kernel-parameters.txt 75 KB

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  1. Kernel Parameters
  2. ~~~~~~~~~~~~~~~~~
  3. The following is a consolidated list of the kernel parameters as implemented
  4. (mostly) by the __setup() macro and sorted into English Dictionary order
  5. (defined as ignoring all punctuation and sorting digits before letters in a
  6. case insensitive manner), and with descriptions where known.
  7. Module parameters for loadable modules are specified only as the
  8. parameter name with optional '=' and value as appropriate, such as:
  9. modprobe usbcore blinkenlights=1
  10. Module parameters for modules that are built into the kernel image
  11. are specified on the kernel command line with the module name plus
  12. '.' plus parameter name, with '=' and value if appropriate, such as:
  13. usbcore.blinkenlights=1
  14. This document may not be entirely up to date and comprehensive. The command
  15. "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
  16. module. Loadable modules, after being loaded into the running kernel, also
  17. reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
  18. parameters may be changed at runtime by the command
  19. "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
  20. The parameters listed below are only valid if certain kernel build options were
  21. enabled and if respective hardware is present. The text in square brackets at
  22. the beginning of each description states the restrictions within which a
  23. parameter is applicable:
  24. ACPI ACPI support is enabled.
  25. AGP AGP (Accelerated Graphics Port) is enabled.
  26. ALSA ALSA sound support is enabled.
  27. APIC APIC support is enabled.
  28. APM Advanced Power Management support is enabled.
  29. AVR32 AVR32 architecture is enabled.
  30. AX25 Appropriate AX.25 support is enabled.
  31. BLACKFIN Blackfin architecture is enabled.
  32. DRM Direct Rendering Management support is enabled.
  33. EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
  34. EFI EFI Partitioning (GPT) is enabled
  35. EIDE EIDE/ATAPI support is enabled.
  36. FB The frame buffer device is enabled.
  37. HW Appropriate hardware is enabled.
  38. IA-64 IA-64 architecture is enabled.
  39. IOSCHED More than one I/O scheduler is enabled.
  40. IP_PNP IP DHCP, BOOTP, or RARP is enabled.
  41. ISAPNP ISA PnP code is enabled.
  42. ISDN Appropriate ISDN support is enabled.
  43. JOY Appropriate joystick support is enabled.
  44. LIBATA Libata driver is enabled
  45. LP Printer support is enabled.
  46. LOOP Loopback device support is enabled.
  47. M68k M68k architecture is enabled.
  48. These options have more detailed description inside of
  49. Documentation/m68k/kernel-options.txt.
  50. MCA MCA bus support is enabled.
  51. MDA MDA console support is enabled.
  52. MOUSE Appropriate mouse support is enabled.
  53. MSI Message Signaled Interrupts (PCI).
  54. MTD MTD (Memory Technology Device) support is enabled.
  55. NET Appropriate network support is enabled.
  56. NUMA NUMA support is enabled.
  57. GENERIC_TIME The generic timeofday code is enabled.
  58. NFS Appropriate NFS support is enabled.
  59. OSS OSS sound support is enabled.
  60. PV_OPS A paravirtualized kernel is enabled.
  61. PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
  62. PARISC The PA-RISC architecture is enabled.
  63. PCI PCI bus support is enabled.
  64. PCIE PCI Express support is enabled.
  65. PCMCIA The PCMCIA subsystem is enabled.
  66. PNP Plug & Play support is enabled.
  67. PPC PowerPC architecture is enabled.
  68. PPT Parallel port support is enabled.
  69. PS2 Appropriate PS/2 support is enabled.
  70. RAM RAM disk support is enabled.
  71. ROOTPLUG The example Root Plug LSM is enabled.
  72. S390 S390 architecture is enabled.
  73. SCSI Appropriate SCSI support is enabled.
  74. A lot of drivers has their options described inside of
  75. Documentation/scsi/.
  76. SECURITY Different security models are enabled.
  77. SELINUX SELinux support is enabled.
  78. SERIAL Serial support is enabled.
  79. SH SuperH architecture is enabled.
  80. SMP The kernel is an SMP kernel.
  81. SPARC Sparc architecture is enabled.
  82. SWSUSP Software suspend (hibernation) is enabled.
  83. SUSPEND System suspend states are enabled.
  84. TS Appropriate touchscreen support is enabled.
  85. USB USB support is enabled.
  86. USBHID USB Human Interface Device support is enabled.
  87. V4L Video For Linux support is enabled.
  88. VGA The VGA console has been enabled.
  89. VT Virtual terminal support is enabled.
  90. WDT Watchdog support is enabled.
  91. XT IBM PC/XT MFM hard disk support is enabled.
  92. X86-32 X86-32, aka i386 architecture is enabled.
  93. X86-64 X86-64 architecture is enabled.
  94. More X86-64 boot options can be found in
  95. Documentation/x86/x86_64/boot-options.txt .
  96. X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
  97. In addition, the following text indicates that the option:
  98. BUGS= Relates to possible processor bugs on the said processor.
  99. KNL Is a kernel start-up parameter.
  100. BOOT Is a boot loader parameter.
  101. Parameters denoted with BOOT are actually interpreted by the boot
  102. loader, and have no meaning to the kernel directly.
  103. Do not modify the syntax of boot loader parameters without extreme
  104. need or coordination with <Documentation/x86/i386/boot.txt>.
  105. There are also arch-specific kernel-parameters not documented here.
  106. See for example <Documentation/x86/x86_64/boot-options.txt>.
  107. Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
  108. a trailing = on the name of any parameter states that that parameter will
  109. be entered as an environment variable, whereas its absence indicates that
  110. it will appear as a kernel argument readable via /proc/cmdline by programs
  111. running once the system is up.
  112. The number of kernel parameters is not limited, but the length of the
  113. complete command line (parameters including spaces etc.) is limited to
  114. a fixed number of characters. This limit depends on the architecture
  115. and is between 256 and 4096 characters. It is defined in the file
  116. ./include/asm/setup.h as COMMAND_LINE_SIZE.
  117. acpi= [HW,ACPI,X86-64,i386]
  118. Advanced Configuration and Power Interface
  119. Format: { force | off | ht | strict | noirq }
  120. force -- enable ACPI if default was off
  121. off -- disable ACPI if default was on
  122. noirq -- do not use ACPI for IRQ routing
  123. ht -- run only enough ACPI to enable Hyper Threading
  124. strict -- Be less tolerant of platforms that are not
  125. strictly ACPI specification compliant.
  126. See also Documentation/power/pm.txt, pci=noacpi
  127. acpi_apic_instance= [ACPI, IOAPIC]
  128. Format: <int>
  129. 2: use 2nd APIC table, if available
  130. 1,0: use 1st APIC table
  131. default: 0
  132. acpi_sleep= [HW,ACPI] Sleep options
  133. Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, old_ordering }
  134. See Documentation/power/video.txt for s3_bios and s3_mode.
  135. s3_beep is for debugging; it makes the PC's speaker beep
  136. as soon as the kernel's real-mode entry point is called.
  137. s4_nohwsig prevents ACPI hardware signature from being
  138. used during resume from hibernation.
  139. old_ordering causes the ACPI 1.0 ordering of the _PTS
  140. control method, wrt putting devices into low power
  141. states, to be enforced (the ACPI 2.0 ordering of _PTS is
  142. used by default).
  143. acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
  144. Format: { level | edge | high | low }
  145. acpi_irq_balance [HW,ACPI]
  146. ACPI will balance active IRQs
  147. default in APIC mode
  148. acpi_irq_nobalance [HW,ACPI]
  149. ACPI will not move active IRQs (default)
  150. default in PIC mode
  151. acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
  152. use by PCI
  153. Format: <irq>,<irq>...
  154. acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
  155. Format: <irq>,<irq>...
  156. acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
  157. acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
  158. Format: To spoof as Windows 98: ="Microsoft Windows"
  159. acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
  160. acpi_osi="string1" # add string1 -- only one string
  161. acpi_osi="!string2" # remove built-in string2
  162. acpi_osi= # disable all strings
  163. acpi_serialize [HW,ACPI] force serialization of AML methods
  164. acpi_skip_timer_override [HW,ACPI]
  165. Recognize and ignore IRQ0/pin2 Interrupt Override.
  166. For broken nForce2 BIOS resulting in XT-PIC timer.
  167. acpi_use_timer_override [HW,ACPI}
  168. Use timer override. For some broken Nvidia NF5 boards
  169. that require a timer override, but don't have
  170. HPET
  171. acpi_backlight= [HW,ACPI]
  172. acpi_backlight=vendor
  173. acpi_backlight=video
  174. If set to vendor, prefer vendor specific driver
  175. (e.g. thinkpad_acpi, sony_acpi, etc.) instead
  176. of the ACPI video.ko driver.
  177. acpi_display_output= [HW,ACPI]
  178. acpi_display_output=vendor
  179. acpi_display_output=video
  180. See above.
  181. acpi.debug_layer= [HW,ACPI]
  182. Format: <int>
  183. Each bit of the <int> indicates an ACPI debug layer,
  184. 1: enable, 0: disable. It is useful for boot time
  185. debugging. After system has booted up, it can be set
  186. via /sys/module/acpi/parameters/debug_layer.
  187. CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
  188. Available bits (add the numbers together) to enable debug output
  189. for specific parts of the ACPI subsystem:
  190. 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
  191. 0x10 namespace 0x20 parser 0x40 dispatcher
  192. 0x80 executer 0x100 resources 0x200 acpica debugger
  193. 0x400 os services 0x800 acpica disassembler.
  194. The number can be in decimal or prefixed with 0x in hex.
  195. Warning: Many of these options can produce a lot of
  196. output and make your system unusable. Be very careful.
  197. acpi.debug_level= [HW,ACPI]
  198. Format: <int>
  199. Each bit of the <int> indicates an ACPI debug level,
  200. which corresponds to the level in an ACPI_DEBUG_PRINT
  201. statement. After system has booted up, this mask
  202. can be set via /sys/module/acpi/parameters/debug_level.
  203. CONFIG_ACPI_DEBUG must be enabled for this to produce
  204. any output. The number can be in decimal or prefixed
  205. with 0x in hex. Some of these options produce so much
  206. output that the system is unusable.
  207. The following global components are defined by the
  208. ACPI CA:
  209. 0x01 error
  210. 0x02 warn
  211. 0x04 init
  212. 0x08 debug object
  213. 0x10 info
  214. 0x20 init names
  215. 0x40 parse
  216. 0x80 load
  217. 0x100 dispatch
  218. 0x200 execute
  219. 0x400 names
  220. 0x800 operation region
  221. 0x1000 bfield
  222. 0x2000 tables
  223. 0x4000 values
  224. 0x8000 objects
  225. 0x10000 resources
  226. 0x20000 user requests
  227. 0x40000 package
  228. The number can be in decimal or prefixed with 0x in hex.
  229. Warning: Many of these options can produce a lot of
  230. output and make your system unusable. Be very careful.
