4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 CLK Common clock infrastructure is enabled.
48 CMA Contiguous Memory Area support is enabled.
49 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
51 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
52 EFI EFI Partitioning (GPT) is enabled
53 EIDE EIDE/ATAPI support is enabled.
54 EVM Extended Verification Module
55 FB The frame buffer device is enabled.
56 FTRACE Function tracing enabled.
57 GCOV GCOV profiling is enabled.
58 HW Appropriate hardware is enabled.
59 IA-64 IA-64 architecture is enabled.
60 IMA Integrity measurement architecture is enabled.
61 IOSCHED More than one I/O scheduler is enabled.
62 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
63 IPV6 IPv6 support is enabled.
64 ISAPNP ISA PnP code is enabled.
65 ISDN Appropriate ISDN support is enabled.
66 JOY Appropriate joystick support is enabled.
67 KGDB Kernel debugger support is enabled.
68 KVM Kernel Virtual Machine support is enabled.
69 LIBATA Libata driver is enabled
70 LP Printer support is enabled.
71 LOOP Loopback device support is enabled.
72 M68k M68k architecture is enabled.
73 These options have more detailed description inside of
74 Documentation/m68k/kernel-options.txt.
75 MDA MDA console support is enabled.
76 MIPS MIPS architecture is enabled.
77 MOUSE Appropriate mouse support is enabled.
78 MSI Message Signaled Interrupts (PCI).
79 MTD MTD (Memory Technology Device) support is enabled.
80 NET Appropriate network support is enabled.
81 NUMA NUMA support is enabled.
82 NFS Appropriate NFS support is enabled.
83 OSS OSS sound support is enabled.
84 PV_OPS A paravirtualized kernel is enabled.
85 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
86 PARISC The PA-RISC architecture is enabled.
87 PCI PCI bus support is enabled.
88 PCIE PCI Express support is enabled.
89 PCMCIA The PCMCIA subsystem is enabled.
90 PNP Plug & Play support is enabled.
91 PPC PowerPC architecture is enabled.
92 PPT Parallel port support is enabled.
93 PS2 Appropriate PS/2 support is enabled.
94 RAM RAM disk support is enabled.
95 S390 S390 architecture is enabled.
96 SCSI Appropriate SCSI support is enabled.
97 A lot of drivers have their options described inside
98 the Documentation/scsi/ sub-directory.
99 SECURITY Different security models are enabled.
100 SELINUX SELinux support is enabled.
101 APPARMOR AppArmor support is enabled.
102 SERIAL Serial support is enabled.
103 SH SuperH architecture is enabled.
104 SMP The kernel is an SMP kernel.
105 SPARC Sparc architecture is enabled.
106 SWSUSP Software suspend (hibernation) is enabled.
107 SUSPEND System suspend states are enabled.
108 TPM TPM drivers are enabled.
109 TS Appropriate touchscreen support is enabled.
110 UMS USB Mass Storage support is enabled.
111 USB USB support is enabled.
112 USBHID USB Human Interface Device support is enabled.
113 V4L Video For Linux support is enabled.
114 VMMIO Driver for memory mapped virtio devices is enabled.
115 VGA The VGA console has been enabled.
116 VT Virtual terminal support is enabled.
117 WDT Watchdog support is enabled.
118 XT IBM PC/XT MFM hard disk support is enabled.
119 X86-32 X86-32, aka i386 architecture is enabled.
120 X86-64 X86-64 architecture is enabled.
121 More X86-64 boot options can be found in
122 Documentation/x86/x86_64/boot-options.txt .
123 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
124 XEN Xen support is enabled
126 In addition, the following text indicates that the option:
128 BUGS= Relates to possible processor bugs on the said processor.
129 KNL Is a kernel start-up parameter.
130 BOOT Is a boot loader parameter.
132 Parameters denoted with BOOT are actually interpreted by the boot
133 loader, and have no meaning to the kernel directly.
134 Do not modify the syntax of boot loader parameters without extreme
135 need or coordination with <Documentation/x86/boot.txt>.
137 There are also arch-specific kernel-parameters not documented here.
138 See for example <Documentation/x86/x86_64/boot-options.txt>.
140 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
141 a trailing = on the name of any parameter states that that parameter will
142 be entered as an environment variable, whereas its absence indicates that
143 it will appear as a kernel argument readable via /proc/cmdline by programs
144 running once the system is up.
146 The number of kernel parameters is not limited, but the length of the
147 complete command line (parameters including spaces etc.) is limited to
148 a fixed number of characters. This limit depends on the architecture
149 and is between 256 and 4096 characters. It is defined in the file
150 ./include/asm/setup.h as COMMAND_LINE_SIZE.
152 Finally, the [KMG] suffix is commonly described after a number of kernel
153 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
154 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
155 bytes respectively. Such letter suffixes can also be entirely omitted.
159 Advanced Configuration and Power Interface
160 Format: { force | off | strict | noirq | rsdt }
161 force -- enable ACPI if default was off
162 off -- disable ACPI if default was on
163 noirq -- do not use ACPI for IRQ routing
164 strict -- Be less tolerant of platforms that are not
165 strictly ACPI specification compliant.
166 rsdt -- prefer RSDT over (default) XSDT
167 copy_dsdt -- copy DSDT to memory
169 See also Documentation/power/runtime_pm.txt, pci=noacpi
171 acpi_rsdp= [ACPI,EFI,KEXEC]
172 Pass the RSDP address to the kernel, mostly used
173 on machines running EFI runtime service to boot the
174 second kernel for kdump.
176 acpi_apic_instance= [ACPI, IOAPIC]
178 2: use 2nd APIC table, if available
179 1,0: use 1st APIC table
182 acpi_backlight= [HW,ACPI]
183 acpi_backlight=vendor
185 If set to vendor, prefer vendor specific driver
186 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
187 of the ACPI video.ko driver.
189 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
190 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
192 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
193 debug output. Bits in debug_layer correspond to a
194 _COMPONENT in an ACPI source file, e.g.,
195 #define _COMPONENT ACPI_PCI_COMPONENT
196 Bits in debug_level correspond to a level in
197 ACPI_DEBUG_PRINT statements, e.g.,
198 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
199 The debug_level mask defaults to "info". See
200 Documentation/acpi/debug.txt for more information about
201 debug layers and levels.
203 Enable processor driver info messages:
204 acpi.debug_layer=0x20000000
205 Enable PCI/PCI interrupt routing info messages:
206 acpi.debug_layer=0x400000
207 Enable AML "Debug" output, i.e., stores to the Debug
208 object while interpreting AML:
209 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
210 Enable all messages related to ACPI hardware:
211 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
213 Some values produce so much output that the system is
214 unusable. The "log_buf_len" parameter may be useful
215 if you need to capture more output.
217 acpi_irq_balance [HW,ACPI]
218 ACPI will balance active IRQs
221 acpi_irq_nobalance [HW,ACPI]
222 ACPI will not move active IRQs (default)
225 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
226 Format: <irq>,<irq>...
228 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
230 Format: <irq>,<irq>...
232 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
234 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
235 Format: To spoof as Windows 98: ="Microsoft Windows"
237 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
238 acpi_osi="string1" # add string1
239 acpi_osi="!string2" # remove string2
240 acpi_osi=!* # remove all strings
241 acpi_osi=! # disable all built-in OS vendor
243 acpi_osi= # disable all strings
245 'acpi_osi=!' can be used in combination with single or
246 multiple 'acpi_osi="string1"' to support specific OS
247 vendor string(s). Note that such command can only
248 affect the default state of the OS vendor strings, thus
249 it cannot affect the default state of the feature group
250 strings and the current state of the OS vendor strings,
251 specifying it multiple times through kernel command line
252 is meaningless. This command is useful when one do not
253 care about the state of the feature group strings which
254 should be controlled by the OSPM.
256 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
257 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
258 can make '_OSI("Windows 2000")' TRUE.
260 'acpi_osi=' cannot be used in combination with other
261 'acpi_osi=' command lines, the _OSI method will not
262 exist in the ACPI namespace. NOTE that such command can
263 only affect the _OSI support state, thus specifying it
264 multiple times through kernel command line is also
267 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
270 'acpi_osi=!*' can be used in combination with single or
271 multiple 'acpi_osi="string1"' to support specific
272 string(s). Note that such command can affect the
273 current state of both the OS vendor strings and the
274 feature group strings, thus specifying it multiple times
275 through kernel command line is meaningful. But it may
276 still not able to affect the final state of a string if
277 there are quirks related to this string. This command
278 is useful when one want to control the state of the
279 feature group strings to debug BIOS issues related to
282 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
283 '_OSI("Module Device")' FALSE.
284 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
285 '_OSI("Module Device")' TRUE.
286 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
288 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
290 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
291 they all will make '_OSI("Windows 2000")' TRUE.
294 Override the pmtimer bug detection: force the kernel
295 to assume that this machine's pmtimer latches its value
296 and always returns good values.
298 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
299 Format: { level | edge | high | low }
301 acpi_serialize [HW,ACPI] force serialization of AML methods
303 acpi_skip_timer_override [HW,ACPI]
304 Recognize and ignore IRQ0/pin2 Interrupt Override.
305 For broken nForce2 BIOS resulting in XT-PIC timer.
307 acpi_sleep= [HW,ACPI] Sleep options
308 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
309 old_ordering, nonvs, sci_force_enable }
310 See Documentation/power/video.txt for information on
312 s3_beep is for debugging; it makes the PC's speaker beep
313 as soon as the kernel's real-mode entry point is called.
314 s4_nohwsig prevents ACPI hardware signature from being
315 used during resume from hibernation.
316 old_ordering causes the ACPI 1.0 ordering of the _PTS
317 control method, with respect to putting devices into
318 low power states, to be enforced (the ACPI 2.0 ordering
319 of _PTS is used by default).
320 nonvs prevents the kernel from saving/restoring the
321 ACPI NVS memory during suspend/hibernation and resume.
322 sci_force_enable causes the kernel to set SCI_EN directly
323 on resume from S1/S3 (which is against the ACPI spec,
324 but some broken systems don't work without it).
326 acpi_use_timer_override [HW,ACPI]
327 Use timer override. For some broken Nvidia NF5 boards
328 that require a timer override, but don't have HPET
330 acpi_enforce_resources= [ACPI]
331 { strict | lax | no }
332 Check for resource conflicts between native drivers
333 and ACPI OperationRegions (SystemIO and SystemMemory
334 only). IO ports and memory declared in ACPI might be
335 used by the ACPI subsystem in arbitrary AML code and
336 can interfere with legacy drivers.
337 strict (default): access to resources claimed by ACPI
338 is denied; legacy drivers trying to access reserved
339 resources will fail to bind to device using them.
340 lax: access to resources claimed by ACPI is allowed;
341 legacy drivers trying to access reserved resources
342 will bind successfully but a warning message is logged.
343 no: ACPI OperationRegions are not marked as reserved,
344 no further checks are performed.
346 add_efi_memmap [EFI; X86] Include EFI memory map in
347 kernel's map of available physical RAM.
350 { off | try_unsupported }
351 off: disable AGP support
352 try_unsupported: try to drive unsupported chipsets
353 (may crash computer or cause data corruption)
356 See Documentation/sound/alsa/alsa-parameters.txt
359 Allow the default userspace alignment fault handler
360 behaviour to be specified. Bit 0 enables warnings,
361 bit 1 enables fixups, and bit 2 sends a segfault.
363 align_va_addr= [X86-64]
364 Align virtual addresses by clearing slice [14:12] when
365 allocating a VMA at process creation time. This option
366 gives you up to 3% performance improvement on AMD F15h
367 machines (where it is enabled by default) for a
368 CPU-intensive style benchmark, and it can vary highly in
369 a microbenchmark depending on workload and compiler.
371 32: only for 32-bit processes
372 64: only for 64-bit processes
373 on: enable for both 32- and 64-bit processes
374 off: disable for both 32- and 64-bit processes
376 alloc_snapshot [FTRACE]
377 Allocate the ftrace snapshot buffer on boot up when the
378 main buffer is allocated. This is handy if debugging
379 and you need to use tracing_snapshot() on boot up, and
380 do not want to use tracing_snapshot_alloc() as it needs
381 to be done where GFP_KERNEL allocations are allowed.
383 amd_iommu= [HW,X86-64]
384 Pass parameters to the AMD IOMMU driver in the system.
386 fullflush - enable flushing of IO/TLB entries when
387 they are unmapped. Otherwise they are
388 flushed before they will be reused, which
390 off - do not initialize any AMD IOMMU found in
392 force_isolation - Force device isolation for all
393 devices. The IOMMU driver is not
394 allowed anymore to lift isolation
395 requirements as needed. This option
396 does not override iommu=pt
398 amd_iommu_dump= [HW,X86-64]
399 Enable AMD IOMMU driver option to dump the ACPI table
400 for AMD IOMMU. With this option enabled, AMD IOMMU
401 driver will print ACPI tables for AMD IOMMU during
402 IOMMU initialization.
404 amijoy.map= [HW,JOY] Amiga joystick support
405 Map of devices attached to JOY0DAT and JOY1DAT
407 See also Documentation/input/joystick.txt
409 analog.map= [HW,JOY] Analog joystick and gamepad support
410 Specifies type or capabilities of an analog joystick
411 connected to one of 16 gameports
412 Format: <type1>,<type2>,..<type16>
415 Power management functions (SPARCstation-4/5 + deriv.)
417 Disable APC CPU standby support. SPARCstation-Fox does
418 not play well with APC CPU idle - disable it if you have
419 APC and your system crashes randomly.
421 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
422 Change the output verbosity whilst booting
423 Format: { quiet (default) | verbose | debug }
424 Change the amount of debugging information output
425 when initialising the APIC and IO-APIC components.
