4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt }
171 force -- enable ACPI if default was off
172 off -- disable ACPI if default was on
173 noirq -- do not use ACPI for IRQ routing
174 strict -- Be less tolerant of platforms that are not
175 strictly ACPI specification compliant.
176 rsdt -- prefer RSDT over (default) XSDT
177 copy_dsdt -- copy DSDT to memory
179 See also Documentation/power/runtime_pm.txt, pci=noacpi
181 acpi_rsdp= [ACPI,EFI,KEXEC]
182 Pass the RSDP address to the kernel, mostly used
183 on machines running EFI runtime service to boot the
184 second kernel for kdump.
186 acpi_apic_instance= [ACPI, IOAPIC]
188 2: use 2nd APIC table, if available
189 1,0: use 1st APIC table
192 acpi_backlight= [HW,ACPI]
193 acpi_backlight=vendor
195 If set to vendor, prefer vendor specific driver
196 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
197 of the ACPI video.ko driver.
199 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
200 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
202 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
203 debug output. Bits in debug_layer correspond to a
204 _COMPONENT in an ACPI source file, e.g.,
205 #define _COMPONENT ACPI_PCI_COMPONENT
206 Bits in debug_level correspond to a level in
207 ACPI_DEBUG_PRINT statements, e.g.,
208 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
209 The debug_level mask defaults to "info". See
210 Documentation/acpi/debug.txt for more information about
211 debug layers and levels.
213 Enable processor driver info messages:
214 acpi.debug_layer=0x20000000
215 Enable PCI/PCI interrupt routing info messages:
216 acpi.debug_layer=0x400000
217 Enable AML "Debug" output, i.e., stores to the Debug
218 object while interpreting AML:
219 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
220 Enable all messages related to ACPI hardware:
221 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
223 Some values produce so much output that the system is
224 unusable. The "log_buf_len" parameter may be useful
225 if you need to capture more output.
227 acpi_force_table_verification [HW,ACPI]
228 Enable table checksum verification during early stage.
229 By default, this is disabled due to x86 early mapping
232 acpi_irq_balance [HW,ACPI]
233 ACPI will balance active IRQs
236 acpi_irq_nobalance [HW,ACPI]
237 ACPI will not move active IRQs (default)
240 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
241 Format: <irq>,<irq>...
243 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
245 Format: <irq>,<irq>...
247 acpi_no_auto_serialize [HW,ACPI]
248 Disable auto-serialization of AML methods
249 AML control methods that contain the opcodes to create
250 named objects will be marked as "Serialized" by the
251 auto-serialization feature.
252 This feature is enabled by default.
253 This option allows to turn off the feature.
255 acpi_no_static_ssdt [HW,ACPI]
256 Disable installation of static SSDTs at early boot time
257 By default, SSDTs contained in the RSDT/XSDT will be
258 installed automatically and they will appear under
259 /sys/firmware/acpi/tables.
260 This option turns off this feature.
261 Note that specifying this option does not affect
262 dynamic table installation which will install SSDT
263 tables to /sys/firmware/acpi/tables/dynamic.
265 acpica_no_return_repair [HW, ACPI]
266 Disable AML predefined validation mechanism
267 This mechanism can repair the evaluation result to make
268 the return objects more ACPI specification compliant.
269 This option is useful for developers to identify the
270 root cause of an AML interpreter issue when the issue
271 has something to do with the repair mechanism.
273 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
274 Format: To spoof as Windows 98: ="Microsoft Windows"
276 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
277 acpi_osi="string1" # add string1
278 acpi_osi="!string2" # remove string2
279 acpi_osi=!* # remove all strings
280 acpi_osi=! # disable all built-in OS vendor
282 acpi_osi= # disable all strings
284 'acpi_osi=!' can be used in combination with single or
285 multiple 'acpi_osi="string1"' to support specific OS
286 vendor string(s). Note that such command can only
287 affect the default state of the OS vendor strings, thus
288 it cannot affect the default state of the feature group
289 strings and the current state of the OS vendor strings,
290 specifying it multiple times through kernel command line
291 is meaningless. This command is useful when one do not
292 care about the state of the feature group strings which
293 should be controlled by the OSPM.
295 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
296 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
297 can make '_OSI("Windows 2000")' TRUE.
299 'acpi_osi=' cannot be used in combination with other
300 'acpi_osi=' command lines, the _OSI method will not
301 exist in the ACPI namespace. NOTE that such command can
302 only affect the _OSI support state, thus specifying it
303 multiple times through kernel command line is also
306 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
309 'acpi_osi=!*' can be used in combination with single or
310 multiple 'acpi_osi="string1"' to support specific
311 string(s). Note that such command can affect the
312 current state of both the OS vendor strings and the
313 feature group strings, thus specifying it multiple times
314 through kernel command line is meaningful. But it may
315 still not able to affect the final state of a string if
316 there are quirks related to this string. This command
317 is useful when one want to control the state of the
318 feature group strings to debug BIOS issues related to
321 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
322 '_OSI("Module Device")' FALSE.
323 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
324 '_OSI("Module Device")' TRUE.
325 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
327 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
329 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
330 they all will make '_OSI("Windows 2000")' TRUE.
333 Override the pmtimer bug detection: force the kernel
334 to assume that this machine's pmtimer latches its value
335 and always returns good values.
337 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
338 Format: { level | edge | high | low }
340 acpi_skip_timer_override [HW,ACPI]
341 Recognize and ignore IRQ0/pin2 Interrupt Override.
342 For broken nForce2 BIOS resulting in XT-PIC timer.
344 acpi_sleep= [HW,ACPI] Sleep options
345 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
346 old_ordering, nonvs, sci_force_enable }
347 See Documentation/power/video.txt for information on
349 s3_beep is for debugging; it makes the PC's speaker beep
350 as soon as the kernel's real-mode entry point is called.
351 s4_nohwsig prevents ACPI hardware signature from being
352 used during resume from hibernation.
353 old_ordering causes the ACPI 1.0 ordering of the _PTS
354 control method, with respect to putting devices into
355 low power states, to be enforced (the ACPI 2.0 ordering
356 of _PTS is used by default).
357 nonvs prevents the kernel from saving/restoring the
358 ACPI NVS memory during suspend/hibernation and resume.
359 sci_force_enable causes the kernel to set SCI_EN directly
360 on resume from S1/S3 (which is against the ACPI spec,
361 but some broken systems don't work without it).
363 acpi_use_timer_override [HW,ACPI]
364 Use timer override. For some broken Nvidia NF5 boards
365 that require a timer override, but don't have HPET
367 acpi_enforce_resources= [ACPI]
368 { strict | lax | no }
369 Check for resource conflicts between native drivers
370 and ACPI OperationRegions (SystemIO and SystemMemory
371 only). IO ports and memory declared in ACPI might be
372 used by the ACPI subsystem in arbitrary AML code and
373 can interfere with legacy drivers.
374 strict (default): access to resources claimed by ACPI
375 is denied; legacy drivers trying to access reserved
376 resources will fail to bind to device using them.
377 lax: access to resources claimed by ACPI is allowed;
378 legacy drivers trying to access reserved resources
379 will bind successfully but a warning message is logged.
380 no: ACPI OperationRegions are not marked as reserved,
381 no further checks are performed.
383 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
386 add_efi_memmap [EFI; X86] Include EFI memory map in
387 kernel's map of available physical RAM.
390 { off | try_unsupported }
391 off: disable AGP support
392 try_unsupported: try to drive unsupported chipsets
393 (may crash computer or cause data corruption)
396 See Documentation/sound/alsa/alsa-parameters.txt
399 Allow the default userspace alignment fault handler
400 behaviour to be specified. Bit 0 enables warnings,
401 bit 1 enables fixups, and bit 2 sends a segfault.
403 align_va_addr= [X86-64]
404 Align virtual addresses by clearing slice [14:12] when
405 allocating a VMA at process creation time. This option
406 gives you up to 3% performance improvement on AMD F15h
407 machines (where it is enabled by default) for a
408 CPU-intensive style benchmark, and it can vary highly in
409 a microbenchmark depending on workload and compiler.
411 32: only for 32-bit processes
412 64: only for 64-bit processes
413 on: enable for both 32- and 64-bit processes
414 off: disable for both 32- and 64-bit processes
416 alloc_snapshot [FTRACE]
417 Allocate the ftrace snapshot buffer on boot up when the
418 main buffer is allocated. This is handy if debugging
419 and you need to use tracing_snapshot() on boot up, and
420 do not want to use tracing_snapshot_alloc() as it needs
421 to be done where GFP_KERNEL allocations are allowed.
423 amd_iommu= [HW,X86-64]
424 Pass parameters to the AMD IOMMU driver in the system.
426 fullflush - enable flushing of IO/TLB entries when
427 they are unmapped. Otherwise they are
428 flushed before they will be reused, which
430 off - do not initialize any AMD IOMMU found in
432 force_isolation - Force device isolation for all
433 devices. The IOMMU driver is not
434 allowed anymore to lift isolation
435 requirements as needed. This option
436 does not override iommu=pt
438 amd_iommu_dump= [HW,X86-64]
439 Enable AMD IOMMU driver option to dump the ACPI table
440 for AMD IOMMU. With this option enabled, AMD IOMMU
441 driver will print ACPI tables for AMD IOMMU during
442 IOMMU initialization.
444 amijoy.map= [HW,JOY] Amiga joystick support
445 Map of devices attached to JOY0DAT and JOY1DAT
447 See also Documentation/input/joystick.txt
449 analog.map= [HW,JOY] Analog joystick and gamepad support
450 Specifies type or capabilities of an analog joystick
451 connected to one of 16 gameports
452 Format: <type1>,<type2>,..<type16>
455 Power management functions (SPARCstation-4/5 + deriv.)
457 Disable APC CPU standby support. SPARCstation-Fox does
458 not play well with APC CPU idle - disable it if you have
459 APC and your system crashes randomly.
461 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
462 Change the output verbosity whilst booting
463 Format: { quiet (default) | verbose | debug }
464 Change the amount of debugging information output
465 when initialising the APIC and IO-APIC components.
468 See Documentation/networking/ipv6.txt.
470 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
471 Limit apic dumping. The parameter defines the maximal
472 number of local apics being dumped. Also it is possible
473 to set it to "all" by meaning -- no limit here.
474 Format: { 1 (default) | 2 | ... | all }.
475 The parameter valid if only apic=debug or
476 apic=verbose is specified.
477 Example: apic=debug show_lapic=all
479 apm= [APM] Advanced Power Management
480 See header of arch/x86/kernel/apm_32.c.
482 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
483 Format: <io>,<irq>,<nodeID>
487 atarimouse= [HW,MOUSE] Atari Mouse
489 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
490 EzKey and similar keyboards
492 atkbd.reset= [HW] Reset keyboard during initialization
494 atkbd.set= [HW] Select keyboard code set
495 Format: <int> (2 = AT (default), 3 = PS/2)
497 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
500 atkbd.softraw= [HW] Choose between synthetic and real raw mode
501 Format: <bool> (0 = real, 1 = synthetic (default))
503 atkbd.softrepeat= [HW]
504 Use software keyboard repeat
506 audit= [KNL] Enable the audit sub-system
507 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
508 0 - kernel audit is disabled and can not be enabled
509 until the next reboot
510 unset - kernel audit is initialized but disabled and
511 will be fully enabled by the userspace auditd.
512 1 - kernel audit is initialized and partially enabled,
513 storing at most audit_backlog_limit messages in
514 RAM until it is fully enabled by the userspace
518 audit_backlog_limit= [KNL] Set the audit queue size limit.
519 Format: <int> (must be >=0)
522 baycom_epp= [HW,AX25]
525 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
527 See header of drivers/net/hamradio/baycom_par.c.
529 baycom_ser_fdx= [HW,AX25]
530 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
531 Format: <io>,<irq>,<mode>[,<baud>]
532 See header of drivers/net/hamradio/baycom_ser_fdx.c.
534 baycom_ser_hdx= [HW,AX25]
535 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
536 Format: <io>,<irq>,<mode>
537 See header of drivers/net/hamradio/baycom_ser_hdx.c.
539 blkdevparts= Manual partition parsing of block device(s) for
540 embedded devices based on command line input.
541 See Documentation/block/cmdline-partition.txt
543 boot_delay= Milliseconds to delay each printk during boot.
544 Values larger than 10 seconds (10000) are changed to
548 bootmem_debug [KNL] Enable bootmem allocator debug messages.
550 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
551 bttv.radio= Most important insmod options are available as
553 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
556 bulk_remove=off [PPC] This parameter disables the use of the pSeries
557 firmware feature for flushing multiple hpte entries
560 c101= [NET] Moxa C101 synchronous serial card
562 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
563 Sometimes CPU hardware bugs make them report the cache
564 size incorrectly. The kernel will attempt work arounds
565 to fix known problems, but for some CPUs it is not
566 possible to determine what the correct size should be.
567 This option provides an override for these situations.
569 ca_keys= [KEYS] This parameter identifies a specific key(s) on
570 the system trusted keyring to be used for certificate
572 format: { id:<keyid> | builtin }
574 cca= [MIPS] Override the kernel pages' cache coherency
575 algorithm. Accepted values range from 0 to 7
576 inclusive. See arch/mips/include/asm/pgtable-bits.h
577 for platform specific values (SB1, Loongson3 and
580 ccw_timeout_log [S390]
581 See Documentation/s390/CommonIO for details.
583 cgroup_disable= [KNL] Disable a particular controller
584 Format: {name of the controller(s) to disable}
585 The effects of cgroup_disable=foo are:
586 - foo isn't auto-mounted if you mount all cgroups in
588 - foo isn't visible as an individually mountable
590 {Currently only "memory" controller deal with this and
591 cut the overhead, others just disable the usage. So
592 only cgroup_disable=memory is actually worthy}
594 checkreqprot [SELINUX] Set initial checkreqprot flag value.
595 Format: { "0" | "1" }
596 See security/selinux/Kconfig help text.
597 0 -- check protection applied by kernel (includes
598 any implied execute protection).
599 1 -- check protection requested by application.
600 Default value is set via a kernel config option.
601 Value can be changed at runtime via
602 /selinux/checkreqprot.
605 See Documentation/s390/CommonIO for details.
608 Keep all clocks already enabled by bootloader on,
609 even if no driver has claimed them. This is useful
610 for debug and development, but should not be
611 needed on a platform with proper driver support.
612 For more information, see Documentation/clk.txt.
614 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
616 Forces specified clocksource (if available) to be used
617 when calculating gettimeofday(). If specified
618 clocksource is not available, it defaults to PIT.
