kernel-parameters.txt 88 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. Hyphens (dashes) and underscores are equivalent in parameter names, so
  15. log_buf_len=1M print-fatal-signals=1
  16. can also be entered as
  17. log-buf-len=1M print_fatal_signals=1
  18. This document may not be entirely up to date and comprehensive. The command
  19. "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
  20. module. Loadable modules, after being loaded into the running kernel, also
  21. reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
  22. parameters may be changed at runtime by the command
  23. "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
  24. The parameters listed below are only valid if certain kernel build options were
  25. enabled and if respective hardware is present. The text in square brackets at
  26. the beginning of each description states the restrictions within which a
  27. parameter is applicable:
  28. ACPI ACPI support is enabled.
  29. AGP AGP (Accelerated Graphics Port) is enabled.
  30. ALSA ALSA sound support is enabled.
  31. APIC APIC support is enabled.
  32. APM Advanced Power Management support is enabled.
  33. AVR32 AVR32 architecture is enabled.
  34. AX25 Appropriate AX.25 support is enabled.
  35. BLACKFIN Blackfin architecture is enabled.
  36. DRM Direct Rendering Management support is enabled.
  37. EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
  38. EFI EFI Partitioning (GPT) is enabled
  39. EIDE EIDE/ATAPI support is enabled.
  40. FB The frame buffer device is enabled.
  41. GCOV GCOV profiling is enabled.
  42. HW Appropriate hardware is enabled.
  43. IA-64 IA-64 architecture is enabled.
  44. IMA Integrity measurement architecture is enabled.
  45. IOSCHED More than one I/O scheduler is enabled.
  46. IP_PNP IP DHCP, BOOTP, or RARP is enabled.
  47. ISAPNP ISA PnP code is enabled.
  48. ISDN Appropriate ISDN support is enabled.
  49. JOY Appropriate joystick support is enabled.
  50. KVM Kernel Virtual Machine support is enabled.
  51. LIBATA Libata driver is enabled
  52. LP Printer support is enabled.
  53. LOOP Loopback device support is enabled.
  54. M68k M68k architecture is enabled.
  55. These options have more detailed description inside of
  56. Documentation/m68k/kernel-options.txt.
  57. MCA MCA bus support is enabled.
  58. MDA MDA console support is enabled.
  59. MOUSE Appropriate mouse support is enabled.
  60. MSI Message Signaled Interrupts (PCI).
  61. MTD MTD (Memory Technology Device) support is enabled.
  62. NET Appropriate network support is enabled.
  63. NUMA NUMA support is enabled.
  64. GENERIC_TIME The generic timeofday code is enabled.
  65. NFS Appropriate NFS support is enabled.
  66. OSS OSS sound support is enabled.
  67. PV_OPS A paravirtualized kernel is enabled.
  68. PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
  69. PARISC The PA-RISC architecture is enabled.
  70. PCI PCI bus support is enabled.
  71. PCIE PCI Express support is enabled.
  72. PCMCIA The PCMCIA subsystem is enabled.
  73. PNP Plug & Play support is enabled.
  74. PPC PowerPC architecture is enabled.
  75. PPT Parallel port support is enabled.
  76. PS2 Appropriate PS/2 support is enabled.
  77. RAM RAM disk support is enabled.
  78. ROOTPLUG The example Root Plug LSM is enabled.
  79. S390 S390 architecture is enabled.
  80. SCSI Appropriate SCSI support is enabled.
  81. A lot of drivers has their options described inside of
  82. Documentation/scsi/.
  83. SECURITY Different security models are enabled.
  84. SELINUX SELinux support is enabled.
  85. SERIAL Serial support is enabled.
  86. SH SuperH architecture is enabled.
  87. SMP The kernel is an SMP kernel.
  88. SPARC Sparc architecture is enabled.
  89. SWSUSP Software suspend (hibernation) is enabled.
  90. SUSPEND System suspend states are enabled.
  91. FTRACE Function tracing enabled.
  92. TS Appropriate touchscreen support is enabled.
  93. UMS USB Mass Storage support is enabled.
  94. USB USB support is enabled.
  95. USBHID USB Human Interface Device support is enabled.
  96. V4L Video For Linux support is enabled.
  97. VGA The VGA console has been enabled.
  98. VT Virtual terminal support is enabled.
  99. WDT Watchdog support is enabled.
  100. XT IBM PC/XT MFM hard disk support is enabled.
  101. X86-32 X86-32, aka i386 architecture is enabled.
  102. X86-64 X86-64 architecture is enabled.
  103. More X86-64 boot options can be found in
  104. Documentation/x86/x86_64/boot-options.txt .
  105. X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
  106. In addition, the following text indicates that the option:
  107. BUGS= Relates to possible processor bugs on the said processor.
  108. KNL Is a kernel start-up parameter.
  109. BOOT Is a boot loader parameter.
  110. Parameters denoted with BOOT are actually interpreted by the boot
  111. loader, and have no meaning to the kernel directly.
  112. Do not modify the syntax of boot loader parameters without extreme
  113. need or coordination with <Documentation/x86/boot.txt>.
  114. There are also arch-specific kernel-parameters not documented here.
  115. See for example <Documentation/x86/x86_64/boot-options.txt>.
  116. Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
  117. a trailing = on the name of any parameter states that that parameter will
  118. be entered as an environment variable, whereas its absence indicates that
  119. it will appear as a kernel argument readable via /proc/cmdline by programs
  120. running once the system is up.
  121. The number of kernel parameters is not limited, but the length of the
  122. complete command line (parameters including spaces etc.) is limited to
  123. a fixed number of characters. This limit depends on the architecture
  124. and is between 256 and 4096 characters. It is defined in the file
  125. ./include/asm/setup.h as COMMAND_LINE_SIZE.
  126. acpi= [HW,ACPI,X86]
  127. Advanced Configuration and Power Interface
  128. Format: { force | off | ht | strict | noirq | rsdt }
  129. force -- enable ACPI if default was off
  130. off -- disable ACPI if default was on
  131. noirq -- do not use ACPI for IRQ routing
  132. ht -- run only enough ACPI to enable Hyper Threading
  133. strict -- Be less tolerant of platforms that are not
  134. strictly ACPI specification compliant.
  135. rsdt -- prefer RSDT over (default) XSDT
  136. See also Documentation/power/pm.txt, pci=noacpi
  137. acpi_apic_instance= [ACPI, IOAPIC]
  138. Format: <int>
  139. 2: use 2nd APIC table, if available
  140. 1,0: use 1st APIC table
  141. default: 0
  142. acpi_backlight= [HW,ACPI]
  143. acpi_backlight=vendor
  144. acpi_backlight=video
  145. If set to vendor, prefer vendor specific driver
  146. (e.g. thinkpad_acpi, sony_acpi, etc.) instead
  147. of the ACPI video.ko driver.
  148. acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
  149. acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
  150. Format: <int>
  151. CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
  152. debug output. Bits in debug_layer correspond to a
  153. _COMPONENT in an ACPI source file, e.g.,
  154. #define _COMPONENT ACPI_PCI_COMPONENT
  155. Bits in debug_level correspond to a level in
  156. ACPI_DEBUG_PRINT statements, e.g.,
  157. ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
  158. The debug_level mask defaults to "info". See
  159. Documentation/acpi/debug.txt for more information about
  160. debug layers and levels.
  161. Enable processor driver info messages:
  162. acpi.debug_layer=0x20000000
  163. Enable PCI/PCI interrupt routing info messages:
  164. acpi.debug_layer=0x400000
  165. Enable AML "Debug" output, i.e., stores to the Debug
  166. object while interpreting AML:
  167. acpi.debug_layer=0xffffffff acpi.debug_level=0x2
  168. Enable all messages related to ACPI hardware:
  169. acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
  170. Some values produce so much output that the system is
  171. unusable. The "log_buf_len" parameter may be useful
  172. if you need to capture more output.
  173. acpi_display_output= [HW,ACPI]
  174. acpi_display_output=vendor
  175. acpi_display_output=video
  176. See above.
  177. acpi_irq_balance [HW,ACPI]
  178. ACPI will balance active IRQs
  179. default in APIC mode
  180. acpi_irq_nobalance [HW,ACPI]
  181. ACPI will not move active IRQs (default)
  182. default in PIC mode
  183. acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
  184. Format: <irq>,<irq>...
  185. acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
  186. use by PCI
  187. Format: <irq>,<irq>...
  188. acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
  189. acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
  190. Format: To spoof as Windows 98: ="Microsoft Windows"
  191. acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
  192. acpi_osi="string1" # add string1 -- only one string
  193. acpi_osi="!string2" # remove built-in string2
  194. acpi_osi= # disable all strings
  195. acpi_pm_good [X86]
  196. Override the pmtimer bug detection: force the kernel
  197. to assume that this machine's pmtimer latches its value
  198. and always returns good values.
  199. acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
  200. Format: { level | edge | high | low }
  201. acpi_serialize [HW,ACPI] force serialization of AML methods
  202. acpi_skip_timer_override [HW,ACPI]
  203. Recognize and ignore IRQ0/pin2 Interrupt Override.
  204. For broken nForce2 BIOS resulting in XT-PIC timer.
  205. acpi_sleep= [HW,ACPI] Sleep options
  206. Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
  207. old_ordering, s4_nonvs }
  208. See Documentation/power/video.txt for information on
  209. s3_bios and s3_mode.
  210. s3_beep is for debugging; it makes the PC's speaker beep
  211. as soon as the kernel's real-mode entry point is called.
  212. s4_nohwsig prevents ACPI hardware signature from being
  213. used during resume from hibernation.
  214. old_ordering causes the ACPI 1.0 ordering of the _PTS
  215. control method, with respect to putting devices into
  216. low power states, to be enforced (the ACPI 2.0 ordering
  217. of _PTS is used by default).
  218. s4_nonvs prevents the kernel from saving/restoring the
  219. ACPI NVS memory during hibernation.
  220. acpi_use_timer_override [HW,ACPI]
  221. Use timer override. For some broken Nvidia NF5 boards
  222. that require a timer override, but don't have HPET
  223. acpi_enforce_resources= [ACPI]
  224. { strict | lax | no }
  225. Check for resource conflicts between native drivers
  226. and ACPI OperationRegions (SystemIO and SystemMemory
  227. only). IO ports and memory declared in ACPI might be
  228. used by the ACPI subsystem in arbitrary AML code and
  229. can interfere with legacy drivers.
  230. strict (default): access to resources claimed by ACPI
  231. is denied; legacy drivers trying to access reserved
  232. resources will fail to bind to device using them.
  233. lax: access to resources claimed by ACPI is allowed;
  234. legacy drivers trying to access reserved resources
  235. will bind successfully but a warning message is logged.
  236. no: ACPI OperationRegions are not marked as reserved,
  237. no further checks are performed.
  238. ad1848= [HW,OSS]
  239. Format: <io>,<irq>,<dma>,<dma2>,<type>
  240. add_efi_memmap [EFI; X86] Include EFI memory map in
  241. kernel's map of available physical RAM.
  242. advansys= [HW,SCSI]
  243. See header of drivers/scsi/advansys.c.
  244. advwdt= [HW,WDT] Advantech WDT
  245. Format: <iostart>,<iostop>
  246. aedsp16= [HW,OSS] Audio Excel DSP 16
  247. Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
  248. See also header of sound/oss/aedsp16.c.
  249. agp= [AGP]
  250. { off | try_unsupported }
  251. off: disable AGP support
  252. try_unsupported: try to drive unsupported chipsets
  253. (may crash computer or cause data corruption)
  254. aha152x= [HW,SCSI]
  255. See Documentation/scsi/aha152x.txt.
  256. aha1542= [HW,SCSI]
  257. Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
  258. aic7xxx= [HW,SCSI]
  259. See Documentation/scsi/aic7xxx.txt.
  260. aic79xx= [HW,SCSI]
  261. See Documentation/scsi/aic79xx.txt.
  262. amd_iommu= [HW,X86-84]
  263. Pass parameters to the AMD IOMMU driver in the system.
  264. Possible values are:
  265. isolate - enable device isolation (each device, as far
  266. as possible, will get its own protection
  267. domain) [default]
  268. share - put every device behind one IOMMU into the
  269. same protection domain
  270. fullflush - enable flushing of IO/TLB entries when
  271. they are unmapped. Otherwise they are
  272. flushed before they will be reused, which
  273. is a lot of faster
  274. amijoy.map= [HW,JOY] Amiga joystick support
  275. Map of devices attached to JOY0DAT and JOY1DAT
  276. Format: <a>,<b>
  277. See also Documentation/kernel/input/joystick.txt
  278. analog.map= [HW,JOY] Analog joystick and gamepad support
  279. Specifies type or capabilities of an analog joystick
  280. connected to one of 16 gameports
  281. Format: <type1>,<type2>,..<type16>
  282. apc= [HW,SPARC]
  283. Power management functions (SPARCstation-4/5 + deriv.)
  284. Format: noidle
  285. Disable APC CPU standby support. SPARCstation-Fox does
  286. not play well with APC CPU idle - disable it if you have
  287. APC and your system crashes randomly.
  288. apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
  289. Change the output verbosity whilst booting
  290. Format: { quiet (default) | verbose | debug }
  291. Change the amount of debugging information output
  292. when initialising the APIC and IO-APIC components.
