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
332 force_isolation - Force device isolation for all
333 devices. The IOMMU driver is not
334 allowed anymore to lift isolation
335 requirements as needed. This option
336 does not override iommu=pt
338 amijoy.map= [HW,JOY] Amiga joystick support
339 Map of devices attached to JOY0DAT and JOY1DAT
341 See also Documentation/input/joystick.txt
343 analog.map= [HW,JOY] Analog joystick and gamepad support
344 Specifies type or capabilities of an analog joystick
345 connected to one of 16 gameports
346 Format: <type1>,<type2>,..<type16>
349 Power management functions (SPARCstation-4/5 + deriv.)
351 Disable APC CPU standby support. SPARCstation-Fox does
352 not play well with APC CPU idle - disable it if you have
353 APC and your system crashes randomly.
355 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
356 Change the output verbosity whilst booting
357 Format: { quiet (default) | verbose | debug }
358 Change the amount of debugging information output
359 when initialising the APIC and IO-APIC components.
362 See Documentation/networking/ipv6.txt.
364 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
365 Limit apic dumping. The parameter defines the maximal
366 number of local apics being dumped. Also it is possible
367 to set it to "all" by meaning -- no limit here.
368 Format: { 1 (default) | 2 | ... | all }.
369 The parameter valid if only apic=debug or
370 apic=verbose is specified.
371 Example: apic=debug show_lapic=all
373 apm= [APM] Advanced Power Management
374 See header of arch/x86/kernel/apm_32.c.
376 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
377 Format: <io>,<irq>,<nodeID>
381 atarimouse= [HW,MOUSE] Atari Mouse
383 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
384 EzKey and similar keyboards
386 atkbd.reset= [HW] Reset keyboard during initialization
388 atkbd.set= [HW] Select keyboard code set
389 Format: <int> (2 = AT (default), 3 = PS/2)
391 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
394 atkbd.softraw= [HW] Choose between synthetic and real raw mode
395 Format: <bool> (0 = real, 1 = synthetic (default))
397 atkbd.softrepeat= [HW]
398 Use software keyboard repeat
402 baycom_epp= [HW,AX25]
405 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
407 See header of drivers/net/hamradio/baycom_par.c.
409 baycom_ser_fdx= [HW,AX25]
410 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
411 Format: <io>,<irq>,<mode>[,<baud>]
412 See header of drivers/net/hamradio/baycom_ser_fdx.c.
414 baycom_ser_hdx= [HW,AX25]
415 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
416 Format: <io>,<irq>,<mode>
417 See header of drivers/net/hamradio/baycom_ser_hdx.c.
419 boot_delay= Milliseconds to delay each printk during boot.
420 Values larger than 10 seconds (10000) are changed to
424 bootmem_debug [KNL] Enable bootmem allocator debug messages.
426 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
427 bttv.radio= Most important insmod options are available as
429 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
432 bulk_remove=off [PPC] This parameter disables the use of the pSeries
433 firmware feature for flushing multiple hpte entries
436 c101= [NET] Moxa C101 synchronous serial card
438 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
439 Sometimes CPU hardware bugs make them report the cache
440 size incorrectly. The kernel will attempt work arounds
441 to fix known problems, but for some CPUs it is not
442 possible to determine what the correct size should be.
443 This option provides an override for these situations.
446 [SECURITY] Disable capabilities. This would normally
447 be used only if an alternative security model is to be
448 configured. Potentially dangerous and should only be
449 used if you are entirely sure of the consequences.
451 ccw_timeout_log [S390]
452 See Documentation/s390/CommonIO for details.
454 cgroup_disable= [KNL] Disable a particular controller
455 Format: {name of the controller(s) to disable}
456 {Currently supported controllers - "memory"}
458 checkreqprot [SELINUX] Set initial checkreqprot flag value.
459 Format: { "0" | "1" }
460 See security/selinux/Kconfig help text.
461 0 -- check protection applied by kernel (includes
462 any implied execute protection).
463 1 -- check protection requested by application.
464 Default value is set via a kernel config option.
465 Value can be changed at runtime via
466 /selinux/checkreqprot.
469 See Documentation/s390/CommonIO for details.
471 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
473 Forces specified clocksource (if available) to be used
474 when calculating gettimeofday(). If specified
475 clocksource is not available, it defaults to PIT.
476 Format: { pit | tsc | cyclone | pmtmr }
478 clocksource= Override the default clocksource
480 Override the default clocksource and use the clocksource
481 with the name specified.
482 Some clocksource names to choose from, depending on
484 [all] jiffies (this is the base, fallback clocksource)
486 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
487 pxa_timer,timer3,32k_counter,timer0_1
489 [X86-32] pit,hpet,tsc;
490 scx200_hrt on Geode; cyclone on IBM x440
498 clearcpuid=BITNUM [X86]
499 Disable CPUID feature X for the kernel. See
500 arch/x86/include/asm/cpufeature.h for the valid bit
501 numbers. Note the Linux specific bits are not necessarily
502 stable over kernel options, but the vendor specific
504 Also note that user programs calling CPUID directly
505 or using the feature without checking anything
506 will still see it. This just prevents it from
507 being used by the kernel or shown in /proc/cpuinfo.
508 Also note the kernel might malfunction if you disable
511 cmo_free_hint= [PPC] Format: { yes | no }
512 Specify whether pages are marked as being inactive
513 when they are freed. This is used in CMO environments
514 to determine OS memory pressure for page stealing by
518 code_bytes [X86] How many bytes of object code to print
523 hpet64 [X86-64,HPET] enable 64-bit mode of the HPET timer (bnc#456700)
525 com20020= [HW,NET] ARCnet - COM20020 chipset
527 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
529 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
533 ARCnet - COM90xx chipset (memory-mapped buffers)
534 Format: <io>[,<irq>[,<memstart>]]
536 condev= [HW,S390] console device
539 console= [KNL] Output console device and options.
541 tty<n> Use the virtual console device <n>.
545 Use the specified serial port. The options are of
546 the form "bbbbpnf", where "bbbb" is the baud rate,
547 "p" is parity ("n", "o", or "e"), "n" is number of
548 bits, and "f" is flow control ("r" for RTS or
549 omit it). Default is "9600n8".
551 See Documentation/serial-console.txt for more
553 Documentation/networking/netconsole.txt for an
556 uart[8250],io,<addr>[,options]
557 uart[8250],mmio,<addr>[,options]
558 Start an early, polled-mode console on the 8250/16550
559 UART at the specified I/O port or MMIO address,
560 switching to the matching ttyS device later. The
561 options are the same as for ttyS, above.
563 If the device connected to the port is not a TTY but a braille
564 device, prepend "brl," before the device type, for instance
566 For now, only VisioBraille is supported.
568 consoleblank= [KNL] The console blank (screen saver) timeout in
569 seconds. Defaults to 10*60 = 10mins. A value of 0
570 disables the blank timer.
573 [KNL] Change the default value for
574 /proc/<pid>/coredump_filter.
575 See also Documentation/filesystems/proc.txt.
577 cpuidle.off=1 [CPU_IDLE]
578 disable the cpuidle sub-system
580 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
582 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
584 crashkernel=size[KMG][@offset[KMG]]
585 [KNL] Using kexec, Linux can switch to a 'crash kernel'
586 upon panic. This parameter reserves the physical
587 memory region [offset, offset + size] for that kernel
588 image. If '@offset' is omitted, then a suitable offset
589 is selected automatically. Check
590 Documentation/kdump/kdump.txt for further details.
592 crashkernel=range1:size1[,range2:size2,...][@offset]
593 [KNL] Same as above, but depends on the memory
594 in the running system. The syntax of range is
595 start-[end] where start and end are both
596 a memory unit (amount[KMG]). See also
597 Documentation/kdump/kdump.txt for an example.
602 cs89x0_media= [HW,NET]
603 Format: { rj45 | aui | bnc }
606 See header of drivers/s390/block/dasd_devmap.c.
608 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
609 (one device per port)
610 Format: <port#>,<type>
611 See also Documentation/input/joystick-parport.txt
613 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
614 time. See Documentation/dynamic-debug-howto.txt for
617 debug [KNL] Enable kernel debugging (events log level).
620 [KNL] verbose self-tests
622 Print debugging info while doing the locking API
624 We default to 0 (no extra messages), setting it to
625 1 will print _a lot_ more information - normally
626 only useful to kernel developers.
628 debug_objects [KNL] Enable object debugging
631 [KNL] Disable object debugging
633 debug_guardpage_minorder=
634 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
635 parameter allows control of the order of pages that will
636 be intentionally kept free (and hence protected) by the
637 buddy allocator. Bigger value increase the probability
638 of catching random memory corruption, but reduce the
639 amount of memory for normal system use. The maximum
640 possible value is MAX_ORDER/2. Setting this parameter
641 to 1 or 2 should be enough to identify most random
642 memory corruption problems caused by bugs in kernel or
643 driver code when a CPU writes to (or reads from) a
644 random memory location. Note that there exists a class
645 of memory corruptions problems caused by buggy H/W or
646 F/W or by drivers badly programing DMA (basically when
647 memory is written at bus level and the CPU MMU is
648 bypassed) which are not detectable by
649 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
650 tracking down these problems.
652 debugpat [X86] Enable PAT debugging
654 decnet.addr= [HW,NET]
655 Format: <area>[,<node>]
656 See also Documentation/networking/decnet.txt.
659 [same as hugepagesz=] The size of the default
660 HugeTLB page size. This is the size represented by
661 the legacy /proc/ hugepages APIs, used for SHM, and
662 default size when mounting hugetlbfs filesystems.
663 Defaults to the default architecture's huge page size
667 Set number of hash buckets for dentry cache.
670 IO parameters + enable/disable command.
672 digiepca= [HW,SERIAL]
673 See drivers/char/README.epca and
674 Documentation/serial/digiepca.txt.
677 See Documentation/networking/ipv6.txt.
679 disable_ddw [PPC/PSERIES]
680 Disable Dynamic DMA Window support. Use this if
681 to workaround buggy firmware.
