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. If the
1063 primary GPT is corrupted, it enables the backup/alternate
1064 GPT to be used instead.
1066 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1067 the "Enable 0" bit of the configuration register.
1070 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1071 the "Enable 0" bit of the configuration register.
1074 grcan.select= [HW] Select which physical interface to use.
1077 grcan.txsize= [HW] Sets the size of the tx buffer.
1078 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1080 grcan.rxsize= [HW] Sets the size of the rx buffer.
1081 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1084 hashdist= [KNL,NUMA] Large hashes allocated during boot
1085 are distributed across NUMA nodes. Defaults on
1086 for 64-bit NUMA, off otherwise.
1087 Format: 0 | 1 (for off | on)
1089 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1091 hd= [EIDE] (E)IDE hard drive subsystem geometry
1092 Format: <cyl>,<head>,<sect>
1095 Disable Hardware Error Source Table (HEST) support;
1096 corresponding firmware-first mode error processing
1097 logic will be disabled.
1099 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1100 size of <nn>. This works even on boxes that have no
1101 highmem otherwise. This also works to reduce highmem
1102 size on bigger boxes.
1104 highres= [KNL] Enable/disable high resolution timer mode.
1105 Valid parameters: "on", "off"
1109 See Documentation/isdn/README.HiSax.
1113 hpet= [X86-32,HPET] option to control HPET usage
1114 Format: { enable (default) | disable | force |
1116 disable: disable HPET and use PIT instead
1117 force: allow force enabled of undocumented chips (ICH4,
1119 verbose: show contents of HPET registers during setup
1121 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1122 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1124 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1125 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1126 On x86-64 and powerpc, this option can be specified
1127 multiple times interleaved with hugepages= to reserve
1128 huge pages of different sizes. Valid pages sizes on
1129 x86-64 are 2M (when the CPU supports "pse") and 1G
1130 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1131 Note that 1GB pages can only be allocated at boot time
1132 using hugepages= and not freed afterwards.
1134 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1135 terminal devices. Valid values: 0..8
1136 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1137 If specified, z/VM IUCV HVC accepts connections
1138 from listed z/VM user IDs only.
1140 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1141 hardware thread id mappings.
1142 Format: <cpu>:<hwthread>
1145 Do not unregister boot console at start. This is only
1146 useful for debugging when something happens in the window
1147 between unregistering the boot console and initializing
1150 i2c_bus= [HW] Override the default board specific I2C bus speed
1151 or register an additional I2C bus that is not
1152 registered from board initialization code.
1156 i8042.debug [HW] Toggle i8042 debug mode
1157 i8042.direct [HW] Put keyboard port into non-translated mode
1158 i8042.dumbkbd [HW] Pretend that controller can only read data from
1159 keyboard and cannot control its state
1160 (Don't attempt to blink the leds)
1161 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1162 i8042.nokbd [HW] Don't check/create keyboard port
1163 i8042.noloop [HW] Disable the AUX Loopback command while probing
1165 i8042.nomux [HW] Don't check presence of an active multiplexing
1167 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1169 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1170 i8042.reset [HW] Reset the controller during init and cleanup
1171 i8042.unlock [HW] Unlock (ignore) the keylock
1175 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1176 indicates that the driver is running on unsupported
1178 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1179 does not match list of supported models.
1181 [HW] Report power status in /proc/i8k
1182 (disabled by default)
1183 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1186 i915.invert_brightness=
1187 [DRM] Invert the sense of the variable that is used to
1188 set the brightness of the panel backlight. Normally a
1189 brightness value of 0 indicates backlight switched off,
1190 and the maximum of the brightness value sets the backlight
1191 to maximum brightness. If this parameter is set to 0
1192 (default) and the machine requires it, or this parameter
1193 is set to 1, a brightness value of 0 sets the backlight
1194 to maximum brightness, and the maximum of the brightness
1195 value switches the backlight off.
1196 -1 -- never invert brightness
1197 0 -- machine default
1198 1 -- force brightness inversion
1201 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1203 ide-core.nodma= [HW] (E)IDE subsystem
1204 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1205 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1206 .cdrom .chs .ignore_cable are additional options
1207 See Documentation/ide/ide.txt.
1209 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1210 Claim all unknown PCI IDE storage controllers.
1213 Format: idle=poll, idle=halt, idle=nomwait
1214 Poll forces a polling idle loop that can slightly
1215 improve the performance of waking up a idle CPU, but
1216 will use a lot of power and make the system run hot.
1218 idle=halt: Halt is forced to be used for CPU idle.
1219 In such case C2/C3 won't be used again.
1220 idle=nomwait: Disable mwait for CPU C-states
1222 ignore_loglevel [KNL]
1223 Ignore loglevel setting - this will print /all/
1224 kernel messages to the console. Useful for debugging.
1225 We also add it as printk module parameter, so users
1226 could change it dynamically, usually by
1227 /sys/module/printk/parameters/ignore_loglevel.
1229 ihash_entries= [KNL]
1230 Set number of hash buckets for inode cache.
1232 ima_appraise= [IMA] appraise integrity measurements
1233 Format: { "off" | "enforce" | "fix" }
1236 ima_appraise_tcb [IMA]
1237 The builtin appraise policy appraises all files
1241 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1245 The list of supported hash algorithms is defined
1246 in crypto/hash_info.h.
1249 Load a policy which meets the needs of the Trusted
1250 Computing Base. This means IMA will measure all
1251 programs exec'd, files mmap'd for exec, and all files
1252 opened for read by uid=0.
1255 Select one of defined IMA measurements template formats.
1256 Formats: { "ima" | "ima-ng" }
1261 Run specified binary instead of /sbin/init as init
1264 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1265 for working out where the kernel is dying during
1268 initrd= [BOOT] Specify the location of the initial ramdisk
1270 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1273 int_pln_enable [x86] Enable power limit notification interrupt
1275 integrity_audit=[IMA]
1276 Format: { "0" | "1" }
1277 0 -- basic integrity auditing messages. (Default)
1278 1 -- additional integrity auditing messages.
1280 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1282 Enable intel iommu driver.
1284 Disable intel iommu driver.
1285 igfx_off [Default Off]
1286 By default, gfx is mapped as normal device. If a gfx
1287 device has a dedicated DMAR unit, the DMAR unit is
1288 bypassed by not enabling DMAR with this option. In
1289 this case, gfx device will use physical address for
1292 With this option iommu will not optimize to look
1293 for io virtual address below 32-bit forcing dual
1294 address cycle on pci bus for cards supporting greater
1295 than 32-bit addressing. The default is to look
1296 for translation below 32-bit and if not available
1297 then look in the higher range.
1298 strict [Default Off]
1299 With this option on every unmap_single operation will
1300 result in a hardware IOTLB flush operation as opposed
1301 to batching them for performance.
1302 sp_off [Default Off]
1303 By default, super page will be supported if Intel IOMMU
1304 has the capability. With this option, super page will
1307 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1308 0 disables intel_idle and fall back on acpi_idle.
1309 1 to 6 specify maximum depth of C-state.
1313 Do not enable intel_pstate as the default
1314 scaling driver for the supported processors
1316 intremap= [X86-64, Intel-IOMMU]
1317 on enable Interrupt Remapping (default)
1318 off disable Interrupt Remapping
1319 nosid disable Source ID checking
1321 BIOS x2APIC opt-out request will be ignored
1323 iomem= Disable strict checking of access to MMIO memory
1324 strict regions from userspace.
1341 io7= [HW] IO7 for Marvel based alpha systems
1342 See comment before marvel_specify_io7 in
1343 arch/alpha/kernel/core_marvel.c.
1345 io_delay= [X86] I/O delay method
1347 Standard port 0x80 based delay
1349 Alternate port 0xed based delay (needed on some systems)
1351 Simple two microseconds delay
1356 See Documentation/filesystems/nfs/nfsroot.txt.
1358 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1359 See comment before ip2_setup() in
1360 drivers/char/ip2/ip2base.c.
1363 When an interrupt is not handled search all handlers
1364 for it. Intended to get systems with badly broken
1368 When an interrupt is not handled search all handlers
1369 for it. Also check all handlers each timer
1370 interrupt. Intended to get systems with badly broken
1374 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1376 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1378 <cpu number>,...,<cpu number>
1380 <cpu number>-<cpu number>
1381 (must be a positive range in ascending order)
1383 <cpu number>,...,<cpu number>-<cpu number>
1385 This option can be used to specify one or more CPUs
1386 to isolate from the general SMP balancing and scheduling
1387 algorithms. You can move a process onto or off an
1388 "isolated" CPU via the CPU affinity syscalls or cpuset.
1389 <cpu number> begins at 0 and the maximum value is
1390 "number of CPUs in system - 1".
1392 This option is the preferred way to isolate CPUs. The
1393 alternative -- manually setting the CPU mask of all
1394 tasks in the system -- can cause problems and
1395 suboptimal load balancer performance.
1399 ivrs_ioapic [HW,X86_64]
1400 Provide an override to the IOAPIC-ID<->DEVICE-ID
1401 mapping provided in the IVRS ACPI table. For
1402 example, to map IOAPIC-ID decimal 10 to
1403 PCI device 00:14.0 write the parameter as:
1404 ivrs_ioapic[10]=00:14.0
1406 ivrs_hpet [HW,X86_64]
1407 Provide an override to the HPET-ID<->DEVICE-ID
1408 mapping provided in the IVRS ACPI table. For
1409 example, to map HPET-ID decimal 0 to
1410 PCI device 00:14.0 write the parameter as:
1411 ivrs_hpet[0]=00:14.0
1413 js= [HW,JOY] Analog joystick
1414 See Documentation/input/joystick.txt.
1418 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1419 specifies the amount of memory usable by the kernel
1420 for non-movable allocations. The requested amount is
1421 spread evenly throughout all nodes in the system. The
1422 remaining memory in each node is used for Movable
1423 pages. In the event, a node is too small to have both
1424 kernelcore and Movable pages, kernelcore pages will
1425 take priority and other nodes will have a larger number
1426 of Movable pages. The Movable zone is used for the
1427 allocation of pages that may be reclaimed or moved
1428 by the page migration subsystem. This means that
1429 HugeTLB pages may not be allocated from this zone.
1430 Note that allocations like PTEs-from-HighMem still
1431 use the HighMem zone if it exists, and the Normal
1432 zone if it does not.
