kernel-parameters.txt 74 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_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/i386/boot.txt>.
  105. There are also arch-specific kernel-parameters not documented here.
  106. See for example <Documentation/x86_64/boot-options.txt>.
  107. Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
  108. a trailing = on the name of any parameter states that that parameter will
  109. be entered as an environment variable, whereas its absence indicates that
  110. it will appear as a kernel argument readable via /proc/cmdline by programs
  111. running once the system is up.
  112. The number of kernel parameters is not limited, but the length of the
  113. complete command line (parameters including spaces etc.) is limited to
  114. a fixed number of characters. This limit depends on the architecture
  115. and is between 256 and 4096 characters. It is defined in the file
  116. ./include/asm/setup.h as COMMAND_LINE_SIZE.
  117. acpi= [HW,ACPI,X86-64,i386]
  118. Advanced Configuration and Power Interface
  119. Format: { force | off | ht | strict | noirq }
  120. force -- enable ACPI if default was off
  121. off -- disable ACPI if default was on
  122. noirq -- do not use ACPI for IRQ routing
  123. ht -- run only enough ACPI to enable Hyper Threading
  124. strict -- Be less tolerant of platforms that are not
  125. strictly ACPI specification compliant.
  126. See also Documentation/power/pm.txt, pci=noacpi
  127. acpi_apic_instance= [ACPI, IOAPIC]
  128. Format: <int>
  129. 2: use 2nd APIC table, if available
  130. 1,0: use 1st APIC table
  131. default: 0
  132. acpi_sleep= [HW,ACPI] Sleep options
  133. Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, old_ordering }
  134. See Documentation/power/video.txt for s3_bios and s3_mode.
  135. s3_beep is for debugging; it makes the PC's speaker beep
  136. as soon as the kernel's real-mode entry point is called.
  137. s4_nohwsig prevents ACPI hardware signature from being
  138. used during resume from hibernation.
  139. old_ordering causes the ACPI 1.0 ordering of the _PTS
  140. control method, wrt putting devices into low power
  141. states, to be enforced (the ACPI 2.0 ordering of _PTS is
  142. used by default).
  143. acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
  144. Format: { level | edge | high | low }
  145. acpi_irq_balance [HW,ACPI]
  146. ACPI will balance active IRQs
  147. default in APIC mode
  148. acpi_irq_nobalance [HW,ACPI]
  149. ACPI will not move active IRQs (default)
  150. default in PIC mode
  151. acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
  152. use by PCI
  153. Format: <irq>,<irq>...
  154. acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
  155. Format: <irq>,<irq>...
  156. acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
  157. acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
  158. Format: To spoof as Windows 98: ="Microsoft Windows"
  159. acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
  160. acpi_osi="string1" # add string1 -- only one string
  161. acpi_osi="!string2" # remove built-in string2
  162. acpi_osi= # disable all strings
  163. acpi_serialize [HW,ACPI] force serialization of AML methods
  164. acpi_skip_timer_override [HW,ACPI]
  165. Recognize and ignore IRQ0/pin2 Interrupt Override.
  166. For broken nForce2 BIOS resulting in XT-PIC timer.
  167. acpi_use_timer_override [HW,ACPI}
  168. Use timer override. For some broken Nvidia NF5 boards
  169. that require a timer override, but don't have
  170. HPET
  171. acpi.debug_layer= [HW,ACPI]
  172. Format: <int>
  173. Each bit of the <int> indicates an ACPI debug layer,
  174. 1: enable, 0: disable. It is useful for boot time
  175. debugging. After system has booted up, it can be set
  176. via /sys/module/acpi/parameters/debug_layer.
  177. CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
  178. Available bits (add the numbers together) to enable debug output
  179. for specific parts of the ACPI subsystem:
  180. 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
  181. 0x10 namespace 0x20 parser 0x40 dispatcher
  182. 0x80 executer 0x100 resources 0x200 acpica debugger
  183. 0x400 os services 0x800 acpica disassembler.
  184. The number can be in decimal or prefixed with 0x in hex.
  185. Warning: Many of these options can produce a lot of
  186. output and make your system unusable. Be very careful.
  187. acpi.debug_level= [HW,ACPI]
  188. Format: <int>
  189. Each bit of the <int> indicates an ACPI debug level,
  190. 1: enable, 0: disable. It is useful for boot time
  191. debugging. After system has booted up, it can be set
  192. via /sys/module/acpi/parameters/debug_level.
  193. CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
  194. Available bits (add the numbers together) to enable different
  195. debug output levels of the ACPI subsystem:
  196. 0x01 error 0x02 warn 0x04 init 0x08 debug object
  197. 0x10 info 0x20 init names 0x40 parse 0x80 load
  198. 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
  199. 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
  200. 0x10000 resources 0x20000 user requests 0x40000 package.
  201. The number can be in decimal or prefixed with 0x in hex.
  202. Warning: Many of these options can produce a lot of
  203. output and make your system unusable. Be very careful.
  204. acpi_pm_good [X86-32,X86-64]
  205. Override the pmtimer bug detection: force the kernel
  206. to assume that this machine's pmtimer latches its value
  207. and always returns good values.
  208. agp= [AGP]
  209. { off | try_unsupported }
  210. off: disable AGP support
  211. try_unsupported: try to drive unsupported chipsets
  212. (may crash computer or cause data corruption)
  213. enable_timer_pin_1 [i386,x86-64]
  214. Enable PIN 1 of APIC timer
  215. Can be useful to work around chipset bugs
  216. (in particular on some ATI chipsets).
  217. The kernel tries to set a reasonable default.
  218. disable_timer_pin_1 [i386,x86-64]
  219. Disable PIN 1 of APIC timer
  220. Can be useful to work around chipset bugs.
  221. ad1848= [HW,OSS]
  222. Format: <io>,<irq>,<dma>,<dma2>,<type>
  223. advansys= [HW,SCSI]
  224. See header of drivers/scsi/advansys.c.
  225. advwdt= [HW,WDT] Advantech WDT
  226. Format: <iostart>,<iostop>
  227. aedsp16= [HW,OSS] Audio Excel DSP 16
  228. Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
  229. See also header of sound/oss/aedsp16.c.
  230. aha152x= [HW,SCSI]
  231. See Documentation/scsi/aha152x.txt.
  232. aha1542= [HW,SCSI]
  233. Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
  234. aic7xxx= [HW,SCSI]
  235. See Documentation/scsi/aic7xxx.txt.
  236. aic79xx= [HW,SCSI]
  237. See Documentation/scsi/aic79xx.txt.
  238. amd_iommu= [HW,X86-84]
  239. Pass parameters to the AMD IOMMU driver in the system.
  240. Possible values are:
  241. isolate - enable device isolation (each device, as far
  242. as possible, will get its own protection
  243. domain)
  244. fullflush - enable flushing of IO/TLB entries when
  245. they are unmapped. Otherwise they are
  246. flushed before they will be reused, which
  247. is a lot of faster
  248. amd_iommu_size= [HW,X86-64]
  249. Define the size of the aperture for the AMD IOMMU
  250. driver. Possible values are:
  251. '32M', '64M' (default), '128M', '256M', '512M', '1G'
  252. amijoy.map= [HW,JOY] Amiga joystick support
  253. Map of devices attached to JOY0DAT and JOY1DAT
  254. Format: <a>,<b>
  255. See also Documentation/kernel/input/joystick.txt
  256. analog.map= [HW,JOY] Analog joystick and gamepad support
  257. Specifies type or capabilities of an analog joystick
  258. connected to one of 16 gameports
  259. Format: <type1>,<type2>,..<type16>
  260. apc= [HW,SPARC]
  261. Power management functions (SPARCstation-4/5 + deriv.)
  262. Format: noidle
  263. Disable APC CPU standby support. SPARCstation-Fox does
  264. not play well with APC CPU idle - disable it if you have
  265. APC and your system crashes randomly.
  266. apic= [APIC,i386] Advanced Programmable Interrupt Controller
  267. Change the output verbosity whilst booting
  268. Format: { quiet (default) | verbose | debug }
  269. Change the amount of debugging information output
  270. when initialising the APIC and IO-APIC components.
  271. apm= [APM] Advanced Power Management
  272. See header of arch/x86/kernel/apm_32.c.
  273. arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
  274. Format: <io>,<irq>,<nodeID>
  275. ataflop= [HW,M68k]
  276. atarimouse= [HW,MOUSE] Atari Mouse
  277. atascsi= [HW,SCSI] Atari SCSI
  278. atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
  279. EzKey and similar keyboards
  280. atkbd.reset= [HW] Reset keyboard during initialization
  281. atkbd.set= [HW] Select keyboard code set
  282. Format: <int> (2 = AT (default), 3 = PS/2)
  283. atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
  284. keyboards
  285. atkbd.softraw= [HW] Choose between synthetic and real raw mode
  286. Format: <bool> (0 = real, 1 = synthetic (default))
  287. atkbd.softrepeat= [HW]
  288. Use software keyboard repeat
  289. autotest [IA64]
  290. baycom_epp= [HW,AX25]
  291. Format: <io>,<mode>
  292. baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
  293. Format: <io>,<mode>
  294. See header of drivers/net/hamradio/baycom_par.c.
  295. baycom_ser_fdx= [HW,AX25]
  296. BayCom Serial Port AX.25 Modem (Full Duplex Mode)
  297. Format: <io>,<irq>,<mode>[,<baud>]
  298. See header of drivers/net/hamradio/baycom_ser_fdx.c.
  299. baycom_ser_hdx= [HW,AX25]
  300. BayCom Serial Port AX.25 Modem (Half Duplex Mode)
  301. Format: <io>,<irq>,<mode>
  302. See header of drivers/net/hamradio/baycom_ser_hdx.c.
  303. boot_delay= Milliseconds to delay each printk during boot.
  304. Values larger than 10 seconds (10000) are changed to
  305. no delay (0).
  306. Format: integer
  307. bootmem_debug [KNL] Enable bootmem allocator debug messages.
