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 CLK Common clock infrastructure is enabled.
48 CMA Contiguous Memory Area support is enabled.
49 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
51 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
52 EFI EFI Partitioning (GPT) is enabled
53 EIDE EIDE/ATAPI support is enabled.
54 EVM Extended Verification Module
55 FB The frame buffer device is enabled.
56 FTRACE Function tracing enabled.
57 GCOV GCOV profiling is enabled.
58 HW Appropriate hardware is enabled.
59 IA-64 IA-64 architecture is enabled.
60 IMA Integrity measurement architecture is enabled.
61 IOSCHED More than one I/O scheduler is enabled.
62 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
63 IPV6 IPv6 support is enabled.
64 ISAPNP ISA PnP code is enabled.
65 ISDN Appropriate ISDN support is enabled.
66 JOY Appropriate joystick support is enabled.
67 KGDB Kernel debugger support is enabled.
68 KVM Kernel Virtual Machine support is enabled.
69 LIBATA Libata driver is enabled
70 LP Printer support is enabled.
71 LOOP Loopback device support is enabled.
72 M68k M68k architecture is enabled.
73 These options have more detailed description inside of
74 Documentation/m68k/kernel-options.txt.
75 MDA MDA console support is enabled.
76 MIPS MIPS architecture is enabled.
77 MOUSE Appropriate mouse support is enabled.
78 MSI Message Signaled Interrupts (PCI).
79 MTD MTD (Memory Technology Device) support is enabled.
80 NET Appropriate network support is enabled.
81 NUMA NUMA support is enabled.
82 NFS Appropriate NFS support is enabled.
83 OSS OSS sound support is enabled.
84 PV_OPS A paravirtualized kernel is enabled.
85 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
86 PARISC The PA-RISC architecture is enabled.
87 PCI PCI bus support is enabled.
88 PCIE PCI Express support is enabled.
89 PCMCIA The PCMCIA subsystem is enabled.
90 PNP Plug & Play support is enabled.
91 PPC PowerPC architecture is enabled.
92 PPT Parallel port support is enabled.
93 PS2 Appropriate PS/2 support is enabled.
94 RAM RAM disk support is enabled.
95 S390 S390 architecture is enabled.
96 SCSI Appropriate SCSI support is enabled.
97 A lot of drivers have their options described inside
98 the Documentation/scsi/ sub-directory.
99 SECURITY Different security models are enabled.
100 SELINUX SELinux support is enabled.
101 APPARMOR AppArmor support is enabled.
102 SERIAL Serial support is enabled.
103 SH SuperH architecture is enabled.
104 SMP The kernel is an SMP kernel.
105 SPARC Sparc architecture is enabled.
106 SWSUSP Software suspend (hibernation) is enabled.
107 SUSPEND System suspend states are enabled.
108 TPM TPM drivers are enabled.
109 TS Appropriate touchscreen support is enabled.
110 UMS USB Mass Storage support is enabled.
111 USB USB support is enabled.
112 USBHID USB Human Interface Device support is enabled.
113 V4L Video For Linux support is enabled.
114 VMMIO Driver for memory mapped virtio devices is enabled.
115 VGA The VGA console has been enabled.
116 VT Virtual terminal support is enabled.
117 WDT Watchdog support is enabled.
118 XT IBM PC/XT MFM hard disk support is enabled.
119 X86-32 X86-32, aka i386 architecture is enabled.
120 X86-64 X86-64 architecture is enabled.
121 More X86-64 boot options can be found in
122 Documentation/x86/x86_64/boot-options.txt .
123 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
124 XEN Xen support is enabled
126 In addition, the following text indicates that the option:
128 BUGS= Relates to possible processor bugs on the said processor.
129 KNL Is a kernel start-up parameter.
130 BOOT Is a boot loader parameter.
132 Parameters denoted with BOOT are actually interpreted by the boot
133 loader, and have no meaning to the kernel directly.
134 Do not modify the syntax of boot loader parameters without extreme
135 need or coordination with <Documentation/x86/boot.txt>.
137 There are also arch-specific kernel-parameters not documented here.
138 See for example <Documentation/x86/x86_64/boot-options.txt>.
140 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
141 a trailing = on the name of any parameter states that that parameter will
142 be entered as an environment variable, whereas its absence indicates that
143 it will appear as a kernel argument readable via /proc/cmdline by programs
144 running once the system is up.
146 The number of kernel parameters is not limited, but the length of the
147 complete command line (parameters including spaces etc.) is limited to
148 a fixed number of characters. This limit depends on the architecture
149 and is between 256 and 4096 characters. It is defined in the file
150 ./include/asm/setup.h as COMMAND_LINE_SIZE.
152 Finally, the [KMG] suffix is commonly described after a number of kernel
153 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
154 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
155 bytes respectively. Such letter suffixes can also be entirely omitted.
159 Advanced Configuration and Power Interface
160 Format: { force | off | strict | noirq | rsdt }
161 force -- enable ACPI if default was off
162 off -- disable ACPI if default was on
163 noirq -- do not use ACPI for IRQ routing
164 strict -- Be less tolerant of platforms that are not
165 strictly ACPI specification compliant.
166 rsdt -- prefer RSDT over (default) XSDT
167 copy_dsdt -- copy DSDT to memory
169 See also Documentation/power/runtime_pm.txt, pci=noacpi
171 acpi_rsdp= [ACPI,EFI,KEXEC]
172 Pass the RSDP address to the kernel, mostly used
173 on machines running EFI runtime service to boot the
174 second kernel for kdump.
176 acpi_apic_instance= [ACPI, IOAPIC]
178 2: use 2nd APIC table, if available
179 1,0: use 1st APIC table
182 acpi_backlight= [HW,ACPI]
183 acpi_backlight=vendor
185 If set to vendor, prefer vendor specific driver
186 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
187 of the ACPI video.ko driver.
189 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
190 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
192 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
193 debug output. Bits in debug_layer correspond to a
194 _COMPONENT in an ACPI source file, e.g.,
195 #define _COMPONENT ACPI_PCI_COMPONENT
196 Bits in debug_level correspond to a level in
197 ACPI_DEBUG_PRINT statements, e.g.,
198 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
199 The debug_level mask defaults to "info". See
200 Documentation/acpi/debug.txt for more information about
201 debug layers and levels.
203 Enable processor driver info messages:
204 acpi.debug_layer=0x20000000
205 Enable PCI/PCI interrupt routing info messages:
206 acpi.debug_layer=0x400000
207 Enable AML "Debug" output, i.e., stores to the Debug
208 object while interpreting AML:
209 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
210 Enable all messages related to ACPI hardware:
211 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
213 Some values produce so much output that the system is
214 unusable. The "log_buf_len" parameter may be useful
215 if you need to capture more output.
217 acpi_irq_balance [HW,ACPI]
218 ACPI will balance active IRQs
221 acpi_irq_nobalance [HW,ACPI]
222 ACPI will not move active IRQs (default)
225 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
226 Format: <irq>,<irq>...
228 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
230 Format: <irq>,<irq>...
232 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
234 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
235 Format: To spoof as Windows 98: ="Microsoft Windows"
237 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
238 acpi_osi="string1" # add string1
239 acpi_osi="!string2" # remove string2
240 acpi_osi=!* # remove all strings
241 acpi_osi=! # disable all built-in OS vendor
243 acpi_osi= # disable all strings
245 'acpi_osi=!' can be used in combination with single or
246 multiple 'acpi_osi="string1"' to support specific OS
247 vendor string(s). Note that such command can only
248 affect the default state of the OS vendor strings, thus
249 it cannot affect the default state of the feature group
250 strings and the current state of the OS vendor strings,
251 specifying it multiple times through kernel command line
252 is meaningless. This command is useful when one do not
253 care about the state of the feature group strings which
254 should be controlled by the OSPM.
256 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
257 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
258 can make '_OSI("Windows 2000")' TRUE.
260 'acpi_osi=' cannot be used in combination with other
261 'acpi_osi=' command lines, the _OSI method will not
262 exist in the ACPI namespace. NOTE that such command can
263 only affect the _OSI support state, thus specifying it
264 multiple times through kernel command line is also
267 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
270 'acpi_osi=!*' can be used in combination with single or
271 multiple 'acpi_osi="string1"' to support specific
272 string(s). Note that such command can affect the
273 current state of both the OS vendor strings and the
274 feature group strings, thus specifying it multiple times
275 through kernel command line is meaningful. But it may
276 still not able to affect the final state of a string if
277 there are quirks related to this string. This command
278 is useful when one want to control the state of the
279 feature group strings to debug BIOS issues related to
282 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
283 '_OSI("Module Device")' FALSE.
284 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
285 '_OSI("Module Device")' TRUE.
286 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
288 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
290 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
291 they all will make '_OSI("Windows 2000")' TRUE.
294 Override the pmtimer bug detection: force the kernel
295 to assume that this machine's pmtimer latches its value
296 and always returns good values.
298 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
299 Format: { level | edge | high | low }
301 acpi_serialize [HW,ACPI] force serialization of AML methods
303 acpi_skip_timer_override [HW,ACPI]
304 Recognize and ignore IRQ0/pin2 Interrupt Override.
305 For broken nForce2 BIOS resulting in XT-PIC timer.
307 acpi_sleep= [HW,ACPI] Sleep options
308 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
309 old_ordering, nonvs, sci_force_enable }
310 See Documentation/power/video.txt for information on
312 s3_beep is for debugging; it makes the PC's speaker beep
313 as soon as the kernel's real-mode entry point is called.
314 s4_nohwsig prevents ACPI hardware signature from being
315 used during resume from hibernation.
316 old_ordering causes the ACPI 1.0 ordering of the _PTS
317 control method, with respect to putting devices into
318 low power states, to be enforced (the ACPI 2.0 ordering
319 of _PTS is used by default).
320 nonvs prevents the kernel from saving/restoring the
321 ACPI NVS memory during suspend/hibernation and resume.
322 sci_force_enable causes the kernel to set SCI_EN directly
323 on resume from S1/S3 (which is against the ACPI spec,
324 but some broken systems don't work without it).
326 acpi_use_timer_override [HW,ACPI]
327 Use timer override. For some broken Nvidia NF5 boards
328 that require a timer override, but don't have HPET
330 acpi_enforce_resources= [ACPI]
331 { strict | lax | no }
332 Check for resource conflicts between native drivers
333 and ACPI OperationRegions (SystemIO and SystemMemory
334 only). IO ports and memory declared in ACPI might be
335 used by the ACPI subsystem in arbitrary AML code and
336 can interfere with legacy drivers.
337 strict (default): access to resources claimed by ACPI
338 is denied; legacy drivers trying to access reserved
339 resources will fail to bind to device using them.
340 lax: access to resources claimed by ACPI is allowed;
341 legacy drivers trying to access reserved resources
342 will bind successfully but a warning message is logged.
343 no: ACPI OperationRegions are not marked as reserved,
344 no further checks are performed.
346 add_efi_memmap [EFI; X86] Include EFI memory map in
347 kernel's map of available physical RAM.
350 { off | try_unsupported }
351 off: disable AGP support
352 try_unsupported: try to drive unsupported chipsets
353 (may crash computer or cause data corruption)
356 See Documentation/sound/alsa/alsa-parameters.txt
359 Allow the default userspace alignment fault handler
360 behaviour to be specified. Bit 0 enables warnings,
361 bit 1 enables fixups, and bit 2 sends a segfault.
363 align_va_addr= [X86-64]
364 Align virtual addresses by clearing slice [14:12] when
365 allocating a VMA at process creation time. This option
366 gives you up to 3% performance improvement on AMD F15h
367 machines (where it is enabled by default) for a
368 CPU-intensive style benchmark, and it can vary highly in
369 a microbenchmark depending on workload and compiler.
371 32: only for 32-bit processes
372 64: only for 64-bit processes
373 on: enable for both 32- and 64-bit processes
374 off: disable for both 32- and 64-bit processes
376 alloc_snapshot [FTRACE]
377 Allocate the ftrace snapshot buffer on boot up when the
378 main buffer is allocated. This is handy if debugging
379 and you need to use tracing_snapshot() on boot up, and
380 do not want to use tracing_snapshot_alloc() as it needs
381 to be done where GFP_KERNEL allocations are allowed.
383 amd_iommu= [HW,X86-64]
384 Pass parameters to the AMD IOMMU driver in the system.
386 fullflush - enable flushing of IO/TLB entries when
387 they are unmapped. Otherwise they are
388 flushed before they will be reused, which
390 off - do not initialize any AMD IOMMU found in
392 force_isolation - Force device isolation for all
393 devices. The IOMMU driver is not
394 allowed anymore to lift isolation
395 requirements as needed. This option
396 does not override iommu=pt
398 amd_iommu_dump= [HW,X86-64]
399 Enable AMD IOMMU driver option to dump the ACPI table
400 for AMD IOMMU. With this option enabled, AMD IOMMU
401 driver will print ACPI tables for AMD IOMMU during
402 IOMMU initialization.
404 amijoy.map= [HW,JOY] Amiga joystick support
405 Map of devices attached to JOY0DAT and JOY1DAT
407 See also Documentation/input/joystick.txt
409 analog.map= [HW,JOY] Analog joystick and gamepad support
410 Specifies type or capabilities of an analog joystick
411 connected to one of 16 gameports
412 Format: <type1>,<type2>,..<type16>
415 Power management functions (SPARCstation-4/5 + deriv.)
417 Disable APC CPU standby support. SPARCstation-Fox does
418 not play well with APC CPU idle - disable it if you have
419 APC and your system crashes randomly.
421 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
422 Change the output verbosity whilst booting
423 Format: { quiet (default) | verbose | debug }
424 Change the amount of debugging information output
425 when initialising the APIC and IO-APIC components.
428 See Documentation/networking/ipv6.txt.
430 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
431 Limit apic dumping. The parameter defines the maximal
432 number of local apics being dumped. Also it is possible
433 to set it to "all" by meaning -- no limit here.
434 Format: { 1 (default) | 2 | ... | all }.
435 The parameter valid if only apic=debug or
436 apic=verbose is specified.
