kernel-parameters.txt 119 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. ARM ARM architecture is enabled.
  34. AVR32 AVR32 architecture is enabled.
  35. AX25 Appropriate AX.25 support is enabled.
  36. BLACKFIN Blackfin architecture is enabled.
  37. CLK Common clock infrastructure is enabled.
  38. CMA Contiguous Memory Area support is enabled.
  39. DRM Direct Rendering Management support is enabled.
  40. DYNAMIC_DEBUG Build in debug messages and enable them at runtime
  41. EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
  42. EFI EFI Partitioning (GPT) is enabled
  43. EIDE EIDE/ATAPI support is enabled.
  44. EVM Extended Verification Module
  45. FB The frame buffer device is enabled.
  46. FTRACE Function tracing enabled.
  47. GCOV GCOV profiling is enabled.
  48. HW Appropriate hardware is enabled.
  49. IA-64 IA-64 architecture is enabled.
  50. IMA Integrity measurement architecture is enabled.
  51. IOSCHED More than one I/O scheduler is enabled.
  52. IP_PNP IP DHCP, BOOTP, or RARP is enabled.
  53. IPV6 IPv6 support is enabled.
  54. ISAPNP ISA PnP code is enabled.
  55. ISDN Appropriate ISDN support is enabled.
  56. JOY Appropriate joystick support is enabled.
  57. KGDB Kernel debugger support is enabled.
  58. KVM Kernel Virtual Machine support is enabled.
  59. LIBATA Libata driver is enabled
  60. LP Printer support is enabled.
  61. LOOP Loopback device support is enabled.
  62. M68k M68k architecture is enabled.
  63. These options have more detailed description inside of
  64. Documentation/m68k/kernel-options.txt.
  65. MDA MDA console support is enabled.
  66. MIPS MIPS architecture is enabled.
  67. MOUSE Appropriate mouse support is enabled.
  68. MSI Message Signaled Interrupts (PCI).
  69. MTD MTD (Memory Technology Device) support is enabled.
  70. NET Appropriate network support is enabled.
  71. NUMA NUMA support is enabled.
  72. NFS Appropriate NFS support is enabled.
  73. OSS OSS sound support is enabled.
  74. PV_OPS A paravirtualized kernel is enabled.
  75. PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
  76. PARISC The PA-RISC architecture is enabled.
  77. PCI PCI bus support is enabled.
  78. PCIE PCI Express support is enabled.
  79. PCMCIA The PCMCIA subsystem is enabled.
  80. PNP Plug & Play support is enabled.
  81. PPC PowerPC architecture is enabled.
  82. PPT Parallel port support is enabled.
  83. PS2 Appropriate PS/2 support is enabled.
  84. RAM RAM disk support is enabled.
  85. S390 S390 architecture is enabled.
  86. SCSI Appropriate SCSI support is enabled.
  87. A lot of drivers have their options described inside
  88. the Documentation/scsi/ sub-directory.
  89. SECURITY Different security models are enabled.
  90. SELINUX SELinux support is enabled.
  91. APPARMOR AppArmor support is enabled.
  92. SERIAL Serial support is enabled.
  93. SH SuperH architecture is enabled.
  94. SMP The kernel is an SMP kernel.
  95. SPARC Sparc architecture is enabled.
  96. SWSUSP Software suspend (hibernation) is enabled.
  97. SUSPEND System suspend states are enabled.
  98. TPM TPM drivers are enabled.
  99. TS Appropriate touchscreen support is enabled.
  100. UMS USB Mass Storage support is enabled.
  101. USB USB support is enabled.
  102. USBHID USB Human Interface Device support is enabled.
  103. V4L Video For Linux support is enabled.
  104. VMMIO Driver for memory mapped virtio devices is enabled.
  105. VGA The VGA console has been enabled.
  106. VT Virtual terminal support is enabled.
  107. WDT Watchdog support is enabled.
  108. XT IBM PC/XT MFM hard disk support is enabled.
  109. X86-32 X86-32, aka i386 architecture is enabled.
  110. X86-64 X86-64 architecture is enabled.
  111. More X86-64 boot options can be found in
  112. Documentation/x86/x86_64/boot-options.txt .
  113. X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
  114. XEN Xen support is enabled
  115. In addition, the following text indicates that the option:
  116. BUGS= Relates to possible processor bugs on the said processor.
  117. KNL Is a kernel start-up parameter.
  118. BOOT Is a boot loader parameter.
  119. Parameters denoted with BOOT are actually interpreted by the boot
  120. loader, and have no meaning to the kernel directly.
  121. Do not modify the syntax of boot loader parameters without extreme
  122. need or coordination with <Documentation/x86/boot.txt>.
  123. There are also arch-specific kernel-parameters not documented here.
  124. See for example <Documentation/x86/x86_64/boot-options.txt>.
  125. Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
  126. a trailing = on the name of any parameter states that that parameter will
  127. be entered as an environment variable, whereas its absence indicates that
  128. it will appear as a kernel argument readable via /proc/cmdline by programs
  129. running once the system is up.
  130. The number of kernel parameters is not limited, but the length of the
  131. complete command line (parameters including spaces etc.) is limited to
  132. a fixed number of characters. This limit depends on the architecture
  133. and is between 256 and 4096 characters. It is defined in the file
  134. ./include/asm/setup.h as COMMAND_LINE_SIZE.
  135. Finally, the [KMG] suffix is commonly described after a number of kernel
  136. parameter values. These 'K', 'M', and 'G' letters represent the _binary_
  137. multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
  138. bytes respectively. Such letter suffixes can also be entirely omitted.
  139. acpi= [HW,ACPI,X86]
  140. Advanced Configuration and Power Interface
  141. Format: { force | off | strict | noirq | rsdt }
  142. force -- enable ACPI if default was off
  143. off -- disable ACPI if default was on
  144. noirq -- do not use ACPI for IRQ routing
  145. strict -- Be less tolerant of platforms that are not
  146. strictly ACPI specification compliant.
  147. rsdt -- prefer RSDT over (default) XSDT
  148. copy_dsdt -- copy DSDT to memory
  149. See also Documentation/power/runtime_pm.txt, pci=noacpi
  150. acpi_rsdp= [ACPI,EFI,KEXEC]
  151. Pass the RSDP address to the kernel, mostly used
  152. on machines running EFI runtime service to boot the
  153. second kernel for kdump.
  154. acpi_apic_instance= [ACPI, IOAPIC]
  155. Format: <int>
  156. 2: use 2nd APIC table, if available
  157. 1,0: use 1st APIC table
  158. default: 0
  159. acpi_backlight= [HW,ACPI]
  160. acpi_backlight=vendor
  161. acpi_backlight=video
  162. If set to vendor, prefer vendor specific driver
  163. (e.g. thinkpad_acpi, sony_acpi, etc.) instead
  164. of the ACPI video.ko driver.
  165. acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
  166. acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
  167. Format: <int>
  168. CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
  169. debug output. Bits in debug_layer correspond to a
  170. _COMPONENT in an ACPI source file, e.g.,
  171. #define _COMPONENT ACPI_PCI_COMPONENT
  172. Bits in debug_level correspond to a level in
  173. ACPI_DEBUG_PRINT statements, e.g.,
  174. ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
  175. The debug_level mask defaults to "info". See
  176. Documentation/acpi/debug.txt for more information about
  177. debug layers and levels.
  178. Enable processor driver info messages:
  179. acpi.debug_layer=0x20000000
  180. Enable PCI/PCI interrupt routing info messages:
  181. acpi.debug_layer=0x400000
  182. Enable AML "Debug" output, i.e., stores to the Debug
  183. object while interpreting AML:
  184. acpi.debug_layer=0xffffffff acpi.debug_level=0x2
  185. Enable all messages related to ACPI hardware:
  186. acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
  187. Some values produce so much output that the system is
  188. unusable. The "log_buf_len" parameter may be useful
  189. if you need to capture more output.
  190. acpi_irq_balance [HW,ACPI]
  191. ACPI will balance active IRQs
  192. default in APIC mode
  193. acpi_irq_nobalance [HW,ACPI]
  194. ACPI will not move active IRQs (default)
  195. default in PIC mode
  196. acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
  197. Format: <irq>,<irq>...
  198. acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
  199. use by PCI
  200. Format: <irq>,<irq>...
  201. acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
  202. acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
  203. Format: To spoof as Windows 98: ="Microsoft Windows"
  204. acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
  205. acpi_osi="string1" # add string1
  206. acpi_osi="!string2" # remove string2
  207. acpi_osi=! # disable all built-in OS vendor
  208. strings
  209. acpi_osi= # disable all strings
  210. 'acpi_osi=!' can be used in combination with single or
  211. multiple 'acpi_osi="string1"' to support specific OS
  212. vendor string(s). Note that such command can only
  213. affect the default state of the OS vendor strings, thus
  214. it cannot affect the default state of the feature group
  215. strings and the current state of the OS vendor strings,
  216. specifying it multiple times through kernel command line
  217. is meaningless.
  218. Examples:
  219. 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
  220. to 'acpi_osi="Windows 2000" acpi_osi=!', they all
  221. can make '_OSI("Windows 2000")' TRUE.
  222. 'acpi_osi=' cannot be used in combination with other
  223. 'acpi_osi=' command lines, the _OSI method will not
  224. exist in the ACPI namespace. NOTE that such command can
  225. only affect the _OSI support state, thus specifying it
  226. multiple times through kernel command line is also
  227. meaningless.
  228. Examples:
  229. 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
  230. FALSE.
  231. acpi_pm_good [X86]
  232. Override the pmtimer bug detection: force the kernel
  233. to assume that this machine's pmtimer latches its value
  234. and always returns good values.
  235. acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
  236. Format: { level | edge | high | low }
  237. acpi_serialize [HW,ACPI] force serialization of AML methods
  238. acpi_skip_timer_override [HW,ACPI]
  239. Recognize and ignore IRQ0/pin2 Interrupt Override.
  240. For broken nForce2 BIOS resulting in XT-PIC timer.
  241. acpi_sleep= [HW,ACPI] Sleep options
  242. Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
  243. old_ordering, nonvs, sci_force_enable }
  244. See Documentation/power/video.txt for information on
  245. s3_bios and s3_mode.
  246. s3_beep is for debugging; it makes the PC's speaker beep
  247. as soon as the kernel's real-mode entry point is called.
  248. s4_nohwsig prevents ACPI hardware signature from being
  249. used during resume from hibernation.
  250. old_ordering causes the ACPI 1.0 ordering of the _PTS
  251. control method, with respect to putting devices into
  252. low power states, to be enforced (the ACPI 2.0 ordering
  253. of _PTS is used by default).
  254. nonvs prevents the kernel from saving/restoring the
  255. ACPI NVS memory during suspend/hibernation and resume.
  256. sci_force_enable causes the kernel to set SCI_EN directly
  257. on resume from S1/S3 (which is against the ACPI spec,
  258. but some broken systems don't work without it).
  259. acpi_use_timer_override [HW,ACPI]
  260. Use timer override. For some broken Nvidia NF5 boards
  261. that require a timer override, but don't have HPET
  262. acpi_enforce_resources= [ACPI]
  263. { strict | lax | no }
  264. Check for resource conflicts between native drivers
  265. and ACPI OperationRegions (SystemIO and SystemMemory
  266. only). IO ports and memory declared in ACPI might be
  267. used by the ACPI subsystem in arbitrary AML code and
  268. can interfere with legacy drivers.
  269. strict (default): access to resources claimed by ACPI
  270. is denied; legacy drivers trying to access reserved
  271. resources will fail to bind to device using them.
  272. lax: access to resources claimed by ACPI is allowed;
  273. legacy drivers trying to access reserved resources
  274. will bind successfully but a warning message is logged.
  275. no: ACPI OperationRegions are not marked as reserved,
  276. no further checks are performed.
  277. add_efi_memmap [EFI; X86] Include EFI memory map in
  278. kernel's map of available physical RAM.
  279. agp= [AGP]
  280. { off | try_unsupported }
  281. off: disable AGP support
  282. try_unsupported: try to drive unsupported chipsets
  283. (may crash computer or cause data corruption)
  284. ALSA [HW,ALSA]
  285. See Documentation/sound/alsa/alsa-parameters.txt
  286. alignment= [KNL,ARM]
  287. Allow the default userspace alignment fault handler
  288. behaviour to be specified. Bit 0 enables warnings,
  289. bit 1 enables fixups, and bit 2 sends a segfault.
  290. align_va_addr= [X86-64]
  291. Align virtual addresses by clearing slice [14:12] when
  292. allocating a VMA at process creation time. This option
  293. gives you up to 3% performance improvement on AMD F15h
  294. machines (where it is enabled by default) for a
  295. CPU-intensive style benchmark, and it can vary highly in
  296. a microbenchmark depending on workload and compiler.
  297. 32: only for 32-bit processes
  298. 64: only for 64-bit processes
  299. on: enable for both 32- and 64-bit processes
  300. off: disable for both 32- and 64-bit processes
  301. alloc_snapshot [FTRACE]
  302. Allocate the ftrace snapshot buffer on boot up when the
  303. main buffer is allocated. This is handy if debugging
  304. and you need to use tracing_snapshot() on boot up, and
  305. do not want to use tracing_snapshot_alloc() as it needs
  306. to be done where GFP_KERNEL allocations are allowed.
  307. amd_iommu= [HW,X86-64]
  308. Pass parameters to the AMD IOMMU driver in the system.
  309. Possible values are:
  310. fullflush - enable flushing of IO/TLB entries when
  311. they are unmapped. Otherwise they are
  312. flushed before they will be reused, which
  313. is a lot of faster
  314. off - do not initialize any AMD IOMMU found in
  315. the system
  316. force_isolation - Force device isolation for all
  317. devices. The IOMMU driver is not
  318. allowed anymore to lift isolation
  319. requirements as needed. This option
  320. does not override iommu=pt
  321. amd_iommu_dump= [HW,X86-64]
  322. Enable AMD IOMMU driver option to dump the ACPI table
  323. for AMD IOMMU. With this option enabled, AMD IOMMU
  324. driver will print ACPI tables for AMD IOMMU during
  325. IOMMU initialization.
  326. amijoy.map= [HW,JOY] Amiga joystick support
  327. Map of devices attached to JOY0DAT and JOY1DAT
  328. Format: <a>,<b>
  329. See also Documentation/input/joystick.txt
  330. analog.map= [HW,JOY] Analog joystick and gamepad support
  331. Specifies type or capabilities of an analog joystick
  332. connected to one of 16 gameports
  333. Format: <type1>,<type2>,..<type16>
  334. apc= [HW,SPARC]
  335. Power management functions (SPARCstation-4/5 + deriv.)
  336. Format: noidle
  337. Disable APC CPU standby support. SPARCstation-Fox does
  338. not play well with APC CPU idle - disable it if you have
  339. APC and your system crashes randomly.
  340. apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
  341. Change the output verbosity whilst booting
  342. Format: { quiet (default) | verbose | debug }
  343. Change the amount of debugging information output
  344. when initialising the APIC and IO-APIC components.
  345. autoconf= [IPV6]
  346. See Documentation/networking/ipv6.txt.
  347. show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
  348. Limit apic dumping. The parameter defines the maximal
  349. number of local apics being dumped. Also it is possible
  350. to set it to "all" by meaning -- no limit here.
  351. Format: { 1 (default) | 2 | ... | all }.
  352. The parameter valid if only apic=debug or
  353. apic=verbose is specified.
  354. Example: apic=debug show_lapic=all
  355. apm= [APM] Advanced Power Management
  356. See header of arch/x86/kernel/apm_32.c.
  357. arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
  358. Format: <io>,<irq>,<nodeID>
  359. ataflop= [HW,M68k]
  360. atarimouse= [HW,MOUSE] Atari Mouse
  361. atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
  362. EzKey and similar keyboards
  363. atkbd.reset= [HW] Reset keyboard during initialization
  364. atkbd.set= [HW] Select keyboard code set
  365. Format: <int> (2 = AT (default), 3 = PS/2)
  366. atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
  367. keyboards
  368. atkbd.softraw= [HW] Choose between synthetic and real raw mode
  369. Format: <bool> (0 = real, 1 = synthetic (default))
  370. atkbd.softrepeat= [HW]
  371. Use software keyboard repeat
  372. baycom_epp= [HW,AX25]
  373. Format: <io>,<mode>
  374. baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
  375. Format: <io>,<mode>
  376. See header of drivers/net/hamradio/baycom_par.c.
  377. baycom_ser_fdx= [HW,AX25]
  378. BayCom Serial Port AX.25 Modem (Full Duplex Mode)
  379. Format: <io>,<irq>,<mode>[,<baud>]
  380. See header of drivers/net/hamradio/baycom_ser_fdx.c.
  381. baycom_ser_hdx= [HW,AX25]
  382. BayCom Serial Port AX.25 Modem (Half Duplex Mode)
  383. Format: <io>,<irq>,<mode>
  384. See header of drivers/net/hamradio/baycom_ser_hdx.c.
  385. boot_delay= Milliseconds to delay each printk during boot.
