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_serialize [HW,ACPI]
233 Disable auto-serialization of AML methods
234 AML control methods that contain the opcodes to create
235 named objects will be marked as "Serialized" by the
236 auto-serialization feature.
237 This feature is enabled by default.
238 This option allows to turn off the feature.
240 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
242 acpica_no_return_repair [HW, ACPI]
243 Disable AML predefined validation mechanism
244 This mechanism can repair the evaluation result to make
245 the return objects more ACPI specification compliant.
246 This option is useful for developers to identify the
247 root cause of an AML interpreter issue when the issue
248 has something to do with the repair mechanism.
250 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
251 Format: To spoof as Windows 98: ="Microsoft Windows"
253 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
254 acpi_osi="string1" # add string1
255 acpi_osi="!string2" # remove string2
256 acpi_osi=!* # remove all strings
257 acpi_osi=! # disable all built-in OS vendor
259 acpi_osi= # disable all strings
261 'acpi_osi=!' can be used in combination with single or
262 multiple 'acpi_osi="string1"' to support specific OS
263 vendor string(s). Note that such command can only
264 affect the default state of the OS vendor strings, thus
265 it cannot affect the default state of the feature group
266 strings and the current state of the OS vendor strings,
267 specifying it multiple times through kernel command line
268 is meaningless. This command is useful when one do not
269 care about the state of the feature group strings which
270 should be controlled by the OSPM.
272 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
273 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
274 can make '_OSI("Windows 2000")' TRUE.
276 'acpi_osi=' cannot be used in combination with other
277 'acpi_osi=' command lines, the _OSI method will not
278 exist in the ACPI namespace. NOTE that such command can
279 only affect the _OSI support state, thus specifying it
280 multiple times through kernel command line is also
283 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
286 'acpi_osi=!*' can be used in combination with single or
287 multiple 'acpi_osi="string1"' to support specific
288 string(s). Note that such command can affect the
289 current state of both the OS vendor strings and the
290 feature group strings, thus specifying it multiple times
291 through kernel command line is meaningful. But it may
292 still not able to affect the final state of a string if
293 there are quirks related to this string. This command
294 is useful when one want to control the state of the
295 feature group strings to debug BIOS issues related to
298 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
299 '_OSI("Module Device")' FALSE.
300 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
301 '_OSI("Module Device")' TRUE.
302 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
304 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
306 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
307 they all will make '_OSI("Windows 2000")' TRUE.
310 Override the pmtimer bug detection: force the kernel
311 to assume that this machine's pmtimer latches its value
312 and always returns good values.
314 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
315 Format: { level | edge | high | low }
317 acpi_skip_timer_override [HW,ACPI]
318 Recognize and ignore IRQ0/pin2 Interrupt Override.
319 For broken nForce2 BIOS resulting in XT-PIC timer.
321 acpi_sleep= [HW,ACPI] Sleep options
322 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
323 old_ordering, nonvs, sci_force_enable }
324 See Documentation/power/video.txt for information on
326 s3_beep is for debugging; it makes the PC's speaker beep
327 as soon as the kernel's real-mode entry point is called.
328 s4_nohwsig prevents ACPI hardware signature from being
329 used during resume from hibernation.
330 old_ordering causes the ACPI 1.0 ordering of the _PTS
331 control method, with respect to putting devices into
332 low power states, to be enforced (the ACPI 2.0 ordering
333 of _PTS is used by default).
334 nonvs prevents the kernel from saving/restoring the
335 ACPI NVS memory during suspend/hibernation and resume.
336 sci_force_enable causes the kernel to set SCI_EN directly
337 on resume from S1/S3 (which is against the ACPI spec,
338 but some broken systems don't work without it).
340 acpi_use_timer_override [HW,ACPI]
341 Use timer override. For some broken Nvidia NF5 boards
342 that require a timer override, but don't have HPET
344 acpi_enforce_resources= [ACPI]
345 { strict | lax | no }
346 Check for resource conflicts between native drivers
347 and ACPI OperationRegions (SystemIO and SystemMemory
348 only). IO ports and memory declared in ACPI might be
349 used by the ACPI subsystem in arbitrary AML code and
350 can interfere with legacy drivers.
351 strict (default): access to resources claimed by ACPI
352 is denied; legacy drivers trying to access reserved
353 resources will fail to bind to device using them.
354 lax: access to resources claimed by ACPI is allowed;
355 legacy drivers trying to access reserved resources
356 will bind successfully but a warning message is logged.
357 no: ACPI OperationRegions are not marked as reserved,
358 no further checks are performed.
360 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
363 add_efi_memmap [EFI; X86] Include EFI memory map in
364 kernel's map of available physical RAM.
367 { off | try_unsupported }
368 off: disable AGP support
369 try_unsupported: try to drive unsupported chipsets
370 (may crash computer or cause data corruption)
373 See Documentation/sound/alsa/alsa-parameters.txt
376 Allow the default userspace alignment fault handler
377 behaviour to be specified. Bit 0 enables warnings,
378 bit 1 enables fixups, and bit 2 sends a segfault.
380 align_va_addr= [X86-64]
381 Align virtual addresses by clearing slice [14:12] when
382 allocating a VMA at process creation time. This option
383 gives you up to 3% performance improvement on AMD F15h
384 machines (where it is enabled by default) for a
385 CPU-intensive style benchmark, and it can vary highly in
386 a microbenchmark depending on workload and compiler.
388 32: only for 32-bit processes
389 64: only for 64-bit processes
390 on: enable for both 32- and 64-bit processes
391 off: disable for both 32- and 64-bit processes
393 alloc_snapshot [FTRACE]
394 Allocate the ftrace snapshot buffer on boot up when the
395 main buffer is allocated. This is handy if debugging
396 and you need to use tracing_snapshot() on boot up, and
397 do not want to use tracing_snapshot_alloc() as it needs
398 to be done where GFP_KERNEL allocations are allowed.
400 amd_iommu= [HW,X86-64]
401 Pass parameters to the AMD IOMMU driver in the system.
403 fullflush - enable flushing of IO/TLB entries when
404 they are unmapped. Otherwise they are
405 flushed before they will be reused, which
407 off - do not initialize any AMD IOMMU found in
409 force_isolation - Force device isolation for all
410 devices. The IOMMU driver is not
411 allowed anymore to lift isolation
412 requirements as needed. This option
413 does not override iommu=pt
415 amd_iommu_dump= [HW,X86-64]
416 Enable AMD IOMMU driver option to dump the ACPI table
417 for AMD IOMMU. With this option enabled, AMD IOMMU
418 driver will print ACPI tables for AMD IOMMU during
419 IOMMU initialization.
421 amijoy.map= [HW,JOY] Amiga joystick support
422 Map of devices attached to JOY0DAT and JOY1DAT
424 See also Documentation/input/joystick.txt
426 analog.map= [HW,JOY] Analog joystick and gamepad support
427 Specifies type or capabilities of an analog joystick
428 connected to one of 16 gameports
429 Format: <type1>,<type2>,..<type16>
432 Power management functions (SPARCstation-4/5 + deriv.)
434 Disable APC CPU standby support. SPARCstation-Fox does
435 not play well with APC CPU idle - disable it if you have
436 APC and your system crashes randomly.
438 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
439 Change the output verbosity whilst booting
440 Format: { quiet (default) | verbose | debug }
441 Change the amount of debugging information output
442 when initialising the APIC and IO-APIC components.
445 See Documentation/networking/ipv6.txt.
447 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
448 Limit apic dumping. The parameter defines the maximal
449 number of local apics being dumped. Also it is possible
450 to set it to "all" by meaning -- no limit here.
451 Format: { 1 (default) | 2 | ... | all }.
452 The parameter valid if only apic=debug or
453 apic=verbose is specified.
454 Example: apic=debug show_lapic=all
456 apm= [APM] Advanced Power Management
457 See header of arch/x86/kernel/apm_32.c.
459 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
460 Format: <io>,<irq>,<nodeID>
464 atarimouse= [HW,MOUSE] Atari Mouse
466 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
467 EzKey and similar keyboards
469 atkbd.reset= [HW] Reset keyboard during initialization
471 atkbd.set= [HW] Select keyboard code set
472 Format: <int> (2 = AT (default), 3 = PS/2)
474 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
477 atkbd.softraw= [HW] Choose between synthetic and real raw mode
478 Format: <bool> (0 = real, 1 = synthetic (default))
480 atkbd.softrepeat= [HW]
481 Use software keyboard repeat
483 audit= [KNL] Enable the audit sub-system
484 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
485 0 - kernel audit is disabled and can not be enabled
486 until the next reboot
487 unset - kernel audit is initialized but disabled and
488 will be fully enabled by the userspace auditd.
489 1 - kernel audit is initialized and partially enabled,
490 storing at most audit_backlog_limit messages in
491 RAM until it is fully enabled by the userspace
495 audit_backlog_limit= [KNL] Set the audit queue size limit.
496 Format: <int> (must be >=0)
499 baycom_epp= [HW,AX25]
502 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
504 See header of drivers/net/hamradio/baycom_par.c.
506 baycom_ser_fdx= [HW,AX25]
507 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
508 Format: <io>,<irq>,<mode>[,<baud>]
509 See header of drivers/net/hamradio/baycom_ser_fdx.c.
511 baycom_ser_hdx= [HW,AX25]
512 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
513 Format: <io>,<irq>,<mode>
514 See header of drivers/net/hamradio/baycom_ser_hdx.c.
516 blkdevparts= Manual partition parsing of block device(s) for
517 embedded devices based on command line input.
518 See Documentation/block/cmdline-partition.txt
520 boot_delay= Milliseconds to delay each printk during boot.
521 Values larger than 10 seconds (10000) are changed to
525 bootmem_debug [KNL] Enable bootmem allocator debug messages.
527 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
528 bttv.radio= Most important insmod options are available as
530 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
533 bulk_remove=off [PPC] This parameter disables the use of the pSeries
534 firmware feature for flushing multiple hpte entries
537 c101= [NET] Moxa C101 synchronous serial card
539 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
540 Sometimes CPU hardware bugs make them report the cache
541 size incorrectly. The kernel will attempt work arounds
542 to fix known problems, but for some CPUs it is not
543 possible to determine what the correct size should be.
544 This option provides an override for these situations.
546 ccw_timeout_log [S390]
547 See Documentation/s390/CommonIO for details.
549 cgroup_disable= [KNL] Disable a particular controller
550 Format: {name of the controller(s) to disable}
551 The effects of cgroup_disable=foo are:
552 - foo isn't auto-mounted if you mount all cgroups in
554 - foo isn't visible as an individually mountable
556 {Currently only "memory" controller deal with this and
557 cut the overhead, others just disable the usage. So
558 only cgroup_disable=memory is actually worthy}
560 checkreqprot [SELINUX] Set initial checkreqprot flag value.
561 Format: { "0" | "1" }
562 See security/selinux/Kconfig help text.
563 0 -- check protection applied by kernel (includes
564 any implied execute protection).
565 1 -- check protection requested by application.
566 Default value is set via a kernel config option.
567 Value can be changed at runtime via
568 /selinux/checkreqprot.
571 See Documentation/s390/CommonIO for details.
574 Keep all clocks already enabled by bootloader on,
575 even if no driver has claimed them. This is useful
576 for debug and development, but should not be
577 needed on a platform with proper driver support.
578 For more information, see Documentation/clk.txt.
580 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
582 Forces specified clocksource (if available) to be used
583 when calculating gettimeofday(). If specified
584 clocksource is not available, it defaults to PIT.
585 Format: { pit | tsc | cyclone | pmtmr }
587 clocksource= Override the default clocksource
589 Override the default clocksource and use the clocksource
590 with the name specified.
591 Some clocksource names to choose from, depending on
593 [all] jiffies (this is the base, fallback clocksource)
595 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
596 pxa_timer,timer3,32k_counter,timer0_1
598 [X86-32] pit,hpet,tsc;
599 scx200_hrt on Geode; cyclone on IBM x440
607 clearcpuid=BITNUM [X86]
608 Disable CPUID feature X for the kernel. See
609 arch/x86/include/asm/cpufeature.h for the valid bit
610 numbers. Note the Linux specific bits are not necessarily
611 stable over kernel options, but the vendor specific
613 Also note that user programs calling CPUID directly
614 or using the feature without checking anything
615 will still see it. This just prevents it from
616 being used by the kernel or shown in /proc/cpuinfo.
617 Also note the kernel might malfunction if you disable
621 Sets the size of kernel global memory area for contiguous
622 memory allocations. For more information, see
623 include/linux/dma-contiguous.h
625 cmo_free_hint= [PPC] Format: { yes | no }
626 Specify whether pages are marked as being inactive
627 when they are freed. This is used in CMO environments
628 to determine OS memory pressure for page stealing by
632 coherent_pool=nn[KMG] [ARM,KNL]
633 Sets the size of memory pool for coherent, atomic dma
634 allocations, by default set to 256K.
636 code_bytes [X86] How many bytes of object code to print
641 com20020= [HW,NET] ARCnet - COM20020 chipset
643 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
645 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
649 ARCnet - COM90xx chipset (memory-mapped buffers)
650 Format: <io>[,<irq>[,<memstart>]]
652 condev= [HW,S390] console device
655 console= [KNL] Output console device and options.
657 tty<n> Use the virtual console device <n>.
