kernel-parameters.txt 75 KB

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  1. Kernel Parameters
  2. ~~~~~~~~~~~~~~~~~
  3. The following is a consolidated list of the kernel parameters as implemented
  4. (mostly) by the __setup() macro and sorted into English Dictionary order
  5. (defined as ignoring all punctuation and sorting digits before letters in a
  6. case insensitive manner), and with descriptions where known.
  7. Module parameters for loadable modules are specified only as the
  8. parameter name with optional '=' and value as appropriate, such as:
  9. modprobe usbcore blinkenlights=1
  10. Module parameters for modules that are built into the kernel image
  11. are specified on the kernel command line with the module name plus
  12. '.' plus parameter name, with '=' and value if appropriate, such as:
  13. usbcore.blinkenlights=1
  14. This document may not be entirely up to date and comprehensive. The command
  15. "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
  16. module. Loadable modules, after being loaded into the running kernel, also
  17. reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
  18. parameters may be changed at runtime by the command
  19. "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
  20. The parameters listed below are only valid if certain kernel build options were
  21. enabled and if respective hardware is present. The text in square brackets at
  22. the beginning of each description states the restrictions within which a
  23. parameter is applicable:
  24. ACPI ACPI support is enabled.
  25. AGP AGP (Accelerated Graphics Port) is enabled.
  26. ALSA ALSA sound support is enabled.
  27. APIC APIC support is enabled.
  28. APM Advanced Power Management support is enabled.
  29. AVR32 AVR32 architecture is enabled.
  30. AX25 Appropriate AX.25 support is enabled.
  31. BLACKFIN Blackfin architecture is enabled.
  32. DRM Direct Rendering Management support is enabled.
  33. EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
  34. EFI EFI Partitioning (GPT) is enabled
  35. EIDE EIDE/ATAPI support is enabled.
  36. FB The frame buffer device is enabled.
  37. HW Appropriate hardware is enabled.
  38. IA-64 IA-64 architecture is enabled.
  39. IOSCHED More than one I/O scheduler is enabled.
  40. IP_PNP IP DHCP, BOOTP, or RARP is enabled.
  41. ISAPNP ISA PnP code is enabled.
  42. ISDN Appropriate ISDN support is enabled.
  43. JOY Appropriate joystick support is enabled.
  44. LIBATA Libata driver is enabled
  45. LP Printer support is enabled.
  46. LOOP Loopback device support is enabled.
  47. M68k M68k architecture is enabled.
  48. These options have more detailed description inside of
  49. Documentation/m68k/kernel-options.txt.
  50. MCA MCA bus support is enabled.
  51. MDA MDA console support is enabled.
  52. MOUSE Appropriate mouse support is enabled.
  53. MSI Message Signaled Interrupts (PCI).
  54. MTD MTD (Memory Technology Device) support is enabled.
  55. NET Appropriate network support is enabled.
  56. NUMA NUMA support is enabled.
  57. GENERIC_TIME The generic timeofday code is enabled.
  58. NFS Appropriate NFS support is enabled.
  59. OSS OSS sound support is enabled.
  60. PV_OPS A paravirtualized kernel is enabled.
  61. PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
  62. PARISC The PA-RISC architecture is enabled.
  63. PCI PCI bus support is enabled.
  64. PCIE PCI Express support is enabled.
  65. PCMCIA The PCMCIA subsystem is enabled.
  66. PNP Plug & Play support is enabled.
  67. PPC PowerPC architecture is enabled.
  68. PPT Parallel port support is enabled.
  69. PS2 Appropriate PS/2 support is enabled.
  70. RAM RAM disk support is enabled.
  71. ROOTPLUG The example Root Plug LSM is enabled.
  72. S390 S390 architecture is enabled.
  73. SCSI Appropriate SCSI support is enabled.
  74. A lot of drivers has their options described inside of
  75. Documentation/scsi/.
  76. SECURITY Different security models are enabled.
  77. SELINUX SELinux support is enabled.
  78. SERIAL Serial support is enabled.
  79. SH SuperH architecture is enabled.
  80. SMP The kernel is an SMP kernel.
  81. SPARC Sparc architecture is enabled.
  82. SWSUSP Software suspend (hibernation) is enabled.
  83. SUSPEND System suspend states are enabled.
  84. TS Appropriate touchscreen support is enabled.
  85. USB USB support is enabled.
  86. USBHID USB Human Interface Device support is enabled.
  87. V4L Video For Linux support is enabled.
  88. VGA The VGA console has been enabled.
  89. VT Virtual terminal support is enabled.
  90. WDT Watchdog support is enabled.
  91. XT IBM PC/XT MFM hard disk support is enabled.
  92. X86-32 X86-32, aka i386 architecture is enabled.
  93. X86-64 X86-64 architecture is enabled.
  94. More X86-64 boot options can be found in
  95. Documentation/x86/x86_64/boot-options.txt .
  96. X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
  97. In addition, the following text indicates that the option:
  98. BUGS= Relates to possible processor bugs on the said processor.
  99. KNL Is a kernel start-up parameter.
  100. BOOT Is a boot loader parameter.
  101. Parameters denoted with BOOT are actually interpreted by the boot
  102. loader, and have no meaning to the kernel directly.
  103. Do not modify the syntax of boot loader parameters without extreme
  104. need or coordination with <Documentation/x86/i386/boot.txt>.
  105. There are also arch-specific kernel-parameters not documented here.
  106. See for example <Documentation/x86/x86_64/boot-options.txt>.
  107. Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
  108. a trailing = on the name of any parameter states that that parameter will
  109. be entered as an environment variable, whereas its absence indicates that
  110. it will appear as a kernel argument readable via /proc/cmdline by programs
  111. running once the system is up.
  112. The number of kernel parameters is not limited, but the length of the
  113. complete command line (parameters including spaces etc.) is limited to
  114. a fixed number of characters. This limit depends on the architecture
  115. and is between 256 and 4096 characters. It is defined in the file
  116. ./include/asm/setup.h as COMMAND_LINE_SIZE.
  117. acpi= [HW,ACPI,X86-64,i386]
  118. Advanced Configuration and Power Interface
  119. Format: { force | off | ht | strict | noirq }
  120. force -- enable ACPI if default was off
  121. off -- disable ACPI if default was on
  122. noirq -- do not use ACPI for IRQ routing
  123. ht -- run only enough ACPI to enable Hyper Threading
  124. strict -- Be less tolerant of platforms that are not
  125. strictly ACPI specification compliant.
  126. See also Documentation/power/pm.txt, pci=noacpi
  127. acpi_apic_instance= [ACPI, IOAPIC]
  128. Format: <int>
  129. 2: use 2nd APIC table, if available
  130. 1,0: use 1st APIC table
  131. default: 0
  132. acpi_sleep= [HW,ACPI] Sleep options
  133. Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, old_ordering }
  134. See Documentation/power/video.txt for s3_bios and s3_mode.
  135. s3_beep is for debugging; it makes the PC's speaker beep
  136. as soon as the kernel's real-mode entry point is called.
  137. s4_nohwsig prevents ACPI hardware signature from being
  138. used during resume from hibernation.
  139. old_ordering causes the ACPI 1.0 ordering of the _PTS
  140. control method, wrt putting devices into low power
  141. states, to be enforced (the ACPI 2.0 ordering of _PTS is
  142. used by default).
  143. acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
  144. Format: { level | edge | high | low }
  145. acpi_irq_balance [HW,ACPI]
  146. ACPI will balance active IRQs
  147. default in APIC mode
  148. acpi_irq_nobalance [HW,ACPI]
  149. ACPI will not move active IRQs (default)
  150. default in PIC mode
  151. acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
  152. use by PCI
  153. Format: <irq>,<irq>...
  154. acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
  155. Format: <irq>,<irq>...
  156. acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
  157. acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
  158. Format: To spoof as Windows 98: ="Microsoft Windows"
  159. acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
  160. acpi_osi="string1" # add string1 -- only one string
  161. acpi_osi="!string2" # remove built-in string2
  162. acpi_osi= # disable all strings
  163. acpi_serialize [HW,ACPI] force serialization of AML methods
  164. acpi_skip_timer_override [HW,ACPI]
  165. Recognize and ignore IRQ0/pin2 Interrupt Override.
  166. For broken nForce2 BIOS resulting in XT-PIC timer.
  167. acpi_use_timer_override [HW,ACPI}
  168. Use timer override. For some broken Nvidia NF5 boards
  169. that require a timer override, but don't have
  170. HPET
  171. acpi_backlight= [HW,ACPI]
  172. acpi_backlight=vendor
  173. acpi_backlight=video
  174. If set to vendor, prefer vendor specific driver
  175. (e.g. thinkpad_acpi, sony_acpi, etc.) instead
  176. of the ACPI video.ko driver.
  177. acpi_display_output= [HW,ACPI]
  178. acpi_display_output=vendor
  179. acpi_display_output=video
  180. See above.
  181. acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
  182. acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
  183. Format: <int>
  184. CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
  185. debug output. Bits in debug_layer correspond to a
  186. _COMPONENT in an ACPI source file, e.g.,
  187. #define _COMPONENT ACPI_PCI_COMPONENT
  188. Bits in debug_level correspond to a level in
  189. ACPI_DEBUG_PRINT statements, e.g.,
  190. ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
  191. The debug_level mask defaults to "info". See
  192. Documentation/acpi/debug.txt for more information about
  193. debug layers and levels.
  194. Enable processor driver info messages:
  195. acpi.debug_layer=0x20000000
  196. Enable PCI/PCI interrupt routing info messages:
  197. acpi.debug_layer=0x400000
  198. Enable AML "Debug" output, i.e., stores to the Debug
  199. object while interpreting AML:
  200. acpi.debug_layer=0xffffffff acpi.debug_level=0x2
  201. Enable all messages related to ACPI hardware:
  202. acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
  203. Some values produce so much output that the system is
  204. unusable. The "log_buf_len" parameter may be useful
  205. if you need to capture more output.
  206. acpi.power_nocheck= [HW,ACPI]
  207. Format: 1/0 enable/disable the check of power state.
  208. On some bogus BIOS the _PSC object/_STA object of
  209. power resource can't return the correct device power
  210. state. In such case it is unneccessary to check its
  211. power state again in power transition.
  212. 1 : disable the power state check
  213. acpi_pm_good [X86-32,X86-64]
  214. Override the pmtimer bug detection: force the kernel
  215. to assume that this machine's pmtimer latches its value
  216. and always returns good values.
  217. agp= [AGP]
  218. { off | try_unsupported }
  219. off: disable AGP support
  220. try_unsupported: try to drive unsupported chipsets
  221. (may crash computer or cause data corruption)
  222. enable_timer_pin_1 [i386,x86-64]
  223. Enable PIN 1 of APIC timer
  224. Can be useful to work around chipset bugs
  225. (in particular on some ATI chipsets).
