kernel-parameters.txt 93 KB

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306307308309310311312313314315316317318319320321322323324325326327328329330331332333334335336337338339340341342343344345346347348349350351352353354355356357358359360361362363364365366367368369370371372373374375376377378379380381382383384385386387388389390391392393394395396397398399400401402403404405406407408409410411412413414415416417418419420421422423424425426427428429430431432433434435436437438439440441442443444445446447448449450451452453454455456457458459460461462463464465466467468469470471472473474475476477478479480481482483484485486487488489490491492493494495496497498499500501502503504505506507508509510511512513514515516517518519520521522523524525526527528529530531532533534535536537538539540541542543544545546547548549550551552553554555556557558559560561562563564565566567568569570571572573574575576577578579580581582583584585586587588589590591592593594595596597598599600601602603604605606607608609610611612613614615616617618619620621622623624625626627628629630631632633634635636637638639640641642643644645646647648649650651652653654655656657658659660661662663664665666667668669670671672673674675676677678679680681682683684685686687688689690691692693694695696697698699700701702703704705706707708709710711712713714715716717718719720721722723724725726727728729730731732733734735736737738739740741742743744745746747748749750751752753754755756757758759760761762763764765766767768769770771772773774775776777778779780781782783784785786787788789790791792793794795796797798799800801802803804805806807808809810811812813814815816817818819820821822823824825826827828829830831832833834835836837838839840841842843844845846847848849850851852853854855856857858859860861862863864865866867868869870871872873874875876877878879880881882883884885886887888889890891892893894895896897898899900901902903904905906907908909910911912913914915916917918919920921922923924925926927928929930931932933934935936937938939940941942943944945946947948949950951952953954955956957958959960961962963964965966967968969970971972973974975976977978979980981982983984985986987988989990991992993994995996997998999100010011002100310041005100610071008100910101011101210131014101510161017101810191020102110221023102410251026102710281029103010311032103310341035103610371038103910401041104210431044104510461047104810491050105110521053105410551056105710581059106010611062106310641065106610671068106910701071107210731074107510761077107810791080108110821083108410851086108710881089109010911092109310941095109610971098109911001101110211031104110511061107110811091110111111121113111411151116111711181119112011211122112311241125112611271128112911301131113211331134113511361137113811391140114111421143114411451146114711481149115011511152115311541155115611571158115911601161116211631164116511661167116811691170117111721173117411751176117711781179118011811182118311841185118611871188118911901191119211931194119511961197119811991200120112021203120412051206120712081209121012111212121312141215121612171218121912201221122212231224122512261227122812291230123112321233123412351236123712381239124012411242124312441245124612471248124912501251125212531254125512561257125812591260126112621263126412651266126712681269127012711272127312741275127612771278127912801281128212831284128512861287128812891290129112921293129412951296129712981299130013011302130313041305130613071308130913101311131213131314131513161317131813191320132113221323132413251326132713281329133013311332133313341335133613371338133913401341134213431344134513461347134813491350135113521353135413551356135713581359136013611362136313641365136613671368136913701371137213731374137513761377137813791380138113821383138413851386138713881389139013911392139313941395139613971398139914001401140214031404140514061407140814091410141114121413141414151416141714181419142014211422142314241425142614271428142914301431143214331434143514361437143814391440144114421443144414451446144714481449145014511452145314541455145614571458145914601461146214631464146514661467146814691470147114721473147414751476147714781479148014811482148314841485148614871488148914901491149214931494149514961497149814991500150115021503150415051506150715081509151015111512151315141515151615171518151915201521152215231524152515261527152815291530153115321533153415351536153715381539154015411542154315441545154615471548154915501551155215531554155515561557155815591560156115621563156415651566156715681569157015711572157315741575157615771578157915801581158215831584158515861587158815891590159115921593159415951596159715981599160016011602160316041605160616071608160916101611161216131614161516161617161816191620162116221623162416251626162716281629163016311632163316341635163616371638163916401641164216431644164516461647164816491650165116521653165416551656165716581659166016611662166316641665166616671668166916701671167216731674167516761677167816791680168116821683168416851686168716881689169016911692169316941695169616971698169917001701170217031704170517061707170817091710171117121713171417151716171717181719172017211722172317241725172617271728172917301731173217331734173517361737173817391740174117421743174417451746174717481749175017511752175317541755175617571758175917601761176217631764176517661767176817691770177117721773177417751776177717781779178017811782178317841785178617871788178917901791179217931794179517961797179817991800180118021803180418051806180718081809181018111812181318141815181618171818181918201821182218231824182518261827182818291830183118321833183418351836183718381839184018411842184318441845184618471848184918501851185218531854185518561857185818591860186118621863186418651866186718681869187018711872187318741875187618771878187918801881188218831884188518861887188818891890189118921893189418951896189718981899190019011902190319041905190619071908190919101911191219131914191519161917191819191920192119221923192419251926192719281929193019311932193319341935193619371938193919401941194219431944194519461947194819491950195119521953195419551956195719581959196019611962196319641965196619671968196919701971197219731974197519761977197819791980198119821983198419851986198719881989199019911992199319941995199619971998199920002001200220032004200520062007200820092010201120122013201420152016201720182019202020212022202320242025202620272028202920302031203220332034203520362037203820392040204120422043204420452046204720482049205020512052205320542055205620572058205920602061206220632064206520662067206820692070207120722073207420752076207720782079208020812082208320842085208620872088208920902091209220932094209520962097209820992100210121022103210421052106210721082109211021112112211321142115211621172118211921202121212221232124212521262127212821292130213121322133213421352136213721382139214021412142214321442145214621472148214921502151215221532154215521562157215821592160216121622163216421652166216721682169217021712172217321742175217621772178217921802181218221832184218521862187218821892190219121922193219421952196219721982199220022012202220322042205220622072208220922102211221222132214221522162217221822192220222122222223222422252226222722282229223022312232223322342235223622372238223922402241224222432244224522462247224822492250225122522253225422552256225722582259226022612262226322642265226622672268226922702271227222732274227522762277227822792280228122822283228422852286228722882289229022912292229322942295229622972298229923002301230223032304230523062307230823092310231123122313231423152316231723182319232023212322232323242325232623272328232923302331233223332334233523362337233823392340234123422343234423452346234723482349235023512352235323542355235623572358235923602361236223632364236523662367236823692370237123722373237423752376237723782379238023812382238323842385238623872388238923902391239223932394239523962397239823992400240124022403240424052406240724082409241024112412241324142415241624172418241924202421242224232424242524262427242824292430243124322433243424352436243724382439244024412442244324442445244624472448244924502451245224532454245524562457245824592460246124622463246424652466246724682469247024712472247324742475247624772478247924802481248224832484248524862487248824892490249124922493249424952496249724982499250025012502250325042505250625072508250925102511251225132514251525162517251825192520252125222523252425252526252725282529253025312532253325342535253625372538253925402541254225432544254525462547254825492550255125522553255425552556255725582559256025612562256325642565256625672568256925702571257225732574257525762577257825792580258125822583258425852586258725882589259025912592259325942595259625972598259926002601260226032604260526062607260826092610261126122613261426152616261726182619262026212622262326242625262626272628262926302631263226332634263526362637263826392640264126422643264426452646264726482649265026512652265326542655265626572658265926602661266226632664266526662667266826692670267126722673267426752676267726782679268026812682268326842685268626872688268926902691269226932694269526962697269826992700270127022703270427052706270727082709271027112712271327142715271627172718271927202721272227232724272527262727272827292730273127322733273427352736273727382739274027412742274327442745274627472748274927502751275227532754275527562757275827592760276127622763276427652766
  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. Hyphens (dashes) and underscores are equivalent in parameter names, so
  15. log_buf_len=1M print-fatal-signals=1
  16. can also be entered as
  17. log-buf-len=1M print_fatal_signals=1
  18. This document may not be entirely up to date and comprehensive. The command
  19. "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
  20. module. Loadable modules, after being loaded into the running kernel, also
  21. reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
  22. parameters may be changed at runtime by the command
  23. "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
  24. The parameters listed below are only valid if certain kernel build options were
  25. enabled and if respective hardware is present. The text in square brackets at
  26. the beginning of each description states the restrictions within which a
  27. parameter is applicable:
  28. ACPI ACPI support is enabled.
  29. AGP AGP (Accelerated Graphics Port) is enabled.
  30. ALSA ALSA sound support is enabled.
  31. APIC APIC support is enabled.
  32. APM Advanced Power Management support is enabled.
  33. AVR32 AVR32 architecture is enabled.
  34. AX25 Appropriate AX.25 support is enabled.
  35. BLACKFIN Blackfin architecture is enabled.
  36. DRM Direct Rendering Management support is enabled.
  37. DYNAMIC_DEBUG Build in debug messages and enable them at runtime
  38. EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
  39. EFI EFI Partitioning (GPT) is enabled
  40. EIDE EIDE/ATAPI support is enabled.
  41. EVM Extended Verification Module
  42. FB The frame buffer device is enabled.
  43. GCOV GCOV profiling is enabled.
  44. HW Appropriate hardware is enabled.
  45. IA-64 IA-64 architecture is enabled.
  46. IMA Integrity measurement architecture is enabled.
  47. IOSCHED More than one I/O scheduler is enabled.
  48. IP_PNP IP DHCP, BOOTP, or RARP is enabled.
  49. IPV6 IPv6 support is enabled.
  50. ISAPNP ISA PnP code is enabled.
  51. ISDN Appropriate ISDN support is enabled.
  52. JOY Appropriate joystick support is enabled.
  53. KGDB Kernel debugger support is enabled.
  54. KVM Kernel Virtual Machine support is enabled.
  55. LIBATA Libata driver is enabled
  56. LP Printer support is enabled.
  57. LOOP Loopback device support is enabled.
  58. M68k M68k architecture is enabled.
  59. These options have more detailed description inside of
  60. Documentation/m68k/kernel-options.txt.
  61. MCA MCA bus support is enabled.
  62. MDA MDA console support is enabled.
  63. MOUSE Appropriate mouse support is enabled.
  64. MSI Message Signaled Interrupts (PCI).
  65. MTD MTD (Memory Technology Device) support is enabled.
  66. NET Appropriate network support is enabled.
  67. NUMA NUMA support is enabled.
  68. NFS Appropriate NFS support is enabled.
  69. OSS OSS sound support is enabled.
  70. PV_OPS A paravirtualized kernel is enabled.
  71. PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
  72. PARISC The PA-RISC architecture is enabled.
  73. PCI PCI bus support is enabled.
  74. PCIE PCI Express support is enabled.
  75. PCMCIA The PCMCIA subsystem is enabled.
  76. PNP Plug & Play support is enabled.
  77. PPC PowerPC architecture is enabled.
  78. PPT Parallel port support is enabled.
  79. PS2 Appropriate PS/2 support is enabled.
  80. RAM RAM disk support is enabled.
  81. S390 S390 architecture is enabled.
  82. SCSI Appropriate SCSI support is enabled.
  83. A lot of drivers have their options described inside
  84. the Documentation/scsi/ sub-directory.
  85. SECURITY Different security models are enabled.
  86. SELINUX SELinux support is enabled.
  87. APPARMOR AppArmor support is enabled.
  88. SERIAL Serial support is enabled.
  89. SH SuperH architecture is enabled.
  90. SMP The kernel is an SMP kernel.
  91. SPARC Sparc architecture is enabled.
  92. SWSUSP Software suspend (hibernation) is enabled.
  93. SUSPEND System suspend states are enabled.
  94. FTRACE Function tracing enabled.
  95. TPM TPM drivers are enabled.
  96. TS Appropriate touchscreen support is enabled.
  97. UMS USB Mass Storage support is enabled.
  98. USB USB support is enabled.
  99. USBHID USB Human Interface Device support is enabled.
  100. V4L Video For Linux support is enabled.
  101. VGA The VGA console has been enabled.
  102. VT Virtual terminal support is enabled.
  103. WDT Watchdog support is enabled.
  104. XT IBM PC/XT MFM hard disk support is enabled.
  105. X86-32 X86-32, aka i386 architecture is enabled.
  106. X86-64 X86-64 architecture is enabled.
  107. More X86-64 boot options can be found in
  108. Documentation/x86/x86_64/boot-options.txt .
  109. X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
  110. XEN Xen support is enabled
  111. In addition, the following text indicates that the option:
  112. BUGS= Relates to possible processor bugs on the said processor.
  113. KNL Is a kernel start-up parameter.
  114. BOOT Is a boot loader parameter.
  115. Parameters denoted with BOOT are actually interpreted by the boot
  116. loader, and have no meaning to the kernel directly.
  117. Do not modify the syntax of boot loader parameters without extreme
  118. need or coordination with <Documentation/x86/boot.txt>.
  119. There are also arch-specific kernel-parameters not documented here.
  120. See for example <Documentation/x86/x86_64/boot-options.txt>.
  121. Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
  122. a trailing = on the name of any parameter states that that parameter will
  123. be entered as an environment variable, whereas its absence indicates that
  124. it will appear as a kernel argument readable via /proc/cmdline by programs
  125. running once the system is up.
  126. The number of kernel parameters is not limited, but the length of the
  127. complete command line (parameters including spaces etc.) is limited to
  128. a fixed number of characters. This limit depends on the architecture
  129. and is between 256 and 4096 characters. It is defined in the file
  130. ./include/asm/setup.h as COMMAND_LINE_SIZE.
  131. Finally, the [KMG] suffix is commonly described after a number of kernel
  132. parameter values. These 'K', 'M', and 'G' letters represent the _binary_
  133. multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
  134. bytes respectively. Such letter suffixes can also be entirely omitted.
  135. acpi= [HW,ACPI,X86]
  136. Advanced Configuration and Power Interface
  137. Format: { force | off | strict | noirq | rsdt }
  138. force -- enable ACPI if default was off
  139. off -- disable ACPI if default was on
  140. noirq -- do not use ACPI for IRQ routing
  141. strict -- Be less tolerant of platforms that are not
  142. strictly ACPI specification compliant.
