4 The following is a consolidated list of the kernel parameters as
5 implemented by the __setup(), core_param() and module_param() macros
6 and sorted into English Dictionary order (defined as ignoring all
7 punctuation and sorting digits before letters in a case insensitive
8 manner), and with descriptions where known.
10 The kernel parses parameters from the kernel command line up to "--";
11 if it doesn't recognize a parameter and it doesn't contain a '.', the
12 parameter gets passed to init: parameters with '=' go into init's
13 environment, others are passed as command line arguments to init.
14 Everything after "--" is passed as an argument to init.
16 Module parameters can be specified in two ways: via the kernel command
17 line with a module name prefix, or via modprobe, e.g.:
19 (kernel command line) usbcore.blinkenlights=1
20 (modprobe command line) modprobe usbcore blinkenlights=1
22 Parameters for modules which are built into the kernel need to be
23 specified on the kernel command line. modprobe looks through the
24 kernel command line (/proc/cmdline) and collects module parameters
25 when it loads a module, so the kernel command line can be used for
28 Hyphens (dashes) and underscores are equivalent in parameter names, so
29 log_buf_len=1M print-fatal-signals=1
30 can also be entered as
31 log-buf-len=1M print_fatal_signals=1
33 Double-quotes can be used to protect spaces in values, e.g.:
34 param="spaces in here"
36 This document may not be entirely up to date and comprehensive. The command
37 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38 module. Loadable modules, after being loaded into the running kernel, also
39 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40 parameters may be changed at runtime by the command
41 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43 The parameters listed below are only valid if certain kernel build options were
44 enabled and if respective hardware is present. The text in square brackets at
45 the beginning of each description states the restrictions within which a
46 parameter is applicable:
48 ACPI ACPI support is enabled.
49 AGP AGP (Accelerated Graphics Port) is enabled.
50 ALSA ALSA sound support is enabled.
51 APIC APIC support is enabled.
52 APM Advanced Power Management support is enabled.
53 ARM ARM architecture is enabled.
54 AVR32 AVR32 architecture is enabled.
55 AX25 Appropriate AX.25 support is enabled.
56 BLACKFIN Blackfin architecture is enabled.
57 CLK Common clock infrastructure is enabled.
58 CMA Contiguous Memory Area support is enabled.
59 DRM Direct Rendering Management support is enabled.
60 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
62 EFI EFI Partitioning (GPT) is enabled
63 EIDE EIDE/ATAPI support is enabled.
64 EVM Extended Verification Module
65 FB The frame buffer device is enabled.
66 FTRACE Function tracing enabled.
67 GCOV GCOV profiling is enabled.
68 HW Appropriate hardware is enabled.
69 IA-64 IA-64 architecture is enabled.
70 IMA Integrity measurement architecture is enabled.
71 IOSCHED More than one I/O scheduler is enabled.
72 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
73 IPV6 IPv6 support is enabled.
74 ISAPNP ISA PnP code is enabled.
75 ISDN Appropriate ISDN support is enabled.
76 JOY Appropriate joystick support is enabled.
77 KGDB Kernel debugger support is enabled.
78 KVM Kernel Virtual Machine support is enabled.
79 LIBATA Libata driver is enabled
80 LP Printer support is enabled.
81 LOOP Loopback device support is enabled.
82 M68k M68k architecture is enabled.
83 These options have more detailed description inside of
84 Documentation/m68k/kernel-options.txt.
85 MDA MDA console support is enabled.
86 MIPS MIPS architecture is enabled.
87 MOUSE Appropriate mouse support is enabled.
88 MSI Message Signaled Interrupts (PCI).
89 MTD MTD (Memory Technology Device) support is enabled.
90 NET Appropriate network support is enabled.
91 NUMA NUMA support is enabled.
92 NFS Appropriate NFS support is enabled.
93 OSS OSS sound support is enabled.
94 PV_OPS A paravirtualized kernel is enabled.
95 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
96 PARISC The PA-RISC architecture is enabled.
97 PCI PCI bus support is enabled.
98 PCIE PCI Express support is enabled.
99 PCMCIA The PCMCIA subsystem is enabled.
100 PNP Plug & Play support is enabled.
101 PPC PowerPC architecture is enabled.
102 PPT Parallel port support is enabled.
103 PS2 Appropriate PS/2 support is enabled.
104 RAM RAM disk support is enabled.
105 S390 S390 architecture is enabled.
106 SCSI Appropriate SCSI support is enabled.
107 A lot of drivers have their options described inside
108 the Documentation/scsi/ sub-directory.
109 SECURITY Different security models are enabled.
110 SELINUX SELinux support is enabled.
111 APPARMOR AppArmor support is enabled.
112 SERIAL Serial support is enabled.
113 SH SuperH architecture is enabled.
114 SMP The kernel is an SMP kernel.
115 SPARC Sparc architecture is enabled.
116 SWSUSP Software suspend (hibernation) is enabled.
117 SUSPEND System suspend states are enabled.
118 TPM TPM drivers are enabled.
119 TS Appropriate touchscreen support is enabled.
120 UMS USB Mass Storage support is enabled.
121 USB USB support is enabled.
122 USBHID USB Human Interface Device support is enabled.
123 V4L Video For Linux support is enabled.
124 VMMIO Driver for memory mapped virtio devices is enabled.
125 VGA The VGA console has been enabled.
126 VT Virtual terminal support is enabled.
127 WDT Watchdog support is enabled.
128 XT IBM PC/XT MFM hard disk support is enabled.
129 X86-32 X86-32, aka i386 architecture is enabled.
130 X86-64 X86-64 architecture is enabled.
131 More X86-64 boot options can be found in
132 Documentation/x86/x86_64/boot-options.txt .
133 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134 XEN Xen support is enabled
136 In addition, the following text indicates that the option:
138 BUGS= Relates to possible processor bugs on the said processor.
139 KNL Is a kernel start-up parameter.
140 BOOT Is a boot loader parameter.
142 Parameters denoted with BOOT are actually interpreted by the boot
143 loader, and have no meaning to the kernel directly.
144 Do not modify the syntax of boot loader parameters without extreme
145 need or coordination with <Documentation/x86/boot.txt>.
147 There are also arch-specific kernel-parameters not documented here.
148 See for example <Documentation/x86/x86_64/boot-options.txt>.
150 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151 a trailing = on the name of any parameter states that that parameter will
152 be entered as an environment variable, whereas its absence indicates that
153 it will appear as a kernel argument readable via /proc/cmdline by programs
154 running once the system is up.
156 The number of kernel parameters is not limited, but the length of the
157 complete command line (parameters including spaces etc.) is limited to
158 a fixed number of characters. This limit depends on the architecture
159 and is between 256 and 4096 characters. It is defined in the file
160 ./include/asm/setup.h as COMMAND_LINE_SIZE.
162 Finally, the [KMG] suffix is commonly described after a number of kernel
163 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165 bytes respectively. Such letter suffixes can also be entirely omitted.
169 Advanced Configuration and Power Interface
170 Format: { force | off | strict | noirq | rsdt }
171 force -- enable ACPI if default was off
172 off -- disable ACPI if default was on
173 noirq -- do not use ACPI for IRQ routing
174 strict -- Be less tolerant of platforms that are not
175 strictly ACPI specification compliant.
176 rsdt -- prefer RSDT over (default) XSDT
177 copy_dsdt -- copy DSDT to memory
179 See also Documentation/power/runtime_pm.txt, pci=noacpi
181 acpi_rsdp= [ACPI,EFI,KEXEC]
182 Pass the RSDP address to the kernel, mostly used
183 on machines running EFI runtime service to boot the
184 second kernel for kdump.
186 acpi_apic_instance= [ACPI, IOAPIC]
188 2: use 2nd APIC table, if available
189 1,0: use 1st APIC table
192 acpi_backlight= [HW,ACPI]
193 acpi_backlight=vendor
195 If set to vendor, prefer vendor specific driver
196 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
197 of the ACPI video.ko driver.
199 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
200 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
202 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
203 debug output. Bits in debug_layer correspond to a
204 _COMPONENT in an ACPI source file, e.g.,
205 #define _COMPONENT ACPI_PCI_COMPONENT
206 Bits in debug_level correspond to a level in
207 ACPI_DEBUG_PRINT statements, e.g.,
208 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
209 The debug_level mask defaults to "info". See
210 Documentation/acpi/debug.txt for more information about
211 debug layers and levels.
213 Enable processor driver info messages:
214 acpi.debug_layer=0x20000000
215 Enable PCI/PCI interrupt routing info messages:
216 acpi.debug_layer=0x400000
217 Enable AML "Debug" output, i.e., stores to the Debug
218 object while interpreting AML:
219 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
220 Enable all messages related to ACPI hardware:
221 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
223 Some values produce so much output that the system is
224 unusable. The "log_buf_len" parameter may be useful
225 if you need to capture more output.
227 acpi_force_table_verification [HW,ACPI]
228 Enable table checksum verification during early stage.
229 By default, this is disabled due to x86 early mapping
232 acpi_irq_balance [HW,ACPI]
233 ACPI will balance active IRQs
236 acpi_irq_nobalance [HW,ACPI]
237 ACPI will not move active IRQs (default)
240 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
241 Format: <irq>,<irq>...
243 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
245 Format: <irq>,<irq>...
247 acpi_no_auto_serialize [HW,ACPI]
248 Disable auto-serialization of AML methods
249 AML control methods that contain the opcodes to create
250 named objects will be marked as "Serialized" by the
251 auto-serialization feature.
252 This feature is enabled by default.
253 This option allows to turn off the feature.
255 acpi_no_static_ssdt [HW,ACPI]
256 Disable installation of static SSDTs at early boot time
257 By default, SSDTs contained in the RSDT/XSDT will be
258 installed automatically and they will appear under
259 /sys/firmware/acpi/tables.
260 This option turns off this feature.
261 Note that specifying this option does not affect
262 dynamic table installation which will install SSDT
263 tables to /sys/firmware/acpi/tables/dynamic.
265 acpica_no_return_repair [HW, ACPI]
266 Disable AML predefined validation mechanism
267 This mechanism can repair the evaluation result to make
268 the return objects more ACPI specification compliant.
269 This option is useful for developers to identify the
270 root cause of an AML interpreter issue when the issue
271 has something to do with the repair mechanism.
273 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
274 Format: To spoof as Windows 98: ="Microsoft Windows"
276 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
277 acpi_osi="string1" # add string1
278 acpi_osi="!string2" # remove string2
279 acpi_osi=!* # remove all strings
280 acpi_osi=! # disable all built-in OS vendor
282 acpi_osi= # disable all strings
284 'acpi_osi=!' can be used in combination with single or
285 multiple 'acpi_osi="string1"' to support specific OS
286 vendor string(s). Note that such command can only
287 affect the default state of the OS vendor strings, thus
288 it cannot affect the default state of the feature group
289 strings and the current state of the OS vendor strings,
290 specifying it multiple times through kernel command line
291 is meaningless. This command is useful when one do not
292 care about the state of the feature group strings which
293 should be controlled by the OSPM.
295 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
296 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
297 can make '_OSI("Windows 2000")' TRUE.
299 'acpi_osi=' cannot be used in combination with other
300 'acpi_osi=' command lines, the _OSI method will not
301 exist in the ACPI namespace. NOTE that such command can
302 only affect the _OSI support state, thus specifying it
303 multiple times through kernel command line is also
306 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
309 'acpi_osi=!*' can be used in combination with single or
310 multiple 'acpi_osi="string1"' to support specific
311 string(s). Note that such command can affect the
312 current state of both the OS vendor strings and the
313 feature group strings, thus specifying it multiple times
314 through kernel command line is meaningful. But it may
315 still not able to affect the final state of a string if
316 there are quirks related to this string. This command
317 is useful when one want to control the state of the
318 feature group strings to debug BIOS issues related to
321 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
322 '_OSI("Module Device")' FALSE.
323 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
324 '_OSI("Module Device")' TRUE.
325 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
327 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
329 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
330 they all will make '_OSI("Windows 2000")' TRUE.
333 Override the pmtimer bug detection: force the kernel
334 to assume that this machine's pmtimer latches its value
335 and always returns good values.
337 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
338 Format: { level | edge | high | low }
340 acpi_skip_timer_override [HW,ACPI]
341 Recognize and ignore IRQ0/pin2 Interrupt Override.
342 For broken nForce2 BIOS resulting in XT-PIC timer.
344 acpi_sleep= [HW,ACPI] Sleep options
345 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
346 old_ordering, nonvs, sci_force_enable }
347 See Documentation/power/video.txt for information on
349 s3_beep is for debugging; it makes the PC's speaker beep
350 as soon as the kernel's real-mode entry point is called.
351 s4_nohwsig prevents ACPI hardware signature from being
352 used during resume from hibernation.
353 old_ordering causes the ACPI 1.0 ordering of the _PTS
354 control method, with respect to putting devices into
355 low power states, to be enforced (the ACPI 2.0 ordering
356 of _PTS is used by default).
357 nonvs prevents the kernel from saving/restoring the
358 ACPI NVS memory during suspend/hibernation and resume.
359 sci_force_enable causes the kernel to set SCI_EN directly
360 on resume from S1/S3 (which is against the ACPI spec,
361 but some broken systems don't work without it).
363 acpi_use_timer_override [HW,ACPI]
364 Use timer override. For some broken Nvidia NF5 boards
365 that require a timer override, but don't have HPET
367 acpi_enforce_resources= [ACPI]
368 { strict | lax | no }
369 Check for resource conflicts between native drivers
370 and ACPI OperationRegions (SystemIO and SystemMemory
371 only). IO ports and memory declared in ACPI might be
372 used by the ACPI subsystem in arbitrary AML code and
373 can interfere with legacy drivers.
374 strict (default): access to resources claimed by ACPI
375 is denied; legacy drivers trying to access reserved
376 resources will fail to bind to device using them.
377 lax: access to resources claimed by ACPI is allowed;
378 legacy drivers trying to access reserved resources
379 will bind successfully but a warning message is logged.
380 no: ACPI OperationRegions are not marked as reserved,
381 no further checks are performed.
383 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
386 add_efi_memmap [EFI; X86] Include EFI memory map in
387 kernel's map of available physical RAM.
390 { off | try_unsupported }
391 off: disable AGP support
392 try_unsupported: try to drive unsupported chipsets
393 (may crash computer or cause data corruption)
396 See Documentation/sound/alsa/alsa-parameters.txt
399 Allow the default userspace alignment fault handler
400 behaviour to be specified. Bit 0 enables warnings,
401 bit 1 enables fixups, and bit 2 sends a segfault.
403 align_va_addr= [X86-64]
404 Align virtual addresses by clearing slice [14:12] when
405 allocating a VMA at process creation time. This option
406 gives you up to 3% performance improvement on AMD F15h
407 machines (where it is enabled by default) for a
408 CPU-intensive style benchmark, and it can vary highly in
409 a microbenchmark depending on workload and compiler.
411 32: only for 32-bit processes
412 64: only for 64-bit processes
413 on: enable for both 32- and 64-bit processes
414 off: disable for both 32- and 64-bit processes
416 alloc_snapshot [FTRACE]
417 Allocate the ftrace snapshot buffer on boot up when the
418 main buffer is allocated. This is handy if debugging
419 and you need to use tracing_snapshot() on boot up, and
420 do not want to use tracing_snapshot_alloc() as it needs
421 to be done where GFP_KERNEL allocations are allowed.
