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 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
47 EFI EFI Partitioning (GPT) is enabled
48 EIDE EIDE/ATAPI support is enabled.
49 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
51 FB The frame buffer device is enabled.
52 GCOV GCOV profiling is enabled.
53 HW Appropriate hardware is enabled.
54 IA-64 IA-64 architecture is enabled.
55 IMA Integrity measurement architecture is enabled.
56 IOSCHED More than one I/O scheduler is enabled.
57 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
58 IPV6 IPv6 support is enabled.
59 ISAPNP ISA PnP code is enabled.
60 ISDN Appropriate ISDN support is enabled.
61 JOY Appropriate joystick support is enabled.
62 KGDB Kernel debugger support is enabled.
63 KVM Kernel Virtual Machine support is enabled.
64 LIBATA Libata driver is enabled
65 LP Printer support is enabled.
66 LOOP Loopback device support is enabled.
67 M68k M68k architecture is enabled.
68 These options have more detailed description inside of
69 Documentation/m68k/kernel-options.txt.
70 MCA MCA bus support is enabled.
71 MDA MDA console support is enabled.
72 MOUSE Appropriate mouse support is enabled.
73 MSI Message Signaled Interrupts (PCI).
74 MTD MTD (Memory Technology Device) support is enabled.
75 NET Appropriate network support is enabled.
76 NUMA NUMA support is enabled.
77 NFS Appropriate NFS support is enabled.
78 OSS OSS sound support is enabled.
79 PV_OPS A paravirtualized kernel is enabled.
80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
81 PARISC The PA-RISC architecture is enabled.
82 PCI PCI bus support is enabled.
83 PCIE PCI Express support is enabled.
84 PCMCIA The PCMCIA subsystem is enabled.
85 PNP Plug & Play support is enabled.
86 PPC PowerPC architecture is enabled.
87 PPT Parallel port support is enabled.
88 PS2 Appropriate PS/2 support is enabled.
89 RAM RAM disk support is enabled.
90 S390 S390 architecture is enabled.
91 SCSI Appropriate SCSI support is enabled.
92 A lot of drivers have their options described inside
93 the Documentation/scsi/ sub-directory.
94 SECURITY Different security models are enabled.
95 SELINUX SELinux support is enabled.
96 APPARMOR AppArmor support is enabled.
97 SERIAL Serial support is enabled.
98 SH SuperH architecture is enabled.
99 SMP The kernel is an SMP kernel.
100 SPARC Sparc architecture is enabled.
101 SWSUSP Software suspend (hibernation) is enabled.
102 SUSPEND System suspend states are enabled.
103 FTRACE Function tracing enabled.
104 TPM TPM drivers are enabled.
105 TS Appropriate touchscreen support is enabled.
106 UMS USB Mass Storage support is enabled.
107 USB USB support is enabled.
108 USBHID USB Human Interface Device support is enabled.
109 V4L Video For Linux support is enabled.
110 VGA The VGA console has been enabled.
111 VT Virtual terminal support is enabled.
112 WDT Watchdog support is enabled.
113 XT IBM PC/XT MFM hard disk support is enabled.
114 X86-32 X86-32, aka i386 architecture is enabled.
115 X86-64 X86-64 architecture is enabled.
116 More X86-64 boot options can be found in
117 Documentation/x86/x86_64/boot-options.txt .
118 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
119 XEN Xen support is enabled
121 In addition, the following text indicates that the option:
123 BUGS= Relates to possible processor bugs on the said processor.
124 KNL Is a kernel start-up parameter.
125 BOOT Is a boot loader parameter.
127 Parameters denoted with BOOT are actually interpreted by the boot
128 loader, and have no meaning to the kernel directly.
129 Do not modify the syntax of boot loader parameters without extreme
130 need or coordination with <Documentation/x86/boot.txt>.
132 There are also arch-specific kernel-parameters not documented here.
133 See for example <Documentation/x86/x86_64/boot-options.txt>.
135 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
136 a trailing = on the name of any parameter states that that parameter will
137 be entered as an environment variable, whereas its absence indicates that
138 it will appear as a kernel argument readable via /proc/cmdline by programs
139 running once the system is up.
141 The number of kernel parameters is not limited, but the length of the
142 complete command line (parameters including spaces etc.) is limited to
143 a fixed number of characters. This limit depends on the architecture
144 and is between 256 and 4096 characters. It is defined in the file
145 ./include/asm/setup.h as COMMAND_LINE_SIZE.
149 Advanced Configuration and Power Interface
150 Format: { force | off | strict | noirq | rsdt }
151 force -- enable ACPI if default was off
152 off -- disable ACPI if default was on
153 noirq -- do not use ACPI for IRQ routing
154 strict -- Be less tolerant of platforms that are not
155 strictly ACPI specification compliant.
156 rsdt -- prefer RSDT over (default) XSDT
157 copy_dsdt -- copy DSDT to memory
159 See also Documentation/power/pm.txt, pci=noacpi
161 acpi_apic_instance= [ACPI, IOAPIC]
163 2: use 2nd APIC table, if available
164 1,0: use 1st APIC table
167 acpi_backlight= [HW,ACPI]
168 acpi_backlight=vendor
170 If set to vendor, prefer vendor specific driver
171 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
172 of the ACPI video.ko driver.
174 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
175 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
177 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
178 debug output. Bits in debug_layer correspond to a
179 _COMPONENT in an ACPI source file, e.g.,
180 #define _COMPONENT ACPI_PCI_COMPONENT
181 Bits in debug_level correspond to a level in
182 ACPI_DEBUG_PRINT statements, e.g.,
183 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
184 The debug_level mask defaults to "info". See
185 Documentation/acpi/debug.txt for more information about
186 debug layers and levels.
188 Enable processor driver info messages:
189 acpi.debug_layer=0x20000000
190 Enable PCI/PCI interrupt routing info messages:
191 acpi.debug_layer=0x400000
192 Enable AML "Debug" output, i.e., stores to the Debug
193 object while interpreting AML:
194 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
195 Enable all messages related to ACPI hardware:
196 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
198 Some values produce so much output that the system is
199 unusable. The "log_buf_len" parameter may be useful
200 if you need to capture more output.
202 acpi_display_output= [HW,ACPI]
203 acpi_display_output=vendor
204 acpi_display_output=video
207 acpi_irq_balance [HW,ACPI]
208 ACPI will balance active IRQs
211 acpi_irq_nobalance [HW,ACPI]
212 ACPI will not move active IRQs (default)
215 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
216 Format: <irq>,<irq>...
218 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
220 Format: <irq>,<irq>...
222 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
224 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
225 Format: To spoof as Windows 98: ="Microsoft Windows"
227 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
228 acpi_osi="string1" # add string1 -- only one string
229 acpi_osi="!string2" # remove built-in string2
230 acpi_osi= # disable all strings
233 Override the pmtimer bug detection: force the kernel
234 to assume that this machine's pmtimer latches its value
235 and always returns good values.
237 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
238 Format: { level | edge | high | low }
240 acpi_serialize [HW,ACPI] force serialization of AML methods
242 acpi_skip_timer_override [HW,ACPI]
243 Recognize and ignore IRQ0/pin2 Interrupt Override.
244 For broken nForce2 BIOS resulting in XT-PIC timer.
246 acpi_sleep= [HW,ACPI] Sleep options
247 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
248 old_ordering, s4_nonvs, sci_force_enable }
249 See Documentation/power/video.txt for information on
251 s3_beep is for debugging; it makes the PC's speaker beep
252 as soon as the kernel's real-mode entry point is called.
253 s4_nohwsig prevents ACPI hardware signature from being
254 used during resume from hibernation.
255 old_ordering causes the ACPI 1.0 ordering of the _PTS
256 control method, with respect to putting devices into
257 low power states, to be enforced (the ACPI 2.0 ordering
258 of _PTS is used by default).
259 nonvs prevents the kernel from saving/restoring the
260 ACPI NVS memory during suspend/hibernation and resume.
261 sci_force_enable causes the kernel to set SCI_EN directly
262 on resume from S1/S3 (which is against the ACPI spec,
263 but some broken systems don't work without it).
265 acpi_use_timer_override [HW,ACPI]
266 Use timer override. For some broken Nvidia NF5 boards
267 that require a timer override, but don't have HPET
269 acpi_enforce_resources= [ACPI]
270 { strict | lax | no }
271 Check for resource conflicts between native drivers
272 and ACPI OperationRegions (SystemIO and SystemMemory
273 only). IO ports and memory declared in ACPI might be
274 used by the ACPI subsystem in arbitrary AML code and
275 can interfere with legacy drivers.
276 strict (default): access to resources claimed by ACPI
277 is denied; legacy drivers trying to access reserved
278 resources will fail to bind to device using them.
279 lax: access to resources claimed by ACPI is allowed;
280 legacy drivers trying to access reserved resources
281 will bind successfully but a warning message is logged.
282 no: ACPI OperationRegions are not marked as reserved,
283 no further checks are performed.
285 add_efi_memmap [EFI; X86] Include EFI memory map in
286 kernel's map of available physical RAM.
289 { off | try_unsupported }
290 off: disable AGP support
291 try_unsupported: try to drive unsupported chipsets
292 (may crash computer or cause data corruption)
295 See Documentation/sound/alsa/alsa-parameters.txt
298 Allow the default userspace alignment fault handler
299 behaviour to be specified. Bit 0 enables warnings,
300 bit 1 enables fixups, and bit 2 sends a segfault.
302 amd_iommu= [HW,X86-84]
303 Pass parameters to the AMD IOMMU driver in the system.
305 fullflush - enable flushing of IO/TLB entries when
306 they are unmapped. Otherwise they are
307 flushed before they will be reused, which
309 off - do not initialize any AMD IOMMU found in
312 amijoy.map= [HW,JOY] Amiga joystick support
313 Map of devices attached to JOY0DAT and JOY1DAT
315 See also Documentation/kernel/input/joystick.txt
317 analog.map= [HW,JOY] Analog joystick and gamepad support
318 Specifies type or capabilities of an analog joystick
319 connected to one of 16 gameports
320 Format: <type1>,<type2>,..<type16>
323 Power management functions (SPARCstation-4/5 + deriv.)
325 Disable APC CPU standby support. SPARCstation-Fox does
326 not play well with APC CPU idle - disable it if you have
327 APC and your system crashes randomly.
329 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
330 Change the output verbosity whilst booting
331 Format: { quiet (default) | verbose | debug }
332 Change the amount of debugging information output
333 when initialising the APIC and IO-APIC components.
