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 baycom_epp= [HW,AX25]
469 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
471 See header of drivers/net/hamradio/baycom_par.c.
473 baycom_ser_fdx= [HW,AX25]
474 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
475 Format: <io>,<irq>,<mode>[,<baud>]
476 See header of drivers/net/hamradio/baycom_ser_fdx.c.
478 baycom_ser_hdx= [HW,AX25]
479 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
480 Format: <io>,<irq>,<mode>
481 See header of drivers/net/hamradio/baycom_ser_hdx.c.
483 boot_delay= Milliseconds to delay each printk during boot.
484 Values larger than 10 seconds (10000) are changed to
488 bootmem_debug [KNL] Enable bootmem allocator debug messages.
490 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
491 bttv.radio= Most important insmod options are available as
493 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
496 bulk_remove=off [PPC] This parameter disables the use of the pSeries
497 firmware feature for flushing multiple hpte entries
500 c101= [NET] Moxa C101 synchronous serial card
502 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
503 Sometimes CPU hardware bugs make them report the cache
504 size incorrectly. The kernel will attempt work arounds
505 to fix known problems, but for some CPUs it is not
506 possible to determine what the correct size should be.
507 This option provides an override for these situations.
509 ccw_timeout_log [S390]
510 See Documentation/s390/CommonIO for details.
512 cgroup_disable= [KNL] Disable a particular controller
513 Format: {name of the controller(s) to disable}
514 The effects of cgroup_disable=foo are:
515 - foo isn't auto-mounted if you mount all cgroups in
517 - foo isn't visible as an individually mountable
519 {Currently only "memory" controller deal with this and
520 cut the overhead, others just disable the usage. So
521 only cgroup_disable=memory is actually worthy}
523 checkreqprot [SELINUX] Set initial checkreqprot flag value.
524 Format: { "0" | "1" }
525 See security/selinux/Kconfig help text.
526 0 -- check protection applied by kernel (includes
527 any implied execute protection).
528 1 -- check protection requested by application.
529 Default value is set via a kernel config option.
530 Value can be changed at runtime via
531 /selinux/checkreqprot.
534 See Documentation/s390/CommonIO for details.
537 Keep all clocks already enabled by bootloader on,
538 even if no driver has claimed them. This is useful
539 for debug and development, but should not be
540 needed on a platform with proper driver support.
541 For more information, see Documentation/clk.txt.
543 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
545 Forces specified clocksource (if available) to be used
546 when calculating gettimeofday(). If specified
547 clocksource is not available, it defaults to PIT.
548 Format: { pit | tsc | cyclone | pmtmr }
550 clocksource= Override the default clocksource
552 Override the default clocksource and use the clocksource
553 with the name specified.
554 Some clocksource names to choose from, depending on
556 [all] jiffies (this is the base, fallback clocksource)
558 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
559 pxa_timer,timer3,32k_counter,timer0_1
561 [X86-32] pit,hpet,tsc;
562 scx200_hrt on Geode; cyclone on IBM x440
570 clearcpuid=BITNUM [X86]
571 Disable CPUID feature X for the kernel. See
572 arch/x86/include/asm/cpufeature.h for the valid bit
573 numbers. Note the Linux specific bits are not necessarily
574 stable over kernel options, but the vendor specific
576 Also note that user programs calling CPUID directly
577 or using the feature without checking anything
578 will still see it. This just prevents it from
579 being used by the kernel or shown in /proc/cpuinfo.
580 Also note the kernel might malfunction if you disable
584 Sets the size of kernel global memory area for contiguous
585 memory allocations. For more information, see
586 include/linux/dma-contiguous.h
588 cmo_free_hint= [PPC] Format: { yes | no }
589 Specify whether pages are marked as being inactive
590 when they are freed. This is used in CMO environments
591 to determine OS memory pressure for page stealing by
595 coherent_pool=nn[KMG] [ARM,KNL]
596 Sets the size of memory pool for coherent, atomic dma
597 allocations, by default set to 256K.
599 code_bytes [X86] How many bytes of object code to print
604 com20020= [HW,NET] ARCnet - COM20020 chipset
606 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
608 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
612 ARCnet - COM90xx chipset (memory-mapped buffers)
613 Format: <io>[,<irq>[,<memstart>]]
615 condev= [HW,S390] console device
618 console= [KNL] Output console device and options.
620 tty<n> Use the virtual console device <n>.
624 Use the specified serial port. The options are of
625 the form "bbbbpnf", where "bbbb" is the baud rate,
626 "p" is parity ("n", "o", or "e"), "n" is number of
627 bits, and "f" is flow control ("r" for RTS or
628 omit it). Default is "9600n8".
630 See Documentation/serial-console.txt for more
632 Documentation/networking/netconsole.txt for an
635 uart[8250],io,<addr>[,options]
636 uart[8250],mmio,<addr>[,options]
637 Start an early, polled-mode console on the 8250/16550
638 UART at the specified I/O port or MMIO address,
639 switching to the matching ttyS device later. The
640 options are the same as for ttyS, above.
641 hvc<n> Use the hypervisor console device <n>. This is for
642 both Xen and PowerPC hypervisors.
644 If the device connected to the port is not a TTY but a braille
645 device, prepend "brl," before the device type, for instance
647 For now, only VisioBraille is supported.
649 consoleblank= [KNL] The console blank (screen saver) timeout in
650 seconds. Defaults to 10*60 = 10mins. A value of 0
651 disables the blank timer.
654 [KNL] Change the default value for
655 /proc/<pid>/coredump_filter.
656 See also Documentation/filesystems/proc.txt.
658 cpuidle.off=1 [CPU_IDLE]
659 disable the cpuidle sub-system
661 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
663 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
665 crashkernel=size[KMG][@offset[KMG]]
666 [KNL] Using kexec, Linux can switch to a 'crash kernel'
667 upon panic. This parameter reserves the physical
668 memory region [offset, offset + size] for that kernel
669 image. If '@offset' is omitted, then a suitable offset
670 is selected automatically. Check
671 Documentation/kdump/kdump.txt for further details.
673 crashkernel=range1:size1[,range2:size2,...][@offset]
674 [KNL] Same as above, but depends on the memory
675 in the running system. The syntax of range is
676 start-[end] where start and end are both
677 a memory unit (amount[KMG]). See also
678 Documentation/kdump/kdump.txt for an example.
680 crashkernel=size[KMG],high
681 [KNL, x86_64] range could be above 4G. Allow kernel
682 to allocate physical memory region from top, so could
683 be above 4G if system have more than 4G ram installed.
684 Otherwise memory region will be allocated below 4G, if
686 It will be ignored if crashkernel=X is specified.
687 crashkernel=size[KMG],low
688 [KNL, x86_64] range under 4G. When crashkernel=X,high
689 is passed, kernel could allocate physical memory region
690 above 4G, that cause second kernel crash on system
691 that require some amount of low memory, e.g. swiotlb
692 requires at least 64M+32K low memory. Kernel would
693 try to allocate 72M below 4G automatically.
694 This one let user to specify own low range under 4G
695 for second kernel instead.
696 0: to disable low allocation.
697 It will be ignored when crashkernel=X,high is not used
698 or memory reserved is below 4G.
703 cs89x0_media= [HW,NET]
704 Format: { rj45 | aui | bnc }
707 See header of drivers/s390/block/dasd_devmap.c.
709 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
710 (one device per port)
711 Format: <port#>,<type>
712 See also Documentation/input/joystick-parport.txt
714 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
715 time. See Documentation/dynamic-debug-howto.txt for
716 details. Deprecated, see dyndbg.
718 debug [KNL] Enable kernel debugging (events log level).
721 [KNL] verbose self-tests
723 Print debugging info while doing the locking API
725 We default to 0 (no extra messages), setting it to
726 1 will print _a lot_ more information - normally
727 only useful to kernel developers.
729 debug_objects [KNL] Enable object debugging
732 [KNL] Disable object debugging
734 debug_guardpage_minorder=
735 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
736 parameter allows control of the order of pages that will
737 be intentionally kept free (and hence protected) by the
738 buddy allocator. Bigger value increase the probability
739 of catching random memory corruption, but reduce the
740 amount of memory for normal system use. The maximum
741 possible value is MAX_ORDER/2. Setting this parameter
742 to 1 or 2 should be enough to identify most random
743 memory corruption problems caused by bugs in kernel or
744 driver code when a CPU writes to (or reads from) a
745 random memory location. Note that there exists a class
746 of memory corruptions problems caused by buggy H/W or
747 F/W or by drivers badly programing DMA (basically when
748 memory is written at bus level and the CPU MMU is
749 bypassed) which are not detectable by
750 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
751 tracking down these problems.
753 debugpat [X86] Enable PAT debugging
755 decnet.addr= [HW,NET]
756 Format: <area>[,<node>]
757 See also Documentation/networking/decnet.txt.
760 [same as hugepagesz=] The size of the default
761 HugeTLB page size. This is the size represented by
762 the legacy /proc/ hugepages APIs, used for SHM, and
763 default size when mounting hugetlbfs filesystems.
764 Defaults to the default architecture's huge page size
768 Set number of hash buckets for dentry cache.
771 IO parameters + enable/disable command.
773 digiepca= [HW,SERIAL]
774 See drivers/char/README.epca and
775 Documentation/serial/digiepca.txt.
778 See Documentation/networking/ipv6.txt.
780 disable_ddw [PPC/PSERIES]
781 Disable Dynamic DMA Window support. Use this if
782 to workaround buggy firmware.
785 See Documentation/networking/ipv6.txt.
787 disable_mtrr_cleanup [X86]
788 The kernel tries to adjust MTRR layout from continuous
789 to discrete, to make X server driver able to add WB
790 entry later. This parameter disables that.
792 disable_mtrr_trim [X86, Intel and AMD only]
793 By default the kernel will trim any uncacheable
794 memory out of your available memory pool based on
795 MTRR settings. This parameter disables that behavior,
796 possibly causing your machine to run very slowly.
798 disable_timer_pin_1 [X86]
799 Disable PIN 1 of APIC timer
800 Can be useful to work around chipset bugs.
802 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
803 this option disables the debugging code at boot.
805 dma_debug_entries=<number>
806 This option allows to tune the number of preallocated
807 entries for DMA-API debugging code. One entry is
808 required per DMA-API allocation. Use this if the
809 DMA-API debugging code disables itself because the
810 architectural default is too low.
812 dma_debug_driver=<driver_name>
813 With this option the DMA-API debugging driver
814 filter feature can be enabled at boot time. Just
815 pass the driver to filter for as the parameter.
816 The filter can be disabled or changed to another
817 driver later using sysfs.
819 drm_kms_helper.edid_firmware=[<connector>:]<file>
820 Broken monitors, graphic adapters and KVMs may
821 send no or incorrect EDID data sets. This parameter
822 allows to specify an EDID data set in the
823 /lib/firmware directory that is used instead.
824 Generic built-in EDID data sets are used, if one of
825 edid/1024x768.bin, edid/1280x1024.bin,
826 edid/1680x1050.bin, or edid/1920x1080.bin is given
827 and no file with the same name exists. Details and
828 instructions how to build your own EDID data are
829 available in Documentation/EDID/HOWTO.txt. An EDID
830 data set will only be used for a particular connector,
831 if its name and a colon are prepended to the EDID
836 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
837 module.dyndbg[="val"]
838 Enable debug messages at boot time. See
839 Documentation/dynamic-debug-howto.txt for details.
841 earlycon= [KNL] Output early console device and options.
842 uart[8250],io,<addr>[,options]
843 uart[8250],mmio,<addr>[,options]
844 uart[8250],mmio32,<addr>[,options]
845 Start an early, polled-mode console on the 8250/16550
846 UART at the specified I/O port or MMIO address.
847 MMIO inter-register address stride is either 8-bit
848 (mmio) or 32-bit (mmio32).
