4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 CLK Common clock infrastructure is enabled.
48 CMA Contiguous Memory Area support is enabled.
49 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
51 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
52 EFI EFI Partitioning (GPT) is enabled
53 EIDE EIDE/ATAPI support is enabled.
54 EVM Extended Verification Module
55 FB The frame buffer device is enabled.
56 FTRACE Function tracing enabled.
57 GCOV GCOV profiling is enabled.
58 HW Appropriate hardware is enabled.
59 IA-64 IA-64 architecture is enabled.
60 IMA Integrity measurement architecture is enabled.
61 IOSCHED More than one I/O scheduler is enabled.
62 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
63 IPV6 IPv6 support is enabled.
64 ISAPNP ISA PnP code is enabled.
65 ISDN Appropriate ISDN support is enabled.
66 JOY Appropriate joystick support is enabled.
67 KGDB Kernel debugger support is enabled.
68 KVM Kernel Virtual Machine support is enabled.
69 LIBATA Libata driver is enabled
70 LP Printer support is enabled.
71 LOOP Loopback device support is enabled.
72 M68k M68k architecture is enabled.
73 These options have more detailed description inside of
74 Documentation/m68k/kernel-options.txt.
75 MDA MDA console support is enabled.
76 MIPS MIPS architecture is enabled.
77 MOUSE Appropriate mouse support is enabled.
78 MSI Message Signaled Interrupts (PCI).
79 MTD MTD (Memory Technology Device) support is enabled.
80 NET Appropriate network support is enabled.
81 NUMA NUMA support is enabled.
82 NFS Appropriate NFS support is enabled.
83 OSS OSS sound support is enabled.
84 PV_OPS A paravirtualized kernel is enabled.
85 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
86 PARISC The PA-RISC architecture is enabled.
87 PCI PCI bus support is enabled.
88 PCIE PCI Express support is enabled.
89 PCMCIA The PCMCIA subsystem is enabled.
90 PNP Plug & Play support is enabled.
91 PPC PowerPC architecture is enabled.
92 PPT Parallel port support is enabled.
93 PS2 Appropriate PS/2 support is enabled.
94 RAM RAM disk support is enabled.
95 S390 S390 architecture is enabled.
96 SCSI Appropriate SCSI support is enabled.
97 A lot of drivers have their options described inside
98 the Documentation/scsi/ sub-directory.
99 SECURITY Different security models are enabled.
100 SELINUX SELinux support is enabled.
101 APPARMOR AppArmor support is enabled.
102 SERIAL Serial support is enabled.
103 SH SuperH architecture is enabled.
104 SMP The kernel is an SMP kernel.
105 SPARC Sparc architecture is enabled.
106 SWSUSP Software suspend (hibernation) is enabled.
107 SUSPEND System suspend states are enabled.
108 TPM TPM drivers are enabled.
109 TS Appropriate touchscreen support is enabled.
110 UMS USB Mass Storage support is enabled.
111 USB USB support is enabled.
112 USBHID USB Human Interface Device support is enabled.
113 V4L Video For Linux support is enabled.
114 VMMIO Driver for memory mapped virtio devices is enabled.
115 VGA The VGA console has been enabled.
116 VT Virtual terminal support is enabled.
117 WDT Watchdog support is enabled.
118 XT IBM PC/XT MFM hard disk support is enabled.
119 X86-32 X86-32, aka i386 architecture is enabled.
120 X86-64 X86-64 architecture is enabled.
121 More X86-64 boot options can be found in
122 Documentation/x86/x86_64/boot-options.txt .
123 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
124 XEN Xen support is enabled
126 In addition, the following text indicates that the option:
128 BUGS= Relates to possible processor bugs on the said processor.
129 KNL Is a kernel start-up parameter.
130 BOOT Is a boot loader parameter.
132 Parameters denoted with BOOT are actually interpreted by the boot
133 loader, and have no meaning to the kernel directly.
134 Do not modify the syntax of boot loader parameters without extreme
135 need or coordination with <Documentation/x86/boot.txt>.
137 There are also arch-specific kernel-parameters not documented here.
138 See for example <Documentation/x86/x86_64/boot-options.txt>.
140 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
141 a trailing = on the name of any parameter states that that parameter will
142 be entered as an environment variable, whereas its absence indicates that
143 it will appear as a kernel argument readable via /proc/cmdline by programs
144 running once the system is up.
146 The number of kernel parameters is not limited, but the length of the
147 complete command line (parameters including spaces etc.) is limited to
148 a fixed number of characters. This limit depends on the architecture
149 and is between 256 and 4096 characters. It is defined in the file
150 ./include/asm/setup.h as COMMAND_LINE_SIZE.
152 Finally, the [KMG] suffix is commonly described after a number of kernel
153 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
154 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
155 bytes respectively. Such letter suffixes can also be entirely omitted.
159 Advanced Configuration and Power Interface
160 Format: { force | off | strict | noirq | rsdt }
161 force -- enable ACPI if default was off
162 off -- disable ACPI if default was on
163 noirq -- do not use ACPI for IRQ routing
164 strict -- Be less tolerant of platforms that are not
165 strictly ACPI specification compliant.
166 rsdt -- prefer RSDT over (default) XSDT
167 copy_dsdt -- copy DSDT to memory
169 See also Documentation/power/runtime_pm.txt, pci=noacpi
171 acpi_rsdp= [ACPI,EFI,KEXEC]
172 Pass the RSDP address to the kernel, mostly used
173 on machines running EFI runtime service to boot the
174 second kernel for kdump.
176 acpi_apic_instance= [ACPI, IOAPIC]
178 2: use 2nd APIC table, if available
179 1,0: use 1st APIC table
182 acpi_backlight= [HW,ACPI]
183 acpi_backlight=vendor
185 If set to vendor, prefer vendor specific driver
186 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
187 of the ACPI video.ko driver.
189 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
190 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
192 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
193 debug output. Bits in debug_layer correspond to a
194 _COMPONENT in an ACPI source file, e.g.,
195 #define _COMPONENT ACPI_PCI_COMPONENT
196 Bits in debug_level correspond to a level in
197 ACPI_DEBUG_PRINT statements, e.g.,
198 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
199 The debug_level mask defaults to "info". See
200 Documentation/acpi/debug.txt for more information about
201 debug layers and levels.
203 Enable processor driver info messages:
204 acpi.debug_layer=0x20000000
205 Enable PCI/PCI interrupt routing info messages:
206 acpi.debug_layer=0x400000
207 Enable AML "Debug" output, i.e., stores to the Debug
208 object while interpreting AML:
209 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
210 Enable all messages related to ACPI hardware:
211 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
213 Some values produce so much output that the system is
214 unusable. The "log_buf_len" parameter may be useful
215 if you need to capture more output.
217 acpi_irq_balance [HW,ACPI]
218 ACPI will balance active IRQs
221 acpi_irq_nobalance [HW,ACPI]
222 ACPI will not move active IRQs (default)
225 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
226 Format: <irq>,<irq>...
228 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
230 Format: <irq>,<irq>...
232 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
234 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
235 Format: To spoof as Windows 98: ="Microsoft Windows"
237 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
238 acpi_osi="string1" # add string1
239 acpi_osi="!string2" # remove string2
240 acpi_osi=!* # remove all strings
241 acpi_osi=! # disable all built-in OS vendor
243 acpi_osi= # disable all strings
245 'acpi_osi=!' can be used in combination with single or
246 multiple 'acpi_osi="string1"' to support specific OS
247 vendor string(s). Note that such command can only
248 affect the default state of the OS vendor strings, thus
249 it cannot affect the default state of the feature group
250 strings and the current state of the OS vendor strings,
251 specifying it multiple times through kernel command line
252 is meaningless. This command is useful when one do not
253 care about the state of the feature group strings which
254 should be controlled by the OSPM.
256 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
257 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
258 can make '_OSI("Windows 2000")' TRUE.
260 'acpi_osi=' cannot be used in combination with other
261 'acpi_osi=' command lines, the _OSI method will not
262 exist in the ACPI namespace. NOTE that such command can
263 only affect the _OSI support state, thus specifying it
264 multiple times through kernel command line is also
267 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
270 'acpi_osi=!*' can be used in combination with single or
271 multiple 'acpi_osi="string1"' to support specific
272 string(s). Note that such command can affect the
273 current state of both the OS vendor strings and the
274 feature group strings, thus specifying it multiple times
275 through kernel command line is meaningful. But it may
276 still not able to affect the final state of a string if
277 there are quirks related to this string. This command
278 is useful when one want to control the state of the
279 feature group strings to debug BIOS issues related to
282 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
283 '_OSI("Module Device")' FALSE.
284 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
285 '_OSI("Module Device")' TRUE.
286 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
288 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
290 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
291 they all will make '_OSI("Windows 2000")' TRUE.
294 Override the pmtimer bug detection: force the kernel
295 to assume that this machine's pmtimer latches its value
296 and always returns good values.
298 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
299 Format: { level | edge | high | low }
301 acpi_serialize [HW,ACPI] force serialization of AML methods
303 acpi_skip_timer_override [HW,ACPI]
304 Recognize and ignore IRQ0/pin2 Interrupt Override.
305 For broken nForce2 BIOS resulting in XT-PIC timer.
307 acpi_sleep= [HW,ACPI] Sleep options
308 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
309 old_ordering, nonvs, sci_force_enable }
310 See Documentation/power/video.txt for information on
312 s3_beep is for debugging; it makes the PC's speaker beep
313 as soon as the kernel's real-mode entry point is called.
314 s4_nohwsig prevents ACPI hardware signature from being
315 used during resume from hibernation.
316 old_ordering causes the ACPI 1.0 ordering of the _PTS
317 control method, with respect to putting devices into
318 low power states, to be enforced (the ACPI 2.0 ordering
319 of _PTS is used by default).
320 nonvs prevents the kernel from saving/restoring the
321 ACPI NVS memory during suspend/hibernation and resume.
322 sci_force_enable causes the kernel to set SCI_EN directly
323 on resume from S1/S3 (which is against the ACPI spec,
324 but some broken systems don't work without it).
326 acpi_use_timer_override [HW,ACPI]
327 Use timer override. For some broken Nvidia NF5 boards
328 that require a timer override, but don't have HPET
330 acpi_enforce_resources= [ACPI]
331 { strict | lax | no }
332 Check for resource conflicts between native drivers
333 and ACPI OperationRegions (SystemIO and SystemMemory
334 only). IO ports and memory declared in ACPI might be
335 used by the ACPI subsystem in arbitrary AML code and
336 can interfere with legacy drivers.
337 strict (default): access to resources claimed by ACPI
338 is denied; legacy drivers trying to access reserved
339 resources will fail to bind to device using them.
340 lax: access to resources claimed by ACPI is allowed;
341 legacy drivers trying to access reserved resources
342 will bind successfully but a warning message is logged.
343 no: ACPI OperationRegions are not marked as reserved,
344 no further checks are performed.
346 add_efi_memmap [EFI; X86] Include EFI memory map in
347 kernel's map of available physical RAM.
350 { off | try_unsupported }
351 off: disable AGP support
352 try_unsupported: try to drive unsupported chipsets
353 (may crash computer or cause data corruption)
356 See Documentation/sound/alsa/alsa-parameters.txt
359 Allow the default userspace alignment fault handler
360 behaviour to be specified. Bit 0 enables warnings,
361 bit 1 enables fixups, and bit 2 sends a segfault.
363 align_va_addr= [X86-64]
364 Align virtual addresses by clearing slice [14:12] when
365 allocating a VMA at process creation time. This option
366 gives you up to 3% performance improvement on AMD F15h
367 machines (where it is enabled by default) for a
368 CPU-intensive style benchmark, and it can vary highly in
369 a microbenchmark depending on workload and compiler.
371 32: only for 32-bit processes
372 64: only for 64-bit processes
373 on: enable for both 32- and 64-bit processes
374 off: disable for both 32- and 64-bit processes
376 alloc_snapshot [FTRACE]
377 Allocate the ftrace snapshot buffer on boot up when the
378 main buffer is allocated. This is handy if debugging
379 and you need to use tracing_snapshot() on boot up, and
380 do not want to use tracing_snapshot_alloc() as it needs
381 to be done where GFP_KERNEL allocations are allowed.
383 amd_iommu= [HW,X86-64]
384 Pass parameters to the AMD IOMMU driver in the system.
386 fullflush - enable flushing of IO/TLB entries when
387 they are unmapped. Otherwise they are
388 flushed before they will be reused, which
390 off - do not initialize any AMD IOMMU found in
392 force_isolation - Force device isolation for all
393 devices. The IOMMU driver is not
394 allowed anymore to lift isolation
395 requirements as needed. This option
396 does not override iommu=pt
398 amd_iommu_dump= [HW,X86-64]
399 Enable AMD IOMMU driver option to dump the ACPI table
400 for AMD IOMMU. With this option enabled, AMD IOMMU
401 driver will print ACPI tables for AMD IOMMU during
402 IOMMU initialization.
404 amijoy.map= [HW,JOY] Amiga joystick support
405 Map of devices attached to JOY0DAT and JOY1DAT
407 See also Documentation/input/joystick.txt
409 analog.map= [HW,JOY] Analog joystick and gamepad support
410 Specifies type or capabilities of an analog joystick
411 connected to one of 16 gameports
412 Format: <type1>,<type2>,..<type16>
415 Power management functions (SPARCstation-4/5 + deriv.)
417 Disable APC CPU standby support. SPARCstation-Fox does
418 not play well with APC CPU idle - disable it if you have
419 APC and your system crashes randomly.
421 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
422 Change the output verbosity whilst booting
423 Format: { quiet (default) | verbose | debug }
424 Change the amount of debugging information output
425 when initialising the APIC and IO-APIC components.
