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 Keep all clocks already enabled by bootloader on,
609 even if no driver has claimed them. This is useful
610 for debug and development, but should not be
611 needed on a platform with proper driver support.
612 For more information, see Documentation/clk.txt.
614 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
616 Forces specified clocksource (if available) to be used
617 when calculating gettimeofday(). If specified
618 clocksource is not available, it defaults to PIT.
619 Format: { pit | tsc | cyclone | pmtmr }
621 clocksource= Override the default clocksource
623 Override the default clocksource and use the clocksource
624 with the name specified.
625 Some clocksource names to choose from, depending on
627 [all] jiffies (this is the base, fallback clocksource)
629 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
630 pxa_timer,timer3,32k_counter,timer0_1
632 [X86-32] pit,hpet,tsc;
633 scx200_hrt on Geode; cyclone on IBM x440
641 clearcpuid=BITNUM [X86]
642 Disable CPUID feature X for the kernel. See
643 arch/x86/include/asm/cpufeature.h for the valid bit
644 numbers. Note the Linux specific bits are not necessarily
645 stable over kernel options, but the vendor specific
647 Also note that user programs calling CPUID directly
648 or using the feature without checking anything
649 will still see it. This just prevents it from
650 being used by the kernel or shown in /proc/cpuinfo.
651 Also note the kernel might malfunction if you disable
654 cma=nn[MG]@[start[MG][-end[MG]]]
656 Sets the size of kernel global memory area for
657 contiguous memory allocations and optionally the
658 placement constraint by the physical address range of
659 memory allocations. A value of 0 disables CMA
660 altogether. For more information, see
661 include/linux/dma-contiguous.h
663 cmo_free_hint= [PPC] Format: { yes | no }
664 Specify whether pages are marked as being inactive
665 when they are freed. This is used in CMO environments
666 to determine OS memory pressure for page stealing by
670 coherent_pool=nn[KMG] [ARM,KNL]
671 Sets the size of memory pool for coherent, atomic dma
672 allocations, by default set to 256K.
674 code_bytes [X86] How many bytes of object code to print
679 com20020= [HW,NET] ARCnet - COM20020 chipset
681 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
683 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
687 ARCnet - COM90xx chipset (memory-mapped buffers)
688 Format: <io>[,<irq>[,<memstart>]]
690 condev= [HW,S390] console device
693 console= [KNL] Output console device and options.
695 tty<n> Use the virtual console device <n>.
699 Use the specified serial port. The options are of
700 the form "bbbbpnf", where "bbbb" is the baud rate,
701 "p" is parity ("n", "o", or "e"), "n" is number of
702 bits, and "f" is flow control ("r" for RTS or
703 omit it). Default is "9600n8".
705 See Documentation/serial-console.txt for more
707 Documentation/networking/netconsole.txt for an
710 uart[8250],io,<addr>[,options]
711 uart[8250],mmio,<addr>[,options]
712 Start an early, polled-mode console on the 8250/16550
713 UART at the specified I/O port or MMIO address,
714 switching to the matching ttyS device later. The
715 options are the same as for ttyS, above.
716 hvc<n> Use the hypervisor console device <n>. This is for
717 both Xen and PowerPC hypervisors.
719 If the device connected to the port is not a TTY but a braille
720 device, prepend "brl," before the device type, for instance
722 For now, only VisioBraille is supported.
724 consoleblank= [KNL] The console blank (screen saver) timeout in
725 seconds. Defaults to 10*60 = 10mins. A value of 0
726 disables the blank timer.
729 [KNL] Change the default value for
730 /proc/<pid>/coredump_filter.
731 See also Documentation/filesystems/proc.txt.
733 cpuidle.off=1 [CPU_IDLE]
734 disable the cpuidle sub-system
736 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
738 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
740 crashkernel=size[KMG][@offset[KMG]]
741 [KNL] Using kexec, Linux can switch to a 'crash kernel'
742 upon panic. This parameter reserves the physical
743 memory region [offset, offset + size] for that kernel
744 image. If '@offset' is omitted, then a suitable offset
745 is selected automatically. Check
746 Documentation/kdump/kdump.txt for further details.
748 crashkernel=range1:size1[,range2:size2,...][@offset]
749 [KNL] Same as above, but depends on the memory
750 in the running system. The syntax of range is
751 start-[end] where start and end are both
752 a memory unit (amount[KMG]). See also
753 Documentation/kdump/kdump.txt for an example.
755 crashkernel=size[KMG],high
756 [KNL, x86_64] range could be above 4G. Allow kernel
757 to allocate physical memory region from top, so could
758 be above 4G if system have more than 4G ram installed.
759 Otherwise memory region will be allocated below 4G, if
761 It will be ignored if crashkernel=X is specified.
762 crashkernel=size[KMG],low
763 [KNL, x86_64] range under 4G. When crashkernel=X,high
764 is passed, kernel could allocate physical memory region
765 above 4G, that cause second kernel crash on system
766 that require some amount of low memory, e.g. swiotlb
767 requires at least 64M+32K low memory. Kernel would
768 try to allocate 72M below 4G automatically.
769 This one let user to specify own low range under 4G
770 for second kernel instead.
771 0: to disable low allocation.
772 It will be ignored when crashkernel=X,high is not used
773 or memory reserved is below 4G.
778 cs89x0_media= [HW,NET]
779 Format: { rj45 | aui | bnc }
782 See header of drivers/s390/block/dasd_devmap.c.
784 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
785 (one device per port)
786 Format: <port#>,<type>
787 See also Documentation/input/joystick-parport.txt
789 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
790 time. See Documentation/dynamic-debug-howto.txt for
791 details. Deprecated, see dyndbg.
793 debug [KNL] Enable kernel debugging (events log level).
796 [KNL] verbose self-tests
798 Print debugging info while doing the locking API
800 We default to 0 (no extra messages), setting it to
801 1 will print _a lot_ more information - normally
802 only useful to kernel developers.
804 debug_objects [KNL] Enable object debugging
807 [KNL] Disable object debugging
809 debug_guardpage_minorder=
810 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
811 parameter allows control of the order of pages that will
812 be intentionally kept free (and hence protected) by the
813 buddy allocator. Bigger value increase the probability
814 of catching random memory corruption, but reduce the
815 amount of memory for normal system use. The maximum
816 possible value is MAX_ORDER/2. Setting this parameter
817 to 1 or 2 should be enough to identify most random
818 memory corruption problems caused by bugs in kernel or
819 driver code when a CPU writes to (or reads from) a
820 random memory location. Note that there exists a class
821 of memory corruptions problems caused by buggy H/W or
822 F/W or by drivers badly programing DMA (basically when
823 memory is written at bus level and the CPU MMU is
824 bypassed) which are not detectable by
825 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
826 tracking down these problems.
828 debugpat [X86] Enable PAT debugging
830 decnet.addr= [HW,NET]
831 Format: <area>[,<node>]
832 See also Documentation/networking/decnet.txt.
835 [same as hugepagesz=] The size of the default
836 HugeTLB page size. This is the size represented by
837 the legacy /proc/ hugepages APIs, used for SHM, and
838 default size when mounting hugetlbfs filesystems.
839 Defaults to the default architecture's huge page size
843 Set number of hash buckets for dentry cache.
846 See Documentation/networking/ipv6.txt.
848 disable_cpu_apicid= [X86,APIC,SMP]
850 The number of initial APIC ID for the
851 corresponding CPU to be disabled at boot,
852 mostly used for the kdump 2nd kernel to
853 disable BSP to wake up multiple CPUs without
854 causing system reset or hang due to sending
857 disable_ddw [PPC/PSERIES]
858 Disable Dynamic DMA Window support. Use this if
859 to workaround buggy firmware.
862 See Documentation/networking/ipv6.txt.
864 disable_mtrr_cleanup [X86]
865 The kernel tries to adjust MTRR layout from continuous
866 to discrete, to make X server driver able to add WB
867 entry later. This parameter disables that.
869 disable_mtrr_trim [X86, Intel and AMD only]
870 By default the kernel will trim any uncacheable
871 memory out of your available memory pool based on
872 MTRR settings. This parameter disables that behavior,
873 possibly causing your machine to run very slowly.
875 disable_timer_pin_1 [X86]
876 Disable PIN 1 of APIC timer
877 Can be useful to work around chipset bugs.
879 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
880 this option disables the debugging code at boot.
882 dma_debug_entries=<number>
883 This option allows to tune the number of preallocated
884 entries for DMA-API debugging code. One entry is
885 required per DMA-API allocation. Use this if the
886 DMA-API debugging code disables itself because the
887 architectural default is too low.
889 dma_debug_driver=<driver_name>
890 With this option the DMA-API debugging driver
891 filter feature can be enabled at boot time. Just
892 pass the driver to filter for as the parameter.
893 The filter can be disabled or changed to another
894 driver later using sysfs.
896 drm_kms_helper.edid_firmware=[<connector>:]<file>
897 Broken monitors, graphic adapters and KVMs may
898 send no or incorrect EDID data sets. This parameter
899 allows to specify an EDID data set in the
900 /lib/firmware directory that is used instead.
901 Generic built-in EDID data sets are used, if one of
902 edid/1024x768.bin, edid/1280x1024.bin,
903 edid/1680x1050.bin, or edid/1920x1080.bin is given
904 and no file with the same name exists. Details and
905 instructions how to build your own EDID data are
906 available in Documentation/EDID/HOWTO.txt. An EDID
907 data set will only be used for a particular connector,
908 if its name and a colon are prepended to the EDID
913 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
914 module.dyndbg[="val"]
915 Enable debug messages at boot time. See
916 Documentation/dynamic-debug-howto.txt for details.
918 early_ioremap_debug [KNL]
919 Enable debug messages in early_ioremap support. This
920 is useful for tracking down temporary early mappings
921 which are not unmapped.
923 earlycon= [KNL] Output early console device and options.
926 Start an early, polled-mode console on a cadence serial
927 port at the specified address. The cadence serial port
928 must already be setup and configured. Options are not
931 uart[8250],io,<addr>[,options]
932 uart[8250],mmio,<addr>[,options]
933 uart[8250],mmio32,<addr>[,options]
934 Start an early, polled-mode console on the 8250/16550
935 UART at the specified I/O port or MMIO address.
936 MMIO inter-register address stride is either 8-bit
937 (mmio) or 32-bit (mmio32).
938 The options are the same as for ttyS, above.
941 Start an early, polled-mode console on a pl011 serial
942 port at the specified address. The pl011 serial port
943 must already be setup and configured. Options are not
947 Start an early, polled-mode console on an msm serial
948 port at the specified address. The serial port
949 must already be setup and configured. Options are not
953 Start an early, polled-mode console on an msm serial
954 dm port at the specified address. The serial port
955 must already be setup and configured. Options are not
958 smh Use ARM semihosting calls for early console.
960 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
964 earlyprintk=serial[,ttySn[,baudrate]]
965 earlyprintk=serial[,0x...[,baudrate]]
966 earlyprintk=ttySn[,baudrate]
967 earlyprintk=dbgp[debugController#]
969 earlyprintk is useful when the kernel crashes before
970 the normal console is initialized. It is not enabled by
971 default because it has some cosmetic problems.
973 Append ",keep" to not disable it when the real console
976 Only one of vga, efi, serial, or usb debug port can
979 Currently only ttyS0 and ttyS1 may be specified by
980 name. Other I/O ports may be explicitly specified
981 on some architectures (x86 and arm at least) by
982 replacing ttySn with an I/O port address, like this:
983 earlyprintk=serial,0x1008,115200
984 You can find the port for a given device in
985 /proc/tty/driver/serial:
986 2: uart:ST16650V2 port:00001008 irq:18 ...
988 Interaction with the standard serial driver is not
991 The VGA and EFI output is eventually overwritten by
994 The xen output can only be used by Xen PV guests.
996 edac_report= [HW,EDAC] Control how to report EDAC event
997 Format: {"on" | "off" | "force"}
998 on: enable EDAC to report H/W event. May be overridden
999 by other higher priority error reporting module.
1000 off: disable H/W event reporting through EDAC.
1001 force: enforce the use of EDAC to report H/W event.
1004 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1007 This is designed to be used in conjunction with
1008 the boot argument: earlyprintk=vga
1011 Format: {"off" | "on" | "skip[mbr]"}
1014 Format: { "old_map" }
1015 old_map [X86-64]: switch to the old ioremap-based EFI
1016 runtime services mapping. 32-bit still uses this one by
1019 efi_no_storage_paranoia [EFI; X86]
1020 Using this parameter you can use more than 50% of
1021 your efi variable storage. Use this parameter only if
1022 you are really sure that your UEFI does sane gc and
1023 fulfills the spec otherwise your board may brick.