  226. The kernel tries to set a reasonable default.
  227. disable_timer_pin_1 [i386,x86-64]
  228. Disable PIN 1 of APIC timer
  229. Can be useful to work around chipset bugs.
  230. ad1848= [HW,OSS]
  231. Format: <io>,<irq>,<dma>,<dma2>,<type>
  232. advansys= [HW,SCSI]
  233. See header of drivers/scsi/advansys.c.
  234. advwdt= [HW,WDT] Advantech WDT
  235. Format: <iostart>,<iostop>
  236. aedsp16= [HW,OSS] Audio Excel DSP 16
  237. Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
  238. See also header of sound/oss/aedsp16.c.
  239. aha152x= [HW,SCSI]
  240. See Documentation/scsi/aha152x.txt.
  241. aha1542= [HW,SCSI]
  242. Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
  243. aic7xxx= [HW,SCSI]
  244. See Documentation/scsi/aic7xxx.txt.
  245. aic79xx= [HW,SCSI]
  246. See Documentation/scsi/aic79xx.txt.
  247. amd_iommu= [HW,X86-84]
  248. Pass parameters to the AMD IOMMU driver in the system.
  249. Possible values are:
  250. isolate - enable device isolation (each device, as far
  251. as possible, will get its own protection
  252. domain) [default]
  253. share - put every device behind one IOMMU into the
  254. same protection domain
  255. fullflush - enable flushing of IO/TLB entries when
  256. they are unmapped. Otherwise they are
  257. flushed before they will be reused, which
  258. is a lot of faster
  259. amd_iommu_size= [HW,X86-64]
  260. Define the size of the aperture for the AMD IOMMU
  261. driver. Possible values are:
  262. '32M', '64M' (default), '128M', '256M', '512M', '1G'
  263. amijoy.map= [HW,JOY] Amiga joystick support
  264. Map of devices attached to JOY0DAT and JOY1DAT
  265. Format: <a>,<b>
  266. See also Documentation/kernel/input/joystick.txt
  267. analog.map= [HW,JOY] Analog joystick and gamepad support
  268. Specifies type or capabilities of an analog joystick
  269. connected to one of 16 gameports
  270. Format: <type1>,<type2>,..<type16>
  271. apc= [HW,SPARC]
  272. Power management functions (SPARCstation-4/5 + deriv.)
  273. Format: noidle
  274. Disable APC CPU standby support. SPARCstation-Fox does
  275. not play well with APC CPU idle - disable it if you have
  276. APC and your system crashes randomly.
  277. apic= [APIC,i386] Advanced Programmable Interrupt Controller
  278. Change the output verbosity whilst booting
  279. Format: { quiet (default) | verbose | debug }
  280. Change the amount of debugging information output
  281. when initialising the APIC and IO-APIC components.
  282. apm= [APM] Advanced Power Management
  283. See header of arch/x86/kernel/apm_32.c.
  284. arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
  285. Format: <io>,<irq>,<nodeID>
  286. ataflop= [HW,M68k]
  287. atarimouse= [HW,MOUSE] Atari Mouse
  288. atascsi= [HW,SCSI] Atari SCSI
  289. atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
  290. EzKey and similar keyboards
  291. atkbd.reset= [HW] Reset keyboard during initialization
  292. atkbd.set= [HW] Select keyboard code set
  293. Format: <int> (2 = AT (default), 3 = PS/2)
  294. atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
  295. keyboards
  296. atkbd.softraw= [HW] Choose between synthetic and real raw mode
  297. Format: <bool> (0 = real, 1 = synthetic (default))
  298. atkbd.softrepeat= [HW]
  299. Use software keyboard repeat
  300. autotest [IA64]
  301. baycom_epp= [HW,AX25]
  302. Format: <io>,<mode>
  303. baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
  304. Format: <io>,<mode>
  305. See header of drivers/net/hamradio/baycom_par.c.
  306. baycom_ser_fdx= [HW,AX25]
  307. BayCom Serial Port AX.25 Modem (Full Duplex Mode)
  308. Format: <io>,<irq>,<mode>[,<baud>]
  309. See header of drivers/net/hamradio/baycom_ser_fdx.c.
  310. baycom_ser_hdx= [HW,AX25]
  311. BayCom Serial Port AX.25 Modem (Half Duplex Mode)
  312. Format: <io>,<irq>,<mode>
  313. See header of drivers/net/hamradio/baycom_ser_hdx.c.
  314. boot_delay= Milliseconds to delay each printk during boot.
  315. Values larger than 10 seconds (10000) are changed to
  316. no delay (0).
  317. Format: integer
  318. bootmem_debug [KNL] Enable bootmem allocator debug messages.
  319. bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
  320. bttv.radio= Most important insmod options are available as
  321. kernel args too.
  322. bttv.pll= See Documentation/video4linux/bttv/Insmod-options
  323. bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
  324. BusLogic= [HW,SCSI]
  325. See drivers/scsi/BusLogic.c, comment before function
  326. BusLogic_ParseDriverOptions().
  327. c101= [NET] Moxa C101 synchronous serial card
  328. cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
  329. Sometimes CPU hardware bugs make them report the cache
  330. size incorrectly. The kernel will attempt work arounds
  331. to fix known problems, but for some CPUs it is not
  332. possible to determine what the correct size should be.
  333. This option provides an override for these situations.
  334. security= [SECURITY] Choose a security module to enable at boot.
  335. If this boot parameter is not specified, only the first
  336. security module asking for security registration will be
  337. loaded. An invalid security module name will be treated
  338. as if no module has been chosen.
  339. capability.disable=
  340. [SECURITY] Disable capabilities. This would normally
  341. be used only if an alternative security model is to be
  342. configured. Potentially dangerous and should only be
  343. used if you are entirely sure of the consequences.
  344. ccw_timeout_log [S390]
  345. See Documentation/s390/CommonIO for details.
  346. cgroup_disable= [KNL] Disable a particular controller
  347. Format: {name of the controller(s) to disable}
  348. {Currently supported controllers - "memory"}
  349. checkreqprot [SELINUX] Set initial checkreqprot flag value.
  350. Format: { "0" | "1" }
  351. See security/selinux/Kconfig help text.
  352. 0 -- check protection applied by kernel (includes
  353. any implied execute protection).
  354. 1 -- check protection requested by application.
  355. Default value is set via a kernel config option.
  356. Value can be changed at runtime via
  357. /selinux/checkreqprot.
  358. cio_ignore= [S390]
  359. See Documentation/s390/CommonIO for details.
  360. clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
  361. [Deprecated]
  362. Forces specified clocksource (if available) to be used
  363. when calculating gettimeofday(). If specified
  364. clocksource is not available, it defaults to PIT.
  365. Format: { pit | tsc | cyclone | pmtmr }
  366. clocksource= [GENERIC_TIME] Override the default clocksource
  367. Format: <string>
  368. Override the default clocksource and use the clocksource
  369. with the name specified.
  370. Some clocksource names to choose from, depending on
  371. the platform:
  372. [all] jiffies (this is the base, fallback clocksource)
  373. [ACPI] acpi_pm
  374. [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
  375. pxa_timer,timer3,32k_counter,timer0_1
  376. [AVR32] avr32
  377. [X86-32] pit,hpet,tsc,vmi-timer;
  378. scx200_hrt on Geode; cyclone on IBM x440
  379. [MIPS] MIPS
  380. [PARISC] cr16
  381. [S390] tod
  382. [SH] SuperH
  383. [SPARC64] tick
  384. [X86-64] hpet,tsc
  385. clearcpuid=BITNUM [X86]
  386. Disable CPUID feature X for the kernel. See
  387. include/asm-x86/cpufeature.h for the valid bit numbers.
  388. Note the Linux specific bits are not necessarily
  389. stable over kernel options, but the vendor specific
  390. ones should be.
  391. Also note that user programs calling CPUID directly
  392. or using the feature without checking anything
  393. will still see it. This just prevents it from
  394. being used by the kernel or shown in /proc/cpuinfo.
  395. Also note the kernel might malfunction if you disable
  396. some critical bits.
  397. code_bytes [IA32/X86_64] How many bytes of object code to print
  398. in an oops report.
  399. Range: 0 - 8192
  400. Default: 64
  401. hpet= [X86-32,HPET] option to control HPET usage
  402. Format: { enable (default) | disable | force }
  403. disable: disable HPET and use PIT instead
  404. force: allow force enabled of undocumented chips (ICH4,
  405. VIA, nVidia)
  406. com20020= [HW,NET] ARCnet - COM20020 chipset
  407. Format:
  408. <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
  409. com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
  410. Format: <io>[,<irq>]
  411. com90xx= [HW,NET]
  412. ARCnet - COM90xx chipset (memory-mapped buffers)
  413. Format: <io>[,<irq>[,<memstart>]]
  414. condev= [HW,S390] console device
  415. conmode=
  416. console= [KNL] Output console device and options.
  417. tty<n> Use the virtual console device <n>.
  418. ttyS<n>[,options]
  419. ttyUSB0[,options]
  420. Use the specified serial port. The options are of
  421. the form "bbbbpnf", where "bbbb" is the baud rate,
  422. "p" is parity ("n", "o", or "e"), "n" is number of
  423. bits, and "f" is flow control ("r" for RTS or
  424. omit it). Default is "9600n8".
  425. See Documentation/serial-console.txt for more
  426. information. See
  427. Documentation/networking/netconsole.txt for an
  428. alternative.
  429. uart[8250],io,<addr>[,options]
  430. uart[8250],mmio,<addr>[,options]
  431. Start an early, polled-mode console on the 8250/16550
  432. UART at the specified I/O port or MMIO address,
  433. switching to the matching ttyS device later. The
  434. options are the same as for ttyS, above.
  435. If the device connected to the port is not a TTY but a braille
  436. device, prepend "brl," before the device type, for instance
  437. console=brl,ttyS0
  438. For now, only VisioBraille is supported.
  439. earlycon= [KNL] Output early console device and options.
  440. uart[8250],io,<addr>[,options]
  441. uart[8250],mmio,<addr>[,options]
  442. Start an early, polled-mode console on the 8250/16550
  443. UART at the specified I/O port or MMIO address.
  444. The options are the same as for ttyS, above.
  445. no_console_suspend
  446. [HW] Never suspend the console
  447. Disable suspending of consoles during suspend and
  448. hibernate operations. Once disabled, debugging
  449. messages can reach various consoles while the rest
  450. of the system is being put to sleep (ie, while
  451. debugging driver suspend/resume hooks). This may
  452. not work reliably with all consoles, but is known
  453. to work with serial and VGA consoles.
