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 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
47 EFI EFI Partitioning (GPT) is enabled
48 EIDE EIDE/ATAPI support is enabled.
49 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
51 FB The frame buffer device is enabled.
52 GCOV GCOV profiling is enabled.
53 HW Appropriate hardware is enabled.
54 IA-64 IA-64 architecture is enabled.
55 IMA Integrity measurement architecture is enabled.
56 IOSCHED More than one I/O scheduler is enabled.
57 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
58 IPV6 IPv6 support is enabled.
59 ISAPNP ISA PnP code is enabled.
60 ISDN Appropriate ISDN support is enabled.
61 JOY Appropriate joystick support is enabled.
62 KGDB Kernel debugger support is enabled.
63 KVM Kernel Virtual Machine support is enabled.
64 LIBATA Libata driver is enabled
65 LP Printer support is enabled.
66 LOOP Loopback device support is enabled.
67 M68k M68k architecture is enabled.
68 These options have more detailed description inside of
69 Documentation/m68k/kernel-options.txt.
70 MCA MCA bus support is enabled.
71 MDA MDA console support is enabled.
72 MOUSE Appropriate mouse support is enabled.
73 MSI Message Signaled Interrupts (PCI).
74 MTD MTD (Memory Technology Device) support is enabled.
75 NET Appropriate network support is enabled.
76 NUMA NUMA support is enabled.
77 NFS Appropriate NFS support is enabled.
78 OSS OSS sound support is enabled.
79 PV_OPS A paravirtualized kernel is enabled.
80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
81 PARISC The PA-RISC architecture is enabled.
82 PCI PCI bus support is enabled.
83 PCIE PCI Express support is enabled.
84 PCMCIA The PCMCIA subsystem is enabled.
85 PNP Plug & Play support is enabled.
86 PPC PowerPC architecture is enabled.
87 PPT Parallel port support is enabled.
88 PS2 Appropriate PS/2 support is enabled.
89 RAM RAM disk support is enabled.
90 S390 S390 architecture is enabled.
91 SCSI Appropriate SCSI support is enabled.
92 A lot of drivers have their options described inside
93 the Documentation/scsi/ sub-directory.
94 SECURITY Different security models are enabled.
95 SELINUX SELinux support is enabled.
96 APPARMOR AppArmor support is enabled.
97 SERIAL Serial support is enabled.
98 SH SuperH architecture is enabled.
99 SMP The kernel is an SMP kernel.
100 SPARC Sparc architecture is enabled.
101 SWSUSP Software suspend (hibernation) is enabled.
102 SUSPEND System suspend states are enabled.
103 FTRACE Function tracing enabled.
104 TPM TPM drivers are enabled.
105 TS Appropriate touchscreen support is enabled.
106 UMS USB Mass Storage support is enabled.
107 USB USB support is enabled.
108 USBHID USB Human Interface Device support is enabled.
109 V4L Video For Linux support is enabled.
110 VGA The VGA console has been enabled.
111 VT Virtual terminal support is enabled.
112 WDT Watchdog support is enabled.
113 XT IBM PC/XT MFM hard disk support is enabled.
114 X86-32 X86-32, aka i386 architecture is enabled.
115 X86-64 X86-64 architecture is enabled.
116 More X86-64 boot options can be found in
117 Documentation/x86/x86_64/boot-options.txt .
118 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
119 XEN Xen support is enabled
121 In addition, the following text indicates that the option:
123 BUGS= Relates to possible processor bugs on the said processor.
124 KNL Is a kernel start-up parameter.
125 BOOT Is a boot loader parameter.
127 Parameters denoted with BOOT are actually interpreted by the boot
128 loader, and have no meaning to the kernel directly.
129 Do not modify the syntax of boot loader parameters without extreme
130 need or coordination with <Documentation/x86/boot.txt>.
132 There are also arch-specific kernel-parameters not documented here.
133 See for example <Documentation/x86/x86_64/boot-options.txt>.
135 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
136 a trailing = on the name of any parameter states that that parameter will
137 be entered as an environment variable, whereas its absence indicates that
138 it will appear as a kernel argument readable via /proc/cmdline by programs
139 running once the system is up.
141 The number of kernel parameters is not limited, but the length of the
142 complete command line (parameters including spaces etc.) is limited to
143 a fixed number of characters. This limit depends on the architecture
144 and is between 256 and 4096 characters. It is defined in the file
145 ./include/asm/setup.h as COMMAND_LINE_SIZE.
149 Advanced Configuration and Power Interface
150 Format: { force | off | strict | noirq | rsdt }
151 force -- enable ACPI if default was off
152 off -- disable ACPI if default was on
153 noirq -- do not use ACPI for IRQ routing
154 strict -- Be less tolerant of platforms that are not
155 strictly ACPI specification compliant.
156 rsdt -- prefer RSDT over (default) XSDT
157 copy_dsdt -- copy DSDT to memory
159 See also Documentation/power/pm.txt, pci=noacpi
161 acpi_apic_instance= [ACPI, IOAPIC]
163 2: use 2nd APIC table, if available
164 1,0: use 1st APIC table
167 acpi_backlight= [HW,ACPI]
168 acpi_backlight=vendor
170 If set to vendor, prefer vendor specific driver
171 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
172 of the ACPI video.ko driver.
174 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
175 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
177 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
178 debug output. Bits in debug_layer correspond to a
179 _COMPONENT in an ACPI source file, e.g.,
180 #define _COMPONENT ACPI_PCI_COMPONENT
181 Bits in debug_level correspond to a level in
182 ACPI_DEBUG_PRINT statements, e.g.,
183 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
184 The debug_level mask defaults to "info". See
185 Documentation/acpi/debug.txt for more information about
186 debug layers and levels.
188 Enable processor driver info messages:
189 acpi.debug_layer=0x20000000
190 Enable PCI/PCI interrupt routing info messages:
191 acpi.debug_layer=0x400000
192 Enable AML "Debug" output, i.e., stores to the Debug
193 object while interpreting AML:
194 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
195 Enable all messages related to ACPI hardware:
196 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
198 Some values produce so much output that the system is
199 unusable. The "log_buf_len" parameter may be useful
200 if you need to capture more output.
202 acpi_display_output= [HW,ACPI]
203 acpi_display_output=vendor
204 acpi_display_output=video
207 acpi_irq_balance [HW,ACPI]
208 ACPI will balance active IRQs
211 acpi_irq_nobalance [HW,ACPI]
212 ACPI will not move active IRQs (default)
215 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
216 Format: <irq>,<irq>...
218 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
220 Format: <irq>,<irq>...
222 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
224 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
225 Format: To spoof as Windows 98: ="Microsoft Windows"
227 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
228 acpi_osi="string1" # add string1 -- only one string
229 acpi_osi="!string2" # remove built-in string2
230 acpi_osi= # disable all strings
233 Override the pmtimer bug detection: force the kernel
234 to assume that this machine's pmtimer latches its value
235 and always returns good values.
237 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
238 Format: { level | edge | high | low }
240 acpi_serialize [HW,ACPI] force serialization of AML methods
242 acpi_skip_timer_override [HW,ACPI]
243 Recognize and ignore IRQ0/pin2 Interrupt Override.
244 For broken nForce2 BIOS resulting in XT-PIC timer.
246 acpi_sleep= [HW,ACPI] Sleep options
247 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
248 old_ordering, s4_nonvs, sci_force_enable }
249 See Documentation/power/video.txt for information on
251 s3_beep is for debugging; it makes the PC's speaker beep
252 as soon as the kernel's real-mode entry point is called.
253 s4_nohwsig prevents ACPI hardware signature from being
254 used during resume from hibernation.
255 old_ordering causes the ACPI 1.0 ordering of the _PTS
256 control method, with respect to putting devices into
257 low power states, to be enforced (the ACPI 2.0 ordering
258 of _PTS is used by default).
259 nonvs prevents the kernel from saving/restoring the
260 ACPI NVS memory during suspend/hibernation and resume.
261 sci_force_enable causes the kernel to set SCI_EN directly
262 on resume from S1/S3 (which is against the ACPI spec,
263 but some broken systems don't work without it).
265 acpi_use_timer_override [HW,ACPI]
266 Use timer override. For some broken Nvidia NF5 boards
267 that require a timer override, but don't have HPET
269 acpi_enforce_resources= [ACPI]
270 { strict | lax | no }
271 Check for resource conflicts between native drivers
272 and ACPI OperationRegions (SystemIO and SystemMemory
273 only). IO ports and memory declared in ACPI might be
274 used by the ACPI subsystem in arbitrary AML code and
275 can interfere with legacy drivers.
276 strict (default): access to resources claimed by ACPI
277 is denied; legacy drivers trying to access reserved
278 resources will fail to bind to device using them.
279 lax: access to resources claimed by ACPI is allowed;
280 legacy drivers trying to access reserved resources
281 will bind successfully but a warning message is logged.
282 no: ACPI OperationRegions are not marked as reserved,
283 no further checks are performed.
285 add_efi_memmap [EFI; X86] Include EFI memory map in
286 kernel's map of available physical RAM.
289 { off | try_unsupported }
290 off: disable AGP support
291 try_unsupported: try to drive unsupported chipsets
292 (may crash computer or cause data corruption)
295 See Documentation/sound/alsa/alsa-parameters.txt
298 Allow the default userspace alignment fault handler
299 behaviour to be specified. Bit 0 enables warnings,
300 bit 1 enables fixups, and bit 2 sends a segfault.
302 amd_iommu= [HW,X86-84]
303 Pass parameters to the AMD IOMMU driver in the system.
305 fullflush - enable flushing of IO/TLB entries when
306 they are unmapped. Otherwise they are
307 flushed before they will be reused, which
309 off - do not initialize any AMD IOMMU found in
312 amijoy.map= [HW,JOY] Amiga joystick support
313 Map of devices attached to JOY0DAT and JOY1DAT
315 See also Documentation/kernel/input/joystick.txt
317 analog.map= [HW,JOY] Analog joystick and gamepad support
318 Specifies type or capabilities of an analog joystick
319 connected to one of 16 gameports
320 Format: <type1>,<type2>,..<type16>
323 Power management functions (SPARCstation-4/5 + deriv.)
325 Disable APC CPU standby support. SPARCstation-Fox does
326 not play well with APC CPU idle - disable it if you have
327 APC and your system crashes randomly.
329 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
330 Change the output verbosity whilst booting
331 Format: { quiet (default) | verbose | debug }
332 Change the amount of debugging information output
333 when initialising the APIC and IO-APIC components.
