4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 CLK Common clock infrastructure is enabled.
48 CMA Contiguous Memory Area support is enabled.
49 DRM Direct Rendering Management support is enabled.
50 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
51 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
52 EFI EFI Partitioning (GPT) is enabled
53 EIDE EIDE/ATAPI support is enabled.
54 EVM Extended Verification Module
55 FB The frame buffer device is enabled.
56 FTRACE Function tracing enabled.
57 GCOV GCOV profiling is enabled.
58 HW Appropriate hardware is enabled.
59 IA-64 IA-64 architecture is enabled.
60 IMA Integrity measurement architecture is enabled.
61 IOSCHED More than one I/O scheduler is enabled.
62 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
63 IPV6 IPv6 support is enabled.
64 ISAPNP ISA PnP code is enabled.
65 ISDN Appropriate ISDN support is enabled.
66 JOY Appropriate joystick support is enabled.
67 KGDB Kernel debugger support is enabled.
68 KVM Kernel Virtual Machine support is enabled.
69 LIBATA Libata driver is enabled
70 LP Printer support is enabled.
71 LOOP Loopback device support is enabled.
72 M68k M68k architecture is enabled.
73 These options have more detailed description inside of
74 Documentation/m68k/kernel-options.txt.
75 MDA MDA console support is enabled.
76 MIPS MIPS architecture is enabled.
77 MOUSE Appropriate mouse support is enabled.
78 MSI Message Signaled Interrupts (PCI).
79 MTD MTD (Memory Technology Device) support is enabled.
80 NET Appropriate network support is enabled.
81 NUMA NUMA support is enabled.
82 NFS Appropriate NFS support is enabled.
83 OSS OSS sound support is enabled.
84 PV_OPS A paravirtualized kernel is enabled.
85 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
86 PARISC The PA-RISC architecture is enabled.
87 PCI PCI bus support is enabled.
88 PCIE PCI Express support is enabled.
89 PCMCIA The PCMCIA subsystem is enabled.
90 PNP Plug & Play support is enabled.
91 PPC PowerPC architecture is enabled.
92 PPT Parallel port support is enabled.
93 PS2 Appropriate PS/2 support is enabled.
94 RAM RAM disk support is enabled.
95 S390 S390 architecture is enabled.
96 SCSI Appropriate SCSI support is enabled.
97 A lot of drivers have their options described inside
98 the Documentation/scsi/ sub-directory.
99 SECURITY Different security models are enabled.
100 SELINUX SELinux support is enabled.
101 APPARMOR AppArmor support is enabled.
102 SERIAL Serial support is enabled.
103 SH SuperH architecture is enabled.
104 SMP The kernel is an SMP kernel.
105 SPARC Sparc architecture is enabled.
106 SWSUSP Software suspend (hibernation) is enabled.
107 SUSPEND System suspend states are enabled.
108 TPM TPM drivers are enabled.
109 TS Appropriate touchscreen support is enabled.
110 UMS USB Mass Storage support is enabled.
111 USB USB support is enabled.
112 USBHID USB Human Interface Device support is enabled.
113 V4L Video For Linux support is enabled.
114 VMMIO Driver for memory mapped virtio devices is enabled.
115 VGA The VGA console has been enabled.
116 VT Virtual terminal support is enabled.
117 WDT Watchdog support is enabled.
118 XT IBM PC/XT MFM hard disk support is enabled.
119 X86-32 X86-32, aka i386 architecture is enabled.
120 X86-64 X86-64 architecture is enabled.
121 More X86-64 boot options can be found in
122 Documentation/x86/x86_64/boot-options.txt .
123 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
124 XEN Xen support is enabled
126 In addition, the following text indicates that the option:
128 BUGS= Relates to possible processor bugs on the said processor.
129 KNL Is a kernel start-up parameter.
130 BOOT Is a boot loader parameter.
132 Parameters denoted with BOOT are actually interpreted by the boot
133 loader, and have no meaning to the kernel directly.
134 Do not modify the syntax of boot loader parameters without extreme
135 need or coordination with <Documentation/x86/boot.txt>.
137 There are also arch-specific kernel-parameters not documented here.
138 See for example <Documentation/x86/x86_64/boot-options.txt>.
140 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
141 a trailing = on the name of any parameter states that that parameter will
142 be entered as an environment variable, whereas its absence indicates that
143 it will appear as a kernel argument readable via /proc/cmdline by programs
144 running once the system is up.
146 The number of kernel parameters is not limited, but the length of the
147 complete command line (parameters including spaces etc.) is limited to
148 a fixed number of characters. This limit depends on the architecture
149 and is between 256 and 4096 characters. It is defined in the file
150 ./include/asm/setup.h as COMMAND_LINE_SIZE.
152 Finally, the [KMG] suffix is commonly described after a number of kernel
153 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
154 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
155 bytes respectively. Such letter suffixes can also be entirely omitted.
159 Advanced Configuration and Power Interface
160 Format: { force | off | strict | noirq | rsdt }
161 force -- enable ACPI if default was off
162 off -- disable ACPI if default was on
163 noirq -- do not use ACPI for IRQ routing
164 strict -- Be less tolerant of platforms that are not
165 strictly ACPI specification compliant.
166 rsdt -- prefer RSDT over (default) XSDT
167 copy_dsdt -- copy DSDT to memory
169 See also Documentation/power/runtime_pm.txt, pci=noacpi
171 acpi_rsdp= [ACPI,EFI,KEXEC]
172 Pass the RSDP address to the kernel, mostly used
173 on machines running EFI runtime service to boot the
174 second kernel for kdump.
176 acpi_apic_instance= [ACPI, IOAPIC]
178 2: use 2nd APIC table, if available
179 1,0: use 1st APIC table
182 acpi_backlight= [HW,ACPI]
183 acpi_backlight=vendor
185 If set to vendor, prefer vendor specific driver
186 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
187 of the ACPI video.ko driver.
189 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
190 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
192 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
193 debug output. Bits in debug_layer correspond to a
194 _COMPONENT in an ACPI source file, e.g.,
195 #define _COMPONENT ACPI_PCI_COMPONENT
196 Bits in debug_level correspond to a level in
197 ACPI_DEBUG_PRINT statements, e.g.,
198 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
199 The debug_level mask defaults to "info". See
200 Documentation/acpi/debug.txt for more information about
201 debug layers and levels.
203 Enable processor driver info messages:
204 acpi.debug_layer=0x20000000
205 Enable PCI/PCI interrupt routing info messages:
206 acpi.debug_layer=0x400000
207 Enable AML "Debug" output, i.e., stores to the Debug
208 object while interpreting AML:
209 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
210 Enable all messages related to ACPI hardware:
211 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
213 Some values produce so much output that the system is
214 unusable. The "log_buf_len" parameter may be useful
215 if you need to capture more output.
217 acpi_irq_balance [HW,ACPI]
218 ACPI will balance active IRQs
221 acpi_irq_nobalance [HW,ACPI]
222 ACPI will not move active IRQs (default)
225 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
226 Format: <irq>,<irq>...
228 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
230 Format: <irq>,<irq>...
232 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
234 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
235 Format: To spoof as Windows 98: ="Microsoft Windows"
237 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
238 acpi_osi="string1" # add string1
239 acpi_osi="!string2" # remove string2
240 acpi_osi=!* # remove all strings
241 acpi_osi=! # disable all built-in OS vendor
243 acpi_osi= # disable all strings
245 'acpi_osi=!' can be used in combination with single or
246 multiple 'acpi_osi="string1"' to support specific OS
247 vendor string(s). Note that such command can only
248 affect the default state of the OS vendor strings, thus
249 it cannot affect the default state of the feature group
250 strings and the current state of the OS vendor strings,
251 specifying it multiple times through kernel command line
252 is meaningless. This command is useful when one do not
253 care about the state of the feature group strings which
254 should be controlled by the OSPM.
256 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
257 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
258 can make '_OSI("Windows 2000")' TRUE.
260 'acpi_osi=' cannot be used in combination with other
261 'acpi_osi=' command lines, the _OSI method will not
262 exist in the ACPI namespace. NOTE that such command can
263 only affect the _OSI support state, thus specifying it
264 multiple times through kernel command line is also
267 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
270 'acpi_osi=!*' can be used in combination with single or
271 multiple 'acpi_osi="string1"' to support specific
272 string(s). Note that such command can affect the
273 current state of both the OS vendor strings and the
274 feature group strings, thus specifying it multiple times
275 through kernel command line is meaningful. But it may
276 still not able to affect the final state of a string if
277 there are quirks related to this string. This command
278 is useful when one want to control the state of the
279 feature group strings to debug BIOS issues related to
282 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
283 '_OSI("Module Device")' FALSE.
284 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
285 '_OSI("Module Device")' TRUE.
286 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
288 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
290 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
291 they all will make '_OSI("Windows 2000")' TRUE.
294 Override the pmtimer bug detection: force the kernel
295 to assume that this machine's pmtimer latches its value
296 and always returns good values.
298 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
299 Format: { level | edge | high | low }
301 acpi_serialize [HW,ACPI] force serialization of AML methods
303 acpi_skip_timer_override [HW,ACPI]
304 Recognize and ignore IRQ0/pin2 Interrupt Override.
305 For broken nForce2 BIOS resulting in XT-PIC timer.
307 acpi_sleep= [HW,ACPI] Sleep options
308 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
309 old_ordering, nonvs, sci_force_enable }
310 See Documentation/power/video.txt for information on
312 s3_beep is for debugging; it makes the PC's speaker beep
313 as soon as the kernel's real-mode entry point is called.
314 s4_nohwsig prevents ACPI hardware signature from being
315 used during resume from hibernation.
316 old_ordering causes the ACPI 1.0 ordering of the _PTS
317 control method, with respect to putting devices into
318 low power states, to be enforced (the ACPI 2.0 ordering
319 of _PTS is used by default).
320 nonvs prevents the kernel from saving/restoring the
321 ACPI NVS memory during suspend/hibernation and resume.
322 sci_force_enable causes the kernel to set SCI_EN directly
323 on resume from S1/S3 (which is against the ACPI spec,
324 but some broken systems don't work without it).
326 acpi_use_timer_override [HW,ACPI]
327 Use timer override. For some broken Nvidia NF5 boards
328 that require a timer override, but don't have HPET
330 acpi_enforce_resources= [ACPI]
331 { strict | lax | no }
332 Check for resource conflicts between native drivers
333 and ACPI OperationRegions (SystemIO and SystemMemory
334 only). IO ports and memory declared in ACPI might be
335 used by the ACPI subsystem in arbitrary AML code and
336 can interfere with legacy drivers.
337 strict (default): access to resources claimed by ACPI
338 is denied; legacy drivers trying to access reserved
339 resources will fail to bind to device using them.
340 lax: access to resources claimed by ACPI is allowed;
341 legacy drivers trying to access reserved resources
342 will bind successfully but a warning message is logged.
343 no: ACPI OperationRegions are not marked as reserved,
344 no further checks are performed.
346 add_efi_memmap [EFI; X86] Include EFI memory map in
347 kernel's map of available physical RAM.
350 { off | try_unsupported }
351 off: disable AGP support
352 try_unsupported: try to drive unsupported chipsets
353 (may crash computer or cause data corruption)
356 See Documentation/sound/alsa/alsa-parameters.txt
359 Allow the default userspace alignment fault handler
360 behaviour to be specified. Bit 0 enables warnings,
361 bit 1 enables fixups, and bit 2 sends a segfault.
363 align_va_addr= [X86-64]
364 Align virtual addresses by clearing slice [14:12] when
365 allocating a VMA at process creation time. This option
366 gives you up to 3% performance improvement on AMD F15h
367 machines (where it is enabled by default) for a
368 CPU-intensive style benchmark, and it can vary highly in
369 a microbenchmark depending on workload and compiler.
371 32: only for 32-bit processes
372 64: only for 64-bit processes
373 on: enable for both 32- and 64-bit processes
374 off: disable for both 32- and 64-bit processes
376 alloc_snapshot [FTRACE]
377 Allocate the ftrace snapshot buffer on boot up when the
378 main buffer is allocated. This is handy if debugging
379 and you need to use tracing_snapshot() on boot up, and
380 do not want to use tracing_snapshot_alloc() as it needs
381 to be done where GFP_KERNEL allocations are allowed.
383 amd_iommu= [HW,X86-64]
384 Pass parameters to the AMD IOMMU driver in the system.
386 fullflush - enable flushing of IO/TLB entries when
387 they are unmapped. Otherwise they are
388 flushed before they will be reused, which
390 off - do not initialize any AMD IOMMU found in
392 force_isolation - Force device isolation for all
393 devices. The IOMMU driver is not
394 allowed anymore to lift isolation
395 requirements as needed. This option
396 does not override iommu=pt
398 amd_iommu_dump= [HW,X86-64]
399 Enable AMD IOMMU driver option to dump the ACPI table
400 for AMD IOMMU. With this option enabled, AMD IOMMU
401 driver will print ACPI tables for AMD IOMMU during
402 IOMMU initialization.
404 amijoy.map= [HW,JOY] Amiga joystick support
405 Map of devices attached to JOY0DAT and JOY1DAT
407 See also Documentation/input/joystick.txt
409 analog.map= [HW,JOY] Analog joystick and gamepad support
410 Specifies type or capabilities of an analog joystick
411 connected to one of 16 gameports
412 Format: <type1>,<type2>,..<type16>
415 Power management functions (SPARCstation-4/5 + deriv.)
417 Disable APC CPU standby support. SPARCstation-Fox does
418 not play well with APC CPU idle - disable it if you have
419 APC and your system crashes randomly.
421 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
422 Change the output verbosity whilst booting
423 Format: { quiet (default) | verbose | debug }
424 Change the amount of debugging information output
425 when initialising the APIC and IO-APIC components.
