4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
168 acpi= [HW,ACPI,X86,ARM64]
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt }
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
178 For ARM64, ONLY "acpi=off" or "acpi=force" are available
180 See also Documentation/power/runtime_pm.txt, pci=noacpi
182 acpi_rsdp= [ACPI,EFI,KEXEC]
183 Pass the RSDP address to the kernel, mostly used
184 on machines running EFI runtime service to boot the
185 second kernel for kdump.
187 acpi_apic_instance= [ACPI, IOAPIC]
189 2: use 2nd APIC table, if available
190 1,0: use 1st APIC table
193 acpi_backlight= [HW,ACPI]
194 acpi_backlight=vendor
196 If set to vendor, prefer vendor specific driver
197 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
198 of the ACPI video.ko driver.
200 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
201 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
203 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
204 debug output. Bits in debug_layer correspond to a
205 _COMPONENT in an ACPI source file, e.g.,
206 #define _COMPONENT ACPI_PCI_COMPONENT
207 Bits in debug_level correspond to a level in
208 ACPI_DEBUG_PRINT statements, e.g.,
209 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
210 The debug_level mask defaults to "info". See
211 Documentation/acpi/debug.txt for more information about
212 debug layers and levels.
214 Enable processor driver info messages:
215 acpi.debug_layer=0x20000000
216 Enable PCI/PCI interrupt routing info messages:
217 acpi.debug_layer=0x400000
218 Enable AML "Debug" output, i.e., stores to the Debug
219 object while interpreting AML:
220 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
221 Enable all messages related to ACPI hardware:
222 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
224 Some values produce so much output that the system is
225 unusable. The "log_buf_len" parameter may be useful
226 if you need to capture more output.
228 acpi_force_table_verification [HW,ACPI]
229 Enable table checksum verification during early stage.
230 By default, this is disabled due to x86 early mapping
233 acpi_irq_balance [HW,ACPI]
234 ACPI will balance active IRQs
237 acpi_irq_nobalance [HW,ACPI]
238 ACPI will not move active IRQs (default)
241 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
242 Format: <irq>,<irq>...
244 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
246 Format: <irq>,<irq>...
248 acpi_no_auto_serialize [HW,ACPI]
249 Disable auto-serialization of AML methods
250 AML control methods that contain the opcodes to create
251 named objects will be marked as "Serialized" by the
252 auto-serialization feature.
253 This feature is enabled by default.
254 This option allows to turn off the feature.
256 acpi_no_static_ssdt [HW,ACPI]
257 Disable installation of static SSDTs at early boot time
258 By default, SSDTs contained in the RSDT/XSDT will be
259 installed automatically and they will appear under
260 /sys/firmware/acpi/tables.
261 This option turns off this feature.
262 Note that specifying this option does not affect
263 dynamic table installation which will install SSDT
264 tables to /sys/firmware/acpi/tables/dynamic.
266 acpica_no_return_repair [HW, ACPI]
267 Disable AML predefined validation mechanism
268 This mechanism can repair the evaluation result to make
269 the return objects more ACPI specification compliant.
270 This option is useful for developers to identify the
271 root cause of an AML interpreter issue when the issue
272 has something to do with the repair mechanism.
274 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
275 Format: To spoof as Windows 98: ="Microsoft Windows"
277 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
278 acpi_osi="string1" # add string1
279 acpi_osi="!string2" # remove string2
280 acpi_osi=!* # remove all strings
281 acpi_osi=! # disable all built-in OS vendor
283 acpi_osi= # disable all strings
285 'acpi_osi=!' can be used in combination with single or
286 multiple 'acpi_osi="string1"' to support specific OS
287 vendor string(s). Note that such command can only
288 affect the default state of the OS vendor strings, thus
289 it cannot affect the default state of the feature group
290 strings and the current state of the OS vendor strings,
291 specifying it multiple times through kernel command line
292 is meaningless. This command is useful when one do not
293 care about the state of the feature group strings which
294 should be controlled by the OSPM.
296 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
297 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
298 can make '_OSI("Windows 2000")' TRUE.
300 'acpi_osi=' cannot be used in combination with other
301 'acpi_osi=' command lines, the _OSI method will not
302 exist in the ACPI namespace. NOTE that such command can
303 only affect the _OSI support state, thus specifying it
304 multiple times through kernel command line is also
307 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
310 'acpi_osi=!*' can be used in combination with single or
311 multiple 'acpi_osi="string1"' to support specific
312 string(s). Note that such command can affect the
313 current state of both the OS vendor strings and the
314 feature group strings, thus specifying it multiple times
315 through kernel command line is meaningful. But it may
316 still not able to affect the final state of a string if
317 there are quirks related to this string. This command
318 is useful when one want to control the state of the
319 feature group strings to debug BIOS issues related to
322 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
323 '_OSI("Module Device")' FALSE.
324 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
325 '_OSI("Module Device")' TRUE.
326 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
328 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
330 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
331 they all will make '_OSI("Windows 2000")' TRUE.
334 Override the pmtimer bug detection: force the kernel
335 to assume that this machine's pmtimer latches its value
336 and always returns good values.
338 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
339 Format: { level | edge | high | low }
341 acpi_skip_timer_override [HW,ACPI]
342 Recognize and ignore IRQ0/pin2 Interrupt Override.
343 For broken nForce2 BIOS resulting in XT-PIC timer.
345 acpi_sleep= [HW,ACPI] Sleep options
346 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
347 old_ordering, nonvs, sci_force_enable }
348 See Documentation/power/video.txt for information on
350 s3_beep is for debugging; it makes the PC's speaker beep
351 as soon as the kernel's real-mode entry point is called.
352 s4_nohwsig prevents ACPI hardware signature from being
353 used during resume from hibernation.
354 old_ordering causes the ACPI 1.0 ordering of the _PTS
355 control method, with respect to putting devices into
356 low power states, to be enforced (the ACPI 2.0 ordering
357 of _PTS is used by default).
358 nonvs prevents the kernel from saving/restoring the
359 ACPI NVS memory during suspend/hibernation and resume.
360 sci_force_enable causes the kernel to set SCI_EN directly
361 on resume from S1/S3 (which is against the ACPI spec,
362 but some broken systems don't work without it).
364 acpi_use_timer_override [HW,ACPI]
365 Use timer override. For some broken Nvidia NF5 boards
366 that require a timer override, but don't have HPET
368 acpi_enforce_resources= [ACPI]
369 { strict | lax | no }
370 Check for resource conflicts between native drivers
371 and ACPI OperationRegions (SystemIO and SystemMemory
372 only). IO ports and memory declared in ACPI might be
373 used by the ACPI subsystem in arbitrary AML code and
374 can interfere with legacy drivers.
375 strict (default): access to resources claimed by ACPI
376 is denied; legacy drivers trying to access reserved
377 resources will fail to bind to device using them.
378 lax: access to resources claimed by ACPI is allowed;
379 legacy drivers trying to access reserved resources
380 will bind successfully but a warning message is logged.
381 no: ACPI OperationRegions are not marked as reserved,
382 no further checks are performed.
384 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
387 add_efi_memmap [EFI; X86] Include EFI memory map in
388 kernel's map of available physical RAM.
391 { off | try_unsupported }
392 off: disable AGP support
393 try_unsupported: try to drive unsupported chipsets
394 (may crash computer or cause data corruption)
397 See Documentation/sound/alsa/alsa-parameters.txt
400 Allow the default userspace alignment fault handler
401 behaviour to be specified. Bit 0 enables warnings,
402 bit 1 enables fixups, and bit 2 sends a segfault.
404 align_va_addr= [X86-64]
405 Align virtual addresses by clearing slice [14:12] when
406 allocating a VMA at process creation time. This option
407 gives you up to 3% performance improvement on AMD F15h
408 machines (where it is enabled by default) for a
409 CPU-intensive style benchmark, and it can vary highly in
410 a microbenchmark depending on workload and compiler.
412 32: only for 32-bit processes
413 64: only for 64-bit processes
414 on: enable for both 32- and 64-bit processes
415 off: disable for both 32- and 64-bit processes
417 alloc_snapshot [FTRACE]
418 Allocate the ftrace snapshot buffer on boot up when the
419 main buffer is allocated. This is handy if debugging
420 and you need to use tracing_snapshot() on boot up, and
421 do not want to use tracing_snapshot_alloc() as it needs
422 to be done where GFP_KERNEL allocations are allowed.
424 amd_iommu= [HW,X86-64]
425 Pass parameters to the AMD IOMMU driver in the system.
427 fullflush - enable flushing of IO/TLB entries when
428 they are unmapped. Otherwise they are
429 flushed before they will be reused, which
431 off - do not initialize any AMD IOMMU found in
433 force_isolation - Force device isolation for all
434 devices. The IOMMU driver is not
435 allowed anymore to lift isolation
436 requirements as needed. This option
437 does not override iommu=pt
439 amd_iommu_dump= [HW,X86-64]
440 Enable AMD IOMMU driver option to dump the ACPI table
441 for AMD IOMMU. With this option enabled, AMD IOMMU
442 driver will print ACPI tables for AMD IOMMU during
443 IOMMU initialization.
445 amijoy.map= [HW,JOY] Amiga joystick support
446 Map of devices attached to JOY0DAT and JOY1DAT
448 See also Documentation/input/joystick.txt
450 analog.map= [HW,JOY] Analog joystick and gamepad support
451 Specifies type or capabilities of an analog joystick
452 connected to one of 16 gameports
453 Format: <type1>,<type2>,..<type16>
456 Power management functions (SPARCstation-4/5 + deriv.)
458 Disable APC CPU standby support. SPARCstation-Fox does
459 not play well with APC CPU idle - disable it if you have
460 APC and your system crashes randomly.
462 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
463 Change the output verbosity whilst booting
464 Format: { quiet (default) | verbose | debug }
465 Change the amount of debugging information output
466 when initialising the APIC and IO-APIC components.
469 See Documentation/networking/ipv6.txt.
471 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
472 Limit apic dumping. The parameter defines the maximal
473 number of local apics being dumped. Also it is possible
474 to set it to "all" by meaning -- no limit here.
475 Format: { 1 (default) | 2 | ... | all }.
476 The parameter valid if only apic=debug or
477 apic=verbose is specified.
478 Example: apic=debug show_lapic=all
480 apm= [APM] Advanced Power Management
481 See header of arch/x86/kernel/apm_32.c.
483 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
484 Format: <io>,<irq>,<nodeID>
488 atarimouse= [HW,MOUSE] Atari Mouse
490 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
491 EzKey and similar keyboards
493 atkbd.reset= [HW] Reset keyboard during initialization
495 atkbd.set= [HW] Select keyboard code set
496 Format: <int> (2 = AT (default), 3 = PS/2)
498 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
501 atkbd.softraw= [HW] Choose between synthetic and real raw mode
502 Format: <bool> (0 = real, 1 = synthetic (default))
504 atkbd.softrepeat= [HW]
505 Use software keyboard repeat
507 audit= [KNL] Enable the audit sub-system
508 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
509 0 - kernel audit is disabled and can not be enabled
510 until the next reboot
511 unset - kernel audit is initialized but disabled and
512 will be fully enabled by the userspace auditd.
513 1 - kernel audit is initialized and partially enabled,
514 storing at most audit_backlog_limit messages in
515 RAM until it is fully enabled by the userspace
519 audit_backlog_limit= [KNL] Set the audit queue size limit.
520 Format: <int> (must be >=0)
523 baycom_epp= [HW,AX25]
526 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
528 See header of drivers/net/hamradio/baycom_par.c.
530 baycom_ser_fdx= [HW,AX25]
531 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
532 Format: <io>,<irq>,<mode>[,<baud>]
533 See header of drivers/net/hamradio/baycom_ser_fdx.c.
535 baycom_ser_hdx= [HW,AX25]
536 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
537 Format: <io>,<irq>,<mode>
538 See header of drivers/net/hamradio/baycom_ser_hdx.c.
540 blkdevparts= Manual partition parsing of block device(s) for
541 embedded devices based on command line input.
542 See Documentation/block/cmdline-partition.txt
544 boot_delay= Milliseconds to delay each printk during boot.
545 Values larger than 10 seconds (10000) are changed to
549 bootmem_debug [KNL] Enable bootmem allocator debug messages.
551 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
552 bttv.radio= Most important insmod options are available as
554 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
557 bulk_remove=off [PPC] This parameter disables the use of the pSeries
558 firmware feature for flushing multiple hpte entries
561 c101= [NET] Moxa C101 synchronous serial card
563 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
564 Sometimes CPU hardware bugs make them report the cache
565 size incorrectly. The kernel will attempt work arounds
566 to fix known problems, but for some CPUs it is not
567 possible to determine what the correct size should be.
568 This option provides an override for these situations.
570 ca_keys= [KEYS] This parameter identifies a specific key(s) on
571 the system trusted keyring to be used for certificate
573 format: { id:<keyid> | builtin }
575 cca= [MIPS] Override the kernel pages' cache coherency
576 algorithm. Accepted values range from 0 to 7
577 inclusive. See arch/mips/include/asm/pgtable-bits.h
578 for platform specific values (SB1, Loongson3 and
581 ccw_timeout_log [S390]
582 See Documentation/s390/CommonIO for details.
584 cgroup_disable= [KNL] Disable a particular controller
585 Format: {name of the controller(s) to disable}
586 The effects of cgroup_disable=foo are:
587 - foo isn't auto-mounted if you mount all cgroups in
589 - foo isn't visible as an individually mountable
591 {Currently only "memory" controller deal with this and
592 cut the overhead, others just disable the usage. So
593 only cgroup_disable=memory is actually worthy}
595 checkreqprot [SELINUX] Set initial checkreqprot flag value.
596 Format: { "0" | "1" }
597 See security/selinux/Kconfig help text.
598 0 -- check protection applied by kernel (includes
599 any implied execute protection).
600 1 -- check protection requested by application.
601 Default value is set via a kernel config option.
602 Value can be changed at runtime via
603 /selinux/checkreqprot.
606 See Documentation/s390/CommonIO for details.
609 Prevents the clock framework from automatically gating
610 clocks that have not been explicitly enabled by a Linux
611 device driver but are enabled in hardware at reset or
612 by the bootloader/firmware. Note that this does not
613 force such clocks to be always-on nor does it reserve
614 those clocks in any way. This parameter is useful for
615 debug and development, but should not be needed on a
616 platform with proper driver support. For more
617 information, see Documentation/clk.txt.
619 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
621 Forces specified clocksource (if available) to be used
622 when calculating gettimeofday(). If specified
623 clocksource is not available, it defaults to PIT.
624 Format: { pit | tsc | cyclone | pmtmr }
626 clocksource= Override the default clocksource
628 Override the default clocksource and use the clocksource
629 with the name specified.
630 Some clocksource names to choose from, depending on
632 [all] jiffies (this is the base, fallback clocksource)
634 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
635 pxa_timer,timer3,32k_counter,timer0_1
637 [X86-32] pit,hpet,tsc;
638 scx200_hrt on Geode; cyclone on IBM x440
646 clearcpuid=BITNUM [X86]
647 Disable CPUID feature X for the kernel. See
648 arch/x86/include/asm/cpufeature.h for the valid bit
649 numbers. Note the Linux specific bits are not necessarily
650 stable over kernel options, but the vendor specific
652 Also note that user programs calling CPUID directly
653 or using the feature without checking anything
654 will still see it. This just prevents it from
655 being used by the kernel or shown in /proc/cpuinfo.