437 Example: apic=debug show_lapic=all
439 apm= [APM] Advanced Power Management
440 See header of arch/x86/kernel/apm_32.c.
442 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
443 Format: <io>,<irq>,<nodeID>
447 atarimouse= [HW,MOUSE] Atari Mouse
449 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
450 EzKey and similar keyboards
452 atkbd.reset= [HW] Reset keyboard during initialization
454 atkbd.set= [HW] Select keyboard code set
455 Format: <int> (2 = AT (default), 3 = PS/2)
457 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
460 atkbd.softraw= [HW] Choose between synthetic and real raw mode
461 Format: <bool> (0 = real, 1 = synthetic (default))
463 atkbd.softrepeat= [HW]
464 Use software keyboard repeat
466 audit= [KNL] Enable the audit sub-system
467 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
468 0 - kernel audit is disabled and can not be enabled
469 until the next reboot
470 unset - kernel audit is initialized but disabled and
471 will be fully enabled by the userspace auditd.
472 1 - kernel audit is initialized and partially enabled,
473 storing at most audit_backlog_limit messages in
474 RAM until it is fully enabled by the userspace
478 audit_backlog_limit= [KNL] Set the audit queue size limit.
479 Format: <int> (must be >=0)
482 baycom_epp= [HW,AX25]
485 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
487 See header of drivers/net/hamradio/baycom_par.c.
489 baycom_ser_fdx= [HW,AX25]
490 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
491 Format: <io>,<irq>,<mode>[,<baud>]
492 See header of drivers/net/hamradio/baycom_ser_fdx.c.
494 baycom_ser_hdx= [HW,AX25]
495 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
496 Format: <io>,<irq>,<mode>
497 See header of drivers/net/hamradio/baycom_ser_hdx.c.
499 blkdevparts= Manual partition parsing of block device(s) for
500 embedded devices based on command line input.
501 See Documentation/block/cmdline-partition.txt
503 boot_delay= Milliseconds to delay each printk during boot.
504 Values larger than 10 seconds (10000) are changed to
508 bootmem_debug [KNL] Enable bootmem allocator debug messages.
510 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
511 bttv.radio= Most important insmod options are available as
513 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
516 bulk_remove=off [PPC] This parameter disables the use of the pSeries
517 firmware feature for flushing multiple hpte entries
520 c101= [NET] Moxa C101 synchronous serial card
522 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
523 Sometimes CPU hardware bugs make them report the cache
524 size incorrectly. The kernel will attempt work arounds
525 to fix known problems, but for some CPUs it is not
526 possible to determine what the correct size should be.
527 This option provides an override for these situations.
529 ccw_timeout_log [S390]
530 See Documentation/s390/CommonIO for details.
532 cgroup_disable= [KNL] Disable a particular controller
533 Format: {name of the controller(s) to disable}
534 The effects of cgroup_disable=foo are:
535 - foo isn't auto-mounted if you mount all cgroups in
537 - foo isn't visible as an individually mountable
539 {Currently only "memory" controller deal with this and
540 cut the overhead, others just disable the usage. So
541 only cgroup_disable=memory is actually worthy}
543 checkreqprot [SELINUX] Set initial checkreqprot flag value.
544 Format: { "0" | "1" }
545 See security/selinux/Kconfig help text.
546 0 -- check protection applied by kernel (includes
547 any implied execute protection).
548 1 -- check protection requested by application.
549 Default value is set via a kernel config option.
550 Value can be changed at runtime via
551 /selinux/checkreqprot.
554 See Documentation/s390/CommonIO for details.
557 Keep all clocks already enabled by bootloader on,
558 even if no driver has claimed them. This is useful
559 for debug and development, but should not be
560 needed on a platform with proper driver support.
561 For more information, see Documentation/clk.txt.
563 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
565 Forces specified clocksource (if available) to be used
566 when calculating gettimeofday(). If specified
567 clocksource is not available, it defaults to PIT.
568 Format: { pit | tsc | cyclone | pmtmr }
570 clocksource= Override the default clocksource
572 Override the default clocksource and use the clocksource
573 with the name specified.
574 Some clocksource names to choose from, depending on
576 [all] jiffies (this is the base, fallback clocksource)
578 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
579 pxa_timer,timer3,32k_counter,timer0_1
581 [X86-32] pit,hpet,tsc;
582 scx200_hrt on Geode; cyclone on IBM x440
590 clearcpuid=BITNUM [X86]
591 Disable CPUID feature X for the kernel. See
592 arch/x86/include/asm/cpufeature.h for the valid bit
593 numbers. Note the Linux specific bits are not necessarily
594 stable over kernel options, but the vendor specific
596 Also note that user programs calling CPUID directly
597 or using the feature without checking anything
598 will still see it. This just prevents it from
599 being used by the kernel or shown in /proc/cpuinfo.
600 Also note the kernel might malfunction if you disable
604 Sets the size of kernel global memory area for contiguous
605 memory allocations. For more information, see
606 include/linux/dma-contiguous.h
608 cmo_free_hint= [PPC] Format: { yes | no }
609 Specify whether pages are marked as being inactive
610 when they are freed. This is used in CMO environments
611 to determine OS memory pressure for page stealing by
615 coherent_pool=nn[KMG] [ARM,KNL]
616 Sets the size of memory pool for coherent, atomic dma
617 allocations, by default set to 256K.
619 code_bytes [X86] How many bytes of object code to print
624 com20020= [HW,NET] ARCnet - COM20020 chipset
626 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
628 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
632 ARCnet - COM90xx chipset (memory-mapped buffers)
633 Format: <io>[,<irq>[,<memstart>]]
635 condev= [HW,S390] console device
638 console= [KNL] Output console device and options.
640 tty<n> Use the virtual console device <n>.
644 Use the specified serial port. The options are of
645 the form "bbbbpnf", where "bbbb" is the baud rate,
646 "p" is parity ("n", "o", or "e"), "n" is number of
647 bits, and "f" is flow control ("r" for RTS or
648 omit it). Default is "9600n8".
650 See Documentation/serial-console.txt for more
652 Documentation/networking/netconsole.txt for an
655 uart[8250],io,<addr>[,options]
656 uart[8250],mmio,<addr>[,options]
657 Start an early, polled-mode console on the 8250/16550
658 UART at the specified I/O port or MMIO address,
659 switching to the matching ttyS device later. The
660 options are the same as for ttyS, above.
661 hvc<n> Use the hypervisor console device <n>. This is for
662 both Xen and PowerPC hypervisors.
664 If the device connected to the port is not a TTY but a braille
665 device, prepend "brl," before the device type, for instance
667 For now, only VisioBraille is supported.
669 consoleblank= [KNL] The console blank (screen saver) timeout in
670 seconds. Defaults to 10*60 = 10mins. A value of 0
671 disables the blank timer.
674 [KNL] Change the default value for
675 /proc/<pid>/coredump_filter.
676 See also Documentation/filesystems/proc.txt.
678 cpuidle.off=1 [CPU_IDLE]
679 disable the cpuidle sub-system
681 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
683 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
685 crashkernel=size[KMG][@offset[KMG]]
686 [KNL] Using kexec, Linux can switch to a 'crash kernel'
687 upon panic. This parameter reserves the physical
688 memory region [offset, offset + size] for that kernel
689 image. If '@offset' is omitted, then a suitable offset
690 is selected automatically. Check
691 Documentation/kdump/kdump.txt for further details.
693 crashkernel=range1:size1[,range2:size2,...][@offset]
694 [KNL] Same as above, but depends on the memory
695 in the running system. The syntax of range is
696 start-[end] where start and end are both
697 a memory unit (amount[KMG]). See also
698 Documentation/kdump/kdump.txt for an example.
700 crashkernel=size[KMG],high
701 [KNL, x86_64] range could be above 4G. Allow kernel
702 to allocate physical memory region from top, so could
703 be above 4G if system have more than 4G ram installed.
704 Otherwise memory region will be allocated below 4G, if
706 It will be ignored if crashkernel=X is specified.
707 crashkernel=size[KMG],low
708 [KNL, x86_64] range under 4G. When crashkernel=X,high
709 is passed, kernel could allocate physical memory region
710 above 4G, that cause second kernel crash on system
711 that require some amount of low memory, e.g. swiotlb
712 requires at least 64M+32K low memory. Kernel would
713 try to allocate 72M below 4G automatically.
714 This one let user to specify own low range under 4G
715 for second kernel instead.
716 0: to disable low allocation.
717 It will be ignored when crashkernel=X,high is not used
718 or memory reserved is below 4G.
723 cs89x0_media= [HW,NET]
724 Format: { rj45 | aui | bnc }
727 See header of drivers/s390/block/dasd_devmap.c.
729 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
730 (one device per port)
731 Format: <port#>,<type>
732 See also Documentation/input/joystick-parport.txt
734 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
735 time. See Documentation/dynamic-debug-howto.txt for
736 details. Deprecated, see dyndbg.
738 debug [KNL] Enable kernel debugging (events log level).
741 [KNL] verbose self-tests
743 Print debugging info while doing the locking API
745 We default to 0 (no extra messages), setting it to
746 1 will print _a lot_ more information - normally
747 only useful to kernel developers.
749 debug_objects [KNL] Enable object debugging
752 [KNL] Disable object debugging
754 debug_guardpage_minorder=
755 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
756 parameter allows control of the order of pages that will
757 be intentionally kept free (and hence protected) by the
758 buddy allocator. Bigger value increase the probability
759 of catching random memory corruption, but reduce the
760 amount of memory for normal system use. The maximum
761 possible value is MAX_ORDER/2. Setting this parameter
762 to 1 or 2 should be enough to identify most random
763 memory corruption problems caused by bugs in kernel or
764 driver code when a CPU writes to (or reads from) a
765 random memory location. Note that there exists a class
766 of memory corruptions problems caused by buggy H/W or
767 F/W or by drivers badly programing DMA (basically when
768 memory is written at bus level and the CPU MMU is
769 bypassed) which are not detectable by
770 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
771 tracking down these problems.
773 debugpat [X86] Enable PAT debugging
775 decnet.addr= [HW,NET]
776 Format: <area>[,<node>]
777 See also Documentation/networking/decnet.txt.
780 [same as hugepagesz=] The size of the default
781 HugeTLB page size. This is the size represented by
782 the legacy /proc/ hugepages APIs, used for SHM, and
783 default size when mounting hugetlbfs filesystems.
784 Defaults to the default architecture's huge page size
788 Set number of hash buckets for dentry cache.
791 IO parameters + enable/disable command.
793 digiepca= [HW,SERIAL]
794 See drivers/char/README.epca and
795 Documentation/serial/digiepca.txt.
798 See Documentation/networking/ipv6.txt.
800 disable_cpu_apicid= [X86,APIC,SMP]
802 The number of initial APIC ID for the
803 corresponding CPU to be disabled at boot,
804 mostly used for the kdump 2nd kernel to
805 disable BSP to wake up multiple CPUs without
806 causing system reset or hang due to sending
809 disable_ddw [PPC/PSERIES]
810 Disable Dynamic DMA Window support. Use this if
811 to workaround buggy firmware.
814 See Documentation/networking/ipv6.txt.
816 disable_mtrr_cleanup [X86]
817 The kernel tries to adjust MTRR layout from continuous
818 to discrete, to make X server driver able to add WB
819 entry later. This parameter disables that.
821 disable_mtrr_trim [X86, Intel and AMD only]
822 By default the kernel will trim any uncacheable
823 memory out of your available memory pool based on
824 MTRR settings. This parameter disables that behavior,
825 possibly causing your machine to run very slowly.
827 disable_timer_pin_1 [X86]
828 Disable PIN 1 of APIC timer
829 Can be useful to work around chipset bugs.
831 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
832 this option disables the debugging code at boot.
834 dma_debug_entries=<number>
835 This option allows to tune the number of preallocated
836 entries for DMA-API debugging code. One entry is
837 required per DMA-API allocation. Use this if the
838 DMA-API debugging code disables itself because the
839 architectural default is too low.
841 dma_debug_driver=<driver_name>
842 With this option the DMA-API debugging driver
843 filter feature can be enabled at boot time. Just
844 pass the driver to filter for as the parameter.
845 The filter can be disabled or changed to another
846 driver later using sysfs.
848 drm_kms_helper.edid_firmware=[<connector>:]<file>
849 Broken monitors, graphic adapters and KVMs may
850 send no or incorrect EDID data sets. This parameter
851 allows to specify an EDID data set in the
852 /lib/firmware directory that is used instead.
853 Generic built-in EDID data sets are used, if one of
854 edid/1024x768.bin, edid/1280x1024.bin,
855 edid/1680x1050.bin, or edid/1920x1080.bin is given
856 and no file with the same name exists. Details and
857 instructions how to build your own EDID data are
858 available in Documentation/EDID/HOWTO.txt. An EDID
859 data set will only be used for a particular connector,
860 if its name and a colon are prepended to the EDID
865 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
866 module.dyndbg[="val"]
867 Enable debug messages at boot time. See
868 Documentation/dynamic-debug-howto.txt for details.
870 earlycon= [KNL] Output early console device and options.
871 uart[8250],io,<addr>[,options]
872 uart[8250],mmio,<addr>[,options]
873 uart[8250],mmio32,<addr>[,options]
874 Start an early, polled-mode console on the 8250/16550
875 UART at the specified I/O port or MMIO address.
876 MMIO inter-register address stride is either 8-bit
877 (mmio) or 32-bit (mmio32).
878 The options are the same as for ttyS, above.
880 earlyprintk= [X86,SH,BLACKFIN,ARM]
884 earlyprintk=serial[,ttySn[,baudrate]]
885 earlyprintk=serial[,0x...[,baudrate]]
886 earlyprintk=ttySn[,baudrate]
887 earlyprintk=dbgp[debugController#]
889 earlyprintk is useful when the kernel crashes before
890 the normal console is initialized. It is not enabled by
891 default because it has some cosmetic problems.