684 See Documentation/networking/ipv6.txt.
686 disable_mtrr_cleanup [X86]
687 The kernel tries to adjust MTRR layout from continuous
688 to discrete, to make X server driver able to add WB
689 entry later. This parameter disables that.
691 disable_mtrr_trim [X86, Intel and AMD only]
692 By default the kernel will trim any uncacheable
693 memory out of your available memory pool based on
694 MTRR settings. This parameter disables that behavior,
695 possibly causing your machine to run very slowly.
697 disable_timer_pin_1 [X86]
698 Disable PIN 1 of APIC timer
699 Can be useful to work around chipset bugs.
701 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
702 this option disables the debugging code at boot.
704 dma_debug_entries=<number>
705 This option allows to tune the number of preallocated
706 entries for DMA-API debugging code. One entry is
707 required per DMA-API allocation. Use this if the
708 DMA-API debugging code disables itself because the
709 architectural default is too low.
711 dma_debug_driver=<driver_name>
712 With this option the DMA-API debugging driver
713 filter feature can be enabled at boot time. Just
714 pass the driver to filter for as the parameter.
715 The filter can be disabled or changed to another
716 driver later using sysfs.
720 earlycon= [KNL] Output early console device and options.
721 uart[8250],io,<addr>[,options]
722 uart[8250],mmio,<addr>[,options]
723 uart[8250],mmio32,<addr>[,options]
724 Start an early, polled-mode console on the 8250/16550
725 UART at the specified I/O port or MMIO address.
726 MMIO inter-register address stride is either 8-bit
727 (mmio) or 32-bit (mmio32).
728 The options are the same as for ttyS, above.
730 earlyprintk= [X86,SH,BLACKFIN]
732 earlyprintk=serial[,ttySn[,baudrate]]
733 earlyprintk=ttySn[,baudrate]
734 earlyprintk=dbgp[debugController#]
736 Append ",keep" to not disable it when the real console
739 Only vga or serial or usb debug port at a time.
741 Currently only ttyS0 and ttyS1 are supported.
743 Interaction with the standard serial driver is not
746 The VGA output is eventually overwritten by the real
749 ekgdboc= [X86,KGDB] Allow early kernel console debugging
752 This is designed to be used in conjunction with
753 the boot argument: earlyprintk=vga
756 Format: {"off" | "on" | "skip[mbr]"}
758 eisa_irq_edge= [PARISC,HW]
759 See header of drivers/parisc/eisa.c.
762 See comment before function elanfreq_setup() in
763 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
766 Format: {"cfq" | "deadline" | "noop"}
767 See Documentation/block/cfq-iosched.txt and
768 Documentation/block/deadline-iosched.txt for details.
770 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
771 Specifies physical address of start of kernel core
772 image elf header and optionally the size. Generally
773 kexec loader will pass this option to capture kernel.
774 See Documentation/kdump/kdump.txt for details.
776 enable_mtrr_cleanup [X86]
777 The kernel tries to adjust MTRR layout from continuous
778 to discrete, to make X server driver able to add WB
779 entry later. This parameter enables that.
781 enable_timer_pin_1 [X86]
782 Enable PIN 1 of APIC timer
783 Can be useful to work around chipset bugs
784 (in particular on some ATI chipsets).
785 The kernel tries to set a reasonable default.
787 enforcing [SELINUX] Set initial enforcing status.
789 See security/selinux/Kconfig help text.
790 0 -- permissive (log only, no denials).
791 1 -- enforcing (deny and log).
793 Value can be changed at runtime via /selinux/enforce.
796 Disable Error Record Serialization Table (ERST)
799 ether= [HW,NET] Ethernet cards parameters
800 This option is obsoleted by the "netdev=" option, which
801 has equivalent usage. See its documentation for details.
805 Permit 'security.evm' to be updated regardless of
806 current integrity status.
810 fail_make_request=[KNL]
811 General fault injection mechanism.
812 Format: <interval>,<probability>,<space>,<times>
813 See also Documentation/fault-injection/.
816 See Documentation/blockdev/floppy.txt.
818 force_pal_cache_flush
819 [IA-64] Avoid check_sal_cache_flush which may hang on
820 buggy SAL_CACHE_FLUSH implementations. Using this
821 parameter will force ia64_sal_cache_flush to call
822 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
825 [FTRACE] will set and start the specified tracer
826 as early as possible in order to facilitate early
829 ftrace_dump_on_oops[=orig_cpu]
830 [FTRACE] will dump the trace buffers on oops.
831 If no parameter is passed, ftrace will dump
832 buffers of all CPUs, but if you pass orig_cpu, it will
833 dump only the buffer of the CPU that triggered the
836 ftrace_filter=[function-list]
837 [FTRACE] Limit the functions traced by the function
838 tracer at boot up. function-list is a comma separated
839 list of functions. This list can be changed at run
840 time by the set_ftrace_filter file in the debugfs
843 ftrace_notrace=[function-list]
844 [FTRACE] Do not trace the functions specified in
845 function-list. This list can be changed at run time
846 by the set_ftrace_notrace file in the debugfs
849 ftrace_graph_filter=[function-list]
850 [FTRACE] Limit the top level callers functions traced
851 by the function graph tracer at boot up.
852 function-list is a comma separated list of functions
853 that can be changed at run time by the
854 set_graph_function file in the debugfs tracing directory.
857 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
858 support via parallel port (up to 5 devices per port)
859 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
860 See also Documentation/input/joystick-parport.txt
864 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
868 gcov_persist= [GCOV] When non-zero (default), profiling data for
869 kernel modules is saved and remains accessible via
870 debugfs, even when the module is unloaded/reloaded.
871 When zero, profiling data is discarded and associated
872 debugfs files are removed at module unload time.
874 gpt [EFI] Forces disk with valid GPT signature but
875 invalid Protective MBR to be treated as GPT.
877 guestdev= [PCI,ACPI,XEN]
878 Format: {<device path>|<sbdf>}][,{<device path>|<sbdf>}[,...]]
879 Format of device path: <hid>[:<uid>]-<dev>.<func>[-<dev>.<func>[,...]][+iomul]
880 Format of sbdf: [<segment>:]<bus>:<dev>.<func>[+iomul]
881 Specifies PCI device for guest domain.
882 If PCI-PCI bridge is specified, all PCI devices
883 behind PCI-PCI bridge are reserved.
884 +iomul means that this PCI function will share
885 IO ports with other +iomul functions under same
886 switch. NOTE: if +iomul is specfied, all the functions
887 of the device will share IO ports.
889 guestiomuldev= [PCI,ACPI,XEN]
890 Format: [sbd][,<sbd>][,...]
891 Format of sbdf: [<segment>:]<bus>:<dev>
892 Note: function shouldn't be specified.
893 Specifies PCI device for IO port multiplexing driver.
895 hashdist= [KNL,NUMA] Large hashes allocated during boot
896 are distributed across NUMA nodes. Defaults on
897 for 64-bit NUMA, off otherwise.
898 Format: 0 | 1 (for off | on)
900 hcl= [IA-64] SGI's Hardware Graph compatibility layer
902 hd= [EIDE] (E)IDE hard drive subsystem geometry
903 Format: <cyl>,<head>,<sect>
906 Disable Hardware Error Source Table (HEST) support;
907 corresponding firmware-first mode error processing
908 logic will be disabled.
910 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
911 size of <nn>. This works even on boxes that have no
912 highmem otherwise. This also works to reduce highmem
913 size on bigger boxes.
915 highres= [KNL] Enable/disable high resolution timer mode.
916 Valid parameters: "on", "off"
920 See Documentation/isdn/README.HiSax.
924 hpet= [X86-32,HPET] option to control HPET usage
925 Format: { enable (default) | disable | force |
927 disable: disable HPET and use PIT instead
928 force: allow force enabled of undocumented chips (ICH4,
930 verbose: show contents of HPET registers during setup
932 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
933 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
934 On x86-64 and powerpc, this option can be specified
935 multiple times interleaved with hugepages= to reserve
936 huge pages of different sizes. Valid pages sizes on
937 x86-64 are 2M (when the CPU supports "pse") and 1G
938 (when the CPU supports the "pdpe1gb" cpuinfo flag)
939 Note that 1GB pages can only be allocated at boot time
940 using hugepages= and not freed afterwards.
942 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
943 terminal devices. Valid values: 0..8
944 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
945 If specified, z/VM IUCV HVC accepts connections
946 from listed z/VM user IDs only.
949 Do not unregister boot console at start. This is only
950 useful for debugging when something happens in the window
951 between unregistering the boot console and initializing
954 i2c_bus= [HW] Override the default board specific I2C bus speed
955 or register an additional I2C bus that is not
956 registered from board initialization code.
960 i8042.debug [HW] Toggle i8042 debug mode
961 i8042.direct [HW] Put keyboard port into non-translated mode
962 i8042.dumbkbd [HW] Pretend that controller can only read data from
963 keyboard and cannot control its state
964 (Don't attempt to blink the leds)
965 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
966 i8042.nokbd [HW] Don't check/create keyboard port
967 i8042.noloop [HW] Disable the AUX Loopback command while probing
969 i8042.nomux [HW] Don't check presence of an active multiplexing
971 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
973 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
974 i8042.reset [HW] Reset the controller during init and cleanup
975 i8042.unlock [HW] Unlock (ignore) the keylock
979 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
980 indicates that the driver is running on unsupported
982 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
983 does not match list of supported models.
985 [HW] Report power status in /proc/i8k
986 (disabled by default)
987 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
991 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
993 ide-core.nodma= [HW] (E)IDE subsystem
994 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
995 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
996 .cdrom .chs .ignore_cable are additional options
997 See Documentation/ide/ide.txt.
999 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1000 Claim all unknown PCI IDE storage controllers.
1003 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1004 Poll forces a polling idle loop that can slightly
1005 improve the performance of waking up a idle CPU, but
1006 will use a lot of power and make the system run hot.