  293. apm= [APM] Advanced Power Management
  294. See header of arch/x86/kernel/apm_32.c.
  295. arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
  296. Format: <io>,<irq>,<nodeID>
  297. ataflop= [HW,M68k]
  298. atarimouse= [HW,MOUSE] Atari Mouse
  299. atascsi= [HW,SCSI] Atari SCSI
  300. atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
  301. EzKey and similar keyboards
  302. atkbd.reset= [HW] Reset keyboard during initialization
  303. atkbd.set= [HW] Select keyboard code set
  304. Format: <int> (2 = AT (default), 3 = PS/2)
  305. atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
  306. keyboards
  307. atkbd.softraw= [HW] Choose between synthetic and real raw mode
  308. Format: <bool> (0 = real, 1 = synthetic (default))
  309. atkbd.softrepeat= [HW]
  310. Use software keyboard repeat
  311. autotest [IA64]
  312. baycom_epp= [HW,AX25]
  313. Format: <io>,<mode>
  314. baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
  315. Format: <io>,<mode>
  316. See header of drivers/net/hamradio/baycom_par.c.
  317. baycom_ser_fdx= [HW,AX25]
  318. BayCom Serial Port AX.25 Modem (Full Duplex Mode)
  319. Format: <io>,<irq>,<mode>[,<baud>]
  320. See header of drivers/net/hamradio/baycom_ser_fdx.c.
  321. baycom_ser_hdx= [HW,AX25]
  322. BayCom Serial Port AX.25 Modem (Half Duplex Mode)
  323. Format: <io>,<irq>,<mode>
  324. See header of drivers/net/hamradio/baycom_ser_hdx.c.
  325. boot_delay= Milliseconds to delay each printk during boot.
  326. Values larger than 10 seconds (10000) are changed to
  327. no delay (0).
  328. Format: integer
  329. bootmem_debug [KNL] Enable bootmem allocator debug messages.
  330. bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
  331. bttv.radio= Most important insmod options are available as
  332. kernel args too.
  333. bttv.pll= See Documentation/video4linux/bttv/Insmod-options
  334. bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
  335. BusLogic= [HW,SCSI]
  336. See drivers/scsi/BusLogic.c, comment before function
  337. BusLogic_ParseDriverOptions().
  338. c101= [NET] Moxa C101 synchronous serial card
  339. cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
  340. Sometimes CPU hardware bugs make them report the cache
  341. size incorrectly. The kernel will attempt work arounds
  342. to fix known problems, but for some CPUs it is not
  343. possible to determine what the correct size should be.
  344. This option provides an override for these situations.
  345. capability.disable=
  346. [SECURITY] Disable capabilities. This would normally
  347. be used only if an alternative security model is to be
  348. configured. Potentially dangerous and should only be
  349. used if you are entirely sure of the consequences.
  350. ccw_timeout_log [S390]
  351. See Documentation/s390/CommonIO for details.
  352. cgroup_disable= [KNL] Disable a particular controller
  353. Format: {name of the controller(s) to disable}
  354. {Currently supported controllers - "memory"}
  355. checkreqprot [SELINUX] Set initial checkreqprot flag value.
  356. Format: { "0" | "1" }
  357. See security/selinux/Kconfig help text.
  358. 0 -- check protection applied by kernel (includes
  359. any implied execute protection).
  360. 1 -- check protection requested by application.
  361. Default value is set via a kernel config option.
  362. Value can be changed at runtime via
  363. /selinux/checkreqprot.
  364. cio_ignore= [S390]
  365. See Documentation/s390/CommonIO for details.
  366. clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
  367. [Deprecated]
  368. Forces specified clocksource (if available) to be used
  369. when calculating gettimeofday(). If specified
  370. clocksource is not available, it defaults to PIT.
  371. Format: { pit | tsc | cyclone | pmtmr }
  372. clocksource= [GENERIC_TIME] Override the default clocksource
  373. Format: <string>
  374. Override the default clocksource and use the clocksource
  375. with the name specified.
  376. Some clocksource names to choose from, depending on
  377. the platform:
  378. [all] jiffies (this is the base, fallback clocksource)
  379. [ACPI] acpi_pm
  380. [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
  381. pxa_timer,timer3,32k_counter,timer0_1
  382. [AVR32] avr32
  383. [X86-32] pit,hpet,tsc,vmi-timer;
  384. scx200_hrt on Geode; cyclone on IBM x440
  385. [MIPS] MIPS
  386. [PARISC] cr16
  387. [S390] tod
  388. [SH] SuperH
  389. [SPARC64] tick
  390. [X86-64] hpet,tsc
  391. clearcpuid=BITNUM [X86]
  392. Disable CPUID feature X for the kernel. See
  393. arch/x86/include/asm/cpufeature.h for the valid bit
  394. numbers. Note the Linux specific bits are not necessarily
  395. stable over kernel options, but the vendor specific
  396. ones should be.
  397. Also note that user programs calling CPUID directly
  398. or using the feature without checking anything
  399. will still see it. This just prevents it from
  400. being used by the kernel or shown in /proc/cpuinfo.
  401. Also note the kernel might malfunction if you disable
  402. some critical bits.
  403. cmo_free_hint= [PPC] Format: { yes | no }
  404. Specify whether pages are marked as being inactive
  405. when they are freed. This is used in CMO environments
  406. to determine OS memory pressure for page stealing by
  407. a hypervisor.
  408. Default: yes
  409. code_bytes [X86] How many bytes of object code to print
  410. in an oops report.
  411. Range: 0 - 8192
  412. Default: 64
  413. com20020= [HW,NET] ARCnet - COM20020 chipset
  414. Format:
  415. <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
  416. com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
  417. Format: <io>[,<irq>]
  418. com90xx= [HW,NET]
  419. ARCnet - COM90xx chipset (memory-mapped buffers)
  420. Format: <io>[,<irq>[,<memstart>]]
  421. condev= [HW,S390] console device
  422. conmode=
  423. console= [KNL] Output console device and options.
  424. tty<n> Use the virtual console device <n>.
  425. ttyS<n>[,options]
  426. ttyUSB0[,options]
  427. Use the specified serial port. The options are of
  428. the form "bbbbpnf", where "bbbb" is the baud rate,
  429. "p" is parity ("n", "o", or "e"), "n" is number of
  430. bits, and "f" is flow control ("r" for RTS or
  431. omit it). Default is "9600n8".
  432. See Documentation/serial-console.txt for more
  433. information. See
  434. Documentation/networking/netconsole.txt for an
  435. alternative.
  436. uart[8250],io,<addr>[,options]
  437. uart[8250],mmio,<addr>[,options]
  438. Start an early, polled-mode console on the 8250/16550
  439. UART at the specified I/O port or MMIO address,
  440. switching to the matching ttyS device later. The
  441. options are the same as for ttyS, above.
  442. If the device connected to the port is not a TTY but a braille
  443. device, prepend "brl," before the device type, for instance
  444. console=brl,ttyS0
  445. For now, only VisioBraille is supported.
  446. consoleblank= [KNL] The console blank (screen saver) timeout in
  447. seconds. Defaults to 10*60 = 10mins. A value of 0
  448. disables the blank timer.
  449. coredump_filter=
  450. [KNL] Change the default value for
  451. /proc/<pid>/coredump_filter.
  452. See also Documentation/filesystems/proc.txt.
  453. cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
  454. Format:
  455. <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
  456. crashkernel=nn[KMG]@ss[KMG]
  457. [KNL] Reserve a chunk of physical memory to
  458. hold a kernel to switch to with kexec on panic.
  459. crashkernel=range1:size1[,range2:size2,...][@offset]
  460. [KNL] Same as above, but depends on the memory
  461. in the running system. The syntax of range is
  462. start-[end] where start and end are both
  463. a memory unit (amount[KMG]). See also
  464. Documentation/kdump/kdump.txt for a example.
  465. cs89x0_dma= [HW,NET]
  466. Format: <dma>
  467. cs89x0_media= [HW,NET]
  468. Format: { rj45 | aui | bnc }
  469. dasd= [HW,NET]
  470. See header of drivers/s390/block/dasd_devmap.c.
  471. db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
  472. (one device per port)
  473. Format: <port#>,<type>
  474. See also Documentation/input/joystick-parport.txt
  475. debug [KNL] Enable kernel debugging (events log level).
  476. debug_locks_verbose=
  477. [KNL] verbose self-tests
  478. Format=<0|1>
  479. Print debugging info while doing the locking API
  480. self-tests.
  481. We default to 0 (no extra messages), setting it to
  482. 1 will print _a lot_ more information - normally
  483. only useful to kernel developers.
  484. debug_objects [KNL] Enable object debugging
  485. no_debug_objects
  486. [KNL] Disable object debugging
  487. debugpat [X86] Enable PAT debugging
  488. decnet.addr= [HW,NET]
  489. Format: <area>[,<node>]
  490. See also Documentation/networking/decnet.txt.
  491. default_hugepagesz=
  492. [same as hugepagesz=] The size of the default
  493. HugeTLB page size. This is the size represented by
  494. the legacy /proc/ hugepages APIs, used for SHM, and
  495. default size when mounting hugetlbfs filesystems.
  496. Defaults to the default architecture's huge page size
  497. if not specified.
  498. dhash_entries= [KNL]
  499. Set number of hash buckets for dentry cache.
  500. digi= [HW,SERIAL]
  501. IO parameters + enable/disable command.
  502. digiepca= [HW,SERIAL]
  503. See drivers/char/README.epca and
  504. Documentation/serial/digiepca.txt.
  505. disable_mtrr_cleanup [X86]
  506. The kernel tries to adjust MTRR layout from continuous
  507. to discrete, to make X server driver able to add WB
  508. entry later. This parameter disables that.
  509. disable_mtrr_trim [X86, Intel and AMD only]
  510. By default the kernel will trim any uncacheable
  511. memory out of your available memory pool based on
  512. MTRR settings. This parameter disables that behavior,
  513. possibly causing your machine to run very slowly.
  514. disable_timer_pin_1 [X86]
  515. Disable PIN 1 of APIC timer
  516. Can be useful to work around chipset bugs.
  517. dmasound= [HW,OSS] Sound subsystem buffers
  518. dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
  519. this option disables the debugging code at boot.
  520. dma_debug_entries=<number>
  521. This option allows to tune the number of preallocated
  522. entries for DMA-API debugging code. One entry is
  523. required per DMA-API allocation. Use this if the
  524. DMA-API debugging code disables itself because the
  525. architectural default is too low.
  526. dma_debug_driver=<driver_name>
  527. With this option the DMA-API debugging driver
  528. filter feature can be enabled at boot time. Just
  529. pass the driver to filter for as the parameter.
  530. The filter can be disabled or changed to another
  531. driver later using sysfs.
  532. dscc4.setup= [NET]
  533. dtc3181e= [HW,SCSI]
  534. dynamic_printk Enables pr_debug()/dev_dbg() calls if
  535. CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
  536. These can also be switched on/off via
  537. <debugfs>/dynamic_printk/modules
  538. earlycon= [KNL] Output early console device and options.
  539. uart[8250],io,<addr>[,options]
  540. uart[8250],mmio,<addr>[,options]
  541. Start an early, polled-mode console on the 8250/16550
  542. UART at the specified I/O port or MMIO address.
  543. The options are the same as for ttyS, above.
  544. earlyprintk= [X86,SH,BLACKFIN]
  545. earlyprintk=vga
  546. earlyprintk=serial[,ttySn[,baudrate]]
  547. earlyprintk=dbgp
  548. Append ",keep" to not disable it when the real console
  549. takes over.
  550. Only vga or serial or usb debug port at a time.
  551. Currently only ttyS0 and ttyS1 are supported.
  552. Interaction with the standard serial driver is not
  553. very good.
