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.
979 Use early console provided by serial driver available
980 on Samsung SoCs, requires selecting proper type and
981 a correct base address of the selected UART port. The
982 serial port must already be setup and configured.
983 Options are not yet supported.
985 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
989 earlyprintk=serial[,ttySn[,baudrate]]
990 earlyprintk=serial[,0x...[,baudrate]]
991 earlyprintk=ttySn[,baudrate]
992 earlyprintk=dbgp[debugController#]
994 earlyprintk is useful when the kernel crashes before
995 the normal console is initialized. It is not enabled by
996 default because it has some cosmetic problems.
998 Append ",keep" to not disable it when the real console
1001 Only one of vga, efi, serial, or usb debug port can
1004 Currently only ttyS0 and ttyS1 may be specified by
1005 name. Other I/O ports may be explicitly specified
1006 on some architectures (x86 and arm at least) by
1007 replacing ttySn with an I/O port address, like this:
1008 earlyprintk=serial,0x1008,115200
1009 You can find the port for a given device in
1010 /proc/tty/driver/serial:
1011 2: uart:ST16650V2 port:00001008 irq:18 ...
1013 Interaction with the standard serial driver is not
1016 The VGA and EFI output is eventually overwritten by
1019 The xen output can only be used by Xen PV guests.
1021 edac_report= [HW,EDAC] Control how to report EDAC event
1022 Format: {"on" | "off" | "force"}
1023 on: enable EDAC to report H/W event. May be overridden
1024 by other higher priority error reporting module.
1025 off: disable H/W event reporting through EDAC.
1026 force: enforce the use of EDAC to report H/W event.
1029 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1032 This is designed to be used in conjunction with
1033 the boot argument: earlyprintk=vga
1036 Format: {"off" | "on" | "skip[mbr]"}
1039 Format: { "old_map", "nochunk", "noruntime" }
1040 old_map [X86-64]: switch to the old ioremap-based EFI
1041 runtime services mapping. 32-bit still uses this one by
1043 nochunk: disable reading files in "chunks" in the EFI
1044 boot stub, as chunking can cause problems with some
1045 firmware implementations.
1046 noruntime : disable EFI runtime services support
1048 efi_no_storage_paranoia [EFI; X86]
1049 Using this parameter you can use more than 50% of
1050 your efi variable storage. Use this parameter only if
1051 you are really sure that your UEFI does sane gc and
1052 fulfills the spec otherwise your board may brick.
1054 eisa_irq_edge= [PARISC,HW]
1055 See header of drivers/parisc/eisa.c.
1058 See comment before function elanfreq_setup() in
1059 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1062 Format: {"cfq" | "deadline" | "noop"}
1063 See Documentation/block/cfq-iosched.txt and
1064 Documentation/block/deadline-iosched.txt for details.
1066 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1067 Specifies physical address of start of kernel core
1068 image elf header and optionally the size. Generally
1069 kexec loader will pass this option to capture kernel.
1070 See Documentation/kdump/kdump.txt for details.
1072 enable_mtrr_cleanup [X86]
1073 The kernel tries to adjust MTRR layout from continuous
1074 to discrete, to make X server driver able to add WB
1075 entry later. This parameter enables that.
1077 enable_timer_pin_1 [X86]
1078 Enable PIN 1 of APIC timer
1079 Can be useful to work around chipset bugs
1080 (in particular on some ATI chipsets).
1081 The kernel tries to set a reasonable default.
1083 enforcing [SELINUX] Set initial enforcing status.
1085 See security/selinux/Kconfig help text.
1086 0 -- permissive (log only, no denials).
1087 1 -- enforcing (deny and log).
1089 Value can be changed at runtime via /selinux/enforce.
1092 Disable Error Record Serialization Table (ERST)
1095 ether= [HW,NET] Ethernet cards parameters
1096 This option is obsoleted by the "netdev=" option, which
1097 has equivalent usage. See its documentation for details.
1101 Permit 'security.evm' to be updated regardless of
1102 current integrity status.
1106 fail_make_request=[KNL]
1107 General fault injection mechanism.
1108 Format: <interval>,<probability>,<space>,<times>
1109 See also Documentation/fault-injection/.
1112 See Documentation/blockdev/floppy.txt.
1114 force_pal_cache_flush
1115 [IA-64] Avoid check_sal_cache_flush which may hang on
1116 buggy SAL_CACHE_FLUSH implementations. Using this
1117 parameter will force ia64_sal_cache_flush to call
1118 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1121 Forcefully enable Physical Address Extension (PAE).
1122 Many Pentium M systems disable PAE but may have a
1123 functionally usable PAE implementation.
1124 Warning: use of this parameter will taint the kernel
1125 and may cause unknown problems.
1128 [FTRACE] will set and start the specified tracer
1129 as early as possible in order to facilitate early
1132 ftrace_dump_on_oops[=orig_cpu]
1133 [FTRACE] will dump the trace buffers on oops.
1134 If no parameter is passed, ftrace will dump
1135 buffers of all CPUs, but if you pass orig_cpu, it will
1136 dump only the buffer of the CPU that triggered the
1139 ftrace_filter=[function-list]
1140 [FTRACE] Limit the functions traced by the function
1141 tracer at boot up. function-list is a comma separated
1142 list of functions. This list can be changed at run
1143 time by the set_ftrace_filter file in the debugfs
1146 ftrace_notrace=[function-list]
1147 [FTRACE] Do not trace the functions specified in
1148 function-list. This list can be changed at run time
1149 by the set_ftrace_notrace file in the debugfs
1152 ftrace_graph_filter=[function-list]
1153 [FTRACE] Limit the top level callers functions traced
1154 by the function graph tracer at boot up.
1155 function-list is a comma separated list of functions
1156 that can be changed at run time by the
1157 set_graph_function file in the debugfs tracing directory.
1159 ftrace_graph_notrace=[function-list]
1160 [FTRACE] Do not trace from the functions specified in
1161 function-list. This list is a comma separated list of
1162 functions that can be changed at run time by the
1163 set_graph_notrace file in the debugfs tracing directory.
1166 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1167 support via parallel port (up to 5 devices per port)
1168 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1169 See also Documentation/input/joystick-parport.txt
1173 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1177 gcov_persist= [GCOV] When non-zero (default), profiling data for
1178 kernel modules is saved and remains accessible via
1179 debugfs, even when the module is unloaded/reloaded.
1180 When zero, profiling data is discarded and associated
1181 debugfs files are removed at module unload time.
1183 gpt [EFI] Forces disk with valid GPT signature but
1184 invalid Protective MBR to be treated as GPT. If the
1185 primary GPT is corrupted, it enables the backup/alternate
1186 GPT to be used instead.
1188 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1189 the "Enable 0" bit of the configuration register.
1192 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1193 the "Enable 0" bit of the configuration register.
1196 grcan.select= [HW] Select which physical interface to use.
1199 grcan.txsize= [HW] Sets the size of the tx buffer.
1200 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1202 grcan.rxsize= [HW] Sets the size of the rx buffer.
1203 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1206 hashdist= [KNL,NUMA] Large hashes allocated during boot
1207 are distributed across NUMA nodes. Defaults on
1208 for 64-bit NUMA, off otherwise.
1209 Format: 0 | 1 (for off | on)
1211 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1213 hd= [EIDE] (E)IDE hard drive subsystem geometry
1214 Format: <cyl>,<head>,<sect>
1217 Disable Hardware Error Source Table (HEST) support;
1218 corresponding firmware-first mode error processing
1219 logic will be disabled.
1221 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1222 size of <nn>. This works even on boxes that have no
1223 highmem otherwise. This also works to reduce highmem
1224 size on bigger boxes.
1226 highres= [KNL] Enable/disable high resolution timer mode.
1227 Valid parameters: "on", "off"
1231 See Documentation/isdn/README.HiSax.
1235 hpet= [X86-32,HPET] option to control HPET usage
1236 Format: { enable (default) | disable | force |
1238 disable: disable HPET and use PIT instead
1239 force: allow force enabled of undocumented chips (ICH4,
1241 verbose: show contents of HPET registers during setup
1243 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1244 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1246 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1247 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1248 On x86-64 and powerpc, this option can be specified
1249 multiple times interleaved with hugepages= to reserve
1250 huge pages of different sizes. Valid pages sizes on
1251 x86-64 are 2M (when the CPU supports "pse") and 1G
1252 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1254 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1255 terminal devices. Valid values: 0..8
1256 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1257 If specified, z/VM IUCV HVC accepts connections
1258 from listed z/VM user IDs only.
1260 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1261 hardware thread id mappings.
1262 Format: <cpu>:<hwthread>
1265 Do not unregister boot console at start. This is only
1266 useful for debugging when something happens in the window
1267 between unregistering the boot console and initializing
1270 i2c_bus= [HW] Override the default board specific I2C bus speed
1271 or register an additional I2C bus that is not
1272 registered from board initialization code.
1276 i8042.debug [HW] Toggle i8042 debug mode
1277 i8042.direct [HW] Put keyboard port into non-translated mode
1278 i8042.dumbkbd [HW] Pretend that controller can only read data from
1279 keyboard and cannot control its state
1280 (Don't attempt to blink the leds)
1281 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1282 i8042.nokbd [HW] Don't check/create keyboard port
1283 i8042.noloop [HW] Disable the AUX Loopback command while probing
1285 i8042.nomux [HW] Don't check presence of an active multiplexing
1287 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1289 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1290 i8042.reset [HW] Reset the controller during init and cleanup
1291 i8042.unlock [HW] Unlock (ignore) the keylock
1292 i8042.kbdreset [HW] Reset device connected to KBD port
1296 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1297 indicates that the driver is running on unsupported
1299 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1300 does not match list of supported models.
1302 [HW] Report power status in /proc/i8k
1303 (disabled by default)
1304 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1307 i915.invert_brightness=
1308 [DRM] Invert the sense of the variable that is used to
1309 set the brightness of the panel backlight. Normally a
1310 brightness value of 0 indicates backlight switched off,
1311 and the maximum of the brightness value sets the backlight
1312 to maximum brightness. If this parameter is set to 0
1313 (default) and the machine requires it, or this parameter
1314 is set to 1, a brightness value of 0 sets the backlight
1315 to maximum brightness, and the maximum of the brightness
1316 value switches the backlight off.
1317 -1 -- never invert brightness
1318 0 -- machine default
1319 1 -- force brightness inversion
1322 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1324 ide-core.nodma= [HW] (E)IDE subsystem
1325 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1326 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1327 .cdrom .chs .ignore_cable are additional options
1328 See Documentation/ide/ide.txt.
1330 ide-generic.probe-mask= [HW] (E)IDE subsystem
1332 Probe mask for legacy ISA IDE ports. Depending on
1333 platform up to 6 ports are supported, enabled by
1334 setting corresponding bits in the mask to 1. The
1335 default value is 0x0, which has a special meaning.
1336 On systems that have PCI, it triggers scanning the
1337 PCI bus for the first and the second port, which
1338 are then probed. On systems without PCI the value
1339 of 0x0 enables probing the two first ports as if it
1342 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1343 Claim all unknown PCI IDE storage controllers.
1346 Format: idle=poll, idle=halt, idle=nomwait
1347 Poll forces a polling idle loop that can slightly
1348 improve the performance of waking up a idle CPU, but
1349 will use a lot of power and make the system run hot.
1351 idle=halt: Halt is forced to be used for CPU idle.
1352 In such case C2/C3 won't be used again.
1353 idle=nomwait: Disable mwait for CPU C-states
1355 ignore_loglevel [KNL]
1356 Ignore loglevel setting - this will print /all/
1357 kernel messages to the console. Useful for debugging.
1358 We also add it as printk module parameter, so users
1359 could change it dynamically, usually by
1360 /sys/module/printk/parameters/ignore_loglevel.
1362 ihash_entries= [KNL]
1363 Set number of hash buckets for inode cache.
1365 ima_appraise= [IMA] appraise integrity measurements
1366 Format: { "off" | "enforce" | "fix" | "log" }
1369 ima_appraise_tcb [IMA]
1370 The builtin appraise policy appraises all files
1374 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1378 The list of supported hash algorithms is defined
1379 in crypto/hash_info.h.
