4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
168 acpi= [HW,ACPI,X86,ARM64]
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt |
172 force -- enable ACPI if default was off
173 off -- disable ACPI if default was on
174 noirq -- do not use ACPI for IRQ routing
175 strict -- Be less tolerant of platforms that are not
176 strictly ACPI specification compliant.
177 rsdt -- prefer RSDT over (default) XSDT
178 copy_dsdt -- copy DSDT to memory
179 For ARM64, ONLY "acpi=off" or "acpi=force" are available
181 See also Documentation/power/runtime_pm.txt, pci=noacpi
183 acpi_apic_instance= [ACPI, IOAPIC]
185 2: use 2nd APIC table, if available
186 1,0: use 1st APIC table
189 acpi_backlight= [HW,ACPI]
190 acpi_backlight=vendor
192 If set to vendor, prefer vendor specific driver
193 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
194 of the ACPI video.ko driver.
196 acpica_no_return_repair [HW, ACPI]
197 Disable AML predefined validation mechanism
198 This mechanism can repair the evaluation result to make
199 the return objects more ACPI specification compliant.
200 This option is useful for developers to identify the
201 root cause of an AML interpreter issue when the issue
202 has something to do with the repair mechanism.
204 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
205 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
207 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
208 debug output. Bits in debug_layer correspond to a
209 _COMPONENT in an ACPI source file, e.g.,
210 #define _COMPONENT ACPI_PCI_COMPONENT
211 Bits in debug_level correspond to a level in
212 ACPI_DEBUG_PRINT statements, e.g.,
213 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
214 The debug_level mask defaults to "info". See
215 Documentation/acpi/debug.txt for more information about
216 debug layers and levels.
218 Enable processor driver info messages:
219 acpi.debug_layer=0x20000000
220 Enable PCI/PCI interrupt routing info messages:
221 acpi.debug_layer=0x400000
222 Enable AML "Debug" output, i.e., stores to the Debug
223 object while interpreting AML:
224 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
225 Enable all messages related to ACPI hardware:
226 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
228 Some values produce so much output that the system is
229 unusable. The "log_buf_len" parameter may be useful
230 if you need to capture more output.
232 acpi_enforce_resources= [ACPI]
233 { strict | lax | no }
234 Check for resource conflicts between native drivers
235 and ACPI OperationRegions (SystemIO and SystemMemory
236 only). IO ports and memory declared in ACPI might be
237 used by the ACPI subsystem in arbitrary AML code and
238 can interfere with legacy drivers.
239 strict (default): access to resources claimed by ACPI
240 is denied; legacy drivers trying to access reserved
241 resources will fail to bind to device using them.
242 lax: access to resources claimed by ACPI is allowed;
243 legacy drivers trying to access reserved resources
244 will bind successfully but a warning message is logged.
245 no: ACPI OperationRegions are not marked as reserved,
246 no further checks are performed.
248 acpi_force_table_verification [HW,ACPI]
249 Enable table checksum verification during early stage.
250 By default, this is disabled due to x86 early mapping
253 acpi_irq_balance [HW,ACPI]
254 ACPI will balance active IRQs
257 acpi_irq_nobalance [HW,ACPI]
258 ACPI will not move active IRQs (default)
261 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
262 Format: <irq>,<irq>...
264 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
266 Format: <irq>,<irq>...
268 acpi_no_auto_serialize [HW,ACPI]
269 Disable auto-serialization of AML methods
270 AML control methods that contain the opcodes to create
271 named objects will be marked as "Serialized" by the
272 auto-serialization feature.
273 This feature is enabled by default.
274 This option allows to turn off the feature.
276 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
279 acpi_no_static_ssdt [HW,ACPI]
280 Disable installation of static SSDTs at early boot time
281 By default, SSDTs contained in the RSDT/XSDT will be
282 installed automatically and they will appear under
283 /sys/firmware/acpi/tables.
284 This option turns off this feature.
285 Note that specifying this option does not affect
286 dynamic table installation which will install SSDT
287 tables to /sys/firmware/acpi/tables/dynamic.
289 acpi_rsdp= [ACPI,EFI,KEXEC]
290 Pass the RSDP address to the kernel, mostly used
291 on machines running EFI runtime service to boot the
292 second kernel for kdump.
294 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
295 Format: To spoof as Windows 98: ="Microsoft Windows"
297 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
298 of 2 which is mandated by ACPI 6) as the supported ACPI
299 specification revision (when using this switch, it may
300 be necessary to carry out a cold reboot _twice_ in a
301 row to make it take effect on the platform firmware).
303 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
304 acpi_osi="string1" # add string1
305 acpi_osi="!string2" # remove string2
306 acpi_osi=!* # remove all strings
307 acpi_osi=! # disable all built-in OS vendor
309 acpi_osi= # disable all strings
311 'acpi_osi=!' can be used in combination with single or
312 multiple 'acpi_osi="string1"' to support specific OS
313 vendor string(s). Note that such command can only
314 affect the default state of the OS vendor strings, thus
315 it cannot affect the default state of the feature group
316 strings and the current state of the OS vendor strings,
317 specifying it multiple times through kernel command line
318 is meaningless. This command is useful when one do not
319 care about the state of the feature group strings which
320 should be controlled by the OSPM.
322 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
323 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
324 can make '_OSI("Windows 2000")' TRUE.
326 'acpi_osi=' cannot be used in combination with other
327 'acpi_osi=' command lines, the _OSI method will not
328 exist in the ACPI namespace. NOTE that such command can
329 only affect the _OSI support state, thus specifying it
330 multiple times through kernel command line is also
333 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
336 'acpi_osi=!*' can be used in combination with single or
337 multiple 'acpi_osi="string1"' to support specific
338 string(s). Note that such command can affect the
339 current state of both the OS vendor strings and the
340 feature group strings, thus specifying it multiple times
341 through kernel command line is meaningful. But it may
342 still not able to affect the final state of a string if
343 there are quirks related to this string. This command
344 is useful when one want to control the state of the
345 feature group strings to debug BIOS issues related to
348 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
349 '_OSI("Module Device")' FALSE.
350 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
351 '_OSI("Module Device")' TRUE.
352 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
354 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
356 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
357 they all will make '_OSI("Windows 2000")' TRUE.
360 Override the pmtimer bug detection: force the kernel
361 to assume that this machine's pmtimer latches its value
362 and always returns good values.
364 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
365 Format: { level | edge | high | low }
367 acpi_skip_timer_override [HW,ACPI]
368 Recognize and ignore IRQ0/pin2 Interrupt Override.
369 For broken nForce2 BIOS resulting in XT-PIC timer.
371 acpi_sleep= [HW,ACPI] Sleep options
372 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
373 old_ordering, nonvs, sci_force_enable }
374 See Documentation/power/video.txt for information on
376 s3_beep is for debugging; it makes the PC's speaker beep
377 as soon as the kernel's real-mode entry point is called.
378 s4_nohwsig prevents ACPI hardware signature from being
379 used during resume from hibernation.
380 old_ordering causes the ACPI 1.0 ordering of the _PTS
381 control method, with respect to putting devices into
382 low power states, to be enforced (the ACPI 2.0 ordering
383 of _PTS is used by default).
384 nonvs prevents the kernel from saving/restoring the
385 ACPI NVS memory during suspend/hibernation and resume.
386 sci_force_enable causes the kernel to set SCI_EN directly
387 on resume from S1/S3 (which is against the ACPI spec,
388 but some broken systems don't work without it).
390 acpi_use_timer_override [HW,ACPI]
391 Use timer override. For some broken Nvidia NF5 boards
392 that require a timer override, but don't have HPET
394 add_efi_memmap [EFI; X86] Include EFI memory map in
395 kernel's map of available physical RAM.
398 { off | try_unsupported }
399 off: disable AGP support
400 try_unsupported: try to drive unsupported chipsets
401 (may crash computer or cause data corruption)
404 See Documentation/sound/alsa/alsa-parameters.txt
407 Allow the default userspace alignment fault handler
408 behaviour to be specified. Bit 0 enables warnings,
409 bit 1 enables fixups, and bit 2 sends a segfault.
411 align_va_addr= [X86-64]
412 Align virtual addresses by clearing slice [14:12] when
413 allocating a VMA at process creation time. This option
414 gives you up to 3% performance improvement on AMD F15h
415 machines (where it is enabled by default) for a
416 CPU-intensive style benchmark, and it can vary highly in
417 a microbenchmark depending on workload and compiler.
419 32: only for 32-bit processes
420 64: only for 64-bit processes
421 on: enable for both 32- and 64-bit processes
422 off: disable for both 32- and 64-bit processes
424 alloc_snapshot [FTRACE]
425 Allocate the ftrace snapshot buffer on boot up when the
426 main buffer is allocated. This is handy if debugging
427 and you need to use tracing_snapshot() on boot up, and
428 do not want to use tracing_snapshot_alloc() as it needs
429 to be done where GFP_KERNEL allocations are allowed.
431 amd_iommu= [HW,X86-64]
432 Pass parameters to the AMD IOMMU driver in the system.
434 fullflush - enable flushing of IO/TLB entries when
435 they are unmapped. Otherwise they are
436 flushed before they will be reused, which
438 off - do not initialize any AMD IOMMU found in
440 force_isolation - Force device isolation for all
441 devices. The IOMMU driver is not
442 allowed anymore to lift isolation
443 requirements as needed. This option
444 does not override iommu=pt
446 amd_iommu_dump= [HW,X86-64]
447 Enable AMD IOMMU driver option to dump the ACPI table
448 for AMD IOMMU. With this option enabled, AMD IOMMU
449 driver will print ACPI tables for AMD IOMMU during
450 IOMMU initialization.
452 amijoy.map= [HW,JOY] Amiga joystick support
453 Map of devices attached to JOY0DAT and JOY1DAT
455 See also Documentation/input/joystick.txt
457 analog.map= [HW,JOY] Analog joystick and gamepad support
458 Specifies type or capabilities of an analog joystick
459 connected to one of 16 gameports
460 Format: <type1>,<type2>,..<type16>
463 Power management functions (SPARCstation-4/5 + deriv.)
465 Disable APC CPU standby support. SPARCstation-Fox does
466 not play well with APC CPU idle - disable it if you have
467 APC and your system crashes randomly.
469 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
470 Change the output verbosity whilst booting
471 Format: { quiet (default) | verbose | debug }
472 Change the amount of debugging information output
473 when initialising the APIC and IO-APIC components.
476 See Documentation/networking/ipv6.txt.
478 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
479 Limit apic dumping. The parameter defines the maximal
480 number of local apics being dumped. Also it is possible
481 to set it to "all" by meaning -- no limit here.
482 Format: { 1 (default) | 2 | ... | all }.
483 The parameter valid if only apic=debug or
484 apic=verbose is specified.
485 Example: apic=debug show_lapic=all
487 apm= [APM] Advanced Power Management
488 See header of arch/x86/kernel/apm_32.c.
490 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
491 Format: <io>,<irq>,<nodeID>
495 atarimouse= [HW,MOUSE] Atari Mouse
497 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
498 EzKey and similar keyboards
500 atkbd.reset= [HW] Reset keyboard during initialization
502 atkbd.set= [HW] Select keyboard code set
503 Format: <int> (2 = AT (default), 3 = PS/2)
505 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
508 atkbd.softraw= [HW] Choose between synthetic and real raw mode
509 Format: <bool> (0 = real, 1 = synthetic (default))
511 atkbd.softrepeat= [HW]
512 Use software keyboard repeat
514 audit= [KNL] Enable the audit sub-system
515 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
516 0 - kernel audit is disabled and can not be enabled
517 until the next reboot
518 unset - kernel audit is initialized but disabled and
519 will be fully enabled by the userspace auditd.
520 1 - kernel audit is initialized and partially enabled,
521 storing at most audit_backlog_limit messages in
522 RAM until it is fully enabled by the userspace
526 audit_backlog_limit= [KNL] Set the audit queue size limit.
527 Format: <int> (must be >=0)
530 baycom_epp= [HW,AX25]
533 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
535 See header of drivers/net/hamradio/baycom_par.c.
537 baycom_ser_fdx= [HW,AX25]
538 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
539 Format: <io>,<irq>,<mode>[,<baud>]
540 See header of drivers/net/hamradio/baycom_ser_fdx.c.
542 baycom_ser_hdx= [HW,AX25]
543 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
544 Format: <io>,<irq>,<mode>
545 See header of drivers/net/hamradio/baycom_ser_hdx.c.
547 blkdevparts= Manual partition parsing of block device(s) for
548 embedded devices based on command line input.
549 See Documentation/block/cmdline-partition.txt
551 boot_delay= Milliseconds to delay each printk during boot.
552 Values larger than 10 seconds (10000) are changed to
556 bootmem_debug [KNL] Enable bootmem allocator debug messages.
558 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
559 bttv.radio= Most important insmod options are available as
561 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
564 bulk_remove=off [PPC] This parameter disables the use of the pSeries
565 firmware feature for flushing multiple hpte entries
568 c101= [NET] Moxa C101 synchronous serial card
570 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
571 Sometimes CPU hardware bugs make them report the cache
572 size incorrectly. The kernel will attempt work arounds
573 to fix known problems, but for some CPUs it is not
574 possible to determine what the correct size should be.
575 This option provides an override for these situations.
577 ca_keys= [KEYS] This parameter identifies a specific key(s) on
578 the system trusted keyring to be used for certificate
580 format: { id:<keyid> | builtin }
582 cca= [MIPS] Override the kernel pages' cache coherency
583 algorithm. Accepted values range from 0 to 7
584 inclusive. See arch/mips/include/asm/pgtable-bits.h
585 for platform specific values (SB1, Loongson3 and
588 ccw_timeout_log [S390]
589 See Documentation/s390/CommonIO for details.
591 cgroup_disable= [KNL] Disable a particular controller
592 Format: {name of the controller(s) to disable}
593 The effects of cgroup_disable=foo are:
594 - foo isn't auto-mounted if you mount all cgroups in
596 - foo isn't visible as an individually mountable
598 {Currently only "memory" controller deal with this and
599 cut the overhead, others just disable the usage. So
600 only cgroup_disable=memory is actually worthy}
602 checkreqprot [SELINUX] Set initial checkreqprot flag value.
603 Format: { "0" | "1" }
604 See security/selinux/Kconfig help text.
605 0 -- check protection applied by kernel (includes
606 any implied execute protection).
607 1 -- check protection requested by application.
608 Default value is set via a kernel config option.
609 Value can be changed at runtime via
610 /selinux/checkreqprot.
613 See Documentation/s390/CommonIO for details.
616 Prevents the clock framework from automatically gating
617 clocks that have not been explicitly enabled by a Linux
618 device driver but are enabled in hardware at reset or
619 by the bootloader/firmware. Note that this does not
620 force such clocks to be always-on nor does it reserve
621 those clocks in any way. This parameter is useful for
622 debug and development, but should not be needed on a
623 platform with proper driver support. For more
624 information, see Documentation/clk.txt.
626 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
628 Forces specified clocksource (if available) to be used
629 when calculating gettimeofday(). If specified
630 clocksource is not available, it defaults to PIT.
631 Format: { pit | tsc | cyclone | pmtmr }
633 clocksource= Override the default clocksource
635 Override the default clocksource and use the clocksource
636 with the name specified.
637 Some clocksource names to choose from, depending on
639 [all] jiffies (this is the base, fallback clocksource)
641 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
642 pxa_timer,timer3,32k_counter,timer0_1
644 [X86-32] pit,hpet,tsc;
645 scx200_hrt on Geode; cyclone on IBM x440
653 clearcpuid=BITNUM [X86]
654 Disable CPUID feature X for the kernel. See
655 arch/x86/include/asm/cpufeature.h for the valid bit
656 numbers. Note the Linux specific bits are not necessarily
657 stable over kernel options, but the vendor specific
659 Also note that user programs calling CPUID directly
660 or using the feature without checking anything
661 will still see it. This just prevents it from
662 being used by the kernel or shown in /proc/cpuinfo.