619 Format: { pit | tsc | cyclone | pmtmr }
621 clocksource= Override the default clocksource
623 Override the default clocksource and use the clocksource
624 with the name specified.
625 Some clocksource names to choose from, depending on
627 [all] jiffies (this is the base, fallback clocksource)
629 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
630 pxa_timer,timer3,32k_counter,timer0_1
632 [X86-32] pit,hpet,tsc;
633 scx200_hrt on Geode; cyclone on IBM x440
641 clearcpuid=BITNUM [X86]
642 Disable CPUID feature X for the kernel. See
643 arch/x86/include/asm/cpufeature.h for the valid bit
644 numbers. Note the Linux specific bits are not necessarily
645 stable over kernel options, but the vendor specific
647 Also note that user programs calling CPUID directly
648 or using the feature without checking anything
649 will still see it. This just prevents it from
650 being used by the kernel or shown in /proc/cpuinfo.
651 Also note the kernel might malfunction if you disable
654 cma=nn[MG]@[start[MG][-end[MG]]]
656 Sets the size of kernel global memory area for
657 contiguous memory allocations and optionally the
658 placement constraint by the physical address range of
659 memory allocations. A value of 0 disables CMA
660 altogether. For more information, see
661 include/linux/dma-contiguous.h
663 cmo_free_hint= [PPC] Format: { yes | no }
664 Specify whether pages are marked as being inactive
665 when they are freed. This is used in CMO environments
666 to determine OS memory pressure for page stealing by
670 coherent_pool=nn[KMG] [ARM,KNL]
671 Sets the size of memory pool for coherent, atomic dma
672 allocations, by default set to 256K.
674 code_bytes [X86] How many bytes of object code to print
679 com20020= [HW,NET] ARCnet - COM20020 chipset
681 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
683 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
687 ARCnet - COM90xx chipset (memory-mapped buffers)
688 Format: <io>[,<irq>[,<memstart>]]
690 condev= [HW,S390] console device
693 console= [KNL] Output console device and options.
695 tty<n> Use the virtual console device <n>.
699 Use the specified serial port. The options are of
700 the form "bbbbpnf", where "bbbb" is the baud rate,
701 "p" is parity ("n", "o", or "e"), "n" is number of
702 bits, and "f" is flow control ("r" for RTS or
703 omit it). Default is "9600n8".
705 See Documentation/serial-console.txt for more
707 Documentation/networking/netconsole.txt for an
710 uart[8250],io,<addr>[,options]
711 uart[8250],mmio,<addr>[,options]
712 Start an early, polled-mode console on the 8250/16550
713 UART at the specified I/O port or MMIO address,
714 switching to the matching ttyS device later. The
715 options are the same as for ttyS, above.
716 hvc<n> Use the hypervisor console device <n>. This is for
717 both Xen and PowerPC hypervisors.
719 If the device connected to the port is not a TTY but a braille
720 device, prepend "brl," before the device type, for instance
722 For now, only VisioBraille is supported.
724 consoleblank= [KNL] The console blank (screen saver) timeout in
725 seconds. Defaults to 10*60 = 10mins. A value of 0
726 disables the blank timer.
729 [KNL] Change the default value for
730 /proc/<pid>/coredump_filter.
731 See also Documentation/filesystems/proc.txt.
733 cpuidle.off=1 [CPU_IDLE]
734 disable the cpuidle sub-system
736 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
738 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
740 crashkernel=size[KMG][@offset[KMG]]
741 [KNL] Using kexec, Linux can switch to a 'crash kernel'
742 upon panic. This parameter reserves the physical
743 memory region [offset, offset + size] for that kernel
744 image. If '@offset' is omitted, then a suitable offset
745 is selected automatically. Check
746 Documentation/kdump/kdump.txt for further details.
748 crashkernel=range1:size1[,range2:size2,...][@offset]
749 [KNL] Same as above, but depends on the memory
750 in the running system. The syntax of range is
751 start-[end] where start and end are both
752 a memory unit (amount[KMG]). See also
753 Documentation/kdump/kdump.txt for an example.
755 crashkernel=size[KMG],high
756 [KNL, x86_64] range could be above 4G. Allow kernel
757 to allocate physical memory region from top, so could
758 be above 4G if system have more than 4G ram installed.
759 Otherwise memory region will be allocated below 4G, if
761 It will be ignored if crashkernel=X is specified.
762 crashkernel=size[KMG],low
763 [KNL, x86_64] range under 4G. When crashkernel=X,high
764 is passed, kernel could allocate physical memory region
765 above 4G, that cause second kernel crash on system
766 that require some amount of low memory, e.g. swiotlb
767 requires at least 64M+32K low memory. Kernel would
768 try to allocate 72M below 4G automatically.
769 This one let user to specify own low range under 4G
770 for second kernel instead.
771 0: to disable low allocation.
772 It will be ignored when crashkernel=X,high is not used
773 or memory reserved is below 4G.
778 cs89x0_media= [HW,NET]
779 Format: { rj45 | aui | bnc }
782 See header of drivers/s390/block/dasd_devmap.c.
784 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
785 (one device per port)
786 Format: <port#>,<type>
787 See also Documentation/input/joystick-parport.txt
789 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
790 time. See Documentation/dynamic-debug-howto.txt for
791 details. Deprecated, see dyndbg.
793 debug [KNL] Enable kernel debugging (events log level).
796 [KNL] verbose self-tests
798 Print debugging info while doing the locking API
800 We default to 0 (no extra messages), setting it to
801 1 will print _a lot_ more information - normally
802 only useful to kernel developers.
804 debug_objects [KNL] Enable object debugging
807 [KNL] Disable object debugging
809 debug_guardpage_minorder=
810 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
811 parameter allows control of the order of pages that will
812 be intentionally kept free (and hence protected) by the
813 buddy allocator. Bigger value increase the probability
814 of catching random memory corruption, but reduce the
815 amount of memory for normal system use. The maximum
816 possible value is MAX_ORDER/2. Setting this parameter
817 to 1 or 2 should be enough to identify most random
818 memory corruption problems caused by bugs in kernel or
819 driver code when a CPU writes to (or reads from) a
820 random memory location. Note that there exists a class
821 of memory corruptions problems caused by buggy H/W or
822 F/W or by drivers badly programing DMA (basically when
823 memory is written at bus level and the CPU MMU is
824 bypassed) which are not detectable by
825 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
826 tracking down these problems.
828 debugpat [X86] Enable PAT debugging
830 decnet.addr= [HW,NET]
831 Format: <area>[,<node>]
832 See also Documentation/networking/decnet.txt.
835 [same as hugepagesz=] The size of the default
836 HugeTLB page size. This is the size represented by
837 the legacy /proc/ hugepages APIs, used for SHM, and
838 default size when mounting hugetlbfs filesystems.
839 Defaults to the default architecture's huge page size
843 Set number of hash buckets for dentry cache.
846 See Documentation/networking/ipv6.txt.
848 disable_cpu_apicid= [X86,APIC,SMP]
850 The number of initial APIC ID for the
851 corresponding CPU to be disabled at boot,
852 mostly used for the kdump 2nd kernel to
853 disable BSP to wake up multiple CPUs without
854 causing system reset or hang due to sending
857 disable_ddw [PPC/PSERIES]
858 Disable Dynamic DMA Window support. Use this if
859 to workaround buggy firmware.
862 See Documentation/networking/ipv6.txt.
864 disable_mtrr_cleanup [X86]
865 The kernel tries to adjust MTRR layout from continuous
866 to discrete, to make X server driver able to add WB
867 entry later. This parameter disables that.
869 disable_mtrr_trim [X86, Intel and AMD only]
870 By default the kernel will trim any uncacheable
871 memory out of your available memory pool based on
872 MTRR settings. This parameter disables that behavior,
873 possibly causing your machine to run very slowly.
875 disable_timer_pin_1 [X86]
876 Disable PIN 1 of APIC timer
877 Can be useful to work around chipset bugs.
879 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
880 this option disables the debugging code at boot.
882 dma_debug_entries=<number>
883 This option allows to tune the number of preallocated
884 entries for DMA-API debugging code. One entry is
885 required per DMA-API allocation. Use this if the
886 DMA-API debugging code disables itself because the
887 architectural default is too low.
889 dma_debug_driver=<driver_name>
890 With this option the DMA-API debugging driver
891 filter feature can be enabled at boot time. Just
892 pass the driver to filter for as the parameter.
893 The filter can be disabled or changed to another
894 driver later using sysfs.
896 drm_kms_helper.edid_firmware=[<connector>:]<file>
897 Broken monitors, graphic adapters and KVMs may
898 send no or incorrect EDID data sets. This parameter
899 allows to specify an EDID data set in the
900 /lib/firmware directory that is used instead.
901 Generic built-in EDID data sets are used, if one of
902 edid/1024x768.bin, edid/1280x1024.bin,
903 edid/1680x1050.bin, or edid/1920x1080.bin is given
904 and no file with the same name exists. Details and
905 instructions how to build your own EDID data are
906 available in Documentation/EDID/HOWTO.txt. An EDID
907 data set will only be used for a particular connector,
908 if its name and a colon are prepended to the EDID
913 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
914 module.dyndbg[="val"]
915 Enable debug messages at boot time. See
916 Documentation/dynamic-debug-howto.txt for details.
918 early_ioremap_debug [KNL]
919 Enable debug messages in early_ioremap support. This
920 is useful for tracking down temporary early mappings
921 which are not unmapped.
923 earlycon= [KNL] Output early console device and options.
926 Start an early, polled-mode console on a cadence serial
927 port at the specified address. The cadence serial port
928 must already be setup and configured. Options are not
931 uart[8250],io,<addr>[,options]
932 uart[8250],mmio,<addr>[,options]
933 uart[8250],mmio32,<addr>[,options]
934 Start an early, polled-mode console on the 8250/16550
935 UART at the specified I/O port or MMIO address.
936 MMIO inter-register address stride is either 8-bit
937 (mmio) or 32-bit (mmio32).
938 The options are the same as for ttyS, above.
941 Start an early, polled-mode console on a pl011 serial
942 port at the specified address. The pl011 serial port
943 must already be setup and configured. Options are not
947 Start an early, polled-mode console on an msm serial
948 port at the specified address. The serial port
949 must already be setup and configured. Options are not
953 Start an early, polled-mode console on an msm serial
954 dm port at the specified address. The serial port
955 must already be setup and configured. Options are not
958 smh Use ARM semihosting calls for early console.
960 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
964 earlyprintk=serial[,ttySn[,baudrate]]
965 earlyprintk=serial[,0x...[,baudrate]]
966 earlyprintk=ttySn[,baudrate]
967 earlyprintk=dbgp[debugController#]
969 earlyprintk is useful when the kernel crashes before
970 the normal console is initialized. It is not enabled by
971 default because it has some cosmetic problems.
973 Append ",keep" to not disable it when the real console
976 Only one of vga, efi, serial, or usb debug port can
979 Currently only ttyS0 and ttyS1 may be specified by
980 name. Other I/O ports may be explicitly specified
981 on some architectures (x86 and arm at least) by
982 replacing ttySn with an I/O port address, like this:
983 earlyprintk=serial,0x1008,115200
984 You can find the port for a given device in
985 /proc/tty/driver/serial:
986 2: uart:ST16650V2 port:00001008 irq:18 ...
988 Interaction with the standard serial driver is not
991 The VGA and EFI output is eventually overwritten by
994 The xen output can only be used by Xen PV guests.
996 edac_report= [HW,EDAC] Control how to report EDAC event
997 Format: {"on" | "off" | "force"}
998 on: enable EDAC to report H/W event. May be overridden
999 by other higher priority error reporting module.
1000 off: disable H/W event reporting through EDAC.
1001 force: enforce the use of EDAC to report H/W event.
1004 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1007 This is designed to be used in conjunction with
1008 the boot argument: earlyprintk=vga
1011 Format: {"off" | "on" | "skip[mbr]"}
1014 Format: { "old_map" }
1015 old_map [X86-64]: switch to the old ioremap-based EFI
1016 runtime services mapping. 32-bit still uses this one by
1019 efi_no_storage_paranoia [EFI; X86]
1020 Using this parameter you can use more than 50% of
1021 your efi variable storage. Use this parameter only if
1022 you are really sure that your UEFI does sane gc and
1023 fulfills the spec otherwise your board may brick.
1025 eisa_irq_edge= [PARISC,HW]
1026 See header of drivers/parisc/eisa.c.
1029 See comment before function elanfreq_setup() in
1030 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1033 Format: {"cfq" | "deadline" | "noop"}
1034 See Documentation/block/cfq-iosched.txt and
1035 Documentation/block/deadline-iosched.txt for details.
1037 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1038 Specifies physical address of start of kernel core
1039 image elf header and optionally the size. Generally
1040 kexec loader will pass this option to capture kernel.
1041 See Documentation/kdump/kdump.txt for details.
1043 enable_mtrr_cleanup [X86]
1044 The kernel tries to adjust MTRR layout from continuous
1045 to discrete, to make X server driver able to add WB
1046 entry later. This parameter enables that.
1048 enable_timer_pin_1 [X86]
1049 Enable PIN 1 of APIC timer
1050 Can be useful to work around chipset bugs
1051 (in particular on some ATI chipsets).
1052 The kernel tries to set a reasonable default.
1054 enforcing [SELINUX] Set initial enforcing status.
1056 See security/selinux/Kconfig help text.
1057 0 -- permissive (log only, no denials).
1058 1 -- enforcing (deny and log).
1060 Value can be changed at runtime via /selinux/enforce.
1063 Disable Error Record Serialization Table (ERST)
1066 ether= [HW,NET] Ethernet cards parameters
1067 This option is obsoleted by the "netdev=" option, which
1068 has equivalent usage. See its documentation for details.
1072 Permit 'security.evm' to be updated regardless of
1073 current integrity status.
1077 fail_make_request=[KNL]
1078 General fault injection mechanism.
1079 Format: <interval>,<probability>,<space>,<times>
1080 See also Documentation/fault-injection/.
1083 See Documentation/blockdev/floppy.txt.
1085 force_pal_cache_flush
1086 [IA-64] Avoid check_sal_cache_flush which may hang on
1087 buggy SAL_CACHE_FLUSH implementations. Using this
1088 parameter will force ia64_sal_cache_flush to call
1089 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1092 Forcefully enable Physical Address Extension (PAE).
1093 Many Pentium M systems disable PAE but may have a
1094 functionally usable PAE implementation.
1095 Warning: use of this parameter will taint the kernel
1096 and may cause unknown problems.
