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.
1038 Use early console provided by Freescale LP UART driver
1039 found on Freescale Vybrid and QorIQ LS1021A processors.
1040 A valid base address must be provided, and the serial
1041 port must already be setup and configured.
1043 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1047 earlyprintk=serial[,ttySn[,baudrate]]
1048 earlyprintk=serial[,0x...[,baudrate]]
1049 earlyprintk=ttySn[,baudrate]
1050 earlyprintk=dbgp[debugController#]
1051 earlyprintk=pciserial,bus:device.function[,baudrate]
1053 earlyprintk is useful when the kernel crashes before
1054 the normal console is initialized. It is not enabled by
1055 default because it has some cosmetic problems.
1057 Append ",keep" to not disable it when the real console
1060 Only one of vga, efi, serial, or usb debug port can
1063 Currently only ttyS0 and ttyS1 may be specified by
1064 name. Other I/O ports may be explicitly specified
1065 on some architectures (x86 and arm at least) by
1066 replacing ttySn with an I/O port address, like this:
1067 earlyprintk=serial,0x1008,115200
1068 You can find the port for a given device in
1069 /proc/tty/driver/serial:
1070 2: uart:ST16650V2 port:00001008 irq:18 ...
1072 Interaction with the standard serial driver is not
1075 The VGA and EFI output is eventually overwritten by
1078 The xen output can only be used by Xen PV guests.
1080 edac_report= [HW,EDAC] Control how to report EDAC event
1081 Format: {"on" | "off" | "force"}
1082 on: enable EDAC to report H/W event. May be overridden
1083 by other higher priority error reporting module.
1084 off: disable H/W event reporting through EDAC.
1085 force: enforce the use of EDAC to report H/W event.
1088 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1091 This is designed to be used in conjunction with
1092 the boot argument: earlyprintk=vga
1095 Format: {"off" | "on" | "skip[mbr]"}
1098 Format: { "old_map", "nochunk", "noruntime", "debug" }
1099 old_map [X86-64]: switch to the old ioremap-based EFI
1100 runtime services mapping. 32-bit still uses this one by
1102 nochunk: disable reading files in "chunks" in the EFI
1103 boot stub, as chunking can cause problems with some
1104 firmware implementations.
1105 noruntime : disable EFI runtime services support
1106 debug: enable misc debug output
1108 efi_no_storage_paranoia [EFI; X86]
1109 Using this parameter you can use more than 50% of
1110 your efi variable storage. Use this parameter only if
1111 you are really sure that your UEFI does sane gc and
1112 fulfills the spec otherwise your board may brick.
1114 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1115 Add arbitrary attribute to specific memory range by
1116 updating original EFI memory map.
1117 Region of memory which aa attribute is added to is
1119 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1120 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1121 attribute is added to range 0x100000000-0x180000000 and
1122 0x10a0000000-0x1120000000.
1124 Using this parameter you can do debugging of EFI memmap
1125 related feature. For example, you can do debugging of
1126 Address Range Mirroring feature even if your box
1129 eisa_irq_edge= [PARISC,HW]
1130 See header of drivers/parisc/eisa.c.
1133 See comment before function elanfreq_setup() in
1134 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1137 Format: {"cfq" | "deadline" | "noop"}
1138 See Documentation/block/cfq-iosched.txt and
1139 Documentation/block/deadline-iosched.txt for details.
1141 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1142 Specifies physical address of start of kernel core
1143 image elf header and optionally the size. Generally
1144 kexec loader will pass this option to capture kernel.
1145 See Documentation/kdump/kdump.txt for details.
1147 enable_mtrr_cleanup [X86]
1148 The kernel tries to adjust MTRR layout from continuous
1149 to discrete, to make X server driver able to add WB
1150 entry later. This parameter enables that.
1152 enable_timer_pin_1 [X86]
1153 Enable PIN 1 of APIC timer
1154 Can be useful to work around chipset bugs
1155 (in particular on some ATI chipsets).
1156 The kernel tries to set a reasonable default.
1158 enforcing [SELINUX] Set initial enforcing status.
1160 See security/selinux/Kconfig help text.
1161 0 -- permissive (log only, no denials).
1162 1 -- enforcing (deny and log).
1164 Value can be changed at runtime via /selinux/enforce.
1167 Disable Error Record Serialization Table (ERST)
1170 ether= [HW,NET] Ethernet cards parameters
1171 This option is obsoleted by the "netdev=" option, which
1172 has equivalent usage. See its documentation for details.
1176 Permit 'security.evm' to be updated regardless of
1177 current integrity status.
1181 fail_make_request=[KNL]
1182 General fault injection mechanism.
1183 Format: <interval>,<probability>,<space>,<times>
1184 See also Documentation/fault-injection/.
1187 See Documentation/blockdev/floppy.txt.
1189 force_pal_cache_flush
1190 [IA-64] Avoid check_sal_cache_flush which may hang on
1191 buggy SAL_CACHE_FLUSH implementations. Using this
1192 parameter will force ia64_sal_cache_flush to call
1193 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1196 Forcefully enable Physical Address Extension (PAE).
1197 Many Pentium M systems disable PAE but may have a
1198 functionally usable PAE implementation.
1199 Warning: use of this parameter will taint the kernel
1200 and may cause unknown problems.
1203 [FTRACE] will set and start the specified tracer
1204 as early as possible in order to facilitate early
1207 ftrace_dump_on_oops[=orig_cpu]
1208 [FTRACE] will dump the trace buffers on oops.
1209 If no parameter is passed, ftrace will dump
1210 buffers of all CPUs, but if you pass orig_cpu, it will
1211 dump only the buffer of the CPU that triggered the
1214 ftrace_filter=[function-list]
1215 [FTRACE] Limit the functions traced by the function
1216 tracer at boot up. function-list is a comma separated
1217 list of functions. This list can be changed at run
1218 time by the set_ftrace_filter file in the debugfs
1221 ftrace_notrace=[function-list]
1222 [FTRACE] Do not trace the functions specified in
1223 function-list. This list can be changed at run time
1224 by the set_ftrace_notrace file in the debugfs
1227 ftrace_graph_filter=[function-list]
1228 [FTRACE] Limit the top level callers functions traced
1229 by the function graph tracer at boot up.
1230 function-list is a comma separated list of functions
1231 that can be changed at run time by the
1232 set_graph_function file in the debugfs tracing directory.
1234 ftrace_graph_notrace=[function-list]
1235 [FTRACE] Do not trace from the functions specified in
1236 function-list. This list is a comma separated list of
1237 functions that can be changed at run time by the
1238 set_graph_notrace file in the debugfs tracing directory.
1241 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1242 support via parallel port (up to 5 devices per port)
1243 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1244 See also Documentation/input/joystick-parport.txt
1248 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1252 gcov_persist= [GCOV] When non-zero (default), profiling data for
1253 kernel modules is saved and remains accessible via
1254 debugfs, even when the module is unloaded/reloaded.
1255 When zero, profiling data is discarded and associated
1256 debugfs files are removed at module unload time.
1258 gpt [EFI] Forces disk with valid GPT signature but
1259 invalid Protective MBR to be treated as GPT. If the
1260 primary GPT is corrupted, it enables the backup/alternate
1261 GPT to be used instead.
1263 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1264 the "Enable 0" bit of the configuration register.
1267 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1268 the "Enable 0" bit of the configuration register.
1271 grcan.select= [HW] Select which physical interface to use.
1274 grcan.txsize= [HW] Sets the size of the tx buffer.
1275 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1277 grcan.rxsize= [HW] Sets the size of the rx buffer.
1278 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1281 hashdist= [KNL,NUMA] Large hashes allocated during boot
1282 are distributed across NUMA nodes. Defaults on
1283 for 64-bit NUMA, off otherwise.
1284 Format: 0 | 1 (for off | on)
1286 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1288 hd= [EIDE] (E)IDE hard drive subsystem geometry
1289 Format: <cyl>,<head>,<sect>
1292 Disable Hardware Error Source Table (HEST) support;
1293 corresponding firmware-first mode error processing
1294 logic will be disabled.
1296 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1297 size of <nn>. This works even on boxes that have no
1298 highmem otherwise. This also works to reduce highmem
1299 size on bigger boxes.
1301 highres= [KNL] Enable/disable high resolution timer mode.
1302 Valid parameters: "on", "off"
1306 See Documentation/isdn/README.HiSax.
1310 hpet= [X86-32,HPET] option to control HPET usage
1311 Format: { enable (default) | disable | force |
1313 disable: disable HPET and use PIT instead
1314 force: allow force enabled of undocumented chips (ICH4,
1316 verbose: show contents of HPET registers during setup
1318 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1319 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1321 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1322 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1323 On x86-64 and powerpc, this option can be specified
1324 multiple times interleaved with hugepages= to reserve
1325 huge pages of different sizes. Valid pages sizes on
1326 x86-64 are 2M (when the CPU supports "pse") and 1G
1327 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1329 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1330 terminal devices. Valid values: 0..8
1331 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1332 If specified, z/VM IUCV HVC accepts connections
1333 from listed z/VM user IDs only.
1335 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1336 hardware thread id mappings.
1337 Format: <cpu>:<hwthread>
1340 Do not unregister boot console at start. This is only
1341 useful for debugging when something happens in the window
1342 between unregistering the boot console and initializing
1345 i2c_bus= [HW] Override the default board specific I2C bus speed
1346 or register an additional I2C bus that is not
1347 registered from board initialization code.
1351 i8042.debug [HW] Toggle i8042 debug mode
1352 i8042.unmask_kbd_data
1353 [HW] Enable printing of interrupt data from the KBD port
1354 (disabled by default, and as a pre-condition
1355 requires that i8042.debug=1 be enabled)
1356 i8042.direct [HW] Put keyboard port into non-translated mode
1357 i8042.dumbkbd [HW] Pretend that controller can only read data from
1358 keyboard and cannot control its state
1359 (Don't attempt to blink the leds)
1360 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1361 i8042.nokbd [HW] Don't check/create keyboard port
1362 i8042.noloop [HW] Disable the AUX Loopback command while probing
1364 i8042.nomux [HW] Don't check presence of an active multiplexing
1366 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1368 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1369 i8042.reset [HW] Reset the controller during init and cleanup
1370 i8042.unlock [HW] Unlock (ignore) the keylock
1371 i8042.kbdreset [HW] Reset device connected to KBD port
1375 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1376 indicates that the driver is running on unsupported
1378 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1379 does not match list of supported models.
1381 [HW] Report power status in /proc/i8k
1382 (disabled by default)
1383 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1386 i915.invert_brightness=
1387 [DRM] Invert the sense of the variable that is used to
1388 set the brightness of the panel backlight. Normally a
1389 brightness value of 0 indicates backlight switched off,
1390 and the maximum of the brightness value sets the backlight
1391 to maximum brightness. If this parameter is set to 0
1392 (default) and the machine requires it, or this parameter
1393 is set to 1, a brightness value of 0 sets the backlight
1394 to maximum brightness, and the maximum of the brightness
1395 value switches the backlight off.
1396 -1 -- never invert brightness
1397 0 -- machine default
1398 1 -- force brightness inversion
1401 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1403 ide-core.nodma= [HW] (E)IDE subsystem
1404 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1405 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1406 .cdrom .chs .ignore_cable are additional options
1407 See Documentation/ide/ide.txt.
1409 ide-generic.probe-mask= [HW] (E)IDE subsystem
1411 Probe mask for legacy ISA IDE ports. Depending on
1412 platform up to 6 ports are supported, enabled by
1413 setting corresponding bits in the mask to 1. The
1414 default value is 0x0, which has a special meaning.
1415 On systems that have PCI, it triggers scanning the
1416 PCI bus for the first and the second port, which
1417 are then probed. On systems without PCI the value
1418 of 0x0 enables probing the two first ports as if it
1421 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1422 Claim all unknown PCI IDE storage controllers.
1425 Format: idle=poll, idle=halt, idle=nomwait
1426 Poll forces a polling idle loop that can slightly
1427 improve the performance of waking up a idle CPU, but
1428 will use a lot of power and make the system run hot.
1430 idle=halt: Halt is forced to be used for CPU idle.
1431 In such case C2/C3 won't be used again.
1432 idle=nomwait: Disable mwait for CPU C-states
1434 ignore_loglevel [KNL]
1435 Ignore loglevel setting - this will print /all/
1436 kernel messages to the console. Useful for debugging.
1437 We also add it as printk module parameter, so users
1438 could change it dynamically, usually by
1439 /sys/module/printk/parameters/ignore_loglevel.
