4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 CLK Common clock infrastructure is enabled.
48 CMA Contiguous Memory Area support is enabled.
49 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
51 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
52 EFI EFI Partitioning (GPT) is enabled
53 EIDE EIDE/ATAPI support is enabled.
54 EVM Extended Verification Module
55 FB The frame buffer device is enabled.
56 FTRACE Function tracing enabled.
57 GCOV GCOV profiling is enabled.
58 HW Appropriate hardware is enabled.
59 IA-64 IA-64 architecture is enabled.
60 IMA Integrity measurement architecture is enabled.
61 IOSCHED More than one I/O scheduler is enabled.
62 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
63 IPV6 IPv6 support is enabled.
64 ISAPNP ISA PnP code is enabled.
65 ISDN Appropriate ISDN support is enabled.
66 JOY Appropriate joystick support is enabled.
67 KGDB Kernel debugger support is enabled.
68 KVM Kernel Virtual Machine support is enabled.
69 LIBATA Libata driver is enabled
70 LP Printer support is enabled.
71 LOOP Loopback device support is enabled.
72 M68k M68k architecture is enabled.
73 These options have more detailed description inside of
74 Documentation/m68k/kernel-options.txt.
75 MDA MDA console support is enabled.
76 MIPS MIPS architecture is enabled.
77 MOUSE Appropriate mouse support is enabled.
78 MSI Message Signaled Interrupts (PCI).
79 MTD MTD (Memory Technology Device) support is enabled.
80 NET Appropriate network support is enabled.
81 NUMA NUMA support is enabled.
82 NFS Appropriate NFS support is enabled.
83 OSS OSS sound support is enabled.
84 PV_OPS A paravirtualized kernel is enabled.
85 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
86 PARISC The PA-RISC architecture is enabled.
87 PCI PCI bus support is enabled.
88 PCIE PCI Express support is enabled.
89 PCMCIA The PCMCIA subsystem is enabled.
90 PNP Plug & Play support is enabled.
91 PPC PowerPC architecture is enabled.
92 PPT Parallel port support is enabled.
93 PS2 Appropriate PS/2 support is enabled.
94 RAM RAM disk support is enabled.
95 S390 S390 architecture is enabled.
96 SCSI Appropriate SCSI support is enabled.
97 A lot of drivers have their options described inside
98 the Documentation/scsi/ sub-directory.
99 SECURITY Different security models are enabled.
100 SELINUX SELinux support is enabled.
101 APPARMOR AppArmor support is enabled.
102 SERIAL Serial support is enabled.
103 SH SuperH architecture is enabled.
104 SMP The kernel is an SMP kernel.
105 SPARC Sparc architecture is enabled.
106 SWSUSP Software suspend (hibernation) is enabled.
107 SUSPEND System suspend states are enabled.
108 TPM TPM drivers are enabled.
109 TS Appropriate touchscreen support is enabled.
110 UMS USB Mass Storage support is enabled.
111 USB USB support is enabled.
112 USBHID USB Human Interface Device support is enabled.
113 V4L Video For Linux support is enabled.
114 VMMIO Driver for memory mapped virtio devices is enabled.
115 VGA The VGA console has been enabled.
116 VT Virtual terminal support is enabled.
117 WDT Watchdog support is enabled.
118 XT IBM PC/XT MFM hard disk support is enabled.
119 X86-32 X86-32, aka i386 architecture is enabled.
120 X86-64 X86-64 architecture is enabled.
121 More X86-64 boot options can be found in
122 Documentation/x86/x86_64/boot-options.txt .
123 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
124 XEN Xen support is enabled
126 In addition, the following text indicates that the option:
128 BUGS= Relates to possible processor bugs on the said processor.
129 KNL Is a kernel start-up parameter.
130 BOOT Is a boot loader parameter.
132 Parameters denoted with BOOT are actually interpreted by the boot
133 loader, and have no meaning to the kernel directly.
134 Do not modify the syntax of boot loader parameters without extreme
135 need or coordination with <Documentation/x86/boot.txt>.
137 There are also arch-specific kernel-parameters not documented here.
138 See for example <Documentation/x86/x86_64/boot-options.txt>.
140 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
141 a trailing = on the name of any parameter states that that parameter will
142 be entered as an environment variable, whereas its absence indicates that
143 it will appear as a kernel argument readable via /proc/cmdline by programs
144 running once the system is up.
146 The number of kernel parameters is not limited, but the length of the
147 complete command line (parameters including spaces etc.) is limited to
148 a fixed number of characters. This limit depends on the architecture
149 and is between 256 and 4096 characters. It is defined in the file
150 ./include/asm/setup.h as COMMAND_LINE_SIZE.
152 Finally, the [KMG] suffix is commonly described after a number of kernel
153 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
154 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
155 bytes respectively. Such letter suffixes can also be entirely omitted.
159 Advanced Configuration and Power Interface
160 Format: { force | off | strict | noirq | rsdt }
161 force -- enable ACPI if default was off
162 off -- disable ACPI if default was on
163 noirq -- do not use ACPI for IRQ routing
164 strict -- Be less tolerant of platforms that are not
165 strictly ACPI specification compliant.
166 rsdt -- prefer RSDT over (default) XSDT
167 copy_dsdt -- copy DSDT to memory
169 See also Documentation/power/runtime_pm.txt, pci=noacpi
171 acpi_rsdp= [ACPI,EFI,KEXEC]
172 Pass the RSDP address to the kernel, mostly used
173 on machines running EFI runtime service to boot the
174 second kernel for kdump.
176 acpi_apic_instance= [ACPI, IOAPIC]
178 2: use 2nd APIC table, if available
179 1,0: use 1st APIC table
182 acpi_backlight= [HW,ACPI]
183 acpi_backlight=vendor
185 If set to vendor, prefer vendor specific driver
186 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
187 of the ACPI video.ko driver.
189 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
190 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
192 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
193 debug output. Bits in debug_layer correspond to a
194 _COMPONENT in an ACPI source file, e.g.,
195 #define _COMPONENT ACPI_PCI_COMPONENT
196 Bits in debug_level correspond to a level in
197 ACPI_DEBUG_PRINT statements, e.g.,
198 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
199 The debug_level mask defaults to "info". See
200 Documentation/acpi/debug.txt for more information about
201 debug layers and levels.
203 Enable processor driver info messages:
204 acpi.debug_layer=0x20000000
205 Enable PCI/PCI interrupt routing info messages:
206 acpi.debug_layer=0x400000
207 Enable AML "Debug" output, i.e., stores to the Debug
208 object while interpreting AML:
209 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
210 Enable all messages related to ACPI hardware:
211 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
213 Some values produce so much output that the system is
214 unusable. The "log_buf_len" parameter may be useful
215 if you need to capture more output.
217 acpi_irq_balance [HW,ACPI]
218 ACPI will balance active IRQs
221 acpi_irq_nobalance [HW,ACPI]
222 ACPI will not move active IRQs (default)
225 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
226 Format: <irq>,<irq>...
228 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
230 Format: <irq>,<irq>...
232 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
234 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
235 Format: To spoof as Windows 98: ="Microsoft Windows"
237 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
238 acpi_osi="string1" # add string1
239 acpi_osi="!string2" # remove string2
240 acpi_osi=!* # remove all strings
241 acpi_osi=! # disable all built-in OS vendor
243 acpi_osi= # disable all strings
245 'acpi_osi=!' can be used in combination with single or
246 multiple 'acpi_osi="string1"' to support specific OS
247 vendor string(s). Note that such command can only
248 affect the default state of the OS vendor strings, thus
249 it cannot affect the default state of the feature group
250 strings and the current state of the OS vendor strings,
251 specifying it multiple times through kernel command line
252 is meaningless. This command is useful when one do not
253 care about the state of the feature group strings which
254 should be controlled by the OSPM.
256 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
257 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
258 can make '_OSI("Windows 2000")' TRUE.
260 'acpi_osi=' cannot be used in combination with other
261 'acpi_osi=' command lines, the _OSI method will not
262 exist in the ACPI namespace. NOTE that such command can
263 only affect the _OSI support state, thus specifying it
264 multiple times through kernel command line is also
267 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
270 'acpi_osi=!*' can be used in combination with single or
271 multiple 'acpi_osi="string1"' to support specific
272 string(s). Note that such command can affect the
273 current state of both the OS vendor strings and the
274 feature group strings, thus specifying it multiple times
275 through kernel command line is meaningful. But it may
276 still not able to affect the final state of a string if
277 there are quirks related to this string. This command
278 is useful when one want to control the state of the
279 feature group strings to debug BIOS issues related to
282 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
283 '_OSI("Module Device")' FALSE.
284 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
285 '_OSI("Module Device")' TRUE.
286 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
288 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
290 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
291 they all will make '_OSI("Windows 2000")' TRUE.
294 Override the pmtimer bug detection: force the kernel
295 to assume that this machine's pmtimer latches its value
296 and always returns good values.
298 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
299 Format: { level | edge | high | low }
301 acpi_serialize [HW,ACPI] force serialization of AML methods
303 acpi_skip_timer_override [HW,ACPI]
304 Recognize and ignore IRQ0/pin2 Interrupt Override.
305 For broken nForce2 BIOS resulting in XT-PIC timer.
307 acpi_sleep= [HW,ACPI] Sleep options
308 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
309 old_ordering, nonvs, sci_force_enable }
310 See Documentation/power/video.txt for information on
312 s3_beep is for debugging; it makes the PC's speaker beep
313 as soon as the kernel's real-mode entry point is called.
314 s4_nohwsig prevents ACPI hardware signature from being
315 used during resume from hibernation.
316 old_ordering causes the ACPI 1.0 ordering of the _PTS
317 control method, with respect to putting devices into
318 low power states, to be enforced (the ACPI 2.0 ordering
319 of _PTS is used by default).
320 nonvs prevents the kernel from saving/restoring the
321 ACPI NVS memory during suspend/hibernation and resume.
322 sci_force_enable causes the kernel to set SCI_EN directly
323 on resume from S1/S3 (which is against the ACPI spec,
324 but some broken systems don't work without it).
326 acpi_use_timer_override [HW,ACPI]
327 Use timer override. For some broken Nvidia NF5 boards
328 that require a timer override, but don't have HPET
330 acpi_enforce_resources= [ACPI]
331 { strict | lax | no }
332 Check for resource conflicts between native drivers
333 and ACPI OperationRegions (SystemIO and SystemMemory
334 only). IO ports and memory declared in ACPI might be
335 used by the ACPI subsystem in arbitrary AML code and
336 can interfere with legacy drivers.
337 strict (default): access to resources claimed by ACPI
338 is denied; legacy drivers trying to access reserved
339 resources will fail to bind to device using them.
340 lax: access to resources claimed by ACPI is allowed;
341 legacy drivers trying to access reserved resources
342 will bind successfully but a warning message is logged.
343 no: ACPI OperationRegions are not marked as reserved,
344 no further checks are performed.
346 add_efi_memmap [EFI; X86] Include EFI memory map in
347 kernel's map of available physical RAM.
350 { off | try_unsupported }
351 off: disable AGP support
352 try_unsupported: try to drive unsupported chipsets
353 (may crash computer or cause data corruption)
356 See Documentation/sound/alsa/alsa-parameters.txt
359 Allow the default userspace alignment fault handler
360 behaviour to be specified. Bit 0 enables warnings,
361 bit 1 enables fixups, and bit 2 sends a segfault.
363 align_va_addr= [X86-64]
364 Align virtual addresses by clearing slice [14:12] when
365 allocating a VMA at process creation time. This option
366 gives you up to 3% performance improvement on AMD F15h
367 machines (where it is enabled by default) for a
368 CPU-intensive style benchmark, and it can vary highly in
369 a microbenchmark depending on workload and compiler.
371 32: only for 32-bit processes
372 64: only for 64-bit processes
373 on: enable for both 32- and 64-bit processes
374 off: disable for both 32- and 64-bit processes
376 alloc_snapshot [FTRACE]
377 Allocate the ftrace snapshot buffer on boot up when the
378 main buffer is allocated. This is handy if debugging
379 and you need to use tracing_snapshot() on boot up, and
380 do not want to use tracing_snapshot_alloc() as it needs
381 to be done where GFP_KERNEL allocations are allowed.
383 amd_iommu= [HW,X86-64]
384 Pass parameters to the AMD IOMMU driver in the system.
386 fullflush - enable flushing of IO/TLB entries when
387 they are unmapped. Otherwise they are
388 flushed before they will be reused, which
390 off - do not initialize any AMD IOMMU found in
392 force_isolation - Force device isolation for all
393 devices. The IOMMU driver is not
394 allowed anymore to lift isolation
395 requirements as needed. This option
396 does not override iommu=pt
398 amd_iommu_dump= [HW,X86-64]
399 Enable AMD IOMMU driver option to dump the ACPI table
400 for AMD IOMMU. With this option enabled, AMD IOMMU
401 driver will print ACPI tables for AMD IOMMU during
402 IOMMU initialization.
404 amijoy.map= [HW,JOY] Amiga joystick support
405 Map of devices attached to JOY0DAT and JOY1DAT
407 See also Documentation/input/joystick.txt
409 analog.map= [HW,JOY] Analog joystick and gamepad support
410 Specifies type or capabilities of an analog joystick
411 connected to one of 16 gameports
412 Format: <type1>,<type2>,..<type16>
415 Power management functions (SPARCstation-4/5 + deriv.)
417 Disable APC CPU standby support. SPARCstation-Fox does
418 not play well with APC CPU idle - disable it if you have
419 APC and your system crashes randomly.
421 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
422 Change the output verbosity whilst booting
423 Format: { quiet (default) | verbose | debug }
424 Change the amount of debugging information output
425 when initialising the APIC and IO-APIC components.
428 See Documentation/networking/ipv6.txt.
430 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
431 Limit apic dumping. The parameter defines the maximal
432 number of local apics being dumped. Also it is possible
433 to set it to "all" by meaning -- no limit here.
