kernel-parameters.txt 68 KB

12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879808182838485868788899091929394959697989910010110210310410510610710810911011111211311411511611711811912012112212312412512612712812913013113213313413513613713813914014114214314414514614714814915015115215315415515615715815916016116216316416516616716816917017117217317417517617717817918018118218318418518618718818919019119219319419519619719819920020120220320420520620720820921021121221321421521621721821922022122222322422522622722822923023123223323423523623723823924024124224324424524624724824925025125225325425525625725825926026126226326426526626726826927027127227327427527627727827928028128228328428528628728828929029129229329429529629729829930030130230330430530630730830931031131231331431531631731831932032132232332432532632732832933033133233333433533633733833934034134234334434534634734834935035135235335435535635735835936036136236336436536636736836937037137237337437537637737837938038138238338438538638738838939039139239339439539639739839940040140240340440540640740840941041141241341441541641741841942042142242342442542642742842943043143243343443543643743843944044144244344444544644744844945045145245345445545645745845946046146246346446546646746846947047147247347447547647747847948048148248348448548648748848949049149249349449549649749849950050150250350450550650750850951051151251351451551651751851952052152252352452552652752852953053153253353453553653753853954054154254354454554654754854955055155255355455555655755855956056156256356456556656756856957057157257357457557657757857958058158258358458558658758858959059159259359459559659759859960060160260360460560660760860961061161261361461561661761861962062162262362462562662762862963063163263363463563663763863964064164264364464564664764864965065165265365465565665765865966066166266366466566666766866967067167267367467567667767867968068168268368468568668768868969069169269369469569669769869970070170270370470570670770870971071171271371471571671771871972072172272372472572672772872973073173273373473573673773873974074174274374474574674774874975075175275375475575675775875976076176276376476576676776876977077177277377477577677777877978078178278378478578678778878979079179279379479579679779879980080180280380480580680780880981081181281381481581681781881982082182282382482582682782882983083183283383483583683783883984084184284384484584684784884985085185285385485585685785885986086186286386486586686786886987087187287387487587687787887988088188288388488588688788888989089189289389489589689789889990090190290390490590690790890991091191291391491591691791891992092192292392492592692792892993093193293393493593693793893994094194294394494594694794894995095195295395495595695795895996096196296396496596696796896997097197297397497597697797897998098198298398498598698798898999099199299399499599699799899910001001100210031004100510061007100810091010101110121013101410151016101710181019102010211022102310241025102610271028102910301031103210331034103510361037103810391040104110421043104410451046104710481049105010511052105310541055105610571058105910601061106210631064106510661067106810691070107110721073107410751076107710781079108010811082108310841085108610871088108910901091109210931094109510961097109810991100110111021103110411051106110711081109111011111112111311141115111611171118111911201121112211231124112511261127112811291130113111321133113411351136113711381139114011411142114311441145114611471148114911501151115211531154115511561157115811591160116111621163116411651166116711681169117011711172117311741175117611771178117911801181118211831184118511861187118811891190119111921193119411951196119711981199120012011202120312041205120612071208120912101211121212131214121512161217121812191220122112221223122412251226122712281229123012311232123312341235123612371238123912401241124212431244124512461247124812491250125112521253125412551256125712581259126012611262126312641265126612671268126912701271127212731274127512761277127812791280128112821283128412851286128712881289129012911292129312941295129612971298129913001301130213031304130513061307130813091310131113121313131413151316131713181319132013211322132313241325132613271328132913301331133213331334133513361337133813391340134113421343134413451346134713481349135013511352135313541355135613571358135913601361136213631364136513661367136813691370137113721373137413751376137713781379138013811382138313841385138613871388138913901391139213931394139513961397139813991400140114021403140414051406140714081409141014111412141314141415141614171418141914201421142214231424142514261427142814291430143114321433143414351436143714381439144014411442144314441445144614471448144914501451145214531454145514561457145814591460146114621463146414651466146714681469147014711472147314741475147614771478147914801481148214831484148514861487148814891490149114921493149414951496149714981499150015011502150315041505150615071508150915101511151215131514151515161517151815191520152115221523152415251526152715281529153015311532153315341535153615371538153915401541154215431544154515461547154815491550155115521553155415551556155715581559156015611562156315641565156615671568156915701571157215731574157515761577157815791580158115821583158415851586158715881589159015911592159315941595159615971598159916001601160216031604160516061607160816091610161116121613161416151616161716181619162016211622162316241625162616271628162916301631163216331634163516361637163816391640164116421643164416451646164716481649165016511652165316541655165616571658165916601661166216631664166516661667166816691670167116721673167416751676167716781679168016811682168316841685168616871688168916901691169216931694169516961697169816991700170117021703170417051706170717081709171017111712171317141715171617171718171917201721172217231724172517261727172817291730173117321733173417351736173717381739174017411742174317441745174617471748174917501751175217531754175517561757175817591760176117621763176417651766176717681769177017711772177317741775177617771778177917801781178217831784178517861787178817891790179117921793179417951796179717981799180018011802180318041805180618071808180918101811181218131814181518161817181818191820182118221823182418251826182718281829183018311832183318341835183618371838183918401841184218431844184518461847184818491850185118521853185418551856185718581859186018611862186318641865186618671868186918701871187218731874187518761877187818791880188118821883188418851886188718881889189018911892189318941895189618971898189919001901190219031904190519061907190819091910191119121913191419151916191719181919192019211922192319241925192619271928192919301931193219331934193519361937193819391940194119421943194419451946194719481949195019511952195319541955195619571958195919601961196219631964196519661967196819691970197119721973197419751976197719781979198019811982198319841985198619871988198919901991199219931994199519961997199819992000200120022003200420052006200720082009201020112012201320142015201620172018201920202021202220232024202520262027202820292030203120322033203420352036203720382039204020412042204320442045204620472048204920502051205220532054205520562057205820592060206120622063206420652066206720682069207020712072207320742075207620772078207920802081208220832084208520862087208820892090209120922093209420952096209720982099210021012102210321042105210621072108210921102111211221132114211521162117211821192120212121222123212421252126212721282129213021312132213321342135213621372138213921402141214221432144214521462147214821492150215121522153215421552156215721582159216021612162216321642165216621672168216921702171217221732174217521762177
  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 is enabled.
  83. TS Appropriate touchscreen support is enabled.
  84. USB USB support is enabled.
  85. USBHID USB Human Interface Device support is enabled.
  86. V4L Video For Linux support is enabled.
  87. VGA The VGA console has been enabled.
  88. VT Virtual terminal support is enabled.
  89. WDT Watchdog support is enabled.
  90. XT IBM PC/XT MFM hard disk support is enabled.
  91. X86-32 X86-32, aka i386 architecture is enabled.
  92. X86-64 X86-64 architecture is enabled.
  93. More X86-64 boot options can be found in
  94. Documentation/x86_64/boot-options.txt .
  95. In addition, the following text indicates that the option:
  96. BUGS= Relates to possible processor bugs on the said processor.
  97. KNL Is a kernel start-up parameter.
  98. BOOT Is a boot loader parameter.
  99. Parameters denoted with BOOT are actually interpreted by the boot
  100. loader, and have no meaning to the kernel directly.
  101. Do not modify the syntax of boot loader parameters without extreme
  102. need or coordination with <Documentation/i386/boot.txt>.
  103. There are also arch-specific kernel-parameters not documented here.
  104. See for example <Documentation/x86_64/boot-options.txt>.
  105. Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
  106. a trailing = on the name of any parameter states that that parameter will
  107. be entered as an environment variable, whereas its absence indicates that
  108. it will appear as a kernel argument readable via /proc/cmdline by programs
  109. running once the system is up.
  110. The number of kernel parameters is not limited, but the length of the
  111. complete command line (parameters including spaces etc.) is limited to
  112. a fixed number of characters. This limit depends on the architecture
  113. and is between 256 and 4096 characters. It is defined in the file
  114. ./include/asm/setup.h as COMMAND_LINE_SIZE.
  115. acpi= [HW,ACPI,X86-64,i386]
  116. Advanced Configuration and Power Interface
  117. Format: { force | off | ht | strict | noirq }
  118. force -- enable ACPI if default was off
  119. off -- disable ACPI if default was on
  120. noirq -- do not use ACPI for IRQ routing
  121. ht -- run only enough ACPI to enable Hyper Threading
  122. strict -- Be less tolerant of platforms that are not
  123. strictly ACPI specification compliant.
  124. See also Documentation/power/pm.txt, pci=noacpi
  125. acpi_apic_instance= [ACPI, IOAPIC]
  126. Format: <int>
  127. 2: use 2nd APIC table, if available
  128. 1,0: use 1st APIC table
  129. default: 0
  130. acpi_sleep= [HW,ACPI] Sleep options
  131. Format: { s3_bios, s3_mode, s3_beep }
  132. See Documentation/power/video.txt for s3_bios and s3_mode.
  133. s3_beep is for debugging; it makes the PC's speaker beep
  134. as soon as the kernel's real-mode entry point is called.
  135. acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
  136. Format: { level | edge | high | low }
  137. acpi_irq_balance [HW,ACPI]
  138. ACPI will balance active IRQs
  139. default in APIC mode
  140. acpi_irq_nobalance [HW,ACPI]
  141. ACPI will not move active IRQs (default)
  142. default in PIC mode
  143. acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
  144. use by PCI
  145. Format: <irq>,<irq>...
  146. acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
  147. Format: <irq>,<irq>...
  148. acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
  149. acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
  150. Format: To spoof as Windows 98: ="Microsoft Windows"
  151. acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
  152. acpi_osi="string1" # add string1 -- only one string
  153. acpi_osi="!string2" # remove built-in string2
  154. acpi_osi= # disable all strings
  155. acpi_serialize [HW,ACPI] force serialization of AML methods
  156. acpi_skip_timer_override [HW,ACPI]
  157. Recognize and ignore IRQ0/pin2 Interrupt Override.
  158. For broken nForce2 BIOS resulting in XT-PIC timer.
  159. acpi_use_timer_override [HW,ACPI}
  160. Use timer override. For some broken Nvidia NF5 boards
  161. that require a timer override, but don't have
  162. HPET
  163. acpi.debug_layer= [HW,ACPI]
  164. Format: <int>
  165. Each bit of the <int> indicates an ACPI debug layer,
  166. 1: enable, 0: disable. It is useful for boot time
  167. debugging. After system has booted up, it can be set
  168. via /sys/module/acpi/parameters/debug_layer.
