4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 CLK Common clock infrastructure is enabled.
48 CMA Contiguous Memory Area support is enabled.
49 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
51 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
52 EFI EFI Partitioning (GPT) is enabled
53 EIDE EIDE/ATAPI support is enabled.
54 EVM Extended Verification Module
55 FB The frame buffer device is enabled.
56 FTRACE Function tracing enabled.
57 GCOV GCOV profiling is enabled.
58 HW Appropriate hardware is enabled.
59 IA-64 IA-64 architecture is enabled.
60 IMA Integrity measurement architecture is enabled.
61 IOSCHED More than one I/O scheduler is enabled.
62 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
63 IPV6 IPv6 support is enabled.
64 ISAPNP ISA PnP code is enabled.
65 ISDN Appropriate ISDN support is enabled.
66 JOY Appropriate joystick support is enabled.
67 KGDB Kernel debugger support is enabled.
68 KVM Kernel Virtual Machine support is enabled.
69 LIBATA Libata driver is enabled
70 LP Printer support is enabled.
71 LOOP Loopback device support is enabled.
72 M68k M68k architecture is enabled.
73 These options have more detailed description inside of
74 Documentation/m68k/kernel-options.txt.
75 MDA MDA console support is enabled.
76 MIPS MIPS architecture is enabled.
77 MOUSE Appropriate mouse support is enabled.
78 MSI Message Signaled Interrupts (PCI).
79 MTD MTD (Memory Technology Device) support is enabled.
80 NET Appropriate network support is enabled.
81 NUMA NUMA support is enabled.
82 NFS Appropriate NFS support is enabled.
83 OSS OSS sound support is enabled.
84 PV_OPS A paravirtualized kernel is enabled.
85 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
86 PARISC The PA-RISC architecture is enabled.
87 PCI PCI bus support is enabled.
88 PCIE PCI Express support is enabled.
89 PCMCIA The PCMCIA subsystem is enabled.
90 PNP Plug & Play support is enabled.
91 PPC PowerPC architecture is enabled.
92 PPT Parallel port support is enabled.
93 PS2 Appropriate PS/2 support is enabled.
94 RAM RAM disk support is enabled.
95 S390 S390 architecture is enabled.
96 SCSI Appropriate SCSI support is enabled.
97 A lot of drivers have their options described inside
98 the Documentation/scsi/ sub-directory.
99 SECURITY Different security models are enabled.
100 SELINUX SELinux support is enabled.
101 APPARMOR AppArmor support is enabled.
102 SERIAL Serial support is enabled.
103 SH SuperH architecture is enabled.
104 SMP The kernel is an SMP kernel.
105 SPARC Sparc architecture is enabled.
106 SWSUSP Software suspend (hibernation) is enabled.
107 SUSPEND System suspend states are enabled.
108 TPM TPM drivers are enabled.
109 TS Appropriate touchscreen support is enabled.
110 UMS USB Mass Storage support is enabled.
111 USB USB support is enabled.
112 USBHID USB Human Interface Device support is enabled.
113 V4L Video For Linux support is enabled.
114 VMMIO Driver for memory mapped virtio devices is enabled.
115 VGA The VGA console has been enabled.
116 VT Virtual terminal support is enabled.
117 WDT Watchdog support is enabled.
118 XT IBM PC/XT MFM hard disk support is enabled.
119 X86-32 X86-32, aka i386 architecture is enabled.
120 X86-64 X86-64 architecture is enabled.
121 More X86-64 boot options can be found in
122 Documentation/x86/x86_64/boot-options.txt .
123 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
124 XEN Xen support is enabled
126 In addition, the following text indicates that the option:
128 BUGS= Relates to possible processor bugs on the said processor.
129 KNL Is a kernel start-up parameter.
130 BOOT Is a boot loader parameter.
132 Parameters denoted with BOOT are actually interpreted by the boot
133 loader, and have no meaning to the kernel directly.
134 Do not modify the syntax of boot loader parameters without extreme
135 need or coordination with <Documentation/x86/boot.txt>.
137 There are also arch-specific kernel-parameters not documented here.
138 See for example <Documentation/x86/x86_64/boot-options.txt>.
140 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
141 a trailing = on the name of any parameter states that that parameter will
142 be entered as an environment variable, whereas its absence indicates that
143 it will appear as a kernel argument readable via /proc/cmdline by programs
144 running once the system is up.
146 The number of kernel parameters is not limited, but the length of the
147 complete command line (parameters including spaces etc.) is limited to
148 a fixed number of characters. This limit depends on the architecture
149 and is between 256 and 4096 characters. It is defined in the file
150 ./include/asm/setup.h as COMMAND_LINE_SIZE.
152 Finally, the [KMG] suffix is commonly described after a number of kernel
153 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
154 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
155 bytes respectively. Such letter suffixes can also be entirely omitted.
159 Advanced Configuration and Power Interface
160 Format: { force | off | strict | noirq | rsdt }
161 force -- enable ACPI if default was off
162 off -- disable ACPI if default was on
163 noirq -- do not use ACPI for IRQ routing
164 strict -- Be less tolerant of platforms that are not
165 strictly ACPI specification compliant.
166 rsdt -- prefer RSDT over (default) XSDT
167 copy_dsdt -- copy DSDT to memory
169 See also Documentation/power/runtime_pm.txt, pci=noacpi
171 acpi_rsdp= [ACPI,EFI,KEXEC]
172 Pass the RSDP address to the kernel, mostly used
173 on machines running EFI runtime service to boot the
174 second kernel for kdump.
176 acpi_apic_instance= [ACPI, IOAPIC]
178 2: use 2nd APIC table, if available
179 1,0: use 1st APIC table
182 acpi_backlight= [HW,ACPI]
183 acpi_backlight=vendor
185 If set to vendor, prefer vendor specific driver
186 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
187 of the ACPI video.ko driver.
189 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
190 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
192 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
193 debug output. Bits in debug_layer correspond to a
194 _COMPONENT in an ACPI source file, e.g.,
195 #define _COMPONENT ACPI_PCI_COMPONENT
196 Bits in debug_level correspond to a level in
197 ACPI_DEBUG_PRINT statements, e.g.,
198 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
199 The debug_level mask defaults to "info". See
200 Documentation/acpi/debug.txt for more information about
201 debug layers and levels.
203 Enable processor driver info messages:
204 acpi.debug_layer=0x20000000
205 Enable PCI/PCI interrupt routing info messages:
206 acpi.debug_layer=0x400000
207 Enable AML "Debug" output, i.e., stores to the Debug
208 object while interpreting AML:
209 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
210 Enable all messages related to ACPI hardware:
211 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
213 Some values produce so much output that the system is
214 unusable. The "log_buf_len" parameter may be useful
215 if you need to capture more output.
217 acpi_irq_balance [HW,ACPI]
218 ACPI will balance active IRQs
221 acpi_irq_nobalance [HW,ACPI]
222 ACPI will not move active IRQs (default)
225 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
226 Format: <irq>,<irq>...
228 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
230 Format: <irq>,<irq>...
232 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
234 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
235 Format: To spoof as Windows 98: ="Microsoft Windows"
237 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
238 acpi_osi="string1" # add string1
239 acpi_osi="!string2" # remove string2
240 acpi_osi=!* # remove all strings
241 acpi_osi=! # disable all built-in OS vendor
243 acpi_osi= # disable all strings
245 'acpi_osi=!' can be used in combination with single or
246 multiple 'acpi_osi="string1"' to support specific OS
247 vendor string(s). Note that such command can only
248 affect the default state of the OS vendor strings, thus
249 it cannot affect the default state of the feature group
250 strings and the current state of the OS vendor strings,
251 specifying it multiple times through kernel command line
252 is meaningless. This command is useful when one do not
253 care about the state of the feature group strings which
254 should be controlled by the OSPM.
256 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
257 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
258 can make '_OSI("Windows 2000")' TRUE.
260 'acpi_osi=' cannot be used in combination with other
261 'acpi_osi=' command lines, the _OSI method will not
262 exist in the ACPI namespace. NOTE that such command can
263 only affect the _OSI support state, thus specifying it
264 multiple times through kernel command line is also
267 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
270 'acpi_osi=!*' can be used in combination with single or
271 multiple 'acpi_osi="string1"' to support specific
272 string(s). Note that such command can affect the
273 current state of both the OS vendor strings and the
274 feature group strings, thus specifying it multiple times
275 through kernel command line is meaningful. But it may
276 still not able to affect the final state of a string if
277 there are quirks related to this string. This command
278 is useful when one want to control the state of the
279 feature group strings to debug BIOS issues related to
282 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
283 '_OSI("Module Device")' FALSE.
284 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
285 '_OSI("Module Device")' TRUE.
286 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
288 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
290 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
291 they all will make '_OSI("Windows 2000")' TRUE.
294 Override the pmtimer bug detection: force the kernel
295 to assume that this machine's pmtimer latches its value
296 and always returns good values.
298 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
299 Format: { level | edge | high | low }
301 acpi_serialize [HW,ACPI] force serialization of AML methods
303 acpi_skip_timer_override [HW,ACPI]
304 Recognize and ignore IRQ0/pin2 Interrupt Override.
305 For broken nForce2 BIOS resulting in XT-PIC timer.
307 acpi_sleep= [HW,ACPI] Sleep options
308 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
309 old_ordering, nonvs, sci_force_enable }
310 See Documentation/power/video.txt for information on
312 s3_beep is for debugging; it makes the PC's speaker beep
313 as soon as the kernel's real-mode entry point is called.
314 s4_nohwsig prevents ACPI hardware signature from being
315 used during resume from hibernation.
316 old_ordering causes the ACPI 1.0 ordering of the _PTS
317 control method, with respect to putting devices into
318 low power states, to be enforced (the ACPI 2.0 ordering
319 of _PTS is used by default).
320 nonvs prevents the kernel from saving/restoring the
321 ACPI NVS memory during suspend/hibernation and resume.
322 sci_force_enable causes the kernel to set SCI_EN directly
323 on resume from S1/S3 (which is against the ACPI spec,
324 but some broken systems don't work without it).
326 acpi_use_timer_override [HW,ACPI]
327 Use timer override. For some broken Nvidia NF5 boards
328 that require a timer override, but don't have HPET
330 acpi_enforce_resources= [ACPI]
331 { strict | lax | no }
332 Check for resource conflicts between native drivers
333 and ACPI OperationRegions (SystemIO and SystemMemory
334 only). IO ports and memory declared in ACPI might be
335 used by the ACPI subsystem in arbitrary AML code and
336 can interfere with legacy drivers.
337 strict (default): access to resources claimed by ACPI
338 is denied; legacy drivers trying to access reserved
339 resources will fail to bind to device using them.
340 lax: access to resources claimed by ACPI is allowed;
341 legacy drivers trying to access reserved resources
342 will bind successfully but a warning message is logged.
343 no: ACPI OperationRegions are not marked as reserved,
344 no further checks are performed.
346 add_efi_memmap [EFI; X86] Include EFI memory map in
347 kernel's map of available physical RAM.
350 { off | try_unsupported }
351 off: disable AGP support
352 try_unsupported: try to drive unsupported chipsets
353 (may crash computer or cause data corruption)
356 See Documentation/sound/alsa/alsa-parameters.txt
359 Allow the default userspace alignment fault handler
360 behaviour to be specified. Bit 0 enables warnings,
361 bit 1 enables fixups, and bit 2 sends a segfault.
363 align_va_addr= [X86-64]
364 Align virtual addresses by clearing slice [14:12] when
365 allocating a VMA at process creation time. This option
366 gives you up to 3% performance improvement on AMD F15h
367 machines (where it is enabled by default) for a
368 CPU-intensive style benchmark, and it can vary highly in
369 a microbenchmark depending on workload and compiler.
371 32: only for 32-bit processes
372 64: only for 64-bit processes
373 on: enable for both 32- and 64-bit processes
374 off: disable for both 32- and 64-bit processes
376 alloc_snapshot [FTRACE]
377 Allocate the ftrace snapshot buffer on boot up when the
378 main buffer is allocated. This is handy if debugging
379 and you need to use tracing_snapshot() on boot up, and
380 do not want to use tracing_snapshot_alloc() as it needs
381 to be done where GFP_KERNEL allocations are allowed.
383 amd_iommu= [HW,X86-64]
384 Pass parameters to the AMD IOMMU driver in the system.
386 fullflush - enable flushing of IO/TLB entries when
387 they are unmapped. Otherwise they are
388 flushed before they will be reused, which
390 off - do not initialize any AMD IOMMU found in
392 force_isolation - Force device isolation for all
393 devices. The IOMMU driver is not
394 allowed anymore to lift isolation
395 requirements as needed. This option
396 does not override iommu=pt
398 amd_iommu_dump= [HW,X86-64]
399 Enable AMD IOMMU driver option to dump the ACPI table
400 for AMD IOMMU. With this option enabled, AMD IOMMU
401 driver will print ACPI tables for AMD IOMMU during
402 IOMMU initialization.
404 amijoy.map= [HW,JOY] Amiga joystick support
405 Map of devices attached to JOY0DAT and JOY1DAT
407 See also Documentation/input/joystick.txt
409 analog.map= [HW,JOY] Analog joystick and gamepad support
410 Specifies type or capabilities of an analog joystick
411 connected to one of 16 gameports
412 Format: <type1>,<type2>,..<type16>
415 Power management functions (SPARCstation-4/5 + deriv.)
417 Disable APC CPU standby support. SPARCstation-Fox does
418 not play well with APC CPU idle - disable it if you have
419 APC and your system crashes randomly.
421 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
422 Change the output verbosity whilst booting
423 Format: { quiet (default) | verbose | debug }
424 Change the amount of debugging information output
425 when initialising the APIC and IO-APIC components.