428 See Documentation/networking/ipv6.txt.
430 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
431 Limit apic dumping. The parameter defines the maximal
432 number of local apics being dumped. Also it is possible
433 to set it to "all" by meaning -- no limit here.
434 Format: { 1 (default) | 2 | ... | all }.
435 The parameter valid if only apic=debug or
436 apic=verbose is specified.
437 Example: apic=debug show_lapic=all
439 apm= [APM] Advanced Power Management
440 See header of arch/x86/kernel/apm_32.c.
442 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
443 Format: <io>,<irq>,<nodeID>
447 atarimouse= [HW,MOUSE] Atari Mouse
449 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
450 EzKey and similar keyboards
452 atkbd.reset= [HW] Reset keyboard during initialization
454 atkbd.set= [HW] Select keyboard code set
455 Format: <int> (2 = AT (default), 3 = PS/2)
457 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
460 atkbd.softraw= [HW] Choose between synthetic and real raw mode
461 Format: <bool> (0 = real, 1 = synthetic (default))
463 atkbd.softrepeat= [HW]
464 Use software keyboard repeat
466 baycom_epp= [HW,AX25]
469 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
471 See header of drivers/net/hamradio/baycom_par.c.
473 baycom_ser_fdx= [HW,AX25]
474 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
475 Format: <io>,<irq>,<mode>[,<baud>]
476 See header of drivers/net/hamradio/baycom_ser_fdx.c.
478 baycom_ser_hdx= [HW,AX25]
479 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
480 Format: <io>,<irq>,<mode>
481 See header of drivers/net/hamradio/baycom_ser_hdx.c.
483 blkdevparts= Manual partition parsing of block device(s) for
484 embedded devices based on command line input.
485 See Documentation/block/cmdline-partition.txt
487 boot_delay= Milliseconds to delay each printk during boot.
488 Values larger than 10 seconds (10000) are changed to
492 bootmem_debug [KNL] Enable bootmem allocator debug messages.
494 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
495 bttv.radio= Most important insmod options are available as
497 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
500 bulk_remove=off [PPC] This parameter disables the use of the pSeries
501 firmware feature for flushing multiple hpte entries
504 c101= [NET] Moxa C101 synchronous serial card
506 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
507 Sometimes CPU hardware bugs make them report the cache
508 size incorrectly. The kernel will attempt work arounds
509 to fix known problems, but for some CPUs it is not
510 possible to determine what the correct size should be.
511 This option provides an override for these situations.
513 ccw_timeout_log [S390]
514 See Documentation/s390/CommonIO for details.
516 cgroup_disable= [KNL] Disable a particular controller
517 Format: {name of the controller(s) to disable}
518 {Currently supported controllers - "memory"}
520 checkreqprot [SELINUX] Set initial checkreqprot flag value.
521 Format: { "0" | "1" }
522 See security/selinux/Kconfig help text.
523 0 -- check protection applied by kernel (includes
524 any implied execute protection).
525 1 -- check protection requested by application.
526 Default value is set via a kernel config option.
527 Value can be changed at runtime via
528 /selinux/checkreqprot.
531 See Documentation/s390/CommonIO for details.
534 Keep all clocks already enabled by bootloader on,
535 even if no driver has claimed them. This is useful
536 for debug and development, but should not be
537 needed on a platform with proper driver support.
538 For more information, see Documentation/clk.txt.
540 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
542 Forces specified clocksource (if available) to be used
543 when calculating gettimeofday(). If specified
544 clocksource is not available, it defaults to PIT.
545 Format: { pit | tsc | cyclone | pmtmr }
547 clocksource= Override the default clocksource
549 Override the default clocksource and use the clocksource
550 with the name specified.
551 Some clocksource names to choose from, depending on
553 [all] jiffies (this is the base, fallback clocksource)
555 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
556 pxa_timer,timer3,32k_counter,timer0_1
558 [X86-32] pit,hpet,tsc;
559 scx200_hrt on Geode; cyclone on IBM x440
567 clearcpuid=BITNUM [X86]
568 Disable CPUID feature X for the kernel. See
569 arch/x86/include/asm/cpufeature.h for the valid bit
570 numbers. Note the Linux specific bits are not necessarily
571 stable over kernel options, but the vendor specific
573 Also note that user programs calling CPUID directly
574 or using the feature without checking anything
575 will still see it. This just prevents it from
576 being used by the kernel or shown in /proc/cpuinfo.
577 Also note the kernel might malfunction if you disable
581 Sets the size of kernel global memory area for contiguous
582 memory allocations. For more information, see
583 include/linux/dma-contiguous.h
585 cmo_free_hint= [PPC] Format: { yes | no }
586 Specify whether pages are marked as being inactive
587 when they are freed. This is used in CMO environments
588 to determine OS memory pressure for page stealing by
592 coherent_pool=nn[KMG] [ARM,KNL]
593 Sets the size of memory pool for coherent, atomic dma
594 allocations, by default set to 256K.
596 code_bytes [X86] How many bytes of object code to print
601 com20020= [HW,NET] ARCnet - COM20020 chipset
603 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
605 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
609 ARCnet - COM90xx chipset (memory-mapped buffers)
610 Format: <io>[,<irq>[,<memstart>]]
612 condev= [HW,S390] console device
615 console= [KNL] Output console device and options.
617 tty<n> Use the virtual console device <n>.
621 Use the specified serial port. The options are of
622 the form "bbbbpnf", where "bbbb" is the baud rate,
623 "p" is parity ("n", "o", or "e"), "n" is number of
624 bits, and "f" is flow control ("r" for RTS or
625 omit it). Default is "9600n8".
627 See Documentation/serial-console.txt for more
629 Documentation/networking/netconsole.txt for an
632 uart[8250],io,<addr>[,options]
633 uart[8250],mmio,<addr>[,options]
634 Start an early, polled-mode console on the 8250/16550
635 UART at the specified I/O port or MMIO address,
636 switching to the matching ttyS device later. The
637 options are the same as for ttyS, above.
638 hvc<n> Use the hypervisor console device <n>. This is for
639 both Xen and PowerPC hypervisors.
641 If the device connected to the port is not a TTY but a braille
642 device, prepend "brl," before the device type, for instance
644 For now, only VisioBraille is supported.
646 consoleblank= [KNL] The console blank (screen saver) timeout in
647 seconds. Defaults to 10*60 = 10mins. A value of 0
648 disables the blank timer.
651 [KNL] Change the default value for
652 /proc/<pid>/coredump_filter.
653 See also Documentation/filesystems/proc.txt.
655 cpuidle.off=1 [CPU_IDLE]
656 disable the cpuidle sub-system
658 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
660 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
662 crashkernel=size[KMG][@offset[KMG]]
663 [KNL] Using kexec, Linux can switch to a 'crash kernel'
664 upon panic. This parameter reserves the physical
665 memory region [offset, offset + size] for that kernel
666 image. If '@offset' is omitted, then a suitable offset
667 is selected automatically. Check
668 Documentation/kdump/kdump.txt for further details.
670 crashkernel=range1:size1[,range2:size2,...][@offset]
671 [KNL] Same as above, but depends on the memory
672 in the running system. The syntax of range is
673 start-[end] where start and end are both
674 a memory unit (amount[KMG]). See also
675 Documentation/kdump/kdump.txt for an example.
677 crashkernel=size[KMG],high
678 [KNL, x86_64] range could be above 4G. Allow kernel
679 to allocate physical memory region from top, so could
680 be above 4G if system have more than 4G ram installed.
681 Otherwise memory region will be allocated below 4G, if
683 It will be ignored if crashkernel=X is specified.
684 crashkernel=size[KMG],low
685 [KNL, x86_64] range under 4G. When crashkernel=X,high
686 is passed, kernel could allocate physical memory region
687 above 4G, that cause second kernel crash on system
688 that require some amount of low memory, e.g. swiotlb
689 requires at least 64M+32K low memory. Kernel would
690 try to allocate 72M below 4G automatically.
691 This one let user to specify own low range under 4G
692 for second kernel instead.
693 0: to disable low allocation.
694 It will be ignored when crashkernel=X,high is not used
695 or memory reserved is below 4G.
700 cs89x0_media= [HW,NET]
701 Format: { rj45 | aui | bnc }
704 See header of drivers/s390/block/dasd_devmap.c.
706 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
707 (one device per port)
708 Format: <port#>,<type>
709 See also Documentation/input/joystick-parport.txt
711 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
712 time. See Documentation/dynamic-debug-howto.txt for
713 details. Deprecated, see dyndbg.
715 debug [KNL] Enable kernel debugging (events log level).
718 [KNL] verbose self-tests
720 Print debugging info while doing the locking API
722 We default to 0 (no extra messages), setting it to
723 1 will print _a lot_ more information - normally
724 only useful to kernel developers.
726 debug_objects [KNL] Enable object debugging
729 [KNL] Disable object debugging
731 debug_guardpage_minorder=
732 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
733 parameter allows control of the order of pages that will
734 be intentionally kept free (and hence protected) by the
735 buddy allocator. Bigger value increase the probability
736 of catching random memory corruption, but reduce the
737 amount of memory for normal system use. The maximum
738 possible value is MAX_ORDER/2. Setting this parameter
739 to 1 or 2 should be enough to identify most random
740 memory corruption problems caused by bugs in kernel or
741 driver code when a CPU writes to (or reads from) a
742 random memory location. Note that there exists a class
743 of memory corruptions problems caused by buggy H/W or
744 F/W or by drivers badly programing DMA (basically when
745 memory is written at bus level and the CPU MMU is
746 bypassed) which are not detectable by
747 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
748 tracking down these problems.
750 debugpat [X86] Enable PAT debugging
752 decnet.addr= [HW,NET]
753 Format: <area>[,<node>]
754 See also Documentation/networking/decnet.txt.
757 [same as hugepagesz=] The size of the default
758 HugeTLB page size. This is the size represented by
759 the legacy /proc/ hugepages APIs, used for SHM, and
760 default size when mounting hugetlbfs filesystems.
761 Defaults to the default architecture's huge page size
765 Set number of hash buckets for dentry cache.
768 IO parameters + enable/disable command.
770 digiepca= [HW,SERIAL]
771 See drivers/char/README.epca and
772 Documentation/serial/digiepca.txt.
775 See Documentation/networking/ipv6.txt.
777 disable_ddw [PPC/PSERIES]
778 Disable Dynamic DMA Window support. Use this if
779 to workaround buggy firmware.
782 See Documentation/networking/ipv6.txt.
784 disable_mtrr_cleanup [X86]
785 The kernel tries to adjust MTRR layout from continuous
786 to discrete, to make X server driver able to add WB
787 entry later. This parameter disables that.
789 disable_mtrr_trim [X86, Intel and AMD only]
790 By default the kernel will trim any uncacheable
791 memory out of your available memory pool based on
792 MTRR settings. This parameter disables that behavior,
793 possibly causing your machine to run very slowly.
795 disable_timer_pin_1 [X86]
796 Disable PIN 1 of APIC timer
797 Can be useful to work around chipset bugs.
799 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
800 this option disables the debugging code at boot.
802 dma_debug_entries=<number>
803 This option allows to tune the number of preallocated
804 entries for DMA-API debugging code. One entry is
805 required per DMA-API allocation. Use this if the
806 DMA-API debugging code disables itself because the
807 architectural default is too low.
809 dma_debug_driver=<driver_name>
810 With this option the DMA-API debugging driver
811 filter feature can be enabled at boot time. Just
812 pass the driver to filter for as the parameter.
813 The filter can be disabled or changed to another
814 driver later using sysfs.
816 drm_kms_helper.edid_firmware=[<connector>:]<file>
817 Broken monitors, graphic adapters and KVMs may
818 send no or incorrect EDID data sets. This parameter
819 allows to specify an EDID data set in the
820 /lib/firmware directory that is used instead.
821 Generic built-in EDID data sets are used, if one of
822 edid/1024x768.bin, edid/1280x1024.bin,
823 edid/1680x1050.bin, or edid/1920x1080.bin is given
824 and no file with the same name exists. Details and
825 instructions how to build your own EDID data are
826 available in Documentation/EDID/HOWTO.txt. An EDID
827 data set will only be used for a particular connector,
828 if its name and a colon are prepended to the EDID
833 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
834 module.dyndbg[="val"]
835 Enable debug messages at boot time. See
836 Documentation/dynamic-debug-howto.txt for details.
838 earlycon= [KNL] Output early console device and options.
839 uart[8250],io,<addr>[,options]
840 uart[8250],mmio,<addr>[,options]
841 uart[8250],mmio32,<addr>[,options]
842 Start an early, polled-mode console on the 8250/16550
843 UART at the specified I/O port or MMIO address.
844 MMIO inter-register address stride is either 8-bit
845 (mmio) or 32-bit (mmio32).
846 The options are the same as for ttyS, above.
848 earlyprintk= [X86,SH,BLACKFIN,ARM]
851 earlyprintk=serial[,ttySn[,baudrate]]
852 earlyprintk=serial[,0x...[,baudrate]]
853 earlyprintk=ttySn[,baudrate]
854 earlyprintk=dbgp[debugController#]
856 earlyprintk is useful when the kernel crashes before
857 the normal console is initialized. It is not enabled by
858 default because it has some cosmetic problems.
860 Append ",keep" to not disable it when the real console
863 Only vga or serial or usb debug port at a time.
865 Currently only ttyS0 and ttyS1 may be specified by
866 name. Other I/O ports may be explicitly specified
867 on some architectures (x86 and arm at least) by
868 replacing ttySn with an I/O port address, like this:
869 earlyprintk=serial,0x1008,115200
870 You can find the port for a given device in
871 /proc/tty/driver/serial:
872 2: uart:ST16650V2 port:00001008 irq:18 ...