663 Also note the kernel might malfunction if you disable
666 cma=nn[MG]@[start[MG][-end[MG]]]
668 Sets the size of kernel global memory area for
669 contiguous memory allocations and optionally the
670 placement constraint by the physical address range of
671 memory allocations. A value of 0 disables CMA
672 altogether. For more information, see
673 include/linux/dma-contiguous.h
675 cmo_free_hint= [PPC] Format: { yes | no }
676 Specify whether pages are marked as being inactive
677 when they are freed. This is used in CMO environments
678 to determine OS memory pressure for page stealing by
682 coherent_pool=nn[KMG] [ARM,KNL]
683 Sets the size of memory pool for coherent, atomic dma
684 allocations, by default set to 256K.
686 code_bytes [X86] How many bytes of object code to print
691 com20020= [HW,NET] ARCnet - COM20020 chipset
693 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
695 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
699 ARCnet - COM90xx chipset (memory-mapped buffers)
700 Format: <io>[,<irq>[,<memstart>]]
702 condev= [HW,S390] console device
705 console= [KNL] Output console device and options.
707 tty<n> Use the virtual console device <n>.
711 Use the specified serial port. The options are of
712 the form "bbbbpnf", where "bbbb" is the baud rate,
713 "p" is parity ("n", "o", or "e"), "n" is number of
714 bits, and "f" is flow control ("r" for RTS or
715 omit it). Default is "9600n8".
717 See Documentation/serial-console.txt for more
719 Documentation/networking/netconsole.txt for an
722 uart[8250],io,<addr>[,options]
723 uart[8250],mmio,<addr>[,options]
724 uart[8250],mmio32,<addr>[,options]
725 uart[8250],0x<addr>[,options]
726 Start an early, polled-mode console on the 8250/16550
727 UART at the specified I/O port or MMIO address,
728 switching to the matching ttyS device later.
729 MMIO inter-register address stride is either 8-bit
730 (mmio) or 32-bit (mmio32).
731 If none of [io|mmio|mmio32], <addr> is assumed to be
732 equivalent to 'mmio'. 'options' are specified in the
733 same format described for ttyS above; if unspecified,
734 the h/w is not re-initialized.
736 hvc<n> Use the hypervisor console device <n>. This is for
737 both Xen and PowerPC hypervisors.
739 If the device connected to the port is not a TTY but a braille
740 device, prepend "brl," before the device type, for instance
742 For now, only VisioBraille is supported.
744 consoleblank= [KNL] The console blank (screen saver) timeout in
745 seconds. Defaults to 10*60 = 10mins. A value of 0
746 disables the blank timer.
749 [KNL] Change the default value for
750 /proc/<pid>/coredump_filter.
751 See also Documentation/filesystems/proc.txt.
753 cpuidle.off=1 [CPU_IDLE]
754 disable the cpuidle sub-system
757 [X86] Delay for N microsec between assert and de-assert
758 of APIC INIT to start processors. This delay occurs
759 on every CPU online, such as boot, and resume from suspend.
762 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
764 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
766 crashkernel=size[KMG][@offset[KMG]]
767 [KNL] Using kexec, Linux can switch to a 'crash kernel'
768 upon panic. This parameter reserves the physical
769 memory region [offset, offset + size] for that kernel
770 image. If '@offset' is omitted, then a suitable offset
771 is selected automatically. Check
772 Documentation/kdump/kdump.txt for further details.
774 crashkernel=range1:size1[,range2:size2,...][@offset]
775 [KNL] Same as above, but depends on the memory
776 in the running system. The syntax of range is
777 start-[end] where start and end are both
778 a memory unit (amount[KMG]). See also
779 Documentation/kdump/kdump.txt for an example.
781 crashkernel=size[KMG],high
782 [KNL, x86_64] range could be above 4G. Allow kernel
783 to allocate physical memory region from top, so could
784 be above 4G if system have more than 4G ram installed.
785 Otherwise memory region will be allocated below 4G, if
787 It will be ignored if crashkernel=X is specified.
788 crashkernel=size[KMG],low
789 [KNL, x86_64] range under 4G. When crashkernel=X,high
790 is passed, kernel could allocate physical memory region
791 above 4G, that cause second kernel crash on system
792 that require some amount of low memory, e.g. swiotlb
793 requires at least 64M+32K low memory, also enough extra
794 low memory is needed to make sure DMA buffers for 32-bit
795 devices won't run out. Kernel would try to allocate at
796 at least 256M below 4G automatically.
797 This one let user to specify own low range under 4G
798 for second kernel instead.
799 0: to disable low allocation.
800 It will be ignored when crashkernel=X,high is not used
801 or memory reserved is below 4G.
806 cs89x0_media= [HW,NET]
807 Format: { rj45 | aui | bnc }
810 See header of drivers/s390/block/dasd_devmap.c.
812 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
813 (one device per port)
814 Format: <port#>,<type>
815 See also Documentation/input/joystick-parport.txt
817 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
818 time. See Documentation/dynamic-debug-howto.txt for
819 details. Deprecated, see dyndbg.
821 debug [KNL] Enable kernel debugging (events log level).
824 [KNL] verbose self-tests
826 Print debugging info while doing the locking API
828 We default to 0 (no extra messages), setting it to
829 1 will print _a lot_ more information - normally
830 only useful to kernel developers.
832 debug_objects [KNL] Enable object debugging
835 [KNL] Disable object debugging
837 debug_guardpage_minorder=
838 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
839 parameter allows control of the order of pages that will
840 be intentionally kept free (and hence protected) by the
841 buddy allocator. Bigger value increase the probability
842 of catching random memory corruption, but reduce the
843 amount of memory for normal system use. The maximum
844 possible value is MAX_ORDER/2. Setting this parameter
845 to 1 or 2 should be enough to identify most random
846 memory corruption problems caused by bugs in kernel or
847 driver code when a CPU writes to (or reads from) a
848 random memory location. Note that there exists a class
849 of memory corruptions problems caused by buggy H/W or
850 F/W or by drivers badly programing DMA (basically when
851 memory is written at bus level and the CPU MMU is
852 bypassed) which are not detectable by
853 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
854 tracking down these problems.
857 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
858 parameter enables the feature at boot time. In
859 default, it is disabled. We can avoid allocating huge
860 chunk of memory for debug pagealloc if we don't enable
861 it at boot time and the system will work mostly same
862 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
863 on: enable the feature
865 debugpat [X86] Enable PAT debugging
867 decnet.addr= [HW,NET]
868 Format: <area>[,<node>]
869 See also Documentation/networking/decnet.txt.
872 [same as hugepagesz=] The size of the default
873 HugeTLB page size. This is the size represented by
874 the legacy /proc/ hugepages APIs, used for SHM, and
875 default size when mounting hugetlbfs filesystems.
876 Defaults to the default architecture's huge page size
880 Set number of hash buckets for dentry cache.
883 See Documentation/networking/ipv6.txt.
885 disable_cpu_apicid= [X86,APIC,SMP]
887 The number of initial APIC ID for the
888 corresponding CPU to be disabled at boot,
889 mostly used for the kdump 2nd kernel to
890 disable BSP to wake up multiple CPUs without
891 causing system reset or hang due to sending
894 disable_ddw [PPC/PSERIES]
895 Disable Dynamic DMA Window support. Use this if
896 to workaround buggy firmware.
899 See Documentation/networking/ipv6.txt.
901 disable_mtrr_cleanup [X86]
902 The kernel tries to adjust MTRR layout from continuous
903 to discrete, to make X server driver able to add WB
904 entry later. This parameter disables that.
906 disable_mtrr_trim [X86, Intel and AMD only]
907 By default the kernel will trim any uncacheable
908 memory out of your available memory pool based on
909 MTRR settings. This parameter disables that behavior,
910 possibly causing your machine to run very slowly.
912 disable_timer_pin_1 [X86]
913 Disable PIN 1 of APIC timer
914 Can be useful to work around chipset bugs.
916 dis_ucode_ldr [X86] Disable the microcode loader.
918 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
919 this option disables the debugging code at boot.
921 dma_debug_entries=<number>
922 This option allows to tune the number of preallocated
923 entries for DMA-API debugging code. One entry is
924 required per DMA-API allocation. Use this if the
925 DMA-API debugging code disables itself because the
926 architectural default is too low.
928 dma_debug_driver=<driver_name>
929 With this option the DMA-API debugging driver
930 filter feature can be enabled at boot time. Just
931 pass the driver to filter for as the parameter.
932 The filter can be disabled or changed to another
933 driver later using sysfs.
935 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
936 Broken monitors, graphic adapters, KVMs and EDIDless
937 panels may send no or incorrect EDID data sets.
938 This parameter allows to specify an EDID data sets
939 in the /lib/firmware directory that are used instead.
940 Generic built-in EDID data sets are used, if one of
941 edid/1024x768.bin, edid/1280x1024.bin,
942 edid/1680x1050.bin, or edid/1920x1080.bin is given
943 and no file with the same name exists. Details and
944 instructions how to build your own EDID data are
945 available in Documentation/EDID/HOWTO.txt. An EDID
946 data set will only be used for a particular connector,
947 if its name and a colon are prepended to the EDID
948 name. Each connector may use a unique EDID data
949 set by separating the files with a comma. An EDID
950 data set with no connector name will be used for
951 any connectors not explicitly specified.
955 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
956 module.dyndbg[="val"]
957 Enable debug messages at boot time. See
958 Documentation/dynamic-debug-howto.txt for details.
960 nompx [X86] Disables Intel Memory Protection Extensions.
961 See Documentation/x86/intel_mpx.txt for more
962 information about the feature.
965 on enable eager fpu restore
966 off disable eager fpu restore
967 auto selects the default scheme, which automatically
968 enables eagerfpu restore for xsaveopt.
970 module.async_probe [KNL]
971 Enable asynchronous probe on this module.
973 early_ioremap_debug [KNL]
974 Enable debug messages in early_ioremap support. This
975 is useful for tracking down temporary early mappings
976 which are not unmapped.
978 earlycon= [KNL] Output early console device and options.
980 When used with no options, the early console is
981 determined by the stdout-path property in device
985 Start an early, polled-mode console on a cadence serial
986 port at the specified address. The cadence serial port
987 must already be setup and configured. Options are not
990 uart[8250],io,<addr>[,options]
991 uart[8250],mmio,<addr>[,options]
992 uart[8250],mmio32,<addr>[,options]
993 uart[8250],mmio32be,<addr>[,options]
994 uart[8250],0x<addr>[,options]
995 Start an early, polled-mode console on the 8250/16550
996 UART at the specified I/O port or MMIO address.
997 MMIO inter-register address stride is either 8-bit
998 (mmio) or 32-bit (mmio32 or mmio32be).
999 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1000 to be equivalent to 'mmio'. 'options' are specified
1001 in the same format described for "console=ttyS<n>"; if
1002 unspecified, the h/w is not initialized.
1005 Start an early, polled-mode console on a pl011 serial
1006 port at the specified address. The pl011 serial port
1007 must already be setup and configured. Options are not
1011 Start an early, polled-mode console on an msm serial
1012 port at the specified address. The serial port
1013 must already be setup and configured. Options are not
1016 msm_serial_dm,<addr>
1017 Start an early, polled-mode console on an msm serial
1018 dm port at the specified address. The serial port
1019 must already be setup and configured. Options are not
1022 smh Use ARM semihosting calls for early console.
1030 Use early console provided by serial driver available
1031 on Samsung SoCs, requires selecting proper type and
1032 a correct base address of the selected UART port. The
1033 serial port must already be setup and configured.
1034 Options are not yet supported.
1036 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1040 earlyprintk=serial[,ttySn[,baudrate]]
1041 earlyprintk=serial[,0x...[,baudrate]]
1042 earlyprintk=ttySn[,baudrate]
1043 earlyprintk=dbgp[debugController#]
1044 earlyprintk=pciserial,bus:device.function[,baudrate]
1046 earlyprintk is useful when the kernel crashes before
1047 the normal console is initialized. It is not enabled by
1048 default because it has some cosmetic problems.
1050 Append ",keep" to not disable it when the real console
1053 Only one of vga, efi, serial, or usb debug port can
1056 Currently only ttyS0 and ttyS1 may be specified by
1057 name. Other I/O ports may be explicitly specified
1058 on some architectures (x86 and arm at least) by
1059 replacing ttySn with an I/O port address, like this:
1060 earlyprintk=serial,0x1008,115200
1061 You can find the port for a given device in
1062 /proc/tty/driver/serial:
1063 2: uart:ST16650V2 port:00001008 irq:18 ...
1065 Interaction with the standard serial driver is not
1068 The VGA and EFI output is eventually overwritten by
1071 The xen output can only be used by Xen PV guests.
1073 edac_report= [HW,EDAC] Control how to report EDAC event
1074 Format: {"on" | "off" | "force"}
1075 on: enable EDAC to report H/W event. May be overridden
1076 by other higher priority error reporting module.
1077 off: disable H/W event reporting through EDAC.
1078 force: enforce the use of EDAC to report H/W event.
1081 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1084 This is designed to be used in conjunction with
1085 the boot argument: earlyprintk=vga
1088 Format: {"off" | "on" | "skip[mbr]"}
1091 Format: { "old_map", "nochunk", "noruntime", "debug" }
1092 old_map [X86-64]: switch to the old ioremap-based EFI
1093 runtime services mapping. 32-bit still uses this one by
1095 nochunk: disable reading files in "chunks" in the EFI
1096 boot stub, as chunking can cause problems with some
1097 firmware implementations.
1098 noruntime : disable EFI runtime services support
1099 debug: enable misc debug output
1101 efi_no_storage_paranoia [EFI; X86]
1102 Using this parameter you can use more than 50% of
1103 your efi variable storage. Use this parameter only if
1104 you are really sure that your UEFI does sane gc and
1105 fulfills the spec otherwise your board may brick.
1107 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1108 Add arbitrary attribute to specific memory range by
1109 updating original EFI memory map.
1110 Region of memory which aa attribute is added to is
1112 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1113 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1114 attribute is added to range 0x100000000-0x180000000 and
1115 0x10a0000000-0x1120000000.
1117 Using this parameter you can do debugging of EFI memmap
1118 related feature. For example, you can do debugging of
1119 Address Range Mirroring feature even if your box
1122 eisa_irq_edge= [PARISC,HW]
1123 See header of drivers/parisc/eisa.c.
1126 See comment before function elanfreq_setup() in
1127 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1130 Format: {"cfq" | "deadline" | "noop"}
1131 See Documentation/block/cfq-iosched.txt and
1132 Documentation/block/deadline-iosched.txt for details.
1134 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1135 Specifies physical address of start of kernel core
1136 image elf header and optionally the size. Generally
1137 kexec loader will pass this option to capture kernel.
1138 See Documentation/kdump/kdump.txt for details.
1140 enable_mtrr_cleanup [X86]
1141 The kernel tries to adjust MTRR layout from continuous
1142 to discrete, to make X server driver able to add WB
1143 entry later. This parameter enables that.
1145 enable_timer_pin_1 [X86]
1146 Enable PIN 1 of APIC timer
1147 Can be useful to work around chipset bugs
1148 (in particular on some ATI chipsets).
1149 The kernel tries to set a reasonable default.
1151 enforcing [SELINUX] Set initial enforcing status.
1153 See security/selinux/Kconfig help text.
1154 0 -- permissive (log only, no denials).
1155 1 -- enforcing (deny and log).
1157 Value can be changed at runtime via /selinux/enforce.
1160 Disable Error Record Serialization Table (ERST)
1163 ether= [HW,NET] Ethernet cards parameters
1164 This option is obsoleted by the "netdev=" option, which
1165 has equivalent usage. See its documentation for details.
1169 Permit 'security.evm' to be updated regardless of
1170 current integrity status.