434 Format: { 1 (default) | 2 | ... | all }.
435 The parameter valid if only apic=debug or
436 apic=verbose is specified.
437 Example: apic=debug show_lapic=all
439 apm= [APM] Advanced Power Management
440 See header of arch/x86/kernel/apm_32.c.
442 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
443 Format: <io>,<irq>,<nodeID>
447 atarimouse= [HW,MOUSE] Atari Mouse
449 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
450 EzKey and similar keyboards
452 atkbd.reset= [HW] Reset keyboard during initialization
454 atkbd.set= [HW] Select keyboard code set
455 Format: <int> (2 = AT (default), 3 = PS/2)
457 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
460 atkbd.softraw= [HW] Choose between synthetic and real raw mode
461 Format: <bool> (0 = real, 1 = synthetic (default))
463 atkbd.softrepeat= [HW]
464 Use software keyboard repeat
466 baycom_epp= [HW,AX25]
469 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
471 See header of drivers/net/hamradio/baycom_par.c.
473 baycom_ser_fdx= [HW,AX25]
474 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
475 Format: <io>,<irq>,<mode>[,<baud>]
476 See header of drivers/net/hamradio/baycom_ser_fdx.c.
478 baycom_ser_hdx= [HW,AX25]
479 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
480 Format: <io>,<irq>,<mode>
481 See header of drivers/net/hamradio/baycom_ser_hdx.c.
483 blkdevparts= Manual partition parsing of block device(s) for
484 embedded devices based on command line input.
485 See Documentation/block/cmdline-partition.txt
487 boot_delay= Milliseconds to delay each printk during boot.
488 Values larger than 10 seconds (10000) are changed to
492 bootmem_debug [KNL] Enable bootmem allocator debug messages.
494 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
495 bttv.radio= Most important insmod options are available as
497 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
500 bulk_remove=off [PPC] This parameter disables the use of the pSeries
501 firmware feature for flushing multiple hpte entries
504 c101= [NET] Moxa C101 synchronous serial card
506 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
507 Sometimes CPU hardware bugs make them report the cache
508 size incorrectly. The kernel will attempt work arounds
509 to fix known problems, but for some CPUs it is not
510 possible to determine what the correct size should be.
511 This option provides an override for these situations.
513 ccw_timeout_log [S390]
514 See Documentation/s390/CommonIO for details.
516 cgroup_disable= [KNL] Disable a particular controller
517 Format: {name of the controller(s) to disable}
518 The effects of cgroup_disable=foo are:
519 - foo isn't auto-mounted if you mount all cgroups in
521 - foo isn't visible as an individually mountable
523 {Currently only "memory" controller deal with this and
524 cut the overhead, others just disable the usage. So
525 only cgroup_disable=memory is actually worthy}
527 checkreqprot [SELINUX] Set initial checkreqprot flag value.
528 Format: { "0" | "1" }
529 See security/selinux/Kconfig help text.
530 0 -- check protection applied by kernel (includes
531 any implied execute protection).
532 1 -- check protection requested by application.
533 Default value is set via a kernel config option.
534 Value can be changed at runtime via
535 /selinux/checkreqprot.
538 See Documentation/s390/CommonIO for details.
541 Keep all clocks already enabled by bootloader on,
542 even if no driver has claimed them. This is useful
543 for debug and development, but should not be
544 needed on a platform with proper driver support.
545 For more information, see Documentation/clk.txt.
547 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
549 Forces specified clocksource (if available) to be used
550 when calculating gettimeofday(). If specified
551 clocksource is not available, it defaults to PIT.
552 Format: { pit | tsc | cyclone | pmtmr }
554 clocksource= Override the default clocksource
556 Override the default clocksource and use the clocksource
557 with the name specified.
558 Some clocksource names to choose from, depending on
560 [all] jiffies (this is the base, fallback clocksource)
562 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
563 pxa_timer,timer3,32k_counter,timer0_1
565 [X86-32] pit,hpet,tsc;
566 scx200_hrt on Geode; cyclone on IBM x440
574 clearcpuid=BITNUM [X86]
575 Disable CPUID feature X for the kernel. See
576 arch/x86/include/asm/cpufeature.h for the valid bit
577 numbers. Note the Linux specific bits are not necessarily
578 stable over kernel options, but the vendor specific
580 Also note that user programs calling CPUID directly
581 or using the feature without checking anything
582 will still see it. This just prevents it from
583 being used by the kernel or shown in /proc/cpuinfo.
584 Also note the kernel might malfunction if you disable
588 Sets the size of kernel global memory area for contiguous
589 memory allocations. For more information, see
590 include/linux/dma-contiguous.h
592 cmo_free_hint= [PPC] Format: { yes | no }
593 Specify whether pages are marked as being inactive
594 when they are freed. This is used in CMO environments
595 to determine OS memory pressure for page stealing by
599 coherent_pool=nn[KMG] [ARM,KNL]
600 Sets the size of memory pool for coherent, atomic dma
601 allocations, by default set to 256K.
603 code_bytes [X86] How many bytes of object code to print
608 com20020= [HW,NET] ARCnet - COM20020 chipset
610 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
612 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
616 ARCnet - COM90xx chipset (memory-mapped buffers)
617 Format: <io>[,<irq>[,<memstart>]]
619 condev= [HW,S390] console device
622 console= [KNL] Output console device and options.
624 tty<n> Use the virtual console device <n>.
628 Use the specified serial port. The options are of
629 the form "bbbbpnf", where "bbbb" is the baud rate,
630 "p" is parity ("n", "o", or "e"), "n" is number of
631 bits, and "f" is flow control ("r" for RTS or
632 omit it). Default is "9600n8".
634 See Documentation/serial-console.txt for more
636 Documentation/networking/netconsole.txt for an
639 uart[8250],io,<addr>[,options]
640 uart[8250],mmio,<addr>[,options]
641 Start an early, polled-mode console on the 8250/16550
642 UART at the specified I/O port or MMIO address,
643 switching to the matching ttyS device later. The
644 options are the same as for ttyS, above.
645 hvc<n> Use the hypervisor console device <n>. This is for
646 both Xen and PowerPC hypervisors.
648 If the device connected to the port is not a TTY but a braille
649 device, prepend "brl," before the device type, for instance
651 For now, only VisioBraille is supported.
653 consoleblank= [KNL] The console blank (screen saver) timeout in
654 seconds. Defaults to 10*60 = 10mins. A value of 0
655 disables the blank timer.
658 [KNL] Change the default value for
659 /proc/<pid>/coredump_filter.
660 See also Documentation/filesystems/proc.txt.
662 cpuidle.off=1 [CPU_IDLE]
663 disable the cpuidle sub-system
665 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
667 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
669 crashkernel=size[KMG][@offset[KMG]]
670 [KNL] Using kexec, Linux can switch to a 'crash kernel'
671 upon panic. This parameter reserves the physical
672 memory region [offset, offset + size] for that kernel
673 image. If '@offset' is omitted, then a suitable offset
674 is selected automatically. Check
675 Documentation/kdump/kdump.txt for further details.
677 crashkernel=range1:size1[,range2:size2,...][@offset]
678 [KNL] Same as above, but depends on the memory
679 in the running system. The syntax of range is
680 start-[end] where start and end are both
681 a memory unit (amount[KMG]). See also
682 Documentation/kdump/kdump.txt for an example.
684 crashkernel=size[KMG],high
685 [KNL, x86_64] range could be above 4G. Allow kernel
686 to allocate physical memory region from top, so could
687 be above 4G if system have more than 4G ram installed.
688 Otherwise memory region will be allocated below 4G, if
690 It will be ignored if crashkernel=X is specified.
691 crashkernel=size[KMG],low
692 [KNL, x86_64] range under 4G. When crashkernel=X,high
693 is passed, kernel could allocate physical memory region
694 above 4G, that cause second kernel crash on system
695 that require some amount of low memory, e.g. swiotlb
696 requires at least 64M+32K low memory. Kernel would
697 try to allocate 72M below 4G automatically.
698 This one let user to specify own low range under 4G
699 for second kernel instead.
700 0: to disable low allocation.
701 It will be ignored when crashkernel=X,high is not used
702 or memory reserved is below 4G.
707 cs89x0_media= [HW,NET]
708 Format: { rj45 | aui | bnc }
711 See header of drivers/s390/block/dasd_devmap.c.
713 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
714 (one device per port)
715 Format: <port#>,<type>
716 See also Documentation/input/joystick-parport.txt
718 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
719 time. See Documentation/dynamic-debug-howto.txt for
720 details. Deprecated, see dyndbg.
722 debug [KNL] Enable kernel debugging (events log level).
725 [KNL] verbose self-tests
727 Print debugging info while doing the locking API
729 We default to 0 (no extra messages), setting it to
730 1 will print _a lot_ more information - normally
731 only useful to kernel developers.
733 debug_objects [KNL] Enable object debugging
736 [KNL] Disable object debugging
738 debug_guardpage_minorder=
739 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
740 parameter allows control of the order of pages that will
741 be intentionally kept free (and hence protected) by the
742 buddy allocator. Bigger value increase the probability
743 of catching random memory corruption, but reduce the
744 amount of memory for normal system use. The maximum
745 possible value is MAX_ORDER/2. Setting this parameter
746 to 1 or 2 should be enough to identify most random
747 memory corruption problems caused by bugs in kernel or
748 driver code when a CPU writes to (or reads from) a
749 random memory location. Note that there exists a class
750 of memory corruptions problems caused by buggy H/W or
751 F/W or by drivers badly programing DMA (basically when
752 memory is written at bus level and the CPU MMU is
753 bypassed) which are not detectable by
754 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
755 tracking down these problems.
757 debugpat [X86] Enable PAT debugging
759 decnet.addr= [HW,NET]
760 Format: <area>[,<node>]
761 See also Documentation/networking/decnet.txt.
764 [same as hugepagesz=] The size of the default
765 HugeTLB page size. This is the size represented by
766 the legacy /proc/ hugepages APIs, used for SHM, and
767 default size when mounting hugetlbfs filesystems.
768 Defaults to the default architecture's huge page size
772 Set number of hash buckets for dentry cache.
775 IO parameters + enable/disable command.
777 digiepca= [HW,SERIAL]
778 See drivers/char/README.epca and
779 Documentation/serial/digiepca.txt.
782 See Documentation/networking/ipv6.txt.
784 disable_cpu_apicid= [X86,APIC,SMP]
786 The number of initial APIC ID for the
787 corresponding CPU to be disabled at boot,
788 mostly used for the kdump 2nd kernel to
789 disable BSP to wake up multiple CPUs without
790 causing system reset or hang due to sending
793 disable_ddw [PPC/PSERIES]
794 Disable Dynamic DMA Window support. Use this if
795 to workaround buggy firmware.
798 See Documentation/networking/ipv6.txt.
800 disable_mtrr_cleanup [X86]
801 The kernel tries to adjust MTRR layout from continuous
802 to discrete, to make X server driver able to add WB
803 entry later. This parameter disables that.
805 disable_mtrr_trim [X86, Intel and AMD only]
806 By default the kernel will trim any uncacheable
807 memory out of your available memory pool based on
808 MTRR settings. This parameter disables that behavior,
809 possibly causing your machine to run very slowly.
811 disable_timer_pin_1 [X86]
812 Disable PIN 1 of APIC timer
813 Can be useful to work around chipset bugs.
815 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
816 this option disables the debugging code at boot.
818 dma_debug_entries=<number>
819 This option allows to tune the number of preallocated
820 entries for DMA-API debugging code. One entry is
821 required per DMA-API allocation. Use this if the
822 DMA-API debugging code disables itself because the
823 architectural default is too low.
825 dma_debug_driver=<driver_name>
826 With this option the DMA-API debugging driver
827 filter feature can be enabled at boot time. Just
828 pass the driver to filter for as the parameter.
829 The filter can be disabled or changed to another
830 driver later using sysfs.
832 drm_kms_helper.edid_firmware=[<connector>:]<file>
833 Broken monitors, graphic adapters and KVMs may
834 send no or incorrect EDID data sets. This parameter
835 allows to specify an EDID data set in the
836 /lib/firmware directory that is used instead.
837 Generic built-in EDID data sets are used, if one of
838 edid/1024x768.bin, edid/1280x1024.bin,
839 edid/1680x1050.bin, or edid/1920x1080.bin is given
840 and no file with the same name exists. Details and
841 instructions how to build your own EDID data are
842 available in Documentation/EDID/HOWTO.txt. An EDID
843 data set will only be used for a particular connector,
844 if its name and a colon are prepended to the EDID
849 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
850 module.dyndbg[="val"]
851 Enable debug messages at boot time. See
852 Documentation/dynamic-debug-howto.txt for details.
854 earlycon= [KNL] Output early console device and options.
855 uart[8250],io,<addr>[,options]
856 uart[8250],mmio,<addr>[,options]
857 uart[8250],mmio32,<addr>[,options]
858 Start an early, polled-mode console on the 8250/16550
859 UART at the specified I/O port or MMIO address.
860 MMIO inter-register address stride is either 8-bit
861 (mmio) or 32-bit (mmio32).
862 The options are the same as for ttyS, above.
864 earlyprintk= [X86,SH,BLACKFIN,ARM]
868 earlyprintk=serial[,ttySn[,baudrate]]
869 earlyprintk=serial[,0x...[,baudrate]]
870 earlyprintk=ttySn[,baudrate]
871 earlyprintk=dbgp[debugController#]
873 earlyprintk is useful when the kernel crashes before
874 the normal console is initialized. It is not enabled by
875 default because it has some cosmetic problems.
877 Append ",keep" to not disable it when the real console
880 Only one of vga, efi, serial, or usb debug port can
883 Currently only ttyS0 and ttyS1 may be specified by
884 name. Other I/O ports may be explicitly specified
885 on some architectures (x86 and arm at least) by
886 replacing ttySn with an I/O port address, like this:
887 earlyprintk=serial,0x1008,115200
888 You can find the port for a given device in
889 /proc/tty/driver/serial:
890 2: uart:ST16650V2 port:00001008 irq:18 ...