1382 Load a policy which meets the needs of the Trusted
1383 Computing Base. This means IMA will measure all
1384 programs exec'd, files mmap'd for exec, and all files
1385 opened for read by uid=0.
1388 Select one of defined IMA measurements template formats.
1389 Formats: { "ima" | "ima-ng" }
1393 [IMA] Define a custom template format.
1394 Format: { "field1|...|fieldN" }
1396 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1397 Format: <min_file_size>
1398 Set the minimal file size for using asynchronous hash.
1399 If left unspecified, ahash usage is disabled.
1401 ahash performance varies for different data sizes on
1402 different crypto accelerators. This option can be used
1403 to achieve the best performance for a particular HW.
1405 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1407 Set hashing buffer size. Default: 4k.
1409 ahash performance varies for different chunk sizes on
1410 different crypto accelerators. This option can be used
1411 to achieve best performance for particular HW.
1415 Run specified binary instead of /sbin/init as init
1418 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1419 for working out where the kernel is dying during
1422 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1423 initcall functions. Useful for debugging built-in
1424 modules and initcalls.
1426 initrd= [BOOT] Specify the location of the initial ramdisk
1428 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1431 int_pln_enable [x86] Enable power limit notification interrupt
1433 integrity_audit=[IMA]
1434 Format: { "0" | "1" }
1435 0 -- basic integrity auditing messages. (Default)
1436 1 -- additional integrity auditing messages.
1438 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1440 Enable intel iommu driver.
1442 Disable intel iommu driver.
1443 igfx_off [Default Off]
1444 By default, gfx is mapped as normal device. If a gfx
1445 device has a dedicated DMAR unit, the DMAR unit is
1446 bypassed by not enabling DMAR with this option. In
1447 this case, gfx device will use physical address for
1450 With this option iommu will not optimize to look
1451 for io virtual address below 32-bit forcing dual
1452 address cycle on pci bus for cards supporting greater
1453 than 32-bit addressing. The default is to look
1454 for translation below 32-bit and if not available
1455 then look in the higher range.
1456 strict [Default Off]
1457 With this option on every unmap_single operation will
1458 result in a hardware IOTLB flush operation as opposed
1459 to batching them for performance.
1460 sp_off [Default Off]
1461 By default, super page will be supported if Intel IOMMU
1462 has the capability. With this option, super page will
1465 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1466 0 disables intel_idle and fall back on acpi_idle.
1467 1 to 6 specify maximum depth of C-state.
1471 Do not enable intel_pstate as the default
1472 scaling driver for the supported processors
1474 Enable intel_pstate on systems that prohibit it by default
1475 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1476 instead of acpi-cpufreq may disable platform features, such
1477 as thermal controls and power capping, that rely on ACPI
1478 P-States information being indicated to OSPM and therefore
1479 should be used with caution. This option does not work with
1480 processors that aren't supported by the intel_pstate driver
1481 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1483 Do not enable hardware P state control (HWP)
1486 Only load intel_pstate on systems which support
1487 hardware P state control (HWP) if available.
1489 intremap= [X86-64, Intel-IOMMU]
1490 on enable Interrupt Remapping (default)
1491 off disable Interrupt Remapping
1492 nosid disable Source ID checking
1494 BIOS x2APIC opt-out request will be ignored
1496 iomem= Disable strict checking of access to MMIO memory
1497 strict regions from userspace.
1512 nobypass [PPC/POWERNV]
1513 Disable IOMMU bypass, using IOMMU for PCI devices.
1516 io7= [HW] IO7 for Marvel based alpha systems
1517 See comment before marvel_specify_io7 in
1518 arch/alpha/kernel/core_marvel.c.
1520 io_delay= [X86] I/O delay method
1522 Standard port 0x80 based delay
1524 Alternate port 0xed based delay (needed on some systems)
1526 Simple two microseconds delay
1531 See Documentation/filesystems/nfs/nfsroot.txt.
1534 When an interrupt is not handled search all handlers
1535 for it. Intended to get systems with badly broken
1539 When an interrupt is not handled search all handlers
1540 for it. Also check all handlers each timer
1541 interrupt. Intended to get systems with badly broken
1545 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1547 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1549 <cpu number>,...,<cpu number>
1551 <cpu number>-<cpu number>
1552 (must be a positive range in ascending order)
1554 <cpu number>,...,<cpu number>-<cpu number>
1556 This option can be used to specify one or more CPUs
1557 to isolate from the general SMP balancing and scheduling
1558 algorithms. You can move a process onto or off an
1559 "isolated" CPU via the CPU affinity syscalls or cpuset.
1560 <cpu number> begins at 0 and the maximum value is
1561 "number of CPUs in system - 1".
1563 This option is the preferred way to isolate CPUs. The
1564 alternative -- manually setting the CPU mask of all
1565 tasks in the system -- can cause problems and
1566 suboptimal load balancer performance.
1570 ivrs_ioapic [HW,X86_64]
1571 Provide an override to the IOAPIC-ID<->DEVICE-ID
1572 mapping provided in the IVRS ACPI table. For
1573 example, to map IOAPIC-ID decimal 10 to
1574 PCI device 00:14.0 write the parameter as:
1575 ivrs_ioapic[10]=00:14.0
1577 ivrs_hpet [HW,X86_64]
1578 Provide an override to the HPET-ID<->DEVICE-ID
1579 mapping provided in the IVRS ACPI table. For
1580 example, to map HPET-ID decimal 0 to
1581 PCI device 00:14.0 write the parameter as:
1582 ivrs_hpet[0]=00:14.0
1584 js= [HW,JOY] Analog joystick
1585 See Documentation/input/joystick.txt.
1588 Enable/disable kernel and module base offset ASLR
1589 (Address Space Layout Randomization) if built into
1590 the kernel. When CONFIG_HIBERNATION is selected,
1591 kASLR is disabled by default. When kASLR is enabled,
1592 hibernation will be disabled.
1596 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1597 specifies the amount of memory usable by the kernel
1598 for non-movable allocations. The requested amount is
1599 spread evenly throughout all nodes in the system. The
1600 remaining memory in each node is used for Movable
1601 pages. In the event, a node is too small to have both
1602 kernelcore and Movable pages, kernelcore pages will
1603 take priority and other nodes will have a larger number
1604 of Movable pages. The Movable zone is used for the
1605 allocation of pages that may be reclaimed or moved
1606 by the page migration subsystem. This means that
1607 HugeTLB pages may not be allocated from this zone.
1608 Note that allocations like PTEs-from-HighMem still
1609 use the HighMem zone if it exists, and the Normal
1610 zone if it does not.
1612 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1613 Format: <Controller#>[,poll interval]
1614 The controller # is the number of the ehci usb debug
1615 port as it is probed via PCI. The poll interval is
1616 optional and is the number seconds in between
1617 each poll cycle to the debug port in case you need
1618 the functionality for interrupting the kernel with
1619 gdb or control-c on the dbgp connection. When
1620 not using this parameter you use sysrq-g to break into
1621 the kernel debugger.
1623 kgdboc= [KGDB,HW] kgdb over consoles.
1624 Requires a tty driver that supports console polling,
1625 or a supported polling keyboard driver (non-usb).
1626 Serial only format: <serial_device>[,baud]
1627 keyboard only format: kbd
1628 keyboard and serial format: kbd,<serial_device>[,baud]
1629 Optional Kernel mode setting:
1630 kms, kbd format: kms,kbd
1631 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1633 kgdbwait [KGDB] Stop kernel execution and enter the
1634 kernel debugger at the earliest opportunity.
1636 kmac= [MIPS] korina ethernet MAC address.
1637 Configure the RouterBoard 532 series on-chip
1638 Ethernet adapter MAC address.
1640 kmemleak= [KNL] Boot-time kmemleak enable/disable
1641 Valid arguments: on, off
1643 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1646 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1647 Valid arguments: 0, 1, 2
1648 kmemcheck=0 (disabled)
1649 kmemcheck=1 (enabled)
1650 kmemcheck=2 (one-shot mode)
1651 Default: 2 (one-shot mode)
1653 kstack=N [X86] Print N words from the kernel stack
1656 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1657 Default is 0 (don't ignore, but inject #GP)
1659 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1663 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1664 Default is 1 (enabled)
1666 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1668 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1670 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1671 (virtualized MMU) support on capable Intel chips.
1672 Default is 1 (enabled)
1674 kvm-intel.emulate_invalid_guest_state=
1675 [KVM,Intel] Enable emulation of invalid guest states
1676 Default is 0 (disabled)
1678 kvm-intel.flexpriority=
1679 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1680 Default is 1 (enabled)
1683 [KVM,Intel] Enable VMX nesting (nVMX).
1684 Default is 0 (disabled)
1686 kvm-intel.unrestricted_guest=
1687 [KVM,Intel] Disable unrestricted guest feature
1688 (virtualized real and unpaged mode) on capable
1689 Intel chips. Default is 1 (enabled)
1691 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1692 feature (tagged TLBs) on capable Intel chips.
1693 Default is 1 (enabled)
1699 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1702 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1703 value for LAPIC timer one-shot implementation. Default
1704 back to the programmable timer unit in the LAPIC.
1706 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1709 libata.dma= [LIBATA] DMA control
1710 libata.dma=0 Disable all PATA and SATA DMA
1711 libata.dma=1 PATA and SATA Disk DMA only
1712 libata.dma=2 ATAPI (CDROM) DMA only
1713 libata.dma=4 Compact Flash DMA only
1714 Combinations also work, so libata.dma=3 enables DMA
1715 for disks and CDROMs, but not CFs.
1717 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1718 libata.ignore_hpa=0 keep BIOS limits (default)
1719 libata.ignore_hpa=1 ignore limits, using full disk
1721 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1725 libata.force= [LIBATA] Force configurations. The format is comma
1726 separated list of "[ID:]VAL" where ID is
1727 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1728 matching port, link or device. Basically, it matches
1729 the ATA ID string printed on console by libata. If
1730 the whole ID part is omitted, the last PORT and DEVICE
1731 values are used. If ID hasn't been specified yet, the
1732 configuration applies to all ports, links and devices.
1734 If only DEVICE is omitted, the parameter applies to
1735 the port and all links and devices behind it. DEVICE
1736 number of 0 either selects the first device or the
1737 first fan-out link behind PMP device. It does not
1738 select the host link. DEVICE number of 15 selects the
1739 host link and device attached to it.
1741 The VAL specifies the configuration to force. As long
1742 as there's no ambiguity shortcut notation is allowed.
1743 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1744 The following configurations can be forced.
1746 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1747 Any ID with matching PORT is used.
1749 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1751 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1752 udma[/][16,25,33,44,66,100,133] notation is also
1755 * [no]ncq: Turn on or off NCQ.
1757 * nohrst, nosrst, norst: suppress hard, soft
1760 * rstonce: only attempt one reset during
1761 hot-unplug link recovery
1763 * dump_id: dump IDENTIFY data.
1765 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1767 * disable: Disable this device.
1769 If there are multiple matching configurations changing
1770 the same attribute, the last one is used.
1772 memblock=debug [KNL] Enable memblock debug messages.
1774 load_ramdisk= [RAM] List of ramdisks to load from floppy
1775 See Documentation/blockdev/ramdisk.txt.
1777 lockd.nlm_grace_period=P [NFS] Assign grace period.
1780 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1783 lockd.nlm_timeout=T [NFS] Assign timeout value.
1786 lockd.nlm_udpport=M [NFS] Assign UDP port.
1789 locktorture.nreaders_stress= [KNL]
1790 Set the number of locking read-acquisition kthreads.
1791 Defaults to being automatically set based on the
1792 number of online CPUs.