428 See Documentation/networking/ipv6.txt.
430 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
431 Limit apic dumping. The parameter defines the maximal
432 number of local apics being dumped. Also it is possible
433 to set it to "all" by meaning -- no limit here.
434 Format: { 1 (default) | 2 | ... | all }.
435 The parameter valid if only apic=debug or
436 apic=verbose is specified.
437 Example: apic=debug show_lapic=all
439 apm= [APM] Advanced Power Management
440 See header of arch/x86/kernel/apm_32.c.
442 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
443 Format: <io>,<irq>,<nodeID>
447 atarimouse= [HW,MOUSE] Atari Mouse
449 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
450 EzKey and similar keyboards
452 atkbd.reset= [HW] Reset keyboard during initialization
454 atkbd.set= [HW] Select keyboard code set
455 Format: <int> (2 = AT (default), 3 = PS/2)
457 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
460 atkbd.softraw= [HW] Choose between synthetic and real raw mode
461 Format: <bool> (0 = real, 1 = synthetic (default))
463 atkbd.softrepeat= [HW]
464 Use software keyboard repeat
466 audit= [KNL] Enable the audit sub-system
467 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
470 audit_backlog_limit= [KNL] Set the audit queue size limit.
471 Format: <int> (must be >=0)
474 baycom_epp= [HW,AX25]
477 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
479 See header of drivers/net/hamradio/baycom_par.c.
481 baycom_ser_fdx= [HW,AX25]
482 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
483 Format: <io>,<irq>,<mode>[,<baud>]
484 See header of drivers/net/hamradio/baycom_ser_fdx.c.
486 baycom_ser_hdx= [HW,AX25]
487 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
488 Format: <io>,<irq>,<mode>
489 See header of drivers/net/hamradio/baycom_ser_hdx.c.
491 blkdevparts= Manual partition parsing of block device(s) for
492 embedded devices based on command line input.
493 See Documentation/block/cmdline-partition.txt
495 boot_delay= Milliseconds to delay each printk during boot.
496 Values larger than 10 seconds (10000) are changed to
500 bootmem_debug [KNL] Enable bootmem allocator debug messages.
502 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
503 bttv.radio= Most important insmod options are available as
505 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
508 bulk_remove=off [PPC] This parameter disables the use of the pSeries
509 firmware feature for flushing multiple hpte entries
512 c101= [NET] Moxa C101 synchronous serial card
514 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
515 Sometimes CPU hardware bugs make them report the cache
516 size incorrectly. The kernel will attempt work arounds
517 to fix known problems, but for some CPUs it is not
518 possible to determine what the correct size should be.
519 This option provides an override for these situations.
521 ccw_timeout_log [S390]
522 See Documentation/s390/CommonIO for details.
524 cgroup_disable= [KNL] Disable a particular controller
525 Format: {name of the controller(s) to disable}
526 {Currently supported controllers - "memory"}
528 checkreqprot [SELINUX] Set initial checkreqprot flag value.
529 Format: { "0" | "1" }
530 See security/selinux/Kconfig help text.
531 0 -- check protection applied by kernel (includes
532 any implied execute protection).
533 1 -- check protection requested by application.
534 Default value is set via a kernel config option.
535 Value can be changed at runtime via
536 /selinux/checkreqprot.
539 See Documentation/s390/CommonIO for details.
542 Keep all clocks already enabled by bootloader on,
543 even if no driver has claimed them. This is useful
544 for debug and development, but should not be
545 needed on a platform with proper driver support.
546 For more information, see Documentation/clk.txt.
548 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
550 Forces specified clocksource (if available) to be used
551 when calculating gettimeofday(). If specified
552 clocksource is not available, it defaults to PIT.
553 Format: { pit | tsc | cyclone | pmtmr }
555 clocksource= Override the default clocksource
557 Override the default clocksource and use the clocksource
558 with the name specified.
559 Some clocksource names to choose from, depending on
561 [all] jiffies (this is the base, fallback clocksource)
563 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
564 pxa_timer,timer3,32k_counter,timer0_1
566 [X86-32] pit,hpet,tsc;
567 scx200_hrt on Geode; cyclone on IBM x440
575 clearcpuid=BITNUM [X86]
576 Disable CPUID feature X for the kernel. See
577 arch/x86/include/asm/cpufeature.h for the valid bit
578 numbers. Note the Linux specific bits are not necessarily
579 stable over kernel options, but the vendor specific
581 Also note that user programs calling CPUID directly
582 or using the feature without checking anything
583 will still see it. This just prevents it from
584 being used by the kernel or shown in /proc/cpuinfo.
585 Also note the kernel might malfunction if you disable
589 Sets the size of kernel global memory area for contiguous
590 memory allocations. For more information, see
591 include/linux/dma-contiguous.h
593 cmo_free_hint= [PPC] Format: { yes | no }
594 Specify whether pages are marked as being inactive
595 when they are freed. This is used in CMO environments
596 to determine OS memory pressure for page stealing by
600 coherent_pool=nn[KMG] [ARM,KNL]
601 Sets the size of memory pool for coherent, atomic dma
602 allocations, by default set to 256K.
604 code_bytes [X86] How many bytes of object code to print
609 com20020= [HW,NET] ARCnet - COM20020 chipset
611 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
613 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
617 ARCnet - COM90xx chipset (memory-mapped buffers)
618 Format: <io>[,<irq>[,<memstart>]]
620 condev= [HW,S390] console device
623 console= [KNL] Output console device and options.
625 tty<n> Use the virtual console device <n>.
629 Use the specified serial port. The options are of
630 the form "bbbbpnf", where "bbbb" is the baud rate,
631 "p" is parity ("n", "o", or "e"), "n" is number of
632 bits, and "f" is flow control ("r" for RTS or
633 omit it). Default is "9600n8".
635 See Documentation/serial-console.txt for more
637 Documentation/networking/netconsole.txt for an
640 uart[8250],io,<addr>[,options]
641 uart[8250],mmio,<addr>[,options]
642 Start an early, polled-mode console on the 8250/16550
643 UART at the specified I/O port or MMIO address,
644 switching to the matching ttyS device later. The
645 options are the same as for ttyS, above.
646 hvc<n> Use the hypervisor console device <n>. This is for
647 both Xen and PowerPC hypervisors.
649 If the device connected to the port is not a TTY but a braille
650 device, prepend "brl," before the device type, for instance
652 For now, only VisioBraille is supported.
654 consoleblank= [KNL] The console blank (screen saver) timeout in
655 seconds. Defaults to 10*60 = 10mins. A value of 0
656 disables the blank timer.
659 [KNL] Change the default value for
660 /proc/<pid>/coredump_filter.
661 See also Documentation/filesystems/proc.txt.
663 cpuidle.off=1 [CPU_IDLE]
664 disable the cpuidle sub-system
666 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
668 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
670 crashkernel=size[KMG][@offset[KMG]]
671 [KNL] Using kexec, Linux can switch to a 'crash kernel'
672 upon panic. This parameter reserves the physical
673 memory region [offset, offset + size] for that kernel
674 image. If '@offset' is omitted, then a suitable offset
675 is selected automatically. Check
676 Documentation/kdump/kdump.txt for further details.
678 crashkernel=range1:size1[,range2:size2,...][@offset]
679 [KNL] Same as above, but depends on the memory
680 in the running system. The syntax of range is
681 start-[end] where start and end are both
682 a memory unit (amount[KMG]). See also
683 Documentation/kdump/kdump.txt for an example.
685 crashkernel=size[KMG],high
686 [KNL, x86_64] range could be above 4G. Allow kernel
687 to allocate physical memory region from top, so could
688 be above 4G if system have more than 4G ram installed.
689 Otherwise memory region will be allocated below 4G, if
691 It will be ignored if crashkernel=X is specified.
692 crashkernel=size[KMG],low
693 [KNL, x86_64] range under 4G. When crashkernel=X,high
694 is passed, kernel could allocate physical memory region
695 above 4G, that cause second kernel crash on system
696 that require some amount of low memory, e.g. swiotlb
697 requires at least 64M+32K low memory. Kernel would
698 try to allocate 72M below 4G automatically.
699 This one let user to specify own low range under 4G
700 for second kernel instead.
701 0: to disable low allocation.
702 It will be ignored when crashkernel=X,high is not used
703 or memory reserved is below 4G.
708 cs89x0_media= [HW,NET]
709 Format: { rj45 | aui | bnc }
712 See header of drivers/s390/block/dasd_devmap.c.
714 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
715 (one device per port)
716 Format: <port#>,<type>
717 See also Documentation/input/joystick-parport.txt
719 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
720 time. See Documentation/dynamic-debug-howto.txt for
721 details. Deprecated, see dyndbg.
723 debug [KNL] Enable kernel debugging (events log level).
726 [KNL] verbose self-tests
728 Print debugging info while doing the locking API
730 We default to 0 (no extra messages), setting it to
731 1 will print _a lot_ more information - normally
732 only useful to kernel developers.
734 debug_objects [KNL] Enable object debugging
737 [KNL] Disable object debugging
739 debug_guardpage_minorder=
740 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
741 parameter allows control of the order of pages that will
742 be intentionally kept free (and hence protected) by the
743 buddy allocator. Bigger value increase the probability
744 of catching random memory corruption, but reduce the
745 amount of memory for normal system use. The maximum
746 possible value is MAX_ORDER/2. Setting this parameter
747 to 1 or 2 should be enough to identify most random
748 memory corruption problems caused by bugs in kernel or
749 driver code when a CPU writes to (or reads from) a
750 random memory location. Note that there exists a class
751 of memory corruptions problems caused by buggy H/W or
752 F/W or by drivers badly programing DMA (basically when
753 memory is written at bus level and the CPU MMU is
754 bypassed) which are not detectable by
755 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
756 tracking down these problems.
758 debugpat [X86] Enable PAT debugging
760 decnet.addr= [HW,NET]
761 Format: <area>[,<node>]
762 See also Documentation/networking/decnet.txt.
765 [same as hugepagesz=] The size of the default
766 HugeTLB page size. This is the size represented by
767 the legacy /proc/ hugepages APIs, used for SHM, and
768 default size when mounting hugetlbfs filesystems.
769 Defaults to the default architecture's huge page size
773 Set number of hash buckets for dentry cache.
776 IO parameters + enable/disable command.
778 digiepca= [HW,SERIAL]
779 See drivers/char/README.epca and
780 Documentation/serial/digiepca.txt.
783 See Documentation/networking/ipv6.txt.
785 disable_ddw [PPC/PSERIES]
786 Disable Dynamic DMA Window support. Use this if
787 to workaround buggy firmware.
790 See Documentation/networking/ipv6.txt.
792 disable_mtrr_cleanup [X86]
793 The kernel tries to adjust MTRR layout from continuous
794 to discrete, to make X server driver able to add WB
795 entry later. This parameter disables that.
797 disable_mtrr_trim [X86, Intel and AMD only]
798 By default the kernel will trim any uncacheable
799 memory out of your available memory pool based on
800 MTRR settings. This parameter disables that behavior,
801 possibly causing your machine to run very slowly.
803 disable_timer_pin_1 [X86]
804 Disable PIN 1 of APIC timer
805 Can be useful to work around chipset bugs.
807 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
808 this option disables the debugging code at boot.
810 dma_debug_entries=<number>
811 This option allows to tune the number of preallocated
812 entries for DMA-API debugging code. One entry is
813 required per DMA-API allocation. Use this if the
814 DMA-API debugging code disables itself because the
815 architectural default is too low.
817 dma_debug_driver=<driver_name>
818 With this option the DMA-API debugging driver
819 filter feature can be enabled at boot time. Just
820 pass the driver to filter for as the parameter.
821 The filter can be disabled or changed to another
822 driver later using sysfs.
824 drm_kms_helper.edid_firmware=[<connector>:]<file>
825 Broken monitors, graphic adapters and KVMs may
826 send no or incorrect EDID data sets. This parameter
827 allows to specify an EDID data set in the
828 /lib/firmware directory that is used instead.
829 Generic built-in EDID data sets are used, if one of
830 edid/1024x768.bin, edid/1280x1024.bin,
831 edid/1680x1050.bin, or edid/1920x1080.bin is given
832 and no file with the same name exists. Details and
833 instructions how to build your own EDID data are
834 available in Documentation/EDID/HOWTO.txt. An EDID
835 data set will only be used for a particular connector,
836 if its name and a colon are prepended to the EDID
841 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
842 module.dyndbg[="val"]
843 Enable debug messages at boot time. See
844 Documentation/dynamic-debug-howto.txt for details.
846 earlycon= [KNL] Output early console device and options.
847 uart[8250],io,<addr>[,options]
848 uart[8250],mmio,<addr>[,options]
849 uart[8250],mmio32,<addr>[,options]
850 Start an early, polled-mode console on the 8250/16550
851 UART at the specified I/O port or MMIO address.
852 MMIO inter-register address stride is either 8-bit
853 (mmio) or 32-bit (mmio32).
854 The options are the same as for ttyS, above.
856 earlyprintk= [X86,SH,BLACKFIN,ARM]
859 earlyprintk=serial[,ttySn[,baudrate]]
860 earlyprintk=serial[,0x...[,baudrate]]
861 earlyprintk=ttySn[,baudrate]
862 earlyprintk=dbgp[debugController#]
864 earlyprintk is useful when the kernel crashes before
865 the normal console is initialized. It is not enabled by
866 default because it has some cosmetic problems.
868 Append ",keep" to not disable it when the real console
871 Only vga or serial or usb debug port at a time.
873 Currently only ttyS0 and ttyS1 may be specified by
874 name. Other I/O ports may be explicitly specified
875 on some architectures (x86 and arm at least) by
876 replacing ttySn with an I/O port address, like this:
877 earlyprintk=serial,0x1008,115200
878 You can find the port for a given device in
879 /proc/tty/driver/serial:
880 2: uart:ST16650V2 port:00001008 irq:18 ...