  231. acpi.power_nocheck= [HW,ACPI]
  232. Format: 1/0 enable/disable the check of power state.
  233. On some bogus BIOS the _PSC object/_STA object of
  234. power resource can't return the correct device power
  235. state. In such case it is unneccessary to check its
  236. power state again in power transition.
  237. 1 : disable the power state check
  238. acpi_pm_good [X86-32,X86-64]
  239. Override the pmtimer bug detection: force the kernel
  240. to assume that this machine's pmtimer latches its value
  241. and always returns good values.
  242. agp= [AGP]
  243. { off | try_unsupported }
  244. off: disable AGP support
  245. try_unsupported: try to drive unsupported chipsets
  246. (may crash computer or cause data corruption)
  247. enable_timer_pin_1 [i386,x86-64]
  248. Enable PIN 1 of APIC timer
  249. Can be useful to work around chipset bugs
  250. (in particular on some ATI chipsets).
  251. The kernel tries to set a reasonable default.
  252. disable_timer_pin_1 [i386,x86-64]
  253. Disable PIN 1 of APIC timer
  254. Can be useful to work around chipset bugs.
  255. ad1848= [HW,OSS]
  256. Format: <io>,<irq>,<dma>,<dma2>,<type>
  257. advansys= [HW,SCSI]
  258. See header of drivers/scsi/advansys.c.
  259. advwdt= [HW,WDT] Advantech WDT
  260. Format: <iostart>,<iostop>
  261. aedsp16= [HW,OSS] Audio Excel DSP 16
  262. Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
  263. See also header of sound/oss/aedsp16.c.
  264. aha152x= [HW,SCSI]
  265. See Documentation/scsi/aha152x.txt.
  266. aha1542= [HW,SCSI]
  267. Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
  268. aic7xxx= [HW,SCSI]
  269. See Documentation/scsi/aic7xxx.txt.
  270. aic79xx= [HW,SCSI]
  271. See Documentation/scsi/aic79xx.txt.
  272. amd_iommu= [HW,X86-84]
  273. Pass parameters to the AMD IOMMU driver in the system.
  274. Possible values are:
  275. isolate - enable device isolation (each device, as far
  276. as possible, will get its own protection
  277. domain)
  278. fullflush - enable flushing of IO/TLB entries when
  279. they are unmapped. Otherwise they are
  280. flushed before they will be reused, which
  281. is a lot of faster
  282. amd_iommu_size= [HW,X86-64]
  283. Define the size of the aperture for the AMD IOMMU
  284. driver. Possible values are:
  285. '32M', '64M' (default), '128M', '256M', '512M', '1G'
  286. amijoy.map= [HW,JOY] Amiga joystick support
  287. Map of devices attached to JOY0DAT and JOY1DAT
  288. Format: <a>,<b>
  289. See also Documentation/kernel/input/joystick.txt
  290. analog.map= [HW,JOY] Analog joystick and gamepad support
  291. Specifies type or capabilities of an analog joystick
  292. connected to one of 16 gameports
  293. Format: <type1>,<type2>,..<type16>
  294. apc= [HW,SPARC]
  295. Power management functions (SPARCstation-4/5 + deriv.)
  296. Format: noidle
  297. Disable APC CPU standby support. SPARCstation-Fox does
  298. not play well with APC CPU idle - disable it if you have
  299. APC and your system crashes randomly.
  300. apic= [APIC,i386] Advanced Programmable Interrupt Controller
  301. Change the output verbosity whilst booting
  302. Format: { quiet (default) | verbose | debug }
  303. Change the amount of debugging information output
  304. when initialising the APIC and IO-APIC components.
  305. apm= [APM] Advanced Power Management
  306. See header of arch/x86/kernel/apm_32.c.
  307. arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
  308. Format: <io>,<irq>,<nodeID>
  309. ataflop= [HW,M68k]
  310. atarimouse= [HW,MOUSE] Atari Mouse
  311. atascsi= [HW,SCSI] Atari SCSI
  312. atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
  313. EzKey and similar keyboards
  314. atkbd.reset= [HW] Reset keyboard during initialization
  315. atkbd.set= [HW] Select keyboard code set
  316. Format: <int> (2 = AT (default), 3 = PS/2)
  317. atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
  318. keyboards
  319. atkbd.softraw= [HW] Choose between synthetic and real raw mode
  320. Format: <bool> (0 = real, 1 = synthetic (default))
  321. atkbd.softrepeat= [HW]
  322. Use software keyboard repeat
  323. autotest [IA64]
  324. baycom_epp= [HW,AX25]
  325. Format: <io>,<mode>
  326. baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
  327. Format: <io>,<mode>
  328. See header of drivers/net/hamradio/baycom_par.c.
  329. baycom_ser_fdx= [HW,AX25]
  330. BayCom Serial Port AX.25 Modem (Full Duplex Mode)
  331. Format: <io>,<irq>,<mode>[,<baud>]
  332. See header of drivers/net/hamradio/baycom_ser_fdx.c.
  333. baycom_ser_hdx= [HW,AX25]
  334. BayCom Serial Port AX.25 Modem (Half Duplex Mode)
  335. Format: <io>,<irq>,<mode>
  336. See header of drivers/net/hamradio/baycom_ser_hdx.c.
  337. boot_delay= Milliseconds to delay each printk during boot.
  338. Values larger than 10 seconds (10000) are changed to
  339. no delay (0).
  340. Format: integer
  341. bootmem_debug [KNL] Enable bootmem allocator debug messages.
  342. bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
  343. bttv.radio= Most important insmod options are available as
  344. kernel args too.
  345. bttv.pll= See Documentation/video4linux/bttv/Insmod-options
  346. bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
  347. BusLogic= [HW,SCSI]
  348. See drivers/scsi/BusLogic.c, comment before function
  349. BusLogic_ParseDriverOptions().
  350. c101= [NET] Moxa C101 synchronous serial card
  351. cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
  352. Sometimes CPU hardware bugs make them report the cache
  353. size incorrectly. The kernel will attempt work arounds
  354. to fix known problems, but for some CPUs it is not
  355. possible to determine what the correct size should be.
  356. This option provides an override for these situations.
  357. security= [SECURITY] Choose a security module to enable at boot.
  358. If this boot parameter is not specified, only the first
  359. security module asking for security registration will be
  360. loaded. An invalid security module name will be treated
  361. as if no module has been chosen.
  362. capability.disable=
  363. [SECURITY] Disable capabilities. This would normally
  364. be used only if an alternative security model is to be
  365. configured. Potentially dangerous and should only be
  366. used if you are entirely sure of the consequences.
  367. ccw_timeout_log [S390]
  368. See Documentation/s390/CommonIO for details.
  369. cgroup_disable= [KNL] Disable a particular controller
  370. Format: {name of the controller(s) to disable}
  371. {Currently supported controllers - "memory"}
  372. checkreqprot [SELINUX] Set initial checkreqprot flag value.
  373. Format: { "0" | "1" }
  374. See security/selinux/Kconfig help text.
  375. 0 -- check protection applied by kernel (includes
  376. any implied execute protection).
  377. 1 -- check protection requested by application.
  378. Default value is set via a kernel config option.
  379. Value can be changed at runtime via
  380. /selinux/checkreqprot.
  381. cio_ignore= [S390]
  382. See Documentation/s390/CommonIO for details.
  383. clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
  384. [Deprecated]
  385. Forces specified clocksource (if available) to be used
  386. when calculating gettimeofday(). If specified
  387. clocksource is not available, it defaults to PIT.
  388. Format: { pit | tsc | cyclone | pmtmr }
  389. clocksource= [GENERIC_TIME] Override the default clocksource
  390. Format: <string>
  391. Override the default clocksource and use the clocksource
  392. with the name specified.
  393. Some clocksource names to choose from, depending on
  394. the platform:
  395. [all] jiffies (this is the base, fallback clocksource)
  396. [ACPI] acpi_pm
  397. [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
  398. pxa_timer,timer3,32k_counter,timer0_1
  399. [AVR32] avr32
  400. [X86-32] pit,hpet,tsc,vmi-timer;
  401. scx200_hrt on Geode; cyclone on IBM x440
  402. [MIPS] MIPS
  403. [PARISC] cr16
  404. [S390] tod
  405. [SH] SuperH
  406. [SPARC64] tick
  407. [X86-64] hpet,tsc
  408. clearcpuid=BITNUM [X86]
  409. Disable CPUID feature X for the kernel. See
  410. include/asm-x86/cpufeature.h for the valid bit numbers.
  411. Note the Linux specific bits are not necessarily
  412. stable over kernel options, but the vendor specific
  413. ones should be.
  414. Also note that user programs calling CPUID directly
  415. or using the feature without checking anything
  416. will still see it. This just prevents it from
  417. being used by the kernel or shown in /proc/cpuinfo.
  418. Also note the kernel might malfunction if you disable
  419. some critical bits.
  420. code_bytes [IA32/X86_64] How many bytes of object code to print
  421. in an oops report.
  422. Range: 0 - 8192
  423. Default: 64
  424. hpet= [X86-32,HPET] option to control HPET usage
  425. Format: { enable (default) | disable | force }
  426. disable: disable HPET and use PIT instead
  427. force: allow force enabled of undocumented chips (ICH4,
  428. VIA, nVidia)
  429. com20020= [HW,NET] ARCnet - COM20020 chipset
  430. Format:
  431. <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
  432. com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
  433. Format: <io>[,<irq>]
  434. com90xx= [HW,NET]
  435. ARCnet - COM90xx chipset (memory-mapped buffers)
  436. Format: <io>[,<irq>[,<memstart>]]
  437. condev= [HW,S390] console device
  438. conmode=
  439. console= [KNL] Output console device and options.
  440. tty<n> Use the virtual console device <n>.
  441. ttyS<n>[,options]
  442. ttyUSB0[,options]
  443. Use the specified serial port. The options are of
  444. the form "bbbbpnf", where "bbbb" is the baud rate,
  445. "p" is parity ("n", "o", or "e"), "n" is number of
  446. bits, and "f" is flow control ("r" for RTS or
  447. omit it). Default is "9600n8".
  448. See Documentation/serial-console.txt for more
  449. information. See
  450. Documentation/networking/netconsole.txt for an
  451. alternative.
  452. uart[8250],io,<addr>[,options]
  453. uart[8250],mmio,<addr>[,options]
  454. Start an early, polled-mode console on the 8250/16550
  455. UART at the specified I/O port or MMIO address,
  456. switching to the matching ttyS device later. The
  457. options are the same as for ttyS, above.
  458. If the device connected to the port is not a TTY but a braille
  459. device, prepend "brl," before the device type, for instance
  460. console=brl,ttyS0
  461. For now, only VisioBraille is supported.
  462. earlycon= [KNL] Output early console device and options.
