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 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 AGP AGP (Accelerated Graphics Port) is enabled.
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
37 AVR32 AVR32 architecture is enabled.
38 AX25 Appropriate AX.25 support is enabled.
39 BLACKFIN Blackfin architecture is enabled.
40 DRM Direct Rendering Management support is enabled.
41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
42 EFI EFI Partitioning (GPT) is enabled
43 EIDE EIDE/ATAPI support is enabled.
44 FB The frame buffer device is enabled.
45 HW Appropriate hardware is enabled.
46 IA-64 IA-64 architecture is enabled.
47 IMA Integrity measurement architecture is enabled.
48 IOSCHED More than one I/O scheduler is enabled.
49 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
50 ISAPNP ISA PnP code is enabled.
51 ISDN Appropriate ISDN support is enabled.
52 JOY Appropriate joystick support is enabled.
53 KMEMTRACE kmemtrace is enabled.
54 LIBATA Libata driver is enabled
55 LP Printer support is enabled.
56 LOOP Loopback device support is enabled.
57 M68k M68k architecture is enabled.
58 These options have more detailed description inside of
59 Documentation/m68k/kernel-options.txt.
60 MCA MCA bus support is enabled.
61 MDA MDA console support is enabled.
62 MOUSE Appropriate mouse support is enabled.
63 MSI Message Signaled Interrupts (PCI).
64 MTD MTD (Memory Technology Device) support is enabled.
65 NET Appropriate network support is enabled.
66 NUMA NUMA support is enabled.
67 GENERIC_TIME The generic timeofday code is enabled.
68 NFS Appropriate NFS support is enabled.
69 OSS OSS sound support is enabled.
70 PV_OPS A paravirtualized kernel is enabled.
71 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
72 PARISC The PA-RISC architecture is enabled.
73 PCI PCI bus support is enabled.
74 PCIE PCI Express support is enabled.
75 PCMCIA The PCMCIA subsystem is enabled.
76 PNP Plug & Play support is enabled.
77 PPC PowerPC architecture is enabled.
78 PPT Parallel port support is enabled.
79 PS2 Appropriate PS/2 support is enabled.
80 RAM RAM disk support is enabled.
81 ROOTPLUG The example Root Plug LSM is enabled.
82 S390 S390 architecture is enabled.
83 SCSI Appropriate SCSI support is enabled.
84 A lot of drivers has their options described inside of
86 SECURITY Different security models are enabled.
87 SELINUX SELinux support is enabled.
88 SERIAL Serial support is enabled.
89 SH SuperH architecture is enabled.
90 SMP The kernel is an SMP kernel.
91 SPARC Sparc architecture is enabled.
92 SWSUSP Software suspend (hibernation) is enabled.
93 SUSPEND System suspend states are enabled.
94 FTRACE Function tracing enabled.
95 TS Appropriate touchscreen support is enabled.
96 UMS USB Mass Storage support is enabled.
97 USB USB support is enabled.
98 USBHID USB Human Interface Device support is enabled.
99 V4L Video For Linux support is enabled.
100 VGA The VGA console has been enabled.
101 VT Virtual terminal support is enabled.
102 WDT Watchdog support is enabled.
103 XT IBM PC/XT MFM hard disk support is enabled.
104 X86-32 X86-32, aka i386 architecture is enabled.
105 X86-64 X86-64 architecture is enabled.
106 More X86-64 boot options can be found in
107 Documentation/x86/x86_64/boot-options.txt .
108 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
110 In addition, the following text indicates that the option:
112 BUGS= Relates to possible processor bugs on the said processor.
113 KNL Is a kernel start-up parameter.
114 BOOT Is a boot loader parameter.
116 Parameters denoted with BOOT are actually interpreted by the boot
117 loader, and have no meaning to the kernel directly.
118 Do not modify the syntax of boot loader parameters without extreme
119 need or coordination with <Documentation/x86/boot.txt>.
121 There are also arch-specific kernel-parameters not documented here.
122 See for example <Documentation/x86/x86_64/boot-options.txt>.
124 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
125 a trailing = on the name of any parameter states that that parameter will
126 be entered as an environment variable, whereas its absence indicates that
127 it will appear as a kernel argument readable via /proc/cmdline by programs
128 running once the system is up.
130 The number of kernel parameters is not limited, but the length of the
131 complete command line (parameters including spaces etc.) is limited to
132 a fixed number of characters. This limit depends on the architecture
133 and is between 256 and 4096 characters. It is defined in the file
134 ./include/asm/setup.h as COMMAND_LINE_SIZE.
137 acpi= [HW,ACPI,X86-64,i386]
138 Advanced Configuration and Power Interface
139 Format: { force | off | ht | strict | noirq | rsdt }
140 force -- enable ACPI if default was off
141 off -- disable ACPI if default was on
142 noirq -- do not use ACPI for IRQ routing
143 ht -- run only enough ACPI to enable Hyper Threading
144 strict -- Be less tolerant of platforms that are not
145 strictly ACPI specification compliant.
146 rsdt -- prefer RSDT over (default) XSDT
148 See also Documentation/power/pm.txt, pci=noacpi
150 acpi_apic_instance= [ACPI, IOAPIC]
152 2: use 2nd APIC table, if available
153 1,0: use 1st APIC table
156 acpi_sleep= [HW,ACPI] Sleep options
157 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
158 old_ordering, s4_nonvs }
159 See Documentation/power/video.txt for information on
161 s3_beep is for debugging; it makes the PC's speaker beep
162 as soon as the kernel's real-mode entry point is called.
163 s4_nohwsig prevents ACPI hardware signature from being
164 used during resume from hibernation.
165 old_ordering causes the ACPI 1.0 ordering of the _PTS
166 control method, with respect to putting devices into
167 low power states, to be enforced (the ACPI 2.0 ordering
168 of _PTS is used by default).
169 s4_nonvs prevents the kernel from saving/restoring the
170 ACPI NVS memory during hibernation.
172 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
173 Format: { level | edge | high | low }
175 acpi_irq_balance [HW,ACPI]
176 ACPI will balance active IRQs
179 acpi_irq_nobalance [HW,ACPI]
180 ACPI will not move active IRQs (default)
183 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
185 Format: <irq>,<irq>...
187 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
188 Format: <irq>,<irq>...
190 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
192 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
193 Format: To spoof as Windows 98: ="Microsoft Windows"
195 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
196 acpi_osi="string1" # add string1 -- only one string
197 acpi_osi="!string2" # remove built-in string2
198 acpi_osi= # disable all strings
200 acpi_serialize [HW,ACPI] force serialization of AML methods
202 acpi_skip_timer_override [HW,ACPI]
203 Recognize and ignore IRQ0/pin2 Interrupt Override.
204 For broken nForce2 BIOS resulting in XT-PIC timer.
205 acpi_use_timer_override [HW,ACPI]
206 Use timer override. For some broken Nvidia NF5 boards
207 that require a timer override, but don't have
210 acpi_backlight= [HW,ACPI]
211 acpi_backlight=vendor
213 If set to vendor, prefer vendor specific driver
214 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
215 of the ACPI video.ko driver.
217 acpi_display_output= [HW,ACPI]
218 acpi_display_output=vendor
219 acpi_display_output=video
222 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
223 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
225 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
226 debug output. Bits in debug_layer correspond to a
227 _COMPONENT in an ACPI source file, e.g.,
228 #define _COMPONENT ACPI_PCI_COMPONENT
229 Bits in debug_level correspond to a level in
230 ACPI_DEBUG_PRINT statements, e.g.,
231 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
232 The debug_level mask defaults to "info". See
233 Documentation/acpi/debug.txt for more information about
234 debug layers and levels.
236 Enable processor driver info messages:
237 acpi.debug_layer=0x20000000
238 Enable PCI/PCI interrupt routing info messages:
239 acpi.debug_layer=0x400000
240 Enable AML "Debug" output, i.e., stores to the Debug
241 object while interpreting AML:
242 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
243 Enable all messages related to ACPI hardware:
244 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
246 Some values produce so much output that the system is
247 unusable. The "log_buf_len" parameter may be useful
248 if you need to capture more output.
250 acpi.power_nocheck= [HW,ACPI]
251 Format: 1/0 enable/disable the check of power state.
252 On some bogus BIOS the _PSC object/_STA object of
253 power resource can't return the correct device power
254 state. In such case it is unneccessary to check its
255 power state again in power transition.
256 1 : disable the power state check
258 acpi_pm_good [X86-32,X86-64]
259 Override the pmtimer bug detection: force the kernel
260 to assume that this machine's pmtimer latches its value
261 and always returns good values.
264 { off | try_unsupported }
265 off: disable AGP support
266 try_unsupported: try to drive unsupported chipsets
267 (may crash computer or cause data corruption)
269 enable_timer_pin_1 [i386,x86-64]
270 Enable PIN 1 of APIC timer
271 Can be useful to work around chipset bugs
272 (in particular on some ATI chipsets).
