4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 DRM Direct Rendering Management support is enabled.
48 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
49 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50 EFI EFI Partitioning (GPT) is enabled
51 EIDE EIDE/ATAPI support is enabled.
52 EVM Extended Verification Module
53 FB The frame buffer device is enabled.
54 FTRACE Function tracing enabled.
55 GCOV GCOV profiling is enabled.
56 HW Appropriate hardware is enabled.
57 IA-64 IA-64 architecture is enabled.
58 IMA Integrity measurement architecture is enabled.
59 IOSCHED More than one I/O scheduler is enabled.
60 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
61 IPV6 IPv6 support is enabled.
62 ISAPNP ISA PnP code is enabled.
63 ISDN Appropriate ISDN support is enabled.
64 JOY Appropriate joystick support is enabled.
65 KGDB Kernel debugger support is enabled.
66 KVM Kernel Virtual Machine support is enabled.
67 LIBATA Libata driver is enabled
68 LP Printer support is enabled.
69 LOOP Loopback device support is enabled.
70 M68k M68k architecture is enabled.
71 These options have more detailed description inside of
72 Documentation/m68k/kernel-options.txt.
73 MCA MCA bus support is enabled.
74 MDA MDA console support is enabled.
75 MIPS MIPS architecture is enabled.
76 MOUSE Appropriate mouse support is enabled.
77 MSI Message Signaled Interrupts (PCI).
78 MTD MTD (Memory Technology Device) support is enabled.
79 NET Appropriate network support is enabled.
80 NUMA NUMA support is enabled.
81 NFS Appropriate NFS support is enabled.
82 OSS OSS sound support is enabled.
83 PV_OPS A paravirtualized kernel is enabled.
84 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
85 PARISC The PA-RISC architecture is enabled.
86 PCI PCI bus support is enabled.
87 PCIE PCI Express support is enabled.
88 PCMCIA The PCMCIA subsystem is enabled.
89 PNP Plug & Play support is enabled.
90 PPC PowerPC architecture is enabled.
91 PPT Parallel port support is enabled.
92 PS2 Appropriate PS/2 support is enabled.
93 RAM RAM disk support is enabled.
94 S390 S390 architecture is enabled.
95 SCSI Appropriate SCSI support is enabled.
96 A lot of drivers have their options described inside
97 the Documentation/scsi/ sub-directory.
98 SECURITY Different security models are enabled.
99 SELINUX SELinux support is enabled.
100 APPARMOR AppArmor support is enabled.
101 SERIAL Serial support is enabled.
102 SH SuperH architecture is enabled.
103 SMP The kernel is an SMP kernel.
104 SPARC Sparc architecture is enabled.
105 SWSUSP Software suspend (hibernation) is enabled.
106 SUSPEND System suspend states are enabled.
107 TPM TPM drivers are enabled.
108 TS Appropriate touchscreen support is enabled.
109 UMS USB Mass Storage support is enabled.
110 USB USB support is enabled.
111 USBHID USB Human Interface Device support is enabled.
112 V4L Video For Linux support is enabled.
113 VGA The VGA console has been enabled.
114 VT Virtual terminal support is enabled.
115 WDT Watchdog support is enabled.
116 XT IBM PC/XT MFM hard disk support is enabled.
117 X86-32 X86-32, aka i386 architecture is enabled.
118 X86-64 X86-64 architecture is enabled.
119 More X86-64 boot options can be found in
120 Documentation/x86/x86_64/boot-options.txt .
121 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
122 XEN Xen support is enabled
124 In addition, the following text indicates that the option:
126 BUGS= Relates to possible processor bugs on the said processor.
127 KNL Is a kernel start-up parameter.
128 BOOT Is a boot loader parameter.
130 Parameters denoted with BOOT are actually interpreted by the boot
131 loader, and have no meaning to the kernel directly.
132 Do not modify the syntax of boot loader parameters without extreme
133 need or coordination with <Documentation/x86/boot.txt>.
135 There are also arch-specific kernel-parameters not documented here.
136 See for example <Documentation/x86/x86_64/boot-options.txt>.
138 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
139 a trailing = on the name of any parameter states that that parameter will
140 be entered as an environment variable, whereas its absence indicates that
141 it will appear as a kernel argument readable via /proc/cmdline by programs
142 running once the system is up.
144 The number of kernel parameters is not limited, but the length of the
145 complete command line (parameters including spaces etc.) is limited to
146 a fixed number of characters. This limit depends on the architecture
147 and is between 256 and 4096 characters. It is defined in the file
148 ./include/asm/setup.h as COMMAND_LINE_SIZE.
150 Finally, the [KMG] suffix is commonly described after a number of kernel
151 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
152 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
153 bytes respectively. Such letter suffixes can also be entirely omitted.
157 Advanced Configuration and Power Interface
158 Format: { force | off | strict | noirq | rsdt }
159 force -- enable ACPI if default was off
160 off -- disable ACPI if default was on
161 noirq -- do not use ACPI for IRQ routing
162 strict -- Be less tolerant of platforms that are not
163 strictly ACPI specification compliant.
164 rsdt -- prefer RSDT over (default) XSDT
165 copy_dsdt -- copy DSDT to memory
167 See also Documentation/power/runtime_pm.txt, pci=noacpi
169 acpi_rsdp= [ACPI,EFI,KEXEC]
170 Pass the RSDP address to the kernel, mostly used
171 on machines running EFI runtime service to boot the
172 second kernel for kdump.
174 acpi_apic_instance= [ACPI, IOAPIC]
176 2: use 2nd APIC table, if available
177 1,0: use 1st APIC table
180 acpi_backlight= [HW,ACPI]
181 acpi_backlight=vendor
183 If set to vendor, prefer vendor specific driver
184 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
185 of the ACPI video.ko driver.
187 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
188 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
190 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
191 debug output. Bits in debug_layer correspond to a
192 _COMPONENT in an ACPI source file, e.g.,
193 #define _COMPONENT ACPI_PCI_COMPONENT
194 Bits in debug_level correspond to a level in
195 ACPI_DEBUG_PRINT statements, e.g.,
196 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
197 The debug_level mask defaults to "info". See
198 Documentation/acpi/debug.txt for more information about
199 debug layers and levels.
201 Enable processor driver info messages:
202 acpi.debug_layer=0x20000000
203 Enable PCI/PCI interrupt routing info messages:
204 acpi.debug_layer=0x400000
205 Enable AML "Debug" output, i.e., stores to the Debug
206 object while interpreting AML:
207 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
208 Enable all messages related to ACPI hardware:
209 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
211 Some values produce so much output that the system is
212 unusable. The "log_buf_len" parameter may be useful
213 if you need to capture more output.
215 acpi_irq_balance [HW,ACPI]
216 ACPI will balance active IRQs
219 acpi_irq_nobalance [HW,ACPI]
220 ACPI will not move active IRQs (default)
223 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
224 Format: <irq>,<irq>...
226 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
228 Format: <irq>,<irq>...
230 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
232 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
233 Format: To spoof as Windows 98: ="Microsoft Windows"
235 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
236 acpi_osi="string1" # add string1 -- only one string
237 acpi_osi="!string2" # remove built-in string2
238 acpi_osi= # disable all strings
241 Override the pmtimer bug detection: force the kernel
242 to assume that this machine's pmtimer latches its value
243 and always returns good values.
245 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
246 Format: { level | edge | high | low }
248 acpi_serialize [HW,ACPI] force serialization of AML methods
250 acpi_skip_timer_override [HW,ACPI]
251 Recognize and ignore IRQ0/pin2 Interrupt Override.
252 For broken nForce2 BIOS resulting in XT-PIC timer.
254 acpi_sleep= [HW,ACPI] Sleep options
255 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
256 old_ordering, nonvs, sci_force_enable }
257 See Documentation/power/video.txt for information on
259 s3_beep is for debugging; it makes the PC's speaker beep
260 as soon as the kernel's real-mode entry point is called.
261 s4_nohwsig prevents ACPI hardware signature from being
262 used during resume from hibernation.
263 old_ordering causes the ACPI 1.0 ordering of the _PTS
264 control method, with respect to putting devices into
265 low power states, to be enforced (the ACPI 2.0 ordering
266 of _PTS is used by default).
267 nonvs prevents the kernel from saving/restoring the
268 ACPI NVS memory during suspend/hibernation and resume.
269 sci_force_enable causes the kernel to set SCI_EN directly
270 on resume from S1/S3 (which is against the ACPI spec,
271 but some broken systems don't work without it).
273 acpi_use_timer_override [HW,ACPI]
274 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer override, but don't have HPET
277 acpi_enforce_resources= [ACPI]
278 { strict | lax | no }
279 Check for resource conflicts between native drivers
280 and ACPI OperationRegions (SystemIO and SystemMemory
281 only). IO ports and memory declared in ACPI might be
282 used by the ACPI subsystem in arbitrary AML code and
283 can interfere with legacy drivers.
284 strict (default): access to resources claimed by ACPI
285 is denied; legacy drivers trying to access reserved
286 resources will fail to bind to device using them.
287 lax: access to resources claimed by ACPI is allowed;
288 legacy drivers trying to access reserved resources
289 will bind successfully but a warning message is logged.
290 no: ACPI OperationRegions are not marked as reserved,
291 no further checks are performed.
293 add_efi_memmap [EFI; X86] Include EFI memory map in
294 kernel's map of available physical RAM.
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
303 See Documentation/sound/alsa/alsa-parameters.txt
306 Allow the default userspace alignment fault handler
307 behaviour to be specified. Bit 0 enables warnings,
308 bit 1 enables fixups, and bit 2 sends a segfault.
310 align_va_addr= [X86-64]
311 Align virtual addresses by clearing slice [14:12] when
312 allocating a VMA at process creation time. This option
313 gives you up to 3% performance improvement on AMD F15h
314 machines (where it is enabled by default) for a
315 CPU-intensive style benchmark, and it can vary highly in
316 a microbenchmark depending on workload and compiler.