  554. The VGA output is eventually overwritten by the real
  555. console.
  556. eata= [HW,SCSI]
  557. edd= [EDD]
  558. Format: {"off" | "on" | "skip[mbr]"}
  559. eisa_irq_edge= [PARISC,HW]
  560. See header of drivers/parisc/eisa.c.
  561. elanfreq= [X86-32]
  562. See comment before function elanfreq_setup() in
  563. arch/x86/kernel/cpu/cpufreq/elanfreq.c.
  564. elevator= [IOSCHED]
  565. Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
  566. See Documentation/block/as-iosched.txt and
  567. Documentation/block/deadline-iosched.txt for details.
  568. elfcorehdr= [IA64,PPC,SH,X86]
  569. Specifies physical address of start of kernel core
  570. image elf header. Generally kexec loader will
  571. pass this option to capture kernel.
  572. See Documentation/kdump/kdump.txt for details.
  573. enable_mtrr_cleanup [X86]
  574. The kernel tries to adjust MTRR layout from continuous
  575. to discrete, to make X server driver able to add WB
  576. entry later. This parameter enables that.
  577. enable_timer_pin_1 [X86]
  578. Enable PIN 1 of APIC timer
  579. Can be useful to work around chipset bugs
  580. (in particular on some ATI chipsets).
  581. The kernel tries to set a reasonable default.
  582. enforcing [SELINUX] Set initial enforcing status.
  583. Format: {"0" | "1"}
  584. See security/selinux/Kconfig help text.
  585. 0 -- permissive (log only, no denials).
  586. 1 -- enforcing (deny and log).
  587. Default value is 0.
  588. Value can be changed at runtime via /selinux/enforce.
  589. ether= [HW,NET] Ethernet cards parameters
  590. This option is obsoleted by the "netdev=" option, which
  591. has equivalent usage. See its documentation for details.
  592. eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
  593. Format: <io>[,<irq>]
  594. failslab=
  595. fail_page_alloc=
  596. fail_make_request=[KNL]
  597. General fault injection mechanism.
  598. Format: <interval>,<probability>,<space>,<times>
  599. See also /Documentation/fault-injection/.
  600. fd_mcs= [HW,SCSI]
  601. See header of drivers/scsi/fd_mcs.c.
  602. fdomain= [HW,SCSI]
  603. See header of drivers/scsi/fdomain.c.
  604. floppy= [HW]
  605. See Documentation/blockdev/floppy.txt.
  606. force_pal_cache_flush
  607. [IA-64] Avoid check_sal_cache_flush which may hang on
  608. buggy SAL_CACHE_FLUSH implementations. Using this
  609. parameter will force ia64_sal_cache_flush to call
  610. ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
  611. ftrace=[tracer]
  612. [FTRACE] will set and start the specified tracer
  613. as early as possible in order to facilitate early
  614. boot debugging.
  615. ftrace_dump_on_oops
  616. [FTRACE] will dump the trace buffers on oops.
  617. ftrace_filter=[function-list]
  618. [FTRACE] Limit the functions traced by the function
  619. tracer at boot up. function-list is a comma separated
  620. list of functions. This list can be changed at run
  621. time by the set_ftrace_filter file in the debugfs
  622. tracing directory.
  623. ftrace_notrace=[function-list]
  624. [FTRACE] Do not trace the functions specified in
  625. function-list. This list can be changed at run time
  626. by the set_ftrace_notrace file in the debugfs
  627. tracing directory.
  628. gamecon.map[2|3]=
  629. [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
  630. support via parallel port (up to 5 devices per port)
  631. Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
  632. See also Documentation/input/joystick-parport.txt
  633. gamma= [HW,DRM]
  634. gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
  635. Format: off | on
  636. default: on
  637. gcov_persist= [GCOV] When non-zero (default), profiling data for
  638. kernel modules is saved and remains accessible via
  639. debugfs, even when the module is unloaded/reloaded.
  640. When zero, profiling data is discarded and associated
  641. debugfs files are removed at module unload time.
  642. gdth= [HW,SCSI]
  643. See header of drivers/scsi/gdth.c.
  644. gpt [EFI] Forces disk with valid GPT signature but
  645. invalid Protective MBR to be treated as GPT.
  646. gvp11= [HW,SCSI]
  647. hashdist= [KNL,NUMA] Large hashes allocated during boot
  648. are distributed across NUMA nodes. Defaults on
  649. for 64bit NUMA, off otherwise.
  650. Format: 0 | 1 (for off | on)
  651. hcl= [IA-64] SGI's Hardware Graph compatibility layer
  652. hd= [EIDE] (E)IDE hard drive subsystem geometry
  653. Format: <cyl>,<head>,<sect>
  654. highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
  655. size of <nn>. This works even on boxes that have no
  656. highmem otherwise. This also works to reduce highmem
  657. size on bigger boxes.
  658. highres= [KNL] Enable/disable high resolution timer mode.
  659. Valid parameters: "on", "off"
  660. Default: "on"
  661. hisax= [HW,ISDN]
  662. See Documentation/isdn/README.HiSax.
  663. hlt [BUGS=ARM,SH]
  664. hpet= [X86-32,HPET] option to control HPET usage
  665. Format: { enable (default) | disable | force |
  666. verbose }
  667. disable: disable HPET and use PIT instead
  668. force: allow force enabled of undocumented chips (ICH4,
  669. VIA, nVidia)
  670. verbose: show contents of HPET registers during setup
  671. hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
  672. hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
  673. On x86-64 and powerpc, this option can be specified
  674. multiple times interleaved with hugepages= to reserve
  675. huge pages of different sizes. Valid pages sizes on
  676. x86-64 are 2M (when the CPU supports "pse") and 1G
  677. (when the CPU supports the "pdpe1gb" cpuinfo flag)
  678. Note that 1GB pages can only be allocated at boot time
  679. using hugepages= and not freed afterwards.
  680. hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
  681. terminal devices. Valid values: 0..8
  682. hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
  683. If specified, z/VM IUCV HVC accepts connections
  684. from listed z/VM user IDs only.
  685. i2c_bus= [HW] Override the default board specific I2C bus speed
  686. or register an additional I2C bus that is not
  687. registered from board initialization code.
  688. Format:
  689. <bus_id>,<clkrate>
  690. i8042.debug [HW] Toggle i8042 debug mode
  691. i8042.direct [HW] Put keyboard port into non-translated mode
  692. i8042.dumbkbd [HW] Pretend that controller can only read data from
  693. keyboard and cannot control its state
  694. (Don't attempt to blink the leds)
  695. i8042.noaux [HW] Don't check for auxiliary (== mouse) port
  696. i8042.nokbd [HW] Don't check/create keyboard port
  697. i8042.noloop [HW] Disable the AUX Loopback command while probing
  698. for the AUX port
  699. i8042.nomux [HW] Don't check presence of an active multiplexing
  700. controller
  701. i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
  702. controllers
  703. i8042.panicblink=
  704. [HW] Frequency with which keyboard LEDs should blink
  705. when kernel panics (default is 0.5 sec)
  706. i8042.reset [HW] Reset the controller during init and cleanup
  707. i8042.unlock [HW] Unlock (ignore) the keylock
  708. i810= [HW,DRM]
  709. i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
  710. indicates that the driver is running on unsupported
  711. hardware.
  712. i8k.force [HW] Activate i8k driver even if SMM BIOS signature
  713. does not match list of supported models.
  714. i8k.power_status
  715. [HW] Report power status in /proc/i8k
  716. (disabled by default)
  717. i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
  718. capability is set.
  719. ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
  720. See Documentation/mca.txt.
  721. icn= [HW,ISDN]
  722. Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
  723. ide-core.nodma= [HW] (E)IDE subsystem
  724. Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
  725. .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
  726. .cdrom .chs .ignore_cable are additional options
  727. See Documentation/ide/ide.txt.
  728. ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
  729. Claim all unknown PCI IDE storage controllers.
  730. idle= [X86]
  731. Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
  732. Poll forces a polling idle loop that can slightly
  733. improve the performance of waking up a idle CPU, but
  734. will use a lot of power and make the system run hot.
  735. Not recommended.
  736. idle=mwait: On systems which support MONITOR/MWAIT but
  737. the kernel chose to not use it because it doesn't save
  738. as much power as a normal idle loop, use the
  739. MONITOR/MWAIT idle loop anyways. Performance should be
  740. the same as idle=poll.
  741. idle=halt: Halt is forced to be used for CPU idle.
  742. In such case C2/C3 won't be used again.
  743. idle=nomwait: Disable mwait for CPU C-states
  744. ignore_loglevel [KNL]
  745. Ignore loglevel setting - this will print /all/
  746. kernel messages to the console. Useful for debugging.
  747. ihash_entries= [KNL]
  748. Set number of hash buckets for inode cache.
  749. ima_audit= [IMA]
  750. Format: { "0" | "1" }
  751. 0 -- integrity auditing messages. (Default)
  752. 1 -- enable informational integrity auditing messages.
  753. ima_hash= [IMA]
  754. Formt: { "sha1" | "md5" }
  755. default: "sha1"
  756. ima_tcb [IMA]
  757. Load a policy which meets the needs of the Trusted
  758. Computing Base. This means IMA will measure all
  759. programs exec'd, files mmap'd for exec, and all files
  760. opened for read by uid=0.
  761. in2000= [HW,SCSI]
  762. See header of drivers/scsi/in2000.c.
  763. init= [KNL]
  764. Format: <full_path>
  765. Run specified binary instead of /sbin/init as init
  766. process.
  767. initcall_debug [KNL] Trace initcalls as they are executed. Useful
  768. for working out where the kernel is dying during
  769. startup.
  770. initrd= [BOOT] Specify the location of the initial ramdisk
  771. inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
  772. Format: <irq>
  773. intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
  774. on
  775. Enable intel iommu driver.
  776. off
  777. Disable intel iommu driver.
  778. igfx_off [Default Off]
  779. By default, gfx is mapped as normal device. If a gfx
  780. device has a dedicated DMAR unit, the DMAR unit is
  781. bypassed by not enabling DMAR with this option. In
  782. this case, gfx device will use physical address for
  783. DMA.
  784. forcedac [x86_64]
  785. With this option iommu will not optimize to look
  786. for io virtual address below 32 bit forcing dual
  787. address cycle on pci bus for cards supporting greater
  788. than 32 bit addressing. The default is to look
  789. for translation below 32 bit and if not available
  790. then look in the higher range.
  791. strict [Default Off]
  792. With this option on every unmap_single operation will
  793. result in a hardware IOTLB flush operation as opposed
  794. to batching them for performance.
  795. inttest= [IA64]
  796. iomem= Disable strict checking of access to MMIO memory
  797. strict regions from userspace.
  798. relaxed
  799. iommu= [x86]
  800. off
  801. force
  802. noforce
  803. biomerge
  804. panic
  805. nopanic
  806. merge
  807. nomerge
  808. forcesac
  809. soft
  810. pt [x86, IA64]
  811. io7= [HW] IO7 for Marvel based alpha systems
  812. See comment before marvel_specify_io7 in
  813. arch/alpha/kernel/core_marvel.c.
  814. io_delay= [X86] I/O delay method
  815. 0x80
  816. Standard port 0x80 based delay
  817. 0xed
  818. Alternate port 0xed based delay (needed on some systems)
  819. udelay
  820. Simple two microseconds delay
  821. none
  822. No delay
  823. ip= [IP_PNP]
  824. See Documentation/filesystems/nfsroot.txt.
  825. ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
  826. See comment before ip2_setup() in
  827. drivers/char/ip2/ip2base.c.
  828. ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
  829. See header of drivers/scsi/ips.c.
  830. irqfixup [HW]
  831. When an interrupt is not handled search all handlers
  832. for it. Intended to get systems with badly broken
  833. firmware running.
  834. irqpoll [HW]
  835. When an interrupt is not handled search all handlers
  836. for it. Also check all handlers each timer
  837. interrupt. Intended to get systems with badly broken
  838. firmware running.
  839. isapnp= [ISAPNP]
  840. Format: <RDP>,<reset>,<pci_scan>,<verbosity>
  841. isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
  842. Format:
  843. <cpu number>,...,<cpu number>
  844. or
  845. <cpu number>-<cpu number>
  846. (must be a positive range in ascending order)
  847. or a mixture
  848. <cpu number>,...,<cpu number>-<cpu number>
  849. This option can be used to specify one or more CPUs
  850. to isolate from the general SMP balancing and scheduling
  851. algorithms. You can move a process onto or off an
  852. "isolated" CPU via the CPU affinity syscalls or cpuset.
