= [HW,S390]
3408 Set s390 IOTLB flushing mode
3410 With strict flushing every unmap operation will result in
3411 an IOTLB flush. Default is lazy flushing before reuse,
3415 See drivers/net/irda/sa1100_ir.c.
3417 sbni= [NET] Granch SBNI12 leased line adapter
3419 sched_debug [KNL] Enables verbose scheduler debug messages.
3421 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3422 xtime_lock contention on larger systems, and/or RCU lock
3423 contention on all systems with CONFIG_MAXSMP set.
3424 Format: { "0" | "1" }
3425 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3427 Note: increases power consumption, thus should only be
3428 enabled if running jitter sensitive (HPC/RT) workloads.
3430 security= [SECURITY] Choose a security module to enable at boot.
3431 If this boot parameter is not specified, only the first
3432 security module asking for security registration will be
3433 loaded. An invalid security module name will be treated
3434 as if no module has been chosen.
3436 selinux= [SELINUX] Disable or enable SELinux at boot time.
3437 Format: { "0" | "1" }
3438 See security/selinux/Kconfig help text.
3441 Default value is set via kernel config option.
3442 If enabled at boot time, /selinux/disable can be used
3443 later to disable prior to initial policy load.
3445 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3446 Format: { "0" | "1" }
3447 See security/apparmor/Kconfig help text
3450 Default value is set via kernel config option.
3452 serialnumber [BUGS=X86-32]
3455 Maximal number of shapers.
3457 show_msr= [x86] show boot-time MSR settings
3458 Format: { <integer> }
3459 Show boot-time (BIOS-initialized) MSR settings.
3460 The parameter means the number of CPUs to show,
3461 for example 1 means boot CPU only.
3469 Disable merging of slabs with similar size. May be
3470 necessary if there is some reason to distinguish
3471 allocs to different slabs. Debug options disable
3472 merging on their own.
3473 For more information see Documentation/vm/slub.txt.
3475 slab_max_order= [MM, SLAB]
3476 Determines the maximum allowed order for slabs.
3477 A high setting may cause OOMs due to memory
3478 fragmentation. Defaults to 1 for systems with
3479 more than 32MB of RAM, 0 otherwise.
3481 slub_debug[=options[,slabs]] [MM, SLUB]
3482 Enabling slub_debug allows one to determine the
3483 culprit if slab objects become corrupted. Enabling
3484 slub_debug can create guard zones around objects and
3485 may poison objects when not in use. Also tracks the
3486 last alloc / free. For more information see
3487 Documentation/vm/slub.txt.
3489 slub_max_order= [MM, SLUB]
3490 Determines the maximum allowed order for slabs.
3491 A high setting may cause OOMs due to memory
3492 fragmentation. For more information see
3493 Documentation/vm/slub.txt.
3495 slub_min_objects= [MM, SLUB]
3496 The minimum number of objects per slab. SLUB will
3497 increase the slab order up to slub_max_order to
3498 generate a sufficiently large slab able to contain
3499 the number of objects indicated. The higher the number
3500 of objects the smaller the overhead of tracking slabs
3501 and the less frequently locks need to be acquired.
3502 For more information see Documentation/vm/slub.txt.
3504 slub_min_order= [MM, SLUB]
3505 Determines the minimum page order for slabs. Must be
3506 lower than slub_max_order.
3507 For more information see Documentation/vm/slub.txt.
3509 slub_nomerge [MM, SLUB]
3510 Same with slab_nomerge. This is supported for legacy.
3511 See slab_nomerge for more information.
3514 Format: <io1>[,<io2>[,...,<io8>]]
3516 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3517 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3518 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3519 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3520 smsc-ircc2.ircc_irq= [HW] IRQ line
3521 smsc-ircc2.ircc_dma= [HW] DMA channel
3522 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3523 0: Toshiba Satellite 1800 (GP data pin select)
3524 1: Fast pin select (default)
3528 [KNL] Should the soft-lockup detector generate panics.
3531 softlockup_all_cpu_backtrace=
3532 [KNL] Should the soft-lockup detector generate
3533 backtraces on all cpus.
