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_force_table_verification [HW,ACPI]
218 Enable table checksum verification during early stage.
219 By default, this is disabled due to x86 early mapping
222 acpi_irq_balance [HW,ACPI]
223 ACPI will balance active IRQs
226 acpi_irq_nobalance [HW,ACPI]
227 ACPI will not move active IRQs (default)
230 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
231 Format: <irq>,<irq>...
233 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
235 Format: <irq>,<irq>...
237 acpi_no_auto_serialize [HW,ACPI]
238 Disable auto-serialization of AML methods
239 AML control methods that contain the opcodes to create
240 named objects will be marked as "Serialized" by the
241 auto-serialization feature.
242 This feature is enabled by default.
243 This option allows to turn off the feature.
245 acpi_no_static_ssdt [HW,ACPI]
246 Disable installation of static SSDTs at early boot time
247 By default, SSDTs contained in the RSDT/XSDT will be
248 installed automatically and they will appear under
249 /sys/firmware/acpi/tables.
250 This option turns off this feature.
251 Note that specifying this option does not affect
252 dynamic table installation which will install SSDT
253 tables to /sys/firmware/acpi/tables/dynamic.
255 acpica_no_return_repair [HW, ACPI]
256 Disable AML predefined validation mechanism
257 This mechanism can repair the evaluation result to make
258 the return objects more ACPI specification compliant.
259 This option is useful for developers to identify the
260 root cause of an AML interpreter issue when the issue
261 has something to do with the repair mechanism.
263 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
264 Format: To spoof as Windows 98: ="Microsoft Windows"
266 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
267 acpi_osi="string1" # add string1
268 acpi_osi="!string2" # remove string2
269 acpi_osi=!* # remove all strings
270 acpi_osi=! # disable all built-in OS vendor
272 acpi_osi= # disable all strings
274 'acpi_osi=!' can be used in combination with single or
275 multiple 'acpi_osi="string1"' to support specific OS
276 vendor string(s). Note that such command can only
277 affect the default state of the OS vendor strings, thus
278 it cannot affect the default state of the feature group
279 strings and the current state of the OS vendor strings,
280 specifying it multiple times through kernel command line
281 is meaningless. This command is useful when one do not
282 care about the state of the feature group strings which
283 should be controlled by the OSPM.
285 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
286 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
287 can make '_OSI("Windows 2000")' TRUE.
289 'acpi_osi=' cannot be used in combination with other
290 'acpi_osi=' command lines, the _OSI method will not
291 exist in the ACPI namespace. NOTE that such command can
292 only affect the _OSI support state, thus specifying it
293 multiple times through kernel command line is also
296 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
299 'acpi_osi=!*' can be used in combination with single or
300 multiple 'acpi_osi="string1"' to support specific
301 string(s). Note that such command can affect the
302 current state of both the OS vendor strings and the
303 feature group strings, thus specifying it multiple times
304 through kernel command line is meaningful. But it may
305 still not able to affect the final state of a string if
306 there are quirks related to this string. This command
307 is useful when one want to control the state of the
308 feature group strings to debug BIOS issues related to
311 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
312 '_OSI("Module Device")' FALSE.
313 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
314 '_OSI("Module Device")' TRUE.
315 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
317 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
319 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
320 they all will make '_OSI("Windows 2000")' TRUE.
323 Override the pmtimer bug detection: force the kernel
324 to assume that this machine's pmtimer latches its value
325 and always returns good values.
327 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
328 Format: { level | edge | high | low }
330 acpi_skip_timer_override [HW,ACPI]
331 Recognize and ignore IRQ0/pin2 Interrupt Override.
332 For broken nForce2 BIOS resulting in XT-PIC timer.
334 acpi_sleep= [HW,ACPI] Sleep options
335 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
336 old_ordering, nonvs, sci_force_enable }
337 See Documentation/power/video.txt for information on
339 s3_beep is for debugging; it makes the PC's speaker beep
340 as soon as the kernel's real-mode entry point is called.
341 s4_nohwsig prevents ACPI hardware signature from being
342 used during resume from hibernation.
343 old_ordering causes the ACPI 1.0 ordering of the _PTS
344 control method, with respect to putting devices into
345 low power states, to be enforced (the ACPI 2.0 ordering
346 of _PTS is used by default).
347 nonvs prevents the kernel from saving/restoring the
348 ACPI NVS memory during suspend/hibernation and resume.
349 sci_force_enable causes the kernel to set SCI_EN directly
350 on resume from S1/S3 (which is against the ACPI spec,
351 but some broken systems don't work without it).
353 acpi_use_timer_override [HW,ACPI]
354 Use timer override. For some broken Nvidia NF5 boards
355 that require a timer override, but don't have HPET
357 acpi_enforce_resources= [ACPI]
358 { strict | lax | no }
359 Check for resource conflicts between native drivers
360 and ACPI OperationRegions (SystemIO and SystemMemory
361 only). IO ports and memory declared in ACPI might be
362 used by the ACPI subsystem in arbitrary AML code and
363 can interfere with legacy drivers.
364 strict (default): access to resources claimed by ACPI
365 is denied; legacy drivers trying to access reserved
366 resources will fail to bind to device using them.
367 lax: access to resources claimed by ACPI is allowed;
368 legacy drivers trying to access reserved resources
369 will bind successfully but a warning message is logged.
370 no: ACPI OperationRegions are not marked as reserved,
371 no further checks are performed.
373 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
376 add_efi_memmap [EFI; X86] Include EFI memory map in
377 kernel's map of available physical RAM.
380 { off | try_unsupported }
381 off: disable AGP support
382 try_unsupported: try to drive unsupported chipsets
383 (may crash computer or cause data corruption)
386 See Documentation/sound/alsa/alsa-parameters.txt
389 Allow the default userspace alignment fault handler
390 behaviour to be specified. Bit 0 enables warnings,
391 bit 1 enables fixups, and bit 2 sends a segfault.
393 align_va_addr= [X86-64]
394 Align virtual addresses by clearing slice [14:12] when
395 allocating a VMA at process creation time. This option
396 gives you up to 3% performance improvement on AMD F15h
397 machines (where it is enabled by default) for a
398 CPU-intensive style benchmark, and it can vary highly in
399 a microbenchmark depending on workload and compiler.
401 32: only for 32-bit processes
402 64: only for 64-bit processes
403 on: enable for both 32- and 64-bit processes
404 off: disable for both 32- and 64-bit processes
406 alloc_snapshot [FTRACE]
407 Allocate the ftrace snapshot buffer on boot up when the
408 main buffer is allocated. This is handy if debugging
409 and you need to use tracing_snapshot() on boot up, and
410 do not want to use tracing_snapshot_alloc() as it needs
411 to be done where GFP_KERNEL allocations are allowed.
413 amd_iommu= [HW,X86-64]
414 Pass parameters to the AMD IOMMU driver in the system.
416 fullflush - enable flushing of IO/TLB entries when
417 they are unmapped. Otherwise they are
418 flushed before they will be reused, which
420 off - do not initialize any AMD IOMMU found in
422 force_isolation - Force device isolation for all
423 devices. The IOMMU driver is not
424 allowed anymore to lift isolation
425 requirements as needed. This option
426 does not override iommu=pt
428 amd_iommu_dump= [HW,X86-64]
429 Enable AMD IOMMU driver option to dump the ACPI table
430 for AMD IOMMU. With this option enabled, AMD IOMMU
431 driver will print ACPI tables for AMD IOMMU during
432 IOMMU initialization.
434 amijoy.map= [HW,JOY] Amiga joystick support
435 Map of devices attached to JOY0DAT and JOY1DAT
437 See also Documentation/input/joystick.txt
439 analog.map= [HW,JOY] Analog joystick and gamepad support
440 Specifies type or capabilities of an analog joystick
441 connected to one of 16 gameports
442 Format: <type1>,<type2>,..<type16>
445 Power management functions (SPARCstation-4/5 + deriv.)
447 Disable APC CPU standby support. SPARCstation-Fox does
448 not play well with APC CPU idle - disable it if you have
449 APC and your system crashes randomly.
451 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
452 Change the output verbosity whilst booting
453 Format: { quiet (default) | verbose | debug }
454 Change the amount of debugging information output
455 when initialising the APIC and IO-APIC components.
458 See Documentation/networking/ipv6.txt.
460 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
461 Limit apic dumping. The parameter defines the maximal
462 number of local apics being dumped. Also it is possible
463 to set it to "all" by meaning -- no limit here.
464 Format: { 1 (default) | 2 | ... | all }.
465 The parameter valid if only apic=debug or
466 apic=verbose is specified.
467 Example: apic=debug show_lapic=all
469 apm= [APM] Advanced Power Management
470 See header of arch/x86/kernel/apm_32.c.
472 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
473 Format: <io>,<irq>,<nodeID>
477 atarimouse= [HW,MOUSE] Atari Mouse
479 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
480 EzKey and similar keyboards
482 atkbd.reset= [HW] Reset keyboard during initialization
484 atkbd.set= [HW] Select keyboard code set
485 Format: <int> (2 = AT (default), 3 = PS/2)
487 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
490 atkbd.softraw= [HW] Choose between synthetic and real raw mode
491 Format: <bool> (0 = real, 1 = synthetic (default))
493 atkbd.softrepeat= [HW]
494 Use software keyboard repeat
496 audit= [KNL] Enable the audit sub-system
497 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
498 0 - kernel audit is disabled and can not be enabled
499 until the next reboot
500 unset - kernel audit is initialized but disabled and
501 will be fully enabled by the userspace auditd.
502 1 - kernel audit is initialized and partially enabled,
503 storing at most audit_backlog_limit messages in
504 RAM until it is fully enabled by the userspace
508 audit_backlog_limit= [KNL] Set the audit queue size limit.
509 Format: <int> (must be >=0)
512 baycom_epp= [HW,AX25]
515 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
517 See header of drivers/net/hamradio/baycom_par.c.
519 baycom_ser_fdx= [HW,AX25]
520 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
521 Format: <io>,<irq>,<mode>[,<baud>]
522 See header of drivers/net/hamradio/baycom_ser_fdx.c.
524 baycom_ser_hdx= [HW,AX25]
525 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
526 Format: <io>,<irq>,<mode>
527 See header of drivers/net/hamradio/baycom_ser_hdx.c.
529 blkdevparts= Manual partition parsing of block device(s) for
530 embedded devices based on command line input.
531 See Documentation/block/cmdline-partition.txt
533 boot_delay= Milliseconds to delay each printk during boot.
534 Values larger than 10 seconds (10000) are changed to
538 bootmem_debug [KNL] Enable bootmem allocator debug messages.
540 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
541 bttv.radio= Most important insmod options are available as
543 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
546 bulk_remove=off [PPC] This parameter disables the use of the pSeries
547 firmware feature for flushing multiple hpte entries
550 c101= [NET] Moxa C101 synchronous serial card
552 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
553 Sometimes CPU hardware bugs make them report the cache
554 size incorrectly. The kernel will attempt work arounds
555 to fix known problems, but for some CPUs it is not
556 possible to determine what the correct size should be.
557 This option provides an override for these situations.
559 ccw_timeout_log [S390]
560 See Documentation/s390/CommonIO for details.
562 cgroup_disable= [KNL] Disable a particular controller
563 Format: {name of the controller(s) to disable}
564 The effects of cgroup_disable=foo are:
565 - foo isn't auto-mounted if you mount all cgroups in
567 - foo isn't visible as an individually mountable
569 {Currently only "memory" controller deal with this and
570 cut the overhead, others just disable the usage. So
571 only cgroup_disable=memory is actually worthy}
573 checkreqprot [SELINUX] Set initial checkreqprot flag value.
574 Format: { "0" | "1" }
575 See security/selinux/Kconfig help text.
576 0 -- check protection applied by kernel (includes
577 any implied execute protection).
578 1 -- check protection requested by application.
579 Default value is set via a kernel config option.
580 Value can be changed at runtime via
581 /selinux/checkreqprot.
584 See Documentation/s390/CommonIO for details.
587 Keep all clocks already enabled by bootloader on,
588 even if no driver has claimed them. This is useful
589 for debug and development, but should not be
590 needed on a platform with proper driver support.
591 For more information, see Documentation/clk.txt.
593 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
595 Forces specified clocksource (if available) to be used
596 when calculating gettimeofday(). If specified
597 clocksource is not available, it defaults to PIT.
598 Format: { pit | tsc | cyclone | pmtmr }
600 clocksource= Override the default clocksource
602 Override the default clocksource and use the clocksource
603 with the name specified.
604 Some clocksource names to choose from, depending on
606 [all] jiffies (this is the base, fallback clocksource)
608 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
609 pxa_timer,timer3,32k_counter,timer0_1
611 [X86-32] pit,hpet,tsc;
612 scx200_hrt on Geode; cyclone on IBM x440
620 clearcpuid=BITNUM [X86]
621 Disable CPUID feature X for the kernel. See
622 arch/x86/include/asm/cpufeature.h for the valid bit
623 numbers. Note the Linux specific bits are not necessarily
624 stable over kernel options, but the vendor specific
626 Also note that user programs calling CPUID directly
627 or using the feature without checking anything
628 will still see it. This just prevents it from
629 being used by the kernel or shown in /proc/cpuinfo.
630 Also note the kernel might malfunction if you disable
634 Sets the size of kernel global memory area for contiguous
635 memory allocations. For more information, see
636 include/linux/dma-contiguous.h
638 cmo_free_hint= [PPC] Format: { yes | no }
639 Specify whether pages are marked as being inactive
640 when they are freed. This is used in CMO environments
641 to determine OS memory pressure for page stealing by
645 coherent_pool=nn[KMG] [ARM,KNL]
646 Sets the size of memory pool for coherent, atomic dma
647 allocations, by default set to 256K.