893 Append ",keep" to not disable it when the real console
896 Only one of vga, efi, serial, or usb debug port can
899 Currently only ttyS0 and ttyS1 may be specified by
900 name. Other I/O ports may be explicitly specified
901 on some architectures (x86 and arm at least) by
902 replacing ttySn with an I/O port address, like this:
903 earlyprintk=serial,0x1008,115200
904 You can find the port for a given device in
905 /proc/tty/driver/serial:
906 2: uart:ST16650V2 port:00001008 irq:18 ...
908 Interaction with the standard serial driver is not
911 The VGA and EFI output is eventually overwritten by
914 The xen output can only be used by Xen PV guests.
916 edac_report= [HW,EDAC] Control how to report EDAC event
917 Format: {"on" | "off" | "force"}
918 on: enable EDAC to report H/W event. May be overridden
919 by other higher priority error reporting module.
920 off: disable H/W event reporting through EDAC.
921 force: enforce the use of EDAC to report H/W event.
924 ekgdboc= [X86,KGDB] Allow early kernel console debugging
927 This is designed to be used in conjunction with
928 the boot argument: earlyprintk=vga
931 Format: {"off" | "on" | "skip[mbr]"}
934 Format: { "old_map" }
935 old_map [X86-64]: switch to the old ioremap-based EFI
936 runtime services mapping. 32-bit still uses this one by
939 efi_no_storage_paranoia [EFI; X86]
940 Using this parameter you can use more than 50% of
941 your efi variable storage. Use this parameter only if
942 you are really sure that your UEFI does sane gc and
943 fulfills the spec otherwise your board may brick.
945 eisa_irq_edge= [PARISC,HW]
946 See header of drivers/parisc/eisa.c.
949 See comment before function elanfreq_setup() in
950 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
953 Format: {"cfq" | "deadline" | "noop"}
954 See Documentation/block/cfq-iosched.txt and
955 Documentation/block/deadline-iosched.txt for details.
957 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
958 Specifies physical address of start of kernel core
959 image elf header and optionally the size. Generally
960 kexec loader will pass this option to capture kernel.
961 See Documentation/kdump/kdump.txt for details.
963 enable_mtrr_cleanup [X86]
964 The kernel tries to adjust MTRR layout from continuous
965 to discrete, to make X server driver able to add WB
966 entry later. This parameter enables that.
968 enable_timer_pin_1 [X86]
969 Enable PIN 1 of APIC timer
970 Can be useful to work around chipset bugs
971 (in particular on some ATI chipsets).
972 The kernel tries to set a reasonable default.
974 enforcing [SELINUX] Set initial enforcing status.
976 See security/selinux/Kconfig help text.
977 0 -- permissive (log only, no denials).
978 1 -- enforcing (deny and log).
980 Value can be changed at runtime via /selinux/enforce.
983 Disable Error Record Serialization Table (ERST)
986 ether= [HW,NET] Ethernet cards parameters
987 This option is obsoleted by the "netdev=" option, which
988 has equivalent usage. See its documentation for details.
992 Permit 'security.evm' to be updated regardless of
993 current integrity status.
997 fail_make_request=[KNL]
998 General fault injection mechanism.
999 Format: <interval>,<probability>,<space>,<times>
1000 See also Documentation/fault-injection/.
1003 See Documentation/blockdev/floppy.txt.
1005 force_pal_cache_flush
1006 [IA-64] Avoid check_sal_cache_flush which may hang on
1007 buggy SAL_CACHE_FLUSH implementations. Using this
1008 parameter will force ia64_sal_cache_flush to call
1009 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1012 [FTRACE] will set and start the specified tracer
1013 as early as possible in order to facilitate early
1016 ftrace_dump_on_oops[=orig_cpu]
1017 [FTRACE] will dump the trace buffers on oops.
1018 If no parameter is passed, ftrace will dump
1019 buffers of all CPUs, but if you pass orig_cpu, it will
1020 dump only the buffer of the CPU that triggered the
1023 ftrace_filter=[function-list]
1024 [FTRACE] Limit the functions traced by the function
1025 tracer at boot up. function-list is a comma separated
1026 list of functions. This list can be changed at run
1027 time by the set_ftrace_filter file in the debugfs
1030 ftrace_notrace=[function-list]
1031 [FTRACE] Do not trace the functions specified in
1032 function-list. This list can be changed at run time
1033 by the set_ftrace_notrace file in the debugfs
1036 ftrace_graph_filter=[function-list]
1037 [FTRACE] Limit the top level callers functions traced
1038 by the function graph tracer at boot up.
1039 function-list is a comma separated list of functions
1040 that can be changed at run time by the
1041 set_graph_function file in the debugfs tracing directory.
1044 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1045 support via parallel port (up to 5 devices per port)
1046 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1047 See also Documentation/input/joystick-parport.txt
1051 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1055 gcov_persist= [GCOV] When non-zero (default), profiling data for
1056 kernel modules is saved and remains accessible via
1057 debugfs, even when the module is unloaded/reloaded.
1058 When zero, profiling data is discarded and associated
1059 debugfs files are removed at module unload time.
1061 gpt [EFI] Forces disk with valid GPT signature but
1062 invalid Protective MBR to be treated as GPT.
1064 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1065 the "Enable 0" bit of the configuration register.
1068 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1069 the "Enable 0" bit of the configuration register.
1072 grcan.select= [HW] Select which physical interface to use.
1075 grcan.txsize= [HW] Sets the size of the tx buffer.
1076 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1078 grcan.rxsize= [HW] Sets the size of the rx buffer.
1079 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1082 hashdist= [KNL,NUMA] Large hashes allocated during boot
1083 are distributed across NUMA nodes. Defaults on
1084 for 64-bit NUMA, off otherwise.
1085 Format: 0 | 1 (for off | on)
1087 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1089 hd= [EIDE] (E)IDE hard drive subsystem geometry
1090 Format: <cyl>,<head>,<sect>
1093 Disable Hardware Error Source Table (HEST) support;
1094 corresponding firmware-first mode error processing
1095 logic will be disabled.
1097 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1098 size of <nn>. This works even on boxes that have no
1099 highmem otherwise. This also works to reduce highmem
1100 size on bigger boxes.
1102 highres= [KNL] Enable/disable high resolution timer mode.
1103 Valid parameters: "on", "off"
1107 See Documentation/isdn/README.HiSax.
1111 hpet= [X86-32,HPET] option to control HPET usage
1112 Format: { enable (default) | disable | force |
1114 disable: disable HPET and use PIT instead
1115 force: allow force enabled of undocumented chips (ICH4,
1117 verbose: show contents of HPET registers during setup
1119 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1120 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1122 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1123 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1124 On x86-64 and powerpc, this option can be specified
1125 multiple times interleaved with hugepages= to reserve
1126 huge pages of different sizes. Valid pages sizes on
1127 x86-64 are 2M (when the CPU supports "pse") and 1G
1128 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1129 Note that 1GB pages can only be allocated at boot time
1130 using hugepages= and not freed afterwards.
1132 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1133 terminal devices. Valid values: 0..8
1134 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1135 If specified, z/VM IUCV HVC accepts connections
1136 from listed z/VM user IDs only.
1138 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1139 hardware thread id mappings.
1140 Format: <cpu>:<hwthread>
1143 Do not unregister boot console at start. This is only
1144 useful for debugging when something happens in the window
1145 between unregistering the boot console and initializing
1148 i2c_bus= [HW] Override the default board specific I2C bus speed
1149 or register an additional I2C bus that is not
1150 registered from board initialization code.
1154 i8042.debug [HW] Toggle i8042 debug mode
1155 i8042.direct [HW] Put keyboard port into non-translated mode
1156 i8042.dumbkbd [HW] Pretend that controller can only read data from
1157 keyboard and cannot control its state
1158 (Don't attempt to blink the leds)
1159 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1160 i8042.nokbd [HW] Don't check/create keyboard port
1161 i8042.noloop [HW] Disable the AUX Loopback command while probing
1163 i8042.nomux [HW] Don't check presence of an active multiplexing
1165 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1167 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1168 i8042.reset [HW] Reset the controller during init and cleanup
1169 i8042.unlock [HW] Unlock (ignore) the keylock
1173 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1174 indicates that the driver is running on unsupported
1176 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1177 does not match list of supported models.
1179 [HW] Report power status in /proc/i8k
1180 (disabled by default)
1181 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1184 i915.invert_brightness=
1185 [DRM] Invert the sense of the variable that is used to
1186 set the brightness of the panel backlight. Normally a
1187 brightness value of 0 indicates backlight switched off,
1188 and the maximum of the brightness value sets the backlight
1189 to maximum brightness. If this parameter is set to 0
1190 (default) and the machine requires it, or this parameter
1191 is set to 1, a brightness value of 0 sets the backlight
1192 to maximum brightness, and the maximum of the brightness
1193 value switches the backlight off.
1194 -1 -- never invert brightness
1195 0 -- machine default
1196 1 -- force brightness inversion
1199 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1201 ide-core.nodma= [HW] (E)IDE subsystem
1202 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1203 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1204 .cdrom .chs .ignore_cable are additional options
1205 See Documentation/ide/ide.txt.
1207 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1208 Claim all unknown PCI IDE storage controllers.
1211 Format: idle=poll, idle=halt, idle=nomwait
1212 Poll forces a polling idle loop that can slightly
1213 improve the performance of waking up a idle CPU, but
1214 will use a lot of power and make the system run hot.
1216 idle=halt: Halt is forced to be used for CPU idle.
1217 In such case C2/C3 won't be used again.
1218 idle=nomwait: Disable mwait for CPU C-states
1220 ignore_loglevel [KNL]
1221 Ignore loglevel setting - this will print /all/
1222 kernel messages to the console. Useful for debugging.
1223 We also add it as printk module parameter, so users
1224 could change it dynamically, usually by
1225 /sys/module/printk/parameters/ignore_loglevel.
1227 ihash_entries= [KNL]
1228 Set number of hash buckets for inode cache.
1230 ima_appraise= [IMA] appraise integrity measurements
1231 Format: { "off" | "enforce" | "fix" }
1234 ima_appraise_tcb [IMA]
1235 The builtin appraise policy appraises all files
1239 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1243 The list of supported hash algorithms is defined
1244 in crypto/hash_info.h.
1247 Load a policy which meets the needs of the Trusted
1248 Computing Base. This means IMA will measure all
1249 programs exec'd, files mmap'd for exec, and all files
1250 opened for read by uid=0.
1253 Select one of defined IMA measurements template formats.
1254 Formats: { "ima" | "ima-ng" }
1259 Run specified binary instead of /sbin/init as init
1262 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1263 for working out where the kernel is dying during
1266 initrd= [BOOT] Specify the location of the initial ramdisk
1268 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1271 int_pln_enable [x86] Enable power limit notification interrupt
1273 integrity_audit=[IMA]
1274 Format: { "0" | "1" }
1275 0 -- basic integrity auditing messages. (Default)
1276 1 -- additional integrity auditing messages.
1278 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1280 Enable intel iommu driver.
1282 Disable intel iommu driver.
1283 igfx_off [Default Off]
1284 By default, gfx is mapped as normal device. If a gfx
1285 device has a dedicated DMAR unit, the DMAR unit is
1286 bypassed by not enabling DMAR with this option. In
1287 this case, gfx device will use physical address for
1290 With this option iommu will not optimize to look
1291 for io virtual address below 32-bit forcing dual
1292 address cycle on pci bus for cards supporting greater
1293 than 32-bit addressing. The default is to look
1294 for translation below 32-bit and if not available
1295 then look in the higher range.
1296 strict [Default Off]
1297 With this option on every unmap_single operation will
1298 result in a hardware IOTLB flush operation as opposed
1299 to batching them for performance.
1300 sp_off [Default Off]
1301 By default, super page will be supported if Intel IOMMU
1302 has the capability. With this option, super page will
1305 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1306 0 disables intel_idle and fall back on acpi_idle.
1307 1 to 6 specify maximum depth of C-state.
1311 Do not enable intel_pstate as the default
1312 scaling driver for the supported processors
1314 intremap= [X86-64, Intel-IOMMU]
1315 on enable Interrupt Remapping (default)
1316 off disable Interrupt Remapping
1317 nosid disable Source ID checking
1319 BIOS x2APIC opt-out request will be ignored
1321 iomem= Disable strict checking of access to MMIO memory
1322 strict regions from userspace.
1339 io7= [HW] IO7 for Marvel based alpha systems
1340 See comment before marvel_specify_io7 in
1341 arch/alpha/kernel/core_marvel.c.
1343 io_delay= [X86] I/O delay method
1345 Standard port 0x80 based delay
1347 Alternate port 0xed based delay (needed on some systems)
1349 Simple two microseconds delay
1354 See Documentation/filesystems/nfs/nfsroot.txt.
1356 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1357 See comment before ip2_setup() in
1358 drivers/char/ip2/ip2base.c.
1361 When an interrupt is not handled search all handlers
1362 for it. Intended to get systems with badly broken
1366 When an interrupt is not handled search all handlers
1367 for it. Also check all handlers each timer
1368 interrupt. Intended to get systems with badly broken
1372 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1374 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1376 <cpu number>,...,<cpu number>
1378 <cpu number>-<cpu number>
1379 (must be a positive range in ascending order)
1381 <cpu number>,...,<cpu number>-<cpu number>
1383 This option can be used to specify one or more CPUs
1384 to isolate from the general SMP balancing and scheduling
1385 algorithms. You can move a process onto or off an
1386 "isolated" CPU via the CPU affinity syscalls or cpuset.
1387 <cpu number> begins at 0 and the maximum value is
1388 "number of CPUs in system - 1".
1390 This option is the preferred way to isolate CPUs. The
1391 alternative -- manually setting the CPU mask of all
1392 tasks in the system -- can cause problems and
1393 suboptimal load balancer performance.