  169. CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
  170. Available bits (add the numbers together) to enable debug output
  171. for specific parts of the ACPI subsystem:
  172. 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
  173. 0x10 namespace 0x20 parser 0x40 dispatcher
  174. 0x80 executer 0x100 resources 0x200 acpica debugger
  175. 0x400 os services 0x800 acpica disassembler.
  176. The number can be in decimal or prefixed with 0x in hex.
  177. Warning: Many of these options can produce a lot of
  178. output and make your system unusable. Be very careful.
  179. acpi.debug_level= [HW,ACPI]
  180. Format: <int>
  181. Each bit of the <int> indicates an ACPI debug level,
  182. 1: enable, 0: disable. It is useful for boot time
  183. debugging. After system has booted up, it can be set
  184. via /sys/module/acpi/parameters/debug_level.
  185. CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
  186. Available bits (add the numbers together) to enable different
  187. debug output levels of the ACPI subsystem:
  188. 0x01 error 0x02 warn 0x04 init 0x08 debug object
  189. 0x10 info 0x20 init names 0x40 parse 0x80 load
  190. 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
  191. 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
  192. 0x10000 resources 0x20000 user requests 0x40000 package.
  193. The number can be in decimal or prefixed with 0x in hex.
  194. Warning: Many of these options can produce a lot of
  195. output and make your system unusable. Be very careful.
  196. acpi_pm_good [X86-32,X86-64]
  197. Override the pmtimer bug detection: force the kernel
  198. to assume that this machine's pmtimer latches its value
  199. and always returns good values.
  200. agp= [AGP]
  201. { off | try_unsupported }
  202. off: disable AGP support
  203. try_unsupported: try to drive unsupported chipsets
  204. (may crash computer or cause data corruption)
  205. enable_timer_pin_1 [i386,x86-64]
  206. Enable PIN 1 of APIC timer
  207. Can be useful to work around chipset bugs
  208. (in particular on some ATI chipsets).
  209. The kernel tries to set a reasonable default.
  210. disable_timer_pin_1 [i386,x86-64]
  211. Disable PIN 1 of APIC timer
  212. Can be useful to work around chipset bugs.
  213. ad1848= [HW,OSS]
  214. Format: <io>,<irq>,<dma>,<dma2>,<type>
  215. advansys= [HW,SCSI]
  216. See header of drivers/scsi/advansys.c.
  217. advwdt= [HW,WDT] Advantech WDT
  218. Format: <iostart>,<iostop>
  219. aedsp16= [HW,OSS] Audio Excel DSP 16
  220. Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
  221. See also header of sound/oss/aedsp16.c.
  222. aha152x= [HW,SCSI]
  223. See Documentation/scsi/aha152x.txt.
  224. aha1542= [HW,SCSI]
  225. Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
  226. aic7xxx= [HW,SCSI]
  227. See Documentation/scsi/aic7xxx.txt.
  228. aic79xx= [HW,SCSI]
  229. See Documentation/scsi/aic79xx.txt.
  230. amijoy.map= [HW,JOY] Amiga joystick support
  231. Map of devices attached to JOY0DAT and JOY1DAT
  232. Format: <a>,<b>
  233. See also Documentation/kernel/input/joystick.txt
  234. analog.map= [HW,JOY] Analog joystick and gamepad support
  235. Specifies type or capabilities of an analog joystick
  236. connected to one of 16 gameports
  237. Format: <type1>,<type2>,..<type16>
  238. apc= [HW,SPARC]
  239. Power management functions (SPARCstation-4/5 + deriv.)
  240. Format: noidle
  241. Disable APC CPU standby support. SPARCstation-Fox does
  242. not play well with APC CPU idle - disable it if you have
  243. APC and your system crashes randomly.
  244. apic= [APIC,i386] Advanced Programmable Interrupt Controller
  245. Change the output verbosity whilst booting
  246. Format: { quiet (default) | verbose | debug }
  247. Change the amount of debugging information output
  248. when initialising the APIC and IO-APIC components.
  249. apm= [APM] Advanced Power Management
  250. See header of arch/i386/kernel/apm.c.
  251. arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
  252. Format: <io>,<irq>,<nodeID>
  253. ataflop= [HW,M68k]
  254. atarimouse= [HW,MOUSE] Atari Mouse
  255. atascsi= [HW,SCSI] Atari SCSI
  256. atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
  257. EzKey and similar keyboards
  258. atkbd.reset= [HW] Reset keyboard during initialization
  259. atkbd.set= [HW] Select keyboard code set
  260. Format: <int> (2 = AT (default), 3 = PS/2)
  261. atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
  262. keyboards
  263. atkbd.softraw= [HW] Choose between synthetic and real raw mode
  264. Format: <bool> (0 = real, 1 = synthetic (default))
  265. atkbd.softrepeat= [HW]
  266. Use software keyboard repeat
  267. autotest [IA64]
  268. baycom_epp= [HW,AX25]
  269. Format: <io>,<mode>
  270. baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
  271. Format: <io>,<mode>
  272. See header of drivers/net/hamradio/baycom_par.c.
  273. baycom_ser_fdx= [HW,AX25]
  274. BayCom Serial Port AX.25 Modem (Full Duplex Mode)
  275. Format: <io>,<irq>,<mode>[,<baud>]
  276. See header of drivers/net/hamradio/baycom_ser_fdx.c.
  277. baycom_ser_hdx= [HW,AX25]
  278. BayCom Serial Port AX.25 Modem (Half Duplex Mode)
  279. Format: <io>,<irq>,<mode>
  280. See header of drivers/net/hamradio/baycom_ser_hdx.c.
  281. boot_delay= Milliseconds to delay each printk during boot.
  282. Values larger than 10 seconds (10000) are changed to
  283. no delay (0).
  284. Format: integer
  285. bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
  286. bttv.radio= Most important insmod options are available as
  287. kernel args too.
  288. bttv.pll= See Documentation/video4linux/bttv/Insmod-options
  289. bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
  290. BusLogic= [HW,SCSI]
  291. See drivers/scsi/BusLogic.c, comment before function
  292. BusLogic_ParseDriverOptions().
  293. c101= [NET] Moxa C101 synchronous serial card
  294. cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
  295. Sometimes CPU hardware bugs make them report the cache
  296. size incorrectly. The kernel will attempt work arounds
  297. to fix known problems, but for some CPUs it is not
  298. possible to determine what the correct size should be.
  299. This option provides an override for these situations.
  300. security= [SECURITY] Choose a security module to enable at boot.
  301. If this boot parameter is not specified, only the first
  302. security module asking for security registration will be
  303. loaded. An invalid security module name will be treated
  304. as if no module has been chosen.
  305. capability.disable=
  306. [SECURITY] Disable capabilities. This would normally
  307. be used only if an alternative security model is to be
  308. configured. Potentially dangerous and should only be
  309. used if you are entirely sure of the consequences.
  310. ccw_timeout_log [S390]
  311. See Documentation/s390/CommonIO for details.
  312. cgroup_disable= [KNL] Disable a particular controller
  313. Format: {name of the controller(s) to disable}
  314. {Currently supported controllers - "memory"}
  315. checkreqprot [SELINUX] Set initial checkreqprot flag value.
  316. Format: { "0" | "1" }
  317. See security/selinux/Kconfig help text.
  318. 0 -- check protection applied by kernel (includes
  319. any implied execute protection).
  320. 1 -- check protection requested by application.
  321. Default value is set via a kernel config option.
  322. Value can be changed at runtime via
  323. /selinux/checkreqprot.
  324. cio_ignore= [S390]
  325. See Documentation/s390/CommonIO for details.
  326. cio_msg= [S390]
  327. See Documentation/s390/CommonIO for details.
  328. clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
  329. [Deprecated]
  330. Forces specified clocksource (if available) to be used
  331. when calculating gettimeofday(). If specified
  332. clocksource is not available, it defaults to PIT.
  333. Format: { pit | tsc | cyclone | pmtmr }
  334. clocksource= [GENERIC_TIME] Override the default clocksource
  335. Format: <string>
  336. Override the default clocksource and use the clocksource
  337. with the name specified.
  338. Some clocksource names to choose from, depending on
  339. the platform:
  340. [all] jiffies (this is the base, fallback clocksource)
  341. [ACPI] acpi_pm
  342. [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
  343. pxa_timer,timer3,32k_counter,timer0_1
  344. [AVR32] avr32
  345. [X86-32] pit,hpet,tsc,vmi-timer;
  346. scx200_hrt on Geode; cyclone on IBM x440
  347. [MIPS] MIPS
  348. [PARISC] cr16
  349. [S390] tod
  350. [SH] SuperH
  351. [SPARC64] tick
  352. [X86-64] hpet,tsc
  353. clearcpuid=BITNUM [X86]
  354. Disable CPUID feature X for the kernel. See
  355. include/asm-x86/cpufeature.h for the valid bit numbers.
  356. Note the Linux specific bits are not necessarily
  357. stable over kernel options, but the vendor specific
  358. ones should be.
  359. Also note that user programs calling CPUID directly
  360. or using the feature without checking anything
  361. will still see it. This just prevents it from
  362. being used by the kernel or shown in /proc/cpuinfo.
  363. Also note the kernel might malfunction if you disable
  364. some critical bits.
  365. code_bytes [IA32/X86_64] How many bytes of object code to print
  366. in an oops report.
  367. Range: 0 - 8192
  368. Default: 64
  369. disable_8254_timer
  370. enable_8254_timer
  371. [IA32/X86_64] Disable/Enable interrupt 0 timer routing
  372. over the 8254 in addition to over the IO-APIC. The
  373. kernel tries to set a sensible default.