1099 [FTRACE] will set and start the specified tracer
1100 as early as possible in order to facilitate early
1103 ftrace_dump_on_oops[=orig_cpu]
1104 [FTRACE] will dump the trace buffers on oops.
1105 If no parameter is passed, ftrace will dump
1106 buffers of all CPUs, but if you pass orig_cpu, it will
1107 dump only the buffer of the CPU that triggered the
1110 ftrace_filter=[function-list]
1111 [FTRACE] Limit the functions traced by the function
1112 tracer at boot up. function-list is a comma separated
1113 list of functions. This list can be changed at run
1114 time by the set_ftrace_filter file in the debugfs
1117 ftrace_notrace=[function-list]
1118 [FTRACE] Do not trace the functions specified in
1119 function-list. This list can be changed at run time
1120 by the set_ftrace_notrace file in the debugfs
1123 ftrace_graph_filter=[function-list]
1124 [FTRACE] Limit the top level callers functions traced
1125 by the function graph tracer at boot up.
1126 function-list is a comma separated list of functions
1127 that can be changed at run time by the
1128 set_graph_function file in the debugfs tracing directory.
1130 ftrace_graph_notrace=[function-list]
1131 [FTRACE] Do not trace from the functions specified in
1132 function-list. This list is a comma separated list of
1133 functions that can be changed at run time by the
1134 set_graph_notrace file in the debugfs tracing directory.
1137 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1138 support via parallel port (up to 5 devices per port)
1139 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1140 See also Documentation/input/joystick-parport.txt
1144 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1148 gcov_persist= [GCOV] When non-zero (default), profiling data for
1149 kernel modules is saved and remains accessible via
1150 debugfs, even when the module is unloaded/reloaded.
1151 When zero, profiling data is discarded and associated
1152 debugfs files are removed at module unload time.
1154 gpt [EFI] Forces disk with valid GPT signature but
1155 invalid Protective MBR to be treated as GPT. If the
1156 primary GPT is corrupted, it enables the backup/alternate
1157 GPT to be used instead.
1159 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1160 the "Enable 0" bit of the configuration register.
1163 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1164 the "Enable 0" bit of the configuration register.
1167 grcan.select= [HW] Select which physical interface to use.
1170 grcan.txsize= [HW] Sets the size of the tx buffer.
1171 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1173 grcan.rxsize= [HW] Sets the size of the rx buffer.
1174 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1177 hashdist= [KNL,NUMA] Large hashes allocated during boot
1178 are distributed across NUMA nodes. Defaults on
1179 for 64-bit NUMA, off otherwise.
1180 Format: 0 | 1 (for off | on)
1182 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1184 hd= [EIDE] (E)IDE hard drive subsystem geometry
1185 Format: <cyl>,<head>,<sect>
1188 Disable Hardware Error Source Table (HEST) support;
1189 corresponding firmware-first mode error processing
1190 logic will be disabled.
1192 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1193 size of <nn>. This works even on boxes that have no
1194 highmem otherwise. This also works to reduce highmem
1195 size on bigger boxes.
1197 highres= [KNL] Enable/disable high resolution timer mode.
1198 Valid parameters: "on", "off"
1202 See Documentation/isdn/README.HiSax.
1206 hpet= [X86-32,HPET] option to control HPET usage
1207 Format: { enable (default) | disable | force |
1209 disable: disable HPET and use PIT instead
1210 force: allow force enabled of undocumented chips (ICH4,
1212 verbose: show contents of HPET registers during setup
1214 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1215 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1217 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1218 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1219 On x86-64 and powerpc, this option can be specified
1220 multiple times interleaved with hugepages= to reserve
1221 huge pages of different sizes. Valid pages sizes on
1222 x86-64 are 2M (when the CPU supports "pse") and 1G
1223 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1224 Note that 1GB pages can only be allocated at boot time
1225 using hugepages= and not freed afterwards.
1227 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1228 terminal devices. Valid values: 0..8
1229 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1230 If specified, z/VM IUCV HVC accepts connections
1231 from listed z/VM user IDs only.
1233 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1234 hardware thread id mappings.
1235 Format: <cpu>:<hwthread>
1238 Do not unregister boot console at start. This is only
1239 useful for debugging when something happens in the window
1240 between unregistering the boot console and initializing
1243 i2c_bus= [HW] Override the default board specific I2C bus speed
1244 or register an additional I2C bus that is not
1245 registered from board initialization code.
1249 i8042.debug [HW] Toggle i8042 debug mode
1250 i8042.direct [HW] Put keyboard port into non-translated mode
1251 i8042.dumbkbd [HW] Pretend that controller can only read data from
1252 keyboard and cannot control its state
1253 (Don't attempt to blink the leds)
1254 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1255 i8042.nokbd [HW] Don't check/create keyboard port
1256 i8042.noloop [HW] Disable the AUX Loopback command while probing
1258 i8042.nomux [HW] Don't check presence of an active multiplexing
1260 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1262 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1263 i8042.reset [HW] Reset the controller during init and cleanup
1264 i8042.unlock [HW] Unlock (ignore) the keylock
1268 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1269 indicates that the driver is running on unsupported
1271 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1272 does not match list of supported models.
1274 [HW] Report power status in /proc/i8k
1275 (disabled by default)
1276 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1279 i915.invert_brightness=
1280 [DRM] Invert the sense of the variable that is used to
1281 set the brightness of the panel backlight. Normally a
1282 brightness value of 0 indicates backlight switched off,
1283 and the maximum of the brightness value sets the backlight
1284 to maximum brightness. If this parameter is set to 0
1285 (default) and the machine requires it, or this parameter
1286 is set to 1, a brightness value of 0 sets the backlight
1287 to maximum brightness, and the maximum of the brightness
1288 value switches the backlight off.
1289 -1 -- never invert brightness
1290 0 -- machine default
1291 1 -- force brightness inversion
1294 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1296 ide-core.nodma= [HW] (E)IDE subsystem
1297 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1298 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1299 .cdrom .chs .ignore_cable are additional options
1300 See Documentation/ide/ide.txt.
1302 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1303 Claim all unknown PCI IDE storage controllers.
1306 Format: idle=poll, idle=halt, idle=nomwait
1307 Poll forces a polling idle loop that can slightly
1308 improve the performance of waking up a idle CPU, but
1309 will use a lot of power and make the system run hot.
1311 idle=halt: Halt is forced to be used for CPU idle.
1312 In such case C2/C3 won't be used again.
1313 idle=nomwait: Disable mwait for CPU C-states
1315 ignore_loglevel [KNL]
1316 Ignore loglevel setting - this will print /all/
1317 kernel messages to the console. Useful for debugging.
1318 We also add it as printk module parameter, so users
1319 could change it dynamically, usually by
1320 /sys/module/printk/parameters/ignore_loglevel.
1322 ihash_entries= [KNL]
1323 Set number of hash buckets for inode cache.
1325 ima_appraise= [IMA] appraise integrity measurements
1326 Format: { "off" | "enforce" | "fix" | "log" }
1329 ima_appraise_tcb [IMA]
1330 The builtin appraise policy appraises all files
1334 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1338 The list of supported hash algorithms is defined
1339 in crypto/hash_info.h.
1342 Load a policy which meets the needs of the Trusted
1343 Computing Base. This means IMA will measure all
1344 programs exec'd, files mmap'd for exec, and all files
1345 opened for read by uid=0.
1348 Select one of defined IMA measurements template formats.
1349 Formats: { "ima" | "ima-ng" }
1352 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1353 Format: <min_file_size>
1354 Set the minimal file size for using asynchronous hash.
1355 If left unspecified, ahash usage is disabled.
1357 ahash performance varies for different data sizes on
1358 different crypto accelerators. This option can be used
1359 to achieve the best performance for a particular HW.
1361 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1363 Set hashing buffer size. Default: 4k.
1365 ahash performance varies for different chunk sizes on
1366 different crypto accelerators. This option can be used
1367 to achieve best performance for particular HW.
1371 Run specified binary instead of /sbin/init as init
1374 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1375 for working out where the kernel is dying during
1378 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1379 initcall functions. Useful for debugging built-in
1380 modules and initcalls.
1382 initrd= [BOOT] Specify the location of the initial ramdisk
1384 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1387 int_pln_enable [x86] Enable power limit notification interrupt
1389 integrity_audit=[IMA]
1390 Format: { "0" | "1" }
1391 0 -- basic integrity auditing messages. (Default)
1392 1 -- additional integrity auditing messages.
1394 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1396 Enable intel iommu driver.
1398 Disable intel iommu driver.
1399 igfx_off [Default Off]
1400 By default, gfx is mapped as normal device. If a gfx
1401 device has a dedicated DMAR unit, the DMAR unit is
1402 bypassed by not enabling DMAR with this option. In
1403 this case, gfx device will use physical address for
1406 With this option iommu will not optimize to look
1407 for io virtual address below 32-bit forcing dual
1408 address cycle on pci bus for cards supporting greater
1409 than 32-bit addressing. The default is to look
1410 for translation below 32-bit and if not available
1411 then look in the higher range.
1412 strict [Default Off]
1413 With this option on every unmap_single operation will
1414 result in a hardware IOTLB flush operation as opposed
1415 to batching them for performance.
1416 sp_off [Default Off]
1417 By default, super page will be supported if Intel IOMMU
1418 has the capability. With this option, super page will
1421 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1422 0 disables intel_idle and fall back on acpi_idle.
1423 1 to 6 specify maximum depth of C-state.
1427 Do not enable intel_pstate as the default
1428 scaling driver for the supported processors
1430 intremap= [X86-64, Intel-IOMMU]
1431 on enable Interrupt Remapping (default)
1432 off disable Interrupt Remapping
1433 nosid disable Source ID checking
1435 BIOS x2APIC opt-out request will be ignored
1437 iomem= Disable strict checking of access to MMIO memory
1438 strict regions from userspace.
1455 io7= [HW] IO7 for Marvel based alpha systems
1456 See comment before marvel_specify_io7 in
1457 arch/alpha/kernel/core_marvel.c.
1459 io_delay= [X86] I/O delay method
1461 Standard port 0x80 based delay
1463 Alternate port 0xed based delay (needed on some systems)
1465 Simple two microseconds delay
1470 See Documentation/filesystems/nfs/nfsroot.txt.
1473 When an interrupt is not handled search all handlers
1474 for it. Intended to get systems with badly broken
1478 When an interrupt is not handled search all handlers
1479 for it. Also check all handlers each timer
1480 interrupt. Intended to get systems with badly broken
1484 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1486 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1488 <cpu number>,...,<cpu number>
1490 <cpu number>-<cpu number>
1491 (must be a positive range in ascending order)
1493 <cpu number>,...,<cpu number>-<cpu number>
1495 This option can be used to specify one or more CPUs
1496 to isolate from the general SMP balancing and scheduling
1497 algorithms. You can move a process onto or off an
1498 "isolated" CPU via the CPU affinity syscalls or cpuset.
1499 <cpu number> begins at 0 and the maximum value is
1500 "number of CPUs in system - 1".
1502 This option is the preferred way to isolate CPUs. The
1503 alternative -- manually setting the CPU mask of all
1504 tasks in the system -- can cause problems and
1505 suboptimal load balancer performance.
1509 ivrs_ioapic [HW,X86_64]
1510 Provide an override to the IOAPIC-ID<->DEVICE-ID
1511 mapping provided in the IVRS ACPI table. For
1512 example, to map IOAPIC-ID decimal 10 to
1513 PCI device 00:14.0 write the parameter as:
1514 ivrs_ioapic[10]=00:14.0
1516 ivrs_hpet [HW,X86_64]
1517 Provide an override to the HPET-ID<->DEVICE-ID
1518 mapping provided in the IVRS ACPI table. For
1519 example, to map HPET-ID decimal 0 to
1520 PCI device 00:14.0 write the parameter as:
1521 ivrs_hpet[0]=00:14.0
1523 js= [HW,JOY] Analog joystick
1524 See Documentation/input/joystick.txt.
1527 Enable/disable kernel and module base offset ASLR
1528 (Address Space Layout Randomization) if built into
1529 the kernel. When CONFIG_HIBERNATION is selected,
1530 kASLR is disabled by default. When kASLR is enabled,
1531 hibernation will be disabled.
1535 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1536 specifies the amount of memory usable by the kernel
1537 for non-movable allocations. The requested amount is
1538 spread evenly throughout all nodes in the system. The
1539 remaining memory in each node is used for Movable
1540 pages. In the event, a node is too small to have both
1541 kernelcore and Movable pages, kernelcore pages will
1542 take priority and other nodes will have a larger number
1543 of Movable pages. The Movable zone is used for the
1544 allocation of pages that may be reclaimed or moved
1545 by the page migration subsystem. This means that
1546 HugeTLB pages may not be allocated from this zone.
1547 Note that allocations like PTEs-from-HighMem still
1548 use the HighMem zone if it exists, and the Normal
1549 zone if it does not.
1551 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1552 Format: <Controller#>[,poll interval]
1553 The controller # is the number of the ehci usb debug
1554 port as it is probed via PCI. The poll interval is
1555 optional and is the number seconds in between
1556 each poll cycle to the debug port in case you need
1557 the functionality for interrupting the kernel with
1558 gdb or control-c on the dbgp connection. When
1559 not using this parameter you use sysrq-g to break into
1560 the kernel debugger.
1562 kgdboc= [KGDB,HW] kgdb over consoles.
1563 Requires a tty driver that supports console polling,
1564 or a supported polling keyboard driver (non-usb).
1565 Serial only format: <serial_device>[,baud]
1566 keyboard only format: kbd
1567 keyboard and serial format: kbd,<serial_device>[,baud]
1568 Optional Kernel mode setting:
1569 kms, kbd format: kms,kbd
1570 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1572 kgdbwait [KGDB] Stop kernel execution and enter the
1573 kernel debugger at the earliest opportunity.
1575 kmac= [MIPS] korina ethernet MAC address.
1576 Configure the RouterBoard 532 series on-chip
1577 Ethernet adapter MAC address.
1579 kmemleak= [KNL] Boot-time kmemleak enable/disable
1580 Valid arguments: on, off
1583 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1584 Valid arguments: 0, 1, 2
1585 kmemcheck=0 (disabled)
1586 kmemcheck=1 (enabled)
1587 kmemcheck=2 (one-shot mode)
1588 Default: 2 (one-shot mode)
1590 kstack=N [X86] Print N words from the kernel stack
1593 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1594 Default is 0 (don't ignore, but inject #GP)
1596 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1600 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1601 Default is 1 (enabled)
1603 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1605 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1607 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1608 (virtualized MMU) support on capable Intel chips.
