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 DRM Direct Rendering Management support is enabled.
47 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
48 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
49 EFI EFI Partitioning (GPT) is enabled
50 EIDE EIDE/ATAPI support is enabled.
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.
147 Finally, the [KMG] suffix is commonly described after a number of kernel
148 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
149 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
150 bytes respectively. Such letter suffixes can also be entirely omitted.
154 Advanced Configuration and Power Interface
155 Format: { force | off | strict | noirq | rsdt }
156 force -- enable ACPI if default was off
157 off -- disable ACPI if default was on
158 noirq -- do not use ACPI for IRQ routing
159 strict -- Be less tolerant of platforms that are not
160 strictly ACPI specification compliant.
161 rsdt -- prefer RSDT over (default) XSDT
162 copy_dsdt -- copy DSDT to memory
164 See also Documentation/power/pm.txt, pci=noacpi
166 acpi_rsdp= [ACPI,EFI,KEXEC]
167 Pass the RSDP address to the kernel, mostly used
168 on machines running EFI runtime service to boot the
169 second kernel for kdump.
171 acpi_apic_instance= [ACPI, IOAPIC]
173 2: use 2nd APIC table, if available
174 1,0: use 1st APIC table
177 acpi_backlight= [HW,ACPI]
178 acpi_backlight=vendor
180 If set to vendor, prefer vendor specific driver
181 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
182 of the ACPI video.ko driver.
184 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
185 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
187 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
188 debug output. Bits in debug_layer correspond to a
189 _COMPONENT in an ACPI source file, e.g.,
190 #define _COMPONENT ACPI_PCI_COMPONENT
191 Bits in debug_level correspond to a level in
192 ACPI_DEBUG_PRINT statements, e.g.,
193 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
194 The debug_level mask defaults to "info". See
195 Documentation/acpi/debug.txt for more information about
196 debug layers and levels.
198 Enable processor driver info messages:
199 acpi.debug_layer=0x20000000
200 Enable PCI/PCI interrupt routing info messages:
201 acpi.debug_layer=0x400000
202 Enable AML "Debug" output, i.e., stores to the Debug
203 object while interpreting AML:
204 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
205 Enable all messages related to ACPI hardware:
206 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
208 Some values produce so much output that the system is
209 unusable. The "log_buf_len" parameter may be useful
210 if you need to capture more output.
212 acpi_irq_balance [HW,ACPI]
213 ACPI will balance active IRQs
216 acpi_irq_nobalance [HW,ACPI]
217 ACPI will not move active IRQs (default)
220 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
221 Format: <irq>,<irq>...
223 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
225 Format: <irq>,<irq>...
227 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
229 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
230 Format: To spoof as Windows 98: ="Microsoft Windows"
232 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
233 acpi_osi="string1" # add string1 -- only one string
234 acpi_osi="!string2" # remove built-in string2
235 acpi_osi= # disable all strings
238 Override the pmtimer bug detection: force the kernel
239 to assume that this machine's pmtimer latches its value
240 and always returns good values.
242 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
243 Format: { level | edge | high | low }
245 acpi_serialize [HW,ACPI] force serialization of AML methods
247 acpi_skip_timer_override [HW,ACPI]
248 Recognize and ignore IRQ0/pin2 Interrupt Override.
249 For broken nForce2 BIOS resulting in XT-PIC timer.
251 acpi_sleep= [HW,ACPI] Sleep options
252 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
253 old_ordering, nonvs, sci_force_enable }
254 See Documentation/power/video.txt for information on
256 s3_beep is for debugging; it makes the PC's speaker beep
257 as soon as the kernel's real-mode entry point is called.
258 s4_nohwsig prevents ACPI hardware signature from being
259 used during resume from hibernation.
260 old_ordering causes the ACPI 1.0 ordering of the _PTS
261 control method, with respect to putting devices into
262 low power states, to be enforced (the ACPI 2.0 ordering
263 of _PTS is used by default).
264 nonvs prevents the kernel from saving/restoring the
265 ACPI NVS memory during suspend/hibernation and resume.
266 sci_force_enable causes the kernel to set SCI_EN directly
267 on resume from S1/S3 (which is against the ACPI spec,
268 but some broken systems don't work without it).
270 acpi_use_timer_override [HW,ACPI]
271 Use timer override. For some broken Nvidia NF5 boards
272 that require a timer override, but don't have HPET
274 acpi_enforce_resources= [ACPI]
275 { strict | lax | no }
276 Check for resource conflicts between native drivers
277 and ACPI OperationRegions (SystemIO and SystemMemory
278 only). IO ports and memory declared in ACPI might be
279 used by the ACPI subsystem in arbitrary AML code and
280 can interfere with legacy drivers.
281 strict (default): access to resources claimed by ACPI
282 is denied; legacy drivers trying to access reserved
283 resources will fail to bind to device using them.
284 lax: access to resources claimed by ACPI is allowed;
285 legacy drivers trying to access reserved resources
286 will bind successfully but a warning message is logged.
287 no: ACPI OperationRegions are not marked as reserved,
288 no further checks are performed.
290 add_efi_memmap [EFI; X86] Include EFI memory map in
291 kernel's map of available physical RAM.
294 { off | try_unsupported }
295 off: disable AGP support
296 try_unsupported: try to drive unsupported chipsets
297 (may crash computer or cause data corruption)
300 See Documentation/sound/alsa/alsa-parameters.txt
303 Allow the default userspace alignment fault handler
304 behaviour to be specified. Bit 0 enables warnings,
305 bit 1 enables fixups, and bit 2 sends a segfault.
307 amd_iommu= [HW,X86-84]
308 Pass parameters to the AMD IOMMU driver in the system.
310 fullflush - enable flushing of IO/TLB entries when
311 they are unmapped. Otherwise they are
312 flushed before they will be reused, which
314 off - do not initialize any AMD IOMMU found in
317 amijoy.map= [HW,JOY] Amiga joystick support
318 Map of devices attached to JOY0DAT and JOY1DAT
320 See also Documentation/kernel/input/joystick.txt
322 analog.map= [HW,JOY] Analog joystick and gamepad support
323 Specifies type or capabilities of an analog joystick
324 connected to one of 16 gameports
325 Format: <type1>,<type2>,..<type16>
328 Power management functions (SPARCstation-4/5 + deriv.)
330 Disable APC CPU standby support. SPARCstation-Fox does
331 not play well with APC CPU idle - disable it if you have
332 APC and your system crashes randomly.
334 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
335 Change the output verbosity whilst booting
336 Format: { quiet (default) | verbose | debug }
337 Change the amount of debugging information output
338 when initialising the APIC and IO-APIC components.
341 See Documentation/networking/ipv6.txt.
343 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
344 Limit apic dumping. The parameter defines the maximal
345 number of local apics being dumped. Also it is possible
346 to set it to "all" by meaning -- no limit here.
347 Format: { 1 (default) | 2 | ... | all }.
348 The parameter valid if only apic=debug or
349 apic=verbose is specified.
350 Example: apic=debug show_lapic=all
352 apm= [APM] Advanced Power Management
353 See header of arch/x86/kernel/apm_32.c.
355 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
356 Format: <io>,<irq>,<nodeID>
360 atarimouse= [HW,MOUSE] Atari Mouse
362 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
363 EzKey and similar keyboards
365 atkbd.reset= [HW] Reset keyboard during initialization
367 atkbd.set= [HW] Select keyboard code set
368 Format: <int> (2 = AT (default), 3 = PS/2)
370 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
373 atkbd.softraw= [HW] Choose between synthetic and real raw mode
374 Format: <bool> (0 = real, 1 = synthetic (default))
376 atkbd.softrepeat= [HW]
377 Use software keyboard repeat
381 baycom_epp= [HW,AX25]
384 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
386 See header of drivers/net/hamradio/baycom_par.c.
388 baycom_ser_fdx= [HW,AX25]
389 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
390 Format: <io>,<irq>,<mode>[,<baud>]
391 See header of drivers/net/hamradio/baycom_ser_fdx.c.
393 baycom_ser_hdx= [HW,AX25]
394 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
395 Format: <io>,<irq>,<mode>
396 See header of drivers/net/hamradio/baycom_ser_hdx.c.
398 boot_delay= Milliseconds to delay each printk during boot.
399 Values larger than 10 seconds (10000) are changed to
403 bootmem_debug [KNL] Enable bootmem allocator debug messages.
405 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
406 bttv.radio= Most important insmod options are available as
408 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
409 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
411 bulk_remove=off [PPC] This parameter disables the use of the pSeries
412 firmware feature for flushing multiple hpte entries
415 c101= [NET] Moxa C101 synchronous serial card
417 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
418 Sometimes CPU hardware bugs make them report the cache
419 size incorrectly. The kernel will attempt work arounds
420 to fix known problems, but for some CPUs it is not
421 possible to determine what the correct size should be.
422 This option provides an override for these situations.
425 [SECURITY] Disable capabilities. This would normally
426 be used only if an alternative security model is to be
427 configured. Potentially dangerous and should only be
428 used if you are entirely sure of the consequences.
430 ccw_timeout_log [S390]
431 See Documentation/s390/CommonIO for details.
433 cgroup_disable= [KNL] Disable a particular controller
434 Format: {name of the controller(s) to disable}
435 {Currently supported controllers - "memory"}
437 checkreqprot [SELINUX] Set initial checkreqprot flag value.
438 Format: { "0" | "1" }
439 See security/selinux/Kconfig help text.
440 0 -- check protection applied by kernel (includes
441 any implied execute protection).
442 1 -- check protection requested by application.
443 Default value is set via a kernel config option.
444 Value can be changed at runtime via
445 /selinux/checkreqprot.
448 See Documentation/s390/CommonIO for details.
450 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
452 Forces specified clocksource (if available) to be used
453 when calculating gettimeofday(). If specified
454 clocksource is not available, it defaults to PIT.
