4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt }
171 force -- enable ACPI if default was off
172 off -- disable ACPI if default was on
173 noirq -- do not use ACPI for IRQ routing
174 strict -- Be less tolerant of platforms that are not
175 strictly ACPI specification compliant.
176 rsdt -- prefer RSDT over (default) XSDT
177 copy_dsdt -- copy DSDT to memory
179 See also Documentation/power/runtime_pm.txt, pci=noacpi
181 acpi_rsdp= [ACPI,EFI,KEXEC]
182 Pass the RSDP address to the kernel, mostly used
183 on machines running EFI runtime service to boot the
184 second kernel for kdump.
186 acpi_apic_instance= [ACPI, IOAPIC]
188 2: use 2nd APIC table, if available
189 1,0: use 1st APIC table
192 acpi_backlight= [HW,ACPI]
193 acpi_backlight=vendor
195 If set to vendor, prefer vendor specific driver
196 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
197 of the ACPI video.ko driver.
199 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
200 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
202 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
203 debug output. Bits in debug_layer correspond to a
204 _COMPONENT in an ACPI source file, e.g.,
205 #define _COMPONENT ACPI_PCI_COMPONENT
206 Bits in debug_level correspond to a level in
207 ACPI_DEBUG_PRINT statements, e.g.,
208 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
209 The debug_level mask defaults to "info". See
210 Documentation/acpi/debug.txt for more information about
211 debug layers and levels.
213 Enable processor driver info messages:
214 acpi.debug_layer=0x20000000
215 Enable PCI/PCI interrupt routing info messages:
216 acpi.debug_layer=0x400000
217 Enable AML "Debug" output, i.e., stores to the Debug
218 object while interpreting AML:
219 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
220 Enable all messages related to ACPI hardware:
221 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
223 Some values produce so much output that the system is
224 unusable. The "log_buf_len" parameter may be useful
225 if you need to capture more output.
227 acpi_force_table_verification [HW,ACPI]
228 Enable table checksum verification during early stage.
229 By default, this is disabled due to x86 early mapping
232 acpi_irq_balance [HW,ACPI]
233 ACPI will balance active IRQs
236 acpi_irq_nobalance [HW,ACPI]
237 ACPI will not move active IRQs (default)
240 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
241 Format: <irq>,<irq>...
243 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
245 Format: <irq>,<irq>...
247 acpi_no_auto_serialize [HW,ACPI]
248 Disable auto-serialization of AML methods
249 AML control methods that contain the opcodes to create
250 named objects will be marked as "Serialized" by the
251 auto-serialization feature.
252 This feature is enabled by default.
253 This option allows to turn off the feature.
255 acpi_no_static_ssdt [HW,ACPI]
256 Disable installation of static SSDTs at early boot time
257 By default, SSDTs contained in the RSDT/XSDT will be
258 installed automatically and they will appear under
259 /sys/firmware/acpi/tables.
260 This option turns off this feature.
261 Note that specifying this option does not affect
262 dynamic table installation which will install SSDT
263 tables to /sys/firmware/acpi/tables/dynamic.
265 acpica_no_return_repair [HW, ACPI]
266 Disable AML predefined validation mechanism
267 This mechanism can repair the evaluation result to make
268 the return objects more ACPI specification compliant.
269 This option is useful for developers to identify the
270 root cause of an AML interpreter issue when the issue
271 has something to do with the repair mechanism.
273 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
274 Format: To spoof as Windows 98: ="Microsoft Windows"
276 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
277 acpi_osi="string1" # add string1
278 acpi_osi="!string2" # remove string2
279 acpi_osi=!* # remove all strings
280 acpi_osi=! # disable all built-in OS vendor
282 acpi_osi= # disable all strings
284 'acpi_osi=!' can be used in combination with single or
285 multiple 'acpi_osi="string1"' to support specific OS
286 vendor string(s). Note that such command can only
287 affect the default state of the OS vendor strings, thus
288 it cannot affect the default state of the feature group
289 strings and the current state of the OS vendor strings,
290 specifying it multiple times through kernel command line
291 is meaningless. This command is useful when one do not
292 care about the state of the feature group strings which
293 should be controlled by the OSPM.
295 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
296 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
297 can make '_OSI("Windows 2000")' TRUE.
299 'acpi_osi=' cannot be used in combination with other
300 'acpi_osi=' command lines, the _OSI method will not
301 exist in the ACPI namespace. NOTE that such command can
302 only affect the _OSI support state, thus specifying it
303 multiple times through kernel command line is also
306 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
309 'acpi_osi=!*' can be used in combination with single or
310 multiple 'acpi_osi="string1"' to support specific
311 string(s). Note that such command can affect the
312 current state of both the OS vendor strings and the
313 feature group strings, thus specifying it multiple times
314 through kernel command line is meaningful. But it may
315 still not able to affect the final state of a string if
316 there are quirks related to this string. This command
317 is useful when one want to control the state of the
318 feature group strings to debug BIOS issues related to
321 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
322 '_OSI("Module Device")' FALSE.
323 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
324 '_OSI("Module Device")' TRUE.
325 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
327 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
329 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
330 they all will make '_OSI("Windows 2000")' TRUE.
333 Override the pmtimer bug detection: force the kernel
334 to assume that this machine's pmtimer latches its value
335 and always returns good values.
337 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
338 Format: { level | edge | high | low }
340 acpi_skip_timer_override [HW,ACPI]
341 Recognize and ignore IRQ0/pin2 Interrupt Override.
342 For broken nForce2 BIOS resulting in XT-PIC timer.
344 acpi_sleep= [HW,ACPI] Sleep options
345 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
346 old_ordering, nonvs, sci_force_enable }
347 See Documentation/power/video.txt for information on
349 s3_beep is for debugging; it makes the PC's speaker beep
350 as soon as the kernel's real-mode entry point is called.
351 s4_nohwsig prevents ACPI hardware signature from being
352 used during resume from hibernation.
353 old_ordering causes the ACPI 1.0 ordering of the _PTS
354 control method, with respect to putting devices into
355 low power states, to be enforced (the ACPI 2.0 ordering
356 of _PTS is used by default).
357 nonvs prevents the kernel from saving/restoring the
358 ACPI NVS memory during suspend/hibernation and resume.
359 sci_force_enable causes the kernel to set SCI_EN directly
360 on resume from S1/S3 (which is against the ACPI spec,
361 but some broken systems don't work without it).
363 acpi_use_timer_override [HW,ACPI]
364 Use timer override. For some broken Nvidia NF5 boards
365 that require a timer override, but don't have HPET
367 acpi_enforce_resources= [ACPI]
368 { strict | lax | no }
369 Check for resource conflicts between native drivers
370 and ACPI OperationRegions (SystemIO and SystemMemory
371 only). IO ports and memory declared in ACPI might be
372 used by the ACPI subsystem in arbitrary AML code and
373 can interfere with legacy drivers.
374 strict (default): access to resources claimed by ACPI
375 is denied; legacy drivers trying to access reserved
376 resources will fail to bind to device using them.
377 lax: access to resources claimed by ACPI is allowed;
378 legacy drivers trying to access reserved resources
379 will bind successfully but a warning message is logged.
380 no: ACPI OperationRegions are not marked as reserved,
381 no further checks are performed.
383 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
386 add_efi_memmap [EFI; X86] Include EFI memory map in
387 kernel's map of available physical RAM.
390 { off | try_unsupported }
391 off: disable AGP support
392 try_unsupported: try to drive unsupported chipsets
393 (may crash computer or cause data corruption)
396 See Documentation/sound/alsa/alsa-parameters.txt
399 Allow the default userspace alignment fault handler
400 behaviour to be specified. Bit 0 enables warnings,
401 bit 1 enables fixups, and bit 2 sends a segfault.
403 align_va_addr= [X86-64]
404 Align virtual addresses by clearing slice [14:12] when
405 allocating a VMA at process creation time. This option
406 gives you up to 3% performance improvement on AMD F15h
407 machines (where it is enabled by default) for a
408 CPU-intensive style benchmark, and it can vary highly in
409 a microbenchmark depending on workload and compiler.
411 32: only for 32-bit processes
412 64: only for 64-bit processes
413 on: enable for both 32- and 64-bit processes
414 off: disable for both 32- and 64-bit processes
416 alloc_snapshot [FTRACE]
417 Allocate the ftrace snapshot buffer on boot up when the
418 main buffer is allocated. This is handy if debugging
419 and you need to use tracing_snapshot() on boot up, and
420 do not want to use tracing_snapshot_alloc() as it needs
421 to be done where GFP_KERNEL allocations are allowed.
423 amd_iommu= [HW,X86-64]
424 Pass parameters to the AMD IOMMU driver in the system.
426 fullflush - enable flushing of IO/TLB entries when
427 they are unmapped. Otherwise they are
428 flushed before they will be reused, which
430 off - do not initialize any AMD IOMMU found in
432 force_isolation - Force device isolation for all
433 devices. The IOMMU driver is not
434 allowed anymore to lift isolation
435 requirements as needed. This option
436 does not override iommu=pt
438 amd_iommu_dump= [HW,X86-64]
439 Enable AMD IOMMU driver option to dump the ACPI table
440 for AMD IOMMU. With this option enabled, AMD IOMMU
441 driver will print ACPI tables for AMD IOMMU during
442 IOMMU initialization.
444 amijoy.map= [HW,JOY] Amiga joystick support
445 Map of devices attached to JOY0DAT and JOY1DAT
447 See also Documentation/input/joystick.txt
449 analog.map= [HW,JOY] Analog joystick and gamepad support
450 Specifies type or capabilities of an analog joystick
451 connected to one of 16 gameports
452 Format: <type1>,<type2>,..<type16>
455 Power management functions (SPARCstation-4/5 + deriv.)
457 Disable APC CPU standby support. SPARCstation-Fox does
458 not play well with APC CPU idle - disable it if you have
459 APC and your system crashes randomly.
461 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
462 Change the output verbosity whilst booting
463 Format: { quiet (default) | verbose | debug }
464 Change the amount of debugging information output
465 when initialising the APIC and IO-APIC components.
468 See Documentation/networking/ipv6.txt.
470 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
471 Limit apic dumping. The parameter defines the maximal
472 number of local apics being dumped. Also it is possible
473 to set it to "all" by meaning -- no limit here.
474 Format: { 1 (default) | 2 | ... | all }.
475 The parameter valid if only apic=debug or
476 apic=verbose is specified.
477 Example: apic=debug show_lapic=all
479 apm= [APM] Advanced Power Management
480 See header of arch/x86/kernel/apm_32.c.
482 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
483 Format: <io>,<irq>,<nodeID>
487 atarimouse= [HW,MOUSE] Atari Mouse
489 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
490 EzKey and similar keyboards
492 atkbd.reset= [HW] Reset keyboard during initialization
494 atkbd.set= [HW] Select keyboard code set
495 Format: <int> (2 = AT (default), 3 = PS/2)
497 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
500 atkbd.softraw= [HW] Choose between synthetic and real raw mode
501 Format: <bool> (0 = real, 1 = synthetic (default))
503 atkbd.softrepeat= [HW]
504 Use software keyboard repeat
506 audit= [KNL] Enable the audit sub-system
507 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
508 0 - kernel audit is disabled and can not be enabled
509 until the next reboot
510 unset - kernel audit is initialized but disabled and
511 will be fully enabled by the userspace auditd.
512 1 - kernel audit is initialized and partially enabled,
513 storing at most audit_backlog_limit messages in
514 RAM until it is fully enabled by the userspace
518 audit_backlog_limit= [KNL] Set the audit queue size limit.
519 Format: <int> (must be >=0)
522 baycom_epp= [HW,AX25]
525 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
527 See header of drivers/net/hamradio/baycom_par.c.
529 baycom_ser_fdx= [HW,AX25]
530 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
531 Format: <io>,<irq>,<mode>[,<baud>]
532 See header of drivers/net/hamradio/baycom_ser_fdx.c.
534 baycom_ser_hdx= [HW,AX25]
535 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
536 Format: <io>,<irq>,<mode>
537 See header of drivers/net/hamradio/baycom_ser_hdx.c.
539 blkdevparts= Manual partition parsing of block device(s) for
540 embedded devices based on command line input.
541 See Documentation/block/cmdline-partition.txt
543 boot_delay= Milliseconds to delay each printk during boot.
544 Values larger than 10 seconds (10000) are changed to
548 bootmem_debug [KNL] Enable bootmem allocator debug messages.
550 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
551 bttv.radio= Most important insmod options are available as
553 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
556 bulk_remove=off [PPC] This parameter disables the use of the pSeries
557 firmware feature for flushing multiple hpte entries
560 c101= [NET] Moxa C101 synchronous serial card
562 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
563 Sometimes CPU hardware bugs make them report the cache
564 size incorrectly. The kernel will attempt work arounds
565 to fix known problems, but for some CPUs it is not
566 possible to determine what the correct size should be.
567 This option provides an override for these situations.
569 ca_keys= [KEYS] This parameter identifies a specific key(s) on
570 the system trusted keyring to be used for certificate
572 format: { id:<keyid> | builtin }
574 cca= [MIPS] Override the kernel pages' cache coherency
575 algorithm. Accepted values range from 0 to 7
576 inclusive. See arch/mips/include/asm/pgtable-bits.h
577 for platform specific values (SB1, Loongson3 and
580 ccw_timeout_log [S390]
581 See Documentation/s390/CommonIO for details.
583 cgroup_disable= [KNL] Disable a particular controller
584 Format: {name of the controller(s) to disable}
585 The effects of cgroup_disable=foo are:
586 - foo isn't auto-mounted if you mount all cgroups in
588 - foo isn't visible as an individually mountable
590 {Currently only "memory" controller deal with this and
591 cut the overhead, others just disable the usage. So
592 only cgroup_disable=memory is actually worthy}
594 checkreqprot [SELINUX] Set initial checkreqprot flag value.
595 Format: { "0" | "1" }
596 See security/selinux/Kconfig help text.
597 0 -- check protection applied by kernel (includes
598 any implied execute protection).
599 1 -- check protection requested by application.
600 Default value is set via a kernel config option.
601 Value can be changed at runtime via
602 /selinux/checkreqprot.
605 See Documentation/s390/CommonIO for details.
608 Prevents the clock framework from automatically gating
609 clocks that have not been explicitly enabled by a Linux
610 device driver but are enabled in hardware at reset or
611 by the bootloader/firmware. Note that this does not
612 force such clocks to be always-on nor does it reserve
613 those clocks in any way. This parameter is useful for
614 debug and development, but should not be needed on a
615 platform with proper driver support. For more
616 information, see Documentation/clk.txt.
618 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
620 Forces specified clocksource (if available) to be used
621 when calculating gettimeofday(). If specified
622 clocksource is not available, it defaults to PIT.
623 Format: { pit | tsc | cyclone | pmtmr }
625 clocksource= Override the default clocksource
627 Override the default clocksource and use the clocksource
628 with the name specified.
