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_irq_balance [HW,ACPI]
203 ACPI will balance active IRQs
206 acpi_irq_nobalance [HW,ACPI]
207 ACPI will not move active IRQs (default)
210 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
211 Format: <irq>,<irq>...
213 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
215 Format: <irq>,<irq>...
217 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
219 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
220 Format: To spoof as Windows 98: ="Microsoft Windows"
222 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
223 acpi_osi="string1" # add string1 -- only one string
224 acpi_osi="!string2" # remove built-in string2
225 acpi_osi= # disable all strings
228 Override the pmtimer bug detection: force the kernel
229 to assume that this machine's pmtimer latches its value
230 and always returns good values.
232 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
233 Format: { level | edge | high | low }
235 acpi_serialize [HW,ACPI] force serialization of AML methods
237 acpi_skip_timer_override [HW,ACPI]
238 Recognize and ignore IRQ0/pin2 Interrupt Override.
239 For broken nForce2 BIOS resulting in XT-PIC timer.
241 acpi_sleep= [HW,ACPI] Sleep options
242 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
243 old_ordering, s4_nonvs, sci_force_enable }
244 See Documentation/power/video.txt for information on
246 s3_beep is for debugging; it makes the PC's speaker beep
247 as soon as the kernel's real-mode entry point is called.
248 s4_nohwsig prevents ACPI hardware signature from being
249 used during resume from hibernation.
250 old_ordering causes the ACPI 1.0 ordering of the _PTS
251 control method, with respect to putting devices into
252 low power states, to be enforced (the ACPI 2.0 ordering
253 of _PTS is used by default).
254 nonvs prevents the kernel from saving/restoring the
255 ACPI NVS memory during suspend/hibernation and resume.
256 sci_force_enable causes the kernel to set SCI_EN directly
257 on resume from S1/S3 (which is against the ACPI spec,
258 but some broken systems don't work without it).
260 acpi_use_timer_override [HW,ACPI]
261 Use timer override. For some broken Nvidia NF5 boards
262 that require a timer override, but don't have HPET
264 acpi_enforce_resources= [ACPI]
265 { strict | lax | no }
266 Check for resource conflicts between native drivers
267 and ACPI OperationRegions (SystemIO and SystemMemory
268 only). IO ports and memory declared in ACPI might be
269 used by the ACPI subsystem in arbitrary AML code and
270 can interfere with legacy drivers.
271 strict (default): access to resources claimed by ACPI
272 is denied; legacy drivers trying to access reserved
273 resources will fail to bind to device using them.
274 lax: access to resources claimed by ACPI is allowed;
275 legacy drivers trying to access reserved resources
276 will bind successfully but a warning message is logged.
277 no: ACPI OperationRegions are not marked as reserved,
278 no further checks are performed.
280 add_efi_memmap [EFI; X86] Include EFI memory map in
281 kernel's map of available physical RAM.
284 { off | try_unsupported }
285 off: disable AGP support
286 try_unsupported: try to drive unsupported chipsets
287 (may crash computer or cause data corruption)
290 See Documentation/sound/alsa/alsa-parameters.txt
293 Allow the default userspace alignment fault handler
294 behaviour to be specified. Bit 0 enables warnings,
295 bit 1 enables fixups, and bit 2 sends a segfault.
297 amd_iommu= [HW,X86-84]
298 Pass parameters to the AMD IOMMU driver in the system.
300 fullflush - enable flushing of IO/TLB entries when
301 they are unmapped. Otherwise they are
302 flushed before they will be reused, which
304 off - do not initialize any AMD IOMMU found in
307 amijoy.map= [HW,JOY] Amiga joystick support
308 Map of devices attached to JOY0DAT and JOY1DAT
310 See also Documentation/kernel/input/joystick.txt
312 analog.map= [HW,JOY] Analog joystick and gamepad support
313 Specifies type or capabilities of an analog joystick
314 connected to one of 16 gameports
315 Format: <type1>,<type2>,..<type16>
318 Power management functions (SPARCstation-4/5 + deriv.)
320 Disable APC CPU standby support. SPARCstation-Fox does
321 not play well with APC CPU idle - disable it if you have
322 APC and your system crashes randomly.
324 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
325 Change the output verbosity whilst booting
326 Format: { quiet (default) | verbose | debug }
327 Change the amount of debugging information output
328 when initialising the APIC and IO-APIC components.
331 See Documentation/networking/ipv6.txt.
333 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
334 Limit apic dumping. The parameter defines the maximal
335 number of local apics being dumped. Also it is possible
336 to set it to "all" by meaning -- no limit here.
337 Format: { 1 (default) | 2 | ... | all }.
338 The parameter valid if only apic=debug or
339 apic=verbose is specified.
340 Example: apic=debug show_lapic=all
342 apm= [APM] Advanced Power Management
343 See header of arch/x86/kernel/apm_32.c.
345 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
346 Format: <io>,<irq>,<nodeID>
350 atarimouse= [HW,MOUSE] Atari Mouse
352 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
353 EzKey and similar keyboards
355 atkbd.reset= [HW] Reset keyboard during initialization
357 atkbd.set= [HW] Select keyboard code set
358 Format: <int> (2 = AT (default), 3 = PS/2)
360 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
363 atkbd.softraw= [HW] Choose between synthetic and real raw mode
364 Format: <bool> (0 = real, 1 = synthetic (default))
366 atkbd.softrepeat= [HW]
367 Use software keyboard repeat
371 baycom_epp= [HW,AX25]
374 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
376 See header of drivers/net/hamradio/baycom_par.c.
378 baycom_ser_fdx= [HW,AX25]
379 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
380 Format: <io>,<irq>,<mode>[,<baud>]
381 See header of drivers/net/hamradio/baycom_ser_fdx.c.
383 baycom_ser_hdx= [HW,AX25]
384 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
385 Format: <io>,<irq>,<mode>
386 See header of drivers/net/hamradio/baycom_ser_hdx.c.
388 boot_delay= Milliseconds to delay each printk during boot.
389 Values larger than 10 seconds (10000) are changed to
393 bootmem_debug [KNL] Enable bootmem allocator debug messages.
395 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
396 bttv.radio= Most important insmod options are available as
398 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
399 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
401 c101= [NET] Moxa C101 synchronous serial card
403 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
404 Sometimes CPU hardware bugs make them report the cache
405 size incorrectly. The kernel will attempt work arounds
406 to fix known problems, but for some CPUs it is not
407 possible to determine what the correct size should be.
408 This option provides an override for these situations.
411 [SECURITY] Disable capabilities. This would normally
412 be used only if an alternative security model is to be
413 configured. Potentially dangerous and should only be
414 used if you are entirely sure of the consequences.
416 ccw_timeout_log [S390]
417 See Documentation/s390/CommonIO for details.
419 cgroup_disable= [KNL] Disable a particular controller
420 Format: {name of the controller(s) to disable}
421 {Currently supported controllers - "memory"}
423 checkreqprot [SELINUX] Set initial checkreqprot flag value.
424 Format: { "0" | "1" }
425 See security/selinux/Kconfig help text.
426 0 -- check protection applied by kernel (includes
427 any implied execute protection).
428 1 -- check protection requested by application.
429 Default value is set via a kernel config option.
430 Value can be changed at runtime via
431 /selinux/checkreqprot.
434 See Documentation/s390/CommonIO for details.
436 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
438 Forces specified clocksource (if available) to be used
439 when calculating gettimeofday(). If specified
440 clocksource is not available, it defaults to PIT.
441 Format: { pit | tsc | cyclone | pmtmr }
443 clocksource= Override the default clocksource
445 Override the default clocksource and use the clocksource
446 with the name specified.
447 Some clocksource names to choose from, depending on
449 [all] jiffies (this is the base, fallback clocksource)
451 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
452 pxa_timer,timer3,32k_counter,timer0_1
454 [X86-32] pit,hpet,tsc;
455 scx200_hrt on Geode; cyclone on IBM x440
463 clearcpuid=BITNUM [X86]
464 Disable CPUID feature X for the kernel. See
465 arch/x86/include/asm/cpufeature.h for the valid bit
466 numbers. Note the Linux specific bits are not necessarily
467 stable over kernel options, but the vendor specific
469 Also note that user programs calling CPUID directly
470 or using the feature without checking anything
471 will still see it. This just prevents it from
472 being used by the kernel or shown in /proc/cpuinfo.
473 Also note the kernel might malfunction if you disable
476 cmo_free_hint= [PPC] Format: { yes | no }
477 Specify whether pages are marked as being inactive
478 when they are freed. This is used in CMO environments
479 to determine OS memory pressure for page stealing by
483 code_bytes [X86] How many bytes of object code to print
488 com20020= [HW,NET] ARCnet - COM20020 chipset
490 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
492 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
496 ARCnet - COM90xx chipset (memory-mapped buffers)
497 Format: <io>[,<irq>[,<memstart>]]
499 condev= [HW,S390] console device
502 console= [KNL] Output console device and options.
504 tty<n> Use the virtual console device <n>.
508 Use the specified serial port. The options are of
509 the form "bbbbpnf", where "bbbb" is the baud rate,
510 "p" is parity ("n", "o", or "e"), "n" is number of
511 bits, and "f" is flow control ("r" for RTS or
512 omit it). Default is "9600n8".