1434 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1435 Format: <Controller#>[,poll interval]
1436 The controller # is the number of the ehci usb debug
1437 port as it is probed via PCI. The poll interval is
1438 optional and is the number seconds in between
1439 each poll cycle to the debug port in case you need
1440 the functionality for interrupting the kernel with
1441 gdb or control-c on the dbgp connection. When
1442 not using this parameter you use sysrq-g to break into
1443 the kernel debugger.
1445 kgdboc= [KGDB,HW] kgdb over consoles.
1446 Requires a tty driver that supports console polling,
1447 or a supported polling keyboard driver (non-usb).
1448 Serial only format: <serial_device>[,baud]
1449 keyboard only format: kbd
1450 keyboard and serial format: kbd,<serial_device>[,baud]
1451 Optional Kernel mode setting:
1452 kms, kbd format: kms,kbd
1453 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1455 kgdbwait [KGDB] Stop kernel execution and enter the
1456 kernel debugger at the earliest opportunity.
1458 kmac= [MIPS] korina ethernet MAC address.
1459 Configure the RouterBoard 532 series on-chip
1460 Ethernet adapter MAC address.
1462 kmemleak= [KNL] Boot-time kmemleak enable/disable
1463 Valid arguments: on, off
1466 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1467 Valid arguments: 0, 1, 2
1468 kmemcheck=0 (disabled)
1469 kmemcheck=1 (enabled)
1470 kmemcheck=2 (one-shot mode)
1471 Default: 2 (one-shot mode)
1473 kstack=N [X86] Print N words from the kernel stack
1476 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1477 Default is 0 (don't ignore, but inject #GP)
1479 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1483 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1484 Default is 1 (enabled)
1486 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1488 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1490 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1491 (virtualized MMU) support on capable Intel chips.
1492 Default is 1 (enabled)
1494 kvm-intel.emulate_invalid_guest_state=
1495 [KVM,Intel] Enable emulation of invalid guest states
1496 Default is 0 (disabled)
1498 kvm-intel.flexpriority=
1499 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1500 Default is 1 (enabled)
1503 [KVM,Intel] Enable VMX nesting (nVMX).
1504 Default is 0 (disabled)
1506 kvm-intel.unrestricted_guest=
1507 [KVM,Intel] Disable unrestricted guest feature
1508 (virtualized real and unpaged mode) on capable
1509 Intel chips. Default is 1 (enabled)
1511 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1512 feature (tagged TLBs) on capable Intel chips.
1513 Default is 1 (enabled)
1519 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1522 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1523 value for LAPIC timer one-shot implementation. Default
1524 back to the programmable timer unit in the LAPIC.
1526 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1529 libata.dma= [LIBATA] DMA control
1530 libata.dma=0 Disable all PATA and SATA DMA
1531 libata.dma=1 PATA and SATA Disk DMA only
1532 libata.dma=2 ATAPI (CDROM) DMA only
1533 libata.dma=4 Compact Flash DMA only
1534 Combinations also work, so libata.dma=3 enables DMA
1535 for disks and CDROMs, but not CFs.
1537 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1538 libata.ignore_hpa=0 keep BIOS limits (default)
1539 libata.ignore_hpa=1 ignore limits, using full disk
1541 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1545 libata.force= [LIBATA] Force configurations. The format is comma
1546 separated list of "[ID:]VAL" where ID is
1547 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1548 matching port, link or device. Basically, it matches
1549 the ATA ID string printed on console by libata. If
1550 the whole ID part is omitted, the last PORT and DEVICE
1551 values are used. If ID hasn't been specified yet, the
1552 configuration applies to all ports, links and devices.
1554 If only DEVICE is omitted, the parameter applies to
1555 the port and all links and devices behind it. DEVICE
1556 number of 0 either selects the first device or the
1557 first fan-out link behind PMP device. It does not
1558 select the host link. DEVICE number of 15 selects the
1559 host link and device attached to it.
1561 The VAL specifies the configuration to force. As long
1562 as there's no ambiguity shortcut notation is allowed.
1563 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1564 The following configurations can be forced.
1566 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1567 Any ID with matching PORT is used.
1569 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1571 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1572 udma[/][16,25,33,44,66,100,133] notation is also
1575 * [no]ncq: Turn on or off NCQ.
1577 * nohrst, nosrst, norst: suppress hard, soft
1580 * rstonce: only attempt one reset during
1581 hot-unplug link recovery
1583 * dump_id: dump IDENTIFY data.
1585 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1587 * disable: Disable this device.
1589 If there are multiple matching configurations changing
1590 the same attribute, the last one is used.
1592 memblock=debug [KNL] Enable memblock debug messages.
1594 load_ramdisk= [RAM] List of ramdisks to load from floppy
1595 See Documentation/blockdev/ramdisk.txt.
1597 lockd.nlm_grace_period=P [NFS] Assign grace period.
1600 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1603 lockd.nlm_timeout=T [NFS] Assign timeout value.
1606 lockd.nlm_udpport=M [NFS] Assign UDP port.
1609 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1612 loglevel= All Kernel Messages with a loglevel smaller than the
1613 console loglevel will be printed to the console. It can
1614 also be changed with klogd or other programs. The
1615 loglevels are defined as follows:
1617 0 (KERN_EMERG) system is unusable
1618 1 (KERN_ALERT) action must be taken immediately
1619 2 (KERN_CRIT) critical conditions
1620 3 (KERN_ERR) error conditions
1621 4 (KERN_WARNING) warning conditions
1622 5 (KERN_NOTICE) normal but significant condition
1623 6 (KERN_INFO) informational
1624 7 (KERN_DEBUG) debug-level messages
1626 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1627 in bytes. n must be a power of two. The default
1628 size is set in the kernel config file.
1630 logo.nologo [FB] Disables display of the built-in Linux logo.
1631 This may be used to provide more screen space for
1632 kernel log messages and is useful when debugging
1633 kernel boot problems.
1635 lp=0 [LP] Specify parallel ports to use, e.g,
1636 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1637 lp=reset first parallel port). 'lp=0' disables the
1638 lp=auto printer driver. 'lp=reset' (which can be
1639 specified in addition to the ports) causes
1640 attached printers to be reset. Using
1641 lp=port1,port2,... specifies the parallel ports
1642 to associate lp devices with, starting with
1643 lp0. A port specification may be 'none' to skip
1644 that lp device, or a parport name such as
1645 'parport0'. Specifying 'lp=auto' instead of a
1646 port specification list means that device IDs
1647 from each port should be examined, to see if
1648 an IEEE 1284-compliant printer is attached; if
1649 so, the driver will manage that printer.
1650 See also header of drivers/char/lp.c.
1653 Sets loops_per_jiffy to given constant, thus avoiding
1654 time-consuming boot-time autodetection (up to 250 ms per
1655 CPU). 0 enables autodetection (default). To determine
1656 the correct value for your kernel, boot with normal
1657 autodetection and see what value is printed. Note that
1658 on SMP systems the preset will be applied to all CPUs,
1659 which is likely to cause problems if your CPUs need
1660 significantly divergent settings. An incorrect value
1661 will cause delays in the kernel to be wrong, leading to
1662 unpredictable I/O errors and other breakage. Although
1663 unlikely, in the extreme case this might damage your
1667 Format: <io>,<irq>,<dma>
1669 machvec= [IA-64] Force the use of a particular machine-vector
1670 (machvec) in a generic kernel.
1671 Example: machvec=hpzx1_swiotlb
1673 machtype= [Loongson] Share the same kernel image file between different
1675 Example: machtype=lemote-yeeloong-2f-7inch
1677 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1678 than or equal to this physical address is ignored.
1680 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1681 should make use of. maxcpus=n : n >= 0 limits the
1682 kernel to using 'n' processors. n=0 is a special case,
1683 it is equivalent to "nosmp", which also disables
1686 max_loop= [LOOP] The number of loop block devices that get
1687 (loop.max_loop) unconditionally pre-created at init time. The default
1688 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1689 of statically allocating a predefined number, loop
1690 devices can be requested on-demand with the
1691 /dev/loop-control interface.
1693 mce [X86-32] Machine Check Exception
1695 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1697 md= [HW] RAID subsystems devices and level
1698 See Documentation/md.txt.
1701 Format: <first>,<last>
1702 Specifies range of consoles to be captured by the MDA.
1704 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1705 Amount of memory to be used when the kernel is not able
1706 to see the whole system memory or for test.
1707 [X86] Work as limiting max address. Use together
1708 with memmap= to avoid physical address space collisions.
1709 Without memmap= PCI devices could be placed at addresses
1710 belonging to unused RAM.
1712 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1716 [KNL,SH] Allow user to override the default size for
1717 per-device physically contiguous DMA buffers.
1719 memmap=exactmap [KNL,X86] Enable setting of an exact
1720 E820 memory map, as specified by the user.
1721 Such memmap=exactmap lines can be constructed based on
1722 BIOS output or other requirements. See the memmap=nn@ss
1725 memmap=nn[KMG]@ss[KMG]
1726 [KNL] Force usage of a specific region of memory
1727 Region of memory to be used, from ss to ss+nn.
1729 memmap=nn[KMG]#ss[KMG]
1730 [KNL,ACPI] Mark specific memory as ACPI data.
1731 Region of memory to be used, from ss to ss+nn.
1733 memmap=nn[KMG]$ss[KMG]
1734 [KNL,ACPI] Mark specific memory as reserved.
1735 Region of memory to be used, from ss to ss+nn.
1736 Example: Exclude memory from 0x18690000-0x1869ffff
1737 memmap=64K$0x18690000
1739 memmap=0x10000$0x18690000
1741 memory_corruption_check=0/1 [X86]
1742 Some BIOSes seem to corrupt the first 64k of
1743 memory when doing things like suspend/resume.