273 The kernel tries to set a reasonable default.
275 disable_timer_pin_1 [i386,x86-64]
276 Disable PIN 1 of APIC timer
277 Can be useful to work around chipset bugs.
280 Format: <io>,<irq>,<dma>,<dma2>,<type>
283 See header of drivers/scsi/advansys.c.
285 advwdt= [HW,WDT] Advantech WDT
286 Format: <iostart>,<iostop>
288 aedsp16= [HW,OSS] Audio Excel DSP 16
289 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
290 See also header of sound/oss/aedsp16.c.
293 See Documentation/scsi/aha152x.txt.
296 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
299 See Documentation/scsi/aic7xxx.txt.
302 See Documentation/scsi/aic79xx.txt.
304 amd_iommu= [HW,X86-84]
305 Pass parameters to the AMD IOMMU driver in the system.
307 isolate - enable device isolation (each device, as far
308 as possible, will get its own protection
310 share - put every device behind one IOMMU into the
311 same protection domain
312 fullflush - enable flushing of IO/TLB entries when
313 they are unmapped. Otherwise they are
314 flushed before they will be reused, which
317 amd_iommu_size= [HW,X86-64]
318 Define the size of the aperture for the AMD IOMMU
319 driver. Possible values are:
320 '32M', '64M' (default), '128M', '256M', '512M', '1G'
322 amijoy.map= [HW,JOY] Amiga joystick support
323 Map of devices attached to JOY0DAT and JOY1DAT
325 See also Documentation/kernel/input/joystick.txt
327 analog.map= [HW,JOY] Analog joystick and gamepad support
328 Specifies type or capabilities of an analog joystick
329 connected to one of 16 gameports
330 Format: <type1>,<type2>,..<type16>
333 Power management functions (SPARCstation-4/5 + deriv.)
335 Disable APC CPU standby support. SPARCstation-Fox does
336 not play well with APC CPU idle - disable it if you have
337 APC and your system crashes randomly.
339 apic= [APIC,i386] Advanced Programmable Interrupt Controller
340 Change the output verbosity whilst booting
341 Format: { quiet (default) | verbose | debug }
342 Change the amount of debugging information output
343 when initialising the APIC and IO-APIC components.
345 apm= [APM] Advanced Power Management
346 See header of arch/x86/kernel/apm_32.c.
348 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
349 Format: <io>,<irq>,<nodeID>
353 atarimouse= [HW,MOUSE] Atari Mouse
355 atascsi= [HW,SCSI] Atari SCSI
357 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
358 EzKey and similar keyboards
360 atkbd.reset= [HW] Reset keyboard during initialization
362 atkbd.set= [HW] Select keyboard code set
363 Format: <int> (2 = AT (default), 3 = PS/2)
365 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
368 atkbd.softraw= [HW] Choose between synthetic and real raw mode
369 Format: <bool> (0 = real, 1 = synthetic (default))
371 atkbd.softrepeat= [HW]
372 Use software keyboard repeat
376 baycom_epp= [HW,AX25]
379 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
381 See header of drivers/net/hamradio/baycom_par.c.
383 baycom_ser_fdx= [HW,AX25]
384 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
385 Format: <io>,<irq>,<mode>[,<baud>]
386 See header of drivers/net/hamradio/baycom_ser_fdx.c.
388 baycom_ser_hdx= [HW,AX25]
389 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
390 Format: <io>,<irq>,<mode>
391 See header of drivers/net/hamradio/baycom_ser_hdx.c.
393 boot_delay= Milliseconds to delay each printk during boot.
394 Values larger than 10 seconds (10000) are changed to
398 bootmem_debug [KNL] Enable bootmem allocator debug messages.
400 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
401 bttv.radio= Most important insmod options are available as
403 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
404 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
407 See drivers/scsi/BusLogic.c, comment before function
408 BusLogic_ParseDriverOptions().
410 c101= [NET] Moxa C101 synchronous serial card
412 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
413 Sometimes CPU hardware bugs make them report the cache
414 size incorrectly. The kernel will attempt work arounds
415 to fix known problems, but for some CPUs it is not
416 possible to determine what the correct size should be.
417 This option provides an override for these situations.
419 security= [SECURITY] Choose a security module to enable at boot.
420 If this boot parameter is not specified, only the first
421 security module asking for security registration will be
422 loaded. An invalid security module name will be treated
423 as if no module has been chosen.
426 [SECURITY] Disable capabilities. This would normally
427 be used only if an alternative security model is to be
428 configured. Potentially dangerous and should only be
429 used if you are entirely sure of the consequences.
431 ccw_timeout_log [S390]
432 See Documentation/s390/CommonIO for details.
434 cgroup_disable= [KNL] Disable a particular controller
435 Format: {name of the controller(s) to disable}
436 {Currently supported controllers - "memory"}
438 checkreqprot [SELINUX] Set initial checkreqprot flag value.
439 Format: { "0" | "1" }
440 See security/selinux/Kconfig help text.
441 0 -- check protection applied by kernel (includes
442 any implied execute protection).
443 1 -- check protection requested by application.
444 Default value is set via a kernel config option.
445 Value can be changed at runtime via
446 /selinux/checkreqprot.
449 See Documentation/s390/CommonIO for details.
451 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
453 Forces specified clocksource (if available) to be used
454 when calculating gettimeofday(). If specified
455 clocksource is not available, it defaults to PIT.
456 Format: { pit | tsc | cyclone | pmtmr }
458 clocksource= [GENERIC_TIME] Override the default clocksource
460 Override the default clocksource and use the clocksource
461 with the name specified.
462 Some clocksource names to choose from, depending on
464 [all] jiffies (this is the base, fallback clocksource)
466 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
467 pxa_timer,timer3,32k_counter,timer0_1
469 [X86-32] pit,hpet,tsc,vmi-timer;
470 scx200_hrt on Geode; cyclone on IBM x440
478 clearcpuid=BITNUM [X86]
479 Disable CPUID feature X for the kernel. See
480 arch/x86/include/asm/cpufeature.h for the valid bit
481 numbers. Note the Linux specific bits are not necessarily
482 stable over kernel options, but the vendor specific
484 Also note that user programs calling CPUID directly
485 or using the feature without checking anything
486 will still see it. This just prevents it from
487 being used by the kernel or shown in /proc/cpuinfo.
488 Also note the kernel might malfunction if you disable
491 code_bytes [IA32/X86_64] How many bytes of object code to print
496 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support
497 this option disables the debugging code at boot.
499 dma_debug_entries=<number>
500 This option allows to tune the number of preallocated
501 entries for DMA-API debugging code. One entry is
502 required per DMA-API allocation. Use this if the
503 DMA-API debugging code disables itself because the
504 architectural default is too low.
506 hpet= [X86-32,HPET] option to control HPET usage
507 Format: { enable (default) | disable | force |
509 disable: disable HPET and use PIT instead
510 force: allow force enabled of undocumented chips (ICH4,
512 verbose: show contents of HPET registers during setup
514 com20020= [HW,NET] ARCnet - COM20020 chipset
516 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
518 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
522 ARCnet - COM90xx chipset (memory-mapped buffers)
523 Format: <io>[,<irq>[,<memstart>]]
525 condev= [HW,S390] console device
528 console= [KNL] Output console device and options.
530 tty<n> Use the virtual console device <n>.
534 Use the specified serial port. The options are of
535 the form "bbbbpnf", where "bbbb" is the baud rate,
536 "p" is parity ("n", "o", or "e"), "n" is number of
537 bits, and "f" is flow control ("r" for RTS or
538 omit it). Default is "9600n8".
540 See Documentation/serial-console.txt for more
542 Documentation/networking/netconsole.txt for an
545 uart[8250],io,<addr>[,options]
546 uart[8250],mmio,<addr>[,options]
547 Start an early, polled-mode console on the 8250/16550
548 UART at the specified I/O port or MMIO address,
549 switching to the matching ttyS device later. The
550 options are the same as for ttyS, above.
552 If the device connected to the port is not a TTY but a braille
553 device, prepend "brl," before the device type, for instance
555 For now, only VisioBraille is supported.
557 earlycon= [KNL] Output early console device and options.
558 uart[8250],io,<addr>[,options]
559 uart[8250],mmio,<addr>[,options]
560 Start an early, polled-mode console on the 8250/16550
561 UART at the specified I/O port or MMIO address.
562 The options are the same as for ttyS, above.
565 [HW] Never suspend the console
566 Disable suspending of consoles during suspend and
567 hibernate operations. Once disabled, debugging
568 messages can reach various consoles while the rest
569 of the system is being put to sleep (ie, while
570 debugging driver suspend/resume hooks). This may
571 not work reliably with all consoles, but is known
572 to work with serial and VGA consoles.
575 [KNL] Change the default value for
576 /proc/<pid>/coredump_filter.
577 See also Documentation/filesystems/proc.txt.
579 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
581 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
583 crashkernel=nn[KMG]@ss[KMG]
584 [KNL] Reserve a chunk of physical memory to
585 hold a kernel to switch to with kexec on panic.
587 crashkernel=range1:size1[,range2:size2,...][@offset]
588 [KNL] Same as above, but depends on the memory
589 in the running system. The syntax of range is
590 start-[end] where start and end are both
591 a memory unit (amount[KMG]). See also
592 Documentation/kdump/kdump.txt for a example.
597 cs89x0_media= [HW,NET]
598 Format: { rj45 | aui | bnc }
601 See header of drivers/s390/block/dasd_devmap.c.
603 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
604 (one device per port)
605 Format: <port#>,<type>
606 See also Documentation/input/joystick-parport.txt
608 debug [KNL] Enable kernel debugging (events log level).
