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. KMEMTRACE kmemtrace is enabled.
  45. LIBATA Libata driver is enabled
  46. LP Printer support is enabled.
  47. LOOP Loopback device support is enabled.
  48. M68k M68k architecture is enabled.
  49. These options have more detailed description inside of
  50. Documentation/m68k/kernel-options.txt.
  51. MCA MCA bus support is enabled.
  52. MDA MDA console support is enabled.
  53. MOUSE Appropriate mouse support is enabled.
  54. MSI Message Signaled Interrupts (PCI).
  55. MTD MTD (Memory Technology Device) support is enabled.
  56. NET Appropriate network support is enabled.
  57. NUMA NUMA support is enabled.
  58. GENERIC_TIME The generic timeofday code is enabled.
  59. NFS Appropriate NFS support is enabled.
  60. OSS OSS sound support is enabled.
  61. PV_OPS A paravirtualized kernel is enabled.
  62. PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
  63. PARISC The PA-RISC architecture is enabled.
  64. PCI PCI bus support is enabled.
  65. PCIE PCI Express support is enabled.
  66. PCMCIA The PCMCIA subsystem is enabled.
  67. PNP Plug & Play support is enabled.
  68. PPC PowerPC architecture is enabled.
  69. PPT Parallel port support is enabled.
  70. PS2 Appropriate PS/2 support is enabled.
  71. RAM RAM disk support is enabled.
  72. ROOTPLUG The example Root Plug LSM is enabled.
  73. S390 S390 architecture is enabled.
  74. SCSI Appropriate SCSI support is enabled.
  75. A lot of drivers has their options described inside of
  76. Documentation/scsi/.
  77. SECURITY Different security models are enabled.
  78. SELINUX SELinux support is enabled.
  79. SERIAL Serial support is enabled.
  80. SH SuperH architecture is enabled.
  81. SMP The kernel is an SMP kernel.
  82. SPARC Sparc architecture is enabled.
  83. SWSUSP Software suspend (hibernation) is enabled.
  84. SUSPEND System suspend states are enabled.
  85. TS Appropriate touchscreen support is enabled.
  86. USB USB support is enabled.
  87. USBHID USB Human Interface Device support is enabled.
  88. V4L Video For Linux support is enabled.
  89. VGA The VGA console has been enabled.
  90. VT Virtual terminal support is enabled.
  91. WDT Watchdog support is enabled.
  92. XT IBM PC/XT MFM hard disk support is enabled.
  93. X86-32 X86-32, aka i386 architecture is enabled.
  94. X86-64 X86-64 architecture is enabled.
  95. More X86-64 boot options can be found in
  96. Documentation/x86/x86_64/boot-options.txt .
  97. X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
  98. In addition, the following text indicates that the option:
  99. BUGS= Relates to possible processor bugs on the said processor.
  100. KNL Is a kernel start-up parameter.
  101. BOOT Is a boot loader parameter.
  102. Parameters denoted with BOOT are actually interpreted by the boot
  103. loader, and have no meaning to the kernel directly.
  104. Do not modify the syntax of boot loader parameters without extreme
  105. need or coordination with <Documentation/x86/i386/boot.txt>.
  106. There are also arch-specific kernel-parameters not documented here.
  107. See for example <Documentation/x86/x86_64/boot-options.txt>.
  108. Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
  109. a trailing = on the name of any parameter states that that parameter will
  110. be entered as an environment variable, whereas its absence indicates that
  111. it will appear as a kernel argument readable via /proc/cmdline by programs
  112. running once the system is up.
  113. The number of kernel parameters is not limited, but the length of the
  114. complete command line (parameters including spaces etc.) is limited to
  115. a fixed number of characters. This limit depends on the architecture
  116. and is between 256 and 4096 characters. It is defined in the file
  117. ./include/asm/setup.h as COMMAND_LINE_SIZE.
  118. acpi= [HW,ACPI,X86-64,i386]
  119. Advanced Configuration and Power Interface
  120. Format: { force | off | ht | strict | noirq }
  121. force -- enable ACPI if default was off
  122. off -- disable ACPI if default was on
  123. noirq -- do not use ACPI for IRQ routing
  124. ht -- run only enough ACPI to enable Hyper Threading
  125. strict -- Be less tolerant of platforms that are not
  126. strictly ACPI specification compliant.
  127. See also Documentation/power/pm.txt, pci=noacpi
  128. acpi_apic_instance= [ACPI, IOAPIC]
  129. Format: <int>
  130. 2: use 2nd APIC table, if available
  131. 1,0: use 1st APIC table
  132. default: 0
  133. acpi_sleep= [HW,ACPI] Sleep options
  134. Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, old_ordering }
  135. See Documentation/power/video.txt for s3_bios and s3_mode.
  136. s3_beep is for debugging; it makes the PC's speaker beep
  137. as soon as the kernel's real-mode entry point is called.
  138. s4_nohwsig prevents ACPI hardware signature from being
  139. used during resume from hibernation.
  140. old_ordering causes the ACPI 1.0 ordering of the _PTS
  141. control method, wrt putting devices into low power
  142. states, to be enforced (the ACPI 2.0 ordering of _PTS is
  143. used by default).
  144. acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
  145. Format: { level | edge | high | low }
  146. acpi_irq_balance [HW,ACPI]
  147. ACPI will balance active IRQs
  148. default in APIC mode
  149. acpi_irq_nobalance [HW,ACPI]
  150. ACPI will not move active IRQs (default)
  151. default in PIC mode
  152. acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
  153. use by PCI
  154. Format: <irq>,<irq>...
  155. acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
  156. Format: <irq>,<irq>...
  157. acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
  158. acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
  159. Format: To spoof as Windows 98: ="Microsoft Windows"
  160. acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
  161. acpi_osi="string1" # add string1 -- only one string
  162. acpi_osi="!string2" # remove built-in string2
  163. acpi_osi= # disable all strings
  164. acpi_serialize [HW,ACPI] force serialization of AML methods
  165. acpi_skip_timer_override [HW,ACPI]
  166. Recognize and ignore IRQ0/pin2 Interrupt Override.
  167. For broken nForce2 BIOS resulting in XT-PIC timer.
  168. acpi_use_timer_override [HW,ACPI}
  169. Use timer override. For some broken Nvidia NF5 boards
  170. that require a timer override, but don't have
  171. HPET
  172. acpi_backlight= [HW,ACPI]
  173. acpi_backlight=vendor
  174. acpi_backlight=video
  175. If set to vendor, prefer vendor specific driver
  176. (e.g. thinkpad_acpi, sony_acpi, etc.) instead
  177. of the ACPI video.ko driver.
  178. acpi_display_output= [HW,ACPI]
  179. acpi_display_output=vendor
  180. acpi_display_output=video
  181. See above.
  182. acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
  183. acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
  184. Format: <int>
  185. CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
  186. debug output. Bits in debug_layer correspond to a
  187. _COMPONENT in an ACPI source file, e.g.,
  188. #define _COMPONENT ACPI_PCI_COMPONENT
  189. Bits in debug_level correspond to a level in
  190. ACPI_DEBUG_PRINT statements, e.g.,
  191. ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
  192. See Documentation/acpi/debug.txt for more information
  193. about debug layers and levels.
  194. Enable AML "Debug" output, i.e., stores to the Debug
  195. object while interpreting AML:
  196. acpi.debug_layer=0xffffffff acpi.debug_level=0x2
  197. Enable PCI/PCI interrupt routing info messages:
  198. acpi.debug_layer=0x400000 acpi.debug_level=0x4
  199. Enable all messages related to ACPI hardware:
  200. acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
  201. Some values produce so much output that the system is
  202. unusable. The "log_buf_len" parameter may be useful
  203. if you need to capture more output.
  204. acpi.power_nocheck= [HW,ACPI]
  205. Format: 1/0 enable/disable the check of power state.
  206. On some bogus BIOS the _PSC object/_STA object of
  207. power resource can't return the correct device power
  208. state. In such case it is unneccessary to check its
  209. power state again in power transition.
  210. 1 : disable the power state check
  211. acpi_pm_good [X86-32,X86-64]
  212. Override the pmtimer bug detection: force the kernel
  213. to assume that this machine's pmtimer latches its value
  214. and always returns good values.
  215. agp= [AGP]
  216. { off | try_unsupported }
  217. off: disable AGP support
  218. try_unsupported: try to drive unsupported chipsets
  219. (may crash computer or cause data corruption)
  220. enable_timer_pin_1 [i386,x86-64]
  221. Enable PIN 1 of APIC timer
  222. Can be useful to work around chipset bugs
  223. (in particular on some ATI chipsets).
  224. The kernel tries to set a reasonable default.
  225. disable_timer_pin_1 [i386,x86-64]
  226. Disable PIN 1 of APIC timer
  227. Can be useful to work around chipset bugs.
  228. ad1848= [HW,OSS]
  229. Format: <io>,<irq>,<dma>,<dma2>,<type>
  230. advansys= [HW,SCSI]
  231. See header of drivers/scsi/advansys.c.
  232. advwdt= [HW,WDT] Advantech WDT
  233. Format: <iostart>,<iostop>
  234. aedsp16= [HW,OSS] Audio Excel DSP 16
  235. Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
  236. See also header of sound/oss/aedsp16.c.
  237. aha152x= [HW,SCSI]
  238. See Documentation/scsi/aha152x.txt.
  239. aha1542= [HW,SCSI]
  240. Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
  241. aic7xxx= [HW,SCSI]
  242. See Documentation/scsi/aic7xxx.txt.
  243. aic79xx= [HW,SCSI]
  244. See Documentation/scsi/aic79xx.txt.
  245. amd_iommu= [HW,X86-84]
  246. Pass parameters to the AMD IOMMU driver in the system.
  247. Possible values are:
  248. isolate - enable device isolation (each device, as far
  249. as possible, will get its own protection
  250. domain) [default]
  251. share - put every device behind one IOMMU into the
  252. same protection domain
  253. fullflush - enable flushing of IO/TLB entries when
  254. they are unmapped. Otherwise they are
  255. flushed before they will be reused, which
  256. is a lot of faster
  257. amd_iommu_size= [HW,X86-64]
  258. Define the size of the aperture for the AMD IOMMU
  259. driver. Possible values are:
  260. '32M', '64M' (default), '128M', '256M', '512M', '1G'
  261. amijoy.map= [HW,JOY] Amiga joystick support
  262. Map of devices attached to JOY0DAT and JOY1DAT
  263. Format: <a>,<b>
  264. See also Documentation/kernel/input/joystick.txt
  265. analog.map= [HW,JOY] Analog joystick and gamepad support
  266. Specifies type or capabilities of an analog joystick
  267. connected to one of 16 gameports
  268. Format: <type1>,<type2>,..<type16>
  269. apc= [HW,SPARC]
  270. Power management functions (SPARCstation-4/5 + deriv.)
  271. Format: noidle
  272. Disable APC CPU standby support. SPARCstation-Fox does
  273. not play well with APC CPU idle - disable it if you have
  274. APC and your system crashes randomly.
  275. apic= [APIC,i386] Advanced Programmable Interrupt Controller
  276. Change the output verbosity whilst booting
  277. Format: { quiet (default) | verbose | debug }
  278. Change the amount of debugging information output
  279. when initialising the APIC and IO-APIC components.