1025 eisa_irq_edge= [PARISC,HW]
1026 See header of drivers/parisc/eisa.c.
1029 See comment before function elanfreq_setup() in
1030 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1033 Format: {"cfq" | "deadline" | "noop"}
1034 See Documentation/block/cfq-iosched.txt and
1035 Documentation/block/deadline-iosched.txt for details.
1037 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1038 Specifies physical address of start of kernel core
1039 image elf header and optionally the size. Generally
1040 kexec loader will pass this option to capture kernel.
1041 See Documentation/kdump/kdump.txt for details.
1043 enable_mtrr_cleanup [X86]
1044 The kernel tries to adjust MTRR layout from continuous
1045 to discrete, to make X server driver able to add WB
1046 entry later. This parameter enables that.
1048 enable_timer_pin_1 [X86]
1049 Enable PIN 1 of APIC timer
1050 Can be useful to work around chipset bugs
1051 (in particular on some ATI chipsets).
1052 The kernel tries to set a reasonable default.
1054 enforcing [SELINUX] Set initial enforcing status.
1056 See security/selinux/Kconfig help text.
1057 0 -- permissive (log only, no denials).
1058 1 -- enforcing (deny and log).
1060 Value can be changed at runtime via /selinux/enforce.
1063 Disable Error Record Serialization Table (ERST)
1066 ether= [HW,NET] Ethernet cards parameters
1067 This option is obsoleted by the "netdev=" option, which
1068 has equivalent usage. See its documentation for details.
1072 Permit 'security.evm' to be updated regardless of
1073 current integrity status.
1077 fail_make_request=[KNL]
1078 General fault injection mechanism.
1079 Format: <interval>,<probability>,<space>,<times>
1080 See also Documentation/fault-injection/.
1083 See Documentation/blockdev/floppy.txt.
1085 force_pal_cache_flush
1086 [IA-64] Avoid check_sal_cache_flush which may hang on
1087 buggy SAL_CACHE_FLUSH implementations. Using this
1088 parameter will force ia64_sal_cache_flush to call
1089 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1092 Forcefully enable Physical Address Extension (PAE).
1093 Many Pentium M systems disable PAE but may have a
1094 functionally usable PAE implementation.
1095 Warning: use of this parameter will taint the kernel
1096 and may cause unknown problems.
1099 [FTRACE] will set and start the specified tracer
1100 as early as possible in order to facilitate early
1103 ftrace_dump_on_oops[=orig_cpu]
1104 [FTRACE] will dump the trace buffers on oops.
1105 If no parameter is passed, ftrace will dump
1106 buffers of all CPUs, but if you pass orig_cpu, it will
1107 dump only the buffer of the CPU that triggered the
1110 ftrace_filter=[function-list]
1111 [FTRACE] Limit the functions traced by the function
1112 tracer at boot up. function-list is a comma separated
1113 list of functions. This list can be changed at run
1114 time by the set_ftrace_filter file in the debugfs
1117 ftrace_notrace=[function-list]
1118 [FTRACE] Do not trace the functions specified in
1119 function-list. This list can be changed at run time
1120 by the set_ftrace_notrace file in the debugfs
1123 ftrace_graph_filter=[function-list]
1124 [FTRACE] Limit the top level callers functions traced
1125 by the function graph tracer at boot up.
1126 function-list is a comma separated list of functions
1127 that can be changed at run time by the
1128 set_graph_function file in the debugfs tracing directory.
1130 ftrace_graph_notrace=[function-list]
1131 [FTRACE] Do not trace from the functions specified in
1132 function-list. This list is a comma separated list of
1133 functions that can be changed at run time by the
1134 set_graph_notrace file in the debugfs tracing directory.
1137 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1138 support via parallel port (up to 5 devices per port)
1139 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1140 See also Documentation/input/joystick-parport.txt
1144 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1148 gcov_persist= [GCOV] When non-zero (default), profiling data for
1149 kernel modules is saved and remains accessible via
1150 debugfs, even when the module is unloaded/reloaded.
1151 When zero, profiling data is discarded and associated
1152 debugfs files are removed at module unload time.
1154 gpt [EFI] Forces disk with valid GPT signature but
1155 invalid Protective MBR to be treated as GPT. If the
1156 primary GPT is corrupted, it enables the backup/alternate
1157 GPT to be used instead.
1159 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1160 the "Enable 0" bit of the configuration register.
1163 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1164 the "Enable 0" bit of the configuration register.
1167 grcan.select= [HW] Select which physical interface to use.
1170 grcan.txsize= [HW] Sets the size of the tx buffer.
1171 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1173 grcan.rxsize= [HW] Sets the size of the rx buffer.
1174 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1177 hashdist= [KNL,NUMA] Large hashes allocated during boot
1178 are distributed across NUMA nodes. Defaults on
1179 for 64-bit NUMA, off otherwise.
1180 Format: 0 | 1 (for off | on)
1182 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1184 hd= [EIDE] (E)IDE hard drive subsystem geometry
1185 Format: <cyl>,<head>,<sect>
1188 Disable Hardware Error Source Table (HEST) support;
1189 corresponding firmware-first mode error processing
1190 logic will be disabled.
1192 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1193 size of <nn>. This works even on boxes that have no
1194 highmem otherwise. This also works to reduce highmem
1195 size on bigger boxes.
1197 highres= [KNL] Enable/disable high resolution timer mode.
1198 Valid parameters: "on", "off"
1202 See Documentation/isdn/README.HiSax.
1206 hpet= [X86-32,HPET] option to control HPET usage
1207 Format: { enable (default) | disable | force |
1209 disable: disable HPET and use PIT instead
1210 force: allow force enabled of undocumented chips (ICH4,
1212 verbose: show contents of HPET registers during setup
1214 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1215 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1217 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1218 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1219 On x86-64 and powerpc, this option can be specified
1220 multiple times interleaved with hugepages= to reserve
1221 huge pages of different sizes. Valid pages sizes on
1222 x86-64 are 2M (when the CPU supports "pse") and 1G
1223 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1224 Note that 1GB pages can only be allocated at boot time
1225 using hugepages= and not freed afterwards.
1227 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1228 terminal devices. Valid values: 0..8
1229 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1230 If specified, z/VM IUCV HVC accepts connections
1231 from listed z/VM user IDs only.
1233 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1234 hardware thread id mappings.
1235 Format: <cpu>:<hwthread>
1238 Do not unregister boot console at start. This is only
1239 useful for debugging when something happens in the window
1240 between unregistering the boot console and initializing
1243 i2c_bus= [HW] Override the default board specific I2C bus speed
1244 or register an additional I2C bus that is not
1245 registered from board initialization code.
1249 i8042.debug [HW] Toggle i8042 debug mode
1250 i8042.direct [HW] Put keyboard port into non-translated mode
1251 i8042.dumbkbd [HW] Pretend that controller can only read data from
1252 keyboard and cannot control its state
1253 (Don't attempt to blink the leds)
1254 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1255 i8042.nokbd [HW] Don't check/create keyboard port
1256 i8042.noloop [HW] Disable the AUX Loopback command while probing
1258 i8042.nomux [HW] Don't check presence of an active multiplexing
1260 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1262 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1263 i8042.reset [HW] Reset the controller during init and cleanup
1264 i8042.unlock [HW] Unlock (ignore) the keylock
1268 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1269 indicates that the driver is running on unsupported
1271 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1272 does not match list of supported models.
1274 [HW] Report power status in /proc/i8k
1275 (disabled by default)
1276 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1279 i915.invert_brightness=
1280 [DRM] Invert the sense of the variable that is used to
1281 set the brightness of the panel backlight. Normally a
1282 brightness value of 0 indicates backlight switched off,
1283 and the maximum of the brightness value sets the backlight
1284 to maximum brightness. If this parameter is set to 0
1285 (default) and the machine requires it, or this parameter
1286 is set to 1, a brightness value of 0 sets the backlight
1287 to maximum brightness, and the maximum of the brightness
1288 value switches the backlight off.
1289 -1 -- never invert brightness
1290 0 -- machine default
1291 1 -- force brightness inversion
1294 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1296 ide-core.nodma= [HW] (E)IDE subsystem
1297 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1298 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1299 .cdrom .chs .ignore_cable are additional options
1300 See Documentation/ide/ide.txt.
1302 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1303 Claim all unknown PCI IDE storage controllers.
1306 Format: idle=poll, idle=halt, idle=nomwait
1307 Poll forces a polling idle loop that can slightly
1308 improve the performance of waking up a idle CPU, but
1309 will use a lot of power and make the system run hot.
1311 idle=halt: Halt is forced to be used for CPU idle.
1312 In such case C2/C3 won't be used again.
1313 idle=nomwait: Disable mwait for CPU C-states
1315 ignore_loglevel [KNL]
1316 Ignore loglevel setting - this will print /all/
1317 kernel messages to the console. Useful for debugging.
1318 We also add it as printk module parameter, so users
1319 could change it dynamically, usually by
1320 /sys/module/printk/parameters/ignore_loglevel.
1322 ihash_entries= [KNL]
1323 Set number of hash buckets for inode cache.
1325 ima_appraise= [IMA] appraise integrity measurements
1326 Format: { "off" | "enforce" | "fix" }
1329 ima_appraise_tcb [IMA]
1330 The builtin appraise policy appraises all files
1334 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1338 The list of supported hash algorithms is defined
1339 in crypto/hash_info.h.
1342 Load a policy which meets the needs of the Trusted
1343 Computing Base. This means IMA will measure all
1344 programs exec'd, files mmap'd for exec, and all files
1345 opened for read by uid=0.
1348 Select one of defined IMA measurements template formats.
1349 Formats: { "ima" | "ima-ng" }
1352 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1353 Format: <min_file_size>
1354 Set the minimal file size for using asynchronous hash.
1355 If left unspecified, ahash usage is disabled.
1357 ahash performance varies for different data sizes on
1358 different crypto accelerators. This option can be used
1359 to achieve the best performance for a particular HW.
1361 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1363 Set hashing buffer size. Default: 4k.
1365 ahash performance varies for different chunk sizes on
1366 different crypto accelerators. This option can be used
1367 to achieve best performance for particular HW.
1371 Run specified binary instead of /sbin/init as init
1374 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1375 for working out where the kernel is dying during
1378 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1379 initcall functions. Useful for debugging built-in
1380 modules and initcalls.
1382 initrd= [BOOT] Specify the location of the initial ramdisk
1384 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1387 int_pln_enable [x86] Enable power limit notification interrupt
1389 integrity_audit=[IMA]
1390 Format: { "0" | "1" }
1391 0 -- basic integrity auditing messages. (Default)
1392 1 -- additional integrity auditing messages.
1394 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1396 Enable intel iommu driver.
1398 Disable intel iommu driver.
1399 igfx_off [Default Off]
1400 By default, gfx is mapped as normal device. If a gfx
1401 device has a dedicated DMAR unit, the DMAR unit is
1402 bypassed by not enabling DMAR with this option. In
1403 this case, gfx device will use physical address for
1406 With this option iommu will not optimize to look
1407 for io virtual address below 32-bit forcing dual
1408 address cycle on pci bus for cards supporting greater
1409 than 32-bit addressing. The default is to look
1410 for translation below 32-bit and if not available
1411 then look in the higher range.
1412 strict [Default Off]
1413 With this option on every unmap_single operation will
1414 result in a hardware IOTLB flush operation as opposed
1415 to batching them for performance.
1416 sp_off [Default Off]
1417 By default, super page will be supported if Intel IOMMU
1418 has the capability. With this option, super page will
1421 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1422 0 disables intel_idle and fall back on acpi_idle.
1423 1 to 6 specify maximum depth of C-state.
1427 Do not enable intel_pstate as the default
1428 scaling driver for the supported processors
1430 intremap= [X86-64, Intel-IOMMU]
1431 on enable Interrupt Remapping (default)
1432 off disable Interrupt Remapping
1433 nosid disable Source ID checking
1435 BIOS x2APIC opt-out request will be ignored
1437 iomem= Disable strict checking of access to MMIO memory
1438 strict regions from userspace.
1455 io7= [HW] IO7 for Marvel based alpha systems
1456 See comment before marvel_specify_io7 in
1457 arch/alpha/kernel/core_marvel.c.