874 Interaction with the standard serial driver is not
877 The VGA output is eventually overwritten by the real
880 The xen output can only be used by Xen PV guests.
882 ekgdboc= [X86,KGDB] Allow early kernel console debugging
885 This is designed to be used in conjunction with
886 the boot argument: earlyprintk=vga
889 Format: {"off" | "on" | "skip[mbr]"}
891 efi_no_storage_paranoia [EFI; X86]
892 Using this parameter you can use more than 50% of
893 your efi variable storage. Use this parameter only if
894 you are really sure that your UEFI does sane gc and
895 fulfills the spec otherwise your board may brick.
897 eisa_irq_edge= [PARISC,HW]
898 See header of drivers/parisc/eisa.c.
901 See comment before function elanfreq_setup() in
902 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
905 Format: {"cfq" | "deadline" | "noop"}
906 See Documentation/block/cfq-iosched.txt and
907 Documentation/block/deadline-iosched.txt for details.
909 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
910 Specifies physical address of start of kernel core
911 image elf header and optionally the size. Generally
912 kexec loader will pass this option to capture kernel.
913 See Documentation/kdump/kdump.txt for details.
915 enable_mtrr_cleanup [X86]
916 The kernel tries to adjust MTRR layout from continuous
917 to discrete, to make X server driver able to add WB
918 entry later. This parameter enables that.
920 enable_timer_pin_1 [X86]
921 Enable PIN 1 of APIC timer
922 Can be useful to work around chipset bugs
923 (in particular on some ATI chipsets).
924 The kernel tries to set a reasonable default.
926 enforcing [SELINUX] Set initial enforcing status.
928 See security/selinux/Kconfig help text.
929 0 -- permissive (log only, no denials).
930 1 -- enforcing (deny and log).
932 Value can be changed at runtime via /selinux/enforce.
935 Disable Error Record Serialization Table (ERST)
938 ether= [HW,NET] Ethernet cards parameters
939 This option is obsoleted by the "netdev=" option, which
940 has equivalent usage. See its documentation for details.
944 Permit 'security.evm' to be updated regardless of
945 current integrity status.
949 fail_make_request=[KNL]
950 General fault injection mechanism.
951 Format: <interval>,<probability>,<space>,<times>
952 See also Documentation/fault-injection/.
955 See Documentation/blockdev/floppy.txt.
957 force_pal_cache_flush
958 [IA-64] Avoid check_sal_cache_flush which may hang on
959 buggy SAL_CACHE_FLUSH implementations. Using this
960 parameter will force ia64_sal_cache_flush to call
961 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
964 [FTRACE] will set and start the specified tracer
965 as early as possible in order to facilitate early
968 ftrace_dump_on_oops[=orig_cpu]
969 [FTRACE] will dump the trace buffers on oops.
970 If no parameter is passed, ftrace will dump
971 buffers of all CPUs, but if you pass orig_cpu, it will
972 dump only the buffer of the CPU that triggered the
975 ftrace_filter=[function-list]
976 [FTRACE] Limit the functions traced by the function
977 tracer at boot up. function-list is a comma separated
978 list of functions. This list can be changed at run
979 time by the set_ftrace_filter file in the debugfs
982 ftrace_notrace=[function-list]
983 [FTRACE] Do not trace the functions specified in
984 function-list. This list can be changed at run time
985 by the set_ftrace_notrace file in the debugfs
988 ftrace_graph_filter=[function-list]
989 [FTRACE] Limit the top level callers functions traced
990 by the function graph tracer at boot up.
991 function-list is a comma separated list of functions
992 that can be changed at run time by the
993 set_graph_function file in the debugfs tracing directory.
996 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
997 support via parallel port (up to 5 devices per port)
998 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
999 See also Documentation/input/joystick-parport.txt
1003 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1007 gcov_persist= [GCOV] When non-zero (default), profiling data for
1008 kernel modules is saved and remains accessible via
1009 debugfs, even when the module is unloaded/reloaded.
1010 When zero, profiling data is discarded and associated
1011 debugfs files are removed at module unload time.
1013 gpt [EFI] Forces disk with valid GPT signature but
1014 invalid Protective MBR to be treated as GPT.
1016 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1017 the "Enable 0" bit of the configuration register.
1020 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1021 the "Enable 0" bit of the configuration register.
1024 grcan.select= [HW] Select which physical interface to use.
1027 grcan.txsize= [HW] Sets the size of the tx buffer.
1028 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1030 grcan.rxsize= [HW] Sets the size of the rx buffer.
1031 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1034 hashdist= [KNL,NUMA] Large hashes allocated during boot
1035 are distributed across NUMA nodes. Defaults on
1036 for 64-bit NUMA, off otherwise.
1037 Format: 0 | 1 (for off | on)
1039 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1041 hd= [EIDE] (E)IDE hard drive subsystem geometry
1042 Format: <cyl>,<head>,<sect>
1045 Disable Hardware Error Source Table (HEST) support;
1046 corresponding firmware-first mode error processing
1047 logic will be disabled.
1049 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1050 size of <nn>. This works even on boxes that have no
1051 highmem otherwise. This also works to reduce highmem
1052 size on bigger boxes.
1054 highres= [KNL] Enable/disable high resolution timer mode.
1055 Valid parameters: "on", "off"
1059 See Documentation/isdn/README.HiSax.
1063 hpet= [X86-32,HPET] option to control HPET usage
1064 Format: { enable (default) | disable | force |
1066 disable: disable HPET and use PIT instead
1067 force: allow force enabled of undocumented chips (ICH4,
1069 verbose: show contents of HPET registers during setup
1071 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1072 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1073 On x86-64 and powerpc, this option can be specified
1074 multiple times interleaved with hugepages= to reserve
1075 huge pages of different sizes. Valid pages sizes on
1076 x86-64 are 2M (when the CPU supports "pse") and 1G
1077 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1078 Note that 1GB pages can only be allocated at boot time
1079 using hugepages= and not freed afterwards.
1081 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1082 terminal devices. Valid values: 0..8
1083 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1084 If specified, z/VM IUCV HVC accepts connections
1085 from listed z/VM user IDs only.
1087 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1088 hardware thread id mappings.
1089 Format: <cpu>:<hwthread>
1092 Do not unregister boot console at start. This is only
1093 useful for debugging when something happens in the window
1094 between unregistering the boot console and initializing
1097 i2c_bus= [HW] Override the default board specific I2C bus speed
1098 or register an additional I2C bus that is not
1099 registered from board initialization code.
1103 i8042.debug [HW] Toggle i8042 debug mode
1104 i8042.direct [HW] Put keyboard port into non-translated mode
1105 i8042.dumbkbd [HW] Pretend that controller can only read data from
1106 keyboard and cannot control its state
1107 (Don't attempt to blink the leds)
1108 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1109 i8042.nokbd [HW] Don't check/create keyboard port
1110 i8042.noloop [HW] Disable the AUX Loopback command while probing
1112 i8042.nomux [HW] Don't check presence of an active multiplexing
1114 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1116 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1117 i8042.reset [HW] Reset the controller during init and cleanup
1118 i8042.unlock [HW] Unlock (ignore) the keylock
1122 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1123 indicates that the driver is running on unsupported
1125 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1126 does not match list of supported models.
1128 [HW] Report power status in /proc/i8k
1129 (disabled by default)
1130 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1133 i915.invert_brightness=
1134 [DRM] Invert the sense of the variable that is used to
1135 set the brightness of the panel backlight. Normally a
1136 brightness value of 0 indicates backlight switched off,
1137 and the maximum of the brightness value sets the backlight
1138 to maximum brightness. If this parameter is set to 0
1139 (default) and the machine requires it, or this parameter
1140 is set to 1, a brightness value of 0 sets the backlight
1141 to maximum brightness, and the maximum of the brightness
1142 value switches the backlight off.
1143 -1 -- never invert brightness
1144 0 -- machine default
1145 1 -- force brightness inversion
1148 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1150 ide-core.nodma= [HW] (E)IDE subsystem
1151 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1152 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1153 .cdrom .chs .ignore_cable are additional options
1154 See Documentation/ide/ide.txt.
1156 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1157 Claim all unknown PCI IDE storage controllers.
1160 Format: idle=poll, idle=halt, idle=nomwait
1161 Poll forces a polling idle loop that can slightly
1162 improve the performance of waking up a idle CPU, but
1163 will use a lot of power and make the system run hot.
1165 idle=halt: Halt is forced to be used for CPU idle.
1166 In such case C2/C3 won't be used again.
1167 idle=nomwait: Disable mwait for CPU C-states
1169 ignore_loglevel [KNL]
1170 Ignore loglevel setting - this will print /all/
1171 kernel messages to the console. Useful for debugging.
1172 We also add it as printk module parameter, so users
1173 could change it dynamically, usually by
1174 /sys/module/printk/parameters/ignore_loglevel.
1176 ihash_entries= [KNL]
1177 Set number of hash buckets for inode cache.
1179 ima_appraise= [IMA] appraise integrity measurements
1180 Format: { "off" | "enforce" | "fix" }
1183 ima_appraise_tcb [IMA]
1184 The builtin appraise policy appraises all files
1188 Format: { "sha1" | "md5" }
1192 Load a policy which meets the needs of the Trusted
1193 Computing Base. This means IMA will measure all
1194 programs exec'd, files mmap'd for exec, and all files
1195 opened for read by uid=0.
1199 Run specified binary instead of /sbin/init as init
1202 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1203 for working out where the kernel is dying during
1206 initrd= [BOOT] Specify the location of the initial ramdisk
1208 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1211 int_pln_enable [x86] Enable power limit notification interrupt
1213 integrity_audit=[IMA]
1214 Format: { "0" | "1" }
1215 0 -- basic integrity auditing messages. (Default)
1216 1 -- additional integrity auditing messages.
1218 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1220 Enable intel iommu driver.
1222 Disable intel iommu driver.
1223 igfx_off [Default Off]
1224 By default, gfx is mapped as normal device. If a gfx
1225 device has a dedicated DMAR unit, the DMAR unit is
1226 bypassed by not enabling DMAR with this option. In
1227 this case, gfx device will use physical address for
1230 With this option iommu will not optimize to look
1231 for io virtual address below 32-bit forcing dual
1232 address cycle on pci bus for cards supporting greater
1233 than 32-bit addressing. The default is to look
1234 for translation below 32-bit and if not available
1235 then look in the higher range.
1236 strict [Default Off]
1237 With this option on every unmap_single operation will
1238 result in a hardware IOTLB flush operation as opposed
1239 to batching them for performance.
1240 sp_off [Default Off]
1241 By default, super page will be supported if Intel IOMMU
1242 has the capability. With this option, super page will
1245 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1246 0 disables intel_idle and fall back on acpi_idle.
1247 1 to 6 specify maximum depth of C-state.
1251 Do not enable intel_pstate as the default
1252 scaling driver for the supported processors
1254 intremap= [X86-64, Intel-IOMMU]
1255 on enable Interrupt Remapping (default)
1256 off disable Interrupt Remapping
1257 nosid disable Source ID checking
1259 BIOS x2APIC opt-out request will be ignored
1261 iomem= Disable strict checking of access to MMIO memory
1262 strict regions from userspace.
1279 io7= [HW] IO7 for Marvel based alpha systems
1280 See comment before marvel_specify_io7 in
1281 arch/alpha/kernel/core_marvel.c.
1283 io_delay= [X86] I/O delay method
1285 Standard port 0x80 based delay
1287 Alternate port 0xed based delay (needed on some systems)
1289 Simple two microseconds delay
1294 See Documentation/filesystems/nfs/nfsroot.txt.
1296 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1297 See comment before ip2_setup() in
1298 drivers/char/ip2/ip2base.c.
1301 When an interrupt is not handled search all handlers
1302 for it. Intended to get systems with badly broken
1306 When an interrupt is not handled search all handlers
1307 for it. Also check all handlers each timer
1308 interrupt. Intended to get systems with badly broken
1312 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1314 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1316 <cpu number>,...,<cpu number>
1318 <cpu number>-<cpu number>
1319 (must be a positive range in ascending order)
1321 <cpu number>,...,<cpu number>-<cpu number>
1323 This option can be used to specify one or more CPUs
1324 to isolate from the general SMP balancing and scheduling
1325 algorithms. You can move a process onto or off an
1326 "isolated" CPU via the CPU affinity syscalls or cpuset.
1327 <cpu number> begins at 0 and the maximum value is
1328 "number of CPUs in system - 1".
1330 This option is the preferred way to isolate CPUs. The
1331 alternative -- manually setting the CPU mask of all
1332 tasks in the system -- can cause problems and
1333 suboptimal load balancer performance.
1337 ivrs_ioapic [HW,X86_64]
1338 Provide an override to the IOAPIC-ID<->DEVICE-ID
1339 mapping provided in the IVRS ACPI table. For
1340 example, to map IOAPIC-ID decimal 10 to
1341 PCI device 00:14.0 write the parameter as:
1342 ivrs_ioapic[10]=00:14.0
1344 ivrs_hpet [HW,X86_64]
1345 Provide an override to the HPET-ID<->DEVICE-ID
1346 mapping provided in the IVRS ACPI table. For
1347 example, to map HPET-ID decimal 0 to
1348 PCI device 00:14.0 write the parameter as:
1349 ivrs_hpet[0]=00:14.0
1351 js= [HW,JOY] Analog joystick
1352 See Documentation/input/joystick.txt.
1356 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1357 specifies the amount of memory usable by the kernel
1358 for non-movable allocations. The requested amount is
1359 spread evenly throughout all nodes in the system. The
1360 remaining memory in each node is used for Movable
1361 pages. In the event, a node is too small to have both
1362 kernelcore and Movable pages, kernelcore pages will
1363 take priority and other nodes will have a larger number
1364 of Movable pages. The Movable zone is used for the
1365 allocation of pages that may be reclaimed or moved
1366 by the page migration subsystem. This means that
1367 HugeTLB pages may not be allocated from this zone.
1368 Note that allocations like PTEs-from-HighMem still
1369 use the HighMem zone if it exists, and the Normal
1370 zone if it does not.