  280. apm= [APM] Advanced Power Management
  281. See header of arch/x86/kernel/apm_32.c.
  282. arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
  283. Format: <io>,<irq>,<nodeID>
  284. ataflop= [HW,M68k]
  285. atarimouse= [HW,MOUSE] Atari Mouse
  286. atascsi= [HW,SCSI] Atari SCSI
  287. atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
  288. EzKey and similar keyboards
  289. atkbd.reset= [HW] Reset keyboard during initialization
  290. atkbd.set= [HW] Select keyboard code set
  291. Format: <int> (2 = AT (default), 3 = PS/2)
  292. atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
  293. keyboards
  294. atkbd.softraw= [HW] Choose between synthetic and real raw mode
  295. Format: <bool> (0 = real, 1 = synthetic (default))
  296. atkbd.softrepeat= [HW]
  297. Use software keyboard repeat
  298. autotest [IA64]
  299. baycom_epp= [HW,AX25]
  300. Format: <io>,<mode>
  301. baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
  302. Format: <io>,<mode>
  303. See header of drivers/net/hamradio/baycom_par.c.
  304. baycom_ser_fdx= [HW,AX25]
  305. BayCom Serial Port AX.25 Modem (Full Duplex Mode)
  306. Format: <io>,<irq>,<mode>[,<baud>]
  307. See header of drivers/net/hamradio/baycom_ser_fdx.c.
  308. baycom_ser_hdx= [HW,AX25]
  309. BayCom Serial Port AX.25 Modem (Half Duplex Mode)
  310. Format: <io>,<irq>,<mode>
  311. See header of drivers/net/hamradio/baycom_ser_hdx.c.
  312. boot_delay= Milliseconds to delay each printk during boot.
  313. Values larger than 10 seconds (10000) are changed to
  314. no delay (0).
  315. Format: integer
  316. bootmem_debug [KNL] Enable bootmem allocator debug messages.
  317. bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
  318. bttv.radio= Most important insmod options are available as
  319. kernel args too.
  320. bttv.pll= See Documentation/video4linux/bttv/Insmod-options
  321. bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
  322. BusLogic= [HW,SCSI]
  323. See drivers/scsi/BusLogic.c, comment before function
  324. BusLogic_ParseDriverOptions().
  325. c101= [NET] Moxa C101 synchronous serial card
  326. cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
  327. Sometimes CPU hardware bugs make them report the cache
  328. size incorrectly. The kernel will attempt work arounds
  329. to fix known problems, but for some CPUs it is not
  330. possible to determine what the correct size should be.
  331. This option provides an override for these situations.
  332. security= [SECURITY] Choose a security module to enable at boot.
  333. If this boot parameter is not specified, only the first
  334. security module asking for security registration will be
  335. loaded. An invalid security module name will be treated
  336. as if no module has been chosen.
  337. capability.disable=
  338. [SECURITY] Disable capabilities. This would normally
  339. be used only if an alternative security model is to be
  340. configured. Potentially dangerous and should only be
  341. used if you are entirely sure of the consequences.
  342. ccw_timeout_log [S390]
  343. See Documentation/s390/CommonIO for details.
  344. cgroup_disable= [KNL] Disable a particular controller
  345. Format: {name of the controller(s) to disable}
  346. {Currently supported controllers - "memory"}
  347. checkreqprot [SELINUX] Set initial checkreqprot flag value.
  348. Format: { "0" | "1" }
  349. See security/selinux/Kconfig help text.
  350. 0 -- check protection applied by kernel (includes
  351. any implied execute protection).
  352. 1 -- check protection requested by application.
  353. Default value is set via a kernel config option.
  354. Value can be changed at runtime via
  355. /selinux/checkreqprot.
  356. cio_ignore= [S390]
  357. See Documentation/s390/CommonIO for details.
  358. clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
  359. [Deprecated]
  360. Forces specified clocksource (if available) to be used
  361. when calculating gettimeofday(). If specified
  362. clocksource is not available, it defaults to PIT.
  363. Format: { pit | tsc | cyclone | pmtmr }
  364. clocksource= [GENERIC_TIME] Override the default clocksource
  365. Format: <string>
  366. Override the default clocksource and use the clocksource
  367. with the name specified.
  368. Some clocksource names to choose from, depending on
  369. the platform:
  370. [all] jiffies (this is the base, fallback clocksource)
  371. [ACPI] acpi_pm
  372. [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
  373. pxa_timer,timer3,32k_counter,timer0_1
  374. [AVR32] avr32
  375. [X86-32] pit,hpet,tsc,vmi-timer;
  376. scx200_hrt on Geode; cyclone on IBM x440
  377. [MIPS] MIPS
  378. [PARISC] cr16
  379. [S390] tod
  380. [SH] SuperH
  381. [SPARC64] tick
  382. [X86-64] hpet,tsc
  383. clearcpuid=BITNUM [X86]
  384. Disable CPUID feature X for the kernel. See
  385. include/asm-x86/cpufeature.h for the valid bit numbers.
  386. Note the Linux specific bits are not necessarily
  387. stable over kernel options, but the vendor specific
  388. ones should be.
  389. Also note that user programs calling CPUID directly
  390. or using the feature without checking anything
  391. will still see it. This just prevents it from
  392. being used by the kernel or shown in /proc/cpuinfo.
  393. Also note the kernel might malfunction if you disable
  394. some critical bits.
  395. code_bytes [IA32/X86_64] How many bytes of object code to print
  396. in an oops report.
  397. Range: 0 - 8192
  398. Default: 64
  399. hpet= [X86-32,HPET] option to control HPET usage
  400. Format: { enable (default) | disable | force }
  401. disable: disable HPET and use PIT instead
  402. force: allow force enabled of undocumented chips (ICH4,
  403. VIA, nVidia)
  404. com20020= [HW,NET] ARCnet - COM20020 chipset
  405. Format:
  406. <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
  407. com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
  408. Format: <io>[,<irq>]
  409. com90xx= [HW,NET]
  410. ARCnet - COM90xx chipset (memory-mapped buffers)
  411. Format: <io>[,<irq>[,<memstart>]]
  412. condev= [HW,S390] console device
  413. conmode=
  414. console= [KNL] Output console device and options.
  415. tty<n> Use the virtual console device <n>.
  416. ttyS<n>[,options]
  417. ttyUSB0[,options]
  418. Use the specified serial port. The options are of
  419. the form "bbbbpnf", where "bbbb" is the baud rate,
  420. "p" is parity ("n", "o", or "e"), "n" is number of
  421. bits, and "f" is flow control ("r" for RTS or
  422. omit it). Default is "9600n8".
  423. See Documentation/serial-console.txt for more
  424. information. See
  425. Documentation/networking/netconsole.txt for an
  426. alternative.
  427. uart[8250],io,<addr>[,options]
  428. uart[8250],mmio,<addr>[,options]
  429. Start an early, polled-mode console on the 8250/16550
  430. UART at the specified I/O port or MMIO address,
  431. switching to the matching ttyS device later. The
  432. options are the same as for ttyS, above.
  433. If the device connected to the port is not a TTY but a braille
  434. device, prepend "brl," before the device type, for instance
  435. console=brl,ttyS0
  436. For now, only VisioBraille is supported.
  437. earlycon= [KNL] Output early console device and options.
  438. uart[8250],io,<addr>[,options]
  439. uart[8250],mmio,<addr>[,options]
  440. Start an early, polled-mode console on the 8250/16550
  441. UART at the specified I/O port or MMIO address.
  442. The options are the same as for ttyS, above.
  443. no_console_suspend
  444. [HW] Never suspend the console
  445. Disable suspending of consoles during suspend and
  446. hibernate operations. Once disabled, debugging
  447. messages can reach various consoles while the rest
  448. of the system is being put to sleep (ie, while
  449. debugging driver suspend/resume hooks). This may
  450. not work reliably with all consoles, but is known
  451. to work with serial and VGA consoles.
  452. cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
  453. Format:
  454. <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
  455. crashkernel=nn[KMG]@ss[KMG]
  456. [KNL] Reserve a chunk of physical memory to
  457. hold a kernel to switch to with kexec on panic.
  458. crashkernel=range1:size1[,range2:size2,...][@offset]
  459. [KNL] Same as above, but depends on the memory
  460. in the running system. The syntax of range is
  461. start-[end] where start and end are both
  462. a memory unit (amount[KMG]). See also
  463. Documentation/kdump/kdump.txt for a example.
  464. cs4232= [HW,OSS]
  465. Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
  466. cs89x0_dma= [HW,NET]
  467. Format: <dma>
  468. cs89x0_media= [HW,NET]
  469. Format: { rj45 | aui | bnc }
  470. dasd= [HW,NET]
  471. See header of drivers/s390/block/dasd_devmap.c.
  472. db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
  473. (one device per port)
  474. Format: <port#>,<type>
  475. See also Documentation/input/joystick-parport.txt
  476. debug [KNL] Enable kernel debugging (events log level).
  477. debug_locks_verbose=
  478. [KNL] verbose self-tests
  479. Format=<0|1>
  480. Print debugging info while doing the locking API
  481. self-tests.
  482. We default to 0 (no extra messages), setting it to
  483. 1 will print _a lot_ more information - normally
  484. only useful to kernel developers.
  485. debug_objects [KNL] Enable object debugging
  486. debugpat [X86] Enable PAT debugging
  487. decnet.addr= [HW,NET]
  488. Format: <area>[,<node>]
  489. See also Documentation/networking/decnet.txt.
  490. vt.default_blu= [VT]
  491. Format: <blue0>,<blue1>,<blue2>,...,<blue15>
  492. Change the default blue palette of the console.
  493. This is a 16-member array composed of values
  494. ranging from 0-255.