1459 io_delay= [X86] I/O delay method
1461 Standard port 0x80 based delay
1463 Alternate port 0xed based delay (needed on some systems)
1465 Simple two microseconds delay
1470 See Documentation/filesystems/nfs/nfsroot.txt.
1473 When an interrupt is not handled search all handlers
1474 for it. Intended to get systems with badly broken
1478 When an interrupt is not handled search all handlers
1479 for it. Also check all handlers each timer
1480 interrupt. Intended to get systems with badly broken
1484 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1486 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1488 <cpu number>,...,<cpu number>
1490 <cpu number>-<cpu number>
1491 (must be a positive range in ascending order)
1493 <cpu number>,...,<cpu number>-<cpu number>
1495 This option can be used to specify one or more CPUs
1496 to isolate from the general SMP balancing and scheduling
1497 algorithms. You can move a process onto or off an
1498 "isolated" CPU via the CPU affinity syscalls or cpuset.
1499 <cpu number> begins at 0 and the maximum value is
1500 "number of CPUs in system - 1".
1502 This option is the preferred way to isolate CPUs. The
1503 alternative -- manually setting the CPU mask of all
1504 tasks in the system -- can cause problems and
1505 suboptimal load balancer performance.
1509 ivrs_ioapic [HW,X86_64]
1510 Provide an override to the IOAPIC-ID<->DEVICE-ID
1511 mapping provided in the IVRS ACPI table. For
1512 example, to map IOAPIC-ID decimal 10 to
1513 PCI device 00:14.0 write the parameter as:
1514 ivrs_ioapic[10]=00:14.0
1516 ivrs_hpet [HW,X86_64]
1517 Provide an override to the HPET-ID<->DEVICE-ID
1518 mapping provided in the IVRS ACPI table. For
1519 example, to map HPET-ID decimal 0 to
1520 PCI device 00:14.0 write the parameter as:
1521 ivrs_hpet[0]=00:14.0
1523 js= [HW,JOY] Analog joystick
1524 See Documentation/input/joystick.txt.
1527 Enable/disable kernel and module base offset ASLR
1528 (Address Space Layout Randomization) if built into
1529 the kernel. When CONFIG_HIBERNATION is selected,
1530 kASLR is disabled by default. When kASLR is enabled,
1531 hibernation will be disabled.
1535 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1536 specifies the amount of memory usable by the kernel
1537 for non-movable allocations. The requested amount is
1538 spread evenly throughout all nodes in the system. The
1539 remaining memory in each node is used for Movable
1540 pages. In the event, a node is too small to have both
1541 kernelcore and Movable pages, kernelcore pages will
1542 take priority and other nodes will have a larger number
1543 of Movable pages. The Movable zone is used for the
1544 allocation of pages that may be reclaimed or moved
1545 by the page migration subsystem. This means that
1546 HugeTLB pages may not be allocated from this zone.
1547 Note that allocations like PTEs-from-HighMem still
1548 use the HighMem zone if it exists, and the Normal
1549 zone if it does not.
1551 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1552 Format: <Controller#>[,poll interval]
1553 The controller # is the number of the ehci usb debug
1554 port as it is probed via PCI. The poll interval is
1555 optional and is the number seconds in between
1556 each poll cycle to the debug port in case you need
1557 the functionality for interrupting the kernel with
1558 gdb or control-c on the dbgp connection. When
1559 not using this parameter you use sysrq-g to break into
1560 the kernel debugger.
1562 kgdboc= [KGDB,HW] kgdb over consoles.
1563 Requires a tty driver that supports console polling,
1564 or a supported polling keyboard driver (non-usb).
1565 Serial only format: <serial_device>[,baud]
1566 keyboard only format: kbd
1567 keyboard and serial format: kbd,<serial_device>[,baud]
1568 Optional Kernel mode setting:
1569 kms, kbd format: kms,kbd
1570 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1572 kgdbwait [KGDB] Stop kernel execution and enter the
1573 kernel debugger at the earliest opportunity.
1575 kmac= [MIPS] korina ethernet MAC address.
1576 Configure the RouterBoard 532 series on-chip
1577 Ethernet adapter MAC address.
1579 kmemleak= [KNL] Boot-time kmemleak enable/disable
1580 Valid arguments: on, off
1583 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1584 Valid arguments: 0, 1, 2
1585 kmemcheck=0 (disabled)
1586 kmemcheck=1 (enabled)
1587 kmemcheck=2 (one-shot mode)
1588 Default: 2 (one-shot mode)
1590 kstack=N [X86] Print N words from the kernel stack
1593 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1594 Default is 0 (don't ignore, but inject #GP)
1596 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1600 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1601 Default is 1 (enabled)
1603 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1605 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1607 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1608 (virtualized MMU) support on capable Intel chips.
1609 Default is 1 (enabled)
1611 kvm-intel.emulate_invalid_guest_state=
1612 [KVM,Intel] Enable emulation of invalid guest states
1613 Default is 0 (disabled)
1615 kvm-intel.flexpriority=
1616 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1617 Default is 1 (enabled)
1620 [KVM,Intel] Enable VMX nesting (nVMX).
1621 Default is 0 (disabled)
1623 kvm-intel.unrestricted_guest=
1624 [KVM,Intel] Disable unrestricted guest feature
1625 (virtualized real and unpaged mode) on capable
1626 Intel chips. Default is 1 (enabled)
1628 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1629 feature (tagged TLBs) on capable Intel chips.
1630 Default is 1 (enabled)
1636 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1639 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1640 value for LAPIC timer one-shot implementation. Default
1641 back to the programmable timer unit in the LAPIC.
1643 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1646 libata.dma= [LIBATA] DMA control
1647 libata.dma=0 Disable all PATA and SATA DMA
1648 libata.dma=1 PATA and SATA Disk DMA only
1649 libata.dma=2 ATAPI (CDROM) DMA only
1650 libata.dma=4 Compact Flash DMA only
1651 Combinations also work, so libata.dma=3 enables DMA
1652 for disks and CDROMs, but not CFs.
1654 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1655 libata.ignore_hpa=0 keep BIOS limits (default)
1656 libata.ignore_hpa=1 ignore limits, using full disk
1658 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1662 libata.force= [LIBATA] Force configurations. The format is comma
1663 separated list of "[ID:]VAL" where ID is
1664 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1665 matching port, link or device. Basically, it matches
1666 the ATA ID string printed on console by libata. If
1667 the whole ID part is omitted, the last PORT and DEVICE
1668 values are used. If ID hasn't been specified yet, the
1669 configuration applies to all ports, links and devices.
1671 If only DEVICE is omitted, the parameter applies to
1672 the port and all links and devices behind it. DEVICE
1673 number of 0 either selects the first device or the
1674 first fan-out link behind PMP device. It does not
1675 select the host link. DEVICE number of 15 selects the
1676 host link and device attached to it.
1678 The VAL specifies the configuration to force. As long
1679 as there's no ambiguity shortcut notation is allowed.
1680 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1681 The following configurations can be forced.
1683 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1684 Any ID with matching PORT is used.
1686 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1688 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1689 udma[/][16,25,33,44,66,100,133] notation is also
1692 * [no]ncq: Turn on or off NCQ.
1694 * nohrst, nosrst, norst: suppress hard, soft
1697 * rstonce: only attempt one reset during
1698 hot-unplug link recovery
1700 * dump_id: dump IDENTIFY data.
1702 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1704 * disable: Disable this device.
1706 If there are multiple matching configurations changing
1707 the same attribute, the last one is used.
1709 memblock=debug [KNL] Enable memblock debug messages.
1711 load_ramdisk= [RAM] List of ramdisks to load from floppy
1712 See Documentation/blockdev/ramdisk.txt.
1714 lockd.nlm_grace_period=P [NFS] Assign grace period.
1717 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1720 lockd.nlm_timeout=T [NFS] Assign timeout value.
1723 lockd.nlm_udpport=M [NFS] Assign UDP port.
1726 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1729 loglevel= All Kernel Messages with a loglevel smaller than the
1730 console loglevel will be printed to the console. It can
1731 also be changed with klogd or other programs. The
1732 loglevels are defined as follows:
1734 0 (KERN_EMERG) system is unusable
1735 1 (KERN_ALERT) action must be taken immediately
1736 2 (KERN_CRIT) critical conditions
1737 3 (KERN_ERR) error conditions
1738 4 (KERN_WARNING) warning conditions
1739 5 (KERN_NOTICE) normal but significant condition
1740 6 (KERN_INFO) informational
1741 7 (KERN_DEBUG) debug-level messages
1743 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1744 in bytes. n must be a power of two and greater
1745 than the minimal size. The minimal size is defined
1746 by LOG_BUF_SHIFT kernel config parameter. There is
1747 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1748 that allows to increase the default size depending on
1749 the number of CPUs. See init/Kconfig for more details.
1751 logo.nologo [FB] Disables display of the built-in Linux logo.
1752 This may be used to provide more screen space for
1753 kernel log messages and is useful when debugging
1754 kernel boot problems.
1756 lp=0 [LP] Specify parallel ports to use, e.g,
1757 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1758 lp=reset first parallel port). 'lp=0' disables the
1759 lp=auto printer driver. 'lp=reset' (which can be
1760 specified in addition to the ports) causes
1761 attached printers to be reset. Using
1762 lp=port1,port2,... specifies the parallel ports
1763 to associate lp devices with, starting with
1764 lp0. A port specification may be 'none' to skip
1765 that lp device, or a parport name such as
1766 'parport0'. Specifying 'lp=auto' instead of a
1767 port specification list means that device IDs
1768 from each port should be examined, to see if
1769 an IEEE 1284-compliant printer is attached; if
1770 so, the driver will manage that printer.
1771 See also header of drivers/char/lp.c.
1774 Sets loops_per_jiffy to given constant, thus avoiding
1775 time-consuming boot-time autodetection (up to 250 ms per
1776 CPU). 0 enables autodetection (default). To determine
1777 the correct value for your kernel, boot with normal
1778 autodetection and see what value is printed. Note that
1779 on SMP systems the preset will be applied to all CPUs,
1780 which is likely to cause problems if your CPUs need
1781 significantly divergent settings. An incorrect value
1782 will cause delays in the kernel to be wrong, leading to
1783 unpredictable I/O errors and other breakage. Although
1784 unlikely, in the extreme case this might damage your
1788 Format: <io>,<irq>,<dma>
1790 machvec= [IA-64] Force the use of a particular machine-vector
1791 (machvec) in a generic kernel.
1792 Example: machvec=hpzx1_swiotlb
1794 machtype= [Loongson] Share the same kernel image file between different
1796 Example: machtype=lemote-yeeloong-2f-7inch
1798 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1799 than or equal to this physical address is ignored.
1801 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1802 should make use of. maxcpus=n : n >= 0 limits the
1803 kernel to using 'n' processors. n=0 is a special case,
1804 it is equivalent to "nosmp", which also disables
1807 max_loop= [LOOP] The number of loop block devices that get
1808 (loop.max_loop) unconditionally pre-created at init time. The default
1809 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1810 of statically allocating a predefined number, loop
1811 devices can be requested on-demand with the
1812 /dev/loop-control interface.
1814 mce [X86-32] Machine Check Exception
1816 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1818 md= [HW] RAID subsystems devices and level
1819 See Documentation/md.txt.
1822 Format: <first>,<last>
1823 Specifies range of consoles to be captured by the MDA.
1825 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1826 Amount of memory to be used when the kernel is not able
1827 to see the whole system memory or for test.
1828 [X86] Work as limiting max address. Use together
1829 with memmap= to avoid physical address space collisions.
1830 Without memmap= PCI devices could be placed at addresses
1831 belonging to unused RAM.
1833 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1837 [KNL,SH] Allow user to override the default size for
1838 per-device physically contiguous DMA buffers.
1840 memmap=exactmap [KNL,X86] Enable setting of an exact
1841 E820 memory map, as specified by the user.
1842 Such memmap=exactmap lines can be constructed based on
1843 BIOS output or other requirements. See the memmap=nn@ss
1846 memmap=nn[KMG]@ss[KMG]
1847 [KNL] Force usage of a specific region of memory.
1848 Region of memory to be used is from ss to ss+nn.
1850 memmap=nn[KMG]#ss[KMG]
1851 [KNL,ACPI] Mark specific memory as ACPI data.
1852 Region of memory to be marked is from ss to ss+nn.
1854 memmap=nn[KMG]$ss[KMG]
1855 [KNL,ACPI] Mark specific memory as reserved.
1856 Region of memory to be reserved is from ss to ss+nn.
1857 Example: Exclude memory from 0x18690000-0x1869ffff
1858 memmap=64K$0x18690000
1860 memmap=0x10000$0x18690000
1862 memory_corruption_check=0/1 [X86]
1863 Some BIOSes seem to corrupt the first 64k of
1864 memory when doing things like suspend/resume.