611 [KNL] verbose self-tests
613 Print debugging info while doing the locking API
615 We default to 0 (no extra messages), setting it to
616 1 will print _a lot_ more information - normally
617 only useful to kernel developers.
619 debug_objects [KNL] Enable object debugging
622 [KNL] Disable object debugging
624 debugpat [X86] Enable PAT debugging
626 decnet.addr= [HW,NET]
627 Format: <area>[,<node>]
628 See also Documentation/networking/decnet.txt.
631 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
632 Change the default blue palette of the console.
633 This is a 16-member array composed of values
637 Format: <green0>,<green1>,<green2>,...,<green15>
638 Change the default green palette of the console.
639 This is a 16-member array composed of values
643 Format: <red0>,<red1>,<red2>,...,<red15>
644 Change the default red palette of the console.
645 This is a 16-member array composed of values
651 Set system-wide default UTF-8 mode for all tty's.
652 Default is 1, i.e. UTF-8 mode is enabled for all
653 newly opened terminals.
656 Set number of hash buckets for dentry cache.
659 IO parameters + enable/disable command.
661 digiepca= [HW,SERIAL]
662 See drivers/char/README.epca and
663 Documentation/serial/digiepca.txt.
665 disable_mtrr_cleanup [X86]
666 enable_mtrr_cleanup [X86]
667 The kernel tries to adjust MTRR layout from continuous
668 to discrete, to make X server driver able to add WB
669 entry later. This parameter enables/disables that.
671 mtrr_chunk_size=nn[KMG] [X86]
672 used for mtrr cleanup. It is largest continous chunk
673 that could hold holes aka. UC entries.
675 mtrr_gran_size=nn[KMG] [X86]
676 Used for mtrr cleanup. It is granularity of mtrr block.
678 Large value could prevent small alignment from
681 mtrr_spare_reg_nr=n [X86]
683 Range: 0,7 : spare reg number
685 Used for mtrr cleanup. It is spare mtrr entries number.
686 Set to 2 or more if your graphical card needs more.
688 disable_mtrr_trim [X86, Intel and AMD only]
689 By default the kernel will trim any uncacheable
690 memory out of your available memory pool based on
691 MTRR settings. This parameter disables that behavior,
692 possibly causing your machine to run very slowly.
694 dmasound= [HW,OSS] Sound subsystem buffers
700 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
702 earlyprintk=serial[,ttySn[,baudrate]]
705 Append ",keep" to not disable it when the real console
708 Only vga or serial or usb debug port at a time.
710 Currently only ttyS0 and ttyS1 are supported.
712 Interaction with the standard serial driver is not
715 The VGA output is eventually overwritten by the real
721 Format: {"off" | "on" | "skip[mbr]"}
723 eisa_irq_edge= [PARISC,HW]
724 See header of drivers/parisc/eisa.c.
727 See comment before function elanfreq_setup() in
728 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
731 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
732 See Documentation/block/as-iosched.txt and
733 Documentation/block/deadline-iosched.txt for details.
735 elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
736 Specifies physical address of start of kernel core
737 image elf header. Generally kexec loader will
738 pass this option to capture kernel.
739 See Documentation/kdump/kdump.txt for details.
741 enforcing [SELINUX] Set initial enforcing status.
743 See security/selinux/Kconfig help text.
744 0 -- permissive (log only, no denials).
745 1 -- enforcing (deny and log).
747 Value can be changed at runtime via /selinux/enforce.
749 ether= [HW,NET] Ethernet cards parameters
750 This option is obsoleted by the "netdev=" option, which
751 has equivalent usage. See its documentation for details.
753 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
758 fail_make_request=[KNL]
759 General fault injection mechanism.
760 Format: <interval>,<probability>,<space>,<times>
761 See also /Documentation/fault-injection/.
764 See header of drivers/scsi/fd_mcs.c.
767 See header of drivers/scsi/fdomain.c.
770 See Documentation/blockdev/floppy.txt.
772 force_pal_cache_flush
773 [IA-64] Avoid check_sal_cache_flush which may hang on
774 buggy SAL_CACHE_FLUSH implementations. Using this
775 parameter will force ia64_sal_cache_flush to call
776 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
779 [ftrace] will set and start the specified tracer
780 as early as possible in order to facilitate early
784 [ftrace] will dump the trace buffers on oops.
787 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
788 support via parallel port (up to 5 devices per port)
789 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
790 See also Documentation/input/joystick-parport.txt
794 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
799 See header of drivers/scsi/gdth.c.
801 gpt [EFI] Forces disk with valid GPT signature but
802 invalid Protective MBR to be treated as GPT.
806 hashdist= [KNL,NUMA] Large hashes allocated during boot
807 are distributed across NUMA nodes. Defaults on
808 for IA-64, off otherwise.
809 Format: 0 | 1 (for off | on)
811 hcl= [IA-64] SGI's Hardware Graph compatibility layer
813 hd= [EIDE] (E)IDE hard drive subsystem geometry
814 Format: <cyl>,<head>,<sect>
816 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
817 size of <nn>. This works even on boxes that have no
818 highmem otherwise. This also works to reduce highmem
819 size on bigger boxes.
821 highres= [KNL] Enable/disable high resolution timer mode.
822 Valid parameters: "on", "off"
826 See Documentation/isdn/README.HiSax.
828 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
829 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
830 On x86-64 and powerpc, this option can be specified
831 multiple times interleaved with hugepages= to reserve
832 huge pages of different sizes. Valid pages sizes on
833 x86-64 are 2M (when the CPU supports "pse") and 1G
834 (when the CPU supports the "pdpe1gb" cpuinfo flag)
835 Note that 1GB pages can only be allocated at boot time
836 using hugepages= and not freed afterwards.
838 [same as hugepagesz=] The size of the default
839 HugeTLB page size. This is the size represented by
840 the legacy /proc/ hugepages APIs, used for SHM, and
841 default size when mounting hugetlbfs filesystems.
842 Defaults to the default architecture's huge page size
847 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
848 terminal devices. Valid values: 0..8
849 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
850 If specified, z/VM IUCV HVC accepts connections
851 from listed z/VM user IDs only.
853 i2c_bus= [HW] Override the default board specific I2C bus speed
854 or register an additional I2C bus that is not
855 registered from board initialization code.
859 i8042.debug [HW] Toggle i8042 debug mode
860 i8042.direct [HW] Put keyboard port into non-translated mode
861 i8042.dumbkbd [HW] Pretend that controller can only read data from
862 keyboard and cannot control its state
863 (Don't attempt to blink the leds)
864 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
865 i8042.nokbd [HW] Don't check/create keyboard port
866 i8042.noloop [HW] Disable the AUX Loopback command while probing
868 i8042.nomux [HW] Don't check presence of an active multiplexing
870 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
873 [HW] Frequency with which keyboard LEDs should blink
874 when kernel panics (default is 0.5 sec)
875 i8042.reset [HW] Reset the controller during init and cleanup
876 i8042.unlock [HW] Unlock (ignore) the keylock
880 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
881 indicates that the driver is running on unsupported
883 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
884 does not match list of supported models.
886 [HW] Report power status in /proc/i8k
887 (disabled by default)
888 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
891 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
892 See Documentation/mca.txt.
895 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
897 ide-core.nodma= [HW] (E)IDE subsystem
898 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
899 .vlb_clock .pci_clock .noflush .noprobe .nowerr .cdrom
900 .chs .ignore_cable are additional options
901 See Documentation/ide/ide.txt.
903 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
904 See Documentation/ide/ide.txt.
907 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
908 Poll forces a polling idle loop that can slightly
909 improve the performance of waking up a idle CPU, but
910 will use a lot of power and make the system run hot.
912 idle=mwait: On systems which support MONITOR/MWAIT but
913 the kernel chose to not use it because it doesn't save
914 as much power as a normal idle loop, use the
915 MONITOR/MWAIT idle loop anyways. Performance should be
916 the same as idle=poll.
917 idle=halt: Halt is forced to be used for CPU idle.
918 In such case C2/C3 won't be used again.
919 idle=nomwait: Disable mwait for CPU C-states
921 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
922 Claim all unknown PCI IDE storage controllers.
924 ignore_loglevel [KNL]
925 Ignore loglevel setting - this will print /all/
926 kernel messages to the console. Useful for debugging.
929 Set number of hash buckets for inode cache.
932 Format: { "0" | "1" }
933 0 -- integrity auditing messages. (Default)
934 1 -- enable informational integrity auditing messages.
937 Formt: { "sha1" | "md5" }
941 See header of drivers/scsi/in2000.c.
945 Run specified binary instead of /sbin/init as init
948 initcall_debug [KNL] Trace initcalls as they are executed. Useful
949 for working out where the kernel is dying during
952 initrd= [BOOT] Specify the location of the initial ramdisk
954 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
959 iomem= Disable strict checking of access to MMIO memory
960 strict regions from userspace.
