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 ccw_timeout_log [S390]
575 See Documentation/s390/CommonIO for details.
577 cgroup_disable= [KNL] Disable a particular controller
578 Format: {name of the controller(s) to disable}
579 The effects of cgroup_disable=foo are:
580 - foo isn't auto-mounted if you mount all cgroups in
582 - foo isn't visible as an individually mountable
584 {Currently only "memory" controller deal with this and
585 cut the overhead, others just disable the usage. So
586 only cgroup_disable=memory is actually worthy}
588 checkreqprot [SELINUX] Set initial checkreqprot flag value.
589 Format: { "0" | "1" }
590 See security/selinux/Kconfig help text.
591 0 -- check protection applied by kernel (includes
592 any implied execute protection).
593 1 -- check protection requested by application.
594 Default value is set via a kernel config option.
595 Value can be changed at runtime via
596 /selinux/checkreqprot.
599 See Documentation/s390/CommonIO for details.
602 Keep all clocks already enabled by bootloader on,
603 even if no driver has claimed them. This is useful
604 for debug and development, but should not be
605 needed on a platform with proper driver support.
606 For more information, see Documentation/clk.txt.
608 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
610 Forces specified clocksource (if available) to be used
611 when calculating gettimeofday(). If specified
612 clocksource is not available, it defaults to PIT.
613 Format: { pit | tsc | cyclone | pmtmr }
615 clocksource= Override the default clocksource
617 Override the default clocksource and use the clocksource
618 with the name specified.
619 Some clocksource names to choose from, depending on
621 [all] jiffies (this is the base, fallback clocksource)
623 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
624 pxa_timer,timer3,32k_counter,timer0_1
626 [X86-32] pit,hpet,tsc;
627 scx200_hrt on Geode; cyclone on IBM x440
635 clearcpuid=BITNUM [X86]
636 Disable CPUID feature X for the kernel. See
637 arch/x86/include/asm/cpufeature.h for the valid bit
638 numbers. Note the Linux specific bits are not necessarily
639 stable over kernel options, but the vendor specific
641 Also note that user programs calling CPUID directly
642 or using the feature without checking anything
643 will still see it. This just prevents it from
644 being used by the kernel or shown in /proc/cpuinfo.
645 Also note the kernel might malfunction if you disable
648 cma=nn[MG]@[start[MG][-end[MG]]]
650 Sets the size of kernel global memory area for
651 contiguous memory allocations and optionally the
652 placement constraint by the physical address range of
653 memory allocations. For more information, see
654 include/linux/dma-contiguous.h
656 cmo_free_hint= [PPC] Format: { yes | no }
657 Specify whether pages are marked as being inactive
658 when they are freed. This is used in CMO environments
659 to determine OS memory pressure for page stealing by
663 coherent_pool=nn[KMG] [ARM,KNL]
664 Sets the size of memory pool for coherent, atomic dma
665 allocations, by default set to 256K.
667 code_bytes [X86] How many bytes of object code to print
672 com20020= [HW,NET] ARCnet - COM20020 chipset
674 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
676 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
680 ARCnet - COM90xx chipset (memory-mapped buffers)
681 Format: <io>[,<irq>[,<memstart>]]
683 condev= [HW,S390] console device
686 console= [KNL] Output console device and options.
688 tty<n> Use the virtual console device <n>.
692 Use the specified serial port. The options are of
693 the form "bbbbpnf", where "bbbb" is the baud rate,
694 "p" is parity ("n", "o", or "e"), "n" is number of
695 bits, and "f" is flow control ("r" for RTS or
696 omit it). Default is "9600n8".
698 See Documentation/serial-console.txt for more
700 Documentation/networking/netconsole.txt for an
703 uart[8250],io,<addr>[,options]
704 uart[8250],mmio,<addr>[,options]
705 Start an early, polled-mode console on the 8250/16550
706 UART at the specified I/O port or MMIO address,
707 switching to the matching ttyS device later. The
708 options are the same as for ttyS, above.
709 hvc<n> Use the hypervisor console device <n>. This is for
710 both Xen and PowerPC hypervisors.
712 If the device connected to the port is not a TTY but a braille
713 device, prepend "brl," before the device type, for instance
715 For now, only VisioBraille is supported.
717 consoleblank= [KNL] The console blank (screen saver) timeout in
718 seconds. Defaults to 10*60 = 10mins. A value of 0
719 disables the blank timer.
722 [KNL] Change the default value for
723 /proc/<pid>/coredump_filter.
724 See also Documentation/filesystems/proc.txt.
726 cpuidle.off=1 [CPU_IDLE]
727 disable the cpuidle sub-system
729 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
731 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
733 crashkernel=size[KMG][@offset[KMG]]
734 [KNL] Using kexec, Linux can switch to a 'crash kernel'
735 upon panic. This parameter reserves the physical
736 memory region [offset, offset + size] for that kernel
737 image. If '@offset' is omitted, then a suitable offset
738 is selected automatically. Check
739 Documentation/kdump/kdump.txt for further details.
741 crashkernel=range1:size1[,range2:size2,...][@offset]
742 [KNL] Same as above, but depends on the memory
743 in the running system. The syntax of range is
744 start-[end] where start and end are both
745 a memory unit (amount[KMG]). See also
746 Documentation/kdump/kdump.txt for an example.
748 crashkernel=size[KMG],high
749 [KNL, x86_64] range could be above 4G. Allow kernel
750 to allocate physical memory region from top, so could
751 be above 4G if system have more than 4G ram installed.
752 Otherwise memory region will be allocated below 4G, if
754 It will be ignored if crashkernel=X is specified.
755 crashkernel=size[KMG],low
756 [KNL, x86_64] range under 4G. When crashkernel=X,high
757 is passed, kernel could allocate physical memory region
758 above 4G, that cause second kernel crash on system
759 that require some amount of low memory, e.g. swiotlb
760 requires at least 64M+32K low memory. Kernel would
761 try to allocate 72M below 4G automatically.
762 This one let user to specify own low range under 4G
763 for second kernel instead.
764 0: to disable low allocation.
765 It will be ignored when crashkernel=X,high is not used
766 or memory reserved is below 4G.
771 cs89x0_media= [HW,NET]
772 Format: { rj45 | aui | bnc }
775 See header of drivers/s390/block/dasd_devmap.c.
777 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
778 (one device per port)
779 Format: <port#>,<type>
780 See also Documentation/input/joystick-parport.txt
782 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
783 time. See Documentation/dynamic-debug-howto.txt for
784 details. Deprecated, see dyndbg.
786 debug [KNL] Enable kernel debugging (events log level).
789 [KNL] verbose self-tests
791 Print debugging info while doing the locking API
793 We default to 0 (no extra messages), setting it to
794 1 will print _a lot_ more information - normally
795 only useful to kernel developers.
797 debug_objects [KNL] Enable object debugging
800 [KNL] Disable object debugging
802 debug_guardpage_minorder=
803 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
804 parameter allows control of the order of pages that will
805 be intentionally kept free (and hence protected) by the
806 buddy allocator. Bigger value increase the probability
807 of catching random memory corruption, but reduce the
808 amount of memory for normal system use. The maximum
809 possible value is MAX_ORDER/2. Setting this parameter
810 to 1 or 2 should be enough to identify most random
811 memory corruption problems caused by bugs in kernel or
812 driver code when a CPU writes to (or reads from) a
813 random memory location. Note that there exists a class
814 of memory corruptions problems caused by buggy H/W or
815 F/W or by drivers badly programing DMA (basically when
816 memory is written at bus level and the CPU MMU is
817 bypassed) which are not detectable by
818 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
819 tracking down these problems.
821 debugpat [X86] Enable PAT debugging
823 decnet.addr= [HW,NET]
824 Format: <area>[,<node>]
825 See also Documentation/networking/decnet.txt.
828 [same as hugepagesz=] The size of the default
829 HugeTLB page size. This is the size represented by
830 the legacy /proc/ hugepages APIs, used for SHM, and
831 default size when mounting hugetlbfs filesystems.
832 Defaults to the default architecture's huge page size
836 Set number of hash buckets for dentry cache.
839 See Documentation/networking/ipv6.txt.
841 disable_cpu_apicid= [X86,APIC,SMP]
843 The number of initial APIC ID for the
844 corresponding CPU to be disabled at boot,
845 mostly used for the kdump 2nd kernel to
846 disable BSP to wake up multiple CPUs without
847 causing system reset or hang due to sending
850 disable_ddw [PPC/PSERIES]
851 Disable Dynamic DMA Window support. Use this if
852 to workaround buggy firmware.
855 See Documentation/networking/ipv6.txt.
857 disable_mtrr_cleanup [X86]
858 The kernel tries to adjust MTRR layout from continuous
859 to discrete, to make X server driver able to add WB
860 entry later. This parameter disables that.
862 disable_mtrr_trim [X86, Intel and AMD only]
863 By default the kernel will trim any uncacheable
864 memory out of your available memory pool based on
865 MTRR settings. This parameter disables that behavior,
866 possibly causing your machine to run very slowly.
868 disable_timer_pin_1 [X86]
869 Disable PIN 1 of APIC timer
870 Can be useful to work around chipset bugs.
872 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
873 this option disables the debugging code at boot.
875 dma_debug_entries=<number>
876 This option allows to tune the number of preallocated
877 entries for DMA-API debugging code. One entry is
878 required per DMA-API allocation. Use this if the
879 DMA-API debugging code disables itself because the
880 architectural default is too low.
882 dma_debug_driver=<driver_name>
883 With this option the DMA-API debugging driver
884 filter feature can be enabled at boot time. Just
885 pass the driver to filter for as the parameter.
886 The filter can be disabled or changed to another
887 driver later using sysfs.
889 drm_kms_helper.edid_firmware=[<connector>:]<file>
890 Broken monitors, graphic adapters and KVMs may
891 send no or incorrect EDID data sets. This parameter
892 allows to specify an EDID data set in the
893 /lib/firmware directory that is used instead.
894 Generic built-in EDID data sets are used, if one of
895 edid/1024x768.bin, edid/1280x1024.bin,
896 edid/1680x1050.bin, or edid/1920x1080.bin is given
897 and no file with the same name exists. Details and
898 instructions how to build your own EDID data are
899 available in Documentation/EDID/HOWTO.txt. An EDID
900 data set will only be used for a particular connector,
901 if its name and a colon are prepended to the EDID
906 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
907 module.dyndbg[="val"]
908 Enable debug messages at boot time. See
909 Documentation/dynamic-debug-howto.txt for details.
911 early_ioremap_debug [KNL]
912 Enable debug messages in early_ioremap support. This
913 is useful for tracking down temporary early mappings
914 which are not unmapped.
916 earlycon= [KNL] Output early console device and options.
918 uart[8250],io,<addr>[,options]
919 uart[8250],mmio,<addr>[,options]
920 uart[8250],mmio32,<addr>[,options]
921 Start an early, polled-mode console on the 8250/16550
922 UART at the specified I/O port or MMIO address.
923 MMIO inter-register address stride is either 8-bit
924 (mmio) or 32-bit (mmio32).
925 The options are the same as for ttyS, above.
928 Start an early, polled-mode console on a pl011 serial
929 port at the specified address. The pl011 serial port
930 must already be setup and configured. Options are not
933 smh Use ARM semihosting calls for early console.
935 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
939 earlyprintk=serial[,ttySn[,baudrate]]
940 earlyprintk=serial[,0x...[,baudrate]]
941 earlyprintk=ttySn[,baudrate]
942 earlyprintk=dbgp[debugController#]
944 earlyprintk is useful when the kernel crashes before
945 the normal console is initialized. It is not enabled by
946 default because it has some cosmetic problems.
948 Append ",keep" to not disable it when the real console
951 Only one of vga, efi, serial, or usb debug port can
954 Currently only ttyS0 and ttyS1 may be specified by
955 name. Other I/O ports may be explicitly specified
956 on some architectures (x86 and arm at least) by
957 replacing ttySn with an I/O port address, like this:
958 earlyprintk=serial,0x1008,115200
959 You can find the port for a given device in
960 /proc/tty/driver/serial:
961 2: uart:ST16650V2 port:00001008 irq:18 ...
963 Interaction with the standard serial driver is not
966 The VGA and EFI output is eventually overwritten by
969 The xen output can only be used by Xen PV guests.
971 edac_report= [HW,EDAC] Control how to report EDAC event
972 Format: {"on" | "off" | "force"}
973 on: enable EDAC to report H/W event. May be overridden
974 by other higher priority error reporting module.