  853. <cpu number> begins at 0 and the maximum value is
  854. "number of CPUs in system - 1".
  855. This option is the preferred way to isolate CPUs. The
  856. alternative -- manually setting the CPU mask of all
  857. tasks in the system -- can cause problems and
  858. suboptimal load balancer performance.
  859. iucv= [HW,NET]
  860. js= [HW,JOY] Analog joystick
  861. See Documentation/input/joystick.txt.
  862. keepinitrd [HW,ARM]
  863. kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
  864. specifies the amount of memory usable by the kernel
  865. for non-movable allocations. The requested amount is
  866. spread evenly throughout all nodes in the system. The
  867. remaining memory in each node is used for Movable
  868. pages. In the event, a node is too small to have both
  869. kernelcore and Movable pages, kernelcore pages will
  870. take priority and other nodes will have a larger number
  871. of kernelcore pages. The Movable zone is used for the
  872. allocation of pages that may be reclaimed or moved
  873. by the page migration subsystem. This means that
  874. HugeTLB pages may not be allocated from this zone.
  875. Note that allocations like PTEs-from-HighMem still
  876. use the HighMem zone if it exists, and the Normal
  877. zone if it does not.
  878. kgdboc= [HW] kgdb over consoles.
  879. Requires a tty driver that supports console polling.
  880. (only serial supported for now)
  881. Format: <serial_device>[,baud]
  882. kmac= [MIPS] korina ethernet MAC address.
  883. Configure the RouterBoard 532 series on-chip
  884. Ethernet adapter MAC address.
  885. kmemleak= [KNL] Boot-time kmemleak enable/disable
  886. Valid arguments: on, off
  887. Default: on
  888. kstack=N [X86] Print N words from the kernel stack
  889. in oops dumps.
  890. kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
  891. Default is 0 (don't ignore, but inject #GP)
  892. kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
  893. Default is 1 (enabled)
  894. kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
  895. Default is 0 (off)
  896. kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
  897. for all guests.
  898. Default is 1 (enabled) if in 64bit or 32bit-PAE mode
  899. kvm-intel.bypass_guest_pf=
  900. [KVM,Intel] Disables bypassing of guest page faults
  901. on Intel chips. Default is 1 (enabled)
  902. kvm-intel.ept= [KVM,Intel] Disable extended page tables
  903. (virtualized MMU) support on capable Intel chips.
  904. Default is 1 (enabled)
  905. kvm-intel.emulate_invalid_guest_state=
  906. [KVM,Intel] Enable emulation of invalid guest states
  907. Default is 0 (disabled)
  908. kvm-intel.flexpriority=
  909. [KVM,Intel] Disable FlexPriority feature (TPR shadow).
  910. Default is 1 (enabled)
  911. kvm-intel.unrestricted_guest=
  912. [KVM,Intel] Disable unrestricted guest feature
  913. (virtualized real and unpaged mode) on capable
  914. Intel chips. Default is 1 (enabled)
  915. kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
  916. feature (tagged TLBs) on capable Intel chips.
  917. Default is 1 (enabled)
  918. l2cr= [PPC]
  919. l3cr= [PPC]
  920. lapic [X86-32,APIC] Enable the local APIC even if BIOS
  921. disabled it.
  922. lapic_timer_c2_ok [X86,APIC] trust the local apic timer
  923. in C2 power state.
  924. libata.dma= [LIBATA] DMA control
  925. libata.dma=0 Disable all PATA and SATA DMA
  926. libata.dma=1 PATA and SATA Disk DMA only
  927. libata.dma=2 ATAPI (CDROM) DMA only
  928. libata.dma=4 Compact Flash DMA only
  929. Combinations also work, so libata.dma=3 enables DMA
  930. for disks and CDROMs, but not CFs.
  931. libata.ignore_hpa= [LIBATA] Ignore HPA limit
  932. libata.ignore_hpa=0 keep BIOS limits (default)
  933. libata.ignore_hpa=1 ignore limits, using full disk
  934. libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
  935. when set.
  936. Format: <int>
  937. libata.force= [LIBATA] Force configurations. The format is comma
  938. separated list of "[ID:]VAL" where ID is
  939. PORT[:DEVICE]. PORT and DEVICE are decimal numbers
  940. matching port, link or device. Basically, it matches
  941. the ATA ID string printed on console by libata. If
  942. the whole ID part is omitted, the last PORT and DEVICE
  943. values are used. If ID hasn't been specified yet, the
  944. configuration applies to all ports, links and devices.
  945. If only DEVICE is omitted, the parameter applies to
  946. the port and all links and devices behind it. DEVICE
  947. number of 0 either selects the first device or the
  948. first fan-out link behind PMP device. It does not
  949. select the host link. DEVICE number of 15 selects the
  950. host link and device attached to it.
  951. The VAL specifies the configuration to force. As long
  952. as there's no ambiguity shortcut notation is allowed.
  953. For example, both 1.5 and 1.5G would work for 1.5Gbps.
  954. The following configurations can be forced.
  955. * Cable type: 40c, 80c, short40c, unk, ign or sata.
  956. Any ID with matching PORT is used.
  957. * SATA link speed limit: 1.5Gbps or 3.0Gbps.
  958. * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
  959. udma[/][16,25,33,44,66,100,133] notation is also
  960. allowed.
  961. * [no]ncq: Turn on or off NCQ.
  962. * nohrst, nosrst, norst: suppress hard, soft
  963. and both resets.
  964. If there are multiple matching configurations changing
  965. the same attribute, the last one is used.
  966. lmb=debug [KNL] Enable lmb debug messages.
  967. load_ramdisk= [RAM] List of ramdisks to load from floppy
  968. See Documentation/blockdev/ramdisk.txt.
  969. lockd.nlm_grace_period=P [NFS] Assign grace period.
  970. Format: <integer>
  971. lockd.nlm_tcpport=N [NFS] Assign TCP port.
  972. Format: <integer>
  973. lockd.nlm_timeout=T [NFS] Assign timeout value.
  974. Format: <integer>
  975. lockd.nlm_udpport=M [NFS] Assign UDP port.
  976. Format: <integer>
  977. logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
  978. Format: <irq>
  979. loglevel= All Kernel Messages with a loglevel smaller than the
  980. console loglevel will be printed to the console. It can
  981. also be changed with klogd or other programs. The
  982. loglevels are defined as follows:
  983. 0 (KERN_EMERG) system is unusable
  984. 1 (KERN_ALERT) action must be taken immediately
  985. 2 (KERN_CRIT) critical conditions
  986. 3 (KERN_ERR) error conditions
  987. 4 (KERN_WARNING) warning conditions
  988. 5 (KERN_NOTICE) normal but significant condition
  989. 6 (KERN_INFO) informational
  990. 7 (KERN_DEBUG) debug-level messages
  991. log_buf_len=n Sets the size of the printk ring buffer, in bytes.
  992. Format: { n | nk | nM }
  993. n must be a power of two. The default size
  994. is set in the kernel config file.
  995. logo.nologo [FB] Disables display of the built-in Linux logo.
  996. This may be used to provide more screen space for
  997. kernel log messages and is useful when debugging
  998. kernel boot problems.
  999. lp=0 [LP] Specify parallel ports to use, e.g,
  1000. lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
  1001. lp=reset first parallel port). 'lp=0' disables the
  1002. lp=auto printer driver. 'lp=reset' (which can be
  1003. specified in addition to the ports) causes
  1004. attached printers to be reset. Using
  1005. lp=port1,port2,... specifies the parallel ports
  1006. to associate lp devices with, starting with
  1007. lp0. A port specification may be 'none' to skip
  1008. that lp device, or a parport name such as
  1009. 'parport0'. Specifying 'lp=auto' instead of a
  1010. port specification list means that device IDs
  1011. from each port should be examined, to see if
  1012. an IEEE 1284-compliant printer is attached; if
  1013. so, the driver will manage that printer.
  1014. See also header of drivers/char/lp.c.
  1015. lpj=n [KNL]
  1016. Sets loops_per_jiffy to given constant, thus avoiding
  1017. time-consuming boot-time autodetection (up to 250 ms per
  1018. CPU). 0 enables autodetection (default). To determine
  1019. the correct value for your kernel, boot with normal
  1020. autodetection and see what value is printed. Note that
  1021. on SMP systems the preset will be applied to all CPUs,
  1022. which is likely to cause problems if your CPUs need
  1023. significantly divergent settings. An incorrect value
  1024. will cause delays in the kernel to be wrong, leading to
  1025. unpredictable I/O errors and other breakage. Although
  1026. unlikely, in the extreme case this might damage your
  1027. hardware.
  1028. ltpc= [NET]
  1029. Format: <io>,<irq>,<dma>
  1030. mac5380= [HW,SCSI] Format:
  1031. <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
  1032. machvec= [IA64] Force the use of a particular machine-vector
  1033. (machvec) in a generic kernel.
  1034. Example: machvec=hpzx1_swiotlb
  1035. max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
  1036. than or equal to this physical address is ignored.
  1037. maxcpus= [SMP] Maximum number of processors that an SMP kernel
  1038. should make use of. maxcpus=n : n >= 0 limits the
  1039. kernel to using 'n' processors. n=0 is a special case,
  1040. it is equivalent to "nosmp", which also disables
  1041. the IO APIC.
  1042. max_loop= [LOOP] Maximum number of loopback devices that can
  1043. be mounted
  1044. Format: <1-256>
  1045. max_luns= [SCSI] Maximum number of LUNs to probe.
  1046. Should be between 1 and 2^32-1.
  1047. max_report_luns=
  1048. [SCSI] Maximum number of LUNs received.
  1049. Should be between 1 and 16384.
  1050. mcatest= [IA-64]
  1051. mce [X86-32] Machine Check Exception
  1052. mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
  1053. md= [HW] RAID subsystems devices and level
  1054. See Documentation/md.txt.
  1055. mdacon= [MDA]
  1056. Format: <first>,<last>
  1057. Specifies range of consoles to be captured by the MDA.
  1058. mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
  1059. Amount of memory to be used when the kernel is not able
  1060. to see the whole system memory or for test.
  1061. [X86-32] Use together with memmap= to avoid physical
  1062. address space collisions. Without memmap= PCI devices
  1063. could be placed at addresses belonging to unused RAM.
  1064. mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
  1065. memory.
  1066. memchunk=nn[KMG]
  1067. [KNL,SH] Allow user to override the default size for
  1068. per-device physically contiguous DMA buffers.
  1069. memmap=exactmap [KNL,X86] Enable setting of an exact
  1070. E820 memory map, as specified by the user.
  1071. Such memmap=exactmap lines can be constructed based on
  1072. BIOS output or other requirements. See the memmap=nn@ss
  1073. option description.
  1074. memmap=nn[KMG]@ss[KMG]
  1075. [KNL] Force usage of a specific region of memory
  1076. Region of memory to be used, from ss to ss+nn.
  1077. memmap=nn[KMG]#ss[KMG]
  1078. [KNL,ACPI] Mark specific memory as ACPI data.
  1079. Region of memory to be used, from ss to ss+nn.
  1080. memmap=nn[KMG]$ss[KMG]
  1081. [KNL,ACPI] Mark specific memory as reserved.
  1082. Region of memory to be used, from ss to ss+nn.
  1083. Example: Exclude memory from 0x18690000-0x1869ffff
  1084. memmap=64K$0x18690000
  1085. or
  1086. memmap=0x10000$0x18690000
  1087. memory_corruption_check=0/1 [X86]
  1088. Some BIOSes seem to corrupt the first 64k of
  1089. memory when doing things like suspend/resume.
  1090. Setting this option will scan the memory
  1091. looking for corruption. Enabling this will
  1092. both detect corruption and prevent the kernel
  1093. from using the memory being corrupted.
  1094. However, its intended as a diagnostic tool; if
  1095. repeatable BIOS-originated corruption always
  1096. affects the same memory, you can use memmap=
  1097. to prevent the kernel from using that memory.
  1098. memory_corruption_check_size=size [X86]
  1099. By default it checks for corruption in the low
  1100. 64k, making this memory unavailable for normal
  1101. use. Use this parameter to scan for
  1102. corruption in more or less memory.
  1103. memory_corruption_check_period=seconds [X86]
  1104. By default it checks for corruption every 60
  1105. seconds. Use this parameter to check at some
  1106. other rate. 0 disables periodic checking.