892 Interaction with the standard serial driver is not
895 The VGA and EFI output is eventually overwritten by
898 The xen output can only be used by Xen PV guests.
900 edac_report= [HW,EDAC] Control how to report EDAC event
901 Format: {"on" | "off" | "force"}
902 on: enable EDAC to report H/W event. May be overridden
903 by other higher priority error reporting module.
904 off: disable H/W event reporting through EDAC.
905 force: enforce the use of EDAC to report H/W event.
908 ekgdboc= [X86,KGDB] Allow early kernel console debugging
911 This is designed to be used in conjunction with
912 the boot argument: earlyprintk=vga
915 Format: {"off" | "on" | "skip[mbr]"}
918 Format: { "old_map" }
919 old_map [X86-64]: switch to the old ioremap-based EFI
920 runtime services mapping. 32-bit still uses this one by
923 efi_no_storage_paranoia [EFI; X86]
924 Using this parameter you can use more than 50% of
925 your efi variable storage. Use this parameter only if
926 you are really sure that your UEFI does sane gc and
927 fulfills the spec otherwise your board may brick.
929 eisa_irq_edge= [PARISC,HW]
930 See header of drivers/parisc/eisa.c.
933 See comment before function elanfreq_setup() in
934 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
937 Format: {"cfq" | "deadline" | "noop"}
938 See Documentation/block/cfq-iosched.txt and
939 Documentation/block/deadline-iosched.txt for details.
941 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
942 Specifies physical address of start of kernel core
943 image elf header and optionally the size. Generally
944 kexec loader will pass this option to capture kernel.
945 See Documentation/kdump/kdump.txt for details.
947 enable_mtrr_cleanup [X86]
948 The kernel tries to adjust MTRR layout from continuous
949 to discrete, to make X server driver able to add WB
950 entry later. This parameter enables that.
952 enable_timer_pin_1 [X86]
953 Enable PIN 1 of APIC timer
954 Can be useful to work around chipset bugs
955 (in particular on some ATI chipsets).
956 The kernel tries to set a reasonable default.
958 enforcing [SELINUX] Set initial enforcing status.
960 See security/selinux/Kconfig help text.
961 0 -- permissive (log only, no denials).
962 1 -- enforcing (deny and log).
964 Value can be changed at runtime via /selinux/enforce.
967 Disable Error Record Serialization Table (ERST)
970 ether= [HW,NET] Ethernet cards parameters
971 This option is obsoleted by the "netdev=" option, which
972 has equivalent usage. See its documentation for details.
976 Permit 'security.evm' to be updated regardless of
977 current integrity status.
981 fail_make_request=[KNL]
982 General fault injection mechanism.
983 Format: <interval>,<probability>,<space>,<times>
984 See also Documentation/fault-injection/.
987 See Documentation/blockdev/floppy.txt.
989 force_pal_cache_flush
990 [IA-64] Avoid check_sal_cache_flush which may hang on
991 buggy SAL_CACHE_FLUSH implementations. Using this
992 parameter will force ia64_sal_cache_flush to call
993 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
996 [FTRACE] will set and start the specified tracer
997 as early as possible in order to facilitate early
1000 ftrace_dump_on_oops[=orig_cpu]
1001 [FTRACE] will dump the trace buffers on oops.
1002 If no parameter is passed, ftrace will dump
1003 buffers of all CPUs, but if you pass orig_cpu, it will
1004 dump only the buffer of the CPU that triggered the
1007 ftrace_filter=[function-list]
1008 [FTRACE] Limit the functions traced by the function
1009 tracer at boot up. function-list is a comma separated
1010 list of functions. This list can be changed at run
1011 time by the set_ftrace_filter file in the debugfs
1014 ftrace_notrace=[function-list]
1015 [FTRACE] Do not trace the functions specified in
1016 function-list. This list can be changed at run time
1017 by the set_ftrace_notrace file in the debugfs
1020 ftrace_graph_filter=[function-list]
1021 [FTRACE] Limit the top level callers functions traced
1022 by the function graph tracer at boot up.
1023 function-list is a comma separated list of functions
1024 that can be changed at run time by the
1025 set_graph_function file in the debugfs tracing directory.
1028 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1029 support via parallel port (up to 5 devices per port)
1030 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1031 See also Documentation/input/joystick-parport.txt
1035 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1039 gcov_persist= [GCOV] When non-zero (default), profiling data for
1040 kernel modules is saved and remains accessible via
1041 debugfs, even when the module is unloaded/reloaded.
1042 When zero, profiling data is discarded and associated
1043 debugfs files are removed at module unload time.
1045 gpt [EFI] Forces disk with valid GPT signature but
1046 invalid Protective MBR to be treated as GPT.
1048 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1049 the "Enable 0" bit of the configuration register.
1052 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1053 the "Enable 0" bit of the configuration register.
1056 grcan.select= [HW] Select which physical interface to use.
1059 grcan.txsize= [HW] Sets the size of the tx buffer.
1060 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1062 grcan.rxsize= [HW] Sets the size of the rx buffer.
1063 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1066 hashdist= [KNL,NUMA] Large hashes allocated during boot
1067 are distributed across NUMA nodes. Defaults on
1068 for 64-bit NUMA, off otherwise.
1069 Format: 0 | 1 (for off | on)
1071 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1073 hd= [EIDE] (E)IDE hard drive subsystem geometry
1074 Format: <cyl>,<head>,<sect>
1077 Disable Hardware Error Source Table (HEST) support;
1078 corresponding firmware-first mode error processing
1079 logic will be disabled.
1081 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1082 size of <nn>. This works even on boxes that have no
1083 highmem otherwise. This also works to reduce highmem
1084 size on bigger boxes.
1086 highres= [KNL] Enable/disable high resolution timer mode.
1087 Valid parameters: "on", "off"
1091 See Documentation/isdn/README.HiSax.
1095 hpet= [X86-32,HPET] option to control HPET usage
1096 Format: { enable (default) | disable | force |
1098 disable: disable HPET and use PIT instead
1099 force: allow force enabled of undocumented chips (ICH4,
1101 verbose: show contents of HPET registers during setup
1103 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1104 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1106 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1107 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1108 On x86-64 and powerpc, this option can be specified
1109 multiple times interleaved with hugepages= to reserve
1110 huge pages of different sizes. Valid pages sizes on
1111 x86-64 are 2M (when the CPU supports "pse") and 1G
1112 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1113 Note that 1GB pages can only be allocated at boot time
1114 using hugepages= and not freed afterwards.
1116 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1117 terminal devices. Valid values: 0..8
1118 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1119 If specified, z/VM IUCV HVC accepts connections
1120 from listed z/VM user IDs only.
1122 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1123 hardware thread id mappings.
1124 Format: <cpu>:<hwthread>
1127 Do not unregister boot console at start. This is only
1128 useful for debugging when something happens in the window
1129 between unregistering the boot console and initializing
1132 i2c_bus= [HW] Override the default board specific I2C bus speed
1133 or register an additional I2C bus that is not
1134 registered from board initialization code.
1138 i8042.debug [HW] Toggle i8042 debug mode
1139 i8042.direct [HW] Put keyboard port into non-translated mode
1140 i8042.dumbkbd [HW] Pretend that controller can only read data from
1141 keyboard and cannot control its state
1142 (Don't attempt to blink the leds)
1143 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1144 i8042.nokbd [HW] Don't check/create keyboard port
1145 i8042.noloop [HW] Disable the AUX Loopback command while probing
1147 i8042.nomux [HW] Don't check presence of an active multiplexing
1149 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1151 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1152 i8042.reset [HW] Reset the controller during init and cleanup
1153 i8042.unlock [HW] Unlock (ignore) the keylock
1157 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1158 indicates that the driver is running on unsupported
1160 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1161 does not match list of supported models.
1163 [HW] Report power status in /proc/i8k
1164 (disabled by default)
1165 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1168 i915.invert_brightness=
1169 [DRM] Invert the sense of the variable that is used to
1170 set the brightness of the panel backlight. Normally a
1171 brightness value of 0 indicates backlight switched off,
1172 and the maximum of the brightness value sets the backlight
1173 to maximum brightness. If this parameter is set to 0
1174 (default) and the machine requires it, or this parameter
1175 is set to 1, a brightness value of 0 sets the backlight
1176 to maximum brightness, and the maximum of the brightness
1177 value switches the backlight off.
1178 -1 -- never invert brightness
1179 0 -- machine default
1180 1 -- force brightness inversion
1183 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1185 ide-core.nodma= [HW] (E)IDE subsystem
1186 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1187 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1188 .cdrom .chs .ignore_cable are additional options
1189 See Documentation/ide/ide.txt.
1191 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1192 Claim all unknown PCI IDE storage controllers.
1195 Format: idle=poll, idle=halt, idle=nomwait
1196 Poll forces a polling idle loop that can slightly
1197 improve the performance of waking up a idle CPU, but
1198 will use a lot of power and make the system run hot.
1200 idle=halt: Halt is forced to be used for CPU idle.
1201 In such case C2/C3 won't be used again.
1202 idle=nomwait: Disable mwait for CPU C-states
1204 ignore_loglevel [KNL]
1205 Ignore loglevel setting - this will print /all/
1206 kernel messages to the console. Useful for debugging.
1207 We also add it as printk module parameter, so users
1208 could change it dynamically, usually by
1209 /sys/module/printk/parameters/ignore_loglevel.
1211 ihash_entries= [KNL]
1212 Set number of hash buckets for inode cache.
1214 ima_appraise= [IMA] appraise integrity measurements
1215 Format: { "off" | "enforce" | "fix" }
1218 ima_appraise_tcb [IMA]
1219 The builtin appraise policy appraises all files
1223 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1227 The list of supported hash algorithms is defined
1228 in crypto/hash_info.h.
1231 Load a policy which meets the needs of the Trusted
1232 Computing Base. This means IMA will measure all
1233 programs exec'd, files mmap'd for exec, and all files
1234 opened for read by uid=0.
1237 Select one of defined IMA measurements template formats.
1238 Formats: { "ima" | "ima-ng" }
1243 Run specified binary instead of /sbin/init as init
1246 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1247 for working out where the kernel is dying during
1250 initrd= [BOOT] Specify the location of the initial ramdisk
1252 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1255 int_pln_enable [x86] Enable power limit notification interrupt
1257 integrity_audit=[IMA]
1258 Format: { "0" | "1" }
1259 0 -- basic integrity auditing messages. (Default)
1260 1 -- additional integrity auditing messages.
1262 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1264 Enable intel iommu driver.
1266 Disable intel iommu driver.
1267 igfx_off [Default Off]
1268 By default, gfx is mapped as normal device. If a gfx
1269 device has a dedicated DMAR unit, the DMAR unit is
1270 bypassed by not enabling DMAR with this option. In
1271 this case, gfx device will use physical address for
1274 With this option iommu will not optimize to look
1275 for io virtual address below 32-bit forcing dual
1276 address cycle on pci bus for cards supporting greater
1277 than 32-bit addressing. The default is to look
1278 for translation below 32-bit and if not available
1279 then look in the higher range.
1280 strict [Default Off]
1281 With this option on every unmap_single operation will
1282 result in a hardware IOTLB flush operation as opposed
1283 to batching them for performance.
1284 sp_off [Default Off]
1285 By default, super page will be supported if Intel IOMMU
1286 has the capability. With this option, super page will
1289 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1290 0 disables intel_idle and fall back on acpi_idle.
1291 1 to 6 specify maximum depth of C-state.
1295 Do not enable intel_pstate as the default
1296 scaling driver for the supported processors
1298 intremap= [X86-64, Intel-IOMMU]
1299 on enable Interrupt Remapping (default)
1300 off disable Interrupt Remapping
1301 nosid disable Source ID checking
1303 BIOS x2APIC opt-out request will be ignored
1305 iomem= Disable strict checking of access to MMIO memory
1306 strict regions from userspace.
1323 io7= [HW] IO7 for Marvel based alpha systems
1324 See comment before marvel_specify_io7 in
1325 arch/alpha/kernel/core_marvel.c.
1327 io_delay= [X86] I/O delay method
1329 Standard port 0x80 based delay
1331 Alternate port 0xed based delay (needed on some systems)
1333 Simple two microseconds delay
1338 See Documentation/filesystems/nfs/nfsroot.txt.
1340 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1341 See comment before ip2_setup() in
1342 drivers/char/ip2/ip2base.c.
1345 When an interrupt is not handled search all handlers
1346 for it. Intended to get systems with badly broken
1350 When an interrupt is not handled search all handlers
1351 for it. Also check all handlers each timer
1352 interrupt. Intended to get systems with badly broken
1356 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1358 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1360 <cpu number>,...,<cpu number>
1362 <cpu number>-<cpu number>
1363 (must be a positive range in ascending order)
1365 <cpu number>,...,<cpu number>-<cpu number>
1367 This option can be used to specify one or more CPUs
1368 to isolate from the general SMP balancing and scheduling
1369 algorithms. You can move a process onto or off an
1370 "isolated" CPU via the CPU affinity syscalls or cpuset.
1371 <cpu number> begins at 0 and the maximum value is
1372 "number of CPUs in system - 1".
1374 This option is the preferred way to isolate CPUs. The
1375 alternative -- manually setting the CPU mask of all
1376 tasks in the system -- can cause problems and
1377 suboptimal load balancer performance.