514 See Documentation/serial-console.txt for more
516 Documentation/networking/netconsole.txt for an
519 uart[8250],io,<addr>[,options]
520 uart[8250],mmio,<addr>[,options]
521 Start an early, polled-mode console on the 8250/16550
522 UART at the specified I/O port or MMIO address,
523 switching to the matching ttyS device later. The
524 options are the same as for ttyS, above.
526 If the device connected to the port is not a TTY but a braille
527 device, prepend "brl," before the device type, for instance
529 For now, only VisioBraille is supported.
531 consoleblank= [KNL] The console blank (screen saver) timeout in
532 seconds. Defaults to 10*60 = 10mins. A value of 0
533 disables the blank timer.
536 [KNL] Change the default value for
537 /proc/<pid>/coredump_filter.
538 See also Documentation/filesystems/proc.txt.
540 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
542 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
544 crashkernel=nn[KMG]@ss[KMG]
545 [KNL] Reserve a chunk of physical memory to
546 hold a kernel to switch to with kexec on panic.
548 crashkernel=range1:size1[,range2:size2,...][@offset]
549 [KNL] Same as above, but depends on the memory
550 in the running system. The syntax of range is
551 start-[end] where start and end are both
552 a memory unit (amount[KMG]). See also
553 Documentation/kdump/kdump.txt for a example.
558 cs89x0_media= [HW,NET]
559 Format: { rj45 | aui | bnc }
562 See header of drivers/s390/block/dasd_devmap.c.
564 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
565 (one device per port)
566 Format: <port#>,<type>
567 See also Documentation/input/joystick-parport.txt
569 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
570 time. See Documentation/dynamic-debug-howto.txt for
573 debug [KNL] Enable kernel debugging (events log level).
576 [KNL] verbose self-tests
578 Print debugging info while doing the locking API
580 We default to 0 (no extra messages), setting it to
581 1 will print _a lot_ more information - normally
582 only useful to kernel developers.
584 debug_objects [KNL] Enable object debugging
587 [KNL] Disable object debugging
589 debugpat [X86] Enable PAT debugging
591 decnet.addr= [HW,NET]
592 Format: <area>[,<node>]
593 See also Documentation/networking/decnet.txt.
596 [same as hugepagesz=] The size of the default
597 HugeTLB page size. This is the size represented by
598 the legacy /proc/ hugepages APIs, used for SHM, and
599 default size when mounting hugetlbfs filesystems.
600 Defaults to the default architecture's huge page size
604 Set number of hash buckets for dentry cache.
607 IO parameters + enable/disable command.
609 digiepca= [HW,SERIAL]
610 See drivers/char/README.epca and
611 Documentation/serial/digiepca.txt.
614 See Documentation/networking/ipv6.txt.
617 See Documentation/networking/ipv6.txt.
619 disable_mtrr_cleanup [X86]
620 The kernel tries to adjust MTRR layout from continuous
621 to discrete, to make X server driver able to add WB
622 entry later. This parameter disables that.
624 disable_mtrr_trim [X86, Intel and AMD only]
625 By default the kernel will trim any uncacheable
626 memory out of your available memory pool based on
627 MTRR settings. This parameter disables that behavior,
628 possibly causing your machine to run very slowly.
630 disable_timer_pin_1 [X86]
631 Disable PIN 1 of APIC timer
632 Can be useful to work around chipset bugs.
634 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
635 this option disables the debugging code at boot.
637 dma_debug_entries=<number>
638 This option allows to tune the number of preallocated
639 entries for DMA-API debugging code. One entry is
640 required per DMA-API allocation. Use this if the
641 DMA-API debugging code disables itself because the
642 architectural default is too low.
644 dma_debug_driver=<driver_name>
645 With this option the DMA-API debugging driver
646 filter feature can be enabled at boot time. Just
647 pass the driver to filter for as the parameter.
648 The filter can be disabled or changed to another
649 driver later using sysfs.
653 dynamic_printk Enables pr_debug()/dev_dbg() calls if
654 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
655 These can also be switched on/off via
656 <debugfs>/dynamic_printk/modules
658 earlycon= [KNL] Output early console device and options.
659 uart[8250],io,<addr>[,options]
660 uart[8250],mmio,<addr>[,options]
661 uart[8250],mmio32,<addr>[,options]
662 Start an early, polled-mode console on the 8250/16550
663 UART at the specified I/O port or MMIO address.
664 MMIO inter-register address stride is either 8bit (mmio)
666 The options are the same as for ttyS, above.
668 earlyprintk= [X86,SH,BLACKFIN]
670 earlyprintk=serial[,ttySn[,baudrate]]
671 earlyprintk=ttySn[,baudrate]
672 earlyprintk=dbgp[debugController#]
674 Append ",keep" to not disable it when the real console
677 Only vga or serial or usb debug port at a time.
679 Currently only ttyS0 and ttyS1 are supported.
681 Interaction with the standard serial driver is not
684 The VGA output is eventually overwritten by the real
687 ekgdboc= [X86,KGDB] Allow early kernel console debugging
690 This is desgined to be used in conjunction with
691 the boot argument: earlyprintk=vga
694 Format: {"off" | "on" | "skip[mbr]"}
696 eisa_irq_edge= [PARISC,HW]
697 See header of drivers/parisc/eisa.c.
700 See comment before function elanfreq_setup() in
701 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
704 Format: {"cfq" | "deadline" | "noop"}
705 See Documentation/block/as-iosched.txt and
706 Documentation/block/deadline-iosched.txt for details.
708 elfcorehdr= [IA64,PPC,SH,X86]
709 Specifies physical address of start of kernel core
710 image elf header. Generally kexec loader will
711 pass this option to capture kernel.
712 See Documentation/kdump/kdump.txt for details.
714 enable_mtrr_cleanup [X86]
715 The kernel tries to adjust MTRR layout from continuous
716 to discrete, to make X server driver able to add WB
717 entry later. This parameter enables that.
719 enable_timer_pin_1 [X86]
720 Enable PIN 1 of APIC timer
721 Can be useful to work around chipset bugs
722 (in particular on some ATI chipsets).
723 The kernel tries to set a reasonable default.
725 enforcing [SELINUX] Set initial enforcing status.
727 See security/selinux/Kconfig help text.
728 0 -- permissive (log only, no denials).
729 1 -- enforcing (deny and log).
731 Value can be changed at runtime via /selinux/enforce.
734 Disable Error Record Serialization Table (ERST)
737 ether= [HW,NET] Ethernet cards parameters
738 This option is obsoleted by the "netdev=" option, which
739 has equivalent usage. See its documentation for details.
743 fail_make_request=[KNL]
744 General fault injection mechanism.
745 Format: <interval>,<probability>,<space>,<times>
746 See also /Documentation/fault-injection/.
749 See Documentation/blockdev/floppy.txt.
751 force_pal_cache_flush
752 [IA-64] Avoid check_sal_cache_flush which may hang on
753 buggy SAL_CACHE_FLUSH implementations. Using this
754 parameter will force ia64_sal_cache_flush to call
755 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
758 [FTRACE] will set and start the specified tracer
759 as early as possible in order to facilitate early
762 ftrace_dump_on_oops[=orig_cpu]
763 [FTRACE] will dump the trace buffers on oops.
764 If no parameter is passed, ftrace will dump
765 buffers of all CPUs, but if you pass orig_cpu, it will
766 dump only the buffer of the CPU that triggered the
769 ftrace_filter=[function-list]
770 [FTRACE] Limit the functions traced by the function
771 tracer at boot up. function-list is a comma separated
772 list of functions. This list can be changed at run
773 time by the set_ftrace_filter file in the debugfs
776 ftrace_notrace=[function-list]
777 [FTRACE] Do not trace the functions specified in
778 function-list. This list can be changed at run time
779 by the set_ftrace_notrace file in the debugfs
782 ftrace_graph_filter=[function-list]
783 [FTRACE] Limit the top level callers functions traced
784 by the function graph tracer at boot up.
785 function-list is a comma separated list of functions
786 that can be changed at run time by the
787 set_graph_function file in the debugfs tracing directory.
790 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
791 support via parallel port (up to 5 devices per port)
792 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
793 See also Documentation/input/joystick-parport.txt
797 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
801 gcov_persist= [GCOV] When non-zero (default), profiling data for
802 kernel modules is saved and remains accessible via
803 debugfs, even when the module is unloaded/reloaded.
804 When zero, profiling data is discarded and associated
805 debugfs files are removed at module unload time.
807 gpt [EFI] Forces disk with valid GPT signature but
808 invalid Protective MBR to be treated as GPT.
810 hashdist= [KNL,NUMA] Large hashes allocated during boot
811 are distributed across NUMA nodes. Defaults on
812 for 64bit NUMA, off otherwise.
813 Format: 0 | 1 (for off | on)
815 hcl= [IA-64] SGI's Hardware Graph compatibility layer
817 hd= [EIDE] (E)IDE hard drive subsystem geometry
818 Format: <cyl>,<head>,<sect>
821 Disable Hardware Error Source Table (HEST) support;
822 corresponding firmware-first mode error processing
823 logic will be disabled.
825 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
826 size of <nn>. This works even on boxes that have no
827 highmem otherwise. This also works to reduce highmem
828 size on bigger boxes.
830 highres= [KNL] Enable/disable high resolution timer mode.