656 Also note the kernel might malfunction if you disable
659 cma=nn[MG]@[start[MG][-end[MG]]]
661 Sets the size of kernel global memory area for
662 contiguous memory allocations and optionally the
663 placement constraint by the physical address range of
664 memory allocations. A value of 0 disables CMA
665 altogether. For more information, see
666 include/linux/dma-contiguous.h
668 cmo_free_hint= [PPC] Format: { yes | no }
669 Specify whether pages are marked as being inactive
670 when they are freed. This is used in CMO environments
671 to determine OS memory pressure for page stealing by
675 coherent_pool=nn[KMG] [ARM,KNL]
676 Sets the size of memory pool for coherent, atomic dma
677 allocations, by default set to 256K.
679 code_bytes [X86] How many bytes of object code to print
684 com20020= [HW,NET] ARCnet - COM20020 chipset
686 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
688 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
692 ARCnet - COM90xx chipset (memory-mapped buffers)
693 Format: <io>[,<irq>[,<memstart>]]
695 condev= [HW,S390] console device
698 console= [KNL] Output console device and options.
700 tty<n> Use the virtual console device <n>.
704 Use the specified serial port. The options are of
705 the form "bbbbpnf", where "bbbb" is the baud rate,
706 "p" is parity ("n", "o", or "e"), "n" is number of
707 bits, and "f" is flow control ("r" for RTS or
708 omit it). Default is "9600n8".
710 See Documentation/serial-console.txt for more
712 Documentation/networking/netconsole.txt for an
715 uart[8250],io,<addr>[,options]
716 uart[8250],mmio,<addr>[,options]
717 uart[8250],mmio32,<addr>[,options]
718 uart[8250],0x<addr>[,options]
719 Start an early, polled-mode console on the 8250/16550
720 UART at the specified I/O port or MMIO address,
721 switching to the matching ttyS device later.
722 MMIO inter-register address stride is either 8-bit
723 (mmio) or 32-bit (mmio32).
724 If none of [io|mmio|mmio32], <addr> is assumed to be
725 equivalent to 'mmio'. 'options' are specified in the
726 same format described for ttyS above; if unspecified,
727 the h/w is not re-initialized.
729 hvc<n> Use the hypervisor console device <n>. This is for
730 both Xen and PowerPC hypervisors.
732 If the device connected to the port is not a TTY but a braille
733 device, prepend "brl," before the device type, for instance
735 For now, only VisioBraille is supported.
737 consoleblank= [KNL] The console blank (screen saver) timeout in
738 seconds. Defaults to 10*60 = 10mins. A value of 0
739 disables the blank timer.
742 [KNL] Change the default value for
743 /proc/<pid>/coredump_filter.
744 See also Documentation/filesystems/proc.txt.
746 cpuidle.off=1 [CPU_IDLE]
747 disable the cpuidle sub-system
749 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
751 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
753 crashkernel=size[KMG][@offset[KMG]]
754 [KNL] Using kexec, Linux can switch to a 'crash kernel'
755 upon panic. This parameter reserves the physical
756 memory region [offset, offset + size] for that kernel
757 image. If '@offset' is omitted, then a suitable offset
758 is selected automatically. Check
759 Documentation/kdump/kdump.txt for further details.
761 crashkernel=range1:size1[,range2:size2,...][@offset]
762 [KNL] Same as above, but depends on the memory
763 in the running system. The syntax of range is
764 start-[end] where start and end are both
765 a memory unit (amount[KMG]). See also
766 Documentation/kdump/kdump.txt for an example.
768 crashkernel=size[KMG],high
769 [KNL, x86_64] range could be above 4G. Allow kernel
770 to allocate physical memory region from top, so could
771 be above 4G if system have more than 4G ram installed.
772 Otherwise memory region will be allocated below 4G, if
774 It will be ignored if crashkernel=X is specified.
775 crashkernel=size[KMG],low
776 [KNL, x86_64] range under 4G. When crashkernel=X,high
777 is passed, kernel could allocate physical memory region
778 above 4G, that cause second kernel crash on system
779 that require some amount of low memory, e.g. swiotlb
780 requires at least 64M+32K low memory. Kernel would
781 try to allocate 72M below 4G automatically.
782 This one let user to specify own low range under 4G
783 for second kernel instead.
784 0: to disable low allocation.
785 It will be ignored when crashkernel=X,high is not used
786 or memory reserved is below 4G.
791 cs89x0_media= [HW,NET]
792 Format: { rj45 | aui | bnc }
795 See header of drivers/s390/block/dasd_devmap.c.
797 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
798 (one device per port)
799 Format: <port#>,<type>
800 See also Documentation/input/joystick-parport.txt
802 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
803 time. See Documentation/dynamic-debug-howto.txt for
804 details. Deprecated, see dyndbg.
806 debug [KNL] Enable kernel debugging (events log level).
809 [KNL] verbose self-tests
811 Print debugging info while doing the locking API
813 We default to 0 (no extra messages), setting it to
814 1 will print _a lot_ more information - normally
815 only useful to kernel developers.
817 debug_objects [KNL] Enable object debugging
820 [KNL] Disable object debugging
822 debug_guardpage_minorder=
823 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
824 parameter allows control of the order of pages that will
825 be intentionally kept free (and hence protected) by the
826 buddy allocator. Bigger value increase the probability
827 of catching random memory corruption, but reduce the
828 amount of memory for normal system use. The maximum
829 possible value is MAX_ORDER/2. Setting this parameter
830 to 1 or 2 should be enough to identify most random
831 memory corruption problems caused by bugs in kernel or
832 driver code when a CPU writes to (or reads from) a
833 random memory location. Note that there exists a class
834 of memory corruptions problems caused by buggy H/W or
835 F/W or by drivers badly programing DMA (basically when
836 memory is written at bus level and the CPU MMU is
837 bypassed) which are not detectable by
838 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
839 tracking down these problems.
842 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
843 parameter enables the feature at boot time. In
844 default, it is disabled. We can avoid allocating huge
845 chunk of memory for debug pagealloc if we don't enable
846 it at boot time and the system will work mostly same
847 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
848 on: enable the feature
850 debugpat [X86] Enable PAT debugging
852 decnet.addr= [HW,NET]
853 Format: <area>[,<node>]
854 See also Documentation/networking/decnet.txt.
857 [same as hugepagesz=] The size of the default
858 HugeTLB page size. This is the size represented by
859 the legacy /proc/ hugepages APIs, used for SHM, and
860 default size when mounting hugetlbfs filesystems.
861 Defaults to the default architecture's huge page size
865 Set number of hash buckets for dentry cache.
868 See Documentation/networking/ipv6.txt.
870 disable_cpu_apicid= [X86,APIC,SMP]
872 The number of initial APIC ID for the
873 corresponding CPU to be disabled at boot,
874 mostly used for the kdump 2nd kernel to
875 disable BSP to wake up multiple CPUs without
876 causing system reset or hang due to sending
879 disable_ddw [PPC/PSERIES]
880 Disable Dynamic DMA Window support. Use this if
881 to workaround buggy firmware.
884 See Documentation/networking/ipv6.txt.
886 disable_mtrr_cleanup [X86]
887 The kernel tries to adjust MTRR layout from continuous
888 to discrete, to make X server driver able to add WB
889 entry later. This parameter disables that.
891 disable_mtrr_trim [X86, Intel and AMD only]
892 By default the kernel will trim any uncacheable
893 memory out of your available memory pool based on
894 MTRR settings. This parameter disables that behavior,
895 possibly causing your machine to run very slowly.
897 disable_timer_pin_1 [X86]
898 Disable PIN 1 of APIC timer
899 Can be useful to work around chipset bugs.
901 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
902 this option disables the debugging code at boot.
904 dma_debug_entries=<number>
905 This option allows to tune the number of preallocated
906 entries for DMA-API debugging code. One entry is
907 required per DMA-API allocation. Use this if the
908 DMA-API debugging code disables itself because the
909 architectural default is too low.
911 dma_debug_driver=<driver_name>
912 With this option the DMA-API debugging driver
913 filter feature can be enabled at boot time. Just
914 pass the driver to filter for as the parameter.
915 The filter can be disabled or changed to another
916 driver later using sysfs.
918 drm_kms_helper.edid_firmware=[<connector>:]<file>
919 Broken monitors, graphic adapters and KVMs may
920 send no or incorrect EDID data sets. This parameter
921 allows to specify an EDID data set in the
922 /lib/firmware directory that is used instead.
923 Generic built-in EDID data sets are used, if one of
924 edid/1024x768.bin, edid/1280x1024.bin,
925 edid/1680x1050.bin, or edid/1920x1080.bin is given
926 and no file with the same name exists. Details and
927 instructions how to build your own EDID data are
928 available in Documentation/EDID/HOWTO.txt. An EDID
929 data set will only be used for a particular connector,
930 if its name and a colon are prepended to the EDID
935 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
936 module.dyndbg[="val"]
937 Enable debug messages at boot time. See
938 Documentation/dynamic-debug-howto.txt for details.
941 on enable eager fpu restore
942 off disable eager fpu restore
943 auto selects the default scheme, which automatically
944 enables eagerfpu restore for xsaveopt.
946 early_ioremap_debug [KNL]
947 Enable debug messages in early_ioremap support. This
948 is useful for tracking down temporary early mappings
949 which are not unmapped.
951 earlycon= [KNL] Output early console device and options.
954 Start an early, polled-mode console on a cadence serial
955 port at the specified address. The cadence serial port
956 must already be setup and configured. Options are not
959 uart[8250],io,<addr>[,options]
960 uart[8250],mmio,<addr>[,options]
961 uart[8250],mmio32,<addr>[,options]
962 uart[8250],0x<addr>[,options]
963 Start an early, polled-mode console on the 8250/16550
964 UART at the specified I/O port or MMIO address.
965 MMIO inter-register address stride is either 8-bit
966 (mmio) or 32-bit (mmio32).
967 If none of [io|mmio|mmio32], <addr> is assumed to be
968 equivalent to 'mmio'. 'options' are specified in the
969 same format described for "console=ttyS<n>"; if
970 unspecified, the h/w is not initialized.
973 Start an early, polled-mode console on a pl011 serial
974 port at the specified address. The pl011 serial port
975 must already be setup and configured. Options are not
979 Start an early, polled-mode console on an msm serial
980 port at the specified address. The serial port
981 must already be setup and configured. Options are not
985 Start an early, polled-mode console on an msm serial
986 dm port at the specified address. The serial port
987 must already be setup and configured. Options are not
990 smh Use ARM semihosting calls for early console.
998 Use early console provided by serial driver available
999 on Samsung SoCs, requires selecting proper type and
1000 a correct base address of the selected UART port. The
1001 serial port must already be setup and configured.
1002 Options are not yet supported.
1004 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1008 earlyprintk=serial[,ttySn[,baudrate]]
1009 earlyprintk=serial[,0x...[,baudrate]]
1010 earlyprintk=ttySn[,baudrate]
1011 earlyprintk=dbgp[debugController#]
1013 earlyprintk is useful when the kernel crashes before
1014 the normal console is initialized. It is not enabled by
1015 default because it has some cosmetic problems.
1017 Append ",keep" to not disable it when the real console
1020 Only one of vga, efi, serial, or usb debug port can
1023 Currently only ttyS0 and ttyS1 may be specified by
1024 name. Other I/O ports may be explicitly specified
1025 on some architectures (x86 and arm at least) by
1026 replacing ttySn with an I/O port address, like this:
1027 earlyprintk=serial,0x1008,115200
1028 You can find the port for a given device in
1029 /proc/tty/driver/serial:
1030 2: uart:ST16650V2 port:00001008 irq:18 ...
1032 Interaction with the standard serial driver is not
1035 The VGA and EFI output is eventually overwritten by
1038 The xen output can only be used by Xen PV guests.
1040 edac_report= [HW,EDAC] Control how to report EDAC event
1041 Format: {"on" | "off" | "force"}
1042 on: enable EDAC to report H/W event. May be overridden
1043 by other higher priority error reporting module.
1044 off: disable H/W event reporting through EDAC.
1045 force: enforce the use of EDAC to report H/W event.
1048 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1051 This is designed to be used in conjunction with
1052 the boot argument: earlyprintk=vga
1055 Format: {"off" | "on" | "skip[mbr]"}
1058 Format: { "old_map", "nochunk", "noruntime", "debug" }
1059 old_map [X86-64]: switch to the old ioremap-based EFI
1060 runtime services mapping. 32-bit still uses this one by
1062 nochunk: disable reading files in "chunks" in the EFI
1063 boot stub, as chunking can cause problems with some
1064 firmware implementations.
1065 noruntime : disable EFI runtime services support
1066 debug: enable misc debug output
1068 efi_no_storage_paranoia [EFI; X86]
1069 Using this parameter you can use more than 50% of
1070 your efi variable storage. Use this parameter only if
1071 you are really sure that your UEFI does sane gc and
1072 fulfills the spec otherwise your board may brick.
1074 eisa_irq_edge= [PARISC,HW]
1075 See header of drivers/parisc/eisa.c.
1078 See comment before function elanfreq_setup() in
1079 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1082 Format: {"cfq" | "deadline" | "noop"}
1083 See Documentation/block/cfq-iosched.txt and
1084 Documentation/block/deadline-iosched.txt for details.
1086 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1087 Specifies physical address of start of kernel core
1088 image elf header and optionally the size. Generally
1089 kexec loader will pass this option to capture kernel.
1090 See Documentation/kdump/kdump.txt for details.
1092 enable_mtrr_cleanup [X86]
1093 The kernel tries to adjust MTRR layout from continuous
1094 to discrete, to make X server driver able to add WB
1095 entry later. This parameter enables that.
1097 enable_timer_pin_1 [X86]
1098 Enable PIN 1 of APIC timer
1099 Can be useful to work around chipset bugs
1100 (in particular on some ATI chipsets).
1101 The kernel tries to set a reasonable default.
1103 enforcing [SELINUX] Set initial enforcing status.
1105 See security/selinux/Kconfig help text.
1106 0 -- permissive (log only, no denials).
1107 1 -- enforcing (deny and log).
1109 Value can be changed at runtime via /selinux/enforce.
1112 Disable Error Record Serialization Table (ERST)
1115 ether= [HW,NET] Ethernet cards parameters
1116 This option is obsoleted by the "netdev=" option, which
1117 has equivalent usage. See its documentation for details.
1121 Permit 'security.evm' to be updated regardless of
1122 current integrity status.
1126 fail_make_request=[KNL]
1127 General fault injection mechanism.
1128 Format: <interval>,<probability>,<space>,<times>
1129 See also Documentation/fault-injection/.
1132 See Documentation/blockdev/floppy.txt.
1134 force_pal_cache_flush
1135 [IA-64] Avoid check_sal_cache_flush which may hang on
1136 buggy SAL_CACHE_FLUSH implementations. Using this
1137 parameter will force ia64_sal_cache_flush to call
1138 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1141 Forcefully enable Physical Address Extension (PAE).
1142 Many Pentium M systems disable PAE but may have a
1143 functionally usable PAE implementation.
1144 Warning: use of this parameter will taint the kernel
1145 and may cause unknown problems.
1148 [FTRACE] will set and start the specified tracer
1149 as early as possible in order to facilitate early
1152 ftrace_dump_on_oops[=orig_cpu]
1153 [FTRACE] will dump the trace buffers on oops.