1609 Default is 1 (enabled)
1611 kvm-intel.emulate_invalid_guest_state=
1612 [KVM,Intel] Enable emulation of invalid guest states
1613 Default is 0 (disabled)
1615 kvm-intel.flexpriority=
1616 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1617 Default is 1 (enabled)
1620 [KVM,Intel] Enable VMX nesting (nVMX).
1621 Default is 0 (disabled)
1623 kvm-intel.unrestricted_guest=
1624 [KVM,Intel] Disable unrestricted guest feature
1625 (virtualized real and unpaged mode) on capable
1626 Intel chips. Default is 1 (enabled)
1628 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1629 feature (tagged TLBs) on capable Intel chips.
1630 Default is 1 (enabled)
1636 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1639 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1640 value for LAPIC timer one-shot implementation. Default
1641 back to the programmable timer unit in the LAPIC.
1643 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1646 libata.dma= [LIBATA] DMA control
1647 libata.dma=0 Disable all PATA and SATA DMA
1648 libata.dma=1 PATA and SATA Disk DMA only
1649 libata.dma=2 ATAPI (CDROM) DMA only
1650 libata.dma=4 Compact Flash DMA only
1651 Combinations also work, so libata.dma=3 enables DMA
1652 for disks and CDROMs, but not CFs.
1654 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1655 libata.ignore_hpa=0 keep BIOS limits (default)
1656 libata.ignore_hpa=1 ignore limits, using full disk
1658 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1662 libata.force= [LIBATA] Force configurations. The format is comma
1663 separated list of "[ID:]VAL" where ID is
1664 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1665 matching port, link or device. Basically, it matches
1666 the ATA ID string printed on console by libata. If
1667 the whole ID part is omitted, the last PORT and DEVICE
1668 values are used. If ID hasn't been specified yet, the
1669 configuration applies to all ports, links and devices.
1671 If only DEVICE is omitted, the parameter applies to
1672 the port and all links and devices behind it. DEVICE
1673 number of 0 either selects the first device or the
1674 first fan-out link behind PMP device. It does not
1675 select the host link. DEVICE number of 15 selects the
1676 host link and device attached to it.
1678 The VAL specifies the configuration to force. As long
1679 as there's no ambiguity shortcut notation is allowed.
1680 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1681 The following configurations can be forced.
1683 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1684 Any ID with matching PORT is used.
1686 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1688 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1689 udma[/][16,25,33,44,66,100,133] notation is also
1692 * [no]ncq: Turn on or off NCQ.
1694 * nohrst, nosrst, norst: suppress hard, soft
1697 * rstonce: only attempt one reset during
1698 hot-unplug link recovery
1700 * dump_id: dump IDENTIFY data.
1702 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1704 * disable: Disable this device.
1706 If there are multiple matching configurations changing
1707 the same attribute, the last one is used.
1709 memblock=debug [KNL] Enable memblock debug messages.
1711 load_ramdisk= [RAM] List of ramdisks to load from floppy
1712 See Documentation/blockdev/ramdisk.txt.
1714 lockd.nlm_grace_period=P [NFS] Assign grace period.
1717 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1720 lockd.nlm_timeout=T [NFS] Assign timeout value.
1723 lockd.nlm_udpport=M [NFS] Assign UDP port.
1726 locktorture.nreaders_stress= [KNL]
1727 Set the number of locking read-acquisition kthreads.
1728 Defaults to being automatically set based on the
1729 number of online CPUs.
1731 locktorture.nwriters_stress= [KNL]
1732 Set the number of locking write-acquisition kthreads.
1734 locktorture.onoff_holdoff= [KNL]
1735 Set time (s) after boot for CPU-hotplug testing.
1737 locktorture.onoff_interval= [KNL]
1738 Set time (s) between CPU-hotplug operations, or
1739 zero to disable CPU-hotplug testing.
1741 locktorture.shuffle_interval= [KNL]
1742 Set task-shuffle interval (jiffies). Shuffling
1743 tasks allows some CPUs to go into dyntick-idle
1744 mode during the locktorture test.
1746 locktorture.shutdown_secs= [KNL]
1747 Set time (s) after boot system shutdown. This
1748 is useful for hands-off automated testing.
1750 locktorture.stat_interval= [KNL]
1751 Time (s) between statistics printk()s.
1753 locktorture.stutter= [KNL]
1754 Time (s) to stutter testing, for example,
1755 specifying five seconds causes the test to run for
1756 five seconds, wait for five seconds, and so on.
1757 This tests the locking primitive's ability to
1758 transition abruptly to and from idle.
1760 locktorture.torture_runnable= [BOOT]
1761 Start locktorture running at boot time.
1763 locktorture.torture_type= [KNL]
1764 Specify the locking implementation to test.
1766 locktorture.verbose= [KNL]
1767 Enable additional printk() statements.
1769 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1772 loglevel= All Kernel Messages with a loglevel smaller than the
1773 console loglevel will be printed to the console. It can
1774 also be changed with klogd or other programs. The
1775 loglevels are defined as follows:
1777 0 (KERN_EMERG) system is unusable
1778 1 (KERN_ALERT) action must be taken immediately
1779 2 (KERN_CRIT) critical conditions
1780 3 (KERN_ERR) error conditions
1781 4 (KERN_WARNING) warning conditions
1782 5 (KERN_NOTICE) normal but significant condition
1783 6 (KERN_INFO) informational
1784 7 (KERN_DEBUG) debug-level messages
1786 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1787 in bytes. n must be a power of two and greater
1788 than the minimal size. The minimal size is defined
1789 by LOG_BUF_SHIFT kernel config parameter. There is
1790 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1791 that allows to increase the default size depending on
1792 the number of CPUs. See init/Kconfig for more details.
1794 logo.nologo [FB] Disables display of the built-in Linux logo.
1795 This may be used to provide more screen space for
1796 kernel log messages and is useful when debugging
1797 kernel boot problems.
1799 lp=0 [LP] Specify parallel ports to use, e.g,
1800 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1801 lp=reset first parallel port). 'lp=0' disables the
1802 lp=auto printer driver. 'lp=reset' (which can be
1803 specified in addition to the ports) causes
1804 attached printers to be reset. Using
1805 lp=port1,port2,... specifies the parallel ports
1806 to associate lp devices with, starting with
1807 lp0. A port specification may be 'none' to skip
1808 that lp device, or a parport name such as
1809 'parport0'. Specifying 'lp=auto' instead of a
1810 port specification list means that device IDs
1811 from each port should be examined, to see if
1812 an IEEE 1284-compliant printer is attached; if
1813 so, the driver will manage that printer.
1814 See also header of drivers/char/lp.c.
1817 Sets loops_per_jiffy to given constant, thus avoiding
1818 time-consuming boot-time autodetection (up to 250 ms per
1819 CPU). 0 enables autodetection (default). To determine
1820 the correct value for your kernel, boot with normal
1821 autodetection and see what value is printed. Note that
1822 on SMP systems the preset will be applied to all CPUs,
1823 which is likely to cause problems if your CPUs need
1824 significantly divergent settings. An incorrect value
1825 will cause delays in the kernel to be wrong, leading to
1826 unpredictable I/O errors and other breakage. Although
1827 unlikely, in the extreme case this might damage your
1831 Format: <io>,<irq>,<dma>
1833 machvec= [IA-64] Force the use of a particular machine-vector
1834 (machvec) in a generic kernel.
1835 Example: machvec=hpzx1_swiotlb
1837 machtype= [Loongson] Share the same kernel image file between different
1839 Example: machtype=lemote-yeeloong-2f-7inch
1841 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1842 than or equal to this physical address is ignored.
1844 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1845 should make use of. maxcpus=n : n >= 0 limits the
1846 kernel to using 'n' processors. n=0 is a special case,
1847 it is equivalent to "nosmp", which also disables
1850 max_loop= [LOOP] The number of loop block devices that get
1851 (loop.max_loop) unconditionally pre-created at init time. The default
1852 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1853 of statically allocating a predefined number, loop
1854 devices can be requested on-demand with the
1855 /dev/loop-control interface.
1857 mce [X86-32] Machine Check Exception
1859 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1861 md= [HW] RAID subsystems devices and level
1862 See Documentation/md.txt.
1865 Format: <first>,<last>
1866 Specifies range of consoles to be captured by the MDA.
1868 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1869 Amount of memory to be used when the kernel is not able
1870 to see the whole system memory or for test.
1871 [X86] Work as limiting max address. Use together
1872 with memmap= to avoid physical address space collisions.
1873 Without memmap= PCI devices could be placed at addresses
1874 belonging to unused RAM.
1876 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1880 [KNL,SH] Allow user to override the default size for
1881 per-device physically contiguous DMA buffers.
1883 memmap=exactmap [KNL,X86] Enable setting of an exact
1884 E820 memory map, as specified by the user.
1885 Such memmap=exactmap lines can be constructed based on
1886 BIOS output or other requirements. See the memmap=nn@ss
1889 memmap=nn[KMG]@ss[KMG]
1890 [KNL] Force usage of a specific region of memory.
1891 Region of memory to be used is from ss to ss+nn.
1893 memmap=nn[KMG]#ss[KMG]
1894 [KNL,ACPI] Mark specific memory as ACPI data.
1895 Region of memory to be marked is from ss to ss+nn.
1897 memmap=nn[KMG]$ss[KMG]
1898 [KNL,ACPI] Mark specific memory as reserved.
1899 Region of memory to be reserved is from ss to ss+nn.
1900 Example: Exclude memory from 0x18690000-0x1869ffff
1901 memmap=64K$0x18690000
1903 memmap=0x10000$0x18690000
1905 memory_corruption_check=0/1 [X86]
1906 Some BIOSes seem to corrupt the first 64k of
1907 memory when doing things like suspend/resume.
1908 Setting this option will scan the memory
1909 looking for corruption. Enabling this will
1910 both detect corruption and prevent the kernel
1911 from using the memory being corrupted.
1912 However, its intended as a diagnostic tool; if
1913 repeatable BIOS-originated corruption always
1914 affects the same memory, you can use memmap=
1915 to prevent the kernel from using that memory.
1917 memory_corruption_check_size=size [X86]
1918 By default it checks for corruption in the low
1919 64k, making this memory unavailable for normal
1920 use. Use this parameter to scan for
1921 corruption in more or less memory.
1923 memory_corruption_check_period=seconds [X86]
1924 By default it checks for corruption every 60
1925 seconds. Use this parameter to check at some
1926 other rate. 0 disables periodic checking.
1928 memtest= [KNL,X86] Enable memtest
1930 default : 0 <disable>
1931 Specifies the number of memtest passes to be
1932 performed. Each pass selects another test
1933 pattern from a given set of patterns. Memtest
1934 fills the memory with this pattern, validates
1935 memory contents and reserves bad memory
1936 regions that are detected.
1938 meye.*= [HW] Set MotionEye Camera parameters
1939 See Documentation/video4linux/meye.txt.
1941 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1942 Multi-Function General Purpose Timers on AMD Geode
1945 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1946 the BIOS has incorrectly applied a workaround. TinyBIOS
1947 version 0.98 is known to be affected, 0.99 fixes the
1948 problem by letting the user disable the workaround.
1952 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1953 physical address is ignored.
1955 mini2440= [ARM,HW,KNL]
1956 Format:[0..2][b][c][t]
1958 MINI2440 configuration specification:
1959 0 - The attached screen is the 3.5" TFT
1960 1 - The attached screen is the 7" TFT
1961 2 - The VGA Shield is attached (1024x768)
1962 Leaving out the screen size parameter will not load
1963 the TFT driver, and the framebuffer will be left
1965 b - Enable backlight. The TFT backlight pin will be
1966 linked to the kernel VESA blanking code and a GPIO
1967 LED. This parameter is not necessary when using the
1969 c - Enable the s3c camera interface.
1970 t - Reserved for enabling touchscreen support. The
1971 touchscreen support is not enabled in the mainstream
1972 kernel as of 2.6.30, a preliminary port can be found
1973 in the "bleeding edge" mini2440 support kernel at
1974 http://repo.or.cz/w/linux-2.6/mini2440.git
1977 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1978 parameter allows control of the logging verbosity for
1979 the additional memory initialisation checks. A value
1980 of 0 disables mminit logging and a level of 4 will
1981 log everything. Information is printed at KERN_DEBUG
1982 so loglevel=8 may also need to be specified.
1985 [KNL] When CONFIG_MODULE_SIG is set, this means that
1986 modules without (valid) signatures will fail to load.
1987 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1988 is always true, so this option does nothing.
1991 [MOUSE] Maximum time between finger touching and
1992 leaving touchpad surface for touch to be considered
1993 a tap and be reported as a left button click (for
1994 touchpads working in absolute mode only).
1996 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1997 reporting absolute coordinates, such as tablets
1998 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1999 reporting absolute coordinates, such as tablets
2001 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2002 is similar to kernelcore except it specifies the
2003 amount of memory used for migratable allocations.
2004 If both kernelcore and movablecore is specified,
2005 then kernelcore will be at *least* the specified
2006 value but may be more. If movablecore on its own
2007 is specified, the administrator must be careful
2008 that the amount of memory usable for all allocations
2011 movable_node [KNL,X86] Boot-time switch to enable the effects
2012 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2014 MTD_Partition= [MTD]
2015 Format: <name>,<region-number>,<size>,<offset>
2017 MTD_Region= [MTD] Format:
2018 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2021 See drivers/mtd/cmdlinepart.c.
2023 multitce=off [PPC] This parameter disables the use of the pSeries
2024 firmware feature for updating multiple TCE entries
2027 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2029 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2031 boundary - index of last SLC block on Flex-OneNAND.
2032 The remaining blocks are configured as MLC blocks.
2033 lock - Configure if Flex-OneNAND boundary should be locked.
2034 Once locked, the boundary cannot be changed.
2035 1 indicates lock status, 0 indicates unlock status.
2038 ARM/S3C2412 JIVE boot control
2040 See arch/arm/mach-s3c2412/mach-jive.c
2042 mtouchusb.raw_coordinates=
2043 [HW] Make the MicroTouch USB driver use raw coordinates
2044 ('y', default) or cooked coordinates ('n')
2046 mtrr_chunk_size=nn[KMG] [X86]
2047 used for mtrr cleanup. It is largest continuous chunk
2048 that could hold holes aka. UC entries.
2050 mtrr_gran_size=nn[KMG] [X86]
2051 Used for mtrr cleanup. It is granularity of mtrr block.
2053 Large value could prevent small alignment from
2056 mtrr_spare_reg_nr=n [X86]
2058 Range: 0,7 : spare reg number
2060 Used for mtrr cleanup. It is spare mtrr entries number.
2061 Set to 2 or more if your graphical card needs more.
2063 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2065 netdev= [NET] Network devices parameters
2066 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2067 Note that mem_start is often overloaded to mean
2068 something different and driver-specific.