  143. rsdt -- prefer RSDT over (default) XSDT
  144. copy_dsdt -- copy DSDT to memory
  145. See also Documentation/power/pm.txt, pci=noacpi
  146. acpi_rsdp= [ACPI,EFI,KEXEC]
  147. Pass the RSDP address to the kernel, mostly used
  148. on machines running EFI runtime service to boot the
  149. second kernel for kdump.
  150. acpi_apic_instance= [ACPI, IOAPIC]
  151. Format: <int>
  152. 2: use 2nd APIC table, if available
  153. 1,0: use 1st APIC table
  154. default: 0
  155. acpi_backlight= [HW,ACPI]
  156. acpi_backlight=vendor
  157. acpi_backlight=video
  158. If set to vendor, prefer vendor specific driver
  159. (e.g. thinkpad_acpi, sony_acpi, etc.) instead
  160. of the ACPI video.ko driver.
  161. acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
  162. acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
  163. Format: <int>
  164. CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
  165. debug output. Bits in debug_layer correspond to a
  166. _COMPONENT in an ACPI source file, e.g.,
  167. #define _COMPONENT ACPI_PCI_COMPONENT
  168. Bits in debug_level correspond to a level in
  169. ACPI_DEBUG_PRINT statements, e.g.,
  170. ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
  171. The debug_level mask defaults to "info". See
  172. Documentation/acpi/debug.txt for more information about
  173. debug layers and levels.
  174. Enable processor driver info messages:
  175. acpi.debug_layer=0x20000000
  176. Enable PCI/PCI interrupt routing info messages:
  177. acpi.debug_layer=0x400000
  178. Enable AML "Debug" output, i.e., stores to the Debug
  179. object while interpreting AML:
  180. acpi.debug_layer=0xffffffff acpi.debug_level=0x2
  181. Enable all messages related to ACPI hardware:
  182. acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
  183. Some values produce so much output that the system is
  184. unusable. The "log_buf_len" parameter may be useful
  185. if you need to capture more output.
  186. acpi_irq_balance [HW,ACPI]
  187. ACPI will balance active IRQs
  188. default in APIC mode
  189. acpi_irq_nobalance [HW,ACPI]
  190. ACPI will not move active IRQs (default)
  191. default in PIC mode
  192. acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
  193. Format: <irq>,<irq>...
  194. acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
  195. use by PCI
  196. Format: <irq>,<irq>...
  197. acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
  198. acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
  199. Format: To spoof as Windows 98: ="Microsoft Windows"
  200. acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
  201. acpi_osi="string1" # add string1 -- only one string
  202. acpi_osi="!string2" # remove built-in string2
  203. acpi_osi= # disable all strings
  204. acpi_pm_good [X86]
  205. Override the pmtimer bug detection: force the kernel
  206. to assume that this machine's pmtimer latches its value
  207. and always returns good values.
  208. acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
  209. Format: { level | edge | high | low }
  210. acpi_serialize [HW,ACPI] force serialization of AML methods
  211. acpi_skip_timer_override [HW,ACPI]
  212. Recognize and ignore IRQ0/pin2 Interrupt Override.
  213. For broken nForce2 BIOS resulting in XT-PIC timer.
  214. acpi_sleep= [HW,ACPI] Sleep options
  215. Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
  216. old_ordering, nonvs, sci_force_enable }
  217. See Documentation/power/video.txt for information on
  218. s3_bios and s3_mode.
  219. s3_beep is for debugging; it makes the PC's speaker beep
  220. as soon as the kernel's real-mode entry point is called.
  221. s4_nohwsig prevents ACPI hardware signature from being
  222. used during resume from hibernation.
  223. old_ordering causes the ACPI 1.0 ordering of the _PTS
  224. control method, with respect to putting devices into
  225. low power states, to be enforced (the ACPI 2.0 ordering
  226. of _PTS is used by default).
  227. nonvs prevents the kernel from saving/restoring the
  228. ACPI NVS memory during suspend/hibernation and resume.
  229. sci_force_enable causes the kernel to set SCI_EN directly
  230. on resume from S1/S3 (which is against the ACPI spec,
  231. but some broken systems don't work without it).
  232. acpi_use_timer_override [HW,ACPI]
  233. Use timer override. For some broken Nvidia NF5 boards
  234. that require a timer override, but don't have HPET
  235. acpi_enforce_resources= [ACPI]
  236. { strict | lax | no }
  237. Check for resource conflicts between native drivers
  238. and ACPI OperationRegions (SystemIO and SystemMemory
  239. only). IO ports and memory declared in ACPI might be
  240. used by the ACPI subsystem in arbitrary AML code and
  241. can interfere with legacy drivers.
  242. strict (default): access to resources claimed by ACPI
  243. is denied; legacy drivers trying to access reserved
  244. resources will fail to bind to device using them.
  245. lax: access to resources claimed by ACPI is allowed;
  246. legacy drivers trying to access reserved resources
  247. will bind successfully but a warning message is logged.
  248. no: ACPI OperationRegions are not marked as reserved,
  249. no further checks are performed.
  250. add_efi_memmap [EFI; X86] Include EFI memory map in
  251. kernel's map of available physical RAM.
  252. agp= [AGP]
  253. { off | try_unsupported }
  254. off: disable AGP support
  255. try_unsupported: try to drive unsupported chipsets
  256. (may crash computer or cause data corruption)
  257. ALSA [HW,ALSA]
  258. See Documentation/sound/alsa/alsa-parameters.txt
  259. alignment= [KNL,ARM]
  260. Allow the default userspace alignment fault handler
  261. behaviour to be specified. Bit 0 enables warnings,
  262. bit 1 enables fixups, and bit 2 sends a segfault.
  263. amd_iommu= [HW,X86-84]
  264. Pass parameters to the AMD IOMMU driver in the system.
  265. Possible values are:
  266. fullflush - enable flushing of IO/TLB entries when
  267. they are unmapped. Otherwise they are
  268. flushed before they will be reused, which
  269. is a lot of faster
  270. off - do not initialize any AMD IOMMU found in
  271. the system
  272. amijoy.map= [HW,JOY] Amiga joystick support
  273. Map of devices attached to JOY0DAT and JOY1DAT
  274. Format: <a>,<b>
  275. See also Documentation/kernel/input/joystick.txt
  276. analog.map= [HW,JOY] Analog joystick and gamepad support
  277. Specifies type or capabilities of an analog joystick
  278. connected to one of 16 gameports
  279. Format: <type1>,<type2>,..<type16>
  280. apc= [HW,SPARC]
  281. Power management functions (SPARCstation-4/5 + deriv.)
  282. Format: noidle
  283. Disable APC CPU standby support. SPARCstation-Fox does
  284. not play well with APC CPU idle - disable it if you have
  285. APC and your system crashes randomly.
  286. apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
  287. Change the output verbosity whilst booting
  288. Format: { quiet (default) | verbose | debug }
  289. Change the amount of debugging information output
  290. when initialising the APIC and IO-APIC components.
  291. autoconf= [IPV6]
  292. See Documentation/networking/ipv6.txt.
  293. show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
  294. Limit apic dumping. The parameter defines the maximal
  295. number of local apics being dumped. Also it is possible
  296. to set it to "all" by meaning -- no limit here.
  297. Format: { 1 (default) | 2 | ... | all }.
  298. The parameter valid if only apic=debug or
  299. apic=verbose is specified.
  300. Example: apic=debug show_lapic=all
  301. apm= [APM] Advanced Power Management
  302. See header of arch/x86/kernel/apm_32.c.
  303. arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
  304. Format: <io>,<irq>,<nodeID>
  305. ataflop= [HW,M68k]
  306. atarimouse= [HW,MOUSE] Atari Mouse
  307. atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
  308. EzKey and similar keyboards
  309. atkbd.reset= [HW] Reset keyboard during initialization
  310. atkbd.set= [HW] Select keyboard code set
  311. Format: <int> (2 = AT (default), 3 = PS/2)
  312. atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
  313. keyboards
  314. atkbd.softraw= [HW] Choose between synthetic and real raw mode
  315. Format: <bool> (0 = real, 1 = synthetic (default))
  316. atkbd.softrepeat= [HW]
  317. Use software keyboard repeat
  318. autotest [IA64]
  319. baycom_epp= [HW,AX25]
  320. Format: <io>,<mode>
  321. baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
  322. Format: <io>,<mode>
  323. See header of drivers/net/hamradio/baycom_par.c.
  324. baycom_ser_fdx= [HW,AX25]
  325. BayCom Serial Port AX.25 Modem (Full Duplex Mode)
  326. Format: <io>,<irq>,<mode>[,<baud>]
  327. See header of drivers/net/hamradio/baycom_ser_fdx.c.
  328. baycom_ser_hdx= [HW,AX25]
  329. BayCom Serial Port AX.25 Modem (Half Duplex Mode)
  330. Format: <io>,<irq>,<mode>
  331. See header of drivers/net/hamradio/baycom_ser_hdx.c.
  332. boot_delay= Milliseconds to delay each printk during boot.
  333. Values larger than 10 seconds (10000) are changed to
  334. no delay (0).
  335. Format: integer
  336. bootmem_debug [KNL] Enable bootmem allocator debug messages.
  337. bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
  338. bttv.radio= Most important insmod options are available as
  339. kernel args too.
  340. bttv.pll= See Documentation/video4linux/bttv/Insmod-options
  341. bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
  342. bulk_remove=off [PPC] This parameter disables the use of the pSeries
  343. firmware feature for flushing multiple hpte entries
  344. at a time.
  345. c101= [NET] Moxa C101 synchronous serial card
  346. cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
  347. Sometimes CPU hardware bugs make them report the cache
  348. size incorrectly. The kernel will attempt work arounds
  349. to fix known problems, but for some CPUs it is not
  350. possible to determine what the correct size should be.
  351. This option provides an override for these situations.
  352. capability.disable=
  353. [SECURITY] Disable capabilities. This would normally
  354. be used only if an alternative security model is to be
  355. configured. Potentially dangerous and should only be
  356. used if you are entirely sure of the consequences.
  357. ccw_timeout_log [S390]
  358. See Documentation/s390/CommonIO for details.
  359. cgroup_disable= [KNL] Disable a particular controller
  360. Format: {name of the controller(s) to disable}
  361. {Currently supported controllers - "memory"}
  362. checkreqprot [SELINUX] Set initial checkreqprot flag value.
  363. Format: { "0" | "1" }
  364. See security/selinux/Kconfig help text.
  365. 0 -- check protection applied by kernel (includes
  366. any implied execute protection).
  367. 1 -- check protection requested by application.
  368. Default value is set via a kernel config option.
  369. Value can be changed at runtime via
  370. /selinux/checkreqprot.
  371. cio_ignore= [S390]
  372. See Documentation/s390/CommonIO for details.
  373. clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
  374. [Deprecated]
  375. Forces specified clocksource (if available) to be used
  376. when calculating gettimeofday(). If specified
  377. clocksource is not available, it defaults to PIT.
  378. Format: { pit | tsc | cyclone | pmtmr }
  379. clocksource= Override the default clocksource
  380. Format: <string>
  381. Override the default clocksource and use the clocksource
  382. with the name specified.
  383. Some clocksource names to choose from, depending on
  384. the platform:
  385. [all] jiffies (this is the base, fallback clocksource)
  386. [ACPI] acpi_pm
  387. [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
  388. pxa_timer,timer3,32k_counter,timer0_1
  389. [AVR32] avr32
  390. [X86-32] pit,hpet,tsc;
  391. scx200_hrt on Geode; cyclone on IBM x440
  392. [MIPS] MIPS
  393. [PARISC] cr16
  394. [S390] tod
  395. [SH] SuperH
  396. [SPARC64] tick
  397. [X86-64] hpet,tsc
  398. clearcpuid=BITNUM [X86]
  399. Disable CPUID feature X for the kernel. See
  400. arch/x86/include/asm/cpufeature.h for the valid bit
  401. numbers. Note the Linux specific bits are not necessarily
  402. stable over kernel options, but the vendor specific
  403. ones should be.
  404. Also note that user programs calling CPUID directly
  405. or using the feature without checking anything
  406. will still see it. This just prevents it from
  407. being used by the kernel or shown in /proc/cpuinfo.
  408. Also note the kernel might malfunction if you disable
  409. some critical bits.
  410. cmo_free_hint= [PPC] Format: { yes | no }
  411. Specify whether pages are marked as being inactive
  412. when they are freed. This is used in CMO environments
  413. to determine OS memory pressure for page stealing by
  414. a hypervisor.
  415. Default: yes
  416. code_bytes [X86] How many bytes of object code to print
  417. in an oops report.
  418. Range: 0 - 8192
  419. Default: 64
  420. com20020= [HW,NET] ARCnet - COM20020 chipset
  421. Format:
  422. <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
  423. com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
  424. Format: <io>[,<irq>]
  425. com90xx= [HW,NET]
  426. ARCnet - COM90xx chipset (memory-mapped buffers)
  427. Format: <io>[,<irq>[,<memstart>]]
  428. condev= [HW,S390] console device
  429. conmode=
  430. console= [KNL] Output console device and options.
  431. tty<n> Use the virtual console device <n>.
  432. ttyS<n>[,options]
  433. ttyUSB0[,options]
  434. Use the specified serial port. The options are of
  435. the form "bbbbpnf", where "bbbb" is the baud rate,
  436. "p" is parity ("n", "o", or "e"), "n" is number of
  437. bits, and "f" is flow control ("r" for RTS or
  438. omit it). Default is "9600n8".
  439. See Documentation/serial-console.txt for more
  440. information. See
  441. Documentation/networking/netconsole.txt for an
  442. alternative.