831 Valid parameters: "on", "off"
835 See Documentation/isdn/README.HiSax.
839 hpet= [X86-32,HPET] option to control HPET usage
840 Format: { enable (default) | disable | force |
842 disable: disable HPET and use PIT instead
843 force: allow force enabled of undocumented chips (ICH4,
845 verbose: show contents of HPET registers during setup
847 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
848 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
849 On x86-64 and powerpc, this option can be specified
850 multiple times interleaved with hugepages= to reserve
851 huge pages of different sizes. Valid pages sizes on
852 x86-64 are 2M (when the CPU supports "pse") and 1G
853 (when the CPU supports the "pdpe1gb" cpuinfo flag)
854 Note that 1GB pages can only be allocated at boot time
855 using hugepages= and not freed afterwards.
857 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
858 terminal devices. Valid values: 0..8
859 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
860 If specified, z/VM IUCV HVC accepts connections
861 from listed z/VM user IDs only.
863 i2c_bus= [HW] Override the default board specific I2C bus speed
864 or register an additional I2C bus that is not
865 registered from board initialization code.
869 i8042.debug [HW] Toggle i8042 debug mode
870 i8042.direct [HW] Put keyboard port into non-translated mode
871 i8042.dumbkbd [HW] Pretend that controller can only read data from
872 keyboard and cannot control its state
873 (Don't attempt to blink the leds)
874 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
875 i8042.nokbd [HW] Don't check/create keyboard port
876 i8042.noloop [HW] Disable the AUX Loopback command while probing
878 i8042.nomux [HW] Don't check presence of an active multiplexing
880 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
882 i8042.reset [HW] Reset the controller during init and cleanup
883 i8042.unlock [HW] Unlock (ignore) the keylock
887 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
888 indicates that the driver is running on unsupported
890 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
891 does not match list of supported models.
893 [HW] Report power status in /proc/i8k
894 (disabled by default)
895 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
899 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
901 ide-core.nodma= [HW] (E)IDE subsystem
902 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
903 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
904 .cdrom .chs .ignore_cable are additional options
905 See Documentation/ide/ide.txt.
907 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
908 Claim all unknown PCI IDE storage controllers.
911 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
912 Poll forces a polling idle loop that can slightly
913 improve the performance of waking up a idle CPU, but
914 will use a lot of power and make the system run hot.
916 idle=mwait: On systems which support MONITOR/MWAIT but
917 the kernel chose to not use it because it doesn't save
918 as much power as a normal idle loop, use the
919 MONITOR/MWAIT idle loop anyways. Performance should be
920 the same as idle=poll.
921 idle=halt: Halt is forced to be used for CPU idle.
922 In such case C2/C3 won't be used again.
923 idle=nomwait: Disable mwait for CPU C-states
925 ignore_loglevel [KNL]
926 Ignore loglevel setting - this will print /all/
927 kernel messages to the console. Useful for debugging.
930 Set number of hash buckets for inode cache.
933 Format: { "0" | "1" }
934 0 -- integrity auditing messages. (Default)
935 1 -- enable informational integrity auditing messages.
938 Format: { "sha1" | "md5" }
942 Load a policy which meets the needs of the Trusted
943 Computing Base. This means IMA will measure all
944 programs exec'd, files mmap'd for exec, and all files
945 opened for read by uid=0.
949 Run specified binary instead of /sbin/init as init
952 initcall_debug [KNL] Trace initcalls as they are executed. Useful
953 for working out where the kernel is dying during
956 initrd= [BOOT] Specify the location of the initial ramdisk
958 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
961 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
963 Enable intel iommu driver.
965 Disable intel iommu driver.
966 igfx_off [Default Off]
967 By default, gfx is mapped as normal device. If a gfx
968 device has a dedicated DMAR unit, the DMAR unit is
969 bypassed by not enabling DMAR with this option. In
970 this case, gfx device will use physical address for
973 With this option iommu will not optimize to look
974 for io virtual address below 32 bit forcing dual
975 address cycle on pci bus for cards supporting greater
976 than 32 bit addressing. The default is to look
977 for translation below 32 bit and if not available
978 then look in the higher range.
980 With this option on every unmap_single operation will
981 result in a hardware IOTLB flush operation as opposed
982 to batching them for performance.
984 intremap= [X86-64, Intel-IOMMU]
985 Format: { on (default) | off | nosid }
986 on enable Interrupt Remapping (default)
987 off disable Interrupt Remapping
988 nosid disable Source ID checking
992 iomem= Disable strict checking of access to MMIO memory
993 strict regions from userspace.
1009 io7= [HW] IO7 for Marvel based alpha systems
1010 See comment before marvel_specify_io7 in
1011 arch/alpha/kernel/core_marvel.c.
1013 io_delay= [X86] I/O delay method
1015 Standard port 0x80 based delay
1017 Alternate port 0xed based delay (needed on some systems)
1019 Simple two microseconds delay
1024 See Documentation/filesystems/nfs/nfsroot.txt.
1026 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1027 See comment before ip2_setup() in
1028 drivers/char/ip2/ip2base.c.
1031 When an interrupt is not handled search all handlers
1032 for it. Intended to get systems with badly broken
1036 When an interrupt is not handled search all handlers
1037 for it. Also check all handlers each timer
1038 interrupt. Intended to get systems with badly broken
1042 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1044 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1046 <cpu number>,...,<cpu number>
1048 <cpu number>-<cpu number>
1049 (must be a positive range in ascending order)
1051 <cpu number>,...,<cpu number>-<cpu number>
1053 This option can be used to specify one or more CPUs
1054 to isolate from the general SMP balancing and scheduling
1055 algorithms. You can move a process onto or off an
1056 "isolated" CPU via the CPU affinity syscalls or cpuset.
1057 <cpu number> begins at 0 and the maximum value is
1058 "number of CPUs in system - 1".
1060 This option is the preferred way to isolate CPUs. The
1061 alternative -- manually setting the CPU mask of all
1062 tasks in the system -- can cause problems and
1063 suboptimal load balancer performance.
1067 js= [HW,JOY] Analog joystick
1068 See Documentation/input/joystick.txt.
1072 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1073 specifies the amount of memory usable by the kernel
1074 for non-movable allocations. The requested amount is
1075 spread evenly throughout all nodes in the system. The
1076 remaining memory in each node is used for Movable
1077 pages. In the event, a node is too small to have both
1078 kernelcore and Movable pages, kernelcore pages will
1079 take priority and other nodes will have a larger number
1080 of kernelcore pages. The Movable zone is used for the
1081 allocation of pages that may be reclaimed or moved
1082 by the page migration subsystem. This means that
1083 HugeTLB pages may not be allocated from this zone.
1084 Note that allocations like PTEs-from-HighMem still
1085 use the HighMem zone if it exists, and the Normal
1086 zone if it does not.
1088 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1089 Format: <Controller#>[,poll interval]
1090 The controller # is the number of the ehci usb debug
1091 port as it is probed via PCI. The poll interval is
1092 optional and is the number seconds in between
1093 each poll cycle to the debug port in case you need
1094 the functionality for interrupting the kernel with
1095 gdb or control-c on the dbgp connection. When
1096 not using this parameter you use sysrq-g to break into
1097 the kernel debugger.
1099 kgdboc= [KGDB,HW] kgdb over consoles.
1100 Requires a tty driver that supports console polling,
1101 or a supported polling keyboard driver (non-usb).
1102 Serial only format: <serial_device>[,baud]
1103 keyboard only format: kbd
1104 keyboard and serial format: kbd,<serial_device>[,baud]
1105 Optional Kernel mode setting:
1106 kms, kbd format: kms,kbd
1107 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1109 kgdbwait [KGDB] Stop kernel execution and enter the
1110 kernel debugger at the earliest opportunity.
1112 kmac= [MIPS] korina ethernet MAC address.
1113 Configure the RouterBoard 532 series on-chip
1114 Ethernet adapter MAC address.
1116 kmemleak= [KNL] Boot-time kmemleak enable/disable
1117 Valid arguments: on, off
1120 kstack=N [X86] Print N words from the kernel stack
1123 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1124 Default is 0 (don't ignore, but inject #GP)
1126 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1127 Default is 1 (enabled)
1129 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1133 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1134 Default is 1 (enabled)
1136 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1138 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1140 kvm-intel.bypass_guest_pf=
1141 [KVM,Intel] Disables bypassing of guest page faults
1142 on Intel chips. Default is 1 (enabled)
1144 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1145 (virtualized MMU) support on capable Intel chips.
1146 Default is 1 (enabled)
1148 kvm-intel.emulate_invalid_guest_state=
1149 [KVM,Intel] Enable emulation of invalid guest states
1150 Default is 0 (disabled)
1152 kvm-intel.flexpriority=
1153 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1154 Default is 1 (enabled)
1156 kvm-intel.unrestricted_guest=
1157 [KVM,Intel] Disable unrestricted guest feature
1158 (virtualized real and unpaged mode) on capable
1159 Intel chips. Default is 1 (enabled)
1161 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1162 feature (tagged TLBs) on capable Intel chips.
1163 Default is 1 (enabled)
1169 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1172 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1175 libata.dma= [LIBATA] DMA control
1176 libata.dma=0 Disable all PATA and SATA DMA
1177 libata.dma=1 PATA and SATA Disk DMA only
1178 libata.dma=2 ATAPI (CDROM) DMA only
1179 libata.dma=4 Compact Flash DMA only
1180 Combinations also work, so libata.dma=3 enables DMA
1181 for disks and CDROMs, but not CFs.