1008 idle=mwait: On systems which support MONITOR/MWAIT but
1009 the kernel chose to not use it because it doesn't save
1010 as much power as a normal idle loop, use the
1011 MONITOR/MWAIT idle loop anyways. Performance should be
1012 the same as idle=poll.
1013 idle=halt: Halt is forced to be used for CPU idle.
1014 In such case C2/C3 won't be used again.
1015 idle=nomwait: Disable mwait for CPU C-states
1017 ignore_loglevel [KNL]
1018 Ignore loglevel setting - this will print /all/
1019 kernel messages to the console. Useful for debugging.
1020 We also add it as printk module parameter, so users
1021 could change it dynamically, usually by
1022 /sys/module/printk/parameters/ignore_loglevel.
1024 ihash_entries= [KNL]
1025 Set number of hash buckets for inode cache.
1028 Format: { "0" | "1" }
1029 0 -- integrity auditing messages. (Default)
1030 1 -- enable informational integrity auditing messages.
1033 Format: { "sha1" | "md5" }
1037 Load a policy which meets the needs of the Trusted
1038 Computing Base. This means IMA will measure all
1039 programs exec'd, files mmap'd for exec, and all files
1040 opened for read by uid=0.
1044 Run specified binary instead of /sbin/init as init
1047 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1048 for working out where the kernel is dying during
1051 initrd= [BOOT] Specify the location of the initial ramdisk
1053 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1056 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1058 Enable intel iommu driver.
1060 Disable intel iommu driver.
1061 igfx_off [Default Off]
1062 By default, gfx is mapped as normal device. If a gfx
1063 device has a dedicated DMAR unit, the DMAR unit is
1064 bypassed by not enabling DMAR with this option. In
1065 this case, gfx device will use physical address for
1068 With this option iommu will not optimize to look
1069 for io virtual address below 32-bit forcing dual
1070 address cycle on pci bus for cards supporting greater
1071 than 32-bit addressing. The default is to look
1072 for translation below 32-bit and if not available
1073 then look in the higher range.
1074 strict [Default Off]
1075 With this option on every unmap_single operation will
1076 result in a hardware IOTLB flush operation as opposed
1077 to batching them for performance.
1078 sp_off [Default Off]
1079 By default, super page will be supported if Intel IOMMU
1080 has the capability. With this option, super page will
1083 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1084 0 disables intel_idle and fall back on acpi_idle.
1085 1 to 6 specify maximum depth of C-state.
1087 intremap= [X86-64, Intel-IOMMU]
1088 on enable Interrupt Remapping (default)
1089 off disable Interrupt Remapping
1090 nosid disable Source ID checking
1092 BIOS x2APIC opt-out request will be ignored
1096 iomem= Disable strict checking of access to MMIO memory
1097 strict regions from userspace.
1112 group_mf [x86, IA-64]
1115 io7= [HW] IO7 for Marvel based alpha systems
1116 See comment before marvel_specify_io7 in
1117 arch/alpha/kernel/core_marvel.c.
1119 io_delay= [X86] I/O delay method
1121 Standard port 0x80 based delay
1123 Alternate port 0xed based delay (needed on some systems)
1125 Simple two microseconds delay
1130 See Documentation/filesystems/nfs/nfsroot.txt.
1132 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1133 See comment before ip2_setup() in
1134 drivers/char/ip2/ip2base.c.
1137 When an interrupt is not handled search all handlers
1138 for it. Intended to get systems with badly broken
1142 When an interrupt is not handled search all handlers
1143 for it. Also check all handlers each timer
1144 interrupt. Intended to get systems with badly broken
1148 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1150 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1152 <cpu number>,...,<cpu number>
1154 <cpu number>-<cpu number>
1155 (must be a positive range in ascending order)
1157 <cpu number>,...,<cpu number>-<cpu number>
1159 This option can be used to specify one or more CPUs
1160 to isolate from the general SMP balancing and scheduling
1161 algorithms. You can move a process onto or off an
1162 "isolated" CPU via the CPU affinity syscalls or cpuset.
1163 <cpu number> begins at 0 and the maximum value is
1164 "number of CPUs in system - 1".
1166 This option is the preferred way to isolate CPUs. The
1167 alternative -- manually setting the CPU mask of all
1168 tasks in the system -- can cause problems and
1169 suboptimal load balancer performance.
1173 js= [HW,JOY] Analog joystick
1174 See Documentation/input/joystick.txt.
1178 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1179 specifies the amount of memory usable by the kernel
1180 for non-movable allocations. The requested amount is
1181 spread evenly throughout all nodes in the system. The
1182 remaining memory in each node is used for Movable
1183 pages. In the event, a node is too small to have both
1184 kernelcore and Movable pages, kernelcore pages will
1185 take priority and other nodes will have a larger number
1186 of kernelcore pages. The Movable zone is used for the
1187 allocation of pages that may be reclaimed or moved
1188 by the page migration subsystem. This means that
1189 HugeTLB pages may not be allocated from this zone.
1190 Note that allocations like PTEs-from-HighMem still
1191 use the HighMem zone if it exists, and the Normal
1192 zone if it does not.
1194 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1195 Format: <Controller#>[,poll interval]
1196 The controller # is the number of the ehci usb debug
1197 port as it is probed via PCI. The poll interval is
1198 optional and is the number seconds in between
1199 each poll cycle to the debug port in case you need
1200 the functionality for interrupting the kernel with
1201 gdb or control-c on the dbgp connection. When
1202 not using this parameter you use sysrq-g to break into
1203 the kernel debugger.
1205 kgdboc= [KGDB,HW] kgdb over consoles.
1206 Requires a tty driver that supports console polling,
1207 or a supported polling keyboard driver (non-usb).
1208 Serial only format: <serial_device>[,baud]
1209 keyboard only format: kbd
1210 keyboard and serial format: kbd,<serial_device>[,baud]
1211 Optional Kernel mode setting:
1212 kms, kbd format: kms,kbd
1213 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1215 kgdbwait [KGDB] Stop kernel execution and enter the
1216 kernel debugger at the earliest opportunity.
1218 kmac= [MIPS] korina ethernet MAC address.
1219 Configure the RouterBoard 532 series on-chip
1220 Ethernet adapter MAC address.
1222 kmemleak= [KNL] Boot-time kmemleak enable/disable
1223 Valid arguments: on, off
1226 kstack=N [X86] Print N words from the kernel stack
1229 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1230 Default is 0 (don't ignore, but inject #GP)
1232 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1236 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1237 Default is 1 (enabled)
1239 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1241 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1243 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1244 (virtualized MMU) support on capable Intel chips.
1245 Default is 1 (enabled)
1247 kvm-intel.emulate_invalid_guest_state=
1248 [KVM,Intel] Enable emulation of invalid guest states
1249 Default is 0 (disabled)
1251 kvm-intel.flexpriority=
1252 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1253 Default is 1 (enabled)
1256 [KVM,Intel] Enable VMX nesting (nVMX).
1257 Default is 0 (disabled)
1259 kvm-intel.unrestricted_guest=
1260 [KVM,Intel] Disable unrestricted guest feature
1261 (virtualized real and unpaged mode) on capable
1262 Intel chips. Default is 1 (enabled)
1264 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1265 feature (tagged TLBs) on capable Intel chips.
1266 Default is 1 (enabled)
1272 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1275 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1278 libata.dma= [LIBATA] DMA control
1279 libata.dma=0 Disable all PATA and SATA DMA
1280 libata.dma=1 PATA and SATA Disk DMA only
1281 libata.dma=2 ATAPI (CDROM) DMA only
1282 libata.dma=4 Compact Flash DMA only
1283 Combinations also work, so libata.dma=3 enables DMA
1284 for disks and CDROMs, but not CFs.
1286 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1287 libata.ignore_hpa=0 keep BIOS limits (default)
1288 libata.ignore_hpa=1 ignore limits, using full disk
1290 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1294 libata.force= [LIBATA] Force configurations. The format is comma
1295 separated list of "[ID:]VAL" where ID is
1296 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1297 matching port, link or device. Basically, it matches
1298 the ATA ID string printed on console by libata. If
1299 the whole ID part is omitted, the last PORT and DEVICE
1300 values are used. If ID hasn't been specified yet, the
1301 configuration applies to all ports, links and devices.
1303 If only DEVICE is omitted, the parameter applies to
1304 the port and all links and devices behind it. DEVICE
1305 number of 0 either selects the first device or the
1306 first fan-out link behind PMP device. It does not
1307 select the host link. DEVICE number of 15 selects the
1308 host link and device attached to it.
1310 The VAL specifies the configuration to force. As long
1311 as there's no ambiguity shortcut notation is allowed.
1312 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1313 The following configurations can be forced.
1315 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1316 Any ID with matching PORT is used.
1318 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1320 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1321 udma[/][16,25,33,44,66,100,133] notation is also
1324 * [no]ncq: Turn on or off NCQ.
1326 * nohrst, nosrst, norst: suppress hard, soft
1329 * dump_id: dump IDENTIFY data.
1331 If there are multiple matching configurations changing
1332 the same attribute, the last one is used.
1334 memblock=debug [KNL] Enable memblock debug messages.
1336 load_ramdisk= [RAM] List of ramdisks to load from floppy
1337 See Documentation/blockdev/ramdisk.txt.
1339 lockd.nlm_grace_period=P [NFS] Assign grace period.
1342 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1345 lockd.nlm_timeout=T [NFS] Assign timeout value.
1348 lockd.nlm_udpport=M [NFS] Assign UDP port.
1351 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1354 loglevel= All Kernel Messages with a loglevel smaller than the
1355 console loglevel will be printed to the console. It can
1356 also be changed with klogd or other programs. The
1357 loglevels are defined as follows:
1359 0 (KERN_EMERG) system is unusable
1360 1 (KERN_ALERT) action must be taken immediately
1361 2 (KERN_CRIT) critical conditions
1362 3 (KERN_ERR) error conditions
1363 4 (KERN_WARNING) warning conditions
1364 5 (KERN_NOTICE) normal but significant condition
1365 6 (KERN_INFO) informational
1366 7 (KERN_DEBUG) debug-level messages
1368 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1369 in bytes. n must be a power of two. The default
1370 size is set in the kernel config file.