1381 ivrs_ioapic [HW,X86_64]
1382 Provide an override to the IOAPIC-ID<->DEVICE-ID
1383 mapping provided in the IVRS ACPI table. For
1384 example, to map IOAPIC-ID decimal 10 to
1385 PCI device 00:14.0 write the parameter as:
1386 ivrs_ioapic[10]=00:14.0
1388 ivrs_hpet [HW,X86_64]
1389 Provide an override to the HPET-ID<->DEVICE-ID
1390 mapping provided in the IVRS ACPI table. For
1391 example, to map HPET-ID decimal 0 to
1392 PCI device 00:14.0 write the parameter as:
1393 ivrs_hpet[0]=00:14.0
1395 js= [HW,JOY] Analog joystick
1396 See Documentation/input/joystick.txt.
1400 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1401 specifies the amount of memory usable by the kernel
1402 for non-movable allocations. The requested amount is
1403 spread evenly throughout all nodes in the system. The
1404 remaining memory in each node is used for Movable
1405 pages. In the event, a node is too small to have both
1406 kernelcore and Movable pages, kernelcore pages will
1407 take priority and other nodes will have a larger number
1408 of Movable pages. The Movable zone is used for the
1409 allocation of pages that may be reclaimed or moved
1410 by the page migration subsystem. This means that
1411 HugeTLB pages may not be allocated from this zone.
1412 Note that allocations like PTEs-from-HighMem still
1413 use the HighMem zone if it exists, and the Normal
1414 zone if it does not.
1416 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1417 Format: <Controller#>[,poll interval]
1418 The controller # is the number of the ehci usb debug
1419 port as it is probed via PCI. The poll interval is
1420 optional and is the number seconds in between
1421 each poll cycle to the debug port in case you need
1422 the functionality for interrupting the kernel with
1423 gdb or control-c on the dbgp connection. When
1424 not using this parameter you use sysrq-g to break into
1425 the kernel debugger.
1427 kgdboc= [KGDB,HW] kgdb over consoles.
1428 Requires a tty driver that supports console polling,
1429 or a supported polling keyboard driver (non-usb).
1430 Serial only format: <serial_device>[,baud]
1431 keyboard only format: kbd
1432 keyboard and serial format: kbd,<serial_device>[,baud]
1433 Optional Kernel mode setting:
1434 kms, kbd format: kms,kbd
1435 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1437 kgdbwait [KGDB] Stop kernel execution and enter the
1438 kernel debugger at the earliest opportunity.
1440 kmac= [MIPS] korina ethernet MAC address.
1441 Configure the RouterBoard 532 series on-chip
1442 Ethernet adapter MAC address.
1444 kmemleak= [KNL] Boot-time kmemleak enable/disable
1445 Valid arguments: on, off
1448 kstack=N [X86] Print N words from the kernel stack
1451 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1452 Default is 0 (don't ignore, but inject #GP)
1454 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1458 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1459 Default is 1 (enabled)
1461 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1463 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1465 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1466 (virtualized MMU) support on capable Intel chips.
1467 Default is 1 (enabled)
1469 kvm-intel.emulate_invalid_guest_state=
1470 [KVM,Intel] Enable emulation of invalid guest states
1471 Default is 0 (disabled)
1473 kvm-intel.flexpriority=
1474 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1475 Default is 1 (enabled)
1478 [KVM,Intel] Enable VMX nesting (nVMX).
1479 Default is 0 (disabled)
1481 kvm-intel.unrestricted_guest=
1482 [KVM,Intel] Disable unrestricted guest feature
1483 (virtualized real and unpaged mode) on capable
1484 Intel chips. Default is 1 (enabled)
1486 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1487 feature (tagged TLBs) on capable Intel chips.
1488 Default is 1 (enabled)
1494 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1497 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1498 value for LAPIC timer one-shot implementation. Default
1499 back to the programmable timer unit in the LAPIC.
1501 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1504 libata.dma= [LIBATA] DMA control
1505 libata.dma=0 Disable all PATA and SATA DMA
1506 libata.dma=1 PATA and SATA Disk DMA only
1507 libata.dma=2 ATAPI (CDROM) DMA only
1508 libata.dma=4 Compact Flash DMA only
1509 Combinations also work, so libata.dma=3 enables DMA
1510 for disks and CDROMs, but not CFs.
1512 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1513 libata.ignore_hpa=0 keep BIOS limits (default)
1514 libata.ignore_hpa=1 ignore limits, using full disk
1516 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1520 libata.force= [LIBATA] Force configurations. The format is comma
1521 separated list of "[ID:]VAL" where ID is
1522 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1523 matching port, link or device. Basically, it matches
1524 the ATA ID string printed on console by libata. If
1525 the whole ID part is omitted, the last PORT and DEVICE
1526 values are used. If ID hasn't been specified yet, the
1527 configuration applies to all ports, links and devices.
1529 If only DEVICE is omitted, the parameter applies to
1530 the port and all links and devices behind it. DEVICE
1531 number of 0 either selects the first device or the
1532 first fan-out link behind PMP device. It does not
1533 select the host link. DEVICE number of 15 selects the
1534 host link and device attached to it.
1536 The VAL specifies the configuration to force. As long
1537 as there's no ambiguity shortcut notation is allowed.
1538 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1539 The following configurations can be forced.
1541 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1542 Any ID with matching PORT is used.
1544 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1546 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1547 udma[/][16,25,33,44,66,100,133] notation is also
1550 * [no]ncq: Turn on or off NCQ.
1552 * nohrst, nosrst, norst: suppress hard, soft
1555 * rstonce: only attempt one reset during
1556 hot-unplug link recovery
1558 * dump_id: dump IDENTIFY data.
1560 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1562 * disable: Disable this device.
1564 If there are multiple matching configurations changing
1565 the same attribute, the last one is used.
1567 memblock=debug [KNL] Enable memblock debug messages.
1569 load_ramdisk= [RAM] List of ramdisks to load from floppy
1570 See Documentation/blockdev/ramdisk.txt.
1572 lockd.nlm_grace_period=P [NFS] Assign grace period.
1575 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1578 lockd.nlm_timeout=T [NFS] Assign timeout value.
1581 lockd.nlm_udpport=M [NFS] Assign UDP port.
1584 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1587 loglevel= All Kernel Messages with a loglevel smaller than the
1588 console loglevel will be printed to the console. It can
1589 also be changed with klogd or other programs. The
1590 loglevels are defined as follows:
1592 0 (KERN_EMERG) system is unusable
1593 1 (KERN_ALERT) action must be taken immediately
1594 2 (KERN_CRIT) critical conditions
1595 3 (KERN_ERR) error conditions
1596 4 (KERN_WARNING) warning conditions
1597 5 (KERN_NOTICE) normal but significant condition
1598 6 (KERN_INFO) informational
1599 7 (KERN_DEBUG) debug-level messages
1601 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1602 in bytes. n must be a power of two. The default
1603 size is set in the kernel config file.
1605 logo.nologo [FB] Disables display of the built-in Linux logo.
1606 This may be used to provide more screen space for
1607 kernel log messages and is useful when debugging
1608 kernel boot problems.
1610 lp=0 [LP] Specify parallel ports to use, e.g,
1611 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1612 lp=reset first parallel port). 'lp=0' disables the
1613 lp=auto printer driver. 'lp=reset' (which can be
1614 specified in addition to the ports) causes
1615 attached printers to be reset. Using
1616 lp=port1,port2,... specifies the parallel ports
1617 to associate lp devices with, starting with
1618 lp0. A port specification may be 'none' to skip
1619 that lp device, or a parport name such as
1620 'parport0'. Specifying 'lp=auto' instead of a
1621 port specification list means that device IDs
1622 from each port should be examined, to see if
1623 an IEEE 1284-compliant printer is attached; if
1624 so, the driver will manage that printer.
1625 See also header of drivers/char/lp.c.
1628 Sets loops_per_jiffy to given constant, thus avoiding
1629 time-consuming boot-time autodetection (up to 250 ms per
1630 CPU). 0 enables autodetection (default). To determine
1631 the correct value for your kernel, boot with normal
1632 autodetection and see what value is printed. Note that
1633 on SMP systems the preset will be applied to all CPUs,
1634 which is likely to cause problems if your CPUs need
1635 significantly divergent settings. An incorrect value
1636 will cause delays in the kernel to be wrong, leading to
1637 unpredictable I/O errors and other breakage. Although
1638 unlikely, in the extreme case this might damage your
1642 Format: <io>,<irq>,<dma>
1644 machvec= [IA-64] Force the use of a particular machine-vector
1645 (machvec) in a generic kernel.
1646 Example: machvec=hpzx1_swiotlb
1648 machtype= [Loongson] Share the same kernel image file between different
1650 Example: machtype=lemote-yeeloong-2f-7inch
1652 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1653 than or equal to this physical address is ignored.
1655 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1656 should make use of. maxcpus=n : n >= 0 limits the
1657 kernel to using 'n' processors. n=0 is a special case,
1658 it is equivalent to "nosmp", which also disables
1661 max_loop= [LOOP] The number of loop block devices that get
1662 (loop.max_loop) unconditionally pre-created at init time. The default
1663 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1664 of statically allocating a predefined number, loop
1665 devices can be requested on-demand with the
1666 /dev/loop-control interface.
1668 mce [X86-32] Machine Check Exception
1670 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1672 md= [HW] RAID subsystems devices and level
1673 See Documentation/md.txt.
1676 Format: <first>,<last>
1677 Specifies range of consoles to be captured by the MDA.
1679 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1680 Amount of memory to be used when the kernel is not able
1681 to see the whole system memory or for test.
1682 [X86] Work as limiting max address. Use together
1683 with memmap= to avoid physical address space collisions.
1684 Without memmap= PCI devices could be placed at addresses
1685 belonging to unused RAM.
1687 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1691 [KNL,SH] Allow user to override the default size for
1692 per-device physically contiguous DMA buffers.
1694 memmap=exactmap [KNL,X86] Enable setting of an exact
1695 E820 memory map, as specified by the user.
1696 Such memmap=exactmap lines can be constructed based on
1697 BIOS output or other requirements. See the memmap=nn@ss
1700 memmap=nn[KMG]@ss[KMG]
1701 [KNL] Force usage of a specific region of memory
1702 Region of memory to be used, from ss to ss+nn.
1704 memmap=nn[KMG]#ss[KMG]
1705 [KNL,ACPI] Mark specific memory as ACPI data.
1706 Region of memory to be used, from ss to ss+nn.
1708 memmap=nn[KMG]$ss[KMG]
1709 [KNL,ACPI] Mark specific memory as reserved.
1710 Region of memory to be used, from ss to ss+nn.
1711 Example: Exclude memory from 0x18690000-0x1869ffff
1712 memmap=64K$0x18690000
1714 memmap=0x10000$0x18690000
1716 memory_corruption_check=0/1 [X86]
1717 Some BIOSes seem to corrupt the first 64k of
1718 memory when doing things like suspend/resume.
1719 Setting this option will scan the memory
1720 looking for corruption. Enabling this will
1721 both detect corruption and prevent the kernel
1722 from using the memory being corrupted.
1723 However, its intended as a diagnostic tool; if
1724 repeatable BIOS-originated corruption always
1725 affects the same memory, you can use memmap=
1726 to prevent the kernel from using that memory.
1728 memory_corruption_check_size=size [X86]
1729 By default it checks for corruption in the low
1730 64k, making this memory unavailable for normal
1731 use. Use this parameter to scan for
1732 corruption in more or less memory.
1734 memory_corruption_check_period=seconds [X86]
1735 By default it checks for corruption every 60
1736 seconds. Use this parameter to check at some
1737 other rate. 0 disables periodic checking.
1739 memtest= [KNL,X86] Enable memtest
1741 default : 0 <disable>
1742 Specifies the number of memtest passes to be
1743 performed. Each pass selects another test
1744 pattern from a given set of patterns. Memtest
1745 fills the memory with this pattern, validates
1746 memory contents and reserves bad memory
1747 regions that are detected.
1749 meye.*= [HW] Set MotionEye Camera parameters
1750 See Documentation/video4linux/meye.txt.
1752 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1753 Multi-Function General Purpose Timers on AMD Geode
1756 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1757 the BIOS has incorrectly applied a workaround. TinyBIOS
1758 version 0.98 is known to be affected, 0.99 fixes the
1759 problem by letting the user disable the workaround.
1763 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1764 physical address is ignored.
1766 mini2440= [ARM,HW,KNL]
1767 Format:[0..2][b][c][t]
1769 MINI2440 configuration specification:
1770 0 - The attached screen is the 3.5" TFT
1771 1 - The attached screen is the 7" TFT
1772 2 - The VGA Shield is attached (1024x768)
1773 Leaving out the screen size parameter will not load
1774 the TFT driver, and the framebuffer will be left
1776 b - Enable backlight. The TFT backlight pin will be
1777 linked to the kernel VESA blanking code and a GPIO
1778 LED. This parameter is not necessary when using the
1780 c - Enable the s3c camera interface.
1781 t - Reserved for enabling touchscreen support. The
1782 touchscreen support is not enabled in the mainstream
1783 kernel as of 2.6.30, a preliminary port can be found
1784 in the "bleeding edge" mini2440 support kernel at
1785 http://repo.or.cz/w/linux-2.6/mini2440.git
1788 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1789 parameter allows control of the logging verbosity for
1790 the additional memory initialisation checks. A value
1791 of 0 disables mminit logging and a level of 4 will
1792 log everything. Information is printed at KERN_DEBUG
1793 so loglevel=8 may also need to be specified.
1796 [KNL] When CONFIG_MODULE_SIG is set, this means that
1797 modules without (valid) signatures will fail to load.
1798 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1799 is always true, so this option does nothing.
1802 [MOUSE] Maximum time between finger touching and
1803 leaving touchpad surface for touch to be considered
1804 a tap and be reported as a left button click (for
1805 touchpads working in absolute mode only).
1807 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1808 reporting absolute coordinates, such as tablets
1809 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1810 reporting absolute coordinates, such as tablets
1812 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1813 is similar to kernelcore except it specifies the
1814 amount of memory used for migratable allocations.
1815 If both kernelcore and movablecore is specified,
1816 then kernelcore will be at *least* the specified
1817 value but may be more. If movablecore on its own
1818 is specified, the administrator must be careful
1819 that the amount of memory usable for all allocations
1822 movable_node [KNL,X86] Boot-time switch to enable the effects
1823 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1825 MTD_Partition= [MTD]
1826 Format: <name>,<region-number>,<size>,<offset>
1828 MTD_Region= [MTD] Format:
1829 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1832 See drivers/mtd/cmdlinepart.c.
