4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 CLK Common clock infrastructure is enabled.
48 CMA Contiguous Memory Area support is enabled.
49 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
51 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
52 EFI EFI Partitioning (GPT) is enabled
53 EIDE EIDE/ATAPI support is enabled.
54 EVM Extended Verification Module
55 FB The frame buffer device is enabled.
56 FTRACE Function tracing enabled.
57 GCOV GCOV profiling is enabled.
58 HW Appropriate hardware is enabled.
59 IA-64 IA-64 architecture is enabled.
60 IMA Integrity measurement architecture is enabled.
61 IOSCHED More than one I/O scheduler is enabled.
62 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
63 IPV6 IPv6 support is enabled.
64 ISAPNP ISA PnP code is enabled.
65 ISDN Appropriate ISDN support is enabled.
66 JOY Appropriate joystick support is enabled.
67 KGDB Kernel debugger support is enabled.
68 KVM Kernel Virtual Machine support is enabled.
69 LIBATA Libata driver is enabled
70 LP Printer support is enabled.
71 LOOP Loopback device support is enabled.
72 M68k M68k architecture is enabled.
73 These options have more detailed description inside of
74 Documentation/m68k/kernel-options.txt.
75 MDA MDA console support is enabled.
76 MIPS MIPS architecture is enabled.
77 MOUSE Appropriate mouse support is enabled.
78 MSI Message Signaled Interrupts (PCI).
79 MTD MTD (Memory Technology Device) support is enabled.
80 NET Appropriate network support is enabled.
81 NUMA NUMA support is enabled.
82 NFS Appropriate NFS support is enabled.
83 OSS OSS sound support is enabled.
84 PV_OPS A paravirtualized kernel is enabled.
85 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
86 PARISC The PA-RISC architecture is enabled.
87 PCI PCI bus support is enabled.
88 PCIE PCI Express support is enabled.
89 PCMCIA The PCMCIA subsystem is enabled.
90 PNP Plug & Play support is enabled.
91 PPC PowerPC architecture is enabled.
92 PPT Parallel port support is enabled.
93 PS2 Appropriate PS/2 support is enabled.
94 RAM RAM disk support is enabled.
95 S390 S390 architecture is enabled.
96 SCSI Appropriate SCSI support is enabled.
97 A lot of drivers have their options described inside
98 the Documentation/scsi/ sub-directory.
99 SECURITY Different security models are enabled.
100 SELINUX SELinux support is enabled.
101 APPARMOR AppArmor support is enabled.
102 SERIAL Serial support is enabled.
103 SH SuperH architecture is enabled.
104 SMP The kernel is an SMP kernel.
105 SPARC Sparc architecture is enabled.
106 SWSUSP Software suspend (hibernation) is enabled.
107 SUSPEND System suspend states are enabled.
108 TPM TPM drivers are enabled.
109 TS Appropriate touchscreen support is enabled.
110 UMS USB Mass Storage support is enabled.
111 USB USB support is enabled.
112 USBHID USB Human Interface Device support is enabled.
113 V4L Video For Linux support is enabled.
114 VMMIO Driver for memory mapped virtio devices is enabled.
115 VGA The VGA console has been enabled.
116 VT Virtual terminal support is enabled.
117 WDT Watchdog support is enabled.
118 XT IBM PC/XT MFM hard disk support is enabled.
119 X86-32 X86-32, aka i386 architecture is enabled.
120 X86-64 X86-64 architecture is enabled.
121 More X86-64 boot options can be found in
122 Documentation/x86/x86_64/boot-options.txt .
123 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
124 XEN Xen support is enabled
126 In addition, the following text indicates that the option:
128 BUGS= Relates to possible processor bugs on the said processor.
129 KNL Is a kernel start-up parameter.
130 BOOT Is a boot loader parameter.
132 Parameters denoted with BOOT are actually interpreted by the boot
133 loader, and have no meaning to the kernel directly.
134 Do not modify the syntax of boot loader parameters without extreme
135 need or coordination with <Documentation/x86/boot.txt>.
137 There are also arch-specific kernel-parameters not documented here.
138 See for example <Documentation/x86/x86_64/boot-options.txt>.
140 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
141 a trailing = on the name of any parameter states that that parameter will
142 be entered as an environment variable, whereas its absence indicates that
143 it will appear as a kernel argument readable via /proc/cmdline by programs
144 running once the system is up.
146 The number of kernel parameters is not limited, but the length of the
147 complete command line (parameters including spaces etc.) is limited to
148 a fixed number of characters. This limit depends on the architecture
149 and is between 256 and 4096 characters. It is defined in the file
150 ./include/asm/setup.h as COMMAND_LINE_SIZE.
152 Finally, the [KMG] suffix is commonly described after a number of kernel
153 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
154 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
155 bytes respectively. Such letter suffixes can also be entirely omitted.
159 Advanced Configuration and Power Interface
160 Format: { force | off | strict | noirq | rsdt }
161 force -- enable ACPI if default was off
162 off -- disable ACPI if default was on
163 noirq -- do not use ACPI for IRQ routing
164 strict -- Be less tolerant of platforms that are not
165 strictly ACPI specification compliant.
166 rsdt -- prefer RSDT over (default) XSDT
167 copy_dsdt -- copy DSDT to memory
169 See also Documentation/power/runtime_pm.txt, pci=noacpi
171 acpi_rsdp= [ACPI,EFI,KEXEC]
172 Pass the RSDP address to the kernel, mostly used
173 on machines running EFI runtime service to boot the
174 second kernel for kdump.
176 acpi_apic_instance= [ACPI, IOAPIC]
178 2: use 2nd APIC table, if available
179 1,0: use 1st APIC table
182 acpi_backlight= [HW,ACPI]
183 acpi_backlight=vendor
185 If set to vendor, prefer vendor specific driver
186 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
187 of the ACPI video.ko driver.
189 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
190 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
192 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
193 debug output. Bits in debug_layer correspond to a
194 _COMPONENT in an ACPI source file, e.g.,
195 #define _COMPONENT ACPI_PCI_COMPONENT
196 Bits in debug_level correspond to a level in
197 ACPI_DEBUG_PRINT statements, e.g.,
198 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
199 The debug_level mask defaults to "info". See
200 Documentation/acpi/debug.txt for more information about
201 debug layers and levels.
203 Enable processor driver info messages:
204 acpi.debug_layer=0x20000000
205 Enable PCI/PCI interrupt routing info messages:
206 acpi.debug_layer=0x400000
207 Enable AML "Debug" output, i.e., stores to the Debug
208 object while interpreting AML:
209 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
210 Enable all messages related to ACPI hardware:
211 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
213 Some values produce so much output that the system is
214 unusable. The "log_buf_len" parameter may be useful
215 if you need to capture more output.
217 acpi_force_table_verification [HW,ACPI]
218 Enable table checksum verification during early stage.
219 By default, this is disabled due to x86 early mapping
222 acpi_irq_balance [HW,ACPI]
223 ACPI will balance active IRQs
226 acpi_irq_nobalance [HW,ACPI]
227 ACPI will not move active IRQs (default)
230 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
231 Format: <irq>,<irq>...
233 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
235 Format: <irq>,<irq>...
237 acpi_no_auto_serialize [HW,ACPI]
238 Disable auto-serialization of AML methods
239 AML control methods that contain the opcodes to create
240 named objects will be marked as "Serialized" by the
241 auto-serialization feature.
242 This feature is enabled by default.
243 This option allows to turn off the feature.
245 acpi_no_static_ssdt [HW,ACPI]
246 Disable installation of static SSDTs at early boot time
247 By default, SSDTs contained in the RSDT/XSDT will be
248 installed automatically and they will appear under
249 /sys/firmware/acpi/tables.
250 This option turns off this feature.
251 Note that specifying this option does not affect
252 dynamic table installation which will install SSDT
253 tables to /sys/firmware/acpi/tables/dynamic.
255 acpica_no_return_repair [HW, ACPI]
256 Disable AML predefined validation mechanism
257 This mechanism can repair the evaluation result to make
258 the return objects more ACPI specification compliant.
259 This option is useful for developers to identify the
260 root cause of an AML interpreter issue when the issue
261 has something to do with the repair mechanism.
263 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
264 Format: To spoof as Windows 98: ="Microsoft Windows"
266 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
267 acpi_osi="string1" # add string1
268 acpi_osi="!string2" # remove string2
269 acpi_osi=!* # remove all strings
270 acpi_osi=! # disable all built-in OS vendor
272 acpi_osi= # disable all strings
274 'acpi_osi=!' can be used in combination with single or
275 multiple 'acpi_osi="string1"' to support specific OS
276 vendor string(s). Note that such command can only
277 affect the default state of the OS vendor strings, thus
278 it cannot affect the default state of the feature group
279 strings and the current state of the OS vendor strings,
280 specifying it multiple times through kernel command line
281 is meaningless. This command is useful when one do not
282 care about the state of the feature group strings which
283 should be controlled by the OSPM.
285 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
286 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
287 can make '_OSI("Windows 2000")' TRUE.
289 'acpi_osi=' cannot be used in combination with other
290 'acpi_osi=' command lines, the _OSI method will not
291 exist in the ACPI namespace. NOTE that such command can
292 only affect the _OSI support state, thus specifying it
293 multiple times through kernel command line is also
296 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
299 'acpi_osi=!*' can be used in combination with single or
300 multiple 'acpi_osi="string1"' to support specific
301 string(s). Note that such command can affect the
302 current state of both the OS vendor strings and the
303 feature group strings, thus specifying it multiple times
304 through kernel command line is meaningful. But it may
305 still not able to affect the final state of a string if
306 there are quirks related to this string. This command
307 is useful when one want to control the state of the
308 feature group strings to debug BIOS issues related to
311 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
312 '_OSI("Module Device")' FALSE.
313 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
314 '_OSI("Module Device")' TRUE.
315 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
317 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
319 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
320 they all will make '_OSI("Windows 2000")' TRUE.
323 Override the pmtimer bug detection: force the kernel
324 to assume that this machine's pmtimer latches its value
325 and always returns good values.
327 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
328 Format: { level | edge | high | low }
330 acpi_skip_timer_override [HW,ACPI]
331 Recognize and ignore IRQ0/pin2 Interrupt Override.
332 For broken nForce2 BIOS resulting in XT-PIC timer.
334 acpi_sleep= [HW,ACPI] Sleep options
335 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
336 old_ordering, nonvs, sci_force_enable }
337 See Documentation/power/video.txt for information on
339 s3_beep is for debugging; it makes the PC's speaker beep
340 as soon as the kernel's real-mode entry point is called.
341 s4_nohwsig prevents ACPI hardware signature from being
342 used during resume from hibernation.
343 old_ordering causes the ACPI 1.0 ordering of the _PTS
344 control method, with respect to putting devices into
345 low power states, to be enforced (the ACPI 2.0 ordering
346 of _PTS is used by default).
347 nonvs prevents the kernel from saving/restoring the
348 ACPI NVS memory during suspend/hibernation and resume.
349 sci_force_enable causes the kernel to set SCI_EN directly
350 on resume from S1/S3 (which is against the ACPI spec,
351 but some broken systems don't work without it).
353 acpi_use_timer_override [HW,ACPI]
354 Use timer override. For some broken Nvidia NF5 boards
355 that require a timer override, but don't have HPET
357 acpi_enforce_resources= [ACPI]
358 { strict | lax | no }
359 Check for resource conflicts between native drivers
360 and ACPI OperationRegions (SystemIO and SystemMemory
361 only). IO ports and memory declared in ACPI might be
362 used by the ACPI subsystem in arbitrary AML code and
363 can interfere with legacy drivers.
364 strict (default): access to resources claimed by ACPI
365 is denied; legacy drivers trying to access reserved
366 resources will fail to bind to device using them.
367 lax: access to resources claimed by ACPI is allowed;
368 legacy drivers trying to access reserved resources
369 will bind successfully but a warning message is logged.
370 no: ACPI OperationRegions are not marked as reserved,
371 no further checks are performed.
373 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
376 add_efi_memmap [EFI; X86] Include EFI memory map in
377 kernel's map of available physical RAM.
380 { off | try_unsupported }
381 off: disable AGP support
382 try_unsupported: try to drive unsupported chipsets
383 (may crash computer or cause data corruption)
386 See Documentation/sound/alsa/alsa-parameters.txt
389 Allow the default userspace alignment fault handler
390 behaviour to be specified. Bit 0 enables warnings,
391 bit 1 enables fixups, and bit 2 sends a segfault.
393 align_va_addr= [X86-64]
394 Align virtual addresses by clearing slice [14:12] when
395 allocating a VMA at process creation time. This option
396 gives you up to 3% performance improvement on AMD F15h
397 machines (where it is enabled by default) for a
398 CPU-intensive style benchmark, and it can vary highly in
399 a microbenchmark depending on workload and compiler.
401 32: only for 32-bit processes
402 64: only for 64-bit processes
403 on: enable for both 32- and 64-bit processes
404 off: disable for both 32- and 64-bit processes
406 alloc_snapshot [FTRACE]
407 Allocate the ftrace snapshot buffer on boot up when the
408 main buffer is allocated. This is handy if debugging
409 and you need to use tracing_snapshot() on boot up, and
410 do not want to use tracing_snapshot_alloc() as it needs
411 to be done where GFP_KERNEL allocations are allowed.
413 amd_iommu= [HW,X86-64]
414 Pass parameters to the AMD IOMMU driver in the system.
416 fullflush - enable flushing of IO/TLB entries when
417 they are unmapped. Otherwise they are
418 flushed before they will be reused, which
420 off - do not initialize any AMD IOMMU found in
422 force_isolation - Force device isolation for all
423 devices. The IOMMU driver is not
424 allowed anymore to lift isolation
425 requirements as needed. This option
426 does not override iommu=pt
428 amd_iommu_dump= [HW,X86-64]
429 Enable AMD IOMMU driver option to dump the ACPI table
430 for AMD IOMMU. With this option enabled, AMD IOMMU
431 driver will print ACPI tables for AMD IOMMU during
432 IOMMU initialization.
434 amijoy.map= [HW,JOY] Amiga joystick support
435 Map of devices attached to JOY0DAT and JOY1DAT
437 See also Documentation/input/joystick.txt
439 analog.map= [HW,JOY] Analog joystick and gamepad support
440 Specifies type or capabilities of an analog joystick
441 connected to one of 16 gameports
442 Format: <type1>,<type2>,..<type16>
445 Power management functions (SPARCstation-4/5 + deriv.)
447 Disable APC CPU standby support. SPARCstation-Fox does
448 not play well with APC CPU idle - disable it if you have
449 APC and your system crashes randomly.
451 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
452 Change the output verbosity whilst booting
453 Format: { quiet (default) | verbose | debug }
454 Change the amount of debugging information output
455 when initialising the APIC and IO-APIC components.