336 See Documentation/networking/ipv6.txt.
338 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
339 Limit apic dumping. The parameter defines the maximal
340 number of local apics being dumped. Also it is possible
341 to set it to "all" by meaning -- no limit here.
342 Format: { 1 (default) | 2 | ... | all }.
343 The parameter valid if only apic=debug or
344 apic=verbose is specified.
345 Example: apic=debug show_lapic=all
347 apm= [APM] Advanced Power Management
348 See header of arch/x86/kernel/apm_32.c.
350 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
351 Format: <io>,<irq>,<nodeID>
355 atarimouse= [HW,MOUSE] Atari Mouse
357 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
358 EzKey and similar keyboards
360 atkbd.reset= [HW] Reset keyboard during initialization
362 atkbd.set= [HW] Select keyboard code set
363 Format: <int> (2 = AT (default), 3 = PS/2)
365 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
368 atkbd.softraw= [HW] Choose between synthetic and real raw mode
369 Format: <bool> (0 = real, 1 = synthetic (default))
371 atkbd.softrepeat= [HW]
372 Use software keyboard repeat
376 baycom_epp= [HW,AX25]
379 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
381 See header of drivers/net/hamradio/baycom_par.c.
383 baycom_ser_fdx= [HW,AX25]
384 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
385 Format: <io>,<irq>,<mode>[,<baud>]
386 See header of drivers/net/hamradio/baycom_ser_fdx.c.
388 baycom_ser_hdx= [HW,AX25]
389 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
390 Format: <io>,<irq>,<mode>
391 See header of drivers/net/hamradio/baycom_ser_hdx.c.
393 boot_delay= Milliseconds to delay each printk during boot.
394 Values larger than 10 seconds (10000) are changed to
398 bootmem_debug [KNL] Enable bootmem allocator debug messages.
400 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
401 bttv.radio= Most important insmod options are available as
403 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
404 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
406 bulk_remove=off [PPC] This parameter disables the use of the pSeries
407 firmware feature for flushing multiple hpte entries
410 c101= [NET] Moxa C101 synchronous serial card
412 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
413 Sometimes CPU hardware bugs make them report the cache
414 size incorrectly. The kernel will attempt work arounds
415 to fix known problems, but for some CPUs it is not
416 possible to determine what the correct size should be.
417 This option provides an override for these situations.
420 [SECURITY] Disable capabilities. This would normally
421 be used only if an alternative security model is to be
422 configured. Potentially dangerous and should only be
423 used if you are entirely sure of the consequences.
425 ccw_timeout_log [S390]
426 See Documentation/s390/CommonIO for details.
428 cgroup_disable= [KNL] Disable a particular controller
429 Format: {name of the controller(s) to disable}
430 {Currently supported controllers - "memory"}
432 checkreqprot [SELINUX] Set initial checkreqprot flag value.
433 Format: { "0" | "1" }
434 See security/selinux/Kconfig help text.
435 0 -- check protection applied by kernel (includes
436 any implied execute protection).
437 1 -- check protection requested by application.
438 Default value is set via a kernel config option.
439 Value can be changed at runtime via
440 /selinux/checkreqprot.
443 See Documentation/s390/CommonIO for details.
445 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
447 Forces specified clocksource (if available) to be used
448 when calculating gettimeofday(). If specified
449 clocksource is not available, it defaults to PIT.
450 Format: { pit | tsc | cyclone | pmtmr }
452 clocksource= Override the default clocksource
454 Override the default clocksource and use the clocksource
455 with the name specified.
456 Some clocksource names to choose from, depending on
458 [all] jiffies (this is the base, fallback clocksource)
460 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
461 pxa_timer,timer3,32k_counter,timer0_1
463 [X86-32] pit,hpet,tsc;
464 scx200_hrt on Geode; cyclone on IBM x440
472 clearcpuid=BITNUM [X86]
473 Disable CPUID feature X for the kernel. See
474 arch/x86/include/asm/cpufeature.h for the valid bit
475 numbers. Note the Linux specific bits are not necessarily
476 stable over kernel options, but the vendor specific
478 Also note that user programs calling CPUID directly
479 or using the feature without checking anything
480 will still see it. This just prevents it from
481 being used by the kernel or shown in /proc/cpuinfo.
482 Also note the kernel might malfunction if you disable
485 cmo_free_hint= [PPC] Format: { yes | no }
486 Specify whether pages are marked as being inactive
487 when they are freed. This is used in CMO environments
488 to determine OS memory pressure for page stealing by
492 code_bytes [X86] How many bytes of object code to print
497 com20020= [HW,NET] ARCnet - COM20020 chipset
499 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
501 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
505 ARCnet - COM90xx chipset (memory-mapped buffers)
506 Format: <io>[,<irq>[,<memstart>]]
508 condev= [HW,S390] console device
511 console= [KNL] Output console device and options.
513 tty<n> Use the virtual console device <n>.
517 Use the specified serial port. The options are of
518 the form "bbbbpnf", where "bbbb" is the baud rate,
519 "p" is parity ("n", "o", or "e"), "n" is number of
520 bits, and "f" is flow control ("r" for RTS or
521 omit it). Default is "9600n8".
523 See Documentation/serial-console.txt for more
525 Documentation/networking/netconsole.txt for an
528 uart[8250],io,<addr>[,options]
529 uart[8250],mmio,<addr>[,options]
530 Start an early, polled-mode console on the 8250/16550
531 UART at the specified I/O port or MMIO address,
532 switching to the matching ttyS device later. The
533 options are the same as for ttyS, above.
535 If the device connected to the port is not a TTY but a braille
536 device, prepend "brl," before the device type, for instance
538 For now, only VisioBraille is supported.
540 consoleblank= [KNL] The console blank (screen saver) timeout in
541 seconds. Defaults to 10*60 = 10mins. A value of 0
542 disables the blank timer.
545 [KNL] Change the default value for
546 /proc/<pid>/coredump_filter.
547 See also Documentation/filesystems/proc.txt.
549 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
551 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
553 crashkernel=nn[KMG]@ss[KMG]
554 [KNL] Reserve a chunk of physical memory to
555 hold a kernel to switch to with kexec on panic.
557 crashkernel=range1:size1[,range2:size2,...][@offset]
558 [KNL] Same as above, but depends on the memory
559 in the running system. The syntax of range is
560 start-[end] where start and end are both
561 a memory unit (amount[KMG]). See also
562 Documentation/kdump/kdump.txt for a example.
567 cs89x0_media= [HW,NET]
568 Format: { rj45 | aui | bnc }
571 See header of drivers/s390/block/dasd_devmap.c.
573 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
574 (one device per port)
575 Format: <port#>,<type>
576 See also Documentation/input/joystick-parport.txt
578 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
579 time. See Documentation/dynamic-debug-howto.txt for
582 debug [KNL] Enable kernel debugging (events log level).
585 [KNL] verbose self-tests
587 Print debugging info while doing the locking API
589 We default to 0 (no extra messages), setting it to
590 1 will print _a lot_ more information - normally
591 only useful to kernel developers.
593 debug_objects [KNL] Enable object debugging
596 [KNL] Disable object debugging
598 debugpat [X86] Enable PAT debugging
600 decnet.addr= [HW,NET]
601 Format: <area>[,<node>]
602 See also Documentation/networking/decnet.txt.
605 [same as hugepagesz=] The size of the default
606 HugeTLB page size. This is the size represented by
607 the legacy /proc/ hugepages APIs, used for SHM, and
608 default size when mounting hugetlbfs filesystems.
609 Defaults to the default architecture's huge page size
613 Set number of hash buckets for dentry cache.
616 IO parameters + enable/disable command.
618 digiepca= [HW,SERIAL]
619 See drivers/char/README.epca and
620 Documentation/serial/digiepca.txt.
623 See Documentation/networking/ipv6.txt.
626 See Documentation/networking/ipv6.txt.
628 disable_mtrr_cleanup [X86]
629 The kernel tries to adjust MTRR layout from continuous
630 to discrete, to make X server driver able to add WB
631 entry later. This parameter disables that.
633 disable_mtrr_trim [X86, Intel and AMD only]
634 By default the kernel will trim any uncacheable
635 memory out of your available memory pool based on
636 MTRR settings. This parameter disables that behavior,
637 possibly causing your machine to run very slowly.
639 disable_timer_pin_1 [X86]
640 Disable PIN 1 of APIC timer
641 Can be useful to work around chipset bugs.
643 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
644 this option disables the debugging code at boot.
646 dma_debug_entries=<number>
647 This option allows to tune the number of preallocated
648 entries for DMA-API debugging code. One entry is
649 required per DMA-API allocation. Use this if the
650 DMA-API debugging code disables itself because the
651 architectural default is too low.
653 dma_debug_driver=<driver_name>
654 With this option the DMA-API debugging driver
655 filter feature can be enabled at boot time. Just
656 pass the driver to filter for as the parameter.
657 The filter can be disabled or changed to another
658 driver later using sysfs.
662 dynamic_printk Enables pr_debug()/dev_dbg() calls if
663 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
664 These can also be switched on/off via
665 <debugfs>/dynamic_printk/modules
667 earlycon= [KNL] Output early console device and options.