849 The options are the same as for ttyS, above.
851 earlyprintk= [X86,SH,BLACKFIN,ARM]
854 earlyprintk=serial[,ttySn[,baudrate]]
855 earlyprintk=serial[,0x...[,baudrate]]
856 earlyprintk=ttySn[,baudrate]
857 earlyprintk=dbgp[debugController#]
859 earlyprintk is useful when the kernel crashes before
860 the normal console is initialized. It is not enabled by
861 default because it has some cosmetic problems.
863 Append ",keep" to not disable it when the real console
866 Only vga or serial or usb debug port at a time.
868 Currently only ttyS0 and ttyS1 may be specified by
869 name. Other I/O ports may be explicitly specified
870 on some architectures (x86 and arm at least) by
871 replacing ttySn with an I/O port address, like this:
872 earlyprintk=serial,0x1008,115200
873 You can find the port for a given device in
874 /proc/tty/driver/serial:
875 2: uart:ST16650V2 port:00001008 irq:18 ...
877 Interaction with the standard serial driver is not
880 The VGA output is eventually overwritten by the real
883 The xen output can only be used by Xen PV guests.
885 ekgdboc= [X86,KGDB] Allow early kernel console debugging
888 This is designed to be used in conjunction with
889 the boot argument: earlyprintk=vga
892 Format: {"off" | "on" | "skip[mbr]"}
894 efi_no_storage_paranoia [EFI; X86]
895 Using this parameter you can use more than 50% of
896 your efi variable storage. Use this parameter only if
897 you are really sure that your UEFI does sane gc and
898 fulfills the spec otherwise your board may brick.
900 eisa_irq_edge= [PARISC,HW]
901 See header of drivers/parisc/eisa.c.
904 See comment before function elanfreq_setup() in
905 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
908 Format: {"cfq" | "deadline" | "noop"}
909 See Documentation/block/cfq-iosched.txt and
910 Documentation/block/deadline-iosched.txt for details.
912 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
913 Specifies physical address of start of kernel core
914 image elf header and optionally the size. Generally
915 kexec loader will pass this option to capture kernel.
916 See Documentation/kdump/kdump.txt for details.
918 enable_mtrr_cleanup [X86]
919 The kernel tries to adjust MTRR layout from continuous
920 to discrete, to make X server driver able to add WB
921 entry later. This parameter enables that.
923 enable_timer_pin_1 [X86]
924 Enable PIN 1 of APIC timer
925 Can be useful to work around chipset bugs
926 (in particular on some ATI chipsets).
927 The kernel tries to set a reasonable default.
929 enforcing [SELINUX] Set initial enforcing status.
931 See security/selinux/Kconfig help text.
932 0 -- permissive (log only, no denials).
933 1 -- enforcing (deny and log).
935 Value can be changed at runtime via /selinux/enforce.
938 Disable Error Record Serialization Table (ERST)
941 ether= [HW,NET] Ethernet cards parameters
942 This option is obsoleted by the "netdev=" option, which
943 has equivalent usage. See its documentation for details.
947 Permit 'security.evm' to be updated regardless of
948 current integrity status.
952 fail_make_request=[KNL]
953 General fault injection mechanism.
954 Format: <interval>,<probability>,<space>,<times>
955 See also Documentation/fault-injection/.
958 See Documentation/blockdev/floppy.txt.
960 force_pal_cache_flush
961 [IA-64] Avoid check_sal_cache_flush which may hang on
962 buggy SAL_CACHE_FLUSH implementations. Using this
963 parameter will force ia64_sal_cache_flush to call
964 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
967 [FTRACE] will set and start the specified tracer
968 as early as possible in order to facilitate early
971 ftrace_dump_on_oops[=orig_cpu]
972 [FTRACE] will dump the trace buffers on oops.
973 If no parameter is passed, ftrace will dump
974 buffers of all CPUs, but if you pass orig_cpu, it will
975 dump only the buffer of the CPU that triggered the
978 ftrace_filter=[function-list]
979 [FTRACE] Limit the functions traced by the function
980 tracer at boot up. function-list is a comma separated
981 list of functions. This list can be changed at run
982 time by the set_ftrace_filter file in the debugfs
985 ftrace_notrace=[function-list]
986 [FTRACE] Do not trace the functions specified in
987 function-list. This list can be changed at run time
988 by the set_ftrace_notrace file in the debugfs
991 ftrace_graph_filter=[function-list]
992 [FTRACE] Limit the top level callers functions traced
993 by the function graph tracer at boot up.
994 function-list is a comma separated list of functions
995 that can be changed at run time by the
996 set_graph_function file in the debugfs tracing directory.
999 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1000 support via parallel port (up to 5 devices per port)
1001 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1002 See also Documentation/input/joystick-parport.txt
1006 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1010 gcov_persist= [GCOV] When non-zero (default), profiling data for
1011 kernel modules is saved and remains accessible via
1012 debugfs, even when the module is unloaded/reloaded.
1013 When zero, profiling data is discarded and associated
1014 debugfs files are removed at module unload time.
1016 gpt [EFI] Forces disk with valid GPT signature but
1017 invalid Protective MBR to be treated as GPT.
1019 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1020 the "Enable 0" bit of the configuration register.
1023 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1024 the "Enable 0" bit of the configuration register.
1027 grcan.select= [HW] Select which physical interface to use.
1030 grcan.txsize= [HW] Sets the size of the tx buffer.
1031 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1033 grcan.rxsize= [HW] Sets the size of the rx buffer.
1034 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1037 hashdist= [KNL,NUMA] Large hashes allocated during boot
1038 are distributed across NUMA nodes. Defaults on
1039 for 64-bit NUMA, off otherwise.
1040 Format: 0 | 1 (for off | on)
1042 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1044 hd= [EIDE] (E)IDE hard drive subsystem geometry
1045 Format: <cyl>,<head>,<sect>
1048 Disable Hardware Error Source Table (HEST) support;
1049 corresponding firmware-first mode error processing
1050 logic will be disabled.
1052 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1053 size of <nn>. This works even on boxes that have no
1054 highmem otherwise. This also works to reduce highmem
1055 size on bigger boxes.
1057 highres= [KNL] Enable/disable high resolution timer mode.
1058 Valid parameters: "on", "off"
1062 See Documentation/isdn/README.HiSax.
1066 hpet= [X86-32,HPET] option to control HPET usage
1067 Format: { enable (default) | disable | force |
1069 disable: disable HPET and use PIT instead
1070 force: allow force enabled of undocumented chips (ICH4,
1072 verbose: show contents of HPET registers during setup
1074 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1075 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1076 On x86-64 and powerpc, this option can be specified
1077 multiple times interleaved with hugepages= to reserve
1078 huge pages of different sizes. Valid pages sizes on
1079 x86-64 are 2M (when the CPU supports "pse") and 1G
1080 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1081 Note that 1GB pages can only be allocated at boot time
1082 using hugepages= and not freed afterwards.
1084 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1085 terminal devices. Valid values: 0..8
1086 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1087 If specified, z/VM IUCV HVC accepts connections
1088 from listed z/VM user IDs only.
1090 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1091 hardware thread id mappings.
1092 Format: <cpu>:<hwthread>
1095 Do not unregister boot console at start. This is only
1096 useful for debugging when something happens in the window
1097 between unregistering the boot console and initializing
1100 i2c_bus= [HW] Override the default board specific I2C bus speed
1101 or register an additional I2C bus that is not
1102 registered from board initialization code.
1106 i8042.debug [HW] Toggle i8042 debug mode
1107 i8042.direct [HW] Put keyboard port into non-translated mode
1108 i8042.dumbkbd [HW] Pretend that controller can only read data from
1109 keyboard and cannot control its state
1110 (Don't attempt to blink the leds)
1111 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1112 i8042.nokbd [HW] Don't check/create keyboard port
1113 i8042.noloop [HW] Disable the AUX Loopback command while probing
1115 i8042.nomux [HW] Don't check presence of an active multiplexing
1117 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1119 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1120 i8042.reset [HW] Reset the controller during init and cleanup
1121 i8042.unlock [HW] Unlock (ignore) the keylock
1125 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1126 indicates that the driver is running on unsupported
1128 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1129 does not match list of supported models.
1131 [HW] Report power status in /proc/i8k
1132 (disabled by default)
1133 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1136 i915.invert_brightness=
1137 [DRM] Invert the sense of the variable that is used to
1138 set the brightness of the panel backlight. Normally a
1139 brightness value of 0 indicates backlight switched off,
1140 and the maximum of the brightness value sets the backlight
1141 to maximum brightness. If this parameter is set to 0
1142 (default) and the machine requires it, or this parameter
1143 is set to 1, a brightness value of 0 sets the backlight
1144 to maximum brightness, and the maximum of the brightness
1145 value switches the backlight off.
1146 -1 -- never invert brightness
1147 0 -- machine default
1148 1 -- force brightness inversion
1151 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1153 ide-core.nodma= [HW] (E)IDE subsystem
1154 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1155 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1156 .cdrom .chs .ignore_cable are additional options
1157 See Documentation/ide/ide.txt.
1159 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1160 Claim all unknown PCI IDE storage controllers.
1163 Format: idle=poll, idle=halt, idle=nomwait
1164 Poll forces a polling idle loop that can slightly
1165 improve the performance of waking up a idle CPU, but
1166 will use a lot of power and make the system run hot.
1168 idle=halt: Halt is forced to be used for CPU idle.
1169 In such case C2/C3 won't be used again.
1170 idle=nomwait: Disable mwait for CPU C-states
1172 ignore_loglevel [KNL]
1173 Ignore loglevel setting - this will print /all/
1174 kernel messages to the console. Useful for debugging.
1175 We also add it as printk module parameter, so users
1176 could change it dynamically, usually by
1177 /sys/module/printk/parameters/ignore_loglevel.
1179 ihash_entries= [KNL]
1180 Set number of hash buckets for inode cache.
1182 ima_appraise= [IMA] appraise integrity measurements
1183 Format: { "off" | "enforce" | "fix" }
1186 ima_appraise_tcb [IMA]
1187 The builtin appraise policy appraises all files
1191 Format: { "sha1" | "md5" }
1195 Load a policy which meets the needs of the Trusted
1196 Computing Base. This means IMA will measure all
1197 programs exec'd, files mmap'd for exec, and all files
1198 opened for read by uid=0.
1202 Run specified binary instead of /sbin/init as init
1205 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1206 for working out where the kernel is dying during
1209 initrd= [BOOT] Specify the location of the initial ramdisk
1211 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1214 int_pln_enable [x86] Enable power limit notification interrupt
1216 integrity_audit=[IMA]
1217 Format: { "0" | "1" }
1218 0 -- basic integrity auditing messages. (Default)
1219 1 -- additional integrity auditing messages.
1221 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1223 Enable intel iommu driver.
1225 Disable intel iommu driver.
1226 igfx_off [Default Off]
1227 By default, gfx is mapped as normal device. If a gfx
1228 device has a dedicated DMAR unit, the DMAR unit is
1229 bypassed by not enabling DMAR with this option. In
1230 this case, gfx device will use physical address for
1233 With this option iommu will not optimize to look
1234 for io virtual address below 32-bit forcing dual
1235 address cycle on pci bus for cards supporting greater
1236 than 32-bit addressing. The default is to look
1237 for translation below 32-bit and if not available
1238 then look in the higher range.
1239 strict [Default Off]
1240 With this option on every unmap_single operation will
1241 result in a hardware IOTLB flush operation as opposed
1242 to batching them for performance.
1243 sp_off [Default Off]
1244 By default, super page will be supported if Intel IOMMU
1245 has the capability. With this option, super page will
1248 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1249 0 disables intel_idle and fall back on acpi_idle.
1250 1 to 6 specify maximum depth of C-state.