1441 ihash_entries= [KNL]
1442 Set number of hash buckets for inode cache.
1444 ima_appraise= [IMA] appraise integrity measurements
1445 Format: { "off" | "enforce" | "fix" | "log" }
1448 ima_appraise_tcb [IMA]
1449 The builtin appraise policy appraises all files
1453 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1457 The list of supported hash algorithms is defined
1458 in crypto/hash_info.h.
1461 The builtin measurement policy to load during IMA
1462 setup. Specyfing "tcb" as the value, measures all
1463 programs exec'd, files mmap'd for exec, and all files
1464 opened with the read mode bit set by either the
1465 effective uid (euid=0) or uid=0.
1468 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1469 Load a policy which meets the needs of the Trusted
1470 Computing Base. This means IMA will measure all
1471 programs exec'd, files mmap'd for exec, and all files
1472 opened for read by uid=0.
1475 Select one of defined IMA measurements template formats.
1476 Formats: { "ima" | "ima-ng" | "ima-sig" }
1480 [IMA] Define a custom template format.
1481 Format: { "field1|...|fieldN" }
1483 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1484 Format: <min_file_size>
1485 Set the minimal file size for using asynchronous hash.
1486 If left unspecified, ahash usage is disabled.
1488 ahash performance varies for different data sizes on
1489 different crypto accelerators. This option can be used
1490 to achieve the best performance for a particular HW.
1492 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1494 Set hashing buffer size. Default: 4k.
1496 ahash performance varies for different chunk sizes on
1497 different crypto accelerators. This option can be used
1498 to achieve best performance for particular HW.
1502 Run specified binary instead of /sbin/init as init
1505 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1506 for working out where the kernel is dying during
1509 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1510 initcall functions. Useful for debugging built-in
1511 modules and initcalls.
1513 initrd= [BOOT] Specify the location of the initial ramdisk
1515 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1518 int_pln_enable [x86] Enable power limit notification interrupt
1520 integrity_audit=[IMA]
1521 Format: { "0" | "1" }
1522 0 -- basic integrity auditing messages. (Default)
1523 1 -- additional integrity auditing messages.
1525 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1527 Enable intel iommu driver.
1529 Disable intel iommu driver.
1530 igfx_off [Default Off]
1531 By default, gfx is mapped as normal device. If a gfx
1532 device has a dedicated DMAR unit, the DMAR unit is
1533 bypassed by not enabling DMAR with this option. In
1534 this case, gfx device will use physical address for
1537 With this option iommu will not optimize to look
1538 for io virtual address below 32-bit forcing dual
1539 address cycle on pci bus for cards supporting greater
1540 than 32-bit addressing. The default is to look
1541 for translation below 32-bit and if not available
1542 then look in the higher range.
1543 strict [Default Off]
1544 With this option on every unmap_single operation will
1545 result in a hardware IOTLB flush operation as opposed
1546 to batching them for performance.
1547 sp_off [Default Off]
1548 By default, super page will be supported if Intel IOMMU
1549 has the capability. With this option, super page will
1551 ecs_off [Default Off]
1552 By default, extended context tables will be supported if
1553 the hardware advertises that it has support both for the
1554 extended tables themselves, and also PASID support. With
1555 this option set, extended tables will not be used even
1556 on hardware which claims to support them.
1558 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1559 0 disables intel_idle and fall back on acpi_idle.
1560 1 to 6 specify maximum depth of C-state.
1564 Do not enable intel_pstate as the default
1565 scaling driver for the supported processors
1567 Enable intel_pstate on systems that prohibit it by default
1568 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1569 instead of acpi-cpufreq may disable platform features, such
1570 as thermal controls and power capping, that rely on ACPI
1571 P-States information being indicated to OSPM and therefore
1572 should be used with caution. This option does not work with
1573 processors that aren't supported by the intel_pstate driver
1574 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1576 Do not enable hardware P state control (HWP)
1579 Only load intel_pstate on systems which support
1580 hardware P state control (HWP) if available.
1582 Don't use ACPI processor performance control objects
1583 _PSS and _PPC specified limits.
1585 intremap= [X86-64, Intel-IOMMU]
1586 on enable Interrupt Remapping (default)
1587 off disable Interrupt Remapping
1588 nosid disable Source ID checking
1590 BIOS x2APIC opt-out request will be ignored
1591 nopost disable Interrupt Posting
1593 iomem= Disable strict checking of access to MMIO memory
1594 strict regions from userspace.
1609 nobypass [PPC/POWERNV]
1610 Disable IOMMU bypass, using IOMMU for PCI devices.
1613 io7= [HW] IO7 for Marvel based alpha systems
1614 See comment before marvel_specify_io7 in
1615 arch/alpha/kernel/core_marvel.c.
1617 io_delay= [X86] I/O delay method
1619 Standard port 0x80 based delay
1621 Alternate port 0xed based delay (needed on some systems)
1623 Simple two microseconds delay
1628 See Documentation/filesystems/nfs/nfsroot.txt.
1631 When an interrupt is not handled search all handlers
1632 for it. Intended to get systems with badly broken
1636 When an interrupt is not handled search all handlers
1637 for it. Also check all handlers each timer
1638 interrupt. Intended to get systems with badly broken
1642 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1644 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1646 <cpu number>,...,<cpu number>
1648 <cpu number>-<cpu number>
1649 (must be a positive range in ascending order)
1651 <cpu number>,...,<cpu number>-<cpu number>
1653 This option can be used to specify one or more CPUs
1654 to isolate from the general SMP balancing and scheduling
1655 algorithms. You can move a process onto or off an
1656 "isolated" CPU via the CPU affinity syscalls or cpuset.
1657 <cpu number> begins at 0 and the maximum value is
1658 "number of CPUs in system - 1".
1660 This option is the preferred way to isolate CPUs. The
1661 alternative -- manually setting the CPU mask of all
1662 tasks in the system -- can cause problems and
1663 suboptimal load balancer performance.
1667 ivrs_ioapic [HW,X86_64]
1668 Provide an override to the IOAPIC-ID<->DEVICE-ID
1669 mapping provided in the IVRS ACPI table. For
1670 example, to map IOAPIC-ID decimal 10 to
1671 PCI device 00:14.0 write the parameter as:
1672 ivrs_ioapic[10]=00:14.0
1674 ivrs_hpet [HW,X86_64]
1675 Provide an override to the HPET-ID<->DEVICE-ID
1676 mapping provided in the IVRS ACPI table. For
1677 example, to map HPET-ID decimal 0 to
1678 PCI device 00:14.0 write the parameter as:
1679 ivrs_hpet[0]=00:14.0
1681 js= [HW,JOY] Analog joystick
1682 See Documentation/input/joystick.txt.
1685 Enable/disable kernel and module base offset ASLR
1686 (Address Space Layout Randomization) if built into
1687 the kernel. When CONFIG_HIBERNATION is selected,
1688 kASLR is disabled by default. When kASLR is enabled,
1689 hibernation will be disabled.
1693 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1694 specifies the amount of memory usable by the kernel
1695 for non-movable allocations. The requested amount is
1696 spread evenly throughout all nodes in the system. The
1697 remaining memory in each node is used for Movable
1698 pages. In the event, a node is too small to have both
1699 kernelcore and Movable pages, kernelcore pages will
1700 take priority and other nodes will have a larger number
1701 of Movable pages. The Movable zone is used for the
1702 allocation of pages that may be reclaimed or moved
1703 by the page migration subsystem. This means that
1704 HugeTLB pages may not be allocated from this zone.
1705 Note that allocations like PTEs-from-HighMem still
1706 use the HighMem zone if it exists, and the Normal
1707 zone if it does not.
1709 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1710 Format: <Controller#>[,poll interval]
1711 The controller # is the number of the ehci usb debug
1712 port as it is probed via PCI. The poll interval is
1713 optional and is the number seconds in between
1714 each poll cycle to the debug port in case you need
1715 the functionality for interrupting the kernel with
1716 gdb or control-c on the dbgp connection. When
1717 not using this parameter you use sysrq-g to break into
1718 the kernel debugger.
1720 kgdboc= [KGDB,HW] kgdb over consoles.
1721 Requires a tty driver that supports console polling,
1722 or a supported polling keyboard driver (non-usb).
1723 Serial only format: <serial_device>[,baud]
1724 keyboard only format: kbd
1725 keyboard and serial format: kbd,<serial_device>[,baud]
1726 Optional Kernel mode setting:
1727 kms, kbd format: kms,kbd
1728 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1730 kgdbwait [KGDB] Stop kernel execution and enter the
1731 kernel debugger at the earliest opportunity.
1733 kmac= [MIPS] korina ethernet MAC address.
1734 Configure the RouterBoard 532 series on-chip
1735 Ethernet adapter MAC address.
1737 kmemleak= [KNL] Boot-time kmemleak enable/disable
1738 Valid arguments: on, off
1740 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1743 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1744 Valid arguments: 0, 1, 2
1745 kmemcheck=0 (disabled)
1746 kmemcheck=1 (enabled)
1747 kmemcheck=2 (one-shot mode)
1748 Default: 2 (one-shot mode)
1750 kstack=N [X86] Print N words from the kernel stack
1753 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1754 Default is 0 (don't ignore, but inject #GP)
1756 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1760 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1761 Default is 1 (enabled)
1763 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1765 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1767 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1768 (virtualized MMU) support on capable Intel chips.
1769 Default is 1 (enabled)
1771 kvm-intel.emulate_invalid_guest_state=
1772 [KVM,Intel] Enable emulation of invalid guest states
1773 Default is 0 (disabled)
1775 kvm-intel.flexpriority=
1776 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1777 Default is 1 (enabled)
1780 [KVM,Intel] Enable VMX nesting (nVMX).
1781 Default is 0 (disabled)
1783 kvm-intel.unrestricted_guest=
1784 [KVM,Intel] Disable unrestricted guest feature
1785 (virtualized real and unpaged mode) on capable
1786 Intel chips. Default is 1 (enabled)
1788 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1789 feature (tagged TLBs) on capable Intel chips.
1790 Default is 1 (enabled)
1796 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1799 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1800 value for LAPIC timer one-shot implementation. Default
1801 back to the programmable timer unit in the LAPIC.
1803 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1806 libata.dma= [LIBATA] DMA control
1807 libata.dma=0 Disable all PATA and SATA DMA
1808 libata.dma=1 PATA and SATA Disk DMA only
1809 libata.dma=2 ATAPI (CDROM) DMA only
1810 libata.dma=4 Compact Flash DMA only
1811 Combinations also work, so libata.dma=3 enables DMA
1812 for disks and CDROMs, but not CFs.
1814 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1815 libata.ignore_hpa=0 keep BIOS limits (default)
1816 libata.ignore_hpa=1 ignore limits, using full disk
1818 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1822 libata.force= [LIBATA] Force configurations. The format is comma
1823 separated list of "[ID:]VAL" where ID is
1824 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1825 matching port, link or device. Basically, it matches
1826 the ATA ID string printed on console by libata. If
1827 the whole ID part is omitted, the last PORT and DEVICE
1828 values are used. If ID hasn't been specified yet, the
1829 configuration applies to all ports, links and devices.
1831 If only DEVICE is omitted, the parameter applies to
1832 the port and all links and devices behind it. DEVICE
1833 number of 0 either selects the first device or the
1834 first fan-out link behind PMP device. It does not
1835 select the host link. DEVICE number of 15 selects the
1836 host link and device attached to it.
1838 The VAL specifies the configuration to force. As long
1839 as there's no ambiguity shortcut notation is allowed.
1840 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1841 The following configurations can be forced.
1843 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1844 Any ID with matching PORT is used.
1846 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1848 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1849 udma[/][16,25,33,44,66,100,133] notation is also
1852 * [no]ncq: Turn on or off NCQ.
1854 * [no]ncqtrim: Turn off queued DSM TRIM.
1856 * nohrst, nosrst, norst: suppress hard, soft
1859 * rstonce: only attempt one reset during
1860 hot-unplug link recovery
1862 * dump_id: dump IDENTIFY data.
1864 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1866 * disable: Disable this device.
1868 If there are multiple matching configurations changing
1869 the same attribute, the last one is used.
1871 memblock=debug [KNL] Enable memblock debug messages.
1873 load_ramdisk= [RAM] List of ramdisks to load from floppy
1874 See Documentation/blockdev/ramdisk.txt.
1876 lockd.nlm_grace_period=P [NFS] Assign grace period.
1879 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1882 lockd.nlm_timeout=T [NFS] Assign timeout value.
1885 lockd.nlm_udpport=M [NFS] Assign UDP port.