428 See Documentation/networking/ipv6.txt.
430 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
431 Limit apic dumping. The parameter defines the maximal
432 number of local apics being dumped. Also it is possible
433 to set it to "all" by meaning -- no limit here.
434 Format: { 1 (default) | 2 | ... | all }.
435 The parameter valid if only apic=debug or
436 apic=verbose is specified.
437 Example: apic=debug show_lapic=all
439 apm= [APM] Advanced Power Management
440 See header of arch/x86/kernel/apm_32.c.
442 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
443 Format: <io>,<irq>,<nodeID>
447 atarimouse= [HW,MOUSE] Atari Mouse
449 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
450 EzKey and similar keyboards
452 atkbd.reset= [HW] Reset keyboard during initialization
454 atkbd.set= [HW] Select keyboard code set
455 Format: <int> (2 = AT (default), 3 = PS/2)
457 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
460 atkbd.softraw= [HW] Choose between synthetic and real raw mode
461 Format: <bool> (0 = real, 1 = synthetic (default))
463 atkbd.softrepeat= [HW]
464 Use software keyboard repeat
466 audit= [KNL] Enable the audit sub-system
467 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
468 0 - kernel audit is disabled and can not be enabled
469 until the next reboot
470 unset - kernel audit is initialized but disabled and
471 will be fully enabled by the userspace auditd.
472 1 - kernel audit is initialized and partially enabled,
473 storing at most audit_backlog_limit messages in
474 RAM until it is fully enabled by the userspace
478 audit_backlog_limit= [KNL] Set the audit queue size limit.
479 Format: <int> (must be >=0)
482 baycom_epp= [HW,AX25]
485 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
487 See header of drivers/net/hamradio/baycom_par.c.
489 baycom_ser_fdx= [HW,AX25]
490 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
491 Format: <io>,<irq>,<mode>[,<baud>]
492 See header of drivers/net/hamradio/baycom_ser_fdx.c.
494 baycom_ser_hdx= [HW,AX25]
495 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
496 Format: <io>,<irq>,<mode>
497 See header of drivers/net/hamradio/baycom_ser_hdx.c.
499 blkdevparts= Manual partition parsing of block device(s) for
500 embedded devices based on command line input.
501 See Documentation/block/cmdline-partition.txt
503 boot_delay= Milliseconds to delay each printk during boot.
504 Values larger than 10 seconds (10000) are changed to
508 bootmem_debug [KNL] Enable bootmem allocator debug messages.
510 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
511 bttv.radio= Most important insmod options are available as
513 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
516 bulk_remove=off [PPC] This parameter disables the use of the pSeries
517 firmware feature for flushing multiple hpte entries
520 c101= [NET] Moxa C101 synchronous serial card
522 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
523 Sometimes CPU hardware bugs make them report the cache
524 size incorrectly. The kernel will attempt work arounds
525 to fix known problems, but for some CPUs it is not
526 possible to determine what the correct size should be.
527 This option provides an override for these situations.
529 ccw_timeout_log [S390]
530 See Documentation/s390/CommonIO for details.
532 cgroup_disable= [KNL] Disable a particular controller
533 Format: {name of the controller(s) to disable}
534 {Currently supported controllers - "memory"}
536 checkreqprot [SELINUX] Set initial checkreqprot flag value.
537 Format: { "0" | "1" }
538 See security/selinux/Kconfig help text.
539 0 -- check protection applied by kernel (includes
540 any implied execute protection).
541 1 -- check protection requested by application.
542 Default value is set via a kernel config option.
543 Value can be changed at runtime via
544 /selinux/checkreqprot.
547 See Documentation/s390/CommonIO for details.
550 Keep all clocks already enabled by bootloader on,
551 even if no driver has claimed them. This is useful
552 for debug and development, but should not be
553 needed on a platform with proper driver support.
554 For more information, see Documentation/clk.txt.
556 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
558 Forces specified clocksource (if available) to be used
559 when calculating gettimeofday(). If specified
560 clocksource is not available, it defaults to PIT.
561 Format: { pit | tsc | cyclone | pmtmr }
563 clocksource= Override the default clocksource
565 Override the default clocksource and use the clocksource
566 with the name specified.
567 Some clocksource names to choose from, depending on
569 [all] jiffies (this is the base, fallback clocksource)
571 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
572 pxa_timer,timer3,32k_counter,timer0_1
574 [X86-32] pit,hpet,tsc;
575 scx200_hrt on Geode; cyclone on IBM x440
583 clearcpuid=BITNUM [X86]
584 Disable CPUID feature X for the kernel. See
585 arch/x86/include/asm/cpufeature.h for the valid bit
586 numbers. Note the Linux specific bits are not necessarily
587 stable over kernel options, but the vendor specific
589 Also note that user programs calling CPUID directly
590 or using the feature without checking anything
591 will still see it. This just prevents it from
592 being used by the kernel or shown in /proc/cpuinfo.
593 Also note the kernel might malfunction if you disable
597 Sets the size of kernel global memory area for contiguous
598 memory allocations. For more information, see
599 include/linux/dma-contiguous.h
601 cmo_free_hint= [PPC] Format: { yes | no }
602 Specify whether pages are marked as being inactive
603 when they are freed. This is used in CMO environments
604 to determine OS memory pressure for page stealing by
608 coherent_pool=nn[KMG] [ARM,KNL]
609 Sets the size of memory pool for coherent, atomic dma
610 allocations, by default set to 256K.
612 code_bytes [X86] How many bytes of object code to print
617 com20020= [HW,NET] ARCnet - COM20020 chipset
619 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
621 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
625 ARCnet - COM90xx chipset (memory-mapped buffers)
626 Format: <io>[,<irq>[,<memstart>]]
628 condev= [HW,S390] console device
631 console= [KNL] Output console device and options.
633 tty<n> Use the virtual console device <n>.
637 Use the specified serial port. The options are of
638 the form "bbbbpnf", where "bbbb" is the baud rate,
639 "p" is parity ("n", "o", or "e"), "n" is number of
640 bits, and "f" is flow control ("r" for RTS or
641 omit it). Default is "9600n8".
643 See Documentation/serial-console.txt for more
645 Documentation/networking/netconsole.txt for an
648 uart[8250],io,<addr>[,options]
649 uart[8250],mmio,<addr>[,options]
650 Start an early, polled-mode console on the 8250/16550
651 UART at the specified I/O port or MMIO address,
652 switching to the matching ttyS device later. The
653 options are the same as for ttyS, above.
654 hvc<n> Use the hypervisor console device <n>. This is for
655 both Xen and PowerPC hypervisors.
657 If the device connected to the port is not a TTY but a braille
658 device, prepend "brl," before the device type, for instance
660 For now, only VisioBraille is supported.
662 consoleblank= [KNL] The console blank (screen saver) timeout in
663 seconds. Defaults to 10*60 = 10mins. A value of 0
664 disables the blank timer.
667 [KNL] Change the default value for
668 /proc/<pid>/coredump_filter.
669 See also Documentation/filesystems/proc.txt.
671 cpuidle.off=1 [CPU_IDLE]
672 disable the cpuidle sub-system
674 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
676 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
678 crashkernel=size[KMG][@offset[KMG]]
679 [KNL] Using kexec, Linux can switch to a 'crash kernel'
680 upon panic. This parameter reserves the physical
681 memory region [offset, offset + size] for that kernel
682 image. If '@offset' is omitted, then a suitable offset
683 is selected automatically. Check
684 Documentation/kdump/kdump.txt for further details.
686 crashkernel=range1:size1[,range2:size2,...][@offset]
687 [KNL] Same as above, but depends on the memory
688 in the running system. The syntax of range is
689 start-[end] where start and end are both
690 a memory unit (amount[KMG]). See also
691 Documentation/kdump/kdump.txt for an example.
693 crashkernel=size[KMG],high
694 [KNL, x86_64] range could be above 4G. Allow kernel
695 to allocate physical memory region from top, so could
696 be above 4G if system have more than 4G ram installed.
697 Otherwise memory region will be allocated below 4G, if
699 It will be ignored if crashkernel=X is specified.
700 crashkernel=size[KMG],low
701 [KNL, x86_64] range under 4G. When crashkernel=X,high
702 is passed, kernel could allocate physical memory region
703 above 4G, that cause second kernel crash on system
704 that require some amount of low memory, e.g. swiotlb
705 requires at least 64M+32K low memory. Kernel would
706 try to allocate 72M below 4G automatically.
707 This one let user to specify own low range under 4G
708 for second kernel instead.
709 0: to disable low allocation.
710 It will be ignored when crashkernel=X,high is not used
711 or memory reserved is below 4G.
716 cs89x0_media= [HW,NET]
717 Format: { rj45 | aui | bnc }
720 See header of drivers/s390/block/dasd_devmap.c.
722 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
723 (one device per port)
724 Format: <port#>,<type>
725 See also Documentation/input/joystick-parport.txt
727 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
728 time. See Documentation/dynamic-debug-howto.txt for
729 details. Deprecated, see dyndbg.
731 debug [KNL] Enable kernel debugging (events log level).
734 [KNL] verbose self-tests
736 Print debugging info while doing the locking API
738 We default to 0 (no extra messages), setting it to
739 1 will print _a lot_ more information - normally
740 only useful to kernel developers.
742 debug_objects [KNL] Enable object debugging
745 [KNL] Disable object debugging
747 debug_guardpage_minorder=
748 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
749 parameter allows control of the order of pages that will
750 be intentionally kept free (and hence protected) by the
751 buddy allocator. Bigger value increase the probability
752 of catching random memory corruption, but reduce the
753 amount of memory for normal system use. The maximum
754 possible value is MAX_ORDER/2. Setting this parameter
755 to 1 or 2 should be enough to identify most random
756 memory corruption problems caused by bugs in kernel or
757 driver code when a CPU writes to (or reads from) a
758 random memory location. Note that there exists a class
759 of memory corruptions problems caused by buggy H/W or
760 F/W or by drivers badly programing DMA (basically when
761 memory is written at bus level and the CPU MMU is
762 bypassed) which are not detectable by
763 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
764 tracking down these problems.
766 debugpat [X86] Enable PAT debugging
768 decnet.addr= [HW,NET]
769 Format: <area>[,<node>]
770 See also Documentation/networking/decnet.txt.
773 [same as hugepagesz=] The size of the default
774 HugeTLB page size. This is the size represented by
775 the legacy /proc/ hugepages APIs, used for SHM, and
776 default size when mounting hugetlbfs filesystems.
777 Defaults to the default architecture's huge page size
781 Set number of hash buckets for dentry cache.
784 IO parameters + enable/disable command.
786 digiepca= [HW,SERIAL]
787 See drivers/char/README.epca and
788 Documentation/serial/digiepca.txt.
791 See Documentation/networking/ipv6.txt.
793 disable_ddw [PPC/PSERIES]
794 Disable Dynamic DMA Window support. Use this if
795 to workaround buggy firmware.
798 See Documentation/networking/ipv6.txt.
800 disable_mtrr_cleanup [X86]
801 The kernel tries to adjust MTRR layout from continuous
802 to discrete, to make X server driver able to add WB
803 entry later. This parameter disables that.
805 disable_mtrr_trim [X86, Intel and AMD only]
806 By default the kernel will trim any uncacheable
807 memory out of your available memory pool based on
808 MTRR settings. This parameter disables that behavior,
809 possibly causing your machine to run very slowly.
811 disable_timer_pin_1 [X86]
812 Disable PIN 1 of APIC timer
813 Can be useful to work around chipset bugs.
815 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
816 this option disables the debugging code at boot.
818 dma_debug_entries=<number>
819 This option allows to tune the number of preallocated
820 entries for DMA-API debugging code. One entry is
821 required per DMA-API allocation. Use this if the
822 DMA-API debugging code disables itself because the
823 architectural default is too low.
825 dma_debug_driver=<driver_name>
826 With this option the DMA-API debugging driver
827 filter feature can be enabled at boot time. Just
828 pass the driver to filter for as the parameter.
829 The filter can be disabled or changed to another
830 driver later using sysfs.
832 drm_kms_helper.edid_firmware=[<connector>:]<file>
833 Broken monitors, graphic adapters and KVMs may
834 send no or incorrect EDID data sets. This parameter
835 allows to specify an EDID data set in the
836 /lib/firmware directory that is used instead.
837 Generic built-in EDID data sets are used, if one of
838 edid/1024x768.bin, edid/1280x1024.bin,
839 edid/1680x1050.bin, or edid/1920x1080.bin is given
840 and no file with the same name exists. Details and
841 instructions how to build your own EDID data are
842 available in Documentation/EDID/HOWTO.txt. An EDID
843 data set will only be used for a particular connector,
844 if its name and a colon are prepended to the EDID
849 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
850 module.dyndbg[="val"]
851 Enable debug messages at boot time. See
852 Documentation/dynamic-debug-howto.txt for details.
854 earlycon= [KNL] Output early console device and options.
855 uart[8250],io,<addr>[,options]
856 uart[8250],mmio,<addr>[,options]
857 uart[8250],mmio32,<addr>[,options]
858 Start an early, polled-mode console on the 8250/16550
859 UART at the specified I/O port or MMIO address.
860 MMIO inter-register address stride is either 8-bit
861 (mmio) or 32-bit (mmio32).
862 The options are the same as for ttyS, above.
864 earlyprintk= [X86,SH,BLACKFIN,ARM]
867 earlyprintk=serial[,ttySn[,baudrate]]
868 earlyprintk=serial[,0x...[,baudrate]]
869 earlyprintk=ttySn[,baudrate]
870 earlyprintk=dbgp[debugController#]
872 earlyprintk is useful when the kernel crashes before
873 the normal console is initialized. It is not enabled by
874 default because it has some cosmetic problems.