1397 ivrs_ioapic [HW,X86_64]
1398 Provide an override to the IOAPIC-ID<->DEVICE-ID
1399 mapping provided in the IVRS ACPI table. For
1400 example, to map IOAPIC-ID decimal 10 to
1401 PCI device 00:14.0 write the parameter as:
1402 ivrs_ioapic[10]=00:14.0
1404 ivrs_hpet [HW,X86_64]
1405 Provide an override to the HPET-ID<->DEVICE-ID
1406 mapping provided in the IVRS ACPI table. For
1407 example, to map HPET-ID decimal 0 to
1408 PCI device 00:14.0 write the parameter as:
1409 ivrs_hpet[0]=00:14.0
1411 js= [HW,JOY] Analog joystick
1412 See Documentation/input/joystick.txt.
1416 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1417 specifies the amount of memory usable by the kernel
1418 for non-movable allocations. The requested amount is
1419 spread evenly throughout all nodes in the system. The
1420 remaining memory in each node is used for Movable
1421 pages. In the event, a node is too small to have both
1422 kernelcore and Movable pages, kernelcore pages will
1423 take priority and other nodes will have a larger number
1424 of Movable pages. The Movable zone is used for the
1425 allocation of pages that may be reclaimed or moved
1426 by the page migration subsystem. This means that
1427 HugeTLB pages may not be allocated from this zone.
1428 Note that allocations like PTEs-from-HighMem still
1429 use the HighMem zone if it exists, and the Normal
1430 zone if it does not.
1432 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1433 Format: <Controller#>[,poll interval]
1434 The controller # is the number of the ehci usb debug
1435 port as it is probed via PCI. The poll interval is
1436 optional and is the number seconds in between
1437 each poll cycle to the debug port in case you need
1438 the functionality for interrupting the kernel with
1439 gdb or control-c on the dbgp connection. When
1440 not using this parameter you use sysrq-g to break into
1441 the kernel debugger.
1443 kgdboc= [KGDB,HW] kgdb over consoles.
1444 Requires a tty driver that supports console polling,
1445 or a supported polling keyboard driver (non-usb).
1446 Serial only format: <serial_device>[,baud]
1447 keyboard only format: kbd
1448 keyboard and serial format: kbd,<serial_device>[,baud]
1449 Optional Kernel mode setting:
1450 kms, kbd format: kms,kbd
1451 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1453 kgdbwait [KGDB] Stop kernel execution and enter the
1454 kernel debugger at the earliest opportunity.
1456 kmac= [MIPS] korina ethernet MAC address.
1457 Configure the RouterBoard 532 series on-chip
1458 Ethernet adapter MAC address.
1460 kmemleak= [KNL] Boot-time kmemleak enable/disable
1461 Valid arguments: on, off
1464 kstack=N [X86] Print N words from the kernel stack
1467 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1468 Default is 0 (don't ignore, but inject #GP)
1470 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1474 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1475 Default is 1 (enabled)
1477 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1479 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1481 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1482 (virtualized MMU) support on capable Intel chips.
1483 Default is 1 (enabled)
1485 kvm-intel.emulate_invalid_guest_state=
1486 [KVM,Intel] Enable emulation of invalid guest states
1487 Default is 0 (disabled)
1489 kvm-intel.flexpriority=
1490 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1491 Default is 1 (enabled)
1494 [KVM,Intel] Enable VMX nesting (nVMX).
1495 Default is 0 (disabled)
1497 kvm-intel.unrestricted_guest=
1498 [KVM,Intel] Disable unrestricted guest feature
1499 (virtualized real and unpaged mode) on capable
1500 Intel chips. Default is 1 (enabled)
1502 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1503 feature (tagged TLBs) on capable Intel chips.
1504 Default is 1 (enabled)
1510 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1513 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1514 value for LAPIC timer one-shot implementation. Default
1515 back to the programmable timer unit in the LAPIC.
1517 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1520 libata.dma= [LIBATA] DMA control
1521 libata.dma=0 Disable all PATA and SATA DMA
1522 libata.dma=1 PATA and SATA Disk DMA only
1523 libata.dma=2 ATAPI (CDROM) DMA only
1524 libata.dma=4 Compact Flash DMA only
1525 Combinations also work, so libata.dma=3 enables DMA
1526 for disks and CDROMs, but not CFs.
1528 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1529 libata.ignore_hpa=0 keep BIOS limits (default)
1530 libata.ignore_hpa=1 ignore limits, using full disk
1532 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1536 libata.force= [LIBATA] Force configurations. The format is comma
1537 separated list of "[ID:]VAL" where ID is
1538 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1539 matching port, link or device. Basically, it matches
1540 the ATA ID string printed on console by libata. If
1541 the whole ID part is omitted, the last PORT and DEVICE
1542 values are used. If ID hasn't been specified yet, the
1543 configuration applies to all ports, links and devices.
1545 If only DEVICE is omitted, the parameter applies to
1546 the port and all links and devices behind it. DEVICE
1547 number of 0 either selects the first device or the
1548 first fan-out link behind PMP device. It does not
1549 select the host link. DEVICE number of 15 selects the
1550 host link and device attached to it.
1552 The VAL specifies the configuration to force. As long
1553 as there's no ambiguity shortcut notation is allowed.
1554 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1555 The following configurations can be forced.
1557 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1558 Any ID with matching PORT is used.
1560 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1562 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1563 udma[/][16,25,33,44,66,100,133] notation is also
1566 * [no]ncq: Turn on or off NCQ.
1568 * nohrst, nosrst, norst: suppress hard, soft
1571 * rstonce: only attempt one reset during
1572 hot-unplug link recovery
1574 * dump_id: dump IDENTIFY data.
1576 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1578 * disable: Disable this device.
1580 If there are multiple matching configurations changing
1581 the same attribute, the last one is used.
1583 memblock=debug [KNL] Enable memblock debug messages.
1585 load_ramdisk= [RAM] List of ramdisks to load from floppy
1586 See Documentation/blockdev/ramdisk.txt.
1588 lockd.nlm_grace_period=P [NFS] Assign grace period.
1591 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1594 lockd.nlm_timeout=T [NFS] Assign timeout value.
1597 lockd.nlm_udpport=M [NFS] Assign UDP port.
1600 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1603 loglevel= All Kernel Messages with a loglevel smaller than the
1604 console loglevel will be printed to the console. It can
1605 also be changed with klogd or other programs. The
1606 loglevels are defined as follows:
1608 0 (KERN_EMERG) system is unusable
1609 1 (KERN_ALERT) action must be taken immediately
1610 2 (KERN_CRIT) critical conditions
1611 3 (KERN_ERR) error conditions
1612 4 (KERN_WARNING) warning conditions
1613 5 (KERN_NOTICE) normal but significant condition
1614 6 (KERN_INFO) informational
1615 7 (KERN_DEBUG) debug-level messages
1617 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1618 in bytes. n must be a power of two. The default
1619 size is set in the kernel config file.
1621 logo.nologo [FB] Disables display of the built-in Linux logo.
1622 This may be used to provide more screen space for
1623 kernel log messages and is useful when debugging
1624 kernel boot problems.
1626 lp=0 [LP] Specify parallel ports to use, e.g,
1627 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1628 lp=reset first parallel port). 'lp=0' disables the
1629 lp=auto printer driver. 'lp=reset' (which can be
1630 specified in addition to the ports) causes
1631 attached printers to be reset. Using
1632 lp=port1,port2,... specifies the parallel ports
1633 to associate lp devices with, starting with
1634 lp0. A port specification may be 'none' to skip
1635 that lp device, or a parport name such as
1636 'parport0'. Specifying 'lp=auto' instead of a
1637 port specification list means that device IDs
1638 from each port should be examined, to see if
1639 an IEEE 1284-compliant printer is attached; if
1640 so, the driver will manage that printer.
1641 See also header of drivers/char/lp.c.
1644 Sets loops_per_jiffy to given constant, thus avoiding
1645 time-consuming boot-time autodetection (up to 250 ms per
1646 CPU). 0 enables autodetection (default). To determine
1647 the correct value for your kernel, boot with normal
1648 autodetection and see what value is printed. Note that
1649 on SMP systems the preset will be applied to all CPUs,
1650 which is likely to cause problems if your CPUs need
1651 significantly divergent settings. An incorrect value
1652 will cause delays in the kernel to be wrong, leading to
1653 unpredictable I/O errors and other breakage. Although
1654 unlikely, in the extreme case this might damage your
1658 Format: <io>,<irq>,<dma>
1660 machvec= [IA-64] Force the use of a particular machine-vector
1661 (machvec) in a generic kernel.
1662 Example: machvec=hpzx1_swiotlb
1664 machtype= [Loongson] Share the same kernel image file between different
1666 Example: machtype=lemote-yeeloong-2f-7inch
1668 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1669 than or equal to this physical address is ignored.
1671 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1672 should make use of. maxcpus=n : n >= 0 limits the
1673 kernel to using 'n' processors. n=0 is a special case,
1674 it is equivalent to "nosmp", which also disables
1677 max_loop= [LOOP] The number of loop block devices that get
1678 (loop.max_loop) unconditionally pre-created at init time. The default
1679 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1680 of statically allocating a predefined number, loop
1681 devices can be requested on-demand with the
1682 /dev/loop-control interface.
1684 mce [X86-32] Machine Check Exception
1686 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1688 md= [HW] RAID subsystems devices and level
1689 See Documentation/md.txt.
1692 Format: <first>,<last>
1693 Specifies range of consoles to be captured by the MDA.
1695 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1696 Amount of memory to be used when the kernel is not able
1697 to see the whole system memory or for test.
1698 [X86] Work as limiting max address. Use together
1699 with memmap= to avoid physical address space collisions.
1700 Without memmap= PCI devices could be placed at addresses
1701 belonging to unused RAM.
1703 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1707 [KNL,SH] Allow user to override the default size for
1708 per-device physically contiguous DMA buffers.
1710 memmap=exactmap [KNL,X86] Enable setting of an exact
1711 E820 memory map, as specified by the user.
1712 Such memmap=exactmap lines can be constructed based on
1713 BIOS output or other requirements. See the memmap=nn@ss
1716 memmap=nn[KMG]@ss[KMG]
1717 [KNL] Force usage of a specific region of memory
1718 Region of memory to be used, from ss to ss+nn.
1720 memmap=nn[KMG]#ss[KMG]
1721 [KNL,ACPI] Mark specific memory as ACPI data.
1722 Region of memory to be used, from ss to ss+nn.
1724 memmap=nn[KMG]$ss[KMG]
1725 [KNL,ACPI] Mark specific memory as reserved.
1726 Region of memory to be used, from ss to ss+nn.
1727 Example: Exclude memory from 0x18690000-0x1869ffff
1728 memmap=64K$0x18690000
1730 memmap=0x10000$0x18690000
1732 memory_corruption_check=0/1 [X86]
1733 Some BIOSes seem to corrupt the first 64k of
1734 memory when doing things like suspend/resume.
1735 Setting this option will scan the memory
1736 looking for corruption. Enabling this will
1737 both detect corruption and prevent the kernel
1738 from using the memory being corrupted.
1739 However, its intended as a diagnostic tool; if
1740 repeatable BIOS-originated corruption always
1741 affects the same memory, you can use memmap=
1742 to prevent the kernel from using that memory.
1744 memory_corruption_check_size=size [X86]
1745 By default it checks for corruption in the low
1746 64k, making this memory unavailable for normal
1747 use. Use this parameter to scan for
1748 corruption in more or less memory.
1750 memory_corruption_check_period=seconds [X86]
1751 By default it checks for corruption every 60
1752 seconds. Use this parameter to check at some
1753 other rate. 0 disables periodic checking.
1755 memtest= [KNL,X86] Enable memtest
1757 default : 0 <disable>
1758 Specifies the number of memtest passes to be
1759 performed. Each pass selects another test
1760 pattern from a given set of patterns. Memtest
1761 fills the memory with this pattern, validates
1762 memory contents and reserves bad memory
1763 regions that are detected.
1765 meye.*= [HW] Set MotionEye Camera parameters
1766 See Documentation/video4linux/meye.txt.
1768 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1769 Multi-Function General Purpose Timers on AMD Geode
1772 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1773 the BIOS has incorrectly applied a workaround. TinyBIOS
1774 version 0.98 is known to be affected, 0.99 fixes the
1775 problem by letting the user disable the workaround.
1779 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1780 physical address is ignored.
1782 mini2440= [ARM,HW,KNL]
1783 Format:[0..2][b][c][t]
1785 MINI2440 configuration specification:
1786 0 - The attached screen is the 3.5" TFT
1787 1 - The attached screen is the 7" TFT
1788 2 - The VGA Shield is attached (1024x768)
1789 Leaving out the screen size parameter will not load
1790 the TFT driver, and the framebuffer will be left
1792 b - Enable backlight. The TFT backlight pin will be
1793 linked to the kernel VESA blanking code and a GPIO
1794 LED. This parameter is not necessary when using the
1796 c - Enable the s3c camera interface.
1797 t - Reserved for enabling touchscreen support. The
1798 touchscreen support is not enabled in the mainstream
1799 kernel as of 2.6.30, a preliminary port can be found
1800 in the "bleeding edge" mini2440 support kernel at
1801 http://repo.or.cz/w/linux-2.6/mini2440.git
1804 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1805 parameter allows control of the logging verbosity for
1806 the additional memory initialisation checks. A value
1807 of 0 disables mminit logging and a level of 4 will
1808 log everything. Information is printed at KERN_DEBUG
1809 so loglevel=8 may also need to be specified.
1812 [KNL] When CONFIG_MODULE_SIG is set, this means that
1813 modules without (valid) signatures will fail to load.
1814 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1815 is always true, so this option does nothing.
1818 [MOUSE] Maximum time between finger touching and
1819 leaving touchpad surface for touch to be considered
1820 a tap and be reported as a left button click (for
1821 touchpads working in absolute mode only).
1823 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1824 reporting absolute coordinates, such as tablets
1825 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1826 reporting absolute coordinates, such as tablets
1828 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1829 is similar to kernelcore except it specifies the
1830 amount of memory used for migratable allocations.
