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.
168 acpi= [HW,ACPI,X86,ARM64]
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
178 For ARM64, ONLY "acpi=off" or "acpi=force" are available
180 See also Documentation/power/runtime_pm.txt, pci=noacpi
182 acpi_rsdp= [ACPI,EFI,KEXEC]
183 Pass the RSDP address to the kernel, mostly used
184 on machines running EFI runtime service to boot the
185 second kernel for kdump.
187 acpi_apic_instance= [ACPI, IOAPIC]
189 2: use 2nd APIC table, if available
190 1,0: use 1st APIC table
193 acpi_backlight= [HW,ACPI]
194 acpi_backlight=vendor
196 If set to vendor, prefer vendor specific driver
197 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
198 of the ACPI video.ko driver.
200 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
201 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
203 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
204 debug output. Bits in debug_layer correspond to a
205 _COMPONENT in an ACPI source file, e.g.,
206 #define _COMPONENT ACPI_PCI_COMPONENT
207 Bits in debug_level correspond to a level in
208 ACPI_DEBUG_PRINT statements, e.g.,
209 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
210 The debug_level mask defaults to "info". See
211 Documentation/acpi/debug.txt for more information about
212 debug layers and levels.
214 Enable processor driver info messages:
215 acpi.debug_layer=0x20000000
216 Enable PCI/PCI interrupt routing info messages:
217 acpi.debug_layer=0x400000
218 Enable AML "Debug" output, i.e., stores to the Debug
219 object while interpreting AML:
220 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
221 Enable all messages related to ACPI hardware:
222 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
224 Some values produce so much output that the system is
225 unusable. The "log_buf_len" parameter may be useful
226 if you need to capture more output.
228 acpi_force_table_verification [HW,ACPI]
229 Enable table checksum verification during early stage.
230 By default, this is disabled due to x86 early mapping
233 acpi_irq_balance [HW,ACPI]
234 ACPI will balance active IRQs
237 acpi_irq_nobalance [HW,ACPI]
238 ACPI will not move active IRQs (default)
241 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
242 Format: <irq>,<irq>...
244 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
246 Format: <irq>,<irq>...
248 acpi_no_auto_serialize [HW,ACPI]
249 Disable auto-serialization of AML methods
250 AML control methods that contain the opcodes to create
251 named objects will be marked as "Serialized" by the
252 auto-serialization feature.
253 This feature is enabled by default.
254 This option allows to turn off the feature.
256 acpi_no_static_ssdt [HW,ACPI]
257 Disable installation of static SSDTs at early boot time
258 By default, SSDTs contained in the RSDT/XSDT will be
259 installed automatically and they will appear under
260 /sys/firmware/acpi/tables.
261 This option turns off this feature.
262 Note that specifying this option does not affect
263 dynamic table installation which will install SSDT
264 tables to /sys/firmware/acpi/tables/dynamic.
266 acpica_no_return_repair [HW, ACPI]
267 Disable AML predefined validation mechanism
268 This mechanism can repair the evaluation result to make
269 the return objects more ACPI specification compliant.
270 This option is useful for developers to identify the
271 root cause of an AML interpreter issue when the issue
272 has something to do with the repair mechanism.
274 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
275 Format: To spoof as Windows 98: ="Microsoft Windows"
277 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
278 acpi_osi="string1" # add string1
279 acpi_osi="!string2" # remove string2
280 acpi_osi=!* # remove all strings
281 acpi_osi=! # disable all built-in OS vendor
283 acpi_osi= # disable all strings
285 'acpi_osi=!' can be used in combination with single or
286 multiple 'acpi_osi="string1"' to support specific OS
287 vendor string(s). Note that such command can only
288 affect the default state of the OS vendor strings, thus
289 it cannot affect the default state of the feature group
290 strings and the current state of the OS vendor strings,
291 specifying it multiple times through kernel command line
292 is meaningless. This command is useful when one do not
293 care about the state of the feature group strings which
294 should be controlled by the OSPM.
296 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
297 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
298 can make '_OSI("Windows 2000")' TRUE.
300 'acpi_osi=' cannot be used in combination with other
301 'acpi_osi=' command lines, the _OSI method will not
302 exist in the ACPI namespace. NOTE that such command can
303 only affect the _OSI support state, thus specifying it
304 multiple times through kernel command line is also
307 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
310 'acpi_osi=!*' can be used in combination with single or
311 multiple 'acpi_osi="string1"' to support specific
312 string(s). Note that such command can affect the
313 current state of both the OS vendor strings and the
314 feature group strings, thus specifying it multiple times
315 through kernel command line is meaningful. But it may
316 still not able to affect the final state of a string if
317 there are quirks related to this string. This command
318 is useful when one want to control the state of the
319 feature group strings to debug BIOS issues related to
322 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
323 '_OSI("Module Device")' FALSE.
324 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
325 '_OSI("Module Device")' TRUE.
326 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
328 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
330 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
331 they all will make '_OSI("Windows 2000")' TRUE.
334 Override the pmtimer bug detection: force the kernel
335 to assume that this machine's pmtimer latches its value
336 and always returns good values.
338 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
339 Format: { level | edge | high | low }
341 acpi_skip_timer_override [HW,ACPI]
342 Recognize and ignore IRQ0/pin2 Interrupt Override.
343 For broken nForce2 BIOS resulting in XT-PIC timer.
345 acpi_sleep= [HW,ACPI] Sleep options
346 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
347 old_ordering, nonvs, sci_force_enable }
348 See Documentation/power/video.txt for information on
350 s3_beep is for debugging; it makes the PC's speaker beep
351 as soon as the kernel's real-mode entry point is called.
352 s4_nohwsig prevents ACPI hardware signature from being
353 used during resume from hibernation.
354 old_ordering causes the ACPI 1.0 ordering of the _PTS
355 control method, with respect to putting devices into
356 low power states, to be enforced (the ACPI 2.0 ordering
357 of _PTS is used by default).
358 nonvs prevents the kernel from saving/restoring the
359 ACPI NVS memory during suspend/hibernation and resume.
360 sci_force_enable causes the kernel to set SCI_EN directly
361 on resume from S1/S3 (which is against the ACPI spec,
362 but some broken systems don't work without it).
364 acpi_use_timer_override [HW,ACPI]
365 Use timer override. For some broken Nvidia NF5 boards
366 that require a timer override, but don't have HPET
368 acpi_enforce_resources= [ACPI]
369 { strict | lax | no }
370 Check for resource conflicts between native drivers
371 and ACPI OperationRegions (SystemIO and SystemMemory
372 only). IO ports and memory declared in ACPI might be
373 used by the ACPI subsystem in arbitrary AML code and
374 can interfere with legacy drivers.
375 strict (default): access to resources claimed by ACPI
376 is denied; legacy drivers trying to access reserved
377 resources will fail to bind to device using them.
378 lax: access to resources claimed by ACPI is allowed;
379 legacy drivers trying to access reserved resources
380 will bind successfully but a warning message is logged.
381 no: ACPI OperationRegions are not marked as reserved,
382 no further checks are performed.
384 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
387 add_efi_memmap [EFI; X86] Include EFI memory map in
388 kernel's map of available physical RAM.
391 { off | try_unsupported }
392 off: disable AGP support
393 try_unsupported: try to drive unsupported chipsets
394 (may crash computer or cause data corruption)
397 See Documentation/sound/alsa/alsa-parameters.txt
400 Allow the default userspace alignment fault handler
401 behaviour to be specified. Bit 0 enables warnings,
402 bit 1 enables fixups, and bit 2 sends a segfault.
404 align_va_addr= [X86-64]
405 Align virtual addresses by clearing slice [14:12] when
406 allocating a VMA at process creation time. This option
407 gives you up to 3% performance improvement on AMD F15h
408 machines (where it is enabled by default) for a
409 CPU-intensive style benchmark, and it can vary highly in
410 a microbenchmark depending on workload and compiler.
412 32: only for 32-bit processes
413 64: only for 64-bit processes
414 on: enable for both 32- and 64-bit processes
415 off: disable for both 32- and 64-bit processes
417 alloc_snapshot [FTRACE]
418 Allocate the ftrace snapshot buffer on boot up when the
419 main buffer is allocated. This is handy if debugging
420 and you need to use tracing_snapshot() on boot up, and
421 do not want to use tracing_snapshot_alloc() as it needs
422 to be done where GFP_KERNEL allocations are allowed.
424 amd_iommu= [HW,X86-64]
425 Pass parameters to the AMD IOMMU driver in the system.
427 fullflush - enable flushing of IO/TLB entries when
428 they are unmapped. Otherwise they are
429 flushed before they will be reused, which
431 off - do not initialize any AMD IOMMU found in
433 force_isolation - Force device isolation for all
434 devices. The IOMMU driver is not
435 allowed anymore to lift isolation
436 requirements as needed. This option
437 does not override iommu=pt
439 amd_iommu_dump= [HW,X86-64]
440 Enable AMD IOMMU driver option to dump the ACPI table
441 for AMD IOMMU. With this option enabled, AMD IOMMU
442 driver will print ACPI tables for AMD IOMMU during
443 IOMMU initialization.
445 amijoy.map= [HW,JOY] Amiga joystick support
446 Map of devices attached to JOY0DAT and JOY1DAT
448 See also Documentation/input/joystick.txt
450 analog.map= [HW,JOY] Analog joystick and gamepad support
451 Specifies type or capabilities of an analog joystick
452 connected to one of 16 gameports
453 Format: <type1>,<type2>,..<type16>
456 Power management functions (SPARCstation-4/5 + deriv.)
458 Disable APC CPU standby support. SPARCstation-Fox does
459 not play well with APC CPU idle - disable it if you have
460 APC and your system crashes randomly.
462 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
463 Change the output verbosity whilst booting
464 Format: { quiet (default) | verbose | debug }
465 Change the amount of debugging information output
466 when initialising the APIC and IO-APIC components.
469 See Documentation/networking/ipv6.txt.
471 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
472 Limit apic dumping. The parameter defines the maximal
473 number of local apics being dumped. Also it is possible
474 to set it to "all" by meaning -- no limit here.
475 Format: { 1 (default) | 2 | ... | all }.
476 The parameter valid if only apic=debug or
477 apic=verbose is specified.
478 Example: apic=debug show_lapic=all
480 apm= [APM] Advanced Power Management
481 See header of arch/x86/kernel/apm_32.c.
483 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
484 Format: <io>,<irq>,<nodeID>
488 atarimouse= [HW,MOUSE] Atari Mouse
490 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
491 EzKey and similar keyboards
493 atkbd.reset= [HW] Reset keyboard during initialization
495 atkbd.set= [HW] Select keyboard code set
496 Format: <int> (2 = AT (default), 3 = PS/2)
498 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
501 atkbd.softraw= [HW] Choose between synthetic and real raw mode
502 Format: <bool> (0 = real, 1 = synthetic (default))
504 atkbd.softrepeat= [HW]
505 Use software keyboard repeat
507 audit= [KNL] Enable the audit sub-system
508 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
509 0 - kernel audit is disabled and can not be enabled
510 until the next reboot
511 unset - kernel audit is initialized but disabled and
512 will be fully enabled by the userspace auditd.
513 1 - kernel audit is initialized and partially enabled,
514 storing at most audit_backlog_limit messages in
515 RAM until it is fully enabled by the userspace
519 audit_backlog_limit= [KNL] Set the audit queue size limit.
520 Format: <int> (must be >=0)
523 baycom_epp= [HW,AX25]
526 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
528 See header of drivers/net/hamradio/baycom_par.c.
530 baycom_ser_fdx= [HW,AX25]
531 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
532 Format: <io>,<irq>,<mode>[,<baud>]
533 See header of drivers/net/hamradio/baycom_ser_fdx.c.
535 baycom_ser_hdx= [HW,AX25]
536 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
537 Format: <io>,<irq>,<mode>
538 See header of drivers/net/hamradio/baycom_ser_hdx.c.
540 blkdevparts= Manual partition parsing of block device(s) for
541 embedded devices based on command line input.
542 See Documentation/block/cmdline-partition.txt
544 boot_delay= Milliseconds to delay each printk during boot.
545 Values larger than 10 seconds (10000) are changed to
549 bootmem_debug [KNL] Enable bootmem allocator debug messages.
551 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
552 bttv.radio= Most important insmod options are available as
554 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
557 bulk_remove=off [PPC] This parameter disables the use of the pSeries
558 firmware feature for flushing multiple hpte entries
561 c101= [NET] Moxa C101 synchronous serial card
563 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
564 Sometimes CPU hardware bugs make them report the cache
565 size incorrectly. The kernel will attempt work arounds
566 to fix known problems, but for some CPUs it is not
567 possible to determine what the correct size should be.
568 This option provides an override for these situations.
570 ca_keys= [KEYS] This parameter identifies a specific key(s) on
571 the system trusted keyring to be used for certificate
573 format: { id:<keyid> | builtin }
575 cca= [MIPS] Override the kernel pages' cache coherency
576 algorithm. Accepted values range from 0 to 7
577 inclusive. See arch/mips/include/asm/pgtable-bits.h
578 for platform specific values (SB1, Loongson3 and
581 ccw_timeout_log [S390]
582 See Documentation/s390/CommonIO for details.
584 cgroup_disable= [KNL] Disable a particular controller
585 Format: {name of the controller(s) to disable}
586 The effects of cgroup_disable=foo are:
587 - foo isn't auto-mounted if you mount all cgroups in
589 - foo isn't visible as an individually mountable
591 {Currently only "memory" controller deal with this and
592 cut the overhead, others just disable the usage. So
593 only cgroup_disable=memory is actually worthy}
595 checkreqprot [SELINUX] Set initial checkreqprot flag value.
596 Format: { "0" | "1" }
597 See security/selinux/Kconfig help text.
598 0 -- check protection applied by kernel (includes
599 any implied execute protection).
600 1 -- check protection requested by application.
601 Default value is set via a kernel config option.
602 Value can be changed at runtime via
603 /selinux/checkreqprot.
606 See Documentation/s390/CommonIO for details.
609 Prevents the clock framework from automatically gating
610 clocks that have not been explicitly enabled by a Linux
611 device driver but are enabled in hardware at reset or
612 by the bootloader/firmware. Note that this does not
613 force such clocks to be always-on nor does it reserve
614 those clocks in any way. This parameter is useful for
615 debug and development, but should not be needed on a
616 platform with proper driver support. For more
617 information, see Documentation/clk.txt.
619 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
621 Forces specified clocksource (if available) to be used
622 when calculating gettimeofday(). If specified
623 clocksource is not available, it defaults to PIT.
624 Format: { pit | tsc | cyclone | pmtmr }
626 clocksource= Override the default clocksource
628 Override the default clocksource and use the clocksource
629 with the name specified.
630 Some clocksource names to choose from, depending on
632 [all] jiffies (this is the base, fallback clocksource)
634 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
635 pxa_timer,timer3,32k_counter,timer0_1
637 [X86-32] pit,hpet,tsc;
638 scx200_hrt on Geode; cyclone on IBM x440
646 clearcpuid=BITNUM [X86]
647 Disable CPUID feature X for the kernel. See
648 arch/x86/include/asm/cpufeature.h for the valid bit
649 numbers. Note the Linux specific bits are not necessarily
650 stable over kernel options, but the vendor specific
652 Also note that user programs calling CPUID directly
653 or using the feature without checking anything
654 will still see it. This just prevents it from
655 being used by the kernel or shown in /proc/cpuinfo.