629 Some clocksource names to choose from, depending on
631 [all] jiffies (this is the base, fallback clocksource)
633 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
634 pxa_timer,timer3,32k_counter,timer0_1
636 [X86-32] pit,hpet,tsc;
637 scx200_hrt on Geode; cyclone on IBM x440
645 clearcpuid=BITNUM [X86]
646 Disable CPUID feature X for the kernel. See
647 arch/x86/include/asm/cpufeature.h for the valid bit
648 numbers. Note the Linux specific bits are not necessarily
649 stable over kernel options, but the vendor specific
651 Also note that user programs calling CPUID directly
652 or using the feature without checking anything
653 will still see it. This just prevents it from
654 being used by the kernel or shown in /proc/cpuinfo.
655 Also note the kernel might malfunction if you disable
658 cma=nn[MG]@[start[MG][-end[MG]]]
660 Sets the size of kernel global memory area for
661 contiguous memory allocations and optionally the
662 placement constraint by the physical address range of
663 memory allocations. A value of 0 disables CMA
664 altogether. For more information, see
665 include/linux/dma-contiguous.h
667 cmo_free_hint= [PPC] Format: { yes | no }
668 Specify whether pages are marked as being inactive
669 when they are freed. This is used in CMO environments
670 to determine OS memory pressure for page stealing by
674 coherent_pool=nn[KMG] [ARM,KNL]
675 Sets the size of memory pool for coherent, atomic dma
676 allocations, by default set to 256K.
678 code_bytes [X86] How many bytes of object code to print
683 com20020= [HW,NET] ARCnet - COM20020 chipset
685 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
687 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
691 ARCnet - COM90xx chipset (memory-mapped buffers)
692 Format: <io>[,<irq>[,<memstart>]]
694 condev= [HW,S390] console device
697 console= [KNL] Output console device and options.
699 tty<n> Use the virtual console device <n>.
703 Use the specified serial port. The options are of
704 the form "bbbbpnf", where "bbbb" is the baud rate,
705 "p" is parity ("n", "o", or "e"), "n" is number of
706 bits, and "f" is flow control ("r" for RTS or
707 omit it). Default is "9600n8".
709 See Documentation/serial-console.txt for more
711 Documentation/networking/netconsole.txt for an
714 uart[8250],io,<addr>[,options]
715 uart[8250],mmio,<addr>[,options]
716 Start an early, polled-mode console on the 8250/16550
717 UART at the specified I/O port or MMIO address,
718 switching to the matching ttyS device later. The
719 options are the same as for ttyS, above.
720 hvc<n> Use the hypervisor console device <n>. This is for
721 both Xen and PowerPC hypervisors.
723 If the device connected to the port is not a TTY but a braille
724 device, prepend "brl," before the device type, for instance
726 For now, only VisioBraille is supported.
728 consoleblank= [KNL] The console blank (screen saver) timeout in
729 seconds. Defaults to 10*60 = 10mins. A value of 0
730 disables the blank timer.
733 [KNL] Change the default value for
734 /proc/<pid>/coredump_filter.
735 See also Documentation/filesystems/proc.txt.
737 cpuidle.off=1 [CPU_IDLE]
738 disable the cpuidle sub-system
740 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
742 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
744 crashkernel=size[KMG][@offset[KMG]]
745 [KNL] Using kexec, Linux can switch to a 'crash kernel'
746 upon panic. This parameter reserves the physical
747 memory region [offset, offset + size] for that kernel
748 image. If '@offset' is omitted, then a suitable offset
749 is selected automatically. Check
750 Documentation/kdump/kdump.txt for further details.
752 crashkernel=range1:size1[,range2:size2,...][@offset]
753 [KNL] Same as above, but depends on the memory
754 in the running system. The syntax of range is
755 start-[end] where start and end are both
756 a memory unit (amount[KMG]). See also
757 Documentation/kdump/kdump.txt for an example.
759 crashkernel=size[KMG],high
760 [KNL, x86_64] range could be above 4G. Allow kernel
761 to allocate physical memory region from top, so could
762 be above 4G if system have more than 4G ram installed.
763 Otherwise memory region will be allocated below 4G, if
765 It will be ignored if crashkernel=X is specified.
766 crashkernel=size[KMG],low
767 [KNL, x86_64] range under 4G. When crashkernel=X,high
768 is passed, kernel could allocate physical memory region
769 above 4G, that cause second kernel crash on system
770 that require some amount of low memory, e.g. swiotlb
771 requires at least 64M+32K low memory. Kernel would
772 try to allocate 72M below 4G automatically.
773 This one let user to specify own low range under 4G
774 for second kernel instead.
775 0: to disable low allocation.
776 It will be ignored when crashkernel=X,high is not used
777 or memory reserved is below 4G.
782 cs89x0_media= [HW,NET]
783 Format: { rj45 | aui | bnc }
786 See header of drivers/s390/block/dasd_devmap.c.
788 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
789 (one device per port)
790 Format: <port#>,<type>
791 See also Documentation/input/joystick-parport.txt
793 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
794 time. See Documentation/dynamic-debug-howto.txt for
795 details. Deprecated, see dyndbg.
797 debug [KNL] Enable kernel debugging (events log level).
800 [KNL] verbose self-tests
802 Print debugging info while doing the locking API
804 We default to 0 (no extra messages), setting it to
805 1 will print _a lot_ more information - normally
806 only useful to kernel developers.
808 debug_objects [KNL] Enable object debugging
811 [KNL] Disable object debugging
813 debug_guardpage_minorder=
814 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
815 parameter allows control of the order of pages that will
816 be intentionally kept free (and hence protected) by the
817 buddy allocator. Bigger value increase the probability
818 of catching random memory corruption, but reduce the
819 amount of memory for normal system use. The maximum
820 possible value is MAX_ORDER/2. Setting this parameter
821 to 1 or 2 should be enough to identify most random
822 memory corruption problems caused by bugs in kernel or
823 driver code when a CPU writes to (or reads from) a
824 random memory location. Note that there exists a class
825 of memory corruptions problems caused by buggy H/W or
826 F/W or by drivers badly programing DMA (basically when
827 memory is written at bus level and the CPU MMU is
828 bypassed) which are not detectable by
829 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
830 tracking down these problems.
833 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
834 parameter enables the feature at boot time. In
835 default, it is disabled. We can avoid allocating huge
836 chunk of memory for debug pagealloc if we don't enable
837 it at boot time and the system will work mostly same
838 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
839 on: enable the feature
841 debugpat [X86] Enable PAT debugging
843 decnet.addr= [HW,NET]
844 Format: <area>[,<node>]
845 See also Documentation/networking/decnet.txt.
848 [same as hugepagesz=] The size of the default
849 HugeTLB page size. This is the size represented by
850 the legacy /proc/ hugepages APIs, used for SHM, and
851 default size when mounting hugetlbfs filesystems.
852 Defaults to the default architecture's huge page size
856 Set number of hash buckets for dentry cache.
859 See Documentation/networking/ipv6.txt.
861 disable_cpu_apicid= [X86,APIC,SMP]
863 The number of initial APIC ID for the
864 corresponding CPU to be disabled at boot,
865 mostly used for the kdump 2nd kernel to
866 disable BSP to wake up multiple CPUs without
867 causing system reset or hang due to sending
870 disable_ddw [PPC/PSERIES]
871 Disable Dynamic DMA Window support. Use this if
872 to workaround buggy firmware.
875 See Documentation/networking/ipv6.txt.
877 disable_mtrr_cleanup [X86]
878 The kernel tries to adjust MTRR layout from continuous
879 to discrete, to make X server driver able to add WB
880 entry later. This parameter disables that.
882 disable_mtrr_trim [X86, Intel and AMD only]
883 By default the kernel will trim any uncacheable
884 memory out of your available memory pool based on
885 MTRR settings. This parameter disables that behavior,
886 possibly causing your machine to run very slowly.
888 disable_timer_pin_1 [X86]
889 Disable PIN 1 of APIC timer
890 Can be useful to work around chipset bugs.
892 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
893 this option disables the debugging code at boot.
895 dma_debug_entries=<number>
896 This option allows to tune the number of preallocated
897 entries for DMA-API debugging code. One entry is
898 required per DMA-API allocation. Use this if the
899 DMA-API debugging code disables itself because the
900 architectural default is too low.
902 dma_debug_driver=<driver_name>
903 With this option the DMA-API debugging driver
904 filter feature can be enabled at boot time. Just
905 pass the driver to filter for as the parameter.
906 The filter can be disabled or changed to another
907 driver later using sysfs.
909 drm_kms_helper.edid_firmware=[<connector>:]<file>
910 Broken monitors, graphic adapters and KVMs may
911 send no or incorrect EDID data sets. This parameter
912 allows to specify an EDID data set in the
913 /lib/firmware directory that is used instead.
914 Generic built-in EDID data sets are used, if one of
915 edid/1024x768.bin, edid/1280x1024.bin,
916 edid/1680x1050.bin, or edid/1920x1080.bin is given
917 and no file with the same name exists. Details and
918 instructions how to build your own EDID data are
919 available in Documentation/EDID/HOWTO.txt. An EDID
920 data set will only be used for a particular connector,
921 if its name and a colon are prepended to the EDID
926 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
927 module.dyndbg[="val"]
928 Enable debug messages at boot time. See
929 Documentation/dynamic-debug-howto.txt for details.
931 early_ioremap_debug [KNL]
932 Enable debug messages in early_ioremap support. This
933 is useful for tracking down temporary early mappings
934 which are not unmapped.
936 earlycon= [KNL] Output early console device and options.
939 Start an early, polled-mode console on a cadence serial
940 port at the specified address. The cadence serial port
941 must already be setup and configured. Options are not
944 uart[8250],io,<addr>[,options]
945 uart[8250],mmio,<addr>[,options]
946 uart[8250],mmio32,<addr>[,options]
947 Start an early, polled-mode console on the 8250/16550
948 UART at the specified I/O port or MMIO address.
949 MMIO inter-register address stride is either 8-bit
950 (mmio) or 32-bit (mmio32).
951 The options are the same as for ttyS, above.
954 Start an early, polled-mode console on a pl011 serial
955 port at the specified address. The pl011 serial port
956 must already be setup and configured. Options are not
960 Start an early, polled-mode console on an msm serial
961 port at the specified address. The serial port
962 must already be setup and configured. Options are not
966 Start an early, polled-mode console on an msm serial
967 dm port at the specified address. The serial port
968 must already be setup and configured. Options are not
971 smh Use ARM semihosting calls for early console.
973 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
977 earlyprintk=serial[,ttySn[,baudrate]]
978 earlyprintk=serial[,0x...[,baudrate]]
979 earlyprintk=ttySn[,baudrate]
980 earlyprintk=dbgp[debugController#]
982 earlyprintk is useful when the kernel crashes before
983 the normal console is initialized. It is not enabled by
984 default because it has some cosmetic problems.
986 Append ",keep" to not disable it when the real console
989 Only one of vga, efi, serial, or usb debug port can
992 Currently only ttyS0 and ttyS1 may be specified by
993 name. Other I/O ports may be explicitly specified
994 on some architectures (x86 and arm at least) by
995 replacing ttySn with an I/O port address, like this:
996 earlyprintk=serial,0x1008,115200
997 You can find the port for a given device in
998 /proc/tty/driver/serial:
999 2: uart:ST16650V2 port:00001008 irq:18 ...
1001 Interaction with the standard serial driver is not
1004 The VGA and EFI output is eventually overwritten by
1007 The xen output can only be used by Xen PV guests.
1009 edac_report= [HW,EDAC] Control how to report EDAC event
1010 Format: {"on" | "off" | "force"}
1011 on: enable EDAC to report H/W event. May be overridden
1012 by other higher priority error reporting module.
1013 off: disable H/W event reporting through EDAC.
1014 force: enforce the use of EDAC to report H/W event.
1017 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1020 This is designed to be used in conjunction with
1021 the boot argument: earlyprintk=vga
1024 Format: {"off" | "on" | "skip[mbr]"}
1027 Format: { "old_map", "nochunk", "noruntime" }
1028 old_map [X86-64]: switch to the old ioremap-based EFI
1029 runtime services mapping. 32-bit still uses this one by
1031 nochunk: disable reading files in "chunks" in the EFI
1032 boot stub, as chunking can cause problems with some
1033 firmware implementations.
1034 noruntime : disable EFI runtime services support
1036 efi_no_storage_paranoia [EFI; X86]
1037 Using this parameter you can use more than 50% of
1038 your efi variable storage. Use this parameter only if
1039 you are really sure that your UEFI does sane gc and
1040 fulfills the spec otherwise your board may brick.
1042 eisa_irq_edge= [PARISC,HW]
1043 See header of drivers/parisc/eisa.c.
1046 See comment before function elanfreq_setup() in
1047 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1050 Format: {"cfq" | "deadline" | "noop"}
1051 See Documentation/block/cfq-iosched.txt and
1052 Documentation/block/deadline-iosched.txt for details.
1054 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1055 Specifies physical address of start of kernel core
1056 image elf header and optionally the size. Generally
1057 kexec loader will pass this option to capture kernel.
1058 See Documentation/kdump/kdump.txt for details.
1060 enable_mtrr_cleanup [X86]
1061 The kernel tries to adjust MTRR layout from continuous
1062 to discrete, to make X server driver able to add WB
1063 entry later. This parameter enables that.
1065 enable_timer_pin_1 [X86]
1066 Enable PIN 1 of APIC timer
1067 Can be useful to work around chipset bugs
1068 (in particular on some ATI chipsets).
1069 The kernel tries to set a reasonable default.
1071 enforcing [SELINUX] Set initial enforcing status.
1073 See security/selinux/Kconfig help text.
1074 0 -- permissive (log only, no denials).
1075 1 -- enforcing (deny and log).
1077 Value can be changed at runtime via /selinux/enforce.
1080 Disable Error Record Serialization Table (ERST)
1083 ether= [HW,NET] Ethernet cards parameters
1084 This option is obsoleted by the "netdev=" option, which
1085 has equivalent usage. See its documentation for details.
1089 Permit 'security.evm' to be updated regardless of
1090 current integrity status.
1094 fail_make_request=[KNL]
1095 General fault injection mechanism.
1096 Format: <interval>,<probability>,<space>,<times>
1097 See also Documentation/fault-injection/.
1100 See Documentation/blockdev/floppy.txt.
1102 force_pal_cache_flush
1103 [IA-64] Avoid check_sal_cache_flush which may hang on
1104 buggy SAL_CACHE_FLUSH implementations. Using this
1105 parameter will force ia64_sal_cache_flush to call
1106 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1109 Forcefully enable Physical Address Extension (PAE).
1110 Many Pentium M systems disable PAE but may have a
1111 functionally usable PAE implementation.
1112 Warning: use of this parameter will taint the kernel
1113 and may cause unknown problems.
1116 [FTRACE] will set and start the specified tracer
1117 as early as possible in order to facilitate early
1120 ftrace_dump_on_oops[=orig_cpu]
1121 [FTRACE] will dump the trace buffers on oops.