  386. Values larger than 10 seconds (10000) are changed to
  387. no delay (0).
  388. Format: integer
  389. bootmem_debug [KNL] Enable bootmem allocator debug messages.
  390. bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
  391. bttv.radio= Most important insmod options are available as
  392. kernel args too.
  393. bttv.pll= See Documentation/video4linux/bttv/Insmod-options
  394. bttv.tuner=
  395. bulk_remove=off [PPC] This parameter disables the use of the pSeries
  396. firmware feature for flushing multiple hpte entries
  397. at a time.
  398. c101= [NET] Moxa C101 synchronous serial card
  399. cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
  400. Sometimes CPU hardware bugs make them report the cache
  401. size incorrectly. The kernel will attempt work arounds
  402. to fix known problems, but for some CPUs it is not
  403. possible to determine what the correct size should be.
  404. This option provides an override for these situations.
  405. ccw_timeout_log [S390]
  406. See Documentation/s390/CommonIO for details.
  407. cgroup_disable= [KNL] Disable a particular controller
  408. Format: {name of the controller(s) to disable}
  409. {Currently supported controllers - "memory"}
  410. checkreqprot [SELINUX] Set initial checkreqprot flag value.
  411. Format: { "0" | "1" }
  412. See security/selinux/Kconfig help text.
  413. 0 -- check protection applied by kernel (includes
  414. any implied execute protection).
  415. 1 -- check protection requested by application.
  416. Default value is set via a kernel config option.
  417. Value can be changed at runtime via
  418. /selinux/checkreqprot.
  419. cio_ignore= [S390]
  420. See Documentation/s390/CommonIO for details.
  421. clk_ignore_unused
  422. [CLK]
  423. Keep all clocks already enabled by bootloader on,
  424. even if no driver has claimed them. This is useful
  425. for debug and development, but should not be
  426. needed on a platform with proper driver support.
  427. For more information, see Documentation/clk.txt.
  428. clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
  429. [Deprecated]
  430. Forces specified clocksource (if available) to be used
  431. when calculating gettimeofday(). If specified
  432. clocksource is not available, it defaults to PIT.
  433. Format: { pit | tsc | cyclone | pmtmr }
  434. clocksource= Override the default clocksource
  435. Format: <string>
  436. Override the default clocksource and use the clocksource
  437. with the name specified.
  438. Some clocksource names to choose from, depending on
  439. the platform:
  440. [all] jiffies (this is the base, fallback clocksource)
  441. [ACPI] acpi_pm
  442. [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
  443. pxa_timer,timer3,32k_counter,timer0_1
  444. [AVR32] avr32
  445. [X86-32] pit,hpet,tsc;
  446. scx200_hrt on Geode; cyclone on IBM x440
  447. [MIPS] MIPS
  448. [PARISC] cr16
  449. [S390] tod
  450. [SH] SuperH
  451. [SPARC64] tick
  452. [X86-64] hpet,tsc
  453. clearcpuid=BITNUM [X86]
  454. Disable CPUID feature X for the kernel. See
  455. arch/x86/include/asm/cpufeature.h for the valid bit
  456. numbers. Note the Linux specific bits are not necessarily
  457. stable over kernel options, but the vendor specific
  458. ones should be.
  459. Also note that user programs calling CPUID directly
  460. or using the feature without checking anything
  461. will still see it. This just prevents it from
  462. being used by the kernel or shown in /proc/cpuinfo.
  463. Also note the kernel might malfunction if you disable
  464. some critical bits.
  465. cma=nn[MG] [ARM,KNL]
  466. Sets the size of kernel global memory area for contiguous
  467. memory allocations. For more information, see
  468. include/linux/dma-contiguous.h
  469. cmo_free_hint= [PPC] Format: { yes | no }
  470. Specify whether pages are marked as being inactive
  471. when they are freed. This is used in CMO environments
  472. to determine OS memory pressure for page stealing by
  473. a hypervisor.
  474. Default: yes
  475. coherent_pool=nn[KMG] [ARM,KNL]
  476. Sets the size of memory pool for coherent, atomic dma
  477. allocations, by default set to 256K.
  478. code_bytes [X86] How many bytes of object code to print
  479. in an oops report.
  480. Range: 0 - 8192
  481. Default: 64
  482. com20020= [HW,NET] ARCnet - COM20020 chipset
  483. Format:
  484. <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
  485. com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
  486. Format: <io>[,<irq>]
  487. com90xx= [HW,NET]
  488. ARCnet - COM90xx chipset (memory-mapped buffers)
  489. Format: <io>[,<irq>[,<memstart>]]
  490. condev= [HW,S390] console device
  491. conmode=
  492. console= [KNL] Output console device and options.
  493. tty<n> Use the virtual console device <n>.
  494. ttyS<n>[,options]
  495. ttyUSB0[,options]
  496. Use the specified serial port. The options are of
  497. the form "bbbbpnf", where "bbbb" is the baud rate,
  498. "p" is parity ("n", "o", or "e"), "n" is number of
  499. bits, and "f" is flow control ("r" for RTS or
  500. omit it). Default is "9600n8".
  501. See Documentation/serial-console.txt for more
  502. information. See
  503. Documentation/networking/netconsole.txt for an
  504. alternative.
  505. uart[8250],io,<addr>[,options]
  506. uart[8250],mmio,<addr>[,options]
  507. Start an early, polled-mode console on the 8250/16550
  508. UART at the specified I/O port or MMIO address,
  509. switching to the matching ttyS device later. The
  510. options are the same as for ttyS, above.
  511. hvc<n> Use the hypervisor console device <n>. This is for
  512. both Xen and PowerPC hypervisors.
  513. If the device connected to the port is not a TTY but a braille
  514. device, prepend "brl," before the device type, for instance
  515. console=brl,ttyS0
  516. For now, only VisioBraille is supported.
  517. consoleblank= [KNL] The console blank (screen saver) timeout in
  518. seconds. Defaults to 10*60 = 10mins. A value of 0
  519. disables the blank timer.
  520. coredump_filter=
  521. [KNL] Change the default value for
  522. /proc/<pid>/coredump_filter.
  523. See also Documentation/filesystems/proc.txt.
  524. cpuidle.off=1 [CPU_IDLE]
  525. disable the cpuidle sub-system
  526. cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
  527. Format:
  528. <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
  529. crashkernel=size[KMG][@offset[KMG]]
  530. [KNL] Using kexec, Linux can switch to a 'crash kernel'
  531. upon panic. This parameter reserves the physical
  532. memory region [offset, offset + size] for that kernel
  533. image. If '@offset' is omitted, then a suitable offset
  534. is selected automatically. Check
  535. Documentation/kdump/kdump.txt for further details.
  536. crashkernel=range1:size1[,range2:size2,...][@offset]
  537. [KNL] Same as above, but depends on the memory
  538. in the running system. The syntax of range is
  539. start-[end] where start and end are both
  540. a memory unit (amount[KMG]). See also
  541. Documentation/kdump/kdump.txt for an example.
  542. crashkernel=size[KMG],high
  543. [KNL, x86_64] range could be above 4G. Allow kernel
  544. to allocate physical memory region from top, so could
  545. be above 4G if system have more than 4G ram installed.
  546. Otherwise memory region will be allocated below 4G, if
  547. available.
  548. It will be ignored if crashkernel=X is specified.
  549. crashkernel=size[KMG],low
  550. [KNL, x86_64] range under 4G. When crashkernel=X,high
  551. is passed, kernel could allocate physical memory region
  552. above 4G, that cause second kernel crash on system
  553. that require some amount of low memory, e.g. swiotlb
  554. requires at least 64M+32K low memory. Kernel would
  555. try to allocate 72M below 4G automatically.
  556. This one let user to specify own low range under 4G
  557. for second kernel instead.
  558. 0: to disable low allocation.
  559. It will be ignored when crashkernel=X,high is not used
  560. or memory reserved is below 4G.
  561. cs89x0_dma= [HW,NET]
  562. Format: <dma>
  563. cs89x0_media= [HW,NET]
  564. Format: { rj45 | aui | bnc }
  565. dasd= [HW,NET]
  566. See header of drivers/s390/block/dasd_devmap.c.
  567. db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
  568. (one device per port)
  569. Format: <port#>,<type>
  570. See also Documentation/input/joystick-parport.txt
  571. ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
  572. time. See Documentation/dynamic-debug-howto.txt for
  573. details. Deprecated, see dyndbg.
  574. debug [KNL] Enable kernel debugging (events log level).
  575. debug_locks_verbose=
  576. [KNL] verbose self-tests
  577. Format=<0|1>
  578. Print debugging info while doing the locking API
  579. self-tests.
  580. We default to 0 (no extra messages), setting it to
  581. 1 will print _a lot_ more information - normally
  582. only useful to kernel developers.
  583. debug_objects [KNL] Enable object debugging
  584. no_debug_objects
  585. [KNL] Disable object debugging
  586. debug_guardpage_minorder=
  587. [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
  588. parameter allows control of the order of pages that will
  589. be intentionally kept free (and hence protected) by the
  590. buddy allocator. Bigger value increase the probability
  591. of catching random memory corruption, but reduce the
  592. amount of memory for normal system use. The maximum
  593. possible value is MAX_ORDER/2. Setting this parameter
  594. to 1 or 2 should be enough to identify most random
  595. memory corruption problems caused by bugs in kernel or
  596. driver code when a CPU writes to (or reads from) a
  597. random memory location. Note that there exists a class
  598. of memory corruptions problems caused by buggy H/W or
  599. F/W or by drivers badly programing DMA (basically when
  600. memory is written at bus level and the CPU MMU is
  601. bypassed) which are not detectable by
  602. CONFIG_DEBUG_PAGEALLOC, hence this option will not help
  603. tracking down these problems.
  604. debugpat [X86] Enable PAT debugging
  605. decnet.addr= [HW,NET]
  606. Format: <area>[,<node>]
  607. See also Documentation/networking/decnet.txt.
  608. default_hugepagesz=
  609. [same as hugepagesz=] The size of the default
  610. HugeTLB page size. This is the size represented by
  611. the legacy /proc/ hugepages APIs, used for SHM, and
  612. default size when mounting hugetlbfs filesystems.
  613. Defaults to the default architecture's huge page size
  614. if not specified.
  615. dhash_entries= [KNL]
  616. Set number of hash buckets for dentry cache.
  617. digi= [HW,SERIAL]
  618. IO parameters + enable/disable command.
  619. digiepca= [HW,SERIAL]
  620. See drivers/char/README.epca and
  621. Documentation/serial/digiepca.txt.
  622. disable= [IPV6]
  623. See Documentation/networking/ipv6.txt.
  624. disable_ddw [PPC/PSERIES]
  625. Disable Dynamic DMA Window support. Use this if
  626. to workaround buggy firmware.
  627. disable_ipv6= [IPV6]
  628. See Documentation/networking/ipv6.txt.
  629. disable_mtrr_cleanup [X86]
  630. The kernel tries to adjust MTRR layout from continuous
  631. to discrete, to make X server driver able to add WB
  632. entry later. This parameter disables that.
  633. disable_mtrr_trim [X86, Intel and AMD only]
  634. By default the kernel will trim any uncacheable
  635. memory out of your available memory pool based on
  636. MTRR settings. This parameter disables that behavior,
  637. possibly causing your machine to run very slowly.
  638. disable_timer_pin_1 [X86]
  639. Disable PIN 1 of APIC timer
  640. Can be useful to work around chipset bugs.
  641. dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
  642. this option disables the debugging code at boot.
  643. dma_debug_entries=<number>
  644. This option allows to tune the number of preallocated
  645. entries for DMA-API debugging code. One entry is
  646. required per DMA-API allocation. Use this if the
  647. DMA-API debugging code disables itself because the
  648. architectural default is too low.
  649. dma_debug_driver=<driver_name>
  650. With this option the DMA-API debugging driver
  651. filter feature can be enabled at boot time. Just
  652. pass the driver to filter for as the parameter.
  653. The filter can be disabled or changed to another
  654. driver later using sysfs.
  655. drm_kms_helper.edid_firmware=[<connector>:]<file>
  656. Broken monitors, graphic adapters and KVMs may
  657. send no or incorrect EDID data sets. This parameter
  658. allows to specify an EDID data set in the
  659. /lib/firmware directory that is used instead.
  660. Generic built-in EDID data sets are used, if one of
  661. edid/1024x768.bin, edid/1280x1024.bin,
  662. edid/1680x1050.bin, or edid/1920x1080.bin is given
  663. and no file with the same name exists. Details and
  664. instructions how to build your own EDID data are
  665. available in Documentation/EDID/HOWTO.txt. An EDID
  666. data set will only be used for a particular connector,
  667. if its name and a colon are prepended to the EDID
  668. name.
  669. dscc4.setup= [NET]
  670. dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
  671. module.dyndbg[="val"]
  672. Enable debug messages at boot time. See
  673. Documentation/dynamic-debug-howto.txt for details.
  674. earlycon= [KNL] Output early console device and options.
  675. uart[8250],io,<addr>[,options]
  676. uart[8250],mmio,<addr>[,options]
  677. uart[8250],mmio32,<addr>[,options]
  678. Start an early, polled-mode console on the 8250/16550
  679. UART at the specified I/O port or MMIO address.
  680. MMIO inter-register address stride is either 8-bit
  681. (mmio) or 32-bit (mmio32).
  682. The options are the same as for ttyS, above.
  683. earlyprintk= [X86,SH,BLACKFIN,ARM]
  684. earlyprintk=vga
  685. earlyprintk=xen
  686. earlyprintk=serial[,ttySn[,baudrate]]
  687. earlyprintk=serial[,0x...[,baudrate]]
  688. earlyprintk=ttySn[,baudrate]
  689. earlyprintk=dbgp[debugController#]
  690. earlyprintk is useful when the kernel crashes before
  691. the normal console is initialized. It is not enabled by
  692. default because it has some cosmetic problems.
  693. Append ",keep" to not disable it when the real console
  694. takes over.
  695. Only vga or serial or usb debug port at a time.
  696. Currently only ttyS0 and ttyS1 may be specified by
  697. name. Other I/O ports may be explicitly specified
  698. on some architectures (x86 and arm at least) by
  699. replacing ttySn with an I/O port address, like this:
  700. earlyprintk=serial,0x1008,115200
  701. You can find the port for a given device in
  702. /proc/tty/driver/serial:
  703. 2: uart:ST16650V2 port:00001008 irq:18 ...
  704. Interaction with the standard serial driver is not
  705. very good.
  706. The VGA output is eventually overwritten by the real
  707. console.
  708. The xen output can only be used by Xen PV guests.
  709. ekgdboc= [X86,KGDB] Allow early kernel console debugging
  710. ekgdboc=kbd
  711. This is designed to be used in conjunction with
  712. the boot argument: earlyprintk=vga
  713. edd= [EDD]
  714. Format: {"off" | "on" | "skip[mbr]"}
  715. efi_no_storage_paranoia [EFI; X86]
  716. Using this parameter you can use more than 50% of
  717. your efi variable storage. Use this parameter only if
  718. you are really sure that your UEFI does sane gc and
  719. fulfills the spec otherwise your board may brick.
  720. eisa_irq_edge= [PARISC,HW]
  721. See header of drivers/parisc/eisa.c.
  722. elanfreq= [X86-32]
  723. See comment before function elanfreq_setup() in
  724. arch/x86/kernel/cpu/cpufreq/elanfreq.c.
  725. elevator= [IOSCHED]
  726. Format: {"cfq" | "deadline" | "noop"}
  727. See Documentation/block/cfq-iosched.txt and
  728. Documentation/block/deadline-iosched.txt for details.
  729. elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
  730. Specifies physical address of start of kernel core
  731. image elf header and optionally the size. Generally
  732. kexec loader will pass this option to capture kernel.