1744 Setting this option will scan the memory
1745 looking for corruption. Enabling this will
1746 both detect corruption and prevent the kernel
1747 from using the memory being corrupted.
1748 However, its intended as a diagnostic tool; if
1749 repeatable BIOS-originated corruption always
1750 affects the same memory, you can use memmap=
1751 to prevent the kernel from using that memory.
1753 memory_corruption_check_size=size [X86]
1754 By default it checks for corruption in the low
1755 64k, making this memory unavailable for normal
1756 use. Use this parameter to scan for
1757 corruption in more or less memory.
1759 memory_corruption_check_period=seconds [X86]
1760 By default it checks for corruption every 60
1761 seconds. Use this parameter to check at some
1762 other rate. 0 disables periodic checking.
1764 memtest= [KNL,X86] Enable memtest
1766 default : 0 <disable>
1767 Specifies the number of memtest passes to be
1768 performed. Each pass selects another test
1769 pattern from a given set of patterns. Memtest
1770 fills the memory with this pattern, validates
1771 memory contents and reserves bad memory
1772 regions that are detected.
1774 meye.*= [HW] Set MotionEye Camera parameters
1775 See Documentation/video4linux/meye.txt.
1777 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1778 Multi-Function General Purpose Timers on AMD Geode
1781 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1782 the BIOS has incorrectly applied a workaround. TinyBIOS
1783 version 0.98 is known to be affected, 0.99 fixes the
1784 problem by letting the user disable the workaround.
1788 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1789 physical address is ignored.
1791 mini2440= [ARM,HW,KNL]
1792 Format:[0..2][b][c][t]
1794 MINI2440 configuration specification:
1795 0 - The attached screen is the 3.5" TFT
1796 1 - The attached screen is the 7" TFT
1797 2 - The VGA Shield is attached (1024x768)
1798 Leaving out the screen size parameter will not load
1799 the TFT driver, and the framebuffer will be left
1801 b - Enable backlight. The TFT backlight pin will be
1802 linked to the kernel VESA blanking code and a GPIO
1803 LED. This parameter is not necessary when using the
1805 c - Enable the s3c camera interface.
1806 t - Reserved for enabling touchscreen support. The
1807 touchscreen support is not enabled in the mainstream
1808 kernel as of 2.6.30, a preliminary port can be found
1809 in the "bleeding edge" mini2440 support kernel at
1810 http://repo.or.cz/w/linux-2.6/mini2440.git
1813 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1814 parameter allows control of the logging verbosity for
1815 the additional memory initialisation checks. A value
1816 of 0 disables mminit logging and a level of 4 will
1817 log everything. Information is printed at KERN_DEBUG
1818 so loglevel=8 may also need to be specified.
1821 [KNL] When CONFIG_MODULE_SIG is set, this means that
1822 modules without (valid) signatures will fail to load.
1823 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1824 is always true, so this option does nothing.
1827 [MOUSE] Maximum time between finger touching and
1828 leaving touchpad surface for touch to be considered
1829 a tap and be reported as a left button click (for
1830 touchpads working in absolute mode only).
1832 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1833 reporting absolute coordinates, such as tablets
1834 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1835 reporting absolute coordinates, such as tablets
1837 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1838 is similar to kernelcore except it specifies the
1839 amount of memory used for migratable allocations.
1840 If both kernelcore and movablecore is specified,
1841 then kernelcore will be at *least* the specified
1842 value but may be more. If movablecore on its own
1843 is specified, the administrator must be careful
1844 that the amount of memory usable for all allocations
1847 movable_node [KNL,X86] Boot-time switch to enable the effects
1848 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1850 MTD_Partition= [MTD]
1851 Format: <name>,<region-number>,<size>,<offset>
1853 MTD_Region= [MTD] Format:
1854 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1857 See drivers/mtd/cmdlinepart.c.
1859 multitce=off [PPC] This parameter disables the use of the pSeries
1860 firmware feature for updating multiple TCE entries
1863 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1865 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1867 boundary - index of last SLC block on Flex-OneNAND.
1868 The remaining blocks are configured as MLC blocks.
1869 lock - Configure if Flex-OneNAND boundary should be locked.
1870 Once locked, the boundary cannot be changed.
1871 1 indicates lock status, 0 indicates unlock status.
1874 ARM/S3C2412 JIVE boot control
1876 See arch/arm/mach-s3c2412/mach-jive.c
1878 mtouchusb.raw_coordinates=
1879 [HW] Make the MicroTouch USB driver use raw coordinates
1880 ('y', default) or cooked coordinates ('n')
1882 mtrr_chunk_size=nn[KMG] [X86]
1883 used for mtrr cleanup. It is largest continuous chunk
1884 that could hold holes aka. UC entries.
1886 mtrr_gran_size=nn[KMG] [X86]
1887 Used for mtrr cleanup. It is granularity of mtrr block.
1889 Large value could prevent small alignment from
1892 mtrr_spare_reg_nr=n [X86]
1894 Range: 0,7 : spare reg number
1896 Used for mtrr cleanup. It is spare mtrr entries number.
1897 Set to 2 or more if your graphical card needs more.
1899 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1901 netdev= [NET] Network devices parameters
1902 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1903 Note that mem_start is often overloaded to mean
1904 something different and driver-specific.
1905 This usage is only documented in each driver source
1909 [NETFILTER] Enable connection tracking flow accounting
1910 0 to disable accounting
1911 1 to enable accounting
1914 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1915 See Documentation/filesystems/nfs/nfsroot.txt.
1917 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1918 See Documentation/filesystems/nfs/nfsroot.txt.
1920 nfsrootdebug [NFS] enable nfsroot debugging messages.
1921 See Documentation/filesystems/nfs/nfsroot.txt.
1923 nfs.callback_tcpport=
1924 [NFS] set the TCP port on which the NFSv4 callback
1925 channel should listen.
1928 [NFS] sets the pathname to the program which is used
1929 to update the NFS client cache entries.
1931 nfs.cache_getent_timeout=
1932 [NFS] sets the timeout after which an attempt to
1933 update a cache entry is deemed to have failed.
1935 nfs.idmap_cache_timeout=
1936 [NFS] set the maximum lifetime for idmapper cache
1940 [NFS] enable 64-bit inode numbers.
1941 If zero, the NFS client will fake up a 32-bit inode
1942 number for the readdir() and stat() syscalls instead
1943 of returning the full 64-bit number.
1944 The default is to return 64-bit inode numbers.
1946 nfs.max_session_slots=
1947 [NFSv4.1] Sets the maximum number of session slots
1948 the client will attempt to negotiate with the server.
1949 This limits the number of simultaneous RPC requests
1950 that the client can send to the NFSv4.1 server.
1951 Note that there is little point in setting this
1952 value higher than the max_tcp_slot_table_limit.
1954 nfs.nfs4_disable_idmapping=
1955 [NFSv4] When set to the default of '1', this option
1956 ensures that both the RPC level authentication
1957 scheme and the NFS level operations agree to use
1958 numeric uids/gids if the mount is using the
1959 'sec=sys' security flavour. In effect it is
1960 disabling idmapping, which can make migration from
1961 legacy NFSv2/v3 systems to NFSv4 easier.
1962 Servers that do not support this mode of operation
1963 will be autodetected by the client, and it will fall
1964 back to using the idmapper.
1965 To turn off this behaviour, set the value to '0'.
1967 [NFS4] Specify an additional fixed unique ident-
1968 ification string that NFSv4 clients can insert into
1969 their nfs_client_id4 string. This is typically a
1970 UUID that is generated at system install time.
1972 nfs.send_implementation_id =
1973 [NFSv4.1] Send client implementation identification
1974 information in exchange_id requests.
1975 If zero, no implementation identification information
1977 The default is to send the implementation identification
1980 nfs.recover_lost_locks =
1981 [NFSv4] Attempt to recover locks that were lost due
1982 to a lease timeout on the server. Please note that
1983 doing this risks data corruption, since there are
1984 no guarantees that the file will remain unchanged
1985 after the locks are lost.
1986 If you want to enable the kernel legacy behaviour of
1987 attempting to recover these locks, then set this
1989 The default parameter value of '0' causes the kernel
1990 not to attempt recovery of lost locks.
1992 nfsd.nfs4_disable_idmapping=
1993 [NFSv4] When set to the default of '1', the NFSv4
1994 server will return only numeric uids and gids to
1995 clients using auth_sys, and will accept numeric uids
1996 and gids from such clients. This is intended to ease
1997 migration from NFSv2/v3.
1999 objlayoutdriver.osd_login_prog=
2000 [NFS] [OBJLAYOUT] sets the pathname to the program which
2001 is used to automatically discover and login into new
2002 osd-targets. Please see:
2003 Documentation/filesystems/pnfs.txt for more explanations
2005 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2006 when a NMI is triggered.
2007 Format: [state][,regs][,debounce][,die]
2009 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2010 Format: [panic,][nopanic,][num]
2012 0 - turn nmi_watchdog off
2013 When panic is specified, panic when an NMI watchdog
2014 timeout occurs (or 'nopanic' to override the opposite
2016 This is useful when you use a panic=... timeout and
2017 need the box quickly up again.
2019 netpoll.carrier_timeout=
2020 [NET] Specifies amount of time (in seconds) that
2021 netpoll should wait for a carrier. By default netpoll
2024 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2025 emulation library even if a 387 maths coprocessor
2029 [HW] Never suspend the console
2030 Disable suspending of consoles during suspend and
2031 hibernate operations. Once disabled, debugging
2032 messages can reach various consoles while the rest
2033 of the system is being put to sleep (ie, while
2034 debugging driver suspend/resume hooks). This may
2035 not work reliably with all consoles, but is known
2036 to work with serial and VGA consoles.
