kernel-parameters.txt 66 KB

1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991001011021031041051061071081091101111121131141151161171181191201211221231241251261271281291301311321331341351361371381391401411421431441451461471481491501511521531541551561571581591601611621631641651661671681691701711721731741751761771781791801811821831841851861871881891901911921931941951961971981992002012022032042052062072082092102112122132142152162172182192202212222232242252262272282292302312322332342352362372382392402412422432442452462472482492502512522532542552562572582592602612622632642652662672682692702712722732742752762772782792802812822832842852862872882892902912922932942952962972982993003013023033043053063073083093103113123133143153163173183193203213223233243253263273283293303313323333343353363373383393403413423433443453463473483493503513523533543553563573583593603613623633643653663673683693703713723733743753763773783793803813823833843853863873883893903913923933943953963973983994004014024034044054064074084094104114124134144154164174184194204214224234244254264274284294304314324334344354364374384394404414424434444454464474484494504514524534544554564574584594604614624634644654664674684694704714724734744754764774784794804814824834844854864874884894904914924934944954964974984995005015025035045055065075085095105115125135145155165175185195205215225235245255265275285295305315325335345355365375385395405415425435445455465475485495505515525535545555565575585595605615625635645655665675685695705715725735745755765775785795805815825835845855865875885895905915925935945955965975985996006016026036046056066076086096106116126136146156166176186196206216226236246256266276286296306316326336346356366376386396406416426436446456466476486496506516526536546556566576586596606616626636646656666676686696706716726736746756766776786796806816826836846856866876886896906916926936946956966976986997007017027037047057067077087097107117127137147157167177187197207217227237247257267277287297307317327337347357367377387397407417427437447457467477487497507517527537547557567577587597607617627637647657667677687697707717727737747757767777787797807817827837847857867877887897907917927937947957967977987998008018028038048058068078088098108118128138148158168178188198208218228238248258268278288298308318328338348358368378388398408418428438448458468478488498508518528538548558568578588598608618628638648658668678688698708718728738748758768778788798808818828838848858868878888898908918928938948958968978988999009019029039049059069079089099109119129139149159169179189199209219229239249259269279289299309319329339349359369379389399409419429439449459469479489499509519529539549559569579589599609619629639649659669679689699709719729739749759769779789799809819829839849859869879889899909919929939949959969979989991000100110021003100410051006100710081009101010111012101310141015101610171018101910201021102210231024102510261027102810291030103110321033103410351036103710381039104010411042104310441045104610471048104910501051105210531054105510561057105810591060106110621063106410651066106710681069107010711072107310741075107610771078107910801081108210831084108510861087108810891090109110921093109410951096109710981099110011011102110311041105110611071108110911101111111211131114111511161117111811191120112111221123112411251126112711281129113011311132113311341135113611371138113911401141114211431144114511461147114811491150115111521153115411551156115711581159116011611162116311641165116611671168116911701171117211731174117511761177117811791180118111821183118411851186118711881189119011911192119311941195119611971198119912001201120212031204120512061207120812091210121112121213121412151216121712181219122012211222122312241225122612271228122912301231123212331234123512361237123812391240124112421243124412451246124712481249125012511252125312541255125612571258125912601261126212631264126512661267126812691270127112721273127412751276127712781279128012811282128312841285128612871288128912901291129212931294129512961297129812991300130113021303130413051306130713081309131013111312131313141315131613171318131913201321132213231324132513261327132813291330133113321333133413351336133713381339134013411342134313441345134613471348134913501351135213531354135513561357135813591360136113621363136413651366136713681369137013711372137313741375137613771378137913801381138213831384138513861387138813891390139113921393139413951396139713981399140014011402140314041405140614071408140914101411141214131414141514161417141814191420142114221423142414251426142714281429143014311432143314341435143614371438143914401441144214431444144514461447144814491450145114521453145414551456145714581459146014611462146314641465146614671468146914701471147214731474147514761477147814791480148114821483148414851486148714881489149014911492149314941495149614971498149915001501150215031504150515061507150815091510151115121513151415151516151715181519152015211522152315241525152615271528152915301531153215331534153515361537153815391540154115421543154415451546154715481549155015511552155315541555155615571558155915601561156215631564156515661567156815691570157115721573157415751576157715781579158015811582158315841585158615871588158915901591159215931594159515961597159815991600160116021603160416051606160716081609161016111612161316141615161616171618161916201621162216231624162516261627162816291630163116321633163416351636163716381639164016411642164316441645164616471648164916501651165216531654165516561657165816591660166116621663166416651666166716681669167016711672167316741675167616771678167916801681168216831684168516861687168816891690169116921693169416951696169716981699170017011702170317041705170617071708170917101711171217131714171517161717171817191720172117221723172417251726172717281729173017311732173317341735173617371738173917401741174217431744174517461747174817491750175117521753175417551756175717581759176017611762176317641765176617671768176917701771177217731774177517761777177817791780178117821783178417851786178717881789179017911792179317941795179617971798179918001801180218031804180518061807180818091810181118121813181418151816181718181819182018211822182318241825182618271828182918301831183218331834183518361837183818391840184118421843184418451846184718481849185018511852185318541855185618571858185918601861186218631864186518661867186818691870187118721873187418751876187718781879188018811882188318841885188618871888188918901891189218931894189518961897189818991900190119021903190419051906190719081909191019111912191319141915191619171918191919201921192219231924192519261927192819291930193119321933193419351936193719381939194019411942194319441945194619471948194919501951195219531954195519561957195819591960196119621963196419651966196719681969197019711972197319741975197619771978197919801981198219831984198519861987198819891990199119921993199419951996199719981999200020012002200320042005200620072008200920102011201220132014201520162017201820192020202120222023202420252026202720282029203020312032203320342035203620372038203920402041204220432044204520462047204820492050205120522053205420552056205720582059206020612062206320642065206620672068206920702071207220732074207520762077207820792080208120822083208420852086208720882089209020912092209320942095209620972098209921002101210221032104210521062107210821092110211121122113211421152116211721182119212021212122
  1. Kernel Parameters
  2. ~~~~~~~~~~~~~~~~~
  3. The following is a consolidated list of the kernel parameters as implemented
  4. (mostly) by the __setup() macro and sorted into English Dictionary order
  5. (defined as ignoring all punctuation and sorting digits before letters in a
  6. case insensitive manner), and with descriptions where known.
  7. Module parameters for loadable modules are specified only as the
  8. parameter name with optional '=' and value as appropriate, such as:
  9. modprobe usbcore blinkenlights=1
  10. Module parameters for modules that are built into the kernel image
  11. are specified on the kernel command line with the module name plus
  12. '.' plus parameter name, with '=' and value if appropriate, such as:
  13. usbcore.blinkenlights=1
  14. This document may not be entirely up to date and comprehensive. The command
  15. "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
  16. module. Loadable modules, after being loaded into the running kernel, also
  17. reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
  18. parameters may be changed at runtime by the command
  19. "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
  20. The parameters listed below are only valid if certain kernel build options were
  21. enabled and if respective hardware is present. The text in square brackets at
  22. the beginning of each description states the restrictions within which a
  23. parameter is applicable:
  24. ACPI ACPI support is enabled.
  25. AGP AGP (Accelerated Graphics Port) is enabled.
  26. ALSA ALSA sound support is enabled.
  27. APIC APIC support is enabled.
  28. APM Advanced Power Management support is enabled.
  29. AVR32 AVR32 architecture is enabled.
  30. AX25 Appropriate AX.25 support is enabled.
  31. BLACKFIN Blackfin architecture is enabled.
  32. DRM Direct Rendering Management support is enabled.
  33. EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
  34. EFI EFI Partitioning (GPT) is enabled
  35. EIDE EIDE/ATAPI support is enabled.
  36. FB The frame buffer device is enabled.
  37. HW Appropriate hardware is enabled.
  38. IA-64 IA-64 architecture is enabled.
  39. IOSCHED More than one I/O scheduler is enabled.
  40. IP_PNP IP DHCP, BOOTP, or RARP is enabled.
  41. ISAPNP ISA PnP code is enabled.
  42. ISDN Appropriate ISDN support is enabled.
  43. JOY Appropriate joystick support is enabled.
  44. LIBATA Libata driver is enabled
  45. LP Printer support is enabled.
  46. LOOP Loopback device support is enabled.
  47. M68k M68k architecture is enabled.
  48. These options have more detailed description inside of
  49. Documentation/m68k/kernel-options.txt.
  50. MCA MCA bus support is enabled.
  51. MDA MDA console support is enabled.
  52. MOUSE Appropriate mouse support is enabled.
  53. MSI Message Signaled Interrupts (PCI).
  54. MTD MTD (Memory Technology Device) support is enabled.
  55. NET Appropriate network support is enabled.
  56. NUMA NUMA support is enabled.
  57. GENERIC_TIME The generic timeofday code is enabled.
  58. NFS Appropriate NFS support is enabled.
  59. OSS OSS sound support is enabled.
  60. PV_OPS A paravirtualized kernel is enabled.
  61. PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
  62. PARISC The PA-RISC architecture is enabled.
  63. PCI PCI bus support is enabled.
  64. PCIE PCI Express support is enabled.
  65. PCMCIA The PCMCIA subsystem is enabled.
  66. PNP Plug & Play support is enabled.
  67. PPC PowerPC architecture is enabled.
  68. PPT Parallel port support is enabled.
  69. PS2 Appropriate PS/2 support is enabled.
  70. RAM RAM disk support is enabled.
  71. ROOTPLUG The example Root Plug LSM is enabled.
  72. S390 S390 architecture is enabled.
  73. SCSI Appropriate SCSI support is enabled.
  74. A lot of drivers has their options described inside of
  75. Documentation/scsi/.
  76. SECURITY Different security models are enabled.
  77. SELINUX SELinux support is enabled.
  78. SERIAL Serial support is enabled.
  79. SH SuperH architecture is enabled.
  80. SMP The kernel is an SMP kernel.
  81. SPARC Sparc architecture is enabled.
  82. SWSUSP Software suspend is enabled.
  83. TS Appropriate touchscreen support is enabled.
  84. USB USB support is enabled.
  85. USBHID USB Human Interface Device support is enabled.
  86. V4L Video For Linux support is enabled.
  87. VGA The VGA console has been enabled.
  88. VT Virtual terminal support is enabled.
  89. WDT Watchdog support is enabled.
  90. XT IBM PC/XT MFM hard disk support is enabled.
  91. X86-32 X86-32, aka i386 architecture is enabled.
  92. X86-64 X86-64 architecture is enabled.
  93. More X86-64 boot options can be found in
  94. Documentation/x86_64/boot-options.txt .
  95. In addition, the following text indicates that the option:
  96. BUGS= Relates to possible processor bugs on the said processor.
  97. KNL Is a kernel start-up parameter.
  98. BOOT Is a boot loader parameter.
  99. Parameters denoted with BOOT are actually interpreted by the boot
  100. loader, and have no meaning to the kernel directly.