336 See Documentation/networking/ipv6.txt.
338 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
339 Limit apic dumping. The parameter defines the maximal
340 number of local apics being dumped. Also it is possible
341 to set it to "all" by meaning -- no limit here.
342 Format: { 1 (default) | 2 | ... | all }.
343 The parameter valid if only apic=debug or
344 apic=verbose is specified.
345 Example: apic=debug show_lapic=all
347 apm= [APM] Advanced Power Management
348 See header of arch/x86/kernel/apm_32.c.
350 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
351 Format: <io>,<irq>,<nodeID>
355 atarimouse= [HW,MOUSE] Atari Mouse
357 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
358 EzKey and similar keyboards
360 atkbd.reset= [HW] Reset keyboard during initialization
362 atkbd.set= [HW] Select keyboard code set
363 Format: <int> (2 = AT (default), 3 = PS/2)
365 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
368 atkbd.softraw= [HW] Choose between synthetic and real raw mode
369 Format: <bool> (0 = real, 1 = synthetic (default))
371 atkbd.softrepeat= [HW]
372 Use software keyboard repeat
376 baycom_epp= [HW,AX25]
379 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
381 See header of drivers/net/hamradio/baycom_par.c.
383 baycom_ser_fdx= [HW,AX25]
384 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
385 Format: <io>,<irq>,<mode>[,<baud>]
386 See header of drivers/net/hamradio/baycom_ser_fdx.c.
388 baycom_ser_hdx= [HW,AX25]
389 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
390 Format: <io>,<irq>,<mode>
391 See header of drivers/net/hamradio/baycom_ser_hdx.c.
393 boot_delay= Milliseconds to delay each printk during boot.
394 Values larger than 10 seconds (10000) are changed to
398 bootmem_debug [KNL] Enable bootmem allocator debug messages.
400 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
401 bttv.radio= Most important insmod options are available as
403 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
404 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
406 bulk_remove=off [PPC] This parameter disables the use of the pSeries
407 firmware feature for flushing multiple hpte entries
410 c101= [NET] Moxa C101 synchronous serial card
412 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
413 Sometimes CPU hardware bugs make them report the cache
414 size incorrectly. The kernel will attempt work arounds
415 to fix known problems, but for some CPUs it is not
416 possible to determine what the correct size should be.
417 This option provides an override for these situations.
420 [SECURITY] Disable capabilities. This would normally
421 be used only if an alternative security model is to be
422 configured. Potentially dangerous and should only be
423 used if you are entirely sure of the consequences.
425 ccw_timeout_log [S390]
426 See Documentation/s390/CommonIO for details.
428 cgroup_disable= [KNL] Disable a particular controller
429 Format: {name of the controller(s) to disable}
430 {Currently supported controllers - "memory"}
432 checkreqprot [SELINUX] Set initial checkreqprot flag value.
433 Format: { "0" | "1" }
434 See security/selinux/Kconfig help text.
435 0 -- check protection applied by kernel (includes
436 any implied execute protection).
437 1 -- check protection requested by application.
438 Default value is set via a kernel config option.
439 Value can be changed at runtime via
440 /selinux/checkreqprot.
443 See Documentation/s390/CommonIO for details.
445 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
447 Forces specified clocksource (if available) to be used
448 when calculating gettimeofday(). If specified
449 clocksource is not available, it defaults to PIT.
450 Format: { pit | tsc | cyclone | pmtmr }
452 clocksource= Override the default clocksource
454 Override the default clocksource and use the clocksource
455 with the name specified.
456 Some clocksource names to choose from, depending on
458 [all] jiffies (this is the base, fallback clocksource)
460 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
461 pxa_timer,timer3,32k_counter,timer0_1
463 [X86-32] pit,hpet,tsc;
464 scx200_hrt on Geode; cyclone on IBM x440
472 clearcpuid=BITNUM [X86]
473 Disable CPUID feature X for the kernel. See
474 arch/x86/include/asm/cpufeature.h for the valid bit
475 numbers. Note the Linux specific bits are not necessarily
476 stable over kernel options, but the vendor specific
478 Also note that user programs calling CPUID directly
479 or using the feature without checking anything
480 will still see it. This just prevents it from
481 being used by the kernel or shown in /proc/cpuinfo.
482 Also note the kernel might malfunction if you disable
485 cmo_free_hint= [PPC] Format: { yes | no }
486 Specify whether pages are marked as being inactive
487 when they are freed. This is used in CMO environments
488 to determine OS memory pressure for page stealing by
492 code_bytes [X86] How many bytes of object code to print
497 com20020= [HW,NET] ARCnet - COM20020 chipset
499 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
501 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
505 ARCnet - COM90xx chipset (memory-mapped buffers)
506 Format: <io>[,<irq>[,<memstart>]]
508 condev= [HW,S390] console device
511 console= [KNL] Output console device and options.
513 tty<n> Use the virtual console device <n>.
517 Use the specified serial port. The options are of
518 the form "bbbbpnf", where "bbbb" is the baud rate,
519 "p" is parity ("n", "o", or "e"), "n" is number of
520 bits, and "f" is flow control ("r" for RTS or
521 omit it). Default is "9600n8".
523 See Documentation/serial-console.txt for more
525 Documentation/networking/netconsole.txt for an
528 uart[8250],io,<addr>[,options]
529 uart[8250],mmio,<addr>[,options]
530 Start an early, polled-mode console on the 8250/16550
531 UART at the specified I/O port or MMIO address,
532 switching to the matching ttyS device later. The
533 options are the same as for ttyS, above.
535 If the device connected to the port is not a TTY but a braille
536 device, prepend "brl," before the device type, for instance
538 For now, only VisioBraille is supported.
540 consoleblank= [KNL] The console blank (screen saver) timeout in
541 seconds. Defaults to 10*60 = 10mins. A value of 0
542 disables the blank timer.
545 [KNL] Change the default value for
546 /proc/<pid>/coredump_filter.
547 See also Documentation/filesystems/proc.txt.
549 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
551 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
553 crashkernel=nn[KMG]@ss[KMG]
554 [KNL] Reserve a chunk of physical memory to
555 hold a kernel to switch to with kexec on panic.
557 crashkernel=range1:size1[,range2:size2,...][@offset]
558 [KNL] Same as above, but depends on the memory
559 in the running system. The syntax of range is
560 start-[end] where start and end are both
561 a memory unit (amount[KMG]). See also
562 Documentation/kdump/kdump.txt for a example.
567 cs89x0_media= [HW,NET]
568 Format: { rj45 | aui | bnc }
571 See header of drivers/s390/block/dasd_devmap.c.
573 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
574 (one device per port)
575 Format: <port#>,<type>
576 See also Documentation/input/joystick-parport.txt
578 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
579 time. See Documentation/dynamic-debug-howto.txt for
582 debug [KNL] Enable kernel debugging (events log level).
585 [KNL] verbose self-tests
587 Print debugging info while doing the locking API
589 We default to 0 (no extra messages), setting it to
590 1 will print _a lot_ more information - normally
591 only useful to kernel developers.
593 debug_objects [KNL] Enable object debugging
596 [KNL] Disable object debugging
598 debugpat [X86] Enable PAT debugging
600 decnet.addr= [HW,NET]
601 Format: <area>[,<node>]
602 See also Documentation/networking/decnet.txt.
605 [same as hugepagesz=] The size of the default
606 HugeTLB page size. This is the size represented by
607 the legacy /proc/ hugepages APIs, used for SHM, and
608 default size when mounting hugetlbfs filesystems.
609 Defaults to the default architecture's huge page size
613 Set number of hash buckets for dentry cache.
616 IO parameters + enable/disable command.
618 digiepca= [HW,SERIAL]
619 See drivers/char/README.epca and
620 Documentation/serial/digiepca.txt.
623 See Documentation/networking/ipv6.txt.
626 See Documentation/networking/ipv6.txt.
628 disable_mtrr_cleanup [X86]
629 The kernel tries to adjust MTRR layout from continuous
630 to discrete, to make X server driver able to add WB
631 entry later. This parameter disables that.
633 disable_mtrr_trim [X86, Intel and AMD only]
634 By default the kernel will trim any uncacheable
635 memory out of your available memory pool based on
636 MTRR settings. This parameter disables that behavior,
637 possibly causing your machine to run very slowly.
639 disable_timer_pin_1 [X86]
640 Disable PIN 1 of APIC timer
641 Can be useful to work around chipset bugs.
643 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
644 this option disables the debugging code at boot.
646 dma_debug_entries=<number>
647 This option allows to tune the number of preallocated
648 entries for DMA-API debugging code. One entry is
649 required per DMA-API allocation. Use this if the
650 DMA-API debugging code disables itself because the
651 architectural default is too low.
653 dma_debug_driver=<driver_name>
654 With this option the DMA-API debugging driver
655 filter feature can be enabled at boot time. Just
656 pass the driver to filter for as the parameter.
657 The filter can be disabled or changed to another
658 driver later using sysfs.
662 earlycon= [KNL] Output early console device and options.