458 See Documentation/networking/ipv6.txt.
460 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
461 Limit apic dumping. The parameter defines the maximal
462 number of local apics being dumped. Also it is possible
463 to set it to "all" by meaning -- no limit here.
464 Format: { 1 (default) | 2 | ... | all }.
465 The parameter valid if only apic=debug or
466 apic=verbose is specified.
467 Example: apic=debug show_lapic=all
469 apm= [APM] Advanced Power Management
470 See header of arch/x86/kernel/apm_32.c.
472 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
473 Format: <io>,<irq>,<nodeID>
477 atarimouse= [HW,MOUSE] Atari Mouse
479 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
480 EzKey and similar keyboards
482 atkbd.reset= [HW] Reset keyboard during initialization
484 atkbd.set= [HW] Select keyboard code set
485 Format: <int> (2 = AT (default), 3 = PS/2)
487 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
490 atkbd.softraw= [HW] Choose between synthetic and real raw mode
491 Format: <bool> (0 = real, 1 = synthetic (default))
493 atkbd.softrepeat= [HW]
494 Use software keyboard repeat
496 audit= [KNL] Enable the audit sub-system
497 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
498 0 - kernel audit is disabled and can not be enabled
499 until the next reboot
500 unset - kernel audit is initialized but disabled and
501 will be fully enabled by the userspace auditd.
502 1 - kernel audit is initialized and partially enabled,
503 storing at most audit_backlog_limit messages in
504 RAM until it is fully enabled by the userspace
508 audit_backlog_limit= [KNL] Set the audit queue size limit.
509 Format: <int> (must be >=0)
512 baycom_epp= [HW,AX25]
515 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
517 See header of drivers/net/hamradio/baycom_par.c.
519 baycom_ser_fdx= [HW,AX25]
520 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
521 Format: <io>,<irq>,<mode>[,<baud>]
522 See header of drivers/net/hamradio/baycom_ser_fdx.c.
524 baycom_ser_hdx= [HW,AX25]
525 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
526 Format: <io>,<irq>,<mode>
527 See header of drivers/net/hamradio/baycom_ser_hdx.c.
529 blkdevparts= Manual partition parsing of block device(s) for
530 embedded devices based on command line input.
531 See Documentation/block/cmdline-partition.txt
533 boot_delay= Milliseconds to delay each printk during boot.
534 Values larger than 10 seconds (10000) are changed to
538 bootmem_debug [KNL] Enable bootmem allocator debug messages.
540 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
541 bttv.radio= Most important insmod options are available as
543 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
546 bulk_remove=off [PPC] This parameter disables the use of the pSeries
547 firmware feature for flushing multiple hpte entries
550 c101= [NET] Moxa C101 synchronous serial card
552 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
553 Sometimes CPU hardware bugs make them report the cache
554 size incorrectly. The kernel will attempt work arounds
555 to fix known problems, but for some CPUs it is not
556 possible to determine what the correct size should be.
557 This option provides an override for these situations.
559 ccw_timeout_log [S390]
560 See Documentation/s390/CommonIO for details.
562 cgroup_disable= [KNL] Disable a particular controller
563 Format: {name of the controller(s) to disable}
564 The effects of cgroup_disable=foo are:
565 - foo isn't auto-mounted if you mount all cgroups in
567 - foo isn't visible as an individually mountable
569 {Currently only "memory" controller deal with this and
570 cut the overhead, others just disable the usage. So
571 only cgroup_disable=memory is actually worthy}
573 checkreqprot [SELINUX] Set initial checkreqprot flag value.
574 Format: { "0" | "1" }
575 See security/selinux/Kconfig help text.
576 0 -- check protection applied by kernel (includes
577 any implied execute protection).
578 1 -- check protection requested by application.
579 Default value is set via a kernel config option.
580 Value can be changed at runtime via
581 /selinux/checkreqprot.
584 See Documentation/s390/CommonIO for details.
587 Keep all clocks already enabled by bootloader on,
588 even if no driver has claimed them. This is useful
589 for debug and development, but should not be
590 needed on a platform with proper driver support.
591 For more information, see Documentation/clk.txt.
593 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
595 Forces specified clocksource (if available) to be used
596 when calculating gettimeofday(). If specified
597 clocksource is not available, it defaults to PIT.
598 Format: { pit | tsc | cyclone | pmtmr }
600 clocksource= Override the default clocksource
602 Override the default clocksource and use the clocksource
603 with the name specified.
604 Some clocksource names to choose from, depending on
606 [all] jiffies (this is the base, fallback clocksource)
608 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
609 pxa_timer,timer3,32k_counter,timer0_1
611 [X86-32] pit,hpet,tsc;
612 scx200_hrt on Geode; cyclone on IBM x440
620 clearcpuid=BITNUM [X86]
621 Disable CPUID feature X for the kernel. See
622 arch/x86/include/asm/cpufeature.h for the valid bit
623 numbers. Note the Linux specific bits are not necessarily
624 stable over kernel options, but the vendor specific
626 Also note that user programs calling CPUID directly
627 or using the feature without checking anything
628 will still see it. This just prevents it from
629 being used by the kernel or shown in /proc/cpuinfo.
630 Also note the kernel might malfunction if you disable
633 cma=nn[MG]@[start[MG][-end[MG]]]
635 Sets the size of kernel global memory area for
636 contiguous memory allocations and optionally the
637 placement constraint by the physical address range of
638 memory allocations. For more information, see
639 include/linux/dma-contiguous.h
641 cmo_free_hint= [PPC] Format: { yes | no }
642 Specify whether pages are marked as being inactive
643 when they are freed. This is used in CMO environments
644 to determine OS memory pressure for page stealing by
648 coherent_pool=nn[KMG] [ARM,KNL]
649 Sets the size of memory pool for coherent, atomic dma
650 allocations, by default set to 256K.
652 code_bytes [X86] How many bytes of object code to print
657 com20020= [HW,NET] ARCnet - COM20020 chipset
659 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
661 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
665 ARCnet - COM90xx chipset (memory-mapped buffers)
666 Format: <io>[,<irq>[,<memstart>]]
668 condev= [HW,S390] console device
671 console= [KNL] Output console device and options.
673 tty<n> Use the virtual console device <n>.
677 Use the specified serial port. The options are of
678 the form "bbbbpnf", where "bbbb" is the baud rate,
679 "p" is parity ("n", "o", or "e"), "n" is number of
680 bits, and "f" is flow control ("r" for RTS or
681 omit it). Default is "9600n8".
683 See Documentation/serial-console.txt for more
685 Documentation/networking/netconsole.txt for an
688 uart[8250],io,<addr>[,options]
689 uart[8250],mmio,<addr>[,options]
690 Start an early, polled-mode console on the 8250/16550
691 UART at the specified I/O port or MMIO address,
692 switching to the matching ttyS device later. The
693 options are the same as for ttyS, above.
694 hvc<n> Use the hypervisor console device <n>. This is for
695 both Xen and PowerPC hypervisors.
697 If the device connected to the port is not a TTY but a braille
698 device, prepend "brl," before the device type, for instance
700 For now, only VisioBraille is supported.
702 consoleblank= [KNL] The console blank (screen saver) timeout in
703 seconds. Defaults to 10*60 = 10mins. A value of 0
704 disables the blank timer.
707 [KNL] Change the default value for
708 /proc/<pid>/coredump_filter.
709 See also Documentation/filesystems/proc.txt.
711 cpuidle.off=1 [CPU_IDLE]
712 disable the cpuidle sub-system
714 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
716 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
718 crashkernel=size[KMG][@offset[KMG]]
719 [KNL] Using kexec, Linux can switch to a 'crash kernel'
720 upon panic. This parameter reserves the physical
721 memory region [offset, offset + size] for that kernel
722 image. If '@offset' is omitted, then a suitable offset
723 is selected automatically. Check
724 Documentation/kdump/kdump.txt for further details.
726 crashkernel=range1:size1[,range2:size2,...][@offset]
727 [KNL] Same as above, but depends on the memory
728 in the running system. The syntax of range is
729 start-[end] where start and end are both
730 a memory unit (amount[KMG]). See also
731 Documentation/kdump/kdump.txt for an example.
733 crashkernel=size[KMG],high
734 [KNL, x86_64] range could be above 4G. Allow kernel
735 to allocate physical memory region from top, so could
736 be above 4G if system have more than 4G ram installed.
737 Otherwise memory region will be allocated below 4G, if
739 It will be ignored if crashkernel=X is specified.
740 crashkernel=size[KMG],low
741 [KNL, x86_64] range under 4G. When crashkernel=X,high
742 is passed, kernel could allocate physical memory region
743 above 4G, that cause second kernel crash on system
744 that require some amount of low memory, e.g. swiotlb
745 requires at least 64M+32K low memory. Kernel would
746 try to allocate 72M below 4G automatically.
747 This one let user to specify own low range under 4G
748 for second kernel instead.
749 0: to disable low allocation.
750 It will be ignored when crashkernel=X,high is not used
751 or memory reserved is below 4G.
756 cs89x0_media= [HW,NET]
757 Format: { rj45 | aui | bnc }
760 See header of drivers/s390/block/dasd_devmap.c.
762 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
763 (one device per port)
764 Format: <port#>,<type>
765 See also Documentation/input/joystick-parport.txt
767 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
768 time. See Documentation/dynamic-debug-howto.txt for
769 details. Deprecated, see dyndbg.
771 debug [KNL] Enable kernel debugging (events log level).
774 [KNL] verbose self-tests
776 Print debugging info while doing the locking API
778 We default to 0 (no extra messages), setting it to
779 1 will print _a lot_ more information - normally
780 only useful to kernel developers.
782 debug_objects [KNL] Enable object debugging
785 [KNL] Disable object debugging
787 debug_guardpage_minorder=
788 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
789 parameter allows control of the order of pages that will
790 be intentionally kept free (and hence protected) by the
791 buddy allocator. Bigger value increase the probability
792 of catching random memory corruption, but reduce the
793 amount of memory for normal system use. The maximum
794 possible value is MAX_ORDER/2. Setting this parameter
795 to 1 or 2 should be enough to identify most random
796 memory corruption problems caused by bugs in kernel or
797 driver code when a CPU writes to (or reads from) a
798 random memory location. Note that there exists a class
799 of memory corruptions problems caused by buggy H/W or
800 F/W or by drivers badly programing DMA (basically when
801 memory is written at bus level and the CPU MMU is
802 bypassed) which are not detectable by
803 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
804 tracking down these problems.
806 debugpat [X86] Enable PAT debugging
808 decnet.addr= [HW,NET]
809 Format: <area>[,<node>]
810 See also Documentation/networking/decnet.txt.
813 [same as hugepagesz=] The size of the default
814 HugeTLB page size. This is the size represented by
815 the legacy /proc/ hugepages APIs, used for SHM, and
816 default size when mounting hugetlbfs filesystems.
817 Defaults to the default architecture's huge page size
821 Set number of hash buckets for dentry cache.
824 See Documentation/networking/ipv6.txt.
826 disable_cpu_apicid= [X86,APIC,SMP]
828 The number of initial APIC ID for the
829 corresponding CPU to be disabled at boot,
830 mostly used for the kdump 2nd kernel to
831 disable BSP to wake up multiple CPUs without
832 causing system reset or hang due to sending
835 disable_ddw [PPC/PSERIES]
836 Disable Dynamic DMA Window support. Use this if
837 to workaround buggy firmware.
840 See Documentation/networking/ipv6.txt.
842 disable_mtrr_cleanup [X86]
843 The kernel tries to adjust MTRR layout from continuous
844 to discrete, to make X server driver able to add WB
845 entry later. This parameter disables that.
847 disable_mtrr_trim [X86, Intel and AMD only]
848 By default the kernel will trim any uncacheable
849 memory out of your available memory pool based on
850 MTRR settings. This parameter disables that behavior,
851 possibly causing your machine to run very slowly.
853 disable_timer_pin_1 [X86]
854 Disable PIN 1 of APIC timer
855 Can be useful to work around chipset bugs.
857 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
858 this option disables the debugging code at boot.
860 dma_debug_entries=<number>
861 This option allows to tune the number of preallocated
862 entries for DMA-API debugging code. One entry is
863 required per DMA-API allocation. Use this if the
864 DMA-API debugging code disables itself because the
865 architectural default is too low.
867 dma_debug_driver=<driver_name>
868 With this option the DMA-API debugging driver
869 filter feature can be enabled at boot time. Just
870 pass the driver to filter for as the parameter.
871 The filter can be disabled or changed to another
872 driver later using sysfs.
874 drm_kms_helper.edid_firmware=[<connector>:]<file>
875 Broken monitors, graphic adapters and KVMs may
876 send no or incorrect EDID data sets. This parameter
877 allows to specify an EDID data set in the
878 /lib/firmware directory that is used instead.
879 Generic built-in EDID data sets are used, if one of
880 edid/1024x768.bin, edid/1280x1024.bin,
881 edid/1680x1050.bin, or edid/1920x1080.bin is given
882 and no file with the same name exists. Details and
883 instructions how to build your own EDID data are
884 available in Documentation/EDID/HOWTO.txt. An EDID
885 data set will only be used for a particular connector,
886 if its name and a colon are prepended to the EDID
891 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
892 module.dyndbg[="val"]
893 Enable debug messages at boot time. See
894 Documentation/dynamic-debug-howto.txt for details.
896 early_ioremap_debug [KNL]
897 Enable debug messages in early_ioremap support. This
898 is useful for tracking down temporary early mappings
899 which are not unmapped.
901 earlycon= [KNL] Output early console device and options.
903 uart[8250],io,<addr>[,options]
904 uart[8250],mmio,<addr>[,options]
905 uart[8250],mmio32,<addr>[,options]
906 Start an early, polled-mode console on the 8250/16550
907 UART at the specified I/O port or MMIO address.
908 MMIO inter-register address stride is either 8-bit
909 (mmio) or 32-bit (mmio32).