  101. Do not modify the syntax of boot loader parameters without extreme
  102. need or coordination with <Documentation/i386/boot.txt>.
  103. There are also arch-specific kernel-parameters not documented here.
  104. See for example <Documentation/x86_64/boot-options.txt>.
  105. Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
  106. a trailing = on the name of any parameter states that that parameter will
  107. be entered as an environment variable, whereas its absence indicates that
  108. it will appear as a kernel argument readable via /proc/cmdline by programs
  109. running once the system is up.
  110. The number of kernel parameters is not limited, but the length of the
  111. complete command line (parameters including spaces etc.) is limited to
  112. a fixed number of characters. This limit depends on the architecture
  113. and is between 256 and 4096 characters. It is defined in the file
  114. ./include/asm/setup.h as COMMAND_LINE_SIZE.
  115. acpi= [HW,ACPI,X86-64,i386]
  116. Advanced Configuration and Power Interface
  117. Format: { force | off | ht | strict | noirq }
  118. force -- enable ACPI if default was off
  119. off -- disable ACPI if default was on
  120. noirq -- do not use ACPI for IRQ routing
  121. ht -- run only enough ACPI to enable Hyper Threading
  122. strict -- Be less tolerant of platforms that are not
  123. strictly ACPI specification compliant.
  124. See also Documentation/power/pm.txt, pci=noacpi
  125. acpi_apic_instance= [ACPI, IOAPIC]
  126. Format: <int>
  127. 2: use 2nd APIC table, if available
  128. 1,0: use 1st APIC table
  129. default: 0
  130. acpi_sleep= [HW,ACPI] Sleep options
  131. Format: { s3_bios, s3_mode, s3_beep }
  132. See Documentation/power/video.txt for s3_bios and s3_mode.
  133. s3_beep is for debugging; it makes the PC's speaker beep
  134. as soon as the kernel's real-mode entry point is called.
  135. acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
  136. Format: { level | edge | high | low }
  137. acpi_irq_balance [HW,ACPI]
  138. ACPI will balance active IRQs
  139. default in APIC mode
  140. acpi_irq_nobalance [HW,ACPI]
  141. ACPI will not move active IRQs (default)
  142. default in PIC mode
  143. acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
  144. use by PCI
  145. Format: <irq>,<irq>...
  146. acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
  147. Format: <irq>,<irq>...
  148. acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
  149. acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
  150. Format: To spoof as Windows 98: ="Microsoft Windows"
  151. acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
  152. acpi_osi="string1" # add string1 -- only one string
  153. acpi_osi="!string2" # remove built-in string2
  154. acpi_osi= # disable all strings
  155. acpi_serialize [HW,ACPI] force serialization of AML methods
  156. acpi_skip_timer_override [HW,ACPI]
  157. Recognize and ignore IRQ0/pin2 Interrupt Override.
  158. For broken nForce2 BIOS resulting in XT-PIC timer.
  159. acpi_use_timer_override [HW,ACPI}
  160. Use timer override. For some broken Nvidia NF5 boards
  161. that require a timer override, but don't have
  162. HPET
  163. acpi.debug_layer= [HW,ACPI]
  164. Format: <int>
  165. Each bit of the <int> indicates an ACPI debug layer,
  166. 1: enable, 0: disable. It is useful for boot time
  167. debugging. After system has booted up, it can be set
  168. via /sys/module/acpi/parameters/debug_layer.
  169. CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
  170. Available bits (add the numbers together) to enable debug output
  171. for specific parts of the ACPI subsystem:
  172. 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
  173. 0x10 namespace 0x20 parser 0x40 dispatcher
  174. 0x80 executer 0x100 resources 0x200 acpica debugger
  175. 0x400 os services 0x800 acpica disassembler.
  176. The number can be in decimal or prefixed with 0x in hex.
  177. Warning: Many of these options can produce a lot of
  178. output and make your system unusable. Be very careful.
  179. acpi.debug_level= [HW,ACPI]
  180. Format: <int>
  181. Each bit of the <int> indicates an ACPI debug level,
  182. 1: enable, 0: disable. It is useful for boot time
  183. debugging. After system has booted up, it can be set
  184. via /sys/module/acpi/parameters/debug_level.
  185. CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
  186. Available bits (add the numbers together) to enable different
  187. debug output levels of the ACPI subsystem:
  188. 0x01 error 0x02 warn 0x04 init 0x08 debug object
  189. 0x10 info 0x20 init names 0x40 parse 0x80 load
  190. 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
  191. 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
  192. 0x10000 resources 0x20000 user requests 0x40000 package.
  193. The number can be in decimal or prefixed with 0x in hex.
  194. Warning: Many of these options can produce a lot of
  195. output and make your system unusable. Be very careful.
  196. acpi_pm_good [X86-32,X86-64]
  197. Override the pmtimer bug detection: force the kernel
  198. to assume that this machine's pmtimer latches its value
  199. and always returns good values.
  200. agp= [AGP]
  201. { off | try_unsupported }
  202. off: disable AGP support
  203. try_unsupported: try to drive unsupported chipsets
  204. (may crash computer or cause data corruption)
  205. enable_timer_pin_1 [i386,x86-64]
  206. Enable PIN 1 of APIC timer
  207. Can be useful to work around chipset bugs
  208. (in particular on some ATI chipsets).
  209. The kernel tries to set a reasonable default.
  210. disable_timer_pin_1 [i386,x86-64]
  211. Disable PIN 1 of APIC timer
  212. Can be useful to work around chipset bugs.
  213. ad1848= [HW,OSS]
  214. Format: <io>,<irq>,<dma>,<dma2>,<type>
  215. advansys= [HW,SCSI]
  216. See header of drivers/scsi/advansys.c.
  217. advwdt= [HW,WDT] Advantech WDT
  218. Format: <iostart>,<iostop>
  219. aedsp16= [HW,OSS] Audio Excel DSP 16
  220. Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
  221. See also header of sound/oss/aedsp16.c.
  222. aha152x= [HW,SCSI]
  223. See Documentation/scsi/aha152x.txt.
  224. aha1542= [HW,SCSI]
  225. Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
  226. aic7xxx= [HW,SCSI]
  227. See Documentation/scsi/aic7xxx.txt.
  228. aic79xx= [HW,SCSI]
  229. See Documentation/scsi/aic79xx.txt.
  230. amijoy.map= [HW,JOY] Amiga joystick support
  231. Map of devices attached to JOY0DAT and JOY1DAT
  232. Format: <a>,<b>
  233. See also Documentation/kernel/input/joystick.txt
  234. analog.map= [HW,JOY] Analog joystick and gamepad support
  235. Specifies type or capabilities of an analog joystick
  236. connected to one of 16 gameports
  237. Format: <type1>,<type2>,..<type16>
  238. apc= [HW,SPARC]
  239. Power management functions (SPARCstation-4/5 + deriv.)
  240. Format: noidle
  241. Disable APC CPU standby support. SPARCstation-Fox does
  242. not play well with APC CPU idle - disable it if you have
  243. APC and your system crashes randomly.
  244. apic= [APIC,i386] Advanced Programmable Interrupt Controller
  245. Change the output verbosity whilst booting
  246. Format: { quiet (default) | verbose | debug }
  247. Change the amount of debugging information output
  248. when initialising the APIC and IO-APIC components.
  249. apm= [APM] Advanced Power Management
  250. See header of arch/i386/kernel/apm.c.
  251. arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
  252. Format: <io>,<irq>,<nodeID>
  253. ataflop= [HW,M68k]
  254. atarimouse= [HW,MOUSE] Atari Mouse
  255. atascsi= [HW,SCSI] Atari SCSI
  256. atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
  257. EzKey and similar keyboards
  258. atkbd.reset= [HW] Reset keyboard during initialization
  259. atkbd.set= [HW] Select keyboard code set
  260. Format: <int> (2 = AT (default), 3 = PS/2)
  261. atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
  262. keyboards
  263. atkbd.softraw= [HW] Choose between synthetic and real raw mode
  264. Format: <bool> (0 = real, 1 = synthetic (default))
  265. atkbd.softrepeat= [HW]
  266. Use software keyboard repeat
  267. autotest [IA64]
  268. baycom_epp= [HW,AX25]
  269. Format: <io>,<mode>
  270. baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
  271. Format: <io>,<mode>
  272. See header of drivers/net/hamradio/baycom_par.c.
  273. baycom_ser_fdx= [HW,AX25]
  274. BayCom Serial Port AX.25 Modem (Full Duplex Mode)
  275. Format: <io>,<irq>,<mode>[,<baud>]
  276. See header of drivers/net/hamradio/baycom_ser_fdx.c.
  277. baycom_ser_hdx= [HW,AX25]
  278. BayCom Serial Port AX.25 Modem (Half Duplex Mode)
  279. Format: <io>,<irq>,<mode>
  280. See header of drivers/net/hamradio/baycom_ser_hdx.c.
  281. boot_delay= Milliseconds to delay each printk during boot.
  282. Values larger than 10 seconds (10000) are changed to
  283. no delay (0).
  284. Format: integer
  285. bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
  286. bttv.radio= Most important insmod options are available as
  287. kernel args too.
  288. bttv.pll= See Documentation/video4linux/bttv/Insmod-options
  289. bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
  290. BusLogic= [HW,SCSI]
  291. See drivers/scsi/BusLogic.c, comment before function
  292. BusLogic_ParseDriverOptions().
  293. c101= [NET] Moxa C101 synchronous serial card
  294. cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
  295. Sometimes CPU hardware bugs make them report the cache
  296. size incorrectly. The kernel will attempt work arounds
  297. to fix known problems, but for some CPUs it is not
  298. possible to determine what the correct size should be.