1122 If no parameter is passed, ftrace will dump
1123 buffers of all CPUs, but if you pass orig_cpu, it will
1124 dump only the buffer of the CPU that triggered the
1127 ftrace_filter=[function-list]
1128 [FTRACE] Limit the functions traced by the function
1129 tracer at boot up. function-list is a comma separated
1130 list of functions. This list can be changed at run
1131 time by the set_ftrace_filter file in the debugfs
1134 ftrace_notrace=[function-list]
1135 [FTRACE] Do not trace the functions specified in
1136 function-list. This list can be changed at run time
1137 by the set_ftrace_notrace file in the debugfs
1140 ftrace_graph_filter=[function-list]
1141 [FTRACE] Limit the top level callers functions traced
1142 by the function graph tracer at boot up.
1143 function-list is a comma separated list of functions
1144 that can be changed at run time by the
1145 set_graph_function file in the debugfs tracing directory.
1147 ftrace_graph_notrace=[function-list]
1148 [FTRACE] Do not trace from the functions specified in
1149 function-list. This list is a comma separated list of
1150 functions that can be changed at run time by the
1151 set_graph_notrace file in the debugfs tracing directory.
1154 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1155 support via parallel port (up to 5 devices per port)
1156 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1157 See also Documentation/input/joystick-parport.txt
1161 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1165 gcov_persist= [GCOV] When non-zero (default), profiling data for
1166 kernel modules is saved and remains accessible via
1167 debugfs, even when the module is unloaded/reloaded.
1168 When zero, profiling data is discarded and associated
1169 debugfs files are removed at module unload time.
1171 gpt [EFI] Forces disk with valid GPT signature but
1172 invalid Protective MBR to be treated as GPT. If the
1173 primary GPT is corrupted, it enables the backup/alternate
1174 GPT to be used instead.
1176 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1177 the "Enable 0" bit of the configuration register.
1180 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1181 the "Enable 0" bit of the configuration register.
1184 grcan.select= [HW] Select which physical interface to use.
1187 grcan.txsize= [HW] Sets the size of the tx buffer.
1188 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1190 grcan.rxsize= [HW] Sets the size of the rx buffer.
1191 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1194 hashdist= [KNL,NUMA] Large hashes allocated during boot
1195 are distributed across NUMA nodes. Defaults on
1196 for 64-bit NUMA, off otherwise.
1197 Format: 0 | 1 (for off | on)
1199 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1201 hd= [EIDE] (E)IDE hard drive subsystem geometry
1202 Format: <cyl>,<head>,<sect>
1205 Disable Hardware Error Source Table (HEST) support;
1206 corresponding firmware-first mode error processing
1207 logic will be disabled.
1209 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1210 size of <nn>. This works even on boxes that have no
1211 highmem otherwise. This also works to reduce highmem
1212 size on bigger boxes.
1214 highres= [KNL] Enable/disable high resolution timer mode.
1215 Valid parameters: "on", "off"
1219 See Documentation/isdn/README.HiSax.
1223 hpet= [X86-32,HPET] option to control HPET usage
1224 Format: { enable (default) | disable | force |
1226 disable: disable HPET and use PIT instead
1227 force: allow force enabled of undocumented chips (ICH4,
1229 verbose: show contents of HPET registers during setup
1231 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1232 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1234 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1235 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1236 On x86-64 and powerpc, this option can be specified
1237 multiple times interleaved with hugepages= to reserve
1238 huge pages of different sizes. Valid pages sizes on
1239 x86-64 are 2M (when the CPU supports "pse") and 1G
1240 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1242 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1243 terminal devices. Valid values: 0..8
1244 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1245 If specified, z/VM IUCV HVC accepts connections
1246 from listed z/VM user IDs only.
1248 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1249 hardware thread id mappings.
1250 Format: <cpu>:<hwthread>
1253 Do not unregister boot console at start. This is only
1254 useful for debugging when something happens in the window
1255 between unregistering the boot console and initializing
1258 i2c_bus= [HW] Override the default board specific I2C bus speed
1259 or register an additional I2C bus that is not
1260 registered from board initialization code.
1264 i8042.debug [HW] Toggle i8042 debug mode
1265 i8042.direct [HW] Put keyboard port into non-translated mode
1266 i8042.dumbkbd [HW] Pretend that controller can only read data from
1267 keyboard and cannot control its state
1268 (Don't attempt to blink the leds)
1269 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1270 i8042.nokbd [HW] Don't check/create keyboard port
1271 i8042.noloop [HW] Disable the AUX Loopback command while probing
1273 i8042.nomux [HW] Don't check presence of an active multiplexing
1275 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1277 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1278 i8042.reset [HW] Reset the controller during init and cleanup
1279 i8042.unlock [HW] Unlock (ignore) the keylock
1280 i8042.kbdreset [HW] Reset device connected to KBD port
1284 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1285 indicates that the driver is running on unsupported
1287 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1288 does not match list of supported models.
1290 [HW] Report power status in /proc/i8k
1291 (disabled by default)
1292 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1295 i915.invert_brightness=
1296 [DRM] Invert the sense of the variable that is used to
1297 set the brightness of the panel backlight. Normally a
1298 brightness value of 0 indicates backlight switched off,
1299 and the maximum of the brightness value sets the backlight
1300 to maximum brightness. If this parameter is set to 0
1301 (default) and the machine requires it, or this parameter
1302 is set to 1, a brightness value of 0 sets the backlight
1303 to maximum brightness, and the maximum of the brightness
1304 value switches the backlight off.
1305 -1 -- never invert brightness
1306 0 -- machine default
1307 1 -- force brightness inversion
1310 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1312 ide-core.nodma= [HW] (E)IDE subsystem
1313 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1314 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1315 .cdrom .chs .ignore_cable are additional options
1316 See Documentation/ide/ide.txt.
1318 ide-generic.probe-mask= [HW] (E)IDE subsystem
1320 Probe mask for legacy ISA IDE ports. Depending on
1321 platform up to 6 ports are supported, enabled by
1322 setting corresponding bits in the mask to 1. The
1323 default value is 0x0, which has a special meaning.
1324 On systems that have PCI, it triggers scanning the
1325 PCI bus for the first and the second port, which
1326 are then probed. On systems without PCI the value
1327 of 0x0 enables probing the two first ports as if it
1330 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1331 Claim all unknown PCI IDE storage controllers.
1334 Format: idle=poll, idle=halt, idle=nomwait
1335 Poll forces a polling idle loop that can slightly
1336 improve the performance of waking up a idle CPU, but
1337 will use a lot of power and make the system run hot.
1339 idle=halt: Halt is forced to be used for CPU idle.
1340 In such case C2/C3 won't be used again.
1341 idle=nomwait: Disable mwait for CPU C-states
1343 ignore_loglevel [KNL]
1344 Ignore loglevel setting - this will print /all/
1345 kernel messages to the console. Useful for debugging.
1346 We also add it as printk module parameter, so users
1347 could change it dynamically, usually by
1348 /sys/module/printk/parameters/ignore_loglevel.
1350 ihash_entries= [KNL]
1351 Set number of hash buckets for inode cache.
1353 ima_appraise= [IMA] appraise integrity measurements
1354 Format: { "off" | "enforce" | "fix" | "log" }
1357 ima_appraise_tcb [IMA]
1358 The builtin appraise policy appraises all files
1362 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1366 The list of supported hash algorithms is defined
1367 in crypto/hash_info.h.
1370 Load a policy which meets the needs of the Trusted
1371 Computing Base. This means IMA will measure all
1372 programs exec'd, files mmap'd for exec, and all files
1373 opened for read by uid=0.
1376 Select one of defined IMA measurements template formats.
1377 Formats: { "ima" | "ima-ng" }
1381 [IMA] Define a custom template format.
1382 Format: { "field1|...|fieldN" }
1384 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1385 Format: <min_file_size>
1386 Set the minimal file size for using asynchronous hash.
1387 If left unspecified, ahash usage is disabled.
1389 ahash performance varies for different data sizes on
1390 different crypto accelerators. This option can be used
1391 to achieve the best performance for a particular HW.
1393 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1395 Set hashing buffer size. Default: 4k.
1397 ahash performance varies for different chunk sizes on
1398 different crypto accelerators. This option can be used
1399 to achieve best performance for particular HW.
1403 Run specified binary instead of /sbin/init as init
1406 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1407 for working out where the kernel is dying during
1410 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1411 initcall functions. Useful for debugging built-in
1412 modules and initcalls.
1414 initrd= [BOOT] Specify the location of the initial ramdisk
1416 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1419 int_pln_enable [x86] Enable power limit notification interrupt
1421 integrity_audit=[IMA]
1422 Format: { "0" | "1" }
1423 0 -- basic integrity auditing messages. (Default)
1424 1 -- additional integrity auditing messages.
1426 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1428 Enable intel iommu driver.
1430 Disable intel iommu driver.
1431 igfx_off [Default Off]
1432 By default, gfx is mapped as normal device. If a gfx
1433 device has a dedicated DMAR unit, the DMAR unit is
1434 bypassed by not enabling DMAR with this option. In
1435 this case, gfx device will use physical address for
1438 With this option iommu will not optimize to look
1439 for io virtual address below 32-bit forcing dual
1440 address cycle on pci bus for cards supporting greater
1441 than 32-bit addressing. The default is to look
1442 for translation below 32-bit and if not available
1443 then look in the higher range.
1444 strict [Default Off]
1445 With this option on every unmap_single operation will
1446 result in a hardware IOTLB flush operation as opposed
1447 to batching them for performance.
1448 sp_off [Default Off]
1449 By default, super page will be supported if Intel IOMMU
1450 has the capability. With this option, super page will
1453 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1454 0 disables intel_idle and fall back on acpi_idle.
1455 1 to 6 specify maximum depth of C-state.
1459 Do not enable intel_pstate as the default
1460 scaling driver for the supported processors
1462 Enable intel_pstate on systems that prohibit it by default
1463 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1464 instead of acpi-cpufreq may disable platform features, such
1465 as thermal controls and power capping, that rely on ACPI
1466 P-States information being indicated to OSPM and therefore
1467 should be used with caution. This option does not work with
1468 processors that aren't supported by the intel_pstate driver
1469 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1471 Do not enable hardware P state control (HWP)
1474 Only load intel_pstate on systems which support
1475 hardware P state control (HWP) if available.
1477 intremap= [X86-64, Intel-IOMMU]
1478 on enable Interrupt Remapping (default)
1479 off disable Interrupt Remapping
1480 nosid disable Source ID checking
1482 BIOS x2APIC opt-out request will be ignored
1484 iomem= Disable strict checking of access to MMIO memory
1485 strict regions from userspace.
1500 nobypass [PPC/POWERNV]
1501 Disable IOMMU bypass, using IOMMU for PCI devices.
1504 io7= [HW] IO7 for Marvel based alpha systems
1505 See comment before marvel_specify_io7 in
1506 arch/alpha/kernel/core_marvel.c.
1508 io_delay= [X86] I/O delay method
1510 Standard port 0x80 based delay
1512 Alternate port 0xed based delay (needed on some systems)
1514 Simple two microseconds delay
1519 See Documentation/filesystems/nfs/nfsroot.txt.
1522 When an interrupt is not handled search all handlers
1523 for it. Intended to get systems with badly broken
1527 When an interrupt is not handled search all handlers
1528 for it. Also check all handlers each timer
1529 interrupt. Intended to get systems with badly broken
1533 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1535 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1537 <cpu number>,...,<cpu number>
1539 <cpu number>-<cpu number>
1540 (must be a positive range in ascending order)
1542 <cpu number>,...,<cpu number>-<cpu number>
1544 This option can be used to specify one or more CPUs
1545 to isolate from the general SMP balancing and scheduling
1546 algorithms. You can move a process onto or off an
1547 "isolated" CPU via the CPU affinity syscalls or cpuset.
1548 <cpu number> begins at 0 and the maximum value is
1549 "number of CPUs in system - 1".
1551 This option is the preferred way to isolate CPUs. The
1552 alternative -- manually setting the CPU mask of all
1553 tasks in the system -- can cause problems and
1554 suboptimal load balancer performance.
1558 ivrs_ioapic [HW,X86_64]
1559 Provide an override to the IOAPIC-ID<->DEVICE-ID
1560 mapping provided in the IVRS ACPI table. For
1561 example, to map IOAPIC-ID decimal 10 to
1562 PCI device 00:14.0 write the parameter as:
1563 ivrs_ioapic[10]=00:14.0
1565 ivrs_hpet [HW,X86_64]
1566 Provide an override to the HPET-ID<->DEVICE-ID
1567 mapping provided in the IVRS ACPI table. For
1568 example, to map HPET-ID decimal 0 to
1569 PCI device 00:14.0 write the parameter as:
1570 ivrs_hpet[0]=00:14.0
1572 js= [HW,JOY] Analog joystick
1573 See Documentation/input/joystick.txt.
1576 Enable/disable kernel and module base offset ASLR
1577 (Address Space Layout Randomization) if built into
1578 the kernel. When CONFIG_HIBERNATION is selected,
1579 kASLR is disabled by default. When kASLR is enabled,
1580 hibernation will be disabled.
1584 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1585 specifies the amount of memory usable by the kernel
1586 for non-movable allocations. The requested amount is
1587 spread evenly throughout all nodes in the system. The
1588 remaining memory in each node is used for Movable
1589 pages. In the event, a node is too small to have both
1590 kernelcore and Movable pages, kernelcore pages will
1591 take priority and other nodes will have a larger number
1592 of Movable pages. The Movable zone is used for the
1593 allocation of pages that may be reclaimed or moved
1594 by the page migration subsystem. This means that
1595 HugeTLB pages may not be allocated from this zone.
1596 Note that allocations like PTEs-from-HighMem still
1597 use the HighMem zone if it exists, and the Normal
1598 zone if it does not.
1600 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1601 Format: <Controller#>[,poll interval]
1602 The controller # is the number of the ehci usb debug
1603 port as it is probed via PCI. The poll interval is
1604 optional and is the number seconds in between
1605 each poll cycle to the debug port in case you need
1606 the functionality for interrupting the kernel with
1607 gdb or control-c on the dbgp connection. When
1608 not using this parameter you use sysrq-g to break into
1609 the kernel debugger.
1611 kgdboc= [KGDB,HW] kgdb over consoles.
1612 Requires a tty driver that supports console polling,
1613 or a supported polling keyboard driver (non-usb).
1614 Serial only format: <serial_device>[,baud]
1615 keyboard only format: kbd
1616 keyboard and serial format: kbd,<serial_device>[,baud]
1617 Optional Kernel mode setting:
1618 kms, kbd format: kms,kbd
1619 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1621 kgdbwait [KGDB] Stop kernel execution and enter the
1622 kernel debugger at the earliest opportunity.
1624 kmac= [MIPS] korina ethernet MAC address.
1625 Configure the RouterBoard 532 series on-chip
1626 Ethernet adapter MAC address.
1628 kmemleak= [KNL] Boot-time kmemleak enable/disable
1629 Valid arguments: on, off
1631 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1634 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1635 Valid arguments: 0, 1, 2
1636 kmemcheck=0 (disabled)
1637 kmemcheck=1 (enabled)
1638 kmemcheck=2 (one-shot mode)
1639 Default: 2 (one-shot mode)
1641 kstack=N [X86] Print N words from the kernel stack
1644 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1645 Default is 0 (don't ignore, but inject #GP)
1647 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1651 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1652 Default is 1 (enabled)
1654 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1656 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1658 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1659 (virtualized MMU) support on capable Intel chips.