318 32: only for 32-bit processes
319 64: only for 64-bit processes
320 on: enable for both 32- and 64-bit processes
321 off: disable for both 32- and 64-bit processes
323 amd_iommu= [HW,X86-64]
324 Pass parameters to the AMD IOMMU driver in the system.
326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
330 off - do not initialize any AMD IOMMU found in
333 amijoy.map= [HW,JOY] Amiga joystick support
334 Map of devices attached to JOY0DAT and JOY1DAT
336 See also Documentation/input/joystick.txt
338 analog.map= [HW,JOY] Analog joystick and gamepad support
339 Specifies type or capabilities of an analog joystick
340 connected to one of 16 gameports
341 Format: <type1>,<type2>,..<type16>
344 Power management functions (SPARCstation-4/5 + deriv.)
346 Disable APC CPU standby support. SPARCstation-Fox does
347 not play well with APC CPU idle - disable it if you have
348 APC and your system crashes randomly.
350 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
351 Change the output verbosity whilst booting
352 Format: { quiet (default) | verbose | debug }
353 Change the amount of debugging information output
354 when initialising the APIC and IO-APIC components.
357 See Documentation/networking/ipv6.txt.
359 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
360 Limit apic dumping. The parameter defines the maximal
361 number of local apics being dumped. Also it is possible
362 to set it to "all" by meaning -- no limit here.
363 Format: { 1 (default) | 2 | ... | all }.
364 The parameter valid if only apic=debug or
365 apic=verbose is specified.
366 Example: apic=debug show_lapic=all
368 apm= [APM] Advanced Power Management
369 See header of arch/x86/kernel/apm_32.c.
371 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
372 Format: <io>,<irq>,<nodeID>
376 atarimouse= [HW,MOUSE] Atari Mouse
378 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
379 EzKey and similar keyboards
381 atkbd.reset= [HW] Reset keyboard during initialization
383 atkbd.set= [HW] Select keyboard code set
384 Format: <int> (2 = AT (default), 3 = PS/2)
386 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
389 atkbd.softraw= [HW] Choose between synthetic and real raw mode
390 Format: <bool> (0 = real, 1 = synthetic (default))
392 atkbd.softrepeat= [HW]
393 Use software keyboard repeat
397 baycom_epp= [HW,AX25]
400 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
402 See header of drivers/net/hamradio/baycom_par.c.
404 baycom_ser_fdx= [HW,AX25]
405 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
406 Format: <io>,<irq>,<mode>[,<baud>]
407 See header of drivers/net/hamradio/baycom_ser_fdx.c.
409 baycom_ser_hdx= [HW,AX25]
410 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
411 Format: <io>,<irq>,<mode>
412 See header of drivers/net/hamradio/baycom_ser_hdx.c.
414 boot_delay= Milliseconds to delay each printk during boot.
415 Values larger than 10 seconds (10000) are changed to
419 bootmem_debug [KNL] Enable bootmem allocator debug messages.
421 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
422 bttv.radio= Most important insmod options are available as
424 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
427 bulk_remove=off [PPC] This parameter disables the use of the pSeries
428 firmware feature for flushing multiple hpte entries
431 c101= [NET] Moxa C101 synchronous serial card
433 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
434 Sometimes CPU hardware bugs make them report the cache
435 size incorrectly. The kernel will attempt work arounds
436 to fix known problems, but for some CPUs it is not
437 possible to determine what the correct size should be.
438 This option provides an override for these situations.
441 [SECURITY] Disable capabilities. This would normally
442 be used only if an alternative security model is to be
443 configured. Potentially dangerous and should only be
444 used if you are entirely sure of the consequences.
446 ccw_timeout_log [S390]
447 See Documentation/s390/CommonIO for details.
449 cgroup_disable= [KNL] Disable a particular controller
450 Format: {name of the controller(s) to disable}
451 {Currently supported controllers - "memory"}
453 checkreqprot [SELINUX] Set initial checkreqprot flag value.
454 Format: { "0" | "1" }
455 See security/selinux/Kconfig help text.
456 0 -- check protection applied by kernel (includes
457 any implied execute protection).
458 1 -- check protection requested by application.
459 Default value is set via a kernel config option.
460 Value can be changed at runtime via
461 /selinux/checkreqprot.
464 See Documentation/s390/CommonIO for details.
466 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
468 Forces specified clocksource (if available) to be used
469 when calculating gettimeofday(). If specified
470 clocksource is not available, it defaults to PIT.
471 Format: { pit | tsc | cyclone | pmtmr }
473 clocksource= Override the default clocksource
475 Override the default clocksource and use the clocksource
476 with the name specified.
477 Some clocksource names to choose from, depending on
479 [all] jiffies (this is the base, fallback clocksource)
481 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
482 pxa_timer,timer3,32k_counter,timer0_1
484 [X86-32] pit,hpet,tsc;
485 scx200_hrt on Geode; cyclone on IBM x440
493 clearcpuid=BITNUM [X86]
494 Disable CPUID feature X for the kernel. See
495 arch/x86/include/asm/cpufeature.h for the valid bit
496 numbers. Note the Linux specific bits are not necessarily
497 stable over kernel options, but the vendor specific
499 Also note that user programs calling CPUID directly
500 or using the feature without checking anything
501 will still see it. This just prevents it from
502 being used by the kernel or shown in /proc/cpuinfo.
503 Also note the kernel might malfunction if you disable
506 cmo_free_hint= [PPC] Format: { yes | no }
507 Specify whether pages are marked as being inactive
508 when they are freed. This is used in CMO environments
509 to determine OS memory pressure for page stealing by
513 code_bytes [X86] How many bytes of object code to print
518 com20020= [HW,NET] ARCnet - COM20020 chipset
520 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
522 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
526 ARCnet - COM90xx chipset (memory-mapped buffers)
527 Format: <io>[,<irq>[,<memstart>]]
529 condev= [HW,S390] console device
532 console= [KNL] Output console device and options.
534 tty<n> Use the virtual console device <n>.
538 Use the specified serial port. The options are of
539 the form "bbbbpnf", where "bbbb" is the baud rate,
540 "p" is parity ("n", "o", or "e"), "n" is number of
541 bits, and "f" is flow control ("r" for RTS or
542 omit it). Default is "9600n8".
544 See Documentation/serial-console.txt for more
546 Documentation/networking/netconsole.txt for an
549 uart[8250],io,<addr>[,options]
550 uart[8250],mmio,<addr>[,options]
551 Start an early, polled-mode console on the 8250/16550
552 UART at the specified I/O port or MMIO address,
553 switching to the matching ttyS device later. The
554 options are the same as for ttyS, above.
555 hvc<n> Use the hypervisor console device <n>. This is for
556 both Xen and PowerPC hypervisors.
558 If the device connected to the port is not a TTY but a braille
559 device, prepend "brl," before the device type, for instance
561 For now, only VisioBraille is supported.
563 consoleblank= [KNL] The console blank (screen saver) timeout in
564 seconds. Defaults to 10*60 = 10mins. A value of 0
565 disables the blank timer.
568 [KNL] Change the default value for
569 /proc/<pid>/coredump_filter.
570 See also Documentation/filesystems/proc.txt.
572 cpuidle.off=1 [CPU_IDLE]
573 disable the cpuidle sub-system
575 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
577 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
579 crashkernel=size[KMG][@offset[KMG]]
580 [KNL] Using kexec, Linux can switch to a 'crash kernel'
581 upon panic. This parameter reserves the physical
582 memory region [offset, offset + size] for that kernel
583 image. If '@offset' is omitted, then a suitable offset
584 is selected automatically. Check
585 Documentation/kdump/kdump.txt for further details.
587 crashkernel=range1:size1[,range2:size2,...][@offset]
588 [KNL] Same as above, but depends on the memory
589 in the running system. The syntax of range is
590 start-[end] where start and end are both
591 a memory unit (amount[KMG]). See also
592 Documentation/kdump/kdump.txt for an example.
597 cs89x0_media= [HW,NET]
598 Format: { rj45 | aui | bnc }
601 See header of drivers/s390/block/dasd_devmap.c.
603 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
604 (one device per port)
605 Format: <port#>,<type>
606 See also Documentation/input/joystick-parport.txt
608 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
609 time. See Documentation/dynamic-debug-howto.txt for
612 debug [KNL] Enable kernel debugging (events log level).
615 [KNL] verbose self-tests
617 Print debugging info while doing the locking API
619 We default to 0 (no extra messages), setting it to
620 1 will print _a lot_ more information - normally
621 only useful to kernel developers.
623 debug_objects [KNL] Enable object debugging
626 [KNL] Disable object debugging
628 debugpat [X86] Enable PAT debugging
630 decnet.addr= [HW,NET]
631 Format: <area>[,<node>]
632 See also Documentation/networking/decnet.txt.
635 [same as hugepagesz=] The size of the default
636 HugeTLB page size. This is the size represented by
637 the legacy /proc/ hugepages APIs, used for SHM, and
638 default size when mounting hugetlbfs filesystems.
639 Defaults to the default architecture's huge page size
643 Set number of hash buckets for dentry cache.
646 IO parameters + enable/disable command.
648 digiepca= [HW,SERIAL]
649 See drivers/char/README.epca and
650 Documentation/serial/digiepca.txt.
653 See Documentation/networking/ipv6.txt.
655 disable_ddw [PPC/PSERIES]
656 Disable Dynamic DMA Window support. Use this if
657 to workaround buggy firmware.
660 See Documentation/networking/ipv6.txt.
662 disable_mtrr_cleanup [X86]
663 The kernel tries to adjust MTRR layout from continuous
664 to discrete, to make X server driver able to add WB
665 entry later. This parameter disables that.