663 uart[8250],io,<addr>[,options]
664 uart[8250],mmio,<addr>[,options]
665 uart[8250],mmio32,<addr>[,options]
666 Start an early, polled-mode console on the 8250/16550
667 UART at the specified I/O port or MMIO address.
668 MMIO inter-register address stride is either 8bit (mmio)
670 The options are the same as for ttyS, above.
672 earlyprintk= [X86,SH,BLACKFIN]
674 earlyprintk=serial[,ttySn[,baudrate]]
675 earlyprintk=ttySn[,baudrate]
676 earlyprintk=dbgp[debugController#]
678 Append ",keep" to not disable it when the real console
681 Only vga or serial or usb debug port at a time.
683 Currently only ttyS0 and ttyS1 are supported.
685 Interaction with the standard serial driver is not
688 The VGA output is eventually overwritten by the real
691 ekgdboc= [X86,KGDB] Allow early kernel console debugging
694 This is desgined to be used in conjunction with
695 the boot argument: earlyprintk=vga
698 Format: {"off" | "on" | "skip[mbr]"}
700 eisa_irq_edge= [PARISC,HW]
701 See header of drivers/parisc/eisa.c.
704 See comment before function elanfreq_setup() in
705 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
708 Format: {"cfq" | "deadline" | "noop"}
709 See Documentation/block/as-iosched.txt and
710 Documentation/block/deadline-iosched.txt for details.
712 elfcorehdr= [IA64,PPC,SH,X86]
713 Specifies physical address of start of kernel core
714 image elf header. Generally kexec loader will
715 pass this option to capture kernel.
716 See Documentation/kdump/kdump.txt for details.
718 enable_mtrr_cleanup [X86]
719 The kernel tries to adjust MTRR layout from continuous
720 to discrete, to make X server driver able to add WB
721 entry later. This parameter enables that.
723 enable_timer_pin_1 [X86]
724 Enable PIN 1 of APIC timer
725 Can be useful to work around chipset bugs
726 (in particular on some ATI chipsets).
727 The kernel tries to set a reasonable default.
729 enforcing [SELINUX] Set initial enforcing status.
731 See security/selinux/Kconfig help text.
732 0 -- permissive (log only, no denials).
733 1 -- enforcing (deny and log).
735 Value can be changed at runtime via /selinux/enforce.
738 Disable Error Record Serialization Table (ERST)
741 ether= [HW,NET] Ethernet cards parameters
742 This option is obsoleted by the "netdev=" option, which
743 has equivalent usage. See its documentation for details.
747 fail_make_request=[KNL]
748 General fault injection mechanism.
749 Format: <interval>,<probability>,<space>,<times>
750 See also /Documentation/fault-injection/.
753 See Documentation/blockdev/floppy.txt.
755 force_pal_cache_flush
756 [IA-64] Avoid check_sal_cache_flush which may hang on
757 buggy SAL_CACHE_FLUSH implementations. Using this
758 parameter will force ia64_sal_cache_flush to call
759 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
762 [FTRACE] will set and start the specified tracer
763 as early as possible in order to facilitate early
766 ftrace_dump_on_oops[=orig_cpu]
767 [FTRACE] will dump the trace buffers on oops.
768 If no parameter is passed, ftrace will dump
769 buffers of all CPUs, but if you pass orig_cpu, it will
770 dump only the buffer of the CPU that triggered the
773 ftrace_filter=[function-list]
774 [FTRACE] Limit the functions traced by the function
775 tracer at boot up. function-list is a comma separated
776 list of functions. This list can be changed at run
777 time by the set_ftrace_filter file in the debugfs
780 ftrace_notrace=[function-list]
781 [FTRACE] Do not trace the functions specified in
782 function-list. This list can be changed at run time
783 by the set_ftrace_notrace file in the debugfs
786 ftrace_graph_filter=[function-list]
787 [FTRACE] Limit the top level callers functions traced
788 by the function graph tracer at boot up.
789 function-list is a comma separated list of functions
790 that can be changed at run time by the
791 set_graph_function file in the debugfs tracing directory.
794 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
795 support via parallel port (up to 5 devices per port)
796 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
797 See also Documentation/input/joystick-parport.txt
801 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
805 gcov_persist= [GCOV] When non-zero (default), profiling data for
806 kernel modules is saved and remains accessible via
807 debugfs, even when the module is unloaded/reloaded.
808 When zero, profiling data is discarded and associated
809 debugfs files are removed at module unload time.
811 gpt [EFI] Forces disk with valid GPT signature but
812 invalid Protective MBR to be treated as GPT.
814 hashdist= [KNL,NUMA] Large hashes allocated during boot
815 are distributed across NUMA nodes. Defaults on
816 for 64bit NUMA, off otherwise.
817 Format: 0 | 1 (for off | on)
819 hcl= [IA-64] SGI's Hardware Graph compatibility layer
821 hd= [EIDE] (E)IDE hard drive subsystem geometry
822 Format: <cyl>,<head>,<sect>
825 Disable Hardware Error Source Table (HEST) support;
826 corresponding firmware-first mode error processing
827 logic will be disabled.
829 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
830 size of <nn>. This works even on boxes that have no
831 highmem otherwise. This also works to reduce highmem
832 size on bigger boxes.
834 highres= [KNL] Enable/disable high resolution timer mode.
835 Valid parameters: "on", "off"
839 See Documentation/isdn/README.HiSax.
843 hpet= [X86-32,HPET] option to control HPET usage
844 Format: { enable (default) | disable | force |
846 disable: disable HPET and use PIT instead
847 force: allow force enabled of undocumented chips (ICH4,
849 verbose: show contents of HPET registers during setup
851 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
852 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
853 On x86-64 and powerpc, this option can be specified
854 multiple times interleaved with hugepages= to reserve
855 huge pages of different sizes. Valid pages sizes on
856 x86-64 are 2M (when the CPU supports "pse") and 1G
857 (when the CPU supports the "pdpe1gb" cpuinfo flag)
858 Note that 1GB pages can only be allocated at boot time
859 using hugepages= and not freed afterwards.
861 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
862 terminal devices. Valid values: 0..8
863 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
864 If specified, z/VM IUCV HVC accepts connections
865 from listed z/VM user IDs only.
867 i2c_bus= [HW] Override the default board specific I2C bus speed
868 or register an additional I2C bus that is not
869 registered from board initialization code.
873 i8042.debug [HW] Toggle i8042 debug mode
874 i8042.direct [HW] Put keyboard port into non-translated mode
875 i8042.dumbkbd [HW] Pretend that controller can only read data from
876 keyboard and cannot control its state
877 (Don't attempt to blink the leds)
878 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
879 i8042.nokbd [HW] Don't check/create keyboard port
880 i8042.noloop [HW] Disable the AUX Loopback command while probing
882 i8042.nomux [HW] Don't check presence of an active multiplexing
884 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
886 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
887 i8042.reset [HW] Reset the controller during init and cleanup
888 i8042.unlock [HW] Unlock (ignore) the keylock
892 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
893 indicates that the driver is running on unsupported
895 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
896 does not match list of supported models.
898 [HW] Report power status in /proc/i8k
899 (disabled by default)
900 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
904 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
906 ide-core.nodma= [HW] (E)IDE subsystem
907 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
908 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
909 .cdrom .chs .ignore_cable are additional options
910 See Documentation/ide/ide.txt.
912 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
913 Claim all unknown PCI IDE storage controllers.
916 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
917 Poll forces a polling idle loop that can slightly
918 improve the performance of waking up a idle CPU, but
919 will use a lot of power and make the system run hot.
921 idle=mwait: On systems which support MONITOR/MWAIT but
922 the kernel chose to not use it because it doesn't save
923 as much power as a normal idle loop, use the
924 MONITOR/MWAIT idle loop anyways. Performance should be
925 the same as idle=poll.
926 idle=halt: Halt is forced to be used for CPU idle.
927 In such case C2/C3 won't be used again.
928 idle=nomwait: Disable mwait for CPU C-states
930 ignore_loglevel [KNL]
931 Ignore loglevel setting - this will print /all/
932 kernel messages to the console. Useful for debugging.
935 Set number of hash buckets for inode cache.
938 Format: { "0" | "1" }
939 0 -- integrity auditing messages. (Default)
940 1 -- enable informational integrity auditing messages.
943 Format: { "sha1" | "md5" }
947 Load a policy which meets the needs of the Trusted
948 Computing Base. This means IMA will measure all
949 programs exec'd, files mmap'd for exec, and all files
950 opened for read by uid=0.
954 Run specified binary instead of /sbin/init as init
957 initcall_debug [KNL] Trace initcalls as they are executed. Useful
958 for working out where the kernel is dying during
961 initrd= [BOOT] Specify the location of the initial ramdisk
963 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
966 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
968 Enable intel iommu driver.
970 Disable intel iommu driver.
971 igfx_off [Default Off]
972 By default, gfx is mapped as normal device. If a gfx
973 device has a dedicated DMAR unit, the DMAR unit is
974 bypassed by not enabling DMAR with this option. In
975 this case, gfx device will use physical address for
978 With this option iommu will not optimize to look
979 for io virtual address below 32 bit forcing dual
980 address cycle on pci bus for cards supporting greater
981 than 32 bit addressing. The default is to look
982 for translation below 32 bit and if not available
983 then look in the higher range.
985 With this option on every unmap_single operation will
986 result in a hardware IOTLB flush operation as opposed
987 to batching them for performance.
989 intremap= [X86-64, Intel-IOMMU]
990 Format: { on (default) | off | nosid }
991 on enable Interrupt Remapping (default)
992 off disable Interrupt Remapping
993 nosid disable Source ID checking
997 iomem= Disable strict checking of access to MMIO memory
998 strict regions from userspace.
1014 io7= [HW] IO7 for Marvel based alpha systems
1015 See comment before marvel_specify_io7 in
1016 arch/alpha/kernel/core_marvel.c.
1018 io_delay= [X86] I/O delay method
1020 Standard port 0x80 based delay
1022 Alternate port 0xed based delay (needed on some systems)
1024 Simple two microseconds delay
1029 See Documentation/filesystems/nfs/nfsroot.txt.
1031 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1032 See comment before ip2_setup() in
1033 drivers/char/ip2/ip2base.c.
1036 When an interrupt is not handled search all handlers
1037 for it. Intended to get systems with badly broken
1041 When an interrupt is not handled search all handlers
1042 for it. Also check all handlers each timer
1043 interrupt. Intended to get systems with badly broken
1047 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1049 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1051 <cpu number>,...,<cpu number>
1053 <cpu number>-<cpu number>
1054 (must be a positive range in ascending order)
1056 <cpu number>,...,<cpu number>-<cpu number>
1058 This option can be used to specify one or more CPUs
1059 to isolate from the general SMP balancing and scheduling
1060 algorithms. You can move a process onto or off an
1061 "isolated" CPU via the CPU affinity syscalls or cpuset.