1372 logo.nologo [FB] Disables display of the built-in Linux logo.
1373 This may be used to provide more screen space for
1374 kernel log messages and is useful when debugging
1375 kernel boot problems.
1377 lp=0 [LP] Specify parallel ports to use, e.g,
1378 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1379 lp=reset first parallel port). 'lp=0' disables the
1380 lp=auto printer driver. 'lp=reset' (which can be
1381 specified in addition to the ports) causes
1382 attached printers to be reset. Using
1383 lp=port1,port2,... specifies the parallel ports
1384 to associate lp devices with, starting with
1385 lp0. A port specification may be 'none' to skip
1386 that lp device, or a parport name such as
1387 'parport0'. Specifying 'lp=auto' instead of a
1388 port specification list means that device IDs
1389 from each port should be examined, to see if
1390 an IEEE 1284-compliant printer is attached; if
1391 so, the driver will manage that printer.
1392 See also header of drivers/char/lp.c.
1395 Sets loops_per_jiffy to given constant, thus avoiding
1396 time-consuming boot-time autodetection (up to 250 ms per
1397 CPU). 0 enables autodetection (default). To determine
1398 the correct value for your kernel, boot with normal
1399 autodetection and see what value is printed. Note that
1400 on SMP systems the preset will be applied to all CPUs,
1401 which is likely to cause problems if your CPUs need
1402 significantly divergent settings. An incorrect value
1403 will cause delays in the kernel to be wrong, leading to
1404 unpredictable I/O errors and other breakage. Although
1405 unlikely, in the extreme case this might damage your
1409 Format: <io>,<irq>,<dma>
1411 machvec= [IA-64] Force the use of a particular machine-vector
1412 (machvec) in a generic kernel.
1413 Example: machvec=hpzx1_swiotlb
1415 machtype= [Loongson] Share the same kernel image file between different
1417 Example: machtype=lemote-yeeloong-2f-7inch
1419 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1420 than or equal to this physical address is ignored.
1422 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1423 should make use of. maxcpus=n : n >= 0 limits the
1424 kernel to using 'n' processors. n=0 is a special case,
1425 it is equivalent to "nosmp", which also disables
1428 max_loop= [LOOP] The number of loop block devices that get
1429 (loop.max_loop) unconditionally pre-created at init time. The default
1430 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1431 of statically allocating a predefined number, loop
1432 devices can be requested on-demand with the
1433 /dev/loop-control interface.
1437 mce [X86-32] Machine Check Exception
1439 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1441 md= [HW] RAID subsystems devices and level
1442 See Documentation/md.txt.
1445 Format: <first>,<last>
1446 Specifies range of consoles to be captured by the MDA.
1448 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1449 Amount of memory to be used when the kernel is not able
1450 to see the whole system memory or for test.
1451 [X86-32] Use together with memmap= to avoid physical
1452 address space collisions. Without memmap= PCI devices
1453 could be placed at addresses belonging to unused RAM.
1455 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1459 [KNL,SH] Allow user to override the default size for
1460 per-device physically contiguous DMA buffers.
1462 memmap=exactmap [KNL,X86] Enable setting of an exact
1463 E820 memory map, as specified by the user.
1464 Such memmap=exactmap lines can be constructed based on
1465 BIOS output or other requirements. See the memmap=nn@ss
1468 memmap=nn[KMG]@ss[KMG]
1469 [KNL] Force usage of a specific region of memory
1470 Region of memory to be used, from ss to ss+nn.
1472 memmap=nn[KMG]#ss[KMG]
1473 [KNL,ACPI] Mark specific memory as ACPI data.
1474 Region of memory to be used, from ss to ss+nn.
1476 memmap=nn[KMG]$ss[KMG]
1477 [KNL,ACPI] Mark specific memory as reserved.
1478 Region of memory to be used, from ss to ss+nn.
1479 Example: Exclude memory from 0x18690000-0x1869ffff
1480 memmap=64K$0x18690000
1482 memmap=0x10000$0x18690000
1484 memory_corruption_check=0/1 [X86]
1485 Some BIOSes seem to corrupt the first 64k of
1486 memory when doing things like suspend/resume.
1487 Setting this option will scan the memory
1488 looking for corruption. Enabling this will
1489 both detect corruption and prevent the kernel
1490 from using the memory being corrupted.
1491 However, its intended as a diagnostic tool; if
1492 repeatable BIOS-originated corruption always
1493 affects the same memory, you can use memmap=
1494 to prevent the kernel from using that memory.
1496 memory_corruption_check_size=size [X86]
1497 By default it checks for corruption in the low
1498 64k, making this memory unavailable for normal
1499 use. Use this parameter to scan for
1500 corruption in more or less memory.
1502 memory_corruption_check_period=seconds [X86]
1503 By default it checks for corruption every 60
1504 seconds. Use this parameter to check at some
1505 other rate. 0 disables periodic checking.
1507 memtest= [KNL,X86] Enable memtest
1509 default : 0 <disable>
1510 Specifies the number of memtest passes to be
1511 performed. Each pass selects another test
1512 pattern from a given set of patterns. Memtest
1513 fills the memory with this pattern, validates
1514 memory contents and reserves bad memory
1515 regions that are detected.
1517 meye.*= [HW] Set MotionEye Camera parameters
1518 See Documentation/video4linux/meye.txt.
1520 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1521 Multi-Function General Purpose Timers on AMD Geode
1524 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1525 the BIOS has incorrectly applied a workaround. TinyBIOS
1526 version 0.98 is known to be affected, 0.99 fixes the
1527 problem by letting the user disable the workaround.
1531 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1532 physical address is ignored.
1534 mini2440= [ARM,HW,KNL]
1535 Format:[0..2][b][c][t]
1537 MINI2440 configuration specification:
1538 0 - The attached screen is the 3.5" TFT
1539 1 - The attached screen is the 7" TFT
1540 2 - The VGA Shield is attached (1024x768)
1541 Leaving out the screen size parameter will not load
1542 the TFT driver, and the framebuffer will be left
1544 b - Enable backlight. The TFT backlight pin will be
1545 linked to the kernel VESA blanking code and a GPIO
1546 LED. This parameter is not necessary when using the
1548 c - Enable the s3c camera interface.
1549 t - Reserved for enabling touchscreen support. The
1550 touchscreen support is not enabled in the mainstream
1551 kernel as of 2.6.30, a preliminary port can be found
1552 in the "bleeding edge" mini2440 support kernel at
1553 http://repo.or.cz/w/linux-2.6/mini2440.git
1556 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1557 parameter allows control of the logging verbosity for
1558 the additional memory initialisation checks. A value
1559 of 0 disables mminit logging and a level of 4 will
1560 log everything. Information is printed at KERN_DEBUG
1561 so loglevel=8 may also need to be specified.
1564 [MOUSE] Maximum time between finger touching and
1565 leaving touchpad surface for touch to be considered
1566 a tap and be reported as a left button click (for
1567 touchpads working in absolute mode only).
1569 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1570 reporting absolute coordinates, such as tablets
1571 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1572 reporting absolute coordinates, such as tablets
1574 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1575 is similar to kernelcore except it specifies the
1576 amount of memory used for migratable allocations.
1577 If both kernelcore and movablecore is specified,
1578 then kernelcore will be at *least* the specified
1579 value but may be more. If movablecore on its own
1580 is specified, the administrator must be careful
1581 that the amount of memory usable for all allocations
1584 MTD_Partition= [MTD]
1585 Format: <name>,<region-number>,<size>,<offset>
1587 MTD_Region= [MTD] Format:
1588 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1591 See drivers/mtd/cmdlinepart.c.
1593 multitce=off [PPC] This parameter disables the use of the pSeries
1594 firmware feature for updating multiple TCE entries
1597 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1599 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1601 boundary - index of last SLC block on Flex-OneNAND.
1602 The remaining blocks are configured as MLC blocks.
1603 lock - Configure if Flex-OneNAND boundary should be locked.
1604 Once locked, the boundary cannot be changed.
1605 1 indicates lock status, 0 indicates unlock status.
1608 ARM/S3C2412 JIVE boot control
1610 See arch/arm/mach-s3c2412/mach-jive.c
1612 mtouchusb.raw_coordinates=
1613 [HW] Make the MicroTouch USB driver use raw coordinates
1614 ('y', default) or cooked coordinates ('n')
1616 mtrr_chunk_size=nn[KMG] [X86]
1617 used for mtrr cleanup. It is largest continuous chunk
1618 that could hold holes aka. UC entries.
1620 mtrr_gran_size=nn[KMG] [X86]
1621 Used for mtrr cleanup. It is granularity of mtrr block.
1623 Large value could prevent small alignment from
1626 mtrr_spare_reg_nr=n [X86]
1628 Range: 0,7 : spare reg number
1630 Used for mtrr cleanup. It is spare mtrr entries number.
1631 Set to 2 or more if your graphical card needs more.
1633 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1635 netdev= [NET] Network devices parameters
1636 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1637 Note that mem_start is often overloaded to mean
1638 something different and driver-specific.
1639 This usage is only documented in each driver source
1643 [NETFILTER] Enable connection tracking flow accounting
1644 0 to disable accounting
1645 1 to enable accounting
1648 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1649 See Documentation/filesystems/nfs/nfsroot.txt.
1651 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1652 See Documentation/filesystems/nfs/nfsroot.txt.
1654 nfsrootdebug [NFS] enable nfsroot debugging messages.
1655 See Documentation/filesystems/nfs/nfsroot.txt.
1657 nfs.callback_tcpport=
1658 [NFS] set the TCP port on which the NFSv4 callback
1659 channel should listen.
1662 [NFS] sets the pathname to the program which is used
1663 to update the NFS client cache entries.