  299. This option provides an override for these situations.
  300. capability.disable=
  301. [SECURITY] Disable capabilities. This would normally
  302. be used only if an alternative security model is to be
  303. configured. Potentially dangerous and should only be
  304. used if you are entirely sure of the consequences.
  305. ccw_timeout_log [S390]
  306. See Documentation/s390/CommonIO for details.
  307. checkreqprot [SELINUX] Set initial checkreqprot flag value.
  308. Format: { "0" | "1" }
  309. See security/selinux/Kconfig help text.
  310. 0 -- check protection applied by kernel (includes
  311. any implied execute protection).
  312. 1 -- check protection requested by application.
  313. Default value is set via a kernel config option.
  314. Value can be changed at runtime via
  315. /selinux/checkreqprot.
  316. cio_ignore= [S390]
  317. See Documentation/s390/CommonIO for details.
  318. cio_msg= [S390]
  319. See Documentation/s390/CommonIO for details.
  320. clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
  321. [Deprecated]
  322. Forces specified clocksource (if available) to be used
  323. when calculating gettimeofday(). If specified
  324. clocksource is not available, it defaults to PIT.
  325. Format: { pit | tsc | cyclone | pmtmr }
  326. clocksource= [GENERIC_TIME] Override the default clocksource
  327. Format: <string>
  328. Override the default clocksource and use the clocksource
  329. with the name specified.
  330. Some clocksource names to choose from, depending on
  331. the platform:
  332. [all] jiffies (this is the base, fallback clocksource)
  333. [ACPI] acpi_pm
  334. [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
  335. pxa_timer,timer3,32k_counter,timer0_1
  336. [AVR32] avr32
  337. [X86-32] pit,hpet,tsc,vmi-timer;
  338. scx200_hrt on Geode; cyclone on IBM x440
  339. [MIPS] MIPS
  340. [PARISC] cr16
  341. [S390] tod
  342. [SH] SuperH
  343. [SPARC64] tick
  344. [X86-64] hpet,tsc
  345. clearcpuid=BITNUM [X86]
  346. Disable CPUID feature X for the kernel. See
  347. include/asm-x86/cpufeature.h for the valid bit numbers.
  348. Note the Linux specific bits are not necessarily
  349. stable over kernel options, but the vendor specific
  350. ones should be.
  351. Also note that user programs calling CPUID directly
  352. or using the feature without checking anything
  353. will still see it. This just prevents it from
  354. being used by the kernel or shown in /proc/cpuinfo.
  355. Also note the kernel might malfunction if you disable
  356. some critical bits.
  357. code_bytes [IA32/X86_64] How many bytes of object code to print
  358. in an oops report.
  359. Range: 0 - 8192
  360. Default: 64
  361. disable_8254_timer
  362. enable_8254_timer
  363. [IA32/X86_64] Disable/Enable interrupt 0 timer routing
  364. over the 8254 in addition to over the IO-APIC. The
  365. kernel tries to set a sensible default.
  366. hpet= [X86-32,HPET] option to control HPET usage
  367. Format: { enable (default) | disable | force }
  368. disable: disable HPET and use PIT instead
  369. force: allow force enabled of undocumented chips (ICH4,
  370. VIA, nVidia)
  371. com20020= [HW,NET] ARCnet - COM20020 chipset
  372. Format:
  373. <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
  374. com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
  375. Format: <io>[,<irq>]
  376. com90xx= [HW,NET]
  377. ARCnet - COM90xx chipset (memory-mapped buffers)
  378. Format: <io>[,<irq>[,<memstart>]]
  379. condev= [HW,S390] console device
  380. conmode=
  381. console= [KNL] Output console device and options.
  382. tty<n> Use the virtual console device <n>.
  383. ttyS<n>[,options]
  384. ttyUSB0[,options]
  385. Use the specified serial port. The options are of
  386. the form "bbbbpnf", where "bbbb" is the baud rate,
  387. "p" is parity ("n", "o", or "e"), "n" is number of
  388. bits, and "f" is flow control ("r" for RTS or
  389. omit it). Default is "9600n8".
  390. See Documentation/serial-console.txt for more
  391. information. See
  392. Documentation/networking/netconsole.txt for an
  393. alternative.
  394. uart[8250],io,<addr>[,options]
  395. uart[8250],mmio,<addr>[,options]
  396. Start an early, polled-mode console on the 8250/16550
  397. UART at the specified I/O port or MMIO address,
  398. switching to the matching ttyS device later. The
  399. options are the same as for ttyS, above.
  400. earlycon= [KNL] Output early console device and options.
  401. uart[8250],io,<addr>[,options]
  402. uart[8250],mmio,<addr>[,options]
  403. Start an early, polled-mode console on the 8250/16550
  404. UART at the specified I/O port or MMIO address.
  405. The options are the same as for ttyS, above.
  406. no_console_suspend
  407. [HW] Never suspend the console
  408. Disable suspending of consoles during suspend and
  409. hibernate operations. Once disabled, debugging
  410. messages can reach various consoles while the rest
  411. of the system is being put to sleep (ie, while
  412. debugging driver suspend/resume hooks). This may
  413. not work reliably with all consoles, but is known
  414. to work with serial and VGA consoles.
  415. cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
  416. Format:
  417. <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
  418. crashkernel=nn[KMG]@ss[KMG]
  419. [KNL] Reserve a chunk of physical memory to
  420. hold a kernel to switch to with kexec on panic.
  421. crashkernel=range1:size1[,range2:size2,...][@offset]
  422. [KNL] Same as above, but depends on the memory
  423. in the running system. The syntax of range is
  424. start-[end] where start and end are both
  425. a memory unit (amount[KMG]). See also
  426. Documentation/kdump/kdump.txt for a example.
  427. cs4232= [HW,OSS]
  428. Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
  429. cs89x0_dma= [HW,NET]
  430. Format: <dma>
  431. cs89x0_media= [HW,NET]
  432. Format: { rj45 | aui | bnc }
  433. dasd= [HW,NET]
  434. See header of drivers/s390/block/dasd_devmap.c.
  435. db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
  436. (one device per port)
  437. Format: <port#>,<type>
  438. See also Documentation/input/joystick-parport.txt
  439. debug [KNL] Enable kernel debugging (events log level).
  440. debug_locks_verbose=
  441. [KNL] verbose self-tests
  442. Format=<0|1>
  443. Print debugging info while doing the locking API
  444. self-tests.
  445. We default to 0 (no extra messages), setting it to
  446. 1 will print _a lot_ more information - normally
  447. only useful to kernel developers.
  448. decnet.addr= [HW,NET]
  449. Format: <area>[,<node>]
  450. See also Documentation/networking/decnet.txt.
  451. vt.default_blu= [VT]
  452. Format: <blue0>,<blue1>,<blue2>,...,<blue15>
  453. Change the default blue palette of the console.
  454. This is a 16-member array composed of values
  455. ranging from 0-255.
  456. vt.default_grn= [VT]
  457. Format: <green0>,<green1>,<green2>,...,<green15>
  458. Change the default green palette of the console.
  459. This is a 16-member array composed of values
  460. ranging from 0-255.
  461. vt.default_red= [VT]
  462. Format: <red0>,<red1>,<red2>,...,<red15>
  463. Change the default red palette of the console.
  464. This is a 16-member array composed of values
  465. ranging from 0-255.
  466. vt.default_utf8=
  467. [VT]
  468. Format=<0|1>
  469. Set system-wide default UTF-8 mode for all tty's.
  470. Default is 1, i.e. UTF-8 mode is enabled for all
  471. newly opened terminals.
  472. dhash_entries= [KNL]
  473. Set number of hash buckets for dentry cache.
  474. digi= [HW,SERIAL]
  475. IO parameters + enable/disable command.
  476. digiepca= [HW,SERIAL]
  477. See drivers/char/README.epca and
  478. Documentation/digiepca.txt.
  479. disable_mtrr_trim [X86, Intel and AMD only]
  480. By default the kernel will trim any uncacheable
  481. memory out of your available memory pool based on
  482. MTRR settings. This parameter disables that behavior,
  483. possibly causing your machine to run very slowly.
  484. dmasound= [HW,OSS] Sound subsystem buffers
  485. dscc4.setup= [NET]
  486. dtc3181e= [HW,SCSI]
  487. earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
  488. earlyprintk=vga
  489. earlyprintk=serial[,ttySn[,baudrate]]
  490. Append ",keep" to not disable it when the real console
  491. takes over.
  492. Only vga or serial at a time, not both.
  493. Currently only ttyS0 and ttyS1 are supported.
  494. Interaction with the standard serial driver is not
  495. very good.
  496. The VGA output is eventually overwritten by the real
  497. console.
  498. eata= [HW,SCSI]
  499. edd= [EDD]
  500. Format: {"of[f]" | "sk[ipmbr]"}
  501. See comment in arch/i386/boot/edd.S
  502. eisa_irq_edge= [PARISC,HW]
  503. See header of drivers/parisc/eisa.c.
  504. elanfreq= [X86-32]
  505. See comment before function elanfreq_setup() in
  506. arch/i386/kernel/cpu/cpufreq/elanfreq.c.
  507. elevator= [IOSCHED]
  508. Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
  509. See Documentation/block/as-iosched.txt and
  510. Documentation/block/deadline-iosched.txt for details.
  511. elfcorehdr= [X86-32, X86_64]
  512. Specifies physical address of start of kernel core
  513. image elf header. Generally kexec loader will
  514. pass this option to capture kernel.
  515. See Documentation/kdump/kdump.txt for details.
  516. enforcing [SELINUX] Set initial enforcing status.
  517. Format: {"0" | "1"}
  518. See security/selinux/Kconfig help text.
  519. 0 -- permissive (log only, no denials).
  520. 1 -- enforcing (deny and log).
  521. Default value is 0.
  522. Value can be changed at runtime via /selinux/enforce.
  523. es1371= [HW,OSS]
  524. Format: <spdif>,[<nomix>,[<amplifier>]]
  525. See also header of sound/oss/es1371.c.
  526. ether= [HW,NET] Ethernet cards parameters
  527. This option is obsoleted by the "netdev=" option, which
  528. has equivalent usage. See its documentation for details.