667 disable_mtrr_trim [X86, Intel and AMD only]
668 By default the kernel will trim any uncacheable
669 memory out of your available memory pool based on
670 MTRR settings. This parameter disables that behavior,
671 possibly causing your machine to run very slowly.
673 disable_timer_pin_1 [X86]
674 Disable PIN 1 of APIC timer
675 Can be useful to work around chipset bugs.
677 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
678 this option disables the debugging code at boot.
680 dma_debug_entries=<number>
681 This option allows to tune the number of preallocated
682 entries for DMA-API debugging code. One entry is
683 required per DMA-API allocation. Use this if the
684 DMA-API debugging code disables itself because the
685 architectural default is too low.
687 dma_debug_driver=<driver_name>
688 With this option the DMA-API debugging driver
689 filter feature can be enabled at boot time. Just
690 pass the driver to filter for as the parameter.
691 The filter can be disabled or changed to another
692 driver later using sysfs.
696 earlycon= [KNL] Output early console device and options.
697 uart[8250],io,<addr>[,options]
698 uart[8250],mmio,<addr>[,options]
699 uart[8250],mmio32,<addr>[,options]
700 Start an early, polled-mode console on the 8250/16550
701 UART at the specified I/O port or MMIO address.
702 MMIO inter-register address stride is either 8-bit
703 (mmio) or 32-bit (mmio32).
704 The options are the same as for ttyS, above.
706 earlyprintk= [X86,SH,BLACKFIN]
709 earlyprintk=serial[,ttySn[,baudrate]]
710 earlyprintk=ttySn[,baudrate]
711 earlyprintk=dbgp[debugController#]
713 Append ",keep" to not disable it when the real console
716 Only vga or serial or usb debug port at a time.
718 Currently only ttyS0 and ttyS1 are supported.
720 Interaction with the standard serial driver is not
723 The VGA output is eventually overwritten by the real
726 The xen output can only be used by Xen PV guests.
728 ekgdboc= [X86,KGDB] Allow early kernel console debugging
731 This is designed to be used in conjunction with
732 the boot argument: earlyprintk=vga
735 Format: {"off" | "on" | "skip[mbr]"}
737 efi_no_storage_paranoia [EFI; X86]
738 Using this parameter you can use more than 50% of
739 your efi variable storage. Use this parameter only if
740 you are really sure that your UEFI does sane gc and
741 fulfills the spec otherwise your board may brick.
743 eisa_irq_edge= [PARISC,HW]
744 See header of drivers/parisc/eisa.c.
747 See comment before function elanfreq_setup() in
748 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
751 Format: {"cfq" | "deadline" | "noop"}
752 See Documentation/block/cfq-iosched.txt and
753 Documentation/block/deadline-iosched.txt for details.
755 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
756 Specifies physical address of start of kernel core
757 image elf header and optionally the size. Generally
758 kexec loader will pass this option to capture kernel.
759 See Documentation/kdump/kdump.txt for details.
761 enable_mtrr_cleanup [X86]
762 The kernel tries to adjust MTRR layout from continuous
763 to discrete, to make X server driver able to add WB
764 entry later. This parameter enables that.
766 enable_timer_pin_1 [X86]
767 Enable PIN 1 of APIC timer
768 Can be useful to work around chipset bugs
769 (in particular on some ATI chipsets).
770 The kernel tries to set a reasonable default.
772 enforcing [SELINUX] Set initial enforcing status.
774 See security/selinux/Kconfig help text.
775 0 -- permissive (log only, no denials).
776 1 -- enforcing (deny and log).
778 Value can be changed at runtime via /selinux/enforce.
781 Disable Error Record Serialization Table (ERST)
784 ether= [HW,NET] Ethernet cards parameters
785 This option is obsoleted by the "netdev=" option, which
786 has equivalent usage. See its documentation for details.
790 Permit 'security.evm' to be updated regardless of
791 current integrity status.
795 fail_make_request=[KNL]
796 General fault injection mechanism.
797 Format: <interval>,<probability>,<space>,<times>
798 See also Documentation/fault-injection/.
801 See Documentation/blockdev/floppy.txt.
803 force_pal_cache_flush
804 [IA-64] Avoid check_sal_cache_flush which may hang on
805 buggy SAL_CACHE_FLUSH implementations. Using this
806 parameter will force ia64_sal_cache_flush to call
807 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
810 [FTRACE] will set and start the specified tracer
811 as early as possible in order to facilitate early
814 ftrace_dump_on_oops[=orig_cpu]
815 [FTRACE] will dump the trace buffers on oops.
816 If no parameter is passed, ftrace will dump
817 buffers of all CPUs, but if you pass orig_cpu, it will
818 dump only the buffer of the CPU that triggered the
821 ftrace_filter=[function-list]
822 [FTRACE] Limit the functions traced by the function
823 tracer at boot up. function-list is a comma separated
824 list of functions. This list can be changed at run
825 time by the set_ftrace_filter file in the debugfs
828 ftrace_notrace=[function-list]
829 [FTRACE] Do not trace the functions specified in
830 function-list. This list can be changed at run time
831 by the set_ftrace_notrace file in the debugfs
834 ftrace_graph_filter=[function-list]
835 [FTRACE] Limit the top level callers functions traced
836 by the function graph tracer at boot up.
837 function-list is a comma separated list of functions
838 that can be changed at run time by the
839 set_graph_function file in the debugfs tracing directory.
842 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
843 support via parallel port (up to 5 devices per port)
844 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
845 See also Documentation/input/joystick-parport.txt
849 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
853 gcov_persist= [GCOV] When non-zero (default), profiling data for
854 kernel modules is saved and remains accessible via
855 debugfs, even when the module is unloaded/reloaded.
856 When zero, profiling data is discarded and associated
857 debugfs files are removed at module unload time.
859 gpt [EFI] Forces disk with valid GPT signature but
860 invalid Protective MBR to be treated as GPT.
862 hashdist= [KNL,NUMA] Large hashes allocated during boot
863 are distributed across NUMA nodes. Defaults on
864 for 64-bit NUMA, off otherwise.
865 Format: 0 | 1 (for off | on)
867 hcl= [IA-64] SGI's Hardware Graph compatibility layer
869 hd= [EIDE] (E)IDE hard drive subsystem geometry
870 Format: <cyl>,<head>,<sect>
873 Disable Hardware Error Source Table (HEST) support;
874 corresponding firmware-first mode error processing
875 logic will be disabled.
877 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
878 size of <nn>. This works even on boxes that have no
879 highmem otherwise. This also works to reduce highmem
880 size on bigger boxes.
882 highres= [KNL] Enable/disable high resolution timer mode.
883 Valid parameters: "on", "off"
887 See Documentation/isdn/README.HiSax.
891 hpet= [X86-32,HPET] option to control HPET usage
892 Format: { enable (default) | disable | force |
894 disable: disable HPET and use PIT instead
895 force: allow force enabled of undocumented chips (ICH4,
897 verbose: show contents of HPET registers during setup
899 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
900 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
901 On x86-64 and powerpc, this option can be specified
902 multiple times interleaved with hugepages= to reserve
903 huge pages of different sizes. Valid pages sizes on
904 x86-64 are 2M (when the CPU supports "pse") and 1G
905 (when the CPU supports the "pdpe1gb" cpuinfo flag)
906 Note that 1GB pages can only be allocated at boot time
907 using hugepages= and not freed afterwards.
909 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
910 terminal devices. Valid values: 0..8
911 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
912 If specified, z/VM IUCV HVC accepts connections
913 from listed z/VM user IDs only.
916 Do not unregister boot console at start. This is only
917 useful for debugging when something happens in the window
918 between unregistering the boot console and initializing
921 i2c_bus= [HW] Override the default board specific I2C bus speed
922 or register an additional I2C bus that is not
923 registered from board initialization code.
927 i8042.debug [HW] Toggle i8042 debug mode
928 i8042.direct [HW] Put keyboard port into non-translated mode
929 i8042.dumbkbd [HW] Pretend that controller can only read data from
930 keyboard and cannot control its state
931 (Don't attempt to blink the leds)
932 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
933 i8042.nokbd [HW] Don't check/create keyboard port
934 i8042.noloop [HW] Disable the AUX Loopback command while probing
936 i8042.nomux [HW] Don't check presence of an active multiplexing
938 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
940 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
941 i8042.reset [HW] Reset the controller during init and cleanup
942 i8042.unlock [HW] Unlock (ignore) the keylock
943 i8042.kbdreset [HW] Reset device connected to KBD port
947 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
948 indicates that the driver is running on unsupported
950 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
951 does not match list of supported models.
953 [HW] Report power status in /proc/i8k
954 (disabled by default)
955 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
958 i915.invert_brightness=
959 [DRM] Invert the sense of the variable that is used to
960 set the brightness of the panel backlight. Normally a
961 brightness value of 0 indicates backlight switched off,
962 and the maximum of the brightness value sets the backlight
963 to maximum brightness. If this parameter is set to 0
964 (default) and the machine requires it, or this parameter
965 is set to 1, a brightness value of 0 sets the backlight
966 to maximum brightness, and the maximum of the brightness
967 value switches the backlight off.
968 -1 -- never invert brightness
970 1 -- force brightness inversion
973 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
975 ide-core.nodma= [HW] (E)IDE subsystem
976 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
977 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
978 .cdrom .chs .ignore_cable are additional options
979 See Documentation/ide/ide.txt.
981 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
982 Claim all unknown PCI IDE storage controllers.
985 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
986 Poll forces a polling idle loop that can slightly
987 improve the performance of waking up a idle CPU, but
988 will use a lot of power and make the system run hot.
990 idle=mwait: On systems which support MONITOR/MWAIT but
991 the kernel chose to not use it because it doesn't save
992 as much power as a normal idle loop, use the
993 MONITOR/MWAIT idle loop anyways. Performance should be
994 the same as idle=poll.
995 idle=halt: Halt is forced to be used for CPU idle.