1254 Do not enable intel_pstate as the default
1255 scaling driver for the supported processors
1257 intremap= [X86-64, Intel-IOMMU]
1258 on enable Interrupt Remapping (default)
1259 off disable Interrupt Remapping
1260 nosid disable Source ID checking
1262 BIOS x2APIC opt-out request will be ignored
1264 iomem= Disable strict checking of access to MMIO memory
1265 strict regions from userspace.
1282 io7= [HW] IO7 for Marvel based alpha systems
1283 See comment before marvel_specify_io7 in
1284 arch/alpha/kernel/core_marvel.c.
1286 io_delay= [X86] I/O delay method
1288 Standard port 0x80 based delay
1290 Alternate port 0xed based delay (needed on some systems)
1292 Simple two microseconds delay
1297 See Documentation/filesystems/nfs/nfsroot.txt.
1299 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1300 See comment before ip2_setup() in
1301 drivers/char/ip2/ip2base.c.
1304 When an interrupt is not handled search all handlers
1305 for it. Intended to get systems with badly broken
1309 When an interrupt is not handled search all handlers
1310 for it. Also check all handlers each timer
1311 interrupt. Intended to get systems with badly broken
1315 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1317 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1319 <cpu number>,...,<cpu number>
1321 <cpu number>-<cpu number>
1322 (must be a positive range in ascending order)
1324 <cpu number>,...,<cpu number>-<cpu number>
1326 This option can be used to specify one or more CPUs
1327 to isolate from the general SMP balancing and scheduling
1328 algorithms. You can move a process onto or off an
1329 "isolated" CPU via the CPU affinity syscalls or cpuset.
1330 <cpu number> begins at 0 and the maximum value is
1331 "number of CPUs in system - 1".
1333 This option is the preferred way to isolate CPUs. The
1334 alternative -- manually setting the CPU mask of all
1335 tasks in the system -- can cause problems and
1336 suboptimal load balancer performance.
1340 ivrs_ioapic [HW,X86_64]
1341 Provide an override to the IOAPIC-ID<->DEVICE-ID
1342 mapping provided in the IVRS ACPI table. For
1343 example, to map IOAPIC-ID decimal 10 to
1344 PCI device 00:14.0 write the parameter as:
1345 ivrs_ioapic[10]=00:14.0
1347 ivrs_hpet [HW,X86_64]
1348 Provide an override to the HPET-ID<->DEVICE-ID
1349 mapping provided in the IVRS ACPI table. For
1350 example, to map HPET-ID decimal 0 to
1351 PCI device 00:14.0 write the parameter as:
1352 ivrs_hpet[0]=00:14.0
1354 js= [HW,JOY] Analog joystick
1355 See Documentation/input/joystick.txt.
1359 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1360 specifies the amount of memory usable by the kernel
1361 for non-movable allocations. The requested amount is
1362 spread evenly throughout all nodes in the system. The
1363 remaining memory in each node is used for Movable
1364 pages. In the event, a node is too small to have both
1365 kernelcore and Movable pages, kernelcore pages will
1366 take priority and other nodes will have a larger number
1367 of kernelcore pages. The Movable zone is used for the
1368 allocation of pages that may be reclaimed or moved
1369 by the page migration subsystem. This means that
1370 HugeTLB pages may not be allocated from this zone.
1371 Note that allocations like PTEs-from-HighMem still
1372 use the HighMem zone if it exists, and the Normal
1373 zone if it does not.
1375 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1376 Format: <Controller#>[,poll interval]
1377 The controller # is the number of the ehci usb debug
1378 port as it is probed via PCI. The poll interval is
1379 optional and is the number seconds in between
1380 each poll cycle to the debug port in case you need
1381 the functionality for interrupting the kernel with
1382 gdb or control-c on the dbgp connection. When
1383 not using this parameter you use sysrq-g to break into
1384 the kernel debugger.
1386 kgdboc= [KGDB,HW] kgdb over consoles.
1387 Requires a tty driver that supports console polling,
1388 or a supported polling keyboard driver (non-usb).
1389 Serial only format: <serial_device>[,baud]
1390 keyboard only format: kbd
1391 keyboard and serial format: kbd,<serial_device>[,baud]
1392 Optional Kernel mode setting:
1393 kms, kbd format: kms,kbd
1394 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1396 kgdbwait [KGDB] Stop kernel execution and enter the
1397 kernel debugger at the earliest opportunity.
1399 kmac= [MIPS] korina ethernet MAC address.
1400 Configure the RouterBoard 532 series on-chip
1401 Ethernet adapter MAC address.
1403 kmemleak= [KNL] Boot-time kmemleak enable/disable
1404 Valid arguments: on, off
1407 kstack=N [X86] Print N words from the kernel stack
1410 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1411 Default is 0 (don't ignore, but inject #GP)
1413 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1417 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1418 Default is 1 (enabled)
1420 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1422 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1424 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1425 (virtualized MMU) support on capable Intel chips.
1426 Default is 1 (enabled)
1428 kvm-intel.emulate_invalid_guest_state=
1429 [KVM,Intel] Enable emulation of invalid guest states
1430 Default is 0 (disabled)
1432 kvm-intel.flexpriority=
1433 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1434 Default is 1 (enabled)
1437 [KVM,Intel] Enable VMX nesting (nVMX).
1438 Default is 0 (disabled)
1440 kvm-intel.unrestricted_guest=
1441 [KVM,Intel] Disable unrestricted guest feature
1442 (virtualized real and unpaged mode) on capable
1443 Intel chips. Default is 1 (enabled)
1445 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1446 feature (tagged TLBs) on capable Intel chips.
1447 Default is 1 (enabled)
1453 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1456 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1457 value for LAPIC timer one-shot implementation. Default
1458 back to the programmable timer unit in the LAPIC.
1460 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1463 libata.dma= [LIBATA] DMA control
1464 libata.dma=0 Disable all PATA and SATA DMA
1465 libata.dma=1 PATA and SATA Disk DMA only
1466 libata.dma=2 ATAPI (CDROM) DMA only
1467 libata.dma=4 Compact Flash DMA only
1468 Combinations also work, so libata.dma=3 enables DMA
1469 for disks and CDROMs, but not CFs.
1471 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1472 libata.ignore_hpa=0 keep BIOS limits (default)
1473 libata.ignore_hpa=1 ignore limits, using full disk
1475 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1479 libata.force= [LIBATA] Force configurations. The format is comma
1480 separated list of "[ID:]VAL" where ID is
1481 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1482 matching port, link or device. Basically, it matches
1483 the ATA ID string printed on console by libata. If
1484 the whole ID part is omitted, the last PORT and DEVICE
1485 values are used. If ID hasn't been specified yet, the
1486 configuration applies to all ports, links and devices.
1488 If only DEVICE is omitted, the parameter applies to
1489 the port and all links and devices behind it. DEVICE
1490 number of 0 either selects the first device or the
1491 first fan-out link behind PMP device. It does not
1492 select the host link. DEVICE number of 15 selects the
1493 host link and device attached to it.
1495 The VAL specifies the configuration to force. As long
1496 as there's no ambiguity shortcut notation is allowed.
1497 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1498 The following configurations can be forced.
1500 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1501 Any ID with matching PORT is used.
1503 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1505 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1506 udma[/][16,25,33,44,66,100,133] notation is also
1509 * [no]ncq: Turn on or off NCQ.
1511 * nohrst, nosrst, norst: suppress hard, soft
1514 * rstonce: only attempt one reset during
1515 hot-unplug link recovery
1517 * dump_id: dump IDENTIFY data.
1519 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1521 If there are multiple matching configurations changing
1522 the same attribute, the last one is used.
1524 memblock=debug [KNL] Enable memblock debug messages.
1526 load_ramdisk= [RAM] List of ramdisks to load from floppy
1527 See Documentation/blockdev/ramdisk.txt.
1529 lockd.nlm_grace_period=P [NFS] Assign grace period.
1532 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1535 lockd.nlm_timeout=T [NFS] Assign timeout value.
1538 lockd.nlm_udpport=M [NFS] Assign UDP port.
1541 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1544 loglevel= All Kernel Messages with a loglevel smaller than the
1545 console loglevel will be printed to the console. It can
1546 also be changed with klogd or other programs. The
1547 loglevels are defined as follows:
1549 0 (KERN_EMERG) system is unusable
1550 1 (KERN_ALERT) action must be taken immediately
1551 2 (KERN_CRIT) critical conditions
1552 3 (KERN_ERR) error conditions
1553 4 (KERN_WARNING) warning conditions
1554 5 (KERN_NOTICE) normal but significant condition
1555 6 (KERN_INFO) informational
1556 7 (KERN_DEBUG) debug-level messages
1558 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1559 in bytes. n must be a power of two. The default
1560 size is set in the kernel config file.
1562 logo.nologo [FB] Disables display of the built-in Linux logo.
1563 This may be used to provide more screen space for
1564 kernel log messages and is useful when debugging
1565 kernel boot problems.
1567 lp=0 [LP] Specify parallel ports to use, e.g,
1568 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1569 lp=reset first parallel port). 'lp=0' disables the
1570 lp=auto printer driver. 'lp=reset' (which can be
1571 specified in addition to the ports) causes
1572 attached printers to be reset. Using
1573 lp=port1,port2,... specifies the parallel ports
1574 to associate lp devices with, starting with
1575 lp0. A port specification may be 'none' to skip
1576 that lp device, or a parport name such as
1577 'parport0'. Specifying 'lp=auto' instead of a
1578 port specification list means that device IDs
1579 from each port should be examined, to see if
1580 an IEEE 1284-compliant printer is attached; if
1581 so, the driver will manage that printer.
1582 See also header of drivers/char/lp.c.
1585 Sets loops_per_jiffy to given constant, thus avoiding
1586 time-consuming boot-time autodetection (up to 250 ms per
1587 CPU). 0 enables autodetection (default). To determine
1588 the correct value for your kernel, boot with normal
1589 autodetection and see what value is printed. Note that
1590 on SMP systems the preset will be applied to all CPUs,
1591 which is likely to cause problems if your CPUs need
1592 significantly divergent settings. An incorrect value
1593 will cause delays in the kernel to be wrong, leading to
1594 unpredictable I/O errors and other breakage. Although
1595 unlikely, in the extreme case this might damage your
1599 Format: <io>,<irq>,<dma>
1601 machvec= [IA-64] Force the use of a particular machine-vector
1602 (machvec) in a generic kernel.
1603 Example: machvec=hpzx1_swiotlb
1605 machtype= [Loongson] Share the same kernel image file between different
1607 Example: machtype=lemote-yeeloong-2f-7inch
1609 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1610 than or equal to this physical address is ignored.
1612 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1613 should make use of. maxcpus=n : n >= 0 limits the
1614 kernel to using 'n' processors. n=0 is a special case,
1615 it is equivalent to "nosmp", which also disables
1618 max_loop= [LOOP] The number of loop block devices that get
1619 (loop.max_loop) unconditionally pre-created at init time. The default
1620 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1621 of statically allocating a predefined number, loop
1622 devices can be requested on-demand with the
1623 /dev/loop-control interface.
1625 mce [X86-32] Machine Check Exception
1627 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1629 md= [HW] RAID subsystems devices and level
1630 See Documentation/md.txt.
1633 Format: <first>,<last>
1634 Specifies range of consoles to be captured by the MDA.
1636 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1637 Amount of memory to be used when the kernel is not able
1638 to see the whole system memory or for test.
1639 [X86] Work as limiting max address. Use together
1640 with memmap= to avoid physical address space collisions.
1641 Without memmap= PCI devices could be placed at addresses
1642 belonging to unused RAM.
1644 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1648 [KNL,SH] Allow user to override the default size for
1649 per-device physically contiguous DMA buffers.
