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.
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt }
171 force -- enable ACPI if default was off
172 off -- disable ACPI if default was on
173 noirq -- do not use ACPI for IRQ routing
174 strict -- Be less tolerant of platforms that are not
175 strictly ACPI specification compliant.
176 rsdt -- prefer RSDT over (default) XSDT
177 copy_dsdt -- copy DSDT to memory
179 See also Documentation/power/runtime_pm.txt, pci=noacpi
181 acpi_rsdp= [ACPI,EFI,KEXEC]
182 Pass the RSDP address to the kernel, mostly used
183 on machines running EFI runtime service to boot the
184 second kernel for kdump.
186 acpi_apic_instance= [ACPI, IOAPIC]
188 2: use 2nd APIC table, if available
189 1,0: use 1st APIC table
192 acpi_backlight= [HW,ACPI]
193 acpi_backlight=vendor
195 If set to vendor, prefer vendor specific driver
196 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
197 of the ACPI video.ko driver.
199 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
200 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
202 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
203 debug output. Bits in debug_layer correspond to a
204 _COMPONENT in an ACPI source file, e.g.,
205 #define _COMPONENT ACPI_PCI_COMPONENT
206 Bits in debug_level correspond to a level in
207 ACPI_DEBUG_PRINT statements, e.g.,
208 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
209 The debug_level mask defaults to "info". See
210 Documentation/acpi/debug.txt for more information about
211 debug layers and levels.
213 Enable processor driver info messages:
214 acpi.debug_layer=0x20000000
215 Enable PCI/PCI interrupt routing info messages:
216 acpi.debug_layer=0x400000
217 Enable AML "Debug" output, i.e., stores to the Debug
218 object while interpreting AML:
219 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
220 Enable all messages related to ACPI hardware:
221 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
223 Some values produce so much output that the system is
224 unusable. The "log_buf_len" parameter may be useful
225 if you need to capture more output.
227 acpi_force_table_verification [HW,ACPI]
228 Enable table checksum verification during early stage.
229 By default, this is disabled due to x86 early mapping
232 acpi_irq_balance [HW,ACPI]
233 ACPI will balance active IRQs
236 acpi_irq_nobalance [HW,ACPI]
237 ACPI will not move active IRQs (default)
240 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
241 Format: <irq>,<irq>...
243 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
245 Format: <irq>,<irq>...
247 acpi_no_auto_serialize [HW,ACPI]
248 Disable auto-serialization of AML methods
249 AML control methods that contain the opcodes to create
250 named objects will be marked as "Serialized" by the
251 auto-serialization feature.
252 This feature is enabled by default.
253 This option allows to turn off the feature.
255 acpi_no_static_ssdt [HW,ACPI]
256 Disable installation of static SSDTs at early boot time
257 By default, SSDTs contained in the RSDT/XSDT will be
258 installed automatically and they will appear under
259 /sys/firmware/acpi/tables.
260 This option turns off this feature.
261 Note that specifying this option does not affect
262 dynamic table installation which will install SSDT
263 tables to /sys/firmware/acpi/tables/dynamic.
265 acpica_no_return_repair [HW, ACPI]
266 Disable AML predefined validation mechanism
267 This mechanism can repair the evaluation result to make
268 the return objects more ACPI specification compliant.
269 This option is useful for developers to identify the
270 root cause of an AML interpreter issue when the issue
271 has something to do with the repair mechanism.
273 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
274 Format: To spoof as Windows 98: ="Microsoft Windows"
276 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
277 acpi_osi="string1" # add string1
278 acpi_osi="!string2" # remove string2
279 acpi_osi=!* # remove all strings
280 acpi_osi=! # disable all built-in OS vendor
282 acpi_osi= # disable all strings
284 'acpi_osi=!' can be used in combination with single or
285 multiple 'acpi_osi="string1"' to support specific OS
286 vendor string(s). Note that such command can only
287 affect the default state of the OS vendor strings, thus
288 it cannot affect the default state of the feature group
289 strings and the current state of the OS vendor strings,
290 specifying it multiple times through kernel command line
291 is meaningless. This command is useful when one do not
292 care about the state of the feature group strings which
293 should be controlled by the OSPM.
295 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
296 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
297 can make '_OSI("Windows 2000")' TRUE.
299 'acpi_osi=' cannot be used in combination with other
300 'acpi_osi=' command lines, the _OSI method will not
301 exist in the ACPI namespace. NOTE that such command can
302 only affect the _OSI support state, thus specifying it
303 multiple times through kernel command line is also
306 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
309 'acpi_osi=!*' can be used in combination with single or
310 multiple 'acpi_osi="string1"' to support specific
311 string(s). Note that such command can affect the
312 current state of both the OS vendor strings and the
313 feature group strings, thus specifying it multiple times
314 through kernel command line is meaningful. But it may
315 still not able to affect the final state of a string if
316 there are quirks related to this string. This command
317 is useful when one want to control the state of the
318 feature group strings to debug BIOS issues related to
321 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
322 '_OSI("Module Device")' FALSE.
323 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
324 '_OSI("Module Device")' TRUE.
325 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
327 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
329 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
330 they all will make '_OSI("Windows 2000")' TRUE.
333 Override the pmtimer bug detection: force the kernel
334 to assume that this machine's pmtimer latches its value
335 and always returns good values.
337 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
338 Format: { level | edge | high | low }
340 acpi_skip_timer_override [HW,ACPI]
341 Recognize and ignore IRQ0/pin2 Interrupt Override.
342 For broken nForce2 BIOS resulting in XT-PIC timer.
344 acpi_sleep= [HW,ACPI] Sleep options
345 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
346 old_ordering, nonvs, sci_force_enable }
347 See Documentation/power/video.txt for information on
349 s3_beep is for debugging; it makes the PC's speaker beep
350 as soon as the kernel's real-mode entry point is called.
351 s4_nohwsig prevents ACPI hardware signature from being
352 used during resume from hibernation.
353 old_ordering causes the ACPI 1.0 ordering of the _PTS
354 control method, with respect to putting devices into
355 low power states, to be enforced (the ACPI 2.0 ordering
356 of _PTS is used by default).
357 nonvs prevents the kernel from saving/restoring the
358 ACPI NVS memory during suspend/hibernation and resume.
359 sci_force_enable causes the kernel to set SCI_EN directly
360 on resume from S1/S3 (which is against the ACPI spec,
361 but some broken systems don't work without it).
363 acpi_use_timer_override [HW,ACPI]
364 Use timer override. For some broken Nvidia NF5 boards
365 that require a timer override, but don't have HPET
367 acpi_enforce_resources= [ACPI]
368 { strict | lax | no }
369 Check for resource conflicts between native drivers
370 and ACPI OperationRegions (SystemIO and SystemMemory
371 only). IO ports and memory declared in ACPI might be
372 used by the ACPI subsystem in arbitrary AML code and
373 can interfere with legacy drivers.
374 strict (default): access to resources claimed by ACPI
375 is denied; legacy drivers trying to access reserved
376 resources will fail to bind to device using them.
377 lax: access to resources claimed by ACPI is allowed;
378 legacy drivers trying to access reserved resources
379 will bind successfully but a warning message is logged.
380 no: ACPI OperationRegions are not marked as reserved,
381 no further checks are performed.
383 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
386 add_efi_memmap [EFI; X86] Include EFI memory map in
387 kernel's map of available physical RAM.
390 { off | try_unsupported }
391 off: disable AGP support
392 try_unsupported: try to drive unsupported chipsets
393 (may crash computer or cause data corruption)
396 See Documentation/sound/alsa/alsa-parameters.txt
399 Allow the default userspace alignment fault handler
400 behaviour to be specified. Bit 0 enables warnings,
401 bit 1 enables fixups, and bit 2 sends a segfault.
403 align_va_addr= [X86-64]
404 Align virtual addresses by clearing slice [14:12] when
405 allocating a VMA at process creation time. This option
406 gives you up to 3% performance improvement on AMD F15h
407 machines (where it is enabled by default) for a
408 CPU-intensive style benchmark, and it can vary highly in
409 a microbenchmark depending on workload and compiler.
411 32: only for 32-bit processes
412 64: only for 64-bit processes
413 on: enable for both 32- and 64-bit processes
414 off: disable for both 32- and 64-bit processes
416 alloc_snapshot [FTRACE]
417 Allocate the ftrace snapshot buffer on boot up when the
418 main buffer is allocated. This is handy if debugging
419 and you need to use tracing_snapshot() on boot up, and
420 do not want to use tracing_snapshot_alloc() as it needs
421 to be done where GFP_KERNEL allocations are allowed.
423 amd_iommu= [HW,X86-64]
424 Pass parameters to the AMD IOMMU driver in the system.
426 fullflush - enable flushing of IO/TLB entries when
427 they are unmapped. Otherwise they are
428 flushed before they will be reused, which
430 off - do not initialize any AMD IOMMU found in
432 force_isolation - Force device isolation for all
433 devices. The IOMMU driver is not
434 allowed anymore to lift isolation
435 requirements as needed. This option
436 does not override iommu=pt
438 amd_iommu_dump= [HW,X86-64]
439 Enable AMD IOMMU driver option to dump the ACPI table
440 for AMD IOMMU. With this option enabled, AMD IOMMU
441 driver will print ACPI tables for AMD IOMMU during
442 IOMMU initialization.
444 amijoy.map= [HW,JOY] Amiga joystick support
445 Map of devices attached to JOY0DAT and JOY1DAT
447 See also Documentation/input/joystick.txt
449 analog.map= [HW,JOY] Analog joystick and gamepad support
450 Specifies type or capabilities of an analog joystick
451 connected to one of 16 gameports
452 Format: <type1>,<type2>,..<type16>
455 Power management functions (SPARCstation-4/5 + deriv.)
457 Disable APC CPU standby support. SPARCstation-Fox does
458 not play well with APC CPU idle - disable it if you have
459 APC and your system crashes randomly.
461 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
462 Change the output verbosity whilst booting
463 Format: { quiet (default) | verbose | debug }
464 Change the amount of debugging information output
465 when initialising the APIC and IO-APIC components.
468 See Documentation/networking/ipv6.txt.
470 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
471 Limit apic dumping. The parameter defines the maximal
472 number of local apics being dumped. Also it is possible
473 to set it to "all" by meaning -- no limit here.
474 Format: { 1 (default) | 2 | ... | all }.
475 The parameter valid if only apic=debug or
476 apic=verbose is specified.
477 Example: apic=debug show_lapic=all
479 apm= [APM] Advanced Power Management
480 See header of arch/x86/kernel/apm_32.c.
482 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
483 Format: <io>,<irq>,<nodeID>
487 atarimouse= [HW,MOUSE] Atari Mouse
489 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
490 EzKey and similar keyboards
492 atkbd.reset= [HW] Reset keyboard during initialization
494 atkbd.set= [HW] Select keyboard code set
495 Format: <int> (2 = AT (default), 3 = PS/2)
497 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
500 atkbd.softraw= [HW] Choose between synthetic and real raw mode
501 Format: <bool> (0 = real, 1 = synthetic (default))
503 atkbd.softrepeat= [HW]
504 Use software keyboard repeat
506 audit= [KNL] Enable the audit sub-system
507 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
508 0 - kernel audit is disabled and can not be enabled
509 until the next reboot
510 unset - kernel audit is initialized but disabled and
511 will be fully enabled by the userspace auditd.
512 1 - kernel audit is initialized and partially enabled,
513 storing at most audit_backlog_limit messages in
514 RAM until it is fully enabled by the userspace
518 audit_backlog_limit= [KNL] Set the audit queue size limit.
519 Format: <int> (must be >=0)
522 baycom_epp= [HW,AX25]
525 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
527 See header of drivers/net/hamradio/baycom_par.c.
529 baycom_ser_fdx= [HW,AX25]
530 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
531 Format: <io>,<irq>,<mode>[,<baud>]
532 See header of drivers/net/hamradio/baycom_ser_fdx.c.
534 baycom_ser_hdx= [HW,AX25]
535 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
536 Format: <io>,<irq>,<mode>
537 See header of drivers/net/hamradio/baycom_ser_hdx.c.
539 blkdevparts= Manual partition parsing of block device(s) for
540 embedded devices based on command line input.
541 See Documentation/block/cmdline-partition.txt
543 boot_delay= Milliseconds to delay each printk during boot.
544 Values larger than 10 seconds (10000) are changed to
548 bootmem_debug [KNL] Enable bootmem allocator debug messages.
550 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
551 bttv.radio= Most important insmod options are available as
553 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
556 bulk_remove=off [PPC] This parameter disables the use of the pSeries
557 firmware feature for flushing multiple hpte entries
560 c101= [NET] Moxa C101 synchronous serial card
562 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
563 Sometimes CPU hardware bugs make them report the cache
564 size incorrectly. The kernel will attempt work arounds
565 to fix known problems, but for some CPUs it is not
566 possible to determine what the correct size should be.
567 This option provides an override for these situations.
569 ca_keys= [KEYS] This parameter identifies a specific key(s) on
570 the system trusted keyring to be used for certificate
572 format: { id:<keyid> | builtin }
574 cca= [MIPS] Override the kernel pages' cache coherency
575 algorithm. Accepted values range from 0 to 7
576 inclusive. See arch/mips/include/asm/pgtable-bits.h
577 for platform specific values (SB1, Loongson3 and
580 ccw_timeout_log [S390]
581 See Documentation/s390/CommonIO for details.
583 cgroup_disable= [KNL] Disable a particular controller
584 Format: {name of the controller(s) to disable}
585 The effects of cgroup_disable=foo are:
586 - foo isn't auto-mounted if you mount all cgroups in
588 - foo isn't visible as an individually mountable
590 {Currently only "memory" controller deal with this and
591 cut the overhead, others just disable the usage. So
592 only cgroup_disable=memory is actually worthy}
594 checkreqprot [SELINUX] Set initial checkreqprot flag value.
595 Format: { "0" | "1" }
596 See security/selinux/Kconfig help text.
597 0 -- check protection applied by kernel (includes
598 any implied execute protection).
599 1 -- check protection requested by application.
600 Default value is set via a kernel config option.
601 Value can be changed at runtime via
602 /selinux/checkreqprot.
605 See Documentation/s390/CommonIO for details.
608 Prevents the clock framework from automatically gating
609 clocks that have not been explicitly enabled by a Linux
610 device driver but are enabled in hardware at reset or
611 by the bootloader/firmware. Note that this does not
612 force such clocks to be always-on nor does it reserve
613 those clocks in any way. This parameter is useful for
614 debug and development, but should not be needed on a
615 platform with proper driver support. For more
616 information, see Documentation/clk.txt.
618 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
620 Forces specified clocksource (if available) to be used
621 when calculating gettimeofday(). If specified
622 clocksource is not available, it defaults to PIT.
