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. See Documentation/acpi/debug.txt for more information
  192. about debug layers and levels.
  193. Enable AML "Debug" output, i.e., stores to the Debug
  194. object while interpreting AML:
  195. acpi.debug_layer=0xffffffff acpi.debug_level=0x2
  196. Enable PCI/PCI interrupt routing info messages:
  197. acpi.debug_layer=0x400000 acpi.debug_level=0x4
  198. Enable all messages related to ACPI hardware:
  199. acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
  200. Some values produce so much output that the system is
  201. unusable. The "log_buf_len" parameter may be useful
  202. if you need to capture more output.
  203. acpi.power_nocheck= [HW,ACPI]
  204. Format: 1/0 enable/disable the check of power state.
  205. On some bogus BIOS the _PSC object/_STA object of
  206. power resource can't return the correct device power
  207. state. In such case it is unneccessary to check its
  208. power state again in power transition.
  209. 1 : disable the power state check
  210. acpi_pm_good [X86-32,X86-64]
  211. Override the pmtimer bug detection: force the kernel
  212. to assume that this machine's pmtimer latches its value
  213. and always returns good values.
  214. agp= [AGP]
  215. { off | try_unsupported }
  216. off: disable AGP support
  217. try_unsupported: try to drive unsupported chipsets
  218. (may crash computer or cause data corruption)
  219. enable_timer_pin_1 [i386,x86-64]
  220. Enable PIN 1 of APIC timer
  221. Can be useful to work around chipset bugs
  222. (in particular on some ATI chipsets).
  223. The kernel tries to set a reasonable default.
  224. disable_timer_pin_1 [i386,x86-64]
  225. Disable PIN 1 of APIC timer
  226. Can be useful to work around chipset bugs.
  227. ad1848= [HW,OSS]
  228. Format: <io>,<irq>,<dma>,<dma2>,<type>
  229. advansys= [HW,SCSI]
  230. See header of drivers/scsi/advansys.c.
  231. advwdt= [HW,WDT] Advantech WDT
  232. Format: <iostart>,<iostop>
  233. aedsp16= [HW,OSS] Audio Excel DSP 16
  234. Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
  235. See also header of sound/oss/aedsp16.c.
  236. aha152x= [HW,SCSI]
  237. See Documentation/scsi/aha152x.txt.
  238. aha1542= [HW,SCSI]
  239. Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
  240. aic7xxx= [HW,SCSI]
  241. See Documentation/scsi/aic7xxx.txt.
  242. aic79xx= [HW,SCSI]
  243. See Documentation/scsi/aic79xx.txt.
  244. amd_iommu= [HW,X86-84]
  245. Pass parameters to the AMD IOMMU driver in the system.
  246. Possible values are:
  247. isolate - enable device isolation (each device, as far
  248. as possible, will get its own protection
  249. domain) [default]
  250. share - put every device behind one IOMMU into the
  251. same protection domain
  252. fullflush - enable flushing of IO/TLB entries when
  253. they are unmapped. Otherwise they are
  254. flushed before they will be reused, which
  255. is a lot of faster
  256. amd_iommu_size= [HW,X86-64]
  257. Define the size of the aperture for the AMD IOMMU
  258. driver. Possible values are:
  259. '32M', '64M' (default), '128M', '256M', '512M', '1G'
  260. amijoy.map= [HW,JOY] Amiga joystick support
  261. Map of devices attached to JOY0DAT and JOY1DAT
  262. Format: <a>,<b>
  263. See also Documentation/kernel/input/joystick.txt
  264. analog.map= [HW,JOY] Analog joystick and gamepad support
  265. Specifies type or capabilities of an analog joystick
  266. connected to one of 16 gameports
  267. Format: <type1>,<type2>,..<type16>
  268. apc= [HW,SPARC]
  269. Power management functions (SPARCstation-4/5 + deriv.)
  270. Format: noidle
  271. Disable APC CPU standby support. SPARCstation-Fox does
  272. not play well with APC CPU idle - disable it if you have
  273. APC and your system crashes randomly.
  274. apic= [APIC,i386] Advanced Programmable Interrupt Controller
  275. Change the output verbosity whilst booting
  276. Format: { quiet (default) | verbose | debug }
  277. Change the amount of debugging information output
  278. when initialising the APIC and IO-APIC components.
  279. apm= [APM] Advanced Power Management
  280. See header of arch/x86/kernel/apm_32.c.
  281. arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
  282. Format: <io>,<irq>,<nodeID>
  283. ataflop= [HW,M68k]
  284. atarimouse= [HW,MOUSE] Atari Mouse
  285. atascsi= [HW,SCSI] Atari SCSI
  286. atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
  287. EzKey and similar keyboards
  288. atkbd.reset= [HW] Reset keyboard during initialization
  289. atkbd.set= [HW] Select keyboard code set
  290. Format: <int> (2 = AT (default), 3 = PS/2)
  291. atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
  292. keyboards
  293. atkbd.softraw= [HW] Choose between synthetic and real raw mode
  294. Format: <bool> (0 = real, 1 = synthetic (default))
  295. atkbd.softrepeat= [HW]
  296. Use software keyboard repeat
  297. autotest [IA64]
  298. baycom_epp= [HW,AX25]
  299. Format: <io>,<mode>
  300. baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
  301. Format: <io>,<mode>
  302. See header of drivers/net/hamradio/baycom_par.c.
  303. baycom_ser_fdx= [HW,AX25]
  304. BayCom Serial Port AX.25 Modem (Full Duplex Mode)
  305. Format: <io>,<irq>,<mode>[,<baud>]
  306. See header of drivers/net/hamradio/baycom_ser_fdx.c.
  307. baycom_ser_hdx= [HW,AX25]
  308. BayCom Serial Port AX.25 Modem (Half Duplex Mode)
  309. Format: <io>,<irq>,<mode>
  310. See header of drivers/net/hamradio/baycom_ser_hdx.c.
  311. boot_delay= Milliseconds to delay each printk during boot.
  312. Values larger than 10 seconds (10000) are changed to
  313. no delay (0).
  314. Format: integer
  315. bootmem_debug [KNL] Enable bootmem allocator debug messages.
  316. bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
  317. bttv.radio= Most important insmod options are available as
  318. kernel args too.
  319. bttv.pll= See Documentation/video4linux/bttv/Insmod-options
  320. bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
  321. BusLogic= [HW,SCSI]
  322. See drivers/scsi/BusLogic.c, comment before function
  323. BusLogic_ParseDriverOptions().
  324. c101= [NET] Moxa C101 synchronous serial card
  325. cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
  326. Sometimes CPU hardware bugs make them report the cache
  327. size incorrectly. The kernel will attempt work arounds
  328. to fix known problems, but for some CPUs it is not
  329. possible to determine what the correct size should be.
  330. This option provides an override for these situations.
  331. security= [SECURITY] Choose a security module to enable at boot.
  332. If this boot parameter is not specified, only the first
  333. security module asking for security registration will be
  334. loaded. An invalid security module name will be treated
  335. as if no module has been chosen.
  336. capability.disable=
  337. [SECURITY] Disable capabilities. This would normally
  338. be used only if an alternative security model is to be
  339. configured. Potentially dangerous and should only be
  340. used if you are entirely sure of the consequences.
  341. ccw_timeout_log [S390]
  342. See Documentation/s390/CommonIO for details.
  343. cgroup_disable= [KNL] Disable a particular controller
  344. Format: {name of the controller(s) to disable}
  345. {Currently supported controllers - "memory"}
  346. checkreqprot [SELINUX] Set initial checkreqprot flag value.
  347. Format: { "0" | "1" }
  348. See security/selinux/Kconfig help text.
  349. 0 -- check protection applied by kernel (includes
  350. any implied execute protection).
  351. 1 -- check protection requested by application.
  352. Default value is set via a kernel config option.
  353. Value can be changed at runtime via
  354. /selinux/checkreqprot.
  355. cio_ignore= [S390]
  356. See Documentation/s390/CommonIO for details.
  357. clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
  358. [Deprecated]
  359. Forces specified clocksource (if available) to be used
  360. when calculating gettimeofday(). If specified
  361. clocksource is not available, it defaults to PIT.
  362. Format: { pit | tsc | cyclone | pmtmr }
  363. clocksource= [GENERIC_TIME] Override the default clocksource
  364. Format: <string>
  365. Override the default clocksource and use the clocksource
  366. with the name specified.
  367. Some clocksource names to choose from, depending on
  368. the platform:
  369. [all] jiffies (this is the base, fallback clocksource)
  370. [ACPI] acpi_pm
  371. [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
  372. pxa_timer,timer3,32k_counter,timer0_1
  373. [AVR32] avr32
  374. [X86-32] pit,hpet,tsc,vmi-timer;
  375. scx200_hrt on Geode; cyclone on IBM x440
  376. [MIPS] MIPS
  377. [PARISC] cr16
  378. [S390] tod
  379. [SH] SuperH
  380. [SPARC64] tick
  381. [X86-64] hpet,tsc
  382. clearcpuid=BITNUM [X86]
  383. Disable CPUID feature X for the kernel. See
  384. include/asm-x86/cpufeature.h for the valid bit numbers.
  385. Note the Linux specific bits are not necessarily
  386. stable over kernel options, but the vendor specific
  387. ones should be.
  388. Also note that user programs calling CPUID directly
  389. or using the feature without checking anything
  390. will still see it. This just prevents it from
  391. being used by the kernel or shown in /proc/cpuinfo.
  392. Also note the kernel might malfunction if you disable
  393. some critical bits.
  394. code_bytes [IA32/X86_64] How many bytes of object code to print
  395. in an oops report.