  443. uart[8250],io,<addr>[,options]
  444. uart[8250],mmio,<addr>[,options]
  445. Start an early, polled-mode console on the 8250/16550
  446. UART at the specified I/O port or MMIO address,
  447. switching to the matching ttyS device later. The
  448. options are the same as for ttyS, above.
  449. If the device connected to the port is not a TTY but a braille
  450. device, prepend "brl," before the device type, for instance
  451. console=brl,ttyS0
  452. For now, only VisioBraille is supported.
  453. consoleblank= [KNL] The console blank (screen saver) timeout in
  454. seconds. Defaults to 10*60 = 10mins. A value of 0
  455. disables the blank timer.
  456. coredump_filter=
  457. [KNL] Change the default value for
  458. /proc/<pid>/coredump_filter.
  459. See also Documentation/filesystems/proc.txt.
  460. cpuidle.off=1 [CPU_IDLE]
  461. disable the cpuidle sub-system
  462. cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
  463. Format:
  464. <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
  465. crashkernel=size[KMG][@offset[KMG]]
  466. [KNL] Using kexec, Linux can switch to a 'crash kernel'
  467. upon panic. This parameter reserves the physical
  468. memory region [offset, offset + size] for that kernel
  469. image. If '@offset' is omitted, then a suitable offset
  470. is selected automatically. Check
  471. Documentation/kdump/kdump.txt for further details.
  472. crashkernel=range1:size1[,range2:size2,...][@offset]
  473. [KNL] Same as above, but depends on the memory
  474. in the running system. The syntax of range is
  475. start-[end] where start and end are both
  476. a memory unit (amount[KMG]). See also
  477. Documentation/kdump/kdump.txt for an example.
  478. cs89x0_dma= [HW,NET]
  479. Format: <dma>
  480. cs89x0_media= [HW,NET]
  481. Format: { rj45 | aui | bnc }
  482. dasd= [HW,NET]
  483. See header of drivers/s390/block/dasd_devmap.c.
  484. db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
  485. (one device per port)
  486. Format: <port#>,<type>
  487. See also Documentation/input/joystick-parport.txt
  488. ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
  489. time. See Documentation/dynamic-debug-howto.txt for
  490. details.
  491. debug [KNL] Enable kernel debugging (events log level).
  492. debug_locks_verbose=
  493. [KNL] verbose self-tests
  494. Format=<0|1>
  495. Print debugging info while doing the locking API
  496. self-tests.
  497. We default to 0 (no extra messages), setting it to
  498. 1 will print _a lot_ more information - normally
  499. only useful to kernel developers.
  500. debug_objects [KNL] Enable object debugging
  501. no_debug_objects
  502. [KNL] Disable object debugging
  503. debugpat [X86] Enable PAT debugging
  504. decnet.addr= [HW,NET]
  505. Format: <area>[,<node>]
  506. See also Documentation/networking/decnet.txt.
  507. default_hugepagesz=
  508. [same as hugepagesz=] The size of the default
  509. HugeTLB page size. This is the size represented by
  510. the legacy /proc/ hugepages APIs, used for SHM, and
  511. default size when mounting hugetlbfs filesystems.
  512. Defaults to the default architecture's huge page size
  513. if not specified.
  514. dhash_entries= [KNL]
  515. Set number of hash buckets for dentry cache.
  516. digi= [HW,SERIAL]
  517. IO parameters + enable/disable command.
  518. digiepca= [HW,SERIAL]
  519. See drivers/char/README.epca and
  520. Documentation/serial/digiepca.txt.
  521. disable= [IPV6]
  522. See Documentation/networking/ipv6.txt.
  523. disable_ddw [PPC/PSERIES]
  524. Disable Dynamic DMA Window support. Use this if
  525. to workaround buggy firmware.
  526. disable_ipv6= [IPV6]
  527. See Documentation/networking/ipv6.txt.
  528. disable_mtrr_cleanup [X86]
  529. The kernel tries to adjust MTRR layout from continuous
  530. to discrete, to make X server driver able to add WB
  531. entry later. This parameter disables that.
  532. disable_mtrr_trim [X86, Intel and AMD only]
  533. By default the kernel will trim any uncacheable
  534. memory out of your available memory pool based on
  535. MTRR settings. This parameter disables that behavior,
  536. possibly causing your machine to run very slowly.
  537. disable_timer_pin_1 [X86]
  538. Disable PIN 1 of APIC timer
  539. Can be useful to work around chipset bugs.
  540. dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
  541. this option disables the debugging code at boot.
  542. dma_debug_entries=<number>
  543. This option allows to tune the number of preallocated
  544. entries for DMA-API debugging code. One entry is
  545. required per DMA-API allocation. Use this if the
  546. DMA-API debugging code disables itself because the
  547. architectural default is too low.
  548. dma_debug_driver=<driver_name>
  549. With this option the DMA-API debugging driver
  550. filter feature can be enabled at boot time. Just
  551. pass the driver to filter for as the parameter.
  552. The filter can be disabled or changed to another
  553. driver later using sysfs.
  554. dscc4.setup= [NET]
  555. earlycon= [KNL] Output early console device and options.
  556. uart[8250],io,<addr>[,options]
  557. uart[8250],mmio,<addr>[,options]
  558. uart[8250],mmio32,<addr>[,options]
  559. Start an early, polled-mode console on the 8250/16550
  560. UART at the specified I/O port or MMIO address.
  561. MMIO inter-register address stride is either 8bit (mmio)
  562. or 32bit (mmio32).
  563. The options are the same as for ttyS, above.
  564. earlyprintk= [X86,SH,BLACKFIN]
  565. earlyprintk=vga
  566. earlyprintk=serial[,ttySn[,baudrate]]
  567. earlyprintk=ttySn[,baudrate]
  568. earlyprintk=dbgp[debugController#]
  569. Append ",keep" to not disable it when the real console
  570. takes over.
  571. Only vga or serial or usb debug port at a time.
  572. Currently only ttyS0 and ttyS1 are supported.
  573. Interaction with the standard serial driver is not
  574. very good.
  575. The VGA output is eventually overwritten by the real
  576. console.
  577. ekgdboc= [X86,KGDB] Allow early kernel console debugging
  578. ekgdboc=kbd
  579. This is designed to be used in conjunction with
  580. the boot argument: earlyprintk=vga
  581. edd= [EDD]
  582. Format: {"off" | "on" | "skip[mbr]"}
  583. eisa_irq_edge= [PARISC,HW]
  584. See header of drivers/parisc/eisa.c.
  585. elanfreq= [X86-32]
  586. See comment before function elanfreq_setup() in
  587. arch/x86/kernel/cpu/cpufreq/elanfreq.c.
  588. elevator= [IOSCHED]
  589. Format: {"cfq" | "deadline" | "noop"}
  590. See Documentation/block/as-iosched.txt and
  591. Documentation/block/deadline-iosched.txt for details.
  592. elfcorehdr= [IA64,PPC,SH,X86]
  593. Specifies physical address of start of kernel core
  594. image elf header. Generally kexec loader will
  595. pass this option to capture kernel.
  596. See Documentation/kdump/kdump.txt for details.
  597. enable_mtrr_cleanup [X86]
  598. The kernel tries to adjust MTRR layout from continuous
  599. to discrete, to make X server driver able to add WB
  600. entry later. This parameter enables that.
  601. enable_timer_pin_1 [X86]
  602. Enable PIN 1 of APIC timer
  603. Can be useful to work around chipset bugs
  604. (in particular on some ATI chipsets).
  605. The kernel tries to set a reasonable default.
  606. enforcing [SELINUX] Set initial enforcing status.
  607. Format: {"0" | "1"}
  608. See security/selinux/Kconfig help text.
  609. 0 -- permissive (log only, no denials).
  610. 1 -- enforcing (deny and log).
  611. Default value is 0.
  612. Value can be changed at runtime via /selinux/enforce.
  613. erst_disable [ACPI]
  614. Disable Error Record Serialization Table (ERST)
  615. support.
  616. ether= [HW,NET] Ethernet cards parameters
  617. This option is obsoleted by the "netdev=" option, which
  618. has equivalent usage. See its documentation for details.
  619. evm= [EVM]
  620. Format: { "fix" }
  621. Permit 'security.evm' to be updated regardless of
  622. current integrity status.
  623. failslab=
  624. fail_page_alloc=
  625. fail_make_request=[KNL]
  626. General fault injection mechanism.
  627. Format: <interval>,<probability>,<space>,<times>
  628. See also /Documentation/fault-injection/.
  629. floppy= [HW]
  630. See Documentation/blockdev/floppy.txt.
  631. force_pal_cache_flush
  632. [IA-64] Avoid check_sal_cache_flush which may hang on
  633. buggy SAL_CACHE_FLUSH implementations. Using this
  634. parameter will force ia64_sal_cache_flush to call
  635. ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
  636. ftrace=[tracer]
  637. [FTRACE] will set and start the specified tracer
  638. as early as possible in order to facilitate early
  639. boot debugging.
  640. ftrace_dump_on_oops[=orig_cpu]
  641. [FTRACE] will dump the trace buffers on oops.
  642. If no parameter is passed, ftrace will dump
  643. buffers of all CPUs, but if you pass orig_cpu, it will
  644. dump only the buffer of the CPU that triggered the
  645. oops.
  646. ftrace_filter=[function-list]
  647. [FTRACE] Limit the functions traced by the function
  648. tracer at boot up. function-list is a comma separated
  649. list of functions. This list can be changed at run
  650. time by the set_ftrace_filter file in the debugfs
  651. tracing directory.
  652. ftrace_notrace=[function-list]
  653. [FTRACE] Do not trace the functions specified in
  654. function-list. This list can be changed at run time
  655. by the set_ftrace_notrace file in the debugfs
  656. tracing directory.
  657. ftrace_graph_filter=[function-list]
  658. [FTRACE] Limit the top level callers functions traced
  659. by the function graph tracer at boot up.
  660. function-list is a comma separated list of functions
  661. that can be changed at run time by the
  662. set_graph_function file in the debugfs tracing directory.
  663. gamecon.map[2|3]=
  664. [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
  665. support via parallel port (up to 5 devices per port)
  666. Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
  667. See also Documentation/input/joystick-parport.txt
  668. gamma= [HW,DRM]
  669. gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
  670. Format: off | on
  671. default: on
  672. gcov_persist= [GCOV] When non-zero (default), profiling data for
  673. kernel modules is saved and remains accessible via
  674. debugfs, even when the module is unloaded/reloaded.
  675. When zero, profiling data is discarded and associated
  676. debugfs files are removed at module unload time.
  677. gpt [EFI] Forces disk with valid GPT signature but
  678. invalid Protective MBR to be treated as GPT.
  679. hashdist= [KNL,NUMA] Large hashes allocated during boot
  680. are distributed across NUMA nodes. Defaults on
  681. for 64bit NUMA, off otherwise.
  682. Format: 0 | 1 (for off | on)
  683. hcl= [IA-64] SGI's Hardware Graph compatibility layer
  684. hd= [EIDE] (E)IDE hard drive subsystem geometry
  685. Format: <cyl>,<head>,<sect>
  686. hest_disable [ACPI]
  687. Disable Hardware Error Source Table (HEST) support;
  688. corresponding firmware-first mode error processing
  689. logic will be disabled.
  690. highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
  691. size of <nn>. This works even on boxes that have no
  692. highmem otherwise. This also works to reduce highmem
  693. size on bigger boxes.
  694. highres= [KNL] Enable/disable high resolution timer mode.
  695. Valid parameters: "on", "off"
  696. Default: "on"
  697. hisax= [HW,ISDN]
  698. See Documentation/isdn/README.HiSax.
  699. hlt [BUGS=ARM,SH]
  700. hpet= [X86-32,HPET] option to control HPET usage
  701. Format: { enable (default) | disable | force |
  702. verbose }
  703. disable: disable HPET and use PIT instead
  704. force: allow force enabled of undocumented chips (ICH4,
  705. VIA, nVidia)
  706. verbose: show contents of HPET registers during setup
  707. hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
  708. hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
  709. On x86-64 and powerpc, this option can be specified
  710. multiple times interleaved with hugepages= to reserve
  711. huge pages of different sizes. Valid pages sizes on
  712. x86-64 are 2M (when the CPU supports "pse") and 1G
  713. (when the CPU supports the "pdpe1gb" cpuinfo flag)
  714. Note that 1GB pages can only be allocated at boot time
  715. using hugepages= and not freed afterwards.
  716. hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
  717. terminal devices. Valid values: 0..8
  718. hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
  719. If specified, z/VM IUCV HVC accepts connections
  720. from listed z/VM user IDs only.
  721. keep_bootcon [KNL]
  722. Do not unregister boot console at start. This is only
  723. useful for debugging when something happens in the window
  724. between unregistering the boot console and initializing
  725. the real console.
  726. i2c_bus= [HW] Override the default board specific I2C bus speed
  727. or register an additional I2C bus that is not
  728. registered from board initialization code.
  729. Format:
  730. <bus_id>,<clkrate>
  731. i8042.debug [HW] Toggle i8042 debug mode
  732. i8042.direct [HW] Put keyboard port into non-translated mode
  733. i8042.dumbkbd [HW] Pretend that controller can only read data from
  734. keyboard and cannot control its state
  735. (Don't attempt to blink the leds)
  736. i8042.noaux [HW] Don't check for auxiliary (== mouse) port
  737. i8042.nokbd [HW] Don't check/create keyboard port
  738. i8042.noloop [HW] Disable the AUX Loopback command while probing
  739. for the AUX port
  740. i8042.nomux [HW] Don't check presence of an active multiplexing
  741. controller
  742. i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
  743. controllers
  744. i8042.notimeout [HW] Ignore timeout condition signalled by conroller
  745. i8042.reset [HW] Reset the controller during init and cleanup
  746. i8042.unlock [HW] Unlock (ignore) the keylock
  747. i810= [HW,DRM]
  748. i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
  749. indicates that the driver is running on unsupported
  750. hardware.
  751. i8k.force [HW] Activate i8k driver even if SMM BIOS signature
  752. does not match list of supported models.