1888 locktorture.nreaders_stress= [KNL]
1889 Set the number of locking read-acquisition kthreads.
1890 Defaults to being automatically set based on the
1891 number of online CPUs.
1893 locktorture.nwriters_stress= [KNL]
1894 Set the number of locking write-acquisition kthreads.
1896 locktorture.onoff_holdoff= [KNL]
1897 Set time (s) after boot for CPU-hotplug testing.
1899 locktorture.onoff_interval= [KNL]
1900 Set time (s) between CPU-hotplug operations, or
1901 zero to disable CPU-hotplug testing.
1903 locktorture.shuffle_interval= [KNL]
1904 Set task-shuffle interval (jiffies). Shuffling
1905 tasks allows some CPUs to go into dyntick-idle
1906 mode during the locktorture test.
1908 locktorture.shutdown_secs= [KNL]
1909 Set time (s) after boot system shutdown. This
1910 is useful for hands-off automated testing.
1912 locktorture.stat_interval= [KNL]
1913 Time (s) between statistics printk()s.
1915 locktorture.stutter= [KNL]
1916 Time (s) to stutter testing, for example,
1917 specifying five seconds causes the test to run for
1918 five seconds, wait for five seconds, and so on.
1919 This tests the locking primitive's ability to
1920 transition abruptly to and from idle.
1922 locktorture.torture_runnable= [BOOT]
1923 Start locktorture running at boot time.
1925 locktorture.torture_type= [KNL]
1926 Specify the locking implementation to test.
1928 locktorture.verbose= [KNL]
1929 Enable additional printk() statements.
1931 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1934 loglevel= All Kernel Messages with a loglevel smaller than the
1935 console loglevel will be printed to the console. It can
1936 also be changed with klogd or other programs. The
1937 loglevels are defined as follows:
1939 0 (KERN_EMERG) system is unusable
1940 1 (KERN_ALERT) action must be taken immediately
1941 2 (KERN_CRIT) critical conditions
1942 3 (KERN_ERR) error conditions
1943 4 (KERN_WARNING) warning conditions
1944 5 (KERN_NOTICE) normal but significant condition
1945 6 (KERN_INFO) informational
1946 7 (KERN_DEBUG) debug-level messages
1948 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1949 in bytes. n must be a power of two and greater
1950 than the minimal size. The minimal size is defined
1951 by LOG_BUF_SHIFT kernel config parameter. There is
1952 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1953 that allows to increase the default size depending on
1954 the number of CPUs. See init/Kconfig for more details.
1956 logo.nologo [FB] Disables display of the built-in Linux logo.
1957 This may be used to provide more screen space for
1958 kernel log messages and is useful when debugging
1959 kernel boot problems.
1961 lp=0 [LP] Specify parallel ports to use, e.g,
1962 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1963 lp=reset first parallel port). 'lp=0' disables the
1964 lp=auto printer driver. 'lp=reset' (which can be
1965 specified in addition to the ports) causes
1966 attached printers to be reset. Using
1967 lp=port1,port2,... specifies the parallel ports
1968 to associate lp devices with, starting with
1969 lp0. A port specification may be 'none' to skip
1970 that lp device, or a parport name such as
1971 'parport0'. Specifying 'lp=auto' instead of a
1972 port specification list means that device IDs
1973 from each port should be examined, to see if
1974 an IEEE 1284-compliant printer is attached; if
1975 so, the driver will manage that printer.
1976 See also header of drivers/char/lp.c.
1979 Sets loops_per_jiffy to given constant, thus avoiding
1980 time-consuming boot-time autodetection (up to 250 ms per
1981 CPU). 0 enables autodetection (default). To determine
1982 the correct value for your kernel, boot with normal
1983 autodetection and see what value is printed. Note that
1984 on SMP systems the preset will be applied to all CPUs,
1985 which is likely to cause problems if your CPUs need
1986 significantly divergent settings. An incorrect value
1987 will cause delays in the kernel to be wrong, leading to
1988 unpredictable I/O errors and other breakage. Although
1989 unlikely, in the extreme case this might damage your
1993 Format: <io>,<irq>,<dma>
1995 machvec= [IA-64] Force the use of a particular machine-vector
1996 (machvec) in a generic kernel.
1997 Example: machvec=hpzx1_swiotlb
1999 machtype= [Loongson] Share the same kernel image file between different
2001 Example: machtype=lemote-yeeloong-2f-7inch
2003 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
2004 than or equal to this physical address is ignored.
2006 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2007 should make use of. maxcpus=n : n >= 0 limits the
2008 kernel to using 'n' processors. n=0 is a special case,
2009 it is equivalent to "nosmp", which also disables
2012 max_loop= [LOOP] The number of loop block devices that get
2013 (loop.max_loop) unconditionally pre-created at init time. The default
2014 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2015 of statically allocating a predefined number, loop
2016 devices can be requested on-demand with the
2017 /dev/loop-control interface.
2019 mce [X86-32] Machine Check Exception
2021 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2023 md= [HW] RAID subsystems devices and level
2024 See Documentation/md.txt.
2027 Format: <first>,<last>
2028 Specifies range of consoles to be captured by the MDA.
2030 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2031 Amount of memory to be used when the kernel is not able
2032 to see the whole system memory or for test.
2033 [X86] Work as limiting max address. Use together
2034 with memmap= to avoid physical address space collisions.
2035 Without memmap= PCI devices could be placed at addresses
2036 belonging to unused RAM.
2038 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2042 [KNL,SH] Allow user to override the default size for
2043 per-device physically contiguous DMA buffers.
2045 memmap=exactmap [KNL,X86] Enable setting of an exact
2046 E820 memory map, as specified by the user.
2047 Such memmap=exactmap lines can be constructed based on
2048 BIOS output or other requirements. See the memmap=nn@ss
2051 memmap=nn[KMG]@ss[KMG]
2052 [KNL] Force usage of a specific region of memory.
2053 Region of memory to be used is from ss to ss+nn.
2055 memmap=nn[KMG]#ss[KMG]
2056 [KNL,ACPI] Mark specific memory as ACPI data.
2057 Region of memory to be marked is from ss to ss+nn.
2059 memmap=nn[KMG]$ss[KMG]
2060 [KNL,ACPI] Mark specific memory as reserved.
2061 Region of memory to be reserved is from ss to ss+nn.
2062 Example: Exclude memory from 0x18690000-0x1869ffff
2063 memmap=64K$0x18690000
2065 memmap=0x10000$0x18690000
2067 memmap=nn[KMG]!ss[KMG]
2068 [KNL,X86] Mark specific memory as protected.
2069 Region of memory to be used, from ss to ss+nn.
2070 The memory region may be marked as e820 type 12 (0xc)
2071 and is NVDIMM or ADR memory.
2073 memory_corruption_check=0/1 [X86]
2074 Some BIOSes seem to corrupt the first 64k of
2075 memory when doing things like suspend/resume.
2076 Setting this option will scan the memory
2077 looking for corruption. Enabling this will
2078 both detect corruption and prevent the kernel
2079 from using the memory being corrupted.
2080 However, its intended as a diagnostic tool; if
2081 repeatable BIOS-originated corruption always
2082 affects the same memory, you can use memmap=
2083 to prevent the kernel from using that memory.
2085 memory_corruption_check_size=size [X86]
2086 By default it checks for corruption in the low
2087 64k, making this memory unavailable for normal
2088 use. Use this parameter to scan for
2089 corruption in more or less memory.
2091 memory_corruption_check_period=seconds [X86]
2092 By default it checks for corruption every 60
2093 seconds. Use this parameter to check at some
2094 other rate. 0 disables periodic checking.
2096 memtest= [KNL,X86,ARM] Enable memtest
2098 default : 0 <disable>
2099 Specifies the number of memtest passes to be
2100 performed. Each pass selects another test
2101 pattern from a given set of patterns. Memtest
2102 fills the memory with this pattern, validates
2103 memory contents and reserves bad memory
2104 regions that are detected.
2106 meye.*= [HW] Set MotionEye Camera parameters
2107 See Documentation/video4linux/meye.txt.
2109 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2110 Multi-Function General Purpose Timers on AMD Geode
2113 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2114 the BIOS has incorrectly applied a workaround. TinyBIOS
2115 version 0.98 is known to be affected, 0.99 fixes the
2116 problem by letting the user disable the workaround.
2120 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2121 physical address is ignored.
2123 mini2440= [ARM,HW,KNL]
2124 Format:[0..2][b][c][t]
2126 MINI2440 configuration specification:
2127 0 - The attached screen is the 3.5" TFT
2128 1 - The attached screen is the 7" TFT
2129 2 - The VGA Shield is attached (1024x768)
2130 Leaving out the screen size parameter will not load
2131 the TFT driver, and the framebuffer will be left
2133 b - Enable backlight. The TFT backlight pin will be
2134 linked to the kernel VESA blanking code and a GPIO
2135 LED. This parameter is not necessary when using the
2137 c - Enable the s3c camera interface.
2138 t - Reserved for enabling touchscreen support. The
2139 touchscreen support is not enabled in the mainstream
2140 kernel as of 2.6.30, a preliminary port can be found
2141 in the "bleeding edge" mini2440 support kernel at
2142 http://repo.or.cz/w/linux-2.6/mini2440.git
2145 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2146 parameter allows control of the logging verbosity for
2147 the additional memory initialisation checks. A value
2148 of 0 disables mminit logging and a level of 4 will
2149 log everything. Information is printed at KERN_DEBUG
2150 so loglevel=8 may also need to be specified.
2153 [KNL] When CONFIG_MODULE_SIG is set, this means that
2154 modules without (valid) signatures will fail to load.
2155 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2156 is always true, so this option does nothing.
2159 [MOUSE] Maximum time between finger touching and
2160 leaving touchpad surface for touch to be considered
2161 a tap and be reported as a left button click (for
2162 touchpads working in absolute mode only).
2164 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2165 reporting absolute coordinates, such as tablets
2166 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2167 reporting absolute coordinates, such as tablets
2169 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2170 is similar to kernelcore except it specifies the
2171 amount of memory used for migratable allocations.
2172 If both kernelcore and movablecore is specified,
2173 then kernelcore will be at *least* the specified
2174 value but may be more. If movablecore on its own
2175 is specified, the administrator must be careful
2176 that the amount of memory usable for all allocations
2179 movable_node [KNL,X86] Boot-time switch to enable the effects
2180 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2182 MTD_Partition= [MTD]
2183 Format: <name>,<region-number>,<size>,<offset>
2185 MTD_Region= [MTD] Format:
2186 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2189 See drivers/mtd/cmdlinepart.c.
2191 multitce=off [PPC] This parameter disables the use of the pSeries
2192 firmware feature for updating multiple TCE entries
2195 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2197 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2199 boundary - index of last SLC block on Flex-OneNAND.
2200 The remaining blocks are configured as MLC blocks.
2201 lock - Configure if Flex-OneNAND boundary should be locked.
2202 Once locked, the boundary cannot be changed.
2203 1 indicates lock status, 0 indicates unlock status.
2206 ARM/S3C2412 JIVE boot control
2208 See arch/arm/mach-s3c2412/mach-jive.c
2210 mtouchusb.raw_coordinates=
2211 [HW] Make the MicroTouch USB driver use raw coordinates
2212 ('y', default) or cooked coordinates ('n')
2214 mtrr_chunk_size=nn[KMG] [X86]
2215 used for mtrr cleanup. It is largest continuous chunk
2216 that could hold holes aka. UC entries.
2218 mtrr_gran_size=nn[KMG] [X86]
2219 Used for mtrr cleanup. It is granularity of mtrr block.
2221 Large value could prevent small alignment from
2224 mtrr_spare_reg_nr=n [X86]
2226 Range: 0,7 : spare reg number
2228 Used for mtrr cleanup. It is spare mtrr entries number.
2229 Set to 2 or more if your graphical card needs more.
2231 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2233 netdev= [NET] Network devices parameters
2234 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2235 Note that mem_start is often overloaded to mean
2236 something different and driver-specific.
2237 This usage is only documented in each driver source
2241 [NETFILTER] Enable connection tracking flow accounting
2242 0 to disable accounting
2243 1 to enable accounting
2246 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2247 See Documentation/filesystems/nfs/nfsroot.txt.
2249 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2250 See Documentation/filesystems/nfs/nfsroot.txt.
2252 nfsrootdebug [NFS] enable nfsroot debugging messages.
2253 See Documentation/filesystems/nfs/nfsroot.txt.
2255 nfs.callback_tcpport=
2256 [NFS] set the TCP port on which the NFSv4 callback
2257 channel should listen.
2260 [NFS] sets the pathname to the program which is used
2261 to update the NFS client cache entries.