423 amd_iommu= [HW,X86-64]
424 Pass parameters to the AMD IOMMU driver in the system.
426 fullflush - enable flushing of IO/TLB entries when
427 they are unmapped. Otherwise they are
428 flushed before they will be reused, which
430 off - do not initialize any AMD IOMMU found in
432 force_isolation - Force device isolation for all
433 devices. The IOMMU driver is not
434 allowed anymore to lift isolation
435 requirements as needed. This option
436 does not override iommu=pt
438 amd_iommu_dump= [HW,X86-64]
439 Enable AMD IOMMU driver option to dump the ACPI table
440 for AMD IOMMU. With this option enabled, AMD IOMMU
441 driver will print ACPI tables for AMD IOMMU during
442 IOMMU initialization.
444 amijoy.map= [HW,JOY] Amiga joystick support
445 Map of devices attached to JOY0DAT and JOY1DAT
447 See also Documentation/input/joystick.txt
449 analog.map= [HW,JOY] Analog joystick and gamepad support
450 Specifies type or capabilities of an analog joystick
451 connected to one of 16 gameports
452 Format: <type1>,<type2>,..<type16>
455 Power management functions (SPARCstation-4/5 + deriv.)
457 Disable APC CPU standby support. SPARCstation-Fox does
458 not play well with APC CPU idle - disable it if you have
459 APC and your system crashes randomly.
461 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
462 Change the output verbosity whilst booting
463 Format: { quiet (default) | verbose | debug }
464 Change the amount of debugging information output
465 when initialising the APIC and IO-APIC components.
468 See Documentation/networking/ipv6.txt.
470 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
471 Limit apic dumping. The parameter defines the maximal
472 number of local apics being dumped. Also it is possible
473 to set it to "all" by meaning -- no limit here.
474 Format: { 1 (default) | 2 | ... | all }.
475 The parameter valid if only apic=debug or
476 apic=verbose is specified.
477 Example: apic=debug show_lapic=all
479 apm= [APM] Advanced Power Management
480 See header of arch/x86/kernel/apm_32.c.
482 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
483 Format: <io>,<irq>,<nodeID>
487 atarimouse= [HW,MOUSE] Atari Mouse
489 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
490 EzKey and similar keyboards
492 atkbd.reset= [HW] Reset keyboard during initialization
494 atkbd.set= [HW] Select keyboard code set
495 Format: <int> (2 = AT (default), 3 = PS/2)
497 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
500 atkbd.softraw= [HW] Choose between synthetic and real raw mode
501 Format: <bool> (0 = real, 1 = synthetic (default))
503 atkbd.softrepeat= [HW]
504 Use software keyboard repeat
506 audit= [KNL] Enable the audit sub-system
507 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
508 0 - kernel audit is disabled and can not be enabled
509 until the next reboot
510 unset - kernel audit is initialized but disabled and
511 will be fully enabled by the userspace auditd.
512 1 - kernel audit is initialized and partially enabled,
513 storing at most audit_backlog_limit messages in
514 RAM until it is fully enabled by the userspace
518 audit_backlog_limit= [KNL] Set the audit queue size limit.
519 Format: <int> (must be >=0)
522 baycom_epp= [HW,AX25]
525 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
527 See header of drivers/net/hamradio/baycom_par.c.
529 baycom_ser_fdx= [HW,AX25]
530 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
531 Format: <io>,<irq>,<mode>[,<baud>]
532 See header of drivers/net/hamradio/baycom_ser_fdx.c.
534 baycom_ser_hdx= [HW,AX25]
535 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
536 Format: <io>,<irq>,<mode>
537 See header of drivers/net/hamradio/baycom_ser_hdx.c.
539 blkdevparts= Manual partition parsing of block device(s) for
540 embedded devices based on command line input.
541 See Documentation/block/cmdline-partition.txt
543 boot_delay= Milliseconds to delay each printk during boot.
544 Values larger than 10 seconds (10000) are changed to
548 bootmem_debug [KNL] Enable bootmem allocator debug messages.
550 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
551 bttv.radio= Most important insmod options are available as
553 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
556 bulk_remove=off [PPC] This parameter disables the use of the pSeries
557 firmware feature for flushing multiple hpte entries
560 c101= [NET] Moxa C101 synchronous serial card
562 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
563 Sometimes CPU hardware bugs make them report the cache
564 size incorrectly. The kernel will attempt work arounds
565 to fix known problems, but for some CPUs it is not
566 possible to determine what the correct size should be.
567 This option provides an override for these situations.
569 ca_keys= [KEYS] This parameter identifies a specific key(s) on
570 the system trusted keyring to be used for certificate
572 format: { id:<keyid> | builtin }
574 cca= [MIPS] Override the kernel pages' cache coherency
575 algorithm. Accepted values range from 0 to 7
576 inclusive. See arch/mips/include/asm/pgtable-bits.h
577 for platform specific values (SB1, Loongson3 and
580 ccw_timeout_log [S390]
581 See Documentation/s390/CommonIO for details.
583 cgroup_disable= [KNL] Disable a particular controller
584 Format: {name of the controller(s) to disable}
585 The effects of cgroup_disable=foo are:
586 - foo isn't auto-mounted if you mount all cgroups in
588 - foo isn't visible as an individually mountable
590 {Currently only "memory" controller deal with this and
591 cut the overhead, others just disable the usage. So
592 only cgroup_disable=memory is actually worthy}
594 checkreqprot [SELINUX] Set initial checkreqprot flag value.
595 Format: { "0" | "1" }
596 See security/selinux/Kconfig help text.
597 0 -- check protection applied by kernel (includes
598 any implied execute protection).
599 1 -- check protection requested by application.
600 Default value is set via a kernel config option.
601 Value can be changed at runtime via
602 /selinux/checkreqprot.
605 See Documentation/s390/CommonIO for details.
608 Prevents the clock framework from automatically gating
609 clocks that have not been explicitly enabled by a Linux
610 device driver but are enabled in hardware at reset or
611 by the bootloader/firmware. Note that this does not
612 force such clocks to be always-on nor does it reserve
613 those clocks in any way. This parameter is useful for
614 debug and development, but should not be needed on a
615 platform with proper driver support. For more
616 information, see Documentation/clk.txt.
618 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
620 Forces specified clocksource (if available) to be used
621 when calculating gettimeofday(). If specified
622 clocksource is not available, it defaults to PIT.
623 Format: { pit | tsc | cyclone | pmtmr }
625 clocksource= Override the default clocksource
627 Override the default clocksource and use the clocksource
628 with the name specified.
629 Some clocksource names to choose from, depending on
631 [all] jiffies (this is the base, fallback clocksource)
633 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
634 pxa_timer,timer3,32k_counter,timer0_1
636 [X86-32] pit,hpet,tsc;
637 scx200_hrt on Geode; cyclone on IBM x440
645 clearcpuid=BITNUM [X86]
646 Disable CPUID feature X for the kernel. See
647 arch/x86/include/asm/cpufeature.h for the valid bit
648 numbers. Note the Linux specific bits are not necessarily
649 stable over kernel options, but the vendor specific
651 Also note that user programs calling CPUID directly
652 or using the feature without checking anything
653 will still see it. This just prevents it from
654 being used by the kernel or shown in /proc/cpuinfo.
655 Also note the kernel might malfunction if you disable
658 cma=nn[MG]@[start[MG][-end[MG]]]
660 Sets the size of kernel global memory area for
661 contiguous memory allocations and optionally the
662 placement constraint by the physical address range of
663 memory allocations. A value of 0 disables CMA
664 altogether. For more information, see
665 include/linux/dma-contiguous.h
667 cmo_free_hint= [PPC] Format: { yes | no }
668 Specify whether pages are marked as being inactive
669 when they are freed. This is used in CMO environments
670 to determine OS memory pressure for page stealing by
674 coherent_pool=nn[KMG] [ARM,KNL]
675 Sets the size of memory pool for coherent, atomic dma
676 allocations, by default set to 256K.
678 code_bytes [X86] How many bytes of object code to print
683 com20020= [HW,NET] ARCnet - COM20020 chipset
685 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
687 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
691 ARCnet - COM90xx chipset (memory-mapped buffers)
692 Format: <io>[,<irq>[,<memstart>]]
694 condev= [HW,S390] console device
697 console= [KNL] Output console device and options.
699 tty<n> Use the virtual console device <n>.
703 Use the specified serial port. The options are of
704 the form "bbbbpnf", where "bbbb" is the baud rate,
705 "p" is parity ("n", "o", or "e"), "n" is number of
706 bits, and "f" is flow control ("r" for RTS or
707 omit it). Default is "9600n8".
709 See Documentation/serial-console.txt for more
711 Documentation/networking/netconsole.txt for an
714 uart[8250],io,<addr>[,options]
715 uart[8250],mmio,<addr>[,options]
716 Start an early, polled-mode console on the 8250/16550
717 UART at the specified I/O port or MMIO address,
718 switching to the matching ttyS device later. The
719 options are the same as for ttyS, above.
720 hvc<n> Use the hypervisor console device <n>. This is for
721 both Xen and PowerPC hypervisors.
723 If the device connected to the port is not a TTY but a braille
724 device, prepend "brl," before the device type, for instance
726 For now, only VisioBraille is supported.
728 consoleblank= [KNL] The console blank (screen saver) timeout in
729 seconds. Defaults to 10*60 = 10mins. A value of 0
730 disables the blank timer.
733 [KNL] Change the default value for
734 /proc/<pid>/coredump_filter.
735 See also Documentation/filesystems/proc.txt.
737 cpuidle.off=1 [CPU_IDLE]
738 disable the cpuidle sub-system
740 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
742 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
744 crashkernel=size[KMG][@offset[KMG]]
745 [KNL] Using kexec, Linux can switch to a 'crash kernel'
746 upon panic. This parameter reserves the physical
747 memory region [offset, offset + size] for that kernel
748 image. If '@offset' is omitted, then a suitable offset
749 is selected automatically. Check
750 Documentation/kdump/kdump.txt for further details.
752 crashkernel=range1:size1[,range2:size2,...][@offset]
753 [KNL] Same as above, but depends on the memory
754 in the running system. The syntax of range is
755 start-[end] where start and end are both
756 a memory unit (amount[KMG]). See also
757 Documentation/kdump/kdump.txt for an example.
759 crashkernel=size[KMG],high
760 [KNL, x86_64] range could be above 4G. Allow kernel
761 to allocate physical memory region from top, so could
762 be above 4G if system have more than 4G ram installed.
763 Otherwise memory region will be allocated below 4G, if
765 It will be ignored if crashkernel=X is specified.
766 crashkernel=size[KMG],low
767 [KNL, x86_64] range under 4G. When crashkernel=X,high
768 is passed, kernel could allocate physical memory region
769 above 4G, that cause second kernel crash on system
770 that require some amount of low memory, e.g. swiotlb
771 requires at least 64M+32K low memory. Kernel would
772 try to allocate 72M below 4G automatically.
773 This one let user to specify own low range under 4G
774 for second kernel instead.
775 0: to disable low allocation.
776 It will be ignored when crashkernel=X,high is not used
777 or memory reserved is below 4G.
782 cs89x0_media= [HW,NET]
783 Format: { rj45 | aui | bnc }
786 See header of drivers/s390/block/dasd_devmap.c.
788 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
789 (one device per port)
790 Format: <port#>,<type>
791 See also Documentation/input/joystick-parport.txt
793 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
794 time. See Documentation/dynamic-debug-howto.txt for
795 details. Deprecated, see dyndbg.
797 debug [KNL] Enable kernel debugging (events log level).
800 [KNL] verbose self-tests
802 Print debugging info while doing the locking API
804 We default to 0 (no extra messages), setting it to
805 1 will print _a lot_ more information - normally
806 only useful to kernel developers.
808 debug_objects [KNL] Enable object debugging
811 [KNL] Disable object debugging
813 debug_guardpage_minorder=
814 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
815 parameter allows control of the order of pages that will
816 be intentionally kept free (and hence protected) by the
817 buddy allocator. Bigger value increase the probability
818 of catching random memory corruption, but reduce the
819 amount of memory for normal system use. The maximum
820 possible value is MAX_ORDER/2. Setting this parameter
821 to 1 or 2 should be enough to identify most random
822 memory corruption problems caused by bugs in kernel or
823 driver code when a CPU writes to (or reads from) a
824 random memory location. Note that there exists a class
825 of memory corruptions problems caused by buggy H/W or
826 F/W or by drivers badly programing DMA (basically when
827 memory is written at bus level and the CPU MMU is
828 bypassed) which are not detectable by
829 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
830 tracking down these problems.
832 debugpat [X86] Enable PAT debugging
834 decnet.addr= [HW,NET]
835 Format: <area>[,<node>]
836 See also Documentation/networking/decnet.txt.
839 [same as hugepagesz=] The size of the default
840 HugeTLB page size. This is the size represented by
841 the legacy /proc/ hugepages APIs, used for SHM, and
842 default size when mounting hugetlbfs filesystems.
843 Defaults to the default architecture's huge page size
847 Set number of hash buckets for dentry cache.
850 See Documentation/networking/ipv6.txt.
852 disable_cpu_apicid= [X86,APIC,SMP]
854 The number of initial APIC ID for the
855 corresponding CPU to be disabled at boot,
856 mostly used for the kdump 2nd kernel to
857 disable BSP to wake up multiple CPUs without
858 causing system reset or hang due to sending
861 disable_ddw [PPC/PSERIES]
862 Disable Dynamic DMA Window support. Use this if
863 to workaround buggy firmware.
866 See Documentation/networking/ipv6.txt.
868 disable_mtrr_cleanup [X86]
869 The kernel tries to adjust MTRR layout from continuous
870 to discrete, to make X server driver able to add WB
871 entry later. This parameter disables that.
873 disable_mtrr_trim [X86, Intel and AMD only]
874 By default the kernel will trim any uncacheable
875 memory out of your available memory pool based on
876 MTRR settings. This parameter disables that behavior,
877 possibly causing your machine to run very slowly.
879 disable_timer_pin_1 [X86]
880 Disable PIN 1 of APIC timer
881 Can be useful to work around chipset bugs.
883 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
884 this option disables the debugging code at boot.
886 dma_debug_entries=<number>
887 This option allows to tune the number of preallocated
888 entries for DMA-API debugging code. One entry is
889 required per DMA-API allocation. Use this if the
890 DMA-API debugging code disables itself because the
891 architectural default is too low.
893 dma_debug_driver=<driver_name>
894 With this option the DMA-API debugging driver
895 filter feature can be enabled at boot time. Just
896 pass the driver to filter for as the parameter.
897 The filter can be disabled or changed to another
898 driver later using sysfs.
900 drm_kms_helper.edid_firmware=[<connector>:]<file>
901 Broken monitors, graphic adapters and KVMs may
902 send no or incorrect EDID data sets. This parameter
903 allows to specify an EDID data set in the
904 /lib/firmware directory that is used instead.
905 Generic built-in EDID data sets are used, if one of
906 edid/1024x768.bin, edid/1280x1024.bin,
907 edid/1680x1050.bin, or edid/1920x1080.bin is given
908 and no file with the same name exists. Details and
909 instructions how to build your own EDID data are
910 available in Documentation/EDID/HOWTO.txt. An EDID
911 data set will only be used for a particular connector,
912 if its name and a colon are prepended to the EDID
917 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
918 module.dyndbg[="val"]
919 Enable debug messages at boot time. See
920 Documentation/dynamic-debug-howto.txt for details.
922 early_ioremap_debug [KNL]
923 Enable debug messages in early_ioremap support. This
924 is useful for tracking down temporary early mappings
925 which are not unmapped.