656 Also note the kernel might malfunction if you disable
659 cma=nn[MG]@[start[MG][-end[MG]]]
661 Sets the size of kernel global memory area for
662 contiguous memory allocations and optionally the
663 placement constraint by the physical address range of
664 memory allocations. A value of 0 disables CMA
665 altogether. For more information, see
666 include/linux/dma-contiguous.h
668 cmo_free_hint= [PPC] Format: { yes | no }
669 Specify whether pages are marked as being inactive
670 when they are freed. This is used in CMO environments
671 to determine OS memory pressure for page stealing by
675 coherent_pool=nn[KMG] [ARM,KNL]
676 Sets the size of memory pool for coherent, atomic dma
677 allocations, by default set to 256K.
679 code_bytes [X86] How many bytes of object code to print
684 com20020= [HW,NET] ARCnet - COM20020 chipset
686 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
688 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
692 ARCnet - COM90xx chipset (memory-mapped buffers)
693 Format: <io>[,<irq>[,<memstart>]]
695 condev= [HW,S390] console device
698 console= [KNL] Output console device and options.
700 tty<n> Use the virtual console device <n>.
704 Use the specified serial port. The options are of
705 the form "bbbbpnf", where "bbbb" is the baud rate,
706 "p" is parity ("n", "o", or "e"), "n" is number of
707 bits, and "f" is flow control ("r" for RTS or
708 omit it). Default is "9600n8".
710 See Documentation/serial-console.txt for more
712 Documentation/networking/netconsole.txt for an
715 uart[8250],io,<addr>[,options]
716 uart[8250],mmio,<addr>[,options]
717 uart[8250],mmio32,<addr>[,options]
718 uart[8250],0x<addr>[,options]
719 Start an early, polled-mode console on the 8250/16550
720 UART at the specified I/O port or MMIO address,
721 switching to the matching ttyS device later.
722 MMIO inter-register address stride is either 8-bit
723 (mmio) or 32-bit (mmio32).
724 If none of [io|mmio|mmio32], <addr> is assumed to be
725 equivalent to 'mmio'. 'options' are specified in the
726 same format described for ttyS above; if unspecified,
727 the h/w is not re-initialized.
729 hvc<n> Use the hypervisor console device <n>. This is for
730 both Xen and PowerPC hypervisors.
732 If the device connected to the port is not a TTY but a braille
733 device, prepend "brl," before the device type, for instance
735 For now, only VisioBraille is supported.
737 consoleblank= [KNL] The console blank (screen saver) timeout in
738 seconds. Defaults to 10*60 = 10mins. A value of 0
739 disables the blank timer.
742 [KNL] Change the default value for
743 /proc/<pid>/coredump_filter.
744 See also Documentation/filesystems/proc.txt.
746 cpuidle.off=1 [CPU_IDLE]
747 disable the cpuidle sub-system
749 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
751 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
753 crashkernel=size[KMG][@offset[KMG]]
754 [KNL] Using kexec, Linux can switch to a 'crash kernel'
755 upon panic. This parameter reserves the physical
756 memory region [offset, offset + size] for that kernel
757 image. If '@offset' is omitted, then a suitable offset
758 is selected automatically. Check
759 Documentation/kdump/kdump.txt for further details.
761 crashkernel=range1:size1[,range2:size2,...][@offset]
762 [KNL] Same as above, but depends on the memory
763 in the running system. The syntax of range is
764 start-[end] where start and end are both
765 a memory unit (amount[KMG]). See also
766 Documentation/kdump/kdump.txt for an example.
768 crashkernel=size[KMG],high
769 [KNL, x86_64] range could be above 4G. Allow kernel
770 to allocate physical memory region from top, so could
771 be above 4G if system have more than 4G ram installed.
772 Otherwise memory region will be allocated below 4G, if
774 It will be ignored if crashkernel=X is specified.
775 crashkernel=size[KMG],low
776 [KNL, x86_64] range under 4G. When crashkernel=X,high
777 is passed, kernel could allocate physical memory region
778 above 4G, that cause second kernel crash on system
779 that require some amount of low memory, e.g. swiotlb
780 requires at least 64M+32K low memory. Kernel would
781 try to allocate 72M below 4G automatically.
782 This one let user to specify own low range under 4G
783 for second kernel instead.
784 0: to disable low allocation.
785 It will be ignored when crashkernel=X,high is not used
786 or memory reserved is below 4G.
791 cs89x0_media= [HW,NET]
792 Format: { rj45 | aui | bnc }
795 See header of drivers/s390/block/dasd_devmap.c.
797 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
798 (one device per port)
799 Format: <port#>,<type>
800 See also Documentation/input/joystick-parport.txt
802 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
803 time. See Documentation/dynamic-debug-howto.txt for
804 details. Deprecated, see dyndbg.
806 debug [KNL] Enable kernel debugging (events log level).
809 [KNL] verbose self-tests
811 Print debugging info while doing the locking API
813 We default to 0 (no extra messages), setting it to
814 1 will print _a lot_ more information - normally
815 only useful to kernel developers.
817 debug_objects [KNL] Enable object debugging
820 [KNL] Disable object debugging
822 debug_guardpage_minorder=
823 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
824 parameter allows control of the order of pages that will
825 be intentionally kept free (and hence protected) by the
826 buddy allocator. Bigger value increase the probability
827 of catching random memory corruption, but reduce the
828 amount of memory for normal system use. The maximum
829 possible value is MAX_ORDER/2. Setting this parameter
830 to 1 or 2 should be enough to identify most random
831 memory corruption problems caused by bugs in kernel or
832 driver code when a CPU writes to (or reads from) a
833 random memory location. Note that there exists a class
834 of memory corruptions problems caused by buggy H/W or
835 F/W or by drivers badly programing DMA (basically when
836 memory is written at bus level and the CPU MMU is
837 bypassed) which are not detectable by
838 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
839 tracking down these problems.
842 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
843 parameter enables the feature at boot time. In
844 default, it is disabled. We can avoid allocating huge
845 chunk of memory for debug pagealloc if we don't enable
846 it at boot time and the system will work mostly same
847 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
848 on: enable the feature
850 debugpat [X86] Enable PAT debugging
852 decnet.addr= [HW,NET]
853 Format: <area>[,<node>]
854 See also Documentation/networking/decnet.txt.
857 [same as hugepagesz=] The size of the default
858 HugeTLB page size. This is the size represented by
859 the legacy /proc/ hugepages APIs, used for SHM, and
860 default size when mounting hugetlbfs filesystems.
861 Defaults to the default architecture's huge page size
865 Set number of hash buckets for dentry cache.
868 See Documentation/networking/ipv6.txt.
870 disable_cpu_apicid= [X86,APIC,SMP]
872 The number of initial APIC ID for the
873 corresponding CPU to be disabled at boot,
874 mostly used for the kdump 2nd kernel to
875 disable BSP to wake up multiple CPUs without
876 causing system reset or hang due to sending
879 disable_ddw [PPC/PSERIES]
880 Disable Dynamic DMA Window support. Use this if
881 to workaround buggy firmware.
884 See Documentation/networking/ipv6.txt.
886 disable_mtrr_cleanup [X86]
887 The kernel tries to adjust MTRR layout from continuous
888 to discrete, to make X server driver able to add WB
889 entry later. This parameter disables that.
891 disable_mtrr_trim [X86, Intel and AMD only]
892 By default the kernel will trim any uncacheable
893 memory out of your available memory pool based on
894 MTRR settings. This parameter disables that behavior,
895 possibly causing your machine to run very slowly.
897 disable_timer_pin_1 [X86]
898 Disable PIN 1 of APIC timer
899 Can be useful to work around chipset bugs.
901 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
902 this option disables the debugging code at boot.
904 dma_debug_entries=<number>
905 This option allows to tune the number of preallocated
906 entries for DMA-API debugging code. One entry is
907 required per DMA-API allocation. Use this if the
908 DMA-API debugging code disables itself because the
909 architectural default is too low.
911 dma_debug_driver=<driver_name>
912 With this option the DMA-API debugging driver
913 filter feature can be enabled at boot time. Just
914 pass the driver to filter for as the parameter.
915 The filter can be disabled or changed to another
916 driver later using sysfs.
918 drm_kms_helper.edid_firmware=[<connector>:]<file>
919 Broken monitors, graphic adapters and KVMs may
920 send no or incorrect EDID data sets. This parameter
921 allows to specify an EDID data set in the
922 /lib/firmware directory that is used instead.
923 Generic built-in EDID data sets are used, if one of
924 edid/1024x768.bin, edid/1280x1024.bin,
925 edid/1680x1050.bin, or edid/1920x1080.bin is given
926 and no file with the same name exists. Details and
927 instructions how to build your own EDID data are
928 available in Documentation/EDID/HOWTO.txt. An EDID
929 data set will only be used for a particular connector,
930 if its name and a colon are prepended to the EDID
935 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
936 module.dyndbg[="val"]
937 Enable debug messages at boot time. See
938 Documentation/dynamic-debug-howto.txt for details.
941 on enable eager fpu restore
942 off disable eager fpu restore
943 auto selects the default scheme, which automatically
944 enables eagerfpu restore for xsaveopt.
946 early_ioremap_debug [KNL]
947 Enable debug messages in early_ioremap support. This
948 is useful for tracking down temporary early mappings
949 which are not unmapped.
951 earlycon= [KNL] Output early console device and options.
954 Start an early, polled-mode console on a cadence serial
955 port at the specified address. The cadence serial port
956 must already be setup and configured. Options are not
959 uart[8250],io,<addr>[,options]
960 uart[8250],mmio,<addr>[,options]
961 uart[8250],mmio32,<addr>[,options]
962 uart[8250],0x<addr>[,options]
963 Start an early, polled-mode console on the 8250/16550
964 UART at the specified I/O port or MMIO address.
965 MMIO inter-register address stride is either 8-bit
966 (mmio) or 32-bit (mmio32).
967 If none of [io|mmio|mmio32], <addr> is assumed to be
968 equivalent to 'mmio'. 'options' are specified in the
969 same format described for "console=ttyS<n>"; if
970 unspecified, the h/w is not initialized.
973 Start an early, polled-mode console on a pl011 serial
974 port at the specified address. The pl011 serial port
975 must already be setup and configured. Options are not
979 Start an early, polled-mode console on an msm serial
980 port at the specified address. The serial port
981 must already be setup and configured. Options are not
985 Start an early, polled-mode console on an msm serial
986 dm port at the specified address. The serial port
987 must already be setup and configured. Options are not
990 smh Use ARM semihosting calls for early console.
998 Use early console provided by serial driver available
999 on Samsung SoCs, requires selecting proper type and
1000 a correct base address of the selected UART port. The
1001 serial port must already be setup and configured.
1002 Options are not yet supported.
1004 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
1008 earlyprintk=serial[,ttySn[,baudrate]]
1009 earlyprintk=serial[,0x...[,baudrate]]
1010 earlyprintk=ttySn[,baudrate]
1011 earlyprintk=dbgp[debugController#]
1013 earlyprintk is useful when the kernel crashes before
1014 the normal console is initialized. It is not enabled by
1015 default because it has some cosmetic problems.
1017 Append ",keep" to not disable it when the real console
1020 Only one of vga, efi, serial, or usb debug port can
1023 Currently only ttyS0 and ttyS1 may be specified by
1024 name. Other I/O ports may be explicitly specified
1025 on some architectures (x86 and arm at least) by
1026 replacing ttySn with an I/O port address, like this:
1027 earlyprintk=serial,0x1008,115200
1028 You can find the port for a given device in
1029 /proc/tty/driver/serial:
1030 2: uart:ST16650V2 port:00001008 irq:18 ...
1032 Interaction with the standard serial driver is not
1035 The VGA and EFI output is eventually overwritten by
1038 The xen output can only be used by Xen PV guests.
1040 edac_report= [HW,EDAC] Control how to report EDAC event
1041 Format: {"on" | "off" | "force"}
1042 on: enable EDAC to report H/W event. May be overridden
1043 by other higher priority error reporting module.
1044 off: disable H/W event reporting through EDAC.
1045 force: enforce the use of EDAC to report H/W event.
1048 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1051 This is designed to be used in conjunction with
1052 the boot argument: earlyprintk=vga
1055 Format: {"off" | "on" | "skip[mbr]"}
1058 Format: { "old_map", "nochunk", "noruntime", "debug" }
1059 old_map [X86-64]: switch to the old ioremap-based EFI
1060 runtime services mapping. 32-bit still uses this one by
1062 nochunk: disable reading files in "chunks" in the EFI
1063 boot stub, as chunking can cause problems with some
1064 firmware implementations.
1065 noruntime : disable EFI runtime services support
1066 debug: enable misc debug output
1068 efi_no_storage_paranoia [EFI; X86]
1069 Using this parameter you can use more than 50% of
1070 your efi variable storage. Use this parameter only if
1071 you are really sure that your UEFI does sane gc and
1072 fulfills the spec otherwise your board may brick.
1074 eisa_irq_edge= [PARISC,HW]
1075 See header of drivers/parisc/eisa.c.
1078 See comment before function elanfreq_setup() in
1079 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1082 Format: {"cfq" | "deadline" | "noop"}
1083 See Documentation/block/cfq-iosched.txt and
1084 Documentation/block/deadline-iosched.txt for details.
1086 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1087 Specifies physical address of start of kernel core
1088 image elf header and optionally the size. Generally
1089 kexec loader will pass this option to capture kernel.
1090 See Documentation/kdump/kdump.txt for details.
1092 enable_mtrr_cleanup [X86]
1093 The kernel tries to adjust MTRR layout from continuous
1094 to discrete, to make X server driver able to add WB
1095 entry later. This parameter enables that.
1097 enable_timer_pin_1 [X86]
1098 Enable PIN 1 of APIC timer
1099 Can be useful to work around chipset bugs
1100 (in particular on some ATI chipsets).
1101 The kernel tries to set a reasonable default.
1103 enforcing [SELINUX] Set initial enforcing status.
1105 See security/selinux/Kconfig help text.
1106 0 -- permissive (log only, no denials).
1107 1 -- enforcing (deny and log).
1109 Value can be changed at runtime via /selinux/enforce.
1112 Disable Error Record Serialization Table (ERST)
1115 ether= [HW,NET] Ethernet cards parameters
1116 This option is obsoleted by the "netdev=" option, which
1117 has equivalent usage. See its documentation for details.
1121 Permit 'security.evm' to be updated regardless of
1122 current integrity status.
1126 fail_make_request=[KNL]
1127 General fault injection mechanism.
1128 Format: <interval>,<probability>,<space>,<times>
1129 See also Documentation/fault-injection/.
1132 See Documentation/blockdev/floppy.txt.
1134 force_pal_cache_flush
1135 [IA-64] Avoid check_sal_cache_flush which may hang on
1136 buggy SAL_CACHE_FLUSH implementations. Using this
1137 parameter will force ia64_sal_cache_flush to call
1138 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1141 Forcefully enable Physical Address Extension (PAE).
1142 Many Pentium M systems disable PAE but may have a
1143 functionally usable PAE implementation.
1144 Warning: use of this parameter will taint the kernel
1145 and may cause unknown problems.
1148 [FTRACE] will set and start the specified tracer
1149 as early as possible in order to facilitate early
1152 ftrace_dump_on_oops[=orig_cpu]
1153 [FTRACE] will dump the trace buffers on oops.