623 Format: { pit | tsc | cyclone | pmtmr }
625 clocksource= Override the default clocksource
627 Override the default clocksource and use the clocksource
628 with the name specified.
629 Some clocksource names to choose from, depending on
631 [all] jiffies (this is the base, fallback clocksource)
633 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
634 pxa_timer,timer3,32k_counter,timer0_1
636 [X86-32] pit,hpet,tsc;
637 scx200_hrt on Geode; cyclone on IBM x440
645 clearcpuid=BITNUM [X86]
646 Disable CPUID feature X for the kernel. See
647 arch/x86/include/asm/cpufeature.h for the valid bit
648 numbers. Note the Linux specific bits are not necessarily
649 stable over kernel options, but the vendor specific
651 Also note that user programs calling CPUID directly
652 or using the feature without checking anything
653 will still see it. This just prevents it from
654 being used by the kernel or shown in /proc/cpuinfo.
655 Also note the kernel might malfunction if you disable
658 cma=nn[MG]@[start[MG][-end[MG]]]
660 Sets the size of kernel global memory area for
661 contiguous memory allocations and optionally the
662 placement constraint by the physical address range of
663 memory allocations. A value of 0 disables CMA
664 altogether. For more information, see
665 include/linux/dma-contiguous.h
667 cmo_free_hint= [PPC] Format: { yes | no }
668 Specify whether pages are marked as being inactive
669 when they are freed. This is used in CMO environments
670 to determine OS memory pressure for page stealing by
674 coherent_pool=nn[KMG] [ARM,KNL]
675 Sets the size of memory pool for coherent, atomic dma
676 allocations, by default set to 256K.
678 code_bytes [X86] How many bytes of object code to print
683 com20020= [HW,NET] ARCnet - COM20020 chipset
685 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
687 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
691 ARCnet - COM90xx chipset (memory-mapped buffers)
692 Format: <io>[,<irq>[,<memstart>]]
694 condev= [HW,S390] console device
697 console= [KNL] Output console device and options.
699 tty<n> Use the virtual console device <n>.
703 Use the specified serial port. The options are of
704 the form "bbbbpnf", where "bbbb" is the baud rate,
705 "p" is parity ("n", "o", or "e"), "n" is number of
706 bits, and "f" is flow control ("r" for RTS or
707 omit it). Default is "9600n8".
709 See Documentation/serial-console.txt for more
711 Documentation/networking/netconsole.txt for an
714 uart[8250],io,<addr>[,options]
715 uart[8250],mmio,<addr>[,options]
716 Start an early, polled-mode console on the 8250/16550
717 UART at the specified I/O port or MMIO address,
718 switching to the matching ttyS device later. The
719 options are the same as for ttyS, above.
720 hvc<n> Use the hypervisor console device <n>. This is for
721 both Xen and PowerPC hypervisors.
723 If the device connected to the port is not a TTY but a braille
724 device, prepend "brl," before the device type, for instance
726 For now, only VisioBraille is supported.
728 consoleblank= [KNL] The console blank (screen saver) timeout in
729 seconds. Defaults to 10*60 = 10mins. A value of 0
730 disables the blank timer.
733 [KNL] Change the default value for
734 /proc/<pid>/coredump_filter.
735 See also Documentation/filesystems/proc.txt.
737 cpuidle.off=1 [CPU_IDLE]
738 disable the cpuidle sub-system
740 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
742 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
744 crashkernel=size[KMG][@offset[KMG]]
745 [KNL] Using kexec, Linux can switch to a 'crash kernel'
746 upon panic. This parameter reserves the physical
747 memory region [offset, offset + size] for that kernel
748 image. If '@offset' is omitted, then a suitable offset
749 is selected automatically. Check
750 Documentation/kdump/kdump.txt for further details.
752 crashkernel=range1:size1[,range2:size2,...][@offset]
753 [KNL] Same as above, but depends on the memory
754 in the running system. The syntax of range is
755 start-[end] where start and end are both
756 a memory unit (amount[KMG]). See also
757 Documentation/kdump/kdump.txt for an example.
759 crashkernel=size[KMG],high
760 [KNL, x86_64] range could be above 4G. Allow kernel
761 to allocate physical memory region from top, so could
762 be above 4G if system have more than 4G ram installed.
763 Otherwise memory region will be allocated below 4G, if
765 It will be ignored if crashkernel=X is specified.
766 crashkernel=size[KMG],low
767 [KNL, x86_64] range under 4G. When crashkernel=X,high
768 is passed, kernel could allocate physical memory region
769 above 4G, that cause second kernel crash on system
770 that require some amount of low memory, e.g. swiotlb
771 requires at least 64M+32K low memory. Kernel would
772 try to allocate 72M below 4G automatically.
773 This one let user to specify own low range under 4G
774 for second kernel instead.
775 0: to disable low allocation.
776 It will be ignored when crashkernel=X,high is not used
777 or memory reserved is below 4G.
782 cs89x0_media= [HW,NET]
783 Format: { rj45 | aui | bnc }
786 See header of drivers/s390/block/dasd_devmap.c.
788 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
789 (one device per port)
790 Format: <port#>,<type>
791 See also Documentation/input/joystick-parport.txt
793 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
794 time. See Documentation/dynamic-debug-howto.txt for
795 details. Deprecated, see dyndbg.
797 debug [KNL] Enable kernel debugging (events log level).
800 [KNL] verbose self-tests
802 Print debugging info while doing the locking API
804 We default to 0 (no extra messages), setting it to
805 1 will print _a lot_ more information - normally
806 only useful to kernel developers.
808 debug_objects [KNL] Enable object debugging
811 [KNL] Disable object debugging
813 debug_guardpage_minorder=
814 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
815 parameter allows control of the order of pages that will
816 be intentionally kept free (and hence protected) by the
817 buddy allocator. Bigger value increase the probability
818 of catching random memory corruption, but reduce the
819 amount of memory for normal system use. The maximum
820 possible value is MAX_ORDER/2. Setting this parameter
821 to 1 or 2 should be enough to identify most random
822 memory corruption problems caused by bugs in kernel or
823 driver code when a CPU writes to (or reads from) a
824 random memory location. Note that there exists a class
825 of memory corruptions problems caused by buggy H/W or
826 F/W or by drivers badly programing DMA (basically when
827 memory is written at bus level and the CPU MMU is
828 bypassed) which are not detectable by
829 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
830 tracking down these problems.
832 debugpat [X86] Enable PAT debugging
834 decnet.addr= [HW,NET]
835 Format: <area>[,<node>]
836 See also Documentation/networking/decnet.txt.
839 [same as hugepagesz=] The size of the default
840 HugeTLB page size. This is the size represented by
841 the legacy /proc/ hugepages APIs, used for SHM, and
842 default size when mounting hugetlbfs filesystems.
843 Defaults to the default architecture's huge page size
847 Set number of hash buckets for dentry cache.
850 See Documentation/networking/ipv6.txt.
852 disable_cpu_apicid= [X86,APIC,SMP]
854 The number of initial APIC ID for the
855 corresponding CPU to be disabled at boot,
856 mostly used for the kdump 2nd kernel to
857 disable BSP to wake up multiple CPUs without
858 causing system reset or hang due to sending
861 disable_ddw [PPC/PSERIES]
862 Disable Dynamic DMA Window support. Use this if
863 to workaround buggy firmware.
866 See Documentation/networking/ipv6.txt.
868 disable_mtrr_cleanup [X86]
869 The kernel tries to adjust MTRR layout from continuous
870 to discrete, to make X server driver able to add WB
871 entry later. This parameter disables that.
873 disable_mtrr_trim [X86, Intel and AMD only]
874 By default the kernel will trim any uncacheable
875 memory out of your available memory pool based on
876 MTRR settings. This parameter disables that behavior,
877 possibly causing your machine to run very slowly.
879 disable_timer_pin_1 [X86]
880 Disable PIN 1 of APIC timer
881 Can be useful to work around chipset bugs.
883 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
884 this option disables the debugging code at boot.
886 dma_debug_entries=<number>
887 This option allows to tune the number of preallocated
888 entries for DMA-API debugging code. One entry is
889 required per DMA-API allocation. Use this if the
890 DMA-API debugging code disables itself because the
891 architectural default is too low.
893 dma_debug_driver=<driver_name>
894 With this option the DMA-API debugging driver
895 filter feature can be enabled at boot time. Just
896 pass the driver to filter for as the parameter.
897 The filter can be disabled or changed to another
898 driver later using sysfs.
900 drm_kms_helper.edid_firmware=[<connector>:]<file>
901 Broken monitors, graphic adapters and KVMs may
902 send no or incorrect EDID data sets. This parameter
903 allows to specify an EDID data set in the
904 /lib/firmware directory that is used instead.
905 Generic built-in EDID data sets are used, if one of
906 edid/1024x768.bin, edid/1280x1024.bin,
907 edid/1680x1050.bin, or edid/1920x1080.bin is given
908 and no file with the same name exists. Details and
909 instructions how to build your own EDID data are
910 available in Documentation/EDID/HOWTO.txt. An EDID
911 data set will only be used for a particular connector,
912 if its name and a colon are prepended to the EDID
917 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
918 module.dyndbg[="val"]
919 Enable debug messages at boot time. See
920 Documentation/dynamic-debug-howto.txt for details.
922 early_ioremap_debug [KNL]
923 Enable debug messages in early_ioremap support. This
924 is useful for tracking down temporary early mappings
925 which are not unmapped.
927 earlycon= [KNL] Output early console device and options.
930 Start an early, polled-mode console on a cadence serial
931 port at the specified address. The cadence serial port
932 must already be setup and configured. Options are not
935 uart[8250],io,<addr>[,options]
936 uart[8250],mmio,<addr>[,options]
937 uart[8250],mmio32,<addr>[,options]
938 Start an early, polled-mode console on the 8250/16550
939 UART at the specified I/O port or MMIO address.
940 MMIO inter-register address stride is either 8-bit
941 (mmio) or 32-bit (mmio32).
942 The options are the same as for ttyS, above.
945 Start an early, polled-mode console on a pl011 serial
946 port at the specified address. The pl011 serial port
947 must already be setup and configured. Options are not
951 Start an early, polled-mode console on an msm serial
952 port at the specified address. The serial port
953 must already be setup and configured. Options are not
957 Start an early, polled-mode console on an msm serial
958 dm port at the specified address. The serial port
959 must already be setup and configured. Options are not
962 smh Use ARM semihosting calls for early console.
964 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
968 earlyprintk=serial[,ttySn[,baudrate]]
969 earlyprintk=serial[,0x...[,baudrate]]
970 earlyprintk=ttySn[,baudrate]
971 earlyprintk=dbgp[debugController#]
973 earlyprintk is useful when the kernel crashes before
974 the normal console is initialized. It is not enabled by
975 default because it has some cosmetic problems.
977 Append ",keep" to not disable it when the real console
980 Only one of vga, efi, serial, or usb debug port can
983 Currently only ttyS0 and ttyS1 may be specified by
984 name. Other I/O ports may be explicitly specified
985 on some architectures (x86 and arm at least) by
986 replacing ttySn with an I/O port address, like this:
987 earlyprintk=serial,0x1008,115200
988 You can find the port for a given device in
989 /proc/tty/driver/serial:
990 2: uart:ST16650V2 port:00001008 irq:18 ...
992 Interaction with the standard serial driver is not
995 The VGA and EFI output is eventually overwritten by
998 The xen output can only be used by Xen PV guests.
1000 edac_report= [HW,EDAC] Control how to report EDAC event
1001 Format: {"on" | "off" | "force"}
1002 on: enable EDAC to report H/W event. May be overridden
1003 by other higher priority error reporting module.
1004 off: disable H/W event reporting through EDAC.
1005 force: enforce the use of EDAC to report H/W event.
1008 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1011 This is designed to be used in conjunction with
1012 the boot argument: earlyprintk=vga
1015 Format: {"off" | "on" | "skip[mbr]"}
1018 Format: { "old_map", "nochunk", "noruntime" }
1019 old_map [X86-64]: switch to the old ioremap-based EFI
1020 runtime services mapping. 32-bit still uses this one by
1022 nochunk: disable reading files in "chunks" in the EFI
1023 boot stub, as chunking can cause problems with some
1024 firmware implementations.
1025 noruntime : disable EFI runtime services support
1027 efi_no_storage_paranoia [EFI; X86]
1028 Using this parameter you can use more than 50% of
1029 your efi variable storage. Use this parameter only if
1030 you are really sure that your UEFI does sane gc and
1031 fulfills the spec otherwise your board may brick.
1033 eisa_irq_edge= [PARISC,HW]
1034 See header of drivers/parisc/eisa.c.
1037 See comment before function elanfreq_setup() in
1038 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1041 Format: {"cfq" | "deadline" | "noop"}
1042 See Documentation/block/cfq-iosched.txt and
1043 Documentation/block/deadline-iosched.txt for details.
1045 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1046 Specifies physical address of start of kernel core
1047 image elf header and optionally the size. Generally
1048 kexec loader will pass this option to capture kernel.
1049 See Documentation/kdump/kdump.txt for details.
1051 enable_mtrr_cleanup [X86]
1052 The kernel tries to adjust MTRR layout from continuous
1053 to discrete, to make X server driver able to add WB
1054 entry later. This parameter enables that.
1056 enable_timer_pin_1 [X86]
1057 Enable PIN 1 of APIC timer
1058 Can be useful to work around chipset bugs
1059 (in particular on some ATI chipsets).
1060 The kernel tries to set a reasonable default.
1062 enforcing [SELINUX] Set initial enforcing status.
1064 See security/selinux/Kconfig help text.
1065 0 -- permissive (log only, no denials).
1066 1 -- enforcing (deny and log).
1068 Value can be changed at runtime via /selinux/enforce.
1071 Disable Error Record Serialization Table (ERST)
1074 ether= [HW,NET] Ethernet cards parameters
1075 This option is obsoleted by the "netdev=" option, which
1076 has equivalent usage. See its documentation for details.
1080 Permit 'security.evm' to be updated regardless of
1081 current integrity status.
1085 fail_make_request=[KNL]
1086 General fault injection mechanism.
1087 Format: <interval>,<probability>,<space>,<times>
1088 See also Documentation/fault-injection/.
1091 See Documentation/blockdev/floppy.txt.
1093 force_pal_cache_flush
1094 [IA-64] Avoid check_sal_cache_flush which may hang on
1095 buggy SAL_CACHE_FLUSH implementations. Using this
1096 parameter will force ia64_sal_cache_flush to call
1097 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1100 Forcefully enable Physical Address Extension (PAE).
1101 Many Pentium M systems disable PAE but may have a
1102 functionally usable PAE implementation.
1103 Warning: use of this parameter will taint the kernel
1104 and may cause unknown problems.