2263 nfs.cache_getent_timeout=
2264 [NFS] sets the timeout after which an attempt to
2265 update a cache entry is deemed to have failed.
2267 nfs.idmap_cache_timeout=
2268 [NFS] set the maximum lifetime for idmapper cache
2272 [NFS] enable 64-bit inode numbers.
2273 If zero, the NFS client will fake up a 32-bit inode
2274 number for the readdir() and stat() syscalls instead
2275 of returning the full 64-bit number.
2276 The default is to return 64-bit inode numbers.
2278 nfs.max_session_slots=
2279 [NFSv4.1] Sets the maximum number of session slots
2280 the client will attempt to negotiate with the server.
2281 This limits the number of simultaneous RPC requests
2282 that the client can send to the NFSv4.1 server.
2283 Note that there is little point in setting this
2284 value higher than the max_tcp_slot_table_limit.
2286 nfs.nfs4_disable_idmapping=
2287 [NFSv4] When set to the default of '1', this option
2288 ensures that both the RPC level authentication
2289 scheme and the NFS level operations agree to use
2290 numeric uids/gids if the mount is using the
2291 'sec=sys' security flavour. In effect it is
2292 disabling idmapping, which can make migration from
2293 legacy NFSv2/v3 systems to NFSv4 easier.
2294 Servers that do not support this mode of operation
2295 will be autodetected by the client, and it will fall
2296 back to using the idmapper.
2297 To turn off this behaviour, set the value to '0'.
2299 [NFS4] Specify an additional fixed unique ident-
2300 ification string that NFSv4 clients can insert into
2301 their nfs_client_id4 string. This is typically a
2302 UUID that is generated at system install time.
2304 nfs.send_implementation_id =
2305 [NFSv4.1] Send client implementation identification
2306 information in exchange_id requests.
2307 If zero, no implementation identification information
2309 The default is to send the implementation identification
2312 nfs.recover_lost_locks =
2313 [NFSv4] Attempt to recover locks that were lost due
2314 to a lease timeout on the server. Please note that
2315 doing this risks data corruption, since there are
2316 no guarantees that the file will remain unchanged
2317 after the locks are lost.
2318 If you want to enable the kernel legacy behaviour of
2319 attempting to recover these locks, then set this
2321 The default parameter value of '0' causes the kernel
2322 not to attempt recovery of lost locks.
2324 nfs4.layoutstats_timer =
2325 [NFSv4.2] Change the rate at which the kernel sends
2326 layoutstats to the pNFS metadata server.
2328 Setting this to value to 0 causes the kernel to use
2329 whatever value is the default set by the layout
2330 driver. A non-zero value sets the minimum interval
2331 in seconds between layoutstats transmissions.
2333 nfsd.nfs4_disable_idmapping=
2334 [NFSv4] When set to the default of '1', the NFSv4
2335 server will return only numeric uids and gids to
2336 clients using auth_sys, and will accept numeric uids
2337 and gids from such clients. This is intended to ease
2338 migration from NFSv2/v3.
2340 objlayoutdriver.osd_login_prog=
2341 [NFS] [OBJLAYOUT] sets the pathname to the program which
2342 is used to automatically discover and login into new
2343 osd-targets. Please see:
2344 Documentation/filesystems/pnfs.txt for more explanations
2346 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2347 when a NMI is triggered.
2348 Format: [state][,regs][,debounce][,die]
2350 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2351 Format: [panic,][nopanic,][num]
2353 0 - turn hardlockup detector in nmi_watchdog off
2354 1 - turn hardlockup detector in nmi_watchdog on
2355 When panic is specified, panic when an NMI watchdog
2356 timeout occurs (or 'nopanic' to override the opposite
2357 default). To disable both hard and soft lockup detectors,
2358 please see 'nowatchdog'.
2359 This is useful when you use a panic=... timeout and
2360 need the box quickly up again.
2362 netpoll.carrier_timeout=
2363 [NET] Specifies amount of time (in seconds) that
2364 netpoll should wait for a carrier. By default netpoll
2367 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2368 emulation library even if a 387 maths coprocessor
2372 [HW] Never suspend the console
2373 Disable suspending of consoles during suspend and
2374 hibernate operations. Once disabled, debugging
2375 messages can reach various consoles while the rest
2376 of the system is being put to sleep (ie, while
2377 debugging driver suspend/resume hooks). This may
2378 not work reliably with all consoles, but is known
2379 to work with serial and VGA consoles.
2380 To facilitate more flexible debugging, we also add
2381 console_suspend, a printk module parameter to control
2382 it. Users could use console_suspend (usually
2383 /sys/module/printk/parameters/console_suspend) to
2384 turn on/off it dynamically.
2386 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2387 caches in the slab allocator. Saves per-node memory,
2388 but will impact performance.
2392 noapic [SMP,APIC] Tells the kernel to not make use of any
2393 IOAPICs that may be present in the system.
2395 noautogroup Disable scheduler automatic task group creation.
2397 nobats [PPC] Do not use BATs for mapping kernel lowmem
2398 on "Classic" PPC cores.
2402 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2404 nodelayacct [KNL] Disable per-task delay accounting
2406 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2408 nodsp [SH] Disable hardware DSP at boot time.
2410 noefi Disable EFI runtime services support.
2415 On X86-32 available only on PAE configured kernels.
2416 noexec=on: enable non-executable mappings (default)
2417 noexec=off: disable non-executable mappings
2420 Disable SMAP (Supervisor Mode Access Prevention)
2421 even if it is supported by processor.
2424 Disable SMEP (Supervisor Mode Execution Prevention)
2425 even if it is supported by processor.
2428 This affects only 32-bit executables.
2429 noexec32=on: enable non-executable mappings (default)
2430 read doesn't imply executable mappings
2431 noexec32=off: disable non-executable mappings
2432 read implies executable mappings
2434 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2436 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2437 register save and restore. The kernel will only save
2438 legacy floating-point registers on task switch.
2440 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2442 noxsave [BUGS=X86] Disables x86 extended register state save
2443 and restore using xsave. The kernel will fallback to
2444 enabling legacy floating-point and sse state.
2446 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2447 register states. The kernel will fall back to use
2448 xsave to save the states. By using this parameter,
2449 performance of saving the states is degraded because
2450 xsave doesn't support modified optimization while
2451 xsaveopt supports it on xsaveopt enabled systems.
2453 noxsaves [X86] Disables xsaves and xrstors used in saving and
2454 restoring x86 extended register state in compacted
2455 form of xsave area. The kernel will fall back to use
2456 xsaveopt and xrstor to save and restore the states
2457 in standard form of xsave area. By using this
2458 parameter, xsave area per process might occupy more
2459 memory on xsaves enabled systems.
2461 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2462 wfi(ARM) instruction doesn't work correctly and not to
2463 use it. This is also useful when using JTAG debugger.
2465 no_file_caps Tells the kernel not to honor file capabilities. The
2466 only way then for a file to be executed with privilege
2467 is to be setuid root or executed by root.
2469 nohalt [IA-64] Tells the kernel not to use the power saving
2470 function PAL_HALT_LIGHT when idle. This increases
2471 power-consumption. On the positive side, it reduces
2472 interrupt wake-up latency, which may improve performance
2473 in certain environments such as networked servers or
2476 nohibernate [HIBERNATION] Disable hibernation and resume.
2478 nohz= [KNL] Boottime enable/disable dynamic ticks
2479 Valid arguments: on, off
2482 nohz_full= [KNL,BOOT]
2483 In kernels built with CONFIG_NO_HZ_FULL=y, set
2484 the specified list of CPUs whose tick will be stopped
2485 whenever possible. The boot CPU will be forced outside
2486 the range to maintain the timekeeping.
2487 The CPUs in this range must also be included in the
2490 noiotrap [SH] Disables trapped I/O port accesses.
2492 noirqdebug [X86-32] Disables the code which attempts to detect and
2493 disable unhandled interrupt sources.
2495 no_timer_check [X86,APIC] Disables the code which tests for
2496 broken timer IRQ sources.
2498 noisapnp [ISAPNP] Disables ISA PnP code.
2500 noinitrd [RAM] Tells the kernel not to load any configured
2503 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2505 [Deprecated - use intremap=off]
2509 nojitter [IA-64] Disables jitter checking for ITC timers.
2511 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2513 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2516 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2517 steal time is computed, but won't influence scheduler
2520 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2522 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2524 noltlbs [PPC] Do not use large page/tlb entries for kernel
2525 lowmem mapping on PPC40x.
2527 nomca [IA-64] Disable machine check abort handling
2529 nomce [X86-32] Disable Machine Check Exception
2531 nomfgpt [X86-32] Disable Multi-Function General Purpose
2532 Timer usage (for AMD Geode machines).
2534 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2535 shutdown the other cpus. Instead use the REBOOT_VECTOR
2538 nomodule Disable module load
2540 nopat [X86] Disable PAT (page attribute table extension of
2541 pagetables) support.
2543 norandmaps Don't use address space randomization. Equivalent to
2544 echo 0 > /proc/sys/kernel/randomize_va_space
2546 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2548 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2549 with UP alternatives
2551 nordrand [X86] Disable kernel use of the RDRAND and
2552 RDSEED instructions even if they are supported
2553 by the processor. RDRAND and RDSEED are still
2554 available to user space applications.
2556 noresume [SWSUSP] Disables resume and restores original swap
2559 no-scroll [VGA] Disables scrollback.
2560 This is required for the Braillex ib80-piezo Braille
2561 reader made by F.H. Papenmeier (Germany).
2565 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2567 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2568 and disable the IO APIC. legacy for "maxcpus=0".
2570 nosoftlockup [KNL] Disable the soft-lockup detector.
2572 nosync [HW,M68K] Disables sync negotiation for all devices.
2574 notsc [BUGS=X86-32] Disable Time Stamp Counter
2576 nousb [USB] Disable the USB subsystem
2578 nowatchdog [KNL] Disable both lockup detectors, i.e.
2579 soft-lockup and NMI watchdog (hard-lockup).
2583 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2585 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2586 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2587 Some features depend on CPU0. Known dependencies are:
2588 1. Resume from suspend/hibernate depends on CPU0.
2589 Suspend/hibernate will fail if CPU0 is offline and you
2590 need to online CPU0 before suspend/hibernate.
2591 2. PIC interrupts also depend on CPU0. CPU0 can't be
2592 removed if a PIC interrupt is detected.
2593 It's said poweroff/reboot may depend on CPU0 on some
2594 machines although I haven't seen such issues so far
2595 after CPU0 is offline on a few tested machines.
2596 If the dependencies are under your control, you can
2597 turn on cpu0_hotplug.
2599 nptcg= [IA-64] Override max number of concurrent global TLB
2600 purges which is reported from either PAL_VM_SUMMARY or
2603 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2604 could support. nr_cpus=n : n >= 1 limits the kernel to
2605 supporting 'n' processors. Later in runtime you can not
2606 use hotplug cpu feature to put more cpu back to online.
2607 just like you compile the kernel NR_CPUS=n
2609 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2611 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2612 Allowed values are enable and disable
2614 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2615 one of ['zone', 'node', 'default'] can be specified
2616 This can be set from sysctl after boot.
2617 See Documentation/sysctl/vm.txt for details.
2619 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2620 See Documentation/debugging-via-ohci1394.txt for more
2623 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2624 Rather than timing out after 20 ms if an EC
2625 command is not properly ACKed, override the length
2626 of the timeout. We have interrupts disabled while
2627 waiting for the ACK, so if this is set too high
2628 interrupts *may* be lost!
2630 omap_mux= [OMAP] Override bootloader pin multiplexing.
2631 Format: <mux_mode0.mode_name=value>...
2632 For example, to override I2C bus2:
2633 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2635 oprofile.timer= [HW]
2636 Use timer interrupt instead of performance counters
2638 oprofile.cpu_type= Force an oprofile cpu type
2639 This might be useful if you have an older oprofile
2640 userland or if you want common events.
2641 Format: { arch_perfmon }
2642 arch_perfmon: [X86] Force use of architectural
2643 perfmon on Intel CPUs instead of the
2644 CPU specific event set.
2645 timer: [X86] Force use of architectural NMI
2646 timer mode (see also oprofile.timer
2647 for generic hr timer mode)
2648 [s390] Force legacy basic mode sampling
2649 (report cpu_type "timer")
2651 oops=panic Always panic on oopses. Default is to just kill the
2652 process, but there is a small probability of
2653 deadlocking the machine.
