4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 CLK Common clock infrastructure is enabled.
48 CMA Contiguous Memory Area support is enabled.
49 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
51 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
52 EFI EFI Partitioning (GPT) is enabled
53 EIDE EIDE/ATAPI support is enabled.
54 EVM Extended Verification Module
55 FB The frame buffer device is enabled.
56 FTRACE Function tracing enabled.
57 GCOV GCOV profiling is enabled.
58 HW Appropriate hardware is enabled.
59 IA-64 IA-64 architecture is enabled.
60 IMA Integrity measurement architecture is enabled.
61 IOSCHED More than one I/O scheduler is enabled.
62 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
63 IPV6 IPv6 support is enabled.
64 ISAPNP ISA PnP code is enabled.
65 ISDN Appropriate ISDN support is enabled.
66 JOY Appropriate joystick support is enabled.
67 KGDB Kernel debugger support is enabled.
68 KVM Kernel Virtual Machine support is enabled.
69 LIBATA Libata driver is enabled
70 LP Printer support is enabled.
71 LOOP Loopback device support is enabled.
72 M68k M68k architecture is enabled.
73 These options have more detailed description inside of
74 Documentation/m68k/kernel-options.txt.
75 MDA MDA console support is enabled.
76 MIPS MIPS architecture is enabled.
77 MOUSE Appropriate mouse support is enabled.
78 MSI Message Signaled Interrupts (PCI).
79 MTD MTD (Memory Technology Device) support is enabled.
80 NET Appropriate network support is enabled.
81 NUMA NUMA support is enabled.
82 NFS Appropriate NFS support is enabled.
83 OSS OSS sound support is enabled.
84 PV_OPS A paravirtualized kernel is enabled.
85 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
86 PARISC The PA-RISC architecture is enabled.
87 PCI PCI bus support is enabled.
88 PCIE PCI Express support is enabled.
89 PCMCIA The PCMCIA subsystem is enabled.
90 PNP Plug & Play support is enabled.
91 PPC PowerPC architecture is enabled.
92 PPT Parallel port support is enabled.
93 PS2 Appropriate PS/2 support is enabled.
94 RAM RAM disk support is enabled.
95 S390 S390 architecture is enabled.
96 SCSI Appropriate SCSI support is enabled.
97 A lot of drivers have their options described inside
98 the Documentation/scsi/ sub-directory.
99 SECURITY Different security models are enabled.
100 SELINUX SELinux support is enabled.
101 APPARMOR AppArmor support is enabled.
102 SERIAL Serial support is enabled.
103 SH SuperH architecture is enabled.
104 SMP The kernel is an SMP kernel.
105 SPARC Sparc architecture is enabled.
106 SWSUSP Software suspend (hibernation) is enabled.
107 SUSPEND System suspend states are enabled.
108 TPM TPM drivers are enabled.
109 TS Appropriate touchscreen support is enabled.
110 UMS USB Mass Storage support is enabled.
111 USB USB support is enabled.
112 USBHID USB Human Interface Device support is enabled.
113 V4L Video For Linux support is enabled.
114 VMMIO Driver for memory mapped virtio devices is enabled.
115 VGA The VGA console has been enabled.
116 VT Virtual terminal support is enabled.
117 WDT Watchdog support is enabled.
118 XT IBM PC/XT MFM hard disk support is enabled.
119 X86-32 X86-32, aka i386 architecture is enabled.
120 X86-64 X86-64 architecture is enabled.
121 More X86-64 boot options can be found in
122 Documentation/x86/x86_64/boot-options.txt .
123 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
124 XEN Xen support is enabled
126 In addition, the following text indicates that the option:
128 BUGS= Relates to possible processor bugs on the said processor.
129 KNL Is a kernel start-up parameter.
130 BOOT Is a boot loader parameter.
132 Parameters denoted with BOOT are actually interpreted by the boot
133 loader, and have no meaning to the kernel directly.
134 Do not modify the syntax of boot loader parameters without extreme
135 need or coordination with <Documentation/x86/boot.txt>.
137 There are also arch-specific kernel-parameters not documented here.
138 See for example <Documentation/x86/x86_64/boot-options.txt>.
140 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
141 a trailing = on the name of any parameter states that that parameter will
142 be entered as an environment variable, whereas its absence indicates that
143 it will appear as a kernel argument readable via /proc/cmdline by programs
144 running once the system is up.
146 The number of kernel parameters is not limited, but the length of the
147 complete command line (parameters including spaces etc.) is limited to
148 a fixed number of characters. This limit depends on the architecture
149 and is between 256 and 4096 characters. It is defined in the file
150 ./include/asm/setup.h as COMMAND_LINE_SIZE.
152 Finally, the [KMG] suffix is commonly described after a number of kernel
153 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
154 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
155 bytes respectively. Such letter suffixes can also be entirely omitted.
159 Advanced Configuration and Power Interface
160 Format: { force | off | strict | noirq | rsdt }
161 force -- enable ACPI if default was off
162 off -- disable ACPI if default was on
163 noirq -- do not use ACPI for IRQ routing
164 strict -- Be less tolerant of platforms that are not
165 strictly ACPI specification compliant.
166 rsdt -- prefer RSDT over (default) XSDT
167 copy_dsdt -- copy DSDT to memory
169 See also Documentation/power/runtime_pm.txt, pci=noacpi
171 acpi_rsdp= [ACPI,EFI,KEXEC]
172 Pass the RSDP address to the kernel, mostly used
173 on machines running EFI runtime service to boot the
174 second kernel for kdump.
176 acpi_apic_instance= [ACPI, IOAPIC]
178 2: use 2nd APIC table, if available
179 1,0: use 1st APIC table
182 acpi_backlight= [HW,ACPI]
183 acpi_backlight=vendor
185 If set to vendor, prefer vendor specific driver
186 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
187 of the ACPI video.ko driver.
189 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
190 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
192 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
193 debug output. Bits in debug_layer correspond to a
194 _COMPONENT in an ACPI source file, e.g.,
195 #define _COMPONENT ACPI_PCI_COMPONENT
196 Bits in debug_level correspond to a level in
197 ACPI_DEBUG_PRINT statements, e.g.,
198 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
199 The debug_level mask defaults to "info". See
200 Documentation/acpi/debug.txt for more information about
201 debug layers and levels.
203 Enable processor driver info messages:
204 acpi.debug_layer=0x20000000
205 Enable PCI/PCI interrupt routing info messages:
206 acpi.debug_layer=0x400000
207 Enable AML "Debug" output, i.e., stores to the Debug
208 object while interpreting AML:
209 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
210 Enable all messages related to ACPI hardware:
211 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
213 Some values produce so much output that the system is
214 unusable. The "log_buf_len" parameter may be useful
215 if you need to capture more output.
217 acpi_irq_balance [HW,ACPI]
218 ACPI will balance active IRQs
221 acpi_irq_nobalance [HW,ACPI]
222 ACPI will not move active IRQs (default)
225 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
226 Format: <irq>,<irq>...
228 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
230 Format: <irq>,<irq>...
232 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
234 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
235 Format: To spoof as Windows 98: ="Microsoft Windows"
237 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
238 acpi_osi="string1" # add string1
239 acpi_osi="!string2" # remove string2
240 acpi_osi=!* # remove all strings
241 acpi_osi=! # disable all built-in OS vendor
243 acpi_osi= # disable all strings
245 'acpi_osi=!' can be used in combination with single or
246 multiple 'acpi_osi="string1"' to support specific OS
247 vendor string(s). Note that such command can only
248 affect the default state of the OS vendor strings, thus
249 it cannot affect the default state of the feature group
250 strings and the current state of the OS vendor strings,
251 specifying it multiple times through kernel command line
252 is meaningless. This command is useful when one do not
253 care about the state of the feature group strings which
254 should be controlled by the OSPM.
256 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
257 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
258 can make '_OSI("Windows 2000")' TRUE.
260 'acpi_osi=' cannot be used in combination with other
261 'acpi_osi=' command lines, the _OSI method will not
262 exist in the ACPI namespace. NOTE that such command can
263 only affect the _OSI support state, thus specifying it
264 multiple times through kernel command line is also
267 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
270 'acpi_osi=!*' can be used in combination with single or
271 multiple 'acpi_osi="string1"' to support specific
272 string(s). Note that such command can affect the
273 current state of both the OS vendor strings and the
274 feature group strings, thus specifying it multiple times
275 through kernel command line is meaningful. But it may
276 still not able to affect the final state of a string if
277 there are quirks related to this string. This command
278 is useful when one want to control the state of the
279 feature group strings to debug BIOS issues related to
282 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
283 '_OSI("Module Device")' FALSE.
284 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
285 '_OSI("Module Device")' TRUE.
286 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
288 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
290 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
291 they all will make '_OSI("Windows 2000")' TRUE.
294 Override the pmtimer bug detection: force the kernel
295 to assume that this machine's pmtimer latches its value
296 and always returns good values.
298 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
299 Format: { level | edge | high | low }
301 acpi_serialize [HW,ACPI] force serialization of AML methods
303 acpi_skip_timer_override [HW,ACPI]
304 Recognize and ignore IRQ0/pin2 Interrupt Override.
305 For broken nForce2 BIOS resulting in XT-PIC timer.
307 acpi_sleep= [HW,ACPI] Sleep options
308 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
309 old_ordering, nonvs, sci_force_enable }
310 See Documentation/power/video.txt for information on
312 s3_beep is for debugging; it makes the PC's speaker beep
313 as soon as the kernel's real-mode entry point is called.
314 s4_nohwsig prevents ACPI hardware signature from being
315 used during resume from hibernation.
316 old_ordering causes the ACPI 1.0 ordering of the _PTS
317 control method, with respect to putting devices into
318 low power states, to be enforced (the ACPI 2.0 ordering
319 of _PTS is used by default).
320 nonvs prevents the kernel from saving/restoring the
321 ACPI NVS memory during suspend/hibernation and resume.
322 sci_force_enable causes the kernel to set SCI_EN directly
323 on resume from S1/S3 (which is against the ACPI spec,
324 but some broken systems don't work without it).
326 acpi_use_timer_override [HW,ACPI]
327 Use timer override. For some broken Nvidia NF5 boards
328 that require a timer override, but don't have HPET
330 acpi_enforce_resources= [ACPI]
331 { strict | lax | no }
332 Check for resource conflicts between native drivers
333 and ACPI OperationRegions (SystemIO and SystemMemory
334 only). IO ports and memory declared in ACPI might be
335 used by the ACPI subsystem in arbitrary AML code and
336 can interfere with legacy drivers.
337 strict (default): access to resources claimed by ACPI
338 is denied; legacy drivers trying to access reserved
339 resources will fail to bind to device using them.
340 lax: access to resources claimed by ACPI is allowed;
341 legacy drivers trying to access reserved resources
342 will bind successfully but a warning message is logged.
343 no: ACPI OperationRegions are not marked as reserved,
344 no further checks are performed.
346 add_efi_memmap [EFI; X86] Include EFI memory map in
347 kernel's map of available physical RAM.
350 { off | try_unsupported }
351 off: disable AGP support
352 try_unsupported: try to drive unsupported chipsets
353 (may crash computer or cause data corruption)
356 See Documentation/sound/alsa/alsa-parameters.txt
359 Allow the default userspace alignment fault handler
360 behaviour to be specified. Bit 0 enables warnings,
361 bit 1 enables fixups, and bit 2 sends a segfault.
363 align_va_addr= [X86-64]
364 Align virtual addresses by clearing slice [14:12] when
365 allocating a VMA at process creation time. This option
366 gives you up to 3% performance improvement on AMD F15h
367 machines (where it is enabled by default) for a
368 CPU-intensive style benchmark, and it can vary highly in
369 a microbenchmark depending on workload and compiler.
371 32: only for 32-bit processes
372 64: only for 64-bit processes
373 on: enable for both 32- and 64-bit processes
374 off: disable for both 32- and 64-bit processes
376 alloc_snapshot [FTRACE]
377 Allocate the ftrace snapshot buffer on boot up when the
378 main buffer is allocated. This is handy if debugging
379 and you need to use tracing_snapshot() on boot up, and
380 do not want to use tracing_snapshot_alloc() as it needs
381 to be done where GFP_KERNEL allocations are allowed.
383 amd_iommu= [HW,X86-64]
384 Pass parameters to the AMD IOMMU driver in the system.
386 fullflush - enable flushing of IO/TLB entries when
387 they are unmapped. Otherwise they are
388 flushed before they will be reused, which
390 off - do not initialize any AMD IOMMU found in
392 force_isolation - Force device isolation for all
393 devices. The IOMMU driver is not
394 allowed anymore to lift isolation
395 requirements as needed. This option
396 does not override iommu=pt
398 amd_iommu_dump= [HW,X86-64]
399 Enable AMD IOMMU driver option to dump the ACPI table
400 for AMD IOMMU. With this option enabled, AMD IOMMU
401 driver will print ACPI tables for AMD IOMMU during
402 IOMMU initialization.
404 amijoy.map= [HW,JOY] Amiga joystick support
405 Map of devices attached to JOY0DAT and JOY1DAT
407 See also Documentation/input/joystick.txt
409 analog.map= [HW,JOY] Analog joystick and gamepad support
410 Specifies type or capabilities of an analog joystick
411 connected to one of 16 gameports
412 Format: <type1>,<type2>,..<type16>
415 Power management functions (SPARCstation-4/5 + deriv.)
417 Disable APC CPU standby support. SPARCstation-Fox does
418 not play well with APC CPU idle - disable it if you have
419 APC and your system crashes randomly.
421 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
422 Change the output verbosity whilst booting
423 Format: { quiet (default) | verbose | debug }
424 Change the amount of debugging information output
425 when initialising the APIC and IO-APIC components.
428 See Documentation/networking/ipv6.txt.
430 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
431 Limit apic dumping. The parameter defines the maximal
432 number of local apics being dumped. Also it is possible
433 to set it to "all" by meaning -- no limit here.