876 Append ",keep" to not disable it when the real console
879 Only vga or serial or usb debug port at a time.
881 Currently only ttyS0 and ttyS1 may be specified by
882 name. Other I/O ports may be explicitly specified
883 on some architectures (x86 and arm at least) by
884 replacing ttySn with an I/O port address, like this:
885 earlyprintk=serial,0x1008,115200
886 You can find the port for a given device in
887 /proc/tty/driver/serial:
888 2: uart:ST16650V2 port:00001008 irq:18 ...
890 Interaction with the standard serial driver is not
893 The VGA output is eventually overwritten by the real
896 The xen output can only be used by Xen PV guests.
898 ekgdboc= [X86,KGDB] Allow early kernel console debugging
901 This is designed to be used in conjunction with
902 the boot argument: earlyprintk=vga
905 Format: {"off" | "on" | "skip[mbr]"}
907 efi_no_storage_paranoia [EFI; X86]
908 Using this parameter you can use more than 50% of
909 your efi variable storage. Use this parameter only if
910 you are really sure that your UEFI does sane gc and
911 fulfills the spec otherwise your board may brick.
913 eisa_irq_edge= [PARISC,HW]
914 See header of drivers/parisc/eisa.c.
917 See comment before function elanfreq_setup() in
918 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
921 Format: {"cfq" | "deadline" | "noop"}
922 See Documentation/block/cfq-iosched.txt and
923 Documentation/block/deadline-iosched.txt for details.
925 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
926 Specifies physical address of start of kernel core
927 image elf header and optionally the size. Generally
928 kexec loader will pass this option to capture kernel.
929 See Documentation/kdump/kdump.txt for details.
931 enable_mtrr_cleanup [X86]
932 The kernel tries to adjust MTRR layout from continuous
933 to discrete, to make X server driver able to add WB
934 entry later. This parameter enables that.
936 enable_timer_pin_1 [X86]
937 Enable PIN 1 of APIC timer
938 Can be useful to work around chipset bugs
939 (in particular on some ATI chipsets).
940 The kernel tries to set a reasonable default.
942 enforcing [SELINUX] Set initial enforcing status.
944 See security/selinux/Kconfig help text.
945 0 -- permissive (log only, no denials).
946 1 -- enforcing (deny and log).
948 Value can be changed at runtime via /selinux/enforce.
951 Disable Error Record Serialization Table (ERST)
954 ether= [HW,NET] Ethernet cards parameters
955 This option is obsoleted by the "netdev=" option, which
956 has equivalent usage. See its documentation for details.
960 Permit 'security.evm' to be updated regardless of
961 current integrity status.
965 fail_make_request=[KNL]
966 General fault injection mechanism.
967 Format: <interval>,<probability>,<space>,<times>
968 See also Documentation/fault-injection/.
971 See Documentation/blockdev/floppy.txt.
973 force_pal_cache_flush
974 [IA-64] Avoid check_sal_cache_flush which may hang on
975 buggy SAL_CACHE_FLUSH implementations. Using this
976 parameter will force ia64_sal_cache_flush to call
977 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
980 [FTRACE] will set and start the specified tracer
981 as early as possible in order to facilitate early
984 ftrace_dump_on_oops[=orig_cpu]
985 [FTRACE] will dump the trace buffers on oops.
986 If no parameter is passed, ftrace will dump
987 buffers of all CPUs, but if you pass orig_cpu, it will
988 dump only the buffer of the CPU that triggered the
991 ftrace_filter=[function-list]
992 [FTRACE] Limit the functions traced by the function
993 tracer at boot up. function-list is a comma separated
994 list of functions. This list can be changed at run
995 time by the set_ftrace_filter file in the debugfs
998 ftrace_notrace=[function-list]
999 [FTRACE] Do not trace the functions specified in
1000 function-list. This list can be changed at run time
1001 by the set_ftrace_notrace file in the debugfs
1004 ftrace_graph_filter=[function-list]
1005 [FTRACE] Limit the top level callers functions traced
1006 by the function graph tracer at boot up.
1007 function-list is a comma separated list of functions
1008 that can be changed at run time by the
1009 set_graph_function file in the debugfs tracing directory.
1012 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1013 support via parallel port (up to 5 devices per port)
1014 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1015 See also Documentation/input/joystick-parport.txt
1019 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1023 gcov_persist= [GCOV] When non-zero (default), profiling data for
1024 kernel modules is saved and remains accessible via
1025 debugfs, even when the module is unloaded/reloaded.
1026 When zero, profiling data is discarded and associated
1027 debugfs files are removed at module unload time.
1029 gpt [EFI] Forces disk with valid GPT signature but
1030 invalid Protective MBR to be treated as GPT.
1032 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1033 the "Enable 0" bit of the configuration register.
1036 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1037 the "Enable 0" bit of the configuration register.
1040 grcan.select= [HW] Select which physical interface to use.
1043 grcan.txsize= [HW] Sets the size of the tx buffer.
1044 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1046 grcan.rxsize= [HW] Sets the size of the rx buffer.
1047 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1050 hashdist= [KNL,NUMA] Large hashes allocated during boot
1051 are distributed across NUMA nodes. Defaults on
1052 for 64-bit NUMA, off otherwise.
1053 Format: 0 | 1 (for off | on)
1055 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1057 hd= [EIDE] (E)IDE hard drive subsystem geometry
1058 Format: <cyl>,<head>,<sect>
1061 Disable Hardware Error Source Table (HEST) support;
1062 corresponding firmware-first mode error processing
1063 logic will be disabled.
1065 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1066 size of <nn>. This works even on boxes that have no
1067 highmem otherwise. This also works to reduce highmem
1068 size on bigger boxes.
1070 highres= [KNL] Enable/disable high resolution timer mode.
1071 Valid parameters: "on", "off"
1075 See Documentation/isdn/README.HiSax.
1079 hpet= [X86-32,HPET] option to control HPET usage
1080 Format: { enable (default) | disable | force |
1082 disable: disable HPET and use PIT instead
1083 force: allow force enabled of undocumented chips (ICH4,
1085 verbose: show contents of HPET registers during setup
1087 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1088 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1089 On x86-64 and powerpc, this option can be specified
1090 multiple times interleaved with hugepages= to reserve
1091 huge pages of different sizes. Valid pages sizes on
1092 x86-64 are 2M (when the CPU supports "pse") and 1G
1093 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1094 Note that 1GB pages can only be allocated at boot time
1095 using hugepages= and not freed afterwards.
1097 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1098 terminal devices. Valid values: 0..8
1099 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1100 If specified, z/VM IUCV HVC accepts connections
1101 from listed z/VM user IDs only.
1103 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1104 hardware thread id mappings.
1105 Format: <cpu>:<hwthread>
1108 Do not unregister boot console at start. This is only
1109 useful for debugging when something happens in the window
1110 between unregistering the boot console and initializing
1113 i2c_bus= [HW] Override the default board specific I2C bus speed
1114 or register an additional I2C bus that is not
1115 registered from board initialization code.
1119 i8042.debug [HW] Toggle i8042 debug mode
1120 i8042.direct [HW] Put keyboard port into non-translated mode
1121 i8042.dumbkbd [HW] Pretend that controller can only read data from
1122 keyboard and cannot control its state
1123 (Don't attempt to blink the leds)
1124 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1125 i8042.nokbd [HW] Don't check/create keyboard port
1126 i8042.noloop [HW] Disable the AUX Loopback command while probing
1128 i8042.nomux [HW] Don't check presence of an active multiplexing
1130 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1132 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1133 i8042.reset [HW] Reset the controller during init and cleanup
1134 i8042.unlock [HW] Unlock (ignore) the keylock
1138 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1139 indicates that the driver is running on unsupported
1141 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1142 does not match list of supported models.
1144 [HW] Report power status in /proc/i8k
1145 (disabled by default)
1146 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1149 i915.invert_brightness=
1150 [DRM] Invert the sense of the variable that is used to
1151 set the brightness of the panel backlight. Normally a
1152 brightness value of 0 indicates backlight switched off,
1153 and the maximum of the brightness value sets the backlight
1154 to maximum brightness. If this parameter is set to 0
1155 (default) and the machine requires it, or this parameter
1156 is set to 1, a brightness value of 0 sets the backlight
1157 to maximum brightness, and the maximum of the brightness
1158 value switches the backlight off.
1159 -1 -- never invert brightness
1160 0 -- machine default
1161 1 -- force brightness inversion
1164 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1166 ide-core.nodma= [HW] (E)IDE subsystem
1167 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1168 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1169 .cdrom .chs .ignore_cable are additional options
1170 See Documentation/ide/ide.txt.
1172 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1173 Claim all unknown PCI IDE storage controllers.
1176 Format: idle=poll, idle=halt, idle=nomwait
1177 Poll forces a polling idle loop that can slightly
1178 improve the performance of waking up a idle CPU, but
1179 will use a lot of power and make the system run hot.
1181 idle=halt: Halt is forced to be used for CPU idle.
1182 In such case C2/C3 won't be used again.
1183 idle=nomwait: Disable mwait for CPU C-states
1185 ignore_loglevel [KNL]
1186 Ignore loglevel setting - this will print /all/
1187 kernel messages to the console. Useful for debugging.
1188 We also add it as printk module parameter, so users
1189 could change it dynamically, usually by
1190 /sys/module/printk/parameters/ignore_loglevel.
1192 ihash_entries= [KNL]
1193 Set number of hash buckets for inode cache.
1195 ima_appraise= [IMA] appraise integrity measurements
1196 Format: { "off" | "enforce" | "fix" }
1199 ima_appraise_tcb [IMA]
1200 The builtin appraise policy appraises all files
1204 Format: { "sha1" | "md5" }
1208 Load a policy which meets the needs of the Trusted
1209 Computing Base. This means IMA will measure all
1210 programs exec'd, files mmap'd for exec, and all files
1211 opened for read by uid=0.
1215 Run specified binary instead of /sbin/init as init
1218 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1219 for working out where the kernel is dying during
1222 initrd= [BOOT] Specify the location of the initial ramdisk
1224 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1227 int_pln_enable [x86] Enable power limit notification interrupt
1229 integrity_audit=[IMA]
1230 Format: { "0" | "1" }
1231 0 -- basic integrity auditing messages. (Default)
1232 1 -- additional integrity auditing messages.
1234 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1236 Enable intel iommu driver.
1238 Disable intel iommu driver.
1239 igfx_off [Default Off]
1240 By default, gfx is mapped as normal device. If a gfx
1241 device has a dedicated DMAR unit, the DMAR unit is
1242 bypassed by not enabling DMAR with this option. In
1243 this case, gfx device will use physical address for
1246 With this option iommu will not optimize to look
1247 for io virtual address below 32-bit forcing dual
1248 address cycle on pci bus for cards supporting greater
1249 than 32-bit addressing. The default is to look
1250 for translation below 32-bit and if not available
1251 then look in the higher range.
1252 strict [Default Off]
1253 With this option on every unmap_single operation will
1254 result in a hardware IOTLB flush operation as opposed
1255 to batching them for performance.
1256 sp_off [Default Off]
1257 By default, super page will be supported if Intel IOMMU
1258 has the capability. With this option, super page will
1261 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1262 0 disables intel_idle and fall back on acpi_idle.
1263 1 to 6 specify maximum depth of C-state.
1267 Do not enable intel_pstate as the default
1268 scaling driver for the supported processors
1270 intremap= [X86-64, Intel-IOMMU]
1271 on enable Interrupt Remapping (default)
1272 off disable Interrupt Remapping
1273 nosid disable Source ID checking
1275 BIOS x2APIC opt-out request will be ignored
1277 iomem= Disable strict checking of access to MMIO memory
1278 strict regions from userspace.
1295 io7= [HW] IO7 for Marvel based alpha systems
1296 See comment before marvel_specify_io7 in
1297 arch/alpha/kernel/core_marvel.c.
1299 io_delay= [X86] I/O delay method
1301 Standard port 0x80 based delay
1303 Alternate port 0xed based delay (needed on some systems)
1305 Simple two microseconds delay
1310 See Documentation/filesystems/nfs/nfsroot.txt.
1312 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1313 See comment before ip2_setup() in
1314 drivers/char/ip2/ip2base.c.
1317 When an interrupt is not handled search all handlers
1318 for it. Intended to get systems with badly broken
1322 When an interrupt is not handled search all handlers
1323 for it. Also check all handlers each timer
1324 interrupt. Intended to get systems with badly broken
1328 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1330 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1332 <cpu number>,...,<cpu number>
1334 <cpu number>-<cpu number>
1335 (must be a positive range in ascending order)
1337 <cpu number>,...,<cpu number>-<cpu number>
1339 This option can be used to specify one or more CPUs
1340 to isolate from the general SMP balancing and scheduling
1341 algorithms. You can move a process onto or off an
1342 "isolated" CPU via the CPU affinity syscalls or cpuset.
1343 <cpu number> begins at 0 and the maximum value is
1344 "number of CPUs in system - 1".
1346 This option is the preferred way to isolate CPUs. The
1347 alternative -- manually setting the CPU mask of all
1348 tasks in the system -- can cause problems and
1349 suboptimal load balancer performance.