661 Use the specified serial port. The options are of
662 the form "bbbbpnf", where "bbbb" is the baud rate,
663 "p" is parity ("n", "o", or "e"), "n" is number of
664 bits, and "f" is flow control ("r" for RTS or
665 omit it). Default is "9600n8".
667 See Documentation/serial-console.txt for more
669 Documentation/networking/netconsole.txt for an
672 uart[8250],io,<addr>[,options]
673 uart[8250],mmio,<addr>[,options]
674 Start an early, polled-mode console on the 8250/16550
675 UART at the specified I/O port or MMIO address,
676 switching to the matching ttyS device later. The
677 options are the same as for ttyS, above.
678 hvc<n> Use the hypervisor console device <n>. This is for
679 both Xen and PowerPC hypervisors.
681 If the device connected to the port is not a TTY but a braille
682 device, prepend "brl," before the device type, for instance
684 For now, only VisioBraille is supported.
686 consoleblank= [KNL] The console blank (screen saver) timeout in
687 seconds. Defaults to 10*60 = 10mins. A value of 0
688 disables the blank timer.
691 [KNL] Change the default value for
692 /proc/<pid>/coredump_filter.
693 See also Documentation/filesystems/proc.txt.
695 cpuidle.off=1 [CPU_IDLE]
696 disable the cpuidle sub-system
698 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
700 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
702 crashkernel=size[KMG][@offset[KMG]]
703 [KNL] Using kexec, Linux can switch to a 'crash kernel'
704 upon panic. This parameter reserves the physical
705 memory region [offset, offset + size] for that kernel
706 image. If '@offset' is omitted, then a suitable offset
707 is selected automatically. Check
708 Documentation/kdump/kdump.txt for further details.
710 crashkernel=range1:size1[,range2:size2,...][@offset]
711 [KNL] Same as above, but depends on the memory
712 in the running system. The syntax of range is
713 start-[end] where start and end are both
714 a memory unit (amount[KMG]). See also
715 Documentation/kdump/kdump.txt for an example.
717 crashkernel=size[KMG],high
718 [KNL, x86_64] range could be above 4G. Allow kernel
719 to allocate physical memory region from top, so could
720 be above 4G if system have more than 4G ram installed.
721 Otherwise memory region will be allocated below 4G, if
723 It will be ignored if crashkernel=X is specified.
724 crashkernel=size[KMG],low
725 [KNL, x86_64] range under 4G. When crashkernel=X,high
726 is passed, kernel could allocate physical memory region
727 above 4G, that cause second kernel crash on system
728 that require some amount of low memory, e.g. swiotlb
729 requires at least 64M+32K low memory. Kernel would
730 try to allocate 72M below 4G automatically.
731 This one let user to specify own low range under 4G
732 for second kernel instead.
733 0: to disable low allocation.
734 It will be ignored when crashkernel=X,high is not used
735 or memory reserved is below 4G.
740 cs89x0_media= [HW,NET]
741 Format: { rj45 | aui | bnc }
744 See header of drivers/s390/block/dasd_devmap.c.
746 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
747 (one device per port)
748 Format: <port#>,<type>
749 See also Documentation/input/joystick-parport.txt
751 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
752 time. See Documentation/dynamic-debug-howto.txt for
753 details. Deprecated, see dyndbg.
755 debug [KNL] Enable kernel debugging (events log level).
758 [KNL] verbose self-tests
760 Print debugging info while doing the locking API
762 We default to 0 (no extra messages), setting it to
763 1 will print _a lot_ more information - normally
764 only useful to kernel developers.
766 debug_objects [KNL] Enable object debugging
769 [KNL] Disable object debugging
771 debug_guardpage_minorder=
772 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
773 parameter allows control of the order of pages that will
774 be intentionally kept free (and hence protected) by the
775 buddy allocator. Bigger value increase the probability
776 of catching random memory corruption, but reduce the
777 amount of memory for normal system use. The maximum
778 possible value is MAX_ORDER/2. Setting this parameter
779 to 1 or 2 should be enough to identify most random
780 memory corruption problems caused by bugs in kernel or
781 driver code when a CPU writes to (or reads from) a
782 random memory location. Note that there exists a class
783 of memory corruptions problems caused by buggy H/W or
784 F/W or by drivers badly programing DMA (basically when
785 memory is written at bus level and the CPU MMU is
786 bypassed) which are not detectable by
787 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
788 tracking down these problems.
790 debugpat [X86] Enable PAT debugging
792 decnet.addr= [HW,NET]
793 Format: <area>[,<node>]
794 See also Documentation/networking/decnet.txt.
797 [same as hugepagesz=] The size of the default
798 HugeTLB page size. This is the size represented by
799 the legacy /proc/ hugepages APIs, used for SHM, and
800 default size when mounting hugetlbfs filesystems.
801 Defaults to the default architecture's huge page size
805 Set number of hash buckets for dentry cache.
808 See Documentation/networking/ipv6.txt.
810 disable_cpu_apicid= [X86,APIC,SMP]
812 The number of initial APIC ID for the
813 corresponding CPU to be disabled at boot,
814 mostly used for the kdump 2nd kernel to
815 disable BSP to wake up multiple CPUs without
816 causing system reset or hang due to sending
819 disable_ddw [PPC/PSERIES]
820 Disable Dynamic DMA Window support. Use this if
821 to workaround buggy firmware.
824 See Documentation/networking/ipv6.txt.
826 disable_mtrr_cleanup [X86]
827 The kernel tries to adjust MTRR layout from continuous
828 to discrete, to make X server driver able to add WB
829 entry later. This parameter disables that.
831 disable_mtrr_trim [X86, Intel and AMD only]
832 By default the kernel will trim any uncacheable
833 memory out of your available memory pool based on
834 MTRR settings. This parameter disables that behavior,
835 possibly causing your machine to run very slowly.
837 disable_timer_pin_1 [X86]
838 Disable PIN 1 of APIC timer
839 Can be useful to work around chipset bugs.
841 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
842 this option disables the debugging code at boot.
844 dma_debug_entries=<number>
845 This option allows to tune the number of preallocated
846 entries for DMA-API debugging code. One entry is
847 required per DMA-API allocation. Use this if the
848 DMA-API debugging code disables itself because the
849 architectural default is too low.
851 dma_debug_driver=<driver_name>
852 With this option the DMA-API debugging driver
853 filter feature can be enabled at boot time. Just
854 pass the driver to filter for as the parameter.
855 The filter can be disabled or changed to another
856 driver later using sysfs.
858 drm_kms_helper.edid_firmware=[<connector>:]<file>
859 Broken monitors, graphic adapters and KVMs may
860 send no or incorrect EDID data sets. This parameter
861 allows to specify an EDID data set in the
862 /lib/firmware directory that is used instead.
863 Generic built-in EDID data sets are used, if one of
864 edid/1024x768.bin, edid/1280x1024.bin,
865 edid/1680x1050.bin, or edid/1920x1080.bin is given
866 and no file with the same name exists. Details and
867 instructions how to build your own EDID data are
868 available in Documentation/EDID/HOWTO.txt. An EDID
869 data set will only be used for a particular connector,
870 if its name and a colon are prepended to the EDID
875 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
876 module.dyndbg[="val"]
877 Enable debug messages at boot time. See
878 Documentation/dynamic-debug-howto.txt for details.
880 early_ioremap_debug [KNL]
881 Enable debug messages in early_ioremap support. This
882 is useful for tracking down temporary early mappings
883 which are not unmapped.
885 earlycon= [KNL] Output early console device and options.
887 uart[8250],io,<addr>[,options]
888 uart[8250],mmio,<addr>[,options]
889 uart[8250],mmio32,<addr>[,options]
890 Start an early, polled-mode console on the 8250/16550
891 UART at the specified I/O port or MMIO address.
892 MMIO inter-register address stride is either 8-bit
893 (mmio) or 32-bit (mmio32).
894 The options are the same as for ttyS, above.
897 Start an early, polled-mode console on a pl011 serial
898 port at the specified address. The pl011 serial port
899 must already be setup and configured. Options are not
902 smh Use ARM semihosting calls for early console.
904 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k]
908 earlyprintk=serial[,ttySn[,baudrate]]
909 earlyprintk=serial[,0x...[,baudrate]]
910 earlyprintk=ttySn[,baudrate]
911 earlyprintk=dbgp[debugController#]
913 earlyprintk is useful when the kernel crashes before
914 the normal console is initialized. It is not enabled by
915 default because it has some cosmetic problems.
917 Append ",keep" to not disable it when the real console
920 Only one of vga, efi, serial, or usb debug port can
923 Currently only ttyS0 and ttyS1 may be specified by
924 name. Other I/O ports may be explicitly specified
925 on some architectures (x86 and arm at least) by
926 replacing ttySn with an I/O port address, like this:
927 earlyprintk=serial,0x1008,115200
928 You can find the port for a given device in
929 /proc/tty/driver/serial:
930 2: uart:ST16650V2 port:00001008 irq:18 ...
932 Interaction with the standard serial driver is not
935 The VGA and EFI output is eventually overwritten by
938 The xen output can only be used by Xen PV guests.
940 edac_report= [HW,EDAC] Control how to report EDAC event
941 Format: {"on" | "off" | "force"}
942 on: enable EDAC to report H/W event. May be overridden
943 by other higher priority error reporting module.
944 off: disable H/W event reporting through EDAC.
945 force: enforce the use of EDAC to report H/W event.
948 ekgdboc= [X86,KGDB] Allow early kernel console debugging
951 This is designed to be used in conjunction with
952 the boot argument: earlyprintk=vga
955 Format: {"off" | "on" | "skip[mbr]"}
958 Format: { "old_map" }
959 old_map [X86-64]: switch to the old ioremap-based EFI
960 runtime services mapping. 32-bit still uses this one by
963 efi_no_storage_paranoia [EFI; X86]
964 Using this parameter you can use more than 50% of
965 your efi variable storage. Use this parameter only if
966 you are really sure that your UEFI does sane gc and
967 fulfills the spec otherwise your board may brick.
969 eisa_irq_edge= [PARISC,HW]
970 See header of drivers/parisc/eisa.c.
973 See comment before function elanfreq_setup() in
974 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
977 Format: {"cfq" | "deadline" | "noop"}
978 See Documentation/block/cfq-iosched.txt and
979 Documentation/block/deadline-iosched.txt for details.
981 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
982 Specifies physical address of start of kernel core
983 image elf header and optionally the size. Generally
984 kexec loader will pass this option to capture kernel.
985 See Documentation/kdump/kdump.txt for details.
987 enable_mtrr_cleanup [X86]
988 The kernel tries to adjust MTRR layout from continuous
989 to discrete, to make X server driver able to add WB
990 entry later. This parameter enables that.
992 enable_timer_pin_1 [X86]
993 Enable PIN 1 of APIC timer
994 Can be useful to work around chipset bugs
995 (in particular on some ATI chipsets).
996 The kernel tries to set a reasonable default.
998 enforcing [SELINUX] Set initial enforcing status.
1000 See security/selinux/Kconfig help text.
1001 0 -- permissive (log only, no denials).
1002 1 -- enforcing (deny and log).
1004 Value can be changed at runtime via /selinux/enforce.
1007 Disable Error Record Serialization Table (ERST)
1010 ether= [HW,NET] Ethernet cards parameters
1011 This option is obsoleted by the "netdev=" option, which
1012 has equivalent usage. See its documentation for details.
1016 Permit 'security.evm' to be updated regardless of
1017 current integrity status.
1021 fail_make_request=[KNL]
1022 General fault injection mechanism.
1023 Format: <interval>,<probability>,<space>,<times>
1024 See also Documentation/fault-injection/.
1027 See Documentation/blockdev/floppy.txt.
1029 force_pal_cache_flush
1030 [IA-64] Avoid check_sal_cache_flush which may hang on
1031 buggy SAL_CACHE_FLUSH implementations. Using this
1032 parameter will force ia64_sal_cache_flush to call
1033 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1036 Forcefully enable Physical Address Extension (PAE).
1037 Many Pentium M systems disable PAE but may have a
1038 functionally usable PAE implementation.
1039 Warning: use of this parameter will taint the kernel
1040 and may cause unknown problems.
1043 [FTRACE] will set and start the specified tracer
1044 as early as possible in order to facilitate early
1047 ftrace_dump_on_oops[=orig_cpu]
1048 [FTRACE] will dump the trace buffers on oops.
1049 If no parameter is passed, ftrace will dump
1050 buffers of all CPUs, but if you pass orig_cpu, it will
1051 dump only the buffer of the CPU that triggered the
1054 ftrace_filter=[function-list]
1055 [FTRACE] Limit the functions traced by the function
1056 tracer at boot up. function-list is a comma separated
1057 list of functions. This list can be changed at run
1058 time by the set_ftrace_filter file in the debugfs
1061 ftrace_notrace=[function-list]
1062 [FTRACE] Do not trace the functions specified in
1063 function-list. This list can be changed at run time
1064 by the set_ftrace_notrace file in the debugfs
1067 ftrace_graph_filter=[function-list]
1068 [FTRACE] Limit the top level callers functions traced
1069 by the function graph tracer at boot up.
1070 function-list is a comma separated list of functions
1071 that can be changed at run time by the
1072 set_graph_function file in the debugfs tracing directory.
1075 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1076 support via parallel port (up to 5 devices per port)
1077 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1078 See also Documentation/input/joystick-parport.txt
1082 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1086 gcov_persist= [GCOV] When non-zero (default), profiling data for
1087 kernel modules is saved and remains accessible via
1088 debugfs, even when the module is unloaded/reloaded.