  454. cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
  455. Format:
  456. <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
  457. crashkernel=nn[KMG]@ss[KMG]
  458. [KNL] Reserve a chunk of physical memory to
  459. hold a kernel to switch to with kexec on panic.
  460. crashkernel=range1:size1[,range2:size2,...][@offset]
  461. [KNL] Same as above, but depends on the memory
  462. in the running system. The syntax of range is
  463. start-[end] where start and end are both
  464. a memory unit (amount[KMG]). See also
  465. Documentation/kdump/kdump.txt for a example.
  466. cs4232= [HW,OSS]
  467. Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
  468. cs89x0_dma= [HW,NET]
  469. Format: <dma>
  470. cs89x0_media= [HW,NET]
  471. Format: { rj45 | aui | bnc }
  472. dasd= [HW,NET]
  473. See header of drivers/s390/block/dasd_devmap.c.
  474. db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
  475. (one device per port)
  476. Format: <port#>,<type>
  477. See also Documentation/input/joystick-parport.txt
  478. debug [KNL] Enable kernel debugging (events log level).
  479. debug_locks_verbose=
  480. [KNL] verbose self-tests
  481. Format=<0|1>
  482. Print debugging info while doing the locking API
  483. self-tests.
  484. We default to 0 (no extra messages), setting it to
  485. 1 will print _a lot_ more information - normally
  486. only useful to kernel developers.
  487. debug_objects [KNL] Enable object debugging
  488. debugpat [X86] Enable PAT debugging
  489. decnet.addr= [HW,NET]
  490. Format: <area>[,<node>]
  491. See also Documentation/networking/decnet.txt.
  492. vt.default_blu= [VT]
  493. Format: <blue0>,<blue1>,<blue2>,...,<blue15>
  494. Change the default blue palette of the console.
  495. This is a 16-member array composed of values
  496. ranging from 0-255.
  497. vt.default_grn= [VT]
  498. Format: <green0>,<green1>,<green2>,...,<green15>
  499. Change the default green palette of the console.
  500. This is a 16-member array composed of values
  501. ranging from 0-255.
  502. vt.default_red= [VT]
  503. Format: <red0>,<red1>,<red2>,...,<red15>
  504. Change the default red palette of the console.
  505. This is a 16-member array composed of values
  506. ranging from 0-255.
  507. vt.default_utf8=
  508. [VT]
  509. Format=<0|1>
  510. Set system-wide default UTF-8 mode for all tty's.
  511. Default is 1, i.e. UTF-8 mode is enabled for all
  512. newly opened terminals.
  513. dhash_entries= [KNL]
  514. Set number of hash buckets for dentry cache.
  515. digi= [HW,SERIAL]
  516. IO parameters + enable/disable command.
  517. digiepca= [HW,SERIAL]
  518. See drivers/char/README.epca and
  519. Documentation/serial/digiepca.txt.
  520. disable_mtrr_cleanup [X86]
  521. enable_mtrr_cleanup [X86]
  522. The kernel tries to adjust MTRR layout from continuous
  523. to discrete, to make X server driver able to add WB
  524. entry later. This parameter enables/disables that.
  525. mtrr_chunk_size=nn[KMG] [X86]
  526. used for mtrr cleanup. It is largest continous chunk
  527. that could hold holes aka. UC entries.
  528. mtrr_gran_size=nn[KMG] [X86]
  529. Used for mtrr cleanup. It is granularity of mtrr block.
  530. Default is 1.
  531. Large value could prevent small alignment from
  532. using up MTRRs.
  533. mtrr_spare_reg_nr=n [X86]
  534. Format: <integer>
  535. Range: 0,7 : spare reg number
  536. Default : 1
  537. Used for mtrr cleanup. It is spare mtrr entries number.
  538. Set to 2 or more if your graphical card needs more.
  539. disable_mtrr_trim [X86, Intel and AMD only]
  540. By default the kernel will trim any uncacheable
  541. memory out of your available memory pool based on
  542. MTRR settings. This parameter disables that behavior,
  543. possibly causing your machine to run very slowly.
  544. dmasound= [HW,OSS] Sound subsystem buffers
  545. dscc4.setup= [NET]
  546. dtc3181e= [HW,SCSI]
  547. earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
  548. earlyprintk=vga
  549. earlyprintk=serial[,ttySn[,baudrate]]
  550. earlyprintk=dbgp
  551. Append ",keep" to not disable it when the real console
  552. takes over.
  553. Only vga or serial or usb debug port at a time.
  554. Currently only ttyS0 and ttyS1 are supported.
  555. Interaction with the standard serial driver is not
  556. very good.
  557. The VGA output is eventually overwritten by the real
  558. console.
  559. eata= [HW,SCSI]
  560. edd= [EDD]
  561. Format: {"off" | "on" | "skip[mbr]"}
  562. eisa_irq_edge= [PARISC,HW]
  563. See header of drivers/parisc/eisa.c.
  564. elanfreq= [X86-32]
  565. See comment before function elanfreq_setup() in
  566. arch/x86/kernel/cpu/cpufreq/elanfreq.c.
  567. elevator= [IOSCHED]
  568. Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
  569. See Documentation/block/as-iosched.txt and
  570. Documentation/block/deadline-iosched.txt for details.
  571. elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
  572. Specifies physical address of start of kernel core
  573. image elf header. Generally kexec loader will
  574. pass this option to capture kernel.
  575. See Documentation/kdump/kdump.txt for details.
  576. enforcing [SELINUX] Set initial enforcing status.
  577. Format: {"0" | "1"}
  578. See security/selinux/Kconfig help text.
  579. 0 -- permissive (log only, no denials).
  580. 1 -- enforcing (deny and log).
  581. Default value is 0.
  582. Value can be changed at runtime via /selinux/enforce.
  583. es1371= [HW,OSS]
  584. Format: <spdif>,[<nomix>,[<amplifier>]]
  585. See also header of sound/oss/es1371.c.
  586. ether= [HW,NET] Ethernet cards parameters
  587. This option is obsoleted by the "netdev=" option, which
  588. has equivalent usage. See its documentation for details.
  589. eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
  590. Format: <io>[,<irq>]
  591. failslab=
  592. fail_page_alloc=
  593. fail_make_request=[KNL]
  594. General fault injection mechanism.
  595. Format: <interval>,<probability>,<space>,<times>
  596. See also /Documentation/fault-injection/.
  597. fd_mcs= [HW,SCSI]
  598. See header of drivers/scsi/fd_mcs.c.
  599. fdomain= [HW,SCSI]
  600. See header of drivers/scsi/fdomain.c.
  601. floppy= [HW]
  602. See Documentation/blockdev/floppy.txt.
  603. force_pal_cache_flush
  604. [IA-64] Avoid check_sal_cache_flush which may hang on
  605. buggy SAL_CACHE_FLUSH implementations. Using this
  606. parameter will force ia64_sal_cache_flush to call
  607. ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
  608. gamecon.map[2|3]=
  609. [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
  610. support via parallel port (up to 5 devices per port)
  611. Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
  612. See also Documentation/input/joystick-parport.txt
  613. gamma= [HW,DRM]
  614. gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
  615. Format: off | on
  616. default: on
  617. gdth= [HW,SCSI]
  618. See header of drivers/scsi/gdth.c.
  619. gpt [EFI] Forces disk with valid GPT signature but
  620. invalid Protective MBR to be treated as GPT.
  621. gvp11= [HW,SCSI]
  622. hashdist= [KNL,NUMA] Large hashes allocated during boot
  623. are distributed across NUMA nodes. Defaults on
  624. for IA-64, off otherwise.
  625. Format: 0 | 1 (for off | on)
  626. hcl= [IA-64] SGI's Hardware Graph compatibility layer
  627. hd= [EIDE] (E)IDE hard drive subsystem geometry
  628. Format: <cyl>,<head>,<sect>
  629. highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
  630. size of <nn>. This works even on boxes that have no
  631. highmem otherwise. This also works to reduce highmem
  632. size on bigger boxes.
  633. highres= [KNL] Enable/disable high resolution timer mode.
  634. Valid parameters: "on", "off"
  635. Default: "on"
  636. hisax= [HW,ISDN]
  637. See Documentation/isdn/README.HiSax.
  638. hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
  639. hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
  640. On x86-64 and powerpc, this option can be specified
  641. multiple times interleaved with hugepages= to reserve
  642. huge pages of different sizes. Valid pages sizes on
  643. x86-64 are 2M (when the CPU supports "pse") and 1G
  644. (when the CPU supports the "pdpe1gb" cpuinfo flag)
  645. Note that 1GB pages can only be allocated at boot time
  646. using hugepages= and not freed afterwards.
  647. default_hugepagesz=
  648. [same as hugepagesz=] The size of the default
  649. HugeTLB page size. This is the size represented by
  650. the legacy /proc/ hugepages APIs, used for SHM, and
  651. default size when mounting hugetlbfs filesystems.
  652. Defaults to the default architecture's huge page size
  653. if not specified.
  654. hlt [BUGS=ARM,SH]
  655. i8042.debug [HW] Toggle i8042 debug mode
  656. i8042.direct [HW] Put keyboard port into non-translated mode
  657. i8042.dumbkbd [HW] Pretend that controller can only read data from
  658. keyboard and cannot control its state
  659. (Don't attempt to blink the leds)
  660. i8042.noaux [HW] Don't check for auxiliary (== mouse) port
  661. i8042.nokbd [HW] Don't check/create keyboard port
  662. i8042.noloop [HW] Disable the AUX Loopback command while probing
  663. for the AUX port
  664. i8042.nomux [HW] Don't check presence of an active multiplexing
  665. controller
  666. i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
  667. controllers
  668. i8042.panicblink=
  669. [HW] Frequency with which keyboard LEDs should blink
  670. when kernel panics (default is 0.5 sec)
  671. i8042.reset [HW] Reset the controller during init and cleanup
  672. i8042.unlock [HW] Unlock (ignore) the keylock
  673. i810= [HW,DRM]
  674. i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
  675. indicates that the driver is running on unsupported
  676. hardware.
  677. i8k.force [HW] Activate i8k driver even if SMM BIOS signature
  678. does not match list of supported models.
  679. i8k.power_status
  680. [HW] Report power status in /proc/i8k
  681. (disabled by default)
  682. i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
  683. capability is set.
  684. ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
  685. See Documentation/mca.txt.
  686. icn= [HW,ISDN]
  687. Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
  688. ide= [HW] (E)IDE subsystem
  689. Format: ide=nodma or ide=doubler
  690. See Documentation/ide/ide.txt.
  691. idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
  692. See Documentation/ide/ide.txt.
  693. idle= [X86]
  694. Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
  695. Poll forces a polling idle loop that can slightly improves the performance
  696. of waking up a idle CPU, but will use a lot of power and make the system
  697. run hot. Not recommended.