1353 ivrs_ioapic [HW,X86_64]
1354 Provide an override to the IOAPIC-ID<->DEVICE-ID
1355 mapping provided in the IVRS ACPI table. For
1356 example, to map IOAPIC-ID decimal 10 to
1357 PCI device 00:14.0 write the parameter as:
1358 ivrs_ioapic[10]=00:14.0
1360 ivrs_hpet [HW,X86_64]
1361 Provide an override to the HPET-ID<->DEVICE-ID
1362 mapping provided in the IVRS ACPI table. For
1363 example, to map HPET-ID decimal 0 to
1364 PCI device 00:14.0 write the parameter as:
1365 ivrs_hpet[0]=00:14.0
1367 js= [HW,JOY] Analog joystick
1368 See Documentation/input/joystick.txt.
1372 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1373 specifies the amount of memory usable by the kernel
1374 for non-movable allocations. The requested amount is
1375 spread evenly throughout all nodes in the system. The
1376 remaining memory in each node is used for Movable
1377 pages. In the event, a node is too small to have both
1378 kernelcore and Movable pages, kernelcore pages will
1379 take priority and other nodes will have a larger number
1380 of Movable pages. The Movable zone is used for the
1381 allocation of pages that may be reclaimed or moved
1382 by the page migration subsystem. This means that
1383 HugeTLB pages may not be allocated from this zone.
1384 Note that allocations like PTEs-from-HighMem still
1385 use the HighMem zone if it exists, and the Normal
1386 zone if it does not.
1388 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1389 Format: <Controller#>[,poll interval]
1390 The controller # is the number of the ehci usb debug
1391 port as it is probed via PCI. The poll interval is
1392 optional and is the number seconds in between
1393 each poll cycle to the debug port in case you need
1394 the functionality for interrupting the kernel with
1395 gdb or control-c on the dbgp connection. When
1396 not using this parameter you use sysrq-g to break into
1397 the kernel debugger.
1399 kgdboc= [KGDB,HW] kgdb over consoles.
1400 Requires a tty driver that supports console polling,
1401 or a supported polling keyboard driver (non-usb).
1402 Serial only format: <serial_device>[,baud]
1403 keyboard only format: kbd
1404 keyboard and serial format: kbd,<serial_device>[,baud]
1405 Optional Kernel mode setting:
1406 kms, kbd format: kms,kbd
1407 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1409 kgdbwait [KGDB] Stop kernel execution and enter the
1410 kernel debugger at the earliest opportunity.
1412 kmac= [MIPS] korina ethernet MAC address.
1413 Configure the RouterBoard 532 series on-chip
1414 Ethernet adapter MAC address.
1416 kmemleak= [KNL] Boot-time kmemleak enable/disable
1417 Valid arguments: on, off
1420 kstack=N [X86] Print N words from the kernel stack
1423 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1424 Default is 0 (don't ignore, but inject #GP)
1426 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1430 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1431 Default is 1 (enabled)
1433 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1435 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1437 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1438 (virtualized MMU) support on capable Intel chips.
1439 Default is 1 (enabled)
1441 kvm-intel.emulate_invalid_guest_state=
1442 [KVM,Intel] Enable emulation of invalid guest states
1443 Default is 0 (disabled)
1445 kvm-intel.flexpriority=
1446 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1447 Default is 1 (enabled)
1450 [KVM,Intel] Enable VMX nesting (nVMX).
1451 Default is 0 (disabled)
1453 kvm-intel.unrestricted_guest=
1454 [KVM,Intel] Disable unrestricted guest feature
1455 (virtualized real and unpaged mode) on capable
1456 Intel chips. Default is 1 (enabled)
1458 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1459 feature (tagged TLBs) on capable Intel chips.
1460 Default is 1 (enabled)
1466 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1469 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1470 value for LAPIC timer one-shot implementation. Default
1471 back to the programmable timer unit in the LAPIC.
1473 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1476 libata.dma= [LIBATA] DMA control
1477 libata.dma=0 Disable all PATA and SATA DMA
1478 libata.dma=1 PATA and SATA Disk DMA only
1479 libata.dma=2 ATAPI (CDROM) DMA only
1480 libata.dma=4 Compact Flash DMA only
1481 Combinations also work, so libata.dma=3 enables DMA
1482 for disks and CDROMs, but not CFs.
1484 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1485 libata.ignore_hpa=0 keep BIOS limits (default)
1486 libata.ignore_hpa=1 ignore limits, using full disk
1488 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1492 libata.force= [LIBATA] Force configurations. The format is comma
1493 separated list of "[ID:]VAL" where ID is
1494 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1495 matching port, link or device. Basically, it matches
1496 the ATA ID string printed on console by libata. If
1497 the whole ID part is omitted, the last PORT and DEVICE
1498 values are used. If ID hasn't been specified yet, the
1499 configuration applies to all ports, links and devices.
1501 If only DEVICE is omitted, the parameter applies to
1502 the port and all links and devices behind it. DEVICE
1503 number of 0 either selects the first device or the
1504 first fan-out link behind PMP device. It does not
1505 select the host link. DEVICE number of 15 selects the
1506 host link and device attached to it.
1508 The VAL specifies the configuration to force. As long
1509 as there's no ambiguity shortcut notation is allowed.
1510 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1511 The following configurations can be forced.
1513 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1514 Any ID with matching PORT is used.
1516 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1518 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1519 udma[/][16,25,33,44,66,100,133] notation is also
1522 * [no]ncq: Turn on or off NCQ.
1524 * nohrst, nosrst, norst: suppress hard, soft
1527 * rstonce: only attempt one reset during
1528 hot-unplug link recovery
1530 * dump_id: dump IDENTIFY data.
1532 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1534 If there are multiple matching configurations changing
1535 the same attribute, the last one is used.
1537 memblock=debug [KNL] Enable memblock debug messages.
1539 load_ramdisk= [RAM] List of ramdisks to load from floppy
1540 See Documentation/blockdev/ramdisk.txt.
1542 lockd.nlm_grace_period=P [NFS] Assign grace period.
1545 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1548 lockd.nlm_timeout=T [NFS] Assign timeout value.
1551 lockd.nlm_udpport=M [NFS] Assign UDP port.
1554 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1557 loglevel= All Kernel Messages with a loglevel smaller than the
1558 console loglevel will be printed to the console. It can
1559 also be changed with klogd or other programs. The
1560 loglevels are defined as follows:
1562 0 (KERN_EMERG) system is unusable
1563 1 (KERN_ALERT) action must be taken immediately
1564 2 (KERN_CRIT) critical conditions
1565 3 (KERN_ERR) error conditions
1566 4 (KERN_WARNING) warning conditions
1567 5 (KERN_NOTICE) normal but significant condition
1568 6 (KERN_INFO) informational
1569 7 (KERN_DEBUG) debug-level messages
1571 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1572 in bytes. n must be a power of two. The default
1573 size is set in the kernel config file.
1575 logo.nologo [FB] Disables display of the built-in Linux logo.
1576 This may be used to provide more screen space for
1577 kernel log messages and is useful when debugging
1578 kernel boot problems.
1580 lp=0 [LP] Specify parallel ports to use, e.g,
1581 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1582 lp=reset first parallel port). 'lp=0' disables the
1583 lp=auto printer driver. 'lp=reset' (which can be
1584 specified in addition to the ports) causes
1585 attached printers to be reset. Using
1586 lp=port1,port2,... specifies the parallel ports
1587 to associate lp devices with, starting with
1588 lp0. A port specification may be 'none' to skip
1589 that lp device, or a parport name such as
1590 'parport0'. Specifying 'lp=auto' instead of a
1591 port specification list means that device IDs
1592 from each port should be examined, to see if
1593 an IEEE 1284-compliant printer is attached; if
1594 so, the driver will manage that printer.
1595 See also header of drivers/char/lp.c.
1598 Sets loops_per_jiffy to given constant, thus avoiding
1599 time-consuming boot-time autodetection (up to 250 ms per
1600 CPU). 0 enables autodetection (default). To determine
1601 the correct value for your kernel, boot with normal
1602 autodetection and see what value is printed. Note that
1603 on SMP systems the preset will be applied to all CPUs,
1604 which is likely to cause problems if your CPUs need
1605 significantly divergent settings. An incorrect value
1606 will cause delays in the kernel to be wrong, leading to
1607 unpredictable I/O errors and other breakage. Although
1608 unlikely, in the extreme case this might damage your
1612 Format: <io>,<irq>,<dma>
1614 machvec= [IA-64] Force the use of a particular machine-vector
1615 (machvec) in a generic kernel.
1616 Example: machvec=hpzx1_swiotlb
1618 machtype= [Loongson] Share the same kernel image file between different
1620 Example: machtype=lemote-yeeloong-2f-7inch
1622 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1623 than or equal to this physical address is ignored.
1625 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1626 should make use of. maxcpus=n : n >= 0 limits the
1627 kernel to using 'n' processors. n=0 is a special case,
1628 it is equivalent to "nosmp", which also disables
1631 max_loop= [LOOP] The number of loop block devices that get
1632 (loop.max_loop) unconditionally pre-created at init time. The default
1633 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1634 of statically allocating a predefined number, loop
1635 devices can be requested on-demand with the
1636 /dev/loop-control interface.
1638 mce [X86-32] Machine Check Exception
1640 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1642 md= [HW] RAID subsystems devices and level
1643 See Documentation/md.txt.
1646 Format: <first>,<last>
1647 Specifies range of consoles to be captured by the MDA.
1649 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1650 Amount of memory to be used when the kernel is not able
1651 to see the whole system memory or for test.
1652 [X86] Work as limiting max address. Use together
1653 with memmap= to avoid physical address space collisions.
1654 Without memmap= PCI devices could be placed at addresses
1655 belonging to unused RAM.
1657 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1661 [KNL,SH] Allow user to override the default size for
1662 per-device physically contiguous DMA buffers.
1664 memmap=exactmap [KNL,X86] Enable setting of an exact
1665 E820 memory map, as specified by the user.
1666 Such memmap=exactmap lines can be constructed based on
1667 BIOS output or other requirements. See the memmap=nn@ss
1670 memmap=nn[KMG]@ss[KMG]
1671 [KNL] Force usage of a specific region of memory
1672 Region of memory to be used, from ss to ss+nn.
1674 memmap=nn[KMG]#ss[KMG]
1675 [KNL,ACPI] Mark specific memory as ACPI data.
1676 Region of memory to be used, from ss to ss+nn.
1678 memmap=nn[KMG]$ss[KMG]
1679 [KNL,ACPI] Mark specific memory as reserved.
1680 Region of memory to be used, from ss to ss+nn.
1681 Example: Exclude memory from 0x18690000-0x1869ffff
1682 memmap=64K$0x18690000
1684 memmap=0x10000$0x18690000
1686 memory_corruption_check=0/1 [X86]
1687 Some BIOSes seem to corrupt the first 64k of
1688 memory when doing things like suspend/resume.
1689 Setting this option will scan the memory
1690 looking for corruption. Enabling this will
1691 both detect corruption and prevent the kernel
1692 from using the memory being corrupted.
1693 However, its intended as a diagnostic tool; if
1694 repeatable BIOS-originated corruption always
1695 affects the same memory, you can use memmap=
1696 to prevent the kernel from using that memory.
1698 memory_corruption_check_size=size [X86]
1699 By default it checks for corruption in the low
1700 64k, making this memory unavailable for normal
1701 use. Use this parameter to scan for
1702 corruption in more or less memory.
1704 memory_corruption_check_period=seconds [X86]
1705 By default it checks for corruption every 60
1706 seconds. Use this parameter to check at some
1707 other rate. 0 disables periodic checking.
1709 memtest= [KNL,X86] Enable memtest
1711 default : 0 <disable>
1712 Specifies the number of memtest passes to be
1713 performed. Each pass selects another test
1714 pattern from a given set of patterns. Memtest
1715 fills the memory with this pattern, validates
1716 memory contents and reserves bad memory
1717 regions that are detected.
1719 meye.*= [HW] Set MotionEye Camera parameters
1720 See Documentation/video4linux/meye.txt.
1722 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1723 Multi-Function General Purpose Timers on AMD Geode
1726 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1727 the BIOS has incorrectly applied a workaround. TinyBIOS
1728 version 0.98 is known to be affected, 0.99 fixes the
1729 problem by letting the user disable the workaround.
1733 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1734 physical address is ignored.
1736 mini2440= [ARM,HW,KNL]
1737 Format:[0..2][b][c][t]
1739 MINI2440 configuration specification:
1740 0 - The attached screen is the 3.5" TFT
1741 1 - The attached screen is the 7" TFT
1742 2 - The VGA Shield is attached (1024x768)
1743 Leaving out the screen size parameter will not load
1744 the TFT driver, and the framebuffer will be left
1746 b - Enable backlight. The TFT backlight pin will be
1747 linked to the kernel VESA blanking code and a GPIO
1748 LED. This parameter is not necessary when using the
1750 c - Enable the s3c camera interface.
1751 t - Reserved for enabling touchscreen support. The
1752 touchscreen support is not enabled in the mainstream
1753 kernel as of 2.6.30, a preliminary port can be found
1754 in the "bleeding edge" mini2440 support kernel at
1755 http://repo.or.cz/w/linux-2.6/mini2440.git
1758 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1759 parameter allows control of the logging verbosity for
1760 the additional memory initialisation checks. A value
1761 of 0 disables mminit logging and a level of 4 will
1762 log everything. Information is printed at KERN_DEBUG
1763 so loglevel=8 may also need to be specified.
1766 [KNL] When CONFIG_MODULE_SIG is set, this means that
1767 modules without (valid) signatures will fail to load.
1768 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1769 is always true, so this option does nothing.
1772 [MOUSE] Maximum time between finger touching and
1773 leaving touchpad surface for touch to be considered
1774 a tap and be reported as a left button click (for
1775 touchpads working in absolute mode only).
1777 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1778 reporting absolute coordinates, such as tablets
1779 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1780 reporting absolute coordinates, such as tablets
1782 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1783 is similar to kernelcore except it specifies the
1784 amount of memory used for migratable allocations.
1785 If both kernelcore and movablecore is specified,
1786 then kernelcore will be at *least* the specified
1787 value but may be more. If movablecore on its own
1788 is specified, the administrator must be careful
1789 that the amount of memory usable for all allocations
1792 MTD_Partition= [MTD]
1793 Format: <name>,<region-number>,<size>,<offset>
1795 MTD_Region= [MTD] Format:
1796 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1799 See drivers/mtd/cmdlinepart.c.