  733. See Documentation/kdump/kdump.txt for details.
  734. enable_mtrr_cleanup [X86]
  735. The kernel tries to adjust MTRR layout from continuous
  736. to discrete, to make X server driver able to add WB
  737. entry later. This parameter enables that.
  738. enable_timer_pin_1 [X86]
  739. Enable PIN 1 of APIC timer
  740. Can be useful to work around chipset bugs
  741. (in particular on some ATI chipsets).
  742. The kernel tries to set a reasonable default.
  743. enforcing [SELINUX] Set initial enforcing status.
  744. Format: {"0" | "1"}
  745. See security/selinux/Kconfig help text.
  746. 0 -- permissive (log only, no denials).
  747. 1 -- enforcing (deny and log).
  748. Default value is 0.
  749. Value can be changed at runtime via /selinux/enforce.
  750. erst_disable [ACPI]
  751. Disable Error Record Serialization Table (ERST)
  752. support.
  753. ether= [HW,NET] Ethernet cards parameters
  754. This option is obsoleted by the "netdev=" option, which
  755. has equivalent usage. See its documentation for details.
  756. evm= [EVM]
  757. Format: { "fix" }
  758. Permit 'security.evm' to be updated regardless of
  759. current integrity status.
  760. failslab=
  761. fail_page_alloc=
  762. fail_make_request=[KNL]
  763. General fault injection mechanism.
  764. Format: <interval>,<probability>,<space>,<times>
  765. See also Documentation/fault-injection/.
  766. floppy= [HW]
  767. See Documentation/blockdev/floppy.txt.
  768. force_pal_cache_flush
  769. [IA-64] Avoid check_sal_cache_flush which may hang on
  770. buggy SAL_CACHE_FLUSH implementations. Using this
  771. parameter will force ia64_sal_cache_flush to call
  772. ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
  773. ftrace=[tracer]
  774. [FTRACE] will set and start the specified tracer
  775. as early as possible in order to facilitate early
  776. boot debugging.
  777. ftrace_dump_on_oops[=orig_cpu]
  778. [FTRACE] will dump the trace buffers on oops.
  779. If no parameter is passed, ftrace will dump
  780. buffers of all CPUs, but if you pass orig_cpu, it will
  781. dump only the buffer of the CPU that triggered the
  782. oops.
  783. ftrace_filter=[function-list]
  784. [FTRACE] Limit the functions traced by the function
  785. tracer at boot up. function-list is a comma separated
  786. list of functions. This list can be changed at run
  787. time by the set_ftrace_filter file in the debugfs
  788. tracing directory.
  789. ftrace_notrace=[function-list]
  790. [FTRACE] Do not trace the functions specified in
  791. function-list. This list can be changed at run time
  792. by the set_ftrace_notrace file in the debugfs
  793. tracing directory.
  794. ftrace_graph_filter=[function-list]
  795. [FTRACE] Limit the top level callers functions traced
  796. by the function graph tracer at boot up.
  797. function-list is a comma separated list of functions
  798. that can be changed at run time by the
  799. set_graph_function file in the debugfs tracing directory.
  800. gamecon.map[2|3]=
  801. [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
  802. support via parallel port (up to 5 devices per port)
  803. Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
  804. See also Documentation/input/joystick-parport.txt
  805. gamma= [HW,DRM]
  806. gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
  807. Format: off | on
  808. default: on
  809. gcov_persist= [GCOV] When non-zero (default), profiling data for
  810. kernel modules is saved and remains accessible via
  811. debugfs, even when the module is unloaded/reloaded.
  812. When zero, profiling data is discarded and associated
  813. debugfs files are removed at module unload time.
  814. gpt [EFI] Forces disk with valid GPT signature but
  815. invalid Protective MBR to be treated as GPT.
  816. grcan.enable0= [HW] Configuration of physical interface 0. Determines
  817. the "Enable 0" bit of the configuration register.
  818. Format: 0 | 1
  819. Default: 0
  820. grcan.enable1= [HW] Configuration of physical interface 1. Determines
  821. the "Enable 0" bit of the configuration register.
  822. Format: 0 | 1
  823. Default: 0
  824. grcan.select= [HW] Select which physical interface to use.
  825. Format: 0 | 1
  826. Default: 0
  827. grcan.txsize= [HW] Sets the size of the tx buffer.
  828. Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
  829. Default: 1024
  830. grcan.rxsize= [HW] Sets the size of the rx buffer.
  831. Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
  832. Default: 1024
  833. hashdist= [KNL,NUMA] Large hashes allocated during boot
  834. are distributed across NUMA nodes. Defaults on
  835. for 64-bit NUMA, off otherwise.
  836. Format: 0 | 1 (for off | on)
  837. hcl= [IA-64] SGI's Hardware Graph compatibility layer
  838. hd= [EIDE] (E)IDE hard drive subsystem geometry
  839. Format: <cyl>,<head>,<sect>
  840. hest_disable [ACPI]
  841. Disable Hardware Error Source Table (HEST) support;
  842. corresponding firmware-first mode error processing
  843. logic will be disabled.
  844. highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
  845. size of <nn>. This works even on boxes that have no
  846. highmem otherwise. This also works to reduce highmem
  847. size on bigger boxes.
  848. highres= [KNL] Enable/disable high resolution timer mode.
  849. Valid parameters: "on", "off"
  850. Default: "on"
  851. hisax= [HW,ISDN]
  852. See Documentation/isdn/README.HiSax.
  853. hlt [BUGS=ARM,SH]
  854. hpet= [X86-32,HPET] option to control HPET usage
  855. Format: { enable (default) | disable | force |
  856. verbose }
  857. disable: disable HPET and use PIT instead
  858. force: allow force enabled of undocumented chips (ICH4,
  859. VIA, nVidia)
  860. verbose: show contents of HPET registers during setup
  861. hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
  862. hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
  863. On x86-64 and powerpc, this option can be specified
  864. multiple times interleaved with hugepages= to reserve
  865. huge pages of different sizes. Valid pages sizes on
  866. x86-64 are 2M (when the CPU supports "pse") and 1G
  867. (when the CPU supports the "pdpe1gb" cpuinfo flag)
  868. Note that 1GB pages can only be allocated at boot time
  869. using hugepages= and not freed afterwards.
  870. hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
  871. terminal devices. Valid values: 0..8
  872. hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
  873. If specified, z/VM IUCV HVC accepts connections
  874. from listed z/VM user IDs only.
  875. hwthread_map= [METAG] Comma-separated list of Linux cpu id to
  876. hardware thread id mappings.
  877. Format: <cpu>:<hwthread>
  878. keep_bootcon [KNL]
  879. Do not unregister boot console at start. This is only
  880. useful for debugging when something happens in the window
  881. between unregistering the boot console and initializing
  882. the real console.
  883. i2c_bus= [HW] Override the default board specific I2C bus speed
  884. or register an additional I2C bus that is not
  885. registered from board initialization code.
  886. Format:
  887. <bus_id>,<clkrate>
  888. i8042.debug [HW] Toggle i8042 debug mode
  889. i8042.direct [HW] Put keyboard port into non-translated mode
  890. i8042.dumbkbd [HW] Pretend that controller can only read data from
  891. keyboard and cannot control its state
  892. (Don't attempt to blink the leds)
  893. i8042.noaux [HW] Don't check for auxiliary (== mouse) port
  894. i8042.nokbd [HW] Don't check/create keyboard port
  895. i8042.noloop [HW] Disable the AUX Loopback command while probing
  896. for the AUX port
  897. i8042.nomux [HW] Don't check presence of an active multiplexing
  898. controller
  899. i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
  900. controllers
  901. i8042.notimeout [HW] Ignore timeout condition signalled by controller
  902. i8042.reset [HW] Reset the controller during init and cleanup
  903. i8042.unlock [HW] Unlock (ignore) the keylock
  904. i810= [HW,DRM]
  905. i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
  906. indicates that the driver is running on unsupported
  907. hardware.
  908. i8k.force [HW] Activate i8k driver even if SMM BIOS signature
  909. does not match list of supported models.
  910. i8k.power_status
  911. [HW] Report power status in /proc/i8k
  912. (disabled by default)
  913. i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
  914. capability is set.
  915. i915.invert_brightness=
  916. [DRM] Invert the sense of the variable that is used to
  917. set the brightness of the panel backlight. Normally a
  918. brightness value of 0 indicates backlight switched off,
  919. and the maximum of the brightness value sets the backlight
  920. to maximum brightness. If this parameter is set to 0
  921. (default) and the machine requires it, or this parameter
  922. is set to 1, a brightness value of 0 sets the backlight
  923. to maximum brightness, and the maximum of the brightness
  924. value switches the backlight off.
  925. -1 -- never invert brightness
  926. 0 -- machine default
  927. 1 -- force brightness inversion
  928. icn= [HW,ISDN]
  929. Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
  930. ide-core.nodma= [HW] (E)IDE subsystem
  931. Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
  932. .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
  933. .cdrom .chs .ignore_cable are additional options
  934. See Documentation/ide/ide.txt.
  935. ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
  936. Claim all unknown PCI IDE storage controllers.
  937. idle= [X86]
  938. Format: idle=poll, idle=halt, idle=nomwait
  939. Poll forces a polling idle loop that can slightly
  940. improve the performance of waking up a idle CPU, but
  941. will use a lot of power and make the system run hot.
  942. Not recommended.
  943. idle=halt: Halt is forced to be used for CPU idle.
  944. In such case C2/C3 won't be used again.
  945. idle=nomwait: Disable mwait for CPU C-states
  946. ignore_loglevel [KNL]
  947. Ignore loglevel setting - this will print /all/
  948. kernel messages to the console. Useful for debugging.
  949. We also add it as printk module parameter, so users
  950. could change it dynamically, usually by
  951. /sys/module/printk/parameters/ignore_loglevel.
  952. ihash_entries= [KNL]
  953. Set number of hash buckets for inode cache.
  954. ima_appraise= [IMA] appraise integrity measurements
  955. Format: { "off" | "enforce" | "fix" }
  956. default: "enforce"
  957. ima_appraise_tcb [IMA]
  958. The builtin appraise policy appraises all files
  959. owned by uid=0.
  960. ima_hash= [IMA]
  961. Format: { "sha1" | "md5" }
  962. default: "sha1"
  963. ima_tcb [IMA]
  964. Load a policy which meets the needs of the Trusted
  965. Computing Base. This means IMA will measure all
  966. programs exec'd, files mmap'd for exec, and all files
  967. opened for read by uid=0.
  968. init= [KNL]
  969. Format: <full_path>
  970. Run specified binary instead of /sbin/init as init
  971. process.
  972. initcall_debug [KNL] Trace initcalls as they are executed. Useful
  973. for working out where the kernel is dying during
  974. startup.
  975. initrd= [BOOT] Specify the location of the initial ramdisk
  976. inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
  977. Format: <irq>
  978. int_pln_enable [x86] Enable power limit notification interrupt
  979. integrity_audit=[IMA]
  980. Format: { "0" | "1" }
  981. 0 -- basic integrity auditing messages. (Default)
  982. 1 -- additional integrity auditing messages.
  983. intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
  984. on
  985. Enable intel iommu driver.
  986. off
  987. Disable intel iommu driver.
  988. igfx_off [Default Off]
  989. By default, gfx is mapped as normal device. If a gfx
  990. device has a dedicated DMAR unit, the DMAR unit is
  991. bypassed by not enabling DMAR with this option. In
  992. this case, gfx device will use physical address for
  993. DMA.
  994. forcedac [x86_64]
  995. With this option iommu will not optimize to look
  996. for io virtual address below 32-bit forcing dual
  997. address cycle on pci bus for cards supporting greater
  998. than 32-bit addressing. The default is to look
  999. for translation below 32-bit and if not available
  1000. then look in the higher range.
  1001. strict [Default Off]
  1002. With this option on every unmap_single operation will
  1003. result in a hardware IOTLB flush operation as opposed
  1004. to batching them for performance.
  1005. sp_off [Default Off]
  1006. By default, super page will be supported if Intel IOMMU
  1007. has the capability. With this option, super page will
  1008. not be supported.
  1009. intel_idle.max_cstate= [KNL,HW,ACPI,X86]
  1010. 0 disables intel_idle and fall back on acpi_idle.
  1011. 1 to 6 specify maximum depth of C-state.
  1012. intel_pstate= [X86]
  1013. disable
  1014. Do not enable intel_pstate as the default
  1015. scaling driver for the supported processors
  1016. intremap= [X86-64, Intel-IOMMU]
  1017. on enable Interrupt Remapping (default)
  1018. off disable Interrupt Remapping
  1019. nosid disable Source ID checking
  1020. no_x2apic_optout
  1021. BIOS x2APIC opt-out request will be ignored
  1022. iomem= Disable strict checking of access to MMIO memory
  1023. strict regions from userspace.
  1024. relaxed
  1025. iommu= [x86]
  1026. off
  1027. force
  1028. noforce
  1029. biomerge
  1030. panic
  1031. nopanic
  1032. merge
  1033. nomerge
  1034. forcesac
  1035. soft
  1036. pt [x86, IA-64]
  1037. io7= [HW] IO7 for Marvel based alpha systems
  1038. See comment before marvel_specify_io7 in
  1039. arch/alpha/kernel/core_marvel.c.
  1040. io_delay= [X86] I/O delay method
  1041. 0x80
  1042. Standard port 0x80 based delay
  1043. 0xed
  1044. Alternate port 0xed based delay (needed on some systems)
  1045. udelay
  1046. Simple two microseconds delay
  1047. none
  1048. No delay
  1049. ip= [IP_PNP]
  1050. See Documentation/filesystems/nfs/nfsroot.txt.
  1051. ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
  1052. See comment before ip2_setup() in
  1053. drivers/char/ip2/ip2base.c.
  1054. irqfixup [HW]
  1055. When an interrupt is not handled search all handlers
  1056. for it. Intended to get systems with badly broken
  1057. firmware running.
  1058. irqpoll [HW]
  1059. When an interrupt is not handled search all handlers
  1060. for it. Also check all handlers each timer
  1061. interrupt. Intended to get systems with badly broken
  1062. firmware running.
  1063. isapnp= [ISAPNP]
  1064. Format: <RDP>,<reset>,<pci_scan>,<verbosity>
  1065. isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
  1066. Format:
  1067. <cpu number>,...,<cpu number>
  1068. or
  1069. <cpu number>-<cpu number>
  1070. (must be a positive range in ascending order)
  1071. or a mixture
  1072. <cpu number>,...,<cpu number>-<cpu number>
  1073. This option can be used to specify one or more CPUs
  1074. to isolate from the general SMP balancing and scheduling
  1075. algorithms. You can move a process onto or off an
  1076. "isolated" CPU via the CPU affinity syscalls or cpuset.
  1077. <cpu number> begins at 0 and the maximum value is
  1078. "number of CPUs in system - 1".
  1079. This option is the preferred way to isolate CPUs. The
  1080. alternative -- manually setting the CPU mask of all
  1081. tasks in the system -- can cause problems and
  1082. suboptimal load balancer performance.
  1083. iucv= [HW,NET]
  1084. ivrs_ioapic [HW,X86_64]
  1085. Provide an override to the IOAPIC-ID<->DEVICE-ID
  1086. mapping provided in the IVRS ACPI table. For
  1087. example, to map IOAPIC-ID decimal 10 to
  1088. PCI device 00:14.0 write the parameter as:
  1089. ivrs_ioapic[10]=00:14.0
  1090. ivrs_hpet [HW,X86_64]
  1091. Provide an override to the HPET-ID<->DEVICE-ID
  1092. mapping provided in the IVRS ACPI table. For
  1093. example, to map HPET-ID decimal 0 to
  1094. PCI device 00:14.0 write the parameter as:
  1095. ivrs_hpet[0]=00:14.0
  1096. js= [HW,JOY] Analog joystick
  1097. See Documentation/input/joystick.txt.
  1098. keepinitrd [HW,ARM]
  1099. kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
  1100. specifies the amount of memory usable by the kernel
  1101. for non-movable allocations. The requested amount is
  1102. spread evenly throughout all nodes in the system. The
  1103. remaining memory in each node is used for Movable
  1104. pages. In the event, a node is too small to have both
  1105. kernelcore and Movable pages, kernelcore pages will
  1106. take priority and other nodes will have a larger number
  1107. of kernelcore pages. The Movable zone is used for the
  1108. allocation of pages that may be reclaimed or moved
  1109. by the page migration subsystem. This means that
  1110. HugeTLB pages may not be allocated from this zone.
  1111. Note that allocations like PTEs-from-HighMem still
  1112. use the HighMem zone if it exists, and the Normal
  1113. zone if it does not.