  529. eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
  530. Format: <io>[,<irq>]
  531. failslab=
  532. fail_page_alloc=
  533. fail_make_request=[KNL]
  534. General fault injection mechanism.
  535. Format: <interval>,<probability>,<space>,<times>
  536. See also /Documentation/fault-injection/.
  537. fd_mcs= [HW,SCSI]
  538. See header of drivers/scsi/fd_mcs.c.
  539. fdomain= [HW,SCSI]
  540. See header of drivers/scsi/fdomain.c.
  541. floppy= [HW]
  542. See Documentation/floppy.txt.
  543. gamecon.map[2|3]=
  544. [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
  545. support via parallel port (up to 5 devices per port)
  546. Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
  547. See also Documentation/input/joystick-parport.txt
  548. gamma= [HW,DRM]
  549. gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
  550. Format: off | on
  551. default: on
  552. gdth= [HW,SCSI]
  553. See header of drivers/scsi/gdth.c.
  554. gpt [EFI] Forces disk with valid GPT signature but
  555. invalid Protective MBR to be treated as GPT.
  556. gvp11= [HW,SCSI]
  557. hashdist= [KNL,NUMA] Large hashes allocated during boot
  558. are distributed across NUMA nodes. Defaults on
  559. for IA-64, off otherwise.
  560. Format: 0 | 1 (for off | on)
  561. hcl= [IA-64] SGI's Hardware Graph compatibility layer
  562. hd= [EIDE] (E)IDE hard drive subsystem geometry
  563. Format: <cyl>,<head>,<sect>
  564. hd?= [HW] (E)IDE subsystem
  565. hd?lun= See Documentation/ide/ide.txt.
  566. highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
  567. size of <nn>. This works even on boxes that have no
  568. highmem otherwise. This also works to reduce highmem
  569. size on bigger boxes.
  570. highres= [KNL] Enable/disable high resolution timer mode.
  571. Valid parameters: "on", "off"
  572. Default: "on"
  573. hisax= [HW,ISDN]
  574. See Documentation/isdn/README.HiSax.
  575. hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
  576. hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
  577. i8042.direct [HW] Put keyboard port into non-translated mode
  578. i8042.dumbkbd [HW] Pretend that controller can only read data from
  579. keyboard and cannot control its state
  580. (Don't attempt to blink the leds)
  581. i8042.noaux [HW] Don't check for auxiliary (== mouse) port
  582. i8042.nokbd [HW] Don't check/create keyboard port
  583. i8042.noloop [HW] Disable the AUX Loopback command while probing
  584. for the AUX port
  585. i8042.nomux [HW] Don't check presence of an active multiplexing
  586. controller
  587. i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
  588. controllers
  589. i8042.panicblink=
  590. [HW] Frequency with which keyboard LEDs should blink
  591. when kernel panics (default is 0.5 sec)
  592. i8042.reset [HW] Reset the controller during init and cleanup
  593. i8042.unlock [HW] Unlock (ignore) the keylock
  594. i810= [HW,DRM]
  595. i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
  596. indicates that the driver is running on unsupported
  597. hardware.
  598. i8k.force [HW] Activate i8k driver even if SMM BIOS signature
  599. does not match list of supported models.
  600. i8k.power_status
  601. [HW] Report power status in /proc/i8k
  602. (disabled by default)
  603. i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
  604. capability is set.
  605. ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
  606. See Documentation/mca.txt.
  607. icn= [HW,ISDN]
  608. Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
  609. ide= [HW] (E)IDE subsystem
  610. Format: ide=nodma or ide=doubler or ide=reverse
  611. See Documentation/ide/ide.txt.
  612. ide?= [HW] (E)IDE subsystem
  613. Format: ide?=noprobe or chipset specific parameters.
  614. See Documentation/ide/ide.txt.
  615. idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
  616. See Documentation/ide/ide.txt.
  617. idle= [X86]
  618. Format: idle=poll or idle=mwait
  619. Poll forces a polling idle loop that can slightly improves the performance
  620. of waking up a idle CPU, but will use a lot of power and make the system
  621. run hot. Not recommended.
  622. idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
  623. to not use it because it doesn't save as much power as a normal idle
  624. loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
  625. as idle=poll.
  626. ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
  627. Claim all unknown PCI IDE storage controllers.
  628. ignore_loglevel [KNL]
  629. Ignore loglevel setting - this will print /all/
  630. kernel messages to the console. Useful for debugging.
  631. ihash_entries= [KNL]
  632. Set number of hash buckets for inode cache.
  633. in2000= [HW,SCSI]
  634. See header of drivers/scsi/in2000.c.
  635. init= [KNL]
  636. Format: <full_path>
  637. Run specified binary instead of /sbin/init as init
  638. process.
  639. initcall_debug [KNL] Trace initcalls as they are executed. Useful
  640. for working out where the kernel is dying during
  641. startup.
  642. initrd= [BOOT] Specify the location of the initial ramdisk
  643. inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
  644. Format: <irq>
  645. inttest= [IA64]
  646. intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
  647. off
  648. Disable intel iommu driver.
  649. igfx_off [Default Off]
  650. By default, gfx is mapped as normal device. If a gfx
  651. device has a dedicated DMAR unit, the DMAR unit is
  652. bypassed by not enabling DMAR with this option. In
  653. this case, gfx device will use physical address for
  654. DMA.
  655. forcedac [x86_64]
  656. With this option iommu will not optimize to look
  657. for io virtual address below 32 bit forcing dual
  658. address cycle on pci bus for cards supporting greater
  659. than 32 bit addressing. The default is to look
  660. for translation below 32 bit and if not available
  661. then look in the higher range.
  662. io_delay= [X86-32,X86-64] I/O delay method
  663. 0x80
  664. Standard port 0x80 based delay
  665. 0xed
  666. Alternate port 0xed based delay (needed on some systems)
  667. udelay
  668. Simple two microseconds delay
  669. none
  670. No delay
  671. io7= [HW] IO7 for Marvel based alpha systems
  672. See comment before marvel_specify_io7 in
  673. arch/alpha/kernel/core_marvel.c.
  674. ip= [IP_PNP]
  675. See Documentation/nfsroot.txt.
  676. ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
  677. See comment before ip2_setup() in
  678. drivers/char/ip2/ip2base.c.
  679. ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
  680. See header of drivers/scsi/ips.c.
  681. ports= [IP_VS_FTP] IPVS ftp helper module
  682. Default is 21.
  683. Up to 8 (IP_VS_APP_MAX_PORTS) ports
  684. may be specified.
  685. Format: <port>,<port>....
  686. irqfixup [HW]
  687. When an interrupt is not handled search all handlers
  688. for it. Intended to get systems with badly broken
  689. firmware running.
  690. irqpoll [HW]
  691. When an interrupt is not handled search all handlers
  692. for it. Also check all handlers each timer
  693. interrupt. Intended to get systems with badly broken
  694. firmware running.
  695. isapnp= [ISAPNP]
  696. Format: <RDP>,<reset>,<pci_scan>,<verbosity>
  697. isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
  698. Format:
  699. <cpu number>,...,<cpu number>
  700. or
  701. <cpu number>-<cpu number> (must be a positive range in ascending order)
  702. or a mixture
  703. <cpu number>,...,<cpu number>-<cpu number>
  704. This option can be used to specify one or more CPUs
  705. to isolate from the general SMP balancing and scheduling
  706. algorithms. The only way to move a process onto or off
  707. an "isolated" CPU is via the CPU affinity syscalls.
  708. <cpu number> begins at 0 and the maximum value is
  709. "number of CPUs in system - 1".
  710. This option is the preferred way to isolate CPUs. The
  711. alternative -- manually setting the CPU mask of all
  712. tasks in the system -- can cause problems and
  713. suboptimal load balancer performance.
  714. iucv= [HW,NET]
  715. js= [HW,JOY] Analog joystick
  716. See Documentation/input/joystick.txt.
  717. kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
  718. specifies the amount of memory usable by the kernel
  719. for non-movable allocations. The requested amount is
  720. spread evenly throughout all nodes in the system. The
  721. remaining memory in each node is used for Movable
  722. pages. In the event, a node is too small to have both
  723. kernelcore and Movable pages, kernelcore pages will
  724. take priority and other nodes will have a larger number
  725. of kernelcore pages. The Movable zone is used for the
  726. allocation of pages that may be reclaimed or moved
  727. by the page migration subsystem. This means that
  728. HugeTLB pages may not be allocated from this zone.
  729. Note that allocations like PTEs-from-HighMem still
  730. use the HighMem zone if it exists, and the Normal
  731. zone if it does not.
  732. movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
  733. is similar to kernelcore except it specifies the
  734. amount of memory used for migratable allocations.
  735. If both kernelcore and movablecore is specified,
  736. then kernelcore will be at *least* the specified
  737. value but may be more. If movablecore on its own
  738. is specified, the administrator must be careful
  739. that the amount of memory usable for all allocations
  740. is not too small.
  741. keepinitrd [HW,ARM]
  742. kstack=N [X86-32,X86-64] Print N words from the kernel stack
  743. in oops dumps.
  744. l2cr= [PPC]
  745. lapic [X86-32,APIC] Enable the local APIC even if BIOS
  746. disabled it.
  747. lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
  748. C2 power state.
  749. libata.dma= [LIBATA] DMA control
  750. libata.dma=0 Disable all PATA and SATA DMA
  751. libata.dma=1 PATA and SATA Disk DMA only
  752. libata.dma=2 ATAPI (CDROM) DMA only
  753. libata.dma=4 Compact Flash DMA only
  754. Combinations also work, so libata.dma=3 enables DMA
  755. for disks and CDROMs, but not CFs.
  756. libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
  757. when set.
  758. Format: <int>
  759. libata.force= [LIBATA] Force configurations. The format is comma
  760. separated list of "[ID:]VAL" where ID is
  761. PORT[:DEVICE]. PORT and DEVICE are decimal numbers
  762. matching port, link or device. Basically, it matches
  763. the ATA ID string printed on console by libata. If
  764. the whole ID part is omitted, the last PORT and DEVICE
  765. values are used. If ID hasn't been specified yet, the
  766. configuration applies to all ports, links and devices.