2037 To facilitate more flexible debugging, we also add
2038 console_suspend, a printk module parameter to control
2039 it. Users could use console_suspend (usually
2040 /sys/module/printk/parameters/console_suspend) to
2041 turn on/off it dynamically.
2043 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2044 caches in the slab allocator. Saves per-node memory,
2045 but will impact performance.
2049 noapic [SMP,APIC] Tells the kernel to not make use of any
2050 IOAPICs that may be present in the system.
2053 Disable kernel base offset ASLR (Address Space
2054 Layout Randomization) if built into the kernel.
2056 noautogroup Disable scheduler automatic task group creation.
2058 nobats [PPC] Do not use BATs for mapping kernel lowmem
2059 on "Classic" PPC cores.
2063 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2065 nodelayacct [KNL] Disable per-task delay accounting
2067 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2069 nodsp [SH] Disable hardware DSP at boot time.
2071 noefi [X86] Disable EFI runtime services support.
2076 On X86-32 available only on PAE configured kernels.
2077 noexec=on: enable non-executable mappings (default)
2078 noexec=off: disable non-executable mappings
2081 Disable SMAP (Supervisor Mode Access Prevention)
2082 even if it is supported by processor.
2085 Disable SMEP (Supervisor Mode Execution Prevention)
2086 even if it is supported by processor.
2089 This affects only 32-bit executables.
2090 noexec32=on: enable non-executable mappings (default)
2091 read doesn't imply executable mappings
2092 noexec32=off: disable non-executable mappings
2093 read implies executable mappings
2095 nofpu [SH] Disable hardware FPU at boot time.
2097 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2098 register save and restore. The kernel will only save
2099 legacy floating-point registers on task switch.
2101 noxsave [BUGS=X86] Disables x86 extended register state save
2102 and restore using xsave. The kernel will fallback to
2103 enabling legacy floating-point and sse state.
2106 on enable eager fpu restore
2107 off disable eager fpu restore
2108 auto selects the default scheme, which automatically
2109 enables eagerfpu restore for xsaveopt.
2111 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2112 wfi(ARM) instruction doesn't work correctly and not to
2113 use it. This is also useful when using JTAG debugger.
2115 no_file_caps Tells the kernel not to honor file capabilities. The
2116 only way then for a file to be executed with privilege
2117 is to be setuid root or executed by root.
2119 nohalt [IA-64] Tells the kernel not to use the power saving
2120 function PAL_HALT_LIGHT when idle. This increases
2121 power-consumption. On the positive side, it reduces
2122 interrupt wake-up latency, which may improve performance
2123 in certain environments such as networked servers or
2126 nohz= [KNL] Boottime enable/disable dynamic ticks
2127 Valid arguments: on, off
2130 nohz_full= [KNL,BOOT]
2131 In kernels built with CONFIG_NO_HZ_FULL=y, set
2132 the specified list of CPUs whose tick will be stopped
2133 whenever possible. The boot CPU will be forced outside
2134 the range to maintain the timekeeping.
2135 The CPUs in this range must also be included in the
2138 noiotrap [SH] Disables trapped I/O port accesses.
2140 noirqdebug [X86-32] Disables the code which attempts to detect and
2141 disable unhandled interrupt sources.
2143 no_timer_check [X86,APIC] Disables the code which tests for
2144 broken timer IRQ sources.
2146 noisapnp [ISAPNP] Disables ISA PnP code.
2148 noinitrd [RAM] Tells the kernel not to load any configured
2151 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2153 [Deprecated - use intremap=off]
2157 nojitter [IA-64] Disables jitter checking for ITC timers.
2159 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2161 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2164 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2165 steal time is computed, but won't influence scheduler
2168 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2170 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2172 noltlbs [PPC] Do not use large page/tlb entries for kernel
2173 lowmem mapping on PPC40x.
2175 nomca [IA-64] Disable machine check abort handling
2177 nomce [X86-32] Machine Check Exception
2179 nomfgpt [X86-32] Disable Multi-Function General Purpose
2180 Timer usage (for AMD Geode machines).
2182 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2183 shutdown the other cpus. Instead use the REBOOT_VECTOR
2186 nomodule Disable module load
2188 nopat [X86] Disable PAT (page attribute table extension of
2189 pagetables) support.
2191 norandmaps Don't use address space randomization. Equivalent to
2192 echo 0 > /proc/sys/kernel/randomize_va_space
2194 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2196 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2197 with UP alternatives
2199 nordrand [X86] Disable the direct use of the RDRAND
2200 instruction even if it is supported by the
2201 processor. RDRAND is still available to user
2204 noresume [SWSUSP] Disables resume and restores original swap
2207 no-scroll [VGA] Disables scrollback.
2208 This is required for the Braillex ib80-piezo Braille
2209 reader made by F.H. Papenmeier (Germany).
2213 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2215 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2216 and disable the IO APIC. legacy for "maxcpus=0".
2218 nosoftlockup [KNL] Disable the soft-lockup detector.
2220 nosync [HW,M68K] Disables sync negotiation for all devices.
2222 notsc [BUGS=X86-32] Disable Time Stamp Counter
2224 nousb [USB] Disable the USB subsystem
2226 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2230 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2232 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2233 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2234 Some features depend on CPU0. Known dependencies are:
2235 1. Resume from suspend/hibernate depends on CPU0.
2236 Suspend/hibernate will fail if CPU0 is offline and you
2237 need to online CPU0 before suspend/hibernate.
2238 2. PIC interrupts also depend on CPU0. CPU0 can't be
2239 removed if a PIC interrupt is detected.
2240 It's said poweroff/reboot may depend on CPU0 on some
2241 machines although I haven't seen such issues so far
2242 after CPU0 is offline on a few tested machines.
2243 If the dependencies are under your control, you can
2244 turn on cpu0_hotplug.
2246 nptcg= [IA-64] Override max number of concurrent global TLB
2247 purges which is reported from either PAL_VM_SUMMARY or
2250 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2251 could support. nr_cpus=n : n >= 1 limits the kernel to
2252 supporting 'n' processors. Later in runtime you can not
2253 use hotplug cpu feature to put more cpu back to online.
2254 just like you compile the kernel NR_CPUS=n
2256 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2258 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2259 Allowed values are enable and disable
2261 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2262 one of ['zone', 'node', 'default'] can be specified
2263 This can be set from sysctl after boot.
2264 See Documentation/sysctl/vm.txt for details.
2266 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2267 See Documentation/debugging-via-ohci1394.txt for more
2270 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2271 Rather than timing out after 20 ms if an EC
2272 command is not properly ACKed, override the length
2273 of the timeout. We have interrupts disabled while
2274 waiting for the ACK, so if this is set too high
2275 interrupts *may* be lost!
2277 omap_mux= [OMAP] Override bootloader pin multiplexing.
2278 Format: <mux_mode0.mode_name=value>...
2279 For example, to override I2C bus2:
2280 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2282 oprofile.timer= [HW]
2283 Use timer interrupt instead of performance counters
2285 oprofile.cpu_type= Force an oprofile cpu type
2286 This might be useful if you have an older oprofile
2287 userland or if you want common events.
2288 Format: { arch_perfmon }
2289 arch_perfmon: [X86] Force use of architectural
2290 perfmon on Intel CPUs instead of the
2291 CPU specific event set.
2292 timer: [X86] Force use of architectural NMI
2293 timer mode (see also oprofile.timer
2294 for generic hr timer mode)
2295 [s390] Force legacy basic mode sampling
2296 (report cpu_type "timer")
2298 oops=panic Always panic on oopses. Default is to just kill the
2299 process, but there is a small probability of
2300 deadlocking the machine.
2301 This will also cause panics on machine check exceptions.
2302 Useful together with panic=30 to trigger a reboot.
2305 See Documentation/sound/oss/oss-parameters.txt
2307 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2308 timeout > 0: seconds before rebooting
2309 timeout = 0: wait forever
2310 timeout < 0: reboot immediately
2313 parkbd.port= [HW] Parallel port number the keyboard adapter is
2314 connected to, default is 0.
2316 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2317 0 for XT, 1 for AT (default is AT).
2320 parport= [HW,PPT] Specify parallel ports. 0 disables.
2321 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2322 Use 'auto' to force the driver to use any
2323 IRQ/DMA settings detected (the default is to
2324 ignore detected IRQ/DMA settings because of
2325 possible conflicts). You can specify the base
2326 address, IRQ, and DMA settings; IRQ and DMA
2327 should be numbers, or 'auto' (for using detected
2328 settings on that particular port), or 'nofifo'
2329 (to avoid using a FIFO even if it is detected).
2330 Parallel ports are assigned in the order they
2331 are specified on the command line, starting
2334 parport_init_mode= [HW,PPT]
2335 Configure VIA parallel port to operate in
2336 a specific mode. This is necessary on Pegasos
2337 computer where firmware has no options for setting
2338 up parallel port mode and sets it to spp.
2339 Currently this function knows 686a and 8231 chips.
2340 Format: [spp|ps2|epp|ecp|ecpepp]
2343 Halt all CPUs after the first oops has been printed for
2344 the specified number of seconds. This is to be used if
2345 your oopses keep scrolling off the screen.
2350 See header of drivers/block/paride/pcd.c.
2351 See also Documentation/blockdev/paride.txt.
2353 pci=option[,option...] [PCI] various PCI subsystem options:
2354 earlydump [X86] dump PCI config space before the kernel
2356 off [X86] don't probe for the PCI bus
2357 bios [X86-32] force use of PCI BIOS, don't access
2358 the hardware directly. Use this if your machine
2359 has a non-standard PCI host bridge.
2360 nobios [X86-32] disallow use of PCI BIOS, only direct
2361 hardware access methods are allowed. Use this
2362 if you experience crashes upon bootup and you
2363 suspect they are caused by the BIOS.
2364 conf1 [X86] Force use of PCI Configuration
2366 conf2 [X86] Force use of PCI Configuration
2368 noaer [PCIE] If the PCIEAER kernel config parameter is
2369 enabled, this kernel boot option can be used to
2370 disable the use of PCIE advanced error reporting.