  308. bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
  309. bttv.radio= Most important insmod options are available as
  310. kernel args too.
  311. bttv.pll= See Documentation/video4linux/bttv/Insmod-options
  312. bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
  313. BusLogic= [HW,SCSI]
  314. See drivers/scsi/BusLogic.c, comment before function
  315. BusLogic_ParseDriverOptions().
  316. c101= [NET] Moxa C101 synchronous serial card
  317. cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
  318. Sometimes CPU hardware bugs make them report the cache
  319. size incorrectly. The kernel will attempt work arounds
  320. to fix known problems, but for some CPUs it is not
  321. possible to determine what the correct size should be.
  322. This option provides an override for these situations.
  323. security= [SECURITY] Choose a security module to enable at boot.
  324. If this boot parameter is not specified, only the first
  325. security module asking for security registration will be
  326. loaded. An invalid security module name will be treated
  327. as if no module has been chosen.
  328. capability.disable=
  329. [SECURITY] Disable capabilities. This would normally
  330. be used only if an alternative security model is to be
  331. configured. Potentially dangerous and should only be
  332. used if you are entirely sure of the consequences.
  333. ccw_timeout_log [S390]
  334. See Documentation/s390/CommonIO for details.
  335. cgroup_disable= [KNL] Disable a particular controller
  336. Format: {name of the controller(s) to disable}
  337. {Currently supported controllers - "memory"}
  338. checkreqprot [SELINUX] Set initial checkreqprot flag value.
  339. Format: { "0" | "1" }
  340. See security/selinux/Kconfig help text.
  341. 0 -- check protection applied by kernel (includes
  342. any implied execute protection).
  343. 1 -- check protection requested by application.
  344. Default value is set via a kernel config option.
  345. Value can be changed at runtime via
  346. /selinux/checkreqprot.
  347. cio_ignore= [S390]
  348. See Documentation/s390/CommonIO for details.
  349. clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
  350. [Deprecated]
  351. Forces specified clocksource (if available) to be used
  352. when calculating gettimeofday(). If specified
  353. clocksource is not available, it defaults to PIT.
  354. Format: { pit | tsc | cyclone | pmtmr }
  355. clocksource= [GENERIC_TIME] Override the default clocksource
  356. Format: <string>
  357. Override the default clocksource and use the clocksource
  358. with the name specified.
  359. Some clocksource names to choose from, depending on
  360. the platform:
  361. [all] jiffies (this is the base, fallback clocksource)
  362. [ACPI] acpi_pm
  363. [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
  364. pxa_timer,timer3,32k_counter,timer0_1
  365. [AVR32] avr32
  366. [X86-32] pit,hpet,tsc,vmi-timer;
  367. scx200_hrt on Geode; cyclone on IBM x440
  368. [MIPS] MIPS
  369. [PARISC] cr16
  370. [S390] tod
  371. [SH] SuperH
  372. [SPARC64] tick
  373. [X86-64] hpet,tsc
  374. clearcpuid=BITNUM [X86]
  375. Disable CPUID feature X for the kernel. See
  376. include/asm-x86/cpufeature.h for the valid bit numbers.
  377. Note the Linux specific bits are not necessarily
  378. stable over kernel options, but the vendor specific
  379. ones should be.
  380. Also note that user programs calling CPUID directly
  381. or using the feature without checking anything
  382. will still see it. This just prevents it from
  383. being used by the kernel or shown in /proc/cpuinfo.
  384. Also note the kernel might malfunction if you disable
  385. some critical bits.
  386. code_bytes [IA32/X86_64] How many bytes of object code to print
  387. in an oops report.
  388. Range: 0 - 8192
  389. Default: 64
  390. hpet= [X86-32,HPET] option to control HPET usage
  391. Format: { enable (default) | disable | force }
  392. disable: disable HPET and use PIT instead
  393. force: allow force enabled of undocumented chips (ICH4,
  394. VIA, nVidia)
  395. com20020= [HW,NET] ARCnet - COM20020 chipset
  396. Format:
  397. <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
  398. com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
  399. Format: <io>[,<irq>]
  400. com90xx= [HW,NET]
  401. ARCnet - COM90xx chipset (memory-mapped buffers)
  402. Format: <io>[,<irq>[,<memstart>]]
  403. condev= [HW,S390] console device
  404. conmode=
  405. console= [KNL] Output console device and options.
  406. tty<n> Use the virtual console device <n>.
  407. ttyS<n>[,options]
  408. ttyUSB0[,options]
  409. Use the specified serial port. The options are of
  410. the form "bbbbpnf", where "bbbb" is the baud rate,
  411. "p" is parity ("n", "o", or "e"), "n" is number of
  412. bits, and "f" is flow control ("r" for RTS or
  413. omit it). Default is "9600n8".
  414. See Documentation/serial-console.txt for more
  415. information. See
  416. Documentation/networking/netconsole.txt for an
  417. alternative.
  418. uart[8250],io,<addr>[,options]
  419. uart[8250],mmio,<addr>[,options]
  420. Start an early, polled-mode console on the 8250/16550
  421. UART at the specified I/O port or MMIO address,
  422. switching to the matching ttyS device later. The
  423. options are the same as for ttyS, above.
  424. If the device connected to the port is not a TTY but a braille
  425. device, prepend "brl," before the device type, for instance
  426. console=brl,ttyS0
  427. For now, only VisioBraille is supported.
  428. earlycon= [KNL] Output early console device and options.
  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. The options are the same as for ttyS, above.
  434. no_console_suspend
  435. [HW] Never suspend the console
  436. Disable suspending of consoles during suspend and
  437. hibernate operations. Once disabled, debugging
  438. messages can reach various consoles while the rest
  439. of the system is being put to sleep (ie, while
  440. debugging driver suspend/resume hooks). This may
  441. not work reliably with all consoles, but is known
  442. to work with serial and VGA consoles.
  443. cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
  444. Format:
  445. <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
  446. crashkernel=nn[KMG]@ss[KMG]
  447. [KNL] Reserve a chunk of physical memory to
  448. hold a kernel to switch to with kexec on panic.
  449. crashkernel=range1:size1[,range2:size2,...][@offset]
  450. [KNL] Same as above, but depends on the memory
  451. in the running system. The syntax of range is
  452. start-[end] where start and end are both
  453. a memory unit (amount[KMG]). See also
  454. Documentation/kdump/kdump.txt for a example.
  455. cs4232= [HW,OSS]
  456. Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
  457. cs89x0_dma= [HW,NET]
  458. Format: <dma>
  459. cs89x0_media= [HW,NET]
  460. Format: { rj45 | aui | bnc }
  461. dasd= [HW,NET]
  462. See header of drivers/s390/block/dasd_devmap.c.
  463. db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
  464. (one device per port)
  465. Format: <port#>,<type>
  466. See also Documentation/input/joystick-parport.txt
  467. debug [KNL] Enable kernel debugging (events log level).
  468. debug_locks_verbose=
  469. [KNL] verbose self-tests
  470. Format=<0|1>
  471. Print debugging info while doing the locking API
  472. self-tests.
  473. We default to 0 (no extra messages), setting it to
  474. 1 will print _a lot_ more information - normally
  475. only useful to kernel developers.
  476. debug_objects [KNL] Enable object debugging
  477. debugpat [X86] Enable PAT debugging
  478. decnet.addr= [HW,NET]
  479. Format: <area>[,<node>]
  480. See also Documentation/networking/decnet.txt.
  481. vt.default_blu= [VT]
  482. Format: <blue0>,<blue1>,<blue2>,...,<blue15>
  483. Change the default blue palette of the console.
  484. This is a 16-member array composed of values
  485. ranging from 0-255.
  486. vt.default_grn= [VT]
  487. Format: <green0>,<green1>,<green2>,...,<green15>
  488. Change the default green palette of the console.
  489. This is a 16-member array composed of values
  490. ranging from 0-255.
  491. vt.default_red= [VT]
  492. Format: <red0>,<red1>,<red2>,...,<red15>
  493. Change the default red palette of the console.
  494. This is a 16-member array composed of values
  495. ranging from 0-255.
  496. vt.default_utf8=
  497. [VT]
  498. Format=<0|1>
  499. Set system-wide default UTF-8 mode for all tty's.
  500. Default is 1, i.e. UTF-8 mode is enabled for all
  501. newly opened terminals.
  502. dhash_entries= [KNL]
  503. Set number of hash buckets for dentry cache.
  504. digi= [HW,SERIAL]
  505. IO parameters + enable/disable command.
  506. digiepca= [HW,SERIAL]
  507. See drivers/char/README.epca and
  508. Documentation/digiepca.txt.
  509. disable_mtrr_cleanup [X86]
  510. enable_mtrr_cleanup [X86]
  511. The kernel tries to adjust MTRR layout from continuous
  512. to discrete, to make X server driver able to add WB
  513. entry later. This parameter enables/disables that.
  514. mtrr_chunk_size=nn[KMG] [X86]
  515. used for mtrr cleanup. It is largest continous chunk
  516. that could hold holes aka. UC entries.
  517. mtrr_gran_size=nn[KMG] [X86]
  518. Used for mtrr cleanup. It is granularity of mtrr block.
  519. Default is 1.
  520. Large value could prevent small alignment from
  521. using up MTRRs.
  522. mtrr_spare_reg_nr=n [X86]
  523. Format: <integer>
  524. Range: 0,7 : spare reg number
  525. Default : 1
  526. Used for mtrr cleanup. It is spare mtrr entries number.
  527. Set to 2 or more if your graphical card needs more.
  528. disable_mtrr_trim [X86, Intel and AMD only]
  529. By default the kernel will trim any uncacheable
  530. memory out of your available memory pool based on
  531. MTRR settings. This parameter disables that behavior,
  532. possibly causing your machine to run very slowly.
  533. dmasound= [HW,OSS] Sound subsystem buffers
  534. dscc4.setup= [NET]
  535. dtc3181e= [HW,SCSI]
  536. earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
  537. earlyprintk=vga
  538. earlyprintk=serial[,ttySn[,baudrate]]
  539. earlyprintk=dbgp
  540. Append ",keep" to not disable it when the real console
  541. takes over.