976 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
978 Enable intel iommu driver.
980 Disable intel iommu driver.
981 igfx_off [Default Off]
982 By default, gfx is mapped as normal device. If a gfx
983 device has a dedicated DMAR unit, the DMAR unit is
984 bypassed by not enabling DMAR with this option. In
985 this case, gfx device will use physical address for
988 With this option iommu will not optimize to look
989 for io virtual address below 32 bit forcing dual
990 address cycle on pci bus for cards supporting greater
991 than 32 bit addressing. The default is to look
992 for translation below 32 bit and if not available
993 then look in the higher range.
995 With this option on every unmap_single operation will
996 result in a hardware IOTLB flush operation as opposed
997 to batching them for performance.
999 io_delay= [X86-32,X86-64] I/O delay method
1001 Standard port 0x80 based delay
1003 Alternate port 0xed based delay (needed on some systems)
1005 Simple two microseconds delay
1009 io7= [HW] IO7 for Marvel based alpha systems
1010 See comment before marvel_specify_io7 in
1011 arch/alpha/kernel/core_marvel.c.
1014 See Documentation/filesystems/nfsroot.txt.
1016 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1017 See comment before ip2_setup() in
1018 drivers/char/ip2/ip2base.c.
1020 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1021 See header of drivers/scsi/ips.c.
1023 ports= [IP_VS_FTP] IPVS ftp helper module
1025 Up to 8 (IP_VS_APP_MAX_PORTS) ports
1027 Format: <port>,<port>....
1030 When an interrupt is not handled search all handlers
1031 for it. Intended to get systems with badly broken
1035 When an interrupt is not handled search all handlers
1036 for it. Also check all handlers each timer
1037 interrupt. Intended to get systems with badly broken
1041 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1043 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1045 <cpu number>,...,<cpu number>
1047 <cpu number>-<cpu number>
1048 (must be a positive range in ascending order)
1050 <cpu number>,...,<cpu number>-<cpu number>
1052 This option can be used to specify one or more CPUs
1053 to isolate from the general SMP balancing and scheduling
1054 algorithms. You can move a process onto or off an
1055 "isolated" CPU via the CPU affinity syscalls or cpuset.
1056 <cpu number> begins at 0 and the maximum value is
1057 "number of CPUs in system - 1".
1059 This option is the preferred way to isolate CPUs. The
1060 alternative -- manually setting the CPU mask of all
1061 tasks in the system -- can cause problems and
1062 suboptimal load balancer performance.
1066 js= [HW,JOY] Analog joystick
1067 See Documentation/input/joystick.txt.
1069 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1070 specifies the amount of memory usable by the kernel
1071 for non-movable allocations. The requested amount is
1072 spread evenly throughout all nodes in the system. The
1073 remaining memory in each node is used for Movable
1074 pages. In the event, a node is too small to have both
1075 kernelcore and Movable pages, kernelcore pages will
1076 take priority and other nodes will have a larger number
1077 of kernelcore pages. The Movable zone is used for the
1078 allocation of pages that may be reclaimed or moved
1079 by the page migration subsystem. This means that
1080 HugeTLB pages may not be allocated from this zone.
1081 Note that allocations like PTEs-from-HighMem still
1082 use the HighMem zone if it exists, and the Normal
1083 zone if it does not.
1085 kmemtrace.enable= [KNL,KMEMTRACE] Format: { yes | no }
1086 Controls whether kmemtrace is enabled
1089 kmemtrace.subbufs=n [KNL,KMEMTRACE] Overrides the number of
1090 subbufs kmemtrace's relay channel has. Set this
1091 higher than default (KMEMTRACE_N_SUBBUFS in code) if
1092 you experience buffer overruns.
1094 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1095 is similar to kernelcore except it specifies the
1096 amount of memory used for migratable allocations.
1097 If both kernelcore and movablecore is specified,
1098 then kernelcore will be at *least* the specified
1099 value but may be more. If movablecore on its own
1100 is specified, the administrator must be careful
1101 that the amount of memory usable for all allocations
1106 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1109 kgdboc= [HW] kgdb over consoles.
1110 Requires a tty driver that supports console polling.
1111 (only serial suported for now)
1112 Format: <serial_device>[,baud]
1114 kmac= [MIPS] korina ethernet MAC address.
1115 Configure the RouterBoard 532 series on-chip
1116 Ethernet adapter MAC address.
1122 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1125 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer
1128 libata.dma= [LIBATA] DMA control
1129 libata.dma=0 Disable all PATA and SATA DMA
1130 libata.dma=1 PATA and SATA Disk DMA only
1131 libata.dma=2 ATAPI (CDROM) DMA only
1132 libata.dma=4 Compact Flash DMA only
1133 Combinations also work, so libata.dma=3 enables DMA
1134 for disks and CDROMs, but not CFs.
1136 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1140 libata.force= [LIBATA] Force configurations. The format is comma
1141 separated list of "[ID:]VAL" where ID is
1142 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1143 matching port, link or device. Basically, it matches
1144 the ATA ID string printed on console by libata. If
1145 the whole ID part is omitted, the last PORT and DEVICE
1146 values are used. If ID hasn't been specified yet, the
1147 configuration applies to all ports, links and devices.
1149 If only DEVICE is omitted, the parameter applies to
1150 the port and all links and devices behind it. DEVICE
1151 number of 0 either selects the first device or the
1152 first fan-out link behind PMP device. It does not
1153 select the host link. DEVICE number of 15 selects the
1154 host link and device attached to it.
1156 The VAL specifies the configuration to force. As long
1157 as there's no ambiguity shortcut notation is allowed.
1158 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1159 The following configurations can be forced.
1161 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1162 Any ID with matching PORT is used.
1164 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1166 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1167 udma[/][16,25,33,44,66,100,133] notation is also
1170 * [no]ncq: Turn on or off NCQ.
1172 * nohrst, nosrst, norst: suppress hard, soft
1175 If there are multiple matching configurations changing
1176 the same attribute, the last one is used.
1178 lmb=debug [KNL] Enable lmb debug messages.
1180 load_ramdisk= [RAM] List of ramdisks to load from floppy
1181 See Documentation/blockdev/ramdisk.txt.
1183 lockd.nlm_grace_period=P [NFS] Assign grace period.
1186 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1189 lockd.nlm_timeout=T [NFS] Assign timeout value.
1192 lockd.nlm_udpport=M [NFS] Assign UDP port.
1195 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1198 loglevel= All Kernel Messages with a loglevel smaller than the
1199 console loglevel will be printed to the console. It can
1200 also be changed with klogd or other programs. The
1201 loglevels are defined as follows:
1203 0 (KERN_EMERG) system is unusable
1204 1 (KERN_ALERT) action must be taken immediately
1205 2 (KERN_CRIT) critical conditions
1206 3 (KERN_ERR) error conditions
1207 4 (KERN_WARNING) warning conditions
1208 5 (KERN_NOTICE) normal but significant condition
1209 6 (KERN_INFO) informational
1210 7 (KERN_DEBUG) debug-level messages
1212 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1213 Format: { n | nk | nM }
1214 n must be a power of two. The default size
1215 is set in the kernel config file.
1217 logo.nologo [FB] Disables display of the built-in Linux logo.
1218 This may be used to provide more screen space for
1219 kernel log messages and is useful when debugging
1220 kernel boot problems.
1222 lp=0 [LP] Specify parallel ports to use, e.g,
1223 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1224 lp=reset first parallel port). 'lp=0' disables the
1225 lp=auto printer driver. 'lp=reset' (which can be
1226 specified in addition to the ports) causes
1227 attached printers to be reset. Using
1228 lp=port1,port2,... specifies the parallel ports
1229 to associate lp devices with, starting with
1230 lp0. A port specification may be 'none' to skip
1231 that lp device, or a parport name such as
1232 'parport0'. Specifying 'lp=auto' instead of a
1233 port specification list means that device IDs
1234 from each port should be examined, to see if
1235 an IEEE 1284-compliant printer is attached; if
1236 so, the driver will manage that printer.
1237 See also header of drivers/char/lp.c.
1240 Sets loops_per_jiffy to given constant, thus avoiding
1241 time-consuming boot-time autodetection (up to 250 ms per
1242 CPU). 0 enables autodetection (default). To determine
1243 the correct value for your kernel, boot with normal
1244 autodetection and see what value is printed. Note that
1245 on SMP systems the preset will be applied to all CPUs,
1246 which is likely to cause problems if your CPUs need
1247 significantly divergent settings. An incorrect value
1248 will cause delays in the kernel to be wrong, leading to
1249 unpredictable I/O errors and other breakage. Although
1250 unlikely, in the extreme case this might damage your
1254 Format: <io>,<irq>,<dma>
1256 mac5380= [HW,SCSI] Format:
1257 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1259 machvec= [IA64] Force the use of a particular machine-vector
1260 (machvec) in a generic kernel.
1261 Example: machvec=hpzx1_swiotlb
1263 max_loop= [LOOP] Maximum number of loopback devices that can
1267 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1268 should make use of. maxcpus=n : n >= 0 limits the
1269 kernel to using 'n' processors. n=0 is a special case,
1270 it is equivalent to "nosmp", which also disables
1273 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater than
1274 or equal to this physical address is ignored.