1834 multitce=off [PPC] This parameter disables the use of the pSeries
1835 firmware feature for updating multiple TCE entries
1838 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1840 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1842 boundary - index of last SLC block on Flex-OneNAND.
1843 The remaining blocks are configured as MLC blocks.
1844 lock - Configure if Flex-OneNAND boundary should be locked.
1845 Once locked, the boundary cannot be changed.
1846 1 indicates lock status, 0 indicates unlock status.
1849 ARM/S3C2412 JIVE boot control
1851 See arch/arm/mach-s3c2412/mach-jive.c
1853 mtouchusb.raw_coordinates=
1854 [HW] Make the MicroTouch USB driver use raw coordinates
1855 ('y', default) or cooked coordinates ('n')
1857 mtrr_chunk_size=nn[KMG] [X86]
1858 used for mtrr cleanup. It is largest continuous chunk
1859 that could hold holes aka. UC entries.
1861 mtrr_gran_size=nn[KMG] [X86]
1862 Used for mtrr cleanup. It is granularity of mtrr block.
1864 Large value could prevent small alignment from
1867 mtrr_spare_reg_nr=n [X86]
1869 Range: 0,7 : spare reg number
1871 Used for mtrr cleanup. It is spare mtrr entries number.
1872 Set to 2 or more if your graphical card needs more.
1874 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1876 netdev= [NET] Network devices parameters
1877 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1878 Note that mem_start is often overloaded to mean
1879 something different and driver-specific.
1880 This usage is only documented in each driver source
1884 [NETFILTER] Enable connection tracking flow accounting
1885 0 to disable accounting
1886 1 to enable accounting
1889 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1890 See Documentation/filesystems/nfs/nfsroot.txt.
1892 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1893 See Documentation/filesystems/nfs/nfsroot.txt.
1895 nfsrootdebug [NFS] enable nfsroot debugging messages.
1896 See Documentation/filesystems/nfs/nfsroot.txt.
1898 nfs.callback_tcpport=
1899 [NFS] set the TCP port on which the NFSv4 callback
1900 channel should listen.
1903 [NFS] sets the pathname to the program which is used
1904 to update the NFS client cache entries.
1906 nfs.cache_getent_timeout=
1907 [NFS] sets the timeout after which an attempt to
1908 update a cache entry is deemed to have failed.
1910 nfs.idmap_cache_timeout=
1911 [NFS] set the maximum lifetime for idmapper cache
1915 [NFS] enable 64-bit inode numbers.
1916 If zero, the NFS client will fake up a 32-bit inode
1917 number for the readdir() and stat() syscalls instead
1918 of returning the full 64-bit number.
1919 The default is to return 64-bit inode numbers.
1921 nfs.max_session_slots=
1922 [NFSv4.1] Sets the maximum number of session slots
1923 the client will attempt to negotiate with the server.
1924 This limits the number of simultaneous RPC requests
1925 that the client can send to the NFSv4.1 server.
1926 Note that there is little point in setting this
1927 value higher than the max_tcp_slot_table_limit.
1929 nfs.nfs4_disable_idmapping=
1930 [NFSv4] When set to the default of '1', this option
1931 ensures that both the RPC level authentication
1932 scheme and the NFS level operations agree to use
1933 numeric uids/gids if the mount is using the
1934 'sec=sys' security flavour. In effect it is
1935 disabling idmapping, which can make migration from
1936 legacy NFSv2/v3 systems to NFSv4 easier.
1937 Servers that do not support this mode of operation
1938 will be autodetected by the client, and it will fall
1939 back to using the idmapper.
1940 To turn off this behaviour, set the value to '0'.
1942 [NFS4] Specify an additional fixed unique ident-
1943 ification string that NFSv4 clients can insert into
1944 their nfs_client_id4 string. This is typically a
1945 UUID that is generated at system install time.
1947 nfs.send_implementation_id =
1948 [NFSv4.1] Send client implementation identification
1949 information in exchange_id requests.
1950 If zero, no implementation identification information
1952 The default is to send the implementation identification
1955 nfs.recover_lost_locks =
1956 [NFSv4] Attempt to recover locks that were lost due
1957 to a lease timeout on the server. Please note that
1958 doing this risks data corruption, since there are
1959 no guarantees that the file will remain unchanged
1960 after the locks are lost.
1961 If you want to enable the kernel legacy behaviour of
1962 attempting to recover these locks, then set this
1964 The default parameter value of '0' causes the kernel
1965 not to attempt recovery of lost locks.
1967 nfsd.nfs4_disable_idmapping=
1968 [NFSv4] When set to the default of '1', the NFSv4
1969 server will return only numeric uids and gids to
1970 clients using auth_sys, and will accept numeric uids
1971 and gids from such clients. This is intended to ease
1972 migration from NFSv2/v3.
1974 objlayoutdriver.osd_login_prog=
1975 [NFS] [OBJLAYOUT] sets the pathname to the program which
1976 is used to automatically discover and login into new
1977 osd-targets. Please see:
1978 Documentation/filesystems/pnfs.txt for more explanations
1980 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1981 when a NMI is triggered.
1982 Format: [state][,regs][,debounce][,die]
1984 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1985 Format: [panic,][nopanic,][num]
1987 0 - turn nmi_watchdog off
1988 When panic is specified, panic when an NMI watchdog
1989 timeout occurs (or 'nopanic' to override the opposite
1991 This is useful when you use a panic=... timeout and
1992 need the box quickly up again.
1994 netpoll.carrier_timeout=
1995 [NET] Specifies amount of time (in seconds) that
1996 netpoll should wait for a carrier. By default netpoll
1999 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
2000 emulation library even if a 387 maths coprocessor
2004 [HW] Never suspend the console
2005 Disable suspending of consoles during suspend and
2006 hibernate operations. Once disabled, debugging
2007 messages can reach various consoles while the rest
2008 of the system is being put to sleep (ie, while
2009 debugging driver suspend/resume hooks). This may
2010 not work reliably with all consoles, but is known
2011 to work with serial and VGA consoles.
2012 To facilitate more flexible debugging, we also add
2013 console_suspend, a printk module parameter to control
2014 it. Users could use console_suspend (usually
2015 /sys/module/printk/parameters/console_suspend) to
2016 turn on/off it dynamically.
2018 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2019 caches in the slab allocator. Saves per-node memory,
2020 but will impact performance.
2024 noapic [SMP,APIC] Tells the kernel to not make use of any
2025 IOAPICs that may be present in the system.
2028 Disable kernel base offset ASLR (Address Space
2029 Layout Randomization) if built into the kernel.
2031 noautogroup Disable scheduler automatic task group creation.
2033 nobats [PPC] Do not use BATs for mapping kernel lowmem
2034 on "Classic" PPC cores.
2038 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2040 nodelayacct [KNL] Disable per-task delay accounting
2042 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2044 nodsp [SH] Disable hardware DSP at boot time.
2046 noefi [X86] Disable EFI runtime services support.
2051 On X86-32 available only on PAE configured kernels.
2052 noexec=on: enable non-executable mappings (default)
2053 noexec=off: disable non-executable mappings
2056 Disable SMAP (Supervisor Mode Access Prevention)
2057 even if it is supported by processor.
2060 Disable SMEP (Supervisor Mode Execution Prevention)
2061 even if it is supported by processor.
2064 This affects only 32-bit executables.
2065 noexec32=on: enable non-executable mappings (default)
2066 read doesn't imply executable mappings
2067 noexec32=off: disable non-executable mappings
2068 read implies executable mappings
2070 nofpu [SH] Disable hardware FPU at boot time.
2072 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2073 register save and restore. The kernel will only save
2074 legacy floating-point registers on task switch.
2076 noxsave [BUGS=X86] Disables x86 extended register state save
2077 and restore using xsave. The kernel will fallback to
2078 enabling legacy floating-point and sse state.
2081 on enable eager fpu restore
2082 off disable eager fpu restore
2083 auto selects the default scheme, which automatically
2084 enables eagerfpu restore for xsaveopt.
2086 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2087 wfi(ARM) instruction doesn't work correctly and not to
2088 use it. This is also useful when using JTAG debugger.
2090 no_file_caps Tells the kernel not to honor file capabilities. The
2091 only way then for a file to be executed with privilege
2092 is to be setuid root or executed by root.
2094 nohalt [IA-64] Tells the kernel not to use the power saving
2095 function PAL_HALT_LIGHT when idle. This increases
2096 power-consumption. On the positive side, it reduces
2097 interrupt wake-up latency, which may improve performance
2098 in certain environments such as networked servers or
2101 nohz= [KNL] Boottime enable/disable dynamic ticks
2102 Valid arguments: on, off
2105 nohz_full= [KNL,BOOT]
2106 In kernels built with CONFIG_NO_HZ_FULL=y, set
2107 the specified list of CPUs whose tick will be stopped
2108 whenever possible. The boot CPU will be forced outside
2109 the range to maintain the timekeeping.
2110 The CPUs in this range must also be included in the
2113 noiotrap [SH] Disables trapped I/O port accesses.
2115 noirqdebug [X86-32] Disables the code which attempts to detect and
2116 disable unhandled interrupt sources.
2118 no_timer_check [X86,APIC] Disables the code which tests for
2119 broken timer IRQ sources.
2121 noisapnp [ISAPNP] Disables ISA PnP code.
2123 noinitrd [RAM] Tells the kernel not to load any configured
2126 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2128 [Deprecated - use intremap=off]
2132 nojitter [IA-64] Disables jitter checking for ITC timers.
2134 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2136 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2139 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2140 steal time is computed, but won't influence scheduler
2143 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2145 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2147 noltlbs [PPC] Do not use large page/tlb entries for kernel
2148 lowmem mapping on PPC40x.
2150 nomca [IA-64] Disable machine check abort handling
2152 nomce [X86-32] Machine Check Exception
2154 nomfgpt [X86-32] Disable Multi-Function General Purpose
2155 Timer usage (for AMD Geode machines).
2157 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2158 shutdown the other cpus. Instead use the REBOOT_VECTOR
2161 nomodule Disable module load
2163 nopat [X86] Disable PAT (page attribute table extension of
2164 pagetables) support.
2166 norandmaps Don't use address space randomization. Equivalent to
2167 echo 0 > /proc/sys/kernel/randomize_va_space
2169 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2171 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2172 with UP alternatives
2174 nordrand [X86] Disable the direct use of the RDRAND
2175 instruction even if it is supported by the
2176 processor. RDRAND is still available to user
2179 noresume [SWSUSP] Disables resume and restores original swap
2182 no-scroll [VGA] Disables scrollback.
2183 This is required for the Braillex ib80-piezo Braille
2184 reader made by F.H. Papenmeier (Germany).
2188 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2190 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2191 and disable the IO APIC. legacy for "maxcpus=0".
2193 nosoftlockup [KNL] Disable the soft-lockup detector.
2195 nosync [HW,M68K] Disables sync negotiation for all devices.
2197 notsc [BUGS=X86-32] Disable Time Stamp Counter
2199 nousb [USB] Disable the USB subsystem
2201 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2205 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2207 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2208 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2209 Some features depend on CPU0. Known dependencies are:
2210 1. Resume from suspend/hibernate depends on CPU0.
2211 Suspend/hibernate will fail if CPU0 is offline and you
2212 need to online CPU0 before suspend/hibernate.
2213 2. PIC interrupts also depend on CPU0. CPU0 can't be
2214 removed if a PIC interrupt is detected.
2215 It's said poweroff/reboot may depend on CPU0 on some
2216 machines although I haven't seen such issues so far
2217 after CPU0 is offline on a few tested machines.
2218 If the dependencies are under your control, you can
2219 turn on cpu0_hotplug.
2221 nptcg= [IA-64] Override max number of concurrent global TLB
2222 purges which is reported from either PAL_VM_SUMMARY or
2225 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2226 could support. nr_cpus=n : n >= 1 limits the kernel to
2227 supporting 'n' processors. Later in runtime you can not
2228 use hotplug cpu feature to put more cpu back to online.
2229 just like you compile the kernel NR_CPUS=n
2231 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2233 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2234 Allowed values are enable and disable
2236 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2237 one of ['zone', 'node', 'default'] can be specified
2238 This can be set from sysctl after boot.
2239 See Documentation/sysctl/vm.txt for details.
2241 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2242 See Documentation/debugging-via-ohci1394.txt for more
2245 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2246 Rather than timing out after 20 ms if an EC
2247 command is not properly ACKed, override the length
2248 of the timeout. We have interrupts disabled while
2249 waiting for the ACK, so if this is set too high
2250 interrupts *may* be lost!
2252 omap_mux= [OMAP] Override bootloader pin multiplexing.
2253 Format: <mux_mode0.mode_name=value>...
2254 For example, to override I2C bus2:
2255 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2257 oprofile.timer= [HW]
2258 Use timer interrupt instead of performance counters
2260 oprofile.cpu_type= Force an oprofile cpu type
2261 This might be useful if you have an older oprofile
2262 userland or if you want common events.
2263 Format: { arch_perfmon }
2264 arch_perfmon: [X86] Force use of architectural
2265 perfmon on Intel CPUs instead of the
2266 CPU specific event set.
2267 timer: [X86] Force use of architectural NMI
2268 timer mode (see also oprofile.timer
2269 for generic hr timer mode)
2270 [s390] Force legacy basic mode sampling
2271 (report cpu_type "timer")
2273 oops=panic Always panic on oopses. Default is to just kill the
2274 process, but there is a small probability of
2275 deadlocking the machine.
2276 This will also cause panics on machine check exceptions.
2277 Useful together with panic=30 to trigger a reboot.
2280 See Documentation/sound/oss/oss-parameters.txt
2282 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2283 timeout > 0: seconds before rebooting
2284 timeout = 0: wait forever
2285 timeout < 0: reboot immediately
2288 parkbd.port= [HW] Parallel port number the keyboard adapter is
2289 connected to, default is 0.