3536 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3537 See Documentation/laptops/sonypi.txt
3539 spia_io_base= [HW,MTD]
3545 Enabled the stack tracer on boot up.
3547 stacktrace_filter=[function-list]
3548 [FTRACE] Limit the functions that the stack tracer
3549 will trace at boot up. function-list is a comma separated
3550 list of functions. This list can be changed at run
3551 time by the stack_trace_filter file in the debugfs
3552 tracing directory. Note, this enables stack tracing
3553 and the stacktrace above is not needed.
3557 Set the STI (builtin display/keyboard on the HP-PARISC
3558 machines) console (graphic card) which should be used
3559 as the initial boot-console.
3560 See also comment in drivers/video/console/sticore.c.
3563 See comment in drivers/video/console/sticore.c.
3566 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3568 sunrpc.min_resvport=
3569 sunrpc.max_resvport=
3571 SunRPC servers often require that client requests
3572 originate from a privileged port (i.e. a port in the
3573 range 0 < portnr < 1024).
3574 An administrator who wishes to reserve some of these
3575 ports for other uses may adjust the range that the
3576 kernel's sunrpc client considers to be privileged
3577 using these two parameters to set the minimum and
3578 maximum port values.
3582 Control how the NFS server code allocates CPUs to
3583 service thread pools. Depending on how many NICs
3584 you have and where their interrupts are bound, this
3585 option will affect which CPUs will do NFS serving.
3586 Note: this parameter cannot be changed while the
3587 NFS server is running.
3589 auto the server chooses an appropriate mode
3590 automatically using heuristics
3591 global a single global pool contains all CPUs
3592 percpu one pool for each CPU
3593 pernode one pool for each NUMA node (equivalent
3594 to global on non-NUMA machines)
3596 sunrpc.tcp_slot_table_entries=
3597 sunrpc.udp_slot_table_entries=
3599 Sets the upper limit on the number of simultaneous
3600 RPC calls that can be sent from the client to a
3601 server. Increasing these values may allow you to
3602 improve throughput, but will also increase the
3603 amount of memory reserved for use by the client.
3605 suspend.pm_test_delay=
3607 Sets the number of seconds to remain in a suspend test
3608 mode before resuming the system (see
3609 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3610 is set. Default value is 5.
3613 [KNL] Enable accounting of swap in memory resource
3614 controller if no parameter or 1 is given or disable
3615 it if 0 is given (See Documentation/cgroups/memory.txt)
3617 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3618 Format: { <int> | force }
3619 <int> -- Number of I/O TLB slabs
3620 force -- force using of bounce buffers even if they
3621 wouldn't be automatically used by the kernel
3625 sysfs.deprecated=0|1 [KNL]
3626 Enable/disable old style sysfs layout for old udev
3627 on older distributions. When this option is enabled
3628 very new udev will not work anymore. When this option
3629 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3630 in older udev will not work anymore.
3631 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3632 the kernel configuration.
3634 sysrq_always_enabled
3636 Ignore sysrq setting - this boot parameter will
3637 neutralize any effect of /proc/sys/kernel/sysrq.
3638 Useful for debugging.
3640 tcpmhash_entries= [KNL,NET]
3641 Set the number of tcp_metrics_hash slots.
3642 Default value is 8192 or 16384 depending on total
3643 ram pages. This is used to specify the TCP metrics
3644 cache size. See Documentation/networking/ip-sysctl.txt
3645 "tcp_no_metrics_save" section for more details.
3649 test_suspend= [SUSPEND][,N]
3650 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3651 standby suspend) or "freeze" (for suspend type freeze)
3652 as the system sleep state during system startup with
3653 the optional capability to repeat N number of times.
3654 The system is woken from this state using a
3655 wakeup-capable RTC alarm.
3657 thash_entries= [KNL,NET]
3658 Set number of hash buckets for TCP connection
3660 thermal.act= [HW,ACPI]
3661 -1: disable all active trip points in all thermal zones
3662 <degrees C>: override all lowest active trip points
3664 thermal.crt= [HW,ACPI]
3665 -1: disable all critical trip points in all thermal zones
3666 <degrees C>: override all critical trip points
3668 thermal.nocrt= [HW,ACPI]
3669 Set to disable actions on ACPI thermal zone
3670 critical and hot trip points.