  463. uart[8250],io,<addr>[,options]
  464. uart[8250],mmio,<addr>[,options]
  465. Start an early, polled-mode console on the 8250/16550
  466. UART at the specified I/O port or MMIO address.
  467. The options are the same as for ttyS, above.
  468. no_console_suspend
  469. [HW] Never suspend the console
  470. Disable suspending of consoles during suspend and
  471. hibernate operations. Once disabled, debugging
  472. messages can reach various consoles while the rest
  473. of the system is being put to sleep (ie, while
  474. debugging driver suspend/resume hooks). This may
  475. not work reliably with all consoles, but is known
  476. to work with serial and VGA consoles.
  477. cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
  478. Format:
  479. <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
  480. crashkernel=nn[KMG]@ss[KMG]
  481. [KNL] Reserve a chunk of physical memory to
  482. hold a kernel to switch to with kexec on panic.
  483. crashkernel=range1:size1[,range2:size2,...][@offset]
  484. [KNL] Same as above, but depends on the memory
  485. in the running system. The syntax of range is
  486. start-[end] where start and end are both
  487. a memory unit (amount[KMG]). See also
  488. Documentation/kdump/kdump.txt for a example.
  489. cs4232= [HW,OSS]
  490. Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
  491. cs89x0_dma= [HW,NET]
  492. Format: <dma>
  493. cs89x0_media= [HW,NET]
  494. Format: { rj45 | aui | bnc }
  495. dasd= [HW,NET]
  496. See header of drivers/s390/block/dasd_devmap.c.
  497. db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
  498. (one device per port)
  499. Format: <port#>,<type>
  500. See also Documentation/input/joystick-parport.txt
  501. debug [KNL] Enable kernel debugging (events log level).
  502. debug_locks_verbose=
  503. [KNL] verbose self-tests
  504. Format=<0|1>
  505. Print debugging info while doing the locking API
  506. self-tests.
  507. We default to 0 (no extra messages), setting it to
  508. 1 will print _a lot_ more information - normally
  509. only useful to kernel developers.
  510. debug_objects [KNL] Enable object debugging
  511. debugpat [X86] Enable PAT debugging
  512. decnet.addr= [HW,NET]
  513. Format: <area>[,<node>]
  514. See also Documentation/networking/decnet.txt.
  515. vt.default_blu= [VT]
  516. Format: <blue0>,<blue1>,<blue2>,...,<blue15>
  517. Change the default blue palette of the console.
  518. This is a 16-member array composed of values
  519. ranging from 0-255.
  520. vt.default_grn= [VT]
  521. Format: <green0>,<green1>,<green2>,...,<green15>
  522. Change the default green palette of the console.
  523. This is a 16-member array composed of values
  524. ranging from 0-255.
  525. vt.default_red= [VT]
  526. Format: <red0>,<red1>,<red2>,...,<red15>
  527. Change the default red palette of the console.
  528. This is a 16-member array composed of values
  529. ranging from 0-255.
  530. vt.default_utf8=
  531. [VT]
  532. Format=<0|1>
  533. Set system-wide default UTF-8 mode for all tty's.
  534. Default is 1, i.e. UTF-8 mode is enabled for all
  535. newly opened terminals.
  536. dhash_entries= [KNL]
  537. Set number of hash buckets for dentry cache.
  538. digi= [HW,SERIAL]
  539. IO parameters + enable/disable command.
  540. digiepca= [HW,SERIAL]
  541. See drivers/char/README.epca and
  542. Documentation/digiepca.txt.
  543. disable_mtrr_cleanup [X86]
  544. enable_mtrr_cleanup [X86]
  545. The kernel tries to adjust MTRR layout from continuous
  546. to discrete, to make X server driver able to add WB
  547. entry later. This parameter enables/disables that.
  548. mtrr_chunk_size=nn[KMG] [X86]
  549. used for mtrr cleanup. It is largest continous chunk
  550. that could hold holes aka. UC entries.
  551. mtrr_gran_size=nn[KMG] [X86]
  552. Used for mtrr cleanup. It is granularity of mtrr block.
  553. Default is 1.
  554. Large value could prevent small alignment from
  555. using up MTRRs.
  556. mtrr_spare_reg_nr=n [X86]
  557. Format: <integer>
  558. Range: 0,7 : spare reg number
  559. Default : 1
  560. Used for mtrr cleanup. It is spare mtrr entries number.
  561. Set to 2 or more if your graphical card needs more.
  562. disable_mtrr_trim [X86, Intel and AMD only]
  563. By default the kernel will trim any uncacheable
  564. memory out of your available memory pool based on
  565. MTRR settings. This parameter disables that behavior,
  566. possibly causing your machine to run very slowly.
  567. dmasound= [HW,OSS] Sound subsystem buffers
  568. dscc4.setup= [NET]
  569. dtc3181e= [HW,SCSI]
  570. earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
  571. earlyprintk=vga
  572. earlyprintk=serial[,ttySn[,baudrate]]
  573. earlyprintk=dbgp
  574. Append ",keep" to not disable it when the real console
  575. takes over.
  576. Only vga or serial or usb debug port at a time.
  577. Currently only ttyS0 and ttyS1 are supported.
  578. Interaction with the standard serial driver is not
  579. very good.
  580. The VGA output is eventually overwritten by the real
  581. console.
  582. eata= [HW,SCSI]
  583. edd= [EDD]
  584. Format: {"off" | "on" | "skip[mbr]"}
  585. eisa_irq_edge= [PARISC,HW]
  586. See header of drivers/parisc/eisa.c.
  587. elanfreq= [X86-32]
  588. See comment before function elanfreq_setup() in
  589. arch/x86/kernel/cpu/cpufreq/elanfreq.c.
  590. elevator= [IOSCHED]
  591. Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
  592. See Documentation/block/as-iosched.txt and
  593. Documentation/block/deadline-iosched.txt for details.
  594. elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
  595. Specifies physical address of start of kernel core
  596. image elf header. Generally kexec loader will
  597. pass this option to capture kernel.
  598. See Documentation/kdump/kdump.txt for details.
  599. enforcing [SELINUX] Set initial enforcing status.
  600. Format: {"0" | "1"}
  601. See security/selinux/Kconfig help text.
  602. 0 -- permissive (log only, no denials).
  603. 1 -- enforcing (deny and log).
  604. Default value is 0.
  605. Value can be changed at runtime via /selinux/enforce.
  606. es1371= [HW,OSS]
  607. Format: <spdif>,[<nomix>,[<amplifier>]]
  608. See also header of sound/oss/es1371.c.
  609. ether= [HW,NET] Ethernet cards parameters
  610. This option is obsoleted by the "netdev=" option, which
  611. has equivalent usage. See its documentation for details.
  612. eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
  613. Format: <io>[,<irq>]
  614. failslab=
  615. fail_page_alloc=
  616. fail_make_request=[KNL]
  617. General fault injection mechanism.
  618. Format: <interval>,<probability>,<space>,<times>
  619. See also /Documentation/fault-injection/.
  620. fd_mcs= [HW,SCSI]
  621. See header of drivers/scsi/fd_mcs.c.
  622. fdomain= [HW,SCSI]
  623. See header of drivers/scsi/fdomain.c.
  624. floppy= [HW]
  625. See Documentation/floppy.txt.
  626. force_pal_cache_flush
  627. [IA-64] Avoid check_sal_cache_flush which may hang on
  628. buggy SAL_CACHE_FLUSH implementations. Using this
  629. parameter will force ia64_sal_cache_flush to call
  630. ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
  631. gamecon.map[2|3]=
  632. [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
  633. support via parallel port (up to 5 devices per port)
  634. Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
  635. See also Documentation/input/joystick-parport.txt
  636. gamma= [HW,DRM]
  637. gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
  638. Format: off | on
  639. default: on
  640. gdth= [HW,SCSI]
  641. See header of drivers/scsi/gdth.c.
  642. gpt [EFI] Forces disk with valid GPT signature but
  643. invalid Protective MBR to be treated as GPT.
  644. gvp11= [HW,SCSI]
  645. hashdist= [KNL,NUMA] Large hashes allocated during boot
  646. are distributed across NUMA nodes. Defaults on
  647. for IA-64, off otherwise.
  648. Format: 0 | 1 (for off | on)
  649. hcl= [IA-64] SGI's Hardware Graph compatibility layer
  650. hd= [EIDE] (E)IDE hard drive subsystem geometry
  651. Format: <cyl>,<head>,<sect>
  652. highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
  653. size of <nn>. This works even on boxes that have no
  654. highmem otherwise. This also works to reduce highmem
  655. size on bigger boxes.
  656. highres= [KNL] Enable/disable high resolution timer mode.
  657. Valid parameters: "on", "off"
  658. Default: "on"
  659. hisax= [HW,ISDN]
  660. See Documentation/isdn/README.HiSax.
  661. hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
  662. hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
  663. On x86-64 and powerpc, this option can be specified
  664. multiple times interleaved with hugepages= to reserve
  665. huge pages of different sizes. Valid pages sizes on
  666. x86-64 are 2M (when the CPU supports "pse") and 1G
  667. (when the CPU supports the "pdpe1gb" cpuinfo flag)
  668. Note that 1GB pages can only be allocated at boot time
  669. using hugepages= and not freed afterwards.
  670. default_hugepagesz=
  671. [same as hugepagesz=] The size of the default
  672. HugeTLB page size. This is the size represented by
  673. the legacy /proc/ hugepages APIs, used for SHM, and
  674. default size when mounting hugetlbfs filesystems.
  675. Defaults to the default architecture's huge page size
  676. if not specified.
  677. hlt [BUGS=ARM,SH]
  678. i8042.debug [HW] Toggle i8042 debug mode
  679. i8042.direct [HW] Put keyboard port into non-translated mode
  680. i8042.dumbkbd [HW] Pretend that controller can only read data from
  681. keyboard and cannot control its state
  682. (Don't attempt to blink the leds)
  683. i8042.noaux [HW] Don't check for auxiliary (== mouse) port
  684. i8042.nokbd [HW] Don't check/create keyboard port
  685. i8042.noloop [HW] Disable the AUX Loopback command while probing
  686. for the AUX port
  687. i8042.nomux [HW] Don't check presence of an active multiplexing
  688. controller
  689. i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
  690. controllers
  691. i8042.panicblink=
  692. [HW] Frequency with which keyboard LEDs should blink
  693. when kernel panics (default is 0.5 sec)
  694. i8042.reset [HW] Reset the controller during init and cleanup
  695. i8042.unlock [HW] Unlock (ignore) the keylock
  696. i810= [HW,DRM]
  697. i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
  698. indicates that the driver is running on unsupported
  699. hardware.
  700. i8k.force [HW] Activate i8k driver even if SMM BIOS signature
  701. does not match list of supported models.