1801 multitce=off [PPC] This parameter disables the use of the pSeries
1802 firmware feature for updating multiple TCE entries
1805 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1807 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1809 boundary - index of last SLC block on Flex-OneNAND.
1810 The remaining blocks are configured as MLC blocks.
1811 lock - Configure if Flex-OneNAND boundary should be locked.
1812 Once locked, the boundary cannot be changed.
1813 1 indicates lock status, 0 indicates unlock status.
1816 ARM/S3C2412 JIVE boot control
1818 See arch/arm/mach-s3c2412/mach-jive.c
1820 mtouchusb.raw_coordinates=
1821 [HW] Make the MicroTouch USB driver use raw coordinates
1822 ('y', default) or cooked coordinates ('n')
1824 mtrr_chunk_size=nn[KMG] [X86]
1825 used for mtrr cleanup. It is largest continuous chunk
1826 that could hold holes aka. UC entries.
1828 mtrr_gran_size=nn[KMG] [X86]
1829 Used for mtrr cleanup. It is granularity of mtrr block.
1831 Large value could prevent small alignment from
1834 mtrr_spare_reg_nr=n [X86]
1836 Range: 0,7 : spare reg number
1838 Used for mtrr cleanup. It is spare mtrr entries number.
1839 Set to 2 or more if your graphical card needs more.
1841 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1843 netdev= [NET] Network devices parameters
1844 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1845 Note that mem_start is often overloaded to mean
1846 something different and driver-specific.
1847 This usage is only documented in each driver source
1851 [NETFILTER] Enable connection tracking flow accounting
1852 0 to disable accounting
1853 1 to enable accounting
1856 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1857 See Documentation/filesystems/nfs/nfsroot.txt.
1859 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1860 See Documentation/filesystems/nfs/nfsroot.txt.
1862 nfsrootdebug [NFS] enable nfsroot debugging messages.
1863 See Documentation/filesystems/nfs/nfsroot.txt.
1865 nfs.callback_tcpport=
1866 [NFS] set the TCP port on which the NFSv4 callback
1867 channel should listen.
1870 [NFS] sets the pathname to the program which is used
1871 to update the NFS client cache entries.
1873 nfs.cache_getent_timeout=
1874 [NFS] sets the timeout after which an attempt to
1875 update a cache entry is deemed to have failed.
1877 nfs.idmap_cache_timeout=
1878 [NFS] set the maximum lifetime for idmapper cache
1882 [NFS] enable 64-bit inode numbers.
1883 If zero, the NFS client will fake up a 32-bit inode
1884 number for the readdir() and stat() syscalls instead
1885 of returning the full 64-bit number.
1886 The default is to return 64-bit inode numbers.
1888 nfs.max_session_slots=
1889 [NFSv4.1] Sets the maximum number of session slots
1890 the client will attempt to negotiate with the server.
1891 This limits the number of simultaneous RPC requests
1892 that the client can send to the NFSv4.1 server.
1893 Note that there is little point in setting this
1894 value higher than the max_tcp_slot_table_limit.
1896 nfs.nfs4_disable_idmapping=
1897 [NFSv4] When set to the default of '1', this option
1898 ensures that both the RPC level authentication
1899 scheme and the NFS level operations agree to use
1900 numeric uids/gids if the mount is using the
1901 'sec=sys' security flavour. In effect it is
1902 disabling idmapping, which can make migration from
1903 legacy NFSv2/v3 systems to NFSv4 easier.
1904 Servers that do not support this mode of operation
1905 will be autodetected by the client, and it will fall
1906 back to using the idmapper.
1907 To turn off this behaviour, set the value to '0'.
1909 [NFS4] Specify an additional fixed unique ident-
1910 ification string that NFSv4 clients can insert into
1911 their nfs_client_id4 string. This is typically a
1912 UUID that is generated at system install time.
1914 nfs.send_implementation_id =
1915 [NFSv4.1] Send client implementation identification
1916 information in exchange_id requests.
1917 If zero, no implementation identification information
1919 The default is to send the implementation identification
1922 nfs.recover_lost_locks =
1923 [NFSv4] Attempt to recover locks that were lost due
1924 to a lease timeout on the server. Please note that
1925 doing this risks data corruption, since there are
1926 no guarantees that the file will remain unchanged
1927 after the locks are lost.
1928 If you want to enable the kernel legacy behaviour of
1929 attempting to recover these locks, then set this
1931 The default parameter value of '0' causes the kernel
1932 not to attempt recovery of lost locks.
1934 nfsd.nfs4_disable_idmapping=
1935 [NFSv4] When set to the default of '1', the NFSv4
1936 server will return only numeric uids and gids to
1937 clients using auth_sys, and will accept numeric uids
1938 and gids from such clients. This is intended to ease
1939 migration from NFSv2/v3.
1941 objlayoutdriver.osd_login_prog=
1942 [NFS] [OBJLAYOUT] sets the pathname to the program which
1943 is used to automatically discover and login into new
1944 osd-targets. Please see:
1945 Documentation/filesystems/pnfs.txt for more explanations
1947 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1948 when a NMI is triggered.
1949 Format: [state][,regs][,debounce][,die]
1951 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1952 Format: [panic,][nopanic,][num]
1954 0 - turn nmi_watchdog off
1955 When panic is specified, panic when an NMI watchdog
1956 timeout occurs (or 'nopanic' to override the opposite
1958 This is useful when you use a panic=... timeout and
1959 need the box quickly up again.
1961 netpoll.carrier_timeout=
1962 [NET] Specifies amount of time (in seconds) that
1963 netpoll should wait for a carrier. By default netpoll
1966 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1967 emulation library even if a 387 maths coprocessor
1971 [HW] Never suspend the console
1972 Disable suspending of consoles during suspend and
1973 hibernate operations. Once disabled, debugging
1974 messages can reach various consoles while the rest
1975 of the system is being put to sleep (ie, while
1976 debugging driver suspend/resume hooks). This may
1977 not work reliably with all consoles, but is known
1978 to work with serial and VGA consoles.
1979 To facilitate more flexible debugging, we also add
1980 console_suspend, a printk module parameter to control
1981 it. Users could use console_suspend (usually
1982 /sys/module/printk/parameters/console_suspend) to
1983 turn on/off it dynamically.
1985 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1986 caches in the slab allocator. Saves per-node memory,
1987 but will impact performance.
1991 noapic [SMP,APIC] Tells the kernel to not make use of any
1992 IOAPICs that may be present in the system.
1994 noautogroup Disable scheduler automatic task group creation.
1996 nobats [PPC] Do not use BATs for mapping kernel lowmem
1997 on "Classic" PPC cores.
2001 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2003 nodelayacct [KNL] Disable per-task delay accounting
2005 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2007 nodsp [SH] Disable hardware DSP at boot time.
2009 noefi [X86] Disable EFI runtime services support.
2014 On X86-32 available only on PAE configured kernels.
2015 noexec=on: enable non-executable mappings (default)
2016 noexec=off: disable non-executable mappings
2019 Disable SMAP (Supervisor Mode Access Prevention)
2020 even if it is supported by processor.
2023 Disable SMEP (Supervisor Mode Execution Prevention)
2024 even if it is supported by processor.
2027 This affects only 32-bit executables.
2028 noexec32=on: enable non-executable mappings (default)
2029 read doesn't imply executable mappings
2030 noexec32=off: disable non-executable mappings
2031 read implies executable mappings
2033 nofpu [SH] Disable hardware FPU at boot time.
2035 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2036 register save and restore. The kernel will only save
2037 legacy floating-point registers on task switch.
2039 noxsave [BUGS=X86] Disables x86 extended register state save
2040 and restore using xsave. The kernel will fallback to
2041 enabling legacy floating-point and sse state.
2044 on enable eager fpu restore
2045 off disable eager fpu restore
2046 auto selects the default scheme, which automatically
2047 enables eagerfpu restore for xsaveopt.
2049 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2050 wfi(ARM) instruction doesn't work correctly and not to
2051 use it. This is also useful when using JTAG debugger.
2053 no_file_caps Tells the kernel not to honor file capabilities. The
2054 only way then for a file to be executed with privilege
2055 is to be setuid root or executed by root.
2057 nohalt [IA-64] Tells the kernel not to use the power saving
2058 function PAL_HALT_LIGHT when idle. This increases
2059 power-consumption. On the positive side, it reduces
2060 interrupt wake-up latency, which may improve performance
2061 in certain environments such as networked servers or
2064 nohz= [KNL] Boottime enable/disable dynamic ticks
2065 Valid arguments: on, off
2068 nohz_full= [KNL,BOOT]
2069 In kernels built with CONFIG_NO_HZ_FULL=y, set
2070 the specified list of CPUs whose tick will be stopped
2071 whenever possible. The boot CPU will be forced outside
2072 the range to maintain the timekeeping.
2073 The CPUs in this range must also be included in the
2076 noiotrap [SH] Disables trapped I/O port accesses.
2078 noirqdebug [X86-32] Disables the code which attempts to detect and
2079 disable unhandled interrupt sources.
2081 no_timer_check [X86,APIC] Disables the code which tests for
2082 broken timer IRQ sources.
2084 noisapnp [ISAPNP] Disables ISA PnP code.
2086 noinitrd [RAM] Tells the kernel not to load any configured
2089 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2091 [Deprecated - use intremap=off]
2095 nojitter [IA-64] Disables jitter checking for ITC timers.
2097 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2099 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2102 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2103 steal time is computed, but won't influence scheduler
2106 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2108 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2110 noltlbs [PPC] Do not use large page/tlb entries for kernel
2111 lowmem mapping on PPC40x.
2113 nomca [IA-64] Disable machine check abort handling
2115 nomce [X86-32] Machine Check Exception
2117 nomfgpt [X86-32] Disable Multi-Function General Purpose
2118 Timer usage (for AMD Geode machines).
2120 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2121 shutdown the other cpus. Instead use the REBOOT_VECTOR
2124 nomodule Disable module load
2126 nopat [X86] Disable PAT (page attribute table extension of
2127 pagetables) support.
2129 norandmaps Don't use address space randomization. Equivalent to
2130 echo 0 > /proc/sys/kernel/randomize_va_space
2132 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2134 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2135 with UP alternatives
2137 nordrand [X86] Disable the direct use of the RDRAND
2138 instruction even if it is supported by the
2139 processor. RDRAND is still available to user
2142 noresume [SWSUSP] Disables resume and restores original swap
2145 no-scroll [VGA] Disables scrollback.
2146 This is required for the Braillex ib80-piezo Braille
2147 reader made by F.H. Papenmeier (Germany).
2151 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2153 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2154 and disable the IO APIC. legacy for "maxcpus=0".
2156 nosoftlockup [KNL] Disable the soft-lockup detector.
2158 nosync [HW,M68K] Disables sync negotiation for all devices.
2160 notsc [BUGS=X86-32] Disable Time Stamp Counter
2162 nousb [USB] Disable the USB subsystem
2164 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2168 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2170 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2171 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2172 Some features depend on CPU0. Known dependencies are:
2173 1. Resume from suspend/hibernate depends on CPU0.
2174 Suspend/hibernate will fail if CPU0 is offline and you
2175 need to online CPU0 before suspend/hibernate.
2176 2. PIC interrupts also depend on CPU0. CPU0 can't be
2177 removed if a PIC interrupt is detected.
2178 It's said poweroff/reboot may depend on CPU0 on some
2179 machines although I haven't seen such issues so far
2180 after CPU0 is offline on a few tested machines.
2181 If the dependencies are under your control, you can
2182 turn on cpu0_hotplug.
2184 nptcg= [IA-64] Override max number of concurrent global TLB
2185 purges which is reported from either PAL_VM_SUMMARY or
2188 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2189 could support. nr_cpus=n : n >= 1 limits the kernel to
2190 supporting 'n' processors. Later in runtime you can not
2191 use hotplug cpu feature to put more cpu back to online.
2192 just like you compile the kernel NR_CPUS=n
2194 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2196 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2197 Allowed values are enable and disable
2199 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2200 one of ['zone', 'node', 'default'] can be specified
2201 This can be set from sysctl after boot.
2202 See Documentation/sysctl/vm.txt for details.
2204 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2205 See Documentation/debugging-via-ohci1394.txt for more
2208 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2209 Rather than timing out after 20 ms if an EC
2210 command is not properly ACKed, override the length
2211 of the timeout. We have interrupts disabled while
2212 waiting for the ACK, so if this is set too high
2213 interrupts *may* be lost!
2215 omap_mux= [OMAP] Override bootloader pin multiplexing.
2216 Format: <mux_mode0.mode_name=value>...
2217 For example, to override I2C bus2:
2218 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2220 oprofile.timer= [HW]
2221 Use timer interrupt instead of performance counters
2223 oprofile.cpu_type= Force an oprofile cpu type
2224 This might be useful if you have an older oprofile
2225 userland or if you want common events.
2226 Format: { arch_perfmon }
2227 arch_perfmon: [X86] Force use of architectural
2228 perfmon on Intel CPUs instead of the
2229 CPU specific event set.
2230 timer: [X86] Force use of architectural NMI
2231 timer mode (see also oprofile.timer
2232 for generic hr timer mode)
2233 [s390] Force legacy basic mode sampling
2234 (report cpu_type "timer")
2236 oops=panic Always panic on oopses. Default is to just kill the
2237 process, but there is a small probability of
2238 deadlocking the machine.
2239 This will also cause panics on machine check exceptions.
2240 Useful together with panic=30 to trigger a reboot.
2243 See Documentation/sound/oss/oss-parameters.txt
2245 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2246 timeout > 0: seconds before rebooting
2247 timeout = 0: wait forever
2248 timeout < 0: reboot immediately
2251 parkbd.port= [HW] Parallel port number the keyboard adapter is
2252 connected to, default is 0.