1276 max_luns= [SCSI] Maximum number of LUNs to probe.
1277 Should be between 1 and 2^32-1.
1280 [SCSI] Maximum number of LUNs received.
1281 Should be between 1 and 16384.
1285 mce [X86-32] Machine Check Exception
1287 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1289 md= [HW] RAID subsystems devices and level
1290 See Documentation/md.txt.
1293 Format: <first>,<last>
1294 Specifies range of consoles to be captured by the MDA.
1296 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1297 Amount of memory to be used when the kernel is not able
1298 to see the whole system memory or for test.
1299 [X86-32] Use together with memmap= to avoid physical
1300 address space collisions. Without memmap= PCI devices
1301 could be placed at addresses belonging to unused RAM.
1303 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1307 [KNL,SH] Allow user to override the default size for
1308 per-device physically contiguous DMA buffers.
1310 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1311 E820 memory map, as specified by the user.
1312 Such memmap=exactmap lines can be constructed based on
1313 BIOS output or other requirements. See the memmap=nn@ss
1316 memmap=nn[KMG]@ss[KMG]
1317 [KNL] Force usage of a specific region of memory
1318 Region of memory to be used, from ss to ss+nn.
1320 memmap=nn[KMG]#ss[KMG]
1321 [KNL,ACPI] Mark specific memory as ACPI data.
1322 Region of memory to be used, from ss to ss+nn.
1324 memmap=nn[KMG]$ss[KMG]
1325 [KNL,ACPI] Mark specific memory as reserved.
1326 Region of memory to be used, from ss to ss+nn.
1327 Example: Exclude memory from 0x18690000-0x1869ffff
1328 memmap=64K$0x18690000
1330 memmap=0x10000$0x18690000
1332 memory_corruption_check=0/1 [X86]
1333 Some BIOSes seem to corrupt the first 64k of
1334 memory when doing things like suspend/resume.
1335 Setting this option will scan the memory
1336 looking for corruption. Enabling this will
1337 both detect corruption and prevent the kernel
1338 from using the memory being corrupted.
1339 However, its intended as a diagnostic tool; if
1340 repeatable BIOS-originated corruption always
1341 affects the same memory, you can use memmap=
1342 to prevent the kernel from using that memory.
1344 memory_corruption_check_size=size [X86]
1345 By default it checks for corruption in the low
1346 64k, making this memory unavailable for normal
1347 use. Use this parameter to scan for
1348 corruption in more or less memory.
1350 memory_corruption_check_period=seconds [X86]
1351 By default it checks for corruption every 60
1352 seconds. Use this parameter to check at some
1353 other rate. 0 disables periodic checking.
1355 memtest= [KNL,X86] Enable memtest
1357 default : 0 <disable>
1358 Specifies the number of memtest passes to be
1359 performed. Each pass selects another test
1360 pattern from a given set of patterns. Memtest
1361 fills the memory with this pattern, validates
1362 memory contents and reserves bad memory
1363 regions that are detected.
1365 meye.*= [HW] Set MotionEye Camera parameters
1366 See Documentation/video4linux/meye.txt.
1368 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1369 Multi-Function General Purpose Timers on AMD Geode
1372 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1373 the BIOS has incorrectly applied a workaround. TinyBIOS
1374 version 0.98 is known to be affected, 0.99 fixes the
1375 problem by letting the user disable the workaround.
1379 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1380 physical address is ignored.
1383 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1384 parameter allows control of the logging verbosity for
1385 the additional memory initialisation checks. A value
1386 of 0 disables mminit logging and a level of 4 will
1387 log everything. Information is printed at KERN_DEBUG
1388 so loglevel=8 may also need to be specified.
1391 [MOUSE] Maximum time between finger touching and
1392 leaving touchpad surface for touch to be considered
1393 a tap and be reported as a left button click (for
1394 touchpads working in absolute mode only).
1396 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1397 reporting absolute coordinates, such as tablets
1398 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1399 reporting absolute coordinates, such as tablets
1404 MTD_Partition= [MTD]
1405 Format: <name>,<region-number>,<size>,<offset>
1407 MTD_Region= [MTD] Format:
1408 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1411 See drivers/mtd/cmdlinepart.c.
1414 ARM/S3C2412 JIVE boot control
1416 See arch/arm/mach-s3c2412/mach-jive.c
1418 mtouchusb.raw_coordinates=
1419 [HW] Make the MicroTouch USB driver use raw coordinates
1420 ('y', default) or cooked coordinates ('n')
1422 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1425 See header of drivers/scsi/NCR_D700.c.
1429 ncr53c400= [HW,SCSI]
1431 ncr53c400a= [HW,SCSI]
1433 ncr53c406a= [HW,SCSI]
1435 ncr53c8xx= [HW,SCSI]
1437 netdev= [NET] Network devices parameters
1438 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1439 Note that mem_start is often overloaded to mean
1440 something different and driver-specific.
1441 This usage is only documented in each driver source
1445 [NETFILTER] Enable connection tracking flow accounting
1446 0 to disable accounting
1447 1 to enable accounting
1448 Default value depends on CONFIG_NF_CT_ACCT that is
1449 going to be removed in 2.6.29.
1452 See Documentation/filesystems/nfsroot.txt.
1454 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1455 See Documentation/filesystems/nfsroot.txt.
1457 nfs.callback_tcpport=
1458 [NFS] set the TCP port on which the NFSv4 callback
1459 channel should listen.
1461 nfs.idmap_cache_timeout=
1462 [NFS] set the maximum lifetime for idmapper cache
1466 [NFS] enable 64-bit inode numbers.
1467 If zero, the NFS client will fake up a 32-bit inode
1468 number for the readdir() and stat() syscalls instead
1469 of returning the full 64-bit number.
1470 The default is to return 64-bit inode numbers.
1472 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1473 when a NMI is triggered.
1474 Format: [state][,regs][,debounce][,die]
1476 nmi_watchdog= [KNL,BUGS=X86-32,X86-64] Debugging features for SMP kernels
1477 Format: [panic,][num]
1479 0 - turn nmi_watchdog off
1480 1 - use the IO-APIC timer for the NMI watchdog
1481 2 - use the local APIC for the NMI watchdog using
1482 a performance counter. Note: This will use one performance
1483 counter and the local APIC's performance vector.
1484 When panic is specified panic when an NMI watchdog timeout occurs.
1485 This is useful when you use a panic=... timeout and need the box
1487 Instead of 1 and 2 it is possible to use the following
1488 symbolic names: lapic and ioapic
1489 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1491 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1492 emulation library even if a 387 maths coprocessor
1495 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1496 caches in the slab allocator. Saves per-node memory,
1497 but will impact performance.
1501 noapic [SMP,APIC] Tells the kernel to not make use of any
1502 IOAPICs that may be present in the system.
1504 nobats [PPC] Do not use BATs for mapping kernel lowmem
1505 on "Classic" PPC cores.
1509 nodelayacct [KNL] Disable per-task delay accounting
1511 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1513 nodsp [SH] Disable hardware DSP at boot time.
1515 noefi [X86-32,X86-64] Disable EFI runtime services support.
1519 noexec [X86-32,X86-64]
1520 On X86-32 available only on PAE configured kernels.
1521 noexec=on: enable non-executable mappings (default)
1522 noexec=off: disable non-executable mappings
1525 This affects only 32-bit executables.
1526 noexec32=on: enable non-executable mappings (default)
1527 read doesn't imply executable mappings
1528 noexec32=off: disable non-executable mappings
1529 read implies executable mappings
1531 nofpu [SH] Disable hardware FPU at boot time.
1533 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1534 register save and restore. The kernel will only save
1535 legacy floating-point registers on task switch.
1537 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1539 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1540 wfi(ARM) instruction doesn't work correctly and not to
1541 use it. This is also useful when using JTAG debugger.
1543 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1544 instruction doesn't work correctly and not to
1547 no_file_caps Tells the kernel not to honor file capabilities. The
1548 only way then for a file to be executed with privilege
1549 is to be setuid root or executed by root.
1551 nohalt [IA-64] Tells the kernel not to use the power saving
1552 function PAL_HALT_LIGHT when idle. This increases
1553 power-consumption. On the positive side, it reduces
1554 interrupt wake-up latency, which may improve performance
1555 in certain environments such as networked servers or
1558 nohz= [KNL] Boottime enable/disable dynamic ticks
1559 Valid arguments: on, off
1562 noiotrap [SH] Disables trapped I/O port accesses.
1564 noirqdebug [X86-32] Disables the code which attempts to detect and
1565 disable unhandled interrupt sources.
1567 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1568 broken timer IRQ sources.
1570 noisapnp [ISAPNP] Disables ISA PnP code.
1572 noinitrd [RAM] Tells the kernel not to load any configured
1577 nojitter [IA64] Disables jitter checking for ITC timers.
1579 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1581 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1583 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1585 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
1586 default x2apic cluster mode on platforms
1589 noltlbs [PPC] Do not use large page/tlb entries for kernel
1590 lowmem mapping on PPC40x.