  702. i8k.power_status
  703. [HW] Report power status in /proc/i8k
  704. (disabled by default)
  705. i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
  706. capability is set.
  707. ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
  708. See Documentation/mca.txt.
  709. icn= [HW,ISDN]
  710. Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
  711. ide= [HW] (E)IDE subsystem
  712. Format: ide=nodma or ide=doubler
  713. See Documentation/ide/ide.txt.
  714. idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
  715. See Documentation/ide/ide.txt.
  716. idle= [X86]
  717. Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
  718. Poll forces a polling idle loop that can slightly improves the performance
  719. of waking up a idle CPU, but will use a lot of power and make the system
  720. run hot. Not recommended.
  721. idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
  722. to not use it because it doesn't save as much power as a normal idle
  723. loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
  724. as idle=poll.
  725. idle=halt. Halt is forced to be used for CPU idle.
  726. In such case C2/C3 won't be used again.
  727. idle=nomwait. Disable mwait for CPU C-states
  728. ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
  729. Claim all unknown PCI IDE storage controllers.
  730. ignore_loglevel [KNL]
  731. Ignore loglevel setting - this will print /all/
  732. kernel messages to the console. Useful for debugging.
  733. ihash_entries= [KNL]
  734. Set number of hash buckets for inode cache.
  735. in2000= [HW,SCSI]
  736. See header of drivers/scsi/in2000.c.
  737. init= [KNL]
  738. Format: <full_path>
  739. Run specified binary instead of /sbin/init as init
  740. process.
  741. initcall_debug [KNL] Trace initcalls as they are executed. Useful
  742. for working out where the kernel is dying during
  743. startup.
  744. initrd= [BOOT] Specify the location of the initial ramdisk
  745. inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
  746. Format: <irq>
  747. inttest= [IA64]
  748. iommu= [x86]
  749. off
  750. force
  751. noforce
  752. biomerge
  753. panic
  754. nopanic
  755. merge
  756. nomerge
  757. forcesac
  758. soft
  759. intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
  760. off
  761. Disable intel iommu driver.
  762. igfx_off [Default Off]
  763. By default, gfx is mapped as normal device. If a gfx
  764. device has a dedicated DMAR unit, the DMAR unit is
  765. bypassed by not enabling DMAR with this option. In
  766. this case, gfx device will use physical address for
  767. DMA.
  768. forcedac [x86_64]
  769. With this option iommu will not optimize to look
  770. for io virtual address below 32 bit forcing dual
  771. address cycle on pci bus for cards supporting greater
  772. than 32 bit addressing. The default is to look
  773. for translation below 32 bit and if not available
  774. then look in the higher range.
  775. strict [Default Off]
  776. With this option on every unmap_single operation will
  777. result in a hardware IOTLB flush operation as opposed
  778. to batching them for performance.
  779. io_delay= [X86-32,X86-64] I/O delay method
  780. 0x80
  781. Standard port 0x80 based delay
  782. 0xed
  783. Alternate port 0xed based delay (needed on some systems)
  784. udelay
  785. Simple two microseconds delay
  786. none
  787. No delay
  788. io7= [HW] IO7 for Marvel based alpha systems
  789. See comment before marvel_specify_io7 in
  790. arch/alpha/kernel/core_marvel.c.
  791. ip= [IP_PNP]
  792. See Documentation/filesystems/nfsroot.txt.
  793. ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
  794. See comment before ip2_setup() in
  795. drivers/char/ip2/ip2base.c.
  796. ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
  797. See header of drivers/scsi/ips.c.
  798. ports= [IP_VS_FTP] IPVS ftp helper module
  799. Default is 21.
  800. Up to 8 (IP_VS_APP_MAX_PORTS) ports
  801. may be specified.
  802. Format: <port>,<port>....
  803. irqfixup [HW]
  804. When an interrupt is not handled search all handlers
  805. for it. Intended to get systems with badly broken
  806. firmware running.
  807. irqpoll [HW]
  808. When an interrupt is not handled search all handlers
  809. for it. Also check all handlers each timer
  810. interrupt. Intended to get systems with badly broken
  811. firmware running.
  812. isapnp= [ISAPNP]
  813. Format: <RDP>,<reset>,<pci_scan>,<verbosity>
  814. isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
  815. Format:
  816. <cpu number>,...,<cpu number>
  817. or
  818. <cpu number>-<cpu number>
  819. (must be a positive range in ascending order)
  820. or a mixture
  821. <cpu number>,...,<cpu number>-<cpu number>
  822. This option can be used to specify one or more CPUs
  823. to isolate from the general SMP balancing and scheduling
  824. algorithms. You can move a process onto or off an
  825. "isolated" CPU via the CPU affinity syscalls or cpuset.
  826. <cpu number> begins at 0 and the maximum value is
  827. "number of CPUs in system - 1".
  828. This option is the preferred way to isolate CPUs. The
  829. alternative -- manually setting the CPU mask of all
  830. tasks in the system -- can cause problems and
  831. suboptimal load balancer performance.
  832. iucv= [HW,NET]
  833. js= [HW,JOY] Analog joystick
  834. See Documentation/input/joystick.txt.
  835. kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
  836. specifies the amount of memory usable by the kernel
  837. for non-movable allocations. The requested amount is
  838. spread evenly throughout all nodes in the system. The
  839. remaining memory in each node is used for Movable
  840. pages. In the event, a node is too small to have both
  841. kernelcore and Movable pages, kernelcore pages will
  842. take priority and other nodes will have a larger number
  843. of kernelcore pages. The Movable zone is used for the
  844. allocation of pages that may be reclaimed or moved
  845. by the page migration subsystem. This means that
  846. HugeTLB pages may not be allocated from this zone.
  847. Note that allocations like PTEs-from-HighMem still
  848. use the HighMem zone if it exists, and the Normal
  849. zone if it does not.
  850. movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
  851. is similar to kernelcore except it specifies the
  852. amount of memory used for migratable allocations.
  853. If both kernelcore and movablecore is specified,
  854. then kernelcore will be at *least* the specified
  855. value but may be more. If movablecore on its own
  856. is specified, the administrator must be careful
  857. that the amount of memory usable for all allocations
  858. is not too small.
  859. keepinitrd [HW,ARM]
  860. kstack=N [X86-32,X86-64] Print N words from the kernel stack
  861. in oops dumps.
  862. kgdboc= [HW] kgdb over consoles.
  863. Requires a tty driver that supports console polling.
  864. (only serial suported for now)
  865. Format: <serial_device>[,baud]
  866. kmac= [MIPS] korina ethernet MAC address.
  867. Configure the RouterBoard 532 series on-chip
  868. Ethernet adapter MAC address.
  869. l2cr= [PPC]
  870. l3cr= [PPC]
  871. lapic [X86-32,APIC] Enable the local APIC even if BIOS
  872. disabled it.
  873. lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
  874. C2 power state.
  875. libata.dma= [LIBATA] DMA control
  876. libata.dma=0 Disable all PATA and SATA DMA
  877. libata.dma=1 PATA and SATA Disk DMA only
  878. libata.dma=2 ATAPI (CDROM) DMA only
  879. libata.dma=4 Compact Flash DMA only
  880. Combinations also work, so libata.dma=3 enables DMA
  881. for disks and CDROMs, but not CFs.
  882. libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
  883. when set.
  884. Format: <int>
  885. libata.force= [LIBATA] Force configurations. The format is comma
  886. separated list of "[ID:]VAL" where ID is
  887. PORT[:DEVICE]. PORT and DEVICE are decimal numbers
  888. matching port, link or device. Basically, it matches
  889. the ATA ID string printed on console by libata. If
  890. the whole ID part is omitted, the last PORT and DEVICE
  891. values are used. If ID hasn't been specified yet, the
  892. configuration applies to all ports, links and devices.
  893. If only DEVICE is omitted, the parameter applies to
  894. the port and all links and devices behind it. DEVICE
  895. number of 0 either selects the first device or the
  896. first fan-out link behind PMP device. It does not
  897. select the host link. DEVICE number of 15 selects the
  898. host link and device attached to it.
  899. The VAL specifies the configuration to force. As long
  900. as there's no ambiguity shortcut notation is allowed.
  901. For example, both 1.5 and 1.5G would work for 1.5Gbps.
  902. The following configurations can be forced.
  903. * Cable type: 40c, 80c, short40c, unk, ign or sata.
  904. Any ID with matching PORT is used.
  905. * SATA link speed limit: 1.5Gbps or 3.0Gbps.
  906. * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
  907. udma[/][16,25,33,44,66,100,133] notation is also
  908. allowed.
  909. * [no]ncq: Turn on or off NCQ.
  910. * nohrst, nosrst, norst: suppress hard, soft
  911. and both resets.
  912. If there are multiple matching configurations changing
  913. the same attribute, the last one is used.
  914. load_ramdisk= [RAM] List of ramdisks to load from floppy
  915. See Documentation/ramdisk.txt.
  916. lockd.nlm_grace_period=P [NFS] Assign grace period.
  917. Format: <integer>
  918. lockd.nlm_tcpport=N [NFS] Assign TCP port.
  919. Format: <integer>
  920. lockd.nlm_timeout=T [NFS] Assign timeout value.
  921. Format: <integer>
  922. lockd.nlm_udpport=M [NFS] Assign UDP port.
  923. Format: <integer>
  924. logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
  925. Format: <irq>
  926. loglevel= All Kernel Messages with a loglevel smaller than the
  927. console loglevel will be printed to the console. It can
  928. also be changed with klogd or other programs. The
  929. loglevels are defined as follows:
  930. 0 (KERN_EMERG) system is unusable
  931. 1 (KERN_ALERT) action must be taken immediately
  932. 2 (KERN_CRIT) critical conditions
  933. 3 (KERN_ERR) error conditions
  934. 4 (KERN_WARNING) warning conditions
  935. 5 (KERN_NOTICE) normal but significant condition
  936. 6 (KERN_INFO) informational
  937. 7 (KERN_DEBUG) debug-level messages
  938. log_buf_len=n Sets the size of the printk ring buffer, in bytes.
  939. Format: { n | nk | nM }
  940. n must be a power of two. The default size
  941. is set in the kernel config file.
  942. logo.nologo [FB] Disables display of the built-in Linux logo.
  943. This may be used to provide more screen space for
  944. kernel log messages and is useful when debugging
  945. kernel boot problems.
  946. lp=0 [LP] Specify parallel ports to use, e.g,
  947. lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
  948. lp=reset first parallel port). 'lp=0' disables the
  949. lp=auto printer driver. 'lp=reset' (which can be
  950. specified in addition to the ports) causes
  951. attached printers to be reset. Using
  952. lp=port1,port2,... specifies the parallel ports
  953. to associate lp devices with, starting with
  954. lp0. A port specification may be 'none' to skip
  955. that lp device, or a parport name such as
  956. 'parport0'. Specifying 'lp=auto' instead of a
  957. port specification list means that device IDs
  958. from each port should be examined, to see if
  959. an IEEE 1284-compliant printer is attached; if
  960. so, the driver will manage that printer.