1174 fail_make_request=[KNL]
1175 General fault injection mechanism.
1176 Format: <interval>,<probability>,<space>,<times>
1177 See also Documentation/fault-injection/.
1180 See Documentation/blockdev/floppy.txt.
1182 force_pal_cache_flush
1183 [IA-64] Avoid check_sal_cache_flush which may hang on
1184 buggy SAL_CACHE_FLUSH implementations. Using this
1185 parameter will force ia64_sal_cache_flush to call
1186 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1189 Forcefully enable Physical Address Extension (PAE).
1190 Many Pentium M systems disable PAE but may have a
1191 functionally usable PAE implementation.
1192 Warning: use of this parameter will taint the kernel
1193 and may cause unknown problems.
1196 [FTRACE] will set and start the specified tracer
1197 as early as possible in order to facilitate early
1200 ftrace_dump_on_oops[=orig_cpu]
1201 [FTRACE] will dump the trace buffers on oops.
1202 If no parameter is passed, ftrace will dump
1203 buffers of all CPUs, but if you pass orig_cpu, it will
1204 dump only the buffer of the CPU that triggered the
1207 ftrace_filter=[function-list]
1208 [FTRACE] Limit the functions traced by the function
1209 tracer at boot up. function-list is a comma separated
1210 list of functions. This list can be changed at run
1211 time by the set_ftrace_filter file in the debugfs
1214 ftrace_notrace=[function-list]
1215 [FTRACE] Do not trace the functions specified in
1216 function-list. This list can be changed at run time
1217 by the set_ftrace_notrace file in the debugfs
1220 ftrace_graph_filter=[function-list]
1221 [FTRACE] Limit the top level callers functions traced
1222 by the function graph tracer at boot up.
1223 function-list is a comma separated list of functions
1224 that can be changed at run time by the
1225 set_graph_function file in the debugfs tracing directory.
1227 ftrace_graph_notrace=[function-list]
1228 [FTRACE] Do not trace from the functions specified in
1229 function-list. This list is a comma separated list of
1230 functions that can be changed at run time by the
1231 set_graph_notrace file in the debugfs tracing directory.
1234 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1235 support via parallel port (up to 5 devices per port)
1236 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1237 See also Documentation/input/joystick-parport.txt
1241 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1245 gcov_persist= [GCOV] When non-zero (default), profiling data for
1246 kernel modules is saved and remains accessible via
1247 debugfs, even when the module is unloaded/reloaded.
1248 When zero, profiling data is discarded and associated
1249 debugfs files are removed at module unload time.
1251 gpt [EFI] Forces disk with valid GPT signature but
1252 invalid Protective MBR to be treated as GPT. If the
1253 primary GPT is corrupted, it enables the backup/alternate
1254 GPT to be used instead.
1256 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1257 the "Enable 0" bit of the configuration register.
1260 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1261 the "Enable 0" bit of the configuration register.
1264 grcan.select= [HW] Select which physical interface to use.
1267 grcan.txsize= [HW] Sets the size of the tx buffer.
1268 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1270 grcan.rxsize= [HW] Sets the size of the rx buffer.
1271 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1274 hashdist= [KNL,NUMA] Large hashes allocated during boot
1275 are distributed across NUMA nodes. Defaults on
1276 for 64-bit NUMA, off otherwise.
1277 Format: 0 | 1 (for off | on)
1279 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1281 hd= [EIDE] (E)IDE hard drive subsystem geometry
1282 Format: <cyl>,<head>,<sect>
1285 Disable Hardware Error Source Table (HEST) support;
1286 corresponding firmware-first mode error processing
1287 logic will be disabled.
1289 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1290 size of <nn>. This works even on boxes that have no
1291 highmem otherwise. This also works to reduce highmem
1292 size on bigger boxes.
1294 highres= [KNL] Enable/disable high resolution timer mode.
1295 Valid parameters: "on", "off"
1299 See Documentation/isdn/README.HiSax.
1303 hpet= [X86-32,HPET] option to control HPET usage
1304 Format: { enable (default) | disable | force |
1306 disable: disable HPET and use PIT instead
1307 force: allow force enabled of undocumented chips (ICH4,
1309 verbose: show contents of HPET registers during setup
1311 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1312 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1314 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1315 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1316 On x86-64 and powerpc, this option can be specified
1317 multiple times interleaved with hugepages= to reserve
1318 huge pages of different sizes. Valid pages sizes on
1319 x86-64 are 2M (when the CPU supports "pse") and 1G
1320 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1322 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1323 terminal devices. Valid values: 0..8
1324 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1325 If specified, z/VM IUCV HVC accepts connections
1326 from listed z/VM user IDs only.
1328 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1329 hardware thread id mappings.
1330 Format: <cpu>:<hwthread>
1333 Do not unregister boot console at start. This is only
1334 useful for debugging when something happens in the window
1335 between unregistering the boot console and initializing
1338 i2c_bus= [HW] Override the default board specific I2C bus speed
1339 or register an additional I2C bus that is not
1340 registered from board initialization code.
1344 i8042.debug [HW] Toggle i8042 debug mode
1345 i8042.unmask_kbd_data
1346 [HW] Enable printing of interrupt data from the KBD port
1347 (disabled by default, and as a pre-condition
1348 requires that i8042.debug=1 be enabled)
1349 i8042.direct [HW] Put keyboard port into non-translated mode
1350 i8042.dumbkbd [HW] Pretend that controller can only read data from
1351 keyboard and cannot control its state
1352 (Don't attempt to blink the leds)
1353 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1354 i8042.nokbd [HW] Don't check/create keyboard port
1355 i8042.noloop [HW] Disable the AUX Loopback command while probing
1357 i8042.nomux [HW] Don't check presence of an active multiplexing
1359 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1361 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1362 i8042.reset [HW] Reset the controller during init and cleanup
1363 i8042.unlock [HW] Unlock (ignore) the keylock
1364 i8042.kbdreset [HW] Reset device connected to KBD port
1368 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1369 indicates that the driver is running on unsupported
1371 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1372 does not match list of supported models.
1374 [HW] Report power status in /proc/i8k
1375 (disabled by default)
1376 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1379 i915.invert_brightness=
1380 [DRM] Invert the sense of the variable that is used to
1381 set the brightness of the panel backlight. Normally a
1382 brightness value of 0 indicates backlight switched off,
1383 and the maximum of the brightness value sets the backlight
1384 to maximum brightness. If this parameter is set to 0
1385 (default) and the machine requires it, or this parameter
1386 is set to 1, a brightness value of 0 sets the backlight
1387 to maximum brightness, and the maximum of the brightness
1388 value switches the backlight off.
1389 -1 -- never invert brightness
1390 0 -- machine default
1391 1 -- force brightness inversion
1394 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1396 ide-core.nodma= [HW] (E)IDE subsystem
1397 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1398 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1399 .cdrom .chs .ignore_cable are additional options
1400 See Documentation/ide/ide.txt.
1402 ide-generic.probe-mask= [HW] (E)IDE subsystem
1404 Probe mask for legacy ISA IDE ports. Depending on
1405 platform up to 6 ports are supported, enabled by
1406 setting corresponding bits in the mask to 1. The
1407 default value is 0x0, which has a special meaning.
1408 On systems that have PCI, it triggers scanning the
1409 PCI bus for the first and the second port, which
1410 are then probed. On systems without PCI the value
1411 of 0x0 enables probing the two first ports as if it
1414 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1415 Claim all unknown PCI IDE storage controllers.
1418 Format: idle=poll, idle=halt, idle=nomwait
1419 Poll forces a polling idle loop that can slightly
1420 improve the performance of waking up a idle CPU, but
1421 will use a lot of power and make the system run hot.
1423 idle=halt: Halt is forced to be used for CPU idle.
1424 In such case C2/C3 won't be used again.
1425 idle=nomwait: Disable mwait for CPU C-states
1427 ignore_loglevel [KNL]
1428 Ignore loglevel setting - this will print /all/
1429 kernel messages to the console. Useful for debugging.
1430 We also add it as printk module parameter, so users
1431 could change it dynamically, usually by
1432 /sys/module/printk/parameters/ignore_loglevel.
1434 ihash_entries= [KNL]
1435 Set number of hash buckets for inode cache.
1437 ima_appraise= [IMA] appraise integrity measurements
1438 Format: { "off" | "enforce" | "fix" | "log" }
1441 ima_appraise_tcb [IMA]
1442 The builtin appraise policy appraises all files
1446 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1450 The list of supported hash algorithms is defined
1451 in crypto/hash_info.h.
1454 The builtin measurement policy to load during IMA
1455 setup. Specyfing "tcb" as the value, measures all
1456 programs exec'd, files mmap'd for exec, and all files
1457 opened with the read mode bit set by either the
1458 effective uid (euid=0) or uid=0.
1461 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1462 Load a policy which meets the needs of the Trusted
1463 Computing Base. This means IMA will measure all
1464 programs exec'd, files mmap'd for exec, and all files
1465 opened for read by uid=0.
1468 Select one of defined IMA measurements template formats.
1469 Formats: { "ima" | "ima-ng" | "ima-sig" }
1473 [IMA] Define a custom template format.
1474 Format: { "field1|...|fieldN" }
1476 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1477 Format: <min_file_size>
1478 Set the minimal file size for using asynchronous hash.
1479 If left unspecified, ahash usage is disabled.
1481 ahash performance varies for different data sizes on
1482 different crypto accelerators. This option can be used
1483 to achieve the best performance for a particular HW.
1485 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1487 Set hashing buffer size. Default: 4k.
1489 ahash performance varies for different chunk sizes on
1490 different crypto accelerators. This option can be used
1491 to achieve best performance for particular HW.
1495 Run specified binary instead of /sbin/init as init
1498 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1499 for working out where the kernel is dying during
1502 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1503 initcall functions. Useful for debugging built-in
1504 modules and initcalls.
1506 initrd= [BOOT] Specify the location of the initial ramdisk
1508 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1511 int_pln_enable [x86] Enable power limit notification interrupt
1513 integrity_audit=[IMA]
1514 Format: { "0" | "1" }
1515 0 -- basic integrity auditing messages. (Default)
1516 1 -- additional integrity auditing messages.
1518 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1520 Enable intel iommu driver.
1522 Disable intel iommu driver.
1523 igfx_off [Default Off]
1524 By default, gfx is mapped as normal device. If a gfx
1525 device has a dedicated DMAR unit, the DMAR unit is
1526 bypassed by not enabling DMAR with this option. In
1527 this case, gfx device will use physical address for
1530 With this option iommu will not optimize to look
1531 for io virtual address below 32-bit forcing dual
1532 address cycle on pci bus for cards supporting greater
1533 than 32-bit addressing. The default is to look
1534 for translation below 32-bit and if not available
1535 then look in the higher range.
1536 strict [Default Off]
1537 With this option on every unmap_single operation will
1538 result in a hardware IOTLB flush operation as opposed
1539 to batching them for performance.
1540 sp_off [Default Off]
1541 By default, super page will be supported if Intel IOMMU
1542 has the capability. With this option, super page will
1544 ecs_off [Default Off]
1545 By default, extended context tables will be supported if
1546 the hardware advertises that it has support both for the
1547 extended tables themselves, and also PASID support. With
1548 this option set, extended tables will not be used even
1549 on hardware which claims to support them.
1551 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1552 0 disables intel_idle and fall back on acpi_idle.
1553 1 to 6 specify maximum depth of C-state.
1557 Do not enable intel_pstate as the default
1558 scaling driver for the supported processors
1560 Enable intel_pstate on systems that prohibit it by default
1561 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1562 instead of acpi-cpufreq may disable platform features, such
1563 as thermal controls and power capping, that rely on ACPI
1564 P-States information being indicated to OSPM and therefore
1565 should be used with caution. This option does not work with
1566 processors that aren't supported by the intel_pstate driver
1567 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1569 Do not enable hardware P state control (HWP)
1572 Only load intel_pstate on systems which support
1573 hardware P state control (HWP) if available.
1575 Don't use ACPI processor performance control objects
1576 _PSS and _PPC specified limits.
1578 intremap= [X86-64, Intel-IOMMU]
1579 on enable Interrupt Remapping (default)
1580 off disable Interrupt Remapping
1581 nosid disable Source ID checking
1583 BIOS x2APIC opt-out request will be ignored
1584 nopost disable Interrupt Posting
1586 iomem= Disable strict checking of access to MMIO memory
1587 strict regions from userspace.
1602 nobypass [PPC/POWERNV]
1603 Disable IOMMU bypass, using IOMMU for PCI devices.
1606 io7= [HW] IO7 for Marvel based alpha systems
1607 See comment before marvel_specify_io7 in
1608 arch/alpha/kernel/core_marvel.c.
1610 io_delay= [X86] I/O delay method
1612 Standard port 0x80 based delay
1614 Alternate port 0xed based delay (needed on some systems)
1616 Simple two microseconds delay
1621 See Documentation/filesystems/nfs/nfsroot.txt.
1624 When an interrupt is not handled search all handlers
1625 for it. Intended to get systems with badly broken
1629 When an interrupt is not handled search all handlers
1630 for it. Also check all handlers each timer
1631 interrupt. Intended to get systems with badly broken
1635 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1637 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1639 <cpu number>,...,<cpu number>
1641 <cpu number>-<cpu number>
1642 (must be a positive range in ascending order)
1644 <cpu number>,...,<cpu number>-<cpu number>
1646 This option can be used to specify one or more CPUs
1647 to isolate from the general SMP balancing and scheduling
1648 algorithms. You can move a process onto or off an
1649 "isolated" CPU via the CPU affinity syscalls or cpuset.
1650 <cpu number> begins at 0 and the maximum value is
1651 "number of CPUs in system - 1".
1653 This option is the preferred way to isolate CPUs. The
1654 alternative -- manually setting the CPU mask of all
1655 tasks in the system -- can cause problems and
1656 suboptimal load balancer performance.
1660 ivrs_ioapic [HW,X86_64]
1661 Provide an override to the IOAPIC-ID<->DEVICE-ID
1662 mapping provided in the IVRS ACPI table. For
1663 example, to map IOAPIC-ID decimal 10 to
1664 PCI device 00:14.0 write the parameter as:
1665 ivrs_ioapic[10]=00:14.0
1667 ivrs_hpet [HW,X86_64]
1668 Provide an override to the HPET-ID<->DEVICE-ID
1669 mapping provided in the IVRS ACPI table. For
1670 example, to map HPET-ID decimal 0 to
1671 PCI device 00:14.0 write the parameter as:
1672 ivrs_hpet[0]=00:14.0
1674 js= [HW,JOY] Analog joystick
1675 See Documentation/input/joystick.txt.
1678 Enable/disable kernel and module base offset ASLR
1679 (Address Space Layout Randomization) if built into
1680 the kernel. When CONFIG_HIBERNATION is selected,
1681 kASLR is disabled by default. When kASLR is enabled,
1682 hibernation will be disabled.
1686 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1687 specifies the amount of memory usable by the kernel
1688 for non-movable allocations. The requested amount is
1689 spread evenly throughout all nodes in the system. The
1690 remaining memory in each node is used for Movable
1691 pages. In the event, a node is too small to have both
1692 kernelcore and Movable pages, kernelcore pages will
1693 take priority and other nodes will have a larger number
1694 of Movable pages. The Movable zone is used for the
1695 allocation of pages that may be reclaimed or moved
1696 by the page migration subsystem. This means that
1697 HugeTLB pages may not be allocated from this zone.
1698 Note that allocations like PTEs-from-HighMem still
1699 use the HighMem zone if it exists, and the Normal
1700 zone if it does not.
1702 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1703 Format: <Controller#>[,poll interval]
1704 The controller # is the number of the ehci usb debug
1705 port as it is probed via PCI. The poll interval is
1706 optional and is the number seconds in between
1707 each poll cycle to the debug port in case you need
1708 the functionality for interrupting the kernel with
1709 gdb or control-c on the dbgp connection. When
1710 not using this parameter you use sysrq-g to break into
1711 the kernel debugger.
1713 kgdboc= [KGDB,HW] kgdb over consoles.
1714 Requires a tty driver that supports console polling,
1715 or a supported polling keyboard driver (non-usb).