1183 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1184 libata.ignore_hpa=0 keep BIOS limits (default)
1185 libata.ignore_hpa=1 ignore limits, using full disk
1187 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1191 libata.force= [LIBATA] Force configurations. The format is comma
1192 separated list of "[ID:]VAL" where ID is
1193 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1194 matching port, link or device. Basically, it matches
1195 the ATA ID string printed on console by libata. If
1196 the whole ID part is omitted, the last PORT and DEVICE
1197 values are used. If ID hasn't been specified yet, the
1198 configuration applies to all ports, links and devices.
1200 If only DEVICE is omitted, the parameter applies to
1201 the port and all links and devices behind it. DEVICE
1202 number of 0 either selects the first device or the
1203 first fan-out link behind PMP device. It does not
1204 select the host link. DEVICE number of 15 selects the
1205 host link and device attached to it.
1207 The VAL specifies the configuration to force. As long
1208 as there's no ambiguity shortcut notation is allowed.
1209 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1210 The following configurations can be forced.
1212 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1213 Any ID with matching PORT is used.
1215 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1217 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1218 udma[/][16,25,33,44,66,100,133] notation is also
1221 * [no]ncq: Turn on or off NCQ.
1223 * nohrst, nosrst, norst: suppress hard, soft
1226 * dump_id: dump IDENTIFY data.
1228 If there are multiple matching configurations changing
1229 the same attribute, the last one is used.
1231 memblock=debug [KNL] Enable memblock debug messages.
1233 load_ramdisk= [RAM] List of ramdisks to load from floppy
1234 See Documentation/blockdev/ramdisk.txt.
1236 lockd.nlm_grace_period=P [NFS] Assign grace period.
1239 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1242 lockd.nlm_timeout=T [NFS] Assign timeout value.
1245 lockd.nlm_udpport=M [NFS] Assign UDP port.
1248 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1251 loglevel= All Kernel Messages with a loglevel smaller than the
1252 console loglevel will be printed to the console. It can
1253 also be changed with klogd or other programs. The
1254 loglevels are defined as follows:
1256 0 (KERN_EMERG) system is unusable
1257 1 (KERN_ALERT) action must be taken immediately
1258 2 (KERN_CRIT) critical conditions
1259 3 (KERN_ERR) error conditions
1260 4 (KERN_WARNING) warning conditions
1261 5 (KERN_NOTICE) normal but significant condition
1262 6 (KERN_INFO) informational
1263 7 (KERN_DEBUG) debug-level messages
1265 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1266 Format: { n | nk | nM }
1267 n must be a power of two. The default size
1268 is set in the kernel config file.
1270 logo.nologo [FB] Disables display of the built-in Linux logo.
1271 This may be used to provide more screen space for
1272 kernel log messages and is useful when debugging
1273 kernel boot problems.
1275 lp=0 [LP] Specify parallel ports to use, e.g,
1276 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1277 lp=reset first parallel port). 'lp=0' disables the
1278 lp=auto printer driver. 'lp=reset' (which can be
1279 specified in addition to the ports) causes
1280 attached printers to be reset. Using
1281 lp=port1,port2,... specifies the parallel ports
1282 to associate lp devices with, starting with
1283 lp0. A port specification may be 'none' to skip
1284 that lp device, or a parport name such as
1285 'parport0'. Specifying 'lp=auto' instead of a
1286 port specification list means that device IDs
1287 from each port should be examined, to see if
1288 an IEEE 1284-compliant printer is attached; if
1289 so, the driver will manage that printer.
1290 See also header of drivers/char/lp.c.
1293 Sets loops_per_jiffy to given constant, thus avoiding
1294 time-consuming boot-time autodetection (up to 250 ms per
1295 CPU). 0 enables autodetection (default). To determine
1296 the correct value for your kernel, boot with normal
1297 autodetection and see what value is printed. Note that
1298 on SMP systems the preset will be applied to all CPUs,
1299 which is likely to cause problems if your CPUs need
1300 significantly divergent settings. An incorrect value
1301 will cause delays in the kernel to be wrong, leading to
1302 unpredictable I/O errors and other breakage. Although
1303 unlikely, in the extreme case this might damage your
1307 Format: <io>,<irq>,<dma>
1309 machvec= [IA64] Force the use of a particular machine-vector
1310 (machvec) in a generic kernel.
1311 Example: machvec=hpzx1_swiotlb
1313 machtype= [Loongson] Share the same kernel image file between different
1315 Example: machtype=lemote-yeeloong-2f-7inch
1317 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1318 than or equal to this physical address is ignored.
1320 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1321 should make use of. maxcpus=n : n >= 0 limits the
1322 kernel to using 'n' processors. n=0 is a special case,
1323 it is equivalent to "nosmp", which also disables
1326 max_loop= [LOOP] Maximum number of loopback devices that can
1332 mce [X86-32] Machine Check Exception
1334 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1336 md= [HW] RAID subsystems devices and level
1337 See Documentation/md.txt.
1340 Format: <first>,<last>
1341 Specifies range of consoles to be captured by the MDA.
1343 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1344 Amount of memory to be used when the kernel is not able
1345 to see the whole system memory or for test.
1346 [X86-32] Use together with memmap= to avoid physical
1347 address space collisions. Without memmap= PCI devices
1348 could be placed at addresses belonging to unused RAM.
1350 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1354 [KNL,SH] Allow user to override the default size for
1355 per-device physically contiguous DMA buffers.
1357 memmap=exactmap [KNL,X86] Enable setting of an exact
1358 E820 memory map, as specified by the user.
1359 Such memmap=exactmap lines can be constructed based on
1360 BIOS output or other requirements. See the memmap=nn@ss
1363 memmap=nn[KMG]@ss[KMG]
1364 [KNL] Force usage of a specific region of memory
1365 Region of memory to be used, from ss to ss+nn.
1367 memmap=nn[KMG]#ss[KMG]
1368 [KNL,ACPI] Mark specific memory as ACPI data.
1369 Region of memory to be used, from ss to ss+nn.
1371 memmap=nn[KMG]$ss[KMG]
1372 [KNL,ACPI] Mark specific memory as reserved.
1373 Region of memory to be used, from ss to ss+nn.
1374 Example: Exclude memory from 0x18690000-0x1869ffff
1375 memmap=64K$0x18690000
1377 memmap=0x10000$0x18690000
1379 memory_corruption_check=0/1 [X86]
1380 Some BIOSes seem to corrupt the first 64k of
1381 memory when doing things like suspend/resume.
1382 Setting this option will scan the memory
1383 looking for corruption. Enabling this will
1384 both detect corruption and prevent the kernel
1385 from using the memory being corrupted.
1386 However, its intended as a diagnostic tool; if
1387 repeatable BIOS-originated corruption always
1388 affects the same memory, you can use memmap=
1389 to prevent the kernel from using that memory.
1391 memory_corruption_check_size=size [X86]
1392 By default it checks for corruption in the low
1393 64k, making this memory unavailable for normal
1394 use. Use this parameter to scan for
1395 corruption in more or less memory.
1397 memory_corruption_check_period=seconds [X86]
1398 By default it checks for corruption every 60
1399 seconds. Use this parameter to check at some
1400 other rate. 0 disables periodic checking.
1402 memtest= [KNL,X86] Enable memtest
1404 default : 0 <disable>
1405 Specifies the number of memtest passes to be
1406 performed. Each pass selects another test
1407 pattern from a given set of patterns. Memtest
1408 fills the memory with this pattern, validates
1409 memory contents and reserves bad memory
1410 regions that are detected.
1412 meye.*= [HW] Set MotionEye Camera parameters
1413 See Documentation/video4linux/meye.txt.
1415 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1416 Multi-Function General Purpose Timers on AMD Geode
1419 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1420 the BIOS has incorrectly applied a workaround. TinyBIOS
1421 version 0.98 is known to be affected, 0.99 fixes the
1422 problem by letting the user disable the workaround.
1426 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1427 physical address is ignored.
1429 mini2440= [ARM,HW,KNL]
1430 Format:[0..2][b][c][t]
1432 MINI2440 configuration specification:
1433 0 - The attached screen is the 3.5" TFT
1434 1 - The attached screen is the 7" TFT
1435 2 - The VGA Shield is attached (1024x768)
1436 Leaving out the screen size parameter will not load
1437 the TFT driver, and the framebuffer will be left
1439 b - Enable backlight. The TFT backlight pin will be
1440 linked to the kernel VESA blanking code and a GPIO
1441 LED. This parameter is not necessary when using the
1443 c - Enable the s3c camera interface.
1444 t - Reserved for enabling touchscreen support. The
1445 touchscreen support is not enabled in the mainstream
1446 kernel as of 2.6.30, a preliminary port can be found
1447 in the "bleeding edge" mini2440 support kernel at
1448 http://repo.or.cz/w/linux-2.6/mini2440.git
1451 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1452 parameter allows control of the logging verbosity for
1453 the additional memory initialisation checks. A value
1454 of 0 disables mminit logging and a level of 4 will
1455 log everything. Information is printed at KERN_DEBUG
1456 so loglevel=8 may also need to be specified.
1459 [MOUSE] Maximum time between finger touching and
1460 leaving touchpad surface for touch to be considered
1461 a tap and be reported as a left button click (for
1462 touchpads working in absolute mode only).