1372 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1373 Format: <Controller#>[,poll interval]
1374 The controller # is the number of the ehci usb debug
1375 port as it is probed via PCI. The poll interval is
1376 optional and is the number seconds in between
1377 each poll cycle to the debug port in case you need
1378 the functionality for interrupting the kernel with
1379 gdb or control-c on the dbgp connection. When
1380 not using this parameter you use sysrq-g to break into
1381 the kernel debugger.
1383 kgdboc= [KGDB,HW] kgdb over consoles.
1384 Requires a tty driver that supports console polling,
1385 or a supported polling keyboard driver (non-usb).
1386 Serial only format: <serial_device>[,baud]
1387 keyboard only format: kbd
1388 keyboard and serial format: kbd,<serial_device>[,baud]
1389 Optional Kernel mode setting:
1390 kms, kbd format: kms,kbd
1391 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1393 kgdbwait [KGDB] Stop kernel execution and enter the
1394 kernel debugger at the earliest opportunity.
1396 kmac= [MIPS] korina ethernet MAC address.
1397 Configure the RouterBoard 532 series on-chip
1398 Ethernet adapter MAC address.
1400 kmemleak= [KNL] Boot-time kmemleak enable/disable
1401 Valid arguments: on, off
1404 kstack=N [X86] Print N words from the kernel stack
1407 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1408 Default is 0 (don't ignore, but inject #GP)
1410 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1414 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1415 Default is 1 (enabled)
1417 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1419 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1421 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1422 (virtualized MMU) support on capable Intel chips.
1423 Default is 1 (enabled)
1425 kvm-intel.emulate_invalid_guest_state=
1426 [KVM,Intel] Enable emulation of invalid guest states
1427 Default is 0 (disabled)
1429 kvm-intel.flexpriority=
1430 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1431 Default is 1 (enabled)
1434 [KVM,Intel] Enable VMX nesting (nVMX).
1435 Default is 0 (disabled)
1437 kvm-intel.unrestricted_guest=
1438 [KVM,Intel] Disable unrestricted guest feature
1439 (virtualized real and unpaged mode) on capable
1440 Intel chips. Default is 1 (enabled)
1442 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1443 feature (tagged TLBs) on capable Intel chips.
1444 Default is 1 (enabled)
1450 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1453 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1454 value for LAPIC timer one-shot implementation. Default
1455 back to the programmable timer unit in the LAPIC.
1457 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1460 libata.dma= [LIBATA] DMA control
1461 libata.dma=0 Disable all PATA and SATA DMA
1462 libata.dma=1 PATA and SATA Disk DMA only
1463 libata.dma=2 ATAPI (CDROM) DMA only
1464 libata.dma=4 Compact Flash DMA only
1465 Combinations also work, so libata.dma=3 enables DMA
1466 for disks and CDROMs, but not CFs.
1468 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1469 libata.ignore_hpa=0 keep BIOS limits (default)
1470 libata.ignore_hpa=1 ignore limits, using full disk
1472 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1476 libata.force= [LIBATA] Force configurations. The format is comma
1477 separated list of "[ID:]VAL" where ID is
1478 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1479 matching port, link or device. Basically, it matches
1480 the ATA ID string printed on console by libata. If
1481 the whole ID part is omitted, the last PORT and DEVICE
1482 values are used. If ID hasn't been specified yet, the
1483 configuration applies to all ports, links and devices.
1485 If only DEVICE is omitted, the parameter applies to
1486 the port and all links and devices behind it. DEVICE
1487 number of 0 either selects the first device or the
1488 first fan-out link behind PMP device. It does not
1489 select the host link. DEVICE number of 15 selects the
1490 host link and device attached to it.
1492 The VAL specifies the configuration to force. As long
1493 as there's no ambiguity shortcut notation is allowed.
1494 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1495 The following configurations can be forced.
1497 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1498 Any ID with matching PORT is used.
1500 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1502 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1503 udma[/][16,25,33,44,66,100,133] notation is also
1506 * [no]ncq: Turn on or off NCQ.
1508 * nohrst, nosrst, norst: suppress hard, soft
1511 * rstonce: only attempt one reset during
1512 hot-unplug link recovery
1514 * dump_id: dump IDENTIFY data.
1516 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1518 If there are multiple matching configurations changing
1519 the same attribute, the last one is used.
1521 memblock=debug [KNL] Enable memblock debug messages.
1523 load_ramdisk= [RAM] List of ramdisks to load from floppy
1524 See Documentation/blockdev/ramdisk.txt.
1526 lockd.nlm_grace_period=P [NFS] Assign grace period.
1529 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1532 lockd.nlm_timeout=T [NFS] Assign timeout value.
1535 lockd.nlm_udpport=M [NFS] Assign UDP port.
1538 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1541 loglevel= All Kernel Messages with a loglevel smaller than the
1542 console loglevel will be printed to the console. It can
1543 also be changed with klogd or other programs. The
1544 loglevels are defined as follows:
1546 0 (KERN_EMERG) system is unusable
1547 1 (KERN_ALERT) action must be taken immediately
1548 2 (KERN_CRIT) critical conditions
1549 3 (KERN_ERR) error conditions
1550 4 (KERN_WARNING) warning conditions
1551 5 (KERN_NOTICE) normal but significant condition
1552 6 (KERN_INFO) informational
1553 7 (KERN_DEBUG) debug-level messages
1555 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1556 in bytes. n must be a power of two. The default
1557 size is set in the kernel config file.
1559 logo.nologo [FB] Disables display of the built-in Linux logo.
1560 This may be used to provide more screen space for
1561 kernel log messages and is useful when debugging
1562 kernel boot problems.
1564 lp=0 [LP] Specify parallel ports to use, e.g,
1565 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1566 lp=reset first parallel port). 'lp=0' disables the
1567 lp=auto printer driver. 'lp=reset' (which can be
1568 specified in addition to the ports) causes
1569 attached printers to be reset. Using
1570 lp=port1,port2,... specifies the parallel ports
1571 to associate lp devices with, starting with
1572 lp0. A port specification may be 'none' to skip
1573 that lp device, or a parport name such as
1574 'parport0'. Specifying 'lp=auto' instead of a
1575 port specification list means that device IDs
1576 from each port should be examined, to see if
1577 an IEEE 1284-compliant printer is attached; if
1578 so, the driver will manage that printer.
1579 See also header of drivers/char/lp.c.
1582 Sets loops_per_jiffy to given constant, thus avoiding
1583 time-consuming boot-time autodetection (up to 250 ms per
1584 CPU). 0 enables autodetection (default). To determine
1585 the correct value for your kernel, boot with normal
1586 autodetection and see what value is printed. Note that
1587 on SMP systems the preset will be applied to all CPUs,
1588 which is likely to cause problems if your CPUs need
1589 significantly divergent settings. An incorrect value
1590 will cause delays in the kernel to be wrong, leading to
1591 unpredictable I/O errors and other breakage. Although
1592 unlikely, in the extreme case this might damage your
1596 Format: <io>,<irq>,<dma>
1598 machvec= [IA-64] Force the use of a particular machine-vector
1599 (machvec) in a generic kernel.
1600 Example: machvec=hpzx1_swiotlb
1602 machtype= [Loongson] Share the same kernel image file between different
1604 Example: machtype=lemote-yeeloong-2f-7inch
1606 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1607 than or equal to this physical address is ignored.
1609 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1610 should make use of. maxcpus=n : n >= 0 limits the
1611 kernel to using 'n' processors. n=0 is a special case,
1612 it is equivalent to "nosmp", which also disables
1615 max_loop= [LOOP] The number of loop block devices that get
1616 (loop.max_loop) unconditionally pre-created at init time. The default
1617 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1618 of statically allocating a predefined number, loop
1619 devices can be requested on-demand with the
1620 /dev/loop-control interface.
1622 mce [X86-32] Machine Check Exception
1624 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1626 md= [HW] RAID subsystems devices and level
1627 See Documentation/md.txt.
1630 Format: <first>,<last>
1631 Specifies range of consoles to be captured by the MDA.
1633 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1634 Amount of memory to be used when the kernel is not able
1635 to see the whole system memory or for test.
1636 [X86] Work as limiting max address. Use together
1637 with memmap= to avoid physical address space collisions.
1638 Without memmap= PCI devices could be placed at addresses
1639 belonging to unused RAM.
1641 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1645 [KNL,SH] Allow user to override the default size for
1646 per-device physically contiguous DMA buffers.
1648 memmap=exactmap [KNL,X86] Enable setting of an exact
1649 E820 memory map, as specified by the user.
1650 Such memmap=exactmap lines can be constructed based on
1651 BIOS output or other requirements. See the memmap=nn@ss
1654 memmap=nn[KMG]@ss[KMG]
1655 [KNL] Force usage of a specific region of memory
1656 Region of memory to be used, from ss to ss+nn.
1658 memmap=nn[KMG]#ss[KMG]
1659 [KNL,ACPI] Mark specific memory as ACPI data.
1660 Region of memory to be used, from ss to ss+nn.
1662 memmap=nn[KMG]$ss[KMG]
1663 [KNL,ACPI] Mark specific memory as reserved.
1664 Region of memory to be used, from ss to ss+nn.
1665 Example: Exclude memory from 0x18690000-0x1869ffff
1666 memmap=64K$0x18690000
1668 memmap=0x10000$0x18690000
1670 memory_corruption_check=0/1 [X86]
1671 Some BIOSes seem to corrupt the first 64k of
1672 memory when doing things like suspend/resume.
1673 Setting this option will scan the memory
1674 looking for corruption. Enabling this will
1675 both detect corruption and prevent the kernel
1676 from using the memory being corrupted.
1677 However, its intended as a diagnostic tool; if
1678 repeatable BIOS-originated corruption always
1679 affects the same memory, you can use memmap=
1680 to prevent the kernel from using that memory.
1682 memory_corruption_check_size=size [X86]
1683 By default it checks for corruption in the low
1684 64k, making this memory unavailable for normal
1685 use. Use this parameter to scan for
1686 corruption in more or less memory.
1688 memory_corruption_check_period=seconds [X86]
1689 By default it checks for corruption every 60
1690 seconds. Use this parameter to check at some
1691 other rate. 0 disables periodic checking.
1693 memtest= [KNL,X86] Enable memtest
1695 default : 0 <disable>
1696 Specifies the number of memtest passes to be
1697 performed. Each pass selects another test
1698 pattern from a given set of patterns. Memtest
1699 fills the memory with this pattern, validates
1700 memory contents and reserves bad memory
1701 regions that are detected.
1703 meye.*= [HW] Set MotionEye Camera parameters
1704 See Documentation/video4linux/meye.txt.
1706 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1707 Multi-Function General Purpose Timers on AMD Geode
1710 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1711 the BIOS has incorrectly applied a workaround. TinyBIOS
1712 version 0.98 is known to be affected, 0.99 fixes the
1713 problem by letting the user disable the workaround.
1717 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1718 physical address is ignored.
1720 mini2440= [ARM,HW,KNL]
1721 Format:[0..2][b][c][t]
1723 MINI2440 configuration specification:
1724 0 - The attached screen is the 3.5" TFT
1725 1 - The attached screen is the 7" TFT
1726 2 - The VGA Shield is attached (1024x768)
1727 Leaving out the screen size parameter will not load
1728 the TFT driver, and the framebuffer will be left
1730 b - Enable backlight. The TFT backlight pin will be
1731 linked to the kernel VESA blanking code and a GPIO
1732 LED. This parameter is not necessary when using the
1734 c - Enable the s3c camera interface.
1735 t - Reserved for enabling touchscreen support. The
1736 touchscreen support is not enabled in the mainstream
1737 kernel as of 2.6.30, a preliminary port can be found
1738 in the "bleeding edge" mini2440 support kernel at
1739 http://repo.or.cz/w/linux-2.6/mini2440.git
1742 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1743 parameter allows control of the logging verbosity for
1744 the additional memory initialisation checks. A value
1745 of 0 disables mminit logging and a level of 4 will
1746 log everything. Information is printed at KERN_DEBUG
1747 so loglevel=8 may also need to be specified.
1750 [KNL] When CONFIG_MODULE_SIG is set, this means that
1751 modules without (valid) signatures will fail to load.
1752 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1753 is always true, so this option does nothing.
1756 [MOUSE] Maximum time between finger touching and
1757 leaving touchpad surface for touch to be considered
1758 a tap and be reported as a left button click (for
1759 touchpads working in absolute mode only).
1761 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1762 reporting absolute coordinates, such as tablets
1763 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1764 reporting absolute coordinates, such as tablets
1766 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1767 is similar to kernelcore except it specifies the
1768 amount of memory used for migratable allocations.
1769 If both kernelcore and movablecore is specified,
1770 then kernelcore will be at *least* the specified
1771 value but may be more. If movablecore on its own
1772 is specified, the administrator must be careful
1773 that the amount of memory usable for all allocations
1776 MTD_Partition= [MTD]
1777 Format: <name>,<region-number>,<size>,<offset>
1779 MTD_Region= [MTD] Format:
1780 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1783 See drivers/mtd/cmdlinepart.c.
1785 multitce=off [PPC] This parameter disables the use of the pSeries
1786 firmware feature for updating multiple TCE entries
1789 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1791 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1793 boundary - index of last SLC block on Flex-OneNAND.
1794 The remaining blocks are configured as MLC blocks.
1795 lock - Configure if Flex-OneNAND boundary should be locked.
1796 Once locked, the boundary cannot be changed.
1797 1 indicates lock status, 0 indicates unlock status.