882 Interaction with the standard serial driver is not
885 The VGA output is eventually overwritten by the real
888 The xen output can only be used by Xen PV guests.
890 ekgdboc= [X86,KGDB] Allow early kernel console debugging
893 This is designed to be used in conjunction with
894 the boot argument: earlyprintk=vga
897 Format: {"off" | "on" | "skip[mbr]"}
899 efi_no_storage_paranoia [EFI; X86]
900 Using this parameter you can use more than 50% of
901 your efi variable storage. Use this parameter only if
902 you are really sure that your UEFI does sane gc and
903 fulfills the spec otherwise your board may brick.
905 eisa_irq_edge= [PARISC,HW]
906 See header of drivers/parisc/eisa.c.
909 See comment before function elanfreq_setup() in
910 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
913 Format: {"cfq" | "deadline" | "noop"}
914 See Documentation/block/cfq-iosched.txt and
915 Documentation/block/deadline-iosched.txt for details.
917 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
918 Specifies physical address of start of kernel core
919 image elf header and optionally the size. Generally
920 kexec loader will pass this option to capture kernel.
921 See Documentation/kdump/kdump.txt for details.
923 enable_mtrr_cleanup [X86]
924 The kernel tries to adjust MTRR layout from continuous
925 to discrete, to make X server driver able to add WB
926 entry later. This parameter enables that.
928 enable_timer_pin_1 [X86]
929 Enable PIN 1 of APIC timer
930 Can be useful to work around chipset bugs
931 (in particular on some ATI chipsets).
932 The kernel tries to set a reasonable default.
934 enforcing [SELINUX] Set initial enforcing status.
936 See security/selinux/Kconfig help text.
937 0 -- permissive (log only, no denials).
938 1 -- enforcing (deny and log).
940 Value can be changed at runtime via /selinux/enforce.
943 Disable Error Record Serialization Table (ERST)
946 ether= [HW,NET] Ethernet cards parameters
947 This option is obsoleted by the "netdev=" option, which
948 has equivalent usage. See its documentation for details.
952 Permit 'security.evm' to be updated regardless of
953 current integrity status.
957 fail_make_request=[KNL]
958 General fault injection mechanism.
959 Format: <interval>,<probability>,<space>,<times>
960 See also Documentation/fault-injection/.
963 See Documentation/blockdev/floppy.txt.
965 force_pal_cache_flush
966 [IA-64] Avoid check_sal_cache_flush which may hang on
967 buggy SAL_CACHE_FLUSH implementations. Using this
968 parameter will force ia64_sal_cache_flush to call
969 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
972 [FTRACE] will set and start the specified tracer
973 as early as possible in order to facilitate early
976 ftrace_dump_on_oops[=orig_cpu]
977 [FTRACE] will dump the trace buffers on oops.
978 If no parameter is passed, ftrace will dump
979 buffers of all CPUs, but if you pass orig_cpu, it will
980 dump only the buffer of the CPU that triggered the
983 ftrace_filter=[function-list]
984 [FTRACE] Limit the functions traced by the function
985 tracer at boot up. function-list is a comma separated
986 list of functions. This list can be changed at run
987 time by the set_ftrace_filter file in the debugfs
990 ftrace_notrace=[function-list]
991 [FTRACE] Do not trace the functions specified in
992 function-list. This list can be changed at run time
993 by the set_ftrace_notrace file in the debugfs
996 ftrace_graph_filter=[function-list]
997 [FTRACE] Limit the top level callers functions traced
998 by the function graph tracer at boot up.
999 function-list is a comma separated list of functions
1000 that can be changed at run time by the
1001 set_graph_function file in the debugfs tracing directory.
1004 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1005 support via parallel port (up to 5 devices per port)
1006 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1007 See also Documentation/input/joystick-parport.txt
1011 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1015 gcov_persist= [GCOV] When non-zero (default), profiling data for
1016 kernel modules is saved and remains accessible via
1017 debugfs, even when the module is unloaded/reloaded.
1018 When zero, profiling data is discarded and associated
1019 debugfs files are removed at module unload time.
1021 gpt [EFI] Forces disk with valid GPT signature but
1022 invalid Protective MBR to be treated as GPT.
1024 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1025 the "Enable 0" bit of the configuration register.
1028 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1029 the "Enable 0" bit of the configuration register.
1032 grcan.select= [HW] Select which physical interface to use.
1035 grcan.txsize= [HW] Sets the size of the tx buffer.
1036 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1038 grcan.rxsize= [HW] Sets the size of the rx buffer.
1039 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1042 hashdist= [KNL,NUMA] Large hashes allocated during boot
1043 are distributed across NUMA nodes. Defaults on
1044 for 64-bit NUMA, off otherwise.
1045 Format: 0 | 1 (for off | on)
1047 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1049 hd= [EIDE] (E)IDE hard drive subsystem geometry
1050 Format: <cyl>,<head>,<sect>
1053 Disable Hardware Error Source Table (HEST) support;
1054 corresponding firmware-first mode error processing
1055 logic will be disabled.
1057 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1058 size of <nn>. This works even on boxes that have no
1059 highmem otherwise. This also works to reduce highmem
1060 size on bigger boxes.
1062 highres= [KNL] Enable/disable high resolution timer mode.
1063 Valid parameters: "on", "off"
1067 See Documentation/isdn/README.HiSax.
1071 hpet= [X86-32,HPET] option to control HPET usage
1072 Format: { enable (default) | disable | force |
1074 disable: disable HPET and use PIT instead
1075 force: allow force enabled of undocumented chips (ICH4,
1077 verbose: show contents of HPET registers during setup
1079 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1080 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1081 On x86-64 and powerpc, this option can be specified
1082 multiple times interleaved with hugepages= to reserve
1083 huge pages of different sizes. Valid pages sizes on
1084 x86-64 are 2M (when the CPU supports "pse") and 1G
1085 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1086 Note that 1GB pages can only be allocated at boot time
1087 using hugepages= and not freed afterwards.
1089 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1090 terminal devices. Valid values: 0..8
1091 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1092 If specified, z/VM IUCV HVC accepts connections
1093 from listed z/VM user IDs only.
1095 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1096 hardware thread id mappings.
1097 Format: <cpu>:<hwthread>
1100 Do not unregister boot console at start. This is only
1101 useful for debugging when something happens in the window
1102 between unregistering the boot console and initializing
1105 i2c_bus= [HW] Override the default board specific I2C bus speed
1106 or register an additional I2C bus that is not
1107 registered from board initialization code.
1111 i8042.debug [HW] Toggle i8042 debug mode
1112 i8042.direct [HW] Put keyboard port into non-translated mode
1113 i8042.dumbkbd [HW] Pretend that controller can only read data from
1114 keyboard and cannot control its state
1115 (Don't attempt to blink the leds)
1116 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1117 i8042.nokbd [HW] Don't check/create keyboard port
1118 i8042.noloop [HW] Disable the AUX Loopback command while probing
1120 i8042.nomux [HW] Don't check presence of an active multiplexing
1122 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1124 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1125 i8042.reset [HW] Reset the controller during init and cleanup
1126 i8042.unlock [HW] Unlock (ignore) the keylock
1130 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1131 indicates that the driver is running on unsupported
1133 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1134 does not match list of supported models.
1136 [HW] Report power status in /proc/i8k
1137 (disabled by default)
1138 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1141 i915.invert_brightness=
1142 [DRM] Invert the sense of the variable that is used to
1143 set the brightness of the panel backlight. Normally a
1144 brightness value of 0 indicates backlight switched off,
1145 and the maximum of the brightness value sets the backlight
1146 to maximum brightness. If this parameter is set to 0
1147 (default) and the machine requires it, or this parameter
1148 is set to 1, a brightness value of 0 sets the backlight
1149 to maximum brightness, and the maximum of the brightness
1150 value switches the backlight off.
1151 -1 -- never invert brightness
1152 0 -- machine default
1153 1 -- force brightness inversion
1156 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1158 ide-core.nodma= [HW] (E)IDE subsystem
1159 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1160 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1161 .cdrom .chs .ignore_cable are additional options
1162 See Documentation/ide/ide.txt.
1164 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1165 Claim all unknown PCI IDE storage controllers.
1168 Format: idle=poll, idle=halt, idle=nomwait
1169 Poll forces a polling idle loop that can slightly
1170 improve the performance of waking up a idle CPU, but
1171 will use a lot of power and make the system run hot.
1173 idle=halt: Halt is forced to be used for CPU idle.
1174 In such case C2/C3 won't be used again.
1175 idle=nomwait: Disable mwait for CPU C-states
1177 ignore_loglevel [KNL]
1178 Ignore loglevel setting - this will print /all/
1179 kernel messages to the console. Useful for debugging.
1180 We also add it as printk module parameter, so users
1181 could change it dynamically, usually by
1182 /sys/module/printk/parameters/ignore_loglevel.
1184 ihash_entries= [KNL]
1185 Set number of hash buckets for inode cache.
1187 ima_appraise= [IMA] appraise integrity measurements
1188 Format: { "off" | "enforce" | "fix" }
1191 ima_appraise_tcb [IMA]
1192 The builtin appraise policy appraises all files
1196 Format: { "sha1" | "md5" }
1200 Load a policy which meets the needs of the Trusted
1201 Computing Base. This means IMA will measure all
1202 programs exec'd, files mmap'd for exec, and all files
1203 opened for read by uid=0.
1207 Run specified binary instead of /sbin/init as init
1210 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1211 for working out where the kernel is dying during
1214 initrd= [BOOT] Specify the location of the initial ramdisk
1216 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1219 int_pln_enable [x86] Enable power limit notification interrupt
1221 integrity_audit=[IMA]
1222 Format: { "0" | "1" }
1223 0 -- basic integrity auditing messages. (Default)
1224 1 -- additional integrity auditing messages.
1226 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1228 Enable intel iommu driver.
1230 Disable intel iommu driver.
1231 igfx_off [Default Off]
1232 By default, gfx is mapped as normal device. If a gfx
1233 device has a dedicated DMAR unit, the DMAR unit is
1234 bypassed by not enabling DMAR with this option. In
1235 this case, gfx device will use physical address for
1238 With this option iommu will not optimize to look
1239 for io virtual address below 32-bit forcing dual
1240 address cycle on pci bus for cards supporting greater
1241 than 32-bit addressing. The default is to look
1242 for translation below 32-bit and if not available
1243 then look in the higher range.
1244 strict [Default Off]
1245 With this option on every unmap_single operation will
1246 result in a hardware IOTLB flush operation as opposed
1247 to batching them for performance.
1248 sp_off [Default Off]
1249 By default, super page will be supported if Intel IOMMU
1250 has the capability. With this option, super page will
1253 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1254 0 disables intel_idle and fall back on acpi_idle.
1255 1 to 6 specify maximum depth of C-state.
1259 Do not enable intel_pstate as the default
1260 scaling driver for the supported processors
1262 intremap= [X86-64, Intel-IOMMU]
1263 on enable Interrupt Remapping (default)
1264 off disable Interrupt Remapping
1265 nosid disable Source ID checking
1267 BIOS x2APIC opt-out request will be ignored
1269 iomem= Disable strict checking of access to MMIO memory
1270 strict regions from userspace.
1287 io7= [HW] IO7 for Marvel based alpha systems
1288 See comment before marvel_specify_io7 in
1289 arch/alpha/kernel/core_marvel.c.
1291 io_delay= [X86] I/O delay method
1293 Standard port 0x80 based delay
1295 Alternate port 0xed based delay (needed on some systems)
1297 Simple two microseconds delay
1302 See Documentation/filesystems/nfs/nfsroot.txt.
1304 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1305 See comment before ip2_setup() in
1306 drivers/char/ip2/ip2base.c.
1309 When an interrupt is not handled search all handlers
1310 for it. Intended to get systems with badly broken
1314 When an interrupt is not handled search all handlers
1315 for it. Also check all handlers each timer
1316 interrupt. Intended to get systems with badly broken
1320 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1322 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1324 <cpu number>,...,<cpu number>
1326 <cpu number>-<cpu number>
1327 (must be a positive range in ascending order)
1329 <cpu number>,...,<cpu number>-<cpu number>
1331 This option can be used to specify one or more CPUs
1332 to isolate from the general SMP balancing and scheduling
1333 algorithms. You can move a process onto or off an
1334 "isolated" CPU via the CPU affinity syscalls or cpuset.
1335 <cpu number> begins at 0 and the maximum value is
1336 "number of CPUs in system - 1".
1338 This option is the preferred way to isolate CPUs. The
1339 alternative -- manually setting the CPU mask of all
1340 tasks in the system -- can cause problems and
1341 suboptimal load balancer performance.
1345 ivrs_ioapic [HW,X86_64]
1346 Provide an override to the IOAPIC-ID<->DEVICE-ID
1347 mapping provided in the IVRS ACPI table. For
1348 example, to map IOAPIC-ID decimal 10 to
1349 PCI device 00:14.0 write the parameter as:
1350 ivrs_ioapic[10]=00:14.0
1352 ivrs_hpet [HW,X86_64]
1353 Provide an override to the HPET-ID<->DEVICE-ID
1354 mapping provided in the IVRS ACPI table. For
1355 example, to map HPET-ID decimal 0 to
1356 PCI device 00:14.0 write the parameter as:
1357 ivrs_hpet[0]=00:14.0
1359 js= [HW,JOY] Analog joystick
1360 See Documentation/input/joystick.txt.
1364 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1365 specifies the amount of memory usable by the kernel
1366 for non-movable allocations. The requested amount is
1367 spread evenly throughout all nodes in the system. The
1368 remaining memory in each node is used for Movable
1369 pages. In the event, a node is too small to have both
1370 kernelcore and Movable pages, kernelcore pages will
1371 take priority and other nodes will have a larger number
1372 of Movable pages. The Movable zone is used for the
1373 allocation of pages that may be reclaimed or moved
1374 by the page migration subsystem. This means that
1375 HugeTLB pages may not be allocated from this zone.
1376 Note that allocations like PTEs-from-HighMem still
1377 use the HighMem zone if it exists, and the Normal
1378 zone if it does not.