  767. If only DEVICE is omitted, the parameter applies to
  768. the port and all links and devices behind it. DEVICE
  769. number of 0 either selects the first device or the
  770. first fan-out link behind PMP device. It does not
  771. select the host link. DEVICE number of 15 selects the
  772. host link and device attached to it.
  773. The VAL specifies the configuration to force. As long
  774. as there's no ambiguity shortcut notation is allowed.
  775. For example, both 1.5 and 1.5G would work for 1.5Gbps.
  776. The following configurations can be forced.
  777. * Cable type: 40c, 80c, short40c, unk, ign or sata.
  778. Any ID with matching PORT is used.
  779. * SATA link speed limit: 1.5Gbps or 3.0Gbps.
  780. * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
  781. udma[/][16,25,33,44,66,100,133] notation is also
  782. allowed.
  783. * [no]ncq: Turn on or off NCQ.
  784. If there are multiple matching configurations changing
  785. the same attribute, the last one is used.
  786. load_ramdisk= [RAM] List of ramdisks to load from floppy
  787. See Documentation/ramdisk.txt.
  788. lockd.nlm_grace_period=P [NFS] Assign grace period.
  789. Format: <integer>
  790. lockd.nlm_tcpport=N [NFS] Assign TCP port.
  791. Format: <integer>
  792. lockd.nlm_timeout=T [NFS] Assign timeout value.
  793. Format: <integer>
  794. lockd.nlm_udpport=M [NFS] Assign UDP port.
  795. Format: <integer>
  796. logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
  797. Format: <irq>
  798. loglevel= All Kernel Messages with a loglevel smaller than the
  799. console loglevel will be printed to the console. It can
  800. also be changed with klogd or other programs. The
  801. loglevels are defined as follows:
  802. 0 (KERN_EMERG) system is unusable
  803. 1 (KERN_ALERT) action must be taken immediately
  804. 2 (KERN_CRIT) critical conditions
  805. 3 (KERN_ERR) error conditions
  806. 4 (KERN_WARNING) warning conditions
  807. 5 (KERN_NOTICE) normal but significant condition
  808. 6 (KERN_INFO) informational
  809. 7 (KERN_DEBUG) debug-level messages
  810. log_buf_len=n Sets the size of the printk ring buffer, in bytes.
  811. Format: { n | nk | nM }
  812. n must be a power of two. The default size
  813. is set in the kernel config file.
  814. logo.nologo [FB] Disables display of the built-in Linux logo.
  815. This may be used to provide more screen space for
  816. kernel log messages and is useful when debugging
  817. kernel boot problems.
  818. lp=0 [LP] Specify parallel ports to use, e.g,
  819. lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
  820. lp=reset first parallel port). 'lp=0' disables the
  821. lp=auto printer driver. 'lp=reset' (which can be
  822. specified in addition to the ports) causes
  823. attached printers to be reset. Using
  824. lp=port1,port2,... specifies the parallel ports
  825. to associate lp devices with, starting with
  826. lp0. A port specification may be 'none' to skip
  827. that lp device, or a parport name such as
  828. 'parport0'. Specifying 'lp=auto' instead of a
  829. port specification list means that device IDs
  830. from each port should be examined, to see if
  831. an IEEE 1284-compliant printer is attached; if
  832. so, the driver will manage that printer.
  833. See also header of drivers/char/lp.c.
  834. lpj=n [KNL]
  835. Sets loops_per_jiffy to given constant, thus avoiding
  836. time-consuming boot-time autodetection (up to 250 ms per
  837. CPU). 0 enables autodetection (default). To determine
  838. the correct value for your kernel, boot with normal
  839. autodetection and see what value is printed. Note that
  840. on SMP systems the preset will be applied to all CPUs,
  841. which is likely to cause problems if your CPUs need
  842. significantly divergent settings. An incorrect value
  843. will cause delays in the kernel to be wrong, leading to
  844. unpredictable I/O errors and other breakage. Although
  845. unlikely, in the extreme case this might damage your
  846. hardware.
  847. ltpc= [NET]
  848. Format: <io>,<irq>,<dma>
  849. mac5380= [HW,SCSI] Format:
  850. <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
  851. mac53c9x= [HW,SCSI] Format:
  852. <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
  853. machvec= [IA64] Force the use of a particular machine-vector
  854. (machvec) in a generic kernel.
  855. Example: machvec=hpzx1_swiotlb
  856. max_loop= [LOOP] Maximum number of loopback devices that can
  857. be mounted
  858. Format: <1-256>
  859. maxcpus= [SMP] Maximum number of processors that an SMP kernel
  860. should make use of. maxcpus=n : n >= 0 limits the
  861. kernel to using 'n' processors. n=0 is a special case,
  862. it is equivalent to "nosmp", which also disables
  863. the IO APIC.
  864. max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
  865. equal to this physical address is ignored.
  866. max_luns= [SCSI] Maximum number of LUNs to probe.
  867. Should be between 1 and 2^32-1.
  868. max_report_luns=
  869. [SCSI] Maximum number of LUNs received.
  870. Should be between 1 and 16384.
  871. mcatest= [IA-64]
  872. mce [X86-32] Machine Check Exception
  873. mce=option [X86-64] See Documentation/x86_64/boot-options.txt
  874. md= [HW] RAID subsystems devices and level
  875. See Documentation/md.txt.
  876. mdacon= [MDA]
  877. Format: <first>,<last>
  878. Specifies range of consoles to be captured by the MDA.
  879. mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
  880. Amount of memory to be used when the kernel is not able
  881. to see the whole system memory or for test.
  882. [X86-32] Use together with memmap= to avoid physical
  883. address space collisions. Without memmap= PCI devices
  884. could be placed at addresses belonging to unused RAM.
  885. mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
  886. memory.
  887. memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
  888. E820 memory map, as specified by the user.
  889. Such memmap=exactmap lines can be constructed based on
  890. BIOS output or other requirements. See the memmap=nn@ss
  891. option description.
  892. memmap=nn[KMG]@ss[KMG]
  893. [KNL] Force usage of a specific region of memory
  894. Region of memory to be used, from ss to ss+nn.
  895. memmap=nn[KMG]#ss[KMG]
  896. [KNL,ACPI] Mark specific memory as ACPI data.
  897. Region of memory to be used, from ss to ss+nn.
  898. memmap=nn[KMG]$ss[KMG]
  899. [KNL,ACPI] Mark specific memory as reserved.
  900. Region of memory to be used, from ss to ss+nn.
  901. Example: Exclude memory from 0x18690000-0x1869ffff
  902. memmap=64K$0x18690000
  903. or
  904. memmap=0x10000$0x18690000
  905. meye.*= [HW] Set MotionEye Camera parameters
  906. See Documentation/video4linux/meye.txt.
  907. mfgpt_irq= [IA-32] Specify the IRQ to use for the
  908. Multi-Function General Purpose Timers on AMD Geode
  909. platforms.
  910. mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
  911. the BIOS has incorrectly applied a workaround. TinyBIOS
  912. version 0.98 is known to be affected, 0.99 fixes the
  913. problem by letting the user disable the workaround.
  914. mga= [HW,DRM]
  915. mousedev.tap_time=
  916. [MOUSE] Maximum time between finger touching and
  917. leaving touchpad surface for touch to be considered
  918. a tap and be reported as a left button click (for
  919. touchpads working in absolute mode only).
  920. Format: <msecs>
  921. mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
  922. reporting absolute coordinates, such as tablets
  923. mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
  924. reporting absolute coordinates, such as tablets
  925. mpu401= [HW,OSS]
  926. Format: <io>,<irq>
  927. MTD_Partition= [MTD]
  928. Format: <name>,<region-number>,<size>,<offset>
  929. MTD_Region= [MTD] Format:
  930. <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
  931. mtdparts= [MTD]
  932. See drivers/mtd/cmdlinepart.c.
  933. mtouchusb.raw_coordinates=
  934. [HW] Make the MicroTouch USB driver use raw coordinates
  935. ('y', default) or cooked coordinates ('n')
  936. n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
  937. NCR_D700= [HW,SCSI]
  938. See header of drivers/scsi/NCR_D700.c.
  939. ncr5380= [HW,SCSI]
  940. ncr53c400= [HW,SCSI]
  941. ncr53c400a= [HW,SCSI]
  942. ncr53c406a= [HW,SCSI]
  943. ncr53c8xx= [HW,SCSI]
  944. netdev= [NET] Network devices parameters
  945. Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
  946. Note that mem_start is often overloaded to mean
  947. something different and driver-specific.
  948. This usage is only documented in each driver source
  949. file if at all.
  950. nfsaddrs= [NFS]
  951. See Documentation/nfsroot.txt.
  952. nfsroot= [NFS] nfs root filesystem for disk-less boxes.
  953. See Documentation/nfsroot.txt.
  954. nfs.callback_tcpport=
  955. [NFS] set the TCP port on which the NFSv4 callback
  956. channel should listen.
  957. nfs.idmap_cache_timeout=
  958. [NFS] set the maximum lifetime for idmapper cache
  959. entries.
  960. nfs.enable_ino64=
  961. [NFS] enable 64-bit inode numbers.
  962. If zero, the NFS client will fake up a 32-bit inode
  963. number for the readdir() and stat() syscalls instead
  964. of returning the full 64-bit number.
  965. The default is to return 64-bit inode numbers.
  966. nmi_debug= [KNL,AVR32] Specify one or more actions to take
  967. when a NMI is triggered.
  968. Format: [state][,regs][,debounce][,die]
  969. nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
  970. no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
  971. emulation library even if a 387 maths coprocessor
  972. is present.
  973. noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
  974. caches in the slab allocator. Saves per-node memory,
  975. but will impact performance.
  976. noalign [KNL,ARM]
  977. noapic [SMP,APIC] Tells the kernel to not make use of any
  978. IOAPICs that may be present in the system.
  979. nobats [PPC] Do not use BATs for mapping kernel lowmem
  980. on "Classic" PPC cores.
  981. nocache [ARM]
  982. nodelayacct [KNL] Disable per-task delay accounting
  983. nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
  984. noefi [X86-32,X86-64] Disable EFI runtime services support.