1062 <cpu number> begins at 0 and the maximum value is
1063 "number of CPUs in system - 1".
1065 This option is the preferred way to isolate CPUs. The
1066 alternative -- manually setting the CPU mask of all
1067 tasks in the system -- can cause problems and
1068 suboptimal load balancer performance.
1072 js= [HW,JOY] Analog joystick
1073 See Documentation/input/joystick.txt.
1077 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1078 specifies the amount of memory usable by the kernel
1079 for non-movable allocations. The requested amount is
1080 spread evenly throughout all nodes in the system. The
1081 remaining memory in each node is used for Movable
1082 pages. In the event, a node is too small to have both
1083 kernelcore and Movable pages, kernelcore pages will
1084 take priority and other nodes will have a larger number
1085 of kernelcore pages. The Movable zone is used for the
1086 allocation of pages that may be reclaimed or moved
1087 by the page migration subsystem. This means that
1088 HugeTLB pages may not be allocated from this zone.
1089 Note that allocations like PTEs-from-HighMem still
1090 use the HighMem zone if it exists, and the Normal
1091 zone if it does not.
1093 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1094 Format: <Controller#>[,poll interval]
1095 The controller # is the number of the ehci usb debug
1096 port as it is probed via PCI. The poll interval is
1097 optional and is the number seconds in between
1098 each poll cycle to the debug port in case you need
1099 the functionality for interrupting the kernel with
1100 gdb or control-c on the dbgp connection. When
1101 not using this parameter you use sysrq-g to break into
1102 the kernel debugger.
1104 kgdboc= [KGDB,HW] kgdb over consoles.
1105 Requires a tty driver that supports console polling,
1106 or a supported polling keyboard driver (non-usb).
1107 Serial only format: <serial_device>[,baud]
1108 keyboard only format: kbd
1109 keyboard and serial format: kbd,<serial_device>[,baud]
1110 Optional Kernel mode setting:
1111 kms, kbd format: kms,kbd
1112 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1114 kgdbwait [KGDB] Stop kernel execution and enter the
1115 kernel debugger at the earliest opportunity.
1117 kmac= [MIPS] korina ethernet MAC address.
1118 Configure the RouterBoard 532 series on-chip
1119 Ethernet adapter MAC address.
1121 kmemleak= [KNL] Boot-time kmemleak enable/disable
1122 Valid arguments: on, off
1125 kstack=N [X86] Print N words from the kernel stack
1128 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1129 Default is 0 (don't ignore, but inject #GP)
1131 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1132 Default is 1 (enabled)
1134 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1138 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1139 Default is 1 (enabled)
1141 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1143 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1145 kvm-intel.bypass_guest_pf=
1146 [KVM,Intel] Disables bypassing of guest page faults
1147 on Intel chips. Default is 1 (enabled)
1149 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1150 (virtualized MMU) support on capable Intel chips.
1151 Default is 1 (enabled)
1153 kvm-intel.emulate_invalid_guest_state=
1154 [KVM,Intel] Enable emulation of invalid guest states
1155 Default is 0 (disabled)
1157 kvm-intel.flexpriority=
1158 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1159 Default is 1 (enabled)
1161 kvm-intel.unrestricted_guest=
1162 [KVM,Intel] Disable unrestricted guest feature
1163 (virtualized real and unpaged mode) on capable
1164 Intel chips. Default is 1 (enabled)
1166 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1167 feature (tagged TLBs) on capable Intel chips.
1168 Default is 1 (enabled)
1174 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1177 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1180 libata.dma= [LIBATA] DMA control
1181 libata.dma=0 Disable all PATA and SATA DMA
1182 libata.dma=1 PATA and SATA Disk DMA only
1183 libata.dma=2 ATAPI (CDROM) DMA only
1184 libata.dma=4 Compact Flash DMA only
1185 Combinations also work, so libata.dma=3 enables DMA
1186 for disks and CDROMs, but not CFs.
1188 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1189 libata.ignore_hpa=0 keep BIOS limits (default)
1190 libata.ignore_hpa=1 ignore limits, using full disk
1192 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1196 libata.force= [LIBATA] Force configurations. The format is comma
1197 separated list of "[ID:]VAL" where ID is
1198 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1199 matching port, link or device. Basically, it matches
1200 the ATA ID string printed on console by libata. If
1201 the whole ID part is omitted, the last PORT and DEVICE
1202 values are used. If ID hasn't been specified yet, the
1203 configuration applies to all ports, links and devices.
1205 If only DEVICE is omitted, the parameter applies to
1206 the port and all links and devices behind it. DEVICE
1207 number of 0 either selects the first device or the
1208 first fan-out link behind PMP device. It does not
1209 select the host link. DEVICE number of 15 selects the
1210 host link and device attached to it.
1212 The VAL specifies the configuration to force. As long
1213 as there's no ambiguity shortcut notation is allowed.
1214 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1215 The following configurations can be forced.
1217 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1218 Any ID with matching PORT is used.
1220 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1222 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1223 udma[/][16,25,33,44,66,100,133] notation is also
1226 * [no]ncq: Turn on or off NCQ.
1228 * nohrst, nosrst, norst: suppress hard, soft
1231 * dump_id: dump IDENTIFY data.
1233 If there are multiple matching configurations changing
1234 the same attribute, the last one is used.
1236 memblock=debug [KNL] Enable memblock debug messages.
1238 load_ramdisk= [RAM] List of ramdisks to load from floppy
1239 See Documentation/blockdev/ramdisk.txt.
1241 lockd.nlm_grace_period=P [NFS] Assign grace period.
1244 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1247 lockd.nlm_timeout=T [NFS] Assign timeout value.
1250 lockd.nlm_udpport=M [NFS] Assign UDP port.
1253 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1256 loglevel= All Kernel Messages with a loglevel smaller than the
1257 console loglevel will be printed to the console. It can
1258 also be changed with klogd or other programs. The
1259 loglevels are defined as follows:
1261 0 (KERN_EMERG) system is unusable
1262 1 (KERN_ALERT) action must be taken immediately
1263 2 (KERN_CRIT) critical conditions
1264 3 (KERN_ERR) error conditions
1265 4 (KERN_WARNING) warning conditions
1266 5 (KERN_NOTICE) normal but significant condition
1267 6 (KERN_INFO) informational
1268 7 (KERN_DEBUG) debug-level messages
1270 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1271 Format: { n | nk | nM }
1272 n must be a power of two. The default size
1273 is set in the kernel config file.
1275 logo.nologo [FB] Disables display of the built-in Linux logo.
1276 This may be used to provide more screen space for
1277 kernel log messages and is useful when debugging
1278 kernel boot problems.
1280 lp=0 [LP] Specify parallel ports to use, e.g,
1281 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1282 lp=reset first parallel port). 'lp=0' disables the
1283 lp=auto printer driver. 'lp=reset' (which can be
1284 specified in addition to the ports) causes
1285 attached printers to be reset. Using
1286 lp=port1,port2,... specifies the parallel ports
1287 to associate lp devices with, starting with
1288 lp0. A port specification may be 'none' to skip
1289 that lp device, or a parport name such as
1290 'parport0'. Specifying 'lp=auto' instead of a
1291 port specification list means that device IDs
1292 from each port should be examined, to see if
1293 an IEEE 1284-compliant printer is attached; if
1294 so, the driver will manage that printer.
1295 See also header of drivers/char/lp.c.
1298 Sets loops_per_jiffy to given constant, thus avoiding
1299 time-consuming boot-time autodetection (up to 250 ms per
1300 CPU). 0 enables autodetection (default). To determine
1301 the correct value for your kernel, boot with normal
1302 autodetection and see what value is printed. Note that
1303 on SMP systems the preset will be applied to all CPUs,
1304 which is likely to cause problems if your CPUs need
1305 significantly divergent settings. An incorrect value
1306 will cause delays in the kernel to be wrong, leading to
1307 unpredictable I/O errors and other breakage. Although
1308 unlikely, in the extreme case this might damage your
1312 Format: <io>,<irq>,<dma>
1314 machvec= [IA64] Force the use of a particular machine-vector
1315 (machvec) in a generic kernel.
1316 Example: machvec=hpzx1_swiotlb
1318 machtype= [Loongson] Share the same kernel image file between different
1320 Example: machtype=lemote-yeeloong-2f-7inch
1322 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1323 than or equal to this physical address is ignored.
1325 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1326 should make use of. maxcpus=n : n >= 0 limits the
1327 kernel to using 'n' processors. n=0 is a special case,
1328 it is equivalent to "nosmp", which also disables
1331 max_loop= [LOOP] Maximum number of loopback devices that can
1337 mce [X86-32] Machine Check Exception
1339 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1341 md= [HW] RAID subsystems devices and level
1342 See Documentation/md.txt.
1345 Format: <first>,<last>
1346 Specifies range of consoles to be captured by the MDA.
1348 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1349 Amount of memory to be used when the kernel is not able
1350 to see the whole system memory or for test.
1351 [X86-32] Use together with memmap= to avoid physical
1352 address space collisions. Without memmap= PCI devices
1353 could be placed at addresses belonging to unused RAM.
1355 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1359 [KNL,SH] Allow user to override the default size for
1360 per-device physically contiguous DMA buffers.
1362 memmap=exactmap [KNL,X86] Enable setting of an exact
1363 E820 memory map, as specified by the user.
1364 Such memmap=exactmap lines can be constructed based on
1365 BIOS output or other requirements. See the memmap=nn@ss
1368 memmap=nn[KMG]@ss[KMG]
1369 [KNL] Force usage of a specific region of memory
1370 Region of memory to be used, from ss to ss+nn.
1372 memmap=nn[KMG]#ss[KMG]
1373 [KNL,ACPI] Mark specific memory as ACPI data.
1374 Region of memory to be used, from ss to ss+nn.
1376 memmap=nn[KMG]$ss[KMG]
1377 [KNL,ACPI] Mark specific memory as reserved.