2291 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2292 0 for XT, 1 for AT (default is AT).
2295 parport= [HW,PPT] Specify parallel ports. 0 disables.
2296 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2297 Use 'auto' to force the driver to use any
2298 IRQ/DMA settings detected (the default is to
2299 ignore detected IRQ/DMA settings because of
2300 possible conflicts). You can specify the base
2301 address, IRQ, and DMA settings; IRQ and DMA
2302 should be numbers, or 'auto' (for using detected
2303 settings on that particular port), or 'nofifo'
2304 (to avoid using a FIFO even if it is detected).
2305 Parallel ports are assigned in the order they
2306 are specified on the command line, starting
2309 parport_init_mode= [HW,PPT]
2310 Configure VIA parallel port to operate in
2311 a specific mode. This is necessary on Pegasos
2312 computer where firmware has no options for setting
2313 up parallel port mode and sets it to spp.
2314 Currently this function knows 686a and 8231 chips.
2315 Format: [spp|ps2|epp|ecp|ecpepp]
2318 Halt all CPUs after the first oops has been printed for
2319 the specified number of seconds. This is to be used if
2320 your oopses keep scrolling off the screen.
2325 See header of drivers/block/paride/pcd.c.
2326 See also Documentation/blockdev/paride.txt.
2328 pci=option[,option...] [PCI] various PCI subsystem options:
2329 earlydump [X86] dump PCI config space before the kernel
2331 off [X86] don't probe for the PCI bus
2332 bios [X86-32] force use of PCI BIOS, don't access
2333 the hardware directly. Use this if your machine
2334 has a non-standard PCI host bridge.
2335 nobios [X86-32] disallow use of PCI BIOS, only direct
2336 hardware access methods are allowed. Use this
2337 if you experience crashes upon bootup and you
2338 suspect they are caused by the BIOS.
2339 conf1 [X86] Force use of PCI Configuration
2341 conf2 [X86] Force use of PCI Configuration
2343 noaer [PCIE] If the PCIEAER kernel config parameter is
2344 enabled, this kernel boot option can be used to
2345 disable the use of PCIE advanced error reporting.
2346 nodomains [PCI] Disable support for multiple PCI
2347 root domains (aka PCI segments, in ACPI-speak).
2348 nommconf [X86] Disable use of MMCONFIG for PCI
2350 check_enable_amd_mmconf [X86] check for and enable
2351 properly configured MMIO access to PCI
2352 config space on AMD family 10h CPU
2353 nomsi [MSI] If the PCI_MSI kernel config parameter is
2354 enabled, this kernel boot option can be used to
2355 disable the use of MSI interrupts system-wide.
2356 noioapicquirk [APIC] Disable all boot interrupt quirks.
2357 Safety option to keep boot IRQs enabled. This
2358 should never be necessary.
2359 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2360 primary IO-APIC for bridges that cannot disable
2361 boot IRQs. This fixes a source of spurious IRQs
2362 when the system masks IRQs.
2363 noioapicreroute [APIC] Disable workaround that uses the
2364 boot IRQ equivalent of an IRQ that connects to
2365 a chipset where boot IRQs cannot be disabled.
2366 The opposite of ioapicreroute.
2367 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2368 routing table. These calls are known to be buggy
2369 on several machines and they hang the machine
2370 when used, but on other computers it's the only
2371 way to get the interrupt routing table. Try
2372 this option if the kernel is unable to allocate
2373 IRQs or discover secondary PCI buses on your
2375 rom [X86] Assign address space to expansion ROMs.
2376 Use with caution as certain devices share
2377 address decoders between ROMs and other
2379 norom [X86] Do not assign address space to
2380 expansion ROMs that do not already have
2381 BIOS assigned address ranges.
2382 nobar [X86] Do not assign address space to the
2383 BARs that weren't assigned by the BIOS.
2384 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2385 assigned automatically to PCI devices. You can
2386 make the kernel exclude IRQs of your ISA cards
2388 pirqaddr=0xAAAAA [X86] Specify the physical address
2389 of the PIRQ table (normally generated
2390 by the BIOS) if it is outside the
2391 F0000h-100000h range.
2392 lastbus=N [X86] Scan all buses thru bus #N. Can be
2393 useful if the kernel is unable to find your
2394 secondary buses and you want to tell it
2395 explicitly which ones they are.
2396 assign-busses [X86] Always assign all PCI bus
2397 numbers ourselves, overriding
2398 whatever the firmware may have done.
2399 usepirqmask [X86] Honor the possible IRQ mask stored
2400 in the BIOS $PIR table. This is needed on
2401 some systems with broken BIOSes, notably
2402 some HP Pavilion N5400 and Omnibook XE3
2403 notebooks. This will have no effect if ACPI
2404 IRQ routing is enabled.
2405 noacpi [X86] Do not use ACPI for IRQ routing
2406 or for PCI scanning.
2407 use_crs [X86] Use PCI host bridge window information
2408 from ACPI. On BIOSes from 2008 or later, this
2409 is enabled by default. If you need to use this,
2410 please report a bug.
2411 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2412 If you need to use this, please report a bug.
2413 routeirq Do IRQ routing for all PCI devices.
2414 This is normally done in pci_enable_device(),
2415 so this option is a temporary workaround
2416 for broken drivers that don't call it.
2417 skip_isa_align [X86] do not align io start addr, so can
2418 handle more pci cards
2419 firmware [ARM] Do not re-enumerate the bus but instead
2420 just use the configuration from the
2421 bootloader. This is currently used on
2422 IXP2000 systems where the bus has to be
2423 configured a certain way for adjunct CPUs.
2424 noearly [X86] Don't do any early type 1 scanning.
2425 This might help on some broken boards which
2426 machine check when some devices' config space
2427 is read. But various workarounds are disabled
2428 and some IOMMU drivers will not work.
2429 bfsort Sort PCI devices into breadth-first order.
2430 This sorting is done to get a device
2431 order compatible with older (<= 2.4) kernels.
2432 nobfsort Don't sort PCI devices into breadth-first order.
2433 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2434 tuning and use the BIOS-configured MPS defaults.
2435 pcie_bus_safe Set every device's MPS to the largest value
2436 supported by all devices below the root complex.
2437 pcie_bus_perf Set device MPS to the largest allowable MPS
2438 based on its parent bus. Also set MRRS (Max
2439 Read Request Size) to the largest supported
2440 value (no larger than the MPS that the device
2441 or bus can support) for best performance.
2442 pcie_bus_peer2peer Set every device's MPS to 128B, which
2443 every device is guaranteed to support. This
2444 configuration allows peer-to-peer DMA between
2445 any pair of devices, possibly at the cost of
2446 reduced performance. This also guarantees
2447 that hot-added devices will work.
2448 cbiosize=nn[KMG] The fixed amount of bus space which is
2449 reserved for the CardBus bridge's IO window.
2450 The default value is 256 bytes.
2451 cbmemsize=nn[KMG] The fixed amount of bus space which is
2452 reserved for the CardBus bridge's memory
2453 window. The default value is 64 megabytes.
2456 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2457 Specifies alignment and device to reassign
2458 aligned memory resources.
2459 If <order of align> is not specified,
2460 PAGE_SIZE is used as alignment.
2461 PCI-PCI bridge can be specified, if resource
2462 windows need to be expanded.
2463 ecrc= Enable/disable PCIe ECRC (transaction layer
2464 end-to-end CRC checking).
2465 bios: Use BIOS/firmware settings. This is the
2469 hpiosize=nn[KMG] The fixed amount of bus space which is
2470 reserved for hotplug bridge's IO window.
2471 Default size is 256 bytes.
2472 hpmemsize=nn[KMG] The fixed amount of bus space which is
2473 reserved for hotplug bridge's memory window.
2474 Default size is 2 megabytes.
2475 realloc= Enable/disable reallocating PCI bridge resources
2476 if allocations done by BIOS are too small to
2477 accommodate resources required by all child
2479 off: Turn realloc off
2481 realloc same as realloc=on
2482 noari do not use PCIe ARI.
2483 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2484 only look for one device below a PCIe downstream
2487 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2490 force Enable ASPM even on devices that claim not to support it.
2491 WARNING: Forcing ASPM on may cause system lockups.
2493 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2494 nomsi Do not use MSI for PCI Express Native Hotplug (this
2495 makes all PCIe ports use INTx for hotplug services).
2497 pcie_ports= [PCIE] PCIe ports handling:
2498 auto Ask the BIOS whether or not to use native PCIe services
2499 associated with PCIe ports (PME, hot-plug, AER). Use
2500 them only if that is allowed by the BIOS.
2501 native Use native PCIe services associated with PCIe ports
2503 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2506 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2507 nomsi Do not use MSI for native PCIe PME signaling (this makes
2508 all PCIe root ports use INTx for all services).
2510 pcmv= [HW,PCMCIA] BadgePAD 4
2513 See Documentation/blockdev/paride.txt.
2515 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2518 See arch/parisc/kernel/pdc_chassis.c
2520 percpu_alloc= Select which percpu first chunk allocator to use.
2521 Currently supported values are "embed" and "page".
2522 Archs may support subset or none of the selections.
2523 See comments in mm/percpu.c for details on each
2524 allocator. This parameter is primarily for debugging
2525 and performance comparison.
2528 See Documentation/blockdev/paride.txt.
2531 See Documentation/blockdev/paride.txt.
2533 pirq= [SMP,APIC] Manual mp-table setup
2534 See Documentation/x86/i386/IO-APIC.txt.
2536 plip= [PPT,NET] Parallel port network link
2537 Format: { parport<nr> | timid | 0 }
2538 See also Documentation/parport.txt.
2540 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2541 Override pmtimer IOPort with a hex value.
2545 Enable PNP debug messages (depends on the
2546 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2547 via /sys/module/pnp/parameters/debug. We always show
2548 current resource usage; turning this on also shows
2549 possible settings and some assignment information.
2555 { on | off | curr | res | no-curr | no-res }
2558 [ISAPNP] Exclude IRQs for the autoconfiguration
2561 [ISAPNP] Exclude DMAs for the autoconfiguration
2563 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2564 Ranges are in pairs (I/O port base and size).
2567 [ISAPNP] Exclude memory regions for the
2569 Ranges are in pairs (memory base and size).
2571 ports= [IP_VS_FTP] IPVS ftp helper module
2573 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2575 Format: <port>,<port>....
2577 print-fatal-signals=
2578 [KNL] debug: print fatal signals
2580 If enabled, warn about various signal handling
2581 related application anomalies: too many signals,
2582 too many POSIX.1 timers, fatal signals causing a
2585 If you hit the warning due to signal overflow,
2586 you might want to try "ulimit -i unlimited".
2590 printk.always_kmsg_dump=
2591 Trigger kmsg_dump for cases other than kernel oops or
2593 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2596 printk.time= Show timing data prefixed to each printk message line
2597 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2599 processor.max_cstate= [HW,ACPI]
2600 Limit processor to maximum C-state
2601 max_cstate=9 overrides any DMI blacklist limit.
2603 processor.nocst [HW,ACPI]
2604 Ignore the _CST method to determine C-states,
2605 instead using the legacy FADT method
2607 profile= [KNL] Enable kernel profiling via /proc/profile
2608 Format: [schedule,]<number>
2609 Param: "schedule" - profile schedule points.
2610 Param: <number> - step/bucket size as a power of 2 for
2611 statistical time based profiling.
2612 Param: "sleep" - profile D-state sleeping (millisecs).
2613 Requires CONFIG_SCHEDSTATS
2614 Param: "kvm" - profile VM exits.
2616 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2618 See Documentation/blockdev/ramdisk.txt.
2620 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2621 probe for; one of (bare|imps|exps|lifebook|any).
2622 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2624 psmouse.resetafter= [HW,MOUSE]
2625 Try to reset the device after so many bad packets
2628 [HW,MOUSE] Set desired mouse resolution, in dpi.
2629 psmouse.smartscroll=
2630 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2631 0 = disabled, 1 = enabled (default).
2633 pstore.backend= Specify the name of the pstore backend to use
2636 See Documentation/blockdev/paride.txt.
2639 [KNL] Number of legacy pty's. Overwrites compiled-in
2642 quiet [KNL] Disable most log messages
2647 See Documentation/md.txt.
2649 ramdisk_blocksize= [RAM]
2650 See Documentation/blockdev/ramdisk.txt.
2652 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2653 See Documentation/blockdev/ramdisk.txt.
2656 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2657 the specified list of CPUs to be no-callback CPUs.
2658 Invocation of these CPUs' RCU callbacks will
2659 be offloaded to "rcuox/N" kthreads created for
2660 that purpose, where "x" is "b" for RCU-bh, "p"
2661 for RCU-preempt, and "s" for RCU-sched, and "N"
2662 is the CPU number. This reduces OS jitter on the
2663 offloaded CPUs, which can be useful for HPC and
2664 real-time workloads. It can also improve energy
2665 efficiency for asymmetric multiprocessors.
2668 Rather than requiring that offloaded CPUs
2669 (specified by rcu_nocbs= above) explicitly
2670 awaken the corresponding "rcuoN" kthreads,
2671 make these kthreads poll for callbacks.
2672 This improves the real-time response for the
2673 offloaded CPUs by relieving them of the need to
2674 wake up the corresponding kthread, but degrades
2675 energy efficiency by requiring that the kthreads
2676 periodically wake up to do the polling.
2678 rcutree.blimit= [KNL]
2679 Set maximum number of finished RCU callbacks to
2680 process in one batch.
2682 rcutree.rcu_fanout_leaf= [KNL]
2683 Increase the number of CPUs assigned to each
2684 leaf rcu_node structure. Useful for very large
2687 rcutree.jiffies_till_first_fqs= [KNL]
2688 Set delay from grace-period initialization to
2689 first attempt to force quiescent states.
2690 Units are jiffies, minimum value is zero,
2691 and maximum value is HZ.