3672 thermal.off= [HW,ACPI]
3673 1: disable ACPI thermal control
3675 thermal.psv= [HW,ACPI]
3676 -1: disable all passive trip points
3677 <degrees C>: override all passive trip points to this
3680 thermal.tzp= [HW,ACPI]
3681 Specify global default ACPI thermal zone polling rate
3682 <deci-seconds>: poll all this frequency
3683 0: no polling (default)
3686 Force threading of all interrupt handlers except those
3687 marked explicitly IRQF_NO_THREAD.
3690 Enable the Transcendent memory driver if built-in.
3692 tmem.cleancache=0|1 [KNL, XEN]
3693 Default is on (1). Disable the usage of the cleancache
3694 API to send anonymous pages to the hypervisor.
3696 tmem.frontswap=0|1 [KNL, XEN]
3697 Default is on (1). Disable the usage of the frontswap
3698 API to send swap pages to the hypervisor. If disabled
3699 the selfballooning and selfshrinking are force disabled.
3701 tmem.selfballooning=0|1 [KNL, XEN]
3702 Default is on (1). Disable the driving of swap pages
3705 tmem.selfshrinking=0|1 [KNL, XEN]
3706 Default is on (1). Partial swapoff that immediately
3707 transfers pages from Xen hypervisor back to the
3708 kernel based on different criteria.
3712 Specify if the kernel should make use of the cpu
3713 topology information if the hardware supports this.
3714 The scheduler will make use of this information and
3715 e.g. base its process migration decisions on it.
3718 topology_updates= [KNL, PPC, NUMA]
3720 Specify if the kernel should ignore (off)
3721 topology updates sent by the hypervisor to this
3726 tpm_suspend_pcr=[HW,TPM]
3727 Format: integer pcr id
3728 Specify that at suspend time, the tpm driver
3729 should extend the specified pcr with zeros,
3730 as a workaround for some chips which fail to
3731 flush the last written pcr on TPM_SaveState.
3732 This will guarantee that all the other pcrs
3735 trace_buf_size=nn[KMG]
3736 [FTRACE] will set tracing buffer size on each cpu.
3738 trace_event=[event-list]
3739 [FTRACE] Set and start specified trace events in order
3740 to facilitate early boot debugging.
3741 See also Documentation/trace/events.txt
3743 trace_options=[option-list]
3744 [FTRACE] Enable or disable tracer options at boot.
3745 The option-list is a comma delimited list of options
3746 that can be enabled or disabled just as if you were
3747 to echo the option name into
3749 /sys/kernel/debug/tracing/trace_options
3751 For example, to enable stacktrace option (to dump the
3752 stack trace of each event), add to the command line:
3754 trace_options=stacktrace
3756 See also Documentation/trace/ftrace.txt "trace options"
3760 Have the tracepoints sent to printk as well as the
3761 tracing ring buffer. This is useful for early boot up
3762 where the system hangs or reboots and does not give the
3763 option for reading the tracing buffer or performing a
3764 ftrace_dump_on_oops.
3766 To turn off having tracepoints sent to printk,
3767 echo 0 > /proc/sys/kernel/tracepoint_printk
3768 Note, echoing 1 into this file without the
3769 tracepoint_printk kernel cmdline option has no effect.
3773 Having tracepoints sent to printk() and activating high
3774 frequency tracepoints such as irq or sched, can cause
3775 the system to live lock.
3778 [FTRACE] enable this option to disable tracing when a
3779 warning is hit. This turns off "tracing_on". Tracing can
3780 be enabled again by echoing '1' into the "tracing_on"
3781 file located in /sys/kernel/debug/tracing/
3783 This option is useful, as it disables the trace before
3784 the WARNING dump is called, which prevents the trace to
3785 be filled with content caused by the warning output.