668 uart[8250],io,<addr>[,options]
669 uart[8250],mmio,<addr>[,options]
670 uart[8250],mmio32,<addr>[,options]
671 Start an early, polled-mode console on the 8250/16550
672 UART at the specified I/O port or MMIO address.
673 MMIO inter-register address stride is either 8bit (mmio)
675 The options are the same as for ttyS, above.
677 earlyprintk= [X86,SH,BLACKFIN]
679 earlyprintk=serial[,ttySn[,baudrate]]
680 earlyprintk=ttySn[,baudrate]
681 earlyprintk=dbgp[debugController#]
683 Append ",keep" to not disable it when the real console
686 Only vga or serial or usb debug port at a time.
688 Currently only ttyS0 and ttyS1 are supported.
690 Interaction with the standard serial driver is not
693 The VGA output is eventually overwritten by the real
696 ekgdboc= [X86,KGDB] Allow early kernel console debugging
699 This is desgined to be used in conjunction with
700 the boot argument: earlyprintk=vga
703 Format: {"off" | "on" | "skip[mbr]"}
705 eisa_irq_edge= [PARISC,HW]
706 See header of drivers/parisc/eisa.c.
709 See comment before function elanfreq_setup() in
710 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
713 Format: {"cfq" | "deadline" | "noop"}
714 See Documentation/block/as-iosched.txt and
715 Documentation/block/deadline-iosched.txt for details.
717 elfcorehdr= [IA64,PPC,SH,X86]
718 Specifies physical address of start of kernel core
719 image elf header. Generally kexec loader will
720 pass this option to capture kernel.
721 See Documentation/kdump/kdump.txt for details.
723 enable_mtrr_cleanup [X86]
724 The kernel tries to adjust MTRR layout from continuous
725 to discrete, to make X server driver able to add WB
726 entry later. This parameter enables that.
728 enable_timer_pin_1 [X86]
729 Enable PIN 1 of APIC timer
730 Can be useful to work around chipset bugs
731 (in particular on some ATI chipsets).
732 The kernel tries to set a reasonable default.
734 enforcing [SELINUX] Set initial enforcing status.
736 See security/selinux/Kconfig help text.
737 0 -- permissive (log only, no denials).
738 1 -- enforcing (deny and log).
740 Value can be changed at runtime via /selinux/enforce.
743 Disable Error Record Serialization Table (ERST)
746 ether= [HW,NET] Ethernet cards parameters
747 This option is obsoleted by the "netdev=" option, which
748 has equivalent usage. See its documentation for details.
752 fail_make_request=[KNL]
753 General fault injection mechanism.
754 Format: <interval>,<probability>,<space>,<times>
755 See also /Documentation/fault-injection/.
758 See Documentation/blockdev/floppy.txt.
760 force_pal_cache_flush
761 [IA-64] Avoid check_sal_cache_flush which may hang on
762 buggy SAL_CACHE_FLUSH implementations. Using this
763 parameter will force ia64_sal_cache_flush to call
764 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
767 [FTRACE] will set and start the specified tracer
768 as early as possible in order to facilitate early
771 ftrace_dump_on_oops[=orig_cpu]
772 [FTRACE] will dump the trace buffers on oops.
773 If no parameter is passed, ftrace will dump
774 buffers of all CPUs, but if you pass orig_cpu, it will
775 dump only the buffer of the CPU that triggered the
778 ftrace_filter=[function-list]
779 [FTRACE] Limit the functions traced by the function
780 tracer at boot up. function-list is a comma separated
781 list of functions. This list can be changed at run
782 time by the set_ftrace_filter file in the debugfs
785 ftrace_notrace=[function-list]
786 [FTRACE] Do not trace the functions specified in
787 function-list. This list can be changed at run time
788 by the set_ftrace_notrace file in the debugfs
791 ftrace_graph_filter=[function-list]
792 [FTRACE] Limit the top level callers functions traced
793 by the function graph tracer at boot up.
794 function-list is a comma separated list of functions
795 that can be changed at run time by the
796 set_graph_function file in the debugfs tracing directory.
799 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
800 support via parallel port (up to 5 devices per port)
801 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
802 See also Documentation/input/joystick-parport.txt
806 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
810 gcov_persist= [GCOV] When non-zero (default), profiling data for
811 kernel modules is saved and remains accessible via
812 debugfs, even when the module is unloaded/reloaded.
813 When zero, profiling data is discarded and associated
814 debugfs files are removed at module unload time.
816 gpt [EFI] Forces disk with valid GPT signature but
817 invalid Protective MBR to be treated as GPT.
819 hashdist= [KNL,NUMA] Large hashes allocated during boot
820 are distributed across NUMA nodes. Defaults on
821 for 64bit NUMA, off otherwise.
822 Format: 0 | 1 (for off | on)
824 hcl= [IA-64] SGI's Hardware Graph compatibility layer
826 hd= [EIDE] (E)IDE hard drive subsystem geometry
827 Format: <cyl>,<head>,<sect>
830 Disable Hardware Error Source Table (HEST) support;
831 corresponding firmware-first mode error processing
832 logic will be disabled.
834 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
835 size of <nn>. This works even on boxes that have no
836 highmem otherwise. This also works to reduce highmem
837 size on bigger boxes.
839 highres= [KNL] Enable/disable high resolution timer mode.
840 Valid parameters: "on", "off"
844 See Documentation/isdn/README.HiSax.
848 hpet= [X86-32,HPET] option to control HPET usage
849 Format: { enable (default) | disable | force |
851 disable: disable HPET and use PIT instead
852 force: allow force enabled of undocumented chips (ICH4,
854 verbose: show contents of HPET registers during setup
856 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
857 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
858 On x86-64 and powerpc, this option can be specified
859 multiple times interleaved with hugepages= to reserve
860 huge pages of different sizes. Valid pages sizes on
861 x86-64 are 2M (when the CPU supports "pse") and 1G
862 (when the CPU supports the "pdpe1gb" cpuinfo flag)
863 Note that 1GB pages can only be allocated at boot time
864 using hugepages= and not freed afterwards.
866 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
867 terminal devices. Valid values: 0..8
868 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
869 If specified, z/VM IUCV HVC accepts connections
870 from listed z/VM user IDs only.
872 i2c_bus= [HW] Override the default board specific I2C bus speed
873 or register an additional I2C bus that is not
874 registered from board initialization code.
878 i8042.debug [HW] Toggle i8042 debug mode
879 i8042.direct [HW] Put keyboard port into non-translated mode
880 i8042.dumbkbd [HW] Pretend that controller can only read data from
881 keyboard and cannot control its state
882 (Don't attempt to blink the leds)
883 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
884 i8042.nokbd [HW] Don't check/create keyboard port
885 i8042.noloop [HW] Disable the AUX Loopback command while probing
887 i8042.nomux [HW] Don't check presence of an active multiplexing
889 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
891 i8042.reset [HW] Reset the controller during init and cleanup
892 i8042.unlock [HW] Unlock (ignore) the keylock
896 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
897 indicates that the driver is running on unsupported
899 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
900 does not match list of supported models.
902 [HW] Report power status in /proc/i8k
903 (disabled by default)
904 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
908 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
910 ide-core.nodma= [HW] (E)IDE subsystem
911 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
912 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
913 .cdrom .chs .ignore_cable are additional options
914 See Documentation/ide/ide.txt.
916 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
917 Claim all unknown PCI IDE storage controllers.
920 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
921 Poll forces a polling idle loop that can slightly
922 improve the performance of waking up a idle CPU, but
923 will use a lot of power and make the system run hot.
925 idle=mwait: On systems which support MONITOR/MWAIT but
926 the kernel chose to not use it because it doesn't save
927 as much power as a normal idle loop, use the
928 MONITOR/MWAIT idle loop anyways. Performance should be
929 the same as idle=poll.
930 idle=halt: Halt is forced to be used for CPU idle.
931 In such case C2/C3 won't be used again.
932 idle=nomwait: Disable mwait for CPU C-states
934 ignore_loglevel [KNL]
935 Ignore loglevel setting - this will print /all/
936 kernel messages to the console. Useful for debugging.
939 Set number of hash buckets for inode cache.
942 Format: { "0" | "1" }
943 0 -- integrity auditing messages. (Default)
944 1 -- enable informational integrity auditing messages.
947 Format: { "sha1" | "md5" }
951 Load a policy which meets the needs of the Trusted
952 Computing Base. This means IMA will measure all
953 programs exec'd, files mmap'd for exec, and all files
954 opened for read by uid=0.
958 Run specified binary instead of /sbin/init as init
961 initcall_debug [KNL] Trace initcalls as they are executed. Useful
962 for working out where the kernel is dying during
965 initrd= [BOOT] Specify the location of the initial ramdisk
967 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
970 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
972 Enable intel iommu driver.
974 Disable intel iommu driver.
975 igfx_off [Default Off]
976 By default, gfx is mapped as normal device. If a gfx
977 device has a dedicated DMAR unit, the DMAR unit is
978 bypassed by not enabling DMAR with this option. In
979 this case, gfx device will use physical address for
982 With this option iommu will not optimize to look
983 for io virtual address below 32 bit forcing dual
984 address cycle on pci bus for cards supporting greater
985 than 32 bit addressing. The default is to look
986 for translation below 32 bit and if not available
987 then look in the higher range.
989 With this option on every unmap_single operation will
990 result in a hardware IOTLB flush operation as opposed
991 to batching them for performance.
993 intremap= [X86-64, Intel-IOMMU]
994 Format: { on (default) | off | nosid }
995 on enable Interrupt Remapping (default)
996 off disable Interrupt Remapping
997 nosid disable Source ID checking
1001 iomem= Disable strict checking of access to MMIO memory
1002 strict regions from userspace.
1018 io7= [HW] IO7 for Marvel based alpha systems
1019 See comment before marvel_specify_io7 in
1020 arch/alpha/kernel/core_marvel.c.
1022 io_delay= [X86] I/O delay method
1024 Standard port 0x80 based delay
1026 Alternate port 0xed based delay (needed on some systems)
1028 Simple two microseconds delay
1033 See Documentation/filesystems/nfs/nfsroot.txt.
1035 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1036 See comment before ip2_setup() in
1037 drivers/char/ip2/ip2base.c.
1040 When an interrupt is not handled search all handlers
1041 for it. Intended to get systems with badly broken
1045 When an interrupt is not handled search all handlers
1046 for it. Also check all handlers each timer
1047 interrupt. Intended to get systems with badly broken
1051 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1053 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1055 <cpu number>,...,<cpu number>
1057 <cpu number>-<cpu number>
1058 (must be a positive range in ascending order)
1060 <cpu number>,...,<cpu number>-<cpu number>
1062 This option can be used to specify one or more CPUs
1063 to isolate from the general SMP balancing and scheduling
1064 algorithms. You can move a process onto or off an
1065 "isolated" CPU via the CPU affinity syscalls or cpuset.