434 Format: { 1 (default) | 2 | ... | all }.
435 The parameter valid if only apic=debug or
436 apic=verbose is specified.
437 Example: apic=debug show_lapic=all
439 apm= [APM] Advanced Power Management
440 See header of arch/x86/kernel/apm_32.c.
442 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
443 Format: <io>,<irq>,<nodeID>
447 atarimouse= [HW,MOUSE] Atari Mouse
449 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
450 EzKey and similar keyboards
452 atkbd.reset= [HW] Reset keyboard during initialization
454 atkbd.set= [HW] Select keyboard code set
455 Format: <int> (2 = AT (default), 3 = PS/2)
457 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
460 atkbd.softraw= [HW] Choose between synthetic and real raw mode
461 Format: <bool> (0 = real, 1 = synthetic (default))
463 atkbd.softrepeat= [HW]
464 Use software keyboard repeat
466 audit= [KNL] Enable the audit sub-system
467 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
468 0 - kernel audit is disabled and can not be enabled
469 until the next reboot
470 unset - kernel audit is initialized but disabled and
471 will be fully enabled by the userspace auditd.
472 1 - kernel audit is initialized and partially enabled,
473 storing at most audit_backlog_limit messages in
474 RAM until it is fully enabled by the userspace
478 audit_backlog_limit= [KNL] Set the audit queue size limit.
479 Format: <int> (must be >=0)
482 baycom_epp= [HW,AX25]
485 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
487 See header of drivers/net/hamradio/baycom_par.c.
489 baycom_ser_fdx= [HW,AX25]
490 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
491 Format: <io>,<irq>,<mode>[,<baud>]
492 See header of drivers/net/hamradio/baycom_ser_fdx.c.
494 baycom_ser_hdx= [HW,AX25]
495 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
496 Format: <io>,<irq>,<mode>
497 See header of drivers/net/hamradio/baycom_ser_hdx.c.
499 blkdevparts= Manual partition parsing of block device(s) for
500 embedded devices based on command line input.
501 See Documentation/block/cmdline-partition.txt
503 boot_delay= Milliseconds to delay each printk during boot.
504 Values larger than 10 seconds (10000) are changed to
508 bootmem_debug [KNL] Enable bootmem allocator debug messages.
510 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
511 bttv.radio= Most important insmod options are available as
513 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
516 bulk_remove=off [PPC] This parameter disables the use of the pSeries
517 firmware feature for flushing multiple hpte entries
520 c101= [NET] Moxa C101 synchronous serial card
522 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
523 Sometimes CPU hardware bugs make them report the cache
524 size incorrectly. The kernel will attempt work arounds
525 to fix known problems, but for some CPUs it is not
526 possible to determine what the correct size should be.
527 This option provides an override for these situations.
529 ccw_timeout_log [S390]
530 See Documentation/s390/CommonIO for details.
532 cgroup_disable= [KNL] Disable a particular controller
533 Format: {name of the controller(s) to disable}
534 The effects of cgroup_disable=foo are:
535 - foo isn't auto-mounted if you mount all cgroups in
537 - foo isn't visible as an individually mountable
539 {Currently only "memory" controller deal with this and
540 cut the overhead, others just disable the usage. So
541 only cgroup_disable=memory is actually worthy}
543 checkreqprot [SELINUX] Set initial checkreqprot flag value.
544 Format: { "0" | "1" }
545 See security/selinux/Kconfig help text.
546 0 -- check protection applied by kernel (includes
547 any implied execute protection).
548 1 -- check protection requested by application.
549 Default value is set via a kernel config option.
550 Value can be changed at runtime via
551 /selinux/checkreqprot.
554 See Documentation/s390/CommonIO for details.
557 Keep all clocks already enabled by bootloader on,
558 even if no driver has claimed them. This is useful
559 for debug and development, but should not be
560 needed on a platform with proper driver support.
561 For more information, see Documentation/clk.txt.
563 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
565 Forces specified clocksource (if available) to be used
566 when calculating gettimeofday(). If specified
567 clocksource is not available, it defaults to PIT.
568 Format: { pit | tsc | cyclone | pmtmr }
570 clocksource= Override the default clocksource
572 Override the default clocksource and use the clocksource
573 with the name specified.
574 Some clocksource names to choose from, depending on
576 [all] jiffies (this is the base, fallback clocksource)
578 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
579 pxa_timer,timer3,32k_counter,timer0_1
581 [X86-32] pit,hpet,tsc;
582 scx200_hrt on Geode; cyclone on IBM x440
590 clearcpuid=BITNUM [X86]
591 Disable CPUID feature X for the kernel. See
592 arch/x86/include/asm/cpufeature.h for the valid bit
593 numbers. Note the Linux specific bits are not necessarily
594 stable over kernel options, but the vendor specific
596 Also note that user programs calling CPUID directly
597 or using the feature without checking anything
598 will still see it. This just prevents it from
599 being used by the kernel or shown in /proc/cpuinfo.
600 Also note the kernel might malfunction if you disable
604 Sets the size of kernel global memory area for contiguous
605 memory allocations. For more information, see
606 include/linux/dma-contiguous.h
608 cmo_free_hint= [PPC] Format: { yes | no }
609 Specify whether pages are marked as being inactive
610 when they are freed. This is used in CMO environments
611 to determine OS memory pressure for page stealing by
615 coherent_pool=nn[KMG] [ARM,KNL]
616 Sets the size of memory pool for coherent, atomic dma
617 allocations, by default set to 256K.
619 code_bytes [X86] How many bytes of object code to print
624 com20020= [HW,NET] ARCnet - COM20020 chipset
626 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
628 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
632 ARCnet - COM90xx chipset (memory-mapped buffers)
633 Format: <io>[,<irq>[,<memstart>]]
635 condev= [HW,S390] console device
638 console= [KNL] Output console device and options.
640 tty<n> Use the virtual console device <n>.
644 Use the specified serial port. The options are of
645 the form "bbbbpnf", where "bbbb" is the baud rate,
646 "p" is parity ("n", "o", or "e"), "n" is number of
647 bits, and "f" is flow control ("r" for RTS or
648 omit it). Default is "9600n8".
650 See Documentation/serial-console.txt for more
652 Documentation/networking/netconsole.txt for an
655 uart[8250],io,<addr>[,options]
656 uart[8250],mmio,<addr>[,options]
657 Start an early, polled-mode console on the 8250/16550
658 UART at the specified I/O port or MMIO address,
659 switching to the matching ttyS device later. The
660 options are the same as for ttyS, above.
661 hvc<n> Use the hypervisor console device <n>. This is for
662 both Xen and PowerPC hypervisors.
664 If the device connected to the port is not a TTY but a braille
665 device, prepend "brl," before the device type, for instance
667 For now, only VisioBraille is supported.
669 consoleblank= [KNL] The console blank (screen saver) timeout in
670 seconds. Defaults to 10*60 = 10mins. A value of 0
671 disables the blank timer.
674 [KNL] Change the default value for
675 /proc/<pid>/coredump_filter.
676 See also Documentation/filesystems/proc.txt.
678 cpuidle.off=1 [CPU_IDLE]
679 disable the cpuidle sub-system
681 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
683 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
685 crashkernel=size[KMG][@offset[KMG]]
686 [KNL] Using kexec, Linux can switch to a 'crash kernel'
687 upon panic. This parameter reserves the physical
688 memory region [offset, offset + size] for that kernel
689 image. If '@offset' is omitted, then a suitable offset
690 is selected automatically. Check
691 Documentation/kdump/kdump.txt for further details.
693 crashkernel=range1:size1[,range2:size2,...][@offset]
694 [KNL] Same as above, but depends on the memory
695 in the running system. The syntax of range is
696 start-[end] where start and end are both
697 a memory unit (amount[KMG]). See also
698 Documentation/kdump/kdump.txt for an example.
700 crashkernel=size[KMG],high
701 [KNL, x86_64] range could be above 4G. Allow kernel
702 to allocate physical memory region from top, so could
703 be above 4G if system have more than 4G ram installed.
704 Otherwise memory region will be allocated below 4G, if
706 It will be ignored if crashkernel=X is specified.
707 crashkernel=size[KMG],low
708 [KNL, x86_64] range under 4G. When crashkernel=X,high
709 is passed, kernel could allocate physical memory region
710 above 4G, that cause second kernel crash on system
711 that require some amount of low memory, e.g. swiotlb
712 requires at least 64M+32K low memory. Kernel would
713 try to allocate 72M below 4G automatically.
714 This one let user to specify own low range under 4G
715 for second kernel instead.
716 0: to disable low allocation.
717 It will be ignored when crashkernel=X,high is not used
718 or memory reserved is below 4G.
723 cs89x0_media= [HW,NET]
724 Format: { rj45 | aui | bnc }
727 See header of drivers/s390/block/dasd_devmap.c.
729 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
730 (one device per port)
731 Format: <port#>,<type>
732 See also Documentation/input/joystick-parport.txt
734 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
735 time. See Documentation/dynamic-debug-howto.txt for
736 details. Deprecated, see dyndbg.
738 debug [KNL] Enable kernel debugging (events log level).
741 [KNL] verbose self-tests
743 Print debugging info while doing the locking API
745 We default to 0 (no extra messages), setting it to
746 1 will print _a lot_ more information - normally
747 only useful to kernel developers.
749 debug_objects [KNL] Enable object debugging
752 [KNL] Disable object debugging
754 debug_guardpage_minorder=
755 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
756 parameter allows control of the order of pages that will
757 be intentionally kept free (and hence protected) by the
758 buddy allocator. Bigger value increase the probability
759 of catching random memory corruption, but reduce the
760 amount of memory for normal system use. The maximum
761 possible value is MAX_ORDER/2. Setting this parameter
762 to 1 or 2 should be enough to identify most random
763 memory corruption problems caused by bugs in kernel or
764 driver code when a CPU writes to (or reads from) a
765 random memory location. Note that there exists a class
766 of memory corruptions problems caused by buggy H/W or
767 F/W or by drivers badly programing DMA (basically when
768 memory is written at bus level and the CPU MMU is
769 bypassed) which are not detectable by
770 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
771 tracking down these problems.
773 debugpat [X86] Enable PAT debugging
775 decnet.addr= [HW,NET]
776 Format: <area>[,<node>]
777 See also Documentation/networking/decnet.txt.
780 [same as hugepagesz=] The size of the default
781 HugeTLB page size. This is the size represented by
782 the legacy /proc/ hugepages APIs, used for SHM, and
783 default size when mounting hugetlbfs filesystems.
784 Defaults to the default architecture's huge page size
788 Set number of hash buckets for dentry cache.
791 IO parameters + enable/disable command.
793 digiepca= [HW,SERIAL]
794 See drivers/char/README.epca and
795 Documentation/serial/digiepca.txt.
798 See Documentation/networking/ipv6.txt.
800 disable_ddw [PPC/PSERIES]
801 Disable Dynamic DMA Window support. Use this if
802 to workaround buggy firmware.
805 See Documentation/networking/ipv6.txt.
807 disable_mtrr_cleanup [X86]
808 The kernel tries to adjust MTRR layout from continuous
809 to discrete, to make X server driver able to add WB
810 entry later. This parameter disables that.
812 disable_mtrr_trim [X86, Intel and AMD only]
813 By default the kernel will trim any uncacheable
814 memory out of your available memory pool based on
815 MTRR settings. This parameter disables that behavior,
816 possibly causing your machine to run very slowly.
818 disable_timer_pin_1 [X86]
819 Disable PIN 1 of APIC timer
820 Can be useful to work around chipset bugs.
822 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
823 this option disables the debugging code at boot.
825 dma_debug_entries=<number>
826 This option allows to tune the number of preallocated
827 entries for DMA-API debugging code. One entry is
828 required per DMA-API allocation. Use this if the
829 DMA-API debugging code disables itself because the
830 architectural default is too low.
832 dma_debug_driver=<driver_name>
833 With this option the DMA-API debugging driver
834 filter feature can be enabled at boot time. Just
835 pass the driver to filter for as the parameter.
836 The filter can be disabled or changed to another
837 driver later using sysfs.
839 drm_kms_helper.edid_firmware=[<connector>:]<file>
840 Broken monitors, graphic adapters and KVMs may
841 send no or incorrect EDID data sets. This parameter
842 allows to specify an EDID data set in the
843 /lib/firmware directory that is used instead.
844 Generic built-in EDID data sets are used, if one of
845 edid/1024x768.bin, edid/1280x1024.bin,
846 edid/1680x1050.bin, or edid/1920x1080.bin is given
847 and no file with the same name exists. Details and
848 instructions how to build your own EDID data are
849 available in Documentation/EDID/HOWTO.txt. An EDID
850 data set will only be used for a particular connector,
851 if its name and a colon are prepended to the EDID
856 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
857 module.dyndbg[="val"]
858 Enable debug messages at boot time. See
859 Documentation/dynamic-debug-howto.txt for details.
861 earlycon= [KNL] Output early console device and options.
862 uart[8250],io,<addr>[,options]
863 uart[8250],mmio,<addr>[,options]
864 uart[8250],mmio32,<addr>[,options]
865 Start an early, polled-mode console on the 8250/16550
866 UART at the specified I/O port or MMIO address.
867 MMIO inter-register address stride is either 8-bit
868 (mmio) or 32-bit (mmio32).
869 The options are the same as for ttyS, above.
871 earlyprintk= [X86,SH,BLACKFIN,ARM]
875 earlyprintk=serial[,ttySn[,baudrate]]
876 earlyprintk=serial[,0x...[,baudrate]]
877 earlyprintk=ttySn[,baudrate]
878 earlyprintk=dbgp[debugController#]
880 earlyprintk is useful when the kernel crashes before
881 the normal console is initialized. It is not enabled by
882 default because it has some cosmetic problems.
884 Append ",keep" to not disable it when the real console
887 Only one of vga, efi, serial, or usb debug port can
890 Currently only ttyS0 and ttyS1 may be specified by
891 name. Other I/O ports may be explicitly specified
892 on some architectures (x86 and arm at least) by
893 replacing ttySn with an I/O port address, like this:
894 earlyprintk=serial,0x1008,115200
895 You can find the port for a given device in
896 /proc/tty/driver/serial:
897 2: uart:ST16650V2 port:00001008 irq:18 ...