  542. Only vga or serial or usb debug port at a time.
  543. Currently only ttyS0 and ttyS1 are supported.
  544. Interaction with the standard serial driver is not
  545. very good.
  546. The VGA output is eventually overwritten by the real
  547. console.
  548. eata= [HW,SCSI]
  549. edd= [EDD]
  550. Format: {"off" | "on" | "skip[mbr]"}
  551. eisa_irq_edge= [PARISC,HW]
  552. See header of drivers/parisc/eisa.c.
  553. elanfreq= [X86-32]
  554. See comment before function elanfreq_setup() in
  555. arch/x86/kernel/cpu/cpufreq/elanfreq.c.
  556. elevator= [IOSCHED]
  557. Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
  558. See Documentation/block/as-iosched.txt and
  559. Documentation/block/deadline-iosched.txt for details.
  560. elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
  561. Specifies physical address of start of kernel core
  562. image elf header. Generally kexec loader will
  563. pass this option to capture kernel.
  564. See Documentation/kdump/kdump.txt for details.
  565. enforcing [SELINUX] Set initial enforcing status.
  566. Format: {"0" | "1"}
  567. See security/selinux/Kconfig help text.
  568. 0 -- permissive (log only, no denials).
  569. 1 -- enforcing (deny and log).
  570. Default value is 0.
  571. Value can be changed at runtime via /selinux/enforce.
  572. es1371= [HW,OSS]
  573. Format: <spdif>,[<nomix>,[<amplifier>]]
  574. See also header of sound/oss/es1371.c.
  575. ether= [HW,NET] Ethernet cards parameters
  576. This option is obsoleted by the "netdev=" option, which
  577. has equivalent usage. See its documentation for details.
  578. eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
  579. Format: <io>[,<irq>]
  580. failslab=
  581. fail_page_alloc=
  582. fail_make_request=[KNL]
  583. General fault injection mechanism.
  584. Format: <interval>,<probability>,<space>,<times>
  585. See also /Documentation/fault-injection/.
  586. fd_mcs= [HW,SCSI]
  587. See header of drivers/scsi/fd_mcs.c.
  588. fdomain= [HW,SCSI]
  589. See header of drivers/scsi/fdomain.c.
  590. floppy= [HW]
  591. See Documentation/floppy.txt.
  592. force_pal_cache_flush
  593. [IA-64] Avoid check_sal_cache_flush which may hang on
  594. buggy SAL_CACHE_FLUSH implementations. Using this
  595. parameter will force ia64_sal_cache_flush to call
  596. ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
  597. gamecon.map[2|3]=
  598. [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
  599. support via parallel port (up to 5 devices per port)
  600. Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
  601. See also Documentation/input/joystick-parport.txt
  602. gamma= [HW,DRM]
  603. gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
  604. Format: off | on
  605. default: on
  606. gdth= [HW,SCSI]
  607. See header of drivers/scsi/gdth.c.
  608. gpt [EFI] Forces disk with valid GPT signature but
  609. invalid Protective MBR to be treated as GPT.
  610. gvp11= [HW,SCSI]
  611. hashdist= [KNL,NUMA] Large hashes allocated during boot
  612. are distributed across NUMA nodes. Defaults on
  613. for IA-64, off otherwise.
  614. Format: 0 | 1 (for off | on)
  615. hcl= [IA-64] SGI's Hardware Graph compatibility layer
  616. hd= [EIDE] (E)IDE hard drive subsystem geometry
  617. Format: <cyl>,<head>,<sect>
  618. highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
  619. size of <nn>. This works even on boxes that have no
  620. highmem otherwise. This also works to reduce highmem
  621. size on bigger boxes.
  622. highres= [KNL] Enable/disable high resolution timer mode.
  623. Valid parameters: "on", "off"
  624. Default: "on"
  625. hisax= [HW,ISDN]
  626. See Documentation/isdn/README.HiSax.
  627. hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
  628. hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
  629. On x86-64 and powerpc, this option can be specified
  630. multiple times interleaved with hugepages= to reserve
  631. huge pages of different sizes. Valid pages sizes on
  632. x86-64 are 2M (when the CPU supports "pse") and 1G
  633. (when the CPU supports the "pdpe1gb" cpuinfo flag)
  634. Note that 1GB pages can only be allocated at boot time
  635. using hugepages= and not freed afterwards.
  636. default_hugepagesz=
  637. [same as hugepagesz=] The size of the default
  638. HugeTLB page size. This is the size represented by
  639. the legacy /proc/ hugepages APIs, used for SHM, and
  640. default size when mounting hugetlbfs filesystems.
  641. Defaults to the default architecture's huge page size
  642. if not specified.
  643. hlt [BUGS=ARM,SH]
  644. i8042.debug [HW] Toggle i8042 debug mode
  645. i8042.direct [HW] Put keyboard port into non-translated mode
  646. i8042.dumbkbd [HW] Pretend that controller can only read data from
  647. keyboard and cannot control its state
  648. (Don't attempt to blink the leds)
  649. i8042.noaux [HW] Don't check for auxiliary (== mouse) port
  650. i8042.nokbd [HW] Don't check/create keyboard port
  651. i8042.noloop [HW] Disable the AUX Loopback command while probing
  652. for the AUX port
  653. i8042.nomux [HW] Don't check presence of an active multiplexing
  654. controller
  655. i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
  656. controllers
  657. i8042.panicblink=
  658. [HW] Frequency with which keyboard LEDs should blink
  659. when kernel panics (default is 0.5 sec)
  660. i8042.reset [HW] Reset the controller during init and cleanup
  661. i8042.unlock [HW] Unlock (ignore) the keylock
  662. i810= [HW,DRM]
  663. i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
  664. indicates that the driver is running on unsupported
  665. hardware.
  666. i8k.force [HW] Activate i8k driver even if SMM BIOS signature
  667. does not match list of supported models.
  668. i8k.power_status
  669. [HW] Report power status in /proc/i8k
  670. (disabled by default)
  671. i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
  672. capability is set.
  673. ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
  674. See Documentation/mca.txt.
  675. icn= [HW,ISDN]
  676. Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
  677. ide= [HW] (E)IDE subsystem
  678. Format: ide=nodma or ide=doubler
  679. See Documentation/ide/ide.txt.
  680. idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
  681. See Documentation/ide/ide.txt.
  682. idle= [X86]
  683. Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
  684. Poll forces a polling idle loop that can slightly improves the performance
  685. of waking up a idle CPU, but will use a lot of power and make the system
  686. run hot. Not recommended.
  687. idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
  688. to not use it because it doesn't save as much power as a normal idle
  689. loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
  690. as idle=poll.
  691. idle=halt. Halt is forced to be used for CPU idle.
  692. In such case C2/C3 won't be used again.
  693. idle=nomwait. Disable mwait for CPU C-states
  694. ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
  695. Claim all unknown PCI IDE storage controllers.
  696. ignore_loglevel [KNL]
  697. Ignore loglevel setting - this will print /all/
  698. kernel messages to the console. Useful for debugging.
  699. ihash_entries= [KNL]
  700. Set number of hash buckets for inode cache.
  701. in2000= [HW,SCSI]
  702. See header of drivers/scsi/in2000.c.
  703. init= [KNL]
  704. Format: <full_path>
  705. Run specified binary instead of /sbin/init as init
  706. process.
  707. initcall_debug [KNL] Trace initcalls as they are executed. Useful
  708. for working out where the kernel is dying during
  709. startup.
  710. initrd= [BOOT] Specify the location of the initial ramdisk
  711. inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
  712. Format: <irq>
  713. inttest= [IA64]
  714. iommu= [x86]
  715. off
  716. force
  717. noforce
  718. biomerge
  719. panic
  720. nopanic
  721. merge
  722. nomerge
  723. forcesac
  724. soft
  725. intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
  726. off
  727. Disable intel iommu driver.
  728. igfx_off [Default Off]
  729. By default, gfx is mapped as normal device. If a gfx
  730. device has a dedicated DMAR unit, the DMAR unit is
  731. bypassed by not enabling DMAR with this option. In
  732. this case, gfx device will use physical address for
  733. DMA.
  734. forcedac [x86_64]
  735. With this option iommu will not optimize to look
  736. for io virtual address below 32 bit forcing dual
  737. address cycle on pci bus for cards supporting greater
  738. than 32 bit addressing. The default is to look
  739. for translation below 32 bit and if not available
  740. then look in the higher range.
  741. strict [Default Off]
  742. With this option on every unmap_single operation will
  743. result in a hardware IOTLB flush operation as opposed
  744. to batching them for performance.
  745. io_delay= [X86-32,X86-64] I/O delay method
  746. 0x80
  747. Standard port 0x80 based delay
  748. 0xed
  749. Alternate port 0xed based delay (needed on some systems)
  750. udelay
  751. Simple two microseconds delay
  752. none
  753. No delay
  754. io7= [HW] IO7 for Marvel based alpha systems
  755. See comment before marvel_specify_io7 in
  756. arch/alpha/kernel/core_marvel.c.
  757. ip= [IP_PNP]
  758. See Documentation/filesystems/nfsroot.txt.
  759. ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
  760. See comment before ip2_setup() in
  761. drivers/char/ip2/ip2base.c.
  762. ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
  763. See header of drivers/scsi/ips.c.
  764. ports= [IP_VS_FTP] IPVS ftp helper module
  765. Default is 21.
  766. Up to 8 (IP_VS_APP_MAX_PORTS) ports
  767. may be specified.
  768. Format: <port>,<port>....
  769. irqfixup [HW]
  770. When an interrupt is not handled search all handlers
  771. for it. Intended to get systems with badly broken
  772. firmware running.
  773. irqpoll [HW]
  774. When an interrupt is not handled search all handlers
  775. for it. Also check all handlers each timer
  776. interrupt. Intended to get systems with badly broken
  777. firmware running.