2693 rcutree.jiffies_till_next_fqs= [KNL]
2694 Set delay between subsequent attempts to force
2695 quiescent states. Units are jiffies, minimum
2696 value is one, and maximum value is HZ.
2698 rcutree.qhimark= [KNL]
2699 Set threshold of queued RCU callbacks beyond which
2700 batch limiting is disabled.
2702 rcutree.qlowmark= [KNL]
2703 Set threshold of queued RCU callbacks below which
2704 batch limiting is re-enabled.
2706 rcutree.rcu_idle_gp_delay= [KNL]
2707 Set wakeup interval for idle CPUs that have
2708 RCU callbacks (RCU_FAST_NO_HZ=y).
2710 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2711 Set wakeup interval for idle CPUs that have
2712 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2713 Lazy RCU callbacks are those which RCU can
2714 prove do nothing more than free memory.
2716 rcutorture.fqs_duration= [KNL]
2717 Set duration of force_quiescent_state bursts.
2719 rcutorture.fqs_holdoff= [KNL]
2720 Set holdoff time within force_quiescent_state bursts.
2722 rcutorture.fqs_stutter= [KNL]
2723 Set wait time between force_quiescent_state bursts.
2725 rcutorture.gp_exp= [KNL]
2726 Use expedited update-side primitives.
2728 rcutorture.gp_normal= [KNL]
2729 Use normal (non-expedited) update-side primitives.
2730 If both gp_exp and gp_normal are set, do both.
2731 If neither gp_exp nor gp_normal are set, still
2734 rcutorture.n_barrier_cbs= [KNL]
2735 Set callbacks/threads for rcu_barrier() testing.
2737 rcutorture.nfakewriters= [KNL]
2738 Set number of concurrent RCU writers. These just
2739 stress RCU, they don't participate in the actual
2740 test, hence the "fake".
2742 rcutorture.nreaders= [KNL]
2743 Set number of RCU readers.
2745 rcutorture.object_debug= [KNL]
2746 Enable debug-object double-call_rcu() testing.
2748 rcutorture.onoff_holdoff= [KNL]
2749 Set time (s) after boot for CPU-hotplug testing.
2751 rcutorture.onoff_interval= [KNL]
2752 Set time (s) between CPU-hotplug operations, or
2753 zero to disable CPU-hotplug testing.
2755 rcutorture.rcutorture_runnable= [BOOT]
2756 Start rcutorture running at boot time.
2758 rcutorture.shuffle_interval= [KNL]
2759 Set task-shuffle interval (s). Shuffling tasks
2760 allows some CPUs to go into dyntick-idle mode
2761 during the rcutorture test.
2763 rcutorture.shutdown_secs= [KNL]
2764 Set time (s) after boot system shutdown. This
2765 is useful for hands-off automated testing.
2767 rcutorture.stall_cpu= [KNL]
2768 Duration of CPU stall (s) to test RCU CPU stall
2769 warnings, zero to disable.
2771 rcutorture.stall_cpu_holdoff= [KNL]
2772 Time to wait (s) after boot before inducing stall.
2774 rcutorture.stat_interval= [KNL]
2775 Time (s) between statistics printk()s.
2777 rcutorture.stutter= [KNL]
2778 Time (s) to stutter testing, for example, specifying
2779 five seconds causes the test to run for five seconds,
2780 wait for five seconds, and so on. This tests RCU's
2781 ability to transition abruptly to and from idle.
2783 rcutorture.test_boost= [KNL]
2784 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2785 "Maybe" means test if the RCU implementation
2786 under test support RCU priority boosting.
2788 rcutorture.test_boost_duration= [KNL]
2789 Duration (s) of each individual boost test.
2791 rcutorture.test_boost_interval= [KNL]
2792 Interval (s) between each boost test.
2794 rcutorture.test_no_idle_hz= [KNL]
2795 Test RCU's dyntick-idle handling. See also the
2796 rcutorture.shuffle_interval parameter.
2798 rcutorture.torture_type= [KNL]
2799 Specify the RCU implementation to test.
2801 rcutorture.verbose= [KNL]
2802 Enable additional printk() statements.
2804 rcupdate.rcu_expedited= [KNL]
2805 Use expedited grace-period primitives, for
2806 example, synchronize_rcu_expedited() instead
2807 of synchronize_rcu(). This reduces latency,
2808 but can increase CPU utilization, degrade
2809 real-time latency, and degrade energy efficiency.
2811 rcupdate.rcu_cpu_stall_suppress= [KNL]
2812 Suppress RCU CPU stall warning messages.
2814 rcupdate.rcu_cpu_stall_timeout= [KNL]
2815 Set timeout for RCU CPU stall warning messages.
2819 Run specified binary instead of /init from the ramdisk,
2820 used for early userspace startup. See initrd.
2823 Format (x86 or x86_64):
2824 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2826 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2828 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2829 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2830 reboot_force is either force or not specified,
2831 reboot_cpu is s[mp]#### with #### being the processor
2832 to be used for rebooting.
2835 [KNL, SMP] Set scheduler's default relax_domain_level.
2836 See Documentation/cgroups/cpusets.txt.
2838 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2840 reservetop= [X86-32]
2842 Reserves a hole at the top of the kernel virtual
2847 Set the amount of memory to reserve for BIOS at
2848 the bottom of the address space.
2850 reset_devices [KNL] Force drivers to reset the underlying device
2851 during initialization.
2854 Specify the partition device for software suspend
2856 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2858 resume_offset= [SWSUSP]
2859 Specify the offset from the beginning of the partition
2860 given by "resume=" at which the swap header is located,
2861 in <PAGE_SIZE> units (needed only for swap files).
2862 See Documentation/power/swsusp-and-swap-files.txt
2864 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2865 read the resume files
2867 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2868 Useful for devices that are detected asynchronously
2869 (e.g. USB and MMC devices).
2871 hibernate= [HIBERNATION]
2872 noresume Don't check if there's a hibernation image
2873 present during boot.
2874 nocompress Don't compress/decompress hibernation images.
2876 retain_initrd [RAM] Keep initrd memory after extraction
2878 rhash_entries= [KNL,NET]
2879 Set number of hash buckets for route cache
2881 riscom8= [HW,SERIAL]
2882 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2884 ro [KNL] Mount root device read-only on boot
2886 root= [KNL] Root filesystem
2887 See name_to_dev_t comment in init/do_mounts.c.
2889 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2890 mount the root filesystem
2892 rootflags= [KNL] Set root filesystem mount option string
2894 rootfstype= [KNL] Set root filesystem type
2896 rootwait [KNL] Wait (indefinitely) for root device to show up.
2897 Useful for devices that are detected asynchronously
2898 (e.g. USB and MMC devices).
2900 rproc_mem=nn[KMG][@address]
2901 [KNL,ARM,CMA] Remoteproc physical memory block.
2902 Memory area to be used by remote processor image,
2905 rw [KNL] Mount root device read-write on boot
2907 S [KNL] Run init in single mode
2910 See drivers/net/irda/sa1100_ir.c.
2912 sbni= [NET] Granch SBNI12 leased line adapter
2914 sched_debug [KNL] Enables verbose scheduler debug messages.
2916 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2917 xtime_lock contention on larger systems, and/or RCU lock
2918 contention on all systems with CONFIG_MAXSMP set.
2919 Format: { "0" | "1" }
2920 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2922 Note: increases power consumption, thus should only be
2923 enabled if running jitter sensitive (HPC/RT) workloads.
2925 security= [SECURITY] Choose a security module to enable at boot.
2926 If this boot parameter is not specified, only the first
2927 security module asking for security registration will be
2928 loaded. An invalid security module name will be treated
2929 as if no module has been chosen.
2931 selinux= [SELINUX] Disable or enable SELinux at boot time.
2932 Format: { "0" | "1" }
2933 See security/selinux/Kconfig help text.
2936 Default value is set via kernel config option.
2937 If enabled at boot time, /selinux/disable can be used
2938 later to disable prior to initial policy load.
2940 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2941 Format: { "0" | "1" }
2942 See security/apparmor/Kconfig help text
2945 Default value is set via kernel config option.
2947 serialnumber [BUGS=X86-32]
2950 Maximal number of shapers.
2952 show_msr= [x86] show boot-time MSR settings
2953 Format: { <integer> }
2954 Show boot-time (BIOS-initialized) MSR settings.
2955 The parameter means the number of CPUs to show,
2956 for example 1 means boot CPU only.
2963 slab_max_order= [MM, SLAB]
2964 Determines the maximum allowed order for slabs.
2965 A high setting may cause OOMs due to memory
2966 fragmentation. Defaults to 1 for systems with
2967 more than 32MB of RAM, 0 otherwise.
2969 slub_debug[=options[,slabs]] [MM, SLUB]
2970 Enabling slub_debug allows one to determine the
2971 culprit if slab objects become corrupted. Enabling
2972 slub_debug can create guard zones around objects and
2973 may poison objects when not in use. Also tracks the
2974 last alloc / free. For more information see
2975 Documentation/vm/slub.txt.
2977 slub_max_order= [MM, SLUB]
2978 Determines the maximum allowed order for slabs.
2979 A high setting may cause OOMs due to memory
2980 fragmentation. For more information see
2981 Documentation/vm/slub.txt.
2983 slub_min_objects= [MM, SLUB]
2984 The minimum number of objects per slab. SLUB will
2985 increase the slab order up to slub_max_order to
2986 generate a sufficiently large slab able to contain
2987 the number of objects indicated. The higher the number
2988 of objects the smaller the overhead of tracking slabs
2989 and the less frequently locks need to be acquired.
2990 For more information see Documentation/vm/slub.txt.
2992 slub_min_order= [MM, SLUB]
2993 Determines the minimum page order for slabs. Must be
2994 lower than slub_max_order.
2995 For more information see Documentation/vm/slub.txt.
2997 slub_nomerge [MM, SLUB]
2998 Disable merging of slabs with similar size. May be
2999 necessary if there is some reason to distinguish
3000 allocs to different slabs. Debug options disable
3001 merging on their own.
3002 For more information see Documentation/vm/slub.txt.
3005 Format: <io1>[,<io2>[,...,<io8>]]
3007 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
3008 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
3009 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
3010 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
3011 smsc-ircc2.ircc_irq= [HW] IRQ line
3012 smsc-ircc2.ircc_dma= [HW] DMA channel
3013 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3014 0: Toshiba Satellite 1800 (GP data pin select)
3015 1: Fast pin select (default)
3019 [KNL] Should the soft-lockup detector generate panics.
3022 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3023 See Documentation/laptops/sonypi.txt
3025 specialix= [HW,SERIAL] Specialix multi-serial port adapter
3026 See Documentation/serial/specialix.txt.
3028 spia_io_base= [HW,MTD]
3034 Enabled the stack tracer on boot up.
3036 stacktrace_filter=[function-list]
3037 [FTRACE] Limit the functions that the stack tracer
3038 will trace at boot up. function-list is a comma separated
3039 list of functions. This list can be changed at run
3040 time by the stack_trace_filter file in the debugfs
3041 tracing directory. Note, this enables stack tracing
3042 and the stacktrace above is not needed.
3046 Set the STI (builtin display/keyboard on the HP-PARISC
3047 machines) console (graphic card) which should be used
3048 as the initial boot-console.
3049 See also comment in drivers/video/console/sticore.c.
3052 See comment in drivers/video/console/sticore.c.
3055 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3057 sunrpc.min_resvport=
3058 sunrpc.max_resvport=
3060 SunRPC servers often require that client requests
3061 originate from a privileged port (i.e. a port in the
3062 range 0 < portnr < 1024).
3063 An administrator who wishes to reserve some of these
3064 ports for other uses may adjust the range that the
3065 kernel's sunrpc client considers to be privileged
3066 using these two parameters to set the minimum and
3067 maximum port values.
3071 Control how the NFS server code allocates CPUs to
3072 service thread pools. Depending on how many NICs
3073 you have and where their interrupts are bound, this
3074 option will affect which CPUs will do NFS serving.
3075 Note: this parameter cannot be changed while the
3076 NFS server is running.
3078 auto the server chooses an appropriate mode
3079 automatically using heuristics
3080 global a single global pool contains all CPUs
3081 percpu one pool for each CPU
3082 pernode one pool for each NUMA node (equivalent
3083 to global on non-NUMA machines)
3085 sunrpc.tcp_slot_table_entries=
3086 sunrpc.udp_slot_table_entries=
3088 Sets the upper limit on the number of simultaneous
3089 RPC calls that can be sent from the client to a
3090 server. Increasing these values may allow you to
3091 improve throughput, but will also increase the
3092 amount of memory reserved for use by the client.
3095 [KNL] Enable accounting of swap in memory resource
3096 controller if no parameter or 1 is given or disable
3097 it if 0 is given (See Documentation/cgroups/memory.txt)
3099 swiotlb= [IA-64] Number of I/O TLB slabs
3103 sysfs.deprecated=0|1 [KNL]
3104 Enable/disable old style sysfs layout for old udev
3105 on older distributions. When this option is enabled
3106 very new udev will not work anymore. When this option
3107 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3108 in older udev will not work anymore.
3109 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3110 the kernel configuration.
3112 sysrq_always_enabled
3114 Ignore sysrq setting - this boot parameter will
3115 neutralize any effect of /proc/sys/kernel/sysrq.
3116 Useful for debugging.
3120 test_suspend= [SUSPEND]
3121 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3122 standby suspend) as the system sleep state to briefly
3123 enter during system startup. The system is woken from
3124 this state using a wakeup-capable RTC alarm.
3126 thash_entries= [KNL,NET]
3127 Set number of hash buckets for TCP connection
3129 thermal.act= [HW,ACPI]
3130 -1: disable all active trip points in all thermal zones
3131 <degrees C>: override all lowest active trip points
3133 thermal.crt= [HW,ACPI]
3134 -1: disable all critical trip points in all thermal zones
3135 <degrees C>: override all critical trip points
3137 thermal.nocrt= [HW,ACPI]
3138 Set to disable actions on ACPI thermal zone
3139 critical and hot trip points.