910 The options are the same as for ttyS, above.
913 Start an early, polled-mode console on a pl011 serial
914 port at the specified address. The pl011 serial port
915 must already be setup and configured. Options are not
918 smh Use ARM semihosting calls for early console.
920 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
924 earlyprintk=serial[,ttySn[,baudrate]]
925 earlyprintk=serial[,0x...[,baudrate]]
926 earlyprintk=ttySn[,baudrate]
927 earlyprintk=dbgp[debugController#]
929 earlyprintk is useful when the kernel crashes before
930 the normal console is initialized. It is not enabled by
931 default because it has some cosmetic problems.
933 Append ",keep" to not disable it when the real console
936 Only one of vga, efi, serial, or usb debug port can
939 Currently only ttyS0 and ttyS1 may be specified by
940 name. Other I/O ports may be explicitly specified
941 on some architectures (x86 and arm at least) by
942 replacing ttySn with an I/O port address, like this:
943 earlyprintk=serial,0x1008,115200
944 You can find the port for a given device in
945 /proc/tty/driver/serial:
946 2: uart:ST16650V2 port:00001008 irq:18 ...
948 Interaction with the standard serial driver is not
951 The VGA and EFI output is eventually overwritten by
954 The xen output can only be used by Xen PV guests.
956 edac_report= [HW,EDAC] Control how to report EDAC event
957 Format: {"on" | "off" | "force"}
958 on: enable EDAC to report H/W event. May be overridden
959 by other higher priority error reporting module.
960 off: disable H/W event reporting through EDAC.
961 force: enforce the use of EDAC to report H/W event.
964 ekgdboc= [X86,KGDB] Allow early kernel console debugging
967 This is designed to be used in conjunction with
968 the boot argument: earlyprintk=vga
971 Format: {"off" | "on" | "skip[mbr]"}
974 Format: { "old_map" }
975 old_map [X86-64]: switch to the old ioremap-based EFI
976 runtime services mapping. 32-bit still uses this one by
979 efi_no_storage_paranoia [EFI; X86]
980 Using this parameter you can use more than 50% of
981 your efi variable storage. Use this parameter only if
982 you are really sure that your UEFI does sane gc and
983 fulfills the spec otherwise your board may brick.
985 eisa_irq_edge= [PARISC,HW]
986 See header of drivers/parisc/eisa.c.
989 See comment before function elanfreq_setup() in
990 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
993 Format: {"cfq" | "deadline" | "noop"}
994 See Documentation/block/cfq-iosched.txt and
995 Documentation/block/deadline-iosched.txt for details.
997 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
998 Specifies physical address of start of kernel core
999 image elf header and optionally the size. Generally
1000 kexec loader will pass this option to capture kernel.
1001 See Documentation/kdump/kdump.txt for details.
1003 enable_mtrr_cleanup [X86]
1004 The kernel tries to adjust MTRR layout from continuous
1005 to discrete, to make X server driver able to add WB
1006 entry later. This parameter enables that.
1008 enable_timer_pin_1 [X86]
1009 Enable PIN 1 of APIC timer
1010 Can be useful to work around chipset bugs
1011 (in particular on some ATI chipsets).
1012 The kernel tries to set a reasonable default.
1014 enforcing [SELINUX] Set initial enforcing status.
1016 See security/selinux/Kconfig help text.
1017 0 -- permissive (log only, no denials).
1018 1 -- enforcing (deny and log).
1020 Value can be changed at runtime via /selinux/enforce.
1023 Disable Error Record Serialization Table (ERST)
1026 ether= [HW,NET] Ethernet cards parameters
1027 This option is obsoleted by the "netdev=" option, which
1028 has equivalent usage. See its documentation for details.
1032 Permit 'security.evm' to be updated regardless of
1033 current integrity status.
1037 fail_make_request=[KNL]
1038 General fault injection mechanism.
1039 Format: <interval>,<probability>,<space>,<times>
1040 See also Documentation/fault-injection/.
1043 See Documentation/blockdev/floppy.txt.
1045 force_pal_cache_flush
1046 [IA-64] Avoid check_sal_cache_flush which may hang on
1047 buggy SAL_CACHE_FLUSH implementations. Using this
1048 parameter will force ia64_sal_cache_flush to call
1049 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1052 Forcefully enable Physical Address Extension (PAE).
1053 Many Pentium M systems disable PAE but may have a
1054 functionally usable PAE implementation.
1055 Warning: use of this parameter will taint the kernel
1056 and may cause unknown problems.
1059 [FTRACE] will set and start the specified tracer
1060 as early as possible in order to facilitate early
1063 ftrace_dump_on_oops[=orig_cpu]
1064 [FTRACE] will dump the trace buffers on oops.
1065 If no parameter is passed, ftrace will dump
1066 buffers of all CPUs, but if you pass orig_cpu, it will
1067 dump only the buffer of the CPU that triggered the
1070 ftrace_filter=[function-list]
1071 [FTRACE] Limit the functions traced by the function
1072 tracer at boot up. function-list is a comma separated
1073 list of functions. This list can be changed at run
1074 time by the set_ftrace_filter file in the debugfs
1077 ftrace_notrace=[function-list]
1078 [FTRACE] Do not trace the functions specified in
1079 function-list. This list can be changed at run time
1080 by the set_ftrace_notrace file in the debugfs
1083 ftrace_graph_filter=[function-list]
1084 [FTRACE] Limit the top level callers functions traced
1085 by the function graph tracer at boot up.
1086 function-list is a comma separated list of functions
1087 that can be changed at run time by the
1088 set_graph_function file in the debugfs tracing directory.
1091 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1092 support via parallel port (up to 5 devices per port)
1093 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1094 See also Documentation/input/joystick-parport.txt
1098 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1102 gcov_persist= [GCOV] When non-zero (default), profiling data for
1103 kernel modules is saved and remains accessible via
1104 debugfs, even when the module is unloaded/reloaded.
1105 When zero, profiling data is discarded and associated
1106 debugfs files are removed at module unload time.
1108 gpt [EFI] Forces disk with valid GPT signature but
1109 invalid Protective MBR to be treated as GPT. If the
1110 primary GPT is corrupted, it enables the backup/alternate
1111 GPT to be used instead.
1113 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1114 the "Enable 0" bit of the configuration register.
1117 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1118 the "Enable 0" bit of the configuration register.
1121 grcan.select= [HW] Select which physical interface to use.
1124 grcan.txsize= [HW] Sets the size of the tx buffer.
1125 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1127 grcan.rxsize= [HW] Sets the size of the rx buffer.
1128 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1131 hashdist= [KNL,NUMA] Large hashes allocated during boot
1132 are distributed across NUMA nodes. Defaults on
1133 for 64-bit NUMA, off otherwise.
1134 Format: 0 | 1 (for off | on)
1136 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1138 hd= [EIDE] (E)IDE hard drive subsystem geometry
1139 Format: <cyl>,<head>,<sect>
1142 Disable Hardware Error Source Table (HEST) support;
1143 corresponding firmware-first mode error processing
1144 logic will be disabled.
1146 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1147 size of <nn>. This works even on boxes that have no
1148 highmem otherwise. This also works to reduce highmem
1149 size on bigger boxes.
1151 highres= [KNL] Enable/disable high resolution timer mode.
1152 Valid parameters: "on", "off"
1156 See Documentation/isdn/README.HiSax.
1160 hpet= [X86-32,HPET] option to control HPET usage
1161 Format: { enable (default) | disable | force |
1163 disable: disable HPET and use PIT instead
1164 force: allow force enabled of undocumented chips (ICH4,
1166 verbose: show contents of HPET registers during setup
1168 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1169 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1171 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1172 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1173 On x86-64 and powerpc, this option can be specified
1174 multiple times interleaved with hugepages= to reserve
1175 huge pages of different sizes. Valid pages sizes on
1176 x86-64 are 2M (when the CPU supports "pse") and 1G
1177 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1178 Note that 1GB pages can only be allocated at boot time
1179 using hugepages= and not freed afterwards.
1181 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1182 terminal devices. Valid values: 0..8
1183 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1184 If specified, z/VM IUCV HVC accepts connections
1185 from listed z/VM user IDs only.
1187 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1188 hardware thread id mappings.
1189 Format: <cpu>:<hwthread>
1192 Do not unregister boot console at start. This is only
1193 useful for debugging when something happens in the window
1194 between unregistering the boot console and initializing
1197 i2c_bus= [HW] Override the default board specific I2C bus speed
1198 or register an additional I2C bus that is not
1199 registered from board initialization code.
1203 i8042.debug [HW] Toggle i8042 debug mode
1204 i8042.direct [HW] Put keyboard port into non-translated mode
1205 i8042.dumbkbd [HW] Pretend that controller can only read data from
1206 keyboard and cannot control its state
1207 (Don't attempt to blink the leds)
1208 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1209 i8042.nokbd [HW] Don't check/create keyboard port
1210 i8042.noloop [HW] Disable the AUX Loopback command while probing
1212 i8042.nomux [HW] Don't check presence of an active multiplexing
1214 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1216 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1217 i8042.reset [HW] Reset the controller during init and cleanup
1218 i8042.unlock [HW] Unlock (ignore) the keylock
1222 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1223 indicates that the driver is running on unsupported
1225 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1226 does not match list of supported models.
1228 [HW] Report power status in /proc/i8k
1229 (disabled by default)
1230 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1233 i915.invert_brightness=
1234 [DRM] Invert the sense of the variable that is used to
1235 set the brightness of the panel backlight. Normally a
1236 brightness value of 0 indicates backlight switched off,
1237 and the maximum of the brightness value sets the backlight
1238 to maximum brightness. If this parameter is set to 0
1239 (default) and the machine requires it, or this parameter
1240 is set to 1, a brightness value of 0 sets the backlight
1241 to maximum brightness, and the maximum of the brightness
1242 value switches the backlight off.
1243 -1 -- never invert brightness
1244 0 -- machine default
1245 1 -- force brightness inversion
1248 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1250 ide-core.nodma= [HW] (E)IDE subsystem
1251 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1252 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1253 .cdrom .chs .ignore_cable are additional options
1254 See Documentation/ide/ide.txt.
1256 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1257 Claim all unknown PCI IDE storage controllers.
1260 Format: idle=poll, idle=halt, idle=nomwait
1261 Poll forces a polling idle loop that can slightly
1262 improve the performance of waking up a idle CPU, but
1263 will use a lot of power and make the system run hot.
1265 idle=halt: Halt is forced to be used for CPU idle.
1266 In such case C2/C3 won't be used again.
1267 idle=nomwait: Disable mwait for CPU C-states
1269 ignore_loglevel [KNL]
1270 Ignore loglevel setting - this will print /all/
1271 kernel messages to the console. Useful for debugging.
1272 We also add it as printk module parameter, so users
1273 could change it dynamically, usually by
1274 /sys/module/printk/parameters/ignore_loglevel.
1276 ihash_entries= [KNL]
1277 Set number of hash buckets for inode cache.
1279 ima_appraise= [IMA] appraise integrity measurements
1280 Format: { "off" | "enforce" | "fix" }
1283 ima_appraise_tcb [IMA]
1284 The builtin appraise policy appraises all files
1288 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1292 The list of supported hash algorithms is defined
1293 in crypto/hash_info.h.
1296 Load a policy which meets the needs of the Trusted
1297 Computing Base. This means IMA will measure all
1298 programs exec'd, files mmap'd for exec, and all files
1299 opened for read by uid=0.
1302 Select one of defined IMA measurements template formats.
1303 Formats: { "ima" | "ima-ng" }
1308 Run specified binary instead of /sbin/init as init
1311 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1312 for working out where the kernel is dying during
1315 initcall_blacklist= [KNL] Do not execute a comma-separated list of
1316 initcall functions. Useful for debugging built-in
1317 modules and initcalls.
1319 initrd= [BOOT] Specify the location of the initial ramdisk
1321 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1324 int_pln_enable [x86] Enable power limit notification interrupt
1326 integrity_audit=[IMA]
1327 Format: { "0" | "1" }
1328 0 -- basic integrity auditing messages. (Default)
1329 1 -- additional integrity auditing messages.
1331 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1333 Enable intel iommu driver.
1335 Disable intel iommu driver.
1336 igfx_off [Default Off]
1337 By default, gfx is mapped as normal device. If a gfx
1338 device has a dedicated DMAR unit, the DMAR unit is
1339 bypassed by not enabling DMAR with this option. In
1340 this case, gfx device will use physical address for
1343 With this option iommu will not optimize to look
1344 for io virtual address below 32-bit forcing dual
1345 address cycle on pci bus for cards supporting greater
1346 than 32-bit addressing. The default is to look
1347 for translation below 32-bit and if not available
1348 then look in the higher range.
1349 strict [Default Off]
1350 With this option on every unmap_single operation will
1351 result in a hardware IOTLB flush operation as opposed
1352 to batching them for performance.
1353 sp_off [Default Off]
1354 By default, super page will be supported if Intel IOMMU
1355 has the capability. With this option, super page will
1358 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1359 0 disables intel_idle and fall back on acpi_idle.
1360 1 to 6 specify maximum depth of C-state.
1364 Do not enable intel_pstate as the default
1365 scaling driver for the supported processors
1367 intremap= [X86-64, Intel-IOMMU]
1368 on enable Interrupt Remapping (default)
1369 off disable Interrupt Remapping
1370 nosid disable Source ID checking
1372 BIOS x2APIC opt-out request will be ignored
1374 iomem= Disable strict checking of access to MMIO memory
1375 strict regions from userspace.
1392 io7= [HW] IO7 for Marvel based alpha systems
1393 See comment before marvel_specify_io7 in
1394 arch/alpha/kernel/core_marvel.c.
1396 io_delay= [X86] I/O delay method
1398 Standard port 0x80 based delay
1400 Alternate port 0xed based delay (needed on some systems)
1402 Simple two microseconds delay
1407 See Documentation/filesystems/nfs/nfsroot.txt.
1409 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1410 See comment before ip2_setup() in
1411 drivers/char/ip2/ip2base.c.
1414 When an interrupt is not handled search all handlers
1415 for it. Intended to get systems with badly broken
1419 When an interrupt is not handled search all handlers
1420 for it. Also check all handlers each timer
1421 interrupt. Intended to get systems with badly broken
1425 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1427 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1429 <cpu number>,...,<cpu number>
1431 <cpu number>-<cpu number>
1432 (must be a positive range in ascending order)
1434 <cpu number>,...,<cpu number>-<cpu number>
1436 This option can be used to specify one or more CPUs
1437 to isolate from the general SMP balancing and scheduling
1438 algorithms. You can move a process onto or off an
1439 "isolated" CPU via the CPU affinity syscalls or cpuset.
