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 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
51 GCOV GCOV profiling is enabled.
52 HW Appropriate hardware is enabled.
53 IA-64 IA-64 architecture is enabled.
54 IMA Integrity measurement architecture is enabled.
55 IOSCHED More than one I/O scheduler is enabled.
56 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
57 IPV6 IPv6 support is enabled.
58 ISAPNP ISA PnP code is enabled.
59 ISDN Appropriate ISDN support is enabled.
60 JOY Appropriate joystick support is enabled.
61 KGDB Kernel debugger support is enabled.
62 KVM Kernel Virtual Machine support is enabled.
63 LIBATA Libata driver is enabled
64 LP Printer support is enabled.
65 LOOP Loopback device support is enabled.
66 M68k M68k architecture is enabled.
67 These options have more detailed description inside of
68 Documentation/m68k/kernel-options.txt.
69 MCA MCA bus support is enabled.
70 MDA MDA console support is enabled.
71 MOUSE Appropriate mouse support is enabled.
72 MSI Message Signaled Interrupts (PCI).
73 MTD MTD (Memory Technology Device) support is enabled.
74 NET Appropriate network support is enabled.
75 NUMA NUMA support is enabled.
76 NFS Appropriate NFS support is enabled.
77 OSS OSS sound support is enabled.
78 PV_OPS A paravirtualized kernel is enabled.
79 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
80 PARISC The PA-RISC architecture is enabled.
81 PCI PCI bus support is enabled.
82 PCIE PCI Express support is enabled.
83 PCMCIA The PCMCIA subsystem is enabled.
84 PNP Plug & Play support is enabled.
85 PPC PowerPC architecture is enabled.
86 PPT Parallel port support is enabled.
87 PS2 Appropriate PS/2 support is enabled.
88 RAM RAM disk support is enabled.
89 S390 S390 architecture is enabled.
90 SCSI Appropriate SCSI support is enabled.
91 A lot of drivers have their options described inside
92 the Documentation/scsi/ sub-directory.
93 SECURITY Different security models are enabled.
94 SELINUX SELinux support is enabled.
95 APPARMOR AppArmor support is enabled.
96 SERIAL Serial support is enabled.
97 SH SuperH architecture is enabled.
98 SMP The kernel is an SMP kernel.
99 SPARC Sparc architecture is enabled.
100 SWSUSP Software suspend (hibernation) is enabled.
101 SUSPEND System suspend states are enabled.
102 FTRACE Function tracing enabled.
103 TPM TPM drivers are enabled.
104 TS Appropriate touchscreen support is enabled.
105 UMS USB Mass Storage support is enabled.
106 USB USB support is enabled.
107 USBHID USB Human Interface Device support is enabled.
108 V4L Video For Linux support is enabled.
109 VGA The VGA console has been enabled.
110 VT Virtual terminal support is enabled.
111 WDT Watchdog support is enabled.
112 XT IBM PC/XT MFM hard disk support is enabled.
113 X86-32 X86-32, aka i386 architecture is enabled.
114 X86-64 X86-64 architecture is enabled.
115 More X86-64 boot options can be found in
116 Documentation/x86/x86_64/boot-options.txt .
117 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
118 XEN Xen support is enabled
120 In addition, the following text indicates that the option:
122 BUGS= Relates to possible processor bugs on the said processor.
123 KNL Is a kernel start-up parameter.
124 BOOT Is a boot loader parameter.
126 Parameters denoted with BOOT are actually interpreted by the boot
127 loader, and have no meaning to the kernel directly.
128 Do not modify the syntax of boot loader parameters without extreme
129 need or coordination with <Documentation/x86/boot.txt>.
131 There are also arch-specific kernel-parameters not documented here.
132 See for example <Documentation/x86/x86_64/boot-options.txt>.
134 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
135 a trailing = on the name of any parameter states that that parameter will
136 be entered as an environment variable, whereas its absence indicates that
137 it will appear as a kernel argument readable via /proc/cmdline by programs
138 running once the system is up.
140 The number of kernel parameters is not limited, but the length of the
141 complete command line (parameters including spaces etc.) is limited to
142 a fixed number of characters. This limit depends on the architecture
143 and is between 256 and 4096 characters. It is defined in the file
144 ./include/asm/setup.h as COMMAND_LINE_SIZE.
148 Advanced Configuration and Power Interface
149 Format: { force | off | strict | noirq | rsdt }
150 force -- enable ACPI if default was off
151 off -- disable ACPI if default was on
152 noirq -- do not use ACPI for IRQ routing
153 strict -- Be less tolerant of platforms that are not
154 strictly ACPI specification compliant.
155 rsdt -- prefer RSDT over (default) XSDT
156 copy_dsdt -- copy DSDT to memory
158 See also Documentation/power/pm.txt, pci=noacpi
160 acpi_apic_instance= [ACPI, IOAPIC]
162 2: use 2nd APIC table, if available
163 1,0: use 1st APIC table
166 acpi_backlight= [HW,ACPI]
167 acpi_backlight=vendor
169 If set to vendor, prefer vendor specific driver
170 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
171 of the ACPI video.ko driver.
173 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
174 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
176 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
177 debug output. Bits in debug_layer correspond to a
178 _COMPONENT in an ACPI source file, e.g.,
179 #define _COMPONENT ACPI_PCI_COMPONENT
180 Bits in debug_level correspond to a level in
181 ACPI_DEBUG_PRINT statements, e.g.,
182 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
183 The debug_level mask defaults to "info". See
184 Documentation/acpi/debug.txt for more information about
185 debug layers and levels.
187 Enable processor driver info messages:
188 acpi.debug_layer=0x20000000
189 Enable PCI/PCI interrupt routing info messages:
190 acpi.debug_layer=0x400000
191 Enable AML "Debug" output, i.e., stores to the Debug
192 object while interpreting AML:
193 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
194 Enable all messages related to ACPI hardware:
195 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
197 Some values produce so much output that the system is
198 unusable. The "log_buf_len" parameter may be useful
199 if you need to capture more output.
201 acpi_display_output= [HW,ACPI]
202 acpi_display_output=vendor
203 acpi_display_output=video
206 acpi_irq_balance [HW,ACPI]
207 ACPI will balance active IRQs
210 acpi_irq_nobalance [HW,ACPI]
211 ACPI will not move active IRQs (default)
214 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
215 Format: <irq>,<irq>...
217 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
219 Format: <irq>,<irq>...
221 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
223 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
224 Format: To spoof as Windows 98: ="Microsoft Windows"
226 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
227 acpi_osi="string1" # add string1 -- only one string
228 acpi_osi="!string2" # remove built-in string2
229 acpi_osi= # disable all strings
232 Override the pmtimer bug detection: force the kernel
233 to assume that this machine's pmtimer latches its value
234 and always returns good values.
236 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
237 Format: { level | edge | high | low }
239 acpi_serialize [HW,ACPI] force serialization of AML methods
241 acpi_skip_timer_override [HW,ACPI]
242 Recognize and ignore IRQ0/pin2 Interrupt Override.
243 For broken nForce2 BIOS resulting in XT-PIC timer.
245 acpi_sleep= [HW,ACPI] Sleep options
246 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
247 old_ordering, s4_nonvs, sci_force_enable }
248 See Documentation/power/video.txt for information on
250 s3_beep is for debugging; it makes the PC's speaker beep
251 as soon as the kernel's real-mode entry point is called.
252 s4_nohwsig prevents ACPI hardware signature from being
253 used during resume from hibernation.
254 old_ordering causes the ACPI 1.0 ordering of the _PTS
255 control method, with respect to putting devices into
256 low power states, to be enforced (the ACPI 2.0 ordering
257 of _PTS is used by default).
258 nonvs prevents the kernel from saving/restoring the
259 ACPI NVS memory during suspend/hibernation and resume.
260 sci_force_enable causes the kernel to set SCI_EN directly
261 on resume from S1/S3 (which is against the ACPI spec,
262 but some broken systems don't work without it).
264 acpi_use_timer_override [HW,ACPI]
265 Use timer override. For some broken Nvidia NF5 boards
266 that require a timer override, but don't have HPET
268 acpi_enforce_resources= [ACPI]
269 { strict | lax | no }
270 Check for resource conflicts between native drivers
271 and ACPI OperationRegions (SystemIO and SystemMemory
272 only). IO ports and memory declared in ACPI might be
273 used by the ACPI subsystem in arbitrary AML code and
274 can interfere with legacy drivers.