899 Interaction with the standard serial driver is not
902 The VGA and EFI output is eventually overwritten by
905 The xen output can only be used by Xen PV guests.
907 edac_report= [HW,EDAC] Control how to report EDAC event
908 Format: {"on" | "off" | "force"}
909 on: enable EDAC to report H/W event. May be overridden
910 by other higher priority error reporting module.
911 off: disable H/W event reporting through EDAC.
912 force: enforce the use of EDAC to report H/W event.
915 ekgdboc= [X86,KGDB] Allow early kernel console debugging
918 This is designed to be used in conjunction with
919 the boot argument: earlyprintk=vga
922 Format: {"off" | "on" | "skip[mbr]"}
925 Format: { "old_map" }
926 old_map [X86-64]: switch to the old ioremap-based EFI
927 runtime services mapping. 32-bit still uses this one by
930 efi_no_storage_paranoia [EFI; X86]
931 Using this parameter you can use more than 50% of
932 your efi variable storage. Use this parameter only if
933 you are really sure that your UEFI does sane gc and
934 fulfills the spec otherwise your board may brick.
936 eisa_irq_edge= [PARISC,HW]
937 See header of drivers/parisc/eisa.c.
940 See comment before function elanfreq_setup() in
941 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
944 Format: {"cfq" | "deadline" | "noop"}
945 See Documentation/block/cfq-iosched.txt and
946 Documentation/block/deadline-iosched.txt for details.
948 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
949 Specifies physical address of start of kernel core
950 image elf header and optionally the size. Generally
951 kexec loader will pass this option to capture kernel.
952 See Documentation/kdump/kdump.txt for details.
954 enable_mtrr_cleanup [X86]
955 The kernel tries to adjust MTRR layout from continuous
956 to discrete, to make X server driver able to add WB
957 entry later. This parameter enables that.
959 enable_timer_pin_1 [X86]
960 Enable PIN 1 of APIC timer
961 Can be useful to work around chipset bugs
962 (in particular on some ATI chipsets).
963 The kernel tries to set a reasonable default.
965 enforcing [SELINUX] Set initial enforcing status.
967 See security/selinux/Kconfig help text.
968 0 -- permissive (log only, no denials).
969 1 -- enforcing (deny and log).
971 Value can be changed at runtime via /selinux/enforce.
974 Disable Error Record Serialization Table (ERST)
977 ether= [HW,NET] Ethernet cards parameters
978 This option is obsoleted by the "netdev=" option, which
979 has equivalent usage. See its documentation for details.
983 Permit 'security.evm' to be updated regardless of
984 current integrity status.
988 fail_make_request=[KNL]
989 General fault injection mechanism.
990 Format: <interval>,<probability>,<space>,<times>
991 See also Documentation/fault-injection/.
994 See Documentation/blockdev/floppy.txt.
996 force_pal_cache_flush
997 [IA-64] Avoid check_sal_cache_flush which may hang on
998 buggy SAL_CACHE_FLUSH implementations. Using this
999 parameter will force ia64_sal_cache_flush to call
1000 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1003 [FTRACE] will set and start the specified tracer
1004 as early as possible in order to facilitate early
1007 ftrace_dump_on_oops[=orig_cpu]
1008 [FTRACE] will dump the trace buffers on oops.
1009 If no parameter is passed, ftrace will dump
1010 buffers of all CPUs, but if you pass orig_cpu, it will
1011 dump only the buffer of the CPU that triggered the
1014 ftrace_filter=[function-list]
1015 [FTRACE] Limit the functions traced by the function
1016 tracer at boot up. function-list is a comma separated
1017 list of functions. This list can be changed at run
1018 time by the set_ftrace_filter file in the debugfs
1021 ftrace_notrace=[function-list]
1022 [FTRACE] Do not trace the functions specified in
1023 function-list. This list can be changed at run time
1024 by the set_ftrace_notrace file in the debugfs
1027 ftrace_graph_filter=[function-list]
1028 [FTRACE] Limit the top level callers functions traced
1029 by the function graph tracer at boot up.
1030 function-list is a comma separated list of functions
1031 that can be changed at run time by the
1032 set_graph_function file in the debugfs tracing directory.
1035 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1036 support via parallel port (up to 5 devices per port)
1037 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1038 See also Documentation/input/joystick-parport.txt
1042 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1046 gcov_persist= [GCOV] When non-zero (default), profiling data for
1047 kernel modules is saved and remains accessible via
1048 debugfs, even when the module is unloaded/reloaded.
1049 When zero, profiling data is discarded and associated
1050 debugfs files are removed at module unload time.
1052 gpt [EFI] Forces disk with valid GPT signature but
1053 invalid Protective MBR to be treated as GPT.
1055 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1056 the "Enable 0" bit of the configuration register.
1059 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1060 the "Enable 0" bit of the configuration register.
1063 grcan.select= [HW] Select which physical interface to use.
1066 grcan.txsize= [HW] Sets the size of the tx buffer.
1067 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1069 grcan.rxsize= [HW] Sets the size of the rx buffer.
1070 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1073 hashdist= [KNL,NUMA] Large hashes allocated during boot
1074 are distributed across NUMA nodes. Defaults on
1075 for 64-bit NUMA, off otherwise.
1076 Format: 0 | 1 (for off | on)
1078 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1080 hd= [EIDE] (E)IDE hard drive subsystem geometry
1081 Format: <cyl>,<head>,<sect>
1084 Disable Hardware Error Source Table (HEST) support;
1085 corresponding firmware-first mode error processing
1086 logic will be disabled.
1088 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1089 size of <nn>. This works even on boxes that have no
1090 highmem otherwise. This also works to reduce highmem
1091 size on bigger boxes.
1093 highres= [KNL] Enable/disable high resolution timer mode.
1094 Valid parameters: "on", "off"
1098 See Documentation/isdn/README.HiSax.
1102 hpet= [X86-32,HPET] option to control HPET usage
1103 Format: { enable (default) | disable | force |
1105 disable: disable HPET and use PIT instead
1106 force: allow force enabled of undocumented chips (ICH4,
1108 verbose: show contents of HPET registers during setup
1110 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1111 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1113 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1114 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1115 On x86-64 and powerpc, this option can be specified
1116 multiple times interleaved with hugepages= to reserve
1117 huge pages of different sizes. Valid pages sizes on
1118 x86-64 are 2M (when the CPU supports "pse") and 1G
1119 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1120 Note that 1GB pages can only be allocated at boot time
1121 using hugepages= and not freed afterwards.
1123 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1124 terminal devices. Valid values: 0..8
1125 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1126 If specified, z/VM IUCV HVC accepts connections
1127 from listed z/VM user IDs only.
1129 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1130 hardware thread id mappings.
1131 Format: <cpu>:<hwthread>
1134 Do not unregister boot console at start. This is only
1135 useful for debugging when something happens in the window
1136 between unregistering the boot console and initializing
1139 i2c_bus= [HW] Override the default board specific I2C bus speed
1140 or register an additional I2C bus that is not
1141 registered from board initialization code.
1145 i8042.debug [HW] Toggle i8042 debug mode
1146 i8042.direct [HW] Put keyboard port into non-translated mode
1147 i8042.dumbkbd [HW] Pretend that controller can only read data from
1148 keyboard and cannot control its state
1149 (Don't attempt to blink the leds)
1150 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1151 i8042.nokbd [HW] Don't check/create keyboard port
1152 i8042.noloop [HW] Disable the AUX Loopback command while probing
1154 i8042.nomux [HW] Don't check presence of an active multiplexing
1156 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1158 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1159 i8042.reset [HW] Reset the controller during init and cleanup
1160 i8042.unlock [HW] Unlock (ignore) the keylock
1164 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1165 indicates that the driver is running on unsupported
1167 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1168 does not match list of supported models.
1170 [HW] Report power status in /proc/i8k
1171 (disabled by default)
1172 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1175 i915.invert_brightness=
1176 [DRM] Invert the sense of the variable that is used to
1177 set the brightness of the panel backlight. Normally a
1178 brightness value of 0 indicates backlight switched off,
1179 and the maximum of the brightness value sets the backlight
1180 to maximum brightness. If this parameter is set to 0
1181 (default) and the machine requires it, or this parameter
1182 is set to 1, a brightness value of 0 sets the backlight
1183 to maximum brightness, and the maximum of the brightness
1184 value switches the backlight off.
1185 -1 -- never invert brightness
1186 0 -- machine default
1187 1 -- force brightness inversion
1190 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1192 ide-core.nodma= [HW] (E)IDE subsystem
1193 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1194 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1195 .cdrom .chs .ignore_cable are additional options
1196 See Documentation/ide/ide.txt.
1198 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1199 Claim all unknown PCI IDE storage controllers.
1202 Format: idle=poll, idle=halt, idle=nomwait
1203 Poll forces a polling idle loop that can slightly
1204 improve the performance of waking up a idle CPU, but
1205 will use a lot of power and make the system run hot.
1207 idle=halt: Halt is forced to be used for CPU idle.
1208 In such case C2/C3 won't be used again.
1209 idle=nomwait: Disable mwait for CPU C-states
1211 ignore_loglevel [KNL]
1212 Ignore loglevel setting - this will print /all/
1213 kernel messages to the console. Useful for debugging.
1214 We also add it as printk module parameter, so users
1215 could change it dynamically, usually by
1216 /sys/module/printk/parameters/ignore_loglevel.
1218 ihash_entries= [KNL]
1219 Set number of hash buckets for inode cache.
1221 ima_appraise= [IMA] appraise integrity measurements
1222 Format: { "off" | "enforce" | "fix" }
1225 ima_appraise_tcb [IMA]
1226 The builtin appraise policy appraises all files
1230 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1234 The list of supported hash algorithms is defined
1235 in crypto/hash_info.h.
1238 Load a policy which meets the needs of the Trusted
1239 Computing Base. This means IMA will measure all
1240 programs exec'd, files mmap'd for exec, and all files
1241 opened for read by uid=0.
1244 Select one of defined IMA measurements template formats.
1245 Formats: { "ima" | "ima-ng" }
1250 Run specified binary instead of /sbin/init as init
1253 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1254 for working out where the kernel is dying during
1257 initrd= [BOOT] Specify the location of the initial ramdisk
1259 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1262 int_pln_enable [x86] Enable power limit notification interrupt
1264 integrity_audit=[IMA]
1265 Format: { "0" | "1" }
1266 0 -- basic integrity auditing messages. (Default)
1267 1 -- additional integrity auditing messages.
1269 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1271 Enable intel iommu driver.
1273 Disable intel iommu driver.
1274 igfx_off [Default Off]
1275 By default, gfx is mapped as normal device. If a gfx
1276 device has a dedicated DMAR unit, the DMAR unit is
1277 bypassed by not enabling DMAR with this option. In
1278 this case, gfx device will use physical address for
1281 With this option iommu will not optimize to look
1282 for io virtual address below 32-bit forcing dual
1283 address cycle on pci bus for cards supporting greater
1284 than 32-bit addressing. The default is to look
1285 for translation below 32-bit and if not available
1286 then look in the higher range.
1287 strict [Default Off]
1288 With this option on every unmap_single operation will
1289 result in a hardware IOTLB flush operation as opposed
1290 to batching them for performance.
1291 sp_off [Default Off]
1292 By default, super page will be supported if Intel IOMMU
1293 has the capability. With this option, super page will
1296 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1297 0 disables intel_idle and fall back on acpi_idle.
1298 1 to 6 specify maximum depth of C-state.
1302 Do not enable intel_pstate as the default
1303 scaling driver for the supported processors
1305 intremap= [X86-64, Intel-IOMMU]
1306 on enable Interrupt Remapping (default)
1307 off disable Interrupt Remapping
1308 nosid disable Source ID checking
1310 BIOS x2APIC opt-out request will be ignored
1312 iomem= Disable strict checking of access to MMIO memory
1313 strict regions from userspace.
1330 io7= [HW] IO7 for Marvel based alpha systems
1331 See comment before marvel_specify_io7 in
1332 arch/alpha/kernel/core_marvel.c.
1334 io_delay= [X86] I/O delay method
1336 Standard port 0x80 based delay
1338 Alternate port 0xed based delay (needed on some systems)
1340 Simple two microseconds delay
1345 See Documentation/filesystems/nfs/nfsroot.txt.
1347 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1348 See comment before ip2_setup() in
1349 drivers/char/ip2/ip2base.c.
1352 When an interrupt is not handled search all handlers
1353 for it. Intended to get systems with badly broken
1357 When an interrupt is not handled search all handlers
1358 for it. Also check all handlers each timer
1359 interrupt. Intended to get systems with badly broken
1363 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1365 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1367 <cpu number>,...,<cpu number>
1369 <cpu number>-<cpu number>
1370 (must be a positive range in ascending order)
1372 <cpu number>,...,<cpu number>-<cpu number>
1374 This option can be used to specify one or more CPUs
1375 to isolate from the general SMP balancing and scheduling
1376 algorithms. You can move a process onto or off an
1377 "isolated" CPU via the CPU affinity syscalls or cpuset.
1378 <cpu number> begins at 0 and the maximum value is
1379 "number of CPUs in system - 1".
1381 This option is the preferred way to isolate CPUs. The
1382 alternative -- manually setting the CPU mask of all
1383 tasks in the system -- can cause problems and
1384 suboptimal load balancer performance.