1440 <cpu number> begins at 0 and the maximum value is
1441 "number of CPUs in system - 1".
1443 This option is the preferred way to isolate CPUs. The
1444 alternative -- manually setting the CPU mask of all
1445 tasks in the system -- can cause problems and
1446 suboptimal load balancer performance.
1450 ivrs_ioapic [HW,X86_64]
1451 Provide an override to the IOAPIC-ID<->DEVICE-ID
1452 mapping provided in the IVRS ACPI table. For
1453 example, to map IOAPIC-ID decimal 10 to
1454 PCI device 00:14.0 write the parameter as:
1455 ivrs_ioapic[10]=00:14.0
1457 ivrs_hpet [HW,X86_64]
1458 Provide an override to the HPET-ID<->DEVICE-ID
1459 mapping provided in the IVRS ACPI table. For
1460 example, to map HPET-ID decimal 0 to
1461 PCI device 00:14.0 write the parameter as:
1462 ivrs_hpet[0]=00:14.0
1464 js= [HW,JOY] Analog joystick
1465 See Documentation/input/joystick.txt.
1469 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1470 specifies the amount of memory usable by the kernel
1471 for non-movable allocations. The requested amount is
1472 spread evenly throughout all nodes in the system. The
1473 remaining memory in each node is used for Movable
1474 pages. In the event, a node is too small to have both
1475 kernelcore and Movable pages, kernelcore pages will
1476 take priority and other nodes will have a larger number
1477 of Movable pages. The Movable zone is used for the
1478 allocation of pages that may be reclaimed or moved
1479 by the page migration subsystem. This means that
1480 HugeTLB pages may not be allocated from this zone.
1481 Note that allocations like PTEs-from-HighMem still
1482 use the HighMem zone if it exists, and the Normal
1483 zone if it does not.
1485 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1486 Format: <Controller#>[,poll interval]
1487 The controller # is the number of the ehci usb debug
1488 port as it is probed via PCI. The poll interval is
1489 optional and is the number seconds in between
1490 each poll cycle to the debug port in case you need
1491 the functionality for interrupting the kernel with
1492 gdb or control-c on the dbgp connection. When
1493 not using this parameter you use sysrq-g to break into
1494 the kernel debugger.
1496 kgdboc= [KGDB,HW] kgdb over consoles.
1497 Requires a tty driver that supports console polling,
1498 or a supported polling keyboard driver (non-usb).
1499 Serial only format: <serial_device>[,baud]
1500 keyboard only format: kbd
1501 keyboard and serial format: kbd,<serial_device>[,baud]
1502 Optional Kernel mode setting:
1503 kms, kbd format: kms,kbd
1504 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1506 kgdbwait [KGDB] Stop kernel execution and enter the
1507 kernel debugger at the earliest opportunity.
1509 kmac= [MIPS] korina ethernet MAC address.
1510 Configure the RouterBoard 532 series on-chip
1511 Ethernet adapter MAC address.
1513 kmemleak= [KNL] Boot-time kmemleak enable/disable
1514 Valid arguments: on, off
1517 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1518 Valid arguments: 0, 1, 2
1519 kmemcheck=0 (disabled)
1520 kmemcheck=1 (enabled)
1521 kmemcheck=2 (one-shot mode)
1522 Default: 2 (one-shot mode)
1524 kstack=N [X86] Print N words from the kernel stack
1527 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1528 Default is 0 (don't ignore, but inject #GP)
1530 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1534 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1535 Default is 1 (enabled)
1537 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1539 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1541 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1542 (virtualized MMU) support on capable Intel chips.
1543 Default is 1 (enabled)
1545 kvm-intel.emulate_invalid_guest_state=
1546 [KVM,Intel] Enable emulation of invalid guest states
1547 Default is 0 (disabled)
1549 kvm-intel.flexpriority=
1550 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1551 Default is 1 (enabled)
1554 [KVM,Intel] Enable VMX nesting (nVMX).
1555 Default is 0 (disabled)
1557 kvm-intel.unrestricted_guest=
1558 [KVM,Intel] Disable unrestricted guest feature
1559 (virtualized real and unpaged mode) on capable
1560 Intel chips. Default is 1 (enabled)
1562 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1563 feature (tagged TLBs) on capable Intel chips.
1564 Default is 1 (enabled)
1570 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1573 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1574 value for LAPIC timer one-shot implementation. Default
1575 back to the programmable timer unit in the LAPIC.
1577 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1580 libata.dma= [LIBATA] DMA control
1581 libata.dma=0 Disable all PATA and SATA DMA
1582 libata.dma=1 PATA and SATA Disk DMA only
1583 libata.dma=2 ATAPI (CDROM) DMA only
1584 libata.dma=4 Compact Flash DMA only
1585 Combinations also work, so libata.dma=3 enables DMA
1586 for disks and CDROMs, but not CFs.
1588 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1589 libata.ignore_hpa=0 keep BIOS limits (default)
1590 libata.ignore_hpa=1 ignore limits, using full disk
1592 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1596 libata.force= [LIBATA] Force configurations. The format is comma
1597 separated list of "[ID:]VAL" where ID is
1598 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1599 matching port, link or device. Basically, it matches
1600 the ATA ID string printed on console by libata. If
1601 the whole ID part is omitted, the last PORT and DEVICE
1602 values are used. If ID hasn't been specified yet, the
1603 configuration applies to all ports, links and devices.
1605 If only DEVICE is omitted, the parameter applies to
1606 the port and all links and devices behind it. DEVICE
1607 number of 0 either selects the first device or the
1608 first fan-out link behind PMP device. It does not
1609 select the host link. DEVICE number of 15 selects the
1610 host link and device attached to it.
1612 The VAL specifies the configuration to force. As long
1613 as there's no ambiguity shortcut notation is allowed.
1614 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1615 The following configurations can be forced.
1617 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1618 Any ID with matching PORT is used.
1620 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1622 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1623 udma[/][16,25,33,44,66,100,133] notation is also
1626 * [no]ncq: Turn on or off NCQ.
1628 * nohrst, nosrst, norst: suppress hard, soft
1631 * rstonce: only attempt one reset during
1632 hot-unplug link recovery
1634 * dump_id: dump IDENTIFY data.
1636 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1638 * disable: Disable this device.
1640 If there are multiple matching configurations changing
1641 the same attribute, the last one is used.
1643 memblock=debug [KNL] Enable memblock debug messages.
1645 load_ramdisk= [RAM] List of ramdisks to load from floppy
1646 See Documentation/blockdev/ramdisk.txt.
1648 lockd.nlm_grace_period=P [NFS] Assign grace period.
1651 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1654 lockd.nlm_timeout=T [NFS] Assign timeout value.
1657 lockd.nlm_udpport=M [NFS] Assign UDP port.
1660 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1663 loglevel= All Kernel Messages with a loglevel smaller than the
1664 console loglevel will be printed to the console. It can
1665 also be changed with klogd or other programs. The
1666 loglevels are defined as follows:
1668 0 (KERN_EMERG) system is unusable
1669 1 (KERN_ALERT) action must be taken immediately
1670 2 (KERN_CRIT) critical conditions
1671 3 (KERN_ERR) error conditions
1672 4 (KERN_WARNING) warning conditions
1673 5 (KERN_NOTICE) normal but significant condition
1674 6 (KERN_INFO) informational
1675 7 (KERN_DEBUG) debug-level messages
1677 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1678 in bytes. n must be a power of two. The default
1679 size is set in the kernel config file.
1681 logo.nologo [FB] Disables display of the built-in Linux logo.
1682 This may be used to provide more screen space for
1683 kernel log messages and is useful when debugging
1684 kernel boot problems.
1686 lp=0 [LP] Specify parallel ports to use, e.g,
1687 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1688 lp=reset first parallel port). 'lp=0' disables the
1689 lp=auto printer driver. 'lp=reset' (which can be
1690 specified in addition to the ports) causes
1691 attached printers to be reset. Using
1692 lp=port1,port2,... specifies the parallel ports
1693 to associate lp devices with, starting with
1694 lp0. A port specification may be 'none' to skip
1695 that lp device, or a parport name such as
1696 'parport0'. Specifying 'lp=auto' instead of a
1697 port specification list means that device IDs
1698 from each port should be examined, to see if
1699 an IEEE 1284-compliant printer is attached; if
1700 so, the driver will manage that printer.
1701 See also header of drivers/char/lp.c.
1704 Sets loops_per_jiffy to given constant, thus avoiding
1705 time-consuming boot-time autodetection (up to 250 ms per
1706 CPU). 0 enables autodetection (default). To determine
1707 the correct value for your kernel, boot with normal
1708 autodetection and see what value is printed. Note that
1709 on SMP systems the preset will be applied to all CPUs,
1710 which is likely to cause problems if your CPUs need
1711 significantly divergent settings. An incorrect value
1712 will cause delays in the kernel to be wrong, leading to
1713 unpredictable I/O errors and other breakage. Although
1714 unlikely, in the extreme case this might damage your
1718 Format: <io>,<irq>,<dma>
1720 machvec= [IA-64] Force the use of a particular machine-vector
1721 (machvec) in a generic kernel.
1722 Example: machvec=hpzx1_swiotlb
1724 machtype= [Loongson] Share the same kernel image file between different
1726 Example: machtype=lemote-yeeloong-2f-7inch
1728 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1729 than or equal to this physical address is ignored.
1731 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1732 should make use of. maxcpus=n : n >= 0 limits the
1733 kernel to using 'n' processors. n=0 is a special case,
1734 it is equivalent to "nosmp", which also disables
1737 max_loop= [LOOP] The number of loop block devices that get
1738 (loop.max_loop) unconditionally pre-created at init time. The default
1739 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1740 of statically allocating a predefined number, loop
1741 devices can be requested on-demand with the
1742 /dev/loop-control interface.
1744 mce [X86-32] Machine Check Exception
1746 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1748 md= [HW] RAID subsystems devices and level
1749 See Documentation/md.txt.
1752 Format: <first>,<last>
1753 Specifies range of consoles to be captured by the MDA.
1755 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1756 Amount of memory to be used when the kernel is not able
1757 to see the whole system memory or for test.
1758 [X86] Work as limiting max address. Use together
1759 with memmap= to avoid physical address space collisions.
1760 Without memmap= PCI devices could be placed at addresses
1761 belonging to unused RAM.
1763 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1767 [KNL,SH] Allow user to override the default size for
1768 per-device physically contiguous DMA buffers.
1770 memmap=exactmap [KNL,X86] Enable setting of an exact
1771 E820 memory map, as specified by the user.
1772 Such memmap=exactmap lines can be constructed based on
1773 BIOS output or other requirements. See the memmap=nn@ss
1776 memmap=nn[KMG]@ss[KMG]
1777 [KNL] Force usage of a specific region of memory.
1778 Region of memory to be used is from ss to ss+nn.
1780 memmap=nn[KMG]#ss[KMG]
1781 [KNL,ACPI] Mark specific memory as ACPI data.
1782 Region of memory to be marked is from ss to ss+nn.
1784 memmap=nn[KMG]$ss[KMG]
1785 [KNL,ACPI] Mark specific memory as reserved.
1786 Region of memory to be reserved is from ss to ss+nn.
1787 Example: Exclude memory from 0x18690000-0x1869ffff
1788 memmap=64K$0x18690000
1790 memmap=0x10000$0x18690000
1792 memory_corruption_check=0/1 [X86]
1793 Some BIOSes seem to corrupt the first 64k of
1794 memory when doing things like suspend/resume.
1795 Setting this option will scan the memory
1796 looking for corruption. Enabling this will
1797 both detect corruption and prevent the kernel
1798 from using the memory being corrupted.
1799 However, its intended as a diagnostic tool; if
1800 repeatable BIOS-originated corruption always
1801 affects the same memory, you can use memmap=
1802 to prevent the kernel from using that memory.
1804 memory_corruption_check_size=size [X86]
1805 By default it checks for corruption in the low
1806 64k, making this memory unavailable for normal
1807 use. Use this parameter to scan for
1808 corruption in more or less memory.
1810 memory_corruption_check_period=seconds [X86]
1811 By default it checks for corruption every 60
1812 seconds. Use this parameter to check at some
1813 other rate. 0 disables periodic checking.
1815 memtest= [KNL,X86] Enable memtest
1817 default : 0 <disable>
1818 Specifies the number of memtest passes to be
1819 performed. Each pass selects another test
1820 pattern from a given set of patterns. Memtest
1821 fills the memory with this pattern, validates
1822 memory contents and reserves bad memory
1823 regions that are detected.
1825 meye.*= [HW] Set MotionEye Camera parameters
1826 See Documentation/video4linux/meye.txt.
1828 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1829 Multi-Function General Purpose Timers on AMD Geode
1832 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1833 the BIOS has incorrectly applied a workaround. TinyBIOS
1834 version 0.98 is known to be affected, 0.99 fixes the
1835 problem by letting the user disable the workaround.
1839 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1840 physical address is ignored.
1842 mini2440= [ARM,HW,KNL]
1843 Format:[0..2][b][c][t]
1845 MINI2440 configuration specification:
1846 0 - The attached screen is the 3.5" TFT
1847 1 - The attached screen is the 7" TFT
1848 2 - The VGA Shield is attached (1024x768)
1849 Leaving out the screen size parameter will not load
1850 the TFT driver, and the framebuffer will be left
1852 b - Enable backlight. The TFT backlight pin will be
1853 linked to the kernel VESA blanking code and a GPIO
1854 LED. This parameter is not necessary when using the
1856 c - Enable the s3c camera interface.
1857 t - Reserved for enabling touchscreen support. The
1858 touchscreen support is not enabled in the mainstream
1859 kernel as of 2.6.30, a preliminary port can be found
1860 in the "bleeding edge" mini2440 support kernel at
1861 http://repo.or.cz/w/linux-2.6/mini2440.git
1864 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1865 parameter allows control of the logging verbosity for
1866 the additional memory initialisation checks. A value
1867 of 0 disables mminit logging and a level of 4 will
1868 log everything. Information is printed at KERN_DEBUG
1869 so loglevel=8 may also need to be specified.
1872 [KNL] When CONFIG_MODULE_SIG is set, this means that
1873 modules without (valid) signatures will fail to load.
1874 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1875 is always true, so this option does nothing.