1154 If no parameter is passed, ftrace will dump
1155 buffers of all CPUs, but if you pass orig_cpu, it will
1156 dump only the buffer of the CPU that triggered the
1159 ftrace_filter=[function-list]
1160 [FTRACE] Limit the functions traced by the function
1161 tracer at boot up. function-list is a comma separated
1162 list of functions. This list can be changed at run
1163 time by the set_ftrace_filter file in the debugfs
1166 ftrace_notrace=[function-list]
1167 [FTRACE] Do not trace the functions specified in
1168 function-list. This list can be changed at run time
1169 by the set_ftrace_notrace file in the debugfs
1172 ftrace_graph_filter=[function-list]
1173 [FTRACE] Limit the top level callers functions traced
1174 by the function graph tracer at boot up.
1175 function-list is a comma separated list of functions
1176 that can be changed at run time by the
1177 set_graph_function file in the debugfs tracing directory.
1179 ftrace_graph_notrace=[function-list]
1180 [FTRACE] Do not trace from the functions specified in
1181 function-list. This list is a comma separated list of
1182 functions that can be changed at run time by the
1183 set_graph_notrace file in the debugfs tracing directory.
1186 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1187 support via parallel port (up to 5 devices per port)
1188 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1189 See also Documentation/input/joystick-parport.txt
1193 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1197 gcov_persist= [GCOV] When non-zero (default), profiling data for
1198 kernel modules is saved and remains accessible via
1199 debugfs, even when the module is unloaded/reloaded.
1200 When zero, profiling data is discarded and associated
1201 debugfs files are removed at module unload time.
1203 gpt [EFI] Forces disk with valid GPT signature but
1204 invalid Protective MBR to be treated as GPT. If the
1205 primary GPT is corrupted, it enables the backup/alternate
1206 GPT to be used instead.
1208 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1209 the "Enable 0" bit of the configuration register.
1212 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1213 the "Enable 0" bit of the configuration register.
1216 grcan.select= [HW] Select which physical interface to use.
1219 grcan.txsize= [HW] Sets the size of the tx buffer.
1220 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1222 grcan.rxsize= [HW] Sets the size of the rx buffer.
1223 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1226 hashdist= [KNL,NUMA] Large hashes allocated during boot
1227 are distributed across NUMA nodes. Defaults on
1228 for 64-bit NUMA, off otherwise.
1229 Format: 0 | 1 (for off | on)
1231 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1233 hd= [EIDE] (E)IDE hard drive subsystem geometry
1234 Format: <cyl>,<head>,<sect>
1237 Disable Hardware Error Source Table (HEST) support;
1238 corresponding firmware-first mode error processing
1239 logic will be disabled.
1241 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1242 size of <nn>. This works even on boxes that have no
1243 highmem otherwise. This also works to reduce highmem
1244 size on bigger boxes.
1246 highres= [KNL] Enable/disable high resolution timer mode.
1247 Valid parameters: "on", "off"
1251 See Documentation/isdn/README.HiSax.
1255 hpet= [X86-32,HPET] option to control HPET usage
1256 Format: { enable (default) | disable | force |
1258 disable: disable HPET and use PIT instead
1259 force: allow force enabled of undocumented chips (ICH4,
1261 verbose: show contents of HPET registers during setup
1263 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1264 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1266 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1267 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1268 On x86-64 and powerpc, this option can be specified
1269 multiple times interleaved with hugepages= to reserve
1270 huge pages of different sizes. Valid pages sizes on
1271 x86-64 are 2M (when the CPU supports "pse") and 1G
1272 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1274 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1275 terminal devices. Valid values: 0..8
1276 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1277 If specified, z/VM IUCV HVC accepts connections
1278 from listed z/VM user IDs only.
1280 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1281 hardware thread id mappings.
1282 Format: <cpu>:<hwthread>
1285 Do not unregister boot console at start. This is only
1286 useful for debugging when something happens in the window
1287 between unregistering the boot console and initializing
1290 i2c_bus= [HW] Override the default board specific I2C bus speed
1291 or register an additional I2C bus that is not
1292 registered from board initialization code.
1296 i8042.debug [HW] Toggle i8042 debug mode
1297 i8042.direct [HW] Put keyboard port into non-translated mode
1298 i8042.dumbkbd [HW] Pretend that controller can only read data from
1299 keyboard and cannot control its state
1300 (Don't attempt to blink the leds)
1301 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1302 i8042.nokbd [HW] Don't check/create keyboard port
1303 i8042.noloop [HW] Disable the AUX Loopback command while probing
1305 i8042.nomux [HW] Don't check presence of an active multiplexing
1307 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1309 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1310 i8042.reset [HW] Reset the controller during init and cleanup
1311 i8042.unlock [HW] Unlock (ignore) the keylock
1312 i8042.kbdreset [HW] Reset device connected to KBD port
1316 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1317 indicates that the driver is running on unsupported
1319 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1320 does not match list of supported models.
1322 [HW] Report power status in /proc/i8k
1323 (disabled by default)
1324 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1327 i915.invert_brightness=
1328 [DRM] Invert the sense of the variable that is used to
1329 set the brightness of the panel backlight. Normally a
1330 brightness value of 0 indicates backlight switched off,
1331 and the maximum of the brightness value sets the backlight
1332 to maximum brightness. If this parameter is set to 0
1333 (default) and the machine requires it, or this parameter
1334 is set to 1, a brightness value of 0 sets the backlight
1335 to maximum brightness, and the maximum of the brightness
1336 value switches the backlight off.
1337 -1 -- never invert brightness
1338 0 -- machine default
1339 1 -- force brightness inversion
1342 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1344 ide-core.nodma= [HW] (E)IDE subsystem
1345 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1346 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1347 .cdrom .chs .ignore_cable are additional options
1348 See Documentation/ide/ide.txt.
1350 ide-generic.probe-mask= [HW] (E)IDE subsystem
1352 Probe mask for legacy ISA IDE ports. Depending on
1353 platform up to 6 ports are supported, enabled by
1354 setting corresponding bits in the mask to 1. The
1355 default value is 0x0, which has a special meaning.
1356 On systems that have PCI, it triggers scanning the
1357 PCI bus for the first and the second port, which
1358 are then probed. On systems without PCI the value
1359 of 0x0 enables probing the two first ports as if it
1362 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1363 Claim all unknown PCI IDE storage controllers.
1366 Format: idle=poll, idle=halt, idle=nomwait
1367 Poll forces a polling idle loop that can slightly
1368 improve the performance of waking up a idle CPU, but
1369 will use a lot of power and make the system run hot.
1371 idle=halt: Halt is forced to be used for CPU idle.
1372 In such case C2/C3 won't be used again.
1373 idle=nomwait: Disable mwait for CPU C-states
1375 ignore_loglevel [KNL]
1376 Ignore loglevel setting - this will print /all/
1377 kernel messages to the console. Useful for debugging.
1378 We also add it as printk module parameter, so users
1379 could change it dynamically, usually by
1380 /sys/module/printk/parameters/ignore_loglevel.
1382 ihash_entries= [KNL]
1383 Set number of hash buckets for inode cache.
1385 ima_appraise= [IMA] appraise integrity measurements
1386 Format: { "off" | "enforce" | "fix" | "log" }
1389 ima_appraise_tcb [IMA]
1390 The builtin appraise policy appraises all files
1394 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1398 The list of supported hash algorithms is defined
1399 in crypto/hash_info.h.
1402 Load a policy which meets the needs of the Trusted
1403 Computing Base. This means IMA will measure all
1404 programs exec'd, files mmap'd for exec, and all files
1405 opened for read by uid=0.
1408 Select one of defined IMA measurements template formats.
1409 Formats: { "ima" | "ima-ng" }
1413 [IMA] Define a custom template format.
1414 Format: { "field1|...|fieldN" }
1416 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1417 Format: <min_file_size>
1418 Set the minimal file size for using asynchronous hash.
1419 If left unspecified, ahash usage is disabled.
1421 ahash performance varies for different data sizes on
1422 different crypto accelerators. This option can be used
1423 to achieve the best performance for a particular HW.
1425 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1427 Set hashing buffer size. Default: 4k.
1429 ahash performance varies for different chunk sizes on
1430 different crypto accelerators. This option can be used
1431 to achieve best performance for particular HW.
1435 Run specified binary instead of /sbin/init as init
1438 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1439 for working out where the kernel is dying during
1442 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1443 initcall functions. Useful for debugging built-in
1444 modules and initcalls.
1446 initrd= [BOOT] Specify the location of the initial ramdisk
1448 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1451 int_pln_enable [x86] Enable power limit notification interrupt
1453 integrity_audit=[IMA]
1454 Format: { "0" | "1" }
1455 0 -- basic integrity auditing messages. (Default)
1456 1 -- additional integrity auditing messages.
1458 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1460 Enable intel iommu driver.
1462 Disable intel iommu driver.
1463 igfx_off [Default Off]
1464 By default, gfx is mapped as normal device. If a gfx
1465 device has a dedicated DMAR unit, the DMAR unit is
1466 bypassed by not enabling DMAR with this option. In
1467 this case, gfx device will use physical address for
1470 With this option iommu will not optimize to look
1471 for io virtual address below 32-bit forcing dual
1472 address cycle on pci bus for cards supporting greater
1473 than 32-bit addressing. The default is to look
1474 for translation below 32-bit and if not available
1475 then look in the higher range.
1476 strict [Default Off]
1477 With this option on every unmap_single operation will
1478 result in a hardware IOTLB flush operation as opposed
1479 to batching them for performance.
1480 sp_off [Default Off]
1481 By default, super page will be supported if Intel IOMMU
1482 has the capability. With this option, super page will
1484 ecs_off [Default Off]
1485 By default, extended context tables will be supported if
1486 the hardware advertises that it has support both for the
1487 extended tables themselves, and also PASID support. With
1488 this option set, extended tables will not be used even
1489 on hardware which claims to support them.
1491 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1492 0 disables intel_idle and fall back on acpi_idle.
1493 1 to 6 specify maximum depth of C-state.
1497 Do not enable intel_pstate as the default
1498 scaling driver for the supported processors
1500 Enable intel_pstate on systems that prohibit it by default
1501 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1502 instead of acpi-cpufreq may disable platform features, such
1503 as thermal controls and power capping, that rely on ACPI
1504 P-States information being indicated to OSPM and therefore
1505 should be used with caution. This option does not work with
1506 processors that aren't supported by the intel_pstate driver
1507 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1509 Do not enable hardware P state control (HWP)
1512 Only load intel_pstate on systems which support
1513 hardware P state control (HWP) if available.
1515 intremap= [X86-64, Intel-IOMMU]
1516 on enable Interrupt Remapping (default)
1517 off disable Interrupt Remapping
1518 nosid disable Source ID checking
1520 BIOS x2APIC opt-out request will be ignored
1522 iomem= Disable strict checking of access to MMIO memory
1523 strict regions from userspace.
1538 nobypass [PPC/POWERNV]
1539 Disable IOMMU bypass, using IOMMU for PCI devices.
1542 io7= [HW] IO7 for Marvel based alpha systems
1543 See comment before marvel_specify_io7 in
1544 arch/alpha/kernel/core_marvel.c.
1546 io_delay= [X86] I/O delay method
1548 Standard port 0x80 based delay
1550 Alternate port 0xed based delay (needed on some systems)
1552 Simple two microseconds delay
1557 See Documentation/filesystems/nfs/nfsroot.txt.
1560 When an interrupt is not handled search all handlers
1561 for it. Intended to get systems with badly broken
1565 When an interrupt is not handled search all handlers
1566 for it. Also check all handlers each timer
1567 interrupt. Intended to get systems with badly broken
1571 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1573 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1575 <cpu number>,...,<cpu number>
1577 <cpu number>-<cpu number>
1578 (must be a positive range in ascending order)
1580 <cpu number>,...,<cpu number>-<cpu number>
1582 This option can be used to specify one or more CPUs
1583 to isolate from the general SMP balancing and scheduling
1584 algorithms. You can move a process onto or off an
1585 "isolated" CPU via the CPU affinity syscalls or cpuset.
1586 <cpu number> begins at 0 and the maximum value is
1587 "number of CPUs in system - 1".
1589 This option is the preferred way to isolate CPUs. The
1590 alternative -- manually setting the CPU mask of all
1591 tasks in the system -- can cause problems and
1592 suboptimal load balancer performance.
1596 ivrs_ioapic [HW,X86_64]
1597 Provide an override to the IOAPIC-ID<->DEVICE-ID
1598 mapping provided in the IVRS ACPI table. For
1599 example, to map IOAPIC-ID decimal 10 to
1600 PCI device 00:14.0 write the parameter as:
1601 ivrs_ioapic[10]=00:14.0
1603 ivrs_hpet [HW,X86_64]
1604 Provide an override to the HPET-ID<->DEVICE-ID
1605 mapping provided in the IVRS ACPI table. For
1606 example, to map HPET-ID decimal 0 to
1607 PCI device 00:14.0 write the parameter as:
1608 ivrs_hpet[0]=00:14.0
1610 js= [HW,JOY] Analog joystick
1611 See Documentation/input/joystick.txt.
1614 Enable/disable kernel and module base offset ASLR
1615 (Address Space Layout Randomization) if built into
1616 the kernel. When CONFIG_HIBERNATION is selected,
1617 kASLR is disabled by default. When kASLR is enabled,
1618 hibernation will be disabled.
1622 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1623 specifies the amount of memory usable by the kernel
1624 for non-movable allocations. The requested amount is
1625 spread evenly throughout all nodes in the system. The
1626 remaining memory in each node is used for Movable
1627 pages. In the event, a node is too small to have both
1628 kernelcore and Movable pages, kernelcore pages will
1629 take priority and other nodes will have a larger number
1630 of Movable pages. The Movable zone is used for the
1631 allocation of pages that may be reclaimed or moved
1632 by the page migration subsystem. This means that
1633 HugeTLB pages may not be allocated from this zone.
1634 Note that allocations like PTEs-from-HighMem still
1635 use the HighMem zone if it exists, and the Normal
1636 zone if it does not.
1638 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1639 Format: <Controller#>[,poll interval]
1640 The controller # is the number of the ehci usb debug
1641 port as it is probed via PCI. The poll interval is
1642 optional and is the number seconds in between
1643 each poll cycle to the debug port in case you need
1644 the functionality for interrupting the kernel with
1645 gdb or control-c on the dbgp connection. When
1646 not using this parameter you use sysrq-g to break into
1647 the kernel debugger.
1649 kgdboc= [KGDB,HW] kgdb over consoles.
1650 Requires a tty driver that supports console polling,
1651 or a supported polling keyboard driver (non-usb).
1652 Serial only format: <serial_device>[,baud]
1653 keyboard only format: kbd
1654 keyboard and serial format: kbd,<serial_device>[,baud]
1655 Optional Kernel mode setting:
1656 kms, kbd format: kms,kbd
1657 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1659 kgdbwait [KGDB] Stop kernel execution and enter the
1660 kernel debugger at the earliest opportunity.
1662 kmac= [MIPS] korina ethernet MAC address.