649 code_bytes [X86] How many bytes of object code to print
654 com20020= [HW,NET] ARCnet - COM20020 chipset
656 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
658 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
662 ARCnet - COM90xx chipset (memory-mapped buffers)
663 Format: <io>[,<irq>[,<memstart>]]
665 condev= [HW,S390] console device
668 console= [KNL] Output console device and options.
670 tty<n> Use the virtual console device <n>.
674 Use the specified serial port. The options are of
675 the form "bbbbpnf", where "bbbb" is the baud rate,
676 "p" is parity ("n", "o", or "e"), "n" is number of
677 bits, and "f" is flow control ("r" for RTS or
678 omit it). Default is "9600n8".
680 See Documentation/serial-console.txt for more
682 Documentation/networking/netconsole.txt for an
685 uart[8250],io,<addr>[,options]
686 uart[8250],mmio,<addr>[,options]
687 Start an early, polled-mode console on the 8250/16550
688 UART at the specified I/O port or MMIO address,
689 switching to the matching ttyS device later. The
690 options are the same as for ttyS, above.
691 hvc<n> Use the hypervisor console device <n>. This is for
692 both Xen and PowerPC hypervisors.
694 If the device connected to the port is not a TTY but a braille
695 device, prepend "brl," before the device type, for instance
697 For now, only VisioBraille is supported.
699 consoleblank= [KNL] The console blank (screen saver) timeout in
700 seconds. Defaults to 10*60 = 10mins. A value of 0
701 disables the blank timer.
704 [KNL] Change the default value for
705 /proc/<pid>/coredump_filter.
706 See also Documentation/filesystems/proc.txt.
708 cpuidle.off=1 [CPU_IDLE]
709 disable the cpuidle sub-system
711 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
713 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
715 crashkernel=size[KMG][@offset[KMG]]
716 [KNL] Using kexec, Linux can switch to a 'crash kernel'
717 upon panic. This parameter reserves the physical
718 memory region [offset, offset + size] for that kernel
719 image. If '@offset' is omitted, then a suitable offset
720 is selected automatically. Check
721 Documentation/kdump/kdump.txt for further details.
723 crashkernel=range1:size1[,range2:size2,...][@offset]
724 [KNL] Same as above, but depends on the memory
725 in the running system. The syntax of range is
726 start-[end] where start and end are both
727 a memory unit (amount[KMG]). See also
728 Documentation/kdump/kdump.txt for an example.
730 crashkernel=size[KMG],high
731 [KNL, x86_64] range could be above 4G. Allow kernel
732 to allocate physical memory region from top, so could
733 be above 4G if system have more than 4G ram installed.
734 Otherwise memory region will be allocated below 4G, if
736 It will be ignored if crashkernel=X is specified.
737 crashkernel=size[KMG],low
738 [KNL, x86_64] range under 4G. When crashkernel=X,high
739 is passed, kernel could allocate physical memory region
740 above 4G, that cause second kernel crash on system
741 that require some amount of low memory, e.g. swiotlb
742 requires at least 64M+32K low memory. Kernel would
743 try to allocate 72M below 4G automatically.
744 This one let user to specify own low range under 4G
745 for second kernel instead.
746 0: to disable low allocation.
747 It will be ignored when crashkernel=X,high is not used
748 or memory reserved is below 4G.
753 cs89x0_media= [HW,NET]
754 Format: { rj45 | aui | bnc }
757 See header of drivers/s390/block/dasd_devmap.c.
759 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
760 (one device per port)
761 Format: <port#>,<type>
762 See also Documentation/input/joystick-parport.txt
764 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
765 time. See Documentation/dynamic-debug-howto.txt for
766 details. Deprecated, see dyndbg.
768 debug [KNL] Enable kernel debugging (events log level).
771 [KNL] verbose self-tests
773 Print debugging info while doing the locking API
775 We default to 0 (no extra messages), setting it to
776 1 will print _a lot_ more information - normally
777 only useful to kernel developers.
779 debug_objects [KNL] Enable object debugging
782 [KNL] Disable object debugging
784 debug_guardpage_minorder=
785 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
786 parameter allows control of the order of pages that will
787 be intentionally kept free (and hence protected) by the
788 buddy allocator. Bigger value increase the probability
789 of catching random memory corruption, but reduce the
790 amount of memory for normal system use. The maximum
791 possible value is MAX_ORDER/2. Setting this parameter
792 to 1 or 2 should be enough to identify most random
793 memory corruption problems caused by bugs in kernel or
794 driver code when a CPU writes to (or reads from) a
795 random memory location. Note that there exists a class
796 of memory corruptions problems caused by buggy H/W or
797 F/W or by drivers badly programing DMA (basically when
798 memory is written at bus level and the CPU MMU is
799 bypassed) which are not detectable by
800 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
801 tracking down these problems.
803 debugpat [X86] Enable PAT debugging
805 decnet.addr= [HW,NET]
806 Format: <area>[,<node>]
807 See also Documentation/networking/decnet.txt.
810 [same as hugepagesz=] The size of the default
811 HugeTLB page size. This is the size represented by
812 the legacy /proc/ hugepages APIs, used for SHM, and
813 default size when mounting hugetlbfs filesystems.
814 Defaults to the default architecture's huge page size
818 Set number of hash buckets for dentry cache.
821 See Documentation/networking/ipv6.txt.
823 disable_cpu_apicid= [X86,APIC,SMP]
825 The number of initial APIC ID for the
826 corresponding CPU to be disabled at boot,
827 mostly used for the kdump 2nd kernel to
828 disable BSP to wake up multiple CPUs without
829 causing system reset or hang due to sending
832 disable_ddw [PPC/PSERIES]
833 Disable Dynamic DMA Window support. Use this if
834 to workaround buggy firmware.
837 See Documentation/networking/ipv6.txt.
839 disable_mtrr_cleanup [X86]
840 The kernel tries to adjust MTRR layout from continuous
841 to discrete, to make X server driver able to add WB
842 entry later. This parameter disables that.
844 disable_mtrr_trim [X86, Intel and AMD only]
845 By default the kernel will trim any uncacheable
846 memory out of your available memory pool based on
847 MTRR settings. This parameter disables that behavior,
848 possibly causing your machine to run very slowly.
850 disable_timer_pin_1 [X86]
851 Disable PIN 1 of APIC timer
852 Can be useful to work around chipset bugs.
854 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
855 this option disables the debugging code at boot.
857 dma_debug_entries=<number>
858 This option allows to tune the number of preallocated
859 entries for DMA-API debugging code. One entry is
860 required per DMA-API allocation. Use this if the
861 DMA-API debugging code disables itself because the
862 architectural default is too low.
864 dma_debug_driver=<driver_name>
865 With this option the DMA-API debugging driver
866 filter feature can be enabled at boot time. Just
867 pass the driver to filter for as the parameter.
868 The filter can be disabled or changed to another
869 driver later using sysfs.
871 drm_kms_helper.edid_firmware=[<connector>:]<file>
872 Broken monitors, graphic adapters and KVMs may
873 send no or incorrect EDID data sets. This parameter
874 allows to specify an EDID data set in the
875 /lib/firmware directory that is used instead.
876 Generic built-in EDID data sets are used, if one of
877 edid/1024x768.bin, edid/1280x1024.bin,
878 edid/1680x1050.bin, or edid/1920x1080.bin is given
879 and no file with the same name exists. Details and
880 instructions how to build your own EDID data are
881 available in Documentation/EDID/HOWTO.txt. An EDID
882 data set will only be used for a particular connector,
883 if its name and a colon are prepended to the EDID
888 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
889 module.dyndbg[="val"]
890 Enable debug messages at boot time. See
891 Documentation/dynamic-debug-howto.txt for details.
893 early_ioremap_debug [KNL]
894 Enable debug messages in early_ioremap support. This
895 is useful for tracking down temporary early mappings
896 which are not unmapped.
898 earlycon= [KNL] Output early console device and options.
899 uart[8250],io,<addr>[,options]
900 uart[8250],mmio,<addr>[,options]
901 uart[8250],mmio32,<addr>[,options]
902 Start an early, polled-mode console on the 8250/16550
903 UART at the specified I/O port or MMIO address.
904 MMIO inter-register address stride is either 8-bit
905 (mmio) or 32-bit (mmio32).
906 The options are the same as for ttyS, above.
908 earlyprintk= [X86,SH,BLACKFIN,ARM]
912 earlyprintk=serial[,ttySn[,baudrate]]
913 earlyprintk=serial[,0x...[,baudrate]]
914 earlyprintk=ttySn[,baudrate]
915 earlyprintk=dbgp[debugController#]
917 earlyprintk is useful when the kernel crashes before
918 the normal console is initialized. It is not enabled by
919 default because it has some cosmetic problems.
921 Append ",keep" to not disable it when the real console
924 Only one of vga, efi, serial, or usb debug port can
927 Currently only ttyS0 and ttyS1 may be specified by
928 name. Other I/O ports may be explicitly specified
929 on some architectures (x86 and arm at least) by
930 replacing ttySn with an I/O port address, like this:
931 earlyprintk=serial,0x1008,115200
932 You can find the port for a given device in
933 /proc/tty/driver/serial:
934 2: uart:ST16650V2 port:00001008 irq:18 ...
936 Interaction with the standard serial driver is not
939 The VGA and EFI output is eventually overwritten by
942 The xen output can only be used by Xen PV guests.
944 edac_report= [HW,EDAC] Control how to report EDAC event
945 Format: {"on" | "off" | "force"}
946 on: enable EDAC to report H/W event. May be overridden
947 by other higher priority error reporting module.
948 off: disable H/W event reporting through EDAC.
949 force: enforce the use of EDAC to report H/W event.
952 ekgdboc= [X86,KGDB] Allow early kernel console debugging
955 This is designed to be used in conjunction with
956 the boot argument: earlyprintk=vga
959 Format: {"off" | "on" | "skip[mbr]"}
962 Format: { "old_map" }
963 old_map [X86-64]: switch to the old ioremap-based EFI
964 runtime services mapping. 32-bit still uses this one by
967 efi_no_storage_paranoia [EFI; X86]
968 Using this parameter you can use more than 50% of
969 your efi variable storage. Use this parameter only if
970 you are really sure that your UEFI does sane gc and
971 fulfills the spec otherwise your board may brick.
973 eisa_irq_edge= [PARISC,HW]
974 See header of drivers/parisc/eisa.c.
977 See comment before function elanfreq_setup() in
978 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
981 Format: {"cfq" | "deadline" | "noop"}
982 See Documentation/block/cfq-iosched.txt and
983 Documentation/block/deadline-iosched.txt for details.
985 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
986 Specifies physical address of start of kernel core
987 image elf header and optionally the size. Generally
988 kexec loader will pass this option to capture kernel.
989 See Documentation/kdump/kdump.txt for details.
991 enable_mtrr_cleanup [X86]
992 The kernel tries to adjust MTRR layout from continuous
993 to discrete, to make X server driver able to add WB
994 entry later. This parameter enables that.
996 enable_timer_pin_1 [X86]
997 Enable PIN 1 of APIC timer
998 Can be useful to work around chipset bugs
999 (in particular on some ATI chipsets).
1000 The kernel tries to set a reasonable default.
1002 enforcing [SELINUX] Set initial enforcing status.
1004 See security/selinux/Kconfig help text.
1005 0 -- permissive (log only, no denials).
1006 1 -- enforcing (deny and log).
1008 Value can be changed at runtime via /selinux/enforce.
1011 Disable Error Record Serialization Table (ERST)
1014 ether= [HW,NET] Ethernet cards parameters
1015 This option is obsoleted by the "netdev=" option, which
1016 has equivalent usage. See its documentation for details.
1020 Permit 'security.evm' to be updated regardless of
1021 current integrity status.
1025 fail_make_request=[KNL]
1026 General fault injection mechanism.
1027 Format: <interval>,<probability>,<space>,<times>
1028 See also Documentation/fault-injection/.
1031 See Documentation/blockdev/floppy.txt.
1033 force_pal_cache_flush
1034 [IA-64] Avoid check_sal_cache_flush which may hang on
1035 buggy SAL_CACHE_FLUSH implementations. Using this
1036 parameter will force ia64_sal_cache_flush to call
1037 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1040 Forcefully enable Physical Address Extension (PAE).
1041 Many Pentium M systems disable PAE but may have a
1042 functionally usable PAE implementation.
1043 Warning: use of this parameter will taint the kernel
1044 and may cause unknown problems.
1047 [FTRACE] will set and start the specified tracer
1048 as early as possible in order to facilitate early
1051 ftrace_dump_on_oops[=orig_cpu]
1052 [FTRACE] will dump the trace buffers on oops.
1053 If no parameter is passed, ftrace will dump
1054 buffers of all CPUs, but if you pass orig_cpu, it will
1055 dump only the buffer of the CPU that triggered the
1058 ftrace_filter=[function-list]
1059 [FTRACE] Limit the functions traced by the function
1060 tracer at boot up. function-list is a comma separated
1061 list of functions. This list can be changed at run
1062 time by the set_ftrace_filter file in the debugfs
1065 ftrace_notrace=[function-list]
1066 [FTRACE] Do not trace the functions specified in
1067 function-list. This list can be changed at run time
1068 by the set_ftrace_notrace file in the debugfs
1071 ftrace_graph_filter=[function-list]
1072 [FTRACE] Limit the top level callers functions traced
1073 by the function graph tracer at boot up.