455 Format: { pit | tsc | cyclone | pmtmr }
457 clocksource= Override the default clocksource
459 Override the default clocksource and use the clocksource
460 with the name specified.
461 Some clocksource names to choose from, depending on
463 [all] jiffies (this is the base, fallback clocksource)
465 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
466 pxa_timer,timer3,32k_counter,timer0_1
468 [X86-32] pit,hpet,tsc;
469 scx200_hrt on Geode; cyclone on IBM x440
477 clearcpuid=BITNUM [X86]
478 Disable CPUID feature X for the kernel. See
479 arch/x86/include/asm/cpufeature.h for the valid bit
480 numbers. Note the Linux specific bits are not necessarily
481 stable over kernel options, but the vendor specific
483 Also note that user programs calling CPUID directly
484 or using the feature without checking anything
485 will still see it. This just prevents it from
486 being used by the kernel or shown in /proc/cpuinfo.
487 Also note the kernel might malfunction if you disable
490 cmo_free_hint= [PPC] Format: { yes | no }
491 Specify whether pages are marked as being inactive
492 when they are freed. This is used in CMO environments
493 to determine OS memory pressure for page stealing by
497 code_bytes [X86] How many bytes of object code to print
502 com20020= [HW,NET] ARCnet - COM20020 chipset
504 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
506 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
510 ARCnet - COM90xx chipset (memory-mapped buffers)
511 Format: <io>[,<irq>[,<memstart>]]
513 condev= [HW,S390] console device
516 console= [KNL] Output console device and options.
518 tty<n> Use the virtual console device <n>.
522 Use the specified serial port. The options are of
523 the form "bbbbpnf", where "bbbb" is the baud rate,
524 "p" is parity ("n", "o", or "e"), "n" is number of
525 bits, and "f" is flow control ("r" for RTS or
526 omit it). Default is "9600n8".
528 See Documentation/serial-console.txt for more
530 Documentation/networking/netconsole.txt for an
533 uart[8250],io,<addr>[,options]
534 uart[8250],mmio,<addr>[,options]
535 Start an early, polled-mode console on the 8250/16550
536 UART at the specified I/O port or MMIO address,
537 switching to the matching ttyS device later. The
538 options are the same as for ttyS, above.
540 If the device connected to the port is not a TTY but a braille
541 device, prepend "brl," before the device type, for instance
543 For now, only VisioBraille is supported.
545 consoleblank= [KNL] The console blank (screen saver) timeout in
546 seconds. Defaults to 10*60 = 10mins. A value of 0
547 disables the blank timer.
550 [KNL] Change the default value for
551 /proc/<pid>/coredump_filter.
552 See also Documentation/filesystems/proc.txt.
554 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
556 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
558 crashkernel=size[KMG][@offset[KMG]]
559 [KNL] Using kexec, Linux can switch to a 'crash kernel'
560 upon panic. This parameter reserves the physical
561 memory region [offset, offset + size] for that kernel
562 image. If '@offset' is omitted, then a suitable offset
563 is selected automatically. Check
564 Documentation/kdump/kdump.txt for further details.
566 crashkernel=range1:size1[,range2:size2,...][@offset]
567 [KNL] Same as above, but depends on the memory
568 in the running system. The syntax of range is
569 start-[end] where start and end are both
570 a memory unit (amount[KMG]). See also
571 Documentation/kdump/kdump.txt for an example.
576 cs89x0_media= [HW,NET]
577 Format: { rj45 | aui | bnc }
580 See header of drivers/s390/block/dasd_devmap.c.
582 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
583 (one device per port)
584 Format: <port#>,<type>
585 See also Documentation/input/joystick-parport.txt
587 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
588 time. See Documentation/dynamic-debug-howto.txt for
591 debug [KNL] Enable kernel debugging (events log level).
594 [KNL] verbose self-tests
596 Print debugging info while doing the locking API
598 We default to 0 (no extra messages), setting it to
599 1 will print _a lot_ more information - normally
600 only useful to kernel developers.
602 debug_objects [KNL] Enable object debugging
605 [KNL] Disable object debugging
607 debugpat [X86] Enable PAT debugging
609 decnet.addr= [HW,NET]
610 Format: <area>[,<node>]
611 See also Documentation/networking/decnet.txt.
614 [same as hugepagesz=] The size of the default
615 HugeTLB page size. This is the size represented by
616 the legacy /proc/ hugepages APIs, used for SHM, and
617 default size when mounting hugetlbfs filesystems.
618 Defaults to the default architecture's huge page size
622 Set number of hash buckets for dentry cache.
625 IO parameters + enable/disable command.
627 digiepca= [HW,SERIAL]
628 See drivers/char/README.epca and
629 Documentation/serial/digiepca.txt.
632 See Documentation/networking/ipv6.txt.
634 disable_ddw [PPC/PSERIES]
635 Disable Dynamic DMA Window support. Use this if
636 to workaround buggy firmware.
639 See Documentation/networking/ipv6.txt.
641 disable_mtrr_cleanup [X86]
642 The kernel tries to adjust MTRR layout from continuous
643 to discrete, to make X server driver able to add WB
644 entry later. This parameter disables that.
646 disable_mtrr_trim [X86, Intel and AMD only]
647 By default the kernel will trim any uncacheable
648 memory out of your available memory pool based on
649 MTRR settings. This parameter disables that behavior,
650 possibly causing your machine to run very slowly.
652 disable_timer_pin_1 [X86]
653 Disable PIN 1 of APIC timer
654 Can be useful to work around chipset bugs.
656 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
657 this option disables the debugging code at boot.
659 dma_debug_entries=<number>
660 This option allows to tune the number of preallocated
661 entries for DMA-API debugging code. One entry is
662 required per DMA-API allocation. Use this if the
663 DMA-API debugging code disables itself because the
664 architectural default is too low.
666 dma_debug_driver=<driver_name>
667 With this option the DMA-API debugging driver
668 filter feature can be enabled at boot time. Just
669 pass the driver to filter for as the parameter.
670 The filter can be disabled or changed to another
671 driver later using sysfs.
675 earlycon= [KNL] Output early console device and options.
676 uart[8250],io,<addr>[,options]
677 uart[8250],mmio,<addr>[,options]
678 uart[8250],mmio32,<addr>[,options]
679 Start an early, polled-mode console on the 8250/16550
680 UART at the specified I/O port or MMIO address.
681 MMIO inter-register address stride is either 8bit (mmio)
683 The options are the same as for ttyS, above.
685 earlyprintk= [X86,SH,BLACKFIN]
687 earlyprintk=serial[,ttySn[,baudrate]]
688 earlyprintk=ttySn[,baudrate]
689 earlyprintk=dbgp[debugController#]
691 Append ",keep" to not disable it when the real console
694 Only vga or serial or usb debug port at a time.
696 Currently only ttyS0 and ttyS1 are supported.
698 Interaction with the standard serial driver is not
701 The VGA output is eventually overwritten by the real
704 ekgdboc= [X86,KGDB] Allow early kernel console debugging
707 This is designed to be used in conjunction with
708 the boot argument: earlyprintk=vga
711 Format: {"off" | "on" | "skip[mbr]"}
713 eisa_irq_edge= [PARISC,HW]
714 See header of drivers/parisc/eisa.c.
717 See comment before function elanfreq_setup() in
718 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
721 Format: {"cfq" | "deadline" | "noop"}
722 See Documentation/block/as-iosched.txt and
723 Documentation/block/deadline-iosched.txt for details.
725 elfcorehdr= [IA64,PPC,SH,X86]
726 Specifies physical address of start of kernel core
727 image elf header. Generally kexec loader will
728 pass this option to capture kernel.
729 See Documentation/kdump/kdump.txt for details.
731 enable_mtrr_cleanup [X86]
732 The kernel tries to adjust MTRR layout from continuous
733 to discrete, to make X server driver able to add WB
734 entry later. This parameter enables that.
736 enable_timer_pin_1 [X86]
737 Enable PIN 1 of APIC timer
738 Can be useful to work around chipset bugs
739 (in particular on some ATI chipsets).
740 The kernel tries to set a reasonable default.
742 enforcing [SELINUX] Set initial enforcing status.
744 See security/selinux/Kconfig help text.
745 0 -- permissive (log only, no denials).
746 1 -- enforcing (deny and log).
748 Value can be changed at runtime via /selinux/enforce.
751 Disable Error Record Serialization Table (ERST)
754 ether= [HW,NET] Ethernet cards parameters
755 This option is obsoleted by the "netdev=" option, which
756 has equivalent usage. See its documentation for details.
760 fail_make_request=[KNL]
761 General fault injection mechanism.
762 Format: <interval>,<probability>,<space>,<times>
763 See also /Documentation/fault-injection/.
766 See Documentation/blockdev/floppy.txt.
768 force_pal_cache_flush
769 [IA-64] Avoid check_sal_cache_flush which may hang on
770 buggy SAL_CACHE_FLUSH implementations. Using this
771 parameter will force ia64_sal_cache_flush to call
772 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
775 [FTRACE] will set and start the specified tracer
776 as early as possible in order to facilitate early
779 ftrace_dump_on_oops[=orig_cpu]
780 [FTRACE] will dump the trace buffers on oops.
781 If no parameter is passed, ftrace will dump
782 buffers of all CPUs, but if you pass orig_cpu, it will
783 dump only the buffer of the CPU that triggered the
786 ftrace_filter=[function-list]
787 [FTRACE] Limit the functions traced by the function
788 tracer at boot up. function-list is a comma separated
789 list of functions. This list can be changed at run
790 time by the set_ftrace_filter file in the debugfs
793 ftrace_notrace=[function-list]
794 [FTRACE] Do not trace the functions specified in
795 function-list. This list can be changed at run time
796 by the set_ftrace_notrace file in the debugfs
799 ftrace_graph_filter=[function-list]
800 [FTRACE] Limit the top level callers functions traced
801 by the function graph tracer at boot up.