1878 [MOUSE] Maximum time between finger touching and
1879 leaving touchpad surface for touch to be considered
1880 a tap and be reported as a left button click (for
1881 touchpads working in absolute mode only).
1883 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1884 reporting absolute coordinates, such as tablets
1885 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1886 reporting absolute coordinates, such as tablets
1888 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1889 is similar to kernelcore except it specifies the
1890 amount of memory used for migratable allocations.
1891 If both kernelcore and movablecore is specified,
1892 then kernelcore will be at *least* the specified
1893 value but may be more. If movablecore on its own
1894 is specified, the administrator must be careful
1895 that the amount of memory usable for all allocations
1898 movable_node [KNL,X86] Boot-time switch to enable the effects
1899 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1901 MTD_Partition= [MTD]
1902 Format: <name>,<region-number>,<size>,<offset>
1904 MTD_Region= [MTD] Format:
1905 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1908 See drivers/mtd/cmdlinepart.c.
1910 multitce=off [PPC] This parameter disables the use of the pSeries
1911 firmware feature for updating multiple TCE entries
1914 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1916 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1918 boundary - index of last SLC block on Flex-OneNAND.
1919 The remaining blocks are configured as MLC blocks.
1920 lock - Configure if Flex-OneNAND boundary should be locked.
1921 Once locked, the boundary cannot be changed.
1922 1 indicates lock status, 0 indicates unlock status.
1925 ARM/S3C2412 JIVE boot control
1927 See arch/arm/mach-s3c2412/mach-jive.c
1929 mtouchusb.raw_coordinates=
1930 [HW] Make the MicroTouch USB driver use raw coordinates
1931 ('y', default) or cooked coordinates ('n')
1933 mtrr_chunk_size=nn[KMG] [X86]
1934 used for mtrr cleanup. It is largest continuous chunk
1935 that could hold holes aka. UC entries.
1937 mtrr_gran_size=nn[KMG] [X86]
1938 Used for mtrr cleanup. It is granularity of mtrr block.
1940 Large value could prevent small alignment from
1943 mtrr_spare_reg_nr=n [X86]
1945 Range: 0,7 : spare reg number
1947 Used for mtrr cleanup. It is spare mtrr entries number.
1948 Set to 2 or more if your graphical card needs more.
1950 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1952 netdev= [NET] Network devices parameters
1953 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1954 Note that mem_start is often overloaded to mean
1955 something different and driver-specific.
1956 This usage is only documented in each driver source
1960 [NETFILTER] Enable connection tracking flow accounting
1961 0 to disable accounting
1962 1 to enable accounting
1965 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1966 See Documentation/filesystems/nfs/nfsroot.txt.
1968 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1969 See Documentation/filesystems/nfs/nfsroot.txt.
1971 nfsrootdebug [NFS] enable nfsroot debugging messages.
1972 See Documentation/filesystems/nfs/nfsroot.txt.
1974 nfs.callback_tcpport=
1975 [NFS] set the TCP port on which the NFSv4 callback
1976 channel should listen.
1979 [NFS] sets the pathname to the program which is used
1980 to update the NFS client cache entries.
1982 nfs.cache_getent_timeout=
1983 [NFS] sets the timeout after which an attempt to
1984 update a cache entry is deemed to have failed.
1986 nfs.idmap_cache_timeout=
1987 [NFS] set the maximum lifetime for idmapper cache
1991 [NFS] enable 64-bit inode numbers.
1992 If zero, the NFS client will fake up a 32-bit inode
1993 number for the readdir() and stat() syscalls instead
1994 of returning the full 64-bit number.
1995 The default is to return 64-bit inode numbers.
1997 nfs.max_session_slots=
1998 [NFSv4.1] Sets the maximum number of session slots
1999 the client will attempt to negotiate with the server.
2000 This limits the number of simultaneous RPC requests
2001 that the client can send to the NFSv4.1 server.
2002 Note that there is little point in setting this
2003 value higher than the max_tcp_slot_table_limit.
2005 nfs.nfs4_disable_idmapping=
2006 [NFSv4] When set to the default of '1', this option
2007 ensures that both the RPC level authentication
2008 scheme and the NFS level operations agree to use
2009 numeric uids/gids if the mount is using the
2010 'sec=sys' security flavour. In effect it is
2011 disabling idmapping, which can make migration from
2012 legacy NFSv2/v3 systems to NFSv4 easier.
2013 Servers that do not support this mode of operation
2014 will be autodetected by the client, and it will fall
2015 back to using the idmapper.
2016 To turn off this behaviour, set the value to '0'.
2018 [NFS4] Specify an additional fixed unique ident-
2019 ification string that NFSv4 clients can insert into
2020 their nfs_client_id4 string. This is typically a
2021 UUID that is generated at system install time.
2023 nfs.send_implementation_id =
2024 [NFSv4.1] Send client implementation identification
2025 information in exchange_id requests.
2026 If zero, no implementation identification information
2028 The default is to send the implementation identification
2031 nfs.recover_lost_locks =
2032 [NFSv4] Attempt to recover locks that were lost due
2033 to a lease timeout on the server. Please note that
2034 doing this risks data corruption, since there are
2035 no guarantees that the file will remain unchanged
2036 after the locks are lost.
2037 If you want to enable the kernel legacy behaviour of
2038 attempting to recover these locks, then set this
2040 The default parameter value of '0' causes the kernel
2041 not to attempt recovery of lost locks.
2043 nfsd.nfs4_disable_idmapping=
2044 [NFSv4] When set to the default of '1', the NFSv4
2045 server will return only numeric uids and gids to
2046 clients using auth_sys, and will accept numeric uids
2047 and gids from such clients. This is intended to ease
2048 migration from NFSv2/v3.
2050 objlayoutdriver.osd_login_prog=
2051 [NFS] [OBJLAYOUT] sets the pathname to the program which
2052 is used to automatically discover and login into new
2053 osd-targets. Please see:
2054 Documentation/filesystems/pnfs.txt for more explanations
2056 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2057 when a NMI is triggered.
2058 Format: [state][,regs][,debounce][,die]
2060 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2061 Format: [panic,][nopanic,][num]
2063 0 - turn nmi_watchdog off
2064 When panic is specified, panic when an NMI watchdog
2065 timeout occurs (or 'nopanic' to override the opposite
2067 This is useful when you use a panic=... timeout and
2068 need the box quickly up again.
2070 netpoll.carrier_timeout=
2071 [NET] Specifies amount of time (in seconds) that
2072 netpoll should wait for a carrier. By default netpoll
2075 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2076 emulation library even if a 387 maths coprocessor
2080 [HW] Never suspend the console
2081 Disable suspending of consoles during suspend and
2082 hibernate operations. Once disabled, debugging
2083 messages can reach various consoles while the rest
2084 of the system is being put to sleep (ie, while
2085 debugging driver suspend/resume hooks). This may
2086 not work reliably with all consoles, but is known
2087 to work with serial and VGA consoles.
2088 To facilitate more flexible debugging, we also add
2089 console_suspend, a printk module parameter to control
2090 it. Users could use console_suspend (usually
2091 /sys/module/printk/parameters/console_suspend) to
2092 turn on/off it dynamically.
2094 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2095 caches in the slab allocator. Saves per-node memory,
2096 but will impact performance.
2100 noapic [SMP,APIC] Tells the kernel to not make use of any
2101 IOAPICs that may be present in the system.
2104 Disable kernel and module base offset ASLR (Address
2105 Space Layout Randomization) if built into the kernel.
2107 noautogroup Disable scheduler automatic task group creation.
2109 nobats [PPC] Do not use BATs for mapping kernel lowmem
2110 on "Classic" PPC cores.
2114 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2116 nodelayacct [KNL] Disable per-task delay accounting
2118 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2120 nodsp [SH] Disable hardware DSP at boot time.
2122 noefi [X86] Disable EFI runtime services support.
2127 On X86-32 available only on PAE configured kernels.
2128 noexec=on: enable non-executable mappings (default)
2129 noexec=off: disable non-executable mappings
2132 Disable SMAP (Supervisor Mode Access Prevention)
2133 even if it is supported by processor.
2136 Disable SMEP (Supervisor Mode Execution Prevention)
2137 even if it is supported by processor.
2140 This affects only 32-bit executables.
2141 noexec32=on: enable non-executable mappings (default)
2142 read doesn't imply executable mappings
2143 noexec32=off: disable non-executable mappings
2144 read implies executable mappings
2146 nofpu [SH] Disable hardware FPU at boot time.
2148 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2149 register save and restore. The kernel will only save
2150 legacy floating-point registers on task switch.
2152 noxsave [BUGS=X86] Disables x86 extended register state save
2153 and restore using xsave. The kernel will fallback to
2154 enabling legacy floating-point and sse state.
2157 on enable eager fpu restore
2158 off disable eager fpu restore
2159 auto selects the default scheme, which automatically
2160 enables eagerfpu restore for xsaveopt.
2162 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2163 wfi(ARM) instruction doesn't work correctly and not to
2164 use it. This is also useful when using JTAG debugger.
2166 no_file_caps Tells the kernel not to honor file capabilities. The
2167 only way then for a file to be executed with privilege
2168 is to be setuid root or executed by root.
2170 nohalt [IA-64] Tells the kernel not to use the power saving
2171 function PAL_HALT_LIGHT when idle. This increases
2172 power-consumption. On the positive side, it reduces
2173 interrupt wake-up latency, which may improve performance
2174 in certain environments such as networked servers or
2177 nohz= [KNL] Boottime enable/disable dynamic ticks
2178 Valid arguments: on, off
2181 nohz_full= [KNL,BOOT]
2182 In kernels built with CONFIG_NO_HZ_FULL=y, set
2183 the specified list of CPUs whose tick will be stopped
2184 whenever possible. The boot CPU will be forced outside
2185 the range to maintain the timekeeping.
2186 The CPUs in this range must also be included in the
2189 noiotrap [SH] Disables trapped I/O port accesses.
2191 noirqdebug [X86-32] Disables the code which attempts to detect and
2192 disable unhandled interrupt sources.
2194 no_timer_check [X86,APIC] Disables the code which tests for
2195 broken timer IRQ sources.
2197 noisapnp [ISAPNP] Disables ISA PnP code.
2199 noinitrd [RAM] Tells the kernel not to load any configured
2202 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2204 [Deprecated - use intremap=off]
2208 nojitter [IA-64] Disables jitter checking for ITC timers.
2210 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2212 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2215 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2216 steal time is computed, but won't influence scheduler
2219 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2221 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2223 noltlbs [PPC] Do not use large page/tlb entries for kernel
2224 lowmem mapping on PPC40x.
2226 nomca [IA-64] Disable machine check abort handling
2228 nomce [X86-32] Machine Check Exception
2230 nomfgpt [X86-32] Disable Multi-Function General Purpose
2231 Timer usage (for AMD Geode machines).
2233 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2234 shutdown the other cpus. Instead use the REBOOT_VECTOR
2237 nomodule Disable module load
2239 nopat [X86] Disable PAT (page attribute table extension of
2240 pagetables) support.
2242 norandmaps Don't use address space randomization. Equivalent to
2243 echo 0 > /proc/sys/kernel/randomize_va_space
2245 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2247 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2248 with UP alternatives
2250 nordrand [X86] Disable kernel use of the RDRAND and
2251 RDSEED instructions even if they are supported
2252 by the processor. RDRAND and RDSEED are still
2253 available to user space applications.
2255 noresume [SWSUSP] Disables resume and restores original swap
2258 no-scroll [VGA] Disables scrollback.
2259 This is required for the Braillex ib80-piezo Braille
2260 reader made by F.H. Papenmeier (Germany).
2264 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2266 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2267 and disable the IO APIC. legacy for "maxcpus=0".
2269 nosoftlockup [KNL] Disable the soft-lockup detector.
2271 nosync [HW,M68K] Disables sync negotiation for all devices.
2273 notsc [BUGS=X86-32] Disable Time Stamp Counter
2275 nousb [USB] Disable the USB subsystem
2277 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2281 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2283 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2284 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2285 Some features depend on CPU0. Known dependencies are:
2286 1. Resume from suspend/hibernate depends on CPU0.
2287 Suspend/hibernate will fail if CPU0 is offline and you
2288 need to online CPU0 before suspend/hibernate.
2289 2. PIC interrupts also depend on CPU0. CPU0 can't be
2290 removed if a PIC interrupt is detected.
2291 It's said poweroff/reboot may depend on CPU0 on some
2292 machines although I haven't seen such issues so far
2293 after CPU0 is offline on a few tested machines.
2294 If the dependencies are under your control, you can
2295 turn on cpu0_hotplug.
2297 nptcg= [IA-64] Override max number of concurrent global TLB
2298 purges which is reported from either PAL_VM_SUMMARY or
2301 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2302 could support. nr_cpus=n : n >= 1 limits the kernel to
2303 supporting 'n' processors. Later in runtime you can not
2304 use hotplug cpu feature to put more cpu back to online.
2305 just like you compile the kernel NR_CPUS=n
2307 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2309 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2310 Allowed values are enable and disable
2312 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2313 one of ['zone', 'node', 'default'] can be specified
2314 This can be set from sysctl after boot.
2315 See Documentation/sysctl/vm.txt for details.
2317 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2318 See Documentation/debugging-via-ohci1394.txt for more
2321 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2322 Rather than timing out after 20 ms if an EC
2323 command is not properly ACKed, override the length
2324 of the timeout. We have interrupts disabled while
2325 waiting for the ACK, so if this is set too high
2326 interrupts *may* be lost!
2328 omap_mux= [OMAP] Override bootloader pin multiplexing.
2329 Format: <mux_mode0.mode_name=value>...
2330 For example, to override I2C bus2:
2331 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2333 oprofile.timer= [HW]
2334 Use timer interrupt instead of performance counters
2336 oprofile.cpu_type= Force an oprofile cpu type
2337 This might be useful if you have an older oprofile
2338 userland or if you want common events.
2339 Format: { arch_perfmon }
2340 arch_perfmon: [X86] Force use of architectural
2341 perfmon on Intel CPUs instead of the
2342 CPU specific event set.
2343 timer: [X86] Force use of architectural NMI
2344 timer mode (see also oprofile.timer
2345 for generic hr timer mode)
2346 [s390] Force legacy basic mode sampling
2347 (report cpu_type "timer")
2349 oops=panic Always panic on oopses. Default is to just kill the
2350 process, but there is a small probability of
2351 deadlocking the machine.