1716 Serial only format: <serial_device>[,baud]
1717 keyboard only format: kbd
1718 keyboard and serial format: kbd,<serial_device>[,baud]
1719 Optional Kernel mode setting:
1720 kms, kbd format: kms,kbd
1721 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1723 kgdbwait [KGDB] Stop kernel execution and enter the
1724 kernel debugger at the earliest opportunity.
1726 kmac= [MIPS] korina ethernet MAC address.
1727 Configure the RouterBoard 532 series on-chip
1728 Ethernet adapter MAC address.
1730 kmemleak= [KNL] Boot-time kmemleak enable/disable
1731 Valid arguments: on, off
1733 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1736 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1737 Valid arguments: 0, 1, 2
1738 kmemcheck=0 (disabled)
1739 kmemcheck=1 (enabled)
1740 kmemcheck=2 (one-shot mode)
1741 Default: 2 (one-shot mode)
1743 kstack=N [X86] Print N words from the kernel stack
1746 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1747 Default is 0 (don't ignore, but inject #GP)
1749 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1753 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1754 Default is 1 (enabled)
1756 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1758 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1760 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1761 (virtualized MMU) support on capable Intel chips.
1762 Default is 1 (enabled)
1764 kvm-intel.emulate_invalid_guest_state=
1765 [KVM,Intel] Enable emulation of invalid guest states
1766 Default is 0 (disabled)
1768 kvm-intel.flexpriority=
1769 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1770 Default is 1 (enabled)
1773 [KVM,Intel] Enable VMX nesting (nVMX).
1774 Default is 0 (disabled)
1776 kvm-intel.unrestricted_guest=
1777 [KVM,Intel] Disable unrestricted guest feature
1778 (virtualized real and unpaged mode) on capable
1779 Intel chips. Default is 1 (enabled)
1781 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1782 feature (tagged TLBs) on capable Intel chips.
1783 Default is 1 (enabled)
1789 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1792 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1793 value for LAPIC timer one-shot implementation. Default
1794 back to the programmable timer unit in the LAPIC.
1796 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1799 libata.dma= [LIBATA] DMA control
1800 libata.dma=0 Disable all PATA and SATA DMA
1801 libata.dma=1 PATA and SATA Disk DMA only
1802 libata.dma=2 ATAPI (CDROM) DMA only
1803 libata.dma=4 Compact Flash DMA only
1804 Combinations also work, so libata.dma=3 enables DMA
1805 for disks and CDROMs, but not CFs.
1807 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1808 libata.ignore_hpa=0 keep BIOS limits (default)
1809 libata.ignore_hpa=1 ignore limits, using full disk
1811 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1815 libata.force= [LIBATA] Force configurations. The format is comma
1816 separated list of "[ID:]VAL" where ID is
1817 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1818 matching port, link or device. Basically, it matches
1819 the ATA ID string printed on console by libata. If
1820 the whole ID part is omitted, the last PORT and DEVICE
1821 values are used. If ID hasn't been specified yet, the
1822 configuration applies to all ports, links and devices.
1824 If only DEVICE is omitted, the parameter applies to
1825 the port and all links and devices behind it. DEVICE
1826 number of 0 either selects the first device or the
1827 first fan-out link behind PMP device. It does not
1828 select the host link. DEVICE number of 15 selects the
1829 host link and device attached to it.
1831 The VAL specifies the configuration to force. As long
1832 as there's no ambiguity shortcut notation is allowed.
1833 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1834 The following configurations can be forced.
1836 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1837 Any ID with matching PORT is used.
1839 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1841 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1842 udma[/][16,25,33,44,66,100,133] notation is also
1845 * [no]ncq: Turn on or off NCQ.
1847 * [no]ncqtrim: Turn off queued DSM TRIM.
1849 * nohrst, nosrst, norst: suppress hard, soft
1852 * rstonce: only attempt one reset during
1853 hot-unplug link recovery
1855 * dump_id: dump IDENTIFY data.
1857 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1859 * disable: Disable this device.
1861 If there are multiple matching configurations changing
1862 the same attribute, the last one is used.
1864 memblock=debug [KNL] Enable memblock debug messages.
1866 load_ramdisk= [RAM] List of ramdisks to load from floppy
1867 See Documentation/blockdev/ramdisk.txt.
1869 lockd.nlm_grace_period=P [NFS] Assign grace period.
1872 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1875 lockd.nlm_timeout=T [NFS] Assign timeout value.
1878 lockd.nlm_udpport=M [NFS] Assign UDP port.
1881 locktorture.nreaders_stress= [KNL]
1882 Set the number of locking read-acquisition kthreads.
1883 Defaults to being automatically set based on the
1884 number of online CPUs.
1886 locktorture.nwriters_stress= [KNL]
1887 Set the number of locking write-acquisition kthreads.
1889 locktorture.onoff_holdoff= [KNL]
1890 Set time (s) after boot for CPU-hotplug testing.
1892 locktorture.onoff_interval= [KNL]
1893 Set time (s) between CPU-hotplug operations, or
1894 zero to disable CPU-hotplug testing.
1896 locktorture.shuffle_interval= [KNL]
1897 Set task-shuffle interval (jiffies). Shuffling
1898 tasks allows some CPUs to go into dyntick-idle
1899 mode during the locktorture test.
1901 locktorture.shutdown_secs= [KNL]
1902 Set time (s) after boot system shutdown. This
1903 is useful for hands-off automated testing.
1905 locktorture.stat_interval= [KNL]
1906 Time (s) between statistics printk()s.
1908 locktorture.stutter= [KNL]
1909 Time (s) to stutter testing, for example,
1910 specifying five seconds causes the test to run for
1911 five seconds, wait for five seconds, and so on.
1912 This tests the locking primitive's ability to
1913 transition abruptly to and from idle.
1915 locktorture.torture_runnable= [BOOT]
1916 Start locktorture running at boot time.
1918 locktorture.torture_type= [KNL]
1919 Specify the locking implementation to test.
1921 locktorture.verbose= [KNL]
1922 Enable additional printk() statements.
1924 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1927 loglevel= All Kernel Messages with a loglevel smaller than the
1928 console loglevel will be printed to the console. It can
1929 also be changed with klogd or other programs. The
1930 loglevels are defined as follows:
1932 0 (KERN_EMERG) system is unusable
1933 1 (KERN_ALERT) action must be taken immediately
1934 2 (KERN_CRIT) critical conditions
1935 3 (KERN_ERR) error conditions
1936 4 (KERN_WARNING) warning conditions
1937 5 (KERN_NOTICE) normal but significant condition
1938 6 (KERN_INFO) informational
1939 7 (KERN_DEBUG) debug-level messages
1941 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1942 in bytes. n must be a power of two and greater
1943 than the minimal size. The minimal size is defined
1944 by LOG_BUF_SHIFT kernel config parameter. There is
1945 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1946 that allows to increase the default size depending on
1947 the number of CPUs. See init/Kconfig for more details.
1949 logo.nologo [FB] Disables display of the built-in Linux logo.
1950 This may be used to provide more screen space for
1951 kernel log messages and is useful when debugging
1952 kernel boot problems.
1954 lp=0 [LP] Specify parallel ports to use, e.g,
1955 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1956 lp=reset first parallel port). 'lp=0' disables the
1957 lp=auto printer driver. 'lp=reset' (which can be
1958 specified in addition to the ports) causes
1959 attached printers to be reset. Using
1960 lp=port1,port2,... specifies the parallel ports
1961 to associate lp devices with, starting with
1962 lp0. A port specification may be 'none' to skip
1963 that lp device, or a parport name such as
1964 'parport0'. Specifying 'lp=auto' instead of a
1965 port specification list means that device IDs
1966 from each port should be examined, to see if
1967 an IEEE 1284-compliant printer is attached; if
1968 so, the driver will manage that printer.
1969 See also header of drivers/char/lp.c.
1972 Sets loops_per_jiffy to given constant, thus avoiding
1973 time-consuming boot-time autodetection (up to 250 ms per
1974 CPU). 0 enables autodetection (default). To determine
1975 the correct value for your kernel, boot with normal
1976 autodetection and see what value is printed. Note that
1977 on SMP systems the preset will be applied to all CPUs,
1978 which is likely to cause problems if your CPUs need
1979 significantly divergent settings. An incorrect value
1980 will cause delays in the kernel to be wrong, leading to
1981 unpredictable I/O errors and other breakage. Although
1982 unlikely, in the extreme case this might damage your
1986 Format: <io>,<irq>,<dma>
1988 machvec= [IA-64] Force the use of a particular machine-vector
1989 (machvec) in a generic kernel.
1990 Example: machvec=hpzx1_swiotlb
1992 machtype= [Loongson] Share the same kernel image file between different
1994 Example: machtype=lemote-yeeloong-2f-7inch
1996 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1997 than or equal to this physical address is ignored.
1999 maxcpus= [SMP] Maximum number of processors that an SMP kernel
2000 should make use of. maxcpus=n : n >= 0 limits the
2001 kernel to using 'n' processors. n=0 is a special case,
2002 it is equivalent to "nosmp", which also disables
2005 max_loop= [LOOP] The number of loop block devices that get
2006 (loop.max_loop) unconditionally pre-created at init time. The default
2007 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2008 of statically allocating a predefined number, loop
2009 devices can be requested on-demand with the
2010 /dev/loop-control interface.
2012 mce [X86-32] Machine Check Exception
2014 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
2016 md= [HW] RAID subsystems devices and level
2017 See Documentation/md.txt.
2020 Format: <first>,<last>
2021 Specifies range of consoles to be captured by the MDA.
2023 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
2024 Amount of memory to be used when the kernel is not able
2025 to see the whole system memory or for test.
2026 [X86] Work as limiting max address. Use together
2027 with memmap= to avoid physical address space collisions.
2028 Without memmap= PCI devices could be placed at addresses
2029 belonging to unused RAM.
2031 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
2035 [KNL,SH] Allow user to override the default size for
2036 per-device physically contiguous DMA buffers.
2038 memmap=exactmap [KNL,X86] Enable setting of an exact
2039 E820 memory map, as specified by the user.
2040 Such memmap=exactmap lines can be constructed based on
2041 BIOS output or other requirements. See the memmap=nn@ss
2044 memmap=nn[KMG]@ss[KMG]
2045 [KNL] Force usage of a specific region of memory.
2046 Region of memory to be used is from ss to ss+nn.
2048 memmap=nn[KMG]#ss[KMG]
2049 [KNL,ACPI] Mark specific memory as ACPI data.
2050 Region of memory to be marked is from ss to ss+nn.
2052 memmap=nn[KMG]$ss[KMG]
2053 [KNL,ACPI] Mark specific memory as reserved.
2054 Region of memory to be reserved is from ss to ss+nn.
2055 Example: Exclude memory from 0x18690000-0x1869ffff
2056 memmap=64K$0x18690000
2058 memmap=0x10000$0x18690000
2060 memmap=nn[KMG]!ss[KMG]
2061 [KNL,X86] Mark specific memory as protected.
2062 Region of memory to be used, from ss to ss+nn.
2063 The memory region may be marked as e820 type 12 (0xc)
2064 and is NVDIMM or ADR memory.
2066 memory_corruption_check=0/1 [X86]
2067 Some BIOSes seem to corrupt the first 64k of
2068 memory when doing things like suspend/resume.
2069 Setting this option will scan the memory
2070 looking for corruption. Enabling this will
2071 both detect corruption and prevent the kernel
2072 from using the memory being corrupted.
2073 However, its intended as a diagnostic tool; if
2074 repeatable BIOS-originated corruption always
2075 affects the same memory, you can use memmap=
2076 to prevent the kernel from using that memory.
2078 memory_corruption_check_size=size [X86]
2079 By default it checks for corruption in the low
2080 64k, making this memory unavailable for normal
2081 use. Use this parameter to scan for
2082 corruption in more or less memory.
2084 memory_corruption_check_period=seconds [X86]
2085 By default it checks for corruption every 60
2086 seconds. Use this parameter to check at some
2087 other rate. 0 disables periodic checking.
2089 memtest= [KNL,X86,ARM] Enable memtest
2091 default : 0 <disable>
2092 Specifies the number of memtest passes to be
2093 performed. Each pass selects another test
2094 pattern from a given set of patterns. Memtest
2095 fills the memory with this pattern, validates
2096 memory contents and reserves bad memory
2097 regions that are detected.
2099 meye.*= [HW] Set MotionEye Camera parameters
2100 See Documentation/video4linux/meye.txt.
2102 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2103 Multi-Function General Purpose Timers on AMD Geode
2106 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2107 the BIOS has incorrectly applied a workaround. TinyBIOS
2108 version 0.98 is known to be affected, 0.99 fixes the
2109 problem by letting the user disable the workaround.
2113 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2114 physical address is ignored.
2116 mini2440= [ARM,HW,KNL]
2117 Format:[0..2][b][c][t]
2119 MINI2440 configuration specification:
2120 0 - The attached screen is the 3.5" TFT
2121 1 - The attached screen is the 7" TFT
2122 2 - The VGA Shield is attached (1024x768)
2123 Leaving out the screen size parameter will not load
2124 the TFT driver, and the framebuffer will be left
2126 b - Enable backlight. The TFT backlight pin will be
2127 linked to the kernel VESA blanking code and a GPIO
2128 LED. This parameter is not necessary when using the
2130 c - Enable the s3c camera interface.
2131 t - Reserved for enabling touchscreen support. The
2132 touchscreen support is not enabled in the mainstream
2133 kernel as of 2.6.30, a preliminary port can be found
2134 in the "bleeding edge" mini2440 support kernel at
2135 http://repo.or.cz/w/linux-2.6/mini2440.git
2138 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2139 parameter allows control of the logging verbosity for
2140 the additional memory initialisation checks. A value
2141 of 0 disables mminit logging and a level of 4 will
2142 log everything. Information is printed at KERN_DEBUG
2143 so loglevel=8 may also need to be specified.
2146 [KNL] When CONFIG_MODULE_SIG is set, this means that
2147 modules without (valid) signatures will fail to load.
2148 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2149 is always true, so this option does nothing.
2152 [MOUSE] Maximum time between finger touching and
2153 leaving touchpad surface for touch to be considered
2154 a tap and be reported as a left button click (for
2155 touchpads working in absolute mode only).
2157 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2158 reporting absolute coordinates, such as tablets
2159 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2160 reporting absolute coordinates, such as tablets
2162 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2163 is similar to kernelcore except it specifies the
2164 amount of memory used for migratable allocations.
2165 If both kernelcore and movablecore is specified,
2166 then kernelcore will be at *least* the specified
2167 value but may be more. If movablecore on its own
2168 is specified, the administrator must be careful
2169 that the amount of memory usable for all allocations
2172 movable_node [KNL,X86] Boot-time switch to enable the effects
2173 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2175 MTD_Partition= [MTD]
2176 Format: <name>,<region-number>,<size>,<offset>
2178 MTD_Region= [MTD] Format:
2179 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2182 See drivers/mtd/cmdlinepart.c.
2184 multitce=off [PPC] This parameter disables the use of the pSeries
2185 firmware feature for updating multiple TCE entries
2188 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2190 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2192 boundary - index of last SLC block on Flex-OneNAND.
2193 The remaining blocks are configured as MLC blocks.
2194 lock - Configure if Flex-OneNAND boundary should be locked.
2195 Once locked, the boundary cannot be changed.
2196 1 indicates lock status, 0 indicates unlock status.
2199 ARM/S3C2412 JIVE boot control
2201 See arch/arm/mach-s3c2412/mach-jive.c
2203 mtouchusb.raw_coordinates=
2204 [HW] Make the MicroTouch USB driver use raw coordinates
2205 ('y', default) or cooked coordinates ('n')
2207 mtrr_chunk_size=nn[KMG] [X86]
2208 used for mtrr cleanup. It is largest continuous chunk
2209 that could hold holes aka. UC entries.