1592 nomca [IA-64] Disable machine check abort handling
1594 nomce [X86-32] Machine Check Exception
1596 nomfgpt [X86-32] Disable Multi-Function General Purpose
1597 Timer usage (for AMD Geode machines).
1599 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1601 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1602 with UP alternatives
1604 noresidual [PPC] Don't use residual data on PReP machines.
1606 noresume [SWSUSP] Disables resume and restores original swap
1609 no-scroll [VGA] Disables scrollback.
1610 This is required for the Braillex ib80-piezo Braille
1611 reader made by F.H. Papenmeier (Germany).
1615 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1617 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1618 and disable the IO APIC. legacy for "maxcpus=0".
1620 nosoftlockup [KNL] Disable the soft-lockup detector.
1622 noswapaccount [KNL] Disable accounting of swap in memory resource
1623 controller. (See Documentation/cgroups/memory.txt)
1625 nosync [HW,M68K] Disables sync negotiation for all devices.
1627 notsc [BUGS=X86-32] Disable Time Stamp Counter
1629 nousb [USB] Disable the USB subsystem
1633 nptcg= [IA64] Override max number of concurrent global TLB
1634 purges which is reported from either PAL_VM_SUMMARY or
1637 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1638 one of ['zone', 'node', 'default'] can be specified
1639 This can be set from sysctl after boot.
1640 See Documentation/sysctl/vm.txt for details.
1642 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1644 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1645 See Documentation/debugging-via-ohci1394.txt for more
1648 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1649 Rather than timing out after 20 ms if an EC
1650 command is not properly ACKed, override the length
1651 of the timeout. We have interrupts disabled while
1652 waiting for the ACK, so if this is set too high
1653 interrupts *may* be lost!
1658 oprofile.timer= [HW]
1659 Use timer interrupt instead of performance counters
1661 osst= [HW,SCSI] SCSI Tape Driver
1662 Format: <buffer_size>,<write_threshold>
1663 See also Documentation/scsi/st.txt.
1665 panic= [KNL] Kernel behaviour on panic
1668 parkbd.port= [HW] Parallel port number the keyboard adapter is
1669 connected to, default is 0.
1671 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1672 0 for XT, 1 for AT (default is AT).
1675 parport= [HW,PPT] Specify parallel ports. 0 disables.
1676 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1677 Use 'auto' to force the driver to use any
1678 IRQ/DMA settings detected (the default is to
1679 ignore detected IRQ/DMA settings because of
1680 possible conflicts). You can specify the base
1681 address, IRQ, and DMA settings; IRQ and DMA
1682 should be numbers, or 'auto' (for using detected
1683 settings on that particular port), or 'nofifo'
1684 (to avoid using a FIFO even if it is detected).
1685 Parallel ports are assigned in the order they
1686 are specified on the command line, starting
1689 parport_init_mode= [HW,PPT]
1690 Configure VIA parallel port to operate in
1691 a specific mode. This is necessary on Pegasos
1692 computer where firmware has no options for setting
1693 up parallel port mode and sets it to spp.
1694 Currently this function knows 686a and 8231 chips.
1695 Format: [spp|ps2|epp|ecp|ecpepp]
1697 pas2= [HW,OSS] Format:
1698 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1701 See header of drivers/scsi/pas16.c.
1704 Halt all CPUs after the first oops has been printed for
1705 the specified number of seconds. This is to be used if
1706 your oopses keep scrolling off the screen.
1711 See header of drivers/block/paride/pcd.c.
1712 See also Documentation/blockdev/paride.txt.
1714 pci=option[,option...] [PCI] various PCI subsystem options:
1715 earlydump [X86] dump PCI config space before the kernel
1717 off [X86] don't probe for the PCI bus
1718 bios [X86-32] force use of PCI BIOS, don't access
1719 the hardware directly. Use this if your machine
1720 has a non-standard PCI host bridge.
1721 nobios [X86-32] disallow use of PCI BIOS, only direct
1722 hardware access methods are allowed. Use this
1723 if you experience crashes upon bootup and you
1724 suspect they are caused by the BIOS.
1725 conf1 [X86] Force use of PCI Configuration
1727 conf2 [X86] Force use of PCI Configuration
1729 noaer [PCIE] If the PCIEAER kernel config parameter is
1730 enabled, this kernel boot option can be used to
1731 disable the use of PCIE advanced error reporting.
1732 nodomains [PCI] Disable support for multiple PCI
1733 root domains (aka PCI segments, in ACPI-speak).
1734 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1736 nomsi [MSI] If the PCI_MSI kernel config parameter is
1737 enabled, this kernel boot option can be used to
1738 disable the use of MSI interrupts system-wide.
1739 noioapicquirk [APIC] Disable all boot interrupt quirks.
1740 Safety option to keep boot IRQs enabled. This
1741 should never be necessary.
1742 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1743 primary IO-APIC for bridges that cannot disable
1744 boot IRQs. This fixes a source of spurious IRQs
1745 when the system masks IRQs.
1746 noioapicreroute [APIC] Disable workaround that uses the
1747 boot IRQ equivalent of an IRQ that connects to
1748 a chipset where boot IRQs cannot be disabled.
1749 The opposite of ioapicreroute.
1750 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1751 routing table. These calls are known to be buggy
1752 on several machines and they hang the machine
1753 when used, but on other computers it's the only
1754 way to get the interrupt routing table. Try
1755 this option if the kernel is unable to allocate
1756 IRQs or discover secondary PCI buses on your
1758 rom [X86] Assign address space to expansion ROMs.
1759 Use with caution as certain devices share
1760 address decoders between ROMs and other
1762 norom [X86] Do not assign address space to
1763 expansion ROMs that do not already have
1764 BIOS assigned address ranges.
1765 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1766 assigned automatically to PCI devices. You can
1767 make the kernel exclude IRQs of your ISA cards
1769 pirqaddr=0xAAAAA [X86] Specify the physical address
1770 of the PIRQ table (normally generated
1771 by the BIOS) if it is outside the
1772 F0000h-100000h range.
1773 lastbus=N [X86] Scan all buses thru bus #N. Can be
1774 useful if the kernel is unable to find your
1775 secondary buses and you want to tell it
1776 explicitly which ones they are.
1777 assign-busses [X86] Always assign all PCI bus
1778 numbers ourselves, overriding
1779 whatever the firmware may have done.
1780 usepirqmask [X86] Honor the possible IRQ mask stored
1781 in the BIOS $PIR table. This is needed on
1782 some systems with broken BIOSes, notably
1783 some HP Pavilion N5400 and Omnibook XE3
1784 notebooks. This will have no effect if ACPI
1785 IRQ routing is enabled.
1786 noacpi [X86] Do not use ACPI for IRQ routing
1787 or for PCI scanning.
1788 use_crs [X86] Use _CRS for PCI resource
1790 routeirq Do IRQ routing for all PCI devices.
1791 This is normally done in pci_enable_device(),
1792 so this option is a temporary workaround
1793 for broken drivers that don't call it.
1794 skip_isa_align [X86] do not align io start addr, so can
1795 handle more pci cards
1796 firmware [ARM] Do not re-enumerate the bus but instead
1797 just use the configuration from the
1798 bootloader. This is currently used on
1799 IXP2000 systems where the bus has to be
1800 configured a certain way for adjunct CPUs.
1801 noearly [X86] Don't do any early type 1 scanning.
1802 This might help on some broken boards which
1803 machine check when some devices' config space
1804 is read. But various workarounds are disabled
1805 and some IOMMU drivers will not work.
1806 bfsort Sort PCI devices into breadth-first order.
1807 This sorting is done to get a device
1808 order compatible with older (<= 2.4) kernels.
1809 nobfsort Don't sort PCI devices into breadth-first order.
1810 cbiosize=nn[KMG] The fixed amount of bus space which is
1811 reserved for the CardBus bridge's IO window.
1812 The default value is 256 bytes.
1813 cbmemsize=nn[KMG] The fixed amount of bus space which is
1814 reserved for the CardBus bridge's memory
1815 window. The default value is 64 megabytes.
1818 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1819 Specifies alignment and device to reassign
1820 aligned memory resources.
1821 If <order of align> is not specified,
1822 PAGE_SIZE is used as alignment.
1823 PCI-PCI bridge can be specified, if resource
1824 windows need to be expanded.
1826 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1829 force Enable ASPM even on devices that claim not to support it.
1830 WARNING: Forcing ASPM on may cause system lockups.
1832 pcmv= [HW,PCMCIA] BadgePAD 4
1835 See Documentation/blockdev/paride.txt.
1837 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1840 See arch/parisc/kernel/pdc_chassis.c
1843 See Documentation/blockdev/paride.txt.
1846 See Documentation/blockdev/paride.txt.
1848 pirq= [SMP,APIC] Manual mp-table setup
1849 See Documentation/x86/i386/IO-APIC.txt.
1851 plip= [PPT,NET] Parallel port network link
1852 Format: { parport<nr> | timid | 0 }
1853 See also Documentation/parport.txt.
1855 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1856 Override pmtimer IOPort with a hex value.
1860 Enable PNP debug messages. This depends on the
1861 CONFIG_PNP_DEBUG_MESSAGES option.
1867 { on | off | curr | res | no-curr | no-res }
1870 [ISAPNP] Exclude IRQs for the autoconfiguration
1873 [ISAPNP] Exclude DMAs for the autoconfiguration
1875 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1876 Ranges are in pairs (I/O port base and size).