2352 This will also cause panics on machine check exceptions.
2353 Useful together with panic=30 to trigger a reboot.
2356 See Documentation/sound/oss/oss-parameters.txt
2358 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2359 timeout > 0: seconds before rebooting
2360 timeout = 0: wait forever
2361 timeout < 0: reboot immediately
2364 crash_kexec_post_notifiers
2365 Run kdump after running panic-notifiers and dumping
2366 kmsg. This only for the users who doubt kdump always
2367 succeeds in any situation.
2368 Note that this also increases risks of kdump failure,
2369 because some panic notifiers can make the crashed
2370 kernel more unstable.
2372 parkbd.port= [HW] Parallel port number the keyboard adapter is
2373 connected to, default is 0.
2375 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2376 0 for XT, 1 for AT (default is AT).
2379 parport= [HW,PPT] Specify parallel ports. 0 disables.
2380 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2381 Use 'auto' to force the driver to use any
2382 IRQ/DMA settings detected (the default is to
2383 ignore detected IRQ/DMA settings because of
2384 possible conflicts). You can specify the base
2385 address, IRQ, and DMA settings; IRQ and DMA
2386 should be numbers, or 'auto' (for using detected
2387 settings on that particular port), or 'nofifo'
2388 (to avoid using a FIFO even if it is detected).
2389 Parallel ports are assigned in the order they
2390 are specified on the command line, starting
2393 parport_init_mode= [HW,PPT]
2394 Configure VIA parallel port to operate in
2395 a specific mode. This is necessary on Pegasos
2396 computer where firmware has no options for setting
2397 up parallel port mode and sets it to spp.
2398 Currently this function knows 686a and 8231 chips.
2399 Format: [spp|ps2|epp|ecp|ecpepp]
2402 Halt all CPUs after the first oops has been printed for
2403 the specified number of seconds. This is to be used if
2404 your oopses keep scrolling off the screen.
2409 See header of drivers/block/paride/pcd.c.
2410 See also Documentation/blockdev/paride.txt.
2412 pci=option[,option...] [PCI] various PCI subsystem options:
2413 earlydump [X86] dump PCI config space before the kernel
2415 off [X86] don't probe for the PCI bus
2416 bios [X86-32] force use of PCI BIOS, don't access
2417 the hardware directly. Use this if your machine
2418 has a non-standard PCI host bridge.
2419 nobios [X86-32] disallow use of PCI BIOS, only direct
2420 hardware access methods are allowed. Use this
2421 if you experience crashes upon bootup and you
2422 suspect they are caused by the BIOS.
2423 conf1 [X86] Force use of PCI Configuration
2425 conf2 [X86] Force use of PCI Configuration
2427 noaer [PCIE] If the PCIEAER kernel config parameter is
2428 enabled, this kernel boot option can be used to
2429 disable the use of PCIE advanced error reporting.
2430 nodomains [PCI] Disable support for multiple PCI
2431 root domains (aka PCI segments, in ACPI-speak).
2432 nommconf [X86] Disable use of MMCONFIG for PCI
2434 check_enable_amd_mmconf [X86] check for and enable
2435 properly configured MMIO access to PCI
2436 config space on AMD family 10h CPU
2437 nomsi [MSI] If the PCI_MSI kernel config parameter is
2438 enabled, this kernel boot option can be used to
2439 disable the use of MSI interrupts system-wide.
2440 noioapicquirk [APIC] Disable all boot interrupt quirks.
2441 Safety option to keep boot IRQs enabled. This
2442 should never be necessary.
2443 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2444 primary IO-APIC for bridges that cannot disable
2445 boot IRQs. This fixes a source of spurious IRQs
2446 when the system masks IRQs.
2447 noioapicreroute [APIC] Disable workaround that uses the
2448 boot IRQ equivalent of an IRQ that connects to
2449 a chipset where boot IRQs cannot be disabled.
2450 The opposite of ioapicreroute.
2451 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2452 routing table. These calls are known to be buggy
2453 on several machines and they hang the machine
2454 when used, but on other computers it's the only
2455 way to get the interrupt routing table. Try
2456 this option if the kernel is unable to allocate
2457 IRQs or discover secondary PCI buses on your
2459 rom [X86] Assign address space to expansion ROMs.
2460 Use with caution as certain devices share
2461 address decoders between ROMs and other
2463 norom [X86] Do not assign address space to
2464 expansion ROMs that do not already have
2465 BIOS assigned address ranges.
2466 nobar [X86] Do not assign address space to the
2467 BARs that weren't assigned by the BIOS.
2468 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2469 assigned automatically to PCI devices. You can
2470 make the kernel exclude IRQs of your ISA cards
2472 pirqaddr=0xAAAAA [X86] Specify the physical address
2473 of the PIRQ table (normally generated
2474 by the BIOS) if it is outside the
2475 F0000h-100000h range.
2476 lastbus=N [X86] Scan all buses thru bus #N. Can be
2477 useful if the kernel is unable to find your
2478 secondary buses and you want to tell it
2479 explicitly which ones they are.
2480 assign-busses [X86] Always assign all PCI bus
2481 numbers ourselves, overriding
2482 whatever the firmware may have done.
2483 usepirqmask [X86] Honor the possible IRQ mask stored
2484 in the BIOS $PIR table. This is needed on
2485 some systems with broken BIOSes, notably
2486 some HP Pavilion N5400 and Omnibook XE3
2487 notebooks. This will have no effect if ACPI
2488 IRQ routing is enabled.
2489 noacpi [X86] Do not use ACPI for IRQ routing
2490 or for PCI scanning.
2491 use_crs [X86] Use PCI host bridge window information
2492 from ACPI. On BIOSes from 2008 or later, this
2493 is enabled by default. If you need to use this,
2494 please report a bug.
2495 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2496 If you need to use this, please report a bug.
2497 routeirq Do IRQ routing for all PCI devices.
2498 This is normally done in pci_enable_device(),
2499 so this option is a temporary workaround
2500 for broken drivers that don't call it.
2501 skip_isa_align [X86] do not align io start addr, so can
2502 handle more pci cards
2503 firmware [ARM] Do not re-enumerate the bus but instead
2504 just use the configuration from the
2505 bootloader. This is currently used on
2506 IXP2000 systems where the bus has to be
2507 configured a certain way for adjunct CPUs.
2508 noearly [X86] Don't do any early type 1 scanning.
2509 This might help on some broken boards which
2510 machine check when some devices' config space
2511 is read. But various workarounds are disabled
2512 and some IOMMU drivers will not work.
2513 bfsort Sort PCI devices into breadth-first order.
2514 This sorting is done to get a device
2515 order compatible with older (<= 2.4) kernels.
2516 nobfsort Don't sort PCI devices into breadth-first order.
2517 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2518 tuning and use the BIOS-configured MPS defaults.
2519 pcie_bus_safe Set every device's MPS to the largest value
2520 supported by all devices below the root complex.
2521 pcie_bus_perf Set device MPS to the largest allowable MPS
2522 based on its parent bus. Also set MRRS (Max
2523 Read Request Size) to the largest supported
2524 value (no larger than the MPS that the device
2525 or bus can support) for best performance.
2526 pcie_bus_peer2peer Set every device's MPS to 128B, which
2527 every device is guaranteed to support. This
2528 configuration allows peer-to-peer DMA between
2529 any pair of devices, possibly at the cost of
2530 reduced performance. This also guarantees
2531 that hot-added devices will work.
2532 cbiosize=nn[KMG] The fixed amount of bus space which is
2533 reserved for the CardBus bridge's IO window.
2534 The default value is 256 bytes.
2535 cbmemsize=nn[KMG] The fixed amount of bus space which is
2536 reserved for the CardBus bridge's memory
2537 window. The default value is 64 megabytes.
2540 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2541 Specifies alignment and device to reassign
2542 aligned memory resources.
2543 If <order of align> is not specified,
2544 PAGE_SIZE is used as alignment.
2545 PCI-PCI bridge can be specified, if resource
2546 windows need to be expanded.
2547 ecrc= Enable/disable PCIe ECRC (transaction layer
2548 end-to-end CRC checking).
2549 bios: Use BIOS/firmware settings. This is the
2553 hpiosize=nn[KMG] The fixed amount of bus space which is
2554 reserved for hotplug bridge's IO window.
2555 Default size is 256 bytes.
2556 hpmemsize=nn[KMG] The fixed amount of bus space which is
2557 reserved for hotplug bridge's memory window.
2558 Default size is 2 megabytes.
2559 realloc= Enable/disable reallocating PCI bridge resources
2560 if allocations done by BIOS are too small to
2561 accommodate resources required by all child
2563 off: Turn realloc off
2565 realloc same as realloc=on
2566 noari do not use PCIe ARI.
2567 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2568 only look for one device below a PCIe downstream
2571 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2574 force Enable ASPM even on devices that claim not to support it.
2575 WARNING: Forcing ASPM on may cause system lockups.
2577 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2578 nomsi Do not use MSI for PCI Express Native Hotplug (this
2579 makes all PCIe ports use INTx for hotplug services).
2581 pcie_ports= [PCIE] PCIe ports handling:
2582 auto Ask the BIOS whether or not to use native PCIe services
2583 associated with PCIe ports (PME, hot-plug, AER). Use
2584 them only if that is allowed by the BIOS.
2585 native Use native PCIe services associated with PCIe ports
2587 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2590 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2591 nomsi Do not use MSI for native PCIe PME signaling (this makes
2592 all PCIe root ports use INTx for all services).
2594 pcmv= [HW,PCMCIA] BadgePAD 4
2598 Keep all power-domains already enabled by bootloader on,
2599 even if no driver has claimed them. This is useful
2600 for debug and development, but should not be
2601 needed on a platform with proper driver support.
2604 See Documentation/blockdev/paride.txt.
2606 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2609 See arch/parisc/kernel/pdc_chassis.c
2611 percpu_alloc= Select which percpu first chunk allocator to use.
2612 Currently supported values are "embed" and "page".
2613 Archs may support subset or none of the selections.
2614 See comments in mm/percpu.c for details on each
2615 allocator. This parameter is primarily for debugging
2616 and performance comparison.
2619 See Documentation/blockdev/paride.txt.
2622 See Documentation/blockdev/paride.txt.
2624 pirq= [SMP,APIC] Manual mp-table setup
2625 See Documentation/x86/i386/IO-APIC.txt.
2627 plip= [PPT,NET] Parallel port network link
2628 Format: { parport<nr> | timid | 0 }
2629 See also Documentation/parport.txt.
2631 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2632 Override pmtimer IOPort with a hex value.
2636 Enable PNP debug messages (depends on the
2637 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2638 via /sys/module/pnp/parameters/debug. We always show
2639 current resource usage; turning this on also shows
2640 possible settings and some assignment information.
2646 { on | off | curr | res | no-curr | no-res }
2649 [ISAPNP] Exclude IRQs for the autoconfiguration
2652 [ISAPNP] Exclude DMAs for the autoconfiguration
2654 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2655 Ranges are in pairs (I/O port base and size).
2658 [ISAPNP] Exclude memory regions for the
2660 Ranges are in pairs (memory base and size).
2662 ports= [IP_VS_FTP] IPVS ftp helper module
2664 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2666 Format: <port>,<port>....
2668 print-fatal-signals=
2669 [KNL] debug: print fatal signals
2671 If enabled, warn about various signal handling
2672 related application anomalies: too many signals,
2673 too many POSIX.1 timers, fatal signals causing a
2676 If you hit the warning due to signal overflow,
2677 you might want to try "ulimit -i unlimited".
2681 printk.always_kmsg_dump=
2682 Trigger kmsg_dump for cases other than kernel oops or
2684 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2687 printk.time= Show timing data prefixed to each printk message line
2688 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2690 processor.max_cstate= [HW,ACPI]
2691 Limit processor to maximum C-state
2692 max_cstate=9 overrides any DMI blacklist limit.
2694 processor.nocst [HW,ACPI]
2695 Ignore the _CST method to determine C-states,
2696 instead using the legacy FADT method
2698 profile= [KNL] Enable kernel profiling via /proc/profile
2699 Format: [schedule,]<number>
2700 Param: "schedule" - profile schedule points.
2701 Param: <number> - step/bucket size as a power of 2 for
2702 statistical time based profiling.
2703 Param: "sleep" - profile D-state sleeping (millisecs).
2704 Requires CONFIG_SCHEDSTATS
2705 Param: "kvm" - profile VM exits.
2707 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2709 See Documentation/blockdev/ramdisk.txt.
2711 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2712 probe for; one of (bare|imps|exps|lifebook|any).
2713 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2715 psmouse.resetafter= [HW,MOUSE]
2716 Try to reset the device after so many bad packets
2719 [HW,MOUSE] Set desired mouse resolution, in dpi.
2720 psmouse.smartscroll=
2721 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2722 0 = disabled, 1 = enabled (default).
2724 pstore.backend= Specify the name of the pstore backend to use
2727 See Documentation/blockdev/paride.txt.
2730 [KNL] Number of legacy pty's. Overwrites compiled-in
2733 quiet [KNL] Disable most log messages
2738 See Documentation/md.txt.
2740 ramdisk_blocksize= [RAM]
2741 See Documentation/blockdev/ramdisk.txt.
2743 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2744 See Documentation/blockdev/ramdisk.txt.
2747 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2748 the specified list of CPUs to be no-callback CPUs.
2749 Invocation of these CPUs' RCU callbacks will
2750 be offloaded to "rcuox/N" kthreads created for
2751 that purpose, where "x" is "b" for RCU-bh, "p"
2752 for RCU-preempt, and "s" for RCU-sched, and "N"
2753 is the CPU number. This reduces OS jitter on the
2754 offloaded CPUs, which can be useful for HPC and
2755 real-time workloads. It can also improve energy
2756 efficiency for asymmetric multiprocessors.
2759 Rather than requiring that offloaded CPUs
2760 (specified by rcu_nocbs= above) explicitly
2761 awaken the corresponding "rcuoN" kthreads,
2762 make these kthreads poll for callbacks.
2763 This improves the real-time response for the
2764 offloaded CPUs by relieving them of the need to
2765 wake up the corresponding kthread, but degrades
2766 energy efficiency by requiring that the kthreads
2767 periodically wake up to do the polling.
2769 rcutree.blimit= [KNL]
2770 Set maximum number of finished RCU callbacks to
2771 process in one batch.