  374. hpet= [X86-32,HPET] option to control HPET usage
  375. Format: { enable (default) | disable | force }
  376. disable: disable HPET and use PIT instead
  377. force: allow force enabled of undocumented chips (ICH4,
  378. VIA, nVidia)
  379. com20020= [HW,NET] ARCnet - COM20020 chipset
  380. Format:
  381. <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
  382. com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
  383. Format: <io>[,<irq>]
  384. com90xx= [HW,NET]
  385. ARCnet - COM90xx chipset (memory-mapped buffers)
  386. Format: <io>[,<irq>[,<memstart>]]
  387. condev= [HW,S390] console device
  388. conmode=
  389. console= [KNL] Output console device and options.
  390. tty<n> Use the virtual console device <n>.
  391. ttyS<n>[,options]
  392. ttyUSB0[,options]
  393. Use the specified serial port. The options are of
  394. the form "bbbbpnf", where "bbbb" is the baud rate,
  395. "p" is parity ("n", "o", or "e"), "n" is number of
  396. bits, and "f" is flow control ("r" for RTS or
  397. omit it). Default is "9600n8".
  398. See Documentation/serial-console.txt for more
  399. information. See
  400. Documentation/networking/netconsole.txt for an
  401. alternative.
  402. uart[8250],io,<addr>[,options]
  403. uart[8250],mmio,<addr>[,options]
  404. Start an early, polled-mode console on the 8250/16550
  405. UART at the specified I/O port or MMIO address,
  406. switching to the matching ttyS device later. The
  407. options are the same as for ttyS, above.
  408. If the device connected to the port is not a TTY but a braille
  409. device, prepend "brl," before the device type, for instance
  410. console=brl,ttyS0
  411. For now, only VisioBraille is supported.
  412. earlycon= [KNL] Output early console device and options.
  413. uart[8250],io,<addr>[,options]
  414. uart[8250],mmio,<addr>[,options]
  415. Start an early, polled-mode console on the 8250/16550
  416. UART at the specified I/O port or MMIO address.
  417. The options are the same as for ttyS, above.
  418. no_console_suspend
  419. [HW] Never suspend the console
  420. Disable suspending of consoles during suspend and
  421. hibernate operations. Once disabled, debugging
  422. messages can reach various consoles while the rest
  423. of the system is being put to sleep (ie, while
  424. debugging driver suspend/resume hooks). This may
  425. not work reliably with all consoles, but is known
  426. to work with serial and VGA consoles.
  427. cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
  428. Format:
  429. <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
  430. crashkernel=nn[KMG]@ss[KMG]
  431. [KNL] Reserve a chunk of physical memory to
  432. hold a kernel to switch to with kexec on panic.
  433. crashkernel=range1:size1[,range2:size2,...][@offset]
  434. [KNL] Same as above, but depends on the memory
  435. in the running system. The syntax of range is
  436. start-[end] where start and end are both
  437. a memory unit (amount[KMG]). See also
  438. Documentation/kdump/kdump.txt for a example.
  439. cs4232= [HW,OSS]
  440. Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
  441. cs89x0_dma= [HW,NET]
  442. Format: <dma>
  443. cs89x0_media= [HW,NET]
  444. Format: { rj45 | aui | bnc }
  445. dasd= [HW,NET]
  446. See header of drivers/s390/block/dasd_devmap.c.
  447. db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
  448. (one device per port)
  449. Format: <port#>,<type>
  450. See also Documentation/input/joystick-parport.txt
  451. debug [KNL] Enable kernel debugging (events log level).
  452. debug_locks_verbose=
  453. [KNL] verbose self-tests
  454. Format=<0|1>
  455. Print debugging info while doing the locking API
  456. self-tests.
  457. We default to 0 (no extra messages), setting it to
  458. 1 will print _a lot_ more information - normally
  459. only useful to kernel developers.
  460. debug_objects [KNL] Enable object debugging
  461. decnet.addr= [HW,NET]
  462. Format: <area>[,<node>]
  463. See also Documentation/networking/decnet.txt.
  464. vt.default_blu= [VT]
  465. Format: <blue0>,<blue1>,<blue2>,...,<blue15>
  466. Change the default blue palette of the console.
  467. This is a 16-member array composed of values
  468. ranging from 0-255.
  469. vt.default_grn= [VT]
  470. Format: <green0>,<green1>,<green2>,...,<green15>
  471. Change the default green palette of the console.
  472. This is a 16-member array composed of values
  473. ranging from 0-255.
  474. vt.default_red= [VT]
  475. Format: <red0>,<red1>,<red2>,...,<red15>
  476. Change the default red palette of the console.
  477. This is a 16-member array composed of values
  478. ranging from 0-255.
  479. vt.default_utf8=
  480. [VT]
  481. Format=<0|1>
  482. Set system-wide default UTF-8 mode for all tty's.
  483. Default is 1, i.e. UTF-8 mode is enabled for all
  484. newly opened terminals.
  485. dhash_entries= [KNL]
  486. Set number of hash buckets for dentry cache.
  487. digi= [HW,SERIAL]
  488. IO parameters + enable/disable command.
  489. digiepca= [HW,SERIAL]
  490. See drivers/char/README.epca and
  491. Documentation/digiepca.txt.
  492. disable_mtrr_trim [X86, Intel and AMD only]
  493. By default the kernel will trim any uncacheable
  494. memory out of your available memory pool based on
  495. MTRR settings. This parameter disables that behavior,
  496. possibly causing your machine to run very slowly.
  497. dmasound= [HW,OSS] Sound subsystem buffers
  498. dscc4.setup= [NET]
  499. dtc3181e= [HW,SCSI]
  500. earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
  501. earlyprintk=vga
  502. earlyprintk=serial[,ttySn[,baudrate]]
  503. Append ",keep" to not disable it when the real console
  504. takes over.
  505. Only vga or serial at a time, not both.
  506. Currently only ttyS0 and ttyS1 are supported.
  507. Interaction with the standard serial driver is not
  508. very good.
  509. The VGA output is eventually overwritten by the real
  510. console.
  511. eata= [HW,SCSI]
  512. edd= [EDD]
  513. Format: {"off" | "on" | "skip[mbr]"}
  514. eisa_irq_edge= [PARISC,HW]
  515. See header of drivers/parisc/eisa.c.
  516. elanfreq= [X86-32]
  517. See comment before function elanfreq_setup() in
  518. arch/i386/kernel/cpu/cpufreq/elanfreq.c.
  519. elevator= [IOSCHED]
  520. Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
  521. See Documentation/block/as-iosched.txt and
  522. Documentation/block/deadline-iosched.txt for details.
  523. elfcorehdr= [X86-32, X86_64]
  524. Specifies physical address of start of kernel core
  525. image elf header. Generally kexec loader will
  526. pass this option to capture kernel.
  527. See Documentation/kdump/kdump.txt for details.
  528. enforcing [SELINUX] Set initial enforcing status.
  529. Format: {"0" | "1"}
  530. See security/selinux/Kconfig help text.
  531. 0 -- permissive (log only, no denials).
  532. 1 -- enforcing (deny and log).
  533. Default value is 0.
  534. Value can be changed at runtime via /selinux/enforce.
  535. es1371= [HW,OSS]
  536. Format: <spdif>,[<nomix>,[<amplifier>]]
  537. See also header of sound/oss/es1371.c.
  538. ether= [HW,NET] Ethernet cards parameters
  539. This option is obsoleted by the "netdev=" option, which
  540. has equivalent usage. See its documentation for details.
  541. eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
  542. Format: <io>[,<irq>]
  543. failslab=
  544. fail_page_alloc=
  545. fail_make_request=[KNL]
  546. General fault injection mechanism.
  547. Format: <interval>,<probability>,<space>,<times>
  548. See also /Documentation/fault-injection/.
  549. fd_mcs= [HW,SCSI]
  550. See header of drivers/scsi/fd_mcs.c.
  551. fdomain= [HW,SCSI]
  552. See header of drivers/scsi/fdomain.c.
  553. floppy= [HW]
  554. See Documentation/floppy.txt.
  555. gamecon.map[2|3]=
  556. [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
  557. support via parallel port (up to 5 devices per port)
  558. Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
  559. See also Documentation/input/joystick-parport.txt
  560. gamma= [HW,DRM]
  561. gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
  562. Format: off | on
  563. default: on
  564. gdth= [HW,SCSI]
  565. See header of drivers/scsi/gdth.c.
  566. gpt [EFI] Forces disk with valid GPT signature but
  567. invalid Protective MBR to be treated as GPT.
  568. gvp11= [HW,SCSI]
  569. hashdist= [KNL,NUMA] Large hashes allocated during boot
  570. are distributed across NUMA nodes. Defaults on
  571. for IA-64, off otherwise.
  572. Format: 0 | 1 (for off | on)
  573. hcl= [IA-64] SGI's Hardware Graph compatibility layer
  574. hd= [EIDE] (E)IDE hard drive subsystem geometry
  575. Format: <cyl>,<head>,<sect>
  576. hd?= [HW] (E)IDE subsystem
  577. hd?lun= See Documentation/ide/ide.txt.
  578. highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
  579. size of <nn>. This works even on boxes that have no
  580. highmem otherwise. This also works to reduce highmem
  581. size on bigger boxes.
  582. highres= [KNL] Enable/disable high resolution timer mode.