275 strict (default): access to resources claimed by ACPI
276 is denied; legacy drivers trying to access reserved
277 resources will fail to bind to device using them.
278 lax: access to resources claimed by ACPI is allowed;
279 legacy drivers trying to access reserved resources
280 will bind successfully but a warning message is logged.
281 no: ACPI OperationRegions are not marked as reserved,
282 no further checks are performed.
284 add_efi_memmap [EFI; X86] Include EFI memory map in
285 kernel's map of available physical RAM.
288 { off | try_unsupported }
289 off: disable AGP support
290 try_unsupported: try to drive unsupported chipsets
291 (may crash computer or cause data corruption)
294 See Documentation/sound/alsa/alsa-parameters.txt
297 Allow the default userspace alignment fault handler
298 behaviour to be specified. Bit 0 enables warnings,
299 bit 1 enables fixups, and bit 2 sends a segfault.
301 amd_iommu= [HW,X86-84]
302 Pass parameters to the AMD IOMMU driver in the system.
304 fullflush - enable flushing of IO/TLB entries when
305 they are unmapped. Otherwise they are
306 flushed before they will be reused, which
308 off - do not initialize any AMD IOMMU found in
311 amijoy.map= [HW,JOY] Amiga joystick support
312 Map of devices attached to JOY0DAT and JOY1DAT
314 See also Documentation/kernel/input/joystick.txt
316 analog.map= [HW,JOY] Analog joystick and gamepad support
317 Specifies type or capabilities of an analog joystick
318 connected to one of 16 gameports
319 Format: <type1>,<type2>,..<type16>
322 Power management functions (SPARCstation-4/5 + deriv.)
324 Disable APC CPU standby support. SPARCstation-Fox does
325 not play well with APC CPU idle - disable it if you have
326 APC and your system crashes randomly.
328 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
329 Change the output verbosity whilst booting
330 Format: { quiet (default) | verbose | debug }
331 Change the amount of debugging information output
332 when initialising the APIC and IO-APIC components.
335 See Documentation/networking/ipv6.txt.
337 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
338 Limit apic dumping. The parameter defines the maximal
339 number of local apics being dumped. Also it is possible
340 to set it to "all" by meaning -- no limit here.
341 Format: { 1 (default) | 2 | ... | all }.
342 The parameter valid if only apic=debug or
343 apic=verbose is specified.
344 Example: apic=debug show_lapic=all
346 apm= [APM] Advanced Power Management
347 See header of arch/x86/kernel/apm_32.c.
349 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
350 Format: <io>,<irq>,<nodeID>
354 atarimouse= [HW,MOUSE] Atari Mouse
356 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
357 EzKey and similar keyboards
359 atkbd.reset= [HW] Reset keyboard during initialization
361 atkbd.set= [HW] Select keyboard code set
362 Format: <int> (2 = AT (default), 3 = PS/2)
364 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
367 atkbd.softraw= [HW] Choose between synthetic and real raw mode
368 Format: <bool> (0 = real, 1 = synthetic (default))
370 atkbd.softrepeat= [HW]
371 Use software keyboard repeat
375 baycom_epp= [HW,AX25]
378 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
380 See header of drivers/net/hamradio/baycom_par.c.
382 baycom_ser_fdx= [HW,AX25]
383 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
384 Format: <io>,<irq>,<mode>[,<baud>]
385 See header of drivers/net/hamradio/baycom_ser_fdx.c.
387 baycom_ser_hdx= [HW,AX25]
388 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
389 Format: <io>,<irq>,<mode>
390 See header of drivers/net/hamradio/baycom_ser_hdx.c.
392 boot_delay= Milliseconds to delay each printk during boot.
393 Values larger than 10 seconds (10000) are changed to
397 bootmem_debug [KNL] Enable bootmem allocator debug messages.
399 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
400 bttv.radio= Most important insmod options are available as
402 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
403 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
405 c101= [NET] Moxa C101 synchronous serial card
407 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
408 Sometimes CPU hardware bugs make them report the cache
409 size incorrectly. The kernel will attempt work arounds
410 to fix known problems, but for some CPUs it is not
411 possible to determine what the correct size should be.
412 This option provides an override for these situations.
415 [SECURITY] Disable capabilities. This would normally
416 be used only if an alternative security model is to be
417 configured. Potentially dangerous and should only be
418 used if you are entirely sure of the consequences.
420 ccw_timeout_log [S390]
421 See Documentation/s390/CommonIO for details.
423 cgroup_disable= [KNL] Disable a particular controller
424 Format: {name of the controller(s) to disable}
425 {Currently supported controllers - "memory"}
427 checkreqprot [SELINUX] Set initial checkreqprot flag value.
428 Format: { "0" | "1" }
429 See security/selinux/Kconfig help text.
430 0 -- check protection applied by kernel (includes
431 any implied execute protection).
432 1 -- check protection requested by application.
433 Default value is set via a kernel config option.
434 Value can be changed at runtime via
435 /selinux/checkreqprot.
438 See Documentation/s390/CommonIO for details.
440 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
442 Forces specified clocksource (if available) to be used
443 when calculating gettimeofday(). If specified
444 clocksource is not available, it defaults to PIT.
445 Format: { pit | tsc | cyclone | pmtmr }
447 clocksource= Override the default clocksource
449 Override the default clocksource and use the clocksource
450 with the name specified.
451 Some clocksource names to choose from, depending on
453 [all] jiffies (this is the base, fallback clocksource)
455 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
456 pxa_timer,timer3,32k_counter,timer0_1
458 [X86-32] pit,hpet,tsc,vmi-timer;
459 scx200_hrt on Geode; cyclone on IBM x440
467 clearcpuid=BITNUM [X86]
468 Disable CPUID feature X for the kernel. See
469 arch/x86/include/asm/cpufeature.h for the valid bit
470 numbers. Note the Linux specific bits are not necessarily
471 stable over kernel options, but the vendor specific
473 Also note that user programs calling CPUID directly
474 or using the feature without checking anything
475 will still see it. This just prevents it from
476 being used by the kernel or shown in /proc/cpuinfo.
477 Also note the kernel might malfunction if you disable
480 cmo_free_hint= [PPC] Format: { yes | no }
481 Specify whether pages are marked as being inactive
482 when they are freed. This is used in CMO environments
483 to determine OS memory pressure for page stealing by
487 code_bytes [X86] How many bytes of object code to print
492 com20020= [HW,NET] ARCnet - COM20020 chipset
494 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
496 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
500 ARCnet - COM90xx chipset (memory-mapped buffers)
501 Format: <io>[,<irq>[,<memstart>]]
503 condev= [HW,S390] console device
506 console= [KNL] Output console device and options.
508 tty<n> Use the virtual console device <n>.
512 Use the specified serial port. The options are of
513 the form "bbbbpnf", where "bbbb" is the baud rate,
514 "p" is parity ("n", "o", or "e"), "n" is number of
515 bits, and "f" is flow control ("r" for RTS or
516 omit it). Default is "9600n8".
518 See Documentation/serial-console.txt for more
520 Documentation/networking/netconsole.txt for an
523 uart[8250],io,<addr>[,options]
524 uart[8250],mmio,<addr>[,options]
525 Start an early, polled-mode console on the 8250/16550
526 UART at the specified I/O port or MMIO address,
527 switching to the matching ttyS device later. The
528 options are the same as for ttyS, above.
530 If the device connected to the port is not a TTY but a braille
531 device, prepend "brl," before the device type, for instance
533 For now, only VisioBraille is supported.
535 consoleblank= [KNL] The console blank (screen saver) timeout in
536 seconds. Defaults to 10*60 = 10mins. A value of 0
537 disables the blank timer.
540 [KNL] Change the default value for
541 /proc/<pid>/coredump_filter.
542 See also Documentation/filesystems/proc.txt.
544 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
546 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
548 crashkernel=nn[KMG]@ss[KMG]
549 [KNL] Reserve a chunk of physical memory to
550 hold a kernel to switch to with kexec on panic.
552 crashkernel=range1:size1[,range2:size2,...][@offset]
553 [KNL] Same as above, but depends on the memory
554 in the running system. The syntax of range is
555 start-[end] where start and end are both
556 a memory unit (amount[KMG]). See also
557 Documentation/kdump/kdump.txt for a example.
562 cs89x0_media= [HW,NET]
563 Format: { rj45 | aui | bnc }
566 See header of drivers/s390/block/dasd_devmap.c.
568 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
569 (one device per port)
570 Format: <port#>,<type>
571 See also Documentation/input/joystick-parport.txt
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: {"anticipatory" | "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.