2254 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2255 0 for XT, 1 for AT (default is AT).
2258 parport= [HW,PPT] Specify parallel ports. 0 disables.
2259 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2260 Use 'auto' to force the driver to use any
2261 IRQ/DMA settings detected (the default is to
2262 ignore detected IRQ/DMA settings because of
2263 possible conflicts). You can specify the base
2264 address, IRQ, and DMA settings; IRQ and DMA
2265 should be numbers, or 'auto' (for using detected
2266 settings on that particular port), or 'nofifo'
2267 (to avoid using a FIFO even if it is detected).
2268 Parallel ports are assigned in the order they
2269 are specified on the command line, starting
2272 parport_init_mode= [HW,PPT]
2273 Configure VIA parallel port to operate in
2274 a specific mode. This is necessary on Pegasos
2275 computer where firmware has no options for setting
2276 up parallel port mode and sets it to spp.
2277 Currently this function knows 686a and 8231 chips.
2278 Format: [spp|ps2|epp|ecp|ecpepp]
2281 Halt all CPUs after the first oops has been printed for
2282 the specified number of seconds. This is to be used if
2283 your oopses keep scrolling off the screen.
2288 See header of drivers/block/paride/pcd.c.
2289 See also Documentation/blockdev/paride.txt.
2291 pci=option[,option...] [PCI] various PCI subsystem options:
2292 earlydump [X86] dump PCI config space before the kernel
2294 off [X86] don't probe for the PCI bus
2295 bios [X86-32] force use of PCI BIOS, don't access
2296 the hardware directly. Use this if your machine
2297 has a non-standard PCI host bridge.
2298 nobios [X86-32] disallow use of PCI BIOS, only direct
2299 hardware access methods are allowed. Use this
2300 if you experience crashes upon bootup and you
2301 suspect they are caused by the BIOS.
2302 conf1 [X86] Force use of PCI Configuration
2304 conf2 [X86] Force use of PCI Configuration
2306 noaer [PCIE] If the PCIEAER kernel config parameter is
2307 enabled, this kernel boot option can be used to
2308 disable the use of PCIE advanced error reporting.
2309 nodomains [PCI] Disable support for multiple PCI
2310 root domains (aka PCI segments, in ACPI-speak).
2311 nommconf [X86] Disable use of MMCONFIG for PCI
2313 check_enable_amd_mmconf [X86] check for and enable
2314 properly configured MMIO access to PCI
2315 config space on AMD family 10h CPU
2316 nomsi [MSI] If the PCI_MSI kernel config parameter is
2317 enabled, this kernel boot option can be used to
2318 disable the use of MSI interrupts system-wide.
2319 noioapicquirk [APIC] Disable all boot interrupt quirks.
2320 Safety option to keep boot IRQs enabled. This
2321 should never be necessary.
2322 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2323 primary IO-APIC for bridges that cannot disable
2324 boot IRQs. This fixes a source of spurious IRQs
2325 when the system masks IRQs.
2326 noioapicreroute [APIC] Disable workaround that uses the
2327 boot IRQ equivalent of an IRQ that connects to
2328 a chipset where boot IRQs cannot be disabled.
2329 The opposite of ioapicreroute.
2330 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2331 routing table. These calls are known to be buggy
2332 on several machines and they hang the machine
2333 when used, but on other computers it's the only
2334 way to get the interrupt routing table. Try
2335 this option if the kernel is unable to allocate
2336 IRQs or discover secondary PCI buses on your
2338 rom [X86] Assign address space to expansion ROMs.
2339 Use with caution as certain devices share
2340 address decoders between ROMs and other
2342 norom [X86] Do not assign address space to
2343 expansion ROMs that do not already have
2344 BIOS assigned address ranges.
2345 nobar [X86] Do not assign address space to the
2346 BARs that weren't assigned by the BIOS.
2347 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2348 assigned automatically to PCI devices. You can
2349 make the kernel exclude IRQs of your ISA cards
2351 pirqaddr=0xAAAAA [X86] Specify the physical address
2352 of the PIRQ table (normally generated
2353 by the BIOS) if it is outside the
2354 F0000h-100000h range.
2355 lastbus=N [X86] Scan all buses thru bus #N. Can be
2356 useful if the kernel is unable to find your
2357 secondary buses and you want to tell it
2358 explicitly which ones they are.
2359 assign-busses [X86] Always assign all PCI bus
2360 numbers ourselves, overriding
2361 whatever the firmware may have done.
2362 usepirqmask [X86] Honor the possible IRQ mask stored
2363 in the BIOS $PIR table. This is needed on
2364 some systems with broken BIOSes, notably
2365 some HP Pavilion N5400 and Omnibook XE3
2366 notebooks. This will have no effect if ACPI
2367 IRQ routing is enabled.
2368 noacpi [X86] Do not use ACPI for IRQ routing
2369 or for PCI scanning.
2370 use_crs [X86] Use PCI host bridge window information
2371 from ACPI. On BIOSes from 2008 or later, this
2372 is enabled by default. If you need to use this,
2373 please report a bug.
2374 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2375 If you need to use this, please report a bug.
2376 routeirq Do IRQ routing for all PCI devices.
2377 This is normally done in pci_enable_device(),
2378 so this option is a temporary workaround
2379 for broken drivers that don't call it.
2380 skip_isa_align [X86] do not align io start addr, so can
2381 handle more pci cards
2382 firmware [ARM] Do not re-enumerate the bus but instead
2383 just use the configuration from the
2384 bootloader. This is currently used on
2385 IXP2000 systems where the bus has to be
2386 configured a certain way for adjunct CPUs.
2387 noearly [X86] Don't do any early type 1 scanning.
2388 This might help on some broken boards which
2389 machine check when some devices' config space
2390 is read. But various workarounds are disabled
2391 and some IOMMU drivers will not work.
2392 bfsort Sort PCI devices into breadth-first order.
2393 This sorting is done to get a device
2394 order compatible with older (<= 2.4) kernels.
2395 nobfsort Don't sort PCI devices into breadth-first order.
2396 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2397 tuning and use the BIOS-configured MPS defaults.
2398 pcie_bus_safe Set every device's MPS to the largest value
2399 supported by all devices below the root complex.
2400 pcie_bus_perf Set device MPS to the largest allowable MPS
2401 based on its parent bus. Also set MRRS (Max
2402 Read Request Size) to the largest supported
2403 value (no larger than the MPS that the device
2404 or bus can support) for best performance.
2405 pcie_bus_peer2peer Set every device's MPS to 128B, which
2406 every device is guaranteed to support. This
2407 configuration allows peer-to-peer DMA between
2408 any pair of devices, possibly at the cost of
2409 reduced performance. This also guarantees
2410 that hot-added devices will work.
2411 cbiosize=nn[KMG] The fixed amount of bus space which is
2412 reserved for the CardBus bridge's IO window.
2413 The default value is 256 bytes.
2414 cbmemsize=nn[KMG] The fixed amount of bus space which is
2415 reserved for the CardBus bridge's memory
2416 window. The default value is 64 megabytes.
2419 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2420 Specifies alignment and device to reassign
2421 aligned memory resources.
2422 If <order of align> is not specified,
2423 PAGE_SIZE is used as alignment.
2424 PCI-PCI bridge can be specified, if resource
2425 windows need to be expanded.
2426 ecrc= Enable/disable PCIe ECRC (transaction layer
2427 end-to-end CRC checking).
2428 bios: Use BIOS/firmware settings. This is the
2432 hpiosize=nn[KMG] The fixed amount of bus space which is
2433 reserved for hotplug bridge's IO window.
2434 Default size is 256 bytes.
2435 hpmemsize=nn[KMG] The fixed amount of bus space which is
2436 reserved for hotplug bridge's memory window.
2437 Default size is 2 megabytes.
2438 realloc= Enable/disable reallocating PCI bridge resources
2439 if allocations done by BIOS are too small to
2440 accommodate resources required by all child
2442 off: Turn realloc off
2444 realloc same as realloc=on
2445 noari do not use PCIe ARI.
2446 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2447 only look for one device below a PCIe downstream
2450 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2453 force Enable ASPM even on devices that claim not to support it.
2454 WARNING: Forcing ASPM on may cause system lockups.
2456 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2457 nomsi Do not use MSI for PCI Express Native Hotplug (this
2458 makes all PCIe ports use INTx for hotplug services).
2460 pcie_ports= [PCIE] PCIe ports handling:
2461 auto Ask the BIOS whether or not to use native PCIe services
2462 associated with PCIe ports (PME, hot-plug, AER). Use
2463 them only if that is allowed by the BIOS.
2464 native Use native PCIe services associated with PCIe ports
2466 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2469 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2470 nomsi Do not use MSI for native PCIe PME signaling (this makes
2471 all PCIe root ports use INTx for all services).
2473 pcmv= [HW,PCMCIA] BadgePAD 4
2476 See Documentation/blockdev/paride.txt.
2478 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2481 See arch/parisc/kernel/pdc_chassis.c
2483 percpu_alloc= Select which percpu first chunk allocator to use.
2484 Currently supported values are "embed" and "page".
2485 Archs may support subset or none of the selections.
2486 See comments in mm/percpu.c for details on each
2487 allocator. This parameter is primarily for debugging
2488 and performance comparison.
2491 See Documentation/blockdev/paride.txt.
2494 See Documentation/blockdev/paride.txt.
2496 pirq= [SMP,APIC] Manual mp-table setup
2497 See Documentation/x86/i386/IO-APIC.txt.
2499 plip= [PPT,NET] Parallel port network link
2500 Format: { parport<nr> | timid | 0 }
2501 See also Documentation/parport.txt.
2503 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2504 Override pmtimer IOPort with a hex value.
2508 Enable PNP debug messages (depends on the
2509 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2510 via /sys/module/pnp/parameters/debug. We always show
2511 current resource usage; turning this on also shows
2512 possible settings and some assignment information.
2518 { on | off | curr | res | no-curr | no-res }
2521 [ISAPNP] Exclude IRQs for the autoconfiguration
2524 [ISAPNP] Exclude DMAs for the autoconfiguration
2526 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2527 Ranges are in pairs (I/O port base and size).
2530 [ISAPNP] Exclude memory regions for the
2532 Ranges are in pairs (memory base and size).
2534 ports= [IP_VS_FTP] IPVS ftp helper module
2536 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2538 Format: <port>,<port>....
2540 print-fatal-signals=
2541 [KNL] debug: print fatal signals
2543 If enabled, warn about various signal handling
2544 related application anomalies: too many signals,
2545 too many POSIX.1 timers, fatal signals causing a
2548 If you hit the warning due to signal overflow,
2549 you might want to try "ulimit -i unlimited".
2553 printk.always_kmsg_dump=
2554 Trigger kmsg_dump for cases other than kernel oops or
2556 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2559 printk.time= Show timing data prefixed to each printk message line
2560 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2562 processor.max_cstate= [HW,ACPI]
2563 Limit processor to maximum C-state
2564 max_cstate=9 overrides any DMI blacklist limit.
2566 processor.nocst [HW,ACPI]
2567 Ignore the _CST method to determine C-states,
2568 instead using the legacy FADT method
2570 profile= [KNL] Enable kernel profiling via /proc/profile
2571 Format: [schedule,]<number>
2572 Param: "schedule" - profile schedule points.
2573 Param: <number> - step/bucket size as a power of 2 for
2574 statistical time based profiling.
2575 Param: "sleep" - profile D-state sleeping (millisecs).
2576 Requires CONFIG_SCHEDSTATS
2577 Param: "kvm" - profile VM exits.
2579 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2581 See Documentation/blockdev/ramdisk.txt.
2583 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2584 probe for; one of (bare|imps|exps|lifebook|any).
2585 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2587 psmouse.resetafter= [HW,MOUSE]
2588 Try to reset the device after so many bad packets
2591 [HW,MOUSE] Set desired mouse resolution, in dpi.
2592 psmouse.smartscroll=
2593 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2594 0 = disabled, 1 = enabled (default).
2596 pstore.backend= Specify the name of the pstore backend to use
2599 See Documentation/blockdev/paride.txt.
2602 [KNL] Number of legacy pty's. Overwrites compiled-in
2605 quiet [KNL] Disable most log messages
2610 See Documentation/md.txt.
2612 ramdisk_blocksize= [RAM]
2613 See Documentation/blockdev/ramdisk.txt.
2615 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2616 See Documentation/blockdev/ramdisk.txt.
2618 rcu_nocbs= [KNL,BOOT]
2619 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2620 the specified list of CPUs to be no-callback CPUs.
2621 Invocation of these CPUs' RCU callbacks will
2622 be offloaded to "rcuox/N" kthreads created for
2623 that purpose, where "x" is "b" for RCU-bh, "p"
2624 for RCU-preempt, and "s" for RCU-sched, and "N"
2625 is the CPU number. This reduces OS jitter on the
2626 offloaded CPUs, which can be useful for HPC and
2628 real-time workloads. It can also improve energy
2629 efficiency for asymmetric multiprocessors.
2631 rcu_nocb_poll [KNL,BOOT]
2632 Rather than requiring that offloaded CPUs
2633 (specified by rcu_nocbs= above) explicitly
2634 awaken the corresponding "rcuoN" kthreads,
2635 make these kthreads poll for callbacks.
2636 This improves the real-time response for the
2637 offloaded CPUs by relieving them of the need to
2638 wake up the corresponding kthread, but degrades
2639 energy efficiency by requiring that the kthreads
2640 periodically wake up to do the polling.
2642 rcutree.blimit= [KNL,BOOT]
2643 Set maximum number of finished RCU callbacks to process
2646 rcutree.fanout_leaf= [KNL,BOOT]
2647 Increase the number of CPUs assigned to each
2648 leaf rcu_node structure. Useful for very large
2651 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2652 Set delay from grace-period initialization to
2653 first attempt to force quiescent states.