2069 This usage is only documented in each driver source
2073 [NETFILTER] Enable connection tracking flow accounting
2074 0 to disable accounting
2075 1 to enable accounting
2078 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2079 See Documentation/filesystems/nfs/nfsroot.txt.
2081 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2082 See Documentation/filesystems/nfs/nfsroot.txt.
2084 nfsrootdebug [NFS] enable nfsroot debugging messages.
2085 See Documentation/filesystems/nfs/nfsroot.txt.
2087 nfs.callback_tcpport=
2088 [NFS] set the TCP port on which the NFSv4 callback
2089 channel should listen.
2092 [NFS] sets the pathname to the program which is used
2093 to update the NFS client cache entries.
2095 nfs.cache_getent_timeout=
2096 [NFS] sets the timeout after which an attempt to
2097 update a cache entry is deemed to have failed.
2099 nfs.idmap_cache_timeout=
2100 [NFS] set the maximum lifetime for idmapper cache
2104 [NFS] enable 64-bit inode numbers.
2105 If zero, the NFS client will fake up a 32-bit inode
2106 number for the readdir() and stat() syscalls instead
2107 of returning the full 64-bit number.
2108 The default is to return 64-bit inode numbers.
2110 nfs.max_session_slots=
2111 [NFSv4.1] Sets the maximum number of session slots
2112 the client will attempt to negotiate with the server.
2113 This limits the number of simultaneous RPC requests
2114 that the client can send to the NFSv4.1 server.
2115 Note that there is little point in setting this
2116 value higher than the max_tcp_slot_table_limit.
2118 nfs.nfs4_disable_idmapping=
2119 [NFSv4] When set to the default of '1', this option
2120 ensures that both the RPC level authentication
2121 scheme and the NFS level operations agree to use
2122 numeric uids/gids if the mount is using the
2123 'sec=sys' security flavour. In effect it is
2124 disabling idmapping, which can make migration from
2125 legacy NFSv2/v3 systems to NFSv4 easier.
2126 Servers that do not support this mode of operation
2127 will be autodetected by the client, and it will fall
2128 back to using the idmapper.
2129 To turn off this behaviour, set the value to '0'.
2131 [NFS4] Specify an additional fixed unique ident-
2132 ification string that NFSv4 clients can insert into
2133 their nfs_client_id4 string. This is typically a
2134 UUID that is generated at system install time.
2136 nfs.send_implementation_id =
2137 [NFSv4.1] Send client implementation identification
2138 information in exchange_id requests.
2139 If zero, no implementation identification information
2141 The default is to send the implementation identification
2144 nfs.recover_lost_locks =
2145 [NFSv4] Attempt to recover locks that were lost due
2146 to a lease timeout on the server. Please note that
2147 doing this risks data corruption, since there are
2148 no guarantees that the file will remain unchanged
2149 after the locks are lost.
2150 If you want to enable the kernel legacy behaviour of
2151 attempting to recover these locks, then set this
2153 The default parameter value of '0' causes the kernel
2154 not to attempt recovery of lost locks.
2156 nfsd.nfs4_disable_idmapping=
2157 [NFSv4] When set to the default of '1', the NFSv4
2158 server will return only numeric uids and gids to
2159 clients using auth_sys, and will accept numeric uids
2160 and gids from such clients. This is intended to ease
2161 migration from NFSv2/v3.
2163 objlayoutdriver.osd_login_prog=
2164 [NFS] [OBJLAYOUT] sets the pathname to the program which
2165 is used to automatically discover and login into new
2166 osd-targets. Please see:
2167 Documentation/filesystems/pnfs.txt for more explanations
2169 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2170 when a NMI is triggered.
2171 Format: [state][,regs][,debounce][,die]
2173 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2174 Format: [panic,][nopanic,][num]
2176 0 - turn nmi_watchdog off
2177 When panic is specified, panic when an NMI watchdog
2178 timeout occurs (or 'nopanic' to override the opposite
2180 This is useful when you use a panic=... timeout and
2181 need the box quickly up again.
2183 netpoll.carrier_timeout=
2184 [NET] Specifies amount of time (in seconds) that
2185 netpoll should wait for a carrier. By default netpoll
2188 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2189 emulation library even if a 387 maths coprocessor
2193 [HW] Never suspend the console
2194 Disable suspending of consoles during suspend and
2195 hibernate operations. Once disabled, debugging
2196 messages can reach various consoles while the rest
2197 of the system is being put to sleep (ie, while
2198 debugging driver suspend/resume hooks). This may
2199 not work reliably with all consoles, but is known
2200 to work with serial and VGA consoles.
2201 To facilitate more flexible debugging, we also add
2202 console_suspend, a printk module parameter to control
2203 it. Users could use console_suspend (usually
2204 /sys/module/printk/parameters/console_suspend) to
2205 turn on/off it dynamically.
2207 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2208 caches in the slab allocator. Saves per-node memory,
2209 but will impact performance.
2213 noapic [SMP,APIC] Tells the kernel to not make use of any
2214 IOAPICs that may be present in the system.
2216 noautogroup Disable scheduler automatic task group creation.
2218 nobats [PPC] Do not use BATs for mapping kernel lowmem
2219 on "Classic" PPC cores.
2223 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2225 nodelayacct [KNL] Disable per-task delay accounting
2227 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2229 nodsp [SH] Disable hardware DSP at boot time.
2231 noefi [X86] Disable EFI runtime services support.
2236 On X86-32 available only on PAE configured kernels.
2237 noexec=on: enable non-executable mappings (default)
2238 noexec=off: disable non-executable mappings
2241 Disable SMAP (Supervisor Mode Access Prevention)
2242 even if it is supported by processor.
2245 Disable SMEP (Supervisor Mode Execution Prevention)
2246 even if it is supported by processor.
2249 This affects only 32-bit executables.
2250 noexec32=on: enable non-executable mappings (default)
2251 read doesn't imply executable mappings
2252 noexec32=off: disable non-executable mappings
2253 read implies executable mappings
2255 nofpu [SH] Disable hardware FPU at boot time.
2257 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2258 register save and restore. The kernel will only save
2259 legacy floating-point registers on task switch.
2261 noxsave [BUGS=X86] Disables x86 extended register state save
2262 and restore using xsave. The kernel will fallback to
2263 enabling legacy floating-point and sse state.
2265 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2266 register states. The kernel will fall back to use
2267 xsave to save the states. By using this parameter,
2268 performance of saving the states is degraded because
2269 xsave doesn't support modified optimization while
2270 xsaveopt supports it on xsaveopt enabled systems.
2272 noxsaves [X86] Disables xsaves and xrstors used in saving and
2273 restoring x86 extended register state in compacted
2274 form of xsave area. The kernel will fall back to use
2275 xsaveopt and xrstor to save and restore the states
2276 in standard form of xsave area. By using this
2277 parameter, xsave area per process might occupy more
2278 memory on xsaves enabled systems.
2281 on enable eager fpu restore
2282 off disable eager fpu restore
2283 auto selects the default scheme, which automatically
2284 enables eagerfpu restore for xsaveopt.
2286 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2287 wfi(ARM) instruction doesn't work correctly and not to
2288 use it. This is also useful when using JTAG debugger.
2290 no_file_caps Tells the kernel not to honor file capabilities. The
2291 only way then for a file to be executed with privilege
2292 is to be setuid root or executed by root.
2294 nohalt [IA-64] Tells the kernel not to use the power saving
2295 function PAL_HALT_LIGHT when idle. This increases
2296 power-consumption. On the positive side, it reduces
2297 interrupt wake-up latency, which may improve performance
2298 in certain environments such as networked servers or
2301 nohibernate [HIBERNATION] Disable hibernation and resume.
2303 nohz= [KNL] Boottime enable/disable dynamic ticks
2304 Valid arguments: on, off
2307 nohz_full= [KNL,BOOT]
2308 In kernels built with CONFIG_NO_HZ_FULL=y, set
2309 the specified list of CPUs whose tick will be stopped
2310 whenever possible. The boot CPU will be forced outside
2311 the range to maintain the timekeeping.
2312 The CPUs in this range must also be included in the
2315 noiotrap [SH] Disables trapped I/O port accesses.
2317 noirqdebug [X86-32] Disables the code which attempts to detect and
2318 disable unhandled interrupt sources.
2320 no_timer_check [X86,APIC] Disables the code which tests for
2321 broken timer IRQ sources.
2323 noisapnp [ISAPNP] Disables ISA PnP code.
2325 noinitrd [RAM] Tells the kernel not to load any configured
2328 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2330 [Deprecated - use intremap=off]
2334 nojitter [IA-64] Disables jitter checking for ITC timers.
2336 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2338 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2341 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2342 steal time is computed, but won't influence scheduler
2345 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2347 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2349 noltlbs [PPC] Do not use large page/tlb entries for kernel
2350 lowmem mapping on PPC40x.
2352 nomca [IA-64] Disable machine check abort handling
2354 nomce [X86-32] Machine Check Exception
2356 nomfgpt [X86-32] Disable Multi-Function General Purpose
2357 Timer usage (for AMD Geode machines).
2359 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2360 shutdown the other cpus. Instead use the REBOOT_VECTOR
2363 nomodule Disable module load
2365 nopat [X86] Disable PAT (page attribute table extension of
2366 pagetables) support.
2368 norandmaps Don't use address space randomization. Equivalent to
2369 echo 0 > /proc/sys/kernel/randomize_va_space
2371 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2373 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2374 with UP alternatives
2376 nordrand [X86] Disable kernel use of the RDRAND and
2377 RDSEED instructions even if they are supported
2378 by the processor. RDRAND and RDSEED are still
2379 available to user space applications.
2381 noresume [SWSUSP] Disables resume and restores original swap
2384 no-scroll [VGA] Disables scrollback.
2385 This is required for the Braillex ib80-piezo Braille
2386 reader made by F.H. Papenmeier (Germany).
2390 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2392 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2393 and disable the IO APIC. legacy for "maxcpus=0".
2395 nosoftlockup [KNL] Disable the soft-lockup detector.
2397 nosync [HW,M68K] Disables sync negotiation for all devices.
2399 notsc [BUGS=X86-32] Disable Time Stamp Counter
2401 nousb [USB] Disable the USB subsystem
2403 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2407 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2409 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2410 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2411 Some features depend on CPU0. Known dependencies are:
2412 1. Resume from suspend/hibernate depends on CPU0.
2413 Suspend/hibernate will fail if CPU0 is offline and you
2414 need to online CPU0 before suspend/hibernate.
2415 2. PIC interrupts also depend on CPU0. CPU0 can't be
2416 removed if a PIC interrupt is detected.
2417 It's said poweroff/reboot may depend on CPU0 on some
2418 machines although I haven't seen such issues so far
2419 after CPU0 is offline on a few tested machines.
2420 If the dependencies are under your control, you can
2421 turn on cpu0_hotplug.
2423 nptcg= [IA-64] Override max number of concurrent global TLB
2424 purges which is reported from either PAL_VM_SUMMARY or
2427 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2428 could support. nr_cpus=n : n >= 1 limits the kernel to
2429 supporting 'n' processors. Later in runtime you can not
2430 use hotplug cpu feature to put more cpu back to online.
2431 just like you compile the kernel NR_CPUS=n
2433 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2435 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2436 Allowed values are enable and disable
2438 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2439 one of ['zone', 'node', 'default'] can be specified
2440 This can be set from sysctl after boot.
2441 See Documentation/sysctl/vm.txt for details.
2443 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2444 See Documentation/debugging-via-ohci1394.txt for more
2447 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2448 Rather than timing out after 20 ms if an EC
2449 command is not properly ACKed, override the length
2450 of the timeout. We have interrupts disabled while
2451 waiting for the ACK, so if this is set too high
2452 interrupts *may* be lost!
2454 omap_mux= [OMAP] Override bootloader pin multiplexing.
2455 Format: <mux_mode0.mode_name=value>...
2456 For example, to override I2C bus2:
2457 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2459 oprofile.timer= [HW]
2460 Use timer interrupt instead of performance counters
2462 oprofile.cpu_type= Force an oprofile cpu type
2463 This might be useful if you have an older oprofile
2464 userland or if you want common events.
2465 Format: { arch_perfmon }
2466 arch_perfmon: [X86] Force use of architectural
2467 perfmon on Intel CPUs instead of the
2468 CPU specific event set.
2469 timer: [X86] Force use of architectural NMI
2470 timer mode (see also oprofile.timer
2471 for generic hr timer mode)
2472 [s390] Force legacy basic mode sampling
2473 (report cpu_type "timer")
2475 oops=panic Always panic on oopses. Default is to just kill the
2476 process, but there is a small probability of
2477 deadlocking the machine.
2478 This will also cause panics on machine check exceptions.
2479 Useful together with panic=30 to trigger a reboot.
2482 See Documentation/sound/oss/oss-parameters.txt
2484 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2485 timeout > 0: seconds before rebooting
2486 timeout = 0: wait forever
2487 timeout < 0: reboot immediately
2490 crash_kexec_post_notifiers
2491 Run kdump after running panic-notifiers and dumping
2492 kmsg. This only for the users who doubt kdump always
2493 succeeds in any situation.
2494 Note that this also increases risks of kdump failure,
2495 because some panic notifiers can make the crashed
2496 kernel more unstable.
2498 parkbd.port= [HW] Parallel port number the keyboard adapter is
2499 connected to, default is 0.
2501 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2502 0 for XT, 1 for AT (default is AT).
2505 parport= [HW,PPT] Specify parallel ports. 0 disables.
2506 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2507 Use 'auto' to force the driver to use any
2508 IRQ/DMA settings detected (the default is to
2509 ignore detected IRQ/DMA settings because of
2510 possible conflicts). You can specify the base
2511 address, IRQ, and DMA settings; IRQ and DMA
2512 should be numbers, or 'auto' (for using detected
2513 settings on that particular port), or 'nofifo'
2514 (to avoid using a FIFO even if it is detected).
2515 Parallel ports are assigned in the order they
2516 are specified on the command line, starting
2519 parport_init_mode= [HW,PPT]
2520 Configure VIA parallel port to operate in
2521 a specific mode. This is necessary on Pegasos
2522 computer where firmware has no options for setting
2523 up parallel port mode and sets it to spp.