  1107. memtest= [KNL,X86] Enable memtest
  1108. Format: <integer>
  1109. default : 0 <disable>
  1110. Specifies the number of memtest passes to be
  1111. performed. Each pass selects another test
  1112. pattern from a given set of patterns. Memtest
  1113. fills the memory with this pattern, validates
  1114. memory contents and reserves bad memory
  1115. regions that are detected.
  1116. meye.*= [HW] Set MotionEye Camera parameters
  1117. See Documentation/video4linux/meye.txt.
  1118. mfgpt_irq= [IA-32] Specify the IRQ to use for the
  1119. Multi-Function General Purpose Timers on AMD Geode
  1120. platforms.
  1121. mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
  1122. the BIOS has incorrectly applied a workaround. TinyBIOS
  1123. version 0.98 is known to be affected, 0.99 fixes the
  1124. problem by letting the user disable the workaround.
  1125. mga= [HW,DRM]
  1126. min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
  1127. physical address is ignored.
  1128. mini2440= [ARM,HW,KNL]
  1129. Format:[0..2][b][c][t]
  1130. Default: "0tb"
  1131. MINI2440 configuration specification:
  1132. 0 - The attached screen is the 3.5" TFT
  1133. 1 - The attached screen is the 7" TFT
  1134. 2 - The VGA Shield is attached (1024x768)
  1135. Leaving out the screen size parameter will not load
  1136. the TFT driver, and the framebuffer will be left
  1137. unconfigured.
  1138. b - Enable backlight. The TFT backlight pin will be
  1139. linked to the kernel VESA blanking code and a GPIO
  1140. LED. This parameter is not necessary when using the
  1141. VGA shield.
  1142. c - Enable the s3c camera interface.
  1143. t - Reserved for enabling touchscreen support. The
  1144. touchscreen support is not enabled in the mainstream
  1145. kernel as of 2.6.30, a preliminary port can be found
  1146. in the "bleeding edge" mini2440 support kernel at
  1147. http://repo.or.cz/w/linux-2.6/mini2440.git
  1148. mminit_loglevel=
  1149. [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
  1150. parameter allows control of the logging verbosity for
  1151. the additional memory initialisation checks. A value
  1152. of 0 disables mminit logging and a level of 4 will
  1153. log everything. Information is printed at KERN_DEBUG
  1154. so loglevel=8 may also need to be specified.
  1155. mousedev.tap_time=
  1156. [MOUSE] Maximum time between finger touching and
  1157. leaving touchpad surface for touch to be considered
  1158. a tap and be reported as a left button click (for
  1159. touchpads working in absolute mode only).
  1160. Format: <msecs>
  1161. mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
  1162. reporting absolute coordinates, such as tablets
  1163. mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
  1164. reporting absolute coordinates, such as tablets
  1165. movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
  1166. is similar to kernelcore except it specifies the
  1167. amount of memory used for migratable allocations.
  1168. If both kernelcore and movablecore is specified,
  1169. then kernelcore will be at *least* the specified
  1170. value but may be more. If movablecore on its own
  1171. is specified, the administrator must be careful
  1172. that the amount of memory usable for all allocations
  1173. is not too small.
  1174. mpu401= [HW,OSS]
  1175. Format: <io>,<irq>
  1176. MTD_Partition= [MTD]
  1177. Format: <name>,<region-number>,<size>,<offset>
  1178. MTD_Region= [MTD] Format:
  1179. <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
  1180. mtdparts= [MTD]
  1181. See drivers/mtd/cmdlinepart.c.
  1182. onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
  1183. Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
  1184. boundary - index of last SLC block on Flex-OneNAND.
  1185. The remaining blocks are configured as MLC blocks.
  1186. lock - Configure if Flex-OneNAND boundary should be locked.
  1187. Once locked, the boundary cannot be changed.
  1188. 1 indicates lock status, 0 indicates unlock status.
  1189. mtdset= [ARM]
  1190. ARM/S3C2412 JIVE boot control
  1191. See arch/arm/mach-s3c2412/mach-jive.c
  1192. mtouchusb.raw_coordinates=
  1193. [HW] Make the MicroTouch USB driver use raw coordinates
  1194. ('y', default) or cooked coordinates ('n')
  1195. mtrr_chunk_size=nn[KMG] [X86]
  1196. used for mtrr cleanup. It is largest continuous chunk
  1197. that could hold holes aka. UC entries.
  1198. mtrr_gran_size=nn[KMG] [X86]
  1199. Used for mtrr cleanup. It is granularity of mtrr block.
  1200. Default is 1.
  1201. Large value could prevent small alignment from
  1202. using up MTRRs.
  1203. mtrr_spare_reg_nr=n [X86]
  1204. Format: <integer>
  1205. Range: 0,7 : spare reg number
  1206. Default : 1
  1207. Used for mtrr cleanup. It is spare mtrr entries number.
  1208. Set to 2 or more if your graphical card needs more.
  1209. n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
  1210. NCR_D700= [HW,SCSI]
  1211. See header of drivers/scsi/NCR_D700.c.
  1212. ncr5380= [HW,SCSI]
  1213. ncr53c400= [HW,SCSI]
  1214. ncr53c400a= [HW,SCSI]
  1215. ncr53c406a= [HW,SCSI]
  1216. ncr53c8xx= [HW,SCSI]
  1217. netdev= [NET] Network devices parameters
  1218. Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
  1219. Note that mem_start is often overloaded to mean
  1220. something different and driver-specific.
  1221. This usage is only documented in each driver source
  1222. file if at all.
  1223. nf_conntrack.acct=
  1224. [NETFILTER] Enable connection tracking flow accounting
  1225. 0 to disable accounting
  1226. 1 to enable accounting
  1227. Default value depends on CONFIG_NF_CT_ACCT that is
  1228. going to be removed in 2.6.29.
  1229. nfsaddrs= [NFS]
  1230. See Documentation/filesystems/nfsroot.txt.
  1231. nfsroot= [NFS] nfs root filesystem for disk-less boxes.
  1232. See Documentation/filesystems/nfsroot.txt.
  1233. nfs.callback_tcpport=
  1234. [NFS] set the TCP port on which the NFSv4 callback
  1235. channel should listen.
  1236. nfs.cache_getent=
  1237. [NFS] sets the pathname to the program which is used
  1238. to update the NFS client cache entries.
  1239. nfs.cache_getent_timeout=
  1240. [NFS] sets the timeout after which an attempt to
  1241. update a cache entry is deemed to have failed.
  1242. nfs.idmap_cache_timeout=
  1243. [NFS] set the maximum lifetime for idmapper cache
  1244. entries.
  1245. nfs.enable_ino64=
  1246. [NFS] enable 64-bit inode numbers.
  1247. If zero, the NFS client will fake up a 32-bit inode
  1248. number for the readdir() and stat() syscalls instead
  1249. of returning the full 64-bit number.
  1250. The default is to return 64-bit inode numbers.
  1251. nmi_debug= [KNL,AVR32] Specify one or more actions to take
  1252. when a NMI is triggered.
  1253. Format: [state][,regs][,debounce][,die]
  1254. nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
  1255. Format: [panic,][num]
  1256. Valid num: 0,1,2
  1257. 0 - turn nmi_watchdog off
  1258. 1 - use the IO-APIC timer for the NMI watchdog
  1259. 2 - use the local APIC for the NMI watchdog using
  1260. a performance counter. Note: This will use one
  1261. performance counter and the local APIC's performance
  1262. vector.
  1263. When panic is specified, panic when an NMI watchdog
  1264. timeout occurs.
  1265. This is useful when you use a panic=... timeout and
  1266. need the box quickly up again.
  1267. Instead of 1 and 2 it is possible to use the following
  1268. symbolic names: lapic and ioapic
  1269. Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
  1270. netpoll.carrier_timeout=
  1271. [NET] Specifies amount of time (in seconds) that
  1272. netpoll should wait for a carrier. By default netpoll
  1273. waits 4 seconds.
  1274. no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
  1275. emulation library even if a 387 maths coprocessor
  1276. is present.
  1277. no_console_suspend
  1278. [HW] Never suspend the console
  1279. Disable suspending of consoles during suspend and
  1280. hibernate operations. Once disabled, debugging
  1281. messages can reach various consoles while the rest
  1282. of the system is being put to sleep (ie, while
  1283. debugging driver suspend/resume hooks). This may
  1284. not work reliably with all consoles, but is known
  1285. to work with serial and VGA consoles.
  1286. noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
  1287. caches in the slab allocator. Saves per-node memory,
  1288. but will impact performance.
  1289. noalign [KNL,ARM]
  1290. noapic [SMP,APIC] Tells the kernel to not make use of any
  1291. IOAPICs that may be present in the system.
  1292. nobats [PPC] Do not use BATs for mapping kernel lowmem
  1293. on "Classic" PPC cores.
  1294. nocache [ARM]
  1295. noclflush [BUGS=X86] Don't use the CLFLUSH instruction
  1296. nodelayacct [KNL] Disable per-task delay accounting
  1297. nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
  1298. nodsp [SH] Disable hardware DSP at boot time.
  1299. noefi [X86] Disable EFI runtime services support.
  1300. noexec [IA-64]
  1301. noexec [X86]
  1302. On X86-32 available only on PAE configured kernels.
  1303. noexec=on: enable non-executable mappings (default)
  1304. noexec=off: disable non-executable mappings
  1305. noexec32 [X86-64]
  1306. This affects only 32-bit executables.
  1307. noexec32=on: enable non-executable mappings (default)
  1308. read doesn't imply executable mappings
  1309. noexec32=off: disable non-executable mappings
  1310. read implies executable mappings
  1311. nofpu [SH] Disable hardware FPU at boot time.
  1312. nofxsr [BUGS=X86-32] Disables x86 floating point extended
  1313. register save and restore. The kernel will only save
  1314. legacy floating-point registers on task switch.
  1315. noxsave [BUGS=X86] Disables x86 extended register state save
  1316. and restore using xsave. The kernel will fallback to
  1317. enabling legacy floating-point and sse state.
  1318. nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
  1319. wfi(ARM) instruction doesn't work correctly and not to
  1320. use it. This is also useful when using JTAG debugger.
  1321. no-hlt [BUGS=X86-32] Tells the kernel that the hlt
  1322. instruction doesn't work correctly and not to
  1323. use it.
  1324. no_file_caps Tells the kernel not to honor file capabilities. The
  1325. only way then for a file to be executed with privilege
  1326. is to be setuid root or executed by root.
  1327. nohalt [IA-64] Tells the kernel not to use the power saving
  1328. function PAL_HALT_LIGHT when idle. This increases
  1329. power-consumption. On the positive side, it reduces
  1330. interrupt wake-up latency, which may improve performance
  1331. in certain environments such as networked servers or
  1332. real-time systems.
  1333. nohz= [KNL] Boottime enable/disable dynamic ticks
  1334. Valid arguments: on, off
  1335. Default: on
  1336. noiotrap [SH] Disables trapped I/O port accesses.
  1337. noirqdebug [X86-32] Disables the code which attempts to detect and
  1338. disable unhandled interrupt sources.
  1339. no_timer_check [X86,APIC] Disables the code which tests for
  1340. broken timer IRQ sources.
  1341. noisapnp [ISAPNP] Disables ISA PnP code.
  1342. noinitrd [RAM] Tells the kernel not to load any configured
  1343. initial RAM disk.
  1344. nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
  1345. remapping.
  1346. nointroute [IA-64]
  1347. nojitter [IA64] Disables jitter checking for ITC timers.
  1348. nolapic [X86-32,APIC] Do not enable or use the local APIC.
  1349. nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
  1350. noltlbs [PPC] Do not use large page/tlb entries for kernel
  1351. lowmem mapping on PPC40x.
  1352. nomca [IA-64] Disable machine check abort handling
  1353. nomce [X86-32] Machine Check Exception
  1354. nomfgpt [X86-32] Disable Multi-Function General Purpose
  1355. Timer usage (for AMD Geode machines).
  1356. norandmaps Don't use address space randomization. Equivalent to
  1357. echo 0 > /proc/sys/kernel/randomize_va_space
  1358. noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
  1359. noreplace-smp [X86-32,SMP] Don't replace SMP instructions
  1360. with UP alternatives
  1361. noresidual [PPC] Don't use residual data on PReP machines.
  1362. noresume [SWSUSP] Disables resume and restores original swap
  1363. space.
  1364. no-scroll [VGA] Disables scrollback.
  1365. This is required for the Braillex ib80-piezo Braille
  1366. reader made by F.H. Papenmeier (Germany).
  1367. nosbagart [IA-64]
  1368. nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
  1369. nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
  1370. and disable the IO APIC. legacy for "maxcpus=0".