3787 This option can also be set at run time via the sysctl
3788 option: kernel/traceoff_on_warning
3790 transparent_hugepage=
3792 Format: [always|madvise|never]
3793 Can be used to control the default behavior of the system
3794 with respect to transparent hugepages.
3795 See Documentation/vm/transhuge.txt for more details.
3797 tsc= Disable clocksource stability checks for TSC.
3799 [x86] reliable: mark tsc clocksource as reliable, this
3800 disables clocksource verification at runtime, as well
3801 as the stability checks done at bootup. Used to enable
3802 high-resolution timer mode on older hardware, and in
3803 virtualized environment.
3804 [x86] noirqtime: Do not use TSC to do irq accounting.
3805 Used to run time disable IRQ_TIME_ACCOUNTING on any
3806 platforms where RDTSC is slow and this accounting
3809 turbografx.map[2|3]= [HW,JOY]
3810 TurboGraFX parallel port interface
3812 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3813 See also Documentation/input/joystick-parport.txt
3815 udbg-immortal [PPC] When debugging early kernel crashes that
3816 happen after console_init() and before a proper
3817 console driver takes over, this boot options might
3818 help "seeing" what's going on.
3820 uhash_entries= [KNL,NET]
3821 Set number of hash buckets for UDP/UDP-Lite connections
3824 [USB] Ignore overcurrent events (default N).
3825 Some badly-designed motherboards generate lots of
3826 bogus events, for ports that aren't wired to
3827 anything. Set this parameter to avoid log spamming.
3828 Note that genuine overcurrent events won't be
3832 [X86] Cause panic on unknown NMI.
3834 usbcore.authorized_default=
3835 [USB] Default USB device authorization:
3836 (default -1 = authorized except for wireless USB,
3837 0 = not authorized, 1 = authorized)
3839 usbcore.autosuspend=
3840 [USB] The autosuspend time delay (in seconds) used
3841 for newly-detected USB devices (default 2). This
3842 is the time required before an idle device will be
3843 autosuspended. Devices for which the delay is set
3844 to a negative value won't be autosuspended at all.
3846 usbcore.usbfs_snoop=
3847 [USB] Set to log all usbfs traffic (default 0 = off).
3849 usbcore.blinkenlights=
3850 [USB] Set to cycle leds on hubs (default 0 = off).
3852 usbcore.old_scheme_first=
3853 [USB] Start with the old device initialization
3854 scheme (default 0 = off).
3856 usbcore.usbfs_memory_mb=
3857 [USB] Memory limit (in MB) for buffers allocated by
3858 usbfs (default = 16, 0 = max = 2047).
3860 usbcore.use_both_schemes=
3861 [USB] Try the other device initialization scheme
3862 if the first one fails (default 1 = enabled).
3864 usbcore.initial_descriptor_timeout=
3865 [USB] Specifies timeout for the initial 64-byte
3866 USB_REQ_GET_DESCRIPTOR request in milliseconds
3867 (default 5000 = 5.0 seconds).
3870 [USBHID] The interval which mice are to be polled at.
3872 usb-storage.delay_use=
3873 [UMS] The delay in seconds before a new device is
3874 scanned for Logical Units (default 1).
3877 [UMS] A list of quirks entries to supplement or
3878 override the built-in unusual_devs list. List
3879 entries are separated by commas. Each entry has
3880 the form VID:PID:Flags where VID and PID are Vendor
3881 and Product ID values (4-digit hex numbers) and
3882 Flags is a set of characters, each corresponding
3883 to a common usb-storage quirk flag as follows:
3884 a = SANE_SENSE (collect more than 18 bytes
3886 b = BAD_SENSE (don't collect more than 18
3887 bytes of sense data);
3888 c = FIX_CAPACITY (decrease the reported
3889 device capacity by one sector);
3890 d = NO_READ_DISC_INFO (don't use
3891 READ_DISC_INFO command);
3892 e = NO_READ_CAPACITY_16 (don't use
3893 READ_CAPACITY_16 command);
3894 f = NO_REPORT_OPCODES (don't use report opcodes
3896 g = MAX_SECTORS_240 (don't transfer more than
3897 240 sectors at a time, uas only);
3898 h = CAPACITY_HEURISTICS (decrease the
3899 reported device capacity by one
3900 sector if the number is odd);
3901 i = IGNORE_DEVICE (don't bind to this
3903 l = NOT_LOCKABLE (don't try to lock and
3904 unlock ejectable media);
3905 m = MAX_SECTORS_64 (don't transfer more
3906 than 64 sectors = 32 KB at a time);
3907 n = INITIAL_READ10 (force a retry of the
3908 initial READ(10) command);
3909 o = CAPACITY_OK (accept the capacity
3910 reported by the device);
3911 p = WRITE_CACHE (the device cache is ON
3913 r = IGNORE_RESIDUE (the device reports
3914 bogus residue values);
3915 s = SINGLE_LUN (the device has only one
3917 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3918 commands, uas only);
3919 u = IGNORE_UAS (don't bind to the uas driver);
3920 w = NO_WP_DETECT (don't test whether the
3921 medium is write-protected).