  985. noexec [IA-64]
  986. noexec [X86-32,X86-64]
  987. noexec=on: enable non-executable mappings (default)
  988. noexec=off: disable nn-executable mappings
  989. nofxsr [BUGS=X86-32] Disables x86 floating point extended
  990. register save and restore. The kernel will only save
  991. legacy floating-point registers on task switch.
  992. noclflush [BUGS=X86] Don't use the CLFLUSH instruction
  993. nohlt [BUGS=ARM]
  994. no-hlt [BUGS=X86-32] Tells the kernel that the hlt
  995. instruction doesn't work correctly and not to
  996. use it.
  997. nohalt [IA-64] Tells the kernel not to use the power saving
  998. function PAL_HALT_LIGHT when idle. This increases
  999. power-consumption. On the positive side, it reduces
  1000. interrupt wake-up latency, which may improve performance
  1001. in certain environments such as networked servers or
  1002. real-time systems.
  1003. nohz= [KNL] Boottime enable/disable dynamic ticks
  1004. Valid arguments: on, off
  1005. Default: on
  1006. noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
  1007. noirqdebug [X86-32] Disables the code which attempts to detect and
  1008. disable unhandled interrupt sources.
  1009. no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
  1010. broken timer IRQ sources.
  1011. noisapnp [ISAPNP] Disables ISA PnP code.
  1012. noinitrd [RAM] Tells the kernel not to load any configured
  1013. initial RAM disk.
  1014. nointroute [IA-64]
  1015. nojitter [IA64] Disables jitter checking for ITC timers.
  1016. nolapic [X86-32,APIC] Do not enable or use the local APIC.
  1017. nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
  1018. noltlbs [PPC] Do not use large page/tlb entries for kernel
  1019. lowmem mapping on PPC40x.
  1020. nomca [IA-64] Disable machine check abort handling
  1021. nomce [X86-32] Machine Check Exception
  1022. nomfgpt [X86-32] Disable Multi-Function General Purpose
  1023. Timer usage (for AMD Geode machines).
  1024. noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
  1025. noreplace-smp [X86-32,SMP] Don't replace SMP instructions
  1026. with UP alternatives
  1027. noresidual [PPC] Don't use residual data on PReP machines.
  1028. noresume [SWSUSP] Disables resume and restores original swap
  1029. space.
  1030. no-scroll [VGA] Disables scrollback.
  1031. This is required for the Braillex ib80-piezo Braille
  1032. reader made by F.H. Papenmeier (Germany).
  1033. nosbagart [IA-64]
  1034. nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
  1035. nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
  1036. and disable the IO APIC. legacy for "maxcpus=0".
  1037. nosoftlockup [KNL] Disable the soft-lockup detector.
  1038. nosync [HW,M68K] Disables sync negotiation for all devices.
  1039. notsc [BUGS=X86-32] Disable Time Stamp Counter
  1040. nousb [USB] Disable the USB subsystem
  1041. nowb [ARM]
  1042. numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
  1043. one of ['zone', 'node', 'default'] can be specified
  1044. This can be set from sysctl after boot.
  1045. See Documentation/sysctl/vm.txt for details.
  1046. nr_uarts= [SERIAL] maximum number of UARTs to be registered.
  1047. opl3= [HW,OSS]
  1048. Format: <io>
  1049. oprofile.timer= [HW]
  1050. Use timer interrupt instead of performance counters
  1051. osst= [HW,SCSI] SCSI Tape Driver
  1052. Format: <buffer_size>,<write_threshold>
  1053. See also Documentation/scsi/st.txt.
  1054. panic= [KNL] Kernel behaviour on panic
  1055. Format: <timeout>
  1056. parkbd.port= [HW] Parallel port number the keyboard adapter is
  1057. connected to, default is 0.
  1058. Format: <parport#>
  1059. parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
  1060. 0 for XT, 1 for AT (default is AT).
  1061. Format: <mode>
  1062. parport= [HW,PPT] Specify parallel ports. 0 disables.
  1063. Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
  1064. Use 'auto' to force the driver to use any
  1065. IRQ/DMA settings detected (the default is to
  1066. ignore detected IRQ/DMA settings because of
  1067. possible conflicts). You can specify the base
  1068. address, IRQ, and DMA settings; IRQ and DMA
  1069. should be numbers, or 'auto' (for using detected
  1070. settings on that particular port), or 'nofifo'
  1071. (to avoid using a FIFO even if it is detected).
  1072. Parallel ports are assigned in the order they
  1073. are specified on the command line, starting
  1074. with parport0.
  1075. parport_init_mode= [HW,PPT]
  1076. Configure VIA parallel port to operate in
  1077. a specific mode. This is necessary on Pegasos
  1078. computer where firmware has no options for setting
  1079. up parallel port mode and sets it to spp.
  1080. Currently this function knows 686a and 8231 chips.
  1081. Format: [spp|ps2|epp|ecp|ecpepp]
  1082. pas2= [HW,OSS] Format:
  1083. <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
  1084. pas16= [HW,SCSI]
  1085. See header of drivers/scsi/pas16.c.
  1086. pause_on_oops=
  1087. Halt all CPUs after the first oops has been printed for
  1088. the specified number of seconds. This is to be used if
  1089. your oopses keep scrolling off the screen.
  1090. pcbit= [HW,ISDN]
  1091. pcd. [PARIDE]
  1092. See header of drivers/block/paride/pcd.c.
  1093. See also Documentation/paride.txt.
  1094. pci=option[,option...] [PCI] various PCI subsystem options:
  1095. off [X86-32] don't probe for the PCI bus
  1096. bios [X86-32] force use of PCI BIOS, don't access
  1097. the hardware directly. Use this if your machine
  1098. has a non-standard PCI host bridge.
  1099. nobios [X86-32] disallow use of PCI BIOS, only direct
  1100. hardware access methods are allowed. Use this
  1101. if you experience crashes upon bootup and you
  1102. suspect they are caused by the BIOS.
  1103. conf1 [X86-32] Force use of PCI Configuration
  1104. Mechanism 1.
  1105. conf2 [X86-32] Force use of PCI Configuration
  1106. Mechanism 2.
  1107. noaer [PCIE] If the PCIEAER kernel config parameter is
  1108. enabled, this kernel boot option can be used to
  1109. disable the use of PCIE advanced error reporting.
  1110. nodomains [PCI] Disable support for multiple PCI
  1111. root domains (aka PCI segments, in ACPI-speak).
  1112. nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
  1113. Configuration
  1114. nomsi [MSI] If the PCI_MSI kernel config parameter is
  1115. enabled, this kernel boot option can be used to
  1116. disable the use of MSI interrupts system-wide.
  1117. nosort [X86-32] Don't sort PCI devices according to
  1118. order given by the PCI BIOS. This sorting is
  1119. done to get a device order compatible with
  1120. older kernels.
  1121. biosirq [X86-32] Use PCI BIOS calls to get the interrupt
  1122. routing table. These calls are known to be buggy
  1123. on several machines and they hang the machine
  1124. when used, but on other computers it's the only
  1125. way to get the interrupt routing table. Try
  1126. this option if the kernel is unable to allocate
  1127. IRQs or discover secondary PCI buses on your
  1128. motherboard.
  1129. rom [X86-32] Assign address space to expansion ROMs.
  1130. Use with caution as certain devices share
  1131. address decoders between ROMs and other
  1132. resources.
  1133. irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
  1134. assigned automatically to PCI devices. You can
  1135. make the kernel exclude IRQs of your ISA cards
  1136. this way.
  1137. pirqaddr=0xAAAAA [X86-32] Specify the physical address
  1138. of the PIRQ table (normally generated
  1139. by the BIOS) if it is outside the
  1140. F0000h-100000h range.
  1141. lastbus=N [X86-32] Scan all buses thru bus #N. Can be
  1142. useful if the kernel is unable to find your
  1143. secondary buses and you want to tell it
  1144. explicitly which ones they are.
  1145. assign-busses [X86-32] Always assign all PCI bus
  1146. numbers ourselves, overriding
  1147. whatever the firmware may have done.
  1148. usepirqmask [X86-32] Honor the possible IRQ mask stored
  1149. in the BIOS $PIR table. This is needed on
  1150. some systems with broken BIOSes, notably
  1151. some HP Pavilion N5400 and Omnibook XE3
  1152. notebooks. This will have no effect if ACPI
  1153. IRQ routing is enabled.
  1154. noacpi [X86-32] Do not use ACPI for IRQ routing
  1155. or for PCI scanning.
  1156. use_crs [X86-32] Use _CRS for PCI resource
  1157. allocation.
  1158. routeirq Do IRQ routing for all PCI devices.
  1159. This is normally done in pci_enable_device(),
  1160. so this option is a temporary workaround
  1161. for broken drivers that don't call it.
  1162. firmware [ARM] Do not re-enumerate the bus but instead
  1163. just use the configuration from the
  1164. bootloader. This is currently used on
  1165. IXP2000 systems where the bus has to be
  1166. configured a certain way for adjunct CPUs.
  1167. noearly [X86] Don't do any early type 1 scanning.
  1168. This might help on some broken boards which
  1169. machine check when some devices' config space
  1170. is read. But various workarounds are disabled
  1171. and some IOMMU drivers will not work.
  1172. bfsort Sort PCI devices into breadth-first order.
  1173. This sorting is done to get a device
  1174. order compatible with older (<= 2.4) kernels.
  1175. nobfsort Don't sort PCI devices into breadth-first order.
  1176. cbiosize=nn[KMG] The fixed amount of bus space which is
  1177. reserved for the CardBus bridge's IO window.
  1178. The default value is 256 bytes.
  1179. cbmemsize=nn[KMG] The fixed amount of bus space which is
  1180. reserved for the CardBus bridge's memory
  1181. window. The default value is 64 megabytes.
  1182. pcmv= [HW,PCMCIA] BadgePAD 4
  1183. pd. [PARIDE]
  1184. See Documentation/paride.txt.
  1185. pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
  1186. boot time.