1388 ivrs_ioapic [HW,X86_64]
1389 Provide an override to the IOAPIC-ID<->DEVICE-ID
1390 mapping provided in the IVRS ACPI table. For
1391 example, to map IOAPIC-ID decimal 10 to
1392 PCI device 00:14.0 write the parameter as:
1393 ivrs_ioapic[10]=00:14.0
1395 ivrs_hpet [HW,X86_64]
1396 Provide an override to the HPET-ID<->DEVICE-ID
1397 mapping provided in the IVRS ACPI table. For
1398 example, to map HPET-ID decimal 0 to
1399 PCI device 00:14.0 write the parameter as:
1400 ivrs_hpet[0]=00:14.0
1402 js= [HW,JOY] Analog joystick
1403 See Documentation/input/joystick.txt.
1407 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1408 specifies the amount of memory usable by the kernel
1409 for non-movable allocations. The requested amount is
1410 spread evenly throughout all nodes in the system. The
1411 remaining memory in each node is used for Movable
1412 pages. In the event, a node is too small to have both
1413 kernelcore and Movable pages, kernelcore pages will
1414 take priority and other nodes will have a larger number
1415 of Movable pages. The Movable zone is used for the
1416 allocation of pages that may be reclaimed or moved
1417 by the page migration subsystem. This means that
1418 HugeTLB pages may not be allocated from this zone.
1419 Note that allocations like PTEs-from-HighMem still
1420 use the HighMem zone if it exists, and the Normal
1421 zone if it does not.
1423 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1424 Format: <Controller#>[,poll interval]
1425 The controller # is the number of the ehci usb debug
1426 port as it is probed via PCI. The poll interval is
1427 optional and is the number seconds in between
1428 each poll cycle to the debug port in case you need
1429 the functionality for interrupting the kernel with
1430 gdb or control-c on the dbgp connection. When
1431 not using this parameter you use sysrq-g to break into
1432 the kernel debugger.
1434 kgdboc= [KGDB,HW] kgdb over consoles.
1435 Requires a tty driver that supports console polling,
1436 or a supported polling keyboard driver (non-usb).
1437 Serial only format: <serial_device>[,baud]
1438 keyboard only format: kbd
1439 keyboard and serial format: kbd,<serial_device>[,baud]
1440 Optional Kernel mode setting:
1441 kms, kbd format: kms,kbd
1442 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1444 kgdbwait [KGDB] Stop kernel execution and enter the
1445 kernel debugger at the earliest opportunity.
1447 kmac= [MIPS] korina ethernet MAC address.
1448 Configure the RouterBoard 532 series on-chip
1449 Ethernet adapter MAC address.
1451 kmemleak= [KNL] Boot-time kmemleak enable/disable
1452 Valid arguments: on, off
1455 kstack=N [X86] Print N words from the kernel stack
1458 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1459 Default is 0 (don't ignore, but inject #GP)
1461 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1465 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1466 Default is 1 (enabled)
1468 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1470 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1472 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1473 (virtualized MMU) support on capable Intel chips.
1474 Default is 1 (enabled)
1476 kvm-intel.emulate_invalid_guest_state=
1477 [KVM,Intel] Enable emulation of invalid guest states
1478 Default is 0 (disabled)
1480 kvm-intel.flexpriority=
1481 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1482 Default is 1 (enabled)
1485 [KVM,Intel] Enable VMX nesting (nVMX).
1486 Default is 0 (disabled)
1488 kvm-intel.unrestricted_guest=
1489 [KVM,Intel] Disable unrestricted guest feature
1490 (virtualized real and unpaged mode) on capable
1491 Intel chips. Default is 1 (enabled)
1493 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1494 feature (tagged TLBs) on capable Intel chips.
1495 Default is 1 (enabled)
1501 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1504 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1505 value for LAPIC timer one-shot implementation. Default
1506 back to the programmable timer unit in the LAPIC.
1508 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1511 libata.dma= [LIBATA] DMA control
1512 libata.dma=0 Disable all PATA and SATA DMA
1513 libata.dma=1 PATA and SATA Disk DMA only
1514 libata.dma=2 ATAPI (CDROM) DMA only
1515 libata.dma=4 Compact Flash DMA only
1516 Combinations also work, so libata.dma=3 enables DMA
1517 for disks and CDROMs, but not CFs.
1519 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1520 libata.ignore_hpa=0 keep BIOS limits (default)
1521 libata.ignore_hpa=1 ignore limits, using full disk
1523 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1527 libata.force= [LIBATA] Force configurations. The format is comma
1528 separated list of "[ID:]VAL" where ID is
1529 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1530 matching port, link or device. Basically, it matches
1531 the ATA ID string printed on console by libata. If
1532 the whole ID part is omitted, the last PORT and DEVICE
1533 values are used. If ID hasn't been specified yet, the
1534 configuration applies to all ports, links and devices.
1536 If only DEVICE is omitted, the parameter applies to
1537 the port and all links and devices behind it. DEVICE
1538 number of 0 either selects the first device or the
1539 first fan-out link behind PMP device. It does not
1540 select the host link. DEVICE number of 15 selects the
1541 host link and device attached to it.
1543 The VAL specifies the configuration to force. As long
1544 as there's no ambiguity shortcut notation is allowed.
1545 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1546 The following configurations can be forced.
1548 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1549 Any ID with matching PORT is used.
1551 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1553 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1554 udma[/][16,25,33,44,66,100,133] notation is also
1557 * [no]ncq: Turn on or off NCQ.
1559 * nohrst, nosrst, norst: suppress hard, soft
1562 * rstonce: only attempt one reset during
1563 hot-unplug link recovery
1565 * dump_id: dump IDENTIFY data.
1567 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1569 * disable: Disable this device.
1571 If there are multiple matching configurations changing
1572 the same attribute, the last one is used.
1574 memblock=debug [KNL] Enable memblock debug messages.
1576 load_ramdisk= [RAM] List of ramdisks to load from floppy
1577 See Documentation/blockdev/ramdisk.txt.
1579 lockd.nlm_grace_period=P [NFS] Assign grace period.
1582 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1585 lockd.nlm_timeout=T [NFS] Assign timeout value.
1588 lockd.nlm_udpport=M [NFS] Assign UDP port.
1591 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1594 loglevel= All Kernel Messages with a loglevel smaller than the
1595 console loglevel will be printed to the console. It can
1596 also be changed with klogd or other programs. The
1597 loglevels are defined as follows:
1599 0 (KERN_EMERG) system is unusable
1600 1 (KERN_ALERT) action must be taken immediately
1601 2 (KERN_CRIT) critical conditions
1602 3 (KERN_ERR) error conditions
1603 4 (KERN_WARNING) warning conditions
1604 5 (KERN_NOTICE) normal but significant condition
1605 6 (KERN_INFO) informational
1606 7 (KERN_DEBUG) debug-level messages
1608 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1609 in bytes. n must be a power of two. The default
1610 size is set in the kernel config file.
1612 logo.nologo [FB] Disables display of the built-in Linux logo.
1613 This may be used to provide more screen space for
1614 kernel log messages and is useful when debugging
1615 kernel boot problems.
1617 lp=0 [LP] Specify parallel ports to use, e.g,
1618 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1619 lp=reset first parallel port). 'lp=0' disables the
1620 lp=auto printer driver. 'lp=reset' (which can be
1621 specified in addition to the ports) causes
1622 attached printers to be reset. Using
1623 lp=port1,port2,... specifies the parallel ports
1624 to associate lp devices with, starting with
1625 lp0. A port specification may be 'none' to skip
1626 that lp device, or a parport name such as
1627 'parport0'. Specifying 'lp=auto' instead of a
1628 port specification list means that device IDs
1629 from each port should be examined, to see if
1630 an IEEE 1284-compliant printer is attached; if
1631 so, the driver will manage that printer.
1632 See also header of drivers/char/lp.c.
1635 Sets loops_per_jiffy to given constant, thus avoiding
1636 time-consuming boot-time autodetection (up to 250 ms per
1637 CPU). 0 enables autodetection (default). To determine
1638 the correct value for your kernel, boot with normal
1639 autodetection and see what value is printed. Note that
1640 on SMP systems the preset will be applied to all CPUs,
1641 which is likely to cause problems if your CPUs need
1642 significantly divergent settings. An incorrect value
1643 will cause delays in the kernel to be wrong, leading to
1644 unpredictable I/O errors and other breakage. Although
1645 unlikely, in the extreme case this might damage your
1649 Format: <io>,<irq>,<dma>
1651 machvec= [IA-64] Force the use of a particular machine-vector
1652 (machvec) in a generic kernel.
1653 Example: machvec=hpzx1_swiotlb
1655 machtype= [Loongson] Share the same kernel image file between different
1657 Example: machtype=lemote-yeeloong-2f-7inch
1659 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1660 than or equal to this physical address is ignored.
1662 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1663 should make use of. maxcpus=n : n >= 0 limits the
1664 kernel to using 'n' processors. n=0 is a special case,
1665 it is equivalent to "nosmp", which also disables
1668 max_loop= [LOOP] The number of loop block devices that get
1669 (loop.max_loop) unconditionally pre-created at init time. The default
1670 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1671 of statically allocating a predefined number, loop
1672 devices can be requested on-demand with the
1673 /dev/loop-control interface.
1675 mce [X86-32] Machine Check Exception
1677 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1679 md= [HW] RAID subsystems devices and level
1680 See Documentation/md.txt.
1683 Format: <first>,<last>
1684 Specifies range of consoles to be captured by the MDA.
1686 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1687 Amount of memory to be used when the kernel is not able
1688 to see the whole system memory or for test.
1689 [X86] Work as limiting max address. Use together
1690 with memmap= to avoid physical address space collisions.
1691 Without memmap= PCI devices could be placed at addresses
1692 belonging to unused RAM.
1694 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1698 [KNL,SH] Allow user to override the default size for
1699 per-device physically contiguous DMA buffers.
1701 memmap=exactmap [KNL,X86] Enable setting of an exact
1702 E820 memory map, as specified by the user.
1703 Such memmap=exactmap lines can be constructed based on
1704 BIOS output or other requirements. See the memmap=nn@ss
1707 memmap=nn[KMG]@ss[KMG]
1708 [KNL] Force usage of a specific region of memory
1709 Region of memory to be used, from ss to ss+nn.
1711 memmap=nn[KMG]#ss[KMG]
1712 [KNL,ACPI] Mark specific memory as ACPI data.
1713 Region of memory to be used, from ss to ss+nn.
1715 memmap=nn[KMG]$ss[KMG]
1716 [KNL,ACPI] Mark specific memory as reserved.
1717 Region of memory to be used, from ss to ss+nn.
1718 Example: Exclude memory from 0x18690000-0x1869ffff
1719 memmap=64K$0x18690000
1721 memmap=0x10000$0x18690000
1723 memory_corruption_check=0/1 [X86]
1724 Some BIOSes seem to corrupt the first 64k of
1725 memory when doing things like suspend/resume.
1726 Setting this option will scan the memory
1727 looking for corruption. Enabling this will
1728 both detect corruption and prevent the kernel
1729 from using the memory being corrupted.
1730 However, its intended as a diagnostic tool; if
1731 repeatable BIOS-originated corruption always
1732 affects the same memory, you can use memmap=
1733 to prevent the kernel from using that memory.
1735 memory_corruption_check_size=size [X86]
1736 By default it checks for corruption in the low
1737 64k, making this memory unavailable for normal
1738 use. Use this parameter to scan for
1739 corruption in more or less memory.
1741 memory_corruption_check_period=seconds [X86]
1742 By default it checks for corruption every 60
1743 seconds. Use this parameter to check at some
1744 other rate. 0 disables periodic checking.
1746 memtest= [KNL,X86] Enable memtest
1748 default : 0 <disable>
1749 Specifies the number of memtest passes to be
1750 performed. Each pass selects another test
1751 pattern from a given set of patterns. Memtest
1752 fills the memory with this pattern, validates
1753 memory contents and reserves bad memory
1754 regions that are detected.
1756 meye.*= [HW] Set MotionEye Camera parameters
1757 See Documentation/video4linux/meye.txt.
1759 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1760 Multi-Function General Purpose Timers on AMD Geode
1763 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1764 the BIOS has incorrectly applied a workaround. TinyBIOS
1765 version 0.98 is known to be affected, 0.99 fixes the
1766 problem by letting the user disable the workaround.
1770 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1771 physical address is ignored.
1773 mini2440= [ARM,HW,KNL]
1774 Format:[0..2][b][c][t]
1776 MINI2440 configuration specification:
1777 0 - The attached screen is the 3.5" TFT
1778 1 - The attached screen is the 7" TFT
1779 2 - The VGA Shield is attached (1024x768)
1780 Leaving out the screen size parameter will not load
1781 the TFT driver, and the framebuffer will be left
1783 b - Enable backlight. The TFT backlight pin will be
1784 linked to the kernel VESA blanking code and a GPIO
1785 LED. This parameter is not necessary when using the
1787 c - Enable the s3c camera interface.
1788 t - Reserved for enabling touchscreen support. The
1789 touchscreen support is not enabled in the mainstream
1790 kernel as of 2.6.30, a preliminary port can be found
1791 in the "bleeding edge" mini2440 support kernel at
1792 http://repo.or.cz/w/linux-2.6/mini2440.git
1795 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1796 parameter allows control of the logging verbosity for
1797 the additional memory initialisation checks. A value
1798 of 0 disables mminit logging and a level of 4 will
1799 log everything. Information is printed at KERN_DEBUG
1800 so loglevel=8 may also need to be specified.
1803 [KNL] When CONFIG_MODULE_SIG is set, this means that
1804 modules without (valid) signatures will fail to load.
1805 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1806 is always true, so this option does nothing.
1809 [MOUSE] Maximum time between finger touching and
1810 leaving touchpad surface for touch to be considered
1811 a tap and be reported as a left button click (for
1812 touchpads working in absolute mode only).
1814 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1815 reporting absolute coordinates, such as tablets
1816 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1817 reporting absolute coordinates, such as tablets
1819 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1820 is similar to kernelcore except it specifies the
1821 amount of memory used for migratable allocations.
1822 If both kernelcore and movablecore is specified,
1823 then kernelcore will be at *least* the specified
1824 value but may be more. If movablecore on its own
1825 is specified, the administrator must be careful
1826 that the amount of memory usable for all allocations
1829 movable_node [KNL,X86] Boot-time switch to enable the effects
1830 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1832 MTD_Partition= [MTD]
1833 Format: <name>,<region-number>,<size>,<offset>
1835 MTD_Region= [MTD] Format:
1836 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1839 See drivers/mtd/cmdlinepart.c.