2371 nodomains [PCI] Disable support for multiple PCI
2372 root domains (aka PCI segments, in ACPI-speak).
2373 nommconf [X86] Disable use of MMCONFIG for PCI
2375 check_enable_amd_mmconf [X86] check for and enable
2376 properly configured MMIO access to PCI
2377 config space on AMD family 10h CPU
2378 nomsi [MSI] If the PCI_MSI kernel config parameter is
2379 enabled, this kernel boot option can be used to
2380 disable the use of MSI interrupts system-wide.
2381 noioapicquirk [APIC] Disable all boot interrupt quirks.
2382 Safety option to keep boot IRQs enabled. This
2383 should never be necessary.
2384 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2385 primary IO-APIC for bridges that cannot disable
2386 boot IRQs. This fixes a source of spurious IRQs
2387 when the system masks IRQs.
2388 noioapicreroute [APIC] Disable workaround that uses the
2389 boot IRQ equivalent of an IRQ that connects to
2390 a chipset where boot IRQs cannot be disabled.
2391 The opposite of ioapicreroute.
2392 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2393 routing table. These calls are known to be buggy
2394 on several machines and they hang the machine
2395 when used, but on other computers it's the only
2396 way to get the interrupt routing table. Try
2397 this option if the kernel is unable to allocate
2398 IRQs or discover secondary PCI buses on your
2400 rom [X86] Assign address space to expansion ROMs.
2401 Use with caution as certain devices share
2402 address decoders between ROMs and other
2404 norom [X86] Do not assign address space to
2405 expansion ROMs that do not already have
2406 BIOS assigned address ranges.
2407 nobar [X86] Do not assign address space to the
2408 BARs that weren't assigned by the BIOS.
2409 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2410 assigned automatically to PCI devices. You can
2411 make the kernel exclude IRQs of your ISA cards
2413 pirqaddr=0xAAAAA [X86] Specify the physical address
2414 of the PIRQ table (normally generated
2415 by the BIOS) if it is outside the
2416 F0000h-100000h range.
2417 lastbus=N [X86] Scan all buses thru bus #N. Can be
2418 useful if the kernel is unable to find your
2419 secondary buses and you want to tell it
2420 explicitly which ones they are.
2421 assign-busses [X86] Always assign all PCI bus
2422 numbers ourselves, overriding
2423 whatever the firmware may have done.
2424 usepirqmask [X86] Honor the possible IRQ mask stored
2425 in the BIOS $PIR table. This is needed on
2426 some systems with broken BIOSes, notably
2427 some HP Pavilion N5400 and Omnibook XE3
2428 notebooks. This will have no effect if ACPI
2429 IRQ routing is enabled.
2430 noacpi [X86] Do not use ACPI for IRQ routing
2431 or for PCI scanning.
2432 use_crs [X86] Use PCI host bridge window information
2433 from ACPI. On BIOSes from 2008 or later, this
2434 is enabled by default. If you need to use this,
2435 please report a bug.
2436 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2437 If you need to use this, please report a bug.
2438 routeirq Do IRQ routing for all PCI devices.
2439 This is normally done in pci_enable_device(),
2440 so this option is a temporary workaround
2441 for broken drivers that don't call it.
2442 skip_isa_align [X86] do not align io start addr, so can
2443 handle more pci cards
2444 firmware [ARM] Do not re-enumerate the bus but instead
2445 just use the configuration from the
2446 bootloader. This is currently used on
2447 IXP2000 systems where the bus has to be
2448 configured a certain way for adjunct CPUs.
2449 noearly [X86] Don't do any early type 1 scanning.
2450 This might help on some broken boards which
2451 machine check when some devices' config space
2452 is read. But various workarounds are disabled
2453 and some IOMMU drivers will not work.
2454 bfsort Sort PCI devices into breadth-first order.
2455 This sorting is done to get a device
2456 order compatible with older (<= 2.4) kernels.
2457 nobfsort Don't sort PCI devices into breadth-first order.
2458 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2459 tuning and use the BIOS-configured MPS defaults.
2460 pcie_bus_safe Set every device's MPS to the largest value
2461 supported by all devices below the root complex.
2462 pcie_bus_perf Set device MPS to the largest allowable MPS
2463 based on its parent bus. Also set MRRS (Max
2464 Read Request Size) to the largest supported
2465 value (no larger than the MPS that the device
2466 or bus can support) for best performance.
2467 pcie_bus_peer2peer Set every device's MPS to 128B, which
2468 every device is guaranteed to support. This
2469 configuration allows peer-to-peer DMA between
2470 any pair of devices, possibly at the cost of
2471 reduced performance. This also guarantees
2472 that hot-added devices will work.
2473 cbiosize=nn[KMG] The fixed amount of bus space which is
2474 reserved for the CardBus bridge's IO window.
2475 The default value is 256 bytes.
2476 cbmemsize=nn[KMG] The fixed amount of bus space which is
2477 reserved for the CardBus bridge's memory
2478 window. The default value is 64 megabytes.
2481 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2482 Specifies alignment and device to reassign
2483 aligned memory resources.
2484 If <order of align> is not specified,
2485 PAGE_SIZE is used as alignment.
2486 PCI-PCI bridge can be specified, if resource
2487 windows need to be expanded.
2488 ecrc= Enable/disable PCIe ECRC (transaction layer
2489 end-to-end CRC checking).
2490 bios: Use BIOS/firmware settings. This is the
2494 hpiosize=nn[KMG] The fixed amount of bus space which is
2495 reserved for hotplug bridge's IO window.
2496 Default size is 256 bytes.
2497 hpmemsize=nn[KMG] The fixed amount of bus space which is
2498 reserved for hotplug bridge's memory window.
2499 Default size is 2 megabytes.
2500 realloc= Enable/disable reallocating PCI bridge resources
2501 if allocations done by BIOS are too small to
2502 accommodate resources required by all child
2504 off: Turn realloc off
2506 realloc same as realloc=on
2507 noari do not use PCIe ARI.
2508 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2509 only look for one device below a PCIe downstream
2512 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2515 force Enable ASPM even on devices that claim not to support it.
2516 WARNING: Forcing ASPM on may cause system lockups.
2518 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2519 nomsi Do not use MSI for PCI Express Native Hotplug (this
2520 makes all PCIe ports use INTx for hotplug services).
2522 pcie_ports= [PCIE] PCIe ports handling:
2523 auto Ask the BIOS whether or not to use native PCIe services
2524 associated with PCIe ports (PME, hot-plug, AER). Use
2525 them only if that is allowed by the BIOS.
2526 native Use native PCIe services associated with PCIe ports
2528 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2531 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2532 nomsi Do not use MSI for native PCIe PME signaling (this makes
2533 all PCIe root ports use INTx for all services).
2535 pcmv= [HW,PCMCIA] BadgePAD 4
2538 See Documentation/blockdev/paride.txt.
2540 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2543 See arch/parisc/kernel/pdc_chassis.c
2545 percpu_alloc= Select which percpu first chunk allocator to use.
2546 Currently supported values are "embed" and "page".
2547 Archs may support subset or none of the selections.
2548 See comments in mm/percpu.c for details on each
2549 allocator. This parameter is primarily for debugging
2550 and performance comparison.
2553 See Documentation/blockdev/paride.txt.
2556 See Documentation/blockdev/paride.txt.
2558 pirq= [SMP,APIC] Manual mp-table setup
2559 See Documentation/x86/i386/IO-APIC.txt.
2561 plip= [PPT,NET] Parallel port network link
2562 Format: { parport<nr> | timid | 0 }
2563 See also Documentation/parport.txt.
2565 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2566 Override pmtimer IOPort with a hex value.
2570 Enable PNP debug messages (depends on the
2571 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2572 via /sys/module/pnp/parameters/debug. We always show
2573 current resource usage; turning this on also shows
2574 possible settings and some assignment information.
2580 { on | off | curr | res | no-curr | no-res }
2583 [ISAPNP] Exclude IRQs for the autoconfiguration
2586 [ISAPNP] Exclude DMAs for the autoconfiguration
2588 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2589 Ranges are in pairs (I/O port base and size).
2592 [ISAPNP] Exclude memory regions for the
2594 Ranges are in pairs (memory base and size).
2596 ports= [IP_VS_FTP] IPVS ftp helper module
2598 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2600 Format: <port>,<port>....
2602 print-fatal-signals=
2603 [KNL] debug: print fatal signals
2605 If enabled, warn about various signal handling
2606 related application anomalies: too many signals,
2607 too many POSIX.1 timers, fatal signals causing a
2610 If you hit the warning due to signal overflow,
2611 you might want to try "ulimit -i unlimited".
2615 printk.always_kmsg_dump=
2616 Trigger kmsg_dump for cases other than kernel oops or
2618 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2621 printk.time= Show timing data prefixed to each printk message line
2622 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2624 processor.max_cstate= [HW,ACPI]
2625 Limit processor to maximum C-state
2626 max_cstate=9 overrides any DMI blacklist limit.
2628 processor.nocst [HW,ACPI]
2629 Ignore the _CST method to determine C-states,
2630 instead using the legacy FADT method
2632 profile= [KNL] Enable kernel profiling via /proc/profile
2633 Format: [schedule,]<number>
2634 Param: "schedule" - profile schedule points.
2635 Param: <number> - step/bucket size as a power of 2 for
2636 statistical time based profiling.
2637 Param: "sleep" - profile D-state sleeping (millisecs).
2638 Requires CONFIG_SCHEDSTATS
2639 Param: "kvm" - profile VM exits.
2641 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2643 See Documentation/blockdev/ramdisk.txt.
2645 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2646 probe for; one of (bare|imps|exps|lifebook|any).
2647 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2649 psmouse.resetafter= [HW,MOUSE]
2650 Try to reset the device after so many bad packets
2653 [HW,MOUSE] Set desired mouse resolution, in dpi.
2654 psmouse.smartscroll=
2655 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2656 0 = disabled, 1 = enabled (default).