1089 When zero, profiling data is discarded and associated
1090 debugfs files are removed at module unload time.
1092 gpt [EFI] Forces disk with valid GPT signature but
1093 invalid Protective MBR to be treated as GPT. If the
1094 primary GPT is corrupted, it enables the backup/alternate
1095 GPT to be used instead.
1097 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1098 the "Enable 0" bit of the configuration register.
1101 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1102 the "Enable 0" bit of the configuration register.
1105 grcan.select= [HW] Select which physical interface to use.
1108 grcan.txsize= [HW] Sets the size of the tx buffer.
1109 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1111 grcan.rxsize= [HW] Sets the size of the rx buffer.
1112 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1115 hashdist= [KNL,NUMA] Large hashes allocated during boot
1116 are distributed across NUMA nodes. Defaults on
1117 for 64-bit NUMA, off otherwise.
1118 Format: 0 | 1 (for off | on)
1120 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1122 hd= [EIDE] (E)IDE hard drive subsystem geometry
1123 Format: <cyl>,<head>,<sect>
1126 Disable Hardware Error Source Table (HEST) support;
1127 corresponding firmware-first mode error processing
1128 logic will be disabled.
1130 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1131 size of <nn>. This works even on boxes that have no
1132 highmem otherwise. This also works to reduce highmem
1133 size on bigger boxes.
1135 highres= [KNL] Enable/disable high resolution timer mode.
1136 Valid parameters: "on", "off"
1140 See Documentation/isdn/README.HiSax.
1144 hpet= [X86-32,HPET] option to control HPET usage
1145 Format: { enable (default) | disable | force |
1147 disable: disable HPET and use PIT instead
1148 force: allow force enabled of undocumented chips (ICH4,
1150 verbose: show contents of HPET registers during setup
1152 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1153 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1155 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1156 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1157 On x86-64 and powerpc, this option can be specified
1158 multiple times interleaved with hugepages= to reserve
1159 huge pages of different sizes. Valid pages sizes on
1160 x86-64 are 2M (when the CPU supports "pse") and 1G
1161 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1162 Note that 1GB pages can only be allocated at boot time
1163 using hugepages= and not freed afterwards.
1165 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1166 terminal devices. Valid values: 0..8
1167 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1168 If specified, z/VM IUCV HVC accepts connections
1169 from listed z/VM user IDs only.
1171 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1172 hardware thread id mappings.
1173 Format: <cpu>:<hwthread>
1176 Do not unregister boot console at start. This is only
1177 useful for debugging when something happens in the window
1178 between unregistering the boot console and initializing
1181 i2c_bus= [HW] Override the default board specific I2C bus speed
1182 or register an additional I2C bus that is not
1183 registered from board initialization code.
1187 i8042.debug [HW] Toggle i8042 debug mode
1188 i8042.direct [HW] Put keyboard port into non-translated mode
1189 i8042.dumbkbd [HW] Pretend that controller can only read data from
1190 keyboard and cannot control its state
1191 (Don't attempt to blink the leds)
1192 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1193 i8042.nokbd [HW] Don't check/create keyboard port
1194 i8042.noloop [HW] Disable the AUX Loopback command while probing
1196 i8042.nomux [HW] Don't check presence of an active multiplexing
1198 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1200 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1201 i8042.reset [HW] Reset the controller during init and cleanup
1202 i8042.unlock [HW] Unlock (ignore) the keylock
1206 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1207 indicates that the driver is running on unsupported
1209 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1210 does not match list of supported models.
1212 [HW] Report power status in /proc/i8k
1213 (disabled by default)
1214 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1217 i915.invert_brightness=
1218 [DRM] Invert the sense of the variable that is used to
1219 set the brightness of the panel backlight. Normally a
1220 brightness value of 0 indicates backlight switched off,
1221 and the maximum of the brightness value sets the backlight
1222 to maximum brightness. If this parameter is set to 0
1223 (default) and the machine requires it, or this parameter
1224 is set to 1, a brightness value of 0 sets the backlight
1225 to maximum brightness, and the maximum of the brightness
1226 value switches the backlight off.
1227 -1 -- never invert brightness
1228 0 -- machine default
1229 1 -- force brightness inversion
1232 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1234 ide-core.nodma= [HW] (E)IDE subsystem
1235 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1236 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1237 .cdrom .chs .ignore_cable are additional options
1238 See Documentation/ide/ide.txt.
1240 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1241 Claim all unknown PCI IDE storage controllers.
1244 Format: idle=poll, idle=halt, idle=nomwait
1245 Poll forces a polling idle loop that can slightly
1246 improve the performance of waking up a idle CPU, but
1247 will use a lot of power and make the system run hot.
1249 idle=halt: Halt is forced to be used for CPU idle.
1250 In such case C2/C3 won't be used again.
1251 idle=nomwait: Disable mwait for CPU C-states
1253 ignore_loglevel [KNL]
1254 Ignore loglevel setting - this will print /all/
1255 kernel messages to the console. Useful for debugging.
1256 We also add it as printk module parameter, so users
1257 could change it dynamically, usually by
1258 /sys/module/printk/parameters/ignore_loglevel.
1260 ihash_entries= [KNL]
1261 Set number of hash buckets for inode cache.
1263 ima_appraise= [IMA] appraise integrity measurements
1264 Format: { "off" | "enforce" | "fix" }
1267 ima_appraise_tcb [IMA]
1268 The builtin appraise policy appraises all files
1272 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1276 The list of supported hash algorithms is defined
1277 in crypto/hash_info.h.
1280 Load a policy which meets the needs of the Trusted
1281 Computing Base. This means IMA will measure all
1282 programs exec'd, files mmap'd for exec, and all files
1283 opened for read by uid=0.
1286 Select one of defined IMA measurements template formats.
1287 Formats: { "ima" | "ima-ng" }
1292 Run specified binary instead of /sbin/init as init
1295 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1296 for working out where the kernel is dying during
1299 initrd= [BOOT] Specify the location of the initial ramdisk
1301 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1304 int_pln_enable [x86] Enable power limit notification interrupt
1306 integrity_audit=[IMA]
1307 Format: { "0" | "1" }
1308 0 -- basic integrity auditing messages. (Default)
1309 1 -- additional integrity auditing messages.
1311 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1313 Enable intel iommu driver.
1315 Disable intel iommu driver.
1316 igfx_off [Default Off]
1317 By default, gfx is mapped as normal device. If a gfx
1318 device has a dedicated DMAR unit, the DMAR unit is
1319 bypassed by not enabling DMAR with this option. In
1320 this case, gfx device will use physical address for
1323 With this option iommu will not optimize to look
1324 for io virtual address below 32-bit forcing dual
1325 address cycle on pci bus for cards supporting greater
1326 than 32-bit addressing. The default is to look
1327 for translation below 32-bit and if not available
1328 then look in the higher range.
1329 strict [Default Off]
1330 With this option on every unmap_single operation will
1331 result in a hardware IOTLB flush operation as opposed
1332 to batching them for performance.
1333 sp_off [Default Off]
1334 By default, super page will be supported if Intel IOMMU
1335 has the capability. With this option, super page will
1338 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1339 0 disables intel_idle and fall back on acpi_idle.
1340 1 to 6 specify maximum depth of C-state.
1344 Do not enable intel_pstate as the default
1345 scaling driver for the supported processors
1347 intremap= [X86-64, Intel-IOMMU]
1348 on enable Interrupt Remapping (default)
1349 off disable Interrupt Remapping
1350 nosid disable Source ID checking
1352 BIOS x2APIC opt-out request will be ignored
1354 iomem= Disable strict checking of access to MMIO memory
1355 strict regions from userspace.
1372 io7= [HW] IO7 for Marvel based alpha systems
1373 See comment before marvel_specify_io7 in
1374 arch/alpha/kernel/core_marvel.c.
1376 io_delay= [X86] I/O delay method
1378 Standard port 0x80 based delay
1380 Alternate port 0xed based delay (needed on some systems)
1382 Simple two microseconds delay
1387 See Documentation/filesystems/nfs/nfsroot.txt.
1389 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1390 See comment before ip2_setup() in
1391 drivers/char/ip2/ip2base.c.
1394 When an interrupt is not handled search all handlers
1395 for it. Intended to get systems with badly broken
1399 When an interrupt is not handled search all handlers
1400 for it. Also check all handlers each timer
1401 interrupt. Intended to get systems with badly broken
1405 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1407 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1409 <cpu number>,...,<cpu number>
1411 <cpu number>-<cpu number>
1412 (must be a positive range in ascending order)
1414 <cpu number>,...,<cpu number>-<cpu number>
1416 This option can be used to specify one or more CPUs
1417 to isolate from the general SMP balancing and scheduling
1418 algorithms. You can move a process onto or off an
1419 "isolated" CPU via the CPU affinity syscalls or cpuset.
1420 <cpu number> begins at 0 and the maximum value is
1421 "number of CPUs in system - 1".
1423 This option is the preferred way to isolate CPUs. The
1424 alternative -- manually setting the CPU mask of all
1425 tasks in the system -- can cause problems and
1426 suboptimal load balancer performance.
1430 ivrs_ioapic [HW,X86_64]
1431 Provide an override to the IOAPIC-ID<->DEVICE-ID
1432 mapping provided in the IVRS ACPI table. For
1433 example, to map IOAPIC-ID decimal 10 to
1434 PCI device 00:14.0 write the parameter as:
1435 ivrs_ioapic[10]=00:14.0
1437 ivrs_hpet [HW,X86_64]
1438 Provide an override to the HPET-ID<->DEVICE-ID
1439 mapping provided in the IVRS ACPI table. For
1440 example, to map HPET-ID decimal 0 to
1441 PCI device 00:14.0 write the parameter as:
1442 ivrs_hpet[0]=00:14.0
1444 js= [HW,JOY] Analog joystick
1445 See Documentation/input/joystick.txt.
1449 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1450 specifies the amount of memory usable by the kernel
1451 for non-movable allocations. The requested amount is
1452 spread evenly throughout all nodes in the system. The
1453 remaining memory in each node is used for Movable
1454 pages. In the event, a node is too small to have both
1455 kernelcore and Movable pages, kernelcore pages will
1456 take priority and other nodes will have a larger number
1457 of Movable pages. The Movable zone is used for the
1458 allocation of pages that may be reclaimed or moved
1459 by the page migration subsystem. This means that
1460 HugeTLB pages may not be allocated from this zone.
1461 Note that allocations like PTEs-from-HighMem still
1462 use the HighMem zone if it exists, and the Normal
1463 zone if it does not.
1465 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1466 Format: <Controller#>[,poll interval]
1467 The controller # is the number of the ehci usb debug
1468 port as it is probed via PCI. The poll interval is
1469 optional and is the number seconds in between
1470 each poll cycle to the debug port in case you need
1471 the functionality for interrupting the kernel with
1472 gdb or control-c on the dbgp connection. When
1473 not using this parameter you use sysrq-g to break into
1474 the kernel debugger.
1476 kgdboc= [KGDB,HW] kgdb over consoles.
1477 Requires a tty driver that supports console polling,
1478 or a supported polling keyboard driver (non-usb).
1479 Serial only format: <serial_device>[,baud]
1480 keyboard only format: kbd
1481 keyboard and serial format: kbd,<serial_device>[,baud]
1482 Optional Kernel mode setting:
1483 kms, kbd format: kms,kbd
1484 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1486 kgdbwait [KGDB] Stop kernel execution and enter the
1487 kernel debugger at the earliest opportunity.
1489 kmac= [MIPS] korina ethernet MAC address.
1490 Configure the RouterBoard 532 series on-chip
1491 Ethernet adapter MAC address.
1493 kmemleak= [KNL] Boot-time kmemleak enable/disable
1494 Valid arguments: on, off
1497 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1498 Valid arguments: 0, 1, 2
1499 kmemcheck=0 (disabled)
1500 kmemcheck=1 (enabled)
1501 kmemcheck=2 (one-shot mode)
1502 Default: 2 (one-shot mode)
1504 kstack=N [X86] Print N words from the kernel stack
1507 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1508 Default is 0 (don't ignore, but inject #GP)
1510 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1514 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1515 Default is 1 (enabled)
1517 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1519 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1521 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1522 (virtualized MMU) support on capable Intel chips.
1523 Default is 1 (enabled)
1525 kvm-intel.emulate_invalid_guest_state=
1526 [KVM,Intel] Enable emulation of invalid guest states
1527 Default is 0 (disabled)
1529 kvm-intel.flexpriority=
1530 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1531 Default is 1 (enabled)
1534 [KVM,Intel] Enable VMX nesting (nVMX).
1535 Default is 0 (disabled)
1537 kvm-intel.unrestricted_guest=
1538 [KVM,Intel] Disable unrestricted guest feature
1539 (virtualized real and unpaged mode) on capable
1540 Intel chips. Default is 1 (enabled)
1542 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1543 feature (tagged TLBs) on capable Intel chips.
1544 Default is 1 (enabled)
1550 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1553 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1554 value for LAPIC timer one-shot implementation. Default
1555 back to the programmable timer unit in the LAPIC.
