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 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
349 add_efi_memmap [EFI; X86] Include EFI memory map in
350 kernel's map of available physical RAM.
353 { off | try_unsupported }
354 off: disable AGP support
355 try_unsupported: try to drive unsupported chipsets
356 (may crash computer or cause data corruption)
359 See Documentation/sound/alsa/alsa-parameters.txt
362 Allow the default userspace alignment fault handler
363 behaviour to be specified. Bit 0 enables warnings,
364 bit 1 enables fixups, and bit 2 sends a segfault.
366 align_va_addr= [X86-64]
367 Align virtual addresses by clearing slice [14:12] when
368 allocating a VMA at process creation time. This option
369 gives you up to 3% performance improvement on AMD F15h
370 machines (where it is enabled by default) for a
371 CPU-intensive style benchmark, and it can vary highly in
372 a microbenchmark depending on workload and compiler.
374 32: only for 32-bit processes
375 64: only for 64-bit processes
376 on: enable for both 32- and 64-bit processes
377 off: disable for both 32- and 64-bit processes
379 alloc_snapshot [FTRACE]
380 Allocate the ftrace snapshot buffer on boot up when the
381 main buffer is allocated. This is handy if debugging
382 and you need to use tracing_snapshot() on boot up, and
383 do not want to use tracing_snapshot_alloc() as it needs
384 to be done where GFP_KERNEL allocations are allowed.
386 amd_iommu= [HW,X86-64]
387 Pass parameters to the AMD IOMMU driver in the system.
389 fullflush - enable flushing of IO/TLB entries when
390 they are unmapped. Otherwise they are
391 flushed before they will be reused, which
393 off - do not initialize any AMD IOMMU found in
395 force_isolation - Force device isolation for all
396 devices. The IOMMU driver is not
397 allowed anymore to lift isolation
398 requirements as needed. This option
399 does not override iommu=pt
401 amd_iommu_dump= [HW,X86-64]
402 Enable AMD IOMMU driver option to dump the ACPI table
403 for AMD IOMMU. With this option enabled, AMD IOMMU
404 driver will print ACPI tables for AMD IOMMU during
405 IOMMU initialization.
407 amijoy.map= [HW,JOY] Amiga joystick support
408 Map of devices attached to JOY0DAT and JOY1DAT
410 See also Documentation/input/joystick.txt
412 analog.map= [HW,JOY] Analog joystick and gamepad support
413 Specifies type or capabilities of an analog joystick
414 connected to one of 16 gameports
415 Format: <type1>,<type2>,..<type16>
418 Power management functions (SPARCstation-4/5 + deriv.)
420 Disable APC CPU standby support. SPARCstation-Fox does
421 not play well with APC CPU idle - disable it if you have
422 APC and your system crashes randomly.
424 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
425 Change the output verbosity whilst booting
426 Format: { quiet (default) | verbose | debug }
427 Change the amount of debugging information output
428 when initialising the APIC and IO-APIC components.
431 See Documentation/networking/ipv6.txt.
433 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
434 Limit apic dumping. The parameter defines the maximal
435 number of local apics being dumped. Also it is possible
436 to set it to "all" by meaning -- no limit here.
437 Format: { 1 (default) | 2 | ... | all }.
438 The parameter valid if only apic=debug or
439 apic=verbose is specified.
440 Example: apic=debug show_lapic=all
442 apm= [APM] Advanced Power Management
443 See header of arch/x86/kernel/apm_32.c.
445 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
446 Format: <io>,<irq>,<nodeID>
450 atarimouse= [HW,MOUSE] Atari Mouse
452 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
453 EzKey and similar keyboards
455 atkbd.reset= [HW] Reset keyboard during initialization
457 atkbd.set= [HW] Select keyboard code set
458 Format: <int> (2 = AT (default), 3 = PS/2)
460 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
463 atkbd.softraw= [HW] Choose between synthetic and real raw mode
464 Format: <bool> (0 = real, 1 = synthetic (default))
466 atkbd.softrepeat= [HW]
467 Use software keyboard repeat
469 baycom_epp= [HW,AX25]
472 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
474 See header of drivers/net/hamradio/baycom_par.c.
476 baycom_ser_fdx= [HW,AX25]
477 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
478 Format: <io>,<irq>,<mode>[,<baud>]
479 See header of drivers/net/hamradio/baycom_ser_fdx.c.
481 baycom_ser_hdx= [HW,AX25]
482 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
483 Format: <io>,<irq>,<mode>
484 See header of drivers/net/hamradio/baycom_ser_hdx.c.
486 blkdevparts= Manual partition parsing of block device(s) for
487 embedded devices based on command line input.
488 See Documentation/block/cmdline-partition.txt
490 boot_delay= Milliseconds to delay each printk during boot.
491 Values larger than 10 seconds (10000) are changed to
495 bootmem_debug [KNL] Enable bootmem allocator debug messages.
497 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
498 bttv.radio= Most important insmod options are available as
500 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
503 bulk_remove=off [PPC] This parameter disables the use of the pSeries
504 firmware feature for flushing multiple hpte entries
507 c101= [NET] Moxa C101 synchronous serial card
509 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
510 Sometimes CPU hardware bugs make them report the cache
511 size incorrectly. The kernel will attempt work arounds
512 to fix known problems, but for some CPUs it is not
513 possible to determine what the correct size should be.
514 This option provides an override for these situations.
516 ccw_timeout_log [S390]
517 See Documentation/s390/CommonIO for details.
519 cgroup_disable= [KNL] Disable a particular controller
520 Format: {name of the controller(s) to disable}
521 {Currently supported controllers - "memory"}
523 checkreqprot [SELINUX] Set initial checkreqprot flag value.
524 Format: { "0" | "1" }
525 See security/selinux/Kconfig help text.
526 0 -- check protection applied by kernel (includes
527 any implied execute protection).
528 1 -- check protection requested by application.
529 Default value is set via a kernel config option.
530 Value can be changed at runtime via
531 /selinux/checkreqprot.
534 See Documentation/s390/CommonIO for details.
537 Keep all clocks already enabled by bootloader on,
538 even if no driver has claimed them. This is useful
539 for debug and development, but should not be
540 needed on a platform with proper driver support.
541 For more information, see Documentation/clk.txt.
543 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
545 Forces specified clocksource (if available) to be used
546 when calculating gettimeofday(). If specified
547 clocksource is not available, it defaults to PIT.
548 Format: { pit | tsc | cyclone | pmtmr }
550 clocksource= Override the default clocksource
552 Override the default clocksource and use the clocksource
553 with the name specified.
554 Some clocksource names to choose from, depending on
556 [all] jiffies (this is the base, fallback clocksource)
558 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
559 pxa_timer,timer3,32k_counter,timer0_1
561 [X86-32] pit,hpet,tsc;
562 scx200_hrt on Geode; cyclone on IBM x440
570 clearcpuid=BITNUM [X86]
571 Disable CPUID feature X for the kernel. See
572 arch/x86/include/asm/cpufeature.h for the valid bit
573 numbers. Note the Linux specific bits are not necessarily
574 stable over kernel options, but the vendor specific
576 Also note that user programs calling CPUID directly
577 or using the feature without checking anything
578 will still see it. This just prevents it from
579 being used by the kernel or shown in /proc/cpuinfo.
580 Also note the kernel might malfunction if you disable
584 Sets the size of kernel global memory area for contiguous
585 memory allocations. For more information, see
586 include/linux/dma-contiguous.h
588 cmo_free_hint= [PPC] Format: { yes | no }
589 Specify whether pages are marked as being inactive
590 when they are freed. This is used in CMO environments
591 to determine OS memory pressure for page stealing by
595 coherent_pool=nn[KMG] [ARM,KNL]
596 Sets the size of memory pool for coherent, atomic dma
597 allocations, by default set to 256K.
599 code_bytes [X86] How many bytes of object code to print
604 com20020= [HW,NET] ARCnet - COM20020 chipset
606 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
608 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
612 ARCnet - COM90xx chipset (memory-mapped buffers)
613 Format: <io>[,<irq>[,<memstart>]]
615 condev= [HW,S390] console device
618 console= [KNL] Output console device and options.
620 tty<n> Use the virtual console device <n>.
624 Use the specified serial port. The options are of
625 the form "bbbbpnf", where "bbbb" is the baud rate,
626 "p" is parity ("n", "o", or "e"), "n" is number of
627 bits, and "f" is flow control ("r" for RTS or
628 omit it). Default is "9600n8".
630 See Documentation/serial-console.txt for more
632 Documentation/networking/netconsole.txt for an
635 uart[8250],io,<addr>[,options]
636 uart[8250],mmio,<addr>[,options]
637 Start an early, polled-mode console on the 8250/16550
638 UART at the specified I/O port or MMIO address,
639 switching to the matching ttyS device later. The
640 options are the same as for ttyS, above.
641 hvc<n> Use the hypervisor console device <n>. This is for
642 both Xen and PowerPC hypervisors.
644 If the device connected to the port is not a TTY but a braille
645 device, prepend "brl," before the device type, for instance
647 For now, only VisioBraille is supported.
649 consoleblank= [KNL] The console blank (screen saver) timeout in
650 seconds. Defaults to 10*60 = 10mins. A value of 0
651 disables the blank timer.
654 [KNL] Change the default value for
655 /proc/<pid>/coredump_filter.
656 See also Documentation/filesystems/proc.txt.
658 cpuidle.off=1 [CPU_IDLE]
659 disable the cpuidle sub-system
661 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
663 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
665 crashkernel=size[KMG][@offset[KMG]]
666 [KNL] Using kexec, Linux can switch to a 'crash kernel'
667 upon panic. This parameter reserves the physical
668 memory region [offset, offset + size] for that kernel
669 image. If '@offset' is omitted, then a suitable offset
670 is selected automatically. Check
671 Documentation/kdump/kdump.txt for further details.
673 crashkernel=range1:size1[,range2:size2,...][@offset]
674 [KNL] Same as above, but depends on the memory
675 in the running system. The syntax of range is
676 start-[end] where start and end are both
677 a memory unit (amount[KMG]). See also
678 Documentation/kdump/kdump.txt for an example.
680 crashkernel=size[KMG],high
681 [KNL, x86_64] range could be above 4G. Allow kernel
682 to allocate physical memory region from top, so could
683 be above 4G if system have more than 4G ram installed.
684 Otherwise memory region will be allocated below 4G, if
686 It will be ignored if crashkernel=X is specified.
687 crashkernel=size[KMG],low
688 [KNL, x86_64] range under 4G. When crashkernel=X,high
689 is passed, kernel could allocate physical memory region
690 above 4G, that cause second kernel crash on system
691 that require some amount of low memory, e.g. swiotlb
692 requires at least 64M+32K low memory. Kernel would
693 try to allocate 72M below 4G automatically.
694 This one let user to specify own low range under 4G
695 for second kernel instead.
696 0: to disable low allocation.
697 It will be ignored when crashkernel=X,high is not used
698 or memory reserved is below 4G.
703 cs89x0_media= [HW,NET]
704 Format: { rj45 | aui | bnc }
707 See header of drivers/s390/block/dasd_devmap.c.
709 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
710 (one device per port)
711 Format: <port#>,<type>
712 See also Documentation/input/joystick-parport.txt
714 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
715 time. See Documentation/dynamic-debug-howto.txt for
716 details. Deprecated, see dyndbg.
718 debug [KNL] Enable kernel debugging (events log level).
721 [KNL] verbose self-tests
723 Print debugging info while doing the locking API
725 We default to 0 (no extra messages), setting it to
726 1 will print _a lot_ more information - normally
727 only useful to kernel developers.
729 debug_objects [KNL] Enable object debugging
732 [KNL] Disable object debugging
734 debug_guardpage_minorder=
735 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
736 parameter allows control of the order of pages that will
737 be intentionally kept free (and hence protected) by the
738 buddy allocator. Bigger value increase the probability
739 of catching random memory corruption, but reduce the
740 amount of memory for normal system use. The maximum
741 possible value is MAX_ORDER/2. Setting this parameter
742 to 1 or 2 should be enough to identify most random
743 memory corruption problems caused by bugs in kernel or
744 driver code when a CPU writes to (or reads from) a
745 random memory location. Note that there exists a class
746 of memory corruptions problems caused by buggy H/W or
747 F/W or by drivers badly programing DMA (basically when
748 memory is written at bus level and the CPU MMU is
749 bypassed) which are not detectable by
750 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
751 tracking down these problems.