1074 function-list is a comma separated list of functions
1075 that can be changed at run time by the
1076 set_graph_function file in the debugfs tracing directory.
1079 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1080 support via parallel port (up to 5 devices per port)
1081 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1082 See also Documentation/input/joystick-parport.txt
1086 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1090 gcov_persist= [GCOV] When non-zero (default), profiling data for
1091 kernel modules is saved and remains accessible via
1092 debugfs, even when the module is unloaded/reloaded.
1093 When zero, profiling data is discarded and associated
1094 debugfs files are removed at module unload time.
1096 gpt [EFI] Forces disk with valid GPT signature but
1097 invalid Protective MBR to be treated as GPT. If the
1098 primary GPT is corrupted, it enables the backup/alternate
1099 GPT to be used instead.
1101 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1102 the "Enable 0" bit of the configuration register.
1105 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1106 the "Enable 0" bit of the configuration register.
1109 grcan.select= [HW] Select which physical interface to use.
1112 grcan.txsize= [HW] Sets the size of the tx buffer.
1113 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1115 grcan.rxsize= [HW] Sets the size of the rx buffer.
1116 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1119 hashdist= [KNL,NUMA] Large hashes allocated during boot
1120 are distributed across NUMA nodes. Defaults on
1121 for 64-bit NUMA, off otherwise.
1122 Format: 0 | 1 (for off | on)
1124 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1126 hd= [EIDE] (E)IDE hard drive subsystem geometry
1127 Format: <cyl>,<head>,<sect>
1130 Disable Hardware Error Source Table (HEST) support;
1131 corresponding firmware-first mode error processing
1132 logic will be disabled.
1134 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1135 size of <nn>. This works even on boxes that have no
1136 highmem otherwise. This also works to reduce highmem
1137 size on bigger boxes.
1139 highres= [KNL] Enable/disable high resolution timer mode.
1140 Valid parameters: "on", "off"
1144 See Documentation/isdn/README.HiSax.
1148 hpet= [X86-32,HPET] option to control HPET usage
1149 Format: { enable (default) | disable | force |
1151 disable: disable HPET and use PIT instead
1152 force: allow force enabled of undocumented chips (ICH4,
1154 verbose: show contents of HPET registers during setup
1156 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1157 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1159 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1160 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1161 On x86-64 and powerpc, this option can be specified
1162 multiple times interleaved with hugepages= to reserve
1163 huge pages of different sizes. Valid pages sizes on
1164 x86-64 are 2M (when the CPU supports "pse") and 1G
1165 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1166 Note that 1GB pages can only be allocated at boot time
1167 using hugepages= and not freed afterwards.
1169 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1170 terminal devices. Valid values: 0..8
1171 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1172 If specified, z/VM IUCV HVC accepts connections
1173 from listed z/VM user IDs only.
1175 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1176 hardware thread id mappings.
1177 Format: <cpu>:<hwthread>
1180 Do not unregister boot console at start. This is only
1181 useful for debugging when something happens in the window
1182 between unregistering the boot console and initializing
1185 i2c_bus= [HW] Override the default board specific I2C bus speed
1186 or register an additional I2C bus that is not
1187 registered from board initialization code.
1191 i8042.debug [HW] Toggle i8042 debug mode
1192 i8042.direct [HW] Put keyboard port into non-translated mode
1193 i8042.dumbkbd [HW] Pretend that controller can only read data from
1194 keyboard and cannot control its state
1195 (Don't attempt to blink the leds)
1196 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1197 i8042.nokbd [HW] Don't check/create keyboard port
1198 i8042.noloop [HW] Disable the AUX Loopback command while probing
1200 i8042.nomux [HW] Don't check presence of an active multiplexing
1202 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1204 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1205 i8042.reset [HW] Reset the controller during init and cleanup
1206 i8042.unlock [HW] Unlock (ignore) the keylock
1210 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1211 indicates that the driver is running on unsupported
1213 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1214 does not match list of supported models.
1216 [HW] Report power status in /proc/i8k
1217 (disabled by default)
1218 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1221 i915.invert_brightness=
1222 [DRM] Invert the sense of the variable that is used to
1223 set the brightness of the panel backlight. Normally a
1224 brightness value of 0 indicates backlight switched off,
1225 and the maximum of the brightness value sets the backlight
1226 to maximum brightness. If this parameter is set to 0
1227 (default) and the machine requires it, or this parameter
1228 is set to 1, a brightness value of 0 sets the backlight
1229 to maximum brightness, and the maximum of the brightness
1230 value switches the backlight off.
1231 -1 -- never invert brightness
1232 0 -- machine default
1233 1 -- force brightness inversion
1236 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1238 ide-core.nodma= [HW] (E)IDE subsystem
1239 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1240 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1241 .cdrom .chs .ignore_cable are additional options
1242 See Documentation/ide/ide.txt.
1244 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1245 Claim all unknown PCI IDE storage controllers.
1248 Format: idle=poll, idle=halt, idle=nomwait
1249 Poll forces a polling idle loop that can slightly
1250 improve the performance of waking up a idle CPU, but
1251 will use a lot of power and make the system run hot.
1253 idle=halt: Halt is forced to be used for CPU idle.
1254 In such case C2/C3 won't be used again.
1255 idle=nomwait: Disable mwait for CPU C-states
1257 ignore_loglevel [KNL]
1258 Ignore loglevel setting - this will print /all/
1259 kernel messages to the console. Useful for debugging.
1260 We also add it as printk module parameter, so users
1261 could change it dynamically, usually by
1262 /sys/module/printk/parameters/ignore_loglevel.
1264 ihash_entries= [KNL]
1265 Set number of hash buckets for inode cache.
1267 ima_appraise= [IMA] appraise integrity measurements
1268 Format: { "off" | "enforce" | "fix" }
1271 ima_appraise_tcb [IMA]
1272 The builtin appraise policy appraises all files
1276 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1280 The list of supported hash algorithms is defined
1281 in crypto/hash_info.h.
1284 Load a policy which meets the needs of the Trusted
1285 Computing Base. This means IMA will measure all
1286 programs exec'd, files mmap'd for exec, and all files
1287 opened for read by uid=0.
1290 Select one of defined IMA measurements template formats.
1291 Formats: { "ima" | "ima-ng" }
1296 Run specified binary instead of /sbin/init as init
1299 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1300 for working out where the kernel is dying during
1303 initrd= [BOOT] Specify the location of the initial ramdisk
1305 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1308 int_pln_enable [x86] Enable power limit notification interrupt
1310 integrity_audit=[IMA]
1311 Format: { "0" | "1" }
1312 0 -- basic integrity auditing messages. (Default)
1313 1 -- additional integrity auditing messages.
1315 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1317 Enable intel iommu driver.
1319 Disable intel iommu driver.
1320 igfx_off [Default Off]
1321 By default, gfx is mapped as normal device. If a gfx
1322 device has a dedicated DMAR unit, the DMAR unit is
1323 bypassed by not enabling DMAR with this option. In
1324 this case, gfx device will use physical address for
1327 With this option iommu will not optimize to look
1328 for io virtual address below 32-bit forcing dual
1329 address cycle on pci bus for cards supporting greater
1330 than 32-bit addressing. The default is to look
1331 for translation below 32-bit and if not available
1332 then look in the higher range.
1333 strict [Default Off]
1334 With this option on every unmap_single operation will
1335 result in a hardware IOTLB flush operation as opposed
1336 to batching them for performance.
1337 sp_off [Default Off]
1338 By default, super page will be supported if Intel IOMMU
1339 has the capability. With this option, super page will
1342 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1343 0 disables intel_idle and fall back on acpi_idle.
1344 1 to 6 specify maximum depth of C-state.
1348 Do not enable intel_pstate as the default
1349 scaling driver for the supported processors
1351 intremap= [X86-64, Intel-IOMMU]
1352 on enable Interrupt Remapping (default)
1353 off disable Interrupt Remapping
1354 nosid disable Source ID checking
1356 BIOS x2APIC opt-out request will be ignored
1358 iomem= Disable strict checking of access to MMIO memory
1359 strict regions from userspace.
1376 io7= [HW] IO7 for Marvel based alpha systems
1377 See comment before marvel_specify_io7 in
1378 arch/alpha/kernel/core_marvel.c.
1380 io_delay= [X86] I/O delay method
1382 Standard port 0x80 based delay
1384 Alternate port 0xed based delay (needed on some systems)
1386 Simple two microseconds delay
1391 See Documentation/filesystems/nfs/nfsroot.txt.
1393 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1394 See comment before ip2_setup() in
1395 drivers/char/ip2/ip2base.c.
1398 When an interrupt is not handled search all handlers
1399 for it. Intended to get systems with badly broken
1403 When an interrupt is not handled search all handlers
1404 for it. Also check all handlers each timer
1405 interrupt. Intended to get systems with badly broken
1409 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1411 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1413 <cpu number>,...,<cpu number>
1415 <cpu number>-<cpu number>
1416 (must be a positive range in ascending order)
1418 <cpu number>,...,<cpu number>-<cpu number>
1420 This option can be used to specify one or more CPUs
1421 to isolate from the general SMP balancing and scheduling
1422 algorithms. You can move a process onto or off an
1423 "isolated" CPU via the CPU affinity syscalls or cpuset.
1424 <cpu number> begins at 0 and the maximum value is
1425 "number of CPUs in system - 1".
1427 This option is the preferred way to isolate CPUs. The
1428 alternative -- manually setting the CPU mask of all
1429 tasks in the system -- can cause problems and
1430 suboptimal load balancer performance.
1434 ivrs_ioapic [HW,X86_64]
1435 Provide an override to the IOAPIC-ID<->DEVICE-ID
1436 mapping provided in the IVRS ACPI table. For
1437 example, to map IOAPIC-ID decimal 10 to
1438 PCI device 00:14.0 write the parameter as:
1439 ivrs_ioapic[10]=00:14.0
1441 ivrs_hpet [HW,X86_64]
1442 Provide an override to the HPET-ID<->DEVICE-ID
1443 mapping provided in the IVRS ACPI table. For
1444 example, to map HPET-ID decimal 0 to
1445 PCI device 00:14.0 write the parameter as:
1446 ivrs_hpet[0]=00:14.0
1448 js= [HW,JOY] Analog joystick
1449 See Documentation/input/joystick.txt.
1453 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1454 specifies the amount of memory usable by the kernel
1455 for non-movable allocations. The requested amount is
1456 spread evenly throughout all nodes in the system. The
1457 remaining memory in each node is used for Movable
1458 pages. In the event, a node is too small to have both
1459 kernelcore and Movable pages, kernelcore pages will
1460 take priority and other nodes will have a larger number
1461 of Movable pages. The Movable zone is used for the
1462 allocation of pages that may be reclaimed or moved
1463 by the page migration subsystem. This means that
1464 HugeTLB pages may not be allocated from this zone.
1465 Note that allocations like PTEs-from-HighMem still
1466 use the HighMem zone if it exists, and the Normal
1467 zone if it does not.
1469 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1470 Format: <Controller#>[,poll interval]
1471 The controller # is the number of the ehci usb debug
1472 port as it is probed via PCI. The poll interval is
1473 optional and is the number seconds in between
1474 each poll cycle to the debug port in case you need
1475 the functionality for interrupting the kernel with
1476 gdb or control-c on the dbgp connection. When
1477 not using this parameter you use sysrq-g to break into
1478 the kernel debugger.
1480 kgdboc= [KGDB,HW] kgdb over consoles.
1481 Requires a tty driver that supports console polling,
1482 or a supported polling keyboard driver (non-usb).
1483 Serial only format: <serial_device>[,baud]
1484 keyboard only format: kbd
1485 keyboard and serial format: kbd,<serial_device>[,baud]
1486 Optional Kernel mode setting:
1487 kms, kbd format: kms,kbd
1488 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1490 kgdbwait [KGDB] Stop kernel execution and enter the
1491 kernel debugger at the earliest opportunity.
1493 kmac= [MIPS] korina ethernet MAC address.
1494 Configure the RouterBoard 532 series on-chip
1495 Ethernet adapter MAC address.
1497 kmemleak= [KNL] Boot-time kmemleak enable/disable
1498 Valid arguments: on, off
1501 kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode
1502 Valid arguments: 0, 1, 2
1503 kmemcheck=0 (disabled)
1504 kmemcheck=1 (enabled)
1505 kmemcheck=2 (one-shot mode)
1506 Default: 2 (one-shot mode)
1508 kstack=N [X86] Print N words from the kernel stack
1511 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1512 Default is 0 (don't ignore, but inject #GP)
1514 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1518 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1519 Default is 1 (enabled)
1521 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1523 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1525 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1526 (virtualized MMU) support on capable Intel chips.
1527 Default is 1 (enabled)
1529 kvm-intel.emulate_invalid_guest_state=
1530 [KVM,Intel] Enable emulation of invalid guest states
1531 Default is 0 (disabled)
1533 kvm-intel.flexpriority=
1534 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1535 Default is 1 (enabled)
1538 [KVM,Intel] Enable VMX nesting (nVMX).
1539 Default is 0 (disabled)
1541 kvm-intel.unrestricted_guest=
1542 [KVM,Intel] Disable unrestricted guest feature
1543 (virtualized real and unpaged mode) on capable
1544 Intel chips. Default is 1 (enabled)
1546 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1547 feature (tagged TLBs) on capable Intel chips.