1380 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1381 Format: <Controller#>[,poll interval]
1382 The controller # is the number of the ehci usb debug
1383 port as it is probed via PCI. The poll interval is
1384 optional and is the number seconds in between
1385 each poll cycle to the debug port in case you need
1386 the functionality for interrupting the kernel with
1387 gdb or control-c on the dbgp connection. When
1388 not using this parameter you use sysrq-g to break into
1389 the kernel debugger.
1391 kgdboc= [KGDB,HW] kgdb over consoles.
1392 Requires a tty driver that supports console polling,
1393 or a supported polling keyboard driver (non-usb).
1394 Serial only format: <serial_device>[,baud]
1395 keyboard only format: kbd
1396 keyboard and serial format: kbd,<serial_device>[,baud]
1397 Optional Kernel mode setting:
1398 kms, kbd format: kms,kbd
1399 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1401 kgdbwait [KGDB] Stop kernel execution and enter the
1402 kernel debugger at the earliest opportunity.
1404 kmac= [MIPS] korina ethernet MAC address.
1405 Configure the RouterBoard 532 series on-chip
1406 Ethernet adapter MAC address.
1408 kmemleak= [KNL] Boot-time kmemleak enable/disable
1409 Valid arguments: on, off
1412 kstack=N [X86] Print N words from the kernel stack
1415 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1416 Default is 0 (don't ignore, but inject #GP)
1418 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1422 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1423 Default is 1 (enabled)
1425 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1427 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1429 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1430 (virtualized MMU) support on capable Intel chips.
1431 Default is 1 (enabled)
1433 kvm-intel.emulate_invalid_guest_state=
1434 [KVM,Intel] Enable emulation of invalid guest states
1435 Default is 0 (disabled)
1437 kvm-intel.flexpriority=
1438 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1439 Default is 1 (enabled)
1442 [KVM,Intel] Enable VMX nesting (nVMX).
1443 Default is 0 (disabled)
1445 kvm-intel.unrestricted_guest=
1446 [KVM,Intel] Disable unrestricted guest feature
1447 (virtualized real and unpaged mode) on capable
1448 Intel chips. Default is 1 (enabled)
1450 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1451 feature (tagged TLBs) on capable Intel chips.
1452 Default is 1 (enabled)
1458 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1461 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1462 value for LAPIC timer one-shot implementation. Default
1463 back to the programmable timer unit in the LAPIC.
1465 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1468 libata.dma= [LIBATA] DMA control
1469 libata.dma=0 Disable all PATA and SATA DMA
1470 libata.dma=1 PATA and SATA Disk DMA only
1471 libata.dma=2 ATAPI (CDROM) DMA only
1472 libata.dma=4 Compact Flash DMA only
1473 Combinations also work, so libata.dma=3 enables DMA
1474 for disks and CDROMs, but not CFs.
1476 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1477 libata.ignore_hpa=0 keep BIOS limits (default)
1478 libata.ignore_hpa=1 ignore limits, using full disk
1480 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1484 libata.force= [LIBATA] Force configurations. The format is comma
1485 separated list of "[ID:]VAL" where ID is
1486 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1487 matching port, link or device. Basically, it matches
1488 the ATA ID string printed on console by libata. If
1489 the whole ID part is omitted, the last PORT and DEVICE
1490 values are used. If ID hasn't been specified yet, the
1491 configuration applies to all ports, links and devices.
1493 If only DEVICE is omitted, the parameter applies to
1494 the port and all links and devices behind it. DEVICE
1495 number of 0 either selects the first device or the
1496 first fan-out link behind PMP device. It does not
1497 select the host link. DEVICE number of 15 selects the
1498 host link and device attached to it.
1500 The VAL specifies the configuration to force. As long
1501 as there's no ambiguity shortcut notation is allowed.
1502 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1503 The following configurations can be forced.
1505 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1506 Any ID with matching PORT is used.
1508 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1510 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1511 udma[/][16,25,33,44,66,100,133] notation is also
1514 * [no]ncq: Turn on or off NCQ.
1516 * nohrst, nosrst, norst: suppress hard, soft
1519 * rstonce: only attempt one reset during
1520 hot-unplug link recovery
1522 * dump_id: dump IDENTIFY data.
1524 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1526 If there are multiple matching configurations changing
1527 the same attribute, the last one is used.
1529 memblock=debug [KNL] Enable memblock debug messages.
1531 load_ramdisk= [RAM] List of ramdisks to load from floppy
1532 See Documentation/blockdev/ramdisk.txt.
1534 lockd.nlm_grace_period=P [NFS] Assign grace period.
1537 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1540 lockd.nlm_timeout=T [NFS] Assign timeout value.
1543 lockd.nlm_udpport=M [NFS] Assign UDP port.
1546 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1549 loglevel= All Kernel Messages with a loglevel smaller than the
1550 console loglevel will be printed to the console. It can
1551 also be changed with klogd or other programs. The
1552 loglevels are defined as follows:
1554 0 (KERN_EMERG) system is unusable
1555 1 (KERN_ALERT) action must be taken immediately
1556 2 (KERN_CRIT) critical conditions
1557 3 (KERN_ERR) error conditions
1558 4 (KERN_WARNING) warning conditions
1559 5 (KERN_NOTICE) normal but significant condition
1560 6 (KERN_INFO) informational
1561 7 (KERN_DEBUG) debug-level messages
1563 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1564 in bytes. n must be a power of two. The default
1565 size is set in the kernel config file.
1567 logo.nologo [FB] Disables display of the built-in Linux logo.
1568 This may be used to provide more screen space for
1569 kernel log messages and is useful when debugging
1570 kernel boot problems.
1572 lp=0 [LP] Specify parallel ports to use, e.g,
1573 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1574 lp=reset first parallel port). 'lp=0' disables the
1575 lp=auto printer driver. 'lp=reset' (which can be
1576 specified in addition to the ports) causes
1577 attached printers to be reset. Using
1578 lp=port1,port2,... specifies the parallel ports
1579 to associate lp devices with, starting with
1580 lp0. A port specification may be 'none' to skip
1581 that lp device, or a parport name such as
1582 'parport0'. Specifying 'lp=auto' instead of a
1583 port specification list means that device IDs
1584 from each port should be examined, to see if
1585 an IEEE 1284-compliant printer is attached; if
1586 so, the driver will manage that printer.
1587 See also header of drivers/char/lp.c.
1590 Sets loops_per_jiffy to given constant, thus avoiding
1591 time-consuming boot-time autodetection (up to 250 ms per
1592 CPU). 0 enables autodetection (default). To determine
1593 the correct value for your kernel, boot with normal
1594 autodetection and see what value is printed. Note that
1595 on SMP systems the preset will be applied to all CPUs,
1596 which is likely to cause problems if your CPUs need
1597 significantly divergent settings. An incorrect value
1598 will cause delays in the kernel to be wrong, leading to
1599 unpredictable I/O errors and other breakage. Although
1600 unlikely, in the extreme case this might damage your
1604 Format: <io>,<irq>,<dma>
1606 machvec= [IA-64] Force the use of a particular machine-vector
1607 (machvec) in a generic kernel.
1608 Example: machvec=hpzx1_swiotlb
1610 machtype= [Loongson] Share the same kernel image file between different
1612 Example: machtype=lemote-yeeloong-2f-7inch
1614 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1615 than or equal to this physical address is ignored.
1617 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1618 should make use of. maxcpus=n : n >= 0 limits the
1619 kernel to using 'n' processors. n=0 is a special case,
1620 it is equivalent to "nosmp", which also disables
1623 max_loop= [LOOP] The number of loop block devices that get
1624 (loop.max_loop) unconditionally pre-created at init time. The default
1625 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1626 of statically allocating a predefined number, loop
1627 devices can be requested on-demand with the
1628 /dev/loop-control interface.
1630 mce [X86-32] Machine Check Exception
1632 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1634 md= [HW] RAID subsystems devices and level
1635 See Documentation/md.txt.
1638 Format: <first>,<last>
1639 Specifies range of consoles to be captured by the MDA.
1641 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1642 Amount of memory to be used when the kernel is not able
1643 to see the whole system memory or for test.
1644 [X86] Work as limiting max address. Use together
1645 with memmap= to avoid physical address space collisions.
1646 Without memmap= PCI devices could be placed at addresses
1647 belonging to unused RAM.
1649 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1653 [KNL,SH] Allow user to override the default size for
1654 per-device physically contiguous DMA buffers.
1656 memmap=exactmap [KNL,X86] Enable setting of an exact
1657 E820 memory map, as specified by the user.
1658 Such memmap=exactmap lines can be constructed based on
1659 BIOS output or other requirements. See the memmap=nn@ss
1662 memmap=nn[KMG]@ss[KMG]
1663 [KNL] Force usage of a specific region of memory
1664 Region of memory to be used, from ss to ss+nn.
1666 memmap=nn[KMG]#ss[KMG]
1667 [KNL,ACPI] Mark specific memory as ACPI data.
1668 Region of memory to be used, from ss to ss+nn.
1670 memmap=nn[KMG]$ss[KMG]
1671 [KNL,ACPI] Mark specific memory as reserved.
1672 Region of memory to be used, from ss to ss+nn.
1673 Example: Exclude memory from 0x18690000-0x1869ffff
1674 memmap=64K$0x18690000
1676 memmap=0x10000$0x18690000
1678 memory_corruption_check=0/1 [X86]
1679 Some BIOSes seem to corrupt the first 64k of
1680 memory when doing things like suspend/resume.
1681 Setting this option will scan the memory
1682 looking for corruption. Enabling this will
1683 both detect corruption and prevent the kernel
1684 from using the memory being corrupted.
1685 However, its intended as a diagnostic tool; if
1686 repeatable BIOS-originated corruption always
1687 affects the same memory, you can use memmap=
1688 to prevent the kernel from using that memory.
1690 memory_corruption_check_size=size [X86]
1691 By default it checks for corruption in the low
1692 64k, making this memory unavailable for normal
1693 use. Use this parameter to scan for
1694 corruption in more or less memory.
1696 memory_corruption_check_period=seconds [X86]
1697 By default it checks for corruption every 60
1698 seconds. Use this parameter to check at some
1699 other rate. 0 disables periodic checking.
1701 memtest= [KNL,X86] Enable memtest
1703 default : 0 <disable>
1704 Specifies the number of memtest passes to be
1705 performed. Each pass selects another test
1706 pattern from a given set of patterns. Memtest
1707 fills the memory with this pattern, validates
1708 memory contents and reserves bad memory
1709 regions that are detected.
1711 meye.*= [HW] Set MotionEye Camera parameters
1712 See Documentation/video4linux/meye.txt.
1714 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1715 Multi-Function General Purpose Timers on AMD Geode
1718 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1719 the BIOS has incorrectly applied a workaround. TinyBIOS
1720 version 0.98 is known to be affected, 0.99 fixes the
1721 problem by letting the user disable the workaround.
1725 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1726 physical address is ignored.
1728 mini2440= [ARM,HW,KNL]
1729 Format:[0..2][b][c][t]
1731 MINI2440 configuration specification:
1732 0 - The attached screen is the 3.5" TFT
1733 1 - The attached screen is the 7" TFT
1734 2 - The VGA Shield is attached (1024x768)
1735 Leaving out the screen size parameter will not load
1736 the TFT driver, and the framebuffer will be left
1738 b - Enable backlight. The TFT backlight pin will be
1739 linked to the kernel VESA blanking code and a GPIO
1740 LED. This parameter is not necessary when using the
1742 c - Enable the s3c camera interface.
1743 t - Reserved for enabling touchscreen support. The
1744 touchscreen support is not enabled in the mainstream
1745 kernel as of 2.6.30, a preliminary port can be found
1746 in the "bleeding edge" mini2440 support kernel at
1747 http://repo.or.cz/w/linux-2.6/mini2440.git
1750 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1751 parameter allows control of the logging verbosity for
1752 the additional memory initialisation checks. A value
1753 of 0 disables mminit logging and a level of 4 will
1754 log everything. Information is printed at KERN_DEBUG
1755 so loglevel=8 may also need to be specified.
1758 [KNL] When CONFIG_MODULE_SIG is set, this means that
1759 modules without (valid) signatures will fail to load.
1760 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1761 is always true, so this option does nothing.
1764 [MOUSE] Maximum time between finger touching and
1765 leaving touchpad surface for touch to be considered
1766 a tap and be reported as a left button click (for
1767 touchpads working in absolute mode only).
1769 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1770 reporting absolute coordinates, such as tablets
1771 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1772 reporting absolute coordinates, such as tablets
1774 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1775 is similar to kernelcore except it specifies the
1776 amount of memory used for migratable allocations.
1777 If both kernelcore and movablecore is specified,
1778 then kernelcore will be at *least* the specified
1779 value but may be more. If movablecore on its own
1780 is specified, the administrator must be careful
1781 that the amount of memory usable for all allocations
1784 MTD_Partition= [MTD]
1785 Format: <name>,<region-number>,<size>,<offset>
1787 MTD_Region= [MTD] Format:
1788 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1791 See drivers/mtd/cmdlinepart.c.