2658 pstore.backend= Specify the name of the pstore backend to use
2661 See Documentation/blockdev/paride.txt.
2664 [KNL] Number of legacy pty's. Overwrites compiled-in
2667 quiet [KNL] Disable most log messages
2672 See Documentation/md.txt.
2674 ramdisk_blocksize= [RAM]
2675 See Documentation/blockdev/ramdisk.txt.
2677 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2678 See Documentation/blockdev/ramdisk.txt.
2681 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2682 the specified list of CPUs to be no-callback CPUs.
2683 Invocation of these CPUs' RCU callbacks will
2684 be offloaded to "rcuox/N" kthreads created for
2685 that purpose, where "x" is "b" for RCU-bh, "p"
2686 for RCU-preempt, and "s" for RCU-sched, and "N"
2687 is the CPU number. This reduces OS jitter on the
2688 offloaded CPUs, which can be useful for HPC and
2689 real-time workloads. It can also improve energy
2690 efficiency for asymmetric multiprocessors.
2693 Rather than requiring that offloaded CPUs
2694 (specified by rcu_nocbs= above) explicitly
2695 awaken the corresponding "rcuoN" kthreads,
2696 make these kthreads poll for callbacks.
2697 This improves the real-time response for the
2698 offloaded CPUs by relieving them of the need to
2699 wake up the corresponding kthread, but degrades
2700 energy efficiency by requiring that the kthreads
2701 periodically wake up to do the polling.
2703 rcutree.blimit= [KNL]
2704 Set maximum number of finished RCU callbacks to
2705 process in one batch.
2707 rcutree.rcu_fanout_leaf= [KNL]
2708 Increase the number of CPUs assigned to each
2709 leaf rcu_node structure. Useful for very large
2712 rcutree.jiffies_till_first_fqs= [KNL]
2713 Set delay from grace-period initialization to
2714 first attempt to force quiescent states.
2715 Units are jiffies, minimum value is zero,
2716 and maximum value is HZ.
2718 rcutree.jiffies_till_next_fqs= [KNL]
2719 Set delay between subsequent attempts to force
2720 quiescent states. Units are jiffies, minimum
2721 value is one, and maximum value is HZ.
2723 rcutree.qhimark= [KNL]
2724 Set threshold of queued RCU callbacks beyond which
2725 batch limiting is disabled.
2727 rcutree.qlowmark= [KNL]
2728 Set threshold of queued RCU callbacks below which
2729 batch limiting is re-enabled.
2731 rcutree.rcu_idle_gp_delay= [KNL]
2732 Set wakeup interval for idle CPUs that have
2733 RCU callbacks (RCU_FAST_NO_HZ=y).
2735 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2736 Set wakeup interval for idle CPUs that have
2737 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2738 Lazy RCU callbacks are those which RCU can
2739 prove do nothing more than free memory.
2741 rcutorture.fqs_duration= [KNL]
2742 Set duration of force_quiescent_state bursts.
2744 rcutorture.fqs_holdoff= [KNL]
2745 Set holdoff time within force_quiescent_state bursts.
2747 rcutorture.fqs_stutter= [KNL]
2748 Set wait time between force_quiescent_state bursts.
2750 rcutorture.gp_exp= [KNL]
2751 Use expedited update-side primitives.
2753 rcutorture.gp_normal= [KNL]
2754 Use normal (non-expedited) update-side primitives.
2755 If both gp_exp and gp_normal are set, do both.
2756 If neither gp_exp nor gp_normal are set, still
2759 rcutorture.n_barrier_cbs= [KNL]
2760 Set callbacks/threads for rcu_barrier() testing.
2762 rcutorture.nfakewriters= [KNL]
2763 Set number of concurrent RCU writers. These just
2764 stress RCU, they don't participate in the actual
2765 test, hence the "fake".
2767 rcutorture.nreaders= [KNL]
2768 Set number of RCU readers.
2770 rcutorture.object_debug= [KNL]
2771 Enable debug-object double-call_rcu() testing.
2773 rcutorture.onoff_holdoff= [KNL]
2774 Set time (s) after boot for CPU-hotplug testing.
2776 rcutorture.onoff_interval= [KNL]
2777 Set time (s) between CPU-hotplug operations, or
2778 zero to disable CPU-hotplug testing.
2780 rcutorture.rcutorture_runnable= [BOOT]
2781 Start rcutorture running at boot time.
2783 rcutorture.shuffle_interval= [KNL]
2784 Set task-shuffle interval (s). Shuffling tasks
2785 allows some CPUs to go into dyntick-idle mode
2786 during the rcutorture test.
2788 rcutorture.shutdown_secs= [KNL]
2789 Set time (s) after boot system shutdown. This
2790 is useful for hands-off automated testing.
2792 rcutorture.stall_cpu= [KNL]
2793 Duration of CPU stall (s) to test RCU CPU stall
2794 warnings, zero to disable.
2796 rcutorture.stall_cpu_holdoff= [KNL]
2797 Time to wait (s) after boot before inducing stall.
2799 rcutorture.stat_interval= [KNL]
2800 Time (s) between statistics printk()s.
2802 rcutorture.stutter= [KNL]
2803 Time (s) to stutter testing, for example, specifying
2804 five seconds causes the test to run for five seconds,
2805 wait for five seconds, and so on. This tests RCU's
2806 ability to transition abruptly to and from idle.
2808 rcutorture.test_boost= [KNL]
2809 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2810 "Maybe" means test if the RCU implementation
2811 under test support RCU priority boosting.
2813 rcutorture.test_boost_duration= [KNL]
2814 Duration (s) of each individual boost test.
2816 rcutorture.test_boost_interval= [KNL]
2817 Interval (s) between each boost test.
2819 rcutorture.test_no_idle_hz= [KNL]
2820 Test RCU's dyntick-idle handling. See also the
2821 rcutorture.shuffle_interval parameter.
2823 rcutorture.torture_type= [KNL]
2824 Specify the RCU implementation to test.
2826 rcutorture.verbose= [KNL]
2827 Enable additional printk() statements.
2829 rcupdate.rcu_expedited= [KNL]
2830 Use expedited grace-period primitives, for
2831 example, synchronize_rcu_expedited() instead
2832 of synchronize_rcu(). This reduces latency,
2833 but can increase CPU utilization, degrade
2834 real-time latency, and degrade energy efficiency.
2836 rcupdate.rcu_cpu_stall_suppress= [KNL]
2837 Suppress RCU CPU stall warning messages.
2839 rcupdate.rcu_cpu_stall_timeout= [KNL]
2840 Set timeout for RCU CPU stall warning messages.
2844 Run specified binary instead of /init from the ramdisk,
2845 used for early userspace startup. See initrd.
2848 Format (x86 or x86_64):
2849 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2851 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2853 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2854 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2855 reboot_force is either force or not specified,
2856 reboot_cpu is s[mp]#### with #### being the processor
2857 to be used for rebooting.
2860 [KNL, SMP] Set scheduler's default relax_domain_level.
2861 See Documentation/cgroups/cpusets.txt.
2863 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2865 reservetop= [X86-32]
2867 Reserves a hole at the top of the kernel virtual
2872 Set the amount of memory to reserve for BIOS at
2873 the bottom of the address space.
2875 reset_devices [KNL] Force drivers to reset the underlying device
2876 during initialization.
2879 Specify the partition device for software suspend
2881 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2883 resume_offset= [SWSUSP]
2884 Specify the offset from the beginning of the partition
2885 given by "resume=" at which the swap header is located,
2886 in <PAGE_SIZE> units (needed only for swap files).
2887 See Documentation/power/swsusp-and-swap-files.txt
2889 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2890 read the resume files
2892 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2893 Useful for devices that are detected asynchronously
2894 (e.g. USB and MMC devices).
2896 hibernate= [HIBERNATION]
2897 noresume Don't check if there's a hibernation image
2898 present during boot.
2899 nocompress Don't compress/decompress hibernation images.
2901 retain_initrd [RAM] Keep initrd memory after extraction
2903 rhash_entries= [KNL,NET]
2904 Set number of hash buckets for route cache
2906 riscom8= [HW,SERIAL]
2907 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2909 ro [KNL] Mount root device read-only on boot
2911 root= [KNL] Root filesystem
2912 See name_to_dev_t comment in init/do_mounts.c.
2914 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2915 mount the root filesystem
2917 rootflags= [KNL] Set root filesystem mount option string
2919 rootfstype= [KNL] Set root filesystem type
2921 rootwait [KNL] Wait (indefinitely) for root device to show up.
2922 Useful for devices that are detected asynchronously
2923 (e.g. USB and MMC devices).
2925 rproc_mem=nn[KMG][@address]
2926 [KNL,ARM,CMA] Remoteproc physical memory block.
2927 Memory area to be used by remote processor image,
2930 rw [KNL] Mount root device read-write on boot
2932 S [KNL] Run init in single mode
2935 See drivers/net/irda/sa1100_ir.c.
2937 sbni= [NET] Granch SBNI12 leased line adapter
2939 sched_debug [KNL] Enables verbose scheduler debug messages.
2941 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2942 xtime_lock contention on larger systems, and/or RCU lock
2943 contention on all systems with CONFIG_MAXSMP set.
2944 Format: { "0" | "1" }
2945 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2947 Note: increases power consumption, thus should only be
2948 enabled if running jitter sensitive (HPC/RT) workloads.
2950 security= [SECURITY] Choose a security module to enable at boot.
2951 If this boot parameter is not specified, only the first
2952 security module asking for security registration will be
2953 loaded. An invalid security module name will be treated
2954 as if no module has been chosen.
2956 selinux= [SELINUX] Disable or enable SELinux at boot time.
2957 Format: { "0" | "1" }
2958 See security/selinux/Kconfig help text.
2961 Default value is set via kernel config option.
2962 If enabled at boot time, /selinux/disable can be used
2963 later to disable prior to initial policy load.