1865 Setting this option will scan the memory
1866 looking for corruption. Enabling this will
1867 both detect corruption and prevent the kernel
1868 from using the memory being corrupted.
1869 However, its intended as a diagnostic tool; if
1870 repeatable BIOS-originated corruption always
1871 affects the same memory, you can use memmap=
1872 to prevent the kernel from using that memory.
1874 memory_corruption_check_size=size [X86]
1875 By default it checks for corruption in the low
1876 64k, making this memory unavailable for normal
1877 use. Use this parameter to scan for
1878 corruption in more or less memory.
1880 memory_corruption_check_period=seconds [X86]
1881 By default it checks for corruption every 60
1882 seconds. Use this parameter to check at some
1883 other rate. 0 disables periodic checking.
1885 memtest= [KNL,X86] Enable memtest
1887 default : 0 <disable>
1888 Specifies the number of memtest passes to be
1889 performed. Each pass selects another test
1890 pattern from a given set of patterns. Memtest
1891 fills the memory with this pattern, validates
1892 memory contents and reserves bad memory
1893 regions that are detected.
1895 meye.*= [HW] Set MotionEye Camera parameters
1896 See Documentation/video4linux/meye.txt.
1898 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1899 Multi-Function General Purpose Timers on AMD Geode
1902 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1903 the BIOS has incorrectly applied a workaround. TinyBIOS
1904 version 0.98 is known to be affected, 0.99 fixes the
1905 problem by letting the user disable the workaround.
1909 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1910 physical address is ignored.
1912 mini2440= [ARM,HW,KNL]
1913 Format:[0..2][b][c][t]
1915 MINI2440 configuration specification:
1916 0 - The attached screen is the 3.5" TFT
1917 1 - The attached screen is the 7" TFT
1918 2 - The VGA Shield is attached (1024x768)
1919 Leaving out the screen size parameter will not load
1920 the TFT driver, and the framebuffer will be left
1922 b - Enable backlight. The TFT backlight pin will be
1923 linked to the kernel VESA blanking code and a GPIO
1924 LED. This parameter is not necessary when using the
1926 c - Enable the s3c camera interface.
1927 t - Reserved for enabling touchscreen support. The
1928 touchscreen support is not enabled in the mainstream
1929 kernel as of 2.6.30, a preliminary port can be found
1930 in the "bleeding edge" mini2440 support kernel at
1931 http://repo.or.cz/w/linux-2.6/mini2440.git
1934 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1935 parameter allows control of the logging verbosity for
1936 the additional memory initialisation checks. A value
1937 of 0 disables mminit logging and a level of 4 will
1938 log everything. Information is printed at KERN_DEBUG
1939 so loglevel=8 may also need to be specified.
1942 [KNL] When CONFIG_MODULE_SIG is set, this means that
1943 modules without (valid) signatures will fail to load.
1944 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1945 is always true, so this option does nothing.
1948 [MOUSE] Maximum time between finger touching and
1949 leaving touchpad surface for touch to be considered
1950 a tap and be reported as a left button click (for
1951 touchpads working in absolute mode only).
1953 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1954 reporting absolute coordinates, such as tablets
1955 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1956 reporting absolute coordinates, such as tablets
1958 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1959 is similar to kernelcore except it specifies the
1960 amount of memory used for migratable allocations.
1961 If both kernelcore and movablecore is specified,
1962 then kernelcore will be at *least* the specified
1963 value but may be more. If movablecore on its own
1964 is specified, the administrator must be careful
1965 that the amount of memory usable for all allocations
1968 movable_node [KNL,X86] Boot-time switch to enable the effects
1969 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1971 MTD_Partition= [MTD]
1972 Format: <name>,<region-number>,<size>,<offset>
1974 MTD_Region= [MTD] Format:
1975 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1978 See drivers/mtd/cmdlinepart.c.
1980 multitce=off [PPC] This parameter disables the use of the pSeries
1981 firmware feature for updating multiple TCE entries
1984 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1986 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1988 boundary - index of last SLC block on Flex-OneNAND.
1989 The remaining blocks are configured as MLC blocks.
1990 lock - Configure if Flex-OneNAND boundary should be locked.
1991 Once locked, the boundary cannot be changed.
1992 1 indicates lock status, 0 indicates unlock status.
1995 ARM/S3C2412 JIVE boot control
1997 See arch/arm/mach-s3c2412/mach-jive.c
1999 mtouchusb.raw_coordinates=
2000 [HW] Make the MicroTouch USB driver use raw coordinates
2001 ('y', default) or cooked coordinates ('n')
2003 mtrr_chunk_size=nn[KMG] [X86]
2004 used for mtrr cleanup. It is largest continuous chunk
2005 that could hold holes aka. UC entries.
2007 mtrr_gran_size=nn[KMG] [X86]
2008 Used for mtrr cleanup. It is granularity of mtrr block.
2010 Large value could prevent small alignment from
2013 mtrr_spare_reg_nr=n [X86]
2015 Range: 0,7 : spare reg number
2017 Used for mtrr cleanup. It is spare mtrr entries number.
2018 Set to 2 or more if your graphical card needs more.
2020 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2022 netdev= [NET] Network devices parameters
2023 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2024 Note that mem_start is often overloaded to mean
2025 something different and driver-specific.
2026 This usage is only documented in each driver source
2030 [NETFILTER] Enable connection tracking flow accounting
2031 0 to disable accounting
2032 1 to enable accounting
2035 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2036 See Documentation/filesystems/nfs/nfsroot.txt.
2038 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2039 See Documentation/filesystems/nfs/nfsroot.txt.
2041 nfsrootdebug [NFS] enable nfsroot debugging messages.
2042 See Documentation/filesystems/nfs/nfsroot.txt.
2044 nfs.callback_tcpport=
2045 [NFS] set the TCP port on which the NFSv4 callback
2046 channel should listen.
2049 [NFS] sets the pathname to the program which is used
2050 to update the NFS client cache entries.
2052 nfs.cache_getent_timeout=
2053 [NFS] sets the timeout after which an attempt to
2054 update a cache entry is deemed to have failed.
2056 nfs.idmap_cache_timeout=
2057 [NFS] set the maximum lifetime for idmapper cache
2061 [NFS] enable 64-bit inode numbers.
2062 If zero, the NFS client will fake up a 32-bit inode
2063 number for the readdir() and stat() syscalls instead
2064 of returning the full 64-bit number.
2065 The default is to return 64-bit inode numbers.
2067 nfs.max_session_slots=
2068 [NFSv4.1] Sets the maximum number of session slots
2069 the client will attempt to negotiate with the server.
2070 This limits the number of simultaneous RPC requests
2071 that the client can send to the NFSv4.1 server.
2072 Note that there is little point in setting this
2073 value higher than the max_tcp_slot_table_limit.
2075 nfs.nfs4_disable_idmapping=
2076 [NFSv4] When set to the default of '1', this option
2077 ensures that both the RPC level authentication
2078 scheme and the NFS level operations agree to use
2079 numeric uids/gids if the mount is using the
2080 'sec=sys' security flavour. In effect it is
2081 disabling idmapping, which can make migration from
2082 legacy NFSv2/v3 systems to NFSv4 easier.
2083 Servers that do not support this mode of operation
2084 will be autodetected by the client, and it will fall
2085 back to using the idmapper.
2086 To turn off this behaviour, set the value to '0'.
2088 [NFS4] Specify an additional fixed unique ident-
2089 ification string that NFSv4 clients can insert into
2090 their nfs_client_id4 string. This is typically a
2091 UUID that is generated at system install time.
2093 nfs.send_implementation_id =
2094 [NFSv4.1] Send client implementation identification
2095 information in exchange_id requests.
2096 If zero, no implementation identification information
2098 The default is to send the implementation identification
2101 nfs.recover_lost_locks =
2102 [NFSv4] Attempt to recover locks that were lost due
2103 to a lease timeout on the server. Please note that
2104 doing this risks data corruption, since there are
2105 no guarantees that the file will remain unchanged
2106 after the locks are lost.
2107 If you want to enable the kernel legacy behaviour of
2108 attempting to recover these locks, then set this
2110 The default parameter value of '0' causes the kernel
2111 not to attempt recovery of lost locks.
2113 nfsd.nfs4_disable_idmapping=
2114 [NFSv4] When set to the default of '1', the NFSv4
2115 server will return only numeric uids and gids to
2116 clients using auth_sys, and will accept numeric uids
2117 and gids from such clients. This is intended to ease
2118 migration from NFSv2/v3.
2120 objlayoutdriver.osd_login_prog=
2121 [NFS] [OBJLAYOUT] sets the pathname to the program which
2122 is used to automatically discover and login into new
2123 osd-targets. Please see:
2124 Documentation/filesystems/pnfs.txt for more explanations
2126 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2127 when a NMI is triggered.
2128 Format: [state][,regs][,debounce][,die]
2130 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2131 Format: [panic,][nopanic,][num]
2133 0 - turn nmi_watchdog off
2134 When panic is specified, panic when an NMI watchdog
2135 timeout occurs (or 'nopanic' to override the opposite
2137 This is useful when you use a panic=... timeout and
2138 need the box quickly up again.
2140 netpoll.carrier_timeout=
2141 [NET] Specifies amount of time (in seconds) that
2142 netpoll should wait for a carrier. By default netpoll
2145 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2146 emulation library even if a 387 maths coprocessor
2150 [HW] Never suspend the console
2151 Disable suspending of consoles during suspend and
2152 hibernate operations. Once disabled, debugging
2153 messages can reach various consoles while the rest
2154 of the system is being put to sleep (ie, while
2155 debugging driver suspend/resume hooks). This may
2156 not work reliably with all consoles, but is known
2157 to work with serial and VGA consoles.
2158 To facilitate more flexible debugging, we also add
2159 console_suspend, a printk module parameter to control
2160 it. Users could use console_suspend (usually
2161 /sys/module/printk/parameters/console_suspend) to
2162 turn on/off it dynamically.
2164 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2165 caches in the slab allocator. Saves per-node memory,
2166 but will impact performance.
2170 noapic [SMP,APIC] Tells the kernel to not make use of any
2171 IOAPICs that may be present in the system.
2173 noautogroup Disable scheduler automatic task group creation.
2175 nobats [PPC] Do not use BATs for mapping kernel lowmem
2176 on "Classic" PPC cores.
2180 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2182 nodelayacct [KNL] Disable per-task delay accounting
2184 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2186 nodsp [SH] Disable hardware DSP at boot time.
2188 noefi [X86] Disable EFI runtime services support.
2193 On X86-32 available only on PAE configured kernels.
2194 noexec=on: enable non-executable mappings (default)
2195 noexec=off: disable non-executable mappings
2198 Disable SMAP (Supervisor Mode Access Prevention)
2199 even if it is supported by processor.
2202 Disable SMEP (Supervisor Mode Execution Prevention)
2203 even if it is supported by processor.
2206 This affects only 32-bit executables.
2207 noexec32=on: enable non-executable mappings (default)
2208 read doesn't imply executable mappings
2209 noexec32=off: disable non-executable mappings
2210 read implies executable mappings
2212 nofpu [SH] Disable hardware FPU at boot time.
2214 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2215 register save and restore. The kernel will only save
2216 legacy floating-point registers on task switch.
2218 noxsave [BUGS=X86] Disables x86 extended register state save
2219 and restore using xsave. The kernel will fallback to
2220 enabling legacy floating-point and sse state.
2222 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2223 register states. The kernel will fall back to use
2224 xsave to save the states. By using this parameter,
2225 performance of saving the states is degraded because
2226 xsave doesn't support modified optimization while
2227 xsaveopt supports it on xsaveopt enabled systems.
2229 noxsaves [X86] Disables xsaves and xrstors used in saving and
2230 restoring x86 extended register state in compacted
2231 form of xsave area. The kernel will fall back to use
2232 xsaveopt and xrstor to save and restore the states
2233 in standard form of xsave area. By using this
2234 parameter, xsave area per process might occupy more
2235 memory on xsaves enabled systems.
2238 on enable eager fpu restore
2239 off disable eager fpu restore
2240 auto selects the default scheme, which automatically
2241 enables eagerfpu restore for xsaveopt.
2243 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2244 wfi(ARM) instruction doesn't work correctly and not to
2245 use it. This is also useful when using JTAG debugger.
2247 no_file_caps Tells the kernel not to honor file capabilities. The
2248 only way then for a file to be executed with privilege
2249 is to be setuid root or executed by root.