3922 Example: quirks=0419:aaf5:rl,0421:0433:rc
3924 user_debug= [KNL,ARM]
3926 See arch/arm/Kconfig.debug help text.
3927 1 - undefined instruction events
3929 4 - invalid data aborts
3932 Example: user_debug=31
3935 [X86] Flags controlling user PTE allocations.
3937 nohigh = do not allocate PTE pages in
3938 HIGHMEM regardless of setting
3942 On X86_32, this is an alias for vdso32=. Otherwise:
3944 vdso=1: enable VDSO (the default)
3945 vdso=0: disable VDSO mapping
3947 vdso32= [X86] Control the 32-bit vDSO
3948 vdso32=1: enable 32-bit VDSO
3949 vdso32=0 or vdso32=2: disable 32-bit VDSO
3951 See the help text for CONFIG_COMPAT_VDSO for more
3952 details. If CONFIG_COMPAT_VDSO is set, the default is
3953 vdso32=0; otherwise, the default is vdso32=1.
3955 For compatibility with older kernels, vdso32=2 is an
3958 Try vdso32=0 if you encounter an error that says:
3959 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3962 vector=percpu: enable percpu vector domain
3964 video= [FB] Frame buffer configuration
3965 See Documentation/fb/modedb.txt.
3967 video.brightness_switch_enabled= [0,1]
3968 If set to 1, on receiving an ACPI notify event
3969 generated by hotkey, video driver will adjust brightness
3970 level and then send out the event to user space through
3971 the allocated input device; If set to 0, video driver
3972 will only send out the event without touching backlight
3977 [VMMIO] Memory mapped virtio (platform) device.
3979 <size>@<baseaddr>:<irq>[:<id>]
3981 <size> := size (can use standard suffixes
3983 <baseaddr> := physical base address
3984 <irq> := interrupt number (as passed to
3986 <id> := (optional) platform device id
3988 virtio_mmio.device=1K@0x100b0000:48:7
3990 Can be used multiple times for multiple devices.
3992 vga= [BOOT,X86-32] Select a particular video mode
3993 See Documentation/x86/boot.txt and
3994 Documentation/svga.txt.
3995 Use vga=ask for menu.
3996 This is actually a boot loader parameter; the value is
3997 passed to the kernel using a special protocol.
3999 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4000 size of <nn>. This can be used to increase the
4001 minimum size (128MB on x86). It can also be used to
4002 decrease the size and leave more room for directly
4005 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4008 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4011 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4015 Controls the behavior of vsyscalls (i.e. calls to
4016 fixed addresses of 0xffffffffff600x00 from legacy
4017 code). Most statically-linked binaries and older
4018 versions of glibc use these calls. Because these
4019 functions are at fixed addresses, they make nice
4020 targets for exploits that can control RIP.
4022 emulate [default] Vsyscalls turn into traps and are
4023 emulated reasonably safely.
4025 native Vsyscalls are native syscall instructions.
4026 This is a little bit faster than trapping
4027 and makes a few dynamic recompilers work
4028 better than they would in emulation mode.
4029 It also makes exploits much easier to write.
4031 none Vsyscalls don't work at all. This makes
4032 them quite hard to use for exploits but
4033 might break your system.