986 iomem= Disable strict checking of access to MMIO memory
987 strict regions from userspace.
1003 io7= [HW] IO7 for Marvel based alpha systems
1004 See comment before marvel_specify_io7 in
1005 arch/alpha/kernel/core_marvel.c.
1007 io_delay= [X86] I/O delay method
1009 Standard port 0x80 based delay
1011 Alternate port 0xed based delay (needed on some systems)
1013 Simple two microseconds delay
1018 See Documentation/filesystems/nfs/nfsroot.txt.
1020 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1021 See comment before ip2_setup() in
1022 drivers/char/ip2/ip2base.c.
1025 When an interrupt is not handled search all handlers
1026 for it. Intended to get systems with badly broken
1030 When an interrupt is not handled search all handlers
1031 for it. Also check all handlers each timer
1032 interrupt. Intended to get systems with badly broken
1036 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1038 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1040 <cpu number>,...,<cpu number>
1042 <cpu number>-<cpu number>
1043 (must be a positive range in ascending order)
1045 <cpu number>,...,<cpu number>-<cpu number>
1047 This option can be used to specify one or more CPUs
1048 to isolate from the general SMP balancing and scheduling
1049 algorithms. You can move a process onto or off an
1050 "isolated" CPU via the CPU affinity syscalls or cpuset.
1051 <cpu number> begins at 0 and the maximum value is
1052 "number of CPUs in system - 1".
1054 This option is the preferred way to isolate CPUs. The
1055 alternative -- manually setting the CPU mask of all
1056 tasks in the system -- can cause problems and
1057 suboptimal load balancer performance.
1061 js= [HW,JOY] Analog joystick
1062 See Documentation/input/joystick.txt.
1066 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1067 specifies the amount of memory usable by the kernel
1068 for non-movable allocations. The requested amount is
1069 spread evenly throughout all nodes in the system. The
1070 remaining memory in each node is used for Movable
1071 pages. In the event, a node is too small to have both
1072 kernelcore and Movable pages, kernelcore pages will
1073 take priority and other nodes will have a larger number
1074 of kernelcore pages. The Movable zone is used for the
1075 allocation of pages that may be reclaimed or moved
1076 by the page migration subsystem. This means that
1077 HugeTLB pages may not be allocated from this zone.
1078 Note that allocations like PTEs-from-HighMem still
1079 use the HighMem zone if it exists, and the Normal
1080 zone if it does not.
1082 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1083 Format: <Controller#>[,poll interval]
1084 The controller # is the number of the ehci usb debug
1085 port as it is probed via PCI. The poll interval is
1086 optional and is the number seconds in between
1087 each poll cycle to the debug port in case you need
1088 the functionality for interrupting the kernel with
1089 gdb or control-c on the dbgp connection. When
1090 not using this parameter you use sysrq-g to break into
1091 the kernel debugger.
1093 kgdboc= [KGDB,HW] kgdb over consoles.
1094 Requires a tty driver that supports console polling,
1095 or a supported polling keyboard driver (non-usb).
1096 Serial only format: <serial_device>[,baud]
1097 keyboard only format: kbd
1098 keyboard and serial format: kbd,<serial_device>[,baud]
1099 Optional Kernel mode setting:
1100 kms, kbd format: kms,kbd
1101 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1103 kgdbwait [KGDB] Stop kernel execution and enter the
1104 kernel debugger at the earliest opportunity.
1106 kmac= [MIPS] korina ethernet MAC address.
1107 Configure the RouterBoard 532 series on-chip
1108 Ethernet adapter MAC address.
1110 kmemleak= [KNL] Boot-time kmemleak enable/disable
1111 Valid arguments: on, off
1114 kstack=N [X86] Print N words from the kernel stack
1117 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1118 Default is 0 (don't ignore, but inject #GP)
1120 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1121 Default is 1 (enabled)
1123 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1126 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1128 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1130 kvm-intel.bypass_guest_pf=
1131 [KVM,Intel] Disables bypassing of guest page faults
1132 on Intel chips. Default is 1 (enabled)
1134 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1135 (virtualized MMU) support on capable Intel chips.
1136 Default is 1 (enabled)
1138 kvm-intel.emulate_invalid_guest_state=
1139 [KVM,Intel] Enable emulation of invalid guest states
1140 Default is 0 (disabled)
1142 kvm-intel.flexpriority=
1143 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1144 Default is 1 (enabled)
1146 kvm-intel.unrestricted_guest=
1147 [KVM,Intel] Disable unrestricted guest feature
1148 (virtualized real and unpaged mode) on capable
1149 Intel chips. Default is 1 (enabled)
1151 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1152 feature (tagged TLBs) on capable Intel chips.
1153 Default is 1 (enabled)
1159 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1162 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1165 libata.dma= [LIBATA] DMA control
1166 libata.dma=0 Disable all PATA and SATA DMA
1167 libata.dma=1 PATA and SATA Disk DMA only
1168 libata.dma=2 ATAPI (CDROM) DMA only
1169 libata.dma=4 Compact Flash DMA only
1170 Combinations also work, so libata.dma=3 enables DMA
1171 for disks and CDROMs, but not CFs.
1173 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1174 libata.ignore_hpa=0 keep BIOS limits (default)
1175 libata.ignore_hpa=1 ignore limits, using full disk
1177 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1181 libata.force= [LIBATA] Force configurations. The format is comma
1182 separated list of "[ID:]VAL" where ID is
1183 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1184 matching port, link or device. Basically, it matches
1185 the ATA ID string printed on console by libata. If
1186 the whole ID part is omitted, the last PORT and DEVICE
1187 values are used. If ID hasn't been specified yet, the
1188 configuration applies to all ports, links and devices.
1190 If only DEVICE is omitted, the parameter applies to
1191 the port and all links and devices behind it. DEVICE
1192 number of 0 either selects the first device or the
1193 first fan-out link behind PMP device. It does not
1194 select the host link. DEVICE number of 15 selects the
1195 host link and device attached to it.
1197 The VAL specifies the configuration to force. As long
1198 as there's no ambiguity shortcut notation is allowed.
1199 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1200 The following configurations can be forced.
1202 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1203 Any ID with matching PORT is used.
1205 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1207 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1208 udma[/][16,25,33,44,66,100,133] notation is also
1211 * [no]ncq: Turn on or off NCQ.
1213 * nohrst, nosrst, norst: suppress hard, soft
1216 * dump_id: dump IDENTIFY data.
1218 If there are multiple matching configurations changing
1219 the same attribute, the last one is used.
1221 memblock=debug [KNL] Enable memblock debug messages.
1223 load_ramdisk= [RAM] List of ramdisks to load from floppy
1224 See Documentation/blockdev/ramdisk.txt.
1226 lockd.nlm_grace_period=P [NFS] Assign grace period.
1229 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1232 lockd.nlm_timeout=T [NFS] Assign timeout value.
1235 lockd.nlm_udpport=M [NFS] Assign UDP port.
1238 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1241 loglevel= All Kernel Messages with a loglevel smaller than the
1242 console loglevel will be printed to the console. It can
1243 also be changed with klogd or other programs. The
1244 loglevels are defined as follows:
1246 0 (KERN_EMERG) system is unusable
1247 1 (KERN_ALERT) action must be taken immediately
1248 2 (KERN_CRIT) critical conditions
1249 3 (KERN_ERR) error conditions
1250 4 (KERN_WARNING) warning conditions
1251 5 (KERN_NOTICE) normal but significant condition
1252 6 (KERN_INFO) informational
1253 7 (KERN_DEBUG) debug-level messages
1255 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1256 Format: { n | nk | nM }
1257 n must be a power of two. The default size
1258 is set in the kernel config file.
1260 logo.nologo [FB] Disables display of the built-in Linux logo.
1261 This may be used to provide more screen space for
1262 kernel log messages and is useful when debugging
1263 kernel boot problems.
1265 lp=0 [LP] Specify parallel ports to use, e.g,
1266 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1267 lp=reset first parallel port). 'lp=0' disables the
1268 lp=auto printer driver. 'lp=reset' (which can be
1269 specified in addition to the ports) causes
1270 attached printers to be reset. Using
1271 lp=port1,port2,... specifies the parallel ports
1272 to associate lp devices with, starting with
1273 lp0. A port specification may be 'none' to skip
1274 that lp device, or a parport name such as
1275 'parport0'. Specifying 'lp=auto' instead of a
1276 port specification list means that device IDs
1277 from each port should be examined, to see if
1278 an IEEE 1284-compliant printer is attached; if
1279 so, the driver will manage that printer.