753 debugpat [X86] Enable PAT debugging
755 decnet.addr= [HW,NET]
756 Format: <area>[,<node>]
757 See also Documentation/networking/decnet.txt.
760 [same as hugepagesz=] The size of the default
761 HugeTLB page size. This is the size represented by
762 the legacy /proc/ hugepages APIs, used for SHM, and
763 default size when mounting hugetlbfs filesystems.
764 Defaults to the default architecture's huge page size
768 Set number of hash buckets for dentry cache.
771 IO parameters + enable/disable command.
773 digiepca= [HW,SERIAL]
774 See drivers/char/README.epca and
775 Documentation/serial/digiepca.txt.
778 See Documentation/networking/ipv6.txt.
780 disable_ddw [PPC/PSERIES]
781 Disable Dynamic DMA Window support. Use this if
782 to workaround buggy firmware.
785 See Documentation/networking/ipv6.txt.
787 disable_mtrr_cleanup [X86]
788 The kernel tries to adjust MTRR layout from continuous
789 to discrete, to make X server driver able to add WB
790 entry later. This parameter disables that.
792 disable_mtrr_trim [X86, Intel and AMD only]
793 By default the kernel will trim any uncacheable
794 memory out of your available memory pool based on
795 MTRR settings. This parameter disables that behavior,
796 possibly causing your machine to run very slowly.
798 disable_timer_pin_1 [X86]
799 Disable PIN 1 of APIC timer
800 Can be useful to work around chipset bugs.
802 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
803 this option disables the debugging code at boot.
805 dma_debug_entries=<number>
806 This option allows to tune the number of preallocated
807 entries for DMA-API debugging code. One entry is
808 required per DMA-API allocation. Use this if the
809 DMA-API debugging code disables itself because the
810 architectural default is too low.
812 dma_debug_driver=<driver_name>
813 With this option the DMA-API debugging driver
814 filter feature can be enabled at boot time. Just
815 pass the driver to filter for as the parameter.
816 The filter can be disabled or changed to another
817 driver later using sysfs.
819 drm_kms_helper.edid_firmware=[<connector>:]<file>
820 Broken monitors, graphic adapters and KVMs may
821 send no or incorrect EDID data sets. This parameter
822 allows to specify an EDID data set in the
823 /lib/firmware directory that is used instead.
824 Generic built-in EDID data sets are used, if one of
825 edid/1024x768.bin, edid/1280x1024.bin,
826 edid/1680x1050.bin, or edid/1920x1080.bin is given
827 and no file with the same name exists. Details and
828 instructions how to build your own EDID data are
829 available in Documentation/EDID/HOWTO.txt. An EDID
830 data set will only be used for a particular connector,
831 if its name and a colon are prepended to the EDID
836 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
837 module.dyndbg[="val"]
838 Enable debug messages at boot time. See
839 Documentation/dynamic-debug-howto.txt for details.
841 earlycon= [KNL] Output early console device and options.
842 uart[8250],io,<addr>[,options]
843 uart[8250],mmio,<addr>[,options]
844 uart[8250],mmio32,<addr>[,options]
845 Start an early, polled-mode console on the 8250/16550
846 UART at the specified I/O port or MMIO address.
847 MMIO inter-register address stride is either 8-bit
848 (mmio) or 32-bit (mmio32).
849 The options are the same as for ttyS, above.
851 earlyprintk= [X86,SH,BLACKFIN,ARM]
855 earlyprintk=serial[,ttySn[,baudrate]]
856 earlyprintk=serial[,0x...[,baudrate]]
857 earlyprintk=ttySn[,baudrate]
858 earlyprintk=dbgp[debugController#]
860 earlyprintk is useful when the kernel crashes before
861 the normal console is initialized. It is not enabled by
862 default because it has some cosmetic problems.
864 Append ",keep" to not disable it when the real console
867 Only one of vga, efi, serial, or usb debug port can
870 Currently only ttyS0 and ttyS1 may be specified by
871 name. Other I/O ports may be explicitly specified
872 on some architectures (x86 and arm at least) by
873 replacing ttySn with an I/O port address, like this:
874 earlyprintk=serial,0x1008,115200
875 You can find the port for a given device in
876 /proc/tty/driver/serial:
877 2: uart:ST16650V2 port:00001008 irq:18 ...
879 Interaction with the standard serial driver is not
882 The VGA and EFI output is eventually overwritten by
885 The xen output can only be used by Xen PV guests.
887 ekgdboc= [X86,KGDB] Allow early kernel console debugging
890 This is designed to be used in conjunction with
891 the boot argument: earlyprintk=vga
894 Format: {"off" | "on" | "skip[mbr]"}
896 efi_no_storage_paranoia [EFI; X86]
897 Using this parameter you can use more than 50% of
898 your efi variable storage. Use this parameter only if
899 you are really sure that your UEFI does sane gc and
900 fulfills the spec otherwise your board may brick.
902 eisa_irq_edge= [PARISC,HW]
903 See header of drivers/parisc/eisa.c.
906 See comment before function elanfreq_setup() in
907 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
910 Format: {"cfq" | "deadline" | "noop"}
911 See Documentation/block/cfq-iosched.txt and
912 Documentation/block/deadline-iosched.txt for details.
914 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
915 Specifies physical address of start of kernel core
916 image elf header and optionally the size. Generally
917 kexec loader will pass this option to capture kernel.
918 See Documentation/kdump/kdump.txt for details.
920 enable_mtrr_cleanup [X86]
921 The kernel tries to adjust MTRR layout from continuous
922 to discrete, to make X server driver able to add WB
923 entry later. This parameter enables that.
925 enable_timer_pin_1 [X86]
926 Enable PIN 1 of APIC timer
927 Can be useful to work around chipset bugs
928 (in particular on some ATI chipsets).
929 The kernel tries to set a reasonable default.
931 enforcing [SELINUX] Set initial enforcing status.
933 See security/selinux/Kconfig help text.
934 0 -- permissive (log only, no denials).
935 1 -- enforcing (deny and log).
937 Value can be changed at runtime via /selinux/enforce.
940 Disable Error Record Serialization Table (ERST)
943 ether= [HW,NET] Ethernet cards parameters
944 This option is obsoleted by the "netdev=" option, which
945 has equivalent usage. See its documentation for details.
949 Permit 'security.evm' to be updated regardless of
950 current integrity status.
954 fail_make_request=[KNL]
955 General fault injection mechanism.
956 Format: <interval>,<probability>,<space>,<times>
957 See also Documentation/fault-injection/.
960 See Documentation/blockdev/floppy.txt.
962 force_pal_cache_flush
963 [IA-64] Avoid check_sal_cache_flush which may hang on
964 buggy SAL_CACHE_FLUSH implementations. Using this
965 parameter will force ia64_sal_cache_flush to call
966 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
969 [FTRACE] will set and start the specified tracer
970 as early as possible in order to facilitate early
973 ftrace_dump_on_oops[=orig_cpu]
974 [FTRACE] will dump the trace buffers on oops.
975 If no parameter is passed, ftrace will dump
976 buffers of all CPUs, but if you pass orig_cpu, it will
977 dump only the buffer of the CPU that triggered the
980 ftrace_filter=[function-list]
981 [FTRACE] Limit the functions traced by the function
982 tracer at boot up. function-list is a comma separated
983 list of functions. This list can be changed at run
984 time by the set_ftrace_filter file in the debugfs
987 ftrace_notrace=[function-list]
988 [FTRACE] Do not trace the functions specified in
989 function-list. This list can be changed at run time
990 by the set_ftrace_notrace file in the debugfs
993 ftrace_graph_filter=[function-list]
994 [FTRACE] Limit the top level callers functions traced
995 by the function graph tracer at boot up.
996 function-list is a comma separated list of functions
997 that can be changed at run time by the
998 set_graph_function file in the debugfs tracing directory.
1001 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1002 support via parallel port (up to 5 devices per port)
1003 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1004 See also Documentation/input/joystick-parport.txt
1008 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1012 gcov_persist= [GCOV] When non-zero (default), profiling data for
1013 kernel modules is saved and remains accessible via
1014 debugfs, even when the module is unloaded/reloaded.
1015 When zero, profiling data is discarded and associated
1016 debugfs files are removed at module unload time.
1018 gpt [EFI] Forces disk with valid GPT signature but
1019 invalid Protective MBR to be treated as GPT.
1021 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1022 the "Enable 0" bit of the configuration register.
1025 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1026 the "Enable 0" bit of the configuration register.
1029 grcan.select= [HW] Select which physical interface to use.
1032 grcan.txsize= [HW] Sets the size of the tx buffer.
1033 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1035 grcan.rxsize= [HW] Sets the size of the rx buffer.
1036 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1039 hashdist= [KNL,NUMA] Large hashes allocated during boot
1040 are distributed across NUMA nodes. Defaults on
1041 for 64-bit NUMA, off otherwise.
1042 Format: 0 | 1 (for off | on)
1044 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1046 hd= [EIDE] (E)IDE hard drive subsystem geometry
1047 Format: <cyl>,<head>,<sect>
1050 Disable Hardware Error Source Table (HEST) support;
1051 corresponding firmware-first mode error processing
1052 logic will be disabled.
1054 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1055 size of <nn>. This works even on boxes that have no
1056 highmem otherwise. This also works to reduce highmem
1057 size on bigger boxes.
1059 highres= [KNL] Enable/disable high resolution timer mode.
1060 Valid parameters: "on", "off"
1064 See Documentation/isdn/README.HiSax.
1068 hpet= [X86-32,HPET] option to control HPET usage
1069 Format: { enable (default) | disable | force |
1071 disable: disable HPET and use PIT instead
1072 force: allow force enabled of undocumented chips (ICH4,
1074 verbose: show contents of HPET registers during setup
1076 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1077 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1079 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1080 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1081 On x86-64 and powerpc, this option can be specified
1082 multiple times interleaved with hugepages= to reserve
1083 huge pages of different sizes. Valid pages sizes on
1084 x86-64 are 2M (when the CPU supports "pse") and 1G
1085 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1086 Note that 1GB pages can only be allocated at boot time
1087 using hugepages= and not freed afterwards.
1089 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1090 terminal devices. Valid values: 0..8
1091 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1092 If specified, z/VM IUCV HVC accepts connections
1093 from listed z/VM user IDs only.
1095 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1096 hardware thread id mappings.
1097 Format: <cpu>:<hwthread>
1100 Do not unregister boot console at start. This is only
1101 useful for debugging when something happens in the window
1102 between unregistering the boot console and initializing
1105 i2c_bus= [HW] Override the default board specific I2C bus speed
1106 or register an additional I2C bus that is not
1107 registered from board initialization code.
1111 i8042.debug [HW] Toggle i8042 debug mode
1112 i8042.direct [HW] Put keyboard port into non-translated mode
1113 i8042.dumbkbd [HW] Pretend that controller can only read data from
1114 keyboard and cannot control its state
1115 (Don't attempt to blink the leds)
1116 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1117 i8042.nokbd [HW] Don't check/create keyboard port
1118 i8042.noloop [HW] Disable the AUX Loopback command while probing
1120 i8042.nomux [HW] Don't check presence of an active multiplexing
1122 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1124 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1125 i8042.reset [HW] Reset the controller during init and cleanup
1126 i8042.unlock [HW] Unlock (ignore) the keylock
1130 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1131 indicates that the driver is running on unsupported
1133 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1134 does not match list of supported models.
1136 [HW] Report power status in /proc/i8k
1137 (disabled by default)
1138 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1141 i915.invert_brightness=
1142 [DRM] Invert the sense of the variable that is used to
1143 set the brightness of the panel backlight. Normally a
1144 brightness value of 0 indicates backlight switched off,
1145 and the maximum of the brightness value sets the backlight
1146 to maximum brightness. If this parameter is set to 0
1147 (default) and the machine requires it, or this parameter
1148 is set to 1, a brightness value of 0 sets the backlight
1149 to maximum brightness, and the maximum of the brightness
1150 value switches the backlight off.
1151 -1 -- never invert brightness
1152 0 -- machine default
1153 1 -- force brightness inversion
1156 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1158 ide-core.nodma= [HW] (E)IDE subsystem
1159 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1160 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1161 .cdrom .chs .ignore_cable are additional options
1162 See Documentation/ide/ide.txt.
1164 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1165 Claim all unknown PCI IDE storage controllers.
1168 Format: idle=poll, idle=halt, idle=nomwait
1169 Poll forces a polling idle loop that can slightly
1170 improve the performance of waking up a idle CPU, but
1171 will use a lot of power and make the system run hot.