  396. Range: 0 - 8192
  397. Default: 64
  398. hpet= [X86-32,HPET] option to control HPET usage
  399. Format: { enable (default) | disable | force }
  400. disable: disable HPET and use PIT instead
  401. force: allow force enabled of undocumented chips (ICH4,
  402. VIA, nVidia)
  403. com20020= [HW,NET] ARCnet - COM20020 chipset
  404. Format:
  405. <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
  406. com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
  407. Format: <io>[,<irq>]
  408. com90xx= [HW,NET]
  409. ARCnet - COM90xx chipset (memory-mapped buffers)
  410. Format: <io>[,<irq>[,<memstart>]]
  411. condev= [HW,S390] console device
  412. conmode=
  413. console= [KNL] Output console device and options.
  414. tty<n> Use the virtual console device <n>.
  415. ttyS<n>[,options]
  416. ttyUSB0[,options]
  417. Use the specified serial port. The options are of
  418. the form "bbbbpnf", where "bbbb" is the baud rate,
  419. "p" is parity ("n", "o", or "e"), "n" is number of
  420. bits, and "f" is flow control ("r" for RTS or
  421. omit it). Default is "9600n8".
  422. See Documentation/serial-console.txt for more
  423. information. See
  424. Documentation/networking/netconsole.txt for an
  425. alternative.
  426. uart[8250],io,<addr>[,options]
  427. uart[8250],mmio,<addr>[,options]
  428. Start an early, polled-mode console on the 8250/16550
  429. UART at the specified I/O port or MMIO address,
  430. switching to the matching ttyS device later. The
  431. options are the same as for ttyS, above.
  432. If the device connected to the port is not a TTY but a braille
  433. device, prepend "brl," before the device type, for instance
  434. console=brl,ttyS0
  435. For now, only VisioBraille is supported.
  436. earlycon= [KNL] Output early console device and options.
  437. uart[8250],io,<addr>[,options]
  438. uart[8250],mmio,<addr>[,options]
  439. Start an early, polled-mode console on the 8250/16550
  440. UART at the specified I/O port or MMIO address.
  441. The options are the same as for ttyS, above.
  442. no_console_suspend
  443. [HW] Never suspend the console
  444. Disable suspending of consoles during suspend and
  445. hibernate operations. Once disabled, debugging
  446. messages can reach various consoles while the rest
  447. of the system is being put to sleep (ie, while
  448. debugging driver suspend/resume hooks). This may
  449. not work reliably with all consoles, but is known
  450. to work with serial and VGA consoles.
  451. cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
  452. Format:
  453. <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
  454. crashkernel=nn[KMG]@ss[KMG]
  455. [KNL] Reserve a chunk of physical memory to
  456. hold a kernel to switch to with kexec on panic.
  457. crashkernel=range1:size1[,range2:size2,...][@offset]
  458. [KNL] Same as above, but depends on the memory
  459. in the running system. The syntax of range is
  460. start-[end] where start and end are both
  461. a memory unit (amount[KMG]). See also
  462. Documentation/kdump/kdump.txt for a example.
  463. cs4232= [HW,OSS]
  464. Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
  465. cs89x0_dma= [HW,NET]
  466. Format: <dma>
  467. cs89x0_media= [HW,NET]
  468. Format: { rj45 | aui | bnc }
  469. dasd= [HW,NET]
  470. See header of drivers/s390/block/dasd_devmap.c.
  471. db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
  472. (one device per port)
  473. Format: <port#>,<type>
  474. See also Documentation/input/joystick-parport.txt
  475. debug [KNL] Enable kernel debugging (events log level).
  476. debug_locks_verbose=
  477. [KNL] verbose self-tests
  478. Format=<0|1>
  479. Print debugging info while doing the locking API
  480. self-tests.
  481. We default to 0 (no extra messages), setting it to
  482. 1 will print _a lot_ more information - normally
  483. only useful to kernel developers.
  484. debug_objects [KNL] Enable object debugging
  485. debugpat [X86] Enable PAT debugging
  486. decnet.addr= [HW,NET]
  487. Format: <area>[,<node>]
  488. See also Documentation/networking/decnet.txt.
  489. vt.default_blu= [VT]
  490. Format: <blue0>,<blue1>,<blue2>,...,<blue15>
  491. Change the default blue palette of the console.
  492. This is a 16-member array composed of values
  493. ranging from 0-255.
  494. vt.default_grn= [VT]
  495. Format: <green0>,<green1>,<green2>,...,<green15>
  496. Change the default green palette of the console.
  497. This is a 16-member array composed of values
  498. ranging from 0-255.
  499. vt.default_red= [VT]
  500. Format: <red0>,<red1>,<red2>,...,<red15>
  501. Change the default red palette of the console.
  502. This is a 16-member array composed of values
  503. ranging from 0-255.
  504. vt.default_utf8=
  505. [VT]
  506. Format=<0|1>
  507. Set system-wide default UTF-8 mode for all tty's.
  508. Default is 1, i.e. UTF-8 mode is enabled for all
  509. newly opened terminals.
  510. dhash_entries= [KNL]
  511. Set number of hash buckets for dentry cache.
  512. digi= [HW,SERIAL]
  513. IO parameters + enable/disable command.
  514. digiepca= [HW,SERIAL]
  515. See drivers/char/README.epca and
  516. Documentation/serial/digiepca.txt.
  517. disable_mtrr_cleanup [X86]
  518. enable_mtrr_cleanup [X86]
  519. The kernel tries to adjust MTRR layout from continuous
  520. to discrete, to make X server driver able to add WB
  521. entry later. This parameter enables/disables that.
  522. mtrr_chunk_size=nn[KMG] [X86]
  523. used for mtrr cleanup. It is largest continous chunk
  524. that could hold holes aka. UC entries.
  525. mtrr_gran_size=nn[KMG] [X86]
  526. Used for mtrr cleanup. It is granularity of mtrr block.
  527. Default is 1.
  528. Large value could prevent small alignment from
  529. using up MTRRs.
  530. mtrr_spare_reg_nr=n [X86]
  531. Format: <integer>
  532. Range: 0,7 : spare reg number
  533. Default : 1
  534. Used for mtrr cleanup. It is spare mtrr entries number.
  535. Set to 2 or more if your graphical card needs more.
  536. disable_mtrr_trim [X86, Intel and AMD only]
  537. By default the kernel will trim any uncacheable
  538. memory out of your available memory pool based on
  539. MTRR settings. This parameter disables that behavior,
  540. possibly causing your machine to run very slowly.
  541. dmasound= [HW,OSS] Sound subsystem buffers
  542. dscc4.setup= [NET]
  543. dtc3181e= [HW,SCSI]
  544. earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
  545. earlyprintk=vga
  546. earlyprintk=serial[,ttySn[,baudrate]]
  547. earlyprintk=dbgp
  548. Append ",keep" to not disable it when the real console
  549. takes over.
  550. Only vga or serial or usb debug port at a time.
  551. Currently only ttyS0 and ttyS1 are supported.
  552. Interaction with the standard serial driver is not
  553. very good.
  554. The VGA output is eventually overwritten by the real
  555. console.
  556. eata= [HW,SCSI]
  557. edd= [EDD]
  558. Format: {"off" | "on" | "skip[mbr]"}
  559. eisa_irq_edge= [PARISC,HW]
  560. See header of drivers/parisc/eisa.c.
  561. elanfreq= [X86-32]
  562. See comment before function elanfreq_setup() in
  563. arch/x86/kernel/cpu/cpufreq/elanfreq.c.
  564. elevator= [IOSCHED]
  565. Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
  566. See Documentation/block/as-iosched.txt and
  567. Documentation/block/deadline-iosched.txt for details.
  568. elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
  569. Specifies physical address of start of kernel core
  570. image elf header. Generally kexec loader will
  571. pass this option to capture kernel.
  572. See Documentation/kdump/kdump.txt for details.
  573. enforcing [SELINUX] Set initial enforcing status.
  574. Format: {"0" | "1"}
  575. See security/selinux/Kconfig help text.
  576. 0 -- permissive (log only, no denials).
  577. 1 -- enforcing (deny and log).
  578. Default value is 0.
  579. Value can be changed at runtime via /selinux/enforce.
  580. es1371= [HW,OSS]
  581. Format: <spdif>,[<nomix>,[<amplifier>]]
  582. See also header of sound/oss/es1371.c.
  583. ether= [HW,NET] Ethernet cards parameters
  584. This option is obsoleted by the "netdev=" option, which
  585. has equivalent usage. See its documentation for details.
  586. eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
  587. Format: <io>[,<irq>]
  588. failslab=
  589. fail_page_alloc=
  590. fail_make_request=[KNL]
  591. General fault injection mechanism.
  592. Format: <interval>,<probability>,<space>,<times>
  593. See also /Documentation/fault-injection/.
  594. fd_mcs= [HW,SCSI]
  595. See header of drivers/scsi/fd_mcs.c.
  596. fdomain= [HW,SCSI]
  597. See header of drivers/scsi/fdomain.c.
  598. floppy= [HW]
  599. See Documentation/blockdev/floppy.txt.
  600. force_pal_cache_flush
  601. [IA-64] Avoid check_sal_cache_flush which may hang on
  602. buggy SAL_CACHE_FLUSH implementations. Using this
  603. parameter will force ia64_sal_cache_flush to call
  604. ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
  605. ftrace=[tracer]
  606. [ftrace] will set and start the specified tracer
  607. as early as possible in order to facilitate early
  608. boot debugging.
  609. ftrace_dump_on_oops
  610. [ftrace] will dump the trace buffers on oops.