2524 Currently this function knows 686a and 8231 chips.
2525 Format: [spp|ps2|epp|ecp|ecpepp]
2528 Halt all CPUs after the first oops has been printed for
2529 the specified number of seconds. This is to be used if
2530 your oopses keep scrolling off the screen.
2535 See header of drivers/block/paride/pcd.c.
2536 See also Documentation/blockdev/paride.txt.
2538 pci=option[,option...] [PCI] various PCI subsystem options:
2539 earlydump [X86] dump PCI config space before the kernel
2541 off [X86] don't probe for the PCI bus
2542 bios [X86-32] force use of PCI BIOS, don't access
2543 the hardware directly. Use this if your machine
2544 has a non-standard PCI host bridge.
2545 nobios [X86-32] disallow use of PCI BIOS, only direct
2546 hardware access methods are allowed. Use this
2547 if you experience crashes upon bootup and you
2548 suspect they are caused by the BIOS.
2549 conf1 [X86] Force use of PCI Configuration
2551 conf2 [X86] Force use of PCI Configuration
2553 noaer [PCIE] If the PCIEAER kernel config parameter is
2554 enabled, this kernel boot option can be used to
2555 disable the use of PCIE advanced error reporting.
2556 nodomains [PCI] Disable support for multiple PCI
2557 root domains (aka PCI segments, in ACPI-speak).
2558 nommconf [X86] Disable use of MMCONFIG for PCI
2560 check_enable_amd_mmconf [X86] check for and enable
2561 properly configured MMIO access to PCI
2562 config space on AMD family 10h CPU
2563 nomsi [MSI] If the PCI_MSI kernel config parameter is
2564 enabled, this kernel boot option can be used to
2565 disable the use of MSI interrupts system-wide.
2566 noioapicquirk [APIC] Disable all boot interrupt quirks.
2567 Safety option to keep boot IRQs enabled. This
2568 should never be necessary.
2569 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2570 primary IO-APIC for bridges that cannot disable
2571 boot IRQs. This fixes a source of spurious IRQs
2572 when the system masks IRQs.
2573 noioapicreroute [APIC] Disable workaround that uses the
2574 boot IRQ equivalent of an IRQ that connects to
2575 a chipset where boot IRQs cannot be disabled.
2576 The opposite of ioapicreroute.
2577 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2578 routing table. These calls are known to be buggy
2579 on several machines and they hang the machine
2580 when used, but on other computers it's the only
2581 way to get the interrupt routing table. Try
2582 this option if the kernel is unable to allocate
2583 IRQs or discover secondary PCI buses on your
2585 rom [X86] Assign address space to expansion ROMs.
2586 Use with caution as certain devices share
2587 address decoders between ROMs and other
2589 norom [X86] Do not assign address space to
2590 expansion ROMs that do not already have
2591 BIOS assigned address ranges.
2592 nobar [X86] Do not assign address space to the
2593 BARs that weren't assigned by the BIOS.
2594 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2595 assigned automatically to PCI devices. You can
2596 make the kernel exclude IRQs of your ISA cards
2598 pirqaddr=0xAAAAA [X86] Specify the physical address
2599 of the PIRQ table (normally generated
2600 by the BIOS) if it is outside the
2601 F0000h-100000h range.
2602 lastbus=N [X86] Scan all buses thru bus #N. Can be
2603 useful if the kernel is unable to find your
2604 secondary buses and you want to tell it
2605 explicitly which ones they are.
2606 assign-busses [X86] Always assign all PCI bus
2607 numbers ourselves, overriding
2608 whatever the firmware may have done.
2609 usepirqmask [X86] Honor the possible IRQ mask stored
2610 in the BIOS $PIR table. This is needed on
2611 some systems with broken BIOSes, notably
2612 some HP Pavilion N5400 and Omnibook XE3
2613 notebooks. This will have no effect if ACPI
2614 IRQ routing is enabled.
2615 noacpi [X86] Do not use ACPI for IRQ routing
2616 or for PCI scanning.
2617 use_crs [X86] Use PCI host bridge window information
2618 from ACPI. On BIOSes from 2008 or later, this
2619 is enabled by default. If you need to use this,
2620 please report a bug.
2621 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2622 If you need to use this, please report a bug.
2623 routeirq Do IRQ routing for all PCI devices.
2624 This is normally done in pci_enable_device(),
2625 so this option is a temporary workaround
2626 for broken drivers that don't call it.
2627 skip_isa_align [X86] do not align io start addr, so can
2628 handle more pci cards
2629 firmware [ARM] Do not re-enumerate the bus but instead
2630 just use the configuration from the
2631 bootloader. This is currently used on
2632 IXP2000 systems where the bus has to be
2633 configured a certain way for adjunct CPUs.
2634 noearly [X86] Don't do any early type 1 scanning.
2635 This might help on some broken boards which
2636 machine check when some devices' config space
2637 is read. But various workarounds are disabled
2638 and some IOMMU drivers will not work.
2639 bfsort Sort PCI devices into breadth-first order.
2640 This sorting is done to get a device
2641 order compatible with older (<= 2.4) kernels.
2642 nobfsort Don't sort PCI devices into breadth-first order.
2643 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2644 tuning and use the BIOS-configured MPS defaults.
2645 pcie_bus_safe Set every device's MPS to the largest value
2646 supported by all devices below the root complex.
2647 pcie_bus_perf Set device MPS to the largest allowable MPS
2648 based on its parent bus. Also set MRRS (Max
2649 Read Request Size) to the largest supported
2650 value (no larger than the MPS that the device
2651 or bus can support) for best performance.
2652 pcie_bus_peer2peer Set every device's MPS to 128B, which
2653 every device is guaranteed to support. This
2654 configuration allows peer-to-peer DMA between
2655 any pair of devices, possibly at the cost of
2656 reduced performance. This also guarantees
2657 that hot-added devices will work.
2658 cbiosize=nn[KMG] The fixed amount of bus space which is
2659 reserved for the CardBus bridge's IO window.
2660 The default value is 256 bytes.
2661 cbmemsize=nn[KMG] The fixed amount of bus space which is
2662 reserved for the CardBus bridge's memory
2663 window. The default value is 64 megabytes.
2666 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2667 Specifies alignment and device to reassign
2668 aligned memory resources.
2669 If <order of align> is not specified,
2670 PAGE_SIZE is used as alignment.
2671 PCI-PCI bridge can be specified, if resource
2672 windows need to be expanded.
2673 ecrc= Enable/disable PCIe ECRC (transaction layer
2674 end-to-end CRC checking).
2675 bios: Use BIOS/firmware settings. This is the
2679 hpiosize=nn[KMG] The fixed amount of bus space which is
2680 reserved for hotplug bridge's IO window.
2681 Default size is 256 bytes.
2682 hpmemsize=nn[KMG] The fixed amount of bus space which is
2683 reserved for hotplug bridge's memory window.
2684 Default size is 2 megabytes.
2685 realloc= Enable/disable reallocating PCI bridge resources
2686 if allocations done by BIOS are too small to
2687 accommodate resources required by all child
2689 off: Turn realloc off
2691 realloc same as realloc=on
2692 noari do not use PCIe ARI.
2693 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2694 only look for one device below a PCIe downstream
2697 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2700 force Enable ASPM even on devices that claim not to support it.
2701 WARNING: Forcing ASPM on may cause system lockups.
2703 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2704 nomsi Do not use MSI for PCI Express Native Hotplug (this
2705 makes all PCIe ports use INTx for hotplug services).
2707 pcie_ports= [PCIE] PCIe ports handling:
2708 auto Ask the BIOS whether or not to use native PCIe services
2709 associated with PCIe ports (PME, hot-plug, AER). Use
2710 them only if that is allowed by the BIOS.
2711 native Use native PCIe services associated with PCIe ports
2713 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2716 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2717 nomsi Do not use MSI for native PCIe PME signaling (this makes
2718 all PCIe root ports use INTx for all services).
2720 pcmv= [HW,PCMCIA] BadgePAD 4
2724 Keep all power-domains already enabled by bootloader on,
2725 even if no driver has claimed them. This is useful
2726 for debug and development, but should not be
2727 needed on a platform with proper driver support.
2730 See Documentation/blockdev/paride.txt.
2732 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2735 See arch/parisc/kernel/pdc_chassis.c
2737 percpu_alloc= Select which percpu first chunk allocator to use.
2738 Currently supported values are "embed" and "page".
2739 Archs may support subset or none of the selections.
2740 See comments in mm/percpu.c for details on each
2741 allocator. This parameter is primarily for debugging
2742 and performance comparison.
2745 See Documentation/blockdev/paride.txt.
2748 See Documentation/blockdev/paride.txt.
2750 pirq= [SMP,APIC] Manual mp-table setup
2751 See Documentation/x86/i386/IO-APIC.txt.
2753 plip= [PPT,NET] Parallel port network link
2754 Format: { parport<nr> | timid | 0 }
2755 See also Documentation/parport.txt.
2757 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2758 Override pmtimer IOPort with a hex value.
2762 Enable PNP debug messages (depends on the
2763 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2764 via /sys/module/pnp/parameters/debug. We always show
2765 current resource usage; turning this on also shows
2766 possible settings and some assignment information.
2772 { on | off | curr | res | no-curr | no-res }
2775 [ISAPNP] Exclude IRQs for the autoconfiguration
2778 [ISAPNP] Exclude DMAs for the autoconfiguration
2780 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2781 Ranges are in pairs (I/O port base and size).
2784 [ISAPNP] Exclude memory regions for the
2786 Ranges are in pairs (memory base and size).
2788 ports= [IP_VS_FTP] IPVS ftp helper module
2790 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2792 Format: <port>,<port>....
2794 print-fatal-signals=
2795 [KNL] debug: print fatal signals
2797 If enabled, warn about various signal handling
2798 related application anomalies: too many signals,
2799 too many POSIX.1 timers, fatal signals causing a
2802 If you hit the warning due to signal overflow,
2803 you might want to try "ulimit -i unlimited".
2807 printk.always_kmsg_dump=
2808 Trigger kmsg_dump for cases other than kernel oops or
2810 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2813 printk.time= Show timing data prefixed to each printk message line
2814 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2816 processor.max_cstate= [HW,ACPI]
2817 Limit processor to maximum C-state
2818 max_cstate=9 overrides any DMI blacklist limit.
2820 processor.nocst [HW,ACPI]
2821 Ignore the _CST method to determine C-states,
2822 instead using the legacy FADT method
2824 profile= [KNL] Enable kernel profiling via /proc/profile
2825 Format: [schedule,]<number>
2826 Param: "schedule" - profile schedule points.
2827 Param: <number> - step/bucket size as a power of 2 for
2828 statistical time based profiling.
2829 Param: "sleep" - profile D-state sleeping (millisecs).
2830 Requires CONFIG_SCHEDSTATS
2831 Param: "kvm" - profile VM exits.
2833 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2835 See Documentation/blockdev/ramdisk.txt.
2837 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2838 probe for; one of (bare|imps|exps|lifebook|any).
2839 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2841 psmouse.resetafter= [HW,MOUSE]
2842 Try to reset the device after so many bad packets
2845 [HW,MOUSE] Set desired mouse resolution, in dpi.
2846 psmouse.smartscroll=
2847 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2848 0 = disabled, 1 = enabled (default).
2850 pstore.backend= Specify the name of the pstore backend to use
2853 See Documentation/blockdev/paride.txt.
2856 [KNL] Number of legacy pty's. Overwrites compiled-in
2859 quiet [KNL] Disable most log messages
2864 See Documentation/md.txt.
2866 ramdisk_blocksize= [RAM]
2867 See Documentation/blockdev/ramdisk.txt.
2869 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2870 See Documentation/blockdev/ramdisk.txt.
2873 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2874 the specified list of CPUs to be no-callback CPUs.
2875 Invocation of these CPUs' RCU callbacks will
2876 be offloaded to "rcuox/N" kthreads created for
2877 that purpose, where "x" is "b" for RCU-bh, "p"
2878 for RCU-preempt, and "s" for RCU-sched, and "N"
2879 is the CPU number. This reduces OS jitter on the
2880 offloaded CPUs, which can be useful for HPC and
2881 real-time workloads. It can also improve energy
2882 efficiency for asymmetric multiprocessors.
2885 Rather than requiring that offloaded CPUs
2886 (specified by rcu_nocbs= above) explicitly
2887 awaken the corresponding "rcuoN" kthreads,
2888 make these kthreads poll for callbacks.
2889 This improves the real-time response for the
2890 offloaded CPUs by relieving them of the need to
2891 wake up the corresponding kthread, but degrades
2892 energy efficiency by requiring that the kthreads
2893 periodically wake up to do the polling.
2895 rcutree.blimit= [KNL]
2896 Set maximum number of finished RCU callbacks to
2897 process in one batch.
2899 rcutree.rcu_fanout_leaf= [KNL]
2900 Increase the number of CPUs assigned to each
2901 leaf rcu_node structure. Useful for very large
2904 rcutree.jiffies_till_sched_qs= [KNL]
2905 Set required age in jiffies for a
2906 given grace period before RCU starts
2907 soliciting quiescent-state help from
2908 rcu_note_context_switch().
2910 rcutree.jiffies_till_first_fqs= [KNL]
2911 Set delay from grace-period initialization to
2912 first attempt to force quiescent states.
2913 Units are jiffies, minimum value is zero,
2914 and maximum value is HZ.
2916 rcutree.jiffies_till_next_fqs= [KNL]
2917 Set delay between subsequent attempts to force
2918 quiescent states. Units are jiffies, minimum
2919 value is one, and maximum value is HZ.
2921 rcutree.rcu_nocb_leader_stride= [KNL]
2922 Set the number of NOCB kthread groups, which
2923 defaults to the square root of the number of
2924 CPUs. Larger numbers reduces the wakeup overhead
2925 on the per-CPU grace-period kthreads, but increases
2926 that same overhead on each group's leader.
2928 rcutree.qhimark= [KNL]
2929 Set threshold of queued RCU callbacks beyond which
2930 batch limiting is disabled.
2932 rcutree.qlowmark= [KNL]
2933 Set threshold of queued RCU callbacks below which
2934 batch limiting is re-enabled.
2936 rcutree.rcu_idle_gp_delay= [KNL]
2937 Set wakeup interval for idle CPUs that have
2938 RCU callbacks (RCU_FAST_NO_HZ=y).
2940 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2941 Set wakeup interval for idle CPUs that have
2942 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2943 Lazy RCU callbacks are those which RCU can
2944 prove do nothing more than free memory.
2946 rcutorture.cbflood_inter_holdoff= [KNL]
2947 Set holdoff time (jiffies) between successive
2948 callback-flood tests.