428 See Documentation/networking/ipv6.txt.
430 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
431 Limit apic dumping. The parameter defines the maximal
432 number of local apics being dumped. Also it is possible
433 to set it to "all" by meaning -- no limit here.
434 Format: { 1 (default) | 2 | ... | all }.
435 The parameter valid if only apic=debug or
436 apic=verbose is specified.
437 Example: apic=debug show_lapic=all
439 apm= [APM] Advanced Power Management
440 See header of arch/x86/kernel/apm_32.c.
442 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
443 Format: <io>,<irq>,<nodeID>
447 atarimouse= [HW,MOUSE] Atari Mouse
449 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
450 EzKey and similar keyboards
452 atkbd.reset= [HW] Reset keyboard during initialization
454 atkbd.set= [HW] Select keyboard code set
455 Format: <int> (2 = AT (default), 3 = PS/2)
457 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
460 atkbd.softraw= [HW] Choose between synthetic and real raw mode
461 Format: <bool> (0 = real, 1 = synthetic (default))
463 atkbd.softrepeat= [HW]
464 Use software keyboard repeat
466 baycom_epp= [HW,AX25]
469 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
471 See header of drivers/net/hamradio/baycom_par.c.
473 baycom_ser_fdx= [HW,AX25]
474 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
475 Format: <io>,<irq>,<mode>[,<baud>]
476 See header of drivers/net/hamradio/baycom_ser_fdx.c.
478 baycom_ser_hdx= [HW,AX25]
479 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
480 Format: <io>,<irq>,<mode>
481 See header of drivers/net/hamradio/baycom_ser_hdx.c.
483 blkdevparts= Manual partition parsing of block device(s) for
484 embedded devices based on command line input.
485 See Documentation/block/cmdline-partition.txt
487 boot_delay= Milliseconds to delay each printk during boot.
488 Values larger than 10 seconds (10000) are changed to
492 bootmem_debug [KNL] Enable bootmem allocator debug messages.
494 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
495 bttv.radio= Most important insmod options are available as
497 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
500 bulk_remove=off [PPC] This parameter disables the use of the pSeries
501 firmware feature for flushing multiple hpte entries
504 c101= [NET] Moxa C101 synchronous serial card
506 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
507 Sometimes CPU hardware bugs make them report the cache
508 size incorrectly. The kernel will attempt work arounds
509 to fix known problems, but for some CPUs it is not
510 possible to determine what the correct size should be.
511 This option provides an override for these situations.
513 ccw_timeout_log [S390]
514 See Documentation/s390/CommonIO for details.
516 cgroup_disable= [KNL] Disable a particular controller
517 Format: {name of the controller(s) to disable}
518 The effects of cgroup_disable=foo are:
519 - foo isn't auto-mounted if you mount all cgroups in
521 - foo isn't visible as an individually mountable
523 {Currently only "memory" controller deal with this and
524 cut the overhead, others just disable the usage. So
525 only cgroup_disable=memory is actually worthy}
527 checkreqprot [SELINUX] Set initial checkreqprot flag value.
528 Format: { "0" | "1" }
529 See security/selinux/Kconfig help text.
530 0 -- check protection applied by kernel (includes
531 any implied execute protection).
532 1 -- check protection requested by application.
533 Default value is set via a kernel config option.
534 Value can be changed at runtime via
535 /selinux/checkreqprot.
538 See Documentation/s390/CommonIO for details.
541 Keep all clocks already enabled by bootloader on,
542 even if no driver has claimed them. This is useful
543 for debug and development, but should not be
544 needed on a platform with proper driver support.
545 For more information, see Documentation/clk.txt.
547 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
549 Forces specified clocksource (if available) to be used
550 when calculating gettimeofday(). If specified
551 clocksource is not available, it defaults to PIT.
552 Format: { pit | tsc | cyclone | pmtmr }
554 clocksource= Override the default clocksource
556 Override the default clocksource and use the clocksource
557 with the name specified.
558 Some clocksource names to choose from, depending on
560 [all] jiffies (this is the base, fallback clocksource)
562 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
563 pxa_timer,timer3,32k_counter,timer0_1
565 [X86-32] pit,hpet,tsc;
566 scx200_hrt on Geode; cyclone on IBM x440
574 clearcpuid=BITNUM [X86]
575 Disable CPUID feature X for the kernel. See
576 arch/x86/include/asm/cpufeature.h for the valid bit
577 numbers. Note the Linux specific bits are not necessarily
578 stable over kernel options, but the vendor specific
580 Also note that user programs calling CPUID directly
581 or using the feature without checking anything
582 will still see it. This just prevents it from
583 being used by the kernel or shown in /proc/cpuinfo.
584 Also note the kernel might malfunction if you disable
588 Sets the size of kernel global memory area for contiguous
589 memory allocations. For more information, see
590 include/linux/dma-contiguous.h
592 cmo_free_hint= [PPC] Format: { yes | no }
593 Specify whether pages are marked as being inactive
594 when they are freed. This is used in CMO environments
595 to determine OS memory pressure for page stealing by
599 coherent_pool=nn[KMG] [ARM,KNL]
600 Sets the size of memory pool for coherent, atomic dma
601 allocations, by default set to 256K.
603 code_bytes [X86] How many bytes of object code to print
608 com20020= [HW,NET] ARCnet - COM20020 chipset
610 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
612 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
616 ARCnet - COM90xx chipset (memory-mapped buffers)
617 Format: <io>[,<irq>[,<memstart>]]
619 condev= [HW,S390] console device
622 console= [KNL] Output console device and options.
624 tty<n> Use the virtual console device <n>.
628 Use the specified serial port. The options are of
629 the form "bbbbpnf", where "bbbb" is the baud rate,
630 "p" is parity ("n", "o", or "e"), "n" is number of
631 bits, and "f" is flow control ("r" for RTS or
632 omit it). Default is "9600n8".
634 See Documentation/serial-console.txt for more
636 Documentation/networking/netconsole.txt for an
639 uart[8250],io,<addr>[,options]
640 uart[8250],mmio,<addr>[,options]
641 Start an early, polled-mode console on the 8250/16550
642 UART at the specified I/O port or MMIO address,
643 switching to the matching ttyS device later. The
644 options are the same as for ttyS, above.
645 hvc<n> Use the hypervisor console device <n>. This is for
646 both Xen and PowerPC hypervisors.
648 If the device connected to the port is not a TTY but a braille
649 device, prepend "brl," before the device type, for instance
651 For now, only VisioBraille is supported.
653 consoleblank= [KNL] The console blank (screen saver) timeout in
654 seconds. Defaults to 10*60 = 10mins. A value of 0
655 disables the blank timer.
658 [KNL] Change the default value for
659 /proc/<pid>/coredump_filter.
660 See also Documentation/filesystems/proc.txt.
662 cpuidle.off=1 [CPU_IDLE]
663 disable the cpuidle sub-system
665 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
667 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
669 crashkernel=size[KMG][@offset[KMG]]
670 [KNL] Using kexec, Linux can switch to a 'crash kernel'
671 upon panic. This parameter reserves the physical
672 memory region [offset, offset + size] for that kernel
673 image. If '@offset' is omitted, then a suitable offset
674 is selected automatically. Check
675 Documentation/kdump/kdump.txt for further details.
677 crashkernel=range1:size1[,range2:size2,...][@offset]
678 [KNL] Same as above, but depends on the memory
679 in the running system. The syntax of range is
680 start-[end] where start and end are both
681 a memory unit (amount[KMG]). See also
682 Documentation/kdump/kdump.txt for an example.
684 crashkernel=size[KMG],high
685 [KNL, x86_64] range could be above 4G. Allow kernel
686 to allocate physical memory region from top, so could
687 be above 4G if system have more than 4G ram installed.
688 Otherwise memory region will be allocated below 4G, if
690 It will be ignored if crashkernel=X is specified.
691 crashkernel=size[KMG],low
692 [KNL, x86_64] range under 4G. When crashkernel=X,high
693 is passed, kernel could allocate physical memory region
694 above 4G, that cause second kernel crash on system
695 that require some amount of low memory, e.g. swiotlb
696 requires at least 64M+32K low memory. Kernel would
697 try to allocate 72M below 4G automatically.
698 This one let user to specify own low range under 4G
699 for second kernel instead.
700 0: to disable low allocation.
701 It will be ignored when crashkernel=X,high is not used
702 or memory reserved is below 4G.
707 cs89x0_media= [HW,NET]
708 Format: { rj45 | aui | bnc }
711 See header of drivers/s390/block/dasd_devmap.c.
713 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
714 (one device per port)
715 Format: <port#>,<type>
716 See also Documentation/input/joystick-parport.txt
718 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
719 time. See Documentation/dynamic-debug-howto.txt for
720 details. Deprecated, see dyndbg.
722 debug [KNL] Enable kernel debugging (events log level).
725 [KNL] verbose self-tests
727 Print debugging info while doing the locking API
729 We default to 0 (no extra messages), setting it to
730 1 will print _a lot_ more information - normally
731 only useful to kernel developers.
733 debug_objects [KNL] Enable object debugging
736 [KNL] Disable object debugging
738 debug_guardpage_minorder=
739 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
740 parameter allows control of the order of pages that will
741 be intentionally kept free (and hence protected) by the
742 buddy allocator. Bigger value increase the probability
743 of catching random memory corruption, but reduce the
744 amount of memory for normal system use. The maximum
745 possible value is MAX_ORDER/2. Setting this parameter
746 to 1 or 2 should be enough to identify most random
747 memory corruption problems caused by bugs in kernel or
748 driver code when a CPU writes to (or reads from) a
749 random memory location. Note that there exists a class
750 of memory corruptions problems caused by buggy H/W or
751 F/W or by drivers badly programing DMA (basically when
752 memory is written at bus level and the CPU MMU is
753 bypassed) which are not detectable by
754 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
755 tracking down these problems.
757 debugpat [X86] Enable PAT debugging
759 decnet.addr= [HW,NET]
760 Format: <area>[,<node>]
761 See also Documentation/networking/decnet.txt.
764 [same as hugepagesz=] The size of the default
765 HugeTLB page size. This is the size represented by
766 the legacy /proc/ hugepages APIs, used for SHM, and
767 default size when mounting hugetlbfs filesystems.
768 Defaults to the default architecture's huge page size
772 Set number of hash buckets for dentry cache.
775 IO parameters + enable/disable command.
777 digiepca= [HW,SERIAL]
778 See drivers/char/README.epca and
779 Documentation/serial/digiepca.txt.
782 See Documentation/networking/ipv6.txt.
784 disable_ddw [PPC/PSERIES]
785 Disable Dynamic DMA Window support. Use this if
786 to workaround buggy firmware.
789 See Documentation/networking/ipv6.txt.
791 disable_mtrr_cleanup [X86]
792 The kernel tries to adjust MTRR layout from continuous
793 to discrete, to make X server driver able to add WB
794 entry later. This parameter disables that.
796 disable_mtrr_trim [X86, Intel and AMD only]
797 By default the kernel will trim any uncacheable
798 memory out of your available memory pool based on
799 MTRR settings. This parameter disables that behavior,
800 possibly causing your machine to run very slowly.
802 disable_timer_pin_1 [X86]
803 Disable PIN 1 of APIC timer
804 Can be useful to work around chipset bugs.
806 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
807 this option disables the debugging code at boot.
809 dma_debug_entries=<number>
810 This option allows to tune the number of preallocated
811 entries for DMA-API debugging code. One entry is
812 required per DMA-API allocation. Use this if the
813 DMA-API debugging code disables itself because the
814 architectural default is too low.
816 dma_debug_driver=<driver_name>
817 With this option the DMA-API debugging driver
818 filter feature can be enabled at boot time. Just
819 pass the driver to filter for as the parameter.
820 The filter can be disabled or changed to another
821 driver later using sysfs.
823 drm_kms_helper.edid_firmware=[<connector>:]<file>
824 Broken monitors, graphic adapters and KVMs may
825 send no or incorrect EDID data sets. This parameter
826 allows to specify an EDID data set in the
827 /lib/firmware directory that is used instead.
828 Generic built-in EDID data sets are used, if one of
829 edid/1024x768.bin, edid/1280x1024.bin,
830 edid/1680x1050.bin, or edid/1920x1080.bin is given
831 and no file with the same name exists. Details and
832 instructions how to build your own EDID data are
833 available in Documentation/EDID/HOWTO.txt. An EDID
834 data set will only be used for a particular connector,
835 if its name and a colon are prepended to the EDID
840 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
841 module.dyndbg[="val"]
842 Enable debug messages at boot time. See
843 Documentation/dynamic-debug-howto.txt for details.
845 earlycon= [KNL] Output early console device and options.
846 uart[8250],io,<addr>[,options]
847 uart[8250],mmio,<addr>[,options]
848 uart[8250],mmio32,<addr>[,options]
849 Start an early, polled-mode console on the 8250/16550
850 UART at the specified I/O port or MMIO address.
851 MMIO inter-register address stride is either 8-bit
852 (mmio) or 32-bit (mmio32).
853 The options are the same as for ttyS, above.
855 earlyprintk= [X86,SH,BLACKFIN,ARM]
859 earlyprintk=serial[,ttySn[,baudrate]]
860 earlyprintk=serial[,0x...[,baudrate]]
861 earlyprintk=ttySn[,baudrate]
862 earlyprintk=dbgp[debugController#]
864 earlyprintk is useful when the kernel crashes before
865 the normal console is initialized. It is not enabled by
866 default because it has some cosmetic problems.
868 Append ",keep" to not disable it when the real console
871 Only one of vga, efi, serial, or usb debug port can
874 Currently only ttyS0 and ttyS1 may be specified by
875 name. Other I/O ports may be explicitly specified
876 on some architectures (x86 and arm at least) by
877 replacing ttySn with an I/O port address, like this:
878 earlyprintk=serial,0x1008,115200
879 You can find the port for a given device in
880 /proc/tty/driver/serial:
881 2: uart:ST16650V2 port:00001008 irq:18 ...