1107 [FTRACE] will set and start the specified tracer
1108 as early as possible in order to facilitate early
1111 ftrace_dump_on_oops[=orig_cpu]
1112 [FTRACE] will dump the trace buffers on oops.
1113 If no parameter is passed, ftrace will dump
1114 buffers of all CPUs, but if you pass orig_cpu, it will
1115 dump only the buffer of the CPU that triggered the
1118 ftrace_filter=[function-list]
1119 [FTRACE] Limit the functions traced by the function
1120 tracer at boot up. function-list is a comma separated
1121 list of functions. This list can be changed at run
1122 time by the set_ftrace_filter file in the debugfs
1125 ftrace_notrace=[function-list]
1126 [FTRACE] Do not trace the functions specified in
1127 function-list. This list can be changed at run time
1128 by the set_ftrace_notrace file in the debugfs
1131 ftrace_graph_filter=[function-list]
1132 [FTRACE] Limit the top level callers functions traced
1133 by the function graph tracer at boot up.
1134 function-list is a comma separated list of functions
1135 that can be changed at run time by the
1136 set_graph_function file in the debugfs tracing directory.
1138 ftrace_graph_notrace=[function-list]
1139 [FTRACE] Do not trace from the functions specified in
1140 function-list. This list is a comma separated list of
1141 functions that can be changed at run time by the
1142 set_graph_notrace file in the debugfs tracing directory.
1145 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1146 support via parallel port (up to 5 devices per port)
1147 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1148 See also Documentation/input/joystick-parport.txt
1152 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1156 gcov_persist= [GCOV] When non-zero (default), profiling data for
1157 kernel modules is saved and remains accessible via
1158 debugfs, even when the module is unloaded/reloaded.
1159 When zero, profiling data is discarded and associated
1160 debugfs files are removed at module unload time.
1162 gpt [EFI] Forces disk with valid GPT signature but
1163 invalid Protective MBR to be treated as GPT. If the
1164 primary GPT is corrupted, it enables the backup/alternate
1165 GPT to be used instead.
1167 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1168 the "Enable 0" bit of the configuration register.
1171 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1172 the "Enable 0" bit of the configuration register.
1175 grcan.select= [HW] Select which physical interface to use.
1178 grcan.txsize= [HW] Sets the size of the tx buffer.
1179 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1181 grcan.rxsize= [HW] Sets the size of the rx buffer.
1182 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1185 hashdist= [KNL,NUMA] Large hashes allocated during boot
1186 are distributed across NUMA nodes. Defaults on
1187 for 64-bit NUMA, off otherwise.
1188 Format: 0 | 1 (for off | on)
1190 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1192 hd= [EIDE] (E)IDE hard drive subsystem geometry
1193 Format: <cyl>,<head>,<sect>
1196 Disable Hardware Error Source Table (HEST) support;
1197 corresponding firmware-first mode error processing
1198 logic will be disabled.
1200 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1201 size of <nn>. This works even on boxes that have no
1202 highmem otherwise. This also works to reduce highmem
1203 size on bigger boxes.
1205 highres= [KNL] Enable/disable high resolution timer mode.
1206 Valid parameters: "on", "off"
1210 See Documentation/isdn/README.HiSax.
1214 hpet= [X86-32,HPET] option to control HPET usage
1215 Format: { enable (default) | disable | force |
1217 disable: disable HPET and use PIT instead
1218 force: allow force enabled of undocumented chips (ICH4,
1220 verbose: show contents of HPET registers during setup
1222 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1223 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1225 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1226 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1227 On x86-64 and powerpc, this option can be specified
1228 multiple times interleaved with hugepages= to reserve
1229 huge pages of different sizes. Valid pages sizes on
1230 x86-64 are 2M (when the CPU supports "pse") and 1G
1231 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1233 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1234 terminal devices. Valid values: 0..8
1235 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1236 If specified, z/VM IUCV HVC accepts connections
1237 from listed z/VM user IDs only.
1239 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1240 hardware thread id mappings.
1241 Format: <cpu>:<hwthread>
1244 Do not unregister boot console at start. This is only
1245 useful for debugging when something happens in the window
1246 between unregistering the boot console and initializing
1249 i2c_bus= [HW] Override the default board specific I2C bus speed
1250 or register an additional I2C bus that is not
1251 registered from board initialization code.
1255 i8042.debug [HW] Toggle i8042 debug mode
1256 i8042.direct [HW] Put keyboard port into non-translated mode
1257 i8042.dumbkbd [HW] Pretend that controller can only read data from
1258 keyboard and cannot control its state
1259 (Don't attempt to blink the leds)
1260 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1261 i8042.nokbd [HW] Don't check/create keyboard port
1262 i8042.noloop [HW] Disable the AUX Loopback command while probing
1264 i8042.nomux [HW] Don't check presence of an active multiplexing
1266 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1268 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1269 i8042.reset [HW] Reset the controller during init and cleanup
1270 i8042.unlock [HW] Unlock (ignore) the keylock
1274 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1275 indicates that the driver is running on unsupported
1277 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1278 does not match list of supported models.
1280 [HW] Report power status in /proc/i8k
1281 (disabled by default)
1282 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1285 i915.invert_brightness=
1286 [DRM] Invert the sense of the variable that is used to
1287 set the brightness of the panel backlight. Normally a
1288 brightness value of 0 indicates backlight switched off,
1289 and the maximum of the brightness value sets the backlight
1290 to maximum brightness. If this parameter is set to 0
1291 (default) and the machine requires it, or this parameter
1292 is set to 1, a brightness value of 0 sets the backlight
1293 to maximum brightness, and the maximum of the brightness
1294 value switches the backlight off.
1295 -1 -- never invert brightness
1296 0 -- machine default
1297 1 -- force brightness inversion
1300 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1302 ide-core.nodma= [HW] (E)IDE subsystem
1303 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1304 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1305 .cdrom .chs .ignore_cable are additional options
1306 See Documentation/ide/ide.txt.
1308 ide-generic.probe-mask= [HW] (E)IDE subsystem
1310 Probe mask for legacy ISA IDE ports. Depending on
1311 platform up to 6 ports are supported, enabled by
1312 setting corresponding bits in the mask to 1. The
1313 default value is 0x0, which has a special meaning.
1314 On systems that have PCI, it triggers scanning the
1315 PCI bus for the first and the second port, which
1316 are then probed. On systems without PCI the value
1317 of 0x0 enables probing the two first ports as if it
1320 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1321 Claim all unknown PCI IDE storage controllers.
1324 Format: idle=poll, idle=halt, idle=nomwait
1325 Poll forces a polling idle loop that can slightly
1326 improve the performance of waking up a idle CPU, but
1327 will use a lot of power and make the system run hot.
1329 idle=halt: Halt is forced to be used for CPU idle.
1330 In such case C2/C3 won't be used again.
1331 idle=nomwait: Disable mwait for CPU C-states
1333 ignore_loglevel [KNL]
1334 Ignore loglevel setting - this will print /all/
1335 kernel messages to the console. Useful for debugging.
1336 We also add it as printk module parameter, so users
1337 could change it dynamically, usually by
1338 /sys/module/printk/parameters/ignore_loglevel.
1340 ihash_entries= [KNL]
1341 Set number of hash buckets for inode cache.
1343 ima_appraise= [IMA] appraise integrity measurements
1344 Format: { "off" | "enforce" | "fix" | "log" }
1347 ima_appraise_tcb [IMA]
1348 The builtin appraise policy appraises all files
1352 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1356 The list of supported hash algorithms is defined
1357 in crypto/hash_info.h.
1360 Load a policy which meets the needs of the Trusted
1361 Computing Base. This means IMA will measure all
1362 programs exec'd, files mmap'd for exec, and all files
1363 opened for read by uid=0.
1366 Select one of defined IMA measurements template formats.
1367 Formats: { "ima" | "ima-ng" }
1370 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1371 Format: <min_file_size>
1372 Set the minimal file size for using asynchronous hash.
1373 If left unspecified, ahash usage is disabled.
1375 ahash performance varies for different data sizes on
1376 different crypto accelerators. This option can be used
1377 to achieve the best performance for a particular HW.
1379 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1381 Set hashing buffer size. Default: 4k.
1383 ahash performance varies for different chunk sizes on
1384 different crypto accelerators. This option can be used
1385 to achieve best performance for particular HW.
1389 Run specified binary instead of /sbin/init as init
1392 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1393 for working out where the kernel is dying during
1396 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1397 initcall functions. Useful for debugging built-in
1398 modules and initcalls.
1400 initrd= [BOOT] Specify the location of the initial ramdisk
1402 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1405 int_pln_enable [x86] Enable power limit notification interrupt
1407 integrity_audit=[IMA]
1408 Format: { "0" | "1" }
1409 0 -- basic integrity auditing messages. (Default)
1410 1 -- additional integrity auditing messages.
1412 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1414 Enable intel iommu driver.
1416 Disable intel iommu driver.
1417 igfx_off [Default Off]
1418 By default, gfx is mapped as normal device. If a gfx
1419 device has a dedicated DMAR unit, the DMAR unit is
1420 bypassed by not enabling DMAR with this option. In
1421 this case, gfx device will use physical address for
1424 With this option iommu will not optimize to look
1425 for io virtual address below 32-bit forcing dual
1426 address cycle on pci bus for cards supporting greater
1427 than 32-bit addressing. The default is to look
1428 for translation below 32-bit and if not available
1429 then look in the higher range.
1430 strict [Default Off]
1431 With this option on every unmap_single operation will
1432 result in a hardware IOTLB flush operation as opposed
1433 to batching them for performance.
1434 sp_off [Default Off]
1435 By default, super page will be supported if Intel IOMMU
1436 has the capability. With this option, super page will
1439 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1440 0 disables intel_idle and fall back on acpi_idle.
1441 1 to 6 specify maximum depth of C-state.
1445 Do not enable intel_pstate as the default
1446 scaling driver for the supported processors
1448 Do not enable hardware P state control (HWP)
1451 intremap= [X86-64, Intel-IOMMU]
1452 on enable Interrupt Remapping (default)
1453 off disable Interrupt Remapping
1454 nosid disable Source ID checking
1456 BIOS x2APIC opt-out request will be ignored
1458 iomem= Disable strict checking of access to MMIO memory
1459 strict regions from userspace.
1476 io7= [HW] IO7 for Marvel based alpha systems
1477 See comment before marvel_specify_io7 in
1478 arch/alpha/kernel/core_marvel.c.
1480 io_delay= [X86] I/O delay method
1482 Standard port 0x80 based delay
1484 Alternate port 0xed based delay (needed on some systems)
1486 Simple two microseconds delay
1491 See Documentation/filesystems/nfs/nfsroot.txt.
1494 When an interrupt is not handled search all handlers
1495 for it. Intended to get systems with badly broken
1499 When an interrupt is not handled search all handlers
1500 for it. Also check all handlers each timer
1501 interrupt. Intended to get systems with badly broken
1505 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1507 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1509 <cpu number>,...,<cpu number>
1511 <cpu number>-<cpu number>
1512 (must be a positive range in ascending order)
1514 <cpu number>,...,<cpu number>-<cpu number>
1516 This option can be used to specify one or more CPUs
1517 to isolate from the general SMP balancing and scheduling
1518 algorithms. You can move a process onto or off an
1519 "isolated" CPU via the CPU affinity syscalls or cpuset.
1520 <cpu number> begins at 0 and the maximum value is
1521 "number of CPUs in system - 1".
1523 This option is the preferred way to isolate CPUs. The
1524 alternative -- manually setting the CPU mask of all
1525 tasks in the system -- can cause problems and
1526 suboptimal load balancer performance.
1530 ivrs_ioapic [HW,X86_64]
1531 Provide an override to the IOAPIC-ID<->DEVICE-ID
1532 mapping provided in the IVRS ACPI table. For
1533 example, to map IOAPIC-ID decimal 10 to
1534 PCI device 00:14.0 write the parameter as:
1535 ivrs_ioapic[10]=00:14.0
1537 ivrs_hpet [HW,X86_64]
1538 Provide an override to the HPET-ID<->DEVICE-ID
1539 mapping provided in the IVRS ACPI table. For
1540 example, to map HPET-ID decimal 0 to
1541 PCI device 00:14.0 write the parameter as:
1542 ivrs_hpet[0]=00:14.0
1544 js= [HW,JOY] Analog joystick
1545 See Documentation/input/joystick.txt.
1548 Enable/disable kernel and module base offset ASLR
1549 (Address Space Layout Randomization) if built into
1550 the kernel. When CONFIG_HIBERNATION is selected,
1551 kASLR is disabled by default. When kASLR is enabled,
1552 hibernation will be disabled.
1556 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1557 specifies the amount of memory usable by the kernel
1558 for non-movable allocations. The requested amount is
1559 spread evenly throughout all nodes in the system. The
1560 remaining memory in each node is used for Movable
1561 pages. In the event, a node is too small to have both
1562 kernelcore and Movable pages, kernelcore pages will
1563 take priority and other nodes will have a larger number
1564 of Movable pages. The Movable zone is used for the
1565 allocation of pages that may be reclaimed or moved
1566 by the page migration subsystem. This means that
1567 HugeTLB pages may not be allocated from this zone.
1568 Note that allocations like PTEs-from-HighMem still
1569 use the HighMem zone if it exists, and the Normal
1570 zone if it does not.
1572 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1573 Format: <Controller#>[,poll interval]
1574 The controller # is the number of the ehci usb debug
1575 port as it is probed via PCI. The poll interval is
1576 optional and is the number seconds in between
1577 each poll cycle to the debug port in case you need
1578 the functionality for interrupting the kernel with
1579 gdb or control-c on the dbgp connection. When
1580 not using this parameter you use sysrq-g to break into
1581 the kernel debugger.
1583 kgdboc= [KGDB,HW] kgdb over consoles.
1584 Requires a tty driver that supports console polling,
1585 or a supported polling keyboard driver (non-usb).
1586 Serial only format: <serial_device>[,baud]
1587 keyboard only format: kbd
1588 keyboard and serial format: kbd,<serial_device>[,baud]
1589 Optional Kernel mode setting:
1590 kms, kbd format: kms,kbd
1591 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1593 kgdbwait [KGDB] Stop kernel execution and enter the
1594 kernel debugger at the earliest opportunity.
1596 kmac= [MIPS] korina ethernet MAC address.
1597 Configure the RouterBoard 532 series on-chip
1598 Ethernet adapter MAC address.
1600 kmemleak= [KNL] Boot-time kmemleak enable/disable
1601 Valid arguments: on, off
1603 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1606 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1607 Valid arguments: 0, 1, 2
1608 kmemcheck=0 (disabled)
1609 kmemcheck=1 (enabled)
1610 kmemcheck=2 (one-shot mode)
1611 Default: 2 (one-shot mode)
1613 kstack=N [X86] Print N words from the kernel stack
1616 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1617 Default is 0 (don't ignore, but inject #GP)
1619 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1623 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1624 Default is 1 (enabled)
1626 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1628 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1630 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1631 (virtualized MMU) support on capable Intel chips.