  611. gamecon.map[2|3]=
  612. [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
  613. support via parallel port (up to 5 devices per port)
  614. Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
  615. See also Documentation/input/joystick-parport.txt
  616. gamma= [HW,DRM]
  617. gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
  618. Format: off | on
  619. default: on
  620. gdth= [HW,SCSI]
  621. See header of drivers/scsi/gdth.c.
  622. gpt [EFI] Forces disk with valid GPT signature but
  623. invalid Protective MBR to be treated as GPT.
  624. gvp11= [HW,SCSI]
  625. hashdist= [KNL,NUMA] Large hashes allocated during boot
  626. are distributed across NUMA nodes. Defaults on
  627. for IA-64, off otherwise.
  628. Format: 0 | 1 (for off | on)
  629. hcl= [IA-64] SGI's Hardware Graph compatibility layer
  630. hd= [EIDE] (E)IDE hard drive subsystem geometry
  631. Format: <cyl>,<head>,<sect>
  632. highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
  633. size of <nn>. This works even on boxes that have no
  634. highmem otherwise. This also works to reduce highmem
  635. size on bigger boxes.
  636. highres= [KNL] Enable/disable high resolution timer mode.
  637. Valid parameters: "on", "off"
  638. Default: "on"
  639. hisax= [HW,ISDN]
  640. See Documentation/isdn/README.HiSax.
  641. hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
  642. hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
  643. On x86-64 and powerpc, this option can be specified
  644. multiple times interleaved with hugepages= to reserve
  645. huge pages of different sizes. Valid pages sizes on
  646. x86-64 are 2M (when the CPU supports "pse") and 1G
  647. (when the CPU supports the "pdpe1gb" cpuinfo flag)
  648. Note that 1GB pages can only be allocated at boot time
  649. using hugepages= and not freed afterwards.
  650. default_hugepagesz=
  651. [same as hugepagesz=] The size of the default
  652. HugeTLB page size. This is the size represented by
  653. the legacy /proc/ hugepages APIs, used for SHM, and
  654. default size when mounting hugetlbfs filesystems.
  655. Defaults to the default architecture's huge page size
  656. if not specified.
  657. hlt [BUGS=ARM,SH]
  658. i8042.debug [HW] Toggle i8042 debug mode
  659. i8042.direct [HW] Put keyboard port into non-translated mode
  660. i8042.dumbkbd [HW] Pretend that controller can only read data from
  661. keyboard and cannot control its state
  662. (Don't attempt to blink the leds)
  663. i8042.noaux [HW] Don't check for auxiliary (== mouse) port
  664. i8042.nokbd [HW] Don't check/create keyboard port
  665. i8042.noloop [HW] Disable the AUX Loopback command while probing
  666. for the AUX port
  667. i8042.nomux [HW] Don't check presence of an active multiplexing
  668. controller
  669. i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
  670. controllers
  671. i8042.panicblink=
  672. [HW] Frequency with which keyboard LEDs should blink
  673. when kernel panics (default is 0.5 sec)
  674. i8042.reset [HW] Reset the controller during init and cleanup
  675. i8042.unlock [HW] Unlock (ignore) the keylock
  676. i810= [HW,DRM]
  677. i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
  678. indicates that the driver is running on unsupported
  679. hardware.
  680. i8k.force [HW] Activate i8k driver even if SMM BIOS signature
  681. does not match list of supported models.
  682. i8k.power_status
  683. [HW] Report power status in /proc/i8k
  684. (disabled by default)
  685. i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
  686. capability is set.
  687. ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
  688. See Documentation/mca.txt.
  689. icn= [HW,ISDN]
  690. Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
  691. ide= [HW] (E)IDE subsystem
  692. Format: ide=nodma or ide=doubler
  693. See Documentation/ide/ide.txt.
  694. idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
  695. See Documentation/ide/ide.txt.
  696. idle= [X86]
  697. Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
  698. Poll forces a polling idle loop that can slightly improves the performance
  699. of waking up a idle CPU, but will use a lot of power and make the system
  700. run hot. Not recommended.
  701. idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
  702. to not use it because it doesn't save as much power as a normal idle
  703. loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
  704. as idle=poll.
  705. idle=halt. Halt is forced to be used for CPU idle.
  706. In such case C2/C3 won't be used again.
  707. idle=nomwait. Disable mwait for CPU C-states
  708. ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
  709. Claim all unknown PCI IDE storage controllers.
  710. ignore_loglevel [KNL]
  711. Ignore loglevel setting - this will print /all/
  712. kernel messages to the console. Useful for debugging.
  713. ihash_entries= [KNL]
  714. Set number of hash buckets for inode cache.
  715. in2000= [HW,SCSI]
  716. See header of drivers/scsi/in2000.c.
  717. init= [KNL]
  718. Format: <full_path>
  719. Run specified binary instead of /sbin/init as init
  720. process.
  721. initcall_debug [KNL] Trace initcalls as they are executed. Useful
  722. for working out where the kernel is dying during
  723. startup.
  724. initrd= [BOOT] Specify the location of the initial ramdisk
  725. inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
  726. Format: <irq>
  727. inttest= [IA64]
  728. iommu= [x86]
  729. off
  730. force
  731. noforce
  732. biomerge
  733. panic
  734. nopanic
  735. merge
  736. nomerge
  737. forcesac
  738. soft
  739. intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
  740. off
  741. Disable intel iommu driver.
  742. igfx_off [Default Off]
  743. By default, gfx is mapped as normal device. If a gfx
  744. device has a dedicated DMAR unit, the DMAR unit is
  745. bypassed by not enabling DMAR with this option. In
  746. this case, gfx device will use physical address for
  747. DMA.
  748. forcedac [x86_64]
  749. With this option iommu will not optimize to look
  750. for io virtual address below 32 bit forcing dual
  751. address cycle on pci bus for cards supporting greater
  752. than 32 bit addressing. The default is to look
  753. for translation below 32 bit and if not available
  754. then look in the higher range.
  755. strict [Default Off]
  756. With this option on every unmap_single operation will
  757. result in a hardware IOTLB flush operation as opposed
  758. to batching them for performance.
  759. io_delay= [X86-32,X86-64] I/O delay method
  760. 0x80
  761. Standard port 0x80 based delay
  762. 0xed
  763. Alternate port 0xed based delay (needed on some systems)
  764. udelay
  765. Simple two microseconds delay
  766. none
  767. No delay
  768. io7= [HW] IO7 for Marvel based alpha systems
  769. See comment before marvel_specify_io7 in
  770. arch/alpha/kernel/core_marvel.c.
  771. ip= [IP_PNP]
  772. See Documentation/filesystems/nfsroot.txt.
  773. ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
  774. See comment before ip2_setup() in
  775. drivers/char/ip2/ip2base.c.
  776. ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
  777. See header of drivers/scsi/ips.c.
  778. ports= [IP_VS_FTP] IPVS ftp helper module
  779. Default is 21.
  780. Up to 8 (IP_VS_APP_MAX_PORTS) ports
  781. may be specified.
  782. Format: <port>,<port>....
  783. irqfixup [HW]
  784. When an interrupt is not handled search all handlers
  785. for it. Intended to get systems with badly broken
  786. firmware running.
  787. irqpoll [HW]
  788. When an interrupt is not handled search all handlers
  789. for it. Also check all handlers each timer
  790. interrupt. Intended to get systems with badly broken
  791. firmware running.
  792. isapnp= [ISAPNP]
  793. Format: <RDP>,<reset>,<pci_scan>,<verbosity>
  794. isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
  795. Format:
  796. <cpu number>,...,<cpu number>
  797. or
  798. <cpu number>-<cpu number>
  799. (must be a positive range in ascending order)
  800. or a mixture
  801. <cpu number>,...,<cpu number>-<cpu number>
  802. This option can be used to specify one or more CPUs
  803. to isolate from the general SMP balancing and scheduling
  804. algorithms. You can move a process onto or off an
  805. "isolated" CPU via the CPU affinity syscalls or cpuset.
  806. <cpu number> begins at 0 and the maximum value is
  807. "number of CPUs in system - 1".
  808. This option is the preferred way to isolate CPUs. The
  809. alternative -- manually setting the CPU mask of all
  810. tasks in the system -- can cause problems and
  811. suboptimal load balancer performance.
  812. iucv= [HW,NET]
  813. js= [HW,JOY] Analog joystick
  814. See Documentation/input/joystick.txt.
  815. kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
  816. specifies the amount of memory usable by the kernel
  817. for non-movable allocations. The requested amount is
  818. spread evenly throughout all nodes in the system. The
  819. remaining memory in each node is used for Movable
  820. pages. In the event, a node is too small to have both
  821. kernelcore and Movable pages, kernelcore pages will
  822. take priority and other nodes will have a larger number
  823. of kernelcore pages. The Movable zone is used for the
  824. allocation of pages that may be reclaimed or moved
  825. by the page migration subsystem. This means that
  826. HugeTLB pages may not be allocated from this zone.
  827. Note that allocations like PTEs-from-HighMem still
  828. use the HighMem zone if it exists, and the Normal
  829. zone if it does not.
  830. movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
  831. is similar to kernelcore except it specifies the
  832. amount of memory used for migratable allocations.
  833. If both kernelcore and movablecore is specified,
  834. then kernelcore will be at *least* the specified
  835. value but may be more. If movablecore on its own
  836. is specified, the administrator must be careful
  837. that the amount of memory usable for all allocations
  838. is not too small.
  839. keepinitrd [HW,ARM]
  840. kstack=N [X86-32,X86-64] Print N words from the kernel stack
  841. in oops dumps.