1651 memmap=exactmap [KNL,X86] Enable setting of an exact
1652 E820 memory map, as specified by the user.
1653 Such memmap=exactmap lines can be constructed based on
1654 BIOS output or other requirements. See the memmap=nn@ss
1657 memmap=nn[KMG]@ss[KMG]
1658 [KNL] Force usage of a specific region of memory
1659 Region of memory to be used, from ss to ss+nn.
1661 memmap=nn[KMG]#ss[KMG]
1662 [KNL,ACPI] Mark specific memory as ACPI data.
1663 Region of memory to be used, from ss to ss+nn.
1665 memmap=nn[KMG]$ss[KMG]
1666 [KNL,ACPI] Mark specific memory as reserved.
1667 Region of memory to be used, from ss to ss+nn.
1668 Example: Exclude memory from 0x18690000-0x1869ffff
1669 memmap=64K$0x18690000
1671 memmap=0x10000$0x18690000
1673 memory_corruption_check=0/1 [X86]
1674 Some BIOSes seem to corrupt the first 64k of
1675 memory when doing things like suspend/resume.
1676 Setting this option will scan the memory
1677 looking for corruption. Enabling this will
1678 both detect corruption and prevent the kernel
1679 from using the memory being corrupted.
1680 However, its intended as a diagnostic tool; if
1681 repeatable BIOS-originated corruption always
1682 affects the same memory, you can use memmap=
1683 to prevent the kernel from using that memory.
1685 memory_corruption_check_size=size [X86]
1686 By default it checks for corruption in the low
1687 64k, making this memory unavailable for normal
1688 use. Use this parameter to scan for
1689 corruption in more or less memory.
1691 memory_corruption_check_period=seconds [X86]
1692 By default it checks for corruption every 60
1693 seconds. Use this parameter to check at some
1694 other rate. 0 disables periodic checking.
1696 memtest= [KNL,X86] Enable memtest
1698 default : 0 <disable>
1699 Specifies the number of memtest passes to be
1700 performed. Each pass selects another test
1701 pattern from a given set of patterns. Memtest
1702 fills the memory with this pattern, validates
1703 memory contents and reserves bad memory
1704 regions that are detected.
1706 meye.*= [HW] Set MotionEye Camera parameters
1707 See Documentation/video4linux/meye.txt.
1709 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1710 Multi-Function General Purpose Timers on AMD Geode
1713 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1714 the BIOS has incorrectly applied a workaround. TinyBIOS
1715 version 0.98 is known to be affected, 0.99 fixes the
1716 problem by letting the user disable the workaround.
1720 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1721 physical address is ignored.
1723 mini2440= [ARM,HW,KNL]
1724 Format:[0..2][b][c][t]
1726 MINI2440 configuration specification:
1727 0 - The attached screen is the 3.5" TFT
1728 1 - The attached screen is the 7" TFT
1729 2 - The VGA Shield is attached (1024x768)
1730 Leaving out the screen size parameter will not load
1731 the TFT driver, and the framebuffer will be left
1733 b - Enable backlight. The TFT backlight pin will be
1734 linked to the kernel VESA blanking code and a GPIO
1735 LED. This parameter is not necessary when using the
1737 c - Enable the s3c camera interface.
1738 t - Reserved for enabling touchscreen support. The
1739 touchscreen support is not enabled in the mainstream
1740 kernel as of 2.6.30, a preliminary port can be found
1741 in the "bleeding edge" mini2440 support kernel at
1742 http://repo.or.cz/w/linux-2.6/mini2440.git
1745 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1746 parameter allows control of the logging verbosity for
1747 the additional memory initialisation checks. A value
1748 of 0 disables mminit logging and a level of 4 will
1749 log everything. Information is printed at KERN_DEBUG
1750 so loglevel=8 may also need to be specified.
1753 [KNL] When CONFIG_MODULE_SIG is set, this means that
1754 modules without (valid) signatures will fail to load.
1755 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1756 is always true, so this option does nothing.
1759 [MOUSE] Maximum time between finger touching and
1760 leaving touchpad surface for touch to be considered
1761 a tap and be reported as a left button click (for
1762 touchpads working in absolute mode only).
1764 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1765 reporting absolute coordinates, such as tablets
1766 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1767 reporting absolute coordinates, such as tablets
1769 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1770 is similar to kernelcore except it specifies the
1771 amount of memory used for migratable allocations.
1772 If both kernelcore and movablecore is specified,
1773 then kernelcore will be at *least* the specified
1774 value but may be more. If movablecore on its own
1775 is specified, the administrator must be careful
1776 that the amount of memory usable for all allocations
1779 MTD_Partition= [MTD]
1780 Format: <name>,<region-number>,<size>,<offset>
1782 MTD_Region= [MTD] Format:
1783 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1786 See drivers/mtd/cmdlinepart.c.
1788 multitce=off [PPC] This parameter disables the use of the pSeries
1789 firmware feature for updating multiple TCE entries
1792 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1794 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1796 boundary - index of last SLC block on Flex-OneNAND.
1797 The remaining blocks are configured as MLC blocks.
1798 lock - Configure if Flex-OneNAND boundary should be locked.
1799 Once locked, the boundary cannot be changed.
1800 1 indicates lock status, 0 indicates unlock status.
1803 ARM/S3C2412 JIVE boot control
1805 See arch/arm/mach-s3c2412/mach-jive.c
1807 mtouchusb.raw_coordinates=
1808 [HW] Make the MicroTouch USB driver use raw coordinates
1809 ('y', default) or cooked coordinates ('n')
1811 mtrr_chunk_size=nn[KMG] [X86]
1812 used for mtrr cleanup. It is largest continuous chunk
1813 that could hold holes aka. UC entries.
1815 mtrr_gran_size=nn[KMG] [X86]
1816 Used for mtrr cleanup. It is granularity of mtrr block.
1818 Large value could prevent small alignment from
1821 mtrr_spare_reg_nr=n [X86]
1823 Range: 0,7 : spare reg number
1825 Used for mtrr cleanup. It is spare mtrr entries number.
1826 Set to 2 or more if your graphical card needs more.
1828 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1830 netdev= [NET] Network devices parameters
1831 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1832 Note that mem_start is often overloaded to mean
1833 something different and driver-specific.
1834 This usage is only documented in each driver source
1838 [NETFILTER] Enable connection tracking flow accounting
1839 0 to disable accounting
1840 1 to enable accounting
1843 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1844 See Documentation/filesystems/nfs/nfsroot.txt.
1846 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1847 See Documentation/filesystems/nfs/nfsroot.txt.
1849 nfsrootdebug [NFS] enable nfsroot debugging messages.
1850 See Documentation/filesystems/nfs/nfsroot.txt.
1852 nfs.callback_tcpport=
1853 [NFS] set the TCP port on which the NFSv4 callback
1854 channel should listen.
1857 [NFS] sets the pathname to the program which is used
1858 to update the NFS client cache entries.
1860 nfs.cache_getent_timeout=
1861 [NFS] sets the timeout after which an attempt to
1862 update a cache entry is deemed to have failed.
1864 nfs.idmap_cache_timeout=
1865 [NFS] set the maximum lifetime for idmapper cache
1869 [NFS] enable 64-bit inode numbers.
1870 If zero, the NFS client will fake up a 32-bit inode
1871 number for the readdir() and stat() syscalls instead
1872 of returning the full 64-bit number.
1873 The default is to return 64-bit inode numbers.
1875 nfs.max_session_slots=
1876 [NFSv4.1] Sets the maximum number of session slots
1877 the client will attempt to negotiate with the server.
1878 This limits the number of simultaneous RPC requests
1879 that the client can send to the NFSv4.1 server.
1880 Note that there is little point in setting this
1881 value higher than the max_tcp_slot_table_limit.
1883 nfs.nfs4_disable_idmapping=
1884 [NFSv4] When set to the default of '1', this option
1885 ensures that both the RPC level authentication
1886 scheme and the NFS level operations agree to use
1887 numeric uids/gids if the mount is using the
1888 'sec=sys' security flavour. In effect it is
1889 disabling idmapping, which can make migration from
1890 legacy NFSv2/v3 systems to NFSv4 easier.
1891 Servers that do not support this mode of operation
1892 will be autodetected by the client, and it will fall
1893 back to using the idmapper.
1894 To turn off this behaviour, set the value to '0'.
1896 [NFS4] Specify an additional fixed unique ident-
1897 ification string that NFSv4 clients can insert into
1898 their nfs_client_id4 string. This is typically a
1899 UUID that is generated at system install time.
1901 nfs.send_implementation_id =
1902 [NFSv4.1] Send client implementation identification
1903 information in exchange_id requests.
1904 If zero, no implementation identification information
1906 The default is to send the implementation identification
1909 nfsd.nfs4_disable_idmapping=
1910 [NFSv4] When set to the default of '1', the NFSv4
1911 server will return only numeric uids and gids to
1912 clients using auth_sys, and will accept numeric uids
1913 and gids from such clients. This is intended to ease
1914 migration from NFSv2/v3.
1916 objlayoutdriver.osd_login_prog=
1917 [NFS] [OBJLAYOUT] sets the pathname to the program which
1918 is used to automatically discover and login into new
1919 osd-targets. Please see:
1920 Documentation/filesystems/pnfs.txt for more explanations
1922 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1923 when a NMI is triggered.
1924 Format: [state][,regs][,debounce][,die]
1926 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1927 Format: [panic,][nopanic,][num]
1929 0 - turn nmi_watchdog off
1930 When panic is specified, panic when an NMI watchdog
1931 timeout occurs (or 'nopanic' to override the opposite
1933 This is useful when you use a panic=... timeout and
1934 need the box quickly up again.
1936 netpoll.carrier_timeout=
1937 [NET] Specifies amount of time (in seconds) that
1938 netpoll should wait for a carrier. By default netpoll
1941 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1942 emulation library even if a 387 maths coprocessor
1946 [HW] Never suspend the console
1947 Disable suspending of consoles during suspend and
1948 hibernate operations. Once disabled, debugging
1949 messages can reach various consoles while the rest
1950 of the system is being put to sleep (ie, while
1951 debugging driver suspend/resume hooks). This may
1952 not work reliably with all consoles, but is known
1953 to work with serial and VGA consoles.
1954 To facilitate more flexible debugging, we also add
1955 console_suspend, a printk module parameter to control
1956 it. Users could use console_suspend (usually
1957 /sys/module/printk/parameters/console_suspend) to
1958 turn on/off it dynamically.
1960 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1961 caches in the slab allocator. Saves per-node memory,
1962 but will impact performance.
1966 noapic [SMP,APIC] Tells the kernel to not make use of any
1967 IOAPICs that may be present in the system.
1969 noautogroup Disable scheduler automatic task group creation.
1971 nobats [PPC] Do not use BATs for mapping kernel lowmem
1972 on "Classic" PPC cores.
1976 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1978 nodelayacct [KNL] Disable per-task delay accounting
1980 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1982 nodsp [SH] Disable hardware DSP at boot time.
1984 noefi [X86] Disable EFI runtime services support.
1989 On X86-32 available only on PAE configured kernels.
1990 noexec=on: enable non-executable mappings (default)
1991 noexec=off: disable non-executable mappings
1994 Disable SMAP (Supervisor Mode Access Prevention)
1995 even if it is supported by processor.
1998 Disable SMEP (Supervisor Mode Execution Prevention)
1999 even if it is supported by processor.
2002 This affects only 32-bit executables.
2003 noexec32=on: enable non-executable mappings (default)
2004 read doesn't imply executable mappings
2005 noexec32=off: disable non-executable mappings
2006 read implies executable mappings
2008 nofpu [SH] Disable hardware FPU at boot time.
2010 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2011 register save and restore. The kernel will only save
2012 legacy floating-point registers on task switch.
2014 noxsave [BUGS=X86] Disables x86 extended register state save
2015 and restore using xsave. The kernel will fallback to
2016 enabling legacy floating-point and sse state.