1173 idle=halt: Halt is forced to be used for CPU idle.
1174 In such case C2/C3 won't be used again.
1175 idle=nomwait: Disable mwait for CPU C-states
1177 ignore_loglevel [KNL]
1178 Ignore loglevel setting - this will print /all/
1179 kernel messages to the console. Useful for debugging.
1180 We also add it as printk module parameter, so users
1181 could change it dynamically, usually by
1182 /sys/module/printk/parameters/ignore_loglevel.
1184 ihash_entries= [KNL]
1185 Set number of hash buckets for inode cache.
1187 ima_appraise= [IMA] appraise integrity measurements
1188 Format: { "off" | "enforce" | "fix" }
1191 ima_appraise_tcb [IMA]
1192 The builtin appraise policy appraises all files
1196 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1200 The list of supported hash algorithms is defined
1201 in crypto/hash_info.h.
1204 Load a policy which meets the needs of the Trusted
1205 Computing Base. This means IMA will measure all
1206 programs exec'd, files mmap'd for exec, and all files
1207 opened for read by uid=0.
1210 Select one of defined IMA measurements template formats.
1211 Formats: { "ima" | "ima-ng" }
1216 Run specified binary instead of /sbin/init as init
1219 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1220 for working out where the kernel is dying during
1223 initrd= [BOOT] Specify the location of the initial ramdisk
1225 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1228 int_pln_enable [x86] Enable power limit notification interrupt
1230 integrity_audit=[IMA]
1231 Format: { "0" | "1" }
1232 0 -- basic integrity auditing messages. (Default)
1233 1 -- additional integrity auditing messages.
1235 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1237 Enable intel iommu driver.
1239 Disable intel iommu driver.
1240 igfx_off [Default Off]
1241 By default, gfx is mapped as normal device. If a gfx
1242 device has a dedicated DMAR unit, the DMAR unit is
1243 bypassed by not enabling DMAR with this option. In
1244 this case, gfx device will use physical address for
1247 With this option iommu will not optimize to look
1248 for io virtual address below 32-bit forcing dual
1249 address cycle on pci bus for cards supporting greater
1250 than 32-bit addressing. The default is to look
1251 for translation below 32-bit and if not available
1252 then look in the higher range.
1253 strict [Default Off]
1254 With this option on every unmap_single operation will
1255 result in a hardware IOTLB flush operation as opposed
1256 to batching them for performance.
1257 sp_off [Default Off]
1258 By default, super page will be supported if Intel IOMMU
1259 has the capability. With this option, super page will
1262 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1263 0 disables intel_idle and fall back on acpi_idle.
1264 1 to 6 specify maximum depth of C-state.
1268 Do not enable intel_pstate as the default
1269 scaling driver for the supported processors
1271 intremap= [X86-64, Intel-IOMMU]
1272 on enable Interrupt Remapping (default)
1273 off disable Interrupt Remapping
1274 nosid disable Source ID checking
1276 BIOS x2APIC opt-out request will be ignored
1278 iomem= Disable strict checking of access to MMIO memory
1279 strict regions from userspace.
1296 io7= [HW] IO7 for Marvel based alpha systems
1297 See comment before marvel_specify_io7 in
1298 arch/alpha/kernel/core_marvel.c.
1300 io_delay= [X86] I/O delay method
1302 Standard port 0x80 based delay
1304 Alternate port 0xed based delay (needed on some systems)
1306 Simple two microseconds delay
1311 See Documentation/filesystems/nfs/nfsroot.txt.
1313 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1314 See comment before ip2_setup() in
1315 drivers/char/ip2/ip2base.c.
1318 When an interrupt is not handled search all handlers
1319 for it. Intended to get systems with badly broken
1323 When an interrupt is not handled search all handlers
1324 for it. Also check all handlers each timer
1325 interrupt. Intended to get systems with badly broken
1329 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1331 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1333 <cpu number>,...,<cpu number>
1335 <cpu number>-<cpu number>
1336 (must be a positive range in ascending order)
1338 <cpu number>,...,<cpu number>-<cpu number>
1340 This option can be used to specify one or more CPUs
1341 to isolate from the general SMP balancing and scheduling
1342 algorithms. You can move a process onto or off an
1343 "isolated" CPU via the CPU affinity syscalls or cpuset.
1344 <cpu number> begins at 0 and the maximum value is
1345 "number of CPUs in system - 1".
1347 This option is the preferred way to isolate CPUs. The
1348 alternative -- manually setting the CPU mask of all
1349 tasks in the system -- can cause problems and
1350 suboptimal load balancer performance.
1354 ivrs_ioapic [HW,X86_64]
1355 Provide an override to the IOAPIC-ID<->DEVICE-ID
1356 mapping provided in the IVRS ACPI table. For
1357 example, to map IOAPIC-ID decimal 10 to
1358 PCI device 00:14.0 write the parameter as:
1359 ivrs_ioapic[10]=00:14.0
1361 ivrs_hpet [HW,X86_64]
1362 Provide an override to the HPET-ID<->DEVICE-ID
1363 mapping provided in the IVRS ACPI table. For
1364 example, to map HPET-ID decimal 0 to
1365 PCI device 00:14.0 write the parameter as:
1366 ivrs_hpet[0]=00:14.0
1368 js= [HW,JOY] Analog joystick
1369 See Documentation/input/joystick.txt.
1373 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1374 specifies the amount of memory usable by the kernel
1375 for non-movable allocations. The requested amount is
1376 spread evenly throughout all nodes in the system. The
1377 remaining memory in each node is used for Movable
1378 pages. In the event, a node is too small to have both
1379 kernelcore and Movable pages, kernelcore pages will
1380 take priority and other nodes will have a larger number
1381 of Movable pages. The Movable zone is used for the
1382 allocation of pages that may be reclaimed or moved
1383 by the page migration subsystem. This means that
1384 HugeTLB pages may not be allocated from this zone.
1385 Note that allocations like PTEs-from-HighMem still
1386 use the HighMem zone if it exists, and the Normal
1387 zone if it does not.
1389 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1390 Format: <Controller#>[,poll interval]
1391 The controller # is the number of the ehci usb debug
1392 port as it is probed via PCI. The poll interval is
1393 optional and is the number seconds in between
1394 each poll cycle to the debug port in case you need
1395 the functionality for interrupting the kernel with
1396 gdb or control-c on the dbgp connection. When
1397 not using this parameter you use sysrq-g to break into
1398 the kernel debugger.
1400 kgdboc= [KGDB,HW] kgdb over consoles.
1401 Requires a tty driver that supports console polling,
1402 or a supported polling keyboard driver (non-usb).
1403 Serial only format: <serial_device>[,baud]
1404 keyboard only format: kbd
1405 keyboard and serial format: kbd,<serial_device>[,baud]
1406 Optional Kernel mode setting:
1407 kms, kbd format: kms,kbd
1408 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1410 kgdbwait [KGDB] Stop kernel execution and enter the
1411 kernel debugger at the earliest opportunity.
1413 kmac= [MIPS] korina ethernet MAC address.
1414 Configure the RouterBoard 532 series on-chip
1415 Ethernet adapter MAC address.
1417 kmemleak= [KNL] Boot-time kmemleak enable/disable
1418 Valid arguments: on, off
1421 kstack=N [X86] Print N words from the kernel stack
1424 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1425 Default is 0 (don't ignore, but inject #GP)
1427 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1431 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1432 Default is 1 (enabled)
1434 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1436 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1438 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1439 (virtualized MMU) support on capable Intel chips.
1440 Default is 1 (enabled)
1442 kvm-intel.emulate_invalid_guest_state=
1443 [KVM,Intel] Enable emulation of invalid guest states
1444 Default is 0 (disabled)
1446 kvm-intel.flexpriority=
1447 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1448 Default is 1 (enabled)
1451 [KVM,Intel] Enable VMX nesting (nVMX).
1452 Default is 0 (disabled)
1454 kvm-intel.unrestricted_guest=
1455 [KVM,Intel] Disable unrestricted guest feature
1456 (virtualized real and unpaged mode) on capable
1457 Intel chips. Default is 1 (enabled)
1459 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1460 feature (tagged TLBs) on capable Intel chips.
1461 Default is 1 (enabled)
1467 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1470 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1471 value for LAPIC timer one-shot implementation. Default
1472 back to the programmable timer unit in the LAPIC.
1474 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1477 libata.dma= [LIBATA] DMA control
1478 libata.dma=0 Disable all PATA and SATA DMA
1479 libata.dma=1 PATA and SATA Disk DMA only
1480 libata.dma=2 ATAPI (CDROM) DMA only
1481 libata.dma=4 Compact Flash DMA only
1482 Combinations also work, so libata.dma=3 enables DMA
1483 for disks and CDROMs, but not CFs.
1485 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1486 libata.ignore_hpa=0 keep BIOS limits (default)
1487 libata.ignore_hpa=1 ignore limits, using full disk
1489 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1493 libata.force= [LIBATA] Force configurations. The format is comma
1494 separated list of "[ID:]VAL" where ID is
1495 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1496 matching port, link or device. Basically, it matches
1497 the ATA ID string printed on console by libata. If
1498 the whole ID part is omitted, the last PORT and DEVICE
1499 values are used. If ID hasn't been specified yet, the
1500 configuration applies to all ports, links and devices.
1502 If only DEVICE is omitted, the parameter applies to
1503 the port and all links and devices behind it. DEVICE
1504 number of 0 either selects the first device or the
1505 first fan-out link behind PMP device. It does not
1506 select the host link. DEVICE number of 15 selects the
1507 host link and device attached to it.
1509 The VAL specifies the configuration to force. As long
1510 as there's no ambiguity shortcut notation is allowed.
1511 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1512 The following configurations can be forced.
1514 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1515 Any ID with matching PORT is used.
1517 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1519 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1520 udma[/][16,25,33,44,66,100,133] notation is also
1523 * [no]ncq: Turn on or off NCQ.
1525 * nohrst, nosrst, norst: suppress hard, soft
1528 * rstonce: only attempt one reset during
1529 hot-unplug link recovery
1531 * dump_id: dump IDENTIFY data.
1533 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1535 * disable: Disable this device.
1537 If there are multiple matching configurations changing
1538 the same attribute, the last one is used.
1540 memblock=debug [KNL] Enable memblock debug messages.
1542 load_ramdisk= [RAM] List of ramdisks to load from floppy
1543 See Documentation/blockdev/ramdisk.txt.
1545 lockd.nlm_grace_period=P [NFS] Assign grace period.
1548 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1551 lockd.nlm_timeout=T [NFS] Assign timeout value.
1554 lockd.nlm_udpport=M [NFS] Assign UDP port.
1557 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1560 loglevel= All Kernel Messages with a loglevel smaller than the
1561 console loglevel will be printed to the console. It can
1562 also be changed with klogd or other programs. The
1563 loglevels are defined as follows:
1565 0 (KERN_EMERG) system is unusable
1566 1 (KERN_ALERT) action must be taken immediately
1567 2 (KERN_CRIT) critical conditions
1568 3 (KERN_ERR) error conditions
1569 4 (KERN_WARNING) warning conditions
1570 5 (KERN_NOTICE) normal but significant condition
1571 6 (KERN_INFO) informational
1572 7 (KERN_DEBUG) debug-level messages
1574 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1575 in bytes. n must be a power of two. The default
1576 size is set in the kernel config file.
1578 logo.nologo [FB] Disables display of the built-in Linux logo.
1579 This may be used to provide more screen space for
1580 kernel log messages and is useful when debugging
1581 kernel boot problems.
1583 lp=0 [LP] Specify parallel ports to use, e.g,
1584 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1585 lp=reset first parallel port). 'lp=0' disables the
1586 lp=auto printer driver. 'lp=reset' (which can be
1587 specified in addition to the ports) causes
1588 attached printers to be reset. Using
1589 lp=port1,port2,... specifies the parallel ports
1590 to associate lp devices with, starting with
1591 lp0. A port specification may be 'none' to skip
1592 that lp device, or a parport name such as
1593 'parport0'. Specifying 'lp=auto' instead of a
1594 port specification list means that device IDs
1595 from each port should be examined, to see if
1596 an IEEE 1284-compliant printer is attached; if
1597 so, the driver will manage that printer.