2211 mtrr_gran_size=nn[KMG] [X86]
2212 Used for mtrr cleanup. It is granularity of mtrr block.
2214 Large value could prevent small alignment from
2217 mtrr_spare_reg_nr=n [X86]
2219 Range: 0,7 : spare reg number
2221 Used for mtrr cleanup. It is spare mtrr entries number.
2222 Set to 2 or more if your graphical card needs more.
2224 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2226 netdev= [NET] Network devices parameters
2227 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2228 Note that mem_start is often overloaded to mean
2229 something different and driver-specific.
2230 This usage is only documented in each driver source
2234 [NETFILTER] Enable connection tracking flow accounting
2235 0 to disable accounting
2236 1 to enable accounting
2239 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2240 See Documentation/filesystems/nfs/nfsroot.txt.
2242 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2243 See Documentation/filesystems/nfs/nfsroot.txt.
2245 nfsrootdebug [NFS] enable nfsroot debugging messages.
2246 See Documentation/filesystems/nfs/nfsroot.txt.
2248 nfs.callback_tcpport=
2249 [NFS] set the TCP port on which the NFSv4 callback
2250 channel should listen.
2253 [NFS] sets the pathname to the program which is used
2254 to update the NFS client cache entries.
2256 nfs.cache_getent_timeout=
2257 [NFS] sets the timeout after which an attempt to
2258 update a cache entry is deemed to have failed.
2260 nfs.idmap_cache_timeout=
2261 [NFS] set the maximum lifetime for idmapper cache
2265 [NFS] enable 64-bit inode numbers.
2266 If zero, the NFS client will fake up a 32-bit inode
2267 number for the readdir() and stat() syscalls instead
2268 of returning the full 64-bit number.
2269 The default is to return 64-bit inode numbers.
2271 nfs.max_session_slots=
2272 [NFSv4.1] Sets the maximum number of session slots
2273 the client will attempt to negotiate with the server.
2274 This limits the number of simultaneous RPC requests
2275 that the client can send to the NFSv4.1 server.
2276 Note that there is little point in setting this
2277 value higher than the max_tcp_slot_table_limit.
2279 nfs.nfs4_disable_idmapping=
2280 [NFSv4] When set to the default of '1', this option
2281 ensures that both the RPC level authentication
2282 scheme and the NFS level operations agree to use
2283 numeric uids/gids if the mount is using the
2284 'sec=sys' security flavour. In effect it is
2285 disabling idmapping, which can make migration from
2286 legacy NFSv2/v3 systems to NFSv4 easier.
2287 Servers that do not support this mode of operation
2288 will be autodetected by the client, and it will fall
2289 back to using the idmapper.
2290 To turn off this behaviour, set the value to '0'.
2292 [NFS4] Specify an additional fixed unique ident-
2293 ification string that NFSv4 clients can insert into
2294 their nfs_client_id4 string. This is typically a
2295 UUID that is generated at system install time.
2297 nfs.send_implementation_id =
2298 [NFSv4.1] Send client implementation identification
2299 information in exchange_id requests.
2300 If zero, no implementation identification information
2302 The default is to send the implementation identification
2305 nfs.recover_lost_locks =
2306 [NFSv4] Attempt to recover locks that were lost due
2307 to a lease timeout on the server. Please note that
2308 doing this risks data corruption, since there are
2309 no guarantees that the file will remain unchanged
2310 after the locks are lost.
2311 If you want to enable the kernel legacy behaviour of
2312 attempting to recover these locks, then set this
2314 The default parameter value of '0' causes the kernel
2315 not to attempt recovery of lost locks.
2317 nfs4.layoutstats_timer =
2318 [NFSv4.2] Change the rate at which the kernel sends
2319 layoutstats to the pNFS metadata server.
2321 Setting this to value to 0 causes the kernel to use
2322 whatever value is the default set by the layout
2323 driver. A non-zero value sets the minimum interval
2324 in seconds between layoutstats transmissions.
2326 nfsd.nfs4_disable_idmapping=
2327 [NFSv4] When set to the default of '1', the NFSv4
2328 server will return only numeric uids and gids to
2329 clients using auth_sys, and will accept numeric uids
2330 and gids from such clients. This is intended to ease
2331 migration from NFSv2/v3.
2333 objlayoutdriver.osd_login_prog=
2334 [NFS] [OBJLAYOUT] sets the pathname to the program which
2335 is used to automatically discover and login into new
2336 osd-targets. Please see:
2337 Documentation/filesystems/pnfs.txt for more explanations
2339 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2340 when a NMI is triggered.
2341 Format: [state][,regs][,debounce][,die]
2343 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2344 Format: [panic,][nopanic,][num]
2346 0 - turn hardlockup detector in nmi_watchdog off
2347 1 - turn hardlockup detector in nmi_watchdog on
2348 When panic is specified, panic when an NMI watchdog
2349 timeout occurs (or 'nopanic' to override the opposite
2350 default). To disable both hard and soft lockup detectors,
2351 please see 'nowatchdog'.
2352 This is useful when you use a panic=... timeout and
2353 need the box quickly up again.
2355 netpoll.carrier_timeout=
2356 [NET] Specifies amount of time (in seconds) that
2357 netpoll should wait for a carrier. By default netpoll
2360 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2361 emulation library even if a 387 maths coprocessor
2365 [HW] Never suspend the console
2366 Disable suspending of consoles during suspend and
2367 hibernate operations. Once disabled, debugging
2368 messages can reach various consoles while the rest
2369 of the system is being put to sleep (ie, while
2370 debugging driver suspend/resume hooks). This may
2371 not work reliably with all consoles, but is known
2372 to work with serial and VGA consoles.
2373 To facilitate more flexible debugging, we also add
2374 console_suspend, a printk module parameter to control
2375 it. Users could use console_suspend (usually
2376 /sys/module/printk/parameters/console_suspend) to
2377 turn on/off it dynamically.
2379 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2380 caches in the slab allocator. Saves per-node memory,
2381 but will impact performance.
2385 noapic [SMP,APIC] Tells the kernel to not make use of any
2386 IOAPICs that may be present in the system.
2388 noautogroup Disable scheduler automatic task group creation.
2390 nobats [PPC] Do not use BATs for mapping kernel lowmem
2391 on "Classic" PPC cores.
2395 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2397 nodelayacct [KNL] Disable per-task delay accounting
2399 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2401 nodsp [SH] Disable hardware DSP at boot time.
2403 noefi Disable EFI runtime services support.
2408 On X86-32 available only on PAE configured kernels.
2409 noexec=on: enable non-executable mappings (default)
2410 noexec=off: disable non-executable mappings
2413 Disable SMAP (Supervisor Mode Access Prevention)
2414 even if it is supported by processor.
2417 Disable SMEP (Supervisor Mode Execution Prevention)
2418 even if it is supported by processor.
2421 This affects only 32-bit executables.
2422 noexec32=on: enable non-executable mappings (default)
2423 read doesn't imply executable mappings
2424 noexec32=off: disable non-executable mappings
2425 read implies executable mappings
2427 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2429 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2430 register save and restore. The kernel will only save
2431 legacy floating-point registers on task switch.
2433 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2435 noxsave [BUGS=X86] Disables x86 extended register state save
2436 and restore using xsave. The kernel will fallback to
2437 enabling legacy floating-point and sse state.
2439 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2440 register states. The kernel will fall back to use
2441 xsave to save the states. By using this parameter,
2442 performance of saving the states is degraded because
2443 xsave doesn't support modified optimization while
2444 xsaveopt supports it on xsaveopt enabled systems.
2446 noxsaves [X86] Disables xsaves and xrstors used in saving and
2447 restoring x86 extended register state in compacted
2448 form of xsave area. The kernel will fall back to use
2449 xsaveopt and xrstor to save and restore the states
2450 in standard form of xsave area. By using this
2451 parameter, xsave area per process might occupy more
2452 memory on xsaves enabled systems.
2454 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2455 wfi(ARM) instruction doesn't work correctly and not to
2456 use it. This is also useful when using JTAG debugger.
2458 no_file_caps Tells the kernel not to honor file capabilities. The
2459 only way then for a file to be executed with privilege
2460 is to be setuid root or executed by root.
2462 nohalt [IA-64] Tells the kernel not to use the power saving
2463 function PAL_HALT_LIGHT when idle. This increases
2464 power-consumption. On the positive side, it reduces
2465 interrupt wake-up latency, which may improve performance
2466 in certain environments such as networked servers or
2469 nohibernate [HIBERNATION] Disable hibernation and resume.
2471 nohz= [KNL] Boottime enable/disable dynamic ticks
2472 Valid arguments: on, off
2475 nohz_full= [KNL,BOOT]
2476 In kernels built with CONFIG_NO_HZ_FULL=y, set
2477 the specified list of CPUs whose tick will be stopped
2478 whenever possible. The boot CPU will be forced outside
2479 the range to maintain the timekeeping.
2480 The CPUs in this range must also be included in the
2483 noiotrap [SH] Disables trapped I/O port accesses.
2485 noirqdebug [X86-32] Disables the code which attempts to detect and
2486 disable unhandled interrupt sources.
2488 no_timer_check [X86,APIC] Disables the code which tests for
2489 broken timer IRQ sources.
2491 noisapnp [ISAPNP] Disables ISA PnP code.
2493 noinitrd [RAM] Tells the kernel not to load any configured
2496 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2498 [Deprecated - use intremap=off]
2502 nojitter [IA-64] Disables jitter checking for ITC timers.
2504 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2506 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2509 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2510 steal time is computed, but won't influence scheduler
2513 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2515 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2517 noltlbs [PPC] Do not use large page/tlb entries for kernel
2518 lowmem mapping on PPC40x.
2520 nomca [IA-64] Disable machine check abort handling
2522 nomce [X86-32] Disable Machine Check Exception
2524 nomfgpt [X86-32] Disable Multi-Function General Purpose
2525 Timer usage (for AMD Geode machines).
2527 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2528 shutdown the other cpus. Instead use the REBOOT_VECTOR
2531 nomodule Disable module load
2533 nopat [X86] Disable PAT (page attribute table extension of
2534 pagetables) support.
2536 norandmaps Don't use address space randomization. Equivalent to
2537 echo 0 > /proc/sys/kernel/randomize_va_space
2539 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2541 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2542 with UP alternatives
2544 nordrand [X86] Disable kernel use of the RDRAND and
2545 RDSEED instructions even if they are supported
2546 by the processor. RDRAND and RDSEED are still
2547 available to user space applications.
2549 noresume [SWSUSP] Disables resume and restores original swap
2552 no-scroll [VGA] Disables scrollback.
2553 This is required for the Braillex ib80-piezo Braille
2554 reader made by F.H. Papenmeier (Germany).
2558 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2560 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2561 and disable the IO APIC. legacy for "maxcpus=0".
2563 nosoftlockup [KNL] Disable the soft-lockup detector.
2565 nosync [HW,M68K] Disables sync negotiation for all devices.
2567 notsc [BUGS=X86-32] Disable Time Stamp Counter
2569 nousb [USB] Disable the USB subsystem
2571 nowatchdog [KNL] Disable both lockup detectors, i.e.
2572 soft-lockup and NMI watchdog (hard-lockup).
2576 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2578 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2579 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2580 Some features depend on CPU0. Known dependencies are:
2581 1. Resume from suspend/hibernate depends on CPU0.
2582 Suspend/hibernate will fail if CPU0 is offline and you
2583 need to online CPU0 before suspend/hibernate.
2584 2. PIC interrupts also depend on CPU0. CPU0 can't be
2585 removed if a PIC interrupt is detected.
2586 It's said poweroff/reboot may depend on CPU0 on some
2587 machines although I haven't seen such issues so far
2588 after CPU0 is offline on a few tested machines.
2589 If the dependencies are under your control, you can
2590 turn on cpu0_hotplug.
2592 nptcg= [IA-64] Override max number of concurrent global TLB
2593 purges which is reported from either PAL_VM_SUMMARY or
2596 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2597 could support. nr_cpus=n : n >= 1 limits the kernel to
2598 supporting 'n' processors. Later in runtime you can not
2599 use hotplug cpu feature to put more cpu back to online.
2600 just like you compile the kernel NR_CPUS=n
2602 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2604 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2605 Allowed values are enable and disable
2607 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2608 one of ['zone', 'node', 'default'] can be specified
2609 This can be set from sysctl after boot.
2610 See Documentation/sysctl/vm.txt for details.
2612 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2613 See Documentation/debugging-via-ohci1394.txt for more
2616 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2617 Rather than timing out after 20 ms if an EC
2618 command is not properly ACKed, override the length
2619 of the timeout. We have interrupts disabled while
2620 waiting for the ACK, so if this is set too high
2621 interrupts *may* be lost!
2623 omap_mux= [OMAP] Override bootloader pin multiplexing.
2624 Format: <mux_mode0.mode_name=value>...
2625 For example, to override I2C bus2:
2626 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2628 oprofile.timer= [HW]
2629 Use timer interrupt instead of performance counters
2631 oprofile.cpu_type= Force an oprofile cpu type
2632 This might be useful if you have an older oprofile
2633 userland or if you want common events.
2634 Format: { arch_perfmon }
2635 arch_perfmon: [X86] Force use of architectural
2636 perfmon on Intel CPUs instead of the
2637 CPU specific event set.
2638 timer: [X86] Force use of architectural NMI
2639 timer mode (see also oprofile.timer
2640 for generic hr timer mode)
2641 [s390] Force legacy basic mode sampling
2642 (report cpu_type "timer")
2644 oops=panic Always panic on oopses. Default is to just kill the
2645 process, but there is a small probability of
2646 deadlocking the machine.
2647 This will also cause panics on machine check exceptions.
2648 Useful together with panic=30 to trigger a reboot.
2651 See Documentation/sound/oss/oss-parameters.txt
2653 page_owner= [KNL] Boot-time page_owner enabling option.
2654 Storage of the information about who allocated
2655 each page is disabled in default. With this switch,
2657 on: enable the feature
2659 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2660 timeout > 0: seconds before rebooting
2661 timeout = 0: wait forever
2662 timeout < 0: reboot immediately
2665 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2668 crash_kexec_post_notifiers
2669 Run kdump after running panic-notifiers and dumping
2670 kmsg. This only for the users who doubt kdump always
2671 succeeds in any situation.
2672 Note that this also increases risks of kdump failure,
2673 because some panic notifiers can make the crashed
2674 kernel more unstable.
2676 parkbd.port= [HW] Parallel port number the keyboard adapter is
2677 connected to, default is 0.
2679 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2680 0 for XT, 1 for AT (default is AT).
2683 parport= [HW,PPT] Specify parallel ports. 0 disables.
2684 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2685 Use 'auto' to force the driver to use any
2686 IRQ/DMA settings detected (the default is to
2687 ignore detected IRQ/DMA settings because of
2688 possible conflicts). You can specify the base
2689 address, IRQ, and DMA settings; IRQ and DMA
2690 should be numbers, or 'auto' (for using detected
2691 settings on that particular port), or 'nofifo'
2692 (to avoid using a FIFO even if it is detected).
2693 Parallel ports are assigned in the order they
2694 are specified on the command line, starting
2697 parport_init_mode= [HW,PPT]
2698 Configure VIA parallel port to operate in
2699 a specific mode. This is necessary on Pegasos
2700 computer where firmware has no options for setting
2701 up parallel port mode and sets it to spp.
2702 Currently this function knows 686a and 8231 chips.
2703 Format: [spp|ps2|epp|ecp|ecpepp]
2706 Halt all CPUs after the first oops has been printed for
2707 the specified number of seconds. This is to be used if
2708 your oopses keep scrolling off the screen.
2713 See header of drivers/block/paride/pcd.c.
2714 See also Documentation/blockdev/paride.txt.
2716 pci=option[,option...] [PCI] various PCI subsystem options:
2717 earlydump [X86] dump PCI config space before the kernel
2719 off [X86] don't probe for the PCI bus
2720 bios [X86-32] force use of PCI BIOS, don't access
2721 the hardware directly. Use this if your machine
2722 has a non-standard PCI host bridge.