  842. kgdboc= [HW] kgdb over consoles.
  843. Requires a tty driver that supports console polling.
  844. (only serial suported for now)
  845. Format: <serial_device>[,baud]
  846. kmac= [MIPS] korina ethernet MAC address.
  847. Configure the RouterBoard 532 series on-chip
  848. Ethernet adapter MAC address.
  849. l2cr= [PPC]
  850. l3cr= [PPC]
  851. lapic [X86-32,APIC] Enable the local APIC even if BIOS
  852. disabled it.
  853. lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
  854. C2 power state.
  855. libata.dma= [LIBATA] DMA control
  856. libata.dma=0 Disable all PATA and SATA DMA
  857. libata.dma=1 PATA and SATA Disk DMA only
  858. libata.dma=2 ATAPI (CDROM) DMA only
  859. libata.dma=4 Compact Flash DMA only
  860. Combinations also work, so libata.dma=3 enables DMA
  861. for disks and CDROMs, but not CFs.
  862. libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
  863. when set.
  864. Format: <int>
  865. libata.force= [LIBATA] Force configurations. The format is comma
  866. separated list of "[ID:]VAL" where ID is
  867. PORT[:DEVICE]. PORT and DEVICE are decimal numbers
  868. matching port, link or device. Basically, it matches
  869. the ATA ID string printed on console by libata. If
  870. the whole ID part is omitted, the last PORT and DEVICE
  871. values are used. If ID hasn't been specified yet, the
  872. configuration applies to all ports, links and devices.
  873. If only DEVICE is omitted, the parameter applies to
  874. the port and all links and devices behind it. DEVICE
  875. number of 0 either selects the first device or the
  876. first fan-out link behind PMP device. It does not
  877. select the host link. DEVICE number of 15 selects the
  878. host link and device attached to it.
  879. The VAL specifies the configuration to force. As long
  880. as there's no ambiguity shortcut notation is allowed.
  881. For example, both 1.5 and 1.5G would work for 1.5Gbps.
  882. The following configurations can be forced.
  883. * Cable type: 40c, 80c, short40c, unk, ign or sata.
  884. Any ID with matching PORT is used.
  885. * SATA link speed limit: 1.5Gbps or 3.0Gbps.
  886. * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
  887. udma[/][16,25,33,44,66,100,133] notation is also
  888. allowed.
  889. * [no]ncq: Turn on or off NCQ.
  890. * nohrst, nosrst, norst: suppress hard, soft
  891. and both resets.
  892. If there are multiple matching configurations changing
  893. the same attribute, the last one is used.
  894. load_ramdisk= [RAM] List of ramdisks to load from floppy
  895. See Documentation/blockdev/ramdisk.txt.
  896. lockd.nlm_grace_period=P [NFS] Assign grace period.
  897. Format: <integer>
  898. lockd.nlm_tcpport=N [NFS] Assign TCP port.
  899. Format: <integer>
  900. lockd.nlm_timeout=T [NFS] Assign timeout value.
  901. Format: <integer>
  902. lockd.nlm_udpport=M [NFS] Assign UDP port.
  903. Format: <integer>
  904. logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
  905. Format: <irq>
  906. loglevel= All Kernel Messages with a loglevel smaller than the
  907. console loglevel will be printed to the console. It can
  908. also be changed with klogd or other programs. The
  909. loglevels are defined as follows:
  910. 0 (KERN_EMERG) system is unusable
  911. 1 (KERN_ALERT) action must be taken immediately
  912. 2 (KERN_CRIT) critical conditions
  913. 3 (KERN_ERR) error conditions
  914. 4 (KERN_WARNING) warning conditions
  915. 5 (KERN_NOTICE) normal but significant condition
  916. 6 (KERN_INFO) informational
  917. 7 (KERN_DEBUG) debug-level messages
  918. log_buf_len=n Sets the size of the printk ring buffer, in bytes.
  919. Format: { n | nk | nM }
  920. n must be a power of two. The default size
  921. is set in the kernel config file.
  922. logo.nologo [FB] Disables display of the built-in Linux logo.
  923. This may be used to provide more screen space for
  924. kernel log messages and is useful when debugging
  925. kernel boot problems.
  926. lp=0 [LP] Specify parallel ports to use, e.g,
  927. lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
  928. lp=reset first parallel port). 'lp=0' disables the
  929. lp=auto printer driver. 'lp=reset' (which can be
  930. specified in addition to the ports) causes
  931. attached printers to be reset. Using
  932. lp=port1,port2,... specifies the parallel ports
  933. to associate lp devices with, starting with
  934. lp0. A port specification may be 'none' to skip
  935. that lp device, or a parport name such as
  936. 'parport0'. Specifying 'lp=auto' instead of a
  937. port specification list means that device IDs
  938. from each port should be examined, to see if
  939. an IEEE 1284-compliant printer is attached; if
  940. so, the driver will manage that printer.
  941. See also header of drivers/char/lp.c.
  942. lpj=n [KNL]
  943. Sets loops_per_jiffy to given constant, thus avoiding
  944. time-consuming boot-time autodetection (up to 250 ms per
  945. CPU). 0 enables autodetection (default). To determine
  946. the correct value for your kernel, boot with normal
  947. autodetection and see what value is printed. Note that
  948. on SMP systems the preset will be applied to all CPUs,
  949. which is likely to cause problems if your CPUs need
  950. significantly divergent settings. An incorrect value
  951. will cause delays in the kernel to be wrong, leading to
  952. unpredictable I/O errors and other breakage. Although
  953. unlikely, in the extreme case this might damage your
  954. hardware.
  955. ltpc= [NET]
  956. Format: <io>,<irq>,<dma>
  957. mac5380= [HW,SCSI] Format:
  958. <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
  959. machvec= [IA64] Force the use of a particular machine-vector
  960. (machvec) in a generic kernel.
  961. Example: machvec=hpzx1_swiotlb
  962. max_loop= [LOOP] Maximum number of loopback devices that can
  963. be mounted
  964. Format: <1-256>
  965. maxcpus= [SMP] Maximum number of processors that an SMP kernel
  966. should make use of. maxcpus=n : n >= 0 limits the
  967. kernel to using 'n' processors. n=0 is a special case,
  968. it is equivalent to "nosmp", which also disables
  969. the IO APIC.
  970. max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater than
  971. or equal to this physical address is ignored.
  972. max_luns= [SCSI] Maximum number of LUNs to probe.
  973. Should be between 1 and 2^32-1.
  974. max_report_luns=
  975. [SCSI] Maximum number of LUNs received.
  976. Should be between 1 and 16384.
  977. mcatest= [IA-64]
  978. mce [X86-32] Machine Check Exception
  979. mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
  980. md= [HW] RAID subsystems devices and level
  981. See Documentation/md.txt.
  982. mdacon= [MDA]
  983. Format: <first>,<last>
  984. Specifies range of consoles to be captured by the MDA.
  985. mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
  986. Amount of memory to be used when the kernel is not able
  987. to see the whole system memory or for test.
  988. [X86-32] Use together with memmap= to avoid physical
  989. address space collisions. Without memmap= PCI devices
  990. could be placed at addresses belonging to unused RAM.
  991. mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
  992. memory.
  993. memchunk=nn[KMG]
  994. [KNL,SH] Allow user to override the default size for
  995. per-device physically contiguous DMA buffers.
  996. memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
  997. E820 memory map, as specified by the user.
  998. Such memmap=exactmap lines can be constructed based on
  999. BIOS output or other requirements. See the memmap=nn@ss
  1000. option description.
  1001. memmap=nn[KMG]@ss[KMG]
  1002. [KNL] Force usage of a specific region of memory
  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 ACPI data.
  1006. Region of memory to be used, from ss to ss+nn.
  1007. memmap=nn[KMG]$ss[KMG]
  1008. [KNL,ACPI] Mark specific memory as reserved.
  1009. Region of memory to be used, from ss to ss+nn.
  1010. Example: Exclude memory from 0x18690000-0x1869ffff
  1011. memmap=64K$0x18690000
  1012. or
  1013. memmap=0x10000$0x18690000
  1014. memory_corruption_check=0/1 [X86]
  1015. Some BIOSes seem to corrupt the first 64k of
  1016. memory when doing things like suspend/resume.
  1017. Setting this option will scan the memory
  1018. looking for corruption. Enabling this will
  1019. both detect corruption and prevent the kernel
  1020. from using the memory being corrupted.
  1021. However, its intended as a diagnostic tool; if
  1022. repeatable BIOS-originated corruption always
  1023. affects the same memory, you can use memmap=
  1024. to prevent the kernel from using that memory.
  1025. memory_corruption_check_size=size [X86]
  1026. By default it checks for corruption in the low
  1027. 64k, making this memory unavailable for normal
  1028. use. Use this parameter to scan for
  1029. corruption in more or less memory.
  1030. memory_corruption_check_period=seconds [X86]
  1031. By default it checks for corruption every 60
  1032. seconds. Use this parameter to check at some
  1033. other rate. 0 disables periodic checking.
  1034. memtest= [KNL,X86] Enable memtest
  1035. Format: <integer>
  1036. range: 0,4 : pattern number
  1037. default : 0 <disable>
  1038. meye.*= [HW] Set MotionEye Camera parameters
  1039. See Documentation/video4linux/meye.txt.
  1040. mfgpt_irq= [IA-32] Specify the IRQ to use for the
  1041. Multi-Function General Purpose Timers on AMD Geode
  1042. platforms.
  1043. mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
  1044. the BIOS has incorrectly applied a workaround. TinyBIOS
  1045. version 0.98 is known to be affected, 0.99 fixes the
  1046. problem by letting the user disable the workaround.