  698. idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
  699. to not use it because it doesn't save as much power as a normal idle
  700. loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
  701. as idle=poll.
  702. idle=halt. Halt is forced to be used for CPU idle.
  703. In such case C2/C3 won't be used again.
  704. idle=nomwait. Disable mwait for CPU C-states
  705. ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
  706. Claim all unknown PCI IDE storage controllers.
  707. ignore_loglevel [KNL]
  708. Ignore loglevel setting - this will print /all/
  709. kernel messages to the console. Useful for debugging.
  710. ihash_entries= [KNL]
  711. Set number of hash buckets for inode cache.
  712. in2000= [HW,SCSI]
  713. See header of drivers/scsi/in2000.c.
  714. init= [KNL]
  715. Format: <full_path>
  716. Run specified binary instead of /sbin/init as init
  717. process.
  718. initcall_debug [KNL] Trace initcalls as they are executed. Useful
  719. for working out where the kernel is dying during
  720. startup.
  721. initrd= [BOOT] Specify the location of the initial ramdisk
  722. inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
  723. Format: <irq>
  724. inttest= [IA64]
  725. iommu= [x86]
  726. off
  727. force
  728. noforce
  729. biomerge
  730. panic
  731. nopanic
  732. merge
  733. nomerge
  734. forcesac
  735. soft
  736. intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
  737. off
  738. Disable intel iommu driver.
  739. igfx_off [Default Off]
  740. By default, gfx is mapped as normal device. If a gfx
  741. device has a dedicated DMAR unit, the DMAR unit is
  742. bypassed by not enabling DMAR with this option. In
  743. this case, gfx device will use physical address for
  744. DMA.
  745. forcedac [x86_64]
  746. With this option iommu will not optimize to look
  747. for io virtual address below 32 bit forcing dual
  748. address cycle on pci bus for cards supporting greater
  749. than 32 bit addressing. The default is to look
  750. for translation below 32 bit and if not available
  751. then look in the higher range.
  752. strict [Default Off]
  753. With this option on every unmap_single operation will
  754. result in a hardware IOTLB flush operation as opposed
  755. to batching them for performance.
  756. io_delay= [X86-32,X86-64] I/O delay method
  757. 0x80
  758. Standard port 0x80 based delay
  759. 0xed
  760. Alternate port 0xed based delay (needed on some systems)
  761. udelay
  762. Simple two microseconds delay
  763. none
  764. No delay
  765. io7= [HW] IO7 for Marvel based alpha systems
  766. See comment before marvel_specify_io7 in
  767. arch/alpha/kernel/core_marvel.c.
  768. ip= [IP_PNP]
  769. See Documentation/filesystems/nfsroot.txt.
  770. ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
  771. See comment before ip2_setup() in
  772. drivers/char/ip2/ip2base.c.
  773. ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
  774. See header of drivers/scsi/ips.c.
  775. ports= [IP_VS_FTP] IPVS ftp helper module
  776. Default is 21.
  777. Up to 8 (IP_VS_APP_MAX_PORTS) ports
  778. may be specified.
  779. Format: <port>,<port>....
  780. irqfixup [HW]
  781. When an interrupt is not handled search all handlers
  782. for it. Intended to get systems with badly broken
  783. firmware running.
  784. irqpoll [HW]
  785. When an interrupt is not handled search all handlers
  786. for it. Also check all handlers each timer
  787. interrupt. Intended to get systems with badly broken
  788. firmware running.
  789. isapnp= [ISAPNP]
  790. Format: <RDP>,<reset>,<pci_scan>,<verbosity>
  791. isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
  792. Format:
  793. <cpu number>,...,<cpu number>
  794. or
  795. <cpu number>-<cpu number>
  796. (must be a positive range in ascending order)
  797. or a mixture
  798. <cpu number>,...,<cpu number>-<cpu number>
  799. This option can be used to specify one or more CPUs
  800. to isolate from the general SMP balancing and scheduling
  801. algorithms. You can move a process onto or off an
  802. "isolated" CPU via the CPU affinity syscalls or cpuset.
  803. <cpu number> begins at 0 and the maximum value is
  804. "number of CPUs in system - 1".
  805. This option is the preferred way to isolate CPUs. The
  806. alternative -- manually setting the CPU mask of all
  807. tasks in the system -- can cause problems and
  808. suboptimal load balancer performance.
  809. iucv= [HW,NET]
  810. js= [HW,JOY] Analog joystick
  811. See Documentation/input/joystick.txt.
  812. kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
  813. specifies the amount of memory usable by the kernel
  814. for non-movable allocations. The requested amount is
  815. spread evenly throughout all nodes in the system. The
  816. remaining memory in each node is used for Movable
  817. pages. In the event, a node is too small to have both
  818. kernelcore and Movable pages, kernelcore pages will
  819. take priority and other nodes will have a larger number
  820. of kernelcore pages. The Movable zone is used for the
  821. allocation of pages that may be reclaimed or moved
  822. by the page migration subsystem. This means that
  823. HugeTLB pages may not be allocated from this zone.
  824. Note that allocations like PTEs-from-HighMem still
  825. use the HighMem zone if it exists, and the Normal
  826. zone if it does not.
  827. movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
  828. is similar to kernelcore except it specifies the
  829. amount of memory used for migratable allocations.
  830. If both kernelcore and movablecore is specified,
  831. then kernelcore will be at *least* the specified
  832. value but may be more. If movablecore on its own
  833. is specified, the administrator must be careful
  834. that the amount of memory usable for all allocations
  835. is not too small.
  836. keepinitrd [HW,ARM]
  837. kstack=N [X86-32,X86-64] Print N words from the kernel stack
  838. in oops dumps.
  839. kgdboc= [HW] kgdb over consoles.
  840. Requires a tty driver that supports console polling.
  841. (only serial suported for now)
  842. Format: <serial_device>[,baud]
  843. kmac= [MIPS] korina ethernet MAC address.
  844. Configure the RouterBoard 532 series on-chip
  845. Ethernet adapter MAC address.
  846. l2cr= [PPC]
  847. l3cr= [PPC]
  848. lapic [X86-32,APIC] Enable the local APIC even if BIOS
  849. disabled it.
  850. lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
  851. C2 power state.
  852. libata.dma= [LIBATA] DMA control
  853. libata.dma=0 Disable all PATA and SATA DMA
  854. libata.dma=1 PATA and SATA Disk DMA only
  855. libata.dma=2 ATAPI (CDROM) DMA only
  856. libata.dma=4 Compact Flash DMA only
  857. Combinations also work, so libata.dma=3 enables DMA
  858. for disks and CDROMs, but not CFs.
  859. libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
  860. when set.
  861. Format: <int>
  862. libata.force= [LIBATA] Force configurations. The format is comma
  863. separated list of "[ID:]VAL" where ID is
  864. PORT[:DEVICE]. PORT and DEVICE are decimal numbers
  865. matching port, link or device. Basically, it matches
  866. the ATA ID string printed on console by libata. If
  867. the whole ID part is omitted, the last PORT and DEVICE
  868. values are used. If ID hasn't been specified yet, the
  869. configuration applies to all ports, links and devices.
  870. If only DEVICE is omitted, the parameter applies to
  871. the port and all links and devices behind it. DEVICE
  872. number of 0 either selects the first device or the
  873. first fan-out link behind PMP device. It does not
  874. select the host link. DEVICE number of 15 selects the
  875. host link and device attached to it.
  876. The VAL specifies the configuration to force. As long
  877. as there's no ambiguity shortcut notation is allowed.
  878. For example, both 1.5 and 1.5G would work for 1.5Gbps.
  879. The following configurations can be forced.
  880. * Cable type: 40c, 80c, short40c, unk, ign or sata.
  881. Any ID with matching PORT is used.
  882. * SATA link speed limit: 1.5Gbps or 3.0Gbps.
  883. * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
  884. udma[/][16,25,33,44,66,100,133] notation is also
  885. allowed.
  886. * [no]ncq: Turn on or off NCQ.
  887. * nohrst, nosrst, norst: suppress hard, soft
  888. and both resets.
  889. If there are multiple matching configurations changing
  890. the same attribute, the last one is used.
  891. load_ramdisk= [RAM] List of ramdisks to load from floppy
  892. See Documentation/blockdev/ramdisk.txt.
  893. lockd.nlm_grace_period=P [NFS] Assign grace period.
  894. Format: <integer>
  895. lockd.nlm_tcpport=N [NFS] Assign TCP port.
  896. Format: <integer>
  897. lockd.nlm_timeout=T [NFS] Assign timeout value.
  898. Format: <integer>
  899. lockd.nlm_udpport=M [NFS] Assign UDP port.
  900. Format: <integer>
  901. logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
  902. Format: <irq>
  903. loglevel= All Kernel Messages with a loglevel smaller than the
  904. console loglevel will be printed to the console. It can
  905. also be changed with klogd or other programs. The
  906. loglevels are defined as follows:
  907. 0 (KERN_EMERG) system is unusable
  908. 1 (KERN_ALERT) action must be taken immediately
  909. 2 (KERN_CRIT) critical conditions
  910. 3 (KERN_ERR) error conditions
  911. 4 (KERN_WARNING) warning conditions
  912. 5 (KERN_NOTICE) normal but significant condition
  913. 6 (KERN_INFO) informational
  914. 7 (KERN_DEBUG) debug-level messages
  915. log_buf_len=n Sets the size of the printk ring buffer, in bytes.
  916. Format: { n | nk | nM }
  917. n must be a power of two. The default size
  918. is set in the kernel config file.
  919. logo.nologo [FB] Disables display of the built-in Linux logo.
  920. This may be used to provide more screen space for
  921. kernel log messages and is useful when debugging
  922. kernel boot problems.
  923. lp=0 [LP] Specify parallel ports to use, e.g,
  924. lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
  925. lp=reset first parallel port). 'lp=0' disables the
  926. lp=auto printer driver. 'lp=reset' (which can be
  927. specified in addition to the ports) causes
  928. attached printers to be reset. Using
  929. lp=port1,port2,... specifies the parallel ports
  930. to associate lp devices with, starting with
  931. lp0. A port specification may be 'none' to skip
  932. that lp device, or a parport name such as
  933. 'parport0'. Specifying 'lp=auto' instead of a
  934. port specification list means that device IDs
  935. from each port should be examined, to see if
  936. an IEEE 1284-compliant printer is attached; if
  937. so, the driver will manage that printer.