1794 locktorture.nwriters_stress= [KNL]
1795 Set the number of locking write-acquisition kthreads.
1797 locktorture.onoff_holdoff= [KNL]
1798 Set time (s) after boot for CPU-hotplug testing.
1800 locktorture.onoff_interval= [KNL]
1801 Set time (s) between CPU-hotplug operations, or
1802 zero to disable CPU-hotplug testing.
1804 locktorture.shuffle_interval= [KNL]
1805 Set task-shuffle interval (jiffies). Shuffling
1806 tasks allows some CPUs to go into dyntick-idle
1807 mode during the locktorture test.
1809 locktorture.shutdown_secs= [KNL]
1810 Set time (s) after boot system shutdown. This
1811 is useful for hands-off automated testing.
1813 locktorture.stat_interval= [KNL]
1814 Time (s) between statistics printk()s.
1816 locktorture.stutter= [KNL]
1817 Time (s) to stutter testing, for example,
1818 specifying five seconds causes the test to run for
1819 five seconds, wait for five seconds, and so on.
1820 This tests the locking primitive's ability to
1821 transition abruptly to and from idle.
1823 locktorture.torture_runnable= [BOOT]
1824 Start locktorture running at boot time.
1826 locktorture.torture_type= [KNL]
1827 Specify the locking implementation to test.
1829 locktorture.verbose= [KNL]
1830 Enable additional printk() statements.
1832 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1835 loglevel= All Kernel Messages with a loglevel smaller than the
1836 console loglevel will be printed to the console. It can
1837 also be changed with klogd or other programs. The
1838 loglevels are defined as follows:
1840 0 (KERN_EMERG) system is unusable
1841 1 (KERN_ALERT) action must be taken immediately
1842 2 (KERN_CRIT) critical conditions
1843 3 (KERN_ERR) error conditions
1844 4 (KERN_WARNING) warning conditions
1845 5 (KERN_NOTICE) normal but significant condition
1846 6 (KERN_INFO) informational
1847 7 (KERN_DEBUG) debug-level messages
1849 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1850 in bytes. n must be a power of two and greater
1851 than the minimal size. The minimal size is defined
1852 by LOG_BUF_SHIFT kernel config parameter. There is
1853 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1854 that allows to increase the default size depending on
1855 the number of CPUs. See init/Kconfig for more details.
1857 logo.nologo [FB] Disables display of the built-in Linux logo.
1858 This may be used to provide more screen space for
1859 kernel log messages and is useful when debugging
1860 kernel boot problems.
1862 lp=0 [LP] Specify parallel ports to use, e.g,
1863 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1864 lp=reset first parallel port). 'lp=0' disables the
1865 lp=auto printer driver. 'lp=reset' (which can be
1866 specified in addition to the ports) causes
1867 attached printers to be reset. Using
1868 lp=port1,port2,... specifies the parallel ports
1869 to associate lp devices with, starting with
1870 lp0. A port specification may be 'none' to skip
1871 that lp device, or a parport name such as
1872 'parport0'. Specifying 'lp=auto' instead of a
1873 port specification list means that device IDs
1874 from each port should be examined, to see if
1875 an IEEE 1284-compliant printer is attached; if
1876 so, the driver will manage that printer.
1877 See also header of drivers/char/lp.c.
1880 Sets loops_per_jiffy to given constant, thus avoiding
1881 time-consuming boot-time autodetection (up to 250 ms per
1882 CPU). 0 enables autodetection (default). To determine
1883 the correct value for your kernel, boot with normal
1884 autodetection and see what value is printed. Note that
1885 on SMP systems the preset will be applied to all CPUs,
1886 which is likely to cause problems if your CPUs need
1887 significantly divergent settings. An incorrect value
1888 will cause delays in the kernel to be wrong, leading to
1889 unpredictable I/O errors and other breakage. Although
1890 unlikely, in the extreme case this might damage your
1894 Format: <io>,<irq>,<dma>
1896 machvec= [IA-64] Force the use of a particular machine-vector
1897 (machvec) in a generic kernel.
1898 Example: machvec=hpzx1_swiotlb
1900 machtype= [Loongson] Share the same kernel image file between different
1902 Example: machtype=lemote-yeeloong-2f-7inch
1904 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1905 than or equal to this physical address is ignored.
1907 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1908 should make use of. maxcpus=n : n >= 0 limits the
1909 kernel to using 'n' processors. n=0 is a special case,
1910 it is equivalent to "nosmp", which also disables
1913 max_loop= [LOOP] The number of loop block devices that get
1914 (loop.max_loop) unconditionally pre-created at init time. The default
1915 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1916 of statically allocating a predefined number, loop
1917 devices can be requested on-demand with the
1918 /dev/loop-control interface.
1920 mce [X86-32] Machine Check Exception
1922 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1924 md= [HW] RAID subsystems devices and level
1925 See Documentation/md.txt.
1928 Format: <first>,<last>
1929 Specifies range of consoles to be captured by the MDA.
1931 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1932 Amount of memory to be used when the kernel is not able
1933 to see the whole system memory or for test.
1934 [X86] Work as limiting max address. Use together
1935 with memmap= to avoid physical address space collisions.
1936 Without memmap= PCI devices could be placed at addresses
1937 belonging to unused RAM.
1939 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1943 [KNL,SH] Allow user to override the default size for
1944 per-device physically contiguous DMA buffers.
1946 memmap=exactmap [KNL,X86] Enable setting of an exact
1947 E820 memory map, as specified by the user.
1948 Such memmap=exactmap lines can be constructed based on
1949 BIOS output or other requirements. See the memmap=nn@ss
1952 memmap=nn[KMG]@ss[KMG]
1953 [KNL] Force usage of a specific region of memory.
1954 Region of memory to be used is from ss to ss+nn.
1956 memmap=nn[KMG]#ss[KMG]
1957 [KNL,ACPI] Mark specific memory as ACPI data.
1958 Region of memory to be marked is from ss to ss+nn.
1960 memmap=nn[KMG]$ss[KMG]
1961 [KNL,ACPI] Mark specific memory as reserved.
1962 Region of memory to be reserved is from ss to ss+nn.
1963 Example: Exclude memory from 0x18690000-0x1869ffff
1964 memmap=64K$0x18690000
1966 memmap=0x10000$0x18690000
1968 memory_corruption_check=0/1 [X86]
1969 Some BIOSes seem to corrupt the first 64k of
1970 memory when doing things like suspend/resume.
1971 Setting this option will scan the memory
1972 looking for corruption. Enabling this will
1973 both detect corruption and prevent the kernel
1974 from using the memory being corrupted.
1975 However, its intended as a diagnostic tool; if
1976 repeatable BIOS-originated corruption always
1977 affects the same memory, you can use memmap=
1978 to prevent the kernel from using that memory.
1980 memory_corruption_check_size=size [X86]
1981 By default it checks for corruption in the low
1982 64k, making this memory unavailable for normal
1983 use. Use this parameter to scan for
1984 corruption in more or less memory.
1986 memory_corruption_check_period=seconds [X86]
1987 By default it checks for corruption every 60
1988 seconds. Use this parameter to check at some
1989 other rate. 0 disables periodic checking.
1991 memtest= [KNL,X86] Enable memtest
1993 default : 0 <disable>
1994 Specifies the number of memtest passes to be
1995 performed. Each pass selects another test
1996 pattern from a given set of patterns. Memtest
1997 fills the memory with this pattern, validates
1998 memory contents and reserves bad memory
1999 regions that are detected.
2001 meye.*= [HW] Set MotionEye Camera parameters
2002 See Documentation/video4linux/meye.txt.
2004 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2005 Multi-Function General Purpose Timers on AMD Geode
2008 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2009 the BIOS has incorrectly applied a workaround. TinyBIOS
2010 version 0.98 is known to be affected, 0.99 fixes the
2011 problem by letting the user disable the workaround.
2015 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2016 physical address is ignored.
2018 mini2440= [ARM,HW,KNL]
2019 Format:[0..2][b][c][t]
2021 MINI2440 configuration specification:
2022 0 - The attached screen is the 3.5" TFT
2023 1 - The attached screen is the 7" TFT
2024 2 - The VGA Shield is attached (1024x768)
2025 Leaving out the screen size parameter will not load
2026 the TFT driver, and the framebuffer will be left
2028 b - Enable backlight. The TFT backlight pin will be
2029 linked to the kernel VESA blanking code and a GPIO
2030 LED. This parameter is not necessary when using the
2032 c - Enable the s3c camera interface.
2033 t - Reserved for enabling touchscreen support. The
2034 touchscreen support is not enabled in the mainstream
2035 kernel as of 2.6.30, a preliminary port can be found
2036 in the "bleeding edge" mini2440 support kernel at
2037 http://repo.or.cz/w/linux-2.6/mini2440.git
2040 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2041 parameter allows control of the logging verbosity for
2042 the additional memory initialisation checks. A value
2043 of 0 disables mminit logging and a level of 4 will
2044 log everything. Information is printed at KERN_DEBUG
2045 so loglevel=8 may also need to be specified.
2048 [KNL] When CONFIG_MODULE_SIG is set, this means that
2049 modules without (valid) signatures will fail to load.
2050 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2051 is always true, so this option does nothing.
2054 [MOUSE] Maximum time between finger touching and
2055 leaving touchpad surface for touch to be considered
2056 a tap and be reported as a left button click (for
2057 touchpads working in absolute mode only).
2059 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2060 reporting absolute coordinates, such as tablets
2061 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2062 reporting absolute coordinates, such as tablets
2064 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2065 is similar to kernelcore except it specifies the
2066 amount of memory used for migratable allocations.
2067 If both kernelcore and movablecore is specified,
2068 then kernelcore will be at *least* the specified
2069 value but may be more. If movablecore on its own
2070 is specified, the administrator must be careful
2071 that the amount of memory usable for all allocations
2074 movable_node [KNL,X86] Boot-time switch to enable the effects
2075 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2077 MTD_Partition= [MTD]
2078 Format: <name>,<region-number>,<size>,<offset>
2080 MTD_Region= [MTD] Format:
2081 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2084 See drivers/mtd/cmdlinepart.c.
2086 multitce=off [PPC] This parameter disables the use of the pSeries
2087 firmware feature for updating multiple TCE entries
2090 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2092 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2094 boundary - index of last SLC block on Flex-OneNAND.
2095 The remaining blocks are configured as MLC blocks.
2096 lock - Configure if Flex-OneNAND boundary should be locked.
2097 Once locked, the boundary cannot be changed.
2098 1 indicates lock status, 0 indicates unlock status.
2101 ARM/S3C2412 JIVE boot control
2103 See arch/arm/mach-s3c2412/mach-jive.c
2105 mtouchusb.raw_coordinates=
2106 [HW] Make the MicroTouch USB driver use raw coordinates
2107 ('y', default) or cooked coordinates ('n')
2109 mtrr_chunk_size=nn[KMG] [X86]
2110 used for mtrr cleanup. It is largest continuous chunk
2111 that could hold holes aka. UC entries.
2113 mtrr_gran_size=nn[KMG] [X86]
2114 Used for mtrr cleanup. It is granularity of mtrr block.
2116 Large value could prevent small alignment from
2119 mtrr_spare_reg_nr=n [X86]
2121 Range: 0,7 : spare reg number
2123 Used for mtrr cleanup. It is spare mtrr entries number.
2124 Set to 2 or more if your graphical card needs more.
2126 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2128 netdev= [NET] Network devices parameters
2129 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2130 Note that mem_start is often overloaded to mean
2131 something different and driver-specific.
2132 This usage is only documented in each driver source
2136 [NETFILTER] Enable connection tracking flow accounting
2137 0 to disable accounting
2138 1 to enable accounting
2141 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2142 See Documentation/filesystems/nfs/nfsroot.txt.
2144 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2145 See Documentation/filesystems/nfs/nfsroot.txt.
2147 nfsrootdebug [NFS] enable nfsroot debugging messages.
2148 See Documentation/filesystems/nfs/nfsroot.txt.
2150 nfs.callback_tcpport=
2151 [NFS] set the TCP port on which the NFSv4 callback
2152 channel should listen.