802 function-list is a comma separated list of functions
803 that can be changed at run time by the
804 set_graph_function file in the debugfs tracing directory.
807 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
808 support via parallel port (up to 5 devices per port)
809 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
810 See also Documentation/input/joystick-parport.txt
814 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
818 gcov_persist= [GCOV] When non-zero (default), profiling data for
819 kernel modules is saved and remains accessible via
820 debugfs, even when the module is unloaded/reloaded.
821 When zero, profiling data is discarded and associated
822 debugfs files are removed at module unload time.
824 gpt [EFI] Forces disk with valid GPT signature but
825 invalid Protective MBR to be treated as GPT.
827 hashdist= [KNL,NUMA] Large hashes allocated during boot
828 are distributed across NUMA nodes. Defaults on
829 for 64bit NUMA, off otherwise.
830 Format: 0 | 1 (for off | on)
832 hcl= [IA-64] SGI's Hardware Graph compatibility layer
834 hd= [EIDE] (E)IDE hard drive subsystem geometry
835 Format: <cyl>,<head>,<sect>
838 Disable Hardware Error Source Table (HEST) support;
839 corresponding firmware-first mode error processing
840 logic will be disabled.
842 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
843 size of <nn>. This works even on boxes that have no
844 highmem otherwise. This also works to reduce highmem
845 size on bigger boxes.
847 highres= [KNL] Enable/disable high resolution timer mode.
848 Valid parameters: "on", "off"
852 See Documentation/isdn/README.HiSax.
856 hpet= [X86-32,HPET] option to control HPET usage
857 Format: { enable (default) | disable | force |
859 disable: disable HPET and use PIT instead
860 force: allow force enabled of undocumented chips (ICH4,
862 verbose: show contents of HPET registers during setup
864 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
865 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
866 On x86-64 and powerpc, this option can be specified
867 multiple times interleaved with hugepages= to reserve
868 huge pages of different sizes. Valid pages sizes on
869 x86-64 are 2M (when the CPU supports "pse") and 1G
870 (when the CPU supports the "pdpe1gb" cpuinfo flag)
871 Note that 1GB pages can only be allocated at boot time
872 using hugepages= and not freed afterwards.
874 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
875 terminal devices. Valid values: 0..8
876 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
877 If specified, z/VM IUCV HVC accepts connections
878 from listed z/VM user IDs only.
881 Do not unregister boot console at start. This is only
882 useful for debugging when something happens in the window
883 between unregistering the boot console and initializing
886 i2c_bus= [HW] Override the default board specific I2C bus speed
887 or register an additional I2C bus that is not
888 registered from board initialization code.
892 i8042.debug [HW] Toggle i8042 debug mode
893 i8042.direct [HW] Put keyboard port into non-translated mode
894 i8042.dumbkbd [HW] Pretend that controller can only read data from
895 keyboard and cannot control its state
896 (Don't attempt to blink the leds)
897 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
898 i8042.nokbd [HW] Don't check/create keyboard port
899 i8042.noloop [HW] Disable the AUX Loopback command while probing
901 i8042.nomux [HW] Don't check presence of an active multiplexing
903 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
905 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
906 i8042.reset [HW] Reset the controller during init and cleanup
907 i8042.unlock [HW] Unlock (ignore) the keylock
911 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
912 indicates that the driver is running on unsupported
914 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
915 does not match list of supported models.
917 [HW] Report power status in /proc/i8k
918 (disabled by default)
919 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
923 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
925 ide-core.nodma= [HW] (E)IDE subsystem
926 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
927 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
928 .cdrom .chs .ignore_cable are additional options
929 See Documentation/ide/ide.txt.
931 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
932 Claim all unknown PCI IDE storage controllers.
935 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
936 Poll forces a polling idle loop that can slightly
937 improve the performance of waking up a idle CPU, but
938 will use a lot of power and make the system run hot.
940 idle=mwait: On systems which support MONITOR/MWAIT but
941 the kernel chose to not use it because it doesn't save
942 as much power as a normal idle loop, use the
943 MONITOR/MWAIT idle loop anyways. Performance should be
944 the same as idle=poll.
945 idle=halt: Halt is forced to be used for CPU idle.
946 In such case C2/C3 won't be used again.
947 idle=nomwait: Disable mwait for CPU C-states
949 ignore_loglevel [KNL]
950 Ignore loglevel setting - this will print /all/
951 kernel messages to the console. Useful for debugging.
954 Set number of hash buckets for inode cache.
957 Format: { "0" | "1" }
958 0 -- integrity auditing messages. (Default)
959 1 -- enable informational integrity auditing messages.
962 Format: { "sha1" | "md5" }
966 Load a policy which meets the needs of the Trusted
967 Computing Base. This means IMA will measure all
968 programs exec'd, files mmap'd for exec, and all files
969 opened for read by uid=0.
973 Run specified binary instead of /sbin/init as init
976 initcall_debug [KNL] Trace initcalls as they are executed. Useful
977 for working out where the kernel is dying during
980 initrd= [BOOT] Specify the location of the initial ramdisk
982 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
985 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
987 Enable intel iommu driver.
989 Disable intel iommu driver.
990 igfx_off [Default Off]
991 By default, gfx is mapped as normal device. If a gfx
992 device has a dedicated DMAR unit, the DMAR unit is
993 bypassed by not enabling DMAR with this option. In
994 this case, gfx device will use physical address for
997 With this option iommu will not optimize to look
998 for io virtual address below 32 bit forcing dual
999 address cycle on pci bus for cards supporting greater
1000 than 32 bit addressing. The default is to look
1001 for translation below 32 bit and if not available
1002 then look in the higher range.
1003 strict [Default Off]
1004 With this option on every unmap_single operation will
1005 result in a hardware IOTLB flush operation as opposed
1006 to batching them for performance.
1007 sp_off [Default Off]
1008 By default, super page will be supported if Intel IOMMU
1009 has the capability. With this option, super page will
1011 intremap= [X86-64, Intel-IOMMU]
1012 Format: { on (default) | off | nosid }
1013 on enable Interrupt Remapping (default)
1014 off disable Interrupt Remapping
1015 nosid disable Source ID checking
1019 iomem= Disable strict checking of access to MMIO memory
1020 strict regions from userspace.
1036 io7= [HW] IO7 for Marvel based alpha systems
1037 See comment before marvel_specify_io7 in
1038 arch/alpha/kernel/core_marvel.c.
1040 io_delay= [X86] I/O delay method
1042 Standard port 0x80 based delay
1044 Alternate port 0xed based delay (needed on some systems)
1046 Simple two microseconds delay
1051 See Documentation/filesystems/nfs/nfsroot.txt.
1053 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1054 See comment before ip2_setup() in
1055 drivers/char/ip2/ip2base.c.
1058 When an interrupt is not handled search all handlers
1059 for it. Intended to get systems with badly broken
1063 When an interrupt is not handled search all handlers
1064 for it. Also check all handlers each timer
1065 interrupt. Intended to get systems with badly broken
1069 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1071 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1073 <cpu number>,...,<cpu number>
1075 <cpu number>-<cpu number>
1076 (must be a positive range in ascending order)
1078 <cpu number>,...,<cpu number>-<cpu number>
1080 This option can be used to specify one or more CPUs
1081 to isolate from the general SMP balancing and scheduling
1082 algorithms. You can move a process onto or off an
1083 "isolated" CPU via the CPU affinity syscalls or cpuset.
1084 <cpu number> begins at 0 and the maximum value is
1085 "number of CPUs in system - 1".
1087 This option is the preferred way to isolate CPUs. The
1088 alternative -- manually setting the CPU mask of all
1089 tasks in the system -- can cause problems and
1090 suboptimal load balancer performance.
1094 js= [HW,JOY] Analog joystick
1095 See Documentation/input/joystick.txt.
1099 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1100 specifies the amount of memory usable by the kernel
1101 for non-movable allocations. The requested amount is
1102 spread evenly throughout all nodes in the system. The
1103 remaining memory in each node is used for Movable
1104 pages. In the event, a node is too small to have both
1105 kernelcore and Movable pages, kernelcore pages will
1106 take priority and other nodes will have a larger number
1107 of kernelcore pages. The Movable zone is used for the
1108 allocation of pages that may be reclaimed or moved
1109 by the page migration subsystem. This means that
1110 HugeTLB pages may not be allocated from this zone.
1111 Note that allocations like PTEs-from-HighMem still
1112 use the HighMem zone if it exists, and the Normal
1113 zone if it does not.
1115 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1116 Format: <Controller#>[,poll interval]
1117 The controller # is the number of the ehci usb debug
1118 port as it is probed via PCI. The poll interval is
1119 optional and is the number seconds in between
1120 each poll cycle to the debug port in case you need
1121 the functionality for interrupting the kernel with
1122 gdb or control-c on the dbgp connection. When
1123 not using this parameter you use sysrq-g to break into
1124 the kernel debugger.
1126 kgdboc= [KGDB,HW] kgdb over consoles.
1127 Requires a tty driver that supports console polling,
1128 or a supported polling keyboard driver (non-usb).
1129 Serial only format: <serial_device>[,baud]
1130 keyboard only format: kbd
1131 keyboard and serial format: kbd,<serial_device>[,baud]
1132 Optional Kernel mode setting:
1133 kms, kbd format: kms,kbd
1134 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1136 kgdbwait [KGDB] Stop kernel execution and enter the
1137 kernel debugger at the earliest opportunity.
1139 kmac= [MIPS] korina ethernet MAC address.
1140 Configure the RouterBoard 532 series on-chip
1141 Ethernet adapter MAC address.
1143 kmemleak= [KNL] Boot-time kmemleak enable/disable
1144 Valid arguments: on, off
1147 kstack=N [X86] Print N words from the kernel stack
1150 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1151 Default is 0 (don't ignore, but inject #GP)
1153 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1154 Default is 1 (enabled)
1156 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1160 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1161 Default is 1 (enabled)
1163 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1165 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1167 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1168 (virtualized MMU) support on capable Intel chips.