883 Interaction with the standard serial driver is not
886 The VGA and EFI output is eventually overwritten by
889 The xen output can only be used by Xen PV guests.
891 ekgdboc= [X86,KGDB] Allow early kernel console debugging
894 This is designed to be used in conjunction with
895 the boot argument: earlyprintk=vga
898 Format: {"off" | "on" | "skip[mbr]"}
900 efi_no_storage_paranoia [EFI; X86]
901 Using this parameter you can use more than 50% of
902 your efi variable storage. Use this parameter only if
903 you are really sure that your UEFI does sane gc and
904 fulfills the spec otherwise your board may brick.
906 eisa_irq_edge= [PARISC,HW]
907 See header of drivers/parisc/eisa.c.
910 See comment before function elanfreq_setup() in
911 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
914 Format: {"cfq" | "deadline" | "noop"}
915 See Documentation/block/cfq-iosched.txt and
916 Documentation/block/deadline-iosched.txt for details.
918 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
919 Specifies physical address of start of kernel core
920 image elf header and optionally the size. Generally
921 kexec loader will pass this option to capture kernel.
922 See Documentation/kdump/kdump.txt for details.
924 enable_mtrr_cleanup [X86]
925 The kernel tries to adjust MTRR layout from continuous
926 to discrete, to make X server driver able to add WB
927 entry later. This parameter enables that.
929 enable_timer_pin_1 [X86]
930 Enable PIN 1 of APIC timer
931 Can be useful to work around chipset bugs
932 (in particular on some ATI chipsets).
933 The kernel tries to set a reasonable default.
935 enforcing [SELINUX] Set initial enforcing status.
937 See security/selinux/Kconfig help text.
938 0 -- permissive (log only, no denials).
939 1 -- enforcing (deny and log).
941 Value can be changed at runtime via /selinux/enforce.
944 Disable Error Record Serialization Table (ERST)
947 ether= [HW,NET] Ethernet cards parameters
948 This option is obsoleted by the "netdev=" option, which
949 has equivalent usage. See its documentation for details.
953 Permit 'security.evm' to be updated regardless of
954 current integrity status.
958 fail_make_request=[KNL]
959 General fault injection mechanism.
960 Format: <interval>,<probability>,<space>,<times>
961 See also Documentation/fault-injection/.
964 See Documentation/blockdev/floppy.txt.
966 force_pal_cache_flush
967 [IA-64] Avoid check_sal_cache_flush which may hang on
968 buggy SAL_CACHE_FLUSH implementations. Using this
969 parameter will force ia64_sal_cache_flush to call
970 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
973 [FTRACE] will set and start the specified tracer
974 as early as possible in order to facilitate early
977 ftrace_dump_on_oops[=orig_cpu]
978 [FTRACE] will dump the trace buffers on oops.
979 If no parameter is passed, ftrace will dump
980 buffers of all CPUs, but if you pass orig_cpu, it will
981 dump only the buffer of the CPU that triggered the
984 ftrace_filter=[function-list]
985 [FTRACE] Limit the functions traced by the function
986 tracer at boot up. function-list is a comma separated
987 list of functions. This list can be changed at run
988 time by the set_ftrace_filter file in the debugfs
991 ftrace_notrace=[function-list]
992 [FTRACE] Do not trace the functions specified in
993 function-list. This list can be changed at run time
994 by the set_ftrace_notrace file in the debugfs
997 ftrace_graph_filter=[function-list]
998 [FTRACE] Limit the top level callers functions traced
999 by the function graph tracer at boot up.
1000 function-list is a comma separated list of functions
1001 that can be changed at run time by the
1002 set_graph_function file in the debugfs tracing directory.
1005 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1006 support via parallel port (up to 5 devices per port)
1007 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1008 See also Documentation/input/joystick-parport.txt
1012 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1016 gcov_persist= [GCOV] When non-zero (default), profiling data for
1017 kernel modules is saved and remains accessible via
1018 debugfs, even when the module is unloaded/reloaded.
1019 When zero, profiling data is discarded and associated
1020 debugfs files are removed at module unload time.
1022 gpt [EFI] Forces disk with valid GPT signature but
1023 invalid Protective MBR to be treated as GPT.
1025 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1026 the "Enable 0" bit of the configuration register.
1029 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1030 the "Enable 0" bit of the configuration register.
1033 grcan.select= [HW] Select which physical interface to use.
1036 grcan.txsize= [HW] Sets the size of the tx buffer.
1037 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1039 grcan.rxsize= [HW] Sets the size of the rx buffer.
1040 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1043 hashdist= [KNL,NUMA] Large hashes allocated during boot
1044 are distributed across NUMA nodes. Defaults on
1045 for 64-bit NUMA, off otherwise.
1046 Format: 0 | 1 (for off | on)
1048 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1050 hd= [EIDE] (E)IDE hard drive subsystem geometry
1051 Format: <cyl>,<head>,<sect>
1054 Disable Hardware Error Source Table (HEST) support;
1055 corresponding firmware-first mode error processing
1056 logic will be disabled.
1058 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1059 size of <nn>. This works even on boxes that have no
1060 highmem otherwise. This also works to reduce highmem
1061 size on bigger boxes.
1063 highres= [KNL] Enable/disable high resolution timer mode.
1064 Valid parameters: "on", "off"
1068 See Documentation/isdn/README.HiSax.
1072 hpet= [X86-32,HPET] option to control HPET usage
1073 Format: { enable (default) | disable | force |
1075 disable: disable HPET and use PIT instead
1076 force: allow force enabled of undocumented chips (ICH4,
1078 verbose: show contents of HPET registers during setup
1080 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1081 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1083 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1084 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1085 On x86-64 and powerpc, this option can be specified
1086 multiple times interleaved with hugepages= to reserve
1087 huge pages of different sizes. Valid pages sizes on
1088 x86-64 are 2M (when the CPU supports "pse") and 1G
1089 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1090 Note that 1GB pages can only be allocated at boot time
1091 using hugepages= and not freed afterwards.
1093 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1094 terminal devices. Valid values: 0..8
1095 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1096 If specified, z/VM IUCV HVC accepts connections
1097 from listed z/VM user IDs only.
1099 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1100 hardware thread id mappings.
1101 Format: <cpu>:<hwthread>
1104 Do not unregister boot console at start. This is only
1105 useful for debugging when something happens in the window
1106 between unregistering the boot console and initializing
1109 i2c_bus= [HW] Override the default board specific I2C bus speed
1110 or register an additional I2C bus that is not
1111 registered from board initialization code.
1115 i8042.debug [HW] Toggle i8042 debug mode
1116 i8042.direct [HW] Put keyboard port into non-translated mode
1117 i8042.dumbkbd [HW] Pretend that controller can only read data from
1118 keyboard and cannot control its state
1119 (Don't attempt to blink the leds)
1120 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1121 i8042.nokbd [HW] Don't check/create keyboard port
1122 i8042.noloop [HW] Disable the AUX Loopback command while probing
1124 i8042.nomux [HW] Don't check presence of an active multiplexing
1126 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1128 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1129 i8042.reset [HW] Reset the controller during init and cleanup
1130 i8042.unlock [HW] Unlock (ignore) the keylock
1134 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1135 indicates that the driver is running on unsupported
1137 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1138 does not match list of supported models.
1140 [HW] Report power status in /proc/i8k
1141 (disabled by default)
1142 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1145 i915.invert_brightness=
1146 [DRM] Invert the sense of the variable that is used to
1147 set the brightness of the panel backlight. Normally a
1148 brightness value of 0 indicates backlight switched off,
1149 and the maximum of the brightness value sets the backlight
1150 to maximum brightness. If this parameter is set to 0
1151 (default) and the machine requires it, or this parameter
1152 is set to 1, a brightness value of 0 sets the backlight
1153 to maximum brightness, and the maximum of the brightness
1154 value switches the backlight off.
1155 -1 -- never invert brightness
1156 0 -- machine default
1157 1 -- force brightness inversion
1160 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1162 ide-core.nodma= [HW] (E)IDE subsystem
1163 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1164 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1165 .cdrom .chs .ignore_cable are additional options
1166 See Documentation/ide/ide.txt.
1168 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1169 Claim all unknown PCI IDE storage controllers.
1172 Format: idle=poll, idle=halt, idle=nomwait
1173 Poll forces a polling idle loop that can slightly
1174 improve the performance of waking up a idle CPU, but
1175 will use a lot of power and make the system run hot.
1177 idle=halt: Halt is forced to be used for CPU idle.
1178 In such case C2/C3 won't be used again.
1179 idle=nomwait: Disable mwait for CPU C-states
1181 ignore_loglevel [KNL]
1182 Ignore loglevel setting - this will print /all/
1183 kernel messages to the console. Useful for debugging.
1184 We also add it as printk module parameter, so users
1185 could change it dynamically, usually by
1186 /sys/module/printk/parameters/ignore_loglevel.
1188 ihash_entries= [KNL]
1189 Set number of hash buckets for inode cache.
1191 ima_appraise= [IMA] appraise integrity measurements
1192 Format: { "off" | "enforce" | "fix" }
1195 ima_appraise_tcb [IMA]
1196 The builtin appraise policy appraises all files
1200 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1204 The list of supported hash algorithms is defined
1205 in crypto/hash_info.h.
1208 Load a policy which meets the needs of the Trusted
1209 Computing Base. This means IMA will measure all
1210 programs exec'd, files mmap'd for exec, and all files
1211 opened for read by uid=0.
1214 Select one of defined IMA measurements template formats.
1215 Formats: { "ima" | "ima-ng" }
1220 Run specified binary instead of /sbin/init as init
1223 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1224 for working out where the kernel is dying during
1227 initrd= [BOOT] Specify the location of the initial ramdisk
1229 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1232 int_pln_enable [x86] Enable power limit notification interrupt
1234 integrity_audit=[IMA]
1235 Format: { "0" | "1" }
1236 0 -- basic integrity auditing messages. (Default)
1237 1 -- additional integrity auditing messages.
1239 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1241 Enable intel iommu driver.
1243 Disable intel iommu driver.
1244 igfx_off [Default Off]
1245 By default, gfx is mapped as normal device. If a gfx
1246 device has a dedicated DMAR unit, the DMAR unit is
1247 bypassed by not enabling DMAR with this option. In
1248 this case, gfx device will use physical address for
1251 With this option iommu will not optimize to look
1252 for io virtual address below 32-bit forcing dual
1253 address cycle on pci bus for cards supporting greater
1254 than 32-bit addressing. The default is to look
1255 for translation below 32-bit and if not available
1256 then look in the higher range.
1257 strict [Default Off]
1258 With this option on every unmap_single operation will
1259 result in a hardware IOTLB flush operation as opposed
1260 to batching them for performance.
1261 sp_off [Default Off]
1262 By default, super page will be supported if Intel IOMMU
1263 has the capability. With this option, super page will
1266 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1267 0 disables intel_idle and fall back on acpi_idle.
1268 1 to 6 specify maximum depth of C-state.
1272 Do not enable intel_pstate as the default
1273 scaling driver for the supported processors
1275 intremap= [X86-64, Intel-IOMMU]
1276 on enable Interrupt Remapping (default)
1277 off disable Interrupt Remapping
1278 nosid disable Source ID checking
1280 BIOS x2APIC opt-out request will be ignored
1282 iomem= Disable strict checking of access to MMIO memory
1283 strict regions from userspace.
1300 io7= [HW] IO7 for Marvel based alpha systems
1301 See comment before marvel_specify_io7 in
1302 arch/alpha/kernel/core_marvel.c.
1304 io_delay= [X86] I/O delay method
1306 Standard port 0x80 based delay
1308 Alternate port 0xed based delay (needed on some systems)
1310 Simple two microseconds delay
1315 See Documentation/filesystems/nfs/nfsroot.txt.
1317 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1318 See comment before ip2_setup() in
1319 drivers/char/ip2/ip2base.c.
1322 When an interrupt is not handled search all handlers
1323 for it. Intended to get systems with badly broken
1327 When an interrupt is not handled search all handlers
1328 for it. Also check all handlers each timer
1329 interrupt. Intended to get systems with badly broken
1333 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1335 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1337 <cpu number>,...,<cpu number>
1339 <cpu number>-<cpu number>
1340 (must be a positive range in ascending order)
1342 <cpu number>,...,<cpu number>-<cpu number>
1344 This option can be used to specify one or more CPUs
1345 to isolate from the general SMP balancing and scheduling
1346 algorithms. You can move a process onto or off an
1347 "isolated" CPU via the CPU affinity syscalls or cpuset.
1348 <cpu number> begins at 0 and the maximum value is
1349 "number of CPUs in system - 1".
1351 This option is the preferred way to isolate CPUs. The
1352 alternative -- manually setting the CPU mask of all
1353 tasks in the system -- can cause problems and
1354 suboptimal load balancer performance.
1358 ivrs_ioapic [HW,X86_64]
1359 Provide an override to the IOAPIC-ID<->DEVICE-ID
1360 mapping provided in the IVRS ACPI table. For
1361 example, to map IOAPIC-ID decimal 10 to
1362 PCI device 00:14.0 write the parameter as:
1363 ivrs_ioapic[10]=00:14.0
1365 ivrs_hpet [HW,X86_64]
1366 Provide an override to the HPET-ID<->DEVICE-ID
1367 mapping provided in the IVRS ACPI table. For
1368 example, to map HPET-ID decimal 0 to
1369 PCI device 00:14.0 write the parameter as:
1370 ivrs_hpet[0]=00:14.0
1372 js= [HW,JOY] Analog joystick
1373 See Documentation/input/joystick.txt.
1377 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1378 specifies the amount of memory usable by the kernel
1379 for non-movable allocations. The requested amount is
1380 spread evenly throughout all nodes in the system. The
1381 remaining memory in each node is used for Movable
1382 pages. In the event, a node is too small to have both
1383 kernelcore and Movable pages, kernelcore pages will
1384 take priority and other nodes will have a larger number
1385 of Movable pages. The Movable zone is used for the
1386 allocation of pages that may be reclaimed or moved
1387 by the page migration subsystem. This means that
1388 HugeTLB pages may not be allocated from this zone.
1389 Note that allocations like PTEs-from-HighMem still
1390 use the HighMem zone if it exists, and the Normal
1391 zone if it does not.