1841 multitce=off [PPC] This parameter disables the use of the pSeries
1842 firmware feature for updating multiple TCE entries
1845 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1847 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1849 boundary - index of last SLC block on Flex-OneNAND.
1850 The remaining blocks are configured as MLC blocks.
1851 lock - Configure if Flex-OneNAND boundary should be locked.
1852 Once locked, the boundary cannot be changed.
1853 1 indicates lock status, 0 indicates unlock status.
1856 ARM/S3C2412 JIVE boot control
1858 See arch/arm/mach-s3c2412/mach-jive.c
1860 mtouchusb.raw_coordinates=
1861 [HW] Make the MicroTouch USB driver use raw coordinates
1862 ('y', default) or cooked coordinates ('n')
1864 mtrr_chunk_size=nn[KMG] [X86]
1865 used for mtrr cleanup. It is largest continuous chunk
1866 that could hold holes aka. UC entries.
1868 mtrr_gran_size=nn[KMG] [X86]
1869 Used for mtrr cleanup. It is granularity of mtrr block.
1871 Large value could prevent small alignment from
1874 mtrr_spare_reg_nr=n [X86]
1876 Range: 0,7 : spare reg number
1878 Used for mtrr cleanup. It is spare mtrr entries number.
1879 Set to 2 or more if your graphical card needs more.
1881 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1883 netdev= [NET] Network devices parameters
1884 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1885 Note that mem_start is often overloaded to mean
1886 something different and driver-specific.
1887 This usage is only documented in each driver source
1891 [NETFILTER] Enable connection tracking flow accounting
1892 0 to disable accounting
1893 1 to enable accounting
1896 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1897 See Documentation/filesystems/nfs/nfsroot.txt.
1899 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1900 See Documentation/filesystems/nfs/nfsroot.txt.
1902 nfsrootdebug [NFS] enable nfsroot debugging messages.
1903 See Documentation/filesystems/nfs/nfsroot.txt.
1905 nfs.callback_tcpport=
1906 [NFS] set the TCP port on which the NFSv4 callback
1907 channel should listen.
1910 [NFS] sets the pathname to the program which is used
1911 to update the NFS client cache entries.
1913 nfs.cache_getent_timeout=
1914 [NFS] sets the timeout after which an attempt to
1915 update a cache entry is deemed to have failed.
1917 nfs.idmap_cache_timeout=
1918 [NFS] set the maximum lifetime for idmapper cache
1922 [NFS] enable 64-bit inode numbers.
1923 If zero, the NFS client will fake up a 32-bit inode
1924 number for the readdir() and stat() syscalls instead
1925 of returning the full 64-bit number.
1926 The default is to return 64-bit inode numbers.
1928 nfs.max_session_slots=
1929 [NFSv4.1] Sets the maximum number of session slots
1930 the client will attempt to negotiate with the server.
1931 This limits the number of simultaneous RPC requests
1932 that the client can send to the NFSv4.1 server.
1933 Note that there is little point in setting this
1934 value higher than the max_tcp_slot_table_limit.
1936 nfs.nfs4_disable_idmapping=
1937 [NFSv4] When set to the default of '1', this option
1938 ensures that both the RPC level authentication
1939 scheme and the NFS level operations agree to use
1940 numeric uids/gids if the mount is using the
1941 'sec=sys' security flavour. In effect it is
1942 disabling idmapping, which can make migration from
1943 legacy NFSv2/v3 systems to NFSv4 easier.
1944 Servers that do not support this mode of operation
1945 will be autodetected by the client, and it will fall
1946 back to using the idmapper.
1947 To turn off this behaviour, set the value to '0'.
1949 [NFS4] Specify an additional fixed unique ident-
1950 ification string that NFSv4 clients can insert into
1951 their nfs_client_id4 string. This is typically a
1952 UUID that is generated at system install time.
1954 nfs.send_implementation_id =
1955 [NFSv4.1] Send client implementation identification
1956 information in exchange_id requests.
1957 If zero, no implementation identification information
1959 The default is to send the implementation identification
1962 nfs.recover_lost_locks =
1963 [NFSv4] Attempt to recover locks that were lost due
1964 to a lease timeout on the server. Please note that
1965 doing this risks data corruption, since there are
1966 no guarantees that the file will remain unchanged
1967 after the locks are lost.
1968 If you want to enable the kernel legacy behaviour of
1969 attempting to recover these locks, then set this
1971 The default parameter value of '0' causes the kernel
1972 not to attempt recovery of lost locks.
1974 nfsd.nfs4_disable_idmapping=
1975 [NFSv4] When set to the default of '1', the NFSv4
1976 server will return only numeric uids and gids to
1977 clients using auth_sys, and will accept numeric uids
1978 and gids from such clients. This is intended to ease
1979 migration from NFSv2/v3.
1981 objlayoutdriver.osd_login_prog=
1982 [NFS] [OBJLAYOUT] sets the pathname to the program which
1983 is used to automatically discover and login into new
1984 osd-targets. Please see:
1985 Documentation/filesystems/pnfs.txt for more explanations
1987 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1988 when a NMI is triggered.
1989 Format: [state][,regs][,debounce][,die]
1991 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1992 Format: [panic,][nopanic,][num]
1994 0 - turn nmi_watchdog off
1995 When panic is specified, panic when an NMI watchdog
1996 timeout occurs (or 'nopanic' to override the opposite
1998 This is useful when you use a panic=... timeout and
1999 need the box quickly up again.
2001 netpoll.carrier_timeout=
2002 [NET] Specifies amount of time (in seconds) that
2003 netpoll should wait for a carrier. By default netpoll
2006 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2007 emulation library even if a 387 maths coprocessor
2011 [HW] Never suspend the console
2012 Disable suspending of consoles during suspend and
2013 hibernate operations. Once disabled, debugging
2014 messages can reach various consoles while the rest
2015 of the system is being put to sleep (ie, while
2016 debugging driver suspend/resume hooks). This may
2017 not work reliably with all consoles, but is known
2018 to work with serial and VGA consoles.
2019 To facilitate more flexible debugging, we also add
2020 console_suspend, a printk module parameter to control
2021 it. Users could use console_suspend (usually
2022 /sys/module/printk/parameters/console_suspend) to
2023 turn on/off it dynamically.
2025 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2026 caches in the slab allocator. Saves per-node memory,
2027 but will impact performance.
2031 noapic [SMP,APIC] Tells the kernel to not make use of any
2032 IOAPICs that may be present in the system.
2035 Disable kernel base offset ASLR (Address Space
2036 Layout Randomization) if built into the kernel.
2038 noautogroup Disable scheduler automatic task group creation.
2040 nobats [PPC] Do not use BATs for mapping kernel lowmem
2041 on "Classic" PPC cores.
2045 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2047 nodelayacct [KNL] Disable per-task delay accounting
2049 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2051 nodsp [SH] Disable hardware DSP at boot time.
2053 noefi [X86] Disable EFI runtime services support.
2058 On X86-32 available only on PAE configured kernels.
2059 noexec=on: enable non-executable mappings (default)
2060 noexec=off: disable non-executable mappings
2063 Disable SMAP (Supervisor Mode Access Prevention)
2064 even if it is supported by processor.
2067 Disable SMEP (Supervisor Mode Execution Prevention)
2068 even if it is supported by processor.
2071 This affects only 32-bit executables.
2072 noexec32=on: enable non-executable mappings (default)
2073 read doesn't imply executable mappings
2074 noexec32=off: disable non-executable mappings
2075 read implies executable mappings
2077 nofpu [SH] Disable hardware FPU at boot time.
2079 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2080 register save and restore. The kernel will only save
2081 legacy floating-point registers on task switch.
2083 noxsave [BUGS=X86] Disables x86 extended register state save
2084 and restore using xsave. The kernel will fallback to
2085 enabling legacy floating-point and sse state.
2088 on enable eager fpu restore
2089 off disable eager fpu restore
2090 auto selects the default scheme, which automatically
2091 enables eagerfpu restore for xsaveopt.
2093 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2094 wfi(ARM) instruction doesn't work correctly and not to
2095 use it. This is also useful when using JTAG debugger.
2097 no_file_caps Tells the kernel not to honor file capabilities. The
2098 only way then for a file to be executed with privilege
2099 is to be setuid root or executed by root.
2101 nohalt [IA-64] Tells the kernel not to use the power saving
2102 function PAL_HALT_LIGHT when idle. This increases
2103 power-consumption. On the positive side, it reduces
2104 interrupt wake-up latency, which may improve performance
2105 in certain environments such as networked servers or
2108 nohz= [KNL] Boottime enable/disable dynamic ticks
2109 Valid arguments: on, off
2112 nohz_full= [KNL,BOOT]
2113 In kernels built with CONFIG_NO_HZ_FULL=y, set
2114 the specified list of CPUs whose tick will be stopped
2115 whenever possible. The boot CPU will be forced outside
2116 the range to maintain the timekeeping.
2117 The CPUs in this range must also be included in the
2120 noiotrap [SH] Disables trapped I/O port accesses.
2122 noirqdebug [X86-32] Disables the code which attempts to detect and
2123 disable unhandled interrupt sources.
2125 no_timer_check [X86,APIC] Disables the code which tests for
2126 broken timer IRQ sources.
2128 noisapnp [ISAPNP] Disables ISA PnP code.
2130 noinitrd [RAM] Tells the kernel not to load any configured
2133 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2135 [Deprecated - use intremap=off]
2139 nojitter [IA-64] Disables jitter checking for ITC timers.
2141 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2143 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2146 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2147 steal time is computed, but won't influence scheduler
2150 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2152 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2154 noltlbs [PPC] Do not use large page/tlb entries for kernel
2155 lowmem mapping on PPC40x.
2157 nomca [IA-64] Disable machine check abort handling
2159 nomce [X86-32] Machine Check Exception
2161 nomfgpt [X86-32] Disable Multi-Function General Purpose
2162 Timer usage (for AMD Geode machines).
2164 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2165 shutdown the other cpus. Instead use the REBOOT_VECTOR
2168 nomodule Disable module load
2170 nopat [X86] Disable PAT (page attribute table extension of
2171 pagetables) support.
2173 norandmaps Don't use address space randomization. Equivalent to
2174 echo 0 > /proc/sys/kernel/randomize_va_space
2176 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2178 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2179 with UP alternatives
2181 nordrand [X86] Disable the direct use of the RDRAND
2182 instruction even if it is supported by the
2183 processor. RDRAND is still available to user
2186 noresume [SWSUSP] Disables resume and restores original swap
2189 no-scroll [VGA] Disables scrollback.
2190 This is required for the Braillex ib80-piezo Braille
2191 reader made by F.H. Papenmeier (Germany).
2195 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2197 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2198 and disable the IO APIC. legacy for "maxcpus=0".
2200 nosoftlockup [KNL] Disable the soft-lockup detector.
2202 nosync [HW,M68K] Disables sync negotiation for all devices.
2204 notsc [BUGS=X86-32] Disable Time Stamp Counter
2206 nousb [USB] Disable the USB subsystem
2208 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2212 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2214 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2215 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2216 Some features depend on CPU0. Known dependencies are:
2217 1. Resume from suspend/hibernate depends on CPU0.
2218 Suspend/hibernate will fail if CPU0 is offline and you
2219 need to online CPU0 before suspend/hibernate.
2220 2. PIC interrupts also depend on CPU0. CPU0 can't be
2221 removed if a PIC interrupt is detected.
2222 It's said poweroff/reboot may depend on CPU0 on some
2223 machines although I haven't seen such issues so far
2224 after CPU0 is offline on a few tested machines.
2225 If the dependencies are under your control, you can
2226 turn on cpu0_hotplug.
2228 nptcg= [IA-64] Override max number of concurrent global TLB
2229 purges which is reported from either PAL_VM_SUMMARY or
2232 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2233 could support. nr_cpus=n : n >= 1 limits the kernel to
2234 supporting 'n' processors. Later in runtime you can not
2235 use hotplug cpu feature to put more cpu back to online.
2236 just like you compile the kernel NR_CPUS=n
2238 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2240 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2241 Allowed values are enable and disable
2243 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2244 one of ['zone', 'node', 'default'] can be specified
2245 This can be set from sysctl after boot.
2246 See Documentation/sysctl/vm.txt for details.
2248 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2249 See Documentation/debugging-via-ohci1394.txt for more
2252 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2253 Rather than timing out after 20 ms if an EC
2254 command is not properly ACKed, override the length
2255 of the timeout. We have interrupts disabled while
2256 waiting for the ACK, so if this is set too high
2257 interrupts *may* be lost!
2259 omap_mux= [OMAP] Override bootloader pin multiplexing.
2260 Format: <mux_mode0.mode_name=value>...
2261 For example, to override I2C bus2:
2262 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2264 oprofile.timer= [HW]
2265 Use timer interrupt instead of performance counters
2267 oprofile.cpu_type= Force an oprofile cpu type
2268 This might be useful if you have an older oprofile
2269 userland or if you want common events.
2270 Format: { arch_perfmon }
2271 arch_perfmon: [X86] Force use of architectural
2272 perfmon on Intel CPUs instead of the
2273 CPU specific event set.
2274 timer: [X86] Force use of architectural NMI
2275 timer mode (see also oprofile.timer
2276 for generic hr timer mode)
2277 [s390] Force legacy basic mode sampling
2278 (report cpu_type "timer")
2280 oops=panic Always panic on oopses. Default is to just kill the
2281 process, but there is a small probability of
2282 deadlocking the machine.
2283 This will also cause panics on machine check exceptions.
2284 Useful together with panic=30 to trigger a reboot.
2287 See Documentation/sound/oss/oss-parameters.txt
2289 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2290 timeout > 0: seconds before rebooting
2291 timeout = 0: wait forever
2292 timeout < 0: reboot immediately
2295 parkbd.port= [HW] Parallel port number the keyboard adapter is
2296 connected to, default is 0.