1793 multitce=off [PPC] This parameter disables the use of the pSeries
1794 firmware feature for updating multiple TCE entries
1797 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1799 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1801 boundary - index of last SLC block on Flex-OneNAND.
1802 The remaining blocks are configured as MLC blocks.
1803 lock - Configure if Flex-OneNAND boundary should be locked.
1804 Once locked, the boundary cannot be changed.
1805 1 indicates lock status, 0 indicates unlock status.
1808 ARM/S3C2412 JIVE boot control
1810 See arch/arm/mach-s3c2412/mach-jive.c
1812 mtouchusb.raw_coordinates=
1813 [HW] Make the MicroTouch USB driver use raw coordinates
1814 ('y', default) or cooked coordinates ('n')
1816 mtrr_chunk_size=nn[KMG] [X86]
1817 used for mtrr cleanup. It is largest continuous chunk
1818 that could hold holes aka. UC entries.
1820 mtrr_gran_size=nn[KMG] [X86]
1821 Used for mtrr cleanup. It is granularity of mtrr block.
1823 Large value could prevent small alignment from
1826 mtrr_spare_reg_nr=n [X86]
1828 Range: 0,7 : spare reg number
1830 Used for mtrr cleanup. It is spare mtrr entries number.
1831 Set to 2 or more if your graphical card needs more.
1833 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1835 netdev= [NET] Network devices parameters
1836 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1837 Note that mem_start is often overloaded to mean
1838 something different and driver-specific.
1839 This usage is only documented in each driver source
1843 [NETFILTER] Enable connection tracking flow accounting
1844 0 to disable accounting
1845 1 to enable accounting
1848 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1849 See Documentation/filesystems/nfs/nfsroot.txt.
1851 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1852 See Documentation/filesystems/nfs/nfsroot.txt.
1854 nfsrootdebug [NFS] enable nfsroot debugging messages.
1855 See Documentation/filesystems/nfs/nfsroot.txt.
1857 nfs.callback_tcpport=
1858 [NFS] set the TCP port on which the NFSv4 callback
1859 channel should listen.
1862 [NFS] sets the pathname to the program which is used
1863 to update the NFS client cache entries.
1865 nfs.cache_getent_timeout=
1866 [NFS] sets the timeout after which an attempt to
1867 update a cache entry is deemed to have failed.
1869 nfs.idmap_cache_timeout=
1870 [NFS] set the maximum lifetime for idmapper cache
1874 [NFS] enable 64-bit inode numbers.
1875 If zero, the NFS client will fake up a 32-bit inode
1876 number for the readdir() and stat() syscalls instead
1877 of returning the full 64-bit number.
1878 The default is to return 64-bit inode numbers.
1880 nfs.max_session_slots=
1881 [NFSv4.1] Sets the maximum number of session slots
1882 the client will attempt to negotiate with the server.
1883 This limits the number of simultaneous RPC requests
1884 that the client can send to the NFSv4.1 server.
1885 Note that there is little point in setting this
1886 value higher than the max_tcp_slot_table_limit.
1888 nfs.nfs4_disable_idmapping=
1889 [NFSv4] When set to the default of '1', this option
1890 ensures that both the RPC level authentication
1891 scheme and the NFS level operations agree to use
1892 numeric uids/gids if the mount is using the
1893 'sec=sys' security flavour. In effect it is
1894 disabling idmapping, which can make migration from
1895 legacy NFSv2/v3 systems to NFSv4 easier.
1896 Servers that do not support this mode of operation
1897 will be autodetected by the client, and it will fall
1898 back to using the idmapper.
1899 To turn off this behaviour, set the value to '0'.
1901 [NFS4] Specify an additional fixed unique ident-
1902 ification string that NFSv4 clients can insert into
1903 their nfs_client_id4 string. This is typically a
1904 UUID that is generated at system install time.
1906 nfs.send_implementation_id =
1907 [NFSv4.1] Send client implementation identification
1908 information in exchange_id requests.
1909 If zero, no implementation identification information
1911 The default is to send the implementation identification
1914 nfs.recover_lost_locks =
1915 [NFSv4] Attempt to recover locks that were lost due
1916 to a lease timeout on the server. Please note that
1917 doing this risks data corruption, since there are
1918 no guarantees that the file will remain unchanged
1919 after the locks are lost.
1920 If you want to enable the kernel legacy behaviour of
1921 attempting to recover these locks, then set this
1923 The default parameter value of '0' causes the kernel
1924 not to attempt recovery of lost locks.
1926 nfsd.nfs4_disable_idmapping=
1927 [NFSv4] When set to the default of '1', the NFSv4
1928 server will return only numeric uids and gids to
1929 clients using auth_sys, and will accept numeric uids
1930 and gids from such clients. This is intended to ease
1931 migration from NFSv2/v3.
1933 objlayoutdriver.osd_login_prog=
1934 [NFS] [OBJLAYOUT] sets the pathname to the program which
1935 is used to automatically discover and login into new
1936 osd-targets. Please see:
1937 Documentation/filesystems/pnfs.txt for more explanations
1939 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1940 when a NMI is triggered.
1941 Format: [state][,regs][,debounce][,die]
1943 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1944 Format: [panic,][nopanic,][num]
1946 0 - turn nmi_watchdog off
1947 When panic is specified, panic when an NMI watchdog
1948 timeout occurs (or 'nopanic' to override the opposite
1950 This is useful when you use a panic=... timeout and
1951 need the box quickly up again.
1953 netpoll.carrier_timeout=
1954 [NET] Specifies amount of time (in seconds) that
1955 netpoll should wait for a carrier. By default netpoll
1958 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1959 emulation library even if a 387 maths coprocessor
1963 [HW] Never suspend the console
1964 Disable suspending of consoles during suspend and
1965 hibernate operations. Once disabled, debugging
1966 messages can reach various consoles while the rest
1967 of the system is being put to sleep (ie, while
1968 debugging driver suspend/resume hooks). This may
1969 not work reliably with all consoles, but is known
1970 to work with serial and VGA consoles.
1971 To facilitate more flexible debugging, we also add
1972 console_suspend, a printk module parameter to control
1973 it. Users could use console_suspend (usually
1974 /sys/module/printk/parameters/console_suspend) to
1975 turn on/off it dynamically.
1977 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1978 caches in the slab allocator. Saves per-node memory,
1979 but will impact performance.
1983 noapic [SMP,APIC] Tells the kernel to not make use of any
1984 IOAPICs that may be present in the system.
1986 noautogroup Disable scheduler automatic task group creation.
1988 nobats [PPC] Do not use BATs for mapping kernel lowmem
1989 on "Classic" PPC cores.
1993 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1995 nodelayacct [KNL] Disable per-task delay accounting
1997 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1999 nodsp [SH] Disable hardware DSP at boot time.
2001 noefi [X86] Disable EFI runtime services support.
2006 On X86-32 available only on PAE configured kernels.
2007 noexec=on: enable non-executable mappings (default)
2008 noexec=off: disable non-executable mappings
2011 Disable SMAP (Supervisor Mode Access Prevention)
2012 even if it is supported by processor.
2015 Disable SMEP (Supervisor Mode Execution Prevention)
2016 even if it is supported by processor.
2019 This affects only 32-bit executables.
2020 noexec32=on: enable non-executable mappings (default)
2021 read doesn't imply executable mappings
2022 noexec32=off: disable non-executable mappings
2023 read implies executable mappings
2025 nofpu [SH] Disable hardware FPU at boot time.
2027 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2028 register save and restore. The kernel will only save
2029 legacy floating-point registers on task switch.
2031 noxsave [BUGS=X86] Disables x86 extended register state save
2032 and restore using xsave. The kernel will fallback to
2033 enabling legacy floating-point and sse state.
2036 on enable eager fpu restore
2037 off disable eager fpu restore
2038 auto selects the default scheme, which automatically
2039 enables eagerfpu restore for xsaveopt.
2041 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2042 wfi(ARM) instruction doesn't work correctly and not to
2043 use it. This is also useful when using JTAG debugger.
2045 no_file_caps Tells the kernel not to honor file capabilities. The
2046 only way then for a file to be executed with privilege
2047 is to be setuid root or executed by root.
2049 nohalt [IA-64] Tells the kernel not to use the power saving
2050 function PAL_HALT_LIGHT when idle. This increases
2051 power-consumption. On the positive side, it reduces
2052 interrupt wake-up latency, which may improve performance
2053 in certain environments such as networked servers or
2056 nohz= [KNL] Boottime enable/disable dynamic ticks
2057 Valid arguments: on, off
2060 nohz_full= [KNL,BOOT]
2061 In kernels built with CONFIG_NO_HZ_FULL=y, set
2062 the specified list of CPUs whose tick will be stopped
2063 whenever possible. The boot CPU will be forced outside
2064 the range to maintain the timekeeping.
2065 The CPUs in this range must also be included in the
2068 noiotrap [SH] Disables trapped I/O port accesses.
2070 noirqdebug [X86-32] Disables the code which attempts to detect and
2071 disable unhandled interrupt sources.
2073 no_timer_check [X86,APIC] Disables the code which tests for
2074 broken timer IRQ sources.
2076 noisapnp [ISAPNP] Disables ISA PnP code.
2078 noinitrd [RAM] Tells the kernel not to load any configured
2081 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2083 [Deprecated - use intremap=off]
2087 nojitter [IA-64] Disables jitter checking for ITC timers.
2089 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2091 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2094 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2095 steal time is computed, but won't influence scheduler
2098 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2100 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2102 noltlbs [PPC] Do not use large page/tlb entries for kernel
2103 lowmem mapping on PPC40x.
2105 nomca [IA-64] Disable machine check abort handling
2107 nomce [X86-32] Machine Check Exception
2109 nomfgpt [X86-32] Disable Multi-Function General Purpose
2110 Timer usage (for AMD Geode machines).
2112 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2113 shutdown the other cpus. Instead use the REBOOT_VECTOR
2116 nomodule Disable module load
2118 nopat [X86] Disable PAT (page attribute table extension of
2119 pagetables) support.
2121 norandmaps Don't use address space randomization. Equivalent to
2122 echo 0 > /proc/sys/kernel/randomize_va_space
2124 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2126 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2127 with UP alternatives
2129 nordrand [X86] Disable the direct use of the RDRAND
2130 instruction even if it is supported by the
2131 processor. RDRAND is still available to user
2134 noresume [SWSUSP] Disables resume and restores original swap
2137 no-scroll [VGA] Disables scrollback.
2138 This is required for the Braillex ib80-piezo Braille
2139 reader made by F.H. Papenmeier (Germany).
2143 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2145 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2146 and disable the IO APIC. legacy for "maxcpus=0".
2148 nosoftlockup [KNL] Disable the soft-lockup detector.
2150 nosync [HW,M68K] Disables sync negotiation for all devices.
2152 notsc [BUGS=X86-32] Disable Time Stamp Counter
2154 nousb [USB] Disable the USB subsystem
2156 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2160 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2162 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2163 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2164 Some features depend on CPU0. Known dependencies are:
2165 1. Resume from suspend/hibernate depends on CPU0.
2166 Suspend/hibernate will fail if CPU0 is offline and you
2167 need to online CPU0 before suspend/hibernate.
2168 2. PIC interrupts also depend on CPU0. CPU0 can't be
2169 removed if a PIC interrupt is detected.
2170 It's said poweroff/reboot may depend on CPU0 on some
2171 machines although I haven't seen such issues so far
2172 after CPU0 is offline on a few tested machines.
2173 If the dependencies are under your control, you can
2174 turn on cpu0_hotplug.
2176 nptcg= [IA-64] Override max number of concurrent global TLB
2177 purges which is reported from either PAL_VM_SUMMARY or
2180 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2181 could support. nr_cpus=n : n >= 1 limits the kernel to
2182 supporting 'n' processors. Later in runtime you can not
2183 use hotplug cpu feature to put more cpu back to online.
2184 just like you compile the kernel NR_CPUS=n
2186 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2188 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2189 Allowed values are enable and disable
2191 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2192 one of ['zone', 'node', 'default'] can be specified
2193 This can be set from sysctl after boot.
2194 See Documentation/sysctl/vm.txt for details.
2196 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2197 See Documentation/debugging-via-ohci1394.txt for more
2200 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2201 Rather than timing out after 20 ms if an EC
2202 command is not properly ACKed, override the length
2203 of the timeout. We have interrupts disabled while
2204 waiting for the ACK, so if this is set too high
2205 interrupts *may* be lost!
2207 omap_mux= [OMAP] Override bootloader pin multiplexing.
2208 Format: <mux_mode0.mode_name=value>...
2209 For example, to override I2C bus2:
2210 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2212 oprofile.timer= [HW]
2213 Use timer interrupt instead of performance counters
2215 oprofile.cpu_type= Force an oprofile cpu type
2216 This might be useful if you have an older oprofile
2217 userland or if you want common events.
2218 Format: { arch_perfmon }
2219 arch_perfmon: [X86] Force use of architectural
2220 perfmon on Intel CPUs instead of the
2221 CPU specific event set.
2222 timer: [X86] Force use of architectural NMI
2223 timer mode (see also oprofile.timer
2224 for generic hr timer mode)
2225 [s390] Force legacy basic mode sampling
2226 (report cpu_type "timer")
2228 oops=panic Always panic on oopses. Default is to just kill the
2229 process, but there is a small probability of
2230 deadlocking the machine.
2231 This will also cause panics on machine check exceptions.
2232 Useful together with panic=30 to trigger a reboot.
2235 See Documentation/sound/oss/oss-parameters.txt
2237 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2238 timeout > 0: seconds before rebooting
2239 timeout = 0: wait forever
2240 timeout < 0: reboot immediately
2243 parkbd.port= [HW] Parallel port number the keyboard adapter is
2244 connected to, default is 0.