1393 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1394 Format: <Controller#>[,poll interval]
1395 The controller # is the number of the ehci usb debug
1396 port as it is probed via PCI. The poll interval is
1397 optional and is the number seconds in between
1398 each poll cycle to the debug port in case you need
1399 the functionality for interrupting the kernel with
1400 gdb or control-c on the dbgp connection. When
1401 not using this parameter you use sysrq-g to break into
1402 the kernel debugger.
1404 kgdboc= [KGDB,HW] kgdb over consoles.
1405 Requires a tty driver that supports console polling,
1406 or a supported polling keyboard driver (non-usb).
1407 Serial only format: <serial_device>[,baud]
1408 keyboard only format: kbd
1409 keyboard and serial format: kbd,<serial_device>[,baud]
1410 Optional Kernel mode setting:
1411 kms, kbd format: kms,kbd
1412 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1414 kgdbwait [KGDB] Stop kernel execution and enter the
1415 kernel debugger at the earliest opportunity.
1417 kmac= [MIPS] korina ethernet MAC address.
1418 Configure the RouterBoard 532 series on-chip
1419 Ethernet adapter MAC address.
1421 kmemleak= [KNL] Boot-time kmemleak enable/disable
1422 Valid arguments: on, off
1425 kstack=N [X86] Print N words from the kernel stack
1428 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1429 Default is 0 (don't ignore, but inject #GP)
1431 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1435 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1436 Default is 1 (enabled)
1438 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1440 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1442 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1443 (virtualized MMU) support on capable Intel chips.
1444 Default is 1 (enabled)
1446 kvm-intel.emulate_invalid_guest_state=
1447 [KVM,Intel] Enable emulation of invalid guest states
1448 Default is 0 (disabled)
1450 kvm-intel.flexpriority=
1451 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1452 Default is 1 (enabled)
1455 [KVM,Intel] Enable VMX nesting (nVMX).
1456 Default is 0 (disabled)
1458 kvm-intel.unrestricted_guest=
1459 [KVM,Intel] Disable unrestricted guest feature
1460 (virtualized real and unpaged mode) on capable
1461 Intel chips. Default is 1 (enabled)
1463 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1464 feature (tagged TLBs) on capable Intel chips.
1465 Default is 1 (enabled)
1471 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1474 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1475 value for LAPIC timer one-shot implementation. Default
1476 back to the programmable timer unit in the LAPIC.
1478 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1481 libata.dma= [LIBATA] DMA control
1482 libata.dma=0 Disable all PATA and SATA DMA
1483 libata.dma=1 PATA and SATA Disk DMA only
1484 libata.dma=2 ATAPI (CDROM) DMA only
1485 libata.dma=4 Compact Flash DMA only
1486 Combinations also work, so libata.dma=3 enables DMA
1487 for disks and CDROMs, but not CFs.
1489 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1490 libata.ignore_hpa=0 keep BIOS limits (default)
1491 libata.ignore_hpa=1 ignore limits, using full disk
1493 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1497 libata.force= [LIBATA] Force configurations. The format is comma
1498 separated list of "[ID:]VAL" where ID is
1499 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1500 matching port, link or device. Basically, it matches
1501 the ATA ID string printed on console by libata. If
1502 the whole ID part is omitted, the last PORT and DEVICE
1503 values are used. If ID hasn't been specified yet, the
1504 configuration applies to all ports, links and devices.
1506 If only DEVICE is omitted, the parameter applies to
1507 the port and all links and devices behind it. DEVICE
1508 number of 0 either selects the first device or the
1509 first fan-out link behind PMP device. It does not
1510 select the host link. DEVICE number of 15 selects the
1511 host link and device attached to it.
1513 The VAL specifies the configuration to force. As long
1514 as there's no ambiguity shortcut notation is allowed.
1515 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1516 The following configurations can be forced.
1518 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1519 Any ID with matching PORT is used.
1521 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1523 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1524 udma[/][16,25,33,44,66,100,133] notation is also
1527 * [no]ncq: Turn on or off NCQ.
1529 * nohrst, nosrst, norst: suppress hard, soft
1532 * rstonce: only attempt one reset during
1533 hot-unplug link recovery
1535 * dump_id: dump IDENTIFY data.
1537 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1539 If there are multiple matching configurations changing
1540 the same attribute, the last one is used.
1542 memblock=debug [KNL] Enable memblock debug messages.
1544 load_ramdisk= [RAM] List of ramdisks to load from floppy
1545 See Documentation/blockdev/ramdisk.txt.
1547 lockd.nlm_grace_period=P [NFS] Assign grace period.
1550 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1553 lockd.nlm_timeout=T [NFS] Assign timeout value.
1556 lockd.nlm_udpport=M [NFS] Assign UDP port.
1559 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1562 loglevel= All Kernel Messages with a loglevel smaller than the
1563 console loglevel will be printed to the console. It can
1564 also be changed with klogd or other programs. The
1565 loglevels are defined as follows:
1567 0 (KERN_EMERG) system is unusable
1568 1 (KERN_ALERT) action must be taken immediately
1569 2 (KERN_CRIT) critical conditions
1570 3 (KERN_ERR) error conditions
1571 4 (KERN_WARNING) warning conditions
1572 5 (KERN_NOTICE) normal but significant condition
1573 6 (KERN_INFO) informational
1574 7 (KERN_DEBUG) debug-level messages
1576 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1577 in bytes. n must be a power of two. The default
1578 size is set in the kernel config file.
1580 logo.nologo [FB] Disables display of the built-in Linux logo.
1581 This may be used to provide more screen space for
1582 kernel log messages and is useful when debugging
1583 kernel boot problems.
1585 lp=0 [LP] Specify parallel ports to use, e.g,
1586 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1587 lp=reset first parallel port). 'lp=0' disables the
1588 lp=auto printer driver. 'lp=reset' (which can be
1589 specified in addition to the ports) causes
1590 attached printers to be reset. Using
1591 lp=port1,port2,... specifies the parallel ports
1592 to associate lp devices with, starting with
1593 lp0. A port specification may be 'none' to skip
1594 that lp device, or a parport name such as
1595 'parport0'. Specifying 'lp=auto' instead of a
1596 port specification list means that device IDs
1597 from each port should be examined, to see if
1598 an IEEE 1284-compliant printer is attached; if
1599 so, the driver will manage that printer.
1600 See also header of drivers/char/lp.c.
1603 Sets loops_per_jiffy to given constant, thus avoiding
1604 time-consuming boot-time autodetection (up to 250 ms per
1605 CPU). 0 enables autodetection (default). To determine
1606 the correct value for your kernel, boot with normal
1607 autodetection and see what value is printed. Note that
1608 on SMP systems the preset will be applied to all CPUs,
1609 which is likely to cause problems if your CPUs need
1610 significantly divergent settings. An incorrect value
1611 will cause delays in the kernel to be wrong, leading to
1612 unpredictable I/O errors and other breakage. Although
1613 unlikely, in the extreme case this might damage your
1617 Format: <io>,<irq>,<dma>
1619 machvec= [IA-64] Force the use of a particular machine-vector
1620 (machvec) in a generic kernel.
1621 Example: machvec=hpzx1_swiotlb
1623 machtype= [Loongson] Share the same kernel image file between different
1625 Example: machtype=lemote-yeeloong-2f-7inch
1627 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1628 than or equal to this physical address is ignored.
1630 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1631 should make use of. maxcpus=n : n >= 0 limits the
1632 kernel to using 'n' processors. n=0 is a special case,
1633 it is equivalent to "nosmp", which also disables
1636 max_loop= [LOOP] The number of loop block devices that get
1637 (loop.max_loop) unconditionally pre-created at init time. The default
1638 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1639 of statically allocating a predefined number, loop
1640 devices can be requested on-demand with the
1641 /dev/loop-control interface.
1643 mce [X86-32] Machine Check Exception
1645 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1647 md= [HW] RAID subsystems devices and level
1648 See Documentation/md.txt.
1651 Format: <first>,<last>
1652 Specifies range of consoles to be captured by the MDA.
1654 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1655 Amount of memory to be used when the kernel is not able
1656 to see the whole system memory or for test.
1657 [X86] Work as limiting max address. Use together
1658 with memmap= to avoid physical address space collisions.
1659 Without memmap= PCI devices could be placed at addresses
1660 belonging to unused RAM.
1662 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1666 [KNL,SH] Allow user to override the default size for
1667 per-device physically contiguous DMA buffers.
1669 memmap=exactmap [KNL,X86] Enable setting of an exact
1670 E820 memory map, as specified by the user.
1671 Such memmap=exactmap lines can be constructed based on
1672 BIOS output or other requirements. See the memmap=nn@ss
1675 memmap=nn[KMG]@ss[KMG]
1676 [KNL] Force usage of a specific region of memory
1677 Region of memory to be used, from ss to ss+nn.
1679 memmap=nn[KMG]#ss[KMG]
1680 [KNL,ACPI] Mark specific memory as ACPI data.
1681 Region of memory to be used, from ss to ss+nn.
1683 memmap=nn[KMG]$ss[KMG]
1684 [KNL,ACPI] Mark specific memory as reserved.
1685 Region of memory to be used, from ss to ss+nn.
1686 Example: Exclude memory from 0x18690000-0x1869ffff
1687 memmap=64K$0x18690000
1689 memmap=0x10000$0x18690000
1691 memory_corruption_check=0/1 [X86]
1692 Some BIOSes seem to corrupt the first 64k of
1693 memory when doing things like suspend/resume.
1694 Setting this option will scan the memory
1695 looking for corruption. Enabling this will
1696 both detect corruption and prevent the kernel
1697 from using the memory being corrupted.
1698 However, its intended as a diagnostic tool; if
1699 repeatable BIOS-originated corruption always
1700 affects the same memory, you can use memmap=
1701 to prevent the kernel from using that memory.
1703 memory_corruption_check_size=size [X86]
1704 By default it checks for corruption in the low
1705 64k, making this memory unavailable for normal
1706 use. Use this parameter to scan for
1707 corruption in more or less memory.
1709 memory_corruption_check_period=seconds [X86]
1710 By default it checks for corruption every 60
1711 seconds. Use this parameter to check at some
1712 other rate. 0 disables periodic checking.
1714 memtest= [KNL,X86] Enable memtest
1716 default : 0 <disable>
1717 Specifies the number of memtest passes to be
1718 performed. Each pass selects another test
1719 pattern from a given set of patterns. Memtest
1720 fills the memory with this pattern, validates
1721 memory contents and reserves bad memory
1722 regions that are detected.
1724 meye.*= [HW] Set MotionEye Camera parameters
1725 See Documentation/video4linux/meye.txt.
1727 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1728 Multi-Function General Purpose Timers on AMD Geode
1731 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1732 the BIOS has incorrectly applied a workaround. TinyBIOS
1733 version 0.98 is known to be affected, 0.99 fixes the
1734 problem by letting the user disable the workaround.
1738 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1739 physical address is ignored.
1741 mini2440= [ARM,HW,KNL]
1742 Format:[0..2][b][c][t]
1744 MINI2440 configuration specification:
1745 0 - The attached screen is the 3.5" TFT
1746 1 - The attached screen is the 7" TFT
1747 2 - The VGA Shield is attached (1024x768)
1748 Leaving out the screen size parameter will not load
1749 the TFT driver, and the framebuffer will be left
1751 b - Enable backlight. The TFT backlight pin will be
1752 linked to the kernel VESA blanking code and a GPIO
1753 LED. This parameter is not necessary when using the
1755 c - Enable the s3c camera interface.
1756 t - Reserved for enabling touchscreen support. The
1757 touchscreen support is not enabled in the mainstream
1758 kernel as of 2.6.30, a preliminary port can be found
1759 in the "bleeding edge" mini2440 support kernel at
1760 http://repo.or.cz/w/linux-2.6/mini2440.git
1763 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1764 parameter allows control of the logging verbosity for
1765 the additional memory initialisation checks. A value
1766 of 0 disables mminit logging and a level of 4 will
1767 log everything. Information is printed at KERN_DEBUG
1768 so loglevel=8 may also need to be specified.
1771 [KNL] When CONFIG_MODULE_SIG is set, this means that
1772 modules without (valid) signatures will fail to load.
1773 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1774 is always true, so this option does nothing.
1777 [MOUSE] Maximum time between finger touching and
1778 leaving touchpad surface for touch to be considered
1779 a tap and be reported as a left button click (for
1780 touchpads working in absolute mode only).
1782 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1783 reporting absolute coordinates, such as tablets
1784 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1785 reporting absolute coordinates, such as tablets
1787 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1788 is similar to kernelcore except it specifies the
1789 amount of memory used for migratable allocations.
1790 If both kernelcore and movablecore is specified,
1791 then kernelcore will be at *least* the specified
1792 value but may be more. If movablecore on its own
1793 is specified, the administrator must be careful
1794 that the amount of memory usable for all allocations
1797 movable_node [KNL,X86] Boot-time switch to enable the effects
1798 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1800 MTD_Partition= [MTD]
1801 Format: <name>,<region-number>,<size>,<offset>
1803 MTD_Region= [MTD] Format:
1804 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1807 See drivers/mtd/cmdlinepart.c.