2155 [NFS] sets the pathname to the program which is used
2156 to update the NFS client cache entries.
2158 nfs.cache_getent_timeout=
2159 [NFS] sets the timeout after which an attempt to
2160 update a cache entry is deemed to have failed.
2162 nfs.idmap_cache_timeout=
2163 [NFS] set the maximum lifetime for idmapper cache
2167 [NFS] enable 64-bit inode numbers.
2168 If zero, the NFS client will fake up a 32-bit inode
2169 number for the readdir() and stat() syscalls instead
2170 of returning the full 64-bit number.
2171 The default is to return 64-bit inode numbers.
2173 nfs.max_session_slots=
2174 [NFSv4.1] Sets the maximum number of session slots
2175 the client will attempt to negotiate with the server.
2176 This limits the number of simultaneous RPC requests
2177 that the client can send to the NFSv4.1 server.
2178 Note that there is little point in setting this
2179 value higher than the max_tcp_slot_table_limit.
2181 nfs.nfs4_disable_idmapping=
2182 [NFSv4] When set to the default of '1', this option
2183 ensures that both the RPC level authentication
2184 scheme and the NFS level operations agree to use
2185 numeric uids/gids if the mount is using the
2186 'sec=sys' security flavour. In effect it is
2187 disabling idmapping, which can make migration from
2188 legacy NFSv2/v3 systems to NFSv4 easier.
2189 Servers that do not support this mode of operation
2190 will be autodetected by the client, and it will fall
2191 back to using the idmapper.
2192 To turn off this behaviour, set the value to '0'.
2194 [NFS4] Specify an additional fixed unique ident-
2195 ification string that NFSv4 clients can insert into
2196 their nfs_client_id4 string. This is typically a
2197 UUID that is generated at system install time.
2199 nfs.send_implementation_id =
2200 [NFSv4.1] Send client implementation identification
2201 information in exchange_id requests.
2202 If zero, no implementation identification information
2204 The default is to send the implementation identification
2207 nfs.recover_lost_locks =
2208 [NFSv4] Attempt to recover locks that were lost due
2209 to a lease timeout on the server. Please note that
2210 doing this risks data corruption, since there are
2211 no guarantees that the file will remain unchanged
2212 after the locks are lost.
2213 If you want to enable the kernel legacy behaviour of
2214 attempting to recover these locks, then set this
2216 The default parameter value of '0' causes the kernel
2217 not to attempt recovery of lost locks.
2219 nfsd.nfs4_disable_idmapping=
2220 [NFSv4] When set to the default of '1', the NFSv4
2221 server will return only numeric uids and gids to
2222 clients using auth_sys, and will accept numeric uids
2223 and gids from such clients. This is intended to ease
2224 migration from NFSv2/v3.
2226 objlayoutdriver.osd_login_prog=
2227 [NFS] [OBJLAYOUT] sets the pathname to the program which
2228 is used to automatically discover and login into new
2229 osd-targets. Please see:
2230 Documentation/filesystems/pnfs.txt for more explanations
2232 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2233 when a NMI is triggered.
2234 Format: [state][,regs][,debounce][,die]
2236 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2237 Format: [panic,][nopanic,][num]
2239 0 - turn nmi_watchdog off
2240 When panic is specified, panic when an NMI watchdog
2241 timeout occurs (or 'nopanic' to override the opposite
2243 This is useful when you use a panic=... timeout and
2244 need the box quickly up again.
2246 netpoll.carrier_timeout=
2247 [NET] Specifies amount of time (in seconds) that
2248 netpoll should wait for a carrier. By default netpoll
2251 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2252 emulation library even if a 387 maths coprocessor
2256 [HW] Never suspend the console
2257 Disable suspending of consoles during suspend and
2258 hibernate operations. Once disabled, debugging
2259 messages can reach various consoles while the rest
2260 of the system is being put to sleep (ie, while
2261 debugging driver suspend/resume hooks). This may
2262 not work reliably with all consoles, but is known
2263 to work with serial and VGA consoles.
2264 To facilitate more flexible debugging, we also add
2265 console_suspend, a printk module parameter to control
2266 it. Users could use console_suspend (usually
2267 /sys/module/printk/parameters/console_suspend) to
2268 turn on/off it dynamically.
2270 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2271 caches in the slab allocator. Saves per-node memory,
2272 but will impact performance.
2276 noapic [SMP,APIC] Tells the kernel to not make use of any
2277 IOAPICs that may be present in the system.
2279 noautogroup Disable scheduler automatic task group creation.
2281 nobats [PPC] Do not use BATs for mapping kernel lowmem
2282 on "Classic" PPC cores.
2286 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2288 nodelayacct [KNL] Disable per-task delay accounting
2290 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2292 nodsp [SH] Disable hardware DSP at boot time.
2294 noefi Disable EFI runtime services support.
2299 On X86-32 available only on PAE configured kernels.
2300 noexec=on: enable non-executable mappings (default)
2301 noexec=off: disable non-executable mappings
2304 Disable SMAP (Supervisor Mode Access Prevention)
2305 even if it is supported by processor.
2308 Disable SMEP (Supervisor Mode Execution Prevention)
2309 even if it is supported by processor.
2312 This affects only 32-bit executables.
2313 noexec32=on: enable non-executable mappings (default)
2314 read doesn't imply executable mappings
2315 noexec32=off: disable non-executable mappings
2316 read implies executable mappings
2318 nofpu [SH] Disable hardware FPU at boot time.
2320 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2321 register save and restore. The kernel will only save
2322 legacy floating-point registers on task switch.
2324 noxsave [BUGS=X86] Disables x86 extended register state save
2325 and restore using xsave. The kernel will fallback to
2326 enabling legacy floating-point and sse state.
2328 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2329 register states. The kernel will fall back to use
2330 xsave to save the states. By using this parameter,
2331 performance of saving the states is degraded because
2332 xsave doesn't support modified optimization while
2333 xsaveopt supports it on xsaveopt enabled systems.
2335 noxsaves [X86] Disables xsaves and xrstors used in saving and
2336 restoring x86 extended register state in compacted
2337 form of xsave area. The kernel will fall back to use
2338 xsaveopt and xrstor to save and restore the states
2339 in standard form of xsave area. By using this
2340 parameter, xsave area per process might occupy more
2341 memory on xsaves enabled systems.
2344 on enable eager fpu restore
2345 off disable eager fpu restore
2346 auto selects the default scheme, which automatically
2347 enables eagerfpu restore for xsaveopt.
2349 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2350 wfi(ARM) instruction doesn't work correctly and not to
2351 use it. This is also useful when using JTAG debugger.
2353 no_file_caps Tells the kernel not to honor file capabilities. The
2354 only way then for a file to be executed with privilege
2355 is to be setuid root or executed by root.
2357 nohalt [IA-64] Tells the kernel not to use the power saving
2358 function PAL_HALT_LIGHT when idle. This increases
2359 power-consumption. On the positive side, it reduces
2360 interrupt wake-up latency, which may improve performance
2361 in certain environments such as networked servers or
2364 nohibernate [HIBERNATION] Disable hibernation and resume.
2366 nohz= [KNL] Boottime enable/disable dynamic ticks
2367 Valid arguments: on, off
2370 nohz_full= [KNL,BOOT]
2371 In kernels built with CONFIG_NO_HZ_FULL=y, set
2372 the specified list of CPUs whose tick will be stopped
2373 whenever possible. The boot CPU will be forced outside
2374 the range to maintain the timekeeping.
2375 The CPUs in this range must also be included in the
2378 noiotrap [SH] Disables trapped I/O port accesses.
2380 noirqdebug [X86-32] Disables the code which attempts to detect and
2381 disable unhandled interrupt sources.
2383 no_timer_check [X86,APIC] Disables the code which tests for
2384 broken timer IRQ sources.
2386 noisapnp [ISAPNP] Disables ISA PnP code.
2388 noinitrd [RAM] Tells the kernel not to load any configured
2391 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2393 [Deprecated - use intremap=off]
2397 nojitter [IA-64] Disables jitter checking for ITC timers.
2399 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2401 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2404 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2405 steal time is computed, but won't influence scheduler
2408 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2410 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2412 noltlbs [PPC] Do not use large page/tlb entries for kernel
2413 lowmem mapping on PPC40x.
2415 nomca [IA-64] Disable machine check abort handling
2417 nomce [X86-32] Machine Check Exception
2419 nomfgpt [X86-32] Disable Multi-Function General Purpose
2420 Timer usage (for AMD Geode machines).
2422 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2423 shutdown the other cpus. Instead use the REBOOT_VECTOR
2426 nomodule Disable module load
2428 nopat [X86] Disable PAT (page attribute table extension of
2429 pagetables) support.
2431 norandmaps Don't use address space randomization. Equivalent to
2432 echo 0 > /proc/sys/kernel/randomize_va_space
2434 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2436 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2437 with UP alternatives
2439 nordrand [X86] Disable kernel use of the RDRAND and
2440 RDSEED instructions even if they are supported
2441 by the processor. RDRAND and RDSEED are still
2442 available to user space applications.
2444 noresume [SWSUSP] Disables resume and restores original swap
2447 no-scroll [VGA] Disables scrollback.
2448 This is required for the Braillex ib80-piezo Braille
2449 reader made by F.H. Papenmeier (Germany).
2453 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2455 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2456 and disable the IO APIC. legacy for "maxcpus=0".
2458 nosoftlockup [KNL] Disable the soft-lockup detector.
2460 nosync [HW,M68K] Disables sync negotiation for all devices.
2462 notsc [BUGS=X86-32] Disable Time Stamp Counter
2464 nousb [USB] Disable the USB subsystem
2466 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2470 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2472 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2473 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2474 Some features depend on CPU0. Known dependencies are:
2475 1. Resume from suspend/hibernate depends on CPU0.
2476 Suspend/hibernate will fail if CPU0 is offline and you
2477 need to online CPU0 before suspend/hibernate.
2478 2. PIC interrupts also depend on CPU0. CPU0 can't be
2479 removed if a PIC interrupt is detected.
2480 It's said poweroff/reboot may depend on CPU0 on some
2481 machines although I haven't seen such issues so far
2482 after CPU0 is offline on a few tested machines.
2483 If the dependencies are under your control, you can
2484 turn on cpu0_hotplug.
2486 nptcg= [IA-64] Override max number of concurrent global TLB
2487 purges which is reported from either PAL_VM_SUMMARY or
2490 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2491 could support. nr_cpus=n : n >= 1 limits the kernel to
2492 supporting 'n' processors. Later in runtime you can not
2493 use hotplug cpu feature to put more cpu back to online.
2494 just like you compile the kernel NR_CPUS=n
2496 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2498 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2499 Allowed values are enable and disable
2501 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2502 one of ['zone', 'node', 'default'] can be specified
2503 This can be set from sysctl after boot.
2504 See Documentation/sysctl/vm.txt for details.
2506 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2507 See Documentation/debugging-via-ohci1394.txt for more
2510 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2511 Rather than timing out after 20 ms if an EC
2512 command is not properly ACKed, override the length
2513 of the timeout. We have interrupts disabled while
2514 waiting for the ACK, so if this is set too high
2515 interrupts *may* be lost!
2517 omap_mux= [OMAP] Override bootloader pin multiplexing.
2518 Format: <mux_mode0.mode_name=value>...
2519 For example, to override I2C bus2:
2520 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2522 oprofile.timer= [HW]
2523 Use timer interrupt instead of performance counters
2525 oprofile.cpu_type= Force an oprofile cpu type
2526 This might be useful if you have an older oprofile
2527 userland or if you want common events.
2528 Format: { arch_perfmon }
2529 arch_perfmon: [X86] Force use of architectural
2530 perfmon on Intel CPUs instead of the
2531 CPU specific event set.
2532 timer: [X86] Force use of architectural NMI
2533 timer mode (see also oprofile.timer
2534 for generic hr timer mode)
2535 [s390] Force legacy basic mode sampling
2536 (report cpu_type "timer")
2538 oops=panic Always panic on oopses. Default is to just kill the
2539 process, but there is a small probability of
2540 deadlocking the machine.