1632 Default is 1 (enabled)
1634 kvm-intel.emulate_invalid_guest_state=
1635 [KVM,Intel] Enable emulation of invalid guest states
1636 Default is 0 (disabled)
1638 kvm-intel.flexpriority=
1639 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1640 Default is 1 (enabled)
1643 [KVM,Intel] Enable VMX nesting (nVMX).
1644 Default is 0 (disabled)
1646 kvm-intel.unrestricted_guest=
1647 [KVM,Intel] Disable unrestricted guest feature
1648 (virtualized real and unpaged mode) on capable
1649 Intel chips. Default is 1 (enabled)
1651 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1652 feature (tagged TLBs) on capable Intel chips.
1653 Default is 1 (enabled)
1659 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1662 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1663 value for LAPIC timer one-shot implementation. Default
1664 back to the programmable timer unit in the LAPIC.
1666 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1669 libata.dma= [LIBATA] DMA control
1670 libata.dma=0 Disable all PATA and SATA DMA
1671 libata.dma=1 PATA and SATA Disk DMA only
1672 libata.dma=2 ATAPI (CDROM) DMA only
1673 libata.dma=4 Compact Flash DMA only
1674 Combinations also work, so libata.dma=3 enables DMA
1675 for disks and CDROMs, but not CFs.
1677 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1678 libata.ignore_hpa=0 keep BIOS limits (default)
1679 libata.ignore_hpa=1 ignore limits, using full disk
1681 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1685 libata.force= [LIBATA] Force configurations. The format is comma
1686 separated list of "[ID:]VAL" where ID is
1687 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1688 matching port, link or device. Basically, it matches
1689 the ATA ID string printed on console by libata. If
1690 the whole ID part is omitted, the last PORT and DEVICE
1691 values are used. If ID hasn't been specified yet, the
1692 configuration applies to all ports, links and devices.
1694 If only DEVICE is omitted, the parameter applies to
1695 the port and all links and devices behind it. DEVICE
1696 number of 0 either selects the first device or the
1697 first fan-out link behind PMP device. It does not
1698 select the host link. DEVICE number of 15 selects the
1699 host link and device attached to it.
1701 The VAL specifies the configuration to force. As long
1702 as there's no ambiguity shortcut notation is allowed.
1703 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1704 The following configurations can be forced.
1706 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1707 Any ID with matching PORT is used.
1709 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1711 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1712 udma[/][16,25,33,44,66,100,133] notation is also
1715 * [no]ncq: Turn on or off NCQ.
1717 * nohrst, nosrst, norst: suppress hard, soft
1720 * rstonce: only attempt one reset during
1721 hot-unplug link recovery
1723 * dump_id: dump IDENTIFY data.
1725 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1727 * disable: Disable this device.
1729 If there are multiple matching configurations changing
1730 the same attribute, the last one is used.
1732 memblock=debug [KNL] Enable memblock debug messages.
1734 load_ramdisk= [RAM] List of ramdisks to load from floppy
1735 See Documentation/blockdev/ramdisk.txt.
1737 lockd.nlm_grace_period=P [NFS] Assign grace period.
1740 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1743 lockd.nlm_timeout=T [NFS] Assign timeout value.
1746 lockd.nlm_udpport=M [NFS] Assign UDP port.
1749 locktorture.nreaders_stress= [KNL]
1750 Set the number of locking read-acquisition kthreads.
1751 Defaults to being automatically set based on the
1752 number of online CPUs.
1754 locktorture.nwriters_stress= [KNL]
1755 Set the number of locking write-acquisition kthreads.
1757 locktorture.onoff_holdoff= [KNL]
1758 Set time (s) after boot for CPU-hotplug testing.
1760 locktorture.onoff_interval= [KNL]
1761 Set time (s) between CPU-hotplug operations, or
1762 zero to disable CPU-hotplug testing.
1764 locktorture.shuffle_interval= [KNL]
1765 Set task-shuffle interval (jiffies). Shuffling
1766 tasks allows some CPUs to go into dyntick-idle
1767 mode during the locktorture test.
1769 locktorture.shutdown_secs= [KNL]
1770 Set time (s) after boot system shutdown. This
1771 is useful for hands-off automated testing.
1773 locktorture.stat_interval= [KNL]
1774 Time (s) between statistics printk()s.
1776 locktorture.stutter= [KNL]
1777 Time (s) to stutter testing, for example,
1778 specifying five seconds causes the test to run for
1779 five seconds, wait for five seconds, and so on.
1780 This tests the locking primitive's ability to
1781 transition abruptly to and from idle.
1783 locktorture.torture_runnable= [BOOT]
1784 Start locktorture running at boot time.
1786 locktorture.torture_type= [KNL]
1787 Specify the locking implementation to test.
1789 locktorture.verbose= [KNL]
1790 Enable additional printk() statements.
1792 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1795 loglevel= All Kernel Messages with a loglevel smaller than the
1796 console loglevel will be printed to the console. It can
1797 also be changed with klogd or other programs. The
1798 loglevels are defined as follows:
1800 0 (KERN_EMERG) system is unusable
1801 1 (KERN_ALERT) action must be taken immediately
1802 2 (KERN_CRIT) critical conditions
1803 3 (KERN_ERR) error conditions
1804 4 (KERN_WARNING) warning conditions
1805 5 (KERN_NOTICE) normal but significant condition
1806 6 (KERN_INFO) informational
1807 7 (KERN_DEBUG) debug-level messages
1809 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1810 in bytes. n must be a power of two and greater
1811 than the minimal size. The minimal size is defined
1812 by LOG_BUF_SHIFT kernel config parameter. There is
1813 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1814 that allows to increase the default size depending on
1815 the number of CPUs. See init/Kconfig for more details.
1817 logo.nologo [FB] Disables display of the built-in Linux logo.
1818 This may be used to provide more screen space for
1819 kernel log messages and is useful when debugging
1820 kernel boot problems.
1822 lp=0 [LP] Specify parallel ports to use, e.g,
1823 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1824 lp=reset first parallel port). 'lp=0' disables the
1825 lp=auto printer driver. 'lp=reset' (which can be
1826 specified in addition to the ports) causes
1827 attached printers to be reset. Using
1828 lp=port1,port2,... specifies the parallel ports
1829 to associate lp devices with, starting with
1830 lp0. A port specification may be 'none' to skip
1831 that lp device, or a parport name such as
1832 'parport0'. Specifying 'lp=auto' instead of a
1833 port specification list means that device IDs
1834 from each port should be examined, to see if
1835 an IEEE 1284-compliant printer is attached; if
1836 so, the driver will manage that printer.
1837 See also header of drivers/char/lp.c.
1840 Sets loops_per_jiffy to given constant, thus avoiding
1841 time-consuming boot-time autodetection (up to 250 ms per
1842 CPU). 0 enables autodetection (default). To determine
1843 the correct value for your kernel, boot with normal
1844 autodetection and see what value is printed. Note that
1845 on SMP systems the preset will be applied to all CPUs,
1846 which is likely to cause problems if your CPUs need
1847 significantly divergent settings. An incorrect value
1848 will cause delays in the kernel to be wrong, leading to
1849 unpredictable I/O errors and other breakage. Although
1850 unlikely, in the extreme case this might damage your
1854 Format: <io>,<irq>,<dma>
1856 machvec= [IA-64] Force the use of a particular machine-vector
1857 (machvec) in a generic kernel.
1858 Example: machvec=hpzx1_swiotlb
1860 machtype= [Loongson] Share the same kernel image file between different
1862 Example: machtype=lemote-yeeloong-2f-7inch
1864 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1865 than or equal to this physical address is ignored.
1867 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1868 should make use of. maxcpus=n : n >= 0 limits the
1869 kernel to using 'n' processors. n=0 is a special case,
1870 it is equivalent to "nosmp", which also disables
1873 max_loop= [LOOP] The number of loop block devices that get
1874 (loop.max_loop) unconditionally pre-created at init time. The default
1875 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1876 of statically allocating a predefined number, loop
1877 devices can be requested on-demand with the
1878 /dev/loop-control interface.
1880 mce [X86-32] Machine Check Exception
1882 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1884 md= [HW] RAID subsystems devices and level
1885 See Documentation/md.txt.
1888 Format: <first>,<last>
1889 Specifies range of consoles to be captured by the MDA.
1891 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1892 Amount of memory to be used when the kernel is not able
1893 to see the whole system memory or for test.
1894 [X86] Work as limiting max address. Use together
1895 with memmap= to avoid physical address space collisions.
1896 Without memmap= PCI devices could be placed at addresses
1897 belonging to unused RAM.
1899 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1903 [KNL,SH] Allow user to override the default size for
1904 per-device physically contiguous DMA buffers.
1906 memmap=exactmap [KNL,X86] Enable setting of an exact
1907 E820 memory map, as specified by the user.
1908 Such memmap=exactmap lines can be constructed based on
1909 BIOS output or other requirements. See the memmap=nn@ss
1912 memmap=nn[KMG]@ss[KMG]
1913 [KNL] Force usage of a specific region of memory.
1914 Region of memory to be used is from ss to ss+nn.
1916 memmap=nn[KMG]#ss[KMG]
1917 [KNL,ACPI] Mark specific memory as ACPI data.
1918 Region of memory to be marked is from ss to ss+nn.
1920 memmap=nn[KMG]$ss[KMG]
1921 [KNL,ACPI] Mark specific memory as reserved.
1922 Region of memory to be reserved is from ss to ss+nn.
1923 Example: Exclude memory from 0x18690000-0x1869ffff
1924 memmap=64K$0x18690000
1926 memmap=0x10000$0x18690000
1928 memory_corruption_check=0/1 [X86]
1929 Some BIOSes seem to corrupt the first 64k of
1930 memory when doing things like suspend/resume.
1931 Setting this option will scan the memory
1932 looking for corruption. Enabling this will
1933 both detect corruption and prevent the kernel
1934 from using the memory being corrupted.
1935 However, its intended as a diagnostic tool; if
1936 repeatable BIOS-originated corruption always
1937 affects the same memory, you can use memmap=
1938 to prevent the kernel from using that memory.
1940 memory_corruption_check_size=size [X86]
1941 By default it checks for corruption in the low
1942 64k, making this memory unavailable for normal
1943 use. Use this parameter to scan for
1944 corruption in more or less memory.
1946 memory_corruption_check_period=seconds [X86]
1947 By default it checks for corruption every 60
1948 seconds. Use this parameter to check at some
1949 other rate. 0 disables periodic checking.
1951 memtest= [KNL,X86] Enable memtest
1953 default : 0 <disable>
1954 Specifies the number of memtest passes to be
1955 performed. Each pass selects another test
1956 pattern from a given set of patterns. Memtest
1957 fills the memory with this pattern, validates
1958 memory contents and reserves bad memory
1959 regions that are detected.
1961 meye.*= [HW] Set MotionEye Camera parameters
1962 See Documentation/video4linux/meye.txt.
1964 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1965 Multi-Function General Purpose Timers on AMD Geode
1968 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1969 the BIOS has incorrectly applied a workaround. TinyBIOS
1970 version 0.98 is known to be affected, 0.99 fixes the
1971 problem by letting the user disable the workaround.
1975 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1976 physical address is ignored.
1978 mini2440= [ARM,HW,KNL]
1979 Format:[0..2][b][c][t]
1981 MINI2440 configuration specification:
1982 0 - The attached screen is the 3.5" TFT
1983 1 - The attached screen is the 7" TFT
1984 2 - The VGA Shield is attached (1024x768)
1985 Leaving out the screen size parameter will not load
1986 the TFT driver, and the framebuffer will be left
1988 b - Enable backlight. The TFT backlight pin will be
1989 linked to the kernel VESA blanking code and a GPIO
1990 LED. This parameter is not necessary when using the
1992 c - Enable the s3c camera interface.
1993 t - Reserved for enabling touchscreen support. The
1994 touchscreen support is not enabled in the mainstream
1995 kernel as of 2.6.30, a preliminary port can be found
1996 in the "bleeding edge" mini2440 support kernel at
1997 http://repo.or.cz/w/linux-2.6/mini2440.git
2000 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2001 parameter allows control of the logging verbosity for
2002 the additional memory initialisation checks. A value
2003 of 0 disables mminit logging and a level of 4 will
2004 log everything. Information is printed at KERN_DEBUG
2005 so loglevel=8 may also need to be specified.
2008 [KNL] When CONFIG_MODULE_SIG is set, this means that
2009 modules without (valid) signatures will fail to load.
2010 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2011 is always true, so this option does nothing.
2014 [MOUSE] Maximum time between finger touching and
2015 leaving touchpad surface for touch to be considered
2016 a tap and be reported as a left button click (for
2017 touchpads working in absolute mode only).
2019 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2020 reporting absolute coordinates, such as tablets
2021 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2022 reporting absolute coordinates, such as tablets
2024 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2025 is similar to kernelcore except it specifies the
2026 amount of memory used for migratable allocations.
2027 If both kernelcore and movablecore is specified,
2028 then kernelcore will be at *least* the specified
2029 value but may be more. If movablecore on its own
2030 is specified, the administrator must be careful
2031 that the amount of memory usable for all allocations
2034 movable_node [KNL,X86] Boot-time switch to enable the effects
2035 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2037 MTD_Partition= [MTD]
2038 Format: <name>,<region-number>,<size>,<offset>
2040 MTD_Region= [MTD] Format:
2041 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2044 See drivers/mtd/cmdlinepart.c.
2046 multitce=off [PPC] This parameter disables the use of the pSeries
2047 firmware feature for updating multiple TCE entries
2050 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2052 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2054 boundary - index of last SLC block on Flex-OneNAND.
2055 The remaining blocks are configured as MLC blocks.
2056 lock - Configure if Flex-OneNAND boundary should be locked.
2057 Once locked, the boundary cannot be changed.
2058 1 indicates lock status, 0 indicates unlock status.
2061 ARM/S3C2412 JIVE boot control
2063 See arch/arm/mach-s3c2412/mach-jive.c
2065 mtouchusb.raw_coordinates=
2066 [HW] Make the MicroTouch USB driver use raw coordinates
2067 ('y', default) or cooked coordinates ('n')
2069 mtrr_chunk_size=nn[KMG] [X86]
2070 used for mtrr cleanup. It is largest continuous chunk
2071 that could hold holes aka. UC entries.