  778. isapnp= [ISAPNP]
  779. Format: <RDP>,<reset>,<pci_scan>,<verbosity>
  780. isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
  781. Format:
  782. <cpu number>,...,<cpu number>
  783. or
  784. <cpu number>-<cpu number> (must be a positive range in ascending order)
  785. or a mixture
  786. <cpu number>,...,<cpu number>-<cpu number>
  787. This option can be used to specify one or more CPUs
  788. to isolate from the general SMP balancing and scheduling
  789. algorithms. The only way to move a process onto or off
  790. an "isolated" CPU is via the CPU affinity syscalls.
  791. <cpu number> begins at 0 and the maximum value is
  792. "number of CPUs in system - 1".
  793. This option is the preferred way to isolate CPUs. The
  794. alternative -- manually setting the CPU mask of all
  795. tasks in the system -- can cause problems and
  796. suboptimal load balancer performance.
  797. iucv= [HW,NET]
  798. js= [HW,JOY] Analog joystick
  799. See Documentation/input/joystick.txt.
  800. kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
  801. specifies the amount of memory usable by the kernel
  802. for non-movable allocations. The requested amount is
  803. spread evenly throughout all nodes in the system. The
  804. remaining memory in each node is used for Movable
  805. pages. In the event, a node is too small to have both
  806. kernelcore and Movable pages, kernelcore pages will
  807. take priority and other nodes will have a larger number
  808. of kernelcore pages. The Movable zone is used for the
  809. allocation of pages that may be reclaimed or moved
  810. by the page migration subsystem. This means that
  811. HugeTLB pages may not be allocated from this zone.
  812. Note that allocations like PTEs-from-HighMem still
  813. use the HighMem zone if it exists, and the Normal
  814. zone if it does not.
  815. movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
  816. is similar to kernelcore except it specifies the
  817. amount of memory used for migratable allocations.
  818. If both kernelcore and movablecore is specified,
  819. then kernelcore will be at *least* the specified
  820. value but may be more. If movablecore on its own
  821. is specified, the administrator must be careful
  822. that the amount of memory usable for all allocations
  823. is not too small.
  824. keepinitrd [HW,ARM]
  825. kstack=N [X86-32,X86-64] Print N words from the kernel stack
  826. in oops dumps.
  827. kgdboc= [HW] kgdb over consoles.
  828. Requires a tty driver that supports console polling.
  829. (only serial suported for now)
  830. Format: <serial_device>[,baud]
  831. kmac= [MIPS] korina ethernet MAC address.
  832. Configure the RouterBoard 532 series on-chip
  833. Ethernet adapter MAC address.
  834. l2cr= [PPC]
  835. l3cr= [PPC]
  836. lapic [X86-32,APIC] Enable the local APIC even if BIOS
  837. disabled it.
  838. lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
  839. C2 power state.
  840. libata.dma= [LIBATA] DMA control
  841. libata.dma=0 Disable all PATA and SATA DMA
  842. libata.dma=1 PATA and SATA Disk DMA only
  843. libata.dma=2 ATAPI (CDROM) DMA only
  844. libata.dma=4 Compact Flash DMA only
  845. Combinations also work, so libata.dma=3 enables DMA
  846. for disks and CDROMs, but not CFs.
  847. libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
  848. when set.
  849. Format: <int>
  850. libata.force= [LIBATA] Force configurations. The format is comma
  851. separated list of "[ID:]VAL" where ID is
  852. PORT[:DEVICE]. PORT and DEVICE are decimal numbers
  853. matching port, link or device. Basically, it matches
  854. the ATA ID string printed on console by libata. If
  855. the whole ID part is omitted, the last PORT and DEVICE
  856. values are used. If ID hasn't been specified yet, the
  857. configuration applies to all ports, links and devices.
  858. If only DEVICE is omitted, the parameter applies to
  859. the port and all links and devices behind it. DEVICE
  860. number of 0 either selects the first device or the
  861. first fan-out link behind PMP device. It does not
  862. select the host link. DEVICE number of 15 selects the
  863. host link and device attached to it.
  864. The VAL specifies the configuration to force. As long
  865. as there's no ambiguity shortcut notation is allowed.
  866. For example, both 1.5 and 1.5G would work for 1.5Gbps.
  867. The following configurations can be forced.
  868. * Cable type: 40c, 80c, short40c, unk, ign or sata.
  869. Any ID with matching PORT is used.
  870. * SATA link speed limit: 1.5Gbps or 3.0Gbps.
  871. * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
  872. udma[/][16,25,33,44,66,100,133] notation is also
  873. allowed.
  874. * [no]ncq: Turn on or off NCQ.
  875. * nohrst, nosrst, norst: suppress hard, soft
  876. and both resets.
  877. If there are multiple matching configurations changing
  878. the same attribute, the last one is used.
  879. load_ramdisk= [RAM] List of ramdisks to load from floppy
  880. See Documentation/ramdisk.txt.
  881. lockd.nlm_grace_period=P [NFS] Assign grace period.
  882. Format: <integer>
  883. lockd.nlm_tcpport=N [NFS] Assign TCP port.
  884. Format: <integer>
  885. lockd.nlm_timeout=T [NFS] Assign timeout value.
  886. Format: <integer>
  887. lockd.nlm_udpport=M [NFS] Assign UDP port.
  888. Format: <integer>
  889. logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
  890. Format: <irq>
  891. loglevel= All Kernel Messages with a loglevel smaller than the
  892. console loglevel will be printed to the console. It can
  893. also be changed with klogd or other programs. The
  894. loglevels are defined as follows:
  895. 0 (KERN_EMERG) system is unusable
  896. 1 (KERN_ALERT) action must be taken immediately
  897. 2 (KERN_CRIT) critical conditions
  898. 3 (KERN_ERR) error conditions
  899. 4 (KERN_WARNING) warning conditions
  900. 5 (KERN_NOTICE) normal but significant condition
  901. 6 (KERN_INFO) informational
  902. 7 (KERN_DEBUG) debug-level messages
  903. log_buf_len=n Sets the size of the printk ring buffer, in bytes.
  904. Format: { n | nk | nM }
  905. n must be a power of two. The default size
  906. is set in the kernel config file.
  907. logo.nologo [FB] Disables display of the built-in Linux logo.
  908. This may be used to provide more screen space for
  909. kernel log messages and is useful when debugging
  910. kernel boot problems.
  911. lp=0 [LP] Specify parallel ports to use, e.g,
  912. lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
  913. lp=reset first parallel port). 'lp=0' disables the
  914. lp=auto printer driver. 'lp=reset' (which can be
  915. specified in addition to the ports) causes
  916. attached printers to be reset. Using
  917. lp=port1,port2,... specifies the parallel ports
  918. to associate lp devices with, starting with
  919. lp0. A port specification may be 'none' to skip
  920. that lp device, or a parport name such as
  921. 'parport0'. Specifying 'lp=auto' instead of a
  922. port specification list means that device IDs
  923. from each port should be examined, to see if
  924. an IEEE 1284-compliant printer is attached; if
  925. so, the driver will manage that printer.
  926. See also header of drivers/char/lp.c.
  927. lpj=n [KNL]
  928. Sets loops_per_jiffy to given constant, thus avoiding
  929. time-consuming boot-time autodetection (up to 250 ms per
  930. CPU). 0 enables autodetection (default). To determine
  931. the correct value for your kernel, boot with normal
  932. autodetection and see what value is printed. Note that
  933. on SMP systems the preset will be applied to all CPUs,
  934. which is likely to cause problems if your CPUs need
  935. significantly divergent settings. An incorrect value
  936. will cause delays in the kernel to be wrong, leading to
  937. unpredictable I/O errors and other breakage. Although
  938. unlikely, in the extreme case this might damage your
  939. hardware.
  940. ltpc= [NET]
  941. Format: <io>,<irq>,<dma>
  942. mac5380= [HW,SCSI] Format:
  943. <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
  944. machvec= [IA64] Force the use of a particular machine-vector
  945. (machvec) in a generic kernel.
  946. Example: machvec=hpzx1_swiotlb
  947. max_loop= [LOOP] Maximum number of loopback devices that can
  948. be mounted
  949. Format: <1-256>
  950. maxcpus= [SMP] Maximum number of processors that an SMP kernel
  951. should make use of. maxcpus=n : n >= 0 limits the
  952. kernel to using 'n' processors. n=0 is a special case,
  953. it is equivalent to "nosmp", which also disables
  954. the IO APIC.
  955. max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
  956. equal to this physical address is ignored.
  957. max_luns= [SCSI] Maximum number of LUNs to probe.
  958. Should be between 1 and 2^32-1.
  959. max_report_luns=
  960. [SCSI] Maximum number of LUNs received.
  961. Should be between 1 and 16384.
  962. mcatest= [IA-64]
  963. mce [X86-32] Machine Check Exception
  964. mce=option [X86-64] See Documentation/x86_64/boot-options.txt
  965. md= [HW] RAID subsystems devices and level
  966. See Documentation/md.txt.
  967. mdacon= [MDA]
  968. Format: <first>,<last>
  969. Specifies range of consoles to be captured by the MDA.
  970. mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
  971. Amount of memory to be used when the kernel is not able
  972. to see the whole system memory or for test.
  973. [X86-32] Use together with memmap= to avoid physical
  974. address space collisions. Without memmap= PCI devices
  975. could be placed at addresses belonging to unused RAM.
  976. mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
  977. memory.
  978. memchunk=nn[KMG]
  979. [KNL,SH] Allow user to override the default size for
  980. per-device physically contiguous DMA buffers.
  981. memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
  982. E820 memory map, as specified by the user.
  983. Such memmap=exactmap lines can be constructed based on
  984. BIOS output or other requirements. See the memmap=nn@ss
  985. option description.
  986. memmap=nn[KMG]@ss[KMG]
  987. [KNL] Force usage of a specific region of memory
  988. Region of memory to be used, from ss to ss+nn.
  989. memmap=nn[KMG]#ss[KMG]
  990. [KNL,ACPI] Mark specific memory as ACPI data.