1665 nfs.cache_getent_timeout=
1666 [NFS] sets the timeout after which an attempt to
1667 update a cache entry is deemed to have failed.
1669 nfs.idmap_cache_timeout=
1670 [NFS] set the maximum lifetime for idmapper cache
1674 [NFS] enable 64-bit inode numbers.
1675 If zero, the NFS client will fake up a 32-bit inode
1676 number for the readdir() and stat() syscalls instead
1677 of returning the full 64-bit number.
1678 The default is to return 64-bit inode numbers.
1680 nfs.nfs4_disable_idmapping=
1681 [NFSv4] When set to the default of '1', this option
1682 ensures that both the RPC level authentication
1683 scheme and the NFS level operations agree to use
1684 numeric uids/gids if the mount is using the
1685 'sec=sys' security flavour. In effect it is
1686 disabling idmapping, which can make migration from
1687 legacy NFSv2/v3 systems to NFSv4 easier.
1688 Servers that do not support this mode of operation
1689 will be autodetected by the client, and it will fall
1690 back to using the idmapper.
1691 To turn off this behaviour, set the value to '0'.
1693 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1694 when a NMI is triggered.
1695 Format: [state][,regs][,debounce][,die]
1697 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1698 Format: [panic,][nopanic,][num]
1700 0 - turn nmi_watchdog off
1701 When panic is specified, panic when an NMI watchdog
1702 timeout occurs (or 'nopanic' to override the opposite
1704 This is useful when you use a panic=... timeout and
1705 need the box quickly up again.
1707 netpoll.carrier_timeout=
1708 [NET] Specifies amount of time (in seconds) that
1709 netpoll should wait for a carrier. By default netpoll
1712 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1713 emulation library even if a 387 maths coprocessor
1717 [HW] Never suspend the console
1718 Disable suspending of consoles during suspend and
1719 hibernate operations. Once disabled, debugging
1720 messages can reach various consoles while the rest
1721 of the system is being put to sleep (ie, while
1722 debugging driver suspend/resume hooks). This may
1723 not work reliably with all consoles, but is known
1724 to work with serial and VGA consoles.
1725 To facilitate more flexible debugging, we also add
1726 console_suspend, a printk module parameter to control
1727 it. Users could use console_suspend (usually
1728 /sys/module/printk/parameters/console_suspend) to
1729 turn on/off it dynamically.
1731 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1732 caches in the slab allocator. Saves per-node memory,
1733 but will impact performance.
1737 noapic [SMP,APIC] Tells the kernel to not make use of any
1738 IOAPICs that may be present in the system.
1740 noautogroup Disable scheduler automatic task group creation.
1742 nobats [PPC] Do not use BATs for mapping kernel lowmem
1743 on "Classic" PPC cores.
1747 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1749 nodelayacct [KNL] Disable per-task delay accounting
1751 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1753 nodsp [SH] Disable hardware DSP at boot time.
1755 noefi [X86] Disable EFI runtime services support.
1760 On X86-32 available only on PAE configured kernels.
1761 noexec=on: enable non-executable mappings (default)
1762 noexec=off: disable non-executable mappings
1765 Disable SMEP (Supervisor Mode Execution Protection)
1766 even if it is supported by processor.
1769 This affects only 32-bit executables.
1770 noexec32=on: enable non-executable mappings (default)
1771 read doesn't imply executable mappings
1772 noexec32=off: disable non-executable mappings
1773 read implies executable mappings
1775 nofpu [SH] Disable hardware FPU at boot time.
1777 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1778 register save and restore. The kernel will only save
1779 legacy floating-point registers on task switch.
1781 noxsave [BUGS=X86] Disables x86 extended register state save
1782 and restore using xsave. The kernel will fallback to
1783 enabling legacy floating-point and sse state.
1785 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1786 wfi(ARM) instruction doesn't work correctly and not to
1787 use it. This is also useful when using JTAG debugger.
1789 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1790 instruction doesn't work correctly and not to
1793 no_file_caps Tells the kernel not to honor file capabilities. The
1794 only way then for a file to be executed with privilege
1795 is to be setuid root or executed by root.
1797 nohalt [IA-64] Tells the kernel not to use the power saving
1798 function PAL_HALT_LIGHT when idle. This increases
1799 power-consumption. On the positive side, it reduces
1800 interrupt wake-up latency, which may improve performance
1801 in certain environments such as networked servers or
1804 nohz= [KNL] Boottime enable/disable dynamic ticks
1805 Valid arguments: on, off
1808 noiotrap [SH] Disables trapped I/O port accesses.
1810 noirqdebug [X86-32] Disables the code which attempts to detect and
1811 disable unhandled interrupt sources.
1813 no_timer_check [X86,APIC] Disables the code which tests for
1814 broken timer IRQ sources.
1816 noisapnp [ISAPNP] Disables ISA PnP code.
1818 noinitrd [RAM] Tells the kernel not to load any configured
1821 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1823 [Deprecated - use intremap=off]
1827 nojitter [IA-64] Disables jitter checking for ITC timers.
1829 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1831 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1834 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1835 steal time is computed, but won't influence scheduler
1838 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1840 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1842 noltlbs [PPC] Do not use large page/tlb entries for kernel
1843 lowmem mapping on PPC40x.
1845 nomca [IA-64] Disable machine check abort handling
1847 nomce [X86-32] Machine Check Exception
1849 nomfgpt [X86-32] Disable Multi-Function General Purpose
1850 Timer usage (for AMD Geode machines).
1852 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1853 shutdown the other cpus. Instead use the REBOOT_VECTOR
1856 nopat [X86] Disable PAT (page attribute table extension of
1857 pagetables) support.
1859 norandmaps Don't use address space randomization. Equivalent to
1860 echo 0 > /proc/sys/kernel/randomize_va_space
1862 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1864 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1865 with UP alternatives
1867 noresidual [PPC] Don't use residual data on PReP machines.
1869 nordrand [X86] Disable the direct use of the RDRAND
1870 instruction even if it is supported by the
1871 processor. RDRAND is still available to user
1874 noresume [SWSUSP] Disables resume and restores original swap
1877 no-scroll [VGA] Disables scrollback.
1878 This is required for the Braillex ib80-piezo Braille
1879 reader made by F.H. Papenmeier (Germany).
1883 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1885 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1886 and disable the IO APIC. legacy for "maxcpus=0".
1888 nosoftlockup [KNL] Disable the soft-lockup detector.
1890 nosync [HW,M68K] Disables sync negotiation for all devices.
1892 notsc [BUGS=X86-32] Disable Time Stamp Counter
1894 nousb [USB] Disable the USB subsystem
1896 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1900 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1902 nptcg= [IA-64] Override max number of concurrent global TLB
1903 purges which is reported from either PAL_VM_SUMMARY or
1906 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1907 could support. nr_cpus=n : n >= 1 limits the kernel to
1908 supporting 'n' processors. Later in runtime you can not
1909 use hotplug cpu feature to put more cpu back to online.
1910 just like you compile the kernel NR_CPUS=n
1912 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1914 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1915 one of ['zone', 'node', 'default'] can be specified
1916 This can be set from sysctl after boot.
1917 See Documentation/sysctl/vm.txt for details.
1919 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1920 See Documentation/debugging-via-ohci1394.txt for more
1923 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1924 Rather than timing out after 20 ms if an EC
1925 command is not properly ACKed, override the length
1926 of the timeout. We have interrupts disabled while
1927 waiting for the ACK, so if this is set too high
1928 interrupts *may* be lost!
1930 omap_mux= [OMAP] Override bootloader pin multiplexing.
1931 Format: <mux_mode0.mode_name=value>...
1932 For example, to override I2C bus2:
1933 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1935 oprofile.timer= [HW]
1936 Use timer interrupt instead of performance counters
1938 oprofile.cpu_type= Force an oprofile cpu type
1939 This might be useful if you have an older oprofile
1940 userland or if you want common events.
1941 Format: { arch_perfmon }
1942 arch_perfmon: [X86] Force use of architectural
1943 perfmon on Intel CPUs instead of the
1944 CPU specific event set.
1945 timer: [X86] Force use of architectural NMI
1946 timer mode (see also oprofile.timer
1947 for generic hr timer mode)
1948 [s390] Force legacy basic mode sampling
1949 (report cpu_type "timer")
1951 oops=panic Always panic on oopses. Default is to just kill the
1952 process, but there is a small probability of
1953 deadlocking the machine.
1954 This will also cause panics on machine check exceptions.
1955 Useful together with panic=30 to trigger a reboot.
1958 See Documentation/sound/oss/oss-parameters.txt
1960 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1961 timeout > 0: seconds before rebooting
1962 timeout = 0: wait forever
1963 timeout < 0: reboot immediately
1966 parkbd.port= [HW] Parallel port number the keyboard adapter is
1967 connected to, default is 0.
1969 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1970 0 for XT, 1 for AT (default is AT).
1973 parport= [HW,PPT] Specify parallel ports. 0 disables.
1974 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1975 Use 'auto' to force the driver to use any
1976 IRQ/DMA settings detected (the default is to
1977 ignore detected IRQ/DMA settings because of
1978 possible conflicts). You can specify the base
1979 address, IRQ, and DMA settings; IRQ and DMA
1980 should be numbers, or 'auto' (for using detected
1981 settings on that particular port), or 'nofifo'
1982 (to avoid using a FIFO even if it is detected).
1983 Parallel ports are assigned in the order they
1984 are specified on the command line, starting
1987 parport_init_mode= [HW,PPT]
1988 Configure VIA parallel port to operate in
1989 a specific mode. This is necessary on Pegasos
1990 computer where firmware has no options for setting
1991 up parallel port mode and sets it to spp.
1992 Currently this function knows 686a and 8231 chips.
1993 Format: [spp|ps2|epp|ecp|ecpepp]
1996 Halt all CPUs after the first oops has been printed for
1997 the specified number of seconds. This is to be used if
1998 your oopses keep scrolling off the screen.