1663 Configure the RouterBoard 532 series on-chip
1664 Ethernet adapter MAC address.
1666 kmemleak= [KNL] Boot-time kmemleak enable/disable
1667 Valid arguments: on, off
1669 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
1672 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1673 Valid arguments: 0, 1, 2
1674 kmemcheck=0 (disabled)
1675 kmemcheck=1 (enabled)
1676 kmemcheck=2 (one-shot mode)
1677 Default: 2 (one-shot mode)
1679 kstack=N [X86] Print N words from the kernel stack
1682 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1683 Default is 0 (don't ignore, but inject #GP)
1685 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1689 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1690 Default is 1 (enabled)
1692 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1694 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1696 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1697 (virtualized MMU) support on capable Intel chips.
1698 Default is 1 (enabled)
1700 kvm-intel.emulate_invalid_guest_state=
1701 [KVM,Intel] Enable emulation of invalid guest states
1702 Default is 0 (disabled)
1704 kvm-intel.flexpriority=
1705 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1706 Default is 1 (enabled)
1709 [KVM,Intel] Enable VMX nesting (nVMX).
1710 Default is 0 (disabled)
1712 kvm-intel.unrestricted_guest=
1713 [KVM,Intel] Disable unrestricted guest feature
1714 (virtualized real and unpaged mode) on capable
1715 Intel chips. Default is 1 (enabled)
1717 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1718 feature (tagged TLBs) on capable Intel chips.
1719 Default is 1 (enabled)
1725 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1728 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1729 value for LAPIC timer one-shot implementation. Default
1730 back to the programmable timer unit in the LAPIC.
1732 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1735 libata.dma= [LIBATA] DMA control
1736 libata.dma=0 Disable all PATA and SATA DMA
1737 libata.dma=1 PATA and SATA Disk DMA only
1738 libata.dma=2 ATAPI (CDROM) DMA only
1739 libata.dma=4 Compact Flash DMA only
1740 Combinations also work, so libata.dma=3 enables DMA
1741 for disks and CDROMs, but not CFs.
1743 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1744 libata.ignore_hpa=0 keep BIOS limits (default)
1745 libata.ignore_hpa=1 ignore limits, using full disk
1747 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1751 libata.force= [LIBATA] Force configurations. The format is comma
1752 separated list of "[ID:]VAL" where ID is
1753 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1754 matching port, link or device. Basically, it matches
1755 the ATA ID string printed on console by libata. If
1756 the whole ID part is omitted, the last PORT and DEVICE
1757 values are used. If ID hasn't been specified yet, the
1758 configuration applies to all ports, links and devices.
1760 If only DEVICE is omitted, the parameter applies to
1761 the port and all links and devices behind it. DEVICE
1762 number of 0 either selects the first device or the
1763 first fan-out link behind PMP device. It does not
1764 select the host link. DEVICE number of 15 selects the
1765 host link and device attached to it.
1767 The VAL specifies the configuration to force. As long
1768 as there's no ambiguity shortcut notation is allowed.
1769 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1770 The following configurations can be forced.
1772 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1773 Any ID with matching PORT is used.
1775 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1777 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1778 udma[/][16,25,33,44,66,100,133] notation is also
1781 * [no]ncq: Turn on or off NCQ.
1783 * nohrst, nosrst, norst: suppress hard, soft
1786 * rstonce: only attempt one reset during
1787 hot-unplug link recovery
1789 * dump_id: dump IDENTIFY data.
1791 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1793 * disable: Disable this device.
1795 If there are multiple matching configurations changing
1796 the same attribute, the last one is used.
1798 memblock=debug [KNL] Enable memblock debug messages.
1800 load_ramdisk= [RAM] List of ramdisks to load from floppy
1801 See Documentation/blockdev/ramdisk.txt.
1803 lockd.nlm_grace_period=P [NFS] Assign grace period.
1806 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1809 lockd.nlm_timeout=T [NFS] Assign timeout value.
1812 lockd.nlm_udpport=M [NFS] Assign UDP port.
1815 locktorture.nreaders_stress= [KNL]
1816 Set the number of locking read-acquisition kthreads.
1817 Defaults to being automatically set based on the
1818 number of online CPUs.
1820 locktorture.nwriters_stress= [KNL]
1821 Set the number of locking write-acquisition kthreads.
1823 locktorture.onoff_holdoff= [KNL]
1824 Set time (s) after boot for CPU-hotplug testing.
1826 locktorture.onoff_interval= [KNL]
1827 Set time (s) between CPU-hotplug operations, or
1828 zero to disable CPU-hotplug testing.
1830 locktorture.shuffle_interval= [KNL]
1831 Set task-shuffle interval (jiffies). Shuffling
1832 tasks allows some CPUs to go into dyntick-idle
1833 mode during the locktorture test.
1835 locktorture.shutdown_secs= [KNL]
1836 Set time (s) after boot system shutdown. This
1837 is useful for hands-off automated testing.
1839 locktorture.stat_interval= [KNL]
1840 Time (s) between statistics printk()s.
1842 locktorture.stutter= [KNL]
1843 Time (s) to stutter testing, for example,
1844 specifying five seconds causes the test to run for
1845 five seconds, wait for five seconds, and so on.
1846 This tests the locking primitive's ability to
1847 transition abruptly to and from idle.
1849 locktorture.torture_runnable= [BOOT]
1850 Start locktorture running at boot time.
1852 locktorture.torture_type= [KNL]
1853 Specify the locking implementation to test.
1855 locktorture.verbose= [KNL]
1856 Enable additional printk() statements.
1858 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1861 loglevel= All Kernel Messages with a loglevel smaller than the
1862 console loglevel will be printed to the console. It can
1863 also be changed with klogd or other programs. The
1864 loglevels are defined as follows:
1866 0 (KERN_EMERG) system is unusable
1867 1 (KERN_ALERT) action must be taken immediately
1868 2 (KERN_CRIT) critical conditions
1869 3 (KERN_ERR) error conditions
1870 4 (KERN_WARNING) warning conditions
1871 5 (KERN_NOTICE) normal but significant condition
1872 6 (KERN_INFO) informational
1873 7 (KERN_DEBUG) debug-level messages
1875 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1876 in bytes. n must be a power of two and greater
1877 than the minimal size. The minimal size is defined
1878 by LOG_BUF_SHIFT kernel config parameter. There is
1879 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1880 that allows to increase the default size depending on
1881 the number of CPUs. See init/Kconfig for more details.
1883 logo.nologo [FB] Disables display of the built-in Linux logo.
1884 This may be used to provide more screen space for
1885 kernel log messages and is useful when debugging
1886 kernel boot problems.
1888 lp=0 [LP] Specify parallel ports to use, e.g,
1889 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1890 lp=reset first parallel port). 'lp=0' disables the
1891 lp=auto printer driver. 'lp=reset' (which can be
1892 specified in addition to the ports) causes
1893 attached printers to be reset. Using
1894 lp=port1,port2,... specifies the parallel ports
1895 to associate lp devices with, starting with
1896 lp0. A port specification may be 'none' to skip
1897 that lp device, or a parport name such as
1898 'parport0'. Specifying 'lp=auto' instead of a
1899 port specification list means that device IDs
1900 from each port should be examined, to see if
1901 an IEEE 1284-compliant printer is attached; if
1902 so, the driver will manage that printer.
1903 See also header of drivers/char/lp.c.
1906 Sets loops_per_jiffy to given constant, thus avoiding
1907 time-consuming boot-time autodetection (up to 250 ms per
1908 CPU). 0 enables autodetection (default). To determine
1909 the correct value for your kernel, boot with normal
1910 autodetection and see what value is printed. Note that
1911 on SMP systems the preset will be applied to all CPUs,
1912 which is likely to cause problems if your CPUs need
1913 significantly divergent settings. An incorrect value
1914 will cause delays in the kernel to be wrong, leading to
1915 unpredictable I/O errors and other breakage. Although
1916 unlikely, in the extreme case this might damage your
1920 Format: <io>,<irq>,<dma>
1922 machvec= [IA-64] Force the use of a particular machine-vector
1923 (machvec) in a generic kernel.
1924 Example: machvec=hpzx1_swiotlb
1926 machtype= [Loongson] Share the same kernel image file between different
1928 Example: machtype=lemote-yeeloong-2f-7inch
1930 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1931 than or equal to this physical address is ignored.
1933 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1934 should make use of. maxcpus=n : n >= 0 limits the
1935 kernel to using 'n' processors. n=0 is a special case,
1936 it is equivalent to "nosmp", which also disables
1939 max_loop= [LOOP] The number of loop block devices that get
1940 (loop.max_loop) unconditionally pre-created at init time. The default
1941 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1942 of statically allocating a predefined number, loop
1943 devices can be requested on-demand with the
1944 /dev/loop-control interface.
1946 mce [X86-32] Machine Check Exception
1948 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1950 md= [HW] RAID subsystems devices and level
1951 See Documentation/md.txt.
1954 Format: <first>,<last>
1955 Specifies range of consoles to be captured by the MDA.
1957 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1958 Amount of memory to be used when the kernel is not able
1959 to see the whole system memory or for test.
1960 [X86] Work as limiting max address. Use together
1961 with memmap= to avoid physical address space collisions.
1962 Without memmap= PCI devices could be placed at addresses
1963 belonging to unused RAM.
1965 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1969 [KNL,SH] Allow user to override the default size for
1970 per-device physically contiguous DMA buffers.
1972 memmap=exactmap [KNL,X86] Enable setting of an exact
1973 E820 memory map, as specified by the user.
1974 Such memmap=exactmap lines can be constructed based on
1975 BIOS output or other requirements. See the memmap=nn@ss
1978 memmap=nn[KMG]@ss[KMG]
1979 [KNL] Force usage of a specific region of memory.
1980 Region of memory to be used is from ss to ss+nn.
1982 memmap=nn[KMG]#ss[KMG]
1983 [KNL,ACPI] Mark specific memory as ACPI data.
1984 Region of memory to be marked is from ss to ss+nn.
1986 memmap=nn[KMG]$ss[KMG]
1987 [KNL,ACPI] Mark specific memory as reserved.
1988 Region of memory to be reserved is from ss to ss+nn.
1989 Example: Exclude memory from 0x18690000-0x1869ffff
1990 memmap=64K$0x18690000
1992 memmap=0x10000$0x18690000
1994 memmap=nn[KMG]!ss[KMG]
1995 [KNL,X86] Mark specific memory as protected.
1996 Region of memory to be used, from ss to ss+nn.
1997 The memory region may be marked as e820 type 12 (0xc)
1998 and is NVDIMM or ADR memory.
2000 memory_corruption_check=0/1 [X86]
2001 Some BIOSes seem to corrupt the first 64k of
2002 memory when doing things like suspend/resume.
2003 Setting this option will scan the memory
2004 looking for corruption. Enabling this will
2005 both detect corruption and prevent the kernel
2006 from using the memory being corrupted.
2007 However, its intended as a diagnostic tool; if
2008 repeatable BIOS-originated corruption always
2009 affects the same memory, you can use memmap=
2010 to prevent the kernel from using that memory.
2012 memory_corruption_check_size=size [X86]
2013 By default it checks for corruption in the low
2014 64k, making this memory unavailable for normal
2015 use. Use this parameter to scan for
2016 corruption in more or less memory.
2018 memory_corruption_check_period=seconds [X86]
2019 By default it checks for corruption every 60
2020 seconds. Use this parameter to check at some
2021 other rate. 0 disables periodic checking.
2023 memtest= [KNL,X86,ARM] Enable memtest
2025 default : 0 <disable>
2026 Specifies the number of memtest passes to be
2027 performed. Each pass selects another test
2028 pattern from a given set of patterns. Memtest
2029 fills the memory with this pattern, validates
2030 memory contents and reserves bad memory
2031 regions that are detected.
2033 meye.*= [HW] Set MotionEye Camera parameters
2034 See Documentation/video4linux/meye.txt.
2036 mfgpt_irq= [IA-32] Specify the IRQ to use for the
2037 Multi-Function General Purpose Timers on AMD Geode
2040 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
2041 the BIOS has incorrectly applied a workaround. TinyBIOS
2042 version 0.98 is known to be affected, 0.99 fixes the
2043 problem by letting the user disable the workaround.
2047 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
2048 physical address is ignored.
2050 mini2440= [ARM,HW,KNL]
2051 Format:[0..2][b][c][t]
2053 MINI2440 configuration specification:
2054 0 - The attached screen is the 3.5" TFT
2055 1 - The attached screen is the 7" TFT
2056 2 - The VGA Shield is attached (1024x768)
2057 Leaving out the screen size parameter will not load
2058 the TFT driver, and the framebuffer will be left
2060 b - Enable backlight. The TFT backlight pin will be
2061 linked to the kernel VESA blanking code and a GPIO
2062 LED. This parameter is not necessary when using the
2064 c - Enable the s3c camera interface.
2065 t - Reserved for enabling touchscreen support. The
2066 touchscreen support is not enabled in the mainstream
2067 kernel as of 2.6.30, a preliminary port can be found
2068 in the "bleeding edge" mini2440 support kernel at
2069 http://repo.or.cz/w/linux-2.6/mini2440.git
2072 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2073 parameter allows control of the logging verbosity for
2074 the additional memory initialisation checks. A value
2075 of 0 disables mminit logging and a level of 4 will
2076 log everything. Information is printed at KERN_DEBUG
2077 so loglevel=8 may also need to be specified.
2080 [KNL] When CONFIG_MODULE_SIG is set, this means that
2081 modules without (valid) signatures will fail to load.
2082 Note that if CONFIG_MODULE_SIG_FORCE is set, that
2083 is always true, so this option does nothing.
2086 [MOUSE] Maximum time between finger touching and
2087 leaving touchpad surface for touch to be considered
2088 a tap and be reported as a left button click (for
2089 touchpads working in absolute mode only).
2091 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
2092 reporting absolute coordinates, such as tablets
2093 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
2094 reporting absolute coordinates, such as tablets
2096 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
2097 is similar to kernelcore except it specifies the
2098 amount of memory used for migratable allocations.
2099 If both kernelcore and movablecore is specified,
2100 then kernelcore will be at *least* the specified
2101 value but may be more. If movablecore on its own
2102 is specified, the administrator must be careful
2103 that the amount of memory usable for all allocations
2106 movable_node [KNL,X86] Boot-time switch to enable the effects
2107 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2109 MTD_Partition= [MTD]
2110 Format: <name>,<region-number>,<size>,<offset>
2112 MTD_Region= [MTD] Format:
2113 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2116 See drivers/mtd/cmdlinepart.c.
2118 multitce=off [PPC] This parameter disables the use of the pSeries
2119 firmware feature for updating multiple TCE entries
2122 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
2124 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2126 boundary - index of last SLC block on Flex-OneNAND.
2127 The remaining blocks are configured as MLC blocks.
2128 lock - Configure if Flex-OneNAND boundary should be locked.
2129 Once locked, the boundary cannot be changed.
2130 1 indicates lock status, 0 indicates unlock status.
2133 ARM/S3C2412 JIVE boot control
2135 See arch/arm/mach-s3c2412/mach-jive.c
2137 mtouchusb.raw_coordinates=
2138 [HW] Make the MicroTouch USB driver use raw coordinates
2139 ('y', default) or cooked coordinates ('n')
2141 mtrr_chunk_size=nn[KMG] [X86]
2142 used for mtrr cleanup. It is largest continuous chunk
2143 that could hold holes aka. UC entries.