  495. vt.default_grn= [VT]
  496. Format: <green0>,<green1>,<green2>,...,<green15>
  497. Change the default green palette of the console.
  498. This is a 16-member array composed of values
  499. ranging from 0-255.
  500. vt.default_red= [VT]
  501. Format: <red0>,<red1>,<red2>,...,<red15>
  502. Change the default red palette of the console.
  503. This is a 16-member array composed of values
  504. ranging from 0-255.
  505. vt.default_utf8=
  506. [VT]
  507. Format=<0|1>
  508. Set system-wide default UTF-8 mode for all tty's.
  509. Default is 1, i.e. UTF-8 mode is enabled for all
  510. newly opened terminals.
  511. dhash_entries= [KNL]
  512. Set number of hash buckets for dentry cache.
  513. digi= [HW,SERIAL]
  514. IO parameters + enable/disable command.
  515. digiepca= [HW,SERIAL]
  516. See drivers/char/README.epca and
  517. Documentation/serial/digiepca.txt.
  518. disable_mtrr_cleanup [X86]
  519. enable_mtrr_cleanup [X86]
  520. The kernel tries to adjust MTRR layout from continuous
  521. to discrete, to make X server driver able to add WB
  522. entry later. This parameter enables/disables that.
  523. mtrr_chunk_size=nn[KMG] [X86]
  524. used for mtrr cleanup. It is largest continous chunk
  525. that could hold holes aka. UC entries.
  526. mtrr_gran_size=nn[KMG] [X86]
  527. Used for mtrr cleanup. It is granularity of mtrr block.
  528. Default is 1.
  529. Large value could prevent small alignment from
  530. using up MTRRs.
  531. mtrr_spare_reg_nr=n [X86]
  532. Format: <integer>
  533. Range: 0,7 : spare reg number
  534. Default : 1
  535. Used for mtrr cleanup. It is spare mtrr entries number.
  536. Set to 2 or more if your graphical card needs more.
  537. disable_mtrr_trim [X86, Intel and AMD only]
  538. By default the kernel will trim any uncacheable
  539. memory out of your available memory pool based on
  540. MTRR settings. This parameter disables that behavior,
  541. possibly causing your machine to run very slowly.
  542. dmasound= [HW,OSS] Sound subsystem buffers
  543. dscc4.setup= [NET]
  544. dtc3181e= [HW,SCSI]
  545. earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
  546. earlyprintk=vga
  547. earlyprintk=serial[,ttySn[,baudrate]]
  548. earlyprintk=dbgp
  549. Append ",keep" to not disable it when the real console
  550. takes over.
  551. Only vga or serial or usb debug port at a time.
  552. Currently only ttyS0 and ttyS1 are supported.
  553. Interaction with the standard serial driver is not
  554. very good.
  555. The VGA output is eventually overwritten by the real
  556. console.
  557. eata= [HW,SCSI]
  558. edd= [EDD]
  559. Format: {"off" | "on" | "skip[mbr]"}
  560. eisa_irq_edge= [PARISC,HW]
  561. See header of drivers/parisc/eisa.c.
  562. elanfreq= [X86-32]
  563. See comment before function elanfreq_setup() in
  564. arch/x86/kernel/cpu/cpufreq/elanfreq.c.
  565. elevator= [IOSCHED]
  566. Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
  567. See Documentation/block/as-iosched.txt and
  568. Documentation/block/deadline-iosched.txt for details.
  569. elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
  570. Specifies physical address of start of kernel core
  571. image elf header. Generally kexec loader will
  572. pass this option to capture kernel.
  573. See Documentation/kdump/kdump.txt for details.
  574. enforcing [SELINUX] Set initial enforcing status.
  575. Format: {"0" | "1"}
  576. See security/selinux/Kconfig help text.
  577. 0 -- permissive (log only, no denials).
  578. 1 -- enforcing (deny and log).
  579. Default value is 0.
  580. Value can be changed at runtime via /selinux/enforce.
  581. es1371= [HW,OSS]
  582. Format: <spdif>,[<nomix>,[<amplifier>]]
  583. See also header of sound/oss/es1371.c.
  584. ether= [HW,NET] Ethernet cards parameters
  585. This option is obsoleted by the "netdev=" option, which
  586. has equivalent usage. See its documentation for details.
  587. eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
  588. Format: <io>[,<irq>]
  589. failslab=
  590. fail_page_alloc=
  591. fail_make_request=[KNL]
  592. General fault injection mechanism.
  593. Format: <interval>,<probability>,<space>,<times>
  594. See also /Documentation/fault-injection/.
  595. fd_mcs= [HW,SCSI]
  596. See header of drivers/scsi/fd_mcs.c.
  597. fdomain= [HW,SCSI]
  598. See header of drivers/scsi/fdomain.c.
  599. floppy= [HW]
  600. See Documentation/blockdev/floppy.txt.
  601. force_pal_cache_flush
  602. [IA-64] Avoid check_sal_cache_flush which may hang on
  603. buggy SAL_CACHE_FLUSH implementations. Using this
  604. parameter will force ia64_sal_cache_flush to call
  605. ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
  606. gamecon.map[2|3]=
  607. [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
  608. support via parallel port (up to 5 devices per port)
  609. Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
  610. See also Documentation/input/joystick-parport.txt
  611. gamma= [HW,DRM]
  612. gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
  613. Format: off | on
  614. default: on
  615. gdth= [HW,SCSI]
  616. See header of drivers/scsi/gdth.c.
  617. gpt [EFI] Forces disk with valid GPT signature but
  618. invalid Protective MBR to be treated as GPT.
  619. gvp11= [HW,SCSI]
  620. hashdist= [KNL,NUMA] Large hashes allocated during boot
  621. are distributed across NUMA nodes. Defaults on
  622. for IA-64, off otherwise.
  623. Format: 0 | 1 (for off | on)
  624. hcl= [IA-64] SGI's Hardware Graph compatibility layer
  625. hd= [EIDE] (E)IDE hard drive subsystem geometry
  626. Format: <cyl>,<head>,<sect>
  627. highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
  628. size of <nn>. This works even on boxes that have no
  629. highmem otherwise. This also works to reduce highmem
  630. size on bigger boxes.
  631. highres= [KNL] Enable/disable high resolution timer mode.
  632. Valid parameters: "on", "off"
  633. Default: "on"
  634. hisax= [HW,ISDN]
  635. See Documentation/isdn/README.HiSax.
  636. hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
  637. hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
  638. On x86-64 and powerpc, this option can be specified
  639. multiple times interleaved with hugepages= to reserve
  640. huge pages of different sizes. Valid pages sizes on
  641. x86-64 are 2M (when the CPU supports "pse") and 1G
  642. (when the CPU supports the "pdpe1gb" cpuinfo flag)
  643. Note that 1GB pages can only be allocated at boot time
  644. using hugepages= and not freed afterwards.
  645. default_hugepagesz=
  646. [same as hugepagesz=] The size of the default
  647. HugeTLB page size. This is the size represented by
  648. the legacy /proc/ hugepages APIs, used for SHM, and
  649. default size when mounting hugetlbfs filesystems.
  650. Defaults to the default architecture's huge page size
  651. if not specified.
  652. hlt [BUGS=ARM,SH]
  653. i8042.debug [HW] Toggle i8042 debug mode
  654. i8042.direct [HW] Put keyboard port into non-translated mode
  655. i8042.dumbkbd [HW] Pretend that controller can only read data from
  656. keyboard and cannot control its state
  657. (Don't attempt to blink the leds)
  658. i8042.noaux [HW] Don't check for auxiliary (== mouse) port
  659. i8042.nokbd [HW] Don't check/create keyboard port
  660. i8042.noloop [HW] Disable the AUX Loopback command while probing
  661. for the AUX port
  662. i8042.nomux [HW] Don't check presence of an active multiplexing
  663. controller
  664. i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
  665. controllers
  666. i8042.panicblink=
  667. [HW] Frequency with which keyboard LEDs should blink
  668. when kernel panics (default is 0.5 sec)
  669. i8042.reset [HW] Reset the controller during init and cleanup
  670. i8042.unlock [HW] Unlock (ignore) the keylock
  671. i810= [HW,DRM]
  672. i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
  673. indicates that the driver is running on unsupported
  674. hardware.
  675. i8k.force [HW] Activate i8k driver even if SMM BIOS signature
  676. does not match list of supported models.
  677. i8k.power_status
  678. [HW] Report power status in /proc/i8k
  679. (disabled by default)
  680. i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
  681. capability is set.
  682. ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
  683. See Documentation/mca.txt.
  684. icn= [HW,ISDN]
  685. Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
  686. ide= [HW] (E)IDE subsystem
  687. Format: ide=nodma or ide=doubler
  688. See Documentation/ide/ide.txt.
  689. idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
  690. See Documentation/ide/ide.txt.
  691. idle= [X86]
  692. Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
  693. Poll forces a polling idle loop that can slightly improves the performance
  694. of waking up a idle CPU, but will use a lot of power and make the system
  695. run hot. Not recommended.
  696. idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
  697. to not use it because it doesn't save as much power as a normal idle
  698. loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
  699. as idle=poll.
  700. idle=halt. Halt is forced to be used for CPU idle.
  701. In such case C2/C3 won't be used again.
  702. idle=nomwait. Disable mwait for CPU C-states
  703. ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
  704. Claim all unknown PCI IDE storage controllers.
  705. ignore_loglevel [KNL]
  706. Ignore loglevel setting - this will print /all/
  707. kernel messages to the console. Useful for debugging.
  708. ihash_entries= [KNL]
  709. Set number of hash buckets for inode cache.
  710. in2000= [HW,SCSI]
  711. See header of drivers/scsi/in2000.c.
  712. init= [KNL]
  713. Format: <full_path>
  714. Run specified binary instead of /sbin/init as init
  715. process.
  716. initcall_debug [KNL] Trace initcalls as they are executed. Useful
  717. for working out where the kernel is dying during
  718. startup.
  719. initrd= [BOOT] Specify the location of the initial ramdisk
  720. inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
  721. Format: <irq>
  722. inttest= [IA64]
  723. iommu= [x86]
  724. off
  725. force
  726. noforce
  727. biomerge
  728. panic
  729. nopanic
  730. merge
  731. nomerge
  732. forcesac
  733. soft
  734. intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
  735. off
  736. Disable intel iommu driver.
  737. igfx_off [Default Off]
  738. By default, gfx is mapped as normal device. If a gfx
  739. device has a dedicated DMAR unit, the DMAR unit is
  740. bypassed by not enabling DMAR with this option. In
  741. this case, gfx device will use physical address for
  742. DMA.
  743. forcedac [x86_64]
  744. With this option iommu will not optimize to look
  745. for io virtual address below 32 bit forcing dual
  746. address cycle on pci bus for cards supporting greater
  747. than 32 bit addressing. The default is to look
  748. for translation below 32 bit and if not available
  749. then look in the higher range.