2654 This will also cause panics on machine check exceptions.
2655 Useful together with panic=30 to trigger a reboot.
2658 See Documentation/sound/oss/oss-parameters.txt
2660 page_owner= [KNL] Boot-time page_owner enabling option.
2661 Storage of the information about who allocated
2662 each page is disabled in default. With this switch,
2664 on: enable the feature
2666 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2667 timeout > 0: seconds before rebooting
2668 timeout = 0: wait forever
2669 timeout < 0: reboot immediately
2672 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2675 crash_kexec_post_notifiers
2676 Run kdump after running panic-notifiers and dumping
2677 kmsg. This only for the users who doubt kdump always
2678 succeeds in any situation.
2679 Note that this also increases risks of kdump failure,
2680 because some panic notifiers can make the crashed
2681 kernel more unstable.
2683 parkbd.port= [HW] Parallel port number the keyboard adapter is
2684 connected to, default is 0.
2686 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2687 0 for XT, 1 for AT (default is AT).
2690 parport= [HW,PPT] Specify parallel ports. 0 disables.
2691 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2692 Use 'auto' to force the driver to use any
2693 IRQ/DMA settings detected (the default is to
2694 ignore detected IRQ/DMA settings because of
2695 possible conflicts). You can specify the base
2696 address, IRQ, and DMA settings; IRQ and DMA
2697 should be numbers, or 'auto' (for using detected
2698 settings on that particular port), or 'nofifo'
2699 (to avoid using a FIFO even if it is detected).
2700 Parallel ports are assigned in the order they
2701 are specified on the command line, starting
2704 parport_init_mode= [HW,PPT]
2705 Configure VIA parallel port to operate in
2706 a specific mode. This is necessary on Pegasos
2707 computer where firmware has no options for setting
2708 up parallel port mode and sets it to spp.
2709 Currently this function knows 686a and 8231 chips.
2710 Format: [spp|ps2|epp|ecp|ecpepp]
2713 Halt all CPUs after the first oops has been printed for
2714 the specified number of seconds. This is to be used if
2715 your oopses keep scrolling off the screen.
2720 See header of drivers/block/paride/pcd.c.
2721 See also Documentation/blockdev/paride.txt.
2723 pci=option[,option...] [PCI] various PCI subsystem options:
2724 earlydump [X86] dump PCI config space before the kernel
2726 off [X86] don't probe for the PCI bus
2727 bios [X86-32] force use of PCI BIOS, don't access
2728 the hardware directly. Use this if your machine
2729 has a non-standard PCI host bridge.
2730 nobios [X86-32] disallow use of PCI BIOS, only direct
2731 hardware access methods are allowed. Use this
2732 if you experience crashes upon bootup and you
2733 suspect they are caused by the BIOS.
2734 conf1 [X86] Force use of PCI Configuration
2736 conf2 [X86] Force use of PCI Configuration
2738 noaer [PCIE] If the PCIEAER kernel config parameter is
2739 enabled, this kernel boot option can be used to
2740 disable the use of PCIE advanced error reporting.
2741 nodomains [PCI] Disable support for multiple PCI
2742 root domains (aka PCI segments, in ACPI-speak).
2743 nommconf [X86] Disable use of MMCONFIG for PCI
2745 check_enable_amd_mmconf [X86] check for and enable
2746 properly configured MMIO access to PCI
2747 config space on AMD family 10h CPU
2748 nomsi [MSI] If the PCI_MSI kernel config parameter is
2749 enabled, this kernel boot option can be used to
2750 disable the use of MSI interrupts system-wide.
2751 noioapicquirk [APIC] Disable all boot interrupt quirks.
2752 Safety option to keep boot IRQs enabled. This
2753 should never be necessary.
2754 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2755 primary IO-APIC for bridges that cannot disable
2756 boot IRQs. This fixes a source of spurious IRQs
2757 when the system masks IRQs.
2758 noioapicreroute [APIC] Disable workaround that uses the
2759 boot IRQ equivalent of an IRQ that connects to
2760 a chipset where boot IRQs cannot be disabled.
2761 The opposite of ioapicreroute.
2762 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2763 routing table. These calls are known to be buggy
2764 on several machines and they hang the machine
2765 when used, but on other computers it's the only
2766 way to get the interrupt routing table. Try
2767 this option if the kernel is unable to allocate
2768 IRQs or discover secondary PCI buses on your
2770 rom [X86] Assign address space to expansion ROMs.
2771 Use with caution as certain devices share
2772 address decoders between ROMs and other
2774 norom [X86] Do not assign address space to
2775 expansion ROMs that do not already have
2776 BIOS assigned address ranges.
2777 nobar [X86] Do not assign address space to the
2778 BARs that weren't assigned by the BIOS.
2779 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2780 assigned automatically to PCI devices. You can
2781 make the kernel exclude IRQs of your ISA cards
2783 pirqaddr=0xAAAAA [X86] Specify the physical address
2784 of the PIRQ table (normally generated
2785 by the BIOS) if it is outside the
2786 F0000h-100000h range.
2787 lastbus=N [X86] Scan all buses thru bus #N. Can be
2788 useful if the kernel is unable to find your
2789 secondary buses and you want to tell it
2790 explicitly which ones they are.
2791 assign-busses [X86] Always assign all PCI bus
2792 numbers ourselves, overriding
2793 whatever the firmware may have done.
2794 usepirqmask [X86] Honor the possible IRQ mask stored
2795 in the BIOS $PIR table. This is needed on
2796 some systems with broken BIOSes, notably
2797 some HP Pavilion N5400 and Omnibook XE3
2798 notebooks. This will have no effect if ACPI
2799 IRQ routing is enabled.
2800 noacpi [X86] Do not use ACPI for IRQ routing
2801 or for PCI scanning.
2802 use_crs [X86] Use PCI host bridge window information
2803 from ACPI. On BIOSes from 2008 or later, this
2804 is enabled by default. If you need to use this,
2805 please report a bug.
2806 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2807 If you need to use this, please report a bug.
2808 routeirq Do IRQ routing for all PCI devices.
2809 This is normally done in pci_enable_device(),
2810 so this option is a temporary workaround
2811 for broken drivers that don't call it.
2812 skip_isa_align [X86] do not align io start addr, so can
2813 handle more pci cards
2814 firmware [ARM] Do not re-enumerate the bus but instead
2815 just use the configuration from the
2816 bootloader. This is currently used on
2817 IXP2000 systems where the bus has to be
2818 configured a certain way for adjunct CPUs.
2819 noearly [X86] Don't do any early type 1 scanning.
2820 This might help on some broken boards which
2821 machine check when some devices' config space
2822 is read. But various workarounds are disabled
2823 and some IOMMU drivers will not work.
2824 bfsort Sort PCI devices into breadth-first order.
2825 This sorting is done to get a device
2826 order compatible with older (<= 2.4) kernels.
2827 nobfsort Don't sort PCI devices into breadth-first order.
2828 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2829 tuning and use the BIOS-configured MPS defaults.
2830 pcie_bus_safe Set every device's MPS to the largest value
2831 supported by all devices below the root complex.
2832 pcie_bus_perf Set device MPS to the largest allowable MPS
2833 based on its parent bus. Also set MRRS (Max
2834 Read Request Size) to the largest supported
2835 value (no larger than the MPS that the device
2836 or bus can support) for best performance.
2837 pcie_bus_peer2peer Set every device's MPS to 128B, which
2838 every device is guaranteed to support. This
2839 configuration allows peer-to-peer DMA between
2840 any pair of devices, possibly at the cost of
2841 reduced performance. This also guarantees
2842 that hot-added devices will work.
2843 cbiosize=nn[KMG] The fixed amount of bus space which is
2844 reserved for the CardBus bridge's IO window.
2845 The default value is 256 bytes.
2846 cbmemsize=nn[KMG] The fixed amount of bus space which is
2847 reserved for the CardBus bridge's memory
2848 window. The default value is 64 megabytes.
2851 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2852 Specifies alignment and device to reassign
2853 aligned memory resources.
2854 If <order of align> is not specified,
2855 PAGE_SIZE is used as alignment.
2856 PCI-PCI bridge can be specified, if resource
2857 windows need to be expanded.
2858 ecrc= Enable/disable PCIe ECRC (transaction layer
2859 end-to-end CRC checking).
2860 bios: Use BIOS/firmware settings. This is the
2864 hpiosize=nn[KMG] The fixed amount of bus space which is
2865 reserved for hotplug bridge's IO window.
2866 Default size is 256 bytes.
2867 hpmemsize=nn[KMG] The fixed amount of bus space which is
2868 reserved for hotplug bridge's memory window.
2869 Default size is 2 megabytes.
2870 realloc= Enable/disable reallocating PCI bridge resources
2871 if allocations done by BIOS are too small to
2872 accommodate resources required by all child
2874 off: Turn realloc off
2876 realloc same as realloc=on
2877 noari do not use PCIe ARI.
2878 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2879 only look for one device below a PCIe downstream
2882 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2885 force Enable ASPM even on devices that claim not to support it.
2886 WARNING: Forcing ASPM on may cause system lockups.
2888 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2889 nomsi Do not use MSI for PCI Express Native Hotplug (this
2890 makes all PCIe ports use INTx for hotplug services).
2892 pcie_ports= [PCIE] PCIe ports handling:
2893 auto Ask the BIOS whether or not to use native PCIe services
2894 associated with PCIe ports (PME, hot-plug, AER). Use
2895 them only if that is allowed by the BIOS.
2896 native Use native PCIe services associated with PCIe ports
2898 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2901 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2902 nomsi Do not use MSI for native PCIe PME signaling (this makes
2903 all PCIe root ports use INTx for all services).
2905 pcmv= [HW,PCMCIA] BadgePAD 4
2909 Keep all power-domains already enabled by bootloader on,
2910 even if no driver has claimed them. This is useful
2911 for debug and development, but should not be
2912 needed on a platform with proper driver support.
2915 See Documentation/blockdev/paride.txt.
2917 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2920 See arch/parisc/kernel/pdc_chassis.c
2922 percpu_alloc= Select which percpu first chunk allocator to use.
2923 Currently supported values are "embed" and "page".
2924 Archs may support subset or none of the selections.
2925 See comments in mm/percpu.c for details on each
2926 allocator. This parameter is primarily for debugging
2927 and performance comparison.
2930 See Documentation/blockdev/paride.txt.
2933 See Documentation/blockdev/paride.txt.
2935 pirq= [SMP,APIC] Manual mp-table setup
2936 See Documentation/x86/i386/IO-APIC.txt.
2938 plip= [PPT,NET] Parallel port network link
2939 Format: { parport<nr> | timid | 0 }
2940 See also Documentation/parport.txt.
2942 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2943 Override pmtimer IOPort with a hex value.
2947 Enable PNP debug messages (depends on the
2948 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2949 via /sys/module/pnp/parameters/debug. We always show
2950 current resource usage; turning this on also shows
2951 possible settings and some assignment information.
2957 { on | off | curr | res | no-curr | no-res }
2960 [ISAPNP] Exclude IRQs for the autoconfiguration
2963 [ISAPNP] Exclude DMAs for the autoconfiguration
2965 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2966 Ranges are in pairs (I/O port base and size).
2969 [ISAPNP] Exclude memory regions for the
2971 Ranges are in pairs (memory base and size).
2973 ports= [IP_VS_FTP] IPVS ftp helper module
2975 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2977 Format: <port>,<port>....
2979 print-fatal-signals=
2980 [KNL] debug: print fatal signals
2982 If enabled, warn about various signal handling
2983 related application anomalies: too many signals,
2984 too many POSIX.1 timers, fatal signals causing a
2987 If you hit the warning due to signal overflow,
2988 you might want to try "ulimit -i unlimited".
2992 printk.always_kmsg_dump=
2993 Trigger kmsg_dump for cases other than kernel oops or
2995 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2998 printk.time= Show timing data prefixed to each printk message line
2999 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
3001 processor.max_cstate= [HW,ACPI]
3002 Limit processor to maximum C-state
3003 max_cstate=9 overrides any DMI blacklist limit.
3005 processor.nocst [HW,ACPI]
3006 Ignore the _CST method to determine C-states,
3007 instead using the legacy FADT method
3009 profile= [KNL] Enable kernel profiling via /proc/profile
3010 Format: [schedule,]<number>
3011 Param: "schedule" - profile schedule points.
3012 Param: <number> - step/bucket size as a power of 2 for
3013 statistical time based profiling.
3014 Param: "sleep" - profile D-state sleeping (millisecs).
3015 Requires CONFIG_SCHEDSTATS
3016 Param: "kvm" - profile VM exits.
3018 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3020 See Documentation/blockdev/ramdisk.txt.