  1047. mga= [HW,DRM]
  1048. min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
  1049. physical address is ignored.
  1050. mminit_loglevel=
  1051. [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
  1052. parameter allows control of the logging verbosity for
  1053. the additional memory initialisation checks. A value
  1054. of 0 disables mminit logging and a level of 4 will
  1055. log everything. Information is printed at KERN_DEBUG
  1056. so loglevel=8 may also need to be specified.
  1057. mousedev.tap_time=
  1058. [MOUSE] Maximum time between finger touching and
  1059. leaving touchpad surface for touch to be considered
  1060. a tap and be reported as a left button click (for
  1061. touchpads working in absolute mode only).
  1062. Format: <msecs>
  1063. mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
  1064. reporting absolute coordinates, such as tablets
  1065. mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
  1066. reporting absolute coordinates, such as tablets
  1067. mpu401= [HW,OSS]
  1068. Format: <io>,<irq>
  1069. MTD_Partition= [MTD]
  1070. Format: <name>,<region-number>,<size>,<offset>
  1071. MTD_Region= [MTD] Format:
  1072. <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
  1073. mtdparts= [MTD]
  1074. See drivers/mtd/cmdlinepart.c.
  1075. mtdset= [ARM]
  1076. ARM/S3C2412 JIVE boot control
  1077. See arch/arm/mach-s3c2412/mach-jive.c
  1078. mtouchusb.raw_coordinates=
  1079. [HW] Make the MicroTouch USB driver use raw coordinates
  1080. ('y', default) or cooked coordinates ('n')
  1081. n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
  1082. NCR_D700= [HW,SCSI]
  1083. See header of drivers/scsi/NCR_D700.c.
  1084. ncr5380= [HW,SCSI]
  1085. ncr53c400= [HW,SCSI]
  1086. ncr53c400a= [HW,SCSI]
  1087. ncr53c406a= [HW,SCSI]
  1088. ncr53c8xx= [HW,SCSI]
  1089. netdev= [NET] Network devices parameters
  1090. Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
  1091. Note that mem_start is often overloaded to mean
  1092. something different and driver-specific.
  1093. This usage is only documented in each driver source
  1094. file if at all.
  1095. nf_conntrack.acct=
  1096. [NETFILTER] Enable connection tracking flow accounting
  1097. 0 to disable accounting
  1098. 1 to enable accounting
  1099. Default value depends on CONFIG_NF_CT_ACCT that is
  1100. going to be removed in 2.6.29.
  1101. nfsaddrs= [NFS]
  1102. See Documentation/filesystems/nfsroot.txt.
  1103. nfsroot= [NFS] nfs root filesystem for disk-less boxes.
  1104. See Documentation/filesystems/nfsroot.txt.
  1105. nfs.callback_tcpport=
  1106. [NFS] set the TCP port on which the NFSv4 callback
  1107. channel should listen.
  1108. nfs.idmap_cache_timeout=
  1109. [NFS] set the maximum lifetime for idmapper cache
  1110. entries.
  1111. nfs.enable_ino64=
  1112. [NFS] enable 64-bit inode numbers.
  1113. If zero, the NFS client will fake up a 32-bit inode
  1114. number for the readdir() and stat() syscalls instead
  1115. of returning the full 64-bit number.
  1116. The default is to return 64-bit inode numbers.
  1117. nmi_debug= [KNL,AVR32] Specify one or more actions to take
  1118. when a NMI is triggered.
  1119. Format: [state][,regs][,debounce][,die]
  1120. nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
  1121. no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
  1122. emulation library even if a 387 maths coprocessor
  1123. is present.
  1124. noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
  1125. caches in the slab allocator. Saves per-node memory,
  1126. but will impact performance.
  1127. noalign [KNL,ARM]
  1128. noapic [SMP,APIC] Tells the kernel to not make use of any
  1129. IOAPICs that may be present in the system.
  1130. nobats [PPC] Do not use BATs for mapping kernel lowmem
  1131. on "Classic" PPC cores.
  1132. nocache [ARM]
  1133. nodelayacct [KNL] Disable per-task delay accounting
  1134. nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
  1135. nodsp [SH] Disable hardware DSP at boot time.
  1136. noefi [X86-32,X86-64] Disable EFI runtime services support.
  1137. noexec [IA-64]
  1138. noexec [X86-32,X86-64]
  1139. On X86-32 available only on PAE configured kernels.
  1140. noexec=on: enable non-executable mappings (default)
  1141. noexec=off: disable non-executable mappings
  1142. noexec32 [X86-64]
  1143. This affects only 32-bit executables.
  1144. noexec32=on: enable non-executable mappings (default)
  1145. read doesn't imply executable mappings
  1146. noexec32=off: disable non-executable mappings
  1147. read implies executable mappings
  1148. nofpu [SH] Disable hardware FPU at boot time.
  1149. nofxsr [BUGS=X86-32] Disables x86 floating point extended
  1150. register save and restore. The kernel will only save
  1151. legacy floating-point registers on task switch.
  1152. noclflush [BUGS=X86] Don't use the CLFLUSH instruction
  1153. nohlt [BUGS=ARM,SH]
  1154. no-hlt [BUGS=X86-32] Tells the kernel that the hlt
  1155. instruction doesn't work correctly and not to
  1156. use it.
  1157. nohalt [IA-64] Tells the kernel not to use the power saving
  1158. function PAL_HALT_LIGHT when idle. This increases
  1159. power-consumption. On the positive side, it reduces
  1160. interrupt wake-up latency, which may improve performance
  1161. in certain environments such as networked servers or
  1162. real-time systems.
  1163. nohz= [KNL] Boottime enable/disable dynamic ticks
  1164. Valid arguments: on, off
  1165. Default: on
  1166. noirqdebug [X86-32] Disables the code which attempts to detect and
  1167. disable unhandled interrupt sources.
  1168. no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
  1169. broken timer IRQ sources.
  1170. noisapnp [ISAPNP] Disables ISA PnP code.
  1171. noinitrd [RAM] Tells the kernel not to load any configured
  1172. initial RAM disk.
  1173. nointroute [IA-64]
  1174. nojitter [IA64] Disables jitter checking for ITC timers.
  1175. nolapic [X86-32,APIC] Do not enable or use the local APIC.
  1176. nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
  1177. nox2apic [X86-64,APIC] Do not enable x2APIC mode.
  1178. x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
  1179. default x2apic cluster mode on platforms
  1180. supporting x2apic.
  1181. noltlbs [PPC] Do not use large page/tlb entries for kernel
  1182. lowmem mapping on PPC40x.
  1183. nomca [IA-64] Disable machine check abort handling
  1184. nomce [X86-32] Machine Check Exception
  1185. nomfgpt [X86-32] Disable Multi-Function General Purpose
  1186. Timer usage (for AMD Geode machines).
  1187. noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
  1188. noreplace-smp [X86-32,SMP] Don't replace SMP instructions
  1189. with UP alternatives
  1190. noresidual [PPC] Don't use residual data on PReP machines.
  1191. noresume [SWSUSP] Disables resume and restores original swap
  1192. space.
  1193. no-scroll [VGA] Disables scrollback.
  1194. This is required for the Braillex ib80-piezo Braille
  1195. reader made by F.H. Papenmeier (Germany).
  1196. nosbagart [IA-64]
  1197. nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
  1198. nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
  1199. and disable the IO APIC. legacy for "maxcpus=0".
  1200. nosoftlockup [KNL] Disable the soft-lockup detector.
  1201. nosync [HW,M68K] Disables sync negotiation for all devices.
  1202. notsc [BUGS=X86-32] Disable Time Stamp Counter
  1203. nousb [USB] Disable the USB subsystem
  1204. nowb [ARM]
  1205. nptcg= [IA64] Override max number of concurrent global TLB
  1206. purges which is reported from either PAL_VM_SUMMARY or
  1207. SAL PALO.
  1208. numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
  1209. one of ['zone', 'node', 'default'] can be specified
  1210. This can be set from sysctl after boot.
  1211. See Documentation/sysctl/vm.txt for details.
  1212. nr_uarts= [SERIAL] maximum number of UARTs to be registered.
  1213. olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
  1214. Rather than timing out after 20 ms if an EC
  1215. command is not properly ACKed, override the length
  1216. of the timeout. We have interrupts disabled while
  1217. waiting for the ACK, so if this is set too high
  1218. interrupts *may* be lost!
  1219. opl3= [HW,OSS]
  1220. Format: <io>
  1221. oprofile.timer= [HW]
  1222. Use timer interrupt instead of performance counters
  1223. osst= [HW,SCSI] SCSI Tape Driver
  1224. Format: <buffer_size>,<write_threshold>
  1225. See also Documentation/scsi/st.txt.
  1226. panic= [KNL] Kernel behaviour on panic
  1227. Format: <timeout>
  1228. parkbd.port= [HW] Parallel port number the keyboard adapter is
  1229. connected to, default is 0.
  1230. Format: <parport#>
  1231. parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
  1232. 0 for XT, 1 for AT (default is AT).
  1233. Format: <mode>
  1234. parport= [HW,PPT] Specify parallel ports. 0 disables.
  1235. Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
  1236. Use 'auto' to force the driver to use any
  1237. IRQ/DMA settings detected (the default is to
  1238. ignore detected IRQ/DMA settings because of
  1239. possible conflicts). You can specify the base
  1240. address, IRQ, and DMA settings; IRQ and DMA
  1241. should be numbers, or 'auto' (for using detected
  1242. settings on that particular port), or 'nofifo'
  1243. (to avoid using a FIFO even if it is detected).