1464 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1465 reporting absolute coordinates, such as tablets
1466 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1467 reporting absolute coordinates, such as tablets
1469 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1470 is similar to kernelcore except it specifies the
1471 amount of memory used for migratable allocations.
1472 If both kernelcore and movablecore is specified,
1473 then kernelcore will be at *least* the specified
1474 value but may be more. If movablecore on its own
1475 is specified, the administrator must be careful
1476 that the amount of memory usable for all allocations
1479 MTD_Partition= [MTD]
1480 Format: <name>,<region-number>,<size>,<offset>
1482 MTD_Region= [MTD] Format:
1483 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1486 See drivers/mtd/cmdlinepart.c.
1488 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1490 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1492 boundary - index of last SLC block on Flex-OneNAND.
1493 The remaining blocks are configured as MLC blocks.
1494 lock - Configure if Flex-OneNAND boundary should be locked.
1495 Once locked, the boundary cannot be changed.
1496 1 indicates lock status, 0 indicates unlock status.
1499 ARM/S3C2412 JIVE boot control
1501 See arch/arm/mach-s3c2412/mach-jive.c
1503 mtouchusb.raw_coordinates=
1504 [HW] Make the MicroTouch USB driver use raw coordinates
1505 ('y', default) or cooked coordinates ('n')
1507 mtrr_chunk_size=nn[KMG] [X86]
1508 used for mtrr cleanup. It is largest continuous chunk
1509 that could hold holes aka. UC entries.
1511 mtrr_gran_size=nn[KMG] [X86]
1512 Used for mtrr cleanup. It is granularity of mtrr block.
1514 Large value could prevent small alignment from
1517 mtrr_spare_reg_nr=n [X86]
1519 Range: 0,7 : spare reg number
1521 Used for mtrr cleanup. It is spare mtrr entries number.
1522 Set to 2 or more if your graphical card needs more.
1524 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1526 netdev= [NET] Network devices parameters
1527 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1528 Note that mem_start is often overloaded to mean
1529 something different and driver-specific.
1530 This usage is only documented in each driver source
1534 [NETFILTER] Enable connection tracking flow accounting
1535 0 to disable accounting
1536 1 to enable accounting
1539 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1540 See Documentation/filesystems/nfs/nfsroot.txt.
1542 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1543 See Documentation/filesystems/nfs/nfsroot.txt.
1545 nfsrootdebug [NFS] enable nfsroot debugging messages.
1546 See Documentation/filesystems/nfs/nfsroot.txt.
1548 nfs.callback_tcpport=
1549 [NFS] set the TCP port on which the NFSv4 callback
1550 channel should listen.
1553 [NFS] sets the pathname to the program which is used
1554 to update the NFS client cache entries.
1556 nfs.cache_getent_timeout=
1557 [NFS] sets the timeout after which an attempt to
1558 update a cache entry is deemed to have failed.
1560 nfs.idmap_cache_timeout=
1561 [NFS] set the maximum lifetime for idmapper cache
1565 [NFS] enable 64-bit inode numbers.
1566 If zero, the NFS client will fake up a 32-bit inode
1567 number for the readdir() and stat() syscalls instead
1568 of returning the full 64-bit number.
1569 The default is to return 64-bit inode numbers.
1571 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1572 when a NMI is triggered.
1573 Format: [state][,regs][,debounce][,die]
1575 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1576 Format: [panic,][num]
1578 0 - turn nmi_watchdog off
1579 1 - use the IO-APIC timer for the NMI watchdog
1580 2 - use the local APIC for the NMI watchdog using
1581 a performance counter. Note: This will use one
1582 performance counter and the local APIC's performance
1584 When panic is specified, panic when an NMI watchdog
1586 This is useful when you use a panic=... timeout and
1587 need the box quickly up again.
1588 Instead of 1 and 2 it is possible to use the following
1589 symbolic names: lapic and ioapic
1590 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1592 netpoll.carrier_timeout=
1593 [NET] Specifies amount of time (in seconds) that
1594 netpoll should wait for a carrier. By default netpoll
1597 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1598 emulation library even if a 387 maths coprocessor
1602 [HW] Never suspend the console
1603 Disable suspending of consoles during suspend and
1604 hibernate operations. Once disabled, debugging
1605 messages can reach various consoles while the rest
1606 of the system is being put to sleep (ie, while
1607 debugging driver suspend/resume hooks). This may
1608 not work reliably with all consoles, but is known
1609 to work with serial and VGA consoles.
1611 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1612 caches in the slab allocator. Saves per-node memory,
1613 but will impact performance.
1617 noapic [SMP,APIC] Tells the kernel to not make use of any
1618 IOAPICs that may be present in the system.
1620 nobats [PPC] Do not use BATs for mapping kernel lowmem
1621 on "Classic" PPC cores.
1625 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1627 nodelayacct [KNL] Disable per-task delay accounting
1629 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1631 nodsp [SH] Disable hardware DSP at boot time.
1633 noefi [X86] Disable EFI runtime services support.
1638 On X86-32 available only on PAE configured kernels.
1639 noexec=on: enable non-executable mappings (default)
1640 noexec=off: disable non-executable mappings
1643 This affects only 32-bit executables.
1644 noexec32=on: enable non-executable mappings (default)
1645 read doesn't imply executable mappings
1646 noexec32=off: disable non-executable mappings
1647 read implies executable mappings
1649 nofpu [SH] Disable hardware FPU at boot time.
1651 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1652 register save and restore. The kernel will only save
1653 legacy floating-point registers on task switch.
1655 noxsave [BUGS=X86] Disables x86 extended register state save
1656 and restore using xsave. The kernel will fallback to
1657 enabling legacy floating-point and sse state.
1659 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1660 wfi(ARM) instruction doesn't work correctly and not to
1661 use it. This is also useful when using JTAG debugger.
1663 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1664 instruction doesn't work correctly and not to
1667 no_file_caps Tells the kernel not to honor file capabilities. The
1668 only way then for a file to be executed with privilege
1669 is to be setuid root or executed by root.
1671 nohalt [IA-64] Tells the kernel not to use the power saving
1672 function PAL_HALT_LIGHT when idle. This increases
1673 power-consumption. On the positive side, it reduces
1674 interrupt wake-up latency, which may improve performance
1675 in certain environments such as networked servers or
1678 nohz= [KNL] Boottime enable/disable dynamic ticks
1679 Valid arguments: on, off
1682 noiotrap [SH] Disables trapped I/O port accesses.
1684 noirqdebug [X86-32] Disables the code which attempts to detect and
1685 disable unhandled interrupt sources.
1687 no_timer_check [X86,APIC] Disables the code which tests for
1688 broken timer IRQ sources.
1690 noisapnp [ISAPNP] Disables ISA PnP code.
1692 noinitrd [RAM] Tells the kernel not to load any configured
1695 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1697 [Deprecated - use intremap=off]
1701 nojitter [IA64] Disables jitter checking for ITC timers.
1703 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1705 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1707 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1709 noltlbs [PPC] Do not use large page/tlb entries for kernel
1710 lowmem mapping on PPC40x.
1712 nomca [IA-64] Disable machine check abort handling
1714 nomce [X86-32] Machine Check Exception
1716 nomfgpt [X86-32] Disable Multi-Function General Purpose
1717 Timer usage (for AMD Geode machines).
1719 nopat [X86] Disable PAT (page attribute table extension of
1720 pagetables) support.
1722 norandmaps Don't use address space randomization. Equivalent to
1723 echo 0 > /proc/sys/kernel/randomize_va_space
1725 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1727 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1728 with UP alternatives
1730 noresidual [PPC] Don't use residual data on PReP machines.
1732 noresume [SWSUSP] Disables resume and restores original swap
1735 no-scroll [VGA] Disables scrollback.
1736 This is required for the Braillex ib80-piezo Braille
1737 reader made by F.H. Papenmeier (Germany).
1741 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1743 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1744 and disable the IO APIC. legacy for "maxcpus=0".
1746 nosoftlockup [KNL] Disable the soft-lockup detector.
1748 noswapaccount [KNL] Disable accounting of swap in memory resource
1749 controller. (See Documentation/cgroups/memory.txt)
1751 nosync [HW,M68K] Disables sync negotiation for all devices.
1753 notsc [BUGS=X86-32] Disable Time Stamp Counter
1755 nousb [USB] Disable the USB subsystem
1757 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1761 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1763 nptcg= [IA64] Override max number of concurrent global TLB
1764 purges which is reported from either PAL_VM_SUMMARY or
1767 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1768 could support. nr_cpus=n : n >= 1 limits the kernel to
1769 supporting 'n' processors. Later in runtime you can not
1770 use hotplug cpu feature to put more cpu back to online.
1771 just like you compile the kernel NR_CPUS=n
1773 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1775 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1776 one of ['zone', 'node', 'default'] can be specified
1777 This can be set from sysctl after boot.
1778 See Documentation/sysctl/vm.txt for details.
1780 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1781 See Documentation/debugging-via-ohci1394.txt for more
1784 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1785 Rather than timing out after 20 ms if an EC
1786 command is not properly ACKed, override the length
1787 of the timeout. We have interrupts disabled while
1788 waiting for the ACK, so if this is set too high
1789 interrupts *may* be lost!
1791 omap_mux= [OMAP] Override bootloader pin multiplexing.