1557 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1560 libata.dma= [LIBATA] DMA control
1561 libata.dma=0 Disable all PATA and SATA DMA
1562 libata.dma=1 PATA and SATA Disk DMA only
1563 libata.dma=2 ATAPI (CDROM) DMA only
1564 libata.dma=4 Compact Flash DMA only
1565 Combinations also work, so libata.dma=3 enables DMA
1566 for disks and CDROMs, but not CFs.
1568 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1569 libata.ignore_hpa=0 keep BIOS limits (default)
1570 libata.ignore_hpa=1 ignore limits, using full disk
1572 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1576 libata.force= [LIBATA] Force configurations. The format is comma
1577 separated list of "[ID:]VAL" where ID is
1578 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1579 matching port, link or device. Basically, it matches
1580 the ATA ID string printed on console by libata. If
1581 the whole ID part is omitted, the last PORT and DEVICE
1582 values are used. If ID hasn't been specified yet, the
1583 configuration applies to all ports, links and devices.
1585 If only DEVICE is omitted, the parameter applies to
1586 the port and all links and devices behind it. DEVICE
1587 number of 0 either selects the first device or the
1588 first fan-out link behind PMP device. It does not
1589 select the host link. DEVICE number of 15 selects the
1590 host link and device attached to it.
1592 The VAL specifies the configuration to force. As long
1593 as there's no ambiguity shortcut notation is allowed.
1594 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1595 The following configurations can be forced.
1597 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1598 Any ID with matching PORT is used.
1600 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1602 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1603 udma[/][16,25,33,44,66,100,133] notation is also
1606 * [no]ncq: Turn on or off NCQ.
1608 * nohrst, nosrst, norst: suppress hard, soft
1611 * rstonce: only attempt one reset during
1612 hot-unplug link recovery
1614 * dump_id: dump IDENTIFY data.
1616 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1618 * disable: Disable this device.
1620 If there are multiple matching configurations changing
1621 the same attribute, the last one is used.
1623 memblock=debug [KNL] Enable memblock debug messages.
1625 load_ramdisk= [RAM] List of ramdisks to load from floppy
1626 See Documentation/blockdev/ramdisk.txt.
1628 lockd.nlm_grace_period=P [NFS] Assign grace period.
1631 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1634 lockd.nlm_timeout=T [NFS] Assign timeout value.
1637 lockd.nlm_udpport=M [NFS] Assign UDP port.
1640 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1643 loglevel= All Kernel Messages with a loglevel smaller than the
1644 console loglevel will be printed to the console. It can
1645 also be changed with klogd or other programs. The
1646 loglevels are defined as follows:
1648 0 (KERN_EMERG) system is unusable
1649 1 (KERN_ALERT) action must be taken immediately
1650 2 (KERN_CRIT) critical conditions
1651 3 (KERN_ERR) error conditions
1652 4 (KERN_WARNING) warning conditions
1653 5 (KERN_NOTICE) normal but significant condition
1654 6 (KERN_INFO) informational
1655 7 (KERN_DEBUG) debug-level messages
1657 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1658 in bytes. n must be a power of two. The default
1659 size is set in the kernel config file.
1661 logo.nologo [FB] Disables display of the built-in Linux logo.
1662 This may be used to provide more screen space for
1663 kernel log messages and is useful when debugging
1664 kernel boot problems.
1666 lp=0 [LP] Specify parallel ports to use, e.g,
1667 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1668 lp=reset first parallel port). 'lp=0' disables the
1669 lp=auto printer driver. 'lp=reset' (which can be
1670 specified in addition to the ports) causes
1671 attached printers to be reset. Using
1672 lp=port1,port2,... specifies the parallel ports
1673 to associate lp devices with, starting with
1674 lp0. A port specification may be 'none' to skip
1675 that lp device, or a parport name such as
1676 'parport0'. Specifying 'lp=auto' instead of a
1677 port specification list means that device IDs
1678 from each port should be examined, to see if
1679 an IEEE 1284-compliant printer is attached; if
1680 so, the driver will manage that printer.
1681 See also header of drivers/char/lp.c.
1684 Sets loops_per_jiffy to given constant, thus avoiding
1685 time-consuming boot-time autodetection (up to 250 ms per
1686 CPU). 0 enables autodetection (default). To determine
1687 the correct value for your kernel, boot with normal
1688 autodetection and see what value is printed. Note that
1689 on SMP systems the preset will be applied to all CPUs,
1690 which is likely to cause problems if your CPUs need
1691 significantly divergent settings. An incorrect value
1692 will cause delays in the kernel to be wrong, leading to
1693 unpredictable I/O errors and other breakage. Although
1694 unlikely, in the extreme case this might damage your
1698 Format: <io>,<irq>,<dma>
1700 machvec= [IA-64] Force the use of a particular machine-vector
1701 (machvec) in a generic kernel.
1702 Example: machvec=hpzx1_swiotlb
1704 machtype= [Loongson] Share the same kernel image file between different
1706 Example: machtype=lemote-yeeloong-2f-7inch
1708 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1709 than or equal to this physical address is ignored.
1711 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1712 should make use of. maxcpus=n : n >= 0 limits the
1713 kernel to using 'n' processors. n=0 is a special case,
1714 it is equivalent to "nosmp", which also disables
1717 max_loop= [LOOP] The number of loop block devices that get
1718 (loop.max_loop) unconditionally pre-created at init time. The default
1719 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1720 of statically allocating a predefined number, loop
1721 devices can be requested on-demand with the
1722 /dev/loop-control interface.
1724 mce [X86-32] Machine Check Exception
1726 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1728 md= [HW] RAID subsystems devices and level
1729 See Documentation/md.txt.
1732 Format: <first>,<last>
1733 Specifies range of consoles to be captured by the MDA.
1735 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1736 Amount of memory to be used when the kernel is not able
1737 to see the whole system memory or for test.
1738 [X86] Work as limiting max address. Use together
1739 with memmap= to avoid physical address space collisions.
1740 Without memmap= PCI devices could be placed at addresses
1741 belonging to unused RAM.
1743 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1747 [KNL,SH] Allow user to override the default size for
1748 per-device physically contiguous DMA buffers.
1750 memmap=exactmap [KNL,X86] Enable setting of an exact
1751 E820 memory map, as specified by the user.
1752 Such memmap=exactmap lines can be constructed based on
1753 BIOS output or other requirements. See the memmap=nn@ss
1756 memmap=nn[KMG]@ss[KMG]
1757 [KNL] Force usage of a specific region of memory.
1758 Region of memory to be used is from ss to ss+nn.
1760 memmap=nn[KMG]#ss[KMG]
1761 [KNL,ACPI] Mark specific memory as ACPI data.
1762 Region of memory to be marked is from ss to ss+nn.
1764 memmap=nn[KMG]$ss[KMG]
1765 [KNL,ACPI] Mark specific memory as reserved.
1766 Region of memory to be reserved is from ss to ss+nn.
1767 Example: Exclude memory from 0x18690000-0x1869ffff
1768 memmap=64K$0x18690000
1770 memmap=0x10000$0x18690000
1772 memory_corruption_check=0/1 [X86]
1773 Some BIOSes seem to corrupt the first 64k of
1774 memory when doing things like suspend/resume.
1775 Setting this option will scan the memory
1776 looking for corruption. Enabling this will
1777 both detect corruption and prevent the kernel
1778 from using the memory being corrupted.
1779 However, its intended as a diagnostic tool; if
1780 repeatable BIOS-originated corruption always
1781 affects the same memory, you can use memmap=
1782 to prevent the kernel from using that memory.
1784 memory_corruption_check_size=size [X86]
1785 By default it checks for corruption in the low
1786 64k, making this memory unavailable for normal
1787 use. Use this parameter to scan for
1788 corruption in more or less memory.
1790 memory_corruption_check_period=seconds [X86]
1791 By default it checks for corruption every 60
1792 seconds. Use this parameter to check at some
1793 other rate. 0 disables periodic checking.
1795 memtest= [KNL,X86] Enable memtest
1797 default : 0 <disable>
1798 Specifies the number of memtest passes to be
1799 performed. Each pass selects another test
1800 pattern from a given set of patterns. Memtest
1801 fills the memory with this pattern, validates
1802 memory contents and reserves bad memory
1803 regions that are detected.
1805 meye.*= [HW] Set MotionEye Camera parameters
1806 See Documentation/video4linux/meye.txt.
1808 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1809 Multi-Function General Purpose Timers on AMD Geode
1812 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1813 the BIOS has incorrectly applied a workaround. TinyBIOS
1814 version 0.98 is known to be affected, 0.99 fixes the
1815 problem by letting the user disable the workaround.
1819 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1820 physical address is ignored.
1822 mini2440= [ARM,HW,KNL]
1823 Format:[0..2][b][c][t]
1825 MINI2440 configuration specification:
1826 0 - The attached screen is the 3.5" TFT
1827 1 - The attached screen is the 7" TFT
1828 2 - The VGA Shield is attached (1024x768)
1829 Leaving out the screen size parameter will not load
1830 the TFT driver, and the framebuffer will be left
1832 b - Enable backlight. The TFT backlight pin will be
1833 linked to the kernel VESA blanking code and a GPIO
1834 LED. This parameter is not necessary when using the
1836 c - Enable the s3c camera interface.
1837 t - Reserved for enabling touchscreen support. The
1838 touchscreen support is not enabled in the mainstream
1839 kernel as of 2.6.30, a preliminary port can be found
1840 in the "bleeding edge" mini2440 support kernel at
1841 http://repo.or.cz/w/linux-2.6/mini2440.git
1844 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1845 parameter allows control of the logging verbosity for
1846 the additional memory initialisation checks. A value
1847 of 0 disables mminit logging and a level of 4 will
1848 log everything. Information is printed at KERN_DEBUG
1849 so loglevel=8 may also need to be specified.
1852 [KNL] When CONFIG_MODULE_SIG is set, this means that
1853 modules without (valid) signatures will fail to load.
1854 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1855 is always true, so this option does nothing.
1858 [MOUSE] Maximum time between finger touching and
1859 leaving touchpad surface for touch to be considered
1860 a tap and be reported as a left button click (for
1861 touchpads working in absolute mode only).
1863 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1864 reporting absolute coordinates, such as tablets
1865 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1866 reporting absolute coordinates, such as tablets
1868 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1869 is similar to kernelcore except it specifies the
1870 amount of memory used for migratable allocations.
1871 If both kernelcore and movablecore is specified,
1872 then kernelcore will be at *least* the specified
1873 value but may be more. If movablecore on its own
1874 is specified, the administrator must be careful
1875 that the amount of memory usable for all allocations
1878 movable_node [KNL,X86] Boot-time switch to enable the effects
1879 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1881 MTD_Partition= [MTD]
1882 Format: <name>,<region-number>,<size>,<offset>
1884 MTD_Region= [MTD] Format:
1885 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1888 See drivers/mtd/cmdlinepart.c.
1890 multitce=off [PPC] This parameter disables the use of the pSeries
1891 firmware feature for updating multiple TCE entries
1894 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1896 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1898 boundary - index of last SLC block on Flex-OneNAND.
1899 The remaining blocks are configured as MLC blocks.
1900 lock - Configure if Flex-OneNAND boundary should be locked.
1901 Once locked, the boundary cannot be changed.
1902 1 indicates lock status, 0 indicates unlock status.
1905 ARM/S3C2412 JIVE boot control
1907 See arch/arm/mach-s3c2412/mach-jive.c
1909 mtouchusb.raw_coordinates=
1910 [HW] Make the MicroTouch USB driver use raw coordinates
1911 ('y', default) or cooked coordinates ('n')
1913 mtrr_chunk_size=nn[KMG] [X86]
1914 used for mtrr cleanup. It is largest continuous chunk
1915 that could hold holes aka. UC entries.
1917 mtrr_gran_size=nn[KMG] [X86]
1918 Used for mtrr cleanup. It is granularity of mtrr block.
1920 Large value could prevent small alignment from
1923 mtrr_spare_reg_nr=n [X86]
1925 Range: 0,7 : spare reg number
1927 Used for mtrr cleanup. It is spare mtrr entries number.
1928 Set to 2 or more if your graphical card needs more.
1930 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1932 netdev= [NET] Network devices parameters
1933 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1934 Note that mem_start is often overloaded to mean
1935 something different and driver-specific.
1936 This usage is only documented in each driver source
1940 [NETFILTER] Enable connection tracking flow accounting
1941 0 to disable accounting
1942 1 to enable accounting
1945 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1946 See Documentation/filesystems/nfs/nfsroot.txt.
1948 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1949 See Documentation/filesystems/nfs/nfsroot.txt.
1951 nfsrootdebug [NFS] enable nfsroot debugging messages.
1952 See Documentation/filesystems/nfs/nfsroot.txt.
1954 nfs.callback_tcpport=
1955 [NFS] set the TCP port on which the NFSv4 callback
1956 channel should listen.
1959 [NFS] sets the pathname to the program which is used
1960 to update the NFS client cache entries.
1962 nfs.cache_getent_timeout=
1963 [NFS] sets the timeout after which an attempt to
1964 update a cache entry is deemed to have failed.
1966 nfs.idmap_cache_timeout=
1967 [NFS] set the maximum lifetime for idmapper cache
1971 [NFS] enable 64-bit inode numbers.
1972 If zero, the NFS client will fake up a 32-bit inode
1973 number for the readdir() and stat() syscalls instead
1974 of returning the full 64-bit number.
1975 The default is to return 64-bit inode numbers.
1977 nfs.max_session_slots=
1978 [NFSv4.1] Sets the maximum number of session slots
1979 the client will attempt to negotiate with the server.