2723 nobios [X86-32] disallow use of PCI BIOS, only direct
2724 hardware access methods are allowed. Use this
2725 if you experience crashes upon bootup and you
2726 suspect they are caused by the BIOS.
2727 conf1 [X86] Force use of PCI Configuration
2729 conf2 [X86] Force use of PCI Configuration
2731 noaer [PCIE] If the PCIEAER kernel config parameter is
2732 enabled, this kernel boot option can be used to
2733 disable the use of PCIE advanced error reporting.
2734 nodomains [PCI] Disable support for multiple PCI
2735 root domains (aka PCI segments, in ACPI-speak).
2736 nommconf [X86] Disable use of MMCONFIG for PCI
2738 check_enable_amd_mmconf [X86] check for and enable
2739 properly configured MMIO access to PCI
2740 config space on AMD family 10h CPU
2741 nomsi [MSI] If the PCI_MSI kernel config parameter is
2742 enabled, this kernel boot option can be used to
2743 disable the use of MSI interrupts system-wide.
2744 noioapicquirk [APIC] Disable all boot interrupt quirks.
2745 Safety option to keep boot IRQs enabled. This
2746 should never be necessary.
2747 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2748 primary IO-APIC for bridges that cannot disable
2749 boot IRQs. This fixes a source of spurious IRQs
2750 when the system masks IRQs.
2751 noioapicreroute [APIC] Disable workaround that uses the
2752 boot IRQ equivalent of an IRQ that connects to
2753 a chipset where boot IRQs cannot be disabled.
2754 The opposite of ioapicreroute.
2755 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2756 routing table. These calls are known to be buggy
2757 on several machines and they hang the machine
2758 when used, but on other computers it's the only
2759 way to get the interrupt routing table. Try
2760 this option if the kernel is unable to allocate
2761 IRQs or discover secondary PCI buses on your
2763 rom [X86] Assign address space to expansion ROMs.
2764 Use with caution as certain devices share
2765 address decoders between ROMs and other
2767 norom [X86] Do not assign address space to
2768 expansion ROMs that do not already have
2769 BIOS assigned address ranges.
2770 nobar [X86] Do not assign address space to the
2771 BARs that weren't assigned by the BIOS.
2772 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2773 assigned automatically to PCI devices. You can
2774 make the kernel exclude IRQs of your ISA cards
2776 pirqaddr=0xAAAAA [X86] Specify the physical address
2777 of the PIRQ table (normally generated
2778 by the BIOS) if it is outside the
2779 F0000h-100000h range.
2780 lastbus=N [X86] Scan all buses thru bus #N. Can be
2781 useful if the kernel is unable to find your
2782 secondary buses and you want to tell it
2783 explicitly which ones they are.
2784 assign-busses [X86] Always assign all PCI bus
2785 numbers ourselves, overriding
2786 whatever the firmware may have done.
2787 usepirqmask [X86] Honor the possible IRQ mask stored
2788 in the BIOS $PIR table. This is needed on
2789 some systems with broken BIOSes, notably
2790 some HP Pavilion N5400 and Omnibook XE3
2791 notebooks. This will have no effect if ACPI
2792 IRQ routing is enabled.
2793 noacpi [X86] Do not use ACPI for IRQ routing
2794 or for PCI scanning.
2795 use_crs [X86] Use PCI host bridge window information
2796 from ACPI. On BIOSes from 2008 or later, this
2797 is enabled by default. If you need to use this,
2798 please report a bug.
2799 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2800 If you need to use this, please report a bug.
2801 routeirq Do IRQ routing for all PCI devices.
2802 This is normally done in pci_enable_device(),
2803 so this option is a temporary workaround
2804 for broken drivers that don't call it.
2805 skip_isa_align [X86] do not align io start addr, so can
2806 handle more pci cards
2807 firmware [ARM] Do not re-enumerate the bus but instead
2808 just use the configuration from the
2809 bootloader. This is currently used on
2810 IXP2000 systems where the bus has to be
2811 configured a certain way for adjunct CPUs.
2812 noearly [X86] Don't do any early type 1 scanning.
2813 This might help on some broken boards which
2814 machine check when some devices' config space
2815 is read. But various workarounds are disabled
2816 and some IOMMU drivers will not work.
2817 bfsort Sort PCI devices into breadth-first order.
2818 This sorting is done to get a device
2819 order compatible with older (<= 2.4) kernels.
2820 nobfsort Don't sort PCI devices into breadth-first order.
2821 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2822 tuning and use the BIOS-configured MPS defaults.
2823 pcie_bus_safe Set every device's MPS to the largest value
2824 supported by all devices below the root complex.
2825 pcie_bus_perf Set device MPS to the largest allowable MPS
2826 based on its parent bus. Also set MRRS (Max
2827 Read Request Size) to the largest supported
2828 value (no larger than the MPS that the device
2829 or bus can support) for best performance.
2830 pcie_bus_peer2peer Set every device's MPS to 128B, which
2831 every device is guaranteed to support. This
2832 configuration allows peer-to-peer DMA between
2833 any pair of devices, possibly at the cost of
2834 reduced performance. This also guarantees
2835 that hot-added devices will work.
2836 cbiosize=nn[KMG] The fixed amount of bus space which is
2837 reserved for the CardBus bridge's IO window.
2838 The default value is 256 bytes.
2839 cbmemsize=nn[KMG] The fixed amount of bus space which is
2840 reserved for the CardBus bridge's memory
2841 window. The default value is 64 megabytes.
2844 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2845 Specifies alignment and device to reassign
2846 aligned memory resources.
2847 If <order of align> is not specified,
2848 PAGE_SIZE is used as alignment.
2849 PCI-PCI bridge can be specified, if resource
2850 windows need to be expanded.
2851 ecrc= Enable/disable PCIe ECRC (transaction layer
2852 end-to-end CRC checking).
2853 bios: Use BIOS/firmware settings. This is the
2857 hpiosize=nn[KMG] The fixed amount of bus space which is
2858 reserved for hotplug bridge's IO window.
2859 Default size is 256 bytes.
2860 hpmemsize=nn[KMG] The fixed amount of bus space which is
2861 reserved for hotplug bridge's memory window.
2862 Default size is 2 megabytes.
2863 realloc= Enable/disable reallocating PCI bridge resources
2864 if allocations done by BIOS are too small to
2865 accommodate resources required by all child
2867 off: Turn realloc off
2869 realloc same as realloc=on
2870 noari do not use PCIe ARI.
2871 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2872 only look for one device below a PCIe downstream
2875 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2878 force Enable ASPM even on devices that claim not to support it.
2879 WARNING: Forcing ASPM on may cause system lockups.
2881 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2882 nomsi Do not use MSI for PCI Express Native Hotplug (this
2883 makes all PCIe ports use INTx for hotplug services).
2885 pcie_ports= [PCIE] PCIe ports handling:
2886 auto Ask the BIOS whether or not to use native PCIe services
2887 associated with PCIe ports (PME, hot-plug, AER). Use
2888 them only if that is allowed by the BIOS.
2889 native Use native PCIe services associated with PCIe ports
2891 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2894 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2895 nomsi Do not use MSI for native PCIe PME signaling (this makes
2896 all PCIe root ports use INTx for all services).
2898 pcmv= [HW,PCMCIA] BadgePAD 4
2902 Keep all power-domains already enabled by bootloader on,
2903 even if no driver has claimed them. This is useful
2904 for debug and development, but should not be
2905 needed on a platform with proper driver support.
2908 See Documentation/blockdev/paride.txt.
2910 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2913 See arch/parisc/kernel/pdc_chassis.c
2915 percpu_alloc= Select which percpu first chunk allocator to use.
2916 Currently supported values are "embed" and "page".
2917 Archs may support subset or none of the selections.
2918 See comments in mm/percpu.c for details on each
2919 allocator. This parameter is primarily for debugging
2920 and performance comparison.
2923 See Documentation/blockdev/paride.txt.
2926 See Documentation/blockdev/paride.txt.
2928 pirq= [SMP,APIC] Manual mp-table setup
2929 See Documentation/x86/i386/IO-APIC.txt.
2931 plip= [PPT,NET] Parallel port network link
2932 Format: { parport<nr> | timid | 0 }
2933 See also Documentation/parport.txt.
2935 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2936 Override pmtimer IOPort with a hex value.
2940 Enable PNP debug messages (depends on the
2941 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2942 via /sys/module/pnp/parameters/debug. We always show
2943 current resource usage; turning this on also shows
2944 possible settings and some assignment information.
2950 { on | off | curr | res | no-curr | no-res }
2953 [ISAPNP] Exclude IRQs for the autoconfiguration
2956 [ISAPNP] Exclude DMAs for the autoconfiguration
2958 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2959 Ranges are in pairs (I/O port base and size).
2962 [ISAPNP] Exclude memory regions for the
2964 Ranges are in pairs (memory base and size).
2966 ports= [IP_VS_FTP] IPVS ftp helper module
2968 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2970 Format: <port>,<port>....
2972 print-fatal-signals=
2973 [KNL] debug: print fatal signals
2975 If enabled, warn about various signal handling
2976 related application anomalies: too many signals,
2977 too many POSIX.1 timers, fatal signals causing a
2980 If you hit the warning due to signal overflow,
2981 you might want to try "ulimit -i unlimited".
2985 printk.always_kmsg_dump=
2986 Trigger kmsg_dump for cases other than kernel oops or
2988 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2991 printk.time= Show timing data prefixed to each printk message line
2992 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2994 processor.max_cstate= [HW,ACPI]
2995 Limit processor to maximum C-state
2996 max_cstate=9 overrides any DMI blacklist limit.
2998 processor.nocst [HW,ACPI]
2999 Ignore the _CST method to determine C-states,
3000 instead using the legacy FADT method
3002 profile= [KNL] Enable kernel profiling via /proc/profile
3003 Format: [schedule,]<number>
3004 Param: "schedule" - profile schedule points.
3005 Param: <number> - step/bucket size as a power of 2 for
3006 statistical time based profiling.
3007 Param: "sleep" - profile D-state sleeping (millisecs).
3008 Requires CONFIG_SCHEDSTATS
3009 Param: "kvm" - profile VM exits.
3011 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
3013 See Documentation/blockdev/ramdisk.txt.
3015 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
3016 probe for; one of (bare|imps|exps|lifebook|any).
3017 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
3019 psmouse.resetafter= [HW,MOUSE]
3020 Try to reset the device after so many bad packets
3023 [HW,MOUSE] Set desired mouse resolution, in dpi.
3024 psmouse.smartscroll=
3025 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
3026 0 = disabled, 1 = enabled (default).
3028 pstore.backend= Specify the name of the pstore backend to use
3031 See Documentation/blockdev/paride.txt.
3034 [KNL] Number of legacy pty's. Overwrites compiled-in
3037 quiet [KNL] Disable most log messages
3042 See Documentation/md.txt.
3044 ramdisk_blocksize= [RAM]
3045 See Documentation/blockdev/ramdisk.txt.
3047 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
3048 See Documentation/blockdev/ramdisk.txt.
3051 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3052 the specified list of CPUs to be no-callback CPUs.
3053 Invocation of these CPUs' RCU callbacks will
3054 be offloaded to "rcuox/N" kthreads created for
3055 that purpose, where "x" is "b" for RCU-bh, "p"
3056 for RCU-preempt, and "s" for RCU-sched, and "N"
3057 is the CPU number. This reduces OS jitter on the
3058 offloaded CPUs, which can be useful for HPC and
3059 real-time workloads. It can also improve energy
3060 efficiency for asymmetric multiprocessors.
3063 Rather than requiring that offloaded CPUs
3064 (specified by rcu_nocbs= above) explicitly
3065 awaken the corresponding "rcuoN" kthreads,
3066 make these kthreads poll for callbacks.
3067 This improves the real-time response for the
3068 offloaded CPUs by relieving them of the need to
3069 wake up the corresponding kthread, but degrades
3070 energy efficiency by requiring that the kthreads
3071 periodically wake up to do the polling.
3073 rcutree.blimit= [KNL]
3074 Set maximum number of finished RCU callbacks to
3075 process in one batch.
3077 rcutree.dump_tree= [KNL]
3078 Dump the structure of the rcu_node combining tree
3079 out at early boot. This is used for diagnostic
3080 purposes, to verify correct tree setup.
3082 rcutree.gp_cleanup_delay= [KNL]
3083 Set the number of jiffies to delay each step of
3084 RCU grace-period cleanup. This only has effect
3085 when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set.
3087 rcutree.gp_init_delay= [KNL]
3088 Set the number of jiffies to delay each step of
3089 RCU grace-period initialization. This only has
3090 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT
3093 rcutree.gp_preinit_delay= [KNL]
3094 Set the number of jiffies to delay each step of
3095 RCU grace-period pre-initialization, that is,
3096 the propagation of recent CPU-hotplug changes up
3097 the rcu_node combining tree. This only has effect
3098 when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set.
3100 rcutree.rcu_fanout_exact= [KNL]
3101 Disable autobalancing of the rcu_node combining
3102 tree. This is used by rcutorture, and might
3103 possibly be useful for architectures having high
3104 cache-to-cache transfer latencies.
3106 rcutree.rcu_fanout_leaf= [KNL]
3107 Change the number of CPUs assigned to each
3108 leaf rcu_node structure. Useful for very
3109 large systems, which will choose the value 64,
3110 and for NUMA systems with large remote-access
3111 latencies, which will choose a value aligned
3112 with the appropriate hardware boundaries.
3114 rcutree.jiffies_till_sched_qs= [KNL]
3115 Set required age in jiffies for a
3116 given grace period before RCU starts
3117 soliciting quiescent-state help from
3118 rcu_note_context_switch().
3120 rcutree.jiffies_till_first_fqs= [KNL]
3121 Set delay from grace-period initialization to
3122 first attempt to force quiescent states.
3123 Units are jiffies, minimum value is zero,
3124 and maximum value is HZ.
3126 rcutree.jiffies_till_next_fqs= [KNL]
3127 Set delay between subsequent attempts to force
3128 quiescent states. Units are jiffies, minimum
3129 value is one, and maximum value is HZ.
3131 rcutree.kthread_prio= [KNL,BOOT]
3132 Set the SCHED_FIFO priority of the RCU per-CPU
3133 kthreads (rcuc/N). This value is also used for
3134 the priority of the RCU boost threads (rcub/N)
3135 and for the RCU grace-period kthreads (rcu_bh,
3136 rcu_preempt, and rcu_sched). If RCU_BOOST is
3137 set, valid values are 1-99 and the default is 1
3138 (the least-favored priority). Otherwise, when
3139 RCU_BOOST is not set, valid values are 0-99 and
3140 the default is zero (non-realtime operation).
3142 rcutree.rcu_nocb_leader_stride= [KNL]
3143 Set the number of NOCB kthread groups, which
3144 defaults to the square root of the number of
3145 CPUs. Larger numbers reduces the wakeup overhead
3146 on the per-CPU grace-period kthreads, but increases
3147 that same overhead on each group's leader.
3149 rcutree.qhimark= [KNL]
3150 Set threshold of queued RCU callbacks beyond which
3151 batch limiting is disabled.
3153 rcutree.qlowmark= [KNL]
3154 Set threshold of queued RCU callbacks below which
3155 batch limiting is re-enabled.
3157 rcutree.rcu_idle_gp_delay= [KNL]
3158 Set wakeup interval for idle CPUs that have
3159 RCU callbacks (RCU_FAST_NO_HZ=y).
3161 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3162 Set wakeup interval for idle CPUs that have
3163 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3164 Lazy RCU callbacks are those which RCU can
3165 prove do nothing more than free memory.
3167 rcutorture.cbflood_inter_holdoff= [KNL]
3168 Set holdoff time (jiffies) between successive
3169 callback-flood tests.
3171 rcutorture.cbflood_intra_holdoff= [KNL]
3172 Set holdoff time (jiffies) between successive
3173 bursts of callbacks within a given callback-flood
3176 rcutorture.cbflood_n_burst= [KNL]
3177 Set the number of bursts making up a given
3178 callback-flood test. Set this to zero to
3179 disable callback-flood testing.