1169 Default is 1 (enabled)
1171 kvm-intel.emulate_invalid_guest_state=
1172 [KVM,Intel] Enable emulation of invalid guest states
1173 Default is 0 (disabled)
1175 kvm-intel.flexpriority=
1176 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1177 Default is 1 (enabled)
1179 kvm-intel.unrestricted_guest=
1180 [KVM,Intel] Disable unrestricted guest feature
1181 (virtualized real and unpaged mode) on capable
1182 Intel chips. Default is 1 (enabled)
1184 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1185 feature (tagged TLBs) on capable Intel chips.
1186 Default is 1 (enabled)
1192 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1195 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1198 libata.dma= [LIBATA] DMA control
1199 libata.dma=0 Disable all PATA and SATA DMA
1200 libata.dma=1 PATA and SATA Disk DMA only
1201 libata.dma=2 ATAPI (CDROM) DMA only
1202 libata.dma=4 Compact Flash DMA only
1203 Combinations also work, so libata.dma=3 enables DMA
1204 for disks and CDROMs, but not CFs.
1206 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1207 libata.ignore_hpa=0 keep BIOS limits (default)
1208 libata.ignore_hpa=1 ignore limits, using full disk
1210 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1214 libata.force= [LIBATA] Force configurations. The format is comma
1215 separated list of "[ID:]VAL" where ID is
1216 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1217 matching port, link or device. Basically, it matches
1218 the ATA ID string printed on console by libata. If
1219 the whole ID part is omitted, the last PORT and DEVICE
1220 values are used. If ID hasn't been specified yet, the
1221 configuration applies to all ports, links and devices.
1223 If only DEVICE is omitted, the parameter applies to
1224 the port and all links and devices behind it. DEVICE
1225 number of 0 either selects the first device or the
1226 first fan-out link behind PMP device. It does not
1227 select the host link. DEVICE number of 15 selects the
1228 host link and device attached to it.
1230 The VAL specifies the configuration to force. As long
1231 as there's no ambiguity shortcut notation is allowed.
1232 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1233 The following configurations can be forced.
1235 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1236 Any ID with matching PORT is used.
1238 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1240 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1241 udma[/][16,25,33,44,66,100,133] notation is also
1244 * [no]ncq: Turn on or off NCQ.
1246 * nohrst, nosrst, norst: suppress hard, soft
1249 * dump_id: dump IDENTIFY data.
1251 If there are multiple matching configurations changing
1252 the same attribute, the last one is used.
1254 memblock=debug [KNL] Enable memblock debug messages.
1256 load_ramdisk= [RAM] List of ramdisks to load from floppy
1257 See Documentation/blockdev/ramdisk.txt.
1259 lockd.nlm_grace_period=P [NFS] Assign grace period.
1262 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1265 lockd.nlm_timeout=T [NFS] Assign timeout value.
1268 lockd.nlm_udpport=M [NFS] Assign UDP port.
1271 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1274 loglevel= All Kernel Messages with a loglevel smaller than the
1275 console loglevel will be printed to the console. It can
1276 also be changed with klogd or other programs. The
1277 loglevels are defined as follows:
1279 0 (KERN_EMERG) system is unusable
1280 1 (KERN_ALERT) action must be taken immediately
1281 2 (KERN_CRIT) critical conditions
1282 3 (KERN_ERR) error conditions
1283 4 (KERN_WARNING) warning conditions
1284 5 (KERN_NOTICE) normal but significant condition
1285 6 (KERN_INFO) informational
1286 7 (KERN_DEBUG) debug-level messages
1288 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1289 in bytes. n must be a power of two. The default
1290 size is set in the kernel config file.
1292 logo.nologo [FB] Disables display of the built-in Linux logo.
1293 This may be used to provide more screen space for
1294 kernel log messages and is useful when debugging
1295 kernel boot problems.
1297 lp=0 [LP] Specify parallel ports to use, e.g,
1298 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1299 lp=reset first parallel port). 'lp=0' disables the
1300 lp=auto printer driver. 'lp=reset' (which can be
1301 specified in addition to the ports) causes
1302 attached printers to be reset. Using
1303 lp=port1,port2,... specifies the parallel ports
1304 to associate lp devices with, starting with
1305 lp0. A port specification may be 'none' to skip
1306 that lp device, or a parport name such as
1307 'parport0'. Specifying 'lp=auto' instead of a
1308 port specification list means that device IDs
1309 from each port should be examined, to see if
1310 an IEEE 1284-compliant printer is attached; if
1311 so, the driver will manage that printer.
1312 See also header of drivers/char/lp.c.
1315 Sets loops_per_jiffy to given constant, thus avoiding
1316 time-consuming boot-time autodetection (up to 250 ms per
1317 CPU). 0 enables autodetection (default). To determine
1318 the correct value for your kernel, boot with normal
1319 autodetection and see what value is printed. Note that
1320 on SMP systems the preset will be applied to all CPUs,
1321 which is likely to cause problems if your CPUs need
1322 significantly divergent settings. An incorrect value
1323 will cause delays in the kernel to be wrong, leading to
1324 unpredictable I/O errors and other breakage. Although
1325 unlikely, in the extreme case this might damage your
1329 Format: <io>,<irq>,<dma>
1331 machvec= [IA64] Force the use of a particular machine-vector
1332 (machvec) in a generic kernel.
1333 Example: machvec=hpzx1_swiotlb
1335 machtype= [Loongson] Share the same kernel image file between different
1337 Example: machtype=lemote-yeeloong-2f-7inch
1339 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1340 than or equal to this physical address is ignored.
1342 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1343 should make use of. maxcpus=n : n >= 0 limits the
1344 kernel to using 'n' processors. n=0 is a special case,
1345 it is equivalent to "nosmp", which also disables
1348 max_loop= [LOOP] Maximum number of loopback devices that can
1354 mce [X86-32] Machine Check Exception
1356 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1358 md= [HW] RAID subsystems devices and level
1359 See Documentation/md.txt.
1362 Format: <first>,<last>
1363 Specifies range of consoles to be captured by the MDA.
1365 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1366 Amount of memory to be used when the kernel is not able
1367 to see the whole system memory or for test.
1368 [X86-32] Use together with memmap= to avoid physical
1369 address space collisions. Without memmap= PCI devices
1370 could be placed at addresses belonging to unused RAM.
1372 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1376 [KNL,SH] Allow user to override the default size for
1377 per-device physically contiguous DMA buffers.
1379 memmap=exactmap [KNL,X86] Enable setting of an exact
1380 E820 memory map, as specified by the user.
1381 Such memmap=exactmap lines can be constructed based on
1382 BIOS output or other requirements. See the memmap=nn@ss
1385 memmap=nn[KMG]@ss[KMG]
1386 [KNL] Force usage of a specific region of memory
1387 Region of memory to be used, from ss to ss+nn.
1389 memmap=nn[KMG]#ss[KMG]
1390 [KNL,ACPI] Mark specific memory as ACPI data.
1391 Region of memory to be used, from ss to ss+nn.
1393 memmap=nn[KMG]$ss[KMG]
1394 [KNL,ACPI] Mark specific memory as reserved.
1395 Region of memory to be used, from ss to ss+nn.
1396 Example: Exclude memory from 0x18690000-0x1869ffff
1397 memmap=64K$0x18690000
1399 memmap=0x10000$0x18690000
1401 memory_corruption_check=0/1 [X86]
1402 Some BIOSes seem to corrupt the first 64k of
1403 memory when doing things like suspend/resume.
1404 Setting this option will scan the memory
1405 looking for corruption. Enabling this will
1406 both detect corruption and prevent the kernel
1407 from using the memory being corrupted.
1408 However, its intended as a diagnostic tool; if
1409 repeatable BIOS-originated corruption always
1410 affects the same memory, you can use memmap=
1411 to prevent the kernel from using that memory.
1413 memory_corruption_check_size=size [X86]
1414 By default it checks for corruption in the low
1415 64k, making this memory unavailable for normal
1416 use. Use this parameter to scan for
1417 corruption in more or less memory.
1419 memory_corruption_check_period=seconds [X86]
1420 By default it checks for corruption every 60
1421 seconds. Use this parameter to check at some
1422 other rate. 0 disables periodic checking.
1424 memtest= [KNL,X86] Enable memtest
1426 default : 0 <disable>
1427 Specifies the number of memtest passes to be
1428 performed. Each pass selects another test
1429 pattern from a given set of patterns. Memtest
1430 fills the memory with this pattern, validates
1431 memory contents and reserves bad memory
1432 regions that are detected.
1434 meye.*= [HW] Set MotionEye Camera parameters
1435 See Documentation/video4linux/meye.txt.
1437 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1438 Multi-Function General Purpose Timers on AMD Geode
1441 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1442 the BIOS has incorrectly applied a workaround. TinyBIOS
1443 version 0.98 is known to be affected, 0.99 fixes the
1444 problem by letting the user disable the workaround.
1448 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1449 physical address is ignored.
1451 mini2440= [ARM,HW,KNL]
1452 Format:[0..2][b][c][t]
1454 MINI2440 configuration specification:
1455 0 - The attached screen is the 3.5" TFT
1456 1 - The attached screen is the 7" TFT
1457 2 - The VGA Shield is attached (1024x768)
1458 Leaving out the screen size parameter will not load
1459 the TFT driver, and the framebuffer will be left
1461 b - Enable backlight. The TFT backlight pin will be
1462 linked to the kernel VESA blanking code and a GPIO
1463 LED. This parameter is not necessary when using the
1465 c - Enable the s3c camera interface.