2019 on enable eager fpu restore
2020 off disable eager fpu restore
2021 auto selects the default scheme, which automatically
2022 enables eagerfpu restore for xsaveopt.
2024 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2025 wfi(ARM) instruction doesn't work correctly and not to
2026 use it. This is also useful when using JTAG debugger.
2028 no_file_caps Tells the kernel not to honor file capabilities. The
2029 only way then for a file to be executed with privilege
2030 is to be setuid root or executed by root.
2032 nohalt [IA-64] Tells the kernel not to use the power saving
2033 function PAL_HALT_LIGHT when idle. This increases
2034 power-consumption. On the positive side, it reduces
2035 interrupt wake-up latency, which may improve performance
2036 in certain environments such as networked servers or
2039 nohz= [KNL] Boottime enable/disable dynamic ticks
2040 Valid arguments: on, off
2043 nohz_full= [KNL,BOOT]
2044 In kernels built with CONFIG_NO_HZ_FULL=y, set
2045 the specified list of CPUs whose tick will be stopped
2046 whenever possible. The boot CPU will be forced outside
2047 the range to maintain the timekeeping.
2048 The CPUs in this range must also be included in the
2051 noiotrap [SH] Disables trapped I/O port accesses.
2053 noirqdebug [X86-32] Disables the code which attempts to detect and
2054 disable unhandled interrupt sources.
2056 no_timer_check [X86,APIC] Disables the code which tests for
2057 broken timer IRQ sources.
2059 noisapnp [ISAPNP] Disables ISA PnP code.
2061 noinitrd [RAM] Tells the kernel not to load any configured
2064 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2066 [Deprecated - use intremap=off]
2070 nojitter [IA-64] Disables jitter checking for ITC timers.
2072 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2074 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2077 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2078 steal time is computed, but won't influence scheduler
2081 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2083 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2085 noltlbs [PPC] Do not use large page/tlb entries for kernel
2086 lowmem mapping on PPC40x.
2088 nomca [IA-64] Disable machine check abort handling
2090 nomce [X86-32] Machine Check Exception
2092 nomfgpt [X86-32] Disable Multi-Function General Purpose
2093 Timer usage (for AMD Geode machines).
2095 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2096 shutdown the other cpus. Instead use the REBOOT_VECTOR
2099 nomodule Disable module load
2101 nopat [X86] Disable PAT (page attribute table extension of
2102 pagetables) support.
2104 norandmaps Don't use address space randomization. Equivalent to
2105 echo 0 > /proc/sys/kernel/randomize_va_space
2107 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2109 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2110 with UP alternatives
2112 nordrand [X86] Disable the direct use of the RDRAND
2113 instruction even if it is supported by the
2114 processor. RDRAND is still available to user
2117 noresume [SWSUSP] Disables resume and restores original swap
2120 no-scroll [VGA] Disables scrollback.
2121 This is required for the Braillex ib80-piezo Braille
2122 reader made by F.H. Papenmeier (Germany).
2126 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2128 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2129 and disable the IO APIC. legacy for "maxcpus=0".
2131 nosoftlockup [KNL] Disable the soft-lockup detector.
2133 nosync [HW,M68K] Disables sync negotiation for all devices.
2135 notsc [BUGS=X86-32] Disable Time Stamp Counter
2137 nousb [USB] Disable the USB subsystem
2139 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2143 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2145 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2146 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2147 Some features depend on CPU0. Known dependencies are:
2148 1. Resume from suspend/hibernate depends on CPU0.
2149 Suspend/hibernate will fail if CPU0 is offline and you
2150 need to online CPU0 before suspend/hibernate.
2151 2. PIC interrupts also depend on CPU0. CPU0 can't be
2152 removed if a PIC interrupt is detected.
2153 It's said poweroff/reboot may depend on CPU0 on some
2154 machines although I haven't seen such issues so far
2155 after CPU0 is offline on a few tested machines.
2156 If the dependencies are under your control, you can
2157 turn on cpu0_hotplug.
2159 nptcg= [IA-64] Override max number of concurrent global TLB
2160 purges which is reported from either PAL_VM_SUMMARY or
2163 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2164 could support. nr_cpus=n : n >= 1 limits the kernel to
2165 supporting 'n' processors. Later in runtime you can not
2166 use hotplug cpu feature to put more cpu back to online.
2167 just like you compile the kernel NR_CPUS=n
2169 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2171 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2172 Allowed values are enable and disable
2174 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2175 one of ['zone', 'node', 'default'] can be specified
2176 This can be set from sysctl after boot.
2177 See Documentation/sysctl/vm.txt for details.
2179 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2180 See Documentation/debugging-via-ohci1394.txt for more
2183 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2184 Rather than timing out after 20 ms if an EC
2185 command is not properly ACKed, override the length
2186 of the timeout. We have interrupts disabled while
2187 waiting for the ACK, so if this is set too high
2188 interrupts *may* be lost!
2190 omap_mux= [OMAP] Override bootloader pin multiplexing.
2191 Format: <mux_mode0.mode_name=value>...
2192 For example, to override I2C bus2:
2193 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2195 oprofile.timer= [HW]
2196 Use timer interrupt instead of performance counters
2198 oprofile.cpu_type= Force an oprofile cpu type
2199 This might be useful if you have an older oprofile
2200 userland or if you want common events.
2201 Format: { arch_perfmon }
2202 arch_perfmon: [X86] Force use of architectural
2203 perfmon on Intel CPUs instead of the
2204 CPU specific event set.
2205 timer: [X86] Force use of architectural NMI
2206 timer mode (see also oprofile.timer
2207 for generic hr timer mode)
2208 [s390] Force legacy basic mode sampling
2209 (report cpu_type "timer")
2211 oops=panic Always panic on oopses. Default is to just kill the
2212 process, but there is a small probability of
2213 deadlocking the machine.
2214 This will also cause panics on machine check exceptions.
2215 Useful together with panic=30 to trigger a reboot.
2218 See Documentation/sound/oss/oss-parameters.txt
2220 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2221 timeout > 0: seconds before rebooting
2222 timeout = 0: wait forever
2223 timeout < 0: reboot immediately
2226 parkbd.port= [HW] Parallel port number the keyboard adapter is
2227 connected to, default is 0.
2229 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2230 0 for XT, 1 for AT (default is AT).
2233 parport= [HW,PPT] Specify parallel ports. 0 disables.
2234 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2235 Use 'auto' to force the driver to use any
2236 IRQ/DMA settings detected (the default is to
2237 ignore detected IRQ/DMA settings because of
2238 possible conflicts). You can specify the base
2239 address, IRQ, and DMA settings; IRQ and DMA
2240 should be numbers, or 'auto' (for using detected
2241 settings on that particular port), or 'nofifo'
2242 (to avoid using a FIFO even if it is detected).
2243 Parallel ports are assigned in the order they
2244 are specified on the command line, starting
2247 parport_init_mode= [HW,PPT]
2248 Configure VIA parallel port to operate in
2249 a specific mode. This is necessary on Pegasos
2250 computer where firmware has no options for setting
2251 up parallel port mode and sets it to spp.
2252 Currently this function knows 686a and 8231 chips.
2253 Format: [spp|ps2|epp|ecp|ecpepp]
2256 Halt all CPUs after the first oops has been printed for
2257 the specified number of seconds. This is to be used if
2258 your oopses keep scrolling off the screen.
2263 See header of drivers/block/paride/pcd.c.
2264 See also Documentation/blockdev/paride.txt.
2266 pci=option[,option...] [PCI] various PCI subsystem options:
2267 earlydump [X86] dump PCI config space before the kernel
2269 off [X86] don't probe for the PCI bus
2270 bios [X86-32] force use of PCI BIOS, don't access
2271 the hardware directly. Use this if your machine
2272 has a non-standard PCI host bridge.
2273 nobios [X86-32] disallow use of PCI BIOS, only direct
2274 hardware access methods are allowed. Use this
2275 if you experience crashes upon bootup and you
2276 suspect they are caused by the BIOS.
2277 conf1 [X86] Force use of PCI Configuration
2279 conf2 [X86] Force use of PCI Configuration
2281 noaer [PCIE] If the PCIEAER kernel config parameter is
2282 enabled, this kernel boot option can be used to
2283 disable the use of PCIE advanced error reporting.
2284 nodomains [PCI] Disable support for multiple PCI
2285 root domains (aka PCI segments, in ACPI-speak).
2286 nommconf [X86] Disable use of MMCONFIG for PCI
2288 check_enable_amd_mmconf [X86] check for and enable
2289 properly configured MMIO access to PCI
2290 config space on AMD family 10h CPU
2291 nomsi [MSI] If the PCI_MSI kernel config parameter is
2292 enabled, this kernel boot option can be used to
2293 disable the use of MSI interrupts system-wide.
2294 noioapicquirk [APIC] Disable all boot interrupt quirks.
2295 Safety option to keep boot IRQs enabled. This
2296 should never be necessary.
2297 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2298 primary IO-APIC for bridges that cannot disable
2299 boot IRQs. This fixes a source of spurious IRQs
2300 when the system masks IRQs.
2301 noioapicreroute [APIC] Disable workaround that uses the
2302 boot IRQ equivalent of an IRQ that connects to
2303 a chipset where boot IRQs cannot be disabled.
2304 The opposite of ioapicreroute.
2305 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2306 routing table. These calls are known to be buggy
2307 on several machines and they hang the machine
2308 when used, but on other computers it's the only
2309 way to get the interrupt routing table. Try
2310 this option if the kernel is unable to allocate
2311 IRQs or discover secondary PCI buses on your
2313 rom [X86] Assign address space to expansion ROMs.
2314 Use with caution as certain devices share
2315 address decoders between ROMs and other
2317 norom [X86] Do not assign address space to
2318 expansion ROMs that do not already have
2319 BIOS assigned address ranges.
2320 nobar [X86] Do not assign address space to the
2321 BARs that weren't assigned by the BIOS.
2322 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2323 assigned automatically to PCI devices. You can
2324 make the kernel exclude IRQs of your ISA cards
2326 pirqaddr=0xAAAAA [X86] Specify the physical address
2327 of the PIRQ table (normally generated
2328 by the BIOS) if it is outside the
2329 F0000h-100000h range.
2330 lastbus=N [X86] Scan all buses thru bus #N. Can be
2331 useful if the kernel is unable to find your
2332 secondary buses and you want to tell it
2333 explicitly which ones they are.
2334 assign-busses [X86] Always assign all PCI bus
2335 numbers ourselves, overriding
2336 whatever the firmware may have done.
2337 usepirqmask [X86] Honor the possible IRQ mask stored
2338 in the BIOS $PIR table. This is needed on
2339 some systems with broken BIOSes, notably
2340 some HP Pavilion N5400 and Omnibook XE3
2341 notebooks. This will have no effect if ACPI
2342 IRQ routing is enabled.
2343 noacpi [X86] Do not use ACPI for IRQ routing
2344 or for PCI scanning.
2345 use_crs [X86] Use PCI host bridge window information
2346 from ACPI. On BIOSes from 2008 or later, this
2347 is enabled by default. If you need to use this,
2348 please report a bug.
2349 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2350 If you need to use this, please report a bug.
2351 routeirq Do IRQ routing for all PCI devices.
2352 This is normally done in pci_enable_device(),
2353 so this option is a temporary workaround
2354 for broken drivers that don't call it.
2355 skip_isa_align [X86] do not align io start addr, so can
2356 handle more pci cards
2357 firmware [ARM] Do not re-enumerate the bus but instead
2358 just use the configuration from the
2359 bootloader. This is currently used on
2360 IXP2000 systems where the bus has to be
2361 configured a certain way for adjunct CPUs.
2362 noearly [X86] Don't do any early type 1 scanning.
2363 This might help on some broken boards which
2364 machine check when some devices' config space
2365 is read. But various workarounds are disabled
2366 and some IOMMU drivers will not work.
