4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 DRM Direct Rendering Management support is enabled.
48 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
49 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50 EFI EFI Partitioning (GPT) is enabled
51 EIDE EIDE/ATAPI support is enabled.
52 EVM Extended Verification Module
53 FB The frame buffer device is enabled.
54 FTRACE Function tracing enabled.
55 GCOV GCOV profiling is enabled.
56 HW Appropriate hardware is enabled.
57 IA-64 IA-64 architecture is enabled.
58 IMA Integrity measurement architecture is enabled.
59 IOSCHED More than one I/O scheduler is enabled.
60 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
61 IPV6 IPv6 support is enabled.
62 ISAPNP ISA PnP code is enabled.
63 ISDN Appropriate ISDN support is enabled.
64 JOY Appropriate joystick support is enabled.
65 KGDB Kernel debugger support is enabled.
66 KVM Kernel Virtual Machine support is enabled.
67 LIBATA Libata driver is enabled
68 LP Printer support is enabled.
69 LOOP Loopback device support is enabled.
70 M68k M68k architecture is enabled.
71 These options have more detailed description inside of
72 Documentation/m68k/kernel-options.txt.
73 MCA MCA bus support is enabled.
74 MDA MDA console support is enabled.
75 MIPS MIPS architecture is enabled.
76 MOUSE Appropriate mouse support is enabled.
77 MSI Message Signaled Interrupts (PCI).
78 MTD MTD (Memory Technology Device) support is enabled.
79 NET Appropriate network support is enabled.
80 NUMA NUMA support is enabled.
81 NFS Appropriate NFS support is enabled.
82 OSS OSS sound support is enabled.
83 PV_OPS A paravirtualized kernel is enabled.
84 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
85 PARISC The PA-RISC architecture is enabled.
86 PCI PCI bus support is enabled.
87 PCIE PCI Express support is enabled.
88 PCMCIA The PCMCIA subsystem is enabled.
89 PNP Plug & Play support is enabled.
90 PPC PowerPC architecture is enabled.
91 PPT Parallel port support is enabled.
92 PS2 Appropriate PS/2 support is enabled.
93 RAM RAM disk support is enabled.
94 S390 S390 architecture is enabled.
95 SCSI Appropriate SCSI support is enabled.
96 A lot of drivers have their options described inside
97 the Documentation/scsi/ sub-directory.
98 SECURITY Different security models are enabled.
99 SELINUX SELinux support is enabled.
100 APPARMOR AppArmor support is enabled.
101 SERIAL Serial support is enabled.
102 SH SuperH architecture is enabled.
103 SMP The kernel is an SMP kernel.
104 SPARC Sparc architecture is enabled.
105 SWSUSP Software suspend (hibernation) is enabled.
106 SUSPEND System suspend states are enabled.
107 TPM TPM drivers are enabled.
108 TS Appropriate touchscreen support is enabled.
109 UMS USB Mass Storage support is enabled.
110 USB USB support is enabled.
111 USBHID USB Human Interface Device support is enabled.
112 V4L Video For Linux support is enabled.
113 VGA The VGA console has been enabled.
114 VT Virtual terminal support is enabled.
115 WDT Watchdog support is enabled.
116 XT IBM PC/XT MFM hard disk support is enabled.
117 X86-32 X86-32, aka i386 architecture is enabled.
118 X86-64 X86-64 architecture is enabled.
119 More X86-64 boot options can be found in
120 Documentation/x86/x86_64/boot-options.txt .
121 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
122 XEN Xen support is enabled
124 In addition, the following text indicates that the option:
126 BUGS= Relates to possible processor bugs on the said processor.
127 KNL Is a kernel start-up parameter.
128 BOOT Is a boot loader parameter.
130 Parameters denoted with BOOT are actually interpreted by the boot
131 loader, and have no meaning to the kernel directly.
132 Do not modify the syntax of boot loader parameters without extreme
133 need or coordination with <Documentation/x86/boot.txt>.
135 There are also arch-specific kernel-parameters not documented here.
136 See for example <Documentation/x86/x86_64/boot-options.txt>.
138 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
139 a trailing = on the name of any parameter states that that parameter will
140 be entered as an environment variable, whereas its absence indicates that
141 it will appear as a kernel argument readable via /proc/cmdline by programs
142 running once the system is up.
144 The number of kernel parameters is not limited, but the length of the
145 complete command line (parameters including spaces etc.) is limited to
146 a fixed number of characters. This limit depends on the architecture
147 and is between 256 and 4096 characters. It is defined in the file
148 ./include/asm/setup.h as COMMAND_LINE_SIZE.
150 Finally, the [KMG] suffix is commonly described after a number of kernel
151 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
152 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
153 bytes respectively. Such letter suffixes can also be entirely omitted.
157 Advanced Configuration and Power Interface
158 Format: { force | off | strict | noirq | rsdt }
159 force -- enable ACPI if default was off
160 off -- disable ACPI if default was on
161 noirq -- do not use ACPI for IRQ routing
162 strict -- Be less tolerant of platforms that are not
163 strictly ACPI specification compliant.
164 rsdt -- prefer RSDT over (default) XSDT
165 copy_dsdt -- copy DSDT to memory
167 See also Documentation/power/runtime_pm.txt, pci=noacpi
169 acpi_rsdp= [ACPI,EFI,KEXEC]
170 Pass the RSDP address to the kernel, mostly used
171 on machines running EFI runtime service to boot the
172 second kernel for kdump.
174 acpi_apic_instance= [ACPI, IOAPIC]
176 2: use 2nd APIC table, if available
177 1,0: use 1st APIC table
180 acpi_backlight= [HW,ACPI]
181 acpi_backlight=vendor
183 If set to vendor, prefer vendor specific driver
184 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
185 of the ACPI video.ko driver.
187 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
188 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
190 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
191 debug output. Bits in debug_layer correspond to a
192 _COMPONENT in an ACPI source file, e.g.,
193 #define _COMPONENT ACPI_PCI_COMPONENT
194 Bits in debug_level correspond to a level in
195 ACPI_DEBUG_PRINT statements, e.g.,
196 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
197 The debug_level mask defaults to "info". See
198 Documentation/acpi/debug.txt for more information about
199 debug layers and levels.
201 Enable processor driver info messages:
202 acpi.debug_layer=0x20000000
203 Enable PCI/PCI interrupt routing info messages:
204 acpi.debug_layer=0x400000
205 Enable AML "Debug" output, i.e., stores to the Debug
206 object while interpreting AML:
207 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
208 Enable all messages related to ACPI hardware:
209 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
211 Some values produce so much output that the system is
212 unusable. The "log_buf_len" parameter may be useful
213 if you need to capture more output.
215 acpi_irq_balance [HW,ACPI]
216 ACPI will balance active IRQs
219 acpi_irq_nobalance [HW,ACPI]
220 ACPI will not move active IRQs (default)
223 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
224 Format: <irq>,<irq>...
226 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
228 Format: <irq>,<irq>...
230 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
232 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
233 Format: To spoof as Windows 98: ="Microsoft Windows"
235 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
236 acpi_osi="string1" # add string1 -- only one string
237 acpi_osi="!string2" # remove built-in string2
238 acpi_osi= # disable all strings
241 Override the pmtimer bug detection: force the kernel
242 to assume that this machine's pmtimer latches its value
243 and always returns good values.
245 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
246 Format: { level | edge | high | low }
248 acpi_serialize [HW,ACPI] force serialization of AML methods
250 acpi_skip_timer_override [HW,ACPI]
251 Recognize and ignore IRQ0/pin2 Interrupt Override.
252 For broken nForce2 BIOS resulting in XT-PIC timer.
254 acpi_sleep= [HW,ACPI] Sleep options
255 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
256 old_ordering, nonvs, sci_force_enable }
257 See Documentation/power/video.txt for information on
259 s3_beep is for debugging; it makes the PC's speaker beep
260 as soon as the kernel's real-mode entry point is called.
261 s4_nohwsig prevents ACPI hardware signature from being
262 used during resume from hibernation.
263 old_ordering causes the ACPI 1.0 ordering of the _PTS
264 control method, with respect to putting devices into
265 low power states, to be enforced (the ACPI 2.0 ordering
266 of _PTS is used by default).
267 nonvs prevents the kernel from saving/restoring the
268 ACPI NVS memory during suspend/hibernation and resume.
269 sci_force_enable causes the kernel to set SCI_EN directly
270 on resume from S1/S3 (which is against the ACPI spec,
271 but some broken systems don't work without it).
273 acpi_use_timer_override [HW,ACPI]
274 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer override, but don't have HPET
277 acpi_enforce_resources= [ACPI]
278 { strict | lax | no }
279 Check for resource conflicts between native drivers
280 and ACPI OperationRegions (SystemIO and SystemMemory
281 only). IO ports and memory declared in ACPI might be
282 used by the ACPI subsystem in arbitrary AML code and
283 can interfere with legacy drivers.
284 strict (default): access to resources claimed by ACPI
285 is denied; legacy drivers trying to access reserved
286 resources will fail to bind to device using them.
287 lax: access to resources claimed by ACPI is allowed;
288 legacy drivers trying to access reserved resources
289 will bind successfully but a warning message is logged.
290 no: ACPI OperationRegions are not marked as reserved,
291 no further checks are performed.
293 add_efi_memmap [EFI; X86] Include EFI memory map in
294 kernel's map of available physical RAM.
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
303 See Documentation/sound/alsa/alsa-parameters.txt
306 Allow the default userspace alignment fault handler
307 behaviour to be specified. Bit 0 enables warnings,
308 bit 1 enables fixups, and bit 2 sends a segfault.
310 align_va_addr= [X86-64]
311 Align virtual addresses by clearing slice [14:12] when
312 allocating a VMA at process creation time. This option
313 gives you up to 3% performance improvement on AMD F15h
314 machines (where it is enabled by default) for a
315 CPU-intensive style benchmark, and it can vary highly in
316 a microbenchmark depending on workload and compiler.