1980 This limits the number of simultaneous RPC requests
1981 that the client can send to the NFSv4.1 server.
1982 Note that there is little point in setting this
1983 value higher than the max_tcp_slot_table_limit.
1985 nfs.nfs4_disable_idmapping=
1986 [NFSv4] When set to the default of '1', this option
1987 ensures that both the RPC level authentication
1988 scheme and the NFS level operations agree to use
1989 numeric uids/gids if the mount is using the
1990 'sec=sys' security flavour. In effect it is
1991 disabling idmapping, which can make migration from
1992 legacy NFSv2/v3 systems to NFSv4 easier.
1993 Servers that do not support this mode of operation
1994 will be autodetected by the client, and it will fall
1995 back to using the idmapper.
1996 To turn off this behaviour, set the value to '0'.
1998 [NFS4] Specify an additional fixed unique ident-
1999 ification string that NFSv4 clients can insert into
2000 their nfs_client_id4 string. This is typically a
2001 UUID that is generated at system install time.
2003 nfs.send_implementation_id =
2004 [NFSv4.1] Send client implementation identification
2005 information in exchange_id requests.
2006 If zero, no implementation identification information
2008 The default is to send the implementation identification
2011 nfs.recover_lost_locks =
2012 [NFSv4] Attempt to recover locks that were lost due
2013 to a lease timeout on the server. Please note that
2014 doing this risks data corruption, since there are
2015 no guarantees that the file will remain unchanged
2016 after the locks are lost.
2017 If you want to enable the kernel legacy behaviour of
2018 attempting to recover these locks, then set this
2020 The default parameter value of '0' causes the kernel
2021 not to attempt recovery of lost locks.
2023 nfsd.nfs4_disable_idmapping=
2024 [NFSv4] When set to the default of '1', the NFSv4
2025 server will return only numeric uids and gids to
2026 clients using auth_sys, and will accept numeric uids
2027 and gids from such clients. This is intended to ease
2028 migration from NFSv2/v3.
2030 objlayoutdriver.osd_login_prog=
2031 [NFS] [OBJLAYOUT] sets the pathname to the program which
2032 is used to automatically discover and login into new
2033 osd-targets. Please see:
2034 Documentation/filesystems/pnfs.txt for more explanations
2036 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2037 when a NMI is triggered.
2038 Format: [state][,regs][,debounce][,die]
2040 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2041 Format: [panic,][nopanic,][num]
2043 0 - turn nmi_watchdog off
2044 When panic is specified, panic when an NMI watchdog
2045 timeout occurs (or 'nopanic' to override the opposite
2047 This is useful when you use a panic=... timeout and
2048 need the box quickly up again.
2050 netpoll.carrier_timeout=
2051 [NET] Specifies amount of time (in seconds) that
2052 netpoll should wait for a carrier. By default netpoll
2055 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2056 emulation library even if a 387 maths coprocessor
2060 [HW] Never suspend the console
2061 Disable suspending of consoles during suspend and
2062 hibernate operations. Once disabled, debugging
2063 messages can reach various consoles while the rest
2064 of the system is being put to sleep (ie, while
2065 debugging driver suspend/resume hooks). This may
2066 not work reliably with all consoles, but is known
2067 to work with serial and VGA consoles.
2068 To facilitate more flexible debugging, we also add
2069 console_suspend, a printk module parameter to control
2070 it. Users could use console_suspend (usually
2071 /sys/module/printk/parameters/console_suspend) to
2072 turn on/off it dynamically.
2074 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2075 caches in the slab allocator. Saves per-node memory,
2076 but will impact performance.
2080 noapic [SMP,APIC] Tells the kernel to not make use of any
2081 IOAPICs that may be present in the system.
2084 Disable kernel and module base offset ASLR (Address
2085 Space Layout Randomization) if built into the kernel.
2087 noautogroup Disable scheduler automatic task group creation.
2089 nobats [PPC] Do not use BATs for mapping kernel lowmem
2090 on "Classic" PPC cores.
2094 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2096 nodelayacct [KNL] Disable per-task delay accounting
2098 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2100 nodsp [SH] Disable hardware DSP at boot time.
2102 noefi [X86] Disable EFI runtime services support.
2107 On X86-32 available only on PAE configured kernels.
2108 noexec=on: enable non-executable mappings (default)
2109 noexec=off: disable non-executable mappings
2112 Disable SMAP (Supervisor Mode Access Prevention)
2113 even if it is supported by processor.
2116 Disable SMEP (Supervisor Mode Execution Prevention)
2117 even if it is supported by processor.
2120 This affects only 32-bit executables.
2121 noexec32=on: enable non-executable mappings (default)
2122 read doesn't imply executable mappings
2123 noexec32=off: disable non-executable mappings
2124 read implies executable mappings
2126 nofpu [SH] Disable hardware FPU at boot time.
2128 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2129 register save and restore. The kernel will only save
2130 legacy floating-point registers on task switch.
2132 noxsave [BUGS=X86] Disables x86 extended register state save
2133 and restore using xsave. The kernel will fallback to
2134 enabling legacy floating-point and sse state.
2137 on enable eager fpu restore
2138 off disable eager fpu restore
2139 auto selects the default scheme, which automatically
2140 enables eagerfpu restore for xsaveopt.
2142 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2143 wfi(ARM) instruction doesn't work correctly and not to
2144 use it. This is also useful when using JTAG debugger.
2146 no_file_caps Tells the kernel not to honor file capabilities. The
2147 only way then for a file to be executed with privilege
2148 is to be setuid root or executed by root.
2150 nohalt [IA-64] Tells the kernel not to use the power saving
2151 function PAL_HALT_LIGHT when idle. This increases
2152 power-consumption. On the positive side, it reduces
2153 interrupt wake-up latency, which may improve performance
2154 in certain environments such as networked servers or
2157 nohz= [KNL] Boottime enable/disable dynamic ticks
2158 Valid arguments: on, off
2161 nohz_full= [KNL,BOOT]
2162 In kernels built with CONFIG_NO_HZ_FULL=y, set
2163 the specified list of CPUs whose tick will be stopped
2164 whenever possible. The boot CPU will be forced outside
2165 the range to maintain the timekeeping.
2166 The CPUs in this range must also be included in the
2169 noiotrap [SH] Disables trapped I/O port accesses.
2171 noirqdebug [X86-32] Disables the code which attempts to detect and
2172 disable unhandled interrupt sources.
2174 no_timer_check [X86,APIC] Disables the code which tests for
2175 broken timer IRQ sources.
2177 noisapnp [ISAPNP] Disables ISA PnP code.
2179 noinitrd [RAM] Tells the kernel not to load any configured
2182 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2184 [Deprecated - use intremap=off]
2188 nojitter [IA-64] Disables jitter checking for ITC timers.
2190 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2192 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2195 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2196 steal time is computed, but won't influence scheduler
2199 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2201 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2203 noltlbs [PPC] Do not use large page/tlb entries for kernel
2204 lowmem mapping on PPC40x.
2206 nomca [IA-64] Disable machine check abort handling
2208 nomce [X86-32] Machine Check Exception
2210 nomfgpt [X86-32] Disable Multi-Function General Purpose
2211 Timer usage (for AMD Geode machines).
2213 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2214 shutdown the other cpus. Instead use the REBOOT_VECTOR
2217 nomodule Disable module load
2219 nopat [X86] Disable PAT (page attribute table extension of
2220 pagetables) support.
2222 norandmaps Don't use address space randomization. Equivalent to
2223 echo 0 > /proc/sys/kernel/randomize_va_space
2225 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2227 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2228 with UP alternatives
2230 nordrand [X86] Disable kernel use of the RDRAND and
2231 RDSEED instructions even if they are supported
2232 by the processor. RDRAND and RDSEED are still
2233 available to user space applications.
2235 noresume [SWSUSP] Disables resume and restores original swap
2238 no-scroll [VGA] Disables scrollback.
2239 This is required for the Braillex ib80-piezo Braille
2240 reader made by F.H. Papenmeier (Germany).
2244 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2246 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2247 and disable the IO APIC. legacy for "maxcpus=0".
2249 nosoftlockup [KNL] Disable the soft-lockup detector.
2251 nosync [HW,M68K] Disables sync negotiation for all devices.
2253 notsc [BUGS=X86-32] Disable Time Stamp Counter
2255 nousb [USB] Disable the USB subsystem
2257 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2261 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2263 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2264 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2265 Some features depend on CPU0. Known dependencies are:
2266 1. Resume from suspend/hibernate depends on CPU0.
2267 Suspend/hibernate will fail if CPU0 is offline and you
2268 need to online CPU0 before suspend/hibernate.
2269 2. PIC interrupts also depend on CPU0. CPU0 can't be
2270 removed if a PIC interrupt is detected.
2271 It's said poweroff/reboot may depend on CPU0 on some
2272 machines although I haven't seen such issues so far
2273 after CPU0 is offline on a few tested machines.
2274 If the dependencies are under your control, you can
2275 turn on cpu0_hotplug.
2277 nptcg= [IA-64] Override max number of concurrent global TLB
2278 purges which is reported from either PAL_VM_SUMMARY or
2281 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2282 could support. nr_cpus=n : n >= 1 limits the kernel to
2283 supporting 'n' processors. Later in runtime you can not
2284 use hotplug cpu feature to put more cpu back to online.
2285 just like you compile the kernel NR_CPUS=n
2287 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2289 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2290 Allowed values are enable and disable
2292 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2293 one of ['zone', 'node', 'default'] can be specified
2294 This can be set from sysctl after boot.
2295 See Documentation/sysctl/vm.txt for details.
2297 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2298 See Documentation/debugging-via-ohci1394.txt for more
2301 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2302 Rather than timing out after 20 ms if an EC
2303 command is not properly ACKed, override the length
2304 of the timeout. We have interrupts disabled while
2305 waiting for the ACK, so if this is set too high
2306 interrupts *may* be lost!
2308 omap_mux= [OMAP] Override bootloader pin multiplexing.
2309 Format: <mux_mode0.mode_name=value>...
2310 For example, to override I2C bus2:
2311 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2313 oprofile.timer= [HW]
2314 Use timer interrupt instead of performance counters
2316 oprofile.cpu_type= Force an oprofile cpu type
2317 This might be useful if you have an older oprofile
2318 userland or if you want common events.
2319 Format: { arch_perfmon }
2320 arch_perfmon: [X86] Force use of architectural
2321 perfmon on Intel CPUs instead of the
2322 CPU specific event set.
2323 timer: [X86] Force use of architectural NMI
2324 timer mode (see also oprofile.timer
2325 for generic hr timer mode)
2326 [s390] Force legacy basic mode sampling
2327 (report cpu_type "timer")
2329 oops=panic Always panic on oopses. Default is to just kill the
2330 process, but there is a small probability of
2331 deadlocking the machine.
2332 This will also cause panics on machine check exceptions.
2333 Useful together with panic=30 to trigger a reboot.
2336 See Documentation/sound/oss/oss-parameters.txt
2338 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2339 timeout > 0: seconds before rebooting
2340 timeout = 0: wait forever
2341 timeout < 0: reboot immediately
2344 parkbd.port= [HW] Parallel port number the keyboard adapter is
2345 connected to, default is 0.
2347 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2348 0 for XT, 1 for AT (default is AT).
2351 parport= [HW,PPT] Specify parallel ports. 0 disables.
2352 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2353 Use 'auto' to force the driver to use any
2354 IRQ/DMA settings detected (the default is to
2355 ignore detected IRQ/DMA settings because of
2356 possible conflicts). You can specify the base
2357 address, IRQ, and DMA settings; IRQ and DMA
2358 should be numbers, or 'auto' (for using detected
2359 settings on that particular port), or 'nofifo'
2360 (to avoid using a FIFO even if it is detected).
2361 Parallel ports are assigned in the order they
2362 are specified on the command line, starting
2365 parport_init_mode= [HW,PPT]
2366 Configure VIA parallel port to operate in
2367 a specific mode. This is necessary on Pegasos
2368 computer where firmware has no options for setting
2369 up parallel port mode and sets it to spp.
2370 Currently this function knows 686a and 8231 chips.
2371 Format: [spp|ps2|epp|ecp|ecpepp]
2374 Halt all CPUs after the first oops has been printed for
2375 the specified number of seconds. This is to be used if
2376 your oopses keep scrolling off the screen.
2381 See header of drivers/block/paride/pcd.c.
2382 See also Documentation/blockdev/paride.txt.
2384 pci=option[,option...] [PCI] various PCI subsystem options:
2385 earlydump [X86] dump PCI config space before the kernel
2387 off [X86] don't probe for the PCI bus
2388 bios [X86-32] force use of PCI BIOS, don't access
2389 the hardware directly. Use this if your machine
2390 has a non-standard PCI host bridge.
2391 nobios [X86-32] disallow use of PCI BIOS, only direct
2392 hardware access methods are allowed. Use this
2393 if you experience crashes upon bootup and you
2394 suspect they are caused by the BIOS.
2395 conf1 [X86] Force use of PCI Configuration
2397 conf2 [X86] Force use of PCI Configuration
2399 noaer [PCIE] If the PCIEAER kernel config parameter is
2400 enabled, this kernel boot option can be used to
2401 disable the use of PCIE advanced error reporting.
2402 nodomains [PCI] Disable support for multiple PCI
2403 root domains (aka PCI segments, in ACPI-speak).