2773 rcutree.rcu_fanout_leaf= [KNL]
2774 Increase the number of CPUs assigned to each
2775 leaf rcu_node structure. Useful for very large
2778 rcutree.jiffies_till_first_fqs= [KNL]
2779 Set delay from grace-period initialization to
2780 first attempt to force quiescent states.
2781 Units are jiffies, minimum value is zero,
2782 and maximum value is HZ.
2784 rcutree.jiffies_till_next_fqs= [KNL]
2785 Set delay between subsequent attempts to force
2786 quiescent states. Units are jiffies, minimum
2787 value is one, and maximum value is HZ.
2789 rcutree.qhimark= [KNL]
2790 Set threshold of queued RCU callbacks beyond which
2791 batch limiting is disabled.
2793 rcutree.qlowmark= [KNL]
2794 Set threshold of queued RCU callbacks below which
2795 batch limiting is re-enabled.
2797 rcutree.rcu_idle_gp_delay= [KNL]
2798 Set wakeup interval for idle CPUs that have
2799 RCU callbacks (RCU_FAST_NO_HZ=y).
2801 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2802 Set wakeup interval for idle CPUs that have
2803 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2804 Lazy RCU callbacks are those which RCU can
2805 prove do nothing more than free memory.
2807 rcutorture.fqs_duration= [KNL]
2808 Set duration of force_quiescent_state bursts.
2810 rcutorture.fqs_holdoff= [KNL]
2811 Set holdoff time within force_quiescent_state bursts.
2813 rcutorture.fqs_stutter= [KNL]
2814 Set wait time between force_quiescent_state bursts.
2816 rcutorture.gp_exp= [KNL]
2817 Use expedited update-side primitives.
2819 rcutorture.gp_normal= [KNL]
2820 Use normal (non-expedited) update-side primitives.
2821 If both gp_exp and gp_normal are set, do both.
2822 If neither gp_exp nor gp_normal are set, still
2825 rcutorture.n_barrier_cbs= [KNL]
2826 Set callbacks/threads for rcu_barrier() testing.
2828 rcutorture.nfakewriters= [KNL]
2829 Set number of concurrent RCU writers. These just
2830 stress RCU, they don't participate in the actual
2831 test, hence the "fake".
2833 rcutorture.nreaders= [KNL]
2834 Set number of RCU readers.
2836 rcutorture.object_debug= [KNL]
2837 Enable debug-object double-call_rcu() testing.
2839 rcutorture.onoff_holdoff= [KNL]
2840 Set time (s) after boot for CPU-hotplug testing.
2842 rcutorture.onoff_interval= [KNL]
2843 Set time (s) between CPU-hotplug operations, or
2844 zero to disable CPU-hotplug testing.
2846 rcutorture.rcutorture_runnable= [BOOT]
2847 Start rcutorture running at boot time.
2849 rcutorture.shuffle_interval= [KNL]
2850 Set task-shuffle interval (s). Shuffling tasks
2851 allows some CPUs to go into dyntick-idle mode
2852 during the rcutorture test.
2854 rcutorture.shutdown_secs= [KNL]
2855 Set time (s) after boot system shutdown. This
2856 is useful for hands-off automated testing.
2858 rcutorture.stall_cpu= [KNL]
2859 Duration of CPU stall (s) to test RCU CPU stall
2860 warnings, zero to disable.
2862 rcutorture.stall_cpu_holdoff= [KNL]
2863 Time to wait (s) after boot before inducing stall.
2865 rcutorture.stat_interval= [KNL]
2866 Time (s) between statistics printk()s.
2868 rcutorture.stutter= [KNL]
2869 Time (s) to stutter testing, for example, specifying
2870 five seconds causes the test to run for five seconds,
2871 wait for five seconds, and so on. This tests RCU's
2872 ability to transition abruptly to and from idle.
2874 rcutorture.test_boost= [KNL]
2875 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2876 "Maybe" means test if the RCU implementation
2877 under test support RCU priority boosting.
2879 rcutorture.test_boost_duration= [KNL]
2880 Duration (s) of each individual boost test.
2882 rcutorture.test_boost_interval= [KNL]
2883 Interval (s) between each boost test.
2885 rcutorture.test_no_idle_hz= [KNL]
2886 Test RCU's dyntick-idle handling. See also the
2887 rcutorture.shuffle_interval parameter.
2889 rcutorture.torture_type= [KNL]
2890 Specify the RCU implementation to test.
2892 rcutorture.verbose= [KNL]
2893 Enable additional printk() statements.
2895 rcupdate.rcu_expedited= [KNL]
2896 Use expedited grace-period primitives, for
2897 example, synchronize_rcu_expedited() instead
2898 of synchronize_rcu(). This reduces latency,
2899 but can increase CPU utilization, degrade
2900 real-time latency, and degrade energy efficiency.
2902 rcupdate.rcu_cpu_stall_suppress= [KNL]
2903 Suppress RCU CPU stall warning messages.
2905 rcupdate.rcu_cpu_stall_timeout= [KNL]
2906 Set timeout for RCU CPU stall warning messages.
2910 Run specified binary instead of /init from the ramdisk,
2911 used for early userspace startup. See initrd.
2914 Format (x86 or x86_64):
2915 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2917 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2919 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2920 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2921 reboot_force is either force or not specified,
2922 reboot_cpu is s[mp]#### with #### being the processor
2923 to be used for rebooting.
2926 [KNL, SMP] Set scheduler's default relax_domain_level.
2927 See Documentation/cgroups/cpusets.txt.
2929 relative_sleep_states=
2930 [SUSPEND] Use sleep state labeling where the deepest
2931 state available other than hibernation is always "mem".
2932 Format: { "0" | "1" }
2933 0 -- Traditional sleep state labels.
2934 1 -- Relative sleep state labels.
2936 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2938 reservetop= [X86-32]
2940 Reserves a hole at the top of the kernel virtual
2945 Set the amount of memory to reserve for BIOS at
2946 the bottom of the address space.
2948 reset_devices [KNL] Force drivers to reset the underlying device
2949 during initialization.
2952 Specify the partition device for software suspend
2954 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2956 resume_offset= [SWSUSP]
2957 Specify the offset from the beginning of the partition
2958 given by "resume=" at which the swap header is located,
2959 in <PAGE_SIZE> units (needed only for swap files).
2960 See Documentation/power/swsusp-and-swap-files.txt
2962 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2963 read the resume files
2965 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2966 Useful for devices that are detected asynchronously
2967 (e.g. USB and MMC devices).
2969 hibernate= [HIBERNATION]
2970 noresume Don't check if there's a hibernation image
2971 present during boot.
2972 nocompress Don't compress/decompress hibernation images.
2974 retain_initrd [RAM] Keep initrd memory after extraction
2976 rhash_entries= [KNL,NET]
2977 Set number of hash buckets for route cache
2979 ro [KNL] Mount root device read-only on boot
2981 root= [KNL] Root filesystem
2982 See name_to_dev_t comment in init/do_mounts.c.
2984 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2985 mount the root filesystem
2987 rootflags= [KNL] Set root filesystem mount option string
2989 rootfstype= [KNL] Set root filesystem type
2991 rootwait [KNL] Wait (indefinitely) for root device to show up.
2992 Useful for devices that are detected asynchronously
2993 (e.g. USB and MMC devices).
2995 rproc_mem=nn[KMG][@address]
2996 [KNL,ARM,CMA] Remoteproc physical memory block.
2997 Memory area to be used by remote processor image,
3000 rw [KNL] Mount root device read-write on boot
3002 S [KNL] Run init in single mode
3005 See drivers/net/irda/sa1100_ir.c.
3007 sbni= [NET] Granch SBNI12 leased line adapter
3009 sched_debug [KNL] Enables verbose scheduler debug messages.
3011 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
3012 xtime_lock contention on larger systems, and/or RCU lock
3013 contention on all systems with CONFIG_MAXSMP set.
3014 Format: { "0" | "1" }
3015 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3017 Note: increases power consumption, thus should only be
3018 enabled if running jitter sensitive (HPC/RT) workloads.
3020 security= [SECURITY] Choose a security module to enable at boot.
3021 If this boot parameter is not specified, only the first
3022 security module asking for security registration will be
3023 loaded. An invalid security module name will be treated
3024 as if no module has been chosen.
3026 selinux= [SELINUX] Disable or enable SELinux at boot time.
3027 Format: { "0" | "1" }
3028 See security/selinux/Kconfig help text.
3031 Default value is set via kernel config option.
3032 If enabled at boot time, /selinux/disable can be used
3033 later to disable prior to initial policy load.
3035 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3036 Format: { "0" | "1" }
3037 See security/apparmor/Kconfig help text
3040 Default value is set via kernel config option.
3042 serialnumber [BUGS=X86-32]
3045 Maximal number of shapers.
3047 show_msr= [x86] show boot-time MSR settings
3048 Format: { <integer> }
3049 Show boot-time (BIOS-initialized) MSR settings.
3050 The parameter means the number of CPUs to show,
3051 for example 1 means boot CPU only.
3058 slab_max_order= [MM, SLAB]
3059 Determines the maximum allowed order for slabs.
3060 A high setting may cause OOMs due to memory
3061 fragmentation. Defaults to 1 for systems with
3062 more than 32MB of RAM, 0 otherwise.
3064 slub_debug[=options[,slabs]] [MM, SLUB]
3065 Enabling slub_debug allows one to determine the
3066 culprit if slab objects become corrupted. Enabling
3067 slub_debug can create guard zones around objects and
3068 may poison objects when not in use. Also tracks the
3069 last alloc / free. For more information see
3070 Documentation/vm/slub.txt.
3072 slub_max_order= [MM, SLUB]
3073 Determines the maximum allowed order for slabs.
3074 A high setting may cause OOMs due to memory
3075 fragmentation. For more information see
3076 Documentation/vm/slub.txt.
3078 slub_min_objects= [MM, SLUB]
3079 The minimum number of objects per slab. SLUB will
3080 increase the slab order up to slub_max_order to
3081 generate a sufficiently large slab able to contain
3082 the number of objects indicated. The higher the number
3083 of objects the smaller the overhead of tracking slabs
3084 and the less frequently locks need to be acquired.
3085 For more information see Documentation/vm/slub.txt.
3087 slub_min_order= [MM, SLUB]
3088 Determines the minimum page order for slabs. Must be
3089 lower than slub_max_order.
3090 For more information see Documentation/vm/slub.txt.
3092 slub_nomerge [MM, SLUB]
3093 Disable merging of slabs with similar size. May be
3094 necessary if there is some reason to distinguish
3095 allocs to different slabs. Debug options disable
3096 merging on their own.
3097 For more information see Documentation/vm/slub.txt.
3100 Format: <io1>[,<io2>[,...,<io8>]]
3102 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3103 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3104 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3105 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3106 smsc-ircc2.ircc_irq= [HW] IRQ line
3107 smsc-ircc2.ircc_dma= [HW] DMA channel
3108 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3109 0: Toshiba Satellite 1800 (GP data pin select)
3110 1: Fast pin select (default)
3114 [KNL] Should the soft-lockup detector generate panics.
3117 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3118 See Documentation/laptops/sonypi.txt
3120 spia_io_base= [HW,MTD]
3126 Enabled the stack tracer on boot up.
3128 stacktrace_filter=[function-list]
3129 [FTRACE] Limit the functions that the stack tracer
3130 will trace at boot up. function-list is a comma separated
3131 list of functions. This list can be changed at run
3132 time by the stack_trace_filter file in the debugfs
3133 tracing directory. Note, this enables stack tracing
3134 and the stacktrace above is not needed.
3138 Set the STI (builtin display/keyboard on the HP-PARISC
3139 machines) console (graphic card) which should be used
3140 as the initial boot-console.
3141 See also comment in drivers/video/console/sticore.c.
3144 See comment in drivers/video/console/sticore.c.
3147 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3149 sunrpc.min_resvport=
3150 sunrpc.max_resvport=
3152 SunRPC servers often require that client requests
3153 originate from a privileged port (i.e. a port in the
3154 range 0 < portnr < 1024).
3155 An administrator who wishes to reserve some of these
3156 ports for other uses may adjust the range that the
3157 kernel's sunrpc client considers to be privileged
3158 using these two parameters to set the minimum and
3159 maximum port values.
3163 Control how the NFS server code allocates CPUs to
3164 service thread pools. Depending on how many NICs
3165 you have and where their interrupts are bound, this
3166 option will affect which CPUs will do NFS serving.
3167 Note: this parameter cannot be changed while the
3168 NFS server is running.
3170 auto the server chooses an appropriate mode
3171 automatically using heuristics
3172 global a single global pool contains all CPUs
3173 percpu one pool for each CPU
3174 pernode one pool for each NUMA node (equivalent
3175 to global on non-NUMA machines)
3177 sunrpc.tcp_slot_table_entries=
3178 sunrpc.udp_slot_table_entries=
3180 Sets the upper limit on the number of simultaneous
3181 RPC calls that can be sent from the client to a
3182 server. Increasing these values may allow you to
3183 improve throughput, but will also increase the
3184 amount of memory reserved for use by the client.
3187 [KNL] Enable accounting of swap in memory resource
3188 controller if no parameter or 1 is given or disable
3189 it if 0 is given (See Documentation/cgroups/memory.txt)
3191 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3192 Format: { <int> | force }
3193 <int> -- Number of I/O TLB slabs
3194 force -- force using of bounce buffers even if they
3195 wouldn't be automatically used by the kernel
3199 sysfs.deprecated=0|1 [KNL]
3200 Enable/disable old style sysfs layout for old udev
3201 on older distributions. When this option is enabled
3202 very new udev will not work anymore. When this option
3203 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3204 in older udev will not work anymore.
3205 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3206 the kernel configuration.
3208 sysrq_always_enabled
3210 Ignore sysrq setting - this boot parameter will
3211 neutralize any effect of /proc/sys/kernel/sysrq.
3212 Useful for debugging.
3216 test_suspend= [SUSPEND]
3217 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3218 standby suspend) as the system sleep state to briefly
3219 enter during system startup. The system is woken from
3220 this state using a wakeup-capable RTC alarm.
3222 thash_entries= [KNL,NET]
3223 Set number of hash buckets for TCP connection
3225 thermal.act= [HW,ACPI]
3226 -1: disable all active trip points in all thermal zones
3227 <degrees C>: override all lowest active trip points
3229 thermal.crt= [HW,ACPI]
3230 -1: disable all critical trip points in all thermal zones
3231 <degrees C>: override all critical trip points
3233 thermal.nocrt= [HW,ACPI]
3234 Set to disable actions on ACPI thermal zone
3235 critical and hot trip points.