975 off: disable H/W event reporting through EDAC.
976 force: enforce the use of EDAC to report H/W event.
979 ekgdboc= [X86,KGDB] Allow early kernel console debugging
982 This is designed to be used in conjunction with
983 the boot argument: earlyprintk=vga
986 Format: {"off" | "on" | "skip[mbr]"}
989 Format: { "old_map" }
990 old_map [X86-64]: switch to the old ioremap-based EFI
991 runtime services mapping. 32-bit still uses this one by
994 efi_no_storage_paranoia [EFI; X86]
995 Using this parameter you can use more than 50% of
996 your efi variable storage. Use this parameter only if
997 you are really sure that your UEFI does sane gc and
998 fulfills the spec otherwise your board may brick.
1000 eisa_irq_edge= [PARISC,HW]
1001 See header of drivers/parisc/eisa.c.
1004 See comment before function elanfreq_setup() in
1005 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1008 Format: {"cfq" | "deadline" | "noop"}
1009 See Documentation/block/cfq-iosched.txt and
1010 Documentation/block/deadline-iosched.txt for details.
1012 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1013 Specifies physical address of start of kernel core
1014 image elf header and optionally the size. Generally
1015 kexec loader will pass this option to capture kernel.
1016 See Documentation/kdump/kdump.txt for details.
1018 enable_mtrr_cleanup [X86]
1019 The kernel tries to adjust MTRR layout from continuous
1020 to discrete, to make X server driver able to add WB
1021 entry later. This parameter enables that.
1023 enable_timer_pin_1 [X86]
1024 Enable PIN 1 of APIC timer
1025 Can be useful to work around chipset bugs
1026 (in particular on some ATI chipsets).
1027 The kernel tries to set a reasonable default.
1029 enforcing [SELINUX] Set initial enforcing status.
1031 See security/selinux/Kconfig help text.
1032 0 -- permissive (log only, no denials).
1033 1 -- enforcing (deny and log).
1035 Value can be changed at runtime via /selinux/enforce.
1038 Disable Error Record Serialization Table (ERST)
1041 ether= [HW,NET] Ethernet cards parameters
1042 This option is obsoleted by the "netdev=" option, which
1043 has equivalent usage. See its documentation for details.
1047 Permit 'security.evm' to be updated regardless of
1048 current integrity status.
1052 fail_make_request=[KNL]
1053 General fault injection mechanism.
1054 Format: <interval>,<probability>,<space>,<times>
1055 See also Documentation/fault-injection/.
1058 See Documentation/blockdev/floppy.txt.
1060 force_pal_cache_flush
1061 [IA-64] Avoid check_sal_cache_flush which may hang on
1062 buggy SAL_CACHE_FLUSH implementations. Using this
1063 parameter will force ia64_sal_cache_flush to call
1064 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1067 Forcefully enable Physical Address Extension (PAE).
1068 Many Pentium M systems disable PAE but may have a
1069 functionally usable PAE implementation.
1070 Warning: use of this parameter will taint the kernel
1071 and may cause unknown problems.
1074 [FTRACE] will set and start the specified tracer
1075 as early as possible in order to facilitate early
1078 ftrace_dump_on_oops[=orig_cpu]
1079 [FTRACE] will dump the trace buffers on oops.
1080 If no parameter is passed, ftrace will dump
1081 buffers of all CPUs, but if you pass orig_cpu, it will
1082 dump only the buffer of the CPU that triggered the
1085 ftrace_filter=[function-list]
1086 [FTRACE] Limit the functions traced by the function
1087 tracer at boot up. function-list is a comma separated
1088 list of functions. This list can be changed at run
1089 time by the set_ftrace_filter file in the debugfs
1092 ftrace_notrace=[function-list]
1093 [FTRACE] Do not trace the functions specified in
1094 function-list. This list can be changed at run time
1095 by the set_ftrace_notrace file in the debugfs
1098 ftrace_graph_filter=[function-list]
1099 [FTRACE] Limit the top level callers functions traced
1100 by the function graph tracer at boot up.
1101 function-list is a comma separated list of functions
1102 that can be changed at run time by the
1103 set_graph_function file in the debugfs tracing directory.
1105 ftrace_graph_notrace=[function-list]
1106 [FTRACE] Do not trace from the functions specified in
1107 function-list. This list is a comma separated list of
1108 functions that can be changed at run time by the
1109 set_graph_notrace file in the debugfs tracing directory.
1112 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1113 support via parallel port (up to 5 devices per port)
1114 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1115 See also Documentation/input/joystick-parport.txt
1119 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1123 gcov_persist= [GCOV] When non-zero (default), profiling data for
1124 kernel modules is saved and remains accessible via
1125 debugfs, even when the module is unloaded/reloaded.
1126 When zero, profiling data is discarded and associated
1127 debugfs files are removed at module unload time.
1129 gpt [EFI] Forces disk with valid GPT signature but
1130 invalid Protective MBR to be treated as GPT. If the
1131 primary GPT is corrupted, it enables the backup/alternate
1132 GPT to be used instead.
1134 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1135 the "Enable 0" bit of the configuration register.
1138 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1139 the "Enable 0" bit of the configuration register.
1142 grcan.select= [HW] Select which physical interface to use.
1145 grcan.txsize= [HW] Sets the size of the tx buffer.
1146 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1148 grcan.rxsize= [HW] Sets the size of the rx buffer.
1149 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1152 hashdist= [KNL,NUMA] Large hashes allocated during boot
1153 are distributed across NUMA nodes. Defaults on
1154 for 64-bit NUMA, off otherwise.
1155 Format: 0 | 1 (for off | on)
1157 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1159 hd= [EIDE] (E)IDE hard drive subsystem geometry
1160 Format: <cyl>,<head>,<sect>
1163 Disable Hardware Error Source Table (HEST) support;
1164 corresponding firmware-first mode error processing
1165 logic will be disabled.
1167 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1168 size of <nn>. This works even on boxes that have no
1169 highmem otherwise. This also works to reduce highmem
1170 size on bigger boxes.
1172 highres= [KNL] Enable/disable high resolution timer mode.
1173 Valid parameters: "on", "off"
1177 See Documentation/isdn/README.HiSax.
1181 hpet= [X86-32,HPET] option to control HPET usage
1182 Format: { enable (default) | disable | force |
1184 disable: disable HPET and use PIT instead
1185 force: allow force enabled of undocumented chips (ICH4,
1187 verbose: show contents of HPET registers during setup
1189 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1190 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1192 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1193 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1194 On x86-64 and powerpc, this option can be specified
1195 multiple times interleaved with hugepages= to reserve
1196 huge pages of different sizes. Valid pages sizes on
1197 x86-64 are 2M (when the CPU supports "pse") and 1G
1198 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1199 Note that 1GB pages can only be allocated at boot time
1200 using hugepages= and not freed afterwards.
1202 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1203 terminal devices. Valid values: 0..8
1204 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1205 If specified, z/VM IUCV HVC accepts connections
1206 from listed z/VM user IDs only.
1208 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1209 hardware thread id mappings.
1210 Format: <cpu>:<hwthread>
1213 Do not unregister boot console at start. This is only
1214 useful for debugging when something happens in the window
1215 between unregistering the boot console and initializing
1218 i2c_bus= [HW] Override the default board specific I2C bus speed
1219 or register an additional I2C bus that is not
1220 registered from board initialization code.
1224 i8042.debug [HW] Toggle i8042 debug mode
1225 i8042.direct [HW] Put keyboard port into non-translated mode
1226 i8042.dumbkbd [HW] Pretend that controller can only read data from
1227 keyboard and cannot control its state
1228 (Don't attempt to blink the leds)
1229 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1230 i8042.nokbd [HW] Don't check/create keyboard port
1231 i8042.noloop [HW] Disable the AUX Loopback command while probing
1233 i8042.nomux [HW] Don't check presence of an active multiplexing
1235 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1237 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1238 i8042.reset [HW] Reset the controller during init and cleanup
1239 i8042.unlock [HW] Unlock (ignore) the keylock
1243 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1244 indicates that the driver is running on unsupported
1246 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1247 does not match list of supported models.
1249 [HW] Report power status in /proc/i8k
1250 (disabled by default)
1251 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1254 i915.invert_brightness=
1255 [DRM] Invert the sense of the variable that is used to
1256 set the brightness of the panel backlight. Normally a
1257 brightness value of 0 indicates backlight switched off,
1258 and the maximum of the brightness value sets the backlight
1259 to maximum brightness. If this parameter is set to 0
1260 (default) and the machine requires it, or this parameter
1261 is set to 1, a brightness value of 0 sets the backlight
1262 to maximum brightness, and the maximum of the brightness
1263 value switches the backlight off.
1264 -1 -- never invert brightness
1265 0 -- machine default
1266 1 -- force brightness inversion
1269 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1271 ide-core.nodma= [HW] (E)IDE subsystem
1272 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1273 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1274 .cdrom .chs .ignore_cable are additional options
1275 See Documentation/ide/ide.txt.
1277 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1278 Claim all unknown PCI IDE storage controllers.
1281 Format: idle=poll, idle=halt, idle=nomwait
1282 Poll forces a polling idle loop that can slightly
1283 improve the performance of waking up a idle CPU, but
1284 will use a lot of power and make the system run hot.
1286 idle=halt: Halt is forced to be used for CPU idle.
1287 In such case C2/C3 won't be used again.
1288 idle=nomwait: Disable mwait for CPU C-states
1290 ignore_loglevel [KNL]
1291 Ignore loglevel setting - this will print /all/
1292 kernel messages to the console. Useful for debugging.
1293 We also add it as printk module parameter, so users
1294 could change it dynamically, usually by
1295 /sys/module/printk/parameters/ignore_loglevel.
1297 ihash_entries= [KNL]
1298 Set number of hash buckets for inode cache.
1300 ima_appraise= [IMA] appraise integrity measurements
1301 Format: { "off" | "enforce" | "fix" }
1304 ima_appraise_tcb [IMA]
1305 The builtin appraise policy appraises all files
1309 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1313 The list of supported hash algorithms is defined
1314 in crypto/hash_info.h.
1317 Load a policy which meets the needs of the Trusted
1318 Computing Base. This means IMA will measure all
1319 programs exec'd, files mmap'd for exec, and all files
1320 opened for read by uid=0.
1323 Select one of defined IMA measurements template formats.
1324 Formats: { "ima" | "ima-ng" }
1327 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1328 Format: <min_file_size>
1329 Set the minimal file size for using asynchronous hash.
1330 If left unspecified, ahash usage is disabled.
1332 ahash performance varies for different data sizes on
1333 different crypto accelerators. This option can be used
1334 to achieve the best performance for a particular HW.
1336 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1338 Set hashing buffer size. Default: 4k.
1340 ahash performance varies for different chunk sizes on
1341 different crypto accelerators. This option can be used
1342 to achieve best performance for particular HW.
1346 Run specified binary instead of /sbin/init as init
1349 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1350 for working out where the kernel is dying during
1353 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1354 initcall functions. Useful for debugging built-in
1355 modules and initcalls.
1357 initrd= [BOOT] Specify the location of the initial ramdisk
1359 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1362 int_pln_enable [x86] Enable power limit notification interrupt
1364 integrity_audit=[IMA]
1365 Format: { "0" | "1" }
1366 0 -- basic integrity auditing messages. (Default)
1367 1 -- additional integrity auditing messages.
1369 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1371 Enable intel iommu driver.
1373 Disable intel iommu driver.
1374 igfx_off [Default Off]
1375 By default, gfx is mapped as normal device. If a gfx
1376 device has a dedicated DMAR unit, the DMAR unit is
1377 bypassed by not enabling DMAR with this option. In
1378 this case, gfx device will use physical address for
1381 With this option iommu will not optimize to look
1382 for io virtual address below 32-bit forcing dual
1383 address cycle on pci bus for cards supporting greater
1384 than 32-bit addressing. The default is to look
1385 for translation below 32-bit and if not available
1386 then look in the higher range.
1387 strict [Default Off]
1388 With this option on every unmap_single operation will
1389 result in a hardware IOTLB flush operation as opposed
1390 to batching them for performance.
1391 sp_off [Default Off]
1392 By default, super page will be supported if Intel IOMMU
1393 has the capability. With this option, super page will
1396 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1397 0 disables intel_idle and fall back on acpi_idle.
1398 1 to 6 specify maximum depth of C-state.