3181 rcutorture.cbflood_n_per_burst= [KNL]
3182 Set the number of callbacks to be registered
3183 in a given burst of a callback-flood test.
3185 rcutorture.fqs_duration= [KNL]
3186 Set duration of force_quiescent_state bursts
3189 rcutorture.fqs_holdoff= [KNL]
3190 Set holdoff time within force_quiescent_state bursts
3193 rcutorture.fqs_stutter= [KNL]
3194 Set wait time between force_quiescent_state bursts
3197 rcutorture.gp_cond= [KNL]
3198 Use conditional/asynchronous update-side
3199 primitives, if available.
3201 rcutorture.gp_exp= [KNL]
3202 Use expedited update-side primitives, if available.
3204 rcutorture.gp_normal= [KNL]
3205 Use normal (non-expedited) asynchronous
3206 update-side primitives, if available.
3208 rcutorture.gp_sync= [KNL]
3209 Use normal (non-expedited) synchronous
3210 update-side primitives, if available. If all
3211 of rcutorture.gp_cond=, rcutorture.gp_exp=,
3212 rcutorture.gp_normal=, and rcutorture.gp_sync=
3213 are zero, rcutorture acts as if is interpreted
3214 they are all non-zero.
3216 rcutorture.n_barrier_cbs= [KNL]
3217 Set callbacks/threads for rcu_barrier() testing.
3219 rcutorture.nfakewriters= [KNL]
3220 Set number of concurrent RCU writers. These just
3221 stress RCU, they don't participate in the actual
3222 test, hence the "fake".
3224 rcutorture.nreaders= [KNL]
3225 Set number of RCU readers. The value -1 selects
3226 N-1, where N is the number of CPUs. A value
3227 "n" less than -1 selects N-n-2, where N is again
3228 the number of CPUs. For example, -2 selects N
3229 (the number of CPUs), -3 selects N+1, and so on.
3231 rcutorture.object_debug= [KNL]
3232 Enable debug-object double-call_rcu() testing.
3234 rcutorture.onoff_holdoff= [KNL]
3235 Set time (s) after boot for CPU-hotplug testing.
3237 rcutorture.onoff_interval= [KNL]
3238 Set time (s) between CPU-hotplug operations, or
3239 zero to disable CPU-hotplug testing.
3241 rcutorture.shuffle_interval= [KNL]
3242 Set task-shuffle interval (s). Shuffling tasks
3243 allows some CPUs to go into dyntick-idle mode
3244 during the rcutorture test.
3246 rcutorture.shutdown_secs= [KNL]
3247 Set time (s) after boot system shutdown. This
3248 is useful for hands-off automated testing.
3250 rcutorture.stall_cpu= [KNL]
3251 Duration of CPU stall (s) to test RCU CPU stall
3252 warnings, zero to disable.
3254 rcutorture.stall_cpu_holdoff= [KNL]
3255 Time to wait (s) after boot before inducing stall.
3257 rcutorture.stat_interval= [KNL]
3258 Time (s) between statistics printk()s.
3260 rcutorture.stutter= [KNL]
3261 Time (s) to stutter testing, for example, specifying
3262 five seconds causes the test to run for five seconds,
3263 wait for five seconds, and so on. This tests RCU's
3264 ability to transition abruptly to and from idle.
3266 rcutorture.test_boost= [KNL]
3267 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3268 "Maybe" means test if the RCU implementation
3269 under test support RCU priority boosting.
3271 rcutorture.test_boost_duration= [KNL]
3272 Duration (s) of each individual boost test.
3274 rcutorture.test_boost_interval= [KNL]
3275 Interval (s) between each boost test.
3277 rcutorture.test_no_idle_hz= [KNL]
3278 Test RCU's dyntick-idle handling. See also the
3279 rcutorture.shuffle_interval parameter.
3281 rcutorture.torture_runnable= [BOOT]
3282 Start rcutorture running at boot time.
3284 rcutorture.torture_type= [KNL]
3285 Specify the RCU implementation to test.
3287 rcutorture.verbose= [KNL]
3288 Enable additional printk() statements.
3290 rcupdate.rcu_expedited= [KNL]
3291 Use expedited grace-period primitives, for
3292 example, synchronize_rcu_expedited() instead
3293 of synchronize_rcu(). This reduces latency,
3294 but can increase CPU utilization, degrade
3295 real-time latency, and degrade energy efficiency.
3297 rcupdate.rcu_cpu_stall_suppress= [KNL]
3298 Suppress RCU CPU stall warning messages.
3300 rcupdate.rcu_cpu_stall_timeout= [KNL]
3301 Set timeout for RCU CPU stall warning messages.
3303 rcupdate.rcu_task_stall_timeout= [KNL]
3304 Set timeout in jiffies for RCU task stall warning
3305 messages. Disable with a value less than or equal
3308 rcupdate.rcu_self_test= [KNL]
3309 Run the RCU early boot self tests
3311 rcupdate.rcu_self_test_bh= [KNL]
3312 Run the RCU bh early boot self tests
3314 rcupdate.rcu_self_test_sched= [KNL]
3315 Run the RCU sched early boot self tests
3319 Run specified binary instead of /init from the ramdisk,
3320 used for early userspace startup. See initrd.
3323 Format (x86 or x86_64):
3324 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3326 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3328 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3329 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3330 reboot_force is either force or not specified,
3331 reboot_cpu is s[mp]#### with #### being the processor
3332 to be used for rebooting.
3335 [KNL, SMP] Set scheduler's default relax_domain_level.
3336 See Documentation/cgroups/cpusets.txt.
3338 relative_sleep_states=
3339 [SUSPEND] Use sleep state labeling where the deepest
3340 state available other than hibernation is always "mem".
3341 Format: { "0" | "1" }
3342 0 -- Traditional sleep state labels.
3343 1 -- Relative sleep state labels.
3345 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3347 reservetop= [X86-32]
3349 Reserves a hole at the top of the kernel virtual
3354 Set the amount of memory to reserve for BIOS at
3355 the bottom of the address space.
3357 reset_devices [KNL] Force drivers to reset the underlying device
3358 during initialization.
3361 Specify the partition device for software suspend
3363 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3365 resume_offset= [SWSUSP]
3366 Specify the offset from the beginning of the partition
3367 given by "resume=" at which the swap header is located,
3368 in <PAGE_SIZE> units (needed only for swap files).
3369 See Documentation/power/swsusp-and-swap-files.txt
3371 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3372 read the resume files
3374 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3375 Useful for devices that are detected asynchronously
3376 (e.g. USB and MMC devices).
3378 hibernate= [HIBERNATION]
3379 noresume Don't check if there's a hibernation image
3380 present during boot.
3381 nocompress Don't compress/decompress hibernation images.
3382 no Disable hibernation and resume.
3384 retain_initrd [RAM] Keep initrd memory after extraction
3386 rfkill.default_state=
3387 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3388 etc. communication is blocked by default.
3391 rfkill.master_switch_mode=
3392 0 The "airplane mode" button does nothing.
3393 1 The "airplane mode" button toggles between everything
3394 blocked and the previous configuration.
3395 2 The "airplane mode" button toggles between everything
3396 blocked and everything unblocked.
3398 rhash_entries= [KNL,NET]
3399 Set number of hash buckets for route cache
3401 ro [KNL] Mount root device read-only on boot
3403 root= [KNL] Root filesystem
3404 See name_to_dev_t comment in init/do_mounts.c.
3406 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3407 mount the root filesystem
3409 rootflags= [KNL] Set root filesystem mount option string
3411 rootfstype= [KNL] Set root filesystem type
3413 rootwait [KNL] Wait (indefinitely) for root device to show up.
3414 Useful for devices that are detected asynchronously
3415 (e.g. USB and MMC devices).
3417 rproc_mem=nn[KMG][@address]
3418 [KNL,ARM,CMA] Remoteproc physical memory block.
3419 Memory area to be used by remote processor image,
3422 rw [KNL] Mount root device read-write on boot
3424 S [KNL] Run init in single mode
3426 s390_iommu= [HW,S390]
3427 Set s390 IOTLB flushing mode
3429 With strict flushing every unmap operation will result in
3430 an IOTLB flush. Default is lazy flushing before reuse,
3434 See drivers/net/irda/sa1100_ir.c.
3436 sbni= [NET] Granch SBNI12 leased line adapter
3438 sched_debug [KNL] Enables verbose scheduler debug messages.
3440 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3441 xtime_lock contention on larger systems, and/or RCU lock
3442 contention on all systems with CONFIG_MAXSMP set.
3443 Format: { "0" | "1" }
3444 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3446 Note: increases power consumption, thus should only be
3447 enabled if running jitter sensitive (HPC/RT) workloads.
3449 security= [SECURITY] Choose a security module to enable at boot.
3450 If this boot parameter is not specified, only the first
3451 security module asking for security registration will be
3452 loaded. An invalid security module name will be treated
3453 as if no module has been chosen.
3455 selinux= [SELINUX] Disable or enable SELinux at boot time.
3456 Format: { "0" | "1" }
3457 See security/selinux/Kconfig help text.
3460 Default value is set via kernel config option.
3461 If enabled at boot time, /selinux/disable can be used
3462 later to disable prior to initial policy load.
3464 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3465 Format: { "0" | "1" }
3466 See security/apparmor/Kconfig help text
3469 Default value is set via kernel config option.
3471 serialnumber [BUGS=X86-32]
3474 Maximal number of shapers.
3476 show_msr= [x86] show boot-time MSR settings
3477 Format: { <integer> }
3478 Show boot-time (BIOS-initialized) MSR settings.
3479 The parameter means the number of CPUs to show,
3480 for example 1 means boot CPU only.
3488 Disable merging of slabs with similar size. May be
3489 necessary if there is some reason to distinguish
3490 allocs to different slabs. Debug options disable
3491 merging on their own.
3492 For more information see Documentation/vm/slub.txt.
3494 slab_max_order= [MM, SLAB]
3495 Determines the maximum allowed order for slabs.
3496 A high setting may cause OOMs due to memory
3497 fragmentation. Defaults to 1 for systems with
3498 more than 32MB of RAM, 0 otherwise.
3500 slub_debug[=options[,slabs]] [MM, SLUB]
3501 Enabling slub_debug allows one to determine the
3502 culprit if slab objects become corrupted. Enabling
3503 slub_debug can create guard zones around objects and
3504 may poison objects when not in use. Also tracks the
3505 last alloc / free. For more information see
3506 Documentation/vm/slub.txt.
3508 slub_max_order= [MM, SLUB]
3509 Determines the maximum allowed order for slabs.
3510 A high setting may cause OOMs due to memory
3511 fragmentation. For more information see
3512 Documentation/vm/slub.txt.
3514 slub_min_objects= [MM, SLUB]
3515 The minimum number of objects per slab. SLUB will
3516 increase the slab order up to slub_max_order to
3517 generate a sufficiently large slab able to contain
3518 the number of objects indicated. The higher the number
3519 of objects the smaller the overhead of tracking slabs
3520 and the less frequently locks need to be acquired.
3521 For more information see Documentation/vm/slub.txt.
3523 slub_min_order= [MM, SLUB]
3524 Determines the minimum page order for slabs. Must be
3525 lower than slub_max_order.
3526 For more information see Documentation/vm/slub.txt.
3528 slub_nomerge [MM, SLUB]
3529 Same with slab_nomerge. This is supported for legacy.
3530 See slab_nomerge for more information.
3533 Format: <io1>[,<io2>[,...,<io8>]]
3535 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3536 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3537 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3538 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3539 smsc-ircc2.ircc_irq= [HW] IRQ line
3540 smsc-ircc2.ircc_dma= [HW] DMA channel
3541 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3542 0: Toshiba Satellite 1800 (GP data pin select)
3543 1: Fast pin select (default)
3547 [KNL] Should the soft-lockup detector generate panics.
3550 softlockup_all_cpu_backtrace=
3551 [KNL] Should the soft-lockup detector generate
3552 backtraces on all cpus.
3555 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3556 See Documentation/laptops/sonypi.txt
3558 spia_io_base= [HW,MTD]
3564 Enabled the stack tracer on boot up.
3566 stacktrace_filter=[function-list]
3567 [FTRACE] Limit the functions that the stack tracer
3568 will trace at boot up. function-list is a comma separated
3569 list of functions. This list can be changed at run
3570 time by the stack_trace_filter file in the debugfs
3571 tracing directory. Note, this enables stack tracing
3572 and the stacktrace above is not needed.
3576 Set the STI (builtin display/keyboard on the HP-PARISC
3577 machines) console (graphic card) which should be used
3578 as the initial boot-console.
3579 See also comment in drivers/video/console/sticore.c.
3582 See comment in drivers/video/console/sticore.c.
3585 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3587 sunrpc.min_resvport=
3588 sunrpc.max_resvport=
3590 SunRPC servers often require that client requests
3591 originate from a privileged port (i.e. a port in the
3592 range 0 < portnr < 1024).
3593 An administrator who wishes to reserve some of these
3594 ports for other uses may adjust the range that the
3595 kernel's sunrpc client considers to be privileged
3596 using these two parameters to set the minimum and
3597 maximum port values.
3601 Control how the NFS server code allocates CPUs to
3602 service thread pools. Depending on how many NICs
3603 you have and where their interrupts are bound, this
3604 option will affect which CPUs will do NFS serving.
3605 Note: this parameter cannot be changed while the
3606 NFS server is running.
3608 auto the server chooses an appropriate mode
3609 automatically using heuristics
3610 global a single global pool contains all CPUs
3611 percpu one pool for each CPU
3612 pernode one pool for each NUMA node (equivalent
3613 to global on non-NUMA machines)
3615 sunrpc.tcp_slot_table_entries=
3616 sunrpc.udp_slot_table_entries=
3618 Sets the upper limit on the number of simultaneous
3619 RPC calls that can be sent from the client to a
3620 server. Increasing these values may allow you to
3621 improve throughput, but will also increase the
3622 amount of memory reserved for use by the client.
3624 suspend.pm_test_delay=
3626 Sets the number of seconds to remain in a suspend test
3627 mode before resuming the system (see
3628 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3629 is set. Default value is 5.
3632 [KNL] Enable accounting of swap in memory resource
3633 controller if no parameter or 1 is given or disable
3634 it if 0 is given (See Documentation/cgroups/memory.txt)
3636 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3637 Format: { <int> | force }
3638 <int> -- Number of I/O TLB slabs
3639 force -- force using of bounce buffers even if they
3640 wouldn't be automatically used by the kernel
3644 sysfs.deprecated=0|1 [KNL]
3645 Enable/disable old style sysfs layout for old udev
3646 on older distributions. When this option is enabled
3647 very new udev will not work anymore. When this option
3648 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3649 in older udev will not work anymore.
3650 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3651 the kernel configuration.
3653 sysrq_always_enabled
3655 Ignore sysrq setting - this boot parameter will
3656 neutralize any effect of /proc/sys/kernel/sysrq.
3657 Useful for debugging.
3659 tcpmhash_entries= [KNL,NET]
3660 Set the number of tcp_metrics_hash slots.
3661 Default value is 8192 or 16384 depending on total
3662 ram pages. This is used to specify the TCP metrics
3663 cache size. See Documentation/networking/ip-sysctl.txt
3664 "tcp_no_metrics_save" section for more details.
3668 test_suspend= [SUSPEND][,N]
3669 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3670 standby suspend) or "freeze" (for suspend type freeze)
3671 as the system sleep state during system startup with
3672 the optional capability to repeat N number of times.
3673 The system is woken from this state using a
3674 wakeup-capable RTC alarm.
3676 thash_entries= [KNL,NET]
3677 Set number of hash buckets for TCP connection
3679 thermal.act= [HW,ACPI]
3680 -1: disable all active trip points in all thermal zones
3681 <degrees C>: override all lowest active trip points
3683 thermal.crt= [HW,ACPI]
3684 -1: disable all critical trip points in all thermal zones
3685 <degrees C>: override all critical trip points
3687 thermal.nocrt= [HW,ACPI]
3688 Set to disable actions on ACPI thermal zone
3689 critical and hot trip points.