1792 Format: <mux_mode0.mode_name=value>...
1793 For example, to override I2C bus2:
1794 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1796 oprofile.timer= [HW]
1797 Use timer interrupt instead of performance counters
1799 oprofile.cpu_type= Force an oprofile cpu type
1800 This might be useful if you have an older oprofile
1801 userland or if you want common events.
1802 Format: { arch_perfmon }
1803 arch_perfmon: [X86] Force use of architectural
1804 perfmon on Intel CPUs instead of the
1805 CPU specific event set.
1808 See Documentation/sound/oss/oss-parameters.txt
1810 panic= [KNL] Kernel behaviour on panic
1813 parkbd.port= [HW] Parallel port number the keyboard adapter is
1814 connected to, default is 0.
1816 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1817 0 for XT, 1 for AT (default is AT).
1820 parport= [HW,PPT] Specify parallel ports. 0 disables.
1821 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1822 Use 'auto' to force the driver to use any
1823 IRQ/DMA settings detected (the default is to
1824 ignore detected IRQ/DMA settings because of
1825 possible conflicts). You can specify the base
1826 address, IRQ, and DMA settings; IRQ and DMA
1827 should be numbers, or 'auto' (for using detected
1828 settings on that particular port), or 'nofifo'
1829 (to avoid using a FIFO even if it is detected).
1830 Parallel ports are assigned in the order they
1831 are specified on the command line, starting
1834 parport_init_mode= [HW,PPT]
1835 Configure VIA parallel port to operate in
1836 a specific mode. This is necessary on Pegasos
1837 computer where firmware has no options for setting
1838 up parallel port mode and sets it to spp.
1839 Currently this function knows 686a and 8231 chips.
1840 Format: [spp|ps2|epp|ecp|ecpepp]
1843 Halt all CPUs after the first oops has been printed for
1844 the specified number of seconds. This is to be used if
1845 your oopses keep scrolling off the screen.
1850 See header of drivers/block/paride/pcd.c.
1851 See also Documentation/blockdev/paride.txt.
1853 pci=option[,option...] [PCI] various PCI subsystem options:
1854 earlydump [X86] dump PCI config space before the kernel
1856 off [X86] don't probe for the PCI bus
1857 bios [X86-32] force use of PCI BIOS, don't access
1858 the hardware directly. Use this if your machine
1859 has a non-standard PCI host bridge.
1860 nobios [X86-32] disallow use of PCI BIOS, only direct
1861 hardware access methods are allowed. Use this
1862 if you experience crashes upon bootup and you
1863 suspect they are caused by the BIOS.
1864 conf1 [X86] Force use of PCI Configuration
1866 conf2 [X86] Force use of PCI Configuration
1868 noaer [PCIE] If the PCIEAER kernel config parameter is
1869 enabled, this kernel boot option can be used to
1870 disable the use of PCIE advanced error reporting.
1871 nodomains [PCI] Disable support for multiple PCI
1872 root domains (aka PCI segments, in ACPI-speak).
1873 nommconf [X86] Disable use of MMCONFIG for PCI
1875 check_enable_amd_mmconf [X86] check for and enable
1876 properly configured MMIO access to PCI
1877 config space on AMD family 10h CPU
1878 nomsi [MSI] If the PCI_MSI kernel config parameter is
1879 enabled, this kernel boot option can be used to
1880 disable the use of MSI interrupts system-wide.
1881 noioapicquirk [APIC] Disable all boot interrupt quirks.
1882 Safety option to keep boot IRQs enabled. This
1883 should never be necessary.
1884 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1885 primary IO-APIC for bridges that cannot disable
1886 boot IRQs. This fixes a source of spurious IRQs
1887 when the system masks IRQs.
1888 noioapicreroute [APIC] Disable workaround that uses the
1889 boot IRQ equivalent of an IRQ that connects to
1890 a chipset where boot IRQs cannot be disabled.
1891 The opposite of ioapicreroute.
1892 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1893 routing table. These calls are known to be buggy
1894 on several machines and they hang the machine
1895 when used, but on other computers it's the only
1896 way to get the interrupt routing table. Try
1897 this option if the kernel is unable to allocate
1898 IRQs or discover secondary PCI buses on your
1900 rom [X86] Assign address space to expansion ROMs.
1901 Use with caution as certain devices share
1902 address decoders between ROMs and other
1904 norom [X86] Do not assign address space to
1905 expansion ROMs that do not already have
1906 BIOS assigned address ranges.
1907 nobar [X86] Do not assign address space to the
1908 BARs that weren't assigned by the BIOS.
1909 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1910 assigned automatically to PCI devices. You can
1911 make the kernel exclude IRQs of your ISA cards
1913 pirqaddr=0xAAAAA [X86] Specify the physical address
1914 of the PIRQ table (normally generated
1915 by the BIOS) if it is outside the
1916 F0000h-100000h range.
1917 lastbus=N [X86] Scan all buses thru bus #N. Can be
1918 useful if the kernel is unable to find your
1919 secondary buses and you want to tell it
1920 explicitly which ones they are.
1921 assign-busses [X86] Always assign all PCI bus
1922 numbers ourselves, overriding
1923 whatever the firmware may have done.
1924 usepirqmask [X86] Honor the possible IRQ mask stored
1925 in the BIOS $PIR table. This is needed on
1926 some systems with broken BIOSes, notably
1927 some HP Pavilion N5400 and Omnibook XE3
1928 notebooks. This will have no effect if ACPI
1929 IRQ routing is enabled.
1930 noacpi [X86] Do not use ACPI for IRQ routing
1931 or for PCI scanning.
1932 use_crs [X86] Use PCI host bridge window information
1933 from ACPI. On BIOSes from 2008 or later, this
1934 is enabled by default. If you need to use this,
1935 please report a bug.
1936 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1937 If you need to use this, please report a bug.
1938 routeirq Do IRQ routing for all PCI devices.
1939 This is normally done in pci_enable_device(),
1940 so this option is a temporary workaround
1941 for broken drivers that don't call it.
1942 skip_isa_align [X86] do not align io start addr, so can
1943 handle more pci cards
1944 firmware [ARM] Do not re-enumerate the bus but instead
1945 just use the configuration from the
1946 bootloader. This is currently used on
1947 IXP2000 systems where the bus has to be
1948 configured a certain way for adjunct CPUs.
1949 noearly [X86] Don't do any early type 1 scanning.
1950 This might help on some broken boards which
1951 machine check when some devices' config space
1952 is read. But various workarounds are disabled
1953 and some IOMMU drivers will not work.
1954 bfsort Sort PCI devices into breadth-first order.
1955 This sorting is done to get a device
1956 order compatible with older (<= 2.4) kernels.
1957 nobfsort Don't sort PCI devices into breadth-first order.
1958 cbiosize=nn[KMG] The fixed amount of bus space which is
1959 reserved for the CardBus bridge's IO window.
1960 The default value is 256 bytes.
1961 cbmemsize=nn[KMG] The fixed amount of bus space which is
1962 reserved for the CardBus bridge's memory
1963 window. The default value is 64 megabytes.
1966 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1967 Specifies alignment and device to reassign
1968 aligned memory resources.
1969 If <order of align> is not specified,
1970 PAGE_SIZE is used as alignment.
1971 PCI-PCI bridge can be specified, if resource
1972 windows need to be expanded.
1973 ecrc= Enable/disable PCIe ECRC (transaction layer
1974 end-to-end CRC checking).
1975 bios: Use BIOS/firmware settings. This is the
1980 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1983 force Enable ASPM even on devices that claim not to support it.
1984 WARNING: Forcing ASPM on may cause system lockups.
1986 pcie_ports= [PCIE] PCIe ports handling:
1987 auto Ask the BIOS whether or not to use native PCIe services
1988 associated with PCIe ports (PME, hot-plug, AER). Use
1989 them only if that is allowed by the BIOS.
1990 native Use native PCIe services associated with PCIe ports
1992 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
1995 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
1996 nomsi Do not use MSI for native PCIe PME signaling (this makes
1997 all PCIe root ports use INTx for all services).
1999 pcmv= [HW,PCMCIA] BadgePAD 4
2002 See Documentation/blockdev/paride.txt.
2004 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2007 See arch/parisc/kernel/pdc_chassis.c
2009 percpu_alloc= Select which percpu first chunk allocator to use.
2010 Currently supported values are "embed" and "page".
2011 Archs may support subset or none of the selections.
2012 See comments in mm/percpu.c for details on each
2013 allocator. This parameter is primarily for debugging
2014 and performance comparison.
2017 See Documentation/blockdev/paride.txt.
2020 See Documentation/blockdev/paride.txt.
2022 pirq= [SMP,APIC] Manual mp-table setup
2023 See Documentation/x86/i386/IO-APIC.txt.
2025 plip= [PPT,NET] Parallel port network link
2026 Format: { parport<nr> | timid | 0 }
2027 See also Documentation/parport.txt.
2029 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2030 Override pmtimer IOPort with a hex value.
2034 Enable PNP debug messages. This depends on the
2035 CONFIG_PNP_DEBUG_MESSAGES option.
2041 { on | off | curr | res | no-curr | no-res }
2044 [ISAPNP] Exclude IRQs for the autoconfiguration
2047 [ISAPNP] Exclude DMAs for the autoconfiguration
2049 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2050 Ranges are in pairs (I/O port base and size).
2053 [ISAPNP] Exclude memory regions for the
2055 Ranges are in pairs (memory base and size).
2057 ports= [IP_VS_FTP] IPVS ftp helper module
2059 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2061 Format: <port>,<port>....