1066 <cpu number> begins at 0 and the maximum value is
1067 "number of CPUs in system - 1".
1069 This option is the preferred way to isolate CPUs. The
1070 alternative -- manually setting the CPU mask of all
1071 tasks in the system -- can cause problems and
1072 suboptimal load balancer performance.
1076 js= [HW,JOY] Analog joystick
1077 See Documentation/input/joystick.txt.
1081 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1082 specifies the amount of memory usable by the kernel
1083 for non-movable allocations. The requested amount is
1084 spread evenly throughout all nodes in the system. The
1085 remaining memory in each node is used for Movable
1086 pages. In the event, a node is too small to have both
1087 kernelcore and Movable pages, kernelcore pages will
1088 take priority and other nodes will have a larger number
1089 of kernelcore pages. The Movable zone is used for the
1090 allocation of pages that may be reclaimed or moved
1091 by the page migration subsystem. This means that
1092 HugeTLB pages may not be allocated from this zone.
1093 Note that allocations like PTEs-from-HighMem still
1094 use the HighMem zone if it exists, and the Normal
1095 zone if it does not.
1097 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1098 Format: <Controller#>[,poll interval]
1099 The controller # is the number of the ehci usb debug
1100 port as it is probed via PCI. The poll interval is
1101 optional and is the number seconds in between
1102 each poll cycle to the debug port in case you need
1103 the functionality for interrupting the kernel with
1104 gdb or control-c on the dbgp connection. When
1105 not using this parameter you use sysrq-g to break into
1106 the kernel debugger.
1108 kgdboc= [KGDB,HW] kgdb over consoles.
1109 Requires a tty driver that supports console polling,
1110 or a supported polling keyboard driver (non-usb).
1111 Serial only format: <serial_device>[,baud]
1112 keyboard only format: kbd
1113 keyboard and serial format: kbd,<serial_device>[,baud]
1114 Optional Kernel mode setting:
1115 kms, kbd format: kms,kbd
1116 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1118 kgdbwait [KGDB] Stop kernel execution and enter the
1119 kernel debugger at the earliest opportunity.
1121 kmac= [MIPS] korina ethernet MAC address.
1122 Configure the RouterBoard 532 series on-chip
1123 Ethernet adapter MAC address.
1125 kmemleak= [KNL] Boot-time kmemleak enable/disable
1126 Valid arguments: on, off
1129 kstack=N [X86] Print N words from the kernel stack
1132 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1133 Default is 0 (don't ignore, but inject #GP)
1135 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1136 Default is 1 (enabled)
1138 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1142 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1143 Default is 1 (enabled)
1145 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1147 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1149 kvm-intel.bypass_guest_pf=
1150 [KVM,Intel] Disables bypassing of guest page faults
1151 on Intel chips. Default is 1 (enabled)
1153 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1154 (virtualized MMU) support on capable Intel chips.
1155 Default is 1 (enabled)
1157 kvm-intel.emulate_invalid_guest_state=
1158 [KVM,Intel] Enable emulation of invalid guest states
1159 Default is 0 (disabled)
1161 kvm-intel.flexpriority=
1162 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1163 Default is 1 (enabled)
1165 kvm-intel.unrestricted_guest=
1166 [KVM,Intel] Disable unrestricted guest feature
1167 (virtualized real and unpaged mode) on capable
1168 Intel chips. Default is 1 (enabled)
1170 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1171 feature (tagged TLBs) on capable Intel chips.
1172 Default is 1 (enabled)
1178 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1181 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1184 libata.dma= [LIBATA] DMA control
1185 libata.dma=0 Disable all PATA and SATA DMA
1186 libata.dma=1 PATA and SATA Disk DMA only
1187 libata.dma=2 ATAPI (CDROM) DMA only
1188 libata.dma=4 Compact Flash DMA only
1189 Combinations also work, so libata.dma=3 enables DMA
1190 for disks and CDROMs, but not CFs.
1192 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1193 libata.ignore_hpa=0 keep BIOS limits (default)
1194 libata.ignore_hpa=1 ignore limits, using full disk
1196 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1200 libata.force= [LIBATA] Force configurations. The format is comma
1201 separated list of "[ID:]VAL" where ID is
1202 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1203 matching port, link or device. Basically, it matches
1204 the ATA ID string printed on console by libata. If
1205 the whole ID part is omitted, the last PORT and DEVICE
1206 values are used. If ID hasn't been specified yet, the
1207 configuration applies to all ports, links and devices.
1209 If only DEVICE is omitted, the parameter applies to
1210 the port and all links and devices behind it. DEVICE
1211 number of 0 either selects the first device or the
1212 first fan-out link behind PMP device. It does not
1213 select the host link. DEVICE number of 15 selects the
1214 host link and device attached to it.
1216 The VAL specifies the configuration to force. As long
1217 as there's no ambiguity shortcut notation is allowed.
1218 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1219 The following configurations can be forced.
1221 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1222 Any ID with matching PORT is used.
1224 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1226 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1227 udma[/][16,25,33,44,66,100,133] notation is also
1230 * [no]ncq: Turn on or off NCQ.
1232 * nohrst, nosrst, norst: suppress hard, soft
1235 * dump_id: dump IDENTIFY data.
1237 If there are multiple matching configurations changing
1238 the same attribute, the last one is used.
1240 memblock=debug [KNL] Enable memblock debug messages.
1242 load_ramdisk= [RAM] List of ramdisks to load from floppy
1243 See Documentation/blockdev/ramdisk.txt.
1245 lockd.nlm_grace_period=P [NFS] Assign grace period.
1248 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1251 lockd.nlm_timeout=T [NFS] Assign timeout value.
1254 lockd.nlm_udpport=M [NFS] Assign UDP port.
1257 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1260 loglevel= All Kernel Messages with a loglevel smaller than the
1261 console loglevel will be printed to the console. It can
1262 also be changed with klogd or other programs. The
1263 loglevels are defined as follows:
1265 0 (KERN_EMERG) system is unusable
1266 1 (KERN_ALERT) action must be taken immediately
1267 2 (KERN_CRIT) critical conditions
1268 3 (KERN_ERR) error conditions
1269 4 (KERN_WARNING) warning conditions
1270 5 (KERN_NOTICE) normal but significant condition
1271 6 (KERN_INFO) informational
1272 7 (KERN_DEBUG) debug-level messages
1274 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1275 Format: { n | nk | nM }
1276 n must be a power of two. The default size
1277 is set in the kernel config file.
1279 logo.nologo [FB] Disables display of the built-in Linux logo.
1280 This may be used to provide more screen space for
1281 kernel log messages and is useful when debugging
1282 kernel boot problems.
1284 lp=0 [LP] Specify parallel ports to use, e.g,
1285 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1286 lp=reset first parallel port). 'lp=0' disables the
1287 lp=auto printer driver. 'lp=reset' (which can be
1288 specified in addition to the ports) causes
1289 attached printers to be reset. Using
1290 lp=port1,port2,... specifies the parallel ports
1291 to associate lp devices with, starting with
1292 lp0. A port specification may be 'none' to skip
1293 that lp device, or a parport name such as
1294 'parport0'. Specifying 'lp=auto' instead of a
1295 port specification list means that device IDs
1296 from each port should be examined, to see if
1297 an IEEE 1284-compliant printer is attached; if
1298 so, the driver will manage that printer.
1299 See also header of drivers/char/lp.c.
1302 Sets loops_per_jiffy to given constant, thus avoiding
1303 time-consuming boot-time autodetection (up to 250 ms per
1304 CPU). 0 enables autodetection (default). To determine
1305 the correct value for your kernel, boot with normal
1306 autodetection and see what value is printed. Note that
1307 on SMP systems the preset will be applied to all CPUs,
1308 which is likely to cause problems if your CPUs need
1309 significantly divergent settings. An incorrect value
1310 will cause delays in the kernel to be wrong, leading to
1311 unpredictable I/O errors and other breakage. Although
1312 unlikely, in the extreme case this might damage your
1316 Format: <io>,<irq>,<dma>
1318 machvec= [IA64] Force the use of a particular machine-vector
1319 (machvec) in a generic kernel.
1320 Example: machvec=hpzx1_swiotlb
1322 machtype= [Loongson] Share the same kernel image file between different
1324 Example: machtype=lemote-yeeloong-2f-7inch
1326 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1327 than or equal to this physical address is ignored.
1329 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1330 should make use of. maxcpus=n : n >= 0 limits the
1331 kernel to using 'n' processors. n=0 is a special case,
1332 it is equivalent to "nosmp", which also disables
1335 max_loop= [LOOP] Maximum number of loopback devices that can
1341 mce [X86-32] Machine Check Exception
1343 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1345 md= [HW] RAID subsystems devices and level
1346 See Documentation/md.txt.
1349 Format: <first>,<last>
1350 Specifies range of consoles to be captured by the MDA.
1352 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1353 Amount of memory to be used when the kernel is not able
1354 to see the whole system memory or for test.
1355 [X86-32] Use together with memmap= to avoid physical
1356 address space collisions. Without memmap= PCI devices
1357 could be placed at addresses belonging to unused RAM.
1359 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1363 [KNL,SH] Allow user to override the default size for
1364 per-device physically contiguous DMA buffers.
1366 memmap=exactmap [KNL,X86] Enable setting of an exact
1367 E820 memory map, as specified by the user.
1368 Such memmap=exactmap lines can be constructed based on
1369 BIOS output or other requirements. See the memmap=nn@ss
1372 memmap=nn[KMG]@ss[KMG]
1373 [KNL] Force usage of a specific region of memory
1374 Region of memory to be used, from ss to ss+nn.
1376 memmap=nn[KMG]#ss[KMG]
1377 [KNL,ACPI] Mark specific memory as ACPI data.
1378 Region of memory to be used, from ss to ss+nn.
1380 memmap=nn[KMG]$ss[KMG]
1381 [KNL,ACPI] Mark specific memory as reserved.