2950 rcutorture.cbflood_intra_holdoff= [KNL]
2951 Set holdoff time (jiffies) between successive
2952 bursts of callbacks within a given callback-flood
2955 rcutorture.cbflood_n_burst= [KNL]
2956 Set the number of bursts making up a given
2957 callback-flood test. Set this to zero to
2958 disable callback-flood testing.
2960 rcutorture.cbflood_n_per_burst= [KNL]
2961 Set the number of callbacks to be registered
2962 in a given burst of a callback-flood test.
2964 rcutorture.fqs_duration= [KNL]
2965 Set duration of force_quiescent_state bursts.
2967 rcutorture.fqs_holdoff= [KNL]
2968 Set holdoff time within force_quiescent_state bursts.
2970 rcutorture.fqs_stutter= [KNL]
2971 Set wait time between force_quiescent_state bursts.
2973 rcutorture.gp_exp= [KNL]
2974 Use expedited update-side primitives.
2976 rcutorture.gp_normal= [KNL]
2977 Use normal (non-expedited) update-side primitives.
2978 If both gp_exp and gp_normal are set, do both.
2979 If neither gp_exp nor gp_normal are set, still
2982 rcutorture.n_barrier_cbs= [KNL]
2983 Set callbacks/threads for rcu_barrier() testing.
2985 rcutorture.nfakewriters= [KNL]
2986 Set number of concurrent RCU writers. These just
2987 stress RCU, they don't participate in the actual
2988 test, hence the "fake".
2990 rcutorture.nreaders= [KNL]
2991 Set number of RCU readers.
2993 rcutorture.object_debug= [KNL]
2994 Enable debug-object double-call_rcu() testing.
2996 rcutorture.onoff_holdoff= [KNL]
2997 Set time (s) after boot for CPU-hotplug testing.
2999 rcutorture.onoff_interval= [KNL]
3000 Set time (s) between CPU-hotplug operations, or
3001 zero to disable CPU-hotplug testing.
3003 rcutorture.torture_runnable= [BOOT]
3004 Start rcutorture running at boot time.
3006 rcutorture.shuffle_interval= [KNL]
3007 Set task-shuffle interval (s). Shuffling tasks
3008 allows some CPUs to go into dyntick-idle mode
3009 during the rcutorture test.
3011 rcutorture.shutdown_secs= [KNL]
3012 Set time (s) after boot system shutdown. This
3013 is useful for hands-off automated testing.
3015 rcutorture.stall_cpu= [KNL]
3016 Duration of CPU stall (s) to test RCU CPU stall
3017 warnings, zero to disable.
3019 rcutorture.stall_cpu_holdoff= [KNL]
3020 Time to wait (s) after boot before inducing stall.
3022 rcutorture.stat_interval= [KNL]
3023 Time (s) between statistics printk()s.
3025 rcutorture.stutter= [KNL]
3026 Time (s) to stutter testing, for example, specifying
3027 five seconds causes the test to run for five seconds,
3028 wait for five seconds, and so on. This tests RCU's
3029 ability to transition abruptly to and from idle.
3031 rcutorture.test_boost= [KNL]
3032 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3033 "Maybe" means test if the RCU implementation
3034 under test support RCU priority boosting.
3036 rcutorture.test_boost_duration= [KNL]
3037 Duration (s) of each individual boost test.
3039 rcutorture.test_boost_interval= [KNL]
3040 Interval (s) between each boost test.
3042 rcutorture.test_no_idle_hz= [KNL]
3043 Test RCU's dyntick-idle handling. See also the
3044 rcutorture.shuffle_interval parameter.
3046 rcutorture.torture_type= [KNL]
3047 Specify the RCU implementation to test.
3049 rcutorture.verbose= [KNL]
3050 Enable additional printk() statements.
3052 rcupdate.rcu_expedited= [KNL]
3053 Use expedited grace-period primitives, for
3054 example, synchronize_rcu_expedited() instead
3055 of synchronize_rcu(). This reduces latency,
3056 but can increase CPU utilization, degrade
3057 real-time latency, and degrade energy efficiency.
3059 rcupdate.rcu_cpu_stall_suppress= [KNL]
3060 Suppress RCU CPU stall warning messages.
3062 rcupdate.rcu_cpu_stall_timeout= [KNL]
3063 Set timeout for RCU CPU stall warning messages.
3065 rcupdate.rcu_task_stall_timeout= [KNL]
3066 Set timeout in jiffies for RCU task stall warning
3067 messages. Disable with a value less than or equal
3072 Run specified binary instead of /init from the ramdisk,
3073 used for early userspace startup. See initrd.
3076 Format (x86 or x86_64):
3077 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3079 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3081 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3082 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3083 reboot_force is either force or not specified,
3084 reboot_cpu is s[mp]#### with #### being the processor
3085 to be used for rebooting.
3088 [KNL, SMP] Set scheduler's default relax_domain_level.
3089 See Documentation/cgroups/cpusets.txt.
3091 relative_sleep_states=
3092 [SUSPEND] Use sleep state labeling where the deepest
3093 state available other than hibernation is always "mem".
3094 Format: { "0" | "1" }
3095 0 -- Traditional sleep state labels.
3096 1 -- Relative sleep state labels.
3098 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3100 reservetop= [X86-32]
3102 Reserves a hole at the top of the kernel virtual
3107 Set the amount of memory to reserve for BIOS at
3108 the bottom of the address space.
3110 reset_devices [KNL] Force drivers to reset the underlying device
3111 during initialization.
3114 Specify the partition device for software suspend
3116 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3118 resume_offset= [SWSUSP]
3119 Specify the offset from the beginning of the partition
3120 given by "resume=" at which the swap header is located,
3121 in <PAGE_SIZE> units (needed only for swap files).
3122 See Documentation/power/swsusp-and-swap-files.txt
3124 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3125 read the resume files
3127 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3128 Useful for devices that are detected asynchronously
3129 (e.g. USB and MMC devices).
3131 hibernate= [HIBERNATION]
3132 noresume Don't check if there's a hibernation image
3133 present during boot.
3134 nocompress Don't compress/decompress hibernation images.
3135 no Disable hibernation and resume.
3137 retain_initrd [RAM] Keep initrd memory after extraction
3139 rhash_entries= [KNL,NET]
3140 Set number of hash buckets for route cache
3142 ro [KNL] Mount root device read-only on boot
3144 root= [KNL] Root filesystem
3145 See name_to_dev_t comment in init/do_mounts.c.
3147 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3148 mount the root filesystem
3150 rootflags= [KNL] Set root filesystem mount option string
3152 rootfstype= [KNL] Set root filesystem type
3154 rootwait [KNL] Wait (indefinitely) for root device to show up.
3155 Useful for devices that are detected asynchronously
3156 (e.g. USB and MMC devices).
3158 rproc_mem=nn[KMG][@address]
3159 [KNL,ARM,CMA] Remoteproc physical memory block.
3160 Memory area to be used by remote processor image,
3163 rw [KNL] Mount root device read-write on boot
3165 S [KNL] Run init in single mode
3167 s390_iommu= [HW,S390]
3168 Set s390 IOTLB flushing mode
3170 With strict flushing every unmap operation will result in
3171 an IOTLB flush. Default is lazy flushing before reuse,
3175 See drivers/net/irda/sa1100_ir.c.
3177 sbni= [NET] Granch SBNI12 leased line adapter
3179 sched_debug [KNL] Enables verbose scheduler debug messages.
3181 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3182 xtime_lock contention on larger systems, and/or RCU lock
3183 contention on all systems with CONFIG_MAXSMP set.
3184 Format: { "0" | "1" }
3185 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3187 Note: increases power consumption, thus should only be
3188 enabled if running jitter sensitive (HPC/RT) workloads.
3190 security= [SECURITY] Choose a security module to enable at boot.
3191 If this boot parameter is not specified, only the first
3192 security module asking for security registration will be
3193 loaded. An invalid security module name will be treated
3194 as if no module has been chosen.
3196 selinux= [SELINUX] Disable or enable SELinux at boot time.
3197 Format: { "0" | "1" }
3198 See security/selinux/Kconfig help text.
3201 Default value is set via kernel config option.
3202 If enabled at boot time, /selinux/disable can be used
3203 later to disable prior to initial policy load.
3205 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3206 Format: { "0" | "1" }
3207 See security/apparmor/Kconfig help text
3210 Default value is set via kernel config option.
3212 serialnumber [BUGS=X86-32]
3215 Maximal number of shapers.
3217 show_msr= [x86] show boot-time MSR settings
3218 Format: { <integer> }
3219 Show boot-time (BIOS-initialized) MSR settings.
3220 The parameter means the number of CPUs to show,
3221 for example 1 means boot CPU only.
3229 Disable merging of slabs with similar size. May be
3230 necessary if there is some reason to distinguish
3231 allocs to different slabs. Debug options disable
3232 merging on their own.
3233 For more information see Documentation/vm/slub.txt.
3235 slab_max_order= [MM, SLAB]
3236 Determines the maximum allowed order for slabs.
3237 A high setting may cause OOMs due to memory
3238 fragmentation. Defaults to 1 for systems with
3239 more than 32MB of RAM, 0 otherwise.
3241 slub_debug[=options[,slabs]] [MM, SLUB]
3242 Enabling slub_debug allows one to determine the
3243 culprit if slab objects become corrupted. Enabling
3244 slub_debug can create guard zones around objects and
3245 may poison objects when not in use. Also tracks the
3246 last alloc / free. For more information see
3247 Documentation/vm/slub.txt.
3249 slub_max_order= [MM, SLUB]
3250 Determines the maximum allowed order for slabs.
3251 A high setting may cause OOMs due to memory
3252 fragmentation. For more information see
3253 Documentation/vm/slub.txt.
3255 slub_min_objects= [MM, SLUB]
3256 The minimum number of objects per slab. SLUB will
3257 increase the slab order up to slub_max_order to
3258 generate a sufficiently large slab able to contain
3259 the number of objects indicated. The higher the number
3260 of objects the smaller the overhead of tracking slabs
3261 and the less frequently locks need to be acquired.
3262 For more information see Documentation/vm/slub.txt.
3264 slub_min_order= [MM, SLUB]
3265 Determines the minimum page order for slabs. Must be
3266 lower than slub_max_order.
3267 For more information see Documentation/vm/slub.txt.
3269 slub_nomerge [MM, SLUB]
3270 Same with slab_nomerge. This is supported for legacy.
3271 See slab_nomerge for more information.
3274 Format: <io1>[,<io2>[,...,<io8>]]
3276 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3277 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3278 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3279 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3280 smsc-ircc2.ircc_irq= [HW] IRQ line
3281 smsc-ircc2.ircc_dma= [HW] DMA channel
3282 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3283 0: Toshiba Satellite 1800 (GP data pin select)
3284 1: Fast pin select (default)
3288 [KNL] Should the soft-lockup detector generate panics.
3291 softlockup_all_cpu_backtrace=
3292 [KNL] Should the soft-lockup detector generate
3293 backtraces on all cpus.
3296 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3297 See Documentation/laptops/sonypi.txt
3299 spia_io_base= [HW,MTD]
3305 Enabled the stack tracer on boot up.
3307 stacktrace_filter=[function-list]
3308 [FTRACE] Limit the functions that the stack tracer
3309 will trace at boot up. function-list is a comma separated
3310 list of functions. This list can be changed at run
3311 time by the stack_trace_filter file in the debugfs
3312 tracing directory. Note, this enables stack tracing
3313 and the stacktrace above is not needed.
3317 Set the STI (builtin display/keyboard on the HP-PARISC
3318 machines) console (graphic card) which should be used
3319 as the initial boot-console.
3320 See also comment in drivers/video/console/sticore.c.
3323 See comment in drivers/video/console/sticore.c.
3326 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3328 sunrpc.min_resvport=
3329 sunrpc.max_resvport=
3331 SunRPC servers often require that client requests
3332 originate from a privileged port (i.e. a port in the
3333 range 0 < portnr < 1024).
3334 An administrator who wishes to reserve some of these
3335 ports for other uses may adjust the range that the
3336 kernel's sunrpc client considers to be privileged
3337 using these two parameters to set the minimum and
3338 maximum port values.
3342 Control how the NFS server code allocates CPUs to
3343 service thread pools. Depending on how many NICs
3344 you have and where their interrupts are bound, this
3345 option will affect which CPUs will do NFS serving.
3346 Note: this parameter cannot be changed while the
3347 NFS server is running.
3349 auto the server chooses an appropriate mode
3350 automatically using heuristics
3351 global a single global pool contains all CPUs
3352 percpu one pool for each CPU
3353 pernode one pool for each NUMA node (equivalent
3354 to global on non-NUMA machines)
3356 sunrpc.tcp_slot_table_entries=
3357 sunrpc.udp_slot_table_entries=
3359 Sets the upper limit on the number of simultaneous
3360 RPC calls that can be sent from the client to a
3361 server. Increasing these values may allow you to
3362 improve throughput, but will also increase the
3363 amount of memory reserved for use by the client.
3366 [KNL] Enable accounting of swap in memory resource
3367 controller if no parameter or 1 is given or disable
3368 it if 0 is given (See Documentation/cgroups/memory.txt)
3370 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3371 Format: { <int> | force }
3372 <int> -- Number of I/O TLB slabs
3373 force -- force using of bounce buffers even if they
3374 wouldn't be automatically used by the kernel
3378 sysfs.deprecated=0|1 [KNL]
3379 Enable/disable old style sysfs layout for old udev
3380 on older distributions. When this option is enabled
3381 very new udev will not work anymore. When this option
3382 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3383 in older udev will not work anymore.
3384 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3385 the kernel configuration.
3387 sysrq_always_enabled
3389 Ignore sysrq setting - this boot parameter will
3390 neutralize any effect of /proc/sys/kernel/sysrq.
3391 Useful for debugging.
3395 test_suspend= [SUSPEND][,N]
3396 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3397 standby suspend) or "freeze" (for suspend type freeze)
3398 as the system sleep state during system startup with
3399 the optional capability to repeat N number of times.
3400 The system is woken from this state using a
3401 wakeup-capable RTC alarm.
3403 thash_entries= [KNL,NET]
3404 Set number of hash buckets for TCP connection
3406 thermal.act= [HW,ACPI]
3407 -1: disable all active trip points in all thermal zones
3408 <degrees C>: override all lowest active trip points
3410 thermal.crt= [HW,ACPI]
3411 -1: disable all critical trip points in all thermal zones
3412 <degrees C>: override all critical trip points
3414 thermal.nocrt= [HW,ACPI]
3415 Set to disable actions on ACPI thermal zone
3416 critical and hot trip points.