  961. See also header of drivers/char/lp.c.
  962. lpj=n [KNL]
  963. Sets loops_per_jiffy to given constant, thus avoiding
  964. time-consuming boot-time autodetection (up to 250 ms per
  965. CPU). 0 enables autodetection (default). To determine
  966. the correct value for your kernel, boot with normal
  967. autodetection and see what value is printed. Note that
  968. on SMP systems the preset will be applied to all CPUs,
  969. which is likely to cause problems if your CPUs need
  970. significantly divergent settings. An incorrect value
  971. will cause delays in the kernel to be wrong, leading to
  972. unpredictable I/O errors and other breakage. Although
  973. unlikely, in the extreme case this might damage your
  974. hardware.
  975. ltpc= [NET]
  976. Format: <io>,<irq>,<dma>
  977. mac5380= [HW,SCSI] Format:
  978. <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
  979. machvec= [IA64] Force the use of a particular machine-vector
  980. (machvec) in a generic kernel.
  981. Example: machvec=hpzx1_swiotlb
  982. max_loop= [LOOP] Maximum number of loopback devices that can
  983. be mounted
  984. Format: <1-256>
  985. maxcpus= [SMP] Maximum number of processors that an SMP kernel
  986. should make use of. maxcpus=n : n >= 0 limits the
  987. kernel to using 'n' processors. n=0 is a special case,
  988. it is equivalent to "nosmp", which also disables
  989. the IO APIC.
  990. max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
  991. equal to this physical address is ignored.
  992. max_luns= [SCSI] Maximum number of LUNs to probe.
  993. Should be between 1 and 2^32-1.
  994. max_report_luns=
  995. [SCSI] Maximum number of LUNs received.
  996. Should be between 1 and 16384.
  997. mcatest= [IA-64]
  998. mce [X86-32] Machine Check Exception
  999. mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
  1000. md= [HW] RAID subsystems devices and level
  1001. See Documentation/md.txt.
  1002. mdacon= [MDA]
  1003. Format: <first>,<last>
  1004. Specifies range of consoles to be captured by the MDA.
  1005. mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
  1006. Amount of memory to be used when the kernel is not able
  1007. to see the whole system memory or for test.
  1008. [X86-32] Use together with memmap= to avoid physical
  1009. address space collisions. Without memmap= PCI devices
  1010. could be placed at addresses belonging to unused RAM.
  1011. mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
  1012. memory.
  1013. memchunk=nn[KMG]
  1014. [KNL,SH] Allow user to override the default size for
  1015. per-device physically contiguous DMA buffers.
  1016. memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
  1017. E820 memory map, as specified by the user.
  1018. Such memmap=exactmap lines can be constructed based on
  1019. BIOS output or other requirements. See the memmap=nn@ss
  1020. option description.
  1021. memmap=nn[KMG]@ss[KMG]
  1022. [KNL] Force usage of a specific region of memory
  1023. Region of memory to be used, from ss to ss+nn.
  1024. memmap=nn[KMG]#ss[KMG]
  1025. [KNL,ACPI] Mark specific memory as ACPI data.
  1026. Region of memory to be used, from ss to ss+nn.
  1027. memmap=nn[KMG]$ss[KMG]
  1028. [KNL,ACPI] Mark specific memory as reserved.
  1029. Region of memory to be used, from ss to ss+nn.
  1030. Example: Exclude memory from 0x18690000-0x1869ffff
  1031. memmap=64K$0x18690000
  1032. or
  1033. memmap=0x10000$0x18690000
  1034. memory_corruption_check=0/1 [X86]
  1035. Some BIOSes seem to corrupt the first 64k of
  1036. memory when doing things like suspend/resume.
  1037. Setting this option will scan the memory
  1038. looking for corruption. Enabling this will
  1039. both detect corruption and prevent the kernel
  1040. from using the memory being corrupted.
  1041. However, its intended as a diagnostic tool; if
  1042. repeatable BIOS-originated corruption always
  1043. affects the same memory, you can use memmap=
  1044. to prevent the kernel from using that memory.
  1045. memory_corruption_check_size=size [X86]
  1046. By default it checks for corruption in the low
  1047. 64k, making this memory unavailable for normal
  1048. use. Use this parameter to scan for
  1049. corruption in more or less memory.
  1050. memory_corruption_check_period=seconds [X86]
  1051. By default it checks for corruption every 60
  1052. seconds. Use this parameter to check at some
  1053. other rate. 0 disables periodic checking.
  1054. memtest= [KNL,X86] Enable memtest
  1055. Format: <integer>
  1056. range: 0,4 : pattern number
  1057. default : 0 <disable>
  1058. meye.*= [HW] Set MotionEye Camera parameters
  1059. See Documentation/video4linux/meye.txt.
  1060. mfgpt_irq= [IA-32] Specify the IRQ to use for the
  1061. Multi-Function General Purpose Timers on AMD Geode
  1062. platforms.
  1063. mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
  1064. the BIOS has incorrectly applied a workaround. TinyBIOS
  1065. version 0.98 is known to be affected, 0.99 fixes the
  1066. problem by letting the user disable the workaround.
  1067. mga= [HW,DRM]
  1068. mminit_loglevel=
  1069. [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
  1070. parameter allows control of the logging verbosity for
  1071. the additional memory initialisation checks. A value
  1072. of 0 disables mminit logging and a level of 4 will
  1073. log everything. Information is printed at KERN_DEBUG
  1074. so loglevel=8 may also need to be specified.
  1075. mousedev.tap_time=
  1076. [MOUSE] Maximum time between finger touching and
  1077. leaving touchpad surface for touch to be considered
  1078. a tap and be reported as a left button click (for
  1079. touchpads working in absolute mode only).
  1080. Format: <msecs>
  1081. mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
  1082. reporting absolute coordinates, such as tablets
  1083. mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
  1084. reporting absolute coordinates, such as tablets
  1085. mpu401= [HW,OSS]
  1086. Format: <io>,<irq>
  1087. MTD_Partition= [MTD]
  1088. Format: <name>,<region-number>,<size>,<offset>
  1089. MTD_Region= [MTD] Format:
  1090. <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
  1091. mtdparts= [MTD]
  1092. See drivers/mtd/cmdlinepart.c.
  1093. mtdset= [ARM]
  1094. ARM/S3C2412 JIVE boot control
  1095. See arch/arm/mach-s3c2412/mach-jive.c
  1096. mtouchusb.raw_coordinates=
  1097. [HW] Make the MicroTouch USB driver use raw coordinates
  1098. ('y', default) or cooked coordinates ('n')
  1099. n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
  1100. NCR_D700= [HW,SCSI]
  1101. See header of drivers/scsi/NCR_D700.c.
  1102. ncr5380= [HW,SCSI]
  1103. ncr53c400= [HW,SCSI]
  1104. ncr53c400a= [HW,SCSI]
  1105. ncr53c406a= [HW,SCSI]
  1106. ncr53c8xx= [HW,SCSI]
  1107. netdev= [NET] Network devices parameters
  1108. Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
  1109. Note that mem_start is often overloaded to mean
  1110. something different and driver-specific.
  1111. This usage is only documented in each driver source
  1112. file if at all.
  1113. nf_conntrack.acct=
  1114. [NETFILTER] Enable connection tracking flow accounting
  1115. 0 to disable accounting
  1116. 1 to enable accounting
  1117. Default value depends on CONFIG_NF_CT_ACCT that is
  1118. going to be removed in 2.6.29.
  1119. nfsaddrs= [NFS]
  1120. See Documentation/filesystems/nfsroot.txt.
  1121. nfsroot= [NFS] nfs root filesystem for disk-less boxes.
  1122. See Documentation/filesystems/nfsroot.txt.
  1123. nfs.callback_tcpport=
  1124. [NFS] set the TCP port on which the NFSv4 callback
  1125. channel should listen.
  1126. nfs.idmap_cache_timeout=
  1127. [NFS] set the maximum lifetime for idmapper cache
  1128. entries.
  1129. nfs.enable_ino64=
  1130. [NFS] enable 64-bit inode numbers.
  1131. If zero, the NFS client will fake up a 32-bit inode
  1132. number for the readdir() and stat() syscalls instead
  1133. of returning the full 64-bit number.
  1134. The default is to return 64-bit inode numbers.
  1135. nmi_debug= [KNL,AVR32] Specify one or more actions to take
  1136. when a NMI is triggered.
  1137. Format: [state][,regs][,debounce][,die]
  1138. nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
  1139. no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
  1140. emulation library even if a 387 maths coprocessor
  1141. is present.
  1142. noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
  1143. caches in the slab allocator. Saves per-node memory,
  1144. but will impact performance.
  1145. noalign [KNL,ARM]
  1146. noapic [SMP,APIC] Tells the kernel to not make use of any
  1147. IOAPICs that may be present in the system.
  1148. nobats [PPC] Do not use BATs for mapping kernel lowmem
  1149. on "Classic" PPC cores.
  1150. nocache [ARM]
  1151. nodelayacct [KNL] Disable per-task delay accounting
  1152. nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
  1153. nodsp [SH] Disable hardware DSP at boot time.
  1154. noefi [X86-32,X86-64] Disable EFI runtime services support.
  1155. noexec [IA-64]
  1156. noexec [X86-32,X86-64]
  1157. On X86-32 available only on PAE configured kernels.
  1158. noexec=on: enable non-executable mappings (default)
  1159. noexec=off: disable non-executable mappings
  1160. noexec32 [X86-64]
  1161. This affects only 32-bit executables.
  1162. noexec32=on: enable non-executable mappings (default)
  1163. read doesn't imply executable mappings
  1164. noexec32=off: disable non-executable mappings
  1165. read implies executable mappings
  1166. nofpu [SH] Disable hardware FPU at boot time.
  1167. nofxsr [BUGS=X86-32] Disables x86 floating point extended
  1168. register save and restore. The kernel will only save
  1169. legacy floating-point registers on task switch.
  1170. noclflush [BUGS=X86] Don't use the CLFLUSH instruction
  1171. nohlt [BUGS=ARM,SH]
  1172. no-hlt [BUGS=X86-32] Tells the kernel that the hlt
  1173. instruction doesn't work correctly and not to
  1174. use it.
  1175. nohalt [IA-64] Tells the kernel not to use the power saving
  1176. function PAL_HALT_LIGHT when idle. This increases
  1177. power-consumption. On the positive side, it reduces
  1178. interrupt wake-up latency, which may improve performance
  1179. in certain environments such as networked servers or
  1180. real-time systems.
  1181. nohz= [KNL] Boottime enable/disable dynamic ticks
  1182. Valid arguments: on, off
  1183. Default: on
  1184. noirqdebug [X86-32] Disables the code which attempts to detect and
  1185. disable unhandled interrupt sources.