1382 Region of memory to be used, from ss to ss+nn.
1383 Example: Exclude memory from 0x18690000-0x1869ffff
1384 memmap=64K$0x18690000
1386 memmap=0x10000$0x18690000
1388 memory_corruption_check=0/1 [X86]
1389 Some BIOSes seem to corrupt the first 64k of
1390 memory when doing things like suspend/resume.
1391 Setting this option will scan the memory
1392 looking for corruption. Enabling this will
1393 both detect corruption and prevent the kernel
1394 from using the memory being corrupted.
1395 However, its intended as a diagnostic tool; if
1396 repeatable BIOS-originated corruption always
1397 affects the same memory, you can use memmap=
1398 to prevent the kernel from using that memory.
1400 memory_corruption_check_size=size [X86]
1401 By default it checks for corruption in the low
1402 64k, making this memory unavailable for normal
1403 use. Use this parameter to scan for
1404 corruption in more or less memory.
1406 memory_corruption_check_period=seconds [X86]
1407 By default it checks for corruption every 60
1408 seconds. Use this parameter to check at some
1409 other rate. 0 disables periodic checking.
1411 memtest= [KNL,X86] Enable memtest
1413 default : 0 <disable>
1414 Specifies the number of memtest passes to be
1415 performed. Each pass selects another test
1416 pattern from a given set of patterns. Memtest
1417 fills the memory with this pattern, validates
1418 memory contents and reserves bad memory
1419 regions that are detected.
1421 meye.*= [HW] Set MotionEye Camera parameters
1422 See Documentation/video4linux/meye.txt.
1424 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1425 Multi-Function General Purpose Timers on AMD Geode
1428 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1429 the BIOS has incorrectly applied a workaround. TinyBIOS
1430 version 0.98 is known to be affected, 0.99 fixes the
1431 problem by letting the user disable the workaround.
1435 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1436 physical address is ignored.
1438 mini2440= [ARM,HW,KNL]
1439 Format:[0..2][b][c][t]
1441 MINI2440 configuration specification:
1442 0 - The attached screen is the 3.5" TFT
1443 1 - The attached screen is the 7" TFT
1444 2 - The VGA Shield is attached (1024x768)
1445 Leaving out the screen size parameter will not load
1446 the TFT driver, and the framebuffer will be left
1448 b - Enable backlight. The TFT backlight pin will be
1449 linked to the kernel VESA blanking code and a GPIO
1450 LED. This parameter is not necessary when using the
1452 c - Enable the s3c camera interface.
1453 t - Reserved for enabling touchscreen support. The
1454 touchscreen support is not enabled in the mainstream
1455 kernel as of 2.6.30, a preliminary port can be found
1456 in the "bleeding edge" mini2440 support kernel at
1457 http://repo.or.cz/w/linux-2.6/mini2440.git
1460 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1461 parameter allows control of the logging verbosity for
1462 the additional memory initialisation checks. A value
1463 of 0 disables mminit logging and a level of 4 will
1464 log everything. Information is printed at KERN_DEBUG
1465 so loglevel=8 may also need to be specified.
1468 [MOUSE] Maximum time between finger touching and
1469 leaving touchpad surface for touch to be considered
1470 a tap and be reported as a left button click (for
1471 touchpads working in absolute mode only).
1473 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1474 reporting absolute coordinates, such as tablets
1475 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1476 reporting absolute coordinates, such as tablets
1478 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1479 is similar to kernelcore except it specifies the
1480 amount of memory used for migratable allocations.
1481 If both kernelcore and movablecore is specified,
1482 then kernelcore will be at *least* the specified
1483 value but may be more. If movablecore on its own
1484 is specified, the administrator must be careful
1485 that the amount of memory usable for all allocations
1488 MTD_Partition= [MTD]
1489 Format: <name>,<region-number>,<size>,<offset>
1491 MTD_Region= [MTD] Format:
1492 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1495 See drivers/mtd/cmdlinepart.c.
1497 multitce=off [PPC] This parameter disables the use of the pSeries
1498 firmware feature for updating multiple TCE entries
1501 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1503 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1505 boundary - index of last SLC block on Flex-OneNAND.
1506 The remaining blocks are configured as MLC blocks.
1507 lock - Configure if Flex-OneNAND boundary should be locked.
1508 Once locked, the boundary cannot be changed.
1509 1 indicates lock status, 0 indicates unlock status.
1512 ARM/S3C2412 JIVE boot control
1514 See arch/arm/mach-s3c2412/mach-jive.c
1516 mtouchusb.raw_coordinates=
1517 [HW] Make the MicroTouch USB driver use raw coordinates
1518 ('y', default) or cooked coordinates ('n')
1520 mtrr_chunk_size=nn[KMG] [X86]
1521 used for mtrr cleanup. It is largest continuous chunk
1522 that could hold holes aka. UC entries.
1524 mtrr_gran_size=nn[KMG] [X86]
1525 Used for mtrr cleanup. It is granularity of mtrr block.
1527 Large value could prevent small alignment from
1530 mtrr_spare_reg_nr=n [X86]
1532 Range: 0,7 : spare reg number
1534 Used for mtrr cleanup. It is spare mtrr entries number.
1535 Set to 2 or more if your graphical card needs more.
1537 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1539 netdev= [NET] Network devices parameters
1540 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1541 Note that mem_start is often overloaded to mean
1542 something different and driver-specific.
1543 This usage is only documented in each driver source
1547 [NETFILTER] Enable connection tracking flow accounting
1548 0 to disable accounting
1549 1 to enable accounting
1552 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1553 See Documentation/filesystems/nfs/nfsroot.txt.
1555 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1556 See Documentation/filesystems/nfs/nfsroot.txt.
1558 nfsrootdebug [NFS] enable nfsroot debugging messages.
1559 See Documentation/filesystems/nfs/nfsroot.txt.
1561 nfs.callback_tcpport=
1562 [NFS] set the TCP port on which the NFSv4 callback
1563 channel should listen.
1566 [NFS] sets the pathname to the program which is used
1567 to update the NFS client cache entries.
1569 nfs.cache_getent_timeout=
1570 [NFS] sets the timeout after which an attempt to
1571 update a cache entry is deemed to have failed.
1573 nfs.idmap_cache_timeout=
1574 [NFS] set the maximum lifetime for idmapper cache
1578 [NFS] enable 64-bit inode numbers.
1579 If zero, the NFS client will fake up a 32-bit inode
1580 number for the readdir() and stat() syscalls instead
1581 of returning the full 64-bit number.
1582 The default is to return 64-bit inode numbers.
1584 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1585 when a NMI is triggered.
1586 Format: [state][,regs][,debounce][,die]
1588 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1589 Format: [panic,][num]
1591 0 - turn nmi_watchdog off
1592 When panic is specified, panic when an NMI watchdog
1594 This is useful when you use a panic=... timeout and
1595 need the box quickly up again.
1597 netpoll.carrier_timeout=
1598 [NET] Specifies amount of time (in seconds) that
1599 netpoll should wait for a carrier. By default netpoll
1602 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1603 emulation library even if a 387 maths coprocessor
1607 [HW] Never suspend the console
1608 Disable suspending of consoles during suspend and
1609 hibernate operations. Once disabled, debugging
1610 messages can reach various consoles while the rest
1611 of the system is being put to sleep (ie, while
1612 debugging driver suspend/resume hooks). This may
1613 not work reliably with all consoles, but is known
1614 to work with serial and VGA consoles.
1616 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1617 caches in the slab allocator. Saves per-node memory,
1618 but will impact performance.
1622 noapic [SMP,APIC] Tells the kernel to not make use of any
1623 IOAPICs that may be present in the system.
1625 noautogroup Disable scheduler automatic task group creation.
1627 nobats [PPC] Do not use BATs for mapping kernel lowmem
1628 on "Classic" PPC cores.
1632 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1634 nodelayacct [KNL] Disable per-task delay accounting
1636 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1638 nodsp [SH] Disable hardware DSP at boot time.
1640 noefi [X86] Disable EFI runtime services support.
1645 On X86-32 available only on PAE configured kernels.
1646 noexec=on: enable non-executable mappings (default)
1647 noexec=off: disable non-executable mappings
1650 This affects only 32-bit executables.
1651 noexec32=on: enable non-executable mappings (default)
1652 read doesn't imply executable mappings
1653 noexec32=off: disable non-executable mappings
1654 read implies executable mappings
1656 nofpu [SH] Disable hardware FPU at boot time.
1658 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1659 register save and restore. The kernel will only save
1660 legacy floating-point registers on task switch.
1662 noxsave [BUGS=X86] Disables x86 extended register state save
1663 and restore using xsave. The kernel will fallback to
1664 enabling legacy floating-point and sse state.
1666 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1667 wfi(ARM) instruction doesn't work correctly and not to
1668 use it. This is also useful when using JTAG debugger.
1670 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1671 instruction doesn't work correctly and not to
1674 no_file_caps Tells the kernel not to honor file capabilities. The
1675 only way then for a file to be executed with privilege
1676 is to be setuid root or executed by root.
1678 nohalt [IA-64] Tells the kernel not to use the power saving
1679 function PAL_HALT_LIGHT when idle. This increases
1680 power-consumption. On the positive side, it reduces
1681 interrupt wake-up latency, which may improve performance
1682 in certain environments such as networked servers or
1685 nohz= [KNL] Boottime enable/disable dynamic ticks
1686 Valid arguments: on, off
1689 noiotrap [SH] Disables trapped I/O port accesses.
1691 noirqdebug [X86-32] Disables the code which attempts to detect and
1692 disable unhandled interrupt sources.
1694 no_timer_check [X86,APIC] Disables the code which tests for
1695 broken timer IRQ sources.
1697 noisapnp [ISAPNP] Disables ISA PnP code.
1699 noinitrd [RAM] Tells the kernel not to load any configured
1702 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1704 [Deprecated - use intremap=off]
1708 nojitter [IA64] Disables jitter checking for ITC timers.
1710 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1712 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1714 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1716 noltlbs [PPC] Do not use large page/tlb entries for kernel
1717 lowmem mapping on PPC40x.