2251 nohalt [IA-64] Tells the kernel not to use the power saving
2252 function PAL_HALT_LIGHT when idle. This increases
2253 power-consumption. On the positive side, it reduces
2254 interrupt wake-up latency, which may improve performance
2255 in certain environments such as networked servers or
2258 nohibernate [HIBERNATION] Disable hibernation and resume.
2260 nohz= [KNL] Boottime enable/disable dynamic ticks
2261 Valid arguments: on, off
2264 nohz_full= [KNL,BOOT]
2265 In kernels built with CONFIG_NO_HZ_FULL=y, set
2266 the specified list of CPUs whose tick will be stopped
2267 whenever possible. The boot CPU will be forced outside
2268 the range to maintain the timekeeping.
2269 The CPUs in this range must also be included in the
2272 noiotrap [SH] Disables trapped I/O port accesses.
2274 noirqdebug [X86-32] Disables the code which attempts to detect and
2275 disable unhandled interrupt sources.
2277 no_timer_check [X86,APIC] Disables the code which tests for
2278 broken timer IRQ sources.
2280 noisapnp [ISAPNP] Disables ISA PnP code.
2282 noinitrd [RAM] Tells the kernel not to load any configured
2285 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2287 [Deprecated - use intremap=off]
2291 nojitter [IA-64] Disables jitter checking for ITC timers.
2293 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2295 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2298 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2299 steal time is computed, but won't influence scheduler
2302 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2304 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2306 noltlbs [PPC] Do not use large page/tlb entries for kernel
2307 lowmem mapping on PPC40x.
2309 nomca [IA-64] Disable machine check abort handling
2311 nomce [X86-32] Machine Check Exception
2313 nomfgpt [X86-32] Disable Multi-Function General Purpose
2314 Timer usage (for AMD Geode machines).
2316 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2317 shutdown the other cpus. Instead use the REBOOT_VECTOR
2320 nomodule Disable module load
2322 nopat [X86] Disable PAT (page attribute table extension of
2323 pagetables) support.
2325 norandmaps Don't use address space randomization. Equivalent to
2326 echo 0 > /proc/sys/kernel/randomize_va_space
2328 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2330 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2331 with UP alternatives
2333 nordrand [X86] Disable kernel use of the RDRAND and
2334 RDSEED instructions even if they are supported
2335 by the processor. RDRAND and RDSEED are still
2336 available to user space applications.
2338 noresume [SWSUSP] Disables resume and restores original swap
2341 no-scroll [VGA] Disables scrollback.
2342 This is required for the Braillex ib80-piezo Braille
2343 reader made by F.H. Papenmeier (Germany).
2347 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2349 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2350 and disable the IO APIC. legacy for "maxcpus=0".
2352 nosoftlockup [KNL] Disable the soft-lockup detector.
2354 nosync [HW,M68K] Disables sync negotiation for all devices.
2356 notsc [BUGS=X86-32] Disable Time Stamp Counter
2358 nousb [USB] Disable the USB subsystem
2360 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2364 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2366 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2367 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2368 Some features depend on CPU0. Known dependencies are:
2369 1. Resume from suspend/hibernate depends on CPU0.
2370 Suspend/hibernate will fail if CPU0 is offline and you
2371 need to online CPU0 before suspend/hibernate.
2372 2. PIC interrupts also depend on CPU0. CPU0 can't be
2373 removed if a PIC interrupt is detected.
2374 It's said poweroff/reboot may depend on CPU0 on some
2375 machines although I haven't seen such issues so far
2376 after CPU0 is offline on a few tested machines.
2377 If the dependencies are under your control, you can
2378 turn on cpu0_hotplug.
2380 nptcg= [IA-64] Override max number of concurrent global TLB
2381 purges which is reported from either PAL_VM_SUMMARY or
2384 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2385 could support. nr_cpus=n : n >= 1 limits the kernel to
2386 supporting 'n' processors. Later in runtime you can not
2387 use hotplug cpu feature to put more cpu back to online.
2388 just like you compile the kernel NR_CPUS=n
2390 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2392 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2393 Allowed values are enable and disable
2395 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2396 one of ['zone', 'node', 'default'] can be specified
2397 This can be set from sysctl after boot.
2398 See Documentation/sysctl/vm.txt for details.
2400 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2401 See Documentation/debugging-via-ohci1394.txt for more
2404 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2405 Rather than timing out after 20 ms if an EC
2406 command is not properly ACKed, override the length
2407 of the timeout. We have interrupts disabled while
2408 waiting for the ACK, so if this is set too high
2409 interrupts *may* be lost!
2411 omap_mux= [OMAP] Override bootloader pin multiplexing.
2412 Format: <mux_mode0.mode_name=value>...
2413 For example, to override I2C bus2:
2414 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2416 oprofile.timer= [HW]
2417 Use timer interrupt instead of performance counters
2419 oprofile.cpu_type= Force an oprofile cpu type
2420 This might be useful if you have an older oprofile
2421 userland or if you want common events.
2422 Format: { arch_perfmon }
2423 arch_perfmon: [X86] Force use of architectural
2424 perfmon on Intel CPUs instead of the
2425 CPU specific event set.
2426 timer: [X86] Force use of architectural NMI
2427 timer mode (see also oprofile.timer
2428 for generic hr timer mode)
2429 [s390] Force legacy basic mode sampling
2430 (report cpu_type "timer")
2432 oops=panic Always panic on oopses. Default is to just kill the
2433 process, but there is a small probability of
2434 deadlocking the machine.
2435 This will also cause panics on machine check exceptions.
2436 Useful together with panic=30 to trigger a reboot.
2439 See Documentation/sound/oss/oss-parameters.txt
2441 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2442 timeout > 0: seconds before rebooting
2443 timeout = 0: wait forever
2444 timeout < 0: reboot immediately
2447 crash_kexec_post_notifiers
2448 Run kdump after running panic-notifiers and dumping
2449 kmsg. This only for the users who doubt kdump always
2450 succeeds in any situation.
2451 Note that this also increases risks of kdump failure,
2452 because some panic notifiers can make the crashed
2453 kernel more unstable.
2455 parkbd.port= [HW] Parallel port number the keyboard adapter is
2456 connected to, default is 0.
2458 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2459 0 for XT, 1 for AT (default is AT).
2462 parport= [HW,PPT] Specify parallel ports. 0 disables.
2463 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2464 Use 'auto' to force the driver to use any
2465 IRQ/DMA settings detected (the default is to
2466 ignore detected IRQ/DMA settings because of
2467 possible conflicts). You can specify the base
2468 address, IRQ, and DMA settings; IRQ and DMA
2469 should be numbers, or 'auto' (for using detected
2470 settings on that particular port), or 'nofifo'
2471 (to avoid using a FIFO even if it is detected).
2472 Parallel ports are assigned in the order they
2473 are specified on the command line, starting
2476 parport_init_mode= [HW,PPT]
2477 Configure VIA parallel port to operate in
2478 a specific mode. This is necessary on Pegasos
2479 computer where firmware has no options for setting
2480 up parallel port mode and sets it to spp.
2481 Currently this function knows 686a and 8231 chips.
2482 Format: [spp|ps2|epp|ecp|ecpepp]
2485 Halt all CPUs after the first oops has been printed for
2486 the specified number of seconds. This is to be used if
2487 your oopses keep scrolling off the screen.
2492 See header of drivers/block/paride/pcd.c.
2493 See also Documentation/blockdev/paride.txt.
2495 pci=option[,option...] [PCI] various PCI subsystem options:
2496 earlydump [X86] dump PCI config space before the kernel
2498 off [X86] don't probe for the PCI bus
2499 bios [X86-32] force use of PCI BIOS, don't access
2500 the hardware directly. Use this if your machine
2501 has a non-standard PCI host bridge.
2502 nobios [X86-32] disallow use of PCI BIOS, only direct
2503 hardware access methods are allowed. Use this
2504 if you experience crashes upon bootup and you
2505 suspect they are caused by the BIOS.
2506 conf1 [X86] Force use of PCI Configuration
2508 conf2 [X86] Force use of PCI Configuration
2510 noaer [PCIE] If the PCIEAER kernel config parameter is
2511 enabled, this kernel boot option can be used to
2512 disable the use of PCIE advanced error reporting.
2513 nodomains [PCI] Disable support for multiple PCI
2514 root domains (aka PCI segments, in ACPI-speak).
2515 nommconf [X86] Disable use of MMCONFIG for PCI
2517 check_enable_amd_mmconf [X86] check for and enable
2518 properly configured MMIO access to PCI
2519 config space on AMD family 10h CPU
2520 nomsi [MSI] If the PCI_MSI kernel config parameter is
2521 enabled, this kernel boot option can be used to
2522 disable the use of MSI interrupts system-wide.
2523 noioapicquirk [APIC] Disable all boot interrupt quirks.
2524 Safety option to keep boot IRQs enabled. This
2525 should never be necessary.
2526 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2527 primary IO-APIC for bridges that cannot disable
2528 boot IRQs. This fixes a source of spurious IRQs
2529 when the system masks IRQs.
2530 noioapicreroute [APIC] Disable workaround that uses the
2531 boot IRQ equivalent of an IRQ that connects to
2532 a chipset where boot IRQs cannot be disabled.
2533 The opposite of ioapicreroute.
2534 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2535 routing table. These calls are known to be buggy
2536 on several machines and they hang the machine
2537 when used, but on other computers it's the only
2538 way to get the interrupt routing table. Try
2539 this option if the kernel is unable to allocate
2540 IRQs or discover secondary PCI buses on your
2542 rom [X86] Assign address space to expansion ROMs.
2543 Use with caution as certain devices share
2544 address decoders between ROMs and other
2546 norom [X86] Do not assign address space to
2547 expansion ROMs that do not already have
2548 BIOS assigned address ranges.
2549 nobar [X86] Do not assign address space to the
2550 BARs that weren't assigned by the BIOS.
2551 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2552 assigned automatically to PCI devices. You can
2553 make the kernel exclude IRQs of your ISA cards
2555 pirqaddr=0xAAAAA [X86] Specify the physical address
2556 of the PIRQ table (normally generated
2557 by the BIOS) if it is outside the
2558 F0000h-100000h range.
2559 lastbus=N [X86] Scan all buses thru bus #N. Can be
2560 useful if the kernel is unable to find your
2561 secondary buses and you want to tell it
2562 explicitly which ones they are.
2563 assign-busses [X86] Always assign all PCI bus
2564 numbers ourselves, overriding
2565 whatever the firmware may have done.
2566 usepirqmask [X86] Honor the possible IRQ mask stored
2567 in the BIOS $PIR table. This is needed on
2568 some systems with broken BIOSes, notably
2569 some HP Pavilion N5400 and Omnibook XE3
2570 notebooks. This will have no effect if ACPI
2571 IRQ routing is enabled.
2572 noacpi [X86] Do not use ACPI for IRQ routing
2573 or for PCI scanning.
2574 use_crs [X86] Use PCI host bridge window information
2575 from ACPI. On BIOSes from 2008 or later, this
2576 is enabled by default. If you need to use this,
2577 please report a bug.
2578 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2579 If you need to use this, please report a bug.
2580 routeirq Do IRQ routing for all PCI devices.
2581 This is normally done in pci_enable_device(),
2582 so this option is a temporary workaround
2583 for broken drivers that don't call it.
2584 skip_isa_align [X86] do not align io start addr, so can
2585 handle more pci cards
2586 firmware [ARM] Do not re-enumerate the bus but instead
2587 just use the configuration from the
2588 bootloader. This is currently used on
2589 IXP2000 systems where the bus has to be
2590 configured a certain way for adjunct CPUs.
2591 noearly [X86] Don't do any early type 1 scanning.
2592 This might help on some broken boards which
2593 machine check when some devices' config space
2594 is read. But various workarounds are disabled
2595 and some IOMMU drivers will not work.
2596 bfsort Sort PCI devices into breadth-first order.
2597 This sorting is done to get a device
2598 order compatible with older (<= 2.4) kernels.
2599 nobfsort Don't sort PCI devices into breadth-first order.
2600 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2601 tuning and use the BIOS-configured MPS defaults.
2602 pcie_bus_safe Set every device's MPS to the largest value
2603 supported by all devices below the root complex.
2604 pcie_bus_perf Set device MPS to the largest allowable MPS
2605 based on its parent bus. Also set MRRS (Max
2606 Read Request Size) to the largest supported
2607 value (no larger than the MPS that the device
2608 or bus can support) for best performance.