2298 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2299 0 for XT, 1 for AT (default is AT).
2302 parport= [HW,PPT] Specify parallel ports. 0 disables.
2303 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2304 Use 'auto' to force the driver to use any
2305 IRQ/DMA settings detected (the default is to
2306 ignore detected IRQ/DMA settings because of
2307 possible conflicts). You can specify the base
2308 address, IRQ, and DMA settings; IRQ and DMA
2309 should be numbers, or 'auto' (for using detected
2310 settings on that particular port), or 'nofifo'
2311 (to avoid using a FIFO even if it is detected).
2312 Parallel ports are assigned in the order they
2313 are specified on the command line, starting
2316 parport_init_mode= [HW,PPT]
2317 Configure VIA parallel port to operate in
2318 a specific mode. This is necessary on Pegasos
2319 computer where firmware has no options for setting
2320 up parallel port mode and sets it to spp.
2321 Currently this function knows 686a and 8231 chips.
2322 Format: [spp|ps2|epp|ecp|ecpepp]
2325 Halt all CPUs after the first oops has been printed for
2326 the specified number of seconds. This is to be used if
2327 your oopses keep scrolling off the screen.
2332 See header of drivers/block/paride/pcd.c.
2333 See also Documentation/blockdev/paride.txt.
2335 pci=option[,option...] [PCI] various PCI subsystem options:
2336 earlydump [X86] dump PCI config space before the kernel
2338 off [X86] don't probe for the PCI bus
2339 bios [X86-32] force use of PCI BIOS, don't access
2340 the hardware directly. Use this if your machine
2341 has a non-standard PCI host bridge.
2342 nobios [X86-32] disallow use of PCI BIOS, only direct
2343 hardware access methods are allowed. Use this
2344 if you experience crashes upon bootup and you
2345 suspect they are caused by the BIOS.
2346 conf1 [X86] Force use of PCI Configuration
2348 conf2 [X86] Force use of PCI Configuration
2350 noaer [PCIE] If the PCIEAER kernel config parameter is
2351 enabled, this kernel boot option can be used to
2352 disable the use of PCIE advanced error reporting.
2353 nodomains [PCI] Disable support for multiple PCI
2354 root domains (aka PCI segments, in ACPI-speak).
2355 nommconf [X86] Disable use of MMCONFIG for PCI
2357 check_enable_amd_mmconf [X86] check for and enable
2358 properly configured MMIO access to PCI
2359 config space on AMD family 10h CPU
2360 nomsi [MSI] If the PCI_MSI kernel config parameter is
2361 enabled, this kernel boot option can be used to
2362 disable the use of MSI interrupts system-wide.
2363 noioapicquirk [APIC] Disable all boot interrupt quirks.
2364 Safety option to keep boot IRQs enabled. This
2365 should never be necessary.
2366 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2367 primary IO-APIC for bridges that cannot disable
2368 boot IRQs. This fixes a source of spurious IRQs
2369 when the system masks IRQs.
2370 noioapicreroute [APIC] Disable workaround that uses the
2371 boot IRQ equivalent of an IRQ that connects to
2372 a chipset where boot IRQs cannot be disabled.
2373 The opposite of ioapicreroute.
2374 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2375 routing table. These calls are known to be buggy
2376 on several machines and they hang the machine
2377 when used, but on other computers it's the only
2378 way to get the interrupt routing table. Try
2379 this option if the kernel is unable to allocate
2380 IRQs or discover secondary PCI buses on your
2382 rom [X86] Assign address space to expansion ROMs.
2383 Use with caution as certain devices share
2384 address decoders between ROMs and other
2386 norom [X86] Do not assign address space to
2387 expansion ROMs that do not already have
2388 BIOS assigned address ranges.
2389 nobar [X86] Do not assign address space to the
2390 BARs that weren't assigned by the BIOS.
2391 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2392 assigned automatically to PCI devices. You can
2393 make the kernel exclude IRQs of your ISA cards
2395 pirqaddr=0xAAAAA [X86] Specify the physical address
2396 of the PIRQ table (normally generated
2397 by the BIOS) if it is outside the
2398 F0000h-100000h range.
2399 lastbus=N [X86] Scan all buses thru bus #N. Can be
2400 useful if the kernel is unable to find your
2401 secondary buses and you want to tell it
2402 explicitly which ones they are.
2403 assign-busses [X86] Always assign all PCI bus
2404 numbers ourselves, overriding
2405 whatever the firmware may have done.
2406 usepirqmask [X86] Honor the possible IRQ mask stored
2407 in the BIOS $PIR table. This is needed on
2408 some systems with broken BIOSes, notably
2409 some HP Pavilion N5400 and Omnibook XE3
2410 notebooks. This will have no effect if ACPI
2411 IRQ routing is enabled.
2412 noacpi [X86] Do not use ACPI for IRQ routing
2413 or for PCI scanning.
2414 use_crs [X86] Use PCI host bridge window information
2415 from ACPI. On BIOSes from 2008 or later, this
2416 is enabled by default. If you need to use this,
2417 please report a bug.
2418 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2419 If you need to use this, please report a bug.
2420 routeirq Do IRQ routing for all PCI devices.
2421 This is normally done in pci_enable_device(),
2422 so this option is a temporary workaround
2423 for broken drivers that don't call it.
2424 skip_isa_align [X86] do not align io start addr, so can
2425 handle more pci cards
2426 firmware [ARM] Do not re-enumerate the bus but instead
2427 just use the configuration from the
2428 bootloader. This is currently used on
2429 IXP2000 systems where the bus has to be
2430 configured a certain way for adjunct CPUs.
2431 noearly [X86] Don't do any early type 1 scanning.
2432 This might help on some broken boards which
2433 machine check when some devices' config space
2434 is read. But various workarounds are disabled
2435 and some IOMMU drivers will not work.
2436 bfsort Sort PCI devices into breadth-first order.
2437 This sorting is done to get a device
2438 order compatible with older (<= 2.4) kernels.
2439 nobfsort Don't sort PCI devices into breadth-first order.
2440 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2441 tuning and use the BIOS-configured MPS defaults.
2442 pcie_bus_safe Set every device's MPS to the largest value
2443 supported by all devices below the root complex.
2444 pcie_bus_perf Set device MPS to the largest allowable MPS
2445 based on its parent bus. Also set MRRS (Max
2446 Read Request Size) to the largest supported
2447 value (no larger than the MPS that the device
2448 or bus can support) for best performance.
2449 pcie_bus_peer2peer Set every device's MPS to 128B, which
2450 every device is guaranteed to support. This
2451 configuration allows peer-to-peer DMA between
2452 any pair of devices, possibly at the cost of
2453 reduced performance. This also guarantees
2454 that hot-added devices will work.
2455 cbiosize=nn[KMG] The fixed amount of bus space which is
2456 reserved for the CardBus bridge's IO window.
2457 The default value is 256 bytes.
2458 cbmemsize=nn[KMG] The fixed amount of bus space which is
2459 reserved for the CardBus bridge's memory
2460 window. The default value is 64 megabytes.
2463 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2464 Specifies alignment and device to reassign
2465 aligned memory resources.
2466 If <order of align> is not specified,
2467 PAGE_SIZE is used as alignment.
2468 PCI-PCI bridge can be specified, if resource
2469 windows need to be expanded.
2470 ecrc= Enable/disable PCIe ECRC (transaction layer
2471 end-to-end CRC checking).
2472 bios: Use BIOS/firmware settings. This is the
2476 hpiosize=nn[KMG] The fixed amount of bus space which is
2477 reserved for hotplug bridge's IO window.
2478 Default size is 256 bytes.
2479 hpmemsize=nn[KMG] The fixed amount of bus space which is
2480 reserved for hotplug bridge's memory window.
2481 Default size is 2 megabytes.
2482 realloc= Enable/disable reallocating PCI bridge resources
2483 if allocations done by BIOS are too small to
2484 accommodate resources required by all child
2486 off: Turn realloc off
2488 realloc same as realloc=on
2489 noari do not use PCIe ARI.
2490 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2491 only look for one device below a PCIe downstream
2494 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2497 force Enable ASPM even on devices that claim not to support it.
2498 WARNING: Forcing ASPM on may cause system lockups.
2500 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2501 nomsi Do not use MSI for PCI Express Native Hotplug (this
2502 makes all PCIe ports use INTx for hotplug services).
2504 pcie_ports= [PCIE] PCIe ports handling:
2505 auto Ask the BIOS whether or not to use native PCIe services
2506 associated with PCIe ports (PME, hot-plug, AER). Use
2507 them only if that is allowed by the BIOS.
2508 native Use native PCIe services associated with PCIe ports
2510 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2513 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2514 nomsi Do not use MSI for native PCIe PME signaling (this makes
2515 all PCIe root ports use INTx for all services).
2517 pcmv= [HW,PCMCIA] BadgePAD 4
2520 See Documentation/blockdev/paride.txt.
2522 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2525 See arch/parisc/kernel/pdc_chassis.c
2527 percpu_alloc= Select which percpu first chunk allocator to use.
2528 Currently supported values are "embed" and "page".
2529 Archs may support subset or none of the selections.
2530 See comments in mm/percpu.c for details on each
2531 allocator. This parameter is primarily for debugging
2532 and performance comparison.
2535 See Documentation/blockdev/paride.txt.
2538 See Documentation/blockdev/paride.txt.
2540 pirq= [SMP,APIC] Manual mp-table setup
2541 See Documentation/x86/i386/IO-APIC.txt.
2543 plip= [PPT,NET] Parallel port network link
2544 Format: { parport<nr> | timid | 0 }
2545 See also Documentation/parport.txt.
2547 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2548 Override pmtimer IOPort with a hex value.
2552 Enable PNP debug messages (depends on the
2553 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2554 via /sys/module/pnp/parameters/debug. We always show
2555 current resource usage; turning this on also shows
2556 possible settings and some assignment information.
2562 { on | off | curr | res | no-curr | no-res }
2565 [ISAPNP] Exclude IRQs for the autoconfiguration
2568 [ISAPNP] Exclude DMAs for the autoconfiguration
2570 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2571 Ranges are in pairs (I/O port base and size).
2574 [ISAPNP] Exclude memory regions for the
2576 Ranges are in pairs (memory base and size).
2578 ports= [IP_VS_FTP] IPVS ftp helper module
2580 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2582 Format: <port>,<port>....
2584 print-fatal-signals=
2585 [KNL] debug: print fatal signals
2587 If enabled, warn about various signal handling
2588 related application anomalies: too many signals,
2589 too many POSIX.1 timers, fatal signals causing a
2592 If you hit the warning due to signal overflow,
2593 you might want to try "ulimit -i unlimited".
2597 printk.always_kmsg_dump=
2598 Trigger kmsg_dump for cases other than kernel oops or
2600 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2603 printk.time= Show timing data prefixed to each printk message line
2604 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2606 processor.max_cstate= [HW,ACPI]
2607 Limit processor to maximum C-state
2608 max_cstate=9 overrides any DMI blacklist limit.
2610 processor.nocst [HW,ACPI]
2611 Ignore the _CST method to determine C-states,
2612 instead using the legacy FADT method
2614 profile= [KNL] Enable kernel profiling via /proc/profile
2615 Format: [schedule,]<number>
2616 Param: "schedule" - profile schedule points.
2617 Param: <number> - step/bucket size as a power of 2 for
2618 statistical time based profiling.
2619 Param: "sleep" - profile D-state sleeping (millisecs).
2620 Requires CONFIG_SCHEDSTATS
2621 Param: "kvm" - profile VM exits.
2623 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2625 See Documentation/blockdev/ramdisk.txt.
2627 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2628 probe for; one of (bare|imps|exps|lifebook|any).
2629 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2631 psmouse.resetafter= [HW,MOUSE]
2632 Try to reset the device after so many bad packets
2635 [HW,MOUSE] Set desired mouse resolution, in dpi.
2636 psmouse.smartscroll=
2637 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2638 0 = disabled, 1 = enabled (default).
2640 pstore.backend= Specify the name of the pstore backend to use
2643 See Documentation/blockdev/paride.txt.
2646 [KNL] Number of legacy pty's. Overwrites compiled-in
2649 quiet [KNL] Disable most log messages
2654 See Documentation/md.txt.
2656 ramdisk_blocksize= [RAM]
2657 See Documentation/blockdev/ramdisk.txt.
2659 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2660 See Documentation/blockdev/ramdisk.txt.
2663 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2664 the specified list of CPUs to be no-callback CPUs.
2665 Invocation of these CPUs' RCU callbacks will
2666 be offloaded to "rcuox/N" kthreads created for
2667 that purpose, where "x" is "b" for RCU-bh, "p"
2668 for RCU-preempt, and "s" for RCU-sched, and "N"
2669 is the CPU number. This reduces OS jitter on the
2670 offloaded CPUs, which can be useful for HPC and
2671 real-time workloads. It can also improve energy
2672 efficiency for asymmetric multiprocessors.
2675 Rather than requiring that offloaded CPUs
2676 (specified by rcu_nocbs= above) explicitly
2677 awaken the corresponding "rcuoN" kthreads,
2678 make these kthreads poll for callbacks.
2679 This improves the real-time response for the
2680 offloaded CPUs by relieving them of the need to
2681 wake up the corresponding kthread, but degrades
2682 energy efficiency by requiring that the kthreads
2683 periodically wake up to do the polling.
2685 rcutree.blimit= [KNL]
2686 Set maximum number of finished RCU callbacks to
2687 process in one batch.
2689 rcutree.rcu_fanout_leaf= [KNL]
2690 Increase the number of CPUs assigned to each
2691 leaf rcu_node structure. Useful for very large
2694 rcutree.jiffies_till_first_fqs= [KNL]
2695 Set delay from grace-period initialization to
2696 first attempt to force quiescent states.
2697 Units are jiffies, minimum value is zero,
2698 and maximum value is HZ.