1548 Default is 1 (enabled)
1554 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1557 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1558 value for LAPIC timer one-shot implementation. Default
1559 back to the programmable timer unit in the LAPIC.
1561 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1564 libata.dma= [LIBATA] DMA control
1565 libata.dma=0 Disable all PATA and SATA DMA
1566 libata.dma=1 PATA and SATA Disk DMA only
1567 libata.dma=2 ATAPI (CDROM) DMA only
1568 libata.dma=4 Compact Flash DMA only
1569 Combinations also work, so libata.dma=3 enables DMA
1570 for disks and CDROMs, but not CFs.
1572 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1573 libata.ignore_hpa=0 keep BIOS limits (default)
1574 libata.ignore_hpa=1 ignore limits, using full disk
1576 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1580 libata.force= [LIBATA] Force configurations. The format is comma
1581 separated list of "[ID:]VAL" where ID is
1582 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1583 matching port, link or device. Basically, it matches
1584 the ATA ID string printed on console by libata. If
1585 the whole ID part is omitted, the last PORT and DEVICE
1586 values are used. If ID hasn't been specified yet, the
1587 configuration applies to all ports, links and devices.
1589 If only DEVICE is omitted, the parameter applies to
1590 the port and all links and devices behind it. DEVICE
1591 number of 0 either selects the first device or the
1592 first fan-out link behind PMP device. It does not
1593 select the host link. DEVICE number of 15 selects the
1594 host link and device attached to it.
1596 The VAL specifies the configuration to force. As long
1597 as there's no ambiguity shortcut notation is allowed.
1598 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1599 The following configurations can be forced.
1601 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1602 Any ID with matching PORT is used.
1604 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1606 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1607 udma[/][16,25,33,44,66,100,133] notation is also
1610 * [no]ncq: Turn on or off NCQ.
1612 * nohrst, nosrst, norst: suppress hard, soft
1615 * rstonce: only attempt one reset during
1616 hot-unplug link recovery
1618 * dump_id: dump IDENTIFY data.
1620 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1622 * disable: Disable this device.
1624 If there are multiple matching configurations changing
1625 the same attribute, the last one is used.
1627 memblock=debug [KNL] Enable memblock debug messages.
1629 load_ramdisk= [RAM] List of ramdisks to load from floppy
1630 See Documentation/blockdev/ramdisk.txt.
1632 lockd.nlm_grace_period=P [NFS] Assign grace period.
1635 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1638 lockd.nlm_timeout=T [NFS] Assign timeout value.
1641 lockd.nlm_udpport=M [NFS] Assign UDP port.
1644 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1647 loglevel= All Kernel Messages with a loglevel smaller than the
1648 console loglevel will be printed to the console. It can
1649 also be changed with klogd or other programs. The
1650 loglevels are defined as follows:
1652 0 (KERN_EMERG) system is unusable
1653 1 (KERN_ALERT) action must be taken immediately
1654 2 (KERN_CRIT) critical conditions
1655 3 (KERN_ERR) error conditions
1656 4 (KERN_WARNING) warning conditions
1657 5 (KERN_NOTICE) normal but significant condition
1658 6 (KERN_INFO) informational
1659 7 (KERN_DEBUG) debug-level messages
1661 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1662 in bytes. n must be a power of two. The default
1663 size is set in the kernel config file.
1665 logo.nologo [FB] Disables display of the built-in Linux logo.
1666 This may be used to provide more screen space for
1667 kernel log messages and is useful when debugging
1668 kernel boot problems.
1670 lp=0 [LP] Specify parallel ports to use, e.g,
1671 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1672 lp=reset first parallel port). 'lp=0' disables the
1673 lp=auto printer driver. 'lp=reset' (which can be
1674 specified in addition to the ports) causes
1675 attached printers to be reset. Using
1676 lp=port1,port2,... specifies the parallel ports
1677 to associate lp devices with, starting with
1678 lp0. A port specification may be 'none' to skip
1679 that lp device, or a parport name such as
1680 'parport0'. Specifying 'lp=auto' instead of a
1681 port specification list means that device IDs
1682 from each port should be examined, to see if
1683 an IEEE 1284-compliant printer is attached; if
1684 so, the driver will manage that printer.
1685 See also header of drivers/char/lp.c.
1688 Sets loops_per_jiffy to given constant, thus avoiding
1689 time-consuming boot-time autodetection (up to 250 ms per
1690 CPU). 0 enables autodetection (default). To determine
1691 the correct value for your kernel, boot with normal
1692 autodetection and see what value is printed. Note that
1693 on SMP systems the preset will be applied to all CPUs,
1694 which is likely to cause problems if your CPUs need
1695 significantly divergent settings. An incorrect value
1696 will cause delays in the kernel to be wrong, leading to
1697 unpredictable I/O errors and other breakage. Although
1698 unlikely, in the extreme case this might damage your
1702 Format: <io>,<irq>,<dma>
1704 machvec= [IA-64] Force the use of a particular machine-vector
1705 (machvec) in a generic kernel.
1706 Example: machvec=hpzx1_swiotlb
1708 machtype= [Loongson] Share the same kernel image file between different
1710 Example: machtype=lemote-yeeloong-2f-7inch
1712 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1713 than or equal to this physical address is ignored.
1715 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1716 should make use of. maxcpus=n : n >= 0 limits the
1717 kernel to using 'n' processors. n=0 is a special case,
1718 it is equivalent to "nosmp", which also disables
1721 max_loop= [LOOP] The number of loop block devices that get
1722 (loop.max_loop) unconditionally pre-created at init time. The default
1723 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1724 of statically allocating a predefined number, loop
1725 devices can be requested on-demand with the
1726 /dev/loop-control interface.
1728 mce [X86-32] Machine Check Exception
1730 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1732 md= [HW] RAID subsystems devices and level
1733 See Documentation/md.txt.
1736 Format: <first>,<last>
1737 Specifies range of consoles to be captured by the MDA.
1739 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1740 Amount of memory to be used when the kernel is not able
1741 to see the whole system memory or for test.
1742 [X86] Work as limiting max address. Use together
1743 with memmap= to avoid physical address space collisions.
1744 Without memmap= PCI devices could be placed at addresses
1745 belonging to unused RAM.
1747 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1751 [KNL,SH] Allow user to override the default size for
1752 per-device physically contiguous DMA buffers.
1754 memmap=exactmap [KNL,X86] Enable setting of an exact
1755 E820 memory map, as specified by the user.
1756 Such memmap=exactmap lines can be constructed based on
1757 BIOS output or other requirements. See the memmap=nn@ss
1760 memmap=nn[KMG]@ss[KMG]
1761 [KNL] Force usage of a specific region of memory.
1762 Region of memory to be used is from ss to ss+nn.
1764 memmap=nn[KMG]#ss[KMG]
1765 [KNL,ACPI] Mark specific memory as ACPI data.
1766 Region of memory to be marked is from ss to ss+nn.
1768 memmap=nn[KMG]$ss[KMG]
1769 [KNL,ACPI] Mark specific memory as reserved.
1770 Region of memory to be reserved is from ss to ss+nn.
1771 Example: Exclude memory from 0x18690000-0x1869ffff
1772 memmap=64K$0x18690000
1774 memmap=0x10000$0x18690000
1776 memory_corruption_check=0/1 [X86]
1777 Some BIOSes seem to corrupt the first 64k of
1778 memory when doing things like suspend/resume.
1779 Setting this option will scan the memory
1780 looking for corruption. Enabling this will
1781 both detect corruption and prevent the kernel
1782 from using the memory being corrupted.
1783 However, its intended as a diagnostic tool; if
1784 repeatable BIOS-originated corruption always
1785 affects the same memory, you can use memmap=
1786 to prevent the kernel from using that memory.
1788 memory_corruption_check_size=size [X86]
1789 By default it checks for corruption in the low
1790 64k, making this memory unavailable for normal
1791 use. Use this parameter to scan for
1792 corruption in more or less memory.
1794 memory_corruption_check_period=seconds [X86]
1795 By default it checks for corruption every 60
1796 seconds. Use this parameter to check at some
1797 other rate. 0 disables periodic checking.
1799 memtest= [KNL,X86] Enable memtest
1801 default : 0 <disable>
1802 Specifies the number of memtest passes to be
1803 performed. Each pass selects another test
1804 pattern from a given set of patterns. Memtest
1805 fills the memory with this pattern, validates
1806 memory contents and reserves bad memory
1807 regions that are detected.
1809 meye.*= [HW] Set MotionEye Camera parameters
1810 See Documentation/video4linux/meye.txt.
1812 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1813 Multi-Function General Purpose Timers on AMD Geode
1816 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1817 the BIOS has incorrectly applied a workaround. TinyBIOS
1818 version 0.98 is known to be affected, 0.99 fixes the
1819 problem by letting the user disable the workaround.
1823 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1824 physical address is ignored.
1826 mini2440= [ARM,HW,KNL]
1827 Format:[0..2][b][c][t]
1829 MINI2440 configuration specification:
1830 0 - The attached screen is the 3.5" TFT
1831 1 - The attached screen is the 7" TFT
1832 2 - The VGA Shield is attached (1024x768)
1833 Leaving out the screen size parameter will not load
1834 the TFT driver, and the framebuffer will be left
1836 b - Enable backlight. The TFT backlight pin will be
1837 linked to the kernel VESA blanking code and a GPIO
1838 LED. This parameter is not necessary when using the
1840 c - Enable the s3c camera interface.
1841 t - Reserved for enabling touchscreen support. The
1842 touchscreen support is not enabled in the mainstream
1843 kernel as of 2.6.30, a preliminary port can be found
1844 in the "bleeding edge" mini2440 support kernel at
1845 http://repo.or.cz/w/linux-2.6/mini2440.git
1848 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1849 parameter allows control of the logging verbosity for
1850 the additional memory initialisation checks. A value
1851 of 0 disables mminit logging and a level of 4 will
1852 log everything. Information is printed at KERN_DEBUG
1853 so loglevel=8 may also need to be specified.
1856 [KNL] When CONFIG_MODULE_SIG is set, this means that
1857 modules without (valid) signatures will fail to load.
1858 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1859 is always true, so this option does nothing.
1862 [MOUSE] Maximum time between finger touching and
1863 leaving touchpad surface for touch to be considered
1864 a tap and be reported as a left button click (for
1865 touchpads working in absolute mode only).
1867 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1868 reporting absolute coordinates, such as tablets
1869 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1870 reporting absolute coordinates, such as tablets
1872 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1873 is similar to kernelcore except it specifies the
1874 amount of memory used for migratable allocations.
1875 If both kernelcore and movablecore is specified,
1876 then kernelcore will be at *least* the specified
1877 value but may be more. If movablecore on its own
1878 is specified, the administrator must be careful
1879 that the amount of memory usable for all allocations
1882 movable_node [KNL,X86] Boot-time switch to enable the effects
1883 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1885 MTD_Partition= [MTD]
1886 Format: <name>,<region-number>,<size>,<offset>
1888 MTD_Region= [MTD] Format:
1889 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1892 See drivers/mtd/cmdlinepart.c.
1894 multitce=off [PPC] This parameter disables the use of the pSeries
1895 firmware feature for updating multiple TCE entries
1898 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1900 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1902 boundary - index of last SLC block on Flex-OneNAND.
1903 The remaining blocks are configured as MLC blocks.
1904 lock - Configure if Flex-OneNAND boundary should be locked.
1905 Once locked, the boundary cannot be changed.
1906 1 indicates lock status, 0 indicates unlock status.
1909 ARM/S3C2412 JIVE boot control
1911 See arch/arm/mach-s3c2412/mach-jive.c
1913 mtouchusb.raw_coordinates=
1914 [HW] Make the MicroTouch USB driver use raw coordinates
1915 ('y', default) or cooked coordinates ('n')
1917 mtrr_chunk_size=nn[KMG] [X86]
1918 used for mtrr cleanup. It is largest continuous chunk
1919 that could hold holes aka. UC entries.
1921 mtrr_gran_size=nn[KMG] [X86]
1922 Used for mtrr cleanup. It is granularity of mtrr block.
1924 Large value could prevent small alignment from
1927 mtrr_spare_reg_nr=n [X86]
1929 Range: 0,7 : spare reg number
1931 Used for mtrr cleanup. It is spare mtrr entries number.
1932 Set to 2 or more if your graphical card needs more.
1934 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1936 netdev= [NET] Network devices parameters
1937 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1938 Note that mem_start is often overloaded to mean
1939 something different and driver-specific.
1940 This usage is only documented in each driver source
1944 [NETFILTER] Enable connection tracking flow accounting
1945 0 to disable accounting
1946 1 to enable accounting
1949 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1950 See Documentation/filesystems/nfs/nfsroot.txt.
1952 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1953 See Documentation/filesystems/nfs/nfsroot.txt.
1955 nfsrootdebug [NFS] enable nfsroot debugging messages.
1956 See Documentation/filesystems/nfs/nfsroot.txt.
1958 nfs.callback_tcpport=
1959 [NFS] set the TCP port on which the NFSv4 callback
1960 channel should listen.
1963 [NFS] sets the pathname to the program which is used
1964 to update the NFS client cache entries.
1966 nfs.cache_getent_timeout=
1967 [NFS] sets the timeout after which an attempt to
1968 update a cache entry is deemed to have failed.
1970 nfs.idmap_cache_timeout=
1971 [NFS] set the maximum lifetime for idmapper cache
1975 [NFS] enable 64-bit inode numbers.