  750. strict [Default Off]
  751. With this option on every unmap_single operation will
  752. result in a hardware IOTLB flush operation as opposed
  753. to batching them for performance.
  754. io_delay= [X86-32,X86-64] I/O delay method
  755. 0x80
  756. Standard port 0x80 based delay
  757. 0xed
  758. Alternate port 0xed based delay (needed on some systems)
  759. udelay
  760. Simple two microseconds delay
  761. none
  762. No delay
  763. io7= [HW] IO7 for Marvel based alpha systems
  764. See comment before marvel_specify_io7 in
  765. arch/alpha/kernel/core_marvel.c.
  766. ip= [IP_PNP]
  767. See Documentation/filesystems/nfsroot.txt.
  768. ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
  769. See comment before ip2_setup() in
  770. drivers/char/ip2/ip2base.c.
  771. ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
  772. See header of drivers/scsi/ips.c.
  773. ports= [IP_VS_FTP] IPVS ftp helper module
  774. Default is 21.
  775. Up to 8 (IP_VS_APP_MAX_PORTS) ports
  776. may be specified.
  777. Format: <port>,<port>....
  778. irqfixup [HW]
  779. When an interrupt is not handled search all handlers
  780. for it. Intended to get systems with badly broken
  781. firmware running.
  782. irqpoll [HW]
  783. When an interrupt is not handled search all handlers
  784. for it. Also check all handlers each timer
  785. interrupt. Intended to get systems with badly broken
  786. firmware running.
  787. isapnp= [ISAPNP]
  788. Format: <RDP>,<reset>,<pci_scan>,<verbosity>
  789. isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
  790. Format:
  791. <cpu number>,...,<cpu number>
  792. or
  793. <cpu number>-<cpu number>
  794. (must be a positive range in ascending order)
  795. or a mixture
  796. <cpu number>,...,<cpu number>-<cpu number>
  797. This option can be used to specify one or more CPUs
  798. to isolate from the general SMP balancing and scheduling
  799. algorithms. You can move a process onto or off an
  800. "isolated" CPU via the CPU affinity syscalls or cpuset.
  801. <cpu number> begins at 0 and the maximum value is
  802. "number of CPUs in system - 1".
  803. This option is the preferred way to isolate CPUs. The
  804. alternative -- manually setting the CPU mask of all
  805. tasks in the system -- can cause problems and
  806. suboptimal load balancer performance.
  807. iucv= [HW,NET]
  808. js= [HW,JOY] Analog joystick
  809. See Documentation/input/joystick.txt.
  810. kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
  811. specifies the amount of memory usable by the kernel
  812. for non-movable allocations. The requested amount is
  813. spread evenly throughout all nodes in the system. The
  814. remaining memory in each node is used for Movable
  815. pages. In the event, a node is too small to have both
  816. kernelcore and Movable pages, kernelcore pages will
  817. take priority and other nodes will have a larger number
  818. of kernelcore pages. The Movable zone is used for the
  819. allocation of pages that may be reclaimed or moved
  820. by the page migration subsystem. This means that
  821. HugeTLB pages may not be allocated from this zone.
  822. Note that allocations like PTEs-from-HighMem still
  823. use the HighMem zone if it exists, and the Normal
  824. zone if it does not.
  825. kmemtrace.enable= [KNL,KMEMTRACE] Format: { yes | no }
  826. Controls whether kmemtrace is enabled
  827. at boot-time.
  828. kmemtrace.subbufs=n [KNL,KMEMTRACE] Overrides the number of
  829. subbufs kmemtrace's relay channel has. Set this
  830. higher than default (KMEMTRACE_N_SUBBUFS in code) if
  831. you experience buffer overruns.
  832. movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
  833. is similar to kernelcore except it specifies the
  834. amount of memory used for migratable allocations.
  835. If both kernelcore and movablecore is specified,
  836. then kernelcore will be at *least* the specified
  837. value but may be more. If movablecore on its own
  838. is specified, the administrator must be careful
  839. that the amount of memory usable for all allocations
  840. is not too small.
  841. keepinitrd [HW,ARM]
  842. kstack=N [X86-32,X86-64] Print N words from the kernel stack
  843. in oops dumps.
  844. kgdboc= [HW] kgdb over consoles.
  845. Requires a tty driver that supports console polling.
  846. (only serial suported for now)
  847. Format: <serial_device>[,baud]
  848. kmac= [MIPS] korina ethernet MAC address.
  849. Configure the RouterBoard 532 series on-chip
  850. Ethernet adapter MAC address.
  851. l2cr= [PPC]
  852. l3cr= [PPC]
  853. lapic [X86-32,APIC] Enable the local APIC even if BIOS
  854. disabled it.
  855. lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
  856. C2 power state.
  857. libata.dma= [LIBATA] DMA control
  858. libata.dma=0 Disable all PATA and SATA DMA
  859. libata.dma=1 PATA and SATA Disk DMA only
  860. libata.dma=2 ATAPI (CDROM) DMA only
  861. libata.dma=4 Compact Flash DMA only
  862. Combinations also work, so libata.dma=3 enables DMA
  863. for disks and CDROMs, but not CFs.
  864. libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
  865. when set.
  866. Format: <int>
  867. libata.force= [LIBATA] Force configurations. The format is comma
  868. separated list of "[ID:]VAL" where ID is
  869. PORT[:DEVICE]. PORT and DEVICE are decimal numbers
  870. matching port, link or device. Basically, it matches
  871. the ATA ID string printed on console by libata. If
  872. the whole ID part is omitted, the last PORT and DEVICE
  873. values are used. If ID hasn't been specified yet, the
  874. configuration applies to all ports, links and devices.
  875. If only DEVICE is omitted, the parameter applies to
  876. the port and all links and devices behind it. DEVICE
  877. number of 0 either selects the first device or the
  878. first fan-out link behind PMP device. It does not
  879. select the host link. DEVICE number of 15 selects the
  880. host link and device attached to it.
  881. The VAL specifies the configuration to force. As long
  882. as there's no ambiguity shortcut notation is allowed.
  883. For example, both 1.5 and 1.5G would work for 1.5Gbps.
  884. The following configurations can be forced.
  885. * Cable type: 40c, 80c, short40c, unk, ign or sata.
  886. Any ID with matching PORT is used.
  887. * SATA link speed limit: 1.5Gbps or 3.0Gbps.
  888. * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
  889. udma[/][16,25,33,44,66,100,133] notation is also
  890. allowed.
  891. * [no]ncq: Turn on or off NCQ.
  892. * nohrst, nosrst, norst: suppress hard, soft
  893. and both resets.
  894. If there are multiple matching configurations changing
  895. the same attribute, the last one is used.
  896. load_ramdisk= [RAM] List of ramdisks to load from floppy
  897. See Documentation/blockdev/ramdisk.txt.
  898. lockd.nlm_grace_period=P [NFS] Assign grace period.
  899. Format: <integer>
  900. lockd.nlm_tcpport=N [NFS] Assign TCP port.
  901. Format: <integer>
  902. lockd.nlm_timeout=T [NFS] Assign timeout value.
  903. Format: <integer>
  904. lockd.nlm_udpport=M [NFS] Assign UDP port.
  905. Format: <integer>
  906. logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
  907. Format: <irq>
  908. loglevel= All Kernel Messages with a loglevel smaller than the
  909. console loglevel will be printed to the console. It can
  910. also be changed with klogd or other programs. The
  911. loglevels are defined as follows:
  912. 0 (KERN_EMERG) system is unusable
  913. 1 (KERN_ALERT) action must be taken immediately
  914. 2 (KERN_CRIT) critical conditions
  915. 3 (KERN_ERR) error conditions
  916. 4 (KERN_WARNING) warning conditions
  917. 5 (KERN_NOTICE) normal but significant condition
  918. 6 (KERN_INFO) informational
  919. 7 (KERN_DEBUG) debug-level messages
  920. log_buf_len=n Sets the size of the printk ring buffer, in bytes.
  921. Format: { n | nk | nM }
  922. n must be a power of two. The default size
  923. is set in the kernel config file.
  924. logo.nologo [FB] Disables display of the built-in Linux logo.
  925. This may be used to provide more screen space for
  926. kernel log messages and is useful when debugging
  927. kernel boot problems.
  928. lp=0 [LP] Specify parallel ports to use, e.g,
  929. lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
  930. lp=reset first parallel port). 'lp=0' disables the
  931. lp=auto printer driver. 'lp=reset' (which can be
  932. specified in addition to the ports) causes
  933. attached printers to be reset. Using
  934. lp=port1,port2,... specifies the parallel ports
  935. to associate lp devices with, starting with
  936. lp0. A port specification may be 'none' to skip
  937. that lp device, or a parport name such as
  938. 'parport0'. Specifying 'lp=auto' instead of a
  939. port specification list means that device IDs
  940. from each port should be examined, to see if
  941. an IEEE 1284-compliant printer is attached; if
  942. so, the driver will manage that printer.
  943. See also header of drivers/char/lp.c.
  944. lpj=n [KNL]
  945. Sets loops_per_jiffy to given constant, thus avoiding
  946. time-consuming boot-time autodetection (up to 250 ms per
  947. CPU). 0 enables autodetection (default). To determine
  948. the correct value for your kernel, boot with normal
  949. autodetection and see what value is printed. Note that
  950. on SMP systems the preset will be applied to all CPUs,
  951. which is likely to cause problems if your CPUs need
  952. significantly divergent settings. An incorrect value
  953. will cause delays in the kernel to be wrong, leading to
  954. unpredictable I/O errors and other breakage. Although
  955. unlikely, in the extreme case this might damage your
  956. hardware.
  957. ltpc= [NET]
  958. Format: <io>,<irq>,<dma>
  959. mac5380= [HW,SCSI] Format:
  960. <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
  961. machvec= [IA64] Force the use of a particular machine-vector
  962. (machvec) in a generic kernel.
  963. Example: machvec=hpzx1_swiotlb
  964. max_loop= [LOOP] Maximum number of loopback devices that can
  965. be mounted
  966. Format: <1-256>
  967. maxcpus= [SMP] Maximum number of processors that an SMP kernel
  968. should make use of. maxcpus=n : n >= 0 limits the
  969. kernel to using 'n' processors. n=0 is a special case,
  970. it is equivalent to "nosmp", which also disables
  971. the IO APIC.