  1187. Format: { 0 | 1 }
  1188. See arch/parisc/kernel/pdc_chassis.c
  1189. pf. [PARIDE]
  1190. See Documentation/paride.txt.
  1191. pg. [PARIDE]
  1192. See Documentation/paride.txt.
  1193. pirq= [SMP,APIC] Manual mp-table setup
  1194. See Documentation/i386/IO-APIC.txt.
  1195. plip= [PPT,NET] Parallel port network link
  1196. Format: { parport<nr> | timid | 0 }
  1197. See also Documentation/parport.txt.
  1198. pnpacpi= [ACPI]
  1199. { off }
  1200. pnpbios= [ISAPNP]
  1201. { on | off | curr | res | no-curr | no-res }
  1202. pnp_reserve_irq=
  1203. [ISAPNP] Exclude IRQs for the autoconfiguration
  1204. pnp_reserve_dma=
  1205. [ISAPNP] Exclude DMAs for the autoconfiguration
  1206. pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
  1207. Ranges are in pairs (I/O port base and size).
  1208. pnp_reserve_mem=
  1209. [ISAPNP] Exclude memory regions for the
  1210. autoconfiguration.
  1211. Ranges are in pairs (memory base and size).
  1212. print-fatal-signals=
  1213. [KNL] debug: print fatal signals
  1214. print-fatal-signals=1: print segfault info to
  1215. the kernel console.
  1216. default: off.
  1217. printk.time= Show timing data prefixed to each printk message line
  1218. Format: <bool> (1/Y/y=enable, 0/N/n=disable)
  1219. profile= [KNL] Enable kernel profiling via /proc/profile
  1220. Format: [schedule,]<number>
  1221. Param: "schedule" - profile schedule points.
  1222. Param: <number> - step/bucket size as a power of 2 for
  1223. statistical time based profiling.
  1224. Param: "sleep" - profile D-state sleeping (millisecs).
  1225. Requires CONFIG_SCHEDSTATS
  1226. Param: "kvm" - profile VM exits.
  1227. processor.max_cstate= [HW,ACPI]
  1228. Limit processor to maximum C-state
  1229. max_cstate=9 overrides any DMI blacklist limit.
  1230. processor.nocst [HW,ACPI]
  1231. Ignore the _CST method to determine C-states,
  1232. instead using the legacy FADT method
  1233. prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
  1234. before loading.
  1235. See Documentation/ramdisk.txt.
  1236. psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
  1237. probe for; one of (bare|imps|exps|lifebook|any).
  1238. psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
  1239. per second.
  1240. psmouse.resetafter= [HW,MOUSE]
  1241. Try to reset the device after so many bad packets
  1242. (0 = never).
  1243. psmouse.resolution=
  1244. [HW,MOUSE] Set desired mouse resolution, in dpi.
  1245. psmouse.smartscroll=
  1246. [HW,MOUSE] Controls Logitech smartscroll autorepeat.
  1247. 0 = disabled, 1 = enabled (default).
  1248. pss= [HW,OSS] Personal Sound System (ECHO ESC614)
  1249. Format:
  1250. <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
  1251. pt. [PARIDE]
  1252. See Documentation/paride.txt.
  1253. pty.legacy_count=
  1254. [KNL] Number of legacy pty's. Overwrites compiled-in
  1255. default number.
  1256. quiet [KNL] Disable most log messages
  1257. r128= [HW,DRM]
  1258. raid= [HW,RAID]
  1259. See Documentation/md.txt.
  1260. ramdisk_blocksize= [RAM]
  1261. See Documentation/ramdisk.txt.
  1262. ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
  1263. See Documentation/ramdisk.txt.
  1264. rcupdate.blimit= [KNL,BOOT]
  1265. Set maximum number of finished RCU callbacks to process
  1266. in one batch.
  1267. rcupdate.qhimark= [KNL,BOOT]
  1268. Set threshold of queued
  1269. RCU callbacks over which batch limiting is disabled.
  1270. rcupdate.qlowmark= [KNL,BOOT]
  1271. Set threshold of queued RCU callbacks below which
  1272. batch limiting is re-enabled.
  1273. rdinit= [KNL]
  1274. Format: <full_path>
  1275. Run specified binary instead of /init from the ramdisk,
  1276. used for early userspace startup. See initrd.
  1277. reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
  1278. Format: <reboot_mode>[,<reboot_mode2>[,...]]
  1279. See arch/*/kernel/reboot.c or arch/*/kernel/process.c
  1280. reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
  1281. reservetop= [X86-32]
  1282. Format: nn[KMG]
  1283. Reserves a hole at the top of the kernel virtual
  1284. address space.
  1285. reset_devices [KNL] Force drivers to reset the underlying device
  1286. during initialization.
  1287. resume= [SWSUSP]
  1288. Specify the partition device for software suspend
  1289. resume_offset= [SWSUSP]
  1290. Specify the offset from the beginning of the partition
  1291. given by "resume=" at which the swap header is located,
  1292. in <PAGE_SIZE> units (needed only for swap files).
  1293. See Documentation/power/swsusp-and-swap-files.txt
  1294. retain_initrd [RAM] Keep initrd memory after extraction
  1295. rhash_entries= [KNL,NET]
  1296. Set number of hash buckets for route cache
  1297. riscom8= [HW,SERIAL]
  1298. Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
  1299. ro [KNL] Mount root device read-only on boot
  1300. root= [KNL] Root filesystem
  1301. rootdelay= [KNL] Delay (in seconds) to pause before attempting to
  1302. mount the root filesystem
  1303. rootflags= [KNL] Set root filesystem mount option string
  1304. rootfstype= [KNL] Set root filesystem type
  1305. rootwait [KNL] Wait (indefinitely) for root device to show up.
  1306. Useful for devices that are detected asynchronously
  1307. (e.g. USB and MMC devices).
  1308. root_plug.vendor_id=
  1309. [ROOTPLUG] Override the default vendor ID
  1310. root_plug.product_id=
  1311. [ROOTPLUG] Override the default product ID
  1312. root_plug.debug=
  1313. [ROOTPLUG] Enable debugging output
  1314. rw [KNL] Mount root device read-write on boot
  1315. S [KNL] Run init in single mode
  1316. sa1100ir [NET]
  1317. See drivers/net/irda/sa1100_ir.c.
  1318. sbni= [NET] Granch SBNI12 leased line adapter
  1319. sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
  1320. Format: <io>[,<timeout>[,<isapnp>]]
  1321. scsi_debug_*= [SCSI]
  1322. See drivers/scsi/scsi_debug.c.
  1323. scsi_default_dev_flags=
  1324. [SCSI] SCSI default device flags
  1325. Format: <integer>
  1326. scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
  1327. Format: <vendor>:<model>:<flags>
  1328. (flags are integer value)
  1329. scsi_logging_level= [SCSI] a bit mask of logging levels
  1330. See drivers/scsi/scsi_logging.h for bits. Also
  1331. settable via sysctl at dev.scsi.logging_level
  1332. (/proc/sys/dev/scsi/logging_level).
  1333. There is also a nice 'scsi_logging_level' script in the
  1334. S390-tools package, available for download at
  1335. http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
  1336. scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
  1337. discovered. async scans them in kernel threads,
  1338. allowing boot to proceed. none ignores them, expecting
  1339. user space to do the scan.
  1340. selinux [SELINUX] Disable or enable SELinux at boot time.
  1341. Format: { "0" | "1" }
  1342. See security/selinux/Kconfig help text.
  1343. 0 -- disable.
  1344. 1 -- enable.
  1345. Default value is set via kernel config option.
  1346. If enabled at boot time, /selinux/disable can be used
  1347. later to disable prior to initial policy load.
  1348. selinux_compat_net =
  1349. [SELINUX] Set initial selinux_compat_net flag value.
  1350. Format: { "0" | "1" }
  1351. 0 -- use new secmark-based packet controls
  1352. 1 -- use legacy packet controls
  1353. Default value is 0 (preferred).
  1354. Value can be changed at runtime via
  1355. /selinux/compat_net.
  1356. serialnumber [BUGS=X86-32]
  1357. shapers= [NET]
  1358. Maximal number of shapers.
  1359. sim710= [SCSI,HW]
  1360. See header of drivers/scsi/sim710.c.
  1361. simeth= [IA-64]
  1362. simscsi=
  1363. slram= [HW,MTD]
  1364. slub_debug[=options[,slabs]] [MM, SLUB]
  1365. Enabling slub_debug allows one to determine the
  1366. culprit if slab objects become corrupted. Enabling
  1367. slub_debug can create guard zones around objects and
  1368. may poison objects when not in use. Also tracks the
  1369. last alloc / free. For more information see
  1370. Documentation/vm/slub.txt.
  1371. slub_max_order= [MM, SLUB]
  1372. Determines the maximum allowed order for slabs.
  1373. A high setting may cause OOMs due to memory
  1374. fragmentation. For more information see
  1375. Documentation/vm/slub.txt.
  1376. slub_min_objects= [MM, SLUB]
  1377. The minimum number of objects per slab. SLUB will
  1378. increase the slab order up to slub_max_order to
  1379. generate a sufficiently large slab able to contain
  1380. the number of objects indicated. The higher the number
  1381. of objects the smaller the overhead of tracking slabs
  1382. and the less frequently locks need to be acquired.
  1383. For more information see Documentation/vm/slub.txt.
  1384. slub_min_order= [MM, SLUB]
  1385. Determines the mininum page order for slabs. Must be
  1386. lower than slub_max_order.
  1387. For more information see Documentation/vm/slub.txt.
  1388. slub_nomerge [MM, SLUB]
  1389. Disable merging of slabs with similar size. May be
  1390. necessary if there is some reason to distinguish
  1391. allocs to different slabs. Debug options disable
  1392. merging on their own.
  1393. For more information see Documentation/vm/slub.txt.
  1394. smart2= [HW]
  1395. Format: <io1>[,<io2>[,...,<io8>]]
  1396. smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
  1397. attempt to substitute SMP alternatives once at boot.