1976 If zero, the NFS client will fake up a 32-bit inode
1977 number for the readdir() and stat() syscalls instead
1978 of returning the full 64-bit number.
1979 The default is to return 64-bit inode numbers.
1981 nfs.max_session_slots=
1982 [NFSv4.1] Sets the maximum number of session slots
1983 the client will attempt to negotiate with the server.
1984 This limits the number of simultaneous RPC requests
1985 that the client can send to the NFSv4.1 server.
1986 Note that there is little point in setting this
1987 value higher than the max_tcp_slot_table_limit.
1989 nfs.nfs4_disable_idmapping=
1990 [NFSv4] When set to the default of '1', this option
1991 ensures that both the RPC level authentication
1992 scheme and the NFS level operations agree to use
1993 numeric uids/gids if the mount is using the
1994 'sec=sys' security flavour. In effect it is
1995 disabling idmapping, which can make migration from
1996 legacy NFSv2/v3 systems to NFSv4 easier.
1997 Servers that do not support this mode of operation
1998 will be autodetected by the client, and it will fall
1999 back to using the idmapper.
2000 To turn off this behaviour, set the value to '0'.
2002 [NFS4] Specify an additional fixed unique ident-
2003 ification string that NFSv4 clients can insert into
2004 their nfs_client_id4 string. This is typically a
2005 UUID that is generated at system install time.
2007 nfs.send_implementation_id =
2008 [NFSv4.1] Send client implementation identification
2009 information in exchange_id requests.
2010 If zero, no implementation identification information
2012 The default is to send the implementation identification
2015 nfs.recover_lost_locks =
2016 [NFSv4] Attempt to recover locks that were lost due
2017 to a lease timeout on the server. Please note that
2018 doing this risks data corruption, since there are
2019 no guarantees that the file will remain unchanged
2020 after the locks are lost.
2021 If you want to enable the kernel legacy behaviour of
2022 attempting to recover these locks, then set this
2024 The default parameter value of '0' causes the kernel
2025 not to attempt recovery of lost locks.
2027 nfsd.nfs4_disable_idmapping=
2028 [NFSv4] When set to the default of '1', the NFSv4
2029 server will return only numeric uids and gids to
2030 clients using auth_sys, and will accept numeric uids
2031 and gids from such clients. This is intended to ease
2032 migration from NFSv2/v3.
2034 objlayoutdriver.osd_login_prog=
2035 [NFS] [OBJLAYOUT] sets the pathname to the program which
2036 is used to automatically discover and login into new
2037 osd-targets. Please see:
2038 Documentation/filesystems/pnfs.txt for more explanations
2040 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
2041 when a NMI is triggered.
2042 Format: [state][,regs][,debounce][,die]
2044 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
2045 Format: [panic,][nopanic,][num]
2047 0 - turn nmi_watchdog off
2048 When panic is specified, panic when an NMI watchdog
2049 timeout occurs (or 'nopanic' to override the opposite
2051 This is useful when you use a panic=... timeout and
2052 need the box quickly up again.
2054 netpoll.carrier_timeout=
2055 [NET] Specifies amount of time (in seconds) that
2056 netpoll should wait for a carrier. By default netpoll
2059 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2060 emulation library even if a 387 maths coprocessor
2064 [HW] Never suspend the console
2065 Disable suspending of consoles during suspend and
2066 hibernate operations. Once disabled, debugging
2067 messages can reach various consoles while the rest
2068 of the system is being put to sleep (ie, while
2069 debugging driver suspend/resume hooks). This may
2070 not work reliably with all consoles, but is known
2071 to work with serial and VGA consoles.
2072 To facilitate more flexible debugging, we also add
2073 console_suspend, a printk module parameter to control
2074 it. Users could use console_suspend (usually
2075 /sys/module/printk/parameters/console_suspend) to
2076 turn on/off it dynamically.
2078 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2079 caches in the slab allocator. Saves per-node memory,
2080 but will impact performance.
2084 noapic [SMP,APIC] Tells the kernel to not make use of any
2085 IOAPICs that may be present in the system.
2088 Disable kernel and module base offset ASLR (Address
2089 Space Layout Randomization) if built into the kernel.
2091 noautogroup Disable scheduler automatic task group creation.
2093 nobats [PPC] Do not use BATs for mapping kernel lowmem
2094 on "Classic" PPC cores.
2098 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2100 nodelayacct [KNL] Disable per-task delay accounting
2102 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2104 nodsp [SH] Disable hardware DSP at boot time.
2106 noefi [X86] Disable EFI runtime services support.
2111 On X86-32 available only on PAE configured kernels.
2112 noexec=on: enable non-executable mappings (default)
2113 noexec=off: disable non-executable mappings
2116 Disable SMAP (Supervisor Mode Access Prevention)
2117 even if it is supported by processor.
2120 Disable SMEP (Supervisor Mode Execution Prevention)
2121 even if it is supported by processor.
2124 This affects only 32-bit executables.
2125 noexec32=on: enable non-executable mappings (default)
2126 read doesn't imply executable mappings
2127 noexec32=off: disable non-executable mappings
2128 read implies executable mappings
2130 nofpu [SH] Disable hardware FPU at boot time.
2132 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2133 register save and restore. The kernel will only save
2134 legacy floating-point registers on task switch.
2136 noxsave [BUGS=X86] Disables x86 extended register state save
2137 and restore using xsave. The kernel will fallback to
2138 enabling legacy floating-point and sse state.
2141 on enable eager fpu restore
2142 off disable eager fpu restore
2143 auto selects the default scheme, which automatically
2144 enables eagerfpu restore for xsaveopt.
2146 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2147 wfi(ARM) instruction doesn't work correctly and not to
2148 use it. This is also useful when using JTAG debugger.
2150 no_file_caps Tells the kernel not to honor file capabilities. The
2151 only way then for a file to be executed with privilege
2152 is to be setuid root or executed by root.
2154 nohalt [IA-64] Tells the kernel not to use the power saving
2155 function PAL_HALT_LIGHT when idle. This increases
2156 power-consumption. On the positive side, it reduces
2157 interrupt wake-up latency, which may improve performance
2158 in certain environments such as networked servers or
2161 nohz= [KNL] Boottime enable/disable dynamic ticks
2162 Valid arguments: on, off
2165 nohz_full= [KNL,BOOT]
2166 In kernels built with CONFIG_NO_HZ_FULL=y, set
2167 the specified list of CPUs whose tick will be stopped
2168 whenever possible. The boot CPU will be forced outside
2169 the range to maintain the timekeeping.
2170 The CPUs in this range must also be included in the
2173 noiotrap [SH] Disables trapped I/O port accesses.
2175 noirqdebug [X86-32] Disables the code which attempts to detect and
2176 disable unhandled interrupt sources.
2178 no_timer_check [X86,APIC] Disables the code which tests for
2179 broken timer IRQ sources.
2181 noisapnp [ISAPNP] Disables ISA PnP code.
2183 noinitrd [RAM] Tells the kernel not to load any configured
2186 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2188 [Deprecated - use intremap=off]
2192 nojitter [IA-64] Disables jitter checking for ITC timers.
2194 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2196 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2199 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2200 steal time is computed, but won't influence scheduler
2203 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2205 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2207 noltlbs [PPC] Do not use large page/tlb entries for kernel
2208 lowmem mapping on PPC40x.
2210 nomca [IA-64] Disable machine check abort handling
2212 nomce [X86-32] Machine Check Exception
2214 nomfgpt [X86-32] Disable Multi-Function General Purpose
2215 Timer usage (for AMD Geode machines).
2217 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2218 shutdown the other cpus. Instead use the REBOOT_VECTOR
2221 nomodule Disable module load
2223 nopat [X86] Disable PAT (page attribute table extension of
2224 pagetables) support.
2226 norandmaps Don't use address space randomization. Equivalent to
2227 echo 0 > /proc/sys/kernel/randomize_va_space
2229 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2231 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2232 with UP alternatives
2234 nordrand [X86] Disable kernel use of the RDRAND and
2235 RDSEED instructions even if they are supported
2236 by the processor. RDRAND and RDSEED are still
2237 available to user space applications.
2239 noresume [SWSUSP] Disables resume and restores original swap
2242 no-scroll [VGA] Disables scrollback.
2243 This is required for the Braillex ib80-piezo Braille
2244 reader made by F.H. Papenmeier (Germany).
2248 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2250 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2251 and disable the IO APIC. legacy for "maxcpus=0".
2253 nosoftlockup [KNL] Disable the soft-lockup detector.
2255 nosync [HW,M68K] Disables sync negotiation for all devices.
2257 notsc [BUGS=X86-32] Disable Time Stamp Counter
2259 nousb [USB] Disable the USB subsystem
2261 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2265 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2267 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2268 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2269 Some features depend on CPU0. Known dependencies are:
2270 1. Resume from suspend/hibernate depends on CPU0.
2271 Suspend/hibernate will fail if CPU0 is offline and you
2272 need to online CPU0 before suspend/hibernate.
2273 2. PIC interrupts also depend on CPU0. CPU0 can't be
2274 removed if a PIC interrupt is detected.
2275 It's said poweroff/reboot may depend on CPU0 on some
2276 machines although I haven't seen such issues so far
2277 after CPU0 is offline on a few tested machines.
2278 If the dependencies are under your control, you can
2279 turn on cpu0_hotplug.
2281 nptcg= [IA-64] Override max number of concurrent global TLB
2282 purges which is reported from either PAL_VM_SUMMARY or
2285 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2286 could support. nr_cpus=n : n >= 1 limits the kernel to
2287 supporting 'n' processors. Later in runtime you can not
2288 use hotplug cpu feature to put more cpu back to online.
2289 just like you compile the kernel NR_CPUS=n
2291 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2293 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2294 Allowed values are enable and disable
2296 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2297 one of ['zone', 'node', 'default'] can be specified
2298 This can be set from sysctl after boot.
2299 See Documentation/sysctl/vm.txt for details.
2301 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2302 See Documentation/debugging-via-ohci1394.txt for more
2305 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2306 Rather than timing out after 20 ms if an EC
2307 command is not properly ACKed, override the length
2308 of the timeout. We have interrupts disabled while
2309 waiting for the ACK, so if this is set too high
2310 interrupts *may* be lost!
2312 omap_mux= [OMAP] Override bootloader pin multiplexing.
2313 Format: <mux_mode0.mode_name=value>...
2314 For example, to override I2C bus2:
2315 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2317 oprofile.timer= [HW]
2318 Use timer interrupt instead of performance counters
2320 oprofile.cpu_type= Force an oprofile cpu type
2321 This might be useful if you have an older oprofile
2322 userland or if you want common events.
2323 Format: { arch_perfmon }
2324 arch_perfmon: [X86] Force use of architectural
2325 perfmon on Intel CPUs instead of the
2326 CPU specific event set.
2327 timer: [X86] Force use of architectural NMI
2328 timer mode (see also oprofile.timer
2329 for generic hr timer mode)
2330 [s390] Force legacy basic mode sampling
2331 (report cpu_type "timer")
2333 oops=panic Always panic on oopses. Default is to just kill the
2334 process, but there is a small probability of
2335 deadlocking the machine.
2336 This will also cause panics on machine check exceptions.
2337 Useful together with panic=30 to trigger a reboot.
2340 See Documentation/sound/oss/oss-parameters.txt
2342 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2343 timeout > 0: seconds before rebooting
2344 timeout = 0: wait forever
2345 timeout < 0: reboot immediately
2348 parkbd.port= [HW] Parallel port number the keyboard adapter is
2349 connected to, default is 0.
2351 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2352 0 for XT, 1 for AT (default is AT).
2355 parport= [HW,PPT] Specify parallel ports. 0 disables.
2356 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2357 Use 'auto' to force the driver to use any
2358 IRQ/DMA settings detected (the default is to
2359 ignore detected IRQ/DMA settings because of
2360 possible conflicts). You can specify the base
2361 address, IRQ, and DMA settings; IRQ and DMA
2362 should be numbers, or 'auto' (for using detected
2363 settings on that particular port), or 'nofifo'
2364 (to avoid using a FIFO even if it is detected).
2365 Parallel ports are assigned in the order they
2366 are specified on the command line, starting
2369 parport_init_mode= [HW,PPT]
2370 Configure VIA parallel port to operate in
2371 a specific mode. This is necessary on Pegasos
2372 computer where firmware has no options for setting
2373 up parallel port mode and sets it to spp.
2374 Currently this function knows 686a and 8231 chips.
2375 Format: [spp|ps2|epp|ecp|ecpepp]
2378 Halt all CPUs after the first oops has been printed for
2379 the specified number of seconds. This is to be used if
2380 your oopses keep scrolling off the screen.
2385 See header of drivers/block/paride/pcd.c.
2386 See also Documentation/blockdev/paride.txt.
2388 pci=option[,option...] [PCI] various PCI subsystem options:
2389 earlydump [X86] dump PCI config space before the kernel
2391 off [X86] don't probe for the PCI bus
2392 bios [X86-32] force use of PCI BIOS, don't access
2393 the hardware directly. Use this if your machine
2394 has a non-standard PCI host bridge.
2395 nobios [X86-32] disallow use of PCI BIOS, only direct
2396 hardware access methods are allowed. Use this
2397 if you experience crashes upon bootup and you
2398 suspect they are caused by the BIOS.
2399 conf1 [X86] Force use of PCI Configuration
2401 conf2 [X86] Force use of PCI Configuration
2403 noaer [PCIE] If the PCIEAER kernel config parameter is
2404 enabled, this kernel boot option can be used to
2405 disable the use of PCIE advanced error reporting.