1378 Region of memory to be used, from ss to ss+nn.
1379 Example: Exclude memory from 0x18690000-0x1869ffff
1380 memmap=64K$0x18690000
1382 memmap=0x10000$0x18690000
1384 memory_corruption_check=0/1 [X86]
1385 Some BIOSes seem to corrupt the first 64k of
1386 memory when doing things like suspend/resume.
1387 Setting this option will scan the memory
1388 looking for corruption. Enabling this will
1389 both detect corruption and prevent the kernel
1390 from using the memory being corrupted.
1391 However, its intended as a diagnostic tool; if
1392 repeatable BIOS-originated corruption always
1393 affects the same memory, you can use memmap=
1394 to prevent the kernel from using that memory.
1396 memory_corruption_check_size=size [X86]
1397 By default it checks for corruption in the low
1398 64k, making this memory unavailable for normal
1399 use. Use this parameter to scan for
1400 corruption in more or less memory.
1402 memory_corruption_check_period=seconds [X86]
1403 By default it checks for corruption every 60
1404 seconds. Use this parameter to check at some
1405 other rate. 0 disables periodic checking.
1407 memtest= [KNL,X86] Enable memtest
1409 default : 0 <disable>
1410 Specifies the number of memtest passes to be
1411 performed. Each pass selects another test
1412 pattern from a given set of patterns. Memtest
1413 fills the memory with this pattern, validates
1414 memory contents and reserves bad memory
1415 regions that are detected.
1417 meye.*= [HW] Set MotionEye Camera parameters
1418 See Documentation/video4linux/meye.txt.
1420 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1421 Multi-Function General Purpose Timers on AMD Geode
1424 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1425 the BIOS has incorrectly applied a workaround. TinyBIOS
1426 version 0.98 is known to be affected, 0.99 fixes the
1427 problem by letting the user disable the workaround.
1431 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1432 physical address is ignored.
1434 mini2440= [ARM,HW,KNL]
1435 Format:[0..2][b][c][t]
1437 MINI2440 configuration specification:
1438 0 - The attached screen is the 3.5" TFT
1439 1 - The attached screen is the 7" TFT
1440 2 - The VGA Shield is attached (1024x768)
1441 Leaving out the screen size parameter will not load
1442 the TFT driver, and the framebuffer will be left
1444 b - Enable backlight. The TFT backlight pin will be
1445 linked to the kernel VESA blanking code and a GPIO
1446 LED. This parameter is not necessary when using the
1448 c - Enable the s3c camera interface.
1449 t - Reserved for enabling touchscreen support. The
1450 touchscreen support is not enabled in the mainstream
1451 kernel as of 2.6.30, a preliminary port can be found
1452 in the "bleeding edge" mini2440 support kernel at
1453 http://repo.or.cz/w/linux-2.6/mini2440.git
1456 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1457 parameter allows control of the logging verbosity for
1458 the additional memory initialisation checks. A value
1459 of 0 disables mminit logging and a level of 4 will
1460 log everything. Information is printed at KERN_DEBUG
1461 so loglevel=8 may also need to be specified.
1464 [MOUSE] Maximum time between finger touching and
1465 leaving touchpad surface for touch to be considered
1466 a tap and be reported as a left button click (for
1467 touchpads working in absolute mode only).
1469 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1470 reporting absolute coordinates, such as tablets
1471 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1472 reporting absolute coordinates, such as tablets
1474 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1475 is similar to kernelcore except it specifies the
1476 amount of memory used for migratable allocations.
1477 If both kernelcore and movablecore is specified,
1478 then kernelcore will be at *least* the specified
1479 value but may be more. If movablecore on its own
1480 is specified, the administrator must be careful
1481 that the amount of memory usable for all allocations
1484 MTD_Partition= [MTD]
1485 Format: <name>,<region-number>,<size>,<offset>
1487 MTD_Region= [MTD] Format:
1488 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1491 See drivers/mtd/cmdlinepart.c.
1493 multitce=off [PPC] This parameter disables the use of the pSeries
1494 firmware feature for updating multiple TCE entries
1497 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1499 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1501 boundary - index of last SLC block on Flex-OneNAND.
1502 The remaining blocks are configured as MLC blocks.
1503 lock - Configure if Flex-OneNAND boundary should be locked.
1504 Once locked, the boundary cannot be changed.
1505 1 indicates lock status, 0 indicates unlock status.
1508 ARM/S3C2412 JIVE boot control
1510 See arch/arm/mach-s3c2412/mach-jive.c
1512 mtouchusb.raw_coordinates=
1513 [HW] Make the MicroTouch USB driver use raw coordinates
1514 ('y', default) or cooked coordinates ('n')
1516 mtrr_chunk_size=nn[KMG] [X86]
1517 used for mtrr cleanup. It is largest continuous chunk
1518 that could hold holes aka. UC entries.
1520 mtrr_gran_size=nn[KMG] [X86]
1521 Used for mtrr cleanup. It is granularity of mtrr block.
1523 Large value could prevent small alignment from
1526 mtrr_spare_reg_nr=n [X86]
1528 Range: 0,7 : spare reg number
1530 Used for mtrr cleanup. It is spare mtrr entries number.
1531 Set to 2 or more if your graphical card needs more.
1533 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1535 netdev= [NET] Network devices parameters
1536 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1537 Note that mem_start is often overloaded to mean
1538 something different and driver-specific.
1539 This usage is only documented in each driver source
1543 [NETFILTER] Enable connection tracking flow accounting
1544 0 to disable accounting
1545 1 to enable accounting
1548 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1549 See Documentation/filesystems/nfs/nfsroot.txt.
1551 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1552 See Documentation/filesystems/nfs/nfsroot.txt.
1554 nfsrootdebug [NFS] enable nfsroot debugging messages.
1555 See Documentation/filesystems/nfs/nfsroot.txt.
1557 nfs.callback_tcpport=
1558 [NFS] set the TCP port on which the NFSv4 callback
1559 channel should listen.
1562 [NFS] sets the pathname to the program which is used
1563 to update the NFS client cache entries.
1565 nfs.cache_getent_timeout=
1566 [NFS] sets the timeout after which an attempt to
1567 update a cache entry is deemed to have failed.
1569 nfs.idmap_cache_timeout=
1570 [NFS] set the maximum lifetime for idmapper cache
1574 [NFS] enable 64-bit inode numbers.
1575 If zero, the NFS client will fake up a 32-bit inode
1576 number for the readdir() and stat() syscalls instead
1577 of returning the full 64-bit number.
1578 The default is to return 64-bit inode numbers.
1580 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1581 when a NMI is triggered.
1582 Format: [state][,regs][,debounce][,die]
1584 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1585 Format: [panic,][num]
1587 0 - turn nmi_watchdog off
1588 When panic is specified, panic when an NMI watchdog
1590 This is useful when you use a panic=... timeout and
1591 need the box quickly up again.
1593 netpoll.carrier_timeout=
1594 [NET] Specifies amount of time (in seconds) that
1595 netpoll should wait for a carrier. By default netpoll
1598 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1599 emulation library even if a 387 maths coprocessor
1603 [HW] Never suspend the console
1604 Disable suspending of consoles during suspend and
1605 hibernate operations. Once disabled, debugging
1606 messages can reach various consoles while the rest
1607 of the system is being put to sleep (ie, while
1608 debugging driver suspend/resume hooks). This may
1609 not work reliably with all consoles, but is known
1610 to work with serial and VGA consoles.
1612 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1613 caches in the slab allocator. Saves per-node memory,
1614 but will impact performance.
1618 noapic [SMP,APIC] Tells the kernel to not make use of any
1619 IOAPICs that may be present in the system.
1621 noautogroup Disable scheduler automatic task group creation.
1623 nobats [PPC] Do not use BATs for mapping kernel lowmem
1624 on "Classic" PPC cores.
1628 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1630 nodelayacct [KNL] Disable per-task delay accounting
1632 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1634 nodsp [SH] Disable hardware DSP at boot time.
1636 noefi [X86] Disable EFI runtime services support.
1641 On X86-32 available only on PAE configured kernels.
1642 noexec=on: enable non-executable mappings (default)
1643 noexec=off: disable non-executable mappings
1646 This affects only 32-bit executables.
1647 noexec32=on: enable non-executable mappings (default)
1648 read doesn't imply executable mappings
1649 noexec32=off: disable non-executable mappings
1650 read implies executable mappings
1652 nofpu [SH] Disable hardware FPU at boot time.
1654 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1655 register save and restore. The kernel will only save
1656 legacy floating-point registers on task switch.
1658 noxsave [BUGS=X86] Disables x86 extended register state save
1659 and restore using xsave. The kernel will fallback to
1660 enabling legacy floating-point and sse state.
1662 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1663 wfi(ARM) instruction doesn't work correctly and not to
1664 use it. This is also useful when using JTAG debugger.
1666 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1667 instruction doesn't work correctly and not to
1670 no_file_caps Tells the kernel not to honor file capabilities. The
1671 only way then for a file to be executed with privilege
1672 is to be setuid root or executed by root.
1674 nohalt [IA-64] Tells the kernel not to use the power saving
1675 function PAL_HALT_LIGHT when idle. This increases
1676 power-consumption. On the positive side, it reduces
1677 interrupt wake-up latency, which may improve performance
1678 in certain environments such as networked servers or
1681 nohz= [KNL] Boottime enable/disable dynamic ticks
1682 Valid arguments: on, off
1685 noiotrap [SH] Disables trapped I/O port accesses.
1687 noirqdebug [X86-32] Disables the code which attempts to detect and
1688 disable unhandled interrupt sources.
1690 no_timer_check [X86,APIC] Disables the code which tests for
1691 broken timer IRQ sources.
1693 noisapnp [ISAPNP] Disables ISA PnP code.
1695 noinitrd [RAM] Tells the kernel not to load any configured
1698 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1700 [Deprecated - use intremap=off]
1704 nojitter [IA64] Disables jitter checking for ITC timers.
1706 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1708 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1711 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1713 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1715 noltlbs [PPC] Do not use large page/tlb entries for kernel
1716 lowmem mapping on PPC40x.