2073 mtrr_gran_size=nn[KMG] [X86]
2074 Used for mtrr cleanup. It is granularity of mtrr block.
2076 Large value could prevent small alignment from
2079 mtrr_spare_reg_nr=n [X86]
2081 Range: 0,7 : spare reg number
2083 Used for mtrr cleanup. It is spare mtrr entries number.
2084 Set to 2 or more if your graphical card needs more.
2086 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2088 netdev= [NET] Network devices parameters
2089 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2090 Note that mem_start is often overloaded to mean
2091 something different and driver-specific.
2092 This usage is only documented in each driver source
2096 [NETFILTER] Enable connection tracking flow accounting
2097 0 to disable accounting
2098 1 to enable accounting
2101 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2102 See Documentation/filesystems/nfs/nfsroot.txt.
2104 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2105 See Documentation/filesystems/nfs/nfsroot.txt.
2107 nfsrootdebug [NFS] enable nfsroot debugging messages.
2108 See Documentation/filesystems/nfs/nfsroot.txt.
2110 nfs.callback_tcpport=
2111 [NFS] set the TCP port on which the NFSv4 callback
2112 channel should listen.
2115 [NFS] sets the pathname to the program which is used
2116 to update the NFS client cache entries.
2118 nfs.cache_getent_timeout=
2119 [NFS] sets the timeout after which an attempt to
2120 update a cache entry is deemed to have failed.
2122 nfs.idmap_cache_timeout=
2123 [NFS] set the maximum lifetime for idmapper cache
2127 [NFS] enable 64-bit inode numbers.
2128 If zero, the NFS client will fake up a 32-bit inode
2129 number for the readdir() and stat() syscalls instead
2130 of returning the full 64-bit number.
2131 The default is to return 64-bit inode numbers.
2133 nfs.max_session_slots=
2134 [NFSv4.1] Sets the maximum number of session slots
2135 the client will attempt to negotiate with the server.
2136 This limits the number of simultaneous RPC requests
2137 that the client can send to the NFSv4.1 server.
2138 Note that there is little point in setting this
2139 value higher than the max_tcp_slot_table_limit.
2141 nfs.nfs4_disable_idmapping=
2142 [NFSv4] When set to the default of '1', this option
2143 ensures that both the RPC level authentication
2144 scheme and the NFS level operations agree to use
2145 numeric uids/gids if the mount is using the
2146 'sec=sys' security flavour. In effect it is
2147 disabling idmapping, which can make migration from
2148 legacy NFSv2/v3 systems to NFSv4 easier.
2149 Servers that do not support this mode of operation
2150 will be autodetected by the client, and it will fall
2151 back to using the idmapper.
2152 To turn off this behaviour, set the value to '0'.
2154 [NFS4] Specify an additional fixed unique ident-
2155 ification string that NFSv4 clients can insert into
2156 their nfs_client_id4 string. This is typically a
2157 UUID that is generated at system install time.
2159 nfs.send_implementation_id =
2160 [NFSv4.1] Send client implementation identification
2161 information in exchange_id requests.
2162 If zero, no implementation identification information
2164 The default is to send the implementation identification
2167 nfs.recover_lost_locks =
2168 [NFSv4] Attempt to recover locks that were lost due
2169 to a lease timeout on the server. Please note that
2170 doing this risks data corruption, since there are
2171 no guarantees that the file will remain unchanged
2172 after the locks are lost.
2173 If you want to enable the kernel legacy behaviour of
2174 attempting to recover these locks, then set this
2176 The default parameter value of '0' causes the kernel
2177 not to attempt recovery of lost locks.
2179 nfsd.nfs4_disable_idmapping=
2180 [NFSv4] When set to the default of '1', the NFSv4
2181 server will return only numeric uids and gids to
2182 clients using auth_sys, and will accept numeric uids
2183 and gids from such clients. This is intended to ease
2184 migration from NFSv2/v3.
2186 objlayoutdriver.osd_login_prog=
2187 [NFS] [OBJLAYOUT] sets the pathname to the program which
2188 is used to automatically discover and login into new
2189 osd-targets. Please see:
2190 Documentation/filesystems/pnfs.txt for more explanations
2192 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2193 when a NMI is triggered.
2194 Format: [state][,regs][,debounce][,die]
2196 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2197 Format: [panic,][nopanic,][num]
2199 0 - turn nmi_watchdog off
2200 When panic is specified, panic when an NMI watchdog
2201 timeout occurs (or 'nopanic' to override the opposite
2203 This is useful when you use a panic=... timeout and
2204 need the box quickly up again.
2206 netpoll.carrier_timeout=
2207 [NET] Specifies amount of time (in seconds) that
2208 netpoll should wait for a carrier. By default netpoll
2211 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2212 emulation library even if a 387 maths coprocessor
2216 [HW] Never suspend the console
2217 Disable suspending of consoles during suspend and
2218 hibernate operations. Once disabled, debugging
2219 messages can reach various consoles while the rest
2220 of the system is being put to sleep (ie, while
2221 debugging driver suspend/resume hooks). This may
2222 not work reliably with all consoles, but is known
2223 to work with serial and VGA consoles.
2224 To facilitate more flexible debugging, we also add
2225 console_suspend, a printk module parameter to control
2226 it. Users could use console_suspend (usually
2227 /sys/module/printk/parameters/console_suspend) to
2228 turn on/off it dynamically.
2230 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2231 caches in the slab allocator. Saves per-node memory,
2232 but will impact performance.
2236 noapic [SMP,APIC] Tells the kernel to not make use of any
2237 IOAPICs that may be present in the system.
2239 noautogroup Disable scheduler automatic task group creation.
2241 nobats [PPC] Do not use BATs for mapping kernel lowmem
2242 on "Classic" PPC cores.
2246 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2248 nodelayacct [KNL] Disable per-task delay accounting
2250 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2252 nodsp [SH] Disable hardware DSP at boot time.
2254 noefi Disable EFI runtime services support.
2259 On X86-32 available only on PAE configured kernels.
2260 noexec=on: enable non-executable mappings (default)
2261 noexec=off: disable non-executable mappings
2264 Disable SMAP (Supervisor Mode Access Prevention)
2265 even if it is supported by processor.
2268 Disable SMEP (Supervisor Mode Execution Prevention)
2269 even if it is supported by processor.
2272 This affects only 32-bit executables.
2273 noexec32=on: enable non-executable mappings (default)
2274 read doesn't imply executable mappings
2275 noexec32=off: disable non-executable mappings
2276 read implies executable mappings
2278 nofpu [SH] Disable hardware FPU at boot time.
2280 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2281 register save and restore. The kernel will only save
2282 legacy floating-point registers on task switch.
2284 noxsave [BUGS=X86] Disables x86 extended register state save
2285 and restore using xsave. The kernel will fallback to
2286 enabling legacy floating-point and sse state.
2288 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2289 register states. The kernel will fall back to use
2290 xsave to save the states. By using this parameter,
2291 performance of saving the states is degraded because
2292 xsave doesn't support modified optimization while
2293 xsaveopt supports it on xsaveopt enabled systems.
2295 noxsaves [X86] Disables xsaves and xrstors used in saving and
2296 restoring x86 extended register state in compacted
2297 form of xsave area. The kernel will fall back to use
2298 xsaveopt and xrstor to save and restore the states
2299 in standard form of xsave area. By using this
2300 parameter, xsave area per process might occupy more
2301 memory on xsaves enabled systems.
2304 on enable eager fpu restore
2305 off disable eager fpu restore
2306 auto selects the default scheme, which automatically
2307 enables eagerfpu restore for xsaveopt.
2309 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2310 wfi(ARM) instruction doesn't work correctly and not to
2311 use it. This is also useful when using JTAG debugger.
2313 no_file_caps Tells the kernel not to honor file capabilities. The
2314 only way then for a file to be executed with privilege
2315 is to be setuid root or executed by root.
2317 nohalt [IA-64] Tells the kernel not to use the power saving
2318 function PAL_HALT_LIGHT when idle. This increases
2319 power-consumption. On the positive side, it reduces
2320 interrupt wake-up latency, which may improve performance
2321 in certain environments such as networked servers or
2324 nohibernate [HIBERNATION] Disable hibernation and resume.
2326 nohz= [KNL] Boottime enable/disable dynamic ticks
2327 Valid arguments: on, off
2330 nohz_full= [KNL,BOOT]
2331 In kernels built with CONFIG_NO_HZ_FULL=y, set
2332 the specified list of CPUs whose tick will be stopped
2333 whenever possible. The boot CPU will be forced outside
2334 the range to maintain the timekeeping.
2335 The CPUs in this range must also be included in the
2338 noiotrap [SH] Disables trapped I/O port accesses.
2340 noirqdebug [X86-32] Disables the code which attempts to detect and
2341 disable unhandled interrupt sources.
2343 no_timer_check [X86,APIC] Disables the code which tests for
2344 broken timer IRQ sources.
2346 noisapnp [ISAPNP] Disables ISA PnP code.
2348 noinitrd [RAM] Tells the kernel not to load any configured
2351 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2353 [Deprecated - use intremap=off]
2357 nojitter [IA-64] Disables jitter checking for ITC timers.
2359 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2361 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2364 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2365 steal time is computed, but won't influence scheduler
2368 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2370 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2372 noltlbs [PPC] Do not use large page/tlb entries for kernel
2373 lowmem mapping on PPC40x.
2375 nomca [IA-64] Disable machine check abort handling
2377 nomce [X86-32] Machine Check Exception
2379 nomfgpt [X86-32] Disable Multi-Function General Purpose
2380 Timer usage (for AMD Geode machines).
2382 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2383 shutdown the other cpus. Instead use the REBOOT_VECTOR
2386 nomodule Disable module load
2388 nopat [X86] Disable PAT (page attribute table extension of
2389 pagetables) support.
2391 norandmaps Don't use address space randomization. Equivalent to
2392 echo 0 > /proc/sys/kernel/randomize_va_space
2394 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2396 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2397 with UP alternatives
2399 nordrand [X86] Disable kernel use of the RDRAND and
2400 RDSEED instructions even if they are supported
2401 by the processor. RDRAND and RDSEED are still
2402 available to user space applications.
2404 noresume [SWSUSP] Disables resume and restores original swap
2407 no-scroll [VGA] Disables scrollback.
2408 This is required for the Braillex ib80-piezo Braille
2409 reader made by F.H. Papenmeier (Germany).
2413 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2415 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2416 and disable the IO APIC. legacy for "maxcpus=0".
2418 nosoftlockup [KNL] Disable the soft-lockup detector.
2420 nosync [HW,M68K] Disables sync negotiation for all devices.
2422 notsc [BUGS=X86-32] Disable Time Stamp Counter
2424 nousb [USB] Disable the USB subsystem
2426 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2430 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2432 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2433 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2434 Some features depend on CPU0. Known dependencies are:
2435 1. Resume from suspend/hibernate depends on CPU0.
2436 Suspend/hibernate will fail if CPU0 is offline and you
2437 need to online CPU0 before suspend/hibernate.
2438 2. PIC interrupts also depend on CPU0. CPU0 can't be
2439 removed if a PIC interrupt is detected.
2440 It's said poweroff/reboot may depend on CPU0 on some
2441 machines although I haven't seen such issues so far
2442 after CPU0 is offline on a few tested machines.
2443 If the dependencies are under your control, you can
2444 turn on cpu0_hotplug.
2446 nptcg= [IA-64] Override max number of concurrent global TLB
2447 purges which is reported from either PAL_VM_SUMMARY or
2450 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2451 could support. nr_cpus=n : n >= 1 limits the kernel to
2452 supporting 'n' processors. Later in runtime you can not
2453 use hotplug cpu feature to put more cpu back to online.
2454 just like you compile the kernel NR_CPUS=n
2456 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2458 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2459 Allowed values are enable and disable
2461 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2462 one of ['zone', 'node', 'default'] can be specified
2463 This can be set from sysctl after boot.
2464 See Documentation/sysctl/vm.txt for details.
2466 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2467 See Documentation/debugging-via-ohci1394.txt for more
2470 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2471 Rather than timing out after 20 ms if an EC
2472 command is not properly ACKed, override the length
2473 of the timeout. We have interrupts disabled while
2474 waiting for the ACK, so if this is set too high
2475 interrupts *may* be lost!
2477 omap_mux= [OMAP] Override bootloader pin multiplexing.
2478 Format: <mux_mode0.mode_name=value>...
2479 For example, to override I2C bus2:
2480 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2482 oprofile.timer= [HW]
2483 Use timer interrupt instead of performance counters
2485 oprofile.cpu_type= Force an oprofile cpu type
2486 This might be useful if you have an older oprofile
2487 userland or if you want common events.
2488 Format: { arch_perfmon }
2489 arch_perfmon: [X86] Force use of architectural
2490 perfmon on Intel CPUs instead of the
2491 CPU specific event set.
2492 timer: [X86] Force use of architectural NMI
2493 timer mode (see also oprofile.timer
2494 for generic hr timer mode)
2495 [s390] Force legacy basic mode sampling
2496 (report cpu_type "timer")
2498 oops=panic Always panic on oopses. Default is to just kill the
2499 process, but there is a small probability of
2500 deadlocking the machine.
2501 This will also cause panics on machine check exceptions.
2502 Useful together with panic=30 to trigger a reboot.
2505 See Documentation/sound/oss/oss-parameters.txt
2507 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2508 timeout > 0: seconds before rebooting
2509 timeout = 0: wait forever
2510 timeout < 0: reboot immediately
2513 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2516 crash_kexec_post_notifiers
2517 Run kdump after running panic-notifiers and dumping
2518 kmsg. This only for the users who doubt kdump always
2519 succeeds in any situation.
2520 Note that this also increases risks of kdump failure,
2521 because some panic notifiers can make the crashed
2522 kernel more unstable.
2524 parkbd.port= [HW] Parallel port number the keyboard adapter is
2525 connected to, default is 0.
2527 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2528 0 for XT, 1 for AT (default is AT).
2531 parport= [HW,PPT] Specify parallel ports. 0 disables.
2532 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2533 Use 'auto' to force the driver to use any
2534 IRQ/DMA settings detected (the default is to
2535 ignore detected IRQ/DMA settings because of
2536 possible conflicts). You can specify the base
2537 address, IRQ, and DMA settings; IRQ and DMA
2538 should be numbers, or 'auto' (for using detected
2539 settings on that particular port), or 'nofifo'
2540 (to avoid using a FIFO even if it is detected).
2541 Parallel ports are assigned in the order they
2542 are specified on the command line, starting
2545 parport_init_mode= [HW,PPT]
2546 Configure VIA parallel port to operate in
2547 a specific mode. This is necessary on Pegasos
2548 computer where firmware has no options for setting
2549 up parallel port mode and sets it to spp.
2550 Currently this function knows 686a and 8231 chips.
2551 Format: [spp|ps2|epp|ecp|ecpepp]
2554 Halt all CPUs after the first oops has been printed for
2555 the specified number of seconds. This is to be used if
2556 your oopses keep scrolling off the screen.