2406 nodomains [PCI] Disable support for multiple PCI
2407 root domains (aka PCI segments, in ACPI-speak).
2408 nommconf [X86] Disable use of MMCONFIG for PCI
2410 check_enable_amd_mmconf [X86] check for and enable
2411 properly configured MMIO access to PCI
2412 config space on AMD family 10h CPU
2413 nomsi [MSI] If the PCI_MSI kernel config parameter is
2414 enabled, this kernel boot option can be used to
2415 disable the use of MSI interrupts system-wide.
2416 noioapicquirk [APIC] Disable all boot interrupt quirks.
2417 Safety option to keep boot IRQs enabled. This
2418 should never be necessary.
2419 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2420 primary IO-APIC for bridges that cannot disable
2421 boot IRQs. This fixes a source of spurious IRQs
2422 when the system masks IRQs.
2423 noioapicreroute [APIC] Disable workaround that uses the
2424 boot IRQ equivalent of an IRQ that connects to
2425 a chipset where boot IRQs cannot be disabled.
2426 The opposite of ioapicreroute.
2427 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2428 routing table. These calls are known to be buggy
2429 on several machines and they hang the machine
2430 when used, but on other computers it's the only
2431 way to get the interrupt routing table. Try
2432 this option if the kernel is unable to allocate
2433 IRQs or discover secondary PCI buses on your
2435 rom [X86] Assign address space to expansion ROMs.
2436 Use with caution as certain devices share
2437 address decoders between ROMs and other
2439 norom [X86] Do not assign address space to
2440 expansion ROMs that do not already have
2441 BIOS assigned address ranges.
2442 nobar [X86] Do not assign address space to the
2443 BARs that weren't assigned by the BIOS.
2444 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2445 assigned automatically to PCI devices. You can
2446 make the kernel exclude IRQs of your ISA cards
2448 pirqaddr=0xAAAAA [X86] Specify the physical address
2449 of the PIRQ table (normally generated
2450 by the BIOS) if it is outside the
2451 F0000h-100000h range.
2452 lastbus=N [X86] Scan all buses thru bus #N. Can be
2453 useful if the kernel is unable to find your
2454 secondary buses and you want to tell it
2455 explicitly which ones they are.
2456 assign-busses [X86] Always assign all PCI bus
2457 numbers ourselves, overriding
2458 whatever the firmware may have done.
2459 usepirqmask [X86] Honor the possible IRQ mask stored
2460 in the BIOS $PIR table. This is needed on
2461 some systems with broken BIOSes, notably
2462 some HP Pavilion N5400 and Omnibook XE3
2463 notebooks. This will have no effect if ACPI
2464 IRQ routing is enabled.
2465 noacpi [X86] Do not use ACPI for IRQ routing
2466 or for PCI scanning.
2467 use_crs [X86] Use PCI host bridge window information
2468 from ACPI. On BIOSes from 2008 or later, this
2469 is enabled by default. If you need to use this,
2470 please report a bug.
2471 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2472 If you need to use this, please report a bug.
2473 routeirq Do IRQ routing for all PCI devices.
2474 This is normally done in pci_enable_device(),
2475 so this option is a temporary workaround
2476 for broken drivers that don't call it.
2477 skip_isa_align [X86] do not align io start addr, so can
2478 handle more pci cards
2479 firmware [ARM] Do not re-enumerate the bus but instead
2480 just use the configuration from the
2481 bootloader. This is currently used on
2482 IXP2000 systems where the bus has to be
2483 configured a certain way for adjunct CPUs.
2484 noearly [X86] Don't do any early type 1 scanning.
2485 This might help on some broken boards which
2486 machine check when some devices' config space
2487 is read. But various workarounds are disabled
2488 and some IOMMU drivers will not work.
2489 bfsort Sort PCI devices into breadth-first order.
2490 This sorting is done to get a device
2491 order compatible with older (<= 2.4) kernels.
2492 nobfsort Don't sort PCI devices into breadth-first order.
2493 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2494 tuning and use the BIOS-configured MPS defaults.
2495 pcie_bus_safe Set every device's MPS to the largest value
2496 supported by all devices below the root complex.
2497 pcie_bus_perf Set device MPS to the largest allowable MPS
2498 based on its parent bus. Also set MRRS (Max
2499 Read Request Size) to the largest supported
2500 value (no larger than the MPS that the device
2501 or bus can support) for best performance.
2502 pcie_bus_peer2peer Set every device's MPS to 128B, which
2503 every device is guaranteed to support. This
2504 configuration allows peer-to-peer DMA between
2505 any pair of devices, possibly at the cost of
2506 reduced performance. This also guarantees
2507 that hot-added devices will work.
2508 cbiosize=nn[KMG] The fixed amount of bus space which is
2509 reserved for the CardBus bridge's IO window.
2510 The default value is 256 bytes.
2511 cbmemsize=nn[KMG] The fixed amount of bus space which is
2512 reserved for the CardBus bridge's memory
2513 window. The default value is 64 megabytes.
2516 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2517 Specifies alignment and device to reassign
2518 aligned memory resources.
2519 If <order of align> is not specified,
2520 PAGE_SIZE is used as alignment.
2521 PCI-PCI bridge can be specified, if resource
2522 windows need to be expanded.
2523 ecrc= Enable/disable PCIe ECRC (transaction layer
2524 end-to-end CRC checking).
2525 bios: Use BIOS/firmware settings. This is the
2529 hpiosize=nn[KMG] The fixed amount of bus space which is
2530 reserved for hotplug bridge's IO window.
2531 Default size is 256 bytes.
2532 hpmemsize=nn[KMG] The fixed amount of bus space which is
2533 reserved for hotplug bridge's memory window.
2534 Default size is 2 megabytes.
2535 realloc= Enable/disable reallocating PCI bridge resources
2536 if allocations done by BIOS are too small to
2537 accommodate resources required by all child
2539 off: Turn realloc off
2541 realloc same as realloc=on
2542 noari do not use PCIe ARI.
2543 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2544 only look for one device below a PCIe downstream
2547 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2550 force Enable ASPM even on devices that claim not to support it.
2551 WARNING: Forcing ASPM on may cause system lockups.
2553 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2554 nomsi Do not use MSI for PCI Express Native Hotplug (this
2555 makes all PCIe ports use INTx for hotplug services).
2557 pcie_ports= [PCIE] PCIe ports handling:
2558 auto Ask the BIOS whether or not to use native PCIe services
2559 associated with PCIe ports (PME, hot-plug, AER). Use
2560 them only if that is allowed by the BIOS.
2561 native Use native PCIe services associated with PCIe ports
2563 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2566 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2567 nomsi Do not use MSI for native PCIe PME signaling (this makes
2568 all PCIe root ports use INTx for all services).
2570 pcmv= [HW,PCMCIA] BadgePAD 4
2574 Keep all power-domains already enabled by bootloader on,
2575 even if no driver has claimed them. This is useful
2576 for debug and development, but should not be
2577 needed on a platform with proper driver support.
2580 See Documentation/blockdev/paride.txt.
2582 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2585 See arch/parisc/kernel/pdc_chassis.c
2587 percpu_alloc= Select which percpu first chunk allocator to use.
2588 Currently supported values are "embed" and "page".
2589 Archs may support subset or none of the selections.
2590 See comments in mm/percpu.c for details on each
2591 allocator. This parameter is primarily for debugging
2592 and performance comparison.
2595 See Documentation/blockdev/paride.txt.
2598 See Documentation/blockdev/paride.txt.
2600 pirq= [SMP,APIC] Manual mp-table setup
2601 See Documentation/x86/i386/IO-APIC.txt.
2603 plip= [PPT,NET] Parallel port network link
2604 Format: { parport<nr> | timid | 0 }
2605 See also Documentation/parport.txt.
2607 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2608 Override pmtimer IOPort with a hex value.
2612 Enable PNP debug messages (depends on the
2613 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2614 via /sys/module/pnp/parameters/debug. We always show
2615 current resource usage; turning this on also shows
2616 possible settings and some assignment information.
2622 { on | off | curr | res | no-curr | no-res }
2625 [ISAPNP] Exclude IRQs for the autoconfiguration
2628 [ISAPNP] Exclude DMAs for the autoconfiguration
2630 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2631 Ranges are in pairs (I/O port base and size).
2634 [ISAPNP] Exclude memory regions for the
2636 Ranges are in pairs (memory base and size).
2638 ports= [IP_VS_FTP] IPVS ftp helper module
2640 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2642 Format: <port>,<port>....
2644 print-fatal-signals=
2645 [KNL] debug: print fatal signals
2647 If enabled, warn about various signal handling
2648 related application anomalies: too many signals,
2649 too many POSIX.1 timers, fatal signals causing a
2652 If you hit the warning due to signal overflow,
2653 you might want to try "ulimit -i unlimited".
2657 printk.always_kmsg_dump=
2658 Trigger kmsg_dump for cases other than kernel oops or
2660 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2663 printk.time= Show timing data prefixed to each printk message line
2664 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2666 processor.max_cstate= [HW,ACPI]
2667 Limit processor to maximum C-state
2668 max_cstate=9 overrides any DMI blacklist limit.
2670 processor.nocst [HW,ACPI]
2671 Ignore the _CST method to determine C-states,
2672 instead using the legacy FADT method
2674 profile= [KNL] Enable kernel profiling via /proc/profile
2675 Format: [schedule,]<number>
2676 Param: "schedule" - profile schedule points.
2677 Param: <number> - step/bucket size as a power of 2 for
2678 statistical time based profiling.
2679 Param: "sleep" - profile D-state sleeping (millisecs).
2680 Requires CONFIG_SCHEDSTATS
2681 Param: "kvm" - profile VM exits.
2683 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2685 See Documentation/blockdev/ramdisk.txt.
2687 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2688 probe for; one of (bare|imps|exps|lifebook|any).
2689 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2691 psmouse.resetafter= [HW,MOUSE]
2692 Try to reset the device after so many bad packets
2695 [HW,MOUSE] Set desired mouse resolution, in dpi.
2696 psmouse.smartscroll=
2697 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2698 0 = disabled, 1 = enabled (default).
2700 pstore.backend= Specify the name of the pstore backend to use
2703 See Documentation/blockdev/paride.txt.
2706 [KNL] Number of legacy pty's. Overwrites compiled-in
2709 quiet [KNL] Disable most log messages
2714 See Documentation/md.txt.
2716 ramdisk_blocksize= [RAM]
2717 See Documentation/blockdev/ramdisk.txt.
2719 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2720 See Documentation/blockdev/ramdisk.txt.
2723 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2724 the specified list of CPUs to be no-callback CPUs.
2725 Invocation of these CPUs' RCU callbacks will
2726 be offloaded to "rcuox/N" kthreads created for
2727 that purpose, where "x" is "b" for RCU-bh, "p"
2728 for RCU-preempt, and "s" for RCU-sched, and "N"
2729 is the CPU number. This reduces OS jitter on the
2730 offloaded CPUs, which can be useful for HPC and
2731 real-time workloads. It can also improve energy
2732 efficiency for asymmetric multiprocessors.
2735 Rather than requiring that offloaded CPUs
2736 (specified by rcu_nocbs= above) explicitly
2737 awaken the corresponding "rcuoN" kthreads,
2738 make these kthreads poll for callbacks.
2739 This improves the real-time response for the
2740 offloaded CPUs by relieving them of the need to
2741 wake up the corresponding kthread, but degrades
2742 energy efficiency by requiring that the kthreads
2743 periodically wake up to do the polling.
2745 rcutree.blimit= [KNL]
2746 Set maximum number of finished RCU callbacks to
2747 process in one batch.
2749 rcutree.rcu_fanout_leaf= [KNL]
2750 Increase the number of CPUs assigned to each
2751 leaf rcu_node structure. Useful for very large
2754 rcutree.jiffies_till_first_fqs= [KNL]
2755 Set delay from grace-period initialization to
2756 first attempt to force quiescent states.
2757 Units are jiffies, minimum value is zero,
2758 and maximum value is HZ.
2760 rcutree.jiffies_till_next_fqs= [KNL]
2761 Set delay between subsequent attempts to force
2762 quiescent states. Units are jiffies, minimum
2763 value is one, and maximum value is HZ.
2765 rcutree.qhimark= [KNL]
2766 Set threshold of queued RCU callbacks beyond which
2767 batch limiting is disabled.
2769 rcutree.qlowmark= [KNL]
2770 Set threshold of queued RCU callbacks below which
2771 batch limiting is re-enabled.
2773 rcutree.rcu_idle_gp_delay= [KNL]
2774 Set wakeup interval for idle CPUs that have
2775 RCU callbacks (RCU_FAST_NO_HZ=y).
2777 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2778 Set wakeup interval for idle CPUs that have
2779 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2780 Lazy RCU callbacks are those which RCU can
2781 prove do nothing more than free memory.
2783 rcutorture.fqs_duration= [KNL]
2784 Set duration of force_quiescent_state bursts.
2786 rcutorture.fqs_holdoff= [KNL]
2787 Set holdoff time within force_quiescent_state bursts.
2789 rcutorture.fqs_stutter= [KNL]
2790 Set wait time between force_quiescent_state bursts.
2792 rcutorture.gp_exp= [KNL]
2793 Use expedited update-side primitives.
2795 rcutorture.gp_normal= [KNL]
2796 Use normal (non-expedited) update-side primitives.
2797 If both gp_exp and gp_normal are set, do both.
2798 If neither gp_exp nor gp_normal are set, still
2801 rcutorture.n_barrier_cbs= [KNL]
2802 Set callbacks/threads for rcu_barrier() testing.
2804 rcutorture.nfakewriters= [KNL]
2805 Set number of concurrent RCU writers. These just
2806 stress RCU, they don't participate in the actual
2807 test, hence the "fake".