3237 thermal.off= [HW,ACPI]
3238 1: disable ACPI thermal control
3240 thermal.psv= [HW,ACPI]
3241 -1: disable all passive trip points
3242 <degrees C>: override all passive trip points to this
3245 thermal.tzp= [HW,ACPI]
3246 Specify global default ACPI thermal zone polling rate
3247 <deci-seconds>: poll all this frequency
3248 0: no polling (default)
3251 Force threading of all interrupt handlers except those
3252 marked explicitly IRQF_NO_THREAD.
3255 Enable the Transcendent memory driver if built-in.
3257 tmem.cleancache=0|1 [KNL, XEN]
3258 Default is on (1). Disable the usage of the cleancache
3259 API to send anonymous pages to the hypervisor.
3261 tmem.frontswap=0|1 [KNL, XEN]
3262 Default is on (1). Disable the usage of the frontswap
3263 API to send swap pages to the hypervisor. If disabled
3264 the selfballooning and selfshrinking are force disabled.
3266 tmem.selfballooning=0|1 [KNL, XEN]
3267 Default is on (1). Disable the driving of swap pages
3270 tmem.selfshrinking=0|1 [KNL, XEN]
3271 Default is on (1). Partial swapoff that immediately
3272 transfers pages from Xen hypervisor back to the
3273 kernel based on different criteria.
3277 Specify if the kernel should make use of the cpu
3278 topology information if the hardware supports this.
3279 The scheduler will make use of this information and
3280 e.g. base its process migration decisions on it.
3285 tpm_suspend_pcr=[HW,TPM]
3286 Format: integer pcr id
3287 Specify that at suspend time, the tpm driver
3288 should extend the specified pcr with zeros,
3289 as a workaround for some chips which fail to
3290 flush the last written pcr on TPM_SaveState.
3291 This will guarantee that all the other pcrs
3294 trace_buf_size=nn[KMG]
3295 [FTRACE] will set tracing buffer size.
3297 trace_event=[event-list]
3298 [FTRACE] Set and start specified trace events in order
3299 to facilitate early boot debugging.
3300 See also Documentation/trace/events.txt
3302 trace_options=[option-list]
3303 [FTRACE] Enable or disable tracer options at boot.
3304 The option-list is a comma delimited list of options
3305 that can be enabled or disabled just as if you were
3306 to echo the option name into
3308 /sys/kernel/debug/tracing/trace_options
3310 For example, to enable stacktrace option (to dump the
3311 stack trace of each event), add to the command line:
3313 trace_options=stacktrace
3315 See also Documentation/trace/ftrace.txt "trace options"
3319 [FTRACE] enable this option to disable tracing when a
3320 warning is hit. This turns off "tracing_on". Tracing can
3321 be enabled again by echoing '1' into the "tracing_on"
3322 file located in /sys/kernel/debug/tracing/
3324 This option is useful, as it disables the trace before
3325 the WARNING dump is called, which prevents the trace to
3326 be filled with content caused by the warning output.
3328 This option can also be set at run time via the sysctl
3329 option: kernel/traceoff_on_warning
3331 transparent_hugepage=
3333 Format: [always|madvise|never]
3334 Can be used to control the default behavior of the system
3335 with respect to transparent hugepages.
3336 See Documentation/vm/transhuge.txt for more details.
3338 tsc= Disable clocksource stability checks for TSC.
3340 [x86] reliable: mark tsc clocksource as reliable, this
3341 disables clocksource verification at runtime, as well
3342 as the stability checks done at bootup. Used to enable
3343 high-resolution timer mode on older hardware, and in
3344 virtualized environment.
3345 [x86] noirqtime: Do not use TSC to do irq accounting.
3346 Used to run time disable IRQ_TIME_ACCOUNTING on any
3347 platforms where RDTSC is slow and this accounting
3350 turbografx.map[2|3]= [HW,JOY]
3351 TurboGraFX parallel port interface
3353 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3354 See also Documentation/input/joystick-parport.txt
3356 udbg-immortal [PPC] When debugging early kernel crashes that
3357 happen after console_init() and before a proper
3358 console driver takes over, this boot options might
3359 help "seeing" what's going on.
3361 uhash_entries= [KNL,NET]
3362 Set number of hash buckets for UDP/UDP-Lite connections
3365 [USB] Ignore overcurrent events (default N).
3366 Some badly-designed motherboards generate lots of
3367 bogus events, for ports that aren't wired to
3368 anything. Set this parameter to avoid log spamming.
3369 Note that genuine overcurrent events won't be
3373 [X86] Cause panic on unknown NMI.
3375 usbcore.authorized_default=
3376 [USB] Default USB device authorization:
3377 (default -1 = authorized except for wireless USB,
3378 0 = not authorized, 1 = authorized)
3380 usbcore.autosuspend=
3381 [USB] The autosuspend time delay (in seconds) used
3382 for newly-detected USB devices (default 2). This
3383 is the time required before an idle device will be
3384 autosuspended. Devices for which the delay is set
3385 to a negative value won't be autosuspended at all.
3387 usbcore.usbfs_snoop=
3388 [USB] Set to log all usbfs traffic (default 0 = off).
3390 usbcore.blinkenlights=
3391 [USB] Set to cycle leds on hubs (default 0 = off).
3393 usbcore.old_scheme_first=
3394 [USB] Start with the old device initialization
3395 scheme (default 0 = off).
3397 usbcore.usbfs_memory_mb=
3398 [USB] Memory limit (in MB) for buffers allocated by
3399 usbfs (default = 16, 0 = max = 2047).
3401 usbcore.use_both_schemes=
3402 [USB] Try the other device initialization scheme
3403 if the first one fails (default 1 = enabled).
3405 usbcore.initial_descriptor_timeout=
3406 [USB] Specifies timeout for the initial 64-byte
3407 USB_REQ_GET_DESCRIPTOR request in milliseconds
3408 (default 5000 = 5.0 seconds).
3411 [USBHID] The interval which mice are to be polled at.
3413 usb-storage.delay_use=
3414 [UMS] The delay in seconds before a new device is
3415 scanned for Logical Units (default 5).
3418 [UMS] A list of quirks entries to supplement or
3419 override the built-in unusual_devs list. List
3420 entries are separated by commas. Each entry has
3421 the form VID:PID:Flags where VID and PID are Vendor
3422 and Product ID values (4-digit hex numbers) and
3423 Flags is a set of characters, each corresponding
3424 to a common usb-storage quirk flag as follows:
3425 a = SANE_SENSE (collect more than 18 bytes
3427 b = BAD_SENSE (don't collect more than 18
3428 bytes of sense data);
3429 c = FIX_CAPACITY (decrease the reported
3430 device capacity by one sector);
3431 d = NO_READ_DISC_INFO (don't use
3432 READ_DISC_INFO command);
3433 e = NO_READ_CAPACITY_16 (don't use
3434 READ_CAPACITY_16 command);
3435 h = CAPACITY_HEURISTICS (decrease the
3436 reported device capacity by one
3437 sector if the number is odd);
3438 i = IGNORE_DEVICE (don't bind to this
3440 l = NOT_LOCKABLE (don't try to lock and
3441 unlock ejectable media);
3442 m = MAX_SECTORS_64 (don't transfer more
3443 than 64 sectors = 32 KB at a time);
3444 n = INITIAL_READ10 (force a retry of the
3445 initial READ(10) command);
3446 o = CAPACITY_OK (accept the capacity
3447 reported by the device);
3448 p = WRITE_CACHE (the device cache is ON
3450 r = IGNORE_RESIDUE (the device reports
3451 bogus residue values);
3452 s = SINGLE_LUN (the device has only one
3454 w = NO_WP_DETECT (don't test whether the
3455 medium is write-protected).
3456 Example: quirks=0419:aaf5:rl,0421:0433:rc
3458 user_debug= [KNL,ARM]
3460 See arch/arm/Kconfig.debug help text.
3461 1 - undefined instruction events
3463 4 - invalid data aborts
3466 Example: user_debug=31
3469 [X86] Flags controlling user PTE allocations.
3471 nohigh = do not allocate PTE pages in
3472 HIGHMEM regardless of setting
3476 On X86_32, this is an alias for vdso32=. Otherwise:
3478 vdso=1: enable VDSO (the default)
3479 vdso=0: disable VDSO mapping
3481 vdso32= [X86] Control the 32-bit vDSO
3482 vdso32=1: enable 32-bit VDSO
3483 vdso32=0 or vdso32=2: disable 32-bit VDSO
3485 See the help text for CONFIG_COMPAT_VDSO for more
3486 details. If CONFIG_COMPAT_VDSO is set, the default is
3487 vdso32=0; otherwise, the default is vdso32=1.
3489 For compatibility with older kernels, vdso32=2 is an
3492 Try vdso32=0 if you encounter an error that says:
3493 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3496 vector=percpu: enable percpu vector domain
3498 video= [FB] Frame buffer configuration
3499 See Documentation/fb/modedb.txt.
3501 video.brightness_switch_enabled= [0,1]
3502 If set to 1, on receiving an ACPI notify event
3503 generated by hotkey, video driver will adjust brightness
3504 level and then send out the event to user space through
3505 the allocated input device; If set to 0, video driver
3506 will only send out the event without touching backlight
3511 [VMMIO] Memory mapped virtio (platform) device.
3513 <size>@<baseaddr>:<irq>[:<id>]
3515 <size> := size (can use standard suffixes
3517 <baseaddr> := physical base address
3518 <irq> := interrupt number (as passed to
3520 <id> := (optional) platform device id
3522 virtio_mmio.device=1K@0x100b0000:48:7
3524 Can be used multiple times for multiple devices.
3526 vga= [BOOT,X86-32] Select a particular video mode
3527 See Documentation/x86/boot.txt and
3528 Documentation/svga.txt.
3529 Use vga=ask for menu.
3530 This is actually a boot loader parameter; the value is
3531 passed to the kernel using a special protocol.
3533 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3534 size of <nn>. This can be used to increase the
3535 minimum size (128MB on x86). It can also be used to
3536 decrease the size and leave more room for directly
3539 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3542 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3545 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3549 Controls the behavior of vsyscalls (i.e. calls to
3550 fixed addresses of 0xffffffffff600x00 from legacy
3551 code). Most statically-linked binaries and older
3552 versions of glibc use these calls. Because these
3553 functions are at fixed addresses, they make nice
3554 targets for exploits that can control RIP.
3556 emulate [default] Vsyscalls turn into traps and are
3557 emulated reasonably safely.
3559 native Vsyscalls are native syscall instructions.
3560 This is a little bit faster than trapping
3561 and makes a few dynamic recompilers work
3562 better than they would in emulation mode.
3563 It also makes exploits much easier to write.
3565 none Vsyscalls don't work at all. This makes
3566 them quite hard to use for exploits but
3567 might break your system.
3569 vt.color= [VT] Default text color.
3570 Format: 0xYX, X = foreground, Y = background.
3571 Default: 0x07 = light gray on black.
3573 vt.cur_default= [VT] Default cursor shape.
3574 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3575 the parameters of the <Esc>[?A;B;Cc escape sequence;
3576 see VGA-softcursor.txt. Default: 2 = underline.
3578 vt.default_blu= [VT]
3579 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3580 Change the default blue palette of the console.
3581 This is a 16-member array composed of values
3584 vt.default_grn= [VT]
3585 Format: <green0>,<green1>,<green2>,...,<green15>
3586 Change the default green palette of the console.
3587 This is a 16-member array composed of values
3590 vt.default_red= [VT]
3591 Format: <red0>,<red1>,<red2>,...,<red15>
3592 Change the default red palette of the console.
3593 This is a 16-member array composed of values
3599 Set system-wide default UTF-8 mode for all tty's.
3600 Default is 1, i.e. UTF-8 mode is enabled for all
3601 newly opened terminals.
3603 vt.global_cursor_default=
3606 Set system-wide default for whether a cursor
3607 is shown on new VTs. Default is -1,
3608 i.e. cursors will be created by default unless
3609 overridden by individual drivers. 0 will hide
3610 cursors, 1 will display them.
3612 vt.italic= [VT] Default color for italic text; 0-15.
3615 vt.underline= [VT] Default color for underlined text; 0-15.
3618 watchdog timers [HW,WDT] For information on watchdog timers,
3619 see Documentation/watchdog/watchdog-parameters.txt
3620 or other driver-specific files in the
3621 Documentation/watchdog/ directory.
3623 workqueue.disable_numa
3624 By default, all work items queued to unbound
3625 workqueues are affine to the NUMA nodes they're
3626 issued on, which results in better behavior in
3627 general. If NUMA affinity needs to be disabled for
3628 whatever reason, this option can be used. Note
3629 that this also can be controlled per-workqueue for
3630 workqueues visible under /sys/bus/workqueue/.
3632 workqueue.power_efficient
3633 Per-cpu workqueues are generally preferred because
3634 they show better performance thanks to cache
3635 locality; unfortunately, per-cpu workqueues tend to
3636 be more power hungry than unbound workqueues.
3638 Enabling this makes the per-cpu workqueues which
3639 were observed to contribute significantly to power
3640 consumption unbound, leading to measurably lower
3641 power usage at the cost of small performance
3644 The default value of this parameter is determined by
3645 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3647 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3648 default x2apic cluster mode on platforms
3651 x86_intel_mid_timer= [X86-32,APBT]
3652 Choose timer option for x86 Intel MID platform.
3653 Two valid options are apbt timer only and lapic timer
3654 plus one apbt timer for broadcast timer.
3655 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3657 xen_emul_unplug= [HW,X86,XEN]
3658 Unplug Xen emulated devices
3659 Format: [unplug0,][unplug1]
3660 ide-disks -- unplug primary master IDE devices
3661 aux-ide-disks -- unplug non-primary-master IDE devices
3662 nics -- unplug network devices
3663 all -- unplug all emulated devices (NICs and IDE disks)
3664 unnecessary -- unplugging emulated devices is
3665 unnecessary even if the host did not respond to
3667 never -- do not unplug even if version check succeeds
3669 xen_nopvspin [X86,XEN]
3670 Disables the ticketlock slowpath using Xen PV
3673 xirc2ps_cs= [NET,PCMCIA]
3675 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3677 ______________________________________________________________________
3681 Add more DRM drivers.