  972. max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater than
  973. or equal to this physical address is ignored.
  974. max_luns= [SCSI] Maximum number of LUNs to probe.
  975. Should be between 1 and 2^32-1.
  976. max_report_luns=
  977. [SCSI] Maximum number of LUNs received.
  978. Should be between 1 and 16384.
  979. mcatest= [IA-64]
  980. mce [X86-32] Machine Check Exception
  981. mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
  982. md= [HW] RAID subsystems devices and level
  983. See Documentation/md.txt.
  984. mdacon= [MDA]
  985. Format: <first>,<last>
  986. Specifies range of consoles to be captured by the MDA.
  987. mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
  988. Amount of memory to be used when the kernel is not able
  989. to see the whole system memory or for test.
  990. [X86-32] Use together with memmap= to avoid physical
  991. address space collisions. Without memmap= PCI devices
  992. could be placed at addresses belonging to unused RAM.
  993. mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
  994. memory.
  995. memchunk=nn[KMG]
  996. [KNL,SH] Allow user to override the default size for
  997. per-device physically contiguous DMA buffers.
  998. memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
  999. E820 memory map, as specified by the user.
  1000. Such memmap=exactmap lines can be constructed based on
  1001. BIOS output or other requirements. See the memmap=nn@ss
  1002. option description.
  1003. memmap=nn[KMG]@ss[KMG]
  1004. [KNL] Force usage of a specific region of memory
  1005. Region of memory to be used, from ss to ss+nn.
  1006. memmap=nn[KMG]#ss[KMG]
  1007. [KNL,ACPI] Mark specific memory as ACPI data.
  1008. Region of memory to be used, from ss to ss+nn.
  1009. memmap=nn[KMG]$ss[KMG]
  1010. [KNL,ACPI] Mark specific memory as reserved.
  1011. Region of memory to be used, from ss to ss+nn.
  1012. Example: Exclude memory from 0x18690000-0x1869ffff
  1013. memmap=64K$0x18690000
  1014. or
  1015. memmap=0x10000$0x18690000
  1016. memory_corruption_check=0/1 [X86]
  1017. Some BIOSes seem to corrupt the first 64k of
  1018. memory when doing things like suspend/resume.
  1019. Setting this option will scan the memory
  1020. looking for corruption. Enabling this will
  1021. both detect corruption and prevent the kernel
  1022. from using the memory being corrupted.
  1023. However, its intended as a diagnostic tool; if
  1024. repeatable BIOS-originated corruption always
  1025. affects the same memory, you can use memmap=
  1026. to prevent the kernel from using that memory.
  1027. memory_corruption_check_size=size [X86]
  1028. By default it checks for corruption in the low
  1029. 64k, making this memory unavailable for normal
  1030. use. Use this parameter to scan for
  1031. corruption in more or less memory.
  1032. memory_corruption_check_period=seconds [X86]
  1033. By default it checks for corruption every 60
  1034. seconds. Use this parameter to check at some
  1035. other rate. 0 disables periodic checking.
  1036. memtest= [KNL,X86] Enable memtest
  1037. Format: <integer>
  1038. range: 0,4 : pattern number
  1039. default : 0 <disable>
  1040. meye.*= [HW] Set MotionEye Camera parameters
  1041. See Documentation/video4linux/meye.txt.
  1042. mfgpt_irq= [IA-32] Specify the IRQ to use for the
  1043. Multi-Function General Purpose Timers on AMD Geode
  1044. platforms.
  1045. mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
  1046. the BIOS has incorrectly applied a workaround. TinyBIOS
  1047. version 0.98 is known to be affected, 0.99 fixes the
  1048. problem by letting the user disable the workaround.
  1049. mga= [HW,DRM]
  1050. min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
  1051. physical address is ignored.
  1052. mminit_loglevel=
  1053. [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
  1054. parameter allows control of the logging verbosity for
  1055. the additional memory initialisation checks. A value
  1056. of 0 disables mminit logging and a level of 4 will
  1057. log everything. Information is printed at KERN_DEBUG
  1058. so loglevel=8 may also need to be specified.
  1059. mousedev.tap_time=
  1060. [MOUSE] Maximum time between finger touching and
  1061. leaving touchpad surface for touch to be considered
  1062. a tap and be reported as a left button click (for
  1063. touchpads working in absolute mode only).
  1064. Format: <msecs>
  1065. mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
  1066. reporting absolute coordinates, such as tablets
  1067. mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
  1068. reporting absolute coordinates, such as tablets
  1069. mpu401= [HW,OSS]
  1070. Format: <io>,<irq>
  1071. MTD_Partition= [MTD]
  1072. Format: <name>,<region-number>,<size>,<offset>
  1073. MTD_Region= [MTD] Format:
  1074. <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
  1075. mtdparts= [MTD]
  1076. See drivers/mtd/cmdlinepart.c.
  1077. mtdset= [ARM]
  1078. ARM/S3C2412 JIVE boot control
  1079. See arch/arm/mach-s3c2412/mach-jive.c
  1080. mtouchusb.raw_coordinates=
  1081. [HW] Make the MicroTouch USB driver use raw coordinates
  1082. ('y', default) or cooked coordinates ('n')
  1083. n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
  1084. NCR_D700= [HW,SCSI]
  1085. See header of drivers/scsi/NCR_D700.c.
  1086. ncr5380= [HW,SCSI]
  1087. ncr53c400= [HW,SCSI]
  1088. ncr53c400a= [HW,SCSI]
  1089. ncr53c406a= [HW,SCSI]
  1090. ncr53c8xx= [HW,SCSI]
  1091. netdev= [NET] Network devices parameters
  1092. Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
  1093. Note that mem_start is often overloaded to mean
  1094. something different and driver-specific.
  1095. This usage is only documented in each driver source
  1096. file if at all.
  1097. nf_conntrack.acct=
  1098. [NETFILTER] Enable connection tracking flow accounting
  1099. 0 to disable accounting
  1100. 1 to enable accounting
  1101. Default value depends on CONFIG_NF_CT_ACCT that is
  1102. going to be removed in 2.6.29.
  1103. nfsaddrs= [NFS]
  1104. See Documentation/filesystems/nfsroot.txt.
  1105. nfsroot= [NFS] nfs root filesystem for disk-less boxes.
  1106. See Documentation/filesystems/nfsroot.txt.
  1107. nfs.callback_tcpport=
  1108. [NFS] set the TCP port on which the NFSv4 callback
  1109. channel should listen.
  1110. nfs.idmap_cache_timeout=
  1111. [NFS] set the maximum lifetime for idmapper cache
  1112. entries.
  1113. nfs.enable_ino64=
  1114. [NFS] enable 64-bit inode numbers.
  1115. If zero, the NFS client will fake up a 32-bit inode
  1116. number for the readdir() and stat() syscalls instead
  1117. of returning the full 64-bit number.
  1118. The default is to return 64-bit inode numbers.
  1119. nmi_debug= [KNL,AVR32] Specify one or more actions to take
  1120. when a NMI is triggered.
  1121. Format: [state][,regs][,debounce][,die]
  1122. nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
  1123. no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
  1124. emulation library even if a 387 maths coprocessor
  1125. is present.
  1126. noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
  1127. caches in the slab allocator. Saves per-node memory,
  1128. but will impact performance.
  1129. noalign [KNL,ARM]
  1130. noapic [SMP,APIC] Tells the kernel to not make use of any
  1131. IOAPICs that may be present in the system.
  1132. nobats [PPC] Do not use BATs for mapping kernel lowmem
  1133. on "Classic" PPC cores.
  1134. nocache [ARM]
  1135. nodelayacct [KNL] Disable per-task delay accounting
  1136. nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
  1137. nodsp [SH] Disable hardware DSP at boot time.
  1138. noefi [X86-32,X86-64] Disable EFI runtime services support.
  1139. noexec [IA-64]
  1140. noexec [X86-32,X86-64]
  1141. On X86-32 available only on PAE configured kernels.
  1142. noexec=on: enable non-executable mappings (default)
  1143. noexec=off: disable non-executable mappings
  1144. noexec32 [X86-64]
  1145. This affects only 32-bit executables.
  1146. noexec32=on: enable non-executable mappings (default)
  1147. read doesn't imply executable mappings
  1148. noexec32=off: disable non-executable mappings
  1149. read implies executable mappings
  1150. nofpu [SH] Disable hardware FPU at boot time.
  1151. nofxsr [BUGS=X86-32] Disables x86 floating point extended
  1152. register save and restore. The kernel will only save
  1153. legacy floating-point registers on task switch.
  1154. noclflush [BUGS=X86] Don't use the CLFLUSH instruction
  1155. nohlt [BUGS=ARM,SH]
  1156. no-hlt [BUGS=X86-32] Tells the kernel that the hlt
  1157. instruction doesn't work correctly and not to
  1158. use it.
  1159. nohalt [IA-64] Tells the kernel not to use the power saving
  1160. function PAL_HALT_LIGHT when idle. This increases
  1161. power-consumption. On the positive side, it reduces
  1162. interrupt wake-up latency, which may improve performance
  1163. in certain environments such as networked servers or
  1164. real-time systems.
  1165. nohz= [KNL] Boottime enable/disable dynamic ticks
  1166. Valid arguments: on, off
  1167. Default: on
  1168. noirqdebug [X86-32] Disables the code which attempts to detect and
  1169. disable unhandled interrupt sources.
  1170. no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
  1171. broken timer IRQ sources.
  1172. noisapnp [ISAPNP] Disables ISA PnP code.
  1173. noinitrd [RAM] Tells the kernel not to load any configured
  1174. initial RAM disk.
  1175. nointroute [IA-64]
  1176. nojitter [IA64] Disables jitter checking for ITC timers.
  1177. nolapic [X86-32,APIC] Do not enable or use the local APIC.
  1178. nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
  1179. nox2apic [X86-64,APIC] Do not enable x2APIC mode.
  1180. x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
  1181. default x2apic cluster mode on platforms
  1182. supporting x2apic.
  1183. noltlbs [PPC] Do not use large page/tlb entries for kernel
  1184. lowmem mapping on PPC40x.
  1185. nomca [IA-64] Disable machine check abort handling
  1186. nomce [X86-32] Machine Check Exception
  1187. nomfgpt [X86-32] Disable Multi-Function General Purpose
  1188. Timer usage (for AMD Geode machines).
  1189. noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
  1190. noreplace-smp [X86-32,SMP] Don't replace SMP instructions
  1191. with UP alternatives
  1192. noresidual [PPC] Don't use residual data on PReP machines.