1154 If no parameter is passed, ftrace will dump
1155 buffers of all CPUs, but if you pass orig_cpu, it will
1156 dump only the buffer of the CPU that triggered the
1159 ftrace_filter=[function-list]
1160 [FTRACE] Limit the functions traced by the function
1161 tracer at boot up. function-list is a comma separated
1162 list of functions. This list can be changed at run
1163 time by the set_ftrace_filter file in the debugfs
1166 ftrace_notrace=[function-list]
1167 [FTRACE] Do not trace the functions specified in
1168 function-list. This list can be changed at run time
1169 by the set_ftrace_notrace file in the debugfs
1172 ftrace_graph_filter=[function-list]
1173 [FTRACE] Limit the top level callers functions traced
1174 by the function graph tracer at boot up.
1175 function-list is a comma separated list of functions
1176 that can be changed at run time by the
1177 set_graph_function file in the debugfs tracing directory.
1179 ftrace_graph_notrace=[function-list]
1180 [FTRACE] Do not trace from the functions specified in
1181 function-list. This list is a comma separated list of
1182 functions that can be changed at run time by the
1183 set_graph_notrace file in the debugfs tracing directory.
1186 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1187 support via parallel port (up to 5 devices per port)
1188 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1189 See also Documentation/input/joystick-parport.txt
1193 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1197 gcov_persist= [GCOV] When non-zero (default), profiling data for
1198 kernel modules is saved and remains accessible via
1199 debugfs, even when the module is unloaded/reloaded.
1200 When zero, profiling data is discarded and associated
1201 debugfs files are removed at module unload time.
1203 gpt [EFI] Forces disk with valid GPT signature but
1204 invalid Protective MBR to be treated as GPT. If the
1205 primary GPT is corrupted, it enables the backup/alternate
1206 GPT to be used instead.
1208 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1209 the "Enable 0" bit of the configuration register.
1212 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1213 the "Enable 0" bit of the configuration register.
1216 grcan.select= [HW] Select which physical interface to use.
1219 grcan.txsize= [HW] Sets the size of the tx buffer.
1220 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1222 grcan.rxsize= [HW] Sets the size of the rx buffer.
1223 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1226 hashdist= [KNL,NUMA] Large hashes allocated during boot
1227 are distributed across NUMA nodes. Defaults on
1228 for 64-bit NUMA, off otherwise.
1229 Format: 0 | 1 (for off | on)
1231 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1233 hd= [EIDE] (E)IDE hard drive subsystem geometry
1234 Format: <cyl>,<head>,<sect>
1237 Disable Hardware Error Source Table (HEST) support;
1238 corresponding firmware-first mode error processing
1239 logic will be disabled.
1241 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1242 size of <nn>. This works even on boxes that have no
1243 highmem otherwise. This also works to reduce highmem
1244 size on bigger boxes.
1246 highres= [KNL] Enable/disable high resolution timer mode.
1247 Valid parameters: "on", "off"
1251 See Documentation/isdn/README.HiSax.
1255 hpet= [X86-32,HPET] option to control HPET usage
1256 Format: { enable (default) | disable | force |
1258 disable: disable HPET and use PIT instead
1259 force: allow force enabled of undocumented chips (ICH4,
1261 verbose: show contents of HPET registers during setup
1263 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1264 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1266 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1267 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1268 On x86-64 and powerpc, this option can be specified
1269 multiple times interleaved with hugepages= to reserve
1270 huge pages of different sizes. Valid pages sizes on
1271 x86-64 are 2M (when the CPU supports "pse") and 1G
1272 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1274 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1275 terminal devices. Valid values: 0..8
1276 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1277 If specified, z/VM IUCV HVC accepts connections
1278 from listed z/VM user IDs only.
1280 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1281 hardware thread id mappings.
1282 Format: <cpu>:<hwthread>
1285 Do not unregister boot console at start. This is only
1286 useful for debugging when something happens in the window
1287 between unregistering the boot console and initializing
1290 i2c_bus= [HW] Override the default board specific I2C bus speed
1291 or register an additional I2C bus that is not
1292 registered from board initialization code.
1296 i8042.debug [HW] Toggle i8042 debug mode
1297 i8042.direct [HW] Put keyboard port into non-translated mode
1298 i8042.dumbkbd [HW] Pretend that controller can only read data from
1299 keyboard and cannot control its state
1300 (Don't attempt to blink the leds)
1301 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1302 i8042.nokbd [HW] Don't check/create keyboard port
1303 i8042.noloop [HW] Disable the AUX Loopback command while probing
1305 i8042.nomux [HW] Don't check presence of an active multiplexing
1307 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1309 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1310 i8042.reset [HW] Reset the controller during init and cleanup
1311 i8042.unlock [HW] Unlock (ignore) the keylock
1312 i8042.kbdreset [HW] Reset device connected to KBD port
1316 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1317 indicates that the driver is running on unsupported
1319 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1320 does not match list of supported models.
1322 [HW] Report power status in /proc/i8k
1323 (disabled by default)
1324 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1327 i915.invert_brightness=
1328 [DRM] Invert the sense of the variable that is used to
1329 set the brightness of the panel backlight. Normally a
1330 brightness value of 0 indicates backlight switched off,
1331 and the maximum of the brightness value sets the backlight
1332 to maximum brightness. If this parameter is set to 0
1333 (default) and the machine requires it, or this parameter
1334 is set to 1, a brightness value of 0 sets the backlight
1335 to maximum brightness, and the maximum of the brightness
1336 value switches the backlight off.
1337 -1 -- never invert brightness
1338 0 -- machine default
1339 1 -- force brightness inversion
1342 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1344 ide-core.nodma= [HW] (E)IDE subsystem
1345 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1346 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1347 .cdrom .chs .ignore_cable are additional options
1348 See Documentation/ide/ide.txt.
1350 ide-generic.probe-mask= [HW] (E)IDE subsystem
1352 Probe mask for legacy ISA IDE ports. Depending on
1353 platform up to 6 ports are supported, enabled by
1354 setting corresponding bits in the mask to 1. The
1355 default value is 0x0, which has a special meaning.
1356 On systems that have PCI, it triggers scanning the
1357 PCI bus for the first and the second port, which
1358 are then probed. On systems without PCI the value
1359 of 0x0 enables probing the two first ports as if it
1362 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1363 Claim all unknown PCI IDE storage controllers.
1366 Format: idle=poll, idle=halt, idle=nomwait
1367 Poll forces a polling idle loop that can slightly
1368 improve the performance of waking up a idle CPU, but
1369 will use a lot of power and make the system run hot.
1371 idle=halt: Halt is forced to be used for CPU idle.
1372 In such case C2/C3 won't be used again.
1373 idle=nomwait: Disable mwait for CPU C-states
1375 ignore_loglevel [KNL]
1376 Ignore loglevel setting - this will print /all/
1377 kernel messages to the console. Useful for debugging.
1378 We also add it as printk module parameter, so users
1379 could change it dynamically, usually by
1380 /sys/module/printk/parameters/ignore_loglevel.
1382 ihash_entries= [KNL]
1383 Set number of hash buckets for inode cache.
1385 ima_appraise= [IMA] appraise integrity measurements
1386 Format: { "off" | "enforce" | "fix" | "log" }
1389 ima_appraise_tcb [IMA]
1390 The builtin appraise policy appraises all files
1394 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1398 The list of supported hash algorithms is defined
1399 in crypto/hash_info.h.
1402 The builtin measurement policy to load during IMA
1403 setup. Specyfing "tcb" as the value, measures all
1404 programs exec'd, files mmap'd for exec, and all files
1405 opened with the read mode bit set by either the
1406 effective uid (euid=0) or uid=0.
1409 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
1410 Load a policy which meets the needs of the Trusted
1411 Computing Base. This means IMA will measure all
1412 programs exec'd, files mmap'd for exec, and all files
1413 opened for read by uid=0.
1416 Select one of defined IMA measurements template formats.
1417 Formats: { "ima" | "ima-ng" }
1421 [IMA] Define a custom template format.
1422 Format: { "field1|...|fieldN" }
1424 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1425 Format: <min_file_size>
1426 Set the minimal file size for using asynchronous hash.
1427 If left unspecified, ahash usage is disabled.
1429 ahash performance varies for different data sizes on
1430 different crypto accelerators. This option can be used
1431 to achieve the best performance for a particular HW.
1433 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1435 Set hashing buffer size. Default: 4k.
1437 ahash performance varies for different chunk sizes on
1438 different crypto accelerators. This option can be used
1439 to achieve best performance for particular HW.
1443 Run specified binary instead of /sbin/init as init
1446 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1447 for working out where the kernel is dying during
1450 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1451 initcall functions. Useful for debugging built-in
1452 modules and initcalls.
1454 initrd= [BOOT] Specify the location of the initial ramdisk
1456 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1459 int_pln_enable [x86] Enable power limit notification interrupt
1461 integrity_audit=[IMA]
1462 Format: { "0" | "1" }
1463 0 -- basic integrity auditing messages. (Default)
1464 1 -- additional integrity auditing messages.
1466 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1468 Enable intel iommu driver.
1470 Disable intel iommu driver.
1471 igfx_off [Default Off]
1472 By default, gfx is mapped as normal device. If a gfx
1473 device has a dedicated DMAR unit, the DMAR unit is
1474 bypassed by not enabling DMAR with this option. In
1475 this case, gfx device will use physical address for
1478 With this option iommu will not optimize to look
1479 for io virtual address below 32-bit forcing dual
1480 address cycle on pci bus for cards supporting greater
1481 than 32-bit addressing. The default is to look
1482 for translation below 32-bit and if not available
1483 then look in the higher range.
1484 strict [Default Off]
1485 With this option on every unmap_single operation will
1486 result in a hardware IOTLB flush operation as opposed
1487 to batching them for performance.
1488 sp_off [Default Off]
1489 By default, super page will be supported if Intel IOMMU
1490 has the capability. With this option, super page will
1492 ecs_off [Default Off]
1493 By default, extended context tables will be supported if
1494 the hardware advertises that it has support both for the
1495 extended tables themselves, and also PASID support. With
1496 this option set, extended tables will not be used even
1497 on hardware which claims to support them.
1499 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1500 0 disables intel_idle and fall back on acpi_idle.
1501 1 to 6 specify maximum depth of C-state.
1505 Do not enable intel_pstate as the default
1506 scaling driver for the supported processors
1508 Enable intel_pstate on systems that prohibit it by default
1509 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1510 instead of acpi-cpufreq may disable platform features, such
1511 as thermal controls and power capping, that rely on ACPI
1512 P-States information being indicated to OSPM and therefore
1513 should be used with caution. This option does not work with
1514 processors that aren't supported by the intel_pstate driver
1515 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1517 Do not enable hardware P state control (HWP)
1520 Only load intel_pstate on systems which support
1521 hardware P state control (HWP) if available.
1523 intremap= [X86-64, Intel-IOMMU]
1524 on enable Interrupt Remapping (default)
1525 off disable Interrupt Remapping
1526 nosid disable Source ID checking
1528 BIOS x2APIC opt-out request will be ignored
1530 iomem= Disable strict checking of access to MMIO memory
1531 strict regions from userspace.
1546 nobypass [PPC/POWERNV]
1547 Disable IOMMU bypass, using IOMMU for PCI devices.
1550 io7= [HW] IO7 for Marvel based alpha systems
1551 See comment before marvel_specify_io7 in
1552 arch/alpha/kernel/core_marvel.c.
1554 io_delay= [X86] I/O delay method
1556 Standard port 0x80 based delay
1558 Alternate port 0xed based delay (needed on some systems)
1560 Simple two microseconds delay
1565 See Documentation/filesystems/nfs/nfsroot.txt.
1567 irqaffinity= [SMP] Set the default irq affinity mask
1569 <cpu number>,...,<cpu number>
1571 <cpu number>-<cpu number>
1572 (must be a positive range in ascending order)
1574 <cpu number>,...,<cpu number>-<cpu number>
1577 When an interrupt is not handled search all handlers
1578 for it. Intended to get systems with badly broken
1582 When an interrupt is not handled search all handlers
1583 for it. Also check all handlers each timer
1584 interrupt. Intended to get systems with badly broken
1588 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1590 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1592 <cpu number>,...,<cpu number>
1594 <cpu number>-<cpu number>
1595 (must be a positive range in ascending order)
1597 <cpu number>,...,<cpu number>-<cpu number>
1599 This option can be used to specify one or more CPUs
1600 to isolate from the general SMP balancing and scheduling
1601 algorithms. You can move a process onto or off an
1602 "isolated" CPU via the CPU affinity syscalls or cpuset.
1603 <cpu number> begins at 0 and the maximum value is
1604 "number of CPUs in system - 1".
1606 This option is the preferred way to isolate CPUs. The
1607 alternative -- manually setting the CPU mask of all
1608 tasks in the system -- can cause problems and
1609 suboptimal load balancer performance.
1613 ivrs_ioapic [HW,X86_64]
1614 Provide an override to the IOAPIC-ID<->DEVICE-ID
1615 mapping provided in the IVRS ACPI table. For
1616 example, to map IOAPIC-ID decimal 10 to
1617 PCI device 00:14.0 write the parameter as:
1618 ivrs_ioapic[10]=00:14.0
1620 ivrs_hpet [HW,X86_64]
1621 Provide an override to the HPET-ID<->DEVICE-ID
1622 mapping provided in the IVRS ACPI table. For
1623 example, to map HPET-ID decimal 0 to
1624 PCI device 00:14.0 write the parameter as:
1625 ivrs_hpet[0]=00:14.0
1627 js= [HW,JOY] Analog joystick
1628 See Documentation/input/joystick.txt.
1631 Enable/disable kernel and module base offset ASLR
1632 (Address Space Layout Randomization) if built into
1633 the kernel. When CONFIG_HIBERNATION is selected,
1634 kASLR is disabled by default. When kASLR is enabled,
1635 hibernation will be disabled.
1639 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1640 specifies the amount of memory usable by the kernel
1641 for non-movable allocations. The requested amount is
1642 spread evenly throughout all nodes in the system. The
1643 remaining memory in each node is used for Movable
1644 pages. In the event, a node is too small to have both
1645 kernelcore and Movable pages, kernelcore pages will
1646 take priority and other nodes will have a larger number
1647 of Movable pages. The Movable zone is used for the
1648 allocation of pages that may be reclaimed or moved
1649 by the page migration subsystem. This means that
1650 HugeTLB pages may not be allocated from this zone.
1651 Note that allocations like PTEs-from-HighMem still
1652 use the HighMem zone if it exists, and the Normal
1653 zone if it does not.
1655 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1656 Format: <Controller#>[,poll interval]
1657 The controller # is the number of the ehci usb debug
1658 port as it is probed via PCI. The poll interval is
1659 optional and is the number seconds in between
1660 each poll cycle to the debug port in case you need
1661 the functionality for interrupting the kernel with
1662 gdb or control-c on the dbgp connection. When
1663 not using this parameter you use sysrq-g to break into
1664 the kernel debugger.
1666 kgdboc= [KGDB,HW] kgdb over consoles.
1667 Requires a tty driver that supports console polling,
1668 or a supported polling keyboard driver (non-usb).
1669 Serial only format: <serial_device>[,baud]
1670 keyboard only format: kbd
1671 keyboard and serial format: kbd,<serial_device>[,baud]
1672 Optional Kernel mode setting:
1673 kms, kbd format: kms,kbd
1674 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1676 kgdbwait [KGDB] Stop kernel execution and enter the
1677 kernel debugger at the earliest opportunity.