1831 If both kernelcore and movablecore is specified,
1832 then kernelcore will be at *least* the specified
1833 value but may be more. If movablecore on its own
1834 is specified, the administrator must be careful
1835 that the amount of memory usable for all allocations
1838 movable_node [KNL,X86] Boot-time switch to enable the effects
1839 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1841 MTD_Partition= [MTD]
1842 Format: <name>,<region-number>,<size>,<offset>
1844 MTD_Region= [MTD] Format:
1845 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1848 See drivers/mtd/cmdlinepart.c.
1850 multitce=off [PPC] This parameter disables the use of the pSeries
1851 firmware feature for updating multiple TCE entries
1854 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1856 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1858 boundary - index of last SLC block on Flex-OneNAND.
1859 The remaining blocks are configured as MLC blocks.
1860 lock - Configure if Flex-OneNAND boundary should be locked.
1861 Once locked, the boundary cannot be changed.
1862 1 indicates lock status, 0 indicates unlock status.
1865 ARM/S3C2412 JIVE boot control
1867 See arch/arm/mach-s3c2412/mach-jive.c
1869 mtouchusb.raw_coordinates=
1870 [HW] Make the MicroTouch USB driver use raw coordinates
1871 ('y', default) or cooked coordinates ('n')
1873 mtrr_chunk_size=nn[KMG] [X86]
1874 used for mtrr cleanup. It is largest continuous chunk
1875 that could hold holes aka. UC entries.
1877 mtrr_gran_size=nn[KMG] [X86]
1878 Used for mtrr cleanup. It is granularity of mtrr block.
1880 Large value could prevent small alignment from
1883 mtrr_spare_reg_nr=n [X86]
1885 Range: 0,7 : spare reg number
1887 Used for mtrr cleanup. It is spare mtrr entries number.
1888 Set to 2 or more if your graphical card needs more.
1890 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1892 netdev= [NET] Network devices parameters
1893 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1894 Note that mem_start is often overloaded to mean
1895 something different and driver-specific.
1896 This usage is only documented in each driver source
1900 [NETFILTER] Enable connection tracking flow accounting
1901 0 to disable accounting
1902 1 to enable accounting
1905 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1906 See Documentation/filesystems/nfs/nfsroot.txt.
1908 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1909 See Documentation/filesystems/nfs/nfsroot.txt.
1911 nfsrootdebug [NFS] enable nfsroot debugging messages.
1912 See Documentation/filesystems/nfs/nfsroot.txt.
1914 nfs.callback_tcpport=
1915 [NFS] set the TCP port on which the NFSv4 callback
1916 channel should listen.
1919 [NFS] sets the pathname to the program which is used
1920 to update the NFS client cache entries.
1922 nfs.cache_getent_timeout=
1923 [NFS] sets the timeout after which an attempt to
1924 update a cache entry is deemed to have failed.
1926 nfs.idmap_cache_timeout=
1927 [NFS] set the maximum lifetime for idmapper cache
1931 [NFS] enable 64-bit inode numbers.
1932 If zero, the NFS client will fake up a 32-bit inode
1933 number for the readdir() and stat() syscalls instead
1934 of returning the full 64-bit number.
1935 The default is to return 64-bit inode numbers.
1937 nfs.max_session_slots=
1938 [NFSv4.1] Sets the maximum number of session slots
1939 the client will attempt to negotiate with the server.
1940 This limits the number of simultaneous RPC requests
1941 that the client can send to the NFSv4.1 server.
1942 Note that there is little point in setting this
1943 value higher than the max_tcp_slot_table_limit.
1945 nfs.nfs4_disable_idmapping=
1946 [NFSv4] When set to the default of '1', this option
1947 ensures that both the RPC level authentication
1948 scheme and the NFS level operations agree to use
1949 numeric uids/gids if the mount is using the
1950 'sec=sys' security flavour. In effect it is
1951 disabling idmapping, which can make migration from
1952 legacy NFSv2/v3 systems to NFSv4 easier.
1953 Servers that do not support this mode of operation
1954 will be autodetected by the client, and it will fall
1955 back to using the idmapper.
1956 To turn off this behaviour, set the value to '0'.
1958 [NFS4] Specify an additional fixed unique ident-
1959 ification string that NFSv4 clients can insert into
1960 their nfs_client_id4 string. This is typically a
1961 UUID that is generated at system install time.
1963 nfs.send_implementation_id =
1964 [NFSv4.1] Send client implementation identification
1965 information in exchange_id requests.
1966 If zero, no implementation identification information
1968 The default is to send the implementation identification
1971 nfs.recover_lost_locks =
1972 [NFSv4] Attempt to recover locks that were lost due
1973 to a lease timeout on the server. Please note that
1974 doing this risks data corruption, since there are
1975 no guarantees that the file will remain unchanged
1976 after the locks are lost.
1977 If you want to enable the kernel legacy behaviour of
1978 attempting to recover these locks, then set this
1980 The default parameter value of '0' causes the kernel
1981 not to attempt recovery of lost locks.
1983 nfsd.nfs4_disable_idmapping=
1984 [NFSv4] When set to the default of '1', the NFSv4
1985 server will return only numeric uids and gids to
1986 clients using auth_sys, and will accept numeric uids
1987 and gids from such clients. This is intended to ease
1988 migration from NFSv2/v3.
1990 objlayoutdriver.osd_login_prog=
1991 [NFS] [OBJLAYOUT] sets the pathname to the program which
1992 is used to automatically discover and login into new
1993 osd-targets. Please see:
1994 Documentation/filesystems/pnfs.txt for more explanations
1996 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1997 when a NMI is triggered.
1998 Format: [state][,regs][,debounce][,die]
2000 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2001 Format: [panic,][nopanic,][num]
2003 0 - turn nmi_watchdog off
2004 When panic is specified, panic when an NMI watchdog
2005 timeout occurs (or 'nopanic' to override the opposite
2007 This is useful when you use a panic=... timeout and
2008 need the box quickly up again.
2010 netpoll.carrier_timeout=
2011 [NET] Specifies amount of time (in seconds) that
2012 netpoll should wait for a carrier. By default netpoll
2015 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2016 emulation library even if a 387 maths coprocessor
2020 [HW] Never suspend the console
2021 Disable suspending of consoles during suspend and
2022 hibernate operations. Once disabled, debugging
2023 messages can reach various consoles while the rest
2024 of the system is being put to sleep (ie, while
2025 debugging driver suspend/resume hooks). This may
2026 not work reliably with all consoles, but is known
2027 to work with serial and VGA consoles.
2028 To facilitate more flexible debugging, we also add
2029 console_suspend, a printk module parameter to control
2030 it. Users could use console_suspend (usually
2031 /sys/module/printk/parameters/console_suspend) to
2032 turn on/off it dynamically.
2034 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2035 caches in the slab allocator. Saves per-node memory,
2036 but will impact performance.
2040 noapic [SMP,APIC] Tells the kernel to not make use of any
2041 IOAPICs that may be present in the system.
2044 Disable kernel base offset ASLR (Address Space
2045 Layout Randomization) if built into the kernel.
2047 noautogroup Disable scheduler automatic task group creation.
2049 nobats [PPC] Do not use BATs for mapping kernel lowmem
2050 on "Classic" PPC cores.
2054 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2056 nodelayacct [KNL] Disable per-task delay accounting
2058 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2060 nodsp [SH] Disable hardware DSP at boot time.
2062 noefi [X86] Disable EFI runtime services support.
2067 On X86-32 available only on PAE configured kernels.
2068 noexec=on: enable non-executable mappings (default)
2069 noexec=off: disable non-executable mappings
2072 Disable SMAP (Supervisor Mode Access Prevention)
2073 even if it is supported by processor.
2076 Disable SMEP (Supervisor Mode Execution Prevention)
2077 even if it is supported by processor.
2080 This affects only 32-bit executables.
2081 noexec32=on: enable non-executable mappings (default)
2082 read doesn't imply executable mappings
2083 noexec32=off: disable non-executable mappings
2084 read implies executable mappings
2086 nofpu [SH] Disable hardware FPU at boot time.
2088 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2089 register save and restore. The kernel will only save
2090 legacy floating-point registers on task switch.
2092 noxsave [BUGS=X86] Disables x86 extended register state save
2093 and restore using xsave. The kernel will fallback to
2094 enabling legacy floating-point and sse state.
2097 on enable eager fpu restore
2098 off disable eager fpu restore
2099 auto selects the default scheme, which automatically
2100 enables eagerfpu restore for xsaveopt.
2102 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2103 wfi(ARM) instruction doesn't work correctly and not to
2104 use it. This is also useful when using JTAG debugger.
2106 no_file_caps Tells the kernel not to honor file capabilities. The
2107 only way then for a file to be executed with privilege
2108 is to be setuid root or executed by root.
2110 nohalt [IA-64] Tells the kernel not to use the power saving
2111 function PAL_HALT_LIGHT when idle. This increases
2112 power-consumption. On the positive side, it reduces
2113 interrupt wake-up latency, which may improve performance
2114 in certain environments such as networked servers or
2117 nohz= [KNL] Boottime enable/disable dynamic ticks
2118 Valid arguments: on, off
2121 nohz_full= [KNL,BOOT]
2122 In kernels built with CONFIG_NO_HZ_FULL=y, set
2123 the specified list of CPUs whose tick will be stopped
2124 whenever possible. The boot CPU will be forced outside
2125 the range to maintain the timekeeping.
2126 The CPUs in this range must also be included in the
2129 noiotrap [SH] Disables trapped I/O port accesses.
2131 noirqdebug [X86-32] Disables the code which attempts to detect and
2132 disable unhandled interrupt sources.
2134 no_timer_check [X86,APIC] Disables the code which tests for
2135 broken timer IRQ sources.
2137 noisapnp [ISAPNP] Disables ISA PnP code.
2139 noinitrd [RAM] Tells the kernel not to load any configured
2142 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2144 [Deprecated - use intremap=off]
2148 nojitter [IA-64] Disables jitter checking for ITC timers.
2150 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2152 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2155 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2156 steal time is computed, but won't influence scheduler
2159 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2161 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2163 noltlbs [PPC] Do not use large page/tlb entries for kernel
2164 lowmem mapping on PPC40x.
2166 nomca [IA-64] Disable machine check abort handling
2168 nomce [X86-32] Machine Check Exception
2170 nomfgpt [X86-32] Disable Multi-Function General Purpose
2171 Timer usage (for AMD Geode machines).
2173 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2174 shutdown the other cpus. Instead use the REBOOT_VECTOR
2177 nomodule Disable module load
2179 nopat [X86] Disable PAT (page attribute table extension of
2180 pagetables) support.
2182 norandmaps Don't use address space randomization. Equivalent to
2183 echo 0 > /proc/sys/kernel/randomize_va_space
2185 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2187 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2188 with UP alternatives
2190 nordrand [X86] Disable the direct use of the RDRAND
2191 instruction even if it is supported by the
2192 processor. RDRAND is still available to user
2195 noresume [SWSUSP] Disables resume and restores original swap
2198 no-scroll [VGA] Disables scrollback.
2199 This is required for the Braillex ib80-piezo Braille
2200 reader made by F.H. Papenmeier (Germany).
2204 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2206 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2207 and disable the IO APIC. legacy for "maxcpus=0".
2209 nosoftlockup [KNL] Disable the soft-lockup detector.
2211 nosync [HW,M68K] Disables sync negotiation for all devices.
2213 notsc [BUGS=X86-32] Disable Time Stamp Counter
2215 nousb [USB] Disable the USB subsystem
2217 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2221 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2223 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2224 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2225 Some features depend on CPU0. Known dependencies are:
2226 1. Resume from suspend/hibernate depends on CPU0.
2227 Suspend/hibernate will fail if CPU0 is offline and you
2228 need to online CPU0 before suspend/hibernate.
2229 2. PIC interrupts also depend on CPU0. CPU0 can't be
2230 removed if a PIC interrupt is detected.
2231 It's said poweroff/reboot may depend on CPU0 on some
2232 machines although I haven't seen such issues so far
2233 after CPU0 is offline on a few tested machines.
2234 If the dependencies are under your control, you can
2235 turn on cpu0_hotplug.
2237 nptcg= [IA-64] Override max number of concurrent global TLB
2238 purges which is reported from either PAL_VM_SUMMARY or
2241 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2242 could support. nr_cpus=n : n >= 1 limits the kernel to
2243 supporting 'n' processors. Later in runtime you can not
2244 use hotplug cpu feature to put more cpu back to online.
2245 just like you compile the kernel NR_CPUS=n
2247 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2249 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2250 Allowed values are enable and disable
2252 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2253 one of ['zone', 'node', 'default'] can be specified
2254 This can be set from sysctl after boot.
2255 See Documentation/sysctl/vm.txt for details.
2257 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2258 See Documentation/debugging-via-ohci1394.txt for more
2261 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2262 Rather than timing out after 20 ms if an EC
2263 command is not properly ACKed, override the length
2264 of the timeout. We have interrupts disabled while
2265 waiting for the ACK, so if this is set too high
2266 interrupts *may* be lost!
2268 omap_mux= [OMAP] Override bootloader pin multiplexing.
2269 Format: <mux_mode0.mode_name=value>...
2270 For example, to override I2C bus2:
2271 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2273 oprofile.timer= [HW]
2274 Use timer interrupt instead of performance counters
2276 oprofile.cpu_type= Force an oprofile cpu type
2277 This might be useful if you have an older oprofile
2278 userland or if you want common events.
2279 Format: { arch_perfmon }
2280 arch_perfmon: [X86] Force use of architectural
2281 perfmon on Intel CPUs instead of the
2282 CPU specific event set.
2283 timer: [X86] Force use of architectural NMI
2284 timer mode (see also oprofile.timer
2285 for generic hr timer mode)
2286 [s390] Force legacy basic mode sampling
2287 (report cpu_type "timer")
2289 oops=panic Always panic on oopses. Default is to just kill the
2290 process, but there is a small probability of
2291 deadlocking the machine.