1800 ARM/S3C2412 JIVE boot control
1802 See arch/arm/mach-s3c2412/mach-jive.c
1804 mtouchusb.raw_coordinates=
1805 [HW] Make the MicroTouch USB driver use raw coordinates
1806 ('y', default) or cooked coordinates ('n')
1808 mtrr_chunk_size=nn[KMG] [X86]
1809 used for mtrr cleanup. It is largest continuous chunk
1810 that could hold holes aka. UC entries.
1812 mtrr_gran_size=nn[KMG] [X86]
1813 Used for mtrr cleanup. It is granularity of mtrr block.
1815 Large value could prevent small alignment from
1818 mtrr_spare_reg_nr=n [X86]
1820 Range: 0,7 : spare reg number
1822 Used for mtrr cleanup. It is spare mtrr entries number.
1823 Set to 2 or more if your graphical card needs more.
1825 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1827 netdev= [NET] Network devices parameters
1828 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1829 Note that mem_start is often overloaded to mean
1830 something different and driver-specific.
1831 This usage is only documented in each driver source
1835 [NETFILTER] Enable connection tracking flow accounting
1836 0 to disable accounting
1837 1 to enable accounting
1840 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1841 See Documentation/filesystems/nfs/nfsroot.txt.
1843 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1844 See Documentation/filesystems/nfs/nfsroot.txt.
1846 nfsrootdebug [NFS] enable nfsroot debugging messages.
1847 See Documentation/filesystems/nfs/nfsroot.txt.
1849 nfs.callback_tcpport=
1850 [NFS] set the TCP port on which the NFSv4 callback
1851 channel should listen.
1854 [NFS] sets the pathname to the program which is used
1855 to update the NFS client cache entries.
1857 nfs.cache_getent_timeout=
1858 [NFS] sets the timeout after which an attempt to
1859 update a cache entry is deemed to have failed.
1861 nfs.idmap_cache_timeout=
1862 [NFS] set the maximum lifetime for idmapper cache
1866 [NFS] enable 64-bit inode numbers.
1867 If zero, the NFS client will fake up a 32-bit inode
1868 number for the readdir() and stat() syscalls instead
1869 of returning the full 64-bit number.
1870 The default is to return 64-bit inode numbers.
1872 nfs.max_session_slots=
1873 [NFSv4.1] Sets the maximum number of session slots
1874 the client will attempt to negotiate with the server.
1875 This limits the number of simultaneous RPC requests
1876 that the client can send to the NFSv4.1 server.
1877 Note that there is little point in setting this
1878 value higher than the max_tcp_slot_table_limit.
1880 nfs.nfs4_disable_idmapping=
1881 [NFSv4] When set to the default of '1', this option
1882 ensures that both the RPC level authentication
1883 scheme and the NFS level operations agree to use
1884 numeric uids/gids if the mount is using the
1885 'sec=sys' security flavour. In effect it is
1886 disabling idmapping, which can make migration from
1887 legacy NFSv2/v3 systems to NFSv4 easier.
1888 Servers that do not support this mode of operation
1889 will be autodetected by the client, and it will fall
1890 back to using the idmapper.
1891 To turn off this behaviour, set the value to '0'.
1893 [NFS4] Specify an additional fixed unique ident-
1894 ification string that NFSv4 clients can insert into
1895 their nfs_client_id4 string. This is typically a
1896 UUID that is generated at system install time.
1898 nfs.send_implementation_id =
1899 [NFSv4.1] Send client implementation identification
1900 information in exchange_id requests.
1901 If zero, no implementation identification information
1903 The default is to send the implementation identification
1906 nfs.recover_lost_locks =
1907 [NFSv4] Attempt to recover locks that were lost due
1908 to a lease timeout on the server. Please note that
1909 doing this risks data corruption, since there are
1910 no guarantees that the file will remain unchanged
1911 after the locks are lost.
1912 If you want to enable the kernel legacy behaviour of
1913 attempting to recover these locks, then set this
1915 The default parameter value of '0' causes the kernel
1916 not to attempt recovery of lost locks.
1918 nfsd.nfs4_disable_idmapping=
1919 [NFSv4] When set to the default of '1', the NFSv4
1920 server will return only numeric uids and gids to
1921 clients using auth_sys, and will accept numeric uids
1922 and gids from such clients. This is intended to ease
1923 migration from NFSv2/v3.
1925 objlayoutdriver.osd_login_prog=
1926 [NFS] [OBJLAYOUT] sets the pathname to the program which
1927 is used to automatically discover and login into new
1928 osd-targets. Please see:
1929 Documentation/filesystems/pnfs.txt for more explanations
1931 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1932 when a NMI is triggered.
1933 Format: [state][,regs][,debounce][,die]
1935 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1936 Format: [panic,][nopanic,][num]
1938 0 - turn nmi_watchdog off
1939 When panic is specified, panic when an NMI watchdog
1940 timeout occurs (or 'nopanic' to override the opposite
1942 This is useful when you use a panic=... timeout and
1943 need the box quickly up again.
1945 netpoll.carrier_timeout=
1946 [NET] Specifies amount of time (in seconds) that
1947 netpoll should wait for a carrier. By default netpoll
1950 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1951 emulation library even if a 387 maths coprocessor
1955 [HW] Never suspend the console
1956 Disable suspending of consoles during suspend and
1957 hibernate operations. Once disabled, debugging
1958 messages can reach various consoles while the rest
1959 of the system is being put to sleep (ie, while
1960 debugging driver suspend/resume hooks). This may
1961 not work reliably with all consoles, but is known
1962 to work with serial and VGA consoles.
1963 To facilitate more flexible debugging, we also add
1964 console_suspend, a printk module parameter to control
1965 it. Users could use console_suspend (usually
1966 /sys/module/printk/parameters/console_suspend) to
1967 turn on/off it dynamically.
1969 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1970 caches in the slab allocator. Saves per-node memory,
1971 but will impact performance.
1975 noapic [SMP,APIC] Tells the kernel to not make use of any
1976 IOAPICs that may be present in the system.
1979 Disable kernel base offset ASLR (Address Space
1980 Layout Randomization) if built into the kernel.
1982 noautogroup Disable scheduler automatic task group creation.
1984 nobats [PPC] Do not use BATs for mapping kernel lowmem
1985 on "Classic" PPC cores.
1989 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1991 nodelayacct [KNL] Disable per-task delay accounting
1993 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1995 nodsp [SH] Disable hardware DSP at boot time.
1997 noefi [X86] Disable EFI runtime services support.
2002 On X86-32 available only on PAE configured kernels.
2003 noexec=on: enable non-executable mappings (default)
2004 noexec=off: disable non-executable mappings
2007 Disable SMAP (Supervisor Mode Access Prevention)
2008 even if it is supported by processor.
2011 Disable SMEP (Supervisor Mode Execution Prevention)
2012 even if it is supported by processor.
2015 This affects only 32-bit executables.
2016 noexec32=on: enable non-executable mappings (default)
2017 read doesn't imply executable mappings
2018 noexec32=off: disable non-executable mappings
2019 read implies executable mappings
2021 nofpu [SH] Disable hardware FPU at boot time.
2023 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2024 register save and restore. The kernel will only save
2025 legacy floating-point registers on task switch.
2027 noxsave [BUGS=X86] Disables x86 extended register state save
2028 and restore using xsave. The kernel will fallback to
2029 enabling legacy floating-point and sse state.
2032 on enable eager fpu restore
2033 off disable eager fpu restore
2034 auto selects the default scheme, which automatically
2035 enables eagerfpu restore for xsaveopt.
2037 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2038 wfi(ARM) instruction doesn't work correctly and not to
2039 use it. This is also useful when using JTAG debugger.
2041 no_file_caps Tells the kernel not to honor file capabilities. The
2042 only way then for a file to be executed with privilege
2043 is to be setuid root or executed by root.
2045 nohalt [IA-64] Tells the kernel not to use the power saving
2046 function PAL_HALT_LIGHT when idle. This increases
2047 power-consumption. On the positive side, it reduces
2048 interrupt wake-up latency, which may improve performance
2049 in certain environments such as networked servers or
2052 nohz= [KNL] Boottime enable/disable dynamic ticks
2053 Valid arguments: on, off
2056 nohz_full= [KNL,BOOT]
2057 In kernels built with CONFIG_NO_HZ_FULL=y, set
2058 the specified list of CPUs whose tick will be stopped
2059 whenever possible. The boot CPU will be forced outside
2060 the range to maintain the timekeeping.
2061 The CPUs in this range must also be included in the
2064 noiotrap [SH] Disables trapped I/O port accesses.
2066 noirqdebug [X86-32] Disables the code which attempts to detect and
2067 disable unhandled interrupt sources.
2069 no_timer_check [X86,APIC] Disables the code which tests for
2070 broken timer IRQ sources.
2072 noisapnp [ISAPNP] Disables ISA PnP code.
2074 noinitrd [RAM] Tells the kernel not to load any configured
2077 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2079 [Deprecated - use intremap=off]
2083 nojitter [IA-64] Disables jitter checking for ITC timers.
2085 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2087 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2090 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2091 steal time is computed, but won't influence scheduler
2094 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2096 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2098 noltlbs [PPC] Do not use large page/tlb entries for kernel
2099 lowmem mapping on PPC40x.
2101 nomca [IA-64] Disable machine check abort handling
2103 nomce [X86-32] Machine Check Exception
2105 nomfgpt [X86-32] Disable Multi-Function General Purpose
2106 Timer usage (for AMD Geode machines).
2108 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2109 shutdown the other cpus. Instead use the REBOOT_VECTOR
2112 nomodule Disable module load
2114 nopat [X86] Disable PAT (page attribute table extension of
2115 pagetables) support.
2117 norandmaps Don't use address space randomization. Equivalent to
2118 echo 0 > /proc/sys/kernel/randomize_va_space
2120 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2122 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2123 with UP alternatives
2125 nordrand [X86] Disable the direct use of the RDRAND
2126 instruction even if it is supported by the
2127 processor. RDRAND is still available to user
2130 noresume [SWSUSP] Disables resume and restores original swap
2133 no-scroll [VGA] Disables scrollback.
2134 This is required for the Braillex ib80-piezo Braille
2135 reader made by F.H. Papenmeier (Germany).
2139 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2141 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2142 and disable the IO APIC. legacy for "maxcpus=0".
2144 nosoftlockup [KNL] Disable the soft-lockup detector.
2146 nosync [HW,M68K] Disables sync negotiation for all devices.
2148 notsc [BUGS=X86-32] Disable Time Stamp Counter
2150 nousb [USB] Disable the USB subsystem
2152 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2156 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2158 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2159 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2160 Some features depend on CPU0. Known dependencies are:
2161 1. Resume from suspend/hibernate depends on CPU0.
2162 Suspend/hibernate will fail if CPU0 is offline and you
2163 need to online CPU0 before suspend/hibernate.
2164 2. PIC interrupts also depend on CPU0. CPU0 can't be
2165 removed if a PIC interrupt is detected.
2166 It's said poweroff/reboot may depend on CPU0 on some
2167 machines although I haven't seen such issues so far
2168 after CPU0 is offline on a few tested machines.
2169 If the dependencies are under your control, you can
2170 turn on cpu0_hotplug.
2172 nptcg= [IA-64] Override max number of concurrent global TLB
2173 purges which is reported from either PAL_VM_SUMMARY or
2176 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2177 could support. nr_cpus=n : n >= 1 limits the kernel to
2178 supporting 'n' processors. Later in runtime you can not
2179 use hotplug cpu feature to put more cpu back to online.
2180 just like you compile the kernel NR_CPUS=n
2182 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2184 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2185 Allowed values are enable and disable
2187 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2188 one of ['zone', 'node', 'default'] can be specified
2189 This can be set from sysctl after boot.
2190 See Documentation/sysctl/vm.txt for details.
2192 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2193 See Documentation/debugging-via-ohci1394.txt for more
2196 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2197 Rather than timing out after 20 ms if an EC
2198 command is not properly ACKed, override the length
2199 of the timeout. We have interrupts disabled while
2200 waiting for the ACK, so if this is set too high
2201 interrupts *may* be lost!
2203 omap_mux= [OMAP] Override bootloader pin multiplexing.
2204 Format: <mux_mode0.mode_name=value>...
2205 For example, to override I2C bus2:
2206 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2208 oprofile.timer= [HW]
2209 Use timer interrupt instead of performance counters
2211 oprofile.cpu_type= Force an oprofile cpu type
2212 This might be useful if you have an older oprofile
2213 userland or if you want common events.
2214 Format: { arch_perfmon }
2215 arch_perfmon: [X86] Force use of architectural
2216 perfmon on Intel CPUs instead of the
2217 CPU specific event set.
2218 timer: [X86] Force use of architectural NMI
2219 timer mode (see also oprofile.timer
2220 for generic hr timer mode)
2221 [s390] Force legacy basic mode sampling
2222 (report cpu_type "timer")
2224 oops=panic Always panic on oopses. Default is to just kill the
2225 process, but there is a small probability of
2226 deadlocking the machine.
2227 This will also cause panics on machine check exceptions.
2228 Useful together with panic=30 to trigger a reboot.
2231 See Documentation/sound/oss/oss-parameters.txt
2233 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2234 timeout > 0: seconds before rebooting
2235 timeout = 0: wait forever
2236 timeout < 0: reboot immediately
2239 parkbd.port= [HW] Parallel port number the keyboard adapter is
2240 connected to, default is 0.
2242 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2243 0 for XT, 1 for AT (default is AT).
2246 parport= [HW,PPT] Specify parallel ports. 0 disables.