2541 This will also cause panics on machine check exceptions.
2542 Useful together with panic=30 to trigger a reboot.
2545 See Documentation/sound/oss/oss-parameters.txt
2547 page_owner= [KNL] Boot-time page_owner enabling option.
2548 Storage of the information about who allocated
2549 each page is disabled in default. With this switch,
2551 on: enable the feature
2553 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2554 timeout > 0: seconds before rebooting
2555 timeout = 0: wait forever
2556 timeout < 0: reboot immediately
2559 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2562 crash_kexec_post_notifiers
2563 Run kdump after running panic-notifiers and dumping
2564 kmsg. This only for the users who doubt kdump always
2565 succeeds in any situation.
2566 Note that this also increases risks of kdump failure,
2567 because some panic notifiers can make the crashed
2568 kernel more unstable.
2570 parkbd.port= [HW] Parallel port number the keyboard adapter is
2571 connected to, default is 0.
2573 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2574 0 for XT, 1 for AT (default is AT).
2577 parport= [HW,PPT] Specify parallel ports. 0 disables.
2578 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2579 Use 'auto' to force the driver to use any
2580 IRQ/DMA settings detected (the default is to
2581 ignore detected IRQ/DMA settings because of
2582 possible conflicts). You can specify the base
2583 address, IRQ, and DMA settings; IRQ and DMA
2584 should be numbers, or 'auto' (for using detected
2585 settings on that particular port), or 'nofifo'
2586 (to avoid using a FIFO even if it is detected).
2587 Parallel ports are assigned in the order they
2588 are specified on the command line, starting
2591 parport_init_mode= [HW,PPT]
2592 Configure VIA parallel port to operate in
2593 a specific mode. This is necessary on Pegasos
2594 computer where firmware has no options for setting
2595 up parallel port mode and sets it to spp.
2596 Currently this function knows 686a and 8231 chips.
2597 Format: [spp|ps2|epp|ecp|ecpepp]
2600 Halt all CPUs after the first oops has been printed for
2601 the specified number of seconds. This is to be used if
2602 your oopses keep scrolling off the screen.
2607 See header of drivers/block/paride/pcd.c.
2608 See also Documentation/blockdev/paride.txt.
2610 pci=option[,option...] [PCI] various PCI subsystem options:
2611 earlydump [X86] dump PCI config space before the kernel
2613 off [X86] don't probe for the PCI bus
2614 bios [X86-32] force use of PCI BIOS, don't access
2615 the hardware directly. Use this if your machine
2616 has a non-standard PCI host bridge.
2617 nobios [X86-32] disallow use of PCI BIOS, only direct
2618 hardware access methods are allowed. Use this
2619 if you experience crashes upon bootup and you
2620 suspect they are caused by the BIOS.
2621 conf1 [X86] Force use of PCI Configuration
2623 conf2 [X86] Force use of PCI Configuration
2625 noaer [PCIE] If the PCIEAER kernel config parameter is
2626 enabled, this kernel boot option can be used to
2627 disable the use of PCIE advanced error reporting.
2628 nodomains [PCI] Disable support for multiple PCI
2629 root domains (aka PCI segments, in ACPI-speak).
2630 nommconf [X86] Disable use of MMCONFIG for PCI
2632 check_enable_amd_mmconf [X86] check for and enable
2633 properly configured MMIO access to PCI
2634 config space on AMD family 10h CPU
2635 nomsi [MSI] If the PCI_MSI kernel config parameter is
2636 enabled, this kernel boot option can be used to
2637 disable the use of MSI interrupts system-wide.
2638 noioapicquirk [APIC] Disable all boot interrupt quirks.
2639 Safety option to keep boot IRQs enabled. This
2640 should never be necessary.
2641 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2642 primary IO-APIC for bridges that cannot disable
2643 boot IRQs. This fixes a source of spurious IRQs
2644 when the system masks IRQs.
2645 noioapicreroute [APIC] Disable workaround that uses the
2646 boot IRQ equivalent of an IRQ that connects to
2647 a chipset where boot IRQs cannot be disabled.
2648 The opposite of ioapicreroute.
2649 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2650 routing table. These calls are known to be buggy
2651 on several machines and they hang the machine
2652 when used, but on other computers it's the only
2653 way to get the interrupt routing table. Try
2654 this option if the kernel is unable to allocate
2655 IRQs or discover secondary PCI buses on your
2657 rom [X86] Assign address space to expansion ROMs.
2658 Use with caution as certain devices share
2659 address decoders between ROMs and other
2661 norom [X86] Do not assign address space to
2662 expansion ROMs that do not already have
2663 BIOS assigned address ranges.
2664 nobar [X86] Do not assign address space to the
2665 BARs that weren't assigned by the BIOS.
2666 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2667 assigned automatically to PCI devices. You can
2668 make the kernel exclude IRQs of your ISA cards
2670 pirqaddr=0xAAAAA [X86] Specify the physical address
2671 of the PIRQ table (normally generated
2672 by the BIOS) if it is outside the
2673 F0000h-100000h range.
2674 lastbus=N [X86] Scan all buses thru bus #N. Can be
2675 useful if the kernel is unable to find your
2676 secondary buses and you want to tell it
2677 explicitly which ones they are.
2678 assign-busses [X86] Always assign all PCI bus
2679 numbers ourselves, overriding
2680 whatever the firmware may have done.
2681 usepirqmask [X86] Honor the possible IRQ mask stored
2682 in the BIOS $PIR table. This is needed on
2683 some systems with broken BIOSes, notably
2684 some HP Pavilion N5400 and Omnibook XE3
2685 notebooks. This will have no effect if ACPI
2686 IRQ routing is enabled.
2687 noacpi [X86] Do not use ACPI for IRQ routing
2688 or for PCI scanning.
2689 use_crs [X86] Use PCI host bridge window information
2690 from ACPI. On BIOSes from 2008 or later, this
2691 is enabled by default. If you need to use this,
2692 please report a bug.
2693 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2694 If you need to use this, please report a bug.
2695 routeirq Do IRQ routing for all PCI devices.
2696 This is normally done in pci_enable_device(),
2697 so this option is a temporary workaround
2698 for broken drivers that don't call it.
2699 skip_isa_align [X86] do not align io start addr, so can
2700 handle more pci cards
2701 firmware [ARM] Do not re-enumerate the bus but instead
2702 just use the configuration from the
2703 bootloader. This is currently used on
2704 IXP2000 systems where the bus has to be
2705 configured a certain way for adjunct CPUs.
2706 noearly [X86] Don't do any early type 1 scanning.
2707 This might help on some broken boards which
2708 machine check when some devices' config space
2709 is read. But various workarounds are disabled
2710 and some IOMMU drivers will not work.
2711 bfsort Sort PCI devices into breadth-first order.
2712 This sorting is done to get a device
2713 order compatible with older (<= 2.4) kernels.
2714 nobfsort Don't sort PCI devices into breadth-first order.
2715 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2716 tuning and use the BIOS-configured MPS defaults.
2717 pcie_bus_safe Set every device's MPS to the largest value
2718 supported by all devices below the root complex.
2719 pcie_bus_perf Set device MPS to the largest allowable MPS
2720 based on its parent bus. Also set MRRS (Max
2721 Read Request Size) to the largest supported
2722 value (no larger than the MPS that the device
2723 or bus can support) for best performance.
2724 pcie_bus_peer2peer Set every device's MPS to 128B, which
2725 every device is guaranteed to support. This
2726 configuration allows peer-to-peer DMA between
2727 any pair of devices, possibly at the cost of
2728 reduced performance. This also guarantees
2729 that hot-added devices will work.
2730 cbiosize=nn[KMG] The fixed amount of bus space which is
2731 reserved for the CardBus bridge's IO window.
2732 The default value is 256 bytes.
2733 cbmemsize=nn[KMG] The fixed amount of bus space which is
2734 reserved for the CardBus bridge's memory
2735 window. The default value is 64 megabytes.
2738 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2739 Specifies alignment and device to reassign
2740 aligned memory resources.
2741 If <order of align> is not specified,
2742 PAGE_SIZE is used as alignment.
2743 PCI-PCI bridge can be specified, if resource
2744 windows need to be expanded.
2745 ecrc= Enable/disable PCIe ECRC (transaction layer
2746 end-to-end CRC checking).
2747 bios: Use BIOS/firmware settings. This is the
2751 hpiosize=nn[KMG] The fixed amount of bus space which is
2752 reserved for hotplug bridge's IO window.
2753 Default size is 256 bytes.
2754 hpmemsize=nn[KMG] The fixed amount of bus space which is
2755 reserved for hotplug bridge's memory window.
2756 Default size is 2 megabytes.
2757 realloc= Enable/disable reallocating PCI bridge resources
2758 if allocations done by BIOS are too small to
2759 accommodate resources required by all child
2761 off: Turn realloc off
2763 realloc same as realloc=on
2764 noari do not use PCIe ARI.
2765 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2766 only look for one device below a PCIe downstream
2769 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2772 force Enable ASPM even on devices that claim not to support it.
2773 WARNING: Forcing ASPM on may cause system lockups.
2775 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2776 nomsi Do not use MSI for PCI Express Native Hotplug (this
2777 makes all PCIe ports use INTx for hotplug services).
2779 pcie_ports= [PCIE] PCIe ports handling:
2780 auto Ask the BIOS whether or not to use native PCIe services
2781 associated with PCIe ports (PME, hot-plug, AER). Use
2782 them only if that is allowed by the BIOS.
2783 native Use native PCIe services associated with PCIe ports
2785 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2788 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2789 nomsi Do not use MSI for native PCIe PME signaling (this makes
2790 all PCIe root ports use INTx for all services).
2792 pcmv= [HW,PCMCIA] BadgePAD 4
2796 Keep all power-domains already enabled by bootloader on,
2797 even if no driver has claimed them. This is useful
2798 for debug and development, but should not be
2799 needed on a platform with proper driver support.
2802 See Documentation/blockdev/paride.txt.
2804 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2807 See arch/parisc/kernel/pdc_chassis.c
2809 percpu_alloc= Select which percpu first chunk allocator to use.
2810 Currently supported values are "embed" and "page".
2811 Archs may support subset or none of the selections.
2812 See comments in mm/percpu.c for details on each
2813 allocator. This parameter is primarily for debugging
2814 and performance comparison.
2817 See Documentation/blockdev/paride.txt.
2820 See Documentation/blockdev/paride.txt.
2822 pirq= [SMP,APIC] Manual mp-table setup
2823 See Documentation/x86/i386/IO-APIC.txt.
2825 plip= [PPT,NET] Parallel port network link
2826 Format: { parport<nr> | timid | 0 }
2827 See also Documentation/parport.txt.
2829 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2830 Override pmtimer IOPort with a hex value.
2834 Enable PNP debug messages (depends on the
2835 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2836 via /sys/module/pnp/parameters/debug. We always show
2837 current resource usage; turning this on also shows
2838 possible settings and some assignment information.
2844 { on | off | curr | res | no-curr | no-res }
2847 [ISAPNP] Exclude IRQs for the autoconfiguration
2850 [ISAPNP] Exclude DMAs for the autoconfiguration
2852 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2853 Ranges are in pairs (I/O port base and size).
2856 [ISAPNP] Exclude memory regions for the
2858 Ranges are in pairs (memory base and size).
2860 ports= [IP_VS_FTP] IPVS ftp helper module
2862 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2864 Format: <port>,<port>....
2866 print-fatal-signals=
2867 [KNL] debug: print fatal signals
2869 If enabled, warn about various signal handling
2870 related application anomalies: too many signals,
2871 too many POSIX.1 timers, fatal signals causing a
2874 If you hit the warning due to signal overflow,
2875 you might want to try "ulimit -i unlimited".
2879 printk.always_kmsg_dump=
2880 Trigger kmsg_dump for cases other than kernel oops or
2882 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2885 printk.time= Show timing data prefixed to each printk message line
2886 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2888 processor.max_cstate= [HW,ACPI]
2889 Limit processor to maximum C-state
2890 max_cstate=9 overrides any DMI blacklist limit.