318 32: only for 32-bit processes
319 64: only for 64-bit processes
320 on: enable for both 32- and 64-bit processes
321 off: disable for both 32- and 64-bit processes
323 amd_iommu= [HW,X86-64]
324 Pass parameters to the AMD IOMMU driver in the system.
326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
330 off - do not initialize any AMD IOMMU found in
333 amijoy.map= [HW,JOY] Amiga joystick support
334 Map of devices attached to JOY0DAT and JOY1DAT
336 See also Documentation/input/joystick.txt
338 analog.map= [HW,JOY] Analog joystick and gamepad support
339 Specifies type or capabilities of an analog joystick
340 connected to one of 16 gameports
341 Format: <type1>,<type2>,..<type16>
344 Power management functions (SPARCstation-4/5 + deriv.)
346 Disable APC CPU standby support. SPARCstation-Fox does
347 not play well with APC CPU idle - disable it if you have
348 APC and your system crashes randomly.
350 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
351 Change the output verbosity whilst booting
352 Format: { quiet (default) | verbose | debug }
353 Change the amount of debugging information output
354 when initialising the APIC and IO-APIC components.
357 See Documentation/networking/ipv6.txt.
359 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
360 Limit apic dumping. The parameter defines the maximal
361 number of local apics being dumped. Also it is possible
362 to set it to "all" by meaning -- no limit here.
363 Format: { 1 (default) | 2 | ... | all }.
364 The parameter valid if only apic=debug or
365 apic=verbose is specified.
366 Example: apic=debug show_lapic=all
368 apm= [APM] Advanced Power Management
369 See header of arch/x86/kernel/apm_32.c.
371 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
372 Format: <io>,<irq>,<nodeID>
376 atarimouse= [HW,MOUSE] Atari Mouse
378 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
379 EzKey and similar keyboards
381 atkbd.reset= [HW] Reset keyboard during initialization
383 atkbd.set= [HW] Select keyboard code set
384 Format: <int> (2 = AT (default), 3 = PS/2)
386 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
389 atkbd.softraw= [HW] Choose between synthetic and real raw mode
390 Format: <bool> (0 = real, 1 = synthetic (default))
392 atkbd.softrepeat= [HW]
393 Use software keyboard repeat
397 baycom_epp= [HW,AX25]
400 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
402 See header of drivers/net/hamradio/baycom_par.c.
404 baycom_ser_fdx= [HW,AX25]
405 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
406 Format: <io>,<irq>,<mode>[,<baud>]
407 See header of drivers/net/hamradio/baycom_ser_fdx.c.
409 baycom_ser_hdx= [HW,AX25]
410 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
411 Format: <io>,<irq>,<mode>
412 See header of drivers/net/hamradio/baycom_ser_hdx.c.
414 boot_delay= Milliseconds to delay each printk during boot.
415 Values larger than 10 seconds (10000) are changed to
419 bootmem_debug [KNL] Enable bootmem allocator debug messages.
421 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
422 bttv.radio= Most important insmod options are available as
424 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
427 bulk_remove=off [PPC] This parameter disables the use of the pSeries
428 firmware feature for flushing multiple hpte entries
431 c101= [NET] Moxa C101 synchronous serial card
433 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
434 Sometimes CPU hardware bugs make them report the cache
435 size incorrectly. The kernel will attempt work arounds
436 to fix known problems, but for some CPUs it is not
437 possible to determine what the correct size should be.
438 This option provides an override for these situations.
441 [SECURITY] Disable capabilities. This would normally
442 be used only if an alternative security model is to be
443 configured. Potentially dangerous and should only be
444 used if you are entirely sure of the consequences.
446 ccw_timeout_log [S390]
447 See Documentation/s390/CommonIO for details.
449 cgroup_disable= [KNL] Disable a particular controller
450 Format: {name of the controller(s) to disable}
451 {Currently supported controllers - "memory"}
453 checkreqprot [SELINUX] Set initial checkreqprot flag value.
454 Format: { "0" | "1" }
455 See security/selinux/Kconfig help text.
456 0 -- check protection applied by kernel (includes
457 any implied execute protection).
458 1 -- check protection requested by application.
459 Default value is set via a kernel config option.
460 Value can be changed at runtime via
461 /selinux/checkreqprot.
464 See Documentation/s390/CommonIO for details.
466 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
468 Forces specified clocksource (if available) to be used
469 when calculating gettimeofday(). If specified
470 clocksource is not available, it defaults to PIT.
471 Format: { pit | tsc | cyclone | pmtmr }
473 clocksource= Override the default clocksource
475 Override the default clocksource and use the clocksource
476 with the name specified.
477 Some clocksource names to choose from, depending on
479 [all] jiffies (this is the base, fallback clocksource)
481 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
482 pxa_timer,timer3,32k_counter,timer0_1
484 [X86-32] pit,hpet,tsc;
485 scx200_hrt on Geode; cyclone on IBM x440
493 clearcpuid=BITNUM [X86]
494 Disable CPUID feature X for the kernel. See
495 arch/x86/include/asm/cpufeature.h for the valid bit
496 numbers. Note the Linux specific bits are not necessarily
497 stable over kernel options, but the vendor specific
499 Also note that user programs calling CPUID directly
500 or using the feature without checking anything
501 will still see it. This just prevents it from
502 being used by the kernel or shown in /proc/cpuinfo.
503 Also note the kernel might malfunction if you disable
506 cmo_free_hint= [PPC] Format: { yes | no }
507 Specify whether pages are marked as being inactive
508 when they are freed. This is used in CMO environments
509 to determine OS memory pressure for page stealing by
513 code_bytes [X86] How many bytes of object code to print
518 com20020= [HW,NET] ARCnet - COM20020 chipset
520 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
522 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
526 ARCnet - COM90xx chipset (memory-mapped buffers)
527 Format: <io>[,<irq>[,<memstart>]]
529 condev= [HW,S390] console device
532 console= [KNL] Output console device and options.
534 tty<n> Use the virtual console device <n>.
538 Use the specified serial port. The options are of
539 the form "bbbbpnf", where "bbbb" is the baud rate,
540 "p" is parity ("n", "o", or "e"), "n" is number of
541 bits, and "f" is flow control ("r" for RTS or
542 omit it). Default is "9600n8".
544 See Documentation/serial-console.txt for more
546 Documentation/networking/netconsole.txt for an
549 uart[8250],io,<addr>[,options]
550 uart[8250],mmio,<addr>[,options]
551 Start an early, polled-mode console on the 8250/16550
552 UART at the specified I/O port or MMIO address,
553 switching to the matching ttyS device later. The
554 options are the same as for ttyS, above.
556 If the device connected to the port is not a TTY but a braille
557 device, prepend "brl," before the device type, for instance
559 For now, only VisioBraille is supported.
561 consoleblank= [KNL] The console blank (screen saver) timeout in
562 seconds. Defaults to 10*60 = 10mins. A value of 0
563 disables the blank timer.
566 [KNL] Change the default value for
567 /proc/<pid>/coredump_filter.
568 See also Documentation/filesystems/proc.txt.
570 cpuidle.off=1 [CPU_IDLE]
571 disable the cpuidle sub-system
573 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
575 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
577 crashkernel=size[KMG][@offset[KMG]]
578 [KNL] Using kexec, Linux can switch to a 'crash kernel'
579 upon panic. This parameter reserves the physical
580 memory region [offset, offset + size] for that kernel
581 image. If '@offset' is omitted, then a suitable offset
582 is selected automatically. Check
583 Documentation/kdump/kdump.txt for further details.
585 crashkernel=range1:size1[,range2:size2,...][@offset]
586 [KNL] Same as above, but depends on the memory
587 in the running system. The syntax of range is
588 start-[end] where start and end are both
589 a memory unit (amount[KMG]). See also
590 Documentation/kdump/kdump.txt for an example.
595 cs89x0_media= [HW,NET]
596 Format: { rj45 | aui | bnc }
599 See header of drivers/s390/block/dasd_devmap.c.
601 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
602 (one device per port)
603 Format: <port#>,<type>
604 See also Documentation/input/joystick-parport.txt
606 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
607 time. See Documentation/dynamic-debug-howto.txt for
610 debug [KNL] Enable kernel debugging (events log level).
613 [KNL] verbose self-tests
615 Print debugging info while doing the locking API
617 We default to 0 (no extra messages), setting it to
618 1 will print _a lot_ more information - normally
619 only useful to kernel developers.
621 debug_objects [KNL] Enable object debugging
624 [KNL] Disable object debugging
626 debugpat [X86] Enable PAT debugging
628 decnet.addr= [HW,NET]
629 Format: <area>[,<node>]
630 See also Documentation/networking/decnet.txt.
633 [same as hugepagesz=] The size of the default
634 HugeTLB page size. This is the size represented by
635 the legacy /proc/ hugepages APIs, used for SHM, and
636 default size when mounting hugetlbfs filesystems.
637 Defaults to the default architecture's huge page size
641 Set number of hash buckets for dentry cache.
644 IO parameters + enable/disable command.
646 digiepca= [HW,SERIAL]
647 See drivers/char/README.epca and
648 Documentation/serial/digiepca.txt.
651 See Documentation/networking/ipv6.txt.
653 disable_ddw [PPC/PSERIES]
654 Disable Dynamic DMA Window support. Use this if
655 to workaround buggy firmware.
658 See Documentation/networking/ipv6.txt.
660 disable_mtrr_cleanup [X86]
661 The kernel tries to adjust MTRR layout from continuous
662 to discrete, to make X server driver able to add WB
663 entry later. This parameter disables that.