  1371. nosoftlockup [KNL] Disable the soft-lockup detector.
  1372. noswapaccount [KNL] Disable accounting of swap in memory resource
  1373. controller. (See Documentation/cgroups/memory.txt)
  1374. nosync [HW,M68K] Disables sync negotiation for all devices.
  1375. notsc [BUGS=X86-32] Disable Time Stamp Counter
  1376. nousb [USB] Disable the USB subsystem
  1377. nowb [ARM]
  1378. nox2apic [X86-64,APIC] Do not enable x2APIC mode.
  1379. nptcg= [IA64] Override max number of concurrent global TLB
  1380. purges which is reported from either PAL_VM_SUMMARY or
  1381. SAL PALO.
  1382. nr_uarts= [SERIAL] maximum number of UARTs to be registered.
  1383. numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
  1384. one of ['zone', 'node', 'default'] can be specified
  1385. This can be set from sysctl after boot.
  1386. See Documentation/sysctl/vm.txt for details.
  1387. ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
  1388. See Documentation/debugging-via-ohci1394.txt for more
  1389. info.
  1390. olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
  1391. Rather than timing out after 20 ms if an EC
  1392. command is not properly ACKed, override the length
  1393. of the timeout. We have interrupts disabled while
  1394. waiting for the ACK, so if this is set too high
  1395. interrupts *may* be lost!
  1396. opl3= [HW,OSS]
  1397. Format: <io>
  1398. oprofile.timer= [HW]
  1399. Use timer interrupt instead of performance counters
  1400. oprofile.cpu_type= Force an oprofile cpu type
  1401. This might be useful if you have an older oprofile
  1402. userland or if you want common events.
  1403. Format: { arch_perfmon }
  1404. arch_perfmon: [X86] Force use of architectural
  1405. perfmon on Intel CPUs instead of the
  1406. CPU specific event set.
  1407. osst= [HW,SCSI] SCSI Tape Driver
  1408. Format: <buffer_size>,<write_threshold>
  1409. See also Documentation/scsi/st.txt.
  1410. panic= [KNL] Kernel behaviour on panic
  1411. Format: <timeout>
  1412. parkbd.port= [HW] Parallel port number the keyboard adapter is
  1413. connected to, default is 0.
  1414. Format: <parport#>
  1415. parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
  1416. 0 for XT, 1 for AT (default is AT).
  1417. Format: <mode>
  1418. parport= [HW,PPT] Specify parallel ports. 0 disables.
  1419. Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
  1420. Use 'auto' to force the driver to use any
  1421. IRQ/DMA settings detected (the default is to
  1422. ignore detected IRQ/DMA settings because of
  1423. possible conflicts). You can specify the base
  1424. address, IRQ, and DMA settings; IRQ and DMA
  1425. should be numbers, or 'auto' (for using detected
  1426. settings on that particular port), or 'nofifo'
  1427. (to avoid using a FIFO even if it is detected).
  1428. Parallel ports are assigned in the order they
  1429. are specified on the command line, starting
  1430. with parport0.
  1431. parport_init_mode= [HW,PPT]
  1432. Configure VIA parallel port to operate in
  1433. a specific mode. This is necessary on Pegasos
  1434. computer where firmware has no options for setting
  1435. up parallel port mode and sets it to spp.
  1436. Currently this function knows 686a and 8231 chips.
  1437. Format: [spp|ps2|epp|ecp|ecpepp]
  1438. pas2= [HW,OSS] Format:
  1439. <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
  1440. pas16= [HW,SCSI]
  1441. See header of drivers/scsi/pas16.c.
  1442. pause_on_oops=
  1443. Halt all CPUs after the first oops has been printed for
  1444. the specified number of seconds. This is to be used if
  1445. your oopses keep scrolling off the screen.
  1446. pcbit= [HW,ISDN]
  1447. pcd. [PARIDE]
  1448. See header of drivers/block/paride/pcd.c.
  1449. See also Documentation/blockdev/paride.txt.
  1450. pci=option[,option...] [PCI] various PCI subsystem options:
  1451. earlydump [X86] dump PCI config space before the kernel
  1452. changes anything
  1453. off [X86] don't probe for the PCI bus
  1454. bios [X86-32] force use of PCI BIOS, don't access
  1455. the hardware directly. Use this if your machine
  1456. has a non-standard PCI host bridge.
  1457. nobios [X86-32] disallow use of PCI BIOS, only direct
  1458. hardware access methods are allowed. Use this
  1459. if you experience crashes upon bootup and you
  1460. suspect they are caused by the BIOS.
  1461. conf1 [X86] Force use of PCI Configuration
  1462. Mechanism 1.
  1463. conf2 [X86] Force use of PCI Configuration
  1464. Mechanism 2.
  1465. noaer [PCIE] If the PCIEAER kernel config parameter is
  1466. enabled, this kernel boot option can be used to
  1467. disable the use of PCIE advanced error reporting.
  1468. nodomains [PCI] Disable support for multiple PCI
  1469. root domains (aka PCI segments, in ACPI-speak).
  1470. nommconf [X86] Disable use of MMCONFIG for PCI
  1471. Configuration
  1472. check_enable_amd_mmconf [X86] check for and enable
  1473. properly configured MMIO access to PCI
  1474. config space on AMD family 10h CPU
  1475. nomsi [MSI] If the PCI_MSI kernel config parameter is
  1476. enabled, this kernel boot option can be used to
  1477. disable the use of MSI interrupts system-wide.
  1478. noioapicquirk [APIC] Disable all boot interrupt quirks.
  1479. Safety option to keep boot IRQs enabled. This
  1480. should never be necessary.
  1481. ioapicreroute [APIC] Enable rerouting of boot IRQs to the
  1482. primary IO-APIC for bridges that cannot disable
  1483. boot IRQs. This fixes a source of spurious IRQs
  1484. when the system masks IRQs.
  1485. noioapicreroute [APIC] Disable workaround that uses the
  1486. boot IRQ equivalent of an IRQ that connects to
  1487. a chipset where boot IRQs cannot be disabled.
  1488. The opposite of ioapicreroute.
  1489. biosirq [X86-32] Use PCI BIOS calls to get the interrupt
  1490. routing table. These calls are known to be buggy
  1491. on several machines and they hang the machine
  1492. when used, but on other computers it's the only
  1493. way to get the interrupt routing table. Try
  1494. this option if the kernel is unable to allocate
  1495. IRQs or discover secondary PCI buses on your
  1496. motherboard.
  1497. rom [X86] Assign address space to expansion ROMs.
  1498. Use with caution as certain devices share
  1499. address decoders between ROMs and other
  1500. resources.
  1501. norom [X86] Do not assign address space to
  1502. expansion ROMs that do not already have
  1503. BIOS assigned address ranges.
  1504. irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
  1505. assigned automatically to PCI devices. You can
  1506. make the kernel exclude IRQs of your ISA cards
  1507. this way.
  1508. pirqaddr=0xAAAAA [X86] Specify the physical address
  1509. of the PIRQ table (normally generated
  1510. by the BIOS) if it is outside the
  1511. F0000h-100000h range.
  1512. lastbus=N [X86] Scan all buses thru bus #N. Can be
  1513. useful if the kernel is unable to find your
  1514. secondary buses and you want to tell it
  1515. explicitly which ones they are.
  1516. assign-busses [X86] Always assign all PCI bus
  1517. numbers ourselves, overriding
  1518. whatever the firmware may have done.
  1519. usepirqmask [X86] Honor the possible IRQ mask stored
  1520. in the BIOS $PIR table. This is needed on
  1521. some systems with broken BIOSes, notably
  1522. some HP Pavilion N5400 and Omnibook XE3
  1523. notebooks. This will have no effect if ACPI
  1524. IRQ routing is enabled.
  1525. noacpi [X86] Do not use ACPI for IRQ routing
  1526. or for PCI scanning.
  1527. use_crs [X86] Use _CRS for PCI resource
  1528. allocation.
  1529. routeirq Do IRQ routing for all PCI devices.
  1530. This is normally done in pci_enable_device(),
  1531. so this option is a temporary workaround
  1532. for broken drivers that don't call it.
  1533. skip_isa_align [X86] do not align io start addr, so can
  1534. handle more pci cards
  1535. firmware [ARM] Do not re-enumerate the bus but instead
  1536. just use the configuration from the
  1537. bootloader. This is currently used on
  1538. IXP2000 systems where the bus has to be
  1539. configured a certain way for adjunct CPUs.
  1540. noearly [X86] Don't do any early type 1 scanning.
  1541. This might help on some broken boards which
  1542. machine check when some devices' config space
  1543. is read. But various workarounds are disabled
  1544. and some IOMMU drivers will not work.
  1545. bfsort Sort PCI devices into breadth-first order.
  1546. This sorting is done to get a device
  1547. order compatible with older (<= 2.4) kernels.
  1548. nobfsort Don't sort PCI devices into breadth-first order.
  1549. cbiosize=nn[KMG] The fixed amount of bus space which is
  1550. reserved for the CardBus bridge's IO window.
  1551. The default value is 256 bytes.
  1552. cbmemsize=nn[KMG] The fixed amount of bus space which is
  1553. reserved for the CardBus bridge's memory
  1554. window. The default value is 64 megabytes.
  1555. resource_alignment=
  1556. Format:
  1557. [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
  1558. Specifies alignment and device to reassign
  1559. aligned memory resources.
  1560. If <order of align> is not specified,
  1561. PAGE_SIZE is used as alignment.
  1562. PCI-PCI bridge can be specified, if resource
  1563. windows need to be expanded.
  1564. ecrc= Enable/disable PCIe ECRC (transaction layer
  1565. end-to-end CRC checking).
  1566. bios: Use BIOS/firmware settings. This is the
  1567. the default.
  1568. off: Turn ECRC off
  1569. on: Turn ECRC on.
  1570. pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
  1571. Management.
  1572. off Disable ASPM.
  1573. force Enable ASPM even on devices that claim not to support it.
  1574. WARNING: Forcing ASPM on may cause system lockups.
  1575. pcmv= [HW,PCMCIA] BadgePAD 4
  1576. pd. [PARIDE]
  1577. See Documentation/blockdev/paride.txt.
  1578. pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
  1579. boot time.
  1580. Format: { 0 | 1 }
  1581. See arch/parisc/kernel/pdc_chassis.c
  1582. percpu_alloc= Select which percpu first chunk allocator to use.
  1583. Currently supported values are "embed" and "page".
  1584. Archs may support subset or none of the selections.
  1585. See comments in mm/percpu.c for details on each
  1586. allocator. This parameter is primarily for debugging
  1587. and performance comparison.
  1588. pf. [PARIDE]
  1589. See Documentation/blockdev/paride.txt.
  1590. pg. [PARIDE]
  1591. See Documentation/blockdev/paride.txt.
  1592. pirq= [SMP,APIC] Manual mp-table setup
  1593. See Documentation/x86/i386/IO-APIC.txt.
  1594. plip= [PPT,NET] Parallel port network link
  1595. Format: { parport<nr> | timid | 0 }
  1596. See also Documentation/parport.txt.
  1597. pmtmr= [X86] Manual setup of pmtmr I/O Port.
  1598. Override pmtimer IOPort with a hex value.
  1599. e.g. pmtmr=0x508
  1600. pnp.debug [PNP]
  1601. Enable PNP debug messages. This depends on the
  1602. CONFIG_PNP_DEBUG_MESSAGES option.
  1603. pnpacpi= [ACPI]
  1604. { off }
  1605. pnpbios= [ISAPNP]
  1606. { on | off | curr | res | no-curr | no-res }
  1607. pnp_reserve_irq=
  1608. [ISAPNP] Exclude IRQs for the autoconfiguration
  1609. pnp_reserve_dma=
  1610. [ISAPNP] Exclude DMAs for the autoconfiguration
  1611. pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
  1612. Ranges are in pairs (I/O port base and size).
  1613. pnp_reserve_mem=
  1614. [ISAPNP] Exclude memory regions for the
  1615. autoconfiguration.
  1616. Ranges are in pairs (memory base and size).
  1617. ports= [IP_VS_FTP] IPVS ftp helper module
  1618. Default is 21.
  1619. Up to 8 (IP_VS_APP_MAX_PORTS) ports
  1620. may be specified.
  1621. Format: <port>,<port>....
  1622. print-fatal-signals=
  1623. [KNL] debug: print fatal signals
  1624. print-fatal-signals=1: print segfault info to
  1625. the kernel console.
  1626. default: off.