2292 This will also cause panics on machine check exceptions.
2293 Useful together with panic=30 to trigger a reboot.
2296 See Documentation/sound/oss/oss-parameters.txt
2298 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2299 timeout > 0: seconds before rebooting
2300 timeout = 0: wait forever
2301 timeout < 0: reboot immediately
2304 parkbd.port= [HW] Parallel port number the keyboard adapter is
2305 connected to, default is 0.
2307 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2308 0 for XT, 1 for AT (default is AT).
2311 parport= [HW,PPT] Specify parallel ports. 0 disables.
2312 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2313 Use 'auto' to force the driver to use any
2314 IRQ/DMA settings detected (the default is to
2315 ignore detected IRQ/DMA settings because of
2316 possible conflicts). You can specify the base
2317 address, IRQ, and DMA settings; IRQ and DMA
2318 should be numbers, or 'auto' (for using detected
2319 settings on that particular port), or 'nofifo'
2320 (to avoid using a FIFO even if it is detected).
2321 Parallel ports are assigned in the order they
2322 are specified on the command line, starting
2325 parport_init_mode= [HW,PPT]
2326 Configure VIA parallel port to operate in
2327 a specific mode. This is necessary on Pegasos
2328 computer where firmware has no options for setting
2329 up parallel port mode and sets it to spp.
2330 Currently this function knows 686a and 8231 chips.
2331 Format: [spp|ps2|epp|ecp|ecpepp]
2334 Halt all CPUs after the first oops has been printed for
2335 the specified number of seconds. This is to be used if
2336 your oopses keep scrolling off the screen.
2341 See header of drivers/block/paride/pcd.c.
2342 See also Documentation/blockdev/paride.txt.
2344 pci=option[,option...] [PCI] various PCI subsystem options:
2345 earlydump [X86] dump PCI config space before the kernel
2347 off [X86] don't probe for the PCI bus
2348 bios [X86-32] force use of PCI BIOS, don't access
2349 the hardware directly. Use this if your machine
2350 has a non-standard PCI host bridge.
2351 nobios [X86-32] disallow use of PCI BIOS, only direct
2352 hardware access methods are allowed. Use this
2353 if you experience crashes upon bootup and you
2354 suspect they are caused by the BIOS.
2355 conf1 [X86] Force use of PCI Configuration
2357 conf2 [X86] Force use of PCI Configuration
2359 noaer [PCIE] If the PCIEAER kernel config parameter is
2360 enabled, this kernel boot option can be used to
2361 disable the use of PCIE advanced error reporting.
2362 nodomains [PCI] Disable support for multiple PCI
2363 root domains (aka PCI segments, in ACPI-speak).
2364 nommconf [X86] Disable use of MMCONFIG for PCI
2366 check_enable_amd_mmconf [X86] check for and enable
2367 properly configured MMIO access to PCI
2368 config space on AMD family 10h CPU
2369 nomsi [MSI] If the PCI_MSI kernel config parameter is
2370 enabled, this kernel boot option can be used to
2371 disable the use of MSI interrupts system-wide.
2372 noioapicquirk [APIC] Disable all boot interrupt quirks.
2373 Safety option to keep boot IRQs enabled. This
2374 should never be necessary.
2375 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2376 primary IO-APIC for bridges that cannot disable
2377 boot IRQs. This fixes a source of spurious IRQs
2378 when the system masks IRQs.
2379 noioapicreroute [APIC] Disable workaround that uses the
2380 boot IRQ equivalent of an IRQ that connects to
2381 a chipset where boot IRQs cannot be disabled.
2382 The opposite of ioapicreroute.
2383 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2384 routing table. These calls are known to be buggy
2385 on several machines and they hang the machine
2386 when used, but on other computers it's the only
2387 way to get the interrupt routing table. Try
2388 this option if the kernel is unable to allocate
2389 IRQs or discover secondary PCI buses on your
2391 rom [X86] Assign address space to expansion ROMs.
2392 Use with caution as certain devices share
2393 address decoders between ROMs and other
2395 norom [X86] Do not assign address space to
2396 expansion ROMs that do not already have
2397 BIOS assigned address ranges.
2398 nobar [X86] Do not assign address space to the
2399 BARs that weren't assigned by the BIOS.
2400 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2401 assigned automatically to PCI devices. You can
2402 make the kernel exclude IRQs of your ISA cards
2404 pirqaddr=0xAAAAA [X86] Specify the physical address
2405 of the PIRQ table (normally generated
2406 by the BIOS) if it is outside the
2407 F0000h-100000h range.
2408 lastbus=N [X86] Scan all buses thru bus #N. Can be
2409 useful if the kernel is unable to find your
2410 secondary buses and you want to tell it
2411 explicitly which ones they are.
2412 assign-busses [X86] Always assign all PCI bus
2413 numbers ourselves, overriding
2414 whatever the firmware may have done.
2415 usepirqmask [X86] Honor the possible IRQ mask stored
2416 in the BIOS $PIR table. This is needed on
2417 some systems with broken BIOSes, notably
2418 some HP Pavilion N5400 and Omnibook XE3
2419 notebooks. This will have no effect if ACPI
2420 IRQ routing is enabled.
2421 noacpi [X86] Do not use ACPI for IRQ routing
2422 or for PCI scanning.
2423 use_crs [X86] Use PCI host bridge window information
2424 from ACPI. On BIOSes from 2008 or later, this
2425 is enabled by default. If you need to use this,
2426 please report a bug.
2427 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2428 If you need to use this, please report a bug.
2429 routeirq Do IRQ routing for all PCI devices.
2430 This is normally done in pci_enable_device(),
2431 so this option is a temporary workaround
2432 for broken drivers that don't call it.
2433 skip_isa_align [X86] do not align io start addr, so can
2434 handle more pci cards
2435 firmware [ARM] Do not re-enumerate the bus but instead
2436 just use the configuration from the
2437 bootloader. This is currently used on
2438 IXP2000 systems where the bus has to be
2439 configured a certain way for adjunct CPUs.
2440 noearly [X86] Don't do any early type 1 scanning.
2441 This might help on some broken boards which
2442 machine check when some devices' config space
2443 is read. But various workarounds are disabled
2444 and some IOMMU drivers will not work.
2445 bfsort Sort PCI devices into breadth-first order.
2446 This sorting is done to get a device
2447 order compatible with older (<= 2.4) kernels.
2448 nobfsort Don't sort PCI devices into breadth-first order.
2449 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2450 tuning and use the BIOS-configured MPS defaults.
2451 pcie_bus_safe Set every device's MPS to the largest value
2452 supported by all devices below the root complex.
2453 pcie_bus_perf Set device MPS to the largest allowable MPS
2454 based on its parent bus. Also set MRRS (Max
2455 Read Request Size) to the largest supported
2456 value (no larger than the MPS that the device
2457 or bus can support) for best performance.
2458 pcie_bus_peer2peer Set every device's MPS to 128B, which
2459 every device is guaranteed to support. This
2460 configuration allows peer-to-peer DMA between
2461 any pair of devices, possibly at the cost of
2462 reduced performance. This also guarantees
2463 that hot-added devices will work.
2464 cbiosize=nn[KMG] The fixed amount of bus space which is
2465 reserved for the CardBus bridge's IO window.
2466 The default value is 256 bytes.
2467 cbmemsize=nn[KMG] The fixed amount of bus space which is
2468 reserved for the CardBus bridge's memory
2469 window. The default value is 64 megabytes.
2472 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2473 Specifies alignment and device to reassign
2474 aligned memory resources.
2475 If <order of align> is not specified,
2476 PAGE_SIZE is used as alignment.
2477 PCI-PCI bridge can be specified, if resource
2478 windows need to be expanded.
2479 ecrc= Enable/disable PCIe ECRC (transaction layer
2480 end-to-end CRC checking).
2481 bios: Use BIOS/firmware settings. This is the
2485 hpiosize=nn[KMG] The fixed amount of bus space which is
2486 reserved for hotplug bridge's IO window.
2487 Default size is 256 bytes.
2488 hpmemsize=nn[KMG] The fixed amount of bus space which is
2489 reserved for hotplug bridge's memory window.
2490 Default size is 2 megabytes.
2491 realloc= Enable/disable reallocating PCI bridge resources
2492 if allocations done by BIOS are too small to
2493 accommodate resources required by all child
2495 off: Turn realloc off
2497 realloc same as realloc=on
2498 noari do not use PCIe ARI.
2499 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2500 only look for one device below a PCIe downstream
2503 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2506 force Enable ASPM even on devices that claim not to support it.
2507 WARNING: Forcing ASPM on may cause system lockups.
2509 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2510 nomsi Do not use MSI for PCI Express Native Hotplug (this
2511 makes all PCIe ports use INTx for hotplug services).
2513 pcie_ports= [PCIE] PCIe ports handling:
2514 auto Ask the BIOS whether or not to use native PCIe services
2515 associated with PCIe ports (PME, hot-plug, AER). Use
2516 them only if that is allowed by the BIOS.
2517 native Use native PCIe services associated with PCIe ports
2519 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2522 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2523 nomsi Do not use MSI for native PCIe PME signaling (this makes
2524 all PCIe root ports use INTx for all services).
2526 pcmv= [HW,PCMCIA] BadgePAD 4
2529 See Documentation/blockdev/paride.txt.
2531 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2534 See arch/parisc/kernel/pdc_chassis.c
2536 percpu_alloc= Select which percpu first chunk allocator to use.
2537 Currently supported values are "embed" and "page".
2538 Archs may support subset or none of the selections.
2539 See comments in mm/percpu.c for details on each
2540 allocator. This parameter is primarily for debugging
2541 and performance comparison.
2544 See Documentation/blockdev/paride.txt.
2547 See Documentation/blockdev/paride.txt.
2549 pirq= [SMP,APIC] Manual mp-table setup
2550 See Documentation/x86/i386/IO-APIC.txt.
2552 plip= [PPT,NET] Parallel port network link
2553 Format: { parport<nr> | timid | 0 }
2554 See also Documentation/parport.txt.
2556 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2557 Override pmtimer IOPort with a hex value.
2561 Enable PNP debug messages (depends on the
2562 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2563 via /sys/module/pnp/parameters/debug. We always show
2564 current resource usage; turning this on also shows
2565 possible settings and some assignment information.
2571 { on | off | curr | res | no-curr | no-res }
2574 [ISAPNP] Exclude IRQs for the autoconfiguration
2577 [ISAPNP] Exclude DMAs for the autoconfiguration
2579 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2580 Ranges are in pairs (I/O port base and size).
2583 [ISAPNP] Exclude memory regions for the
2585 Ranges are in pairs (memory base and size).
2587 ports= [IP_VS_FTP] IPVS ftp helper module
2589 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2591 Format: <port>,<port>....
2593 print-fatal-signals=
2594 [KNL] debug: print fatal signals
2596 If enabled, warn about various signal handling
2597 related application anomalies: too many signals,
2598 too many POSIX.1 timers, fatal signals causing a
2601 If you hit the warning due to signal overflow,
2602 you might want to try "ulimit -i unlimited".
2606 printk.always_kmsg_dump=
2607 Trigger kmsg_dump for cases other than kernel oops or
2609 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2612 printk.time= Show timing data prefixed to each printk message line
2613 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2615 processor.max_cstate= [HW,ACPI]
2616 Limit processor to maximum C-state
2617 max_cstate=9 overrides any DMI blacklist limit.
2619 processor.nocst [HW,ACPI]
2620 Ignore the _CST method to determine C-states,
2621 instead using the legacy FADT method
2623 profile= [KNL] Enable kernel profiling via /proc/profile
2624 Format: [schedule,]<number>
2625 Param: "schedule" - profile schedule points.
2626 Param: <number> - step/bucket size as a power of 2 for
2627 statistical time based profiling.
2628 Param: "sleep" - profile D-state sleeping (millisecs).
2629 Requires CONFIG_SCHEDSTATS
2630 Param: "kvm" - profile VM exits.
2632 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2634 See Documentation/blockdev/ramdisk.txt.
2636 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2637 probe for; one of (bare|imps|exps|lifebook|any).
2638 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2640 psmouse.resetafter= [HW,MOUSE]
2641 Try to reset the device after so many bad packets
2644 [HW,MOUSE] Set desired mouse resolution, in dpi.
2645 psmouse.smartscroll=
2646 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2647 0 = disabled, 1 = enabled (default).
2649 pstore.backend= Specify the name of the pstore backend to use
2652 See Documentation/blockdev/paride.txt.
2655 [KNL] Number of legacy pty's. Overwrites compiled-in
2658 quiet [KNL] Disable most log messages
2663 See Documentation/md.txt.
2665 ramdisk_blocksize= [RAM]
2666 See Documentation/blockdev/ramdisk.txt.
2668 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2669 See Documentation/blockdev/ramdisk.txt.
2672 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2673 the specified list of CPUs to be no-callback CPUs.
2674 Invocation of these CPUs' RCU callbacks will
2675 be offloaded to "rcuox/N" kthreads created for
2676 that purpose, where "x" is "b" for RCU-bh, "p"
2677 for RCU-preempt, and "s" for RCU-sched, and "N"
2678 is the CPU number. This reduces OS jitter on the
2679 offloaded CPUs, which can be useful for HPC and
2680 real-time workloads. It can also improve energy
2681 efficiency for asymmetric multiprocessors.
2684 Rather than requiring that offloaded CPUs
2685 (specified by rcu_nocbs= above) explicitly
2686 awaken the corresponding "rcuoN" kthreads,
2687 make these kthreads poll for callbacks.
2688 This improves the real-time response for the
2689 offloaded CPUs by relieving them of the need to
2690 wake up the corresponding kthread, but degrades
2691 energy efficiency by requiring that the kthreads
2692 periodically wake up to do the polling.
2694 rcutree.blimit= [KNL]
2695 Set maximum number of finished RCU callbacks to
2696 process in one batch.
2698 rcutree.rcu_fanout_leaf= [KNL]
2699 Increase the number of CPUs assigned to each
2700 leaf rcu_node structure. Useful for very large
2703 rcutree.jiffies_till_first_fqs= [KNL]
2704 Set delay from grace-period initialization to
2705 first attempt to force quiescent states.