2145 mtrr_gran_size=nn[KMG] [X86]
2146 Used for mtrr cleanup. It is granularity of mtrr block.
2148 Large value could prevent small alignment from
2151 mtrr_spare_reg_nr=n [X86]
2153 Range: 0,7 : spare reg number
2155 Used for mtrr cleanup. It is spare mtrr entries number.
2156 Set to 2 or more if your graphical card needs more.
2158 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
2160 netdev= [NET] Network devices parameters
2161 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2162 Note that mem_start is often overloaded to mean
2163 something different and driver-specific.
2164 This usage is only documented in each driver source
2168 [NETFILTER] Enable connection tracking flow accounting
2169 0 to disable accounting
2170 1 to enable accounting
2173 nfsaddrs= [NFS] Deprecated. Use ip= instead.
2174 See Documentation/filesystems/nfs/nfsroot.txt.
2176 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
2177 See Documentation/filesystems/nfs/nfsroot.txt.
2179 nfsrootdebug [NFS] enable nfsroot debugging messages.
2180 See Documentation/filesystems/nfs/nfsroot.txt.
2182 nfs.callback_tcpport=
2183 [NFS] set the TCP port on which the NFSv4 callback
2184 channel should listen.
2187 [NFS] sets the pathname to the program which is used
2188 to update the NFS client cache entries.
2190 nfs.cache_getent_timeout=
2191 [NFS] sets the timeout after which an attempt to
2192 update a cache entry is deemed to have failed.
2194 nfs.idmap_cache_timeout=
2195 [NFS] set the maximum lifetime for idmapper cache
2199 [NFS] enable 64-bit inode numbers.
2200 If zero, the NFS client will fake up a 32-bit inode
2201 number for the readdir() and stat() syscalls instead
2202 of returning the full 64-bit number.
2203 The default is to return 64-bit inode numbers.
2205 nfs.max_session_slots=
2206 [NFSv4.1] Sets the maximum number of session slots
2207 the client will attempt to negotiate with the server.
2208 This limits the number of simultaneous RPC requests
2209 that the client can send to the NFSv4.1 server.
2210 Note that there is little point in setting this
2211 value higher than the max_tcp_slot_table_limit.
2213 nfs.nfs4_disable_idmapping=
2214 [NFSv4] When set to the default of '1', this option
2215 ensures that both the RPC level authentication
2216 scheme and the NFS level operations agree to use
2217 numeric uids/gids if the mount is using the
2218 'sec=sys' security flavour. In effect it is
2219 disabling idmapping, which can make migration from
2220 legacy NFSv2/v3 systems to NFSv4 easier.
2221 Servers that do not support this mode of operation
2222 will be autodetected by the client, and it will fall
2223 back to using the idmapper.
2224 To turn off this behaviour, set the value to '0'.
2226 [NFS4] Specify an additional fixed unique ident-
2227 ification string that NFSv4 clients can insert into
2228 their nfs_client_id4 string. This is typically a
2229 UUID that is generated at system install time.
2231 nfs.send_implementation_id =
2232 [NFSv4.1] Send client implementation identification
2233 information in exchange_id requests.
2234 If zero, no implementation identification information
2236 The default is to send the implementation identification
2239 nfs.recover_lost_locks =
2240 [NFSv4] Attempt to recover locks that were lost due
2241 to a lease timeout on the server. Please note that
2242 doing this risks data corruption, since there are
2243 no guarantees that the file will remain unchanged
2244 after the locks are lost.
2245 If you want to enable the kernel legacy behaviour of
2246 attempting to recover these locks, then set this
2248 The default parameter value of '0' causes the kernel
2249 not to attempt recovery of lost locks.
2251 nfsd.nfs4_disable_idmapping=
2252 [NFSv4] When set to the default of '1', the NFSv4
2253 server will return only numeric uids and gids to
2254 clients using auth_sys, and will accept numeric uids
2255 and gids from such clients. This is intended to ease
2256 migration from NFSv2/v3.
2258 objlayoutdriver.osd_login_prog=
2259 [NFS] [OBJLAYOUT] sets the pathname to the program which
2260 is used to automatically discover and login into new
2261 osd-targets. Please see:
2262 Documentation/filesystems/pnfs.txt for more explanations
2264 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2265 when a NMI is triggered.
2266 Format: [state][,regs][,debounce][,die]
2268 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2269 Format: [panic,][nopanic,][num]
2271 0 - turn nmi_watchdog off
2272 1 - turn nmi_watchdog on
2273 When panic is specified, panic when an NMI watchdog
2274 timeout occurs (or 'nopanic' to override the opposite
2276 This is useful when you use a panic=... timeout and
2277 need the box quickly up again.
2279 netpoll.carrier_timeout=
2280 [NET] Specifies amount of time (in seconds) that
2281 netpoll should wait for a carrier. By default netpoll
2284 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2285 emulation library even if a 387 maths coprocessor
2289 [HW] Never suspend the console
2290 Disable suspending of consoles during suspend and
2291 hibernate operations. Once disabled, debugging
2292 messages can reach various consoles while the rest
2293 of the system is being put to sleep (ie, while
2294 debugging driver suspend/resume hooks). This may
2295 not work reliably with all consoles, but is known
2296 to work with serial and VGA consoles.
2297 To facilitate more flexible debugging, we also add
2298 console_suspend, a printk module parameter to control
2299 it. Users could use console_suspend (usually
2300 /sys/module/printk/parameters/console_suspend) to
2301 turn on/off it dynamically.
2303 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2304 caches in the slab allocator. Saves per-node memory,
2305 but will impact performance.
2309 noapic [SMP,APIC] Tells the kernel to not make use of any
2310 IOAPICs that may be present in the system.
2312 noautogroup Disable scheduler automatic task group creation.
2314 nobats [PPC] Do not use BATs for mapping kernel lowmem
2315 on "Classic" PPC cores.
2319 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2321 nodelayacct [KNL] Disable per-task delay accounting
2323 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2325 nodsp [SH] Disable hardware DSP at boot time.
2327 noefi Disable EFI runtime services support.
2332 On X86-32 available only on PAE configured kernels.
2333 noexec=on: enable non-executable mappings (default)
2334 noexec=off: disable non-executable mappings
2337 Disable SMAP (Supervisor Mode Access Prevention)
2338 even if it is supported by processor.
2341 Disable SMEP (Supervisor Mode Execution Prevention)
2342 even if it is supported by processor.
2345 This affects only 32-bit executables.
2346 noexec32=on: enable non-executable mappings (default)
2347 read doesn't imply executable mappings
2348 noexec32=off: disable non-executable mappings
2349 read implies executable mappings
2351 nofpu [MIPS,SH] Disable hardware FPU at boot time.
2353 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2354 register save and restore. The kernel will only save
2355 legacy floating-point registers on task switch.
2357 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
2359 noxsave [BUGS=X86] Disables x86 extended register state save
2360 and restore using xsave. The kernel will fallback to
2361 enabling legacy floating-point and sse state.
2363 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
2364 register states. The kernel will fall back to use
2365 xsave to save the states. By using this parameter,
2366 performance of saving the states is degraded because
2367 xsave doesn't support modified optimization while
2368 xsaveopt supports it on xsaveopt enabled systems.
2370 noxsaves [X86] Disables xsaves and xrstors used in saving and
2371 restoring x86 extended register state in compacted
2372 form of xsave area. The kernel will fall back to use
2373 xsaveopt and xrstor to save and restore the states
2374 in standard form of xsave area. By using this
2375 parameter, xsave area per process might occupy more
2376 memory on xsaves enabled systems.
2378 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2379 wfi(ARM) instruction doesn't work correctly and not to
2380 use it. This is also useful when using JTAG debugger.
2382 no_file_caps Tells the kernel not to honor file capabilities. The
2383 only way then for a file to be executed with privilege
2384 is to be setuid root or executed by root.
2386 nohalt [IA-64] Tells the kernel not to use the power saving
2387 function PAL_HALT_LIGHT when idle. This increases
2388 power-consumption. On the positive side, it reduces
2389 interrupt wake-up latency, which may improve performance
2390 in certain environments such as networked servers or
2393 nohibernate [HIBERNATION] Disable hibernation and resume.
2395 nohz= [KNL] Boottime enable/disable dynamic ticks
2396 Valid arguments: on, off
2399 nohz_full= [KNL,BOOT]
2400 In kernels built with CONFIG_NO_HZ_FULL=y, set
2401 the specified list of CPUs whose tick will be stopped
2402 whenever possible. The boot CPU will be forced outside
2403 the range to maintain the timekeeping.
2404 The CPUs in this range must also be included in the
2407 noiotrap [SH] Disables trapped I/O port accesses.
2409 noirqdebug [X86-32] Disables the code which attempts to detect and
2410 disable unhandled interrupt sources.
2412 no_timer_check [X86,APIC] Disables the code which tests for
2413 broken timer IRQ sources.
2415 noisapnp [ISAPNP] Disables ISA PnP code.
2417 noinitrd [RAM] Tells the kernel not to load any configured
2420 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2422 [Deprecated - use intremap=off]
2426 nojitter [IA-64] Disables jitter checking for ITC timers.
2428 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2430 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2433 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2434 steal time is computed, but won't influence scheduler
2437 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2439 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2441 noltlbs [PPC] Do not use large page/tlb entries for kernel
2442 lowmem mapping on PPC40x.
2444 nomca [IA-64] Disable machine check abort handling
2446 nomce [X86-32] Machine Check Exception
2448 nomfgpt [X86-32] Disable Multi-Function General Purpose
2449 Timer usage (for AMD Geode machines).
2451 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2452 shutdown the other cpus. Instead use the REBOOT_VECTOR
2455 nomodule Disable module load
2457 nopat [X86] Disable PAT (page attribute table extension of
2458 pagetables) support.
2460 norandmaps Don't use address space randomization. Equivalent to
2461 echo 0 > /proc/sys/kernel/randomize_va_space
2463 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2465 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2466 with UP alternatives
2468 nordrand [X86] Disable kernel use of the RDRAND and
2469 RDSEED instructions even if they are supported
2470 by the processor. RDRAND and RDSEED are still
2471 available to user space applications.
2473 noresume [SWSUSP] Disables resume and restores original swap
2476 no-scroll [VGA] Disables scrollback.
2477 This is required for the Braillex ib80-piezo Braille
2478 reader made by F.H. Papenmeier (Germany).
2482 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2484 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2485 and disable the IO APIC. legacy for "maxcpus=0".
2487 nosoftlockup [KNL] Disable the soft-lockup detector.
2489 nosync [HW,M68K] Disables sync negotiation for all devices.
2491 notsc [BUGS=X86-32] Disable Time Stamp Counter
2493 nousb [USB] Disable the USB subsystem
2495 nowatchdog [KNL] Disable both lockup detectors, i.e.
2496 soft-lockup and NMI watchdog (hard-lockup).
2500 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2502 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2503 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2504 Some features depend on CPU0. Known dependencies are:
2505 1. Resume from suspend/hibernate depends on CPU0.
2506 Suspend/hibernate will fail if CPU0 is offline and you
2507 need to online CPU0 before suspend/hibernate.
2508 2. PIC interrupts also depend on CPU0. CPU0 can't be
2509 removed if a PIC interrupt is detected.
2510 It's said poweroff/reboot may depend on CPU0 on some
2511 machines although I haven't seen such issues so far
2512 after CPU0 is offline on a few tested machines.
2513 If the dependencies are under your control, you can
2514 turn on cpu0_hotplug.
2516 nptcg= [IA-64] Override max number of concurrent global TLB
2517 purges which is reported from either PAL_VM_SUMMARY or
2520 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2521 could support. nr_cpus=n : n >= 1 limits the kernel to
2522 supporting 'n' processors. Later in runtime you can not
2523 use hotplug cpu feature to put more cpu back to online.
2524 just like you compile the kernel NR_CPUS=n
2526 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2528 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2529 Allowed values are enable and disable
2531 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2532 one of ['zone', 'node', 'default'] can be specified
2533 This can be set from sysctl after boot.
2534 See Documentation/sysctl/vm.txt for details.
2536 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2537 See Documentation/debugging-via-ohci1394.txt for more
2540 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2541 Rather than timing out after 20 ms if an EC
2542 command is not properly ACKed, override the length
2543 of the timeout. We have interrupts disabled while
2544 waiting for the ACK, so if this is set too high
2545 interrupts *may* be lost!
2547 omap_mux= [OMAP] Override bootloader pin multiplexing.
2548 Format: <mux_mode0.mode_name=value>...
2549 For example, to override I2C bus2:
2550 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2552 oprofile.timer= [HW]
2553 Use timer interrupt instead of performance counters
2555 oprofile.cpu_type= Force an oprofile cpu type
2556 This might be useful if you have an older oprofile
2557 userland or if you want common events.
2558 Format: { arch_perfmon }
2559 arch_perfmon: [X86] Force use of architectural
2560 perfmon on Intel CPUs instead of the
2561 CPU specific event set.
2562 timer: [X86] Force use of architectural NMI
2563 timer mode (see also oprofile.timer
2564 for generic hr timer mode)
2565 [s390] Force legacy basic mode sampling
2566 (report cpu_type "timer")
2568 oops=panic Always panic on oopses. Default is to just kill the
2569 process, but there is a small probability of
2570 deadlocking the machine.
2571 This will also cause panics on machine check exceptions.
2572 Useful together with panic=30 to trigger a reboot.
2575 See Documentation/sound/oss/oss-parameters.txt
2577 page_owner= [KNL] Boot-time page_owner enabling option.
2578 Storage of the information about who allocated
2579 each page is disabled in default. With this switch,
2581 on: enable the feature
2583 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2584 timeout > 0: seconds before rebooting
2585 timeout = 0: wait forever
2586 timeout < 0: reboot immediately
2589 panic_on_warn panic() instead of WARN(). Useful to cause kdump
2592 crash_kexec_post_notifiers
2593 Run kdump after running panic-notifiers and dumping
2594 kmsg. This only for the users who doubt kdump always
2595 succeeds in any situation.
2596 Note that this also increases risks of kdump failure,
2597 because some panic notifiers can make the crashed
2598 kernel more unstable.
2600 parkbd.port= [HW] Parallel port number the keyboard adapter is
2601 connected to, default is 0.
2603 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2604 0 for XT, 1 for AT (default is AT).
2607 parport= [HW,PPT] Specify parallel ports. 0 disables.
2608 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2609 Use 'auto' to force the driver to use any
2610 IRQ/DMA settings detected (the default is to
2611 ignore detected IRQ/DMA settings because of
2612 possible conflicts). You can specify the base
2613 address, IRQ, and DMA settings; IRQ and DMA
2614 should be numbers, or 'auto' (for using detected
2615 settings on that particular port), or 'nofifo'
2616 (to avoid using a FIFO even if it is detected).
2617 Parallel ports are assigned in the order they
2618 are specified on the command line, starting
2621 parport_init_mode= [HW,PPT]
2622 Configure VIA parallel port to operate in
2623 a specific mode. This is necessary on Pegasos
2624 computer where firmware has no options for setting
2625 up parallel port mode and sets it to spp.
2626 Currently this function knows 686a and 8231 chips.
2627 Format: [spp|ps2|epp|ecp|ecpepp]
2630 Halt all CPUs after the first oops has been printed for
2631 the specified number of seconds. This is to be used if
2632 your oopses keep scrolling off the screen.
2637 See header of drivers/block/paride/pcd.c.
2638 See also Documentation/blockdev/paride.txt.
2640 pci=option[,option...] [PCI] various PCI subsystem options:
2641 earlydump [X86] dump PCI config space before the kernel
2643 off [X86] don't probe for the PCI bus
2644 bios [X86-32] force use of PCI BIOS, don't access
2645 the hardware directly. Use this if your machine
2646 has a non-standard PCI host bridge.