1679 kmac= [MIPS] korina ethernet MAC address.
1680 Configure the RouterBoard 532 series on-chip
1681 Ethernet adapter MAC address.
1683 kmemleak= [KNL] Boot-time kmemleak enable/disable
1684 Valid arguments: on, off
1686 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1689 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1690 Valid arguments: 0, 1, 2
1691 kmemcheck=0 (disabled)
1692 kmemcheck=1 (enabled)
1693 kmemcheck=2 (one-shot mode)
1694 Default: 2 (one-shot mode)
1696 kstack=N [X86] Print N words from the kernel stack
1699 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1700 Default is 0 (don't ignore, but inject #GP)
1702 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1706 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1707 Default is 1 (enabled)
1709 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1711 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1713 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1714 (virtualized MMU) support on capable Intel chips.
1715 Default is 1 (enabled)
1717 kvm-intel.emulate_invalid_guest_state=
1718 [KVM,Intel] Enable emulation of invalid guest states
1719 Default is 0 (disabled)
1721 kvm-intel.flexpriority=
1722 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1723 Default is 1 (enabled)
1726 [KVM,Intel] Enable VMX nesting (nVMX).
1727 Default is 0 (disabled)
1729 kvm-intel.unrestricted_guest=
1730 [KVM,Intel] Disable unrestricted guest feature
1731 (virtualized real and unpaged mode) on capable
1732 Intel chips. Default is 1 (enabled)
1734 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1735 feature (tagged TLBs) on capable Intel chips.
1736 Default is 1 (enabled)
1742 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1745 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1746 value for LAPIC timer one-shot implementation. Default
1747 back to the programmable timer unit in the LAPIC.
1749 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1752 libata.dma= [LIBATA] DMA control
1753 libata.dma=0 Disable all PATA and SATA DMA
1754 libata.dma=1 PATA and SATA Disk DMA only
1755 libata.dma=2 ATAPI (CDROM) DMA only
1756 libata.dma=4 Compact Flash DMA only
1757 Combinations also work, so libata.dma=3 enables DMA
1758 for disks and CDROMs, but not CFs.
1760 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1761 libata.ignore_hpa=0 keep BIOS limits (default)
1762 libata.ignore_hpa=1 ignore limits, using full disk
1764 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1768 libata.force= [LIBATA] Force configurations. The format is comma
1769 separated list of "[ID:]VAL" where ID is
1770 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1771 matching port, link or device. Basically, it matches
1772 the ATA ID string printed on console by libata. If
1773 the whole ID part is omitted, the last PORT and DEVICE
1774 values are used. If ID hasn't been specified yet, the
1775 configuration applies to all ports, links and devices.
1777 If only DEVICE is omitted, the parameter applies to
1778 the port and all links and devices behind it. DEVICE
1779 number of 0 either selects the first device or the
1780 first fan-out link behind PMP device. It does not
1781 select the host link. DEVICE number of 15 selects the
1782 host link and device attached to it.
1784 The VAL specifies the configuration to force. As long
1785 as there's no ambiguity shortcut notation is allowed.
1786 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1787 The following configurations can be forced.
1789 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1790 Any ID with matching PORT is used.
1792 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1794 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1795 udma[/][16,25,33,44,66,100,133] notation is also
1798 * [no]ncq: Turn on or off NCQ.
1800 * nohrst, nosrst, norst: suppress hard, soft
1803 * rstonce: only attempt one reset during
1804 hot-unplug link recovery
1806 * dump_id: dump IDENTIFY data.
1808 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1810 * disable: Disable this device.
1812 If there are multiple matching configurations changing
1813 the same attribute, the last one is used.
1815 memblock=debug [KNL] Enable memblock debug messages.
1817 load_ramdisk= [RAM] List of ramdisks to load from floppy
1818 See Documentation/blockdev/ramdisk.txt.
1820 lockd.nlm_grace_period=P [NFS] Assign grace period.
1823 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1826 lockd.nlm_timeout=T [NFS] Assign timeout value.
1829 lockd.nlm_udpport=M [NFS] Assign UDP port.
1832 locktorture.nreaders_stress= [KNL]
1833 Set the number of locking read-acquisition kthreads.
1834 Defaults to being automatically set based on the
1835 number of online CPUs.
1837 locktorture.nwriters_stress= [KNL]
1838 Set the number of locking write-acquisition kthreads.
1840 locktorture.onoff_holdoff= [KNL]
1841 Set time (s) after boot for CPU-hotplug testing.
1843 locktorture.onoff_interval= [KNL]
1844 Set time (s) between CPU-hotplug operations, or
1845 zero to disable CPU-hotplug testing.
1847 locktorture.shuffle_interval= [KNL]
1848 Set task-shuffle interval (jiffies). Shuffling
1849 tasks allows some CPUs to go into dyntick-idle
1850 mode during the locktorture test.
1852 locktorture.shutdown_secs= [KNL]
1853 Set time (s) after boot system shutdown. This
1854 is useful for hands-off automated testing.
1856 locktorture.stat_interval= [KNL]
1857 Time (s) between statistics printk()s.
1859 locktorture.stutter= [KNL]
1860 Time (s) to stutter testing, for example,
1861 specifying five seconds causes the test to run for
1862 five seconds, wait for five seconds, and so on.
1863 This tests the locking primitive's ability to
1864 transition abruptly to and from idle.
1866 locktorture.torture_runnable= [BOOT]
1867 Start locktorture running at boot time.
1869 locktorture.torture_type= [KNL]
1870 Specify the locking implementation to test.
1872 locktorture.verbose= [KNL]
1873 Enable additional printk() statements.
1875 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1878 loglevel= All Kernel Messages with a loglevel smaller than the
1879 console loglevel will be printed to the console. It can
1880 also be changed with klogd or other programs. The
1881 loglevels are defined as follows:
1883 0 (KERN_EMERG) system is unusable
1884 1 (KERN_ALERT) action must be taken immediately
1885 2 (KERN_CRIT) critical conditions
1886 3 (KERN_ERR) error conditions
1887 4 (KERN_WARNING) warning conditions
1888 5 (KERN_NOTICE) normal but significant condition
1889 6 (KERN_INFO) informational
1890 7 (KERN_DEBUG) debug-level messages
1892 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1893 in bytes. n must be a power of two and greater
1894 than the minimal size. The minimal size is defined
1895 by LOG_BUF_SHIFT kernel config parameter. There is
1896 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1897 that allows to increase the default size depending on
1898 the number of CPUs. See init/Kconfig for more details.
1900 logo.nologo [FB] Disables display of the built-in Linux logo.
1901 This may be used to provide more screen space for
1902 kernel log messages and is useful when debugging
1903 kernel boot problems.
1905 lp=0 [LP] Specify parallel ports to use, e.g,
1906 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1907 lp=reset first parallel port). 'lp=0' disables the
1908 lp=auto printer driver. 'lp=reset' (which can be
1909 specified in addition to the ports) causes
1910 attached printers to be reset. Using
1911 lp=port1,port2,... specifies the parallel ports
1912 to associate lp devices with, starting with
1913 lp0. A port specification may be 'none' to skip
1914 that lp device, or a parport name such as
1915 'parport0'. Specifying 'lp=auto' instead of a
1916 port specification list means that device IDs
1917 from each port should be examined, to see if
1918 an IEEE 1284-compliant printer is attached; if
1919 so, the driver will manage that printer.
1920 See also header of drivers/char/lp.c.
1923 Sets loops_per_jiffy to given constant, thus avoiding
1924 time-consuming boot-time autodetection (up to 250 ms per
1925 CPU). 0 enables autodetection (default). To determine
1926 the correct value for your kernel, boot with normal
1927 autodetection and see what value is printed. Note that
1928 on SMP systems the preset will be applied to all CPUs,
1929 which is likely to cause problems if your CPUs need
1930 significantly divergent settings. An incorrect value
1931 will cause delays in the kernel to be wrong, leading to
1932 unpredictable I/O errors and other breakage. Although
1933 unlikely, in the extreme case this might damage your
1937 Format: <io>,<irq>,<dma>
1939 machvec= [IA-64] Force the use of a particular machine-vector
1940 (machvec) in a generic kernel.
1941 Example: machvec=hpzx1_swiotlb
1943 machtype= [Loongson] Share the same kernel image file between different
1945 Example: machtype=lemote-yeeloong-2f-7inch
1947 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1948 than or equal to this physical address is ignored.
1950 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1951 should make use of. maxcpus=n : n >= 0 limits the
1952 kernel to using 'n' processors. n=0 is a special case,
1953 it is equivalent to "nosmp", which also disables
1956 max_loop= [LOOP] The number of loop block devices that get
1957 (loop.max_loop) unconditionally pre-created at init time. The default
1958 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1959 of statically allocating a predefined number, loop
1960 devices can be requested on-demand with the
1961 /dev/loop-control interface.
1963 mce [X86-32] Machine Check Exception
1965 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1967 md= [HW] RAID subsystems devices and level
1968 See Documentation/md.txt.
1971 Format: <first>,<last>
1972 Specifies range of consoles to be captured by the MDA.
1974 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1975 Amount of memory to be used when the kernel is not able
1976 to see the whole system memory or for test.
1977 [X86] Work as limiting max address. Use together
1978 with memmap= to avoid physical address space collisions.
1979 Without memmap= PCI devices could be placed at addresses
1980 belonging to unused RAM.
1982 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1986 [KNL,SH] Allow user to override the default size for
1987 per-device physically contiguous DMA buffers.
1989 memmap=exactmap [KNL,X86] Enable setting of an exact
1990 E820 memory map, as specified by the user.
1991 Such memmap=exactmap lines can be constructed based on
1992 BIOS output or other requirements. See the memmap=nn@ss
1995 memmap=nn[KMG]@ss[KMG]
1996 [KNL] Force usage of a specific region of memory.
1997 Region of memory to be used is from ss to ss+nn.
1999 memmap=nn[KMG]#ss[KMG]
2000 [KNL,ACPI] Mark specific memory as ACPI data.
2001 Region of memory to be marked is from ss to ss+nn.
2003 memmap=nn[KMG]$ss[KMG]
2004 [KNL,ACPI] Mark specific memory as reserved.
2005 Region of memory to be reserved is from ss to ss+nn.
2006 Example: Exclude memory from 0x18690000-0x1869ffff
2007 memmap=64K$0x18690000
2009 memmap=0x10000$0x18690000
2011 memmap=nn[KMG]!ss[KMG]
2012 [KNL,X86] Mark specific memory as protected.
2013 Region of memory to be used, from ss to ss+nn.
2014 The memory region may be marked as e820 type 12 (0xc)
2015 and is NVDIMM or ADR memory.
2017 memory_corruption_check=0/1 [X86]
2018 Some BIOSes seem to corrupt the first 64k of
2019 memory when doing things like suspend/resume.
2020 Setting this option will scan the memory
2021 looking for corruption. Enabling this will
2022 both detect corruption and prevent the kernel
2023 from using the memory being corrupted.
2024 However, its intended as a diagnostic tool; if
2025 repeatable BIOS-originated corruption always
2026 affects the same memory, you can use memmap=
2027 to prevent the kernel from using that memory.
2029 memory_corruption_check_size=size [X86]
2030 By default it checks for corruption in the low
2031 64k, making this memory unavailable for normal
2032 use. Use this parameter to scan for
2033 corruption in more or less memory.
2035 memory_corruption_check_period=seconds [X86]
2036 By default it checks for corruption every 60
2037 seconds. Use this parameter to check at some
2038 other rate. 0 disables periodic checking.
2040 memtest= [KNL,X86,ARM] Enable memtest
2042 default : 0 <disable>
2043 Specifies the number of memtest passes to be
2044 performed. Each pass selects another test
2045 pattern from a given set of patterns. Memtest
2046 fills the memory with this pattern, validates
2047 memory contents and reserves bad memory
2048 regions that are detected.
2050 meye.*= [HW] Set MotionEye Camera parameters
2051 See Documentation/video4linux/meye.txt.
2053 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2054 Multi-Function General Purpose Timers on AMD Geode
2057 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2058 the BIOS has incorrectly applied a workaround. TinyBIOS
2059 version 0.98 is known to be affected, 0.99 fixes the
2060 problem by letting the user disable the workaround.
2064 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2065 physical address is ignored.
2067 mini2440= [ARM,HW,KNL]
2068 Format:[0..2][b][c][t]
2070 MINI2440 configuration specification:
2071 0 - The attached screen is the 3.5" TFT
2072 1 - The attached screen is the 7" TFT
2073 2 - The VGA Shield is attached (1024x768)
2074 Leaving out the screen size parameter will not load
2075 the TFT driver, and the framebuffer will be left
2077 b - Enable backlight. The TFT backlight pin will be
2078 linked to the kernel VESA blanking code and a GPIO
2079 LED. This parameter is not necessary when using the
2081 c - Enable the s3c camera interface.
2082 t - Reserved for enabling touchscreen support. The
2083 touchscreen support is not enabled in the mainstream
2084 kernel as of 2.6.30, a preliminary port can be found
2085 in the "bleeding edge" mini2440 support kernel at
2086 http://repo.or.cz/w/linux-2.6/mini2440.git
2089 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2090 parameter allows control of the logging verbosity for
2091 the additional memory initialisation checks. A value
2092 of 0 disables mminit logging and a level of 4 will
2093 log everything. Information is printed at KERN_DEBUG
2094 so loglevel=8 may also need to be specified.
2097 [KNL] When CONFIG_MODULE_SIG is set, this means that
2098 modules without (valid) signatures will fail to load.
2099 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2100 is always true, so this option does nothing.
2103 [MOUSE] Maximum time between finger touching and
2104 leaving touchpad surface for touch to be considered
2105 a tap and be reported as a left button click (for
2106 touchpads working in absolute mode only).
2108 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2109 reporting absolute coordinates, such as tablets
2110 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2111 reporting absolute coordinates, such as tablets
2113 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2114 is similar to kernelcore except it specifies the
2115 amount of memory used for migratable allocations.
2116 If both kernelcore and movablecore is specified,
2117 then kernelcore will be at *least* the specified
2118 value but may be more. If movablecore on its own
2119 is specified, the administrator must be careful
2120 that the amount of memory usable for all allocations
2123 movable_node [KNL,X86] Boot-time switch to enable the effects
2124 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2126 MTD_Partition= [MTD]
2127 Format: <name>,<region-number>,<size>,<offset>
2129 MTD_Region= [MTD] Format:
2130 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2133 See drivers/mtd/cmdlinepart.c.
2135 multitce=off [PPC] This parameter disables the use of the pSeries
2136 firmware feature for updating multiple TCE entries
2139 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2141 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2143 boundary - index of last SLC block on Flex-OneNAND.
2144 The remaining blocks are configured as MLC blocks.
2145 lock - Configure if Flex-OneNAND boundary should be locked.
2146 Once locked, the boundary cannot be changed.
2147 1 indicates lock status, 0 indicates unlock status.
2150 ARM/S3C2412 JIVE boot control
2152 See arch/arm/mach-s3c2412/mach-jive.c
2154 mtouchusb.raw_coordinates=
2155 [HW] Make the MicroTouch USB driver use raw coordinates
2156 ('y', default) or cooked coordinates ('n')
2158 mtrr_chunk_size=nn[KMG] [X86]
2159 used for mtrr cleanup. It is largest continuous chunk
2160 that could hold holes aka. UC entries.