1660 Default is 1 (enabled)
1662 kvm-intel.emulate_invalid_guest_state=
1663 [KVM,Intel] Enable emulation of invalid guest states
1664 Default is 0 (disabled)
1666 kvm-intel.flexpriority=
1667 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1668 Default is 1 (enabled)
1671 [KVM,Intel] Enable VMX nesting (nVMX).
1672 Default is 0 (disabled)
1674 kvm-intel.unrestricted_guest=
1675 [KVM,Intel] Disable unrestricted guest feature
1676 (virtualized real and unpaged mode) on capable
1677 Intel chips. Default is 1 (enabled)
1679 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1680 feature (tagged TLBs) on capable Intel chips.
1681 Default is 1 (enabled)
1687 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1690 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1691 value for LAPIC timer one-shot implementation. Default
1692 back to the programmable timer unit in the LAPIC.
1694 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1697 libata.dma= [LIBATA] DMA control
1698 libata.dma=0 Disable all PATA and SATA DMA
1699 libata.dma=1 PATA and SATA Disk DMA only
1700 libata.dma=2 ATAPI (CDROM) DMA only
1701 libata.dma=4 Compact Flash DMA only
1702 Combinations also work, so libata.dma=3 enables DMA
1703 for disks and CDROMs, but not CFs.
1705 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1706 libata.ignore_hpa=0 keep BIOS limits (default)
1707 libata.ignore_hpa=1 ignore limits, using full disk
1709 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1713 libata.force= [LIBATA] Force configurations. The format is comma
1714 separated list of "[ID:]VAL" where ID is
1715 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1716 matching port, link or device. Basically, it matches
1717 the ATA ID string printed on console by libata. If
1718 the whole ID part is omitted, the last PORT and DEVICE
1719 values are used. If ID hasn't been specified yet, the
1720 configuration applies to all ports, links and devices.
1722 If only DEVICE is omitted, the parameter applies to
1723 the port and all links and devices behind it. DEVICE
1724 number of 0 either selects the first device or the
1725 first fan-out link behind PMP device. It does not
1726 select the host link. DEVICE number of 15 selects the
1727 host link and device attached to it.
1729 The VAL specifies the configuration to force. As long
1730 as there's no ambiguity shortcut notation is allowed.
1731 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1732 The following configurations can be forced.
1734 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1735 Any ID with matching PORT is used.
1737 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1739 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1740 udma[/][16,25,33,44,66,100,133] notation is also
1743 * [no]ncq: Turn on or off NCQ.
1745 * nohrst, nosrst, norst: suppress hard, soft
1748 * rstonce: only attempt one reset during
1749 hot-unplug link recovery
1751 * dump_id: dump IDENTIFY data.
1753 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1755 * disable: Disable this device.
1757 If there are multiple matching configurations changing
1758 the same attribute, the last one is used.
1760 memblock=debug [KNL] Enable memblock debug messages.
1762 load_ramdisk= [RAM] List of ramdisks to load from floppy
1763 See Documentation/blockdev/ramdisk.txt.
1765 lockd.nlm_grace_period=P [NFS] Assign grace period.
1768 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1771 lockd.nlm_timeout=T [NFS] Assign timeout value.
1774 lockd.nlm_udpport=M [NFS] Assign UDP port.
1777 locktorture.nreaders_stress= [KNL]
1778 Set the number of locking read-acquisition kthreads.
1779 Defaults to being automatically set based on the
1780 number of online CPUs.
1782 locktorture.nwriters_stress= [KNL]
1783 Set the number of locking write-acquisition kthreads.
1785 locktorture.onoff_holdoff= [KNL]
1786 Set time (s) after boot for CPU-hotplug testing.
1788 locktorture.onoff_interval= [KNL]
1789 Set time (s) between CPU-hotplug operations, or
1790 zero to disable CPU-hotplug testing.
1792 locktorture.shuffle_interval= [KNL]
1793 Set task-shuffle interval (jiffies). Shuffling
1794 tasks allows some CPUs to go into dyntick-idle
1795 mode during the locktorture test.
1797 locktorture.shutdown_secs= [KNL]
1798 Set time (s) after boot system shutdown. This
1799 is useful for hands-off automated testing.
1801 locktorture.stat_interval= [KNL]
1802 Time (s) between statistics printk()s.
1804 locktorture.stutter= [KNL]
1805 Time (s) to stutter testing, for example,
1806 specifying five seconds causes the test to run for
1807 five seconds, wait for five seconds, and so on.
1808 This tests the locking primitive's ability to
1809 transition abruptly to and from idle.
1811 locktorture.torture_runnable= [BOOT]
1812 Start locktorture running at boot time.
1814 locktorture.torture_type= [KNL]
1815 Specify the locking implementation to test.
1817 locktorture.verbose= [KNL]
1818 Enable additional printk() statements.
1820 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1823 loglevel= All Kernel Messages with a loglevel smaller than the
1824 console loglevel will be printed to the console. It can
1825 also be changed with klogd or other programs. The
1826 loglevels are defined as follows:
1828 0 (KERN_EMERG) system is unusable
1829 1 (KERN_ALERT) action must be taken immediately
1830 2 (KERN_CRIT) critical conditions
1831 3 (KERN_ERR) error conditions
1832 4 (KERN_WARNING) warning conditions
1833 5 (KERN_NOTICE) normal but significant condition
1834 6 (KERN_INFO) informational
1835 7 (KERN_DEBUG) debug-level messages
1837 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1838 in bytes. n must be a power of two and greater
1839 than the minimal size. The minimal size is defined
1840 by LOG_BUF_SHIFT kernel config parameter. There is
1841 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1842 that allows to increase the default size depending on
1843 the number of CPUs. See init/Kconfig for more details.
1845 logo.nologo [FB] Disables display of the built-in Linux logo.
1846 This may be used to provide more screen space for
1847 kernel log messages and is useful when debugging
1848 kernel boot problems.
1850 lp=0 [LP] Specify parallel ports to use, e.g,
1851 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1852 lp=reset first parallel port). 'lp=0' disables the
1853 lp=auto printer driver. 'lp=reset' (which can be
1854 specified in addition to the ports) causes
1855 attached printers to be reset. Using
1856 lp=port1,port2,... specifies the parallel ports
1857 to associate lp devices with, starting with
1858 lp0. A port specification may be 'none' to skip
1859 that lp device, or a parport name such as
1860 'parport0'. Specifying 'lp=auto' instead of a
1861 port specification list means that device IDs
1862 from each port should be examined, to see if
1863 an IEEE 1284-compliant printer is attached; if
1864 so, the driver will manage that printer.
1865 See also header of drivers/char/lp.c.
1868 Sets loops_per_jiffy to given constant, thus avoiding
1869 time-consuming boot-time autodetection (up to 250 ms per
1870 CPU). 0 enables autodetection (default). To determine
1871 the correct value for your kernel, boot with normal
1872 autodetection and see what value is printed. Note that
1873 on SMP systems the preset will be applied to all CPUs,
1874 which is likely to cause problems if your CPUs need
1875 significantly divergent settings. An incorrect value
1876 will cause delays in the kernel to be wrong, leading to
1877 unpredictable I/O errors and other breakage. Although
1878 unlikely, in the extreme case this might damage your
1882 Format: <io>,<irq>,<dma>
1884 machvec= [IA-64] Force the use of a particular machine-vector
1885 (machvec) in a generic kernel.
1886 Example: machvec=hpzx1_swiotlb
1888 machtype= [Loongson] Share the same kernel image file between different
1890 Example: machtype=lemote-yeeloong-2f-7inch
1892 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1893 than or equal to this physical address is ignored.
1895 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1896 should make use of. maxcpus=n : n >= 0 limits the
1897 kernel to using 'n' processors. n=0 is a special case,
1898 it is equivalent to "nosmp", which also disables
1901 max_loop= [LOOP] The number of loop block devices that get
1902 (loop.max_loop) unconditionally pre-created at init time. The default
1903 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1904 of statically allocating a predefined number, loop
1905 devices can be requested on-demand with the
1906 /dev/loop-control interface.
1908 mce [X86-32] Machine Check Exception
1910 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1912 md= [HW] RAID subsystems devices and level
1913 See Documentation/md.txt.
1916 Format: <first>,<last>
1917 Specifies range of consoles to be captured by the MDA.
1919 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1920 Amount of memory to be used when the kernel is not able
1921 to see the whole system memory or for test.
1922 [X86] Work as limiting max address. Use together
1923 with memmap= to avoid physical address space collisions.
1924 Without memmap= PCI devices could be placed at addresses
1925 belonging to unused RAM.
1927 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1931 [KNL,SH] Allow user to override the default size for
1932 per-device physically contiguous DMA buffers.
1934 memmap=exactmap [KNL,X86] Enable setting of an exact
1935 E820 memory map, as specified by the user.
1936 Such memmap=exactmap lines can be constructed based on
1937 BIOS output or other requirements. See the memmap=nn@ss
1940 memmap=nn[KMG]@ss[KMG]
1941 [KNL] Force usage of a specific region of memory.
1942 Region of memory to be used is from ss to ss+nn.
1944 memmap=nn[KMG]#ss[KMG]
1945 [KNL,ACPI] Mark specific memory as ACPI data.
1946 Region of memory to be marked is from ss to ss+nn.
1948 memmap=nn[KMG]$ss[KMG]
1949 [KNL,ACPI] Mark specific memory as reserved.
1950 Region of memory to be reserved is from ss to ss+nn.
1951 Example: Exclude memory from 0x18690000-0x1869ffff
1952 memmap=64K$0x18690000
1954 memmap=0x10000$0x18690000
1956 memory_corruption_check=0/1 [X86]
1957 Some BIOSes seem to corrupt the first 64k of
1958 memory when doing things like suspend/resume.
1959 Setting this option will scan the memory
1960 looking for corruption. Enabling this will
1961 both detect corruption and prevent the kernel
1962 from using the memory being corrupted.
1963 However, its intended as a diagnostic tool; if
1964 repeatable BIOS-originated corruption always
1965 affects the same memory, you can use memmap=
1966 to prevent the kernel from using that memory.
1968 memory_corruption_check_size=size [X86]
1969 By default it checks for corruption in the low
1970 64k, making this memory unavailable for normal
1971 use. Use this parameter to scan for
1972 corruption in more or less memory.
1974 memory_corruption_check_period=seconds [X86]
1975 By default it checks for corruption every 60
1976 seconds. Use this parameter to check at some
1977 other rate. 0 disables periodic checking.
1979 memtest= [KNL,X86] Enable memtest
1981 default : 0 <disable>
1982 Specifies the number of memtest passes to be
1983 performed. Each pass selects another test
1984 pattern from a given set of patterns. Memtest
1985 fills the memory with this pattern, validates
1986 memory contents and reserves bad memory
1987 regions that are detected.
1989 meye.*= [HW] Set MotionEye Camera parameters
1990 See Documentation/video4linux/meye.txt.
1992 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1993 Multi-Function General Purpose Timers on AMD Geode
1996 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1997 the BIOS has incorrectly applied a workaround. TinyBIOS
1998 version 0.98 is known to be affected, 0.99 fixes the
1999 problem by letting the user disable the workaround.
2003 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2004 physical address is ignored.
2006 mini2440= [ARM,HW,KNL]
2007 Format:[0..2][b][c][t]
2009 MINI2440 configuration specification:
2010 0 - The attached screen is the 3.5" TFT
2011 1 - The attached screen is the 7" TFT
2012 2 - The VGA Shield is attached (1024x768)
2013 Leaving out the screen size parameter will not load
2014 the TFT driver, and the framebuffer will be left
2016 b - Enable backlight. The TFT backlight pin will be
2017 linked to the kernel VESA blanking code and a GPIO
2018 LED. This parameter is not necessary when using the
2020 c - Enable the s3c camera interface.
2021 t - Reserved for enabling touchscreen support. The
2022 touchscreen support is not enabled in the mainstream
2023 kernel as of 2.6.30, a preliminary port can be found
2024 in the "bleeding edge" mini2440 support kernel at
2025 http://repo.or.cz/w/linux-2.6/mini2440.git
2028 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2029 parameter allows control of the logging verbosity for
2030 the additional memory initialisation checks. A value
2031 of 0 disables mminit logging and a level of 4 will
2032 log everything. Information is printed at KERN_DEBUG
2033 so loglevel=8 may also need to be specified.
2036 [KNL] When CONFIG_MODULE_SIG is set, this means that
2037 modules without (valid) signatures will fail to load.
2038 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2039 is always true, so this option does nothing.
2042 [MOUSE] Maximum time between finger touching and
2043 leaving touchpad surface for touch to be considered
2044 a tap and be reported as a left button click (for
2045 touchpads working in absolute mode only).
2047 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2048 reporting absolute coordinates, such as tablets
2049 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2050 reporting absolute coordinates, such as tablets
2052 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2053 is similar to kernelcore except it specifies the
2054 amount of memory used for migratable allocations.
2055 If both kernelcore and movablecore is specified,
2056 then kernelcore will be at *least* the specified
2057 value but may be more. If movablecore on its own
2058 is specified, the administrator must be careful
2059 that the amount of memory usable for all allocations
2062 movable_node [KNL,X86] Boot-time switch to enable the effects
2063 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2065 MTD_Partition= [MTD]
2066 Format: <name>,<region-number>,<size>,<offset>
2068 MTD_Region= [MTD] Format:
2069 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2072 See drivers/mtd/cmdlinepart.c.
2074 multitce=off [PPC] This parameter disables the use of the pSeries
2075 firmware feature for updating multiple TCE entries
2078 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2080 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2082 boundary - index of last SLC block on Flex-OneNAND.
2083 The remaining blocks are configured as MLC blocks.
2084 lock - Configure if Flex-OneNAND boundary should be locked.
2085 Once locked, the boundary cannot be changed.
2086 1 indicates lock status, 0 indicates unlock status.
2089 ARM/S3C2412 JIVE boot control
2091 See arch/arm/mach-s3c2412/mach-jive.c
2093 mtouchusb.raw_coordinates=
2094 [HW] Make the MicroTouch USB driver use raw coordinates
2095 ('y', default) or cooked coordinates ('n')
2097 mtrr_chunk_size=nn[KMG] [X86]
2098 used for mtrr cleanup. It is largest continuous chunk
2099 that could hold holes aka. UC entries.
2101 mtrr_gran_size=nn[KMG] [X86]
2102 Used for mtrr cleanup. It is granularity of mtrr block.
2104 Large value could prevent small alignment from
2107 mtrr_spare_reg_nr=n [X86]
2109 Range: 0,7 : spare reg number
2111 Used for mtrr cleanup. It is spare mtrr entries number.
2112 Set to 2 or more if your graphical card needs more.
2114 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2116 netdev= [NET] Network devices parameters
2117 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2118 Note that mem_start is often overloaded to mean
2119 something different and driver-specific.