  1114. kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
  1115. Format: <Controller#>[,poll interval]
  1116. The controller # is the number of the ehci usb debug
  1117. port as it is probed via PCI. The poll interval is
  1118. optional and is the number seconds in between
  1119. each poll cycle to the debug port in case you need
  1120. the functionality for interrupting the kernel with
  1121. gdb or control-c on the dbgp connection. When
  1122. not using this parameter you use sysrq-g to break into
  1123. the kernel debugger.
  1124. kgdboc= [KGDB,HW] kgdb over consoles.
  1125. Requires a tty driver that supports console polling,
  1126. or a supported polling keyboard driver (non-usb).
  1127. Serial only format: <serial_device>[,baud]
  1128. keyboard only format: kbd
  1129. keyboard and serial format: kbd,<serial_device>[,baud]
  1130. Optional Kernel mode setting:
  1131. kms, kbd format: kms,kbd
  1132. kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
  1133. kgdbwait [KGDB] Stop kernel execution and enter the
  1134. kernel debugger at the earliest opportunity.
  1135. kmac= [MIPS] korina ethernet MAC address.
  1136. Configure the RouterBoard 532 series on-chip
  1137. Ethernet adapter MAC address.
  1138. kmemleak= [KNL] Boot-time kmemleak enable/disable
  1139. Valid arguments: on, off
  1140. Default: on
  1141. kstack=N [X86] Print N words from the kernel stack
  1142. in oops dumps.
  1143. kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
  1144. Default is 0 (don't ignore, but inject #GP)
  1145. kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
  1146. KVM MMU at runtime.
  1147. Default is 0 (off)
  1148. kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
  1149. Default is 1 (enabled)
  1150. kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
  1151. for all guests.
  1152. Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
  1153. kvm-intel.ept= [KVM,Intel] Disable extended page tables
  1154. (virtualized MMU) support on capable Intel chips.
  1155. Default is 1 (enabled)
  1156. kvm-intel.emulate_invalid_guest_state=
  1157. [KVM,Intel] Enable emulation of invalid guest states
  1158. Default is 0 (disabled)
  1159. kvm-intel.flexpriority=
  1160. [KVM,Intel] Disable FlexPriority feature (TPR shadow).
  1161. Default is 1 (enabled)
  1162. kvm-intel.nested=
  1163. [KVM,Intel] Enable VMX nesting (nVMX).
  1164. Default is 0 (disabled)
  1165. kvm-intel.unrestricted_guest=
  1166. [KVM,Intel] Disable unrestricted guest feature
  1167. (virtualized real and unpaged mode) on capable
  1168. Intel chips. Default is 1 (enabled)
  1169. kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
  1170. feature (tagged TLBs) on capable Intel chips.
  1171. Default is 1 (enabled)
  1172. l2cr= [PPC]
  1173. l3cr= [PPC]
  1174. lapic [X86-32,APIC] Enable the local APIC even if BIOS
  1175. disabled it.
  1176. lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
  1177. value for LAPIC timer one-shot implementation. Default
  1178. back to the programmable timer unit in the LAPIC.
  1179. lapic_timer_c2_ok [X86,APIC] trust the local apic timer
  1180. in C2 power state.
  1181. libata.dma= [LIBATA] DMA control
  1182. libata.dma=0 Disable all PATA and SATA DMA
  1183. libata.dma=1 PATA and SATA Disk DMA only
  1184. libata.dma=2 ATAPI (CDROM) DMA only
  1185. libata.dma=4 Compact Flash DMA only
  1186. Combinations also work, so libata.dma=3 enables DMA
  1187. for disks and CDROMs, but not CFs.
  1188. libata.ignore_hpa= [LIBATA] Ignore HPA limit
  1189. libata.ignore_hpa=0 keep BIOS limits (default)
  1190. libata.ignore_hpa=1 ignore limits, using full disk
  1191. libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
  1192. when set.
  1193. Format: <int>
  1194. libata.force= [LIBATA] Force configurations. The format is comma
  1195. separated list of "[ID:]VAL" where ID is
  1196. PORT[.DEVICE]. PORT and DEVICE are decimal numbers
  1197. matching port, link or device. Basically, it matches
  1198. the ATA ID string printed on console by libata. If
  1199. the whole ID part is omitted, the last PORT and DEVICE
  1200. values are used. If ID hasn't been specified yet, the
  1201. configuration applies to all ports, links and devices.
  1202. If only DEVICE is omitted, the parameter applies to
  1203. the port and all links and devices behind it. DEVICE
  1204. number of 0 either selects the first device or the
  1205. first fan-out link behind PMP device. It does not
  1206. select the host link. DEVICE number of 15 selects the
  1207. host link and device attached to it.
  1208. The VAL specifies the configuration to force. As long
  1209. as there's no ambiguity shortcut notation is allowed.
  1210. For example, both 1.5 and 1.5G would work for 1.5Gbps.
  1211. The following configurations can be forced.
  1212. * Cable type: 40c, 80c, short40c, unk, ign or sata.
  1213. Any ID with matching PORT is used.
  1214. * SATA link speed limit: 1.5Gbps or 3.0Gbps.
  1215. * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
  1216. udma[/][16,25,33,44,66,100,133] notation is also
  1217. allowed.
  1218. * [no]ncq: Turn on or off NCQ.
  1219. * nohrst, nosrst, norst: suppress hard, soft
  1220. and both resets.
  1221. * rstonce: only attempt one reset during
  1222. hot-unplug link recovery
  1223. * dump_id: dump IDENTIFY data.
  1224. * atapi_dmadir: Enable ATAPI DMADIR bridge support
  1225. If there are multiple matching configurations changing
  1226. the same attribute, the last one is used.
  1227. memblock=debug [KNL] Enable memblock debug messages.
  1228. load_ramdisk= [RAM] List of ramdisks to load from floppy
  1229. See Documentation/blockdev/ramdisk.txt.
  1230. lockd.nlm_grace_period=P [NFS] Assign grace period.
  1231. Format: <integer>
  1232. lockd.nlm_tcpport=N [NFS] Assign TCP port.
  1233. Format: <integer>
  1234. lockd.nlm_timeout=T [NFS] Assign timeout value.
  1235. Format: <integer>
  1236. lockd.nlm_udpport=M [NFS] Assign UDP port.
  1237. Format: <integer>
  1238. logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
  1239. Format: <irq>
  1240. loglevel= All Kernel Messages with a loglevel smaller than the
  1241. console loglevel will be printed to the console. It can
  1242. also be changed with klogd or other programs. The
  1243. loglevels are defined as follows:
  1244. 0 (KERN_EMERG) system is unusable
  1245. 1 (KERN_ALERT) action must be taken immediately
  1246. 2 (KERN_CRIT) critical conditions
  1247. 3 (KERN_ERR) error conditions
  1248. 4 (KERN_WARNING) warning conditions
  1249. 5 (KERN_NOTICE) normal but significant condition
  1250. 6 (KERN_INFO) informational
  1251. 7 (KERN_DEBUG) debug-level messages
  1252. log_buf_len=n[KMG] Sets the size of the printk ring buffer,
  1253. in bytes. n must be a power of two. The default
  1254. size is set in the kernel config file.
  1255. logo.nologo [FB] Disables display of the built-in Linux logo.
  1256. This may be used to provide more screen space for
  1257. kernel log messages and is useful when debugging
  1258. kernel boot problems.
  1259. lp=0 [LP] Specify parallel ports to use, e.g,
  1260. lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
  1261. lp=reset first parallel port). 'lp=0' disables the
  1262. lp=auto printer driver. 'lp=reset' (which can be
  1263. specified in addition to the ports) causes
  1264. attached printers to be reset. Using
  1265. lp=port1,port2,... specifies the parallel ports
  1266. to associate lp devices with, starting with
  1267. lp0. A port specification may be 'none' to skip
  1268. that lp device, or a parport name such as
  1269. 'parport0'. Specifying 'lp=auto' instead of a
  1270. port specification list means that device IDs
  1271. from each port should be examined, to see if
  1272. an IEEE 1284-compliant printer is attached; if
  1273. so, the driver will manage that printer.
  1274. See also header of drivers/char/lp.c.
  1275. lpj=n [KNL]
  1276. Sets loops_per_jiffy to given constant, thus avoiding
  1277. time-consuming boot-time autodetection (up to 250 ms per
  1278. CPU). 0 enables autodetection (default). To determine
  1279. the correct value for your kernel, boot with normal
  1280. autodetection and see what value is printed. Note that
  1281. on SMP systems the preset will be applied to all CPUs,
  1282. which is likely to cause problems if your CPUs need
  1283. significantly divergent settings. An incorrect value
  1284. will cause delays in the kernel to be wrong, leading to
  1285. unpredictable I/O errors and other breakage. Although
  1286. unlikely, in the extreme case this might damage your
  1287. hardware.
  1288. ltpc= [NET]
  1289. Format: <io>,<irq>,<dma>
  1290. machvec= [IA-64] Force the use of a particular machine-vector
  1291. (machvec) in a generic kernel.
  1292. Example: machvec=hpzx1_swiotlb
  1293. machtype= [Loongson] Share the same kernel image file between different
  1294. yeeloong laptop.
  1295. Example: machtype=lemote-yeeloong-2f-7inch
  1296. max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
  1297. than or equal to this physical address is ignored.
  1298. maxcpus= [SMP] Maximum number of processors that an SMP kernel
  1299. should make use of. maxcpus=n : n >= 0 limits the
  1300. kernel to using 'n' processors. n=0 is a special case,
  1301. it is equivalent to "nosmp", which also disables
  1302. the IO APIC.
  1303. max_loop= [LOOP] The number of loop block devices that get
  1304. (loop.max_loop) unconditionally pre-created at init time. The default
  1305. number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
  1306. of statically allocating a predefined number, loop
  1307. devices can be requested on-demand with the
  1308. /dev/loop-control interface.
  1309. mce [X86-32] Machine Check Exception
  1310. mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
  1311. md= [HW] RAID subsystems devices and level
  1312. See Documentation/md.txt.
  1313. mdacon= [MDA]
  1314. Format: <first>,<last>
  1315. Specifies range of consoles to be captured by the MDA.
  1316. mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
  1317. Amount of memory to be used when the kernel is not able
  1318. to see the whole system memory or for test.
  1319. [X86] Work as limiting max address. Use together
  1320. with memmap= to avoid physical address space collisions.
  1321. Without memmap= PCI devices could be placed at addresses
  1322. belonging to unused RAM.
  1323. mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
  1324. memory.
  1325. memchunk=nn[KMG]
  1326. [KNL,SH] Allow user to override the default size for
  1327. per-device physically contiguous DMA buffers.
  1328. memmap=exactmap [KNL,X86] Enable setting of an exact
  1329. E820 memory map, as specified by the user.
  1330. Such memmap=exactmap lines can be constructed based on
  1331. BIOS output or other requirements. See the memmap=nn@ss
  1332. option description.
  1333. memmap=nn[KMG]@ss[KMG]
  1334. [KNL] Force usage of a specific region of memory
  1335. Region of memory to be used, from ss to ss+nn.
  1336. memmap=nn[KMG]#ss[KMG]
  1337. [KNL,ACPI] Mark specific memory as ACPI data.
  1338. Region of memory to be used, from ss to ss+nn.
  1339. memmap=nn[KMG]$ss[KMG]
  1340. [KNL,ACPI] Mark specific memory as reserved.
  1341. Region of memory to be used, from ss to ss+nn.
  1342. Example: Exclude memory from 0x18690000-0x1869ffff
  1343. memmap=64K$0x18690000
  1344. or
  1345. memmap=0x10000$0x18690000
  1346. memory_corruption_check=0/1 [X86]
  1347. Some BIOSes seem to corrupt the first 64k of
  1348. memory when doing things like suspend/resume.
  1349. Setting this option will scan the memory
  1350. looking for corruption. Enabling this will
  1351. both detect corruption and prevent the kernel
  1352. from using the memory being corrupted.
  1353. However, its intended as a diagnostic tool; if
  1354. repeatable BIOS-originated corruption always
  1355. affects the same memory, you can use memmap=
  1356. to prevent the kernel from using that memory.
  1357. memory_corruption_check_size=size [X86]
  1358. By default it checks for corruption in the low
  1359. 64k, making this memory unavailable for normal
  1360. use. Use this parameter to scan for
  1361. corruption in more or less memory.
  1362. memory_corruption_check_period=seconds [X86]
  1363. By default it checks for corruption every 60
  1364. seconds. Use this parameter to check at some
  1365. other rate. 0 disables periodic checking.
  1366. memtest= [KNL,X86] Enable memtest
  1367. Format: <integer>
  1368. default : 0 <disable>
  1369. Specifies the number of memtest passes to be
  1370. performed. Each pass selects another test
  1371. pattern from a given set of patterns. Memtest
  1372. fills the memory with this pattern, validates
  1373. memory contents and reserves bad memory
  1374. regions that are detected.
  1375. meye.*= [HW] Set MotionEye Camera parameters
  1376. See Documentation/video4linux/meye.txt.
  1377. mfgpt_irq= [IA-32] Specify the IRQ to use for the
  1378. Multi-Function General Purpose Timers on AMD Geode
  1379. platforms.
  1380. mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
  1381. the BIOS has incorrectly applied a workaround. TinyBIOS
  1382. version 0.98 is known to be affected, 0.99 fixes the
  1383. problem by letting the user disable the workaround.
  1384. mga= [HW,DRM]
  1385. min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
  1386. physical address is ignored.
  1387. mini2440= [ARM,HW,KNL]
  1388. Format:[0..2][b][c][t]
  1389. Default: "0tb"
  1390. MINI2440 configuration specification:
  1391. 0 - The attached screen is the 3.5" TFT
  1392. 1 - The attached screen is the 7" TFT
  1393. 2 - The VGA Shield is attached (1024x768)
  1394. Leaving out the screen size parameter will not load
  1395. the TFT driver, and the framebuffer will be left
  1396. unconfigured.
  1397. b - Enable backlight. The TFT backlight pin will be
  1398. linked to the kernel VESA blanking code and a GPIO
  1399. LED. This parameter is not necessary when using the
  1400. VGA shield.
  1401. c - Enable the s3c camera interface.
  1402. t - Reserved for enabling touchscreen support. The
  1403. touchscreen support is not enabled in the mainstream
  1404. kernel as of 2.6.30, a preliminary port can be found
  1405. in the "bleeding edge" mini2440 support kernel at
  1406. http://repo.or.cz/w/linux-2.6/mini2440.git
  1407. mminit_loglevel=
  1408. [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
  1409. parameter allows control of the logging verbosity for
  1410. the additional memory initialisation checks. A value
  1411. of 0 disables mminit logging and a level of 4 will
  1412. log everything. Information is printed at KERN_DEBUG
  1413. so loglevel=8 may also need to be specified.
  1414. module.sig_enforce
  1415. [KNL] When CONFIG_MODULE_SIG is set, this means that
  1416. modules without (valid) signatures will fail to load.
  1417. Note that if CONFIG_MODULE_SIG_FORCE is set, that
  1418. is always true, so this option does nothing.
  1419. mousedev.tap_time=
  1420. [MOUSE] Maximum time between finger touching and
  1421. leaving touchpad surface for touch to be considered
  1422. a tap and be reported as a left button click (for
  1423. touchpads working in absolute mode only).
  1424. Format: <msecs>
  1425. mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
  1426. reporting absolute coordinates, such as tablets
  1427. mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
  1428. reporting absolute coordinates, such as tablets
  1429. movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
  1430. is similar to kernelcore except it specifies the
  1431. amount of memory used for migratable allocations.
  1432. If both kernelcore and movablecore is specified,
  1433. then kernelcore will be at *least* the specified
  1434. value but may be more. If movablecore on its own
  1435. is specified, the administrator must be careful
  1436. that the amount of memory usable for all allocations
  1437. is not too small.
  1438. MTD_Partition= [MTD]
  1439. Format: <name>,<region-number>,<size>,<offset>
  1440. MTD_Region= [MTD] Format:
  1441. <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
  1442. mtdparts= [MTD]
  1443. See drivers/mtd/cmdlinepart.c.
  1444. multitce=off [PPC] This parameter disables the use of the pSeries
  1445. firmware feature for updating multiple TCE entries
  1446. at a time.