2892 processor.nocst [HW,ACPI]
2893 Ignore the _CST method to determine C-states,
2894 instead using the legacy FADT method
2896 profile= [KNL] Enable kernel profiling via /proc/profile
2897 Format: [schedule,]<number>
2898 Param: "schedule" - profile schedule points.
2899 Param: <number> - step/bucket size as a power of 2 for
2900 statistical time based profiling.
2901 Param: "sleep" - profile D-state sleeping (millisecs).
2902 Requires CONFIG_SCHEDSTATS
2903 Param: "kvm" - profile VM exits.
2905 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2907 See Documentation/blockdev/ramdisk.txt.
2909 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2910 probe for; one of (bare|imps|exps|lifebook|any).
2911 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2913 psmouse.resetafter= [HW,MOUSE]
2914 Try to reset the device after so many bad packets
2917 [HW,MOUSE] Set desired mouse resolution, in dpi.
2918 psmouse.smartscroll=
2919 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2920 0 = disabled, 1 = enabled (default).
2922 pstore.backend= Specify the name of the pstore backend to use
2925 See Documentation/blockdev/paride.txt.
2928 [KNL] Number of legacy pty's. Overwrites compiled-in
2931 quiet [KNL] Disable most log messages
2936 See Documentation/md.txt.
2938 ramdisk_blocksize= [RAM]
2939 See Documentation/blockdev/ramdisk.txt.
2941 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2942 See Documentation/blockdev/ramdisk.txt.
2945 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2946 the specified list of CPUs to be no-callback CPUs.
2947 Invocation of these CPUs' RCU callbacks will
2948 be offloaded to "rcuox/N" kthreads created for
2949 that purpose, where "x" is "b" for RCU-bh, "p"
2950 for RCU-preempt, and "s" for RCU-sched, and "N"
2951 is the CPU number. This reduces OS jitter on the
2952 offloaded CPUs, which can be useful for HPC and
2953 real-time workloads. It can also improve energy
2954 efficiency for asymmetric multiprocessors.
2957 Rather than requiring that offloaded CPUs
2958 (specified by rcu_nocbs= above) explicitly
2959 awaken the corresponding "rcuoN" kthreads,
2960 make these kthreads poll for callbacks.
2961 This improves the real-time response for the
2962 offloaded CPUs by relieving them of the need to
2963 wake up the corresponding kthread, but degrades
2964 energy efficiency by requiring that the kthreads
2965 periodically wake up to do the polling.
2967 rcutree.blimit= [KNL]
2968 Set maximum number of finished RCU callbacks to
2969 process in one batch.
2971 rcutree.rcu_fanout_leaf= [KNL]
2972 Increase the number of CPUs assigned to each
2973 leaf rcu_node structure. Useful for very large
2976 rcutree.jiffies_till_sched_qs= [KNL]
2977 Set required age in jiffies for a
2978 given grace period before RCU starts
2979 soliciting quiescent-state help from
2980 rcu_note_context_switch().
2982 rcutree.jiffies_till_first_fqs= [KNL]
2983 Set delay from grace-period initialization to
2984 first attempt to force quiescent states.
2985 Units are jiffies, minimum value is zero,
2986 and maximum value is HZ.
2988 rcutree.jiffies_till_next_fqs= [KNL]
2989 Set delay between subsequent attempts to force
2990 quiescent states. Units are jiffies, minimum
2991 value is one, and maximum value is HZ.
2993 rcutree.kthread_prio= [KNL,BOOT]
2994 Set the SCHED_FIFO priority of the RCU
2995 per-CPU kthreads (rcuc/N). This value is also
2996 used for the priority of the RCU boost threads
2997 (rcub/N). Valid values are 1-99 and the default
2998 is 1 (the least-favored priority).
3000 rcutree.rcu_nocb_leader_stride= [KNL]
3001 Set the number of NOCB kthread groups, which
3002 defaults to the square root of the number of
3003 CPUs. Larger numbers reduces the wakeup overhead
3004 on the per-CPU grace-period kthreads, but increases
3005 that same overhead on each group's leader.
3007 rcutree.qhimark= [KNL]
3008 Set threshold of queued RCU callbacks beyond which
3009 batch limiting is disabled.
3011 rcutree.qlowmark= [KNL]
3012 Set threshold of queued RCU callbacks below which
3013 batch limiting is re-enabled.
3015 rcutree.rcu_idle_gp_delay= [KNL]
3016 Set wakeup interval for idle CPUs that have
3017 RCU callbacks (RCU_FAST_NO_HZ=y).
3019 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3020 Set wakeup interval for idle CPUs that have
3021 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3022 Lazy RCU callbacks are those which RCU can
3023 prove do nothing more than free memory.
3025 rcutorture.cbflood_inter_holdoff= [KNL]
3026 Set holdoff time (jiffies) between successive
3027 callback-flood tests.
3029 rcutorture.cbflood_intra_holdoff= [KNL]
3030 Set holdoff time (jiffies) between successive
3031 bursts of callbacks within a given callback-flood
3034 rcutorture.cbflood_n_burst= [KNL]
3035 Set the number of bursts making up a given
3036 callback-flood test. Set this to zero to
3037 disable callback-flood testing.
3039 rcutorture.cbflood_n_per_burst= [KNL]
3040 Set the number of callbacks to be registered
3041 in a given burst of a callback-flood test.
3043 rcutorture.fqs_duration= [KNL]
3044 Set duration of force_quiescent_state bursts.
3046 rcutorture.fqs_holdoff= [KNL]
3047 Set holdoff time within force_quiescent_state bursts.
3049 rcutorture.fqs_stutter= [KNL]
3050 Set wait time between force_quiescent_state bursts.
3052 rcutorture.gp_exp= [KNL]
3053 Use expedited update-side primitives.
3055 rcutorture.gp_normal= [KNL]
3056 Use normal (non-expedited) update-side primitives.
3057 If both gp_exp and gp_normal are set, do both.
3058 If neither gp_exp nor gp_normal are set, still
3061 rcutorture.n_barrier_cbs= [KNL]
3062 Set callbacks/threads for rcu_barrier() testing.
3064 rcutorture.nfakewriters= [KNL]
3065 Set number of concurrent RCU writers. These just
3066 stress RCU, they don't participate in the actual
3067 test, hence the "fake".
3069 rcutorture.nreaders= [KNL]
3070 Set number of RCU readers.
3072 rcutorture.object_debug= [KNL]
3073 Enable debug-object double-call_rcu() testing.
3075 rcutorture.onoff_holdoff= [KNL]
3076 Set time (s) after boot for CPU-hotplug testing.
3078 rcutorture.onoff_interval= [KNL]
3079 Set time (s) between CPU-hotplug operations, or
3080 zero to disable CPU-hotplug testing.
3082 rcutorture.torture_runnable= [BOOT]
3083 Start rcutorture running at boot time.
3085 rcutorture.shuffle_interval= [KNL]
3086 Set task-shuffle interval (s). Shuffling tasks
3087 allows some CPUs to go into dyntick-idle mode
3088 during the rcutorture test.
3090 rcutorture.shutdown_secs= [KNL]
3091 Set time (s) after boot system shutdown. This
3092 is useful for hands-off automated testing.
3094 rcutorture.stall_cpu= [KNL]
3095 Duration of CPU stall (s) to test RCU CPU stall
3096 warnings, zero to disable.
3098 rcutorture.stall_cpu_holdoff= [KNL]
3099 Time to wait (s) after boot before inducing stall.
3101 rcutorture.stat_interval= [KNL]
3102 Time (s) between statistics printk()s.
3104 rcutorture.stutter= [KNL]
3105 Time (s) to stutter testing, for example, specifying
3106 five seconds causes the test to run for five seconds,
3107 wait for five seconds, and so on. This tests RCU's
3108 ability to transition abruptly to and from idle.
3110 rcutorture.test_boost= [KNL]
3111 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3112 "Maybe" means test if the RCU implementation
3113 under test support RCU priority boosting.
3115 rcutorture.test_boost_duration= [KNL]
3116 Duration (s) of each individual boost test.
3118 rcutorture.test_boost_interval= [KNL]
3119 Interval (s) between each boost test.
3121 rcutorture.test_no_idle_hz= [KNL]
3122 Test RCU's dyntick-idle handling. See also the
3123 rcutorture.shuffle_interval parameter.
3125 rcutorture.torture_type= [KNL]
3126 Specify the RCU implementation to test.
3128 rcutorture.verbose= [KNL]
3129 Enable additional printk() statements.
3131 rcupdate.rcu_expedited= [KNL]
3132 Use expedited grace-period primitives, for
3133 example, synchronize_rcu_expedited() instead
3134 of synchronize_rcu(). This reduces latency,
3135 but can increase CPU utilization, degrade
3136 real-time latency, and degrade energy efficiency.
3138 rcupdate.rcu_cpu_stall_suppress= [KNL]
3139 Suppress RCU CPU stall warning messages.
3141 rcupdate.rcu_cpu_stall_timeout= [KNL]
3142 Set timeout for RCU CPU stall warning messages.
3144 rcupdate.rcu_task_stall_timeout= [KNL]
3145 Set timeout in jiffies for RCU task stall warning
3146 messages. Disable with a value less than or equal
3149 rcupdate.rcu_self_test= [KNL]
3150 Run the RCU early boot self tests
3152 rcupdate.rcu_self_test_bh= [KNL]
3153 Run the RCU bh early boot self tests
3155 rcupdate.rcu_self_test_sched= [KNL]
3156 Run the RCU sched early boot self tests
3160 Run specified binary instead of /init from the ramdisk,
3161 used for early userspace startup. See initrd.
3164 Format (x86 or x86_64):
3165 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3167 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3169 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3170 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3171 reboot_force is either force or not specified,
3172 reboot_cpu is s[mp]#### with #### being the processor
3173 to be used for rebooting.
3176 [KNL, SMP] Set scheduler's default relax_domain_level.
3177 See Documentation/cgroups/cpusets.txt.
3179 relative_sleep_states=
3180 [SUSPEND] Use sleep state labeling where the deepest
3181 state available other than hibernation is always "mem".
3182 Format: { "0" | "1" }
3183 0 -- Traditional sleep state labels.
3184 1 -- Relative sleep state labels.
3186 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3188 reservetop= [X86-32]
3190 Reserves a hole at the top of the kernel virtual
3195 Set the amount of memory to reserve for BIOS at
3196 the bottom of the address space.
3198 reset_devices [KNL] Force drivers to reset the underlying device
3199 during initialization.
3202 Specify the partition device for software suspend
3204 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3206 resume_offset= [SWSUSP]
3207 Specify the offset from the beginning of the partition
3208 given by "resume=" at which the swap header is located,
3209 in <PAGE_SIZE> units (needed only for swap files).
3210 See Documentation/power/swsusp-and-swap-files.txt
3212 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3213 read the resume files
3215 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3216 Useful for devices that are detected asynchronously
3217 (e.g. USB and MMC devices).
3219 hibernate= [HIBERNATION]
3220 noresume Don't check if there's a hibernation image
3221 present during boot.
3222 nocompress Don't compress/decompress hibernation images.
3223 no Disable hibernation and resume.
3225 retain_initrd [RAM] Keep initrd memory after extraction
3227 rfkill.default_state=
3228 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3229 etc. communication is blocked by default.
3232 rfkill.master_switch_mode=
3233 0 The "airplane mode" button does nothing.
3234 1 The "airplane mode" button toggles between everything
3235 blocked and the previous configuration.
3236 2 The "airplane mode" button toggles between everything
3237 blocked and everything unblocked.
3239 rhash_entries= [KNL,NET]
3240 Set number of hash buckets for route cache
3242 ro [KNL] Mount root device read-only on boot
3244 root= [KNL] Root filesystem
3245 See name_to_dev_t comment in init/do_mounts.c.
3247 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3248 mount the root filesystem
3250 rootflags= [KNL] Set root filesystem mount option string
3252 rootfstype= [KNL] Set root filesystem type
3254 rootwait [KNL] Wait (indefinitely) for root device to show up.