665 disable_mtrr_trim [X86, Intel and AMD only]
666 By default the kernel will trim any uncacheable
667 memory out of your available memory pool based on
668 MTRR settings. This parameter disables that behavior,
669 possibly causing your machine to run very slowly.
671 disable_timer_pin_1 [X86]
672 Disable PIN 1 of APIC timer
673 Can be useful to work around chipset bugs.
675 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
676 this option disables the debugging code at boot.
678 dma_debug_entries=<number>
679 This option allows to tune the number of preallocated
680 entries for DMA-API debugging code. One entry is
681 required per DMA-API allocation. Use this if the
682 DMA-API debugging code disables itself because the
683 architectural default is too low.
685 dma_debug_driver=<driver_name>
686 With this option the DMA-API debugging driver
687 filter feature can be enabled at boot time. Just
688 pass the driver to filter for as the parameter.
689 The filter can be disabled or changed to another
690 driver later using sysfs.
694 earlycon= [KNL] Output early console device and options.
695 uart[8250],io,<addr>[,options]
696 uart[8250],mmio,<addr>[,options]
697 uart[8250],mmio32,<addr>[,options]
698 Start an early, polled-mode console on the 8250/16550
699 UART at the specified I/O port or MMIO address.
700 MMIO inter-register address stride is either 8-bit
701 (mmio) or 32-bit (mmio32).
702 The options are the same as for ttyS, above.
704 earlyprintk= [X86,SH,BLACKFIN]
707 earlyprintk=serial[,ttySn[,baudrate]]
708 earlyprintk=ttySn[,baudrate]
709 earlyprintk=dbgp[debugController#]
711 Append ",keep" to not disable it when the real console
714 Only vga or serial or usb debug port at a time.
716 Currently only ttyS0 and ttyS1 are supported.
718 Interaction with the standard serial driver is not
721 The VGA output is eventually overwritten by the real
724 The xen output can only be used by Xen PV guests.
726 ekgdboc= [X86,KGDB] Allow early kernel console debugging
729 This is designed to be used in conjunction with
730 the boot argument: earlyprintk=vga
733 Format: {"off" | "on" | "skip[mbr]"}
735 eisa_irq_edge= [PARISC,HW]
736 See header of drivers/parisc/eisa.c.
739 See comment before function elanfreq_setup() in
740 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
743 Format: {"cfq" | "deadline" | "noop"}
744 See Documentation/block/cfq-iosched.txt and
745 Documentation/block/deadline-iosched.txt for details.
747 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
748 Specifies physical address of start of kernel core
749 image elf header and optionally the size. Generally
750 kexec loader will pass this option to capture kernel.
751 See Documentation/kdump/kdump.txt for details.
753 enable_mtrr_cleanup [X86]
754 The kernel tries to adjust MTRR layout from continuous
755 to discrete, to make X server driver able to add WB
756 entry later. This parameter enables that.
758 enable_timer_pin_1 [X86]
759 Enable PIN 1 of APIC timer
760 Can be useful to work around chipset bugs
761 (in particular on some ATI chipsets).
762 The kernel tries to set a reasonable default.
764 enforcing [SELINUX] Set initial enforcing status.
766 See security/selinux/Kconfig help text.
767 0 -- permissive (log only, no denials).
768 1 -- enforcing (deny and log).
770 Value can be changed at runtime via /selinux/enforce.
773 Disable Error Record Serialization Table (ERST)
776 ether= [HW,NET] Ethernet cards parameters
777 This option is obsoleted by the "netdev=" option, which
778 has equivalent usage. See its documentation for details.
782 Permit 'security.evm' to be updated regardless of
783 current integrity status.
787 fail_make_request=[KNL]
788 General fault injection mechanism.
789 Format: <interval>,<probability>,<space>,<times>
790 See also Documentation/fault-injection/.
793 See Documentation/blockdev/floppy.txt.
795 force_pal_cache_flush
796 [IA-64] Avoid check_sal_cache_flush which may hang on
797 buggy SAL_CACHE_FLUSH implementations. Using this
798 parameter will force ia64_sal_cache_flush to call
799 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
802 [FTRACE] will set and start the specified tracer
803 as early as possible in order to facilitate early
806 ftrace_dump_on_oops[=orig_cpu]
807 [FTRACE] will dump the trace buffers on oops.
808 If no parameter is passed, ftrace will dump
809 buffers of all CPUs, but if you pass orig_cpu, it will
810 dump only the buffer of the CPU that triggered the
813 ftrace_filter=[function-list]
814 [FTRACE] Limit the functions traced by the function
815 tracer at boot up. function-list is a comma separated
816 list of functions. This list can be changed at run
817 time by the set_ftrace_filter file in the debugfs
820 ftrace_notrace=[function-list]
821 [FTRACE] Do not trace the functions specified in
822 function-list. This list can be changed at run time
823 by the set_ftrace_notrace file in the debugfs
826 ftrace_graph_filter=[function-list]
827 [FTRACE] Limit the top level callers functions traced
828 by the function graph tracer at boot up.
829 function-list is a comma separated list of functions
830 that can be changed at run time by the
831 set_graph_function file in the debugfs tracing directory.
834 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
835 support via parallel port (up to 5 devices per port)
836 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
837 See also Documentation/input/joystick-parport.txt
841 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
845 gcov_persist= [GCOV] When non-zero (default), profiling data for
846 kernel modules is saved and remains accessible via
847 debugfs, even when the module is unloaded/reloaded.
848 When zero, profiling data is discarded and associated
849 debugfs files are removed at module unload time.
851 gpt [EFI] Forces disk with valid GPT signature but
852 invalid Protective MBR to be treated as GPT.
854 hashdist= [KNL,NUMA] Large hashes allocated during boot
855 are distributed across NUMA nodes. Defaults on
856 for 64-bit NUMA, off otherwise.
857 Format: 0 | 1 (for off | on)
859 hcl= [IA-64] SGI's Hardware Graph compatibility layer
861 hd= [EIDE] (E)IDE hard drive subsystem geometry
862 Format: <cyl>,<head>,<sect>
865 Disable Hardware Error Source Table (HEST) support;
866 corresponding firmware-first mode error processing
867 logic will be disabled.
869 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
870 size of <nn>. This works even on boxes that have no
871 highmem otherwise. This also works to reduce highmem
872 size on bigger boxes.
874 highres= [KNL] Enable/disable high resolution timer mode.
875 Valid parameters: "on", "off"
879 See Documentation/isdn/README.HiSax.
883 hpet= [X86-32,HPET] option to control HPET usage
884 Format: { enable (default) | disable | force |
886 disable: disable HPET and use PIT instead
887 force: allow force enabled of undocumented chips (ICH4,
889 verbose: show contents of HPET registers during setup
891 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
892 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
893 On x86-64 and powerpc, this option can be specified
894 multiple times interleaved with hugepages= to reserve
895 huge pages of different sizes. Valid pages sizes on
896 x86-64 are 2M (when the CPU supports "pse") and 1G
897 (when the CPU supports the "pdpe1gb" cpuinfo flag)
898 Note that 1GB pages can only be allocated at boot time
899 using hugepages= and not freed afterwards.
901 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
902 terminal devices. Valid values: 0..8
903 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
904 If specified, z/VM IUCV HVC accepts connections
905 from listed z/VM user IDs only.
908 Do not unregister boot console at start. This is only
909 useful for debugging when something happens in the window
910 between unregistering the boot console and initializing
913 i2c_bus= [HW] Override the default board specific I2C bus speed
914 or register an additional I2C bus that is not
915 registered from board initialization code.
919 i8042.debug [HW] Toggle i8042 debug mode
920 i8042.direct [HW] Put keyboard port into non-translated mode
921 i8042.dumbkbd [HW] Pretend that controller can only read data from
922 keyboard and cannot control its state
923 (Don't attempt to blink the leds)
924 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
925 i8042.nokbd [HW] Don't check/create keyboard port
926 i8042.noloop [HW] Disable the AUX Loopback command while probing
928 i8042.nomux [HW] Don't check presence of an active multiplexing
930 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
932 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
933 i8042.reset [HW] Reset the controller during init and cleanup
934 i8042.unlock [HW] Unlock (ignore) the keylock
938 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
939 indicates that the driver is running on unsupported
941 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
942 does not match list of supported models.
944 [HW] Report power status in /proc/i8k
945 (disabled by default)
946 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
950 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
952 ide-core.nodma= [HW] (E)IDE subsystem
953 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
954 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
955 .cdrom .chs .ignore_cable are additional options
956 See Documentation/ide/ide.txt.
958 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
959 Claim all unknown PCI IDE storage controllers.
962 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
963 Poll forces a polling idle loop that can slightly
964 improve the performance of waking up a idle CPU, but
965 will use a lot of power and make the system run hot.
967 idle=mwait: On systems which support MONITOR/MWAIT but
968 the kernel chose to not use it because it doesn't save
969 as much power as a normal idle loop, use the
970 MONITOR/MWAIT idle loop anyways. Performance should be
971 the same as idle=poll.
972 idle=halt: Halt is forced to be used for CPU idle.
973 In such case C2/C3 won't be used again.
974 idle=nomwait: Disable mwait for CPU C-states
976 ignore_loglevel [KNL]
977 Ignore loglevel setting - this will print /all/
978 kernel messages to the console. Useful for debugging.
979 We also add it as printk module parameter, so users
980 could change it dynamically, usually by
981 /sys/module/printk/parameters/ignore_loglevel.
984 Set number of hash buckets for inode cache.
987 Format: { "0" | "1" }
988 0 -- integrity auditing messages. (Default)
989 1 -- enable informational integrity auditing messages.
992 Format: { "sha1" | "md5" }
996 Load a policy which meets the needs of the Trusted
997 Computing Base. This means IMA will measure all
998 programs exec'd, files mmap'd for exec, and all files
999 opened for read by uid=0.