  1627. printk.time= Show timing data prefixed to each printk message line
  1628. Format: <bool> (1/Y/y=enable, 0/N/n=disable)
  1629. processor.max_cstate= [HW,ACPI]
  1630. Limit processor to maximum C-state
  1631. max_cstate=9 overrides any DMI blacklist limit.
  1632. processor.nocst [HW,ACPI]
  1633. Ignore the _CST method to determine C-states,
  1634. instead using the legacy FADT method
  1635. profile= [KNL] Enable kernel profiling via /proc/profile
  1636. Format: [schedule,]<number>
  1637. Param: "schedule" - profile schedule points.
  1638. Param: <number> - step/bucket size as a power of 2 for
  1639. statistical time based profiling.
  1640. Param: "sleep" - profile D-state sleeping (millisecs).
  1641. Requires CONFIG_SCHEDSTATS
  1642. Param: "kvm" - profile VM exits.
  1643. prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
  1644. before loading.
  1645. See Documentation/blockdev/ramdisk.txt.
  1646. psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
  1647. probe for; one of (bare|imps|exps|lifebook|any).
  1648. psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
  1649. per second.
  1650. psmouse.resetafter= [HW,MOUSE]
  1651. Try to reset the device after so many bad packets
  1652. (0 = never).
  1653. psmouse.resolution=
  1654. [HW,MOUSE] Set desired mouse resolution, in dpi.
  1655. psmouse.smartscroll=
  1656. [HW,MOUSE] Controls Logitech smartscroll autorepeat.
  1657. 0 = disabled, 1 = enabled (default).
  1658. pss= [HW,OSS] Personal Sound System (ECHO ESC614)
  1659. Format:
  1660. <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
  1661. pt. [PARIDE]
  1662. See Documentation/blockdev/paride.txt.
  1663. pty.legacy_count=
  1664. [KNL] Number of legacy pty's. Overwrites compiled-in
  1665. default number.
  1666. quiet [KNL] Disable most log messages
  1667. r128= [HW,DRM]
  1668. raid= [HW,RAID]
  1669. See Documentation/md.txt.
  1670. ramdisk_blocksize= [RAM]
  1671. See Documentation/blockdev/ramdisk.txt.
  1672. ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
  1673. See Documentation/blockdev/ramdisk.txt.
  1674. rcupdate.blimit= [KNL,BOOT]
  1675. Set maximum number of finished RCU callbacks to process
  1676. in one batch.
  1677. rcupdate.qhimark= [KNL,BOOT]
  1678. Set threshold of queued
  1679. RCU callbacks over which batch limiting is disabled.
  1680. rcupdate.qlowmark= [KNL,BOOT]
  1681. Set threshold of queued RCU callbacks below which
  1682. batch limiting is re-enabled.
  1683. rdinit= [KNL]
  1684. Format: <full_path>
  1685. Run specified binary instead of /init from the ramdisk,
  1686. used for early userspace startup. See initrd.
  1687. reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
  1688. Format: <reboot_mode>[,<reboot_mode2>[,...]]
  1689. See arch/*/kernel/reboot.c or arch/*/kernel/process.c
  1690. relax_domain_level=
  1691. [KNL, SMP] Set scheduler's default relax_domain_level.
  1692. See Documentation/cgroups/cpusets.txt.
  1693. reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
  1694. reservetop= [X86-32]
  1695. Format: nn[KMG]
  1696. Reserves a hole at the top of the kernel virtual
  1697. address space.
  1698. reset_devices [KNL] Force drivers to reset the underlying device
  1699. during initialization.
  1700. resume= [SWSUSP]
  1701. Specify the partition device for software suspend
  1702. resume_offset= [SWSUSP]
  1703. Specify the offset from the beginning of the partition
  1704. given by "resume=" at which the swap header is located,
  1705. in <PAGE_SIZE> units (needed only for swap files).
  1706. See Documentation/power/swsusp-and-swap-files.txt
  1707. retain_initrd [RAM] Keep initrd memory after extraction
  1708. rhash_entries= [KNL,NET]
  1709. Set number of hash buckets for route cache
  1710. riscom8= [HW,SERIAL]
  1711. Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
  1712. ro [KNL] Mount root device read-only on boot
  1713. root= [KNL] Root filesystem
  1714. rootdelay= [KNL] Delay (in seconds) to pause before attempting to
  1715. mount the root filesystem
  1716. rootflags= [KNL] Set root filesystem mount option string
  1717. rootfstype= [KNL] Set root filesystem type
  1718. rootwait [KNL] Wait (indefinitely) for root device to show up.
  1719. Useful for devices that are detected asynchronously
  1720. (e.g. USB and MMC devices).
  1721. root_plug.vendor_id=
  1722. [ROOTPLUG] Override the default vendor ID
  1723. root_plug.product_id=
  1724. [ROOTPLUG] Override the default product ID
  1725. root_plug.debug=
  1726. [ROOTPLUG] Enable debugging output
  1727. rw [KNL] Mount root device read-write on boot
  1728. S [KNL] Run init in single mode
  1729. sa1100ir [NET]
  1730. See drivers/net/irda/sa1100_ir.c.
  1731. sbni= [NET] Granch SBNI12 leased line adapter
  1732. sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
  1733. Format: <io>[,<timeout>[,<isapnp>]]
  1734. scsi_debug_*= [SCSI]
  1735. See drivers/scsi/scsi_debug.c.
  1736. scsi_default_dev_flags=
  1737. [SCSI] SCSI default device flags
  1738. Format: <integer>
  1739. scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
  1740. Format: <vendor>:<model>:<flags>
  1741. (flags are integer value)
  1742. scsi_logging_level= [SCSI] a bit mask of logging levels
  1743. See drivers/scsi/scsi_logging.h for bits. Also
  1744. settable via sysctl at dev.scsi.logging_level
  1745. (/proc/sys/dev/scsi/logging_level).
  1746. There is also a nice 'scsi_logging_level' script in the
  1747. S390-tools package, available for download at
  1748. http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
  1749. scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
  1750. discovered. async scans them in kernel threads,
  1751. allowing boot to proceed. none ignores them, expecting
  1752. user space to do the scan.
  1753. security= [SECURITY] Choose a security module to enable at boot.
  1754. If this boot parameter is not specified, only the first
  1755. security module asking for security registration will be
  1756. loaded. An invalid security module name will be treated
  1757. as if no module has been chosen.
  1758. selinux= [SELINUX] Disable or enable SELinux at boot time.
  1759. Format: { "0" | "1" }
  1760. See security/selinux/Kconfig help text.
  1761. 0 -- disable.
  1762. 1 -- enable.
  1763. Default value is set via kernel config option.
  1764. If enabled at boot time, /selinux/disable can be used
  1765. later to disable prior to initial policy load.
  1766. serialnumber [BUGS=X86-32]
  1767. shapers= [NET]
  1768. Maximal number of shapers.
  1769. show_msr= [x86] show boot-time MSR settings
  1770. Format: { <integer> }
  1771. Show boot-time (BIOS-initialized) MSR settings.
  1772. The parameter means the number of CPUs to show,
  1773. for example 1 means boot CPU only.
  1774. sim710= [SCSI,HW]
  1775. See header of drivers/scsi/sim710.c.
  1776. simeth= [IA-64]
  1777. simscsi=
  1778. slram= [HW,MTD]
  1779. slub_debug[=options[,slabs]] [MM, SLUB]
  1780. Enabling slub_debug allows one to determine the
  1781. culprit if slab objects become corrupted. Enabling
  1782. slub_debug can create guard zones around objects and
  1783. may poison objects when not in use. Also tracks the
  1784. last alloc / free. For more information see
  1785. Documentation/vm/slub.txt.
  1786. slub_max_order= [MM, SLUB]
  1787. Determines the maximum allowed order for slabs.
  1788. A high setting may cause OOMs due to memory
  1789. fragmentation. For more information see
  1790. Documentation/vm/slub.txt.
  1791. slub_min_objects= [MM, SLUB]
  1792. The minimum number of objects per slab. SLUB will
  1793. increase the slab order up to slub_max_order to
  1794. generate a sufficiently large slab able to contain
  1795. the number of objects indicated. The higher the number
  1796. of objects the smaller the overhead of tracking slabs
  1797. and the less frequently locks need to be acquired.
  1798. For more information see Documentation/vm/slub.txt.
  1799. slub_min_order= [MM, SLUB]
  1800. Determines the mininum page order for slabs. Must be
  1801. lower than slub_max_order.
  1802. For more information see Documentation/vm/slub.txt.
  1803. slub_nomerge [MM, SLUB]
  1804. Disable merging of slabs with similar size. May be
  1805. necessary if there is some reason to distinguish
  1806. allocs to different slabs. Debug options disable
  1807. merging on their own.
  1808. For more information see Documentation/vm/slub.txt.
  1809. smart2= [HW]
  1810. Format: <io1>[,<io2>[,...,<io8>]]
  1811. smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
  1812. attempt to substitute SMP alternatives once at boot.
  1813. smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
  1814. smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
  1815. smsc-ircc2.ircc_sir= [HW] SIR base I/O port
  1816. smsc-ircc2.ircc_fir= [HW] FIR base I/O port
  1817. smsc-ircc2.ircc_irq= [HW] IRQ line
  1818. smsc-ircc2.ircc_dma= [HW] DMA channel
  1819. smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
  1820. 0: Toshiba Satellite 1800 (GP data pin select)
  1821. 1: Fast pin select (default)
  1822. 2: ATC IRMode
  1823. snd-ad1816a= [HW,ALSA]
  1824. snd-ad1848= [HW,ALSA]
  1825. snd-ali5451= [HW,ALSA]
  1826. snd-als100= [HW,ALSA]
  1827. snd-als4000= [HW,ALSA]
  1828. snd-azt2320= [HW,ALSA]
  1829. snd-cmi8330= [HW,ALSA]
  1830. snd-cmipci= [HW,ALSA]
  1831. snd-cs4231= [HW,ALSA]
  1832. snd-cs4232= [HW,ALSA]
  1833. snd-cs4236= [HW,ALSA]
  1834. snd-cs4281= [HW,ALSA]
  1835. snd-cs46xx= [HW,ALSA]
  1836. snd-dt019x= [HW,ALSA]
  1837. snd-dummy= [HW,ALSA]
  1838. snd-emu10k1= [HW,ALSA]
  1839. snd-ens1370= [HW,ALSA]
  1840. snd-ens1371= [HW,ALSA]
  1841. snd-es968= [HW,ALSA]
  1842. snd-es1688= [HW,ALSA]
  1843. snd-es18xx= [HW,ALSA]
  1844. snd-es1938= [HW,ALSA]
  1845. snd-es1968= [HW,ALSA]
  1846. snd-fm801= [HW,ALSA]
  1847. snd-gusclassic= [HW,ALSA]
  1848. snd-gusextreme= [HW,ALSA]
  1849. snd-gusmax= [HW,ALSA]
  1850. snd-hdsp= [HW,ALSA]
  1851. snd-ice1712= [HW,ALSA]
  1852. snd-intel8x0= [HW,ALSA]
  1853. snd-interwave= [HW,ALSA]
  1854. snd-interwave-stb=
  1855. [HW,ALSA]
  1856. snd-korg1212= [HW,ALSA]
  1857. snd-maestro3= [HW,ALSA]
  1858. snd-mpu401= [HW,ALSA]
  1859. snd-mtpav= [HW,ALSA]
  1860. snd-nm256= [HW,ALSA]
  1861. snd-opl3sa2= [HW,ALSA]
  1862. snd-opti92x-ad1848=
  1863. [HW,ALSA]
  1864. snd-opti92x-cs4231=
  1865. [HW,ALSA]
  1866. snd-opti93x= [HW,ALSA]
  1867. snd-pmac= [HW,ALSA]
  1868. snd-rme32= [HW,ALSA]
  1869. snd-rme96= [HW,ALSA]
  1870. snd-rme9652= [HW,ALSA]
  1871. snd-sb8= [HW,ALSA]
  1872. snd-sb16= [HW,ALSA]
  1873. snd-sbawe= [HW,ALSA]
  1874. snd-serial= [HW,ALSA]
  1875. snd-sgalaxy= [HW,ALSA]
  1876. snd-sonicvibes= [HW,ALSA]
  1877. snd-sun-amd7930=
  1878. [HW,ALSA]
  1879. snd-sun-cs4231= [HW,ALSA]
  1880. snd-trident= [HW,ALSA]
  1881. snd-usb-audio= [HW,ALSA,USB]
  1882. snd-via82xx= [HW,ALSA]
  1883. snd-virmidi= [HW,ALSA]
  1884. snd-wavefront= [HW,ALSA]
  1885. snd-ymfpci= [HW,ALSA]
  1886. softlockup_panic=
  1887. [KNL] Should the soft-lockup detector generate panics.