2654 Units are jiffies, minimum value is zero,
2655 and maximum value is HZ.
2657 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2658 Set delay between subsequent attempts to force
2659 quiescent states. Units are jiffies, minimum
2660 value is one, and maximum value is HZ.
2662 rcutree.qhimark= [KNL,BOOT]
2663 Set threshold of queued
2664 RCU callbacks over which batch limiting is disabled.
2666 rcutree.qlowmark= [KNL,BOOT]
2667 Set threshold of queued RCU callbacks below which
2668 batch limiting is re-enabled.
2670 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2671 Suppress RCU CPU stall warning messages.
2673 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2674 Set timeout for RCU CPU stall warning messages.
2676 rcutree.rcu_idle_gp_delay= [KNL,BOOT]
2677 Set wakeup interval for idle CPUs that have
2678 RCU callbacks (RCU_FAST_NO_HZ=y).
2680 rcutree.rcu_idle_lazy_gp_delay= [KNL,BOOT]
2681 Set wakeup interval for idle CPUs that have
2682 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2683 Lazy RCU callbacks are those which RCU can
2684 prove do nothing more than free memory.
2686 rcutorture.fqs_duration= [KNL,BOOT]
2687 Set duration of force_quiescent_state bursts.
2689 rcutorture.fqs_holdoff= [KNL,BOOT]
2690 Set holdoff time within force_quiescent_state bursts.
2692 rcutorture.fqs_stutter= [KNL,BOOT]
2693 Set wait time between force_quiescent_state bursts.
2695 rcutorture.irqreader= [KNL,BOOT]
2696 Test RCU readers from irq handlers.
2698 rcutorture.n_barrier_cbs= [KNL,BOOT]
2699 Set callbacks/threads for rcu_barrier() testing.
2701 rcutorture.nfakewriters= [KNL,BOOT]
2702 Set number of concurrent RCU writers. These just
2703 stress RCU, they don't participate in the actual
2704 test, hence the "fake".
2706 rcutorture.nreaders= [KNL,BOOT]
2707 Set number of RCU readers.
2709 rcutorture.onoff_holdoff= [KNL,BOOT]
2710 Set time (s) after boot for CPU-hotplug testing.
2712 rcutorture.onoff_interval= [KNL,BOOT]
2713 Set time (s) between CPU-hotplug operations, or
2714 zero to disable CPU-hotplug testing.
2716 rcutorture.shuffle_interval= [KNL,BOOT]
2717 Set task-shuffle interval (s). Shuffling tasks
2718 allows some CPUs to go into dyntick-idle mode
2719 during the rcutorture test.
2721 rcutorture.shutdown_secs= [KNL,BOOT]
2722 Set time (s) after boot system shutdown. This
2723 is useful for hands-off automated testing.
2725 rcutorture.stall_cpu= [KNL,BOOT]
2726 Duration of CPU stall (s) to test RCU CPU stall
2727 warnings, zero to disable.
2729 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2730 Time to wait (s) after boot before inducing stall.
2732 rcutorture.stat_interval= [KNL,BOOT]
2733 Time (s) between statistics printk()s.
2735 rcutorture.stutter= [KNL,BOOT]
2736 Time (s) to stutter testing, for example, specifying
2737 five seconds causes the test to run for five seconds,
2738 wait for five seconds, and so on. This tests RCU's
2739 ability to transition abruptly to and from idle.
2741 rcutorture.test_boost= [KNL,BOOT]
2742 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2743 "Maybe" means test if the RCU implementation
2744 under test support RCU priority boosting.
2746 rcutorture.test_boost_duration= [KNL,BOOT]
2747 Duration (s) of each individual boost test.
2749 rcutorture.test_boost_interval= [KNL,BOOT]
2750 Interval (s) between each boost test.
2752 rcutorture.test_no_idle_hz= [KNL,BOOT]
2753 Test RCU's dyntick-idle handling. See also the
2754 rcutorture.shuffle_interval parameter.
2756 rcutorture.torture_type= [KNL,BOOT]
2757 Specify the RCU implementation to test.
2759 rcutorture.verbose= [KNL,BOOT]
2760 Enable additional printk() statements.
2764 Run specified binary instead of /init from the ramdisk,
2765 used for early userspace startup. See initrd.
2768 Format (x86 or x86_64):
2769 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2771 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2773 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2774 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2775 reboot_force is either force or not specified,
2776 reboot_cpu is s[mp]#### with #### being the processor
2777 to be used for rebooting.
2780 [KNL, SMP] Set scheduler's default relax_domain_level.
2781 See Documentation/cgroups/cpusets.txt.
2783 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2785 reservetop= [X86-32]
2787 Reserves a hole at the top of the kernel virtual
2792 Set the amount of memory to reserve for BIOS at
2793 the bottom of the address space.
2795 reset_devices [KNL] Force drivers to reset the underlying device
2796 during initialization.
2799 Specify the partition device for software suspend
2801 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2803 resume_offset= [SWSUSP]
2804 Specify the offset from the beginning of the partition
2805 given by "resume=" at which the swap header is located,
2806 in <PAGE_SIZE> units (needed only for swap files).
2807 See Documentation/power/swsusp-and-swap-files.txt
2809 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2810 read the resume files
2812 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2813 Useful for devices that are detected asynchronously
2814 (e.g. USB and MMC devices).
2816 hibernate= [HIBERNATION]
2817 noresume Don't check if there's a hibernation image
2818 present during boot.
2819 nocompress Don't compress/decompress hibernation images.
2821 retain_initrd [RAM] Keep initrd memory after extraction
2823 rhash_entries= [KNL,NET]
2824 Set number of hash buckets for route cache
2826 riscom8= [HW,SERIAL]
2827 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2829 ro [KNL] Mount root device read-only on boot
2831 root= [KNL] Root filesystem
2832 See name_to_dev_t comment in init/do_mounts.c.
2834 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2835 mount the root filesystem
2837 rootflags= [KNL] Set root filesystem mount option string
2839 rootfstype= [KNL] Set root filesystem type
2841 rootwait [KNL] Wait (indefinitely) for root device to show up.
2842 Useful for devices that are detected asynchronously
2843 (e.g. USB and MMC devices).
2845 rproc_mem=nn[KMG][@address]
2846 [KNL,ARM,CMA] Remoteproc physical memory block.
2847 Memory area to be used by remote processor image,
2850 rw [KNL] Mount root device read-write on boot
2852 S [KNL] Run init in single mode
2855 See drivers/net/irda/sa1100_ir.c.
2857 sbni= [NET] Granch SBNI12 leased line adapter
2859 sched_debug [KNL] Enables verbose scheduler debug messages.
2861 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2862 xtime_lock contention on larger systems, and/or RCU lock
2863 contention on all systems with CONFIG_MAXSMP set.
2864 Format: { "0" | "1" }
2865 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2867 Note: increases power consumption, thus should only be
2868 enabled if running jitter sensitive (HPC/RT) workloads.
2870 security= [SECURITY] Choose a security module to enable at boot.
2871 If this boot parameter is not specified, only the first
2872 security module asking for security registration will be
2873 loaded. An invalid security module name will be treated
2874 as if no module has been chosen.
2876 selinux= [SELINUX] Disable or enable SELinux at boot time.
2877 Format: { "0" | "1" }
2878 See security/selinux/Kconfig help text.
2881 Default value is set via kernel config option.
2882 If enabled at boot time, /selinux/disable can be used
2883 later to disable prior to initial policy load.
2885 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2886 Format: { "0" | "1" }
2887 See security/apparmor/Kconfig help text
2890 Default value is set via kernel config option.
2892 serialnumber [BUGS=X86-32]
2895 Maximal number of shapers.
2897 show_msr= [x86] show boot-time MSR settings
2898 Format: { <integer> }
2899 Show boot-time (BIOS-initialized) MSR settings.
2900 The parameter means the number of CPUs to show,
2901 for example 1 means boot CPU only.
2908 slab_max_order= [MM, SLAB]
2909 Determines the maximum allowed order for slabs.
2910 A high setting may cause OOMs due to memory
2911 fragmentation. Defaults to 1 for systems with
2912 more than 32MB of RAM, 0 otherwise.
2914 slub_debug[=options[,slabs]] [MM, SLUB]
2915 Enabling slub_debug allows one to determine the
2916 culprit if slab objects become corrupted. Enabling
2917 slub_debug can create guard zones around objects and
2918 may poison objects when not in use. Also tracks the
2919 last alloc / free. For more information see
2920 Documentation/vm/slub.txt.
2922 slub_max_order= [MM, SLUB]
2923 Determines the maximum allowed order for slabs.
2924 A high setting may cause OOMs due to memory
2925 fragmentation. For more information see
2926 Documentation/vm/slub.txt.
2928 slub_min_objects= [MM, SLUB]
2929 The minimum number of objects per slab. SLUB will
2930 increase the slab order up to slub_max_order to
2931 generate a sufficiently large slab able to contain
2932 the number of objects indicated. The higher the number
2933 of objects the smaller the overhead of tracking slabs
2934 and the less frequently locks need to be acquired.
2935 For more information see Documentation/vm/slub.txt.
2937 slub_min_order= [MM, SLUB]
2938 Determines the minimum page order for slabs. Must be
2939 lower than slub_max_order.
2940 For more information see Documentation/vm/slub.txt.
2942 slub_nomerge [MM, SLUB]
2943 Disable merging of slabs with similar size. May be
2944 necessary if there is some reason to distinguish
2945 allocs to different slabs. Debug options disable
2946 merging on their own.
2947 For more information see Documentation/vm/slub.txt.
2950 Format: <io1>[,<io2>[,...,<io8>]]
2952 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2953 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2954 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2955 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2956 smsc-ircc2.ircc_irq= [HW] IRQ line
2957 smsc-ircc2.ircc_dma= [HW] DMA channel
2958 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2959 0: Toshiba Satellite 1800 (GP data pin select)
2960 1: Fast pin select (default)
2964 [KNL] Should the soft-lockup detector generate panics.
2967 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2968 See Documentation/laptops/sonypi.txt
2970 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2971 See Documentation/serial/specialix.txt.
2973 spia_io_base= [HW,MTD]
2979 Enabled the stack tracer on boot up.
2981 stacktrace_filter=[function-list]
2982 [FTRACE] Limit the functions that the stack tracer
2983 will trace at boot up. function-list is a comma separated
2984 list of functions. This list can be changed at run
2985 time by the stack_trace_filter file in the debugfs
2986 tracing directory. Note, this enables stack tracing
2987 and the stacktrace above is not needed.
2991 Set the STI (builtin display/keyboard on the HP-PARISC
2992 machines) console (graphic card) which should be used
2993 as the initial boot-console.
2994 See also comment in drivers/video/console/sticore.c.
2997 See comment in drivers/video/console/sticore.c.
3000 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3002 sunrpc.min_resvport=
3003 sunrpc.max_resvport=
3005 SunRPC servers often require that client requests
3006 originate from a privileged port (i.e. a port in the
3007 range 0 < portnr < 1024).
3008 An administrator who wishes to reserve some of these
3009 ports for other uses may adjust the range that the
3010 kernel's sunrpc client considers to be privileged
3011 using these two parameters to set the minimum and
3012 maximum port values.
3016 Control how the NFS server code allocates CPUs to
3017 service thread pools. Depending on how many NICs
3018 you have and where their interrupts are bound, this
3019 option will affect which CPUs will do NFS serving.
3020 Note: this parameter cannot be changed while the
3021 NFS server is running.
3023 auto the server chooses an appropriate mode
3024 automatically using heuristics
3025 global a single global pool contains all CPUs
3026 percpu one pool for each CPU
3027 pernode one pool for each NUMA node (equivalent
3028 to global on non-NUMA machines)
3030 sunrpc.tcp_slot_table_entries=
3031 sunrpc.udp_slot_table_entries=
3033 Sets the upper limit on the number of simultaneous
3034 RPC calls that can be sent from the client to a
3035 server. Increasing these values may allow you to
3036 improve throughput, but will also increase the
3037 amount of memory reserved for use by the client.
3040 [KNL] Enable accounting of swap in memory resource
3041 controller if no parameter or 1 is given or disable
3042 it if 0 is given (See Documentation/cgroups/memory.txt)
3044 swiotlb= [IA-64] Number of I/O TLB slabs
3048 sysfs.deprecated=0|1 [KNL]
3049 Enable/disable old style sysfs layout for old udev
3050 on older distributions. When this option is enabled
3051 very new udev will not work anymore. When this option
3052 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3053 in older udev will not work anymore.
3054 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3055 the kernel configuration.
3057 sysrq_always_enabled
3059 Ignore sysrq setting - this boot parameter will
3060 neutralize any effect of /proc/sys/kernel/sysrq.
3061 Useful for debugging.
3065 test_suspend= [SUSPEND]
3066 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3067 standby suspend) as the system sleep state to briefly
3068 enter during system startup. The system is woken from
3069 this state using a wakeup-capable RTC alarm.
3071 thash_entries= [KNL,NET]
3072 Set number of hash buckets for TCP connection
3074 thermal.act= [HW,ACPI]
3075 -1: disable all active trip points in all thermal zones
3076 <degrees C>: override all lowest active trip points
3078 thermal.crt= [HW,ACPI]
3079 -1: disable all critical trip points in all thermal zones
3080 <degrees C>: override all critical trip points
3082 thermal.nocrt= [HW,ACPI]
3083 Set to disable actions on ACPI thermal zone
3084 critical and hot trip points.