  938. See also header of drivers/char/lp.c.
  939. lpj=n [KNL]
  940. Sets loops_per_jiffy to given constant, thus avoiding
  941. time-consuming boot-time autodetection (up to 250 ms per
  942. CPU). 0 enables autodetection (default). To determine
  943. the correct value for your kernel, boot with normal
  944. autodetection and see what value is printed. Note that
  945. on SMP systems the preset will be applied to all CPUs,
  946. which is likely to cause problems if your CPUs need
  947. significantly divergent settings. An incorrect value
  948. will cause delays in the kernel to be wrong, leading to
  949. unpredictable I/O errors and other breakage. Although
  950. unlikely, in the extreme case this might damage your
  951. hardware.
  952. ltpc= [NET]
  953. Format: <io>,<irq>,<dma>
  954. mac5380= [HW,SCSI] Format:
  955. <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
  956. machvec= [IA64] Force the use of a particular machine-vector
  957. (machvec) in a generic kernel.
  958. Example: machvec=hpzx1_swiotlb
  959. max_loop= [LOOP] Maximum number of loopback devices that can
  960. be mounted
  961. Format: <1-256>
  962. maxcpus= [SMP] Maximum number of processors that an SMP kernel
  963. should make use of. maxcpus=n : n >= 0 limits the
  964. kernel to using 'n' processors. n=0 is a special case,
  965. it is equivalent to "nosmp", which also disables
  966. the IO APIC.
  967. max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater than
  968. or equal to this physical address is ignored.
  969. max_luns= [SCSI] Maximum number of LUNs to probe.
  970. Should be between 1 and 2^32-1.
  971. max_report_luns=
  972. [SCSI] Maximum number of LUNs received.
  973. Should be between 1 and 16384.
  974. mcatest= [IA-64]
  975. mce [X86-32] Machine Check Exception
  976. mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
  977. md= [HW] RAID subsystems devices and level
  978. See Documentation/md.txt.
  979. mdacon= [MDA]
  980. Format: <first>,<last>
  981. Specifies range of consoles to be captured by the MDA.
  982. mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
  983. Amount of memory to be used when the kernel is not able
  984. to see the whole system memory or for test.
  985. [X86-32] Use together with memmap= to avoid physical
  986. address space collisions. Without memmap= PCI devices
  987. could be placed at addresses belonging to unused RAM.
  988. mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
  989. memory.
  990. memchunk=nn[KMG]
  991. [KNL,SH] Allow user to override the default size for
  992. per-device physically contiguous DMA buffers.
  993. memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
  994. E820 memory map, as specified by the user.
  995. Such memmap=exactmap lines can be constructed based on
  996. BIOS output or other requirements. See the memmap=nn@ss
  997. option description.
  998. memmap=nn[KMG]@ss[KMG]
  999. [KNL] Force usage of a specific region of memory
  1000. Region of memory to be used, from ss to ss+nn.
  1001. memmap=nn[KMG]#ss[KMG]
  1002. [KNL,ACPI] Mark specific memory as ACPI data.
  1003. Region of memory to be used, from ss to ss+nn.
  1004. memmap=nn[KMG]$ss[KMG]
  1005. [KNL,ACPI] Mark specific memory as reserved.
  1006. Region of memory to be used, from ss to ss+nn.
  1007. Example: Exclude memory from 0x18690000-0x1869ffff
  1008. memmap=64K$0x18690000
  1009. or
  1010. memmap=0x10000$0x18690000
  1011. memory_corruption_check=0/1 [X86]
  1012. Some BIOSes seem to corrupt the first 64k of
  1013. memory when doing things like suspend/resume.
  1014. Setting this option will scan the memory
  1015. looking for corruption. Enabling this will
  1016. both detect corruption and prevent the kernel
  1017. from using the memory being corrupted.
  1018. However, its intended as a diagnostic tool; if
  1019. repeatable BIOS-originated corruption always
  1020. affects the same memory, you can use memmap=
  1021. to prevent the kernel from using that memory.
  1022. memory_corruption_check_size=size [X86]
  1023. By default it checks for corruption in the low
  1024. 64k, making this memory unavailable for normal
  1025. use. Use this parameter to scan for
  1026. corruption in more or less memory.
  1027. memory_corruption_check_period=seconds [X86]
  1028. By default it checks for corruption every 60
  1029. seconds. Use this parameter to check at some
  1030. other rate. 0 disables periodic checking.
  1031. memtest= [KNL,X86] Enable memtest
  1032. Format: <integer>
  1033. range: 0,4 : pattern number
  1034. default : 0 <disable>
  1035. meye.*= [HW] Set MotionEye Camera parameters
  1036. See Documentation/video4linux/meye.txt.
  1037. mfgpt_irq= [IA-32] Specify the IRQ to use for the
  1038. Multi-Function General Purpose Timers on AMD Geode
  1039. platforms.
  1040. mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
  1041. the BIOS has incorrectly applied a workaround. TinyBIOS
  1042. version 0.98 is known to be affected, 0.99 fixes the
  1043. problem by letting the user disable the workaround.
  1044. mga= [HW,DRM]
  1045. min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
  1046. physical address is ignored.
  1047. mminit_loglevel=
  1048. [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
  1049. parameter allows control of the logging verbosity for
  1050. the additional memory initialisation checks. A value
  1051. of 0 disables mminit logging and a level of 4 will
  1052. log everything. Information is printed at KERN_DEBUG
  1053. so loglevel=8 may also need to be specified.
  1054. mousedev.tap_time=
  1055. [MOUSE] Maximum time between finger touching and
  1056. leaving touchpad surface for touch to be considered
  1057. a tap and be reported as a left button click (for
  1058. touchpads working in absolute mode only).
  1059. Format: <msecs>
  1060. mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
  1061. reporting absolute coordinates, such as tablets
  1062. mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
  1063. reporting absolute coordinates, such as tablets
  1064. mpu401= [HW,OSS]
  1065. Format: <io>,<irq>
  1066. MTD_Partition= [MTD]
  1067. Format: <name>,<region-number>,<size>,<offset>
  1068. MTD_Region= [MTD] Format:
  1069. <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
  1070. mtdparts= [MTD]
  1071. See drivers/mtd/cmdlinepart.c.
  1072. mtdset= [ARM]
  1073. ARM/S3C2412 JIVE boot control
  1074. See arch/arm/mach-s3c2412/mach-jive.c
  1075. mtouchusb.raw_coordinates=
  1076. [HW] Make the MicroTouch USB driver use raw coordinates
  1077. ('y', default) or cooked coordinates ('n')
  1078. n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
  1079. NCR_D700= [HW,SCSI]
  1080. See header of drivers/scsi/NCR_D700.c.
  1081. ncr5380= [HW,SCSI]
  1082. ncr53c400= [HW,SCSI]
  1083. ncr53c400a= [HW,SCSI]
  1084. ncr53c406a= [HW,SCSI]
  1085. ncr53c8xx= [HW,SCSI]
  1086. netdev= [NET] Network devices parameters
  1087. Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
  1088. Note that mem_start is often overloaded to mean
  1089. something different and driver-specific.
  1090. This usage is only documented in each driver source
  1091. file if at all.
  1092. nf_conntrack.acct=
  1093. [NETFILTER] Enable connection tracking flow accounting
  1094. 0 to disable accounting
  1095. 1 to enable accounting
  1096. Default value depends on CONFIG_NF_CT_ACCT that is
  1097. going to be removed in 2.6.29.
  1098. nfsaddrs= [NFS]
  1099. See Documentation/filesystems/nfsroot.txt.
  1100. nfsroot= [NFS] nfs root filesystem for disk-less boxes.
  1101. See Documentation/filesystems/nfsroot.txt.
  1102. nfs.callback_tcpport=
  1103. [NFS] set the TCP port on which the NFSv4 callback
  1104. channel should listen.
  1105. nfs.idmap_cache_timeout=
  1106. [NFS] set the maximum lifetime for idmapper cache
  1107. entries.
  1108. nfs.enable_ino64=
  1109. [NFS] enable 64-bit inode numbers.
  1110. If zero, the NFS client will fake up a 32-bit inode
  1111. number for the readdir() and stat() syscalls instead
  1112. of returning the full 64-bit number.
  1113. The default is to return 64-bit inode numbers.
  1114. nmi_debug= [KNL,AVR32] Specify one or more actions to take
  1115. when a NMI is triggered.
  1116. Format: [state][,regs][,debounce][,die]
  1117. nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
  1118. no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
  1119. emulation library even if a 387 maths coprocessor
  1120. is present.
  1121. noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
  1122. caches in the slab allocator. Saves per-node memory,
  1123. but will impact performance.
  1124. noalign [KNL,ARM]
  1125. noapic [SMP,APIC] Tells the kernel to not make use of any
  1126. IOAPICs that may be present in the system.
  1127. nobats [PPC] Do not use BATs for mapping kernel lowmem
  1128. on "Classic" PPC cores.
  1129. nocache [ARM]
  1130. nodelayacct [KNL] Disable per-task delay accounting
  1131. nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
  1132. nodsp [SH] Disable hardware DSP at boot time.
  1133. noefi [X86-32,X86-64] Disable EFI runtime services support.
  1134. noexec [IA-64]
  1135. noexec [X86-32,X86-64]
  1136. On X86-32 available only on PAE configured kernels.
  1137. noexec=on: enable non-executable mappings (default)
  1138. noexec=off: disable non-executable mappings
  1139. noexec32 [X86-64]
  1140. This affects only 32-bit executables.
  1141. noexec32=on: enable non-executable mappings (default)
  1142. read doesn't imply executable mappings
  1143. noexec32=off: disable non-executable mappings
  1144. read implies executable mappings
  1145. nofpu [SH] Disable hardware FPU at boot time.
  1146. nofxsr [BUGS=X86-32] Disables x86 floating point extended
  1147. register save and restore. The kernel will only save
  1148. legacy floating-point registers on task switch.
  1149. noclflush [BUGS=X86] Don't use the CLFLUSH instruction
  1150. nohlt [BUGS=ARM,SH]
  1151. no-hlt [BUGS=X86-32] Tells the kernel that the hlt
  1152. instruction doesn't work correctly and not to
  1153. use it.
  1154. nohalt [IA-64] Tells the kernel not to use the power saving
  1155. function PAL_HALT_LIGHT when idle. This increases
  1156. power-consumption. On the positive side, it reduces
  1157. interrupt wake-up latency, which may improve performance
  1158. in certain environments such as networked servers or
  1159. real-time systems.
  1160. nohz= [KNL] Boottime enable/disable dynamic ticks
  1161. Valid arguments: on, off
  1162. Default: on
  1163. noirqdebug [X86-32] Disables the code which attempts to detect and
  1164. disable unhandled interrupt sources.
  1165. no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
  1166. broken timer IRQ sources.
  1167. noisapnp [ISAPNP] Disables ISA PnP code.
  1168. noinitrd [RAM] Tells the kernel not to load any configured
  1169. initial RAM disk.