1402 Do not enable intel_pstate as the default
1403 scaling driver for the supported processors
1405 intremap= [X86-64, Intel-IOMMU]
1406 on enable Interrupt Remapping (default)
1407 off disable Interrupt Remapping
1408 nosid disable Source ID checking
1410 BIOS x2APIC opt-out request will be ignored
1412 iomem= Disable strict checking of access to MMIO memory
1413 strict regions from userspace.
1430 io7= [HW] IO7 for Marvel based alpha systems
1431 See comment before marvel_specify_io7 in
1432 arch/alpha/kernel/core_marvel.c.
1434 io_delay= [X86] I/O delay method
1436 Standard port 0x80 based delay
1438 Alternate port 0xed based delay (needed on some systems)
1440 Simple two microseconds delay
1445 See Documentation/filesystems/nfs/nfsroot.txt.
1448 When an interrupt is not handled search all handlers
1449 for it. Intended to get systems with badly broken
1453 When an interrupt is not handled search all handlers
1454 for it. Also check all handlers each timer
1455 interrupt. Intended to get systems with badly broken
1459 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1461 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1463 <cpu number>,...,<cpu number>
1465 <cpu number>-<cpu number>
1466 (must be a positive range in ascending order)
1468 <cpu number>,...,<cpu number>-<cpu number>
1470 This option can be used to specify one or more CPUs
1471 to isolate from the general SMP balancing and scheduling
1472 algorithms. You can move a process onto or off an
1473 "isolated" CPU via the CPU affinity syscalls or cpuset.
1474 <cpu number> begins at 0 and the maximum value is
1475 "number of CPUs in system - 1".
1477 This option is the preferred way to isolate CPUs. The
1478 alternative -- manually setting the CPU mask of all
1479 tasks in the system -- can cause problems and
1480 suboptimal load balancer performance.
1484 ivrs_ioapic [HW,X86_64]
1485 Provide an override to the IOAPIC-ID<->DEVICE-ID
1486 mapping provided in the IVRS ACPI table. For
1487 example, to map IOAPIC-ID decimal 10 to
1488 PCI device 00:14.0 write the parameter as:
1489 ivrs_ioapic[10]=00:14.0
1491 ivrs_hpet [HW,X86_64]
1492 Provide an override to the HPET-ID<->DEVICE-ID
1493 mapping provided in the IVRS ACPI table. For
1494 example, to map HPET-ID decimal 0 to
1495 PCI device 00:14.0 write the parameter as:
1496 ivrs_hpet[0]=00:14.0
1498 js= [HW,JOY] Analog joystick
1499 See Documentation/input/joystick.txt.
1502 Enable/disable kernel and module base offset ASLR
1503 (Address Space Layout Randomization) if built into
1504 the kernel. When CONFIG_HIBERNATION is selected,
1505 kASLR is disabled by default. When kASLR is enabled,
1506 hibernation will be disabled.
1510 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1511 specifies the amount of memory usable by the kernel
1512 for non-movable allocations. The requested amount is
1513 spread evenly throughout all nodes in the system. The
1514 remaining memory in each node is used for Movable
1515 pages. In the event, a node is too small to have both
1516 kernelcore and Movable pages, kernelcore pages will
1517 take priority and other nodes will have a larger number
1518 of Movable pages. The Movable zone is used for the
1519 allocation of pages that may be reclaimed or moved
1520 by the page migration subsystem. This means that
1521 HugeTLB pages may not be allocated from this zone.
1522 Note that allocations like PTEs-from-HighMem still
1523 use the HighMem zone if it exists, and the Normal
1524 zone if it does not.
1526 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1527 Format: <Controller#>[,poll interval]
1528 The controller # is the number of the ehci usb debug
1529 port as it is probed via PCI. The poll interval is
1530 optional and is the number seconds in between
1531 each poll cycle to the debug port in case you need
1532 the functionality for interrupting the kernel with
1533 gdb or control-c on the dbgp connection. When
1534 not using this parameter you use sysrq-g to break into
1535 the kernel debugger.
1537 kgdboc= [KGDB,HW] kgdb over consoles.
1538 Requires a tty driver that supports console polling,
1539 or a supported polling keyboard driver (non-usb).
1540 Serial only format: <serial_device>[,baud]
1541 keyboard only format: kbd
1542 keyboard and serial format: kbd,<serial_device>[,baud]
1543 Optional Kernel mode setting:
1544 kms, kbd format: kms,kbd
1545 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1547 kgdbwait [KGDB] Stop kernel execution and enter the
1548 kernel debugger at the earliest opportunity.
1550 kmac= [MIPS] korina ethernet MAC address.
1551 Configure the RouterBoard 532 series on-chip
1552 Ethernet adapter MAC address.
1554 kmemleak= [KNL] Boot-time kmemleak enable/disable
1555 Valid arguments: on, off
1558 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1559 Valid arguments: 0, 1, 2
1560 kmemcheck=0 (disabled)
1561 kmemcheck=1 (enabled)
1562 kmemcheck=2 (one-shot mode)
1563 Default: 2 (one-shot mode)
1565 kstack=N [X86] Print N words from the kernel stack
1568 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1569 Default is 0 (don't ignore, but inject #GP)
1571 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1575 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1576 Default is 1 (enabled)
1578 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1580 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1582 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1583 (virtualized MMU) support on capable Intel chips.
1584 Default is 1 (enabled)
1586 kvm-intel.emulate_invalid_guest_state=
1587 [KVM,Intel] Enable emulation of invalid guest states
1588 Default is 0 (disabled)
1590 kvm-intel.flexpriority=
1591 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1592 Default is 1 (enabled)
1595 [KVM,Intel] Enable VMX nesting (nVMX).
1596 Default is 0 (disabled)
1598 kvm-intel.unrestricted_guest=
1599 [KVM,Intel] Disable unrestricted guest feature
1600 (virtualized real and unpaged mode) on capable
1601 Intel chips. Default is 1 (enabled)
1603 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1604 feature (tagged TLBs) on capable Intel chips.
1605 Default is 1 (enabled)
1611 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1614 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1615 value for LAPIC timer one-shot implementation. Default
1616 back to the programmable timer unit in the LAPIC.
1618 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1621 libata.dma= [LIBATA] DMA control
1622 libata.dma=0 Disable all PATA and SATA DMA
1623 libata.dma=1 PATA and SATA Disk DMA only
1624 libata.dma=2 ATAPI (CDROM) DMA only
1625 libata.dma=4 Compact Flash DMA only
1626 Combinations also work, so libata.dma=3 enables DMA
1627 for disks and CDROMs, but not CFs.
1629 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1630 libata.ignore_hpa=0 keep BIOS limits (default)
1631 libata.ignore_hpa=1 ignore limits, using full disk
1633 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1637 libata.force= [LIBATA] Force configurations. The format is comma
1638 separated list of "[ID:]VAL" where ID is
1639 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1640 matching port, link or device. Basically, it matches
1641 the ATA ID string printed on console by libata. If
1642 the whole ID part is omitted, the last PORT and DEVICE
1643 values are used. If ID hasn't been specified yet, the
1644 configuration applies to all ports, links and devices.
1646 If only DEVICE is omitted, the parameter applies to
1647 the port and all links and devices behind it. DEVICE
1648 number of 0 either selects the first device or the
1649 first fan-out link behind PMP device. It does not
1650 select the host link. DEVICE number of 15 selects the
1651 host link and device attached to it.
1653 The VAL specifies the configuration to force. As long
1654 as there's no ambiguity shortcut notation is allowed.
1655 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1656 The following configurations can be forced.
1658 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1659 Any ID with matching PORT is used.
1661 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1663 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1664 udma[/][16,25,33,44,66,100,133] notation is also
1667 * [no]ncq: Turn on or off NCQ.
1669 * nohrst, nosrst, norst: suppress hard, soft
1672 * rstonce: only attempt one reset during
1673 hot-unplug link recovery
1675 * dump_id: dump IDENTIFY data.
1677 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1679 * disable: Disable this device.
1681 If there are multiple matching configurations changing
1682 the same attribute, the last one is used.
1684 memblock=debug [KNL] Enable memblock debug messages.
1686 load_ramdisk= [RAM] List of ramdisks to load from floppy
1687 See Documentation/blockdev/ramdisk.txt.
1689 lockd.nlm_grace_period=P [NFS] Assign grace period.
1692 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1695 lockd.nlm_timeout=T [NFS] Assign timeout value.
1698 lockd.nlm_udpport=M [NFS] Assign UDP port.
1701 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1704 loglevel= All Kernel Messages with a loglevel smaller than the
1705 console loglevel will be printed to the console. It can
1706 also be changed with klogd or other programs. The
1707 loglevels are defined as follows:
1709 0 (KERN_EMERG) system is unusable
1710 1 (KERN_ALERT) action must be taken immediately
1711 2 (KERN_CRIT) critical conditions
1712 3 (KERN_ERR) error conditions
1713 4 (KERN_WARNING) warning conditions
1714 5 (KERN_NOTICE) normal but significant condition
1715 6 (KERN_INFO) informational
1716 7 (KERN_DEBUG) debug-level messages
1718 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1719 in bytes. n must be a power of two and greater
1720 than the minimal size. The minimal size is defined
1721 by LOG_BUF_SHIFT kernel config parameter. There is
1722 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1723 that allows to increase the default size depending on
1724 the number of CPUs. See init/Kconfig for more details.
1726 logo.nologo [FB] Disables display of the built-in Linux logo.
1727 This may be used to provide more screen space for
1728 kernel log messages and is useful when debugging
1729 kernel boot problems.
1731 lp=0 [LP] Specify parallel ports to use, e.g,
1732 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1733 lp=reset first parallel port). 'lp=0' disables the
1734 lp=auto printer driver. 'lp=reset' (which can be
1735 specified in addition to the ports) causes
1736 attached printers to be reset. Using
1737 lp=port1,port2,... specifies the parallel ports
1738 to associate lp devices with, starting with
1739 lp0. A port specification may be 'none' to skip
1740 that lp device, or a parport name such as
1741 'parport0'. Specifying 'lp=auto' instead of a
1742 port specification list means that device IDs
1743 from each port should be examined, to see if
1744 an IEEE 1284-compliant printer is attached; if
1745 so, the driver will manage that printer.
1746 See also header of drivers/char/lp.c.
1749 Sets loops_per_jiffy to given constant, thus avoiding
1750 time-consuming boot-time autodetection (up to 250 ms per
1751 CPU). 0 enables autodetection (default). To determine
1752 the correct value for your kernel, boot with normal
1753 autodetection and see what value is printed. Note that
1754 on SMP systems the preset will be applied to all CPUs,
1755 which is likely to cause problems if your CPUs need
1756 significantly divergent settings. An incorrect value
1757 will cause delays in the kernel to be wrong, leading to
1758 unpredictable I/O errors and other breakage. Although
1759 unlikely, in the extreme case this might damage your
1763 Format: <io>,<irq>,<dma>
1765 machvec= [IA-64] Force the use of a particular machine-vector
1766 (machvec) in a generic kernel.
1767 Example: machvec=hpzx1_swiotlb
1769 machtype= [Loongson] Share the same kernel image file between different
1771 Example: machtype=lemote-yeeloong-2f-7inch
1773 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1774 than or equal to this physical address is ignored.
1776 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1777 should make use of. maxcpus=n : n >= 0 limits the
1778 kernel to using 'n' processors. n=0 is a special case,
1779 it is equivalent to "nosmp", which also disables
1782 max_loop= [LOOP] The number of loop block devices that get
1783 (loop.max_loop) unconditionally pre-created at init time. The default
1784 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1785 of statically allocating a predefined number, loop
1786 devices can be requested on-demand with the
1787 /dev/loop-control interface.
1789 mce [X86-32] Machine Check Exception
1791 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1793 md= [HW] RAID subsystems devices and level
1794 See Documentation/md.txt.
1797 Format: <first>,<last>
1798 Specifies range of consoles to be captured by the MDA.
1800 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1801 Amount of memory to be used when the kernel is not able
1802 to see the whole system memory or for test.
1803 [X86] Work as limiting max address. Use together
1804 with memmap= to avoid physical address space collisions.
1805 Without memmap= PCI devices could be placed at addresses
1806 belonging to unused RAM.
1808 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1812 [KNL,SH] Allow user to override the default size for
1813 per-device physically contiguous DMA buffers.
1815 memmap=exactmap [KNL,X86] Enable setting of an exact
1816 E820 memory map, as specified by the user.
1817 Such memmap=exactmap lines can be constructed based on
1818 BIOS output or other requirements. See the memmap=nn@ss
1821 memmap=nn[KMG]@ss[KMG]
1822 [KNL] Force usage of a specific region of memory.