1809 multitce=off [PPC] This parameter disables the use of the pSeries
1810 firmware feature for updating multiple TCE entries
1813 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1815 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1817 boundary - index of last SLC block on Flex-OneNAND.
1818 The remaining blocks are configured as MLC blocks.
1819 lock - Configure if Flex-OneNAND boundary should be locked.
1820 Once locked, the boundary cannot be changed.
1821 1 indicates lock status, 0 indicates unlock status.
1824 ARM/S3C2412 JIVE boot control
1826 See arch/arm/mach-s3c2412/mach-jive.c
1828 mtouchusb.raw_coordinates=
1829 [HW] Make the MicroTouch USB driver use raw coordinates
1830 ('y', default) or cooked coordinates ('n')
1832 mtrr_chunk_size=nn[KMG] [X86]
1833 used for mtrr cleanup. It is largest continuous chunk
1834 that could hold holes aka. UC entries.
1836 mtrr_gran_size=nn[KMG] [X86]
1837 Used for mtrr cleanup. It is granularity of mtrr block.
1839 Large value could prevent small alignment from
1842 mtrr_spare_reg_nr=n [X86]
1844 Range: 0,7 : spare reg number
1846 Used for mtrr cleanup. It is spare mtrr entries number.
1847 Set to 2 or more if your graphical card needs more.
1849 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1851 netdev= [NET] Network devices parameters
1852 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1853 Note that mem_start is often overloaded to mean
1854 something different and driver-specific.
1855 This usage is only documented in each driver source
1859 [NETFILTER] Enable connection tracking flow accounting
1860 0 to disable accounting
1861 1 to enable accounting
1864 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1865 See Documentation/filesystems/nfs/nfsroot.txt.
1867 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1868 See Documentation/filesystems/nfs/nfsroot.txt.
1870 nfsrootdebug [NFS] enable nfsroot debugging messages.
1871 See Documentation/filesystems/nfs/nfsroot.txt.
1873 nfs.callback_tcpport=
1874 [NFS] set the TCP port on which the NFSv4 callback
1875 channel should listen.
1878 [NFS] sets the pathname to the program which is used
1879 to update the NFS client cache entries.
1881 nfs.cache_getent_timeout=
1882 [NFS] sets the timeout after which an attempt to
1883 update a cache entry is deemed to have failed.
1885 nfs.idmap_cache_timeout=
1886 [NFS] set the maximum lifetime for idmapper cache
1890 [NFS] enable 64-bit inode numbers.
1891 If zero, the NFS client will fake up a 32-bit inode
1892 number for the readdir() and stat() syscalls instead
1893 of returning the full 64-bit number.
1894 The default is to return 64-bit inode numbers.
1896 nfs.max_session_slots=
1897 [NFSv4.1] Sets the maximum number of session slots
1898 the client will attempt to negotiate with the server.
1899 This limits the number of simultaneous RPC requests
1900 that the client can send to the NFSv4.1 server.
1901 Note that there is little point in setting this
1902 value higher than the max_tcp_slot_table_limit.
1904 nfs.nfs4_disable_idmapping=
1905 [NFSv4] When set to the default of '1', this option
1906 ensures that both the RPC level authentication
1907 scheme and the NFS level operations agree to use
1908 numeric uids/gids if the mount is using the
1909 'sec=sys' security flavour. In effect it is
1910 disabling idmapping, which can make migration from
1911 legacy NFSv2/v3 systems to NFSv4 easier.
1912 Servers that do not support this mode of operation
1913 will be autodetected by the client, and it will fall
1914 back to using the idmapper.
1915 To turn off this behaviour, set the value to '0'.
1917 [NFS4] Specify an additional fixed unique ident-
1918 ification string that NFSv4 clients can insert into
1919 their nfs_client_id4 string. This is typically a
1920 UUID that is generated at system install time.
1922 nfs.send_implementation_id =
1923 [NFSv4.1] Send client implementation identification
1924 information in exchange_id requests.
1925 If zero, no implementation identification information
1927 The default is to send the implementation identification
1930 nfs.recover_lost_locks =
1931 [NFSv4] Attempt to recover locks that were lost due
1932 to a lease timeout on the server. Please note that
1933 doing this risks data corruption, since there are
1934 no guarantees that the file will remain unchanged
1935 after the locks are lost.
1936 If you want to enable the kernel legacy behaviour of
1937 attempting to recover these locks, then set this
1939 The default parameter value of '0' causes the kernel
1940 not to attempt recovery of lost locks.
1942 nfsd.nfs4_disable_idmapping=
1943 [NFSv4] When set to the default of '1', the NFSv4
1944 server will return only numeric uids and gids to
1945 clients using auth_sys, and will accept numeric uids
1946 and gids from such clients. This is intended to ease
1947 migration from NFSv2/v3.
1949 objlayoutdriver.osd_login_prog=
1950 [NFS] [OBJLAYOUT] sets the pathname to the program which
1951 is used to automatically discover and login into new
1952 osd-targets. Please see:
1953 Documentation/filesystems/pnfs.txt for more explanations
1955 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1956 when a NMI is triggered.
1957 Format: [state][,regs][,debounce][,die]
1959 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1960 Format: [panic,][nopanic,][num]
1962 0 - turn nmi_watchdog off
1963 When panic is specified, panic when an NMI watchdog
1964 timeout occurs (or 'nopanic' to override the opposite
1966 This is useful when you use a panic=... timeout and
1967 need the box quickly up again.
1969 netpoll.carrier_timeout=
1970 [NET] Specifies amount of time (in seconds) that
1971 netpoll should wait for a carrier. By default netpoll
1974 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1975 emulation library even if a 387 maths coprocessor
1979 [HW] Never suspend the console
1980 Disable suspending of consoles during suspend and
1981 hibernate operations. Once disabled, debugging
1982 messages can reach various consoles while the rest
1983 of the system is being put to sleep (ie, while
1984 debugging driver suspend/resume hooks). This may
1985 not work reliably with all consoles, but is known
1986 to work with serial and VGA consoles.
1987 To facilitate more flexible debugging, we also add
1988 console_suspend, a printk module parameter to control
1989 it. Users could use console_suspend (usually
1990 /sys/module/printk/parameters/console_suspend) to
1991 turn on/off it dynamically.
1993 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1994 caches in the slab allocator. Saves per-node memory,
1995 but will impact performance.
1999 noapic [SMP,APIC] Tells the kernel to not make use of any
2000 IOAPICs that may be present in the system.
2002 noautogroup Disable scheduler automatic task group creation.
2004 nobats [PPC] Do not use BATs for mapping kernel lowmem
2005 on "Classic" PPC cores.
2009 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2011 nodelayacct [KNL] Disable per-task delay accounting
2013 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2015 nodsp [SH] Disable hardware DSP at boot time.
2017 noefi [X86] Disable EFI runtime services support.
2022 On X86-32 available only on PAE configured kernels.
2023 noexec=on: enable non-executable mappings (default)
2024 noexec=off: disable non-executable mappings
2027 Disable SMAP (Supervisor Mode Access Prevention)
2028 even if it is supported by processor.
2031 Disable SMEP (Supervisor Mode Execution Prevention)
2032 even if it is supported by processor.
2035 This affects only 32-bit executables.
2036 noexec32=on: enable non-executable mappings (default)
2037 read doesn't imply executable mappings
2038 noexec32=off: disable non-executable mappings
2039 read implies executable mappings
2041 nofpu [SH] Disable hardware FPU at boot time.
2043 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2044 register save and restore. The kernel will only save
2045 legacy floating-point registers on task switch.
2047 noxsave [BUGS=X86] Disables x86 extended register state save
2048 and restore using xsave. The kernel will fallback to
2049 enabling legacy floating-point and sse state.
2052 on enable eager fpu restore
2053 off disable eager fpu restore
2054 auto selects the default scheme, which automatically
2055 enables eagerfpu restore for xsaveopt.
2057 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2058 wfi(ARM) instruction doesn't work correctly and not to
2059 use it. This is also useful when using JTAG debugger.
2061 no_file_caps Tells the kernel not to honor file capabilities. The
2062 only way then for a file to be executed with privilege
2063 is to be setuid root or executed by root.
2065 nohalt [IA-64] Tells the kernel not to use the power saving
2066 function PAL_HALT_LIGHT when idle. This increases
2067 power-consumption. On the positive side, it reduces
2068 interrupt wake-up latency, which may improve performance
2069 in certain environments such as networked servers or
2072 nohz= [KNL] Boottime enable/disable dynamic ticks
2073 Valid arguments: on, off
2076 nohz_full= [KNL,BOOT]
2077 In kernels built with CONFIG_NO_HZ_FULL=y, set
2078 the specified list of CPUs whose tick will be stopped
2079 whenever possible. The boot CPU will be forced outside
2080 the range to maintain the timekeeping.
2081 The CPUs in this range must also be included in the
2084 noiotrap [SH] Disables trapped I/O port accesses.
2086 noirqdebug [X86-32] Disables the code which attempts to detect and
2087 disable unhandled interrupt sources.
2089 no_timer_check [X86,APIC] Disables the code which tests for
2090 broken timer IRQ sources.
2092 noisapnp [ISAPNP] Disables ISA PnP code.
2094 noinitrd [RAM] Tells the kernel not to load any configured
2097 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2099 [Deprecated - use intremap=off]
2103 nojitter [IA-64] Disables jitter checking for ITC timers.
2105 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2107 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2110 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2111 steal time is computed, but won't influence scheduler
2114 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2116 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2118 noltlbs [PPC] Do not use large page/tlb entries for kernel
2119 lowmem mapping on PPC40x.
2121 nomca [IA-64] Disable machine check abort handling
2123 nomce [X86-32] Machine Check Exception
2125 nomfgpt [X86-32] Disable Multi-Function General Purpose
2126 Timer usage (for AMD Geode machines).
2128 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2129 shutdown the other cpus. Instead use the REBOOT_VECTOR
2132 nomodule Disable module load
2134 nopat [X86] Disable PAT (page attribute table extension of
2135 pagetables) support.
2137 norandmaps Don't use address space randomization. Equivalent to
2138 echo 0 > /proc/sys/kernel/randomize_va_space
2140 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2142 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2143 with UP alternatives
2145 nordrand [X86] Disable the direct use of the RDRAND
2146 instruction even if it is supported by the
2147 processor. RDRAND is still available to user
2150 noresume [SWSUSP] Disables resume and restores original swap
2153 no-scroll [VGA] Disables scrollback.
2154 This is required for the Braillex ib80-piezo Braille
2155 reader made by F.H. Papenmeier (Germany).
2159 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2161 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2162 and disable the IO APIC. legacy for "maxcpus=0".
2164 nosoftlockup [KNL] Disable the soft-lockup detector.
2166 nosync [HW,M68K] Disables sync negotiation for all devices.
2168 notsc [BUGS=X86-32] Disable Time Stamp Counter
2170 nousb [USB] Disable the USB subsystem
2172 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2176 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2178 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2179 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2180 Some features depend on CPU0. Known dependencies are:
2181 1. Resume from suspend/hibernate depends on CPU0.
2182 Suspend/hibernate will fail if CPU0 is offline and you
2183 need to online CPU0 before suspend/hibernate.
2184 2. PIC interrupts also depend on CPU0. CPU0 can't be
2185 removed if a PIC interrupt is detected.
2186 It's said poweroff/reboot may depend on CPU0 on some
2187 machines although I haven't seen such issues so far
2188 after CPU0 is offline on a few tested machines.
2189 If the dependencies are under your control, you can
2190 turn on cpu0_hotplug.
2192 nptcg= [IA-64] Override max number of concurrent global TLB
2193 purges which is reported from either PAL_VM_SUMMARY or
2196 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2197 could support. nr_cpus=n : n >= 1 limits the kernel to
2198 supporting 'n' processors. Later in runtime you can not
2199 use hotplug cpu feature to put more cpu back to online.
2200 just like you compile the kernel NR_CPUS=n
2202 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2204 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2205 Allowed values are enable and disable
2207 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2208 one of ['zone', 'node', 'default'] can be specified
2209 This can be set from sysctl after boot.
2210 See Documentation/sysctl/vm.txt for details.
2212 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2213 See Documentation/debugging-via-ohci1394.txt for more
2216 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2217 Rather than timing out after 20 ms if an EC
2218 command is not properly ACKed, override the length
2219 of the timeout. We have interrupts disabled while
2220 waiting for the ACK, so if this is set too high
2221 interrupts *may* be lost!
2223 omap_mux= [OMAP] Override bootloader pin multiplexing.
2224 Format: <mux_mode0.mode_name=value>...
2225 For example, to override I2C bus2:
2226 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2228 oprofile.timer= [HW]
2229 Use timer interrupt instead of performance counters
2231 oprofile.cpu_type= Force an oprofile cpu type
2232 This might be useful if you have an older oprofile
2233 userland or if you want common events.
2234 Format: { arch_perfmon }
2235 arch_perfmon: [X86] Force use of architectural
2236 perfmon on Intel CPUs instead of the
2237 CPU specific event set.
2238 timer: [X86] Force use of architectural NMI
2239 timer mode (see also oprofile.timer
2240 for generic hr timer mode)
2241 [s390] Force legacy basic mode sampling
2242 (report cpu_type "timer")
2244 oops=panic Always panic on oopses. Default is to just kill the
2245 process, but there is a small probability of
2246 deadlocking the machine.
2247 This will also cause panics on machine check exceptions.
2248 Useful together with panic=30 to trigger a reboot.
2251 See Documentation/sound/oss/oss-parameters.txt
2253 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2254 timeout > 0: seconds before rebooting
2255 timeout = 0: wait forever
2256 timeout < 0: reboot immediately
2259 parkbd.port= [HW] Parallel port number the keyboard adapter is
2260 connected to, default is 0.
2262 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2263 0 for XT, 1 for AT (default is AT).
2266 parport= [HW,PPT] Specify parallel ports. 0 disables.