2367 bfsort Sort PCI devices into breadth-first order.
2368 This sorting is done to get a device
2369 order compatible with older (<= 2.4) kernels.
2370 nobfsort Don't sort PCI devices into breadth-first order.
2371 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2372 tuning and use the BIOS-configured MPS defaults.
2373 pcie_bus_safe Set every device's MPS to the largest value
2374 supported by all devices below the root complex.
2375 pcie_bus_perf Set device MPS to the largest allowable MPS
2376 based on its parent bus. Also set MRRS (Max
2377 Read Request Size) to the largest supported
2378 value (no larger than the MPS that the device
2379 or bus can support) for best performance.
2380 pcie_bus_peer2peer Set every device's MPS to 128B, which
2381 every device is guaranteed to support. This
2382 configuration allows peer-to-peer DMA between
2383 any pair of devices, possibly at the cost of
2384 reduced performance. This also guarantees
2385 that hot-added devices will work.
2386 cbiosize=nn[KMG] The fixed amount of bus space which is
2387 reserved for the CardBus bridge's IO window.
2388 The default value is 256 bytes.
2389 cbmemsize=nn[KMG] The fixed amount of bus space which is
2390 reserved for the CardBus bridge's memory
2391 window. The default value is 64 megabytes.
2394 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2395 Specifies alignment and device to reassign
2396 aligned memory resources.
2397 If <order of align> is not specified,
2398 PAGE_SIZE is used as alignment.
2399 PCI-PCI bridge can be specified, if resource
2400 windows need to be expanded.
2401 ecrc= Enable/disable PCIe ECRC (transaction layer
2402 end-to-end CRC checking).
2403 bios: Use BIOS/firmware settings. This is the
2407 hpiosize=nn[KMG] The fixed amount of bus space which is
2408 reserved for hotplug bridge's IO window.
2409 Default size is 256 bytes.
2410 hpmemsize=nn[KMG] The fixed amount of bus space which is
2411 reserved for hotplug bridge's memory window.
2412 Default size is 2 megabytes.
2413 realloc= Enable/disable reallocating PCI bridge resources
2414 if allocations done by BIOS are too small to
2415 accommodate resources required by all child
2417 off: Turn realloc off
2419 realloc same as realloc=on
2420 noari do not use PCIe ARI.
2421 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2422 only look for one device below a PCIe downstream
2425 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2428 force Enable ASPM even on devices that claim not to support it.
2429 WARNING: Forcing ASPM on may cause system lockups.
2431 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2432 nomsi Do not use MSI for PCI Express Native Hotplug (this
2433 makes all PCIe ports use INTx for hotplug services).
2435 pcie_ports= [PCIE] PCIe ports handling:
2436 auto Ask the BIOS whether or not to use native PCIe services
2437 associated with PCIe ports (PME, hot-plug, AER). Use
2438 them only if that is allowed by the BIOS.
2439 native Use native PCIe services associated with PCIe ports
2441 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2444 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2445 nomsi Do not use MSI for native PCIe PME signaling (this makes
2446 all PCIe root ports use INTx for all services).
2448 pcmv= [HW,PCMCIA] BadgePAD 4
2451 See Documentation/blockdev/paride.txt.
2453 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2456 See arch/parisc/kernel/pdc_chassis.c
2458 percpu_alloc= Select which percpu first chunk allocator to use.
2459 Currently supported values are "embed" and "page".
2460 Archs may support subset or none of the selections.
2461 See comments in mm/percpu.c for details on each
2462 allocator. This parameter is primarily for debugging
2463 and performance comparison.
2466 See Documentation/blockdev/paride.txt.
2469 See Documentation/blockdev/paride.txt.
2471 pirq= [SMP,APIC] Manual mp-table setup
2472 See Documentation/x86/i386/IO-APIC.txt.
2474 plip= [PPT,NET] Parallel port network link
2475 Format: { parport<nr> | timid | 0 }
2476 See also Documentation/parport.txt.
2478 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2479 Override pmtimer IOPort with a hex value.
2483 Enable PNP debug messages (depends on the
2484 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2485 via /sys/module/pnp/parameters/debug. We always show
2486 current resource usage; turning this on also shows
2487 possible settings and some assignment information.
2493 { on | off | curr | res | no-curr | no-res }
2496 [ISAPNP] Exclude IRQs for the autoconfiguration
2499 [ISAPNP] Exclude DMAs for the autoconfiguration
2501 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2502 Ranges are in pairs (I/O port base and size).
2505 [ISAPNP] Exclude memory regions for the
2507 Ranges are in pairs (memory base and size).
2509 ports= [IP_VS_FTP] IPVS ftp helper module
2511 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2513 Format: <port>,<port>....
2515 print-fatal-signals=
2516 [KNL] debug: print fatal signals
2518 If enabled, warn about various signal handling
2519 related application anomalies: too many signals,
2520 too many POSIX.1 timers, fatal signals causing a
2523 If you hit the warning due to signal overflow,
2524 you might want to try "ulimit -i unlimited".
2528 printk.always_kmsg_dump=
2529 Trigger kmsg_dump for cases other than kernel oops or
2531 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2534 printk.time= Show timing data prefixed to each printk message line
2535 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2537 processor.max_cstate= [HW,ACPI]
2538 Limit processor to maximum C-state
2539 max_cstate=9 overrides any DMI blacklist limit.
2541 processor.nocst [HW,ACPI]
2542 Ignore the _CST method to determine C-states,
2543 instead using the legacy FADT method
2545 profile= [KNL] Enable kernel profiling via /proc/profile
2546 Format: [schedule,]<number>
2547 Param: "schedule" - profile schedule points.
2548 Param: <number> - step/bucket size as a power of 2 for
2549 statistical time based profiling.
2550 Param: "sleep" - profile D-state sleeping (millisecs).
2551 Requires CONFIG_SCHEDSTATS
2552 Param: "kvm" - profile VM exits.
2554 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2556 See Documentation/blockdev/ramdisk.txt.
2558 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2559 probe for; one of (bare|imps|exps|lifebook|any).
2560 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2562 psmouse.resetafter= [HW,MOUSE]
2563 Try to reset the device after so many bad packets
2566 [HW,MOUSE] Set desired mouse resolution, in dpi.
2567 psmouse.smartscroll=
2568 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2569 0 = disabled, 1 = enabled (default).
2571 pstore.backend= Specify the name of the pstore backend to use
2574 See Documentation/blockdev/paride.txt.
2577 [KNL] Number of legacy pty's. Overwrites compiled-in
2580 quiet [KNL] Disable most log messages
2585 See Documentation/md.txt.
2587 ramdisk_blocksize= [RAM]
2588 See Documentation/blockdev/ramdisk.txt.
2590 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2591 See Documentation/blockdev/ramdisk.txt.
2593 rcu_nocbs= [KNL,BOOT]
2594 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2595 the specified list of CPUs to be no-callback CPUs.
2596 Invocation of these CPUs' RCU callbacks will
2597 be offloaded to "rcuox/N" kthreads created for
2598 that purpose, where "x" is "b" for RCU-bh, "p"
2599 for RCU-preempt, and "s" for RCU-sched, and "N"
2600 is the CPU number. This reduces OS jitter on the
2601 offloaded CPUs, which can be useful for HPC and
2603 real-time workloads. It can also improve energy
2604 efficiency for asymmetric multiprocessors.
2606 rcu_nocb_poll [KNL,BOOT]
2607 Rather than requiring that offloaded CPUs
2608 (specified by rcu_nocbs= above) explicitly
2609 awaken the corresponding "rcuoN" kthreads,
2610 make these kthreads poll for callbacks.
2611 This improves the real-time response for the
2612 offloaded CPUs by relieving them of the need to
2613 wake up the corresponding kthread, but degrades
2614 energy efficiency by requiring that the kthreads
2615 periodically wake up to do the polling.
2617 rcutree.blimit= [KNL,BOOT]
2618 Set maximum number of finished RCU callbacks to process
2621 rcutree.fanout_leaf= [KNL,BOOT]
2622 Increase the number of CPUs assigned to each
2623 leaf rcu_node structure. Useful for very large
2626 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2627 Set delay from grace-period initialization to
2628 first attempt to force quiescent states.
2629 Units are jiffies, minimum value is zero,
2630 and maximum value is HZ.
2632 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2633 Set delay between subsequent attempts to force
2634 quiescent states. Units are jiffies, minimum
2635 value is one, and maximum value is HZ.
2637 rcutree.qhimark= [KNL,BOOT]
2638 Set threshold of queued
2639 RCU callbacks over which batch limiting is disabled.
2641 rcutree.qlowmark= [KNL,BOOT]
2642 Set threshold of queued RCU callbacks below which
2643 batch limiting is re-enabled.
2645 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2646 Suppress RCU CPU stall warning messages.
2648 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2649 Set timeout for RCU CPU stall warning messages.
2651 rcutree.rcu_idle_gp_delay= [KNL,BOOT]
2652 Set wakeup interval for idle CPUs that have
2653 RCU callbacks (RCU_FAST_NO_HZ=y).
2655 rcutree.rcu_idle_lazy_gp_delay= [KNL,BOOT]
2656 Set wakeup interval for idle CPUs that have
2657 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2658 Lazy RCU callbacks are those which RCU can
2659 prove do nothing more than free memory.
2661 rcutorture.fqs_duration= [KNL,BOOT]
2662 Set duration of force_quiescent_state bursts.
2664 rcutorture.fqs_holdoff= [KNL,BOOT]
2665 Set holdoff time within force_quiescent_state bursts.
2667 rcutorture.fqs_stutter= [KNL,BOOT]
2668 Set wait time between force_quiescent_state bursts.
2670 rcutorture.irqreader= [KNL,BOOT]
2671 Test RCU readers from irq handlers.
2673 rcutorture.n_barrier_cbs= [KNL,BOOT]
2674 Set callbacks/threads for rcu_barrier() testing.
2676 rcutorture.nfakewriters= [KNL,BOOT]
2677 Set number of concurrent RCU writers. These just
2678 stress RCU, they don't participate in the actual
2679 test, hence the "fake".
2681 rcutorture.nreaders= [KNL,BOOT]
2682 Set number of RCU readers.
2684 rcutorture.onoff_holdoff= [KNL,BOOT]
2685 Set time (s) after boot for CPU-hotplug testing.
2687 rcutorture.onoff_interval= [KNL,BOOT]
2688 Set time (s) between CPU-hotplug operations, or
2689 zero to disable CPU-hotplug testing.
2691 rcutorture.shuffle_interval= [KNL,BOOT]
2692 Set task-shuffle interval (s). Shuffling tasks
2693 allows some CPUs to go into dyntick-idle mode
2694 during the rcutorture test.
2696 rcutorture.shutdown_secs= [KNL,BOOT]
2697 Set time (s) after boot system shutdown. This
2698 is useful for hands-off automated testing.
2700 rcutorture.stall_cpu= [KNL,BOOT]
2701 Duration of CPU stall (s) to test RCU CPU stall
2702 warnings, zero to disable.
2704 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2705 Time to wait (s) after boot before inducing stall.
2707 rcutorture.stat_interval= [KNL,BOOT]
2708 Time (s) between statistics printk()s.
2710 rcutorture.stutter= [KNL,BOOT]
2711 Time (s) to stutter testing, for example, specifying
2712 five seconds causes the test to run for five seconds,
2713 wait for five seconds, and so on. This tests RCU's
2714 ability to transition abruptly to and from idle.
2716 rcutorture.test_boost= [KNL,BOOT]
2717 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2718 "Maybe" means test if the RCU implementation
2719 under test support RCU priority boosting.