1466 t - Reserved for enabling touchscreen support. The
1467 touchscreen support is not enabled in the mainstream
1468 kernel as of 2.6.30, a preliminary port can be found
1469 in the "bleeding edge" mini2440 support kernel at
1470 http://repo.or.cz/w/linux-2.6/mini2440.git
1473 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1474 parameter allows control of the logging verbosity for
1475 the additional memory initialisation checks. A value
1476 of 0 disables mminit logging and a level of 4 will
1477 log everything. Information is printed at KERN_DEBUG
1478 so loglevel=8 may also need to be specified.
1481 [MOUSE] Maximum time between finger touching and
1482 leaving touchpad surface for touch to be considered
1483 a tap and be reported as a left button click (for
1484 touchpads working in absolute mode only).
1486 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1487 reporting absolute coordinates, such as tablets
1488 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1489 reporting absolute coordinates, such as tablets
1491 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1492 is similar to kernelcore except it specifies the
1493 amount of memory used for migratable allocations.
1494 If both kernelcore and movablecore is specified,
1495 then kernelcore will be at *least* the specified
1496 value but may be more. If movablecore on its own
1497 is specified, the administrator must be careful
1498 that the amount of memory usable for all allocations
1501 MTD_Partition= [MTD]
1502 Format: <name>,<region-number>,<size>,<offset>
1504 MTD_Region= [MTD] Format:
1505 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1508 See drivers/mtd/cmdlinepart.c.
1510 multitce=off [PPC] This parameter disables the use of the pSeries
1511 firmware feature for updating multiple TCE entries
1514 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1516 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1518 boundary - index of last SLC block on Flex-OneNAND.
1519 The remaining blocks are configured as MLC blocks.
1520 lock - Configure if Flex-OneNAND boundary should be locked.
1521 Once locked, the boundary cannot be changed.
1522 1 indicates lock status, 0 indicates unlock status.
1525 ARM/S3C2412 JIVE boot control
1527 See arch/arm/mach-s3c2412/mach-jive.c
1529 mtouchusb.raw_coordinates=
1530 [HW] Make the MicroTouch USB driver use raw coordinates
1531 ('y', default) or cooked coordinates ('n')
1533 mtrr_chunk_size=nn[KMG] [X86]
1534 used for mtrr cleanup. It is largest continuous chunk
1535 that could hold holes aka. UC entries.
1537 mtrr_gran_size=nn[KMG] [X86]
1538 Used for mtrr cleanup. It is granularity of mtrr block.
1540 Large value could prevent small alignment from
1543 mtrr_spare_reg_nr=n [X86]
1545 Range: 0,7 : spare reg number
1547 Used for mtrr cleanup. It is spare mtrr entries number.
1548 Set to 2 or more if your graphical card needs more.
1550 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1552 netdev= [NET] Network devices parameters
1553 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1554 Note that mem_start is often overloaded to mean
1555 something different and driver-specific.
1556 This usage is only documented in each driver source
1560 [NETFILTER] Enable connection tracking flow accounting
1561 0 to disable accounting
1562 1 to enable accounting
1565 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1566 See Documentation/filesystems/nfs/nfsroot.txt.
1568 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1569 See Documentation/filesystems/nfs/nfsroot.txt.
1571 nfsrootdebug [NFS] enable nfsroot debugging messages.
1572 See Documentation/filesystems/nfs/nfsroot.txt.
1574 nfs.callback_tcpport=
1575 [NFS] set the TCP port on which the NFSv4 callback
1576 channel should listen.
1579 [NFS] sets the pathname to the program which is used
1580 to update the NFS client cache entries.
1582 nfs.cache_getent_timeout=
1583 [NFS] sets the timeout after which an attempt to
1584 update a cache entry is deemed to have failed.
1586 nfs.idmap_cache_timeout=
1587 [NFS] set the maximum lifetime for idmapper cache
1591 [NFS] enable 64-bit inode numbers.
1592 If zero, the NFS client will fake up a 32-bit inode
1593 number for the readdir() and stat() syscalls instead
1594 of returning the full 64-bit number.
1595 The default is to return 64-bit inode numbers.
1597 nfs.nfs4_disable_idmapping=
1598 [NFSv4] When set, this option disables the NFSv4
1599 idmapper on the client, but only if the mount
1600 is using the 'sec=sys' security flavour. This may
1601 make migration from legacy NFSv2/v3 systems easier
1602 provided that the server has the appropriate support.
1603 The default is to always enable NFSv4 idmapping.
1605 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1606 when a NMI is triggered.
1607 Format: [state][,regs][,debounce][,die]
1609 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1610 Format: [panic,][nopanic,][num]
1612 0 - turn nmi_watchdog off
1613 When panic is specified, panic when an NMI watchdog
1614 timeout occurs (or 'nopanic' to override the opposite
1616 This is useful when you use a panic=... timeout and
1617 need the box quickly up again.
1619 netpoll.carrier_timeout=
1620 [NET] Specifies amount of time (in seconds) that
1621 netpoll should wait for a carrier. By default netpoll
1624 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1625 emulation library even if a 387 maths coprocessor
1629 [HW] Never suspend the console
1630 Disable suspending of consoles during suspend and
1631 hibernate operations. Once disabled, debugging
1632 messages can reach various consoles while the rest
1633 of the system is being put to sleep (ie, while
1634 debugging driver suspend/resume hooks). This may
1635 not work reliably with all consoles, but is known
1636 to work with serial and VGA consoles.
1638 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1639 caches in the slab allocator. Saves per-node memory,
1640 but will impact performance.
1644 noapic [SMP,APIC] Tells the kernel to not make use of any
1645 IOAPICs that may be present in the system.
1647 noautogroup Disable scheduler automatic task group creation.
1649 nobats [PPC] Do not use BATs for mapping kernel lowmem
1650 on "Classic" PPC cores.
1654 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1656 nodelayacct [KNL] Disable per-task delay accounting
1658 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1660 nodsp [SH] Disable hardware DSP at boot time.
1662 noefi [X86] Disable EFI runtime services support.
1667 On X86-32 available only on PAE configured kernels.
1668 noexec=on: enable non-executable mappings (default)
1669 noexec=off: disable non-executable mappings
1672 Disable SMEP (Supervisor Mode Execution Protection)
1673 even if it is supported by processor.
1676 This affects only 32-bit executables.
1677 noexec32=on: enable non-executable mappings (default)
1678 read doesn't imply executable mappings
1679 noexec32=off: disable non-executable mappings
1680 read implies executable mappings
1682 nofpu [SH] Disable hardware FPU at boot time.
1684 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1685 register save and restore. The kernel will only save
1686 legacy floating-point registers on task switch.
1688 noxsave [BUGS=X86] Disables x86 extended register state save
1689 and restore using xsave. The kernel will fallback to
1690 enabling legacy floating-point and sse state.
1692 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1693 wfi(ARM) instruction doesn't work correctly and not to
1694 use it. This is also useful when using JTAG debugger.
1696 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1697 instruction doesn't work correctly and not to
1700 no_file_caps Tells the kernel not to honor file capabilities. The
1701 only way then for a file to be executed with privilege
1702 is to be setuid root or executed by root.
1704 nohalt [IA-64] Tells the kernel not to use the power saving
1705 function PAL_HALT_LIGHT when idle. This increases
1706 power-consumption. On the positive side, it reduces
1707 interrupt wake-up latency, which may improve performance
1708 in certain environments such as networked servers or
1711 nohz= [KNL] Boottime enable/disable dynamic ticks
1712 Valid arguments: on, off
1715 noiotrap [SH] Disables trapped I/O port accesses.
1717 noirqdebug [X86-32] Disables the code which attempts to detect and
1718 disable unhandled interrupt sources.
1720 no_timer_check [X86,APIC] Disables the code which tests for
1721 broken timer IRQ sources.
1723 noisapnp [ISAPNP] Disables ISA PnP code.
1725 noinitrd [RAM] Tells the kernel not to load any configured
1728 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1730 [Deprecated - use intremap=off]
1734 nojitter [IA64] Disables jitter checking for ITC timers.
1736 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1738 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1741 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1742 steal time is computed, but won't influence scheduler
1745 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1747 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1749 noltlbs [PPC] Do not use large page/tlb entries for kernel
1750 lowmem mapping on PPC40x.
1752 nomca [IA-64] Disable machine check abort handling
1754 nomce [X86-32] Machine Check Exception
1756 nomfgpt [X86-32] Disable Multi-Function General Purpose
1757 Timer usage (for AMD Geode machines).
1759 nopat [X86] Disable PAT (page attribute table extension of
1760 pagetables) support.
1762 norandmaps Don't use address space randomization. Equivalent to
1763 echo 0 > /proc/sys/kernel/randomize_va_space
1765 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1767 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1768 with UP alternatives
1770 noresidual [PPC] Don't use residual data on PReP machines.
1772 noresume [SWSUSP] Disables resume and restores original swap
1775 no-scroll [VGA] Disables scrollback.
1776 This is required for the Braillex ib80-piezo Braille
1777 reader made by F.H. Papenmeier (Germany).
1781 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1783 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1784 and disable the IO APIC. legacy for "maxcpus=0".
1786 nosoftlockup [KNL] Disable the soft-lockup detector.
1788 nosync [HW,M68K] Disables sync negotiation for all devices.
1790 notsc [BUGS=X86-32] Disable Time Stamp Counter
1792 nousb [USB] Disable the USB subsystem
1794 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1798 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1800 nptcg= [IA64] Override max number of concurrent global TLB
1801 purges which is reported from either PAL_VM_SUMMARY or
1804 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1805 could support. nr_cpus=n : n >= 1 limits the kernel to
1806 supporting 'n' processors. Later in runtime you can not
1807 use hotplug cpu feature to put more cpu back to online.
1808 just like you compile the kernel NR_CPUS=n
1810 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1812 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1813 one of ['zone', 'node', 'default'] can be specified
1814 This can be set from sysctl after boot.
1815 See Documentation/sysctl/vm.txt for details.
1817 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1818 See Documentation/debugging-via-ohci1394.txt for more
1821 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1822 Rather than timing out after 20 ms if an EC
1823 command is not properly ACKed, override the length
1824 of the timeout. We have interrupts disabled while
1825 waiting for the ACK, so if this is set too high
1826 interrupts *may* be lost!