3255 Useful for devices that are detected asynchronously
3256 (e.g. USB and MMC devices).
3258 rproc_mem=nn[KMG][@address]
3259 [KNL,ARM,CMA] Remoteproc physical memory block.
3260 Memory area to be used by remote processor image,
3263 rw [KNL] Mount root device read-write on boot
3265 S [KNL] Run init in single mode
3267 s390_iommu= [HW,S390]
3268 Set s390 IOTLB flushing mode
3270 With strict flushing every unmap operation will result in
3271 an IOTLB flush. Default is lazy flushing before reuse,
3275 See drivers/net/irda/sa1100_ir.c.
3277 sbni= [NET] Granch SBNI12 leased line adapter
3279 sched_debug [KNL] Enables verbose scheduler debug messages.
3281 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3282 xtime_lock contention on larger systems, and/or RCU lock
3283 contention on all systems with CONFIG_MAXSMP set.
3284 Format: { "0" | "1" }
3285 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3287 Note: increases power consumption, thus should only be
3288 enabled if running jitter sensitive (HPC/RT) workloads.
3290 security= [SECURITY] Choose a security module to enable at boot.
3291 If this boot parameter is not specified, only the first
3292 security module asking for security registration will be
3293 loaded. An invalid security module name will be treated
3294 as if no module has been chosen.
3296 selinux= [SELINUX] Disable or enable SELinux at boot time.
3297 Format: { "0" | "1" }
3298 See security/selinux/Kconfig help text.
3301 Default value is set via kernel config option.
3302 If enabled at boot time, /selinux/disable can be used
3303 later to disable prior to initial policy load.
3305 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3306 Format: { "0" | "1" }
3307 See security/apparmor/Kconfig help text
3310 Default value is set via kernel config option.
3312 serialnumber [BUGS=X86-32]
3315 Maximal number of shapers.
3317 show_msr= [x86] show boot-time MSR settings
3318 Format: { <integer> }
3319 Show boot-time (BIOS-initialized) MSR settings.
3320 The parameter means the number of CPUs to show,
3321 for example 1 means boot CPU only.
3329 Disable merging of slabs with similar size. May be
3330 necessary if there is some reason to distinguish
3331 allocs to different slabs. Debug options disable
3332 merging on their own.
3333 For more information see Documentation/vm/slub.txt.
3335 slab_max_order= [MM, SLAB]
3336 Determines the maximum allowed order for slabs.
3337 A high setting may cause OOMs due to memory
3338 fragmentation. Defaults to 1 for systems with
3339 more than 32MB of RAM, 0 otherwise.
3341 slub_debug[=options[,slabs]] [MM, SLUB]
3342 Enabling slub_debug allows one to determine the
3343 culprit if slab objects become corrupted. Enabling
3344 slub_debug can create guard zones around objects and
3345 may poison objects when not in use. Also tracks the
3346 last alloc / free. For more information see
3347 Documentation/vm/slub.txt.
3349 slub_max_order= [MM, SLUB]
3350 Determines the maximum allowed order for slabs.
3351 A high setting may cause OOMs due to memory
3352 fragmentation. For more information see
3353 Documentation/vm/slub.txt.
3355 slub_min_objects= [MM, SLUB]
3356 The minimum number of objects per slab. SLUB will
3357 increase the slab order up to slub_max_order to
3358 generate a sufficiently large slab able to contain
3359 the number of objects indicated. The higher the number
3360 of objects the smaller the overhead of tracking slabs
3361 and the less frequently locks need to be acquired.
3362 For more information see Documentation/vm/slub.txt.
3364 slub_min_order= [MM, SLUB]
3365 Determines the minimum page order for slabs. Must be
3366 lower than slub_max_order.
3367 For more information see Documentation/vm/slub.txt.
3369 slub_nomerge [MM, SLUB]
3370 Same with slab_nomerge. This is supported for legacy.
3371 See slab_nomerge for more information.
3374 Format: <io1>[,<io2>[,...,<io8>]]
3376 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3377 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3378 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3379 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3380 smsc-ircc2.ircc_irq= [HW] IRQ line
3381 smsc-ircc2.ircc_dma= [HW] DMA channel
3382 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3383 0: Toshiba Satellite 1800 (GP data pin select)
3384 1: Fast pin select (default)
3388 [KNL] Should the soft-lockup detector generate panics.
3391 softlockup_all_cpu_backtrace=
3392 [KNL] Should the soft-lockup detector generate
3393 backtraces on all cpus.
3396 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3397 See Documentation/laptops/sonypi.txt
3399 spia_io_base= [HW,MTD]
3405 Enabled the stack tracer on boot up.
3407 stacktrace_filter=[function-list]
3408 [FTRACE] Limit the functions that the stack tracer
3409 will trace at boot up. function-list is a comma separated
3410 list of functions. This list can be changed at run
3411 time by the stack_trace_filter file in the debugfs
3412 tracing directory. Note, this enables stack tracing
3413 and the stacktrace above is not needed.
3417 Set the STI (builtin display/keyboard on the HP-PARISC
3418 machines) console (graphic card) which should be used
3419 as the initial boot-console.
3420 See also comment in drivers/video/console/sticore.c.
3423 See comment in drivers/video/console/sticore.c.
3426 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3428 sunrpc.min_resvport=
3429 sunrpc.max_resvport=
3431 SunRPC servers often require that client requests
3432 originate from a privileged port (i.e. a port in the
3433 range 0 < portnr < 1024).
3434 An administrator who wishes to reserve some of these
3435 ports for other uses may adjust the range that the
3436 kernel's sunrpc client considers to be privileged
3437 using these two parameters to set the minimum and
3438 maximum port values.
3442 Control how the NFS server code allocates CPUs to
3443 service thread pools. Depending on how many NICs
3444 you have and where their interrupts are bound, this
3445 option will affect which CPUs will do NFS serving.
3446 Note: this parameter cannot be changed while the
3447 NFS server is running.
3449 auto the server chooses an appropriate mode
3450 automatically using heuristics
3451 global a single global pool contains all CPUs
3452 percpu one pool for each CPU
3453 pernode one pool for each NUMA node (equivalent
3454 to global on non-NUMA machines)
3456 sunrpc.tcp_slot_table_entries=
3457 sunrpc.udp_slot_table_entries=
3459 Sets the upper limit on the number of simultaneous
3460 RPC calls that can be sent from the client to a
3461 server. Increasing these values may allow you to
3462 improve throughput, but will also increase the
3463 amount of memory reserved for use by the client.
3466 [KNL] Enable accounting of swap in memory resource
3467 controller if no parameter or 1 is given or disable
3468 it if 0 is given (See Documentation/cgroups/memory.txt)
3470 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3471 Format: { <int> | force }
3472 <int> -- Number of I/O TLB slabs
3473 force -- force using of bounce buffers even if they
3474 wouldn't be automatically used by the kernel
3478 sysfs.deprecated=0|1 [KNL]
3479 Enable/disable old style sysfs layout for old udev
3480 on older distributions. When this option is enabled
3481 very new udev will not work anymore. When this option
3482 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3483 in older udev will not work anymore.
3484 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3485 the kernel configuration.
3487 sysrq_always_enabled
3489 Ignore sysrq setting - this boot parameter will
3490 neutralize any effect of /proc/sys/kernel/sysrq.
3491 Useful for debugging.
3493 tcpmhash_entries= [KNL,NET]
3494 Set the number of tcp_metrics_hash slots.
3495 Default value is 8192 or 16384 depending on total
3496 ram pages. This is used to specify the TCP metrics
3497 cache size. See Documentation/networking/ip-sysctl.txt
3498 "tcp_no_metrics_save" section for more details.
3502 test_suspend= [SUSPEND][,N]
3503 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3504 standby suspend) or "freeze" (for suspend type freeze)
3505 as the system sleep state during system startup with
3506 the optional capability to repeat N number of times.
3507 The system is woken from this state using a
3508 wakeup-capable RTC alarm.
3510 thash_entries= [KNL,NET]
3511 Set number of hash buckets for TCP connection
3513 thermal.act= [HW,ACPI]
3514 -1: disable all active trip points in all thermal zones
3515 <degrees C>: override all lowest active trip points
3517 thermal.crt= [HW,ACPI]
3518 -1: disable all critical trip points in all thermal zones
3519 <degrees C>: override all critical trip points
3521 thermal.nocrt= [HW,ACPI]
3522 Set to disable actions on ACPI thermal zone
3523 critical and hot trip points.
3525 thermal.off= [HW,ACPI]
3526 1: disable ACPI thermal control
3528 thermal.psv= [HW,ACPI]
3529 -1: disable all passive trip points
3530 <degrees C>: override all passive trip points to this
3533 thermal.tzp= [HW,ACPI]
3534 Specify global default ACPI thermal zone polling rate
3535 <deci-seconds>: poll all this frequency
3536 0: no polling (default)
3539 Force threading of all interrupt handlers except those
3540 marked explicitly IRQF_NO_THREAD.
3543 Enable the Transcendent memory driver if built-in.
3545 tmem.cleancache=0|1 [KNL, XEN]
3546 Default is on (1). Disable the usage of the cleancache
3547 API to send anonymous pages to the hypervisor.
3549 tmem.frontswap=0|1 [KNL, XEN]
3550 Default is on (1). Disable the usage of the frontswap
3551 API to send swap pages to the hypervisor. If disabled
3552 the selfballooning and selfshrinking are force disabled.
3554 tmem.selfballooning=0|1 [KNL, XEN]
3555 Default is on (1). Disable the driving of swap pages
3558 tmem.selfshrinking=0|1 [KNL, XEN]
3559 Default is on (1). Partial swapoff that immediately
3560 transfers pages from Xen hypervisor back to the
3561 kernel based on different criteria.
3565 Specify if the kernel should make use of the cpu
3566 topology information if the hardware supports this.
3567 The scheduler will make use of this information and
3568 e.g. base its process migration decisions on it.
3571 topology_updates= [KNL, PPC, NUMA]
3573 Specify if the kernel should ignore (off)
3574 topology updates sent by the hypervisor to this
3579 tpm_suspend_pcr=[HW,TPM]
3580 Format: integer pcr id
3581 Specify that at suspend time, the tpm driver
3582 should extend the specified pcr with zeros,
3583 as a workaround for some chips which fail to
3584 flush the last written pcr on TPM_SaveState.
3585 This will guarantee that all the other pcrs
3588 trace_buf_size=nn[KMG]
3589 [FTRACE] will set tracing buffer size on each cpu.
3591 trace_event=[event-list]
3592 [FTRACE] Set and start specified trace events in order
3593 to facilitate early boot debugging.
3594 See also Documentation/trace/events.txt
3596 trace_options=[option-list]
3597 [FTRACE] Enable or disable tracer options at boot.
3598 The option-list is a comma delimited list of options
3599 that can be enabled or disabled just as if you were
3600 to echo the option name into
3602 /sys/kernel/debug/tracing/trace_options
3604 For example, to enable stacktrace option (to dump the
3605 stack trace of each event), add to the command line:
3607 trace_options=stacktrace
3609 See also Documentation/trace/ftrace.txt "trace options"
3613 Have the tracepoints sent to printk as well as the
3614 tracing ring buffer. This is useful for early boot up
3615 where the system hangs or reboots and does not give the
3616 option for reading the tracing buffer or performing a
3617 ftrace_dump_on_oops.
3619 To turn off having tracepoints sent to printk,
3620 echo 0 > /proc/sys/kernel/tracepoint_printk
3621 Note, echoing 1 into this file without the
3622 tracepoint_printk kernel cmdline option has no effect.
3626 Having tracepoints sent to printk() and activating high
3627 frequency tracepoints such as irq or sched, can cause
3628 the system to live lock.