  1447. onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
  1448. Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
  1449. boundary - index of last SLC block on Flex-OneNAND.
  1450. The remaining blocks are configured as MLC blocks.
  1451. lock - Configure if Flex-OneNAND boundary should be locked.
  1452. Once locked, the boundary cannot be changed.
  1453. 1 indicates lock status, 0 indicates unlock status.
  1454. mtdset= [ARM]
  1455. ARM/S3C2412 JIVE boot control
  1456. See arch/arm/mach-s3c2412/mach-jive.c
  1457. mtouchusb.raw_coordinates=
  1458. [HW] Make the MicroTouch USB driver use raw coordinates
  1459. ('y', default) or cooked coordinates ('n')
  1460. mtrr_chunk_size=nn[KMG] [X86]
  1461. used for mtrr cleanup. It is largest continuous chunk
  1462. that could hold holes aka. UC entries.
  1463. mtrr_gran_size=nn[KMG] [X86]
  1464. Used for mtrr cleanup. It is granularity of mtrr block.
  1465. Default is 1.
  1466. Large value could prevent small alignment from
  1467. using up MTRRs.
  1468. mtrr_spare_reg_nr=n [X86]
  1469. Format: <integer>
  1470. Range: 0,7 : spare reg number
  1471. Default : 1
  1472. Used for mtrr cleanup. It is spare mtrr entries number.
  1473. Set to 2 or more if your graphical card needs more.
  1474. n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
  1475. netdev= [NET] Network devices parameters
  1476. Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
  1477. Note that mem_start is often overloaded to mean
  1478. something different and driver-specific.
  1479. This usage is only documented in each driver source
  1480. file if at all.
  1481. nf_conntrack.acct=
  1482. [NETFILTER] Enable connection tracking flow accounting
  1483. 0 to disable accounting
  1484. 1 to enable accounting
  1485. Default value is 0.
  1486. nfsaddrs= [NFS] Deprecated. Use ip= instead.
  1487. See Documentation/filesystems/nfs/nfsroot.txt.
  1488. nfsroot= [NFS] nfs root filesystem for disk-less boxes.
  1489. See Documentation/filesystems/nfs/nfsroot.txt.
  1490. nfsrootdebug [NFS] enable nfsroot debugging messages.
  1491. See Documentation/filesystems/nfs/nfsroot.txt.
  1492. nfs.callback_tcpport=
  1493. [NFS] set the TCP port on which the NFSv4 callback
  1494. channel should listen.
  1495. nfs.cache_getent=
  1496. [NFS] sets the pathname to the program which is used
  1497. to update the NFS client cache entries.
  1498. nfs.cache_getent_timeout=
  1499. [NFS] sets the timeout after which an attempt to
  1500. update a cache entry is deemed to have failed.
  1501. nfs.idmap_cache_timeout=
  1502. [NFS] set the maximum lifetime for idmapper cache
  1503. entries.
  1504. nfs.enable_ino64=
  1505. [NFS] enable 64-bit inode numbers.
  1506. If zero, the NFS client will fake up a 32-bit inode
  1507. number for the readdir() and stat() syscalls instead
  1508. of returning the full 64-bit number.
  1509. The default is to return 64-bit inode numbers.
  1510. nfs.max_session_slots=
  1511. [NFSv4.1] Sets the maximum number of session slots
  1512. the client will attempt to negotiate with the server.
  1513. This limits the number of simultaneous RPC requests
  1514. that the client can send to the NFSv4.1 server.
  1515. Note that there is little point in setting this
  1516. value higher than the max_tcp_slot_table_limit.
  1517. nfs.nfs4_disable_idmapping=
  1518. [NFSv4] When set to the default of '1', this option
  1519. ensures that both the RPC level authentication
  1520. scheme and the NFS level operations agree to use
  1521. numeric uids/gids if the mount is using the
  1522. 'sec=sys' security flavour. In effect it is
  1523. disabling idmapping, which can make migration from
  1524. legacy NFSv2/v3 systems to NFSv4 easier.
  1525. Servers that do not support this mode of operation
  1526. will be autodetected by the client, and it will fall
  1527. back to using the idmapper.
  1528. To turn off this behaviour, set the value to '0'.
  1529. nfs.nfs4_unique_id=
  1530. [NFS4] Specify an additional fixed unique ident-
  1531. ification string that NFSv4 clients can insert into
  1532. their nfs_client_id4 string. This is typically a
  1533. UUID that is generated at system install time.
  1534. nfs.send_implementation_id =
  1535. [NFSv4.1] Send client implementation identification
  1536. information in exchange_id requests.
  1537. If zero, no implementation identification information
  1538. will be sent.
  1539. The default is to send the implementation identification
  1540. information.
  1541. nfsd.nfs4_disable_idmapping=
  1542. [NFSv4] When set to the default of '1', the NFSv4
  1543. server will return only numeric uids and gids to
  1544. clients using auth_sys, and will accept numeric uids
  1545. and gids from such clients. This is intended to ease
  1546. migration from NFSv2/v3.
  1547. objlayoutdriver.osd_login_prog=
  1548. [NFS] [OBJLAYOUT] sets the pathname to the program which
  1549. is used to automatically discover and login into new
  1550. osd-targets. Please see:
  1551. Documentation/filesystems/pnfs.txt for more explanations
  1552. nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
  1553. when a NMI is triggered.
  1554. Format: [state][,regs][,debounce][,die]
  1555. nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
  1556. Format: [panic,][nopanic,][num]
  1557. Valid num: 0
  1558. 0 - turn nmi_watchdog off
  1559. When panic is specified, panic when an NMI watchdog
  1560. timeout occurs (or 'nopanic' to override the opposite
  1561. default).
  1562. This is useful when you use a panic=... timeout and
  1563. need the box quickly up again.
  1564. netpoll.carrier_timeout=
  1565. [NET] Specifies amount of time (in seconds) that
  1566. netpoll should wait for a carrier. By default netpoll
  1567. waits 4 seconds.
  1568. no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
  1569. emulation library even if a 387 maths coprocessor
  1570. is present.
  1571. no_console_suspend
  1572. [HW] Never suspend the console
  1573. Disable suspending of consoles during suspend and
  1574. hibernate operations. Once disabled, debugging
  1575. messages can reach various consoles while the rest
  1576. of the system is being put to sleep (ie, while
  1577. debugging driver suspend/resume hooks). This may
  1578. not work reliably with all consoles, but is known
  1579. to work with serial and VGA consoles.
  1580. To facilitate more flexible debugging, we also add
  1581. console_suspend, a printk module parameter to control
  1582. it. Users could use console_suspend (usually
  1583. /sys/module/printk/parameters/console_suspend) to
  1584. turn on/off it dynamically.
  1585. noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
  1586. caches in the slab allocator. Saves per-node memory,
  1587. but will impact performance.
  1588. noalign [KNL,ARM]
  1589. noapic [SMP,APIC] Tells the kernel to not make use of any
  1590. IOAPICs that may be present in the system.
  1591. noautogroup Disable scheduler automatic task group creation.
  1592. nobats [PPC] Do not use BATs for mapping kernel lowmem
  1593. on "Classic" PPC cores.
  1594. nocache [ARM]
  1595. noclflush [BUGS=X86] Don't use the CLFLUSH instruction
  1596. nodelayacct [KNL] Disable per-task delay accounting
  1597. nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
  1598. nodsp [SH] Disable hardware DSP at boot time.
  1599. noefi [X86] Disable EFI runtime services support.
  1600. noexec [IA-64]
  1601. noexec [X86]
  1602. On X86-32 available only on PAE configured kernels.
  1603. noexec=on: enable non-executable mappings (default)
  1604. noexec=off: disable non-executable mappings
  1605. nosmap [X86]
  1606. Disable SMAP (Supervisor Mode Access Prevention)
  1607. even if it is supported by processor.
  1608. nosmep [X86]
  1609. Disable SMEP (Supervisor Mode Execution Prevention)
  1610. even if it is supported by processor.
  1611. noexec32 [X86-64]
  1612. This affects only 32-bit executables.
  1613. noexec32=on: enable non-executable mappings (default)
  1614. read doesn't imply executable mappings
  1615. noexec32=off: disable non-executable mappings
  1616. read implies executable mappings
  1617. nofpu [SH] Disable hardware FPU at boot time.
  1618. nofxsr [BUGS=X86-32] Disables x86 floating point extended
  1619. register save and restore. The kernel will only save
  1620. legacy floating-point registers on task switch.
  1621. noxsave [BUGS=X86] Disables x86 extended register state save
  1622. and restore using xsave. The kernel will fallback to
  1623. enabling legacy floating-point and sse state.
  1624. eagerfpu= [X86]
  1625. on enable eager fpu restore
  1626. off disable eager fpu restore
  1627. auto selects the default scheme, which automatically
  1628. enables eagerfpu restore for xsaveopt.
  1629. nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
  1630. wfi(ARM) instruction doesn't work correctly and not to
  1631. use it. This is also useful when using JTAG debugger.
  1632. no_file_caps Tells the kernel not to honor file capabilities. The
  1633. only way then for a file to be executed with privilege
  1634. is to be setuid root or executed by root.
  1635. nohalt [IA-64] Tells the kernel not to use the power saving
  1636. function PAL_HALT_LIGHT when idle. This increases
  1637. power-consumption. On the positive side, it reduces
  1638. interrupt wake-up latency, which may improve performance
  1639. in certain environments such as networked servers or
  1640. real-time systems.
  1641. nohz= [KNL] Boottime enable/disable dynamic ticks
  1642. Valid arguments: on, off
  1643. Default: on
  1644. nohz_full= [KNL,BOOT]
  1645. In kernels built with CONFIG_NO_HZ_FULL=y, set
  1646. the specified list of CPUs whose tick will be stopped
  1647. whenever possible. The boot CPU will be forced outside
  1648. the range to maintain the timekeeping.
  1649. The CPUs in this range must also be included in the
  1650. rcu_nocbs= set.
  1651. noiotrap [SH] Disables trapped I/O port accesses.
  1652. noirqdebug [X86-32] Disables the code which attempts to detect and
  1653. disable unhandled interrupt sources.
  1654. no_timer_check [X86,APIC] Disables the code which tests for
  1655. broken timer IRQ sources.
  1656. noisapnp [ISAPNP] Disables ISA PnP code.
  1657. noinitrd [RAM] Tells the kernel not to load any configured
  1658. initial RAM disk.
  1659. nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
  1660. remapping.
  1661. [Deprecated - use intremap=off]
  1662. nointroute [IA-64]
  1663. nojitter [IA-64] Disables jitter checking for ITC timers.
  1664. no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
  1665. no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
  1666. fault handling.
  1667. no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
  1668. steal time is computed, but won't influence scheduler
  1669. behaviour
  1670. nolapic [X86-32,APIC] Do not enable or use the local APIC.
  1671. nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
  1672. noltlbs [PPC] Do not use large page/tlb entries for kernel
  1673. lowmem mapping on PPC40x.
  1674. nomca [IA-64] Disable machine check abort handling
  1675. nomce [X86-32] Machine Check Exception
  1676. nomfgpt [X86-32] Disable Multi-Function General Purpose
  1677. Timer usage (for AMD Geode machines).
  1678. nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
  1679. shutdown the other cpus. Instead use the REBOOT_VECTOR
  1680. irq.
  1681. nomodule Disable module load
  1682. nopat [X86] Disable PAT (page attribute table extension of
  1683. pagetables) support.
  1684. norandmaps Don't use address space randomization. Equivalent to
  1685. echo 0 > /proc/sys/kernel/randomize_va_space
  1686. noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
  1687. noreplace-smp [X86-32,SMP] Don't replace SMP instructions
  1688. with UP alternatives
  1689. nordrand [X86] Disable the direct use of the RDRAND
  1690. instruction even if it is supported by the
  1691. processor. RDRAND is still available to user
  1692. space applications.
  1693. noresume [SWSUSP] Disables resume and restores original swap
  1694. space.
  1695. no-scroll [VGA] Disables scrollback.
  1696. This is required for the Braillex ib80-piezo Braille
  1697. reader made by F.H. Papenmeier (Germany).
  1698. nosbagart [IA-64]
  1699. nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
  1700. nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
  1701. and disable the IO APIC. legacy for "maxcpus=0".
  1702. nosoftlockup [KNL] Disable the soft-lockup detector.
  1703. nosync [HW,M68K] Disables sync negotiation for all devices.
  1704. notsc [BUGS=X86-32] Disable Time Stamp Counter
  1705. nousb [USB] Disable the USB subsystem
  1706. nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
  1707. nowb [ARM]
  1708. nox2apic [X86-64,APIC] Do not enable x2APIC mode.
  1709. cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
  1710. CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
  1711. Some features depend on CPU0. Known dependencies are:
  1712. 1. Resume from suspend/hibernate depends on CPU0.
  1713. Suspend/hibernate will fail if CPU0 is offline and you
  1714. need to online CPU0 before suspend/hibernate.
  1715. 2. PIC interrupts also depend on CPU0. CPU0 can't be
  1716. removed if a PIC interrupt is detected.
  1717. It's said poweroff/reboot may depend on CPU0 on some
  1718. machines although I haven't seen such issues so far
  1719. after CPU0 is offline on a few tested machines.
  1720. If the dependencies are under your control, you can
  1721. turn on cpu0_hotplug.
  1722. nptcg= [IA-64] Override max number of concurrent global TLB
  1723. purges which is reported from either PAL_VM_SUMMARY or
  1724. SAL PALO.
  1725. nr_cpus= [SMP] Maximum number of processors that an SMP kernel
  1726. could support. nr_cpus=n : n >= 1 limits the kernel to
  1727. supporting 'n' processors. Later in runtime you can not
  1728. use hotplug cpu feature to put more cpu back to online.
  1729. just like you compile the kernel NR_CPUS=n
  1730. nr_uarts= [SERIAL] maximum number of UARTs to be registered.
  1731. numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
  1732. Allowed values are enable and disable
  1733. numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
  1734. one of ['zone', 'node', 'default'] can be specified
  1735. This can be set from sysctl after boot.
  1736. See Documentation/sysctl/vm.txt for details.
  1737. ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
  1738. See Documentation/debugging-via-ohci1394.txt for more
  1739. info.
  1740. olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
  1741. Rather than timing out after 20 ms if an EC
  1742. command is not properly ACKed, override the length
  1743. of the timeout. We have interrupts disabled while
  1744. waiting for the ACK, so if this is set too high
  1745. interrupts *may* be lost!
  1746. omap_mux= [OMAP] Override bootloader pin multiplexing.
  1747. Format: <mux_mode0.mode_name=value>...
  1748. For example, to override I2C bus2:
  1749. omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
  1750. oprofile.timer= [HW]
  1751. Use timer interrupt instead of performance counters
  1752. oprofile.cpu_type= Force an oprofile cpu type
  1753. This might be useful if you have an older oprofile
  1754. userland or if you want common events.
  1755. Format: { arch_perfmon }
  1756. arch_perfmon: [X86] Force use of architectural
  1757. perfmon on Intel CPUs instead of the
  1758. CPU specific event set.
  1759. timer: [X86] Force use of architectural NMI
  1760. timer mode (see also oprofile.timer
  1761. for generic hr timer mode)
  1762. [s390] Force legacy basic mode sampling
  1763. (report cpu_type "timer")
  1764. oops=panic Always panic on oopses. Default is to just kill the
  1765. process, but there is a small probability of
  1766. deadlocking the machine.
  1767. This will also cause panics on machine check exceptions.
  1768. Useful together with panic=30 to trigger a reboot.
  1769. OSS [HW,OSS]
  1770. See Documentation/sound/oss/oss-parameters.txt
  1771. panic= [KNL] Kernel behaviour on panic: delay <timeout>
  1772. timeout > 0: seconds before rebooting
  1773. timeout = 0: wait forever
  1774. timeout < 0: reboot immediately
  1775. Format: <timeout>
  1776. parkbd.port= [HW] Parallel port number the keyboard adapter is
  1777. connected to, default is 0.
  1778. Format: <parport#>
  1779. parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
  1780. 0 for XT, 1 for AT (default is AT).
  1781. Format: <mode>
  1782. parport= [HW,PPT] Specify parallel ports. 0 disables.