1828 omap_mux= [OMAP] Override bootloader pin multiplexing.
1829 Format: <mux_mode0.mode_name=value>...
1830 For example, to override I2C bus2:
1831 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1833 oprofile.timer= [HW]
1834 Use timer interrupt instead of performance counters
1836 oprofile.cpu_type= Force an oprofile cpu type
1837 This might be useful if you have an older oprofile
1838 userland or if you want common events.
1839 Format: { arch_perfmon }
1840 arch_perfmon: [X86] Force use of architectural
1841 perfmon on Intel CPUs instead of the
1842 CPU specific event set.
1844 oops=panic Always panic on oopses. Default is to just kill the
1845 process, but there is a small probability of
1846 deadlocking the machine.
1847 This will also cause panics on machine check exceptions.
1848 Useful together with panic=30 to trigger a reboot.
1851 See Documentation/sound/oss/oss-parameters.txt
1853 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1854 timeout > 0: seconds before rebooting
1855 timeout = 0: wait forever
1856 timeout < 0: reboot immediately
1859 parkbd.port= [HW] Parallel port number the keyboard adapter is
1860 connected to, default is 0.
1862 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1863 0 for XT, 1 for AT (default is AT).
1866 parport= [HW,PPT] Specify parallel ports. 0 disables.
1867 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1868 Use 'auto' to force the driver to use any
1869 IRQ/DMA settings detected (the default is to
1870 ignore detected IRQ/DMA settings because of
1871 possible conflicts). You can specify the base
1872 address, IRQ, and DMA settings; IRQ and DMA
1873 should be numbers, or 'auto' (for using detected
1874 settings on that particular port), or 'nofifo'
1875 (to avoid using a FIFO even if it is detected).
1876 Parallel ports are assigned in the order they
1877 are specified on the command line, starting
1880 parport_init_mode= [HW,PPT]
1881 Configure VIA parallel port to operate in
1882 a specific mode. This is necessary on Pegasos
1883 computer where firmware has no options for setting
1884 up parallel port mode and sets it to spp.
1885 Currently this function knows 686a and 8231 chips.
1886 Format: [spp|ps2|epp|ecp|ecpepp]
1889 Halt all CPUs after the first oops has been printed for
1890 the specified number of seconds. This is to be used if
1891 your oopses keep scrolling off the screen.
1896 See header of drivers/block/paride/pcd.c.
1897 See also Documentation/blockdev/paride.txt.
1899 pci=option[,option...] [PCI] various PCI subsystem options:
1900 earlydump [X86] dump PCI config space before the kernel
1902 off [X86] don't probe for the PCI bus
1903 bios [X86-32] force use of PCI BIOS, don't access
1904 the hardware directly. Use this if your machine
1905 has a non-standard PCI host bridge.
1906 nobios [X86-32] disallow use of PCI BIOS, only direct
1907 hardware access methods are allowed. Use this
1908 if you experience crashes upon bootup and you
1909 suspect they are caused by the BIOS.
1910 conf1 [X86] Force use of PCI Configuration
1912 conf2 [X86] Force use of PCI Configuration
1914 noaer [PCIE] If the PCIEAER kernel config parameter is
1915 enabled, this kernel boot option can be used to
1916 disable the use of PCIE advanced error reporting.
1917 nodomains [PCI] Disable support for multiple PCI
1918 root domains (aka PCI segments, in ACPI-speak).
1919 nommconf [X86] Disable use of MMCONFIG for PCI
1921 check_enable_amd_mmconf [X86] check for and enable
1922 properly configured MMIO access to PCI
1923 config space on AMD family 10h CPU
1924 nomsi [MSI] If the PCI_MSI kernel config parameter is
1925 enabled, this kernel boot option can be used to
1926 disable the use of MSI interrupts system-wide.
1927 noioapicquirk [APIC] Disable all boot interrupt quirks.
1928 Safety option to keep boot IRQs enabled. This
1929 should never be necessary.
1930 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1931 primary IO-APIC for bridges that cannot disable
1932 boot IRQs. This fixes a source of spurious IRQs
1933 when the system masks IRQs.
1934 noioapicreroute [APIC] Disable workaround that uses the
1935 boot IRQ equivalent of an IRQ that connects to
1936 a chipset where boot IRQs cannot be disabled.
1937 The opposite of ioapicreroute.
1938 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1939 routing table. These calls are known to be buggy
1940 on several machines and they hang the machine
1941 when used, but on other computers it's the only
1942 way to get the interrupt routing table. Try
1943 this option if the kernel is unable to allocate
1944 IRQs or discover secondary PCI buses on your
1946 rom [X86] Assign address space to expansion ROMs.
1947 Use with caution as certain devices share
1948 address decoders between ROMs and other
1950 norom [X86] Do not assign address space to
1951 expansion ROMs that do not already have
1952 BIOS assigned address ranges.
1953 nobar [X86] Do not assign address space to the
1954 BARs that weren't assigned by the BIOS.
1955 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1956 assigned automatically to PCI devices. You can
1957 make the kernel exclude IRQs of your ISA cards
1959 pirqaddr=0xAAAAA [X86] Specify the physical address
1960 of the PIRQ table (normally generated
1961 by the BIOS) if it is outside the
1962 F0000h-100000h range.
1963 lastbus=N [X86] Scan all buses thru bus #N. Can be
1964 useful if the kernel is unable to find your
1965 secondary buses and you want to tell it
1966 explicitly which ones they are.
1967 assign-busses [X86] Always assign all PCI bus
1968 numbers ourselves, overriding
1969 whatever the firmware may have done.
1970 usepirqmask [X86] Honor the possible IRQ mask stored
1971 in the BIOS $PIR table. This is needed on
1972 some systems with broken BIOSes, notably
1973 some HP Pavilion N5400 and Omnibook XE3
1974 notebooks. This will have no effect if ACPI
1975 IRQ routing is enabled.
1976 noacpi [X86] Do not use ACPI for IRQ routing
1977 or for PCI scanning.
1978 use_crs [X86] Use PCI host bridge window information
1979 from ACPI. On BIOSes from 2008 or later, this
1980 is enabled by default. If you need to use this,
1981 please report a bug.
1982 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1983 If you need to use this, please report a bug.
1984 routeirq Do IRQ routing for all PCI devices.
1985 This is normally done in pci_enable_device(),
1986 so this option is a temporary workaround
1987 for broken drivers that don't call it.
1988 skip_isa_align [X86] do not align io start addr, so can
1989 handle more pci cards
1990 firmware [ARM] Do not re-enumerate the bus but instead
1991 just use the configuration from the
1992 bootloader. This is currently used on
1993 IXP2000 systems where the bus has to be
1994 configured a certain way for adjunct CPUs.
1995 noearly [X86] Don't do any early type 1 scanning.
1996 This might help on some broken boards which
1997 machine check when some devices' config space
1998 is read. But various workarounds are disabled
1999 and some IOMMU drivers will not work.
2000 bfsort Sort PCI devices into breadth-first order.
2001 This sorting is done to get a device
2002 order compatible with older (<= 2.4) kernels.
2003 nobfsort Don't sort PCI devices into breadth-first order.
2004 cbiosize=nn[KMG] The fixed amount of bus space which is
2005 reserved for the CardBus bridge's IO window.
2006 The default value is 256 bytes.
2007 cbmemsize=nn[KMG] The fixed amount of bus space which is
2008 reserved for the CardBus bridge's memory
2009 window. The default value is 64 megabytes.
2012 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2013 Specifies alignment and device to reassign
2014 aligned memory resources.
2015 If <order of align> is not specified,
2016 PAGE_SIZE is used as alignment.
2017 PCI-PCI bridge can be specified, if resource
2018 windows need to be expanded.
2019 ecrc= Enable/disable PCIe ECRC (transaction layer
2020 end-to-end CRC checking).
2021 bios: Use BIOS/firmware settings. This is the
2025 realloc reallocate PCI resources if allocations done by BIOS
2028 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2031 force Enable ASPM even on devices that claim not to support it.
2032 WARNING: Forcing ASPM on may cause system lockups.
2034 pcie_ports= [PCIE] PCIe ports handling:
2035 auto Ask the BIOS whether or not to use native PCIe services
2036 associated with PCIe ports (PME, hot-plug, AER). Use
2037 them only if that is allowed by the BIOS.
2038 native Use native PCIe services associated with PCIe ports
2040 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2043 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2044 nomsi Do not use MSI for native PCIe PME signaling (this makes
2045 all PCIe root ports use INTx for all services).
2047 pcmv= [HW,PCMCIA] BadgePAD 4
2050 See Documentation/blockdev/paride.txt.
2052 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2055 See arch/parisc/kernel/pdc_chassis.c
2057 percpu_alloc= Select which percpu first chunk allocator to use.
2058 Currently supported values are "embed" and "page".
2059 Archs may support subset or none of the selections.
2060 See comments in mm/percpu.c for details on each
2061 allocator. This parameter is primarily for debugging
2062 and performance comparison.
2065 See Documentation/blockdev/paride.txt.
2068 See Documentation/blockdev/paride.txt.
2070 pirq= [SMP,APIC] Manual mp-table setup
2071 See Documentation/x86/i386/IO-APIC.txt.
2073 plip= [PPT,NET] Parallel port network link
2074 Format: { parport<nr> | timid | 0 }
2075 See also Documentation/parport.txt.
2077 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2078 Override pmtimer IOPort with a hex value.
2082 Enable PNP debug messages. This depends on the
2083 CONFIG_PNP_DEBUG_MESSAGES option.
2089 { on | off | curr | res | no-curr | no-res }
2092 [ISAPNP] Exclude IRQs for the autoconfiguration
2095 [ISAPNP] Exclude DMAs for the autoconfiguration
2097 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2098 Ranges are in pairs (I/O port base and size).