2965 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2966 Format: { "0" | "1" }
2967 See security/apparmor/Kconfig help text
2970 Default value is set via kernel config option.
2972 serialnumber [BUGS=X86-32]
2975 Maximal number of shapers.
2977 show_msr= [x86] show boot-time MSR settings
2978 Format: { <integer> }
2979 Show boot-time (BIOS-initialized) MSR settings.
2980 The parameter means the number of CPUs to show,
2981 for example 1 means boot CPU only.
2988 slab_max_order= [MM, SLAB]
2989 Determines the maximum allowed order for slabs.
2990 A high setting may cause OOMs due to memory
2991 fragmentation. Defaults to 1 for systems with
2992 more than 32MB of RAM, 0 otherwise.
2994 slub_debug[=options[,slabs]] [MM, SLUB]
2995 Enabling slub_debug allows one to determine the
2996 culprit if slab objects become corrupted. Enabling
2997 slub_debug can create guard zones around objects and
2998 may poison objects when not in use. Also tracks the
2999 last alloc / free. For more information see
3000 Documentation/vm/slub.txt.
3002 slub_max_order= [MM, SLUB]
3003 Determines the maximum allowed order for slabs.
3004 A high setting may cause OOMs due to memory
3005 fragmentation. For more information see
3006 Documentation/vm/slub.txt.
3008 slub_min_objects= [MM, SLUB]
3009 The minimum number of objects per slab. SLUB will
3010 increase the slab order up to slub_max_order to
3011 generate a sufficiently large slab able to contain
3012 the number of objects indicated. The higher the number
3013 of objects the smaller the overhead of tracking slabs
3014 and the less frequently locks need to be acquired.
3015 For more information see Documentation/vm/slub.txt.
3017 slub_min_order= [MM, SLUB]
3018 Determines the minimum page order for slabs. Must be
3019 lower than slub_max_order.
3020 For more information see Documentation/vm/slub.txt.
3022 slub_nomerge [MM, SLUB]
3023 Disable merging of slabs with similar size. May be
3024 necessary if there is some reason to distinguish
3025 allocs to different slabs. Debug options disable
3026 merging on their own.
3027 For more information see Documentation/vm/slub.txt.
3030 Format: <io1>[,<io2>[,...,<io8>]]
3032 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3033 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3034 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3035 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3036 smsc-ircc2.ircc_irq= [HW] IRQ line
3037 smsc-ircc2.ircc_dma= [HW] DMA channel
3038 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3039 0: Toshiba Satellite 1800 (GP data pin select)
3040 1: Fast pin select (default)
3044 [KNL] Should the soft-lockup detector generate panics.
3047 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3048 See Documentation/laptops/sonypi.txt
3050 specialix= [HW,SERIAL] Specialix multi-serial port adapter
3051 See Documentation/serial/specialix.txt.
3053 spia_io_base= [HW,MTD]
3059 Enabled the stack tracer on boot up.
3061 stacktrace_filter=[function-list]
3062 [FTRACE] Limit the functions that the stack tracer
3063 will trace at boot up. function-list is a comma separated
3064 list of functions. This list can be changed at run
3065 time by the stack_trace_filter file in the debugfs
3066 tracing directory. Note, this enables stack tracing
3067 and the stacktrace above is not needed.
3071 Set the STI (builtin display/keyboard on the HP-PARISC
3072 machines) console (graphic card) which should be used
3073 as the initial boot-console.
3074 See also comment in drivers/video/console/sticore.c.
3077 See comment in drivers/video/console/sticore.c.
3080 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3082 sunrpc.min_resvport=
3083 sunrpc.max_resvport=
3085 SunRPC servers often require that client requests
3086 originate from a privileged port (i.e. a port in the
3087 range 0 < portnr < 1024).
3088 An administrator who wishes to reserve some of these
3089 ports for other uses may adjust the range that the
3090 kernel's sunrpc client considers to be privileged
3091 using these two parameters to set the minimum and
3092 maximum port values.
3096 Control how the NFS server code allocates CPUs to
3097 service thread pools. Depending on how many NICs
3098 you have and where their interrupts are bound, this
3099 option will affect which CPUs will do NFS serving.
3100 Note: this parameter cannot be changed while the
3101 NFS server is running.
3103 auto the server chooses an appropriate mode
3104 automatically using heuristics
3105 global a single global pool contains all CPUs
3106 percpu one pool for each CPU
3107 pernode one pool for each NUMA node (equivalent
3108 to global on non-NUMA machines)
3110 sunrpc.tcp_slot_table_entries=
3111 sunrpc.udp_slot_table_entries=
3113 Sets the upper limit on the number of simultaneous
3114 RPC calls that can be sent from the client to a
3115 server. Increasing these values may allow you to
3116 improve throughput, but will also increase the
3117 amount of memory reserved for use by the client.
3120 [KNL] Enable accounting of swap in memory resource
3121 controller if no parameter or 1 is given or disable
3122 it if 0 is given (See Documentation/cgroups/memory.txt)
3124 swiotlb= [IA-64] Number of I/O TLB slabs
3128 sysfs.deprecated=0|1 [KNL]
3129 Enable/disable old style sysfs layout for old udev
3130 on older distributions. When this option is enabled
3131 very new udev will not work anymore. When this option
3132 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3133 in older udev will not work anymore.
3134 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3135 the kernel configuration.
3137 sysrq_always_enabled
3139 Ignore sysrq setting - this boot parameter will
3140 neutralize any effect of /proc/sys/kernel/sysrq.
3141 Useful for debugging.
3145 test_suspend= [SUSPEND]
3146 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3147 standby suspend) as the system sleep state to briefly
3148 enter during system startup. The system is woken from
3149 this state using a wakeup-capable RTC alarm.
3151 thash_entries= [KNL,NET]
3152 Set number of hash buckets for TCP connection
3154 thermal.act= [HW,ACPI]
3155 -1: disable all active trip points in all thermal zones
3156 <degrees C>: override all lowest active trip points
3158 thermal.crt= [HW,ACPI]
3159 -1: disable all critical trip points in all thermal zones
3160 <degrees C>: override all critical trip points
3162 thermal.nocrt= [HW,ACPI]
3163 Set to disable actions on ACPI thermal zone
3164 critical and hot trip points.
3166 thermal.off= [HW,ACPI]
3167 1: disable ACPI thermal control
3169 thermal.psv= [HW,ACPI]
3170 -1: disable all passive trip points
3171 <degrees C>: override all passive trip points to this
3174 thermal.tzp= [HW,ACPI]
3175 Specify global default ACPI thermal zone polling rate
3176 <deci-seconds>: poll all this frequency
3177 0: no polling (default)
3180 Force threading of all interrupt handlers except those
3181 marked explicitly IRQF_NO_THREAD.
3184 Enable the Transcendent memory driver if built-in.
3186 tmem.cleancache=0|1 [KNL, XEN]
3187 Default is on (1). Disable the usage of the cleancache
3188 API to send anonymous pages to the hypervisor.
3190 tmem.frontswap=0|1 [KNL, XEN]
3191 Default is on (1). Disable the usage of the frontswap
3192 API to send swap pages to the hypervisor. If disabled
3193 the selfballooning and selfshrinking are force disabled.
3195 tmem.selfballooning=0|1 [KNL, XEN]
3196 Default is on (1). Disable the driving of swap pages
3199 tmem.selfshrinking=0|1 [KNL, XEN]
3200 Default is on (1). Partial swapoff that immediately
3201 transfers pages from Xen hypervisor back to the
3202 kernel based on different criteria.
3206 Specify if the kernel should make use of the cpu
3207 topology information if the hardware supports this.
3208 The scheduler will make use of this information and
3209 e.g. base its process migration decisions on it.
3214 tpm_suspend_pcr=[HW,TPM]
3215 Format: integer pcr id
3216 Specify that at suspend time, the tpm driver
3217 should extend the specified pcr with zeros,
3218 as a workaround for some chips which fail to
3219 flush the last written pcr on TPM_SaveState.
3220 This will guarantee that all the other pcrs
3223 trace_buf_size=nn[KMG]
3224 [FTRACE] will set tracing buffer size.
3226 trace_event=[event-list]
3227 [FTRACE] Set and start specified trace events in order
3228 to facilitate early boot debugging.
3229 See also Documentation/trace/events.txt
3231 trace_options=[option-list]
3232 [FTRACE] Enable or disable tracer options at boot.
3233 The option-list is a comma delimited list of options
3234 that can be enabled or disabled just as if you were
3235 to echo the option name into
3237 /sys/kernel/debug/tracing/trace_options
3239 For example, to enable stacktrace option (to dump the
3240 stack trace of each event), add to the command line:
3242 trace_options=stacktrace
3244 See also Documentation/trace/ftrace.txt "trace options"
3248 [FTRACE] enable this option to disable tracing when a
3249 warning is hit. This turns off "tracing_on". Tracing can
3250 be enabled again by echoing '1' into the "tracing_on"
3251 file located in /sys/kernel/debug/tracing/
3253 This option is useful, as it disables the trace before
3254 the WARNING dump is called, which prevents the trace to
3255 be filled with content caused by the warning output.
3257 This option can also be set at run time via the sysctl
3258 option: kernel/traceoff_on_warning
3260 transparent_hugepage=
3262 Format: [always|madvise|never]
3263 Can be used to control the default behavior of the system
3264 with respect to transparent hugepages.
3265 See Documentation/vm/transhuge.txt for more details.
3267 tsc= Disable clocksource stability checks for TSC.
3269 [x86] reliable: mark tsc clocksource as reliable, this
3270 disables clocksource verification at runtime, as well
3271 as the stability checks done at bootup. Used to enable
3272 high-resolution timer mode on older hardware, and in
3273 virtualized environment.
3274 [x86] noirqtime: Do not use TSC to do irq accounting.
3275 Used to run time disable IRQ_TIME_ACCOUNTING on any
3276 platforms where RDTSC is slow and this accounting
3279 turbografx.map[2|3]= [HW,JOY]
3280 TurboGraFX parallel port interface
3282 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3283 See also Documentation/input/joystick-parport.txt
3285 udbg-immortal [PPC] When debugging early kernel crashes that
3286 happen after console_init() and before a proper
3287 console driver takes over, this boot options might
3288 help "seeing" what's going on.