  583. Valid parameters: "on", "off"
  584. Default: "on"
  585. hisax= [HW,ISDN]
  586. See Documentation/isdn/README.HiSax.
  587. hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
  588. hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
  589. i8042.direct [HW] Put keyboard port into non-translated mode
  590. i8042.dumbkbd [HW] Pretend that controller can only read data from
  591. keyboard and cannot control its state
  592. (Don't attempt to blink the leds)
  593. i8042.noaux [HW] Don't check for auxiliary (== mouse) port
  594. i8042.nokbd [HW] Don't check/create keyboard port
  595. i8042.noloop [HW] Disable the AUX Loopback command while probing
  596. for the AUX port
  597. i8042.nomux [HW] Don't check presence of an active multiplexing
  598. controller
  599. i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
  600. controllers
  601. i8042.panicblink=
  602. [HW] Frequency with which keyboard LEDs should blink
  603. when kernel panics (default is 0.5 sec)
  604. i8042.reset [HW] Reset the controller during init and cleanup
  605. i8042.unlock [HW] Unlock (ignore) the keylock
  606. i810= [HW,DRM]
  607. i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
  608. indicates that the driver is running on unsupported
  609. hardware.
  610. i8k.force [HW] Activate i8k driver even if SMM BIOS signature
  611. does not match list of supported models.
  612. i8k.power_status
  613. [HW] Report power status in /proc/i8k
  614. (disabled by default)
  615. i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
  616. capability is set.
  617. ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
  618. See Documentation/mca.txt.
  619. icn= [HW,ISDN]
  620. Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
  621. ide= [HW] (E)IDE subsystem
  622. Format: ide=nodma or ide=doubler
  623. See Documentation/ide/ide.txt.
  624. idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
  625. See Documentation/ide/ide.txt.
  626. idle= [X86]
  627. Format: idle=poll or idle=mwait
  628. Poll forces a polling idle loop that can slightly improves the performance
  629. of waking up a idle CPU, but will use a lot of power and make the system
  630. run hot. Not recommended.
  631. idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
  632. to not use it because it doesn't save as much power as a normal idle
  633. loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
  634. as idle=poll.
  635. ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
  636. Claim all unknown PCI IDE storage controllers.
  637. ignore_loglevel [KNL]
  638. Ignore loglevel setting - this will print /all/
  639. kernel messages to the console. Useful for debugging.
  640. ihash_entries= [KNL]
  641. Set number of hash buckets for inode cache.
  642. in2000= [HW,SCSI]
  643. See header of drivers/scsi/in2000.c.
  644. init= [KNL]
  645. Format: <full_path>
  646. Run specified binary instead of /sbin/init as init
  647. process.
  648. initcall_debug [KNL] Trace initcalls as they are executed. Useful
  649. for working out where the kernel is dying during
  650. startup.
  651. initrd= [BOOT] Specify the location of the initial ramdisk
  652. inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
  653. Format: <irq>
  654. inttest= [IA64]
  655. iommu= [x86]
  656. off
  657. force
  658. noforce
  659. biomerge
  660. panic
  661. nopanic
  662. merge
  663. nomerge
  664. forcesac
  665. soft
  666. intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
  667. off
  668. Disable intel iommu driver.
  669. igfx_off [Default Off]
  670. By default, gfx is mapped as normal device. If a gfx
  671. device has a dedicated DMAR unit, the DMAR unit is
  672. bypassed by not enabling DMAR with this option. In
  673. this case, gfx device will use physical address for
  674. DMA.
  675. forcedac [x86_64]
  676. With this option iommu will not optimize to look
  677. for io virtual address below 32 bit forcing dual
  678. address cycle on pci bus for cards supporting greater
  679. than 32 bit addressing. The default is to look
  680. for translation below 32 bit and if not available
  681. then look in the higher range.
  682. strict [Default Off]
  683. With this option on every unmap_single operation will
  684. result in a hardware IOTLB flush operation as opposed
  685. to batching them for performance.
  686. io_delay= [X86-32,X86-64] I/O delay method
  687. 0x80
  688. Standard port 0x80 based delay
  689. 0xed
  690. Alternate port 0xed based delay (needed on some systems)
  691. udelay
  692. Simple two microseconds delay
  693. none
  694. No delay
  695. io7= [HW] IO7 for Marvel based alpha systems
  696. See comment before marvel_specify_io7 in
  697. arch/alpha/kernel/core_marvel.c.
  698. ip= [IP_PNP]
  699. See Documentation/filesystems/nfsroot.txt.
  700. ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
  701. See comment before ip2_setup() in
  702. drivers/char/ip2/ip2base.c.
  703. ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
  704. See header of drivers/scsi/ips.c.
  705. ports= [IP_VS_FTP] IPVS ftp helper module
  706. Default is 21.
  707. Up to 8 (IP_VS_APP_MAX_PORTS) ports
  708. may be specified.
  709. Format: <port>,<port>....
  710. irqfixup [HW]
  711. When an interrupt is not handled search all handlers
  712. for it. Intended to get systems with badly broken
  713. firmware running.
  714. irqpoll [HW]
  715. When an interrupt is not handled search all handlers
  716. for it. Also check all handlers each timer
  717. interrupt. Intended to get systems with badly broken
  718. firmware running.
  719. isapnp= [ISAPNP]
  720. Format: <RDP>,<reset>,<pci_scan>,<verbosity>
  721. isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
  722. Format:
  723. <cpu number>,...,<cpu number>
  724. or
  725. <cpu number>-<cpu number> (must be a positive range in ascending order)
  726. or a mixture
  727. <cpu number>,...,<cpu number>-<cpu number>
  728. This option can be used to specify one or more CPUs
  729. to isolate from the general SMP balancing and scheduling
  730. algorithms. The only way to move a process onto or off
  731. an "isolated" CPU is via the CPU affinity syscalls.
  732. <cpu number> begins at 0 and the maximum value is
  733. "number of CPUs in system - 1".
  734. This option is the preferred way to isolate CPUs. The
  735. alternative -- manually setting the CPU mask of all
  736. tasks in the system -- can cause problems and
  737. suboptimal load balancer performance.
  738. iucv= [HW,NET]
  739. js= [HW,JOY] Analog joystick
  740. See Documentation/input/joystick.txt.
  741. kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
  742. specifies the amount of memory usable by the kernel
  743. for non-movable allocations. The requested amount is
  744. spread evenly throughout all nodes in the system. The
  745. remaining memory in each node is used for Movable
  746. pages. In the event, a node is too small to have both
  747. kernelcore and Movable pages, kernelcore pages will
  748. take priority and other nodes will have a larger number
  749. of kernelcore pages. The Movable zone is used for the
  750. allocation of pages that may be reclaimed or moved
  751. by the page migration subsystem. This means that
  752. HugeTLB pages may not be allocated from this zone.
  753. Note that allocations like PTEs-from-HighMem still
  754. use the HighMem zone if it exists, and the Normal
  755. zone if it does not.
  756. movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
  757. is similar to kernelcore except it specifies the
  758. amount of memory used for migratable allocations.
  759. If both kernelcore and movablecore is specified,
  760. then kernelcore will be at *least* the specified
  761. value but may be more. If movablecore on its own
  762. is specified, the administrator must be careful
  763. that the amount of memory usable for all allocations
  764. is not too small.
  765. keepinitrd [HW,ARM]
  766. kstack=N [X86-32,X86-64] Print N words from the kernel stack
  767. in oops dumps.
  768. kgdboc= [HW] kgdb over consoles.
  769. Requires a tty driver that supports console polling.
  770. (only serial suported for now)
  771. Format: <serial_device>[,baud]
  772. l2cr= [PPC]
  773. l3cr= [PPC]
  774. lapic [X86-32,APIC] Enable the local APIC even if BIOS
  775. disabled it.
  776. lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
  777. C2 power state.
  778. libata.dma= [LIBATA] DMA control
  779. libata.dma=0 Disable all PATA and SATA DMA
  780. libata.dma=1 PATA and SATA Disk DMA only
  781. libata.dma=2 ATAPI (CDROM) DMA only
  782. libata.dma=4 Compact Flash DMA only
  783. Combinations also work, so libata.dma=3 enables DMA
  784. for disks and CDROMs, but not CFs.
  785. libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
  786. when set.
  787. Format: <int>
  788. libata.force= [LIBATA] Force configurations. The format is comma
  789. separated list of "[ID:]VAL" where ID is
  790. PORT[:DEVICE]. PORT and DEVICE are decimal numbers
  791. matching port, link or device. Basically, it matches
  792. the ATA ID string printed on console by libata. If
  793. the whole ID part is omitted, the last PORT and DEVICE
  794. values are used. If ID hasn't been specified yet, the
  795. configuration applies to all ports, links and devices.
  796. If only DEVICE is omitted, the parameter applies to
  797. the port and all links and devices behind it. DEVICE
  798. number of 0 either selects the first device or the
  799. first fan-out link behind PMP device. It does not
  800. select the host link. DEVICE number of 15 selects the
  801. host link and device attached to it.
  802. The VAL specifies the configuration to force. As long
  803. as there's no ambiguity shortcut notation is allowed.
  804. For example, both 1.5 and 1.5G would work for 1.5Gbps.
  805. The following configurations can be forced.
  806. * Cable type: 40c, 80c, short40c, unk, ign or sata.
  807. Any ID with matching PORT is used.
  808. * SATA link speed limit: 1.5Gbps or 3.0Gbps.
  809. * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
  810. udma[/][16,25,33,44,66,100,133] notation is also
  811. allowed.
  812. * [no]ncq: Turn on or off NCQ.
  813. If there are multiple matching configurations changing
  814. the same attribute, the last one is used.
  815. load_ramdisk= [RAM] List of ramdisks to load from floppy
  816. See Documentation/ramdisk.txt.
  817. lockd.nlm_grace_period=P [NFS] Assign grace period.
  818. Format: <integer>
  819. lockd.nlm_tcpport=N [NFS] Assign TCP port.
  820. Format: <integer>
  821. lockd.nlm_timeout=T [NFS] Assign timeout value.
  822. Format: <integer>
  823. lockd.nlm_udpport=M [NFS] Assign UDP port.