1718 nomca [IA-64] Disable machine check abort handling
1720 nomce [X86-32] Machine Check Exception
1722 nomfgpt [X86-32] Disable Multi-Function General Purpose
1723 Timer usage (for AMD Geode machines).
1725 nopat [X86] Disable PAT (page attribute table extension of
1726 pagetables) support.
1728 norandmaps Don't use address space randomization. Equivalent to
1729 echo 0 > /proc/sys/kernel/randomize_va_space
1731 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1733 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1734 with UP alternatives
1736 noresidual [PPC] Don't use residual data on PReP machines.
1738 noresume [SWSUSP] Disables resume and restores original swap
1741 no-scroll [VGA] Disables scrollback.
1742 This is required for the Braillex ib80-piezo Braille
1743 reader made by F.H. Papenmeier (Germany).
1747 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1749 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1750 and disable the IO APIC. legacy for "maxcpus=0".
1752 nosoftlockup [KNL] Disable the soft-lockup detector.
1754 noswapaccount [KNL] Disable accounting of swap in memory resource
1755 controller. (See Documentation/cgroups/memory.txt)
1757 nosync [HW,M68K] Disables sync negotiation for all devices.
1759 notsc [BUGS=X86-32] Disable Time Stamp Counter
1761 nousb [USB] Disable the USB subsystem
1763 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1767 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1769 nptcg= [IA64] Override max number of concurrent global TLB
1770 purges which is reported from either PAL_VM_SUMMARY or
1773 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1774 could support. nr_cpus=n : n >= 1 limits the kernel to
1775 supporting 'n' processors. Later in runtime you can not
1776 use hotplug cpu feature to put more cpu back to online.
1777 just like you compile the kernel NR_CPUS=n
1779 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1781 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1782 one of ['zone', 'node', 'default'] can be specified
1783 This can be set from sysctl after boot.
1784 See Documentation/sysctl/vm.txt for details.
1786 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1787 See Documentation/debugging-via-ohci1394.txt for more
1790 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1791 Rather than timing out after 20 ms if an EC
1792 command is not properly ACKed, override the length
1793 of the timeout. We have interrupts disabled while
1794 waiting for the ACK, so if this is set too high
1795 interrupts *may* be lost!
1797 omap_mux= [OMAP] Override bootloader pin multiplexing.
1798 Format: <mux_mode0.mode_name=value>...
1799 For example, to override I2C bus2:
1800 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1802 oprofile.timer= [HW]
1803 Use timer interrupt instead of performance counters
1805 oprofile.cpu_type= Force an oprofile cpu type
1806 This might be useful if you have an older oprofile
1807 userland or if you want common events.
1808 Format: { arch_perfmon }
1809 arch_perfmon: [X86] Force use of architectural
1810 perfmon on Intel CPUs instead of the
1811 CPU specific event set.
1814 See Documentation/sound/oss/oss-parameters.txt
1816 panic= [KNL] Kernel behaviour on panic
1819 parkbd.port= [HW] Parallel port number the keyboard adapter is
1820 connected to, default is 0.
1822 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1823 0 for XT, 1 for AT (default is AT).
1826 parport= [HW,PPT] Specify parallel ports. 0 disables.
1827 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1828 Use 'auto' to force the driver to use any
1829 IRQ/DMA settings detected (the default is to
1830 ignore detected IRQ/DMA settings because of
1831 possible conflicts). You can specify the base
1832 address, IRQ, and DMA settings; IRQ and DMA
1833 should be numbers, or 'auto' (for using detected
1834 settings on that particular port), or 'nofifo'
1835 (to avoid using a FIFO even if it is detected).
1836 Parallel ports are assigned in the order they
1837 are specified on the command line, starting
1840 parport_init_mode= [HW,PPT]
1841 Configure VIA parallel port to operate in
1842 a specific mode. This is necessary on Pegasos
1843 computer where firmware has no options for setting
1844 up parallel port mode and sets it to spp.
1845 Currently this function knows 686a and 8231 chips.
1846 Format: [spp|ps2|epp|ecp|ecpepp]
1849 Halt all CPUs after the first oops has been printed for
1850 the specified number of seconds. This is to be used if
1851 your oopses keep scrolling off the screen.
1856 See header of drivers/block/paride/pcd.c.
1857 See also Documentation/blockdev/paride.txt.
1859 pci=option[,option...] [PCI] various PCI subsystem options:
1860 earlydump [X86] dump PCI config space before the kernel
1862 off [X86] don't probe for the PCI bus
1863 bios [X86-32] force use of PCI BIOS, don't access
1864 the hardware directly. Use this if your machine
1865 has a non-standard PCI host bridge.
1866 nobios [X86-32] disallow use of PCI BIOS, only direct
1867 hardware access methods are allowed. Use this
1868 if you experience crashes upon bootup and you
1869 suspect they are caused by the BIOS.
1870 conf1 [X86] Force use of PCI Configuration
1872 conf2 [X86] Force use of PCI Configuration
1874 noaer [PCIE] If the PCIEAER kernel config parameter is
1875 enabled, this kernel boot option can be used to
1876 disable the use of PCIE advanced error reporting.
1877 nodomains [PCI] Disable support for multiple PCI
1878 root domains (aka PCI segments, in ACPI-speak).
1879 nommconf [X86] Disable use of MMCONFIG for PCI
1881 check_enable_amd_mmconf [X86] check for and enable
1882 properly configured MMIO access to PCI
1883 config space on AMD family 10h CPU
1884 nomsi [MSI] If the PCI_MSI kernel config parameter is
1885 enabled, this kernel boot option can be used to
1886 disable the use of MSI interrupts system-wide.
1887 noioapicquirk [APIC] Disable all boot interrupt quirks.
1888 Safety option to keep boot IRQs enabled. This
1889 should never be necessary.
1890 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1891 primary IO-APIC for bridges that cannot disable
1892 boot IRQs. This fixes a source of spurious IRQs
1893 when the system masks IRQs.
1894 noioapicreroute [APIC] Disable workaround that uses the
1895 boot IRQ equivalent of an IRQ that connects to
1896 a chipset where boot IRQs cannot be disabled.
1897 The opposite of ioapicreroute.
1898 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1899 routing table. These calls are known to be buggy
1900 on several machines and they hang the machine
1901 when used, but on other computers it's the only
1902 way to get the interrupt routing table. Try
1903 this option if the kernel is unable to allocate
1904 IRQs or discover secondary PCI buses on your
1906 rom [X86] Assign address space to expansion ROMs.
1907 Use with caution as certain devices share
1908 address decoders between ROMs and other
1910 norom [X86] Do not assign address space to
1911 expansion ROMs that do not already have
1912 BIOS assigned address ranges.
1913 nobar [X86] Do not assign address space to the
1914 BARs that weren't assigned by the BIOS.
1915 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1916 assigned automatically to PCI devices. You can
1917 make the kernel exclude IRQs of your ISA cards
1919 pirqaddr=0xAAAAA [X86] Specify the physical address
1920 of the PIRQ table (normally generated
1921 by the BIOS) if it is outside the
1922 F0000h-100000h range.
1923 lastbus=N [X86] Scan all buses thru bus #N. Can be
1924 useful if the kernel is unable to find your
1925 secondary buses and you want to tell it
1926 explicitly which ones they are.
1927 assign-busses [X86] Always assign all PCI bus
1928 numbers ourselves, overriding
1929 whatever the firmware may have done.
1930 usepirqmask [X86] Honor the possible IRQ mask stored
1931 in the BIOS $PIR table. This is needed on
1932 some systems with broken BIOSes, notably
1933 some HP Pavilion N5400 and Omnibook XE3
1934 notebooks. This will have no effect if ACPI
1935 IRQ routing is enabled.
1936 noacpi [X86] Do not use ACPI for IRQ routing
1937 or for PCI scanning.
1938 use_crs [X86] Use PCI host bridge window information
1939 from ACPI. On BIOSes from 2008 or later, this
1940 is enabled by default. If you need to use this,
1941 please report a bug.
1942 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1943 If you need to use this, please report a bug.
1944 routeirq Do IRQ routing for all PCI devices.
1945 This is normally done in pci_enable_device(),
1946 so this option is a temporary workaround
1947 for broken drivers that don't call it.
1948 skip_isa_align [X86] do not align io start addr, so can
1949 handle more pci cards
1950 firmware [ARM] Do not re-enumerate the bus but instead
1951 just use the configuration from the
1952 bootloader. This is currently used on
1953 IXP2000 systems where the bus has to be
1954 configured a certain way for adjunct CPUs.
1955 noearly [X86] Don't do any early type 1 scanning.
1956 This might help on some broken boards which
1957 machine check when some devices' config space
1958 is read. But various workarounds are disabled
1959 and some IOMMU drivers will not work.
1960 bfsort Sort PCI devices into breadth-first order.
1961 This sorting is done to get a device
1962 order compatible with older (<= 2.4) kernels.
1963 nobfsort Don't sort PCI devices into breadth-first order.
1964 cbiosize=nn[KMG] The fixed amount of bus space which is
1965 reserved for the CardBus bridge's IO window.
1966 The default value is 256 bytes.
1967 cbmemsize=nn[KMG] The fixed amount of bus space which is
1968 reserved for the CardBus bridge's memory
1969 window. The default value is 64 megabytes.
1972 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1973 Specifies alignment and device to reassign
1974 aligned memory resources.
1975 If <order of align> is not specified,
1976 PAGE_SIZE is used as alignment.
1977 PCI-PCI bridge can be specified, if resource
1978 windows need to be expanded.
1979 ecrc= Enable/disable PCIe ECRC (transaction layer
1980 end-to-end CRC checking).
1981 bios: Use BIOS/firmware settings. This is the
1986 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1989 force Enable ASPM even on devices that claim not to support it.
1990 WARNING: Forcing ASPM on may cause system lockups.
1992 pcie_ports= [PCIE] PCIe ports handling:
1993 auto Ask the BIOS whether or not to use native PCIe services
1994 associated with PCIe ports (PME, hot-plug, AER). Use
1995 them only if that is allowed by the BIOS.
1996 native Use native PCIe services associated with PCIe ports
1998 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2001 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2002 nomsi Do not use MSI for native PCIe PME signaling (this makes
2003 all PCIe root ports use INTx for all services).