  1193. noresume [SWSUSP] Disables resume and restores original swap
  1194. space.
  1195. no-scroll [VGA] Disables scrollback.
  1196. This is required for the Braillex ib80-piezo Braille
  1197. reader made by F.H. Papenmeier (Germany).
  1198. nosbagart [IA-64]
  1199. nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
  1200. nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
  1201. and disable the IO APIC. legacy for "maxcpus=0".
  1202. nosoftlockup [KNL] Disable the soft-lockup detector.
  1203. nosync [HW,M68K] Disables sync negotiation for all devices.
  1204. notsc [BUGS=X86-32] Disable Time Stamp Counter
  1205. nousb [USB] Disable the USB subsystem
  1206. nowb [ARM]
  1207. nptcg= [IA64] Override max number of concurrent global TLB
  1208. purges which is reported from either PAL_VM_SUMMARY or
  1209. SAL PALO.
  1210. numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
  1211. one of ['zone', 'node', 'default'] can be specified
  1212. This can be set from sysctl after boot.
  1213. See Documentation/sysctl/vm.txt for details.
  1214. nr_uarts= [SERIAL] maximum number of UARTs to be registered.
  1215. olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
  1216. Rather than timing out after 20 ms if an EC
  1217. command is not properly ACKed, override the length
  1218. of the timeout. We have interrupts disabled while
  1219. waiting for the ACK, so if this is set too high
  1220. interrupts *may* be lost!
  1221. opl3= [HW,OSS]
  1222. Format: <io>
  1223. oprofile.timer= [HW]
  1224. Use timer interrupt instead of performance counters
  1225. osst= [HW,SCSI] SCSI Tape Driver
  1226. Format: <buffer_size>,<write_threshold>
  1227. See also Documentation/scsi/st.txt.
  1228. panic= [KNL] Kernel behaviour on panic
  1229. Format: <timeout>
  1230. parkbd.port= [HW] Parallel port number the keyboard adapter is
  1231. connected to, default is 0.
  1232. Format: <parport#>
  1233. parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
  1234. 0 for XT, 1 for AT (default is AT).
  1235. Format: <mode>
  1236. parport= [HW,PPT] Specify parallel ports. 0 disables.
  1237. Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
  1238. Use 'auto' to force the driver to use any
  1239. IRQ/DMA settings detected (the default is to
  1240. ignore detected IRQ/DMA settings because of
  1241. possible conflicts). You can specify the base
  1242. address, IRQ, and DMA settings; IRQ and DMA
  1243. should be numbers, or 'auto' (for using detected
  1244. settings on that particular port), or 'nofifo'
  1245. (to avoid using a FIFO even if it is detected).
  1246. Parallel ports are assigned in the order they
  1247. are specified on the command line, starting
  1248. with parport0.
  1249. parport_init_mode= [HW,PPT]
  1250. Configure VIA parallel port to operate in
  1251. a specific mode. This is necessary on Pegasos
  1252. computer where firmware has no options for setting
  1253. up parallel port mode and sets it to spp.
  1254. Currently this function knows 686a and 8231 chips.
  1255. Format: [spp|ps2|epp|ecp|ecpepp]
  1256. pas2= [HW,OSS] Format:
  1257. <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
  1258. pas16= [HW,SCSI]
  1259. See header of drivers/scsi/pas16.c.
  1260. pause_on_oops=
  1261. Halt all CPUs after the first oops has been printed for
  1262. the specified number of seconds. This is to be used if
  1263. your oopses keep scrolling off the screen.
  1264. pcbit= [HW,ISDN]
  1265. pcd. [PARIDE]
  1266. See header of drivers/block/paride/pcd.c.
  1267. See also Documentation/blockdev/paride.txt.
  1268. pci=option[,option...] [PCI] various PCI subsystem options:
  1269. off [X86] don't probe for the PCI bus
  1270. bios [X86-32] force use of PCI BIOS, don't access
  1271. the hardware directly. Use this if your machine
  1272. has a non-standard PCI host bridge.
  1273. nobios [X86-32] disallow use of PCI BIOS, only direct
  1274. hardware access methods are allowed. Use this
  1275. if you experience crashes upon bootup and you
  1276. suspect they are caused by the BIOS.
  1277. conf1 [X86] Force use of PCI Configuration
  1278. Mechanism 1.
  1279. conf2 [X86] Force use of PCI Configuration
  1280. Mechanism 2.
  1281. noaer [PCIE] If the PCIEAER kernel config parameter is
  1282. enabled, this kernel boot option can be used to
  1283. disable the use of PCIE advanced error reporting.
  1284. nodomains [PCI] Disable support for multiple PCI
  1285. root domains (aka PCI segments, in ACPI-speak).
  1286. nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
  1287. Configuration
  1288. nomsi [MSI] If the PCI_MSI kernel config parameter is
  1289. enabled, this kernel boot option can be used to
  1290. disable the use of MSI interrupts system-wide.
  1291. biosirq [X86-32] Use PCI BIOS calls to get the interrupt
  1292. routing table. These calls are known to be buggy
  1293. on several machines and they hang the machine
  1294. when used, but on other computers it's the only
  1295. way to get the interrupt routing table. Try
  1296. this option if the kernel is unable to allocate
  1297. IRQs or discover secondary PCI buses on your
  1298. motherboard.
  1299. rom [X86] Assign address space to expansion ROMs.
  1300. Use with caution as certain devices share
  1301. address decoders between ROMs and other
  1302. resources.
  1303. norom [X86] Do not assign address space to
  1304. expansion ROMs that do not already have
  1305. BIOS assigned address ranges.
  1306. irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
  1307. assigned automatically to PCI devices. You can
  1308. make the kernel exclude IRQs of your ISA cards
  1309. this way.
  1310. pirqaddr=0xAAAAA [X86] Specify the physical address
  1311. of the PIRQ table (normally generated
  1312. by the BIOS) if it is outside the
  1313. F0000h-100000h range.
  1314. lastbus=N [X86] Scan all buses thru bus #N. Can be
  1315. useful if the kernel is unable to find your
  1316. secondary buses and you want to tell it
  1317. explicitly which ones they are.
  1318. assign-busses [X86] Always assign all PCI bus
  1319. numbers ourselves, overriding
  1320. whatever the firmware may have done.
  1321. usepirqmask [X86] Honor the possible IRQ mask stored
  1322. in the BIOS $PIR table. This is needed on
  1323. some systems with broken BIOSes, notably
  1324. some HP Pavilion N5400 and Omnibook XE3
  1325. notebooks. This will have no effect if ACPI
  1326. IRQ routing is enabled.
  1327. noacpi [X86] Do not use ACPI for IRQ routing
  1328. or for PCI scanning.
  1329. use_crs [X86] Use _CRS for PCI resource
  1330. allocation.
  1331. routeirq Do IRQ routing for all PCI devices.
  1332. This is normally done in pci_enable_device(),
  1333. so this option is a temporary workaround
  1334. for broken drivers that don't call it.
  1335. skip_isa_align [X86] do not align io start addr, so can
  1336. handle more pci cards
  1337. firmware [ARM] Do not re-enumerate the bus but instead
  1338. just use the configuration from the
  1339. bootloader. This is currently used on
  1340. IXP2000 systems where the bus has to be
  1341. configured a certain way for adjunct CPUs.
  1342. noearly [X86] Don't do any early type 1 scanning.
  1343. This might help on some broken boards which
  1344. machine check when some devices' config space
  1345. is read. But various workarounds are disabled
  1346. and some IOMMU drivers will not work.
  1347. bfsort Sort PCI devices into breadth-first order.
  1348. This sorting is done to get a device
  1349. order compatible with older (<= 2.4) kernels.
  1350. nobfsort Don't sort PCI devices into breadth-first order.
  1351. cbiosize=nn[KMG] The fixed amount of bus space which is
  1352. reserved for the CardBus bridge's IO window.
  1353. The default value is 256 bytes.
  1354. cbmemsize=nn[KMG] The fixed amount of bus space which is
  1355. reserved for the CardBus bridge's memory
  1356. window. The default value is 64 megabytes.
  1357. pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
  1358. Management.
  1359. off Disable ASPM.
  1360. force Enable ASPM even on devices that claim not to support it.
  1361. WARNING: Forcing ASPM on may cause system lockups.
  1362. pcmv= [HW,PCMCIA] BadgePAD 4
  1363. pd. [PARIDE]
  1364. See Documentation/blockdev/paride.txt.
  1365. pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
  1366. boot time.
  1367. Format: { 0 | 1 }
  1368. See arch/parisc/kernel/pdc_chassis.c
  1369. pf. [PARIDE]
  1370. See Documentation/blockdev/paride.txt.
  1371. pg. [PARIDE]
  1372. See Documentation/blockdev/paride.txt.
  1373. pirq= [SMP,APIC] Manual mp-table setup
  1374. See Documentation/x86/i386/IO-APIC.txt.
  1375. plip= [PPT,NET] Parallel port network link
  1376. Format: { parport<nr> | timid | 0 }
  1377. See also Documentation/parport.txt.
  1378. pmtmr= [X86] Manual setup of pmtmr I/O Port.
  1379. Override pmtimer IOPort with a hex value.
  1380. e.g. pmtmr=0x508
  1381. pnp.debug [PNP]
  1382. Enable PNP debug messages. This depends on the
  1383. CONFIG_PNP_DEBUG_MESSAGES option.
  1384. pnpacpi= [ACPI]
  1385. { off }
  1386. pnpbios= [ISAPNP]
  1387. { on | off | curr | res | no-curr | no-res }
  1388. pnp_reserve_irq=
  1389. [ISAPNP] Exclude IRQs for the autoconfiguration
  1390. pnp_reserve_dma=
  1391. [ISAPNP] Exclude DMAs for the autoconfiguration
  1392. pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
  1393. Ranges are in pairs (I/O port base and size).
  1394. pnp_reserve_mem=
  1395. [ISAPNP] Exclude memory regions for the
  1396. autoconfiguration.
  1397. Ranges are in pairs (memory base and size).
  1398. dynamic_printk
  1399. Enables pr_debug()/dev_dbg() calls if
  1400. CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. These can also
  1401. be switched on/off via <debugfs>/dynamic_printk/modules
  1402. print-fatal-signals=
  1403. [KNL] debug: print fatal signals
  1404. print-fatal-signals=1: print segfault info to
  1405. the kernel console.