1003 Run specified binary instead of /sbin/init as init
1006 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1007 for working out where the kernel is dying during
1010 initrd= [BOOT] Specify the location of the initial ramdisk
1012 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1015 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1017 Enable intel iommu driver.
1019 Disable intel iommu driver.
1020 igfx_off [Default Off]
1021 By default, gfx is mapped as normal device. If a gfx
1022 device has a dedicated DMAR unit, the DMAR unit is
1023 bypassed by not enabling DMAR with this option. In
1024 this case, gfx device will use physical address for
1027 With this option iommu will not optimize to look
1028 for io virtual address below 32-bit forcing dual
1029 address cycle on pci bus for cards supporting greater
1030 than 32-bit addressing. The default is to look
1031 for translation below 32-bit and if not available
1032 then look in the higher range.
1033 strict [Default Off]
1034 With this option on every unmap_single operation will
1035 result in a hardware IOTLB flush operation as opposed
1036 to batching them for performance.
1037 sp_off [Default Off]
1038 By default, super page will be supported if Intel IOMMU
1039 has the capability. With this option, super page will
1041 intremap= [X86-64, Intel-IOMMU]
1042 on enable Interrupt Remapping (default)
1043 off disable Interrupt Remapping
1044 nosid disable Source ID checking
1046 BIOS x2APIC opt-out request will be ignored
1050 iomem= Disable strict checking of access to MMIO memory
1051 strict regions from userspace.
1067 io7= [HW] IO7 for Marvel based alpha systems
1068 See comment before marvel_specify_io7 in
1069 arch/alpha/kernel/core_marvel.c.
1071 io_delay= [X86] I/O delay method
1073 Standard port 0x80 based delay
1075 Alternate port 0xed based delay (needed on some systems)
1077 Simple two microseconds delay
1082 See Documentation/filesystems/nfs/nfsroot.txt.
1084 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1085 See comment before ip2_setup() in
1086 drivers/char/ip2/ip2base.c.
1089 When an interrupt is not handled search all handlers
1090 for it. Intended to get systems with badly broken
1094 When an interrupt is not handled search all handlers
1095 for it. Also check all handlers each timer
1096 interrupt. Intended to get systems with badly broken
1100 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1102 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1104 <cpu number>,...,<cpu number>
1106 <cpu number>-<cpu number>
1107 (must be a positive range in ascending order)
1109 <cpu number>,...,<cpu number>-<cpu number>
1111 This option can be used to specify one or more CPUs
1112 to isolate from the general SMP balancing and scheduling
1113 algorithms. You can move a process onto or off an
1114 "isolated" CPU via the CPU affinity syscalls or cpuset.
1115 <cpu number> begins at 0 and the maximum value is
1116 "number of CPUs in system - 1".
1118 This option is the preferred way to isolate CPUs. The
1119 alternative -- manually setting the CPU mask of all
1120 tasks in the system -- can cause problems and
1121 suboptimal load balancer performance.
1125 js= [HW,JOY] Analog joystick
1126 See Documentation/input/joystick.txt.
1130 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1131 specifies the amount of memory usable by the kernel
1132 for non-movable allocations. The requested amount is
1133 spread evenly throughout all nodes in the system. The
1134 remaining memory in each node is used for Movable
1135 pages. In the event, a node is too small to have both
1136 kernelcore and Movable pages, kernelcore pages will
1137 take priority and other nodes will have a larger number
1138 of kernelcore pages. The Movable zone is used for the
1139 allocation of pages that may be reclaimed or moved
1140 by the page migration subsystem. This means that
1141 HugeTLB pages may not be allocated from this zone.
1142 Note that allocations like PTEs-from-HighMem still
1143 use the HighMem zone if it exists, and the Normal
1144 zone if it does not.
1146 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1147 Format: <Controller#>[,poll interval]
1148 The controller # is the number of the ehci usb debug
1149 port as it is probed via PCI. The poll interval is
1150 optional and is the number seconds in between
1151 each poll cycle to the debug port in case you need
1152 the functionality for interrupting the kernel with
1153 gdb or control-c on the dbgp connection. When
1154 not using this parameter you use sysrq-g to break into
1155 the kernel debugger.
1157 kgdboc= [KGDB,HW] kgdb over consoles.
1158 Requires a tty driver that supports console polling,
1159 or a supported polling keyboard driver (non-usb).
1160 Serial only format: <serial_device>[,baud]
1161 keyboard only format: kbd
1162 keyboard and serial format: kbd,<serial_device>[,baud]
1163 Optional Kernel mode setting:
1164 kms, kbd format: kms,kbd
1165 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1167 kgdbwait [KGDB] Stop kernel execution and enter the
1168 kernel debugger at the earliest opportunity.
1170 kmac= [MIPS] korina ethernet MAC address.
1171 Configure the RouterBoard 532 series on-chip
1172 Ethernet adapter MAC address.
1174 kmemleak= [KNL] Boot-time kmemleak enable/disable
1175 Valid arguments: on, off
1178 kstack=N [X86] Print N words from the kernel stack
1181 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1182 Default is 0 (don't ignore, but inject #GP)
1184 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1185 Default is 1 (enabled)
1187 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1191 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1192 Default is 1 (enabled)
1194 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1196 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1198 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1199 (virtualized MMU) support on capable Intel chips.
1200 Default is 1 (enabled)
1202 kvm-intel.emulate_invalid_guest_state=
1203 [KVM,Intel] Enable emulation of invalid guest states
1204 Default is 0 (disabled)
1206 kvm-intel.flexpriority=
1207 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1208 Default is 1 (enabled)
1211 [KVM,Intel] Enable VMX nesting (nVMX).
1212 Default is 0 (disabled)
1214 kvm-intel.unrestricted_guest=
1215 [KVM,Intel] Disable unrestricted guest feature
1216 (virtualized real and unpaged mode) on capable
1217 Intel chips. Default is 1 (enabled)
1219 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1220 feature (tagged TLBs) on capable Intel chips.
1221 Default is 1 (enabled)
1227 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1230 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1233 libata.dma= [LIBATA] DMA control
1234 libata.dma=0 Disable all PATA and SATA DMA
1235 libata.dma=1 PATA and SATA Disk DMA only
1236 libata.dma=2 ATAPI (CDROM) DMA only
1237 libata.dma=4 Compact Flash DMA only
1238 Combinations also work, so libata.dma=3 enables DMA
1239 for disks and CDROMs, but not CFs.
1241 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1242 libata.ignore_hpa=0 keep BIOS limits (default)
1243 libata.ignore_hpa=1 ignore limits, using full disk
1245 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1249 libata.force= [LIBATA] Force configurations. The format is comma
1250 separated list of "[ID:]VAL" where ID is
1251 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1252 matching port, link or device. Basically, it matches
1253 the ATA ID string printed on console by libata. If
1254 the whole ID part is omitted, the last PORT and DEVICE
1255 values are used. If ID hasn't been specified yet, the
1256 configuration applies to all ports, links and devices.
1258 If only DEVICE is omitted, the parameter applies to
1259 the port and all links and devices behind it. DEVICE
1260 number of 0 either selects the first device or the
1261 first fan-out link behind PMP device. It does not
1262 select the host link. DEVICE number of 15 selects the
1263 host link and device attached to it.
1265 The VAL specifies the configuration to force. As long
1266 as there's no ambiguity shortcut notation is allowed.
1267 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1268 The following configurations can be forced.
1270 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1271 Any ID with matching PORT is used.
1273 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1275 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1276 udma[/][16,25,33,44,66,100,133] notation is also
1279 * [no]ncq: Turn on or off NCQ.
1281 * nohrst, nosrst, norst: suppress hard, soft
1284 * dump_id: dump IDENTIFY data.
1286 If there are multiple matching configurations changing
1287 the same attribute, the last one is used.
1289 memblock=debug [KNL] Enable memblock debug messages.
1291 load_ramdisk= [RAM] List of ramdisks to load from floppy
1292 See Documentation/blockdev/ramdisk.txt.
1294 lockd.nlm_grace_period=P [NFS] Assign grace period.
1297 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1300 lockd.nlm_timeout=T [NFS] Assign timeout value.
1303 lockd.nlm_udpport=M [NFS] Assign UDP port.
1306 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1309 loglevel= All Kernel Messages with a loglevel smaller than the
1310 console loglevel will be printed to the console. It can
1311 also be changed with klogd or other programs. The
1312 loglevels are defined as follows:
1314 0 (KERN_EMERG) system is unusable
1315 1 (KERN_ALERT) action must be taken immediately
1316 2 (KERN_CRIT) critical conditions
1317 3 (KERN_ERR) error conditions
1318 4 (KERN_WARNING) warning conditions
1319 5 (KERN_NOTICE) normal but significant condition
1320 6 (KERN_INFO) informational
1321 7 (KERN_DEBUG) debug-level messages
1323 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1324 in bytes. n must be a power of two. The default
1325 size is set in the kernel config file.
1327 logo.nologo [FB] Disables display of the built-in Linux logo.
1328 This may be used to provide more screen space for
1329 kernel log messages and is useful when debugging
1330 kernel boot problems.
1332 lp=0 [LP] Specify parallel ports to use, e.g,
1333 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1334 lp=reset first parallel port). 'lp=0' disables the
1335 lp=auto printer driver. 'lp=reset' (which can be
1336 specified in addition to the ports) causes
1337 attached printers to be reset. Using
1338 lp=port1,port2,... specifies the parallel ports
1339 to associate lp devices with, starting with
1340 lp0. A port specification may be 'none' to skip
1341 that lp device, or a parport name such as
1342 'parport0'. Specifying 'lp=auto' instead of a
1343 port specification list means that device IDs
1344 from each port should be examined, to see if
1345 an IEEE 1284-compliant printer is attached; if
1346 so, the driver will manage that printer.