2120 This usage is only documented in each driver source
2124 [NETFILTER] Enable connection tracking flow accounting
2125 0 to disable accounting
2126 1 to enable accounting
2129 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2130 See Documentation/filesystems/nfs/nfsroot.txt.
2132 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2133 See Documentation/filesystems/nfs/nfsroot.txt.
2135 nfsrootdebug [NFS] enable nfsroot debugging messages.
2136 See Documentation/filesystems/nfs/nfsroot.txt.
2138 nfs.callback_tcpport=
2139 [NFS] set the TCP port on which the NFSv4 callback
2140 channel should listen.
2143 [NFS] sets the pathname to the program which is used
2144 to update the NFS client cache entries.
2146 nfs.cache_getent_timeout=
2147 [NFS] sets the timeout after which an attempt to
2148 update a cache entry is deemed to have failed.
2150 nfs.idmap_cache_timeout=
2151 [NFS] set the maximum lifetime for idmapper cache
2155 [NFS] enable 64-bit inode numbers.
2156 If zero, the NFS client will fake up a 32-bit inode
2157 number for the readdir() and stat() syscalls instead
2158 of returning the full 64-bit number.
2159 The default is to return 64-bit inode numbers.
2161 nfs.max_session_slots=
2162 [NFSv4.1] Sets the maximum number of session slots
2163 the client will attempt to negotiate with the server.
2164 This limits the number of simultaneous RPC requests
2165 that the client can send to the NFSv4.1 server.
2166 Note that there is little point in setting this
2167 value higher than the max_tcp_slot_table_limit.
2169 nfs.nfs4_disable_idmapping=
2170 [NFSv4] When set to the default of '1', this option
2171 ensures that both the RPC level authentication
2172 scheme and the NFS level operations agree to use
2173 numeric uids/gids if the mount is using the
2174 'sec=sys' security flavour. In effect it is
2175 disabling idmapping, which can make migration from
2176 legacy NFSv2/v3 systems to NFSv4 easier.
2177 Servers that do not support this mode of operation
2178 will be autodetected by the client, and it will fall
2179 back to using the idmapper.
2180 To turn off this behaviour, set the value to '0'.
2182 [NFS4] Specify an additional fixed unique ident-
2183 ification string that NFSv4 clients can insert into
2184 their nfs_client_id4 string. This is typically a
2185 UUID that is generated at system install time.
2187 nfs.send_implementation_id =
2188 [NFSv4.1] Send client implementation identification
2189 information in exchange_id requests.
2190 If zero, no implementation identification information
2192 The default is to send the implementation identification
2195 nfs.recover_lost_locks =
2196 [NFSv4] Attempt to recover locks that were lost due
2197 to a lease timeout on the server. Please note that
2198 doing this risks data corruption, since there are
2199 no guarantees that the file will remain unchanged
2200 after the locks are lost.
2201 If you want to enable the kernel legacy behaviour of
2202 attempting to recover these locks, then set this
2204 The default parameter value of '0' causes the kernel
2205 not to attempt recovery of lost locks.
2207 nfsd.nfs4_disable_idmapping=
2208 [NFSv4] When set to the default of '1', the NFSv4
2209 server will return only numeric uids and gids to
2210 clients using auth_sys, and will accept numeric uids
2211 and gids from such clients. This is intended to ease
2212 migration from NFSv2/v3.
2214 objlayoutdriver.osd_login_prog=
2215 [NFS] [OBJLAYOUT] sets the pathname to the program which
2216 is used to automatically discover and login into new
2217 osd-targets. Please see:
2218 Documentation/filesystems/pnfs.txt for more explanations
2220 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2221 when a NMI is triggered.
2222 Format: [state][,regs][,debounce][,die]
2224 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2225 Format: [panic,][nopanic,][num]
2227 0 - turn nmi_watchdog off
2228 When panic is specified, panic when an NMI watchdog
2229 timeout occurs (or 'nopanic' to override the opposite
2231 This is useful when you use a panic=... timeout and
2232 need the box quickly up again.
2234 netpoll.carrier_timeout=
2235 [NET] Specifies amount of time (in seconds) that
2236 netpoll should wait for a carrier. By default netpoll
2239 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2240 emulation library even if a 387 maths coprocessor
2244 [HW] Never suspend the console
2245 Disable suspending of consoles during suspend and
2246 hibernate operations. Once disabled, debugging
2247 messages can reach various consoles while the rest
2248 of the system is being put to sleep (ie, while
2249 debugging driver suspend/resume hooks). This may
2250 not work reliably with all consoles, but is known
2251 to work with serial and VGA consoles.
2252 To facilitate more flexible debugging, we also add
2253 console_suspend, a printk module parameter to control
2254 it. Users could use console_suspend (usually
2255 /sys/module/printk/parameters/console_suspend) to
2256 turn on/off it dynamically.
2258 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2259 caches in the slab allocator. Saves per-node memory,
2260 but will impact performance.
2264 noapic [SMP,APIC] Tells the kernel to not make use of any
2265 IOAPICs that may be present in the system.
2267 noautogroup Disable scheduler automatic task group creation.
2269 nobats [PPC] Do not use BATs for mapping kernel lowmem
2270 on "Classic" PPC cores.
2274 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2276 nodelayacct [KNL] Disable per-task delay accounting
2278 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2280 nodsp [SH] Disable hardware DSP at boot time.
2282 noefi Disable EFI runtime services support.
2287 On X86-32 available only on PAE configured kernels.
2288 noexec=on: enable non-executable mappings (default)
2289 noexec=off: disable non-executable mappings
2292 Disable SMAP (Supervisor Mode Access Prevention)
2293 even if it is supported by processor.
2296 Disable SMEP (Supervisor Mode Execution Prevention)
2297 even if it is supported by processor.
2300 This affects only 32-bit executables.
2301 noexec32=on: enable non-executable mappings (default)
2302 read doesn't imply executable mappings
2303 noexec32=off: disable non-executable mappings
2304 read implies executable mappings
2306 nofpu [SH] Disable hardware FPU at boot time.
2308 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2309 register save and restore. The kernel will only save
2310 legacy floating-point registers on task switch.
2312 noxsave [BUGS=X86] Disables x86 extended register state save
2313 and restore using xsave. The kernel will fallback to
2314 enabling legacy floating-point and sse state.
2316 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2317 register states. The kernel will fall back to use
2318 xsave to save the states. By using this parameter,
2319 performance of saving the states is degraded because
2320 xsave doesn't support modified optimization while
2321 xsaveopt supports it on xsaveopt enabled systems.
2323 noxsaves [X86] Disables xsaves and xrstors used in saving and
2324 restoring x86 extended register state in compacted
2325 form of xsave area. The kernel will fall back to use
2326 xsaveopt and xrstor to save and restore the states
2327 in standard form of xsave area. By using this
2328 parameter, xsave area per process might occupy more
2329 memory on xsaves enabled systems.
2332 on enable eager fpu restore
2333 off disable eager fpu restore
2334 auto selects the default scheme, which automatically
2335 enables eagerfpu restore for xsaveopt.
2337 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2338 wfi(ARM) instruction doesn't work correctly and not to
2339 use it. This is also useful when using JTAG debugger.
2341 no_file_caps Tells the kernel not to honor file capabilities. The
2342 only way then for a file to be executed with privilege
2343 is to be setuid root or executed by root.
2345 nohalt [IA-64] Tells the kernel not to use the power saving
2346 function PAL_HALT_LIGHT when idle. This increases
2347 power-consumption. On the positive side, it reduces
2348 interrupt wake-up latency, which may improve performance
2349 in certain environments such as networked servers or
2352 nohibernate [HIBERNATION] Disable hibernation and resume.
2354 nohz= [KNL] Boottime enable/disable dynamic ticks
2355 Valid arguments: on, off
2358 nohz_full= [KNL,BOOT]
2359 In kernels built with CONFIG_NO_HZ_FULL=y, set
2360 the specified list of CPUs whose tick will be stopped
2361 whenever possible. The boot CPU will be forced outside
2362 the range to maintain the timekeeping.
2363 The CPUs in this range must also be included in the
2366 noiotrap [SH] Disables trapped I/O port accesses.
2368 noirqdebug [X86-32] Disables the code which attempts to detect and
2369 disable unhandled interrupt sources.
2371 no_timer_check [X86,APIC] Disables the code which tests for
2372 broken timer IRQ sources.
2374 noisapnp [ISAPNP] Disables ISA PnP code.
2376 noinitrd [RAM] Tells the kernel not to load any configured
2379 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2381 [Deprecated - use intremap=off]
2385 nojitter [IA-64] Disables jitter checking for ITC timers.
2387 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2389 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2392 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2393 steal time is computed, but won't influence scheduler
2396 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2398 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2400 noltlbs [PPC] Do not use large page/tlb entries for kernel
2401 lowmem mapping on PPC40x.
2403 nomca [IA-64] Disable machine check abort handling
2405 nomce [X86-32] Machine Check Exception
2407 nomfgpt [X86-32] Disable Multi-Function General Purpose
2408 Timer usage (for AMD Geode machines).
2410 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2411 shutdown the other cpus. Instead use the REBOOT_VECTOR
2414 nomodule Disable module load
2416 nopat [X86] Disable PAT (page attribute table extension of
2417 pagetables) support.
2419 norandmaps Don't use address space randomization. Equivalent to
2420 echo 0 > /proc/sys/kernel/randomize_va_space
2422 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2424 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2425 with UP alternatives
2427 nordrand [X86] Disable kernel use of the RDRAND and
2428 RDSEED instructions even if they are supported
2429 by the processor. RDRAND and RDSEED are still
2430 available to user space applications.
2432 noresume [SWSUSP] Disables resume and restores original swap
2435 no-scroll [VGA] Disables scrollback.
2436 This is required for the Braillex ib80-piezo Braille
2437 reader made by F.H. Papenmeier (Germany).
2441 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2443 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2444 and disable the IO APIC. legacy for "maxcpus=0".
2446 nosoftlockup [KNL] Disable the soft-lockup detector.
2448 nosync [HW,M68K] Disables sync negotiation for all devices.
2450 notsc [BUGS=X86-32] Disable Time Stamp Counter
2452 nousb [USB] Disable the USB subsystem
2454 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2458 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2460 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2461 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2462 Some features depend on CPU0. Known dependencies are:
2463 1. Resume from suspend/hibernate depends on CPU0.
2464 Suspend/hibernate will fail if CPU0 is offline and you
2465 need to online CPU0 before suspend/hibernate.
2466 2. PIC interrupts also depend on CPU0. CPU0 can't be
2467 removed if a PIC interrupt is detected.
2468 It's said poweroff/reboot may depend on CPU0 on some
2469 machines although I haven't seen such issues so far
2470 after CPU0 is offline on a few tested machines.
2471 If the dependencies are under your control, you can
2472 turn on cpu0_hotplug.
2474 nptcg= [IA-64] Override max number of concurrent global TLB
2475 purges which is reported from either PAL_VM_SUMMARY or
2478 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2479 could support. nr_cpus=n : n >= 1 limits the kernel to
2480 supporting 'n' processors. Later in runtime you can not
2481 use hotplug cpu feature to put more cpu back to online.
2482 just like you compile the kernel NR_CPUS=n
2484 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2486 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2487 Allowed values are enable and disable
2489 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2490 one of ['zone', 'node', 'default'] can be specified
2491 This can be set from sysctl after boot.
2492 See Documentation/sysctl/vm.txt for details.
2494 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2495 See Documentation/debugging-via-ohci1394.txt for more
2498 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2499 Rather than timing out after 20 ms if an EC
2500 command is not properly ACKed, override the length
2501 of the timeout. We have interrupts disabled while
2502 waiting for the ACK, so if this is set too high
2503 interrupts *may* be lost!
2505 omap_mux= [OMAP] Override bootloader pin multiplexing.
2506 Format: <mux_mode0.mode_name=value>...
2507 For example, to override I2C bus2:
2508 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2510 oprofile.timer= [HW]
2511 Use timer interrupt instead of performance counters
2513 oprofile.cpu_type= Force an oprofile cpu type
2514 This might be useful if you have an older oprofile
2515 userland or if you want common events.
2516 Format: { arch_perfmon }
2517 arch_perfmon: [X86] Force use of architectural
2518 perfmon on Intel CPUs instead of the
2519 CPU specific event set.
2520 timer: [X86] Force use of architectural NMI
2521 timer mode (see also oprofile.timer
2522 for generic hr timer mode)
2523 [s390] Force legacy basic mode sampling
2524 (report cpu_type "timer")
2526 oops=panic Always panic on oopses. Default is to just kill the
2527 process, but there is a small probability of
2528 deadlocking the machine.
2529 This will also cause panics on machine check exceptions.
2530 Useful together with panic=30 to trigger a reboot.
2533 See Documentation/sound/oss/oss-parameters.txt
2535 page_owner= [KNL] Boot-time page_owner enabling option.
2536 Storage of the information about who allocated
2537 each page is disabled in default. With this switch,
2539 on: enable the feature
2541 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2542 timeout > 0: seconds before rebooting
2543 timeout = 0: wait forever
2544 timeout < 0: reboot immediately
2547 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2550 crash_kexec_post_notifiers
2551 Run kdump after running panic-notifiers and dumping
2552 kmsg. This only for the users who doubt kdump always
2553 succeeds in any situation.
2554 Note that this also increases risks of kdump failure,
2555 because some panic notifiers can make the crashed
2556 kernel more unstable.
2558 parkbd.port= [HW] Parallel port number the keyboard adapter is
2559 connected to, default is 0.
2561 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2562 0 for XT, 1 for AT (default is AT).
2565 parport= [HW,PPT] Specify parallel ports. 0 disables.
2566 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2567 Use 'auto' to force the driver to use any
2568 IRQ/DMA settings detected (the default is to
2569 ignore detected IRQ/DMA settings because of
2570 possible conflicts). You can specify the base
2571 address, IRQ, and DMA settings; IRQ and DMA
2572 should be numbers, or 'auto' (for using detected
2573 settings on that particular port), or 'nofifo'
2574 (to avoid using a FIFO even if it is detected).
2575 Parallel ports are assigned in the order they
2576 are specified on the command line, starting
2579 parport_init_mode= [HW,PPT]
2580 Configure VIA parallel port to operate in
2581 a specific mode. This is necessary on Pegasos
2582 computer where firmware has no options for setting
2583 up parallel port mode and sets it to spp.
2584 Currently this function knows 686a and 8231 chips.
2585 Format: [spp|ps2|epp|ecp|ecpepp]
2588 Halt all CPUs after the first oops has been printed for
2589 the specified number of seconds. This is to be used if
2590 your oopses keep scrolling off the screen.
2595 See header of drivers/block/paride/pcd.c.
2596 See also Documentation/blockdev/paride.txt.
2598 pci=option[,option...] [PCI] various PCI subsystem options:
2599 earlydump [X86] dump PCI config space before the kernel
2601 off [X86] don't probe for the PCI bus
2602 bios [X86-32] force use of PCI BIOS, don't access
2603 the hardware directly. Use this if your machine
2604 has a non-standard PCI host bridge.