2247 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2248 Use 'auto' to force the driver to use any
2249 IRQ/DMA settings detected (the default is to
2250 ignore detected IRQ/DMA settings because of
2251 possible conflicts). You can specify the base
2252 address, IRQ, and DMA settings; IRQ and DMA
2253 should be numbers, or 'auto' (for using detected
2254 settings on that particular port), or 'nofifo'
2255 (to avoid using a FIFO even if it is detected).
2256 Parallel ports are assigned in the order they
2257 are specified on the command line, starting
2260 parport_init_mode= [HW,PPT]
2261 Configure VIA parallel port to operate in
2262 a specific mode. This is necessary on Pegasos
2263 computer where firmware has no options for setting
2264 up parallel port mode and sets it to spp.
2265 Currently this function knows 686a and 8231 chips.
2266 Format: [spp|ps2|epp|ecp|ecpepp]
2269 Halt all CPUs after the first oops has been printed for
2270 the specified number of seconds. This is to be used if
2271 your oopses keep scrolling off the screen.
2276 See header of drivers/block/paride/pcd.c.
2277 See also Documentation/blockdev/paride.txt.
2279 pci=option[,option...] [PCI] various PCI subsystem options:
2280 earlydump [X86] dump PCI config space before the kernel
2282 off [X86] don't probe for the PCI bus
2283 bios [X86-32] force use of PCI BIOS, don't access
2284 the hardware directly. Use this if your machine
2285 has a non-standard PCI host bridge.
2286 nobios [X86-32] disallow use of PCI BIOS, only direct
2287 hardware access methods are allowed. Use this
2288 if you experience crashes upon bootup and you
2289 suspect they are caused by the BIOS.
2290 conf1 [X86] Force use of PCI Configuration
2292 conf2 [X86] Force use of PCI Configuration
2294 noaer [PCIE] If the PCIEAER kernel config parameter is
2295 enabled, this kernel boot option can be used to
2296 disable the use of PCIE advanced error reporting.
2297 nodomains [PCI] Disable support for multiple PCI
2298 root domains (aka PCI segments, in ACPI-speak).
2299 nommconf [X86] Disable use of MMCONFIG for PCI
2301 check_enable_amd_mmconf [X86] check for and enable
2302 properly configured MMIO access to PCI
2303 config space on AMD family 10h CPU
2304 nomsi [MSI] If the PCI_MSI kernel config parameter is
2305 enabled, this kernel boot option can be used to
2306 disable the use of MSI interrupts system-wide.
2307 noioapicquirk [APIC] Disable all boot interrupt quirks.
2308 Safety option to keep boot IRQs enabled. This
2309 should never be necessary.
2310 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2311 primary IO-APIC for bridges that cannot disable
2312 boot IRQs. This fixes a source of spurious IRQs
2313 when the system masks IRQs.
2314 noioapicreroute [APIC] Disable workaround that uses the
2315 boot IRQ equivalent of an IRQ that connects to
2316 a chipset where boot IRQs cannot be disabled.
2317 The opposite of ioapicreroute.
2318 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2319 routing table. These calls are known to be buggy
2320 on several machines and they hang the machine
2321 when used, but on other computers it's the only
2322 way to get the interrupt routing table. Try
2323 this option if the kernel is unable to allocate
2324 IRQs or discover secondary PCI buses on your
2326 rom [X86] Assign address space to expansion ROMs.
2327 Use with caution as certain devices share
2328 address decoders between ROMs and other
2330 norom [X86] Do not assign address space to
2331 expansion ROMs that do not already have
2332 BIOS assigned address ranges.
2333 nobar [X86] Do not assign address space to the
2334 BARs that weren't assigned by the BIOS.
2335 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2336 assigned automatically to PCI devices. You can
2337 make the kernel exclude IRQs of your ISA cards
2339 pirqaddr=0xAAAAA [X86] Specify the physical address
2340 of the PIRQ table (normally generated
2341 by the BIOS) if it is outside the
2342 F0000h-100000h range.
2343 lastbus=N [X86] Scan all buses thru bus #N. Can be
2344 useful if the kernel is unable to find your
2345 secondary buses and you want to tell it
2346 explicitly which ones they are.
2347 assign-busses [X86] Always assign all PCI bus
2348 numbers ourselves, overriding
2349 whatever the firmware may have done.
2350 usepirqmask [X86] Honor the possible IRQ mask stored
2351 in the BIOS $PIR table. This is needed on
2352 some systems with broken BIOSes, notably
2353 some HP Pavilion N5400 and Omnibook XE3
2354 notebooks. This will have no effect if ACPI
2355 IRQ routing is enabled.
2356 noacpi [X86] Do not use ACPI for IRQ routing
2357 or for PCI scanning.
2358 use_crs [X86] Use PCI host bridge window information
2359 from ACPI. On BIOSes from 2008 or later, this
2360 is enabled by default. If you need to use this,
2361 please report a bug.
2362 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2363 If you need to use this, please report a bug.
2364 routeirq Do IRQ routing for all PCI devices.
2365 This is normally done in pci_enable_device(),
2366 so this option is a temporary workaround
2367 for broken drivers that don't call it.
2368 skip_isa_align [X86] do not align io start addr, so can
2369 handle more pci cards
2370 firmware [ARM] Do not re-enumerate the bus but instead
2371 just use the configuration from the
2372 bootloader. This is currently used on
2373 IXP2000 systems where the bus has to be
2374 configured a certain way for adjunct CPUs.
2375 noearly [X86] Don't do any early type 1 scanning.
2376 This might help on some broken boards which
2377 machine check when some devices' config space
2378 is read. But various workarounds are disabled
2379 and some IOMMU drivers will not work.
2380 bfsort Sort PCI devices into breadth-first order.
2381 This sorting is done to get a device
2382 order compatible with older (<= 2.4) kernels.
2383 nobfsort Don't sort PCI devices into breadth-first order.
2384 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2385 tuning and use the BIOS-configured MPS defaults.
2386 pcie_bus_safe Set every device's MPS to the largest value
2387 supported by all devices below the root complex.
2388 pcie_bus_perf Set device MPS to the largest allowable MPS
2389 based on its parent bus. Also set MRRS (Max
2390 Read Request Size) to the largest supported
2391 value (no larger than the MPS that the device
2392 or bus can support) for best performance.
2393 pcie_bus_peer2peer Set every device's MPS to 128B, which
2394 every device is guaranteed to support. This
2395 configuration allows peer-to-peer DMA between
2396 any pair of devices, possibly at the cost of
2397 reduced performance. This also guarantees
2398 that hot-added devices will work.
2399 cbiosize=nn[KMG] The fixed amount of bus space which is
2400 reserved for the CardBus bridge's IO window.
2401 The default value is 256 bytes.
2402 cbmemsize=nn[KMG] The fixed amount of bus space which is
2403 reserved for the CardBus bridge's memory
2404 window. The default value is 64 megabytes.
2407 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2408 Specifies alignment and device to reassign
2409 aligned memory resources.
2410 If <order of align> is not specified,
2411 PAGE_SIZE is used as alignment.
2412 PCI-PCI bridge can be specified, if resource
2413 windows need to be expanded.
2414 ecrc= Enable/disable PCIe ECRC (transaction layer
2415 end-to-end CRC checking).
2416 bios: Use BIOS/firmware settings. This is the
2420 hpiosize=nn[KMG] The fixed amount of bus space which is
2421 reserved for hotplug bridge's IO window.
2422 Default size is 256 bytes.
2423 hpmemsize=nn[KMG] The fixed amount of bus space which is
2424 reserved for hotplug bridge's memory window.
2425 Default size is 2 megabytes.
2426 realloc= Enable/disable reallocating PCI bridge resources
2427 if allocations done by BIOS are too small to
2428 accommodate resources required by all child
2430 off: Turn realloc off
2432 realloc same as realloc=on
2433 noari do not use PCIe ARI.
2434 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2435 only look for one device below a PCIe downstream
2438 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2441 force Enable ASPM even on devices that claim not to support it.
2442 WARNING: Forcing ASPM on may cause system lockups.
2444 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2445 nomsi Do not use MSI for PCI Express Native Hotplug (this
2446 makes all PCIe ports use INTx for hotplug services).
2448 pcie_ports= [PCIE] PCIe ports handling:
2449 auto Ask the BIOS whether or not to use native PCIe services
2450 associated with PCIe ports (PME, hot-plug, AER). Use
2451 them only if that is allowed by the BIOS.
2452 native Use native PCIe services associated with PCIe ports
2454 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2457 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2458 nomsi Do not use MSI for native PCIe PME signaling (this makes
2459 all PCIe root ports use INTx for all services).
2461 pcmv= [HW,PCMCIA] BadgePAD 4
2464 See Documentation/blockdev/paride.txt.
2466 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2469 See arch/parisc/kernel/pdc_chassis.c
2471 percpu_alloc= Select which percpu first chunk allocator to use.
2472 Currently supported values are "embed" and "page".
2473 Archs may support subset or none of the selections.
2474 See comments in mm/percpu.c for details on each
2475 allocator. This parameter is primarily for debugging
2476 and performance comparison.
2479 See Documentation/blockdev/paride.txt.
2482 See Documentation/blockdev/paride.txt.
2484 pirq= [SMP,APIC] Manual mp-table setup
2485 See Documentation/x86/i386/IO-APIC.txt.
2487 plip= [PPT,NET] Parallel port network link
2488 Format: { parport<nr> | timid | 0 }
2489 See also Documentation/parport.txt.
2491 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2492 Override pmtimer IOPort with a hex value.
2496 Enable PNP debug messages (depends on the
2497 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2498 via /sys/module/pnp/parameters/debug. We always show
2499 current resource usage; turning this on also shows
2500 possible settings and some assignment information.
2506 { on | off | curr | res | no-curr | no-res }
2509 [ISAPNP] Exclude IRQs for the autoconfiguration
2512 [ISAPNP] Exclude DMAs for the autoconfiguration
2514 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2515 Ranges are in pairs (I/O port base and size).
2518 [ISAPNP] Exclude memory regions for the
2520 Ranges are in pairs (memory base and size).
2522 ports= [IP_VS_FTP] IPVS ftp helper module
2524 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2526 Format: <port>,<port>....
2528 print-fatal-signals=
2529 [KNL] debug: print fatal signals
2531 If enabled, warn about various signal handling
2532 related application anomalies: too many signals,
2533 too many POSIX.1 timers, fatal signals causing a
2536 If you hit the warning due to signal overflow,
2537 you might want to try "ulimit -i unlimited".
2541 printk.always_kmsg_dump=
2542 Trigger kmsg_dump for cases other than kernel oops or
2544 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2547 printk.time= Show timing data prefixed to each printk message line
2548 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2550 processor.max_cstate= [HW,ACPI]
2551 Limit processor to maximum C-state
2552 max_cstate=9 overrides any DMI blacklist limit.
2554 processor.nocst [HW,ACPI]
2555 Ignore the _CST method to determine C-states,
2556 instead using the legacy FADT method
2558 profile= [KNL] Enable kernel profiling via /proc/profile
2559 Format: [schedule,]<number>
2560 Param: "schedule" - profile schedule points.
2561 Param: <number> - step/bucket size as a power of 2 for
2562 statistical time based profiling.
2563 Param: "sleep" - profile D-state sleeping (millisecs).
2564 Requires CONFIG_SCHEDSTATS
2565 Param: "kvm" - profile VM exits.
2567 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2569 See Documentation/blockdev/ramdisk.txt.
2571 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2572 probe for; one of (bare|imps|exps|lifebook|any).
2573 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2575 psmouse.resetafter= [HW,MOUSE]
2576 Try to reset the device after so many bad packets
2579 [HW,MOUSE] Set desired mouse resolution, in dpi.
2580 psmouse.smartscroll=
2581 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2582 0 = disabled, 1 = enabled (default).
2584 pstore.backend= Specify the name of the pstore backend to use
2587 See Documentation/blockdev/paride.txt.
2590 [KNL] Number of legacy pty's. Overwrites compiled-in
2593 quiet [KNL] Disable most log messages
2598 See Documentation/md.txt.
2600 ramdisk_blocksize= [RAM]
2601 See Documentation/blockdev/ramdisk.txt.
2603 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2604 See Documentation/blockdev/ramdisk.txt.
2607 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2608 the specified list of CPUs to be no-callback CPUs.
2609 Invocation of these CPUs' RCU callbacks will
2610 be offloaded to "rcuox/N" kthreads created for
2611 that purpose, where "x" is "b" for RCU-bh, "p"
2612 for RCU-preempt, and "s" for RCU-sched, and "N"
2613 is the CPU number. This reduces OS jitter on the
2614 offloaded CPUs, which can be useful for HPC and
2616 real-time workloads. It can also improve energy
2617 efficiency for asymmetric multiprocessors.
2620 Rather than requiring that offloaded CPUs
2621 (specified by rcu_nocbs= above) explicitly
2622 awaken the corresponding "rcuoN" kthreads,
2623 make these kthreads poll for callbacks.
2624 This improves the real-time response for the
2625 offloaded CPUs by relieving them of the need to
2626 wake up the corresponding kthread, but degrades
2627 energy efficiency by requiring that the kthreads
2628 periodically wake up to do the polling.
2630 rcutree.blimit= [KNL]
2631 Set maximum number of finished RCU callbacks to process
2634 rcutree.rcu_fanout_leaf= [KNL]
2635 Increase the number of CPUs assigned to each
2636 leaf rcu_node structure. Useful for very large
2639 rcutree.jiffies_till_first_fqs= [KNL]
2640 Set delay from grace-period initialization to
2641 first attempt to force quiescent states.
2642 Units are jiffies, minimum value is zero,
2643 and maximum value is HZ.
2645 rcutree.jiffies_till_next_fqs= [KNL]
2646 Set delay between subsequent attempts to force
2647 quiescent states. Units are jiffies, minimum
2648 value is one, and maximum value is HZ.