1280 See also header of drivers/char/lp.c.
1283 Sets loops_per_jiffy to given constant, thus avoiding
1284 time-consuming boot-time autodetection (up to 250 ms per
1285 CPU). 0 enables autodetection (default). To determine
1286 the correct value for your kernel, boot with normal
1287 autodetection and see what value is printed. Note that
1288 on SMP systems the preset will be applied to all CPUs,
1289 which is likely to cause problems if your CPUs need
1290 significantly divergent settings. An incorrect value
1291 will cause delays in the kernel to be wrong, leading to
1292 unpredictable I/O errors and other breakage. Although
1293 unlikely, in the extreme case this might damage your
1297 Format: <io>,<irq>,<dma>
1299 machvec= [IA64] Force the use of a particular machine-vector
1300 (machvec) in a generic kernel.
1301 Example: machvec=hpzx1_swiotlb
1303 machtype= [Loongson] Share the same kernel image file between different
1305 Example: machtype=lemote-yeeloong-2f-7inch
1307 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1308 than or equal to this physical address is ignored.
1310 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1311 should make use of. maxcpus=n : n >= 0 limits the
1312 kernel to using 'n' processors. n=0 is a special case,
1313 it is equivalent to "nosmp", which also disables
1316 max_loop= [LOOP] Maximum number of loopback devices that can
1322 mce [X86-32] Machine Check Exception
1324 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1326 md= [HW] RAID subsystems devices and level
1327 See Documentation/md.txt.
1330 Format: <first>,<last>
1331 Specifies range of consoles to be captured by the MDA.
1333 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1334 Amount of memory to be used when the kernel is not able
1335 to see the whole system memory or for test.
1336 [X86-32] Use together with memmap= to avoid physical
1337 address space collisions. Without memmap= PCI devices
1338 could be placed at addresses belonging to unused RAM.
1340 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1344 [KNL,SH] Allow user to override the default size for
1345 per-device physically contiguous DMA buffers.
1347 memmap=exactmap [KNL,X86] Enable setting of an exact
1348 E820 memory map, as specified by the user.
1349 Such memmap=exactmap lines can be constructed based on
1350 BIOS output or other requirements. See the memmap=nn@ss
1353 memmap=nn[KMG]@ss[KMG]
1354 [KNL] Force usage of a specific region of memory
1355 Region of memory to be used, from ss to ss+nn.
1357 memmap=nn[KMG]#ss[KMG]
1358 [KNL,ACPI] Mark specific memory as ACPI data.
1359 Region of memory to be used, from ss to ss+nn.
1361 memmap=nn[KMG]$ss[KMG]
1362 [KNL,ACPI] Mark specific memory as reserved.
1363 Region of memory to be used, from ss to ss+nn.
1364 Example: Exclude memory from 0x18690000-0x1869ffff
1365 memmap=64K$0x18690000
1367 memmap=0x10000$0x18690000
1369 memory_corruption_check=0/1 [X86]
1370 Some BIOSes seem to corrupt the first 64k of
1371 memory when doing things like suspend/resume.
1372 Setting this option will scan the memory
1373 looking for corruption. Enabling this will
1374 both detect corruption and prevent the kernel
1375 from using the memory being corrupted.
1376 However, its intended as a diagnostic tool; if
1377 repeatable BIOS-originated corruption always
1378 affects the same memory, you can use memmap=
1379 to prevent the kernel from using that memory.
1381 memory_corruption_check_size=size [X86]
1382 By default it checks for corruption in the low
1383 64k, making this memory unavailable for normal
1384 use. Use this parameter to scan for
1385 corruption in more or less memory.
1387 memory_corruption_check_period=seconds [X86]
1388 By default it checks for corruption every 60
1389 seconds. Use this parameter to check at some
1390 other rate. 0 disables periodic checking.
1392 memtest= [KNL,X86] Enable memtest
1394 default : 0 <disable>
1395 Specifies the number of memtest passes to be
1396 performed. Each pass selects another test
1397 pattern from a given set of patterns. Memtest
1398 fills the memory with this pattern, validates
1399 memory contents and reserves bad memory
1400 regions that are detected.
1402 meye.*= [HW] Set MotionEye Camera parameters
1403 See Documentation/video4linux/meye.txt.
1405 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1406 Multi-Function General Purpose Timers on AMD Geode
1409 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1410 the BIOS has incorrectly applied a workaround. TinyBIOS
1411 version 0.98 is known to be affected, 0.99 fixes the
1412 problem by letting the user disable the workaround.
1416 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1417 physical address is ignored.
1419 mini2440= [ARM,HW,KNL]
1420 Format:[0..2][b][c][t]
1422 MINI2440 configuration specification:
1423 0 - The attached screen is the 3.5" TFT
1424 1 - The attached screen is the 7" TFT
1425 2 - The VGA Shield is attached (1024x768)
1426 Leaving out the screen size parameter will not load
1427 the TFT driver, and the framebuffer will be left
1429 b - Enable backlight. The TFT backlight pin will be
1430 linked to the kernel VESA blanking code and a GPIO
1431 LED. This parameter is not necessary when using the
1433 c - Enable the s3c camera interface.
1434 t - Reserved for enabling touchscreen support. The
1435 touchscreen support is not enabled in the mainstream
1436 kernel as of 2.6.30, a preliminary port can be found
1437 in the "bleeding edge" mini2440 support kernel at
1438 http://repo.or.cz/w/linux-2.6/mini2440.git
1441 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1442 parameter allows control of the logging verbosity for
1443 the additional memory initialisation checks. A value
1444 of 0 disables mminit logging and a level of 4 will
1445 log everything. Information is printed at KERN_DEBUG
1446 so loglevel=8 may also need to be specified.
1449 [MOUSE] Maximum time between finger touching and
1450 leaving touchpad surface for touch to be considered
1451 a tap and be reported as a left button click (for
1452 touchpads working in absolute mode only).
1454 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1455 reporting absolute coordinates, such as tablets
1456 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1457 reporting absolute coordinates, such as tablets
1459 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1460 is similar to kernelcore except it specifies the
1461 amount of memory used for migratable allocations.
1462 If both kernelcore and movablecore is specified,
1463 then kernelcore will be at *least* the specified
1464 value but may be more. If movablecore on its own
1465 is specified, the administrator must be careful
1466 that the amount of memory usable for all allocations
1469 MTD_Partition= [MTD]
1470 Format: <name>,<region-number>,<size>,<offset>
1472 MTD_Region= [MTD] Format:
1473 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1476 See drivers/mtd/cmdlinepart.c.
1478 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1480 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1482 boundary - index of last SLC block on Flex-OneNAND.
1483 The remaining blocks are configured as MLC blocks.
1484 lock - Configure if Flex-OneNAND boundary should be locked.
1485 Once locked, the boundary cannot be changed.
1486 1 indicates lock status, 0 indicates unlock status.
1489 ARM/S3C2412 JIVE boot control
1491 See arch/arm/mach-s3c2412/mach-jive.c
1493 mtouchusb.raw_coordinates=
1494 [HW] Make the MicroTouch USB driver use raw coordinates
1495 ('y', default) or cooked coordinates ('n')
1497 mtrr_chunk_size=nn[KMG] [X86]
1498 used for mtrr cleanup. It is largest continuous chunk
1499 that could hold holes aka. UC entries.
1501 mtrr_gran_size=nn[KMG] [X86]
1502 Used for mtrr cleanup. It is granularity of mtrr block.
1504 Large value could prevent small alignment from
1507 mtrr_spare_reg_nr=n [X86]
1509 Range: 0,7 : spare reg number
1511 Used for mtrr cleanup. It is spare mtrr entries number.
1512 Set to 2 or more if your graphical card needs more.
1514 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1516 netdev= [NET] Network devices parameters
1517 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1518 Note that mem_start is often overloaded to mean
1519 something different and driver-specific.
1520 This usage is only documented in each driver source
1524 [NETFILTER] Enable connection tracking flow accounting
1525 0 to disable accounting
1526 1 to enable accounting
1530 See Documentation/filesystems/nfs/nfsroot.txt.
1532 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1533 See Documentation/filesystems/nfs/nfsroot.txt.
1535 nfs.callback_tcpport=
1536 [NFS] set the TCP port on which the NFSv4 callback
1537 channel should listen.
1540 [NFS] sets the pathname to the program which is used
1541 to update the NFS client cache entries.