1879 [ISAPNP] Exclude memory regions for the
1881 Ranges are in pairs (memory base and size).
1883 print-fatal-signals=
1884 [KNL] debug: print fatal signals
1885 print-fatal-signals=1: print segfault info to
1889 printk.time= Show timing data prefixed to each printk message line
1890 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1892 profile= [KNL] Enable kernel profiling via /proc/profile
1893 Format: [schedule,]<number>
1894 Param: "schedule" - profile schedule points.
1895 Param: <number> - step/bucket size as a power of 2 for
1896 statistical time based profiling.
1897 Param: "sleep" - profile D-state sleeping (millisecs).
1898 Requires CONFIG_SCHEDSTATS
1899 Param: "kvm" - profile VM exits.
1901 processor.max_cstate= [HW,ACPI]
1902 Limit processor to maximum C-state
1903 max_cstate=9 overrides any DMI blacklist limit.
1905 processor.nocst [HW,ACPI]
1906 Ignore the _CST method to determine C-states,
1907 instead using the legacy FADT method
1909 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1911 See Documentation/blockdev/ramdisk.txt.
1913 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1914 probe for; one of (bare|imps|exps|lifebook|any).
1915 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1917 psmouse.resetafter= [HW,MOUSE]
1918 Try to reset the device after so many bad packets
1921 [HW,MOUSE] Set desired mouse resolution, in dpi.
1922 psmouse.smartscroll=
1923 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1924 0 = disabled, 1 = enabled (default).
1926 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1928 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1931 See Documentation/blockdev/paride.txt.
1934 [KNL] Number of legacy pty's. Overwrites compiled-in
1937 quiet [KNL] Disable most log messages
1942 See Documentation/md.txt.
1944 ramdisk_blocksize= [RAM]
1945 See Documentation/blockdev/ramdisk.txt.
1947 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1948 See Documentation/blockdev/ramdisk.txt.
1950 rcupdate.blimit= [KNL,BOOT]
1951 Set maximum number of finished RCU callbacks to process
1954 rcupdate.qhimark= [KNL,BOOT]
1955 Set threshold of queued
1956 RCU callbacks over which batch limiting is disabled.
1958 rcupdate.qlowmark= [KNL,BOOT]
1959 Set threshold of queued RCU callbacks below which
1960 batch limiting is re-enabled.
1964 Run specified binary instead of /init from the ramdisk,
1965 used for early userspace startup. See initrd.
1967 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1968 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1969 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1972 [KNL, SMP] Set scheduler's default relax_domain_level.
1973 See Documentation/cgroups/cpusets.txt.
1975 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1977 reservetop= [X86-32]
1979 Reserves a hole at the top of the kernel virtual
1982 reset_devices [KNL] Force drivers to reset the underlying device
1983 during initialization.
1986 Specify the partition device for software suspend
1988 resume_offset= [SWSUSP]
1989 Specify the offset from the beginning of the partition
1990 given by "resume=" at which the swap header is located,
1991 in <PAGE_SIZE> units (needed only for swap files).
1992 See Documentation/power/swsusp-and-swap-files.txt
1994 retain_initrd [RAM] Keep initrd memory after extraction
1996 rhash_entries= [KNL,NET]
1997 Set number of hash buckets for route cache
1999 riscom8= [HW,SERIAL]
2000 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2002 ro [KNL] Mount root device read-only on boot
2004 root= [KNL] Root filesystem
2006 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2007 mount the root filesystem
2009 rootflags= [KNL] Set root filesystem mount option string
2011 rootfstype= [KNL] Set root filesystem type
2013 rootwait [KNL] Wait (indefinitely) for root device to show up.
2014 Useful for devices that are detected asynchronously
2015 (e.g. USB and MMC devices).
2017 root_plug.vendor_id=
2018 [ROOTPLUG] Override the default vendor ID
2020 root_plug.product_id=
2021 [ROOTPLUG] Override the default product ID
2024 [ROOTPLUG] Enable debugging output
2026 rw [KNL] Mount root device read-write on boot
2028 S [KNL] Run init in single mode
2031 See drivers/net/irda/sa1100_ir.c.
2033 sbni= [NET] Granch SBNI12 leased line adapter
2035 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2036 Format: <io>[,<timeout>[,<isapnp>]]
2038 scsi_debug_*= [SCSI]
2039 See drivers/scsi/scsi_debug.c.
2041 scsi_default_dev_flags=
2042 [SCSI] SCSI default device flags
2045 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2046 Format: <vendor>:<model>:<flags>
2047 (flags are integer value)
2049 scsi_logging_level= [SCSI] a bit mask of logging levels
2050 See drivers/scsi/scsi_logging.h for bits. Also
2051 settable via sysctl at dev.scsi.logging_level
2052 (/proc/sys/dev/scsi/logging_level).
2053 There is also a nice 'scsi_logging_level' script in the
2054 S390-tools package, available for download at
2055 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2057 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2058 discovered. async scans them in kernel threads,
2059 allowing boot to proceed. none ignores them, expecting
2060 user space to do the scan.
2062 selinux [SELINUX] Disable or enable SELinux at boot time.
2063 Format: { "0" | "1" }
2064 See security/selinux/Kconfig help text.
2067 Default value is set via kernel config option.
2068 If enabled at boot time, /selinux/disable can be used
2069 later to disable prior to initial policy load.
2071 serialnumber [BUGS=X86-32]
2074 Maximal number of shapers.
2076 show_msr= [x86] show boot-time MSR settings
2077 Format: { <integer> }
2078 Show boot-time (BIOS-initialized) MSR settings.
2079 The parameter means the number of CPUs to show,
2080 for example 1 means boot CPU only.
2083 See header of drivers/scsi/sim710.c.
2090 slub_debug[=options[,slabs]] [MM, SLUB]
2091 Enabling slub_debug allows one to determine the
2092 culprit if slab objects become corrupted. Enabling
2093 slub_debug can create guard zones around objects and
2094 may poison objects when not in use. Also tracks the
2095 last alloc / free. For more information see
2096 Documentation/vm/slub.txt.
2098 slub_max_order= [MM, SLUB]
2099 Determines the maximum allowed order for slabs.
2100 A high setting may cause OOMs due to memory
2101 fragmentation. For more information see
2102 Documentation/vm/slub.txt.
2104 slub_min_objects= [MM, SLUB]
2105 The minimum number of objects per slab. SLUB will
2106 increase the slab order up to slub_max_order to
2107 generate a sufficiently large slab able to contain
2108 the number of objects indicated. The higher the number
2109 of objects the smaller the overhead of tracking slabs
2110 and the less frequently locks need to be acquired.
2111 For more information see Documentation/vm/slub.txt.
2113 slub_min_order= [MM, SLUB]
2114 Determines the mininum page order for slabs. Must be
2115 lower than slub_max_order.
2116 For more information see Documentation/vm/slub.txt.
2118 slub_nomerge [MM, SLUB]
2119 Disable merging of slabs with similar size. May be
2120 necessary if there is some reason to distinguish
2121 allocs to different slabs. Debug options disable
2122 merging on their own.
2123 For more information see Documentation/vm/slub.txt.
2126 Format: <io1>[,<io2>[,...,<io8>]]
2128 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2129 attempt to substitute SMP alternatives once at boot.
2131 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2132 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2133 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2134 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2135 smsc-ircc2.ircc_irq= [HW] IRQ line
2136 smsc-ircc2.ircc_dma= [HW] DMA channel
2137 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2138 0: Toshiba Satellite 1800 (GP data pin select)
2139 1: Fast pin select (default)
2142 snd-ad1816a= [HW,ALSA]
2144 snd-ad1848= [HW,ALSA]
2146 snd-ali5451= [HW,ALSA]
2148 snd-als100= [HW,ALSA]
2150 snd-als4000= [HW,ALSA]
2152 snd-azt2320= [HW,ALSA]
2154 snd-cmi8330= [HW,ALSA]
2156 snd-cmipci= [HW,ALSA]
2158 snd-cs4231= [HW,ALSA]
2160 snd-cs4232= [HW,ALSA]
2162 snd-cs4236= [HW,ALSA]
2164 snd-cs4281= [HW,ALSA]
2166 snd-cs46xx= [HW,ALSA]
2168 snd-dt019x= [HW,ALSA]
2170 snd-dummy= [HW,ALSA]
2172 snd-emu10k1= [HW,ALSA]
2174 snd-ens1370= [HW,ALSA]
2176 snd-ens1371= [HW,ALSA]
2178 snd-es968= [HW,ALSA]
2180 snd-es1688= [HW,ALSA]
2182 snd-es18xx= [HW,ALSA]
2184 snd-es1938= [HW,ALSA]
2186 snd-es1968= [HW,ALSA]
2188 snd-fm801= [HW,ALSA]
2190 snd-gusclassic= [HW,ALSA]
2192 snd-gusextreme= [HW,ALSA]
2194 snd-gusmax= [HW,ALSA]
2198 snd-ice1712= [HW,ALSA]
2200 snd-intel8x0= [HW,ALSA]
2202 snd-interwave= [HW,ALSA]
2207 snd-korg1212= [HW,ALSA]
2209 snd-maestro3= [HW,ALSA]
2211 snd-mpu401= [HW,ALSA]
2213 snd-mtpav= [HW,ALSA]
2215 snd-nm256= [HW,ALSA]
2217 snd-opl3sa2= [HW,ALSA]
2225 snd-opti93x= [HW,ALSA]
2229 snd-rme32= [HW,ALSA]
2231 snd-rme96= [HW,ALSA]
2233 snd-rme9652= [HW,ALSA]
2239 snd-sbawe= [HW,ALSA]
2241 snd-serial= [HW,ALSA]
2243 snd-sgalaxy= [HW,ALSA]
2245 snd-sonicvibes= [HW,ALSA]
2250 snd-sun-cs4231= [HW,ALSA]
2252 snd-trident= [HW,ALSA]
2254 snd-usb-audio= [HW,ALSA,USB]
2256 snd-via82xx= [HW,ALSA]
2258 snd-virmidi= [HW,ALSA]
2260 snd-wavefront= [HW,ALSA]
2262 snd-ymfpci= [HW,ALSA]
2265 [KNL] Should the soft-lockup detector generate panics.