1598 See also header of drivers/char/lp.c.
1601 Sets loops_per_jiffy to given constant, thus avoiding
1602 time-consuming boot-time autodetection (up to 250 ms per
1603 CPU). 0 enables autodetection (default). To determine
1604 the correct value for your kernel, boot with normal
1605 autodetection and see what value is printed. Note that
1606 on SMP systems the preset will be applied to all CPUs,
1607 which is likely to cause problems if your CPUs need
1608 significantly divergent settings. An incorrect value
1609 will cause delays in the kernel to be wrong, leading to
1610 unpredictable I/O errors and other breakage. Although
1611 unlikely, in the extreme case this might damage your
1615 Format: <io>,<irq>,<dma>
1617 machvec= [IA-64] Force the use of a particular machine-vector
1618 (machvec) in a generic kernel.
1619 Example: machvec=hpzx1_swiotlb
1621 machtype= [Loongson] Share the same kernel image file between different
1623 Example: machtype=lemote-yeeloong-2f-7inch
1625 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1626 than or equal to this physical address is ignored.
1628 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1629 should make use of. maxcpus=n : n >= 0 limits the
1630 kernel to using 'n' processors. n=0 is a special case,
1631 it is equivalent to "nosmp", which also disables
1634 max_loop= [LOOP] The number of loop block devices that get
1635 (loop.max_loop) unconditionally pre-created at init time. The default
1636 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1637 of statically allocating a predefined number, loop
1638 devices can be requested on-demand with the
1639 /dev/loop-control interface.
1641 mce [X86-32] Machine Check Exception
1643 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1645 md= [HW] RAID subsystems devices and level
1646 See Documentation/md.txt.
1649 Format: <first>,<last>
1650 Specifies range of consoles to be captured by the MDA.
1652 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1653 Amount of memory to be used when the kernel is not able
1654 to see the whole system memory or for test.
1655 [X86] Work as limiting max address. Use together
1656 with memmap= to avoid physical address space collisions.
1657 Without memmap= PCI devices could be placed at addresses
1658 belonging to unused RAM.
1660 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1664 [KNL,SH] Allow user to override the default size for
1665 per-device physically contiguous DMA buffers.
1667 memmap=exactmap [KNL,X86] Enable setting of an exact
1668 E820 memory map, as specified by the user.
1669 Such memmap=exactmap lines can be constructed based on
1670 BIOS output or other requirements. See the memmap=nn@ss
1673 memmap=nn[KMG]@ss[KMG]
1674 [KNL] Force usage of a specific region of memory
1675 Region of memory to be used, from ss to ss+nn.
1677 memmap=nn[KMG]#ss[KMG]
1678 [KNL,ACPI] Mark specific memory as ACPI data.
1679 Region of memory to be used, from ss to ss+nn.
1681 memmap=nn[KMG]$ss[KMG]
1682 [KNL,ACPI] Mark specific memory as reserved.
1683 Region of memory to be used, from ss to ss+nn.
1684 Example: Exclude memory from 0x18690000-0x1869ffff
1685 memmap=64K$0x18690000
1687 memmap=0x10000$0x18690000
1689 memory_corruption_check=0/1 [X86]
1690 Some BIOSes seem to corrupt the first 64k of
1691 memory when doing things like suspend/resume.
1692 Setting this option will scan the memory
1693 looking for corruption. Enabling this will
1694 both detect corruption and prevent the kernel
1695 from using the memory being corrupted.
1696 However, its intended as a diagnostic tool; if
1697 repeatable BIOS-originated corruption always
1698 affects the same memory, you can use memmap=
1699 to prevent the kernel from using that memory.
1701 memory_corruption_check_size=size [X86]
1702 By default it checks for corruption in the low
1703 64k, making this memory unavailable for normal
1704 use. Use this parameter to scan for
1705 corruption in more or less memory.
1707 memory_corruption_check_period=seconds [X86]
1708 By default it checks for corruption every 60
1709 seconds. Use this parameter to check at some
1710 other rate. 0 disables periodic checking.
1712 memtest= [KNL,X86] Enable memtest
1714 default : 0 <disable>
1715 Specifies the number of memtest passes to be
1716 performed. Each pass selects another test
1717 pattern from a given set of patterns. Memtest
1718 fills the memory with this pattern, validates
1719 memory contents and reserves bad memory
1720 regions that are detected.
1722 meye.*= [HW] Set MotionEye Camera parameters
1723 See Documentation/video4linux/meye.txt.
1725 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1726 Multi-Function General Purpose Timers on AMD Geode
1729 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1730 the BIOS has incorrectly applied a workaround. TinyBIOS
1731 version 0.98 is known to be affected, 0.99 fixes the
1732 problem by letting the user disable the workaround.
1736 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1737 physical address is ignored.
1739 mini2440= [ARM,HW,KNL]
1740 Format:[0..2][b][c][t]
1742 MINI2440 configuration specification:
1743 0 - The attached screen is the 3.5" TFT
1744 1 - The attached screen is the 7" TFT
1745 2 - The VGA Shield is attached (1024x768)
1746 Leaving out the screen size parameter will not load
1747 the TFT driver, and the framebuffer will be left
1749 b - Enable backlight. The TFT backlight pin will be
1750 linked to the kernel VESA blanking code and a GPIO
1751 LED. This parameter is not necessary when using the
1753 c - Enable the s3c camera interface.
1754 t - Reserved for enabling touchscreen support. The
1755 touchscreen support is not enabled in the mainstream
1756 kernel as of 2.6.30, a preliminary port can be found
1757 in the "bleeding edge" mini2440 support kernel at
1758 http://repo.or.cz/w/linux-2.6/mini2440.git
1761 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1762 parameter allows control of the logging verbosity for
1763 the additional memory initialisation checks. A value
1764 of 0 disables mminit logging and a level of 4 will
1765 log everything. Information is printed at KERN_DEBUG
1766 so loglevel=8 may also need to be specified.
1769 [KNL] When CONFIG_MODULE_SIG is set, this means that
1770 modules without (valid) signatures will fail to load.
1771 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1772 is always true, so this option does nothing.
1775 [MOUSE] Maximum time between finger touching and
1776 leaving touchpad surface for touch to be considered
1777 a tap and be reported as a left button click (for
1778 touchpads working in absolute mode only).
1780 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1781 reporting absolute coordinates, such as tablets
1782 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1783 reporting absolute coordinates, such as tablets
1785 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1786 is similar to kernelcore except it specifies the
1787 amount of memory used for migratable allocations.
1788 If both kernelcore and movablecore is specified,
1789 then kernelcore will be at *least* the specified
1790 value but may be more. If movablecore on its own
1791 is specified, the administrator must be careful
1792 that the amount of memory usable for all allocations
1795 movable_node [KNL,X86] Boot-time switch to enable the effects
1796 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1798 MTD_Partition= [MTD]
1799 Format: <name>,<region-number>,<size>,<offset>
1801 MTD_Region= [MTD] Format:
1802 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1805 See drivers/mtd/cmdlinepart.c.
1807 multitce=off [PPC] This parameter disables the use of the pSeries
1808 firmware feature for updating multiple TCE entries
1811 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1813 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1815 boundary - index of last SLC block on Flex-OneNAND.
1816 The remaining blocks are configured as MLC blocks.
1817 lock - Configure if Flex-OneNAND boundary should be locked.
1818 Once locked, the boundary cannot be changed.
1819 1 indicates lock status, 0 indicates unlock status.
1822 ARM/S3C2412 JIVE boot control
1824 See arch/arm/mach-s3c2412/mach-jive.c
1826 mtouchusb.raw_coordinates=
1827 [HW] Make the MicroTouch USB driver use raw coordinates
1828 ('y', default) or cooked coordinates ('n')
1830 mtrr_chunk_size=nn[KMG] [X86]
1831 used for mtrr cleanup. It is largest continuous chunk
1832 that could hold holes aka. UC entries.
1834 mtrr_gran_size=nn[KMG] [X86]
1835 Used for mtrr cleanup. It is granularity of mtrr block.
1837 Large value could prevent small alignment from
1840 mtrr_spare_reg_nr=n [X86]
1842 Range: 0,7 : spare reg number
1844 Used for mtrr cleanup. It is spare mtrr entries number.
1845 Set to 2 or more if your graphical card needs more.
1847 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1849 netdev= [NET] Network devices parameters
1850 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1851 Note that mem_start is often overloaded to mean
1852 something different and driver-specific.
1853 This usage is only documented in each driver source
1857 [NETFILTER] Enable connection tracking flow accounting
1858 0 to disable accounting
1859 1 to enable accounting
1862 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1863 See Documentation/filesystems/nfs/nfsroot.txt.
1865 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1866 See Documentation/filesystems/nfs/nfsroot.txt.
1868 nfsrootdebug [NFS] enable nfsroot debugging messages.
1869 See Documentation/filesystems/nfs/nfsroot.txt.
1871 nfs.callback_tcpport=
1872 [NFS] set the TCP port on which the NFSv4 callback
1873 channel should listen.
1876 [NFS] sets the pathname to the program which is used
1877 to update the NFS client cache entries.
1879 nfs.cache_getent_timeout=
1880 [NFS] sets the timeout after which an attempt to
1881 update a cache entry is deemed to have failed.
1883 nfs.idmap_cache_timeout=
1884 [NFS] set the maximum lifetime for idmapper cache
1888 [NFS] enable 64-bit inode numbers.
1889 If zero, the NFS client will fake up a 32-bit inode
1890 number for the readdir() and stat() syscalls instead
1891 of returning the full 64-bit number.
1892 The default is to return 64-bit inode numbers.
1894 nfs.max_session_slots=
1895 [NFSv4.1] Sets the maximum number of session slots
1896 the client will attempt to negotiate with the server.
1897 This limits the number of simultaneous RPC requests
1898 that the client can send to the NFSv4.1 server.
1899 Note that there is little point in setting this
1900 value higher than the max_tcp_slot_table_limit.
1902 nfs.nfs4_disable_idmapping=
1903 [NFSv4] When set to the default of '1', this option
1904 ensures that both the RPC level authentication
1905 scheme and the NFS level operations agree to use
1906 numeric uids/gids if the mount is using the
1907 'sec=sys' security flavour. In effect it is
1908 disabling idmapping, which can make migration from
1909 legacy NFSv2/v3 systems to NFSv4 easier.
1910 Servers that do not support this mode of operation
1911 will be autodetected by the client, and it will fall
1912 back to using the idmapper.
1913 To turn off this behaviour, set the value to '0'.
1915 [NFS4] Specify an additional fixed unique ident-
1916 ification string that NFSv4 clients can insert into
1917 their nfs_client_id4 string. This is typically a
1918 UUID that is generated at system install time.
1920 nfs.send_implementation_id =
1921 [NFSv4.1] Send client implementation identification
1922 information in exchange_id requests.
1923 If zero, no implementation identification information
1925 The default is to send the implementation identification
1928 nfs.recover_lost_locks =
1929 [NFSv4] Attempt to recover locks that were lost due
1930 to a lease timeout on the server. Please note that
1931 doing this risks data corruption, since there are
1932 no guarantees that the file will remain unchanged
1933 after the locks are lost.
1934 If you want to enable the kernel legacy behaviour of
1935 attempting to recover these locks, then set this
1937 The default parameter value of '0' causes the kernel
1938 not to attempt recovery of lost locks.
1940 nfsd.nfs4_disable_idmapping=
1941 [NFSv4] When set to the default of '1', the NFSv4
1942 server will return only numeric uids and gids to
1943 clients using auth_sys, and will accept numeric uids
1944 and gids from such clients. This is intended to ease
1945 migration from NFSv2/v3.
1947 objlayoutdriver.osd_login_prog=
1948 [NFS] [OBJLAYOUT] sets the pathname to the program which
1949 is used to automatically discover and login into new
1950 osd-targets. Please see:
1951 Documentation/filesystems/pnfs.txt for more explanations
1953 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1954 when a NMI is triggered.
1955 Format: [state][,regs][,debounce][,die]
1957 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1958 Format: [panic,][nopanic,][num]
1960 0 - turn nmi_watchdog off
1961 When panic is specified, panic when an NMI watchdog
1962 timeout occurs (or 'nopanic' to override the opposite
1964 This is useful when you use a panic=... timeout and
1965 need the box quickly up again.
1967 netpoll.carrier_timeout=
1968 [NET] Specifies amount of time (in seconds) that
1969 netpoll should wait for a carrier. By default netpoll
1972 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1973 emulation library even if a 387 maths coprocessor
1977 [HW] Never suspend the console
1978 Disable suspending of consoles during suspend and
1979 hibernate operations. Once disabled, debugging
1980 messages can reach various consoles while the rest
1981 of the system is being put to sleep (ie, while
1982 debugging driver suspend/resume hooks). This may
1983 not work reliably with all consoles, but is known
1984 to work with serial and VGA consoles.