996 In such case C2/C3 won't be used again.
997 idle=nomwait: Disable mwait for CPU C-states
999 ignore_loglevel [KNL]
1000 Ignore loglevel setting - this will print /all/
1001 kernel messages to the console. Useful for debugging.
1002 We also add it as printk module parameter, so users
1003 could change it dynamically, usually by
1004 /sys/module/printk/parameters/ignore_loglevel.
1006 ihash_entries= [KNL]
1007 Set number of hash buckets for inode cache.
1010 Format: { "0" | "1" }
1011 0 -- integrity auditing messages. (Default)
1012 1 -- enable informational integrity auditing messages.
1015 Format: { "sha1" | "md5" }
1019 Load a policy which meets the needs of the Trusted
1020 Computing Base. This means IMA will measure all
1021 programs exec'd, files mmap'd for exec, and all files
1022 opened for read by uid=0.
1026 Run specified binary instead of /sbin/init as init
1029 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1030 for working out where the kernel is dying during
1033 initrd= [BOOT] Specify the location of the initial ramdisk
1035 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1038 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1040 Enable intel iommu driver.
1042 Disable intel iommu driver.
1043 igfx_off [Default Off]
1044 By default, gfx is mapped as normal device. If a gfx
1045 device has a dedicated DMAR unit, the DMAR unit is
1046 bypassed by not enabling DMAR with this option. In
1047 this case, gfx device will use physical address for
1050 With this option iommu will not optimize to look
1051 for io virtual address below 32-bit forcing dual
1052 address cycle on pci bus for cards supporting greater
1053 than 32-bit addressing. The default is to look
1054 for translation below 32-bit and if not available
1055 then look in the higher range.
1056 strict [Default Off]
1057 With this option on every unmap_single operation will
1058 result in a hardware IOTLB flush operation as opposed
1059 to batching them for performance.
1060 sp_off [Default Off]
1061 By default, super page will be supported if Intel IOMMU
1062 has the capability. With this option, super page will
1064 intremap= [X86-64, Intel-IOMMU]
1065 on enable Interrupt Remapping (default)
1066 off disable Interrupt Remapping
1067 nosid disable Source ID checking
1069 BIOS x2APIC opt-out request will be ignored
1073 iomem= Disable strict checking of access to MMIO memory
1074 strict regions from userspace.
1090 io7= [HW] IO7 for Marvel based alpha systems
1091 See comment before marvel_specify_io7 in
1092 arch/alpha/kernel/core_marvel.c.
1094 io_delay= [X86] I/O delay method
1096 Standard port 0x80 based delay
1098 Alternate port 0xed based delay (needed on some systems)
1100 Simple two microseconds delay
1105 See Documentation/filesystems/nfs/nfsroot.txt.
1107 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1108 See comment before ip2_setup() in
1109 drivers/char/ip2/ip2base.c.
1112 When an interrupt is not handled search all handlers
1113 for it. Intended to get systems with badly broken
1117 When an interrupt is not handled search all handlers
1118 for it. Also check all handlers each timer
1119 interrupt. Intended to get systems with badly broken
1123 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1125 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1127 <cpu number>,...,<cpu number>
1129 <cpu number>-<cpu number>
1130 (must be a positive range in ascending order)
1132 <cpu number>,...,<cpu number>-<cpu number>
1134 This option can be used to specify one or more CPUs
1135 to isolate from the general SMP balancing and scheduling
1136 algorithms. You can move a process onto or off an
1137 "isolated" CPU via the CPU affinity syscalls or cpuset.
1138 <cpu number> begins at 0 and the maximum value is
1139 "number of CPUs in system - 1".
1141 This option is the preferred way to isolate CPUs. The
1142 alternative -- manually setting the CPU mask of all
1143 tasks in the system -- can cause problems and
1144 suboptimal load balancer performance.
1148 js= [HW,JOY] Analog joystick
1149 See Documentation/input/joystick.txt.
1153 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1154 specifies the amount of memory usable by the kernel
1155 for non-movable allocations. The requested amount is
1156 spread evenly throughout all nodes in the system. The
1157 remaining memory in each node is used for Movable
1158 pages. In the event, a node is too small to have both
1159 kernelcore and Movable pages, kernelcore pages will
1160 take priority and other nodes will have a larger number
1161 of kernelcore pages. The Movable zone is used for the
1162 allocation of pages that may be reclaimed or moved
1163 by the page migration subsystem. This means that
1164 HugeTLB pages may not be allocated from this zone.
1165 Note that allocations like PTEs-from-HighMem still
1166 use the HighMem zone if it exists, and the Normal
1167 zone if it does not.
1169 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1170 Format: <Controller#>[,poll interval]
1171 The controller # is the number of the ehci usb debug
1172 port as it is probed via PCI. The poll interval is
1173 optional and is the number seconds in between
1174 each poll cycle to the debug port in case you need
1175 the functionality for interrupting the kernel with
1176 gdb or control-c on the dbgp connection. When
1177 not using this parameter you use sysrq-g to break into
1178 the kernel debugger.
1180 kgdboc= [KGDB,HW] kgdb over consoles.
1181 Requires a tty driver that supports console polling,
1182 or a supported polling keyboard driver (non-usb).
1183 Serial only format: <serial_device>[,baud]
1184 keyboard only format: kbd
1185 keyboard and serial format: kbd,<serial_device>[,baud]
1186 Optional Kernel mode setting:
1187 kms, kbd format: kms,kbd
1188 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1190 kgdbwait [KGDB] Stop kernel execution and enter the
1191 kernel debugger at the earliest opportunity.
1193 kmac= [MIPS] korina ethernet MAC address.
1194 Configure the RouterBoard 532 series on-chip
1195 Ethernet adapter MAC address.
1197 kmemleak= [KNL] Boot-time kmemleak enable/disable
1198 Valid arguments: on, off
1201 kstack=N [X86] Print N words from the kernel stack
1204 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1205 Default is 0 (don't ignore, but inject #GP)
1207 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1208 Default is 1 (enabled)
1210 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1214 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1215 Default is 1 (enabled)
1217 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1219 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1221 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1222 (virtualized MMU) support on capable Intel chips.
1223 Default is 1 (enabled)
1225 kvm-intel.emulate_invalid_guest_state=
1226 [KVM,Intel] Enable emulation of invalid guest states
1227 Default is 0 (disabled)
1229 kvm-intel.flexpriority=
1230 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1231 Default is 1 (enabled)
1234 [KVM,Intel] Enable VMX nesting (nVMX).
1235 Default is 0 (disabled)
1237 kvm-intel.unrestricted_guest=
1238 [KVM,Intel] Disable unrestricted guest feature
1239 (virtualized real and unpaged mode) on capable
1240 Intel chips. Default is 1 (enabled)
1242 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1243 feature (tagged TLBs) on capable Intel chips.
1244 Default is 1 (enabled)
1250 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1253 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1256 libata.dma= [LIBATA] DMA control
1257 libata.dma=0 Disable all PATA and SATA DMA
1258 libata.dma=1 PATA and SATA Disk DMA only
1259 libata.dma=2 ATAPI (CDROM) DMA only
1260 libata.dma=4 Compact Flash DMA only
1261 Combinations also work, so libata.dma=3 enables DMA
1262 for disks and CDROMs, but not CFs.
1264 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1265 libata.ignore_hpa=0 keep BIOS limits (default)
1266 libata.ignore_hpa=1 ignore limits, using full disk
1268 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1272 libata.force= [LIBATA] Force configurations. The format is comma
1273 separated list of "[ID:]VAL" where ID is
1274 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1275 matching port, link or device. Basically, it matches
1276 the ATA ID string printed on console by libata. If
1277 the whole ID part is omitted, the last PORT and DEVICE
1278 values are used. If ID hasn't been specified yet, the
1279 configuration applies to all ports, links and devices.
1281 If only DEVICE is omitted, the parameter applies to
1282 the port and all links and devices behind it. DEVICE
1283 number of 0 either selects the first device or the
1284 first fan-out link behind PMP device. It does not
1285 select the host link. DEVICE number of 15 selects the
1286 host link and device attached to it.
1288 The VAL specifies the configuration to force. As long
1289 as there's no ambiguity shortcut notation is allowed.
1290 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1291 The following configurations can be forced.
1293 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1294 Any ID with matching PORT is used.
1296 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1298 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1299 udma[/][16,25,33,44,66,100,133] notation is also
1302 * [no]ncq: Turn on or off NCQ.
1304 * nohrst, nosrst, norst: suppress hard, soft
1307 * dump_id: dump IDENTIFY data.
1309 * disable: Disable this device.
1311 If there are multiple matching configurations changing
1312 the same attribute, the last one is used.
1314 memblock=debug [KNL] Enable memblock debug messages.
1316 load_ramdisk= [RAM] List of ramdisks to load from floppy
1317 See Documentation/blockdev/ramdisk.txt.
1319 lockd.nlm_grace_period=P [NFS] Assign grace period.
1322 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1325 lockd.nlm_timeout=T [NFS] Assign timeout value.
1328 lockd.nlm_udpport=M [NFS] Assign UDP port.
1331 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1334 loglevel= All Kernel Messages with a loglevel smaller than the
1335 console loglevel will be printed to the console. It can
1336 also be changed with klogd or other programs. The
1337 loglevels are defined as follows:
1339 0 (KERN_EMERG) system is unusable
1340 1 (KERN_ALERT) action must be taken immediately
1341 2 (KERN_CRIT) critical conditions
1342 3 (KERN_ERR) error conditions
1343 4 (KERN_WARNING) warning conditions
1344 5 (KERN_NOTICE) normal but significant condition
1345 6 (KERN_INFO) informational
1346 7 (KERN_DEBUG) debug-level messages
1348 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1349 in bytes. n must be a power of two. The default
1350 size is set in the kernel config file.
