kernel-parameters.txt 75 KB

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