1543 nfs.cache_getent_timeout=
1544 [NFS] sets the timeout after which an attempt to
1545 update a cache entry is deemed to have failed.
1547 nfs.idmap_cache_timeout=
1548 [NFS] set the maximum lifetime for idmapper cache
1552 [NFS] enable 64-bit inode numbers.
1553 If zero, the NFS client will fake up a 32-bit inode
1554 number for the readdir() and stat() syscalls instead
1555 of returning the full 64-bit number.
1556 The default is to return 64-bit inode numbers.
1558 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1559 when a NMI is triggered.
1560 Format: [state][,regs][,debounce][,die]
1562 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1563 Format: [panic,][num]
1565 0 - turn nmi_watchdog off
1566 1 - use the IO-APIC timer for the NMI watchdog
1567 2 - use the local APIC for the NMI watchdog using
1568 a performance counter. Note: This will use one
1569 performance counter and the local APIC's performance
1571 When panic is specified, panic when an NMI watchdog
1573 This is useful when you use a panic=... timeout and
1574 need the box quickly up again.
1575 Instead of 1 and 2 it is possible to use the following
1576 symbolic names: lapic and ioapic
1577 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1579 netpoll.carrier_timeout=
1580 [NET] Specifies amount of time (in seconds) that
1581 netpoll should wait for a carrier. By default netpoll
1584 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1585 emulation library even if a 387 maths coprocessor
1589 [HW] Never suspend the console
1590 Disable suspending of consoles during suspend and
1591 hibernate operations. Once disabled, debugging
1592 messages can reach various consoles while the rest
1593 of the system is being put to sleep (ie, while
1594 debugging driver suspend/resume hooks). This may
1595 not work reliably with all consoles, but is known
1596 to work with serial and VGA consoles.
1598 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1599 caches in the slab allocator. Saves per-node memory,
1600 but will impact performance.
1604 noapic [SMP,APIC] Tells the kernel to not make use of any
1605 IOAPICs that may be present in the system.
1607 nobats [PPC] Do not use BATs for mapping kernel lowmem
1608 on "Classic" PPC cores.
1612 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1614 nodelayacct [KNL] Disable per-task delay accounting
1616 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1618 nodsp [SH] Disable hardware DSP at boot time.
1620 noefi [X86] Disable EFI runtime services support.
1625 On X86-32 available only on PAE configured kernels.
1626 noexec=on: enable non-executable mappings (default)
1627 noexec=off: disable non-executable mappings
1630 This affects only 32-bit executables.
1631 noexec32=on: enable non-executable mappings (default)
1632 read doesn't imply executable mappings
1633 noexec32=off: disable non-executable mappings
1634 read implies executable mappings
1636 nofpu [SH] Disable hardware FPU at boot time.
1638 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1639 register save and restore. The kernel will only save
1640 legacy floating-point registers on task switch.
1642 noxsave [BUGS=X86] Disables x86 extended register state save
1643 and restore using xsave. The kernel will fallback to
1644 enabling legacy floating-point and sse state.
1646 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1647 wfi(ARM) instruction doesn't work correctly and not to
1648 use it. This is also useful when using JTAG debugger.
1650 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1651 instruction doesn't work correctly and not to
1654 no_file_caps Tells the kernel not to honor file capabilities. The
1655 only way then for a file to be executed with privilege
1656 is to be setuid root or executed by root.
1658 nohalt [IA-64] Tells the kernel not to use the power saving
1659 function PAL_HALT_LIGHT when idle. This increases
1660 power-consumption. On the positive side, it reduces
1661 interrupt wake-up latency, which may improve performance
1662 in certain environments such as networked servers or
1665 nohz= [KNL] Boottime enable/disable dynamic ticks
1666 Valid arguments: on, off
1669 noiotrap [SH] Disables trapped I/O port accesses.
1671 noirqdebug [X86-32] Disables the code which attempts to detect and
1672 disable unhandled interrupt sources.
1674 no_timer_check [X86,APIC] Disables the code which tests for
1675 broken timer IRQ sources.
1677 noisapnp [ISAPNP] Disables ISA PnP code.
1679 noinitrd [RAM] Tells the kernel not to load any configured
1682 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1687 nojitter [IA64] Disables jitter checking for ITC timers.
1689 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1691 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1693 noltlbs [PPC] Do not use large page/tlb entries for kernel
1694 lowmem mapping on PPC40x.
1696 nomca [IA-64] Disable machine check abort handling
1698 nomce [X86-32] Machine Check Exception
1700 nomfgpt [X86-32] Disable Multi-Function General Purpose
1701 Timer usage (for AMD Geode machines).
1703 nopat [X86] Disable PAT (page attribute table extension of
1704 pagetables) support.
1706 norandmaps Don't use address space randomization. Equivalent to
1707 echo 0 > /proc/sys/kernel/randomize_va_space
1709 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1711 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1712 with UP alternatives
1714 noresidual [PPC] Don't use residual data on PReP machines.
1716 noresume [SWSUSP] Disables resume and restores original swap
1719 no-scroll [VGA] Disables scrollback.
1720 This is required for the Braillex ib80-piezo Braille
1721 reader made by F.H. Papenmeier (Germany).
1725 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1727 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1728 and disable the IO APIC. legacy for "maxcpus=0".
1730 nosoftlockup [KNL] Disable the soft-lockup detector.
1732 noswapaccount [KNL] Disable accounting of swap in memory resource
1733 controller. (See Documentation/cgroups/memory.txt)
1735 nosync [HW,M68K] Disables sync negotiation for all devices.
1737 notsc [BUGS=X86-32] Disable Time Stamp Counter
1739 nousb [USB] Disable the USB subsystem
1741 nowatchdog [KNL] Disable the lockup detector.
1745 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1747 nptcg= [IA64] Override max number of concurrent global TLB
1748 purges which is reported from either PAL_VM_SUMMARY or
1751 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1752 could support. nr_cpus=n : n >= 1 limits the kernel to
1753 supporting 'n' processors. Later in runtime you can not
1754 use hotplug cpu feature to put more cpu back to online.
1755 just like you compile the kernel NR_CPUS=n
1757 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1759 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1760 one of ['zone', 'node', 'default'] can be specified
1761 This can be set from sysctl after boot.
1762 See Documentation/sysctl/vm.txt for details.
1764 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1765 See Documentation/debugging-via-ohci1394.txt for more
1768 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1769 Rather than timing out after 20 ms if an EC
1770 command is not properly ACKed, override the length
1771 of the timeout. We have interrupts disabled while
1772 waiting for the ACK, so if this is set too high
1773 interrupts *may* be lost!
1775 omap_mux= [OMAP] Override bootloader pin multiplexing.
1776 Format: <mux_mode0.mode_name=value>...
1777 For example, to override I2C bus2:
1778 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1780 oprofile.timer= [HW]
1781 Use timer interrupt instead of performance counters
1783 oprofile.cpu_type= Force an oprofile cpu type
1784 This might be useful if you have an older oprofile
1785 userland or if you want common events.
1786 Format: { arch_perfmon }
1787 arch_perfmon: [X86] Force use of architectural
1788 perfmon on Intel CPUs instead of the
1789 CPU specific event set.
1792 See Documentation/sound/oss/oss-parameters.txt
1794 panic= [KNL] Kernel behaviour on panic
1797 parkbd.port= [HW] Parallel port number the keyboard adapter is
1798 connected to, default is 0.
1800 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1801 0 for XT, 1 for AT (default is AT).
1804 parport= [HW,PPT] Specify parallel ports. 0 disables.
1805 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1806 Use 'auto' to force the driver to use any
1807 IRQ/DMA settings detected (the default is to
1808 ignore detected IRQ/DMA settings because of
1809 possible conflicts). You can specify the base
1810 address, IRQ, and DMA settings; IRQ and DMA
1811 should be numbers, or 'auto' (for using detected
1812 settings on that particular port), or 'nofifo'
1813 (to avoid using a FIFO even if it is detected).
1814 Parallel ports are assigned in the order they
1815 are specified on the command line, starting
1818 parport_init_mode= [HW,PPT]
1819 Configure VIA parallel port to operate in
1820 a specific mode. This is necessary on Pegasos
1821 computer where firmware has no options for setting
1822 up parallel port mode and sets it to spp.
1823 Currently this function knows 686a and 8231 chips.
1824 Format: [spp|ps2|epp|ecp|ecpepp]
1827 Halt all CPUs after the first oops has been printed for
1828 the specified number of seconds. This is to be used if
1829 your oopses keep scrolling off the screen.