2650 rcutree.qhimark= [KNL]
2651 Set threshold of queued
2652 RCU callbacks over which batch limiting is disabled.
2654 rcutree.qlowmark= [KNL]
2655 Set threshold of queued RCU callbacks below which
2656 batch limiting is re-enabled.
2658 rcutree.rcu_idle_gp_delay= [KNL]
2659 Set wakeup interval for idle CPUs that have
2660 RCU callbacks (RCU_FAST_NO_HZ=y).
2662 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2663 Set wakeup interval for idle CPUs that have
2664 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2665 Lazy RCU callbacks are those which RCU can
2666 prove do nothing more than free memory.
2668 rcutorture.fqs_duration= [KNL]
2669 Set duration of force_quiescent_state bursts.
2671 rcutorture.fqs_holdoff= [KNL]
2672 Set holdoff time within force_quiescent_state bursts.
2674 rcutorture.fqs_stutter= [KNL]
2675 Set wait time between force_quiescent_state bursts.
2677 rcutorture.gp_exp= [KNL]
2678 Use expedited update-side primitives.
2680 rcutorture.gp_normal= [KNL]
2681 Use normal (non-expedited) update-side primitives.
2682 If both gp_exp and gp_normal are set, do both.
2683 If neither gp_exp nor gp_normal are set, still
2686 rcutorture.n_barrier_cbs= [KNL]
2687 Set callbacks/threads for rcu_barrier() testing.
2689 rcutorture.nfakewriters= [KNL]
2690 Set number of concurrent RCU writers. These just
2691 stress RCU, they don't participate in the actual
2692 test, hence the "fake".
2694 rcutorture.nreaders= [KNL]
2695 Set number of RCU readers.
2697 rcutorture.object_debug= [KNL]
2698 Enable debug-object double-call_rcu() testing.
2700 rcutorture.onoff_holdoff= [KNL]
2701 Set time (s) after boot for CPU-hotplug testing.
2703 rcutorture.onoff_interval= [KNL]
2704 Set time (s) between CPU-hotplug operations, or
2705 zero to disable CPU-hotplug testing.
2707 rcutorture.rcutorture_runnable= [BOOT]
2708 Start rcutorture running at boot time.
2710 rcutorture.shuffle_interval= [KNL]
2711 Set task-shuffle interval (s). Shuffling tasks
2712 allows some CPUs to go into dyntick-idle mode
2713 during the rcutorture test.
2715 rcutorture.shutdown_secs= [KNL]
2716 Set time (s) after boot system shutdown. This
2717 is useful for hands-off automated testing.
2719 rcutorture.stall_cpu= [KNL]
2720 Duration of CPU stall (s) to test RCU CPU stall
2721 warnings, zero to disable.
2723 rcutorture.stall_cpu_holdoff= [KNL]
2724 Time to wait (s) after boot before inducing stall.
2726 rcutorture.stat_interval= [KNL]
2727 Time (s) between statistics printk()s.
2729 rcutorture.stutter= [KNL]
2730 Time (s) to stutter testing, for example, specifying
2731 five seconds causes the test to run for five seconds,
2732 wait for five seconds, and so on. This tests RCU's
2733 ability to transition abruptly to and from idle.
2735 rcutorture.test_boost= [KNL]
2736 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2737 "Maybe" means test if the RCU implementation
2738 under test support RCU priority boosting.
2740 rcutorture.test_boost_duration= [KNL]
2741 Duration (s) of each individual boost test.
2743 rcutorture.test_boost_interval= [KNL]
2744 Interval (s) between each boost test.
2746 rcutorture.test_no_idle_hz= [KNL]
2747 Test RCU's dyntick-idle handling. See also the
2748 rcutorture.shuffle_interval parameter.
2750 rcutorture.torture_type= [KNL]
2751 Specify the RCU implementation to test.
2753 rcutorture.verbose= [KNL]
2754 Enable additional printk() statements.
2756 rcupdate.rcu_expedited= [KNL]
2757 Use expedited grace-period primitives, for
2758 example, synchronize_rcu_expedited() instead
2759 of synchronize_rcu(). This reduces latency,
2760 but can increase CPU utilization, degrade
2761 real-time latency, and degrade energy efficiency.
2763 rcupdate.rcu_cpu_stall_suppress= [KNL]
2764 Suppress RCU CPU stall warning messages.
2766 rcupdate.rcu_cpu_stall_timeout= [KNL]
2767 Set timeout for RCU CPU stall warning messages.
2771 Run specified binary instead of /init from the ramdisk,
2772 used for early userspace startup. See initrd.
2775 Format (x86 or x86_64):
2776 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2778 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2780 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2781 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2782 reboot_force is either force or not specified,
2783 reboot_cpu is s[mp]#### with #### being the processor
2784 to be used for rebooting.
2787 [KNL, SMP] Set scheduler's default relax_domain_level.
2788 See Documentation/cgroups/cpusets.txt.
2790 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2792 reservetop= [X86-32]
2794 Reserves a hole at the top of the kernel virtual
2799 Set the amount of memory to reserve for BIOS at
2800 the bottom of the address space.
2802 reset_devices [KNL] Force drivers to reset the underlying device
2803 during initialization.
2806 Specify the partition device for software suspend
2808 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2810 resume_offset= [SWSUSP]
2811 Specify the offset from the beginning of the partition
2812 given by "resume=" at which the swap header is located,
2813 in <PAGE_SIZE> units (needed only for swap files).
2814 See Documentation/power/swsusp-and-swap-files.txt
2816 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2817 read the resume files
2819 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2820 Useful for devices that are detected asynchronously
2821 (e.g. USB and MMC devices).
2823 hibernate= [HIBERNATION]
2824 noresume Don't check if there's a hibernation image
2825 present during boot.
2826 nocompress Don't compress/decompress hibernation images.
2828 retain_initrd [RAM] Keep initrd memory after extraction
2830 rhash_entries= [KNL,NET]
2831 Set number of hash buckets for route cache
2833 riscom8= [HW,SERIAL]
2834 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2836 ro [KNL] Mount root device read-only on boot
2838 root= [KNL] Root filesystem
2839 See name_to_dev_t comment in init/do_mounts.c.
2841 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2842 mount the root filesystem
2844 rootflags= [KNL] Set root filesystem mount option string
2846 rootfstype= [KNL] Set root filesystem type
2848 rootwait [KNL] Wait (indefinitely) for root device to show up.
2849 Useful for devices that are detected asynchronously
2850 (e.g. USB and MMC devices).
2852 rproc_mem=nn[KMG][@address]
2853 [KNL,ARM,CMA] Remoteproc physical memory block.
2854 Memory area to be used by remote processor image,
2857 rw [KNL] Mount root device read-write on boot
2859 S [KNL] Run init in single mode
2862 See drivers/net/irda/sa1100_ir.c.
2864 sbni= [NET] Granch SBNI12 leased line adapter
2866 sched_debug [KNL] Enables verbose scheduler debug messages.
2868 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2869 xtime_lock contention on larger systems, and/or RCU lock
2870 contention on all systems with CONFIG_MAXSMP set.
2871 Format: { "0" | "1" }
2872 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2874 Note: increases power consumption, thus should only be
2875 enabled if running jitter sensitive (HPC/RT) workloads.
2877 security= [SECURITY] Choose a security module to enable at boot.
2878 If this boot parameter is not specified, only the first
2879 security module asking for security registration will be
2880 loaded. An invalid security module name will be treated
2881 as if no module has been chosen.
2883 selinux= [SELINUX] Disable or enable SELinux at boot time.
2884 Format: { "0" | "1" }
2885 See security/selinux/Kconfig help text.
2888 Default value is set via kernel config option.
2889 If enabled at boot time, /selinux/disable can be used
2890 later to disable prior to initial policy load.
2892 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2893 Format: { "0" | "1" }
2894 See security/apparmor/Kconfig help text
2897 Default value is set via kernel config option.
2899 serialnumber [BUGS=X86-32]
2902 Maximal number of shapers.
2904 show_msr= [x86] show boot-time MSR settings
2905 Format: { <integer> }
2906 Show boot-time (BIOS-initialized) MSR settings.
2907 The parameter means the number of CPUs to show,
2908 for example 1 means boot CPU only.
2915 slab_max_order= [MM, SLAB]
2916 Determines the maximum allowed order for slabs.
2917 A high setting may cause OOMs due to memory
2918 fragmentation. Defaults to 1 for systems with
2919 more than 32MB of RAM, 0 otherwise.
2921 slub_debug[=options[,slabs]] [MM, SLUB]
2922 Enabling slub_debug allows one to determine the
2923 culprit if slab objects become corrupted. Enabling
2924 slub_debug can create guard zones around objects and
2925 may poison objects when not in use. Also tracks the
2926 last alloc / free. For more information see
2927 Documentation/vm/slub.txt.
2929 slub_max_order= [MM, SLUB]
2930 Determines the maximum allowed order for slabs.
2931 A high setting may cause OOMs due to memory
2932 fragmentation. For more information see
2933 Documentation/vm/slub.txt.
2935 slub_min_objects= [MM, SLUB]
2936 The minimum number of objects per slab. SLUB will
2937 increase the slab order up to slub_max_order to
2938 generate a sufficiently large slab able to contain
2939 the number of objects indicated. The higher the number
2940 of objects the smaller the overhead of tracking slabs
2941 and the less frequently locks need to be acquired.
2942 For more information see Documentation/vm/slub.txt.
2944 slub_min_order= [MM, SLUB]
2945 Determines the minimum page order for slabs. Must be
2946 lower than slub_max_order.
2947 For more information see Documentation/vm/slub.txt.
2949 slub_nomerge [MM, SLUB]
2950 Disable merging of slabs with similar size. May be
2951 necessary if there is some reason to distinguish
2952 allocs to different slabs. Debug options disable
2953 merging on their own.
2954 For more information see Documentation/vm/slub.txt.
2957 Format: <io1>[,<io2>[,...,<io8>]]
2959 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2960 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2961 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2962 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2963 smsc-ircc2.ircc_irq= [HW] IRQ line
2964 smsc-ircc2.ircc_dma= [HW] DMA channel
2965 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2966 0: Toshiba Satellite 1800 (GP data pin select)
2967 1: Fast pin select (default)
2971 [KNL] Should the soft-lockup detector generate panics.
2974 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2975 See Documentation/laptops/sonypi.txt
2977 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2978 See Documentation/serial/specialix.txt.
2980 spia_io_base= [HW,MTD]
2986 Enabled the stack tracer on boot up.
2988 stacktrace_filter=[function-list]
2989 [FTRACE] Limit the functions that the stack tracer
2990 will trace at boot up. function-list is a comma separated
2991 list of functions. This list can be changed at run
2992 time by the stack_trace_filter file in the debugfs
2993 tracing directory. Note, this enables stack tracing
2994 and the stacktrace above is not needed.
2998 Set the STI (builtin display/keyboard on the HP-PARISC
2999 machines) console (graphic card) which should be used
3000 as the initial boot-console.
3001 See also comment in drivers/video/console/sticore.c.
3004 See comment in drivers/video/console/sticore.c.
3007 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3009 sunrpc.min_resvport=
3010 sunrpc.max_resvport=
3012 SunRPC servers often require that client requests
3013 originate from a privileged port (i.e. a port in the
3014 range 0 < portnr < 1024).
3015 An administrator who wishes to reserve some of these
3016 ports for other uses may adjust the range that the
3017 kernel's sunrpc client considers to be privileged
3018 using these two parameters to set the minimum and
3019 maximum port values.
3023 Control how the NFS server code allocates CPUs to
3024 service thread pools. Depending on how many NICs
3025 you have and where their interrupts are bound, this
3026 option will affect which CPUs will do NFS serving.
3027 Note: this parameter cannot be changed while the
3028 NFS server is running.
3030 auto the server chooses an appropriate mode
3031 automatically using heuristics
3032 global a single global pool contains all CPUs
3033 percpu one pool for each CPU
3034 pernode one pool for each NUMA node (equivalent
3035 to global on non-NUMA machines)
3037 sunrpc.tcp_slot_table_entries=
3038 sunrpc.udp_slot_table_entries=
3040 Sets the upper limit on the number of simultaneous
3041 RPC calls that can be sent from the client to a
3042 server. Increasing these values may allow you to
3043 improve throughput, but will also increase the
3044 amount of memory reserved for use by the client.
3047 [KNL] Enable accounting of swap in memory resource
3048 controller if no parameter or 1 is given or disable
3049 it if 0 is given (See Documentation/cgroups/memory.txt)
3051 swiotlb= [IA-64] Number of I/O TLB slabs
3055 sysfs.deprecated=0|1 [KNL]
3056 Enable/disable old style sysfs layout for old udev
3057 on older distributions. When this option is enabled
3058 very new udev will not work anymore. When this option
3059 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3060 in older udev will not work anymore.
3061 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3062 the kernel configuration.
3064 sysrq_always_enabled
3066 Ignore sysrq setting - this boot parameter will
3067 neutralize any effect of /proc/sys/kernel/sysrq.
3068 Useful for debugging.
3072 test_suspend= [SUSPEND]
3073 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3074 standby suspend) as the system sleep state to briefly
3075 enter during system startup. The system is woken from
3076 this state using a wakeup-capable RTC alarm.
3078 thash_entries= [KNL,NET]
3079 Set number of hash buckets for TCP connection
3081 thermal.act= [HW,ACPI]
3082 -1: disable all active trip points in all thermal zones
3083 <degrees C>: override all lowest active trip points
3085 thermal.crt= [HW,ACPI]
3086 -1: disable all critical trip points in all thermal zones
3087 <degrees C>: override all critical trip points
3089 thermal.nocrt= [HW,ACPI]
3090 Set to disable actions on ACPI thermal zone
3091 critical and hot trip points.