1823 Region of memory to be used is from ss to ss+nn.
1825 memmap=nn[KMG]#ss[KMG]
1826 [KNL,ACPI] Mark specific memory as ACPI data.
1827 Region of memory to be marked is from ss to ss+nn.
1829 memmap=nn[KMG]$ss[KMG]
1830 [KNL,ACPI] Mark specific memory as reserved.
1831 Region of memory to be reserved is from ss to ss+nn.
1832 Example: Exclude memory from 0x18690000-0x1869ffff
1833 memmap=64K$0x18690000
1835 memmap=0x10000$0x18690000
1837 memory_corruption_check=0/1 [X86]
1838 Some BIOSes seem to corrupt the first 64k of
1839 memory when doing things like suspend/resume.
1840 Setting this option will scan the memory
1841 looking for corruption. Enabling this will
1842 both detect corruption and prevent the kernel
1843 from using the memory being corrupted.
1844 However, its intended as a diagnostic tool; if
1845 repeatable BIOS-originated corruption always
1846 affects the same memory, you can use memmap=
1847 to prevent the kernel from using that memory.
1849 memory_corruption_check_size=size [X86]
1850 By default it checks for corruption in the low
1851 64k, making this memory unavailable for normal
1852 use. Use this parameter to scan for
1853 corruption in more or less memory.
1855 memory_corruption_check_period=seconds [X86]
1856 By default it checks for corruption every 60
1857 seconds. Use this parameter to check at some
1858 other rate. 0 disables periodic checking.
1860 memtest= [KNL,X86] Enable memtest
1862 default : 0 <disable>
1863 Specifies the number of memtest passes to be
1864 performed. Each pass selects another test
1865 pattern from a given set of patterns. Memtest
1866 fills the memory with this pattern, validates
1867 memory contents and reserves bad memory
1868 regions that are detected.
1870 meye.*= [HW] Set MotionEye Camera parameters
1871 See Documentation/video4linux/meye.txt.
1873 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1874 Multi-Function General Purpose Timers on AMD Geode
1877 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1878 the BIOS has incorrectly applied a workaround. TinyBIOS
1879 version 0.98 is known to be affected, 0.99 fixes the
1880 problem by letting the user disable the workaround.
1884 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1885 physical address is ignored.
1887 mini2440= [ARM,HW,KNL]
1888 Format:[0..2][b][c][t]
1890 MINI2440 configuration specification:
1891 0 - The attached screen is the 3.5" TFT
1892 1 - The attached screen is the 7" TFT
1893 2 - The VGA Shield is attached (1024x768)
1894 Leaving out the screen size parameter will not load
1895 the TFT driver, and the framebuffer will be left
1897 b - Enable backlight. The TFT backlight pin will be
1898 linked to the kernel VESA blanking code and a GPIO
1899 LED. This parameter is not necessary when using the
1901 c - Enable the s3c camera interface.
1902 t - Reserved for enabling touchscreen support. The
1903 touchscreen support is not enabled in the mainstream
1904 kernel as of 2.6.30, a preliminary port can be found
1905 in the "bleeding edge" mini2440 support kernel at
1906 http://repo.or.cz/w/linux-2.6/mini2440.git
1909 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1910 parameter allows control of the logging verbosity for
1911 the additional memory initialisation checks. A value
1912 of 0 disables mminit logging and a level of 4 will
1913 log everything. Information is printed at KERN_DEBUG
1914 so loglevel=8 may also need to be specified.
1917 [KNL] When CONFIG_MODULE_SIG is set, this means that
1918 modules without (valid) signatures will fail to load.
1919 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1920 is always true, so this option does nothing.
1923 [MOUSE] Maximum time between finger touching and
1924 leaving touchpad surface for touch to be considered
1925 a tap and be reported as a left button click (for
1926 touchpads working in absolute mode only).
1928 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1929 reporting absolute coordinates, such as tablets
1930 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1931 reporting absolute coordinates, such as tablets
1933 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1934 is similar to kernelcore except it specifies the
1935 amount of memory used for migratable allocations.
1936 If both kernelcore and movablecore is specified,
1937 then kernelcore will be at *least* the specified
1938 value but may be more. If movablecore on its own
1939 is specified, the administrator must be careful
1940 that the amount of memory usable for all allocations
1943 movable_node [KNL,X86] Boot-time switch to enable the effects
1944 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1946 MTD_Partition= [MTD]
1947 Format: <name>,<region-number>,<size>,<offset>
1949 MTD_Region= [MTD] Format:
1950 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1953 See drivers/mtd/cmdlinepart.c.
1955 multitce=off [PPC] This parameter disables the use of the pSeries
1956 firmware feature for updating multiple TCE entries
1959 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1961 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1963 boundary - index of last SLC block on Flex-OneNAND.
1964 The remaining blocks are configured as MLC blocks.
1965 lock - Configure if Flex-OneNAND boundary should be locked.
1966 Once locked, the boundary cannot be changed.
1967 1 indicates lock status, 0 indicates unlock status.
1970 ARM/S3C2412 JIVE boot control
1972 See arch/arm/mach-s3c2412/mach-jive.c
1974 mtouchusb.raw_coordinates=
1975 [HW] Make the MicroTouch USB driver use raw coordinates
1976 ('y', default) or cooked coordinates ('n')
1978 mtrr_chunk_size=nn[KMG] [X86]
1979 used for mtrr cleanup. It is largest continuous chunk
1980 that could hold holes aka. UC entries.
1982 mtrr_gran_size=nn[KMG] [X86]
1983 Used for mtrr cleanup. It is granularity of mtrr block.
1985 Large value could prevent small alignment from
1988 mtrr_spare_reg_nr=n [X86]
1990 Range: 0,7 : spare reg number
1992 Used for mtrr cleanup. It is spare mtrr entries number.
1993 Set to 2 or more if your graphical card needs more.
1995 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1997 netdev= [NET] Network devices parameters
1998 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1999 Note that mem_start is often overloaded to mean
2000 something different and driver-specific.
2001 This usage is only documented in each driver source
2005 [NETFILTER] Enable connection tracking flow accounting
2006 0 to disable accounting
2007 1 to enable accounting
2010 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2011 See Documentation/filesystems/nfs/nfsroot.txt.
2013 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2014 See Documentation/filesystems/nfs/nfsroot.txt.
2016 nfsrootdebug [NFS] enable nfsroot debugging messages.
2017 See Documentation/filesystems/nfs/nfsroot.txt.
2019 nfs.callback_tcpport=
2020 [NFS] set the TCP port on which the NFSv4 callback
2021 channel should listen.
2024 [NFS] sets the pathname to the program which is used
2025 to update the NFS client cache entries.
2027 nfs.cache_getent_timeout=
2028 [NFS] sets the timeout after which an attempt to
2029 update a cache entry is deemed to have failed.
2031 nfs.idmap_cache_timeout=
2032 [NFS] set the maximum lifetime for idmapper cache
2036 [NFS] enable 64-bit inode numbers.
2037 If zero, the NFS client will fake up a 32-bit inode
2038 number for the readdir() and stat() syscalls instead
2039 of returning the full 64-bit number.
2040 The default is to return 64-bit inode numbers.
2042 nfs.max_session_slots=
2043 [NFSv4.1] Sets the maximum number of session slots
2044 the client will attempt to negotiate with the server.
2045 This limits the number of simultaneous RPC requests
2046 that the client can send to the NFSv4.1 server.
2047 Note that there is little point in setting this
2048 value higher than the max_tcp_slot_table_limit.
2050 nfs.nfs4_disable_idmapping=
2051 [NFSv4] When set to the default of '1', this option
2052 ensures that both the RPC level authentication
2053 scheme and the NFS level operations agree to use
2054 numeric uids/gids if the mount is using the
2055 'sec=sys' security flavour. In effect it is
2056 disabling idmapping, which can make migration from
2057 legacy NFSv2/v3 systems to NFSv4 easier.
2058 Servers that do not support this mode of operation
2059 will be autodetected by the client, and it will fall
2060 back to using the idmapper.
2061 To turn off this behaviour, set the value to '0'.
2063 [NFS4] Specify an additional fixed unique ident-
2064 ification string that NFSv4 clients can insert into
2065 their nfs_client_id4 string. This is typically a
2066 UUID that is generated at system install time.
2068 nfs.send_implementation_id =
2069 [NFSv4.1] Send client implementation identification
2070 information in exchange_id requests.
2071 If zero, no implementation identification information
2073 The default is to send the implementation identification
2076 nfs.recover_lost_locks =
2077 [NFSv4] Attempt to recover locks that were lost due
2078 to a lease timeout on the server. Please note that
2079 doing this risks data corruption, since there are
2080 no guarantees that the file will remain unchanged
2081 after the locks are lost.
2082 If you want to enable the kernel legacy behaviour of
2083 attempting to recover these locks, then set this
2085 The default parameter value of '0' causes the kernel
2086 not to attempt recovery of lost locks.
2088 nfsd.nfs4_disable_idmapping=
2089 [NFSv4] When set to the default of '1', the NFSv4
2090 server will return only numeric uids and gids to
2091 clients using auth_sys, and will accept numeric uids
2092 and gids from such clients. This is intended to ease
2093 migration from NFSv2/v3.
2095 objlayoutdriver.osd_login_prog=
2096 [NFS] [OBJLAYOUT] sets the pathname to the program which
2097 is used to automatically discover and login into new
2098 osd-targets. Please see:
2099 Documentation/filesystems/pnfs.txt for more explanations
2101 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2102 when a NMI is triggered.
2103 Format: [state][,regs][,debounce][,die]
2105 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2106 Format: [panic,][nopanic,][num]
2108 0 - turn nmi_watchdog off
2109 When panic is specified, panic when an NMI watchdog
2110 timeout occurs (or 'nopanic' to override the opposite
2112 This is useful when you use a panic=... timeout and
2113 need the box quickly up again.
2115 netpoll.carrier_timeout=
2116 [NET] Specifies amount of time (in seconds) that
2117 netpoll should wait for a carrier. By default netpoll
2120 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2121 emulation library even if a 387 maths coprocessor
2125 [HW] Never suspend the console
2126 Disable suspending of consoles during suspend and
2127 hibernate operations. Once disabled, debugging
2128 messages can reach various consoles while the rest
2129 of the system is being put to sleep (ie, while
2130 debugging driver suspend/resume hooks). This may
2131 not work reliably with all consoles, but is known
2132 to work with serial and VGA consoles.
2133 To facilitate more flexible debugging, we also add
2134 console_suspend, a printk module parameter to control
2135 it. Users could use console_suspend (usually
2136 /sys/module/printk/parameters/console_suspend) to
2137 turn on/off it dynamically.
2139 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2140 caches in the slab allocator. Saves per-node memory,
2141 but will impact performance.
2145 noapic [SMP,APIC] Tells the kernel to not make use of any
2146 IOAPICs that may be present in the system.
2148 noautogroup Disable scheduler automatic task group creation.
2150 nobats [PPC] Do not use BATs for mapping kernel lowmem
2151 on "Classic" PPC cores.
2155 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2157 nodelayacct [KNL] Disable per-task delay accounting
2159 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2161 nodsp [SH] Disable hardware DSP at boot time.
2163 noefi [X86] Disable EFI runtime services support.
2168 On X86-32 available only on PAE configured kernels.
2169 noexec=on: enable non-executable mappings (default)
2170 noexec=off: disable non-executable mappings
2173 Disable SMAP (Supervisor Mode Access Prevention)
2174 even if it is supported by processor.
2177 Disable SMEP (Supervisor Mode Execution Prevention)
2178 even if it is supported by processor.
2181 This affects only 32-bit executables.
2182 noexec32=on: enable non-executable mappings (default)
2183 read doesn't imply executable mappings
2184 noexec32=off: disable non-executable mappings
2185 read implies executable mappings
2187 nofpu [SH] Disable hardware FPU at boot time.
2189 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2190 register save and restore. The kernel will only save
2191 legacy floating-point registers on task switch.
2193 noxsave [BUGS=X86] Disables x86 extended register state save
2194 and restore using xsave. The kernel will fallback to
2195 enabling legacy floating-point and sse state.
2198 on enable eager fpu restore
2199 off disable eager fpu restore
2200 auto selects the default scheme, which automatically
2201 enables eagerfpu restore for xsaveopt.