  824. Format: <integer>
  825. logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
  826. Format: <irq>
  827. loglevel= All Kernel Messages with a loglevel smaller than the
  828. console loglevel will be printed to the console. It can
  829. also be changed with klogd or other programs. The
  830. loglevels are defined as follows:
  831. 0 (KERN_EMERG) system is unusable
  832. 1 (KERN_ALERT) action must be taken immediately
  833. 2 (KERN_CRIT) critical conditions
  834. 3 (KERN_ERR) error conditions
  835. 4 (KERN_WARNING) warning conditions
  836. 5 (KERN_NOTICE) normal but significant condition
  837. 6 (KERN_INFO) informational
  838. 7 (KERN_DEBUG) debug-level messages
  839. log_buf_len=n Sets the size of the printk ring buffer, in bytes.
  840. Format: { n | nk | nM }
  841. n must be a power of two. The default size
  842. is set in the kernel config file.
  843. logo.nologo [FB] Disables display of the built-in Linux logo.
  844. This may be used to provide more screen space for
  845. kernel log messages and is useful when debugging
  846. kernel boot problems.
  847. lp=0 [LP] Specify parallel ports to use, e.g,
  848. lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
  849. lp=reset first parallel port). 'lp=0' disables the
  850. lp=auto printer driver. 'lp=reset' (which can be
  851. specified in addition to the ports) causes
  852. attached printers to be reset. Using
  853. lp=port1,port2,... specifies the parallel ports
  854. to associate lp devices with, starting with
  855. lp0. A port specification may be 'none' to skip
  856. that lp device, or a parport name such as
  857. 'parport0'. Specifying 'lp=auto' instead of a
  858. port specification list means that device IDs
  859. from each port should be examined, to see if
  860. an IEEE 1284-compliant printer is attached; if
  861. so, the driver will manage that printer.
  862. See also header of drivers/char/lp.c.
  863. lpj=n [KNL]
  864. Sets loops_per_jiffy to given constant, thus avoiding
  865. time-consuming boot-time autodetection (up to 250 ms per
  866. CPU). 0 enables autodetection (default). To determine
  867. the correct value for your kernel, boot with normal
  868. autodetection and see what value is printed. Note that
  869. on SMP systems the preset will be applied to all CPUs,
  870. which is likely to cause problems if your CPUs need
  871. significantly divergent settings. An incorrect value
  872. will cause delays in the kernel to be wrong, leading to
  873. unpredictable I/O errors and other breakage. Although
  874. unlikely, in the extreme case this might damage your
  875. hardware.
  876. ltpc= [NET]
  877. Format: <io>,<irq>,<dma>
  878. mac5380= [HW,SCSI] Format:
  879. <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
  880. machvec= [IA64] Force the use of a particular machine-vector
  881. (machvec) in a generic kernel.
  882. Example: machvec=hpzx1_swiotlb
  883. max_loop= [LOOP] Maximum number of loopback devices that can
  884. be mounted
  885. Format: <1-256>
  886. maxcpus= [SMP] Maximum number of processors that an SMP kernel
  887. should make use of. maxcpus=n : n >= 0 limits the
  888. kernel to using 'n' processors. n=0 is a special case,
  889. it is equivalent to "nosmp", which also disables
  890. the IO APIC.
  891. max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
  892. equal to this physical address is ignored.
  893. max_luns= [SCSI] Maximum number of LUNs to probe.
  894. Should be between 1 and 2^32-1.
  895. max_report_luns=
  896. [SCSI] Maximum number of LUNs received.
  897. Should be between 1 and 16384.
  898. mcatest= [IA-64]
  899. mce [X86-32] Machine Check Exception
  900. mce=option [X86-64] See Documentation/x86_64/boot-options.txt
  901. md= [HW] RAID subsystems devices and level
  902. See Documentation/md.txt.
  903. mdacon= [MDA]
  904. Format: <first>,<last>
  905. Specifies range of consoles to be captured by the MDA.
  906. mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
  907. Amount of memory to be used when the kernel is not able
  908. to see the whole system memory or for test.
  909. [X86-32] Use together with memmap= to avoid physical
  910. address space collisions. Without memmap= PCI devices
  911. could be placed at addresses belonging to unused RAM.
  912. mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
  913. memory.
  914. memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
  915. E820 memory map, as specified by the user.
  916. Such memmap=exactmap lines can be constructed based on
  917. BIOS output or other requirements. See the memmap=nn@ss
  918. option description.
  919. memmap=nn[KMG]@ss[KMG]
  920. [KNL] Force usage of a specific region of memory
  921. Region of memory to be used, from ss to ss+nn.
  922. memmap=nn[KMG]#ss[KMG]
  923. [KNL,ACPI] Mark specific memory as ACPI data.
  924. Region of memory to be used, from ss to ss+nn.
  925. memmap=nn[KMG]$ss[KMG]
  926. [KNL,ACPI] Mark specific memory as reserved.
  927. Region of memory to be used, from ss to ss+nn.
  928. Example: Exclude memory from 0x18690000-0x1869ffff
  929. memmap=64K$0x18690000
  930. or
  931. memmap=0x10000$0x18690000
  932. memtest= [KNL,X86_64] Enable memtest
  933. Format: <integer>
  934. range: 0,4 : pattern number
  935. default : 0 <disable>
  936. meye.*= [HW] Set MotionEye Camera parameters
  937. See Documentation/video4linux/meye.txt.
  938. mfgpt_irq= [IA-32] Specify the IRQ to use for the
  939. Multi-Function General Purpose Timers on AMD Geode
  940. platforms.
  941. mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
  942. the BIOS has incorrectly applied a workaround. TinyBIOS
  943. version 0.98 is known to be affected, 0.99 fixes the
  944. problem by letting the user disable the workaround.
  945. mga= [HW,DRM]
  946. mousedev.tap_time=
  947. [MOUSE] Maximum time between finger touching and
  948. leaving touchpad surface for touch to be considered
  949. a tap and be reported as a left button click (for
  950. touchpads working in absolute mode only).
  951. Format: <msecs>
  952. mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
  953. reporting absolute coordinates, such as tablets
  954. mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
  955. reporting absolute coordinates, such as tablets
  956. mpu401= [HW,OSS]
  957. Format: <io>,<irq>
  958. MTD_Partition= [MTD]
  959. Format: <name>,<region-number>,<size>,<offset>
  960. MTD_Region= [MTD] Format:
  961. <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
  962. mtdparts= [MTD]
  963. See drivers/mtd/cmdlinepart.c.
  964. mtouchusb.raw_coordinates=
  965. [HW] Make the MicroTouch USB driver use raw coordinates
  966. ('y', default) or cooked coordinates ('n')
  967. n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
  968. NCR_D700= [HW,SCSI]
  969. See header of drivers/scsi/NCR_D700.c.
  970. ncr5380= [HW,SCSI]
  971. ncr53c400= [HW,SCSI]
  972. ncr53c400a= [HW,SCSI]
  973. ncr53c406a= [HW,SCSI]
  974. ncr53c8xx= [HW,SCSI]
  975. netdev= [NET] Network devices parameters
  976. Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
  977. Note that mem_start is often overloaded to mean
  978. something different and driver-specific.
  979. This usage is only documented in each driver source
  980. file if at all.
  981. nfsaddrs= [NFS]
  982. See Documentation/filesystems/nfsroot.txt.
  983. nfsroot= [NFS] nfs root filesystem for disk-less boxes.
  984. See Documentation/filesystems/nfsroot.txt.
  985. nfs.callback_tcpport=
  986. [NFS] set the TCP port on which the NFSv4 callback
  987. channel should listen.
  988. nfs.idmap_cache_timeout=
  989. [NFS] set the maximum lifetime for idmapper cache
  990. entries.
  991. nfs.enable_ino64=
  992. [NFS] enable 64-bit inode numbers.
  993. If zero, the NFS client will fake up a 32-bit inode
  994. number for the readdir() and stat() syscalls instead
  995. of returning the full 64-bit number.
  996. The default is to return 64-bit inode numbers.
  997. nmi_debug= [KNL,AVR32] Specify one or more actions to take
  998. when a NMI is triggered.
  999. Format: [state][,regs][,debounce][,die]
  1000. nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
  1001. no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
  1002. emulation library even if a 387 maths coprocessor
  1003. is present.
  1004. noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
  1005. caches in the slab allocator. Saves per-node memory,
  1006. but will impact performance.
  1007. noalign [KNL,ARM]
  1008. noapic [SMP,APIC] Tells the kernel to not make use of any
  1009. IOAPICs that may be present in the system.
  1010. nobats [PPC] Do not use BATs for mapping kernel lowmem
  1011. on "Classic" PPC cores.
  1012. nocache [ARM]
  1013. nodelayacct [KNL] Disable per-task delay accounting
  1014. nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
  1015. noefi [X86-32,X86-64] Disable EFI runtime services support.
  1016. noexec [IA-64]
  1017. noexec [X86-32,X86-64]
  1018. On X86-32 available only on PAE configured kernels.
  1019. noexec=on: enable non-executable mappings (default)
  1020. noexec=off: disable non-executable mappings
  1021. noexec32 [X86-64]
  1022. This affects only 32-bit executables.
  1023. noexec32=on: enable non-executable mappings (default)
  1024. read doesn't imply executable mappings
  1025. noexec32=off: disable non-executable mappings
  1026. read implies executable mappings
  1027. nofxsr [BUGS=X86-32] Disables x86 floating point extended
  1028. register save and restore. The kernel will only save
  1029. legacy floating-point registers on task switch.
  1030. noclflush [BUGS=X86] Don't use the CLFLUSH instruction
  1031. nohlt [BUGS=ARM]
  1032. no-hlt [BUGS=X86-32] Tells the kernel that the hlt
  1033. instruction doesn't work correctly and not to
  1034. use it.
  1035. nohalt [IA-64] Tells the kernel not to use the power saving
  1036. function PAL_HALT_LIGHT when idle. This increases
  1037. power-consumption. On the positive side, it reduces
  1038. interrupt wake-up latency, which may improve performance
  1039. in certain environments such as networked servers or
  1040. real-time systems.
  1041. nohz= [KNL] Boottime enable/disable dynamic ticks
  1042. Valid arguments: on, off
  1043. Default: on
  1044. noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
  1045. noirqdebug [X86-32] Disables the code which attempts to detect and
  1046. disable unhandled interrupt sources.