  753. i8k.power_status
  754. [HW] Report power status in /proc/i8k
  755. (disabled by default)
  756. i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
  757. capability is set.
  758. icn= [HW,ISDN]
  759. Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
  760. ide-core.nodma= [HW] (E)IDE subsystem
  761. Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
  762. .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
  763. .cdrom .chs .ignore_cable are additional options
  764. See Documentation/ide/ide.txt.
  765. ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
  766. Claim all unknown PCI IDE storage controllers.
  767. idle= [X86]
  768. Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
  769. Poll forces a polling idle loop that can slightly
  770. improve the performance of waking up a idle CPU, but
  771. will use a lot of power and make the system run hot.
  772. Not recommended.
  773. idle=mwait: On systems which support MONITOR/MWAIT but
  774. the kernel chose to not use it because it doesn't save
  775. as much power as a normal idle loop, use the
  776. MONITOR/MWAIT idle loop anyways. Performance should be
  777. the same as idle=poll.
  778. idle=halt: Halt is forced to be used for CPU idle.
  779. In such case C2/C3 won't be used again.
  780. idle=nomwait: Disable mwait for CPU C-states
  781. ignore_loglevel [KNL]
  782. Ignore loglevel setting - this will print /all/
  783. kernel messages to the console. Useful for debugging.
  784. ihash_entries= [KNL]
  785. Set number of hash buckets for inode cache.
  786. ima_audit= [IMA]
  787. Format: { "0" | "1" }
  788. 0 -- integrity auditing messages. (Default)
  789. 1 -- enable informational integrity auditing messages.
  790. ima_hash= [IMA]
  791. Format: { "sha1" | "md5" }
  792. default: "sha1"
  793. ima_tcb [IMA]
  794. Load a policy which meets the needs of the Trusted
  795. Computing Base. This means IMA will measure all
  796. programs exec'd, files mmap'd for exec, and all files
  797. opened for read by uid=0.
  798. init= [KNL]
  799. Format: <full_path>
  800. Run specified binary instead of /sbin/init as init
  801. process.
  802. initcall_debug [KNL] Trace initcalls as they are executed. Useful
  803. for working out where the kernel is dying during
  804. startup.
  805. initrd= [BOOT] Specify the location of the initial ramdisk
  806. inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
  807. Format: <irq>
  808. intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
  809. on
  810. Enable intel iommu driver.
  811. off
  812. Disable intel iommu driver.
  813. igfx_off [Default Off]
  814. By default, gfx is mapped as normal device. If a gfx
  815. device has a dedicated DMAR unit, the DMAR unit is
  816. bypassed by not enabling DMAR with this option. In
  817. this case, gfx device will use physical address for
  818. DMA.
  819. forcedac [x86_64]
  820. With this option iommu will not optimize to look
  821. for io virtual address below 32 bit forcing dual
  822. address cycle on pci bus for cards supporting greater
  823. than 32 bit addressing. The default is to look
  824. for translation below 32 bit and if not available
  825. then look in the higher range.
  826. strict [Default Off]
  827. With this option on every unmap_single operation will
  828. result in a hardware IOTLB flush operation as opposed
  829. to batching them for performance.
  830. sp_off [Default Off]
  831. By default, super page will be supported if Intel IOMMU
  832. has the capability. With this option, super page will
  833. not be supported.
  834. intremap= [X86-64, Intel-IOMMU]
  835. Format: { on (default) | off | nosid }
  836. on enable Interrupt Remapping (default)
  837. off disable Interrupt Remapping
  838. nosid disable Source ID checking
  839. inttest= [IA64]
  840. iomem= Disable strict checking of access to MMIO memory
  841. strict regions from userspace.
  842. relaxed
  843. iommu= [x86]
  844. off
  845. force
  846. noforce
  847. biomerge
  848. panic
  849. nopanic
  850. merge
  851. nomerge
  852. forcesac
  853. soft
  854. pt [x86, IA64]
  855. io7= [HW] IO7 for Marvel based alpha systems
  856. See comment before marvel_specify_io7 in
  857. arch/alpha/kernel/core_marvel.c.
  858. io_delay= [X86] I/O delay method
  859. 0x80
  860. Standard port 0x80 based delay
  861. 0xed
  862. Alternate port 0xed based delay (needed on some systems)
  863. udelay
  864. Simple two microseconds delay
  865. none
  866. No delay
  867. ip= [IP_PNP]
  868. See Documentation/filesystems/nfs/nfsroot.txt.
  869. ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
  870. See comment before ip2_setup() in
  871. drivers/char/ip2/ip2base.c.
  872. irqfixup [HW]
  873. When an interrupt is not handled search all handlers
  874. for it. Intended to get systems with badly broken
  875. firmware running.
  876. irqpoll [HW]
  877. When an interrupt is not handled search all handlers
  878. for it. Also check all handlers each timer
  879. interrupt. Intended to get systems with badly broken
  880. firmware running.
  881. isapnp= [ISAPNP]
  882. Format: <RDP>,<reset>,<pci_scan>,<verbosity>
  883. isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
  884. Format:
  885. <cpu number>,...,<cpu number>
  886. or
  887. <cpu number>-<cpu number>
  888. (must be a positive range in ascending order)
  889. or a mixture
  890. <cpu number>,...,<cpu number>-<cpu number>
  891. This option can be used to specify one or more CPUs
  892. to isolate from the general SMP balancing and scheduling
  893. algorithms. You can move a process onto or off an
  894. "isolated" CPU via the CPU affinity syscalls or cpuset.
  895. <cpu number> begins at 0 and the maximum value is
  896. "number of CPUs in system - 1".
  897. This option is the preferred way to isolate CPUs. The
  898. alternative -- manually setting the CPU mask of all
  899. tasks in the system -- can cause problems and
  900. suboptimal load balancer performance.
  901. iucv= [HW,NET]
  902. js= [HW,JOY] Analog joystick
  903. See Documentation/input/joystick.txt.
  904. keepinitrd [HW,ARM]
  905. kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
  906. specifies the amount of memory usable by the kernel
  907. for non-movable allocations. The requested amount is
  908. spread evenly throughout all nodes in the system. The
  909. remaining memory in each node is used for Movable
  910. pages. In the event, a node is too small to have both
  911. kernelcore and Movable pages, kernelcore pages will
  912. take priority and other nodes will have a larger number
  913. of kernelcore pages. The Movable zone is used for the
  914. allocation of pages that may be reclaimed or moved
  915. by the page migration subsystem. This means that
  916. HugeTLB pages may not be allocated from this zone.
  917. Note that allocations like PTEs-from-HighMem still
  918. use the HighMem zone if it exists, and the Normal
  919. zone if it does not.
  920. kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
  921. Format: <Controller#>[,poll interval]
  922. The controller # is the number of the ehci usb debug
  923. port as it is probed via PCI. The poll interval is
  924. optional and is the number seconds in between
  925. each poll cycle to the debug port in case you need
  926. the functionality for interrupting the kernel with
  927. gdb or control-c on the dbgp connection. When
  928. not using this parameter you use sysrq-g to break into
  929. the kernel debugger.
  930. kgdboc= [KGDB,HW] kgdb over consoles.
  931. Requires a tty driver that supports console polling,
  932. or a supported polling keyboard driver (non-usb).
  933. Serial only format: <serial_device>[,baud]
  934. keyboard only format: kbd
  935. keyboard and serial format: kbd,<serial_device>[,baud]
  936. Optional Kernel mode setting:
  937. kms, kbd format: kms,kbd
  938. kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
  939. kgdbwait [KGDB] Stop kernel execution and enter the
  940. kernel debugger at the earliest opportunity.
  941. kmac= [MIPS] korina ethernet MAC address.
  942. Configure the RouterBoard 532 series on-chip
  943. Ethernet adapter MAC address.
  944. kmemleak= [KNL] Boot-time kmemleak enable/disable
  945. Valid arguments: on, off
  946. Default: on
  947. kstack=N [X86] Print N words from the kernel stack
  948. in oops dumps.
  949. kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
  950. Default is 0 (don't ignore, but inject #GP)
  951. kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
  952. Default is 1 (enabled)
  953. kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
  954. KVM MMU at runtime.
  955. Default is 0 (off)
  956. kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
  957. Default is 1 (enabled)
  958. kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
  959. for all guests.
  960. Default is 1 (enabled) if in 64bit or 32bit-PAE mode
  961. kvm-intel.ept= [KVM,Intel] Disable extended page tables
  962. (virtualized MMU) support on capable Intel chips.
  963. Default is 1 (enabled)
  964. kvm-intel.emulate_invalid_guest_state=
  965. [KVM,Intel] Enable emulation of invalid guest states
  966. Default is 0 (disabled)
  967. kvm-intel.flexpriority=
  968. [KVM,Intel] Disable FlexPriority feature (TPR shadow).
  969. Default is 1 (enabled)
  970. kvm-intel.unrestricted_guest=
  971. [KVM,Intel] Disable unrestricted guest feature
  972. (virtualized real and unpaged mode) on capable
  973. Intel chips. Default is 1 (enabled)
  974. kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
  975. feature (tagged TLBs) on capable Intel chips.
  976. Default is 1 (enabled)
  977. l2cr= [PPC]
  978. l3cr= [PPC]
  979. lapic [X86-32,APIC] Enable the local APIC even if BIOS
  980. disabled it.
  981. lapic_timer_c2_ok [X86,APIC] trust the local apic timer
  982. in C2 power state.
  983. libata.dma= [LIBATA] DMA control
  984. libata.dma=0 Disable all PATA and SATA DMA
  985. libata.dma=1 PATA and SATA Disk DMA only
  986. libata.dma=2 ATAPI (CDROM) DMA only
  987. libata.dma=4 Compact Flash DMA only
  988. Combinations also work, so libata.dma=3 enables DMA
  989. for disks and CDROMs, but not CFs.
  990. libata.ignore_hpa= [LIBATA] Ignore HPA limit
  991. libata.ignore_hpa=0 keep BIOS limits (default)
  992. libata.ignore_hpa=1 ignore limits, using full disk
  993. libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
  994. when set.
  995. Format: <int>
  996. libata.force= [LIBATA] Force configurations. The format is comma
  997. separated list of "[ID:]VAL" where ID is
  998. PORT[.DEVICE]. PORT and DEVICE are decimal numbers
  999. matching port, link or device. Basically, it matches
  1000. the ATA ID string printed on console by libata. If
  1001. the whole ID part is omitted, the last PORT and DEVICE
  1002. values are used. If ID hasn't been specified yet, the
  1003. configuration applies to all ports, links and devices.
  1004. If only DEVICE is omitted, the parameter applies to
  1005. the port and all links and devices behind it. DEVICE
  1006. number of 0 either selects the first device or the
  1007. first fan-out link behind PMP device. It does not
  1008. select the host link. DEVICE number of 15 selects the
  1009. host link and device attached to it.
  1010. The VAL specifies the configuration to force. As long
  1011. as there's no ambiguity shortcut notation is allowed.
  1012. For example, both 1.5 and 1.5G would work for 1.5Gbps.
  1013. The following configurations can be forced.
  1014. * Cable type: 40c, 80c, short40c, unk, ign or sata.
  1015. Any ID with matching PORT is used.
  1016. * SATA link speed limit: 1.5Gbps or 3.0Gbps.
  1017. * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
  1018. udma[/][16,25,33,44,66,100,133] notation is also
  1019. allowed.
  1020. * [no]ncq: Turn on or off NCQ.
  1021. * nohrst, nosrst, norst: suppress hard, soft
  1022. and both resets.
  1023. * dump_id: dump IDENTIFY data.
  1024. If there are multiple matching configurations changing
  1025. the same attribute, the last one is used.
  1026. memblock=debug [KNL] Enable memblock debug messages.
  1027. load_ramdisk= [RAM] List of ramdisks to load from floppy
  1028. See Documentation/blockdev/ramdisk.txt.
  1029. lockd.nlm_grace_period=P [NFS] Assign grace period.
  1030. Format: <integer>
  1031. lockd.nlm_tcpport=N [NFS] Assign TCP port.
  1032. Format: <integer>
  1033. lockd.nlm_timeout=T [NFS] Assign timeout value.
  1034. Format: <integer>
  1035. lockd.nlm_udpport=M [NFS] Assign UDP port.
  1036. Format: <integer>
  1037. logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
  1038. Format: <irq>
  1039. loglevel= All Kernel Messages with a loglevel smaller than the
  1040. console loglevel will be printed to the console. It can
  1041. also be changed with klogd or other programs. The
  1042. loglevels are defined as follows:
  1043. 0 (KERN_EMERG) system is unusable
  1044. 1 (KERN_ALERT) action must be taken immediately
  1045. 2 (KERN_CRIT) critical conditions
  1046. 3 (KERN_ERR) error conditions
  1047. 4 (KERN_WARNING) warning conditions
  1048. 5 (KERN_NOTICE) normal but significant condition
  1049. 6 (KERN_INFO) informational
  1050. 7 (KERN_DEBUG) debug-level messages
  1051. log_buf_len=n[KMG] Sets the size of the printk ring buffer,
  1052. in bytes. n must be a power of two. The default
  1053. size is set in the kernel config file.
  1054. logo.nologo [FB] Disables display of the built-in Linux logo.
  1055. This may be used to provide more screen space for
  1056. kernel log messages and is useful when debugging
  1057. kernel boot problems.
  1058. lp=0 [LP] Specify parallel ports to use, e.g,
  1059. lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
  1060. lp=reset first parallel port). 'lp=0' disables the
  1061. lp=auto printer driver. 'lp=reset' (which can be
  1062. specified in addition to the ports) causes
  1063. attached printers to be reset. Using
  1064. lp=port1,port2,... specifies the parallel ports
  1065. to associate lp devices with, starting with
  1066. lp0. A port specification may be 'none' to skip
  1067. that lp device, or a parport name such as
  1068. 'parport0'. Specifying 'lp=auto' instead of a
  1069. port specification list means that device IDs
  1070. from each port should be examined, to see if
  1071. an IEEE 1284-compliant printer is attached; if
  1072. so, the driver will manage that printer.