2561 See header of drivers/block/paride/pcd.c.
2562 See also Documentation/blockdev/paride.txt.
2564 pci=option[,option...] [PCI] various PCI subsystem options:
2565 earlydump [X86] dump PCI config space before the kernel
2567 off [X86] don't probe for the PCI bus
2568 bios [X86-32] force use of PCI BIOS, don't access
2569 the hardware directly. Use this if your machine
2570 has a non-standard PCI host bridge.
2571 nobios [X86-32] disallow use of PCI BIOS, only direct
2572 hardware access methods are allowed. Use this
2573 if you experience crashes upon bootup and you
2574 suspect they are caused by the BIOS.
2575 conf1 [X86] Force use of PCI Configuration
2577 conf2 [X86] Force use of PCI Configuration
2579 noaer [PCIE] If the PCIEAER kernel config parameter is
2580 enabled, this kernel boot option can be used to
2581 disable the use of PCIE advanced error reporting.
2582 nodomains [PCI] Disable support for multiple PCI
2583 root domains (aka PCI segments, in ACPI-speak).
2584 nommconf [X86] Disable use of MMCONFIG for PCI
2586 check_enable_amd_mmconf [X86] check for and enable
2587 properly configured MMIO access to PCI
2588 config space on AMD family 10h CPU
2589 nomsi [MSI] If the PCI_MSI kernel config parameter is
2590 enabled, this kernel boot option can be used to
2591 disable the use of MSI interrupts system-wide.
2592 noioapicquirk [APIC] Disable all boot interrupt quirks.
2593 Safety option to keep boot IRQs enabled. This
2594 should never be necessary.
2595 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2596 primary IO-APIC for bridges that cannot disable
2597 boot IRQs. This fixes a source of spurious IRQs
2598 when the system masks IRQs.
2599 noioapicreroute [APIC] Disable workaround that uses the
2600 boot IRQ equivalent of an IRQ that connects to
2601 a chipset where boot IRQs cannot be disabled.
2602 The opposite of ioapicreroute.
2603 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2604 routing table. These calls are known to be buggy
2605 on several machines and they hang the machine
2606 when used, but on other computers it's the only
2607 way to get the interrupt routing table. Try
2608 this option if the kernel is unable to allocate
2609 IRQs or discover secondary PCI buses on your
2611 rom [X86] Assign address space to expansion ROMs.
2612 Use with caution as certain devices share
2613 address decoders between ROMs and other
2615 norom [X86] Do not assign address space to
2616 expansion ROMs that do not already have
2617 BIOS assigned address ranges.
2618 nobar [X86] Do not assign address space to the
2619 BARs that weren't assigned by the BIOS.
2620 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2621 assigned automatically to PCI devices. You can
2622 make the kernel exclude IRQs of your ISA cards
2624 pirqaddr=0xAAAAA [X86] Specify the physical address
2625 of the PIRQ table (normally generated
2626 by the BIOS) if it is outside the
2627 F0000h-100000h range.
2628 lastbus=N [X86] Scan all buses thru bus #N. Can be
2629 useful if the kernel is unable to find your
2630 secondary buses and you want to tell it
2631 explicitly which ones they are.
2632 assign-busses [X86] Always assign all PCI bus
2633 numbers ourselves, overriding
2634 whatever the firmware may have done.
2635 usepirqmask [X86] Honor the possible IRQ mask stored
2636 in the BIOS $PIR table. This is needed on
2637 some systems with broken BIOSes, notably
2638 some HP Pavilion N5400 and Omnibook XE3
2639 notebooks. This will have no effect if ACPI
2640 IRQ routing is enabled.
2641 noacpi [X86] Do not use ACPI for IRQ routing
2642 or for PCI scanning.
2643 use_crs [X86] Use PCI host bridge window information
2644 from ACPI. On BIOSes from 2008 or later, this
2645 is enabled by default. If you need to use this,
2646 please report a bug.
2647 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2648 If you need to use this, please report a bug.
2649 routeirq Do IRQ routing for all PCI devices.
2650 This is normally done in pci_enable_device(),
2651 so this option is a temporary workaround
2652 for broken drivers that don't call it.
2653 skip_isa_align [X86] do not align io start addr, so can
2654 handle more pci cards
2655 firmware [ARM] Do not re-enumerate the bus but instead
2656 just use the configuration from the
2657 bootloader. This is currently used on
2658 IXP2000 systems where the bus has to be
2659 configured a certain way for adjunct CPUs.
2660 noearly [X86] Don't do any early type 1 scanning.
2661 This might help on some broken boards which
2662 machine check when some devices' config space
2663 is read. But various workarounds are disabled
2664 and some IOMMU drivers will not work.
2665 bfsort Sort PCI devices into breadth-first order.
2666 This sorting is done to get a device
2667 order compatible with older (<= 2.4) kernels.
2668 nobfsort Don't sort PCI devices into breadth-first order.
2669 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2670 tuning and use the BIOS-configured MPS defaults.
2671 pcie_bus_safe Set every device's MPS to the largest value
2672 supported by all devices below the root complex.
2673 pcie_bus_perf Set device MPS to the largest allowable MPS
2674 based on its parent bus. Also set MRRS (Max
2675 Read Request Size) to the largest supported
2676 value (no larger than the MPS that the device
2677 or bus can support) for best performance.
2678 pcie_bus_peer2peer Set every device's MPS to 128B, which
2679 every device is guaranteed to support. This
2680 configuration allows peer-to-peer DMA between
2681 any pair of devices, possibly at the cost of
2682 reduced performance. This also guarantees
2683 that hot-added devices will work.
2684 cbiosize=nn[KMG] The fixed amount of bus space which is
2685 reserved for the CardBus bridge's IO window.
2686 The default value is 256 bytes.
2687 cbmemsize=nn[KMG] The fixed amount of bus space which is
2688 reserved for the CardBus bridge's memory
2689 window. The default value is 64 megabytes.
2692 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2693 Specifies alignment and device to reassign
2694 aligned memory resources.
2695 If <order of align> is not specified,
2696 PAGE_SIZE is used as alignment.
2697 PCI-PCI bridge can be specified, if resource
2698 windows need to be expanded.
2699 ecrc= Enable/disable PCIe ECRC (transaction layer
2700 end-to-end CRC checking).
2701 bios: Use BIOS/firmware settings. This is the
2705 hpiosize=nn[KMG] The fixed amount of bus space which is
2706 reserved for hotplug bridge's IO window.
2707 Default size is 256 bytes.
2708 hpmemsize=nn[KMG] The fixed amount of bus space which is
2709 reserved for hotplug bridge's memory window.
2710 Default size is 2 megabytes.
2711 realloc= Enable/disable reallocating PCI bridge resources
2712 if allocations done by BIOS are too small to
2713 accommodate resources required by all child
2715 off: Turn realloc off
2717 realloc same as realloc=on
2718 noari do not use PCIe ARI.
2719 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2720 only look for one device below a PCIe downstream
2723 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2726 force Enable ASPM even on devices that claim not to support it.
2727 WARNING: Forcing ASPM on may cause system lockups.
2729 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2730 nomsi Do not use MSI for PCI Express Native Hotplug (this
2731 makes all PCIe ports use INTx for hotplug services).
2733 pcie_ports= [PCIE] PCIe ports handling:
2734 auto Ask the BIOS whether or not to use native PCIe services
2735 associated with PCIe ports (PME, hot-plug, AER). Use
2736 them only if that is allowed by the BIOS.
2737 native Use native PCIe services associated with PCIe ports
2739 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2742 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2743 nomsi Do not use MSI for native PCIe PME signaling (this makes
2744 all PCIe root ports use INTx for all services).
2746 pcmv= [HW,PCMCIA] BadgePAD 4
2750 Keep all power-domains already enabled by bootloader on,
2751 even if no driver has claimed them. This is useful
2752 for debug and development, but should not be
2753 needed on a platform with proper driver support.
2756 See Documentation/blockdev/paride.txt.
2758 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2761 See arch/parisc/kernel/pdc_chassis.c
2763 percpu_alloc= Select which percpu first chunk allocator to use.
2764 Currently supported values are "embed" and "page".
2765 Archs may support subset or none of the selections.
2766 See comments in mm/percpu.c for details on each
2767 allocator. This parameter is primarily for debugging
2768 and performance comparison.
2771 See Documentation/blockdev/paride.txt.
2774 See Documentation/blockdev/paride.txt.
2776 pirq= [SMP,APIC] Manual mp-table setup
2777 See Documentation/x86/i386/IO-APIC.txt.
2779 plip= [PPT,NET] Parallel port network link
2780 Format: { parport<nr> | timid | 0 }
2781 See also Documentation/parport.txt.
2783 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2784 Override pmtimer IOPort with a hex value.
2788 Enable PNP debug messages (depends on the
2789 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2790 via /sys/module/pnp/parameters/debug. We always show
2791 current resource usage; turning this on also shows
2792 possible settings and some assignment information.
2798 { on | off | curr | res | no-curr | no-res }
2801 [ISAPNP] Exclude IRQs for the autoconfiguration
2804 [ISAPNP] Exclude DMAs for the autoconfiguration
2806 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2807 Ranges are in pairs (I/O port base and size).
2810 [ISAPNP] Exclude memory regions for the
2812 Ranges are in pairs (memory base and size).
2814 ports= [IP_VS_FTP] IPVS ftp helper module
2816 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2818 Format: <port>,<port>....
2820 print-fatal-signals=
2821 [KNL] debug: print fatal signals
2823 If enabled, warn about various signal handling
2824 related application anomalies: too many signals,
2825 too many POSIX.1 timers, fatal signals causing a
2828 If you hit the warning due to signal overflow,
2829 you might want to try "ulimit -i unlimited".
2833 printk.always_kmsg_dump=
2834 Trigger kmsg_dump for cases other than kernel oops or
2836 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2839 printk.time= Show timing data prefixed to each printk message line
2840 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2842 processor.max_cstate= [HW,ACPI]
2843 Limit processor to maximum C-state
2844 max_cstate=9 overrides any DMI blacklist limit.
2846 processor.nocst [HW,ACPI]
2847 Ignore the _CST method to determine C-states,
2848 instead using the legacy FADT method
2850 profile= [KNL] Enable kernel profiling via /proc/profile
2851 Format: [schedule,]<number>
2852 Param: "schedule" - profile schedule points.
2853 Param: <number> - step/bucket size as a power of 2 for
2854 statistical time based profiling.
2855 Param: "sleep" - profile D-state sleeping (millisecs).
2856 Requires CONFIG_SCHEDSTATS
2857 Param: "kvm" - profile VM exits.
2859 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2861 See Documentation/blockdev/ramdisk.txt.
2863 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2864 probe for; one of (bare|imps|exps|lifebook|any).
2865 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2867 psmouse.resetafter= [HW,MOUSE]
2868 Try to reset the device after so many bad packets
2871 [HW,MOUSE] Set desired mouse resolution, in dpi.
2872 psmouse.smartscroll=
2873 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2874 0 = disabled, 1 = enabled (default).
2876 pstore.backend= Specify the name of the pstore backend to use
2879 See Documentation/blockdev/paride.txt.
2882 [KNL] Number of legacy pty's. Overwrites compiled-in
2885 quiet [KNL] Disable most log messages
2890 See Documentation/md.txt.
2892 ramdisk_blocksize= [RAM]
2893 See Documentation/blockdev/ramdisk.txt.
2895 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2896 See Documentation/blockdev/ramdisk.txt.
2899 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2900 the specified list of CPUs to be no-callback CPUs.
2901 Invocation of these CPUs' RCU callbacks will
2902 be offloaded to "rcuox/N" kthreads created for
2903 that purpose, where "x" is "b" for RCU-bh, "p"
2904 for RCU-preempt, and "s" for RCU-sched, and "N"
2905 is the CPU number. This reduces OS jitter on the
2906 offloaded CPUs, which can be useful for HPC and
2907 real-time workloads. It can also improve energy
2908 efficiency for asymmetric multiprocessors.
2911 Rather than requiring that offloaded CPUs
2912 (specified by rcu_nocbs= above) explicitly
2913 awaken the corresponding "rcuoN" kthreads,
2914 make these kthreads poll for callbacks.
2915 This improves the real-time response for the
2916 offloaded CPUs by relieving them of the need to
2917 wake up the corresponding kthread, but degrades
2918 energy efficiency by requiring that the kthreads
2919 periodically wake up to do the polling.
2921 rcutree.blimit= [KNL]
2922 Set maximum number of finished RCU callbacks to
2923 process in one batch.
2925 rcutree.rcu_fanout_leaf= [KNL]
2926 Increase the number of CPUs assigned to each
2927 leaf rcu_node structure. Useful for very large
2930 rcutree.jiffies_till_sched_qs= [KNL]
2931 Set required age in jiffies for a
2932 given grace period before RCU starts
2933 soliciting quiescent-state help from
2934 rcu_note_context_switch().
2936 rcutree.jiffies_till_first_fqs= [KNL]
2937 Set delay from grace-period initialization to
2938 first attempt to force quiescent states.
2939 Units are jiffies, minimum value is zero,
2940 and maximum value is HZ.
2942 rcutree.jiffies_till_next_fqs= [KNL]
2943 Set delay between subsequent attempts to force
2944 quiescent states. Units are jiffies, minimum
2945 value is one, and maximum value is HZ.
2947 rcutree.kthread_prio= [KNL,BOOT]
2948 Set the SCHED_FIFO priority of the RCU
2949 per-CPU kthreads (rcuc/N). This value is also
2950 used for the priority of the RCU boost threads
2951 (rcub/N). Valid values are 1-99 and the default
2952 is 1 (the least-favored priority).
2954 rcutree.rcu_nocb_leader_stride= [KNL]
2955 Set the number of NOCB kthread groups, which
2956 defaults to the square root of the number of
2957 CPUs. Larger numbers reduces the wakeup overhead
2958 on the per-CPU grace-period kthreads, but increases
2959 that same overhead on each group's leader.
2961 rcutree.qhimark= [KNL]
2962 Set threshold of queued RCU callbacks beyond which
2963 batch limiting is disabled.
2965 rcutree.qlowmark= [KNL]
2966 Set threshold of queued RCU callbacks below which
2967 batch limiting is re-enabled.
2969 rcutree.rcu_idle_gp_delay= [KNL]
2970 Set wakeup interval for idle CPUs that have
2971 RCU callbacks (RCU_FAST_NO_HZ=y).
2973 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2974 Set wakeup interval for idle CPUs that have
2975 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2976 Lazy RCU callbacks are those which RCU can
2977 prove do nothing more than free memory.
2979 rcutorture.cbflood_inter_holdoff= [KNL]
2980 Set holdoff time (jiffies) between successive
2981 callback-flood tests.