  1783. Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
  1784. Use 'auto' to force the driver to use any
  1785. IRQ/DMA settings detected (the default is to
  1786. ignore detected IRQ/DMA settings because of
  1787. possible conflicts). You can specify the base
  1788. address, IRQ, and DMA settings; IRQ and DMA
  1789. should be numbers, or 'auto' (for using detected
  1790. settings on that particular port), or 'nofifo'
  1791. (to avoid using a FIFO even if it is detected).
  1792. Parallel ports are assigned in the order they
  1793. are specified on the command line, starting
  1794. with parport0.
  1795. parport_init_mode= [HW,PPT]
  1796. Configure VIA parallel port to operate in
  1797. a specific mode. This is necessary on Pegasos
  1798. computer where firmware has no options for setting
  1799. up parallel port mode and sets it to spp.
  1800. Currently this function knows 686a and 8231 chips.
  1801. Format: [spp|ps2|epp|ecp|ecpepp]
  1802. pause_on_oops=
  1803. Halt all CPUs after the first oops has been printed for
  1804. the specified number of seconds. This is to be used if
  1805. your oopses keep scrolling off the screen.
  1806. pcbit= [HW,ISDN]
  1807. pcd. [PARIDE]
  1808. See header of drivers/block/paride/pcd.c.
  1809. See also Documentation/blockdev/paride.txt.
  1810. pci=option[,option...] [PCI] various PCI subsystem options:
  1811. earlydump [X86] dump PCI config space before the kernel
  1812. changes anything
  1813. off [X86] don't probe for the PCI bus
  1814. bios [X86-32] force use of PCI BIOS, don't access
  1815. the hardware directly. Use this if your machine
  1816. has a non-standard PCI host bridge.
  1817. nobios [X86-32] disallow use of PCI BIOS, only direct
  1818. hardware access methods are allowed. Use this
  1819. if you experience crashes upon bootup and you
  1820. suspect they are caused by the BIOS.
  1821. conf1 [X86] Force use of PCI Configuration
  1822. Mechanism 1.
  1823. conf2 [X86] Force use of PCI Configuration
  1824. Mechanism 2.
  1825. noaer [PCIE] If the PCIEAER kernel config parameter is
  1826. enabled, this kernel boot option can be used to
  1827. disable the use of PCIE advanced error reporting.
  1828. nodomains [PCI] Disable support for multiple PCI
  1829. root domains (aka PCI segments, in ACPI-speak).
  1830. nommconf [X86] Disable use of MMCONFIG for PCI
  1831. Configuration
  1832. check_enable_amd_mmconf [X86] check for and enable
  1833. properly configured MMIO access to PCI
  1834. config space on AMD family 10h CPU
  1835. nomsi [MSI] If the PCI_MSI kernel config parameter is
  1836. enabled, this kernel boot option can be used to
  1837. disable the use of MSI interrupts system-wide.
  1838. noioapicquirk [APIC] Disable all boot interrupt quirks.
  1839. Safety option to keep boot IRQs enabled. This
  1840. should never be necessary.
  1841. ioapicreroute [APIC] Enable rerouting of boot IRQs to the
  1842. primary IO-APIC for bridges that cannot disable
  1843. boot IRQs. This fixes a source of spurious IRQs
  1844. when the system masks IRQs.
  1845. noioapicreroute [APIC] Disable workaround that uses the
  1846. boot IRQ equivalent of an IRQ that connects to
  1847. a chipset where boot IRQs cannot be disabled.
  1848. The opposite of ioapicreroute.
  1849. biosirq [X86-32] Use PCI BIOS calls to get the interrupt
  1850. routing table. These calls are known to be buggy
  1851. on several machines and they hang the machine
  1852. when used, but on other computers it's the only
  1853. way to get the interrupt routing table. Try
  1854. this option if the kernel is unable to allocate
  1855. IRQs or discover secondary PCI buses on your
  1856. motherboard.
  1857. rom [X86] Assign address space to expansion ROMs.
  1858. Use with caution as certain devices share
  1859. address decoders between ROMs and other
  1860. resources.
  1861. norom [X86] Do not assign address space to
  1862. expansion ROMs that do not already have
  1863. BIOS assigned address ranges.
  1864. nobar [X86] Do not assign address space to the
  1865. BARs that weren't assigned by the BIOS.
  1866. irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
  1867. assigned automatically to PCI devices. You can
  1868. make the kernel exclude IRQs of your ISA cards
  1869. this way.
  1870. pirqaddr=0xAAAAA [X86] Specify the physical address
  1871. of the PIRQ table (normally generated
  1872. by the BIOS) if it is outside the
  1873. F0000h-100000h range.
  1874. lastbus=N [X86] Scan all buses thru bus #N. Can be
  1875. useful if the kernel is unable to find your
  1876. secondary buses and you want to tell it
  1877. explicitly which ones they are.
  1878. assign-busses [X86] Always assign all PCI bus
  1879. numbers ourselves, overriding
  1880. whatever the firmware may have done.
  1881. usepirqmask [X86] Honor the possible IRQ mask stored
  1882. in the BIOS $PIR table. This is needed on
  1883. some systems with broken BIOSes, notably
  1884. some HP Pavilion N5400 and Omnibook XE3
  1885. notebooks. This will have no effect if ACPI
  1886. IRQ routing is enabled.
  1887. noacpi [X86] Do not use ACPI for IRQ routing
  1888. or for PCI scanning.
  1889. use_crs [X86] Use PCI host bridge window information
  1890. from ACPI. On BIOSes from 2008 or later, this
  1891. is enabled by default. If you need to use this,
  1892. please report a bug.
  1893. nocrs [X86] Ignore PCI host bridge windows from ACPI.
  1894. If you need to use this, please report a bug.
  1895. routeirq Do IRQ routing for all PCI devices.
  1896. This is normally done in pci_enable_device(),
  1897. so this option is a temporary workaround
  1898. for broken drivers that don't call it.
  1899. skip_isa_align [X86] do not align io start addr, so can
  1900. handle more pci cards
  1901. firmware [ARM] Do not re-enumerate the bus but instead
  1902. just use the configuration from the
  1903. bootloader. This is currently used on
  1904. IXP2000 systems where the bus has to be
  1905. configured a certain way for adjunct CPUs.
  1906. noearly [X86] Don't do any early type 1 scanning.
  1907. This might help on some broken boards which
  1908. machine check when some devices' config space
  1909. is read. But various workarounds are disabled
  1910. and some IOMMU drivers will not work.
  1911. bfsort Sort PCI devices into breadth-first order.
  1912. This sorting is done to get a device
  1913. order compatible with older (<= 2.4) kernels.
  1914. nobfsort Don't sort PCI devices into breadth-first order.
  1915. pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
  1916. tuning and use the BIOS-configured MPS defaults.
  1917. pcie_bus_safe Set every device's MPS to the largest value
  1918. supported by all devices below the root complex.
  1919. pcie_bus_perf Set device MPS to the largest allowable MPS
  1920. based on its parent bus. Also set MRRS (Max
  1921. Read Request Size) to the largest supported
  1922. value (no larger than the MPS that the device
  1923. or bus can support) for best performance.
  1924. pcie_bus_peer2peer Set every device's MPS to 128B, which
  1925. every device is guaranteed to support. This
  1926. configuration allows peer-to-peer DMA between
  1927. any pair of devices, possibly at the cost of
  1928. reduced performance. This also guarantees
  1929. that hot-added devices will work.
  1930. cbiosize=nn[KMG] The fixed amount of bus space which is
  1931. reserved for the CardBus bridge's IO window.
  1932. The default value is 256 bytes.
  1933. cbmemsize=nn[KMG] The fixed amount of bus space which is
  1934. reserved for the CardBus bridge's memory
  1935. window. The default value is 64 megabytes.
  1936. resource_alignment=
  1937. Format:
  1938. [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
  1939. Specifies alignment and device to reassign
  1940. aligned memory resources.
  1941. If <order of align> is not specified,
  1942. PAGE_SIZE is used as alignment.
  1943. PCI-PCI bridge can be specified, if resource
  1944. windows need to be expanded.
  1945. ecrc= Enable/disable PCIe ECRC (transaction layer
  1946. end-to-end CRC checking).
  1947. bios: Use BIOS/firmware settings. This is the
  1948. the default.
  1949. off: Turn ECRC off
  1950. on: Turn ECRC on.
  1951. hpiosize=nn[KMG] The fixed amount of bus space which is
  1952. reserved for hotplug bridge's IO window.
  1953. Default size is 256 bytes.
  1954. hpmemsize=nn[KMG] The fixed amount of bus space which is
  1955. reserved for hotplug bridge's memory window.
  1956. Default size is 2 megabytes.
  1957. realloc= Enable/disable reallocating PCI bridge resources
  1958. if allocations done by BIOS are too small to
  1959. accommodate resources required by all child
  1960. devices.
  1961. off: Turn realloc off
  1962. on: Turn realloc on
  1963. realloc same as realloc=on
  1964. noari do not use PCIe ARI.
  1965. pcie_scan_all Scan all possible PCIe devices. Otherwise we
  1966. only look for one device below a PCIe downstream
  1967. port.
  1968. pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
  1969. Management.
  1970. off Disable ASPM.
  1971. force Enable ASPM even on devices that claim not to support it.
  1972. WARNING: Forcing ASPM on may cause system lockups.
  1973. pcie_hp= [PCIE] PCI Express Hotplug driver options:
  1974. nomsi Do not use MSI for PCI Express Native Hotplug (this
  1975. makes all PCIe ports use INTx for hotplug services).
  1976. pcie_ports= [PCIE] PCIe ports handling:
  1977. auto Ask the BIOS whether or not to use native PCIe services
  1978. associated with PCIe ports (PME, hot-plug, AER). Use
  1979. them only if that is allowed by the BIOS.
  1980. native Use native PCIe services associated with PCIe ports
  1981. unconditionally.
  1982. compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
  1983. ports driver.
  1984. pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
  1985. nomsi Do not use MSI for native PCIe PME signaling (this makes
  1986. all PCIe root ports use INTx for all services).
  1987. pcmv= [HW,PCMCIA] BadgePAD 4
  1988. pd. [PARIDE]
  1989. See Documentation/blockdev/paride.txt.
  1990. pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
  1991. boot time.
  1992. Format: { 0 | 1 }
  1993. See arch/parisc/kernel/pdc_chassis.c
  1994. percpu_alloc= Select which percpu first chunk allocator to use.
  1995. Currently supported values are "embed" and "page".
  1996. Archs may support subset or none of the selections.
  1997. See comments in mm/percpu.c for details on each
  1998. allocator. This parameter is primarily for debugging
  1999. and performance comparison.
  2000. pf. [PARIDE]
  2001. See Documentation/blockdev/paride.txt.
  2002. pg. [PARIDE]
  2003. See Documentation/blockdev/paride.txt.
  2004. pirq= [SMP,APIC] Manual mp-table setup
  2005. See Documentation/x86/i386/IO-APIC.txt.
  2006. plip= [PPT,NET] Parallel port network link
  2007. Format: { parport<nr> | timid | 0 }
  2008. See also Documentation/parport.txt.
  2009. pmtmr= [X86] Manual setup of pmtmr I/O Port.
  2010. Override pmtimer IOPort with a hex value.
  2011. e.g. pmtmr=0x508
  2012. pnp.debug=1 [PNP]
  2013. Enable PNP debug messages (depends on the
  2014. CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
  2015. via /sys/module/pnp/parameters/debug. We always show
  2016. current resource usage; turning this on also shows
  2017. possible settings and some assignment information.
  2018. pnpacpi= [ACPI]
  2019. { off }
  2020. pnpbios= [ISAPNP]
  2021. { on | off | curr | res | no-curr | no-res }
  2022. pnp_reserve_irq=
  2023. [ISAPNP] Exclude IRQs for the autoconfiguration
  2024. pnp_reserve_dma=
  2025. [ISAPNP] Exclude DMAs for the autoconfiguration
  2026. pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
  2027. Ranges are in pairs (I/O port base and size).
  2028. pnp_reserve_mem=
  2029. [ISAPNP] Exclude memory regions for the
  2030. autoconfiguration.
  2031. Ranges are in pairs (memory base and size).
  2032. ports= [IP_VS_FTP] IPVS ftp helper module
  2033. Default is 21.
  2034. Up to 8 (IP_VS_APP_MAX_PORTS) ports
  2035. may be specified.
  2036. Format: <port>,<port>....
  2037. print-fatal-signals=
  2038. [KNL] debug: print fatal signals
  2039. If enabled, warn about various signal handling
  2040. related application anomalies: too many signals,
  2041. too many POSIX.1 timers, fatal signals causing a
  2042. coredump - etc.
  2043. If you hit the warning due to signal overflow,
  2044. you might want to try "ulimit -i unlimited".
  2045. default: off.
  2046. printk.always_kmsg_dump=
  2047. Trigger kmsg_dump for cases other than kernel oops or
  2048. panics
  2049. Format: <bool> (1/Y/y=enable, 0/N/n=disable)
  2050. default: disabled
  2051. printk.time= Show timing data prefixed to each printk message line
  2052. Format: <bool> (1/Y/y=enable, 0/N/n=disable)
  2053. processor.max_cstate= [HW,ACPI]
  2054. Limit processor to maximum C-state
  2055. max_cstate=9 overrides any DMI blacklist limit.
  2056. processor.nocst [HW,ACPI]
  2057. Ignore the _CST method to determine C-states,
  2058. instead using the legacy FADT method
  2059. profile= [KNL] Enable kernel profiling via /proc/profile
  2060. Format: [schedule,]<number>
  2061. Param: "schedule" - profile schedule points.
  2062. Param: <number> - step/bucket size as a power of 2 for
  2063. statistical time based profiling.
  2064. Param: "sleep" - profile D-state sleeping (millisecs).
  2065. Requires CONFIG_SCHEDSTATS
  2066. Param: "kvm" - profile VM exits.
  2067. prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
  2068. before loading.
  2069. See Documentation/blockdev/ramdisk.txt.
  2070. psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
  2071. probe for; one of (bare|imps|exps|lifebook|any).
  2072. psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
  2073. per second.
  2074. psmouse.resetafter= [HW,MOUSE]
  2075. Try to reset the device after so many bad packets
  2076. (0 = never).
  2077. psmouse.resolution=
  2078. [HW,MOUSE] Set desired mouse resolution, in dpi.
  2079. psmouse.smartscroll=
  2080. [HW,MOUSE] Controls Logitech smartscroll autorepeat.
  2081. 0 = disabled, 1 = enabled (default).
  2082. pstore.backend= Specify the name of the pstore backend to use
  2083. pt. [PARIDE]
  2084. See Documentation/blockdev/paride.txt.
  2085. pty.legacy_count=
  2086. [KNL] Number of legacy pty's. Overwrites compiled-in
  2087. default number.
  2088. quiet [KNL] Disable most log messages
  2089. r128= [HW,DRM]
  2090. raid= [HW,RAID]
  2091. See Documentation/md.txt.
  2092. ramdisk_blocksize= [RAM]
  2093. See Documentation/blockdev/ramdisk.txt.
  2094. ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
  2095. See Documentation/blockdev/ramdisk.txt.
  2096. rcu_nocbs= [KNL,BOOT]
  2097. In kernels built with CONFIG_RCU_NOCB_CPU=y, set
  2098. the specified list of CPUs to be no-callback CPUs.
  2099. Invocation of these CPUs' RCU callbacks will
  2100. be offloaded to "rcuox/N" kthreads created for
  2101. that purpose, where "x" is "b" for RCU-bh, "p"
  2102. for RCU-preempt, and "s" for RCU-sched, and "N"
  2103. is the CPU number. This reduces OS jitter on the
  2104. offloaded CPUs, which can be useful for HPC and
  2105. real-time workloads. It can also improve energy
  2106. efficiency for asymmetric multiprocessors.
  2107. rcu_nocb_poll [KNL,BOOT]
  2108. Rather than requiring that offloaded CPUs
  2109. (specified by rcu_nocbs= above) explicitly
  2110. awaken the corresponding "rcuoN" kthreads,
  2111. make these kthreads poll for callbacks.
  2112. This improves the real-time response for the
  2113. offloaded CPUs by relieving them of the need to
  2114. wake up the corresponding kthread, but degrades
  2115. energy efficiency by requiring that the kthreads
  2116. periodically wake up to do the polling.
  2117. rcutree.blimit= [KNL,BOOT]
  2118. Set maximum number of finished RCU callbacks to process
  2119. in one batch.