2609 pcie_bus_peer2peer Set every device's MPS to 128B, which
2610 every device is guaranteed to support. This
2611 configuration allows peer-to-peer DMA between
2612 any pair of devices, possibly at the cost of
2613 reduced performance. This also guarantees
2614 that hot-added devices will work.
2615 cbiosize=nn[KMG] The fixed amount of bus space which is
2616 reserved for the CardBus bridge's IO window.
2617 The default value is 256 bytes.
2618 cbmemsize=nn[KMG] The fixed amount of bus space which is
2619 reserved for the CardBus bridge's memory
2620 window. The default value is 64 megabytes.
2623 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2624 Specifies alignment and device to reassign
2625 aligned memory resources.
2626 If <order of align> is not specified,
2627 PAGE_SIZE is used as alignment.
2628 PCI-PCI bridge can be specified, if resource
2629 windows need to be expanded.
2630 ecrc= Enable/disable PCIe ECRC (transaction layer
2631 end-to-end CRC checking).
2632 bios: Use BIOS/firmware settings. This is the
2636 hpiosize=nn[KMG] The fixed amount of bus space which is
2637 reserved for hotplug bridge's IO window.
2638 Default size is 256 bytes.
2639 hpmemsize=nn[KMG] The fixed amount of bus space which is
2640 reserved for hotplug bridge's memory window.
2641 Default size is 2 megabytes.
2642 realloc= Enable/disable reallocating PCI bridge resources
2643 if allocations done by BIOS are too small to
2644 accommodate resources required by all child
2646 off: Turn realloc off
2648 realloc same as realloc=on
2649 noari do not use PCIe ARI.
2650 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2651 only look for one device below a PCIe downstream
2654 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2657 force Enable ASPM even on devices that claim not to support it.
2658 WARNING: Forcing ASPM on may cause system lockups.
2660 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2661 nomsi Do not use MSI for PCI Express Native Hotplug (this
2662 makes all PCIe ports use INTx for hotplug services).
2664 pcie_ports= [PCIE] PCIe ports handling:
2665 auto Ask the BIOS whether or not to use native PCIe services
2666 associated with PCIe ports (PME, hot-plug, AER). Use
2667 them only if that is allowed by the BIOS.
2668 native Use native PCIe services associated with PCIe ports
2670 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2673 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2674 nomsi Do not use MSI for native PCIe PME signaling (this makes
2675 all PCIe root ports use INTx for all services).
2677 pcmv= [HW,PCMCIA] BadgePAD 4
2681 Keep all power-domains already enabled by bootloader on,
2682 even if no driver has claimed them. This is useful
2683 for debug and development, but should not be
2684 needed on a platform with proper driver support.
2687 See Documentation/blockdev/paride.txt.
2689 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2692 See arch/parisc/kernel/pdc_chassis.c
2694 percpu_alloc= Select which percpu first chunk allocator to use.
2695 Currently supported values are "embed" and "page".
2696 Archs may support subset or none of the selections.
2697 See comments in mm/percpu.c for details on each
2698 allocator. This parameter is primarily for debugging
2699 and performance comparison.
2702 See Documentation/blockdev/paride.txt.
2705 See Documentation/blockdev/paride.txt.
2707 pirq= [SMP,APIC] Manual mp-table setup
2708 See Documentation/x86/i386/IO-APIC.txt.
2710 plip= [PPT,NET] Parallel port network link
2711 Format: { parport<nr> | timid | 0 }
2712 See also Documentation/parport.txt.
2714 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2715 Override pmtimer IOPort with a hex value.
2719 Enable PNP debug messages (depends on the
2720 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2721 via /sys/module/pnp/parameters/debug. We always show
2722 current resource usage; turning this on also shows
2723 possible settings and some assignment information.
2729 { on | off | curr | res | no-curr | no-res }
2732 [ISAPNP] Exclude IRQs for the autoconfiguration
2735 [ISAPNP] Exclude DMAs for the autoconfiguration
2737 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2738 Ranges are in pairs (I/O port base and size).
2741 [ISAPNP] Exclude memory regions for the
2743 Ranges are in pairs (memory base and size).
2745 ports= [IP_VS_FTP] IPVS ftp helper module
2747 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2749 Format: <port>,<port>....
2751 print-fatal-signals=
2752 [KNL] debug: print fatal signals
2754 If enabled, warn about various signal handling
2755 related application anomalies: too many signals,
2756 too many POSIX.1 timers, fatal signals causing a
2759 If you hit the warning due to signal overflow,
2760 you might want to try "ulimit -i unlimited".
2764 printk.always_kmsg_dump=
2765 Trigger kmsg_dump for cases other than kernel oops or
2767 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2770 printk.time= Show timing data prefixed to each printk message line
2771 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2773 processor.max_cstate= [HW,ACPI]
2774 Limit processor to maximum C-state
2775 max_cstate=9 overrides any DMI blacklist limit.
2777 processor.nocst [HW,ACPI]
2778 Ignore the _CST method to determine C-states,
2779 instead using the legacy FADT method
2781 profile= [KNL] Enable kernel profiling via /proc/profile
2782 Format: [schedule,]<number>
2783 Param: "schedule" - profile schedule points.
2784 Param: <number> - step/bucket size as a power of 2 for
2785 statistical time based profiling.
2786 Param: "sleep" - profile D-state sleeping (millisecs).
2787 Requires CONFIG_SCHEDSTATS
2788 Param: "kvm" - profile VM exits.
2790 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2792 See Documentation/blockdev/ramdisk.txt.
2794 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2795 probe for; one of (bare|imps|exps|lifebook|any).
2796 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2798 psmouse.resetafter= [HW,MOUSE]
2799 Try to reset the device after so many bad packets
2802 [HW,MOUSE] Set desired mouse resolution, in dpi.
2803 psmouse.smartscroll=
2804 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2805 0 = disabled, 1 = enabled (default).
2807 pstore.backend= Specify the name of the pstore backend to use
2810 See Documentation/blockdev/paride.txt.
2813 [KNL] Number of legacy pty's. Overwrites compiled-in
2816 quiet [KNL] Disable most log messages
2821 See Documentation/md.txt.
2823 ramdisk_blocksize= [RAM]
2824 See Documentation/blockdev/ramdisk.txt.
2826 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2827 See Documentation/blockdev/ramdisk.txt.
2830 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2831 the specified list of CPUs to be no-callback CPUs.
2832 Invocation of these CPUs' RCU callbacks will
2833 be offloaded to "rcuox/N" kthreads created for
2834 that purpose, where "x" is "b" for RCU-bh, "p"
2835 for RCU-preempt, and "s" for RCU-sched, and "N"
2836 is the CPU number. This reduces OS jitter on the
2837 offloaded CPUs, which can be useful for HPC and
2838 real-time workloads. It can also improve energy
2839 efficiency for asymmetric multiprocessors.
2842 Rather than requiring that offloaded CPUs
2843 (specified by rcu_nocbs= above) explicitly
2844 awaken the corresponding "rcuoN" kthreads,
2845 make these kthreads poll for callbacks.
2846 This improves the real-time response for the
2847 offloaded CPUs by relieving them of the need to
2848 wake up the corresponding kthread, but degrades
2849 energy efficiency by requiring that the kthreads
2850 periodically wake up to do the polling.
2852 rcutree.blimit= [KNL]
2853 Set maximum number of finished RCU callbacks to
2854 process in one batch.
2856 rcutree.rcu_fanout_leaf= [KNL]
2857 Increase the number of CPUs assigned to each
2858 leaf rcu_node structure. Useful for very large
2861 rcutree.jiffies_till_sched_qs= [KNL]
2862 Set required age in jiffies for a
2863 given grace period before RCU starts
2864 soliciting quiescent-state help from
2865 rcu_note_context_switch().
2867 rcutree.jiffies_till_first_fqs= [KNL]
2868 Set delay from grace-period initialization to
2869 first attempt to force quiescent states.
2870 Units are jiffies, minimum value is zero,
2871 and maximum value is HZ.
2873 rcutree.jiffies_till_next_fqs= [KNL]
2874 Set delay between subsequent attempts to force
2875 quiescent states. Units are jiffies, minimum
2876 value is one, and maximum value is HZ.
2878 rcutree.rcu_nocb_leader_stride= [KNL]
2879 Set the number of NOCB kthread groups, which
2880 defaults to the square root of the number of
2881 CPUs. Larger numbers reduces the wakeup overhead
2882 on the per-CPU grace-period kthreads, but increases
2883 that same overhead on each group's leader.
2885 rcutree.qhimark= [KNL]
2886 Set threshold of queued RCU callbacks beyond which
2887 batch limiting is disabled.
2889 rcutree.qlowmark= [KNL]
2890 Set threshold of queued RCU callbacks below which
2891 batch limiting is re-enabled.
2893 rcutree.rcu_idle_gp_delay= [KNL]
2894 Set wakeup interval for idle CPUs that have
2895 RCU callbacks (RCU_FAST_NO_HZ=y).
2897 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2898 Set wakeup interval for idle CPUs that have
2899 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2900 Lazy RCU callbacks are those which RCU can
2901 prove do nothing more than free memory.
2903 rcutorture.fqs_duration= [KNL]
2904 Set duration of force_quiescent_state bursts.
2906 rcutorture.fqs_holdoff= [KNL]
2907 Set holdoff time within force_quiescent_state bursts.
2909 rcutorture.fqs_stutter= [KNL]
2910 Set wait time between force_quiescent_state bursts.
2912 rcutorture.gp_exp= [KNL]
2913 Use expedited update-side primitives.
2915 rcutorture.gp_normal= [KNL]
2916 Use normal (non-expedited) update-side primitives.
2917 If both gp_exp and gp_normal are set, do both.
2918 If neither gp_exp nor gp_normal are set, still
2921 rcutorture.n_barrier_cbs= [KNL]
2922 Set callbacks/threads for rcu_barrier() testing.
2924 rcutorture.nfakewriters= [KNL]
2925 Set number of concurrent RCU writers. These just
2926 stress RCU, they don't participate in the actual
2927 test, hence the "fake".
2929 rcutorture.nreaders= [KNL]
2930 Set number of RCU readers.
2932 rcutorture.object_debug= [KNL]
2933 Enable debug-object double-call_rcu() testing.
2935 rcutorture.onoff_holdoff= [KNL]
2936 Set time (s) after boot for CPU-hotplug testing.
2938 rcutorture.onoff_interval= [KNL]
2939 Set time (s) between CPU-hotplug operations, or
2940 zero to disable CPU-hotplug testing.
2942 rcutorture.rcutorture_runnable= [BOOT]
2943 Start rcutorture running at boot time.
2945 rcutorture.shuffle_interval= [KNL]
2946 Set task-shuffle interval (s). Shuffling tasks
2947 allows some CPUs to go into dyntick-idle mode
2948 during the rcutorture test.
2950 rcutorture.shutdown_secs= [KNL]
2951 Set time (s) after boot system shutdown. This
2952 is useful for hands-off automated testing.
2954 rcutorture.stall_cpu= [KNL]
2955 Duration of CPU stall (s) to test RCU CPU stall
2956 warnings, zero to disable.
2958 rcutorture.stall_cpu_holdoff= [KNL]
2959 Time to wait (s) after boot before inducing stall.
2961 rcutorture.stat_interval= [KNL]
2962 Time (s) between statistics printk()s.
2964 rcutorture.stutter= [KNL]
2965 Time (s) to stutter testing, for example, specifying
2966 five seconds causes the test to run for five seconds,
2967 wait for five seconds, and so on. This tests RCU's
2968 ability to transition abruptly to and from idle.
2970 rcutorture.test_boost= [KNL]
2971 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2972 "Maybe" means test if the RCU implementation
2973 under test support RCU priority boosting.
2975 rcutorture.test_boost_duration= [KNL]
2976 Duration (s) of each individual boost test.
2978 rcutorture.test_boost_interval= [KNL]
2979 Interval (s) between each boost test.
2981 rcutorture.test_no_idle_hz= [KNL]
2982 Test RCU's dyntick-idle handling. See also the
2983 rcutorture.shuffle_interval parameter.
2985 rcutorture.torture_type= [KNL]
2986 Specify the RCU implementation to test.
2988 rcutorture.verbose= [KNL]
2989 Enable additional printk() statements.
2991 rcupdate.rcu_expedited= [KNL]
2992 Use expedited grace-period primitives, for
2993 example, synchronize_rcu_expedited() instead
2994 of synchronize_rcu(). This reduces latency,
2995 but can increase CPU utilization, degrade
2996 real-time latency, and degrade energy efficiency.