1347 See also header of drivers/char/lp.c.
1350 Sets loops_per_jiffy to given constant, thus avoiding
1351 time-consuming boot-time autodetection (up to 250 ms per
1352 CPU). 0 enables autodetection (default). To determine
1353 the correct value for your kernel, boot with normal
1354 autodetection and see what value is printed. Note that
1355 on SMP systems the preset will be applied to all CPUs,
1356 which is likely to cause problems if your CPUs need
1357 significantly divergent settings. An incorrect value
1358 will cause delays in the kernel to be wrong, leading to
1359 unpredictable I/O errors and other breakage. Although
1360 unlikely, in the extreme case this might damage your
1364 Format: <io>,<irq>,<dma>
1366 machvec= [IA-64] Force the use of a particular machine-vector
1367 (machvec) in a generic kernel.
1368 Example: machvec=hpzx1_swiotlb
1370 machtype= [Loongson] Share the same kernel image file between different
1372 Example: machtype=lemote-yeeloong-2f-7inch
1374 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1375 than or equal to this physical address is ignored.
1377 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1378 should make use of. maxcpus=n : n >= 0 limits the
1379 kernel to using 'n' processors. n=0 is a special case,
1380 it is equivalent to "nosmp", which also disables
1383 max_loop= [LOOP] The number of loop block devices that get
1384 (loop.max_loop) unconditionally pre-created at init time. The default
1385 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1386 of statically allocating a predefined number, loop
1387 devices can be requested on-demand with the
1388 /dev/loop-control interface.
1392 mce [X86-32] Machine Check Exception
1394 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1396 md= [HW] RAID subsystems devices and level
1397 See Documentation/md.txt.
1400 Format: <first>,<last>
1401 Specifies range of consoles to be captured by the MDA.
1403 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1404 Amount of memory to be used when the kernel is not able
1405 to see the whole system memory or for test.
1406 [X86-32] Use together with memmap= to avoid physical
1407 address space collisions. Without memmap= PCI devices
1408 could be placed at addresses belonging to unused RAM.
1410 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1414 [KNL,SH] Allow user to override the default size for
1415 per-device physically contiguous DMA buffers.
1417 memmap=exactmap [KNL,X86] Enable setting of an exact
1418 E820 memory map, as specified by the user.
1419 Such memmap=exactmap lines can be constructed based on
1420 BIOS output or other requirements. See the memmap=nn@ss
1423 memmap=nn[KMG]@ss[KMG]
1424 [KNL] Force usage of a specific region of memory
1425 Region of memory to be used, from ss to ss+nn.
1427 memmap=nn[KMG]#ss[KMG]
1428 [KNL,ACPI] Mark specific memory as ACPI data.
1429 Region of memory to be used, from ss to ss+nn.
1431 memmap=nn[KMG]$ss[KMG]
1432 [KNL,ACPI] Mark specific memory as reserved.
1433 Region of memory to be used, from ss to ss+nn.
1434 Example: Exclude memory from 0x18690000-0x1869ffff
1435 memmap=64K$0x18690000
1437 memmap=0x10000$0x18690000
1439 memory_corruption_check=0/1 [X86]
1440 Some BIOSes seem to corrupt the first 64k of
1441 memory when doing things like suspend/resume.
1442 Setting this option will scan the memory
1443 looking for corruption. Enabling this will
1444 both detect corruption and prevent the kernel
1445 from using the memory being corrupted.
1446 However, its intended as a diagnostic tool; if
1447 repeatable BIOS-originated corruption always
1448 affects the same memory, you can use memmap=
1449 to prevent the kernel from using that memory.
1451 memory_corruption_check_size=size [X86]
1452 By default it checks for corruption in the low
1453 64k, making this memory unavailable for normal
1454 use. Use this parameter to scan for
1455 corruption in more or less memory.
1457 memory_corruption_check_period=seconds [X86]
1458 By default it checks for corruption every 60
1459 seconds. Use this parameter to check at some
1460 other rate. 0 disables periodic checking.
1462 memtest= [KNL,X86] Enable memtest
1464 default : 0 <disable>
1465 Specifies the number of memtest passes to be
1466 performed. Each pass selects another test
1467 pattern from a given set of patterns. Memtest
1468 fills the memory with this pattern, validates
1469 memory contents and reserves bad memory
1470 regions that are detected.
1472 meye.*= [HW] Set MotionEye Camera parameters
1473 See Documentation/video4linux/meye.txt.
1475 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1476 Multi-Function General Purpose Timers on AMD Geode
1479 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1480 the BIOS has incorrectly applied a workaround. TinyBIOS
1481 version 0.98 is known to be affected, 0.99 fixes the
1482 problem by letting the user disable the workaround.
1486 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1487 physical address is ignored.
1489 mini2440= [ARM,HW,KNL]
1490 Format:[0..2][b][c][t]
1492 MINI2440 configuration specification:
1493 0 - The attached screen is the 3.5" TFT
1494 1 - The attached screen is the 7" TFT
1495 2 - The VGA Shield is attached (1024x768)
1496 Leaving out the screen size parameter will not load
1497 the TFT driver, and the framebuffer will be left
1499 b - Enable backlight. The TFT backlight pin will be
1500 linked to the kernel VESA blanking code and a GPIO
1501 LED. This parameter is not necessary when using the
1503 c - Enable the s3c camera interface.
1504 t - Reserved for enabling touchscreen support. The
1505 touchscreen support is not enabled in the mainstream
1506 kernel as of 2.6.30, a preliminary port can be found
1507 in the "bleeding edge" mini2440 support kernel at
1508 http://repo.or.cz/w/linux-2.6/mini2440.git
1511 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1512 parameter allows control of the logging verbosity for
1513 the additional memory initialisation checks. A value
1514 of 0 disables mminit logging and a level of 4 will
1515 log everything. Information is printed at KERN_DEBUG
1516 so loglevel=8 may also need to be specified.
1519 [MOUSE] Maximum time between finger touching and
1520 leaving touchpad surface for touch to be considered
1521 a tap and be reported as a left button click (for
1522 touchpads working in absolute mode only).
1524 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1525 reporting absolute coordinates, such as tablets
1526 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1527 reporting absolute coordinates, such as tablets
1529 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1530 is similar to kernelcore except it specifies the
1531 amount of memory used for migratable allocations.
1532 If both kernelcore and movablecore is specified,
1533 then kernelcore will be at *least* the specified
1534 value but may be more. If movablecore on its own
1535 is specified, the administrator must be careful
1536 that the amount of memory usable for all allocations
1539 MTD_Partition= [MTD]
1540 Format: <name>,<region-number>,<size>,<offset>
1542 MTD_Region= [MTD] Format:
1543 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1546 See drivers/mtd/cmdlinepart.c.
1548 multitce=off [PPC] This parameter disables the use of the pSeries
1549 firmware feature for updating multiple TCE entries
1552 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1554 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1556 boundary - index of last SLC block on Flex-OneNAND.
1557 The remaining blocks are configured as MLC blocks.
1558 lock - Configure if Flex-OneNAND boundary should be locked.
1559 Once locked, the boundary cannot be changed.
1560 1 indicates lock status, 0 indicates unlock status.
1563 ARM/S3C2412 JIVE boot control
1565 See arch/arm/mach-s3c2412/mach-jive.c
1567 mtouchusb.raw_coordinates=
1568 [HW] Make the MicroTouch USB driver use raw coordinates
1569 ('y', default) or cooked coordinates ('n')
1571 mtrr_chunk_size=nn[KMG] [X86]
1572 used for mtrr cleanup. It is largest continuous chunk
1573 that could hold holes aka. UC entries.
1575 mtrr_gran_size=nn[KMG] [X86]
1576 Used for mtrr cleanup. It is granularity of mtrr block.
1578 Large value could prevent small alignment from
1581 mtrr_spare_reg_nr=n [X86]
1583 Range: 0,7 : spare reg number
1585 Used for mtrr cleanup. It is spare mtrr entries number.
1586 Set to 2 or more if your graphical card needs more.
1588 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1590 netdev= [NET] Network devices parameters
1591 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1592 Note that mem_start is often overloaded to mean
1593 something different and driver-specific.
1594 This usage is only documented in each driver source
1598 [NETFILTER] Enable connection tracking flow accounting
1599 0 to disable accounting
1600 1 to enable accounting
1603 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1604 See Documentation/filesystems/nfs/nfsroot.txt.
1606 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1607 See Documentation/filesystems/nfs/nfsroot.txt.
1609 nfsrootdebug [NFS] enable nfsroot debugging messages.
1610 See Documentation/filesystems/nfs/nfsroot.txt.
1612 nfs.callback_tcpport=
1613 [NFS] set the TCP port on which the NFSv4 callback
1614 channel should listen.
1617 [NFS] sets the pathname to the program which is used
1618 to update the NFS client cache entries.
1620 nfs.cache_getent_timeout=
1621 [NFS] sets the timeout after which an attempt to
1622 update a cache entry is deemed to have failed.
1624 nfs.idmap_cache_timeout=
1625 [NFS] set the maximum lifetime for idmapper cache
1629 [NFS] enable 64-bit inode numbers.
1630 If zero, the NFS client will fake up a 32-bit inode
1631 number for the readdir() and stat() syscalls instead
1632 of returning the full 64-bit number.
1633 The default is to return 64-bit inode numbers.
1635 nfs.nfs4_disable_idmapping=
1636 [NFSv4] When set, this option disables the NFSv4
1637 idmapper on the client, but only if the mount
1638 is using the 'sec=sys' security flavour. This may
1639 make migration from legacy NFSv2/v3 systems easier
1640 provided that the server has the appropriate support.
1641 The default is to always enable NFSv4 idmapping.
1643 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1644 when a NMI is triggered.