2162 mtrr_gran_size=nn[KMG] [X86]
2163 Used for mtrr cleanup. It is granularity of mtrr block.
2165 Large value could prevent small alignment from
2168 mtrr_spare_reg_nr=n [X86]
2170 Range: 0,7 : spare reg number
2172 Used for mtrr cleanup. It is spare mtrr entries number.
2173 Set to 2 or more if your graphical card needs more.
2175 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2177 netdev= [NET] Network devices parameters
2178 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2179 Note that mem_start is often overloaded to mean
2180 something different and driver-specific.
2181 This usage is only documented in each driver source
2185 [NETFILTER] Enable connection tracking flow accounting
2186 0 to disable accounting
2187 1 to enable accounting
2190 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2191 See Documentation/filesystems/nfs/nfsroot.txt.
2193 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2194 See Documentation/filesystems/nfs/nfsroot.txt.
2196 nfsrootdebug [NFS] enable nfsroot debugging messages.
2197 See Documentation/filesystems/nfs/nfsroot.txt.
2199 nfs.callback_tcpport=
2200 [NFS] set the TCP port on which the NFSv4 callback
2201 channel should listen.
2204 [NFS] sets the pathname to the program which is used
2205 to update the NFS client cache entries.
2207 nfs.cache_getent_timeout=
2208 [NFS] sets the timeout after which an attempt to
2209 update a cache entry is deemed to have failed.
2211 nfs.idmap_cache_timeout=
2212 [NFS] set the maximum lifetime for idmapper cache
2216 [NFS] enable 64-bit inode numbers.
2217 If zero, the NFS client will fake up a 32-bit inode
2218 number for the readdir() and stat() syscalls instead
2219 of returning the full 64-bit number.
2220 The default is to return 64-bit inode numbers.
2222 nfs.max_session_slots=
2223 [NFSv4.1] Sets the maximum number of session slots
2224 the client will attempt to negotiate with the server.
2225 This limits the number of simultaneous RPC requests
2226 that the client can send to the NFSv4.1 server.
2227 Note that there is little point in setting this
2228 value higher than the max_tcp_slot_table_limit.
2230 nfs.nfs4_disable_idmapping=
2231 [NFSv4] When set to the default of '1', this option
2232 ensures that both the RPC level authentication
2233 scheme and the NFS level operations agree to use
2234 numeric uids/gids if the mount is using the
2235 'sec=sys' security flavour. In effect it is
2236 disabling idmapping, which can make migration from
2237 legacy NFSv2/v3 systems to NFSv4 easier.
2238 Servers that do not support this mode of operation
2239 will be autodetected by the client, and it will fall
2240 back to using the idmapper.
2241 To turn off this behaviour, set the value to '0'.
2243 [NFS4] Specify an additional fixed unique ident-
2244 ification string that NFSv4 clients can insert into
2245 their nfs_client_id4 string. This is typically a
2246 UUID that is generated at system install time.
2248 nfs.send_implementation_id =
2249 [NFSv4.1] Send client implementation identification
2250 information in exchange_id requests.
2251 If zero, no implementation identification information
2253 The default is to send the implementation identification
2256 nfs.recover_lost_locks =
2257 [NFSv4] Attempt to recover locks that were lost due
2258 to a lease timeout on the server. Please note that
2259 doing this risks data corruption, since there are
2260 no guarantees that the file will remain unchanged
2261 after the locks are lost.
2262 If you want to enable the kernel legacy behaviour of
2263 attempting to recover these locks, then set this
2265 The default parameter value of '0' causes the kernel
2266 not to attempt recovery of lost locks.
2268 nfsd.nfs4_disable_idmapping=
2269 [NFSv4] When set to the default of '1', the NFSv4
2270 server will return only numeric uids and gids to
2271 clients using auth_sys, and will accept numeric uids
2272 and gids from such clients. This is intended to ease
2273 migration from NFSv2/v3.
2275 objlayoutdriver.osd_login_prog=
2276 [NFS] [OBJLAYOUT] sets the pathname to the program which
2277 is used to automatically discover and login into new
2278 osd-targets. Please see:
2279 Documentation/filesystems/pnfs.txt for more explanations
2281 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2282 when a NMI is triggered.
2283 Format: [state][,regs][,debounce][,die]
2285 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2286 Format: [panic,][nopanic,][num]
2288 0 - turn nmi_watchdog off
2289 1 - turn nmi_watchdog on
2290 When panic is specified, panic when an NMI watchdog
2291 timeout occurs (or 'nopanic' to override the opposite
2293 This is useful when you use a panic=... timeout and
2294 need the box quickly up again.
2296 netpoll.carrier_timeout=
2297 [NET] Specifies amount of time (in seconds) that
2298 netpoll should wait for a carrier. By default netpoll
2301 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2302 emulation library even if a 387 maths coprocessor
2306 [HW] Never suspend the console
2307 Disable suspending of consoles during suspend and
2308 hibernate operations. Once disabled, debugging
2309 messages can reach various consoles while the rest
2310 of the system is being put to sleep (ie, while
2311 debugging driver suspend/resume hooks). This may
2312 not work reliably with all consoles, but is known
2313 to work with serial and VGA consoles.
2314 To facilitate more flexible debugging, we also add
2315 console_suspend, a printk module parameter to control
2316 it. Users could use console_suspend (usually
2317 /sys/module/printk/parameters/console_suspend) to
2318 turn on/off it dynamically.
2320 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2321 caches in the slab allocator. Saves per-node memory,
2322 but will impact performance.
2326 noapic [SMP,APIC] Tells the kernel to not make use of any
2327 IOAPICs that may be present in the system.
2329 noautogroup Disable scheduler automatic task group creation.
2331 nobats [PPC] Do not use BATs for mapping kernel lowmem
2332 on "Classic" PPC cores.
2336 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2338 nodelayacct [KNL] Disable per-task delay accounting
2340 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2342 nodsp [SH] Disable hardware DSP at boot time.
2344 noefi Disable EFI runtime services support.
2349 On X86-32 available only on PAE configured kernels.
2350 noexec=on: enable non-executable mappings (default)
2351 noexec=off: disable non-executable mappings
2354 Disable SMAP (Supervisor Mode Access Prevention)
2355 even if it is supported by processor.
2358 Disable SMEP (Supervisor Mode Execution Prevention)
2359 even if it is supported by processor.
2362 This affects only 32-bit executables.
2363 noexec32=on: enable non-executable mappings (default)
2364 read doesn't imply executable mappings
2365 noexec32=off: disable non-executable mappings
2366 read implies executable mappings
2368 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2370 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2371 register save and restore. The kernel will only save
2372 legacy floating-point registers on task switch.
2374 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2376 noxsave [BUGS=X86] Disables x86 extended register state save
2377 and restore using xsave. The kernel will fallback to
2378 enabling legacy floating-point and sse state.
2380 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2381 register states. The kernel will fall back to use
2382 xsave to save the states. By using this parameter,
2383 performance of saving the states is degraded because
2384 xsave doesn't support modified optimization while
2385 xsaveopt supports it on xsaveopt enabled systems.
2387 noxsaves [X86] Disables xsaves and xrstors used in saving and
2388 restoring x86 extended register state in compacted
2389 form of xsave area. The kernel will fall back to use
2390 xsaveopt and xrstor to save and restore the states
2391 in standard form of xsave area. By using this
2392 parameter, xsave area per process might occupy more
2393 memory on xsaves enabled systems.
2395 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2396 wfi(ARM) instruction doesn't work correctly and not to
2397 use it. This is also useful when using JTAG debugger.
2399 no_file_caps Tells the kernel not to honor file capabilities. The
2400 only way then for a file to be executed with privilege
2401 is to be setuid root or executed by root.
2403 nohalt [IA-64] Tells the kernel not to use the power saving
2404 function PAL_HALT_LIGHT when idle. This increases
2405 power-consumption. On the positive side, it reduces
2406 interrupt wake-up latency, which may improve performance
2407 in certain environments such as networked servers or
2410 nohibernate [HIBERNATION] Disable hibernation and resume.
2412 nohz= [KNL] Boottime enable/disable dynamic ticks
2413 Valid arguments: on, off
2416 nohz_full= [KNL,BOOT]
2417 In kernels built with CONFIG_NO_HZ_FULL=y, set
2418 the specified list of CPUs whose tick will be stopped
2419 whenever possible. The boot CPU will be forced outside
2420 the range to maintain the timekeeping.
2421 The CPUs in this range must also be included in the
2424 noiotrap [SH] Disables trapped I/O port accesses.
2426 noirqdebug [X86-32] Disables the code which attempts to detect and
2427 disable unhandled interrupt sources.
2429 no_timer_check [X86,APIC] Disables the code which tests for
2430 broken timer IRQ sources.
2432 noisapnp [ISAPNP] Disables ISA PnP code.
2434 noinitrd [RAM] Tells the kernel not to load any configured
2437 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2439 [Deprecated - use intremap=off]
2443 nojitter [IA-64] Disables jitter checking for ITC timers.
2445 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2447 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2450 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2451 steal time is computed, but won't influence scheduler
2454 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2456 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2458 noltlbs [PPC] Do not use large page/tlb entries for kernel
2459 lowmem mapping on PPC40x.
2461 nomca [IA-64] Disable machine check abort handling
2463 nomce [X86-32] Machine Check Exception
2465 nomfgpt [X86-32] Disable Multi-Function General Purpose
2466 Timer usage (for AMD Geode machines).
2468 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2469 shutdown the other cpus. Instead use the REBOOT_VECTOR
2472 nomodule Disable module load
2474 nopat [X86] Disable PAT (page attribute table extension of
2475 pagetables) support.
2477 norandmaps Don't use address space randomization. Equivalent to
2478 echo 0 > /proc/sys/kernel/randomize_va_space
2480 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2482 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2483 with UP alternatives
2485 nordrand [X86] Disable kernel use of the RDRAND and
2486 RDSEED instructions even if they are supported
2487 by the processor. RDRAND and RDSEED are still
2488 available to user space applications.
2490 noresume [SWSUSP] Disables resume and restores original swap
2493 no-scroll [VGA] Disables scrollback.
2494 This is required for the Braillex ib80-piezo Braille
2495 reader made by F.H. Papenmeier (Germany).
2499 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2501 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2502 and disable the IO APIC. legacy for "maxcpus=0".
2504 nosoftlockup [KNL] Disable the soft-lockup detector.
2506 nosync [HW,M68K] Disables sync negotiation for all devices.
2508 notsc [BUGS=X86-32] Disable Time Stamp Counter
2510 nousb [USB] Disable the USB subsystem
2512 nowatchdog [KNL] Disable both lockup detectors, i.e.
2513 soft-lockup and NMI watchdog (hard-lockup).
2517 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2519 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2520 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2521 Some features depend on CPU0. Known dependencies are:
2522 1. Resume from suspend/hibernate depends on CPU0.
2523 Suspend/hibernate will fail if CPU0 is offline and you
2524 need to online CPU0 before suspend/hibernate.
2525 2. PIC interrupts also depend on CPU0. CPU0 can't be
2526 removed if a PIC interrupt is detected.
2527 It's said poweroff/reboot may depend on CPU0 on some
2528 machines although I haven't seen such issues so far
2529 after CPU0 is offline on a few tested machines.
2530 If the dependencies are under your control, you can
2531 turn on cpu0_hotplug.
2533 nptcg= [IA-64] Override max number of concurrent global TLB
2534 purges which is reported from either PAL_VM_SUMMARY or
2537 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2538 could support. nr_cpus=n : n >= 1 limits the kernel to
2539 supporting 'n' processors. Later in runtime you can not
2540 use hotplug cpu feature to put more cpu back to online.
2541 just like you compile the kernel NR_CPUS=n
2543 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2545 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2546 Allowed values are enable and disable
2548 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2549 one of ['zone', 'node', 'default'] can be specified
2550 This can be set from sysctl after boot.
2551 See Documentation/sysctl/vm.txt for details.
2553 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2554 See Documentation/debugging-via-ohci1394.txt for more
2557 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2558 Rather than timing out after 20 ms if an EC
2559 command is not properly ACKed, override the length
2560 of the timeout. We have interrupts disabled while
2561 waiting for the ACK, so if this is set too high
2562 interrupts *may* be lost!
2564 omap_mux= [OMAP] Override bootloader pin multiplexing.
2565 Format: <mux_mode0.mode_name=value>...
2566 For example, to override I2C bus2:
2567 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2569 oprofile.timer= [HW]
2570 Use timer interrupt instead of performance counters
2572 oprofile.cpu_type= Force an oprofile cpu type
2573 This might be useful if you have an older oprofile
2574 userland or if you want common events.
2575 Format: { arch_perfmon }
2576 arch_perfmon: [X86] Force use of architectural
2577 perfmon on Intel CPUs instead of the
2578 CPU specific event set.
2579 timer: [X86] Force use of architectural NMI
2580 timer mode (see also oprofile.timer
2581 for generic hr timer mode)
2582 [s390] Force legacy basic mode sampling
2583 (report cpu_type "timer")
2585 oops=panic Always panic on oopses. Default is to just kill the
2586 process, but there is a small probability of
2587 deadlocking the machine.
2588 This will also cause panics on machine check exceptions.
2589 Useful together with panic=30 to trigger a reboot.
2592 See Documentation/sound/oss/oss-parameters.txt
2594 page_owner= [KNL] Boot-time page_owner enabling option.
2595 Storage of the information about who allocated
2596 each page is disabled in default. With this switch,
2598 on: enable the feature
2600 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2601 timeout > 0: seconds before rebooting
2602 timeout = 0: wait forever
2603 timeout < 0: reboot immediately
2606 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2609 crash_kexec_post_notifiers
2610 Run kdump after running panic-notifiers and dumping
2611 kmsg. This only for the users who doubt kdump always
2612 succeeds in any situation.
2613 Note that this also increases risks of kdump failure,
2614 because some panic notifiers can make the crashed
2615 kernel more unstable.
2617 parkbd.port= [HW] Parallel port number the keyboard adapter is
2618 connected to, default is 0.
2620 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2621 0 for XT, 1 for AT (default is AT).
2624 parport= [HW,PPT] Specify parallel ports. 0 disables.
2625 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2626 Use 'auto' to force the driver to use any
2627 IRQ/DMA settings detected (the default is to
2628 ignore detected IRQ/DMA settings because of
2629 possible conflicts). You can specify the base
2630 address, IRQ, and DMA settings; IRQ and DMA
2631 should be numbers, or 'auto' (for using detected
2632 settings on that particular port), or 'nofifo'
2633 (to avoid using a FIFO even if it is detected).
2634 Parallel ports are assigned in the order they
2635 are specified on the command line, starting
2638 parport_init_mode= [HW,PPT]
2639 Configure VIA parallel port to operate in
2640 a specific mode. This is necessary on Pegasos
2641 computer where firmware has no options for setting
2642 up parallel port mode and sets it to spp.
2643 Currently this function knows 686a and 8231 chips.
2644 Format: [spp|ps2|epp|ecp|ecpepp]
2647 Halt all CPUs after the first oops has been printed for
2648 the specified number of seconds. This is to be used if
2649 your oopses keep scrolling off the screen.