  1888. sonypi.*= [HW] Sony Programmable I/O Control Device driver
  1889. See Documentation/sonypi.txt
  1890. specialix= [HW,SERIAL] Specialix multi-serial port adapter
  1891. See Documentation/serial/specialix.txt.
  1892. spia_io_base= [HW,MTD]
  1893. spia_fio_base=
  1894. spia_pedr=
  1895. spia_peddr=
  1896. sscape= [HW,OSS]
  1897. Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
  1898. st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
  1899. See Documentation/scsi/st.txt.
  1900. stacktrace [FTRACE]
  1901. Enabled the stack tracer on boot up.
  1902. sti= [PARISC,HW]
  1903. Format: <num>
  1904. Set the STI (builtin display/keyboard on the HP-PARISC
  1905. machines) console (graphic card) which should be used
  1906. as the initial boot-console.
  1907. See also comment in drivers/video/console/sticore.c.
  1908. sti_font= [HW]
  1909. See comment in drivers/video/console/sticore.c.
  1910. stifb= [HW]
  1911. Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
  1912. sunrpc.min_resvport=
  1913. sunrpc.max_resvport=
  1914. [NFS,SUNRPC]
  1915. SunRPC servers often require that client requests
  1916. originate from a privileged port (i.e. a port in the
  1917. range 0 < portnr < 1024).
  1918. An administrator who wishes to reserve some of these
  1919. ports for other uses may adjust the range that the
  1920. kernel's sunrpc client considers to be privileged
  1921. using these two parameters to set the minimum and
  1922. maximum port values.
  1923. sunrpc.pool_mode=
  1924. [NFS]
  1925. Control how the NFS server code allocates CPUs to
  1926. service thread pools. Depending on how many NICs
  1927. you have and where their interrupts are bound, this
  1928. option will affect which CPUs will do NFS serving.
  1929. Note: this parameter cannot be changed while the
  1930. NFS server is running.
  1931. auto the server chooses an appropriate mode
  1932. automatically using heuristics
  1933. global a single global pool contains all CPUs
  1934. percpu one pool for each CPU
  1935. pernode one pool for each NUMA node (equivalent
  1936. to global on non-NUMA machines)
  1937. sunrpc.tcp_slot_table_entries=
  1938. sunrpc.udp_slot_table_entries=
  1939. [NFS,SUNRPC]
  1940. Sets the upper limit on the number of simultaneous
  1941. RPC calls that can be sent from the client to a
  1942. server. Increasing these values may allow you to
  1943. improve throughput, but will also increase the
  1944. amount of memory reserved for use by the client.
  1945. swiotlb= [IA-64] Number of I/O TLB slabs
  1946. switches= [HW,M68k]
  1947. sym53c416= [HW,SCSI]
  1948. See header of drivers/scsi/sym53c416.c.
  1949. sysrq_always_enabled
  1950. [KNL]
  1951. Ignore sysrq setting - this boot parameter will
  1952. neutralize any effect of /proc/sys/kernel/sysrq.
  1953. Useful for debugging.
  1954. t128= [HW,SCSI]
  1955. See header of drivers/scsi/t128.c.
  1956. tdfx= [HW,DRM]
  1957. test_suspend= [SUSPEND]
  1958. Specify "mem" (for Suspend-to-RAM) or "standby" (for
  1959. standby suspend) as the system sleep state to briefly
  1960. enter during system startup. The system is woken from
  1961. this state using a wakeup-capable RTC alarm.
  1962. thash_entries= [KNL,NET]
  1963. Set number of hash buckets for TCP connection
  1964. thermal.act= [HW,ACPI]
  1965. -1: disable all active trip points in all thermal zones
  1966. <degrees C>: override all lowest active trip points
  1967. thermal.crt= [HW,ACPI]
  1968. -1: disable all critical trip points in all thermal zones
  1969. <degrees C>: override all critical trip points
  1970. thermal.nocrt= [HW,ACPI]
  1971. Set to disable actions on ACPI thermal zone
  1972. critical and hot trip points.
  1973. thermal.off= [HW,ACPI]
  1974. 1: disable ACPI thermal control
  1975. thermal.psv= [HW,ACPI]
  1976. -1: disable all passive trip points
  1977. <degrees C>: override all passive trip points to this
  1978. value
  1979. thermal.tzp= [HW,ACPI]
  1980. Specify global default ACPI thermal zone polling rate
  1981. <deci-seconds>: poll all this frequency
  1982. 0: no polling (default)
  1983. tmscsim= [HW,SCSI]
  1984. See comment before function dc390_setup() in
  1985. drivers/scsi/tmscsim.c.
  1986. topology= [S390]
  1987. Format: {off | on}
  1988. Specify if the kernel should make use of the cpu
  1989. topology informations if the hardware supports these.
  1990. The scheduler will make use of these informations and
  1991. e.g. base its process migration decisions on it.
  1992. Default is off.
  1993. tp720= [HW,PS2]
  1994. trace_buf_size=nn[KMG]
  1995. [FTRACE] will set tracing buffer size.
  1996. trace_event=[event-list]
  1997. [FTRACE] Set and start specified trace events in order
  1998. to facilitate early boot debugging.
  1999. See also Documentation/trace/events.txt
  2000. trix= [HW,OSS] MediaTrix AudioTrix Pro
  2001. Format:
  2002. <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
  2003. tsc= Disable clocksource-must-verify flag for TSC.
  2004. Format: <string>
  2005. [x86] reliable: mark tsc clocksource as reliable, this
  2006. disables clocksource verification at runtime.
  2007. Used to enable high-resolution timer mode on older
  2008. hardware, and in virtualized environment.
  2009. turbografx.map[2|3]= [HW,JOY]
  2010. TurboGraFX parallel port interface
  2011. Format:
  2012. <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
  2013. See also Documentation/input/joystick-parport.txt
  2014. u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
  2015. See header of drivers/scsi/u14-34f.c.
  2016. uart401= [HW,OSS]
  2017. Format: <io>,<irq>
  2018. uart6850= [HW,OSS]
  2019. Format: <io>,<irq>
  2020. uhci-hcd.ignore_oc=
  2021. [USB] Ignore overcurrent events (default N).
  2022. Some badly-designed motherboards generate lots of
  2023. bogus events, for ports that aren't wired to
  2024. anything. Set this parameter to avoid log spamming.
  2025. Note that genuine overcurrent events won't be
  2026. reported either.
  2027. unknown_nmi_panic
  2028. [X86]
  2029. Set unknown_nmi_panic=1 early on boot.
  2030. usbcore.autosuspend=
  2031. [USB] The autosuspend time delay (in seconds) used
  2032. for newly-detected USB devices (default 2). This
  2033. is the time required before an idle device will be
  2034. autosuspended. Devices for which the delay is set
  2035. to a negative value won't be autosuspended at all.
  2036. usbcore.usbfs_snoop=
  2037. [USB] Set to log all usbfs traffic (default 0 = off).
  2038. usbcore.blinkenlights=
  2039. [USB] Set to cycle leds on hubs (default 0 = off).
  2040. usbcore.old_scheme_first=
  2041. [USB] Start with the old device initialization
  2042. scheme (default 0 = off).
  2043. usbcore.use_both_schemes=
  2044. [USB] Try the other device initialization scheme
  2045. if the first one fails (default 1 = enabled).
  2046. usbcore.initial_descriptor_timeout=
  2047. [USB] Specifies timeout for the initial 64-byte
  2048. USB_REQ_GET_DESCRIPTOR request in milliseconds
  2049. (default 5000 = 5.0 seconds).
  2050. usbhid.mousepoll=
  2051. [USBHID] The interval which mice are to be polled at.
  2052. usb-storage.delay_use=
  2053. [UMS] The delay in seconds before a new device is
  2054. scanned for Logical Units (default 5).
  2055. usb-storage.quirks=
  2056. [UMS] A list of quirks entries to supplement or
  2057. override the built-in unusual_devs list. List
  2058. entries are separated by commas. Each entry has
  2059. the form VID:PID:Flags where VID and PID are Vendor
  2060. and Product ID values (4-digit hex numbers) and
  2061. Flags is a set of characters, each corresponding
  2062. to a common usb-storage quirk flag as follows:
  2063. a = SANE_SENSE (collect more than 18 bytes
  2064. of sense data);
  2065. c = FIX_CAPACITY (decrease the reported
  2066. device capacity by one sector);
  2067. h = CAPACITY_HEURISTICS (decrease the
  2068. reported device capacity by one
  2069. sector if the number is odd);
  2070. i = IGNORE_DEVICE (don't bind to this
  2071. device);
  2072. l = NOT_LOCKABLE (don't try to lock and
  2073. unlock ejectable media);
  2074. m = MAX_SECTORS_64 (don't transfer more
  2075. than 64 sectors = 32 KB at a time);
  2076. o = CAPACITY_OK (accept the capacity
  2077. reported by the device);
  2078. r = IGNORE_RESIDUE (the device reports
  2079. bogus residue values);
  2080. s = SINGLE_LUN (the device has only one
  2081. Logical Unit);
  2082. w = NO_WP_DETECT (don't test whether the
  2083. medium is write-protected).
  2084. Example: quirks=0419:aaf5:rl,0421:0433:rc
  2085. vdso= [X86,SH]
  2086. vdso=2: enable compat VDSO (default with COMPAT_VDSO)
  2087. vdso=1: enable VDSO (default)
  2088. vdso=0: disable VDSO mapping
  2089. vdso32= [X86]
  2090. vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
  2091. vdso32=1: enable 32-bit VDSO (default)
  2092. vdso32=0: disable 32-bit VDSO mapping
  2093. vector= [IA-64,SMP]
  2094. vector=percpu: enable percpu vector domain
  2095. video= [FB] Frame buffer configuration
  2096. See Documentation/fb/modedb.txt.
  2097. vga= [BOOT,X86-32] Select a particular video mode
  2098. See Documentation/x86/boot.txt and
  2099. Documentation/svga.txt.
  2100. Use vga=ask for menu.
  2101. This is actually a boot loader parameter; the value is
  2102. passed to the kernel using a special protocol.
  2103. vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
  2104. size of <nn>. This can be used to increase the
  2105. minimum size (128MB on x86). It can also be used to
  2106. decrease the size and leave more room for directly
  2107. mapped kernel RAM.
  2108. vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
  2109. Format: <command>
  2110. vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
  2111. Format: <command>
  2112. vmpoff= [KNL,S390] Perform z/VM CP command after power off.
  2113. Format: <command>
  2114. vt.default_blu= [VT]
  2115. Format: <blue0>,<blue1>,<blue2>,...,<blue15>
  2116. Change the default blue palette of the console.
  2117. This is a 16-member array composed of values
  2118. ranging from 0-255.
  2119. vt.default_grn= [VT]
  2120. Format: <green0>,<green1>,<green2>,...,<green15>
  2121. Change the default green palette of the console.
  2122. This is a 16-member array composed of values
  2123. ranging from 0-255.
  2124. vt.default_red= [VT]
  2125. Format: <red0>,<red1>,<red2>,...,<red15>
  2126. Change the default red palette of the console.
  2127. This is a 16-member array composed of values
  2128. ranging from 0-255.
  2129. vt.default_utf8=
  2130. [VT]
  2131. Format=<0|1>
  2132. Set system-wide default UTF-8 mode for all tty's.
  2133. Default is 1, i.e. UTF-8 mode is enabled for all
  2134. newly opened terminals.
  2135. waveartist= [HW,OSS]
  2136. Format: <io>,<irq>,<dma>,<dma2>
  2137. wd33c93= [HW,SCSI]
  2138. See header of drivers/scsi/wd33c93.c.
  2139. wd7000= [HW,SCSI]
  2140. See header of drivers/scsi/wd7000.c.
  2141. wdt= [WDT] Watchdog
  2142. See Documentation/watchdog/wdt.txt.
  2143. x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
  2144. default x2apic cluster mode on platforms
  2145. supporting x2apic.
  2146. xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
  2147. xd_geo= See header of drivers/block/xd.c.
  2148. xirc2ps_cs= [NET,PCMCIA]
  2149. Format:
  2150. <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
  2151. ______________________________________________________________________
  2152. TODO:
  2153. Add documentation for ALSA options.
  2154. Add more DRM drivers.