927 earlycon= [KNL] Output early console device and options.
930 Start an early, polled-mode console on a cadence serial
931 port at the specified address. The cadence serial port
932 must already be setup and configured. Options are not
935 uart[8250],io,<addr>[,options]
936 uart[8250],mmio,<addr>[,options]
937 uart[8250],mmio32,<addr>[,options]
938 Start an early, polled-mode console on the 8250/16550
939 UART at the specified I/O port or MMIO address.
940 MMIO inter-register address stride is either 8-bit
941 (mmio) or 32-bit (mmio32).
942 The options are the same as for ttyS, above.
945 Start an early, polled-mode console on a pl011 serial
946 port at the specified address. The pl011 serial port
947 must already be setup and configured. Options are not
951 Start an early, polled-mode console on an msm serial
952 port at the specified address. The serial port
953 must already be setup and configured. Options are not
957 Start an early, polled-mode console on an msm serial
958 dm port at the specified address. The serial port
959 must already be setup and configured. Options are not
962 smh Use ARM semihosting calls for early console.
964 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
968 earlyprintk=serial[,ttySn[,baudrate]]
969 earlyprintk=serial[,0x...[,baudrate]]
970 earlyprintk=ttySn[,baudrate]
971 earlyprintk=dbgp[debugController#]
973 earlyprintk is useful when the kernel crashes before
974 the normal console is initialized. It is not enabled by
975 default because it has some cosmetic problems.
977 Append ",keep" to not disable it when the real console
980 Only one of vga, efi, serial, or usb debug port can
983 Currently only ttyS0 and ttyS1 may be specified by
984 name. Other I/O ports may be explicitly specified
985 on some architectures (x86 and arm at least) by
986 replacing ttySn with an I/O port address, like this:
987 earlyprintk=serial,0x1008,115200
988 You can find the port for a given device in
989 /proc/tty/driver/serial:
990 2: uart:ST16650V2 port:00001008 irq:18 ...
992 Interaction with the standard serial driver is not
995 The VGA and EFI output is eventually overwritten by
998 The xen output can only be used by Xen PV guests.
1000 edac_report= [HW,EDAC] Control how to report EDAC event
1001 Format: {"on" | "off" | "force"}
1002 on: enable EDAC to report H/W event. May be overridden
1003 by other higher priority error reporting module.
1004 off: disable H/W event reporting through EDAC.
1005 force: enforce the use of EDAC to report H/W event.
1008 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1011 This is designed to be used in conjunction with
1012 the boot argument: earlyprintk=vga
1015 Format: {"off" | "on" | "skip[mbr]"}
1018 Format: { "old_map", "nochunk", "noruntime" }
1019 old_map [X86-64]: switch to the old ioremap-based EFI
1020 runtime services mapping. 32-bit still uses this one by
1022 nochunk: disable reading files in "chunks" in the EFI
1023 boot stub, as chunking can cause problems with some
1024 firmware implementations.
1025 noruntime : disable EFI runtime services support
1027 efi_no_storage_paranoia [EFI; X86]
1028 Using this parameter you can use more than 50% of
1029 your efi variable storage. Use this parameter only if
1030 you are really sure that your UEFI does sane gc and
1031 fulfills the spec otherwise your board may brick.
1033 eisa_irq_edge= [PARISC,HW]
1034 See header of drivers/parisc/eisa.c.
1037 See comment before function elanfreq_setup() in
1038 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1041 Format: {"cfq" | "deadline" | "noop"}
1042 See Documentation/block/cfq-iosched.txt and
1043 Documentation/block/deadline-iosched.txt for details.
1045 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1046 Specifies physical address of start of kernel core
1047 image elf header and optionally the size. Generally
1048 kexec loader will pass this option to capture kernel.
1049 See Documentation/kdump/kdump.txt for details.
1051 enable_mtrr_cleanup [X86]
1052 The kernel tries to adjust MTRR layout from continuous
1053 to discrete, to make X server driver able to add WB
1054 entry later. This parameter enables that.
1056 enable_timer_pin_1 [X86]
1057 Enable PIN 1 of APIC timer
1058 Can be useful to work around chipset bugs
1059 (in particular on some ATI chipsets).
1060 The kernel tries to set a reasonable default.
1062 enforcing [SELINUX] Set initial enforcing status.
1064 See security/selinux/Kconfig help text.
1065 0 -- permissive (log only, no denials).
1066 1 -- enforcing (deny and log).
1068 Value can be changed at runtime via /selinux/enforce.
1071 Disable Error Record Serialization Table (ERST)
1074 ether= [HW,NET] Ethernet cards parameters
1075 This option is obsoleted by the "netdev=" option, which
1076 has equivalent usage. See its documentation for details.
1080 Permit 'security.evm' to be updated regardless of
1081 current integrity status.
1085 fail_make_request=[KNL]
1086 General fault injection mechanism.
1087 Format: <interval>,<probability>,<space>,<times>
1088 See also Documentation/fault-injection/.
1091 See Documentation/blockdev/floppy.txt.
1093 force_pal_cache_flush
1094 [IA-64] Avoid check_sal_cache_flush which may hang on
1095 buggy SAL_CACHE_FLUSH implementations. Using this
1096 parameter will force ia64_sal_cache_flush to call
1097 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1100 Forcefully enable Physical Address Extension (PAE).
1101 Many Pentium M systems disable PAE but may have a
1102 functionally usable PAE implementation.
1103 Warning: use of this parameter will taint the kernel
1104 and may cause unknown problems.
1107 [FTRACE] will set and start the specified tracer
1108 as early as possible in order to facilitate early
1111 ftrace_dump_on_oops[=orig_cpu]
1112 [FTRACE] will dump the trace buffers on oops.
1113 If no parameter is passed, ftrace will dump
1114 buffers of all CPUs, but if you pass orig_cpu, it will
1115 dump only the buffer of the CPU that triggered the
1118 ftrace_filter=[function-list]
1119 [FTRACE] Limit the functions traced by the function
1120 tracer at boot up. function-list is a comma separated
1121 list of functions. This list can be changed at run
1122 time by the set_ftrace_filter file in the debugfs
1125 ftrace_notrace=[function-list]
1126 [FTRACE] Do not trace the functions specified in
1127 function-list. This list can be changed at run time
1128 by the set_ftrace_notrace file in the debugfs
1131 ftrace_graph_filter=[function-list]
1132 [FTRACE] Limit the top level callers functions traced
1133 by the function graph tracer at boot up.
1134 function-list is a comma separated list of functions
1135 that can be changed at run time by the
1136 set_graph_function file in the debugfs tracing directory.
1138 ftrace_graph_notrace=[function-list]
1139 [FTRACE] Do not trace from the functions specified in
1140 function-list. This list is a comma separated list of
1141 functions that can be changed at run time by the
1142 set_graph_notrace file in the debugfs tracing directory.
1145 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1146 support via parallel port (up to 5 devices per port)
1147 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1148 See also Documentation/input/joystick-parport.txt
1152 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1156 gcov_persist= [GCOV] When non-zero (default), profiling data for
1157 kernel modules is saved and remains accessible via
1158 debugfs, even when the module is unloaded/reloaded.
1159 When zero, profiling data is discarded and associated
1160 debugfs files are removed at module unload time.
1162 gpt [EFI] Forces disk with valid GPT signature but
1163 invalid Protective MBR to be treated as GPT. If the
1164 primary GPT is corrupted, it enables the backup/alternate
1165 GPT to be used instead.
1167 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1168 the "Enable 0" bit of the configuration register.
1171 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1172 the "Enable 0" bit of the configuration register.
1175 grcan.select= [HW] Select which physical interface to use.
1178 grcan.txsize= [HW] Sets the size of the tx buffer.
1179 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1181 grcan.rxsize= [HW] Sets the size of the rx buffer.
1182 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1185 hashdist= [KNL,NUMA] Large hashes allocated during boot
1186 are distributed across NUMA nodes. Defaults on
1187 for 64-bit NUMA, off otherwise.
1188 Format: 0 | 1 (for off | on)
1190 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1192 hd= [EIDE] (E)IDE hard drive subsystem geometry
1193 Format: <cyl>,<head>,<sect>
1196 Disable Hardware Error Source Table (HEST) support;
1197 corresponding firmware-first mode error processing
1198 logic will be disabled.
1200 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1201 size of <nn>. This works even on boxes that have no
1202 highmem otherwise. This also works to reduce highmem
1203 size on bigger boxes.
1205 highres= [KNL] Enable/disable high resolution timer mode.
1206 Valid parameters: "on", "off"
1210 See Documentation/isdn/README.HiSax.
1214 hpet= [X86-32,HPET] option to control HPET usage
1215 Format: { enable (default) | disable | force |
1217 disable: disable HPET and use PIT instead
1218 force: allow force enabled of undocumented chips (ICH4,
1220 verbose: show contents of HPET registers during setup
1222 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1223 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1225 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1226 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1227 On x86-64 and powerpc, this option can be specified
1228 multiple times interleaved with hugepages= to reserve
1229 huge pages of different sizes. Valid pages sizes on
1230 x86-64 are 2M (when the CPU supports "pse") and 1G
1231 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1232 Note that 1GB pages can only be allocated at boot time
1233 using hugepages= and not freed afterwards.
1235 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1236 terminal devices. Valid values: 0..8
1237 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1238 If specified, z/VM IUCV HVC accepts connections
1239 from listed z/VM user IDs only.
1241 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1242 hardware thread id mappings.
1243 Format: <cpu>:<hwthread>
1246 Do not unregister boot console at start. This is only
1247 useful for debugging when something happens in the window
1248 between unregistering the boot console and initializing
1251 i2c_bus= [HW] Override the default board specific I2C bus speed
1252 or register an additional I2C bus that is not
1253 registered from board initialization code.
1257 i8042.debug [HW] Toggle i8042 debug mode
1258 i8042.direct [HW] Put keyboard port into non-translated mode
1259 i8042.dumbkbd [HW] Pretend that controller can only read data from
1260 keyboard and cannot control its state
1261 (Don't attempt to blink the leds)
1262 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1263 i8042.nokbd [HW] Don't check/create keyboard port
1264 i8042.noloop [HW] Disable the AUX Loopback command while probing
1266 i8042.nomux [HW] Don't check presence of an active multiplexing
1267 controller. Default: true.
1268 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1270 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1271 i8042.reset [HW] Reset the controller during init and cleanup
1272 i8042.unlock [HW] Unlock (ignore) the keylock
1276 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1277 indicates that the driver is running on unsupported
1279 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1280 does not match list of supported models.
1282 [HW] Report power status in /proc/i8k
1283 (disabled by default)
1284 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1287 i915.invert_brightness=
1288 [DRM] Invert the sense of the variable that is used to
1289 set the brightness of the panel backlight. Normally a
1290 brightness value of 0 indicates backlight switched off,
1291 and the maximum of the brightness value sets the backlight
1292 to maximum brightness. If this parameter is set to 0
1293 (default) and the machine requires it, or this parameter
1294 is set to 1, a brightness value of 0 sets the backlight
1295 to maximum brightness, and the maximum of the brightness
1296 value switches the backlight off.
1297 -1 -- never invert brightness
1298 0 -- machine default
1299 1 -- force brightness inversion
1302 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1304 ide-core.nodma= [HW] (E)IDE subsystem
1305 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1306 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1307 .cdrom .chs .ignore_cable are additional options
1308 See Documentation/ide/ide.txt.
1310 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1311 Claim all unknown PCI IDE storage controllers.
1314 Format: idle=poll, idle=halt, idle=nomwait
1315 Poll forces a polling idle loop that can slightly
1316 improve the performance of waking up a idle CPU, but
1317 will use a lot of power and make the system run hot.
1319 idle=halt: Halt is forced to be used for CPU idle.
1320 In such case C2/C3 won't be used again.
1321 idle=nomwait: Disable mwait for CPU C-states
1323 ignore_loglevel [KNL]
1324 Ignore loglevel setting - this will print /all/
1325 kernel messages to the console. Useful for debugging.
1326 We also add it as printk module parameter, so users
1327 could change it dynamically, usually by
1328 /sys/module/printk/parameters/ignore_loglevel.
1330 ihash_entries= [KNL]
1331 Set number of hash buckets for inode cache.
1333 ima_appraise= [IMA] appraise integrity measurements
1334 Format: { "off" | "enforce" | "fix" | "log" }
1337 ima_appraise_tcb [IMA]
1338 The builtin appraise policy appraises all files
1342 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1346 The list of supported hash algorithms is defined
1347 in crypto/hash_info.h.
1350 Load a policy which meets the needs of the Trusted
1351 Computing Base. This means IMA will measure all
1352 programs exec'd, files mmap'd for exec, and all files
1353 opened for read by uid=0.
1356 Select one of defined IMA measurements template formats.
1357 Formats: { "ima" | "ima-ng" }
1360 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1361 Format: <min_file_size>
1362 Set the minimal file size for using asynchronous hash.
1363 If left unspecified, ahash usage is disabled.
1365 ahash performance varies for different data sizes on
1366 different crypto accelerators. This option can be used
1367 to achieve the best performance for a particular HW.
1369 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1371 Set hashing buffer size. Default: 4k.
1373 ahash performance varies for different chunk sizes on
1374 different crypto accelerators. This option can be used
1375 to achieve best performance for particular HW.
1379 Run specified binary instead of /sbin/init as init
1382 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1383 for working out where the kernel is dying during
1386 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1387 initcall functions. Useful for debugging built-in
1388 modules and initcalls.
1390 initrd= [BOOT] Specify the location of the initial ramdisk
1392 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1395 int_pln_enable [x86] Enable power limit notification interrupt
1397 integrity_audit=[IMA]
1398 Format: { "0" | "1" }
1399 0 -- basic integrity auditing messages. (Default)
1400 1 -- additional integrity auditing messages.
1402 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1404 Enable intel iommu driver.
1406 Disable intel iommu driver.
1407 igfx_off [Default Off]
1408 By default, gfx is mapped as normal device. If a gfx
1409 device has a dedicated DMAR unit, the DMAR unit is
1410 bypassed by not enabling DMAR with this option. In
1411 this case, gfx device will use physical address for
1414 With this option iommu will not optimize to look
1415 for io virtual address below 32-bit forcing dual
1416 address cycle on pci bus for cards supporting greater
1417 than 32-bit addressing. The default is to look
1418 for translation below 32-bit and if not available
1419 then look in the higher range.
1420 strict [Default Off]
1421 With this option on every unmap_single operation will
1422 result in a hardware IOTLB flush operation as opposed
1423 to batching them for performance.
1424 sp_off [Default Off]
1425 By default, super page will be supported if Intel IOMMU
1426 has the capability. With this option, super page will
1429 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1430 0 disables intel_idle and fall back on acpi_idle.
1431 1 to 6 specify maximum depth of C-state.
1435 Do not enable intel_pstate as the default
1436 scaling driver for the supported processors
1438 intremap= [X86-64, Intel-IOMMU]
1439 on enable Interrupt Remapping (default)
1440 off disable Interrupt Remapping
1441 nosid disable Source ID checking
1443 BIOS x2APIC opt-out request will be ignored
1445 iomem= Disable strict checking of access to MMIO memory
1446 strict regions from userspace.
1463 io7= [HW] IO7 for Marvel based alpha systems
1464 See comment before marvel_specify_io7 in
1465 arch/alpha/kernel/core_marvel.c.