  1047. no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
  1048. broken timer IRQ sources.
  1049. noisapnp [ISAPNP] Disables ISA PnP code.
  1050. noinitrd [RAM] Tells the kernel not to load any configured
  1051. initial RAM disk.
  1052. nointroute [IA-64]
  1053. nojitter [IA64] Disables jitter checking for ITC timers.
  1054. nolapic [X86-32,APIC] Do not enable or use the local APIC.
  1055. nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
  1056. noltlbs [PPC] Do not use large page/tlb entries for kernel
  1057. lowmem mapping on PPC40x.
  1058. nomca [IA-64] Disable machine check abort handling
  1059. nomce [X86-32] Machine Check Exception
  1060. nomfgpt [X86-32] Disable Multi-Function General Purpose
  1061. Timer usage (for AMD Geode machines).
  1062. noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
  1063. noreplace-smp [X86-32,SMP] Don't replace SMP instructions
  1064. with UP alternatives
  1065. noresidual [PPC] Don't use residual data on PReP machines.
  1066. noresume [SWSUSP] Disables resume and restores original swap
  1067. space.
  1068. no-scroll [VGA] Disables scrollback.
  1069. This is required for the Braillex ib80-piezo Braille
  1070. reader made by F.H. Papenmeier (Germany).
  1071. nosbagart [IA-64]
  1072. nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
  1073. nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
  1074. and disable the IO APIC. legacy for "maxcpus=0".
  1075. nosoftlockup [KNL] Disable the soft-lockup detector.
  1076. nosync [HW,M68K] Disables sync negotiation for all devices.
  1077. notsc [BUGS=X86-32] Disable Time Stamp Counter
  1078. nousb [USB] Disable the USB subsystem
  1079. nowb [ARM]
  1080. nptcg= [IA64] Override max number of concurrent global TLB
  1081. purges which is reported from either PAL_VM_SUMMARY or
  1082. SAL PALO.
  1083. numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
  1084. one of ['zone', 'node', 'default'] can be specified
  1085. This can be set from sysctl after boot.
  1086. See Documentation/sysctl/vm.txt for details.
  1087. nr_uarts= [SERIAL] maximum number of UARTs to be registered.
  1088. olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
  1089. Rather than timing out after 20 ms if an EC
  1090. command is not properly ACKed, override the length
  1091. of the timeout. We have interrupts disabled while
  1092. waiting for the ACK, so if this is set too high
  1093. interrupts *may* be lost!
  1094. opl3= [HW,OSS]
  1095. Format: <io>
  1096. oprofile.timer= [HW]
  1097. Use timer interrupt instead of performance counters
  1098. osst= [HW,SCSI] SCSI Tape Driver
  1099. Format: <buffer_size>,<write_threshold>
  1100. See also Documentation/scsi/st.txt.
  1101. panic= [KNL] Kernel behaviour on panic
  1102. Format: <timeout>
  1103. parkbd.port= [HW] Parallel port number the keyboard adapter is
  1104. connected to, default is 0.
  1105. Format: <parport#>
  1106. parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
  1107. 0 for XT, 1 for AT (default is AT).
  1108. Format: <mode>
  1109. parport= [HW,PPT] Specify parallel ports. 0 disables.
  1110. Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
  1111. Use 'auto' to force the driver to use any
  1112. IRQ/DMA settings detected (the default is to
  1113. ignore detected IRQ/DMA settings because of
  1114. possible conflicts). You can specify the base
  1115. address, IRQ, and DMA settings; IRQ and DMA
  1116. should be numbers, or 'auto' (for using detected
  1117. settings on that particular port), or 'nofifo'
  1118. (to avoid using a FIFO even if it is detected).
  1119. Parallel ports are assigned in the order they
  1120. are specified on the command line, starting
  1121. with parport0.
  1122. parport_init_mode= [HW,PPT]
  1123. Configure VIA parallel port to operate in
  1124. a specific mode. This is necessary on Pegasos
  1125. computer where firmware has no options for setting
  1126. up parallel port mode and sets it to spp.
  1127. Currently this function knows 686a and 8231 chips.
  1128. Format: [spp|ps2|epp|ecp|ecpepp]
  1129. pas2= [HW,OSS] Format:
  1130. <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
  1131. pas16= [HW,SCSI]
  1132. See header of drivers/scsi/pas16.c.
  1133. pause_on_oops=
  1134. Halt all CPUs after the first oops has been printed for
  1135. the specified number of seconds. This is to be used if
  1136. your oopses keep scrolling off the screen.
  1137. pcbit= [HW,ISDN]
  1138. pcd. [PARIDE]
  1139. See header of drivers/block/paride/pcd.c.
  1140. See also Documentation/paride.txt.
  1141. pci=option[,option...] [PCI] various PCI subsystem options:
  1142. off [X86-32] don't probe for the PCI bus
  1143. bios [X86-32] force use of PCI BIOS, don't access
  1144. the hardware directly. Use this if your machine
  1145. has a non-standard PCI host bridge.
  1146. nobios [X86-32] disallow use of PCI BIOS, only direct
  1147. hardware access methods are allowed. Use this
  1148. if you experience crashes upon bootup and you
  1149. suspect they are caused by the BIOS.
  1150. conf1 [X86-32] Force use of PCI Configuration
  1151. Mechanism 1.
  1152. conf2 [X86-32] Force use of PCI Configuration
  1153. Mechanism 2.
  1154. noaer [PCIE] If the PCIEAER kernel config parameter is
  1155. enabled, this kernel boot option can be used to
  1156. disable the use of PCIE advanced error reporting.
  1157. nodomains [PCI] Disable support for multiple PCI
  1158. root domains (aka PCI segments, in ACPI-speak).
  1159. nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
  1160. Configuration
  1161. nomsi [MSI] If the PCI_MSI kernel config parameter is
  1162. enabled, this kernel boot option can be used to
  1163. disable the use of MSI interrupts system-wide.
  1164. biosirq [X86-32] Use PCI BIOS calls to get the interrupt
  1165. routing table. These calls are known to be buggy
  1166. on several machines and they hang the machine
  1167. when used, but on other computers it's the only
  1168. way to get the interrupt routing table. Try
  1169. this option if the kernel is unable to allocate
  1170. IRQs or discover secondary PCI buses on your
  1171. motherboard.
  1172. rom [X86-32] Assign address space to expansion ROMs.
  1173. Use with caution as certain devices share
  1174. address decoders between ROMs and other
  1175. resources.
  1176. irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
  1177. assigned automatically to PCI devices. You can
  1178. make the kernel exclude IRQs of your ISA cards
  1179. this way.
  1180. pirqaddr=0xAAAAA [X86-32] Specify the physical address
  1181. of the PIRQ table (normally generated
  1182. by the BIOS) if it is outside the
  1183. F0000h-100000h range.
  1184. lastbus=N [X86-32] Scan all buses thru bus #N. Can be
  1185. useful if the kernel is unable to find your
  1186. secondary buses and you want to tell it
  1187. explicitly which ones they are.
  1188. assign-busses [X86-32] Always assign all PCI bus
  1189. numbers ourselves, overriding
  1190. whatever the firmware may have done.
  1191. usepirqmask [X86-32] Honor the possible IRQ mask stored
  1192. in the BIOS $PIR table. This is needed on
  1193. some systems with broken BIOSes, notably
  1194. some HP Pavilion N5400 and Omnibook XE3
  1195. notebooks. This will have no effect if ACPI
  1196. IRQ routing is enabled.
  1197. noacpi [X86-32] Do not use ACPI for IRQ routing
  1198. or for PCI scanning.
  1199. use_crs [X86-32] Use _CRS for PCI resource
  1200. allocation.
  1201. routeirq Do IRQ routing for all PCI devices.
  1202. This is normally done in pci_enable_device(),
  1203. so this option is a temporary workaround
  1204. for broken drivers that don't call it.
  1205. skip_isa_align [X86] do not align io start addr, so can
  1206. handle more pci cards
  1207. firmware [ARM] Do not re-enumerate the bus but instead
  1208. just use the configuration from the
  1209. bootloader. This is currently used on
  1210. IXP2000 systems where the bus has to be
  1211. configured a certain way for adjunct CPUs.
  1212. noearly [X86] Don't do any early type 1 scanning.
  1213. This might help on some broken boards which
  1214. machine check when some devices' config space
  1215. is read. But various workarounds are disabled
  1216. and some IOMMU drivers will not work.
  1217. bfsort Sort PCI devices into breadth-first order.
  1218. This sorting is done to get a device
  1219. order compatible with older (<= 2.4) kernels.
  1220. nobfsort Don't sort PCI devices into breadth-first order.
  1221. cbiosize=nn[KMG] The fixed amount of bus space which is
  1222. reserved for the CardBus bridge's IO window.
  1223. The default value is 256 bytes.
  1224. cbmemsize=nn[KMG] The fixed amount of bus space which is
  1225. reserved for the CardBus bridge's memory
  1226. window. The default value is 64 megabytes.
  1227. pcmv= [HW,PCMCIA] BadgePAD 4
  1228. pd. [PARIDE]
  1229. See Documentation/paride.txt.
  1230. pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
  1231. boot time.
  1232. Format: { 0 | 1 }
  1233. See arch/parisc/kernel/pdc_chassis.c
  1234. pf. [PARIDE]
  1235. See Documentation/paride.txt.
  1236. pg. [PARIDE]
  1237. See Documentation/paride.txt.
  1238. pirq= [SMP,APIC] Manual mp-table setup
  1239. See Documentation/i386/IO-APIC.txt.
  1240. plip= [PPT,NET] Parallel port network link
  1241. Format: { parport<nr> | timid | 0 }
  1242. See also Documentation/parport.txt.
  1243. pnpacpi= [ACPI]
  1244. { off }
  1245. pnpbios= [ISAPNP]
  1246. { on | off | curr | res | no-curr | no-res }
  1247. pnp_reserve_irq=
  1248. [ISAPNP] Exclude IRQs for the autoconfiguration
  1249. pnp_reserve_dma=
  1250. [ISAPNP] Exclude DMAs for the autoconfiguration
  1251. pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
  1252. Ranges are in pairs (I/O port base and size).
  1253. pnp_reserve_mem=
  1254. [ISAPNP] Exclude memory regions for the
  1255. autoconfiguration.