  1073. See also header of drivers/char/lp.c.
  1074. lpj=n [KNL]
  1075. Sets loops_per_jiffy to given constant, thus avoiding
  1076. time-consuming boot-time autodetection (up to 250 ms per
  1077. CPU). 0 enables autodetection (default). To determine
  1078. the correct value for your kernel, boot with normal
  1079. autodetection and see what value is printed. Note that
  1080. on SMP systems the preset will be applied to all CPUs,
  1081. which is likely to cause problems if your CPUs need
  1082. significantly divergent settings. An incorrect value
  1083. will cause delays in the kernel to be wrong, leading to
  1084. unpredictable I/O errors and other breakage. Although
  1085. unlikely, in the extreme case this might damage your
  1086. hardware.
  1087. ltpc= [NET]
  1088. Format: <io>,<irq>,<dma>
  1089. machvec= [IA64] Force the use of a particular machine-vector
  1090. (machvec) in a generic kernel.
  1091. Example: machvec=hpzx1_swiotlb
  1092. machtype= [Loongson] Share the same kernel image file between different
  1093. yeeloong laptop.
  1094. Example: machtype=lemote-yeeloong-2f-7inch
  1095. max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
  1096. than or equal to this physical address is ignored.
  1097. maxcpus= [SMP] Maximum number of processors that an SMP kernel
  1098. should make use of. maxcpus=n : n >= 0 limits the
  1099. kernel to using 'n' processors. n=0 is a special case,
  1100. it is equivalent to "nosmp", which also disables
  1101. the IO APIC.
  1102. max_loop= [LOOP] Maximum number of loopback devices that can
  1103. be mounted
  1104. Format: <1-256>
  1105. mcatest= [IA-64]
  1106. mce [X86-32] Machine Check Exception
  1107. mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
  1108. md= [HW] RAID subsystems devices and level
  1109. See Documentation/md.txt.
  1110. mdacon= [MDA]
  1111. Format: <first>,<last>
  1112. Specifies range of consoles to be captured by the MDA.
  1113. mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
  1114. Amount of memory to be used when the kernel is not able
  1115. to see the whole system memory or for test.
  1116. [X86-32] Use together with memmap= to avoid physical
  1117. address space collisions. Without memmap= PCI devices
  1118. could be placed at addresses belonging to unused RAM.
  1119. mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
  1120. memory.
  1121. memchunk=nn[KMG]
  1122. [KNL,SH] Allow user to override the default size for
  1123. per-device physically contiguous DMA buffers.
  1124. memmap=exactmap [KNL,X86] Enable setting of an exact
  1125. E820 memory map, as specified by the user.
  1126. Such memmap=exactmap lines can be constructed based on
  1127. BIOS output or other requirements. See the memmap=nn@ss
  1128. option description.
  1129. memmap=nn[KMG]@ss[KMG]
  1130. [KNL] Force usage of a specific region of memory
  1131. Region of memory to be used, from ss to ss+nn.
  1132. memmap=nn[KMG]#ss[KMG]
  1133. [KNL,ACPI] Mark specific memory as ACPI data.
  1134. Region of memory to be used, from ss to ss+nn.
  1135. memmap=nn[KMG]$ss[KMG]
  1136. [KNL,ACPI] Mark specific memory as reserved.
  1137. Region of memory to be used, from ss to ss+nn.
  1138. Example: Exclude memory from 0x18690000-0x1869ffff
  1139. memmap=64K$0x18690000
  1140. or
  1141. memmap=0x10000$0x18690000
  1142. memory_corruption_check=0/1 [X86]
  1143. Some BIOSes seem to corrupt the first 64k of
  1144. memory when doing things like suspend/resume.
  1145. Setting this option will scan the memory
  1146. looking for corruption. Enabling this will
  1147. both detect corruption and prevent the kernel
  1148. from using the memory being corrupted.
  1149. However, its intended as a diagnostic tool; if
  1150. repeatable BIOS-originated corruption always
  1151. affects the same memory, you can use memmap=
  1152. to prevent the kernel from using that memory.
  1153. memory_corruption_check_size=size [X86]
  1154. By default it checks for corruption in the low
  1155. 64k, making this memory unavailable for normal
  1156. use. Use this parameter to scan for
  1157. corruption in more or less memory.
  1158. memory_corruption_check_period=seconds [X86]
  1159. By default it checks for corruption every 60
  1160. seconds. Use this parameter to check at some
  1161. other rate. 0 disables periodic checking.
  1162. memtest= [KNL,X86] Enable memtest
  1163. Format: <integer>
  1164. default : 0 <disable>
  1165. Specifies the number of memtest passes to be
  1166. performed. Each pass selects another test
  1167. pattern from a given set of patterns. Memtest
  1168. fills the memory with this pattern, validates
  1169. memory contents and reserves bad memory
  1170. regions that are detected.
  1171. meye.*= [HW] Set MotionEye Camera parameters
  1172. See Documentation/video4linux/meye.txt.
  1173. mfgpt_irq= [IA-32] Specify the IRQ to use for the
  1174. Multi-Function General Purpose Timers on AMD Geode
  1175. platforms.
  1176. mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
  1177. the BIOS has incorrectly applied a workaround. TinyBIOS
  1178. version 0.98 is known to be affected, 0.99 fixes the
  1179. problem by letting the user disable the workaround.
  1180. mga= [HW,DRM]
  1181. min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
  1182. physical address is ignored.
  1183. mini2440= [ARM,HW,KNL]
  1184. Format:[0..2][b][c][t]
  1185. Default: "0tb"
  1186. MINI2440 configuration specification:
  1187. 0 - The attached screen is the 3.5" TFT
  1188. 1 - The attached screen is the 7" TFT
  1189. 2 - The VGA Shield is attached (1024x768)
  1190. Leaving out the screen size parameter will not load
  1191. the TFT driver, and the framebuffer will be left
  1192. unconfigured.
  1193. b - Enable backlight. The TFT backlight pin will be
  1194. linked to the kernel VESA blanking code and a GPIO
  1195. LED. This parameter is not necessary when using the
  1196. VGA shield.
  1197. c - Enable the s3c camera interface.
  1198. t - Reserved for enabling touchscreen support. The
  1199. touchscreen support is not enabled in the mainstream
  1200. kernel as of 2.6.30, a preliminary port can be found
  1201. in the "bleeding edge" mini2440 support kernel at
  1202. http://repo.or.cz/w/linux-2.6/mini2440.git
  1203. mminit_loglevel=
  1204. [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
  1205. parameter allows control of the logging verbosity for
  1206. the additional memory initialisation checks. A value
  1207. of 0 disables mminit logging and a level of 4 will
  1208. log everything. Information is printed at KERN_DEBUG
  1209. so loglevel=8 may also need to be specified.
  1210. mousedev.tap_time=
  1211. [MOUSE] Maximum time between finger touching and
  1212. leaving touchpad surface for touch to be considered
  1213. a tap and be reported as a left button click (for
  1214. touchpads working in absolute mode only).
  1215. Format: <msecs>
  1216. mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
  1217. reporting absolute coordinates, such as tablets
  1218. mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
  1219. reporting absolute coordinates, such as tablets
  1220. movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
  1221. is similar to kernelcore except it specifies the
  1222. amount of memory used for migratable allocations.
  1223. If both kernelcore and movablecore is specified,
  1224. then kernelcore will be at *least* the specified
  1225. value but may be more. If movablecore on its own
  1226. is specified, the administrator must be careful
  1227. that the amount of memory usable for all allocations
  1228. is not too small.
  1229. MTD_Partition= [MTD]
  1230. Format: <name>,<region-number>,<size>,<offset>
  1231. MTD_Region= [MTD] Format:
  1232. <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
  1233. mtdparts= [MTD]
  1234. See drivers/mtd/cmdlinepart.c.
  1235. multitce=off [PPC] This parameter disables the use of the pSeries
  1236. firmware feature for updating multiple TCE entries
  1237. at a time.
  1238. onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
  1239. Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
  1240. boundary - index of last SLC block on Flex-OneNAND.
  1241. The remaining blocks are configured as MLC blocks.
  1242. lock - Configure if Flex-OneNAND boundary should be locked.
  1243. Once locked, the boundary cannot be changed.
  1244. 1 indicates lock status, 0 indicates unlock status.
  1245. mtdset= [ARM]
  1246. ARM/S3C2412 JIVE boot control
  1247. See arch/arm/mach-s3c2412/mach-jive.c
  1248. mtouchusb.raw_coordinates=
  1249. [HW] Make the MicroTouch USB driver use raw coordinates
  1250. ('y', default) or cooked coordinates ('n')
  1251. mtrr_chunk_size=nn[KMG] [X86]
  1252. used for mtrr cleanup. It is largest continuous chunk
  1253. that could hold holes aka. UC entries.
  1254. mtrr_gran_size=nn[KMG] [X86]
  1255. Used for mtrr cleanup. It is granularity of mtrr block.
  1256. Default is 1.
  1257. Large value could prevent small alignment from
  1258. using up MTRRs.
  1259. mtrr_spare_reg_nr=n [X86]
  1260. Format: <integer>
  1261. Range: 0,7 : spare reg number
  1262. Default : 1
  1263. Used for mtrr cleanup. It is spare mtrr entries number.
  1264. Set to 2 or more if your graphical card needs more.
  1265. n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
  1266. netdev= [NET] Network devices parameters
  1267. Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
  1268. Note that mem_start is often overloaded to mean
  1269. something different and driver-specific.
  1270. This usage is only documented in each driver source
  1271. file if at all.
  1272. nf_conntrack.acct=
  1273. [NETFILTER] Enable connection tracking flow accounting
  1274. 0 to disable accounting
  1275. 1 to enable accounting
  1276. Default value is 0.
  1277. nfsaddrs= [NFS] Deprecated. Use ip= instead.
  1278. See Documentation/filesystems/nfs/nfsroot.txt.
  1279. nfsroot= [NFS] nfs root filesystem for disk-less boxes.
  1280. See Documentation/filesystems/nfs/nfsroot.txt.
  1281. nfsrootdebug [NFS] enable nfsroot debugging messages.
  1282. See Documentation/filesystems/nfs/nfsroot.txt.
  1283. nfs.callback_tcpport=
  1284. [NFS] set the TCP port on which the NFSv4 callback
  1285. channel should listen.
  1286. nfs.cache_getent=
  1287. [NFS] sets the pathname to the program which is used
  1288. to update the NFS client cache entries.
  1289. nfs.cache_getent_timeout=
  1290. [NFS] sets the timeout after which an attempt to
  1291. update a cache entry is deemed to have failed.
  1292. nfs.idmap_cache_timeout=
  1293. [NFS] set the maximum lifetime for idmapper cache
  1294. entries.
  1295. nfs.enable_ino64=
  1296. [NFS] enable 64-bit inode numbers.
  1297. If zero, the NFS client will fake up a 32-bit inode
  1298. number for the readdir() and stat() syscalls instead
  1299. of returning the full 64-bit number.
  1300. The default is to return 64-bit inode numbers.
  1301. nfs.nfs4_disable_idmapping=
  1302. [NFSv4] When set, this option disables the NFSv4
  1303. idmapper on the client, but only if the mount
  1304. is using the 'sec=sys' security flavour. This may
  1305. make migration from legacy NFSv2/v3 systems easier
  1306. provided that the server has the appropriate support.
  1307. The default is to always enable NFSv4 idmapping.
  1308. nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
  1309. when a NMI is triggered.
  1310. Format: [state][,regs][,debounce][,die]
  1311. nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
  1312. Format: [panic,][nopanic,][num]
  1313. Valid num: 0
  1314. 0 - turn nmi_watchdog off
  1315. When panic is specified, panic when an NMI watchdog
  1316. timeout occurs (or 'nopanic' to override the opposite
  1317. default).
  1318. This is useful when you use a panic=... timeout and
  1319. need the box quickly up again.
  1320. netpoll.carrier_timeout=
  1321. [NET] Specifies amount of time (in seconds) that
  1322. netpoll should wait for a carrier. By default netpoll
  1323. waits 4 seconds.
  1324. no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
  1325. emulation library even if a 387 maths coprocessor
  1326. is present.
  1327. no_console_suspend
  1328. [HW] Never suspend the console
  1329. Disable suspending of consoles during suspend and
  1330. hibernate operations. Once disabled, debugging
  1331. messages can reach various consoles while the rest
  1332. of the system is being put to sleep (ie, while
  1333. debugging driver suspend/resume hooks). This may
  1334. not work reliably with all consoles, but is known
  1335. to work with serial and VGA consoles.
  1336. noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
  1337. caches in the slab allocator. Saves per-node memory,
  1338. but will impact performance.
  1339. noalign [KNL,ARM]
  1340. noapic [SMP,APIC] Tells the kernel to not make use of any
  1341. IOAPICs that may be present in the system.
  1342. noautogroup Disable scheduler automatic task group creation.
  1343. nobats [PPC] Do not use BATs for mapping kernel lowmem
  1344. on "Classic" PPC cores.
  1345. nocache [ARM]
  1346. noclflush [BUGS=X86] Don't use the CLFLUSH instruction
  1347. nodelayacct [KNL] Disable per-task delay accounting
  1348. nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
  1349. nodsp [SH] Disable hardware DSP at boot time.
  1350. noefi [X86] Disable EFI runtime services support.
  1351. noexec [IA-64]
  1352. noexec [X86]
  1353. On X86-32 available only on PAE configured kernels.
  1354. noexec=on: enable non-executable mappings (default)
  1355. noexec=off: disable non-executable mappings
  1356. nosmep [X86]
  1357. Disable SMEP (Supervisor Mode Execution Protection)
  1358. even if it is supported by processor.