2101 [ISAPNP] Exclude memory regions for the
2103 Ranges are in pairs (memory base and size).
2105 ports= [IP_VS_FTP] IPVS ftp helper module
2107 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2109 Format: <port>,<port>....
2111 print-fatal-signals=
2112 [KNL] debug: print fatal signals
2114 If enabled, warn about various signal handling
2115 related application anomalies: too many signals,
2116 too many POSIX.1 timers, fatal signals causing a
2119 If you hit the warning due to signal overflow,
2120 you might want to try "ulimit -i unlimited".
2124 printk.time= Show timing data prefixed to each printk message line
2125 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2127 processor.max_cstate= [HW,ACPI]
2128 Limit processor to maximum C-state
2129 max_cstate=9 overrides any DMI blacklist limit.
2131 processor.nocst [HW,ACPI]
2132 Ignore the _CST method to determine C-states,
2133 instead using the legacy FADT method
2135 profile= [KNL] Enable kernel profiling via /proc/profile
2136 Format: [schedule,]<number>
2137 Param: "schedule" - profile schedule points.
2138 Param: <number> - step/bucket size as a power of 2 for
2139 statistical time based profiling.
2140 Param: "sleep" - profile D-state sleeping (millisecs).
2141 Requires CONFIG_SCHEDSTATS
2142 Param: "kvm" - profile VM exits.
2144 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2146 See Documentation/blockdev/ramdisk.txt.
2148 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2149 probe for; one of (bare|imps|exps|lifebook|any).
2150 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2152 psmouse.resetafter= [HW,MOUSE]
2153 Try to reset the device after so many bad packets
2156 [HW,MOUSE] Set desired mouse resolution, in dpi.
2157 psmouse.smartscroll=
2158 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2159 0 = disabled, 1 = enabled (default).
2161 pstore.backend= Specify the name of the pstore backend to use
2164 See Documentation/blockdev/paride.txt.
2167 [KNL] Number of legacy pty's. Overwrites compiled-in
2170 quiet [KNL] Disable most log messages
2175 See Documentation/md.txt.
2177 ramdisk_blocksize= [RAM]
2178 See Documentation/blockdev/ramdisk.txt.
2180 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2181 See Documentation/blockdev/ramdisk.txt.
2183 rcupdate.blimit= [KNL,BOOT]
2184 Set maximum number of finished RCU callbacks to process
2187 rcupdate.qhimark= [KNL,BOOT]
2188 Set threshold of queued
2189 RCU callbacks over which batch limiting is disabled.
2191 rcupdate.qlowmark= [KNL,BOOT]
2192 Set threshold of queued RCU callbacks below which
2193 batch limiting is re-enabled.
2197 Run specified binary instead of /init from the ramdisk,
2198 used for early userspace startup. See initrd.
2200 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2201 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2202 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2205 [KNL, SMP] Set scheduler's default relax_domain_level.
2206 See Documentation/cgroups/cpusets.txt.
2208 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2210 reservetop= [X86-32]
2212 Reserves a hole at the top of the kernel virtual
2217 Set the amount of memory to reserve for BIOS at
2218 the bottom of the address space.
2220 reset_devices [KNL] Force drivers to reset the underlying device
2221 during initialization.
2224 Specify the partition device for software suspend
2226 resume_offset= [SWSUSP]
2227 Specify the offset from the beginning of the partition
2228 given by "resume=" at which the swap header is located,
2229 in <PAGE_SIZE> units (needed only for swap files).
2230 See Documentation/power/swsusp-and-swap-files.txt
2232 hibernate= [HIBERNATION]
2233 noresume Don't check if there's a hibernation image
2234 present during boot.
2235 nocompress Don't compress/decompress hibernation images.
2237 retain_initrd [RAM] Keep initrd memory after extraction
2239 rhash_entries= [KNL,NET]
2240 Set number of hash buckets for route cache
2242 riscom8= [HW,SERIAL]
2243 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2245 ro [KNL] Mount root device read-only on boot
2247 root= [KNL] Root filesystem
2249 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2250 mount the root filesystem
2252 rootflags= [KNL] Set root filesystem mount option string
2254 rootfstype= [KNL] Set root filesystem type
2256 rootwait [KNL] Wait (indefinitely) for root device to show up.
2257 Useful for devices that are detected asynchronously
2258 (e.g. USB and MMC devices).
2260 rw [KNL] Mount root device read-write on boot
2262 S [KNL] Run init in single mode
2265 See drivers/net/irda/sa1100_ir.c.
2267 sbni= [NET] Granch SBNI12 leased line adapter
2269 sched_debug [KNL] Enables verbose scheduler debug messages.
2271 security= [SECURITY] Choose a security module to enable at boot.
2272 If this boot parameter is not specified, only the first
2273 security module asking for security registration will be
2274 loaded. An invalid security module name will be treated
2275 as if no module has been chosen.
2277 selinux= [SELINUX] Disable or enable SELinux at boot time.
2278 Format: { "0" | "1" }
2279 See security/selinux/Kconfig help text.
2282 Default value is set via kernel config option.
2283 If enabled at boot time, /selinux/disable can be used
2284 later to disable prior to initial policy load.
2286 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2287 Format: { "0" | "1" }
2288 See security/apparmor/Kconfig help text
2291 Default value is set via kernel config option.
2293 serialnumber [BUGS=X86-32]
2296 Maximal number of shapers.
2298 show_msr= [x86] show boot-time MSR settings
2299 Format: { <integer> }
2300 Show boot-time (BIOS-initialized) MSR settings.
2301 The parameter means the number of CPUs to show,
2302 for example 1 means boot CPU only.
2309 slub_debug[=options[,slabs]] [MM, SLUB]
2310 Enabling slub_debug allows one to determine the
2311 culprit if slab objects become corrupted. Enabling
2312 slub_debug can create guard zones around objects and
2313 may poison objects when not in use. Also tracks the
2314 last alloc / free. For more information see
2315 Documentation/vm/slub.txt.
2317 slub_max_order= [MM, SLUB]
2318 Determines the maximum allowed order for slabs.
2319 A high setting may cause OOMs due to memory
2320 fragmentation. For more information see
2321 Documentation/vm/slub.txt.
2323 slub_min_objects= [MM, SLUB]
2324 The minimum number of objects per slab. SLUB will
2325 increase the slab order up to slub_max_order to
2326 generate a sufficiently large slab able to contain
2327 the number of objects indicated. The higher the number
2328 of objects the smaller the overhead of tracking slabs
2329 and the less frequently locks need to be acquired.
2330 For more information see Documentation/vm/slub.txt.
2332 slub_min_order= [MM, SLUB]
2333 Determines the mininum page order for slabs. Must be
2334 lower than slub_max_order.
2335 For more information see Documentation/vm/slub.txt.
2337 slub_nomerge [MM, SLUB]
2338 Disable merging of slabs with similar size. May be
2339 necessary if there is some reason to distinguish
2340 allocs to different slabs. Debug options disable
2341 merging on their own.
2342 For more information see Documentation/vm/slub.txt.
2345 Format: <io1>[,<io2>[,...,<io8>]]
2347 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2348 attempt to substitute SMP alternatives once at boot.
2350 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2351 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2352 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2353 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2354 smsc-ircc2.ircc_irq= [HW] IRQ line
2355 smsc-ircc2.ircc_dma= [HW] DMA channel
2356 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2357 0: Toshiba Satellite 1800 (GP data pin select)
2358 1: Fast pin select (default)
2362 [KNL] Should the soft-lockup detector generate panics.
2365 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2366 See Documentation/sonypi.txt
2368 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2369 See Documentation/serial/specialix.txt.
2371 spia_io_base= [HW,MTD]
2377 Enabled the stack tracer on boot up.
2381 Set the STI (builtin display/keyboard on the HP-PARISC
2382 machines) console (graphic card) which should be used
2383 as the initial boot-console.
2384 See also comment in drivers/video/console/sticore.c.
2387 See comment in drivers/video/console/sticore.c.
2390 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2392 sunrpc.min_resvport=
2393 sunrpc.max_resvport=
2395 SunRPC servers often require that client requests
2396 originate from a privileged port (i.e. a port in the
2397 range 0 < portnr < 1024).
2398 An administrator who wishes to reserve some of these
2399 ports for other uses may adjust the range that the
2400 kernel's sunrpc client considers to be privileged
2401 using these two parameters to set the minimum and
2402 maximum port values.
2406 Control how the NFS server code allocates CPUs to
2407 service thread pools. Depending on how many NICs
2408 you have and where their interrupts are bound, this
2409 option will affect which CPUs will do NFS serving.
2410 Note: this parameter cannot be changed while the
2411 NFS server is running.
2413 auto the server chooses an appropriate mode
2414 automatically using heuristics
2415 global a single global pool contains all CPUs
2416 percpu one pool for each CPU
2417 pernode one pool for each NUMA node (equivalent
2418 to global on non-NUMA machines)
2420 sunrpc.tcp_slot_table_entries=
2421 sunrpc.udp_slot_table_entries=
2423 Sets the upper limit on the number of simultaneous
2424 RPC calls that can be sent from the client to a
2425 server. Increasing these values may allow you to
2426 improve throughput, but will also increase the
2427 amount of memory reserved for use by the client.
2430 [KNL] Enable accounting of swap in memory resource
2431 controller if no parameter or 1 is given or disable
2432 it if 0 is given (See Documentation/cgroups/memory.txt)
2434 swiotlb= [IA-64] Number of I/O TLB slabs
2438 sysfs.deprecated=0|1 [KNL]
2439 Enable/disable old style sysfs layout for old udev
2440 on older distributions. When this option is enabled
2441 very new udev will not work anymore. When this option
2442 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2443 in older udev will not work anymore.
2444 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2445 the kernel configuration.