2605 nobios [X86-32] disallow use of PCI BIOS, only direct
2606 hardware access methods are allowed. Use this
2607 if you experience crashes upon bootup and you
2608 suspect they are caused by the BIOS.
2609 conf1 [X86] Force use of PCI Configuration
2611 conf2 [X86] Force use of PCI Configuration
2613 noaer [PCIE] If the PCIEAER kernel config parameter is
2614 enabled, this kernel boot option can be used to
2615 disable the use of PCIE advanced error reporting.
2616 nodomains [PCI] Disable support for multiple PCI
2617 root domains (aka PCI segments, in ACPI-speak).
2618 nommconf [X86] Disable use of MMCONFIG for PCI
2620 check_enable_amd_mmconf [X86] check for and enable
2621 properly configured MMIO access to PCI
2622 config space on AMD family 10h CPU
2623 nomsi [MSI] If the PCI_MSI kernel config parameter is
2624 enabled, this kernel boot option can be used to
2625 disable the use of MSI interrupts system-wide.
2626 noioapicquirk [APIC] Disable all boot interrupt quirks.
2627 Safety option to keep boot IRQs enabled. This
2628 should never be necessary.
2629 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2630 primary IO-APIC for bridges that cannot disable
2631 boot IRQs. This fixes a source of spurious IRQs
2632 when the system masks IRQs.
2633 noioapicreroute [APIC] Disable workaround that uses the
2634 boot IRQ equivalent of an IRQ that connects to
2635 a chipset where boot IRQs cannot be disabled.
2636 The opposite of ioapicreroute.
2637 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2638 routing table. These calls are known to be buggy
2639 on several machines and they hang the machine
2640 when used, but on other computers it's the only
2641 way to get the interrupt routing table. Try
2642 this option if the kernel is unable to allocate
2643 IRQs or discover secondary PCI buses on your
2645 rom [X86] Assign address space to expansion ROMs.
2646 Use with caution as certain devices share
2647 address decoders between ROMs and other
2649 norom [X86] Do not assign address space to
2650 expansion ROMs that do not already have
2651 BIOS assigned address ranges.
2652 nobar [X86] Do not assign address space to the
2653 BARs that weren't assigned by the BIOS.
2654 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2655 assigned automatically to PCI devices. You can
2656 make the kernel exclude IRQs of your ISA cards
2658 pirqaddr=0xAAAAA [X86] Specify the physical address
2659 of the PIRQ table (normally generated
2660 by the BIOS) if it is outside the
2661 F0000h-100000h range.
2662 lastbus=N [X86] Scan all buses thru bus #N. Can be
2663 useful if the kernel is unable to find your
2664 secondary buses and you want to tell it
2665 explicitly which ones they are.
2666 assign-busses [X86] Always assign all PCI bus
2667 numbers ourselves, overriding
2668 whatever the firmware may have done.
2669 usepirqmask [X86] Honor the possible IRQ mask stored
2670 in the BIOS $PIR table. This is needed on
2671 some systems with broken BIOSes, notably
2672 some HP Pavilion N5400 and Omnibook XE3
2673 notebooks. This will have no effect if ACPI
2674 IRQ routing is enabled.
2675 noacpi [X86] Do not use ACPI for IRQ routing
2676 or for PCI scanning.
2677 use_crs [X86] Use PCI host bridge window information
2678 from ACPI. On BIOSes from 2008 or later, this
2679 is enabled by default. If you need to use this,
2680 please report a bug.
2681 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2682 If you need to use this, please report a bug.
2683 routeirq Do IRQ routing for all PCI devices.
2684 This is normally done in pci_enable_device(),
2685 so this option is a temporary workaround
2686 for broken drivers that don't call it.
2687 skip_isa_align [X86] do not align io start addr, so can
2688 handle more pci cards
2689 firmware [ARM] Do not re-enumerate the bus but instead
2690 just use the configuration from the
2691 bootloader. This is currently used on
2692 IXP2000 systems where the bus has to be
2693 configured a certain way for adjunct CPUs.
2694 noearly [X86] Don't do any early type 1 scanning.
2695 This might help on some broken boards which
2696 machine check when some devices' config space
2697 is read. But various workarounds are disabled
2698 and some IOMMU drivers will not work.
2699 bfsort Sort PCI devices into breadth-first order.
2700 This sorting is done to get a device
2701 order compatible with older (<= 2.4) kernels.
2702 nobfsort Don't sort PCI devices into breadth-first order.
2703 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2704 tuning and use the BIOS-configured MPS defaults.
2705 pcie_bus_safe Set every device's MPS to the largest value
2706 supported by all devices below the root complex.
2707 pcie_bus_perf Set device MPS to the largest allowable MPS
2708 based on its parent bus. Also set MRRS (Max
2709 Read Request Size) to the largest supported
2710 value (no larger than the MPS that the device
2711 or bus can support) for best performance.
2712 pcie_bus_peer2peer Set every device's MPS to 128B, which
2713 every device is guaranteed to support. This
2714 configuration allows peer-to-peer DMA between
2715 any pair of devices, possibly at the cost of
2716 reduced performance. This also guarantees
2717 that hot-added devices will work.
2718 cbiosize=nn[KMG] The fixed amount of bus space which is
2719 reserved for the CardBus bridge's IO window.
2720 The default value is 256 bytes.
2721 cbmemsize=nn[KMG] The fixed amount of bus space which is
2722 reserved for the CardBus bridge's memory
2723 window. The default value is 64 megabytes.
2726 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2727 Specifies alignment and device to reassign
2728 aligned memory resources.
2729 If <order of align> is not specified,
2730 PAGE_SIZE is used as alignment.
2731 PCI-PCI bridge can be specified, if resource
2732 windows need to be expanded.
2733 ecrc= Enable/disable PCIe ECRC (transaction layer
2734 end-to-end CRC checking).
2735 bios: Use BIOS/firmware settings. This is the
2739 hpiosize=nn[KMG] The fixed amount of bus space which is
2740 reserved for hotplug bridge's IO window.
2741 Default size is 256 bytes.
2742 hpmemsize=nn[KMG] The fixed amount of bus space which is
2743 reserved for hotplug bridge's memory window.
2744 Default size is 2 megabytes.
2745 realloc= Enable/disable reallocating PCI bridge resources
2746 if allocations done by BIOS are too small to
2747 accommodate resources required by all child
2749 off: Turn realloc off
2751 realloc same as realloc=on
2752 noari do not use PCIe ARI.
2753 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2754 only look for one device below a PCIe downstream
2757 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2760 force Enable ASPM even on devices that claim not to support it.
2761 WARNING: Forcing ASPM on may cause system lockups.
2763 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2764 nomsi Do not use MSI for PCI Express Native Hotplug (this
2765 makes all PCIe ports use INTx for hotplug services).
2767 pcie_ports= [PCIE] PCIe ports handling:
2768 auto Ask the BIOS whether or not to use native PCIe services
2769 associated with PCIe ports (PME, hot-plug, AER). Use
2770 them only if that is allowed by the BIOS.
2771 native Use native PCIe services associated with PCIe ports
2773 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2776 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2777 nomsi Do not use MSI for native PCIe PME signaling (this makes
2778 all PCIe root ports use INTx for all services).
2780 pcmv= [HW,PCMCIA] BadgePAD 4
2784 Keep all power-domains already enabled by bootloader on,
2785 even if no driver has claimed them. This is useful
2786 for debug and development, but should not be
2787 needed on a platform with proper driver support.
2790 See Documentation/blockdev/paride.txt.
2792 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2795 See arch/parisc/kernel/pdc_chassis.c
2797 percpu_alloc= Select which percpu first chunk allocator to use.
2798 Currently supported values are "embed" and "page".
2799 Archs may support subset or none of the selections.
2800 See comments in mm/percpu.c for details on each
2801 allocator. This parameter is primarily for debugging
2802 and performance comparison.
2805 See Documentation/blockdev/paride.txt.
2808 See Documentation/blockdev/paride.txt.
2810 pirq= [SMP,APIC] Manual mp-table setup
2811 See Documentation/x86/i386/IO-APIC.txt.
2813 plip= [PPT,NET] Parallel port network link
2814 Format: { parport<nr> | timid | 0 }
2815 See also Documentation/parport.txt.
2817 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2818 Override pmtimer IOPort with a hex value.
2822 Enable PNP debug messages (depends on the
2823 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2824 via /sys/module/pnp/parameters/debug. We always show
2825 current resource usage; turning this on also shows
2826 possible settings and some assignment information.
2832 { on | off | curr | res | no-curr | no-res }
2835 [ISAPNP] Exclude IRQs for the autoconfiguration
2838 [ISAPNP] Exclude DMAs for the autoconfiguration
2840 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2841 Ranges are in pairs (I/O port base and size).
2844 [ISAPNP] Exclude memory regions for the
2846 Ranges are in pairs (memory base and size).
2848 ports= [IP_VS_FTP] IPVS ftp helper module
2850 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2852 Format: <port>,<port>....
2854 print-fatal-signals=
2855 [KNL] debug: print fatal signals
2857 If enabled, warn about various signal handling
2858 related application anomalies: too many signals,
2859 too many POSIX.1 timers, fatal signals causing a
2862 If you hit the warning due to signal overflow,
2863 you might want to try "ulimit -i unlimited".
2867 printk.always_kmsg_dump=
2868 Trigger kmsg_dump for cases other than kernel oops or
2870 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2873 printk.time= Show timing data prefixed to each printk message line
2874 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2876 processor.max_cstate= [HW,ACPI]
2877 Limit processor to maximum C-state
2878 max_cstate=9 overrides any DMI blacklist limit.
2880 processor.nocst [HW,ACPI]
2881 Ignore the _CST method to determine C-states,
2882 instead using the legacy FADT method
2884 profile= [KNL] Enable kernel profiling via /proc/profile
2885 Format: [schedule,]<number>
2886 Param: "schedule" - profile schedule points.
2887 Param: <number> - step/bucket size as a power of 2 for
2888 statistical time based profiling.
2889 Param: "sleep" - profile D-state sleeping (millisecs).
2890 Requires CONFIG_SCHEDSTATS
2891 Param: "kvm" - profile VM exits.
2893 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2895 See Documentation/blockdev/ramdisk.txt.
2897 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2898 probe for; one of (bare|imps|exps|lifebook|any).
2899 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2901 psmouse.resetafter= [HW,MOUSE]
2902 Try to reset the device after so many bad packets
2905 [HW,MOUSE] Set desired mouse resolution, in dpi.
2906 psmouse.smartscroll=
2907 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2908 0 = disabled, 1 = enabled (default).
2910 pstore.backend= Specify the name of the pstore backend to use
2913 See Documentation/blockdev/paride.txt.
2916 [KNL] Number of legacy pty's. Overwrites compiled-in
2919 quiet [KNL] Disable most log messages
2924 See Documentation/md.txt.
2926 ramdisk_blocksize= [RAM]
2927 See Documentation/blockdev/ramdisk.txt.
2929 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2930 See Documentation/blockdev/ramdisk.txt.
2933 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2934 the specified list of CPUs to be no-callback CPUs.
2935 Invocation of these CPUs' RCU callbacks will
2936 be offloaded to "rcuox/N" kthreads created for
2937 that purpose, where "x" is "b" for RCU-bh, "p"
2938 for RCU-preempt, and "s" for RCU-sched, and "N"
2939 is the CPU number. This reduces OS jitter on the
2940 offloaded CPUs, which can be useful for HPC and
2941 real-time workloads. It can also improve energy
2942 efficiency for asymmetric multiprocessors.
2945 Rather than requiring that offloaded CPUs
2946 (specified by rcu_nocbs= above) explicitly
2947 awaken the corresponding "rcuoN" kthreads,
2948 make these kthreads poll for callbacks.
2949 This improves the real-time response for the
2950 offloaded CPUs by relieving them of the need to
2951 wake up the corresponding kthread, but degrades
2952 energy efficiency by requiring that the kthreads
2953 periodically wake up to do the polling.
2955 rcutree.blimit= [KNL]
2956 Set maximum number of finished RCU callbacks to
2957 process in one batch.
2959 rcutree.rcu_fanout_leaf= [KNL]
2960 Increase the number of CPUs assigned to each
2961 leaf rcu_node structure. Useful for very large
2964 rcutree.jiffies_till_sched_qs= [KNL]
2965 Set required age in jiffies for a
2966 given grace period before RCU starts
2967 soliciting quiescent-state help from
2968 rcu_note_context_switch().
2970 rcutree.jiffies_till_first_fqs= [KNL]
2971 Set delay from grace-period initialization to
2972 first attempt to force quiescent states.
2973 Units are jiffies, minimum value is zero,
2974 and maximum value is HZ.
2976 rcutree.jiffies_till_next_fqs= [KNL]
2977 Set delay between subsequent attempts to force
2978 quiescent states. Units are jiffies, minimum
2979 value is one, and maximum value is HZ.
2981 rcutree.kthread_prio= [KNL,BOOT]
2982 Set the SCHED_FIFO priority of the RCU
2983 per-CPU kthreads (rcuc/N). This value is also
2984 used for the priority of the RCU boost threads
2985 (rcub/N). Valid values are 1-99 and the default
2986 is 1 (the least-favored priority).
2988 rcutree.rcu_nocb_leader_stride= [KNL]
2989 Set the number of NOCB kthread groups, which
2990 defaults to the square root of the number of
2991 CPUs. Larger numbers reduces the wakeup overhead
2992 on the per-CPU grace-period kthreads, but increases
2993 that same overhead on each group's leader.
2995 rcutree.qhimark= [KNL]
2996 Set threshold of queued RCU callbacks beyond which
2997 batch limiting is disabled.
2999 rcutree.qlowmark= [KNL]
3000 Set threshold of queued RCU callbacks below which
3001 batch limiting is re-enabled.
3003 rcutree.rcu_idle_gp_delay= [KNL]
3004 Set wakeup interval for idle CPUs that have
3005 RCU callbacks (RCU_FAST_NO_HZ=y).
3007 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3008 Set wakeup interval for idle CPUs that have
3009 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3010 Lazy RCU callbacks are those which RCU can
3011 prove do nothing more than free memory.
3013 rcutorture.cbflood_inter_holdoff= [KNL]
3014 Set holdoff time (jiffies) between successive
3015 callback-flood tests.
3017 rcutorture.cbflood_intra_holdoff= [KNL]
3018 Set holdoff time (jiffies) between successive
3019 bursts of callbacks within a given callback-flood
3022 rcutorture.cbflood_n_burst= [KNL]
3023 Set the number of bursts making up a given
3024 callback-flood test. Set this to zero to
3025 disable callback-flood testing.
3027 rcutorture.cbflood_n_per_burst= [KNL]
3028 Set the number of callbacks to be registered
3029 in a given burst of a callback-flood test.