  1359. noexec32 [X86-64]
  1360. This affects only 32-bit executables.
  1361. noexec32=on: enable non-executable mappings (default)
  1362. read doesn't imply executable mappings
  1363. noexec32=off: disable non-executable mappings
  1364. read implies executable mappings
  1365. nofpu [SH] Disable hardware FPU at boot time.
  1366. nofxsr [BUGS=X86-32] Disables x86 floating point extended
  1367. register save and restore. The kernel will only save
  1368. legacy floating-point registers on task switch.
  1369. noxsave [BUGS=X86] Disables x86 extended register state save
  1370. and restore using xsave. The kernel will fallback to
  1371. enabling legacy floating-point and sse state.
  1372. nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
  1373. wfi(ARM) instruction doesn't work correctly and not to
  1374. use it. This is also useful when using JTAG debugger.
  1375. no-hlt [BUGS=X86-32] Tells the kernel that the hlt
  1376. instruction doesn't work correctly and not to
  1377. use it.
  1378. no_file_caps Tells the kernel not to honor file capabilities. The
  1379. only way then for a file to be executed with privilege
  1380. is to be setuid root or executed by root.
  1381. nohalt [IA-64] Tells the kernel not to use the power saving
  1382. function PAL_HALT_LIGHT when idle. This increases
  1383. power-consumption. On the positive side, it reduces
  1384. interrupt wake-up latency, which may improve performance
  1385. in certain environments such as networked servers or
  1386. real-time systems.
  1387. nohz= [KNL] Boottime enable/disable dynamic ticks
  1388. Valid arguments: on, off
  1389. Default: on
  1390. noiotrap [SH] Disables trapped I/O port accesses.
  1391. noirqdebug [X86-32] Disables the code which attempts to detect and
  1392. disable unhandled interrupt sources.
  1393. no_timer_check [X86,APIC] Disables the code which tests for
  1394. broken timer IRQ sources.
  1395. noisapnp [ISAPNP] Disables ISA PnP code.
  1396. noinitrd [RAM] Tells the kernel not to load any configured
  1397. initial RAM disk.
  1398. nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
  1399. remapping.
  1400. [Deprecated - use intremap=off]
  1401. nointroute [IA-64]
  1402. nojitter [IA64] Disables jitter checking for ITC timers.
  1403. no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
  1404. no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
  1405. fault handling.
  1406. no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
  1407. steal time is computed, but won't influence scheduler
  1408. behaviour
  1409. nolapic [X86-32,APIC] Do not enable or use the local APIC.
  1410. nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
  1411. noltlbs [PPC] Do not use large page/tlb entries for kernel
  1412. lowmem mapping on PPC40x.
  1413. nomca [IA-64] Disable machine check abort handling
  1414. nomce [X86-32] Machine Check Exception
  1415. nomfgpt [X86-32] Disable Multi-Function General Purpose
  1416. Timer usage (for AMD Geode machines).
  1417. nopat [X86] Disable PAT (page attribute table extension of
  1418. pagetables) support.
  1419. norandmaps Don't use address space randomization. Equivalent to
  1420. echo 0 > /proc/sys/kernel/randomize_va_space
  1421. noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
  1422. noreplace-smp [X86-32,SMP] Don't replace SMP instructions
  1423. with UP alternatives
  1424. noresidual [PPC] Don't use residual data on PReP machines.
  1425. noresume [SWSUSP] Disables resume and restores original swap
  1426. space.
  1427. no-scroll [VGA] Disables scrollback.
  1428. This is required for the Braillex ib80-piezo Braille
  1429. reader made by F.H. Papenmeier (Germany).
  1430. nosbagart [IA-64]
  1431. nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
  1432. nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
  1433. and disable the IO APIC. legacy for "maxcpus=0".
  1434. nosoftlockup [KNL] Disable the soft-lockup detector.
  1435. nosync [HW,M68K] Disables sync negotiation for all devices.
  1436. notsc [BUGS=X86-32] Disable Time Stamp Counter
  1437. nousb [USB] Disable the USB subsystem
  1438. nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
  1439. nowb [ARM]
  1440. nox2apic [X86-64,APIC] Do not enable x2APIC mode.
  1441. nptcg= [IA64] Override max number of concurrent global TLB
  1442. purges which is reported from either PAL_VM_SUMMARY or
  1443. SAL PALO.
  1444. nr_cpus= [SMP] Maximum number of processors that an SMP kernel
  1445. could support. nr_cpus=n : n >= 1 limits the kernel to
  1446. supporting 'n' processors. Later in runtime you can not
  1447. use hotplug cpu feature to put more cpu back to online.
  1448. just like you compile the kernel NR_CPUS=n
  1449. nr_uarts= [SERIAL] maximum number of UARTs to be registered.
  1450. numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
  1451. one of ['zone', 'node', 'default'] can be specified
  1452. This can be set from sysctl after boot.
  1453. See Documentation/sysctl/vm.txt for details.
  1454. ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
  1455. See Documentation/debugging-via-ohci1394.txt for more
  1456. info.
  1457. olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
  1458. Rather than timing out after 20 ms if an EC
  1459. command is not properly ACKed, override the length
  1460. of the timeout. We have interrupts disabled while
  1461. waiting for the ACK, so if this is set too high
  1462. interrupts *may* be lost!
  1463. omap_mux= [OMAP] Override bootloader pin multiplexing.
  1464. Format: <mux_mode0.mode_name=value>...
  1465. For example, to override I2C bus2:
  1466. omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
  1467. oprofile.timer= [HW]
  1468. Use timer interrupt instead of performance counters
  1469. oprofile.cpu_type= Force an oprofile cpu type
  1470. This might be useful if you have an older oprofile
  1471. userland or if you want common events.
  1472. Format: { arch_perfmon }
  1473. arch_perfmon: [X86] Force use of architectural
  1474. perfmon on Intel CPUs instead of the
  1475. CPU specific event set.
  1476. oops=panic Always panic on oopses. Default is to just kill the
  1477. process, but there is a small probability of
  1478. deadlocking the machine.
  1479. This will also cause panics on machine check exceptions.
  1480. Useful together with panic=30 to trigger a reboot.
  1481. OSS [HW,OSS]
  1482. See Documentation/sound/oss/oss-parameters.txt
  1483. panic= [KNL] Kernel behaviour on panic: delay <timeout>
  1484. timeout > 0: seconds before rebooting
  1485. timeout = 0: wait forever
  1486. timeout < 0: reboot immediately
  1487. Format: <timeout>
  1488. parkbd.port= [HW] Parallel port number the keyboard adapter is
  1489. connected to, default is 0.
  1490. Format: <parport#>
  1491. parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
  1492. 0 for XT, 1 for AT (default is AT).
  1493. Format: <mode>
  1494. parport= [HW,PPT] Specify parallel ports. 0 disables.
  1495. Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
  1496. Use 'auto' to force the driver to use any
  1497. IRQ/DMA settings detected (the default is to
  1498. ignore detected IRQ/DMA settings because of
  1499. possible conflicts). You can specify the base
  1500. address, IRQ, and DMA settings; IRQ and DMA
  1501. should be numbers, or 'auto' (for using detected
  1502. settings on that particular port), or 'nofifo'
  1503. (to avoid using a FIFO even if it is detected).
  1504. Parallel ports are assigned in the order they
  1505. are specified on the command line, starting
  1506. with parport0.
  1507. parport_init_mode= [HW,PPT]
  1508. Configure VIA parallel port to operate in
  1509. a specific mode. This is necessary on Pegasos
  1510. computer where firmware has no options for setting
  1511. up parallel port mode and sets it to spp.
  1512. Currently this function knows 686a and 8231 chips.
  1513. Format: [spp|ps2|epp|ecp|ecpepp]
  1514. pause_on_oops=
  1515. Halt all CPUs after the first oops has been printed for
  1516. the specified number of seconds. This is to be used if
  1517. your oopses keep scrolling off the screen.
  1518. pcbit= [HW,ISDN]
  1519. pcd. [PARIDE]
  1520. See header of drivers/block/paride/pcd.c.
  1521. See also Documentation/blockdev/paride.txt.
  1522. pci=option[,option...] [PCI] various PCI subsystem options:
  1523. earlydump [X86] dump PCI config space before the kernel
  1524. changes anything
  1525. off [X86] don't probe for the PCI bus
  1526. bios [X86-32] force use of PCI BIOS, don't access
  1527. the hardware directly. Use this if your machine
  1528. has a non-standard PCI host bridge.
  1529. nobios [X86-32] disallow use of PCI BIOS, only direct
  1530. hardware access methods are allowed. Use this
  1531. if you experience crashes upon bootup and you
  1532. suspect they are caused by the BIOS.
  1533. conf1 [X86] Force use of PCI Configuration
  1534. Mechanism 1.
  1535. conf2 [X86] Force use of PCI Configuration
  1536. Mechanism 2.
  1537. noaer [PCIE] If the PCIEAER kernel config parameter is
  1538. enabled, this kernel boot option can be used to
  1539. disable the use of PCIE advanced error reporting.
  1540. nodomains [PCI] Disable support for multiple PCI
  1541. root domains (aka PCI segments, in ACPI-speak).
  1542. nommconf [X86] Disable use of MMCONFIG for PCI
  1543. Configuration
  1544. check_enable_amd_mmconf [X86] check for and enable
  1545. properly configured MMIO access to PCI
  1546. config space on AMD family 10h CPU
  1547. nomsi [MSI] If the PCI_MSI kernel config parameter is
  1548. enabled, this kernel boot option can be used to
  1549. disable the use of MSI interrupts system-wide.
  1550. noioapicquirk [APIC] Disable all boot interrupt quirks.
  1551. Safety option to keep boot IRQs enabled. This
  1552. should never be necessary.
  1553. ioapicreroute [APIC] Enable rerouting of boot IRQs to the
  1554. primary IO-APIC for bridges that cannot disable
  1555. boot IRQs. This fixes a source of spurious IRQs
  1556. when the system masks IRQs.
  1557. noioapicreroute [APIC] Disable workaround that uses the
  1558. boot IRQ equivalent of an IRQ that connects to
  1559. a chipset where boot IRQs cannot be disabled.
  1560. The opposite of ioapicreroute.
  1561. biosirq [X86-32] Use PCI BIOS calls to get the interrupt
  1562. routing table. These calls are known to be buggy
  1563. on several machines and they hang the machine
  1564. when used, but on other computers it's the only
  1565. way to get the interrupt routing table. Try
  1566. this option if the kernel is unable to allocate
  1567. IRQs or discover secondary PCI buses on your
  1568. motherboard.
  1569. rom [X86] Assign address space to expansion ROMs.
  1570. Use with caution as certain devices share
  1571. address decoders between ROMs and other
  1572. resources.
  1573. norom [X86] Do not assign address space to
  1574. expansion ROMs that do not already have
  1575. BIOS assigned address ranges.
  1576. nobar [X86] Do not assign address space to the
  1577. BARs that weren't assigned by the BIOS.
  1578. irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
  1579. assigned automatically to PCI devices. You can
  1580. make the kernel exclude IRQs of your ISA cards
  1581. this way.
  1582. pirqaddr=0xAAAAA [X86] Specify the physical address
  1583. of the PIRQ table (normally generated
  1584. by the BIOS) if it is outside the
  1585. F0000h-100000h range.
  1586. lastbus=N [X86] Scan all buses thru bus #N. Can be
  1587. useful if the kernel is unable to find your
  1588. secondary buses and you want to tell it
  1589. explicitly which ones they are.
  1590. assign-busses [X86] Always assign all PCI bus
  1591. numbers ourselves, overriding
  1592. whatever the firmware may have done.
  1593. usepirqmask [X86] Honor the possible IRQ mask stored
  1594. in the BIOS $PIR table. This is needed on
  1595. some systems with broken BIOSes, notably
  1596. some HP Pavilion N5400 and Omnibook XE3
  1597. notebooks. This will have no effect if ACPI
  1598. IRQ routing is enabled.
  1599. noacpi [X86] Do not use ACPI for IRQ routing
  1600. or for PCI scanning.
  1601. use_crs [X86] Use PCI host bridge window information
  1602. from ACPI. On BIOSes from 2008 or later, this
  1603. is enabled by default. If you need to use this,
  1604. please report a bug.
  1605. nocrs [X86] Ignore PCI host bridge windows from ACPI.
  1606. If you need to use this, please report a bug.
  1607. routeirq Do IRQ routing for all PCI devices.
  1608. This is normally done in pci_enable_device(),
  1609. so this option is a temporary workaround
  1610. for broken drivers that don't call it.
  1611. skip_isa_align [X86] do not align io start addr, so can
  1612. handle more pci cards
  1613. firmware [ARM] Do not re-enumerate the bus but instead
  1614. just use the configuration from the
  1615. bootloader. This is currently used on
  1616. IXP2000 systems where the bus has to be
  1617. configured a certain way for adjunct CPUs.
  1618. noearly [X86] Don't do any early type 1 scanning.
  1619. This might help on some broken boards which
  1620. machine check when some devices' config space
  1621. is read. But various workarounds are disabled
  1622. and some IOMMU drivers will not work.
  1623. bfsort Sort PCI devices into breadth-first order.
  1624. This sorting is done to get a device
  1625. order compatible with older (<= 2.4) kernels.
  1626. nobfsort Don't sort PCI devices into breadth-first order.
  1627. cbiosize=nn[KMG] The fixed amount of bus space which is
  1628. reserved for the CardBus bridge's IO window.
  1629. The default value is 256 bytes.
  1630. cbmemsize=nn[KMG] The fixed amount of bus space which is
  1631. reserved for the CardBus bridge's memory
  1632. window. The default value is 64 megabytes.
  1633. resource_alignment=
  1634. Format:
  1635. [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
  1636. Specifies alignment and device to reassign
  1637. aligned memory resources.
  1638. If <order of align> is not specified,
  1639. PAGE_SIZE is used as alignment.
  1640. PCI-PCI bridge can be specified, if resource
  1641. windows need to be expanded.