  991. Region of memory to be used, from ss to ss+nn.
  992. memmap=nn[KMG]$ss[KMG]
  993. [KNL,ACPI] Mark specific memory as reserved.
  994. Region of memory to be used, from ss to ss+nn.
  995. Example: Exclude memory from 0x18690000-0x1869ffff
  996. memmap=64K$0x18690000
  997. or
  998. memmap=0x10000$0x18690000
  999. memory_corruption_check=0/1 [X86]
  1000. Some BIOSes seem to corrupt the first 64k of
  1001. memory when doing things like suspend/resume.
  1002. Setting this option will scan the memory
  1003. looking for corruption. Enabling this will
  1004. both detect corruption and prevent the kernel
  1005. from using the memory being corrupted.
  1006. However, its intended as a diagnostic tool; if
  1007. repeatable BIOS-originated corruption always
  1008. affects the same memory, you can use memmap=
  1009. to prevent the kernel from using that memory.
  1010. memory_corruption_check_size=size [X86]
  1011. By default it checks for corruption in the low
  1012. 64k, making this memory unavailable for normal
  1013. use. Use this parameter to scan for
  1014. corruption in more or less memory.
  1015. memory_corruption_check_period=seconds [X86]
  1016. By default it checks for corruption every 60
  1017. seconds. Use this parameter to check at some
  1018. other rate. 0 disables periodic checking.
  1019. memtest= [KNL,X86] Enable memtest
  1020. Format: <integer>
  1021. range: 0,4 : pattern number
  1022. default : 0 <disable>
  1023. meye.*= [HW] Set MotionEye Camera parameters
  1024. See Documentation/video4linux/meye.txt.
  1025. mfgpt_irq= [IA-32] Specify the IRQ to use for the
  1026. Multi-Function General Purpose Timers on AMD Geode
  1027. platforms.
  1028. mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
  1029. the BIOS has incorrectly applied a workaround. TinyBIOS
  1030. version 0.98 is known to be affected, 0.99 fixes the
  1031. problem by letting the user disable the workaround.
  1032. mga= [HW,DRM]
  1033. mminit_loglevel=
  1034. [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
  1035. parameter allows control of the logging verbosity for
  1036. the additional memory initialisation checks. A value
  1037. of 0 disables mminit logging and a level of 4 will
  1038. log everything. Information is printed at KERN_DEBUG
  1039. so loglevel=8 may also need to be specified.
  1040. mousedev.tap_time=
  1041. [MOUSE] Maximum time between finger touching and
  1042. leaving touchpad surface for touch to be considered
  1043. a tap and be reported as a left button click (for
  1044. touchpads working in absolute mode only).
  1045. Format: <msecs>
  1046. mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
  1047. reporting absolute coordinates, such as tablets
  1048. mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
  1049. reporting absolute coordinates, such as tablets
  1050. mpu401= [HW,OSS]
  1051. Format: <io>,<irq>
  1052. MTD_Partition= [MTD]
  1053. Format: <name>,<region-number>,<size>,<offset>
  1054. MTD_Region= [MTD] Format:
  1055. <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
  1056. mtdparts= [MTD]
  1057. See drivers/mtd/cmdlinepart.c.
  1058. mtdset= [ARM]
  1059. ARM/S3C2412 JIVE boot control
  1060. See arch/arm/mach-s3c2412/mach-jive.c
  1061. mtouchusb.raw_coordinates=
  1062. [HW] Make the MicroTouch USB driver use raw coordinates
  1063. ('y', default) or cooked coordinates ('n')
  1064. n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
  1065. NCR_D700= [HW,SCSI]
  1066. See header of drivers/scsi/NCR_D700.c.
  1067. ncr5380= [HW,SCSI]
  1068. ncr53c400= [HW,SCSI]
  1069. ncr53c400a= [HW,SCSI]
  1070. ncr53c406a= [HW,SCSI]
  1071. ncr53c8xx= [HW,SCSI]
  1072. netdev= [NET] Network devices parameters
  1073. Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
  1074. Note that mem_start is often overloaded to mean
  1075. something different and driver-specific.
  1076. This usage is only documented in each driver source
  1077. file if at all.
  1078. nf_conntrack.acct=
  1079. [NETFILTER] Enable connection tracking flow accounting
  1080. 0 to disable accounting
  1081. 1 to enable accounting
  1082. Default value depends on CONFIG_NF_CT_ACCT that is
  1083. going to be removed in 2.6.29.
  1084. nfsaddrs= [NFS]
  1085. See Documentation/filesystems/nfsroot.txt.
  1086. nfsroot= [NFS] nfs root filesystem for disk-less boxes.
  1087. See Documentation/filesystems/nfsroot.txt.
  1088. nfs.callback_tcpport=
  1089. [NFS] set the TCP port on which the NFSv4 callback
  1090. channel should listen.
  1091. nfs.idmap_cache_timeout=
  1092. [NFS] set the maximum lifetime for idmapper cache
  1093. entries.
  1094. nfs.enable_ino64=
  1095. [NFS] enable 64-bit inode numbers.
  1096. If zero, the NFS client will fake up a 32-bit inode
  1097. number for the readdir() and stat() syscalls instead
  1098. of returning the full 64-bit number.
  1099. The default is to return 64-bit inode numbers.
  1100. nmi_debug= [KNL,AVR32] Specify one or more actions to take
  1101. when a NMI is triggered.
  1102. Format: [state][,regs][,debounce][,die]
  1103. nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
  1104. no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
  1105. emulation library even if a 387 maths coprocessor
  1106. is present.
  1107. noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
  1108. caches in the slab allocator. Saves per-node memory,
  1109. but will impact performance.
  1110. noalign [KNL,ARM]
  1111. noapic [SMP,APIC] Tells the kernel to not make use of any
  1112. IOAPICs that may be present in the system.
  1113. nobats [PPC] Do not use BATs for mapping kernel lowmem
  1114. on "Classic" PPC cores.
  1115. nocache [ARM]
  1116. nodelayacct [KNL] Disable per-task delay accounting
  1117. nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
  1118. nodsp [SH] Disable hardware DSP at boot time.
  1119. noefi [X86-32,X86-64] Disable EFI runtime services support.
  1120. noexec [IA-64]
  1121. noexec [X86-32,X86-64]
  1122. On X86-32 available only on PAE configured kernels.
  1123. noexec=on: enable non-executable mappings (default)
  1124. noexec=off: disable non-executable mappings
  1125. noexec32 [X86-64]
  1126. This affects only 32-bit executables.
  1127. noexec32=on: enable non-executable mappings (default)
  1128. read doesn't imply executable mappings
  1129. noexec32=off: disable non-executable mappings
  1130. read implies executable mappings
  1131. nofpu [SH] Disable hardware FPU at boot time.
  1132. nofxsr [BUGS=X86-32] Disables x86 floating point extended
  1133. register save and restore. The kernel will only save
  1134. legacy floating-point registers on task switch.
  1135. noclflush [BUGS=X86] Don't use the CLFLUSH instruction
  1136. nohlt [BUGS=ARM,SH]
  1137. no-hlt [BUGS=X86-32] Tells the kernel that the hlt
  1138. instruction doesn't work correctly and not to
  1139. use it.
  1140. nohalt [IA-64] Tells the kernel not to use the power saving
  1141. function PAL_HALT_LIGHT when idle. This increases
  1142. power-consumption. On the positive side, it reduces
  1143. interrupt wake-up latency, which may improve performance
  1144. in certain environments such as networked servers or
  1145. real-time systems.
  1146. nohz= [KNL] Boottime enable/disable dynamic ticks
  1147. Valid arguments: on, off
  1148. Default: on
  1149. noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
  1150. noirqdebug [X86-32] Disables the code which attempts to detect and
  1151. disable unhandled interrupt sources.
  1152. no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
  1153. broken timer IRQ sources.
  1154. noisapnp [ISAPNP] Disables ISA PnP code.
  1155. noinitrd [RAM] Tells the kernel not to load any configured
  1156. initial RAM disk.
  1157. nointroute [IA-64]
  1158. nojitter [IA64] Disables jitter checking for ITC timers.
  1159. nolapic [X86-32,APIC] Do not enable or use the local APIC.
  1160. nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
  1161. nox2apic [X86-64,APIC] Do not enable x2APIC mode.
  1162. x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
  1163. default x2apic cluster mode on platforms
  1164. supporting x2apic.
  1165. noltlbs [PPC] Do not use large page/tlb entries for kernel
  1166. lowmem mapping on PPC40x.
  1167. nomca [IA-64] Disable machine check abort handling
  1168. nomce [X86-32] Machine Check Exception
  1169. nomfgpt [X86-32] Disable Multi-Function General Purpose
  1170. Timer usage (for AMD Geode machines).
  1171. noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
  1172. noreplace-smp [X86-32,SMP] Don't replace SMP instructions
  1173. with UP alternatives
  1174. noresidual [PPC] Don't use residual data on PReP machines.
  1175. noresume [SWSUSP] Disables resume and restores original swap
  1176. space.
  1177. no-scroll [VGA] Disables scrollback.
  1178. This is required for the Braillex ib80-piezo Braille
  1179. reader made by F.H. Papenmeier (Germany).
  1180. nosbagart [IA-64]
  1181. nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
  1182. nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
  1183. and disable the IO APIC. legacy for "maxcpus=0".
  1184. nosoftlockup [KNL] Disable the soft-lockup detector.
  1185. nosync [HW,M68K] Disables sync negotiation for all devices.
  1186. notsc [BUGS=X86-32] Disable Time Stamp Counter
  1187. nousb [USB] Disable the USB subsystem
  1188. nowb [ARM]
  1189. nptcg= [IA64] Override max number of concurrent global TLB
  1190. purges which is reported from either PAL_VM_SUMMARY or
  1191. SAL PALO.
  1192. numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
  1193. one of ['zone', 'node', 'default'] can be specified
  1194. This can be set from sysctl after boot.
  1195. See Documentation/sysctl/vm.txt for details.
  1196. nr_uarts= [SERIAL] maximum number of UARTs to be registered.