1645 Format: [state][,regs][,debounce][,die]
1647 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1648 Format: [panic,][nopanic,][num]
1650 0 - turn nmi_watchdog off
1651 When panic is specified, panic when an NMI watchdog
1652 timeout occurs (or 'nopanic' to override the opposite
1654 This is useful when you use a panic=... timeout and
1655 need the box quickly up again.
1657 netpoll.carrier_timeout=
1658 [NET] Specifies amount of time (in seconds) that
1659 netpoll should wait for a carrier. By default netpoll
1662 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1663 emulation library even if a 387 maths coprocessor
1667 [HW] Never suspend the console
1668 Disable suspending of consoles during suspend and
1669 hibernate operations. Once disabled, debugging
1670 messages can reach various consoles while the rest
1671 of the system is being put to sleep (ie, while
1672 debugging driver suspend/resume hooks). This may
1673 not work reliably with all consoles, but is known
1674 to work with serial and VGA consoles.
1675 To facilitate more flexible debugging, we also add
1676 console_suspend, a printk module parameter to control
1677 it. Users could use console_suspend (usually
1678 /sys/module/printk/parameters/console_suspend) to
1679 turn on/off it dynamically.
1681 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1682 caches in the slab allocator. Saves per-node memory,
1683 but will impact performance.
1687 noapic [SMP,APIC] Tells the kernel to not make use of any
1688 IOAPICs that may be present in the system.
1690 noautogroup Disable scheduler automatic task group creation.
1692 nobats [PPC] Do not use BATs for mapping kernel lowmem
1693 on "Classic" PPC cores.
1697 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1699 nodelayacct [KNL] Disable per-task delay accounting
1701 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1703 nodsp [SH] Disable hardware DSP at boot time.
1705 noefi [X86] Disable EFI runtime services support.
1710 On X86-32 available only on PAE configured kernels.
1711 noexec=on: enable non-executable mappings (default)
1712 noexec=off: disable non-executable mappings
1715 Disable SMEP (Supervisor Mode Execution Protection)
1716 even if it is supported by processor.
1719 This affects only 32-bit executables.
1720 noexec32=on: enable non-executable mappings (default)
1721 read doesn't imply executable mappings
1722 noexec32=off: disable non-executable mappings
1723 read implies executable mappings
1725 nofpu [SH] Disable hardware FPU at boot time.
1727 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1728 register save and restore. The kernel will only save
1729 legacy floating-point registers on task switch.
1731 noxsave [BUGS=X86] Disables x86 extended register state save
1732 and restore using xsave. The kernel will fallback to
1733 enabling legacy floating-point and sse state.
1735 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1736 wfi(ARM) instruction doesn't work correctly and not to
1737 use it. This is also useful when using JTAG debugger.
1739 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1740 instruction doesn't work correctly and not to
1743 no_file_caps Tells the kernel not to honor file capabilities. The
1744 only way then for a file to be executed with privilege
1745 is to be setuid root or executed by root.
1747 nohalt [IA-64] Tells the kernel not to use the power saving
1748 function PAL_HALT_LIGHT when idle. This increases
1749 power-consumption. On the positive side, it reduces
1750 interrupt wake-up latency, which may improve performance
1751 in certain environments such as networked servers or
1754 nohz= [KNL] Boottime enable/disable dynamic ticks
1755 Valid arguments: on, off
1758 noiotrap [SH] Disables trapped I/O port accesses.
1760 noirqdebug [X86-32] Disables the code which attempts to detect and
1761 disable unhandled interrupt sources.
1763 no_timer_check [X86,APIC] Disables the code which tests for
1764 broken timer IRQ sources.
1766 noisapnp [ISAPNP] Disables ISA PnP code.
1768 noinitrd [RAM] Tells the kernel not to load any configured
1771 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1773 [Deprecated - use intremap=off]
1777 nojitter [IA-64] Disables jitter checking for ITC timers.
1779 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1781 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1784 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1785 steal time is computed, but won't influence scheduler
1788 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1790 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1792 noltlbs [PPC] Do not use large page/tlb entries for kernel
1793 lowmem mapping on PPC40x.
1795 nomca [IA-64] Disable machine check abort handling
1797 nomce [X86-32] Machine Check Exception
1799 nomfgpt [X86-32] Disable Multi-Function General Purpose
1800 Timer usage (for AMD Geode machines).
1802 nopat [X86] Disable PAT (page attribute table extension of
1803 pagetables) support.
1805 norandmaps Don't use address space randomization. Equivalent to
1806 echo 0 > /proc/sys/kernel/randomize_va_space
1808 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1810 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1811 with UP alternatives
1813 noresidual [PPC] Don't use residual data on PReP machines.
1815 nordrand [X86] Disable the direct use of the RDRAND
1816 instruction even if it is supported by the
1817 processor. RDRAND is still available to user
1820 noresume [SWSUSP] Disables resume and restores original swap
1823 no-scroll [VGA] Disables scrollback.
1824 This is required for the Braillex ib80-piezo Braille
1825 reader made by F.H. Papenmeier (Germany).
1829 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1831 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1832 and disable the IO APIC. legacy for "maxcpus=0".
1834 nosoftlockup [KNL] Disable the soft-lockup detector.
1836 nosync [HW,M68K] Disables sync negotiation for all devices.
1838 notsc [BUGS=X86-32] Disable Time Stamp Counter
1840 nousb [USB] Disable the USB subsystem
1842 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1846 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1848 nptcg= [IA-64] Override max number of concurrent global TLB
1849 purges which is reported from either PAL_VM_SUMMARY or
1852 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1853 could support. nr_cpus=n : n >= 1 limits the kernel to
1854 supporting 'n' processors. Later in runtime you can not
1855 use hotplug cpu feature to put more cpu back to online.
1856 just like you compile the kernel NR_CPUS=n
1858 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1860 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1861 one of ['zone', 'node', 'default'] can be specified
1862 This can be set from sysctl after boot.
1863 See Documentation/sysctl/vm.txt for details.
1865 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1866 See Documentation/debugging-via-ohci1394.txt for more
1869 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1870 Rather than timing out after 20 ms if an EC
1871 command is not properly ACKed, override the length
1872 of the timeout. We have interrupts disabled while
1873 waiting for the ACK, so if this is set too high
1874 interrupts *may* be lost!
1876 omap_mux= [OMAP] Override bootloader pin multiplexing.
1877 Format: <mux_mode0.mode_name=value>...
1878 For example, to override I2C bus2:
1879 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1881 oprofile.timer= [HW]
1882 Use timer interrupt instead of performance counters
1884 oprofile.cpu_type= Force an oprofile cpu type
1885 This might be useful if you have an older oprofile
1886 userland or if you want common events.
1887 Format: { arch_perfmon }
1888 arch_perfmon: [X86] Force use of architectural
1889 perfmon on Intel CPUs instead of the
1890 CPU specific event set.
1892 oops=panic Always panic on oopses. Default is to just kill the
1893 process, but there is a small probability of
1894 deadlocking the machine.
1895 This will also cause panics on machine check exceptions.
1896 Useful together with panic=30 to trigger a reboot.
1899 See Documentation/sound/oss/oss-parameters.txt
1901 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1902 timeout > 0: seconds before rebooting
1903 timeout = 0: wait forever
1904 timeout < 0: reboot immediately
1907 parkbd.port= [HW] Parallel port number the keyboard adapter is
1908 connected to, default is 0.
1910 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1911 0 for XT, 1 for AT (default is AT).
1914 parport= [HW,PPT] Specify parallel ports. 0 disables.
1915 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1916 Use 'auto' to force the driver to use any
1917 IRQ/DMA settings detected (the default is to
1918 ignore detected IRQ/DMA settings because of
1919 possible conflicts). You can specify the base
1920 address, IRQ, and DMA settings; IRQ and DMA
1921 should be numbers, or 'auto' (for using detected
1922 settings on that particular port), or 'nofifo'
1923 (to avoid using a FIFO even if it is detected).
1924 Parallel ports are assigned in the order they
1925 are specified on the command line, starting
1928 parport_init_mode= [HW,PPT]
1929 Configure VIA parallel port to operate in
1930 a specific mode. This is necessary on Pegasos
1931 computer where firmware has no options for setting
1932 up parallel port mode and sets it to spp.
1933 Currently this function knows 686a and 8231 chips.
1934 Format: [spp|ps2|epp|ecp|ecpepp]
1937 Halt all CPUs after the first oops has been printed for
1938 the specified number of seconds. This is to be used if
1939 your oopses keep scrolling off the screen.
1944 See header of drivers/block/paride/pcd.c.
1945 See also Documentation/blockdev/paride.txt.
1947 pci=option[,option...] [PCI] various PCI subsystem options:
1948 earlydump [X86] dump PCI config space before the kernel
1950 off [X86] don't probe for the PCI bus
1951 bios [X86-32] force use of PCI BIOS, don't access
1952 the hardware directly. Use this if your machine
1953 has a non-standard PCI host bridge.
1954 nobios [X86-32] disallow use of PCI BIOS, only direct
1955 hardware access methods are allowed. Use this
1956 if you experience crashes upon bootup and you
1957 suspect they are caused by the BIOS.
1958 conf1 [X86] Force use of PCI Configuration
1960 conf2 [X86] Force use of PCI Configuration
1962 noaer [PCIE] If the PCIEAER kernel config parameter is
1963 enabled, this kernel boot option can be used to
1964 disable the use of PCIE advanced error reporting.
1965 nodomains [PCI] Disable support for multiple PCI
1966 root domains (aka PCI segments, in ACPI-speak).
1967 nommconf [X86] Disable use of MMCONFIG for PCI
1969 check_enable_amd_mmconf [X86] check for and enable
1970 properly configured MMIO access to PCI
1971 config space on AMD family 10h CPU
1972 nomsi [MSI] If the PCI_MSI kernel config parameter is
1973 enabled, this kernel boot option can be used to
1974 disable the use of MSI interrupts system-wide.