2809 rcutorture.nreaders= [KNL]
2810 Set number of RCU readers.
2812 rcutorture.object_debug= [KNL]
2813 Enable debug-object double-call_rcu() testing.
2815 rcutorture.onoff_holdoff= [KNL]
2816 Set time (s) after boot for CPU-hotplug testing.
2818 rcutorture.onoff_interval= [KNL]
2819 Set time (s) between CPU-hotplug operations, or
2820 zero to disable CPU-hotplug testing.
2822 rcutorture.rcutorture_runnable= [BOOT]
2823 Start rcutorture running at boot time.
2825 rcutorture.shuffle_interval= [KNL]
2826 Set task-shuffle interval (s). Shuffling tasks
2827 allows some CPUs to go into dyntick-idle mode
2828 during the rcutorture test.
2830 rcutorture.shutdown_secs= [KNL]
2831 Set time (s) after boot system shutdown. This
2832 is useful for hands-off automated testing.
2834 rcutorture.stall_cpu= [KNL]
2835 Duration of CPU stall (s) to test RCU CPU stall
2836 warnings, zero to disable.
2838 rcutorture.stall_cpu_holdoff= [KNL]
2839 Time to wait (s) after boot before inducing stall.
2841 rcutorture.stat_interval= [KNL]
2842 Time (s) between statistics printk()s.
2844 rcutorture.stutter= [KNL]
2845 Time (s) to stutter testing, for example, specifying
2846 five seconds causes the test to run for five seconds,
2847 wait for five seconds, and so on. This tests RCU's
2848 ability to transition abruptly to and from idle.
2850 rcutorture.test_boost= [KNL]
2851 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2852 "Maybe" means test if the RCU implementation
2853 under test support RCU priority boosting.
2855 rcutorture.test_boost_duration= [KNL]
2856 Duration (s) of each individual boost test.
2858 rcutorture.test_boost_interval= [KNL]
2859 Interval (s) between each boost test.
2861 rcutorture.test_no_idle_hz= [KNL]
2862 Test RCU's dyntick-idle handling. See also the
2863 rcutorture.shuffle_interval parameter.
2865 rcutorture.torture_type= [KNL]
2866 Specify the RCU implementation to test.
2868 rcutorture.verbose= [KNL]
2869 Enable additional printk() statements.
2871 rcupdate.rcu_expedited= [KNL]
2872 Use expedited grace-period primitives, for
2873 example, synchronize_rcu_expedited() instead
2874 of synchronize_rcu(). This reduces latency,
2875 but can increase CPU utilization, degrade
2876 real-time latency, and degrade energy efficiency.
2878 rcupdate.rcu_cpu_stall_suppress= [KNL]
2879 Suppress RCU CPU stall warning messages.
2881 rcupdate.rcu_cpu_stall_timeout= [KNL]
2882 Set timeout for RCU CPU stall warning messages.
2886 Run specified binary instead of /init from the ramdisk,
2887 used for early userspace startup. See initrd.
2890 Format (x86 or x86_64):
2891 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2893 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2895 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2896 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2897 reboot_force is either force or not specified,
2898 reboot_cpu is s[mp]#### with #### being the processor
2899 to be used for rebooting.
2902 [KNL, SMP] Set scheduler's default relax_domain_level.
2903 See Documentation/cgroups/cpusets.txt.
2905 relative_sleep_states=
2906 [SUSPEND] Use sleep state labeling where the deepest
2907 state available other than hibernation is always "mem".
2908 Format: { "0" | "1" }
2909 0 -- Traditional sleep state labels.
2910 1 -- Relative sleep state labels.
2912 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2914 reservetop= [X86-32]
2916 Reserves a hole at the top of the kernel virtual
2921 Set the amount of memory to reserve for BIOS at
2922 the bottom of the address space.
2924 reset_devices [KNL] Force drivers to reset the underlying device
2925 during initialization.
2928 Specify the partition device for software suspend
2930 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2932 resume_offset= [SWSUSP]
2933 Specify the offset from the beginning of the partition
2934 given by "resume=" at which the swap header is located,
2935 in <PAGE_SIZE> units (needed only for swap files).
2936 See Documentation/power/swsusp-and-swap-files.txt
2938 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2939 read the resume files
2941 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2942 Useful for devices that are detected asynchronously
2943 (e.g. USB and MMC devices).
2945 hibernate= [HIBERNATION]
2946 noresume Don't check if there's a hibernation image
2947 present during boot.
2948 nocompress Don't compress/decompress hibernation images.
2950 retain_initrd [RAM] Keep initrd memory after extraction
2952 rhash_entries= [KNL,NET]
2953 Set number of hash buckets for route cache
2955 ro [KNL] Mount root device read-only on boot
2957 root= [KNL] Root filesystem
2958 See name_to_dev_t comment in init/do_mounts.c.
2960 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2961 mount the root filesystem
2963 rootflags= [KNL] Set root filesystem mount option string
2965 rootfstype= [KNL] Set root filesystem type
2967 rootwait [KNL] Wait (indefinitely) for root device to show up.
2968 Useful for devices that are detected asynchronously
2969 (e.g. USB and MMC devices).
2971 rproc_mem=nn[KMG][@address]
2972 [KNL,ARM,CMA] Remoteproc physical memory block.
2973 Memory area to be used by remote processor image,
2976 rw [KNL] Mount root device read-write on boot
2978 S [KNL] Run init in single mode
2981 See drivers/net/irda/sa1100_ir.c.
2983 sbni= [NET] Granch SBNI12 leased line adapter
2985 sched_debug [KNL] Enables verbose scheduler debug messages.
2987 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2988 xtime_lock contention on larger systems, and/or RCU lock
2989 contention on all systems with CONFIG_MAXSMP set.
2990 Format: { "0" | "1" }
2991 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2993 Note: increases power consumption, thus should only be
2994 enabled if running jitter sensitive (HPC/RT) workloads.
2996 security= [SECURITY] Choose a security module to enable at boot.
2997 If this boot parameter is not specified, only the first
2998 security module asking for security registration will be
2999 loaded. An invalid security module name will be treated
3000 as if no module has been chosen.
3002 selinux= [SELINUX] Disable or enable SELinux at boot time.
3003 Format: { "0" | "1" }
3004 See security/selinux/Kconfig help text.
3007 Default value is set via kernel config option.
3008 If enabled at boot time, /selinux/disable can be used
3009 later to disable prior to initial policy load.
3011 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
3012 Format: { "0" | "1" }
3013 See security/apparmor/Kconfig help text
3016 Default value is set via kernel config option.
3018 serialnumber [BUGS=X86-32]
3021 Maximal number of shapers.
3023 show_msr= [x86] show boot-time MSR settings
3024 Format: { <integer> }
3025 Show boot-time (BIOS-initialized) MSR settings.
3026 The parameter means the number of CPUs to show,
3027 for example 1 means boot CPU only.
3034 slab_max_order= [MM, SLAB]
3035 Determines the maximum allowed order for slabs.
3036 A high setting may cause OOMs due to memory
3037 fragmentation. Defaults to 1 for systems with
3038 more than 32MB of RAM, 0 otherwise.
3040 slub_debug[=options[,slabs]] [MM, SLUB]
3041 Enabling slub_debug allows one to determine the
3042 culprit if slab objects become corrupted. Enabling
3043 slub_debug can create guard zones around objects and
3044 may poison objects when not in use. Also tracks the
3045 last alloc / free. For more information see
3046 Documentation/vm/slub.txt.
3048 slub_max_order= [MM, SLUB]
3049 Determines the maximum allowed order for slabs.
3050 A high setting may cause OOMs due to memory
3051 fragmentation. For more information see
3052 Documentation/vm/slub.txt.
3054 slub_min_objects= [MM, SLUB]
3055 The minimum number of objects per slab. SLUB will
3056 increase the slab order up to slub_max_order to
3057 generate a sufficiently large slab able to contain
3058 the number of objects indicated. The higher the number
3059 of objects the smaller the overhead of tracking slabs
3060 and the less frequently locks need to be acquired.
3061 For more information see Documentation/vm/slub.txt.
3063 slub_min_order= [MM, SLUB]
3064 Determines the minimum page order for slabs. Must be
3065 lower than slub_max_order.
3066 For more information see Documentation/vm/slub.txt.
3068 slub_nomerge [MM, SLUB]
3069 Disable merging of slabs with similar size. May be
3070 necessary if there is some reason to distinguish
3071 allocs to different slabs. Debug options disable
3072 merging on their own.
3073 For more information see Documentation/vm/slub.txt.
3076 Format: <io1>[,<io2>[,...,<io8>]]
3078 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3079 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3080 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3081 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3082 smsc-ircc2.ircc_irq= [HW] IRQ line
3083 smsc-ircc2.ircc_dma= [HW] DMA channel
3084 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3085 0: Toshiba Satellite 1800 (GP data pin select)
3086 1: Fast pin select (default)
3090 [KNL] Should the soft-lockup detector generate panics.
3093 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3094 See Documentation/laptops/sonypi.txt
3096 spia_io_base= [HW,MTD]
3102 Enabled the stack tracer on boot up.
3104 stacktrace_filter=[function-list]
3105 [FTRACE] Limit the functions that the stack tracer
3106 will trace at boot up. function-list is a comma separated
3107 list of functions. This list can be changed at run
3108 time by the stack_trace_filter file in the debugfs
3109 tracing directory. Note, this enables stack tracing
3110 and the stacktrace above is not needed.
3114 Set the STI (builtin display/keyboard on the HP-PARISC
3115 machines) console (graphic card) which should be used
3116 as the initial boot-console.
3117 See also comment in drivers/video/console/sticore.c.
3120 See comment in drivers/video/console/sticore.c.
3123 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3125 sunrpc.min_resvport=
3126 sunrpc.max_resvport=
3128 SunRPC servers often require that client requests
3129 originate from a privileged port (i.e. a port in the
3130 range 0 < portnr < 1024).
3131 An administrator who wishes to reserve some of these
3132 ports for other uses may adjust the range that the
3133 kernel's sunrpc client considers to be privileged
3134 using these two parameters to set the minimum and
3135 maximum port values.
3139 Control how the NFS server code allocates CPUs to
3140 service thread pools. Depending on how many NICs
3141 you have and where their interrupts are bound, this
3142 option will affect which CPUs will do NFS serving.
3143 Note: this parameter cannot be changed while the
3144 NFS server is running.
3146 auto the server chooses an appropriate mode
3147 automatically using heuristics
3148 global a single global pool contains all CPUs
3149 percpu one pool for each CPU
3150 pernode one pool for each NUMA node (equivalent
3151 to global on non-NUMA machines)
3153 sunrpc.tcp_slot_table_entries=
3154 sunrpc.udp_slot_table_entries=
3156 Sets the upper limit on the number of simultaneous
3157 RPC calls that can be sent from the client to a
3158 server. Increasing these values may allow you to
3159 improve throughput, but will also increase the
3160 amount of memory reserved for use by the client.
3163 [KNL] Enable accounting of swap in memory resource
3164 controller if no parameter or 1 is given or disable
3165 it if 0 is given (See Documentation/cgroups/memory.txt)
3167 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3168 Format: { <int> | force }
3169 <int> -- Number of I/O TLB slabs
3170 force -- force using of bounce buffers even if they
3171 wouldn't be automatically used by the kernel
3175 sysfs.deprecated=0|1 [KNL]
3176 Enable/disable old style sysfs layout for old udev
3177 on older distributions. When this option is enabled
3178 very new udev will not work anymore. When this option
3179 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3180 in older udev will not work anymore.
3181 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3182 the kernel configuration.
3184 sysrq_always_enabled
3186 Ignore sysrq setting - this boot parameter will
3187 neutralize any effect of /proc/sys/kernel/sysrq.
3188 Useful for debugging.
3192 test_suspend= [SUSPEND]
3193 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3194 standby suspend) as the system sleep state to briefly
3195 enter during system startup. The system is woken from
3196 this state using a wakeup-capable RTC alarm.
3198 thash_entries= [KNL,NET]
3199 Set number of hash buckets for TCP connection
3201 thermal.act= [HW,ACPI]
3202 -1: disable all active trip points in all thermal zones
3203 <degrees C>: override all lowest active trip points
3205 thermal.crt= [HW,ACPI]
3206 -1: disable all critical trip points in all thermal zones
3207 <degrees C>: override all critical trip points
3209 thermal.nocrt= [HW,ACPI]
3210 Set to disable actions on ACPI thermal zone
3211 critical and hot trip points.
3213 thermal.off= [HW,ACPI]
3214 1: disable ACPI thermal control
3216 thermal.psv= [HW,ACPI]
3217 -1: disable all passive trip points
3218 <degrees C>: override all passive trip points to this
3221 thermal.tzp= [HW,ACPI]
3222 Specify global default ACPI thermal zone polling rate
3223 <deci-seconds>: poll all this frequency
3224 0: no polling (default)
3227 Force threading of all interrupt handlers except those
3228 marked explicitly IRQF_NO_THREAD.
3231 Enable the Transcendent memory driver if built-in.
3233 tmem.cleancache=0|1 [KNL, XEN]
3234 Default is on (1). Disable the usage of the cleancache
3235 API to send anonymous pages to the hypervisor.
3237 tmem.frontswap=0|1 [KNL, XEN]
3238 Default is on (1). Disable the usage of the frontswap
3239 API to send swap pages to the hypervisor. If disabled
3240 the selfballooning and selfshrinking are force disabled.