  1197. olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
  1198. Rather than timing out after 20 ms if an EC
  1199. command is not properly ACKed, override the length
  1200. of the timeout. We have interrupts disabled while
  1201. waiting for the ACK, so if this is set too high
  1202. interrupts *may* be lost!
  1203. opl3= [HW,OSS]
  1204. Format: <io>
  1205. oprofile.timer= [HW]
  1206. Use timer interrupt instead of performance counters
  1207. osst= [HW,SCSI] SCSI Tape Driver
  1208. Format: <buffer_size>,<write_threshold>
  1209. See also Documentation/scsi/st.txt.
  1210. panic= [KNL] Kernel behaviour on panic
  1211. Format: <timeout>
  1212. parkbd.port= [HW] Parallel port number the keyboard adapter is
  1213. connected to, default is 0.
  1214. Format: <parport#>
  1215. parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
  1216. 0 for XT, 1 for AT (default is AT).
  1217. Format: <mode>
  1218. parport= [HW,PPT] Specify parallel ports. 0 disables.
  1219. Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
  1220. Use 'auto' to force the driver to use any
  1221. IRQ/DMA settings detected (the default is to
  1222. ignore detected IRQ/DMA settings because of
  1223. possible conflicts). You can specify the base
  1224. address, IRQ, and DMA settings; IRQ and DMA
  1225. should be numbers, or 'auto' (for using detected
  1226. settings on that particular port), or 'nofifo'
  1227. (to avoid using a FIFO even if it is detected).
  1228. Parallel ports are assigned in the order they
  1229. are specified on the command line, starting
  1230. with parport0.
  1231. parport_init_mode= [HW,PPT]
  1232. Configure VIA parallel port to operate in
  1233. a specific mode. This is necessary on Pegasos
  1234. computer where firmware has no options for setting
  1235. up parallel port mode and sets it to spp.
  1236. Currently this function knows 686a and 8231 chips.
  1237. Format: [spp|ps2|epp|ecp|ecpepp]
  1238. pas2= [HW,OSS] Format:
  1239. <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
  1240. pas16= [HW,SCSI]
  1241. See header of drivers/scsi/pas16.c.
  1242. pause_on_oops=
  1243. Halt all CPUs after the first oops has been printed for
  1244. the specified number of seconds. This is to be used if
  1245. your oopses keep scrolling off the screen.
  1246. pcbit= [HW,ISDN]
  1247. pcd. [PARIDE]
  1248. See header of drivers/block/paride/pcd.c.
  1249. See also Documentation/paride.txt.
  1250. pci=option[,option...] [PCI] various PCI subsystem options:
  1251. off [X86] don't probe for the PCI bus
  1252. bios [X86-32] force use of PCI BIOS, don't access
  1253. the hardware directly. Use this if your machine
  1254. has a non-standard PCI host bridge.
  1255. nobios [X86-32] disallow use of PCI BIOS, only direct
  1256. hardware access methods are allowed. Use this
  1257. if you experience crashes upon bootup and you
  1258. suspect they are caused by the BIOS.
  1259. conf1 [X86] Force use of PCI Configuration
  1260. Mechanism 1.
  1261. conf2 [X86] Force use of PCI Configuration
  1262. Mechanism 2.
  1263. noaer [PCIE] If the PCIEAER kernel config parameter is
  1264. enabled, this kernel boot option can be used to
  1265. disable the use of PCIE advanced error reporting.
  1266. nodomains [PCI] Disable support for multiple PCI
  1267. root domains (aka PCI segments, in ACPI-speak).
  1268. nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
  1269. Configuration
  1270. nomsi [MSI] If the PCI_MSI kernel config parameter is
  1271. enabled, this kernel boot option can be used to
  1272. disable the use of MSI interrupts system-wide.
  1273. biosirq [X86-32] Use PCI BIOS calls to get the interrupt
  1274. routing table. These calls are known to be buggy
  1275. on several machines and they hang the machine
  1276. when used, but on other computers it's the only
  1277. way to get the interrupt routing table. Try
  1278. this option if the kernel is unable to allocate
  1279. IRQs or discover secondary PCI buses on your
  1280. motherboard.
  1281. rom [X86] Assign address space to expansion ROMs.
  1282. Use with caution as certain devices share
  1283. address decoders between ROMs and other
  1284. resources.
  1285. norom [X86] Do not assign address space to
  1286. expansion ROMs that do not already have
  1287. BIOS assigned address ranges.
  1288. irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
  1289. assigned automatically to PCI devices. You can
  1290. make the kernel exclude IRQs of your ISA cards
  1291. this way.
  1292. pirqaddr=0xAAAAA [X86] Specify the physical address
  1293. of the PIRQ table (normally generated
  1294. by the BIOS) if it is outside the
  1295. F0000h-100000h range.
  1296. lastbus=N [X86] Scan all buses thru bus #N. Can be
  1297. useful if the kernel is unable to find your
  1298. secondary buses and you want to tell it
  1299. explicitly which ones they are.
  1300. assign-busses [X86] Always assign all PCI bus
  1301. numbers ourselves, overriding
  1302. whatever the firmware may have done.
  1303. usepirqmask [X86] Honor the possible IRQ mask stored
  1304. in the BIOS $PIR table. This is needed on
  1305. some systems with broken BIOSes, notably
  1306. some HP Pavilion N5400 and Omnibook XE3
  1307. notebooks. This will have no effect if ACPI
  1308. IRQ routing is enabled.
  1309. noacpi [X86] Do not use ACPI for IRQ routing
  1310. or for PCI scanning.
  1311. use_crs [X86] Use _CRS for PCI resource
  1312. allocation.
  1313. routeirq Do IRQ routing for all PCI devices.
  1314. This is normally done in pci_enable_device(),
  1315. so this option is a temporary workaround
  1316. for broken drivers that don't call it.
  1317. skip_isa_align [X86] do not align io start addr, so can
  1318. handle more pci cards
  1319. firmware [ARM] Do not re-enumerate the bus but instead
  1320. just use the configuration from the
  1321. bootloader. This is currently used on
  1322. IXP2000 systems where the bus has to be
  1323. configured a certain way for adjunct CPUs.
  1324. noearly [X86] Don't do any early type 1 scanning.
  1325. This might help on some broken boards which
  1326. machine check when some devices' config space
  1327. is read. But various workarounds are disabled
  1328. and some IOMMU drivers will not work.
  1329. bfsort Sort PCI devices into breadth-first order.
  1330. This sorting is done to get a device
  1331. order compatible with older (<= 2.4) kernels.
  1332. nobfsort Don't sort PCI devices into breadth-first order.
  1333. cbiosize=nn[KMG] The fixed amount of bus space which is
  1334. reserved for the CardBus bridge's IO window.
  1335. The default value is 256 bytes.
  1336. cbmemsize=nn[KMG] The fixed amount of bus space which is
  1337. reserved for the CardBus bridge's memory
  1338. window. The default value is 64 megabytes.
  1339. pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
  1340. Management.
  1341. off Disable ASPM.
  1342. force Enable ASPM even on devices that claim not to support it.
  1343. WARNING: Forcing ASPM on may cause system lockups.
  1344. pcmv= [HW,PCMCIA] BadgePAD 4
  1345. pd. [PARIDE]
  1346. See Documentation/paride.txt.
  1347. pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
  1348. boot time.
  1349. Format: { 0 | 1 }
  1350. See arch/parisc/kernel/pdc_chassis.c
  1351. pf. [PARIDE]
  1352. See Documentation/paride.txt.
  1353. pg. [PARIDE]
  1354. See Documentation/paride.txt.
  1355. pirq= [SMP,APIC] Manual mp-table setup
  1356. See Documentation/i386/IO-APIC.txt.
  1357. plip= [PPT,NET] Parallel port network link
  1358. Format: { parport<nr> | timid | 0 }
  1359. See also Documentation/parport.txt.
  1360. pmtmr= [X86] Manual setup of pmtmr I/O Port.
  1361. Override pmtimer IOPort with a hex value.
  1362. e.g. pmtmr=0x508
  1363. pnpacpi= [ACPI]
  1364. { off }
  1365. pnpbios= [ISAPNP]
  1366. { on | off | curr | res | no-curr | no-res }
  1367. pnp_reserve_irq=
  1368. [ISAPNP] Exclude IRQs for the autoconfiguration
  1369. pnp_reserve_dma=
  1370. [ISAPNP] Exclude DMAs for the autoconfiguration
  1371. pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
  1372. Ranges are in pairs (I/O port base and size).
  1373. pnp_reserve_mem=
  1374. [ISAPNP] Exclude memory regions for the
  1375. autoconfiguration.
  1376. Ranges are in pairs (memory base and size).
  1377. dynamic_printk
  1378. Enables pr_debug()/dev_dbg() calls if
  1379. CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. These can also
  1380. be switched on/off via <debugfs>/dynamic_printk/modules
  1381. print-fatal-signals=
  1382. [KNL] debug: print fatal signals
  1383. print-fatal-signals=1: print segfault info to
  1384. the kernel console.
  1385. default: off.
  1386. printk.time= Show timing data prefixed to each printk message line
  1387. Format: <bool> (1/Y/y=enable, 0/N/n=disable)
  1388. profile= [KNL] Enable kernel profiling via /proc/profile
  1389. Format: [schedule,]<number>
  1390. Param: "schedule" - profile schedule points.
  1391. Param: <number> - step/bucket size as a power of 2 for
  1392. statistical time based profiling.
  1393. Param: "sleep" - profile D-state sleeping (millisecs).
  1394. Requires CONFIG_SCHEDSTATS
  1395. Param: "kvm" - profile VM exits.
  1396. processor.max_cstate= [HW,ACPI]
  1397. Limit processor to maximum C-state
  1398. max_cstate=9 overrides any DMI blacklist limit.
  1399. processor.nocst [HW,ACPI]
  1400. Ignore the _CST method to determine C-states,
  1401. instead using the legacy FADT method
  1402. prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
  1403. before loading.