1719 nomca [IA-64] Disable machine check abort handling
1721 nomce [X86-32] Machine Check Exception
1723 nomfgpt [X86-32] Disable Multi-Function General Purpose
1724 Timer usage (for AMD Geode machines).
1726 nopat [X86] Disable PAT (page attribute table extension of
1727 pagetables) support.
1729 norandmaps Don't use address space randomization. Equivalent to
1730 echo 0 > /proc/sys/kernel/randomize_va_space
1732 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1734 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1735 with UP alternatives
1737 noresidual [PPC] Don't use residual data on PReP machines.
1739 noresume [SWSUSP] Disables resume and restores original swap
1742 no-scroll [VGA] Disables scrollback.
1743 This is required for the Braillex ib80-piezo Braille
1744 reader made by F.H. Papenmeier (Germany).
1748 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1750 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1751 and disable the IO APIC. legacy for "maxcpus=0".
1753 nosoftlockup [KNL] Disable the soft-lockup detector.
1755 noswapaccount [KNL] Disable accounting of swap in memory resource
1756 controller. (See Documentation/cgroups/memory.txt)
1758 nosync [HW,M68K] Disables sync negotiation for all devices.
1760 notsc [BUGS=X86-32] Disable Time Stamp Counter
1762 nousb [USB] Disable the USB subsystem
1764 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1768 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1770 nptcg= [IA64] Override max number of concurrent global TLB
1771 purges which is reported from either PAL_VM_SUMMARY or
1774 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1775 could support. nr_cpus=n : n >= 1 limits the kernel to
1776 supporting 'n' processors. Later in runtime you can not
1777 use hotplug cpu feature to put more cpu back to online.
1778 just like you compile the kernel NR_CPUS=n
1780 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1782 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1783 one of ['zone', 'node', 'default'] can be specified
1784 This can be set from sysctl after boot.
1785 See Documentation/sysctl/vm.txt for details.
1787 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1788 See Documentation/debugging-via-ohci1394.txt for more
1791 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1792 Rather than timing out after 20 ms if an EC
1793 command is not properly ACKed, override the length
1794 of the timeout. We have interrupts disabled while
1795 waiting for the ACK, so if this is set too high
1796 interrupts *may* be lost!
1798 omap_mux= [OMAP] Override bootloader pin multiplexing.
1799 Format: <mux_mode0.mode_name=value>...
1800 For example, to override I2C bus2:
1801 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1803 oprofile.timer= [HW]
1804 Use timer interrupt instead of performance counters
1806 oprofile.cpu_type= Force an oprofile cpu type
1807 This might be useful if you have an older oprofile
1808 userland or if you want common events.
1809 Format: { arch_perfmon }
1810 arch_perfmon: [X86] Force use of architectural
1811 perfmon on Intel CPUs instead of the
1812 CPU specific event set.
1815 See Documentation/sound/oss/oss-parameters.txt
1817 panic= [KNL] Kernel behaviour on panic
1820 parkbd.port= [HW] Parallel port number the keyboard adapter is
1821 connected to, default is 0.
1823 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1824 0 for XT, 1 for AT (default is AT).
1827 parport= [HW,PPT] Specify parallel ports. 0 disables.
1828 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1829 Use 'auto' to force the driver to use any
1830 IRQ/DMA settings detected (the default is to
1831 ignore detected IRQ/DMA settings because of
1832 possible conflicts). You can specify the base
1833 address, IRQ, and DMA settings; IRQ and DMA
1834 should be numbers, or 'auto' (for using detected
1835 settings on that particular port), or 'nofifo'
1836 (to avoid using a FIFO even if it is detected).
1837 Parallel ports are assigned in the order they
1838 are specified on the command line, starting
1841 parport_init_mode= [HW,PPT]
1842 Configure VIA parallel port to operate in
1843 a specific mode. This is necessary on Pegasos
1844 computer where firmware has no options for setting
1845 up parallel port mode and sets it to spp.
1846 Currently this function knows 686a and 8231 chips.
1847 Format: [spp|ps2|epp|ecp|ecpepp]
1850 Halt all CPUs after the first oops has been printed for
1851 the specified number of seconds. This is to be used if
1852 your oopses keep scrolling off the screen.
1857 See header of drivers/block/paride/pcd.c.
1858 See also Documentation/blockdev/paride.txt.
1860 pci=option[,option...] [PCI] various PCI subsystem options:
1861 earlydump [X86] dump PCI config space before the kernel
1863 off [X86] don't probe for the PCI bus
1864 bios [X86-32] force use of PCI BIOS, don't access
1865 the hardware directly. Use this if your machine
1866 has a non-standard PCI host bridge.
1867 nobios [X86-32] disallow use of PCI BIOS, only direct
1868 hardware access methods are allowed. Use this
1869 if you experience crashes upon bootup and you
1870 suspect they are caused by the BIOS.
1871 conf1 [X86] Force use of PCI Configuration
1873 conf2 [X86] Force use of PCI Configuration
1875 noaer [PCIE] If the PCIEAER kernel config parameter is
1876 enabled, this kernel boot option can be used to
1877 disable the use of PCIE advanced error reporting.
1878 nodomains [PCI] Disable support for multiple PCI
1879 root domains (aka PCI segments, in ACPI-speak).
1880 nommconf [X86] Disable use of MMCONFIG for PCI
1882 check_enable_amd_mmconf [X86] check for and enable
1883 properly configured MMIO access to PCI
1884 config space on AMD family 10h CPU
1885 nomsi [MSI] If the PCI_MSI kernel config parameter is
1886 enabled, this kernel boot option can be used to
1887 disable the use of MSI interrupts system-wide.
1888 noioapicquirk [APIC] Disable all boot interrupt quirks.
1889 Safety option to keep boot IRQs enabled. This
1890 should never be necessary.
1891 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1892 primary IO-APIC for bridges that cannot disable
1893 boot IRQs. This fixes a source of spurious IRQs
1894 when the system masks IRQs.
1895 noioapicreroute [APIC] Disable workaround that uses the
1896 boot IRQ equivalent of an IRQ that connects to
1897 a chipset where boot IRQs cannot be disabled.
1898 The opposite of ioapicreroute.
1899 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1900 routing table. These calls are known to be buggy
1901 on several machines and they hang the machine
1902 when used, but on other computers it's the only
1903 way to get the interrupt routing table. Try
1904 this option if the kernel is unable to allocate
1905 IRQs or discover secondary PCI buses on your
1907 rom [X86] Assign address space to expansion ROMs.
1908 Use with caution as certain devices share
1909 address decoders between ROMs and other
1911 norom [X86] Do not assign address space to
1912 expansion ROMs that do not already have
1913 BIOS assigned address ranges.
1914 nobar [X86] Do not assign address space to the
1915 BARs that weren't assigned by the BIOS.
1916 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1917 assigned automatically to PCI devices. You can
1918 make the kernel exclude IRQs of your ISA cards
1920 pirqaddr=0xAAAAA [X86] Specify the physical address
1921 of the PIRQ table (normally generated
1922 by the BIOS) if it is outside the
1923 F0000h-100000h range.
1924 lastbus=N [X86] Scan all buses thru bus #N. Can be
1925 useful if the kernel is unable to find your
1926 secondary buses and you want to tell it
1927 explicitly which ones they are.
1928 assign-busses [X86] Always assign all PCI bus
1929 numbers ourselves, overriding
1930 whatever the firmware may have done.
1931 usepirqmask [X86] Honor the possible IRQ mask stored
1932 in the BIOS $PIR table. This is needed on
1933 some systems with broken BIOSes, notably
1934 some HP Pavilion N5400 and Omnibook XE3
1935 notebooks. This will have no effect if ACPI
1936 IRQ routing is enabled.
1937 noacpi [X86] Do not use ACPI for IRQ routing
1938 or for PCI scanning.
1939 use_crs [X86] Use PCI host bridge window information
1940 from ACPI. On BIOSes from 2008 or later, this
1941 is enabled by default. If you need to use this,
1942 please report a bug.
1943 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1944 If you need to use this, please report a bug.
1945 routeirq Do IRQ routing for all PCI devices.
1946 This is normally done in pci_enable_device(),
1947 so this option is a temporary workaround
1948 for broken drivers that don't call it.
1949 skip_isa_align [X86] do not align io start addr, so can
1950 handle more pci cards
1951 firmware [ARM] Do not re-enumerate the bus but instead
1952 just use the configuration from the
1953 bootloader. This is currently used on
1954 IXP2000 systems where the bus has to be
1955 configured a certain way for adjunct CPUs.
1956 noearly [X86] Don't do any early type 1 scanning.
1957 This might help on some broken boards which
1958 machine check when some devices' config space
1959 is read. But various workarounds are disabled
1960 and some IOMMU drivers will not work.
1961 bfsort Sort PCI devices into breadth-first order.
1962 This sorting is done to get a device
1963 order compatible with older (<= 2.4) kernels.
1964 nobfsort Don't sort PCI devices into breadth-first order.
1965 cbiosize=nn[KMG] The fixed amount of bus space which is
1966 reserved for the CardBus bridge's IO window.
1967 The default value is 256 bytes.
1968 cbmemsize=nn[KMG] The fixed amount of bus space which is
1969 reserved for the CardBus bridge's memory
1970 window. The default value is 64 megabytes.
1973 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1974 Specifies alignment and device to reassign
1975 aligned memory resources.
1976 If <order of align> is not specified,
1977 PAGE_SIZE is used as alignment.
1978 PCI-PCI bridge can be specified, if resource
1979 windows need to be expanded.
1980 ecrc= Enable/disable PCIe ECRC (transaction layer
1981 end-to-end CRC checking).
1982 bios: Use BIOS/firmware settings. This is the
1987 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1990 force Enable ASPM even on devices that claim not to support it.
1991 WARNING: Forcing ASPM on may cause system lockups.
1993 pcie_ports= [PCIE] PCIe ports handling:
1994 auto Ask the BIOS whether or not to use native PCIe services
1995 associated with PCIe ports (PME, hot-plug, AER). Use
1996 them only if that is allowed by the BIOS.
1997 native Use native PCIe services associated with PCIe ports
1999 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2002 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2003 nomsi Do not use MSI for native PCIe PME signaling (this makes
2004 all PCIe root ports use INTx for all services).