2998 rcupdate.rcu_cpu_stall_suppress= [KNL]
2999 Suppress RCU CPU stall warning messages.
3001 rcupdate.rcu_cpu_stall_timeout= [KNL]
3002 Set timeout for RCU CPU stall warning messages.
3006 Run specified binary instead of /init from the ramdisk,
3007 used for early userspace startup. See initrd.
3010 Format (x86 or x86_64):
3011 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3013 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3015 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3016 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3017 reboot_force is either force or not specified,
3018 reboot_cpu is s[mp]#### with #### being the processor
3019 to be used for rebooting.
3022 [KNL, SMP] Set scheduler's default relax_domain_level.
3023 See Documentation/cgroups/cpusets.txt.
3025 relative_sleep_states=
3026 [SUSPEND] Use sleep state labeling where the deepest
3027 state available other than hibernation is always "mem".
3028 Format: { "0" | "1" }
3029 0 -- Traditional sleep state labels.
3030 1 -- Relative sleep state labels.
3032 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3034 reservetop= [X86-32]
3036 Reserves a hole at the top of the kernel virtual
3041 Set the amount of memory to reserve for BIOS at
3042 the bottom of the address space.
3044 reset_devices [KNL] Force drivers to reset the underlying device
3045 during initialization.
3048 Specify the partition device for software suspend
3050 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3052 resume_offset= [SWSUSP]
3053 Specify the offset from the beginning of the partition
3054 given by "resume=" at which the swap header is located,
3055 in <PAGE_SIZE> units (needed only for swap files).
3056 See Documentation/power/swsusp-and-swap-files.txt
3058 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3059 read the resume files
3061 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3062 Useful for devices that are detected asynchronously
3063 (e.g. USB and MMC devices).
3065 hibernate= [HIBERNATION]
3066 noresume Don't check if there's a hibernation image
3067 present during boot.
3068 nocompress Don't compress/decompress hibernation images.
3069 no Disable hibernation and resume.
3071 retain_initrd [RAM] Keep initrd memory after extraction
3073 rhash_entries= [KNL,NET]
3074 Set number of hash buckets for route cache
3076 ro [KNL] Mount root device read-only on boot
3078 root= [KNL] Root filesystem
3079 See name_to_dev_t comment in init/do_mounts.c.
3081 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3082 mount the root filesystem
3084 rootflags= [KNL] Set root filesystem mount option string
3086 rootfstype= [KNL] Set root filesystem type
3088 rootwait [KNL] Wait (indefinitely) for root device to show up.
3089 Useful for devices that are detected asynchronously
3090 (e.g. USB and MMC devices).
3092 rproc_mem=nn[KMG][@address]
3093 [KNL,ARM,CMA] Remoteproc physical memory block.
3094 Memory area to be used by remote processor image,
3097 rw [KNL] Mount root device read-write on boot
3099 S [KNL] Run init in single mode
3101 s390_iommu= [HW,S390]
3102 Set s390 IOTLB flushing mode
3104 With strict flushing every unmap operation will result in
3105 an IOTLB flush. Default is lazy flushing before reuse,
3109 See drivers/net/irda/sa1100_ir.c.
3111 sbni= [NET] Granch SBNI12 leased line adapter
3113 sched_debug [KNL] Enables verbose scheduler debug messages.
3115 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3116 xtime_lock contention on larger systems, and/or RCU lock
3117 contention on all systems with CONFIG_MAXSMP set.
3118 Format: { "0" | "1" }
3119 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3121 Note: increases power consumption, thus should only be
3122 enabled if running jitter sensitive (HPC/RT) workloads.
3124 security= [SECURITY] Choose a security module to enable at boot.
3125 If this boot parameter is not specified, only the first
3126 security module asking for security registration will be
3127 loaded. An invalid security module name will be treated
3128 as if no module has been chosen.
3130 selinux= [SELINUX] Disable or enable SELinux at boot time.
3131 Format: { "0" | "1" }
3132 See security/selinux/Kconfig help text.
3135 Default value is set via kernel config option.
3136 If enabled at boot time, /selinux/disable can be used
3137 later to disable prior to initial policy load.
3139 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3140 Format: { "0" | "1" }
3141 See security/apparmor/Kconfig help text
3144 Default value is set via kernel config option.
3146 serialnumber [BUGS=X86-32]
3149 Maximal number of shapers.
3151 show_msr= [x86] show boot-time MSR settings
3152 Format: { <integer> }
3153 Show boot-time (BIOS-initialized) MSR settings.
3154 The parameter means the number of CPUs to show,
3155 for example 1 means boot CPU only.
3163 Disable merging of slabs with similar size. May be
3164 necessary if there is some reason to distinguish
3165 allocs to different slabs. Debug options disable
3166 merging on their own.
3167 For more information see Documentation/vm/slub.txt.
3169 slab_max_order= [MM, SLAB]
3170 Determines the maximum allowed order for slabs.
3171 A high setting may cause OOMs due to memory
3172 fragmentation. Defaults to 1 for systems with
3173 more than 32MB of RAM, 0 otherwise.
3175 slub_debug[=options[,slabs]] [MM, SLUB]
3176 Enabling slub_debug allows one to determine the
3177 culprit if slab objects become corrupted. Enabling
3178 slub_debug can create guard zones around objects and
3179 may poison objects when not in use. Also tracks the
3180 last alloc / free. For more information see
3181 Documentation/vm/slub.txt.
3183 slub_max_order= [MM, SLUB]
3184 Determines the maximum allowed order for slabs.
3185 A high setting may cause OOMs due to memory
3186 fragmentation. For more information see
3187 Documentation/vm/slub.txt.
3189 slub_min_objects= [MM, SLUB]
3190 The minimum number of objects per slab. SLUB will
3191 increase the slab order up to slub_max_order to
3192 generate a sufficiently large slab able to contain
3193 the number of objects indicated. The higher the number
3194 of objects the smaller the overhead of tracking slabs
3195 and the less frequently locks need to be acquired.
3196 For more information see Documentation/vm/slub.txt.
3198 slub_min_order= [MM, SLUB]
3199 Determines the minimum page order for slabs. Must be
3200 lower than slub_max_order.
3201 For more information see Documentation/vm/slub.txt.
3203 slub_nomerge [MM, SLUB]
3204 Same with slab_nomerge. This is supported for legacy.
3205 See slab_nomerge for more information.
3208 Format: <io1>[,<io2>[,...,<io8>]]
3210 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3211 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3212 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3213 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3214 smsc-ircc2.ircc_irq= [HW] IRQ line
3215 smsc-ircc2.ircc_dma= [HW] DMA channel
3216 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3217 0: Toshiba Satellite 1800 (GP data pin select)
3218 1: Fast pin select (default)
3222 [KNL] Should the soft-lockup detector generate panics.
3225 softlockup_all_cpu_backtrace=
3226 [KNL] Should the soft-lockup detector generate
3227 backtraces on all cpus.
3230 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3231 See Documentation/laptops/sonypi.txt
3233 spia_io_base= [HW,MTD]
3239 Enabled the stack tracer on boot up.
3241 stacktrace_filter=[function-list]
3242 [FTRACE] Limit the functions that the stack tracer
3243 will trace at boot up. function-list is a comma separated
3244 list of functions. This list can be changed at run
3245 time by the stack_trace_filter file in the debugfs
3246 tracing directory. Note, this enables stack tracing
3247 and the stacktrace above is not needed.
3251 Set the STI (builtin display/keyboard on the HP-PARISC
3252 machines) console (graphic card) which should be used
3253 as the initial boot-console.
3254 See also comment in drivers/video/console/sticore.c.
3257 See comment in drivers/video/console/sticore.c.
3260 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3262 sunrpc.min_resvport=
3263 sunrpc.max_resvport=
3265 SunRPC servers often require that client requests
3266 originate from a privileged port (i.e. a port in the
3267 range 0 < portnr < 1024).
3268 An administrator who wishes to reserve some of these
3269 ports for other uses may adjust the range that the
3270 kernel's sunrpc client considers to be privileged
3271 using these two parameters to set the minimum and
3272 maximum port values.
3276 Control how the NFS server code allocates CPUs to
3277 service thread pools. Depending on how many NICs
3278 you have and where their interrupts are bound, this
3279 option will affect which CPUs will do NFS serving.
3280 Note: this parameter cannot be changed while the
3281 NFS server is running.
3283 auto the server chooses an appropriate mode
3284 automatically using heuristics
3285 global a single global pool contains all CPUs
3286 percpu one pool for each CPU
3287 pernode one pool for each NUMA node (equivalent
3288 to global on non-NUMA machines)
3290 sunrpc.tcp_slot_table_entries=
3291 sunrpc.udp_slot_table_entries=
3293 Sets the upper limit on the number of simultaneous
3294 RPC calls that can be sent from the client to a
3295 server. Increasing these values may allow you to
3296 improve throughput, but will also increase the
3297 amount of memory reserved for use by the client.
3300 [KNL] Enable accounting of swap in memory resource
3301 controller if no parameter or 1 is given or disable
3302 it if 0 is given (See Documentation/cgroups/memory.txt)
3304 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3305 Format: { <int> | force }
3306 <int> -- Number of I/O TLB slabs
3307 force -- force using of bounce buffers even if they
3308 wouldn't be automatically used by the kernel
3312 sysfs.deprecated=0|1 [KNL]
3313 Enable/disable old style sysfs layout for old udev
3314 on older distributions. When this option is enabled
3315 very new udev will not work anymore. When this option
3316 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3317 in older udev will not work anymore.
3318 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3319 the kernel configuration.
3321 sysrq_always_enabled
3323 Ignore sysrq setting - this boot parameter will
3324 neutralize any effect of /proc/sys/kernel/sysrq.
3325 Useful for debugging.
3329 test_suspend= [SUSPEND][,N]
3330 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3331 standby suspend) or "freeze" (for suspend type freeze)
3332 as the system sleep state during system startup with
3333 the optional capability to repeat N number of times.
3334 The system is woken from this state using a
3335 wakeup-capable RTC alarm.
3337 thash_entries= [KNL,NET]
3338 Set number of hash buckets for TCP connection
3340 thermal.act= [HW,ACPI]
3341 -1: disable all active trip points in all thermal zones
3342 <degrees C>: override all lowest active trip points
3344 thermal.crt= [HW,ACPI]
3345 -1: disable all critical trip points in all thermal zones
3346 <degrees C>: override all critical trip points
3348 thermal.nocrt= [HW,ACPI]
3349 Set to disable actions on ACPI thermal zone
3350 critical and hot trip points.
3352 thermal.off= [HW,ACPI]
3353 1: disable ACPI thermal control
3355 thermal.psv= [HW,ACPI]
3356 -1: disable all passive trip points
3357 <degrees C>: override all passive trip points to this
3360 thermal.tzp= [HW,ACPI]
3361 Specify global default ACPI thermal zone polling rate
3362 <deci-seconds>: poll all this frequency
3363 0: no polling (default)
3366 Force threading of all interrupt handlers except those
3367 marked explicitly IRQF_NO_THREAD.
3370 Enable the Transcendent memory driver if built-in.
3372 tmem.cleancache=0|1 [KNL, XEN]
3373 Default is on (1). Disable the usage of the cleancache
3374 API to send anonymous pages to the hypervisor.
3376 tmem.frontswap=0|1 [KNL, XEN]
3377 Default is on (1). Disable the usage of the frontswap
3378 API to send swap pages to the hypervisor. If disabled
3379 the selfballooning and selfshrinking are force disabled.
3381 tmem.selfballooning=0|1 [KNL, XEN]
3382 Default is on (1). Disable the driving of swap pages
3385 tmem.selfshrinking=0|1 [KNL, XEN]
3386 Default is on (1). Partial swapoff that immediately
3387 transfers pages from Xen hypervisor back to the
3388 kernel based on different criteria.
3392 Specify if the kernel should make use of the cpu
3393 topology information if the hardware supports this.
3394 The scheduler will make use of this information and
3395 e.g. base its process migration decisions on it.
3400 tpm_suspend_pcr=[HW,TPM]
3401 Format: integer pcr id
3402 Specify that at suspend time, the tpm driver
3403 should extend the specified pcr with zeros,
3404 as a workaround for some chips which fail to
3405 flush the last written pcr on TPM_SaveState.
3406 This will guarantee that all the other pcrs
3409 trace_buf_size=nn[KMG]
3410 [FTRACE] will set tracing buffer size.
3412 trace_event=[event-list]
3413 [FTRACE] Set and start specified trace events in order
3414 to facilitate early boot debugging.