2983 rcutorture.cbflood_intra_holdoff= [KNL]
2984 Set holdoff time (jiffies) between successive
2985 bursts of callbacks within a given callback-flood
2988 rcutorture.cbflood_n_burst= [KNL]
2989 Set the number of bursts making up a given
2990 callback-flood test. Set this to zero to
2991 disable callback-flood testing.
2993 rcutorture.cbflood_n_per_burst= [KNL]
2994 Set the number of callbacks to be registered
2995 in a given burst of a callback-flood test.
2997 rcutorture.fqs_duration= [KNL]
2998 Set duration of force_quiescent_state bursts.
3000 rcutorture.fqs_holdoff= [KNL]
3001 Set holdoff time within force_quiescent_state bursts.
3003 rcutorture.fqs_stutter= [KNL]
3004 Set wait time between force_quiescent_state bursts.
3006 rcutorture.gp_exp= [KNL]
3007 Use expedited update-side primitives.
3009 rcutorture.gp_normal= [KNL]
3010 Use normal (non-expedited) update-side primitives.
3011 If both gp_exp and gp_normal are set, do both.
3012 If neither gp_exp nor gp_normal are set, still
3015 rcutorture.n_barrier_cbs= [KNL]
3016 Set callbacks/threads for rcu_barrier() testing.
3018 rcutorture.nfakewriters= [KNL]
3019 Set number of concurrent RCU writers. These just
3020 stress RCU, they don't participate in the actual
3021 test, hence the "fake".
3023 rcutorture.nreaders= [KNL]
3024 Set number of RCU readers.
3026 rcutorture.object_debug= [KNL]
3027 Enable debug-object double-call_rcu() testing.
3029 rcutorture.onoff_holdoff= [KNL]
3030 Set time (s) after boot for CPU-hotplug testing.
3032 rcutorture.onoff_interval= [KNL]
3033 Set time (s) between CPU-hotplug operations, or
3034 zero to disable CPU-hotplug testing.
3036 rcutorture.torture_runnable= [BOOT]
3037 Start rcutorture running at boot time.
3039 rcutorture.shuffle_interval= [KNL]
3040 Set task-shuffle interval (s). Shuffling tasks
3041 allows some CPUs to go into dyntick-idle mode
3042 during the rcutorture test.
3044 rcutorture.shutdown_secs= [KNL]
3045 Set time (s) after boot system shutdown. This
3046 is useful for hands-off automated testing.
3048 rcutorture.stall_cpu= [KNL]
3049 Duration of CPU stall (s) to test RCU CPU stall
3050 warnings, zero to disable.
3052 rcutorture.stall_cpu_holdoff= [KNL]
3053 Time to wait (s) after boot before inducing stall.
3055 rcutorture.stat_interval= [KNL]
3056 Time (s) between statistics printk()s.
3058 rcutorture.stutter= [KNL]
3059 Time (s) to stutter testing, for example, specifying
3060 five seconds causes the test to run for five seconds,
3061 wait for five seconds, and so on. This tests RCU's
3062 ability to transition abruptly to and from idle.
3064 rcutorture.test_boost= [KNL]
3065 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3066 "Maybe" means test if the RCU implementation
3067 under test support RCU priority boosting.
3069 rcutorture.test_boost_duration= [KNL]
3070 Duration (s) of each individual boost test.
3072 rcutorture.test_boost_interval= [KNL]
3073 Interval (s) between each boost test.
3075 rcutorture.test_no_idle_hz= [KNL]
3076 Test RCU's dyntick-idle handling. See also the
3077 rcutorture.shuffle_interval parameter.
3079 rcutorture.torture_type= [KNL]
3080 Specify the RCU implementation to test.
3082 rcutorture.verbose= [KNL]
3083 Enable additional printk() statements.
3085 rcupdate.rcu_expedited= [KNL]
3086 Use expedited grace-period primitives, for
3087 example, synchronize_rcu_expedited() instead
3088 of synchronize_rcu(). This reduces latency,
3089 but can increase CPU utilization, degrade
3090 real-time latency, and degrade energy efficiency.
3092 rcupdate.rcu_cpu_stall_suppress= [KNL]
3093 Suppress RCU CPU stall warning messages.
3095 rcupdate.rcu_cpu_stall_timeout= [KNL]
3096 Set timeout for RCU CPU stall warning messages.
3098 rcupdate.rcu_task_stall_timeout= [KNL]
3099 Set timeout in jiffies for RCU task stall warning
3100 messages. Disable with a value less than or equal
3103 rcupdate.rcu_self_test= [KNL]
3104 Run the RCU early boot self tests
3106 rcupdate.rcu_self_test_bh= [KNL]
3107 Run the RCU bh early boot self tests
3109 rcupdate.rcu_self_test_sched= [KNL]
3110 Run the RCU sched early boot self tests
3114 Run specified binary instead of /init from the ramdisk,
3115 used for early userspace startup. See initrd.
3118 Format (x86 or x86_64):
3119 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3121 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3123 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3124 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3125 reboot_force is either force or not specified,
3126 reboot_cpu is s[mp]#### with #### being the processor
3127 to be used for rebooting.
3130 [KNL, SMP] Set scheduler's default relax_domain_level.
3131 See Documentation/cgroups/cpusets.txt.
3133 relative_sleep_states=
3134 [SUSPEND] Use sleep state labeling where the deepest
3135 state available other than hibernation is always "mem".
3136 Format: { "0" | "1" }
3137 0 -- Traditional sleep state labels.
3138 1 -- Relative sleep state labels.
3140 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3142 reservetop= [X86-32]
3144 Reserves a hole at the top of the kernel virtual
3149 Set the amount of memory to reserve for BIOS at
3150 the bottom of the address space.
3152 reset_devices [KNL] Force drivers to reset the underlying device
3153 during initialization.
3156 Specify the partition device for software suspend
3158 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3160 resume_offset= [SWSUSP]
3161 Specify the offset from the beginning of the partition
3162 given by "resume=" at which the swap header is located,
3163 in <PAGE_SIZE> units (needed only for swap files).
3164 See Documentation/power/swsusp-and-swap-files.txt
3166 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3167 read the resume files
3169 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3170 Useful for devices that are detected asynchronously
3171 (e.g. USB and MMC devices).
3173 hibernate= [HIBERNATION]
3174 noresume Don't check if there's a hibernation image
3175 present during boot.
3176 nocompress Don't compress/decompress hibernation images.
3177 no Disable hibernation and resume.
3179 retain_initrd [RAM] Keep initrd memory after extraction
3181 rhash_entries= [KNL,NET]
3182 Set number of hash buckets for route cache
3184 ro [KNL] Mount root device read-only on boot
3186 root= [KNL] Root filesystem
3187 See name_to_dev_t comment in init/do_mounts.c.
3189 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3190 mount the root filesystem
3192 rootflags= [KNL] Set root filesystem mount option string
3194 rootfstype= [KNL] Set root filesystem type
3196 rootwait [KNL] Wait (indefinitely) for root device to show up.
3197 Useful for devices that are detected asynchronously
3198 (e.g. USB and MMC devices).
3200 rproc_mem=nn[KMG][@address]
3201 [KNL,ARM,CMA] Remoteproc physical memory block.
3202 Memory area to be used by remote processor image,
3205 rw [KNL] Mount root device read-write on boot
3207 S [KNL] Run init in single mode
3209 s390_iommu= [HW,S390]
3210 Set s390 IOTLB flushing mode
3212 With strict flushing every unmap operation will result in
3213 an IOTLB flush. Default is lazy flushing before reuse,
3217 See drivers/net/irda/sa1100_ir.c.
3219 sbni= [NET] Granch SBNI12 leased line adapter
3221 sched_debug [KNL] Enables verbose scheduler debug messages.
3223 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3224 xtime_lock contention on larger systems, and/or RCU lock
3225 contention on all systems with CONFIG_MAXSMP set.
3226 Format: { "0" | "1" }
3227 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3229 Note: increases power consumption, thus should only be
3230 enabled if running jitter sensitive (HPC/RT) workloads.
3232 security= [SECURITY] Choose a security module to enable at boot.
3233 If this boot parameter is not specified, only the first
3234 security module asking for security registration will be
3235 loaded. An invalid security module name will be treated
3236 as if no module has been chosen.
3238 selinux= [SELINUX] Disable or enable SELinux at boot time.
3239 Format: { "0" | "1" }
3240 See security/selinux/Kconfig help text.
3243 Default value is set via kernel config option.
3244 If enabled at boot time, /selinux/disable can be used
3245 later to disable prior to initial policy load.
3247 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3248 Format: { "0" | "1" }
3249 See security/apparmor/Kconfig help text
3252 Default value is set via kernel config option.
3254 serialnumber [BUGS=X86-32]
3257 Maximal number of shapers.
3259 show_msr= [x86] show boot-time MSR settings
3260 Format: { <integer> }
3261 Show boot-time (BIOS-initialized) MSR settings.
3262 The parameter means the number of CPUs to show,
3263 for example 1 means boot CPU only.
3271 Disable merging of slabs with similar size. May be
3272 necessary if there is some reason to distinguish
3273 allocs to different slabs. Debug options disable
3274 merging on their own.
3275 For more information see Documentation/vm/slub.txt.
3277 slab_max_order= [MM, SLAB]
3278 Determines the maximum allowed order for slabs.
3279 A high setting may cause OOMs due to memory
3280 fragmentation. Defaults to 1 for systems with
3281 more than 32MB of RAM, 0 otherwise.
3283 slub_debug[=options[,slabs]] [MM, SLUB]
3284 Enabling slub_debug allows one to determine the
3285 culprit if slab objects become corrupted. Enabling
3286 slub_debug can create guard zones around objects and
3287 may poison objects when not in use. Also tracks the
3288 last alloc / free. For more information see
3289 Documentation/vm/slub.txt.
3291 slub_max_order= [MM, SLUB]
3292 Determines the maximum allowed order for slabs.
3293 A high setting may cause OOMs due to memory
3294 fragmentation. For more information see
3295 Documentation/vm/slub.txt.
3297 slub_min_objects= [MM, SLUB]
3298 The minimum number of objects per slab. SLUB will
3299 increase the slab order up to slub_max_order to
3300 generate a sufficiently large slab able to contain
3301 the number of objects indicated. The higher the number
3302 of objects the smaller the overhead of tracking slabs
3303 and the less frequently locks need to be acquired.
3304 For more information see Documentation/vm/slub.txt.
3306 slub_min_order= [MM, SLUB]
3307 Determines the minimum page order for slabs. Must be
3308 lower than slub_max_order.
3309 For more information see Documentation/vm/slub.txt.
3311 slub_nomerge [MM, SLUB]
3312 Same with slab_nomerge. This is supported for legacy.
3313 See slab_nomerge for more information.
3316 Format: <io1>[,<io2>[,...,<io8>]]
3318 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3319 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3320 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3321 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3322 smsc-ircc2.ircc_irq= [HW] IRQ line
3323 smsc-ircc2.ircc_dma= [HW] DMA channel
3324 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3325 0: Toshiba Satellite 1800 (GP data pin select)
3326 1: Fast pin select (default)
3330 [KNL] Should the soft-lockup detector generate panics.
3333 softlockup_all_cpu_backtrace=
3334 [KNL] Should the soft-lockup detector generate
3335 backtraces on all cpus.
3338 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3339 See Documentation/laptops/sonypi.txt
3341 spia_io_base= [HW,MTD]
3347 Enabled the stack tracer on boot up.
3349 stacktrace_filter=[function-list]
3350 [FTRACE] Limit the functions that the stack tracer
3351 will trace at boot up. function-list is a comma separated
3352 list of functions. This list can be changed at run
3353 time by the stack_trace_filter file in the debugfs
3354 tracing directory. Note, this enables stack tracing
3355 and the stacktrace above is not needed.
3359 Set the STI (builtin display/keyboard on the HP-PARISC
3360 machines) console (graphic card) which should be used
3361 as the initial boot-console.
3362 See also comment in drivers/video/console/sticore.c.
3365 See comment in drivers/video/console/sticore.c.
3368 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3370 sunrpc.min_resvport=
3371 sunrpc.max_resvport=
3373 SunRPC servers often require that client requests
3374 originate from a privileged port (i.e. a port in the
3375 range 0 < portnr < 1024).
3376 An administrator who wishes to reserve some of these
3377 ports for other uses may adjust the range that the
3378 kernel's sunrpc client considers to be privileged
3379 using these two parameters to set the minimum and
3380 maximum port values.
3384 Control how the NFS server code allocates CPUs to
3385 service thread pools. Depending on how many NICs
3386 you have and where their interrupts are bound, this
3387 option will affect which CPUs will do NFS serving.
3388 Note: this parameter cannot be changed while the
3389 NFS server is running.
3391 auto the server chooses an appropriate mode
3392 automatically using heuristics
3393 global a single global pool contains all CPUs
3394 percpu one pool for each CPU
3395 pernode one pool for each NUMA node (equivalent
3396 to global on non-NUMA machines)
3398 sunrpc.tcp_slot_table_entries=
3399 sunrpc.udp_slot_table_entries=
3401 Sets the upper limit on the number of simultaneous
3402 RPC calls that can be sent from the client to a
3403 server. Increasing these values may allow you to
3404 improve throughput, but will also increase the
3405 amount of memory reserved for use by the client.
3408 [KNL] Enable accounting of swap in memory resource
3409 controller if no parameter or 1 is given or disable
3410 it if 0 is given (See Documentation/cgroups/memory.txt)
3412 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3413 Format: { <int> | force }
3414 <int> -- Number of I/O TLB slabs
3415 force -- force using of bounce buffers even if they
3416 wouldn't be automatically used by the kernel
3420 sysfs.deprecated=0|1 [KNL]
3421 Enable/disable old style sysfs layout for old udev
3422 on older distributions. When this option is enabled
3423 very new udev will not work anymore. When this option
3424 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3425 in older udev will not work anymore.
3426 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3427 the kernel configuration.
3429 sysrq_always_enabled
3431 Ignore sysrq setting - this boot parameter will
3432 neutralize any effect of /proc/sys/kernel/sysrq.
3433 Useful for debugging.
3437 test_suspend= [SUSPEND][,N]
3438 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3439 standby suspend) or "freeze" (for suspend type freeze)
3440 as the system sleep state during system startup with
3441 the optional capability to repeat N number of times.
3442 The system is woken from this state using a
3443 wakeup-capable RTC alarm.
3445 thash_entries= [KNL,NET]
3446 Set number of hash buckets for TCP connection
3448 thermal.act= [HW,ACPI]
3449 -1: disable all active trip points in all thermal zones
3450 <degrees C>: override all lowest active trip points
3452 thermal.crt= [HW,ACPI]
3453 -1: disable all critical trip points in all thermal zones
3454 <degrees C>: override all critical trip points
3456 thermal.nocrt= [HW,ACPI]
3457 Set to disable actions on ACPI thermal zone
3458 critical and hot trip points.