3691 thermal.off= [HW,ACPI]
3692 1: disable ACPI thermal control
3694 thermal.psv= [HW,ACPI]
3695 -1: disable all passive trip points
3696 <degrees C>: override all passive trip points to this
3699 thermal.tzp= [HW,ACPI]
3700 Specify global default ACPI thermal zone polling rate
3701 <deci-seconds>: poll all this frequency
3702 0: no polling (default)
3705 Force threading of all interrupt handlers except those
3706 marked explicitly IRQF_NO_THREAD.
3709 Enable the Transcendent memory driver if built-in.
3711 tmem.cleancache=0|1 [KNL, XEN]
3712 Default is on (1). Disable the usage of the cleancache
3713 API to send anonymous pages to the hypervisor.
3715 tmem.frontswap=0|1 [KNL, XEN]
3716 Default is on (1). Disable the usage of the frontswap
3717 API to send swap pages to the hypervisor. If disabled
3718 the selfballooning and selfshrinking are force disabled.
3720 tmem.selfballooning=0|1 [KNL, XEN]
3721 Default is on (1). Disable the driving of swap pages
3724 tmem.selfshrinking=0|1 [KNL, XEN]
3725 Default is on (1). Partial swapoff that immediately
3726 transfers pages from Xen hypervisor back to the
3727 kernel based on different criteria.
3731 Specify if the kernel should make use of the cpu
3732 topology information if the hardware supports this.
3733 The scheduler will make use of this information and
3734 e.g. base its process migration decisions on it.
3737 topology_updates= [KNL, PPC, NUMA]
3739 Specify if the kernel should ignore (off)
3740 topology updates sent by the hypervisor to this
3745 tpm_suspend_pcr=[HW,TPM]
3746 Format: integer pcr id
3747 Specify that at suspend time, the tpm driver
3748 should extend the specified pcr with zeros,
3749 as a workaround for some chips which fail to
3750 flush the last written pcr on TPM_SaveState.
3751 This will guarantee that all the other pcrs
3754 trace_buf_size=nn[KMG]
3755 [FTRACE] will set tracing buffer size on each cpu.
3757 trace_event=[event-list]
3758 [FTRACE] Set and start specified trace events in order
3759 to facilitate early boot debugging.
3760 See also Documentation/trace/events.txt
3762 trace_options=[option-list]
3763 [FTRACE] Enable or disable tracer options at boot.
3764 The option-list is a comma delimited list of options
3765 that can be enabled or disabled just as if you were
3766 to echo the option name into
3768 /sys/kernel/debug/tracing/trace_options
3770 For example, to enable stacktrace option (to dump the
3771 stack trace of each event), add to the command line:
3773 trace_options=stacktrace
3775 See also Documentation/trace/ftrace.txt "trace options"
3779 Have the tracepoints sent to printk as well as the
3780 tracing ring buffer. This is useful for early boot up
3781 where the system hangs or reboots and does not give the
3782 option for reading the tracing buffer or performing a
3783 ftrace_dump_on_oops.
3785 To turn off having tracepoints sent to printk,
3786 echo 0 > /proc/sys/kernel/tracepoint_printk
3787 Note, echoing 1 into this file without the
3788 tracepoint_printk kernel cmdline option has no effect.
3792 Having tracepoints sent to printk() and activating high
3793 frequency tracepoints such as irq or sched, can cause
3794 the system to live lock.
3797 [FTRACE] enable this option to disable tracing when a
3798 warning is hit. This turns off "tracing_on". Tracing can
3799 be enabled again by echoing '1' into the "tracing_on"
3800 file located in /sys/kernel/debug/tracing/
3802 This option is useful, as it disables the trace before
3803 the WARNING dump is called, which prevents the trace to
3804 be filled with content caused by the warning output.
3806 This option can also be set at run time via the sysctl
3807 option: kernel/traceoff_on_warning
3809 transparent_hugepage=
3811 Format: [always|madvise|never]
3812 Can be used to control the default behavior of the system
3813 with respect to transparent hugepages.
3814 See Documentation/vm/transhuge.txt for more details.
3816 tsc= Disable clocksource stability checks for TSC.
3818 [x86] reliable: mark tsc clocksource as reliable, this
3819 disables clocksource verification at runtime, as well
3820 as the stability checks done at bootup. Used to enable
3821 high-resolution timer mode on older hardware, and in
3822 virtualized environment.
3823 [x86] noirqtime: Do not use TSC to do irq accounting.
3824 Used to run time disable IRQ_TIME_ACCOUNTING on any
3825 platforms where RDTSC is slow and this accounting
3828 turbografx.map[2|3]= [HW,JOY]
3829 TurboGraFX parallel port interface
3831 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3832 See also Documentation/input/joystick-parport.txt
3834 udbg-immortal [PPC] When debugging early kernel crashes that
3835 happen after console_init() and before a proper
3836 console driver takes over, this boot options might
3837 help "seeing" what's going on.
3839 uhash_entries= [KNL,NET]
3840 Set number of hash buckets for UDP/UDP-Lite connections
3843 [USB] Ignore overcurrent events (default N).
3844 Some badly-designed motherboards generate lots of
3845 bogus events, for ports that aren't wired to
3846 anything. Set this parameter to avoid log spamming.
3847 Note that genuine overcurrent events won't be
3851 [X86] Cause panic on unknown NMI.
3853 usbcore.authorized_default=
3854 [USB] Default USB device authorization:
3855 (default -1 = authorized except for wireless USB,
3856 0 = not authorized, 1 = authorized)
3858 usbcore.autosuspend=
3859 [USB] The autosuspend time delay (in seconds) used
3860 for newly-detected USB devices (default 2). This
3861 is the time required before an idle device will be
3862 autosuspended. Devices for which the delay is set
3863 to a negative value won't be autosuspended at all.
3865 usbcore.usbfs_snoop=
3866 [USB] Set to log all usbfs traffic (default 0 = off).
3868 usbcore.blinkenlights=
3869 [USB] Set to cycle leds on hubs (default 0 = off).
3871 usbcore.old_scheme_first=
3872 [USB] Start with the old device initialization
3873 scheme (default 0 = off).
3875 usbcore.usbfs_memory_mb=
3876 [USB] Memory limit (in MB) for buffers allocated by
3877 usbfs (default = 16, 0 = max = 2047).
3879 usbcore.use_both_schemes=
3880 [USB] Try the other device initialization scheme
3881 if the first one fails (default 1 = enabled).
3883 usbcore.initial_descriptor_timeout=
3884 [USB] Specifies timeout for the initial 64-byte
3885 USB_REQ_GET_DESCRIPTOR request in milliseconds
3886 (default 5000 = 5.0 seconds).
3889 [USBHID] The interval which mice are to be polled at.
3891 usb-storage.delay_use=
3892 [UMS] The delay in seconds before a new device is
3893 scanned for Logical Units (default 1).
3896 [UMS] A list of quirks entries to supplement or
3897 override the built-in unusual_devs list. List
3898 entries are separated by commas. Each entry has
3899 the form VID:PID:Flags where VID and PID are Vendor
3900 and Product ID values (4-digit hex numbers) and
3901 Flags is a set of characters, each corresponding
3902 to a common usb-storage quirk flag as follows:
3903 a = SANE_SENSE (collect more than 18 bytes
3905 b = BAD_SENSE (don't collect more than 18
3906 bytes of sense data);
3907 c = FIX_CAPACITY (decrease the reported
3908 device capacity by one sector);
3909 d = NO_READ_DISC_INFO (don't use
3910 READ_DISC_INFO command);
3911 e = NO_READ_CAPACITY_16 (don't use
3912 READ_CAPACITY_16 command);
3913 f = NO_REPORT_OPCODES (don't use report opcodes
3915 g = MAX_SECTORS_240 (don't transfer more than
3916 240 sectors at a time, uas only);
3917 h = CAPACITY_HEURISTICS (decrease the
3918 reported device capacity by one
3919 sector if the number is odd);
3920 i = IGNORE_DEVICE (don't bind to this
3922 l = NOT_LOCKABLE (don't try to lock and
3923 unlock ejectable media);
3924 m = MAX_SECTORS_64 (don't transfer more
3925 than 64 sectors = 32 KB at a time);
3926 n = INITIAL_READ10 (force a retry of the
3927 initial READ(10) command);
3928 o = CAPACITY_OK (accept the capacity
3929 reported by the device);
3930 p = WRITE_CACHE (the device cache is ON
3932 r = IGNORE_RESIDUE (the device reports
3933 bogus residue values);
3934 s = SINGLE_LUN (the device has only one
3936 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3937 commands, uas only);
3938 u = IGNORE_UAS (don't bind to the uas driver);
3939 w = NO_WP_DETECT (don't test whether the
3940 medium is write-protected).
3941 Example: quirks=0419:aaf5:rl,0421:0433:rc
3943 user_debug= [KNL,ARM]
3945 See arch/arm/Kconfig.debug help text.
3946 1 - undefined instruction events
3948 4 - invalid data aborts
3951 Example: user_debug=31
3954 [X86] Flags controlling user PTE allocations.
3956 nohigh = do not allocate PTE pages in
3957 HIGHMEM regardless of setting
3961 On X86_32, this is an alias for vdso32=. Otherwise:
3963 vdso=1: enable VDSO (the default)
3964 vdso=0: disable VDSO mapping
3966 vdso32= [X86] Control the 32-bit vDSO
3967 vdso32=1: enable 32-bit VDSO
3968 vdso32=0 or vdso32=2: disable 32-bit VDSO
3970 See the help text for CONFIG_COMPAT_VDSO for more
3971 details. If CONFIG_COMPAT_VDSO is set, the default is
3972 vdso32=0; otherwise, the default is vdso32=1.
3974 For compatibility with older kernels, vdso32=2 is an
3977 Try vdso32=0 if you encounter an error that says:
3978 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3981 vector=percpu: enable percpu vector domain
3983 video= [FB] Frame buffer configuration
3984 See Documentation/fb/modedb.txt.
3986 video.brightness_switch_enabled= [0,1]
3987 If set to 1, on receiving an ACPI notify event
3988 generated by hotkey, video driver will adjust brightness
3989 level and then send out the event to user space through
3990 the allocated input device; If set to 0, video driver
3991 will only send out the event without touching backlight
3996 [VMMIO] Memory mapped virtio (platform) device.
3998 <size>@<baseaddr>:<irq>[:<id>]
4000 <size> := size (can use standard suffixes
4002 <baseaddr> := physical base address
4003 <irq> := interrupt number (as passed to
4005 <id> := (optional) platform device id
4007 virtio_mmio.device=1K@0x100b0000:48:7
4009 Can be used multiple times for multiple devices.
4011 vga= [BOOT,X86-32] Select a particular video mode
4012 See Documentation/x86/boot.txt and
4013 Documentation/svga.txt.
4014 Use vga=ask for menu.
4015 This is actually a boot loader parameter; the value is
4016 passed to the kernel using a special protocol.
4018 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
4019 size of <nn>. This can be used to increase the
4020 minimum size (128MB on x86). It can also be used to
4021 decrease the size and leave more room for directly
4024 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
4027 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
4030 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
4034 Controls the behavior of vsyscalls (i.e. calls to
4035 fixed addresses of 0xffffffffff600x00 from legacy
4036 code). Most statically-linked binaries and older
4037 versions of glibc use these calls. Because these
4038 functions are at fixed addresses, they make nice
4039 targets for exploits that can control RIP.
4041 emulate [default] Vsyscalls turn into traps and are
4042 emulated reasonably safely.
4044 native Vsyscalls are native syscall instructions.
4045 This is a little bit faster than trapping
4046 and makes a few dynamic recompilers work
4047 better than they would in emulation mode.
4048 It also makes exploits much easier to write.
4050 none Vsyscalls don't work at all. This makes
4051 them quite hard to use for exploits but
4052 might break your system.
4054 vt.color= [VT] Default text color.
4055 Format: 0xYX, X = foreground, Y = background.
4056 Default: 0x07 = light gray on black.
4058 vt.cur_default= [VT] Default cursor shape.
4059 Format: 0xCCBBAA, where AA, BB, and CC are the same as
4060 the parameters of the <Esc>[?A;B;Cc escape sequence;
4061 see VGA-softcursor.txt. Default: 2 = underline.
4063 vt.default_blu= [VT]
4064 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4065 Change the default blue palette of the console.
4066 This is a 16-member array composed of values
4069 vt.default_grn= [VT]
4070 Format: <green0>,<green1>,<green2>,...,<green15>
4071 Change the default green palette of the console.
4072 This is a 16-member array composed of values
4075 vt.default_red= [VT]
4076 Format: <red0>,<red1>,<red2>,...,<red15>
4077 Change the default red palette of the console.
4078 This is a 16-member array composed of values
4084 Set system-wide default UTF-8 mode for all tty's.
4085 Default is 1, i.e. UTF-8 mode is enabled for all
4086 newly opened terminals.
4088 vt.global_cursor_default=
4091 Set system-wide default for whether a cursor
4092 is shown on new VTs. Default is -1,
4093 i.e. cursors will be created by default unless
4094 overridden by individual drivers. 0 will hide
4095 cursors, 1 will display them.
4097 vt.italic= [VT] Default color for italic text; 0-15.
4100 vt.underline= [VT] Default color for underlined text; 0-15.
4103 watchdog timers [HW,WDT] For information on watchdog timers,
4104 see Documentation/watchdog/watchdog-parameters.txt
4105 or other driver-specific files in the
4106 Documentation/watchdog/ directory.
4108 workqueue.disable_numa
4109 By default, all work items queued to unbound
4110 workqueues are affine to the NUMA nodes they're
4111 issued on, which results in better behavior in
4112 general. If NUMA affinity needs to be disabled for
4113 whatever reason, this option can be used. Note
4114 that this also can be controlled per-workqueue for
4115 workqueues visible under /sys/bus/workqueue/.
4117 workqueue.power_efficient
4118 Per-cpu workqueues are generally preferred because
4119 they show better performance thanks to cache
4120 locality; unfortunately, per-cpu workqueues tend to
4121 be more power hungry than unbound workqueues.
4123 Enabling this makes the per-cpu workqueues which
4124 were observed to contribute significantly to power
4125 consumption unbound, leading to measurably lower
4126 power usage at the cost of small performance
4129 The default value of this parameter is determined by
4130 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4132 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4133 default x2apic cluster mode on platforms
4136 x86_intel_mid_timer= [X86-32,APBT]
4137 Choose timer option for x86 Intel MID platform.
4138 Two valid options are apbt timer only and lapic timer
4139 plus one apbt timer for broadcast timer.
4140 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4142 xen_512gb_limit [KNL,X86-64,XEN]
4143 Restricts the kernel running paravirtualized under Xen
4144 to use only up to 512 GB of RAM. The reason to do so is
4145 crash analysis tools and Xen tools for doing domain
4146 save/restore/migration must be enabled to handle larger
4149 xen_emul_unplug= [HW,X86,XEN]
4150 Unplug Xen emulated devices
4151 Format: [unplug0,][unplug1]
4152 ide-disks -- unplug primary master IDE devices
4153 aux-ide-disks -- unplug non-primary-master IDE devices
4154 nics -- unplug network devices
4155 all -- unplug all emulated devices (NICs and IDE disks)
4156 unnecessary -- unplugging emulated devices is
4157 unnecessary even if the host did not respond to
4159 never -- do not unplug even if version check succeeds
4161 xen_nopvspin [X86,XEN]
4162 Disables the ticketlock slowpath using Xen PV
4166 Disables the PV optimizations forcing the HVM guest to
4167 run as generic HVM guest with no PV drivers.
4169 xirc2ps_cs= [NET,PCMCIA]
4171 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4173 ______________________________________________________________________
4177 Add more DRM drivers.
projects / karo-tx-linux.git / blob