2404 nommconf [X86] Disable use of MMCONFIG for PCI
2406 check_enable_amd_mmconf [X86] check for and enable
2407 properly configured MMIO access to PCI
2408 config space on AMD family 10h CPU
2409 nomsi [MSI] If the PCI_MSI kernel config parameter is
2410 enabled, this kernel boot option can be used to
2411 disable the use of MSI interrupts system-wide.
2412 noioapicquirk [APIC] Disable all boot interrupt quirks.
2413 Safety option to keep boot IRQs enabled. This
2414 should never be necessary.
2415 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2416 primary IO-APIC for bridges that cannot disable
2417 boot IRQs. This fixes a source of spurious IRQs
2418 when the system masks IRQs.
2419 noioapicreroute [APIC] Disable workaround that uses the
2420 boot IRQ equivalent of an IRQ that connects to
2421 a chipset where boot IRQs cannot be disabled.
2422 The opposite of ioapicreroute.
2423 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2424 routing table. These calls are known to be buggy
2425 on several machines and they hang the machine
2426 when used, but on other computers it's the only
2427 way to get the interrupt routing table. Try
2428 this option if the kernel is unable to allocate
2429 IRQs or discover secondary PCI buses on your
2431 rom [X86] Assign address space to expansion ROMs.
2432 Use with caution as certain devices share
2433 address decoders between ROMs and other
2435 norom [X86] Do not assign address space to
2436 expansion ROMs that do not already have
2437 BIOS assigned address ranges.
2438 nobar [X86] Do not assign address space to the
2439 BARs that weren't assigned by the BIOS.
2440 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2441 assigned automatically to PCI devices. You can
2442 make the kernel exclude IRQs of your ISA cards
2444 pirqaddr=0xAAAAA [X86] Specify the physical address
2445 of the PIRQ table (normally generated
2446 by the BIOS) if it is outside the
2447 F0000h-100000h range.
2448 lastbus=N [X86] Scan all buses thru bus #N. Can be
2449 useful if the kernel is unable to find your
2450 secondary buses and you want to tell it
2451 explicitly which ones they are.
2452 assign-busses [X86] Always assign all PCI bus
2453 numbers ourselves, overriding
2454 whatever the firmware may have done.
2455 usepirqmask [X86] Honor the possible IRQ mask stored
2456 in the BIOS $PIR table. This is needed on
2457 some systems with broken BIOSes, notably
2458 some HP Pavilion N5400 and Omnibook XE3
2459 notebooks. This will have no effect if ACPI
2460 IRQ routing is enabled.
2461 noacpi [X86] Do not use ACPI for IRQ routing
2462 or for PCI scanning.
2463 use_crs [X86] Use PCI host bridge window information
2464 from ACPI. On BIOSes from 2008 or later, this
2465 is enabled by default. If you need to use this,
2466 please report a bug.
2467 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2468 If you need to use this, please report a bug.
2469 routeirq Do IRQ routing for all PCI devices.
2470 This is normally done in pci_enable_device(),
2471 so this option is a temporary workaround
2472 for broken drivers that don't call it.
2473 skip_isa_align [X86] do not align io start addr, so can
2474 handle more pci cards
2475 firmware [ARM] Do not re-enumerate the bus but instead
2476 just use the configuration from the
2477 bootloader. This is currently used on
2478 IXP2000 systems where the bus has to be
2479 configured a certain way for adjunct CPUs.
2480 noearly [X86] Don't do any early type 1 scanning.
2481 This might help on some broken boards which
2482 machine check when some devices' config space
2483 is read. But various workarounds are disabled
2484 and some IOMMU drivers will not work.
2485 bfsort Sort PCI devices into breadth-first order.
2486 This sorting is done to get a device
2487 order compatible with older (<= 2.4) kernels.
2488 nobfsort Don't sort PCI devices into breadth-first order.
2489 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2490 tuning and use the BIOS-configured MPS defaults.
2491 pcie_bus_safe Set every device's MPS to the largest value
2492 supported by all devices below the root complex.
2493 pcie_bus_perf Set device MPS to the largest allowable MPS
2494 based on its parent bus. Also set MRRS (Max
2495 Read Request Size) to the largest supported
2496 value (no larger than the MPS that the device
2497 or bus can support) for best performance.
2498 pcie_bus_peer2peer Set every device's MPS to 128B, which
2499 every device is guaranteed to support. This
2500 configuration allows peer-to-peer DMA between
2501 any pair of devices, possibly at the cost of
2502 reduced performance. This also guarantees
2503 that hot-added devices will work.
2504 cbiosize=nn[KMG] The fixed amount of bus space which is
2505 reserved for the CardBus bridge's IO window.
2506 The default value is 256 bytes.
2507 cbmemsize=nn[KMG] The fixed amount of bus space which is
2508 reserved for the CardBus bridge's memory
2509 window. The default value is 64 megabytes.
2512 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2513 Specifies alignment and device to reassign
2514 aligned memory resources.
2515 If <order of align> is not specified,
2516 PAGE_SIZE is used as alignment.
2517 PCI-PCI bridge can be specified, if resource
2518 windows need to be expanded.
2519 ecrc= Enable/disable PCIe ECRC (transaction layer
2520 end-to-end CRC checking).
2521 bios: Use BIOS/firmware settings. This is the
2525 hpiosize=nn[KMG] The fixed amount of bus space which is
2526 reserved for hotplug bridge's IO window.
2527 Default size is 256 bytes.
2528 hpmemsize=nn[KMG] The fixed amount of bus space which is
2529 reserved for hotplug bridge's memory window.
2530 Default size is 2 megabytes.
2531 realloc= Enable/disable reallocating PCI bridge resources
2532 if allocations done by BIOS are too small to
2533 accommodate resources required by all child
2535 off: Turn realloc off
2537 realloc same as realloc=on
2538 noari do not use PCIe ARI.
2539 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2540 only look for one device below a PCIe downstream
2543 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2546 force Enable ASPM even on devices that claim not to support it.
2547 WARNING: Forcing ASPM on may cause system lockups.
2549 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2550 nomsi Do not use MSI for PCI Express Native Hotplug (this
2551 makes all PCIe ports use INTx for hotplug services).
2553 pcie_ports= [PCIE] PCIe ports handling:
2554 auto Ask the BIOS whether or not to use native PCIe services
2555 associated with PCIe ports (PME, hot-plug, AER). Use
2556 them only if that is allowed by the BIOS.
2557 native Use native PCIe services associated with PCIe ports
2559 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2562 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2563 nomsi Do not use MSI for native PCIe PME signaling (this makes
2564 all PCIe root ports use INTx for all services).
2566 pcmv= [HW,PCMCIA] BadgePAD 4
2570 Keep all power-domains already enabled by bootloader on,
2571 even if no driver has claimed them. This is useful
2572 for debug and development, but should not be
2573 needed on a platform with proper driver support.
2576 See Documentation/blockdev/paride.txt.
2578 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2581 See arch/parisc/kernel/pdc_chassis.c
2583 percpu_alloc= Select which percpu first chunk allocator to use.
2584 Currently supported values are "embed" and "page".
2585 Archs may support subset or none of the selections.
2586 See comments in mm/percpu.c for details on each
2587 allocator. This parameter is primarily for debugging
2588 and performance comparison.
2591 See Documentation/blockdev/paride.txt.
2594 See Documentation/blockdev/paride.txt.
2596 pirq= [SMP,APIC] Manual mp-table setup
2597 See Documentation/x86/i386/IO-APIC.txt.
2599 plip= [PPT,NET] Parallel port network link
2600 Format: { parport<nr> | timid | 0 }
2601 See also Documentation/parport.txt.
2603 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2604 Override pmtimer IOPort with a hex value.
2608 Enable PNP debug messages (depends on the
2609 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2610 via /sys/module/pnp/parameters/debug. We always show
2611 current resource usage; turning this on also shows
2612 possible settings and some assignment information.
2618 { on | off | curr | res | no-curr | no-res }
2621 [ISAPNP] Exclude IRQs for the autoconfiguration
2624 [ISAPNP] Exclude DMAs for the autoconfiguration
2626 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2627 Ranges are in pairs (I/O port base and size).
2630 [ISAPNP] Exclude memory regions for the
2632 Ranges are in pairs (memory base and size).
2634 ports= [IP_VS_FTP] IPVS ftp helper module
2636 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2638 Format: <port>,<port>....
2640 print-fatal-signals=
2641 [KNL] debug: print fatal signals
2643 If enabled, warn about various signal handling
2644 related application anomalies: too many signals,
2645 too many POSIX.1 timers, fatal signals causing a
2648 If you hit the warning due to signal overflow,
2649 you might want to try "ulimit -i unlimited".
2653 printk.always_kmsg_dump=
2654 Trigger kmsg_dump for cases other than kernel oops or
2656 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2659 printk.time= Show timing data prefixed to each printk message line
2660 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2662 processor.max_cstate= [HW,ACPI]
2663 Limit processor to maximum C-state
2664 max_cstate=9 overrides any DMI blacklist limit.
2666 processor.nocst [HW,ACPI]
2667 Ignore the _CST method to determine C-states,
2668 instead using the legacy FADT method
2670 profile= [KNL] Enable kernel profiling via /proc/profile
2671 Format: [schedule,]<number>
2672 Param: "schedule" - profile schedule points.
2673 Param: <number> - step/bucket size as a power of 2 for
2674 statistical time based profiling.
2675 Param: "sleep" - profile D-state sleeping (millisecs).
2676 Requires CONFIG_SCHEDSTATS
2677 Param: "kvm" - profile VM exits.
2679 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2681 See Documentation/blockdev/ramdisk.txt.
2683 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2684 probe for; one of (bare|imps|exps|lifebook|any).
2685 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2687 psmouse.resetafter= [HW,MOUSE]
2688 Try to reset the device after so many bad packets
2691 [HW,MOUSE] Set desired mouse resolution, in dpi.
2692 psmouse.smartscroll=
2693 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2694 0 = disabled, 1 = enabled (default).
2696 pstore.backend= Specify the name of the pstore backend to use
2699 See Documentation/blockdev/paride.txt.
2702 [KNL] Number of legacy pty's. Overwrites compiled-in
2705 quiet [KNL] Disable most log messages
2710 See Documentation/md.txt.
2712 ramdisk_blocksize= [RAM]
2713 See Documentation/blockdev/ramdisk.txt.
2715 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2716 See Documentation/blockdev/ramdisk.txt.
2719 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2720 the specified list of CPUs to be no-callback CPUs.
2721 Invocation of these CPUs' RCU callbacks will
2722 be offloaded to "rcuox/N" kthreads created for
2723 that purpose, where "x" is "b" for RCU-bh, "p"
2724 for RCU-preempt, and "s" for RCU-sched, and "N"
2725 is the CPU number. This reduces OS jitter on the
2726 offloaded CPUs, which can be useful for HPC and
2727 real-time workloads. It can also improve energy
2728 efficiency for asymmetric multiprocessors.
2731 Rather than requiring that offloaded CPUs
2732 (specified by rcu_nocbs= above) explicitly
2733 awaken the corresponding "rcuoN" kthreads,
2734 make these kthreads poll for callbacks.
2735 This improves the real-time response for the
2736 offloaded CPUs by relieving them of the need to
2737 wake up the corresponding kthread, but degrades
2738 energy efficiency by requiring that the kthreads
2739 periodically wake up to do the polling.
2741 rcutree.blimit= [KNL]
2742 Set maximum number of finished RCU callbacks to
2743 process in one batch.
2745 rcutree.rcu_fanout_leaf= [KNL]
2746 Increase the number of CPUs assigned to each
2747 leaf rcu_node structure. Useful for very large
2750 rcutree.jiffies_till_first_fqs= [KNL]
2751 Set delay from grace-period initialization to
2752 first attempt to force quiescent states.
2753 Units are jiffies, minimum value is zero,
2754 and maximum value is HZ.
2756 rcutree.jiffies_till_next_fqs= [KNL]
2757 Set delay between subsequent attempts to force
2758 quiescent states. Units are jiffies, minimum
2759 value is one, and maximum value is HZ.
2761 rcutree.qhimark= [KNL]
2762 Set threshold of queued RCU callbacks beyond which
2763 batch limiting is disabled.
2765 rcutree.qlowmark= [KNL]
2766 Set threshold of queued RCU callbacks below which
2767 batch limiting is re-enabled.
2769 rcutree.rcu_idle_gp_delay= [KNL]
2770 Set wakeup interval for idle CPUs that have
2771 RCU callbacks (RCU_FAST_NO_HZ=y).
2773 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2774 Set wakeup interval for idle CPUs that have
2775 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2776 Lazy RCU callbacks are those which RCU can
2777 prove do nothing more than free memory.
2779 rcutorture.fqs_duration= [KNL]
2780 Set duration of force_quiescent_state bursts.
2782 rcutorture.fqs_holdoff= [KNL]
2783 Set holdoff time within force_quiescent_state bursts.
2785 rcutorture.fqs_stutter= [KNL]
2786 Set wait time between force_quiescent_state bursts.
2788 rcutorture.gp_exp= [KNL]
2789 Use expedited update-side primitives.
2791 rcutorture.gp_normal= [KNL]
2792 Use normal (non-expedited) update-side primitives.
2793 If both gp_exp and gp_normal are set, do both.
2794 If neither gp_exp nor gp_normal are set, still
2797 rcutorture.n_barrier_cbs= [KNL]
2798 Set callbacks/threads for rcu_barrier() testing.
2800 rcutorture.nfakewriters= [KNL]
2801 Set number of concurrent RCU writers. These just
2802 stress RCU, they don't participate in the actual
2803 test, hence the "fake".