1985 To facilitate more flexible debugging, we also add
1986 console_suspend, a printk module parameter to control
1987 it. Users could use console_suspend (usually
1988 /sys/module/printk/parameters/console_suspend) to
1989 turn on/off it dynamically.
1991 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1992 caches in the slab allocator. Saves per-node memory,
1993 but will impact performance.
1997 noapic [SMP,APIC] Tells the kernel to not make use of any
1998 IOAPICs that may be present in the system.
2000 noautogroup Disable scheduler automatic task group creation.
2002 nobats [PPC] Do not use BATs for mapping kernel lowmem
2003 on "Classic" PPC cores.
2007 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2009 nodelayacct [KNL] Disable per-task delay accounting
2011 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2013 nodsp [SH] Disable hardware DSP at boot time.
2015 noefi [X86] Disable EFI runtime services support.
2020 On X86-32 available only on PAE configured kernels.
2021 noexec=on: enable non-executable mappings (default)
2022 noexec=off: disable non-executable mappings
2025 Disable SMAP (Supervisor Mode Access Prevention)
2026 even if it is supported by processor.
2029 Disable SMEP (Supervisor Mode Execution Prevention)
2030 even if it is supported by processor.
2033 This affects only 32-bit executables.
2034 noexec32=on: enable non-executable mappings (default)
2035 read doesn't imply executable mappings
2036 noexec32=off: disable non-executable mappings
2037 read implies executable mappings
2039 nofpu [SH] Disable hardware FPU at boot time.
2041 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2042 register save and restore. The kernel will only save
2043 legacy floating-point registers on task switch.
2045 noxsave [BUGS=X86] Disables x86 extended register state save
2046 and restore using xsave. The kernel will fallback to
2047 enabling legacy floating-point and sse state.
2050 on enable eager fpu restore
2051 off disable eager fpu restore
2052 auto selects the default scheme, which automatically
2053 enables eagerfpu restore for xsaveopt.
2055 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2056 wfi(ARM) instruction doesn't work correctly and not to
2057 use it. This is also useful when using JTAG debugger.
2059 no_file_caps Tells the kernel not to honor file capabilities. The
2060 only way then for a file to be executed with privilege
2061 is to be setuid root or executed by root.
2063 nohalt [IA-64] Tells the kernel not to use the power saving
2064 function PAL_HALT_LIGHT when idle. This increases
2065 power-consumption. On the positive side, it reduces
2066 interrupt wake-up latency, which may improve performance
2067 in certain environments such as networked servers or
2070 nohz= [KNL] Boottime enable/disable dynamic ticks
2071 Valid arguments: on, off
2074 nohz_full= [KNL,BOOT]
2075 In kernels built with CONFIG_NO_HZ_FULL=y, set
2076 the specified list of CPUs whose tick will be stopped
2077 whenever possible. The boot CPU will be forced outside
2078 the range to maintain the timekeeping.
2079 The CPUs in this range must also be included in the
2082 noiotrap [SH] Disables trapped I/O port accesses.
2084 noirqdebug [X86-32] Disables the code which attempts to detect and
2085 disable unhandled interrupt sources.
2087 no_timer_check [X86,APIC] Disables the code which tests for
2088 broken timer IRQ sources.
2090 noisapnp [ISAPNP] Disables ISA PnP code.
2092 noinitrd [RAM] Tells the kernel not to load any configured
2095 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2097 [Deprecated - use intremap=off]
2101 nojitter [IA-64] Disables jitter checking for ITC timers.
2103 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2105 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2108 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2109 steal time is computed, but won't influence scheduler
2112 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2114 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2116 noltlbs [PPC] Do not use large page/tlb entries for kernel
2117 lowmem mapping on PPC40x.
2119 nomca [IA-64] Disable machine check abort handling
2121 nomce [X86-32] Machine Check Exception
2123 nomfgpt [X86-32] Disable Multi-Function General Purpose
2124 Timer usage (for AMD Geode machines).
2126 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2127 shutdown the other cpus. Instead use the REBOOT_VECTOR
2130 nomodule Disable module load
2132 nopat [X86] Disable PAT (page attribute table extension of
2133 pagetables) support.
2135 norandmaps Don't use address space randomization. Equivalent to
2136 echo 0 > /proc/sys/kernel/randomize_va_space
2138 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2140 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2141 with UP alternatives
2143 nordrand [X86] Disable the direct use of the RDRAND
2144 instruction even if it is supported by the
2145 processor. RDRAND is still available to user
2148 noresume [SWSUSP] Disables resume and restores original swap
2151 no-scroll [VGA] Disables scrollback.
2152 This is required for the Braillex ib80-piezo Braille
2153 reader made by F.H. Papenmeier (Germany).
2157 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2159 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2160 and disable the IO APIC. legacy for "maxcpus=0".
2162 nosoftlockup [KNL] Disable the soft-lockup detector.
2164 nosync [HW,M68K] Disables sync negotiation for all devices.
2166 notsc [BUGS=X86-32] Disable Time Stamp Counter
2168 nousb [USB] Disable the USB subsystem
2170 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2174 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2176 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2177 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2178 Some features depend on CPU0. Known dependencies are:
2179 1. Resume from suspend/hibernate depends on CPU0.
2180 Suspend/hibernate will fail if CPU0 is offline and you
2181 need to online CPU0 before suspend/hibernate.
2182 2. PIC interrupts also depend on CPU0. CPU0 can't be
2183 removed if a PIC interrupt is detected.
2184 It's said poweroff/reboot may depend on CPU0 on some
2185 machines although I haven't seen such issues so far
2186 after CPU0 is offline on a few tested machines.
2187 If the dependencies are under your control, you can
2188 turn on cpu0_hotplug.
2190 nptcg= [IA-64] Override max number of concurrent global TLB
2191 purges which is reported from either PAL_VM_SUMMARY or
2194 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2195 could support. nr_cpus=n : n >= 1 limits the kernel to
2196 supporting 'n' processors. Later in runtime you can not
2197 use hotplug cpu feature to put more cpu back to online.
2198 just like you compile the kernel NR_CPUS=n
2200 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2202 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2203 Allowed values are enable and disable
2205 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2206 one of ['zone', 'node', 'default'] can be specified
2207 This can be set from sysctl after boot.
2208 See Documentation/sysctl/vm.txt for details.
2210 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2211 See Documentation/debugging-via-ohci1394.txt for more
2214 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2215 Rather than timing out after 20 ms if an EC
2216 command is not properly ACKed, override the length
2217 of the timeout. We have interrupts disabled while
2218 waiting for the ACK, so if this is set too high
2219 interrupts *may* be lost!
2221 omap_mux= [OMAP] Override bootloader pin multiplexing.
2222 Format: <mux_mode0.mode_name=value>...
2223 For example, to override I2C bus2:
2224 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2226 oprofile.timer= [HW]
2227 Use timer interrupt instead of performance counters
2229 oprofile.cpu_type= Force an oprofile cpu type
2230 This might be useful if you have an older oprofile
2231 userland or if you want common events.
2232 Format: { arch_perfmon }
2233 arch_perfmon: [X86] Force use of architectural
2234 perfmon on Intel CPUs instead of the
2235 CPU specific event set.
2236 timer: [X86] Force use of architectural NMI
2237 timer mode (see also oprofile.timer
2238 for generic hr timer mode)
2239 [s390] Force legacy basic mode sampling
2240 (report cpu_type "timer")
2242 oops=panic Always panic on oopses. Default is to just kill the
2243 process, but there is a small probability of
2244 deadlocking the machine.
2245 This will also cause panics on machine check exceptions.
2246 Useful together with panic=30 to trigger a reboot.
2249 See Documentation/sound/oss/oss-parameters.txt
2251 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2252 timeout > 0: seconds before rebooting
2253 timeout = 0: wait forever
2254 timeout < 0: reboot immediately
2257 parkbd.port= [HW] Parallel port number the keyboard adapter is
2258 connected to, default is 0.
2260 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2261 0 for XT, 1 for AT (default is AT).
2264 parport= [HW,PPT] Specify parallel ports. 0 disables.
2265 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2266 Use 'auto' to force the driver to use any
2267 IRQ/DMA settings detected (the default is to
2268 ignore detected IRQ/DMA settings because of
2269 possible conflicts). You can specify the base
2270 address, IRQ, and DMA settings; IRQ and DMA
2271 should be numbers, or 'auto' (for using detected
2272 settings on that particular port), or 'nofifo'
2273 (to avoid using a FIFO even if it is detected).
2274 Parallel ports are assigned in the order they
2275 are specified on the command line, starting
2278 parport_init_mode= [HW,PPT]
2279 Configure VIA parallel port to operate in
2280 a specific mode. This is necessary on Pegasos
2281 computer where firmware has no options for setting
2282 up parallel port mode and sets it to spp.
2283 Currently this function knows 686a and 8231 chips.
2284 Format: [spp|ps2|epp|ecp|ecpepp]
2287 Halt all CPUs after the first oops has been printed for
2288 the specified number of seconds. This is to be used if
2289 your oopses keep scrolling off the screen.
2294 See header of drivers/block/paride/pcd.c.
2295 See also Documentation/blockdev/paride.txt.
2297 pci=option[,option...] [PCI] various PCI subsystem options:
2298 earlydump [X86] dump PCI config space before the kernel
2300 off [X86] don't probe for the PCI bus
2301 bios [X86-32] force use of PCI BIOS, don't access
2302 the hardware directly. Use this if your machine
2303 has a non-standard PCI host bridge.
2304 nobios [X86-32] disallow use of PCI BIOS, only direct
2305 hardware access methods are allowed. Use this
2306 if you experience crashes upon bootup and you
2307 suspect they are caused by the BIOS.
2308 conf1 [X86] Force use of PCI Configuration
2310 conf2 [X86] Force use of PCI Configuration
2312 noaer [PCIE] If the PCIEAER kernel config parameter is
2313 enabled, this kernel boot option can be used to
2314 disable the use of PCIE advanced error reporting.
2315 nodomains [PCI] Disable support for multiple PCI
2316 root domains (aka PCI segments, in ACPI-speak).
2317 nommconf [X86] Disable use of MMCONFIG for PCI
2319 check_enable_amd_mmconf [X86] check for and enable
2320 properly configured MMIO access to PCI
2321 config space on AMD family 10h CPU
2322 nomsi [MSI] If the PCI_MSI kernel config parameter is
2323 enabled, this kernel boot option can be used to
2324 disable the use of MSI interrupts system-wide.
2325 noioapicquirk [APIC] Disable all boot interrupt quirks.
2326 Safety option to keep boot IRQs enabled. This
2327 should never be necessary.
2328 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2329 primary IO-APIC for bridges that cannot disable
2330 boot IRQs. This fixes a source of spurious IRQs
2331 when the system masks IRQs.
2332 noioapicreroute [APIC] Disable workaround that uses the
2333 boot IRQ equivalent of an IRQ that connects to
2334 a chipset where boot IRQs cannot be disabled.
2335 The opposite of ioapicreroute.
2336 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2337 routing table. These calls are known to be buggy
2338 on several machines and they hang the machine
2339 when used, but on other computers it's the only
2340 way to get the interrupt routing table. Try
2341 this option if the kernel is unable to allocate
2342 IRQs or discover secondary PCI buses on your
2344 rom [X86] Assign address space to expansion ROMs.
2345 Use with caution as certain devices share
2346 address decoders between ROMs and other
2348 norom [X86] Do not assign address space to
2349 expansion ROMs that do not already have
2350 BIOS assigned address ranges.
2351 nobar [X86] Do not assign address space to the
2352 BARs that weren't assigned by the BIOS.
2353 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2354 assigned automatically to PCI devices. You can
2355 make the kernel exclude IRQs of your ISA cards
2357 pirqaddr=0xAAAAA [X86] Specify the physical address
2358 of the PIRQ table (normally generated
2359 by the BIOS) if it is outside the
2360 F0000h-100000h range.
2361 lastbus=N [X86] Scan all buses thru bus #N. Can be
2362 useful if the kernel is unable to find your
2363 secondary buses and you want to tell it
2364 explicitly which ones they are.
2365 assign-busses [X86] Always assign all PCI bus
2366 numbers ourselves, overriding
2367 whatever the firmware may have done.