2700 rcutree.jiffies_till_next_fqs= [KNL]
2701 Set delay between subsequent attempts to force
2702 quiescent states. Units are jiffies, minimum
2703 value is one, and maximum value is HZ.
2705 rcutree.qhimark= [KNL]
2706 Set threshold of queued RCU callbacks beyond which
2707 batch limiting is disabled.
2709 rcutree.qlowmark= [KNL]
2710 Set threshold of queued RCU callbacks below which
2711 batch limiting is re-enabled.
2713 rcutree.rcu_idle_gp_delay= [KNL]
2714 Set wakeup interval for idle CPUs that have
2715 RCU callbacks (RCU_FAST_NO_HZ=y).
2717 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2718 Set wakeup interval for idle CPUs that have
2719 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2720 Lazy RCU callbacks are those which RCU can
2721 prove do nothing more than free memory.
2723 rcutorture.fqs_duration= [KNL]
2724 Set duration of force_quiescent_state bursts.
2726 rcutorture.fqs_holdoff= [KNL]
2727 Set holdoff time within force_quiescent_state bursts.
2729 rcutorture.fqs_stutter= [KNL]
2730 Set wait time between force_quiescent_state bursts.
2732 rcutorture.gp_exp= [KNL]
2733 Use expedited update-side primitives.
2735 rcutorture.gp_normal= [KNL]
2736 Use normal (non-expedited) update-side primitives.
2737 If both gp_exp and gp_normal are set, do both.
2738 If neither gp_exp nor gp_normal are set, still
2741 rcutorture.n_barrier_cbs= [KNL]
2742 Set callbacks/threads for rcu_barrier() testing.
2744 rcutorture.nfakewriters= [KNL]
2745 Set number of concurrent RCU writers. These just
2746 stress RCU, they don't participate in the actual
2747 test, hence the "fake".
2749 rcutorture.nreaders= [KNL]
2750 Set number of RCU readers.
2752 rcutorture.object_debug= [KNL]
2753 Enable debug-object double-call_rcu() testing.
2755 rcutorture.onoff_holdoff= [KNL]
2756 Set time (s) after boot for CPU-hotplug testing.
2758 rcutorture.onoff_interval= [KNL]
2759 Set time (s) between CPU-hotplug operations, or
2760 zero to disable CPU-hotplug testing.
2762 rcutorture.rcutorture_runnable= [BOOT]
2763 Start rcutorture running at boot time.
2765 rcutorture.shuffle_interval= [KNL]
2766 Set task-shuffle interval (s). Shuffling tasks
2767 allows some CPUs to go into dyntick-idle mode
2768 during the rcutorture test.
2770 rcutorture.shutdown_secs= [KNL]
2771 Set time (s) after boot system shutdown. This
2772 is useful for hands-off automated testing.
2774 rcutorture.stall_cpu= [KNL]
2775 Duration of CPU stall (s) to test RCU CPU stall
2776 warnings, zero to disable.
2778 rcutorture.stall_cpu_holdoff= [KNL]
2779 Time to wait (s) after boot before inducing stall.
2781 rcutorture.stat_interval= [KNL]
2782 Time (s) between statistics printk()s.
2784 rcutorture.stutter= [KNL]
2785 Time (s) to stutter testing, for example, specifying
2786 five seconds causes the test to run for five seconds,
2787 wait for five seconds, and so on. This tests RCU's
2788 ability to transition abruptly to and from idle.
2790 rcutorture.test_boost= [KNL]
2791 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2792 "Maybe" means test if the RCU implementation
2793 under test support RCU priority boosting.
2795 rcutorture.test_boost_duration= [KNL]
2796 Duration (s) of each individual boost test.
2798 rcutorture.test_boost_interval= [KNL]
2799 Interval (s) between each boost test.
2801 rcutorture.test_no_idle_hz= [KNL]
2802 Test RCU's dyntick-idle handling. See also the
2803 rcutorture.shuffle_interval parameter.
2805 rcutorture.torture_type= [KNL]
2806 Specify the RCU implementation to test.
2808 rcutorture.verbose= [KNL]
2809 Enable additional printk() statements.
2811 rcupdate.rcu_expedited= [KNL]
2812 Use expedited grace-period primitives, for
2813 example, synchronize_rcu_expedited() instead
2814 of synchronize_rcu(). This reduces latency,
2815 but can increase CPU utilization, degrade
2816 real-time latency, and degrade energy efficiency.
2818 rcupdate.rcu_cpu_stall_suppress= [KNL]
2819 Suppress RCU CPU stall warning messages.
2821 rcupdate.rcu_cpu_stall_timeout= [KNL]
2822 Set timeout for RCU CPU stall warning messages.
2826 Run specified binary instead of /init from the ramdisk,
2827 used for early userspace startup. See initrd.
2830 Format (x86 or x86_64):
2831 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2833 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2835 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2836 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2837 reboot_force is either force or not specified,
2838 reboot_cpu is s[mp]#### with #### being the processor
2839 to be used for rebooting.
2842 [KNL, SMP] Set scheduler's default relax_domain_level.
2843 See Documentation/cgroups/cpusets.txt.
2845 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2847 reservetop= [X86-32]
2849 Reserves a hole at the top of the kernel virtual
2854 Set the amount of memory to reserve for BIOS at
2855 the bottom of the address space.
2857 reset_devices [KNL] Force drivers to reset the underlying device
2858 during initialization.
2861 Specify the partition device for software suspend
2863 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2865 resume_offset= [SWSUSP]
2866 Specify the offset from the beginning of the partition
2867 given by "resume=" at which the swap header is located,
2868 in <PAGE_SIZE> units (needed only for swap files).
2869 See Documentation/power/swsusp-and-swap-files.txt
2871 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2872 read the resume files
2874 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2875 Useful for devices that are detected asynchronously
2876 (e.g. USB and MMC devices).
2878 hibernate= [HIBERNATION]
2879 noresume Don't check if there's a hibernation image
2880 present during boot.
2881 nocompress Don't compress/decompress hibernation images.
2883 retain_initrd [RAM] Keep initrd memory after extraction
2885 rhash_entries= [KNL,NET]
2886 Set number of hash buckets for route cache
2888 riscom8= [HW,SERIAL]
2889 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2891 ro [KNL] Mount root device read-only on boot
2893 root= [KNL] Root filesystem
2894 See name_to_dev_t comment in init/do_mounts.c.
2896 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2897 mount the root filesystem
2899 rootflags= [KNL] Set root filesystem mount option string
2901 rootfstype= [KNL] Set root filesystem type
2903 rootwait [KNL] Wait (indefinitely) for root device to show up.
2904 Useful for devices that are detected asynchronously
2905 (e.g. USB and MMC devices).
2907 rproc_mem=nn[KMG][@address]
2908 [KNL,ARM,CMA] Remoteproc physical memory block.
2909 Memory area to be used by remote processor image,
2912 rw [KNL] Mount root device read-write on boot
2914 S [KNL] Run init in single mode
2917 See drivers/net/irda/sa1100_ir.c.
2919 sbni= [NET] Granch SBNI12 leased line adapter
2921 sched_debug [KNL] Enables verbose scheduler debug messages.
2923 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2924 xtime_lock contention on larger systems, and/or RCU lock
2925 contention on all systems with CONFIG_MAXSMP set.
2926 Format: { "0" | "1" }
2927 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2929 Note: increases power consumption, thus should only be
2930 enabled if running jitter sensitive (HPC/RT) workloads.
2932 security= [SECURITY] Choose a security module to enable at boot.
2933 If this boot parameter is not specified, only the first
2934 security module asking for security registration will be
2935 loaded. An invalid security module name will be treated
2936 as if no module has been chosen.
2938 selinux= [SELINUX] Disable or enable SELinux at boot time.
2939 Format: { "0" | "1" }
2940 See security/selinux/Kconfig help text.
2943 Default value is set via kernel config option.
2944 If enabled at boot time, /selinux/disable can be used
2945 later to disable prior to initial policy load.
2947 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2948 Format: { "0" | "1" }
2949 See security/apparmor/Kconfig help text
2952 Default value is set via kernel config option.
2954 serialnumber [BUGS=X86-32]
2957 Maximal number of shapers.
2959 show_msr= [x86] show boot-time MSR settings
2960 Format: { <integer> }
2961 Show boot-time (BIOS-initialized) MSR settings.
2962 The parameter means the number of CPUs to show,
2963 for example 1 means boot CPU only.
2970 slab_max_order= [MM, SLAB]
2971 Determines the maximum allowed order for slabs.
2972 A high setting may cause OOMs due to memory
2973 fragmentation. Defaults to 1 for systems with
2974 more than 32MB of RAM, 0 otherwise.
2976 slub_debug[=options[,slabs]] [MM, SLUB]
2977 Enabling slub_debug allows one to determine the
2978 culprit if slab objects become corrupted. Enabling
2979 slub_debug can create guard zones around objects and
2980 may poison objects when not in use. Also tracks the
2981 last alloc / free. For more information see
2982 Documentation/vm/slub.txt.
2984 slub_max_order= [MM, SLUB]
2985 Determines the maximum allowed order for slabs.
2986 A high setting may cause OOMs due to memory
2987 fragmentation. For more information see
2988 Documentation/vm/slub.txt.
2990 slub_min_objects= [MM, SLUB]
2991 The minimum number of objects per slab. SLUB will
2992 increase the slab order up to slub_max_order to
2993 generate a sufficiently large slab able to contain
2994 the number of objects indicated. The higher the number
2995 of objects the smaller the overhead of tracking slabs
2996 and the less frequently locks need to be acquired.
2997 For more information see Documentation/vm/slub.txt.
2999 slub_min_order= [MM, SLUB]
3000 Determines the minimum page order for slabs. Must be
3001 lower than slub_max_order.
3002 For more information see Documentation/vm/slub.txt.
3004 slub_nomerge [MM, SLUB]
3005 Disable merging of slabs with similar size. May be
3006 necessary if there is some reason to distinguish
3007 allocs to different slabs. Debug options disable
3008 merging on their own.
3009 For more information see Documentation/vm/slub.txt.
3012 Format: <io1>[,<io2>[,...,<io8>]]
3014 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3015 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3016 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3017 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3018 smsc-ircc2.ircc_irq= [HW] IRQ line
3019 smsc-ircc2.ircc_dma= [HW] DMA channel
3020 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3021 0: Toshiba Satellite 1800 (GP data pin select)
3022 1: Fast pin select (default)
3026 [KNL] Should the soft-lockup detector generate panics.
3029 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3030 See Documentation/laptops/sonypi.txt
3032 specialix= [HW,SERIAL] Specialix multi-serial port adapter
3033 See Documentation/serial/specialix.txt.
3035 spia_io_base= [HW,MTD]
3041 Enabled the stack tracer on boot up.
3043 stacktrace_filter=[function-list]
3044 [FTRACE] Limit the functions that the stack tracer
3045 will trace at boot up. function-list is a comma separated
3046 list of functions. This list can be changed at run
3047 time by the stack_trace_filter file in the debugfs
3048 tracing directory. Note, this enables stack tracing
3049 and the stacktrace above is not needed.
3053 Set the STI (builtin display/keyboard on the HP-PARISC
3054 machines) console (graphic card) which should be used
3055 as the initial boot-console.
3056 See also comment in drivers/video/console/sticore.c.
3059 See comment in drivers/video/console/sticore.c.
3062 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3064 sunrpc.min_resvport=
3065 sunrpc.max_resvport=
3067 SunRPC servers often require that client requests
3068 originate from a privileged port (i.e. a port in the
3069 range 0 < portnr < 1024).
3070 An administrator who wishes to reserve some of these
3071 ports for other uses may adjust the range that the
3072 kernel's sunrpc client considers to be privileged
3073 using these two parameters to set the minimum and
3074 maximum port values.
3078 Control how the NFS server code allocates CPUs to
3079 service thread pools. Depending on how many NICs
3080 you have and where their interrupts are bound, this
3081 option will affect which CPUs will do NFS serving.
3082 Note: this parameter cannot be changed while the
3083 NFS server is running.
3085 auto the server chooses an appropriate mode
3086 automatically using heuristics
3087 global a single global pool contains all CPUs
3088 percpu one pool for each CPU
3089 pernode one pool for each NUMA node (equivalent
3090 to global on non-NUMA machines)
3092 sunrpc.tcp_slot_table_entries=
3093 sunrpc.udp_slot_table_entries=
3095 Sets the upper limit on the number of simultaneous
3096 RPC calls that can be sent from the client to a
3097 server. Increasing these values may allow you to
3098 improve throughput, but will also increase the
3099 amount of memory reserved for use by the client.
3102 [KNL] Enable accounting of swap in memory resource
3103 controller if no parameter or 1 is given or disable
3104 it if 0 is given (See Documentation/cgroups/memory.txt)
3106 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
3107 Format: { <int> | force }
3108 <int> -- Number of I/O TLB slabs
3109 force -- force using of bounce buffers even if they
3110 wouldn't be automatically used by the kernel
3114 sysfs.deprecated=0|1 [KNL]
3115 Enable/disable old style sysfs layout for old udev
3116 on older distributions. When this option is enabled
3117 very new udev will not work anymore. When this option
3118 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3119 in older udev will not work anymore.
3120 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3121 the kernel configuration.
3123 sysrq_always_enabled
3125 Ignore sysrq setting - this boot parameter will
3126 neutralize any effect of /proc/sys/kernel/sysrq.
3127 Useful for debugging.
3131 test_suspend= [SUSPEND]
3132 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3133 standby suspend) as the system sleep state to briefly
3134 enter during system startup. The system is woken from
3135 this state using a wakeup-capable RTC alarm.
3137 thash_entries= [KNL,NET]
3138 Set number of hash buckets for TCP connection
3140 thermal.act= [HW,ACPI]
3141 -1: disable all active trip points in all thermal zones
3142 <degrees C>: override all lowest active trip points
3144 thermal.crt= [HW,ACPI]
3145 -1: disable all critical trip points in all thermal zones
3146 <degrees C>: override all critical trip points
3148 thermal.nocrt= [HW,ACPI]
3149 Set to disable actions on ACPI thermal zone
3150 critical and hot trip points.