  1244. Parallel ports are assigned in the order they
  1245. are specified on the command line, starting
  1246. with parport0.
  1247. parport_init_mode= [HW,PPT]
  1248. Configure VIA parallel port to operate in
  1249. a specific mode. This is necessary on Pegasos
  1250. computer where firmware has no options for setting
  1251. up parallel port mode and sets it to spp.
  1252. Currently this function knows 686a and 8231 chips.
  1253. Format: [spp|ps2|epp|ecp|ecpepp]
  1254. pas2= [HW,OSS] Format:
  1255. <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
  1256. pas16= [HW,SCSI]
  1257. See header of drivers/scsi/pas16.c.
  1258. pause_on_oops=
  1259. Halt all CPUs after the first oops has been printed for
  1260. the specified number of seconds. This is to be used if
  1261. your oopses keep scrolling off the screen.
  1262. pcbit= [HW,ISDN]
  1263. pcd. [PARIDE]
  1264. See header of drivers/block/paride/pcd.c.
  1265. See also Documentation/blockdev/paride.txt.
  1266. pci=option[,option...] [PCI] various PCI subsystem options:
  1267. off [X86] don't probe for the PCI bus
  1268. bios [X86-32] force use of PCI BIOS, don't access
  1269. the hardware directly. Use this if your machine
  1270. has a non-standard PCI host bridge.
  1271. nobios [X86-32] disallow use of PCI BIOS, only direct
  1272. hardware access methods are allowed. Use this
  1273. if you experience crashes upon bootup and you
  1274. suspect they are caused by the BIOS.
  1275. conf1 [X86] Force use of PCI Configuration
  1276. Mechanism 1.
  1277. conf2 [X86] Force use of PCI Configuration
  1278. Mechanism 2.
  1279. noaer [PCIE] If the PCIEAER kernel config parameter is
  1280. enabled, this kernel boot option can be used to
  1281. disable the use of PCIE advanced error reporting.
  1282. nodomains [PCI] Disable support for multiple PCI
  1283. root domains (aka PCI segments, in ACPI-speak).
  1284. nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
  1285. Configuration
  1286. nomsi [MSI] If the PCI_MSI kernel config parameter is
  1287. enabled, this kernel boot option can be used to
  1288. disable the use of MSI interrupts system-wide.
  1289. biosirq [X86-32] Use PCI BIOS calls to get the interrupt
  1290. routing table. These calls are known to be buggy
  1291. on several machines and they hang the machine
  1292. when used, but on other computers it's the only
  1293. way to get the interrupt routing table. Try
  1294. this option if the kernel is unable to allocate
  1295. IRQs or discover secondary PCI buses on your
  1296. motherboard.
  1297. rom [X86] Assign address space to expansion ROMs.
  1298. Use with caution as certain devices share
  1299. address decoders between ROMs and other
  1300. resources.
  1301. norom [X86] Do not assign address space to
  1302. expansion ROMs that do not already have
  1303. BIOS assigned address ranges.
  1304. irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
  1305. assigned automatically to PCI devices. You can
  1306. make the kernel exclude IRQs of your ISA cards
  1307. this way.
  1308. pirqaddr=0xAAAAA [X86] Specify the physical address
  1309. of the PIRQ table (normally generated
  1310. by the BIOS) if it is outside the
  1311. F0000h-100000h range.
  1312. lastbus=N [X86] Scan all buses thru bus #N. Can be
  1313. useful if the kernel is unable to find your
  1314. secondary buses and you want to tell it
  1315. explicitly which ones they are.
  1316. assign-busses [X86] Always assign all PCI bus
  1317. numbers ourselves, overriding
  1318. whatever the firmware may have done.
  1319. usepirqmask [X86] Honor the possible IRQ mask stored
  1320. in the BIOS $PIR table. This is needed on
  1321. some systems with broken BIOSes, notably
  1322. some HP Pavilion N5400 and Omnibook XE3
  1323. notebooks. This will have no effect if ACPI
  1324. IRQ routing is enabled.
  1325. noacpi [X86] Do not use ACPI for IRQ routing
  1326. or for PCI scanning.
  1327. use_crs [X86] Use _CRS for PCI resource
  1328. allocation.
  1329. routeirq Do IRQ routing for all PCI devices.
  1330. This is normally done in pci_enable_device(),
  1331. so this option is a temporary workaround
  1332. for broken drivers that don't call it.
  1333. skip_isa_align [X86] do not align io start addr, so can
  1334. handle more pci cards
  1335. firmware [ARM] Do not re-enumerate the bus but instead
  1336. just use the configuration from the
  1337. bootloader. This is currently used on
  1338. IXP2000 systems where the bus has to be
  1339. configured a certain way for adjunct CPUs.
  1340. noearly [X86] Don't do any early type 1 scanning.
  1341. This might help on some broken boards which
  1342. machine check when some devices' config space
  1343. is read. But various workarounds are disabled
  1344. and some IOMMU drivers will not work.
  1345. bfsort Sort PCI devices into breadth-first order.
  1346. This sorting is done to get a device
  1347. order compatible with older (<= 2.4) kernels.
  1348. nobfsort Don't sort PCI devices into breadth-first order.
  1349. cbiosize=nn[KMG] The fixed amount of bus space which is
  1350. reserved for the CardBus bridge's IO window.
  1351. The default value is 256 bytes.
  1352. cbmemsize=nn[KMG] The fixed amount of bus space which is
  1353. reserved for the CardBus bridge's memory
  1354. window. The default value is 64 megabytes.
  1355. pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
  1356. Management.
  1357. off Disable ASPM.
  1358. force Enable ASPM even on devices that claim not to support it.
  1359. WARNING: Forcing ASPM on may cause system lockups.
  1360. pcmv= [HW,PCMCIA] BadgePAD 4
  1361. pd. [PARIDE]
  1362. See Documentation/blockdev/paride.txt.
  1363. pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
  1364. boot time.
  1365. Format: { 0 | 1 }
  1366. See arch/parisc/kernel/pdc_chassis.c
  1367. pf. [PARIDE]
  1368. See Documentation/blockdev/paride.txt.
  1369. pg. [PARIDE]
  1370. See Documentation/blockdev/paride.txt.
  1371. pirq= [SMP,APIC] Manual mp-table setup
  1372. See Documentation/x86/i386/IO-APIC.txt.
  1373. plip= [PPT,NET] Parallel port network link
  1374. Format: { parport<nr> | timid | 0 }
  1375. See also Documentation/parport.txt.
  1376. pmtmr= [X86] Manual setup of pmtmr I/O Port.
  1377. Override pmtimer IOPort with a hex value.
  1378. e.g. pmtmr=0x508
  1379. pnp.debug [PNP]
  1380. Enable PNP debug messages. This depends on the
  1381. CONFIG_PNP_DEBUG_MESSAGES option.
  1382. pnpacpi= [ACPI]
  1383. { off }
  1384. pnpbios= [ISAPNP]
  1385. { on | off | curr | res | no-curr | no-res }
  1386. pnp_reserve_irq=
  1387. [ISAPNP] Exclude IRQs for the autoconfiguration
  1388. pnp_reserve_dma=
  1389. [ISAPNP] Exclude DMAs for the autoconfiguration
  1390. pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
  1391. Ranges are in pairs (I/O port base and size).
  1392. pnp_reserve_mem=
  1393. [ISAPNP] Exclude memory regions for the
  1394. autoconfiguration.
  1395. Ranges are in pairs (memory base and size).
  1396. dynamic_printk
  1397. Enables pr_debug()/dev_dbg() calls if
  1398. CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. These can also
  1399. be switched on/off via <debugfs>/dynamic_printk/modules
  1400. print-fatal-signals=
  1401. [KNL] debug: print fatal signals
  1402. print-fatal-signals=1: print segfault info to
  1403. the kernel console.
  1404. default: off.
  1405. printk.time= Show timing data prefixed to each printk message line
  1406. Format: <bool> (1/Y/y=enable, 0/N/n=disable)
  1407. profile= [KNL] Enable kernel profiling via /proc/profile
  1408. Format: [schedule,]<number>
  1409. Param: "schedule" - profile schedule points.
  1410. Param: <number> - step/bucket size as a power of 2 for
  1411. statistical time based profiling.
  1412. Param: "sleep" - profile D-state sleeping (millisecs).
  1413. Requires CONFIG_SCHEDSTATS
  1414. Param: "kvm" - profile VM exits.
  1415. processor.max_cstate= [HW,ACPI]
  1416. Limit processor to maximum C-state
  1417. max_cstate=9 overrides any DMI blacklist limit.
  1418. processor.nocst [HW,ACPI]
  1419. Ignore the _CST method to determine C-states,
  1420. instead using the legacy FADT method
  1421. prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
  1422. before loading.
  1423. See Documentation/blockdev/ramdisk.txt.
  1424. psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
  1425. probe for; one of (bare|imps|exps|lifebook|any).
  1426. psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
  1427. per second.
  1428. psmouse.resetafter= [HW,MOUSE]
  1429. Try to reset the device after so many bad packets
  1430. (0 = never).
  1431. psmouse.resolution=
  1432. [HW,MOUSE] Set desired mouse resolution, in dpi.
  1433. psmouse.smartscroll=
  1434. [HW,MOUSE] Controls Logitech smartscroll autorepeat.
  1435. 0 = disabled, 1 = enabled (default).
  1436. pss= [HW,OSS] Personal Sound System (ECHO ESC614)
  1437. Format:
  1438. <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
  1439. pt. [PARIDE]
  1440. See Documentation/blockdev/paride.txt.
  1441. pty.legacy_count=
  1442. [KNL] Number of legacy pty's. Overwrites compiled-in
  1443. default number.