  1398. smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
  1399. smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
  1400. smsc-ircc2.ircc_sir= [HW] SIR base I/O port
  1401. smsc-ircc2.ircc_fir= [HW] FIR base I/O port
  1402. smsc-ircc2.ircc_irq= [HW] IRQ line
  1403. smsc-ircc2.ircc_dma= [HW] DMA channel
  1404. smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
  1405. 0: Toshiba Satellite 1800 (GP data pin select)
  1406. 1: Fast pin select (default)
  1407. 2: ATC IRMode
  1408. snd-ad1816a= [HW,ALSA]
  1409. snd-ad1848= [HW,ALSA]
  1410. snd-ali5451= [HW,ALSA]
  1411. snd-als100= [HW,ALSA]
  1412. snd-als4000= [HW,ALSA]
  1413. snd-azt2320= [HW,ALSA]
  1414. snd-cmi8330= [HW,ALSA]
  1415. snd-cmipci= [HW,ALSA]
  1416. snd-cs4231= [HW,ALSA]
  1417. snd-cs4232= [HW,ALSA]
  1418. snd-cs4236= [HW,ALSA]
  1419. snd-cs4281= [HW,ALSA]
  1420. snd-cs46xx= [HW,ALSA]
  1421. snd-dt019x= [HW,ALSA]
  1422. snd-dummy= [HW,ALSA]
  1423. snd-emu10k1= [HW,ALSA]
  1424. snd-ens1370= [HW,ALSA]
  1425. snd-ens1371= [HW,ALSA]
  1426. snd-es968= [HW,ALSA]
  1427. snd-es1688= [HW,ALSA]
  1428. snd-es18xx= [HW,ALSA]
  1429. snd-es1938= [HW,ALSA]
  1430. snd-es1968= [HW,ALSA]
  1431. snd-fm801= [HW,ALSA]
  1432. snd-gusclassic= [HW,ALSA]
  1433. snd-gusextreme= [HW,ALSA]
  1434. snd-gusmax= [HW,ALSA]
  1435. snd-hdsp= [HW,ALSA]
  1436. snd-ice1712= [HW,ALSA]
  1437. snd-intel8x0= [HW,ALSA]
  1438. snd-interwave= [HW,ALSA]
  1439. snd-interwave-stb=
  1440. [HW,ALSA]
  1441. snd-korg1212= [HW,ALSA]
  1442. snd-maestro3= [HW,ALSA]
  1443. snd-mpu401= [HW,ALSA]
  1444. snd-mtpav= [HW,ALSA]
  1445. snd-nm256= [HW,ALSA]
  1446. snd-opl3sa2= [HW,ALSA]
  1447. snd-opti92x-ad1848=
  1448. [HW,ALSA]
  1449. snd-opti92x-cs4231=
  1450. [HW,ALSA]
  1451. snd-opti93x= [HW,ALSA]
  1452. snd-pmac= [HW,ALSA]
  1453. snd-rme32= [HW,ALSA]
  1454. snd-rme96= [HW,ALSA]
  1455. snd-rme9652= [HW,ALSA]
  1456. snd-sb8= [HW,ALSA]
  1457. snd-sb16= [HW,ALSA]
  1458. snd-sbawe= [HW,ALSA]
  1459. snd-serial= [HW,ALSA]
  1460. snd-sgalaxy= [HW,ALSA]
  1461. snd-sonicvibes= [HW,ALSA]
  1462. snd-sun-amd7930=
  1463. [HW,ALSA]
  1464. snd-sun-cs4231= [HW,ALSA]
  1465. snd-trident= [HW,ALSA]
  1466. snd-usb-audio= [HW,ALSA,USB]
  1467. snd-via82xx= [HW,ALSA]
  1468. snd-virmidi= [HW,ALSA]
  1469. snd-wavefront= [HW,ALSA]
  1470. snd-ymfpci= [HW,ALSA]
  1471. sonypi.*= [HW] Sony Programmable I/O Control Device driver
  1472. See Documentation/sonypi.txt
  1473. specialix= [HW,SERIAL] Specialix multi-serial port adapter
  1474. See Documentation/specialix.txt.
  1475. spia_io_base= [HW,MTD]
  1476. spia_fio_base=
  1477. spia_pedr=
  1478. spia_peddr=
  1479. sscape= [HW,OSS]
  1480. Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
  1481. st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
  1482. See Documentation/scsi/st.txt.
  1483. sti= [PARISC,HW]
  1484. Format: <num>
  1485. Set the STI (builtin display/keyboard on the HP-PARISC
  1486. machines) console (graphic card) which should be used
  1487. as the initial boot-console.
  1488. See also comment in drivers/video/console/sticore.c.
  1489. sti_font= [HW]
  1490. See comment in drivers/video/console/sticore.c.
  1491. stifb= [HW]
  1492. Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
  1493. sunrpc.pool_mode=
  1494. [NFS]
  1495. Control how the NFS server code allocates CPUs to
  1496. service thread pools. Depending on how many NICs
  1497. you have and where their interrupts are bound, this
  1498. option will affect which CPUs will do NFS serving.
  1499. Note: this parameter cannot be changed while the
  1500. NFS server is running.
  1501. auto the server chooses an appropriate mode
  1502. automatically using heuristics
  1503. global a single global pool contains all CPUs
  1504. percpu one pool for each CPU
  1505. pernode one pool for each NUMA node (equivalent
  1506. to global on non-NUMA machines)
  1507. swiotlb= [IA-64] Number of I/O TLB slabs
  1508. switches= [HW,M68k]
  1509. sym53c416= [HW,SCSI]
  1510. See header of drivers/scsi/sym53c416.c.
  1511. sysrq_always_enabled
  1512. [KNL]
  1513. Ignore sysrq setting - this boot parameter will
  1514. neutralize any effect of /proc/sys/kernel/sysrq.
  1515. Useful for debugging.
  1516. t128= [HW,SCSI]
  1517. See header of drivers/scsi/t128.c.
  1518. tdfx= [HW,DRM]
  1519. thash_entries= [KNL,NET]
  1520. Set number of hash buckets for TCP connection
  1521. thermal.act= [HW,ACPI]
  1522. -1: disable all active trip points in all thermal zones
  1523. <degrees C>: override all lowest active trip points
  1524. thermal.crt= [HW,ACPI]
  1525. -1: disable all critical trip points in all thermal zones
  1526. <degrees C>: lower all critical trip points
  1527. thermal.nocrt= [HW,ACPI]
  1528. Set to disable actions on ACPI thermal zone
  1529. critical and hot trip points.
  1530. thermal.off= [HW,ACPI]
  1531. 1: disable ACPI thermal control
  1532. thermal.psv= [HW,ACPI]
  1533. -1: disable all passive trip points
  1534. <degrees C>: override all passive trip points to this value
  1535. thermal.tzp= [HW,ACPI]
  1536. Specify global default ACPI thermal zone polling rate
  1537. <deci-seconds>: poll all this frequency
  1538. 0: no polling (default)
  1539. tipar.timeout= [HW,PPT]
  1540. Set communications timeout in tenths of a second
  1541. (default 15).
  1542. tipar.delay= [HW,PPT]
  1543. Set inter-bit delay in microseconds (default 10).
  1544. tmscsim= [HW,SCSI]
  1545. See comment before function dc390_setup() in
  1546. drivers/scsi/tmscsim.c.
  1547. tp720= [HW,PS2]
  1548. trix= [HW,OSS] MediaTrix AudioTrix Pro
  1549. Format:
  1550. <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
  1551. turbografx.map[2|3]= [HW,JOY]
  1552. TurboGraFX parallel port interface
  1553. Format:
  1554. <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
  1555. See also Documentation/input/joystick-parport.txt
  1556. u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
  1557. See header of drivers/scsi/u14-34f.c.
  1558. uart401= [HW,OSS]
  1559. Format: <io>,<irq>
  1560. uart6850= [HW,OSS]
  1561. Format: <io>,<irq>
  1562. uhci-hcd.ignore_oc=
  1563. [USB] Ignore overcurrent events (default N).
  1564. Some badly-designed motherboards generate lots of
  1565. bogus events, for ports that aren't wired to
  1566. anything. Set this parameter to avoid log spamming.
  1567. Note that genuine overcurrent events won't be
  1568. reported either.
  1569. usbcore.autosuspend=
  1570. [USB] The autosuspend time delay (in seconds) used
  1571. for newly-detected USB devices (default 2). This
  1572. is the time required before an idle device will be
  1573. autosuspended. Devices for which the delay is set
  1574. to a negative value won't be autosuspended at all.
  1575. usbhid.mousepoll=
  1576. [USBHID] The interval which mice are to be polled at.
  1577. vdso= [X86-32,SH,x86-64]
  1578. vdso=2: enable compat VDSO (default with COMPAT_VDSO)
  1579. vdso=1: enable VDSO (default)
  1580. vdso=0: disable VDSO mapping
  1581. vdso32= [X86-32,X86-64]
  1582. vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
  1583. vdso32=1: enable 32-bit VDSO (default)
  1584. vdso32=0: disable 32-bit VDSO mapping
  1585. vector= [IA-64,SMP]
  1586. vector=percpu: enable percpu vector domain
  1587. video= [FB] Frame buffer configuration
  1588. See Documentation/fb/modedb.txt.
  1589. vga= [BOOT,X86-32] Select a particular video mode
  1590. See Documentation/i386/boot.txt and
  1591. Documentation/svga.txt.
  1592. Use vga=ask for menu.
  1593. This is actually a boot loader parameter; the value is
  1594. passed to the kernel using a special protocol.
  1595. vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
  1596. size of <nn>. This can be used to increase the
  1597. minimum size (128MB on x86). It can also be used to
  1598. decrease the size and leave more room for directly
  1599. mapped kernel RAM.
  1600. vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
  1601. Format: <command>
  1602. vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
  1603. Format: <command>
  1604. vmpoff= [KNL,S390] Perform z/VM CP command after power off.
  1605. Format: <command>
  1606. waveartist= [HW,OSS]
  1607. Format: <io>,<irq>,<dma>,<dma2>
  1608. wd33c93= [HW,SCSI]
  1609. See header of drivers/scsi/wd33c93.c.
  1610. wd7000= [HW,SCSI]
  1611. See header of drivers/scsi/wd7000.c.
  1612. wdt= [WDT] Watchdog
  1613. See Documentation/watchdog/wdt.txt.
  1614. xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
  1615. xd_geo= See header of drivers/block/xd.c.
  1616. xirc2ps_cs= [NET,PCMCIA]
  1617. Format:
  1618. <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
  1619. norandmaps Don't use address space randomization
  1620. Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
  1621. ______________________________________________________________________
  1622. TODO:
  1623. Add documentation for ALSA options.
  1624. Add more DRM drivers.