1352 logo.nologo [FB] Disables display of the built-in Linux logo.
1353 This may be used to provide more screen space for
1354 kernel log messages and is useful when debugging
1355 kernel boot problems.
1357 lp=0 [LP] Specify parallel ports to use, e.g,
1358 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1359 lp=reset first parallel port). 'lp=0' disables the
1360 lp=auto printer driver. 'lp=reset' (which can be
1361 specified in addition to the ports) causes
1362 attached printers to be reset. Using
1363 lp=port1,port2,... specifies the parallel ports
1364 to associate lp devices with, starting with
1365 lp0. A port specification may be 'none' to skip
1366 that lp device, or a parport name such as
1367 'parport0'. Specifying 'lp=auto' instead of a
1368 port specification list means that device IDs
1369 from each port should be examined, to see if
1370 an IEEE 1284-compliant printer is attached; if
1371 so, the driver will manage that printer.
1372 See also header of drivers/char/lp.c.
1375 Sets loops_per_jiffy to given constant, thus avoiding
1376 time-consuming boot-time autodetection (up to 250 ms per
1377 CPU). 0 enables autodetection (default). To determine
1378 the correct value for your kernel, boot with normal
1379 autodetection and see what value is printed. Note that
1380 on SMP systems the preset will be applied to all CPUs,
1381 which is likely to cause problems if your CPUs need
1382 significantly divergent settings. An incorrect value
1383 will cause delays in the kernel to be wrong, leading to
1384 unpredictable I/O errors and other breakage. Although
1385 unlikely, in the extreme case this might damage your
1389 Format: <io>,<irq>,<dma>
1391 machvec= [IA-64] Force the use of a particular machine-vector
1392 (machvec) in a generic kernel.
1393 Example: machvec=hpzx1_swiotlb
1395 machtype= [Loongson] Share the same kernel image file between different
1397 Example: machtype=lemote-yeeloong-2f-7inch
1399 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1400 than or equal to this physical address is ignored.
1402 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1403 should make use of. maxcpus=n : n >= 0 limits the
1404 kernel to using 'n' processors. n=0 is a special case,
1405 it is equivalent to "nosmp", which also disables
1408 max_loop= [LOOP] The number of loop block devices that get
1409 (loop.max_loop) unconditionally pre-created at init time. The default
1410 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1411 of statically allocating a predefined number, loop
1412 devices can be requested on-demand with the
1413 /dev/loop-control interface.
1417 mce [X86-32] Machine Check Exception
1419 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1421 md= [HW] RAID subsystems devices and level
1422 See Documentation/md.txt.
1425 Format: <first>,<last>
1426 Specifies range of consoles to be captured by the MDA.
1428 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1429 Amount of memory to be used when the kernel is not able
1430 to see the whole system memory or for test.
1431 [X86-32] Use together with memmap= to avoid physical
1432 address space collisions. Without memmap= PCI devices
1433 could be placed at addresses belonging to unused RAM.
1435 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1439 [KNL,SH] Allow user to override the default size for
1440 per-device physically contiguous DMA buffers.
1442 memmap=exactmap [KNL,X86] Enable setting of an exact
1443 E820 memory map, as specified by the user.
1444 Such memmap=exactmap lines can be constructed based on
1445 BIOS output or other requirements. See the memmap=nn@ss
1448 memmap=nn[KMG]@ss[KMG]
1449 [KNL] Force usage of a specific region of memory
1450 Region of memory to be used, from ss to ss+nn.
1452 memmap=nn[KMG]#ss[KMG]
1453 [KNL,ACPI] Mark specific memory as ACPI data.
1454 Region of memory to be used, from ss to ss+nn.
1456 memmap=nn[KMG]$ss[KMG]
1457 [KNL,ACPI] Mark specific memory as reserved.
1458 Region of memory to be used, from ss to ss+nn.
1459 Example: Exclude memory from 0x18690000-0x1869ffff
1460 memmap=64K$0x18690000
1462 memmap=0x10000$0x18690000
1464 memory_corruption_check=0/1 [X86]
1465 Some BIOSes seem to corrupt the first 64k of
1466 memory when doing things like suspend/resume.
1467 Setting this option will scan the memory
1468 looking for corruption. Enabling this will
1469 both detect corruption and prevent the kernel
1470 from using the memory being corrupted.
1471 However, its intended as a diagnostic tool; if
1472 repeatable BIOS-originated corruption always
1473 affects the same memory, you can use memmap=
1474 to prevent the kernel from using that memory.
1476 memory_corruption_check_size=size [X86]
1477 By default it checks for corruption in the low
1478 64k, making this memory unavailable for normal
1479 use. Use this parameter to scan for
1480 corruption in more or less memory.
1482 memory_corruption_check_period=seconds [X86]
1483 By default it checks for corruption every 60
1484 seconds. Use this parameter to check at some
1485 other rate. 0 disables periodic checking.
1487 memtest= [KNL,X86] Enable memtest
1489 default : 0 <disable>
1490 Specifies the number of memtest passes to be
1491 performed. Each pass selects another test
1492 pattern from a given set of patterns. Memtest
1493 fills the memory with this pattern, validates
1494 memory contents and reserves bad memory
1495 regions that are detected.
1497 meye.*= [HW] Set MotionEye Camera parameters
1498 See Documentation/video4linux/meye.txt.
1500 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1501 Multi-Function General Purpose Timers on AMD Geode
1504 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1505 the BIOS has incorrectly applied a workaround. TinyBIOS
1506 version 0.98 is known to be affected, 0.99 fixes the
1507 problem by letting the user disable the workaround.
1511 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1512 physical address is ignored.
1514 mini2440= [ARM,HW,KNL]
1515 Format:[0..2][b][c][t]
1517 MINI2440 configuration specification:
1518 0 - The attached screen is the 3.5" TFT
1519 1 - The attached screen is the 7" TFT
1520 2 - The VGA Shield is attached (1024x768)
1521 Leaving out the screen size parameter will not load
1522 the TFT driver, and the framebuffer will be left
1524 b - Enable backlight. The TFT backlight pin will be
1525 linked to the kernel VESA blanking code and a GPIO
1526 LED. This parameter is not necessary when using the
1528 c - Enable the s3c camera interface.
1529 t - Reserved for enabling touchscreen support. The
1530 touchscreen support is not enabled in the mainstream
1531 kernel as of 2.6.30, a preliminary port can be found
1532 in the "bleeding edge" mini2440 support kernel at
1533 http://repo.or.cz/w/linux-2.6/mini2440.git
1536 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1537 parameter allows control of the logging verbosity for
1538 the additional memory initialisation checks. A value
1539 of 0 disables mminit logging and a level of 4 will
1540 log everything. Information is printed at KERN_DEBUG
1541 so loglevel=8 may also need to be specified.
1544 [MOUSE] Maximum time between finger touching and
1545 leaving touchpad surface for touch to be considered
1546 a tap and be reported as a left button click (for
1547 touchpads working in absolute mode only).
1549 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1550 reporting absolute coordinates, such as tablets
1551 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1552 reporting absolute coordinates, such as tablets
1554 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1555 is similar to kernelcore except it specifies the
1556 amount of memory used for migratable allocations.
1557 If both kernelcore and movablecore is specified,
1558 then kernelcore will be at *least* the specified
1559 value but may be more. If movablecore on its own
1560 is specified, the administrator must be careful
1561 that the amount of memory usable for all allocations
1564 MTD_Partition= [MTD]
1565 Format: <name>,<region-number>,<size>,<offset>
1567 MTD_Region= [MTD] Format:
1568 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1571 See drivers/mtd/cmdlinepart.c.
1573 multitce=off [PPC] This parameter disables the use of the pSeries
1574 firmware feature for updating multiple TCE entries
1577 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1579 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1581 boundary - index of last SLC block on Flex-OneNAND.
1582 The remaining blocks are configured as MLC blocks.
1583 lock - Configure if Flex-OneNAND boundary should be locked.
1584 Once locked, the boundary cannot be changed.
1585 1 indicates lock status, 0 indicates unlock status.
1588 ARM/S3C2412 JIVE boot control
1590 See arch/arm/mach-s3c2412/mach-jive.c
1592 mtouchusb.raw_coordinates=
1593 [HW] Make the MicroTouch USB driver use raw coordinates
1594 ('y', default) or cooked coordinates ('n')
1596 mtrr_chunk_size=nn[KMG] [X86]
1597 used for mtrr cleanup. It is largest continuous chunk
1598 that could hold holes aka. UC entries.
1600 mtrr_gran_size=nn[KMG] [X86]
1601 Used for mtrr cleanup. It is granularity of mtrr block.
1603 Large value could prevent small alignment from
1606 mtrr_spare_reg_nr=n [X86]
1608 Range: 0,7 : spare reg number
1610 Used for mtrr cleanup. It is spare mtrr entries number.
1611 Set to 2 or more if your graphical card needs more.
1613 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1615 netdev= [NET] Network devices parameters
1616 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1617 Note that mem_start is often overloaded to mean
1618 something different and driver-specific.
1619 This usage is only documented in each driver source
1623 [NETFILTER] Enable connection tracking flow accounting
1624 0 to disable accounting
1625 1 to enable accounting
1628 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1629 See Documentation/filesystems/nfs/nfsroot.txt.
1631 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1632 See Documentation/filesystems/nfs/nfsroot.txt.
1634 nfsrootdebug [NFS] enable nfsroot debugging messages.
1635 See Documentation/filesystems/nfs/nfsroot.txt.
1637 nfs.callback_tcpport=
1638 [NFS] set the TCP port on which the NFSv4 callback
1639 channel should listen.
1642 [NFS] sets the pathname to the program which is used
1643 to update the NFS client cache entries.
1645 nfs.cache_getent_timeout=
1646 [NFS] sets the timeout after which an attempt to
1647 update a cache entry is deemed to have failed.