1834 See header of drivers/block/paride/pcd.c.
1835 See also Documentation/blockdev/paride.txt.
1837 pci=option[,option...] [PCI] various PCI subsystem options:
1838 earlydump [X86] dump PCI config space before the kernel
1840 off [X86] don't probe for the PCI bus
1841 bios [X86-32] force use of PCI BIOS, don't access
1842 the hardware directly. Use this if your machine
1843 has a non-standard PCI host bridge.
1844 nobios [X86-32] disallow use of PCI BIOS, only direct
1845 hardware access methods are allowed. Use this
1846 if you experience crashes upon bootup and you
1847 suspect they are caused by the BIOS.
1848 conf1 [X86] Force use of PCI Configuration
1850 conf2 [X86] Force use of PCI Configuration
1852 noaer [PCIE] If the PCIEAER kernel config parameter is
1853 enabled, this kernel boot option can be used to
1854 disable the use of PCIE advanced error reporting.
1855 nodomains [PCI] Disable support for multiple PCI
1856 root domains (aka PCI segments, in ACPI-speak).
1857 nommconf [X86] Disable use of MMCONFIG for PCI
1859 check_enable_amd_mmconf [X86] check for and enable
1860 properly configured MMIO access to PCI
1861 config space on AMD family 10h CPU
1862 nomsi [MSI] If the PCI_MSI kernel config parameter is
1863 enabled, this kernel boot option can be used to
1864 disable the use of MSI interrupts system-wide.
1865 noioapicquirk [APIC] Disable all boot interrupt quirks.
1866 Safety option to keep boot IRQs enabled. This
1867 should never be necessary.
1868 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1869 primary IO-APIC for bridges that cannot disable
1870 boot IRQs. This fixes a source of spurious IRQs
1871 when the system masks IRQs.
1872 noioapicreroute [APIC] Disable workaround that uses the
1873 boot IRQ equivalent of an IRQ that connects to
1874 a chipset where boot IRQs cannot be disabled.
1875 The opposite of ioapicreroute.
1876 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1877 routing table. These calls are known to be buggy
1878 on several machines and they hang the machine
1879 when used, but on other computers it's the only
1880 way to get the interrupt routing table. Try
1881 this option if the kernel is unable to allocate
1882 IRQs or discover secondary PCI buses on your
1884 rom [X86] Assign address space to expansion ROMs.
1885 Use with caution as certain devices share
1886 address decoders between ROMs and other
1888 norom [X86] Do not assign address space to
1889 expansion ROMs that do not already have
1890 BIOS assigned address ranges.
1891 nobar [X86] Do not assign address space to the
1892 BARs that weren't assigned by the BIOS.
1893 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1894 assigned automatically to PCI devices. You can
1895 make the kernel exclude IRQs of your ISA cards
1897 pirqaddr=0xAAAAA [X86] Specify the physical address
1898 of the PIRQ table (normally generated
1899 by the BIOS) if it is outside the
1900 F0000h-100000h range.
1901 lastbus=N [X86] Scan all buses thru bus #N. Can be
1902 useful if the kernel is unable to find your
1903 secondary buses and you want to tell it
1904 explicitly which ones they are.
1905 assign-busses [X86] Always assign all PCI bus
1906 numbers ourselves, overriding
1907 whatever the firmware may have done.
1908 usepirqmask [X86] Honor the possible IRQ mask stored
1909 in the BIOS $PIR table. This is needed on
1910 some systems with broken BIOSes, notably
1911 some HP Pavilion N5400 and Omnibook XE3
1912 notebooks. This will have no effect if ACPI
1913 IRQ routing is enabled.
1914 noacpi [X86] Do not use ACPI for IRQ routing
1915 or for PCI scanning.
1916 use_crs [X86] Use PCI host bridge window information
1917 from ACPI. On BIOSes from 2008 or later, this
1918 is enabled by default. If you need to use this,
1919 please report a bug.
1920 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1921 If you need to use this, please report a bug.
1922 routeirq Do IRQ routing for all PCI devices.
1923 This is normally done in pci_enable_device(),
1924 so this option is a temporary workaround
1925 for broken drivers that don't call it.
1926 skip_isa_align [X86] do not align io start addr, so can
1927 handle more pci cards
1928 firmware [ARM] Do not re-enumerate the bus but instead
1929 just use the configuration from the
1930 bootloader. This is currently used on
1931 IXP2000 systems where the bus has to be
1932 configured a certain way for adjunct CPUs.
1933 noearly [X86] Don't do any early type 1 scanning.
1934 This might help on some broken boards which
1935 machine check when some devices' config space
1936 is read. But various workarounds are disabled
1937 and some IOMMU drivers will not work.
1938 bfsort Sort PCI devices into breadth-first order.
1939 This sorting is done to get a device
1940 order compatible with older (<= 2.4) kernels.
1941 nobfsort Don't sort PCI devices into breadth-first order.
1942 cbiosize=nn[KMG] The fixed amount of bus space which is
1943 reserved for the CardBus bridge's IO window.
1944 The default value is 256 bytes.
1945 cbmemsize=nn[KMG] The fixed amount of bus space which is
1946 reserved for the CardBus bridge's memory
1947 window. The default value is 64 megabytes.
1950 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1951 Specifies alignment and device to reassign
1952 aligned memory resources.
1953 If <order of align> is not specified,
1954 PAGE_SIZE is used as alignment.
1955 PCI-PCI bridge can be specified, if resource
1956 windows need to be expanded.
1957 ecrc= Enable/disable PCIe ECRC (transaction layer
1958 end-to-end CRC checking).
1959 bios: Use BIOS/firmware settings. This is the
1964 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1967 force Enable ASPM even on devices that claim not to support it.
1968 WARNING: Forcing ASPM on may cause system lockups.
1970 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
1971 Format: {auto|force}[,nomsi]
1972 auto Use native PCIe PME signaling if the BIOS allows the
1973 kernel to control PCIe config registers of root ports.
1974 force Use native PCIe PME signaling even if the BIOS refuses
1975 to allow the kernel to control the relevant PCIe config
1977 nomsi Do not use MSI for native PCIe PME signaling (this makes
1978 all PCIe root ports use INTx for everything).
1980 pcmv= [HW,PCMCIA] BadgePAD 4
1983 See Documentation/blockdev/paride.txt.
1985 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1988 See arch/parisc/kernel/pdc_chassis.c
1990 percpu_alloc= Select which percpu first chunk allocator to use.
1991 Currently supported values are "embed" and "page".
1992 Archs may support subset or none of the selections.
1993 See comments in mm/percpu.c for details on each
1994 allocator. This parameter is primarily for debugging
1995 and performance comparison.
1998 See Documentation/blockdev/paride.txt.
2001 See Documentation/blockdev/paride.txt.
2003 pirq= [SMP,APIC] Manual mp-table setup
2004 See Documentation/x86/i386/IO-APIC.txt.
2006 plip= [PPT,NET] Parallel port network link
2007 Format: { parport<nr> | timid | 0 }
2008 See also Documentation/parport.txt.
2010 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2011 Override pmtimer IOPort with a hex value.
2015 Enable PNP debug messages. This depends on the
2016 CONFIG_PNP_DEBUG_MESSAGES option.
2022 { on | off | curr | res | no-curr | no-res }
2025 [ISAPNP] Exclude IRQs for the autoconfiguration
2028 [ISAPNP] Exclude DMAs for the autoconfiguration
2030 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2031 Ranges are in pairs (I/O port base and size).
2034 [ISAPNP] Exclude memory regions for the
2036 Ranges are in pairs (memory base and size).
2038 ports= [IP_VS_FTP] IPVS ftp helper module
2040 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2042 Format: <port>,<port>....
2044 print-fatal-signals=
2045 [KNL] debug: print fatal signals
2047 If enabled, warn about various signal handling
2048 related application anomalies: too many signals,
2049 too many POSIX.1 timers, fatal signals causing a
2052 If you hit the warning due to signal overflow,
2053 you might want to try "ulimit -i unlimited".
2057 printk.time= Show timing data prefixed to each printk message line
2058 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2060 processor.max_cstate= [HW,ACPI]
2061 Limit processor to maximum C-state
2062 max_cstate=9 overrides any DMI blacklist limit.