  1444. quiet [KNL] Disable most log messages
  1445. r128= [HW,DRM]
  1446. raid= [HW,RAID]
  1447. See Documentation/md.txt.
  1448. ramdisk_blocksize= [RAM]
  1449. See Documentation/blockdev/ramdisk.txt.
  1450. ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
  1451. See Documentation/blockdev/ramdisk.txt.
  1452. rcupdate.blimit= [KNL,BOOT]
  1453. Set maximum number of finished RCU callbacks to process
  1454. in one batch.
  1455. rcupdate.qhimark= [KNL,BOOT]
  1456. Set threshold of queued
  1457. RCU callbacks over which batch limiting is disabled.
  1458. rcupdate.qlowmark= [KNL,BOOT]
  1459. Set threshold of queued RCU callbacks below which
  1460. batch limiting is re-enabled.
  1461. rdinit= [KNL]
  1462. Format: <full_path>
  1463. Run specified binary instead of /init from the ramdisk,
  1464. used for early userspace startup. See initrd.
  1465. reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
  1466. Format: <reboot_mode>[,<reboot_mode2>[,...]]
  1467. See arch/*/kernel/reboot.c or arch/*/kernel/process.c
  1468. relax_domain_level=
  1469. [KNL, SMP] Set scheduler's default relax_domain_level.
  1470. See Documentation/cpusets.txt.
  1471. reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
  1472. reservetop= [X86-32]
  1473. Format: nn[KMG]
  1474. Reserves a hole at the top of the kernel virtual
  1475. address space.
  1476. reset_devices [KNL] Force drivers to reset the underlying device
  1477. during initialization.
  1478. resume= [SWSUSP]
  1479. Specify the partition device for software suspend
  1480. resume_offset= [SWSUSP]
  1481. Specify the offset from the beginning of the partition
  1482. given by "resume=" at which the swap header is located,
  1483. in <PAGE_SIZE> units (needed only for swap files).
  1484. See Documentation/power/swsusp-and-swap-files.txt
  1485. retain_initrd [RAM] Keep initrd memory after extraction
  1486. rhash_entries= [KNL,NET]
  1487. Set number of hash buckets for route cache
  1488. riscom8= [HW,SERIAL]
  1489. Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
  1490. ro [KNL] Mount root device read-only on boot
  1491. root= [KNL] Root filesystem
  1492. rootdelay= [KNL] Delay (in seconds) to pause before attempting to
  1493. mount the root filesystem
  1494. rootflags= [KNL] Set root filesystem mount option string
  1495. rootfstype= [KNL] Set root filesystem type
  1496. rootwait [KNL] Wait (indefinitely) for root device to show up.
  1497. Useful for devices that are detected asynchronously
  1498. (e.g. USB and MMC devices).
  1499. root_plug.vendor_id=
  1500. [ROOTPLUG] Override the default vendor ID
  1501. root_plug.product_id=
  1502. [ROOTPLUG] Override the default product ID
  1503. root_plug.debug=
  1504. [ROOTPLUG] Enable debugging output
  1505. rw [KNL] Mount root device read-write on boot
  1506. S [KNL] Run init in single mode
  1507. sa1100ir [NET]
  1508. See drivers/net/irda/sa1100_ir.c.
  1509. sbni= [NET] Granch SBNI12 leased line adapter
  1510. sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
  1511. Format: <io>[,<timeout>[,<isapnp>]]
  1512. scsi_debug_*= [SCSI]
  1513. See drivers/scsi/scsi_debug.c.
  1514. scsi_default_dev_flags=
  1515. [SCSI] SCSI default device flags
  1516. Format: <integer>
  1517. scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
  1518. Format: <vendor>:<model>:<flags>
  1519. (flags are integer value)
  1520. scsi_logging_level= [SCSI] a bit mask of logging levels
  1521. See drivers/scsi/scsi_logging.h for bits. Also
  1522. settable via sysctl at dev.scsi.logging_level
  1523. (/proc/sys/dev/scsi/logging_level).
  1524. There is also a nice 'scsi_logging_level' script in the
  1525. S390-tools package, available for download at
  1526. http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
  1527. scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
  1528. discovered. async scans them in kernel threads,
  1529. allowing boot to proceed. none ignores them, expecting
  1530. user space to do the scan.
  1531. selinux [SELINUX] Disable or enable SELinux at boot time.
  1532. Format: { "0" | "1" }
  1533. See security/selinux/Kconfig help text.
  1534. 0 -- disable.
  1535. 1 -- enable.
  1536. Default value is set via kernel config option.
  1537. If enabled at boot time, /selinux/disable can be used
  1538. later to disable prior to initial policy load.
  1539. selinux_compat_net =
  1540. [SELINUX] Set initial selinux_compat_net flag value.
  1541. Format: { "0" | "1" }
  1542. 0 -- use new secmark-based packet controls
  1543. 1 -- use legacy packet controls
  1544. Default value is 0 (preferred).
  1545. Value can be changed at runtime via
  1546. /selinux/compat_net.
  1547. serialnumber [BUGS=X86-32]
  1548. shapers= [NET]
  1549. Maximal number of shapers.
  1550. show_msr= [x86] show boot-time MSR settings
  1551. Format: { <integer> }
  1552. Show boot-time (BIOS-initialized) MSR settings.
  1553. The parameter means the number of CPUs to show,
  1554. for example 1 means boot CPU only.
  1555. sim710= [SCSI,HW]
  1556. See header of drivers/scsi/sim710.c.
  1557. simeth= [IA-64]
  1558. simscsi=
  1559. slram= [HW,MTD]
  1560. slub_debug[=options[,slabs]] [MM, SLUB]
  1561. Enabling slub_debug allows one to determine the
  1562. culprit if slab objects become corrupted. Enabling
  1563. slub_debug can create guard zones around objects and
  1564. may poison objects when not in use. Also tracks the
  1565. last alloc / free. For more information see
  1566. Documentation/vm/slub.txt.
  1567. slub_max_order= [MM, SLUB]
  1568. Determines the maximum allowed order for slabs.
  1569. A high setting may cause OOMs due to memory
  1570. fragmentation. For more information see
  1571. Documentation/vm/slub.txt.
  1572. slub_min_objects= [MM, SLUB]
  1573. The minimum number of objects per slab. SLUB will
  1574. increase the slab order up to slub_max_order to
  1575. generate a sufficiently large slab able to contain
  1576. the number of objects indicated. The higher the number
  1577. of objects the smaller the overhead of tracking slabs
  1578. and the less frequently locks need to be acquired.
  1579. For more information see Documentation/vm/slub.txt.
  1580. slub_min_order= [MM, SLUB]
  1581. Determines the mininum page order for slabs. Must be
  1582. lower than slub_max_order.
  1583. For more information see Documentation/vm/slub.txt.
  1584. slub_nomerge [MM, SLUB]
  1585. Disable merging of slabs with similar size. May be
  1586. necessary if there is some reason to distinguish
  1587. allocs to different slabs. Debug options disable
  1588. merging on their own.
  1589. For more information see Documentation/vm/slub.txt.
  1590. smart2= [HW]
  1591. Format: <io1>[,<io2>[,...,<io8>]]
  1592. smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
  1593. attempt to substitute SMP alternatives once at boot.
  1594. smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
  1595. smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
  1596. smsc-ircc2.ircc_sir= [HW] SIR base I/O port
  1597. smsc-ircc2.ircc_fir= [HW] FIR base I/O port
  1598. smsc-ircc2.ircc_irq= [HW] IRQ line
  1599. smsc-ircc2.ircc_dma= [HW] DMA channel
  1600. smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
  1601. 0: Toshiba Satellite 1800 (GP data pin select)
  1602. 1: Fast pin select (default)
  1603. 2: ATC IRMode
  1604. snd-ad1816a= [HW,ALSA]
  1605. snd-ad1848= [HW,ALSA]
  1606. snd-ali5451= [HW,ALSA]
  1607. snd-als100= [HW,ALSA]
  1608. snd-als4000= [HW,ALSA]
  1609. snd-azt2320= [HW,ALSA]
  1610. snd-cmi8330= [HW,ALSA]
  1611. snd-cmipci= [HW,ALSA]
  1612. snd-cs4231= [HW,ALSA]
  1613. snd-cs4232= [HW,ALSA]
  1614. snd-cs4236= [HW,ALSA]
  1615. snd-cs4281= [HW,ALSA]
  1616. snd-cs46xx= [HW,ALSA]
  1617. snd-dt019x= [HW,ALSA]
  1618. snd-dummy= [HW,ALSA]
  1619. snd-emu10k1= [HW,ALSA]
  1620. snd-ens1370= [HW,ALSA]
  1621. snd-ens1371= [HW,ALSA]
  1622. snd-es968= [HW,ALSA]
  1623. snd-es1688= [HW,ALSA]
  1624. snd-es18xx= [HW,ALSA]
  1625. snd-es1938= [HW,ALSA]
  1626. snd-es1968= [HW,ALSA]
  1627. snd-fm801= [HW,ALSA]
  1628. snd-gusclassic= [HW,ALSA]
  1629. snd-gusextreme= [HW,ALSA]
  1630. snd-gusmax= [HW,ALSA]
  1631. snd-hdsp= [HW,ALSA]
  1632. snd-ice1712= [HW,ALSA]
  1633. snd-intel8x0= [HW,ALSA]
  1634. snd-interwave= [HW,ALSA]
  1635. snd-interwave-stb=
  1636. [HW,ALSA]
  1637. snd-korg1212= [HW,ALSA]
  1638. snd-maestro3= [HW,ALSA]
  1639. snd-mpu401= [HW,ALSA]
  1640. snd-mtpav= [HW,ALSA]
  1641. snd-nm256= [HW,ALSA]
  1642. snd-opl3sa2= [HW,ALSA]
  1643. snd-opti92x-ad1848=
  1644. [HW,ALSA]
  1645. snd-opti92x-cs4231=
  1646. [HW,ALSA]
  1647. snd-opti93x= [HW,ALSA]
  1648. snd-pmac= [HW,ALSA]
  1649. snd-rme32= [HW,ALSA]
  1650. snd-rme96= [HW,ALSA]
  1651. snd-rme9652= [HW,ALSA]
  1652. snd-sb8= [HW,ALSA]
  1653. snd-sb16= [HW,ALSA]
  1654. snd-sbawe= [HW,ALSA]
  1655. snd-serial= [HW,ALSA]
  1656. snd-sgalaxy= [HW,ALSA]
  1657. snd-sonicvibes= [HW,ALSA]
  1658. snd-sun-amd7930=
  1659. [HW,ALSA]
  1660. snd-sun-cs4231= [HW,ALSA]
  1661. snd-trident= [HW,ALSA]
  1662. snd-usb-audio= [HW,ALSA,USB]
  1663. snd-via82xx= [HW,ALSA]
  1664. snd-virmidi= [HW,ALSA]
  1665. snd-wavefront= [HW,ALSA]
  1666. snd-ymfpci= [HW,ALSA]
  1667. softlockup_panic=
  1668. [KNL] Should the soft-lockup detector generate panics.