2246 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2247 0 for XT, 1 for AT (default is AT).
2250 parport= [HW,PPT] Specify parallel ports. 0 disables.
2251 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2252 Use 'auto' to force the driver to use any
2253 IRQ/DMA settings detected (the default is to
2254 ignore detected IRQ/DMA settings because of
2255 possible conflicts). You can specify the base
2256 address, IRQ, and DMA settings; IRQ and DMA
2257 should be numbers, or 'auto' (for using detected
2258 settings on that particular port), or 'nofifo'
2259 (to avoid using a FIFO even if it is detected).
2260 Parallel ports are assigned in the order they
2261 are specified on the command line, starting
2264 parport_init_mode= [HW,PPT]
2265 Configure VIA parallel port to operate in
2266 a specific mode. This is necessary on Pegasos
2267 computer where firmware has no options for setting
2268 up parallel port mode and sets it to spp.
2269 Currently this function knows 686a and 8231 chips.
2270 Format: [spp|ps2|epp|ecp|ecpepp]
2273 Halt all CPUs after the first oops has been printed for
2274 the specified number of seconds. This is to be used if
2275 your oopses keep scrolling off the screen.
2280 See header of drivers/block/paride/pcd.c.
2281 See also Documentation/blockdev/paride.txt.
2283 pci=option[,option...] [PCI] various PCI subsystem options:
2284 earlydump [X86] dump PCI config space before the kernel
2286 off [X86] don't probe for the PCI bus
2287 bios [X86-32] force use of PCI BIOS, don't access
2288 the hardware directly. Use this if your machine
2289 has a non-standard PCI host bridge.
2290 nobios [X86-32] disallow use of PCI BIOS, only direct
2291 hardware access methods are allowed. Use this
2292 if you experience crashes upon bootup and you
2293 suspect they are caused by the BIOS.
2294 conf1 [X86] Force use of PCI Configuration
2296 conf2 [X86] Force use of PCI Configuration
2298 noaer [PCIE] If the PCIEAER kernel config parameter is
2299 enabled, this kernel boot option can be used to
2300 disable the use of PCIE advanced error reporting.
2301 nodomains [PCI] Disable support for multiple PCI
2302 root domains (aka PCI segments, in ACPI-speak).
2303 nommconf [X86] Disable use of MMCONFIG for PCI
2305 check_enable_amd_mmconf [X86] check for and enable
2306 properly configured MMIO access to PCI
2307 config space on AMD family 10h CPU
2308 nomsi [MSI] If the PCI_MSI kernel config parameter is
2309 enabled, this kernel boot option can be used to
2310 disable the use of MSI interrupts system-wide.
2311 noioapicquirk [APIC] Disable all boot interrupt quirks.
2312 Safety option to keep boot IRQs enabled. This
2313 should never be necessary.
2314 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2315 primary IO-APIC for bridges that cannot disable
2316 boot IRQs. This fixes a source of spurious IRQs
2317 when the system masks IRQs.
2318 noioapicreroute [APIC] Disable workaround that uses the
2319 boot IRQ equivalent of an IRQ that connects to
2320 a chipset where boot IRQs cannot be disabled.
2321 The opposite of ioapicreroute.
2322 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2323 routing table. These calls are known to be buggy
2324 on several machines and they hang the machine
2325 when used, but on other computers it's the only
2326 way to get the interrupt routing table. Try
2327 this option if the kernel is unable to allocate
2328 IRQs or discover secondary PCI buses on your
2330 rom [X86] Assign address space to expansion ROMs.
2331 Use with caution as certain devices share
2332 address decoders between ROMs and other
2334 norom [X86] Do not assign address space to
2335 expansion ROMs that do not already have
2336 BIOS assigned address ranges.
2337 nobar [X86] Do not assign address space to the
2338 BARs that weren't assigned by the BIOS.
2339 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2340 assigned automatically to PCI devices. You can
2341 make the kernel exclude IRQs of your ISA cards
2343 pirqaddr=0xAAAAA [X86] Specify the physical address
2344 of the PIRQ table (normally generated
2345 by the BIOS) if it is outside the
2346 F0000h-100000h range.
2347 lastbus=N [X86] Scan all buses thru bus #N. Can be
2348 useful if the kernel is unable to find your
2349 secondary buses and you want to tell it
2350 explicitly which ones they are.
2351 assign-busses [X86] Always assign all PCI bus
2352 numbers ourselves, overriding
2353 whatever the firmware may have done.
2354 usepirqmask [X86] Honor the possible IRQ mask stored
2355 in the BIOS $PIR table. This is needed on
2356 some systems with broken BIOSes, notably
2357 some HP Pavilion N5400 and Omnibook XE3
2358 notebooks. This will have no effect if ACPI
2359 IRQ routing is enabled.
2360 noacpi [X86] Do not use ACPI for IRQ routing
2361 or for PCI scanning.
2362 use_crs [X86] Use PCI host bridge window information
2363 from ACPI. On BIOSes from 2008 or later, this
2364 is enabled by default. If you need to use this,
2365 please report a bug.
2366 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2367 If you need to use this, please report a bug.
2368 routeirq Do IRQ routing for all PCI devices.
2369 This is normally done in pci_enable_device(),
2370 so this option is a temporary workaround
2371 for broken drivers that don't call it.
2372 skip_isa_align [X86] do not align io start addr, so can
2373 handle more pci cards
2374 firmware [ARM] Do not re-enumerate the bus but instead
2375 just use the configuration from the
2376 bootloader. This is currently used on
2377 IXP2000 systems where the bus has to be
2378 configured a certain way for adjunct CPUs.
2379 noearly [X86] Don't do any early type 1 scanning.
2380 This might help on some broken boards which
2381 machine check when some devices' config space
2382 is read. But various workarounds are disabled
2383 and some IOMMU drivers will not work.
2384 bfsort Sort PCI devices into breadth-first order.
2385 This sorting is done to get a device
2386 order compatible with older (<= 2.4) kernels.
2387 nobfsort Don't sort PCI devices into breadth-first order.
2388 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2389 tuning and use the BIOS-configured MPS defaults.
2390 pcie_bus_safe Set every device's MPS to the largest value
2391 supported by all devices below the root complex.
2392 pcie_bus_perf Set device MPS to the largest allowable MPS
2393 based on its parent bus. Also set MRRS (Max
2394 Read Request Size) to the largest supported
2395 value (no larger than the MPS that the device
2396 or bus can support) for best performance.
2397 pcie_bus_peer2peer Set every device's MPS to 128B, which
2398 every device is guaranteed to support. This
2399 configuration allows peer-to-peer DMA between
2400 any pair of devices, possibly at the cost of
2401 reduced performance. This also guarantees
2402 that hot-added devices will work.
2403 cbiosize=nn[KMG] The fixed amount of bus space which is
2404 reserved for the CardBus bridge's IO window.
2405 The default value is 256 bytes.
2406 cbmemsize=nn[KMG] The fixed amount of bus space which is
2407 reserved for the CardBus bridge's memory
2408 window. The default value is 64 megabytes.
2411 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2412 Specifies alignment and device to reassign
2413 aligned memory resources.
2414 If <order of align> is not specified,
2415 PAGE_SIZE is used as alignment.
2416 PCI-PCI bridge can be specified, if resource
2417 windows need to be expanded.
2418 ecrc= Enable/disable PCIe ECRC (transaction layer
2419 end-to-end CRC checking).
2420 bios: Use BIOS/firmware settings. This is the
2424 hpiosize=nn[KMG] The fixed amount of bus space which is
2425 reserved for hotplug bridge's IO window.
2426 Default size is 256 bytes.
2427 hpmemsize=nn[KMG] The fixed amount of bus space which is
2428 reserved for hotplug bridge's memory window.
2429 Default size is 2 megabytes.
2430 realloc= Enable/disable reallocating PCI bridge resources
2431 if allocations done by BIOS are too small to
2432 accommodate resources required by all child
2434 off: Turn realloc off
2436 realloc same as realloc=on
2437 noari do not use PCIe ARI.
2438 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2439 only look for one device below a PCIe downstream
2442 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2445 force Enable ASPM even on devices that claim not to support it.
2446 WARNING: Forcing ASPM on may cause system lockups.
2448 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2449 nomsi Do not use MSI for PCI Express Native Hotplug (this
2450 makes all PCIe ports use INTx for hotplug services).
2452 pcie_ports= [PCIE] PCIe ports handling:
2453 auto Ask the BIOS whether or not to use native PCIe services
2454 associated with PCIe ports (PME, hot-plug, AER). Use
2455 them only if that is allowed by the BIOS.
2456 native Use native PCIe services associated with PCIe ports
2458 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2461 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2462 nomsi Do not use MSI for native PCIe PME signaling (this makes
2463 all PCIe root ports use INTx for all services).
2465 pcmv= [HW,PCMCIA] BadgePAD 4
2468 See Documentation/blockdev/paride.txt.
2470 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2473 See arch/parisc/kernel/pdc_chassis.c
2475 percpu_alloc= Select which percpu first chunk allocator to use.
2476 Currently supported values are "embed" and "page".
2477 Archs may support subset or none of the selections.
2478 See comments in mm/percpu.c for details on each
2479 allocator. This parameter is primarily for debugging
2480 and performance comparison.
2483 See Documentation/blockdev/paride.txt.
2486 See Documentation/blockdev/paride.txt.
2488 pirq= [SMP,APIC] Manual mp-table setup
2489 See Documentation/x86/i386/IO-APIC.txt.
2491 plip= [PPT,NET] Parallel port network link
2492 Format: { parport<nr> | timid | 0 }
2493 See also Documentation/parport.txt.
2495 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2496 Override pmtimer IOPort with a hex value.
2500 Enable PNP debug messages (depends on the
2501 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2502 via /sys/module/pnp/parameters/debug. We always show
2503 current resource usage; turning this on also shows
2504 possible settings and some assignment information.
2510 { on | off | curr | res | no-curr | no-res }
2513 [ISAPNP] Exclude IRQs for the autoconfiguration
2516 [ISAPNP] Exclude DMAs for the autoconfiguration
2518 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2519 Ranges are in pairs (I/O port base and size).
2522 [ISAPNP] Exclude memory regions for the
2524 Ranges are in pairs (memory base and size).
2526 ports= [IP_VS_FTP] IPVS ftp helper module
2528 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2530 Format: <port>,<port>....
2532 print-fatal-signals=
2533 [KNL] debug: print fatal signals
2535 If enabled, warn about various signal handling
2536 related application anomalies: too many signals,
2537 too many POSIX.1 timers, fatal signals causing a
2540 If you hit the warning due to signal overflow,
2541 you might want to try "ulimit -i unlimited".
2545 printk.always_kmsg_dump=
2546 Trigger kmsg_dump for cases other than kernel oops or
2548 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2551 printk.time= Show timing data prefixed to each printk message line
2552 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2554 processor.max_cstate= [HW,ACPI]
2555 Limit processor to maximum C-state
2556 max_cstate=9 overrides any DMI blacklist limit.
2558 processor.nocst [HW,ACPI]
2559 Ignore the _CST method to determine C-states,
2560 instead using the legacy FADT method
2562 profile= [KNL] Enable kernel profiling via /proc/profile
2563 Format: [schedule,]<number>
2564 Param: "schedule" - profile schedule points.
2565 Param: <number> - step/bucket size as a power of 2 for
2566 statistical time based profiling.
2567 Param: "sleep" - profile D-state sleeping (millisecs).
2568 Requires CONFIG_SCHEDSTATS
2569 Param: "kvm" - profile VM exits.
2571 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2573 See Documentation/blockdev/ramdisk.txt.
2575 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2576 probe for; one of (bare|imps|exps|lifebook|any).
2577 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2579 psmouse.resetafter= [HW,MOUSE]
2580 Try to reset the device after so many bad packets
2583 [HW,MOUSE] Set desired mouse resolution, in dpi.
2584 psmouse.smartscroll=
2585 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2586 0 = disabled, 1 = enabled (default).
2588 pstore.backend= Specify the name of the pstore backend to use
2591 See Documentation/blockdev/paride.txt.
2594 [KNL] Number of legacy pty's. Overwrites compiled-in
2597 quiet [KNL] Disable most log messages
2602 See Documentation/md.txt.
2604 ramdisk_blocksize= [RAM]
2605 See Documentation/blockdev/ramdisk.txt.
2607 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2608 See Documentation/blockdev/ramdisk.txt.
2610 rcu_nocbs= [KNL,BOOT]
2611 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2612 the specified list of CPUs to be no-callback CPUs.
2613 Invocation of these CPUs' RCU callbacks will
2614 be offloaded to "rcuox/N" kthreads created for
2615 that purpose, where "x" is "b" for RCU-bh, "p"
2616 for RCU-preempt, and "s" for RCU-sched, and "N"
2617 is the CPU number. This reduces OS jitter on the
2618 offloaded CPUs, which can be useful for HPC and
2620 real-time workloads. It can also improve energy
2621 efficiency for asymmetric multiprocessors.
2623 rcu_nocb_poll [KNL,BOOT]
2624 Rather than requiring that offloaded CPUs
2625 (specified by rcu_nocbs= above) explicitly
2626 awaken the corresponding "rcuoN" kthreads,
2627 make these kthreads poll for callbacks.
2628 This improves the real-time response for the
2629 offloaded CPUs by relieving them of the need to
2630 wake up the corresponding kthread, but degrades
2631 energy efficiency by requiring that the kthreads
2632 periodically wake up to do the polling.
2634 rcutree.blimit= [KNL,BOOT]
2635 Set maximum number of finished RCU callbacks to process
2638 rcutree.fanout_leaf= [KNL,BOOT]
2639 Increase the number of CPUs assigned to each
2640 leaf rcu_node structure. Useful for very large
2643 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2644 Set delay from grace-period initialization to
2645 first attempt to force quiescent states.