3086 thermal.off= [HW,ACPI]
3087 1: disable ACPI thermal control
3089 thermal.psv= [HW,ACPI]
3090 -1: disable all passive trip points
3091 <degrees C>: override all passive trip points to this
3094 thermal.tzp= [HW,ACPI]
3095 Specify global default ACPI thermal zone polling rate
3096 <deci-seconds>: poll all this frequency
3097 0: no polling (default)
3100 Force threading of all interrupt handlers except those
3101 marked explicitly IRQF_NO_THREAD.
3104 Enable the Transcendent memory driver if built-in.
3106 tmem.cleancache=0|1 [KNL, XEN]
3107 Default is on (1). Disable the usage of the cleancache
3108 API to send anonymous pages to the hypervisor.
3110 tmem.frontswap=0|1 [KNL, XEN]
3111 Default is on (1). Disable the usage of the frontswap
3112 API to send swap pages to the hypervisor. If disabled
3113 the selfballooning and selfshrinking are force disabled.
3115 tmem.selfballooning=0|1 [KNL, XEN]
3116 Default is on (1). Disable the driving of swap pages
3119 tmem.selfshrinking=0|1 [KNL, XEN]
3120 Default is on (1). Partial swapoff that immediately
3121 transfers pages from Xen hypervisor back to the
3122 kernel based on different criteria.
3126 Specify if the kernel should make use of the cpu
3127 topology information if the hardware supports this.
3128 The scheduler will make use of this information and
3129 e.g. base its process migration decisions on it.
3134 tpm_suspend_pcr=[HW,TPM]
3135 Format: integer pcr id
3136 Specify that at suspend time, the tpm driver
3137 should extend the specified pcr with zeros,
3138 as a workaround for some chips which fail to
3139 flush the last written pcr on TPM_SaveState.
3140 This will guarantee that all the other pcrs
3143 trace_buf_size=nn[KMG]
3144 [FTRACE] will set tracing buffer size.
3146 trace_event=[event-list]
3147 [FTRACE] Set and start specified trace events in order
3148 to facilitate early boot debugging.
3149 See also Documentation/trace/events.txt
3151 trace_options=[option-list]
3152 [FTRACE] Enable or disable tracer options at boot.
3153 The option-list is a comma delimited list of options
3154 that can be enabled or disabled just as if you were
3155 to echo the option name into
3157 /sys/kernel/debug/tracing/trace_options
3159 For example, to enable stacktrace option (to dump the
3160 stack trace of each event), add to the command line:
3162 trace_options=stacktrace
3164 See also Documentation/trace/ftrace.txt "trace options"
3168 [FTRACE] enable this option to disable tracing when a
3169 warning is hit. This turns off "tracing_on". Tracing can
3170 be enabled again by echoing '1' into the "tracing_on"
3171 file located in /sys/kernel/debug/tracing/
3173 This option is useful, as it disables the trace before
3174 the WARNING dump is called, which prevents the trace to
3175 be filled with content caused by the warning output.
3177 This option can also be set at run time via the sysctl
3178 option: kernel/traceoff_on_warning
3180 transparent_hugepage=
3182 Format: [always|madvise|never]
3183 Can be used to control the default behavior of the system
3184 with respect to transparent hugepages.
3185 See Documentation/vm/transhuge.txt for more details.
3187 tsc= Disable clocksource stability checks for TSC.
3189 [x86] reliable: mark tsc clocksource as reliable, this
3190 disables clocksource verification at runtime, as well
3191 as the stability checks done at bootup. Used to enable
3192 high-resolution timer mode on older hardware, and in
3193 virtualized environment.
3194 [x86] noirqtime: Do not use TSC to do irq accounting.
3195 Used to run time disable IRQ_TIME_ACCOUNTING on any
3196 platforms where RDTSC is slow and this accounting
3199 turbografx.map[2|3]= [HW,JOY]
3200 TurboGraFX parallel port interface
3202 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3203 See also Documentation/input/joystick-parport.txt
3205 udbg-immortal [PPC] When debugging early kernel crashes that
3206 happen after console_init() and before a proper
3207 console driver takes over, this boot options might
3208 help "seeing" what's going on.
3210 uhash_entries= [KNL,NET]
3211 Set number of hash buckets for UDP/UDP-Lite connections
3214 [USB] Ignore overcurrent events (default N).
3215 Some badly-designed motherboards generate lots of
3216 bogus events, for ports that aren't wired to
3217 anything. Set this parameter to avoid log spamming.
3218 Note that genuine overcurrent events won't be
3222 [X86] Cause panic on unknown NMI.
3224 usbcore.authorized_default=
3225 [USB] Default USB device authorization:
3226 (default -1 = authorized except for wireless USB,
3227 0 = not authorized, 1 = authorized)
3229 usbcore.autosuspend=
3230 [USB] The autosuspend time delay (in seconds) used
3231 for newly-detected USB devices (default 2). This
3232 is the time required before an idle device will be
3233 autosuspended. Devices for which the delay is set
3234 to a negative value won't be autosuspended at all.
3236 usbcore.usbfs_snoop=
3237 [USB] Set to log all usbfs traffic (default 0 = off).
3239 usbcore.blinkenlights=
3240 [USB] Set to cycle leds on hubs (default 0 = off).
3242 usbcore.old_scheme_first=
3243 [USB] Start with the old device initialization
3244 scheme (default 0 = off).
3246 usbcore.usbfs_memory_mb=
3247 [USB] Memory limit (in MB) for buffers allocated by
3248 usbfs (default = 16, 0 = max = 2047).
3250 usbcore.use_both_schemes=
3251 [USB] Try the other device initialization scheme
3252 if the first one fails (default 1 = enabled).
3254 usbcore.initial_descriptor_timeout=
3255 [USB] Specifies timeout for the initial 64-byte
3256 USB_REQ_GET_DESCRIPTOR request in milliseconds
3257 (default 5000 = 5.0 seconds).
3260 [USBHID] The interval which mice are to be polled at.
3262 usb-storage.delay_use=
3263 [UMS] The delay in seconds before a new device is
3264 scanned for Logical Units (default 5).
3267 [UMS] A list of quirks entries to supplement or
3268 override the built-in unusual_devs list. List
3269 entries are separated by commas. Each entry has
3270 the form VID:PID:Flags where VID and PID are Vendor
3271 and Product ID values (4-digit hex numbers) and
3272 Flags is a set of characters, each corresponding
3273 to a common usb-storage quirk flag as follows:
3274 a = SANE_SENSE (collect more than 18 bytes
3276 b = BAD_SENSE (don't collect more than 18
3277 bytes of sense data);
3278 c = FIX_CAPACITY (decrease the reported
3279 device capacity by one sector);
3280 d = NO_READ_DISC_INFO (don't use
3281 READ_DISC_INFO command);
3282 e = NO_READ_CAPACITY_16 (don't use
3283 READ_CAPACITY_16 command);
3284 h = CAPACITY_HEURISTICS (decrease the
3285 reported device capacity by one
3286 sector if the number is odd);
3287 i = IGNORE_DEVICE (don't bind to this
3289 l = NOT_LOCKABLE (don't try to lock and
3290 unlock ejectable media);
3291 m = MAX_SECTORS_64 (don't transfer more
3292 than 64 sectors = 32 KB at a time);
3293 n = INITIAL_READ10 (force a retry of the
3294 initial READ(10) command);
3295 o = CAPACITY_OK (accept the capacity
3296 reported by the device);
3297 p = WRITE_CACHE (the device cache is ON
3299 r = IGNORE_RESIDUE (the device reports
3300 bogus residue values);
3301 s = SINGLE_LUN (the device has only one
3303 w = NO_WP_DETECT (don't test whether the
3304 medium is write-protected).
3305 Example: quirks=0419:aaf5:rl,0421:0433:rc
3307 user_debug= [KNL,ARM]
3309 See arch/arm/Kconfig.debug help text.
3310 1 - undefined instruction events
3312 4 - invalid data aborts
3315 Example: user_debug=31
3318 [X86] Flags controlling user PTE allocations.
3320 nohigh = do not allocate PTE pages in
3321 HIGHMEM regardless of setting
3325 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3326 vdso=1: enable VDSO (default)
3327 vdso=0: disable VDSO mapping
3330 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3331 vdso32=1: enable 32-bit VDSO (default)
3332 vdso32=0: disable 32-bit VDSO mapping
3335 vector=percpu: enable percpu vector domain
3337 video= [FB] Frame buffer configuration
3338 See Documentation/fb/modedb.txt.
3340 video.brightness_switch_enabled= [0,1]
3341 If set to 1, on receiving an ACPI notify event
3342 generated by hotkey, video driver will adjust brightness
3343 level and then send out the event to user space through
3344 the allocated input device; If set to 0, video driver
3345 will only send out the event without touching backlight
3350 [VMMIO] Memory mapped virtio (platform) device.
3352 <size>@<baseaddr>:<irq>[:<id>]
3354 <size> := size (can use standard suffixes
3356 <baseaddr> := physical base address
3357 <irq> := interrupt number (as passed to
3359 <id> := (optional) platform device id
3361 virtio_mmio.device=1K@0x100b0000:48:7
3363 Can be used multiple times for multiple devices.
3365 vga= [BOOT,X86-32] Select a particular video mode
3366 See Documentation/x86/boot.txt and
3367 Documentation/svga.txt.
3368 Use vga=ask for menu.
3369 This is actually a boot loader parameter; the value is
3370 passed to the kernel using a special protocol.
3372 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3373 size of <nn>. This can be used to increase the
3374 minimum size (128MB on x86). It can also be used to
3375 decrease the size and leave more room for directly
3378 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3381 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3384 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3388 Controls the behavior of vsyscalls (i.e. calls to
3389 fixed addresses of 0xffffffffff600x00 from legacy
3390 code). Most statically-linked binaries and older
3391 versions of glibc use these calls. Because these
3392 functions are at fixed addresses, they make nice
3393 targets for exploits that can control RIP.
3395 emulate [default] Vsyscalls turn into traps and are
3396 emulated reasonably safely.
3398 native Vsyscalls are native syscall instructions.
3399 This is a little bit faster than trapping
3400 and makes a few dynamic recompilers work
3401 better than they would in emulation mode.
3402 It also makes exploits much easier to write.
3404 none Vsyscalls don't work at all. This makes
3405 them quite hard to use for exploits but
3406 might break your system.
3408 vt.color= [VT] Default text color.
3409 Format: 0xYX, X = foreground, Y = background.
3410 Default: 0x07 = light gray on black.
3412 vt.cur_default= [VT] Default cursor shape.
3413 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3414 the parameters of the <Esc>[?A;B;Cc escape sequence;
3415 see VGA-softcursor.txt. Default: 2 = underline.
3417 vt.default_blu= [VT]
3418 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3419 Change the default blue palette of the console.
3420 This is a 16-member array composed of values
3423 vt.default_grn= [VT]
3424 Format: <green0>,<green1>,<green2>,...,<green15>
3425 Change the default green palette of the console.
3426 This is a 16-member array composed of values
3429 vt.default_red= [VT]
3430 Format: <red0>,<red1>,<red2>,...,<red15>
3431 Change the default red palette of the console.
3432 This is a 16-member array composed of values
3438 Set system-wide default UTF-8 mode for all tty's.
3439 Default is 1, i.e. UTF-8 mode is enabled for all
3440 newly opened terminals.
3442 vt.global_cursor_default=
3445 Set system-wide default for whether a cursor
3446 is shown on new VTs. Default is -1,
3447 i.e. cursors will be created by default unless
3448 overridden by individual drivers. 0 will hide
3449 cursors, 1 will display them.
3451 vt.italic= [VT] Default color for italic text; 0-15.
3454 vt.underline= [VT] Default color for underlined text; 0-15.
3457 watchdog timers [HW,WDT] For information on watchdog timers,
3458 see Documentation/watchdog/watchdog-parameters.txt
3459 or other driver-specific files in the
3460 Documentation/watchdog/ directory.
3462 workqueue.disable_numa
3463 By default, all work items queued to unbound
3464 workqueues are affine to the NUMA nodes they're
3465 issued on, which results in better behavior in
3466 general. If NUMA affinity needs to be disabled for
3467 whatever reason, this option can be used. Note
3468 that this also can be controlled per-workqueue for
3469 workqueues visible under /sys/bus/workqueue/.
3471 workqueue.power_efficient
3472 Per-cpu workqueues are generally preferred because
3473 they show better performance thanks to cache
3474 locality; unfortunately, per-cpu workqueues tend to
3475 be more power hungry than unbound workqueues.
3477 Enabling this makes the per-cpu workqueues which
3478 were observed to contribute significantly to power
3479 consumption unbound, leading to measurably lower
3480 power usage at the cost of small performance
3483 The default value of this parameter is determined by
3484 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3486 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3487 default x2apic cluster mode on platforms
3490 x86_mrst_timer= [X86-32,APBT]
3491 Choose timer option for x86 Moorestown MID platform.
3492 Two valid options are apbt timer only and lapic timer
3493 plus one apbt timer for broadcast timer.
3494 x86_mrst_timer=apbt_only | lapic_and_apbt
3496 xen_emul_unplug= [HW,X86,XEN]
3497 Unplug Xen emulated devices
3498 Format: [unplug0,][unplug1]
3499 ide-disks -- unplug primary master IDE devices
3500 aux-ide-disks -- unplug non-primary-master IDE devices
3501 nics -- unplug network devices
3502 all -- unplug all emulated devices (NICs and IDE disks)
3503 unnecessary -- unplugging emulated devices is
3504 unnecessary even if the host did not respond to
3506 never -- do not unplug even if version check succeeds
3508 xen_nopvspin [X86,XEN]
3509 Disables the ticketlock slowpath using Xen PV
3512 xirc2ps_cs= [NET,PCMCIA]
3514 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3516 ______________________________________________________________________
3520 Add more DRM drivers.
projects / ~andy / linux / blob