3460 thermal.off= [HW,ACPI]
3461 1: disable ACPI thermal control
3463 thermal.psv= [HW,ACPI]
3464 -1: disable all passive trip points
3465 <degrees C>: override all passive trip points to this
3468 thermal.tzp= [HW,ACPI]
3469 Specify global default ACPI thermal zone polling rate
3470 <deci-seconds>: poll all this frequency
3471 0: no polling (default)
3474 Force threading of all interrupt handlers except those
3475 marked explicitly IRQF_NO_THREAD.
3478 Enable the Transcendent memory driver if built-in.
3480 tmem.cleancache=0|1 [KNL, XEN]
3481 Default is on (1). Disable the usage of the cleancache
3482 API to send anonymous pages to the hypervisor.
3484 tmem.frontswap=0|1 [KNL, XEN]
3485 Default is on (1). Disable the usage of the frontswap
3486 API to send swap pages to the hypervisor. If disabled
3487 the selfballooning and selfshrinking are force disabled.
3489 tmem.selfballooning=0|1 [KNL, XEN]
3490 Default is on (1). Disable the driving of swap pages
3493 tmem.selfshrinking=0|1 [KNL, XEN]
3494 Default is on (1). Partial swapoff that immediately
3495 transfers pages from Xen hypervisor back to the
3496 kernel based on different criteria.
3500 Specify if the kernel should make use of the cpu
3501 topology information if the hardware supports this.
3502 The scheduler will make use of this information and
3503 e.g. base its process migration decisions on it.
3506 topology_updates= [KNL, PPC, NUMA]
3508 Specify if the kernel should ignore (off)
3509 topology updates sent by the hypervisor to this
3514 tpm_suspend_pcr=[HW,TPM]
3515 Format: integer pcr id
3516 Specify that at suspend time, the tpm driver
3517 should extend the specified pcr with zeros,
3518 as a workaround for some chips which fail to
3519 flush the last written pcr on TPM_SaveState.
3520 This will guarantee that all the other pcrs
3523 trace_buf_size=nn[KMG]
3524 [FTRACE] will set tracing buffer size on each cpu.
3526 trace_event=[event-list]
3527 [FTRACE] Set and start specified trace events in order
3528 to facilitate early boot debugging.
3529 See also Documentation/trace/events.txt
3531 trace_options=[option-list]
3532 [FTRACE] Enable or disable tracer options at boot.
3533 The option-list is a comma delimited list of options
3534 that can be enabled or disabled just as if you were
3535 to echo the option name into
3537 /sys/kernel/debug/tracing/trace_options
3539 For example, to enable stacktrace option (to dump the
3540 stack trace of each event), add to the command line:
3542 trace_options=stacktrace
3544 See also Documentation/trace/ftrace.txt "trace options"
3548 [FTRACE] enable this option to disable tracing when a
3549 warning is hit. This turns off "tracing_on". Tracing can
3550 be enabled again by echoing '1' into the "tracing_on"
3551 file located in /sys/kernel/debug/tracing/
3553 This option is useful, as it disables the trace before
3554 the WARNING dump is called, which prevents the trace to
3555 be filled with content caused by the warning output.
3557 This option can also be set at run time via the sysctl
3558 option: kernel/traceoff_on_warning
3560 transparent_hugepage=
3562 Format: [always|madvise|never]
3563 Can be used to control the default behavior of the system
3564 with respect to transparent hugepages.
3565 See Documentation/vm/transhuge.txt for more details.
3567 tsc= Disable clocksource stability checks for TSC.
3569 [x86] reliable: mark tsc clocksource as reliable, this
3570 disables clocksource verification at runtime, as well
3571 as the stability checks done at bootup. Used to enable
3572 high-resolution timer mode on older hardware, and in
3573 virtualized environment.
3574 [x86] noirqtime: Do not use TSC to do irq accounting.
3575 Used to run time disable IRQ_TIME_ACCOUNTING on any
3576 platforms where RDTSC is slow and this accounting
3579 turbografx.map[2|3]= [HW,JOY]
3580 TurboGraFX parallel port interface
3582 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3583 See also Documentation/input/joystick-parport.txt
3585 udbg-immortal [PPC] When debugging early kernel crashes that
3586 happen after console_init() and before a proper
3587 console driver takes over, this boot options might
3588 help "seeing" what's going on.
3590 uhash_entries= [KNL,NET]
3591 Set number of hash buckets for UDP/UDP-Lite connections
3594 [USB] Ignore overcurrent events (default N).
3595 Some badly-designed motherboards generate lots of
3596 bogus events, for ports that aren't wired to
3597 anything. Set this parameter to avoid log spamming.
3598 Note that genuine overcurrent events won't be
3602 [X86] Cause panic on unknown NMI.
3604 usbcore.authorized_default=
3605 [USB] Default USB device authorization:
3606 (default -1 = authorized except for wireless USB,
3607 0 = not authorized, 1 = authorized)
3609 usbcore.autosuspend=
3610 [USB] The autosuspend time delay (in seconds) used
3611 for newly-detected USB devices (default 2). This
3612 is the time required before an idle device will be
3613 autosuspended. Devices for which the delay is set
3614 to a negative value won't be autosuspended at all.
3616 usbcore.usbfs_snoop=
3617 [USB] Set to log all usbfs traffic (default 0 = off).
3619 usbcore.blinkenlights=
3620 [USB] Set to cycle leds on hubs (default 0 = off).
3622 usbcore.old_scheme_first=
3623 [USB] Start with the old device initialization
3624 scheme (default 0 = off).
3626 usbcore.usbfs_memory_mb=
3627 [USB] Memory limit (in MB) for buffers allocated by
3628 usbfs (default = 16, 0 = max = 2047).
3630 usbcore.use_both_schemes=
3631 [USB] Try the other device initialization scheme
3632 if the first one fails (default 1 = enabled).
3634 usbcore.initial_descriptor_timeout=
3635 [USB] Specifies timeout for the initial 64-byte
3636 USB_REQ_GET_DESCRIPTOR request in milliseconds
3637 (default 5000 = 5.0 seconds).
3640 [USBHID] The interval which mice are to be polled at.
3642 usb-storage.delay_use=
3643 [UMS] The delay in seconds before a new device is
3644 scanned for Logical Units (default 1).
3647 [UMS] A list of quirks entries to supplement or
3648 override the built-in unusual_devs list. List
3649 entries are separated by commas. Each entry has
3650 the form VID:PID:Flags where VID and PID are Vendor
3651 and Product ID values (4-digit hex numbers) and
3652 Flags is a set of characters, each corresponding
3653 to a common usb-storage quirk flag as follows:
3654 a = SANE_SENSE (collect more than 18 bytes
3656 b = BAD_SENSE (don't collect more than 18
3657 bytes of sense data);
3658 c = FIX_CAPACITY (decrease the reported
3659 device capacity by one sector);
3660 d = NO_READ_DISC_INFO (don't use
3661 READ_DISC_INFO command);
3662 e = NO_READ_CAPACITY_16 (don't use
3663 READ_CAPACITY_16 command);
3664 f = NO_REPORT_OPCODES (don't use report opcodes
3666 h = CAPACITY_HEURISTICS (decrease the
3667 reported device capacity by one
3668 sector if the number is odd);
3669 i = IGNORE_DEVICE (don't bind to this
3671 l = NOT_LOCKABLE (don't try to lock and
3672 unlock ejectable media);
3673 m = MAX_SECTORS_64 (don't transfer more
3674 than 64 sectors = 32 KB at a time);
3675 n = INITIAL_READ10 (force a retry of the
3676 initial READ(10) command);
3677 o = CAPACITY_OK (accept the capacity
3678 reported by the device);
3679 p = WRITE_CACHE (the device cache is ON
3681 r = IGNORE_RESIDUE (the device reports
3682 bogus residue values);
3683 s = SINGLE_LUN (the device has only one
3685 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3686 commands, uas only);
3687 u = IGNORE_UAS (don't bind to the uas driver);
3688 w = NO_WP_DETECT (don't test whether the
3689 medium is write-protected).
3690 Example: quirks=0419:aaf5:rl,0421:0433:rc
3692 user_debug= [KNL,ARM]
3694 See arch/arm/Kconfig.debug help text.
3695 1 - undefined instruction events
3697 4 - invalid data aborts
3700 Example: user_debug=31
3703 [X86] Flags controlling user PTE allocations.
3705 nohigh = do not allocate PTE pages in
3706 HIGHMEM regardless of setting
3710 On X86_32, this is an alias for vdso32=. Otherwise:
3712 vdso=1: enable VDSO (the default)
3713 vdso=0: disable VDSO mapping
3715 vdso32= [X86] Control the 32-bit vDSO
3716 vdso32=1: enable 32-bit VDSO
3717 vdso32=0 or vdso32=2: disable 32-bit VDSO
3719 See the help text for CONFIG_COMPAT_VDSO for more
3720 details. If CONFIG_COMPAT_VDSO is set, the default is
3721 vdso32=0; otherwise, the default is vdso32=1.
3723 For compatibility with older kernels, vdso32=2 is an
3726 Try vdso32=0 if you encounter an error that says:
3727 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3730 vector=percpu: enable percpu vector domain
3732 video= [FB] Frame buffer configuration
3733 See Documentation/fb/modedb.txt.
3735 video.brightness_switch_enabled= [0,1]
3736 If set to 1, on receiving an ACPI notify event
3737 generated by hotkey, video driver will adjust brightness
3738 level and then send out the event to user space through
3739 the allocated input device; If set to 0, video driver
3740 will only send out the event without touching backlight
3745 [VMMIO] Memory mapped virtio (platform) device.
3747 <size>@<baseaddr>:<irq>[:<id>]
3749 <size> := size (can use standard suffixes
3751 <baseaddr> := physical base address
3752 <irq> := interrupt number (as passed to
3754 <id> := (optional) platform device id
3756 virtio_mmio.device=1K@0x100b0000:48:7
3758 Can be used multiple times for multiple devices.
3760 vga= [BOOT,X86-32] Select a particular video mode
3761 See Documentation/x86/boot.txt and
3762 Documentation/svga.txt.
3763 Use vga=ask for menu.
3764 This is actually a boot loader parameter; the value is
3765 passed to the kernel using a special protocol.
3767 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3768 size of <nn>. This can be used to increase the
3769 minimum size (128MB on x86). It can also be used to
3770 decrease the size and leave more room for directly
3773 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3776 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3779 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3783 Controls the behavior of vsyscalls (i.e. calls to
3784 fixed addresses of 0xffffffffff600x00 from legacy
3785 code). Most statically-linked binaries and older
3786 versions of glibc use these calls. Because these
3787 functions are at fixed addresses, they make nice
3788 targets for exploits that can control RIP.
3790 emulate [default] Vsyscalls turn into traps and are
3791 emulated reasonably safely.
3793 native Vsyscalls are native syscall instructions.
3794 This is a little bit faster than trapping
3795 and makes a few dynamic recompilers work
3796 better than they would in emulation mode.
3797 It also makes exploits much easier to write.
3799 none Vsyscalls don't work at all. This makes
3800 them quite hard to use for exploits but
3801 might break your system.
3803 vt.color= [VT] Default text color.
3804 Format: 0xYX, X = foreground, Y = background.
3805 Default: 0x07 = light gray on black.
3807 vt.cur_default= [VT] Default cursor shape.
3808 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3809 the parameters of the <Esc>[?A;B;Cc escape sequence;
3810 see VGA-softcursor.txt. Default: 2 = underline.
3812 vt.default_blu= [VT]
3813 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3814 Change the default blue palette of the console.
3815 This is a 16-member array composed of values
3818 vt.default_grn= [VT]
3819 Format: <green0>,<green1>,<green2>,...,<green15>
3820 Change the default green palette of the console.
3821 This is a 16-member array composed of values
3824 vt.default_red= [VT]
3825 Format: <red0>,<red1>,<red2>,...,<red15>
3826 Change the default red palette of the console.
3827 This is a 16-member array composed of values
3833 Set system-wide default UTF-8 mode for all tty's.
3834 Default is 1, i.e. UTF-8 mode is enabled for all
3835 newly opened terminals.
3837 vt.global_cursor_default=
3840 Set system-wide default for whether a cursor
3841 is shown on new VTs. Default is -1,
3842 i.e. cursors will be created by default unless
3843 overridden by individual drivers. 0 will hide
3844 cursors, 1 will display them.
3846 vt.italic= [VT] Default color for italic text; 0-15.
3849 vt.underline= [VT] Default color for underlined text; 0-15.
3852 watchdog timers [HW,WDT] For information on watchdog timers,
3853 see Documentation/watchdog/watchdog-parameters.txt
3854 or other driver-specific files in the
3855 Documentation/watchdog/ directory.
3857 workqueue.disable_numa
3858 By default, all work items queued to unbound
3859 workqueues are affine to the NUMA nodes they're
3860 issued on, which results in better behavior in
3861 general. If NUMA affinity needs to be disabled for
3862 whatever reason, this option can be used. Note
3863 that this also can be controlled per-workqueue for
3864 workqueues visible under /sys/bus/workqueue/.
3866 workqueue.power_efficient
3867 Per-cpu workqueues are generally preferred because
3868 they show better performance thanks to cache
3869 locality; unfortunately, per-cpu workqueues tend to
3870 be more power hungry than unbound workqueues.
3872 Enabling this makes the per-cpu workqueues which
3873 were observed to contribute significantly to power
3874 consumption unbound, leading to measurably lower
3875 power usage at the cost of small performance
3878 The default value of this parameter is determined by
3879 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3881 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3882 default x2apic cluster mode on platforms
3885 x86_intel_mid_timer= [X86-32,APBT]
3886 Choose timer option for x86 Intel MID platform.
3887 Two valid options are apbt timer only and lapic timer
3888 plus one apbt timer for broadcast timer.
3889 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3891 xen_emul_unplug= [HW,X86,XEN]
3892 Unplug Xen emulated devices
3893 Format: [unplug0,][unplug1]
3894 ide-disks -- unplug primary master IDE devices
3895 aux-ide-disks -- unplug non-primary-master IDE devices
3896 nics -- unplug network devices
3897 all -- unplug all emulated devices (NICs and IDE disks)
3898 unnecessary -- unplugging emulated devices is
3899 unnecessary even if the host did not respond to
3901 never -- do not unplug even if version check succeeds
3903 xen_nopvspin [X86,XEN]
3904 Disables the ticketlock slowpath using Xen PV
3908 Disables the PV optimizations forcing the HVM guest to
3909 run as generic HVM guest with no PV drivers.
3911 xirc2ps_cs= [NET,PCMCIA]
3913 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3915 ______________________________________________________________________
3919 Add more DRM drivers.
projects / linux.git / blob