1649 nfs.idmap_cache_timeout=
1650 [NFS] set the maximum lifetime for idmapper cache
1654 [NFS] enable 64-bit inode numbers.
1655 If zero, the NFS client will fake up a 32-bit inode
1656 number for the readdir() and stat() syscalls instead
1657 of returning the full 64-bit number.
1658 The default is to return 64-bit inode numbers.
1660 nfs.nfs4_disable_idmapping=
1661 [NFSv4] When set, this option disables the NFSv4
1662 idmapper on the client, but only if the mount
1663 is using the 'sec=sys' security flavour. This may
1664 make migration from legacy NFSv2/v3 systems easier
1665 provided that the server has the appropriate support.
1666 The default is to always enable NFSv4 idmapping.
1668 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1669 when a NMI is triggered.
1670 Format: [state][,regs][,debounce][,die]
1672 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1673 Format: [panic,][nopanic,][num]
1675 0 - turn nmi_watchdog off
1676 When panic is specified, panic when an NMI watchdog
1677 timeout occurs (or 'nopanic' to override the opposite
1679 This is useful when you use a panic=... timeout and
1680 need the box quickly up again.
1682 netpoll.carrier_timeout=
1683 [NET] Specifies amount of time (in seconds) that
1684 netpoll should wait for a carrier. By default netpoll
1687 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1688 emulation library even if a 387 maths coprocessor
1692 [HW] Never suspend the console
1693 Disable suspending of consoles during suspend and
1694 hibernate operations. Once disabled, debugging
1695 messages can reach various consoles while the rest
1696 of the system is being put to sleep (ie, while
1697 debugging driver suspend/resume hooks). This may
1698 not work reliably with all consoles, but is known
1699 to work with serial and VGA consoles.
1700 To facilitate more flexible debugging, we also add
1701 console_suspend, a printk module parameter to control
1702 it. Users could use console_suspend (usually
1703 /sys/module/printk/parameters/console_suspend) to
1704 turn on/off it dynamically.
1706 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1707 caches in the slab allocator. Saves per-node memory,
1708 but will impact performance.
1712 noapic [SMP,APIC] Tells the kernel to not make use of any
1713 IOAPICs that may be present in the system.
1715 noautogroup Disable scheduler automatic task group creation.
1717 nobats [PPC] Do not use BATs for mapping kernel lowmem
1718 on "Classic" PPC cores.
1722 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1724 nodelayacct [KNL] Disable per-task delay accounting
1726 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1728 nodsp [SH] Disable hardware DSP at boot time.
1730 noefi [X86] Disable EFI runtime services support.
1735 On X86-32 available only on PAE configured kernels.
1736 noexec=on: enable non-executable mappings (default)
1737 noexec=off: disable non-executable mappings
1740 Disable SMEP (Supervisor Mode Execution Protection)
1741 even if it is supported by processor.
1744 This affects only 32-bit executables.
1745 noexec32=on: enable non-executable mappings (default)
1746 read doesn't imply executable mappings
1747 noexec32=off: disable non-executable mappings
1748 read implies executable mappings
1750 nofpu [SH] Disable hardware FPU at boot time.
1752 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1753 register save and restore. The kernel will only save
1754 legacy floating-point registers on task switch.
1756 noxsave [BUGS=X86] Disables x86 extended register state save
1757 and restore using xsave. The kernel will fallback to
1758 enabling legacy floating-point and sse state.
1760 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1761 wfi(ARM) instruction doesn't work correctly and not to
1762 use it. This is also useful when using JTAG debugger.
1764 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1765 instruction doesn't work correctly and not to
1768 no_file_caps Tells the kernel not to honor file capabilities. The
1769 only way then for a file to be executed with privilege
1770 is to be setuid root or executed by root.
1772 nohalt [IA-64] Tells the kernel not to use the power saving
1773 function PAL_HALT_LIGHT when idle. This increases
1774 power-consumption. On the positive side, it reduces
1775 interrupt wake-up latency, which may improve performance
1776 in certain environments such as networked servers or
1779 nohz= [KNL] Boottime enable/disable dynamic ticks
1780 Valid arguments: on, off
1783 noiotrap [SH] Disables trapped I/O port accesses.
1785 noirqdebug [X86-32] Disables the code which attempts to detect and
1786 disable unhandled interrupt sources.
1788 no_timer_check [X86,APIC] Disables the code which tests for
1789 broken timer IRQ sources.
1791 noisapnp [ISAPNP] Disables ISA PnP code.
1793 noinitrd [RAM] Tells the kernel not to load any configured
1796 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1798 [Deprecated - use intremap=off]
1802 nojitter [IA-64] Disables jitter checking for ITC timers.
1804 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1806 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1809 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1810 steal time is computed, but won't influence scheduler
1813 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1815 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1817 noltlbs [PPC] Do not use large page/tlb entries for kernel
1818 lowmem mapping on PPC40x.
1820 nomca [IA-64] Disable machine check abort handling
1822 nomce [X86-32] Machine Check Exception
1824 nomfgpt [X86-32] Disable Multi-Function General Purpose
1825 Timer usage (for AMD Geode machines).
1827 nopat [X86] Disable PAT (page attribute table extension of
1828 pagetables) support.
1830 norandmaps Don't use address space randomization. Equivalent to
1831 echo 0 > /proc/sys/kernel/randomize_va_space
1833 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1835 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1836 with UP alternatives
1838 noresidual [PPC] Don't use residual data on PReP machines.
1840 nordrand [X86] Disable the direct use of the RDRAND
1841 instruction even if it is supported by the
1842 processor. RDRAND is still available to user
1845 noresume [SWSUSP] Disables resume and restores original swap
1848 no-scroll [VGA] Disables scrollback.
1849 This is required for the Braillex ib80-piezo Braille
1850 reader made by F.H. Papenmeier (Germany).
1854 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1856 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1857 and disable the IO APIC. legacy for "maxcpus=0".
1859 nosoftlockup [KNL] Disable the soft-lockup detector.
1861 nosync [HW,M68K] Disables sync negotiation for all devices.
1863 notsc [BUGS=X86-32] Disable Time Stamp Counter
1865 nousb [USB] Disable the USB subsystem
1867 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1871 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1873 nptcg= [IA-64] Override max number of concurrent global TLB
1874 purges which is reported from either PAL_VM_SUMMARY or
1877 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1878 could support. nr_cpus=n : n >= 1 limits the kernel to
1879 supporting 'n' processors. Later in runtime you can not
1880 use hotplug cpu feature to put more cpu back to online.
1881 just like you compile the kernel NR_CPUS=n
1883 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1885 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1886 one of ['zone', 'node', 'default'] can be specified
1887 This can be set from sysctl after boot.
1888 See Documentation/sysctl/vm.txt for details.
1890 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1891 See Documentation/debugging-via-ohci1394.txt for more
1894 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1895 Rather than timing out after 20 ms if an EC
1896 command is not properly ACKed, override the length
1897 of the timeout. We have interrupts disabled while
1898 waiting for the ACK, so if this is set too high
1899 interrupts *may* be lost!
1901 omap_mux= [OMAP] Override bootloader pin multiplexing.
1902 Format: <mux_mode0.mode_name=value>...
1903 For example, to override I2C bus2:
1904 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1906 oprofile.timer= [HW]
1907 Use timer interrupt instead of performance counters
1909 oprofile.cpu_type= Force an oprofile cpu type
1910 This might be useful if you have an older oprofile
1911 userland or if you want common events.
1912 Format: { arch_perfmon }
1913 arch_perfmon: [X86] Force use of architectural
1914 perfmon on Intel CPUs instead of the
1915 CPU specific event set.
1917 oops=panic Always panic on oopses. Default is to just kill the
1918 process, but there is a small probability of
1919 deadlocking the machine.
1920 This will also cause panics on machine check exceptions.
1921 Useful together with panic=30 to trigger a reboot.
1924 See Documentation/sound/oss/oss-parameters.txt
1926 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1927 timeout > 0: seconds before rebooting
1928 timeout = 0: wait forever
1929 timeout < 0: reboot immediately
1932 parkbd.port= [HW] Parallel port number the keyboard adapter is
1933 connected to, default is 0.
1935 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1936 0 for XT, 1 for AT (default is AT).
1939 parport= [HW,PPT] Specify parallel ports. 0 disables.
1940 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1941 Use 'auto' to force the driver to use any
1942 IRQ/DMA settings detected (the default is to
1943 ignore detected IRQ/DMA settings because of
1944 possible conflicts). You can specify the base
1945 address, IRQ, and DMA settings; IRQ and DMA
1946 should be numbers, or 'auto' (for using detected
1947 settings on that particular port), or 'nofifo'
1948 (to avoid using a FIFO even if it is detected).
1949 Parallel ports are assigned in the order they
1950 are specified on the command line, starting
1953 parport_init_mode= [HW,PPT]
1954 Configure VIA parallel port to operate in
1955 a specific mode. This is necessary on Pegasos
1956 computer where firmware has no options for setting
1957 up parallel port mode and sets it to spp.
1958 Currently this function knows 686a and 8231 chips.
1959 Format: [spp|ps2|epp|ecp|ecpepp]
1962 Halt all CPUs after the first oops has been printed for
1963 the specified number of seconds. This is to be used if
1964 your oopses keep scrolling off the screen.
1969 See header of drivers/block/paride/pcd.c.
1970 See also Documentation/blockdev/paride.txt.
1972 pci=option[,option...] [PCI] various PCI subsystem options:
1973 earlydump [X86] dump PCI config space before the kernel
1975 off [X86] don't probe for the PCI bus
1976 bios [X86-32] force use of PCI BIOS, don't access
1977 the hardware directly. Use this if your machine
1978 has a non-standard PCI host bridge.
1979 nobios [X86-32] disallow use of PCI BIOS, only direct
1980 hardware access methods are allowed. Use this
1981 if you experience crashes upon bootup and you
1982 suspect they are caused by the BIOS.