2447 sysrq_always_enabled
2449 Ignore sysrq setting - this boot parameter will
2450 neutralize any effect of /proc/sys/kernel/sysrq.
2451 Useful for debugging.
2455 test_suspend= [SUSPEND]
2456 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2457 standby suspend) as the system sleep state to briefly
2458 enter during system startup. The system is woken from
2459 this state using a wakeup-capable RTC alarm.
2461 thash_entries= [KNL,NET]
2462 Set number of hash buckets for TCP connection
2464 thermal.act= [HW,ACPI]
2465 -1: disable all active trip points in all thermal zones
2466 <degrees C>: override all lowest active trip points
2468 thermal.crt= [HW,ACPI]
2469 -1: disable all critical trip points in all thermal zones
2470 <degrees C>: override all critical trip points
2472 thermal.nocrt= [HW,ACPI]
2473 Set to disable actions on ACPI thermal zone
2474 critical and hot trip points.
2476 thermal.off= [HW,ACPI]
2477 1: disable ACPI thermal control
2479 thermal.psv= [HW,ACPI]
2480 -1: disable all passive trip points
2481 <degrees C>: override all passive trip points to this
2484 thermal.tzp= [HW,ACPI]
2485 Specify global default ACPI thermal zone polling rate
2486 <deci-seconds>: poll all this frequency
2487 0: no polling (default)
2490 Force threading of all interrupt handlers except those
2491 marked explicitely IRQF_NO_THREAD.
2495 Specify if the kernel should make use of the cpu
2496 topology information if the hardware supports this.
2497 The scheduler will make use of this information and
2498 e.g. base its process migration decisions on it.
2503 tpm_suspend_pcr=[HW,TPM]
2504 Format: integer pcr id
2505 Specify that at suspend time, the tpm driver
2506 should extend the specified pcr with zeros,
2507 as a workaround for some chips which fail to
2508 flush the last written pcr on TPM_SaveState.
2509 This will guarantee that all the other pcrs
2512 trace_buf_size=nn[KMG]
2513 [FTRACE] will set tracing buffer size.
2515 trace_event=[event-list]
2516 [FTRACE] Set and start specified trace events in order
2517 to facilitate early boot debugging.
2518 See also Documentation/trace/events.txt
2520 tsc= Disable clocksource stability checks for TSC.
2522 [x86] reliable: mark tsc clocksource as reliable, this
2523 disables clocksource verification at runtime, as well
2524 as the stability checks done at bootup. Used to enable
2525 high-resolution timer mode on older hardware, and in
2526 virtualized environment.
2527 [x86] noirqtime: Do not use TSC to do irq accounting.
2528 Used to run time disable IRQ_TIME_ACCOUNTING on any
2529 platforms where RDTSC is slow and this accounting
2532 turbografx.map[2|3]= [HW,JOY]
2533 TurboGraFX parallel port interface
2535 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2536 See also Documentation/input/joystick-parport.txt
2538 udbg-immortal [PPC] When debugging early kernel crashes that
2539 happen after console_init() and before a proper
2540 console driver takes over, this boot options might
2541 help "seeing" what's going on.
2543 uhash_entries= [KNL,NET]
2544 Set number of hash buckets for UDP/UDP-Lite connections
2547 [USB] Ignore overcurrent events (default N).
2548 Some badly-designed motherboards generate lots of
2549 bogus events, for ports that aren't wired to
2550 anything. Set this parameter to avoid log spamming.
2551 Note that genuine overcurrent events won't be
2555 [X86] Cause panic on unknown NMI.
2557 usbcore.authorized_default=
2558 [USB] Default USB device authorization:
2559 (default -1 = authorized except for wireless USB,
2560 0 = not authorized, 1 = authorized)
2562 usbcore.autosuspend=
2563 [USB] The autosuspend time delay (in seconds) used
2564 for newly-detected USB devices (default 2). This
2565 is the time required before an idle device will be
2566 autosuspended. Devices for which the delay is set
2567 to a negative value won't be autosuspended at all.
2569 usbcore.usbfs_snoop=
2570 [USB] Set to log all usbfs traffic (default 0 = off).
2572 usbcore.blinkenlights=
2573 [USB] Set to cycle leds on hubs (default 0 = off).
2575 usbcore.old_scheme_first=
2576 [USB] Start with the old device initialization
2577 scheme (default 0 = off).
2579 usbcore.use_both_schemes=
2580 [USB] Try the other device initialization scheme
2581 if the first one fails (default 1 = enabled).
2583 usbcore.initial_descriptor_timeout=
2584 [USB] Specifies timeout for the initial 64-byte
2585 USB_REQ_GET_DESCRIPTOR request in milliseconds
2586 (default 5000 = 5.0 seconds).
2589 [USBHID] The interval which mice are to be polled at.
2591 usb-storage.delay_use=
2592 [UMS] The delay in seconds before a new device is
2593 scanned for Logical Units (default 5).
2596 [UMS] A list of quirks entries to supplement or
2597 override the built-in unusual_devs list. List
2598 entries are separated by commas. Each entry has
2599 the form VID:PID:Flags where VID and PID are Vendor
2600 and Product ID values (4-digit hex numbers) and
2601 Flags is a set of characters, each corresponding
2602 to a common usb-storage quirk flag as follows:
2603 a = SANE_SENSE (collect more than 18 bytes
2605 b = BAD_SENSE (don't collect more than 18
2606 bytes of sense data);
2607 c = FIX_CAPACITY (decrease the reported
2608 device capacity by one sector);
2609 d = NO_READ_DISC_INFO (don't use
2610 READ_DISC_INFO command);
2611 e = NO_READ_CAPACITY_16 (don't use
2612 READ_CAPACITY_16 command);
2613 h = CAPACITY_HEURISTICS (decrease the
2614 reported device capacity by one
2615 sector if the number is odd);
2616 i = IGNORE_DEVICE (don't bind to this
2618 l = NOT_LOCKABLE (don't try to lock and
2619 unlock ejectable media);
2620 m = MAX_SECTORS_64 (don't transfer more
2621 than 64 sectors = 32 KB at a time);
2622 n = INITIAL_READ10 (force a retry of the
2623 initial READ(10) command);
2624 o = CAPACITY_OK (accept the capacity
2625 reported by the device);
2626 r = IGNORE_RESIDUE (the device reports
2627 bogus residue values);
2628 s = SINGLE_LUN (the device has only one
2630 w = NO_WP_DETECT (don't test whether the
2631 medium is write-protected).
2632 Example: quirks=0419:aaf5:rl,0421:0433:rc
2635 [X86] Flags controlling user PTE allocations.
2637 nohigh = do not allocate PTE pages in
2638 HIGHMEM regardless of setting
2642 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2643 vdso=1: enable VDSO (default)
2644 vdso=0: disable VDSO mapping
2647 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2648 vdso32=1: enable 32-bit VDSO (default)
2649 vdso32=0: disable 32-bit VDSO mapping
2652 vector=percpu: enable percpu vector domain
2654 video= [FB] Frame buffer configuration
2655 See Documentation/fb/modedb.txt.
2657 vga= [BOOT,X86-32] Select a particular video mode
2658 See Documentation/x86/boot.txt and
2659 Documentation/svga.txt.
2660 Use vga=ask for menu.
2661 This is actually a boot loader parameter; the value is
2662 passed to the kernel using a special protocol.
2664 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2665 size of <nn>. This can be used to increase the
2666 minimum size (128MB on x86). It can also be used to
2667 decrease the size and leave more room for directly
2670 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2673 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2676 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2679 vt.cur_default= [VT] Default cursor shape.
2680 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2681 the parameters of the <Esc>[?A;B;Cc escape sequence;
2682 see VGA-softcursor.txt. Default: 2 = underline.
2684 vt.default_blu= [VT]
2685 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2686 Change the default blue palette of the console.
2687 This is a 16-member array composed of values
2690 vt.default_grn= [VT]
2691 Format: <green0>,<green1>,<green2>,...,<green15>
2692 Change the default green palette of the console.
2693 This is a 16-member array composed of values
2696 vt.default_red= [VT]
2697 Format: <red0>,<red1>,<red2>,...,<red15>
2698 Change the default red palette of the console.
2699 This is a 16-member array composed of values
2705 Set system-wide default UTF-8 mode for all tty's.
2706 Default is 1, i.e. UTF-8 mode is enabled for all
2707 newly opened terminals.
2709 vt.global_cursor_default=
2712 Set system-wide default for whether a cursor
2713 is shown on new VTs. Default is -1,
2714 i.e. cursors will be created by default unless
2715 overridden by individual drivers. 0 will hide
2716 cursors, 1 will display them.
2718 watchdog timers [HW,WDT] For information on watchdog timers,
2719 see Documentation/watchdog/watchdog-parameters.txt
2720 or other driver-specific files in the
2721 Documentation/watchdog/ directory.
2723 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2724 default x2apic cluster mode on platforms
2727 x86_mrst_timer= [X86-32,APBT]
2728 Choose timer option for x86 Moorestown MID platform.
2729 Two valid options are apbt timer only and lapic timer
2730 plus one apbt timer for broadcast timer.
2731 x86_mrst_timer=apbt_only | lapic_and_apbt
2733 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2734 xd_geo= See header of drivers/block/xd.c.
2736 xen_emul_unplug= [HW,X86,XEN]
2737 Unplug Xen emulated devices
2738 Format: [unplug0,][unplug1]
2739 ide-disks -- unplug primary master IDE devices
2740 aux-ide-disks -- unplug non-primary-master IDE devices
2741 nics -- unplug network devices
2742 all -- unplug all emulated devices (NICs and IDE disks)
2743 unnecessary -- unplugging emulated devices is
2744 unnecessary even if the host did not respond to
2746 never -- do not unplug even if version check succeeds
2748 xirc2ps_cs= [NET,PCMCIA]
2750 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2752 ______________________________________________________________________
2756 Add more DRM drivers.
projects / mirror_ubuntu-artful-kernel.git / blob