2064 processor.nocst [HW,ACPI]
2065 Ignore the _CST method to determine C-states,
2066 instead using the legacy FADT method
2068 profile= [KNL] Enable kernel profiling via /proc/profile
2069 Format: [schedule,]<number>
2070 Param: "schedule" - profile schedule points.
2071 Param: <number> - step/bucket size as a power of 2 for
2072 statistical time based profiling.
2073 Param: "sleep" - profile D-state sleeping (millisecs).
2074 Requires CONFIG_SCHEDSTATS
2075 Param: "kvm" - profile VM exits.
2077 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2079 See Documentation/blockdev/ramdisk.txt.
2081 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2082 probe for; one of (bare|imps|exps|lifebook|any).
2083 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2085 psmouse.resetafter= [HW,MOUSE]
2086 Try to reset the device after so many bad packets
2089 [HW,MOUSE] Set desired mouse resolution, in dpi.
2090 psmouse.smartscroll=
2091 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2092 0 = disabled, 1 = enabled (default).
2095 See Documentation/blockdev/paride.txt.
2098 [KNL] Number of legacy pty's. Overwrites compiled-in
2101 quiet [KNL] Disable most log messages
2106 See Documentation/md.txt.
2108 ramdisk_blocksize= [RAM]
2109 See Documentation/blockdev/ramdisk.txt.
2111 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2112 See Documentation/blockdev/ramdisk.txt.
2114 rcupdate.blimit= [KNL,BOOT]
2115 Set maximum number of finished RCU callbacks to process
2118 rcupdate.qhimark= [KNL,BOOT]
2119 Set threshold of queued
2120 RCU callbacks over which batch limiting is disabled.
2122 rcupdate.qlowmark= [KNL,BOOT]
2123 Set threshold of queued RCU callbacks below which
2124 batch limiting is re-enabled.
2128 Run specified binary instead of /init from the ramdisk,
2129 used for early userspace startup. See initrd.
2131 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2132 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2133 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2136 [KNL, SMP] Set scheduler's default relax_domain_level.
2137 See Documentation/cgroups/cpusets.txt.
2139 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2141 reservetop= [X86-32]
2143 Reserves a hole at the top of the kernel virtual
2146 reset_devices [KNL] Force drivers to reset the underlying device
2147 during initialization.
2150 Specify the partition device for software suspend
2152 resume_offset= [SWSUSP]
2153 Specify the offset from the beginning of the partition
2154 given by "resume=" at which the swap header is located,
2155 in <PAGE_SIZE> units (needed only for swap files).
2156 See Documentation/power/swsusp-and-swap-files.txt
2158 retain_initrd [RAM] Keep initrd memory after extraction
2160 rhash_entries= [KNL,NET]
2161 Set number of hash buckets for route cache
2163 riscom8= [HW,SERIAL]
2164 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2166 ro [KNL] Mount root device read-only on boot
2168 root= [KNL] Root filesystem
2170 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2171 mount the root filesystem
2173 rootflags= [KNL] Set root filesystem mount option string
2175 rootfstype= [KNL] Set root filesystem type
2177 rootwait [KNL] Wait (indefinitely) for root device to show up.
2178 Useful for devices that are detected asynchronously
2179 (e.g. USB and MMC devices).
2181 rw [KNL] Mount root device read-write on boot
2183 S [KNL] Run init in single mode
2186 See drivers/net/irda/sa1100_ir.c.
2188 sbni= [NET] Granch SBNI12 leased line adapter
2190 sched_debug [KNL] Enables verbose scheduler debug messages.
2192 security= [SECURITY] Choose a security module to enable at boot.
2193 If this boot parameter is not specified, only the first
2194 security module asking for security registration will be
2195 loaded. An invalid security module name will be treated
2196 as if no module has been chosen.
2198 selinux= [SELINUX] Disable or enable SELinux at boot time.
2199 Format: { "0" | "1" }
2200 See security/selinux/Kconfig help text.
2203 Default value is set via kernel config option.
2204 If enabled at boot time, /selinux/disable can be used
2205 later to disable prior to initial policy load.
2207 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2208 Format: { "0" | "1" }
2209 See security/apparmor/Kconfig help text
2212 Default value is set via kernel config option.
2214 serialnumber [BUGS=X86-32]
2217 Maximal number of shapers.
2219 show_msr= [x86] show boot-time MSR settings
2220 Format: { <integer> }
2221 Show boot-time (BIOS-initialized) MSR settings.
2222 The parameter means the number of CPUs to show,
2223 for example 1 means boot CPU only.
2230 slub_debug[=options[,slabs]] [MM, SLUB]
2231 Enabling slub_debug allows one to determine the
2232 culprit if slab objects become corrupted. Enabling
2233 slub_debug can create guard zones around objects and
2234 may poison objects when not in use. Also tracks the
2235 last alloc / free. For more information see
2236 Documentation/vm/slub.txt.
2238 slub_max_order= [MM, SLUB]
2239 Determines the maximum allowed order for slabs.
2240 A high setting may cause OOMs due to memory
2241 fragmentation. For more information see
2242 Documentation/vm/slub.txt.
2244 slub_min_objects= [MM, SLUB]
2245 The minimum number of objects per slab. SLUB will
2246 increase the slab order up to slub_max_order to
2247 generate a sufficiently large slab able to contain
2248 the number of objects indicated. The higher the number
2249 of objects the smaller the overhead of tracking slabs
2250 and the less frequently locks need to be acquired.
2251 For more information see Documentation/vm/slub.txt.
2253 slub_min_order= [MM, SLUB]
2254 Determines the mininum page order for slabs. Must be
2255 lower than slub_max_order.
2256 For more information see Documentation/vm/slub.txt.
2258 slub_nomerge [MM, SLUB]
2259 Disable merging of slabs with similar size. May be
2260 necessary if there is some reason to distinguish
2261 allocs to different slabs. Debug options disable
2262 merging on their own.
2263 For more information see Documentation/vm/slub.txt.
2266 Format: <io1>[,<io2>[,...,<io8>]]
2268 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2269 attempt to substitute SMP alternatives once at boot.
2271 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2272 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2273 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2274 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2275 smsc-ircc2.ircc_irq= [HW] IRQ line
2276 smsc-ircc2.ircc_dma= [HW] DMA channel
2277 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2278 0: Toshiba Satellite 1800 (GP data pin select)
2279 1: Fast pin select (default)
2283 [KNL] Should the soft-lockup detector generate panics.
2285 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2286 See Documentation/sonypi.txt
2288 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2289 See Documentation/serial/specialix.txt.
2291 spia_io_base= [HW,MTD]
2297 Enabled the stack tracer on boot up.
2301 Set the STI (builtin display/keyboard on the HP-PARISC
2302 machines) console (graphic card) which should be used
2303 as the initial boot-console.
2304 See also comment in drivers/video/console/sticore.c.
2307 See comment in drivers/video/console/sticore.c.
2310 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2312 sunrpc.min_resvport=
2313 sunrpc.max_resvport=
2315 SunRPC servers often require that client requests
2316 originate from a privileged port (i.e. a port in the
2317 range 0 < portnr < 1024).
2318 An administrator who wishes to reserve some of these
2319 ports for other uses may adjust the range that the
2320 kernel's sunrpc client considers to be privileged
2321 using these two parameters to set the minimum and
2322 maximum port values.
2326 Control how the NFS server code allocates CPUs to
2327 service thread pools. Depending on how many NICs
2328 you have and where their interrupts are bound, this
2329 option will affect which CPUs will do NFS serving.
2330 Note: this parameter cannot be changed while the
2331 NFS server is running.
2333 auto the server chooses an appropriate mode
2334 automatically using heuristics
2335 global a single global pool contains all CPUs
2336 percpu one pool for each CPU
2337 pernode one pool for each NUMA node (equivalent
2338 to global on non-NUMA machines)
2340 sunrpc.tcp_slot_table_entries=
2341 sunrpc.udp_slot_table_entries=
2343 Sets the upper limit on the number of simultaneous
2344 RPC calls that can be sent from the client to a
2345 server. Increasing these values may allow you to
2346 improve throughput, but will also increase the
2347 amount of memory reserved for use by the client.
2349 swiotlb= [IA-64] Number of I/O TLB slabs
2353 sysrq_always_enabled
2355 Ignore sysrq setting - this boot parameter will
2356 neutralize any effect of /proc/sys/kernel/sysrq.
2357 Useful for debugging.
2361 test_suspend= [SUSPEND]
2362 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2363 standby suspend) as the system sleep state to briefly
2364 enter during system startup. The system is woken from
2365 this state using a wakeup-capable RTC alarm.