1983 conf1 [X86] Force use of PCI Configuration
1985 conf2 [X86] Force use of PCI Configuration
1987 noaer [PCIE] If the PCIEAER kernel config parameter is
1988 enabled, this kernel boot option can be used to
1989 disable the use of PCIE advanced error reporting.
1990 nodomains [PCI] Disable support for multiple PCI
1991 root domains (aka PCI segments, in ACPI-speak).
1992 nommconf [X86] Disable use of MMCONFIG for PCI
1994 check_enable_amd_mmconf [X86] check for and enable
1995 properly configured MMIO access to PCI
1996 config space on AMD family 10h CPU
1997 nomsi [MSI] If the PCI_MSI kernel config parameter is
1998 enabled, this kernel boot option can be used to
1999 disable the use of MSI interrupts system-wide.
2000 noioapicquirk [APIC] Disable all boot interrupt quirks.
2001 Safety option to keep boot IRQs enabled. This
2002 should never be necessary.
2003 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2004 primary IO-APIC for bridges that cannot disable
2005 boot IRQs. This fixes a source of spurious IRQs
2006 when the system masks IRQs.
2007 noioapicreroute [APIC] Disable workaround that uses the
2008 boot IRQ equivalent of an IRQ that connects to
2009 a chipset where boot IRQs cannot be disabled.
2010 The opposite of ioapicreroute.
2011 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2012 routing table. These calls are known to be buggy
2013 on several machines and they hang the machine
2014 when used, but on other computers it's the only
2015 way to get the interrupt routing table. Try
2016 this option if the kernel is unable to allocate
2017 IRQs or discover secondary PCI buses on your
2019 rom [X86] Assign address space to expansion ROMs.
2020 Use with caution as certain devices share
2021 address decoders between ROMs and other
2023 norom [X86] Do not assign address space to
2024 expansion ROMs that do not already have
2025 BIOS assigned address ranges.
2026 nobar [X86] Do not assign address space to the
2027 BARs that weren't assigned by the BIOS.
2028 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2029 assigned automatically to PCI devices. You can
2030 make the kernel exclude IRQs of your ISA cards
2032 pirqaddr=0xAAAAA [X86] Specify the physical address
2033 of the PIRQ table (normally generated
2034 by the BIOS) if it is outside the
2035 F0000h-100000h range.
2036 lastbus=N [X86] Scan all buses thru bus #N. Can be
2037 useful if the kernel is unable to find your
2038 secondary buses and you want to tell it
2039 explicitly which ones they are.
2040 assign-busses [X86] Always assign all PCI bus
2041 numbers ourselves, overriding
2042 whatever the firmware may have done.
2043 usepirqmask [X86] Honor the possible IRQ mask stored
2044 in the BIOS $PIR table. This is needed on
2045 some systems with broken BIOSes, notably
2046 some HP Pavilion N5400 and Omnibook XE3
2047 notebooks. This will have no effect if ACPI
2048 IRQ routing is enabled.
2049 noacpi [X86] Do not use ACPI for IRQ routing
2050 or for PCI scanning.
2051 use_crs [X86] Use PCI host bridge window information
2052 from ACPI. On BIOSes from 2008 or later, this
2053 is enabled by default. If you need to use this,
2054 please report a bug.
2055 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2056 If you need to use this, please report a bug.
2057 routeirq Do IRQ routing for all PCI devices.
2058 This is normally done in pci_enable_device(),
2059 so this option is a temporary workaround
2060 for broken drivers that don't call it.
2061 skip_isa_align [X86] do not align io start addr, so can
2062 handle more pci cards
2063 firmware [ARM] Do not re-enumerate the bus but instead
2064 just use the configuration from the
2065 bootloader. This is currently used on
2066 IXP2000 systems where the bus has to be
2067 configured a certain way for adjunct CPUs.
2068 noearly [X86] Don't do any early type 1 scanning.
2069 This might help on some broken boards which
2070 machine check when some devices' config space
2071 is read. But various workarounds are disabled
2072 and some IOMMU drivers will not work.
2073 bfsort Sort PCI devices into breadth-first order.
2074 This sorting is done to get a device
2075 order compatible with older (<= 2.4) kernels.
2076 nobfsort Don't sort PCI devices into breadth-first order.
2077 cbiosize=nn[KMG] The fixed amount of bus space which is
2078 reserved for the CardBus bridge's IO window.
2079 The default value is 256 bytes.
2080 cbmemsize=nn[KMG] The fixed amount of bus space which is
2081 reserved for the CardBus bridge's memory
2082 window. The default value is 64 megabytes.
2085 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2086 Specifies alignment and device to reassign
2087 aligned memory resources.
2088 If <order of align> is not specified,
2089 PAGE_SIZE is used as alignment.
2090 PCI-PCI bridge can be specified, if resource
2091 windows need to be expanded.
2092 ecrc= Enable/disable PCIe ECRC (transaction layer
2093 end-to-end CRC checking).
2094 bios: Use BIOS/firmware settings. This is the
2098 realloc reallocate PCI resources if allocations done by BIOS
2101 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2104 force Enable ASPM even on devices that claim not to support it.
2105 WARNING: Forcing ASPM on may cause system lockups.
2107 pcie_ports= [PCIE] PCIe ports handling:
2108 auto Ask the BIOS whether or not to use native PCIe services
2109 associated with PCIe ports (PME, hot-plug, AER). Use
2110 them only if that is allowed by the BIOS.
2111 native Use native PCIe services associated with PCIe ports
2113 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2116 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2117 nomsi Do not use MSI for native PCIe PME signaling (this makes
2118 all PCIe root ports use INTx for all services).
2120 pcmv= [HW,PCMCIA] BadgePAD 4
2123 See Documentation/blockdev/paride.txt.
2125 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2128 See arch/parisc/kernel/pdc_chassis.c
2130 percpu_alloc= Select which percpu first chunk allocator to use.
2131 Currently supported values are "embed" and "page".
2132 Archs may support subset or none of the selections.
2133 See comments in mm/percpu.c for details on each
2134 allocator. This parameter is primarily for debugging
2135 and performance comparison.
2138 See Documentation/blockdev/paride.txt.
2141 See Documentation/blockdev/paride.txt.
2143 pirq= [SMP,APIC] Manual mp-table setup
2144 See Documentation/x86/i386/IO-APIC.txt.
2146 plip= [PPT,NET] Parallel port network link
2147 Format: { parport<nr> | timid | 0 }
2148 See also Documentation/parport.txt.
2150 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2151 Override pmtimer IOPort with a hex value.
2155 Enable PNP debug messages (depends on the
2156 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2157 via /sys/module/pnp/parameters/debug. We always show
2158 current resource usage; turning this on also shows
2159 possible settings and some assignment information.
2165 { on | off | curr | res | no-curr | no-res }
2168 [ISAPNP] Exclude IRQs for the autoconfiguration
2171 [ISAPNP] Exclude DMAs for the autoconfiguration
2173 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2174 Ranges are in pairs (I/O port base and size).
2177 [ISAPNP] Exclude memory regions for the
2179 Ranges are in pairs (memory base and size).
2181 ports= [IP_VS_FTP] IPVS ftp helper module
2183 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2185 Format: <port>,<port>....
2187 print-fatal-signals=
2188 [KNL] debug: print fatal signals
2190 If enabled, warn about various signal handling
2191 related application anomalies: too many signals,
2192 too many POSIX.1 timers, fatal signals causing a
2195 If you hit the warning due to signal overflow,
2196 you might want to try "ulimit -i unlimited".
2200 printk.time= Show timing data prefixed to each printk message line
2201 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2203 processor.max_cstate= [HW,ACPI]
2204 Limit processor to maximum C-state
2205 max_cstate=9 overrides any DMI blacklist limit.
2207 processor.nocst [HW,ACPI]
2208 Ignore the _CST method to determine C-states,
2209 instead using the legacy FADT method
2211 profile= [KNL] Enable kernel profiling via /proc/profile
2212 Format: [schedule,]<number>
2213 Param: "schedule" - profile schedule points.
2214 Param: <number> - step/bucket size as a power of 2 for
2215 statistical time based profiling.
2216 Param: "sleep" - profile D-state sleeping (millisecs).
2217 Requires CONFIG_SCHEDSTATS
2218 Param: "kvm" - profile VM exits.
2220 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2222 See Documentation/blockdev/ramdisk.txt.
2224 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2225 probe for; one of (bare|imps|exps|lifebook|any).
2226 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2228 psmouse.resetafter= [HW,MOUSE]
2229 Try to reset the device after so many bad packets
2232 [HW,MOUSE] Set desired mouse resolution, in dpi.
2233 psmouse.smartscroll=
2234 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2235 0 = disabled, 1 = enabled (default).
2237 pstore.backend= Specify the name of the pstore backend to use
2240 See Documentation/blockdev/paride.txt.
2243 [KNL] Number of legacy pty's. Overwrites compiled-in
2246 quiet [KNL] Disable most log messages
2251 See Documentation/md.txt.
2253 ramdisk_blocksize= [RAM]
2254 See Documentation/blockdev/ramdisk.txt.
2256 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2257 See Documentation/blockdev/ramdisk.txt.
2259 rcupdate.blimit= [KNL,BOOT]
2260 Set maximum number of finished RCU callbacks to process
2263 rcupdate.qhimark= [KNL,BOOT]
2264 Set threshold of queued
2265 RCU callbacks over which batch limiting is disabled.
2267 rcupdate.qlowmark= [KNL,BOOT]
2268 Set threshold of queued RCU callbacks below which
2269 batch limiting is re-enabled.
2273 Run specified binary instead of /init from the ramdisk,
2274 used for early userspace startup. See initrd.
2276 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2277 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2278 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2281 [KNL, SMP] Set scheduler's default relax_domain_level.