2805 rcutorture.nreaders= [KNL]
2806 Set number of RCU readers.
2808 rcutorture.object_debug= [KNL]
2809 Enable debug-object double-call_rcu() testing.
2811 rcutorture.onoff_holdoff= [KNL]
2812 Set time (s) after boot for CPU-hotplug testing.
2814 rcutorture.onoff_interval= [KNL]
2815 Set time (s) between CPU-hotplug operations, or
2816 zero to disable CPU-hotplug testing.
2818 rcutorture.rcutorture_runnable= [BOOT]
2819 Start rcutorture running at boot time.
2821 rcutorture.shuffle_interval= [KNL]
2822 Set task-shuffle interval (s). Shuffling tasks
2823 allows some CPUs to go into dyntick-idle mode
2824 during the rcutorture test.
2826 rcutorture.shutdown_secs= [KNL]
2827 Set time (s) after boot system shutdown. This
2828 is useful for hands-off automated testing.
2830 rcutorture.stall_cpu= [KNL]
2831 Duration of CPU stall (s) to test RCU CPU stall
2832 warnings, zero to disable.
2834 rcutorture.stall_cpu_holdoff= [KNL]
2835 Time to wait (s) after boot before inducing stall.
2837 rcutorture.stat_interval= [KNL]
2838 Time (s) between statistics printk()s.
2840 rcutorture.stutter= [KNL]
2841 Time (s) to stutter testing, for example, specifying
2842 five seconds causes the test to run for five seconds,
2843 wait for five seconds, and so on. This tests RCU's
2844 ability to transition abruptly to and from idle.
2846 rcutorture.test_boost= [KNL]
2847 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2848 "Maybe" means test if the RCU implementation
2849 under test support RCU priority boosting.
2851 rcutorture.test_boost_duration= [KNL]
2852 Duration (s) of each individual boost test.
2854 rcutorture.test_boost_interval= [KNL]
2855 Interval (s) between each boost test.
2857 rcutorture.test_no_idle_hz= [KNL]
2858 Test RCU's dyntick-idle handling. See also the
2859 rcutorture.shuffle_interval parameter.
2861 rcutorture.torture_type= [KNL]
2862 Specify the RCU implementation to test.
2864 rcutorture.verbose= [KNL]
2865 Enable additional printk() statements.
2867 rcupdate.rcu_expedited= [KNL]
2868 Use expedited grace-period primitives, for
2869 example, synchronize_rcu_expedited() instead
2870 of synchronize_rcu(). This reduces latency,
2871 but can increase CPU utilization, degrade
2872 real-time latency, and degrade energy efficiency.
2874 rcupdate.rcu_cpu_stall_suppress= [KNL]
2875 Suppress RCU CPU stall warning messages.
2877 rcupdate.rcu_cpu_stall_timeout= [KNL]
2878 Set timeout for RCU CPU stall warning messages.
2882 Run specified binary instead of /init from the ramdisk,
2883 used for early userspace startup. See initrd.
2886 Format (x86 or x86_64):
2887 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2889 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2891 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2892 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2893 reboot_force is either force or not specified,
2894 reboot_cpu is s[mp]#### with #### being the processor
2895 to be used for rebooting.
2898 [KNL, SMP] Set scheduler's default relax_domain_level.
2899 See Documentation/cgroups/cpusets.txt.
2901 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2903 reservetop= [X86-32]
2905 Reserves a hole at the top of the kernel virtual
2910 Set the amount of memory to reserve for BIOS at
2911 the bottom of the address space.
2913 reset_devices [KNL] Force drivers to reset the underlying device
2914 during initialization.
2917 Specify the partition device for software suspend
2919 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2921 resume_offset= [SWSUSP]
2922 Specify the offset from the beginning of the partition
2923 given by "resume=" at which the swap header is located,
2924 in <PAGE_SIZE> units (needed only for swap files).
2925 See Documentation/power/swsusp-and-swap-files.txt
2927 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2928 read the resume files
2930 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2931 Useful for devices that are detected asynchronously
2932 (e.g. USB and MMC devices).
2934 hibernate= [HIBERNATION]
2935 noresume Don't check if there's a hibernation image
2936 present during boot.
2937 nocompress Don't compress/decompress hibernation images.
2939 retain_initrd [RAM] Keep initrd memory after extraction
2941 rhash_entries= [KNL,NET]
2942 Set number of hash buckets for route cache
2944 ro [KNL] Mount root device read-only on boot
2946 root= [KNL] Root filesystem
2947 See name_to_dev_t comment in init/do_mounts.c.
2949 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2950 mount the root filesystem
2952 rootflags= [KNL] Set root filesystem mount option string
2954 rootfstype= [KNL] Set root filesystem type
2956 rootwait [KNL] Wait (indefinitely) for root device to show up.
2957 Useful for devices that are detected asynchronously
2958 (e.g. USB and MMC devices).
2960 rproc_mem=nn[KMG][@address]
2961 [KNL,ARM,CMA] Remoteproc physical memory block.
2962 Memory area to be used by remote processor image,
2965 rw [KNL] Mount root device read-write on boot
2967 S [KNL] Run init in single mode
2970 See drivers/net/irda/sa1100_ir.c.
2972 sbni= [NET] Granch SBNI12 leased line adapter
2974 sched_debug [KNL] Enables verbose scheduler debug messages.
2976 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2977 xtime_lock contention on larger systems, and/or RCU lock
2978 contention on all systems with CONFIG_MAXSMP set.
2979 Format: { "0" | "1" }
2980 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2982 Note: increases power consumption, thus should only be
2983 enabled if running jitter sensitive (HPC/RT) workloads.
2985 security= [SECURITY] Choose a security module to enable at boot.
2986 If this boot parameter is not specified, only the first
2987 security module asking for security registration will be
2988 loaded. An invalid security module name will be treated
2989 as if no module has been chosen.
2991 selinux= [SELINUX] Disable or enable SELinux at boot time.
2992 Format: { "0" | "1" }
2993 See security/selinux/Kconfig help text.
2996 Default value is set via kernel config option.
2997 If enabled at boot time, /selinux/disable can be used
2998 later to disable prior to initial policy load.
3000 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3001 Format: { "0" | "1" }
3002 See security/apparmor/Kconfig help text
3005 Default value is set via kernel config option.
3007 serialnumber [BUGS=X86-32]
3010 Maximal number of shapers.
3012 show_msr= [x86] show boot-time MSR settings
3013 Format: { <integer> }
3014 Show boot-time (BIOS-initialized) MSR settings.
3015 The parameter means the number of CPUs to show,
3016 for example 1 means boot CPU only.
3023 slab_max_order= [MM, SLAB]
3024 Determines the maximum allowed order for slabs.
3025 A high setting may cause OOMs due to memory
3026 fragmentation. Defaults to 1 for systems with
3027 more than 32MB of RAM, 0 otherwise.
3029 slub_debug[=options[,slabs]] [MM, SLUB]
3030 Enabling slub_debug allows one to determine the
3031 culprit if slab objects become corrupted. Enabling
3032 slub_debug can create guard zones around objects and
3033 may poison objects when not in use. Also tracks the
3034 last alloc / free. For more information see
3035 Documentation/vm/slub.txt.
3037 slub_max_order= [MM, SLUB]
3038 Determines the maximum allowed order for slabs.
3039 A high setting may cause OOMs due to memory
3040 fragmentation. For more information see
3041 Documentation/vm/slub.txt.
3043 slub_min_objects= [MM, SLUB]
3044 The minimum number of objects per slab. SLUB will
3045 increase the slab order up to slub_max_order to
3046 generate a sufficiently large slab able to contain
3047 the number of objects indicated. The higher the number
3048 of objects the smaller the overhead of tracking slabs
3049 and the less frequently locks need to be acquired.
3050 For more information see Documentation/vm/slub.txt.
3052 slub_min_order= [MM, SLUB]
3053 Determines the minimum page order for slabs. Must be
3054 lower than slub_max_order.
3055 For more information see Documentation/vm/slub.txt.
3057 slub_nomerge [MM, SLUB]
3058 Disable merging of slabs with similar size. May be
3059 necessary if there is some reason to distinguish
3060 allocs to different slabs. Debug options disable
3061 merging on their own.
3062 For more information see Documentation/vm/slub.txt.
3065 Format: <io1>[,<io2>[,...,<io8>]]
3067 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3068 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3069 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3070 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3071 smsc-ircc2.ircc_irq= [HW] IRQ line
3072 smsc-ircc2.ircc_dma= [HW] DMA channel
3073 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3074 0: Toshiba Satellite 1800 (GP data pin select)
3075 1: Fast pin select (default)
3079 [KNL] Should the soft-lockup detector generate panics.
3082 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3083 See Documentation/laptops/sonypi.txt
3085 spia_io_base= [HW,MTD]
3091 Enabled the stack tracer on boot up.
3093 stacktrace_filter=[function-list]
3094 [FTRACE] Limit the functions that the stack tracer
3095 will trace at boot up. function-list is a comma separated
3096 list of functions. This list can be changed at run
3097 time by the stack_trace_filter file in the debugfs
3098 tracing directory. Note, this enables stack tracing
3099 and the stacktrace above is not needed.
3103 Set the STI (builtin display/keyboard on the HP-PARISC
3104 machines) console (graphic card) which should be used
3105 as the initial boot-console.
3106 See also comment in drivers/video/console/sticore.c.
3109 See comment in drivers/video/console/sticore.c.
3112 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3114 sunrpc.min_resvport=
3115 sunrpc.max_resvport=
3117 SunRPC servers often require that client requests
3118 originate from a privileged port (i.e. a port in the
3119 range 0 < portnr < 1024).
3120 An administrator who wishes to reserve some of these
3121 ports for other uses may adjust the range that the
3122 kernel's sunrpc client considers to be privileged
3123 using these two parameters to set the minimum and
3124 maximum port values.
3128 Control how the NFS server code allocates CPUs to
3129 service thread pools. Depending on how many NICs
3130 you have and where their interrupts are bound, this
3131 option will affect which CPUs will do NFS serving.
3132 Note: this parameter cannot be changed while the
3133 NFS server is running.
3135 auto the server chooses an appropriate mode
3136 automatically using heuristics
3137 global a single global pool contains all CPUs
3138 percpu one pool for each CPU
3139 pernode one pool for each NUMA node (equivalent
3140 to global on non-NUMA machines)
3142 sunrpc.tcp_slot_table_entries=
3143 sunrpc.udp_slot_table_entries=
3145 Sets the upper limit on the number of simultaneous
3146 RPC calls that can be sent from the client to a
3147 server. Increasing these values may allow you to
3148 improve throughput, but will also increase the
3149 amount of memory reserved for use by the client.
3152 [KNL] Enable accounting of swap in memory resource
3153 controller if no parameter or 1 is given or disable
3154 it if 0 is given (See Documentation/cgroups/memory.txt)
3156 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3157 Format: { <int> | force }
3158 <int> -- Number of I/O TLB slabs
3159 force -- force using of bounce buffers even if they
3160 wouldn't be automatically used by the kernel
3164 sysfs.deprecated=0|1 [KNL]
3165 Enable/disable old style sysfs layout for old udev
3166 on older distributions. When this option is enabled
3167 very new udev will not work anymore. When this option
3168 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3169 in older udev will not work anymore.
3170 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3171 the kernel configuration.
3173 sysrq_always_enabled
3175 Ignore sysrq setting - this boot parameter will
3176 neutralize any effect of /proc/sys/kernel/sysrq.
3177 Useful for debugging.
3181 test_suspend= [SUSPEND]
3182 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3183 standby suspend) as the system sleep state to briefly
3184 enter during system startup. The system is woken from
3185 this state using a wakeup-capable RTC alarm.
3187 thash_entries= [KNL,NET]
3188 Set number of hash buckets for TCP connection
3190 thermal.act= [HW,ACPI]
3191 -1: disable all active trip points in all thermal zones
3192 <degrees C>: override all lowest active trip points
3194 thermal.crt= [HW,ACPI]
3195 -1: disable all critical trip points in all thermal zones
3196 <degrees C>: override all critical trip points
3198 thermal.nocrt= [HW,ACPI]
3199 Set to disable actions on ACPI thermal zone
3200 critical and hot trip points.
3202 thermal.off= [HW,ACPI]
3203 1: disable ACPI thermal control
3205 thermal.psv= [HW,ACPI]
3206 -1: disable all passive trip points
3207 <degrees C>: override all passive trip points to this
3210 thermal.tzp= [HW,ACPI]
3211 Specify global default ACPI thermal zone polling rate
3212 <deci-seconds>: poll all this frequency
3213 0: no polling (default)
3216 Force threading of all interrupt handlers except those
3217 marked explicitly IRQF_NO_THREAD.
3220 Enable the Transcendent memory driver if built-in.
3222 tmem.cleancache=0|1 [KNL, XEN]
3223 Default is on (1). Disable the usage of the cleancache
3224 API to send anonymous pages to the hypervisor.
3226 tmem.frontswap=0|1 [KNL, XEN]
3227 Default is on (1). Disable the usage of the frontswap
3228 API to send swap pages to the hypervisor. If disabled
3229 the selfballooning and selfshrinking are force disabled.