  1170. nointroute [IA-64]
  1171. nojitter [IA64] Disables jitter checking for ITC timers.
  1172. nolapic [X86-32,APIC] Do not enable or use the local APIC.
  1173. nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
  1174. nox2apic [X86-64,APIC] Do not enable x2APIC mode.
  1175. x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
  1176. default x2apic cluster mode on platforms
  1177. supporting x2apic.
  1178. noltlbs [PPC] Do not use large page/tlb entries for kernel
  1179. lowmem mapping on PPC40x.
  1180. nomca [IA-64] Disable machine check abort handling
  1181. nomce [X86-32] Machine Check Exception
  1182. nomfgpt [X86-32] Disable Multi-Function General Purpose
  1183. Timer usage (for AMD Geode machines).
  1184. noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
  1185. noreplace-smp [X86-32,SMP] Don't replace SMP instructions
  1186. with UP alternatives
  1187. noresidual [PPC] Don't use residual data on PReP machines.
  1188. noresume [SWSUSP] Disables resume and restores original swap
  1189. space.
  1190. no-scroll [VGA] Disables scrollback.
  1191. This is required for the Braillex ib80-piezo Braille
  1192. reader made by F.H. Papenmeier (Germany).
  1193. nosbagart [IA-64]
  1194. nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
  1195. nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
  1196. and disable the IO APIC. legacy for "maxcpus=0".
  1197. nosoftlockup [KNL] Disable the soft-lockup detector.
  1198. nosync [HW,M68K] Disables sync negotiation for all devices.
  1199. notsc [BUGS=X86-32] Disable Time Stamp Counter
  1200. nousb [USB] Disable the USB subsystem
  1201. nowb [ARM]
  1202. nptcg= [IA64] Override max number of concurrent global TLB
  1203. purges which is reported from either PAL_VM_SUMMARY or
  1204. SAL PALO.
  1205. numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
  1206. one of ['zone', 'node', 'default'] can be specified
  1207. This can be set from sysctl after boot.
  1208. See Documentation/sysctl/vm.txt for details.
  1209. nr_uarts= [SERIAL] maximum number of UARTs to be registered.
  1210. olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
  1211. Rather than timing out after 20 ms if an EC
  1212. command is not properly ACKed, override the length
  1213. of the timeout. We have interrupts disabled while
  1214. waiting for the ACK, so if this is set too high
  1215. interrupts *may* be lost!
  1216. opl3= [HW,OSS]
  1217. Format: <io>
  1218. oprofile.timer= [HW]
  1219. Use timer interrupt instead of performance counters
  1220. osst= [HW,SCSI] SCSI Tape Driver
  1221. Format: <buffer_size>,<write_threshold>
  1222. See also Documentation/scsi/st.txt.
  1223. panic= [KNL] Kernel behaviour on panic
  1224. Format: <timeout>
  1225. parkbd.port= [HW] Parallel port number the keyboard adapter is
  1226. connected to, default is 0.
  1227. Format: <parport#>
  1228. parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
  1229. 0 for XT, 1 for AT (default is AT).
  1230. Format: <mode>
  1231. parport= [HW,PPT] Specify parallel ports. 0 disables.
  1232. Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
  1233. Use 'auto' to force the driver to use any
  1234. IRQ/DMA settings detected (the default is to
  1235. ignore detected IRQ/DMA settings because of
  1236. possible conflicts). You can specify the base
  1237. address, IRQ, and DMA settings; IRQ and DMA
  1238. should be numbers, or 'auto' (for using detected
  1239. settings on that particular port), or 'nofifo'
  1240. (to avoid using a FIFO even if it is detected).
  1241. Parallel ports are assigned in the order they
  1242. are specified on the command line, starting
  1243. with parport0.
  1244. parport_init_mode= [HW,PPT]
  1245. Configure VIA parallel port to operate in
  1246. a specific mode. This is necessary on Pegasos
  1247. computer where firmware has no options for setting
  1248. up parallel port mode and sets it to spp.
  1249. Currently this function knows 686a and 8231 chips.
  1250. Format: [spp|ps2|epp|ecp|ecpepp]
  1251. pas2= [HW,OSS] Format:
  1252. <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
  1253. pas16= [HW,SCSI]
  1254. See header of drivers/scsi/pas16.c.
  1255. pause_on_oops=
  1256. Halt all CPUs after the first oops has been printed for
  1257. the specified number of seconds. This is to be used if
  1258. your oopses keep scrolling off the screen.
  1259. pcbit= [HW,ISDN]
  1260. pcd. [PARIDE]
  1261. See header of drivers/block/paride/pcd.c.
  1262. See also Documentation/blockdev/paride.txt.
  1263. pci=option[,option...] [PCI] various PCI subsystem options:
  1264. off [X86] don't probe for the PCI bus
  1265. bios [X86-32] force use of PCI BIOS, don't access
  1266. the hardware directly. Use this if your machine
  1267. has a non-standard PCI host bridge.
  1268. nobios [X86-32] disallow use of PCI BIOS, only direct
  1269. hardware access methods are allowed. Use this
  1270. if you experience crashes upon bootup and you
  1271. suspect they are caused by the BIOS.
  1272. conf1 [X86] Force use of PCI Configuration
  1273. Mechanism 1.
  1274. conf2 [X86] Force use of PCI Configuration
  1275. Mechanism 2.
  1276. noaer [PCIE] If the PCIEAER kernel config parameter is
  1277. enabled, this kernel boot option can be used to
  1278. disable the use of PCIE advanced error reporting.
  1279. nodomains [PCI] Disable support for multiple PCI
  1280. root domains (aka PCI segments, in ACPI-speak).
  1281. nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
  1282. Configuration
  1283. nomsi [MSI] If the PCI_MSI kernel config parameter is
  1284. enabled, this kernel boot option can be used to
  1285. disable the use of MSI interrupts system-wide.
  1286. biosirq [X86-32] Use PCI BIOS calls to get the interrupt
  1287. routing table. These calls are known to be buggy
  1288. on several machines and they hang the machine
  1289. when used, but on other computers it's the only
  1290. way to get the interrupt routing table. Try
  1291. this option if the kernel is unable to allocate
  1292. IRQs or discover secondary PCI buses on your
  1293. motherboard.
  1294. rom [X86] Assign address space to expansion ROMs.
  1295. Use with caution as certain devices share
  1296. address decoders between ROMs and other
  1297. resources.
  1298. norom [X86] Do not assign address space to
  1299. expansion ROMs that do not already have
  1300. BIOS assigned address ranges.
  1301. irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
  1302. assigned automatically to PCI devices. You can
  1303. make the kernel exclude IRQs of your ISA cards
  1304. this way.
  1305. pirqaddr=0xAAAAA [X86] Specify the physical address
  1306. of the PIRQ table (normally generated
  1307. by the BIOS) if it is outside the
  1308. F0000h-100000h range.
  1309. lastbus=N [X86] Scan all buses thru bus #N. Can be
  1310. useful if the kernel is unable to find your
  1311. secondary buses and you want to tell it
  1312. explicitly which ones they are.
  1313. assign-busses [X86] Always assign all PCI bus
  1314. numbers ourselves, overriding
  1315. whatever the firmware may have done.
  1316. usepirqmask [X86] Honor the possible IRQ mask stored
  1317. in the BIOS $PIR table. This is needed on
  1318. some systems with broken BIOSes, notably
  1319. some HP Pavilion N5400 and Omnibook XE3
  1320. notebooks. This will have no effect if ACPI
  1321. IRQ routing is enabled.
  1322. noacpi [X86] Do not use ACPI for IRQ routing
  1323. or for PCI scanning.
  1324. use_crs [X86] Use _CRS for PCI resource
  1325. allocation.
  1326. routeirq Do IRQ routing for all PCI devices.
  1327. This is normally done in pci_enable_device(),
  1328. so this option is a temporary workaround
  1329. for broken drivers that don't call it.
  1330. skip_isa_align [X86] do not align io start addr, so can
  1331. handle more pci cards
  1332. firmware [ARM] Do not re-enumerate the bus but instead
  1333. just use the configuration from the
  1334. bootloader. This is currently used on
  1335. IXP2000 systems where the bus has to be
  1336. configured a certain way for adjunct CPUs.
  1337. noearly [X86] Don't do any early type 1 scanning.
  1338. This might help on some broken boards which
  1339. machine check when some devices' config space
  1340. is read. But various workarounds are disabled
  1341. and some IOMMU drivers will not work.
  1342. bfsort Sort PCI devices into breadth-first order.
  1343. This sorting is done to get a device
  1344. order compatible with older (<= 2.4) kernels.
  1345. nobfsort Don't sort PCI devices into breadth-first order.
  1346. cbiosize=nn[KMG] The fixed amount of bus space which is
  1347. reserved for the CardBus bridge's IO window.
  1348. The default value is 256 bytes.
  1349. cbmemsize=nn[KMG] The fixed amount of bus space which is
  1350. reserved for the CardBus bridge's memory
  1351. window. The default value is 64 megabytes.
  1352. pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
  1353. Management.
  1354. off Disable ASPM.
  1355. force Enable ASPM even on devices that claim not to support it.
  1356. WARNING: Forcing ASPM on may cause system lockups.
  1357. pcmv= [HW,PCMCIA] BadgePAD 4
  1358. pd. [PARIDE]
  1359. See Documentation/blockdev/paride.txt.
  1360. pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
  1361. boot time.
  1362. Format: { 0 | 1 }
  1363. See arch/parisc/kernel/pdc_chassis.c
  1364. pf. [PARIDE]
  1365. See Documentation/blockdev/paride.txt.
  1366. pg. [PARIDE]
  1367. See Documentation/blockdev/paride.txt.
  1368. pirq= [SMP,APIC] Manual mp-table setup
  1369. See Documentation/x86/i386/IO-APIC.txt.
  1370. plip= [PPT,NET] Parallel port network link
  1371. Format: { parport<nr> | timid | 0 }
  1372. See also Documentation/parport.txt.
  1373. pmtmr= [X86] Manual setup of pmtmr I/O Port.
  1374. Override pmtimer IOPort with a hex value.
  1375. e.g. pmtmr=0x508
  1376. pnp.debug [PNP]
  1377. Enable PNP debug messages. This depends on the
  1378. CONFIG_PNP_DEBUG_MESSAGES option.
  1379. pnpacpi= [ACPI]
  1380. { off }
  1381. pnpbios= [ISAPNP]
  1382. { on | off | curr | res | no-curr | no-res }
  1383. pnp_reserve_irq=
  1384. [ISAPNP] Exclude IRQs for the autoconfiguration
  1385. pnp_reserve_dma=
  1386. [ISAPNP] Exclude DMAs for the autoconfiguration
  1387. pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
  1388. Ranges are in pairs (I/O port base and size).
  1389. pnp_reserve_mem=
  1390. [ISAPNP] Exclude memory regions for the
  1391. autoconfiguration.