2646 Units are jiffies, minimum value is zero,
2647 and maximum value is HZ.
2649 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2650 Set delay between subsequent attempts to force
2651 quiescent states. Units are jiffies, minimum
2652 value is one, and maximum value is HZ.
2654 rcutree.qhimark= [KNL,BOOT]
2655 Set threshold of queued
2656 RCU callbacks over which batch limiting is disabled.
2658 rcutree.qlowmark= [KNL,BOOT]
2659 Set threshold of queued RCU callbacks below which
2660 batch limiting is re-enabled.
2662 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2663 Suppress RCU CPU stall warning messages.
2665 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2666 Set timeout for RCU CPU stall warning messages.
2668 rcutree.rcu_idle_gp_delay= [KNL,BOOT]
2669 Set wakeup interval for idle CPUs that have
2670 RCU callbacks (RCU_FAST_NO_HZ=y).
2672 rcutree.rcu_idle_lazy_gp_delay= [KNL,BOOT]
2673 Set wakeup interval for idle CPUs that have
2674 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2675 Lazy RCU callbacks are those which RCU can
2676 prove do nothing more than free memory.
2678 rcutorture.fqs_duration= [KNL,BOOT]
2679 Set duration of force_quiescent_state bursts.
2681 rcutorture.fqs_holdoff= [KNL,BOOT]
2682 Set holdoff time within force_quiescent_state bursts.
2684 rcutorture.fqs_stutter= [KNL,BOOT]
2685 Set wait time between force_quiescent_state bursts.
2687 rcutorture.irqreader= [KNL,BOOT]
2688 Test RCU readers from irq handlers.
2690 rcutorture.n_barrier_cbs= [KNL,BOOT]
2691 Set callbacks/threads for rcu_barrier() testing.
2693 rcutorture.nfakewriters= [KNL,BOOT]
2694 Set number of concurrent RCU writers. These just
2695 stress RCU, they don't participate in the actual
2696 test, hence the "fake".
2698 rcutorture.nreaders= [KNL,BOOT]
2699 Set number of RCU readers.
2701 rcutorture.onoff_holdoff= [KNL,BOOT]
2702 Set time (s) after boot for CPU-hotplug testing.
2704 rcutorture.onoff_interval= [KNL,BOOT]
2705 Set time (s) between CPU-hotplug operations, or
2706 zero to disable CPU-hotplug testing.
2708 rcutorture.shuffle_interval= [KNL,BOOT]
2709 Set task-shuffle interval (s). Shuffling tasks
2710 allows some CPUs to go into dyntick-idle mode
2711 during the rcutorture test.
2713 rcutorture.shutdown_secs= [KNL,BOOT]
2714 Set time (s) after boot system shutdown. This
2715 is useful for hands-off automated testing.
2717 rcutorture.stall_cpu= [KNL,BOOT]
2718 Duration of CPU stall (s) to test RCU CPU stall
2719 warnings, zero to disable.
2721 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2722 Time to wait (s) after boot before inducing stall.
2724 rcutorture.stat_interval= [KNL,BOOT]
2725 Time (s) between statistics printk()s.
2727 rcutorture.stutter= [KNL,BOOT]
2728 Time (s) to stutter testing, for example, specifying
2729 five seconds causes the test to run for five seconds,
2730 wait for five seconds, and so on. This tests RCU's
2731 ability to transition abruptly to and from idle.
2733 rcutorture.test_boost= [KNL,BOOT]
2734 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2735 "Maybe" means test if the RCU implementation
2736 under test support RCU priority boosting.
2738 rcutorture.test_boost_duration= [KNL,BOOT]
2739 Duration (s) of each individual boost test.
2741 rcutorture.test_boost_interval= [KNL,BOOT]
2742 Interval (s) between each boost test.
2744 rcutorture.test_no_idle_hz= [KNL,BOOT]
2745 Test RCU's dyntick-idle handling. See also the
2746 rcutorture.shuffle_interval parameter.
2748 rcutorture.torture_type= [KNL,BOOT]
2749 Specify the RCU implementation to test.
2751 rcutorture.verbose= [KNL,BOOT]
2752 Enable additional printk() statements.
2756 Run specified binary instead of /init from the ramdisk,
2757 used for early userspace startup. See initrd.
2760 Format (x86 or x86_64):
2761 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2763 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2765 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2766 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2767 reboot_force is either force or not specified,
2768 reboot_cpu is s[mp]#### with #### being the processor
2769 to be used for rebooting.
2772 [KNL, SMP] Set scheduler's default relax_domain_level.
2773 See Documentation/cgroups/cpusets.txt.
2775 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2777 reservetop= [X86-32]
2779 Reserves a hole at the top of the kernel virtual
2784 Set the amount of memory to reserve for BIOS at
2785 the bottom of the address space.
2787 reset_devices [KNL] Force drivers to reset the underlying device
2788 during initialization.
2791 Specify the partition device for software suspend
2793 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2795 resume_offset= [SWSUSP]
2796 Specify the offset from the beginning of the partition
2797 given by "resume=" at which the swap header is located,
2798 in <PAGE_SIZE> units (needed only for swap files).
2799 See Documentation/power/swsusp-and-swap-files.txt
2801 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2802 read the resume files
2804 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2805 Useful for devices that are detected asynchronously
2806 (e.g. USB and MMC devices).
2808 hibernate= [HIBERNATION]
2809 noresume Don't check if there's a hibernation image
2810 present during boot.
2811 nocompress Don't compress/decompress hibernation images.
2813 retain_initrd [RAM] Keep initrd memory after extraction
2815 rhash_entries= [KNL,NET]
2816 Set number of hash buckets for route cache
2818 riscom8= [HW,SERIAL]
2819 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2821 ro [KNL] Mount root device read-only on boot
2823 root= [KNL] Root filesystem
2824 See name_to_dev_t comment in init/do_mounts.c.
2826 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2827 mount the root filesystem
2829 rootflags= [KNL] Set root filesystem mount option string
2831 rootfstype= [KNL] Set root filesystem type
2833 rootwait [KNL] Wait (indefinitely) for root device to show up.
2834 Useful for devices that are detected asynchronously
2835 (e.g. USB and MMC devices).
2837 rproc_mem=nn[KMG][@address]
2838 [KNL,ARM,CMA] Remoteproc physical memory block.
2839 Memory area to be used by remote processor image,
2842 rw [KNL] Mount root device read-write on boot
2844 S [KNL] Run init in single mode
2847 See drivers/net/irda/sa1100_ir.c.
2849 sbni= [NET] Granch SBNI12 leased line adapter
2851 sched_debug [KNL] Enables verbose scheduler debug messages.
2853 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2854 xtime_lock contention on larger systems, and/or RCU lock
2855 contention on all systems with CONFIG_MAXSMP set.
2856 Format: { "0" | "1" }
2857 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2859 Note: increases power consumption, thus should only be
2860 enabled if running jitter sensitive (HPC/RT) workloads.
2862 security= [SECURITY] Choose a security module to enable at boot.
2863 If this boot parameter is not specified, only the first
2864 security module asking for security registration will be
2865 loaded. An invalid security module name will be treated
2866 as if no module has been chosen.
2868 selinux= [SELINUX] Disable or enable SELinux at boot time.
2869 Format: { "0" | "1" }
2870 See security/selinux/Kconfig help text.
2873 Default value is set via kernel config option.
2874 If enabled at boot time, /selinux/disable can be used
2875 later to disable prior to initial policy load.
2877 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2878 Format: { "0" | "1" }
2879 See security/apparmor/Kconfig help text
2882 Default value is set via kernel config option.
2884 serialnumber [BUGS=X86-32]
2887 Maximal number of shapers.
2889 show_msr= [x86] show boot-time MSR settings
2890 Format: { <integer> }
2891 Show boot-time (BIOS-initialized) MSR settings.
2892 The parameter means the number of CPUs to show,
2893 for example 1 means boot CPU only.
2900 slab_max_order= [MM, SLAB]
2901 Determines the maximum allowed order for slabs.
2902 A high setting may cause OOMs due to memory
2903 fragmentation. Defaults to 1 for systems with
2904 more than 32MB of RAM, 0 otherwise.
2906 slub_debug[=options[,slabs]] [MM, SLUB]
2907 Enabling slub_debug allows one to determine the
2908 culprit if slab objects become corrupted. Enabling
2909 slub_debug can create guard zones around objects and
2910 may poison objects when not in use. Also tracks the
2911 last alloc / free. For more information see
2912 Documentation/vm/slub.txt.
2914 slub_max_order= [MM, SLUB]
2915 Determines the maximum allowed order for slabs.
2916 A high setting may cause OOMs due to memory
2917 fragmentation. For more information see
2918 Documentation/vm/slub.txt.
2920 slub_min_objects= [MM, SLUB]
2921 The minimum number of objects per slab. SLUB will
2922 increase the slab order up to slub_max_order to
2923 generate a sufficiently large slab able to contain
2924 the number of objects indicated. The higher the number
2925 of objects the smaller the overhead of tracking slabs
2926 and the less frequently locks need to be acquired.
2927 For more information see Documentation/vm/slub.txt.
2929 slub_min_order= [MM, SLUB]
2930 Determines the minimum page order for slabs. Must be
2931 lower than slub_max_order.
2932 For more information see Documentation/vm/slub.txt.
2934 slub_nomerge [MM, SLUB]
2935 Disable merging of slabs with similar size. May be
2936 necessary if there is some reason to distinguish
2937 allocs to different slabs. Debug options disable
2938 merging on their own.
2939 For more information see Documentation/vm/slub.txt.
2942 Format: <io1>[,<io2>[,...,<io8>]]
2944 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2945 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2946 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2947 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2948 smsc-ircc2.ircc_irq= [HW] IRQ line
2949 smsc-ircc2.ircc_dma= [HW] DMA channel
2950 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2951 0: Toshiba Satellite 1800 (GP data pin select)
2952 1: Fast pin select (default)
2956 [KNL] Should the soft-lockup detector generate panics.
2959 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2960 See Documentation/laptops/sonypi.txt
2962 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2963 See Documentation/serial/specialix.txt.
2965 spia_io_base= [HW,MTD]
2971 Enabled the stack tracer on boot up.
2973 stacktrace_filter=[function-list]
2974 [FTRACE] Limit the functions that the stack tracer
2975 will trace at boot up. function-list is a comma separated
2976 list of functions. This list can be changed at run
2977 time by the stack_trace_filter file in the debugfs
2978 tracing directory. Note, this enables stack tracing
2979 and the stacktrace above is not needed.
2983 Set the STI (builtin display/keyboard on the HP-PARISC
2984 machines) console (graphic card) which should be used
2985 as the initial boot-console.
2986 See also comment in drivers/video/console/sticore.c.
2989 See comment in drivers/video/console/sticore.c.
2992 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2994 sunrpc.min_resvport=
2995 sunrpc.max_resvport=
2997 SunRPC servers often require that client requests
2998 originate from a privileged port (i.e. a port in the
2999 range 0 < portnr < 1024).
3000 An administrator who wishes to reserve some of these
3001 ports for other uses may adjust the range that the
3002 kernel's sunrpc client considers to be privileged
3003 using these two parameters to set the minimum and
3004 maximum port values.
3008 Control how the NFS server code allocates CPUs to
3009 service thread pools. Depending on how many NICs
3010 you have and where their interrupts are bound, this
3011 option will affect which CPUs will do NFS serving.
3012 Note: this parameter cannot be changed while the
3013 NFS server is running.
3015 auto the server chooses an appropriate mode
3016 automatically using heuristics
3017 global a single global pool contains all CPUs
3018 percpu one pool for each CPU
3019 pernode one pool for each NUMA node (equivalent
3020 to global on non-NUMA machines)
3022 sunrpc.tcp_slot_table_entries=
3023 sunrpc.udp_slot_table_entries=
3025 Sets the upper limit on the number of simultaneous
3026 RPC calls that can be sent from the client to a
3027 server. Increasing these values may allow you to
3028 improve throughput, but will also increase the
3029 amount of memory reserved for use by the client.
3032 [KNL] Enable accounting of swap in memory resource
3033 controller if no parameter or 1 is given or disable
3034 it if 0 is given (See Documentation/cgroups/memory.txt)
3036 swiotlb= [IA-64] Number of I/O TLB slabs
3040 sysfs.deprecated=0|1 [KNL]
3041 Enable/disable old style sysfs layout for old udev
3042 on older distributions. When this option is enabled
3043 very new udev will not work anymore. When this option
3044 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3045 in older udev will not work anymore.
3046 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3047 the kernel configuration.
3049 sysrq_always_enabled
3051 Ignore sysrq setting - this boot parameter will
3052 neutralize any effect of /proc/sys/kernel/sysrq.
3053 Useful for debugging.
3057 test_suspend= [SUSPEND]
3058 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3059 standby suspend) as the system sleep state to briefly
3060 enter during system startup. The system is woken from
3061 this state using a wakeup-capable RTC alarm.
3063 thash_entries= [KNL,NET]
3064 Set number of hash buckets for TCP connection
3066 thermal.act= [HW,ACPI]
3067 -1: disable all active trip points in all thermal zones
3068 <degrees C>: override all lowest active trip points
3070 thermal.crt= [HW,ACPI]
3071 -1: disable all critical trip points in all thermal zones
3072 <degrees C>: override all critical trip points
3074 thermal.nocrt= [HW,ACPI]
3075 Set to disable actions on ACPI thermal zone
3076 critical and hot trip points.