3231 tmem.selfballooning=0|1 [KNL, XEN]
3232 Default is on (1). Disable the driving of swap pages
3235 tmem.selfshrinking=0|1 [KNL, XEN]
3236 Default is on (1). Partial swapoff that immediately
3237 transfers pages from Xen hypervisor back to the
3238 kernel based on different criteria.
3242 Specify if the kernel should make use of the cpu
3243 topology information if the hardware supports this.
3244 The scheduler will make use of this information and
3245 e.g. base its process migration decisions on it.
3250 tpm_suspend_pcr=[HW,TPM]
3251 Format: integer pcr id
3252 Specify that at suspend time, the tpm driver
3253 should extend the specified pcr with zeros,
3254 as a workaround for some chips which fail to
3255 flush the last written pcr on TPM_SaveState.
3256 This will guarantee that all the other pcrs
3259 trace_buf_size=nn[KMG]
3260 [FTRACE] will set tracing buffer size.
3262 trace_event=[event-list]
3263 [FTRACE] Set and start specified trace events in order
3264 to facilitate early boot debugging.
3265 See also Documentation/trace/events.txt
3267 trace_options=[option-list]
3268 [FTRACE] Enable or disable tracer options at boot.
3269 The option-list is a comma delimited list of options
3270 that can be enabled or disabled just as if you were
3271 to echo the option name into
3273 /sys/kernel/debug/tracing/trace_options
3275 For example, to enable stacktrace option (to dump the
3276 stack trace of each event), add to the command line:
3278 trace_options=stacktrace
3280 See also Documentation/trace/ftrace.txt "trace options"
3284 [FTRACE] enable this option to disable tracing when a
3285 warning is hit. This turns off "tracing_on". Tracing can
3286 be enabled again by echoing '1' into the "tracing_on"
3287 file located in /sys/kernel/debug/tracing/
3289 This option is useful, as it disables the trace before
3290 the WARNING dump is called, which prevents the trace to
3291 be filled with content caused by the warning output.
3293 This option can also be set at run time via the sysctl
3294 option: kernel/traceoff_on_warning
3296 transparent_hugepage=
3298 Format: [always|madvise|never]
3299 Can be used to control the default behavior of the system
3300 with respect to transparent hugepages.
3301 See Documentation/vm/transhuge.txt for more details.
3303 tsc= Disable clocksource stability checks for TSC.
3305 [x86] reliable: mark tsc clocksource as reliable, this
3306 disables clocksource verification at runtime, as well
3307 as the stability checks done at bootup. Used to enable
3308 high-resolution timer mode on older hardware, and in
3309 virtualized environment.
3310 [x86] noirqtime: Do not use TSC to do irq accounting.
3311 Used to run time disable IRQ_TIME_ACCOUNTING on any
3312 platforms where RDTSC is slow and this accounting
3315 turbografx.map[2|3]= [HW,JOY]
3316 TurboGraFX parallel port interface
3318 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3319 See also Documentation/input/joystick-parport.txt
3321 udbg-immortal [PPC] When debugging early kernel crashes that
3322 happen after console_init() and before a proper
3323 console driver takes over, this boot options might
3324 help "seeing" what's going on.
3326 uhash_entries= [KNL,NET]
3327 Set number of hash buckets for UDP/UDP-Lite connections
3330 [USB] Ignore overcurrent events (default N).
3331 Some badly-designed motherboards generate lots of
3332 bogus events, for ports that aren't wired to
3333 anything. Set this parameter to avoid log spamming.
3334 Note that genuine overcurrent events won't be
3338 [X86] Cause panic on unknown NMI.
3340 usbcore.authorized_default=
3341 [USB] Default USB device authorization:
3342 (default -1 = authorized except for wireless USB,
3343 0 = not authorized, 1 = authorized)
3345 usbcore.autosuspend=
3346 [USB] The autosuspend time delay (in seconds) used
3347 for newly-detected USB devices (default 2). This
3348 is the time required before an idle device will be
3349 autosuspended. Devices for which the delay is set
3350 to a negative value won't be autosuspended at all.
3352 usbcore.usbfs_snoop=
3353 [USB] Set to log all usbfs traffic (default 0 = off).
3355 usbcore.blinkenlights=
3356 [USB] Set to cycle leds on hubs (default 0 = off).
3358 usbcore.old_scheme_first=
3359 [USB] Start with the old device initialization
3360 scheme (default 0 = off).
3362 usbcore.usbfs_memory_mb=
3363 [USB] Memory limit (in MB) for buffers allocated by
3364 usbfs (default = 16, 0 = max = 2047).
3366 usbcore.use_both_schemes=
3367 [USB] Try the other device initialization scheme
3368 if the first one fails (default 1 = enabled).
3370 usbcore.initial_descriptor_timeout=
3371 [USB] Specifies timeout for the initial 64-byte
3372 USB_REQ_GET_DESCRIPTOR request in milliseconds
3373 (default 5000 = 5.0 seconds).
3376 [USBHID] The interval which mice are to be polled at.
3378 usb-storage.delay_use=
3379 [UMS] The delay in seconds before a new device is
3380 scanned for Logical Units (default 5).
3383 [UMS] A list of quirks entries to supplement or
3384 override the built-in unusual_devs list. List
3385 entries are separated by commas. Each entry has
3386 the form VID:PID:Flags where VID and PID are Vendor
3387 and Product ID values (4-digit hex numbers) and
3388 Flags is a set of characters, each corresponding
3389 to a common usb-storage quirk flag as follows:
3390 a = SANE_SENSE (collect more than 18 bytes
3392 b = BAD_SENSE (don't collect more than 18
3393 bytes of sense data);
3394 c = FIX_CAPACITY (decrease the reported
3395 device capacity by one sector);
3396 d = NO_READ_DISC_INFO (don't use
3397 READ_DISC_INFO command);
3398 e = NO_READ_CAPACITY_16 (don't use
3399 READ_CAPACITY_16 command);
3400 h = CAPACITY_HEURISTICS (decrease the
3401 reported device capacity by one
3402 sector if the number is odd);
3403 i = IGNORE_DEVICE (don't bind to this
3405 l = NOT_LOCKABLE (don't try to lock and
3406 unlock ejectable media);
3407 m = MAX_SECTORS_64 (don't transfer more
3408 than 64 sectors = 32 KB at a time);
3409 n = INITIAL_READ10 (force a retry of the
3410 initial READ(10) command);
3411 o = CAPACITY_OK (accept the capacity
3412 reported by the device);
3413 p = WRITE_CACHE (the device cache is ON
3415 r = IGNORE_RESIDUE (the device reports
3416 bogus residue values);
3417 s = SINGLE_LUN (the device has only one
3419 w = NO_WP_DETECT (don't test whether the
3420 medium is write-protected).
3421 Example: quirks=0419:aaf5:rl,0421:0433:rc
3423 user_debug= [KNL,ARM]
3425 See arch/arm/Kconfig.debug help text.
3426 1 - undefined instruction events
3428 4 - invalid data aborts
3431 Example: user_debug=31
3434 [X86] Flags controlling user PTE allocations.
3436 nohigh = do not allocate PTE pages in
3437 HIGHMEM regardless of setting
3441 On X86_32, this is an alias for vdso32=. Otherwise:
3443 vdso=1: enable VDSO (the default)
3444 vdso=0: disable VDSO mapping
3446 vdso32= [X86] Control the 32-bit vDSO
3447 vdso32=1: enable 32-bit VDSO
3448 vdso32=0 or vdso32=2: disable 32-bit VDSO
3450 See the help text for CONFIG_COMPAT_VDSO for more
3451 details. If CONFIG_COMPAT_VDSO is set, the default is
3452 vdso32=0; otherwise, the default is vdso32=1.
3454 For compatibility with older kernels, vdso32=2 is an
3457 Try vdso32=0 if you encounter an error that says:
3458 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3461 vector=percpu: enable percpu vector domain
3463 video= [FB] Frame buffer configuration
3464 See Documentation/fb/modedb.txt.
3466 video.brightness_switch_enabled= [0,1]
3467 If set to 1, on receiving an ACPI notify event
3468 generated by hotkey, video driver will adjust brightness
3469 level and then send out the event to user space through
3470 the allocated input device; If set to 0, video driver
3471 will only send out the event without touching backlight
3476 [VMMIO] Memory mapped virtio (platform) device.
3478 <size>@<baseaddr>:<irq>[:<id>]
3480 <size> := size (can use standard suffixes
3482 <baseaddr> := physical base address
3483 <irq> := interrupt number (as passed to
3485 <id> := (optional) platform device id
3487 virtio_mmio.device=1K@0x100b0000:48:7
3489 Can be used multiple times for multiple devices.
3491 vga= [BOOT,X86-32] Select a particular video mode
3492 See Documentation/x86/boot.txt and
3493 Documentation/svga.txt.
3494 Use vga=ask for menu.
3495 This is actually a boot loader parameter; the value is
3496 passed to the kernel using a special protocol.
3498 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3499 size of <nn>. This can be used to increase the
3500 minimum size (128MB on x86). It can also be used to
3501 decrease the size and leave more room for directly
3504 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3507 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3510 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3514 Controls the behavior of vsyscalls (i.e. calls to
3515 fixed addresses of 0xffffffffff600x00 from legacy
3516 code). Most statically-linked binaries and older
3517 versions of glibc use these calls. Because these
3518 functions are at fixed addresses, they make nice
3519 targets for exploits that can control RIP.
3521 emulate [default] Vsyscalls turn into traps and are
3522 emulated reasonably safely.
3524 native Vsyscalls are native syscall instructions.
3525 This is a little bit faster than trapping
3526 and makes a few dynamic recompilers work
3527 better than they would in emulation mode.
3528 It also makes exploits much easier to write.
3530 none Vsyscalls don't work at all. This makes
3531 them quite hard to use for exploits but
3532 might break your system.
3534 vt.color= [VT] Default text color.
3535 Format: 0xYX, X = foreground, Y = background.
3536 Default: 0x07 = light gray on black.
3538 vt.cur_default= [VT] Default cursor shape.
3539 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3540 the parameters of the <Esc>[?A;B;Cc escape sequence;
3541 see VGA-softcursor.txt. Default: 2 = underline.
3543 vt.default_blu= [VT]
3544 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3545 Change the default blue palette of the console.
3546 This is a 16-member array composed of values
3549 vt.default_grn= [VT]
3550 Format: <green0>,<green1>,<green2>,...,<green15>
3551 Change the default green palette of the console.
3552 This is a 16-member array composed of values
3555 vt.default_red= [VT]
3556 Format: <red0>,<red1>,<red2>,...,<red15>
3557 Change the default red palette of the console.
3558 This is a 16-member array composed of values
3564 Set system-wide default UTF-8 mode for all tty's.
3565 Default is 1, i.e. UTF-8 mode is enabled for all
3566 newly opened terminals.
3568 vt.global_cursor_default=
3571 Set system-wide default for whether a cursor
3572 is shown on new VTs. Default is -1,
3573 i.e. cursors will be created by default unless
3574 overridden by individual drivers. 0 will hide
3575 cursors, 1 will display them.
3577 vt.italic= [VT] Default color for italic text; 0-15.
3580 vt.underline= [VT] Default color for underlined text; 0-15.
3583 watchdog timers [HW,WDT] For information on watchdog timers,
3584 see Documentation/watchdog/watchdog-parameters.txt
3585 or other driver-specific files in the
3586 Documentation/watchdog/ directory.
3588 workqueue.disable_numa
3589 By default, all work items queued to unbound
3590 workqueues are affine to the NUMA nodes they're
3591 issued on, which results in better behavior in
3592 general. If NUMA affinity needs to be disabled for
3593 whatever reason, this option can be used. Note
3594 that this also can be controlled per-workqueue for
3595 workqueues visible under /sys/bus/workqueue/.
3597 workqueue.power_efficient
3598 Per-cpu workqueues are generally preferred because
3599 they show better performance thanks to cache
3600 locality; unfortunately, per-cpu workqueues tend to
3601 be more power hungry than unbound workqueues.
3603 Enabling this makes the per-cpu workqueues which
3604 were observed to contribute significantly to power
3605 consumption unbound, leading to measurably lower
3606 power usage at the cost of small performance
3609 The default value of this parameter is determined by
3610 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3612 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3613 default x2apic cluster mode on platforms
3616 x86_intel_mid_timer= [X86-32,APBT]
3617 Choose timer option for x86 Intel MID platform.
3618 Two valid options are apbt timer only and lapic timer
3619 plus one apbt timer for broadcast timer.
3620 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3622 xen_emul_unplug= [HW,X86,XEN]
3623 Unplug Xen emulated devices
3624 Format: [unplug0,][unplug1]
3625 ide-disks -- unplug primary master IDE devices
3626 aux-ide-disks -- unplug non-primary-master IDE devices
3627 nics -- unplug network devices
3628 all -- unplug all emulated devices (NICs and IDE disks)
3629 unnecessary -- unplugging emulated devices is
3630 unnecessary even if the host did not respond to
3632 never -- do not unplug even if version check succeeds
3634 xen_nopvspin [X86,XEN]
3635 Disables the ticketlock slowpath using Xen PV
3638 xirc2ps_cs= [NET,PCMCIA]
3640 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3642 ______________________________________________________________________
3646 Add more DRM drivers.