  1392. Ranges are in pairs (memory base and size).
  1393. dynamic_printk
  1394. Enables pr_debug()/dev_dbg() calls if
  1395. CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. These can also
  1396. be switched on/off via <debugfs>/dynamic_printk/modules
  1397. print-fatal-signals=
  1398. [KNL] debug: print fatal signals
  1399. print-fatal-signals=1: print segfault info to
  1400. the kernel console.
  1401. default: off.
  1402. printk.time= Show timing data prefixed to each printk message line
  1403. Format: <bool> (1/Y/y=enable, 0/N/n=disable)
  1404. profile= [KNL] Enable kernel profiling via /proc/profile
  1405. Format: [schedule,]<number>
  1406. Param: "schedule" - profile schedule points.
  1407. Param: <number> - step/bucket size as a power of 2 for
  1408. statistical time based profiling.
  1409. Param: "sleep" - profile D-state sleeping (millisecs).
  1410. Requires CONFIG_SCHEDSTATS
  1411. Param: "kvm" - profile VM exits.
  1412. processor.max_cstate= [HW,ACPI]
  1413. Limit processor to maximum C-state
  1414. max_cstate=9 overrides any DMI blacklist limit.
  1415. processor.nocst [HW,ACPI]
  1416. Ignore the _CST method to determine C-states,
  1417. instead using the legacy FADT method
  1418. prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
  1419. before loading.
  1420. See Documentation/blockdev/ramdisk.txt.
  1421. psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
  1422. probe for; one of (bare|imps|exps|lifebook|any).
  1423. psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
  1424. per second.
  1425. psmouse.resetafter= [HW,MOUSE]
  1426. Try to reset the device after so many bad packets
  1427. (0 = never).
  1428. psmouse.resolution=
  1429. [HW,MOUSE] Set desired mouse resolution, in dpi.
  1430. psmouse.smartscroll=
  1431. [HW,MOUSE] Controls Logitech smartscroll autorepeat.
  1432. 0 = disabled, 1 = enabled (default).
  1433. pss= [HW,OSS] Personal Sound System (ECHO ESC614)
  1434. Format:
  1435. <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
  1436. pt. [PARIDE]
  1437. See Documentation/blockdev/paride.txt.
  1438. pty.legacy_count=
  1439. [KNL] Number of legacy pty's. Overwrites compiled-in
  1440. default number.
  1441. quiet [KNL] Disable most log messages
  1442. r128= [HW,DRM]
  1443. raid= [HW,RAID]
  1444. See Documentation/md.txt.
  1445. ramdisk_blocksize= [RAM]
  1446. See Documentation/blockdev/ramdisk.txt.
  1447. ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
  1448. See Documentation/blockdev/ramdisk.txt.
  1449. rcupdate.blimit= [KNL,BOOT]
  1450. Set maximum number of finished RCU callbacks to process
  1451. in one batch.
  1452. rcupdate.qhimark= [KNL,BOOT]
  1453. Set threshold of queued
  1454. RCU callbacks over which batch limiting is disabled.
  1455. rcupdate.qlowmark= [KNL,BOOT]
  1456. Set threshold of queued RCU callbacks below which
  1457. batch limiting is re-enabled.
  1458. rdinit= [KNL]
  1459. Format: <full_path>
  1460. Run specified binary instead of /init from the ramdisk,
  1461. used for early userspace startup. See initrd.
  1462. reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
  1463. Format: <reboot_mode>[,<reboot_mode2>[,...]]
  1464. See arch/*/kernel/reboot.c or arch/*/kernel/process.c
  1465. relax_domain_level=
  1466. [KNL, SMP] Set scheduler's default relax_domain_level.
  1467. See Documentation/cpusets.txt.
  1468. reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
  1469. reservetop= [X86-32]
  1470. Format: nn[KMG]
  1471. Reserves a hole at the top of the kernel virtual
  1472. address space.
  1473. reset_devices [KNL] Force drivers to reset the underlying device
  1474. during initialization.
  1475. resume= [SWSUSP]
  1476. Specify the partition device for software suspend
  1477. resume_offset= [SWSUSP]
  1478. Specify the offset from the beginning of the partition
  1479. given by "resume=" at which the swap header is located,
  1480. in <PAGE_SIZE> units (needed only for swap files).
  1481. See Documentation/power/swsusp-and-swap-files.txt
  1482. retain_initrd [RAM] Keep initrd memory after extraction
  1483. rhash_entries= [KNL,NET]
  1484. Set number of hash buckets for route cache
  1485. riscom8= [HW,SERIAL]
  1486. Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
  1487. ro [KNL] Mount root device read-only on boot
  1488. root= [KNL] Root filesystem
  1489. rootdelay= [KNL] Delay (in seconds) to pause before attempting to
  1490. mount the root filesystem
  1491. rootflags= [KNL] Set root filesystem mount option string
  1492. rootfstype= [KNL] Set root filesystem type
  1493. rootwait [KNL] Wait (indefinitely) for root device to show up.
  1494. Useful for devices that are detected asynchronously
  1495. (e.g. USB and MMC devices).
  1496. root_plug.vendor_id=
  1497. [ROOTPLUG] Override the default vendor ID
  1498. root_plug.product_id=
  1499. [ROOTPLUG] Override the default product ID
  1500. root_plug.debug=
  1501. [ROOTPLUG] Enable debugging output
  1502. rw [KNL] Mount root device read-write on boot
  1503. S [KNL] Run init in single mode
  1504. sa1100ir [NET]
  1505. See drivers/net/irda/sa1100_ir.c.
  1506. sbni= [NET] Granch SBNI12 leased line adapter
  1507. sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
  1508. Format: <io>[,<timeout>[,<isapnp>]]
  1509. scsi_debug_*= [SCSI]
  1510. See drivers/scsi/scsi_debug.c.
  1511. scsi_default_dev_flags=
  1512. [SCSI] SCSI default device flags
  1513. Format: <integer>
  1514. scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
  1515. Format: <vendor>:<model>:<flags>
  1516. (flags are integer value)
  1517. scsi_logging_level= [SCSI] a bit mask of logging levels
  1518. See drivers/scsi/scsi_logging.h for bits. Also
  1519. settable via sysctl at dev.scsi.logging_level
  1520. (/proc/sys/dev/scsi/logging_level).
  1521. There is also a nice 'scsi_logging_level' script in the
  1522. S390-tools package, available for download at
  1523. http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
  1524. scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
  1525. discovered. async scans them in kernel threads,
  1526. allowing boot to proceed. none ignores them, expecting
  1527. user space to do the scan.
  1528. selinux [SELINUX] Disable or enable SELinux at boot time.
  1529. Format: { "0" | "1" }
  1530. See security/selinux/Kconfig help text.
  1531. 0 -- disable.
  1532. 1 -- enable.
  1533. Default value is set via kernel config option.
  1534. If enabled at boot time, /selinux/disable can be used
  1535. later to disable prior to initial policy load.
  1536. selinux_compat_net =
  1537. [SELINUX] Set initial selinux_compat_net flag value.
  1538. Format: { "0" | "1" }
  1539. 0 -- use new secmark-based packet controls
  1540. 1 -- use legacy packet controls
  1541. Default value is 0 (preferred).
  1542. Value can be changed at runtime via
  1543. /selinux/compat_net.
  1544. serialnumber [BUGS=X86-32]
  1545. shapers= [NET]
  1546. Maximal number of shapers.
  1547. show_msr= [x86] show boot-time MSR settings
  1548. Format: { <integer> }
  1549. Show boot-time (BIOS-initialized) MSR settings.
  1550. The parameter means the number of CPUs to show,
  1551. for example 1 means boot CPU only.
  1552. sim710= [SCSI,HW]
  1553. See header of drivers/scsi/sim710.c.
  1554. simeth= [IA-64]
  1555. simscsi=
  1556. slram= [HW,MTD]
  1557. slub_debug[=options[,slabs]] [MM, SLUB]
  1558. Enabling slub_debug allows one to determine the
  1559. culprit if slab objects become corrupted. Enabling
  1560. slub_debug can create guard zones around objects and
  1561. may poison objects when not in use. Also tracks the
  1562. last alloc / free. For more information see
  1563. Documentation/vm/slub.txt.
  1564. slub_max_order= [MM, SLUB]
  1565. Determines the maximum allowed order for slabs.
  1566. A high setting may cause OOMs due to memory
  1567. fragmentation. For more information see
  1568. Documentation/vm/slub.txt.
  1569. slub_min_objects= [MM, SLUB]
  1570. The minimum number of objects per slab. SLUB will
  1571. increase the slab order up to slub_max_order to
  1572. generate a sufficiently large slab able to contain
  1573. the number of objects indicated. The higher the number
  1574. of objects the smaller the overhead of tracking slabs
  1575. and the less frequently locks need to be acquired.
  1576. For more information see Documentation/vm/slub.txt.
  1577. slub_min_order= [MM, SLUB]
  1578. Determines the mininum page order for slabs. Must be
  1579. lower than slub_max_order.
  1580. For more information see Documentation/vm/slub.txt.
  1581. slub_nomerge [MM, SLUB]
  1582. Disable merging of slabs with similar size. May be
  1583. necessary if there is some reason to distinguish
  1584. allocs to different slabs. Debug options disable
  1585. merging on their own.
  1586. For more information see Documentation/vm/slub.txt.
  1587. smart2= [HW]
  1588. Format: <io1>[,<io2>[,...,<io8>]]
  1589. smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
  1590. attempt to substitute SMP alternatives once at boot.