2647 nobios [X86-32] disallow use of PCI BIOS, only direct
2648 hardware access methods are allowed. Use this
2649 if you experience crashes upon bootup and you
2650 suspect they are caused by the BIOS.
2651 conf1 [X86] Force use of PCI Configuration
2653 conf2 [X86] Force use of PCI Configuration
2655 noaer [PCIE] If the PCIEAER kernel config parameter is
2656 enabled, this kernel boot option can be used to
2657 disable the use of PCIE advanced error reporting.
2658 nodomains [PCI] Disable support for multiple PCI
2659 root domains (aka PCI segments, in ACPI-speak).
2660 nommconf [X86] Disable use of MMCONFIG for PCI
2662 check_enable_amd_mmconf [X86] check for and enable
2663 properly configured MMIO access to PCI
2664 config space on AMD family 10h CPU
2665 nomsi [MSI] If the PCI_MSI kernel config parameter is
2666 enabled, this kernel boot option can be used to
2667 disable the use of MSI interrupts system-wide.
2668 noioapicquirk [APIC] Disable all boot interrupt quirks.
2669 Safety option to keep boot IRQs enabled. This
2670 should never be necessary.
2671 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2672 primary IO-APIC for bridges that cannot disable
2673 boot IRQs. This fixes a source of spurious IRQs
2674 when the system masks IRQs.
2675 noioapicreroute [APIC] Disable workaround that uses the
2676 boot IRQ equivalent of an IRQ that connects to
2677 a chipset where boot IRQs cannot be disabled.
2678 The opposite of ioapicreroute.
2679 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2680 routing table. These calls are known to be buggy
2681 on several machines and they hang the machine
2682 when used, but on other computers it's the only
2683 way to get the interrupt routing table. Try
2684 this option if the kernel is unable to allocate
2685 IRQs or discover secondary PCI buses on your
2687 rom [X86] Assign address space to expansion ROMs.
2688 Use with caution as certain devices share
2689 address decoders between ROMs and other
2691 norom [X86] Do not assign address space to
2692 expansion ROMs that do not already have
2693 BIOS assigned address ranges.
2694 nobar [X86] Do not assign address space to the
2695 BARs that weren't assigned by the BIOS.
2696 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2697 assigned automatically to PCI devices. You can
2698 make the kernel exclude IRQs of your ISA cards
2700 pirqaddr=0xAAAAA [X86] Specify the physical address
2701 of the PIRQ table (normally generated
2702 by the BIOS) if it is outside the
2703 F0000h-100000h range.
2704 lastbus=N [X86] Scan all buses thru bus #N. Can be
2705 useful if the kernel is unable to find your
2706 secondary buses and you want to tell it
2707 explicitly which ones they are.
2708 assign-busses [X86] Always assign all PCI bus
2709 numbers ourselves, overriding
2710 whatever the firmware may have done.
2711 usepirqmask [X86] Honor the possible IRQ mask stored
2712 in the BIOS $PIR table. This is needed on
2713 some systems with broken BIOSes, notably
2714 some HP Pavilion N5400 and Omnibook XE3
2715 notebooks. This will have no effect if ACPI
2716 IRQ routing is enabled.
2717 noacpi [X86] Do not use ACPI for IRQ routing
2718 or for PCI scanning.
2719 use_crs [X86] Use PCI host bridge window information
2720 from ACPI. On BIOSes from 2008 or later, this
2721 is enabled by default. If you need to use this,
2722 please report a bug.
2723 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2724 If you need to use this, please report a bug.
2725 routeirq Do IRQ routing for all PCI devices.
2726 This is normally done in pci_enable_device(),
2727 so this option is a temporary workaround
2728 for broken drivers that don't call it.
2729 skip_isa_align [X86] do not align io start addr, so can
2730 handle more pci cards
2731 firmware [ARM] Do not re-enumerate the bus but instead
2732 just use the configuration from the
2733 bootloader. This is currently used on
2734 IXP2000 systems where the bus has to be
2735 configured a certain way for adjunct CPUs.
2736 noearly [X86] Don't do any early type 1 scanning.
2737 This might help on some broken boards which
2738 machine check when some devices' config space
2739 is read. But various workarounds are disabled
2740 and some IOMMU drivers will not work.
2741 bfsort Sort PCI devices into breadth-first order.
2742 This sorting is done to get a device
2743 order compatible with older (<= 2.4) kernels.
2744 nobfsort Don't sort PCI devices into breadth-first order.
2745 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2746 tuning and use the BIOS-configured MPS defaults.
2747 pcie_bus_safe Set every device's MPS to the largest value
2748 supported by all devices below the root complex.
2749 pcie_bus_perf Set device MPS to the largest allowable MPS
2750 based on its parent bus. Also set MRRS (Max
2751 Read Request Size) to the largest supported
2752 value (no larger than the MPS that the device
2753 or bus can support) for best performance.
2754 pcie_bus_peer2peer Set every device's MPS to 128B, which
2755 every device is guaranteed to support. This
2756 configuration allows peer-to-peer DMA between
2757 any pair of devices, possibly at the cost of
2758 reduced performance. This also guarantees
2759 that hot-added devices will work.
2760 cbiosize=nn[KMG] The fixed amount of bus space which is
2761 reserved for the CardBus bridge's IO window.
2762 The default value is 256 bytes.
2763 cbmemsize=nn[KMG] The fixed amount of bus space which is
2764 reserved for the CardBus bridge's memory
2765 window. The default value is 64 megabytes.
2768 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2769 Specifies alignment and device to reassign
2770 aligned memory resources.
2771 If <order of align> is not specified,
2772 PAGE_SIZE is used as alignment.
2773 PCI-PCI bridge can be specified, if resource
2774 windows need to be expanded.
2775 ecrc= Enable/disable PCIe ECRC (transaction layer
2776 end-to-end CRC checking).
2777 bios: Use BIOS/firmware settings. This is the
2781 hpiosize=nn[KMG] The fixed amount of bus space which is
2782 reserved for hotplug bridge's IO window.
2783 Default size is 256 bytes.
2784 hpmemsize=nn[KMG] The fixed amount of bus space which is
2785 reserved for hotplug bridge's memory window.
2786 Default size is 2 megabytes.
2787 realloc= Enable/disable reallocating PCI bridge resources
2788 if allocations done by BIOS are too small to
2789 accommodate resources required by all child
2791 off: Turn realloc off
2793 realloc same as realloc=on
2794 noari do not use PCIe ARI.
2795 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2796 only look for one device below a PCIe downstream
2799 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2802 force Enable ASPM even on devices that claim not to support it.
2803 WARNING: Forcing ASPM on may cause system lockups.
2805 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2806 nomsi Do not use MSI for PCI Express Native Hotplug (this
2807 makes all PCIe ports use INTx for hotplug services).
2809 pcie_ports= [PCIE] PCIe ports handling:
2810 auto Ask the BIOS whether or not to use native PCIe services
2811 associated with PCIe ports (PME, hot-plug, AER). Use
2812 them only if that is allowed by the BIOS.
2813 native Use native PCIe services associated with PCIe ports
2815 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2818 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2819 nomsi Do not use MSI for native PCIe PME signaling (this makes
2820 all PCIe root ports use INTx for all services).
2822 pcmv= [HW,PCMCIA] BadgePAD 4
2826 Keep all power-domains already enabled by bootloader on,
2827 even if no driver has claimed them. This is useful
2828 for debug and development, but should not be
2829 needed on a platform with proper driver support.
2832 See Documentation/blockdev/paride.txt.
2834 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2837 See arch/parisc/kernel/pdc_chassis.c
2839 percpu_alloc= Select which percpu first chunk allocator to use.
2840 Currently supported values are "embed" and "page".
2841 Archs may support subset or none of the selections.
2842 See comments in mm/percpu.c for details on each
2843 allocator. This parameter is primarily for debugging
2844 and performance comparison.
2847 See Documentation/blockdev/paride.txt.
2850 See Documentation/blockdev/paride.txt.
2852 pirq= [SMP,APIC] Manual mp-table setup
2853 See Documentation/x86/i386/IO-APIC.txt.
2855 plip= [PPT,NET] Parallel port network link
2856 Format: { parport<nr> | timid | 0 }
2857 See also Documentation/parport.txt.
2859 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2860 Override pmtimer IOPort with a hex value.
2864 Enable PNP debug messages (depends on the
2865 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2866 via /sys/module/pnp/parameters/debug. We always show
2867 current resource usage; turning this on also shows
2868 possible settings and some assignment information.
2874 { on | off | curr | res | no-curr | no-res }
2877 [ISAPNP] Exclude IRQs for the autoconfiguration
2880 [ISAPNP] Exclude DMAs for the autoconfiguration
2882 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2883 Ranges are in pairs (I/O port base and size).
2886 [ISAPNP] Exclude memory regions for the
2888 Ranges are in pairs (memory base and size).
2890 ports= [IP_VS_FTP] IPVS ftp helper module
2892 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2894 Format: <port>,<port>....
2896 print-fatal-signals=
2897 [KNL] debug: print fatal signals
2899 If enabled, warn about various signal handling
2900 related application anomalies: too many signals,
2901 too many POSIX.1 timers, fatal signals causing a
2904 If you hit the warning due to signal overflow,
2905 you might want to try "ulimit -i unlimited".
2909 printk.always_kmsg_dump=
2910 Trigger kmsg_dump for cases other than kernel oops or
2912 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2915 printk.time= Show timing data prefixed to each printk message line
2916 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2918 processor.max_cstate= [HW,ACPI]
2919 Limit processor to maximum C-state
2920 max_cstate=9 overrides any DMI blacklist limit.
2922 processor.nocst [HW,ACPI]
2923 Ignore the _CST method to determine C-states,
2924 instead using the legacy FADT method
2926 profile= [KNL] Enable kernel profiling via /proc/profile
2927 Format: [schedule,]<number>
2928 Param: "schedule" - profile schedule points.
2929 Param: <number> - step/bucket size as a power of 2 for
2930 statistical time based profiling.
2931 Param: "sleep" - profile D-state sleeping (millisecs).
2932 Requires CONFIG_SCHEDSTATS
2933 Param: "kvm" - profile VM exits.
2935 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2937 See Documentation/blockdev/ramdisk.txt.
2939 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2940 probe for; one of (bare|imps|exps|lifebook|any).
2941 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2943 psmouse.resetafter= [HW,MOUSE]
2944 Try to reset the device after so many bad packets
2947 [HW,MOUSE] Set desired mouse resolution, in dpi.
2948 psmouse.smartscroll=
2949 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2950 0 = disabled, 1 = enabled (default).
2952 pstore.backend= Specify the name of the pstore backend to use
2955 See Documentation/blockdev/paride.txt.
2958 [KNL] Number of legacy pty's. Overwrites compiled-in
2961 quiet [KNL] Disable most log messages
2966 See Documentation/md.txt.
2968 ramdisk_blocksize= [RAM]
2969 See Documentation/blockdev/ramdisk.txt.
2971 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2972 See Documentation/blockdev/ramdisk.txt.
2975 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2976 the specified list of CPUs to be no-callback CPUs.
2977 Invocation of these CPUs' RCU callbacks will
2978 be offloaded to "rcuox/N" kthreads created for
2979 that purpose, where "x" is "b" for RCU-bh, "p"
2980 for RCU-preempt, and "s" for RCU-sched, and "N"
2981 is the CPU number. This reduces OS jitter on the
2982 offloaded CPUs, which can be useful for HPC and
2983 real-time workloads. It can also improve energy
2984 efficiency for asymmetric multiprocessors.
2987 Rather than requiring that offloaded CPUs
2988 (specified by rcu_nocbs= above) explicitly
2989 awaken the corresponding "rcuoN" kthreads,
2990 make these kthreads poll for callbacks.
2991 This improves the real-time response for the
2992 offloaded CPUs by relieving them of the need to
2993 wake up the corresponding kthread, but degrades
2994 energy efficiency by requiring that the kthreads
2995 periodically wake up to do the polling.
2997 rcutree.blimit= [KNL]
2998 Set maximum number of finished RCU callbacks to
2999 process in one batch.
3001 rcutree.gp_init_delay= [KNL]
3002 Set the number of jiffies to delay each step of
3003 RCU grace-period initialization. This only has
3004 effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT is
3007 rcutree.rcu_fanout_leaf= [KNL]
3008 Increase the number of CPUs assigned to each
3009 leaf rcu_node structure. Useful for very large
3012 rcutree.jiffies_till_sched_qs= [KNL]
3013 Set required age in jiffies for a
3014 given grace period before RCU starts
3015 soliciting quiescent-state help from
3016 rcu_note_context_switch().
3018 rcutree.jiffies_till_first_fqs= [KNL]
3019 Set delay from grace-period initialization to
3020 first attempt to force quiescent states.
3021 Units are jiffies, minimum value is zero,
3022 and maximum value is HZ.
3024 rcutree.jiffies_till_next_fqs= [KNL]
3025 Set delay between subsequent attempts to force
3026 quiescent states. Units are jiffies, minimum
3027 value is one, and maximum value is HZ.
3029 rcutree.kthread_prio= [KNL,BOOT]
3030 Set the SCHED_FIFO priority of the RCU per-CPU
3031 kthreads (rcuc/N). This value is also used for
3032 the priority of the RCU boost threads (rcub/N)
3033 and for the RCU grace-period kthreads (rcu_bh,
3034 rcu_preempt, and rcu_sched). If RCU_BOOST is
3035 set, valid values are 1-99 and the default is 1
3036 (the least-favored priority). Otherwise, when
3037 RCU_BOOST is not set, valid values are 0-99 and
3038 the default is zero (non-realtime operation).
3040 rcutree.rcu_nocb_leader_stride= [KNL]
3041 Set the number of NOCB kthread groups, which
3042 defaults to the square root of the number of
3043 CPUs. Larger numbers reduces the wakeup overhead
3044 on the per-CPU grace-period kthreads, but increases
3045 that same overhead on each group's leader.
3047 rcutree.qhimark= [KNL]
3048 Set threshold of queued RCU callbacks beyond which
3049 batch limiting is disabled.
3051 rcutree.qlowmark= [KNL]
3052 Set threshold of queued RCU callbacks below which
3053 batch limiting is re-enabled.
3055 rcutree.rcu_idle_gp_delay= [KNL]
3056 Set wakeup interval for idle CPUs that have
3057 RCU callbacks (RCU_FAST_NO_HZ=y).
3059 rcutree.rcu_idle_lazy_gp_delay= [KNL]
3060 Set wakeup interval for idle CPUs that have
3061 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3062 Lazy RCU callbacks are those which RCU can
3063 prove do nothing more than free memory.
3065 rcutorture.cbflood_inter_holdoff= [KNL]
3066 Set holdoff time (jiffies) between successive
3067 callback-flood tests.
3069 rcutorture.cbflood_intra_holdoff= [KNL]
3070 Set holdoff time (jiffies) between successive
3071 bursts of callbacks within a given callback-flood
3074 rcutorture.cbflood_n_burst= [KNL]
3075 Set the number of bursts making up a given
3076 callback-flood test. Set this to zero to
3077 disable callback-flood testing.