2721 rcutorture.test_boost_duration= [KNL,BOOT]
2722 Duration (s) of each individual boost test.
2724 rcutorture.test_boost_interval= [KNL,BOOT]
2725 Interval (s) between each boost test.
2727 rcutorture.test_no_idle_hz= [KNL,BOOT]
2728 Test RCU's dyntick-idle handling. See also the
2729 rcutorture.shuffle_interval parameter.
2731 rcutorture.torture_type= [KNL,BOOT]
2732 Specify the RCU implementation to test.
2734 rcutorture.verbose= [KNL,BOOT]
2735 Enable additional printk() statements.
2739 Run specified binary instead of /init from the ramdisk,
2740 used for early userspace startup. See initrd.
2743 Format (x86 or x86_64):
2744 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2746 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2748 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2749 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2750 reboot_force is either force or not specified,
2751 reboot_cpu is s[mp]#### with #### being the processor
2752 to be used for rebooting.
2755 [KNL, SMP] Set scheduler's default relax_domain_level.
2756 See Documentation/cgroups/cpusets.txt.
2758 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2760 reservetop= [X86-32]
2762 Reserves a hole at the top of the kernel virtual
2767 Set the amount of memory to reserve for BIOS at
2768 the bottom of the address space.
2770 reset_devices [KNL] Force drivers to reset the underlying device
2771 during initialization.
2774 Specify the partition device for software suspend
2776 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2778 resume_offset= [SWSUSP]
2779 Specify the offset from the beginning of the partition
2780 given by "resume=" at which the swap header is located,
2781 in <PAGE_SIZE> units (needed only for swap files).
2782 See Documentation/power/swsusp-and-swap-files.txt
2784 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2785 read the resume files
2787 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2788 Useful for devices that are detected asynchronously
2789 (e.g. USB and MMC devices).
2791 hibernate= [HIBERNATION]
2792 noresume Don't check if there's a hibernation image
2793 present during boot.
2794 nocompress Don't compress/decompress hibernation images.
2796 retain_initrd [RAM] Keep initrd memory after extraction
2798 rhash_entries= [KNL,NET]
2799 Set number of hash buckets for route cache
2801 riscom8= [HW,SERIAL]
2802 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2804 ro [KNL] Mount root device read-only on boot
2806 root= [KNL] Root filesystem
2807 See name_to_dev_t comment in init/do_mounts.c.
2809 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2810 mount the root filesystem
2812 rootflags= [KNL] Set root filesystem mount option string
2814 rootfstype= [KNL] Set root filesystem type
2816 rootwait [KNL] Wait (indefinitely) for root device to show up.
2817 Useful for devices that are detected asynchronously
2818 (e.g. USB and MMC devices).
2820 rproc_mem=nn[KMG][@address]
2821 [KNL,ARM,CMA] Remoteproc physical memory block.
2822 Memory area to be used by remote processor image,
2825 rw [KNL] Mount root device read-write on boot
2827 S [KNL] Run init in single mode
2830 See drivers/net/irda/sa1100_ir.c.
2832 sbni= [NET] Granch SBNI12 leased line adapter
2834 sched_debug [KNL] Enables verbose scheduler debug messages.
2836 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2837 xtime_lock contention on larger systems, and/or RCU lock
2838 contention on all systems with CONFIG_MAXSMP set.
2839 Format: { "0" | "1" }
2840 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2842 Note: increases power consumption, thus should only be
2843 enabled if running jitter sensitive (HPC/RT) workloads.
2845 security= [SECURITY] Choose a security module to enable at boot.
2846 If this boot parameter is not specified, only the first
2847 security module asking for security registration will be
2848 loaded. An invalid security module name will be treated
2849 as if no module has been chosen.
2851 selinux= [SELINUX] Disable or enable SELinux at boot time.
2852 Format: { "0" | "1" }
2853 See security/selinux/Kconfig help text.
2856 Default value is set via kernel config option.
2857 If enabled at boot time, /selinux/disable can be used
2858 later to disable prior to initial policy load.
2860 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2861 Format: { "0" | "1" }
2862 See security/apparmor/Kconfig help text
2865 Default value is set via kernel config option.
2867 serialnumber [BUGS=X86-32]
2870 Maximal number of shapers.
2872 show_msr= [x86] show boot-time MSR settings
2873 Format: { <integer> }
2874 Show boot-time (BIOS-initialized) MSR settings.
2875 The parameter means the number of CPUs to show,
2876 for example 1 means boot CPU only.
2883 slab_max_order= [MM, SLAB]
2884 Determines the maximum allowed order for slabs.
2885 A high setting may cause OOMs due to memory
2886 fragmentation. Defaults to 1 for systems with
2887 more than 32MB of RAM, 0 otherwise.
2889 slub_debug[=options[,slabs]] [MM, SLUB]
2890 Enabling slub_debug allows one to determine the
2891 culprit if slab objects become corrupted. Enabling
2892 slub_debug can create guard zones around objects and
2893 may poison objects when not in use. Also tracks the
2894 last alloc / free. For more information see
2895 Documentation/vm/slub.txt.
2897 slub_max_order= [MM, SLUB]
2898 Determines the maximum allowed order for slabs.
2899 A high setting may cause OOMs due to memory
2900 fragmentation. For more information see
2901 Documentation/vm/slub.txt.
2903 slub_min_objects= [MM, SLUB]
2904 The minimum number of objects per slab. SLUB will
2905 increase the slab order up to slub_max_order to
2906 generate a sufficiently large slab able to contain
2907 the number of objects indicated. The higher the number
2908 of objects the smaller the overhead of tracking slabs
2909 and the less frequently locks need to be acquired.
2910 For more information see Documentation/vm/slub.txt.
2912 slub_min_order= [MM, SLUB]
2913 Determines the minimum page order for slabs. Must be
2914 lower than slub_max_order.
2915 For more information see Documentation/vm/slub.txt.
2917 slub_nomerge [MM, SLUB]
2918 Disable merging of slabs with similar size. May be
2919 necessary if there is some reason to distinguish
2920 allocs to different slabs. Debug options disable
2921 merging on their own.
2922 For more information see Documentation/vm/slub.txt.
2925 Format: <io1>[,<io2>[,...,<io8>]]
2927 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2928 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2929 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2930 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2931 smsc-ircc2.ircc_irq= [HW] IRQ line
2932 smsc-ircc2.ircc_dma= [HW] DMA channel
2933 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2934 0: Toshiba Satellite 1800 (GP data pin select)
2935 1: Fast pin select (default)
2939 [KNL] Should the soft-lockup detector generate panics.
2942 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2943 See Documentation/laptops/sonypi.txt
2945 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2946 See Documentation/serial/specialix.txt.
2948 spia_io_base= [HW,MTD]
2954 Enabled the stack tracer on boot up.
2956 stacktrace_filter=[function-list]
2957 [FTRACE] Limit the functions that the stack tracer
2958 will trace at boot up. function-list is a comma separated
2959 list of functions. This list can be changed at run
2960 time by the stack_trace_filter file in the debugfs
2961 tracing directory. Note, this enables stack tracing
2962 and the stacktrace above is not needed.
2966 Set the STI (builtin display/keyboard on the HP-PARISC
2967 machines) console (graphic card) which should be used
2968 as the initial boot-console.
2969 See also comment in drivers/video/console/sticore.c.
2972 See comment in drivers/video/console/sticore.c.
2975 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2977 sunrpc.min_resvport=
2978 sunrpc.max_resvport=
2980 SunRPC servers often require that client requests
2981 originate from a privileged port (i.e. a port in the
2982 range 0 < portnr < 1024).
2983 An administrator who wishes to reserve some of these
2984 ports for other uses may adjust the range that the
2985 kernel's sunrpc client considers to be privileged
2986 using these two parameters to set the minimum and
2987 maximum port values.
2991 Control how the NFS server code allocates CPUs to
2992 service thread pools. Depending on how many NICs
2993 you have and where their interrupts are bound, this
2994 option will affect which CPUs will do NFS serving.
2995 Note: this parameter cannot be changed while the
2996 NFS server is running.
2998 auto the server chooses an appropriate mode
2999 automatically using heuristics
3000 global a single global pool contains all CPUs
3001 percpu one pool for each CPU
3002 pernode one pool for each NUMA node (equivalent
3003 to global on non-NUMA machines)
3005 sunrpc.tcp_slot_table_entries=
3006 sunrpc.udp_slot_table_entries=
3008 Sets the upper limit on the number of simultaneous
3009 RPC calls that can be sent from the client to a
3010 server. Increasing these values may allow you to
3011 improve throughput, but will also increase the
3012 amount of memory reserved for use by the client.
3015 [KNL] Enable accounting of swap in memory resource
3016 controller if no parameter or 1 is given or disable
3017 it if 0 is given (See Documentation/cgroups/memory.txt)
3019 swiotlb= [IA-64] Number of I/O TLB slabs
3023 sysfs.deprecated=0|1 [KNL]
3024 Enable/disable old style sysfs layout for old udev
3025 on older distributions. When this option is enabled
3026 very new udev will not work anymore. When this option
3027 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3028 in older udev will not work anymore.
3029 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3030 the kernel configuration.
3032 sysrq_always_enabled
3034 Ignore sysrq setting - this boot parameter will
3035 neutralize any effect of /proc/sys/kernel/sysrq.
3036 Useful for debugging.
3040 test_suspend= [SUSPEND]
3041 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3042 standby suspend) as the system sleep state to briefly
3043 enter during system startup. The system is woken from
3044 this state using a wakeup-capable RTC alarm.
3046 thash_entries= [KNL,NET]
3047 Set number of hash buckets for TCP connection
3049 thermal.act= [HW,ACPI]
3050 -1: disable all active trip points in all thermal zones
3051 <degrees C>: override all lowest active trip points
3053 thermal.crt= [HW,ACPI]
3054 -1: disable all critical trip points in all thermal zones
3055 <degrees C>: override all critical trip points
3057 thermal.nocrt= [HW,ACPI]
3058 Set to disable actions on ACPI thermal zone
3059 critical and hot trip points.
3061 thermal.off= [HW,ACPI]
3062 1: disable ACPI thermal control
3064 thermal.psv= [HW,ACPI]
3065 -1: disable all passive trip points
3066 <degrees C>: override all passive trip points to this
3069 thermal.tzp= [HW,ACPI]
3070 Specify global default ACPI thermal zone polling rate
3071 <deci-seconds>: poll all this frequency
3072 0: no polling (default)
3075 Force threading of all interrupt handlers except those
3076 marked explicitly IRQF_NO_THREAD.
3079 Enable the Transcendent memory driver if built-in.
3081 tmem.cleancache=0|1 [KNL, XEN]
3082 Default is on (1). Disable the usage of the cleancache
3083 API to send anonymous pages to the hypervisor.
3085 tmem.frontswap=0|1 [KNL, XEN]
3086 Default is on (1). Disable the usage of the frontswap
3087 API to send swap pages to the hypervisor. If disabled
3088 the selfballooning and selfshrinking are force disabled.
3090 tmem.selfballooning=0|1 [KNL, XEN]
3091 Default is on (1). Disable the driving of swap pages
3094 tmem.selfshrinking=0|1 [KNL, XEN]
3095 Default is on (1). Partial swapoff that immediately
3096 transfers pages from Xen hypervisor back to the
3097 kernel based on different criteria.
3101 Specify if the kernel should make use of the cpu
3102 topology information if the hardware supports this.
3103 The scheduler will make use of this information and
3104 e.g. base its process migration decisions on it.
3109 tpm_suspend_pcr=[HW,TPM]
3110 Format: integer pcr id
3111 Specify that at suspend time, the tpm driver
3112 should extend the specified pcr with zeros,
3113 as a workaround for some chips which fail to
3114 flush the last written pcr on TPM_SaveState.
3115 This will guarantee that all the other pcrs
3118 trace_buf_size=nn[KMG]
3119 [FTRACE] will set tracing buffer size.
3121 trace_event=[event-list]
3122 [FTRACE] Set and start specified trace events in order
3123 to facilitate early boot debugging.