2368 usepirqmask [X86] Honor the possible IRQ mask stored
2369 in the BIOS $PIR table. This is needed on
2370 some systems with broken BIOSes, notably
2371 some HP Pavilion N5400 and Omnibook XE3
2372 notebooks. This will have no effect if ACPI
2373 IRQ routing is enabled.
2374 noacpi [X86] Do not use ACPI for IRQ routing
2375 or for PCI scanning.
2376 use_crs [X86] Use PCI host bridge window information
2377 from ACPI. On BIOSes from 2008 or later, this
2378 is enabled by default. If you need to use this,
2379 please report a bug.
2380 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2381 If you need to use this, please report a bug.
2382 routeirq Do IRQ routing for all PCI devices.
2383 This is normally done in pci_enable_device(),
2384 so this option is a temporary workaround
2385 for broken drivers that don't call it.
2386 skip_isa_align [X86] do not align io start addr, so can
2387 handle more pci cards
2388 firmware [ARM] Do not re-enumerate the bus but instead
2389 just use the configuration from the
2390 bootloader. This is currently used on
2391 IXP2000 systems where the bus has to be
2392 configured a certain way for adjunct CPUs.
2393 noearly [X86] Don't do any early type 1 scanning.
2394 This might help on some broken boards which
2395 machine check when some devices' config space
2396 is read. But various workarounds are disabled
2397 and some IOMMU drivers will not work.
2398 bfsort Sort PCI devices into breadth-first order.
2399 This sorting is done to get a device
2400 order compatible with older (<= 2.4) kernels.
2401 nobfsort Don't sort PCI devices into breadth-first order.
2402 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2403 tuning and use the BIOS-configured MPS defaults.
2404 pcie_bus_safe Set every device's MPS to the largest value
2405 supported by all devices below the root complex.
2406 pcie_bus_perf Set device MPS to the largest allowable MPS
2407 based on its parent bus. Also set MRRS (Max
2408 Read Request Size) to the largest supported
2409 value (no larger than the MPS that the device
2410 or bus can support) for best performance.
2411 pcie_bus_peer2peer Set every device's MPS to 128B, which
2412 every device is guaranteed to support. This
2413 configuration allows peer-to-peer DMA between
2414 any pair of devices, possibly at the cost of
2415 reduced performance. This also guarantees
2416 that hot-added devices will work.
2417 cbiosize=nn[KMG] The fixed amount of bus space which is
2418 reserved for the CardBus bridge's IO window.
2419 The default value is 256 bytes.
2420 cbmemsize=nn[KMG] The fixed amount of bus space which is
2421 reserved for the CardBus bridge's memory
2422 window. The default value is 64 megabytes.
2425 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2426 Specifies alignment and device to reassign
2427 aligned memory resources.
2428 If <order of align> is not specified,
2429 PAGE_SIZE is used as alignment.
2430 PCI-PCI bridge can be specified, if resource
2431 windows need to be expanded.
2432 ecrc= Enable/disable PCIe ECRC (transaction layer
2433 end-to-end CRC checking).
2434 bios: Use BIOS/firmware settings. This is the
2438 hpiosize=nn[KMG] The fixed amount of bus space which is
2439 reserved for hotplug bridge's IO window.
2440 Default size is 256 bytes.
2441 hpmemsize=nn[KMG] The fixed amount of bus space which is
2442 reserved for hotplug bridge's memory window.
2443 Default size is 2 megabytes.
2444 realloc= Enable/disable reallocating PCI bridge resources
2445 if allocations done by BIOS are too small to
2446 accommodate resources required by all child
2448 off: Turn realloc off
2450 realloc same as realloc=on
2451 noari do not use PCIe ARI.
2452 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2453 only look for one device below a PCIe downstream
2456 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2459 force Enable ASPM even on devices that claim not to support it.
2460 WARNING: Forcing ASPM on may cause system lockups.
2462 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2463 nomsi Do not use MSI for PCI Express Native Hotplug (this
2464 makes all PCIe ports use INTx for hotplug services).
2466 pcie_ports= [PCIE] PCIe ports handling:
2467 auto Ask the BIOS whether or not to use native PCIe services
2468 associated with PCIe ports (PME, hot-plug, AER). Use
2469 them only if that is allowed by the BIOS.
2470 native Use native PCIe services associated with PCIe ports
2472 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2475 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2476 nomsi Do not use MSI for native PCIe PME signaling (this makes
2477 all PCIe root ports use INTx for all services).
2479 pcmv= [HW,PCMCIA] BadgePAD 4
2482 See Documentation/blockdev/paride.txt.
2484 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2487 See arch/parisc/kernel/pdc_chassis.c
2489 percpu_alloc= Select which percpu first chunk allocator to use.
2490 Currently supported values are "embed" and "page".
2491 Archs may support subset or none of the selections.
2492 See comments in mm/percpu.c for details on each
2493 allocator. This parameter is primarily for debugging
2494 and performance comparison.
2497 See Documentation/blockdev/paride.txt.
2500 See Documentation/blockdev/paride.txt.
2502 pirq= [SMP,APIC] Manual mp-table setup
2503 See Documentation/x86/i386/IO-APIC.txt.
2505 plip= [PPT,NET] Parallel port network link
2506 Format: { parport<nr> | timid | 0 }
2507 See also Documentation/parport.txt.
2509 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2510 Override pmtimer IOPort with a hex value.
2514 Enable PNP debug messages (depends on the
2515 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2516 via /sys/module/pnp/parameters/debug. We always show
2517 current resource usage; turning this on also shows
2518 possible settings and some assignment information.
2524 { on | off | curr | res | no-curr | no-res }
2527 [ISAPNP] Exclude IRQs for the autoconfiguration
2530 [ISAPNP] Exclude DMAs for the autoconfiguration
2532 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2533 Ranges are in pairs (I/O port base and size).
2536 [ISAPNP] Exclude memory regions for the
2538 Ranges are in pairs (memory base and size).
2540 ports= [IP_VS_FTP] IPVS ftp helper module
2542 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2544 Format: <port>,<port>....
2546 print-fatal-signals=
2547 [KNL] debug: print fatal signals
2549 If enabled, warn about various signal handling
2550 related application anomalies: too many signals,
2551 too many POSIX.1 timers, fatal signals causing a
2554 If you hit the warning due to signal overflow,
2555 you might want to try "ulimit -i unlimited".
2559 printk.always_kmsg_dump=
2560 Trigger kmsg_dump for cases other than kernel oops or
2562 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2565 printk.time= Show timing data prefixed to each printk message line
2566 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2568 processor.max_cstate= [HW,ACPI]
2569 Limit processor to maximum C-state
2570 max_cstate=9 overrides any DMI blacklist limit.
2572 processor.nocst [HW,ACPI]
2573 Ignore the _CST method to determine C-states,
2574 instead using the legacy FADT method
2576 profile= [KNL] Enable kernel profiling via /proc/profile
2577 Format: [schedule,]<number>
2578 Param: "schedule" - profile schedule points.
2579 Param: <number> - step/bucket size as a power of 2 for
2580 statistical time based profiling.
2581 Param: "sleep" - profile D-state sleeping (millisecs).
2582 Requires CONFIG_SCHEDSTATS
2583 Param: "kvm" - profile VM exits.
2585 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2587 See Documentation/blockdev/ramdisk.txt.
2589 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2590 probe for; one of (bare|imps|exps|lifebook|any).
2591 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2593 psmouse.resetafter= [HW,MOUSE]
2594 Try to reset the device after so many bad packets
2597 [HW,MOUSE] Set desired mouse resolution, in dpi.
2598 psmouse.smartscroll=
2599 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2600 0 = disabled, 1 = enabled (default).
2602 pstore.backend= Specify the name of the pstore backend to use
2605 See Documentation/blockdev/paride.txt.
2608 [KNL] Number of legacy pty's. Overwrites compiled-in
2611 quiet [KNL] Disable most log messages
2616 See Documentation/md.txt.
2618 ramdisk_blocksize= [RAM]
2619 See Documentation/blockdev/ramdisk.txt.
2621 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2622 See Documentation/blockdev/ramdisk.txt.
2625 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2626 the specified list of CPUs to be no-callback CPUs.
2627 Invocation of these CPUs' RCU callbacks will
2628 be offloaded to "rcuox/N" kthreads created for
2629 that purpose, where "x" is "b" for RCU-bh, "p"
2630 for RCU-preempt, and "s" for RCU-sched, and "N"
2631 is the CPU number. This reduces OS jitter on the
2632 offloaded CPUs, which can be useful for HPC and
2634 real-time workloads. It can also improve energy
2635 efficiency for asymmetric multiprocessors.
2638 Rather than requiring that offloaded CPUs
2639 (specified by rcu_nocbs= above) explicitly
2640 awaken the corresponding "rcuoN" kthreads,
2641 make these kthreads poll for callbacks.
2642 This improves the real-time response for the
2643 offloaded CPUs by relieving them of the need to
2644 wake up the corresponding kthread, but degrades
2645 energy efficiency by requiring that the kthreads
2646 periodically wake up to do the polling.
2648 rcutree.blimit= [KNL]
2649 Set maximum number of finished RCU callbacks to process
2652 rcutree.rcu_fanout_leaf= [KNL]
2653 Increase the number of CPUs assigned to each
2654 leaf rcu_node structure. Useful for very large
2657 rcutree.jiffies_till_first_fqs= [KNL]
2658 Set delay from grace-period initialization to
2659 first attempt to force quiescent states.
2660 Units are jiffies, minimum value is zero,
2661 and maximum value is HZ.
2663 rcutree.jiffies_till_next_fqs= [KNL]
2664 Set delay between subsequent attempts to force
2665 quiescent states. Units are jiffies, minimum
2666 value is one, and maximum value is HZ.
2668 rcutree.qhimark= [KNL]
2669 Set threshold of queued
2670 RCU callbacks over which batch limiting is disabled.
2672 rcutree.qlowmark= [KNL]
2673 Set threshold of queued RCU callbacks below which
2674 batch limiting is re-enabled.
2676 rcutree.rcu_idle_gp_delay= [KNL]
2677 Set wakeup interval for idle CPUs that have
2678 RCU callbacks (RCU_FAST_NO_HZ=y).
2680 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2681 Set wakeup interval for idle CPUs that have
2682 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2683 Lazy RCU callbacks are those which RCU can
2684 prove do nothing more than free memory.
2686 rcutorture.fqs_duration= [KNL]
2687 Set duration of force_quiescent_state bursts.
2689 rcutorture.fqs_holdoff= [KNL]
2690 Set holdoff time within force_quiescent_state bursts.
2692 rcutorture.fqs_stutter= [KNL]
2693 Set wait time between force_quiescent_state bursts.
2695 rcutorture.gp_exp= [KNL]
2696 Use expedited update-side primitives.
2698 rcutorture.gp_normal= [KNL]
2699 Use normal (non-expedited) update-side primitives.
2700 If both gp_exp and gp_normal are set, do both.
2701 If neither gp_exp nor gp_normal are set, still
2704 rcutorture.n_barrier_cbs= [KNL]
2705 Set callbacks/threads for rcu_barrier() testing.
2707 rcutorture.nfakewriters= [KNL]
2708 Set number of concurrent RCU writers. These just
2709 stress RCU, they don't participate in the actual
2710 test, hence the "fake".
2712 rcutorture.nreaders= [KNL]
2713 Set number of RCU readers.
2715 rcutorture.object_debug= [KNL]
2716 Enable debug-object double-call_rcu() testing.
2718 rcutorture.onoff_holdoff= [KNL]
2719 Set time (s) after boot for CPU-hotplug testing.
2721 rcutorture.onoff_interval= [KNL]
2722 Set time (s) between CPU-hotplug operations, or
2723 zero to disable CPU-hotplug testing.
2725 rcutorture.rcutorture_runnable= [BOOT]
2726 Start rcutorture running at boot time.
2728 rcutorture.shuffle_interval= [KNL]
2729 Set task-shuffle interval (s). Shuffling tasks
2730 allows some CPUs to go into dyntick-idle mode
2731 during the rcutorture test.
2733 rcutorture.shutdown_secs= [KNL]
2734 Set time (s) after boot system shutdown. This
2735 is useful for hands-off automated testing.
2737 rcutorture.stall_cpu= [KNL]
2738 Duration of CPU stall (s) to test RCU CPU stall
2739 warnings, zero to disable.