  1404. See Documentation/ramdisk.txt.
  1405. psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
  1406. probe for; one of (bare|imps|exps|lifebook|any).
  1407. psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
  1408. per second.
  1409. psmouse.resetafter= [HW,MOUSE]
  1410. Try to reset the device after so many bad packets
  1411. (0 = never).
  1412. psmouse.resolution=
  1413. [HW,MOUSE] Set desired mouse resolution, in dpi.
  1414. psmouse.smartscroll=
  1415. [HW,MOUSE] Controls Logitech smartscroll autorepeat.
  1416. 0 = disabled, 1 = enabled (default).
  1417. pss= [HW,OSS] Personal Sound System (ECHO ESC614)
  1418. Format:
  1419. <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
  1420. pt. [PARIDE]
  1421. See Documentation/paride.txt.
  1422. pty.legacy_count=
  1423. [KNL] Number of legacy pty's. Overwrites compiled-in
  1424. default number.
  1425. quiet [KNL] Disable most log messages
  1426. r128= [HW,DRM]
  1427. raid= [HW,RAID]
  1428. See Documentation/md.txt.
  1429. ramdisk_blocksize= [RAM]
  1430. See Documentation/ramdisk.txt.
  1431. ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
  1432. See Documentation/ramdisk.txt.
  1433. rcupdate.blimit= [KNL,BOOT]
  1434. Set maximum number of finished RCU callbacks to process
  1435. in one batch.
  1436. rcupdate.qhimark= [KNL,BOOT]
  1437. Set threshold of queued
  1438. RCU callbacks over which batch limiting is disabled.
  1439. rcupdate.qlowmark= [KNL,BOOT]
  1440. Set threshold of queued RCU callbacks below which
  1441. batch limiting is re-enabled.
  1442. rdinit= [KNL]
  1443. Format: <full_path>
  1444. Run specified binary instead of /init from the ramdisk,
  1445. used for early userspace startup. See initrd.
  1446. reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
  1447. Format: <reboot_mode>[,<reboot_mode2>[,...]]
  1448. See arch/*/kernel/reboot.c or arch/*/kernel/process.c
  1449. relax_domain_level=
  1450. [KNL, SMP] Set scheduler's default relax_domain_level.
  1451. See Documentation/cpusets.txt.
  1452. reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
  1453. reservetop= [X86-32]
  1454. Format: nn[KMG]
  1455. Reserves a hole at the top of the kernel virtual
  1456. address space.
  1457. reset_devices [KNL] Force drivers to reset the underlying device
  1458. during initialization.
  1459. resume= [SWSUSP]
  1460. Specify the partition device for software suspend
  1461. resume_offset= [SWSUSP]
  1462. Specify the offset from the beginning of the partition
  1463. given by "resume=" at which the swap header is located,
  1464. in <PAGE_SIZE> units (needed only for swap files).
  1465. See Documentation/power/swsusp-and-swap-files.txt
  1466. retain_initrd [RAM] Keep initrd memory after extraction
  1467. rhash_entries= [KNL,NET]
  1468. Set number of hash buckets for route cache
  1469. riscom8= [HW,SERIAL]
  1470. Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
  1471. ro [KNL] Mount root device read-only on boot
  1472. root= [KNL] Root filesystem
  1473. rootdelay= [KNL] Delay (in seconds) to pause before attempting to
  1474. mount the root filesystem
  1475. rootflags= [KNL] Set root filesystem mount option string
  1476. rootfstype= [KNL] Set root filesystem type
  1477. rootwait [KNL] Wait (indefinitely) for root device to show up.
  1478. Useful for devices that are detected asynchronously
  1479. (e.g. USB and MMC devices).
  1480. root_plug.vendor_id=
  1481. [ROOTPLUG] Override the default vendor ID
  1482. root_plug.product_id=
  1483. [ROOTPLUG] Override the default product ID
  1484. root_plug.debug=
  1485. [ROOTPLUG] Enable debugging output
  1486. rw [KNL] Mount root device read-write on boot
  1487. S [KNL] Run init in single mode
  1488. sa1100ir [NET]
  1489. See drivers/net/irda/sa1100_ir.c.
  1490. sbni= [NET] Granch SBNI12 leased line adapter
  1491. sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
  1492. Format: <io>[,<timeout>[,<isapnp>]]
  1493. scsi_debug_*= [SCSI]
  1494. See drivers/scsi/scsi_debug.c.
  1495. scsi_default_dev_flags=
  1496. [SCSI] SCSI default device flags
  1497. Format: <integer>
  1498. scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
  1499. Format: <vendor>:<model>:<flags>
  1500. (flags are integer value)
  1501. scsi_logging_level= [SCSI] a bit mask of logging levels
  1502. See drivers/scsi/scsi_logging.h for bits. Also
  1503. settable via sysctl at dev.scsi.logging_level
  1504. (/proc/sys/dev/scsi/logging_level).
  1505. There is also a nice 'scsi_logging_level' script in the
  1506. S390-tools package, available for download at
  1507. http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
  1508. scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
  1509. discovered. async scans them in kernel threads,
  1510. allowing boot to proceed. none ignores them, expecting
  1511. user space to do the scan.
  1512. selinux [SELINUX] Disable or enable SELinux at boot time.
  1513. Format: { "0" | "1" }
  1514. See security/selinux/Kconfig help text.
  1515. 0 -- disable.
  1516. 1 -- enable.
  1517. Default value is set via kernel config option.
  1518. If enabled at boot time, /selinux/disable can be used
  1519. later to disable prior to initial policy load.
  1520. selinux_compat_net =
  1521. [SELINUX] Set initial selinux_compat_net flag value.
  1522. Format: { "0" | "1" }
  1523. 0 -- use new secmark-based packet controls
  1524. 1 -- use legacy packet controls
  1525. Default value is 0 (preferred).
  1526. Value can be changed at runtime via
  1527. /selinux/compat_net.
  1528. serialnumber [BUGS=X86-32]
  1529. shapers= [NET]
  1530. Maximal number of shapers.
  1531. show_msr= [x86] show boot-time MSR settings
  1532. Format: { <integer> }
  1533. Show boot-time (BIOS-initialized) MSR settings.
  1534. The parameter means the number of CPUs to show,
  1535. for example 1 means boot CPU only.
  1536. sim710= [SCSI,HW]
  1537. See header of drivers/scsi/sim710.c.
  1538. simeth= [IA-64]
  1539. simscsi=
  1540. slram= [HW,MTD]
  1541. slub_debug[=options[,slabs]] [MM, SLUB]
  1542. Enabling slub_debug allows one to determine the
  1543. culprit if slab objects become corrupted. Enabling
  1544. slub_debug can create guard zones around objects and
  1545. may poison objects when not in use. Also tracks the
  1546. last alloc / free. For more information see
  1547. Documentation/vm/slub.txt.
  1548. slub_max_order= [MM, SLUB]
  1549. Determines the maximum allowed order for slabs.
  1550. A high setting may cause OOMs due to memory
  1551. fragmentation. For more information see
  1552. Documentation/vm/slub.txt.
  1553. slub_min_objects= [MM, SLUB]
  1554. The minimum number of objects per slab. SLUB will
  1555. increase the slab order up to slub_max_order to
  1556. generate a sufficiently large slab able to contain
  1557. the number of objects indicated. The higher the number
  1558. of objects the smaller the overhead of tracking slabs
  1559. and the less frequently locks need to be acquired.
  1560. For more information see Documentation/vm/slub.txt.
  1561. slub_min_order= [MM, SLUB]
  1562. Determines the mininum page order for slabs. Must be
  1563. lower than slub_max_order.
  1564. For more information see Documentation/vm/slub.txt.
  1565. slub_nomerge [MM, SLUB]
  1566. Disable merging of slabs with similar size. May be
  1567. necessary if there is some reason to distinguish
  1568. allocs to different slabs. Debug options disable
  1569. merging on their own.
  1570. For more information see Documentation/vm/slub.txt.
  1571. smart2= [HW]
  1572. Format: <io1>[,<io2>[,...,<io8>]]
  1573. smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
  1574. attempt to substitute SMP alternatives once at boot.