2006 pcmv= [HW,PCMCIA] BadgePAD 4
2009 See Documentation/blockdev/paride.txt.
2011 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2014 See arch/parisc/kernel/pdc_chassis.c
2016 percpu_alloc= Select which percpu first chunk allocator to use.
2017 Currently supported values are "embed" and "page".
2018 Archs may support subset or none of the selections.
2019 See comments in mm/percpu.c for details on each
2020 allocator. This parameter is primarily for debugging
2021 and performance comparison.
2024 See Documentation/blockdev/paride.txt.
2027 See Documentation/blockdev/paride.txt.
2029 pirq= [SMP,APIC] Manual mp-table setup
2030 See Documentation/x86/i386/IO-APIC.txt.
2032 plip= [PPT,NET] Parallel port network link
2033 Format: { parport<nr> | timid | 0 }
2034 See also Documentation/parport.txt.
2036 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2037 Override pmtimer IOPort with a hex value.
2041 Enable PNP debug messages. This depends on the
2042 CONFIG_PNP_DEBUG_MESSAGES option.
2048 { on | off | curr | res | no-curr | no-res }
2051 [ISAPNP] Exclude IRQs for the autoconfiguration
2054 [ISAPNP] Exclude DMAs for the autoconfiguration
2056 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2057 Ranges are in pairs (I/O port base and size).
2060 [ISAPNP] Exclude memory regions for the
2062 Ranges are in pairs (memory base and size).
2064 ports= [IP_VS_FTP] IPVS ftp helper module
2066 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2068 Format: <port>,<port>....
2070 print-fatal-signals=
2071 [KNL] debug: print fatal signals
2073 If enabled, warn about various signal handling
2074 related application anomalies: too many signals,
2075 too many POSIX.1 timers, fatal signals causing a
2078 If you hit the warning due to signal overflow,
2079 you might want to try "ulimit -i unlimited".
2083 printk.time= Show timing data prefixed to each printk message line
2084 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2086 processor.max_cstate= [HW,ACPI]
2087 Limit processor to maximum C-state
2088 max_cstate=9 overrides any DMI blacklist limit.
2090 processor.nocst [HW,ACPI]
2091 Ignore the _CST method to determine C-states,
2092 instead using the legacy FADT method
2094 profile= [KNL] Enable kernel profiling via /proc/profile
2095 Format: [schedule,]<number>
2096 Param: "schedule" - profile schedule points.
2097 Param: <number> - step/bucket size as a power of 2 for
2098 statistical time based profiling.
2099 Param: "sleep" - profile D-state sleeping (millisecs).
2100 Requires CONFIG_SCHEDSTATS
2101 Param: "kvm" - profile VM exits.
2103 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2105 See Documentation/blockdev/ramdisk.txt.
2107 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2108 probe for; one of (bare|imps|exps|lifebook|any).
2109 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2111 psmouse.resetafter= [HW,MOUSE]
2112 Try to reset the device after so many bad packets
2115 [HW,MOUSE] Set desired mouse resolution, in dpi.
2116 psmouse.smartscroll=
2117 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2118 0 = disabled, 1 = enabled (default).
2121 See Documentation/blockdev/paride.txt.
2124 [KNL] Number of legacy pty's. Overwrites compiled-in
2127 quiet [KNL] Disable most log messages
2132 See Documentation/md.txt.
2134 ramdisk_blocksize= [RAM]
2135 See Documentation/blockdev/ramdisk.txt.
2137 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2138 See Documentation/blockdev/ramdisk.txt.
2140 rcupdate.blimit= [KNL,BOOT]
2141 Set maximum number of finished RCU callbacks to process
2144 rcupdate.qhimark= [KNL,BOOT]
2145 Set threshold of queued
2146 RCU callbacks over which batch limiting is disabled.
2148 rcupdate.qlowmark= [KNL,BOOT]
2149 Set threshold of queued RCU callbacks below which
2150 batch limiting is re-enabled.
2154 Run specified binary instead of /init from the ramdisk,
2155 used for early userspace startup. See initrd.
2157 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2158 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2159 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2162 [KNL, SMP] Set scheduler's default relax_domain_level.
2163 See Documentation/cgroups/cpusets.txt.
2165 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2167 reservetop= [X86-32]
2169 Reserves a hole at the top of the kernel virtual
2174 Set the amount of memory to reserve for BIOS at
2175 the bottom of the address space.
2177 reset_devices [KNL] Force drivers to reset the underlying device
2178 during initialization.
2181 Specify the partition device for software suspend
2183 resume_offset= [SWSUSP]
2184 Specify the offset from the beginning of the partition
2185 given by "resume=" at which the swap header is located,
2186 in <PAGE_SIZE> units (needed only for swap files).
2187 See Documentation/power/swsusp-and-swap-files.txt
2189 hibernate= [HIBERNATION]
2190 noresume Don't check if there's a hibernation image
2191 present during boot.
2192 nocompress Don't compress/decompress hibernation images.
2194 retain_initrd [RAM] Keep initrd memory after extraction
2196 rhash_entries= [KNL,NET]
2197 Set number of hash buckets for route cache
2199 riscom8= [HW,SERIAL]
2200 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2202 ro [KNL] Mount root device read-only on boot
2204 root= [KNL] Root filesystem
2206 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2207 mount the root filesystem
2209 rootflags= [KNL] Set root filesystem mount option string
2211 rootfstype= [KNL] Set root filesystem type
2213 rootwait [KNL] Wait (indefinitely) for root device to show up.
2214 Useful for devices that are detected asynchronously
2215 (e.g. USB and MMC devices).
2217 rw [KNL] Mount root device read-write on boot
2219 S [KNL] Run init in single mode
2222 See drivers/net/irda/sa1100_ir.c.
2224 sbni= [NET] Granch SBNI12 leased line adapter
2226 sched_debug [KNL] Enables verbose scheduler debug messages.
2228 security= [SECURITY] Choose a security module to enable at boot.
2229 If this boot parameter is not specified, only the first
2230 security module asking for security registration will be
2231 loaded. An invalid security module name will be treated
2232 as if no module has been chosen.
2234 selinux= [SELINUX] Disable or enable SELinux at boot time.
2235 Format: { "0" | "1" }
2236 See security/selinux/Kconfig help text.
2239 Default value is set via kernel config option.
2240 If enabled at boot time, /selinux/disable can be used
2241 later to disable prior to initial policy load.
2243 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2244 Format: { "0" | "1" }
2245 See security/apparmor/Kconfig help text
2248 Default value is set via kernel config option.
2250 serialnumber [BUGS=X86-32]
2253 Maximal number of shapers.
2255 show_msr= [x86] show boot-time MSR settings
2256 Format: { <integer> }
2257 Show boot-time (BIOS-initialized) MSR settings.
2258 The parameter means the number of CPUs to show,
2259 for example 1 means boot CPU only.
2266 slub_debug[=options[,slabs]] [MM, SLUB]
2267 Enabling slub_debug allows one to determine the
2268 culprit if slab objects become corrupted. Enabling
2269 slub_debug can create guard zones around objects and
2270 may poison objects when not in use. Also tracks the
2271 last alloc / free. For more information see
2272 Documentation/vm/slub.txt.
2274 slub_max_order= [MM, SLUB]
2275 Determines the maximum allowed order for slabs.
2276 A high setting may cause OOMs due to memory
2277 fragmentation. For more information see
2278 Documentation/vm/slub.txt.
2280 slub_min_objects= [MM, SLUB]
2281 The minimum number of objects per slab. SLUB will
2282 increase the slab order up to slub_max_order to
2283 generate a sufficiently large slab able to contain
2284 the number of objects indicated. The higher the number
2285 of objects the smaller the overhead of tracking slabs
2286 and the less frequently locks need to be acquired.
2287 For more information see Documentation/vm/slub.txt.
2289 slub_min_order= [MM, SLUB]
2290 Determines the mininum page order for slabs. Must be
2291 lower than slub_max_order.
2292 For more information see Documentation/vm/slub.txt.
2294 slub_nomerge [MM, SLUB]
2295 Disable merging of slabs with similar size. May be
2296 necessary if there is some reason to distinguish
2297 allocs to different slabs. Debug options disable
2298 merging on their own.
2299 For more information see Documentation/vm/slub.txt.
2302 Format: <io1>[,<io2>[,...,<io8>]]
2304 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2305 attempt to substitute SMP alternatives once at boot.
2307 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2308 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2309 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2310 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2311 smsc-ircc2.ircc_irq= [HW] IRQ line
2312 smsc-ircc2.ircc_dma= [HW] DMA channel
2313 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2314 0: Toshiba Satellite 1800 (GP data pin select)
2315 1: Fast pin select (default)
2319 [KNL] Should the soft-lockup detector generate panics.
2321 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2322 See Documentation/sonypi.txt
2324 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2325 See Documentation/serial/specialix.txt.
2327 spia_io_base= [HW,MTD]
2333 Enabled the stack tracer on boot up.
2337 Set the STI (builtin display/keyboard on the HP-PARISC
2338 machines) console (graphic card) which should be used
2339 as the initial boot-console.
2340 See also comment in drivers/video/console/sticore.c.
2343 See comment in drivers/video/console/sticore.c.
2346 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2348 sunrpc.min_resvport=
2349 sunrpc.max_resvport=
2351 SunRPC servers often require that client requests
2352 originate from a privileged port (i.e. a port in the
2353 range 0 < portnr < 1024).
2354 An administrator who wishes to reserve some of these
2355 ports for other uses may adjust the range that the
2356 kernel's sunrpc client considers to be privileged
2357 using these two parameters to set the minimum and
2358 maximum port values.
2362 Control how the NFS server code allocates CPUs to
2363 service thread pools. Depending on how many NICs
2364 you have and where their interrupts are bound, this
2365 option will affect which CPUs will do NFS serving.