3022 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3023 probe for; one of (bare|imps|exps|lifebook|any).
3024 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3026 psmouse.resetafter= [HW,MOUSE]
3027 Try to reset the device after so many bad packets
3030 [HW,MOUSE] Set desired mouse resolution, in dpi.
3031 psmouse.smartscroll=
3032 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3033 0 = disabled, 1 = enabled (default).
3035 pstore.backend= Specify the name of the pstore backend to use
3038 See Documentation/blockdev/paride.txt.
3041 [KNL] Number of legacy pty's. Overwrites compiled-in
3044 quiet [KNL] Disable most log messages
3049 See Documentation/md.txt.
3051 ramdisk_blocksize= [RAM]
3052 See Documentation/blockdev/ramdisk.txt.
3054 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3055 See Documentation/blockdev/ramdisk.txt.
3058 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3059 the specified list of CPUs to be no-callback CPUs.
3060 Invocation of these CPUs' RCU callbacks will
3061 be offloaded to "rcuox/N" kthreads created for
3062 that purpose, where "x" is "b" for RCU-bh, "p"
3063 for RCU-preempt, and "s" for RCU-sched, and "N"
3064 is the CPU number. This reduces OS jitter on the
3065 offloaded CPUs, which can be useful for HPC and
3066 real-time workloads. It can also improve energy
3067 efficiency for asymmetric multiprocessors.
3070 Rather than requiring that offloaded CPUs
3071 (specified by rcu_nocbs= above) explicitly
3072 awaken the corresponding "rcuoN" kthreads,
3073 make these kthreads poll for callbacks.
3074 This improves the real-time response for the
3075 offloaded CPUs by relieving them of the need to
3076 wake up the corresponding kthread, but degrades
3077 energy efficiency by requiring that the kthreads
3078 periodically wake up to do the polling.
3080 rcutree.blimit= [KNL]
3081 Set maximum number of finished RCU callbacks to
3082 process in one batch.
3084 rcutree.dump_tree= [KNL]
3085 Dump the structure of the rcu_node combining tree
3086 out at early boot. This is used for diagnostic
3087 purposes, to verify correct tree setup.
3089 rcutree.gp_cleanup_delay= [KNL]
3090 Set the number of jiffies to delay each step of
3091 RCU grace-period cleanup. This only has effect
3092 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3094 rcutree.gp_init_delay= [KNL]
3095 Set the number of jiffies to delay each step of
3096 RCU grace-period initialization. This only has
3097 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3100 rcutree.gp_preinit_delay= [KNL]
3101 Set the number of jiffies to delay each step of
3102 RCU grace-period pre-initialization, that is,
3103 the propagation of recent CPU-hotplug changes up
3104 the rcu_node combining tree. This only has effect
3105 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3107 rcutree.rcu_fanout_exact= [KNL]
3108 Disable autobalancing of the rcu_node combining
3109 tree. This is used by rcutorture, and might
3110 possibly be useful for architectures having high
3111 cache-to-cache transfer latencies.
3113 rcutree.rcu_fanout_leaf= [KNL]
3114 Change the number of CPUs assigned to each
3115 leaf rcu_node structure. Useful for very
3116 large systems, which will choose the value 64,
3117 and for NUMA systems with large remote-access
3118 latencies, which will choose a value aligned
3119 with the appropriate hardware boundaries.
3121 rcutree.jiffies_till_sched_qs= [KNL]
3122 Set required age in jiffies for a
3123 given grace period before RCU starts
3124 soliciting quiescent-state help from
3125 rcu_note_context_switch().
3127 rcutree.jiffies_till_first_fqs= [KNL]
3128 Set delay from grace-period initialization to
3129 first attempt to force quiescent states.
3130 Units are jiffies, minimum value is zero,
3131 and maximum value is HZ.
3133 rcutree.jiffies_till_next_fqs= [KNL]
3134 Set delay between subsequent attempts to force
3135 quiescent states. Units are jiffies, minimum
3136 value is one, and maximum value is HZ.
3138 rcutree.kthread_prio= [KNL,BOOT]
3139 Set the SCHED_FIFO priority of the RCU per-CPU
3140 kthreads (rcuc/N). This value is also used for
3141 the priority of the RCU boost threads (rcub/N)
3142 and for the RCU grace-period kthreads (rcu_bh,
3143 rcu_preempt, and rcu_sched). If RCU_BOOST is
3144 set, valid values are 1-99 and the default is 1
3145 (the least-favored priority). Otherwise, when
3146 RCU_BOOST is not set, valid values are 0-99 and
3147 the default is zero (non-realtime operation).
3149 rcutree.rcu_nocb_leader_stride= [KNL]
3150 Set the number of NOCB kthread groups, which
3151 defaults to the square root of the number of
3152 CPUs. Larger numbers reduces the wakeup overhead
3153 on the per-CPU grace-period kthreads, but increases
3154 that same overhead on each group's leader.
3156 rcutree.qhimark= [KNL]
3157 Set threshold of queued RCU callbacks beyond which
3158 batch limiting is disabled.
3160 rcutree.qlowmark= [KNL]
3161 Set threshold of queued RCU callbacks below which
3162 batch limiting is re-enabled.
3164 rcutree.rcu_idle_gp_delay= [KNL]
3165 Set wakeup interval for idle CPUs that have
3166 RCU callbacks (RCU_FAST_NO_HZ=y).
3168 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3169 Set wakeup interval for idle CPUs that have
3170 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3171 Lazy RCU callbacks are those which RCU can
3172 prove do nothing more than free memory.
3174 rcutorture.cbflood_inter_holdoff= [KNL]
3175 Set holdoff time (jiffies) between successive
3176 callback-flood tests.
3178 rcutorture.cbflood_intra_holdoff= [KNL]
3179 Set holdoff time (jiffies) between successive
3180 bursts of callbacks within a given callback-flood
3183 rcutorture.cbflood_n_burst= [KNL]
3184 Set the number of bursts making up a given
3185 callback-flood test. Set this to zero to
3186 disable callback-flood testing.
3188 rcutorture.cbflood_n_per_burst= [KNL]
3189 Set the number of callbacks to be registered
3190 in a given burst of a callback-flood test.
3192 rcutorture.fqs_duration= [KNL]
3193 Set duration of force_quiescent_state bursts
3196 rcutorture.fqs_holdoff= [KNL]
3197 Set holdoff time within force_quiescent_state bursts
3200 rcutorture.fqs_stutter= [KNL]
3201 Set wait time between force_quiescent_state bursts
3204 rcutorture.gp_cond= [KNL]
3205 Use conditional/asynchronous update-side
3206 primitives, if available.
3208 rcutorture.gp_exp= [KNL]
3209 Use expedited update-side primitives, if available.
3211 rcutorture.gp_normal= [KNL]
3212 Use normal (non-expedited) asynchronous
3213 update-side primitives, if available.
3215 rcutorture.gp_sync= [KNL]
3216 Use normal (non-expedited) synchronous
3217 update-side primitives, if available. If all
3218 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3219 rcutorture.gp_normal=, and rcutorture.gp_sync=
3220 are zero, rcutorture acts as if is interpreted
3221 they are all non-zero.
3223 rcutorture.n_barrier_cbs= [KNL]
3224 Set callbacks/threads for rcu_barrier() testing.
3226 rcutorture.nfakewriters= [KNL]
3227 Set number of concurrent RCU writers. These just
3228 stress RCU, they don't participate in the actual
3229 test, hence the "fake".
3231 rcutorture.nreaders= [KNL]
3232 Set number of RCU readers. The value -1 selects
3233 N-1, where N is the number of CPUs. A value
3234 "n" less than -1 selects N-n-2, where N is again
3235 the number of CPUs. For example, -2 selects N
3236 (the number of CPUs), -3 selects N+1, and so on.
3238 rcutorture.object_debug= [KNL]
3239 Enable debug-object double-call_rcu() testing.
3241 rcutorture.onoff_holdoff= [KNL]
3242 Set time (s) after boot for CPU-hotplug testing.
3244 rcutorture.onoff_interval= [KNL]
3245 Set time (s) between CPU-hotplug operations, or
3246 zero to disable CPU-hotplug testing.
3248 rcutorture.shuffle_interval= [KNL]
3249 Set task-shuffle interval (s). Shuffling tasks
3250 allows some CPUs to go into dyntick-idle mode
3251 during the rcutorture test.
3253 rcutorture.shutdown_secs= [KNL]
3254 Set time (s) after boot system shutdown. This
3255 is useful for hands-off automated testing.
3257 rcutorture.stall_cpu= [KNL]
3258 Duration of CPU stall (s) to test RCU CPU stall
3259 warnings, zero to disable.
3261 rcutorture.stall_cpu_holdoff= [KNL]
3262 Time to wait (s) after boot before inducing stall.
3264 rcutorture.stat_interval= [KNL]
3265 Time (s) between statistics printk()s.
3267 rcutorture.stutter= [KNL]
3268 Time (s) to stutter testing, for example, specifying
3269 five seconds causes the test to run for five seconds,
3270 wait for five seconds, and so on. This tests RCU's
3271 ability to transition abruptly to and from idle.
3273 rcutorture.test_boost= [KNL]
3274 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3275 "Maybe" means test if the RCU implementation
3276 under test support RCU priority boosting.
3278 rcutorture.test_boost_duration= [KNL]
3279 Duration (s) of each individual boost test.
3281 rcutorture.test_boost_interval= [KNL]
3282 Interval (s) between each boost test.
3284 rcutorture.test_no_idle_hz= [KNL]
3285 Test RCU's dyntick-idle handling. See also the
3286 rcutorture.shuffle_interval parameter.
3288 rcutorture.torture_runnable= [BOOT]
3289 Start rcutorture running at boot time.
3291 rcutorture.torture_type= [KNL]
3292 Specify the RCU implementation to test.
3294 rcutorture.verbose= [KNL]
3295 Enable additional printk() statements.
3297 rcupdate.rcu_expedited= [KNL]
3298 Use expedited grace-period primitives, for
3299 example, synchronize_rcu_expedited() instead
3300 of synchronize_rcu(). This reduces latency,
3301 but can increase CPU utilization, degrade
3302 real-time latency, and degrade energy efficiency.
3304 rcupdate.rcu_cpu_stall_suppress= [KNL]
3305 Suppress RCU CPU stall warning messages.
3307 rcupdate.rcu_cpu_stall_timeout= [KNL]
3308 Set timeout for RCU CPU stall warning messages.
3310 rcupdate.rcu_task_stall_timeout= [KNL]
3311 Set timeout in jiffies for RCU task stall warning
3312 messages. Disable with a value less than or equal
3315 rcupdate.rcu_self_test= [KNL]
3316 Run the RCU early boot self tests
3318 rcupdate.rcu_self_test_bh= [KNL]
3319 Run the RCU bh early boot self tests
3321 rcupdate.rcu_self_test_sched= [KNL]
3322 Run the RCU sched early boot self tests
3326 Run specified binary instead of /init from the ramdisk,
3327 used for early userspace startup. See initrd.
3330 Format (x86 or x86_64):
3331 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3333 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3335 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3336 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3337 reboot_force is either force or not specified,
3338 reboot_cpu is s[mp]#### with #### being the processor
3339 to be used for rebooting.
3342 [KNL, SMP] Set scheduler's default relax_domain_level.
3343 See Documentation/cgroups/cpusets.txt.
3345 relative_sleep_states=
3346 [SUSPEND] Use sleep state labeling where the deepest
3347 state available other than hibernation is always "mem".
3348 Format: { "0" | "1" }
3349 0 -- Traditional sleep state labels.
3350 1 -- Relative sleep state labels.
3352 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3354 reservetop= [X86-32]
3356 Reserves a hole at the top of the kernel virtual
3361 Set the amount of memory to reserve for BIOS at
3362 the bottom of the address space.
3364 reset_devices [KNL] Force drivers to reset the underlying device
3365 during initialization.
3368 Specify the partition device for software suspend
3370 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3372 resume_offset= [SWSUSP]
3373 Specify the offset from the beginning of the partition
3374 given by "resume=" at which the swap header is located,
3375 in <PAGE_SIZE> units (needed only for swap files).
3376 See Documentation/power/swsusp-and-swap-files.txt
3378 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3379 read the resume files
3381 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3382 Useful for devices that are detected asynchronously
3383 (e.g. USB and MMC devices).
3385 hibernate= [HIBERNATION]
3386 noresume Don't check if there's a hibernation image
3387 present during boot.
3388 nocompress Don't compress/decompress hibernation images.
3389 no Disable hibernation and resume.