  1669. sonypi.*= [HW] Sony Programmable I/O Control Device driver
  1670. See Documentation/sonypi.txt
  1671. specialix= [HW,SERIAL] Specialix multi-serial port adapter
  1672. See Documentation/serial/specialix.txt.
  1673. spia_io_base= [HW,MTD]
  1674. spia_fio_base=
  1675. spia_pedr=
  1676. spia_peddr=
  1677. sscape= [HW,OSS]
  1678. Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
  1679. st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
  1680. See Documentation/scsi/st.txt.
  1681. sti= [PARISC,HW]
  1682. Format: <num>
  1683. Set the STI (builtin display/keyboard on the HP-PARISC
  1684. machines) console (graphic card) which should be used
  1685. as the initial boot-console.
  1686. See also comment in drivers/video/console/sticore.c.
  1687. sti_font= [HW]
  1688. See comment in drivers/video/console/sticore.c.
  1689. stifb= [HW]
  1690. Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
  1691. sunrpc.pool_mode=
  1692. [NFS]
  1693. Control how the NFS server code allocates CPUs to
  1694. service thread pools. Depending on how many NICs
  1695. you have and where their interrupts are bound, this
  1696. option will affect which CPUs will do NFS serving.
  1697. Note: this parameter cannot be changed while the
  1698. NFS server is running.
  1699. auto the server chooses an appropriate mode
  1700. automatically using heuristics
  1701. global a single global pool contains all CPUs
  1702. percpu one pool for each CPU
  1703. pernode one pool for each NUMA node (equivalent
  1704. to global on non-NUMA machines)
  1705. swiotlb= [IA-64] Number of I/O TLB slabs
  1706. switches= [HW,M68k]
  1707. sym53c416= [HW,SCSI]
  1708. See header of drivers/scsi/sym53c416.c.
  1709. sysrq_always_enabled
  1710. [KNL]
  1711. Ignore sysrq setting - this boot parameter will
  1712. neutralize any effect of /proc/sys/kernel/sysrq.
  1713. Useful for debugging.
  1714. t128= [HW,SCSI]
  1715. See header of drivers/scsi/t128.c.
  1716. tdfx= [HW,DRM]
  1717. test_suspend= [SUSPEND]
  1718. Specify "mem" (for Suspend-to-RAM) or "standby" (for
  1719. standby suspend) as the system sleep state to briefly
  1720. enter during system startup. The system is woken from
  1721. this state using a wakeup-capable RTC alarm.
  1722. thash_entries= [KNL,NET]
  1723. Set number of hash buckets for TCP connection
  1724. thermal.act= [HW,ACPI]
  1725. -1: disable all active trip points in all thermal zones
  1726. <degrees C>: override all lowest active trip points
  1727. thermal.crt= [HW,ACPI]
  1728. -1: disable all critical trip points in all thermal zones
  1729. <degrees C>: override all critical trip points
  1730. thermal.nocrt= [HW,ACPI]
  1731. Set to disable actions on ACPI thermal zone
  1732. critical and hot trip points.
  1733. thermal.off= [HW,ACPI]
  1734. 1: disable ACPI thermal control
  1735. thermal.psv= [HW,ACPI]
  1736. -1: disable all passive trip points
  1737. <degrees C>: override all passive trip points to this value
  1738. thermal.tzp= [HW,ACPI]
  1739. Specify global default ACPI thermal zone polling rate
  1740. <deci-seconds>: poll all this frequency
  1741. 0: no polling (default)
  1742. tmscsim= [HW,SCSI]
  1743. See comment before function dc390_setup() in
  1744. drivers/scsi/tmscsim.c.
  1745. tp720= [HW,PS2]
  1746. trix= [HW,OSS] MediaTrix AudioTrix Pro
  1747. Format:
  1748. <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
  1749. turbografx.map[2|3]= [HW,JOY]
  1750. TurboGraFX parallel port interface
  1751. Format:
  1752. <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
  1753. See also Documentation/input/joystick-parport.txt
  1754. u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
  1755. See header of drivers/scsi/u14-34f.c.
  1756. uart401= [HW,OSS]
  1757. Format: <io>,<irq>
  1758. uart6850= [HW,OSS]
  1759. Format: <io>,<irq>
  1760. uhci-hcd.ignore_oc=
  1761. [USB] Ignore overcurrent events (default N).
  1762. Some badly-designed motherboards generate lots of
  1763. bogus events, for ports that aren't wired to
  1764. anything. Set this parameter to avoid log spamming.
  1765. Note that genuine overcurrent events won't be
  1766. reported either.
  1767. unknown_nmi_panic
  1768. [X86-32,X86-64]
  1769. Set unknown_nmi_panic=1 early on boot.
  1770. usbcore.autosuspend=
  1771. [USB] The autosuspend time delay (in seconds) used
  1772. for newly-detected USB devices (default 2). This
  1773. is the time required before an idle device will be
  1774. autosuspended. Devices for which the delay is set
  1775. to a negative value won't be autosuspended at all.
  1776. usbcore.usbfs_snoop=
  1777. [USB] Set to log all usbfs traffic (default 0 = off).
  1778. usbcore.blinkenlights=
  1779. [USB] Set to cycle leds on hubs (default 0 = off).
  1780. usbcore.old_scheme_first=
  1781. [USB] Start with the old device initialization
  1782. scheme (default 0 = off).
  1783. usbcore.use_both_schemes=
  1784. [USB] Try the other device initialization scheme
  1785. if the first one fails (default 1 = enabled).
  1786. usbcore.initial_descriptor_timeout=
  1787. [USB] Specifies timeout for the initial 64-byte
  1788. USB_REQ_GET_DESCRIPTOR request in milliseconds
  1789. (default 5000 = 5.0 seconds).
  1790. usbhid.mousepoll=
  1791. [USBHID] The interval which mice are to be polled at.
  1792. add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
  1793. kernel's map of available physical RAM.
  1794. vdso= [X86-32,SH,x86-64]
  1795. vdso=2: enable compat VDSO (default with COMPAT_VDSO)
  1796. vdso=1: enable VDSO (default)
  1797. vdso=0: disable VDSO mapping
  1798. vdso32= [X86-32,X86-64]
  1799. vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
  1800. vdso32=1: enable 32-bit VDSO (default)
  1801. vdso32=0: disable 32-bit VDSO mapping
  1802. vector= [IA-64,SMP]
  1803. vector=percpu: enable percpu vector domain
  1804. video= [FB] Frame buffer configuration
  1805. See Documentation/fb/modedb.txt.
  1806. vga= [BOOT,X86-32] Select a particular video mode
  1807. See Documentation/x86/i386/boot.txt and
  1808. Documentation/svga.txt.
  1809. Use vga=ask for menu.
  1810. This is actually a boot loader parameter; the value is
  1811. passed to the kernel using a special protocol.
  1812. vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
  1813. size of <nn>. This can be used to increase the
  1814. minimum size (128MB on x86). It can also be used to
  1815. decrease the size and leave more room for directly
  1816. mapped kernel RAM.
  1817. vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
  1818. Format: <command>
  1819. vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
  1820. Format: <command>
  1821. vmpoff= [KNL,S390] Perform z/VM CP command after power off.
  1822. Format: <command>
  1823. waveartist= [HW,OSS]
  1824. Format: <io>,<irq>,<dma>,<dma2>
  1825. wd33c93= [HW,SCSI]
  1826. See header of drivers/scsi/wd33c93.c.
  1827. wd7000= [HW,SCSI]
  1828. See header of drivers/scsi/wd7000.c.
  1829. wdt= [WDT] Watchdog
  1830. See Documentation/watchdog/wdt.txt.
  1831. xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
  1832. xd_geo= See header of drivers/block/xd.c.
  1833. xirc2ps_cs= [NET,PCMCIA]
  1834. Format:
  1835. <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
  1836. norandmaps Don't use address space randomization
  1837. Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
  1838. ______________________________________________________________________
  1839. TODO:
  1840. Add documentation for ALSA options.
  1841. Add more DRM drivers.