1467 io_delay= [X86] I/O delay method
1469 Standard port 0x80 based delay
1471 Alternate port 0xed based delay (needed on some systems)
1473 Simple two microseconds delay
1478 See Documentation/filesystems/nfs/nfsroot.txt.
1481 When an interrupt is not handled search all handlers
1482 for it. Intended to get systems with badly broken
1486 When an interrupt is not handled search all handlers
1487 for it. Also check all handlers each timer
1488 interrupt. Intended to get systems with badly broken
1492 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1494 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1496 <cpu number>,...,<cpu number>
1498 <cpu number>-<cpu number>
1499 (must be a positive range in ascending order)
1501 <cpu number>,...,<cpu number>-<cpu number>
1503 This option can be used to specify one or more CPUs
1504 to isolate from the general SMP balancing and scheduling
1505 algorithms. You can move a process onto or off an
1506 "isolated" CPU via the CPU affinity syscalls or cpuset.
1507 <cpu number> begins at 0 and the maximum value is
1508 "number of CPUs in system - 1".
1510 This option is the preferred way to isolate CPUs. The
1511 alternative -- manually setting the CPU mask of all
1512 tasks in the system -- can cause problems and
1513 suboptimal load balancer performance.
1517 ivrs_ioapic [HW,X86_64]
1518 Provide an override to the IOAPIC-ID<->DEVICE-ID
1519 mapping provided in the IVRS ACPI table. For
1520 example, to map IOAPIC-ID decimal 10 to
1521 PCI device 00:14.0 write the parameter as:
1522 ivrs_ioapic[10]=00:14.0
1524 ivrs_hpet [HW,X86_64]
1525 Provide an override to the HPET-ID<->DEVICE-ID
1526 mapping provided in the IVRS ACPI table. For
1527 example, to map HPET-ID decimal 0 to
1528 PCI device 00:14.0 write the parameter as:
1529 ivrs_hpet[0]=00:14.0
1531 js= [HW,JOY] Analog joystick
1532 See Documentation/input/joystick.txt.
1535 Enable/disable kernel and module base offset ASLR
1536 (Address Space Layout Randomization) if built into
1537 the kernel. When CONFIG_HIBERNATION is selected,
1538 kASLR is disabled by default. When kASLR is enabled,
1539 hibernation will be disabled.
1543 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1544 specifies the amount of memory usable by the kernel
1545 for non-movable allocations. The requested amount is
1546 spread evenly throughout all nodes in the system. The
1547 remaining memory in each node is used for Movable
1548 pages. In the event, a node is too small to have both
1549 kernelcore and Movable pages, kernelcore pages will
1550 take priority and other nodes will have a larger number
1551 of Movable pages. The Movable zone is used for the
1552 allocation of pages that may be reclaimed or moved
1553 by the page migration subsystem. This means that
1554 HugeTLB pages may not be allocated from this zone.
1555 Note that allocations like PTEs-from-HighMem still
1556 use the HighMem zone if it exists, and the Normal
1557 zone if it does not.
1559 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1560 Format: <Controller#>[,poll interval]
1561 The controller # is the number of the ehci usb debug
1562 port as it is probed via PCI. The poll interval is
1563 optional and is the number seconds in between
1564 each poll cycle to the debug port in case you need
1565 the functionality for interrupting the kernel with
1566 gdb or control-c on the dbgp connection. When
1567 not using this parameter you use sysrq-g to break into
1568 the kernel debugger.
1570 kgdboc= [KGDB,HW] kgdb over consoles.
1571 Requires a tty driver that supports console polling,
1572 or a supported polling keyboard driver (non-usb).
1573 Serial only format: <serial_device>[,baud]
1574 keyboard only format: kbd
1575 keyboard and serial format: kbd,<serial_device>[,baud]
1576 Optional Kernel mode setting:
1577 kms, kbd format: kms,kbd
1578 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1580 kgdbwait [KGDB] Stop kernel execution and enter the
1581 kernel debugger at the earliest opportunity.
1583 kmac= [MIPS] korina ethernet MAC address.
1584 Configure the RouterBoard 532 series on-chip
1585 Ethernet adapter MAC address.
1587 kmemleak= [KNL] Boot-time kmemleak enable/disable
1588 Valid arguments: on, off
1591 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1592 Valid arguments: 0, 1, 2
1593 kmemcheck=0 (disabled)
1594 kmemcheck=1 (enabled)
1595 kmemcheck=2 (one-shot mode)
1596 Default: 2 (one-shot mode)
1598 kstack=N [X86] Print N words from the kernel stack
1601 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1602 Default is 0 (don't ignore, but inject #GP)
1604 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1608 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1609 Default is 1 (enabled)
1611 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1613 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1615 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1616 (virtualized MMU) support on capable Intel chips.
1617 Default is 1 (enabled)
1619 kvm-intel.emulate_invalid_guest_state=
1620 [KVM,Intel] Enable emulation of invalid guest states
1621 Default is 0 (disabled)
1623 kvm-intel.flexpriority=
1624 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1625 Default is 1 (enabled)
1628 [KVM,Intel] Enable VMX nesting (nVMX).
1629 Default is 0 (disabled)
1631 kvm-intel.unrestricted_guest=
1632 [KVM,Intel] Disable unrestricted guest feature
1633 (virtualized real and unpaged mode) on capable
1634 Intel chips. Default is 1 (enabled)
1636 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1637 feature (tagged TLBs) on capable Intel chips.
1638 Default is 1 (enabled)
1644 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1647 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1648 value for LAPIC timer one-shot implementation. Default
1649 back to the programmable timer unit in the LAPIC.
1651 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1654 libata.dma= [LIBATA] DMA control
1655 libata.dma=0 Disable all PATA and SATA DMA
1656 libata.dma=1 PATA and SATA Disk DMA only
1657 libata.dma=2 ATAPI (CDROM) DMA only
1658 libata.dma=4 Compact Flash DMA only
1659 Combinations also work, so libata.dma=3 enables DMA
1660 for disks and CDROMs, but not CFs.
1662 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1663 libata.ignore_hpa=0 keep BIOS limits (default)
1664 libata.ignore_hpa=1 ignore limits, using full disk
1666 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1670 libata.force= [LIBATA] Force configurations. The format is comma
1671 separated list of "[ID:]VAL" where ID is
1672 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1673 matching port, link or device. Basically, it matches
1674 the ATA ID string printed on console by libata. If
1675 the whole ID part is omitted, the last PORT and DEVICE
1676 values are used. If ID hasn't been specified yet, the
1677 configuration applies to all ports, links and devices.
1679 If only DEVICE is omitted, the parameter applies to
1680 the port and all links and devices behind it. DEVICE
1681 number of 0 either selects the first device or the
1682 first fan-out link behind PMP device. It does not
1683 select the host link. DEVICE number of 15 selects the
1684 host link and device attached to it.
1686 The VAL specifies the configuration to force. As long
1687 as there's no ambiguity shortcut notation is allowed.
1688 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1689 The following configurations can be forced.
1691 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1692 Any ID with matching PORT is used.
1694 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1696 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1697 udma[/][16,25,33,44,66,100,133] notation is also
1700 * [no]ncq: Turn on or off NCQ.
1702 * nohrst, nosrst, norst: suppress hard, soft
1705 * rstonce: only attempt one reset during
1706 hot-unplug link recovery
1708 * dump_id: dump IDENTIFY data.
1710 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1712 * disable: Disable this device.
1714 If there are multiple matching configurations changing
1715 the same attribute, the last one is used.
1717 memblock=debug [KNL] Enable memblock debug messages.
1719 load_ramdisk= [RAM] List of ramdisks to load from floppy
1720 See Documentation/blockdev/ramdisk.txt.
1722 lockd.nlm_grace_period=P [NFS] Assign grace period.
1725 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1728 lockd.nlm_timeout=T [NFS] Assign timeout value.
1731 lockd.nlm_udpport=M [NFS] Assign UDP port.
1734 locktorture.nreaders_stress= [KNL]
1735 Set the number of locking read-acquisition kthreads.
1736 Defaults to being automatically set based on the
1737 number of online CPUs.
1739 locktorture.nwriters_stress= [KNL]
1740 Set the number of locking write-acquisition kthreads.
1742 locktorture.onoff_holdoff= [KNL]
1743 Set time (s) after boot for CPU-hotplug testing.
1745 locktorture.onoff_interval= [KNL]
1746 Set time (s) between CPU-hotplug operations, or
1747 zero to disable CPU-hotplug testing.
1749 locktorture.shuffle_interval= [KNL]
1750 Set task-shuffle interval (jiffies). Shuffling
1751 tasks allows some CPUs to go into dyntick-idle
1752 mode during the locktorture test.
1754 locktorture.shutdown_secs= [KNL]
1755 Set time (s) after boot system shutdown. This
1756 is useful for hands-off automated testing.
1758 locktorture.stat_interval= [KNL]
1759 Time (s) between statistics printk()s.
1761 locktorture.stutter= [KNL]
1762 Time (s) to stutter testing, for example,
1763 specifying five seconds causes the test to run for
1764 five seconds, wait for five seconds, and so on.
1765 This tests the locking primitive's ability to
1766 transition abruptly to and from idle.
1768 locktorture.torture_runnable= [BOOT]
1769 Start locktorture running at boot time.
1771 locktorture.torture_type= [KNL]
1772 Specify the locking implementation to test.
1774 locktorture.verbose= [KNL]
1775 Enable additional printk() statements.
1777 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1780 loglevel= All Kernel Messages with a loglevel smaller than the
1781 console loglevel will be printed to the console. It can
1782 also be changed with klogd or other programs. The
1783 loglevels are defined as follows:
1785 0 (KERN_EMERG) system is unusable
1786 1 (KERN_ALERT) action must be taken immediately
1787 2 (KERN_CRIT) critical conditions
1788 3 (KERN_ERR) error conditions
1789 4 (KERN_WARNING) warning conditions
1790 5 (KERN_NOTICE) normal but significant condition
1791 6 (KERN_INFO) informational
1792 7 (KERN_DEBUG) debug-level messages
1794 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1795 in bytes. n must be a power of two and greater
1796 than the minimal size. The minimal size is defined
1797 by LOG_BUF_SHIFT kernel config parameter. There is
1798 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1799 that allows to increase the default size depending on
1800 the number of CPUs. See init/Kconfig for more details.
1802 logo.nologo [FB] Disables display of the built-in Linux logo.
1803 This may be used to provide more screen space for
1804 kernel log messages and is useful when debugging
1805 kernel boot problems.
1807 lp=0 [LP] Specify parallel ports to use, e.g,
1808 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1809 lp=reset first parallel port). 'lp=0' disables the
1810 lp=auto printer driver. 'lp=reset' (which can be
1811 specified in addition to the ports) causes
1812 attached printers to be reset. Using
1813 lp=port1,port2,... specifies the parallel ports
1814 to associate lp devices with, starting with
1815 lp0. A port specification may be 'none' to skip
1816 that lp device, or a parport name such as
1817 'parport0'. Specifying 'lp=auto' instead of a
1818 port specification list means that device IDs
1819 from each port should be examined, to see if
1820 an IEEE 1284-compliant printer is attached; if
1821 so, the driver will manage that printer.
1822 See also header of drivers/char/lp.c.
1825 Sets loops_per_jiffy to given constant, thus avoiding
1826 time-consuming boot-time autodetection (up to 250 ms per
1827 CPU). 0 enables autodetection (default). To determine
1828 the correct value for your kernel, boot with normal
1829 autodetection and see what value is printed. Note that
1830 on SMP systems the preset will be applied to all CPUs,
1831 which is likely to cause problems if your CPUs need
1832 significantly divergent settings. An incorrect value
1833 will cause delays in the kernel to be wrong, leading to
1834 unpredictable I/O errors and other breakage. Although
1835 unlikely, in the extreme case this might damage your
1839 Format: <io>,<irq>,<dma>
1841 machvec= [IA-64] Force the use of a particular machine-vector
1842 (machvec) in a generic kernel.
1843 Example: machvec=hpzx1_swiotlb
1845 machtype= [Loongson] Share the same kernel image file between different
1847 Example: machtype=lemote-yeeloong-2f-7inch
1849 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1850 than or equal to this physical address is ignored.
1852 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1853 should make use of. maxcpus=n : n >= 0 limits the
1854 kernel to using 'n' processors. n=0 is a special case,
1855 it is equivalent to "nosmp", which also disables
1858 max_loop= [LOOP] The number of loop block devices that get
1859 (loop.max_loop) unconditionally pre-created at init time. The default
1860 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1861 of statically allocating a predefined number, loop
1862 devices can be requested on-demand with the
1863 /dev/loop-control interface.
1865 mce [X86-32] Machine Check Exception
1867 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1869 md= [HW] RAID subsystems devices and level
1870 See Documentation/md.txt.
1873 Format: <first>,<last>
1874 Specifies range of consoles to be captured by the MDA.
1876 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1877 Amount of memory to be used when the kernel is not able
1878 to see the whole system memory or for test.
1879 [X86] Work as limiting max address. Use together
1880 with memmap= to avoid physical address space collisions.
1881 Without memmap= PCI devices could be placed at addresses
1882 belonging to unused RAM.
1884 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1888 [KNL,SH] Allow user to override the default size for
1889 per-device physically contiguous DMA buffers.
1891 memmap=exactmap [KNL,X86] Enable setting of an exact
1892 E820 memory map, as specified by the user.
1893 Such memmap=exactmap lines can be constructed based on
1894 BIOS output or other requirements. See the memmap=nn@ss
1897 memmap=nn[KMG]@ss[KMG]
1898 [KNL] Force usage of a specific region of memory.
1899 Region of memory to be used is from ss to ss+nn.
1901 memmap=nn[KMG]#ss[KMG]
1902 [KNL,ACPI] Mark specific memory as ACPI data.
1903 Region of memory to be marked is from ss to ss+nn.
1905 memmap=nn[KMG]$ss[KMG]
1906 [KNL,ACPI] Mark specific memory as reserved.
1907 Region of memory to be reserved is from ss to ss+nn.
1908 Example: Exclude memory from 0x18690000-0x1869ffff
1909 memmap=64K$0x18690000
1911 memmap=0x10000$0x18690000
1913 memory_corruption_check=0/1 [X86]
1914 Some BIOSes seem to corrupt the first 64k of
1915 memory when doing things like suspend/resume.
1916 Setting this option will scan the memory
1917 looking for corruption. Enabling this will
1918 both detect corruption and prevent the kernel
1919 from using the memory being corrupted.
1920 However, its intended as a diagnostic tool; if
1921 repeatable BIOS-originated corruption always
1922 affects the same memory, you can use memmap=
1923 to prevent the kernel from using that memory.
1925 memory_corruption_check_size=size [X86]
1926 By default it checks for corruption in the low
1927 64k, making this memory unavailable for normal
1928 use. Use this parameter to scan for
1929 corruption in more or less memory.
1931 memory_corruption_check_period=seconds [X86]
1932 By default it checks for corruption every 60
1933 seconds. Use this parameter to check at some
1934 other rate. 0 disables periodic checking.
1936 memtest= [KNL,X86] Enable memtest
1938 default : 0 <disable>
1939 Specifies the number of memtest passes to be
1940 performed. Each pass selects another test
1941 pattern from a given set of patterns. Memtest
1942 fills the memory with this pattern, validates
1943 memory contents and reserves bad memory
1944 regions that are detected.
1946 meye.*= [HW] Set MotionEye Camera parameters
1947 See Documentation/video4linux/meye.txt.
1949 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1950 Multi-Function General Purpose Timers on AMD Geode
1953 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1954 the BIOS has incorrectly applied a workaround. TinyBIOS
1955 version 0.98 is known to be affected, 0.99 fixes the
1956 problem by letting the user disable the workaround.