  1256. Ranges are in pairs (memory base and size).
  1257. print-fatal-signals=
  1258. [KNL] debug: print fatal signals
  1259. print-fatal-signals=1: print segfault info to
  1260. the kernel console.
  1261. default: off.
  1262. printk.time= Show timing data prefixed to each printk message line
  1263. Format: <bool> (1/Y/y=enable, 0/N/n=disable)
  1264. profile= [KNL] Enable kernel profiling via /proc/profile
  1265. Format: [schedule,]<number>
  1266. Param: "schedule" - profile schedule points.
  1267. Param: <number> - step/bucket size as a power of 2 for
  1268. statistical time based profiling.
  1269. Param: "sleep" - profile D-state sleeping (millisecs).
  1270. Requires CONFIG_SCHEDSTATS
  1271. Param: "kvm" - profile VM exits.
  1272. processor.max_cstate= [HW,ACPI]
  1273. Limit processor to maximum C-state
  1274. max_cstate=9 overrides any DMI blacklist limit.
  1275. processor.nocst [HW,ACPI]
  1276. Ignore the _CST method to determine C-states,
  1277. instead using the legacy FADT method
  1278. prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
  1279. before loading.
  1280. See Documentation/ramdisk.txt.
  1281. psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
  1282. probe for; one of (bare|imps|exps|lifebook|any).
  1283. psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
  1284. per second.
  1285. psmouse.resetafter= [HW,MOUSE]
  1286. Try to reset the device after so many bad packets
  1287. (0 = never).
  1288. psmouse.resolution=
  1289. [HW,MOUSE] Set desired mouse resolution, in dpi.
  1290. psmouse.smartscroll=
  1291. [HW,MOUSE] Controls Logitech smartscroll autorepeat.
  1292. 0 = disabled, 1 = enabled (default).
  1293. pss= [HW,OSS] Personal Sound System (ECHO ESC614)
  1294. Format:
  1295. <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
  1296. pt. [PARIDE]
  1297. See Documentation/paride.txt.
  1298. pty.legacy_count=
  1299. [KNL] Number of legacy pty's. Overwrites compiled-in
  1300. default number.
  1301. quiet [KNL] Disable most log messages
  1302. r128= [HW,DRM]
  1303. raid= [HW,RAID]
  1304. See Documentation/md.txt.
  1305. ramdisk_blocksize= [RAM]
  1306. See Documentation/ramdisk.txt.
  1307. ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
  1308. See Documentation/ramdisk.txt.
  1309. rcupdate.blimit= [KNL,BOOT]
  1310. Set maximum number of finished RCU callbacks to process
  1311. in one batch.
  1312. rcupdate.qhimark= [KNL,BOOT]
  1313. Set threshold of queued
  1314. RCU callbacks over which batch limiting is disabled.
  1315. rcupdate.qlowmark= [KNL,BOOT]
  1316. Set threshold of queued RCU callbacks below which
  1317. batch limiting is re-enabled.
  1318. rdinit= [KNL]
  1319. Format: <full_path>
  1320. Run specified binary instead of /init from the ramdisk,
  1321. used for early userspace startup. See initrd.
  1322. reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
  1323. Format: <reboot_mode>[,<reboot_mode2>[,...]]
  1324. See arch/*/kernel/reboot.c or arch/*/kernel/process.c
  1325. reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
  1326. reservetop= [X86-32]
  1327. Format: nn[KMG]
  1328. Reserves a hole at the top of the kernel virtual
  1329. address space.
  1330. reset_devices [KNL] Force drivers to reset the underlying device
  1331. during initialization.
  1332. resume= [SWSUSP]
  1333. Specify the partition device for software suspend
  1334. resume_offset= [SWSUSP]
  1335. Specify the offset from the beginning of the partition
  1336. given by "resume=" at which the swap header is located,
  1337. in <PAGE_SIZE> units (needed only for swap files).
  1338. See Documentation/power/swsusp-and-swap-files.txt
  1339. retain_initrd [RAM] Keep initrd memory after extraction
  1340. rhash_entries= [KNL,NET]
  1341. Set number of hash buckets for route cache
  1342. riscom8= [HW,SERIAL]
  1343. Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
  1344. ro [KNL] Mount root device read-only on boot
  1345. root= [KNL] Root filesystem
  1346. rootdelay= [KNL] Delay (in seconds) to pause before attempting to
  1347. mount the root filesystem
  1348. rootflags= [KNL] Set root filesystem mount option string
  1349. rootfstype= [KNL] Set root filesystem type
  1350. rootwait [KNL] Wait (indefinitely) for root device to show up.
  1351. Useful for devices that are detected asynchronously
  1352. (e.g. USB and MMC devices).
  1353. root_plug.vendor_id=
  1354. [ROOTPLUG] Override the default vendor ID
  1355. root_plug.product_id=
  1356. [ROOTPLUG] Override the default product ID
  1357. root_plug.debug=
  1358. [ROOTPLUG] Enable debugging output
  1359. rw [KNL] Mount root device read-write on boot
  1360. S [KNL] Run init in single mode
  1361. sa1100ir [NET]
  1362. See drivers/net/irda/sa1100_ir.c.
  1363. sbni= [NET] Granch SBNI12 leased line adapter
  1364. sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
  1365. Format: <io>[,<timeout>[,<isapnp>]]
  1366. scsi_debug_*= [SCSI]
  1367. See drivers/scsi/scsi_debug.c.
  1368. scsi_default_dev_flags=
  1369. [SCSI] SCSI default device flags
  1370. Format: <integer>
  1371. scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
  1372. Format: <vendor>:<model>:<flags>
  1373. (flags are integer value)
  1374. scsi_logging_level= [SCSI] a bit mask of logging levels
  1375. See drivers/scsi/scsi_logging.h for bits. Also
  1376. settable via sysctl at dev.scsi.logging_level
  1377. (/proc/sys/dev/scsi/logging_level).
  1378. There is also a nice 'scsi_logging_level' script in the
  1379. S390-tools package, available for download at
  1380. http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
  1381. scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
  1382. discovered. async scans them in kernel threads,
  1383. allowing boot to proceed. none ignores them, expecting
  1384. user space to do the scan.
  1385. selinux [SELINUX] Disable or enable SELinux at boot time.
  1386. Format: { "0" | "1" }
  1387. See security/selinux/Kconfig help text.
  1388. 0 -- disable.
  1389. 1 -- enable.
  1390. Default value is set via kernel config option.
  1391. If enabled at boot time, /selinux/disable can be used
  1392. later to disable prior to initial policy load.
  1393. selinux_compat_net =
  1394. [SELINUX] Set initial selinux_compat_net flag value.
  1395. Format: { "0" | "1" }
  1396. 0 -- use new secmark-based packet controls
  1397. 1 -- use legacy packet controls
  1398. Default value is 0 (preferred).
  1399. Value can be changed at runtime via
  1400. /selinux/compat_net.
  1401. serialnumber [BUGS=X86-32]
  1402. shapers= [NET]
  1403. Maximal number of shapers.
  1404. sim710= [SCSI,HW]
  1405. See header of drivers/scsi/sim710.c.
  1406. simeth= [IA-64]
  1407. simscsi=
  1408. slram= [HW,MTD]
  1409. slub_debug[=options[,slabs]] [MM, SLUB]
  1410. Enabling slub_debug allows one to determine the
  1411. culprit if slab objects become corrupted. Enabling
  1412. slub_debug can create guard zones around objects and
  1413. may poison objects when not in use. Also tracks the
  1414. last alloc / free. For more information see
  1415. Documentation/vm/slub.txt.
  1416. slub_max_order= [MM, SLUB]
  1417. Determines the maximum allowed order for slabs.
  1418. A high setting may cause OOMs due to memory
  1419. fragmentation. For more information see
  1420. Documentation/vm/slub.txt.
  1421. slub_min_objects= [MM, SLUB]
  1422. The minimum number of objects per slab. SLUB will
  1423. increase the slab order up to slub_max_order to
  1424. generate a sufficiently large slab able to contain
  1425. the number of objects indicated. The higher the number
  1426. of objects the smaller the overhead of tracking slabs
  1427. and the less frequently locks need to be acquired.
  1428. For more information see Documentation/vm/slub.txt.
  1429. slub_min_order= [MM, SLUB]
  1430. Determines the mininum page order for slabs. Must be
  1431. lower than slub_max_order.
  1432. For more information see Documentation/vm/slub.txt.
  1433. slub_nomerge [MM, SLUB]
  1434. Disable merging of slabs with similar size. May be
  1435. necessary if there is some reason to distinguish
  1436. allocs to different slabs. Debug options disable
  1437. merging on their own.
  1438. For more information see Documentation/vm/slub.txt.
  1439. smart2= [HW]
  1440. Format: <io1>[,<io2>[,...,<io8>]]
  1441. smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
  1442. attempt to substitute SMP alternatives once at boot.