2267 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2268 Use 'auto' to force the driver to use any
2269 IRQ/DMA settings detected (the default is to
2270 ignore detected IRQ/DMA settings because of
2271 possible conflicts). You can specify the base
2272 address, IRQ, and DMA settings; IRQ and DMA
2273 should be numbers, or 'auto' (for using detected
2274 settings on that particular port), or 'nofifo'
2275 (to avoid using a FIFO even if it is detected).
2276 Parallel ports are assigned in the order they
2277 are specified on the command line, starting
2280 parport_init_mode= [HW,PPT]
2281 Configure VIA parallel port to operate in
2282 a specific mode. This is necessary on Pegasos
2283 computer where firmware has no options for setting
2284 up parallel port mode and sets it to spp.
2285 Currently this function knows 686a and 8231 chips.
2286 Format: [spp|ps2|epp|ecp|ecpepp]
2289 Halt all CPUs after the first oops has been printed for
2290 the specified number of seconds. This is to be used if
2291 your oopses keep scrolling off the screen.
2296 See header of drivers/block/paride/pcd.c.
2297 See also Documentation/blockdev/paride.txt.
2299 pci=option[,option...] [PCI] various PCI subsystem options:
2300 earlydump [X86] dump PCI config space before the kernel
2302 off [X86] don't probe for the PCI bus
2303 bios [X86-32] force use of PCI BIOS, don't access
2304 the hardware directly. Use this if your machine
2305 has a non-standard PCI host bridge.
2306 nobios [X86-32] disallow use of PCI BIOS, only direct
2307 hardware access methods are allowed. Use this
2308 if you experience crashes upon bootup and you
2309 suspect they are caused by the BIOS.
2310 conf1 [X86] Force use of PCI Configuration
2312 conf2 [X86] Force use of PCI Configuration
2314 noaer [PCIE] If the PCIEAER kernel config parameter is
2315 enabled, this kernel boot option can be used to
2316 disable the use of PCIE advanced error reporting.
2317 nodomains [PCI] Disable support for multiple PCI
2318 root domains (aka PCI segments, in ACPI-speak).
2319 nommconf [X86] Disable use of MMCONFIG for PCI
2321 check_enable_amd_mmconf [X86] check for and enable
2322 properly configured MMIO access to PCI
2323 config space on AMD family 10h CPU
2324 nomsi [MSI] If the PCI_MSI kernel config parameter is
2325 enabled, this kernel boot option can be used to
2326 disable the use of MSI interrupts system-wide.
2327 noioapicquirk [APIC] Disable all boot interrupt quirks.
2328 Safety option to keep boot IRQs enabled. This
2329 should never be necessary.
2330 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2331 primary IO-APIC for bridges that cannot disable
2332 boot IRQs. This fixes a source of spurious IRQs
2333 when the system masks IRQs.
2334 noioapicreroute [APIC] Disable workaround that uses the
2335 boot IRQ equivalent of an IRQ that connects to
2336 a chipset where boot IRQs cannot be disabled.
2337 The opposite of ioapicreroute.
2338 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2339 routing table. These calls are known to be buggy
2340 on several machines and they hang the machine
2341 when used, but on other computers it's the only
2342 way to get the interrupt routing table. Try
2343 this option if the kernel is unable to allocate
2344 IRQs or discover secondary PCI buses on your
2346 rom [X86] Assign address space to expansion ROMs.
2347 Use with caution as certain devices share
2348 address decoders between ROMs and other
2350 norom [X86] Do not assign address space to
2351 expansion ROMs that do not already have
2352 BIOS assigned address ranges.
2353 nobar [X86] Do not assign address space to the
2354 BARs that weren't assigned by the BIOS.
2355 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2356 assigned automatically to PCI devices. You can
2357 make the kernel exclude IRQs of your ISA cards
2359 pirqaddr=0xAAAAA [X86] Specify the physical address
2360 of the PIRQ table (normally generated
2361 by the BIOS) if it is outside the
2362 F0000h-100000h range.
2363 lastbus=N [X86] Scan all buses thru bus #N. Can be
2364 useful if the kernel is unable to find your
2365 secondary buses and you want to tell it
2366 explicitly which ones they are.
2367 assign-busses [X86] Always assign all PCI bus
2368 numbers ourselves, overriding
2369 whatever the firmware may have done.
2370 usepirqmask [X86] Honor the possible IRQ mask stored
2371 in the BIOS $PIR table. This is needed on
2372 some systems with broken BIOSes, notably
2373 some HP Pavilion N5400 and Omnibook XE3
2374 notebooks. This will have no effect if ACPI
2375 IRQ routing is enabled.
2376 noacpi [X86] Do not use ACPI for IRQ routing
2377 or for PCI scanning.
2378 use_crs [X86] Use PCI host bridge window information
2379 from ACPI. On BIOSes from 2008 or later, this
2380 is enabled by default. If you need to use this,
2381 please report a bug.
2382 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2383 If you need to use this, please report a bug.
2384 routeirq Do IRQ routing for all PCI devices.
2385 This is normally done in pci_enable_device(),
2386 so this option is a temporary workaround
2387 for broken drivers that don't call it.
2388 skip_isa_align [X86] do not align io start addr, so can
2389 handle more pci cards
2390 firmware [ARM] Do not re-enumerate the bus but instead
2391 just use the configuration from the
2392 bootloader. This is currently used on
2393 IXP2000 systems where the bus has to be
2394 configured a certain way for adjunct CPUs.
2395 noearly [X86] Don't do any early type 1 scanning.
2396 This might help on some broken boards which
2397 machine check when some devices' config space
2398 is read. But various workarounds are disabled
2399 and some IOMMU drivers will not work.
2400 bfsort Sort PCI devices into breadth-first order.
2401 This sorting is done to get a device
2402 order compatible with older (<= 2.4) kernels.
2403 nobfsort Don't sort PCI devices into breadth-first order.
2404 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2405 tuning and use the BIOS-configured MPS defaults.
2406 pcie_bus_safe Set every device's MPS to the largest value
2407 supported by all devices below the root complex.
2408 pcie_bus_perf Set device MPS to the largest allowable MPS
2409 based on its parent bus. Also set MRRS (Max
2410 Read Request Size) to the largest supported
2411 value (no larger than the MPS that the device
2412 or bus can support) for best performance.
2413 pcie_bus_peer2peer Set every device's MPS to 128B, which
2414 every device is guaranteed to support. This
2415 configuration allows peer-to-peer DMA between
2416 any pair of devices, possibly at the cost of
2417 reduced performance. This also guarantees
2418 that hot-added devices will work.
2419 cbiosize=nn[KMG] The fixed amount of bus space which is
2420 reserved for the CardBus bridge's IO window.
2421 The default value is 256 bytes.
2422 cbmemsize=nn[KMG] The fixed amount of bus space which is
2423 reserved for the CardBus bridge's memory
2424 window. The default value is 64 megabytes.
2427 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2428 Specifies alignment and device to reassign
2429 aligned memory resources.
2430 If <order of align> is not specified,
2431 PAGE_SIZE is used as alignment.
2432 PCI-PCI bridge can be specified, if resource
2433 windows need to be expanded.
2434 ecrc= Enable/disable PCIe ECRC (transaction layer
2435 end-to-end CRC checking).
2436 bios: Use BIOS/firmware settings. This is the
2440 hpiosize=nn[KMG] The fixed amount of bus space which is
2441 reserved for hotplug bridge's IO window.
2442 Default size is 256 bytes.
2443 hpmemsize=nn[KMG] The fixed amount of bus space which is
2444 reserved for hotplug bridge's memory window.
2445 Default size is 2 megabytes.
2446 realloc= Enable/disable reallocating PCI bridge resources
2447 if allocations done by BIOS are too small to
2448 accommodate resources required by all child
2450 off: Turn realloc off
2452 realloc same as realloc=on
2453 noari do not use PCIe ARI.
2454 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2455 only look for one device below a PCIe downstream
2458 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2461 force Enable ASPM even on devices that claim not to support it.
2462 WARNING: Forcing ASPM on may cause system lockups.
2464 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2465 nomsi Do not use MSI for PCI Express Native Hotplug (this
2466 makes all PCIe ports use INTx for hotplug services).
2468 pcie_ports= [PCIE] PCIe ports handling:
2469 auto Ask the BIOS whether or not to use native PCIe services
2470 associated with PCIe ports (PME, hot-plug, AER). Use
2471 them only if that is allowed by the BIOS.
2472 native Use native PCIe services associated with PCIe ports
2474 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2477 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2478 nomsi Do not use MSI for native PCIe PME signaling (this makes
2479 all PCIe root ports use INTx for all services).
2481 pcmv= [HW,PCMCIA] BadgePAD 4
2484 See Documentation/blockdev/paride.txt.
2486 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2489 See arch/parisc/kernel/pdc_chassis.c
2491 percpu_alloc= Select which percpu first chunk allocator to use.
2492 Currently supported values are "embed" and "page".
2493 Archs may support subset or none of the selections.
2494 See comments in mm/percpu.c for details on each
2495 allocator. This parameter is primarily for debugging
2496 and performance comparison.
2499 See Documentation/blockdev/paride.txt.
2502 See Documentation/blockdev/paride.txt.
2504 pirq= [SMP,APIC] Manual mp-table setup
2505 See Documentation/x86/i386/IO-APIC.txt.
2507 plip= [PPT,NET] Parallel port network link
2508 Format: { parport<nr> | timid | 0 }
2509 See also Documentation/parport.txt.
2511 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2512 Override pmtimer IOPort with a hex value.
2516 Enable PNP debug messages (depends on the
2517 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2518 via /sys/module/pnp/parameters/debug. We always show
2519 current resource usage; turning this on also shows
2520 possible settings and some assignment information.
2526 { on | off | curr | res | no-curr | no-res }
2529 [ISAPNP] Exclude IRQs for the autoconfiguration
2532 [ISAPNP] Exclude DMAs for the autoconfiguration
2534 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2535 Ranges are in pairs (I/O port base and size).
2538 [ISAPNP] Exclude memory regions for the
2540 Ranges are in pairs (memory base and size).
2542 ports= [IP_VS_FTP] IPVS ftp helper module
2544 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2546 Format: <port>,<port>....
2548 print-fatal-signals=
2549 [KNL] debug: print fatal signals
2551 If enabled, warn about various signal handling
2552 related application anomalies: too many signals,
2553 too many POSIX.1 timers, fatal signals causing a
2556 If you hit the warning due to signal overflow,
2557 you might want to try "ulimit -i unlimited".
2561 printk.always_kmsg_dump=
2562 Trigger kmsg_dump for cases other than kernel oops or
2564 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2567 printk.time= Show timing data prefixed to each printk message line
2568 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2570 processor.max_cstate= [HW,ACPI]
2571 Limit processor to maximum C-state
2572 max_cstate=9 overrides any DMI blacklist limit.
2574 processor.nocst [HW,ACPI]
2575 Ignore the _CST method to determine C-states,
2576 instead using the legacy FADT method
2578 profile= [KNL] Enable kernel profiling via /proc/profile
2579 Format: [schedule,]<number>
2580 Param: "schedule" - profile schedule points.
2581 Param: <number> - step/bucket size as a power of 2 for
2582 statistical time based profiling.
2583 Param: "sleep" - profile D-state sleeping (millisecs).
2584 Requires CONFIG_SCHEDSTATS
2585 Param: "kvm" - profile VM exits.
2587 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2589 See Documentation/blockdev/ramdisk.txt.
2591 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2592 probe for; one of (bare|imps|exps|lifebook|any).
2593 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2595 psmouse.resetafter= [HW,MOUSE]
2596 Try to reset the device after so many bad packets
2599 [HW,MOUSE] Set desired mouse resolution, in dpi.
2600 psmouse.smartscroll=
2601 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2602 0 = disabled, 1 = enabled (default).
2604 pstore.backend= Specify the name of the pstore backend to use
2607 See Documentation/blockdev/paride.txt.
2610 [KNL] Number of legacy pty's. Overwrites compiled-in
2613 quiet [KNL] Disable most log messages
2618 See Documentation/md.txt.
2620 ramdisk_blocksize= [RAM]
2621 See Documentation/blockdev/ramdisk.txt.
2623 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2624 See Documentation/blockdev/ramdisk.txt.
2627 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2628 the specified list of CPUs to be no-callback CPUs.
2629 Invocation of these CPUs' RCU callbacks will
2630 be offloaded to "rcuox/N" kthreads created for
2631 that purpose, where "x" is "b" for RCU-bh, "p"
2632 for RCU-preempt, and "s" for RCU-sched, and "N"
2633 is the CPU number. This reduces OS jitter on the
2634 offloaded CPUs, which can be useful for HPC and
2636 real-time workloads. It can also improve energy
2637 efficiency for asymmetric multiprocessors.
2640 Rather than requiring that offloaded CPUs
2641 (specified by rcu_nocbs= above) explicitly
2642 awaken the corresponding "rcuoN" kthreads,
2643 make these kthreads poll for callbacks.
2644 This improves the real-time response for the
2645 offloaded CPUs by relieving them of the need to
2646 wake up the corresponding kthread, but degrades
2647 energy efficiency by requiring that the kthreads
2648 periodically wake up to do the polling.
2650 rcutree.blimit= [KNL]
2651 Set maximum number of finished RCU callbacks to process
2654 rcutree.rcu_fanout_leaf= [KNL]
2655 Increase the number of CPUs assigned to each
2656 leaf rcu_node structure. Useful for very large
2659 rcutree.jiffies_till_first_fqs= [KNL]
2660 Set delay from grace-period initialization to
2661 first attempt to force quiescent states.
2662 Units are jiffies, minimum value is zero,
2663 and maximum value is HZ.
2665 rcutree.jiffies_till_next_fqs= [KNL]
2666 Set delay between subsequent attempts to force
2667 quiescent states. Units are jiffies, minimum
2668 value is one, and maximum value is HZ.