2282 See Documentation/cgroups/cpusets.txt.
2284 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2286 reservetop= [X86-32]
2288 Reserves a hole at the top of the kernel virtual
2293 Set the amount of memory to reserve for BIOS at
2294 the bottom of the address space.
2296 reset_devices [KNL] Force drivers to reset the underlying device
2297 during initialization.
2300 Specify the partition device for software suspend
2302 resume_offset= [SWSUSP]
2303 Specify the offset from the beginning of the partition
2304 given by "resume=" at which the swap header is located,
2305 in <PAGE_SIZE> units (needed only for swap files).
2306 See Documentation/power/swsusp-and-swap-files.txt
2308 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2309 read the resume files
2311 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2312 Useful for devices that are detected asynchronously
2313 (e.g. USB and MMC devices).
2315 hibernate= [HIBERNATION]
2316 noresume Don't check if there's a hibernation image
2317 present during boot.
2318 nocompress Don't compress/decompress hibernation images.
2320 retain_initrd [RAM] Keep initrd memory after extraction
2322 rhash_entries= [KNL,NET]
2323 Set number of hash buckets for route cache
2325 riscom8= [HW,SERIAL]
2326 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2328 ro [KNL] Mount root device read-only on boot
2330 root= [KNL] Root filesystem
2331 See name_to_dev_t comment in init/do_mounts.c.
2333 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2334 mount the root filesystem
2336 rootflags= [KNL] Set root filesystem mount option string
2338 rootfstype= [KNL] Set root filesystem type
2340 rootwait [KNL] Wait (indefinitely) for root device to show up.
2341 Useful for devices that are detected asynchronously
2342 (e.g. USB and MMC devices).
2344 rw [KNL] Mount root device read-write on boot
2346 S [KNL] Run init in single mode
2349 See drivers/net/irda/sa1100_ir.c.
2351 sbni= [NET] Granch SBNI12 leased line adapter
2353 sched_debug [KNL] Enables verbose scheduler debug messages.
2355 security= [SECURITY] Choose a security module to enable at boot.
2356 If this boot parameter is not specified, only the first
2357 security module asking for security registration will be
2358 loaded. An invalid security module name will be treated
2359 as if no module has been chosen.
2361 selinux= [SELINUX] Disable or enable SELinux at boot time.
2362 Format: { "0" | "1" }
2363 See security/selinux/Kconfig help text.
2366 Default value is set via kernel config option.
2367 If enabled at boot time, /selinux/disable can be used
2368 later to disable prior to initial policy load.
2370 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2371 Format: { "0" | "1" }
2372 See security/apparmor/Kconfig help text
2375 Default value is set via kernel config option.
2377 serialnumber [BUGS=X86-32]
2380 Maximal number of shapers.
2382 show_msr= [x86] show boot-time MSR settings
2383 Format: { <integer> }
2384 Show boot-time (BIOS-initialized) MSR settings.
2385 The parameter means the number of CPUs to show,
2386 for example 1 means boot CPU only.
2393 slub_debug[=options[,slabs]] [MM, SLUB]
2394 Enabling slub_debug allows one to determine the
2395 culprit if slab objects become corrupted. Enabling
2396 slub_debug can create guard zones around objects and
2397 may poison objects when not in use. Also tracks the
2398 last alloc / free. For more information see
2399 Documentation/vm/slub.txt.
2401 slub_max_order= [MM, SLUB]
2402 Determines the maximum allowed order for slabs.
2403 A high setting may cause OOMs due to memory
2404 fragmentation. For more information see
2405 Documentation/vm/slub.txt.
2407 slub_min_objects= [MM, SLUB]
2408 The minimum number of objects per slab. SLUB will
2409 increase the slab order up to slub_max_order to
2410 generate a sufficiently large slab able to contain
2411 the number of objects indicated. The higher the number
2412 of objects the smaller the overhead of tracking slabs
2413 and the less frequently locks need to be acquired.
2414 For more information see Documentation/vm/slub.txt.
2416 slub_min_order= [MM, SLUB]
2417 Determines the mininum page order for slabs. Must be
2418 lower than slub_max_order.
2419 For more information see Documentation/vm/slub.txt.
2421 slub_nomerge [MM, SLUB]
2422 Disable merging of slabs with similar size. May be
2423 necessary if there is some reason to distinguish
2424 allocs to different slabs. Debug options disable
2425 merging on their own.
2426 For more information see Documentation/vm/slub.txt.
2429 Format: <io1>[,<io2>[,...,<io8>]]
2431 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2432 attempt to substitute SMP alternatives once at boot.
2434 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2435 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2436 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2437 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2438 smsc-ircc2.ircc_irq= [HW] IRQ line
2439 smsc-ircc2.ircc_dma= [HW] DMA channel
2440 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2441 0: Toshiba Satellite 1800 (GP data pin select)
2442 1: Fast pin select (default)
2446 [KNL] Should the soft-lockup detector generate panics.
2449 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2450 See Documentation/laptops/sonypi.txt
2452 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2453 See Documentation/serial/specialix.txt.
2455 spia_io_base= [HW,MTD]
2461 Enabled the stack tracer on boot up.
2465 Set the STI (builtin display/keyboard on the HP-PARISC
2466 machines) console (graphic card) which should be used
2467 as the initial boot-console.
2468 See also comment in drivers/video/console/sticore.c.
2471 See comment in drivers/video/console/sticore.c.
2474 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2476 sunrpc.min_resvport=
2477 sunrpc.max_resvport=
2479 SunRPC servers often require that client requests
2480 originate from a privileged port (i.e. a port in the
2481 range 0 < portnr < 1024).
2482 An administrator who wishes to reserve some of these
2483 ports for other uses may adjust the range that the
2484 kernel's sunrpc client considers to be privileged
2485 using these two parameters to set the minimum and
2486 maximum port values.
2490 Control how the NFS server code allocates CPUs to
2491 service thread pools. Depending on how many NICs
2492 you have and where their interrupts are bound, this
2493 option will affect which CPUs will do NFS serving.
2494 Note: this parameter cannot be changed while the
2495 NFS server is running.
2497 auto the server chooses an appropriate mode
2498 automatically using heuristics
2499 global a single global pool contains all CPUs
2500 percpu one pool for each CPU
2501 pernode one pool for each NUMA node (equivalent
2502 to global on non-NUMA machines)
2504 sunrpc.tcp_slot_table_entries=
2505 sunrpc.udp_slot_table_entries=
2507 Sets the upper limit on the number of simultaneous
2508 RPC calls that can be sent from the client to a
2509 server. Increasing these values may allow you to
2510 improve throughput, but will also increase the
2511 amount of memory reserved for use by the client.
2514 [KNL] Enable accounting of swap in memory resource
2515 controller if no parameter or 1 is given or disable
2516 it if 0 is given (See Documentation/cgroups/memory.txt)
2518 swiotlb= [IA-64] Number of I/O TLB slabs
2522 sysfs.deprecated=0|1 [KNL]
2523 Enable/disable old style sysfs layout for old udev
2524 on older distributions. When this option is enabled
2525 very new udev will not work anymore. When this option
2526 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2527 in older udev will not work anymore.
2528 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2529 the kernel configuration.
2531 sysrq_always_enabled
2533 Ignore sysrq setting - this boot parameter will
2534 neutralize any effect of /proc/sys/kernel/sysrq.
2535 Useful for debugging.
2539 test_suspend= [SUSPEND]
2540 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2541 standby suspend) as the system sleep state to briefly
2542 enter during system startup. The system is woken from
2543 this state using a wakeup-capable RTC alarm.
2545 thash_entries= [KNL,NET]
2546 Set number of hash buckets for TCP connection
2548 thermal.act= [HW,ACPI]
2549 -1: disable all active trip points in all thermal zones
2550 <degrees C>: override all lowest active trip points
2552 thermal.crt= [HW,ACPI]
2553 -1: disable all critical trip points in all thermal zones
2554 <degrees C>: override all critical trip points
2556 thermal.nocrt= [HW,ACPI]
2557 Set to disable actions on ACPI thermal zone
2558 critical and hot trip points.
2560 thermal.off= [HW,ACPI]
2561 1: disable ACPI thermal control
2563 thermal.psv= [HW,ACPI]
2564 -1: disable all passive trip points
2565 <degrees C>: override all passive trip points to this
2568 thermal.tzp= [HW,ACPI]
2569 Specify global default ACPI thermal zone polling rate
2570 <deci-seconds>: poll all this frequency
2571 0: no polling (default)
2574 Force threading of all interrupt handlers except those
2575 marked explicitely IRQF_NO_THREAD.
2579 Specify if the kernel should make use of the cpu
2580 topology information if the hardware supports this.
2581 The scheduler will make use of this information and
2582 e.g. base its process migration decisions on it.
2587 tpm_suspend_pcr=[HW,TPM]
2588 Format: integer pcr id
2589 Specify that at suspend time, the tpm driver
2590 should extend the specified pcr with zeros,
2591 as a workaround for some chips which fail to
2592 flush the last written pcr on TPM_SaveState.
2593 This will guarantee that all the other pcrs
2596 trace_buf_size=nn[KMG]
2597 [FTRACE] will set tracing buffer size.
2599 trace_event=[event-list]
2600 [FTRACE] Set and start specified trace events in order
2601 to facilitate early boot debugging.
2602 See also Documentation/trace/events.txt
2604 tsc= Disable clocksource stability checks for TSC.
2606 [x86] reliable: mark tsc clocksource as reliable, this
2607 disables clocksource verification at runtime, as well
2608 as the stability checks done at bootup. Used to enable
2609 high-resolution timer mode on older hardware, and in
2610 virtualized environment.
2611 [x86] noirqtime: Do not use TSC to do irq accounting.
2612 Used to run time disable IRQ_TIME_ACCOUNTING on any
git.openpandora.org / pandora-kernel.git / blob