3242 tmem.selfballooning=0|1 [KNL, XEN]
3243 Default is on (1). Disable the driving of swap pages
3246 tmem.selfshrinking=0|1 [KNL, XEN]
3247 Default is on (1). Partial swapoff that immediately
3248 transfers pages from Xen hypervisor back to the
3249 kernel based on different criteria.
3253 Specify if the kernel should make use of the cpu
3254 topology information if the hardware supports this.
3255 The scheduler will make use of this information and
3256 e.g. base its process migration decisions on it.
3261 tpm_suspend_pcr=[HW,TPM]
3262 Format: integer pcr id
3263 Specify that at suspend time, the tpm driver
3264 should extend the specified pcr with zeros,
3265 as a workaround for some chips which fail to
3266 flush the last written pcr on TPM_SaveState.
3267 This will guarantee that all the other pcrs
3270 trace_buf_size=nn[KMG]
3271 [FTRACE] will set tracing buffer size.
3273 trace_event=[event-list]
3274 [FTRACE] Set and start specified trace events in order
3275 to facilitate early boot debugging.
3276 See also Documentation/trace/events.txt
3278 trace_options=[option-list]
3279 [FTRACE] Enable or disable tracer options at boot.
3280 The option-list is a comma delimited list of options
3281 that can be enabled or disabled just as if you were
3282 to echo the option name into
3284 /sys/kernel/debug/tracing/trace_options
3286 For example, to enable stacktrace option (to dump the
3287 stack trace of each event), add to the command line:
3289 trace_options=stacktrace
3291 See also Documentation/trace/ftrace.txt "trace options"
3295 [FTRACE] enable this option to disable tracing when a
3296 warning is hit. This turns off "tracing_on". Tracing can
3297 be enabled again by echoing '1' into the "tracing_on"
3298 file located in /sys/kernel/debug/tracing/
3300 This option is useful, as it disables the trace before
3301 the WARNING dump is called, which prevents the trace to
3302 be filled with content caused by the warning output.
3304 This option can also be set at run time via the sysctl
3305 option: kernel/traceoff_on_warning
3307 transparent_hugepage=
3309 Format: [always|madvise|never]
3310 Can be used to control the default behavior of the system
3311 with respect to transparent hugepages.
3312 See Documentation/vm/transhuge.txt for more details.
3314 tsc= Disable clocksource stability checks for TSC.
3316 [x86] reliable: mark tsc clocksource as reliable, this
3317 disables clocksource verification at runtime, as well
3318 as the stability checks done at bootup. Used to enable
3319 high-resolution timer mode on older hardware, and in
3320 virtualized environment.
3321 [x86] noirqtime: Do not use TSC to do irq accounting.
3322 Used to run time disable IRQ_TIME_ACCOUNTING on any
3323 platforms where RDTSC is slow and this accounting
3326 turbografx.map[2|3]= [HW,JOY]
3327 TurboGraFX parallel port interface
3329 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3330 See also Documentation/input/joystick-parport.txt
3332 udbg-immortal [PPC] When debugging early kernel crashes that
3333 happen after console_init() and before a proper
3334 console driver takes over, this boot options might
3335 help "seeing" what's going on.
3337 uhash_entries= [KNL,NET]
3338 Set number of hash buckets for UDP/UDP-Lite connections
3341 [USB] Ignore overcurrent events (default N).
3342 Some badly-designed motherboards generate lots of
3343 bogus events, for ports that aren't wired to
3344 anything. Set this parameter to avoid log spamming.
3345 Note that genuine overcurrent events won't be
3349 [X86] Cause panic on unknown NMI.
3351 usbcore.authorized_default=
3352 [USB] Default USB device authorization:
3353 (default -1 = authorized except for wireless USB,
3354 0 = not authorized, 1 = authorized)
3356 usbcore.autosuspend=
3357 [USB] The autosuspend time delay (in seconds) used
3358 for newly-detected USB devices (default 2). This
3359 is the time required before an idle device will be
3360 autosuspended. Devices for which the delay is set
3361 to a negative value won't be autosuspended at all.
3363 usbcore.usbfs_snoop=
3364 [USB] Set to log all usbfs traffic (default 0 = off).
3366 usbcore.blinkenlights=
3367 [USB] Set to cycle leds on hubs (default 0 = off).
3369 usbcore.old_scheme_first=
3370 [USB] Start with the old device initialization
3371 scheme (default 0 = off).
3373 usbcore.usbfs_memory_mb=
3374 [USB] Memory limit (in MB) for buffers allocated by
3375 usbfs (default = 16, 0 = max = 2047).
3377 usbcore.use_both_schemes=
3378 [USB] Try the other device initialization scheme
3379 if the first one fails (default 1 = enabled).
3381 usbcore.initial_descriptor_timeout=
3382 [USB] Specifies timeout for the initial 64-byte
3383 USB_REQ_GET_DESCRIPTOR request in milliseconds
3384 (default 5000 = 5.0 seconds).
3387 [USBHID] The interval which mice are to be polled at.
3389 usb-storage.delay_use=
3390 [UMS] The delay in seconds before a new device is
3391 scanned for Logical Units (default 5).
3394 [UMS] A list of quirks entries to supplement or
3395 override the built-in unusual_devs list. List
3396 entries are separated by commas. Each entry has
3397 the form VID:PID:Flags where VID and PID are Vendor
3398 and Product ID values (4-digit hex numbers) and
3399 Flags is a set of characters, each corresponding
3400 to a common usb-storage quirk flag as follows:
3401 a = SANE_SENSE (collect more than 18 bytes
3403 b = BAD_SENSE (don't collect more than 18
3404 bytes of sense data);
3405 c = FIX_CAPACITY (decrease the reported
3406 device capacity by one sector);
3407 d = NO_READ_DISC_INFO (don't use
3408 READ_DISC_INFO command);
3409 e = NO_READ_CAPACITY_16 (don't use
3410 READ_CAPACITY_16 command);
3411 h = CAPACITY_HEURISTICS (decrease the
3412 reported device capacity by one
3413 sector if the number is odd);
3414 i = IGNORE_DEVICE (don't bind to this
3416 l = NOT_LOCKABLE (don't try to lock and
3417 unlock ejectable media);
3418 m = MAX_SECTORS_64 (don't transfer more
3419 than 64 sectors = 32 KB at a time);
3420 n = INITIAL_READ10 (force a retry of the
3421 initial READ(10) command);
3422 o = CAPACITY_OK (accept the capacity
3423 reported by the device);
3424 p = WRITE_CACHE (the device cache is ON
3426 r = IGNORE_RESIDUE (the device reports
3427 bogus residue values);
3428 s = SINGLE_LUN (the device has only one
3430 w = NO_WP_DETECT (don't test whether the
3431 medium is write-protected).
3432 Example: quirks=0419:aaf5:rl,0421:0433:rc
3434 user_debug= [KNL,ARM]
3436 See arch/arm/Kconfig.debug help text.
3437 1 - undefined instruction events
3439 4 - invalid data aborts
3442 Example: user_debug=31
3445 [X86] Flags controlling user PTE allocations.
3447 nohigh = do not allocate PTE pages in
3448 HIGHMEM regardless of setting
3452 On X86_32, this is an alias for vdso32=. Otherwise:
3454 vdso=1: enable VDSO (the default)
3455 vdso=0: disable VDSO mapping
3457 vdso32= [X86] Control the 32-bit vDSO
3458 vdso32=1: enable 32-bit VDSO
3459 vdso32=0 or vdso32=2: disable 32-bit VDSO
3461 See the help text for CONFIG_COMPAT_VDSO for more
3462 details. If CONFIG_COMPAT_VDSO is set, the default is
3463 vdso32=0; otherwise, the default is vdso32=1.
3465 For compatibility with older kernels, vdso32=2 is an
3468 Try vdso32=0 if you encounter an error that says:
3469 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3472 vector=percpu: enable percpu vector domain
3474 video= [FB] Frame buffer configuration
3475 See Documentation/fb/modedb.txt.
3477 video.brightness_switch_enabled= [0,1]
3478 If set to 1, on receiving an ACPI notify event
3479 generated by hotkey, video driver will adjust brightness
3480 level and then send out the event to user space through
3481 the allocated input device; If set to 0, video driver
3482 will only send out the event without touching backlight
3487 [VMMIO] Memory mapped virtio (platform) device.
3489 <size>@<baseaddr>:<irq>[:<id>]
3491 <size> := size (can use standard suffixes
3493 <baseaddr> := physical base address
3494 <irq> := interrupt number (as passed to
3496 <id> := (optional) platform device id
3498 virtio_mmio.device=1K@0x100b0000:48:7
3500 Can be used multiple times for multiple devices.
3502 vga= [BOOT,X86-32] Select a particular video mode
3503 See Documentation/x86/boot.txt and
3504 Documentation/svga.txt.
3505 Use vga=ask for menu.
3506 This is actually a boot loader parameter; the value is
3507 passed to the kernel using a special protocol.
3509 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3510 size of <nn>. This can be used to increase the
3511 minimum size (128MB on x86). It can also be used to
3512 decrease the size and leave more room for directly
3515 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3518 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3521 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3525 Controls the behavior of vsyscalls (i.e. calls to
3526 fixed addresses of 0xffffffffff600x00 from legacy
3527 code). Most statically-linked binaries and older
3528 versions of glibc use these calls. Because these
3529 functions are at fixed addresses, they make nice
3530 targets for exploits that can control RIP.
3532 emulate [default] Vsyscalls turn into traps and are
3533 emulated reasonably safely.
3535 native Vsyscalls are native syscall instructions.
3536 This is a little bit faster than trapping
3537 and makes a few dynamic recompilers work
3538 better than they would in emulation mode.
3539 It also makes exploits much easier to write.
3541 none Vsyscalls don't work at all. This makes
3542 them quite hard to use for exploits but
3543 might break your system.
3545 vt.color= [VT] Default text color.
3546 Format: 0xYX, X = foreground, Y = background.
3547 Default: 0x07 = light gray on black.
3549 vt.cur_default= [VT] Default cursor shape.
3550 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3551 the parameters of the <Esc>[?A;B;Cc escape sequence;
3552 see VGA-softcursor.txt. Default: 2 = underline.
3554 vt.default_blu= [VT]
3555 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3556 Change the default blue palette of the console.
3557 This is a 16-member array composed of values
3560 vt.default_grn= [VT]
3561 Format: <green0>,<green1>,<green2>,...,<green15>
3562 Change the default green palette of the console.
3563 This is a 16-member array composed of values
3566 vt.default_red= [VT]
3567 Format: <red0>,<red1>,<red2>,...,<red15>
3568 Change the default red palette of the console.
3569 This is a 16-member array composed of values
3575 Set system-wide default UTF-8 mode for all tty's.
3576 Default is 1, i.e. UTF-8 mode is enabled for all
3577 newly opened terminals.
3579 vt.global_cursor_default=
3582 Set system-wide default for whether a cursor
3583 is shown on new VTs. Default is -1,
3584 i.e. cursors will be created by default unless
3585 overridden by individual drivers. 0 will hide
3586 cursors, 1 will display them.
3588 vt.italic= [VT] Default color for italic text; 0-15.
3591 vt.underline= [VT] Default color for underlined text; 0-15.
3594 watchdog timers [HW,WDT] For information on watchdog timers,
3595 see Documentation/watchdog/watchdog-parameters.txt
3596 or other driver-specific files in the
3597 Documentation/watchdog/ directory.
3599 workqueue.disable_numa
3600 By default, all work items queued to unbound
3601 workqueues are affine to the NUMA nodes they're
3602 issued on, which results in better behavior in
3603 general. If NUMA affinity needs to be disabled for
3604 whatever reason, this option can be used. Note
3605 that this also can be controlled per-workqueue for
3606 workqueues visible under /sys/bus/workqueue/.
3608 workqueue.power_efficient
3609 Per-cpu workqueues are generally preferred because
3610 they show better performance thanks to cache
3611 locality; unfortunately, per-cpu workqueues tend to
3612 be more power hungry than unbound workqueues.
3614 Enabling this makes the per-cpu workqueues which
3615 were observed to contribute significantly to power
3616 consumption unbound, leading to measurably lower
3617 power usage at the cost of small performance
3620 The default value of this parameter is determined by
3621 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3623 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3624 default x2apic cluster mode on platforms
3627 x86_intel_mid_timer= [X86-32,APBT]
3628 Choose timer option for x86 Intel MID platform.
3629 Two valid options are apbt timer only and lapic timer
3630 plus one apbt timer for broadcast timer.
3631 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3633 xen_emul_unplug= [HW,X86,XEN]
3634 Unplug Xen emulated devices
3635 Format: [unplug0,][unplug1]
3636 ide-disks -- unplug primary master IDE devices
3637 aux-ide-disks -- unplug non-primary-master IDE devices
3638 nics -- unplug network devices
3639 all -- unplug all emulated devices (NICs and IDE disks)
3640 unnecessary -- unplugging emulated devices is
3641 unnecessary even if the host did not respond to
3643 never -- do not unplug even if version check succeeds
3645 xen_nopvspin [X86,XEN]
3646 Disables the ticketlock slowpath using Xen PV
3649 xirc2ps_cs= [NET,PCMCIA]
3651 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3653 ______________________________________________________________________
3657 Add more DRM drivers.
projects / karo-tx-linux.git / blob