2003 See header of drivers/block/paride/pcd.c.
2004 See also Documentation/blockdev/paride.txt.
2006 pci=option[,option...] [PCI] various PCI subsystem options:
2007 earlydump [X86] dump PCI config space before the kernel
2009 off [X86] don't probe for the PCI bus
2010 bios [X86-32] force use of PCI BIOS, don't access
2011 the hardware directly. Use this if your machine
2012 has a non-standard PCI host bridge.
2013 nobios [X86-32] disallow use of PCI BIOS, only direct
2014 hardware access methods are allowed. Use this
2015 if you experience crashes upon bootup and you
2016 suspect they are caused by the BIOS.
2017 conf1 [X86] Force use of PCI Configuration
2019 conf2 [X86] Force use of PCI Configuration
2021 noaer [PCIE] If the PCIEAER kernel config parameter is
2022 enabled, this kernel boot option can be used to
2023 disable the use of PCIE advanced error reporting.
2024 nodomains [PCI] Disable support for multiple PCI
2025 root domains (aka PCI segments, in ACPI-speak).
2026 nommconf [X86] Disable use of MMCONFIG for PCI
2028 check_enable_amd_mmconf [X86] check for and enable
2029 properly configured MMIO access to PCI
2030 config space on AMD family 10h CPU
2031 nomsi [MSI] If the PCI_MSI kernel config parameter is
2032 enabled, this kernel boot option can be used to
2033 disable the use of MSI interrupts system-wide.
2034 noioapicquirk [APIC] Disable all boot interrupt quirks.
2035 Safety option to keep boot IRQs enabled. This
2036 should never be necessary.
2037 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2038 primary IO-APIC for bridges that cannot disable
2039 boot IRQs. This fixes a source of spurious IRQs
2040 when the system masks IRQs.
2041 noioapicreroute [APIC] Disable workaround that uses the
2042 boot IRQ equivalent of an IRQ that connects to
2043 a chipset where boot IRQs cannot be disabled.
2044 The opposite of ioapicreroute.
2045 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2046 routing table. These calls are known to be buggy
2047 on several machines and they hang the machine
2048 when used, but on other computers it's the only
2049 way to get the interrupt routing table. Try
2050 this option if the kernel is unable to allocate
2051 IRQs or discover secondary PCI buses on your
2053 rom [X86] Assign address space to expansion ROMs.
2054 Use with caution as certain devices share
2055 address decoders between ROMs and other
2057 norom [X86] Do not assign address space to
2058 expansion ROMs that do not already have
2059 BIOS assigned address ranges.
2060 nobar [X86] Do not assign address space to the
2061 BARs that weren't assigned by the BIOS.
2062 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2063 assigned automatically to PCI devices. You can
2064 make the kernel exclude IRQs of your ISA cards
2066 pirqaddr=0xAAAAA [X86] Specify the physical address
2067 of the PIRQ table (normally generated
2068 by the BIOS) if it is outside the
2069 F0000h-100000h range.
2070 lastbus=N [X86] Scan all buses thru bus #N. Can be
2071 useful if the kernel is unable to find your
2072 secondary buses and you want to tell it
2073 explicitly which ones they are.
2074 assign-busses [X86] Always assign all PCI bus
2075 numbers ourselves, overriding
2076 whatever the firmware may have done.
2077 usepirqmask [X86] Honor the possible IRQ mask stored
2078 in the BIOS $PIR table. This is needed on
2079 some systems with broken BIOSes, notably
2080 some HP Pavilion N5400 and Omnibook XE3
2081 notebooks. This will have no effect if ACPI
2082 IRQ routing is enabled.
2083 noacpi [X86] Do not use ACPI for IRQ routing
2084 or for PCI scanning.
2085 use_crs [X86] Use PCI host bridge window information
2086 from ACPI. On BIOSes from 2008 or later, this
2087 is enabled by default. If you need to use this,
2088 please report a bug.
2089 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2090 If you need to use this, please report a bug.
2091 routeirq Do IRQ routing for all PCI devices.
2092 This is normally done in pci_enable_device(),
2093 so this option is a temporary workaround
2094 for broken drivers that don't call it.
2095 skip_isa_align [X86] do not align io start addr, so can
2096 handle more pci cards
2097 firmware [ARM] Do not re-enumerate the bus but instead
2098 just use the configuration from the
2099 bootloader. This is currently used on
2100 IXP2000 systems where the bus has to be
2101 configured a certain way for adjunct CPUs.
2102 noearly [X86] Don't do any early type 1 scanning.
2103 This might help on some broken boards which
2104 machine check when some devices' config space
2105 is read. But various workarounds are disabled
2106 and some IOMMU drivers will not work.
2107 bfsort Sort PCI devices into breadth-first order.
2108 This sorting is done to get a device
2109 order compatible with older (<= 2.4) kernels.
2110 nobfsort Don't sort PCI devices into breadth-first order.
2111 cbiosize=nn[KMG] The fixed amount of bus space which is
2112 reserved for the CardBus bridge's IO window.
2113 The default value is 256 bytes.
2114 cbmemsize=nn[KMG] The fixed amount of bus space which is
2115 reserved for the CardBus bridge's memory
2116 window. The default value is 64 megabytes.
2119 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2120 Specifies alignment and device to reassign
2121 aligned memory resources.
2122 If <order of align> is not specified,
2123 PAGE_SIZE is used as alignment.
2124 PCI-PCI bridge can be specified, if resource
2125 windows need to be expanded.
2126 ecrc= Enable/disable PCIe ECRC (transaction layer
2127 end-to-end CRC checking).
2128 bios: Use BIOS/firmware settings. This is the
2132 realloc reallocate PCI resources if allocations done by BIOS
2136 Format: [<sbdf>[+IO<size>][+MEM<size>]][,<sbdf>...]
2137 Format of sbdf: [<segment>:]<bus>:<dev>.<func>
2138 Specifies the least reserved io size or memory size
2139 which is assigned to PCI bridge even when no child
2140 pci device exists. This is useful with PCI hotplug.
2142 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2145 force Enable ASPM even on devices that claim not to support it.
2146 WARNING: Forcing ASPM on may cause system lockups.
2148 pcie_ports= [PCIE] PCIe ports handling:
2149 auto Ask the BIOS whether or not to use native PCIe services
2150 associated with PCIe ports (PME, hot-plug, AER). Use
2151 them only if that is allowed by the BIOS.
2152 native Use native PCIe services associated with PCIe ports
2154 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2157 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2158 nomsi Do not use MSI for native PCIe PME signaling (this makes
2159 all PCIe root ports use INTx for all services).
2161 pcmv= [HW,PCMCIA] BadgePAD 4
2164 See Documentation/blockdev/paride.txt.
2166 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2169 See arch/parisc/kernel/pdc_chassis.c
2171 percpu_alloc= Select which percpu first chunk allocator to use.
2172 Currently supported values are "embed" and "page".
2173 Archs may support subset or none of the selections.
2174 See comments in mm/percpu.c for details on each
2175 allocator. This parameter is primarily for debugging
2176 and performance comparison.
2179 See Documentation/blockdev/paride.txt.
2182 See Documentation/blockdev/paride.txt.
2184 pirq= [SMP,APIC] Manual mp-table setup
2185 See Documentation/x86/i386/IO-APIC.txt.
2187 plip= [PPT,NET] Parallel port network link
2188 Format: { parport<nr> | timid | 0 }
2189 See also Documentation/parport.txt.
2191 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2192 Override pmtimer IOPort with a hex value.
2196 Enable PNP debug messages (depends on the
2197 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2198 via /sys/module/pnp/parameters/debug. We always show
2199 current resource usage; turning this on also shows
2200 possible settings and some assignment information.
2206 { on | off | curr | res | no-curr | no-res }
2209 [ISAPNP] Exclude IRQs for the autoconfiguration
2212 [ISAPNP] Exclude DMAs for the autoconfiguration
2214 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2215 Ranges are in pairs (I/O port base and size).
2218 [ISAPNP] Exclude memory regions for the
2220 Ranges are in pairs (memory base and size).
2222 ports= [IP_VS_FTP] IPVS ftp helper module
2224 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2226 Format: <port>,<port>....
2228 print-fatal-signals=
2229 [KNL] debug: print fatal signals
2231 If enabled, warn about various signal handling
2232 related application anomalies: too many signals,
2233 too many POSIX.1 timers, fatal signals causing a
2236 If you hit the warning due to signal overflow,
2237 you might want to try "ulimit -i unlimited".
2241 printk.time= Show timing data prefixed to each printk message line
2242 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2244 processor.max_cstate= [HW,ACPI]
2245 Limit processor to maximum C-state
2246 max_cstate=9 overrides any DMI blacklist limit.
2248 processor.nocst [HW,ACPI]
2249 Ignore the _CST method to determine C-states,
2250 instead using the legacy FADT method
2252 profile= [KNL] Enable kernel profiling via /proc/profile
2253 Format: [schedule,]<number>
2254 Param: "schedule" - profile schedule points.
2255 Param: <number> - step/bucket size as a power of 2 for
2256 statistical time based profiling.
2257 Param: "sleep" - profile D-state sleeping (millisecs).
2258 Requires CONFIG_SCHEDSTATS
2259 Param: "kvm" - profile VM exits.
2261 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2263 See Documentation/blockdev/ramdisk.txt.
2265 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2266 probe for; one of (bare|imps|exps|lifebook|any).
2267 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2269 psmouse.resetafter= [HW,MOUSE]
2270 Try to reset the device after so many bad packets
2273 [HW,MOUSE] Set desired mouse resolution, in dpi.
2274 psmouse.smartscroll=
2275 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2276 0 = disabled, 1 = enabled (default).
2278 pstore.backend= Specify the name of the pstore backend to use
2281 See Documentation/blockdev/paride.txt.
2284 [KNL] Number of legacy pty's. Overwrites compiled-in
2287 quiet [KNL] Disable most log messages
2292 See Documentation/md.txt.
2294 ramdisk_blocksize= [RAM]
2295 See Documentation/blockdev/ramdisk.txt.
2297 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2298 See Documentation/blockdev/ramdisk.txt.