3078 thermal.off= [HW,ACPI]
3079 1: disable ACPI thermal control
3081 thermal.psv= [HW,ACPI]
3082 -1: disable all passive trip points
3083 <degrees C>: override all passive trip points to this
3086 thermal.tzp= [HW,ACPI]
3087 Specify global default ACPI thermal zone polling rate
3088 <deci-seconds>: poll all this frequency
3089 0: no polling (default)
3092 Force threading of all interrupt handlers except those
3093 marked explicitly IRQF_NO_THREAD.
3096 Enable the Transcendent memory driver if built-in.
3098 tmem.cleancache=0|1 [KNL, XEN]
3099 Default is on (1). Disable the usage of the cleancache
3100 API to send anonymous pages to the hypervisor.
3102 tmem.frontswap=0|1 [KNL, XEN]
3103 Default is on (1). Disable the usage of the frontswap
3104 API to send swap pages to the hypervisor. If disabled
3105 the selfballooning and selfshrinking are force disabled.
3107 tmem.selfballooning=0|1 [KNL, XEN]
3108 Default is on (1). Disable the driving of swap pages
3111 tmem.selfshrinking=0|1 [KNL, XEN]
3112 Default is on (1). Partial swapoff that immediately
3113 transfers pages from Xen hypervisor back to the
3114 kernel based on different criteria.
3118 Specify if the kernel should make use of the cpu
3119 topology information if the hardware supports this.
3120 The scheduler will make use of this information and
3121 e.g. base its process migration decisions on it.
3126 tpm_suspend_pcr=[HW,TPM]
3127 Format: integer pcr id
3128 Specify that at suspend time, the tpm driver
3129 should extend the specified pcr with zeros,
3130 as a workaround for some chips which fail to
3131 flush the last written pcr on TPM_SaveState.
3132 This will guarantee that all the other pcrs
3135 trace_buf_size=nn[KMG]
3136 [FTRACE] will set tracing buffer size.
3138 trace_event=[event-list]
3139 [FTRACE] Set and start specified trace events in order
3140 to facilitate early boot debugging.
3141 See also Documentation/trace/events.txt
3143 trace_options=[option-list]
3144 [FTRACE] Enable or disable tracer options at boot.
3145 The option-list is a comma delimited list of options
3146 that can be enabled or disabled just as if you were
3147 to echo the option name into
3149 /sys/kernel/debug/tracing/trace_options
3151 For example, to enable stacktrace option (to dump the
3152 stack trace of each event), add to the command line:
3154 trace_options=stacktrace
3156 See also Documentation/trace/ftrace.txt "trace options"
3160 [FTRACE] enable this option to disable tracing when a
3161 warning is hit. This turns off "tracing_on". Tracing can
3162 be enabled again by echoing '1' into the "tracing_on"
3163 file located in /sys/kernel/debug/tracing/
3165 This option is useful, as it disables the trace before
3166 the WARNING dump is called, which prevents the trace to
3167 be filled with content caused by the warning output.
3169 This option can also be set at run time via the sysctl
3170 option: kernel/traceoff_on_warning
3172 transparent_hugepage=
3174 Format: [always|madvise|never]
3175 Can be used to control the default behavior of the system
3176 with respect to transparent hugepages.
3177 See Documentation/vm/transhuge.txt for more details.
3179 tsc= Disable clocksource stability checks for TSC.
3181 [x86] reliable: mark tsc clocksource as reliable, this
3182 disables clocksource verification at runtime, as well
3183 as the stability checks done at bootup. Used to enable
3184 high-resolution timer mode on older hardware, and in
3185 virtualized environment.
3186 [x86] noirqtime: Do not use TSC to do irq accounting.
3187 Used to run time disable IRQ_TIME_ACCOUNTING on any
3188 platforms where RDTSC is slow and this accounting
3191 turbografx.map[2|3]= [HW,JOY]
3192 TurboGraFX parallel port interface
3194 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3195 See also Documentation/input/joystick-parport.txt
3197 udbg-immortal [PPC] When debugging early kernel crashes that
3198 happen after console_init() and before a proper
3199 console driver takes over, this boot options might
3200 help "seeing" what's going on.
3202 uhash_entries= [KNL,NET]
3203 Set number of hash buckets for UDP/UDP-Lite connections
3206 [USB] Ignore overcurrent events (default N).
3207 Some badly-designed motherboards generate lots of
3208 bogus events, for ports that aren't wired to
3209 anything. Set this parameter to avoid log spamming.
3210 Note that genuine overcurrent events won't be
3214 [X86] Cause panic on unknown NMI.
3216 usbcore.authorized_default=
3217 [USB] Default USB device authorization:
3218 (default -1 = authorized except for wireless USB,
3219 0 = not authorized, 1 = authorized)
3221 usbcore.autosuspend=
3222 [USB] The autosuspend time delay (in seconds) used
3223 for newly-detected USB devices (default 2). This
3224 is the time required before an idle device will be
3225 autosuspended. Devices for which the delay is set
3226 to a negative value won't be autosuspended at all.
3228 usbcore.usbfs_snoop=
3229 [USB] Set to log all usbfs traffic (default 0 = off).
3231 usbcore.blinkenlights=
3232 [USB] Set to cycle leds on hubs (default 0 = off).
3234 usbcore.old_scheme_first=
3235 [USB] Start with the old device initialization
3236 scheme (default 0 = off).
3238 usbcore.usbfs_memory_mb=
3239 [USB] Memory limit (in MB) for buffers allocated by
3240 usbfs (default = 16, 0 = max = 2047).
3242 usbcore.use_both_schemes=
3243 [USB] Try the other device initialization scheme
3244 if the first one fails (default 1 = enabled).
3246 usbcore.initial_descriptor_timeout=
3247 [USB] Specifies timeout for the initial 64-byte
3248 USB_REQ_GET_DESCRIPTOR request in milliseconds
3249 (default 5000 = 5.0 seconds).
3252 [USBHID] The interval which mice are to be polled at.
3254 usb-storage.delay_use=
3255 [UMS] The delay in seconds before a new device is
3256 scanned for Logical Units (default 5).
3259 [UMS] A list of quirks entries to supplement or
3260 override the built-in unusual_devs list. List
3261 entries are separated by commas. Each entry has
3262 the form VID:PID:Flags where VID and PID are Vendor
3263 and Product ID values (4-digit hex numbers) and
3264 Flags is a set of characters, each corresponding
3265 to a common usb-storage quirk flag as follows:
3266 a = SANE_SENSE (collect more than 18 bytes
3268 b = BAD_SENSE (don't collect more than 18
3269 bytes of sense data);
3270 c = FIX_CAPACITY (decrease the reported
3271 device capacity by one sector);
3272 d = NO_READ_DISC_INFO (don't use
3273 READ_DISC_INFO command);
3274 e = NO_READ_CAPACITY_16 (don't use
3275 READ_CAPACITY_16 command);
3276 h = CAPACITY_HEURISTICS (decrease the
3277 reported device capacity by one
3278 sector if the number is odd);
3279 i = IGNORE_DEVICE (don't bind to this
3281 l = NOT_LOCKABLE (don't try to lock and
3282 unlock ejectable media);
3283 m = MAX_SECTORS_64 (don't transfer more
3284 than 64 sectors = 32 KB at a time);
3285 n = INITIAL_READ10 (force a retry of the
3286 initial READ(10) command);
3287 o = CAPACITY_OK (accept the capacity
3288 reported by the device);
3289 p = WRITE_CACHE (the device cache is ON
3291 r = IGNORE_RESIDUE (the device reports
3292 bogus residue values);
3293 s = SINGLE_LUN (the device has only one
3295 w = NO_WP_DETECT (don't test whether the
3296 medium is write-protected).
3297 Example: quirks=0419:aaf5:rl,0421:0433:rc
3299 user_debug= [KNL,ARM]
3301 See arch/arm/Kconfig.debug help text.
3302 1 - undefined instruction events
3304 4 - invalid data aborts
3307 Example: user_debug=31
3310 [X86] Flags controlling user PTE allocations.
3312 nohigh = do not allocate PTE pages in
3313 HIGHMEM regardless of setting
3317 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3318 vdso=1: enable VDSO (default)
3319 vdso=0: disable VDSO mapping
3322 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3323 vdso32=1: enable 32-bit VDSO (default)
3324 vdso32=0: disable 32-bit VDSO mapping
3327 vector=percpu: enable percpu vector domain
3329 video= [FB] Frame buffer configuration
3330 See Documentation/fb/modedb.txt.
3332 video.brightness_switch_enabled= [0,1]
3333 If set to 1, on receiving an ACPI notify event
3334 generated by hotkey, video driver will adjust brightness
3335 level and then send out the event to user space through
3336 the allocated input device; If set to 0, video driver
3337 will only send out the event without touching backlight
3342 [VMMIO] Memory mapped virtio (platform) device.
3344 <size>@<baseaddr>:<irq>[:<id>]
3346 <size> := size (can use standard suffixes
3348 <baseaddr> := physical base address
3349 <irq> := interrupt number (as passed to
3351 <id> := (optional) platform device id
3353 virtio_mmio.device=1K@0x100b0000:48:7
3355 Can be used multiple times for multiple devices.
3357 vga= [BOOT,X86-32] Select a particular video mode
3358 See Documentation/x86/boot.txt and
3359 Documentation/svga.txt.
3360 Use vga=ask for menu.
3361 This is actually a boot loader parameter; the value is
3362 passed to the kernel using a special protocol.
3364 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3365 size of <nn>. This can be used to increase the
3366 minimum size (128MB on x86). It can also be used to
3367 decrease the size and leave more room for directly
3370 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3373 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3376 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3380 Controls the behavior of vsyscalls (i.e. calls to
3381 fixed addresses of 0xffffffffff600x00 from legacy
3382 code). Most statically-linked binaries and older
3383 versions of glibc use these calls. Because these
3384 functions are at fixed addresses, they make nice
3385 targets for exploits that can control RIP.
3387 emulate [default] Vsyscalls turn into traps and are
3388 emulated reasonably safely.
3390 native Vsyscalls are native syscall instructions.
3391 This is a little bit faster than trapping
3392 and makes a few dynamic recompilers work
3393 better than they would in emulation mode.
3394 It also makes exploits much easier to write.
3396 none Vsyscalls don't work at all. This makes
3397 them quite hard to use for exploits but
3398 might break your system.
3400 vt.color= [VT] Default text color.
3401 Format: 0xYX, X = foreground, Y = background.
3402 Default: 0x07 = light gray on black.
3404 vt.cur_default= [VT] Default cursor shape.
3405 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3406 the parameters of the <Esc>[?A;B;Cc escape sequence;
3407 see VGA-softcursor.txt. Default: 2 = underline.
3409 vt.default_blu= [VT]
3410 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3411 Change the default blue palette of the console.
3412 This is a 16-member array composed of values
3415 vt.default_grn= [VT]
3416 Format: <green0>,<green1>,<green2>,...,<green15>
3417 Change the default green palette of the console.
3418 This is a 16-member array composed of values
3421 vt.default_red= [VT]
3422 Format: <red0>,<red1>,<red2>,...,<red15>
3423 Change the default red palette of the console.
3424 This is a 16-member array composed of values
3430 Set system-wide default UTF-8 mode for all tty's.
3431 Default is 1, i.e. UTF-8 mode is enabled for all
3432 newly opened terminals.
3434 vt.global_cursor_default=
3437 Set system-wide default for whether a cursor
3438 is shown on new VTs. Default is -1,
3439 i.e. cursors will be created by default unless
3440 overridden by individual drivers. 0 will hide
3441 cursors, 1 will display them.
3443 vt.italic= [VT] Default color for italic text; 0-15.
3446 vt.underline= [VT] Default color for underlined text; 0-15.
3449 watchdog timers [HW,WDT] For information on watchdog timers,
3450 see Documentation/watchdog/watchdog-parameters.txt
3451 or other driver-specific files in the
3452 Documentation/watchdog/ directory.
3454 workqueue.disable_numa
3455 By default, all work items queued to unbound
3456 workqueues are affine to the NUMA nodes they're
3457 issued on, which results in better behavior in
3458 general. If NUMA affinity needs to be disabled for
3459 whatever reason, this option can be used. Note
3460 that this also can be controlled per-workqueue for
3461 workqueues visible under /sys/bus/workqueue/.
3463 workqueue.power_efficient
3464 Per-cpu workqueues are generally preferred because
3465 they show better performance thanks to cache
3466 locality; unfortunately, per-cpu workqueues tend to
3467 be more power hungry than unbound workqueues.
3469 Enabling this makes the per-cpu workqueues which
3470 were observed to contribute significantly to power
3471 consumption unbound, leading to measurably lower
3472 power usage at the cost of small performance
3475 The default value of this parameter is determined by
3476 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3478 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3479 default x2apic cluster mode on platforms
3482 x86_mrst_timer= [X86-32,APBT]
3483 Choose timer option for x86 Moorestown MID platform.
3484 Two valid options are apbt timer only and lapic timer
3485 plus one apbt timer for broadcast timer.
3486 x86_mrst_timer=apbt_only | lapic_and_apbt
3488 xen_emul_unplug= [HW,X86,XEN]
3489 Unplug Xen emulated devices
3490 Format: [unplug0,][unplug1]
3491 ide-disks -- unplug primary master IDE devices
3492 aux-ide-disks -- unplug non-primary-master IDE devices
3493 nics -- unplug network devices
3494 all -- unplug all emulated devices (NICs and IDE disks)
3495 unnecessary -- unplugging emulated devices is
3496 unnecessary even if the host did not respond to
3498 never -- do not unplug even if version check succeeds
3500 xen_nopvspin [X86,XEN]
3501 Disables the ticketlock slowpath using Xen PV
3504 xirc2ps_cs= [NET,PCMCIA]
3506 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3508 ______________________________________________________________________
3512 Add more DRM drivers.
projects / ~andy / linux / blob