  1575. smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
  1576. smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
  1577. smsc-ircc2.ircc_sir= [HW] SIR base I/O port
  1578. smsc-ircc2.ircc_fir= [HW] FIR base I/O port
  1579. smsc-ircc2.ircc_irq= [HW] IRQ line
  1580. smsc-ircc2.ircc_dma= [HW] DMA channel
  1581. smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
  1582. 0: Toshiba Satellite 1800 (GP data pin select)
  1583. 1: Fast pin select (default)
  1584. 2: ATC IRMode
  1585. snd-ad1816a= [HW,ALSA]
  1586. snd-ad1848= [HW,ALSA]
  1587. snd-ali5451= [HW,ALSA]
  1588. snd-als100= [HW,ALSA]
  1589. snd-als4000= [HW,ALSA]
  1590. snd-azt2320= [HW,ALSA]
  1591. snd-cmi8330= [HW,ALSA]
  1592. snd-cmipci= [HW,ALSA]
  1593. snd-cs4231= [HW,ALSA]
  1594. snd-cs4232= [HW,ALSA]
  1595. snd-cs4236= [HW,ALSA]
  1596. snd-cs4281= [HW,ALSA]
  1597. snd-cs46xx= [HW,ALSA]
  1598. snd-dt019x= [HW,ALSA]
  1599. snd-dummy= [HW,ALSA]
  1600. snd-emu10k1= [HW,ALSA]
  1601. snd-ens1370= [HW,ALSA]
  1602. snd-ens1371= [HW,ALSA]
  1603. snd-es968= [HW,ALSA]
  1604. snd-es1688= [HW,ALSA]
  1605. snd-es18xx= [HW,ALSA]
  1606. snd-es1938= [HW,ALSA]
  1607. snd-es1968= [HW,ALSA]
  1608. snd-fm801= [HW,ALSA]
  1609. snd-gusclassic= [HW,ALSA]
  1610. snd-gusextreme= [HW,ALSA]
  1611. snd-gusmax= [HW,ALSA]
  1612. snd-hdsp= [HW,ALSA]
  1613. snd-ice1712= [HW,ALSA]
  1614. snd-intel8x0= [HW,ALSA]
  1615. snd-interwave= [HW,ALSA]
  1616. snd-interwave-stb=
  1617. [HW,ALSA]
  1618. snd-korg1212= [HW,ALSA]
  1619. snd-maestro3= [HW,ALSA]
  1620. snd-mpu401= [HW,ALSA]
  1621. snd-mtpav= [HW,ALSA]
  1622. snd-nm256= [HW,ALSA]
  1623. snd-opl3sa2= [HW,ALSA]
  1624. snd-opti92x-ad1848=
  1625. [HW,ALSA]
  1626. snd-opti92x-cs4231=
  1627. [HW,ALSA]
  1628. snd-opti93x= [HW,ALSA]
  1629. snd-pmac= [HW,ALSA]
  1630. snd-rme32= [HW,ALSA]
  1631. snd-rme96= [HW,ALSA]
  1632. snd-rme9652= [HW,ALSA]
  1633. snd-sb8= [HW,ALSA]
  1634. snd-sb16= [HW,ALSA]
  1635. snd-sbawe= [HW,ALSA]
  1636. snd-serial= [HW,ALSA]
  1637. snd-sgalaxy= [HW,ALSA]
  1638. snd-sonicvibes= [HW,ALSA]
  1639. snd-sun-amd7930=
  1640. [HW,ALSA]
  1641. snd-sun-cs4231= [HW,ALSA]
  1642. snd-trident= [HW,ALSA]
  1643. snd-usb-audio= [HW,ALSA,USB]
  1644. snd-via82xx= [HW,ALSA]
  1645. snd-virmidi= [HW,ALSA]
  1646. snd-wavefront= [HW,ALSA]
  1647. snd-ymfpci= [HW,ALSA]
  1648. softlockup_panic=
  1649. [KNL] Should the soft-lockup detector generate panics.
  1650. sonypi.*= [HW] Sony Programmable I/O Control Device driver
  1651. See Documentation/sonypi.txt
  1652. specialix= [HW,SERIAL] Specialix multi-serial port adapter
  1653. See Documentation/specialix.txt.
  1654. spia_io_base= [HW,MTD]
  1655. spia_fio_base=
  1656. spia_pedr=
  1657. spia_peddr=
  1658. sscape= [HW,OSS]
  1659. Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
  1660. st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
  1661. See Documentation/scsi/st.txt.
  1662. sti= [PARISC,HW]
  1663. Format: <num>
  1664. Set the STI (builtin display/keyboard on the HP-PARISC
  1665. machines) console (graphic card) which should be used
  1666. as the initial boot-console.
  1667. See also comment in drivers/video/console/sticore.c.
  1668. sti_font= [HW]
  1669. See comment in drivers/video/console/sticore.c.
  1670. stifb= [HW]
  1671. Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
  1672. sunrpc.pool_mode=
  1673. [NFS]
  1674. Control how the NFS server code allocates CPUs to
  1675. service thread pools. Depending on how many NICs
  1676. you have and where their interrupts are bound, this
  1677. option will affect which CPUs will do NFS serving.
  1678. Note: this parameter cannot be changed while the
  1679. NFS server is running.
  1680. auto the server chooses an appropriate mode
  1681. automatically using heuristics
  1682. global a single global pool contains all CPUs
  1683. percpu one pool for each CPU
  1684. pernode one pool for each NUMA node (equivalent
  1685. to global on non-NUMA machines)
  1686. swiotlb= [IA-64] Number of I/O TLB slabs
  1687. switches= [HW,M68k]
  1688. sym53c416= [HW,SCSI]
  1689. See header of drivers/scsi/sym53c416.c.
  1690. sysrq_always_enabled
  1691. [KNL]
  1692. Ignore sysrq setting - this boot parameter will
  1693. neutralize any effect of /proc/sys/kernel/sysrq.
  1694. Useful for debugging.
  1695. t128= [HW,SCSI]
  1696. See header of drivers/scsi/t128.c.
  1697. tdfx= [HW,DRM]
  1698. test_suspend= [SUSPEND]
  1699. Specify "mem" (for Suspend-to-RAM) or "standby" (for
  1700. standby suspend) as the system sleep state to briefly
  1701. enter during system startup. The system is woken from
  1702. this state using a wakeup-capable RTC alarm.
  1703. thash_entries= [KNL,NET]
  1704. Set number of hash buckets for TCP connection
  1705. thermal.act= [HW,ACPI]
  1706. -1: disable all active trip points in all thermal zones
  1707. <degrees C>: override all lowest active trip points
  1708. thermal.crt= [HW,ACPI]
  1709. -1: disable all critical trip points in all thermal zones
  1710. <degrees C>: lower all critical trip points
  1711. thermal.nocrt= [HW,ACPI]
  1712. Set to disable actions on ACPI thermal zone
  1713. critical and hot trip points.
  1714. thermal.off= [HW,ACPI]
  1715. 1: disable ACPI thermal control
  1716. thermal.psv= [HW,ACPI]
  1717. -1: disable all passive trip points
  1718. <degrees C>: override all passive trip points to this value
  1719. thermal.tzp= [HW,ACPI]
  1720. Specify global default ACPI thermal zone polling rate
  1721. <deci-seconds>: poll all this frequency
  1722. 0: no polling (default)
  1723. tmscsim= [HW,SCSI]
  1724. See comment before function dc390_setup() in
  1725. drivers/scsi/tmscsim.c.
  1726. tp720= [HW,PS2]
  1727. trix= [HW,OSS] MediaTrix AudioTrix Pro
  1728. Format:
  1729. <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
  1730. turbografx.map[2|3]= [HW,JOY]
  1731. TurboGraFX parallel port interface
  1732. Format:
  1733. <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
  1734. See also Documentation/input/joystick-parport.txt
  1735. u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
  1736. See header of drivers/scsi/u14-34f.c.
  1737. uart401= [HW,OSS]
  1738. Format: <io>,<irq>
  1739. uart6850= [HW,OSS]
  1740. Format: <io>,<irq>
  1741. uhci-hcd.ignore_oc=
  1742. [USB] Ignore overcurrent events (default N).
  1743. Some badly-designed motherboards generate lots of
  1744. bogus events, for ports that aren't wired to
  1745. anything. Set this parameter to avoid log spamming.
  1746. Note that genuine overcurrent events won't be
  1747. reported either.
  1748. unknown_nmi_panic
  1749. [X86-32,X86-64]
  1750. Set unknown_nmi_panic=1 early on boot.
  1751. usbcore.autosuspend=
  1752. [USB] The autosuspend time delay (in seconds) used
  1753. for newly-detected USB devices (default 2). This
  1754. is the time required before an idle device will be
  1755. autosuspended. Devices for which the delay is set
  1756. to a negative value won't be autosuspended at all.
  1757. usbcore.usbfs_snoop=
  1758. [USB] Set to log all usbfs traffic (default 0 = off).
  1759. usbcore.blinkenlights=
  1760. [USB] Set to cycle leds on hubs (default 0 = off).
  1761. usbcore.old_scheme_first=
  1762. [USB] Start with the old device initialization
  1763. scheme (default 0 = off).
  1764. usbcore.use_both_schemes=
  1765. [USB] Try the other device initialization scheme
  1766. if the first one fails (default 1 = enabled).
  1767. usbcore.initial_descriptor_timeout=
  1768. [USB] Specifies timeout for the initial 64-byte
  1769. USB_REQ_GET_DESCRIPTOR request in milliseconds
  1770. (default 5000 = 5.0 seconds).
  1771. usbhid.mousepoll=
  1772. [USBHID] The interval which mice are to be polled at.
  1773. add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
  1774. kernel's map of available physical RAM.
  1775. vdso= [X86-32,SH,x86-64]
  1776. vdso=2: enable compat VDSO (default with COMPAT_VDSO)
  1777. vdso=1: enable VDSO (default)
  1778. vdso=0: disable VDSO mapping
  1779. vdso32= [X86-32,X86-64]
  1780. vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
  1781. vdso32=1: enable 32-bit VDSO (default)
  1782. vdso32=0: disable 32-bit VDSO mapping
  1783. vector= [IA-64,SMP]
  1784. vector=percpu: enable percpu vector domain
  1785. video= [FB] Frame buffer configuration
  1786. See Documentation/fb/modedb.txt.
  1787. vga= [BOOT,X86-32] Select a particular video mode
  1788. See Documentation/i386/boot.txt and
  1789. Documentation/svga.txt.
  1790. Use vga=ask for menu.
  1791. This is actually a boot loader parameter; the value is
  1792. passed to the kernel using a special protocol.
  1793. vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
  1794. size of <nn>. This can be used to increase the
  1795. minimum size (128MB on x86). It can also be used to
  1796. decrease the size and leave more room for directly
  1797. mapped kernel RAM.
  1798. vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
  1799. Format: <command>
  1800. vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
  1801. Format: <command>
  1802. vmpoff= [KNL,S390] Perform z/VM CP command after power off.
  1803. Format: <command>
  1804. waveartist= [HW,OSS]
  1805. Format: <io>,<irq>,<dma>,<dma2>
  1806. wd33c93= [HW,SCSI]
  1807. See header of drivers/scsi/wd33c93.c.
  1808. wd7000= [HW,SCSI]
  1809. See header of drivers/scsi/wd7000.c.
  1810. wdt= [WDT] Watchdog
  1811. See Documentation/watchdog/wdt.txt.
  1812. xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
  1813. xd_geo= See header of drivers/block/xd.c.
  1814. xirc2ps_cs= [NET,PCMCIA]
  1815. Format:
  1816. <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
  1817. norandmaps Don't use address space randomization
  1818. Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
  1819. ______________________________________________________________________
  1820. TODO:
  1821. Add documentation for ALSA options.
  1822. Add more DRM drivers.