2741 rcutorture.stall_cpu_holdoff= [KNL]
2742 Time to wait (s) after boot before inducing stall.
2744 rcutorture.stat_interval= [KNL]
2745 Time (s) between statistics printk()s.
2747 rcutorture.stutter= [KNL]
2748 Time (s) to stutter testing, for example, specifying
2749 five seconds causes the test to run for five seconds,
2750 wait for five seconds, and so on. This tests RCU's
2751 ability to transition abruptly to and from idle.
2753 rcutorture.test_boost= [KNL]
2754 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2755 "Maybe" means test if the RCU implementation
2756 under test support RCU priority boosting.
2758 rcutorture.test_boost_duration= [KNL]
2759 Duration (s) of each individual boost test.
2761 rcutorture.test_boost_interval= [KNL]
2762 Interval (s) between each boost test.
2764 rcutorture.test_no_idle_hz= [KNL]
2765 Test RCU's dyntick-idle handling. See also the
2766 rcutorture.shuffle_interval parameter.
2768 rcutorture.torture_type= [KNL]
2769 Specify the RCU implementation to test.
2771 rcutorture.verbose= [KNL]
2772 Enable additional printk() statements.
2774 rcupdate.rcu_expedited= [KNL]
2775 Use expedited grace-period primitives, for
2776 example, synchronize_rcu_expedited() instead
2777 of synchronize_rcu(). This reduces latency,
2778 but can increase CPU utilization, degrade
2779 real-time latency, and degrade energy efficiency.
2781 rcupdate.rcu_cpu_stall_suppress= [KNL]
2782 Suppress RCU CPU stall warning messages.
2784 rcupdate.rcu_cpu_stall_timeout= [KNL]
2785 Set timeout for RCU CPU stall warning messages.
2789 Run specified binary instead of /init from the ramdisk,
2790 used for early userspace startup. See initrd.
2793 Format (x86 or x86_64):
2794 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2796 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2798 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2799 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2800 reboot_force is either force or not specified,
2801 reboot_cpu is s[mp]#### with #### being the processor
2802 to be used for rebooting.
2805 [KNL, SMP] Set scheduler's default relax_domain_level.
2806 See Documentation/cgroups/cpusets.txt.
2808 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2810 reservetop= [X86-32]
2812 Reserves a hole at the top of the kernel virtual
2817 Set the amount of memory to reserve for BIOS at
2818 the bottom of the address space.
2820 reset_devices [KNL] Force drivers to reset the underlying device
2821 during initialization.
2824 Specify the partition device for software suspend
2826 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2828 resume_offset= [SWSUSP]
2829 Specify the offset from the beginning of the partition
2830 given by "resume=" at which the swap header is located,
2831 in <PAGE_SIZE> units (needed only for swap files).
2832 See Documentation/power/swsusp-and-swap-files.txt
2834 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2835 read the resume files
2837 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2838 Useful for devices that are detected asynchronously
2839 (e.g. USB and MMC devices).
2841 hibernate= [HIBERNATION]
2842 noresume Don't check if there's a hibernation image
2843 present during boot.
2844 nocompress Don't compress/decompress hibernation images.
2846 retain_initrd [RAM] Keep initrd memory after extraction
2848 rhash_entries= [KNL,NET]
2849 Set number of hash buckets for route cache
2851 riscom8= [HW,SERIAL]
2852 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2854 ro [KNL] Mount root device read-only on boot
2856 root= [KNL] Root filesystem
2857 See name_to_dev_t comment in init/do_mounts.c.
2859 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2860 mount the root filesystem
2862 rootflags= [KNL] Set root filesystem mount option string
2864 rootfstype= [KNL] Set root filesystem type
2866 rootwait [KNL] Wait (indefinitely) for root device to show up.
2867 Useful for devices that are detected asynchronously
2868 (e.g. USB and MMC devices).
2870 rproc_mem=nn[KMG][@address]
2871 [KNL,ARM,CMA] Remoteproc physical memory block.
2872 Memory area to be used by remote processor image,
2875 rw [KNL] Mount root device read-write on boot
2877 S [KNL] Run init in single mode
2880 See drivers/net/irda/sa1100_ir.c.
2882 sbni= [NET] Granch SBNI12 leased line adapter
2884 sched_debug [KNL] Enables verbose scheduler debug messages.
2886 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2887 xtime_lock contention on larger systems, and/or RCU lock
2888 contention on all systems with CONFIG_MAXSMP set.
2889 Format: { "0" | "1" }
2890 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2892 Note: increases power consumption, thus should only be
2893 enabled if running jitter sensitive (HPC/RT) workloads.
2895 security= [SECURITY] Choose a security module to enable at boot.
2896 If this boot parameter is not specified, only the first
2897 security module asking for security registration will be
2898 loaded. An invalid security module name will be treated
2899 as if no module has been chosen.
2901 selinux= [SELINUX] Disable or enable SELinux at boot time.
2902 Format: { "0" | "1" }
2903 See security/selinux/Kconfig help text.
2906 Default value is set via kernel config option.
2907 If enabled at boot time, /selinux/disable can be used
2908 later to disable prior to initial policy load.
2910 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2911 Format: { "0" | "1" }
2912 See security/apparmor/Kconfig help text
2915 Default value is set via kernel config option.
2917 serialnumber [BUGS=X86-32]
2920 Maximal number of shapers.
2922 show_msr= [x86] show boot-time MSR settings
2923 Format: { <integer> }
2924 Show boot-time (BIOS-initialized) MSR settings.
2925 The parameter means the number of CPUs to show,
2926 for example 1 means boot CPU only.
2933 slab_max_order= [MM, SLAB]
2934 Determines the maximum allowed order for slabs.
2935 A high setting may cause OOMs due to memory
2936 fragmentation. Defaults to 1 for systems with
2937 more than 32MB of RAM, 0 otherwise.
2939 slub_debug[=options[,slabs]] [MM, SLUB]
2940 Enabling slub_debug allows one to determine the
2941 culprit if slab objects become corrupted. Enabling
2942 slub_debug can create guard zones around objects and
2943 may poison objects when not in use. Also tracks the
2944 last alloc / free. For more information see
2945 Documentation/vm/slub.txt.
2947 slub_max_order= [MM, SLUB]
2948 Determines the maximum allowed order for slabs.
2949 A high setting may cause OOMs due to memory
2950 fragmentation. For more information see
2951 Documentation/vm/slub.txt.
2953 slub_min_objects= [MM, SLUB]
2954 The minimum number of objects per slab. SLUB will
2955 increase the slab order up to slub_max_order to
2956 generate a sufficiently large slab able to contain
2957 the number of objects indicated. The higher the number
2958 of objects the smaller the overhead of tracking slabs
2959 and the less frequently locks need to be acquired.
2960 For more information see Documentation/vm/slub.txt.
2962 slub_min_order= [MM, SLUB]
2963 Determines the minimum page order for slabs. Must be
2964 lower than slub_max_order.
2965 For more information see Documentation/vm/slub.txt.
2967 slub_nomerge [MM, SLUB]
2968 Disable merging of slabs with similar size. May be
2969 necessary if there is some reason to distinguish
2970 allocs to different slabs. Debug options disable
2971 merging on their own.
2972 For more information see Documentation/vm/slub.txt.
2975 Format: <io1>[,<io2>[,...,<io8>]]
2977 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2978 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2979 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2980 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2981 smsc-ircc2.ircc_irq= [HW] IRQ line
2982 smsc-ircc2.ircc_dma= [HW] DMA channel
2983 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2984 0: Toshiba Satellite 1800 (GP data pin select)
2985 1: Fast pin select (default)
2989 [KNL] Should the soft-lockup detector generate panics.
2992 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2993 See Documentation/laptops/sonypi.txt
2995 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2996 See Documentation/serial/specialix.txt.
2998 spia_io_base= [HW,MTD]
3004 Enabled the stack tracer on boot up.
3006 stacktrace_filter=[function-list]
3007 [FTRACE] Limit the functions that the stack tracer
3008 will trace at boot up. function-list is a comma separated
3009 list of functions. This list can be changed at run
3010 time by the stack_trace_filter file in the debugfs
3011 tracing directory. Note, this enables stack tracing
3012 and the stacktrace above is not needed.
3016 Set the STI (builtin display/keyboard on the HP-PARISC
3017 machines) console (graphic card) which should be used
3018 as the initial boot-console.
3019 See also comment in drivers/video/console/sticore.c.
3022 See comment in drivers/video/console/sticore.c.
3025 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3027 sunrpc.min_resvport=
3028 sunrpc.max_resvport=
3030 SunRPC servers often require that client requests
3031 originate from a privileged port (i.e. a port in the
3032 range 0 < portnr < 1024).
3033 An administrator who wishes to reserve some of these
3034 ports for other uses may adjust the range that the
3035 kernel's sunrpc client considers to be privileged
3036 using these two parameters to set the minimum and
3037 maximum port values.
3041 Control how the NFS server code allocates CPUs to
3042 service thread pools. Depending on how many NICs
3043 you have and where their interrupts are bound, this
3044 option will affect which CPUs will do NFS serving.
3045 Note: this parameter cannot be changed while the
3046 NFS server is running.
3048 auto the server chooses an appropriate mode
3049 automatically using heuristics
3050 global a single global pool contains all CPUs
3051 percpu one pool for each CPU
3052 pernode one pool for each NUMA node (equivalent
3053 to global on non-NUMA machines)
3055 sunrpc.tcp_slot_table_entries=
3056 sunrpc.udp_slot_table_entries=
3058 Sets the upper limit on the number of simultaneous
3059 RPC calls that can be sent from the client to a
3060 server. Increasing these values may allow you to
3061 improve throughput, but will also increase the
3062 amount of memory reserved for use by the client.
3065 [KNL] Enable accounting of swap in memory resource
3066 controller if no parameter or 1 is given or disable
3067 it if 0 is given (See Documentation/cgroups/memory.txt)
3069 swiotlb= [IA-64] Number of I/O TLB slabs
3073 sysfs.deprecated=0|1 [KNL]
3074 Enable/disable old style sysfs layout for old udev
3075 on older distributions. When this option is enabled
3076 very new udev will not work anymore. When this option
3077 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3078 in older udev will not work anymore.
3079 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3080 the kernel configuration.
3082 sysrq_always_enabled
3084 Ignore sysrq setting - this boot parameter will
3085 neutralize any effect of /proc/sys/kernel/sysrq.
3086 Useful for debugging.
3090 test_suspend= [SUSPEND]
3091 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3092 standby suspend) as the system sleep state to briefly
3093 enter during system startup. The system is woken from
3094 this state using a wakeup-capable RTC alarm.
3096 thash_entries= [KNL,NET]
3097 Set number of hash buckets for TCP connection
3099 thermal.act= [HW,ACPI]
3100 -1: disable all active trip points in all thermal zones
3101 <degrees C>: override all lowest active trip points
3103 thermal.crt= [HW,ACPI]
3104 -1: disable all critical trip points in all thermal zones
3105 <degrees C>: override all critical trip points
3107 thermal.nocrt= [HW,ACPI]
3108 Set to disable actions on ACPI thermal zone
3109 critical and hot trip points.
3111 thermal.off= [HW,ACPI]
3112 1: disable ACPI thermal control
3114 thermal.psv= [HW,ACPI]
3115 -1: disable all passive trip points
3116 <degrees C>: override all passive trip points to this
3119 thermal.tzp= [HW,ACPI]
3120 Specify global default ACPI thermal zone polling rate
3121 <deci-seconds>: poll all this frequency
3122 0: no polling (default)
3125 Force threading of all interrupt handlers except those
3126 marked explicitly IRQF_NO_THREAD.
3129 Enable the Transcendent memory driver if built-in.
3131 tmem.cleancache=0|1 [KNL, XEN]
3132 Default is on (1). Disable the usage of the cleancache
3133 API to send anonymous pages to the hypervisor.
3135 tmem.frontswap=0|1 [KNL, XEN]
3136 Default is on (1). Disable the usage of the frontswap
3137 API to send swap pages to the hypervisor. If disabled
3138 the selfballooning and selfshrinking are force disabled.
3140 tmem.selfballooning=0|1 [KNL, XEN]
3141 Default is on (1). Disable the driving of swap pages
3144 tmem.selfshrinking=0|1 [KNL, XEN]
3145 Default is on (1). Partial swapoff that immediately
3146 transfers pages from Xen hypervisor back to the
3147 kernel based on different criteria.
3151 Specify if the kernel should make use of the cpu
3152 topology information if the hardware supports this.