2203 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2204 wfi(ARM) instruction doesn't work correctly and not to
2205 use it. This is also useful when using JTAG debugger.
2207 no_file_caps Tells the kernel not to honor file capabilities. The
2208 only way then for a file to be executed with privilege
2209 is to be setuid root or executed by root.
2211 nohalt [IA-64] Tells the kernel not to use the power saving
2212 function PAL_HALT_LIGHT when idle. This increases
2213 power-consumption. On the positive side, it reduces
2214 interrupt wake-up latency, which may improve performance
2215 in certain environments such as networked servers or
2218 nohibernate [HIBERNATION] Disable hibernation and resume.
2220 nohz= [KNL] Boottime enable/disable dynamic ticks
2221 Valid arguments: on, off
2224 nohz_full= [KNL,BOOT]
2225 In kernels built with CONFIG_NO_HZ_FULL=y, set
2226 the specified list of CPUs whose tick will be stopped
2227 whenever possible. The boot CPU will be forced outside
2228 the range to maintain the timekeeping.
2229 The CPUs in this range must also be included in the
2232 noiotrap [SH] Disables trapped I/O port accesses.
2234 noirqdebug [X86-32] Disables the code which attempts to detect and
2235 disable unhandled interrupt sources.
2237 no_timer_check [X86,APIC] Disables the code which tests for
2238 broken timer IRQ sources.
2240 noisapnp [ISAPNP] Disables ISA PnP code.
2242 noinitrd [RAM] Tells the kernel not to load any configured
2245 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2247 [Deprecated - use intremap=off]
2251 nojitter [IA-64] Disables jitter checking for ITC timers.
2253 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2255 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2258 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2259 steal time is computed, but won't influence scheduler
2262 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2264 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2266 noltlbs [PPC] Do not use large page/tlb entries for kernel
2267 lowmem mapping on PPC40x.
2269 nomca [IA-64] Disable machine check abort handling
2271 nomce [X86-32] Machine Check Exception
2273 nomfgpt [X86-32] Disable Multi-Function General Purpose
2274 Timer usage (for AMD Geode machines).
2276 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2277 shutdown the other cpus. Instead use the REBOOT_VECTOR
2280 nomodule Disable module load
2282 nopat [X86] Disable PAT (page attribute table extension of
2283 pagetables) support.
2285 norandmaps Don't use address space randomization. Equivalent to
2286 echo 0 > /proc/sys/kernel/randomize_va_space
2288 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2290 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2291 with UP alternatives
2293 nordrand [X86] Disable kernel use of the RDRAND and
2294 RDSEED instructions even if they are supported
2295 by the processor. RDRAND and RDSEED are still
2296 available to user space applications.
2298 noresume [SWSUSP] Disables resume and restores original swap
2301 no-scroll [VGA] Disables scrollback.
2302 This is required for the Braillex ib80-piezo Braille
2303 reader made by F.H. Papenmeier (Germany).
2307 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2309 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2310 and disable the IO APIC. legacy for "maxcpus=0".
2312 nosoftlockup [KNL] Disable the soft-lockup detector.
2314 nosync [HW,M68K] Disables sync negotiation for all devices.
2316 notsc [BUGS=X86-32] Disable Time Stamp Counter
2318 nousb [USB] Disable the USB subsystem
2320 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2324 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2326 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2327 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2328 Some features depend on CPU0. Known dependencies are:
2329 1. Resume from suspend/hibernate depends on CPU0.
2330 Suspend/hibernate will fail if CPU0 is offline and you
2331 need to online CPU0 before suspend/hibernate.
2332 2. PIC interrupts also depend on CPU0. CPU0 can't be
2333 removed if a PIC interrupt is detected.
2334 It's said poweroff/reboot may depend on CPU0 on some
2335 machines although I haven't seen such issues so far
2336 after CPU0 is offline on a few tested machines.
2337 If the dependencies are under your control, you can
2338 turn on cpu0_hotplug.
2340 nptcg= [IA-64] Override max number of concurrent global TLB
2341 purges which is reported from either PAL_VM_SUMMARY or
2344 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2345 could support. nr_cpus=n : n >= 1 limits the kernel to
2346 supporting 'n' processors. Later in runtime you can not
2347 use hotplug cpu feature to put more cpu back to online.
2348 just like you compile the kernel NR_CPUS=n
2350 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2352 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2353 Allowed values are enable and disable
2355 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2356 one of ['zone', 'node', 'default'] can be specified
2357 This can be set from sysctl after boot.
2358 See Documentation/sysctl/vm.txt for details.
2360 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2361 See Documentation/debugging-via-ohci1394.txt for more
2364 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2365 Rather than timing out after 20 ms if an EC
2366 command is not properly ACKed, override the length
2367 of the timeout. We have interrupts disabled while
2368 waiting for the ACK, so if this is set too high
2369 interrupts *may* be lost!
2371 omap_mux= [OMAP] Override bootloader pin multiplexing.
2372 Format: <mux_mode0.mode_name=value>...
2373 For example, to override I2C bus2:
2374 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2376 oprofile.timer= [HW]
2377 Use timer interrupt instead of performance counters
2379 oprofile.cpu_type= Force an oprofile cpu type
2380 This might be useful if you have an older oprofile
2381 userland or if you want common events.
2382 Format: { arch_perfmon }
2383 arch_perfmon: [X86] Force use of architectural
2384 perfmon on Intel CPUs instead of the
2385 CPU specific event set.
2386 timer: [X86] Force use of architectural NMI
2387 timer mode (see also oprofile.timer
2388 for generic hr timer mode)
2389 [s390] Force legacy basic mode sampling
2390 (report cpu_type "timer")
2392 oops=panic Always panic on oopses. Default is to just kill the
2393 process, but there is a small probability of
2394 deadlocking the machine.
2395 This will also cause panics on machine check exceptions.
2396 Useful together with panic=30 to trigger a reboot.
2399 See Documentation/sound/oss/oss-parameters.txt
2401 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2402 timeout > 0: seconds before rebooting
2403 timeout = 0: wait forever
2404 timeout < 0: reboot immediately
2407 crash_kexec_post_notifiers
2408 Run kdump after running panic-notifiers and dumping
2409 kmsg. This only for the users who doubt kdump always
2410 succeeds in any situation.
2411 Note that this also increases risks of kdump failure,
2412 because some panic notifiers can make the crashed
2413 kernel more unstable.
2415 parkbd.port= [HW] Parallel port number the keyboard adapter is
2416 connected to, default is 0.
2418 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2419 0 for XT, 1 for AT (default is AT).
2422 parport= [HW,PPT] Specify parallel ports. 0 disables.
2423 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2424 Use 'auto' to force the driver to use any
2425 IRQ/DMA settings detected (the default is to
2426 ignore detected IRQ/DMA settings because of
2427 possible conflicts). You can specify the base
2428 address, IRQ, and DMA settings; IRQ and DMA
2429 should be numbers, or 'auto' (for using detected
2430 settings on that particular port), or 'nofifo'
2431 (to avoid using a FIFO even if it is detected).
2432 Parallel ports are assigned in the order they
2433 are specified on the command line, starting
2436 parport_init_mode= [HW,PPT]
2437 Configure VIA parallel port to operate in
2438 a specific mode. This is necessary on Pegasos
2439 computer where firmware has no options for setting
2440 up parallel port mode and sets it to spp.
2441 Currently this function knows 686a and 8231 chips.
2442 Format: [spp|ps2|epp|ecp|ecpepp]
2445 Halt all CPUs after the first oops has been printed for
2446 the specified number of seconds. This is to be used if
2447 your oopses keep scrolling off the screen.
2452 See header of drivers/block/paride/pcd.c.
2453 See also Documentation/blockdev/paride.txt.
2455 pci=option[,option...] [PCI] various PCI subsystem options:
2456 earlydump [X86] dump PCI config space before the kernel
2458 off [X86] don't probe for the PCI bus
2459 bios [X86-32] force use of PCI BIOS, don't access
2460 the hardware directly. Use this if your machine
2461 has a non-standard PCI host bridge.
2462 nobios [X86-32] disallow use of PCI BIOS, only direct
2463 hardware access methods are allowed. Use this
2464 if you experience crashes upon bootup and you
2465 suspect they are caused by the BIOS.
2466 conf1 [X86] Force use of PCI Configuration
2468 conf2 [X86] Force use of PCI Configuration
2470 noaer [PCIE] If the PCIEAER kernel config parameter is
2471 enabled, this kernel boot option can be used to
2472 disable the use of PCIE advanced error reporting.
2473 nodomains [PCI] Disable support for multiple PCI
2474 root domains (aka PCI segments, in ACPI-speak).
2475 nommconf [X86] Disable use of MMCONFIG for PCI
2477 check_enable_amd_mmconf [X86] check for and enable
2478 properly configured MMIO access to PCI
2479 config space on AMD family 10h CPU
2480 nomsi [MSI] If the PCI_MSI kernel config parameter is
2481 enabled, this kernel boot option can be used to
2482 disable the use of MSI interrupts system-wide.
2483 noioapicquirk [APIC] Disable all boot interrupt quirks.
2484 Safety option to keep boot IRQs enabled. This
2485 should never be necessary.
2486 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2487 primary IO-APIC for bridges that cannot disable
2488 boot IRQs. This fixes a source of spurious IRQs
2489 when the system masks IRQs.
2490 noioapicreroute [APIC] Disable workaround that uses the
2491 boot IRQ equivalent of an IRQ that connects to
2492 a chipset where boot IRQs cannot be disabled.
2493 The opposite of ioapicreroute.
2494 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2495 routing table. These calls are known to be buggy
2496 on several machines and they hang the machine
2497 when used, but on other computers it's the only
2498 way to get the interrupt routing table. Try
2499 this option if the kernel is unable to allocate
2500 IRQs or discover secondary PCI buses on your
2502 rom [X86] Assign address space to expansion ROMs.
2503 Use with caution as certain devices share
2504 address decoders between ROMs and other
2506 norom [X86] Do not assign address space to
2507 expansion ROMs that do not already have
2508 BIOS assigned address ranges.
2509 nobar [X86] Do not assign address space to the
2510 BARs that weren't assigned by the BIOS.
2511 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2512 assigned automatically to PCI devices. You can
2513 make the kernel exclude IRQs of your ISA cards
2515 pirqaddr=0xAAAAA [X86] Specify the physical address
2516 of the PIRQ table (normally generated
2517 by the BIOS) if it is outside the
2518 F0000h-100000h range.
2519 lastbus=N [X86] Scan all buses thru bus #N. Can be
2520 useful if the kernel is unable to find your
2521 secondary buses and you want to tell it
2522 explicitly which ones they are.
2523 assign-busses [X86] Always assign all PCI bus
2524 numbers ourselves, overriding
2525 whatever the firmware may have done.
2526 usepirqmask [X86] Honor the possible IRQ mask stored
2527 in the BIOS $PIR table. This is needed on
2528 some systems with broken BIOSes, notably
2529 some HP Pavilion N5400 and Omnibook XE3
2530 notebooks. This will have no effect if ACPI
2531 IRQ routing is enabled.
2532 noacpi [X86] Do not use ACPI for IRQ routing
2533 or for PCI scanning.
2534 use_crs [X86] Use PCI host bridge window information
2535 from ACPI. On BIOSes from 2008 or later, this
2536 is enabled by default. If you need to use this,
2537 please report a bug.
2538 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2539 If you need to use this, please report a bug.
2540 routeirq Do IRQ routing for all PCI devices.
2541 This is normally done in pci_enable_device(),
2542 so this option is a temporary workaround
2543 for broken drivers that don't call it.
2544 skip_isa_align [X86] do not align io start addr, so can
2545 handle more pci cards
2546 firmware [ARM] Do not re-enumerate the bus but instead
2547 just use the configuration from the
2548 bootloader. This is currently used on
2549 IXP2000 systems where the bus has to be
2550 configured a certain way for adjunct CPUs.
2551 noearly [X86] Don't do any early type 1 scanning.
2552 This might help on some broken boards which
2553 machine check when some devices' config space
2554 is read. But various workarounds are disabled
2555 and some IOMMU drivers will not work.
2556 bfsort Sort PCI devices into breadth-first order.
2557 This sorting is done to get a device
2558 order compatible with older (<= 2.4) kernels.
2559 nobfsort Don't sort PCI devices into breadth-first order.
2560 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2561 tuning and use the BIOS-configured MPS defaults.
2562 pcie_bus_safe Set every device's MPS to the largest value
2563 supported by all devices below the root complex.