1960 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1961 physical address is ignored.
1963 mini2440= [ARM,HW,KNL]
1964 Format:[0..2][b][c][t]
1966 MINI2440 configuration specification:
1967 0 - The attached screen is the 3.5" TFT
1968 1 - The attached screen is the 7" TFT
1969 2 - The VGA Shield is attached (1024x768)
1970 Leaving out the screen size parameter will not load
1971 the TFT driver, and the framebuffer will be left
1973 b - Enable backlight. The TFT backlight pin will be
1974 linked to the kernel VESA blanking code and a GPIO
1975 LED. This parameter is not necessary when using the
1977 c - Enable the s3c camera interface.
1978 t - Reserved for enabling touchscreen support. The
1979 touchscreen support is not enabled in the mainstream
1980 kernel as of 2.6.30, a preliminary port can be found
1981 in the "bleeding edge" mini2440 support kernel at
1982 http://repo.or.cz/w/linux-2.6/mini2440.git
1985 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1986 parameter allows control of the logging verbosity for
1987 the additional memory initialisation checks. A value
1988 of 0 disables mminit logging and a level of 4 will
1989 log everything. Information is printed at KERN_DEBUG
1990 so loglevel=8 may also need to be specified.
1993 [KNL] When CONFIG_MODULE_SIG is set, this means that
1994 modules without (valid) signatures will fail to load.
1995 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1996 is always true, so this option does nothing.
1999 [MOUSE] Maximum time between finger touching and
2000 leaving touchpad surface for touch to be considered
2001 a tap and be reported as a left button click (for
2002 touchpads working in absolute mode only).
2004 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2005 reporting absolute coordinates, such as tablets
2006 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2007 reporting absolute coordinates, such as tablets
2009 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2010 is similar to kernelcore except it specifies the
2011 amount of memory used for migratable allocations.
2012 If both kernelcore and movablecore is specified,
2013 then kernelcore will be at *least* the specified
2014 value but may be more. If movablecore on its own
2015 is specified, the administrator must be careful
2016 that the amount of memory usable for all allocations
2019 movable_node [KNL,X86] Boot-time switch to enable the effects
2020 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2022 MTD_Partition= [MTD]
2023 Format: <name>,<region-number>,<size>,<offset>
2025 MTD_Region= [MTD] Format:
2026 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2029 See drivers/mtd/cmdlinepart.c.
2031 multitce=off [PPC] This parameter disables the use of the pSeries
2032 firmware feature for updating multiple TCE entries
2035 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2037 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2039 boundary - index of last SLC block on Flex-OneNAND.
2040 The remaining blocks are configured as MLC blocks.
2041 lock - Configure if Flex-OneNAND boundary should be locked.
2042 Once locked, the boundary cannot be changed.
2043 1 indicates lock status, 0 indicates unlock status.
2046 ARM/S3C2412 JIVE boot control
2048 See arch/arm/mach-s3c2412/mach-jive.c
2050 mtouchusb.raw_coordinates=
2051 [HW] Make the MicroTouch USB driver use raw coordinates
2052 ('y', default) or cooked coordinates ('n')
2054 mtrr_chunk_size=nn[KMG] [X86]
2055 used for mtrr cleanup. It is largest continuous chunk
2056 that could hold holes aka. UC entries.
2058 mtrr_gran_size=nn[KMG] [X86]
2059 Used for mtrr cleanup. It is granularity of mtrr block.
2061 Large value could prevent small alignment from
2064 mtrr_spare_reg_nr=n [X86]
2066 Range: 0,7 : spare reg number
2068 Used for mtrr cleanup. It is spare mtrr entries number.
2069 Set to 2 or more if your graphical card needs more.
2071 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2073 netdev= [NET] Network devices parameters
2074 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2075 Note that mem_start is often overloaded to mean
2076 something different and driver-specific.
2077 This usage is only documented in each driver source
2081 [NETFILTER] Enable connection tracking flow accounting
2082 0 to disable accounting
2083 1 to enable accounting
2086 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2087 See Documentation/filesystems/nfs/nfsroot.txt.
2089 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2090 See Documentation/filesystems/nfs/nfsroot.txt.
2092 nfsrootdebug [NFS] enable nfsroot debugging messages.
2093 See Documentation/filesystems/nfs/nfsroot.txt.
2095 nfs.callback_tcpport=
2096 [NFS] set the TCP port on which the NFSv4 callback
2097 channel should listen.
2100 [NFS] sets the pathname to the program which is used
2101 to update the NFS client cache entries.
2103 nfs.cache_getent_timeout=
2104 [NFS] sets the timeout after which an attempt to
2105 update a cache entry is deemed to have failed.
2107 nfs.idmap_cache_timeout=
2108 [NFS] set the maximum lifetime for idmapper cache
2112 [NFS] enable 64-bit inode numbers.
2113 If zero, the NFS client will fake up a 32-bit inode
2114 number for the readdir() and stat() syscalls instead
2115 of returning the full 64-bit number.
2116 The default is to return 64-bit inode numbers.
2118 nfs.max_session_slots=
2119 [NFSv4.1] Sets the maximum number of session slots
2120 the client will attempt to negotiate with the server.
2121 This limits the number of simultaneous RPC requests
2122 that the client can send to the NFSv4.1 server.
2123 Note that there is little point in setting this
2124 value higher than the max_tcp_slot_table_limit.
2126 nfs.nfs4_disable_idmapping=
2127 [NFSv4] When set to the default of '1', this option
2128 ensures that both the RPC level authentication
2129 scheme and the NFS level operations agree to use
2130 numeric uids/gids if the mount is using the
2131 'sec=sys' security flavour. In effect it is
2132 disabling idmapping, which can make migration from
2133 legacy NFSv2/v3 systems to NFSv4 easier.
2134 Servers that do not support this mode of operation
2135 will be autodetected by the client, and it will fall
2136 back to using the idmapper.
2137 To turn off this behaviour, set the value to '0'.
2139 [NFS4] Specify an additional fixed unique ident-
2140 ification string that NFSv4 clients can insert into
2141 their nfs_client_id4 string. This is typically a
2142 UUID that is generated at system install time.
2144 nfs.send_implementation_id =
2145 [NFSv4.1] Send client implementation identification
2146 information in exchange_id requests.
2147 If zero, no implementation identification information
2149 The default is to send the implementation identification
2152 nfs.recover_lost_locks =
2153 [NFSv4] Attempt to recover locks that were lost due
2154 to a lease timeout on the server. Please note that
2155 doing this risks data corruption, since there are
2156 no guarantees that the file will remain unchanged
2157 after the locks are lost.
2158 If you want to enable the kernel legacy behaviour of
2159 attempting to recover these locks, then set this
2161 The default parameter value of '0' causes the kernel
2162 not to attempt recovery of lost locks.
2164 nfsd.nfs4_disable_idmapping=
2165 [NFSv4] When set to the default of '1', the NFSv4
2166 server will return only numeric uids and gids to
2167 clients using auth_sys, and will accept numeric uids
2168 and gids from such clients. This is intended to ease
2169 migration from NFSv2/v3.
2171 objlayoutdriver.osd_login_prog=
2172 [NFS] [OBJLAYOUT] sets the pathname to the program which
2173 is used to automatically discover and login into new
2174 osd-targets. Please see:
2175 Documentation/filesystems/pnfs.txt for more explanations
2177 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2178 when a NMI is triggered.
2179 Format: [state][,regs][,debounce][,die]
2181 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2182 Format: [panic,][nopanic,][num]
2184 0 - turn nmi_watchdog off
2185 When panic is specified, panic when an NMI watchdog
2186 timeout occurs (or 'nopanic' to override the opposite
2188 This is useful when you use a panic=... timeout and
2189 need the box quickly up again.
2191 netpoll.carrier_timeout=
2192 [NET] Specifies amount of time (in seconds) that
2193 netpoll should wait for a carrier. By default netpoll
2196 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2197 emulation library even if a 387 maths coprocessor
2201 [HW] Never suspend the console
2202 Disable suspending of consoles during suspend and
2203 hibernate operations. Once disabled, debugging
2204 messages can reach various consoles while the rest
2205 of the system is being put to sleep (ie, while
2206 debugging driver suspend/resume hooks). This may
2207 not work reliably with all consoles, but is known
2208 to work with serial and VGA consoles.
2209 To facilitate more flexible debugging, we also add
2210 console_suspend, a printk module parameter to control
2211 it. Users could use console_suspend (usually
2212 /sys/module/printk/parameters/console_suspend) to
2213 turn on/off it dynamically.
2215 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2216 caches in the slab allocator. Saves per-node memory,
2217 but will impact performance.
2221 noapic [SMP,APIC] Tells the kernel to not make use of any
2222 IOAPICs that may be present in the system.
2224 noautogroup Disable scheduler automatic task group creation.
2226 nobats [PPC] Do not use BATs for mapping kernel lowmem
2227 on "Classic" PPC cores.
2231 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2233 nodelayacct [KNL] Disable per-task delay accounting
2235 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2237 nodsp [SH] Disable hardware DSP at boot time.
2239 noefi Disable EFI runtime services support.
2244 On X86-32 available only on PAE configured kernels.
2245 noexec=on: enable non-executable mappings (default)
2246 noexec=off: disable non-executable mappings
2249 Disable SMAP (Supervisor Mode Access Prevention)
2250 even if it is supported by processor.
2253 Disable SMEP (Supervisor Mode Execution Prevention)
2254 even if it is supported by processor.
2257 This affects only 32-bit executables.
2258 noexec32=on: enable non-executable mappings (default)
2259 read doesn't imply executable mappings
2260 noexec32=off: disable non-executable mappings
2261 read implies executable mappings
2263 nofpu [SH] Disable hardware FPU at boot time.
2265 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2266 register save and restore. The kernel will only save
2267 legacy floating-point registers on task switch.
2269 noxsave [BUGS=X86] Disables x86 extended register state save
2270 and restore using xsave. The kernel will fallback to
2271 enabling legacy floating-point and sse state.
2273 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2274 register states. The kernel will fall back to use
2275 xsave to save the states. By using this parameter,
2276 performance of saving the states is degraded because
2277 xsave doesn't support modified optimization while
2278 xsaveopt supports it on xsaveopt enabled systems.
2280 noxsaves [X86] Disables xsaves and xrstors used in saving and
2281 restoring x86 extended register state in compacted
2282 form of xsave area. The kernel will fall back to use
2283 xsaveopt and xrstor to save and restore the states
2284 in standard form of xsave area. By using this
2285 parameter, xsave area per process might occupy more
2286 memory on xsaves enabled systems.
2289 on enable eager fpu restore
2290 off disable eager fpu restore
2291 auto selects the default scheme, which automatically
2292 enables eagerfpu restore for xsaveopt.
2294 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2295 wfi(ARM) instruction doesn't work correctly and not to
2296 use it. This is also useful when using JTAG debugger.
2298 no_file_caps Tells the kernel not to honor file capabilities. The
2299 only way then for a file to be executed with privilege
2300 is to be setuid root or executed by root.
2302 nohalt [IA-64] Tells the kernel not to use the power saving
2303 function PAL_HALT_LIGHT when idle. This increases
2304 power-consumption. On the positive side, it reduces
2305 interrupt wake-up latency, which may improve performance
2306 in certain environments such as networked servers or
2309 nohibernate [HIBERNATION] Disable hibernation and resume.
2311 nohz= [KNL] Boottime enable/disable dynamic ticks
2312 Valid arguments: on, off
2315 nohz_full= [KNL,BOOT]
2316 In kernels built with CONFIG_NO_HZ_FULL=y, set
2317 the specified list of CPUs whose tick will be stopped
2318 whenever possible. The boot CPU will be forced outside
2319 the range to maintain the timekeeping.
2320 The CPUs in this range must also be included in the
2323 noiotrap [SH] Disables trapped I/O port accesses.
2325 noirqdebug [X86-32] Disables the code which attempts to detect and
2326 disable unhandled interrupt sources.
2328 no_timer_check [X86,APIC] Disables the code which tests for
2329 broken timer IRQ sources.
2331 noisapnp [ISAPNP] Disables ISA PnP code.
2333 noinitrd [RAM] Tells the kernel not to load any configured
2336 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2338 [Deprecated - use intremap=off]
2342 nojitter [IA-64] Disables jitter checking for ITC timers.
2344 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2346 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2349 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2350 steal time is computed, but won't influence scheduler
2353 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2355 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2357 noltlbs [PPC] Do not use large page/tlb entries for kernel
2358 lowmem mapping on PPC40x.
2360 nomca [IA-64] Disable machine check abort handling
2362 nomce [X86-32] Machine Check Exception
2364 nomfgpt [X86-32] Disable Multi-Function General Purpose
2365 Timer usage (for AMD Geode machines).
2367 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2368 shutdown the other cpus. Instead use the REBOOT_VECTOR
2371 nomodule Disable module load
2373 nopat [X86] Disable PAT (page attribute table extension of
2374 pagetables) support.
2376 norandmaps Don't use address space randomization. Equivalent to
2377 echo 0 > /proc/sys/kernel/randomize_va_space
2379 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2381 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2382 with UP alternatives
2384 nordrand [X86] Disable kernel use of the RDRAND and
2385 RDSEED instructions even if they are supported
2386 by the processor. RDRAND and RDSEED are still
2387 available to user space applications.
2389 noresume [SWSUSP] Disables resume and restores original swap
2392 no-scroll [VGA] Disables scrollback.
2393 This is required for the Braillex ib80-piezo Braille
2394 reader made by F.H. Papenmeier (Germany).
2398 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2400 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2401 and disable the IO APIC. legacy for "maxcpus=0".
2403 nosoftlockup [KNL] Disable the soft-lockup detector.
2405 nosync [HW,M68K] Disables sync negotiation for all devices.
2407 notsc [BUGS=X86-32] Disable Time Stamp Counter
2409 nousb [USB] Disable the USB subsystem
2411 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2415 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2417 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2418 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2419 Some features depend on CPU0. Known dependencies are:
2420 1. Resume from suspend/hibernate depends on CPU0.
2421 Suspend/hibernate will fail if CPU0 is offline and you
2422 need to online CPU0 before suspend/hibernate.
2423 2. PIC interrupts also depend on CPU0. CPU0 can't be
2424 removed if a PIC interrupt is detected.
2425 It's said poweroff/reboot may depend on CPU0 on some
2426 machines although I haven't seen such issues so far
2427 after CPU0 is offline on a few tested machines.
2428 If the dependencies are under your control, you can
2429 turn on cpu0_hotplug.
2431 nptcg= [IA-64] Override max number of concurrent global TLB
2432 purges which is reported from either PAL_VM_SUMMARY or
2435 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2436 could support. nr_cpus=n : n >= 1 limits the kernel to
2437 supporting 'n' processors. Later in runtime you can not
2438 use hotplug cpu feature to put more cpu back to online.
2439 just like you compile the kernel NR_CPUS=n
2441 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2443 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2444 Allowed values are enable and disable
2446 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2447 one of ['zone', 'node', 'default'] can be specified
2448 This can be set from sysctl after boot.
2449 See Documentation/sysctl/vm.txt for details.
2451 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2452 See Documentation/debugging-via-ohci1394.txt for more
2455 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2456 Rather than timing out after 20 ms if an EC
2457 command is not properly ACKed, override the length
2458 of the timeout. We have interrupts disabled while
2459 waiting for the ACK, so if this is set too high
2460 interrupts *may* be lost!