3141 thermal.off= [HW,ACPI]
3142 1: disable ACPI thermal control
3144 thermal.psv= [HW,ACPI]
3145 -1: disable all passive trip points
3146 <degrees C>: override all passive trip points to this
3149 thermal.tzp= [HW,ACPI]
3150 Specify global default ACPI thermal zone polling rate
3151 <deci-seconds>: poll all this frequency
3152 0: no polling (default)
3155 Force threading of all interrupt handlers except those
3156 marked explicitly IRQF_NO_THREAD.
3159 Enable the Transcendent memory driver if built-in.
3161 tmem.cleancache=0|1 [KNL, XEN]
3162 Default is on (1). Disable the usage of the cleancache
3163 API to send anonymous pages to the hypervisor.
3165 tmem.frontswap=0|1 [KNL, XEN]
3166 Default is on (1). Disable the usage of the frontswap
3167 API to send swap pages to the hypervisor. If disabled
3168 the selfballooning and selfshrinking are force disabled.
3170 tmem.selfballooning=0|1 [KNL, XEN]
3171 Default is on (1). Disable the driving of swap pages
3174 tmem.selfshrinking=0|1 [KNL, XEN]
3175 Default is on (1). Partial swapoff that immediately
3176 transfers pages from Xen hypervisor back to the
3177 kernel based on different criteria.
3181 Specify if the kernel should make use of the cpu
3182 topology information if the hardware supports this.
3183 The scheduler will make use of this information and
3184 e.g. base its process migration decisions on it.
3189 tpm_suspend_pcr=[HW,TPM]
3190 Format: integer pcr id
3191 Specify that at suspend time, the tpm driver
3192 should extend the specified pcr with zeros,
3193 as a workaround for some chips which fail to
3194 flush the last written pcr on TPM_SaveState.
3195 This will guarantee that all the other pcrs
3198 trace_buf_size=nn[KMG]
3199 [FTRACE] will set tracing buffer size.
3201 trace_event=[event-list]
3202 [FTRACE] Set and start specified trace events in order
3203 to facilitate early boot debugging.
3204 See also Documentation/trace/events.txt
3206 trace_options=[option-list]
3207 [FTRACE] Enable or disable tracer options at boot.
3208 The option-list is a comma delimited list of options
3209 that can be enabled or disabled just as if you were
3210 to echo the option name into
3212 /sys/kernel/debug/tracing/trace_options
3214 For example, to enable stacktrace option (to dump the
3215 stack trace of each event), add to the command line:
3217 trace_options=stacktrace
3219 See also Documentation/trace/ftrace.txt "trace options"
3223 [FTRACE] enable this option to disable tracing when a
3224 warning is hit. This turns off "tracing_on". Tracing can
3225 be enabled again by echoing '1' into the "tracing_on"
3226 file located in /sys/kernel/debug/tracing/
3228 This option is useful, as it disables the trace before
3229 the WARNING dump is called, which prevents the trace to
3230 be filled with content caused by the warning output.
3232 This option can also be set at run time via the sysctl
3233 option: kernel/traceoff_on_warning
3235 transparent_hugepage=
3237 Format: [always|madvise|never]
3238 Can be used to control the default behavior of the system
3239 with respect to transparent hugepages.
3240 See Documentation/vm/transhuge.txt for more details.
3242 tsc= Disable clocksource stability checks for TSC.
3244 [x86] reliable: mark tsc clocksource as reliable, this
3245 disables clocksource verification at runtime, as well
3246 as the stability checks done at bootup. Used to enable
3247 high-resolution timer mode on older hardware, and in
3248 virtualized environment.
3249 [x86] noirqtime: Do not use TSC to do irq accounting.
3250 Used to run time disable IRQ_TIME_ACCOUNTING on any
3251 platforms where RDTSC is slow and this accounting
3254 turbografx.map[2|3]= [HW,JOY]
3255 TurboGraFX parallel port interface
3257 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3258 See also Documentation/input/joystick-parport.txt
3260 udbg-immortal [PPC] When debugging early kernel crashes that
3261 happen after console_init() and before a proper
3262 console driver takes over, this boot options might
3263 help "seeing" what's going on.
3265 uhash_entries= [KNL,NET]
3266 Set number of hash buckets for UDP/UDP-Lite connections
3269 [USB] Ignore overcurrent events (default N).
3270 Some badly-designed motherboards generate lots of
3271 bogus events, for ports that aren't wired to
3272 anything. Set this parameter to avoid log spamming.
3273 Note that genuine overcurrent events won't be
3277 [X86] Cause panic on unknown NMI.
3279 usbcore.authorized_default=
3280 [USB] Default USB device authorization:
3281 (default -1 = authorized except for wireless USB,
3282 0 = not authorized, 1 = authorized)
3284 usbcore.autosuspend=
3285 [USB] The autosuspend time delay (in seconds) used
3286 for newly-detected USB devices (default 2). This
3287 is the time required before an idle device will be
3288 autosuspended. Devices for which the delay is set
3289 to a negative value won't be autosuspended at all.
3291 usbcore.usbfs_snoop=
3292 [USB] Set to log all usbfs traffic (default 0 = off).
3294 usbcore.blinkenlights=
3295 [USB] Set to cycle leds on hubs (default 0 = off).
3297 usbcore.old_scheme_first=
3298 [USB] Start with the old device initialization
3299 scheme (default 0 = off).
3301 usbcore.usbfs_memory_mb=
3302 [USB] Memory limit (in MB) for buffers allocated by
3303 usbfs (default = 16, 0 = max = 2047).
3305 usbcore.use_both_schemes=
3306 [USB] Try the other device initialization scheme
3307 if the first one fails (default 1 = enabled).
3309 usbcore.initial_descriptor_timeout=
3310 [USB] Specifies timeout for the initial 64-byte
3311 USB_REQ_GET_DESCRIPTOR request in milliseconds
3312 (default 5000 = 5.0 seconds).
3315 [USBHID] The interval which mice are to be polled at.
3317 usb-storage.delay_use=
3318 [UMS] The delay in seconds before a new device is
3319 scanned for Logical Units (default 5).
3322 [UMS] A list of quirks entries to supplement or
3323 override the built-in unusual_devs list. List
3324 entries are separated by commas. Each entry has
3325 the form VID:PID:Flags where VID and PID are Vendor
3326 and Product ID values (4-digit hex numbers) and
3327 Flags is a set of characters, each corresponding
3328 to a common usb-storage quirk flag as follows:
3329 a = SANE_SENSE (collect more than 18 bytes
3331 b = BAD_SENSE (don't collect more than 18
3332 bytes of sense data);
3333 c = FIX_CAPACITY (decrease the reported
3334 device capacity by one sector);
3335 d = NO_READ_DISC_INFO (don't use
3336 READ_DISC_INFO command);
3337 e = NO_READ_CAPACITY_16 (don't use
3338 READ_CAPACITY_16 command);
3339 h = CAPACITY_HEURISTICS (decrease the
3340 reported device capacity by one
3341 sector if the number is odd);
3342 i = IGNORE_DEVICE (don't bind to this
3344 l = NOT_LOCKABLE (don't try to lock and
3345 unlock ejectable media);
3346 m = MAX_SECTORS_64 (don't transfer more
3347 than 64 sectors = 32 KB at a time);
3348 n = INITIAL_READ10 (force a retry of the
3349 initial READ(10) command);
3350 o = CAPACITY_OK (accept the capacity
3351 reported by the device);
3352 p = WRITE_CACHE (the device cache is ON
3354 r = IGNORE_RESIDUE (the device reports
3355 bogus residue values);
3356 s = SINGLE_LUN (the device has only one
3358 w = NO_WP_DETECT (don't test whether the
3359 medium is write-protected).
3360 Example: quirks=0419:aaf5:rl,0421:0433:rc
3362 user_debug= [KNL,ARM]
3364 See arch/arm/Kconfig.debug help text.
3365 1 - undefined instruction events
3367 4 - invalid data aborts
3370 Example: user_debug=31
3373 [X86] Flags controlling user PTE allocations.
3375 nohigh = do not allocate PTE pages in
3376 HIGHMEM regardless of setting
3380 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3381 vdso=1: enable VDSO (default)
3382 vdso=0: disable VDSO mapping
3385 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3386 vdso32=1: enable 32-bit VDSO (default)
3387 vdso32=0: disable 32-bit VDSO mapping
3390 vector=percpu: enable percpu vector domain
3392 video= [FB] Frame buffer configuration
3393 See Documentation/fb/modedb.txt.
3395 video.brightness_switch_enabled= [0,1]
3396 If set to 1, on receiving an ACPI notify event
3397 generated by hotkey, video driver will adjust brightness
3398 level and then send out the event to user space through
3399 the allocated input device; If set to 0, video driver
3400 will only send out the event without touching backlight
3405 [VMMIO] Memory mapped virtio (platform) device.
3407 <size>@<baseaddr>:<irq>[:<id>]
3409 <size> := size (can use standard suffixes
3411 <baseaddr> := physical base address
3412 <irq> := interrupt number (as passed to
3414 <id> := (optional) platform device id
3416 virtio_mmio.device=1K@0x100b0000:48:7
3418 Can be used multiple times for multiple devices.
3420 vga= [BOOT,X86-32] Select a particular video mode
3421 See Documentation/x86/boot.txt and
3422 Documentation/svga.txt.
3423 Use vga=ask for menu.
3424 This is actually a boot loader parameter; the value is
3425 passed to the kernel using a special protocol.
3427 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3428 size of <nn>. This can be used to increase the
3429 minimum size (128MB on x86). It can also be used to
3430 decrease the size and leave more room for directly
3433 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3436 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3439 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3443 Controls the behavior of vsyscalls (i.e. calls to
3444 fixed addresses of 0xffffffffff600x00 from legacy
3445 code). Most statically-linked binaries and older
3446 versions of glibc use these calls. Because these
3447 functions are at fixed addresses, they make nice
3448 targets for exploits that can control RIP.
3450 emulate [default] Vsyscalls turn into traps and are
3451 emulated reasonably safely.
3453 native Vsyscalls are native syscall instructions.
3454 This is a little bit faster than trapping
3455 and makes a few dynamic recompilers work
3456 better than they would in emulation mode.
3457 It also makes exploits much easier to write.
3459 none Vsyscalls don't work at all. This makes
3460 them quite hard to use for exploits but
3461 might break your system.
3463 vt.color= [VT] Default text color.
3464 Format: 0xYX, X = foreground, Y = background.
3465 Default: 0x07 = light gray on black.
3467 vt.cur_default= [VT] Default cursor shape.
3468 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3469 the parameters of the <Esc>[?A;B;Cc escape sequence;
3470 see VGA-softcursor.txt. Default: 2 = underline.
3472 vt.default_blu= [VT]
3473 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3474 Change the default blue palette of the console.
3475 This is a 16-member array composed of values
3478 vt.default_grn= [VT]
3479 Format: <green0>,<green1>,<green2>,...,<green15>
3480 Change the default green palette of the console.
3481 This is a 16-member array composed of values
3484 vt.default_red= [VT]
3485 Format: <red0>,<red1>,<red2>,...,<red15>
3486 Change the default red palette of the console.
3487 This is a 16-member array composed of values
3493 Set system-wide default UTF-8 mode for all tty's.
3494 Default is 1, i.e. UTF-8 mode is enabled for all
3495 newly opened terminals.
3497 vt.global_cursor_default=
3500 Set system-wide default for whether a cursor
3501 is shown on new VTs. Default is -1,
3502 i.e. cursors will be created by default unless
3503 overridden by individual drivers. 0 will hide
3504 cursors, 1 will display them.
3506 vt.italic= [VT] Default color for italic text; 0-15.
3509 vt.underline= [VT] Default color for underlined text; 0-15.
3512 watchdog timers [HW,WDT] For information on watchdog timers,
3513 see Documentation/watchdog/watchdog-parameters.txt
3514 or other driver-specific files in the
3515 Documentation/watchdog/ directory.
3517 workqueue.disable_numa
3518 By default, all work items queued to unbound
3519 workqueues are affine to the NUMA nodes they're
3520 issued on, which results in better behavior in
3521 general. If NUMA affinity needs to be disabled for
3522 whatever reason, this option can be used. Note
3523 that this also can be controlled per-workqueue for
3524 workqueues visible under /sys/bus/workqueue/.
3526 workqueue.power_efficient
3527 Per-cpu workqueues are generally preferred because
3528 they show better performance thanks to cache
3529 locality; unfortunately, per-cpu workqueues tend to
3530 be more power hungry than unbound workqueues.
3532 Enabling this makes the per-cpu workqueues which
3533 were observed to contribute significantly to power
3534 consumption unbound, leading to measurably lower
3535 power usage at the cost of small performance
3538 The default value of this parameter is determined by
3539 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3541 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3542 default x2apic cluster mode on platforms
3545 x86_intel_mid_timer= [X86-32,APBT]
3546 Choose timer option for x86 Intel MID platform.
3547 Two valid options are apbt timer only and lapic timer
3548 plus one apbt timer for broadcast timer.
3549 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3551 xen_emul_unplug= [HW,X86,XEN]
3552 Unplug Xen emulated devices
3553 Format: [unplug0,][unplug1]
3554 ide-disks -- unplug primary master IDE devices
3555 aux-ide-disks -- unplug non-primary-master IDE devices
3556 nics -- unplug network devices
3557 all -- unplug all emulated devices (NICs and IDE disks)
3558 unnecessary -- unplugging emulated devices is
3559 unnecessary even if the host did not respond to
3561 never -- do not unplug even if version check succeeds
3563 xen_nopvspin [X86,XEN]
3564 Disables the ticketlock slowpath using Xen PV
3567 xirc2ps_cs= [NET,PCMCIA]
3569 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3571 ______________________________________________________________________
3575 Add more DRM drivers.
projects / karo-tx-linux.git / blob