  1406. default: off.
  1407. printk.time= Show timing data prefixed to each printk message line
  1408. Format: <bool> (1/Y/y=enable, 0/N/n=disable)
  1409. profile= [KNL] Enable kernel profiling via /proc/profile
  1410. Format: [schedule,]<number>
  1411. Param: "schedule" - profile schedule points.
  1412. Param: <number> - step/bucket size as a power of 2 for
  1413. statistical time based profiling.
  1414. Param: "sleep" - profile D-state sleeping (millisecs).
  1415. Requires CONFIG_SCHEDSTATS
  1416. Param: "kvm" - profile VM exits.
  1417. processor.max_cstate= [HW,ACPI]
  1418. Limit processor to maximum C-state
  1419. max_cstate=9 overrides any DMI blacklist limit.
  1420. processor.nocst [HW,ACPI]
  1421. Ignore the _CST method to determine C-states,
  1422. instead using the legacy FADT method
  1423. prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
  1424. before loading.
  1425. See Documentation/blockdev/ramdisk.txt.
  1426. psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
  1427. probe for; one of (bare|imps|exps|lifebook|any).
  1428. psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
  1429. per second.
  1430. psmouse.resetafter= [HW,MOUSE]
  1431. Try to reset the device after so many bad packets
  1432. (0 = never).
  1433. psmouse.resolution=
  1434. [HW,MOUSE] Set desired mouse resolution, in dpi.
  1435. psmouse.smartscroll=
  1436. [HW,MOUSE] Controls Logitech smartscroll autorepeat.
  1437. 0 = disabled, 1 = enabled (default).
  1438. pss= [HW,OSS] Personal Sound System (ECHO ESC614)
  1439. Format:
  1440. <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
  1441. pt. [PARIDE]
  1442. See Documentation/blockdev/paride.txt.
  1443. pty.legacy_count=
  1444. [KNL] Number of legacy pty's. Overwrites compiled-in
  1445. default number.
  1446. quiet [KNL] Disable most log messages
  1447. r128= [HW,DRM]
  1448. raid= [HW,RAID]
  1449. See Documentation/md.txt.
  1450. ramdisk_blocksize= [RAM]
  1451. See Documentation/blockdev/ramdisk.txt.
  1452. ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
  1453. See Documentation/blockdev/ramdisk.txt.
  1454. rcupdate.blimit= [KNL,BOOT]
  1455. Set maximum number of finished RCU callbacks to process
  1456. in one batch.
  1457. rcupdate.qhimark= [KNL,BOOT]
  1458. Set threshold of queued
  1459. RCU callbacks over which batch limiting is disabled.
  1460. rcupdate.qlowmark= [KNL,BOOT]
  1461. Set threshold of queued RCU callbacks below which
  1462. batch limiting is re-enabled.
  1463. rdinit= [KNL]
  1464. Format: <full_path>
  1465. Run specified binary instead of /init from the ramdisk,
  1466. used for early userspace startup. See initrd.
  1467. reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
  1468. Format: <reboot_mode>[,<reboot_mode2>[,...]]
  1469. See arch/*/kernel/reboot.c or arch/*/kernel/process.c
  1470. relax_domain_level=
  1471. [KNL, SMP] Set scheduler's default relax_domain_level.
  1472. See Documentation/cpusets.txt.
  1473. reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
  1474. reservetop= [X86-32]
  1475. Format: nn[KMG]
  1476. Reserves a hole at the top of the kernel virtual
  1477. address space.
  1478. reset_devices [KNL] Force drivers to reset the underlying device
  1479. during initialization.
  1480. resume= [SWSUSP]
  1481. Specify the partition device for software suspend
  1482. resume_offset= [SWSUSP]
  1483. Specify the offset from the beginning of the partition
  1484. given by "resume=" at which the swap header is located,
  1485. in <PAGE_SIZE> units (needed only for swap files).
  1486. See Documentation/power/swsusp-and-swap-files.txt
  1487. retain_initrd [RAM] Keep initrd memory after extraction
  1488. rhash_entries= [KNL,NET]
  1489. Set number of hash buckets for route cache
  1490. riscom8= [HW,SERIAL]
  1491. Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
  1492. ro [KNL] Mount root device read-only on boot
  1493. root= [KNL] Root filesystem
  1494. rootdelay= [KNL] Delay (in seconds) to pause before attempting to
  1495. mount the root filesystem
  1496. rootflags= [KNL] Set root filesystem mount option string
  1497. rootfstype= [KNL] Set root filesystem type
  1498. rootwait [KNL] Wait (indefinitely) for root device to show up.
  1499. Useful for devices that are detected asynchronously
  1500. (e.g. USB and MMC devices).
  1501. root_plug.vendor_id=
  1502. [ROOTPLUG] Override the default vendor ID
  1503. root_plug.product_id=
  1504. [ROOTPLUG] Override the default product ID
  1505. root_plug.debug=
  1506. [ROOTPLUG] Enable debugging output
  1507. rw [KNL] Mount root device read-write on boot
  1508. S [KNL] Run init in single mode
  1509. sa1100ir [NET]
  1510. See drivers/net/irda/sa1100_ir.c.
  1511. sbni= [NET] Granch SBNI12 leased line adapter
  1512. sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
  1513. Format: <io>[,<timeout>[,<isapnp>]]
  1514. scsi_debug_*= [SCSI]
  1515. See drivers/scsi/scsi_debug.c.
  1516. scsi_default_dev_flags=
  1517. [SCSI] SCSI default device flags
  1518. Format: <integer>
  1519. scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
  1520. Format: <vendor>:<model>:<flags>
  1521. (flags are integer value)
  1522. scsi_logging_level= [SCSI] a bit mask of logging levels
  1523. See drivers/scsi/scsi_logging.h for bits. Also
  1524. settable via sysctl at dev.scsi.logging_level
  1525. (/proc/sys/dev/scsi/logging_level).
  1526. There is also a nice 'scsi_logging_level' script in the
  1527. S390-tools package, available for download at
  1528. http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
  1529. scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
  1530. discovered. async scans them in kernel threads,
  1531. allowing boot to proceed. none ignores them, expecting
  1532. user space to do the scan.
  1533. selinux [SELINUX] Disable or enable SELinux at boot time.
  1534. Format: { "0" | "1" }
  1535. See security/selinux/Kconfig help text.
  1536. 0 -- disable.
  1537. 1 -- enable.
  1538. Default value is set via kernel config option.
  1539. If enabled at boot time, /selinux/disable can be used
  1540. later to disable prior to initial policy load.
  1541. selinux_compat_net =
  1542. [SELINUX] Set initial selinux_compat_net flag value.
  1543. Format: { "0" | "1" }
  1544. 0 -- use new secmark-based packet controls
  1545. 1 -- use legacy packet controls
  1546. Default value is 0 (preferred).
  1547. Value can be changed at runtime via
  1548. /selinux/compat_net.
  1549. serialnumber [BUGS=X86-32]
  1550. shapers= [NET]
  1551. Maximal number of shapers.
  1552. show_msr= [x86] show boot-time MSR settings
  1553. Format: { <integer> }
  1554. Show boot-time (BIOS-initialized) MSR settings.
  1555. The parameter means the number of CPUs to show,
  1556. for example 1 means boot CPU only.
  1557. sim710= [SCSI,HW]
  1558. See header of drivers/scsi/sim710.c.
  1559. simeth= [IA-64]
  1560. simscsi=
  1561. slram= [HW,MTD]
  1562. slub_debug[=options[,slabs]] [MM, SLUB]
  1563. Enabling slub_debug allows one to determine the
  1564. culprit if slab objects become corrupted. Enabling
  1565. slub_debug can create guard zones around objects and
  1566. may poison objects when not in use. Also tracks the
  1567. last alloc / free. For more information see
  1568. Documentation/vm/slub.txt.
  1569. slub_max_order= [MM, SLUB]
  1570. Determines the maximum allowed order for slabs.
  1571. A high setting may cause OOMs due to memory
  1572. fragmentation. For more information see
  1573. Documentation/vm/slub.txt.
  1574. slub_min_objects= [MM, SLUB]
  1575. The minimum number of objects per slab. SLUB will
  1576. increase the slab order up to slub_max_order to
  1577. generate a sufficiently large slab able to contain
  1578. the number of objects indicated. The higher the number
  1579. of objects the smaller the overhead of tracking slabs
  1580. and the less frequently locks need to be acquired.
  1581. For more information see Documentation/vm/slub.txt.
  1582. slub_min_order= [MM, SLUB]
  1583. Determines the mininum page order for slabs. Must be
  1584. lower than slub_max_order.
  1585. For more information see Documentation/vm/slub.txt.
  1586. slub_nomerge [MM, SLUB]
  1587. Disable merging of slabs with similar size. May be
  1588. necessary if there is some reason to distinguish
  1589. allocs to different slabs. Debug options disable
  1590. merging on their own.
  1591. For more information see Documentation/vm/slub.txt.
  1592. smart2= [HW]
  1593. Format: <io1>[,<io2>[,...,<io8>]]
  1594. smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
  1595. attempt to substitute SMP alternatives once at boot.