4035 vt.color= [VT] Default text color.
4036 Format: 0xYX, X = foreground, Y = background.
4037 Default: 0x07 = light gray on black.
4039 vt.cur_default= [VT] Default cursor shape.
4040 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4041 the parameters of the <Esc>[?A;B;Cc escape sequence;
4042 see VGA-softcursor.txt. Default: 2 = underline.
4044 vt.default_blu= [VT]
4045 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4046 Change the default blue palette of the console.
4047 This is a 16-member array composed of values
4050 vt.default_grn= [VT]
4051 Format: <green0>,<green1>,<green2>,...,<green15>
4052 Change the default green palette of the console.
4053 This is a 16-member array composed of values
4056 vt.default_red= [VT]
4057 Format: <red0>,<red1>,<red2>,...,<red15>
4058 Change the default red palette of the console.
4059 This is a 16-member array composed of values
4065 Set system-wide default UTF-8 mode for all tty's.
4066 Default is 1, i.e. UTF-8 mode is enabled for all
4067 newly opened terminals.
4069 vt.global_cursor_default=
4072 Set system-wide default for whether a cursor
4073 is shown on new VTs. Default is -1,
4074 i.e. cursors will be created by default unless
4075 overridden by individual drivers. 0 will hide
4076 cursors, 1 will display them.
4078 vt.italic= [VT] Default color for italic text; 0-15.
4081 vt.underline= [VT] Default color for underlined text; 0-15.
4084 watchdog timers [HW,WDT] For information on watchdog timers,
4085 see Documentation/watchdog/watchdog-parameters.txt
4086 or other driver-specific files in the
4087 Documentation/watchdog/ directory.
4089 workqueue.disable_numa
4090 By default, all work items queued to unbound
4091 workqueues are affine to the NUMA nodes they're
4092 issued on, which results in better behavior in
4093 general. If NUMA affinity needs to be disabled for
4094 whatever reason, this option can be used. Note
4095 that this also can be controlled per-workqueue for
4096 workqueues visible under /sys/bus/workqueue/.
4098 workqueue.power_efficient
4099 Per-cpu workqueues are generally preferred because
4100 they show better performance thanks to cache
4101 locality; unfortunately, per-cpu workqueues tend to
4102 be more power hungry than unbound workqueues.
4104 Enabling this makes the per-cpu workqueues which
4105 were observed to contribute significantly to power
4106 consumption unbound, leading to measurably lower
4107 power usage at the cost of small performance
4110 The default value of this parameter is determined by
4111 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4113 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4114 default x2apic cluster mode on platforms
4117 x86_intel_mid_timer= [X86-32,APBT]
4118 Choose timer option for x86 Intel MID platform.
4119 Two valid options are apbt timer only and lapic timer
4120 plus one apbt timer for broadcast timer.
4121 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4123 xen_512gb_limit [KNL,X86-64,XEN]
4124 Restricts the kernel running paravirtualized under Xen
4125 to use only up to 512 GB of RAM. The reason to do so is
4126 crash analysis tools and Xen tools for doing domain
4127 save/restore/migration must be enabled to handle larger
4130 xen_emul_unplug= [HW,X86,XEN]
4131 Unplug Xen emulated devices
4132 Format: [unplug0,][unplug1]
4133 ide-disks -- unplug primary master IDE devices
4134 aux-ide-disks -- unplug non-primary-master IDE devices
4135 nics -- unplug network devices
4136 all -- unplug all emulated devices (NICs and IDE disks)
4137 unnecessary -- unplugging emulated devices is
4138 unnecessary even if the host did not respond to
4140 never -- do not unplug even if version check succeeds
4142 xen_nopvspin [X86,XEN]
4143 Disables the ticketlock slowpath using Xen PV
4147 Disables the PV optimizations forcing the HVM guest to
4148 run as generic HVM guest with no PV drivers.
4150 xirc2ps_cs= [NET,PCMCIA]
4152 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4154 ______________________________________________________________________
4158 Add more DRM drivers.
projects / karo-tx-linux.git / blob