2366 Note: this parameter cannot be changed while the
2367 NFS server is running.
2369 auto the server chooses an appropriate mode
2370 automatically using heuristics
2371 global a single global pool contains all CPUs
2372 percpu one pool for each CPU
2373 pernode one pool for each NUMA node (equivalent
2374 to global on non-NUMA machines)
2376 sunrpc.tcp_slot_table_entries=
2377 sunrpc.udp_slot_table_entries=
2379 Sets the upper limit on the number of simultaneous
2380 RPC calls that can be sent from the client to a
2381 server. Increasing these values may allow you to
2382 improve throughput, but will also increase the
2383 amount of memory reserved for use by the client.
2386 [KNL] Enable accounting of swap in memory resource
2387 controller if no parameter or 1 is given or disable
2388 it if 0 is given (See Documentation/cgroups/memory.txt)
2390 swiotlb= [IA-64] Number of I/O TLB slabs
2394 sysfs.deprecated=0|1 [KNL]
2395 Enable/disable old style sysfs layout for old udev
2396 on older distributions. When this option is enabled
2397 very new udev will not work anymore. When this option
2398 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2399 in older udev will not work anymore.
2400 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2401 the kernel configuration.
2403 sysrq_always_enabled
2405 Ignore sysrq setting - this boot parameter will
2406 neutralize any effect of /proc/sys/kernel/sysrq.
2407 Useful for debugging.
2411 test_suspend= [SUSPEND]
2412 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2413 standby suspend) as the system sleep state to briefly
2414 enter during system startup. The system is woken from
2415 this state using a wakeup-capable RTC alarm.
2417 thash_entries= [KNL,NET]
2418 Set number of hash buckets for TCP connection
2420 thermal.act= [HW,ACPI]
2421 -1: disable all active trip points in all thermal zones
2422 <degrees C>: override all lowest active trip points
2424 thermal.crt= [HW,ACPI]
2425 -1: disable all critical trip points in all thermal zones
2426 <degrees C>: override all critical trip points
2428 thermal.nocrt= [HW,ACPI]
2429 Set to disable actions on ACPI thermal zone
2430 critical and hot trip points.
2432 thermal.off= [HW,ACPI]
2433 1: disable ACPI thermal control
2435 thermal.psv= [HW,ACPI]
2436 -1: disable all passive trip points
2437 <degrees C>: override all passive trip points to this
2440 thermal.tzp= [HW,ACPI]
2441 Specify global default ACPI thermal zone polling rate
2442 <deci-seconds>: poll all this frequency
2443 0: no polling (default)
2447 Specify if the kernel should make use of the cpu
2448 topology informations if the hardware supports these.
2449 The scheduler will make use of these informations and
2450 e.g. base its process migration decisions on it.
2455 tpm_suspend_pcr=[HW,TPM]
2456 Format: integer pcr id
2457 Specify that at suspend time, the tpm driver
2458 should extend the specified pcr with zeros,
2459 as a workaround for some chips which fail to
2460 flush the last written pcr on TPM_SaveState.
2461 This will guarantee that all the other pcrs
2464 trace_buf_size=nn[KMG]
2465 [FTRACE] will set tracing buffer size.
2467 trace_event=[event-list]
2468 [FTRACE] Set and start specified trace events in order
2469 to facilitate early boot debugging.
2470 See also Documentation/trace/events.txt
2472 tsc= Disable clocksource stability checks for TSC.
2474 [x86] reliable: mark tsc clocksource as reliable, this
2475 disables clocksource verification at runtime, as well
2476 as the stability checks done at bootup. Used to enable
2477 high-resolution timer mode on older hardware, and in
2478 virtualized environment.
2479 [x86] noirqtime: Do not use TSC to do irq accounting.
2480 Used to run time disable IRQ_TIME_ACCOUNTING on any
2481 platforms where RDTSC is slow and this accounting
2484 turbografx.map[2|3]= [HW,JOY]
2485 TurboGraFX parallel port interface
2487 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2488 See also Documentation/input/joystick-parport.txt
2490 uhash_entries= [KNL,NET]
2491 Set number of hash buckets for UDP/UDP-Lite connections
2494 [USB] Ignore overcurrent events (default N).
2495 Some badly-designed motherboards generate lots of
2496 bogus events, for ports that aren't wired to
2497 anything. Set this parameter to avoid log spamming.
2498 Note that genuine overcurrent events won't be
2503 Set unknown_nmi_panic=1 early on boot.
2505 usbcore.autosuspend=
2506 [USB] The autosuspend time delay (in seconds) used
2507 for newly-detected USB devices (default 2). This
2508 is the time required before an idle device will be
2509 autosuspended. Devices for which the delay is set
2510 to a negative value won't be autosuspended at all.
2512 usbcore.usbfs_snoop=
2513 [USB] Set to log all usbfs traffic (default 0 = off).
2515 usbcore.blinkenlights=
2516 [USB] Set to cycle leds on hubs (default 0 = off).
2518 usbcore.old_scheme_first=
2519 [USB] Start with the old device initialization
2520 scheme (default 0 = off).
2522 usbcore.use_both_schemes=
2523 [USB] Try the other device initialization scheme
2524 if the first one fails (default 1 = enabled).
2526 usbcore.initial_descriptor_timeout=
2527 [USB] Specifies timeout for the initial 64-byte
2528 USB_REQ_GET_DESCRIPTOR request in milliseconds
2529 (default 5000 = 5.0 seconds).
2532 [USBHID] The interval which mice are to be polled at.
2534 usb-storage.delay_use=
2535 [UMS] The delay in seconds before a new device is
2536 scanned for Logical Units (default 5).
2539 [UMS] A list of quirks entries to supplement or
2540 override the built-in unusual_devs list. List
2541 entries are separated by commas. Each entry has
2542 the form VID:PID:Flags where VID and PID are Vendor
2543 and Product ID values (4-digit hex numbers) and
2544 Flags is a set of characters, each corresponding
2545 to a common usb-storage quirk flag as follows:
2546 a = SANE_SENSE (collect more than 18 bytes
2548 b = BAD_SENSE (don't collect more than 18
2549 bytes of sense data);
2550 c = FIX_CAPACITY (decrease the reported
2551 device capacity by one sector);
2552 h = CAPACITY_HEURISTICS (decrease the
2553 reported device capacity by one
2554 sector if the number is odd);
2555 i = IGNORE_DEVICE (don't bind to this
2557 l = NOT_LOCKABLE (don't try to lock and
2558 unlock ejectable media);
2559 m = MAX_SECTORS_64 (don't transfer more
2560 than 64 sectors = 32 KB at a time);
2561 o = CAPACITY_OK (accept the capacity
2562 reported by the device);
2563 r = IGNORE_RESIDUE (the device reports
2564 bogus residue values);
2565 s = SINGLE_LUN (the device has only one
2567 w = NO_WP_DETECT (don't test whether the
2568 medium is write-protected).
2569 Example: quirks=0419:aaf5:rl,0421:0433:rc
2572 [X86] Flags controlling user PTE allocations.
2574 nohigh = do not allocate PTE pages in
2575 HIGHMEM regardless of setting
2579 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2580 vdso=1: enable VDSO (default)
2581 vdso=0: disable VDSO mapping
2584 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2585 vdso32=1: enable 32-bit VDSO (default)
2586 vdso32=0: disable 32-bit VDSO mapping
2589 vector=percpu: enable percpu vector domain
2591 video= [FB] Frame buffer configuration
2592 See Documentation/fb/modedb.txt.
2594 vga= [BOOT,X86-32] Select a particular video mode
2595 See Documentation/x86/boot.txt and
2596 Documentation/svga.txt.
2597 Use vga=ask for menu.
2598 This is actually a boot loader parameter; the value is
2599 passed to the kernel using a special protocol.
2601 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2602 size of <nn>. This can be used to increase the
2603 minimum size (128MB on x86). It can also be used to
2604 decrease the size and leave more room for directly
2607 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2610 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2613 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2616 vt.cur_default= [VT] Default cursor shape.
2617 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2618 the parameters of the <Esc>[?A;B;Cc escape sequence;
2619 see VGA-softcursor.txt. Default: 2 = underline.
2621 vt.default_blu= [VT]
2622 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2623 Change the default blue palette of the console.
2624 This is a 16-member array composed of values
2627 vt.default_grn= [VT]
2628 Format: <green0>,<green1>,<green2>,...,<green15>
2629 Change the default green palette of the console.
2630 This is a 16-member array composed of values
2633 vt.default_red= [VT]
2634 Format: <red0>,<red1>,<red2>,...,<red15>
2635 Change the default red palette of the console.
2636 This is a 16-member array composed of values
2642 Set system-wide default UTF-8 mode for all tty's.
2643 Default is 1, i.e. UTF-8 mode is enabled for all
2644 newly opened terminals.
2646 vt.global_cursor_default=
2649 Set system-wide default for whether a cursor
2650 is shown on new VTs. Default is -1,
2651 i.e. cursors will be created by default unless
2652 overridden by individual drivers. 0 will hide
2653 cursors, 1 will display them.
2655 watchdog timers [HW,WDT] For information on watchdog timers,
2656 see Documentation/watchdog/watchdog-parameters.txt
2657 or other driver-specific files in the
2658 Documentation/watchdog/ directory.
2660 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2661 default x2apic cluster mode on platforms
2664 x86_mrst_timer= [X86-32,APBT]
2665 Choose timer option for x86 Moorestown MID platform.
2666 Two valid options are apbt timer only and lapic timer
2667 plus one apbt timer for broadcast timer.
2668 x86_mrst_timer=apbt_only | lapic_and_apbt
2670 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2671 xd_geo= See header of drivers/block/xd.c.
2673 xen_emul_unplug= [HW,X86,XEN]
2674 Unplug Xen emulated devices
2675 Format: [unplug0,][unplug1]
2676 ide-disks -- unplug primary master IDE devices
2677 aux-ide-disks -- unplug non-primary-master IDE devices
2678 nics -- unplug network devices
2679 all -- unplug all emulated devices (NICs and IDE disks)
2680 unnecessary -- unplugging emulated devices is
2681 unnecessary even if the host did not respond to
2683 never -- do not unplug even if version check succeeds
2685 xirc2ps_cs= [NET,PCMCIA]
2687 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2689 ______________________________________________________________________
2693 Add more DRM drivers.
projects / mirror_ubuntu-eoan-kernel.git / blob