  1642. ecrc= Enable/disable PCIe ECRC (transaction layer
  1643. end-to-end CRC checking).
  1644. bios: Use BIOS/firmware settings. This is the
  1645. the default.
  1646. off: Turn ECRC off
  1647. on: Turn ECRC on.
  1648. realloc reallocate PCI resources if allocations done by BIOS
  1649. are erroneous.
  1650. pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
  1651. Management.
  1652. off Disable ASPM.
  1653. force Enable ASPM even on devices that claim not to support it.
  1654. WARNING: Forcing ASPM on may cause system lockups.
  1655. pcie_ports= [PCIE] PCIe ports handling:
  1656. auto Ask the BIOS whether or not to use native PCIe services
  1657. associated with PCIe ports (PME, hot-plug, AER). Use
  1658. them only if that is allowed by the BIOS.
  1659. native Use native PCIe services associated with PCIe ports
  1660. unconditionally.
  1661. compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
  1662. ports driver.
  1663. pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
  1664. nomsi Do not use MSI for native PCIe PME signaling (this makes
  1665. all PCIe root ports use INTx for all services).
  1666. pcmv= [HW,PCMCIA] BadgePAD 4
  1667. pd. [PARIDE]
  1668. See Documentation/blockdev/paride.txt.
  1669. pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
  1670. boot time.
  1671. Format: { 0 | 1 }
  1672. See arch/parisc/kernel/pdc_chassis.c
  1673. percpu_alloc= Select which percpu first chunk allocator to use.
  1674. Currently supported values are "embed" and "page".
  1675. Archs may support subset or none of the selections.
  1676. See comments in mm/percpu.c for details on each
  1677. allocator. This parameter is primarily for debugging
  1678. and performance comparison.
  1679. pf. [PARIDE]
  1680. See Documentation/blockdev/paride.txt.
  1681. pg. [PARIDE]
  1682. See Documentation/blockdev/paride.txt.
  1683. pirq= [SMP,APIC] Manual mp-table setup
  1684. See Documentation/x86/i386/IO-APIC.txt.
  1685. plip= [PPT,NET] Parallel port network link
  1686. Format: { parport<nr> | timid | 0 }
  1687. See also Documentation/parport.txt.
  1688. pmtmr= [X86] Manual setup of pmtmr I/O Port.
  1689. Override pmtimer IOPort with a hex value.
  1690. e.g. pmtmr=0x508
  1691. pnp.debug [PNP]
  1692. Enable PNP debug messages. This depends on the
  1693. CONFIG_PNP_DEBUG_MESSAGES option.
  1694. pnpacpi= [ACPI]
  1695. { off }
  1696. pnpbios= [ISAPNP]
  1697. { on | off | curr | res | no-curr | no-res }
  1698. pnp_reserve_irq=
  1699. [ISAPNP] Exclude IRQs for the autoconfiguration
  1700. pnp_reserve_dma=
  1701. [ISAPNP] Exclude DMAs for the autoconfiguration
  1702. pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
  1703. Ranges are in pairs (I/O port base and size).
  1704. pnp_reserve_mem=
  1705. [ISAPNP] Exclude memory regions for the
  1706. autoconfiguration.
  1707. Ranges are in pairs (memory base and size).
  1708. ports= [IP_VS_FTP] IPVS ftp helper module
  1709. Default is 21.
  1710. Up to 8 (IP_VS_APP_MAX_PORTS) ports
  1711. may be specified.
  1712. Format: <port>,<port>....
  1713. print-fatal-signals=
  1714. [KNL] debug: print fatal signals
  1715. If enabled, warn about various signal handling
  1716. related application anomalies: too many signals,
  1717. too many POSIX.1 timers, fatal signals causing a
  1718. coredump - etc.
  1719. If you hit the warning due to signal overflow,
  1720. you might want to try "ulimit -i unlimited".
  1721. default: off.
  1722. printk.time= Show timing data prefixed to each printk message line
  1723. Format: <bool> (1/Y/y=enable, 0/N/n=disable)
  1724. processor.max_cstate= [HW,ACPI]
  1725. Limit processor to maximum C-state
  1726. max_cstate=9 overrides any DMI blacklist limit.
  1727. processor.nocst [HW,ACPI]
  1728. Ignore the _CST method to determine C-states,
  1729. instead using the legacy FADT method
  1730. profile= [KNL] Enable kernel profiling via /proc/profile
  1731. Format: [schedule,]<number>
  1732. Param: "schedule" - profile schedule points.
  1733. Param: <number> - step/bucket size as a power of 2 for
  1734. statistical time based profiling.
  1735. Param: "sleep" - profile D-state sleeping (millisecs).
  1736. Requires CONFIG_SCHEDSTATS
  1737. Param: "kvm" - profile VM exits.
  1738. prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
  1739. before loading.
  1740. See Documentation/blockdev/ramdisk.txt.
  1741. psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
  1742. probe for; one of (bare|imps|exps|lifebook|any).
  1743. psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
  1744. per second.
  1745. psmouse.resetafter= [HW,MOUSE]
  1746. Try to reset the device after so many bad packets
  1747. (0 = never).
  1748. psmouse.resolution=
  1749. [HW,MOUSE] Set desired mouse resolution, in dpi.
  1750. psmouse.smartscroll=
  1751. [HW,MOUSE] Controls Logitech smartscroll autorepeat.
  1752. 0 = disabled, 1 = enabled (default).
  1753. pstore.backend= Specify the name of the pstore backend to use
  1754. pt. [PARIDE]
  1755. See Documentation/blockdev/paride.txt.
  1756. pty.legacy_count=
  1757. [KNL] Number of legacy pty's. Overwrites compiled-in
  1758. default number.
  1759. quiet [KNL] Disable most log messages
  1760. r128= [HW,DRM]
  1761. raid= [HW,RAID]
  1762. See Documentation/md.txt.
  1763. ramdisk_blocksize= [RAM]
  1764. See Documentation/blockdev/ramdisk.txt.
  1765. ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
  1766. See Documentation/blockdev/ramdisk.txt.
  1767. rcupdate.blimit= [KNL,BOOT]
  1768. Set maximum number of finished RCU callbacks to process
  1769. in one batch.
  1770. rcupdate.qhimark= [KNL,BOOT]
  1771. Set threshold of queued
  1772. RCU callbacks over which batch limiting is disabled.
  1773. rcupdate.qlowmark= [KNL,BOOT]
  1774. Set threshold of queued RCU callbacks below which
  1775. batch limiting is re-enabled.
  1776. rdinit= [KNL]
  1777. Format: <full_path>
  1778. Run specified binary instead of /init from the ramdisk,
  1779. used for early userspace startup. See initrd.
  1780. reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
  1781. Format: <reboot_mode>[,<reboot_mode2>[,...]]
  1782. See arch/*/kernel/reboot.c or arch/*/kernel/process.c
  1783. relax_domain_level=
  1784. [KNL, SMP] Set scheduler's default relax_domain_level.
  1785. See Documentation/cgroups/cpusets.txt.
  1786. reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
  1787. reservetop= [X86-32]
  1788. Format: nn[KMG]
  1789. Reserves a hole at the top of the kernel virtual
  1790. address space.
  1791. reservelow= [X86]
  1792. Format: nn[K]
  1793. Set the amount of memory to reserve for BIOS at
  1794. the bottom of the address space.
  1795. reset_devices [KNL] Force drivers to reset the underlying device
  1796. during initialization.
  1797. resume= [SWSUSP]
  1798. Specify the partition device for software suspend
  1799. resume_offset= [SWSUSP]
  1800. Specify the offset from the beginning of the partition
  1801. given by "resume=" at which the swap header is located,
  1802. in <PAGE_SIZE> units (needed only for swap files).
  1803. See Documentation/power/swsusp-and-swap-files.txt
  1804. hibernate= [HIBERNATION]
  1805. noresume Don't check if there's a hibernation image
  1806. present during boot.
  1807. nocompress Don't compress/decompress hibernation images.
  1808. retain_initrd [RAM] Keep initrd memory after extraction
  1809. rhash_entries= [KNL,NET]
  1810. Set number of hash buckets for route cache
  1811. riscom8= [HW,SERIAL]
  1812. Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
  1813. ro [KNL] Mount root device read-only on boot
  1814. root= [KNL] Root filesystem
  1815. See name_to_dev_t comment in init/do_mounts.c.
  1816. rootdelay= [KNL] Delay (in seconds) to pause before attempting to
  1817. mount the root filesystem
  1818. rootflags= [KNL] Set root filesystem mount option string
  1819. rootfstype= [KNL] Set root filesystem type
  1820. rootwait [KNL] Wait (indefinitely) for root device to show up.
  1821. Useful for devices that are detected asynchronously
  1822. (e.g. USB and MMC devices).
  1823. rw [KNL] Mount root device read-write on boot
  1824. S [KNL] Run init in single mode
  1825. sa1100ir [NET]
  1826. See drivers/net/irda/sa1100_ir.c.
  1827. sbni= [NET] Granch SBNI12 leased line adapter
  1828. sched_debug [KNL] Enables verbose scheduler debug messages.
  1829. security= [SECURITY] Choose a security module to enable at boot.
  1830. If this boot parameter is not specified, only the first
  1831. security module asking for security registration will be
  1832. loaded. An invalid security module name will be treated
  1833. as if no module has been chosen.
  1834. selinux= [SELINUX] Disable or enable SELinux at boot time.
  1835. Format: { "0" | "1" }
  1836. See security/selinux/Kconfig help text.
  1837. 0 -- disable.
  1838. 1 -- enable.
  1839. Default value is set via kernel config option.
  1840. If enabled at boot time, /selinux/disable can be used
  1841. later to disable prior to initial policy load.
  1842. apparmor= [APPARMOR] Disable or enable AppArmor at boot time
  1843. Format: { "0" | "1" }
  1844. See security/apparmor/Kconfig help text
  1845. 0 -- disable.
  1846. 1 -- enable.
  1847. Default value is set via kernel config option.
  1848. serialnumber [BUGS=X86-32]
  1849. shapers= [NET]
  1850. Maximal number of shapers.
  1851. show_msr= [x86] show boot-time MSR settings
  1852. Format: { <integer> }
  1853. Show boot-time (BIOS-initialized) MSR settings.
  1854. The parameter means the number of CPUs to show,
  1855. for example 1 means boot CPU only.
  1856. simeth= [IA-64]
  1857. simscsi=
  1858. slram= [HW,MTD]
  1859. slub_debug[=options[,slabs]] [MM, SLUB]
  1860. Enabling slub_debug allows one to determine the
  1861. culprit if slab objects become corrupted. Enabling
  1862. slub_debug can create guard zones around objects and
  1863. may poison objects when not in use. Also tracks the
  1864. last alloc / free. For more information see
  1865. Documentation/vm/slub.txt.
  1866. slub_max_order= [MM, SLUB]
  1867. Determines the maximum allowed order for slabs.
  1868. A high setting may cause OOMs due to memory
  1869. fragmentation. For more information see
  1870. Documentation/vm/slub.txt.
  1871. slub_min_objects= [MM, SLUB]
  1872. The minimum number of objects per slab. SLUB will
  1873. increase the slab order up to slub_max_order to
  1874. generate a sufficiently large slab able to contain
  1875. the number of objects indicated. The higher the number
  1876. of objects the smaller the overhead of tracking slabs
  1877. and the less frequently locks need to be acquired.
  1878. For more information see Documentation/vm/slub.txt.
  1879. slub_min_order= [MM, SLUB]
  1880. Determines the mininum page order for slabs. Must be
  1881. lower than slub_max_order.
  1882. For more information see Documentation/vm/slub.txt.
  1883. slub_nomerge [MM, SLUB]
  1884. Disable merging of slabs with similar size. May be
  1885. necessary if there is some reason to distinguish
  1886. allocs to different slabs. Debug options disable
  1887. merging on their own.
  1888. For more information see Documentation/vm/slub.txt.
  1889. smart2= [HW]
  1890. Format: <io1>[,<io2>[,...,<io8>]]
  1891. smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
  1892. attempt to substitute SMP alternatives once at boot.
  1893. smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
  1894. smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
  1895. smsc-ircc2.ircc_sir= [HW] SIR base I/O port
  1896. smsc-ircc2.ircc_fir= [HW] FIR base I/O port
  1897. smsc-ircc2.ircc_irq= [HW] IRQ line
  1898. smsc-ircc2.ircc_dma= [HW] DMA channel
  1899. smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
  1900. 0: Toshiba Satellite 1800 (GP data pin select)
  1901. 1: Fast pin select (default)
  1902. 2: ATC IRMode
  1903. softlockup_panic=
  1904. [KNL] Should the soft-lockup detector generate panics.
  1905. Format: <integer>
  1906. sonypi.*= [HW] Sony Programmable I/O Control Device driver
  1907. See Documentation/sonypi.txt
  1908. specialix= [HW,SERIAL] Specialix multi-serial port adapter
  1909. See Documentation/serial/specialix.txt.
  1910. spia_io_base= [HW,MTD]
  1911. spia_fio_base=
  1912. spia_pedr=
  1913. spia_peddr=
  1914. stacktrace [FTRACE]
  1915. Enabled the stack tracer on boot up.
  1916. sti= [PARISC,HW]
  1917. Format: <num>
  1918. Set the STI (builtin display/keyboard on the HP-PARISC
  1919. machines) console (graphic card) which should be used
  1920. as the initial boot-console.
  1921. See also comment in drivers/video/console/sticore.c.
  1922. sti_font= [HW]
  1923. See comment in drivers/video/console/sticore.c.
  1924. stifb= [HW]
  1925. Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
  1926. sunrpc.min_resvport=
  1927. sunrpc.max_resvport=
  1928. [NFS,SUNRPC]
  1929. SunRPC servers often require that client requests
  1930. originate from a privileged port (i.e. a port in the
  1931. range 0 < portnr < 1024).