2267 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2268 See Documentation/sonypi.txt
2270 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2271 See Documentation/serial/specialix.txt.
2273 spia_io_base= [HW,MTD]
2279 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2281 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2282 See Documentation/scsi/st.txt.
2285 Enabled the stack tracer on boot up.
2289 Set the STI (builtin display/keyboard on the HP-PARISC
2290 machines) console (graphic card) which should be used
2291 as the initial boot-console.
2292 See also comment in drivers/video/console/sticore.c.
2295 See comment in drivers/video/console/sticore.c.
2298 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2302 Control how the NFS server code allocates CPUs to
2303 service thread pools. Depending on how many NICs
2304 you have and where their interrupts are bound, this
2305 option will affect which CPUs will do NFS serving.
2306 Note: this parameter cannot be changed while the
2307 NFS server is running.
2309 auto the server chooses an appropriate mode
2310 automatically using heuristics
2311 global a single global pool contains all CPUs
2312 percpu one pool for each CPU
2313 pernode one pool for each NUMA node (equivalent
2314 to global on non-NUMA machines)
2316 swiotlb= [IA-64] Number of I/O TLB slabs
2320 sym53c416= [HW,SCSI]
2321 See header of drivers/scsi/sym53c416.c.
2323 sysrq_always_enabled
2325 Ignore sysrq setting - this boot parameter will
2326 neutralize any effect of /proc/sys/kernel/sysrq.
2327 Useful for debugging.
2330 See header of drivers/scsi/t128.c.
2334 test_suspend= [SUSPEND]
2335 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2336 standby suspend) as the system sleep state to briefly
2337 enter during system startup. The system is woken from
2338 this state using a wakeup-capable RTC alarm.
2340 thash_entries= [KNL,NET]
2341 Set number of hash buckets for TCP connection
2343 thermal.act= [HW,ACPI]
2344 -1: disable all active trip points in all thermal zones
2345 <degrees C>: override all lowest active trip points
2347 thermal.crt= [HW,ACPI]
2348 -1: disable all critical trip points in all thermal zones
2349 <degrees C>: override all critical trip points
2351 thermal.nocrt= [HW,ACPI]
2352 Set to disable actions on ACPI thermal zone
2353 critical and hot trip points.
2355 thermal.off= [HW,ACPI]
2356 1: disable ACPI thermal control
2358 thermal.psv= [HW,ACPI]
2359 -1: disable all passive trip points
2360 <degrees C>: override all passive trip points to this
2363 thermal.tzp= [HW,ACPI]
2364 Specify global default ACPI thermal zone polling rate
2365 <deci-seconds>: poll all this frequency
2366 0: no polling (default)
2369 See comment before function dc390_setup() in
2370 drivers/scsi/tmscsim.c.
2374 Specify if the kernel should make use of the cpu
2375 topology informations if the hardware supports these.
2376 The scheduler will make use of these informations and
2377 e.g. base its process migration decisions on it.
2382 trace_buf_size=nn[KMG] [ftrace] will set tracing buffer size.
2384 trix= [HW,OSS] MediaTrix AudioTrix Pro
2386 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2388 tsc= Disable clocksource-must-verify flag for TSC.
2390 [x86] reliable: mark tsc clocksource as reliable, this
2391 disables clocksource verification at runtime.
2392 Used to enable high-resolution timer mode on older
2393 hardware, and in virtualized environment.
2395 turbografx.map[2|3]= [HW,JOY]
2396 TurboGraFX parallel port interface
2398 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2399 See also Documentation/input/joystick-parport.txt
2401 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2402 See header of drivers/scsi/u14-34f.c.
2411 [USB] Ignore overcurrent events (default N).
2412 Some badly-designed motherboards generate lots of
2413 bogus events, for ports that aren't wired to
2414 anything. Set this parameter to avoid log spamming.
2415 Note that genuine overcurrent events won't be
2420 Set unknown_nmi_panic=1 early on boot.
2422 usbcore.autosuspend=
2423 [USB] The autosuspend time delay (in seconds) used
2424 for newly-detected USB devices (default 2). This
2425 is the time required before an idle device will be
2426 autosuspended. Devices for which the delay is set
2427 to a negative value won't be autosuspended at all.
2429 usbcore.usbfs_snoop=
2430 [USB] Set to log all usbfs traffic (default 0 = off).
2432 usbcore.blinkenlights=
2433 [USB] Set to cycle leds on hubs (default 0 = off).
2435 usbcore.old_scheme_first=
2436 [USB] Start with the old device initialization
2437 scheme (default 0 = off).
2439 usbcore.use_both_schemes=
2440 [USB] Try the other device initialization scheme
2441 if the first one fails (default 1 = enabled).
2443 usbcore.initial_descriptor_timeout=
2444 [USB] Specifies timeout for the initial 64-byte
2445 USB_REQ_GET_DESCRIPTOR request in milliseconds
2446 (default 5000 = 5.0 seconds).
2449 [USBHID] The interval which mice are to be polled at.
2451 usb-storage.delay_use=
2452 [UMS] The delay in seconds before a new device is
2453 scanned for Logical Units (default 5).
2456 [UMS] A list of quirks entries to supplement or
2457 override the built-in unusual_devs list. List
2458 entries are separated by commas. Each entry has
2459 the form VID:PID:Flags where VID and PID are Vendor
2460 and Product ID values (4-digit hex numbers) and
2461 Flags is a set of characters, each corresponding
2462 to a common usb-storage quirk flag as follows:
2463 a = SANE_SENSE (collect more than 18 bytes
2465 c = FIX_CAPACITY (decrease the reported
2466 device capacity by one sector);
2467 h = CAPACITY_HEURISTICS (decrease the
2468 reported device capacity by one
2469 sector if the number is odd);
2470 i = IGNORE_DEVICE (don't bind to this
2472 l = NOT_LOCKABLE (don't try to lock and
2473 unlock ejectable media);
2474 m = MAX_SECTORS_64 (don't transfer more
2475 than 64 sectors = 32 KB at a time);
2476 o = CAPACITY_OK (accept the capacity
2477 reported by the device);
2478 r = IGNORE_RESIDUE (the device reports
2479 bogus residue values);
2480 s = SINGLE_LUN (the device has only one
2482 w = NO_WP_DETECT (don't test whether the
2483 medium is write-protected).
2484 Example: quirks=0419:aaf5:rl,0421:0433:rc
2486 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2487 kernel's map of available physical RAM.
2489 vdso= [X86-32,SH,x86-64]
2490 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2491 vdso=1: enable VDSO (default)
2492 vdso=0: disable VDSO mapping
2494 vdso32= [X86-32,X86-64]
2495 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2496 vdso32=1: enable 32-bit VDSO (default)
2497 vdso32=0: disable 32-bit VDSO mapping
2500 vector=percpu: enable percpu vector domain
2502 video= [FB] Frame buffer configuration
2503 See Documentation/fb/modedb.txt.
2505 vga= [BOOT,X86-32] Select a particular video mode
2506 See Documentation/x86/boot.txt and
2507 Documentation/svga.txt.
2508 Use vga=ask for menu.
2509 This is actually a boot loader parameter; the value is
2510 passed to the kernel using a special protocol.
2512 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2513 size of <nn>. This can be used to increase the
2514 minimum size (128MB on x86). It can also be used to
2515 decrease the size and leave more room for directly
2518 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2521 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2524 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2527 waveartist= [HW,OSS]
2528 Format: <io>,<irq>,<dma>,<dma2>
2531 See header of drivers/scsi/wd33c93.c.
2534 See header of drivers/scsi/wd7000.c.
2537 See Documentation/watchdog/wdt.txt.
2539 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2540 xd_geo= See header of drivers/block/xd.c.
2542 xirc2ps_cs= [NET,PCMCIA]
2544 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2546 norandmaps Don't use address space randomization. Equivalent to
2547 echo 0 > /proc/sys/kernel/randomize_va_space
2549 ______________________________________________________________________
2553 Add documentation for ALSA options.
2554 Add more DRM drivers.