2300 rcupdate.blimit= [KNL,BOOT]
2301 Set maximum number of finished RCU callbacks to process
2304 rcupdate.qhimark= [KNL,BOOT]
2305 Set threshold of queued
2306 RCU callbacks over which batch limiting is disabled.
2308 rcupdate.qlowmark= [KNL,BOOT]
2309 Set threshold of queued RCU callbacks below which
2310 batch limiting is re-enabled.
2314 Run specified binary instead of /init from the ramdisk,
2315 used for early userspace startup. See initrd.
2317 reassign_resources [PCI,ACPI,XEN]
2318 Use guestdev= parameter to reassign device's
2319 resources, or specify =all here.
2321 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2322 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2323 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2326 [KNL, SMP] Set scheduler's default relax_domain_level.
2327 See Documentation/cgroups/cpusets.txt.
2329 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2331 reservetop= [X86-32]
2333 Reserves a hole at the top of the kernel virtual
2338 Set the amount of memory to reserve for BIOS at
2339 the bottom of the address space.
2341 reset_devices [KNL] Force drivers to reset the underlying device
2342 during initialization.
2345 Specify the partition device for software suspend
2347 resume_offset= [SWSUSP]
2348 Specify the offset from the beginning of the partition
2349 given by "resume=" at which the swap header is located,
2350 in <PAGE_SIZE> units (needed only for swap files).
2351 See Documentation/power/swsusp-and-swap-files.txt
2353 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2354 read the resume files
2356 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2357 Useful for devices that are detected asynchronously
2358 (e.g. USB and MMC devices).
2360 hibernate= [HIBERNATION]
2361 noresume Don't check if there's a hibernation image
2362 present during boot.
2363 nocompress Don't compress/decompress hibernation images.
2365 retain_initrd [RAM] Keep initrd memory after extraction
2367 rhash_entries= [KNL,NET]
2368 Set number of hash buckets for route cache
2370 riscom8= [HW,SERIAL]
2371 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2373 ro [KNL] Mount root device read-only on boot
2375 root= [KNL] Root filesystem
2376 See name_to_dev_t comment in init/do_mounts.c.
2378 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2379 mount the root filesystem
2381 rootflags= [KNL] Set root filesystem mount option string
2383 rootfstype= [KNL] Set root filesystem type
2385 rootwait [KNL] Wait (indefinitely) for root device to show up.
2386 Useful for devices that are detected asynchronously
2387 (e.g. USB and MMC devices).
2389 rw [KNL] Mount root device read-write on boot
2391 S [KNL] Run init in single mode
2394 See drivers/net/irda/sa1100_ir.c.
2396 sbni= [NET] Granch SBNI12 leased line adapter
2398 sched_debug [KNL] Enables verbose scheduler debug messages.
2400 security= [SECURITY] Choose a security module to enable at boot.
2401 If this boot parameter is not specified, only the first
2402 security module asking for security registration will be
2403 loaded. An invalid security module name will be treated
2404 as if no module has been chosen.
2406 selinux= [SELINUX] Disable or enable SELinux at boot time.
2407 Format: { "0" | "1" }
2408 See security/selinux/Kconfig help text.
2411 Default value is set via kernel config option.
2412 If enabled at boot time, /selinux/disable can be used
2413 later to disable prior to initial policy load.
2415 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2416 Format: { "0" | "1" }
2417 See security/apparmor/Kconfig help text
2420 Default value is set via kernel config option.
2422 serialnumber [BUGS=X86-32]
2425 Maximal number of shapers.
2427 show_msr= [x86] show boot-time MSR settings
2428 Format: { <integer> }
2429 Show boot-time (BIOS-initialized) MSR settings.
2430 The parameter means the number of CPUs to show,
2431 for example 1 means boot CPU only.
2438 slab_max_order= [MM, SLAB]
2439 Determines the maximum allowed order for slabs.
2440 A high setting may cause OOMs due to memory
2441 fragmentation. Defaults to 1 for systems with
2442 more than 32MB of RAM, 0 otherwise.
2444 slub_debug[=options[,slabs]] [MM, SLUB]
2445 Enabling slub_debug allows one to determine the
2446 culprit if slab objects become corrupted. Enabling
2447 slub_debug can create guard zones around objects and
2448 may poison objects when not in use. Also tracks the
2449 last alloc / free. For more information see
2450 Documentation/vm/slub.txt.
2452 slub_max_order= [MM, SLUB]
2453 Determines the maximum allowed order for slabs.
2454 A high setting may cause OOMs due to memory
2455 fragmentation. For more information see
2456 Documentation/vm/slub.txt.
2458 slub_min_objects= [MM, SLUB]
2459 The minimum number of objects per slab. SLUB will
2460 increase the slab order up to slub_max_order to
2461 generate a sufficiently large slab able to contain
2462 the number of objects indicated. The higher the number
2463 of objects the smaller the overhead of tracking slabs
2464 and the less frequently locks need to be acquired.
2465 For more information see Documentation/vm/slub.txt.
2467 slub_min_order= [MM, SLUB]
2468 Determines the mininum page order for slabs. Must be
2469 lower than slub_max_order.
2470 For more information see Documentation/vm/slub.txt.
2472 slub_nomerge [MM, SLUB]
2473 Disable merging of slabs with similar size. May be
2474 necessary if there is some reason to distinguish
2475 allocs to different slabs. Debug options disable
2476 merging on their own.
2477 For more information see Documentation/vm/slub.txt.
2480 Format: <io1>[,<io2>[,...,<io8>]]
2482 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2483 attempt to substitute SMP alternatives once at boot.
2485 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2486 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2487 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2488 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2489 smsc-ircc2.ircc_irq= [HW] IRQ line
2490 smsc-ircc2.ircc_dma= [HW] DMA channel
2491 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2492 0: Toshiba Satellite 1800 (GP data pin select)
2493 1: Fast pin select (default)
2497 [KNL] Should the soft-lockup detector generate panics.
2500 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2501 See Documentation/laptops/sonypi.txt
2503 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2504 See Documentation/serial/specialix.txt.
2506 spia_io_base= [HW,MTD]
2512 Enabled the stack tracer on boot up.
2514 stacktrace_filter=[function-list]
2515 [FTRACE] Limit the functions that the stack tracer
2516 will trace at boot up. function-list is a comma separated
2517 list of functions. This list can be changed at run
2518 time by the stack_trace_filter file in the debugfs
2519 tracing directory. Note, this enables stack tracing
2520 and the stacktrace above is not needed.
2524 Set the STI (builtin display/keyboard on the HP-PARISC
2525 machines) console (graphic card) which should be used
2526 as the initial boot-console.
2527 See also comment in drivers/video/console/sticore.c.
2530 See comment in drivers/video/console/sticore.c.
2533 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2535 sunrpc.min_resvport=
2536 sunrpc.max_resvport=
2538 SunRPC servers often require that client requests
2539 originate from a privileged port (i.e. a port in the
2540 range 0 < portnr < 1024).
2541 An administrator who wishes to reserve some of these
2542 ports for other uses may adjust the range that the
2543 kernel's sunrpc client considers to be privileged
2544 using these two parameters to set the minimum and
2545 maximum port values.
2549 Control how the NFS server code allocates CPUs to
2550 service thread pools. Depending on how many NICs
2551 you have and where their interrupts are bound, this
2552 option will affect which CPUs will do NFS serving.
2553 Note: this parameter cannot be changed while the
2554 NFS server is running.
2556 auto the server chooses an appropriate mode
2557 automatically using heuristics
2558 global a single global pool contains all CPUs
2559 percpu one pool for each CPU
2560 pernode one pool for each NUMA node (equivalent
2561 to global on non-NUMA machines)
2563 sunrpc.tcp_slot_table_entries=
2564 sunrpc.udp_slot_table_entries=
2566 Sets the upper limit on the number of simultaneous
2567 RPC calls that can be sent from the client to a
2568 server. Increasing these values may allow you to
2569 improve throughput, but will also increase the
2570 amount of memory reserved for use by the client.
2573 [KNL] Enable accounting of swap in memory resource
2574 controller if no parameter or 1 is given or disable
2575 it if 0 is given (See Documentation/cgroups/memory.txt)
2577 swiotlb= [IA-64] Number of I/O TLB slabs
2581 sysfs.deprecated=0|1 [KNL]
2582 Enable/disable old style sysfs layout for old udev
2583 on older distributions. When this option is enabled
2584 very new udev will not work anymore. When this option
2585 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2586 in older udev will not work anymore.
2587 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2588 the kernel configuration.
2590 sysrq_always_enabled
2592 Ignore sysrq setting - this boot parameter will
2593 neutralize any effect of /proc/sys/kernel/sysrq.
2594 Useful for debugging.
2598 test_suspend= [SUSPEND]
2599 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2600 standby suspend) as the system sleep state to briefly
2601 enter during system startup. The system is woken from
2602 this state using a wakeup-capable RTC alarm.
2604 thash_entries= [KNL,NET]
2605 Set number of hash buckets for TCP connection
2607 thermal.act= [HW,ACPI]
2608 -1: disable all active trip points in all thermal zones
2609 <degrees C>: override all lowest active trip points
2611 thermal.crt= [HW,ACPI]
2612 -1: disable all critical trip points in all thermal zones
2613 <degrees C>: override all critical trip points
2615 thermal.nocrt= [HW,ACPI]
2616 Set to disable actions on ACPI thermal zone
2617 critical and hot trip points.
2619 thermal.off= [HW,ACPI]
2620 1: disable ACPI thermal control
2622 thermal.psv= [HW,ACPI]
2623 -1: disable all passive trip points
2624 <degrees C>: override all passive trip points to this
2627 thermal.tzp= [HW,ACPI]
2628 Specify global default ACPI thermal zone polling rate
2629 <deci-seconds>: poll all this frequency
2630 0: no polling (default)
2633 Force threading of all interrupt handlers except those
2634 marked explicitely IRQF_NO_THREAD.