3031 rcutorture.fqs_duration= [KNL]
3032 Set duration of force_quiescent_state bursts.
3034 rcutorture.fqs_holdoff= [KNL]
3035 Set holdoff time within force_quiescent_state bursts.
3037 rcutorture.fqs_stutter= [KNL]
3038 Set wait time between force_quiescent_state bursts.
3040 rcutorture.gp_exp= [KNL]
3041 Use expedited update-side primitives.
3043 rcutorture.gp_normal= [KNL]
3044 Use normal (non-expedited) update-side primitives.
3045 If both gp_exp and gp_normal are set, do both.
3046 If neither gp_exp nor gp_normal are set, still
3049 rcutorture.n_barrier_cbs= [KNL]
3050 Set callbacks/threads for rcu_barrier() testing.
3052 rcutorture.nfakewriters= [KNL]
3053 Set number of concurrent RCU writers. These just
3054 stress RCU, they don't participate in the actual
3055 test, hence the "fake".
3057 rcutorture.nreaders= [KNL]
3058 Set number of RCU readers.
3060 rcutorture.object_debug= [KNL]
3061 Enable debug-object double-call_rcu() testing.
3063 rcutorture.onoff_holdoff= [KNL]
3064 Set time (s) after boot for CPU-hotplug testing.
3066 rcutorture.onoff_interval= [KNL]
3067 Set time (s) between CPU-hotplug operations, or
3068 zero to disable CPU-hotplug testing.
3070 rcutorture.torture_runnable= [BOOT]
3071 Start rcutorture running at boot time.
3073 rcutorture.shuffle_interval= [KNL]
3074 Set task-shuffle interval (s). Shuffling tasks
3075 allows some CPUs to go into dyntick-idle mode
3076 during the rcutorture test.
3078 rcutorture.shutdown_secs= [KNL]
3079 Set time (s) after boot system shutdown. This
3080 is useful for hands-off automated testing.
3082 rcutorture.stall_cpu= [KNL]
3083 Duration of CPU stall (s) to test RCU CPU stall
3084 warnings, zero to disable.
3086 rcutorture.stall_cpu_holdoff= [KNL]
3087 Time to wait (s) after boot before inducing stall.
3089 rcutorture.stat_interval= [KNL]
3090 Time (s) between statistics printk()s.
3092 rcutorture.stutter= [KNL]
3093 Time (s) to stutter testing, for example, specifying
3094 five seconds causes the test to run for five seconds,
3095 wait for five seconds, and so on. This tests RCU's
3096 ability to transition abruptly to and from idle.
3098 rcutorture.test_boost= [KNL]
3099 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3100 "Maybe" means test if the RCU implementation
3101 under test support RCU priority boosting.
3103 rcutorture.test_boost_duration= [KNL]
3104 Duration (s) of each individual boost test.
3106 rcutorture.test_boost_interval= [KNL]
3107 Interval (s) between each boost test.
3109 rcutorture.test_no_idle_hz= [KNL]
3110 Test RCU's dyntick-idle handling. See also the
3111 rcutorture.shuffle_interval parameter.
3113 rcutorture.torture_type= [KNL]
3114 Specify the RCU implementation to test.
3116 rcutorture.verbose= [KNL]
3117 Enable additional printk() statements.
3119 rcupdate.rcu_expedited= [KNL]
3120 Use expedited grace-period primitives, for
3121 example, synchronize_rcu_expedited() instead
3122 of synchronize_rcu(). This reduces latency,
3123 but can increase CPU utilization, degrade
3124 real-time latency, and degrade energy efficiency.
3126 rcupdate.rcu_cpu_stall_suppress= [KNL]
3127 Suppress RCU CPU stall warning messages.
3129 rcupdate.rcu_cpu_stall_timeout= [KNL]
3130 Set timeout for RCU CPU stall warning messages.
3132 rcupdate.rcu_task_stall_timeout= [KNL]
3133 Set timeout in jiffies for RCU task stall warning
3134 messages. Disable with a value less than or equal
3137 rcupdate.rcu_self_test= [KNL]
3138 Run the RCU early boot self tests
3140 rcupdate.rcu_self_test_bh= [KNL]
3141 Run the RCU bh early boot self tests
3143 rcupdate.rcu_self_test_sched= [KNL]
3144 Run the RCU sched early boot self tests
3148 Run specified binary instead of /init from the ramdisk,
3149 used for early userspace startup. See initrd.
3152 Format (x86 or x86_64):
3153 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3155 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3157 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3158 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3159 reboot_force is either force or not specified,
3160 reboot_cpu is s[mp]#### with #### being the processor
3161 to be used for rebooting.
3164 [KNL, SMP] Set scheduler's default relax_domain_level.
3165 See Documentation/cgroups/cpusets.txt.
3167 relative_sleep_states=
3168 [SUSPEND] Use sleep state labeling where the deepest
3169 state available other than hibernation is always "mem".
3170 Format: { "0" | "1" }
3171 0 -- Traditional sleep state labels.
3172 1 -- Relative sleep state labels.
3174 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3176 reservetop= [X86-32]
3178 Reserves a hole at the top of the kernel virtual
3183 Set the amount of memory to reserve for BIOS at
3184 the bottom of the address space.
3186 reset_devices [KNL] Force drivers to reset the underlying device
3187 during initialization.
3190 Specify the partition device for software suspend
3192 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3194 resume_offset= [SWSUSP]
3195 Specify the offset from the beginning of the partition
3196 given by "resume=" at which the swap header is located,
3197 in <PAGE_SIZE> units (needed only for swap files).
3198 See Documentation/power/swsusp-and-swap-files.txt
3200 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3201 read the resume files
3203 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3204 Useful for devices that are detected asynchronously
3205 (e.g. USB and MMC devices).
3207 hibernate= [HIBERNATION]
3208 noresume Don't check if there's a hibernation image
3209 present during boot.
3210 nocompress Don't compress/decompress hibernation images.
3211 no Disable hibernation and resume.
3213 retain_initrd [RAM] Keep initrd memory after extraction
3215 rfkill.default_state=
3216 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3217 etc. communication is blocked by default.
3220 rfkill.master_switch_mode=
3221 0 The "airplane mode" button does nothing.
3222 1 The "airplane mode" button toggles between everything
3223 blocked and the previous configuration.
3224 2 The "airplane mode" button toggles between everything
3225 blocked and everything unblocked.
3227 rhash_entries= [KNL,NET]
3228 Set number of hash buckets for route cache
3230 ro [KNL] Mount root device read-only on boot
3232 root= [KNL] Root filesystem
3233 See name_to_dev_t comment in init/do_mounts.c.
3235 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3236 mount the root filesystem
3238 rootflags= [KNL] Set root filesystem mount option string
3240 rootfstype= [KNL] Set root filesystem type
3242 rootwait [KNL] Wait (indefinitely) for root device to show up.
3243 Useful for devices that are detected asynchronously
3244 (e.g. USB and MMC devices).
3246 rproc_mem=nn[KMG][@address]
3247 [KNL,ARM,CMA] Remoteproc physical memory block.
3248 Memory area to be used by remote processor image,
3251 rw [KNL] Mount root device read-write on boot
3253 S [KNL] Run init in single mode
3255 s390_iommu= [HW,S390]
3256 Set s390 IOTLB flushing mode
3258 With strict flushing every unmap operation will result in
3259 an IOTLB flush. Default is lazy flushing before reuse,
3263 See drivers/net/irda/sa1100_ir.c.
3265 sbni= [NET] Granch SBNI12 leased line adapter
3267 sched_debug [KNL] Enables verbose scheduler debug messages.
3269 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3270 xtime_lock contention on larger systems, and/or RCU lock
3271 contention on all systems with CONFIG_MAXSMP set.
3272 Format: { "0" | "1" }
3273 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3275 Note: increases power consumption, thus should only be
3276 enabled if running jitter sensitive (HPC/RT) workloads.
3278 security= [SECURITY] Choose a security module to enable at boot.
3279 If this boot parameter is not specified, only the first
3280 security module asking for security registration will be
3281 loaded. An invalid security module name will be treated
3282 as if no module has been chosen.
3284 selinux= [SELINUX] Disable or enable SELinux at boot time.
3285 Format: { "0" | "1" }
3286 See security/selinux/Kconfig help text.
3289 Default value is set via kernel config option.
3290 If enabled at boot time, /selinux/disable can be used
3291 later to disable prior to initial policy load.
3293 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3294 Format: { "0" | "1" }
3295 See security/apparmor/Kconfig help text
3298 Default value is set via kernel config option.
3300 serialnumber [BUGS=X86-32]
3303 Maximal number of shapers.
3305 show_msr= [x86] show boot-time MSR settings
3306 Format: { <integer> }
3307 Show boot-time (BIOS-initialized) MSR settings.
3308 The parameter means the number of CPUs to show,
3309 for example 1 means boot CPU only.
3317 Disable merging of slabs with similar size. May be
3318 necessary if there is some reason to distinguish
3319 allocs to different slabs. Debug options disable
3320 merging on their own.
3321 For more information see Documentation/vm/slub.txt.
3323 slab_max_order= [MM, SLAB]
3324 Determines the maximum allowed order for slabs.
3325 A high setting may cause OOMs due to memory
3326 fragmentation. Defaults to 1 for systems with
3327 more than 32MB of RAM, 0 otherwise.
3329 slub_debug[=options[,slabs]] [MM, SLUB]
3330 Enabling slub_debug allows one to determine the
3331 culprit if slab objects become corrupted. Enabling
3332 slub_debug can create guard zones around objects and
3333 may poison objects when not in use. Also tracks the
3334 last alloc / free. For more information see
3335 Documentation/vm/slub.txt.
3337 slub_max_order= [MM, SLUB]
3338 Determines the maximum allowed order for slabs.
3339 A high setting may cause OOMs due to memory
3340 fragmentation. For more information see
3341 Documentation/vm/slub.txt.
3343 slub_min_objects= [MM, SLUB]
3344 The minimum number of objects per slab. SLUB will
3345 increase the slab order up to slub_max_order to
3346 generate a sufficiently large slab able to contain
3347 the number of objects indicated. The higher the number
3348 of objects the smaller the overhead of tracking slabs
3349 and the less frequently locks need to be acquired.
3350 For more information see Documentation/vm/slub.txt.
3352 slub_min_order= [MM, SLUB]
3353 Determines the minimum page order for slabs. Must be
3354 lower than slub_max_order.
3355 For more information see Documentation/vm/slub.txt.
3357 slub_nomerge [MM, SLUB]
3358 Same with slab_nomerge. This is supported for legacy.
3359 See slab_nomerge for more information.
3362 Format: <io1>[,<io2>[,...,<io8>]]
3364 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3365 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3366 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3367 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3368 smsc-ircc2.ircc_irq= [HW] IRQ line
3369 smsc-ircc2.ircc_dma= [HW] DMA channel
3370 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3371 0: Toshiba Satellite 1800 (GP data pin select)
3372 1: Fast pin select (default)
3376 [KNL] Should the soft-lockup detector generate panics.
3379 softlockup_all_cpu_backtrace=
3380 [KNL] Should the soft-lockup detector generate
3381 backtraces on all cpus.
3384 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3385 See Documentation/laptops/sonypi.txt
3387 spia_io_base= [HW,MTD]
3393 Enabled the stack tracer on boot up.
3395 stacktrace_filter=[function-list]
3396 [FTRACE] Limit the functions that the stack tracer
3397 will trace at boot up. function-list is a comma separated
3398 list of functions. This list can be changed at run
3399 time by the stack_trace_filter file in the debugfs
3400 tracing directory. Note, this enables stack tracing
3401 and the stacktrace above is not needed.
3405 Set the STI (builtin display/keyboard on the HP-PARISC
3406 machines) console (graphic card) which should be used
3407 as the initial boot-console.
3408 See also comment in drivers/video/console/sticore.c.
3411 See comment in drivers/video/console/sticore.c.
3414 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3416 sunrpc.min_resvport=
3417 sunrpc.max_resvport=
3419 SunRPC servers often require that client requests
3420 originate from a privileged port (i.e. a port in the
3421 range 0 < portnr < 1024).
3422 An administrator who wishes to reserve some of these
3423 ports for other uses may adjust the range that the
3424 kernel's sunrpc client considers to be privileged
3425 using these two parameters to set the minimum and
3426 maximum port values.
3430 Control how the NFS server code allocates CPUs to
3431 service thread pools. Depending on how many NICs
3432 you have and where their interrupts are bound, this
3433 option will affect which CPUs will do NFS serving.
3434 Note: this parameter cannot be changed while the
3435 NFS server is running.
3437 auto the server chooses an appropriate mode
3438 automatically using heuristics
3439 global a single global pool contains all CPUs
3440 percpu one pool for each CPU
3441 pernode one pool for each NUMA node (equivalent
3442 to global on non-NUMA machines)
3444 sunrpc.tcp_slot_table_entries=
3445 sunrpc.udp_slot_table_entries=
3447 Sets the upper limit on the number of simultaneous
3448 RPC calls that can be sent from the client to a
3449 server. Increasing these values may allow you to
3450 improve throughput, but will also increase the
3451 amount of memory reserved for use by the client.
3454 [KNL] Enable accounting of swap in memory resource
3455 controller if no parameter or 1 is given or disable
3456 it if 0 is given (See Documentation/cgroups/memory.txt)
3458 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3459 Format: { <int> | force }
3460 <int> -- Number of I/O TLB slabs
3461 force -- force using of bounce buffers even if they
3462 wouldn't be automatically used by the kernel
3466 sysfs.deprecated=0|1 [KNL]
3467 Enable/disable old style sysfs layout for old udev
3468 on older distributions. When this option is enabled
3469 very new udev will not work anymore. When this option
3470 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3471 in older udev will not work anymore.
3472 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3473 the kernel configuration.
3475 sysrq_always_enabled
3477 Ignore sysrq setting - this boot parameter will
3478 neutralize any effect of /proc/sys/kernel/sysrq.
3479 Useful for debugging.
3481 tcpmhash_entries= [KNL,NET]
3482 Set the number of tcp_metrics_hash slots.
3483 Default value is 8192 or 16384 depending on total
3484 ram pages. This is used to specify the TCP metrics
3485 cache size. See Documentation/networking/ip-sysctl.txt
3486 "tcp_no_metrics_save" section for more details.
3490 test_suspend= [SUSPEND][,N]
3491 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3492 standby suspend) or "freeze" (for suspend type freeze)
3493 as the system sleep state during system startup with
3494 the optional capability to repeat N number of times.
3495 The system is woken from this state using a
3496 wakeup-capable RTC alarm.
3498 thash_entries= [KNL,NET]
3499 Set number of hash buckets for TCP connection
3501 thermal.act= [HW,ACPI]
3502 -1: disable all active trip points in all thermal zones
3503 <degrees C>: override all lowest active trip points
3505 thermal.crt= [HW,ACPI]
3506 -1: disable all critical trip points in all thermal zones
3507 <degrees C>: override all critical trip points
3509 thermal.nocrt= [HW,ACPI]
3510 Set to disable actions on ACPI thermal zone
3511 critical and hot trip points.