2564 pcie_bus_perf Set device MPS to the largest allowable MPS
2565 based on its parent bus. Also set MRRS (Max
2566 Read Request Size) to the largest supported
2567 value (no larger than the MPS that the device
2568 or bus can support) for best performance.
2569 pcie_bus_peer2peer Set every device's MPS to 128B, which
2570 every device is guaranteed to support. This
2571 configuration allows peer-to-peer DMA between
2572 any pair of devices, possibly at the cost of
2573 reduced performance. This also guarantees
2574 that hot-added devices will work.
2575 cbiosize=nn[KMG] The fixed amount of bus space which is
2576 reserved for the CardBus bridge's IO window.
2577 The default value is 256 bytes.
2578 cbmemsize=nn[KMG] The fixed amount of bus space which is
2579 reserved for the CardBus bridge's memory
2580 window. The default value is 64 megabytes.
2583 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2584 Specifies alignment and device to reassign
2585 aligned memory resources.
2586 If <order of align> is not specified,
2587 PAGE_SIZE is used as alignment.
2588 PCI-PCI bridge can be specified, if resource
2589 windows need to be expanded.
2590 ecrc= Enable/disable PCIe ECRC (transaction layer
2591 end-to-end CRC checking).
2592 bios: Use BIOS/firmware settings. This is the
2596 hpiosize=nn[KMG] The fixed amount of bus space which is
2597 reserved for hotplug bridge's IO window.
2598 Default size is 256 bytes.
2599 hpmemsize=nn[KMG] The fixed amount of bus space which is
2600 reserved for hotplug bridge's memory window.
2601 Default size is 2 megabytes.
2602 realloc= Enable/disable reallocating PCI bridge resources
2603 if allocations done by BIOS are too small to
2604 accommodate resources required by all child
2606 off: Turn realloc off
2608 realloc same as realloc=on
2609 noari do not use PCIe ARI.
2610 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2611 only look for one device below a PCIe downstream
2614 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2617 force Enable ASPM even on devices that claim not to support it.
2618 WARNING: Forcing ASPM on may cause system lockups.
2620 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2621 nomsi Do not use MSI for PCI Express Native Hotplug (this
2622 makes all PCIe ports use INTx for hotplug services).
2624 pcie_ports= [PCIE] PCIe ports handling:
2625 auto Ask the BIOS whether or not to use native PCIe services
2626 associated with PCIe ports (PME, hot-plug, AER). Use
2627 them only if that is allowed by the BIOS.
2628 native Use native PCIe services associated with PCIe ports
2630 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2633 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2634 nomsi Do not use MSI for native PCIe PME signaling (this makes
2635 all PCIe root ports use INTx for all services).
2637 pcmv= [HW,PCMCIA] BadgePAD 4
2641 Keep all power-domains already enabled by bootloader on,
2642 even if no driver has claimed them. This is useful
2643 for debug and development, but should not be
2644 needed on a platform with proper driver support.
2647 See Documentation/blockdev/paride.txt.
2649 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2652 See arch/parisc/kernel/pdc_chassis.c
2654 percpu_alloc= Select which percpu first chunk allocator to use.
2655 Currently supported values are "embed" and "page".
2656 Archs may support subset or none of the selections.
2657 See comments in mm/percpu.c for details on each
2658 allocator. This parameter is primarily for debugging
2659 and performance comparison.
2662 See Documentation/blockdev/paride.txt.
2665 See Documentation/blockdev/paride.txt.
2667 pirq= [SMP,APIC] Manual mp-table setup
2668 See Documentation/x86/i386/IO-APIC.txt.
2670 plip= [PPT,NET] Parallel port network link
2671 Format: { parport<nr> | timid | 0 }
2672 See also Documentation/parport.txt.
2674 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2675 Override pmtimer IOPort with a hex value.
2679 Enable PNP debug messages (depends on the
2680 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2681 via /sys/module/pnp/parameters/debug. We always show
2682 current resource usage; turning this on also shows
2683 possible settings and some assignment information.
2689 { on | off | curr | res | no-curr | no-res }
2692 [ISAPNP] Exclude IRQs for the autoconfiguration
2695 [ISAPNP] Exclude DMAs for the autoconfiguration
2697 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2698 Ranges are in pairs (I/O port base and size).
2701 [ISAPNP] Exclude memory regions for the
2703 Ranges are in pairs (memory base and size).
2705 ports= [IP_VS_FTP] IPVS ftp helper module
2707 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2709 Format: <port>,<port>....
2711 print-fatal-signals=
2712 [KNL] debug: print fatal signals
2714 If enabled, warn about various signal handling
2715 related application anomalies: too many signals,
2716 too many POSIX.1 timers, fatal signals causing a
2719 If you hit the warning due to signal overflow,
2720 you might want to try "ulimit -i unlimited".
2724 printk.always_kmsg_dump=
2725 Trigger kmsg_dump for cases other than kernel oops or
2727 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2730 printk.time= Show timing data prefixed to each printk message line
2731 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2733 processor.max_cstate= [HW,ACPI]
2734 Limit processor to maximum C-state
2735 max_cstate=9 overrides any DMI blacklist limit.
2737 processor.nocst [HW,ACPI]
2738 Ignore the _CST method to determine C-states,
2739 instead using the legacy FADT method
2741 profile= [KNL] Enable kernel profiling via /proc/profile
2742 Format: [schedule,]<number>
2743 Param: "schedule" - profile schedule points.
2744 Param: <number> - step/bucket size as a power of 2 for
2745 statistical time based profiling.
2746 Param: "sleep" - profile D-state sleeping (millisecs).
2747 Requires CONFIG_SCHEDSTATS
2748 Param: "kvm" - profile VM exits.
2750 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2752 See Documentation/blockdev/ramdisk.txt.
2754 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2755 probe for; one of (bare|imps|exps|lifebook|any).
2756 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2758 psmouse.resetafter= [HW,MOUSE]
2759 Try to reset the device after so many bad packets
2762 [HW,MOUSE] Set desired mouse resolution, in dpi.
2763 psmouse.smartscroll=
2764 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2765 0 = disabled, 1 = enabled (default).
2767 pstore.backend= Specify the name of the pstore backend to use
2770 See Documentation/blockdev/paride.txt.
2773 [KNL] Number of legacy pty's. Overwrites compiled-in
2776 quiet [KNL] Disable most log messages
2781 See Documentation/md.txt.
2783 ramdisk_blocksize= [RAM]
2784 See Documentation/blockdev/ramdisk.txt.
2786 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2787 See Documentation/blockdev/ramdisk.txt.
2790 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2791 the specified list of CPUs to be no-callback CPUs.
2792 Invocation of these CPUs' RCU callbacks will
2793 be offloaded to "rcuox/N" kthreads created for
2794 that purpose, where "x" is "b" for RCU-bh, "p"
2795 for RCU-preempt, and "s" for RCU-sched, and "N"
2796 is the CPU number. This reduces OS jitter on the
2797 offloaded CPUs, which can be useful for HPC and
2798 real-time workloads. It can also improve energy
2799 efficiency for asymmetric multiprocessors.
2802 Rather than requiring that offloaded CPUs
2803 (specified by rcu_nocbs= above) explicitly
2804 awaken the corresponding "rcuoN" kthreads,
2805 make these kthreads poll for callbacks.
2806 This improves the real-time response for the
2807 offloaded CPUs by relieving them of the need to
2808 wake up the corresponding kthread, but degrades
2809 energy efficiency by requiring that the kthreads
2810 periodically wake up to do the polling.
2812 rcutree.blimit= [KNL]
2813 Set maximum number of finished RCU callbacks to
2814 process in one batch.
2816 rcutree.rcu_fanout_leaf= [KNL]
2817 Increase the number of CPUs assigned to each
2818 leaf rcu_node structure. Useful for very large
2821 rcutree.jiffies_till_sched_qs= [KNL]
2822 Set required age in jiffies for a
2823 given grace period before RCU starts
2824 soliciting quiescent-state help from
2825 rcu_note_context_switch().
2827 rcutree.jiffies_till_first_fqs= [KNL]
2828 Set delay from grace-period initialization to
2829 first attempt to force quiescent states.
2830 Units are jiffies, minimum value is zero,
2831 and maximum value is HZ.
2833 rcutree.jiffies_till_next_fqs= [KNL]
2834 Set delay between subsequent attempts to force
2835 quiescent states. Units are jiffies, minimum
2836 value is one, and maximum value is HZ.
2838 rcutree.rcu_nocb_leader_stride= [KNL]
2839 Set the number of NOCB kthread groups, which
2840 defaults to the square root of the number of
2841 CPUs. Larger numbers reduces the wakeup overhead
2842 on the per-CPU grace-period kthreads, but increases
2843 that same overhead on each group's leader.
2845 rcutree.qhimark= [KNL]
2846 Set threshold of queued RCU callbacks beyond which
2847 batch limiting is disabled.
2849 rcutree.qlowmark= [KNL]
2850 Set threshold of queued RCU callbacks below which
2851 batch limiting is re-enabled.
2853 rcutree.rcu_idle_gp_delay= [KNL]
2854 Set wakeup interval for idle CPUs that have
2855 RCU callbacks (RCU_FAST_NO_HZ=y).
2857 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2858 Set wakeup interval for idle CPUs that have
2859 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2860 Lazy RCU callbacks are those which RCU can
2861 prove do nothing more than free memory.
2863 rcutorture.fqs_duration= [KNL]
2864 Set duration of force_quiescent_state bursts.
2866 rcutorture.fqs_holdoff= [KNL]
2867 Set holdoff time within force_quiescent_state bursts.
2869 rcutorture.fqs_stutter= [KNL]
2870 Set wait time between force_quiescent_state bursts.
2872 rcutorture.gp_exp= [KNL]
2873 Use expedited update-side primitives.
2875 rcutorture.gp_normal= [KNL]
2876 Use normal (non-expedited) update-side primitives.
2877 If both gp_exp and gp_normal are set, do both.
2878 If neither gp_exp nor gp_normal are set, still
2881 rcutorture.n_barrier_cbs= [KNL]
2882 Set callbacks/threads for rcu_barrier() testing.
2884 rcutorture.nfakewriters= [KNL]
2885 Set number of concurrent RCU writers. These just
2886 stress RCU, they don't participate in the actual
2887 test, hence the "fake".
2889 rcutorture.nreaders= [KNL]
2890 Set number of RCU readers.
2892 rcutorture.object_debug= [KNL]
2893 Enable debug-object double-call_rcu() testing.
2895 rcutorture.onoff_holdoff= [KNL]
2896 Set time (s) after boot for CPU-hotplug testing.
2898 rcutorture.onoff_interval= [KNL]
2899 Set time (s) between CPU-hotplug operations, or
2900 zero to disable CPU-hotplug testing.
2902 rcutorture.rcutorture_runnable= [BOOT]
2903 Start rcutorture running at boot time.
2905 rcutorture.shuffle_interval= [KNL]
2906 Set task-shuffle interval (s). Shuffling tasks
2907 allows some CPUs to go into dyntick-idle mode
2908 during the rcutorture test.
2910 rcutorture.shutdown_secs= [KNL]
2911 Set time (s) after boot system shutdown. This
2912 is useful for hands-off automated testing.
2914 rcutorture.stall_cpu= [KNL]
2915 Duration of CPU stall (s) to test RCU CPU stall
2916 warnings, zero to disable.
2918 rcutorture.stall_cpu_holdoff= [KNL]
2919 Time to wait (s) after boot before inducing stall.
2921 rcutorture.stat_interval= [KNL]
2922 Time (s) between statistics printk()s.
2924 rcutorture.stutter= [KNL]
2925 Time (s) to stutter testing, for example, specifying
2926 five seconds causes the test to run for five seconds,
2927 wait for five seconds, and so on. This tests RCU's
2928 ability to transition abruptly to and from idle.
2930 rcutorture.test_boost= [KNL]
2931 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2932 "Maybe" means test if the RCU implementation
2933 under test support RCU priority boosting.
2935 rcutorture.test_boost_duration= [KNL]
2936 Duration (s) of each individual boost test.
2938 rcutorture.test_boost_interval= [KNL]
2939 Interval (s) between each boost test.
2941 rcutorture.test_no_idle_hz= [KNL]
2942 Test RCU's dyntick-idle handling. See also the
2943 rcutorture.shuffle_interval parameter.