3391 retain_initrd [RAM] Keep initrd memory after extraction
3393 rfkill.default_state=
3394 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3395 etc. communication is blocked by default.
3398 rfkill.master_switch_mode=
3399 0 The "airplane mode" button does nothing.
3400 1 The "airplane mode" button toggles between everything
3401 blocked and the previous configuration.
3402 2 The "airplane mode" button toggles between everything
3403 blocked and everything unblocked.
3405 rhash_entries= [KNL,NET]
3406 Set number of hash buckets for route cache
3408 ro [KNL] Mount root device read-only on boot
3410 root= [KNL] Root filesystem
3411 See name_to_dev_t comment in init/do_mounts.c.
3413 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3414 mount the root filesystem
3416 rootflags= [KNL] Set root filesystem mount option string
3418 rootfstype= [KNL] Set root filesystem type
3420 rootwait [KNL] Wait (indefinitely) for root device to show up.
3421 Useful for devices that are detected asynchronously
3422 (e.g. USB and MMC devices).
3424 rproc_mem=nn[KMG][@address]
3425 [KNL,ARM,CMA] Remoteproc physical memory block.
3426 Memory area to be used by remote processor image,
3429 rw [KNL] Mount root device read-write on boot
3431 S [KNL] Run init in single mode
3433 s390_iommu= [HW,S390]
3434 Set s390 IOTLB flushing mode
3436 With strict flushing every unmap operation will result in
3437 an IOTLB flush. Default is lazy flushing before reuse,
3441 See drivers/net/irda/sa1100_ir.c.
3443 sbni= [NET] Granch SBNI12 leased line adapter
3445 sched_debug [KNL] Enables verbose scheduler debug messages.
3447 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3448 xtime_lock contention on larger systems, and/or RCU lock
3449 contention on all systems with CONFIG_MAXSMP set.
3450 Format: { "0" | "1" }
3451 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3453 Note: increases power consumption, thus should only be
3454 enabled if running jitter sensitive (HPC/RT) workloads.
3456 security= [SECURITY] Choose a security module to enable at boot.
3457 If this boot parameter is not specified, only the first
3458 security module asking for security registration will be
3459 loaded. An invalid security module name will be treated
3460 as if no module has been chosen.
3462 selinux= [SELINUX] Disable or enable SELinux at boot time.
3463 Format: { "0" | "1" }
3464 See security/selinux/Kconfig help text.
3467 Default value is set via kernel config option.
3468 If enabled at boot time, /selinux/disable can be used
3469 later to disable prior to initial policy load.
3471 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3472 Format: { "0" | "1" }
3473 See security/apparmor/Kconfig help text
3476 Default value is set via kernel config option.
3478 serialnumber [BUGS=X86-32]
3481 Maximal number of shapers.
3483 show_msr= [x86] show boot-time MSR settings
3484 Format: { <integer> }
3485 Show boot-time (BIOS-initialized) MSR settings.
3486 The parameter means the number of CPUs to show,
3487 for example 1 means boot CPU only.
3495 Disable merging of slabs with similar size. May be
3496 necessary if there is some reason to distinguish
3497 allocs to different slabs. Debug options disable
3498 merging on their own.
3499 For more information see Documentation/vm/slub.txt.
3501 slab_max_order= [MM, SLAB]
3502 Determines the maximum allowed order for slabs.
3503 A high setting may cause OOMs due to memory
3504 fragmentation. Defaults to 1 for systems with
3505 more than 32MB of RAM, 0 otherwise.
3507 slub_debug[=options[,slabs]] [MM, SLUB]
3508 Enabling slub_debug allows one to determine the
3509 culprit if slab objects become corrupted. Enabling
3510 slub_debug can create guard zones around objects and
3511 may poison objects when not in use. Also tracks the
3512 last alloc / free. For more information see
3513 Documentation/vm/slub.txt.
3515 slub_max_order= [MM, SLUB]
3516 Determines the maximum allowed order for slabs.
3517 A high setting may cause OOMs due to memory
3518 fragmentation. For more information see
3519 Documentation/vm/slub.txt.
3521 slub_min_objects= [MM, SLUB]
3522 The minimum number of objects per slab. SLUB will
3523 increase the slab order up to slub_max_order to
3524 generate a sufficiently large slab able to contain
3525 the number of objects indicated. The higher the number
3526 of objects the smaller the overhead of tracking slabs
3527 and the less frequently locks need to be acquired.
3528 For more information see Documentation/vm/slub.txt.
3530 slub_min_order= [MM, SLUB]
3531 Determines the minimum page order for slabs. Must be
3532 lower than slub_max_order.
3533 For more information see Documentation/vm/slub.txt.
3535 slub_nomerge [MM, SLUB]
3536 Same with slab_nomerge. This is supported for legacy.
3537 See slab_nomerge for more information.
3540 Format: <io1>[,<io2>[,...,<io8>]]
3542 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3543 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3544 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3545 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3546 smsc-ircc2.ircc_irq= [HW] IRQ line
3547 smsc-ircc2.ircc_dma= [HW] DMA channel
3548 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3549 0: Toshiba Satellite 1800 (GP data pin select)
3550 1: Fast pin select (default)
3554 [KNL] Should the soft-lockup detector generate panics.
3557 softlockup_all_cpu_backtrace=
3558 [KNL] Should the soft-lockup detector generate
3559 backtraces on all cpus.
3562 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3563 See Documentation/laptops/sonypi.txt
3565 spia_io_base= [HW,MTD]
3571 Enabled the stack tracer on boot up.
3573 stacktrace_filter=[function-list]
3574 [FTRACE] Limit the functions that the stack tracer
3575 will trace at boot up. function-list is a comma separated
3576 list of functions. This list can be changed at run
3577 time by the stack_trace_filter file in the debugfs
3578 tracing directory. Note, this enables stack tracing
3579 and the stacktrace above is not needed.
3583 Set the STI (builtin display/keyboard on the HP-PARISC
3584 machines) console (graphic card) which should be used
3585 as the initial boot-console.
3586 See also comment in drivers/video/console/sticore.c.
3589 See comment in drivers/video/console/sticore.c.
3592 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3594 sunrpc.min_resvport=
3595 sunrpc.max_resvport=
3597 SunRPC servers often require that client requests
3598 originate from a privileged port (i.e. a port in the
3599 range 0 < portnr < 1024).
3600 An administrator who wishes to reserve some of these
3601 ports for other uses may adjust the range that the
3602 kernel's sunrpc client considers to be privileged
3603 using these two parameters to set the minimum and
3604 maximum port values.
3608 Control how the NFS server code allocates CPUs to
3609 service thread pools. Depending on how many NICs
3610 you have and where their interrupts are bound, this
3611 option will affect which CPUs will do NFS serving.
3612 Note: this parameter cannot be changed while the
3613 NFS server is running.
3615 auto the server chooses an appropriate mode
3616 automatically using heuristics
3617 global a single global pool contains all CPUs
3618 percpu one pool for each CPU
3619 pernode one pool for each NUMA node (equivalent
3620 to global on non-NUMA machines)
3622 sunrpc.tcp_slot_table_entries=
3623 sunrpc.udp_slot_table_entries=
3625 Sets the upper limit on the number of simultaneous
3626 RPC calls that can be sent from the client to a
3627 server. Increasing these values may allow you to
3628 improve throughput, but will also increase the
3629 amount of memory reserved for use by the client.
3631 suspend.pm_test_delay=
3633 Sets the number of seconds to remain in a suspend test
3634 mode before resuming the system (see
3635 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3636 is set. Default value is 5.
3639 [KNL] Enable accounting of swap in memory resource
3640 controller if no parameter or 1 is given or disable
3641 it if 0 is given (See Documentation/cgroups/memory.txt)
3643 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3644 Format: { <int> | force }
3645 <int> -- Number of I/O TLB slabs
3646 force -- force using of bounce buffers even if they
3647 wouldn't be automatically used by the kernel
3651 sysfs.deprecated=0|1 [KNL]
3652 Enable/disable old style sysfs layout for old udev
3653 on older distributions. When this option is enabled
3654 very new udev will not work anymore. When this option
3655 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3656 in older udev will not work anymore.
3657 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3658 the kernel configuration.
3660 sysrq_always_enabled
3662 Ignore sysrq setting - this boot parameter will
3663 neutralize any effect of /proc/sys/kernel/sysrq.
3664 Useful for debugging.
3666 tcpmhash_entries= [KNL,NET]
3667 Set the number of tcp_metrics_hash slots.
3668 Default value is 8192 or 16384 depending on total
3669 ram pages. This is used to specify the TCP metrics
3670 cache size. See Documentation/networking/ip-sysctl.txt
3671 "tcp_no_metrics_save" section for more details.
3675 test_suspend= [SUSPEND][,N]
3676 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3677 standby suspend) or "freeze" (for suspend type freeze)
3678 as the system sleep state during system startup with
3679 the optional capability to repeat N number of times.
3680 The system is woken from this state using a
3681 wakeup-capable RTC alarm.
3683 thash_entries= [KNL,NET]
3684 Set number of hash buckets for TCP connection
3686 thermal.act= [HW,ACPI]
3687 -1: disable all active trip points in all thermal zones
3688 <degrees C>: override all lowest active trip points
3690 thermal.crt= [HW,ACPI]
3691 -1: disable all critical trip points in all thermal zones
3692 <degrees C>: override all critical trip points
3694 thermal.nocrt= [HW,ACPI]
3695 Set to disable actions on ACPI thermal zone
3696 critical and hot trip points.
3698 thermal.off= [HW,ACPI]
3699 1: disable ACPI thermal control
3701 thermal.psv= [HW,ACPI]
3702 -1: disable all passive trip points
3703 <degrees C>: override all passive trip points to this
3706 thermal.tzp= [HW,ACPI]
3707 Specify global default ACPI thermal zone polling rate
3708 <deci-seconds>: poll all this frequency
3709 0: no polling (default)
3712 Force threading of all interrupt handlers except those
3713 marked explicitly IRQF_NO_THREAD.
3716 Enable the Transcendent memory driver if built-in.
3718 tmem.cleancache=0|1 [KNL, XEN]
3719 Default is on (1). Disable the usage of the cleancache
3720 API to send anonymous pages to the hypervisor.
3722 tmem.frontswap=0|1 [KNL, XEN]
3723 Default is on (1). Disable the usage of the frontswap
3724 API to send swap pages to the hypervisor. If disabled
3725 the selfballooning and selfshrinking are force disabled.
3727 tmem.selfballooning=0|1 [KNL, XEN]
3728 Default is on (1). Disable the driving of swap pages
3731 tmem.selfshrinking=0|1 [KNL, XEN]
3732 Default is on (1). Partial swapoff that immediately
3733 transfers pages from Xen hypervisor back to the
3734 kernel based on different criteria.
3738 Specify if the kernel should make use of the cpu
3739 topology information if the hardware supports this.
3740 The scheduler will make use of this information and
3741 e.g. base its process migration decisions on it.
3744 topology_updates= [KNL, PPC, NUMA]
3746 Specify if the kernel should ignore (off)
3747 topology updates sent by the hypervisor to this
3752 tpm_suspend_pcr=[HW,TPM]
3753 Format: integer pcr id
3754 Specify that at suspend time, the tpm driver
3755 should extend the specified pcr with zeros,
3756 as a workaround for some chips which fail to
3757 flush the last written pcr on TPM_SaveState.
3758 This will guarantee that all the other pcrs
3761 trace_buf_size=nn[KMG]
3762 [FTRACE] will set tracing buffer size on each cpu.
3764 trace_event=[event-list]
3765 [FTRACE] Set and start specified trace events in order
3766 to facilitate early boot debugging.
3767 See also Documentation/trace/events.txt
3769 trace_options=[option-list]
3770 [FTRACE] Enable or disable tracer options at boot.
3771 The option-list is a comma delimited list of options
3772 that can be enabled or disabled just as if you were
3773 to echo the option name into
3775 /sys/kernel/debug/tracing/trace_options
3777 For example, to enable stacktrace option (to dump the
3778 stack trace of each event), add to the command line:
3780 trace_options=stacktrace
3782 See also Documentation/trace/ftrace.txt "trace options"
3786 Have the tracepoints sent to printk as well as the
3787 tracing ring buffer. This is useful for early boot up
3788 where the system hangs or reboots and does not give the
3789 option for reading the tracing buffer or performing a
3790 ftrace_dump_on_oops.
3792 To turn off having tracepoints sent to printk,
3793 echo 0 > /proc/sys/kernel/tracepoint_printk
3794 Note, echoing 1 into this file without the
3795 tracepoint_printk kernel cmdline option has no effect.