  2120. rcutree.fanout_leaf= [KNL,BOOT]
  2121. Increase the number of CPUs assigned to each
  2122. leaf rcu_node structure. Useful for very large
  2123. systems.
  2124. rcutree.jiffies_till_first_fqs= [KNL,BOOT]
  2125. Set delay from grace-period initialization to
  2126. first attempt to force quiescent states.
  2127. Units are jiffies, minimum value is zero,
  2128. and maximum value is HZ.
  2129. rcutree.jiffies_till_next_fqs= [KNL,BOOT]
  2130. Set delay between subsequent attempts to force
  2131. quiescent states. Units are jiffies, minimum
  2132. value is one, and maximum value is HZ.
  2133. rcutree.qhimark= [KNL,BOOT]
  2134. Set threshold of queued
  2135. RCU callbacks over which batch limiting is disabled.
  2136. rcutree.qlowmark= [KNL,BOOT]
  2137. Set threshold of queued RCU callbacks below which
  2138. batch limiting is re-enabled.
  2139. rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
  2140. Suppress RCU CPU stall warning messages.
  2141. rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
  2142. Set timeout for RCU CPU stall warning messages.
  2143. rcutree.rcu_idle_gp_delay= [KNL,BOOT]
  2144. Set wakeup interval for idle CPUs that have
  2145. RCU callbacks (RCU_FAST_NO_HZ=y).
  2146. rcutree.rcu_idle_lazy_gp_delay= [KNL,BOOT]
  2147. Set wakeup interval for idle CPUs that have
  2148. only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
  2149. Lazy RCU callbacks are those which RCU can
  2150. prove do nothing more than free memory.
  2151. rcutorture.fqs_duration= [KNL,BOOT]
  2152. Set duration of force_quiescent_state bursts.
  2153. rcutorture.fqs_holdoff= [KNL,BOOT]
  2154. Set holdoff time within force_quiescent_state bursts.
  2155. rcutorture.fqs_stutter= [KNL,BOOT]
  2156. Set wait time between force_quiescent_state bursts.
  2157. rcutorture.irqreader= [KNL,BOOT]
  2158. Test RCU readers from irq handlers.
  2159. rcutorture.n_barrier_cbs= [KNL,BOOT]
  2160. Set callbacks/threads for rcu_barrier() testing.
  2161. rcutorture.nfakewriters= [KNL,BOOT]
  2162. Set number of concurrent RCU writers. These just
  2163. stress RCU, they don't participate in the actual
  2164. test, hence the "fake".
  2165. rcutorture.nreaders= [KNL,BOOT]
  2166. Set number of RCU readers.
  2167. rcutorture.onoff_holdoff= [KNL,BOOT]
  2168. Set time (s) after boot for CPU-hotplug testing.
  2169. rcutorture.onoff_interval= [KNL,BOOT]
  2170. Set time (s) between CPU-hotplug operations, or
  2171. zero to disable CPU-hotplug testing.
  2172. rcutorture.shuffle_interval= [KNL,BOOT]
  2173. Set task-shuffle interval (s). Shuffling tasks
  2174. allows some CPUs to go into dyntick-idle mode
  2175. during the rcutorture test.
  2176. rcutorture.shutdown_secs= [KNL,BOOT]
  2177. Set time (s) after boot system shutdown. This
  2178. is useful for hands-off automated testing.
  2179. rcutorture.stall_cpu= [KNL,BOOT]
  2180. Duration of CPU stall (s) to test RCU CPU stall
  2181. warnings, zero to disable.
  2182. rcutorture.stall_cpu_holdoff= [KNL,BOOT]
  2183. Time to wait (s) after boot before inducing stall.
  2184. rcutorture.stat_interval= [KNL,BOOT]
  2185. Time (s) between statistics printk()s.
  2186. rcutorture.stutter= [KNL,BOOT]
  2187. Time (s) to stutter testing, for example, specifying
  2188. five seconds causes the test to run for five seconds,
  2189. wait for five seconds, and so on. This tests RCU's
  2190. ability to transition abruptly to and from idle.
  2191. rcutorture.test_boost= [KNL,BOOT]
  2192. Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
  2193. "Maybe" means test if the RCU implementation
  2194. under test support RCU priority boosting.
  2195. rcutorture.test_boost_duration= [KNL,BOOT]
  2196. Duration (s) of each individual boost test.
  2197. rcutorture.test_boost_interval= [KNL,BOOT]
  2198. Interval (s) between each boost test.
  2199. rcutorture.test_no_idle_hz= [KNL,BOOT]
  2200. Test RCU's dyntick-idle handling. See also the
  2201. rcutorture.shuffle_interval parameter.
  2202. rcutorture.torture_type= [KNL,BOOT]
  2203. Specify the RCU implementation to test.
  2204. rcutorture.verbose= [KNL,BOOT]
  2205. Enable additional printk() statements.
  2206. rdinit= [KNL]
  2207. Format: <full_path>
  2208. Run specified binary instead of /init from the ramdisk,
  2209. used for early userspace startup. See initrd.
  2210. reboot= [KNL]
  2211. Format (x86 or x86_64):
  2212. [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
  2213. [[,]s[mp]#### \
  2214. [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
  2215. [[,]f[orce]
  2216. Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
  2217. reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
  2218. reboot_force is either force or not specified,
  2219. reboot_cpu is s[mp]#### with #### being the processor
  2220. to be used for rebooting.
  2221. relax_domain_level=
  2222. [KNL, SMP] Set scheduler's default relax_domain_level.
  2223. See Documentation/cgroups/cpusets.txt.
  2224. reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
  2225. reservetop= [X86-32]
  2226. Format: nn[KMG]
  2227. Reserves a hole at the top of the kernel virtual
  2228. address space.
  2229. reservelow= [X86]
  2230. Format: nn[K]
  2231. Set the amount of memory to reserve for BIOS at
  2232. the bottom of the address space.
  2233. reset_devices [KNL] Force drivers to reset the underlying device
  2234. during initialization.
  2235. resume= [SWSUSP]
  2236. Specify the partition device for software suspend
  2237. Format:
  2238. {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
  2239. resume_offset= [SWSUSP]
  2240. Specify the offset from the beginning of the partition
  2241. given by "resume=" at which the swap header is located,
  2242. in <PAGE_SIZE> units (needed only for swap files).
  2243. See Documentation/power/swsusp-and-swap-files.txt
  2244. resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
  2245. read the resume files
  2246. resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
  2247. Useful for devices that are detected asynchronously
  2248. (e.g. USB and MMC devices).
  2249. hibernate= [HIBERNATION]
  2250. noresume Don't check if there's a hibernation image
  2251. present during boot.
  2252. nocompress Don't compress/decompress hibernation images.
  2253. retain_initrd [RAM] Keep initrd memory after extraction
  2254. rhash_entries= [KNL,NET]
  2255. Set number of hash buckets for route cache
  2256. riscom8= [HW,SERIAL]
  2257. Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
  2258. ro [KNL] Mount root device read-only on boot
  2259. root= [KNL] Root filesystem
  2260. See name_to_dev_t comment in init/do_mounts.c.
  2261. rootdelay= [KNL] Delay (in seconds) to pause before attempting to
  2262. mount the root filesystem
  2263. rootflags= [KNL] Set root filesystem mount option string
  2264. rootfstype= [KNL] Set root filesystem type
  2265. rootwait [KNL] Wait (indefinitely) for root device to show up.
  2266. Useful for devices that are detected asynchronously
  2267. (e.g. USB and MMC devices).
  2268. rproc_mem=nn[KMG][@address]
  2269. [KNL,ARM,CMA] Remoteproc physical memory block.
  2270. Memory area to be used by remote processor image,
  2271. managed by CMA.
  2272. rw [KNL] Mount root device read-write on boot
  2273. S [KNL] Run init in single mode
  2274. sa1100ir [NET]
  2275. See drivers/net/irda/sa1100_ir.c.
  2276. sbni= [NET] Granch SBNI12 leased line adapter
  2277. sched_debug [KNL] Enables verbose scheduler debug messages.
  2278. skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
  2279. xtime_lock contention on larger systems, and/or RCU lock
  2280. contention on all systems with CONFIG_MAXSMP set.
  2281. Format: { "0" | "1" }
  2282. 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
  2283. 1 -- enable.
  2284. Note: increases power consumption, thus should only be
  2285. enabled if running jitter sensitive (HPC/RT) workloads.
  2286. security= [SECURITY] Choose a security module to enable at boot.
  2287. If this boot parameter is not specified, only the first
  2288. security module asking for security registration will be
  2289. loaded. An invalid security module name will be treated
  2290. as if no module has been chosen.
  2291. selinux= [SELINUX] Disable or enable SELinux at boot time.
  2292. Format: { "0" | "1" }
  2293. See security/selinux/Kconfig help text.
  2294. 0 -- disable.
  2295. 1 -- enable.
  2296. Default value is set via kernel config option.
  2297. If enabled at boot time, /selinux/disable can be used
  2298. later to disable prior to initial policy load.
  2299. apparmor= [APPARMOR] Disable or enable AppArmor at boot time
  2300. Format: { "0" | "1" }
  2301. See security/apparmor/Kconfig help text
  2302. 0 -- disable.
  2303. 1 -- enable.
  2304. Default value is set via kernel config option.
  2305. serialnumber [BUGS=X86-32]
  2306. shapers= [NET]
  2307. Maximal number of shapers.
  2308. show_msr= [x86] show boot-time MSR settings
  2309. Format: { <integer> }
  2310. Show boot-time (BIOS-initialized) MSR settings.
  2311. The parameter means the number of CPUs to show,
  2312. for example 1 means boot CPU only.
  2313. simeth= [IA-64]
  2314. simscsi=
  2315. slram= [HW,MTD]
  2316. slab_max_order= [MM, SLAB]
  2317. Determines the maximum allowed order for slabs.
  2318. A high setting may cause OOMs due to memory
  2319. fragmentation. Defaults to 1 for systems with
  2320. more than 32MB of RAM, 0 otherwise.
  2321. slub_debug[=options[,slabs]] [MM, SLUB]
  2322. Enabling slub_debug allows one to determine the
  2323. culprit if slab objects become corrupted. Enabling
  2324. slub_debug can create guard zones around objects and
  2325. may poison objects when not in use. Also tracks the
  2326. last alloc / free. For more information see
  2327. Documentation/vm/slub.txt.
  2328. slub_max_order= [MM, SLUB]
  2329. Determines the maximum allowed order for slabs.
  2330. A high setting may cause OOMs due to memory
  2331. fragmentation. For more information see
  2332. Documentation/vm/slub.txt.
  2333. slub_min_objects= [MM, SLUB]
  2334. The minimum number of objects per slab. SLUB will
  2335. increase the slab order up to slub_max_order to
  2336. generate a sufficiently large slab able to contain
  2337. the number of objects indicated. The higher the number
  2338. of objects the smaller the overhead of tracking slabs
  2339. and the less frequently locks need to be acquired.
  2340. For more information see Documentation/vm/slub.txt.
  2341. slub_min_order= [MM, SLUB]
  2342. Determines the minimum page order for slabs. Must be
  2343. lower than slub_max_order.
  2344. For more information see Documentation/vm/slub.txt.
  2345. slub_nomerge [MM, SLUB]
  2346. Disable merging of slabs with similar size. May be
  2347. necessary if there is some reason to distinguish
  2348. allocs to different slabs. Debug options disable
  2349. merging on their own.
  2350. For more information see Documentation/vm/slub.txt.
  2351. smart2= [HW]
  2352. Format: <io1>[,<io2>[,...,<io8>]]
  2353. smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
  2354. smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
  2355. smsc-ircc2.ircc_sir= [HW] SIR base I/O port
  2356. smsc-ircc2.ircc_fir= [HW] FIR base I/O port
  2357. smsc-ircc2.ircc_irq= [HW] IRQ line
  2358. smsc-ircc2.ircc_dma= [HW] DMA channel
  2359. smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
  2360. 0: Toshiba Satellite 1800 (GP data pin select)
  2361. 1: Fast pin select (default)
  2362. 2: ATC IRMode
  2363. softlockup_panic=
  2364. [KNL] Should the soft-lockup detector generate panics.
  2365. Format: <integer>
  2366. sonypi.*= [HW] Sony Programmable I/O Control Device driver
  2367. See Documentation/laptops/sonypi.txt
  2368. specialix= [HW,SERIAL] Specialix multi-serial port adapter
  2369. See Documentation/serial/specialix.txt.
  2370. spia_io_base= [HW,MTD]
  2371. spia_fio_base=
  2372. spia_pedr=
  2373. spia_peddr=
  2374. stacktrace [FTRACE]
  2375. Enabled the stack tracer on boot up.
  2376. stacktrace_filter=[function-list]
  2377. [FTRACE] Limit the functions that the stack tracer
  2378. will trace at boot up. function-list is a comma separated
  2379. list of functions. This list can be changed at run
  2380. time by the stack_trace_filter file in the debugfs
  2381. tracing directory. Note, this enables stack tracing
  2382. and the stacktrace above is not needed.
  2383. sti= [PARISC,HW]
  2384. Format: <num>
  2385. Set the STI (builtin display/keyboard on the HP-PARISC
  2386. machines) console (graphic card) which should be used
  2387. as the initial boot-console.
  2388. See also comment in drivers/video/console/sticore.c.
  2389. sti_font= [HW]
  2390. See comment in drivers/video/console/sticore.c.
  2391. stifb= [HW]
  2392. Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
  2393. sunrpc.min_resvport=
  2394. sunrpc.max_resvport=
  2395. [NFS,SUNRPC]
  2396. SunRPC servers often require that client requests
  2397. originate from a privileged port (i.e. a port in the
  2398. range 0 < portnr < 1024).
  2399. An administrator who wishes to reserve some of these
  2400. ports for other uses may adjust the range that the
  2401. kernel's sunrpc client considers to be privileged
  2402. using these two parameters to set the minimum and
  2403. maximum port values.
  2404. sunrpc.pool_mode=
  2405. [NFS]
  2406. Control how the NFS server code allocates CPUs to
  2407. service thread pools. Depending on how many NICs
  2408. you have and where their interrupts are bound, this
  2409. option will affect which CPUs will do NFS serving.
  2410. Note: this parameter cannot be changed while the
  2411. NFS server is running.
  2412. auto the server chooses an appropriate mode
  2413. automatically using heuristics
  2414. global a single global pool contains all CPUs
  2415. percpu one pool for each CPU
  2416. pernode one pool for each NUMA node (equivalent
  2417. to global on non-NUMA machines)
  2418. sunrpc.tcp_slot_table_entries=
  2419. sunrpc.udp_slot_table_entries=
  2420. [NFS,SUNRPC]
  2421. Sets the upper limit on the number of simultaneous
  2422. RPC calls that can be sent from the client to a
  2423. server. Increasing these values may allow you to
  2424. improve throughput, but will also increase the
  2425. amount of memory reserved for use by the client.
  2426. swapaccount[=0|1]
  2427. [KNL] Enable accounting of swap in memory resource
  2428. controller if no parameter or 1 is given or disable
  2429. it if 0 is given (See Documentation/cgroups/memory.txt)
  2430. swiotlb= [IA-64] Number of I/O TLB slabs
  2431. switches= [HW,M68k]
  2432. sysfs.deprecated=0|1 [KNL]
  2433. Enable/disable old style sysfs layout for old udev
  2434. on older distributions. When this option is enabled
  2435. very new udev will not work anymore. When this option
  2436. is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
  2437. in older udev will not work anymore.
  2438. Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
  2439. the kernel configuration.
  2440. sysrq_always_enabled
  2441. [KNL]
  2442. Ignore sysrq setting - this boot parameter will
  2443. neutralize any effect of /proc/sys/kernel/sysrq.
  2444. Useful for debugging.
  2445. tdfx= [HW,DRM]
  2446. test_suspend= [SUSPEND]
  2447. Specify "mem" (for Suspend-to-RAM) or "standby" (for
  2448. standby suspend) as the system sleep state to briefly
  2449. enter during system startup. The system is woken from
  2450. this state using a wakeup-capable RTC alarm.
  2451. thash_entries= [KNL,NET]
  2452. Set number of hash buckets for TCP connection
  2453. thermal.act= [HW,ACPI]
  2454. -1: disable all active trip points in all thermal zones
  2455. <degrees C>: override all lowest active trip points
  2456. thermal.crt= [HW,ACPI]
  2457. -1: disable all critical trip points in all thermal zones
  2458. <degrees C>: override all critical trip points
  2459. thermal.nocrt= [HW,ACPI]
  2460. Set to disable actions on ACPI thermal zone
  2461. critical and hot trip points.