3418 thermal.off= [HW,ACPI]
3419 1: disable ACPI thermal control
3421 thermal.psv= [HW,ACPI]
3422 -1: disable all passive trip points
3423 <degrees C>: override all passive trip points to this
3426 thermal.tzp= [HW,ACPI]
3427 Specify global default ACPI thermal zone polling rate
3428 <deci-seconds>: poll all this frequency
3429 0: no polling (default)
3432 Force threading of all interrupt handlers except those
3433 marked explicitly IRQF_NO_THREAD.
3436 Enable the Transcendent memory driver if built-in.
3438 tmem.cleancache=0|1 [KNL, XEN]
3439 Default is on (1). Disable the usage of the cleancache
3440 API to send anonymous pages to the hypervisor.
3442 tmem.frontswap=0|1 [KNL, XEN]
3443 Default is on (1). Disable the usage of the frontswap
3444 API to send swap pages to the hypervisor. If disabled
3445 the selfballooning and selfshrinking are force disabled.
3447 tmem.selfballooning=0|1 [KNL, XEN]
3448 Default is on (1). Disable the driving of swap pages
3451 tmem.selfshrinking=0|1 [KNL, XEN]
3452 Default is on (1). Partial swapoff that immediately
3453 transfers pages from Xen hypervisor back to the
3454 kernel based on different criteria.
3458 Specify if the kernel should make use of the cpu
3459 topology information if the hardware supports this.
3460 The scheduler will make use of this information and
3461 e.g. base its process migration decisions on it.
3466 tpm_suspend_pcr=[HW,TPM]
3467 Format: integer pcr id
3468 Specify that at suspend time, the tpm driver
3469 should extend the specified pcr with zeros,
3470 as a workaround for some chips which fail to
3471 flush the last written pcr on TPM_SaveState.
3472 This will guarantee that all the other pcrs
3475 trace_buf_size=nn[KMG]
3476 [FTRACE] will set tracing buffer size.
3478 trace_event=[event-list]
3479 [FTRACE] Set and start specified trace events in order
3480 to facilitate early boot debugging.
3481 See also Documentation/trace/events.txt
3483 trace_options=[option-list]
3484 [FTRACE] Enable or disable tracer options at boot.
3485 The option-list is a comma delimited list of options
3486 that can be enabled or disabled just as if you were
3487 to echo the option name into
3489 /sys/kernel/debug/tracing/trace_options
3491 For example, to enable stacktrace option (to dump the
3492 stack trace of each event), add to the command line:
3494 trace_options=stacktrace
3496 See also Documentation/trace/ftrace.txt "trace options"
3500 [FTRACE] enable this option to disable tracing when a
3501 warning is hit. This turns off "tracing_on". Tracing can
3502 be enabled again by echoing '1' into the "tracing_on"
3503 file located in /sys/kernel/debug/tracing/
3505 This option is useful, as it disables the trace before
3506 the WARNING dump is called, which prevents the trace to
3507 be filled with content caused by the warning output.
3509 This option can also be set at run time via the sysctl
3510 option: kernel/traceoff_on_warning
3512 transparent_hugepage=
3514 Format: [always|madvise|never]
3515 Can be used to control the default behavior of the system
3516 with respect to transparent hugepages.
3517 See Documentation/vm/transhuge.txt for more details.
3519 tsc= Disable clocksource stability checks for TSC.
3521 [x86] reliable: mark tsc clocksource as reliable, this
3522 disables clocksource verification at runtime, as well
3523 as the stability checks done at bootup. Used to enable
3524 high-resolution timer mode on older hardware, and in
3525 virtualized environment.
3526 [x86] noirqtime: Do not use TSC to do irq accounting.
3527 Used to run time disable IRQ_TIME_ACCOUNTING on any
3528 platforms where RDTSC is slow and this accounting
3531 turbografx.map[2|3]= [HW,JOY]
3532 TurboGraFX parallel port interface
3534 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3535 See also Documentation/input/joystick-parport.txt
3537 udbg-immortal [PPC] When debugging early kernel crashes that
3538 happen after console_init() and before a proper
3539 console driver takes over, this boot options might
3540 help "seeing" what's going on.
3542 uhash_entries= [KNL,NET]
3543 Set number of hash buckets for UDP/UDP-Lite connections
3546 [USB] Ignore overcurrent events (default N).
3547 Some badly-designed motherboards generate lots of
3548 bogus events, for ports that aren't wired to
3549 anything. Set this parameter to avoid log spamming.
3550 Note that genuine overcurrent events won't be
3554 [X86] Cause panic on unknown NMI.
3556 usbcore.authorized_default=
3557 [USB] Default USB device authorization:
3558 (default -1 = authorized except for wireless USB,
3559 0 = not authorized, 1 = authorized)
3561 usbcore.autosuspend=
3562 [USB] The autosuspend time delay (in seconds) used
3563 for newly-detected USB devices (default 2). This
3564 is the time required before an idle device will be
3565 autosuspended. Devices for which the delay is set
3566 to a negative value won't be autosuspended at all.
3568 usbcore.usbfs_snoop=
3569 [USB] Set to log all usbfs traffic (default 0 = off).
3571 usbcore.blinkenlights=
3572 [USB] Set to cycle leds on hubs (default 0 = off).
3574 usbcore.old_scheme_first=
3575 [USB] Start with the old device initialization
3576 scheme (default 0 = off).
3578 usbcore.usbfs_memory_mb=
3579 [USB] Memory limit (in MB) for buffers allocated by
3580 usbfs (default = 16, 0 = max = 2047).
3582 usbcore.use_both_schemes=
3583 [USB] Try the other device initialization scheme
3584 if the first one fails (default 1 = enabled).
3586 usbcore.initial_descriptor_timeout=
3587 [USB] Specifies timeout for the initial 64-byte
3588 USB_REQ_GET_DESCRIPTOR request in milliseconds
3589 (default 5000 = 5.0 seconds).
3592 [USBHID] The interval which mice are to be polled at.
3594 usb-storage.delay_use=
3595 [UMS] The delay in seconds before a new device is
3596 scanned for Logical Units (default 5).
3599 [UMS] A list of quirks entries to supplement or
3600 override the built-in unusual_devs list. List
3601 entries are separated by commas. Each entry has
3602 the form VID:PID:Flags where VID and PID are Vendor
3603 and Product ID values (4-digit hex numbers) and
3604 Flags is a set of characters, each corresponding
3605 to a common usb-storage quirk flag as follows:
3606 a = SANE_SENSE (collect more than 18 bytes
3608 b = BAD_SENSE (don't collect more than 18
3609 bytes of sense data);
3610 c = FIX_CAPACITY (decrease the reported
3611 device capacity by one sector);
3612 d = NO_READ_DISC_INFO (don't use
3613 READ_DISC_INFO command);
3614 e = NO_READ_CAPACITY_16 (don't use
3615 READ_CAPACITY_16 command);
3616 f = NO_REPORT_OPCODES (don't use report opcodes
3618 h = CAPACITY_HEURISTICS (decrease the
3619 reported device capacity by one
3620 sector if the number is odd);
3621 i = IGNORE_DEVICE (don't bind to this
3623 l = NOT_LOCKABLE (don't try to lock and
3624 unlock ejectable media);
3625 m = MAX_SECTORS_64 (don't transfer more
3626 than 64 sectors = 32 KB at a time);
3627 n = INITIAL_READ10 (force a retry of the
3628 initial READ(10) command);
3629 o = CAPACITY_OK (accept the capacity
3630 reported by the device);
3631 p = WRITE_CACHE (the device cache is ON
3633 r = IGNORE_RESIDUE (the device reports
3634 bogus residue values);
3635 s = SINGLE_LUN (the device has only one
3637 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3638 commands, uas only);
3639 u = IGNORE_UAS (don't bind to the uas driver);
3640 w = NO_WP_DETECT (don't test whether the
3641 medium is write-protected).
3642 Example: quirks=0419:aaf5:rl,0421:0433:rc
3644 user_debug= [KNL,ARM]
3646 See arch/arm/Kconfig.debug help text.
3647 1 - undefined instruction events
3649 4 - invalid data aborts
3652 Example: user_debug=31
3655 [X86] Flags controlling user PTE allocations.
3657 nohigh = do not allocate PTE pages in
3658 HIGHMEM regardless of setting
3662 On X86_32, this is an alias for vdso32=. Otherwise:
3664 vdso=1: enable VDSO (the default)
3665 vdso=0: disable VDSO mapping
3667 vdso32= [X86] Control the 32-bit vDSO
3668 vdso32=1: enable 32-bit VDSO
3669 vdso32=0 or vdso32=2: disable 32-bit VDSO
3671 See the help text for CONFIG_COMPAT_VDSO for more
3672 details. If CONFIG_COMPAT_VDSO is set, the default is
3673 vdso32=0; otherwise, the default is vdso32=1.
3675 For compatibility with older kernels, vdso32=2 is an
3678 Try vdso32=0 if you encounter an error that says:
3679 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3682 vector=percpu: enable percpu vector domain
3684 video= [FB] Frame buffer configuration
3685 See Documentation/fb/modedb.txt.
3687 video.brightness_switch_enabled= [0,1]
3688 If set to 1, on receiving an ACPI notify event
3689 generated by hotkey, video driver will adjust brightness
3690 level and then send out the event to user space through
3691 the allocated input device; If set to 0, video driver
3692 will only send out the event without touching backlight
3697 [VMMIO] Memory mapped virtio (platform) device.
3699 <size>@<baseaddr>:<irq>[:<id>]
3701 <size> := size (can use standard suffixes
3703 <baseaddr> := physical base address
3704 <irq> := interrupt number (as passed to
3706 <id> := (optional) platform device id
3708 virtio_mmio.device=1K@0x100b0000:48:7
3710 Can be used multiple times for multiple devices.
3712 vga= [BOOT,X86-32] Select a particular video mode
3713 See Documentation/x86/boot.txt and
3714 Documentation/svga.txt.
3715 Use vga=ask for menu.
3716 This is actually a boot loader parameter; the value is
3717 passed to the kernel using a special protocol.
3719 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3720 size of <nn>. This can be used to increase the
3721 minimum size (128MB on x86). It can also be used to
3722 decrease the size and leave more room for directly
3725 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3728 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3731 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3735 Controls the behavior of vsyscalls (i.e. calls to
3736 fixed addresses of 0xffffffffff600x00 from legacy
3737 code). Most statically-linked binaries and older
3738 versions of glibc use these calls. Because these
3739 functions are at fixed addresses, they make nice
3740 targets for exploits that can control RIP.
3742 emulate [default] Vsyscalls turn into traps and are
3743 emulated reasonably safely.
3745 native Vsyscalls are native syscall instructions.
3746 This is a little bit faster than trapping
3747 and makes a few dynamic recompilers work
3748 better than they would in emulation mode.
3749 It also makes exploits much easier to write.
3751 none Vsyscalls don't work at all. This makes
3752 them quite hard to use for exploits but
3753 might break your system.
3755 vt.color= [VT] Default text color.
3756 Format: 0xYX, X = foreground, Y = background.
3757 Default: 0x07 = light gray on black.
3759 vt.cur_default= [VT] Default cursor shape.
3760 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3761 the parameters of the <Esc>[?A;B;Cc escape sequence;
3762 see VGA-softcursor.txt. Default: 2 = underline.
3764 vt.default_blu= [VT]
3765 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3766 Change the default blue palette of the console.
3767 This is a 16-member array composed of values
3770 vt.default_grn= [VT]
3771 Format: <green0>,<green1>,<green2>,...,<green15>
3772 Change the default green palette of the console.
3773 This is a 16-member array composed of values
3776 vt.default_red= [VT]
3777 Format: <red0>,<red1>,<red2>,...,<red15>
3778 Change the default red palette of the console.
3779 This is a 16-member array composed of values
3785 Set system-wide default UTF-8 mode for all tty's.
3786 Default is 1, i.e. UTF-8 mode is enabled for all
3787 newly opened terminals.
3789 vt.global_cursor_default=
3792 Set system-wide default for whether a cursor
3793 is shown on new VTs. Default is -1,
3794 i.e. cursors will be created by default unless
3795 overridden by individual drivers. 0 will hide
3796 cursors, 1 will display them.
3798 vt.italic= [VT] Default color for italic text; 0-15.
3801 vt.underline= [VT] Default color for underlined text; 0-15.
3804 watchdog timers [HW,WDT] For information on watchdog timers,
3805 see Documentation/watchdog/watchdog-parameters.txt
3806 or other driver-specific files in the
3807 Documentation/watchdog/ directory.
3809 workqueue.disable_numa
3810 By default, all work items queued to unbound
3811 workqueues are affine to the NUMA nodes they're
3812 issued on, which results in better behavior in
3813 general. If NUMA affinity needs to be disabled for
3814 whatever reason, this option can be used. Note
3815 that this also can be controlled per-workqueue for
3816 workqueues visible under /sys/bus/workqueue/.
3818 workqueue.power_efficient
3819 Per-cpu workqueues are generally preferred because
3820 they show better performance thanks to cache
3821 locality; unfortunately, per-cpu workqueues tend to
3822 be more power hungry than unbound workqueues.
3824 Enabling this makes the per-cpu workqueues which
3825 were observed to contribute significantly to power
3826 consumption unbound, leading to measurably lower
3827 power usage at the cost of small performance
3830 The default value of this parameter is determined by
3831 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3833 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3834 default x2apic cluster mode on platforms
3837 x86_intel_mid_timer= [X86-32,APBT]
3838 Choose timer option for x86 Intel MID platform.
3839 Two valid options are apbt timer only and lapic timer
3840 plus one apbt timer for broadcast timer.
3841 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3843 xen_emul_unplug= [HW,X86,XEN]
3844 Unplug Xen emulated devices
3845 Format: [unplug0,][unplug1]
3846 ide-disks -- unplug primary master IDE devices
3847 aux-ide-disks -- unplug non-primary-master IDE devices
3848 nics -- unplug network devices
3849 all -- unplug all emulated devices (NICs and IDE disks)
3850 unnecessary -- unplugging emulated devices is
3851 unnecessary even if the host did not respond to
3853 never -- do not unplug even if version check succeeds
3855 xen_nopvspin [X86,XEN]
3856 Disables the ticketlock slowpath using Xen PV
3860 Disables the PV optimizations forcing the HVM guest to
3861 run as generic HVM guest with no PV drivers.
3863 xirc2ps_cs= [NET,PCMCIA]
3865 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3867 ______________________________________________________________________
3871 Add more DRM drivers.
projects / cascardo / linux.git / blob