2063 print-fatal-signals=
2064 [KNL] debug: print fatal signals
2066 If enabled, warn about various signal handling
2067 related application anomalies: too many signals,
2068 too many POSIX.1 timers, fatal signals causing a
2071 If you hit the warning due to signal overflow,
2072 you might want to try "ulimit -i unlimited".
2076 printk.time= Show timing data prefixed to each printk message line
2077 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2079 processor.max_cstate= [HW,ACPI]
2080 Limit processor to maximum C-state
2081 max_cstate=9 overrides any DMI blacklist limit.
2083 processor.nocst [HW,ACPI]
2084 Ignore the _CST method to determine C-states,
2085 instead using the legacy FADT method
2087 profile= [KNL] Enable kernel profiling via /proc/profile
2088 Format: [schedule,]<number>
2089 Param: "schedule" - profile schedule points.
2090 Param: <number> - step/bucket size as a power of 2 for
2091 statistical time based profiling.
2092 Param: "sleep" - profile D-state sleeping (millisecs).
2093 Requires CONFIG_SCHEDSTATS
2094 Param: "kvm" - profile VM exits.
2096 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2098 See Documentation/blockdev/ramdisk.txt.
2100 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2101 probe for; one of (bare|imps|exps|lifebook|any).
2102 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2104 psmouse.resetafter= [HW,MOUSE]
2105 Try to reset the device after so many bad packets
2108 [HW,MOUSE] Set desired mouse resolution, in dpi.
2109 psmouse.smartscroll=
2110 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2111 0 = disabled, 1 = enabled (default).
2114 See Documentation/blockdev/paride.txt.
2117 [KNL] Number of legacy pty's. Overwrites compiled-in
2120 quiet [KNL] Disable most log messages
2125 See Documentation/md.txt.
2127 ramdisk_blocksize= [RAM]
2128 See Documentation/blockdev/ramdisk.txt.
2130 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2131 See Documentation/blockdev/ramdisk.txt.
2133 rcupdate.blimit= [KNL,BOOT]
2134 Set maximum number of finished RCU callbacks to process
2137 rcupdate.qhimark= [KNL,BOOT]
2138 Set threshold of queued
2139 RCU callbacks over which batch limiting is disabled.
2141 rcupdate.qlowmark= [KNL,BOOT]
2142 Set threshold of queued RCU callbacks below which
2143 batch limiting is re-enabled.
2147 Run specified binary instead of /init from the ramdisk,
2148 used for early userspace startup. See initrd.
2150 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2151 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2152 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2155 [KNL, SMP] Set scheduler's default relax_domain_level.
2156 See Documentation/cgroups/cpusets.txt.
2158 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2160 reservetop= [X86-32]
2162 Reserves a hole at the top of the kernel virtual
2167 Set the amount of memory to reserve for BIOS at
2168 the bottom of the address space.
2170 reset_devices [KNL] Force drivers to reset the underlying device
2171 during initialization.
2174 Specify the partition device for software suspend
2176 resume_offset= [SWSUSP]
2177 Specify the offset from the beginning of the partition
2178 given by "resume=" at which the swap header is located,
2179 in <PAGE_SIZE> units (needed only for swap files).
2180 See Documentation/power/swsusp-and-swap-files.txt
2182 hibernate= [HIBERNATION]
2183 noresume Don't check if there's a hibernation image
2184 present during boot.
2185 nocompress Don't compress/decompress hibernation images.
2187 retain_initrd [RAM] Keep initrd memory after extraction
2189 rhash_entries= [KNL,NET]
2190 Set number of hash buckets for route cache
2192 riscom8= [HW,SERIAL]
2193 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2195 ro [KNL] Mount root device read-only on boot
2197 root= [KNL] Root filesystem
2199 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2200 mount the root filesystem
2202 rootflags= [KNL] Set root filesystem mount option string
2204 rootfstype= [KNL] Set root filesystem type
2206 rootwait [KNL] Wait (indefinitely) for root device to show up.
2207 Useful for devices that are detected asynchronously
2208 (e.g. USB and MMC devices).
2210 rw [KNL] Mount root device read-write on boot
2212 S [KNL] Run init in single mode
2215 See drivers/net/irda/sa1100_ir.c.
2217 sbni= [NET] Granch SBNI12 leased line adapter
2219 sched_debug [KNL] Enables verbose scheduler debug messages.
2221 security= [SECURITY] Choose a security module to enable at boot.
2222 If this boot parameter is not specified, only the first
2223 security module asking for security registration will be
2224 loaded. An invalid security module name will be treated
2225 as if no module has been chosen.
2227 selinux= [SELINUX] Disable or enable SELinux at boot time.
2228 Format: { "0" | "1" }
2229 See security/selinux/Kconfig help text.
2232 Default value is set via kernel config option.
2233 If enabled at boot time, /selinux/disable can be used
2234 later to disable prior to initial policy load.
2236 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2237 Format: { "0" | "1" }
2238 See security/apparmor/Kconfig help text
2241 Default value is set via kernel config option.
2243 serialnumber [BUGS=X86-32]
2246 Maximal number of shapers.
2248 show_msr= [x86] show boot-time MSR settings
2249 Format: { <integer> }
2250 Show boot-time (BIOS-initialized) MSR settings.
2251 The parameter means the number of CPUs to show,
2252 for example 1 means boot CPU only.
2259 slub_debug[=options[,slabs]] [MM, SLUB]
2260 Enabling slub_debug allows one to determine the
2261 culprit if slab objects become corrupted. Enabling
2262 slub_debug can create guard zones around objects and
2263 may poison objects when not in use. Also tracks the
2264 last alloc / free. For more information see
2265 Documentation/vm/slub.txt.
2267 slub_max_order= [MM, SLUB]
2268 Determines the maximum allowed order for slabs.
2269 A high setting may cause OOMs due to memory
2270 fragmentation. For more information see
2271 Documentation/vm/slub.txt.
2273 slub_min_objects= [MM, SLUB]
2274 The minimum number of objects per slab. SLUB will
2275 increase the slab order up to slub_max_order to
2276 generate a sufficiently large slab able to contain
2277 the number of objects indicated. The higher the number
2278 of objects the smaller the overhead of tracking slabs
2279 and the less frequently locks need to be acquired.
2280 For more information see Documentation/vm/slub.txt.
2282 slub_min_order= [MM, SLUB]
2283 Determines the mininum page order for slabs. Must be
2284 lower than slub_max_order.
2285 For more information see Documentation/vm/slub.txt.
2287 slub_nomerge [MM, SLUB]
2288 Disable merging of slabs with similar size. May be
2289 necessary if there is some reason to distinguish
2290 allocs to different slabs. Debug options disable
2291 merging on their own.
2292 For more information see Documentation/vm/slub.txt.
2295 Format: <io1>[,<io2>[,...,<io8>]]
2297 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2298 attempt to substitute SMP alternatives once at boot.
2300 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2301 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2302 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2303 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2304 smsc-ircc2.ircc_irq= [HW] IRQ line
2305 smsc-ircc2.ircc_dma= [HW] DMA channel
2306 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2307 0: Toshiba Satellite 1800 (GP data pin select)
2308 1: Fast pin select (default)
2312 [KNL] Should the soft-lockup detector generate panics.
2314 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2315 See Documentation/sonypi.txt
2317 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2318 See Documentation/serial/specialix.txt.
2320 spia_io_base= [HW,MTD]
2326 Enabled the stack tracer on boot up.
2330 Set the STI (builtin display/keyboard on the HP-PARISC
2331 machines) console (graphic card) which should be used
2332 as the initial boot-console.
2333 See also comment in drivers/video/console/sticore.c.
2336 See comment in drivers/video/console/sticore.c.
2339 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2341 sunrpc.min_resvport=
2342 sunrpc.max_resvport=
2344 SunRPC servers often require that client requests
2345 originate from a privileged port (i.e. a port in the
2346 range 0 < portnr < 1024).
2347 An administrator who wishes to reserve some of these
2348 ports for other uses may adjust the range that the
2349 kernel's sunrpc client considers to be privileged
2350 using these two parameters to set the minimum and
2351 maximum port values.
2355 Control how the NFS server code allocates CPUs to
2356 service thread pools. Depending on how many NICs
2357 you have and where their interrupts are bound, this
2358 option will affect which CPUs will do NFS serving.
2359 Note: this parameter cannot be changed while the
2360 NFS server is running.
2362 auto the server chooses an appropriate mode
2363 automatically using heuristics
2364 global a single global pool contains all CPUs
2365 percpu one pool for each CPU
2366 pernode one pool for each NUMA node (equivalent
2367 to global on non-NUMA machines)
2369 sunrpc.tcp_slot_table_entries=
2370 sunrpc.udp_slot_table_entries=
2372 Sets the upper limit on the number of simultaneous
2373 RPC calls that can be sent from the client to a
2374 server. Increasing these values may allow you to
2375 improve throughput, but will also increase the
2376 amount of memory reserved for use by the client.
2379 [KNL] Enable accounting of swap in memory resource
2380 controller if no parameter or 1 is given or disable
2381 it if 0 is given (See Documentation/cgroups/memory.txt)
2383 swiotlb= [IA-64] Number of I/O TLB slabs
2387 sysfs.deprecated=0|1 [KNL]
2388 Enable/disable old style sysfs layout for old udev
2389 on older distributions. When this option is enabled
2390 very new udev will not work anymore. When this option
2391 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2392 in older udev will not work anymore.