3124 See also Documentation/trace/events.txt
3126 trace_options=[option-list]
3127 [FTRACE] Enable or disable tracer options at boot.
3128 The option-list is a comma delimited list of options
3129 that can be enabled or disabled just as if you were
3130 to echo the option name into
3132 /sys/kernel/debug/tracing/trace_options
3134 For example, to enable stacktrace option (to dump the
3135 stack trace of each event), add to the command line:
3137 trace_options=stacktrace
3139 See also Documentation/trace/ftrace.txt "trace options"
3143 [FTRACE] enable this option to disable tracing when a
3144 warning is hit. This turns off "tracing_on". Tracing can
3145 be enabled again by echoing '1' into the "tracing_on"
3146 file located in /sys/kernel/debug/tracing/
3148 This option is useful, as it disables the trace before
3149 the WARNING dump is called, which prevents the trace to
3150 be filled with content caused by the warning output.
3152 This option can also be set at run time via the sysctl
3153 option: kernel/traceoff_on_warning
3155 transparent_hugepage=
3157 Format: [always|madvise|never]
3158 Can be used to control the default behavior of the system
3159 with respect to transparent hugepages.
3160 See Documentation/vm/transhuge.txt for more details.
3162 tsc= Disable clocksource stability checks for TSC.
3164 [x86] reliable: mark tsc clocksource as reliable, this
3165 disables clocksource verification at runtime, as well
3166 as the stability checks done at bootup. Used to enable
3167 high-resolution timer mode on older hardware, and in
3168 virtualized environment.
3169 [x86] noirqtime: Do not use TSC to do irq accounting.
3170 Used to run time disable IRQ_TIME_ACCOUNTING on any
3171 platforms where RDTSC is slow and this accounting
3174 turbografx.map[2|3]= [HW,JOY]
3175 TurboGraFX parallel port interface
3177 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3178 See also Documentation/input/joystick-parport.txt
3180 udbg-immortal [PPC] When debugging early kernel crashes that
3181 happen after console_init() and before a proper
3182 console driver takes over, this boot options might
3183 help "seeing" what's going on.
3185 uhash_entries= [KNL,NET]
3186 Set number of hash buckets for UDP/UDP-Lite connections
3189 [USB] Ignore overcurrent events (default N).
3190 Some badly-designed motherboards generate lots of
3191 bogus events, for ports that aren't wired to
3192 anything. Set this parameter to avoid log spamming.
3193 Note that genuine overcurrent events won't be
3197 [X86] Cause panic on unknown NMI.
3199 usbcore.authorized_default=
3200 [USB] Default USB device authorization:
3201 (default -1 = authorized except for wireless USB,
3202 0 = not authorized, 1 = authorized)
3204 usbcore.autosuspend=
3205 [USB] The autosuspend time delay (in seconds) used
3206 for newly-detected USB devices (default 2). This
3207 is the time required before an idle device will be
3208 autosuspended. Devices for which the delay is set
3209 to a negative value won't be autosuspended at all.
3211 usbcore.usbfs_snoop=
3212 [USB] Set to log all usbfs traffic (default 0 = off).
3214 usbcore.blinkenlights=
3215 [USB] Set to cycle leds on hubs (default 0 = off).
3217 usbcore.old_scheme_first=
3218 [USB] Start with the old device initialization
3219 scheme (default 0 = off).
3221 usbcore.usbfs_memory_mb=
3222 [USB] Memory limit (in MB) for buffers allocated by
3223 usbfs (default = 16, 0 = max = 2047).
3225 usbcore.use_both_schemes=
3226 [USB] Try the other device initialization scheme
3227 if the first one fails (default 1 = enabled).
3229 usbcore.initial_descriptor_timeout=
3230 [USB] Specifies timeout for the initial 64-byte
3231 USB_REQ_GET_DESCRIPTOR request in milliseconds
3232 (default 5000 = 5.0 seconds).
3235 [USBHID] The interval which mice are to be polled at.
3237 usb-storage.delay_use=
3238 [UMS] The delay in seconds before a new device is
3239 scanned for Logical Units (default 5).
3242 [UMS] A list of quirks entries to supplement or
3243 override the built-in unusual_devs list. List
3244 entries are separated by commas. Each entry has
3245 the form VID:PID:Flags where VID and PID are Vendor
3246 and Product ID values (4-digit hex numbers) and
3247 Flags is a set of characters, each corresponding
3248 to a common usb-storage quirk flag as follows:
3249 a = SANE_SENSE (collect more than 18 bytes
3251 b = BAD_SENSE (don't collect more than 18
3252 bytes of sense data);
3253 c = FIX_CAPACITY (decrease the reported
3254 device capacity by one sector);
3255 d = NO_READ_DISC_INFO (don't use
3256 READ_DISC_INFO command);
3257 e = NO_READ_CAPACITY_16 (don't use
3258 READ_CAPACITY_16 command);
3259 h = CAPACITY_HEURISTICS (decrease the
3260 reported device capacity by one
3261 sector if the number is odd);
3262 i = IGNORE_DEVICE (don't bind to this
3264 l = NOT_LOCKABLE (don't try to lock and
3265 unlock ejectable media);
3266 m = MAX_SECTORS_64 (don't transfer more
3267 than 64 sectors = 32 KB at a time);
3268 n = INITIAL_READ10 (force a retry of the
3269 initial READ(10) command);
3270 o = CAPACITY_OK (accept the capacity
3271 reported by the device);
3272 p = WRITE_CACHE (the device cache is ON
3274 r = IGNORE_RESIDUE (the device reports
3275 bogus residue values);
3276 s = SINGLE_LUN (the device has only one
3278 w = NO_WP_DETECT (don't test whether the
3279 medium is write-protected).
3280 Example: quirks=0419:aaf5:rl,0421:0433:rc
3282 user_debug= [KNL,ARM]
3284 See arch/arm/Kconfig.debug help text.
3285 1 - undefined instruction events
3287 4 - invalid data aborts
3290 Example: user_debug=31
3293 [X86] Flags controlling user PTE allocations.
3295 nohigh = do not allocate PTE pages in
3296 HIGHMEM regardless of setting
3300 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3301 vdso=1: enable VDSO (default)
3302 vdso=0: disable VDSO mapping
3305 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3306 vdso32=1: enable 32-bit VDSO (default)
3307 vdso32=0: disable 32-bit VDSO mapping
3310 vector=percpu: enable percpu vector domain
3312 video= [FB] Frame buffer configuration
3313 See Documentation/fb/modedb.txt.
3315 video.brightness_switch_enabled= [0,1]
3316 If set to 1, on receiving an ACPI notify event
3317 generated by hotkey, video driver will adjust brightness
3318 level and then send out the event to user space through
3319 the allocated input device; If set to 0, video driver
3320 will only send out the event without touching backlight
3325 [VMMIO] Memory mapped virtio (platform) device.
3327 <size>@<baseaddr>:<irq>[:<id>]
3329 <size> := size (can use standard suffixes
3331 <baseaddr> := physical base address
3332 <irq> := interrupt number (as passed to
3334 <id> := (optional) platform device id
3336 virtio_mmio.device=1K@0x100b0000:48:7
3338 Can be used multiple times for multiple devices.
3340 vga= [BOOT,X86-32] Select a particular video mode
3341 See Documentation/x86/boot.txt and
3342 Documentation/svga.txt.
3343 Use vga=ask for menu.
3344 This is actually a boot loader parameter; the value is
3345 passed to the kernel using a special protocol.
3347 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3348 size of <nn>. This can be used to increase the
3349 minimum size (128MB on x86). It can also be used to
3350 decrease the size and leave more room for directly
3353 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3356 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3359 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3363 Controls the behavior of vsyscalls (i.e. calls to
3364 fixed addresses of 0xffffffffff600x00 from legacy
3365 code). Most statically-linked binaries and older
3366 versions of glibc use these calls. Because these
3367 functions are at fixed addresses, they make nice
3368 targets for exploits that can control RIP.
3370 emulate [default] Vsyscalls turn into traps and are
3371 emulated reasonably safely.
3373 native Vsyscalls are native syscall instructions.
3374 This is a little bit faster than trapping
3375 and makes a few dynamic recompilers work
3376 better than they would in emulation mode.
3377 It also makes exploits much easier to write.
3379 none Vsyscalls don't work at all. This makes
3380 them quite hard to use for exploits but
3381 might break your system.
3383 vt.color= [VT] Default text color.
3384 Format: 0xYX, X = foreground, Y = background.
3385 Default: 0x07 = light gray on black.
3387 vt.cur_default= [VT] Default cursor shape.
3388 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3389 the parameters of the <Esc>[?A;B;Cc escape sequence;
3390 see VGA-softcursor.txt. Default: 2 = underline.
3392 vt.default_blu= [VT]
3393 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3394 Change the default blue palette of the console.
3395 This is a 16-member array composed of values
3398 vt.default_grn= [VT]
3399 Format: <green0>,<green1>,<green2>,...,<green15>
3400 Change the default green palette of the console.
3401 This is a 16-member array composed of values
3404 vt.default_red= [VT]
3405 Format: <red0>,<red1>,<red2>,...,<red15>
3406 Change the default red palette of the console.
3407 This is a 16-member array composed of values
3413 Set system-wide default UTF-8 mode for all tty's.
3414 Default is 1, i.e. UTF-8 mode is enabled for all
3415 newly opened terminals.
3417 vt.global_cursor_default=
3420 Set system-wide default for whether a cursor
3421 is shown on new VTs. Default is -1,
3422 i.e. cursors will be created by default unless
3423 overridden by individual drivers. 0 will hide
3424 cursors, 1 will display them.
3426 vt.italic= [VT] Default color for italic text; 0-15.
3429 vt.underline= [VT] Default color for underlined text; 0-15.
3432 watchdog timers [HW,WDT] For information on watchdog timers,
3433 see Documentation/watchdog/watchdog-parameters.txt
3434 or other driver-specific files in the
3435 Documentation/watchdog/ directory.
3437 workqueue.disable_numa
3438 By default, all work items queued to unbound
3439 workqueues are affine to the NUMA nodes they're
3440 issued on, which results in better behavior in
3441 general. If NUMA affinity needs to be disabled for
3442 whatever reason, this option can be used. Note
3443 that this also can be controlled per-workqueue for
3444 workqueues visible under /sys/bus/workqueue/.
3446 workqueue.power_efficient
3447 Per-cpu workqueues are generally preferred because
3448 they show better performance thanks to cache
3449 locality; unfortunately, per-cpu workqueues tend to
3450 be more power hungry than unbound workqueues.
3452 Enabling this makes the per-cpu workqueues which
3453 were observed to contribute significantly to power
3454 consumption unbound, leading to measurably lower
3455 power usage at the cost of small performance
3458 The default value of this parameter is determined by
3459 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3461 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3462 default x2apic cluster mode on platforms
3465 x86_mrst_timer= [X86-32,APBT]
3466 Choose timer option for x86 Moorestown MID platform.
3467 Two valid options are apbt timer only and lapic timer
3468 plus one apbt timer for broadcast timer.
3469 x86_mrst_timer=apbt_only | lapic_and_apbt
3471 xen_emul_unplug= [HW,X86,XEN]
3472 Unplug Xen emulated devices
3473 Format: [unplug0,][unplug1]
3474 ide-disks -- unplug primary master IDE devices
3475 aux-ide-disks -- unplug non-primary-master IDE devices
3476 nics -- unplug network devices
3477 all -- unplug all emulated devices (NICs and IDE disks)
3478 unnecessary -- unplugging emulated devices is
3479 unnecessary even if the host did not respond to
3481 never -- do not unplug even if version check succeeds
3483 xirc2ps_cs= [NET,PCMCIA]
3485 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3487 ______________________________________________________________________
3491 Add more DRM drivers.