2638 Specify if the kernel should make use of the cpu
2639 topology information if the hardware supports this.
2640 The scheduler will make use of this information and
2641 e.g. base its process migration decisions on it.
2646 tpm_suspend_pcr=[HW,TPM]
2647 Format: integer pcr id
2648 Specify that at suspend time, the tpm driver
2649 should extend the specified pcr with zeros,
2650 as a workaround for some chips which fail to
2651 flush the last written pcr on TPM_SaveState.
2652 This will guarantee that all the other pcrs
2655 trace_buf_size=nn[KMG]
2656 [FTRACE] will set tracing buffer size.
2658 trace_event=[event-list]
2659 [FTRACE] Set and start specified trace events in order
2660 to facilitate early boot debugging.
2661 See also Documentation/trace/events.txt
2663 tsc= Disable clocksource stability checks for TSC.
2665 [x86] reliable: mark tsc clocksource as reliable, this
2666 disables clocksource verification at runtime, as well
2667 as the stability checks done at bootup. Used to enable
2668 high-resolution timer mode on older hardware, and in
2669 virtualized environment.
2670 [x86] noirqtime: Do not use TSC to do irq accounting.
2671 Used to run time disable IRQ_TIME_ACCOUNTING on any
2672 platforms where RDTSC is slow and this accounting
2675 turbografx.map[2|3]= [HW,JOY]
2676 TurboGraFX parallel port interface
2678 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2679 See also Documentation/input/joystick-parport.txt
2681 udbg-immortal [PPC] When debugging early kernel crashes that
2682 happen after console_init() and before a proper
2683 console driver takes over, this boot options might
2684 help "seeing" what's going on.
2686 uhash_entries= [KNL,NET]
2687 Set number of hash buckets for UDP/UDP-Lite connections
2690 [USB] Ignore overcurrent events (default N).
2691 Some badly-designed motherboards generate lots of
2692 bogus events, for ports that aren't wired to
2693 anything. Set this parameter to avoid log spamming.
2694 Note that genuine overcurrent events won't be
2698 [X86] Cause panic on unknown NMI.
2700 unsupported Allow loading of unsupported kernel modules:
2701 0 = only allow supported modules,
2702 1 = warn when loading unsupported modules,
2705 CONFIG_ENTERPRISE_SUPPORT must be enabled for this
2708 usbcore.authorized_default=
2709 [USB] Default USB device authorization:
2710 (default -1 = authorized except for wireless USB,
2711 0 = not authorized, 1 = authorized)
2713 usbcore.autosuspend=
2714 [USB] The autosuspend time delay (in seconds) used
2715 for newly-detected USB devices (default 2). This
2716 is the time required before an idle device will be
2717 autosuspended. Devices for which the delay is set
2718 to a negative value won't be autosuspended at all.
2720 usbcore.usbfs_snoop=
2721 [USB] Set to log all usbfs traffic (default 0 = off).
2723 usbcore.blinkenlights=
2724 [USB] Set to cycle leds on hubs (default 0 = off).
2726 usbcore.old_scheme_first=
2727 [USB] Start with the old device initialization
2728 scheme (default 0 = off).
2730 usbcore.usbfs_memory_mb=
2731 [USB] Memory limit (in MB) for buffers allocated by
2732 usbfs (default = 16, 0 = max = 2047).
2734 usbcore.use_both_schemes=
2735 [USB] Try the other device initialization scheme
2736 if the first one fails (default 1 = enabled).
2738 usbcore.initial_descriptor_timeout=
2739 [USB] Specifies timeout for the initial 64-byte
2740 USB_REQ_GET_DESCRIPTOR request in milliseconds
2741 (default 5000 = 5.0 seconds).
2744 [USBHID] The interval which mice are to be polled at.
2746 usb-storage.delay_use=
2747 [UMS] The delay in seconds before a new device is
2748 scanned for Logical Units (default 5).
2751 [UMS] A list of quirks entries to supplement or
2752 override the built-in unusual_devs list. List
2753 entries are separated by commas. Each entry has
2754 the form VID:PID:Flags where VID and PID are Vendor
2755 and Product ID values (4-digit hex numbers) and
2756 Flags is a set of characters, each corresponding
2757 to a common usb-storage quirk flag as follows:
2758 a = SANE_SENSE (collect more than 18 bytes
2760 b = BAD_SENSE (don't collect more than 18
2761 bytes of sense data);
2762 c = FIX_CAPACITY (decrease the reported
2763 device capacity by one sector);
2764 d = NO_READ_DISC_INFO (don't use
2765 READ_DISC_INFO command);
2766 e = NO_READ_CAPACITY_16 (don't use
2767 READ_CAPACITY_16 command);
2768 h = CAPACITY_HEURISTICS (decrease the
2769 reported device capacity by one
2770 sector if the number is odd);
2771 i = IGNORE_DEVICE (don't bind to this
2773 l = NOT_LOCKABLE (don't try to lock and
2774 unlock ejectable media);
2775 m = MAX_SECTORS_64 (don't transfer more
2776 than 64 sectors = 32 KB at a time);
2777 n = INITIAL_READ10 (force a retry of the
2778 initial READ(10) command);
2779 o = CAPACITY_OK (accept the capacity
2780 reported by the device);
2781 r = IGNORE_RESIDUE (the device reports
2782 bogus residue values);
2783 s = SINGLE_LUN (the device has only one
2785 w = NO_WP_DETECT (don't test whether the
2786 medium is write-protected).
2787 Example: quirks=0419:aaf5:rl,0421:0433:rc
2789 user_debug= [KNL,ARM]
2791 See arch/arm/Kconfig.debug help text.
2792 1 - undefined instruction events
2794 4 - invalid data aborts
2797 Example: user_debug=31
2800 [X86] Flags controlling user PTE allocations.
2802 nohigh = do not allocate PTE pages in
2803 HIGHMEM regardless of setting
2807 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2808 vdso=1: enable VDSO (default)
2809 vdso=0: disable VDSO mapping
2812 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2813 vdso32=1: enable 32-bit VDSO (default)
2814 vdso32=0: disable 32-bit VDSO mapping
2817 vector=percpu: enable percpu vector domain
2819 video= [FB] Frame buffer configuration
2820 See Documentation/fb/modedb.txt.
2822 vga= [BOOT,X86-32] Select a particular video mode
2823 See Documentation/x86/boot.txt and
2824 Documentation/svga.txt.
2825 Use vga=ask for menu.
2826 This is actually a boot loader parameter; the value is
2827 passed to the kernel using a special protocol.
2829 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2830 size of <nn>. This can be used to increase the
2831 minimum size (128MB on x86). It can also be used to
2832 decrease the size and leave more room for directly
2835 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2838 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2841 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2845 Controls the behavior of vsyscalls (i.e. calls to
2846 fixed addresses of 0xffffffffff600x00 from legacy
2847 code). Most statically-linked binaries and older
2848 versions of glibc use these calls. Because these
2849 functions are at fixed addresses, they make nice
2850 targets for exploits that can control RIP.
2852 emulate [default] Vsyscalls turn into traps and are
2853 emulated reasonably safely.
2855 native Vsyscalls are native syscall instructions.
2856 This is a little bit faster than trapping
2857 and makes a few dynamic recompilers work
2858 better than they would in emulation mode.
2859 It also makes exploits much easier to write.
2861 none Vsyscalls don't work at all. This makes
2862 them quite hard to use for exploits but
2863 might break your system.
2865 vt.cur_default= [VT] Default cursor shape.
2866 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2867 the parameters of the <Esc>[?A;B;Cc escape sequence;
2868 see VGA-softcursor.txt. Default: 2 = underline.
2870 vt.default_blu= [VT]
2871 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2872 Change the default blue palette of the console.
2873 This is a 16-member array composed of values
2876 vt.default_grn= [VT]
2877 Format: <green0>,<green1>,<green2>,...,<green15>
2878 Change the default green palette of the console.
2879 This is a 16-member array composed of values
2882 vt.default_red= [VT]
2883 Format: <red0>,<red1>,<red2>,...,<red15>
2884 Change the default red palette of the console.
2885 This is a 16-member array composed of values
2891 Set system-wide default UTF-8 mode for all tty's.
2892 Default is 1, i.e. UTF-8 mode is enabled for all
2893 newly opened terminals.
2895 vt.global_cursor_default=
2898 Set system-wide default for whether a cursor
2899 is shown on new VTs. Default is -1,
2900 i.e. cursors will be created by default unless
2901 overridden by individual drivers. 0 will hide
2902 cursors, 1 will display them.
2904 watchdog timers [HW,WDT] For information on watchdog timers,
2905 see Documentation/watchdog/watchdog-parameters.txt
2906 or other driver-specific files in the
2907 Documentation/watchdog/ directory.
2909 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2910 default x2apic cluster mode on platforms
2913 x86_mrst_timer= [X86-32,APBT]
2914 Choose timer option for x86 Moorestown MID platform.
2915 Two valid options are apbt timer only and lapic timer
2916 plus one apbt timer for broadcast timer.
2917 x86_mrst_timer=apbt_only | lapic_and_apbt
2919 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2920 xd_geo= See header of drivers/block/xd.c.
2922 xen_emul_unplug= [HW,X86,XEN]
2923 Unplug Xen emulated devices
2924 Format: [unplug0,][unplug1]
2925 ide-disks -- unplug primary master IDE devices
2926 aux-ide-disks -- unplug non-primary-master IDE devices
2927 nics -- unplug network devices
2928 all -- unplug all emulated devices (NICs and IDE disks)
2929 unnecessary -- unplugging emulated devices is
2930 unnecessary even if the host did not respond to
2932 never -- do not unplug even if version check succeeds
2934 xirc2ps_cs= [NET,PCMCIA]
2936 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2938 ______________________________________________________________________
2942 Add more DRM drivers.
projects / linux-flexiantxendom0-3.2.10.git / blob