3079 rcutorture.cbflood_n_per_burst= [KNL]
3080 Set the number of callbacks to be registered
3081 in a given burst of a callback-flood test.
3083 rcutorture.fqs_duration= [KNL]
3084 Set duration of force_quiescent_state bursts.
3086 rcutorture.fqs_holdoff= [KNL]
3087 Set holdoff time within force_quiescent_state bursts.
3089 rcutorture.fqs_stutter= [KNL]
3090 Set wait time between force_quiescent_state bursts.
3092 rcutorture.gp_exp= [KNL]
3093 Use expedited update-side primitives.
3095 rcutorture.gp_normal= [KNL]
3096 Use normal (non-expedited) update-side primitives.
3097 If both gp_exp and gp_normal are set, do both.
3098 If neither gp_exp nor gp_normal are set, still
3101 rcutorture.n_barrier_cbs= [KNL]
3102 Set callbacks/threads for rcu_barrier() testing.
3104 rcutorture.nfakewriters= [KNL]
3105 Set number of concurrent RCU writers. These just
3106 stress RCU, they don't participate in the actual
3107 test, hence the "fake".
3109 rcutorture.nreaders= [KNL]
3110 Set number of RCU readers.
3112 rcutorture.object_debug= [KNL]
3113 Enable debug-object double-call_rcu() testing.
3115 rcutorture.onoff_holdoff= [KNL]
3116 Set time (s) after boot for CPU-hotplug testing.
3118 rcutorture.onoff_interval= [KNL]
3119 Set time (s) between CPU-hotplug operations, or
3120 zero to disable CPU-hotplug testing.
3122 rcutorture.torture_runnable= [BOOT]
3123 Start rcutorture running at boot time.
3125 rcutorture.shuffle_interval= [KNL]
3126 Set task-shuffle interval (s). Shuffling tasks
3127 allows some CPUs to go into dyntick-idle mode
3128 during the rcutorture test.
3130 rcutorture.shutdown_secs= [KNL]
3131 Set time (s) after boot system shutdown. This
3132 is useful for hands-off automated testing.
3134 rcutorture.stall_cpu= [KNL]
3135 Duration of CPU stall (s) to test RCU CPU stall
3136 warnings, zero to disable.
3138 rcutorture.stall_cpu_holdoff= [KNL]
3139 Time to wait (s) after boot before inducing stall.
3141 rcutorture.stat_interval= [KNL]
3142 Time (s) between statistics printk()s.
3144 rcutorture.stutter= [KNL]
3145 Time (s) to stutter testing, for example, specifying
3146 five seconds causes the test to run for five seconds,
3147 wait for five seconds, and so on. This tests RCU's
3148 ability to transition abruptly to and from idle.
3150 rcutorture.test_boost= [KNL]
3151 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
3152 "Maybe" means test if the RCU implementation
3153 under test support RCU priority boosting.
3155 rcutorture.test_boost_duration= [KNL]
3156 Duration (s) of each individual boost test.
3158 rcutorture.test_boost_interval= [KNL]
3159 Interval (s) between each boost test.
3161 rcutorture.test_no_idle_hz= [KNL]
3162 Test RCU's dyntick-idle handling. See also the
3163 rcutorture.shuffle_interval parameter.
3165 rcutorture.torture_type= [KNL]
3166 Specify the RCU implementation to test.
3168 rcutorture.verbose= [KNL]
3169 Enable additional printk() statements.
3171 rcupdate.rcu_expedited= [KNL]
3172 Use expedited grace-period primitives, for
3173 example, synchronize_rcu_expedited() instead
3174 of synchronize_rcu(). This reduces latency,
3175 but can increase CPU utilization, degrade
3176 real-time latency, and degrade energy efficiency.
3178 rcupdate.rcu_cpu_stall_suppress= [KNL]
3179 Suppress RCU CPU stall warning messages.
3181 rcupdate.rcu_cpu_stall_timeout= [KNL]
3182 Set timeout for RCU CPU stall warning messages.
3184 rcupdate.rcu_task_stall_timeout= [KNL]
3185 Set timeout in jiffies for RCU task stall warning
3186 messages. Disable with a value less than or equal
3189 rcupdate.rcu_self_test= [KNL]
3190 Run the RCU early boot self tests
3192 rcupdate.rcu_self_test_bh= [KNL]
3193 Run the RCU bh early boot self tests
3195 rcupdate.rcu_self_test_sched= [KNL]
3196 Run the RCU sched early boot self tests
3200 Run specified binary instead of /init from the ramdisk,
3201 used for early userspace startup. See initrd.
3204 Format (x86 or x86_64):
3205 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3207 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3209 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3210 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3211 reboot_force is either force or not specified,
3212 reboot_cpu is s[mp]#### with #### being the processor
3213 to be used for rebooting.
3216 [KNL, SMP] Set scheduler's default relax_domain_level.
3217 See Documentation/cgroups/cpusets.txt.
3219 relative_sleep_states=
3220 [SUSPEND] Use sleep state labeling where the deepest
3221 state available other than hibernation is always "mem".
3222 Format: { "0" | "1" }
3223 0 -- Traditional sleep state labels.
3224 1 -- Relative sleep state labels.
3226 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
3228 reservetop= [X86-32]
3230 Reserves a hole at the top of the kernel virtual
3235 Set the amount of memory to reserve for BIOS at
3236 the bottom of the address space.
3238 reset_devices [KNL] Force drivers to reset the underlying device
3239 during initialization.
3242 Specify the partition device for software suspend
3244 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3246 resume_offset= [SWSUSP]
3247 Specify the offset from the beginning of the partition
3248 given by "resume=" at which the swap header is located,
3249 in <PAGE_SIZE> units (needed only for swap files).
3250 See Documentation/power/swsusp-and-swap-files.txt
3252 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
3253 read the resume files
3255 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
3256 Useful for devices that are detected asynchronously
3257 (e.g. USB and MMC devices).
3259 hibernate= [HIBERNATION]
3260 noresume Don't check if there's a hibernation image
3261 present during boot.
3262 nocompress Don't compress/decompress hibernation images.
3263 no Disable hibernation and resume.
3265 retain_initrd [RAM] Keep initrd memory after extraction
3267 rfkill.default_state=
3268 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
3269 etc. communication is blocked by default.
3272 rfkill.master_switch_mode=
3273 0 The "airplane mode" button does nothing.
3274 1 The "airplane mode" button toggles between everything
3275 blocked and the previous configuration.
3276 2 The "airplane mode" button toggles between everything
3277 blocked and everything unblocked.
3279 rhash_entries= [KNL,NET]
3280 Set number of hash buckets for route cache
3282 ro [KNL] Mount root device read-only on boot
3284 root= [KNL] Root filesystem
3285 See name_to_dev_t comment in init/do_mounts.c.
3287 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
3288 mount the root filesystem
3290 rootflags= [KNL] Set root filesystem mount option string
3292 rootfstype= [KNL] Set root filesystem type
3294 rootwait [KNL] Wait (indefinitely) for root device to show up.
3295 Useful for devices that are detected asynchronously
3296 (e.g. USB and MMC devices).
3298 rproc_mem=nn[KMG][@address]
3299 [KNL,ARM,CMA] Remoteproc physical memory block.
3300 Memory area to be used by remote processor image,
3303 rw [KNL] Mount root device read-write on boot
3305 S [KNL] Run init in single mode
3307 s390_iommu= [HW,S390]
3308 Set s390 IOTLB flushing mode
3310 With strict flushing every unmap operation will result in
3311 an IOTLB flush. Default is lazy flushing before reuse,
3315 See drivers/net/irda/sa1100_ir.c.
3317 sbni= [NET] Granch SBNI12 leased line adapter
3319 sched_debug [KNL] Enables verbose scheduler debug messages.
3321 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3322 xtime_lock contention on larger systems, and/or RCU lock
3323 contention on all systems with CONFIG_MAXSMP set.
3324 Format: { "0" | "1" }
3325 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3327 Note: increases power consumption, thus should only be
3328 enabled if running jitter sensitive (HPC/RT) workloads.
3330 security= [SECURITY] Choose a security module to enable at boot.
3331 If this boot parameter is not specified, only the first
3332 security module asking for security registration will be
3333 loaded. An invalid security module name will be treated
3334 as if no module has been chosen.
3336 selinux= [SELINUX] Disable or enable SELinux at boot time.
3337 Format: { "0" | "1" }
3338 See security/selinux/Kconfig help text.
3341 Default value is set via kernel config option.
3342 If enabled at boot time, /selinux/disable can be used
3343 later to disable prior to initial policy load.
3345 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3346 Format: { "0" | "1" }
3347 See security/apparmor/Kconfig help text
3350 Default value is set via kernel config option.
3352 serialnumber [BUGS=X86-32]
3355 Maximal number of shapers.
3357 show_msr= [x86] show boot-time MSR settings
3358 Format: { <integer> }
3359 Show boot-time (BIOS-initialized) MSR settings.
3360 The parameter means the number of CPUs to show,
3361 for example 1 means boot CPU only.
3369 Disable merging of slabs with similar size. May be
3370 necessary if there is some reason to distinguish
3371 allocs to different slabs. Debug options disable
3372 merging on their own.
3373 For more information see Documentation/vm/slub.txt.
3375 slab_max_order= [MM, SLAB]
3376 Determines the maximum allowed order for slabs.
3377 A high setting may cause OOMs due to memory
3378 fragmentation. Defaults to 1 for systems with
3379 more than 32MB of RAM, 0 otherwise.
3381 slub_debug[=options[,slabs]] [MM, SLUB]
3382 Enabling slub_debug allows one to determine the
3383 culprit if slab objects become corrupted. Enabling
3384 slub_debug can create guard zones around objects and
3385 may poison objects when not in use. Also tracks the
3386 last alloc / free. For more information see
3387 Documentation/vm/slub.txt.
3389 slub_max_order= [MM, SLUB]
3390 Determines the maximum allowed order for slabs.
3391 A high setting may cause OOMs due to memory
3392 fragmentation. For more information see
3393 Documentation/vm/slub.txt.
3395 slub_min_objects= [MM, SLUB]
3396 The minimum number of objects per slab. SLUB will
3397 increase the slab order up to slub_max_order to
3398 generate a sufficiently large slab able to contain
3399 the number of objects indicated. The higher the number
3400 of objects the smaller the overhead of tracking slabs
3401 and the less frequently locks need to be acquired.
3402 For more information see Documentation/vm/slub.txt.
3404 slub_min_order= [MM, SLUB]
3405 Determines the minimum page order for slabs. Must be
3406 lower than slub_max_order.
3407 For more information see Documentation/vm/slub.txt.
3409 slub_nomerge [MM, SLUB]
3410 Same with slab_nomerge. This is supported for legacy.
3411 See slab_nomerge for more information.
3414 Format: <io1>[,<io2>[,...,<io8>]]
3416 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3417 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3418 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3419 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3420 smsc-ircc2.ircc_irq= [HW] IRQ line
3421 smsc-ircc2.ircc_dma= [HW] DMA channel
3422 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3423 0: Toshiba Satellite 1800 (GP data pin select)
3424 1: Fast pin select (default)
3428 [KNL] Should the soft-lockup detector generate panics.
3431 softlockup_all_cpu_backtrace=
3432 [KNL] Should the soft-lockup detector generate
3433 backtraces on all cpus.
3436 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3437 See Documentation/laptops/sonypi.txt
3439 spia_io_base= [HW,MTD]
3445 Enabled the stack tracer on boot up.
3447 stacktrace_filter=[function-list]
3448 [FTRACE] Limit the functions that the stack tracer
3449 will trace at boot up. function-list is a comma separated
3450 list of functions. This list can be changed at run
3451 time by the stack_trace_filter file in the debugfs
3452 tracing directory. Note, this enables stack tracing
3453 and the stacktrace above is not needed.
3457 Set the STI (builtin display/keyboard on the HP-PARISC
3458 machines) console (graphic card) which should be used
3459 as the initial boot-console.
3460 See also comment in drivers/video/console/sticore.c.
3463 See comment in drivers/video/console/sticore.c.
3466 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3468 sunrpc.min_resvport=
3469 sunrpc.max_resvport=
3471 SunRPC servers often require that client requests
3472 originate from a privileged port (i.e. a port in the
3473 range 0 < portnr < 1024).
3474 An administrator who wishes to reserve some of these
3475 ports for other uses may adjust the range that the
3476 kernel's sunrpc client considers to be privileged
3477 using these two parameters to set the minimum and
3478 maximum port values.
3482 Control how the NFS server code allocates CPUs to
3483 service thread pools. Depending on how many NICs
3484 you have and where their interrupts are bound, this
3485 option will affect which CPUs will do NFS serving.
3486 Note: this parameter cannot be changed while the
3487 NFS server is running.
3489 auto the server chooses an appropriate mode
3490 automatically using heuristics
3491 global a single global pool contains all CPUs
3492 percpu one pool for each CPU
3493 pernode one pool for each NUMA node (equivalent
3494 to global on non-NUMA machines)
3496 sunrpc.tcp_slot_table_entries=
3497 sunrpc.udp_slot_table_entries=
3499 Sets the upper limit on the number of simultaneous
3500 RPC calls that can be sent from the client to a
3501 server. Increasing these values may allow you to
3502 improve throughput, but will also increase the
3503 amount of memory reserved for use by the client.
3505 suspend.pm_test_delay=
3507 Sets the number of seconds to remain in a suspend test
3508 mode before resuming the system (see
3509 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3510 is set. Default value is 5.
3513 [KNL] Enable accounting of swap in memory resource
3514 controller if no parameter or 1 is given or disable
3515 it if 0 is given (See Documentation/cgroups/memory.txt)
3517 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3518 Format: { <int> | force }
3519 <int> -- Number of I/O TLB slabs
3520 force -- force using of bounce buffers even if they
3521 wouldn't be automatically used by the kernel
3525 sysfs.deprecated=0|1 [KNL]
3526 Enable/disable old style sysfs layout for old udev
3527 on older distributions. When this option is enabled
3528 very new udev will not work anymore. When this option
3529 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3530 in older udev will not work anymore.
3531 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3532 the kernel configuration.
3534 sysrq_always_enabled
3536 Ignore sysrq setting - this boot parameter will
3537 neutralize any effect of /proc/sys/kernel/sysrq.
3538 Useful for debugging.
3540 tcpmhash_entries= [KNL,NET]
3541 Set the number of tcp_metrics_hash slots.
3542 Default value is 8192 or 16384 depending on total
3543 ram pages. This is used to specify the TCP metrics
3544 cache size. See Documentation/networking/ip-sysctl.txt
3545 "tcp_no_metrics_save" section for more details.
3549 test_suspend= [SUSPEND][,N]
3550 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3551 standby suspend) or "freeze" (for suspend type freeze)
3552 as the system sleep state during system startup with
3553 the optional capability to repeat N number of times.
3554 The system is woken from this state using a
3555 wakeup-capable RTC alarm.
3557 thash_entries= [KNL,NET]
3558 Set number of hash buckets for TCP connection
3560 thermal.act= [HW,ACPI]
3561 -1: disable all active trip points in all thermal zones
3562 <degrees C>: override all lowest active trip points
3564 thermal.crt= [HW,ACPI]
3565 -1: disable all critical trip points in all thermal zones
3566 <degrees C>: override all critical trip points
3568 thermal.nocrt= [HW,ACPI]
3569 Set to disable actions on ACPI thermal zone
3570 critical and hot trip points.