3152 thermal.off= [HW,ACPI]
3153 1: disable ACPI thermal control
3155 thermal.psv= [HW,ACPI]
3156 -1: disable all passive trip points
3157 <degrees C>: override all passive trip points to this
3160 thermal.tzp= [HW,ACPI]
3161 Specify global default ACPI thermal zone polling rate
3162 <deci-seconds>: poll all this frequency
3163 0: no polling (default)
3166 Force threading of all interrupt handlers except those
3167 marked explicitly IRQF_NO_THREAD.
3170 Enable the Transcendent memory driver if built-in.
3172 tmem.cleancache=0|1 [KNL, XEN]
3173 Default is on (1). Disable the usage of the cleancache
3174 API to send anonymous pages to the hypervisor.
3176 tmem.frontswap=0|1 [KNL, XEN]
3177 Default is on (1). Disable the usage of the frontswap
3178 API to send swap pages to the hypervisor. If disabled
3179 the selfballooning and selfshrinking are force disabled.
3181 tmem.selfballooning=0|1 [KNL, XEN]
3182 Default is on (1). Disable the driving of swap pages
3185 tmem.selfshrinking=0|1 [KNL, XEN]
3186 Default is on (1). Partial swapoff that immediately
3187 transfers pages from Xen hypervisor back to the
3188 kernel based on different criteria.
3192 Specify if the kernel should make use of the cpu
3193 topology information if the hardware supports this.
3194 The scheduler will make use of this information and
3195 e.g. base its process migration decisions on it.
3200 tpm_suspend_pcr=[HW,TPM]
3201 Format: integer pcr id
3202 Specify that at suspend time, the tpm driver
3203 should extend the specified pcr with zeros,
3204 as a workaround for some chips which fail to
3205 flush the last written pcr on TPM_SaveState.
3206 This will guarantee that all the other pcrs
3209 trace_buf_size=nn[KMG]
3210 [FTRACE] will set tracing buffer size.
3212 trace_event=[event-list]
3213 [FTRACE] Set and start specified trace events in order
3214 to facilitate early boot debugging.
3215 See also Documentation/trace/events.txt
3217 trace_options=[option-list]
3218 [FTRACE] Enable or disable tracer options at boot.
3219 The option-list is a comma delimited list of options
3220 that can be enabled or disabled just as if you were
3221 to echo the option name into
3223 /sys/kernel/debug/tracing/trace_options
3225 For example, to enable stacktrace option (to dump the
3226 stack trace of each event), add to the command line:
3228 trace_options=stacktrace
3230 See also Documentation/trace/ftrace.txt "trace options"
3234 [FTRACE] enable this option to disable tracing when a
3235 warning is hit. This turns off "tracing_on". Tracing can
3236 be enabled again by echoing '1' into the "tracing_on"
3237 file located in /sys/kernel/debug/tracing/
3239 This option is useful, as it disables the trace before
3240 the WARNING dump is called, which prevents the trace to
3241 be filled with content caused by the warning output.
3243 This option can also be set at run time via the sysctl
3244 option: kernel/traceoff_on_warning
3246 transparent_hugepage=
3248 Format: [always|madvise|never]
3249 Can be used to control the default behavior of the system
3250 with respect to transparent hugepages.
3251 See Documentation/vm/transhuge.txt for more details.
3253 tsc= Disable clocksource stability checks for TSC.
3255 [x86] reliable: mark tsc clocksource as reliable, this
3256 disables clocksource verification at runtime, as well
3257 as the stability checks done at bootup. Used to enable
3258 high-resolution timer mode on older hardware, and in
3259 virtualized environment.
3260 [x86] noirqtime: Do not use TSC to do irq accounting.
3261 Used to run time disable IRQ_TIME_ACCOUNTING on any
3262 platforms where RDTSC is slow and this accounting
3265 turbografx.map[2|3]= [HW,JOY]
3266 TurboGraFX parallel port interface
3268 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3269 See also Documentation/input/joystick-parport.txt
3271 udbg-immortal [PPC] When debugging early kernel crashes that
3272 happen after console_init() and before a proper
3273 console driver takes over, this boot options might
3274 help "seeing" what's going on.
3276 uhash_entries= [KNL,NET]
3277 Set number of hash buckets for UDP/UDP-Lite connections
3280 [USB] Ignore overcurrent events (default N).
3281 Some badly-designed motherboards generate lots of
3282 bogus events, for ports that aren't wired to
3283 anything. Set this parameter to avoid log spamming.
3284 Note that genuine overcurrent events won't be
3288 [X86] Cause panic on unknown NMI.
3290 usbcore.authorized_default=
3291 [USB] Default USB device authorization:
3292 (default -1 = authorized except for wireless USB,
3293 0 = not authorized, 1 = authorized)
3295 usbcore.autosuspend=
3296 [USB] The autosuspend time delay (in seconds) used
3297 for newly-detected USB devices (default 2). This
3298 is the time required before an idle device will be
3299 autosuspended. Devices for which the delay is set
3300 to a negative value won't be autosuspended at all.
3302 usbcore.usbfs_snoop=
3303 [USB] Set to log all usbfs traffic (default 0 = off).
3305 usbcore.blinkenlights=
3306 [USB] Set to cycle leds on hubs (default 0 = off).
3308 usbcore.old_scheme_first=
3309 [USB] Start with the old device initialization
3310 scheme (default 0 = off).
3312 usbcore.usbfs_memory_mb=
3313 [USB] Memory limit (in MB) for buffers allocated by
3314 usbfs (default = 16, 0 = max = 2047).
3316 usbcore.use_both_schemes=
3317 [USB] Try the other device initialization scheme
3318 if the first one fails (default 1 = enabled).
3320 usbcore.initial_descriptor_timeout=
3321 [USB] Specifies timeout for the initial 64-byte
3322 USB_REQ_GET_DESCRIPTOR request in milliseconds
3323 (default 5000 = 5.0 seconds).
3326 [USBHID] The interval which mice are to be polled at.
3328 usb-storage.delay_use=
3329 [UMS] The delay in seconds before a new device is
3330 scanned for Logical Units (default 5).
3333 [UMS] A list of quirks entries to supplement or
3334 override the built-in unusual_devs list. List
3335 entries are separated by commas. Each entry has
3336 the form VID:PID:Flags where VID and PID are Vendor
3337 and Product ID values (4-digit hex numbers) and
3338 Flags is a set of characters, each corresponding
3339 to a common usb-storage quirk flag as follows:
3340 a = SANE_SENSE (collect more than 18 bytes
3342 b = BAD_SENSE (don't collect more than 18
3343 bytes of sense data);
3344 c = FIX_CAPACITY (decrease the reported
3345 device capacity by one sector);
3346 d = NO_READ_DISC_INFO (don't use
3347 READ_DISC_INFO command);
3348 e = NO_READ_CAPACITY_16 (don't use
3349 READ_CAPACITY_16 command);
3350 h = CAPACITY_HEURISTICS (decrease the
3351 reported device capacity by one
3352 sector if the number is odd);
3353 i = IGNORE_DEVICE (don't bind to this
3355 l = NOT_LOCKABLE (don't try to lock and
3356 unlock ejectable media);
3357 m = MAX_SECTORS_64 (don't transfer more
3358 than 64 sectors = 32 KB at a time);
3359 n = INITIAL_READ10 (force a retry of the
3360 initial READ(10) command);
3361 o = CAPACITY_OK (accept the capacity
3362 reported by the device);
3363 p = WRITE_CACHE (the device cache is ON
3365 r = IGNORE_RESIDUE (the device reports
3366 bogus residue values);
3367 s = SINGLE_LUN (the device has only one
3369 w = NO_WP_DETECT (don't test whether the
3370 medium is write-protected).
3371 Example: quirks=0419:aaf5:rl,0421:0433:rc
3373 user_debug= [KNL,ARM]
3375 See arch/arm/Kconfig.debug help text.
3376 1 - undefined instruction events
3378 4 - invalid data aborts
3381 Example: user_debug=31
3384 [X86] Flags controlling user PTE allocations.
3386 nohigh = do not allocate PTE pages in
3387 HIGHMEM regardless of setting
3391 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3392 vdso=1: enable VDSO (default)
3393 vdso=0: disable VDSO mapping
3396 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3397 vdso32=1: enable 32-bit VDSO (default)
3398 vdso32=0: disable 32-bit VDSO mapping
3401 vector=percpu: enable percpu vector domain
3403 video= [FB] Frame buffer configuration
3404 See Documentation/fb/modedb.txt.
3406 video.brightness_switch_enabled= [0,1]
3407 If set to 1, on receiving an ACPI notify event
3408 generated by hotkey, video driver will adjust brightness
3409 level and then send out the event to user space through
3410 the allocated input device; If set to 0, video driver
3411 will only send out the event without touching backlight
3416 [VMMIO] Memory mapped virtio (platform) device.
3418 <size>@<baseaddr>:<irq>[:<id>]
3420 <size> := size (can use standard suffixes
3422 <baseaddr> := physical base address
3423 <irq> := interrupt number (as passed to
3425 <id> := (optional) platform device id
3427 virtio_mmio.device=1K@0x100b0000:48:7
3429 Can be used multiple times for multiple devices.
3431 vga= [BOOT,X86-32] Select a particular video mode
3432 See Documentation/x86/boot.txt and
3433 Documentation/svga.txt.
3434 Use vga=ask for menu.
3435 This is actually a boot loader parameter; the value is
3436 passed to the kernel using a special protocol.
3438 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3439 size of <nn>. This can be used to increase the
3440 minimum size (128MB on x86). It can also be used to
3441 decrease the size and leave more room for directly
3444 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3447 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3450 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3454 Controls the behavior of vsyscalls (i.e. calls to
3455 fixed addresses of 0xffffffffff600x00 from legacy
3456 code). Most statically-linked binaries and older
3457 versions of glibc use these calls. Because these
3458 functions are at fixed addresses, they make nice
3459 targets for exploits that can control RIP.
3461 emulate [default] Vsyscalls turn into traps and are
3462 emulated reasonably safely.
3464 native Vsyscalls are native syscall instructions.
3465 This is a little bit faster than trapping
3466 and makes a few dynamic recompilers work
3467 better than they would in emulation mode.
3468 It also makes exploits much easier to write.
3470 none Vsyscalls don't work at all. This makes
3471 them quite hard to use for exploits but
3472 might break your system.
3474 vt.color= [VT] Default text color.
3475 Format: 0xYX, X = foreground, Y = background.
3476 Default: 0x07 = light gray on black.
3478 vt.cur_default= [VT] Default cursor shape.
3479 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3480 the parameters of the <Esc>[?A;B;Cc escape sequence;
3481 see VGA-softcursor.txt. Default: 2 = underline.
3483 vt.default_blu= [VT]
3484 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3485 Change the default blue palette of the console.
3486 This is a 16-member array composed of values
3489 vt.default_grn= [VT]
3490 Format: <green0>,<green1>,<green2>,...,<green15>
3491 Change the default green palette of the console.
3492 This is a 16-member array composed of values
3495 vt.default_red= [VT]
3496 Format: <red0>,<red1>,<red2>,...,<red15>
3497 Change the default red palette of the console.
3498 This is a 16-member array composed of values
3504 Set system-wide default UTF-8 mode for all tty's.
3505 Default is 1, i.e. UTF-8 mode is enabled for all
3506 newly opened terminals.
3508 vt.global_cursor_default=
3511 Set system-wide default for whether a cursor
3512 is shown on new VTs. Default is -1,
3513 i.e. cursors will be created by default unless
3514 overridden by individual drivers. 0 will hide
3515 cursors, 1 will display them.
3517 vt.italic= [VT] Default color for italic text; 0-15.
3520 vt.underline= [VT] Default color for underlined text; 0-15.
3523 watchdog timers [HW,WDT] For information on watchdog timers,
3524 see Documentation/watchdog/watchdog-parameters.txt
3525 or other driver-specific files in the
3526 Documentation/watchdog/ directory.
3528 workqueue.disable_numa
3529 By default, all work items queued to unbound
3530 workqueues are affine to the NUMA nodes they're
3531 issued on, which results in better behavior in
3532 general. If NUMA affinity needs to be disabled for
3533 whatever reason, this option can be used. Note
3534 that this also can be controlled per-workqueue for
3535 workqueues visible under /sys/bus/workqueue/.
3537 workqueue.power_efficient
3538 Per-cpu workqueues are generally preferred because
3539 they show better performance thanks to cache
3540 locality; unfortunately, per-cpu workqueues tend to
3541 be more power hungry than unbound workqueues.
3543 Enabling this makes the per-cpu workqueues which
3544 were observed to contribute significantly to power
3545 consumption unbound, leading to measurably lower
3546 power usage at the cost of small performance
3549 The default value of this parameter is determined by
3550 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3552 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3553 default x2apic cluster mode on platforms
3556 x86_intel_mid_timer= [X86-32,APBT]
3557 Choose timer option for x86 Intel MID platform.
3558 Two valid options are apbt timer only and lapic timer
3559 plus one apbt timer for broadcast timer.
3560 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3562 xen_emul_unplug= [HW,X86,XEN]
3563 Unplug Xen emulated devices
3564 Format: [unplug0,][unplug1]
3565 ide-disks -- unplug primary master IDE devices
3566 aux-ide-disks -- unplug non-primary-master IDE devices
3567 nics -- unplug network devices
3568 all -- unplug all emulated devices (NICs and IDE disks)
3569 unnecessary -- unplugging emulated devices is
3570 unnecessary even if the host did not respond to
3572 never -- do not unplug even if version check succeeds
3574 xen_nopvspin [X86,XEN]
3575 Disables the ticketlock slowpath using Xen PV
3578 xirc2ps_cs= [NET,PCMCIA]
3580 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3582 ______________________________________________________________________
3586 Add more DRM drivers.
projects / karo-tx-linux.git / blob