  1591. smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
  1592. smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
  1593. smsc-ircc2.ircc_sir= [HW] SIR base I/O port
  1594. smsc-ircc2.ircc_fir= [HW] FIR base I/O port
  1595. smsc-ircc2.ircc_irq= [HW] IRQ line
  1596. smsc-ircc2.ircc_dma= [HW] DMA channel
  1597. smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
  1598. 0: Toshiba Satellite 1800 (GP data pin select)
  1599. 1: Fast pin select (default)
  1600. 2: ATC IRMode
  1601. snd-ad1816a= [HW,ALSA]
  1602. snd-ad1848= [HW,ALSA]
  1603. snd-ali5451= [HW,ALSA]
  1604. snd-als100= [HW,ALSA]
  1605. snd-als4000= [HW,ALSA]
  1606. snd-azt2320= [HW,ALSA]
  1607. snd-cmi8330= [HW,ALSA]
  1608. snd-cmipci= [HW,ALSA]
  1609. snd-cs4231= [HW,ALSA]
  1610. snd-cs4232= [HW,ALSA]
  1611. snd-cs4236= [HW,ALSA]
  1612. snd-cs4281= [HW,ALSA]
  1613. snd-cs46xx= [HW,ALSA]
  1614. snd-dt019x= [HW,ALSA]
  1615. snd-dummy= [HW,ALSA]
  1616. snd-emu10k1= [HW,ALSA]
  1617. snd-ens1370= [HW,ALSA]
  1618. snd-ens1371= [HW,ALSA]
  1619. snd-es968= [HW,ALSA]
  1620. snd-es1688= [HW,ALSA]
  1621. snd-es18xx= [HW,ALSA]
  1622. snd-es1938= [HW,ALSA]
  1623. snd-es1968= [HW,ALSA]
  1624. snd-fm801= [HW,ALSA]
  1625. snd-gusclassic= [HW,ALSA]
  1626. snd-gusextreme= [HW,ALSA]
  1627. snd-gusmax= [HW,ALSA]
  1628. snd-hdsp= [HW,ALSA]
  1629. snd-ice1712= [HW,ALSA]
  1630. snd-intel8x0= [HW,ALSA]
  1631. snd-interwave= [HW,ALSA]
  1632. snd-interwave-stb=
  1633. [HW,ALSA]
  1634. snd-korg1212= [HW,ALSA]
  1635. snd-maestro3= [HW,ALSA]
  1636. snd-mpu401= [HW,ALSA]
  1637. snd-mtpav= [HW,ALSA]
  1638. snd-nm256= [HW,ALSA]
  1639. snd-opl3sa2= [HW,ALSA]
  1640. snd-opti92x-ad1848=
  1641. [HW,ALSA]
  1642. snd-opti92x-cs4231=
  1643. [HW,ALSA]
  1644. snd-opti93x= [HW,ALSA]
  1645. snd-pmac= [HW,ALSA]
  1646. snd-rme32= [HW,ALSA]
  1647. snd-rme96= [HW,ALSA]
  1648. snd-rme9652= [HW,ALSA]
  1649. snd-sb8= [HW,ALSA]
  1650. snd-sb16= [HW,ALSA]
  1651. snd-sbawe= [HW,ALSA]
  1652. snd-serial= [HW,ALSA]
  1653. snd-sgalaxy= [HW,ALSA]
  1654. snd-sonicvibes= [HW,ALSA]
  1655. snd-sun-amd7930=
  1656. [HW,ALSA]
  1657. snd-sun-cs4231= [HW,ALSA]
  1658. snd-trident= [HW,ALSA]
  1659. snd-usb-audio= [HW,ALSA,USB]
  1660. snd-via82xx= [HW,ALSA]
  1661. snd-virmidi= [HW,ALSA]
  1662. snd-wavefront= [HW,ALSA]
  1663. snd-ymfpci= [HW,ALSA]
  1664. softlockup_panic=
  1665. [KNL] Should the soft-lockup detector generate panics.
  1666. sonypi.*= [HW] Sony Programmable I/O Control Device driver
  1667. See Documentation/sonypi.txt
  1668. specialix= [HW,SERIAL] Specialix multi-serial port adapter
  1669. See Documentation/serial/specialix.txt.
  1670. spia_io_base= [HW,MTD]
  1671. spia_fio_base=
  1672. spia_pedr=
  1673. spia_peddr=
  1674. sscape= [HW,OSS]
  1675. Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
  1676. st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
  1677. See Documentation/scsi/st.txt.
  1678. sti= [PARISC,HW]
  1679. Format: <num>
  1680. Set the STI (builtin display/keyboard on the HP-PARISC
  1681. machines) console (graphic card) which should be used
  1682. as the initial boot-console.
  1683. See also comment in drivers/video/console/sticore.c.
  1684. sti_font= [HW]
  1685. See comment in drivers/video/console/sticore.c.
  1686. stifb= [HW]
  1687. Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
  1688. sunrpc.pool_mode=
  1689. [NFS]
  1690. Control how the NFS server code allocates CPUs to
  1691. service thread pools. Depending on how many NICs
  1692. you have and where their interrupts are bound, this
  1693. option will affect which CPUs will do NFS serving.
  1694. Note: this parameter cannot be changed while the
  1695. NFS server is running.
  1696. auto the server chooses an appropriate mode
  1697. automatically using heuristics
  1698. global a single global pool contains all CPUs
  1699. percpu one pool for each CPU
  1700. pernode one pool for each NUMA node (equivalent
  1701. to global on non-NUMA machines)
  1702. swiotlb= [IA-64] Number of I/O TLB slabs
  1703. switches= [HW,M68k]
  1704. sym53c416= [HW,SCSI]
  1705. See header of drivers/scsi/sym53c416.c.
  1706. sysrq_always_enabled
  1707. [KNL]
  1708. Ignore sysrq setting - this boot parameter will
  1709. neutralize any effect of /proc/sys/kernel/sysrq.
  1710. Useful for debugging.
  1711. t128= [HW,SCSI]
  1712. See header of drivers/scsi/t128.c.
  1713. tdfx= [HW,DRM]
  1714. test_suspend= [SUSPEND]
  1715. Specify "mem" (for Suspend-to-RAM) or "standby" (for
  1716. standby suspend) as the system sleep state to briefly
  1717. enter during system startup. The system is woken from
  1718. this state using a wakeup-capable RTC alarm.
  1719. thash_entries= [KNL,NET]
  1720. Set number of hash buckets for TCP connection
  1721. thermal.act= [HW,ACPI]
  1722. -1: disable all active trip points in all thermal zones
  1723. <degrees C>: override all lowest active trip points
  1724. thermal.crt= [HW,ACPI]
  1725. -1: disable all critical trip points in all thermal zones
  1726. <degrees C>: override all critical trip points
  1727. thermal.nocrt= [HW,ACPI]
  1728. Set to disable actions on ACPI thermal zone
  1729. critical and hot trip points.
  1730. thermal.off= [HW,ACPI]
  1731. 1: disable ACPI thermal control
  1732. thermal.psv= [HW,ACPI]
  1733. -1: disable all passive trip points
  1734. <degrees C>: override all passive trip points to this value
  1735. thermal.tzp= [HW,ACPI]
  1736. Specify global default ACPI thermal zone polling rate
  1737. <deci-seconds>: poll all this frequency
  1738. 0: no polling (default)
  1739. tmscsim= [HW,SCSI]
  1740. See comment before function dc390_setup() in
  1741. drivers/scsi/tmscsim.c.
  1742. tp720= [HW,PS2]
  1743. trix= [HW,OSS] MediaTrix AudioTrix Pro
  1744. Format:
  1745. <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
  1746. turbografx.map[2|3]= [HW,JOY]
  1747. TurboGraFX parallel port interface
  1748. Format:
  1749. <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
  1750. See also Documentation/input/joystick-parport.txt
  1751. u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
  1752. See header of drivers/scsi/u14-34f.c.
  1753. uart401= [HW,OSS]
  1754. Format: <io>,<irq>
  1755. uart6850= [HW,OSS]
  1756. Format: <io>,<irq>
  1757. uhci-hcd.ignore_oc=
  1758. [USB] Ignore overcurrent events (default N).
  1759. Some badly-designed motherboards generate lots of
  1760. bogus events, for ports that aren't wired to
  1761. anything. Set this parameter to avoid log spamming.
  1762. Note that genuine overcurrent events won't be
  1763. reported either.
  1764. unknown_nmi_panic
  1765. [X86-32,X86-64]
  1766. Set unknown_nmi_panic=1 early on boot.
  1767. usbcore.autosuspend=
  1768. [USB] The autosuspend time delay (in seconds) used
  1769. for newly-detected USB devices (default 2). This
  1770. is the time required before an idle device will be
  1771. autosuspended. Devices for which the delay is set
  1772. to a negative value won't be autosuspended at all.
  1773. usbcore.usbfs_snoop=
  1774. [USB] Set to log all usbfs traffic (default 0 = off).
  1775. usbcore.blinkenlights=
  1776. [USB] Set to cycle leds on hubs (default 0 = off).
  1777. usbcore.old_scheme_first=
  1778. [USB] Start with the old device initialization
  1779. scheme (default 0 = off).
  1780. usbcore.use_both_schemes=
  1781. [USB] Try the other device initialization scheme
  1782. if the first one fails (default 1 = enabled).
  1783. usbcore.initial_descriptor_timeout=
  1784. [USB] Specifies timeout for the initial 64-byte
  1785. USB_REQ_GET_DESCRIPTOR request in milliseconds
  1786. (default 5000 = 5.0 seconds).
  1787. usbhid.mousepoll=
  1788. [USBHID] The interval which mice are to be polled at.
  1789. add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
  1790. kernel's map of available physical RAM.
  1791. vdso= [X86-32,SH,x86-64]
  1792. vdso=2: enable compat VDSO (default with COMPAT_VDSO)
  1793. vdso=1: enable VDSO (default)
  1794. vdso=0: disable VDSO mapping
  1795. vdso32= [X86-32,X86-64]
  1796. vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
  1797. vdso32=1: enable 32-bit VDSO (default)
  1798. vdso32=0: disable 32-bit VDSO mapping
  1799. vector= [IA-64,SMP]
  1800. vector=percpu: enable percpu vector domain
  1801. video= [FB] Frame buffer configuration
  1802. See Documentation/fb/modedb.txt.
  1803. vga= [BOOT,X86-32] Select a particular video mode
  1804. See Documentation/x86/i386/boot.txt and
  1805. Documentation/svga.txt.
  1806. Use vga=ask for menu.
  1807. This is actually a boot loader parameter; the value is
  1808. passed to the kernel using a special protocol.
  1809. vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
  1810. size of <nn>. This can be used to increase the
  1811. minimum size (128MB on x86). It can also be used to
  1812. decrease the size and leave more room for directly
  1813. mapped kernel RAM.
  1814. vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
  1815. Format: <command>
  1816. vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
  1817. Format: <command>
  1818. vmpoff= [KNL,S390] Perform z/VM CP command after power off.
  1819. Format: <command>
  1820. waveartist= [HW,OSS]
  1821. Format: <io>,<irq>,<dma>,<dma2>
  1822. wd33c93= [HW,SCSI]
  1823. See header of drivers/scsi/wd33c93.c.
  1824. wd7000= [HW,SCSI]
  1825. See header of drivers/scsi/wd7000.c.
  1826. wdt= [WDT] Watchdog
  1827. See Documentation/watchdog/wdt.txt.
  1828. xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
  1829. xd_geo= See header of drivers/block/xd.c.
  1830. xirc2ps_cs= [NET,PCMCIA]
  1831. Format:
  1832. <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
  1833. norandmaps Don't use address space randomization
  1834. Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
  1835. ______________________________________________________________________
  1836. TODO:
  1837. Add documentation for ALSA options.
  1838. Add more DRM drivers.