  1186. no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
  1187. broken timer IRQ sources.
  1188. noisapnp [ISAPNP] Disables ISA PnP code.
  1189. noinitrd [RAM] Tells the kernel not to load any configured
  1190. initial RAM disk.
  1191. nointroute [IA-64]
  1192. nojitter [IA64] Disables jitter checking for ITC timers.
  1193. nolapic [X86-32,APIC] Do not enable or use the local APIC.
  1194. nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
  1195. nox2apic [X86-64,APIC] Do not enable x2APIC mode.
  1196. x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
  1197. default x2apic cluster mode on platforms
  1198. supporting x2apic.
  1199. noltlbs [PPC] Do not use large page/tlb entries for kernel
  1200. lowmem mapping on PPC40x.
  1201. nomca [IA-64] Disable machine check abort handling
  1202. nomce [X86-32] Machine Check Exception
  1203. nomfgpt [X86-32] Disable Multi-Function General Purpose
  1204. Timer usage (for AMD Geode machines).
  1205. noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
  1206. noreplace-smp [X86-32,SMP] Don't replace SMP instructions
  1207. with UP alternatives
  1208. noresidual [PPC] Don't use residual data on PReP machines.
  1209. noresume [SWSUSP] Disables resume and restores original swap
  1210. space.
  1211. no-scroll [VGA] Disables scrollback.
  1212. This is required for the Braillex ib80-piezo Braille
  1213. reader made by F.H. Papenmeier (Germany).
  1214. nosbagart [IA-64]
  1215. nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
  1216. nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
  1217. and disable the IO APIC. legacy for "maxcpus=0".
  1218. nosoftlockup [KNL] Disable the soft-lockup detector.
  1219. nosync [HW,M68K] Disables sync negotiation for all devices.
  1220. notsc [BUGS=X86-32] Disable Time Stamp Counter
  1221. nousb [USB] Disable the USB subsystem
  1222. nowb [ARM]
  1223. nptcg= [IA64] Override max number of concurrent global TLB
  1224. purges which is reported from either PAL_VM_SUMMARY or
  1225. SAL PALO.
  1226. numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
  1227. one of ['zone', 'node', 'default'] can be specified
  1228. This can be set from sysctl after boot.
  1229. See Documentation/sysctl/vm.txt for details.
  1230. nr_uarts= [SERIAL] maximum number of UARTs to be registered.
  1231. olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
  1232. Rather than timing out after 20 ms if an EC
  1233. command is not properly ACKed, override the length
  1234. of the timeout. We have interrupts disabled while
  1235. waiting for the ACK, so if this is set too high
  1236. interrupts *may* be lost!
  1237. opl3= [HW,OSS]
  1238. Format: <io>
  1239. oprofile.timer= [HW]
  1240. Use timer interrupt instead of performance counters
  1241. osst= [HW,SCSI] SCSI Tape Driver
  1242. Format: <buffer_size>,<write_threshold>
  1243. See also Documentation/scsi/st.txt.
  1244. panic= [KNL] Kernel behaviour on panic
  1245. Format: <timeout>
  1246. parkbd.port= [HW] Parallel port number the keyboard adapter is
  1247. connected to, default is 0.
  1248. Format: <parport#>
  1249. parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
  1250. 0 for XT, 1 for AT (default is AT).
  1251. Format: <mode>
  1252. parport= [HW,PPT] Specify parallel ports. 0 disables.
  1253. Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
  1254. Use 'auto' to force the driver to use any
  1255. IRQ/DMA settings detected (the default is to
  1256. ignore detected IRQ/DMA settings because of
  1257. possible conflicts). You can specify the base
  1258. address, IRQ, and DMA settings; IRQ and DMA
  1259. should be numbers, or 'auto' (for using detected
  1260. settings on that particular port), or 'nofifo'
  1261. (to avoid using a FIFO even if it is detected).
  1262. Parallel ports are assigned in the order they
  1263. are specified on the command line, starting
  1264. with parport0.
  1265. parport_init_mode= [HW,PPT]
  1266. Configure VIA parallel port to operate in
  1267. a specific mode. This is necessary on Pegasos
  1268. computer where firmware has no options for setting
  1269. up parallel port mode and sets it to spp.
  1270. Currently this function knows 686a and 8231 chips.
  1271. Format: [spp|ps2|epp|ecp|ecpepp]
  1272. pas2= [HW,OSS] Format:
  1273. <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
  1274. pas16= [HW,SCSI]
  1275. See header of drivers/scsi/pas16.c.
  1276. pause_on_oops=
  1277. Halt all CPUs after the first oops has been printed for
  1278. the specified number of seconds. This is to be used if
  1279. your oopses keep scrolling off the screen.
  1280. pcbit= [HW,ISDN]
  1281. pcd. [PARIDE]
  1282. See header of drivers/block/paride/pcd.c.
  1283. See also Documentation/paride.txt.
  1284. pci=option[,option...] [PCI] various PCI subsystem options:
  1285. off [X86] don't probe for the PCI bus
  1286. bios [X86-32] force use of PCI BIOS, don't access
  1287. the hardware directly. Use this if your machine
  1288. has a non-standard PCI host bridge.
  1289. nobios [X86-32] disallow use of PCI BIOS, only direct
  1290. hardware access methods are allowed. Use this
  1291. if you experience crashes upon bootup and you
  1292. suspect they are caused by the BIOS.
  1293. conf1 [X86] Force use of PCI Configuration
  1294. Mechanism 1.
  1295. conf2 [X86] Force use of PCI Configuration
  1296. Mechanism 2.
  1297. noaer [PCIE] If the PCIEAER kernel config parameter is
  1298. enabled, this kernel boot option can be used to
  1299. disable the use of PCIE advanced error reporting.
  1300. nodomains [PCI] Disable support for multiple PCI
  1301. root domains (aka PCI segments, in ACPI-speak).
  1302. nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
  1303. Configuration
  1304. nomsi [MSI] If the PCI_MSI kernel config parameter is
  1305. enabled, this kernel boot option can be used to
  1306. disable the use of MSI interrupts system-wide.
  1307. biosirq [X86-32] Use PCI BIOS calls to get the interrupt
  1308. routing table. These calls are known to be buggy
  1309. on several machines and they hang the machine
  1310. when used, but on other computers it's the only
  1311. way to get the interrupt routing table. Try
  1312. this option if the kernel is unable to allocate
  1313. IRQs or discover secondary PCI buses on your
  1314. motherboard.
  1315. rom [X86] Assign address space to expansion ROMs.
  1316. Use with caution as certain devices share
  1317. address decoders between ROMs and other
  1318. resources.
  1319. norom [X86] Do not assign address space to
  1320. expansion ROMs that do not already have
  1321. BIOS assigned address ranges.
  1322. irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
  1323. assigned automatically to PCI devices. You can
  1324. make the kernel exclude IRQs of your ISA cards
  1325. this way.
  1326. pirqaddr=0xAAAAA [X86] Specify the physical address
  1327. of the PIRQ table (normally generated
  1328. by the BIOS) if it is outside the
  1329. F0000h-100000h range.
  1330. lastbus=N [X86] Scan all buses thru bus #N. Can be
  1331. useful if the kernel is unable to find your
  1332. secondary buses and you want to tell it
  1333. explicitly which ones they are.
  1334. assign-busses [X86] Always assign all PCI bus
  1335. numbers ourselves, overriding
  1336. whatever the firmware may have done.
  1337. usepirqmask [X86] Honor the possible IRQ mask stored
  1338. in the BIOS $PIR table. This is needed on
  1339. some systems with broken BIOSes, notably
  1340. some HP Pavilion N5400 and Omnibook XE3
  1341. notebooks. This will have no effect if ACPI
  1342. IRQ routing is enabled.
  1343. noacpi [X86] Do not use ACPI for IRQ routing
  1344. or for PCI scanning.
  1345. use_crs [X86] Use _CRS for PCI resource
  1346. allocation.
  1347. routeirq Do IRQ routing for all PCI devices.
  1348. This is normally done in pci_enable_device(),
  1349. so this option is a temporary workaround
  1350. for broken drivers that don't call it.
  1351. skip_isa_align [X86] do not align io start addr, so can
  1352. handle more pci cards
  1353. firmware [ARM] Do not re-enumerate the bus but instead
  1354. just use the configuration from the
  1355. bootloader. This is currently used on
  1356. IXP2000 systems where the bus has to be
  1357. configured a certain way for adjunct CPUs.
  1358. noearly [X86] Don't do any early type 1 scanning.
  1359. This might help on some broken boards which
  1360. machine check when some devices' config space
  1361. is read. But various workarounds are disabled
  1362. and some IOMMU drivers will not work.
  1363. bfsort Sort PCI devices into breadth-first order.
  1364. This sorting is done to get a device
  1365. order compatible with older (<= 2.4) kernels.
  1366. nobfsort Don't sort PCI devices into breadth-first order.
  1367. cbiosize=nn[KMG] The fixed amount of bus space which is
  1368. reserved for the CardBus bridge's IO window.
  1369. The default value is 256 bytes.
  1370. cbmemsize=nn[KMG] The fixed amount of bus space which is
  1371. reserved for the CardBus bridge's memory
  1372. window. The default value is 64 megabytes.
  1373. pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
  1374. Management.
  1375. off Disable ASPM.
  1376. force Enable ASPM even on devices that claim not to support it.
  1377. WARNING: Forcing ASPM on may cause system lockups.
  1378. pcmv= [HW,PCMCIA] BadgePAD 4
  1379. pd. [PARIDE]
  1380. See Documentation/paride.txt.
  1381. pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
  1382. boot time.
  1383. Format: { 0 | 1 }
  1384. See arch/parisc/kernel/pdc_chassis.c
  1385. pf. [PARIDE]
  1386. See Documentation/paride.txt.
  1387. pg. [PARIDE]
  1388. See Documentation/paride.txt.
  1389. pirq= [SMP,APIC] Manual mp-table setup
  1390. See Documentation/x86/i386/IO-APIC.txt.
  1391. plip= [PPT,NET] Parallel port network link
  1392. Format: { parport<nr> | timid | 0 }
  1393. See also Documentation/parport.txt.
  1394. pmtmr= [X86] Manual setup of pmtmr I/O Port.
  1395. Override pmtimer IOPort with a hex value.
  1396. e.g. pmtmr=0x508
  1397. pnp.debug [PNP]
  1398. Enable PNP debug messages. This depends on the
  1399. CONFIG_PNP_DEBUG_MESSAGES option.
  1400. pnpacpi= [ACPI]
  1401. { off }
  1402. pnpbios= [ISAPNP]
  1403. { on | off | curr | res | no-curr | no-res }
  1404. pnp_reserve_irq=
  1405. [ISAPNP] Exclude IRQs for the autoconfiguration
  1406. pnp_reserve_dma=
  1407. [ISAPNP] Exclude DMAs for the autoconfiguration
  1408. pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
  1409. Ranges are in pairs (I/O port base and size).
  1410. pnp_reserve_mem=
  1411. [ISAPNP] Exclude memory regions for the
  1412. autoconfiguration.