2393 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2394 the kernel configuration.
2396 sysrq_always_enabled
2398 Ignore sysrq setting - this boot parameter will
2399 neutralize any effect of /proc/sys/kernel/sysrq.
2400 Useful for debugging.
2404 test_suspend= [SUSPEND]
2405 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2406 standby suspend) as the system sleep state to briefly
2407 enter during system startup. The system is woken from
2408 this state using a wakeup-capable RTC alarm.
2410 thash_entries= [KNL,NET]
2411 Set number of hash buckets for TCP connection
2413 thermal.act= [HW,ACPI]
2414 -1: disable all active trip points in all thermal zones
2415 <degrees C>: override all lowest active trip points
2417 thermal.crt= [HW,ACPI]
2418 -1: disable all critical trip points in all thermal zones
2419 <degrees C>: override all critical trip points
2421 thermal.nocrt= [HW,ACPI]
2422 Set to disable actions on ACPI thermal zone
2423 critical and hot trip points.
2425 thermal.off= [HW,ACPI]
2426 1: disable ACPI thermal control
2428 thermal.psv= [HW,ACPI]
2429 -1: disable all passive trip points
2430 <degrees C>: override all passive trip points to this
2433 thermal.tzp= [HW,ACPI]
2434 Specify global default ACPI thermal zone polling rate
2435 <deci-seconds>: poll all this frequency
2436 0: no polling (default)
2440 Specify if the kernel should make use of the cpu
2441 topology informations if the hardware supports these.
2442 The scheduler will make use of these informations and
2443 e.g. base its process migration decisions on it.
2448 tpm_suspend_pcr=[HW,TPM]
2449 Format: integer pcr id
2450 Specify that at suspend time, the tpm driver
2451 should extend the specified pcr with zeros,
2452 as a workaround for some chips which fail to
2453 flush the last written pcr on TPM_SaveState.
2454 This will guarantee that all the other pcrs
2457 trace_buf_size=nn[KMG]
2458 [FTRACE] will set tracing buffer size.
2460 trace_event=[event-list]
2461 [FTRACE] Set and start specified trace events in order
2462 to facilitate early boot debugging.
2463 See also Documentation/trace/events.txt
2465 tsc= Disable clocksource-must-verify flag for TSC.
2467 [x86] reliable: mark tsc clocksource as reliable, this
2468 disables clocksource verification at runtime.
2469 Used to enable high-resolution timer mode on older
2470 hardware, and in virtualized environment.
2471 [x86] noirqtime: Do not use TSC to do irq accounting.
2472 Used to run time disable IRQ_TIME_ACCOUNTING on any
2473 platforms where RDTSC is slow and this accounting
2476 turbografx.map[2|3]= [HW,JOY]
2477 TurboGraFX parallel port interface
2479 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2480 See also Documentation/input/joystick-parport.txt
2482 uhash_entries= [KNL,NET]
2483 Set number of hash buckets for UDP/UDP-Lite connections
2486 [USB] Ignore overcurrent events (default N).
2487 Some badly-designed motherboards generate lots of
2488 bogus events, for ports that aren't wired to
2489 anything. Set this parameter to avoid log spamming.
2490 Note that genuine overcurrent events won't be
2495 Set unknown_nmi_panic=1 early on boot.
2497 usbcore.autosuspend=
2498 [USB] The autosuspend time delay (in seconds) used
2499 for newly-detected USB devices (default 2). This
2500 is the time required before an idle device will be
2501 autosuspended. Devices for which the delay is set
2502 to a negative value won't be autosuspended at all.
2504 usbcore.usbfs_snoop=
2505 [USB] Set to log all usbfs traffic (default 0 = off).
2507 usbcore.blinkenlights=
2508 [USB] Set to cycle leds on hubs (default 0 = off).
2510 usbcore.old_scheme_first=
2511 [USB] Start with the old device initialization
2512 scheme (default 0 = off).
2514 usbcore.use_both_schemes=
2515 [USB] Try the other device initialization scheme
2516 if the first one fails (default 1 = enabled).
2518 usbcore.initial_descriptor_timeout=
2519 [USB] Specifies timeout for the initial 64-byte
2520 USB_REQ_GET_DESCRIPTOR request in milliseconds
2521 (default 5000 = 5.0 seconds).
2524 [USBHID] The interval which mice are to be polled at.
2526 usb-storage.delay_use=
2527 [UMS] The delay in seconds before a new device is
2528 scanned for Logical Units (default 5).
2531 [UMS] A list of quirks entries to supplement or
2532 override the built-in unusual_devs list. List
2533 entries are separated by commas. Each entry has
2534 the form VID:PID:Flags where VID and PID are Vendor
2535 and Product ID values (4-digit hex numbers) and
2536 Flags is a set of characters, each corresponding
2537 to a common usb-storage quirk flag as follows:
2538 a = SANE_SENSE (collect more than 18 bytes
2540 b = BAD_SENSE (don't collect more than 18
2541 bytes of sense data);
2542 c = FIX_CAPACITY (decrease the reported
2543 device capacity by one sector);
2544 h = CAPACITY_HEURISTICS (decrease the
2545 reported device capacity by one
2546 sector if the number is odd);
2547 i = IGNORE_DEVICE (don't bind to this
2549 l = NOT_LOCKABLE (don't try to lock and
2550 unlock ejectable media);
2551 m = MAX_SECTORS_64 (don't transfer more
2552 than 64 sectors = 32 KB at a time);
2553 o = CAPACITY_OK (accept the capacity
2554 reported by the device);
2555 r = IGNORE_RESIDUE (the device reports
2556 bogus residue values);
2557 s = SINGLE_LUN (the device has only one
2559 w = NO_WP_DETECT (don't test whether the
2560 medium is write-protected).
2561 Example: quirks=0419:aaf5:rl,0421:0433:rc
2564 [X86] Flags controlling user PTE allocations.
2566 nohigh = do not allocate PTE pages in
2567 HIGHMEM regardless of setting
2571 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2572 vdso=1: enable VDSO (default)
2573 vdso=0: disable VDSO mapping
2576 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2577 vdso32=1: enable 32-bit VDSO (default)
2578 vdso32=0: disable 32-bit VDSO mapping
2581 vector=percpu: enable percpu vector domain
2583 video= [FB] Frame buffer configuration
2584 See Documentation/fb/modedb.txt.
2586 vga= [BOOT,X86-32] Select a particular video mode
2587 See Documentation/x86/boot.txt and
2588 Documentation/svga.txt.
2589 Use vga=ask for menu.
2590 This is actually a boot loader parameter; the value is
2591 passed to the kernel using a special protocol.
2593 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2594 size of <nn>. This can be used to increase the
2595 minimum size (128MB on x86). It can also be used to
2596 decrease the size and leave more room for directly
2599 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2602 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2605 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2608 vt.cur_default= [VT] Default cursor shape.
2609 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2610 the parameters of the <Esc>[?A;B;Cc escape sequence;
2611 see VGA-softcursor.txt. Default: 2 = underline.
2613 vt.default_blu= [VT]
2614 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2615 Change the default blue palette of the console.
2616 This is a 16-member array composed of values
2619 vt.default_grn= [VT]
2620 Format: <green0>,<green1>,<green2>,...,<green15>
2621 Change the default green palette of the console.
2622 This is a 16-member array composed of values
2625 vt.default_red= [VT]
2626 Format: <red0>,<red1>,<red2>,...,<red15>
2627 Change the default red palette of the console.
2628 This is a 16-member array composed of values
2634 Set system-wide default UTF-8 mode for all tty's.
2635 Default is 1, i.e. UTF-8 mode is enabled for all
2636 newly opened terminals.
2638 vt.global_cursor_default=
2641 Set system-wide default for whether a cursor
2642 is shown on new VTs. Default is -1,
2643 i.e. cursors will be created by default unless
2644 overridden by individual drivers. 0 will hide
2645 cursors, 1 will display them.
2647 watchdog timers [HW,WDT] For information on watchdog timers,
2648 see Documentation/watchdog/watchdog-parameters.txt
2649 or other driver-specific files in the
2650 Documentation/watchdog/ directory.
2652 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2653 default x2apic cluster mode on platforms
2656 x86_mrst_timer= [X86-32,APBT]
2657 Choose timer option for x86 Moorestown MID platform.
2658 Two valid options are apbt timer only and lapic timer
2659 plus one apbt timer for broadcast timer.
2660 x86_mrst_timer=apbt_only | lapic_and_apbt
2662 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2663 xd_geo= See header of drivers/block/xd.c.
2665 xen_emul_unplug= [HW,X86,XEN]
2666 Unplug Xen emulated devices
2667 Format: [unplug0,][unplug1]
2668 ide-disks -- unplug primary master IDE devices
2669 aux-ide-disks -- unplug non-primary-master IDE devices
2670 nics -- unplug network devices
2671 all -- unplug all emulated devices (NICs and IDE disks)
2672 unnecessary -- unplugging emulated devices is
2673 unnecessary even if the host did not respond to
2675 never -- do not unplug even if version check succeeds
2677 xirc2ps_cs= [NET,PCMCIA]
2679 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2681 ______________________________________________________________________
2685 Add more DRM drivers.
projects / mirror_ubuntu-artful-kernel.git / blob