2945 rcutorture.torture_type= [KNL]
2946 Specify the RCU implementation to test.
2948 rcutorture.verbose= [KNL]
2949 Enable additional printk() statements.
2951 rcupdate.rcu_expedited= [KNL]
2952 Use expedited grace-period primitives, for
2953 example, synchronize_rcu_expedited() instead
2954 of synchronize_rcu(). This reduces latency,
2955 but can increase CPU utilization, degrade
2956 real-time latency, and degrade energy efficiency.
2958 rcupdate.rcu_cpu_stall_suppress= [KNL]
2959 Suppress RCU CPU stall warning messages.
2961 rcupdate.rcu_cpu_stall_timeout= [KNL]
2962 Set timeout for RCU CPU stall warning messages.
2966 Run specified binary instead of /init from the ramdisk,
2967 used for early userspace startup. See initrd.
2970 Format (x86 or x86_64):
2971 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2973 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2975 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2976 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2977 reboot_force is either force or not specified,
2978 reboot_cpu is s[mp]#### with #### being the processor
2979 to be used for rebooting.
2982 [KNL, SMP] Set scheduler's default relax_domain_level.
2983 See Documentation/cgroups/cpusets.txt.
2985 relative_sleep_states=
2986 [SUSPEND] Use sleep state labeling where the deepest
2987 state available other than hibernation is always "mem".
2988 Format: { "0" | "1" }
2989 0 -- Traditional sleep state labels.
2990 1 -- Relative sleep state labels.
2992 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2994 reservetop= [X86-32]
2996 Reserves a hole at the top of the kernel virtual
3001 Set the amount of memory to reserve for BIOS at
3002 the bottom of the address space.
3004 reset_devices [KNL] Force drivers to reset the underlying device
3005 during initialization.
3008 Specify the partition device for software suspend
3010 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3012 resume_offset= [SWSUSP]
3013 Specify the offset from the beginning of the partition
3014 given by "resume=" at which the swap header is located,
3015 in <PAGE_SIZE> units (needed only for swap files).
3016 See Documentation/power/swsusp-and-swap-files.txt
3018 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3019 read the resume files
3021 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3022 Useful for devices that are detected asynchronously
3023 (e.g. USB and MMC devices).
3025 hibernate= [HIBERNATION]
3026 noresume Don't check if there's a hibernation image
3027 present during boot.
3028 nocompress Don't compress/decompress hibernation images.
3029 no Disable hibernation and resume.
3031 retain_initrd [RAM] Keep initrd memory after extraction
3033 rhash_entries= [KNL,NET]
3034 Set number of hash buckets for route cache
3036 ro [KNL] Mount root device read-only on boot
3038 root= [KNL] Root filesystem
3039 See name_to_dev_t comment in init/do_mounts.c.
3041 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3042 mount the root filesystem
3044 rootflags= [KNL] Set root filesystem mount option string
3046 rootfstype= [KNL] Set root filesystem type
3048 rootwait [KNL] Wait (indefinitely) for root device to show up.
3049 Useful for devices that are detected asynchronously
3050 (e.g. USB and MMC devices).
3052 rproc_mem=nn[KMG][@address]
3053 [KNL,ARM,CMA] Remoteproc physical memory block.
3054 Memory area to be used by remote processor image,
3057 rw [KNL] Mount root device read-write on boot
3059 S [KNL] Run init in single mode
3061 s390_iommu= [HW,S390]
3062 Set s390 IOTLB flushing mode
3064 With strict flushing every unmap operation will result in
3065 an IOTLB flush. Default is lazy flushing before reuse,
3069 See drivers/net/irda/sa1100_ir.c.
3071 sbni= [NET] Granch SBNI12 leased line adapter
3073 sched_debug [KNL] Enables verbose scheduler debug messages.
3075 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3076 xtime_lock contention on larger systems, and/or RCU lock
3077 contention on all systems with CONFIG_MAXSMP set.
3078 Format: { "0" | "1" }
3079 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3081 Note: increases power consumption, thus should only be
3082 enabled if running jitter sensitive (HPC/RT) workloads.
3084 security= [SECURITY] Choose a security module to enable at boot.
3085 If this boot parameter is not specified, only the first
3086 security module asking for security registration will be
3087 loaded. An invalid security module name will be treated
3088 as if no module has been chosen.
3090 selinux= [SELINUX] Disable or enable SELinux at boot time.
3091 Format: { "0" | "1" }
3092 See security/selinux/Kconfig help text.
3095 Default value is set via kernel config option.
3096 If enabled at boot time, /selinux/disable can be used
3097 later to disable prior to initial policy load.
3099 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3100 Format: { "0" | "1" }
3101 See security/apparmor/Kconfig help text
3104 Default value is set via kernel config option.
3106 serialnumber [BUGS=X86-32]
3109 Maximal number of shapers.
3111 show_msr= [x86] show boot-time MSR settings
3112 Format: { <integer> }
3113 Show boot-time (BIOS-initialized) MSR settings.
3114 The parameter means the number of CPUs to show,
3115 for example 1 means boot CPU only.
3122 slab_max_order= [MM, SLAB]
3123 Determines the maximum allowed order for slabs.
3124 A high setting may cause OOMs due to memory
3125 fragmentation. Defaults to 1 for systems with
3126 more than 32MB of RAM, 0 otherwise.
3128 slub_debug[=options[,slabs]] [MM, SLUB]
3129 Enabling slub_debug allows one to determine the
3130 culprit if slab objects become corrupted. Enabling
3131 slub_debug can create guard zones around objects and
3132 may poison objects when not in use. Also tracks the
3133 last alloc / free. For more information see
3134 Documentation/vm/slub.txt.
3136 slub_max_order= [MM, SLUB]
3137 Determines the maximum allowed order for slabs.
3138 A high setting may cause OOMs due to memory
3139 fragmentation. For more information see
3140 Documentation/vm/slub.txt.
3142 slub_min_objects= [MM, SLUB]
3143 The minimum number of objects per slab. SLUB will
3144 increase the slab order up to slub_max_order to
3145 generate a sufficiently large slab able to contain
3146 the number of objects indicated. The higher the number
3147 of objects the smaller the overhead of tracking slabs
3148 and the less frequently locks need to be acquired.
3149 For more information see Documentation/vm/slub.txt.
3151 slub_min_order= [MM, SLUB]
3152 Determines the minimum page order for slabs. Must be
3153 lower than slub_max_order.
3154 For more information see Documentation/vm/slub.txt.
3156 slub_nomerge [MM, SLUB]
3157 Disable merging of slabs with similar size. May be
3158 necessary if there is some reason to distinguish
3159 allocs to different slabs. Debug options disable
3160 merging on their own.
3161 For more information see Documentation/vm/slub.txt.
3164 Format: <io1>[,<io2>[,...,<io8>]]
3166 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3167 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3168 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3169 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3170 smsc-ircc2.ircc_irq= [HW] IRQ line
3171 smsc-ircc2.ircc_dma= [HW] DMA channel
3172 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3173 0: Toshiba Satellite 1800 (GP data pin select)
3174 1: Fast pin select (default)
3178 [KNL] Should the soft-lockup detector generate panics.
3181 softlockup_all_cpu_backtrace=
3182 [KNL] Should the soft-lockup detector generate
3183 backtraces on all cpus.
3186 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3187 See Documentation/laptops/sonypi.txt
3189 spia_io_base= [HW,MTD]
3195 Enabled the stack tracer on boot up.
3197 stacktrace_filter=[function-list]
3198 [FTRACE] Limit the functions that the stack tracer
3199 will trace at boot up. function-list is a comma separated
3200 list of functions. This list can be changed at run
3201 time by the stack_trace_filter file in the debugfs
3202 tracing directory. Note, this enables stack tracing
3203 and the stacktrace above is not needed.
3207 Set the STI (builtin display/keyboard on the HP-PARISC
3208 machines) console (graphic card) which should be used
3209 as the initial boot-console.
3210 See also comment in drivers/video/console/sticore.c.
3213 See comment in drivers/video/console/sticore.c.
3216 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3218 sunrpc.min_resvport=
3219 sunrpc.max_resvport=
3221 SunRPC servers often require that client requests
3222 originate from a privileged port (i.e. a port in the
3223 range 0 < portnr < 1024).
3224 An administrator who wishes to reserve some of these
3225 ports for other uses may adjust the range that the
3226 kernel's sunrpc client considers to be privileged
3227 using these two parameters to set the minimum and
3228 maximum port values.
3232 Control how the NFS server code allocates CPUs to
3233 service thread pools. Depending on how many NICs
3234 you have and where their interrupts are bound, this
3235 option will affect which CPUs will do NFS serving.
3236 Note: this parameter cannot be changed while the
3237 NFS server is running.
3239 auto the server chooses an appropriate mode
3240 automatically using heuristics
3241 global a single global pool contains all CPUs
3242 percpu one pool for each CPU
3243 pernode one pool for each NUMA node (equivalent
3244 to global on non-NUMA machines)
3246 sunrpc.tcp_slot_table_entries=
3247 sunrpc.udp_slot_table_entries=
3249 Sets the upper limit on the number of simultaneous
3250 RPC calls that can be sent from the client to a
3251 server. Increasing these values may allow you to
3252 improve throughput, but will also increase the
3253 amount of memory reserved for use by the client.
3256 [KNL] Enable accounting of swap in memory resource
3257 controller if no parameter or 1 is given or disable
3258 it if 0 is given (See Documentation/cgroups/memory.txt)
3260 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3261 Format: { <int> | force }
3262 <int> -- Number of I/O TLB slabs
3263 force -- force using of bounce buffers even if they
3264 wouldn't be automatically used by the kernel
3268 sysfs.deprecated=0|1 [KNL]
3269 Enable/disable old style sysfs layout for old udev
3270 on older distributions. When this option is enabled
3271 very new udev will not work anymore. When this option
3272 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3273 in older udev will not work anymore.
3274 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3275 the kernel configuration.
3277 sysrq_always_enabled
3279 Ignore sysrq setting - this boot parameter will
3280 neutralize any effect of /proc/sys/kernel/sysrq.
3281 Useful for debugging.
3285 test_suspend= [SUSPEND]
3286 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3287 standby suspend) as the system sleep state to briefly
3288 enter during system startup. The system is woken from
3289 this state using a wakeup-capable RTC alarm.
3291 thash_entries= [KNL,NET]
3292 Set number of hash buckets for TCP connection
3294 thermal.act= [HW,ACPI]
3295 -1: disable all active trip points in all thermal zones
3296 <degrees C>: override all lowest active trip points
3298 thermal.crt= [HW,ACPI]
3299 -1: disable all critical trip points in all thermal zones
3300 <degrees C>: override all critical trip points
3302 thermal.nocrt= [HW,ACPI]
3303 Set to disable actions on ACPI thermal zone
3304 critical and hot trip points.
3306 thermal.off= [HW,ACPI]
3307 1: disable ACPI thermal control
3309 thermal.psv= [HW,ACPI]
3310 -1: disable all passive trip points
3311 <degrees C>: override all passive trip points to this
3314 thermal.tzp= [HW,ACPI]
3315 Specify global default ACPI thermal zone polling rate
3316 <deci-seconds>: poll all this frequency
3317 0: no polling (default)
3320 Force threading of all interrupt handlers except those
3321 marked explicitly IRQF_NO_THREAD.
3324 Enable the Transcendent memory driver if built-in.
3326 tmem.cleancache=0|1 [KNL, XEN]
3327 Default is on (1). Disable the usage of the cleancache
3328 API to send anonymous pages to the hypervisor.
3330 tmem.frontswap=0|1 [KNL, XEN]
3331 Default is on (1). Disable the usage of the frontswap
3332 API to send swap pages to the hypervisor. If disabled
3333 the selfballooning and selfshrinking are force disabled.
3335 tmem.selfballooning=0|1 [KNL, XEN]
3336 Default is on (1). Disable the driving of swap pages
3339 tmem.selfshrinking=0|1 [KNL, XEN]
3340 Default is on (1). Partial swapoff that immediately
3341 transfers pages from Xen hypervisor back to the
3342 kernel based on different criteria.
3346 Specify if the kernel should make use of the cpu
3347 topology information if the hardware supports this.
3348 The scheduler will make use of this information and
3349 e.g. base its process migration decisions on it.
3354 tpm_suspend_pcr=[HW,TPM]
3355 Format: integer pcr id
3356 Specify that at suspend time, the tpm driver
3357 should extend the specified pcr with zeros,
3358 as a workaround for some chips which fail to
3359 flush the last written pcr on TPM_SaveState.
3360 This will guarantee that all the other pcrs
3363 trace_buf_size=nn[KMG]
3364 [FTRACE] will set tracing buffer size.