  1413. Ranges are in pairs (memory base and size).
  1414. dynamic_printk
  1415. Enables pr_debug()/dev_dbg() calls if
  1416. CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. These can also
  1417. be switched on/off via <debugfs>/dynamic_printk/modules
  1418. print-fatal-signals=
  1419. [KNL] debug: print fatal signals
  1420. print-fatal-signals=1: print segfault info to
  1421. the kernel console.
  1422. default: off.
  1423. printk.time= Show timing data prefixed to each printk message line
  1424. Format: <bool> (1/Y/y=enable, 0/N/n=disable)
  1425. profile= [KNL] Enable kernel profiling via /proc/profile
  1426. Format: [schedule,]<number>
  1427. Param: "schedule" - profile schedule points.
  1428. Param: <number> - step/bucket size as a power of 2 for
  1429. statistical time based profiling.
  1430. Param: "sleep" - profile D-state sleeping (millisecs).
  1431. Requires CONFIG_SCHEDSTATS
  1432. Param: "kvm" - profile VM exits.
  1433. processor.max_cstate= [HW,ACPI]
  1434. Limit processor to maximum C-state
  1435. max_cstate=9 overrides any DMI blacklist limit.
  1436. processor.nocst [HW,ACPI]
  1437. Ignore the _CST method to determine C-states,
  1438. instead using the legacy FADT method
  1439. prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
  1440. before loading.
  1441. See Documentation/ramdisk.txt.
  1442. psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
  1443. probe for; one of (bare|imps|exps|lifebook|any).
  1444. psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
  1445. per second.
  1446. psmouse.resetafter= [HW,MOUSE]
  1447. Try to reset the device after so many bad packets
  1448. (0 = never).
  1449. psmouse.resolution=
  1450. [HW,MOUSE] Set desired mouse resolution, in dpi.
  1451. psmouse.smartscroll=
  1452. [HW,MOUSE] Controls Logitech smartscroll autorepeat.
  1453. 0 = disabled, 1 = enabled (default).
  1454. pss= [HW,OSS] Personal Sound System (ECHO ESC614)
  1455. Format:
  1456. <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
  1457. pt. [PARIDE]
  1458. See Documentation/paride.txt.
  1459. pty.legacy_count=
  1460. [KNL] Number of legacy pty's. Overwrites compiled-in
  1461. default number.
  1462. quiet [KNL] Disable most log messages
  1463. r128= [HW,DRM]
  1464. raid= [HW,RAID]
  1465. See Documentation/md.txt.
  1466. ramdisk_blocksize= [RAM]
  1467. See Documentation/ramdisk.txt.
  1468. ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
  1469. See Documentation/ramdisk.txt.
  1470. rcupdate.blimit= [KNL,BOOT]
  1471. Set maximum number of finished RCU callbacks to process
  1472. in one batch.
  1473. rcupdate.qhimark= [KNL,BOOT]
  1474. Set threshold of queued
  1475. RCU callbacks over which batch limiting is disabled.
  1476. rcupdate.qlowmark= [KNL,BOOT]
  1477. Set threshold of queued RCU callbacks below which
  1478. batch limiting is re-enabled.
  1479. rdinit= [KNL]
  1480. Format: <full_path>
  1481. Run specified binary instead of /init from the ramdisk,
  1482. used for early userspace startup. See initrd.
  1483. reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
  1484. Format: <reboot_mode>[,<reboot_mode2>[,...]]
  1485. See arch/*/kernel/reboot.c or arch/*/kernel/process.c
  1486. relax_domain_level=
  1487. [KNL, SMP] Set scheduler's default relax_domain_level.
  1488. See Documentation/cpusets.txt.
  1489. reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
  1490. reservetop= [X86-32]
  1491. Format: nn[KMG]
  1492. Reserves a hole at the top of the kernel virtual
  1493. address space.
  1494. reset_devices [KNL] Force drivers to reset the underlying device
  1495. during initialization.
  1496. resume= [SWSUSP]
  1497. Specify the partition device for software suspend
  1498. resume_offset= [SWSUSP]
  1499. Specify the offset from the beginning of the partition
  1500. given by "resume=" at which the swap header is located,
  1501. in <PAGE_SIZE> units (needed only for swap files).
  1502. See Documentation/power/swsusp-and-swap-files.txt
  1503. retain_initrd [RAM] Keep initrd memory after extraction
  1504. rhash_entries= [KNL,NET]
  1505. Set number of hash buckets for route cache
  1506. riscom8= [HW,SERIAL]
  1507. Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
  1508. ro [KNL] Mount root device read-only on boot
  1509. root= [KNL] Root filesystem
  1510. rootdelay= [KNL] Delay (in seconds) to pause before attempting to
  1511. mount the root filesystem
  1512. rootflags= [KNL] Set root filesystem mount option string
  1513. rootfstype= [KNL] Set root filesystem type
  1514. rootwait [KNL] Wait (indefinitely) for root device to show up.
  1515. Useful for devices that are detected asynchronously
  1516. (e.g. USB and MMC devices).
  1517. root_plug.vendor_id=
  1518. [ROOTPLUG] Override the default vendor ID
  1519. root_plug.product_id=
  1520. [ROOTPLUG] Override the default product ID
  1521. root_plug.debug=
  1522. [ROOTPLUG] Enable debugging output
  1523. rw [KNL] Mount root device read-write on boot
  1524. S [KNL] Run init in single mode
  1525. sa1100ir [NET]
  1526. See drivers/net/irda/sa1100_ir.c.
  1527. sbni= [NET] Granch SBNI12 leased line adapter
  1528. sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
  1529. Format: <io>[,<timeout>[,<isapnp>]]
  1530. scsi_debug_*= [SCSI]
  1531. See drivers/scsi/scsi_debug.c.
  1532. scsi_default_dev_flags=
  1533. [SCSI] SCSI default device flags
  1534. Format: <integer>
  1535. scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
  1536. Format: <vendor>:<model>:<flags>
  1537. (flags are integer value)
  1538. scsi_logging_level= [SCSI] a bit mask of logging levels
  1539. See drivers/scsi/scsi_logging.h for bits. Also
  1540. settable via sysctl at dev.scsi.logging_level
  1541. (/proc/sys/dev/scsi/logging_level).
  1542. There is also a nice 'scsi_logging_level' script in the
  1543. S390-tools package, available for download at
  1544. http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
  1545. scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
  1546. discovered. async scans them in kernel threads,
  1547. allowing boot to proceed. none ignores them, expecting
  1548. user space to do the scan.
  1549. selinux [SELINUX] Disable or enable SELinux at boot time.
  1550. Format: { "0" | "1" }
  1551. See security/selinux/Kconfig help text.
  1552. 0 -- disable.
  1553. 1 -- enable.
  1554. Default value is set via kernel config option.
  1555. If enabled at boot time, /selinux/disable can be used
  1556. later to disable prior to initial policy load.
  1557. selinux_compat_net =
  1558. [SELINUX] Set initial selinux_compat_net flag value.
  1559. Format: { "0" | "1" }
  1560. 0 -- use new secmark-based packet controls
  1561. 1 -- use legacy packet controls
  1562. Default value is 0 (preferred).
  1563. Value can be changed at runtime via
  1564. /selinux/compat_net.
  1565. serialnumber [BUGS=X86-32]
  1566. shapers= [NET]
  1567. Maximal number of shapers.
  1568. show_msr= [x86] show boot-time MSR settings
  1569. Format: { <integer> }
  1570. Show boot-time (BIOS-initialized) MSR settings.
  1571. The parameter means the number of CPUs to show,
  1572. for example 1 means boot CPU only.
  1573. sim710= [SCSI,HW]
  1574. See header of drivers/scsi/sim710.c.
  1575. simeth= [IA-64]
  1576. simscsi=
  1577. slram= [HW,MTD]
  1578. slub_debug[=options[,slabs]] [MM, SLUB]
  1579. Enabling slub_debug allows one to determine the
  1580. culprit if slab objects become corrupted. Enabling
  1581. slub_debug can create guard zones around objects and
  1582. may poison objects when not in use. Also tracks the
  1583. last alloc / free. For more information see
  1584. Documentation/vm/slub.txt.
  1585. slub_max_order= [MM, SLUB]
  1586. Determines the maximum allowed order for slabs.
  1587. A high setting may cause OOMs due to memory
  1588. fragmentation. For more information see
  1589. Documentation/vm/slub.txt.
  1590. slub_min_objects= [MM, SLUB]
  1591. The minimum number of objects per slab. SLUB will
  1592. increase the slab order up to slub_max_order to
  1593. generate a sufficiently large slab able to contain
  1594. the number of objects indicated. The higher the number
  1595. of objects the smaller the overhead of tracking slabs
  1596. and the less frequently locks need to be acquired.
  1597. For more information see Documentation/vm/slub.txt.
  1598. slub_min_order= [MM, SLUB]
  1599. Determines the mininum page order for slabs. Must be
  1600. lower than slub_max_order.
  1601. For more information see Documentation/vm/slub.txt.
  1602. slub_nomerge [MM, SLUB]
  1603. Disable merging of slabs with similar size. May be
  1604. necessary if there is some reason to distinguish
  1605. allocs to different slabs. Debug options disable
  1606. merging on their own.
  1607. For more information see Documentation/vm/slub.txt.
  1608. smart2= [HW]
  1609. Format: <io1>[,<io2>[,...,<io8>]]
  1610. smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
  1611. attempt to substitute SMP alternatives once at boot.