2462 omap_mux= [OMAP] Override bootloader pin multiplexing.
2463 Format: <mux_mode0.mode_name=value>...
2464 For example, to override I2C bus2:
2465 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2467 oprofile.timer= [HW]
2468 Use timer interrupt instead of performance counters
2470 oprofile.cpu_type= Force an oprofile cpu type
2471 This might be useful if you have an older oprofile
2472 userland or if you want common events.
2473 Format: { arch_perfmon }
2474 arch_perfmon: [X86] Force use of architectural
2475 perfmon on Intel CPUs instead of the
2476 CPU specific event set.
2477 timer: [X86] Force use of architectural NMI
2478 timer mode (see also oprofile.timer
2479 for generic hr timer mode)
2480 [s390] Force legacy basic mode sampling
2481 (report cpu_type "timer")
2483 oops=panic Always panic on oopses. Default is to just kill the
2484 process, but there is a small probability of
2485 deadlocking the machine.
2486 This will also cause panics on machine check exceptions.
2487 Useful together with panic=30 to trigger a reboot.
2490 See Documentation/sound/oss/oss-parameters.txt
2492 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2493 timeout > 0: seconds before rebooting
2494 timeout = 0: wait forever
2495 timeout < 0: reboot immediately
2498 crash_kexec_post_notifiers
2499 Run kdump after running panic-notifiers and dumping
2500 kmsg. This only for the users who doubt kdump always
2501 succeeds in any situation.
2502 Note that this also increases risks of kdump failure,
2503 because some panic notifiers can make the crashed
2504 kernel more unstable.
2506 parkbd.port= [HW] Parallel port number the keyboard adapter is
2507 connected to, default is 0.
2509 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2510 0 for XT, 1 for AT (default is AT).
2513 parport= [HW,PPT] Specify parallel ports. 0 disables.
2514 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2515 Use 'auto' to force the driver to use any
2516 IRQ/DMA settings detected (the default is to
2517 ignore detected IRQ/DMA settings because of
2518 possible conflicts). You can specify the base
2519 address, IRQ, and DMA settings; IRQ and DMA
2520 should be numbers, or 'auto' (for using detected
2521 settings on that particular port), or 'nofifo'
2522 (to avoid using a FIFO even if it is detected).
2523 Parallel ports are assigned in the order they
2524 are specified on the command line, starting
2527 parport_init_mode= [HW,PPT]
2528 Configure VIA parallel port to operate in
2529 a specific mode. This is necessary on Pegasos
2530 computer where firmware has no options for setting
2531 up parallel port mode and sets it to spp.
2532 Currently this function knows 686a and 8231 chips.
2533 Format: [spp|ps2|epp|ecp|ecpepp]
2536 Halt all CPUs after the first oops has been printed for
2537 the specified number of seconds. This is to be used if
2538 your oopses keep scrolling off the screen.
2543 See header of drivers/block/paride/pcd.c.
2544 See also Documentation/blockdev/paride.txt.
2546 pci=option[,option...] [PCI] various PCI subsystem options:
2547 earlydump [X86] dump PCI config space before the kernel
2549 off [X86] don't probe for the PCI bus
2550 bios [X86-32] force use of PCI BIOS, don't access
2551 the hardware directly. Use this if your machine
2552 has a non-standard PCI host bridge.
2553 nobios [X86-32] disallow use of PCI BIOS, only direct
2554 hardware access methods are allowed. Use this
2555 if you experience crashes upon bootup and you
2556 suspect they are caused by the BIOS.
2557 conf1 [X86] Force use of PCI Configuration
2559 conf2 [X86] Force use of PCI Configuration
2561 noaer [PCIE] If the PCIEAER kernel config parameter is
2562 enabled, this kernel boot option can be used to
2563 disable the use of PCIE advanced error reporting.
2564 nodomains [PCI] Disable support for multiple PCI
2565 root domains (aka PCI segments, in ACPI-speak).
2566 nommconf [X86] Disable use of MMCONFIG for PCI
2568 check_enable_amd_mmconf [X86] check for and enable
2569 properly configured MMIO access to PCI
2570 config space on AMD family 10h CPU
2571 nomsi [MSI] If the PCI_MSI kernel config parameter is
2572 enabled, this kernel boot option can be used to
2573 disable the use of MSI interrupts system-wide.
2574 noioapicquirk [APIC] Disable all boot interrupt quirks.
2575 Safety option to keep boot IRQs enabled. This
2576 should never be necessary.
2577 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2578 primary IO-APIC for bridges that cannot disable
2579 boot IRQs. This fixes a source of spurious IRQs
2580 when the system masks IRQs.
2581 noioapicreroute [APIC] Disable workaround that uses the
2582 boot IRQ equivalent of an IRQ that connects to
2583 a chipset where boot IRQs cannot be disabled.
2584 The opposite of ioapicreroute.
2585 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2586 routing table. These calls are known to be buggy
2587 on several machines and they hang the machine
2588 when used, but on other computers it's the only
2589 way to get the interrupt routing table. Try
2590 this option if the kernel is unable to allocate
2591 IRQs or discover secondary PCI buses on your
2593 rom [X86] Assign address space to expansion ROMs.
2594 Use with caution as certain devices share
2595 address decoders between ROMs and other
2597 norom [X86] Do not assign address space to
2598 expansion ROMs that do not already have
2599 BIOS assigned address ranges.
2600 nobar [X86] Do not assign address space to the
2601 BARs that weren't assigned by the BIOS.
2602 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2603 assigned automatically to PCI devices. You can
2604 make the kernel exclude IRQs of your ISA cards
2606 pirqaddr=0xAAAAA [X86] Specify the physical address
2607 of the PIRQ table (normally generated
2608 by the BIOS) if it is outside the
2609 F0000h-100000h range.
2610 lastbus=N [X86] Scan all buses thru bus #N. Can be
2611 useful if the kernel is unable to find your
2612 secondary buses and you want to tell it
2613 explicitly which ones they are.
2614 assign-busses [X86] Always assign all PCI bus
2615 numbers ourselves, overriding
2616 whatever the firmware may have done.
2617 usepirqmask [X86] Honor the possible IRQ mask stored
2618 in the BIOS $PIR table. This is needed on
2619 some systems with broken BIOSes, notably
2620 some HP Pavilion N5400 and Omnibook XE3
2621 notebooks. This will have no effect if ACPI
2622 IRQ routing is enabled.
2623 noacpi [X86] Do not use ACPI for IRQ routing
2624 or for PCI scanning.
2625 use_crs [X86] Use PCI host bridge window information
2626 from ACPI. On BIOSes from 2008 or later, this
2627 is enabled by default. If you need to use this,
2628 please report a bug.
2629 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2630 If you need to use this, please report a bug.
2631 routeirq Do IRQ routing for all PCI devices.
2632 This is normally done in pci_enable_device(),
2633 so this option is a temporary workaround
2634 for broken drivers that don't call it.
2635 skip_isa_align [X86] do not align io start addr, so can
2636 handle more pci cards
2637 firmware [ARM] Do not re-enumerate the bus but instead
2638 just use the configuration from the
2639 bootloader. This is currently used on
2640 IXP2000 systems where the bus has to be
2641 configured a certain way for adjunct CPUs.
2642 noearly [X86] Don't do any early type 1 scanning.
2643 This might help on some broken boards which
2644 machine check when some devices' config space
2645 is read. But various workarounds are disabled
2646 and some IOMMU drivers will not work.
2647 bfsort Sort PCI devices into breadth-first order.
2648 This sorting is done to get a device
2649 order compatible with older (<= 2.4) kernels.
2650 nobfsort Don't sort PCI devices into breadth-first order.
2651 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2652 tuning and use the BIOS-configured MPS defaults.
2653 pcie_bus_safe Set every device's MPS to the largest value
2654 supported by all devices below the root complex.
2655 pcie_bus_perf Set device MPS to the largest allowable MPS
2656 based on its parent bus. Also set MRRS (Max
2657 Read Request Size) to the largest supported
2658 value (no larger than the MPS that the device
2659 or bus can support) for best performance.
2660 pcie_bus_peer2peer Set every device's MPS to 128B, which
2661 every device is guaranteed to support. This
2662 configuration allows peer-to-peer DMA between
2663 any pair of devices, possibly at the cost of
2664 reduced performance. This also guarantees
2665 that hot-added devices will work.
2666 cbiosize=nn[KMG] The fixed amount of bus space which is
2667 reserved for the CardBus bridge's IO window.
2668 The default value is 256 bytes.
2669 cbmemsize=nn[KMG] The fixed amount of bus space which is
2670 reserved for the CardBus bridge's memory
2671 window. The default value is 64 megabytes.
2674 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2675 Specifies alignment and device to reassign
2676 aligned memory resources.
2677 If <order of align> is not specified,
2678 PAGE_SIZE is used as alignment.
2679 PCI-PCI bridge can be specified, if resource
2680 windows need to be expanded.
2681 ecrc= Enable/disable PCIe ECRC (transaction layer
2682 end-to-end CRC checking).
2683 bios: Use BIOS/firmware settings. This is the
2687 hpiosize=nn[KMG] The fixed amount of bus space which is
2688 reserved for hotplug bridge's IO window.
2689 Default size is 256 bytes.
2690 hpmemsize=nn[KMG] The fixed amount of bus space which is
2691 reserved for hotplug bridge's memory window.
2692 Default size is 2 megabytes.
2693 realloc= Enable/disable reallocating PCI bridge resources
2694 if allocations done by BIOS are too small to
2695 accommodate resources required by all child
2697 off: Turn realloc off
2699 realloc same as realloc=on
2700 noari do not use PCIe ARI.
2701 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2702 only look for one device below a PCIe downstream
2705 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2708 force Enable ASPM even on devices that claim not to support it.
2709 WARNING: Forcing ASPM on may cause system lockups.
2711 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2712 nomsi Do not use MSI for PCI Express Native Hotplug (this
2713 makes all PCIe ports use INTx for hotplug services).
2715 pcie_ports= [PCIE] PCIe ports handling:
2716 auto Ask the BIOS whether or not to use native PCIe services
2717 associated with PCIe ports (PME, hot-plug, AER). Use
2718 them only if that is allowed by the BIOS.
2719 native Use native PCIe services associated with PCIe ports
2721 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2724 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2725 nomsi Do not use MSI for native PCIe PME signaling (this makes
2726 all PCIe root ports use INTx for all services).
2728 pcmv= [HW,PCMCIA] BadgePAD 4
2732 Keep all power-domains already enabled by bootloader on,
2733 even if no driver has claimed them. This is useful
2734 for debug and development, but should not be
2735 needed on a platform with proper driver support.
2738 See Documentation/blockdev/paride.txt.
2740 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2743 See arch/parisc/kernel/pdc_chassis.c
2745 percpu_alloc= Select which percpu first chunk allocator to use.
2746 Currently supported values are "embed" and "page".
2747 Archs may support subset or none of the selections.
2748 See comments in mm/percpu.c for details on each
2749 allocator. This parameter is primarily for debugging
2750 and performance comparison.
2753 See Documentation/blockdev/paride.txt.
2756 See Documentation/blockdev/paride.txt.
2758 pirq= [SMP,APIC] Manual mp-table setup
2759 See Documentation/x86/i386/IO-APIC.txt.
2761 plip= [PPT,NET] Parallel port network link
2762 Format: { parport<nr> | timid | 0 }
2763 See also Documentation/parport.txt.
2765 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2766 Override pmtimer IOPort with a hex value.
2770 Enable PNP debug messages (depends on the
2771 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2772 via /sys/module/pnp/parameters/debug. We always show
2773 current resource usage; turning this on also shows
2774 possible settings and some assignment information.
2780 { on | off | curr | res | no-curr | no-res }
2783 [ISAPNP] Exclude IRQs for the autoconfiguration
2786 [ISAPNP] Exclude DMAs for the autoconfiguration
2788 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2789 Ranges are in pairs (I/O port base and size).
2792 [ISAPNP] Exclude memory regions for the
2794 Ranges are in pairs (memory base and size).
2796 ports= [IP_VS_FTP] IPVS ftp helper module
2798 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2800 Format: <port>,<port>....
2802 print-fatal-signals=
2803 [KNL] debug: print fatal signals
2805 If enabled, warn about various signal handling
2806 related application anomalies: too many signals,
2807 too many POSIX.1 timers, fatal signals causing a
2810 If you hit the warning due to signal overflow,
2811 you might want to try "ulimit -i unlimited".
2815 printk.always_kmsg_dump=
2816 Trigger kmsg_dump for cases other than kernel oops or
2818 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2821 printk.time= Show timing data prefixed to each printk message line
2822 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2824 processor.max_cstate= [HW,ACPI]
2825 Limit processor to maximum C-state
2826 max_cstate=9 overrides any DMI blacklist limit.
2828 processor.nocst [HW,ACPI]
2829 Ignore the _CST method to determine C-states,
2830 instead using the legacy FADT method
2832 profile= [KNL] Enable kernel profiling via /proc/profile
2833 Format: [schedule,]<number>
2834 Param: "schedule" - profile schedule points.
2835 Param: <number> - step/bucket size as a power of 2 for
2836 statistical time based profiling.
2837 Param: "sleep" - profile D-state sleeping (millisecs).
2838 Requires CONFIG_SCHEDSTATS
2839 Param: "kvm" - profile VM exits.
2841 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2843 See Documentation/blockdev/ramdisk.txt.
2845 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2846 probe for; one of (bare|imps|exps|lifebook|any).
2847 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2849 psmouse.resetafter= [HW,MOUSE]
2850 Try to reset the device after so many bad packets
2853 [HW,MOUSE] Set desired mouse resolution, in dpi.
2854 psmouse.smartscroll=
2855 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2856 0 = disabled, 1 = enabled (default).
2858 pstore.backend= Specify the name of the pstore backend to use
2861 See Documentation/blockdev/paride.txt.
2864 [KNL] Number of legacy pty's. Overwrites compiled-in
2867 quiet [KNL] Disable most log messages
2872 See Documentation/md.txt.
2874 ramdisk_blocksize= [RAM]
2875 See Documentation/blockdev/ramdisk.txt.
2877 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2878 See Documentation/blockdev/ramdisk.txt.
2881 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2882 the specified list of CPUs to be no-callback CPUs.
2883 Invocation of these CPUs' RCU callbacks will
2884 be offloaded to "rcuox/N" kthreads created for
2885 that purpose, where "x" is "b" for RCU-bh, "p"
2886 for RCU-preempt, and "s" for RCU-sched, and "N"
2887 is the CPU number. This reduces OS jitter on the
2888 offloaded CPUs, which can be useful for HPC and
2889 real-time workloads. It can also improve energy
2890 efficiency for asymmetric multiprocessors.
2893 Rather than requiring that offloaded CPUs
2894 (specified by rcu_nocbs= above) explicitly
2895 awaken the corresponding "rcuoN" kthreads,
2896 make these kthreads poll for callbacks.
2897 This improves the real-time response for the
2898 offloaded CPUs by relieving them of the need to
2899 wake up the corresponding kthread, but degrades
2900 energy efficiency by requiring that the kthreads
2901 periodically wake up to do the polling.
2903 rcutree.blimit= [KNL]
2904 Set maximum number of finished RCU callbacks to
2905 process in one batch.
2907 rcutree.rcu_fanout_leaf= [KNL]
2908 Increase the number of CPUs assigned to each
2909 leaf rcu_node structure. Useful for very large
2912 rcutree.jiffies_till_sched_qs= [KNL]
2913 Set required age in jiffies for a
2914 given grace period before RCU starts
2915 soliciting quiescent-state help from
2916 rcu_note_context_switch().