  1596. smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
  1597. smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
  1598. smsc-ircc2.ircc_sir= [HW] SIR base I/O port
  1599. smsc-ircc2.ircc_fir= [HW] FIR base I/O port
  1600. smsc-ircc2.ircc_irq= [HW] IRQ line
  1601. smsc-ircc2.ircc_dma= [HW] DMA channel
  1602. smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
  1603. 0: Toshiba Satellite 1800 (GP data pin select)
  1604. 1: Fast pin select (default)
  1605. 2: ATC IRMode
  1606. snd-ad1816a= [HW,ALSA]
  1607. snd-ad1848= [HW,ALSA]
  1608. snd-ali5451= [HW,ALSA]
  1609. snd-als100= [HW,ALSA]
  1610. snd-als4000= [HW,ALSA]
  1611. snd-azt2320= [HW,ALSA]
  1612. snd-cmi8330= [HW,ALSA]
  1613. snd-cmipci= [HW,ALSA]
  1614. snd-cs4231= [HW,ALSA]
  1615. snd-cs4232= [HW,ALSA]
  1616. snd-cs4236= [HW,ALSA]
  1617. snd-cs4281= [HW,ALSA]
  1618. snd-cs46xx= [HW,ALSA]
  1619. snd-dt019x= [HW,ALSA]
  1620. snd-dummy= [HW,ALSA]
  1621. snd-emu10k1= [HW,ALSA]
  1622. snd-ens1370= [HW,ALSA]
  1623. snd-ens1371= [HW,ALSA]
  1624. snd-es968= [HW,ALSA]
  1625. snd-es1688= [HW,ALSA]
  1626. snd-es18xx= [HW,ALSA]
  1627. snd-es1938= [HW,ALSA]
  1628. snd-es1968= [HW,ALSA]
  1629. snd-fm801= [HW,ALSA]
  1630. snd-gusclassic= [HW,ALSA]
  1631. snd-gusextreme= [HW,ALSA]
  1632. snd-gusmax= [HW,ALSA]
  1633. snd-hdsp= [HW,ALSA]
  1634. snd-ice1712= [HW,ALSA]
  1635. snd-intel8x0= [HW,ALSA]
  1636. snd-interwave= [HW,ALSA]
  1637. snd-interwave-stb=
  1638. [HW,ALSA]
  1639. snd-korg1212= [HW,ALSA]
  1640. snd-maestro3= [HW,ALSA]
  1641. snd-mpu401= [HW,ALSA]
  1642. snd-mtpav= [HW,ALSA]
  1643. snd-nm256= [HW,ALSA]
  1644. snd-opl3sa2= [HW,ALSA]
  1645. snd-opti92x-ad1848=
  1646. [HW,ALSA]
  1647. snd-opti92x-cs4231=
  1648. [HW,ALSA]
  1649. snd-opti93x= [HW,ALSA]
  1650. snd-pmac= [HW,ALSA]
  1651. snd-rme32= [HW,ALSA]
  1652. snd-rme96= [HW,ALSA]
  1653. snd-rme9652= [HW,ALSA]
  1654. snd-sb8= [HW,ALSA]
  1655. snd-sb16= [HW,ALSA]
  1656. snd-sbawe= [HW,ALSA]
  1657. snd-serial= [HW,ALSA]
  1658. snd-sgalaxy= [HW,ALSA]
  1659. snd-sonicvibes= [HW,ALSA]
  1660. snd-sun-amd7930=
  1661. [HW,ALSA]
  1662. snd-sun-cs4231= [HW,ALSA]
  1663. snd-trident= [HW,ALSA]
  1664. snd-usb-audio= [HW,ALSA,USB]
  1665. snd-via82xx= [HW,ALSA]
  1666. snd-virmidi= [HW,ALSA]
  1667. snd-wavefront= [HW,ALSA]
  1668. snd-ymfpci= [HW,ALSA]
  1669. softlockup_panic=
  1670. [KNL] Should the soft-lockup detector generate panics.
  1671. sonypi.*= [HW] Sony Programmable I/O Control Device driver
  1672. See Documentation/sonypi.txt
  1673. specialix= [HW,SERIAL] Specialix multi-serial port adapter
  1674. See Documentation/serial/specialix.txt.
  1675. spia_io_base= [HW,MTD]
  1676. spia_fio_base=
  1677. spia_pedr=
  1678. spia_peddr=
  1679. sscape= [HW,OSS]
  1680. Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
  1681. st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
  1682. See Documentation/scsi/st.txt.
  1683. sti= [PARISC,HW]
  1684. Format: <num>
  1685. Set the STI (builtin display/keyboard on the HP-PARISC
  1686. machines) console (graphic card) which should be used
  1687. as the initial boot-console.
  1688. See also comment in drivers/video/console/sticore.c.
  1689. sti_font= [HW]
  1690. See comment in drivers/video/console/sticore.c.
  1691. stifb= [HW]
  1692. Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
  1693. sunrpc.pool_mode=
  1694. [NFS]
  1695. Control how the NFS server code allocates CPUs to
  1696. service thread pools. Depending on how many NICs
  1697. you have and where their interrupts are bound, this
  1698. option will affect which CPUs will do NFS serving.
  1699. Note: this parameter cannot be changed while the
  1700. NFS server is running.
  1701. auto the server chooses an appropriate mode
  1702. automatically using heuristics
  1703. global a single global pool contains all CPUs
  1704. percpu one pool for each CPU
  1705. pernode one pool for each NUMA node (equivalent
  1706. to global on non-NUMA machines)
  1707. swiotlb= [IA-64] Number of I/O TLB slabs
  1708. switches= [HW,M68k]
  1709. sym53c416= [HW,SCSI]
  1710. See header of drivers/scsi/sym53c416.c.
  1711. sysrq_always_enabled
  1712. [KNL]
  1713. Ignore sysrq setting - this boot parameter will
  1714. neutralize any effect of /proc/sys/kernel/sysrq.
  1715. Useful for debugging.
  1716. t128= [HW,SCSI]
  1717. See header of drivers/scsi/t128.c.
  1718. tdfx= [HW,DRM]
  1719. test_suspend= [SUSPEND]
  1720. Specify "mem" (for Suspend-to-RAM) or "standby" (for
  1721. standby suspend) as the system sleep state to briefly
  1722. enter during system startup. The system is woken from
  1723. this state using a wakeup-capable RTC alarm.
  1724. thash_entries= [KNL,NET]
  1725. Set number of hash buckets for TCP connection
  1726. thermal.act= [HW,ACPI]
  1727. -1: disable all active trip points in all thermal zones
  1728. <degrees C>: override all lowest active trip points
  1729. thermal.crt= [HW,ACPI]
  1730. -1: disable all critical trip points in all thermal zones
  1731. <degrees C>: override all critical trip points
  1732. thermal.nocrt= [HW,ACPI]
  1733. Set to disable actions on ACPI thermal zone
  1734. critical and hot trip points.
  1735. thermal.off= [HW,ACPI]
  1736. 1: disable ACPI thermal control
  1737. thermal.psv= [HW,ACPI]
  1738. -1: disable all passive trip points
  1739. <degrees C>: override all passive trip points to this value
  1740. thermal.tzp= [HW,ACPI]
  1741. Specify global default ACPI thermal zone polling rate
  1742. <deci-seconds>: poll all this frequency
  1743. 0: no polling (default)
  1744. tmscsim= [HW,SCSI]
  1745. See comment before function dc390_setup() in
  1746. drivers/scsi/tmscsim.c.
  1747. tp720= [HW,PS2]
  1748. trix= [HW,OSS] MediaTrix AudioTrix Pro
  1749. Format:
  1750. <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
  1751. turbografx.map[2|3]= [HW,JOY]
  1752. TurboGraFX parallel port interface
  1753. Format:
  1754. <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
  1755. See also Documentation/input/joystick-parport.txt
  1756. u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
  1757. See header of drivers/scsi/u14-34f.c.
  1758. uart401= [HW,OSS]
  1759. Format: <io>,<irq>
  1760. uart6850= [HW,OSS]
  1761. Format: <io>,<irq>
  1762. uhci-hcd.ignore_oc=
  1763. [USB] Ignore overcurrent events (default N).
  1764. Some badly-designed motherboards generate lots of
  1765. bogus events, for ports that aren't wired to
  1766. anything. Set this parameter to avoid log spamming.
  1767. Note that genuine overcurrent events won't be
  1768. reported either.
  1769. unknown_nmi_panic
  1770. [X86-32,X86-64]
  1771. Set unknown_nmi_panic=1 early on boot.
  1772. usbcore.autosuspend=
  1773. [USB] The autosuspend time delay (in seconds) used
  1774. for newly-detected USB devices (default 2). This
  1775. is the time required before an idle device will be
  1776. autosuspended. Devices for which the delay is set
  1777. to a negative value won't be autosuspended at all.
  1778. usbcore.usbfs_snoop=
  1779. [USB] Set to log all usbfs traffic (default 0 = off).
  1780. usbcore.blinkenlights=
  1781. [USB] Set to cycle leds on hubs (default 0 = off).
  1782. usbcore.old_scheme_first=
  1783. [USB] Start with the old device initialization
  1784. scheme (default 0 = off).
  1785. usbcore.use_both_schemes=
  1786. [USB] Try the other device initialization scheme
  1787. if the first one fails (default 1 = enabled).
  1788. usbcore.initial_descriptor_timeout=
  1789. [USB] Specifies timeout for the initial 64-byte
  1790. USB_REQ_GET_DESCRIPTOR request in milliseconds
  1791. (default 5000 = 5.0 seconds).
  1792. usbhid.mousepoll=
  1793. [USBHID] The interval which mice are to be polled at.
  1794. add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
  1795. kernel's map of available physical RAM.
  1796. vdso= [X86-32,SH,x86-64]
  1797. vdso=2: enable compat VDSO (default with COMPAT_VDSO)
  1798. vdso=1: enable VDSO (default)
  1799. vdso=0: disable VDSO mapping
  1800. vdso32= [X86-32,X86-64]
  1801. vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
  1802. vdso32=1: enable 32-bit VDSO (default)
  1803. vdso32=0: disable 32-bit VDSO mapping
  1804. vector= [IA-64,SMP]
  1805. vector=percpu: enable percpu vector domain
  1806. video= [FB] Frame buffer configuration
  1807. See Documentation/fb/modedb.txt.
  1808. vga= [BOOT,X86-32] Select a particular video mode
  1809. See Documentation/x86/i386/boot.txt and
  1810. Documentation/svga.txt.
  1811. Use vga=ask for menu.
  1812. This is actually a boot loader parameter; the value is
  1813. passed to the kernel using a special protocol.
  1814. vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
  1815. size of <nn>. This can be used to increase the
  1816. minimum size (128MB on x86). It can also be used to
  1817. decrease the size and leave more room for directly
  1818. mapped kernel RAM.
  1819. vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
  1820. Format: <command>
  1821. vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
  1822. Format: <command>
  1823. vmpoff= [KNL,S390] Perform z/VM CP command after power off.
  1824. Format: <command>
  1825. waveartist= [HW,OSS]
  1826. Format: <io>,<irq>,<dma>,<dma2>
  1827. wd33c93= [HW,SCSI]
  1828. See header of drivers/scsi/wd33c93.c.
  1829. wd7000= [HW,SCSI]
  1830. See header of drivers/scsi/wd7000.c.
  1831. wdt= [WDT] Watchdog
  1832. See Documentation/watchdog/wdt.txt.
  1833. xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
  1834. xd_geo= See header of drivers/block/xd.c.
  1835. xirc2ps_cs= [NET,PCMCIA]
  1836. Format:
  1837. <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
  1838. norandmaps Don't use address space randomization
  1839. Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
  1840. ______________________________________________________________________
  1841. TODO:
  1842. Add documentation for ALSA options.
  1843. Add more DRM drivers.