1975 noioapicquirk [APIC] Disable all boot interrupt quirks.
1976 Safety option to keep boot IRQs enabled. This
1977 should never be necessary.
1978 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1979 primary IO-APIC for bridges that cannot disable
1980 boot IRQs. This fixes a source of spurious IRQs
1981 when the system masks IRQs.
1982 noioapicreroute [APIC] Disable workaround that uses the
1983 boot IRQ equivalent of an IRQ that connects to
1984 a chipset where boot IRQs cannot be disabled.
1985 The opposite of ioapicreroute.
1986 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1987 routing table. These calls are known to be buggy
1988 on several machines and they hang the machine
1989 when used, but on other computers it's the only
1990 way to get the interrupt routing table. Try
1991 this option if the kernel is unable to allocate
1992 IRQs or discover secondary PCI buses on your
1994 rom [X86] Assign address space to expansion ROMs.
1995 Use with caution as certain devices share
1996 address decoders between ROMs and other
1998 norom [X86] Do not assign address space to
1999 expansion ROMs that do not already have
2000 BIOS assigned address ranges.
2001 nobar [X86] Do not assign address space to the
2002 BARs that weren't assigned by the BIOS.
2003 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2004 assigned automatically to PCI devices. You can
2005 make the kernel exclude IRQs of your ISA cards
2007 pirqaddr=0xAAAAA [X86] Specify the physical address
2008 of the PIRQ table (normally generated
2009 by the BIOS) if it is outside the
2010 F0000h-100000h range.
2011 lastbus=N [X86] Scan all buses thru bus #N. Can be
2012 useful if the kernel is unable to find your
2013 secondary buses and you want to tell it
2014 explicitly which ones they are.
2015 assign-busses [X86] Always assign all PCI bus
2016 numbers ourselves, overriding
2017 whatever the firmware may have done.
2018 usepirqmask [X86] Honor the possible IRQ mask stored
2019 in the BIOS $PIR table. This is needed on
2020 some systems with broken BIOSes, notably
2021 some HP Pavilion N5400 and Omnibook XE3
2022 notebooks. This will have no effect if ACPI
2023 IRQ routing is enabled.
2024 noacpi [X86] Do not use ACPI for IRQ routing
2025 or for PCI scanning.
2026 use_crs [X86] Use PCI host bridge window information
2027 from ACPI. On BIOSes from 2008 or later, this
2028 is enabled by default. If you need to use this,
2029 please report a bug.
2030 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2031 If you need to use this, please report a bug.
2032 routeirq Do IRQ routing for all PCI devices.
2033 This is normally done in pci_enable_device(),
2034 so this option is a temporary workaround
2035 for broken drivers that don't call it.
2036 skip_isa_align [X86] do not align io start addr, so can
2037 handle more pci cards
2038 firmware [ARM] Do not re-enumerate the bus but instead
2039 just use the configuration from the
2040 bootloader. This is currently used on
2041 IXP2000 systems where the bus has to be
2042 configured a certain way for adjunct CPUs.
2043 noearly [X86] Don't do any early type 1 scanning.
2044 This might help on some broken boards which
2045 machine check when some devices' config space
2046 is read. But various workarounds are disabled
2047 and some IOMMU drivers will not work.
2048 bfsort Sort PCI devices into breadth-first order.
2049 This sorting is done to get a device
2050 order compatible with older (<= 2.4) kernels.
2051 nobfsort Don't sort PCI devices into breadth-first order.
2052 cbiosize=nn[KMG] The fixed amount of bus space which is
2053 reserved for the CardBus bridge's IO window.
2054 The default value is 256 bytes.
2055 cbmemsize=nn[KMG] The fixed amount of bus space which is
2056 reserved for the CardBus bridge's memory
2057 window. The default value is 64 megabytes.
2060 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2061 Specifies alignment and device to reassign
2062 aligned memory resources.
2063 If <order of align> is not specified,
2064 PAGE_SIZE is used as alignment.
2065 PCI-PCI bridge can be specified, if resource
2066 windows need to be expanded.
2067 ecrc= Enable/disable PCIe ECRC (transaction layer
2068 end-to-end CRC checking).
2069 bios: Use BIOS/firmware settings. This is the
2073 realloc reallocate PCI resources if allocations done by BIOS
2076 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2079 force Enable ASPM even on devices that claim not to support it.
2080 WARNING: Forcing ASPM on may cause system lockups.
2082 pcie_ports= [PCIE] PCIe ports handling:
2083 auto Ask the BIOS whether or not to use native PCIe services
2084 associated with PCIe ports (PME, hot-plug, AER). Use
2085 them only if that is allowed by the BIOS.
2086 native Use native PCIe services associated with PCIe ports
2088 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2091 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2092 nomsi Do not use MSI for native PCIe PME signaling (this makes
2093 all PCIe root ports use INTx for all services).
2095 pcmv= [HW,PCMCIA] BadgePAD 4
2098 See Documentation/blockdev/paride.txt.
2100 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2103 See arch/parisc/kernel/pdc_chassis.c
2105 percpu_alloc= Select which percpu first chunk allocator to use.
2106 Currently supported values are "embed" and "page".
2107 Archs may support subset or none of the selections.
2108 See comments in mm/percpu.c for details on each
2109 allocator. This parameter is primarily for debugging
2110 and performance comparison.
2113 See Documentation/blockdev/paride.txt.
2116 See Documentation/blockdev/paride.txt.
2118 pirq= [SMP,APIC] Manual mp-table setup
2119 See Documentation/x86/i386/IO-APIC.txt.
2121 plip= [PPT,NET] Parallel port network link
2122 Format: { parport<nr> | timid | 0 }
2123 See also Documentation/parport.txt.
2125 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2126 Override pmtimer IOPort with a hex value.
2130 Enable PNP debug messages (depends on the
2131 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2132 via /sys/module/pnp/parameters/debug. We always show
2133 current resource usage; turning this on also shows
2134 possible settings and some assignment information.
2140 { on | off | curr | res | no-curr | no-res }
2143 [ISAPNP] Exclude IRQs for the autoconfiguration
2146 [ISAPNP] Exclude DMAs for the autoconfiguration
2148 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2149 Ranges are in pairs (I/O port base and size).
2152 [ISAPNP] Exclude memory regions for the
2154 Ranges are in pairs (memory base and size).
2156 ports= [IP_VS_FTP] IPVS ftp helper module
2158 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2160 Format: <port>,<port>....
2162 print-fatal-signals=
2163 [KNL] debug: print fatal signals
2165 If enabled, warn about various signal handling
2166 related application anomalies: too many signals,
2167 too many POSIX.1 timers, fatal signals causing a
2170 If you hit the warning due to signal overflow,
2171 you might want to try "ulimit -i unlimited".
2175 printk.time= Show timing data prefixed to each printk message line
2176 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2178 processor.max_cstate= [HW,ACPI]
2179 Limit processor to maximum C-state
2180 max_cstate=9 overrides any DMI blacklist limit.
2182 processor.nocst [HW,ACPI]
2183 Ignore the _CST method to determine C-states,
2184 instead using the legacy FADT method
2186 profile= [KNL] Enable kernel profiling via /proc/profile
2187 Format: [schedule,]<number>
2188 Param: "schedule" - profile schedule points.
2189 Param: <number> - step/bucket size as a power of 2 for
2190 statistical time based profiling.
2191 Param: "sleep" - profile D-state sleeping (millisecs).
2192 Requires CONFIG_SCHEDSTATS
2193 Param: "kvm" - profile VM exits.
2195 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2197 See Documentation/blockdev/ramdisk.txt.
2199 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2200 probe for; one of (bare|imps|exps|lifebook|any).
2201 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2203 psmouse.resetafter= [HW,MOUSE]
2204 Try to reset the device after so many bad packets
2207 [HW,MOUSE] Set desired mouse resolution, in dpi.
2208 psmouse.smartscroll=
2209 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2210 0 = disabled, 1 = enabled (default).
2212 pstore.backend= Specify the name of the pstore backend to use
2215 See Documentation/blockdev/paride.txt.
2218 [KNL] Number of legacy pty's. Overwrites compiled-in
2221 quiet [KNL] Disable most log messages
2226 See Documentation/md.txt.
2228 ramdisk_blocksize= [RAM]
2229 See Documentation/blockdev/ramdisk.txt.
2231 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2232 See Documentation/blockdev/ramdisk.txt.
2234 rcupdate.blimit= [KNL,BOOT]
2235 Set maximum number of finished RCU callbacks to process
2238 rcupdate.qhimark= [KNL,BOOT]
2239 Set threshold of queued
2240 RCU callbacks over which batch limiting is disabled.
2242 rcupdate.qlowmark= [KNL,BOOT]
2243 Set threshold of queued RCU callbacks below which
2244 batch limiting is re-enabled.
2248 Run specified binary instead of /init from the ramdisk,
2249 used for early userspace startup. See initrd.
2251 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2252 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2253 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2256 [KNL, SMP] Set scheduler's default relax_domain_level.
2257 See Documentation/cgroups/cpusets.txt.
2259 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2261 reservetop= [X86-32]
2263 Reserves a hole at the top of the kernel virtual
2268 Set the amount of memory to reserve for BIOS at
2269 the bottom of the address space.
2271 reset_devices [KNL] Force drivers to reset the underlying device
2272 during initialization.
2275 Specify the partition device for software suspend
2277 resume_offset= [SWSUSP]
2278 Specify the offset from the beginning of the partition
2279 given by "resume=" at which the swap header is located,
2280 in <PAGE_SIZE> units (needed only for swap files).
2281 See Documentation/power/swsusp-and-swap-files.txt
2283 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2284 read the resume files
2286 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2287 Useful for devices that are detected asynchronously
2288 (e.g. USB and MMC devices).
2290 hibernate= [HIBERNATION]
2291 noresume Don't check if there's a hibernation image
2292 present during boot.