  1932. An administrator who wishes to reserve some of these
  1933. ports for other uses may adjust the range that the
  1934. kernel's sunrpc client considers to be privileged
  1935. using these two parameters to set the minimum and
  1936. maximum port values.
  1937. sunrpc.pool_mode=
  1938. [NFS]
  1939. Control how the NFS server code allocates CPUs to
  1940. service thread pools. Depending on how many NICs
  1941. you have and where their interrupts are bound, this
  1942. option will affect which CPUs will do NFS serving.
  1943. Note: this parameter cannot be changed while the
  1944. NFS server is running.
  1945. auto the server chooses an appropriate mode
  1946. automatically using heuristics
  1947. global a single global pool contains all CPUs
  1948. percpu one pool for each CPU
  1949. pernode one pool for each NUMA node (equivalent
  1950. to global on non-NUMA machines)
  1951. sunrpc.tcp_slot_table_entries=
  1952. sunrpc.udp_slot_table_entries=
  1953. [NFS,SUNRPC]
  1954. Sets the upper limit on the number of simultaneous
  1955. RPC calls that can be sent from the client to a
  1956. server. Increasing these values may allow you to
  1957. improve throughput, but will also increase the
  1958. amount of memory reserved for use by the client.
  1959. swapaccount[=0|1]
  1960. [KNL] Enable accounting of swap in memory resource
  1961. controller if no parameter or 1 is given or disable
  1962. it if 0 is given (See Documentation/cgroups/memory.txt)
  1963. swiotlb= [IA-64] Number of I/O TLB slabs
  1964. switches= [HW,M68k]
  1965. sysfs.deprecated=0|1 [KNL]
  1966. Enable/disable old style sysfs layout for old udev
  1967. on older distributions. When this option is enabled
  1968. very new udev will not work anymore. When this option
  1969. is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
  1970. in older udev will not work anymore.
  1971. Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
  1972. the kernel configuration.
  1973. sysrq_always_enabled
  1974. [KNL]
  1975. Ignore sysrq setting - this boot parameter will
  1976. neutralize any effect of /proc/sys/kernel/sysrq.
  1977. Useful for debugging.
  1978. tdfx= [HW,DRM]
  1979. test_suspend= [SUSPEND]
  1980. Specify "mem" (for Suspend-to-RAM) or "standby" (for
  1981. standby suspend) as the system sleep state to briefly
  1982. enter during system startup. The system is woken from
  1983. this state using a wakeup-capable RTC alarm.
  1984. thash_entries= [KNL,NET]
  1985. Set number of hash buckets for TCP connection
  1986. thermal.act= [HW,ACPI]
  1987. -1: disable all active trip points in all thermal zones
  1988. <degrees C>: override all lowest active trip points
  1989. thermal.crt= [HW,ACPI]
  1990. -1: disable all critical trip points in all thermal zones
  1991. <degrees C>: override all critical trip points
  1992. thermal.nocrt= [HW,ACPI]
  1993. Set to disable actions on ACPI thermal zone
  1994. critical and hot trip points.
  1995. thermal.off= [HW,ACPI]
  1996. 1: disable ACPI thermal control
  1997. thermal.psv= [HW,ACPI]
  1998. -1: disable all passive trip points
  1999. <degrees C>: override all passive trip points to this
  2000. value
  2001. thermal.tzp= [HW,ACPI]
  2002. Specify global default ACPI thermal zone polling rate
  2003. <deci-seconds>: poll all this frequency
  2004. 0: no polling (default)
  2005. threadirqs [KNL]
  2006. Force threading of all interrupt handlers except those
  2007. marked explicitely IRQF_NO_THREAD.
  2008. topology= [S390]
  2009. Format: {off | on}
  2010. Specify if the kernel should make use of the cpu
  2011. topology information if the hardware supports this.
  2012. The scheduler will make use of this information and
  2013. e.g. base its process migration decisions on it.
  2014. Default is on.
  2015. tp720= [HW,PS2]
  2016. tpm_suspend_pcr=[HW,TPM]
  2017. Format: integer pcr id
  2018. Specify that at suspend time, the tpm driver
  2019. should extend the specified pcr with zeros,
  2020. as a workaround for some chips which fail to
  2021. flush the last written pcr on TPM_SaveState.
  2022. This will guarantee that all the other pcrs
  2023. are saved.
  2024. trace_buf_size=nn[KMG]
  2025. [FTRACE] will set tracing buffer size.
  2026. trace_event=[event-list]
  2027. [FTRACE] Set and start specified trace events in order
  2028. to facilitate early boot debugging.
  2029. See also Documentation/trace/events.txt
  2030. tsc= Disable clocksource stability checks for TSC.
  2031. Format: <string>
  2032. [x86] reliable: mark tsc clocksource as reliable, this
  2033. disables clocksource verification at runtime, as well
  2034. as the stability checks done at bootup. Used to enable
  2035. high-resolution timer mode on older hardware, and in
  2036. virtualized environment.
  2037. [x86] noirqtime: Do not use TSC to do irq accounting.
  2038. Used to run time disable IRQ_TIME_ACCOUNTING on any
  2039. platforms where RDTSC is slow and this accounting
  2040. can add overhead.
  2041. turbografx.map[2|3]= [HW,JOY]
  2042. TurboGraFX parallel port interface
  2043. Format:
  2044. <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
  2045. See also Documentation/input/joystick-parport.txt
  2046. udbg-immortal [PPC] When debugging early kernel crashes that
  2047. happen after console_init() and before a proper
  2048. console driver takes over, this boot options might
  2049. help "seeing" what's going on.
  2050. uhash_entries= [KNL,NET]
  2051. Set number of hash buckets for UDP/UDP-Lite connections
  2052. uhci-hcd.ignore_oc=
  2053. [USB] Ignore overcurrent events (default N).
  2054. Some badly-designed motherboards generate lots of
  2055. bogus events, for ports that aren't wired to
  2056. anything. Set this parameter to avoid log spamming.
  2057. Note that genuine overcurrent events won't be
  2058. reported either.
  2059. unknown_nmi_panic
  2060. [X86] Cause panic on unknown NMI.
  2061. usbcore.authorized_default=
  2062. [USB] Default USB device authorization:
  2063. (default -1 = authorized except for wireless USB,
  2064. 0 = not authorized, 1 = authorized)
  2065. usbcore.autosuspend=
  2066. [USB] The autosuspend time delay (in seconds) used
  2067. for newly-detected USB devices (default 2). This
  2068. is the time required before an idle device will be
  2069. autosuspended. Devices for which the delay is set
  2070. to a negative value won't be autosuspended at all.
  2071. usbcore.usbfs_snoop=
  2072. [USB] Set to log all usbfs traffic (default 0 = off).
  2073. usbcore.blinkenlights=
  2074. [USB] Set to cycle leds on hubs (default 0 = off).
  2075. usbcore.old_scheme_first=
  2076. [USB] Start with the old device initialization
  2077. scheme (default 0 = off).
  2078. usbcore.use_both_schemes=
  2079. [USB] Try the other device initialization scheme
  2080. if the first one fails (default 1 = enabled).
  2081. usbcore.initial_descriptor_timeout=
  2082. [USB] Specifies timeout for the initial 64-byte
  2083. USB_REQ_GET_DESCRIPTOR request in milliseconds
  2084. (default 5000 = 5.0 seconds).
  2085. usbhid.mousepoll=
  2086. [USBHID] The interval which mice are to be polled at.
  2087. usb-storage.delay_use=
  2088. [UMS] The delay in seconds before a new device is
  2089. scanned for Logical Units (default 5).
  2090. usb-storage.quirks=
  2091. [UMS] A list of quirks entries to supplement or
  2092. override the built-in unusual_devs list. List
  2093. entries are separated by commas. Each entry has
  2094. the form VID:PID:Flags where VID and PID are Vendor
  2095. and Product ID values (4-digit hex numbers) and
  2096. Flags is a set of characters, each corresponding
  2097. to a common usb-storage quirk flag as follows:
  2098. a = SANE_SENSE (collect more than 18 bytes
  2099. of sense data);
  2100. b = BAD_SENSE (don't collect more than 18
  2101. bytes of sense data);
  2102. c = FIX_CAPACITY (decrease the reported
  2103. device capacity by one sector);
  2104. d = NO_READ_DISC_INFO (don't use
  2105. READ_DISC_INFO command);
  2106. e = NO_READ_CAPACITY_16 (don't use
  2107. READ_CAPACITY_16 command);
  2108. h = CAPACITY_HEURISTICS (decrease the
  2109. reported device capacity by one
  2110. sector if the number is odd);
  2111. i = IGNORE_DEVICE (don't bind to this
  2112. device);
  2113. l = NOT_LOCKABLE (don't try to lock and
  2114. unlock ejectable media);
  2115. m = MAX_SECTORS_64 (don't transfer more
  2116. than 64 sectors = 32 KB at a time);
  2117. n = INITIAL_READ10 (force a retry of the
  2118. initial READ(10) command);
  2119. o = CAPACITY_OK (accept the capacity
  2120. reported by the device);
  2121. r = IGNORE_RESIDUE (the device reports
  2122. bogus residue values);
  2123. s = SINGLE_LUN (the device has only one
  2124. Logical Unit);
  2125. w = NO_WP_DETECT (don't test whether the
  2126. medium is write-protected).
  2127. Example: quirks=0419:aaf5:rl,0421:0433:rc
  2128. userpte=
  2129. [X86] Flags controlling user PTE allocations.
  2130. nohigh = do not allocate PTE pages in
  2131. HIGHMEM regardless of setting
  2132. of CONFIG_HIGHPTE.
  2133. vdso= [X86,SH]
  2134. vdso=2: enable compat VDSO (default with COMPAT_VDSO)
  2135. vdso=1: enable VDSO (default)
  2136. vdso=0: disable VDSO mapping
  2137. vdso32= [X86]
  2138. vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
  2139. vdso32=1: enable 32-bit VDSO (default)
  2140. vdso32=0: disable 32-bit VDSO mapping
  2141. vector= [IA-64,SMP]
  2142. vector=percpu: enable percpu vector domain
  2143. video= [FB] Frame buffer configuration
  2144. See Documentation/fb/modedb.txt.
  2145. vga= [BOOT,X86-32] Select a particular video mode
  2146. See Documentation/x86/boot.txt and
  2147. Documentation/svga.txt.
  2148. Use vga=ask for menu.
  2149. This is actually a boot loader parameter; the value is
  2150. passed to the kernel using a special protocol.
  2151. vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
  2152. size of <nn>. This can be used to increase the
  2153. minimum size (128MB on x86). It can also be used to
  2154. decrease the size and leave more room for directly
  2155. mapped kernel RAM.
  2156. vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
  2157. Format: <command>
  2158. vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
  2159. Format: <command>
  2160. vmpoff= [KNL,S390] Perform z/VM CP command after power off.
  2161. Format: <command>
  2162. vt.cur_default= [VT] Default cursor shape.
  2163. Format: 0xCCBBAA, where AA, BB, and CC are the same as
  2164. the parameters of the <Esc>[?A;B;Cc escape sequence;
  2165. see VGA-softcursor.txt. Default: 2 = underline.
  2166. vt.default_blu= [VT]
  2167. Format: <blue0>,<blue1>,<blue2>,...,<blue15>
  2168. Change the default blue palette of the console.
  2169. This is a 16-member array composed of values
  2170. ranging from 0-255.
  2171. vt.default_grn= [VT]
  2172. Format: <green0>,<green1>,<green2>,...,<green15>
  2173. Change the default green palette of the console.
  2174. This is a 16-member array composed of values
  2175. ranging from 0-255.
  2176. vt.default_red= [VT]
  2177. Format: <red0>,<red1>,<red2>,...,<red15>
  2178. Change the default red palette of the console.
  2179. This is a 16-member array composed of values
  2180. ranging from 0-255.
  2181. vt.default_utf8=
  2182. [VT]
  2183. Format=<0|1>
  2184. Set system-wide default UTF-8 mode for all tty's.
  2185. Default is 1, i.e. UTF-8 mode is enabled for all
  2186. newly opened terminals.
  2187. vt.global_cursor_default=
  2188. [VT]
  2189. Format=<-1|0|1>
  2190. Set system-wide default for whether a cursor
  2191. is shown on new VTs. Default is -1,
  2192. i.e. cursors will be created by default unless
  2193. overridden by individual drivers. 0 will hide
  2194. cursors, 1 will display them.
  2195. watchdog timers [HW,WDT] For information on watchdog timers,
  2196. see Documentation/watchdog/watchdog-parameters.txt
  2197. or other driver-specific files in the
  2198. Documentation/watchdog/ directory.
  2199. x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
  2200. default x2apic cluster mode on platforms
  2201. supporting x2apic.
  2202. x86_mrst_timer= [X86-32,APBT]
  2203. Choose timer option for x86 Moorestown MID platform.
  2204. Two valid options are apbt timer only and lapic timer
  2205. plus one apbt timer for broadcast timer.
  2206. x86_mrst_timer=apbt_only | lapic_and_apbt
  2207. xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
  2208. xd_geo= See header of drivers/block/xd.c.
  2209. xen_emul_unplug= [HW,X86,XEN]
  2210. Unplug Xen emulated devices
  2211. Format: [unplug0,][unplug1]
  2212. ide-disks -- unplug primary master IDE devices
  2213. aux-ide-disks -- unplug non-primary-master IDE devices
  2214. nics -- unplug network devices
  2215. all -- unplug all emulated devices (NICs and IDE disks)
  2216. unnecessary -- unplugging emulated devices is
  2217. unnecessary even if the host did not respond to
  2218. the unplug protocol
  2219. never -- do not unplug even if version check succeeds
  2220. xirc2ps_cs= [NET,PCMCIA]
  2221. Format:
  2222. <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
  2223. ______________________________________________________________________
  2224. TODO:
  2225. Add more DRM drivers.