3366 trace_event=[event-list]
3367 [FTRACE] Set and start specified trace events in order
3368 to facilitate early boot debugging.
3369 See also Documentation/trace/events.txt
3371 trace_options=[option-list]
3372 [FTRACE] Enable or disable tracer options at boot.
3373 The option-list is a comma delimited list of options
3374 that can be enabled or disabled just as if you were
3375 to echo the option name into
3377 /sys/kernel/debug/tracing/trace_options
3379 For example, to enable stacktrace option (to dump the
3380 stack trace of each event), add to the command line:
3382 trace_options=stacktrace
3384 See also Documentation/trace/ftrace.txt "trace options"
3388 [FTRACE] enable this option to disable tracing when a
3389 warning is hit. This turns off "tracing_on". Tracing can
3390 be enabled again by echoing '1' into the "tracing_on"
3391 file located in /sys/kernel/debug/tracing/
3393 This option is useful, as it disables the trace before
3394 the WARNING dump is called, which prevents the trace to
3395 be filled with content caused by the warning output.
3397 This option can also be set at run time via the sysctl
3398 option: kernel/traceoff_on_warning
3400 transparent_hugepage=
3402 Format: [always|madvise|never]
3403 Can be used to control the default behavior of the system
3404 with respect to transparent hugepages.
3405 See Documentation/vm/transhuge.txt for more details.
3407 tsc= Disable clocksource stability checks for TSC.
3409 [x86] reliable: mark tsc clocksource as reliable, this
3410 disables clocksource verification at runtime, as well
3411 as the stability checks done at bootup. Used to enable
3412 high-resolution timer mode on older hardware, and in
3413 virtualized environment.
3414 [x86] noirqtime: Do not use TSC to do irq accounting.
3415 Used to run time disable IRQ_TIME_ACCOUNTING on any
3416 platforms where RDTSC is slow and this accounting
3419 turbografx.map[2|3]= [HW,JOY]
3420 TurboGraFX parallel port interface
3422 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3423 See also Documentation/input/joystick-parport.txt
3425 udbg-immortal [PPC] When debugging early kernel crashes that
3426 happen after console_init() and before a proper
3427 console driver takes over, this boot options might
3428 help "seeing" what's going on.
3430 uhash_entries= [KNL,NET]
3431 Set number of hash buckets for UDP/UDP-Lite connections
3434 [USB] Ignore overcurrent events (default N).
3435 Some badly-designed motherboards generate lots of
3436 bogus events, for ports that aren't wired to
3437 anything. Set this parameter to avoid log spamming.
3438 Note that genuine overcurrent events won't be
3442 [X86] Cause panic on unknown NMI.
3444 usbcore.authorized_default=
3445 [USB] Default USB device authorization:
3446 (default -1 = authorized except for wireless USB,
3447 0 = not authorized, 1 = authorized)
3449 usbcore.autosuspend=
3450 [USB] The autosuspend time delay (in seconds) used
3451 for newly-detected USB devices (default 2). This
3452 is the time required before an idle device will be
3453 autosuspended. Devices for which the delay is set
3454 to a negative value won't be autosuspended at all.
3456 usbcore.usbfs_snoop=
3457 [USB] Set to log all usbfs traffic (default 0 = off).
3459 usbcore.blinkenlights=
3460 [USB] Set to cycle leds on hubs (default 0 = off).
3462 usbcore.old_scheme_first=
3463 [USB] Start with the old device initialization
3464 scheme (default 0 = off).
3466 usbcore.usbfs_memory_mb=
3467 [USB] Memory limit (in MB) for buffers allocated by
3468 usbfs (default = 16, 0 = max = 2047).
3470 usbcore.use_both_schemes=
3471 [USB] Try the other device initialization scheme
3472 if the first one fails (default 1 = enabled).
3474 usbcore.initial_descriptor_timeout=
3475 [USB] Specifies timeout for the initial 64-byte
3476 USB_REQ_GET_DESCRIPTOR request in milliseconds
3477 (default 5000 = 5.0 seconds).
3480 [USBHID] The interval which mice are to be polled at.
3482 usb-storage.delay_use=
3483 [UMS] The delay in seconds before a new device is
3484 scanned for Logical Units (default 5).
3487 [UMS] A list of quirks entries to supplement or
3488 override the built-in unusual_devs list. List
3489 entries are separated by commas. Each entry has
3490 the form VID:PID:Flags where VID and PID are Vendor
3491 and Product ID values (4-digit hex numbers) and
3492 Flags is a set of characters, each corresponding
3493 to a common usb-storage quirk flag as follows:
3494 a = SANE_SENSE (collect more than 18 bytes
3496 b = BAD_SENSE (don't collect more than 18
3497 bytes of sense data);
3498 c = FIX_CAPACITY (decrease the reported
3499 device capacity by one sector);
3500 d = NO_READ_DISC_INFO (don't use
3501 READ_DISC_INFO command);
3502 e = NO_READ_CAPACITY_16 (don't use
3503 READ_CAPACITY_16 command);
3504 h = CAPACITY_HEURISTICS (decrease the
3505 reported device capacity by one
3506 sector if the number is odd);
3507 i = IGNORE_DEVICE (don't bind to this
3509 l = NOT_LOCKABLE (don't try to lock and
3510 unlock ejectable media);
3511 m = MAX_SECTORS_64 (don't transfer more
3512 than 64 sectors = 32 KB at a time);
3513 n = INITIAL_READ10 (force a retry of the
3514 initial READ(10) command);
3515 o = CAPACITY_OK (accept the capacity
3516 reported by the device);
3517 p = WRITE_CACHE (the device cache is ON
3519 r = IGNORE_RESIDUE (the device reports
3520 bogus residue values);
3521 s = SINGLE_LUN (the device has only one
3523 w = NO_WP_DETECT (don't test whether the
3524 medium is write-protected).
3525 Example: quirks=0419:aaf5:rl,0421:0433:rc
3527 user_debug= [KNL,ARM]
3529 See arch/arm/Kconfig.debug help text.
3530 1 - undefined instruction events
3532 4 - invalid data aborts
3535 Example: user_debug=31
3538 [X86] Flags controlling user PTE allocations.
3540 nohigh = do not allocate PTE pages in
3541 HIGHMEM regardless of setting
3545 On X86_32, this is an alias for vdso32=. Otherwise:
3547 vdso=1: enable VDSO (the default)
3548 vdso=0: disable VDSO mapping
3550 vdso32= [X86] Control the 32-bit vDSO
3551 vdso32=1: enable 32-bit VDSO
3552 vdso32=0 or vdso32=2: disable 32-bit VDSO
3554 See the help text for CONFIG_COMPAT_VDSO for more
3555 details. If CONFIG_COMPAT_VDSO is set, the default is
3556 vdso32=0; otherwise, the default is vdso32=1.
3558 For compatibility with older kernels, vdso32=2 is an
3561 Try vdso32=0 if you encounter an error that says:
3562 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3565 vector=percpu: enable percpu vector domain
3567 video= [FB] Frame buffer configuration
3568 See Documentation/fb/modedb.txt.
3570 video.brightness_switch_enabled= [0,1]
3571 If set to 1, on receiving an ACPI notify event
3572 generated by hotkey, video driver will adjust brightness
3573 level and then send out the event to user space through
3574 the allocated input device; If set to 0, video driver
3575 will only send out the event without touching backlight
3580 [VMMIO] Memory mapped virtio (platform) device.
3582 <size>@<baseaddr>:<irq>[:<id>]
3584 <size> := size (can use standard suffixes
3586 <baseaddr> := physical base address
3587 <irq> := interrupt number (as passed to
3589 <id> := (optional) platform device id
3591 virtio_mmio.device=1K@0x100b0000:48:7
3593 Can be used multiple times for multiple devices.
3595 vga= [BOOT,X86-32] Select a particular video mode
3596 See Documentation/x86/boot.txt and
3597 Documentation/svga.txt.
3598 Use vga=ask for menu.
3599 This is actually a boot loader parameter; the value is
3600 passed to the kernel using a special protocol.
3602 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3603 size of <nn>. This can be used to increase the
3604 minimum size (128MB on x86). It can also be used to
3605 decrease the size and leave more room for directly
3608 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3611 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3614 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3618 Controls the behavior of vsyscalls (i.e. calls to
3619 fixed addresses of 0xffffffffff600x00 from legacy
3620 code). Most statically-linked binaries and older
3621 versions of glibc use these calls. Because these
3622 functions are at fixed addresses, they make nice
3623 targets for exploits that can control RIP.
3625 emulate [default] Vsyscalls turn into traps and are
3626 emulated reasonably safely.
3628 native Vsyscalls are native syscall instructions.
3629 This is a little bit faster than trapping
3630 and makes a few dynamic recompilers work
3631 better than they would in emulation mode.
3632 It also makes exploits much easier to write.
3634 none Vsyscalls don't work at all. This makes
3635 them quite hard to use for exploits but
3636 might break your system.
3638 vt.color= [VT] Default text color.
3639 Format: 0xYX, X = foreground, Y = background.
3640 Default: 0x07 = light gray on black.
3642 vt.cur_default= [VT] Default cursor shape.
3643 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3644 the parameters of the <Esc>[?A;B;Cc escape sequence;
3645 see VGA-softcursor.txt. Default: 2 = underline.
3647 vt.default_blu= [VT]
3648 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3649 Change the default blue palette of the console.
3650 This is a 16-member array composed of values
3653 vt.default_grn= [VT]
3654 Format: <green0>,<green1>,<green2>,...,<green15>
3655 Change the default green palette of the console.
3656 This is a 16-member array composed of values
3659 vt.default_red= [VT]
3660 Format: <red0>,<red1>,<red2>,...,<red15>
3661 Change the default red palette of the console.
3662 This is a 16-member array composed of values
3668 Set system-wide default UTF-8 mode for all tty's.
3669 Default is 1, i.e. UTF-8 mode is enabled for all
3670 newly opened terminals.
3672 vt.global_cursor_default=
3675 Set system-wide default for whether a cursor
3676 is shown on new VTs. Default is -1,
3677 i.e. cursors will be created by default unless
3678 overridden by individual drivers. 0 will hide
3679 cursors, 1 will display them.
3681 vt.italic= [VT] Default color for italic text; 0-15.
3684 vt.underline= [VT] Default color for underlined text; 0-15.
3687 watchdog timers [HW,WDT] For information on watchdog timers,
3688 see Documentation/watchdog/watchdog-parameters.txt
3689 or other driver-specific files in the
3690 Documentation/watchdog/ directory.
3692 workqueue.disable_numa
3693 By default, all work items queued to unbound
3694 workqueues are affine to the NUMA nodes they're
3695 issued on, which results in better behavior in
3696 general. If NUMA affinity needs to be disabled for
3697 whatever reason, this option can be used. Note
3698 that this also can be controlled per-workqueue for
3699 workqueues visible under /sys/bus/workqueue/.
3701 workqueue.power_efficient
3702 Per-cpu workqueues are generally preferred because
3703 they show better performance thanks to cache
3704 locality; unfortunately, per-cpu workqueues tend to
3705 be more power hungry than unbound workqueues.
3707 Enabling this makes the per-cpu workqueues which
3708 were observed to contribute significantly to power
3709 consumption unbound, leading to measurably lower
3710 power usage at the cost of small performance
3713 The default value of this parameter is determined by
3714 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3716 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3717 default x2apic cluster mode on platforms
3720 x86_intel_mid_timer= [X86-32,APBT]
3721 Choose timer option for x86 Intel MID platform.
3722 Two valid options are apbt timer only and lapic timer
3723 plus one apbt timer for broadcast timer.
3724 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3726 xen_emul_unplug= [HW,X86,XEN]
3727 Unplug Xen emulated devices
3728 Format: [unplug0,][unplug1]
3729 ide-disks -- unplug primary master IDE devices
3730 aux-ide-disks -- unplug non-primary-master IDE devices
3731 nics -- unplug network devices
3732 all -- unplug all emulated devices (NICs and IDE disks)
3733 unnecessary -- unplugging emulated devices is
3734 unnecessary even if the host did not respond to
3736 never -- do not unplug even if version check succeeds
3738 xen_nopvspin [X86,XEN]
3739 Disables the ticketlock slowpath using Xen PV
3742 xirc2ps_cs= [NET,PCMCIA]
3744 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3746 ______________________________________________________________________
3750 Add more DRM drivers.
projects / cascardo / linux.git / blob