2293 nocompress Don't compress/decompress hibernation images.
2295 retain_initrd [RAM] Keep initrd memory after extraction
2297 rhash_entries= [KNL,NET]
2298 Set number of hash buckets for route cache
2300 riscom8= [HW,SERIAL]
2301 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2303 ro [KNL] Mount root device read-only on boot
2305 root= [KNL] Root filesystem
2306 See name_to_dev_t comment in init/do_mounts.c.
2308 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2309 mount the root filesystem
2311 rootflags= [KNL] Set root filesystem mount option string
2313 rootfstype= [KNL] Set root filesystem type
2315 rootwait [KNL] Wait (indefinitely) for root device to show up.
2316 Useful for devices that are detected asynchronously
2317 (e.g. USB and MMC devices).
2319 rw [KNL] Mount root device read-write on boot
2321 S [KNL] Run init in single mode
2324 See drivers/net/irda/sa1100_ir.c.
2326 sbni= [NET] Granch SBNI12 leased line adapter
2328 sched_debug [KNL] Enables verbose scheduler debug messages.
2330 security= [SECURITY] Choose a security module to enable at boot.
2331 If this boot parameter is not specified, only the first
2332 security module asking for security registration will be
2333 loaded. An invalid security module name will be treated
2334 as if no module has been chosen.
2336 selinux= [SELINUX] Disable or enable SELinux at boot time.
2337 Format: { "0" | "1" }
2338 See security/selinux/Kconfig help text.
2341 Default value is set via kernel config option.
2342 If enabled at boot time, /selinux/disable can be used
2343 later to disable prior to initial policy load.
2345 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2346 Format: { "0" | "1" }
2347 See security/apparmor/Kconfig help text
2350 Default value is set via kernel config option.
2352 serialnumber [BUGS=X86-32]
2355 Maximal number of shapers.
2357 show_msr= [x86] show boot-time MSR settings
2358 Format: { <integer> }
2359 Show boot-time (BIOS-initialized) MSR settings.
2360 The parameter means the number of CPUs to show,
2361 for example 1 means boot CPU only.
2368 slub_debug[=options[,slabs]] [MM, SLUB]
2369 Enabling slub_debug allows one to determine the
2370 culprit if slab objects become corrupted. Enabling
2371 slub_debug can create guard zones around objects and
2372 may poison objects when not in use. Also tracks the
2373 last alloc / free. For more information see
2374 Documentation/vm/slub.txt.
2376 slub_max_order= [MM, SLUB]
2377 Determines the maximum allowed order for slabs.
2378 A high setting may cause OOMs due to memory
2379 fragmentation. For more information see
2380 Documentation/vm/slub.txt.
2382 slub_min_objects= [MM, SLUB]
2383 The minimum number of objects per slab. SLUB will
2384 increase the slab order up to slub_max_order to
2385 generate a sufficiently large slab able to contain
2386 the number of objects indicated. The higher the number
2387 of objects the smaller the overhead of tracking slabs
2388 and the less frequently locks need to be acquired.
2389 For more information see Documentation/vm/slub.txt.
2391 slub_min_order= [MM, SLUB]
2392 Determines the mininum page order for slabs. Must be
2393 lower than slub_max_order.
2394 For more information see Documentation/vm/slub.txt.
2396 slub_nomerge [MM, SLUB]
2397 Disable merging of slabs with similar size. May be
2398 necessary if there is some reason to distinguish
2399 allocs to different slabs. Debug options disable
2400 merging on their own.
2401 For more information see Documentation/vm/slub.txt.
2404 Format: <io1>[,<io2>[,...,<io8>]]
2406 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2407 attempt to substitute SMP alternatives once at boot.
2409 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2410 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2411 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2412 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2413 smsc-ircc2.ircc_irq= [HW] IRQ line
2414 smsc-ircc2.ircc_dma= [HW] DMA channel
2415 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2416 0: Toshiba Satellite 1800 (GP data pin select)
2417 1: Fast pin select (default)
2421 [KNL] Should the soft-lockup detector generate panics.
2424 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2425 See Documentation/laptops/sonypi.txt
2427 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2428 See Documentation/serial/specialix.txt.
2430 spia_io_base= [HW,MTD]
2436 Enabled the stack tracer on boot up.
2440 Set the STI (builtin display/keyboard on the HP-PARISC
2441 machines) console (graphic card) which should be used
2442 as the initial boot-console.
2443 See also comment in drivers/video/console/sticore.c.
2446 See comment in drivers/video/console/sticore.c.
2449 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2451 sunrpc.min_resvport=
2452 sunrpc.max_resvport=
2454 SunRPC servers often require that client requests
2455 originate from a privileged port (i.e. a port in the
2456 range 0 < portnr < 1024).
2457 An administrator who wishes to reserve some of these
2458 ports for other uses may adjust the range that the
2459 kernel's sunrpc client considers to be privileged
2460 using these two parameters to set the minimum and
2461 maximum port values.
2465 Control how the NFS server code allocates CPUs to
2466 service thread pools. Depending on how many NICs
2467 you have and where their interrupts are bound, this
2468 option will affect which CPUs will do NFS serving.
2469 Note: this parameter cannot be changed while the
2470 NFS server is running.
2472 auto the server chooses an appropriate mode
2473 automatically using heuristics
2474 global a single global pool contains all CPUs
2475 percpu one pool for each CPU
2476 pernode one pool for each NUMA node (equivalent
2477 to global on non-NUMA machines)
2479 sunrpc.tcp_slot_table_entries=
2480 sunrpc.udp_slot_table_entries=
2482 Sets the upper limit on the number of simultaneous
2483 RPC calls that can be sent from the client to a
2484 server. Increasing these values may allow you to
2485 improve throughput, but will also increase the
2486 amount of memory reserved for use by the client.
2489 [KNL] Enable accounting of swap in memory resource
2490 controller if no parameter or 1 is given or disable
2491 it if 0 is given (See Documentation/cgroups/memory.txt)
2493 swiotlb= [IA-64] Number of I/O TLB slabs
2497 sysfs.deprecated=0|1 [KNL]
2498 Enable/disable old style sysfs layout for old udev
2499 on older distributions. When this option is enabled
2500 very new udev will not work anymore. When this option
2501 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2502 in older udev will not work anymore.
2503 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2504 the kernel configuration.
2506 sysrq_always_enabled
2508 Ignore sysrq setting - this boot parameter will
2509 neutralize any effect of /proc/sys/kernel/sysrq.
2510 Useful for debugging.
2514 test_suspend= [SUSPEND]
2515 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2516 standby suspend) as the system sleep state to briefly
2517 enter during system startup. The system is woken from
2518 this state using a wakeup-capable RTC alarm.
2520 thash_entries= [KNL,NET]
2521 Set number of hash buckets for TCP connection
2523 thermal.act= [HW,ACPI]
2524 -1: disable all active trip points in all thermal zones
2525 <degrees C>: override all lowest active trip points
2527 thermal.crt= [HW,ACPI]
2528 -1: disable all critical trip points in all thermal zones
2529 <degrees C>: override all critical trip points
2531 thermal.nocrt= [HW,ACPI]
2532 Set to disable actions on ACPI thermal zone
2533 critical and hot trip points.
2535 thermal.off= [HW,ACPI]
2536 1: disable ACPI thermal control
2538 thermal.psv= [HW,ACPI]
2539 -1: disable all passive trip points
2540 <degrees C>: override all passive trip points to this
2543 thermal.tzp= [HW,ACPI]
2544 Specify global default ACPI thermal zone polling rate
2545 <deci-seconds>: poll all this frequency
2546 0: no polling (default)
2549 Force threading of all interrupt handlers except those
2550 marked explicitely IRQF_NO_THREAD.
2554 Specify if the kernel should make use of the cpu
2555 topology information if the hardware supports this.
2556 The scheduler will make use of this information and
2557 e.g. base its process migration decisions on it.
2562 tpm_suspend_pcr=[HW,TPM]
2563 Format: integer pcr id
2564 Specify that at suspend time, the tpm driver
2565 should extend the specified pcr with zeros,
2566 as a workaround for some chips which fail to
2567 flush the last written pcr on TPM_SaveState.
2568 This will guarantee that all the other pcrs
2571 trace_buf_size=nn[KMG]
2572 [FTRACE] will set tracing buffer size.
2574 trace_event=[event-list]
2575 [FTRACE] Set and start specified trace events in order
2576 to facilitate early boot debugging.
2577 See also Documentation/trace/events.txt
2579 tsc= Disable clocksource stability checks for TSC.
2581 [x86] reliable: mark tsc clocksource as reliable, this
2582 disables clocksource verification at runtime, as well
2583 as the stability checks done at bootup. Used to enable
2584 high-resolution timer mode on older hardware, and in
2585 virtualized environment.
2586 [x86] noirqtime: Do not use TSC to do irq accounting.
2587 Used to run time disable IRQ_TIME_ACCOUNTING on any
2588 platforms where RDTSC is slow and this accounting
2591 turbografx.map[2|3]= [HW,JOY]
2592 TurboGraFX parallel port interface
2594 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2595 See also Documentation/input/joystick-parport.txt
2597 udbg-immortal [PPC] When debugging early kernel crashes that
2598 happen after console_init() and before a proper
2599 console driver takes over, this boot options might
2600 help "seeing" what's going on.
2602 uhash_entries= [KNL,NET]
2603 Set number of hash buckets for UDP/UDP-Lite connections
2606 [USB] Ignore overcurrent events (default N).
2607 Some badly-designed motherboards generate lots of
2608 bogus events, for ports that aren't wired to
2609 anything. Set this parameter to avoid log spamming.
2610 Note that genuine overcurrent events won't be
2614 [X86] Cause panic on unknown NMI.
git.openpandora.org / pandora-kernel.git / blob