2706 Units are jiffies, minimum value is zero,
2707 and maximum value is HZ.
2709 rcutree.jiffies_till_next_fqs= [KNL]
2710 Set delay between subsequent attempts to force
2711 quiescent states. Units are jiffies, minimum
2712 value is one, and maximum value is HZ.
2714 rcutree.qhimark= [KNL]
2715 Set threshold of queued RCU callbacks beyond which
2716 batch limiting is disabled.
2718 rcutree.qlowmark= [KNL]
2719 Set threshold of queued RCU callbacks below which
2720 batch limiting is re-enabled.
2722 rcutree.rcu_idle_gp_delay= [KNL]
2723 Set wakeup interval for idle CPUs that have
2724 RCU callbacks (RCU_FAST_NO_HZ=y).
2726 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2727 Set wakeup interval for idle CPUs that have
2728 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2729 Lazy RCU callbacks are those which RCU can
2730 prove do nothing more than free memory.
2732 rcutorture.fqs_duration= [KNL]
2733 Set duration of force_quiescent_state bursts.
2735 rcutorture.fqs_holdoff= [KNL]
2736 Set holdoff time within force_quiescent_state bursts.
2738 rcutorture.fqs_stutter= [KNL]
2739 Set wait time between force_quiescent_state bursts.
2741 rcutorture.gp_exp= [KNL]
2742 Use expedited update-side primitives.
2744 rcutorture.gp_normal= [KNL]
2745 Use normal (non-expedited) update-side primitives.
2746 If both gp_exp and gp_normal are set, do both.
2747 If neither gp_exp nor gp_normal are set, still
2750 rcutorture.n_barrier_cbs= [KNL]
2751 Set callbacks/threads for rcu_barrier() testing.
2753 rcutorture.nfakewriters= [KNL]
2754 Set number of concurrent RCU writers. These just
2755 stress RCU, they don't participate in the actual
2756 test, hence the "fake".
2758 rcutorture.nreaders= [KNL]
2759 Set number of RCU readers.
2761 rcutorture.object_debug= [KNL]
2762 Enable debug-object double-call_rcu() testing.
2764 rcutorture.onoff_holdoff= [KNL]
2765 Set time (s) after boot for CPU-hotplug testing.
2767 rcutorture.onoff_interval= [KNL]
2768 Set time (s) between CPU-hotplug operations, or
2769 zero to disable CPU-hotplug testing.
2771 rcutorture.rcutorture_runnable= [BOOT]
2772 Start rcutorture running at boot time.
2774 rcutorture.shuffle_interval= [KNL]
2775 Set task-shuffle interval (s). Shuffling tasks
2776 allows some CPUs to go into dyntick-idle mode
2777 during the rcutorture test.
2779 rcutorture.shutdown_secs= [KNL]
2780 Set time (s) after boot system shutdown. This
2781 is useful for hands-off automated testing.
2783 rcutorture.stall_cpu= [KNL]
2784 Duration of CPU stall (s) to test RCU CPU stall
2785 warnings, zero to disable.
2787 rcutorture.stall_cpu_holdoff= [KNL]
2788 Time to wait (s) after boot before inducing stall.
2790 rcutorture.stat_interval= [KNL]
2791 Time (s) between statistics printk()s.
2793 rcutorture.stutter= [KNL]
2794 Time (s) to stutter testing, for example, specifying
2795 five seconds causes the test to run for five seconds,
2796 wait for five seconds, and so on. This tests RCU's
2797 ability to transition abruptly to and from idle.
2799 rcutorture.test_boost= [KNL]
2800 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2801 "Maybe" means test if the RCU implementation
2802 under test support RCU priority boosting.
2804 rcutorture.test_boost_duration= [KNL]
2805 Duration (s) of each individual boost test.
2807 rcutorture.test_boost_interval= [KNL]
2808 Interval (s) between each boost test.
2810 rcutorture.test_no_idle_hz= [KNL]
2811 Test RCU's dyntick-idle handling. See also the
2812 rcutorture.shuffle_interval parameter.
2814 rcutorture.torture_type= [KNL]
2815 Specify the RCU implementation to test.
2817 rcutorture.verbose= [KNL]
2818 Enable additional printk() statements.
2820 rcupdate.rcu_expedited= [KNL]
2821 Use expedited grace-period primitives, for
2822 example, synchronize_rcu_expedited() instead
2823 of synchronize_rcu(). This reduces latency,
2824 but can increase CPU utilization, degrade
2825 real-time latency, and degrade energy efficiency.
2827 rcupdate.rcu_cpu_stall_suppress= [KNL]
2828 Suppress RCU CPU stall warning messages.
2830 rcupdate.rcu_cpu_stall_timeout= [KNL]
2831 Set timeout for RCU CPU stall warning messages.
2835 Run specified binary instead of /init from the ramdisk,
2836 used for early userspace startup. See initrd.
2839 Format (x86 or x86_64):
2840 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2842 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2844 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2845 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2846 reboot_force is either force or not specified,
2847 reboot_cpu is s[mp]#### with #### being the processor
2848 to be used for rebooting.
2851 [KNL, SMP] Set scheduler's default relax_domain_level.
2852 See Documentation/cgroups/cpusets.txt.
2854 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2856 reservetop= [X86-32]
2858 Reserves a hole at the top of the kernel virtual
2863 Set the amount of memory to reserve for BIOS at
2864 the bottom of the address space.
2866 reset_devices [KNL] Force drivers to reset the underlying device
2867 during initialization.
2870 Specify the partition device for software suspend
2872 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2874 resume_offset= [SWSUSP]
2875 Specify the offset from the beginning of the partition
2876 given by "resume=" at which the swap header is located,
2877 in <PAGE_SIZE> units (needed only for swap files).
2878 See Documentation/power/swsusp-and-swap-files.txt
2880 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2881 read the resume files
2883 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2884 Useful for devices that are detected asynchronously
2885 (e.g. USB and MMC devices).
2887 hibernate= [HIBERNATION]
2888 noresume Don't check if there's a hibernation image
2889 present during boot.
2890 nocompress Don't compress/decompress hibernation images.
2892 retain_initrd [RAM] Keep initrd memory after extraction
2894 rhash_entries= [KNL,NET]
2895 Set number of hash buckets for route cache
2897 riscom8= [HW,SERIAL]
2898 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2900 ro [KNL] Mount root device read-only on boot
2902 root= [KNL] Root filesystem
2903 See name_to_dev_t comment in init/do_mounts.c.
2905 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2906 mount the root filesystem
2908 rootflags= [KNL] Set root filesystem mount option string
2910 rootfstype= [KNL] Set root filesystem type
2912 rootwait [KNL] Wait (indefinitely) for root device to show up.
2913 Useful for devices that are detected asynchronously
2914 (e.g. USB and MMC devices).
2916 rproc_mem=nn[KMG][@address]
2917 [KNL,ARM,CMA] Remoteproc physical memory block.
2918 Memory area to be used by remote processor image,
2921 rw [KNL] Mount root device read-write on boot
2923 S [KNL] Run init in single mode
2926 See drivers/net/irda/sa1100_ir.c.
2928 sbni= [NET] Granch SBNI12 leased line adapter
2930 sched_debug [KNL] Enables verbose scheduler debug messages.
2932 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2933 xtime_lock contention on larger systems, and/or RCU lock
2934 contention on all systems with CONFIG_MAXSMP set.
2935 Format: { "0" | "1" }
2936 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2938 Note: increases power consumption, thus should only be
2939 enabled if running jitter sensitive (HPC/RT) workloads.
2941 security= [SECURITY] Choose a security module to enable at boot.
2942 If this boot parameter is not specified, only the first
2943 security module asking for security registration will be
2944 loaded. An invalid security module name will be treated
2945 as if no module has been chosen.
2947 selinux= [SELINUX] Disable or enable SELinux at boot time.
2948 Format: { "0" | "1" }
2949 See security/selinux/Kconfig help text.
2952 Default value is set via kernel config option.
2953 If enabled at boot time, /selinux/disable can be used
2954 later to disable prior to initial policy load.
2956 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2957 Format: { "0" | "1" }
2958 See security/apparmor/Kconfig help text
2961 Default value is set via kernel config option.
2963 serialnumber [BUGS=X86-32]
2966 Maximal number of shapers.
2968 show_msr= [x86] show boot-time MSR settings
2969 Format: { <integer> }
2970 Show boot-time (BIOS-initialized) MSR settings.
2971 The parameter means the number of CPUs to show,
2972 for example 1 means boot CPU only.
2979 slab_max_order= [MM, SLAB]
2980 Determines the maximum allowed order for slabs.
2981 A high setting may cause OOMs due to memory
2982 fragmentation. Defaults to 1 for systems with
2983 more than 32MB of RAM, 0 otherwise.
2985 slub_debug[=options[,slabs]] [MM, SLUB]
2986 Enabling slub_debug allows one to determine the
2987 culprit if slab objects become corrupted. Enabling
2988 slub_debug can create guard zones around objects and
2989 may poison objects when not in use. Also tracks the
2990 last alloc / free. For more information see
2991 Documentation/vm/slub.txt.
2993 slub_max_order= [MM, SLUB]
2994 Determines the maximum allowed order for slabs.
2995 A high setting may cause OOMs due to memory
2996 fragmentation. For more information see
2997 Documentation/vm/slub.txt.
2999 slub_min_objects= [MM, SLUB]
3000 The minimum number of objects per slab. SLUB will
3001 increase the slab order up to slub_max_order to
3002 generate a sufficiently large slab able to contain
3003 the number of objects indicated. The higher the number
3004 of objects the smaller the overhead of tracking slabs
3005 and the less frequently locks need to be acquired.
3006 For more information see Documentation/vm/slub.txt.
3008 slub_min_order= [MM, SLUB]
3009 Determines the minimum page order for slabs. Must be
3010 lower than slub_max_order.
3011 For more information see Documentation/vm/slub.txt.
3013 slub_nomerge [MM, SLUB]
3014 Disable merging of slabs with similar size. May be
3015 necessary if there is some reason to distinguish
3016 allocs to different slabs. Debug options disable
3017 merging on their own.
3018 For more information see Documentation/vm/slub.txt.
3021 Format: <io1>[,<io2>[,...,<io8>]]
3023 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3024 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3025 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3026 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3027 smsc-ircc2.ircc_irq= [HW] IRQ line
3028 smsc-ircc2.ircc_dma= [HW] DMA channel
3029 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3030 0: Toshiba Satellite 1800 (GP data pin select)
3031 1: Fast pin select (default)
3035 [KNL] Should the soft-lockup detector generate panics.
3038 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3039 See Documentation/laptops/sonypi.txt
3041 specialix= [HW,SERIAL] Specialix multi-serial port adapter
3042 See Documentation/serial/specialix.txt.
3044 spia_io_base= [HW,MTD]
3050 Enabled the stack tracer on boot up.
3052 stacktrace_filter=[function-list]
3053 [FTRACE] Limit the functions that the stack tracer
3054 will trace at boot up. function-list is a comma separated
3055 list of functions. This list can be changed at run
3056 time by the stack_trace_filter file in the debugfs
3057 tracing directory. Note, this enables stack tracing
3058 and the stacktrace above is not needed.
3062 Set the STI (builtin display/keyboard on the HP-PARISC
3063 machines) console (graphic card) which should be used
3064 as the initial boot-console.
3065 See also comment in drivers/video/console/sticore.c.
3068 See comment in drivers/video/console/sticore.c.
3071 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3073 sunrpc.min_resvport=
3074 sunrpc.max_resvport=
3076 SunRPC servers often require that client requests
3077 originate from a privileged port (i.e. a port in the
3078 range 0 < portnr < 1024).
3079 An administrator who wishes to reserve some of these
3080 ports for other uses may adjust the range that the
3081 kernel's sunrpc client considers to be privileged
3082 using these two parameters to set the minimum and
3083 maximum port values.
3087 Control how the NFS server code allocates CPUs to
3088 service thread pools. Depending on how many NICs
3089 you have and where their interrupts are bound, this
3090 option will affect which CPUs will do NFS serving.
3091 Note: this parameter cannot be changed while the
3092 NFS server is running.
3094 auto the server chooses an appropriate mode
3095 automatically using heuristics
3096 global a single global pool contains all CPUs
3097 percpu one pool for each CPU
3098 pernode one pool for each NUMA node (equivalent
3099 to global on non-NUMA machines)
3101 sunrpc.tcp_slot_table_entries=
3102 sunrpc.udp_slot_table_entries=
3104 Sets the upper limit on the number of simultaneous
3105 RPC calls that can be sent from the client to a
3106 server. Increasing these values may allow you to
3107 improve throughput, but will also increase the
3108 amount of memory reserved for use by the client.
3111 [KNL] Enable accounting of swap in memory resource
3112 controller if no parameter or 1 is given or disable
3113 it if 0 is given (See Documentation/cgroups/memory.txt)
3115 swiotlb= [IA-64] Number of I/O TLB slabs
3119 sysfs.deprecated=0|1 [KNL]
3120 Enable/disable old style sysfs layout for old udev
3121 on older distributions. When this option is enabled
3122 very new udev will not work anymore. When this option
3123 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3124 in older udev will not work anymore.
3125 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3126 the kernel configuration.
3128 sysrq_always_enabled
3130 Ignore sysrq setting - this boot parameter will
3131 neutralize any effect of /proc/sys/kernel/sysrq.
3132 Useful for debugging.
3136 test_suspend= [SUSPEND]
3137 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3138 standby suspend) as the system sleep state to briefly
3139 enter during system startup. The system is woken from
3140 this state using a wakeup-capable RTC alarm.
3142 thash_entries= [KNL,NET]
3143 Set number of hash buckets for TCP connection
3145 thermal.act= [HW,ACPI]
3146 -1: disable all active trip points in all thermal zones
3147 <degrees C>: override all lowest active trip points
3149 thermal.crt= [HW,ACPI]
3150 -1: disable all critical trip points in all thermal zones
3151 <degrees C>: override all critical trip points
3153 thermal.nocrt= [HW,ACPI]
3154 Set to disable actions on ACPI thermal zone
3155 critical and hot trip points.