2918 rcutree.jiffies_till_first_fqs= [KNL]
2919 Set delay from grace-period initialization to
2920 first attempt to force quiescent states.
2921 Units are jiffies, minimum value is zero,
2922 and maximum value is HZ.
2924 rcutree.jiffies_till_next_fqs= [KNL]
2925 Set delay between subsequent attempts to force
2926 quiescent states. Units are jiffies, minimum
2927 value is one, and maximum value is HZ.
2929 rcutree.rcu_nocb_leader_stride= [KNL]
2930 Set the number of NOCB kthread groups, which
2931 defaults to the square root of the number of
2932 CPUs. Larger numbers reduces the wakeup overhead
2933 on the per-CPU grace-period kthreads, but increases
2934 that same overhead on each group's leader.
2936 rcutree.qhimark= [KNL]
2937 Set threshold of queued RCU callbacks beyond which
2938 batch limiting is disabled.
2940 rcutree.qlowmark= [KNL]
2941 Set threshold of queued RCU callbacks below which
2942 batch limiting is re-enabled.
2944 rcutree.rcu_idle_gp_delay= [KNL]
2945 Set wakeup interval for idle CPUs that have
2946 RCU callbacks (RCU_FAST_NO_HZ=y).
2948 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2949 Set wakeup interval for idle CPUs that have
2950 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2951 Lazy RCU callbacks are those which RCU can
2952 prove do nothing more than free memory.
2954 rcutorture.cbflood_inter_holdoff= [KNL]
2955 Set holdoff time (jiffies) between successive
2956 callback-flood tests.
2958 rcutorture.cbflood_intra_holdoff= [KNL]
2959 Set holdoff time (jiffies) between successive
2960 bursts of callbacks within a given callback-flood
2963 rcutorture.cbflood_n_burst= [KNL]
2964 Set the number of bursts making up a given
2965 callback-flood test. Set this to zero to
2966 disable callback-flood testing.
2968 rcutorture.cbflood_n_per_burst= [KNL]
2969 Set the number of callbacks to be registered
2970 in a given burst of a callback-flood test.
2972 rcutorture.fqs_duration= [KNL]
2973 Set duration of force_quiescent_state bursts.
2975 rcutorture.fqs_holdoff= [KNL]
2976 Set holdoff time within force_quiescent_state bursts.
2978 rcutorture.fqs_stutter= [KNL]
2979 Set wait time between force_quiescent_state bursts.
2981 rcutorture.gp_exp= [KNL]
2982 Use expedited update-side primitives.
2984 rcutorture.gp_normal= [KNL]
2985 Use normal (non-expedited) update-side primitives.
2986 If both gp_exp and gp_normal are set, do both.
2987 If neither gp_exp nor gp_normal are set, still
2990 rcutorture.n_barrier_cbs= [KNL]
2991 Set callbacks/threads for rcu_barrier() testing.
2993 rcutorture.nfakewriters= [KNL]
2994 Set number of concurrent RCU writers. These just
2995 stress RCU, they don't participate in the actual
2996 test, hence the "fake".
2998 rcutorture.nreaders= [KNL]
2999 Set number of RCU readers.
3001 rcutorture.object_debug= [KNL]
3002 Enable debug-object double-call_rcu() testing.
3004 rcutorture.onoff_holdoff= [KNL]
3005 Set time (s) after boot for CPU-hotplug testing.
3007 rcutorture.onoff_interval= [KNL]
3008 Set time (s) between CPU-hotplug operations, or
3009 zero to disable CPU-hotplug testing.
3011 rcutorture.torture_runnable= [BOOT]
3012 Start rcutorture running at boot time.
3014 rcutorture.shuffle_interval= [KNL]
3015 Set task-shuffle interval (s). Shuffling tasks
3016 allows some CPUs to go into dyntick-idle mode
3017 during the rcutorture test.
3019 rcutorture.shutdown_secs= [KNL]
3020 Set time (s) after boot system shutdown. This
3021 is useful for hands-off automated testing.
3023 rcutorture.stall_cpu= [KNL]
3024 Duration of CPU stall (s) to test RCU CPU stall
3025 warnings, zero to disable.
3027 rcutorture.stall_cpu_holdoff= [KNL]
3028 Time to wait (s) after boot before inducing stall.
3030 rcutorture.stat_interval= [KNL]
3031 Time (s) between statistics printk()s.
3033 rcutorture.stutter= [KNL]
3034 Time (s) to stutter testing, for example, specifying
3035 five seconds causes the test to run for five seconds,
3036 wait for five seconds, and so on. This tests RCU's
3037 ability to transition abruptly to and from idle.
3039 rcutorture.test_boost= [KNL]
3040 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3041 "Maybe" means test if the RCU implementation
3042 under test support RCU priority boosting.
3044 rcutorture.test_boost_duration= [KNL]
3045 Duration (s) of each individual boost test.
3047 rcutorture.test_boost_interval= [KNL]
3048 Interval (s) between each boost test.
3050 rcutorture.test_no_idle_hz= [KNL]
3051 Test RCU's dyntick-idle handling. See also the
3052 rcutorture.shuffle_interval parameter.
3054 rcutorture.torture_type= [KNL]
3055 Specify the RCU implementation to test.
3057 rcutorture.verbose= [KNL]
3058 Enable additional printk() statements.
3060 rcupdate.rcu_expedited= [KNL]
3061 Use expedited grace-period primitives, for
3062 example, synchronize_rcu_expedited() instead
3063 of synchronize_rcu(). This reduces latency,
3064 but can increase CPU utilization, degrade
3065 real-time latency, and degrade energy efficiency.
3067 rcupdate.rcu_cpu_stall_suppress= [KNL]
3068 Suppress RCU CPU stall warning messages.
3070 rcupdate.rcu_cpu_stall_timeout= [KNL]
3071 Set timeout for RCU CPU stall warning messages.
3073 rcupdate.rcu_task_stall_timeout= [KNL]
3074 Set timeout in jiffies for RCU task stall warning
3075 messages. Disable with a value less than or equal
3080 Run specified binary instead of /init from the ramdisk,
3081 used for early userspace startup. See initrd.
3084 Format (x86 or x86_64):
3085 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3087 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3089 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3090 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3091 reboot_force is either force or not specified,
3092 reboot_cpu is s[mp]#### with #### being the processor
3093 to be used for rebooting.
3096 [KNL, SMP] Set scheduler's default relax_domain_level.
3097 See Documentation/cgroups/cpusets.txt.
3099 relative_sleep_states=
3100 [SUSPEND] Use sleep state labeling where the deepest
3101 state available other than hibernation is always "mem".
3102 Format: { "0" | "1" }
3103 0 -- Traditional sleep state labels.
3104 1 -- Relative sleep state labels.
3106 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3108 reservetop= [X86-32]
3110 Reserves a hole at the top of the kernel virtual
3115 Set the amount of memory to reserve for BIOS at
3116 the bottom of the address space.
3118 reset_devices [KNL] Force drivers to reset the underlying device
3119 during initialization.
3122 Specify the partition device for software suspend
3124 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3126 resume_offset= [SWSUSP]
3127 Specify the offset from the beginning of the partition
3128 given by "resume=" at which the swap header is located,
3129 in <PAGE_SIZE> units (needed only for swap files).
3130 See Documentation/power/swsusp-and-swap-files.txt
3132 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3133 read the resume files
3135 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3136 Useful for devices that are detected asynchronously
3137 (e.g. USB and MMC devices).
3139 hibernate= [HIBERNATION]
3140 noresume Don't check if there's a hibernation image
3141 present during boot.
3142 nocompress Don't compress/decompress hibernation images.
3143 no Disable hibernation and resume.
3145 retain_initrd [RAM] Keep initrd memory after extraction
3147 rhash_entries= [KNL,NET]
3148 Set number of hash buckets for route cache
3150 ro [KNL] Mount root device read-only on boot
3152 root= [KNL] Root filesystem
3153 See name_to_dev_t comment in init/do_mounts.c.
3155 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3156 mount the root filesystem
3158 rootflags= [KNL] Set root filesystem mount option string
3160 rootfstype= [KNL] Set root filesystem type
3162 rootwait [KNL] Wait (indefinitely) for root device to show up.
3163 Useful for devices that are detected asynchronously
3164 (e.g. USB and MMC devices).
3166 rproc_mem=nn[KMG][@address]
3167 [KNL,ARM,CMA] Remoteproc physical memory block.
3168 Memory area to be used by remote processor image,
3171 rw [KNL] Mount root device read-write on boot
3173 S [KNL] Run init in single mode
3175 s390_iommu= [HW,S390]
3176 Set s390 IOTLB flushing mode
3178 With strict flushing every unmap operation will result in
3179 an IOTLB flush. Default is lazy flushing before reuse,
3183 See drivers/net/irda/sa1100_ir.c.
3185 sbni= [NET] Granch SBNI12 leased line adapter
3187 sched_debug [KNL] Enables verbose scheduler debug messages.
3189 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3190 xtime_lock contention on larger systems, and/or RCU lock
3191 contention on all systems with CONFIG_MAXSMP set.
3192 Format: { "0" | "1" }
3193 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3195 Note: increases power consumption, thus should only be
3196 enabled if running jitter sensitive (HPC/RT) workloads.
3198 security= [SECURITY] Choose a security module to enable at boot.
3199 If this boot parameter is not specified, only the first
3200 security module asking for security registration will be
3201 loaded. An invalid security module name will be treated
3202 as if no module has been chosen.
3204 selinux= [SELINUX] Disable or enable SELinux at boot time.
3205 Format: { "0" | "1" }
3206 See security/selinux/Kconfig help text.
3209 Default value is set via kernel config option.
3210 If enabled at boot time, /selinux/disable can be used
3211 later to disable prior to initial policy load.
3213 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3214 Format: { "0" | "1" }
3215 See security/apparmor/Kconfig help text
3218 Default value is set via kernel config option.
3220 serialnumber [BUGS=X86-32]
3223 Maximal number of shapers.
3225 show_msr= [x86] show boot-time MSR settings
3226 Format: { <integer> }
3227 Show boot-time (BIOS-initialized) MSR settings.
3228 The parameter means the number of CPUs to show,
3229 for example 1 means boot CPU only.
3237 Disable merging of slabs with similar size. May be
3238 necessary if there is some reason to distinguish
3239 allocs to different slabs. Debug options disable
3240 merging on their own.
3241 For more information see Documentation/vm/slub.txt.
3243 slab_max_order= [MM, SLAB]
3244 Determines the maximum allowed order for slabs.
3245 A high setting may cause OOMs due to memory
3246 fragmentation. Defaults to 1 for systems with
3247 more than 32MB of RAM, 0 otherwise.
3249 slub_debug[=options[,slabs]] [MM, SLUB]
3250 Enabling slub_debug allows one to determine the
3251 culprit if slab objects become corrupted. Enabling
3252 slub_debug can create guard zones around objects and
3253 may poison objects when not in use. Also tracks the
3254 last alloc / free. For more information see
3255 Documentation/vm/slub.txt.
3257 slub_max_order= [MM, SLUB]
3258 Determines the maximum allowed order for slabs.
3259 A high setting may cause OOMs due to memory
3260 fragmentation. For more information see
3261 Documentation/vm/slub.txt.
3263 slub_min_objects= [MM, SLUB]
3264 The minimum number of objects per slab. SLUB will
3265 increase the slab order up to slub_max_order to
3266 generate a sufficiently large slab able to contain
3267 the number of objects indicated. The higher the number
3268 of objects the smaller the overhead of tracking slabs
3269 and the less frequently locks need to be acquired.
3270 For more information see Documentation/vm/slub.txt.
3272 slub_min_order= [MM, SLUB]
3273 Determines the minimum page order for slabs. Must be
3274 lower than slub_max_order.
3275 For more information see Documentation/vm/slub.txt.
3277 slub_nomerge [MM, SLUB]
3278 Same with slab_nomerge. This is supported for legacy.
3279 See slab_nomerge for more information.
3282 Format: <io1>[,<io2>[,...,<io8>]]
3284 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3285 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3286 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3287 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3288 smsc-ircc2.ircc_irq= [HW] IRQ line
3289 smsc-ircc2.ircc_dma= [HW] DMA channel
3290 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3291 0: Toshiba Satellite 1800 (GP data pin select)
3292 1: Fast pin select (default)
3296 [KNL] Should the soft-lockup detector generate panics.
3299 softlockup_all_cpu_backtrace=
3300 [KNL] Should the soft-lockup detector generate
3301 backtraces on all cpus.
3304 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3305 See Documentation/laptops/sonypi.txt
3307 spia_io_base= [HW,MTD]
3313 Enabled the stack tracer on boot up.
3315 stacktrace_filter=[function-list]
3316 [FTRACE] Limit the functions that the stack tracer
3317 will trace at boot up. function-list is a comma separated
3318 list of functions. This list can be changed at run
3319 time by the stack_trace_filter file in the debugfs
3320 tracing directory. Note, this enables stack tracing
3321 and the stacktrace above is not needed.
3325 Set the STI (builtin display/keyboard on the HP-PARISC
3326 machines) console (graphic card) which should be used
3327 as the initial boot-console.
3328 See also comment in drivers/video/console/sticore.c.
3331 See comment in drivers/video/console/sticore.c.
3334 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3336 sunrpc.min_resvport=
3337 sunrpc.max_resvport=
3339 SunRPC servers often require that client requests
3340 originate from a privileged port (i.e. a port in the
3341 range 0 < portnr < 1024).
3342 An administrator who wishes to reserve some of these
3343 ports for other uses may adjust the range that the
3344 kernel's sunrpc client considers to be privileged
3345 using these two parameters to set the minimum and
3346 maximum port values.
3350 Control how the NFS server code allocates CPUs to
3351 service thread pools. Depending on how many NICs
3352 you have and where their interrupts are bound, this
3353 option will affect which CPUs will do NFS serving.
3354 Note: this parameter cannot be changed while the
3355 NFS server is running.
3357 auto the server chooses an appropriate mode
3358 automatically using heuristics
3359 global a single global pool contains all CPUs
3360 percpu one pool for each CPU
3361 pernode one pool for each NUMA node (equivalent
3362 to global on non-NUMA machines)
3364 sunrpc.tcp_slot_table_entries=
3365 sunrpc.udp_slot_table_entries=
3367 Sets the upper limit on the number of simultaneous
3368 RPC calls that can be sent from the client to a
3369 server. Increasing these values may allow you to
3370 improve throughput, but will also increase the
3371 amount of memory reserved for use by the client.
3374 [KNL] Enable accounting of swap in memory resource
3375 controller if no parameter or 1 is given or disable
3376 it if 0 is given (See Documentation/cgroups/memory.txt)
3378 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3379 Format: { <int> | force }
3380 <int> -- Number of I/O TLB slabs
3381 force -- force using of bounce buffers even if they
3382 wouldn't be automatically used by the kernel
3386 sysfs.deprecated=0|1 [KNL]
3387 Enable/disable old style sysfs layout for old udev
3388 on older distributions. When this option is enabled
3389 very new udev will not work anymore. When this option
3390 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3391 in older udev will not work anymore.
3392 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3393 the kernel configuration.
3395 sysrq_always_enabled
3397 Ignore sysrq setting - this boot parameter will
3398 neutralize any effect of /proc/sys/kernel/sysrq.