3572 thermal.off= [HW,ACPI]
3573 1: disable ACPI thermal control
3575 thermal.psv= [HW,ACPI]
3576 -1: disable all passive trip points
3577 <degrees C>: override all passive trip points to this
3580 thermal.tzp= [HW,ACPI]
3581 Specify global default ACPI thermal zone polling rate
3582 <deci-seconds>: poll all this frequency
3583 0: no polling (default)
3586 Force threading of all interrupt handlers except those
3587 marked explicitly IRQF_NO_THREAD.
3590 Enable the Transcendent memory driver if built-in.
3592 tmem.cleancache=0|1 [KNL, XEN]
3593 Default is on (1). Disable the usage of the cleancache
3594 API to send anonymous pages to the hypervisor.
3596 tmem.frontswap=0|1 [KNL, XEN]
3597 Default is on (1). Disable the usage of the frontswap
3598 API to send swap pages to the hypervisor. If disabled
3599 the selfballooning and selfshrinking are force disabled.
3601 tmem.selfballooning=0|1 [KNL, XEN]
3602 Default is on (1). Disable the driving of swap pages
3605 tmem.selfshrinking=0|1 [KNL, XEN]
3606 Default is on (1). Partial swapoff that immediately
3607 transfers pages from Xen hypervisor back to the
3608 kernel based on different criteria.
3612 Specify if the kernel should make use of the cpu
3613 topology information if the hardware supports this.
3614 The scheduler will make use of this information and
3615 e.g. base its process migration decisions on it.
3618 topology_updates= [KNL, PPC, NUMA]
3620 Specify if the kernel should ignore (off)
3621 topology updates sent by the hypervisor to this
3626 tpm_suspend_pcr=[HW,TPM]
3627 Format: integer pcr id
3628 Specify that at suspend time, the tpm driver
3629 should extend the specified pcr with zeros,
3630 as a workaround for some chips which fail to
3631 flush the last written pcr on TPM_SaveState.
3632 This will guarantee that all the other pcrs
3635 trace_buf_size=nn[KMG]
3636 [FTRACE] will set tracing buffer size on each cpu.
3638 trace_event=[event-list]
3639 [FTRACE] Set and start specified trace events in order
3640 to facilitate early boot debugging.
3641 See also Documentation/trace/events.txt
3643 trace_options=[option-list]
3644 [FTRACE] Enable or disable tracer options at boot.
3645 The option-list is a comma delimited list of options
3646 that can be enabled or disabled just as if you were
3647 to echo the option name into
3649 /sys/kernel/debug/tracing/trace_options
3651 For example, to enable stacktrace option (to dump the
3652 stack trace of each event), add to the command line:
3654 trace_options=stacktrace
3656 See also Documentation/trace/ftrace.txt "trace options"
3660 Have the tracepoints sent to printk as well as the
3661 tracing ring buffer. This is useful for early boot up
3662 where the system hangs or reboots and does not give the
3663 option for reading the tracing buffer or performing a
3664 ftrace_dump_on_oops.
3666 To turn off having tracepoints sent to printk,
3667 echo 0 > /proc/sys/kernel/tracepoint_printk
3668 Note, echoing 1 into this file without the
3669 tracepoint_printk kernel cmdline option has no effect.
3673 Having tracepoints sent to printk() and activating high
3674 frequency tracepoints such as irq or sched, can cause
3675 the system to live lock.
3678 [FTRACE] enable this option to disable tracing when a
3679 warning is hit. This turns off "tracing_on". Tracing can
3680 be enabled again by echoing '1' into the "tracing_on"
3681 file located in /sys/kernel/debug/tracing/
3683 This option is useful, as it disables the trace before
3684 the WARNING dump is called, which prevents the trace to
3685 be filled with content caused by the warning output.
3687 This option can also be set at run time via the sysctl
3688 option: kernel/traceoff_on_warning
3690 transparent_hugepage=
3692 Format: [always|madvise|never]
3693 Can be used to control the default behavior of the system
3694 with respect to transparent hugepages.
3695 See Documentation/vm/transhuge.txt for more details.
3697 tsc= Disable clocksource stability checks for TSC.
3699 [x86] reliable: mark tsc clocksource as reliable, this
3700 disables clocksource verification at runtime, as well
3701 as the stability checks done at bootup. Used to enable
3702 high-resolution timer mode on older hardware, and in
3703 virtualized environment.
3704 [x86] noirqtime: Do not use TSC to do irq accounting.
3705 Used to run time disable IRQ_TIME_ACCOUNTING on any
3706 platforms where RDTSC is slow and this accounting
3709 turbografx.map[2|3]= [HW,JOY]
3710 TurboGraFX parallel port interface
3712 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3713 See also Documentation/input/joystick-parport.txt
3715 udbg-immortal [PPC] When debugging early kernel crashes that
3716 happen after console_init() and before a proper
3717 console driver takes over, this boot options might
3718 help "seeing" what's going on.
3720 uhash_entries= [KNL,NET]
3721 Set number of hash buckets for UDP/UDP-Lite connections
3724 [USB] Ignore overcurrent events (default N).
3725 Some badly-designed motherboards generate lots of
3726 bogus events, for ports that aren't wired to
3727 anything. Set this parameter to avoid log spamming.
3728 Note that genuine overcurrent events won't be
3732 [X86] Cause panic on unknown NMI.
3734 usbcore.authorized_default=
3735 [USB] Default USB device authorization:
3736 (default -1 = authorized except for wireless USB,
3737 0 = not authorized, 1 = authorized)
3739 usbcore.autosuspend=
3740 [USB] The autosuspend time delay (in seconds) used
3741 for newly-detected USB devices (default 2). This
3742 is the time required before an idle device will be
3743 autosuspended. Devices for which the delay is set
3744 to a negative value won't be autosuspended at all.
3746 usbcore.usbfs_snoop=
3747 [USB] Set to log all usbfs traffic (default 0 = off).
3749 usbcore.blinkenlights=
3750 [USB] Set to cycle leds on hubs (default 0 = off).
3752 usbcore.old_scheme_first=
3753 [USB] Start with the old device initialization
3754 scheme (default 0 = off).
3756 usbcore.usbfs_memory_mb=
3757 [USB] Memory limit (in MB) for buffers allocated by
3758 usbfs (default = 16, 0 = max = 2047).
3760 usbcore.use_both_schemes=
3761 [USB] Try the other device initialization scheme
3762 if the first one fails (default 1 = enabled).
3764 usbcore.initial_descriptor_timeout=
3765 [USB] Specifies timeout for the initial 64-byte
3766 USB_REQ_GET_DESCRIPTOR request in milliseconds
3767 (default 5000 = 5.0 seconds).
3770 [USBHID] The interval which mice are to be polled at.
3772 usb-storage.delay_use=
3773 [UMS] The delay in seconds before a new device is
3774 scanned for Logical Units (default 1).
3777 [UMS] A list of quirks entries to supplement or
3778 override the built-in unusual_devs list. List
3779 entries are separated by commas. Each entry has
3780 the form VID:PID:Flags where VID and PID are Vendor
3781 and Product ID values (4-digit hex numbers) and
3782 Flags is a set of characters, each corresponding
3783 to a common usb-storage quirk flag as follows:
3784 a = SANE_SENSE (collect more than 18 bytes
3786 b = BAD_SENSE (don't collect more than 18
3787 bytes of sense data);
3788 c = FIX_CAPACITY (decrease the reported
3789 device capacity by one sector);
3790 d = NO_READ_DISC_INFO (don't use
3791 READ_DISC_INFO command);
3792 e = NO_READ_CAPACITY_16 (don't use
3793 READ_CAPACITY_16 command);
3794 f = NO_REPORT_OPCODES (don't use report opcodes
3796 h = CAPACITY_HEURISTICS (decrease the
3797 reported device capacity by one
3798 sector if the number is odd);
3799 i = IGNORE_DEVICE (don't bind to this
3801 l = NOT_LOCKABLE (don't try to lock and
3802 unlock ejectable media);
3803 m = MAX_SECTORS_64 (don't transfer more
3804 than 64 sectors = 32 KB at a time);
3805 n = INITIAL_READ10 (force a retry of the
3806 initial READ(10) command);
3807 o = CAPACITY_OK (accept the capacity
3808 reported by the device);
3809 p = WRITE_CACHE (the device cache is ON
3811 r = IGNORE_RESIDUE (the device reports
3812 bogus residue values);
3813 s = SINGLE_LUN (the device has only one
3815 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3816 commands, uas only);
3817 u = IGNORE_UAS (don't bind to the uas driver);
3818 w = NO_WP_DETECT (don't test whether the
3819 medium is write-protected).
3820 Example: quirks=0419:aaf5:rl,0421:0433:rc
3822 user_debug= [KNL,ARM]
3824 See arch/arm/Kconfig.debug help text.
3825 1 - undefined instruction events
3827 4 - invalid data aborts
3830 Example: user_debug=31
3833 [X86] Flags controlling user PTE allocations.
3835 nohigh = do not allocate PTE pages in
3836 HIGHMEM regardless of setting
3840 On X86_32, this is an alias for vdso32=. Otherwise:
3842 vdso=1: enable VDSO (the default)
3843 vdso=0: disable VDSO mapping
3845 vdso32= [X86] Control the 32-bit vDSO
3846 vdso32=1: enable 32-bit VDSO
3847 vdso32=0 or vdso32=2: disable 32-bit VDSO
3849 See the help text for CONFIG_COMPAT_VDSO for more
3850 details. If CONFIG_COMPAT_VDSO is set, the default is
3851 vdso32=0; otherwise, the default is vdso32=1.
3853 For compatibility with older kernels, vdso32=2 is an
3856 Try vdso32=0 if you encounter an error that says:
3857 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3860 vector=percpu: enable percpu vector domain
3862 video= [FB] Frame buffer configuration
3863 See Documentation/fb/modedb.txt.
3865 video.brightness_switch_enabled= [0,1]
3866 If set to 1, on receiving an ACPI notify event
3867 generated by hotkey, video driver will adjust brightness
3868 level and then send out the event to user space through
3869 the allocated input device; If set to 0, video driver
3870 will only send out the event without touching backlight
3875 [VMMIO] Memory mapped virtio (platform) device.
3877 <size>@<baseaddr>:<irq>[:<id>]
3879 <size> := size (can use standard suffixes
3881 <baseaddr> := physical base address
3882 <irq> := interrupt number (as passed to
3884 <id> := (optional) platform device id
3886 virtio_mmio.device=1K@0x100b0000:48:7
3888 Can be used multiple times for multiple devices.
3890 vga= [BOOT,X86-32] Select a particular video mode
3891 See Documentation/x86/boot.txt and
3892 Documentation/svga.txt.
3893 Use vga=ask for menu.
3894 This is actually a boot loader parameter; the value is
3895 passed to the kernel using a special protocol.
3897 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3898 size of <nn>. This can be used to increase the
3899 minimum size (128MB on x86). It can also be used to
3900 decrease the size and leave more room for directly
3903 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3906 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3909 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3913 Controls the behavior of vsyscalls (i.e. calls to
3914 fixed addresses of 0xffffffffff600x00 from legacy
3915 code). Most statically-linked binaries and older
3916 versions of glibc use these calls. Because these
3917 functions are at fixed addresses, they make nice
3918 targets for exploits that can control RIP.
3920 emulate [default] Vsyscalls turn into traps and are
3921 emulated reasonably safely.
3923 native Vsyscalls are native syscall instructions.
3924 This is a little bit faster than trapping
3925 and makes a few dynamic recompilers work
3926 better than they would in emulation mode.
3927 It also makes exploits much easier to write.
3929 none Vsyscalls don't work at all. This makes
3930 them quite hard to use for exploits but
3931 might break your system.
3933 vt.color= [VT] Default text color.
3934 Format: 0xYX, X = foreground, Y = background.
3935 Default: 0x07 = light gray on black.
3937 vt.cur_default= [VT] Default cursor shape.
3938 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3939 the parameters of the <Esc>[?A;B;Cc escape sequence;
3940 see VGA-softcursor.txt. Default: 2 = underline.
3942 vt.default_blu= [VT]
3943 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3944 Change the default blue palette of the console.
3945 This is a 16-member array composed of values
3948 vt.default_grn= [VT]
3949 Format: <green0>,<green1>,<green2>,...,<green15>
3950 Change the default green palette of the console.
3951 This is a 16-member array composed of values
3954 vt.default_red= [VT]
3955 Format: <red0>,<red1>,<red2>,...,<red15>
3956 Change the default red palette of the console.
3957 This is a 16-member array composed of values
3963 Set system-wide default UTF-8 mode for all tty's.
3964 Default is 1, i.e. UTF-8 mode is enabled for all
3965 newly opened terminals.
3967 vt.global_cursor_default=
3970 Set system-wide default for whether a cursor
3971 is shown on new VTs. Default is -1,
3972 i.e. cursors will be created by default unless
3973 overridden by individual drivers. 0 will hide
3974 cursors, 1 will display them.
3976 vt.italic= [VT] Default color for italic text; 0-15.
3979 vt.underline= [VT] Default color for underlined text; 0-15.
3982 watchdog timers [HW,WDT] For information on watchdog timers,
3983 see Documentation/watchdog/watchdog-parameters.txt
3984 or other driver-specific files in the
3985 Documentation/watchdog/ directory.
3987 workqueue.disable_numa
3988 By default, all work items queued to unbound
3989 workqueues are affine to the NUMA nodes they're
3990 issued on, which results in better behavior in
3991 general. If NUMA affinity needs to be disabled for
3992 whatever reason, this option can be used. Note
3993 that this also can be controlled per-workqueue for
3994 workqueues visible under /sys/bus/workqueue/.
3996 workqueue.power_efficient
3997 Per-cpu workqueues are generally preferred because
3998 they show better performance thanks to cache
3999 locality; unfortunately, per-cpu workqueues tend to
4000 be more power hungry than unbound workqueues.
4002 Enabling this makes the per-cpu workqueues which
4003 were observed to contribute significantly to power
4004 consumption unbound, leading to measurably lower
4005 power usage at the cost of small performance
4008 The default value of this parameter is determined by
4009 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4011 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
4012 default x2apic cluster mode on platforms
4015 x86_intel_mid_timer= [X86-32,APBT]
4016 Choose timer option for x86 Intel MID platform.
4017 Two valid options are apbt timer only and lapic timer
4018 plus one apbt timer for broadcast timer.
4019 x86_intel_mid_timer=apbt_only | lapic_and_apbt
4021 xen_emul_unplug= [HW,X86,XEN]
4022 Unplug Xen emulated devices
4023 Format: [unplug0,][unplug1]
4024 ide-disks -- unplug primary master IDE devices
4025 aux-ide-disks -- unplug non-primary-master IDE devices
4026 nics -- unplug network devices
4027 all -- unplug all emulated devices (NICs and IDE disks)
4028 unnecessary -- unplugging emulated devices is
4029 unnecessary even if the host did not respond to
4031 never -- do not unplug even if version check succeeds
4033 xen_nopvspin [X86,XEN]
4034 Disables the ticketlock slowpath using Xen PV
4038 Disables the PV optimizations forcing the HVM guest to
4039 run as generic HVM guest with no PV drivers.
4041 xirc2ps_cs= [NET,PCMCIA]
4043 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4045 ______________________________________________________________________
4049 Add more DRM drivers.
git.samba.org / sfrench / cifs-2.6.git / blob