2005 pcmv= [HW,PCMCIA] BadgePAD 4
2008 See Documentation/blockdev/paride.txt.
2010 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2013 See arch/parisc/kernel/pdc_chassis.c
2015 percpu_alloc= Select which percpu first chunk allocator to use.
2016 Currently supported values are "embed" and "page".
2017 Archs may support subset or none of the selections.
2018 See comments in mm/percpu.c for details on each
2019 allocator. This parameter is primarily for debugging
2020 and performance comparison.
2023 See Documentation/blockdev/paride.txt.
2026 See Documentation/blockdev/paride.txt.
2028 pirq= [SMP,APIC] Manual mp-table setup
2029 See Documentation/x86/i386/IO-APIC.txt.
2031 plip= [PPT,NET] Parallel port network link
2032 Format: { parport<nr> | timid | 0 }
2033 See also Documentation/parport.txt.
2035 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2036 Override pmtimer IOPort with a hex value.
2040 Enable PNP debug messages. This depends on the
2041 CONFIG_PNP_DEBUG_MESSAGES option.
2047 { on | off | curr | res | no-curr | no-res }
2050 [ISAPNP] Exclude IRQs for the autoconfiguration
2053 [ISAPNP] Exclude DMAs for the autoconfiguration
2055 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2056 Ranges are in pairs (I/O port base and size).
2059 [ISAPNP] Exclude memory regions for the
2061 Ranges are in pairs (memory base and size).
2063 ports= [IP_VS_FTP] IPVS ftp helper module
2065 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2067 Format: <port>,<port>....
2069 print-fatal-signals=
2070 [KNL] debug: print fatal signals
2072 If enabled, warn about various signal handling
2073 related application anomalies: too many signals,
2074 too many POSIX.1 timers, fatal signals causing a
2077 If you hit the warning due to signal overflow,
2078 you might want to try "ulimit -i unlimited".
2082 printk.time= Show timing data prefixed to each printk message line
2083 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2085 processor.max_cstate= [HW,ACPI]
2086 Limit processor to maximum C-state
2087 max_cstate=9 overrides any DMI blacklist limit.
2089 processor.nocst [HW,ACPI]
2090 Ignore the _CST method to determine C-states,
2091 instead using the legacy FADT method
2093 profile= [KNL] Enable kernel profiling via /proc/profile
2094 Format: [schedule,]<number>
2095 Param: "schedule" - profile schedule points.
2096 Param: <number> - step/bucket size as a power of 2 for
2097 statistical time based profiling.
2098 Param: "sleep" - profile D-state sleeping (millisecs).
2099 Requires CONFIG_SCHEDSTATS
2100 Param: "kvm" - profile VM exits.
2102 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2104 See Documentation/blockdev/ramdisk.txt.
2106 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2107 probe for; one of (bare|imps|exps|lifebook|any).
2108 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2110 psmouse.resetafter= [HW,MOUSE]
2111 Try to reset the device after so many bad packets
2114 [HW,MOUSE] Set desired mouse resolution, in dpi.
2115 psmouse.smartscroll=
2116 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2117 0 = disabled, 1 = enabled (default).
2120 See Documentation/blockdev/paride.txt.
2123 [KNL] Number of legacy pty's. Overwrites compiled-in
2126 quiet [KNL] Disable most log messages
2131 See Documentation/md.txt.
2133 ramdisk_blocksize= [RAM]
2134 See Documentation/blockdev/ramdisk.txt.
2136 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2137 See Documentation/blockdev/ramdisk.txt.
2139 rcupdate.blimit= [KNL,BOOT]
2140 Set maximum number of finished RCU callbacks to process
2143 rcupdate.qhimark= [KNL,BOOT]
2144 Set threshold of queued
2145 RCU callbacks over which batch limiting is disabled.
2147 rcupdate.qlowmark= [KNL,BOOT]
2148 Set threshold of queued RCU callbacks below which
2149 batch limiting is re-enabled.
2153 Run specified binary instead of /init from the ramdisk,
2154 used for early userspace startup. See initrd.
2156 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2157 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2158 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2161 [KNL, SMP] Set scheduler's default relax_domain_level.
2162 See Documentation/cgroups/cpusets.txt.
2164 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2166 reservetop= [X86-32]
2168 Reserves a hole at the top of the kernel virtual
2173 Set the amount of memory to reserve for BIOS at
2174 the bottom of the address space.
2176 reset_devices [KNL] Force drivers to reset the underlying device
2177 during initialization.
2180 Specify the partition device for software suspend
2182 resume_offset= [SWSUSP]
2183 Specify the offset from the beginning of the partition
2184 given by "resume=" at which the swap header is located,
2185 in <PAGE_SIZE> units (needed only for swap files).
2186 See Documentation/power/swsusp-and-swap-files.txt
2188 hibernate= [HIBERNATION]
2189 noresume Don't check if there's a hibernation image
2190 present during boot.
2191 nocompress Don't compress/decompress hibernation images.
2193 retain_initrd [RAM] Keep initrd memory after extraction
2195 rhash_entries= [KNL,NET]
2196 Set number of hash buckets for route cache
2198 riscom8= [HW,SERIAL]
2199 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2201 ro [KNL] Mount root device read-only on boot
2203 root= [KNL] Root filesystem
2205 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2206 mount the root filesystem
2208 rootflags= [KNL] Set root filesystem mount option string
2210 rootfstype= [KNL] Set root filesystem type
2212 rootwait [KNL] Wait (indefinitely) for root device to show up.
2213 Useful for devices that are detected asynchronously
2214 (e.g. USB and MMC devices).
2216 rw [KNL] Mount root device read-write on boot
2218 S [KNL] Run init in single mode
2221 See drivers/net/irda/sa1100_ir.c.
2223 sbni= [NET] Granch SBNI12 leased line adapter
2225 sched_debug [KNL] Enables verbose scheduler debug messages.
2227 security= [SECURITY] Choose a security module to enable at boot.
2228 If this boot parameter is not specified, only the first
2229 security module asking for security registration will be
2230 loaded. An invalid security module name will be treated
2231 as if no module has been chosen.
2233 selinux= [SELINUX] Disable or enable SELinux at boot time.
2234 Format: { "0" | "1" }
2235 See security/selinux/Kconfig help text.
2238 Default value is set via kernel config option.
2239 If enabled at boot time, /selinux/disable can be used
2240 later to disable prior to initial policy load.
2242 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2243 Format: { "0" | "1" }
2244 See security/apparmor/Kconfig help text
2247 Default value is set via kernel config option.
2249 serialnumber [BUGS=X86-32]
2252 Maximal number of shapers.
2254 show_msr= [x86] show boot-time MSR settings
2255 Format: { <integer> }
2256 Show boot-time (BIOS-initialized) MSR settings.
2257 The parameter means the number of CPUs to show,
2258 for example 1 means boot CPU only.
2265 slub_debug[=options[,slabs]] [MM, SLUB]
2266 Enabling slub_debug allows one to determine the
2267 culprit if slab objects become corrupted. Enabling
2268 slub_debug can create guard zones around objects and
2269 may poison objects when not in use. Also tracks the
2270 last alloc / free. For more information see
2271 Documentation/vm/slub.txt.
2273 slub_max_order= [MM, SLUB]
2274 Determines the maximum allowed order for slabs.
2275 A high setting may cause OOMs due to memory
2276 fragmentation. For more information see
2277 Documentation/vm/slub.txt.
2279 slub_min_objects= [MM, SLUB]
2280 The minimum number of objects per slab. SLUB will
2281 increase the slab order up to slub_max_order to
2282 generate a sufficiently large slab able to contain
2283 the number of objects indicated. The higher the number
2284 of objects the smaller the overhead of tracking slabs
2285 and the less frequently locks need to be acquired.
2286 For more information see Documentation/vm/slub.txt.
2288 slub_min_order= [MM, SLUB]
2289 Determines the mininum page order for slabs. Must be
2290 lower than slub_max_order.
2291 For more information see Documentation/vm/slub.txt.
2293 slub_nomerge [MM, SLUB]
2294 Disable merging of slabs with similar size. May be
2295 necessary if there is some reason to distinguish
2296 allocs to different slabs. Debug options disable
2297 merging on their own.
2298 For more information see Documentation/vm/slub.txt.
2301 Format: <io1>[,<io2>[,...,<io8>]]
2303 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2304 attempt to substitute SMP alternatives once at boot.
2306 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2307 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2308 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2309 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2310 smsc-ircc2.ircc_irq= [HW] IRQ line
2311 smsc-ircc2.ircc_dma= [HW] DMA channel
2312 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2313 0: Toshiba Satellite 1800 (GP data pin select)
2314 1: Fast pin select (default)
2318 [KNL] Should the soft-lockup detector generate panics.
2320 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2321 See Documentation/sonypi.txt
2323 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2324 See Documentation/serial/specialix.txt.
2326 spia_io_base= [HW,MTD]
2332 Enabled the stack tracer on boot up.
2336 Set the STI (builtin display/keyboard on the HP-PARISC
2337 machines) console (graphic card) which should be used
2338 as the initial boot-console.
2339 See also comment in drivers/video/console/sticore.c.
2342 See comment in drivers/video/console/sticore.c.
2345 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2347 sunrpc.min_resvport=
2348 sunrpc.max_resvport=
2350 SunRPC servers often require that client requests
2351 originate from a privileged port (i.e. a port in the
2352 range 0 < portnr < 1024).
2353 An administrator who wishes to reserve some of these
2354 ports for other uses may adjust the range that the
2355 kernel's sunrpc client considers to be privileged
2356 using these two parameters to set the minimum and
2357 maximum port values.
2361 Control how the NFS server code allocates CPUs to
2362 service thread pools. Depending on how many NICs
2363 you have and where their interrupts are bound, this
2364 option will affect which CPUs will do NFS serving.