3399 Useful for debugging.
3403 test_suspend= [SUSPEND][,N]
3404 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3405 standby suspend) or "freeze" (for suspend type freeze)
3406 as the system sleep state during system startup with
3407 the optional capability to repeat N number of times.
3408 The system is woken from this state using a
3409 wakeup-capable RTC alarm.
3411 thash_entries= [KNL,NET]
3412 Set number of hash buckets for TCP connection
3414 thermal.act= [HW,ACPI]
3415 -1: disable all active trip points in all thermal zones
3416 <degrees C>: override all lowest active trip points
3418 thermal.crt= [HW,ACPI]
3419 -1: disable all critical trip points in all thermal zones
3420 <degrees C>: override all critical trip points
3422 thermal.nocrt= [HW,ACPI]
3423 Set to disable actions on ACPI thermal zone
3424 critical and hot trip points.
3426 thermal.off= [HW,ACPI]
3427 1: disable ACPI thermal control
3429 thermal.psv= [HW,ACPI]
3430 -1: disable all passive trip points
3431 <degrees C>: override all passive trip points to this
3434 thermal.tzp= [HW,ACPI]
3435 Specify global default ACPI thermal zone polling rate
3436 <deci-seconds>: poll all this frequency
3437 0: no polling (default)
3440 Force threading of all interrupt handlers except those
3441 marked explicitly IRQF_NO_THREAD.
3444 Enable the Transcendent memory driver if built-in.
3446 tmem.cleancache=0|1 [KNL, XEN]
3447 Default is on (1). Disable the usage of the cleancache
3448 API to send anonymous pages to the hypervisor.
3450 tmem.frontswap=0|1 [KNL, XEN]
3451 Default is on (1). Disable the usage of the frontswap
3452 API to send swap pages to the hypervisor. If disabled
3453 the selfballooning and selfshrinking are force disabled.
3455 tmem.selfballooning=0|1 [KNL, XEN]
3456 Default is on (1). Disable the driving of swap pages
3459 tmem.selfshrinking=0|1 [KNL, XEN]
3460 Default is on (1). Partial swapoff that immediately
3461 transfers pages from Xen hypervisor back to the
3462 kernel based on different criteria.
3466 Specify if the kernel should make use of the cpu
3467 topology information if the hardware supports this.
3468 The scheduler will make use of this information and
3469 e.g. base its process migration decisions on it.
3472 topology_updates= [KNL, PPC, NUMA]
3474 Specify if the kernel should ignore (off)
3475 topology updates sent by the hypervisor to this
3480 tpm_suspend_pcr=[HW,TPM]
3481 Format: integer pcr id
3482 Specify that at suspend time, the tpm driver
3483 should extend the specified pcr with zeros,
3484 as a workaround for some chips which fail to
3485 flush the last written pcr on TPM_SaveState.
3486 This will guarantee that all the other pcrs
3489 trace_buf_size=nn[KMG]
3490 [FTRACE] will set tracing buffer size.
3492 trace_event=[event-list]
3493 [FTRACE] Set and start specified trace events in order
3494 to facilitate early boot debugging.
3495 See also Documentation/trace/events.txt
3497 trace_options=[option-list]
3498 [FTRACE] Enable or disable tracer options at boot.
3499 The option-list is a comma delimited list of options
3500 that can be enabled or disabled just as if you were
3501 to echo the option name into
3503 /sys/kernel/debug/tracing/trace_options
3505 For example, to enable stacktrace option (to dump the
3506 stack trace of each event), add to the command line:
3508 trace_options=stacktrace
3510 See also Documentation/trace/ftrace.txt "trace options"
3514 [FTRACE] enable this option to disable tracing when a
3515 warning is hit. This turns off "tracing_on". Tracing can
3516 be enabled again by echoing '1' into the "tracing_on"
3517 file located in /sys/kernel/debug/tracing/
3519 This option is useful, as it disables the trace before
3520 the WARNING dump is called, which prevents the trace to
3521 be filled with content caused by the warning output.
3523 This option can also be set at run time via the sysctl
3524 option: kernel/traceoff_on_warning
3526 transparent_hugepage=
3528 Format: [always|madvise|never]
3529 Can be used to control the default behavior of the system
3530 with respect to transparent hugepages.
3531 See Documentation/vm/transhuge.txt for more details.
3533 tsc= Disable clocksource stability checks for TSC.
3535 [x86] reliable: mark tsc clocksource as reliable, this
3536 disables clocksource verification at runtime, as well
3537 as the stability checks done at bootup. Used to enable
3538 high-resolution timer mode on older hardware, and in
3539 virtualized environment.
3540 [x86] noirqtime: Do not use TSC to do irq accounting.
3541 Used to run time disable IRQ_TIME_ACCOUNTING on any
3542 platforms where RDTSC is slow and this accounting
3545 turbografx.map[2|3]= [HW,JOY]
3546 TurboGraFX parallel port interface
3548 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3549 See also Documentation/input/joystick-parport.txt
3551 udbg-immortal [PPC] When debugging early kernel crashes that
3552 happen after console_init() and before a proper
3553 console driver takes over, this boot options might
3554 help "seeing" what's going on.
3556 uhash_entries= [KNL,NET]
3557 Set number of hash buckets for UDP/UDP-Lite connections
3560 [USB] Ignore overcurrent events (default N).
3561 Some badly-designed motherboards generate lots of
3562 bogus events, for ports that aren't wired to
3563 anything. Set this parameter to avoid log spamming.
3564 Note that genuine overcurrent events won't be
3568 [X86] Cause panic on unknown NMI.
3570 usbcore.authorized_default=
3571 [USB] Default USB device authorization:
3572 (default -1 = authorized except for wireless USB,
3573 0 = not authorized, 1 = authorized)
3575 usbcore.autosuspend=
3576 [USB] The autosuspend time delay (in seconds) used
3577 for newly-detected USB devices (default 2). This
3578 is the time required before an idle device will be
3579 autosuspended. Devices for which the delay is set
3580 to a negative value won't be autosuspended at all.
3582 usbcore.usbfs_snoop=
3583 [USB] Set to log all usbfs traffic (default 0 = off).
3585 usbcore.blinkenlights=
3586 [USB] Set to cycle leds on hubs (default 0 = off).
3588 usbcore.old_scheme_first=
3589 [USB] Start with the old device initialization
3590 scheme (default 0 = off).
3592 usbcore.usbfs_memory_mb=
3593 [USB] Memory limit (in MB) for buffers allocated by
3594 usbfs (default = 16, 0 = max = 2047).
3596 usbcore.use_both_schemes=
3597 [USB] Try the other device initialization scheme
3598 if the first one fails (default 1 = enabled).
3600 usbcore.initial_descriptor_timeout=
3601 [USB] Specifies timeout for the initial 64-byte
3602 USB_REQ_GET_DESCRIPTOR request in milliseconds
3603 (default 5000 = 5.0 seconds).
3606 [USBHID] The interval which mice are to be polled at.
3608 usb-storage.delay_use=
3609 [UMS] The delay in seconds before a new device is
3610 scanned for Logical Units (default 5).
3613 [UMS] A list of quirks entries to supplement or
3614 override the built-in unusual_devs list. List
3615 entries are separated by commas. Each entry has
3616 the form VID:PID:Flags where VID and PID are Vendor
3617 and Product ID values (4-digit hex numbers) and
3618 Flags is a set of characters, each corresponding
3619 to a common usb-storage quirk flag as follows:
3620 a = SANE_SENSE (collect more than 18 bytes
3622 b = BAD_SENSE (don't collect more than 18
3623 bytes of sense data);
3624 c = FIX_CAPACITY (decrease the reported
3625 device capacity by one sector);
3626 d = NO_READ_DISC_INFO (don't use
3627 READ_DISC_INFO command);
3628 e = NO_READ_CAPACITY_16 (don't use
3629 READ_CAPACITY_16 command);
3630 f = NO_REPORT_OPCODES (don't use report opcodes
3632 h = CAPACITY_HEURISTICS (decrease the
3633 reported device capacity by one
3634 sector if the number is odd);
3635 i = IGNORE_DEVICE (don't bind to this
3637 l = NOT_LOCKABLE (don't try to lock and
3638 unlock ejectable media);
3639 m = MAX_SECTORS_64 (don't transfer more
3640 than 64 sectors = 32 KB at a time);
3641 n = INITIAL_READ10 (force a retry of the
3642 initial READ(10) command);
3643 o = CAPACITY_OK (accept the capacity
3644 reported by the device);
3645 p = WRITE_CACHE (the device cache is ON
3647 r = IGNORE_RESIDUE (the device reports
3648 bogus residue values);
3649 s = SINGLE_LUN (the device has only one
3651 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3652 commands, uas only);
3653 u = IGNORE_UAS (don't bind to the uas driver);
3654 w = NO_WP_DETECT (don't test whether the
3655 medium is write-protected).
3656 Example: quirks=0419:aaf5:rl,0421:0433:rc
3658 user_debug= [KNL,ARM]
3660 See arch/arm/Kconfig.debug help text.
3661 1 - undefined instruction events
3663 4 - invalid data aborts
3666 Example: user_debug=31
3669 [X86] Flags controlling user PTE allocations.
3671 nohigh = do not allocate PTE pages in
3672 HIGHMEM regardless of setting
3676 On X86_32, this is an alias for vdso32=. Otherwise:
3678 vdso=1: enable VDSO (the default)
3679 vdso=0: disable VDSO mapping
3681 vdso32= [X86] Control the 32-bit vDSO
3682 vdso32=1: enable 32-bit VDSO
3683 vdso32=0 or vdso32=2: disable 32-bit VDSO
3685 See the help text for CONFIG_COMPAT_VDSO for more
3686 details. If CONFIG_COMPAT_VDSO is set, the default is
3687 vdso32=0; otherwise, the default is vdso32=1.
3689 For compatibility with older kernels, vdso32=2 is an
3692 Try vdso32=0 if you encounter an error that says:
3693 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3696 vector=percpu: enable percpu vector domain
3698 video= [FB] Frame buffer configuration
3699 See Documentation/fb/modedb.txt.
3701 video.brightness_switch_enabled= [0,1]
3702 If set to 1, on receiving an ACPI notify event
3703 generated by hotkey, video driver will adjust brightness
3704 level and then send out the event to user space through
3705 the allocated input device; If set to 0, video driver
3706 will only send out the event without touching backlight
3711 [VMMIO] Memory mapped virtio (platform) device.
3713 <size>@<baseaddr>:<irq>[:<id>]
3715 <size> := size (can use standard suffixes
3717 <baseaddr> := physical base address
3718 <irq> := interrupt number (as passed to
3720 <id> := (optional) platform device id
3722 virtio_mmio.device=1K@0x100b0000:48:7
3724 Can be used multiple times for multiple devices.
3726 vga= [BOOT,X86-32] Select a particular video mode
3727 See Documentation/x86/boot.txt and
3728 Documentation/svga.txt.
3729 Use vga=ask for menu.
3730 This is actually a boot loader parameter; the value is
3731 passed to the kernel using a special protocol.
3733 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3734 size of <nn>. This can be used to increase the
3735 minimum size (128MB on x86). It can also be used to
3736 decrease the size and leave more room for directly
3739 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3742 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3745 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3749 Controls the behavior of vsyscalls (i.e. calls to
3750 fixed addresses of 0xffffffffff600x00 from legacy
3751 code). Most statically-linked binaries and older
3752 versions of glibc use these calls. Because these
3753 functions are at fixed addresses, they make nice
3754 targets for exploits that can control RIP.
3756 emulate [default] Vsyscalls turn into traps and are
3757 emulated reasonably safely.
3759 native Vsyscalls are native syscall instructions.
3760 This is a little bit faster than trapping
3761 and makes a few dynamic recompilers work
3762 better than they would in emulation mode.
3763 It also makes exploits much easier to write.
3765 none Vsyscalls don't work at all. This makes
3766 them quite hard to use for exploits but
3767 might break your system.
3769 vt.color= [VT] Default text color.
3770 Format: 0xYX, X = foreground, Y = background.
3771 Default: 0x07 = light gray on black.
3773 vt.cur_default= [VT] Default cursor shape.
3774 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3775 the parameters of the <Esc>[?A;B;Cc escape sequence;
3776 see VGA-softcursor.txt. Default: 2 = underline.
3778 vt.default_blu= [VT]
3779 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3780 Change the default blue palette of the console.
3781 This is a 16-member array composed of values
3784 vt.default_grn= [VT]
3785 Format: <green0>,<green1>,<green2>,...,<green15>
3786 Change the default green palette of the console.
3787 This is a 16-member array composed of values
3790 vt.default_red= [VT]
3791 Format: <red0>,<red1>,<red2>,...,<red15>
3792 Change the default red palette of the console.
3793 This is a 16-member array composed of values
3799 Set system-wide default UTF-8 mode for all tty's.
3800 Default is 1, i.e. UTF-8 mode is enabled for all
3801 newly opened terminals.
3803 vt.global_cursor_default=
3806 Set system-wide default for whether a cursor
3807 is shown on new VTs. Default is -1,
3808 i.e. cursors will be created by default unless
3809 overridden by individual drivers. 0 will hide
3810 cursors, 1 will display them.
3812 vt.italic= [VT] Default color for italic text; 0-15.
3815 vt.underline= [VT] Default color for underlined text; 0-15.
3818 watchdog timers [HW,WDT] For information on watchdog timers,
3819 see Documentation/watchdog/watchdog-parameters.txt
3820 or other driver-specific files in the
3821 Documentation/watchdog/ directory.
3823 workqueue.disable_numa
3824 By default, all work items queued to unbound
3825 workqueues are affine to the NUMA nodes they're
3826 issued on, which results in better behavior in
3827 general. If NUMA affinity needs to be disabled for
3828 whatever reason, this option can be used. Note
3829 that this also can be controlled per-workqueue for
3830 workqueues visible under /sys/bus/workqueue/.
3832 workqueue.power_efficient
3833 Per-cpu workqueues are generally preferred because
3834 they show better performance thanks to cache
3835 locality; unfortunately, per-cpu workqueues tend to
3836 be more power hungry than unbound workqueues.
3838 Enabling this makes the per-cpu workqueues which
3839 were observed to contribute significantly to power
3840 consumption unbound, leading to measurably lower
3841 power usage at the cost of small performance
3844 The default value of this parameter is determined by
3845 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3847 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3848 default x2apic cluster mode on platforms
3851 x86_intel_mid_timer= [X86-32,APBT]
3852 Choose timer option for x86 Intel MID platform.
3853 Two valid options are apbt timer only and lapic timer
3854 plus one apbt timer for broadcast timer.
3855 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3857 xen_emul_unplug= [HW,X86,XEN]
3858 Unplug Xen emulated devices
3859 Format: [unplug0,][unplug1]
3860 ide-disks -- unplug primary master IDE devices
3861 aux-ide-disks -- unplug non-primary-master IDE devices
3862 nics -- unplug network devices
3863 all -- unplug all emulated devices (NICs and IDE disks)
3864 unnecessary -- unplugging emulated devices is
3865 unnecessary even if the host did not respond to
3867 never -- do not unplug even if version check succeeds
3869 xen_nopvspin [X86,XEN]
3870 Disables the ticketlock slowpath using Xen PV
3874 Disables the PV optimizations forcing the HVM guest to
3875 run as generic HVM guest with no PV drivers.
3877 xirc2ps_cs= [NET,PCMCIA]
3879 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3881 ______________________________________________________________________
3885 Add more DRM drivers.
git.samba.org / sfrench / cifs-2.6.git / blob