2670 rcutree.qhimark= [KNL]
2671 Set threshold of queued
2672 RCU callbacks over which batch limiting is disabled.
2674 rcutree.qlowmark= [KNL]
2675 Set threshold of queued RCU callbacks below which
2676 batch limiting is re-enabled.
2678 rcutree.rcu_idle_gp_delay= [KNL]
2679 Set wakeup interval for idle CPUs that have
2680 RCU callbacks (RCU_FAST_NO_HZ=y).
2682 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2683 Set wakeup interval for idle CPUs that have
2684 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2685 Lazy RCU callbacks are those which RCU can
2686 prove do nothing more than free memory.
2688 rcutorture.fqs_duration= [KNL]
2689 Set duration of force_quiescent_state bursts.
2691 rcutorture.fqs_holdoff= [KNL]
2692 Set holdoff time within force_quiescent_state bursts.
2694 rcutorture.fqs_stutter= [KNL]
2695 Set wait time between force_quiescent_state bursts.
2697 rcutorture.gp_exp= [KNL]
2698 Use expedited update-side primitives.
2700 rcutorture.gp_normal= [KNL]
2701 Use normal (non-expedited) update-side primitives.
2702 If both gp_exp and gp_normal are set, do both.
2703 If neither gp_exp nor gp_normal are set, still
2706 rcutorture.n_barrier_cbs= [KNL]
2707 Set callbacks/threads for rcu_barrier() testing.
2709 rcutorture.nfakewriters= [KNL]
2710 Set number of concurrent RCU writers. These just
2711 stress RCU, they don't participate in the actual
2712 test, hence the "fake".
2714 rcutorture.nreaders= [KNL]
2715 Set number of RCU readers.
2717 rcutorture.object_debug= [KNL]
2718 Enable debug-object double-call_rcu() testing.
2720 rcutorture.onoff_holdoff= [KNL]
2721 Set time (s) after boot for CPU-hotplug testing.
2723 rcutorture.onoff_interval= [KNL]
2724 Set time (s) between CPU-hotplug operations, or
2725 zero to disable CPU-hotplug testing.
2727 rcutorture.rcutorture_runnable= [BOOT]
2728 Start rcutorture running at boot time.
2730 rcutorture.shuffle_interval= [KNL]
2731 Set task-shuffle interval (s). Shuffling tasks
2732 allows some CPUs to go into dyntick-idle mode
2733 during the rcutorture test.
2735 rcutorture.shutdown_secs= [KNL]
2736 Set time (s) after boot system shutdown. This
2737 is useful for hands-off automated testing.
2739 rcutorture.stall_cpu= [KNL]
2740 Duration of CPU stall (s) to test RCU CPU stall
2741 warnings, zero to disable.
2743 rcutorture.stall_cpu_holdoff= [KNL]
2744 Time to wait (s) after boot before inducing stall.
2746 rcutorture.stat_interval= [KNL]
2747 Time (s) between statistics printk()s.
2749 rcutorture.stutter= [KNL]
2750 Time (s) to stutter testing, for example, specifying
2751 five seconds causes the test to run for five seconds,
2752 wait for five seconds, and so on. This tests RCU's
2753 ability to transition abruptly to and from idle.
2755 rcutorture.test_boost= [KNL]
2756 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2757 "Maybe" means test if the RCU implementation
2758 under test support RCU priority boosting.
2760 rcutorture.test_boost_duration= [KNL]
2761 Duration (s) of each individual boost test.
2763 rcutorture.test_boost_interval= [KNL]
2764 Interval (s) between each boost test.
2766 rcutorture.test_no_idle_hz= [KNL]
2767 Test RCU's dyntick-idle handling. See also the
2768 rcutorture.shuffle_interval parameter.
2770 rcutorture.torture_type= [KNL]
2771 Specify the RCU implementation to test.
2773 rcutorture.verbose= [KNL]
2774 Enable additional printk() statements.
2776 rcupdate.rcu_expedited= [KNL]
2777 Use expedited grace-period primitives, for
2778 example, synchronize_rcu_expedited() instead
2779 of synchronize_rcu(). This reduces latency,
2780 but can increase CPU utilization, degrade
2781 real-time latency, and degrade energy efficiency.
2783 rcupdate.rcu_cpu_stall_suppress= [KNL]
2784 Suppress RCU CPU stall warning messages.
2786 rcupdate.rcu_cpu_stall_timeout= [KNL]
2787 Set timeout for RCU CPU stall warning messages.
2791 Run specified binary instead of /init from the ramdisk,
2792 used for early userspace startup. See initrd.
2795 Format (x86 or x86_64):
2796 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2798 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2800 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2801 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2802 reboot_force is either force or not specified,
2803 reboot_cpu is s[mp]#### with #### being the processor
2804 to be used for rebooting.
2807 [KNL, SMP] Set scheduler's default relax_domain_level.
2808 See Documentation/cgroups/cpusets.txt.
2810 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2812 reservetop= [X86-32]
2814 Reserves a hole at the top of the kernel virtual
2819 Set the amount of memory to reserve for BIOS at
2820 the bottom of the address space.
2822 reset_devices [KNL] Force drivers to reset the underlying device
2823 during initialization.
2826 Specify the partition device for software suspend
2828 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2830 resume_offset= [SWSUSP]
2831 Specify the offset from the beginning of the partition
2832 given by "resume=" at which the swap header is located,
2833 in <PAGE_SIZE> units (needed only for swap files).
2834 See Documentation/power/swsusp-and-swap-files.txt
2836 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2837 read the resume files
2839 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2840 Useful for devices that are detected asynchronously
2841 (e.g. USB and MMC devices).
2843 hibernate= [HIBERNATION]
2844 noresume Don't check if there's a hibernation image
2845 present during boot.
2846 nocompress Don't compress/decompress hibernation images.
2848 retain_initrd [RAM] Keep initrd memory after extraction
2850 rhash_entries= [KNL,NET]
2851 Set number of hash buckets for route cache
2853 riscom8= [HW,SERIAL]
2854 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2856 ro [KNL] Mount root device read-only on boot
2858 root= [KNL] Root filesystem
2859 See name_to_dev_t comment in init/do_mounts.c.
2861 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2862 mount the root filesystem
2864 rootflags= [KNL] Set root filesystem mount option string
2866 rootfstype= [KNL] Set root filesystem type
2868 rootwait [KNL] Wait (indefinitely) for root device to show up.
2869 Useful for devices that are detected asynchronously
2870 (e.g. USB and MMC devices).
2872 rproc_mem=nn[KMG][@address]
2873 [KNL,ARM,CMA] Remoteproc physical memory block.
2874 Memory area to be used by remote processor image,
2877 rw [KNL] Mount root device read-write on boot
2879 S [KNL] Run init in single mode
2882 See drivers/net/irda/sa1100_ir.c.
2884 sbni= [NET] Granch SBNI12 leased line adapter
2886 sched_debug [KNL] Enables verbose scheduler debug messages.
2888 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2889 xtime_lock contention on larger systems, and/or RCU lock
2890 contention on all systems with CONFIG_MAXSMP set.
2891 Format: { "0" | "1" }
2892 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2894 Note: increases power consumption, thus should only be
2895 enabled if running jitter sensitive (HPC/RT) workloads.
2897 security= [SECURITY] Choose a security module to enable at boot.
2898 If this boot parameter is not specified, only the first
2899 security module asking for security registration will be
2900 loaded. An invalid security module name will be treated
2901 as if no module has been chosen.
2903 selinux= [SELINUX] Disable or enable SELinux at boot time.
2904 Format: { "0" | "1" }
2905 See security/selinux/Kconfig help text.
2908 Default value is set via kernel config option.
2909 If enabled at boot time, /selinux/disable can be used
2910 later to disable prior to initial policy load.
2912 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2913 Format: { "0" | "1" }
2914 See security/apparmor/Kconfig help text
2917 Default value is set via kernel config option.
2919 serialnumber [BUGS=X86-32]
2922 Maximal number of shapers.
2924 show_msr= [x86] show boot-time MSR settings
2925 Format: { <integer> }
2926 Show boot-time (BIOS-initialized) MSR settings.
2927 The parameter means the number of CPUs to show,
2928 for example 1 means boot CPU only.
2935 slab_max_order= [MM, SLAB]
2936 Determines the maximum allowed order for slabs.
2937 A high setting may cause OOMs due to memory
2938 fragmentation. Defaults to 1 for systems with
2939 more than 32MB of RAM, 0 otherwise.
2941 slub_debug[=options[,slabs]] [MM, SLUB]
2942 Enabling slub_debug allows one to determine the
2943 culprit if slab objects become corrupted. Enabling
2944 slub_debug can create guard zones around objects and
2945 may poison objects when not in use. Also tracks the
2946 last alloc / free. For more information see
2947 Documentation/vm/slub.txt.
2949 slub_max_order= [MM, SLUB]
2950 Determines the maximum allowed order for slabs.
2951 A high setting may cause OOMs due to memory
2952 fragmentation. For more information see
2953 Documentation/vm/slub.txt.
2955 slub_min_objects= [MM, SLUB]
2956 The minimum number of objects per slab. SLUB will
2957 increase the slab order up to slub_max_order to
2958 generate a sufficiently large slab able to contain
2959 the number of objects indicated. The higher the number
2960 of objects the smaller the overhead of tracking slabs
2961 and the less frequently locks need to be acquired.
2962 For more information see Documentation/vm/slub.txt.
2964 slub_min_order= [MM, SLUB]
2965 Determines the minimum page order for slabs. Must be
2966 lower than slub_max_order.
2967 For more information see Documentation/vm/slub.txt.
2969 slub_nomerge [MM, SLUB]
2970 Disable merging of slabs with similar size. May be
2971 necessary if there is some reason to distinguish
2972 allocs to different slabs. Debug options disable
2973 merging on their own.
2974 For more information see Documentation/vm/slub.txt.
2977 Format: <io1>[,<io2>[,...,<io8>]]
2979 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2980 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2981 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2982 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2983 smsc-ircc2.ircc_irq= [HW] IRQ line
2984 smsc-ircc2.ircc_dma= [HW] DMA channel
2985 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2986 0: Toshiba Satellite 1800 (GP data pin select)
2987 1: Fast pin select (default)
2991 [KNL] Should the soft-lockup detector generate panics.
2994 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2995 See Documentation/laptops/sonypi.txt
2997 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2998 See Documentation/serial/specialix.txt.
3000 spia_io_base= [HW,MTD]
3006 Enabled the stack tracer on boot up.
3008 stacktrace_filter=[function-list]
3009 [FTRACE] Limit the functions that the stack tracer
3010 will trace at boot up. function-list is a comma separated
3011 list of functions. This list can be changed at run
3012 time by the stack_trace_filter file in the debugfs
3013 tracing directory. Note, this enables stack tracing
3014 and the stacktrace above is not needed.
3018 Set the STI (builtin display/keyboard on the HP-PARISC
3019 machines) console (graphic card) which should be used
3020 as the initial boot-console.
3021 See also comment in drivers/video/console/sticore.c.
3024 See comment in drivers/video/console/sticore.c.
3027 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3029 sunrpc.min_resvport=
3030 sunrpc.max_resvport=
3032 SunRPC servers often require that client requests
3033 originate from a privileged port (i.e. a port in the
3034 range 0 < portnr < 1024).
3035 An administrator who wishes to reserve some of these
3036 ports for other uses may adjust the range that the
3037 kernel's sunrpc client considers to be privileged
3038 using these two parameters to set the minimum and
3039 maximum port values.
3043 Control how the NFS server code allocates CPUs to
3044 service thread pools. Depending on how many NICs
3045 you have and where their interrupts are bound, this
3046 option will affect which CPUs will do NFS serving.
3047 Note: this parameter cannot be changed while the
3048 NFS server is running.
3050 auto the server chooses an appropriate mode
3051 automatically using heuristics
3052 global a single global pool contains all CPUs
3053 percpu one pool for each CPU
3054 pernode one pool for each NUMA node (equivalent
3055 to global on non-NUMA machines)
3057 sunrpc.tcp_slot_table_entries=
3058 sunrpc.udp_slot_table_entries=
3060 Sets the upper limit on the number of simultaneous
3061 RPC calls that can be sent from the client to a
3062 server. Increasing these values may allow you to
3063 improve throughput, but will also increase the
3064 amount of memory reserved for use by the client.
3067 [KNL] Enable accounting of swap in memory resource
3068 controller if no parameter or 1 is given or disable
3069 it if 0 is given (See Documentation/cgroups/memory.txt)
3071 swiotlb= [IA-64] Number of I/O TLB slabs
3075 sysfs.deprecated=0|1 [KNL]
3076 Enable/disable old style sysfs layout for old udev
3077 on older distributions. When this option is enabled
3078 very new udev will not work anymore. When this option
3079 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3080 in older udev will not work anymore.
3081 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3082 the kernel configuration.
3084 sysrq_always_enabled
3086 Ignore sysrq setting - this boot parameter will
3087 neutralize any effect of /proc/sys/kernel/sysrq.
3088 Useful for debugging.
3092 test_suspend= [SUSPEND]
3093 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3094 standby suspend) as the system sleep state to briefly
3095 enter during system startup. The system is woken from
3096 this state using a wakeup-capable RTC alarm.
3098 thash_entries= [KNL,NET]
3099 Set number of hash buckets for TCP connection
3101 thermal.act= [HW,ACPI]
3102 -1: disable all active trip points in all thermal zones
3103 <degrees C>: override all lowest active trip points
3105 thermal.crt= [HW,ACPI]
3106 -1: disable all critical trip points in all thermal zones
3107 <degrees C>: override all critical trip points
3109 thermal.nocrt= [HW,ACPI]
3110 Set to disable actions on ACPI thermal zone
3111 critical and hot trip points.