2365 Note: this parameter cannot be changed while the
2366 NFS server is running.
2368 auto the server chooses an appropriate mode
2369 automatically using heuristics
2370 global a single global pool contains all CPUs
2371 percpu one pool for each CPU
2372 pernode one pool for each NUMA node (equivalent
2373 to global on non-NUMA machines)
2375 sunrpc.tcp_slot_table_entries=
2376 sunrpc.udp_slot_table_entries=
2378 Sets the upper limit on the number of simultaneous
2379 RPC calls that can be sent from the client to a
2380 server. Increasing these values may allow you to
2381 improve throughput, but will also increase the
2382 amount of memory reserved for use by the client.
2385 [KNL] Enable accounting of swap in memory resource
2386 controller if no parameter or 1 is given or disable
2387 it if 0 is given (See Documentation/cgroups/memory.txt)
2389 swiotlb= [IA-64] Number of I/O TLB slabs
2393 sysfs.deprecated=0|1 [KNL]
2394 Enable/disable old style sysfs layout for old udev
2395 on older distributions. When this option is enabled
2396 very new udev will not work anymore. When this option
2397 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2398 in older udev will not work anymore.
2399 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2400 the kernel configuration.
2402 sysrq_always_enabled
2404 Ignore sysrq setting - this boot parameter will
2405 neutralize any effect of /proc/sys/kernel/sysrq.
2406 Useful for debugging.
2410 test_suspend= [SUSPEND]
2411 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2412 standby suspend) as the system sleep state to briefly
2413 enter during system startup. The system is woken from
2414 this state using a wakeup-capable RTC alarm.
2416 thash_entries= [KNL,NET]
2417 Set number of hash buckets for TCP connection
2419 thermal.act= [HW,ACPI]
2420 -1: disable all active trip points in all thermal zones
2421 <degrees C>: override all lowest active trip points
2423 thermal.crt= [HW,ACPI]
2424 -1: disable all critical trip points in all thermal zones
2425 <degrees C>: override all critical trip points
2427 thermal.nocrt= [HW,ACPI]
2428 Set to disable actions on ACPI thermal zone
2429 critical and hot trip points.
2431 thermal.off= [HW,ACPI]
2432 1: disable ACPI thermal control
2434 thermal.psv= [HW,ACPI]
2435 -1: disable all passive trip points
2436 <degrees C>: override all passive trip points to this
2439 thermal.tzp= [HW,ACPI]
2440 Specify global default ACPI thermal zone polling rate
2441 <deci-seconds>: poll all this frequency
2442 0: no polling (default)
2446 Specify if the kernel should make use of the cpu
2447 topology informations if the hardware supports these.
2448 The scheduler will make use of these informations and
2449 e.g. base its process migration decisions on it.
2454 tpm_suspend_pcr=[HW,TPM]
2455 Format: integer pcr id
2456 Specify that at suspend time, the tpm driver
2457 should extend the specified pcr with zeros,
2458 as a workaround for some chips which fail to
2459 flush the last written pcr on TPM_SaveState.
2460 This will guarantee that all the other pcrs
2463 trace_buf_size=nn[KMG]
2464 [FTRACE] will set tracing buffer size.
2466 trace_event=[event-list]
2467 [FTRACE] Set and start specified trace events in order
2468 to facilitate early boot debugging.
2469 See also Documentation/trace/events.txt
2471 tsc= Disable clocksource stability checks for TSC.
2473 [x86] reliable: mark tsc clocksource as reliable, this
2474 disables clocksource verification at runtime, as well
2475 as the stability checks done at bootup. Used to enable
2476 high-resolution timer mode on older hardware, and in
2477 virtualized environment.
2478 [x86] noirqtime: Do not use TSC to do irq accounting.
2479 Used to run time disable IRQ_TIME_ACCOUNTING on any
2480 platforms where RDTSC is slow and this accounting
2483 turbografx.map[2|3]= [HW,JOY]
2484 TurboGraFX parallel port interface
2486 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2487 See also Documentation/input/joystick-parport.txt
2489 uhash_entries= [KNL,NET]
2490 Set number of hash buckets for UDP/UDP-Lite connections
2493 [USB] Ignore overcurrent events (default N).
2494 Some badly-designed motherboards generate lots of
2495 bogus events, for ports that aren't wired to
2496 anything. Set this parameter to avoid log spamming.
2497 Note that genuine overcurrent events won't be
2502 Set unknown_nmi_panic=1 early on boot.
2504 usbcore.autosuspend=
2505 [USB] The autosuspend time delay (in seconds) used
2506 for newly-detected USB devices (default 2). This
2507 is the time required before an idle device will be
2508 autosuspended. Devices for which the delay is set
2509 to a negative value won't be autosuspended at all.
2511 usbcore.usbfs_snoop=
2512 [USB] Set to log all usbfs traffic (default 0 = off).
2514 usbcore.blinkenlights=
2515 [USB] Set to cycle leds on hubs (default 0 = off).
2517 usbcore.old_scheme_first=
2518 [USB] Start with the old device initialization
2519 scheme (default 0 = off).
2521 usbcore.use_both_schemes=
2522 [USB] Try the other device initialization scheme
2523 if the first one fails (default 1 = enabled).
2525 usbcore.initial_descriptor_timeout=
2526 [USB] Specifies timeout for the initial 64-byte
2527 USB_REQ_GET_DESCRIPTOR request in milliseconds
2528 (default 5000 = 5.0 seconds).
2531 [USBHID] The interval which mice are to be polled at.
2533 usb-storage.delay_use=
2534 [UMS] The delay in seconds before a new device is
2535 scanned for Logical Units (default 5).
2538 [UMS] A list of quirks entries to supplement or
2539 override the built-in unusual_devs list. List
2540 entries are separated by commas. Each entry has
2541 the form VID:PID:Flags where VID and PID are Vendor
2542 and Product ID values (4-digit hex numbers) and
2543 Flags is a set of characters, each corresponding
2544 to a common usb-storage quirk flag as follows:
2545 a = SANE_SENSE (collect more than 18 bytes
2547 b = BAD_SENSE (don't collect more than 18
2548 bytes of sense data);
2549 c = FIX_CAPACITY (decrease the reported
2550 device capacity by one sector);
2551 h = CAPACITY_HEURISTICS (decrease the
2552 reported device capacity by one
2553 sector if the number is odd);
2554 i = IGNORE_DEVICE (don't bind to this
2556 l = NOT_LOCKABLE (don't try to lock and
2557 unlock ejectable media);
2558 m = MAX_SECTORS_64 (don't transfer more
2559 than 64 sectors = 32 KB at a time);
2560 o = CAPACITY_OK (accept the capacity
2561 reported by the device);
2562 r = IGNORE_RESIDUE (the device reports
2563 bogus residue values);
2564 s = SINGLE_LUN (the device has only one
2566 w = NO_WP_DETECT (don't test whether the
2567 medium is write-protected).
2568 Example: quirks=0419:aaf5:rl,0421:0433:rc
2571 [X86] Flags controlling user PTE allocations.
2573 nohigh = do not allocate PTE pages in
2574 HIGHMEM regardless of setting
2578 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2579 vdso=1: enable VDSO (default)
2580 vdso=0: disable VDSO mapping
2583 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2584 vdso32=1: enable 32-bit VDSO (default)
2585 vdso32=0: disable 32-bit VDSO mapping
2588 vector=percpu: enable percpu vector domain
2590 video= [FB] Frame buffer configuration
2591 See Documentation/fb/modedb.txt.
2593 vga= [BOOT,X86-32] Select a particular video mode
2594 See Documentation/x86/boot.txt and
2595 Documentation/svga.txt.
2596 Use vga=ask for menu.
2597 This is actually a boot loader parameter; the value is
2598 passed to the kernel using a special protocol.
2600 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2601 size of <nn>. This can be used to increase the
2602 minimum size (128MB on x86). It can also be used to
2603 decrease the size and leave more room for directly
2606 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2609 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2612 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2615 vt.cur_default= [VT] Default cursor shape.
2616 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2617 the parameters of the <Esc>[?A;B;Cc escape sequence;
2618 see VGA-softcursor.txt. Default: 2 = underline.
2620 vt.default_blu= [VT]
2621 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2622 Change the default blue palette of the console.
2623 This is a 16-member array composed of values
2626 vt.default_grn= [VT]
2627 Format: <green0>,<green1>,<green2>,...,<green15>
2628 Change the default green palette of the console.
2629 This is a 16-member array composed of values
2632 vt.default_red= [VT]
2633 Format: <red0>,<red1>,<red2>,...,<red15>
2634 Change the default red palette of the console.
2635 This is a 16-member array composed of values
2641 Set system-wide default UTF-8 mode for all tty's.
2642 Default is 1, i.e. UTF-8 mode is enabled for all
2643 newly opened terminals.
2645 vt.global_cursor_default=
2648 Set system-wide default for whether a cursor
2649 is shown on new VTs. Default is -1,
2650 i.e. cursors will be created by default unless
2651 overridden by individual drivers. 0 will hide
2652 cursors, 1 will display them.
2654 watchdog timers [HW,WDT] For information on watchdog timers,
2655 see Documentation/watchdog/watchdog-parameters.txt
2656 or other driver-specific files in the
2657 Documentation/watchdog/ directory.
2659 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2660 default x2apic cluster mode on platforms
2663 x86_mrst_timer= [X86-32,APBT]
2664 Choose timer option for x86 Moorestown MID platform.
2665 Two valid options are apbt timer only and lapic timer
2666 plus one apbt timer for broadcast timer.
2667 x86_mrst_timer=apbt_only | lapic_and_apbt
2669 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2670 xd_geo= See header of drivers/block/xd.c.
2672 xen_emul_unplug= [HW,X86,XEN]
2673 Unplug Xen emulated devices
2674 Format: [unplug0,][unplug1]
2675 ide-disks -- unplug primary master IDE devices
2676 aux-ide-disks -- unplug non-primary-master IDE devices
2677 nics -- unplug network devices
2678 all -- unplug all emulated devices (NICs and IDE disks)
2679 unnecessary -- unplugging emulated devices is
2680 unnecessary even if the host did not respond to
2682 never -- do not unplug even if version check succeeds
2684 xirc2ps_cs= [NET,PCMCIA]
2686 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2688 ______________________________________________________________________
2692 Add more DRM drivers.
projects / mirror_ubuntu-artful-kernel.git / blob