3157 thermal.off= [HW,ACPI]
3158 1: disable ACPI thermal control
3160 thermal.psv= [HW,ACPI]
3161 -1: disable all passive trip points
3162 <degrees C>: override all passive trip points to this
3165 thermal.tzp= [HW,ACPI]
3166 Specify global default ACPI thermal zone polling rate
3167 <deci-seconds>: poll all this frequency
3168 0: no polling (default)
3171 Force threading of all interrupt handlers except those
3172 marked explicitly IRQF_NO_THREAD.
3175 Enable the Transcendent memory driver if built-in.
3177 tmem.cleancache=0|1 [KNL, XEN]
3178 Default is on (1). Disable the usage of the cleancache
3179 API to send anonymous pages to the hypervisor.
3181 tmem.frontswap=0|1 [KNL, XEN]
3182 Default is on (1). Disable the usage of the frontswap
3183 API to send swap pages to the hypervisor. If disabled
3184 the selfballooning and selfshrinking are force disabled.
3186 tmem.selfballooning=0|1 [KNL, XEN]
3187 Default is on (1). Disable the driving of swap pages
3190 tmem.selfshrinking=0|1 [KNL, XEN]
3191 Default is on (1). Partial swapoff that immediately
3192 transfers pages from Xen hypervisor back to the
3193 kernel based on different criteria.
3197 Specify if the kernel should make use of the cpu
3198 topology information if the hardware supports this.
3199 The scheduler will make use of this information and
3200 e.g. base its process migration decisions on it.
3205 tpm_suspend_pcr=[HW,TPM]
3206 Format: integer pcr id
3207 Specify that at suspend time, the tpm driver
3208 should extend the specified pcr with zeros,
3209 as a workaround for some chips which fail to
3210 flush the last written pcr on TPM_SaveState.
3211 This will guarantee that all the other pcrs
3214 trace_buf_size=nn[KMG]
3215 [FTRACE] will set tracing buffer size.
3217 trace_event=[event-list]
3218 [FTRACE] Set and start specified trace events in order
3219 to facilitate early boot debugging.
3220 See also Documentation/trace/events.txt
3222 trace_options=[option-list]
3223 [FTRACE] Enable or disable tracer options at boot.
3224 The option-list is a comma delimited list of options
3225 that can be enabled or disabled just as if you were
3226 to echo the option name into
3228 /sys/kernel/debug/tracing/trace_options
3230 For example, to enable stacktrace option (to dump the
3231 stack trace of each event), add to the command line:
3233 trace_options=stacktrace
3235 See also Documentation/trace/ftrace.txt "trace options"
3239 [FTRACE] enable this option to disable tracing when a
3240 warning is hit. This turns off "tracing_on". Tracing can
3241 be enabled again by echoing '1' into the "tracing_on"
3242 file located in /sys/kernel/debug/tracing/
3244 This option is useful, as it disables the trace before
3245 the WARNING dump is called, which prevents the trace to
3246 be filled with content caused by the warning output.
3248 This option can also be set at run time via the sysctl
3249 option: kernel/traceoff_on_warning
3251 transparent_hugepage=
3253 Format: [always|madvise|never]
3254 Can be used to control the default behavior of the system
3255 with respect to transparent hugepages.
3256 See Documentation/vm/transhuge.txt for more details.
3258 tsc= Disable clocksource stability checks for TSC.
3260 [x86] reliable: mark tsc clocksource as reliable, this
3261 disables clocksource verification at runtime, as well
3262 as the stability checks done at bootup. Used to enable
3263 high-resolution timer mode on older hardware, and in
3264 virtualized environment.
3265 [x86] noirqtime: Do not use TSC to do irq accounting.
3266 Used to run time disable IRQ_TIME_ACCOUNTING on any
3267 platforms where RDTSC is slow and this accounting
3270 turbografx.map[2|3]= [HW,JOY]
3271 TurboGraFX parallel port interface
3273 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3274 See also Documentation/input/joystick-parport.txt
3276 udbg-immortal [PPC] When debugging early kernel crashes that
3277 happen after console_init() and before a proper
3278 console driver takes over, this boot options might
3279 help "seeing" what's going on.
3281 uhash_entries= [KNL,NET]
3282 Set number of hash buckets for UDP/UDP-Lite connections
3285 [USB] Ignore overcurrent events (default N).
3286 Some badly-designed motherboards generate lots of
3287 bogus events, for ports that aren't wired to
3288 anything. Set this parameter to avoid log spamming.
3289 Note that genuine overcurrent events won't be
3293 [X86] Cause panic on unknown NMI.
3295 usbcore.authorized_default=
3296 [USB] Default USB device authorization:
3297 (default -1 = authorized except for wireless USB,
3298 0 = not authorized, 1 = authorized)
3300 usbcore.autosuspend=
3301 [USB] The autosuspend time delay (in seconds) used
3302 for newly-detected USB devices (default 2). This
3303 is the time required before an idle device will be
3304 autosuspended. Devices for which the delay is set
3305 to a negative value won't be autosuspended at all.
3307 usbcore.usbfs_snoop=
3308 [USB] Set to log all usbfs traffic (default 0 = off).
3310 usbcore.blinkenlights=
3311 [USB] Set to cycle leds on hubs (default 0 = off).
3313 usbcore.old_scheme_first=
3314 [USB] Start with the old device initialization
3315 scheme (default 0 = off).
3317 usbcore.usbfs_memory_mb=
3318 [USB] Memory limit (in MB) for buffers allocated by
3319 usbfs (default = 16, 0 = max = 2047).
3321 usbcore.use_both_schemes=
3322 [USB] Try the other device initialization scheme
3323 if the first one fails (default 1 = enabled).
3325 usbcore.initial_descriptor_timeout=
3326 [USB] Specifies timeout for the initial 64-byte
3327 USB_REQ_GET_DESCRIPTOR request in milliseconds
3328 (default 5000 = 5.0 seconds).
3331 [USBHID] The interval which mice are to be polled at.
3333 usb-storage.delay_use=
3334 [UMS] The delay in seconds before a new device is
3335 scanned for Logical Units (default 5).
3338 [UMS] A list of quirks entries to supplement or
3339 override the built-in unusual_devs list. List
3340 entries are separated by commas. Each entry has
3341 the form VID:PID:Flags where VID and PID are Vendor
3342 and Product ID values (4-digit hex numbers) and
3343 Flags is a set of characters, each corresponding
3344 to a common usb-storage quirk flag as follows:
3345 a = SANE_SENSE (collect more than 18 bytes
3347 b = BAD_SENSE (don't collect more than 18
3348 bytes of sense data);
3349 c = FIX_CAPACITY (decrease the reported
3350 device capacity by one sector);
3351 d = NO_READ_DISC_INFO (don't use
3352 READ_DISC_INFO command);
3353 e = NO_READ_CAPACITY_16 (don't use
3354 READ_CAPACITY_16 command);
3355 h = CAPACITY_HEURISTICS (decrease the
3356 reported device capacity by one
3357 sector if the number is odd);
3358 i = IGNORE_DEVICE (don't bind to this
3360 l = NOT_LOCKABLE (don't try to lock and
3361 unlock ejectable media);
3362 m = MAX_SECTORS_64 (don't transfer more
3363 than 64 sectors = 32 KB at a time);
3364 n = INITIAL_READ10 (force a retry of the
3365 initial READ(10) command);
3366 o = CAPACITY_OK (accept the capacity
3367 reported by the device);
3368 p = WRITE_CACHE (the device cache is ON
3370 r = IGNORE_RESIDUE (the device reports
3371 bogus residue values);
3372 s = SINGLE_LUN (the device has only one
3374 w = NO_WP_DETECT (don't test whether the
3375 medium is write-protected).
3376 Example: quirks=0419:aaf5:rl,0421:0433:rc
3378 user_debug= [KNL,ARM]
3380 See arch/arm/Kconfig.debug help text.
3381 1 - undefined instruction events
3383 4 - invalid data aborts
3386 Example: user_debug=31
3389 [X86] Flags controlling user PTE allocations.
3391 nohigh = do not allocate PTE pages in
3392 HIGHMEM regardless of setting
3396 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3397 vdso=1: enable VDSO (default)
3398 vdso=0: disable VDSO mapping
3401 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3402 vdso32=1: enable 32-bit VDSO (default)
3403 vdso32=0: disable 32-bit VDSO mapping
3406 vector=percpu: enable percpu vector domain
3408 video= [FB] Frame buffer configuration
3409 See Documentation/fb/modedb.txt.
3411 video.brightness_switch_enabled= [0,1]
3412 If set to 1, on receiving an ACPI notify event
3413 generated by hotkey, video driver will adjust brightness
3414 level and then send out the event to user space through
3415 the allocated input device; If set to 0, video driver
3416 will only send out the event without touching backlight
3421 [VMMIO] Memory mapped virtio (platform) device.
3423 <size>@<baseaddr>:<irq>[:<id>]
3425 <size> := size (can use standard suffixes
3427 <baseaddr> := physical base address
3428 <irq> := interrupt number (as passed to
3430 <id> := (optional) platform device id
3432 virtio_mmio.device=1K@0x100b0000:48:7
3434 Can be used multiple times for multiple devices.
3436 vga= [BOOT,X86-32] Select a particular video mode
3437 See Documentation/x86/boot.txt and
3438 Documentation/svga.txt.
3439 Use vga=ask for menu.
3440 This is actually a boot loader parameter; the value is
3441 passed to the kernel using a special protocol.
3443 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3444 size of <nn>. This can be used to increase the
3445 minimum size (128MB on x86). It can also be used to
3446 decrease the size and leave more room for directly
3449 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3452 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3455 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3459 Controls the behavior of vsyscalls (i.e. calls to
3460 fixed addresses of 0xffffffffff600x00 from legacy
3461 code). Most statically-linked binaries and older
3462 versions of glibc use these calls. Because these
3463 functions are at fixed addresses, they make nice
3464 targets for exploits that can control RIP.
3466 emulate [default] Vsyscalls turn into traps and are
3467 emulated reasonably safely.
3469 native Vsyscalls are native syscall instructions.
3470 This is a little bit faster than trapping
3471 and makes a few dynamic recompilers work
3472 better than they would in emulation mode.
3473 It also makes exploits much easier to write.
3475 none Vsyscalls don't work at all. This makes
3476 them quite hard to use for exploits but
3477 might break your system.
3479 vt.color= [VT] Default text color.
3480 Format: 0xYX, X = foreground, Y = background.
3481 Default: 0x07 = light gray on black.
3483 vt.cur_default= [VT] Default cursor shape.
3484 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3485 the parameters of the <Esc>[?A;B;Cc escape sequence;
3486 see VGA-softcursor.txt. Default: 2 = underline.
3488 vt.default_blu= [VT]
3489 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3490 Change the default blue palette of the console.
3491 This is a 16-member array composed of values
3494 vt.default_grn= [VT]
3495 Format: <green0>,<green1>,<green2>,...,<green15>
3496 Change the default green palette of the console.
3497 This is a 16-member array composed of values
3500 vt.default_red= [VT]
3501 Format: <red0>,<red1>,<red2>,...,<red15>
3502 Change the default red palette of the console.
3503 This is a 16-member array composed of values
3509 Set system-wide default UTF-8 mode for all tty's.
3510 Default is 1, i.e. UTF-8 mode is enabled for all
3511 newly opened terminals.
3513 vt.global_cursor_default=
3516 Set system-wide default for whether a cursor
3517 is shown on new VTs. Default is -1,
3518 i.e. cursors will be created by default unless
3519 overridden by individual drivers. 0 will hide
3520 cursors, 1 will display them.
3522 vt.italic= [VT] Default color for italic text; 0-15.
3525 vt.underline= [VT] Default color for underlined text; 0-15.
3528 watchdog timers [HW,WDT] For information on watchdog timers,
3529 see Documentation/watchdog/watchdog-parameters.txt
3530 or other driver-specific files in the
3531 Documentation/watchdog/ directory.
3533 workqueue.disable_numa
3534 By default, all work items queued to unbound
3535 workqueues are affine to the NUMA nodes they're
3536 issued on, which results in better behavior in
3537 general. If NUMA affinity needs to be disabled for
3538 whatever reason, this option can be used. Note
3539 that this also can be controlled per-workqueue for
3540 workqueues visible under /sys/bus/workqueue/.
3542 workqueue.power_efficient
3543 Per-cpu workqueues are generally preferred because
3544 they show better performance thanks to cache
3545 locality; unfortunately, per-cpu workqueues tend to
3546 be more power hungry than unbound workqueues.
3548 Enabling this makes the per-cpu workqueues which
3549 were observed to contribute significantly to power
3550 consumption unbound, leading to measurably lower
3551 power usage at the cost of small performance
3554 The default value of this parameter is determined by
3555 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3557 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3558 default x2apic cluster mode on platforms
3561 x86_intel_mid_timer= [X86-32,APBT]
3562 Choose timer option for x86 Intel MID platform.
3563 Two valid options are apbt timer only and lapic timer
3564 plus one apbt timer for broadcast timer.
3565 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3567 xen_emul_unplug= [HW,X86,XEN]
3568 Unplug Xen emulated devices
3569 Format: [unplug0,][unplug1]
3570 ide-disks -- unplug primary master IDE devices
3571 aux-ide-disks -- unplug non-primary-master IDE devices
3572 nics -- unplug network devices
3573 all -- unplug all emulated devices (NICs and IDE disks)
3574 unnecessary -- unplugging emulated devices is
3575 unnecessary even if the host did not respond to
3577 never -- do not unplug even if version check succeeds
3579 xen_nopvspin [X86,XEN]
3580 Disables the ticketlock slowpath using Xen PV
3583 xirc2ps_cs= [NET,PCMCIA]
3585 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3587 ______________________________________________________________________
3591 Add more DRM drivers.
projects / karo-tx-linux.git / blob