3113 thermal.off= [HW,ACPI]
3114 1: disable ACPI thermal control
3116 thermal.psv= [HW,ACPI]
3117 -1: disable all passive trip points
3118 <degrees C>: override all passive trip points to this
3121 thermal.tzp= [HW,ACPI]
3122 Specify global default ACPI thermal zone polling rate
3123 <deci-seconds>: poll all this frequency
3124 0: no polling (default)
3127 Force threading of all interrupt handlers except those
3128 marked explicitly IRQF_NO_THREAD.
3131 Enable the Transcendent memory driver if built-in.
3133 tmem.cleancache=0|1 [KNL, XEN]
3134 Default is on (1). Disable the usage of the cleancache
3135 API to send anonymous pages to the hypervisor.
3137 tmem.frontswap=0|1 [KNL, XEN]
3138 Default is on (1). Disable the usage of the frontswap
3139 API to send swap pages to the hypervisor. If disabled
3140 the selfballooning and selfshrinking are force disabled.
3142 tmem.selfballooning=0|1 [KNL, XEN]
3143 Default is on (1). Disable the driving of swap pages
3146 tmem.selfshrinking=0|1 [KNL, XEN]
3147 Default is on (1). Partial swapoff that immediately
3148 transfers pages from Xen hypervisor back to the
3149 kernel based on different criteria.
3153 Specify if the kernel should make use of the cpu
3154 topology information if the hardware supports this.
3155 The scheduler will make use of this information and
3156 e.g. base its process migration decisions on it.
3161 tpm_suspend_pcr=[HW,TPM]
3162 Format: integer pcr id
3163 Specify that at suspend time, the tpm driver
3164 should extend the specified pcr with zeros,
3165 as a workaround for some chips which fail to
3166 flush the last written pcr on TPM_SaveState.
3167 This will guarantee that all the other pcrs
3170 trace_buf_size=nn[KMG]
3171 [FTRACE] will set tracing buffer size.
3173 trace_event=[event-list]
3174 [FTRACE] Set and start specified trace events in order
3175 to facilitate early boot debugging.
3176 See also Documentation/trace/events.txt
3178 trace_options=[option-list]
3179 [FTRACE] Enable or disable tracer options at boot.
3180 The option-list is a comma delimited list of options
3181 that can be enabled or disabled just as if you were
3182 to echo the option name into
3184 /sys/kernel/debug/tracing/trace_options
3186 For example, to enable stacktrace option (to dump the
3187 stack trace of each event), add to the command line:
3189 trace_options=stacktrace
3191 See also Documentation/trace/ftrace.txt "trace options"
3195 [FTRACE] enable this option to disable tracing when a
3196 warning is hit. This turns off "tracing_on". Tracing can
3197 be enabled again by echoing '1' into the "tracing_on"
3198 file located in /sys/kernel/debug/tracing/
3200 This option is useful, as it disables the trace before
3201 the WARNING dump is called, which prevents the trace to
3202 be filled with content caused by the warning output.
3204 This option can also be set at run time via the sysctl
3205 option: kernel/traceoff_on_warning
3207 transparent_hugepage=
3209 Format: [always|madvise|never]
3210 Can be used to control the default behavior of the system
3211 with respect to transparent hugepages.
3212 See Documentation/vm/transhuge.txt for more details.
3214 tsc= Disable clocksource stability checks for TSC.
3216 [x86] reliable: mark tsc clocksource as reliable, this
3217 disables clocksource verification at runtime, as well
3218 as the stability checks done at bootup. Used to enable
3219 high-resolution timer mode on older hardware, and in
3220 virtualized environment.
3221 [x86] noirqtime: Do not use TSC to do irq accounting.
3222 Used to run time disable IRQ_TIME_ACCOUNTING on any
3223 platforms where RDTSC is slow and this accounting
3226 turbografx.map[2|3]= [HW,JOY]
3227 TurboGraFX parallel port interface
3229 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3230 See also Documentation/input/joystick-parport.txt
3232 udbg-immortal [PPC] When debugging early kernel crashes that
3233 happen after console_init() and before a proper
3234 console driver takes over, this boot options might
3235 help "seeing" what's going on.
3237 uhash_entries= [KNL,NET]
3238 Set number of hash buckets for UDP/UDP-Lite connections
3241 [USB] Ignore overcurrent events (default N).
3242 Some badly-designed motherboards generate lots of
3243 bogus events, for ports that aren't wired to
3244 anything. Set this parameter to avoid log spamming.
3245 Note that genuine overcurrent events won't be
3249 [X86] Cause panic on unknown NMI.
3251 usbcore.authorized_default=
3252 [USB] Default USB device authorization:
3253 (default -1 = authorized except for wireless USB,
3254 0 = not authorized, 1 = authorized)
3256 usbcore.autosuspend=
3257 [USB] The autosuspend time delay (in seconds) used
3258 for newly-detected USB devices (default 2). This
3259 is the time required before an idle device will be
3260 autosuspended. Devices for which the delay is set
3261 to a negative value won't be autosuspended at all.
3263 usbcore.usbfs_snoop=
3264 [USB] Set to log all usbfs traffic (default 0 = off).
3266 usbcore.blinkenlights=
3267 [USB] Set to cycle leds on hubs (default 0 = off).
3269 usbcore.old_scheme_first=
3270 [USB] Start with the old device initialization
3271 scheme (default 0 = off).
3273 usbcore.usbfs_memory_mb=
3274 [USB] Memory limit (in MB) for buffers allocated by
3275 usbfs (default = 16, 0 = max = 2047).
3277 usbcore.use_both_schemes=
3278 [USB] Try the other device initialization scheme
3279 if the first one fails (default 1 = enabled).
3281 usbcore.initial_descriptor_timeout=
3282 [USB] Specifies timeout for the initial 64-byte
3283 USB_REQ_GET_DESCRIPTOR request in milliseconds
3284 (default 5000 = 5.0 seconds).
3287 [USBHID] The interval which mice are to be polled at.
3289 usb-storage.delay_use=
3290 [UMS] The delay in seconds before a new device is
3291 scanned for Logical Units (default 5).
3294 [UMS] A list of quirks entries to supplement or
3295 override the built-in unusual_devs list. List
3296 entries are separated by commas. Each entry has
3297 the form VID:PID:Flags where VID and PID are Vendor
3298 and Product ID values (4-digit hex numbers) and
3299 Flags is a set of characters, each corresponding
3300 to a common usb-storage quirk flag as follows:
3301 a = SANE_SENSE (collect more than 18 bytes
3303 b = BAD_SENSE (don't collect more than 18
3304 bytes of sense data);
3305 c = FIX_CAPACITY (decrease the reported
3306 device capacity by one sector);
3307 d = NO_READ_DISC_INFO (don't use
3308 READ_DISC_INFO command);
3309 e = NO_READ_CAPACITY_16 (don't use
3310 READ_CAPACITY_16 command);
3311 h = CAPACITY_HEURISTICS (decrease the
3312 reported device capacity by one
3313 sector if the number is odd);
3314 i = IGNORE_DEVICE (don't bind to this
3316 l = NOT_LOCKABLE (don't try to lock and
3317 unlock ejectable media);
3318 m = MAX_SECTORS_64 (don't transfer more
3319 than 64 sectors = 32 KB at a time);
3320 n = INITIAL_READ10 (force a retry of the
3321 initial READ(10) command);
3322 o = CAPACITY_OK (accept the capacity
3323 reported by the device);
3324 p = WRITE_CACHE (the device cache is ON
3326 r = IGNORE_RESIDUE (the device reports
3327 bogus residue values);
3328 s = SINGLE_LUN (the device has only one
3330 w = NO_WP_DETECT (don't test whether the
3331 medium is write-protected).
3332 Example: quirks=0419:aaf5:rl,0421:0433:rc
3334 user_debug= [KNL,ARM]
3336 See arch/arm/Kconfig.debug help text.
3337 1 - undefined instruction events
3339 4 - invalid data aborts
3342 Example: user_debug=31
3345 [X86] Flags controlling user PTE allocations.
3347 nohigh = do not allocate PTE pages in
3348 HIGHMEM regardless of setting
3352 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3353 vdso=1: enable VDSO (default)
3354 vdso=0: disable VDSO mapping
3357 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3358 vdso32=1: enable 32-bit VDSO (default)
3359 vdso32=0: disable 32-bit VDSO mapping
3362 vector=percpu: enable percpu vector domain
3364 video= [FB] Frame buffer configuration
3365 See Documentation/fb/modedb.txt.
3367 video.brightness_switch_enabled= [0,1]
3368 If set to 1, on receiving an ACPI notify event
3369 generated by hotkey, video driver will adjust brightness
3370 level and then send out the event to user space through
3371 the allocated input device; If set to 0, video driver
3372 will only send out the event without touching backlight
3377 [VMMIO] Memory mapped virtio (platform) device.
3379 <size>@<baseaddr>:<irq>[:<id>]
3381 <size> := size (can use standard suffixes
3383 <baseaddr> := physical base address
3384 <irq> := interrupt number (as passed to
3386 <id> := (optional) platform device id
3388 virtio_mmio.device=1K@0x100b0000:48:7
3390 Can be used multiple times for multiple devices.
3392 vga= [BOOT,X86-32] Select a particular video mode
3393 See Documentation/x86/boot.txt and
3394 Documentation/svga.txt.
3395 Use vga=ask for menu.
3396 This is actually a boot loader parameter; the value is
3397 passed to the kernel using a special protocol.
3399 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3400 size of <nn>. This can be used to increase the
3401 minimum size (128MB on x86). It can also be used to
3402 decrease the size and leave more room for directly
3405 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3408 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3411 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3415 Controls the behavior of vsyscalls (i.e. calls to
3416 fixed addresses of 0xffffffffff600x00 from legacy
3417 code). Most statically-linked binaries and older
3418 versions of glibc use these calls. Because these
3419 functions are at fixed addresses, they make nice
3420 targets for exploits that can control RIP.
3422 emulate [default] Vsyscalls turn into traps and are
3423 emulated reasonably safely.
3425 native Vsyscalls are native syscall instructions.
3426 This is a little bit faster than trapping
3427 and makes a few dynamic recompilers work
3428 better than they would in emulation mode.
3429 It also makes exploits much easier to write.
3431 none Vsyscalls don't work at all. This makes
3432 them quite hard to use for exploits but
3433 might break your system.
3435 vt.color= [VT] Default text color.
3436 Format: 0xYX, X = foreground, Y = background.
3437 Default: 0x07 = light gray on black.
3439 vt.cur_default= [VT] Default cursor shape.
3440 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3441 the parameters of the <Esc>[?A;B;Cc escape sequence;
3442 see VGA-softcursor.txt. Default: 2 = underline.
3444 vt.default_blu= [VT]
3445 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3446 Change the default blue palette of the console.
3447 This is a 16-member array composed of values
3450 vt.default_grn= [VT]
3451 Format: <green0>,<green1>,<green2>,...,<green15>
3452 Change the default green palette of the console.
3453 This is a 16-member array composed of values
3456 vt.default_red= [VT]
3457 Format: <red0>,<red1>,<red2>,...,<red15>
3458 Change the default red palette of the console.
3459 This is a 16-member array composed of values
3465 Set system-wide default UTF-8 mode for all tty's.
3466 Default is 1, i.e. UTF-8 mode is enabled for all
3467 newly opened terminals.
3469 vt.global_cursor_default=
3472 Set system-wide default for whether a cursor
3473 is shown on new VTs. Default is -1,
3474 i.e. cursors will be created by default unless
3475 overridden by individual drivers. 0 will hide
3476 cursors, 1 will display them.
3478 vt.italic= [VT] Default color for italic text; 0-15.
3481 vt.underline= [VT] Default color for underlined text; 0-15.
3484 watchdog timers [HW,WDT] For information on watchdog timers,
3485 see Documentation/watchdog/watchdog-parameters.txt
3486 or other driver-specific files in the
3487 Documentation/watchdog/ directory.
3489 workqueue.disable_numa
3490 By default, all work items queued to unbound
3491 workqueues are affine to the NUMA nodes they're
3492 issued on, which results in better behavior in
3493 general. If NUMA affinity needs to be disabled for
3494 whatever reason, this option can be used. Note
3495 that this also can be controlled per-workqueue for
3496 workqueues visible under /sys/bus/workqueue/.
3498 workqueue.power_efficient
3499 Per-cpu workqueues are generally preferred because
3500 they show better performance thanks to cache
3501 locality; unfortunately, per-cpu workqueues tend to
3502 be more power hungry than unbound workqueues.
3504 Enabling this makes the per-cpu workqueues which
3505 were observed to contribute significantly to power
3506 consumption unbound, leading to measurably lower
3507 power usage at the cost of small performance
3510 The default value of this parameter is determined by
3511 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3513 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3514 default x2apic cluster mode on platforms
3517 x86_intel_mid_timer= [X86-32,APBT]
3518 Choose timer option for x86 Intel MID platform.
3519 Two valid options are apbt timer only and lapic timer
3520 plus one apbt timer for broadcast timer.
3521 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3523 xen_emul_unplug= [HW,X86,XEN]
3524 Unplug Xen emulated devices
3525 Format: [unplug0,][unplug1]
3526 ide-disks -- unplug primary master IDE devices
3527 aux-ide-disks -- unplug non-primary-master IDE devices
3528 nics -- unplug network devices
3529 all -- unplug all emulated devices (NICs and IDE disks)
3530 unnecessary -- unplugging emulated devices is
3531 unnecessary even if the host did not respond to
3533 never -- do not unplug even if version check succeeds
3535 xen_nopvspin [X86,XEN]
3536 Disables the ticketlock slowpath using Xen PV
3539 xirc2ps_cs= [NET,PCMCIA]
3541 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3543 ______________________________________________________________________
3547 Add more DRM drivers.