3153 The scheduler will make use of this information and
3154 e.g. base its process migration decisions on it.
3159 tpm_suspend_pcr=[HW,TPM]
3160 Format: integer pcr id
3161 Specify that at suspend time, the tpm driver
3162 should extend the specified pcr with zeros,
3163 as a workaround for some chips which fail to
3164 flush the last written pcr on TPM_SaveState.
3165 This will guarantee that all the other pcrs
3168 trace_buf_size=nn[KMG]
3169 [FTRACE] will set tracing buffer size.
3171 trace_event=[event-list]
3172 [FTRACE] Set and start specified trace events in order
3173 to facilitate early boot debugging.
3174 See also Documentation/trace/events.txt
3176 trace_options=[option-list]
3177 [FTRACE] Enable or disable tracer options at boot.
3178 The option-list is a comma delimited list of options
3179 that can be enabled or disabled just as if you were
3180 to echo the option name into
3182 /sys/kernel/debug/tracing/trace_options
3184 For example, to enable stacktrace option (to dump the
3185 stack trace of each event), add to the command line:
3187 trace_options=stacktrace
3189 See also Documentation/trace/ftrace.txt "trace options"
3193 [FTRACE] enable this option to disable tracing when a
3194 warning is hit. This turns off "tracing_on". Tracing can
3195 be enabled again by echoing '1' into the "tracing_on"
3196 file located in /sys/kernel/debug/tracing/
3198 This option is useful, as it disables the trace before
3199 the WARNING dump is called, which prevents the trace to
3200 be filled with content caused by the warning output.
3202 This option can also be set at run time via the sysctl
3203 option: kernel/traceoff_on_warning
3205 transparent_hugepage=
3207 Format: [always|madvise|never]
3208 Can be used to control the default behavior of the system
3209 with respect to transparent hugepages.
3210 See Documentation/vm/transhuge.txt for more details.
3212 tsc= Disable clocksource stability checks for TSC.
3214 [x86] reliable: mark tsc clocksource as reliable, this
3215 disables clocksource verification at runtime, as well
3216 as the stability checks done at bootup. Used to enable
3217 high-resolution timer mode on older hardware, and in
3218 virtualized environment.
3219 [x86] noirqtime: Do not use TSC to do irq accounting.
3220 Used to run time disable IRQ_TIME_ACCOUNTING on any
3221 platforms where RDTSC is slow and this accounting
3224 turbografx.map[2|3]= [HW,JOY]
3225 TurboGraFX parallel port interface
3227 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3228 See also Documentation/input/joystick-parport.txt
3230 udbg-immortal [PPC] When debugging early kernel crashes that
3231 happen after console_init() and before a proper
3232 console driver takes over, this boot options might
3233 help "seeing" what's going on.
3235 uhash_entries= [KNL,NET]
3236 Set number of hash buckets for UDP/UDP-Lite connections
3239 [USB] Ignore overcurrent events (default N).
3240 Some badly-designed motherboards generate lots of
3241 bogus events, for ports that aren't wired to
3242 anything. Set this parameter to avoid log spamming.
3243 Note that genuine overcurrent events won't be
3247 [X86] Cause panic on unknown NMI.
3249 usbcore.authorized_default=
3250 [USB] Default USB device authorization:
3251 (default -1 = authorized except for wireless USB,
3252 0 = not authorized, 1 = authorized)
3254 usbcore.autosuspend=
3255 [USB] The autosuspend time delay (in seconds) used
3256 for newly-detected USB devices (default 2). This
3257 is the time required before an idle device will be
3258 autosuspended. Devices for which the delay is set
3259 to a negative value won't be autosuspended at all.
3261 usbcore.usbfs_snoop=
3262 [USB] Set to log all usbfs traffic (default 0 = off).
3264 usbcore.blinkenlights=
3265 [USB] Set to cycle leds on hubs (default 0 = off).
3267 usbcore.old_scheme_first=
3268 [USB] Start with the old device initialization
3269 scheme (default 0 = off).
3271 usbcore.usbfs_memory_mb=
3272 [USB] Memory limit (in MB) for buffers allocated by
3273 usbfs (default = 16, 0 = max = 2047).
3275 usbcore.use_both_schemes=
3276 [USB] Try the other device initialization scheme
3277 if the first one fails (default 1 = enabled).
3279 usbcore.initial_descriptor_timeout=
3280 [USB] Specifies timeout for the initial 64-byte
3281 USB_REQ_GET_DESCRIPTOR request in milliseconds
3282 (default 5000 = 5.0 seconds).
3285 [USBHID] The interval which mice are to be polled at.
3287 usb-storage.delay_use=
3288 [UMS] The delay in seconds before a new device is
3289 scanned for Logical Units (default 5).
3292 [UMS] A list of quirks entries to supplement or
3293 override the built-in unusual_devs list. List
3294 entries are separated by commas. Each entry has
3295 the form VID:PID:Flags where VID and PID are Vendor
3296 and Product ID values (4-digit hex numbers) and
3297 Flags is a set of characters, each corresponding
3298 to a common usb-storage quirk flag as follows:
3299 a = SANE_SENSE (collect more than 18 bytes
3301 b = BAD_SENSE (don't collect more than 18
3302 bytes of sense data);
3303 c = FIX_CAPACITY (decrease the reported
3304 device capacity by one sector);
3305 d = NO_READ_DISC_INFO (don't use
3306 READ_DISC_INFO command);
3307 e = NO_READ_CAPACITY_16 (don't use
3308 READ_CAPACITY_16 command);
3309 h = CAPACITY_HEURISTICS (decrease the
3310 reported device capacity by one
3311 sector if the number is odd);
3312 i = IGNORE_DEVICE (don't bind to this
3314 l = NOT_LOCKABLE (don't try to lock and
3315 unlock ejectable media);
3316 m = MAX_SECTORS_64 (don't transfer more
3317 than 64 sectors = 32 KB at a time);
3318 n = INITIAL_READ10 (force a retry of the
3319 initial READ(10) command);
3320 o = CAPACITY_OK (accept the capacity
3321 reported by the device);
3322 p = WRITE_CACHE (the device cache is ON
3324 r = IGNORE_RESIDUE (the device reports
3325 bogus residue values);
3326 s = SINGLE_LUN (the device has only one
3328 w = NO_WP_DETECT (don't test whether the
3329 medium is write-protected).
3330 Example: quirks=0419:aaf5:rl,0421:0433:rc
3332 user_debug= [KNL,ARM]
3334 See arch/arm/Kconfig.debug help text.
3335 1 - undefined instruction events
3337 4 - invalid data aborts
3340 Example: user_debug=31
3343 [X86] Flags controlling user PTE allocations.
3345 nohigh = do not allocate PTE pages in
3346 HIGHMEM regardless of setting
3350 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3351 vdso=1: enable VDSO (default)
3352 vdso=0: disable VDSO mapping
3355 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3356 vdso32=1: enable 32-bit VDSO (default)
3357 vdso32=0: disable 32-bit VDSO mapping
3360 vector=percpu: enable percpu vector domain
3362 video= [FB] Frame buffer configuration
3363 See Documentation/fb/modedb.txt.
3365 video.brightness_switch_enabled= [0,1]
3366 If set to 1, on receiving an ACPI notify event
3367 generated by hotkey, video driver will adjust brightness
3368 level and then send out the event to user space through
3369 the allocated input device; If set to 0, video driver
3370 will only send out the event without touching backlight
3375 [VMMIO] Memory mapped virtio (platform) device.
3377 <size>@<baseaddr>:<irq>[:<id>]
3379 <size> := size (can use standard suffixes
3381 <baseaddr> := physical base address
3382 <irq> := interrupt number (as passed to
3384 <id> := (optional) platform device id
3386 virtio_mmio.device=1K@0x100b0000:48:7
3388 Can be used multiple times for multiple devices.
3390 vga= [BOOT,X86-32] Select a particular video mode
3391 See Documentation/x86/boot.txt and
3392 Documentation/svga.txt.
3393 Use vga=ask for menu.
3394 This is actually a boot loader parameter; the value is
3395 passed to the kernel using a special protocol.
3397 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3398 size of <nn>. This can be used to increase the
3399 minimum size (128MB on x86). It can also be used to
3400 decrease the size and leave more room for directly
3403 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3406 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3409 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3413 Controls the behavior of vsyscalls (i.e. calls to
3414 fixed addresses of 0xffffffffff600x00 from legacy
3415 code). Most statically-linked binaries and older
3416 versions of glibc use these calls. Because these
3417 functions are at fixed addresses, they make nice
3418 targets for exploits that can control RIP.
3420 emulate [default] Vsyscalls turn into traps and are
3421 emulated reasonably safely.
3423 native Vsyscalls are native syscall instructions.
3424 This is a little bit faster than trapping
3425 and makes a few dynamic recompilers work
3426 better than they would in emulation mode.
3427 It also makes exploits much easier to write.
3429 none Vsyscalls don't work at all. This makes
3430 them quite hard to use for exploits but
3431 might break your system.
3433 vt.color= [VT] Default text color.
3434 Format: 0xYX, X = foreground, Y = background.
3435 Default: 0x07 = light gray on black.
3437 vt.cur_default= [VT] Default cursor shape.
3438 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3439 the parameters of the <Esc>[?A;B;Cc escape sequence;
3440 see VGA-softcursor.txt. Default: 2 = underline.
3442 vt.default_blu= [VT]
3443 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3444 Change the default blue palette of the console.
3445 This is a 16-member array composed of values
3448 vt.default_grn= [VT]
3449 Format: <green0>,<green1>,<green2>,...,<green15>
3450 Change the default green palette of the console.
3451 This is a 16-member array composed of values
3454 vt.default_red= [VT]
3455 Format: <red0>,<red1>,<red2>,...,<red15>
3456 Change the default red palette of the console.
3457 This is a 16-member array composed of values
3463 Set system-wide default UTF-8 mode for all tty's.
3464 Default is 1, i.e. UTF-8 mode is enabled for all
3465 newly opened terminals.
3467 vt.global_cursor_default=
3470 Set system-wide default for whether a cursor
3471 is shown on new VTs. Default is -1,
3472 i.e. cursors will be created by default unless
3473 overridden by individual drivers. 0 will hide
3474 cursors, 1 will display them.
3476 vt.italic= [VT] Default color for italic text; 0-15.
3479 vt.underline= [VT] Default color for underlined text; 0-15.
3482 watchdog timers [HW,WDT] For information on watchdog timers,
3483 see Documentation/watchdog/watchdog-parameters.txt
3484 or other driver-specific files in the
3485 Documentation/watchdog/ directory.
3487 workqueue.disable_numa
3488 By default, all work items queued to unbound
3489 workqueues are affine to the NUMA nodes they're
3490 issued on, which results in better behavior in
3491 general. If NUMA affinity needs to be disabled for
3492 whatever reason, this option can be used. Note
3493 that this also can be controlled per-workqueue for
3494 workqueues visible under /sys/bus/workqueue/.
3496 workqueue.power_efficient
3497 Per-cpu workqueues are generally preferred because
3498 they show better performance thanks to cache
3499 locality; unfortunately, per-cpu workqueues tend to
3500 be more power hungry than unbound workqueues.
3502 Enabling this makes the per-cpu workqueues which
3503 were observed to contribute significantly to power
3504 consumption unbound, leading to measurably lower
3505 power usage at the cost of small performance
3508 The default value of this parameter is determined by
3509 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3511 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3512 default x2apic cluster mode on platforms
3515 x86_intel_mid_timer= [X86-32,APBT]
3516 Choose timer option for x86 Intel MID platform.
3517 Two valid options are apbt timer only and lapic timer
3518 plus one apbt timer for broadcast timer.
3519 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3521 xen_emul_unplug= [HW,X86,XEN]
3522 Unplug Xen emulated devices
3523 Format: [unplug0,][unplug1]
3524 ide-disks -- unplug primary master IDE devices
3525 aux-ide-disks -- unplug non-primary-master IDE devices
3526 nics -- unplug network devices
3527 all -- unplug all emulated devices (NICs and IDE disks)
3528 unnecessary -- unplugging emulated devices is
3529 unnecessary even if the host did not respond to
3531 never -- do not unplug even if version check succeeds
3533 xen_nopvspin [X86,XEN]
3534 Disables the ticketlock slowpath using Xen PV
3537 xirc2ps_cs= [NET,PCMCIA]
3539 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3541 ______________________________________________________________________
3545 Add more DRM drivers.