2654 See header of drivers/block/paride/pcd.c.
2655 See also Documentation/blockdev/paride.txt.
2657 pci=option[,option...] [PCI] various PCI subsystem options:
2658 earlydump [X86] dump PCI config space before the kernel
2660 off [X86] don't probe for the PCI bus
2661 bios [X86-32] force use of PCI BIOS, don't access
2662 the hardware directly. Use this if your machine
2663 has a non-standard PCI host bridge.
2664 nobios [X86-32] disallow use of PCI BIOS, only direct
2665 hardware access methods are allowed. Use this
2666 if you experience crashes upon bootup and you
2667 suspect they are caused by the BIOS.
2668 conf1 [X86] Force use of PCI Configuration
2670 conf2 [X86] Force use of PCI Configuration
2672 noaer [PCIE] If the PCIEAER kernel config parameter is
2673 enabled, this kernel boot option can be used to
2674 disable the use of PCIE advanced error reporting.
2675 nodomains [PCI] Disable support for multiple PCI
2676 root domains (aka PCI segments, in ACPI-speak).
2677 nommconf [X86] Disable use of MMCONFIG for PCI
2679 check_enable_amd_mmconf [X86] check for and enable
2680 properly configured MMIO access to PCI
2681 config space on AMD family 10h CPU
2682 nomsi [MSI] If the PCI_MSI kernel config parameter is
2683 enabled, this kernel boot option can be used to
2684 disable the use of MSI interrupts system-wide.
2685 noioapicquirk [APIC] Disable all boot interrupt quirks.
2686 Safety option to keep boot IRQs enabled. This
2687 should never be necessary.
2688 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2689 primary IO-APIC for bridges that cannot disable
2690 boot IRQs. This fixes a source of spurious IRQs
2691 when the system masks IRQs.
2692 noioapicreroute [APIC] Disable workaround that uses the
2693 boot IRQ equivalent of an IRQ that connects to
2694 a chipset where boot IRQs cannot be disabled.
2695 The opposite of ioapicreroute.
2696 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2697 routing table. These calls are known to be buggy
2698 on several machines and they hang the machine
2699 when used, but on other computers it's the only
2700 way to get the interrupt routing table. Try
2701 this option if the kernel is unable to allocate
2702 IRQs or discover secondary PCI buses on your
2704 rom [X86] Assign address space to expansion ROMs.
2705 Use with caution as certain devices share
2706 address decoders between ROMs and other
2708 norom [X86] Do not assign address space to
2709 expansion ROMs that do not already have
2710 BIOS assigned address ranges.
2711 nobar [X86] Do not assign address space to the
2712 BARs that weren't assigned by the BIOS.
2713 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2714 assigned automatically to PCI devices. You can
2715 make the kernel exclude IRQs of your ISA cards
2717 pirqaddr=0xAAAAA [X86] Specify the physical address
2718 of the PIRQ table (normally generated
2719 by the BIOS) if it is outside the
2720 F0000h-100000h range.
2721 lastbus=N [X86] Scan all buses thru bus #N. Can be
2722 useful if the kernel is unable to find your
2723 secondary buses and you want to tell it
2724 explicitly which ones they are.
2725 assign-busses [X86] Always assign all PCI bus
2726 numbers ourselves, overriding
2727 whatever the firmware may have done.
2728 usepirqmask [X86] Honor the possible IRQ mask stored
2729 in the BIOS $PIR table. This is needed on
2730 some systems with broken BIOSes, notably
2731 some HP Pavilion N5400 and Omnibook XE3
2732 notebooks. This will have no effect if ACPI
2733 IRQ routing is enabled.
2734 noacpi [X86] Do not use ACPI for IRQ routing
2735 or for PCI scanning.
2736 use_crs [X86] Use PCI host bridge window information
2737 from ACPI. On BIOSes from 2008 or later, this
2738 is enabled by default. If you need to use this,
2739 please report a bug.
2740 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2741 If you need to use this, please report a bug.
2742 routeirq Do IRQ routing for all PCI devices.
2743 This is normally done in pci_enable_device(),
2744 so this option is a temporary workaround
2745 for broken drivers that don't call it.
2746 skip_isa_align [X86] do not align io start addr, so can
2747 handle more pci cards
2748 firmware [ARM] Do not re-enumerate the bus but instead
2749 just use the configuration from the
2750 bootloader. This is currently used on
2751 IXP2000 systems where the bus has to be
2752 configured a certain way for adjunct CPUs.
2753 noearly [X86] Don't do any early type 1 scanning.
2754 This might help on some broken boards which
2755 machine check when some devices' config space
2756 is read. But various workarounds are disabled
2757 and some IOMMU drivers will not work.
2758 bfsort Sort PCI devices into breadth-first order.
2759 This sorting is done to get a device
2760 order compatible with older (<= 2.4) kernels.
2761 nobfsort Don't sort PCI devices into breadth-first order.
2762 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2763 tuning and use the BIOS-configured MPS defaults.
2764 pcie_bus_safe Set every device's MPS to the largest value
2765 supported by all devices below the root complex.
2766 pcie_bus_perf Set device MPS to the largest allowable MPS
2767 based on its parent bus. Also set MRRS (Max
2768 Read Request Size) to the largest supported
2769 value (no larger than the MPS that the device
2770 or bus can support) for best performance.
2771 pcie_bus_peer2peer Set every device's MPS to 128B, which
2772 every device is guaranteed to support. This
2773 configuration allows peer-to-peer DMA between
2774 any pair of devices, possibly at the cost of
2775 reduced performance. This also guarantees
2776 that hot-added devices will work.
2777 cbiosize=nn[KMG] The fixed amount of bus space which is
2778 reserved for the CardBus bridge's IO window.
2779 The default value is 256 bytes.
2780 cbmemsize=nn[KMG] The fixed amount of bus space which is
2781 reserved for the CardBus bridge's memory
2782 window. The default value is 64 megabytes.
2785 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2786 Specifies alignment and device to reassign
2787 aligned memory resources.
2788 If <order of align> is not specified,
2789 PAGE_SIZE is used as alignment.
2790 PCI-PCI bridge can be specified, if resource
2791 windows need to be expanded.
2792 ecrc= Enable/disable PCIe ECRC (transaction layer
2793 end-to-end CRC checking).
2794 bios: Use BIOS/firmware settings. This is the
2798 hpiosize=nn[KMG] The fixed amount of bus space which is
2799 reserved for hotplug bridge's IO window.
2800 Default size is 256 bytes.
2801 hpmemsize=nn[KMG] The fixed amount of bus space which is
2802 reserved for hotplug bridge's memory window.
2803 Default size is 2 megabytes.
2804 realloc= Enable/disable reallocating PCI bridge resources
2805 if allocations done by BIOS are too small to
2806 accommodate resources required by all child
2808 off: Turn realloc off
2810 realloc same as realloc=on
2811 noari do not use PCIe ARI.
2812 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2813 only look for one device below a PCIe downstream
2816 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2819 force Enable ASPM even on devices that claim not to support it.
2820 WARNING: Forcing ASPM on may cause system lockups.
2822 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2823 nomsi Do not use MSI for PCI Express Native Hotplug (this
2824 makes all PCIe ports use INTx for hotplug services).
2826 pcie_ports= [PCIE] PCIe ports handling:
2827 auto Ask the BIOS whether or not to use native PCIe services
2828 associated with PCIe ports (PME, hot-plug, AER). Use
2829 them only if that is allowed by the BIOS.
2830 native Use native PCIe services associated with PCIe ports
2832 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2835 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2836 nomsi Do not use MSI for native PCIe PME signaling (this makes
2837 all PCIe root ports use INTx for all services).
2839 pcmv= [HW,PCMCIA] BadgePAD 4
2843 Keep all power-domains already enabled by bootloader on,
2844 even if no driver has claimed them. This is useful
2845 for debug and development, but should not be
2846 needed on a platform with proper driver support.
2849 See Documentation/blockdev/paride.txt.
2851 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2854 See arch/parisc/kernel/pdc_chassis.c
2856 percpu_alloc= Select which percpu first chunk allocator to use.
2857 Currently supported values are "embed" and "page".
2858 Archs may support subset or none of the selections.
2859 See comments in mm/percpu.c for details on each
2860 allocator. This parameter is primarily for debugging
2861 and performance comparison.
2864 See Documentation/blockdev/paride.txt.
2867 See Documentation/blockdev/paride.txt.
2869 pirq= [SMP,APIC] Manual mp-table setup
2870 See Documentation/x86/i386/IO-APIC.txt.
2872 plip= [PPT,NET] Parallel port network link
2873 Format: { parport<nr> | timid | 0 }
2874 See also Documentation/parport.txt.
2876 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2877 Override pmtimer IOPort with a hex value.
2881 Enable PNP debug messages (depends on the
2882 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2883 via /sys/module/pnp/parameters/debug. We always show
2884 current resource usage; turning this on also shows
2885 possible settings and some assignment information.
2891 { on | off | curr | res | no-curr | no-res }
2894 [ISAPNP] Exclude IRQs for the autoconfiguration
2897 [ISAPNP] Exclude DMAs for the autoconfiguration
2899 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2900 Ranges are in pairs (I/O port base and size).
2903 [ISAPNP] Exclude memory regions for the
2905 Ranges are in pairs (memory base and size).
2907 ports= [IP_VS_FTP] IPVS ftp helper module
2909 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2911 Format: <port>,<port>....
2913 print-fatal-signals=
2914 [KNL] debug: print fatal signals
2916 If enabled, warn about various signal handling
2917 related application anomalies: too many signals,
2918 too many POSIX.1 timers, fatal signals causing a
2921 If you hit the warning due to signal overflow,
2922 you might want to try "ulimit -i unlimited".
2926 printk.always_kmsg_dump=
2927 Trigger kmsg_dump for cases other than kernel oops or
2929 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2932 printk.time= Show timing data prefixed to each printk message line
2933 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2935 processor.max_cstate= [HW,ACPI]
2936 Limit processor to maximum C-state
2937 max_cstate=9 overrides any DMI blacklist limit.
2939 processor.nocst [HW,ACPI]
2940 Ignore the _CST method to determine C-states,
2941 instead using the legacy FADT method
2943 profile= [KNL] Enable kernel profiling via /proc/profile
2944 Format: [schedule,]<number>
2945 Param: "schedule" - profile schedule points.
2946 Param: <number> - step/bucket size as a power of 2 for
2947 statistical time based profiling.
2948 Param: "sleep" - profile D-state sleeping (millisecs).
2949 Requires CONFIG_SCHEDSTATS
2950 Param: "kvm" - profile VM exits.
2952 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2954 See Documentation/blockdev/ramdisk.txt.
2956 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2957 probe for; one of (bare|imps|exps|lifebook|any).
2958 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2960 psmouse.resetafter= [HW,MOUSE]
2961 Try to reset the device after so many bad packets
2964 [HW,MOUSE] Set desired mouse resolution, in dpi.
2965 psmouse.smartscroll=
2966 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2967 0 = disabled, 1 = enabled (default).
2969 pstore.backend= Specify the name of the pstore backend to use
2972 See Documentation/blockdev/paride.txt.
2975 [KNL] Number of legacy pty's. Overwrites compiled-in
2978 quiet [KNL] Disable most log messages
2983 See Documentation/md.txt.
2985 ramdisk_blocksize= [RAM]
2986 See Documentation/blockdev/ramdisk.txt.
2988 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2989 See Documentation/blockdev/ramdisk.txt.
2992 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2993 the specified list of CPUs to be no-callback CPUs.
2994 Invocation of these CPUs' RCU callbacks will
2995 be offloaded to "rcuox/N" kthreads created for
2996 that purpose, where "x" is "b" for RCU-bh, "p"
2997 for RCU-preempt, and "s" for RCU-sched, and "N"
2998 is the CPU number. This reduces OS jitter on the
2999 offloaded CPUs, which can be useful for HPC and
3000 real-time workloads. It can also improve energy
3001 efficiency for asymmetric multiprocessors.
3004 Rather than requiring that offloaded CPUs
3005 (specified by rcu_nocbs= above) explicitly
3006 awaken the corresponding "rcuoN" kthreads,
3007 make these kthreads poll for callbacks.
3008 This improves the real-time response for the
3009 offloaded CPUs by relieving them of the need to
3010 wake up the corresponding kthread, but degrades
3011 energy efficiency by requiring that the kthreads
3012 periodically wake up to do the polling.
3014 rcutree.blimit= [KNL]
3015 Set maximum number of finished RCU callbacks to
3016 process in one batch.
3018 rcutree.gp_init_delay= [KNL]
3019 Set the number of jiffies to delay each step of
3020 RCU grace-period initialization. This only has
3021 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT is
3024 rcutree.rcu_fanout_leaf= [KNL]
3025 Increase the number of CPUs assigned to each
3026 leaf rcu_node structure. Useful for very large
3029 rcutree.jiffies_till_sched_qs= [KNL]
3030 Set required age in jiffies for a
3031 given grace period before RCU starts
3032 soliciting quiescent-state help from
3033 rcu_note_context_switch().
3035 rcutree.jiffies_till_first_fqs= [KNL]
3036 Set delay from grace-period initialization to
3037 first attempt to force quiescent states.
3038 Units are jiffies, minimum value is zero,
3039 and maximum value is HZ.
3041 rcutree.jiffies_till_next_fqs= [KNL]
3042 Set delay between subsequent attempts to force
3043 quiescent states. Units are jiffies, minimum
3044 value is one, and maximum value is HZ.
3046 rcutree.kthread_prio= [KNL,BOOT]
3047 Set the SCHED_FIFO priority of the RCU per-CPU
3048 kthreads (rcuc/N). This value is also used for
3049 the priority of the RCU boost threads (rcub/N)
3050 and for the RCU grace-period kthreads (rcu_bh,
3051 rcu_preempt, and rcu_sched). If RCU_BOOST is
3052 set, valid values are 1-99 and the default is 1
3053 (the least-favored priority). Otherwise, when
3054 RCU_BOOST is not set, valid values are 0-99 and
3055 the default is zero (non-realtime operation).
3057 rcutree.rcu_nocb_leader_stride= [KNL]
3058 Set the number of NOCB kthread groups, which
3059 defaults to the square root of the number of
3060 CPUs. Larger numbers reduces the wakeup overhead
3061 on the per-CPU grace-period kthreads, but increases
3062 that same overhead on each group's leader.
3064 rcutree.qhimark= [KNL]
3065 Set threshold of queued RCU callbacks beyond which
3066 batch limiting is disabled.
3068 rcutree.qlowmark= [KNL]
3069 Set threshold of queued RCU callbacks below which
3070 batch limiting is re-enabled.
3072 rcutree.rcu_idle_gp_delay= [KNL]
3073 Set wakeup interval for idle CPUs that have
3074 RCU callbacks (RCU_FAST_NO_HZ=y).
3076 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3077 Set wakeup interval for idle CPUs that have
3078 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3079 Lazy RCU callbacks are those which RCU can
3080 prove do nothing more than free memory.
3082 rcutorture.cbflood_inter_holdoff= [KNL]
3083 Set holdoff time (jiffies) between successive
3084 callback-flood tests.
3086 rcutorture.cbflood_intra_holdoff= [KNL]
3087 Set holdoff time (jiffies) between successive
3088 bursts of callbacks within a given callback-flood
3091 rcutorture.cbflood_n_burst= [KNL]
3092 Set the number of bursts making up a given
3093 callback-flood test. Set this to zero to
3094 disable callback-flood testing.
3096 rcutorture.cbflood_n_per_burst= [KNL]
3097 Set the number of callbacks to be registered
3098 in a given burst of a callback-flood test.