3513 thermal.off= [HW,ACPI]
3514 1: disable ACPI thermal control
3516 thermal.psv= [HW,ACPI]
3517 -1: disable all passive trip points
3518 <degrees C>: override all passive trip points to this
3521 thermal.tzp= [HW,ACPI]
3522 Specify global default ACPI thermal zone polling rate
3523 <deci-seconds>: poll all this frequency
3524 0: no polling (default)
3527 Force threading of all interrupt handlers except those
3528 marked explicitly IRQF_NO_THREAD.
3531 Enable the Transcendent memory driver if built-in.
3533 tmem.cleancache=0|1 [KNL, XEN]
3534 Default is on (1). Disable the usage of the cleancache
3535 API to send anonymous pages to the hypervisor.
3537 tmem.frontswap=0|1 [KNL, XEN]
3538 Default is on (1). Disable the usage of the frontswap
3539 API to send swap pages to the hypervisor. If disabled
3540 the selfballooning and selfshrinking are force disabled.
3542 tmem.selfballooning=0|1 [KNL, XEN]
3543 Default is on (1). Disable the driving of swap pages
3546 tmem.selfshrinking=0|1 [KNL, XEN]
3547 Default is on (1). Partial swapoff that immediately
3548 transfers pages from Xen hypervisor back to the
3549 kernel based on different criteria.
3553 Specify if the kernel should make use of the cpu
3554 topology information if the hardware supports this.
3555 The scheduler will make use of this information and
3556 e.g. base its process migration decisions on it.
3559 topology_updates= [KNL, PPC, NUMA]
3561 Specify if the kernel should ignore (off)
3562 topology updates sent by the hypervisor to this
3567 tpm_suspend_pcr=[HW,TPM]
3568 Format: integer pcr id
3569 Specify that at suspend time, the tpm driver
3570 should extend the specified pcr with zeros,
3571 as a workaround for some chips which fail to
3572 flush the last written pcr on TPM_SaveState.
3573 This will guarantee that all the other pcrs
3576 trace_buf_size=nn[KMG]
3577 [FTRACE] will set tracing buffer size on each cpu.
3579 trace_event=[event-list]
3580 [FTRACE] Set and start specified trace events in order
3581 to facilitate early boot debugging.
3582 See also Documentation/trace/events.txt
3584 trace_options=[option-list]
3585 [FTRACE] Enable or disable tracer options at boot.
3586 The option-list is a comma delimited list of options
3587 that can be enabled or disabled just as if you were
3588 to echo the option name into
3590 /sys/kernel/debug/tracing/trace_options
3592 For example, to enable stacktrace option (to dump the
3593 stack trace of each event), add to the command line:
3595 trace_options=stacktrace
3597 See also Documentation/trace/ftrace.txt "trace options"
3601 Have the tracepoints sent to printk as well as the
3602 tracing ring buffer. This is useful for early boot up
3603 where the system hangs or reboots and does not give the
3604 option for reading the tracing buffer or performing a
3605 ftrace_dump_on_oops.
3607 To turn off having tracepoints sent to printk,
3608 echo 0 > /proc/sys/kernel/tracepoint_printk
3609 Note, echoing 1 into this file without the
3610 tracepoint_printk kernel cmdline option has no effect.
3614 Having tracepoints sent to printk() and activating high
3615 frequency tracepoints such as irq or sched, can cause
3616 the system to live lock.
3619 [FTRACE] enable this option to disable tracing when a
3620 warning is hit. This turns off "tracing_on". Tracing can
3621 be enabled again by echoing '1' into the "tracing_on"
3622 file located in /sys/kernel/debug/tracing/
3624 This option is useful, as it disables the trace before
3625 the WARNING dump is called, which prevents the trace to
3626 be filled with content caused by the warning output.
3628 This option can also be set at run time via the sysctl
3629 option: kernel/traceoff_on_warning
3631 transparent_hugepage=
3633 Format: [always|madvise|never]
3634 Can be used to control the default behavior of the system
3635 with respect to transparent hugepages.
3636 See Documentation/vm/transhuge.txt for more details.
3638 tsc= Disable clocksource stability checks for TSC.
3640 [x86] reliable: mark tsc clocksource as reliable, this
3641 disables clocksource verification at runtime, as well
3642 as the stability checks done at bootup. Used to enable
3643 high-resolution timer mode on older hardware, and in
3644 virtualized environment.
3645 [x86] noirqtime: Do not use TSC to do irq accounting.
3646 Used to run time disable IRQ_TIME_ACCOUNTING on any
3647 platforms where RDTSC is slow and this accounting
3650 turbografx.map[2|3]= [HW,JOY]
3651 TurboGraFX parallel port interface
3653 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3654 See also Documentation/input/joystick-parport.txt
3656 udbg-immortal [PPC] When debugging early kernel crashes that
3657 happen after console_init() and before a proper
3658 console driver takes over, this boot options might
3659 help "seeing" what's going on.
3661 uhash_entries= [KNL,NET]
3662 Set number of hash buckets for UDP/UDP-Lite connections
3665 [USB] Ignore overcurrent events (default N).
3666 Some badly-designed motherboards generate lots of
3667 bogus events, for ports that aren't wired to
3668 anything. Set this parameter to avoid log spamming.
3669 Note that genuine overcurrent events won't be
3673 [X86] Cause panic on unknown NMI.
3675 usbcore.authorized_default=
3676 [USB] Default USB device authorization:
3677 (default -1 = authorized except for wireless USB,
3678 0 = not authorized, 1 = authorized)
3680 usbcore.autosuspend=
3681 [USB] The autosuspend time delay (in seconds) used
3682 for newly-detected USB devices (default 2). This
3683 is the time required before an idle device will be
3684 autosuspended. Devices for which the delay is set
3685 to a negative value won't be autosuspended at all.
3687 usbcore.usbfs_snoop=
3688 [USB] Set to log all usbfs traffic (default 0 = off).
3690 usbcore.blinkenlights=
3691 [USB] Set to cycle leds on hubs (default 0 = off).
3693 usbcore.old_scheme_first=
3694 [USB] Start with the old device initialization
3695 scheme (default 0 = off).
3697 usbcore.usbfs_memory_mb=
3698 [USB] Memory limit (in MB) for buffers allocated by
3699 usbfs (default = 16, 0 = max = 2047).
3701 usbcore.use_both_schemes=
3702 [USB] Try the other device initialization scheme
3703 if the first one fails (default 1 = enabled).
3705 usbcore.initial_descriptor_timeout=
3706 [USB] Specifies timeout for the initial 64-byte
3707 USB_REQ_GET_DESCRIPTOR request in milliseconds
3708 (default 5000 = 5.0 seconds).
3711 [USBHID] The interval which mice are to be polled at.
3713 usb-storage.delay_use=
3714 [UMS] The delay in seconds before a new device is
3715 scanned for Logical Units (default 1).
3718 [UMS] A list of quirks entries to supplement or
3719 override the built-in unusual_devs list. List
3720 entries are separated by commas. Each entry has
3721 the form VID:PID:Flags where VID and PID are Vendor
3722 and Product ID values (4-digit hex numbers) and
3723 Flags is a set of characters, each corresponding
3724 to a common usb-storage quirk flag as follows:
3725 a = SANE_SENSE (collect more than 18 bytes
3727 b = BAD_SENSE (don't collect more than 18
3728 bytes of sense data);
3729 c = FIX_CAPACITY (decrease the reported
3730 device capacity by one sector);
3731 d = NO_READ_DISC_INFO (don't use
3732 READ_DISC_INFO command);
3733 e = NO_READ_CAPACITY_16 (don't use
3734 READ_CAPACITY_16 command);
3735 f = NO_REPORT_OPCODES (don't use report opcodes
3737 h = CAPACITY_HEURISTICS (decrease the
3738 reported device capacity by one
3739 sector if the number is odd);
3740 i = IGNORE_DEVICE (don't bind to this
3742 l = NOT_LOCKABLE (don't try to lock and
3743 unlock ejectable media);
3744 m = MAX_SECTORS_64 (don't transfer more
3745 than 64 sectors = 32 KB at a time);
3746 n = INITIAL_READ10 (force a retry of the
3747 initial READ(10) command);
3748 o = CAPACITY_OK (accept the capacity
3749 reported by the device);
3750 p = WRITE_CACHE (the device cache is ON
3752 r = IGNORE_RESIDUE (the device reports
3753 bogus residue values);
3754 s = SINGLE_LUN (the device has only one
3756 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3757 commands, uas only);
3758 u = IGNORE_UAS (don't bind to the uas driver);
3759 w = NO_WP_DETECT (don't test whether the
3760 medium is write-protected).
3761 Example: quirks=0419:aaf5:rl,0421:0433:rc
3763 user_debug= [KNL,ARM]
3765 See arch/arm/Kconfig.debug help text.
3766 1 - undefined instruction events
3768 4 - invalid data aborts
3771 Example: user_debug=31
3774 [X86] Flags controlling user PTE allocations.
3776 nohigh = do not allocate PTE pages in
3777 HIGHMEM regardless of setting
3781 On X86_32, this is an alias for vdso32=. Otherwise:
3783 vdso=1: enable VDSO (the default)
3784 vdso=0: disable VDSO mapping
3786 vdso32= [X86] Control the 32-bit vDSO
3787 vdso32=1: enable 32-bit VDSO
3788 vdso32=0 or vdso32=2: disable 32-bit VDSO
3790 See the help text for CONFIG_COMPAT_VDSO for more
3791 details. If CONFIG_COMPAT_VDSO is set, the default is
3792 vdso32=0; otherwise, the default is vdso32=1.
3794 For compatibility with older kernels, vdso32=2 is an
3797 Try vdso32=0 if you encounter an error that says:
3798 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3801 vector=percpu: enable percpu vector domain
3803 video= [FB] Frame buffer configuration
3804 See Documentation/fb/modedb.txt.
3806 video.brightness_switch_enabled= [0,1]
3807 If set to 1, on receiving an ACPI notify event
3808 generated by hotkey, video driver will adjust brightness
3809 level and then send out the event to user space through
3810 the allocated input device; If set to 0, video driver
3811 will only send out the event without touching backlight
3816 [VMMIO] Memory mapped virtio (platform) device.
3818 <size>@<baseaddr>:<irq>[:<id>]
3820 <size> := size (can use standard suffixes
3822 <baseaddr> := physical base address
3823 <irq> := interrupt number (as passed to
3825 <id> := (optional) platform device id
3827 virtio_mmio.device=1K@0x100b0000:48:7
3829 Can be used multiple times for multiple devices.
3831 vga= [BOOT,X86-32] Select a particular video mode
3832 See Documentation/x86/boot.txt and
3833 Documentation/svga.txt.
3834 Use vga=ask for menu.
3835 This is actually a boot loader parameter; the value is
3836 passed to the kernel using a special protocol.
3838 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3839 size of <nn>. This can be used to increase the
3840 minimum size (128MB on x86). It can also be used to
3841 decrease the size and leave more room for directly
3844 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3847 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3850 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3854 Controls the behavior of vsyscalls (i.e. calls to
3855 fixed addresses of 0xffffffffff600x00 from legacy
3856 code). Most statically-linked binaries and older
3857 versions of glibc use these calls. Because these
3858 functions are at fixed addresses, they make nice
3859 targets for exploits that can control RIP.
3861 emulate [default] Vsyscalls turn into traps and are
3862 emulated reasonably safely.
3864 native Vsyscalls are native syscall instructions.
3865 This is a little bit faster than trapping
3866 and makes a few dynamic recompilers work
3867 better than they would in emulation mode.
3868 It also makes exploits much easier to write.
3870 none Vsyscalls don't work at all. This makes
3871 them quite hard to use for exploits but
3872 might break your system.
3874 vt.color= [VT] Default text color.
3875 Format: 0xYX, X = foreground, Y = background.
3876 Default: 0x07 = light gray on black.
3878 vt.cur_default= [VT] Default cursor shape.
3879 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3880 the parameters of the <Esc>[?A;B;Cc escape sequence;
3881 see VGA-softcursor.txt. Default: 2 = underline.
3883 vt.default_blu= [VT]
3884 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3885 Change the default blue palette of the console.
3886 This is a 16-member array composed of values
3889 vt.default_grn= [VT]
3890 Format: <green0>,<green1>,<green2>,...,<green15>
3891 Change the default green palette of the console.
3892 This is a 16-member array composed of values
3895 vt.default_red= [VT]
3896 Format: <red0>,<red1>,<red2>,...,<red15>
3897 Change the default red palette of the console.
3898 This is a 16-member array composed of values
3904 Set system-wide default UTF-8 mode for all tty's.
3905 Default is 1, i.e. UTF-8 mode is enabled for all
3906 newly opened terminals.
3908 vt.global_cursor_default=
3911 Set system-wide default for whether a cursor
3912 is shown on new VTs. Default is -1,
3913 i.e. cursors will be created by default unless
3914 overridden by individual drivers. 0 will hide
3915 cursors, 1 will display them.
3917 vt.italic= [VT] Default color for italic text; 0-15.
3920 vt.underline= [VT] Default color for underlined text; 0-15.
3923 watchdog timers [HW,WDT] For information on watchdog timers,
3924 see Documentation/watchdog/watchdog-parameters.txt
3925 or other driver-specific files in the
3926 Documentation/watchdog/ directory.
3928 workqueue.disable_numa
3929 By default, all work items queued to unbound
3930 workqueues are affine to the NUMA nodes they're
3931 issued on, which results in better behavior in
3932 general. If NUMA affinity needs to be disabled for
3933 whatever reason, this option can be used. Note
3934 that this also can be controlled per-workqueue for
3935 workqueues visible under /sys/bus/workqueue/.
3937 workqueue.power_efficient
3938 Per-cpu workqueues are generally preferred because
3939 they show better performance thanks to cache
3940 locality; unfortunately, per-cpu workqueues tend to
3941 be more power hungry than unbound workqueues.
3943 Enabling this makes the per-cpu workqueues which
3944 were observed to contribute significantly to power
3945 consumption unbound, leading to measurably lower
3946 power usage at the cost of small performance
3949 The default value of this parameter is determined by
3950 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3952 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3953 default x2apic cluster mode on platforms
3956 x86_intel_mid_timer= [X86-32,APBT]
3957 Choose timer option for x86 Intel MID platform.
3958 Two valid options are apbt timer only and lapic timer
3959 plus one apbt timer for broadcast timer.
3960 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3962 xen_emul_unplug= [HW,X86,XEN]
3963 Unplug Xen emulated devices
3964 Format: [unplug0,][unplug1]
3965 ide-disks -- unplug primary master IDE devices
3966 aux-ide-disks -- unplug non-primary-master IDE devices
3967 nics -- unplug network devices
3968 all -- unplug all emulated devices (NICs and IDE disks)
3969 unnecessary -- unplugging emulated devices is
3970 unnecessary even if the host did not respond to
3972 never -- do not unplug even if version check succeeds
3974 xen_nopvspin [X86,XEN]
3975 Disables the ticketlock slowpath using Xen PV
3979 Disables the PV optimizations forcing the HVM guest to
3980 run as generic HVM guest with no PV drivers.
3982 xirc2ps_cs= [NET,PCMCIA]
3984 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3986 ______________________________________________________________________
3990 Add more DRM drivers.
projects / linux-drm-fsl-dcu.git / blob