3799 Having tracepoints sent to printk() and activating high
3800 frequency tracepoints such as irq or sched, can cause
3801 the system to live lock.
3804 [FTRACE] enable this option to disable tracing when a
3805 warning is hit. This turns off "tracing_on". Tracing can
3806 be enabled again by echoing '1' into the "tracing_on"
3807 file located in /sys/kernel/debug/tracing/
3809 This option is useful, as it disables the trace before
3810 the WARNING dump is called, which prevents the trace to
3811 be filled with content caused by the warning output.
3813 This option can also be set at run time via the sysctl
3814 option: kernel/traceoff_on_warning
3816 transparent_hugepage=
3818 Format: [always|madvise|never]
3819 Can be used to control the default behavior of the system
3820 with respect to transparent hugepages.
3821 See Documentation/vm/transhuge.txt for more details.
3823 tsc= Disable clocksource stability checks for TSC.
3825 [x86] reliable: mark tsc clocksource as reliable, this
3826 disables clocksource verification at runtime, as well
3827 as the stability checks done at bootup. Used to enable
3828 high-resolution timer mode on older hardware, and in
3829 virtualized environment.
3830 [x86] noirqtime: Do not use TSC to do irq accounting.
3831 Used to run time disable IRQ_TIME_ACCOUNTING on any
3832 platforms where RDTSC is slow and this accounting
3835 turbografx.map[2|3]= [HW,JOY]
3836 TurboGraFX parallel port interface
3838 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3839 See also Documentation/input/joystick-parport.txt
3841 udbg-immortal [PPC] When debugging early kernel crashes that
3842 happen after console_init() and before a proper
3843 console driver takes over, this boot options might
3844 help "seeing" what's going on.
3846 uhash_entries= [KNL,NET]
3847 Set number of hash buckets for UDP/UDP-Lite connections
3850 [USB] Ignore overcurrent events (default N).
3851 Some badly-designed motherboards generate lots of
3852 bogus events, for ports that aren't wired to
3853 anything. Set this parameter to avoid log spamming.
3854 Note that genuine overcurrent events won't be
3858 [X86] Cause panic on unknown NMI.
3860 usbcore.authorized_default=
3861 [USB] Default USB device authorization:
3862 (default -1 = authorized except for wireless USB,
3863 0 = not authorized, 1 = authorized)
3865 usbcore.autosuspend=
3866 [USB] The autosuspend time delay (in seconds) used
3867 for newly-detected USB devices (default 2). This
3868 is the time required before an idle device will be
3869 autosuspended. Devices for which the delay is set
3870 to a negative value won't be autosuspended at all.
3872 usbcore.usbfs_snoop=
3873 [USB] Set to log all usbfs traffic (default 0 = off).
3875 usbcore.blinkenlights=
3876 [USB] Set to cycle leds on hubs (default 0 = off).
3878 usbcore.old_scheme_first=
3879 [USB] Start with the old device initialization
3880 scheme (default 0 = off).
3882 usbcore.usbfs_memory_mb=
3883 [USB] Memory limit (in MB) for buffers allocated by
3884 usbfs (default = 16, 0 = max = 2047).
3886 usbcore.use_both_schemes=
3887 [USB] Try the other device initialization scheme
3888 if the first one fails (default 1 = enabled).
3890 usbcore.initial_descriptor_timeout=
3891 [USB] Specifies timeout for the initial 64-byte
3892 USB_REQ_GET_DESCRIPTOR request in milliseconds
3893 (default 5000 = 5.0 seconds).
3896 [USBHID] The interval which mice are to be polled at.
3898 usb-storage.delay_use=
3899 [UMS] The delay in seconds before a new device is
3900 scanned for Logical Units (default 1).
3903 [UMS] A list of quirks entries to supplement or
3904 override the built-in unusual_devs list. List
3905 entries are separated by commas. Each entry has
3906 the form VID:PID:Flags where VID and PID are Vendor
3907 and Product ID values (4-digit hex numbers) and
3908 Flags is a set of characters, each corresponding
3909 to a common usb-storage quirk flag as follows:
3910 a = SANE_SENSE (collect more than 18 bytes
3912 b = BAD_SENSE (don't collect more than 18
3913 bytes of sense data);
3914 c = FIX_CAPACITY (decrease the reported
3915 device capacity by one sector);
3916 d = NO_READ_DISC_INFO (don't use
3917 READ_DISC_INFO command);
3918 e = NO_READ_CAPACITY_16 (don't use
3919 READ_CAPACITY_16 command);
3920 f = NO_REPORT_OPCODES (don't use report opcodes
3922 g = MAX_SECTORS_240 (don't transfer more than
3923 240 sectors at a time, uas only);
3924 h = CAPACITY_HEURISTICS (decrease the
3925 reported device capacity by one
3926 sector if the number is odd);
3927 i = IGNORE_DEVICE (don't bind to this
3929 l = NOT_LOCKABLE (don't try to lock and
3930 unlock ejectable media);
3931 m = MAX_SECTORS_64 (don't transfer more
3932 than 64 sectors = 32 KB at a time);
3933 n = INITIAL_READ10 (force a retry of the
3934 initial READ(10) command);
3935 o = CAPACITY_OK (accept the capacity
3936 reported by the device);
3937 p = WRITE_CACHE (the device cache is ON
3939 r = IGNORE_RESIDUE (the device reports
3940 bogus residue values);
3941 s = SINGLE_LUN (the device has only one
3943 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3944 commands, uas only);
3945 u = IGNORE_UAS (don't bind to the uas driver);
3946 w = NO_WP_DETECT (don't test whether the
3947 medium is write-protected).
3948 Example: quirks=0419:aaf5:rl,0421:0433:rc
3950 user_debug= [KNL,ARM]
3952 See arch/arm/Kconfig.debug help text.
3953 1 - undefined instruction events
3955 4 - invalid data aborts
3958 Example: user_debug=31
3961 [X86] Flags controlling user PTE allocations.
3963 nohigh = do not allocate PTE pages in
3964 HIGHMEM regardless of setting
3968 On X86_32, this is an alias for vdso32=. Otherwise:
3970 vdso=1: enable VDSO (the default)
3971 vdso=0: disable VDSO mapping
3973 vdso32= [X86] Control the 32-bit vDSO
3974 vdso32=1: enable 32-bit VDSO
3975 vdso32=0 or vdso32=2: disable 32-bit VDSO
3977 See the help text for CONFIG_COMPAT_VDSO for more
3978 details. If CONFIG_COMPAT_VDSO is set, the default is
3979 vdso32=0; otherwise, the default is vdso32=1.
3981 For compatibility with older kernels, vdso32=2 is an
3984 Try vdso32=0 if you encounter an error that says:
3985 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3988 vector=percpu: enable percpu vector domain
3990 video= [FB] Frame buffer configuration
3991 See Documentation/fb/modedb.txt.
3993 video.brightness_switch_enabled= [0,1]
3994 If set to 1, on receiving an ACPI notify event
3995 generated by hotkey, video driver will adjust brightness
3996 level and then send out the event to user space through
3997 the allocated input device; If set to 0, video driver
3998 will only send out the event without touching backlight
4003 [VMMIO] Memory mapped virtio (platform) device.
4005 <size>@<baseaddr>:<irq>[:<id>]
4007 <size> := size (can use standard suffixes
4009 <baseaddr> := physical base address
4010 <irq> := interrupt number (as passed to
4012 <id> := (optional) platform device id
4014 virtio_mmio.device=1K@0x100b0000:48:7
4016 Can be used multiple times for multiple devices.
4018 vga= [BOOT,X86-32] Select a particular video mode
4019 See Documentation/x86/boot.txt and
4020 Documentation/svga.txt.
4021 Use vga=ask for menu.
4022 This is actually a boot loader parameter; the value is
4023 passed to the kernel using a special protocol.
4025 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4026 size of <nn>. This can be used to increase the
4027 minimum size (128MB on x86). It can also be used to
4028 decrease the size and leave more room for directly
4031 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4034 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4037 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4041 Controls the behavior of vsyscalls (i.e. calls to
4042 fixed addresses of 0xffffffffff600x00 from legacy
4043 code). Most statically-linked binaries and older
4044 versions of glibc use these calls. Because these
4045 functions are at fixed addresses, they make nice
4046 targets for exploits that can control RIP.
4048 emulate [default] Vsyscalls turn into traps and are
4049 emulated reasonably safely.
4051 native Vsyscalls are native syscall instructions.
4052 This is a little bit faster than trapping
4053 and makes a few dynamic recompilers work
4054 better than they would in emulation mode.
4055 It also makes exploits much easier to write.
4057 none Vsyscalls don't work at all. This makes
4058 them quite hard to use for exploits but
4059 might break your system.
4061 vt.color= [VT] Default text color.
4062 Format: 0xYX, X = foreground, Y = background.
4063 Default: 0x07 = light gray on black.
4065 vt.cur_default= [VT] Default cursor shape.
4066 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4067 the parameters of the <Esc>[?A;B;Cc escape sequence;
4068 see VGA-softcursor.txt. Default: 2 = underline.
4070 vt.default_blu= [VT]
4071 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4072 Change the default blue palette of the console.
4073 This is a 16-member array composed of values
4076 vt.default_grn= [VT]
4077 Format: <green0>,<green1>,<green2>,...,<green15>
4078 Change the default green palette of the console.
4079 This is a 16-member array composed of values
4082 vt.default_red= [VT]
4083 Format: <red0>,<red1>,<red2>,...,<red15>
4084 Change the default red palette of the console.
4085 This is a 16-member array composed of values
4091 Set system-wide default UTF-8 mode for all tty's.
4092 Default is 1, i.e. UTF-8 mode is enabled for all
4093 newly opened terminals.
4095 vt.global_cursor_default=
4098 Set system-wide default for whether a cursor
4099 is shown on new VTs. Default is -1,
4100 i.e. cursors will be created by default unless
4101 overridden by individual drivers. 0 will hide
4102 cursors, 1 will display them.
4104 vt.italic= [VT] Default color for italic text; 0-15.
4107 vt.underline= [VT] Default color for underlined text; 0-15.
4110 watchdog timers [HW,WDT] For information on watchdog timers,
4111 see Documentation/watchdog/watchdog-parameters.txt
4112 or other driver-specific files in the
4113 Documentation/watchdog/ directory.
4115 workqueue.disable_numa
4116 By default, all work items queued to unbound
4117 workqueues are affine to the NUMA nodes they're
4118 issued on, which results in better behavior in
4119 general. If NUMA affinity needs to be disabled for
4120 whatever reason, this option can be used. Note
4121 that this also can be controlled per-workqueue for
4122 workqueues visible under /sys/bus/workqueue/.
4124 workqueue.power_efficient
4125 Per-cpu workqueues are generally preferred because
4126 they show better performance thanks to cache
4127 locality; unfortunately, per-cpu workqueues tend to
4128 be more power hungry than unbound workqueues.
4130 Enabling this makes the per-cpu workqueues which
4131 were observed to contribute significantly to power
4132 consumption unbound, leading to measurably lower
4133 power usage at the cost of small performance
4136 The default value of this parameter is determined by
4137 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4139 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4140 default x2apic cluster mode on platforms
4143 x86_intel_mid_timer= [X86-32,APBT]
4144 Choose timer option for x86 Intel MID platform.
4145 Two valid options are apbt timer only and lapic timer
4146 plus one apbt timer for broadcast timer.
4147 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4149 xen_512gb_limit [KNL,X86-64,XEN]
4150 Restricts the kernel running paravirtualized under Xen
4151 to use only up to 512 GB of RAM. The reason to do so is
4152 crash analysis tools and Xen tools for doing domain
4153 save/restore/migration must be enabled to handle larger
4156 xen_emul_unplug= [HW,X86,XEN]
4157 Unplug Xen emulated devices
4158 Format: [unplug0,][unplug1]
4159 ide-disks -- unplug primary master IDE devices
4160 aux-ide-disks -- unplug non-primary-master IDE devices
4161 nics -- unplug network devices
4162 all -- unplug all emulated devices (NICs and IDE disks)
4163 unnecessary -- unplugging emulated devices is
4164 unnecessary even if the host did not respond to
4166 never -- do not unplug even if version check succeeds
4168 xen_nopvspin [X86,XEN]
4169 Disables the ticketlock slowpath using Xen PV
4173 Disables the PV optimizations forcing the HVM guest to
4174 run as generic HVM guest with no PV drivers.
4176 xirc2ps_cs= [NET,PCMCIA]
4178 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4180 ______________________________________________________________________
4184 Add more DRM drivers.
projects / karo-tx-linux.git / blob