3100 rcutorture.fqs_duration= [KNL]
3101 Set duration of force_quiescent_state bursts.
3103 rcutorture.fqs_holdoff= [KNL]
3104 Set holdoff time within force_quiescent_state bursts.
3106 rcutorture.fqs_stutter= [KNL]
3107 Set wait time between force_quiescent_state bursts.
3109 rcutorture.gp_exp= [KNL]
3110 Use expedited update-side primitives.
3112 rcutorture.gp_normal= [KNL]
3113 Use normal (non-expedited) update-side primitives.
3114 If both gp_exp and gp_normal are set, do both.
3115 If neither gp_exp nor gp_normal are set, still
3118 rcutorture.n_barrier_cbs= [KNL]
3119 Set callbacks/threads for rcu_barrier() testing.
3121 rcutorture.nfakewriters= [KNL]
3122 Set number of concurrent RCU writers. These just
3123 stress RCU, they don't participate in the actual
3124 test, hence the "fake".
3126 rcutorture.nreaders= [KNL]
3127 Set number of RCU readers.
3129 rcutorture.object_debug= [KNL]
3130 Enable debug-object double-call_rcu() testing.
3132 rcutorture.onoff_holdoff= [KNL]
3133 Set time (s) after boot for CPU-hotplug testing.
3135 rcutorture.onoff_interval= [KNL]
3136 Set time (s) between CPU-hotplug operations, or
3137 zero to disable CPU-hotplug testing.
3139 rcutorture.torture_runnable= [BOOT]
3140 Start rcutorture running at boot time.
3142 rcutorture.shuffle_interval= [KNL]
3143 Set task-shuffle interval (s). Shuffling tasks
3144 allows some CPUs to go into dyntick-idle mode
3145 during the rcutorture test.
3147 rcutorture.shutdown_secs= [KNL]
3148 Set time (s) after boot system shutdown. This
3149 is useful for hands-off automated testing.
3151 rcutorture.stall_cpu= [KNL]
3152 Duration of CPU stall (s) to test RCU CPU stall
3153 warnings, zero to disable.
3155 rcutorture.stall_cpu_holdoff= [KNL]
3156 Time to wait (s) after boot before inducing stall.
3158 rcutorture.stat_interval= [KNL]
3159 Time (s) between statistics printk()s.
3161 rcutorture.stutter= [KNL]
3162 Time (s) to stutter testing, for example, specifying
3163 five seconds causes the test to run for five seconds,
3164 wait for five seconds, and so on. This tests RCU's
3165 ability to transition abruptly to and from idle.
3167 rcutorture.test_boost= [KNL]
3168 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3169 "Maybe" means test if the RCU implementation
3170 under test support RCU priority boosting.
3172 rcutorture.test_boost_duration= [KNL]
3173 Duration (s) of each individual boost test.
3175 rcutorture.test_boost_interval= [KNL]
3176 Interval (s) between each boost test.
3178 rcutorture.test_no_idle_hz= [KNL]
3179 Test RCU's dyntick-idle handling. See also the
3180 rcutorture.shuffle_interval parameter.
3182 rcutorture.torture_type= [KNL]
3183 Specify the RCU implementation to test.
3185 rcutorture.verbose= [KNL]
3186 Enable additional printk() statements.
3188 rcupdate.rcu_expedited= [KNL]
3189 Use expedited grace-period primitives, for
3190 example, synchronize_rcu_expedited() instead
3191 of synchronize_rcu(). This reduces latency,
3192 but can increase CPU utilization, degrade
3193 real-time latency, and degrade energy efficiency.
3195 rcupdate.rcu_cpu_stall_suppress= [KNL]
3196 Suppress RCU CPU stall warning messages.
3198 rcupdate.rcu_cpu_stall_timeout= [KNL]
3199 Set timeout for RCU CPU stall warning messages.
3201 rcupdate.rcu_task_stall_timeout= [KNL]
3202 Set timeout in jiffies for RCU task stall warning
3203 messages. Disable with a value less than or equal
3206 rcupdate.rcu_self_test= [KNL]
3207 Run the RCU early boot self tests
3209 rcupdate.rcu_self_test_bh= [KNL]
3210 Run the RCU bh early boot self tests
3212 rcupdate.rcu_self_test_sched= [KNL]
3213 Run the RCU sched early boot self tests
3217 Run specified binary instead of /init from the ramdisk,
3218 used for early userspace startup. See initrd.
3221 Format (x86 or x86_64):
3222 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3224 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3226 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3227 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3228 reboot_force is either force or not specified,
3229 reboot_cpu is s[mp]#### with #### being the processor
3230 to be used for rebooting.
3233 [KNL, SMP] Set scheduler's default relax_domain_level.
3234 See Documentation/cgroups/cpusets.txt.
3236 relative_sleep_states=
3237 [SUSPEND] Use sleep state labeling where the deepest
3238 state available other than hibernation is always "mem".
3239 Format: { "0" | "1" }
3240 0 -- Traditional sleep state labels.
3241 1 -- Relative sleep state labels.
3243 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3245 reservetop= [X86-32]
3247 Reserves a hole at the top of the kernel virtual
3252 Set the amount of memory to reserve for BIOS at
3253 the bottom of the address space.
3255 reset_devices [KNL] Force drivers to reset the underlying device
3256 during initialization.
3259 Specify the partition device for software suspend
3261 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3263 resume_offset= [SWSUSP]
3264 Specify the offset from the beginning of the partition
3265 given by "resume=" at which the swap header is located,
3266 in <PAGE_SIZE> units (needed only for swap files).
3267 See Documentation/power/swsusp-and-swap-files.txt
3269 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3270 read the resume files
3272 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3273 Useful for devices that are detected asynchronously
3274 (e.g. USB and MMC devices).
3276 hibernate= [HIBERNATION]
3277 noresume Don't check if there's a hibernation image
3278 present during boot.
3279 nocompress Don't compress/decompress hibernation images.
3280 no Disable hibernation and resume.
3282 retain_initrd [RAM] Keep initrd memory after extraction
3284 rfkill.default_state=
3285 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3286 etc. communication is blocked by default.
3289 rfkill.master_switch_mode=
3290 0 The "airplane mode" button does nothing.
3291 1 The "airplane mode" button toggles between everything
3292 blocked and the previous configuration.
3293 2 The "airplane mode" button toggles between everything
3294 blocked and everything unblocked.
3296 rhash_entries= [KNL,NET]
3297 Set number of hash buckets for route cache
3299 ro [KNL] Mount root device read-only on boot
3301 root= [KNL] Root filesystem
3302 See name_to_dev_t comment in init/do_mounts.c.
3304 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3305 mount the root filesystem
3307 rootflags= [KNL] Set root filesystem mount option string
3309 rootfstype= [KNL] Set root filesystem type
3311 rootwait [KNL] Wait (indefinitely) for root device to show up.
3312 Useful for devices that are detected asynchronously
3313 (e.g. USB and MMC devices).
3315 rproc_mem=nn[KMG][@address]
3316 [KNL,ARM,CMA] Remoteproc physical memory block.
3317 Memory area to be used by remote processor image,
3320 rw [KNL] Mount root device read-write on boot
3322 S [KNL] Run init in single mode
3324 s390_iommu= [HW,S390]
3325 Set s390 IOTLB flushing mode
3327 With strict flushing every unmap operation will result in
3328 an IOTLB flush. Default is lazy flushing before reuse,
3332 See drivers/net/irda/sa1100_ir.c.
3334 sbni= [NET] Granch SBNI12 leased line adapter
3336 sched_debug [KNL] Enables verbose scheduler debug messages.
3338 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3339 xtime_lock contention on larger systems, and/or RCU lock
3340 contention on all systems with CONFIG_MAXSMP set.
3341 Format: { "0" | "1" }
3342 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3344 Note: increases power consumption, thus should only be
3345 enabled if running jitter sensitive (HPC/RT) workloads.
3347 security= [SECURITY] Choose a security module to enable at boot.
3348 If this boot parameter is not specified, only the first
3349 security module asking for security registration will be
3350 loaded. An invalid security module name will be treated
3351 as if no module has been chosen.
3353 selinux= [SELINUX] Disable or enable SELinux at boot time.
3354 Format: { "0" | "1" }
3355 See security/selinux/Kconfig help text.
3358 Default value is set via kernel config option.
3359 If enabled at boot time, /selinux/disable can be used
3360 later to disable prior to initial policy load.
3362 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3363 Format: { "0" | "1" }
3364 See security/apparmor/Kconfig help text
3367 Default value is set via kernel config option.
3369 serialnumber [BUGS=X86-32]
3372 Maximal number of shapers.
3374 show_msr= [x86] show boot-time MSR settings
3375 Format: { <integer> }
3376 Show boot-time (BIOS-initialized) MSR settings.
3377 The parameter means the number of CPUs to show,
3378 for example 1 means boot CPU only.
3386 Disable merging of slabs with similar size. May be
3387 necessary if there is some reason to distinguish
3388 allocs to different slabs. Debug options disable
3389 merging on their own.
3390 For more information see Documentation/vm/slub.txt.
3392 slab_max_order= [MM, SLAB]
3393 Determines the maximum allowed order for slabs.
3394 A high setting may cause OOMs due to memory
3395 fragmentation. Defaults to 1 for systems with
3396 more than 32MB of RAM, 0 otherwise.
3398 slub_debug[=options[,slabs]] [MM, SLUB]
3399 Enabling slub_debug allows one to determine the
3400 culprit if slab objects become corrupted. Enabling
3401 slub_debug can create guard zones around objects and
3402 may poison objects when not in use. Also tracks the
3403 last alloc / free. For more information see
3404 Documentation/vm/slub.txt.
3406 slub_max_order= [MM, SLUB]
3407 Determines the maximum allowed order for slabs.
3408 A high setting may cause OOMs due to memory
3409 fragmentation. For more information see
3410 Documentation/vm/slub.txt.
3412 slub_min_objects= [MM, SLUB]
3413 The minimum number of objects per slab. SLUB will
3414 increase the slab order up to slub_max_order to
3415 generate a sufficiently large slab able to contain
3416 the number of objects indicated. The higher the number
3417 of objects the smaller the overhead of tracking slabs
3418 and the less frequently locks need to be acquired.
3419 For more information see Documentation/vm/slub.txt.
3421 slub_min_order= [MM, SLUB]
3422 Determines the minimum page order for slabs. Must be
3423 lower than slub_max_order.
3424 For more information see Documentation/vm/slub.txt.
3426 slub_nomerge [MM, SLUB]
3427 Same with slab_nomerge. This is supported for legacy.
3428 See slab_nomerge for more information.
3431 Format: <io1>[,<io2>[,...,<io8>]]
3433 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3434 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3435 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3436 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3437 smsc-ircc2.ircc_irq= [HW] IRQ line
3438 smsc-ircc2.ircc_dma= [HW] DMA channel
3439 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3440 0: Toshiba Satellite 1800 (GP data pin select)
3441 1: Fast pin select (default)
3445 [KNL] Should the soft-lockup detector generate panics.
3448 softlockup_all_cpu_backtrace=
3449 [KNL] Should the soft-lockup detector generate
3450 backtraces on all cpus.
3453 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3454 See Documentation/laptops/sonypi.txt
3456 spia_io_base= [HW,MTD]
3462 Enabled the stack tracer on boot up.
3464 stacktrace_filter=[function-list]
3465 [FTRACE] Limit the functions that the stack tracer
3466 will trace at boot up. function-list is a comma separated
3467 list of functions. This list can be changed at run
3468 time by the stack_trace_filter file in the debugfs
3469 tracing directory. Note, this enables stack tracing
3470 and the stacktrace above is not needed.
3474 Set the STI (builtin display/keyboard on the HP-PARISC
3475 machines) console (graphic card) which should be used
3476 as the initial boot-console.
3477 See also comment in drivers/video/console/sticore.c.
3480 See comment in drivers/video/console/sticore.c.
3483 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3485 sunrpc.min_resvport=
3486 sunrpc.max_resvport=
3488 SunRPC servers often require that client requests
3489 originate from a privileged port (i.e. a port in the
3490 range 0 < portnr < 1024).
3491 An administrator who wishes to reserve some of these
3492 ports for other uses may adjust the range that the
3493 kernel's sunrpc client considers to be privileged
3494 using these two parameters to set the minimum and
3495 maximum port values.
3499 Control how the NFS server code allocates CPUs to
3500 service thread pools. Depending on how many NICs
3501 you have and where their interrupts are bound, this
3502 option will affect which CPUs will do NFS serving.
3503 Note: this parameter cannot be changed while the
3504 NFS server is running.
3506 auto the server chooses an appropriate mode
3507 automatically using heuristics
3508 global a single global pool contains all CPUs
3509 percpu one pool for each CPU
3510 pernode one pool for each NUMA node (equivalent
3511 to global on non-NUMA machines)
3513 sunrpc.tcp_slot_table_entries=
3514 sunrpc.udp_slot_table_entries=
3516 Sets the upper limit on the number of simultaneous
3517 RPC calls that can be sent from the client to a
3518 server. Increasing these values may allow you to
3519 improve throughput, but will also increase the
3520 amount of memory reserved for use by the client.
3522 suspend.pm_test_delay=
3524 Sets the number of seconds to remain in a suspend test
3525 mode before resuming the system (see
3526 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3527 is set. Default value is 5.
3530 [KNL] Enable accounting of swap in memory resource
3531 controller if no parameter or 1 is given or disable
3532 it if 0 is given (See Documentation/cgroups/memory.txt)
3534 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3535 Format: { <int> | force }
3536 <int> -- Number of I/O TLB slabs
3537 force -- force using of bounce buffers even if they
3538 wouldn't be automatically used by the kernel
3542 sysfs.deprecated=0|1 [KNL]
3543 Enable/disable old style sysfs layout for old udev
3544 on older distributions. When this option is enabled
3545 very new udev will not work anymore. When this option
3546 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3547 in older udev will not work anymore.
3548 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3549 the kernel configuration.
3551 sysrq_always_enabled
3553 Ignore sysrq setting - this boot parameter will
3554 neutralize any effect of /proc/sys/kernel/sysrq.
3555 Useful for debugging.
3557 tcpmhash_entries= [KNL,NET]
3558 Set the number of tcp_metrics_hash slots.
3559 Default value is 8192 or 16384 depending on total
3560 ram pages. This is used to specify the TCP metrics
3561 cache size. See Documentation/networking/ip-sysctl.txt
3562 "tcp_no_metrics_save" section for more details.
3566 test_suspend= [SUSPEND][,N]
3567 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3568 standby suspend) or "freeze" (for suspend type freeze)
3569 as the system sleep state during system startup with
3570 the optional capability to repeat N number of times.
3571 The system is woken from this state using a
3572 wakeup-capable RTC alarm.
3574 thash_entries= [KNL,NET]
3575 Set number of hash buckets for TCP connection
3577 thermal.act= [HW,ACPI]
3578 -1: disable all active trip points in all thermal zones
3579 <degrees C>: override all lowest active trip points
3581 thermal.crt= [HW,ACPI]
3582 -1: disable all critical trip points in all thermal zones
3583 <degrees C>: override all critical trip points
3585 thermal.nocrt= [HW,ACPI]
3586 Set to disable actions on ACPI thermal zone
3587 critical and hot trip points.