3093 thermal.off= [HW,ACPI]
3094 1: disable ACPI thermal control
3096 thermal.psv= [HW,ACPI]
3097 -1: disable all passive trip points
3098 <degrees C>: override all passive trip points to this
3101 thermal.tzp= [HW,ACPI]
3102 Specify global default ACPI thermal zone polling rate
3103 <deci-seconds>: poll all this frequency
3104 0: no polling (default)
3107 Force threading of all interrupt handlers except those
3108 marked explicitly IRQF_NO_THREAD.
3111 Enable the Transcendent memory driver if built-in.
3113 tmem.cleancache=0|1 [KNL, XEN]
3114 Default is on (1). Disable the usage of the cleancache
3115 API to send anonymous pages to the hypervisor.
3117 tmem.frontswap=0|1 [KNL, XEN]
3118 Default is on (1). Disable the usage of the frontswap
3119 API to send swap pages to the hypervisor. If disabled
3120 the selfballooning and selfshrinking are force disabled.
3122 tmem.selfballooning=0|1 [KNL, XEN]
3123 Default is on (1). Disable the driving of swap pages
3126 tmem.selfshrinking=0|1 [KNL, XEN]
3127 Default is on (1). Partial swapoff that immediately
3128 transfers pages from Xen hypervisor back to the
3129 kernel based on different criteria.
3133 Specify if the kernel should make use of the cpu
3134 topology information if the hardware supports this.
3135 The scheduler will make use of this information and
3136 e.g. base its process migration decisions on it.
3141 tpm_suspend_pcr=[HW,TPM]
3142 Format: integer pcr id
3143 Specify that at suspend time, the tpm driver
3144 should extend the specified pcr with zeros,
3145 as a workaround for some chips which fail to
3146 flush the last written pcr on TPM_SaveState.
3147 This will guarantee that all the other pcrs
3150 trace_buf_size=nn[KMG]
3151 [FTRACE] will set tracing buffer size.
3153 trace_event=[event-list]
3154 [FTRACE] Set and start specified trace events in order
3155 to facilitate early boot debugging.
3156 See also Documentation/trace/events.txt
3158 trace_options=[option-list]
3159 [FTRACE] Enable or disable tracer options at boot.
3160 The option-list is a comma delimited list of options
3161 that can be enabled or disabled just as if you were
3162 to echo the option name into
3164 /sys/kernel/debug/tracing/trace_options
3166 For example, to enable stacktrace option (to dump the
3167 stack trace of each event), add to the command line:
3169 trace_options=stacktrace
3171 See also Documentation/trace/ftrace.txt "trace options"
3175 [FTRACE] enable this option to disable tracing when a
3176 warning is hit. This turns off "tracing_on". Tracing can
3177 be enabled again by echoing '1' into the "tracing_on"
3178 file located in /sys/kernel/debug/tracing/
3180 This option is useful, as it disables the trace before
3181 the WARNING dump is called, which prevents the trace to
3182 be filled with content caused by the warning output.
3184 This option can also be set at run time via the sysctl
3185 option: kernel/traceoff_on_warning
3187 transparent_hugepage=
3189 Format: [always|madvise|never]
3190 Can be used to control the default behavior of the system
3191 with respect to transparent hugepages.
3192 See Documentation/vm/transhuge.txt for more details.
3194 tsc= Disable clocksource stability checks for TSC.
3196 [x86] reliable: mark tsc clocksource as reliable, this
3197 disables clocksource verification at runtime, as well
3198 as the stability checks done at bootup. Used to enable
3199 high-resolution timer mode on older hardware, and in
3200 virtualized environment.
3201 [x86] noirqtime: Do not use TSC to do irq accounting.
3202 Used to run time disable IRQ_TIME_ACCOUNTING on any
3203 platforms where RDTSC is slow and this accounting
3206 turbografx.map[2|3]= [HW,JOY]
3207 TurboGraFX parallel port interface
3209 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3210 See also Documentation/input/joystick-parport.txt
3212 udbg-immortal [PPC] When debugging early kernel crashes that
3213 happen after console_init() and before a proper
3214 console driver takes over, this boot options might
3215 help "seeing" what's going on.
3217 uhash_entries= [KNL,NET]
3218 Set number of hash buckets for UDP/UDP-Lite connections
3221 [USB] Ignore overcurrent events (default N).
3222 Some badly-designed motherboards generate lots of
3223 bogus events, for ports that aren't wired to
3224 anything. Set this parameter to avoid log spamming.
3225 Note that genuine overcurrent events won't be
3229 [X86] Cause panic on unknown NMI.
3231 usbcore.authorized_default=
3232 [USB] Default USB device authorization:
3233 (default -1 = authorized except for wireless USB,
3234 0 = not authorized, 1 = authorized)
3236 usbcore.autosuspend=
3237 [USB] The autosuspend time delay (in seconds) used
3238 for newly-detected USB devices (default 2). This
3239 is the time required before an idle device will be
3240 autosuspended. Devices for which the delay is set
3241 to a negative value won't be autosuspended at all.
3243 usbcore.usbfs_snoop=
3244 [USB] Set to log all usbfs traffic (default 0 = off).
3246 usbcore.blinkenlights=
3247 [USB] Set to cycle leds on hubs (default 0 = off).
3249 usbcore.old_scheme_first=
3250 [USB] Start with the old device initialization
3251 scheme (default 0 = off).
3253 usbcore.usbfs_memory_mb=
3254 [USB] Memory limit (in MB) for buffers allocated by
3255 usbfs (default = 16, 0 = max = 2047).
3257 usbcore.use_both_schemes=
3258 [USB] Try the other device initialization scheme
3259 if the first one fails (default 1 = enabled).
3261 usbcore.initial_descriptor_timeout=
3262 [USB] Specifies timeout for the initial 64-byte
3263 USB_REQ_GET_DESCRIPTOR request in milliseconds
3264 (default 5000 = 5.0 seconds).
3267 [USBHID] The interval which mice are to be polled at.
3269 usb-storage.delay_use=
3270 [UMS] The delay in seconds before a new device is
3271 scanned for Logical Units (default 5).
3274 [UMS] A list of quirks entries to supplement or
3275 override the built-in unusual_devs list. List
3276 entries are separated by commas. Each entry has
3277 the form VID:PID:Flags where VID and PID are Vendor
3278 and Product ID values (4-digit hex numbers) and
3279 Flags is a set of characters, each corresponding
3280 to a common usb-storage quirk flag as follows:
3281 a = SANE_SENSE (collect more than 18 bytes
3283 b = BAD_SENSE (don't collect more than 18
3284 bytes of sense data);
3285 c = FIX_CAPACITY (decrease the reported
3286 device capacity by one sector);
3287 d = NO_READ_DISC_INFO (don't use
3288 READ_DISC_INFO command);
3289 e = NO_READ_CAPACITY_16 (don't use
3290 READ_CAPACITY_16 command);
3291 h = CAPACITY_HEURISTICS (decrease the
3292 reported device capacity by one
3293 sector if the number is odd);
3294 i = IGNORE_DEVICE (don't bind to this
3296 l = NOT_LOCKABLE (don't try to lock and
3297 unlock ejectable media);
3298 m = MAX_SECTORS_64 (don't transfer more
3299 than 64 sectors = 32 KB at a time);
3300 n = INITIAL_READ10 (force a retry of the
3301 initial READ(10) command);
3302 o = CAPACITY_OK (accept the capacity
3303 reported by the device);
3304 p = WRITE_CACHE (the device cache is ON
3306 r = IGNORE_RESIDUE (the device reports
3307 bogus residue values);
3308 s = SINGLE_LUN (the device has only one
3310 w = NO_WP_DETECT (don't test whether the
3311 medium is write-protected).
3312 Example: quirks=0419:aaf5:rl,0421:0433:rc
3314 user_debug= [KNL,ARM]
3316 See arch/arm/Kconfig.debug help text.
3317 1 - undefined instruction events
3319 4 - invalid data aborts
3322 Example: user_debug=31
3325 [X86] Flags controlling user PTE allocations.
3327 nohigh = do not allocate PTE pages in
3328 HIGHMEM regardless of setting
3332 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3333 vdso=1: enable VDSO (default)
3334 vdso=0: disable VDSO mapping
3337 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3338 vdso32=1: enable 32-bit VDSO (default)
3339 vdso32=0: disable 32-bit VDSO mapping
3342 vector=percpu: enable percpu vector domain
3344 video= [FB] Frame buffer configuration
3345 See Documentation/fb/modedb.txt.
3347 video.brightness_switch_enabled= [0,1]
3348 If set to 1, on receiving an ACPI notify event
3349 generated by hotkey, video driver will adjust brightness
3350 level and then send out the event to user space through
3351 the allocated input device; If set to 0, video driver
3352 will only send out the event without touching backlight
3357 [VMMIO] Memory mapped virtio (platform) device.
3359 <size>@<baseaddr>:<irq>[:<id>]
3361 <size> := size (can use standard suffixes
3363 <baseaddr> := physical base address
3364 <irq> := interrupt number (as passed to
3366 <id> := (optional) platform device id
3368 virtio_mmio.device=1K@0x100b0000:48:7
3370 Can be used multiple times for multiple devices.
3372 vga= [BOOT,X86-32] Select a particular video mode
3373 See Documentation/x86/boot.txt and
3374 Documentation/svga.txt.
3375 Use vga=ask for menu.
3376 This is actually a boot loader parameter; the value is
3377 passed to the kernel using a special protocol.
3379 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3380 size of <nn>. This can be used to increase the
3381 minimum size (128MB on x86). It can also be used to
3382 decrease the size and leave more room for directly
3385 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3388 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3391 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3395 Controls the behavior of vsyscalls (i.e. calls to
3396 fixed addresses of 0xffffffffff600x00 from legacy
3397 code). Most statically-linked binaries and older
3398 versions of glibc use these calls. Because these
3399 functions are at fixed addresses, they make nice
3400 targets for exploits that can control RIP.
3402 emulate [default] Vsyscalls turn into traps and are
3403 emulated reasonably safely.
3405 native Vsyscalls are native syscall instructions.
3406 This is a little bit faster than trapping
3407 and makes a few dynamic recompilers work
3408 better than they would in emulation mode.
3409 It also makes exploits much easier to write.
3411 none Vsyscalls don't work at all. This makes
3412 them quite hard to use for exploits but
3413 might break your system.
3415 vt.color= [VT] Default text color.
3416 Format: 0xYX, X = foreground, Y = background.
3417 Default: 0x07 = light gray on black.
3419 vt.cur_default= [VT] Default cursor shape.
3420 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3421 the parameters of the <Esc>[?A;B;Cc escape sequence;
3422 see VGA-softcursor.txt. Default: 2 = underline.
3424 vt.default_blu= [VT]
3425 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3426 Change the default blue palette of the console.
3427 This is a 16-member array composed of values
3430 vt.default_grn= [VT]
3431 Format: <green0>,<green1>,<green2>,...,<green15>
3432 Change the default green palette of the console.
3433 This is a 16-member array composed of values
3436 vt.default_red= [VT]
3437 Format: <red0>,<red1>,<red2>,...,<red15>
3438 Change the default red palette of the console.
3439 This is a 16-member array composed of values
3445 Set system-wide default UTF-8 mode for all tty's.
3446 Default is 1, i.e. UTF-8 mode is enabled for all
3447 newly opened terminals.
3449 vt.global_cursor_default=
3452 Set system-wide default for whether a cursor
3453 is shown on new VTs. Default is -1,
3454 i.e. cursors will be created by default unless
3455 overridden by individual drivers. 0 will hide
3456 cursors, 1 will display them.
3458 vt.italic= [VT] Default color for italic text; 0-15.
3461 vt.underline= [VT] Default color for underlined text; 0-15.
3464 watchdog timers [HW,WDT] For information on watchdog timers,
3465 see Documentation/watchdog/watchdog-parameters.txt
3466 or other driver-specific files in the
3467 Documentation/watchdog/ directory.
3469 workqueue.disable_numa
3470 By default, all work items queued to unbound
3471 workqueues are affine to the NUMA nodes they're
3472 issued on, which results in better behavior in
3473 general. If NUMA affinity needs to be disabled for
3474 whatever reason, this option can be used. Note
3475 that this also can be controlled per-workqueue for
3476 workqueues visible under /sys/bus/workqueue/.
3478 workqueue.power_efficient
3479 Per-cpu workqueues are generally preferred because
3480 they show better performance thanks to cache
3481 locality; unfortunately, per-cpu workqueues tend to
3482 be more power hungry than unbound workqueues.
3484 Enabling this makes the per-cpu workqueues which
3485 were observed to contribute significantly to power
3486 consumption unbound, leading to measurably lower
3487 power usage at the cost of small performance
3490 The default value of this parameter is determined by
3491 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3493 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3494 default x2apic cluster mode on platforms
3497 x86_intel_mid_timer= [X86-32,APBT]
3498 Choose timer option for x86 Intel MID platform.
3499 Two valid options are apbt timer only and lapic timer
3500 plus one apbt timer for broadcast timer.
3501 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3503 xen_emul_unplug= [HW,X86,XEN]
3504 Unplug Xen emulated devices
3505 Format: [unplug0,][unplug1]
3506 ide-disks -- unplug primary master IDE devices
3507 aux-ide-disks -- unplug non-primary-master IDE devices
3508 nics -- unplug network devices
3509 all -- unplug all emulated devices (NICs and IDE disks)
3510 unnecessary -- unplugging emulated devices is
3511 unnecessary even if the host did not respond to
3513 never -- do not unplug even if version check succeeds
3515 xen_nopvspin [X86,XEN]
3516 Disables the ticketlock slowpath using Xen PV
3519 xirc2ps_cs= [NET,PCMCIA]
3521 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3523 ______________________________________________________________________
3527 Add more DRM drivers.
projects / karo-tx-linux.git / blob