  2462. thermal.off= [HW,ACPI]
  2463. 1: disable ACPI thermal control
  2464. thermal.psv= [HW,ACPI]
  2465. -1: disable all passive trip points
  2466. <degrees C>: override all passive trip points to this
  2467. value
  2468. thermal.tzp= [HW,ACPI]
  2469. Specify global default ACPI thermal zone polling rate
  2470. <deci-seconds>: poll all this frequency
  2471. 0: no polling (default)
  2472. threadirqs [KNL]
  2473. Force threading of all interrupt handlers except those
  2474. marked explicitly IRQF_NO_THREAD.
  2475. tmem [KNL,XEN]
  2476. Enable the Transcendent memory driver if built-in.
  2477. tmem.cleancache=0|1 [KNL, XEN]
  2478. Default is on (1). Disable the usage of the cleancache
  2479. API to send anonymous pages to the hypervisor.
  2480. tmem.frontswap=0|1 [KNL, XEN]
  2481. Default is on (1). Disable the usage of the frontswap
  2482. API to send swap pages to the hypervisor. If disabled
  2483. the selfballooning and selfshrinking are force disabled.
  2484. tmem.selfballooning=0|1 [KNL, XEN]
  2485. Default is on (1). Disable the driving of swap pages
  2486. to the hypervisor.
  2487. tmem.selfshrinking=0|1 [KNL, XEN]
  2488. Default is on (1). Partial swapoff that immediately
  2489. transfers pages from Xen hypervisor back to the
  2490. kernel based on different criteria.
  2491. topology= [S390]
  2492. Format: {off | on}
  2493. Specify if the kernel should make use of the cpu
  2494. topology information if the hardware supports this.
  2495. The scheduler will make use of this information and
  2496. e.g. base its process migration decisions on it.
  2497. Default is on.
  2498. tp720= [HW,PS2]
  2499. tpm_suspend_pcr=[HW,TPM]
  2500. Format: integer pcr id
  2501. Specify that at suspend time, the tpm driver
  2502. should extend the specified pcr with zeros,
  2503. as a workaround for some chips which fail to
  2504. flush the last written pcr on TPM_SaveState.
  2505. This will guarantee that all the other pcrs
  2506. are saved.
  2507. trace_buf_size=nn[KMG]
  2508. [FTRACE] will set tracing buffer size.
  2509. trace_event=[event-list]
  2510. [FTRACE] Set and start specified trace events in order
  2511. to facilitate early boot debugging.
  2512. See also Documentation/trace/events.txt
  2513. trace_options=[option-list]
  2514. [FTRACE] Enable or disable tracer options at boot.
  2515. The option-list is a comma delimited list of options
  2516. that can be enabled or disabled just as if you were
  2517. to echo the option name into
  2518. /sys/kernel/debug/tracing/trace_options
  2519. For example, to enable stacktrace option (to dump the
  2520. stack trace of each event), add to the command line:
  2521. trace_options=stacktrace
  2522. See also Documentation/trace/ftrace.txt "trace options"
  2523. section.
  2524. traceoff_on_warning
  2525. [FTRACE] enable this option to disable tracing when a
  2526. warning is hit. This turns off "tracing_on". Tracing can
  2527. be enabled again by echoing '1' into the "tracing_on"
  2528. file located in /sys/kernel/debug/tracing/
  2529. This option is useful, as it disables the trace before
  2530. the WARNING dump is called, which prevents the trace to
  2531. be filled with content caused by the warning output.
  2532. This option can also be set at run time via the sysctl
  2533. option: kernel/traceoff_on_warning
  2534. transparent_hugepage=
  2535. [KNL]
  2536. Format: [always|madvise|never]
  2537. Can be used to control the default behavior of the system
  2538. with respect to transparent hugepages.
  2539. See Documentation/vm/transhuge.txt for more details.
  2540. tsc= Disable clocksource stability checks for TSC.
  2541. Format: <string>
  2542. [x86] reliable: mark tsc clocksource as reliable, this
  2543. disables clocksource verification at runtime, as well
  2544. as the stability checks done at bootup. Used to enable
  2545. high-resolution timer mode on older hardware, and in
  2546. virtualized environment.
  2547. [x86] noirqtime: Do not use TSC to do irq accounting.
  2548. Used to run time disable IRQ_TIME_ACCOUNTING on any
  2549. platforms where RDTSC is slow and this accounting
  2550. can add overhead.
  2551. turbografx.map[2|3]= [HW,JOY]
  2552. TurboGraFX parallel port interface
  2553. Format:
  2554. <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
  2555. See also Documentation/input/joystick-parport.txt
  2556. udbg-immortal [PPC] When debugging early kernel crashes that
  2557. happen after console_init() and before a proper
  2558. console driver takes over, this boot options might
  2559. help "seeing" what's going on.
  2560. uhash_entries= [KNL,NET]
  2561. Set number of hash buckets for UDP/UDP-Lite connections
  2562. uhci-hcd.ignore_oc=
  2563. [USB] Ignore overcurrent events (default N).
  2564. Some badly-designed motherboards generate lots of
  2565. bogus events, for ports that aren't wired to
  2566. anything. Set this parameter to avoid log spamming.
  2567. Note that genuine overcurrent events won't be
  2568. reported either.
  2569. unknown_nmi_panic
  2570. [X86] Cause panic on unknown NMI.
  2571. usbcore.authorized_default=
  2572. [USB] Default USB device authorization:
  2573. (default -1 = authorized except for wireless USB,
  2574. 0 = not authorized, 1 = authorized)
  2575. usbcore.autosuspend=
  2576. [USB] The autosuspend time delay (in seconds) used
  2577. for newly-detected USB devices (default 2). This
  2578. is the time required before an idle device will be
  2579. autosuspended. Devices for which the delay is set
  2580. to a negative value won't be autosuspended at all.
  2581. usbcore.usbfs_snoop=
  2582. [USB] Set to log all usbfs traffic (default 0 = off).
  2583. usbcore.blinkenlights=
  2584. [USB] Set to cycle leds on hubs (default 0 = off).
  2585. usbcore.old_scheme_first=
  2586. [USB] Start with the old device initialization
  2587. scheme (default 0 = off).
  2588. usbcore.usbfs_memory_mb=
  2589. [USB] Memory limit (in MB) for buffers allocated by
  2590. usbfs (default = 16, 0 = max = 2047).
  2591. usbcore.use_both_schemes=
  2592. [USB] Try the other device initialization scheme
  2593. if the first one fails (default 1 = enabled).
  2594. usbcore.initial_descriptor_timeout=
  2595. [USB] Specifies timeout for the initial 64-byte
  2596. USB_REQ_GET_DESCRIPTOR request in milliseconds
  2597. (default 5000 = 5.0 seconds).
  2598. usbhid.mousepoll=
  2599. [USBHID] The interval which mice are to be polled at.
  2600. usb-storage.delay_use=
  2601. [UMS] The delay in seconds before a new device is
  2602. scanned for Logical Units (default 5).
  2603. usb-storage.quirks=
  2604. [UMS] A list of quirks entries to supplement or
  2605. override the built-in unusual_devs list. List
  2606. entries are separated by commas. Each entry has
  2607. the form VID:PID:Flags where VID and PID are Vendor
  2608. and Product ID values (4-digit hex numbers) and
  2609. Flags is a set of characters, each corresponding
  2610. to a common usb-storage quirk flag as follows:
  2611. a = SANE_SENSE (collect more than 18 bytes
  2612. of sense data);
  2613. b = BAD_SENSE (don't collect more than 18
  2614. bytes of sense data);
  2615. c = FIX_CAPACITY (decrease the reported
  2616. device capacity by one sector);
  2617. d = NO_READ_DISC_INFO (don't use
  2618. READ_DISC_INFO command);
  2619. e = NO_READ_CAPACITY_16 (don't use
  2620. READ_CAPACITY_16 command);
  2621. h = CAPACITY_HEURISTICS (decrease the
  2622. reported device capacity by one
  2623. sector if the number is odd);
  2624. i = IGNORE_DEVICE (don't bind to this
  2625. device);
  2626. l = NOT_LOCKABLE (don't try to lock and
  2627. unlock ejectable media);
  2628. m = MAX_SECTORS_64 (don't transfer more
  2629. than 64 sectors = 32 KB at a time);
  2630. n = INITIAL_READ10 (force a retry of the
  2631. initial READ(10) command);
  2632. o = CAPACITY_OK (accept the capacity
  2633. reported by the device);
  2634. p = WRITE_CACHE (the device cache is ON
  2635. by default);
  2636. r = IGNORE_RESIDUE (the device reports
  2637. bogus residue values);
  2638. s = SINGLE_LUN (the device has only one
  2639. Logical Unit);
  2640. w = NO_WP_DETECT (don't test whether the
  2641. medium is write-protected).
  2642. Example: quirks=0419:aaf5:rl,0421:0433:rc
  2643. user_debug= [KNL,ARM]
  2644. Format: <int>
  2645. See arch/arm/Kconfig.debug help text.
  2646. 1 - undefined instruction events
  2647. 2 - system calls
  2648. 4 - invalid data aborts
  2649. 8 - SIGSEGV faults
  2650. 16 - SIGBUS faults
  2651. Example: user_debug=31
  2652. userpte=
  2653. [X86] Flags controlling user PTE allocations.
  2654. nohigh = do not allocate PTE pages in
  2655. HIGHMEM regardless of setting
  2656. of CONFIG_HIGHPTE.
  2657. vdso= [X86,SH]
  2658. vdso=2: enable compat VDSO (default with COMPAT_VDSO)
  2659. vdso=1: enable VDSO (default)
  2660. vdso=0: disable VDSO mapping
  2661. vdso32= [X86]
  2662. vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
  2663. vdso32=1: enable 32-bit VDSO (default)
  2664. vdso32=0: disable 32-bit VDSO mapping
  2665. vector= [IA-64,SMP]
  2666. vector=percpu: enable percpu vector domain
  2667. video= [FB] Frame buffer configuration
  2668. See Documentation/fb/modedb.txt.
  2669. video.brightness_switch_enabled= [0,1]
  2670. If set to 1, on receiving an ACPI notify event
  2671. generated by hotkey, video driver will adjust brightness
  2672. level and then send out the event to user space through
  2673. the allocated input device; If set to 0, video driver
  2674. will only send out the event without touching backlight
  2675. brightness level.
  2676. default: 1
  2677. virtio_mmio.device=
  2678. [VMMIO] Memory mapped virtio (platform) device.
  2679. <size>@<baseaddr>:<irq>[:<id>]
  2680. where:
  2681. <size> := size (can use standard suffixes
  2682. like K, M and G)
  2683. <baseaddr> := physical base address
  2684. <irq> := interrupt number (as passed to
  2685. request_irq())
  2686. <id> := (optional) platform device id
  2687. example:
  2688. virtio_mmio.device=1K@0x100b0000:48:7
  2689. Can be used multiple times for multiple devices.
  2690. vga= [BOOT,X86-32] Select a particular video mode
  2691. See Documentation/x86/boot.txt and
  2692. Documentation/svga.txt.
  2693. Use vga=ask for menu.
  2694. This is actually a boot loader parameter; the value is
  2695. passed to the kernel using a special protocol.
  2696. vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
  2697. size of <nn>. This can be used to increase the
  2698. minimum size (128MB on x86). It can also be used to
  2699. decrease the size and leave more room for directly
  2700. mapped kernel RAM.
  2701. vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
  2702. Format: <command>
  2703. vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
  2704. Format: <command>
  2705. vmpoff= [KNL,S390] Perform z/VM CP command after power off.
  2706. Format: <command>
  2707. vsyscall= [X86-64]
  2708. Controls the behavior of vsyscalls (i.e. calls to
  2709. fixed addresses of 0xffffffffff600x00 from legacy
  2710. code). Most statically-linked binaries and older
  2711. versions of glibc use these calls. Because these
  2712. functions are at fixed addresses, they make nice
  2713. targets for exploits that can control RIP.
  2714. emulate [default] Vsyscalls turn into traps and are
  2715. emulated reasonably safely.
  2716. native Vsyscalls are native syscall instructions.
  2717. This is a little bit faster than trapping
  2718. and makes a few dynamic recompilers work
  2719. better than they would in emulation mode.
  2720. It also makes exploits much easier to write.
  2721. none Vsyscalls don't work at all. This makes
  2722. them quite hard to use for exploits but
  2723. might break your system.
  2724. vt.cur_default= [VT] Default cursor shape.
  2725. Format: 0xCCBBAA, where AA, BB, and CC are the same as
  2726. the parameters of the <Esc>[?A;B;Cc escape sequence;
  2727. see VGA-softcursor.txt. Default: 2 = underline.
  2728. vt.default_blu= [VT]
  2729. Format: <blue0>,<blue1>,<blue2>,...,<blue15>
  2730. Change the default blue palette of the console.
  2731. This is a 16-member array composed of values
  2732. ranging from 0-255.
  2733. vt.default_grn= [VT]
  2734. Format: <green0>,<green1>,<green2>,...,<green15>
  2735. Change the default green palette of the console.
  2736. This is a 16-member array composed of values
  2737. ranging from 0-255.
  2738. vt.default_red= [VT]
  2739. Format: <red0>,<red1>,<red2>,...,<red15>
  2740. Change the default red palette of the console.
  2741. This is a 16-member array composed of values
  2742. ranging from 0-255.
  2743. vt.default_utf8=
  2744. [VT]
  2745. Format=<0|1>
  2746. Set system-wide default UTF-8 mode for all tty's.
  2747. Default is 1, i.e. UTF-8 mode is enabled for all
  2748. newly opened terminals.
  2749. vt.global_cursor_default=
  2750. [VT]
  2751. Format=<-1|0|1>
  2752. Set system-wide default for whether a cursor
  2753. is shown on new VTs. Default is -1,
  2754. i.e. cursors will be created by default unless
  2755. overridden by individual drivers. 0 will hide
  2756. cursors, 1 will display them.
  2757. watchdog timers [HW,WDT] For information on watchdog timers,
  2758. see Documentation/watchdog/watchdog-parameters.txt
  2759. or other driver-specific files in the
  2760. Documentation/watchdog/ directory.
  2761. workqueue.disable_numa
  2762. By default, all work items queued to unbound
  2763. workqueues are affine to the NUMA nodes they're
  2764. issued on, which results in better behavior in
  2765. general. If NUMA affinity needs to be disabled for
  2766. whatever reason, this option can be used. Note
  2767. that this also can be controlled per-workqueue for
  2768. workqueues visible under /sys/bus/workqueue/.
  2769. workqueue.power_efficient
  2770. Per-cpu workqueues are generally preferred because
  2771. they show better performance thanks to cache
  2772. locality; unfortunately, per-cpu workqueues tend to
  2773. be more power hungry than unbound workqueues.
  2774. Enabling this makes the per-cpu workqueues which
  2775. were observed to contribute significantly to power
  2776. consumption unbound, leading to measurably lower
  2777. power usage at the cost of small performance
  2778. overhead.
  2779. The default value of this parameter is determined by
  2780. the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
  2781. x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
  2782. default x2apic cluster mode on platforms
  2783. supporting x2apic.
  2784. x86_mrst_timer= [X86-32,APBT]
  2785. Choose timer option for x86 Moorestown MID platform.
  2786. Two valid options are apbt timer only and lapic timer
  2787. plus one apbt timer for broadcast timer.
  2788. x86_mrst_timer=apbt_only | lapic_and_apbt
  2789. xen_emul_unplug= [HW,X86,XEN]
  2790. Unplug Xen emulated devices
  2791. Format: [unplug0,][unplug1]
  2792. ide-disks -- unplug primary master IDE devices
  2793. aux-ide-disks -- unplug non-primary-master IDE devices
  2794. nics -- unplug network devices
  2795. all -- unplug all emulated devices (NICs and IDE disks)
  2796. unnecessary -- unplugging emulated devices is
  2797. unnecessary even if the host did not respond to
  2798. the unplug protocol
  2799. never -- do not unplug even if version check succeeds
  2800. xirc2ps_cs= [NET,PCMCIA]
  2801. Format:
  2802. <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
  2803. ______________________________________________________________________
  2804. TODO:
  2805. Add more DRM drivers.