3631 [FTRACE] enable this option to disable tracing when a
3632 warning is hit. This turns off "tracing_on". Tracing can
3633 be enabled again by echoing '1' into the "tracing_on"
3634 file located in /sys/kernel/debug/tracing/
3636 This option is useful, as it disables the trace before
3637 the WARNING dump is called, which prevents the trace to
3638 be filled with content caused by the warning output.
3640 This option can also be set at run time via the sysctl
3641 option: kernel/traceoff_on_warning
3643 transparent_hugepage=
3645 Format: [always|madvise|never]
3646 Can be used to control the default behavior of the system
3647 with respect to transparent hugepages.
3648 See Documentation/vm/transhuge.txt for more details.
3650 tsc= Disable clocksource stability checks for TSC.
3652 [x86] reliable: mark tsc clocksource as reliable, this
3653 disables clocksource verification at runtime, as well
3654 as the stability checks done at bootup. Used to enable
3655 high-resolution timer mode on older hardware, and in
3656 virtualized environment.
3657 [x86] noirqtime: Do not use TSC to do irq accounting.
3658 Used to run time disable IRQ_TIME_ACCOUNTING on any
3659 platforms where RDTSC is slow and this accounting
3662 turbografx.map[2|3]= [HW,JOY]
3663 TurboGraFX parallel port interface
3665 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3666 See also Documentation/input/joystick-parport.txt
3668 udbg-immortal [PPC] When debugging early kernel crashes that
3669 happen after console_init() and before a proper
3670 console driver takes over, this boot options might
3671 help "seeing" what's going on.
3673 uhash_entries= [KNL,NET]
3674 Set number of hash buckets for UDP/UDP-Lite connections
3677 [USB] Ignore overcurrent events (default N).
3678 Some badly-designed motherboards generate lots of
3679 bogus events, for ports that aren't wired to
3680 anything. Set this parameter to avoid log spamming.
3681 Note that genuine overcurrent events won't be
3685 [X86] Cause panic on unknown NMI.
3687 usbcore.authorized_default=
3688 [USB] Default USB device authorization:
3689 (default -1 = authorized except for wireless USB,
3690 0 = not authorized, 1 = authorized)
3692 usbcore.autosuspend=
3693 [USB] The autosuspend time delay (in seconds) used
3694 for newly-detected USB devices (default 2). This
3695 is the time required before an idle device will be
3696 autosuspended. Devices for which the delay is set
3697 to a negative value won't be autosuspended at all.
3699 usbcore.usbfs_snoop=
3700 [USB] Set to log all usbfs traffic (default 0 = off).
3702 usbcore.blinkenlights=
3703 [USB] Set to cycle leds on hubs (default 0 = off).
3705 usbcore.old_scheme_first=
3706 [USB] Start with the old device initialization
3707 scheme (default 0 = off).
3709 usbcore.usbfs_memory_mb=
3710 [USB] Memory limit (in MB) for buffers allocated by
3711 usbfs (default = 16, 0 = max = 2047).
3713 usbcore.use_both_schemes=
3714 [USB] Try the other device initialization scheme
3715 if the first one fails (default 1 = enabled).
3717 usbcore.initial_descriptor_timeout=
3718 [USB] Specifies timeout for the initial 64-byte
3719 USB_REQ_GET_DESCRIPTOR request in milliseconds
3720 (default 5000 = 5.0 seconds).
3723 [USBHID] The interval which mice are to be polled at.
3725 usb-storage.delay_use=
3726 [UMS] The delay in seconds before a new device is
3727 scanned for Logical Units (default 1).
3730 [UMS] A list of quirks entries to supplement or
3731 override the built-in unusual_devs list. List
3732 entries are separated by commas. Each entry has
3733 the form VID:PID:Flags where VID and PID are Vendor
3734 and Product ID values (4-digit hex numbers) and
3735 Flags is a set of characters, each corresponding
3736 to a common usb-storage quirk flag as follows:
3737 a = SANE_SENSE (collect more than 18 bytes
3739 b = BAD_SENSE (don't collect more than 18
3740 bytes of sense data);
3741 c = FIX_CAPACITY (decrease the reported
3742 device capacity by one sector);
3743 d = NO_READ_DISC_INFO (don't use
3744 READ_DISC_INFO command);
3745 e = NO_READ_CAPACITY_16 (don't use
3746 READ_CAPACITY_16 command);
3747 f = NO_REPORT_OPCODES (don't use report opcodes
3749 h = CAPACITY_HEURISTICS (decrease the
3750 reported device capacity by one
3751 sector if the number is odd);
3752 i = IGNORE_DEVICE (don't bind to this
3754 l = NOT_LOCKABLE (don't try to lock and
3755 unlock ejectable media);
3756 m = MAX_SECTORS_64 (don't transfer more
3757 than 64 sectors = 32 KB at a time);
3758 n = INITIAL_READ10 (force a retry of the
3759 initial READ(10) command);
3760 o = CAPACITY_OK (accept the capacity
3761 reported by the device);
3762 p = WRITE_CACHE (the device cache is ON
3764 r = IGNORE_RESIDUE (the device reports
3765 bogus residue values);
3766 s = SINGLE_LUN (the device has only one
3768 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3769 commands, uas only);
3770 u = IGNORE_UAS (don't bind to the uas driver);
3771 w = NO_WP_DETECT (don't test whether the
3772 medium is write-protected).
3773 Example: quirks=0419:aaf5:rl,0421:0433:rc
3775 user_debug= [KNL,ARM]
3777 See arch/arm/Kconfig.debug help text.
3778 1 - undefined instruction events
3780 4 - invalid data aborts
3783 Example: user_debug=31
3786 [X86] Flags controlling user PTE allocations.
3788 nohigh = do not allocate PTE pages in
3789 HIGHMEM regardless of setting
3793 On X86_32, this is an alias for vdso32=. Otherwise:
3795 vdso=1: enable VDSO (the default)
3796 vdso=0: disable VDSO mapping
3798 vdso32= [X86] Control the 32-bit vDSO
3799 vdso32=1: enable 32-bit VDSO
3800 vdso32=0 or vdso32=2: disable 32-bit VDSO
3802 See the help text for CONFIG_COMPAT_VDSO for more
3803 details. If CONFIG_COMPAT_VDSO is set, the default is
3804 vdso32=0; otherwise, the default is vdso32=1.
3806 For compatibility with older kernels, vdso32=2 is an
3809 Try vdso32=0 if you encounter an error that says:
3810 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3813 vector=percpu: enable percpu vector domain
3815 video= [FB] Frame buffer configuration
3816 See Documentation/fb/modedb.txt.
3818 video.brightness_switch_enabled= [0,1]
3819 If set to 1, on receiving an ACPI notify event
3820 generated by hotkey, video driver will adjust brightness
3821 level and then send out the event to user space through
3822 the allocated input device; If set to 0, video driver
3823 will only send out the event without touching backlight
3828 [VMMIO] Memory mapped virtio (platform) device.
3830 <size>@<baseaddr>:<irq>[:<id>]
3832 <size> := size (can use standard suffixes
3834 <baseaddr> := physical base address
3835 <irq> := interrupt number (as passed to
3837 <id> := (optional) platform device id
3839 virtio_mmio.device=1K@0x100b0000:48:7
3841 Can be used multiple times for multiple devices.
3843 vga= [BOOT,X86-32] Select a particular video mode
3844 See Documentation/x86/boot.txt and
3845 Documentation/svga.txt.
3846 Use vga=ask for menu.
3847 This is actually a boot loader parameter; the value is
3848 passed to the kernel using a special protocol.
3850 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3851 size of <nn>. This can be used to increase the
3852 minimum size (128MB on x86). It can also be used to
3853 decrease the size and leave more room for directly
3856 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3859 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3862 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3866 Controls the behavior of vsyscalls (i.e. calls to
3867 fixed addresses of 0xffffffffff600x00 from legacy
3868 code). Most statically-linked binaries and older
3869 versions of glibc use these calls. Because these
3870 functions are at fixed addresses, they make nice
3871 targets for exploits that can control RIP.
3873 emulate [default] Vsyscalls turn into traps and are
3874 emulated reasonably safely.
3876 native Vsyscalls are native syscall instructions.
3877 This is a little bit faster than trapping
3878 and makes a few dynamic recompilers work
3879 better than they would in emulation mode.
3880 It also makes exploits much easier to write.
3882 none Vsyscalls don't work at all. This makes
3883 them quite hard to use for exploits but
3884 might break your system.
3886 vt.color= [VT] Default text color.
3887 Format: 0xYX, X = foreground, Y = background.
3888 Default: 0x07 = light gray on black.
3890 vt.cur_default= [VT] Default cursor shape.
3891 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3892 the parameters of the <Esc>[?A;B;Cc escape sequence;
3893 see VGA-softcursor.txt. Default: 2 = underline.
3895 vt.default_blu= [VT]
3896 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3897 Change the default blue palette of the console.
3898 This is a 16-member array composed of values
3901 vt.default_grn= [VT]
3902 Format: <green0>,<green1>,<green2>,...,<green15>
3903 Change the default green palette of the console.
3904 This is a 16-member array composed of values
3907 vt.default_red= [VT]
3908 Format: <red0>,<red1>,<red2>,...,<red15>
3909 Change the default red palette of the console.
3910 This is a 16-member array composed of values
3916 Set system-wide default UTF-8 mode for all tty's.
3917 Default is 1, i.e. UTF-8 mode is enabled for all
3918 newly opened terminals.
3920 vt.global_cursor_default=
3923 Set system-wide default for whether a cursor
3924 is shown on new VTs. Default is -1,
3925 i.e. cursors will be created by default unless
3926 overridden by individual drivers. 0 will hide
3927 cursors, 1 will display them.
3929 vt.italic= [VT] Default color for italic text; 0-15.
3932 vt.underline= [VT] Default color for underlined text; 0-15.
3935 watchdog timers [HW,WDT] For information on watchdog timers,
3936 see Documentation/watchdog/watchdog-parameters.txt
3937 or other driver-specific files in the
3938 Documentation/watchdog/ directory.
3940 workqueue.disable_numa
3941 By default, all work items queued to unbound
3942 workqueues are affine to the NUMA nodes they're
3943 issued on, which results in better behavior in
3944 general. If NUMA affinity needs to be disabled for
3945 whatever reason, this option can be used. Note
3946 that this also can be controlled per-workqueue for
3947 workqueues visible under /sys/bus/workqueue/.
3949 workqueue.power_efficient
3950 Per-cpu workqueues are generally preferred because
3951 they show better performance thanks to cache
3952 locality; unfortunately, per-cpu workqueues tend to
3953 be more power hungry than unbound workqueues.
3955 Enabling this makes the per-cpu workqueues which
3956 were observed to contribute significantly to power
3957 consumption unbound, leading to measurably lower
3958 power usage at the cost of small performance
3961 The default value of this parameter is determined by
3962 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3964 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3965 default x2apic cluster mode on platforms
3968 x86_intel_mid_timer= [X86-32,APBT]
3969 Choose timer option for x86 Intel MID platform.
3970 Two valid options are apbt timer only and lapic timer
3971 plus one apbt timer for broadcast timer.
3972 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3974 xen_emul_unplug= [HW,X86,XEN]
3975 Unplug Xen emulated devices
3976 Format: [unplug0,][unplug1]
3977 ide-disks -- unplug primary master IDE devices
3978 aux-ide-disks -- unplug non-primary-master IDE devices
3979 nics -- unplug network devices
3980 all -- unplug all emulated devices (NICs and IDE disks)
3981 unnecessary -- unplugging emulated devices is
3982 unnecessary even if the host did not respond to
3984 never -- do not unplug even if version check succeeds
3986 xen_nopvspin [X86,XEN]
3987 Disables the ticketlock slowpath using Xen PV
3991 Disables the PV optimizations forcing the HVM guest to
3992 run as generic HVM guest with no PV drivers.
3994 xirc2ps_cs= [NET,PCMCIA]
3996 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3998 ______________________________________________________________________
4002 Add more DRM drivers.
projects / karo-tx-linux.git / blob