3415 See also Documentation/trace/events.txt
3417 trace_options=[option-list]
3418 [FTRACE] Enable or disable tracer options at boot.
3419 The option-list is a comma delimited list of options
3420 that can be enabled or disabled just as if you were
3421 to echo the option name into
3423 /sys/kernel/debug/tracing/trace_options
3425 For example, to enable stacktrace option (to dump the
3426 stack trace of each event), add to the command line:
3428 trace_options=stacktrace
3430 See also Documentation/trace/ftrace.txt "trace options"
3434 [FTRACE] enable this option to disable tracing when a
3435 warning is hit. This turns off "tracing_on". Tracing can
3436 be enabled again by echoing '1' into the "tracing_on"
3437 file located in /sys/kernel/debug/tracing/
3439 This option is useful, as it disables the trace before
3440 the WARNING dump is called, which prevents the trace to
3441 be filled with content caused by the warning output.
3443 This option can also be set at run time via the sysctl
3444 option: kernel/traceoff_on_warning
3446 transparent_hugepage=
3448 Format: [always|madvise|never]
3449 Can be used to control the default behavior of the system
3450 with respect to transparent hugepages.
3451 See Documentation/vm/transhuge.txt for more details.
3453 tsc= Disable clocksource stability checks for TSC.
3455 [x86] reliable: mark tsc clocksource as reliable, this
3456 disables clocksource verification at runtime, as well
3457 as the stability checks done at bootup. Used to enable
3458 high-resolution timer mode on older hardware, and in
3459 virtualized environment.
3460 [x86] noirqtime: Do not use TSC to do irq accounting.
3461 Used to run time disable IRQ_TIME_ACCOUNTING on any
3462 platforms where RDTSC is slow and this accounting
3465 turbografx.map[2|3]= [HW,JOY]
3466 TurboGraFX parallel port interface
3468 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3469 See also Documentation/input/joystick-parport.txt
3471 udbg-immortal [PPC] When debugging early kernel crashes that
3472 happen after console_init() and before a proper
3473 console driver takes over, this boot options might
3474 help "seeing" what's going on.
3476 uhash_entries= [KNL,NET]
3477 Set number of hash buckets for UDP/UDP-Lite connections
3480 [USB] Ignore overcurrent events (default N).
3481 Some badly-designed motherboards generate lots of
3482 bogus events, for ports that aren't wired to
3483 anything. Set this parameter to avoid log spamming.
3484 Note that genuine overcurrent events won't be
3488 [X86] Cause panic on unknown NMI.
3490 usbcore.authorized_default=
3491 [USB] Default USB device authorization:
3492 (default -1 = authorized except for wireless USB,
3493 0 = not authorized, 1 = authorized)
3495 usbcore.autosuspend=
3496 [USB] The autosuspend time delay (in seconds) used
3497 for newly-detected USB devices (default 2). This
3498 is the time required before an idle device will be
3499 autosuspended. Devices for which the delay is set
3500 to a negative value won't be autosuspended at all.
3502 usbcore.usbfs_snoop=
3503 [USB] Set to log all usbfs traffic (default 0 = off).
3505 usbcore.blinkenlights=
3506 [USB] Set to cycle leds on hubs (default 0 = off).
3508 usbcore.old_scheme_first=
3509 [USB] Start with the old device initialization
3510 scheme (default 0 = off).
3512 usbcore.usbfs_memory_mb=
3513 [USB] Memory limit (in MB) for buffers allocated by
3514 usbfs (default = 16, 0 = max = 2047).
3516 usbcore.use_both_schemes=
3517 [USB] Try the other device initialization scheme
3518 if the first one fails (default 1 = enabled).
3520 usbcore.initial_descriptor_timeout=
3521 [USB] Specifies timeout for the initial 64-byte
3522 USB_REQ_GET_DESCRIPTOR request in milliseconds
3523 (default 5000 = 5.0 seconds).
3526 [USBHID] The interval which mice are to be polled at.
3528 usb-storage.delay_use=
3529 [UMS] The delay in seconds before a new device is
3530 scanned for Logical Units (default 5).
3533 [UMS] A list of quirks entries to supplement or
3534 override the built-in unusual_devs list. List
3535 entries are separated by commas. Each entry has
3536 the form VID:PID:Flags where VID and PID are Vendor
3537 and Product ID values (4-digit hex numbers) and
3538 Flags is a set of characters, each corresponding
3539 to a common usb-storage quirk flag as follows:
3540 a = SANE_SENSE (collect more than 18 bytes
3542 b = BAD_SENSE (don't collect more than 18
3543 bytes of sense data);
3544 c = FIX_CAPACITY (decrease the reported
3545 device capacity by one sector);
3546 d = NO_READ_DISC_INFO (don't use
3547 READ_DISC_INFO command);
3548 e = NO_READ_CAPACITY_16 (don't use
3549 READ_CAPACITY_16 command);
3550 f = NO_REPORT_OPCODES (don't use report opcodes
3552 h = CAPACITY_HEURISTICS (decrease the
3553 reported device capacity by one
3554 sector if the number is odd);
3555 i = IGNORE_DEVICE (don't bind to this
3557 l = NOT_LOCKABLE (don't try to lock and
3558 unlock ejectable media);
3559 m = MAX_SECTORS_64 (don't transfer more
3560 than 64 sectors = 32 KB at a time);
3561 n = INITIAL_READ10 (force a retry of the
3562 initial READ(10) command);
3563 o = CAPACITY_OK (accept the capacity
3564 reported by the device);
3565 p = WRITE_CACHE (the device cache is ON
3567 r = IGNORE_RESIDUE (the device reports
3568 bogus residue values);
3569 s = SINGLE_LUN (the device has only one
3571 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3572 commands, uas only);
3573 u = IGNORE_UAS (don't bind to the uas driver);
3574 w = NO_WP_DETECT (don't test whether the
3575 medium is write-protected).
3576 Example: quirks=0419:aaf5:rl,0421:0433:rc
3578 user_debug= [KNL,ARM]
3580 See arch/arm/Kconfig.debug help text.
3581 1 - undefined instruction events
3583 4 - invalid data aborts
3586 Example: user_debug=31
3589 [X86] Flags controlling user PTE allocations.
3591 nohigh = do not allocate PTE pages in
3592 HIGHMEM regardless of setting
3596 On X86_32, this is an alias for vdso32=. Otherwise:
3598 vdso=1: enable VDSO (the default)
3599 vdso=0: disable VDSO mapping
3601 vdso32= [X86] Control the 32-bit vDSO
3602 vdso32=1: enable 32-bit VDSO
3603 vdso32=0 or vdso32=2: disable 32-bit VDSO
3605 See the help text for CONFIG_COMPAT_VDSO for more
3606 details. If CONFIG_COMPAT_VDSO is set, the default is
3607 vdso32=0; otherwise, the default is vdso32=1.
3609 For compatibility with older kernels, vdso32=2 is an
3612 Try vdso32=0 if you encounter an error that says:
3613 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3616 vector=percpu: enable percpu vector domain
3618 video= [FB] Frame buffer configuration
3619 See Documentation/fb/modedb.txt.
3621 video.brightness_switch_enabled= [0,1]
3622 If set to 1, on receiving an ACPI notify event
3623 generated by hotkey, video driver will adjust brightness
3624 level and then send out the event to user space through
3625 the allocated input device; If set to 0, video driver
3626 will only send out the event without touching backlight
3631 [VMMIO] Memory mapped virtio (platform) device.
3633 <size>@<baseaddr>:<irq>[:<id>]
3635 <size> := size (can use standard suffixes
3637 <baseaddr> := physical base address
3638 <irq> := interrupt number (as passed to
3640 <id> := (optional) platform device id
3642 virtio_mmio.device=1K@0x100b0000:48:7
3644 Can be used multiple times for multiple devices.
3646 vga= [BOOT,X86-32] Select a particular video mode
3647 See Documentation/x86/boot.txt and
3648 Documentation/svga.txt.
3649 Use vga=ask for menu.
3650 This is actually a boot loader parameter; the value is
3651 passed to the kernel using a special protocol.
3653 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3654 size of <nn>. This can be used to increase the
3655 minimum size (128MB on x86). It can also be used to
3656 decrease the size and leave more room for directly
3659 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3662 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3665 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3669 Controls the behavior of vsyscalls (i.e. calls to
3670 fixed addresses of 0xffffffffff600x00 from legacy
3671 code). Most statically-linked binaries and older
3672 versions of glibc use these calls. Because these
3673 functions are at fixed addresses, they make nice
3674 targets for exploits that can control RIP.
3676 emulate [default] Vsyscalls turn into traps and are
3677 emulated reasonably safely.
3679 native Vsyscalls are native syscall instructions.
3680 This is a little bit faster than trapping
3681 and makes a few dynamic recompilers work
3682 better than they would in emulation mode.
3683 It also makes exploits much easier to write.
3685 none Vsyscalls don't work at all. This makes
3686 them quite hard to use for exploits but
3687 might break your system.
3689 vt.color= [VT] Default text color.
3690 Format: 0xYX, X = foreground, Y = background.
3691 Default: 0x07 = light gray on black.
3693 vt.cur_default= [VT] Default cursor shape.
3694 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3695 the parameters of the <Esc>[?A;B;Cc escape sequence;
3696 see VGA-softcursor.txt. Default: 2 = underline.
3698 vt.default_blu= [VT]
3699 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3700 Change the default blue palette of the console.
3701 This is a 16-member array composed of values
3704 vt.default_grn= [VT]
3705 Format: <green0>,<green1>,<green2>,...,<green15>
3706 Change the default green palette of the console.
3707 This is a 16-member array composed of values
3710 vt.default_red= [VT]
3711 Format: <red0>,<red1>,<red2>,...,<red15>
3712 Change the default red palette of the console.
3713 This is a 16-member array composed of values
3719 Set system-wide default UTF-8 mode for all tty's.
3720 Default is 1, i.e. UTF-8 mode is enabled for all
3721 newly opened terminals.
3723 vt.global_cursor_default=
3726 Set system-wide default for whether a cursor
3727 is shown on new VTs. Default is -1,
3728 i.e. cursors will be created by default unless
3729 overridden by individual drivers. 0 will hide
3730 cursors, 1 will display them.
3732 vt.italic= [VT] Default color for italic text; 0-15.
3735 vt.underline= [VT] Default color for underlined text; 0-15.
3738 watchdog timers [HW,WDT] For information on watchdog timers,
3739 see Documentation/watchdog/watchdog-parameters.txt
3740 or other driver-specific files in the
3741 Documentation/watchdog/ directory.
3743 workqueue.disable_numa
3744 By default, all work items queued to unbound
3745 workqueues are affine to the NUMA nodes they're
3746 issued on, which results in better behavior in
3747 general. If NUMA affinity needs to be disabled for
3748 whatever reason, this option can be used. Note
3749 that this also can be controlled per-workqueue for
3750 workqueues visible under /sys/bus/workqueue/.
3752 workqueue.power_efficient
3753 Per-cpu workqueues are generally preferred because
3754 they show better performance thanks to cache
3755 locality; unfortunately, per-cpu workqueues tend to
3756 be more power hungry than unbound workqueues.
3758 Enabling this makes the per-cpu workqueues which
3759 were observed to contribute significantly to power
3760 consumption unbound, leading to measurably lower
3761 power usage at the cost of small performance
3764 The default value of this parameter is determined by
3765 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3767 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3768 default x2apic cluster mode on platforms
3771 x86_intel_mid_timer= [X86-32,APBT]
3772 Choose timer option for x86 Intel MID platform.
3773 Two valid options are apbt timer only and lapic timer
3774 plus one apbt timer for broadcast timer.
3775 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3777 xen_emul_unplug= [HW,X86,XEN]
3778 Unplug Xen emulated devices
3779 Format: [unplug0,][unplug1]
3780 ide-disks -- unplug primary master IDE devices
3781 aux-ide-disks -- unplug non-primary-master IDE devices
3782 nics -- unplug network devices
3783 all -- unplug all emulated devices (NICs and IDE disks)
3784 unnecessary -- unplugging emulated devices is
3785 unnecessary even if the host did not respond to
3787 never -- do not unplug even if version check succeeds
3789 xen_nopvspin [X86,XEN]
3790 Disables the ticketlock slowpath using Xen PV
3794 Disables the PV optimizations forcing the HVM guest to
3795 run as generic HVM guest with no PV drivers.
3797 xirc2ps_cs= [NET,PCMCIA]
3799 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3801 ______________________________________________________________________
3805 Add more DRM drivers.
git.samba.org / sfrench / cifs-2.6.git / blob