3290 uhash_entries= [KNL,NET]
3291 Set number of hash buckets for UDP/UDP-Lite connections
3294 [USB] Ignore overcurrent events (default N).
3295 Some badly-designed motherboards generate lots of
3296 bogus events, for ports that aren't wired to
3297 anything. Set this parameter to avoid log spamming.
3298 Note that genuine overcurrent events won't be
3302 [X86] Cause panic on unknown NMI.
3304 usbcore.authorized_default=
3305 [USB] Default USB device authorization:
3306 (default -1 = authorized except for wireless USB,
3307 0 = not authorized, 1 = authorized)
3309 usbcore.autosuspend=
3310 [USB] The autosuspend time delay (in seconds) used
3311 for newly-detected USB devices (default 2). This
3312 is the time required before an idle device will be
3313 autosuspended. Devices for which the delay is set
3314 to a negative value won't be autosuspended at all.
3316 usbcore.usbfs_snoop=
3317 [USB] Set to log all usbfs traffic (default 0 = off).
3319 usbcore.blinkenlights=
3320 [USB] Set to cycle leds on hubs (default 0 = off).
3322 usbcore.old_scheme_first=
3323 [USB] Start with the old device initialization
3324 scheme (default 0 = off).
3326 usbcore.usbfs_memory_mb=
3327 [USB] Memory limit (in MB) for buffers allocated by
3328 usbfs (default = 16, 0 = max = 2047).
3330 usbcore.use_both_schemes=
3331 [USB] Try the other device initialization scheme
3332 if the first one fails (default 1 = enabled).
3334 usbcore.initial_descriptor_timeout=
3335 [USB] Specifies timeout for the initial 64-byte
3336 USB_REQ_GET_DESCRIPTOR request in milliseconds
3337 (default 5000 = 5.0 seconds).
3340 [USBHID] The interval which mice are to be polled at.
3342 usb-storage.delay_use=
3343 [UMS] The delay in seconds before a new device is
3344 scanned for Logical Units (default 5).
3347 [UMS] A list of quirks entries to supplement or
3348 override the built-in unusual_devs list. List
3349 entries are separated by commas. Each entry has
3350 the form VID:PID:Flags where VID and PID are Vendor
3351 and Product ID values (4-digit hex numbers) and
3352 Flags is a set of characters, each corresponding
3353 to a common usb-storage quirk flag as follows:
3354 a = SANE_SENSE (collect more than 18 bytes
3356 b = BAD_SENSE (don't collect more than 18
3357 bytes of sense data);
3358 c = FIX_CAPACITY (decrease the reported
3359 device capacity by one sector);
3360 d = NO_READ_DISC_INFO (don't use
3361 READ_DISC_INFO command);
3362 e = NO_READ_CAPACITY_16 (don't use
3363 READ_CAPACITY_16 command);
3364 h = CAPACITY_HEURISTICS (decrease the
3365 reported device capacity by one
3366 sector if the number is odd);
3367 i = IGNORE_DEVICE (don't bind to this
3369 l = NOT_LOCKABLE (don't try to lock and
3370 unlock ejectable media);
3371 m = MAX_SECTORS_64 (don't transfer more
3372 than 64 sectors = 32 KB at a time);
3373 n = INITIAL_READ10 (force a retry of the
3374 initial READ(10) command);
3375 o = CAPACITY_OK (accept the capacity
3376 reported by the device);
3377 p = WRITE_CACHE (the device cache is ON
3379 r = IGNORE_RESIDUE (the device reports
3380 bogus residue values);
3381 s = SINGLE_LUN (the device has only one
3383 w = NO_WP_DETECT (don't test whether the
3384 medium is write-protected).
3385 Example: quirks=0419:aaf5:rl,0421:0433:rc
3387 user_debug= [KNL,ARM]
3389 See arch/arm/Kconfig.debug help text.
3390 1 - undefined instruction events
3392 4 - invalid data aborts
3395 Example: user_debug=31
3398 [X86] Flags controlling user PTE allocations.
3400 nohigh = do not allocate PTE pages in
3401 HIGHMEM regardless of setting
3405 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3406 vdso=1: enable VDSO (default)
3407 vdso=0: disable VDSO mapping
3410 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3411 vdso32=1: enable 32-bit VDSO (default)
3412 vdso32=0: disable 32-bit VDSO mapping
3415 vector=percpu: enable percpu vector domain
3417 video= [FB] Frame buffer configuration
3418 See Documentation/fb/modedb.txt.
3420 video.brightness_switch_enabled= [0,1]
3421 If set to 1, on receiving an ACPI notify event
3422 generated by hotkey, video driver will adjust brightness
3423 level and then send out the event to user space through
3424 the allocated input device; If set to 0, video driver
3425 will only send out the event without touching backlight
3430 [VMMIO] Memory mapped virtio (platform) device.
3432 <size>@<baseaddr>:<irq>[:<id>]
3434 <size> := size (can use standard suffixes
3436 <baseaddr> := physical base address
3437 <irq> := interrupt number (as passed to
3439 <id> := (optional) platform device id
3441 virtio_mmio.device=1K@0x100b0000:48:7
3443 Can be used multiple times for multiple devices.
3445 vga= [BOOT,X86-32] Select a particular video mode
3446 See Documentation/x86/boot.txt and
3447 Documentation/svga.txt.
3448 Use vga=ask for menu.
3449 This is actually a boot loader parameter; the value is
3450 passed to the kernel using a special protocol.
3452 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3453 size of <nn>. This can be used to increase the
3454 minimum size (128MB on x86). It can also be used to
3455 decrease the size and leave more room for directly
3458 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3461 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3464 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3468 Controls the behavior of vsyscalls (i.e. calls to
3469 fixed addresses of 0xffffffffff600x00 from legacy
3470 code). Most statically-linked binaries and older
3471 versions of glibc use these calls. Because these
3472 functions are at fixed addresses, they make nice
3473 targets for exploits that can control RIP.
3475 emulate [default] Vsyscalls turn into traps and are
3476 emulated reasonably safely.
3478 native Vsyscalls are native syscall instructions.
3479 This is a little bit faster than trapping
3480 and makes a few dynamic recompilers work
3481 better than they would in emulation mode.
3482 It also makes exploits much easier to write.
3484 none Vsyscalls don't work at all. This makes
3485 them quite hard to use for exploits but
3486 might break your system.
3488 vt.color= [VT] Default text color.
3489 Format: 0xYX, X = foreground, Y = background.
3490 Default: 0x07 = light gray on black.
3492 vt.cur_default= [VT] Default cursor shape.
3493 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3494 the parameters of the <Esc>[?A;B;Cc escape sequence;
3495 see VGA-softcursor.txt. Default: 2 = underline.
3497 vt.default_blu= [VT]
3498 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3499 Change the default blue palette of the console.
3500 This is a 16-member array composed of values
3503 vt.default_grn= [VT]
3504 Format: <green0>,<green1>,<green2>,...,<green15>
3505 Change the default green palette of the console.
3506 This is a 16-member array composed of values
3509 vt.default_red= [VT]
3510 Format: <red0>,<red1>,<red2>,...,<red15>
3511 Change the default red palette of the console.
3512 This is a 16-member array composed of values
3518 Set system-wide default UTF-8 mode for all tty's.
3519 Default is 1, i.e. UTF-8 mode is enabled for all
3520 newly opened terminals.
3522 vt.global_cursor_default=
3525 Set system-wide default for whether a cursor
3526 is shown on new VTs. Default is -1,
3527 i.e. cursors will be created by default unless
3528 overridden by individual drivers. 0 will hide
3529 cursors, 1 will display them.
3531 vt.italic= [VT] Default color for italic text; 0-15.
3534 vt.underline= [VT] Default color for underlined text; 0-15.
3537 watchdog timers [HW,WDT] For information on watchdog timers,
3538 see Documentation/watchdog/watchdog-parameters.txt
3539 or other driver-specific files in the
3540 Documentation/watchdog/ directory.
3542 workqueue.disable_numa
3543 By default, all work items queued to unbound
3544 workqueues are affine to the NUMA nodes they're
3545 issued on, which results in better behavior in
3546 general. If NUMA affinity needs to be disabled for
3547 whatever reason, this option can be used. Note
3548 that this also can be controlled per-workqueue for
3549 workqueues visible under /sys/bus/workqueue/.
3551 workqueue.power_efficient
3552 Per-cpu workqueues are generally preferred because
3553 they show better performance thanks to cache
3554 locality; unfortunately, per-cpu workqueues tend to
3555 be more power hungry than unbound workqueues.
3557 Enabling this makes the per-cpu workqueues which
3558 were observed to contribute significantly to power
3559 consumption unbound, leading to measurably lower
3560 power usage at the cost of small performance
3563 The default value of this parameter is determined by
3564 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3566 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3567 default x2apic cluster mode on platforms
3570 x86_intel_mid_timer= [X86-32,APBT]
3571 Choose timer option for x86 Intel MID platform.
3572 Two valid options are apbt timer only and lapic timer
3573 plus one apbt timer for broadcast timer.
3574 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3576 xen_emul_unplug= [HW,X86,XEN]
3577 Unplug Xen emulated devices
3578 Format: [unplug0,][unplug1]
3579 ide-disks -- unplug primary master IDE devices
3580 aux-ide-disks -- unplug non-primary-master IDE devices
3581 nics -- unplug network devices
3582 all -- unplug all emulated devices (NICs and IDE disks)
3583 unnecessary -- unplugging emulated devices is
3584 unnecessary even if the host did not respond to
3586 never -- do not unplug even if version check succeeds
3588 xen_nopvspin [X86,XEN]
3589 Disables the ticketlock slowpath using Xen PV
3592 xirc2ps_cs= [NET,PCMCIA]
3594 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3596 ______________________________________________________________________
3600 Add more DRM drivers.
projects / firefly-linux-kernel-4.4.55.git / blob