  1612. smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
  1613. smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
  1614. smsc-ircc2.ircc_sir= [HW] SIR base I/O port
  1615. smsc-ircc2.ircc_fir= [HW] FIR base I/O port
  1616. smsc-ircc2.ircc_irq= [HW] IRQ line
  1617. smsc-ircc2.ircc_dma= [HW] DMA channel
  1618. smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
  1619. 0: Toshiba Satellite 1800 (GP data pin select)
  1620. 1: Fast pin select (default)
  1621. 2: ATC IRMode
  1622. snd-ad1816a= [HW,ALSA]
  1623. snd-ad1848= [HW,ALSA]
  1624. snd-ali5451= [HW,ALSA]
  1625. snd-als100= [HW,ALSA]
  1626. snd-als4000= [HW,ALSA]
  1627. snd-azt2320= [HW,ALSA]
  1628. snd-cmi8330= [HW,ALSA]
  1629. snd-cmipci= [HW,ALSA]
  1630. snd-cs4231= [HW,ALSA]
  1631. snd-cs4232= [HW,ALSA]
  1632. snd-cs4236= [HW,ALSA]
  1633. snd-cs4281= [HW,ALSA]
  1634. snd-cs46xx= [HW,ALSA]
  1635. snd-dt019x= [HW,ALSA]
  1636. snd-dummy= [HW,ALSA]
  1637. snd-emu10k1= [HW,ALSA]
  1638. snd-ens1370= [HW,ALSA]
  1639. snd-ens1371= [HW,ALSA]
  1640. snd-es968= [HW,ALSA]
  1641. snd-es1688= [HW,ALSA]
  1642. snd-es18xx= [HW,ALSA]
  1643. snd-es1938= [HW,ALSA]
  1644. snd-es1968= [HW,ALSA]
  1645. snd-fm801= [HW,ALSA]
  1646. snd-gusclassic= [HW,ALSA]
  1647. snd-gusextreme= [HW,ALSA]
  1648. snd-gusmax= [HW,ALSA]
  1649. snd-hdsp= [HW,ALSA]
  1650. snd-ice1712= [HW,ALSA]
  1651. snd-intel8x0= [HW,ALSA]
  1652. snd-interwave= [HW,ALSA]
  1653. snd-interwave-stb=
  1654. [HW,ALSA]
  1655. snd-korg1212= [HW,ALSA]
  1656. snd-maestro3= [HW,ALSA]
  1657. snd-mpu401= [HW,ALSA]
  1658. snd-mtpav= [HW,ALSA]
  1659. snd-nm256= [HW,ALSA]
  1660. snd-opl3sa2= [HW,ALSA]
  1661. snd-opti92x-ad1848=
  1662. [HW,ALSA]
  1663. snd-opti92x-cs4231=
  1664. [HW,ALSA]
  1665. snd-opti93x= [HW,ALSA]
  1666. snd-pmac= [HW,ALSA]
  1667. snd-rme32= [HW,ALSA]
  1668. snd-rme96= [HW,ALSA]
  1669. snd-rme9652= [HW,ALSA]
  1670. snd-sb8= [HW,ALSA]
  1671. snd-sb16= [HW,ALSA]
  1672. snd-sbawe= [HW,ALSA]
  1673. snd-serial= [HW,ALSA]
  1674. snd-sgalaxy= [HW,ALSA]
  1675. snd-sonicvibes= [HW,ALSA]
  1676. snd-sun-amd7930=
  1677. [HW,ALSA]
  1678. snd-sun-cs4231= [HW,ALSA]
  1679. snd-trident= [HW,ALSA]
  1680. snd-usb-audio= [HW,ALSA,USB]
  1681. snd-via82xx= [HW,ALSA]
  1682. snd-virmidi= [HW,ALSA]
  1683. snd-wavefront= [HW,ALSA]
  1684. snd-ymfpci= [HW,ALSA]
  1685. softlockup_panic=
  1686. [KNL] Should the soft-lockup detector generate panics.
  1687. sonypi.*= [HW] Sony Programmable I/O Control Device driver
  1688. See Documentation/sonypi.txt
  1689. specialix= [HW,SERIAL] Specialix multi-serial port adapter
  1690. See Documentation/specialix.txt.
  1691. spia_io_base= [HW,MTD]
  1692. spia_fio_base=
  1693. spia_pedr=
  1694. spia_peddr=
  1695. sscape= [HW,OSS]
  1696. Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
  1697. st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
  1698. See Documentation/scsi/st.txt.
  1699. sti= [PARISC,HW]
  1700. Format: <num>
  1701. Set the STI (builtin display/keyboard on the HP-PARISC
  1702. machines) console (graphic card) which should be used
  1703. as the initial boot-console.
  1704. See also comment in drivers/video/console/sticore.c.
  1705. sti_font= [HW]
  1706. See comment in drivers/video/console/sticore.c.
  1707. stifb= [HW]
  1708. Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
  1709. sunrpc.pool_mode=
  1710. [NFS]
  1711. Control how the NFS server code allocates CPUs to
  1712. service thread pools. Depending on how many NICs
  1713. you have and where their interrupts are bound, this
  1714. option will affect which CPUs will do NFS serving.
  1715. Note: this parameter cannot be changed while the
  1716. NFS server is running.
  1717. auto the server chooses an appropriate mode
  1718. automatically using heuristics
  1719. global a single global pool contains all CPUs
  1720. percpu one pool for each CPU
  1721. pernode one pool for each NUMA node (equivalent
  1722. to global on non-NUMA machines)
  1723. swiotlb= [IA-64] Number of I/O TLB slabs
  1724. switches= [HW,M68k]
  1725. sym53c416= [HW,SCSI]
  1726. See header of drivers/scsi/sym53c416.c.
  1727. sysrq_always_enabled
  1728. [KNL]
  1729. Ignore sysrq setting - this boot parameter will
  1730. neutralize any effect of /proc/sys/kernel/sysrq.
  1731. Useful for debugging.
  1732. t128= [HW,SCSI]
  1733. See header of drivers/scsi/t128.c.
  1734. tdfx= [HW,DRM]
  1735. test_suspend= [SUSPEND]
  1736. Specify "mem" (for Suspend-to-RAM) or "standby" (for
  1737. standby suspend) as the system sleep state to briefly
  1738. enter during system startup. The system is woken from
  1739. this state using a wakeup-capable RTC alarm.
  1740. thash_entries= [KNL,NET]
  1741. Set number of hash buckets for TCP connection
  1742. thermal.act= [HW,ACPI]
  1743. -1: disable all active trip points in all thermal zones
  1744. <degrees C>: override all lowest active trip points
  1745. thermal.crt= [HW,ACPI]
  1746. -1: disable all critical trip points in all thermal zones
  1747. <degrees C>: override all critical trip points
  1748. thermal.nocrt= [HW,ACPI]
  1749. Set to disable actions on ACPI thermal zone
  1750. critical and hot trip points.
  1751. thermal.off= [HW,ACPI]
  1752. 1: disable ACPI thermal control
  1753. thermal.psv= [HW,ACPI]
  1754. -1: disable all passive trip points
  1755. <degrees C>: override all passive trip points to this value
  1756. thermal.tzp= [HW,ACPI]
  1757. Specify global default ACPI thermal zone polling rate
  1758. <deci-seconds>: poll all this frequency
  1759. 0: no polling (default)
  1760. tmscsim= [HW,SCSI]
  1761. See comment before function dc390_setup() in
  1762. drivers/scsi/tmscsim.c.
  1763. tp720= [HW,PS2]
  1764. trix= [HW,OSS] MediaTrix AudioTrix Pro
  1765. Format:
  1766. <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
  1767. turbografx.map[2|3]= [HW,JOY]
  1768. TurboGraFX parallel port interface
  1769. Format:
  1770. <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
  1771. See also Documentation/input/joystick-parport.txt
  1772. u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
  1773. See header of drivers/scsi/u14-34f.c.
  1774. uart401= [HW,OSS]
  1775. Format: <io>,<irq>
  1776. uart6850= [HW,OSS]
  1777. Format: <io>,<irq>
  1778. uhci-hcd.ignore_oc=
  1779. [USB] Ignore overcurrent events (default N).
  1780. Some badly-designed motherboards generate lots of
  1781. bogus events, for ports that aren't wired to
  1782. anything. Set this parameter to avoid log spamming.
  1783. Note that genuine overcurrent events won't be
  1784. reported either.
  1785. unknown_nmi_panic
  1786. [X86-32,X86-64]
  1787. Set unknown_nmi_panic=1 early on boot.
  1788. usbcore.autosuspend=
  1789. [USB] The autosuspend time delay (in seconds) used
  1790. for newly-detected USB devices (default 2). This
  1791. is the time required before an idle device will be
  1792. autosuspended. Devices for which the delay is set
  1793. to a negative value won't be autosuspended at all.
  1794. usbcore.usbfs_snoop=
  1795. [USB] Set to log all usbfs traffic (default 0 = off).
  1796. usbcore.blinkenlights=
  1797. [USB] Set to cycle leds on hubs (default 0 = off).
  1798. usbcore.old_scheme_first=
  1799. [USB] Start with the old device initialization
  1800. scheme (default 0 = off).
  1801. usbcore.use_both_schemes=
  1802. [USB] Try the other device initialization scheme
  1803. if the first one fails (default 1 = enabled).
  1804. usbcore.initial_descriptor_timeout=
  1805. [USB] Specifies timeout for the initial 64-byte
  1806. USB_REQ_GET_DESCRIPTOR request in milliseconds
  1807. (default 5000 = 5.0 seconds).
  1808. usbhid.mousepoll=
  1809. [USBHID] The interval which mice are to be polled at.
  1810. add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
  1811. kernel's map of available physical RAM.
  1812. vdso= [X86-32,SH,x86-64]
  1813. vdso=2: enable compat VDSO (default with COMPAT_VDSO)
  1814. vdso=1: enable VDSO (default)
  1815. vdso=0: disable VDSO mapping
  1816. vdso32= [X86-32,X86-64]
  1817. vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
  1818. vdso32=1: enable 32-bit VDSO (default)
  1819. vdso32=0: disable 32-bit VDSO mapping
  1820. vector= [IA-64,SMP]
  1821. vector=percpu: enable percpu vector domain
  1822. video= [FB] Frame buffer configuration
  1823. See Documentation/fb/modedb.txt.
  1824. vga= [BOOT,X86-32] Select a particular video mode
  1825. See Documentation/x86/i386/boot.txt and
  1826. Documentation/svga.txt.
  1827. Use vga=ask for menu.
  1828. This is actually a boot loader parameter; the value is
  1829. passed to the kernel using a special protocol.
  1830. vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
  1831. size of <nn>. This can be used to increase the
  1832. minimum size (128MB on x86). It can also be used to
  1833. decrease the size and leave more room for directly
  1834. mapped kernel RAM.
  1835. vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
  1836. Format: <command>
  1837. vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
  1838. Format: <command>
  1839. vmpoff= [KNL,S390] Perform z/VM CP command after power off.
  1840. Format: <command>
  1841. waveartist= [HW,OSS]
  1842. Format: <io>,<irq>,<dma>,<dma2>
  1843. wd33c93= [HW,SCSI]
  1844. See header of drivers/scsi/wd33c93.c.
  1845. wd7000= [HW,SCSI]
  1846. See header of drivers/scsi/wd7000.c.
  1847. wdt= [WDT] Watchdog
  1848. See Documentation/watchdog/wdt.txt.
  1849. xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
  1850. xd_geo= See header of drivers/block/xd.c.
  1851. xirc2ps_cs= [NET,PCMCIA]
  1852. Format:
  1853. <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
  1854. norandmaps Don't use address space randomization
  1855. Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
  1856. ______________________________________________________________________
  1857. TODO:
  1858. Add documentation for ALSA options.
  1859. Add more DRM drivers.