3589 thermal.off= [HW,ACPI]
3590 1: disable ACPI thermal control
3592 thermal.psv= [HW,ACPI]
3593 -1: disable all passive trip points
3594 <degrees C>: override all passive trip points to this
3597 thermal.tzp= [HW,ACPI]
3598 Specify global default ACPI thermal zone polling rate
3599 <deci-seconds>: poll all this frequency
3600 0: no polling (default)
3603 Force threading of all interrupt handlers except those
3604 marked explicitly IRQF_NO_THREAD.
3607 Enable the Transcendent memory driver if built-in.
3609 tmem.cleancache=0|1 [KNL, XEN]
3610 Default is on (1). Disable the usage of the cleancache
3611 API to send anonymous pages to the hypervisor.
3613 tmem.frontswap=0|1 [KNL, XEN]
3614 Default is on (1). Disable the usage of the frontswap
3615 API to send swap pages to the hypervisor. If disabled
3616 the selfballooning and selfshrinking are force disabled.
3618 tmem.selfballooning=0|1 [KNL, XEN]
3619 Default is on (1). Disable the driving of swap pages
3622 tmem.selfshrinking=0|1 [KNL, XEN]
3623 Default is on (1). Partial swapoff that immediately
3624 transfers pages from Xen hypervisor back to the
3625 kernel based on different criteria.
3629 Specify if the kernel should make use of the cpu
3630 topology information if the hardware supports this.
3631 The scheduler will make use of this information and
3632 e.g. base its process migration decisions on it.
3635 topology_updates= [KNL, PPC, NUMA]
3637 Specify if the kernel should ignore (off)
3638 topology updates sent by the hypervisor to this
3643 tpm_suspend_pcr=[HW,TPM]
3644 Format: integer pcr id
3645 Specify that at suspend time, the tpm driver
3646 should extend the specified pcr with zeros,
3647 as a workaround for some chips which fail to
3648 flush the last written pcr on TPM_SaveState.
3649 This will guarantee that all the other pcrs
3652 trace_buf_size=nn[KMG]
3653 [FTRACE] will set tracing buffer size on each cpu.
3655 trace_event=[event-list]
3656 [FTRACE] Set and start specified trace events in order
3657 to facilitate early boot debugging.
3658 See also Documentation/trace/events.txt
3660 trace_options=[option-list]
3661 [FTRACE] Enable or disable tracer options at boot.
3662 The option-list is a comma delimited list of options
3663 that can be enabled or disabled just as if you were
3664 to echo the option name into
3666 /sys/kernel/debug/tracing/trace_options
3668 For example, to enable stacktrace option (to dump the
3669 stack trace of each event), add to the command line:
3671 trace_options=stacktrace
3673 See also Documentation/trace/ftrace.txt "trace options"
3677 Have the tracepoints sent to printk as well as the
3678 tracing ring buffer. This is useful for early boot up
3679 where the system hangs or reboots and does not give the
3680 option for reading the tracing buffer or performing a
3681 ftrace_dump_on_oops.
3683 To turn off having tracepoints sent to printk,
3684 echo 0 > /proc/sys/kernel/tracepoint_printk
3685 Note, echoing 1 into this file without the
3686 tracepoint_printk kernel cmdline option has no effect.
3690 Having tracepoints sent to printk() and activating high
3691 frequency tracepoints such as irq or sched, can cause
3692 the system to live lock.
3695 [FTRACE] enable this option to disable tracing when a
3696 warning is hit. This turns off "tracing_on". Tracing can
3697 be enabled again by echoing '1' into the "tracing_on"
3698 file located in /sys/kernel/debug/tracing/
3700 This option is useful, as it disables the trace before
3701 the WARNING dump is called, which prevents the trace to
3702 be filled with content caused by the warning output.
3704 This option can also be set at run time via the sysctl
3705 option: kernel/traceoff_on_warning
3707 transparent_hugepage=
3709 Format: [always|madvise|never]
3710 Can be used to control the default behavior of the system
3711 with respect to transparent hugepages.
3712 See Documentation/vm/transhuge.txt for more details.
3714 tsc= Disable clocksource stability checks for TSC.
3716 [x86] reliable: mark tsc clocksource as reliable, this
3717 disables clocksource verification at runtime, as well
3718 as the stability checks done at bootup. Used to enable
3719 high-resolution timer mode on older hardware, and in
3720 virtualized environment.
3721 [x86] noirqtime: Do not use TSC to do irq accounting.
3722 Used to run time disable IRQ_TIME_ACCOUNTING on any
3723 platforms where RDTSC is slow and this accounting
3726 turbografx.map[2|3]= [HW,JOY]
3727 TurboGraFX parallel port interface
3729 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3730 See also Documentation/input/joystick-parport.txt
3732 udbg-immortal [PPC] When debugging early kernel crashes that
3733 happen after console_init() and before a proper
3734 console driver takes over, this boot options might
3735 help "seeing" what's going on.
3737 uhash_entries= [KNL,NET]
3738 Set number of hash buckets for UDP/UDP-Lite connections
3741 [USB] Ignore overcurrent events (default N).
3742 Some badly-designed motherboards generate lots of
3743 bogus events, for ports that aren't wired to
3744 anything. Set this parameter to avoid log spamming.
3745 Note that genuine overcurrent events won't be
3749 [X86] Cause panic on unknown NMI.
3751 usbcore.authorized_default=
3752 [USB] Default USB device authorization:
3753 (default -1 = authorized except for wireless USB,
3754 0 = not authorized, 1 = authorized)
3756 usbcore.autosuspend=
3757 [USB] The autosuspend time delay (in seconds) used
3758 for newly-detected USB devices (default 2). This
3759 is the time required before an idle device will be
3760 autosuspended. Devices for which the delay is set
3761 to a negative value won't be autosuspended at all.
3763 usbcore.usbfs_snoop=
3764 [USB] Set to log all usbfs traffic (default 0 = off).
3766 usbcore.blinkenlights=
3767 [USB] Set to cycle leds on hubs (default 0 = off).
3769 usbcore.old_scheme_first=
3770 [USB] Start with the old device initialization
3771 scheme (default 0 = off).
3773 usbcore.usbfs_memory_mb=
3774 [USB] Memory limit (in MB) for buffers allocated by
3775 usbfs (default = 16, 0 = max = 2047).
3777 usbcore.use_both_schemes=
3778 [USB] Try the other device initialization scheme
3779 if the first one fails (default 1 = enabled).
3781 usbcore.initial_descriptor_timeout=
3782 [USB] Specifies timeout for the initial 64-byte
3783 USB_REQ_GET_DESCRIPTOR request in milliseconds
3784 (default 5000 = 5.0 seconds).
3787 [USBHID] The interval which mice are to be polled at.
3789 usb-storage.delay_use=
3790 [UMS] The delay in seconds before a new device is
3791 scanned for Logical Units (default 1).
3794 [UMS] A list of quirks entries to supplement or
3795 override the built-in unusual_devs list. List
3796 entries are separated by commas. Each entry has
3797 the form VID:PID:Flags where VID and PID are Vendor
3798 and Product ID values (4-digit hex numbers) and
3799 Flags is a set of characters, each corresponding
3800 to a common usb-storage quirk flag as follows:
3801 a = SANE_SENSE (collect more than 18 bytes
3803 b = BAD_SENSE (don't collect more than 18
3804 bytes of sense data);
3805 c = FIX_CAPACITY (decrease the reported
3806 device capacity by one sector);
3807 d = NO_READ_DISC_INFO (don't use
3808 READ_DISC_INFO command);
3809 e = NO_READ_CAPACITY_16 (don't use
3810 READ_CAPACITY_16 command);
3811 f = NO_REPORT_OPCODES (don't use report opcodes
3813 g = MAX_SECTORS_240 (don't transfer more than
3814 240 sectors at a time, uas only);
3815 h = CAPACITY_HEURISTICS (decrease the
3816 reported device capacity by one
3817 sector if the number is odd);
3818 i = IGNORE_DEVICE (don't bind to this
3820 j = NO_REPORT_LUNS (don't use report luns
3822 l = NOT_LOCKABLE (don't try to lock and
3823 unlock ejectable media);
3824 m = MAX_SECTORS_64 (don't transfer more
3825 than 64 sectors = 32 KB at a time);
3826 n = INITIAL_READ10 (force a retry of the
3827 initial READ(10) command);
3828 o = CAPACITY_OK (accept the capacity
3829 reported by the device);
3830 p = WRITE_CACHE (the device cache is ON
3832 r = IGNORE_RESIDUE (the device reports
3833 bogus residue values);
3834 s = SINGLE_LUN (the device has only one
3836 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3837 commands, uas only);
3838 u = IGNORE_UAS (don't bind to the uas driver);
3839 w = NO_WP_DETECT (don't test whether the
3840 medium is write-protected).
3841 Example: quirks=0419:aaf5:rl,0421:0433:rc
3843 user_debug= [KNL,ARM]
3845 See arch/arm/Kconfig.debug help text.
3846 1 - undefined instruction events
3848 4 - invalid data aborts
3851 Example: user_debug=31
3854 [X86] Flags controlling user PTE allocations.
3856 nohigh = do not allocate PTE pages in
3857 HIGHMEM regardless of setting
3861 On X86_32, this is an alias for vdso32=. Otherwise:
3863 vdso=1: enable VDSO (the default)
3864 vdso=0: disable VDSO mapping
3866 vdso32= [X86] Control the 32-bit vDSO
3867 vdso32=1: enable 32-bit VDSO
3868 vdso32=0 or vdso32=2: disable 32-bit VDSO
3870 See the help text for CONFIG_COMPAT_VDSO for more
3871 details. If CONFIG_COMPAT_VDSO is set, the default is
3872 vdso32=0; otherwise, the default is vdso32=1.
3874 For compatibility with older kernels, vdso32=2 is an
3877 Try vdso32=0 if you encounter an error that says:
3878 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3881 vector=percpu: enable percpu vector domain
3883 video= [FB] Frame buffer configuration
3884 See Documentation/fb/modedb.txt.
3886 video.brightness_switch_enabled= [0,1]
3887 If set to 1, on receiving an ACPI notify event
3888 generated by hotkey, video driver will adjust brightness
3889 level and then send out the event to user space through
3890 the allocated input device; If set to 0, video driver
3891 will only send out the event without touching backlight
3896 [VMMIO] Memory mapped virtio (platform) device.
3898 <size>@<baseaddr>:<irq>[:<id>]
3900 <size> := size (can use standard suffixes
3902 <baseaddr> := physical base address
3903 <irq> := interrupt number (as passed to
3905 <id> := (optional) platform device id
3907 virtio_mmio.device=1K@0x100b0000:48:7
3909 Can be used multiple times for multiple devices.
3911 vga= [BOOT,X86-32] Select a particular video mode
3912 See Documentation/x86/boot.txt and
3913 Documentation/svga.txt.
3914 Use vga=ask for menu.
3915 This is actually a boot loader parameter; the value is
3916 passed to the kernel using a special protocol.
3918 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3919 size of <nn>. This can be used to increase the
3920 minimum size (128MB on x86). It can also be used to
3921 decrease the size and leave more room for directly
3924 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3927 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3930 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3934 Controls the behavior of vsyscalls (i.e. calls to
3935 fixed addresses of 0xffffffffff600x00 from legacy
3936 code). Most statically-linked binaries and older
3937 versions of glibc use these calls. Because these
3938 functions are at fixed addresses, they make nice
3939 targets for exploits that can control RIP.
3941 emulate [default] Vsyscalls turn into traps and are
3942 emulated reasonably safely.
3944 native Vsyscalls are native syscall instructions.
3945 This is a little bit faster than trapping
3946 and makes a few dynamic recompilers work
3947 better than they would in emulation mode.
3948 It also makes exploits much easier to write.
3950 none Vsyscalls don't work at all. This makes
3951 them quite hard to use for exploits but
3952 might break your system.
3954 vt.color= [VT] Default text color.
3955 Format: 0xYX, X = foreground, Y = background.
3956 Default: 0x07 = light gray on black.
3958 vt.cur_default= [VT] Default cursor shape.
3959 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3960 the parameters of the <Esc>[?A;B;Cc escape sequence;
3961 see VGA-softcursor.txt. Default: 2 = underline.
3963 vt.default_blu= [VT]
3964 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3965 Change the default blue palette of the console.
3966 This is a 16-member array composed of values
3969 vt.default_grn= [VT]
3970 Format: <green0>,<green1>,<green2>,...,<green15>
3971 Change the default green palette of the console.
3972 This is a 16-member array composed of values
3975 vt.default_red= [VT]
3976 Format: <red0>,<red1>,<red2>,...,<red15>
3977 Change the default red palette of the console.
3978 This is a 16-member array composed of values
3984 Set system-wide default UTF-8 mode for all tty's.
3985 Default is 1, i.e. UTF-8 mode is enabled for all
3986 newly opened terminals.
3988 vt.global_cursor_default=
3991 Set system-wide default for whether a cursor
3992 is shown on new VTs. Default is -1,
3993 i.e. cursors will be created by default unless
3994 overridden by individual drivers. 0 will hide
3995 cursors, 1 will display them.
3997 vt.italic= [VT] Default color for italic text; 0-15.
4000 vt.underline= [VT] Default color for underlined text; 0-15.
4003 watchdog timers [HW,WDT] For information on watchdog timers,
4004 see Documentation/watchdog/watchdog-parameters.txt
4005 or other driver-specific files in the
4006 Documentation/watchdog/ directory.
4008 workqueue.disable_numa
4009 By default, all work items queued to unbound
4010 workqueues are affine to the NUMA nodes they're
4011 issued on, which results in better behavior in
4012 general. If NUMA affinity needs to be disabled for
4013 whatever reason, this option can be used. Note
4014 that this also can be controlled per-workqueue for
4015 workqueues visible under /sys/bus/workqueue/.
4017 workqueue.power_efficient
4018 Per-cpu workqueues are generally preferred because
4019 they show better performance thanks to cache
4020 locality; unfortunately, per-cpu workqueues tend to
4021 be more power hungry than unbound workqueues.
4023 Enabling this makes the per-cpu workqueues which
4024 were observed to contribute significantly to power
4025 consumption unbound, leading to measurably lower
4026 power usage at the cost of small performance
4029 The default value of this parameter is determined by
4030 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4032 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4033 default x2apic cluster mode on platforms
4036 x86_intel_mid_timer= [X86-32,APBT]
4037 Choose timer option for x86 Intel MID platform.
4038 Two valid options are apbt timer only and lapic timer
4039 plus one apbt timer for broadcast timer.
4040 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4042 xen_emul_unplug= [HW,X86,XEN]
4043 Unplug Xen emulated devices
4044 Format: [unplug0,][unplug1]
4045 ide-disks -- unplug primary master IDE devices
4046 aux-ide-disks -- unplug non-primary-master IDE devices
4047 nics -- unplug network devices
4048 all -- unplug all emulated devices (NICs and IDE disks)
4049 unnecessary -- unplugging emulated devices is
4050 unnecessary even if the host did not respond to
4052 never -- do not unplug even if version check succeeds
4054 xen_nopvspin [X86,XEN]
4055 Disables the ticketlock slowpath using Xen PV
4059 Disables the PV optimizations forcing the HVM guest to
4060 run as generic HVM guest with no PV drivers.
4062 xirc2ps_cs= [NET,PCMCIA]
4064 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4066 ______________________________________________________________________
4070 Add more DRM drivers.
projects / platform / kernel / linux-exynos.git / blob