2367 thash_entries= [KNL,NET]
2368 Set number of hash buckets for TCP connection
2370 thermal.act= [HW,ACPI]
2371 -1: disable all active trip points in all thermal zones
2372 <degrees C>: override all lowest active trip points
2374 thermal.crt= [HW,ACPI]
2375 -1: disable all critical trip points in all thermal zones
2376 <degrees C>: override all critical trip points
2378 thermal.nocrt= [HW,ACPI]
2379 Set to disable actions on ACPI thermal zone
2380 critical and hot trip points.
2382 thermal.off= [HW,ACPI]
2383 1: disable ACPI thermal control
2385 thermal.psv= [HW,ACPI]
2386 -1: disable all passive trip points
2387 <degrees C>: override all passive trip points to this
2390 thermal.tzp= [HW,ACPI]
2391 Specify global default ACPI thermal zone polling rate
2392 <deci-seconds>: poll all this frequency
2393 0: no polling (default)
2397 Specify if the kernel should make use of the cpu
2398 topology informations if the hardware supports these.
2399 The scheduler will make use of these informations and
2400 e.g. base its process migration decisions on it.
2405 tpm_suspend_pcr=[HW,TPM]
2406 Format: integer pcr id
2407 Specify that at suspend time, the tpm driver
2408 should extend the specified pcr with zeros,
2409 as a workaround for some chips which fail to
2410 flush the last written pcr on TPM_SaveState.
2411 This will guarantee that all the other pcrs
2414 trace_buf_size=nn[KMG]
2415 [FTRACE] will set tracing buffer size.
2417 trace_event=[event-list]
2418 [FTRACE] Set and start specified trace events in order
2419 to facilitate early boot debugging.
2420 See also Documentation/trace/events.txt
2422 tsc= Disable clocksource-must-verify flag for TSC.
2424 [x86] reliable: mark tsc clocksource as reliable, this
2425 disables clocksource verification at runtime.
2426 Used to enable high-resolution timer mode on older
2427 hardware, and in virtualized environment.
2429 turbografx.map[2|3]= [HW,JOY]
2430 TurboGraFX parallel port interface
2432 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2433 See also Documentation/input/joystick-parport.txt
2435 uhash_entries= [KNL,NET]
2436 Set number of hash buckets for UDP/UDP-Lite connections
2439 [USB] Ignore overcurrent events (default N).
2440 Some badly-designed motherboards generate lots of
2441 bogus events, for ports that aren't wired to
2442 anything. Set this parameter to avoid log spamming.
2443 Note that genuine overcurrent events won't be
2448 Set unknown_nmi_panic=1 early on boot.
2450 usbcore.autosuspend=
2451 [USB] The autosuspend time delay (in seconds) used
2452 for newly-detected USB devices (default 2). This
2453 is the time required before an idle device will be
2454 autosuspended. Devices for which the delay is set
2455 to a negative value won't be autosuspended at all.
2457 usbcore.usbfs_snoop=
2458 [USB] Set to log all usbfs traffic (default 0 = off).
2460 usbcore.blinkenlights=
2461 [USB] Set to cycle leds on hubs (default 0 = off).
2463 usbcore.old_scheme_first=
2464 [USB] Start with the old device initialization
2465 scheme (default 0 = off).
2467 usbcore.use_both_schemes=
2468 [USB] Try the other device initialization scheme
2469 if the first one fails (default 1 = enabled).
2471 usbcore.initial_descriptor_timeout=
2472 [USB] Specifies timeout for the initial 64-byte
2473 USB_REQ_GET_DESCRIPTOR request in milliseconds
2474 (default 5000 = 5.0 seconds).
2477 [USBHID] The interval which mice are to be polled at.
2479 usb-storage.delay_use=
2480 [UMS] The delay in seconds before a new device is
2481 scanned for Logical Units (default 5).
2484 [UMS] A list of quirks entries to supplement or
2485 override the built-in unusual_devs list. List
2486 entries are separated by commas. Each entry has
2487 the form VID:PID:Flags where VID and PID are Vendor
2488 and Product ID values (4-digit hex numbers) and
2489 Flags is a set of characters, each corresponding
2490 to a common usb-storage quirk flag as follows:
2491 a = SANE_SENSE (collect more than 18 bytes
2493 b = BAD_SENSE (don't collect more than 18
2494 bytes of sense data);
2495 c = FIX_CAPACITY (decrease the reported
2496 device capacity by one sector);
2497 h = CAPACITY_HEURISTICS (decrease the
2498 reported device capacity by one
2499 sector if the number is odd);
2500 i = IGNORE_DEVICE (don't bind to this
2502 l = NOT_LOCKABLE (don't try to lock and
2503 unlock ejectable media);
2504 m = MAX_SECTORS_64 (don't transfer more
2505 than 64 sectors = 32 KB at a time);
2506 o = CAPACITY_OK (accept the capacity
2507 reported by the device);
2508 r = IGNORE_RESIDUE (the device reports
2509 bogus residue values);
2510 s = SINGLE_LUN (the device has only one
2512 w = NO_WP_DETECT (don't test whether the
2513 medium is write-protected).
2514 Example: quirks=0419:aaf5:rl,0421:0433:rc
2517 [X86] Flags controlling user PTE allocations.
2519 nohigh = do not allocate PTE pages in
2520 HIGHMEM regardless of setting
2524 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2525 vdso=1: enable VDSO (default)
2526 vdso=0: disable VDSO mapping
2529 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2530 vdso32=1: enable 32-bit VDSO (default)
2531 vdso32=0: disable 32-bit VDSO mapping
2534 vector=percpu: enable percpu vector domain
2536 video= [FB] Frame buffer configuration
2537 See Documentation/fb/modedb.txt.
2539 vga= [BOOT,X86-32] Select a particular video mode
2540 See Documentation/x86/boot.txt and
2541 Documentation/svga.txt.
2542 Use vga=ask for menu.
2543 This is actually a boot loader parameter; the value is
2544 passed to the kernel using a special protocol.
2546 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2547 size of <nn>. This can be used to increase the
2548 minimum size (128MB on x86). It can also be used to
2549 decrease the size and leave more room for directly
2552 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2555 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2558 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2561 vt.cur_default= [VT] Default cursor shape.
2562 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2563 the parameters of the <Esc>[?A;B;Cc escape sequence;
2564 see VGA-softcursor.txt. Default: 2 = underline.
2566 vt.default_blu= [VT]
2567 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2568 Change the default blue palette of the console.
2569 This is a 16-member array composed of values
2572 vt.default_grn= [VT]
2573 Format: <green0>,<green1>,<green2>,...,<green15>
2574 Change the default green palette of the console.
2575 This is a 16-member array composed of values
2578 vt.default_red= [VT]
2579 Format: <red0>,<red1>,<red2>,...,<red15>
2580 Change the default red palette of the console.
2581 This is a 16-member array composed of values
2587 Set system-wide default UTF-8 mode for all tty's.
2588 Default is 1, i.e. UTF-8 mode is enabled for all
2589 newly opened terminals.
2591 vt.global_cursor_default=
2594 Set system-wide default for whether a cursor
2595 is shown on new VTs. Default is -1,
2596 i.e. cursors will be created by default unless
2597 overridden by individual drivers. 0 will hide
2598 cursors, 1 will display them.
2600 watchdog timers [HW,WDT] For information on watchdog timers,
2601 see Documentation/watchdog/watchdog-parameters.txt
2602 or other driver-specific files in the
2603 Documentation/watchdog/ directory.
2605 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2606 default x2apic cluster mode on platforms
2609 x86_mrst_timer= [X86-32,APBT]
2610 Choose timer option for x86 Moorestown MID platform.
2611 Two valid options are apbt timer only and lapic timer
2612 plus one apbt timer for broadcast timer.
2613 x86_mrst_timer=apbt_only | lapic_and_apbt
2615 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2616 xd_geo= See header of drivers/block/xd.c.
2618 xen_emul_unplug= [HW,X86,XEN]
2619 Unplug Xen emulated devices
2620 Format: [unplug0,][unplug1]
2621 ide-disks -- unplug primary master IDE devices
2622 aux-ide-disks -- unplug non-primary-master IDE devices
2623 nics -- unplug network devices
2624 all -- unplug all emulated devices (NICs and IDE disks)
2625 ignore -- continue loading the Xen platform PCI driver even
2626 if the version check failed
2628 xirc2ps_cs= [NET,PCMCIA]
2630 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2632 ______________________________________________________________________
2636 Add more DRM drivers.