  1443. smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
  1444. smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
  1445. smsc-ircc2.ircc_sir= [HW] SIR base I/O port
  1446. smsc-ircc2.ircc_fir= [HW] FIR base I/O port
  1447. smsc-ircc2.ircc_irq= [HW] IRQ line
  1448. smsc-ircc2.ircc_dma= [HW] DMA channel
  1449. smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
  1450. 0: Toshiba Satellite 1800 (GP data pin select)
  1451. 1: Fast pin select (default)
  1452. 2: ATC IRMode
  1453. snd-ad1816a= [HW,ALSA]
  1454. snd-ad1848= [HW,ALSA]
  1455. snd-ali5451= [HW,ALSA]
  1456. snd-als100= [HW,ALSA]
  1457. snd-als4000= [HW,ALSA]
  1458. snd-azt2320= [HW,ALSA]
  1459. snd-cmi8330= [HW,ALSA]
  1460. snd-cmipci= [HW,ALSA]
  1461. snd-cs4231= [HW,ALSA]
  1462. snd-cs4232= [HW,ALSA]
  1463. snd-cs4236= [HW,ALSA]
  1464. snd-cs4281= [HW,ALSA]
  1465. snd-cs46xx= [HW,ALSA]
  1466. snd-dt019x= [HW,ALSA]
  1467. snd-dummy= [HW,ALSA]
  1468. snd-emu10k1= [HW,ALSA]
  1469. snd-ens1370= [HW,ALSA]
  1470. snd-ens1371= [HW,ALSA]
  1471. snd-es968= [HW,ALSA]
  1472. snd-es1688= [HW,ALSA]
  1473. snd-es18xx= [HW,ALSA]
  1474. snd-es1938= [HW,ALSA]
  1475. snd-es1968= [HW,ALSA]
  1476. snd-fm801= [HW,ALSA]
  1477. snd-gusclassic= [HW,ALSA]
  1478. snd-gusextreme= [HW,ALSA]
  1479. snd-gusmax= [HW,ALSA]
  1480. snd-hdsp= [HW,ALSA]
  1481. snd-ice1712= [HW,ALSA]
  1482. snd-intel8x0= [HW,ALSA]
  1483. snd-interwave= [HW,ALSA]
  1484. snd-interwave-stb=
  1485. [HW,ALSA]
  1486. snd-korg1212= [HW,ALSA]
  1487. snd-maestro3= [HW,ALSA]
  1488. snd-mpu401= [HW,ALSA]
  1489. snd-mtpav= [HW,ALSA]
  1490. snd-nm256= [HW,ALSA]
  1491. snd-opl3sa2= [HW,ALSA]
  1492. snd-opti92x-ad1848=
  1493. [HW,ALSA]
  1494. snd-opti92x-cs4231=
  1495. [HW,ALSA]
  1496. snd-opti93x= [HW,ALSA]
  1497. snd-pmac= [HW,ALSA]
  1498. snd-rme32= [HW,ALSA]
  1499. snd-rme96= [HW,ALSA]
  1500. snd-rme9652= [HW,ALSA]
  1501. snd-sb8= [HW,ALSA]
  1502. snd-sb16= [HW,ALSA]
  1503. snd-sbawe= [HW,ALSA]
  1504. snd-serial= [HW,ALSA]
  1505. snd-sgalaxy= [HW,ALSA]
  1506. snd-sonicvibes= [HW,ALSA]
  1507. snd-sun-amd7930=
  1508. [HW,ALSA]
  1509. snd-sun-cs4231= [HW,ALSA]
  1510. snd-trident= [HW,ALSA]
  1511. snd-usb-audio= [HW,ALSA,USB]
  1512. snd-via82xx= [HW,ALSA]
  1513. snd-virmidi= [HW,ALSA]
  1514. snd-wavefront= [HW,ALSA]
  1515. snd-ymfpci= [HW,ALSA]
  1516. sonypi.*= [HW] Sony Programmable I/O Control Device driver
  1517. See Documentation/sonypi.txt
  1518. specialix= [HW,SERIAL] Specialix multi-serial port adapter
  1519. See Documentation/specialix.txt.
  1520. spia_io_base= [HW,MTD]
  1521. spia_fio_base=
  1522. spia_pedr=
  1523. spia_peddr=
  1524. sscape= [HW,OSS]
  1525. Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
  1526. st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
  1527. See Documentation/scsi/st.txt.
  1528. sti= [PARISC,HW]
  1529. Format: <num>
  1530. Set the STI (builtin display/keyboard on the HP-PARISC
  1531. machines) console (graphic card) which should be used
  1532. as the initial boot-console.
  1533. See also comment in drivers/video/console/sticore.c.
  1534. sti_font= [HW]
  1535. See comment in drivers/video/console/sticore.c.
  1536. stifb= [HW]
  1537. Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
  1538. sunrpc.pool_mode=
  1539. [NFS]
  1540. Control how the NFS server code allocates CPUs to
  1541. service thread pools. Depending on how many NICs
  1542. you have and where their interrupts are bound, this
  1543. option will affect which CPUs will do NFS serving.
  1544. Note: this parameter cannot be changed while the
  1545. NFS server is running.
  1546. auto the server chooses an appropriate mode
  1547. automatically using heuristics
  1548. global a single global pool contains all CPUs
  1549. percpu one pool for each CPU
  1550. pernode one pool for each NUMA node (equivalent
  1551. to global on non-NUMA machines)
  1552. swiotlb= [IA-64] Number of I/O TLB slabs
  1553. switches= [HW,M68k]
  1554. sym53c416= [HW,SCSI]
  1555. See header of drivers/scsi/sym53c416.c.
  1556. sysrq_always_enabled
  1557. [KNL]
  1558. Ignore sysrq setting - this boot parameter will
  1559. neutralize any effect of /proc/sys/kernel/sysrq.
  1560. Useful for debugging.
  1561. t128= [HW,SCSI]
  1562. See header of drivers/scsi/t128.c.
  1563. tdfx= [HW,DRM]
  1564. thash_entries= [KNL,NET]
  1565. Set number of hash buckets for TCP connection
  1566. thermal.act= [HW,ACPI]
  1567. -1: disable all active trip points in all thermal zones
  1568. <degrees C>: override all lowest active trip points
  1569. thermal.crt= [HW,ACPI]
  1570. -1: disable all critical trip points in all thermal zones
  1571. <degrees C>: lower all critical trip points
  1572. thermal.nocrt= [HW,ACPI]
  1573. Set to disable actions on ACPI thermal zone
  1574. critical and hot trip points.
  1575. thermal.off= [HW,ACPI]
  1576. 1: disable ACPI thermal control
  1577. thermal.psv= [HW,ACPI]
  1578. -1: disable all passive trip points
  1579. <degrees C>: override all passive trip points to this value
  1580. thermal.tzp= [HW,ACPI]
  1581. Specify global default ACPI thermal zone polling rate
  1582. <deci-seconds>: poll all this frequency
  1583. 0: no polling (default)
  1584. tipar.timeout= [HW,PPT]
  1585. Set communications timeout in tenths of a second
  1586. (default 15).
  1587. tipar.delay= [HW,PPT]
  1588. Set inter-bit delay in microseconds (default 10).
  1589. tmscsim= [HW,SCSI]
  1590. See comment before function dc390_setup() in
  1591. drivers/scsi/tmscsim.c.
  1592. tp720= [HW,PS2]
  1593. trix= [HW,OSS] MediaTrix AudioTrix Pro
  1594. Format:
  1595. <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
  1596. turbografx.map[2|3]= [HW,JOY]
  1597. TurboGraFX parallel port interface
  1598. Format:
  1599. <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
  1600. See also Documentation/input/joystick-parport.txt
  1601. u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
  1602. See header of drivers/scsi/u14-34f.c.
  1603. uart401= [HW,OSS]
  1604. Format: <io>,<irq>
  1605. uart6850= [HW,OSS]
  1606. Format: <io>,<irq>
  1607. uhci-hcd.ignore_oc=
  1608. [USB] Ignore overcurrent events (default N).
  1609. Some badly-designed motherboards generate lots of
  1610. bogus events, for ports that aren't wired to
  1611. anything. Set this parameter to avoid log spamming.
  1612. Note that genuine overcurrent events won't be
  1613. reported either.
  1614. usbcore.autosuspend=
  1615. [USB] The autosuspend time delay (in seconds) used
  1616. for newly-detected USB devices (default 2). This
  1617. is the time required before an idle device will be
  1618. autosuspended. Devices for which the delay is set
  1619. to a negative value won't be autosuspended at all.
  1620. usbhid.mousepoll=
  1621. [USBHID] The interval which mice are to be polled at.
  1622. vdso= [X86-32,SH,x86-64]
  1623. vdso=2: enable compat VDSO (default with COMPAT_VDSO)
  1624. vdso=1: enable VDSO (default)
  1625. vdso=0: disable VDSO mapping
  1626. vdso32= [X86-32,X86-64]
  1627. vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
  1628. vdso32=1: enable 32-bit VDSO (default)
  1629. vdso32=0: disable 32-bit VDSO mapping
  1630. vector= [IA-64,SMP]
  1631. vector=percpu: enable percpu vector domain
  1632. video= [FB] Frame buffer configuration
  1633. See Documentation/fb/modedb.txt.
  1634. vga= [BOOT,X86-32] Select a particular video mode
  1635. See Documentation/i386/boot.txt and
  1636. Documentation/svga.txt.
  1637. Use vga=ask for menu.
  1638. This is actually a boot loader parameter; the value is
  1639. passed to the kernel using a special protocol.
  1640. vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
  1641. size of <nn>. This can be used to increase the
  1642. minimum size (128MB on x86). It can also be used to
  1643. decrease the size and leave more room for directly
  1644. mapped kernel RAM.
  1645. vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
  1646. Format: <command>
  1647. vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
  1648. Format: <command>
  1649. vmpoff= [KNL,S390] Perform z/VM CP command after power off.
  1650. Format: <command>
  1651. waveartist= [HW,OSS]
  1652. Format: <io>,<irq>,<dma>,<dma2>
  1653. wd33c93= [HW,SCSI]
  1654. See header of drivers/scsi/wd33c93.c.
  1655. wd7000= [HW,SCSI]
  1656. See header of drivers/scsi/wd7000.c.
  1657. wdt= [WDT] Watchdog
  1658. See Documentation/watchdog/wdt.txt.
  1659. xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
  1660. xd_geo= See header of drivers/block/xd.c.
  1661. xirc2ps_cs= [NET,PCMCIA]
  1662. Format:
  1663. <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
  1664. norandmaps Don't use address space randomization
  1665. Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
  1666. ______________________________________________________________________
  1667. TODO:
  1668. Add documentation for ALSA options.
  1669. Add more DRM drivers.