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 {Currently supported controllers - "memory"}
520 checkreqprot [SELINUX] Set initial checkreqprot flag value.
521 Format: { "0" | "1" }
522 See security/selinux/Kconfig help text.
523 0 -- check protection applied by kernel (includes
524 any implied execute protection).
525 1 -- check protection requested by application.
526 Default value is set via a kernel config option.
527 Value can be changed at runtime via
528 /selinux/checkreqprot.
531 See Documentation/s390/CommonIO for details.
534 Keep all clocks already enabled by bootloader on,
535 even if no driver has claimed them. This is useful
536 for debug and development, but should not be
537 needed on a platform with proper driver support.
538 For more information, see Documentation/clk.txt.
540 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
542 Forces specified clocksource (if available) to be used
543 when calculating gettimeofday(). If specified
544 clocksource is not available, it defaults to PIT.
545 Format: { pit | tsc | cyclone | pmtmr }
547 clocksource= Override the default clocksource
549 Override the default clocksource and use the clocksource
550 with the name specified.
551 Some clocksource names to choose from, depending on
553 [all] jiffies (this is the base, fallback clocksource)
555 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
556 pxa_timer,timer3,32k_counter,timer0_1
558 [X86-32] pit,hpet,tsc;
559 scx200_hrt on Geode; cyclone on IBM x440
567 clearcpuid=BITNUM [X86]
568 Disable CPUID feature X for the kernel. See
569 arch/x86/include/asm/cpufeature.h for the valid bit
570 numbers. Note the Linux specific bits are not necessarily
571 stable over kernel options, but the vendor specific
573 Also note that user programs calling CPUID directly
574 or using the feature without checking anything
575 will still see it. This just prevents it from
576 being used by the kernel or shown in /proc/cpuinfo.
577 Also note the kernel might malfunction if you disable
581 Sets the size of kernel global memory area for contiguous
582 memory allocations. For more information, see
583 include/linux/dma-contiguous.h
585 cmo_free_hint= [PPC] Format: { yes | no }
586 Specify whether pages are marked as being inactive
587 when they are freed. This is used in CMO environments
588 to determine OS memory pressure for page stealing by
592 coherent_pool=nn[KMG] [ARM,KNL]
593 Sets the size of memory pool for coherent, atomic dma
594 allocations, by default set to 256K.
596 code_bytes [X86] How many bytes of object code to print
601 com20020= [HW,NET] ARCnet - COM20020 chipset
603 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
605 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
609 ARCnet - COM90xx chipset (memory-mapped buffers)
610 Format: <io>[,<irq>[,<memstart>]]
612 condev= [HW,S390] console device
615 console= [KNL] Output console device and options.
617 tty<n> Use the virtual console device <n>.
621 Use the specified serial port. The options are of
622 the form "bbbbpnf", where "bbbb" is the baud rate,
623 "p" is parity ("n", "o", or "e"), "n" is number of
624 bits, and "f" is flow control ("r" for RTS or
625 omit it). Default is "9600n8".
627 See Documentation/serial-console.txt for more
629 Documentation/networking/netconsole.txt for an
632 uart[8250],io,<addr>[,options]
633 uart[8250],mmio,<addr>[,options]
634 Start an early, polled-mode console on the 8250/16550
635 UART at the specified I/O port or MMIO address,
636 switching to the matching ttyS device later. The
637 options are the same as for ttyS, above.
638 hvc<n> Use the hypervisor console device <n>. This is for
639 both Xen and PowerPC hypervisors.
641 If the device connected to the port is not a TTY but a braille
642 device, prepend "brl," before the device type, for instance
644 For now, only VisioBraille is supported.
646 consoleblank= [KNL] The console blank (screen saver) timeout in
647 seconds. Defaults to 10*60 = 10mins. A value of 0
648 disables the blank timer.
651 [KNL] Change the default value for
652 /proc/<pid>/coredump_filter.
653 See also Documentation/filesystems/proc.txt.
655 cpuidle.off=1 [CPU_IDLE]
656 disable the cpuidle sub-system
658 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
660 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
662 crashkernel=size[KMG][@offset[KMG]]
663 [KNL] Using kexec, Linux can switch to a 'crash kernel'
664 upon panic. This parameter reserves the physical
665 memory region [offset, offset + size] for that kernel
666 image. If '@offset' is omitted, then a suitable offset
667 is selected automatically. Check
668 Documentation/kdump/kdump.txt for further details.
670 crashkernel=range1:size1[,range2:size2,...][@offset]
671 [KNL] Same as above, but depends on the memory
672 in the running system. The syntax of range is
673 start-[end] where start and end are both
674 a memory unit (amount[KMG]). See also
675 Documentation/kdump/kdump.txt for an example.
677 crashkernel=size[KMG],high
678 [KNL, x86_64] range could be above 4G. Allow kernel
679 to allocate physical memory region from top, so could
680 be above 4G if system have more than 4G ram installed.
681 Otherwise memory region will be allocated below 4G, if
683 It will be ignored if crashkernel=X is specified.
684 crashkernel=size[KMG],low
685 [KNL, x86_64] range under 4G. When crashkernel=X,high
686 is passed, kernel could allocate physical memory region
687 above 4G, that cause second kernel crash on system
688 that require some amount of low memory, e.g. swiotlb
689 requires at least 64M+32K low memory. Kernel would
690 try to allocate 72M below 4G automatically.
691 This one let user to specify own low range under 4G
692 for second kernel instead.
693 0: to disable low allocation.
694 It will be ignored when crashkernel=X,high is not used
695 or memory reserved is below 4G.
700 cs89x0_media= [HW,NET]
701 Format: { rj45 | aui | bnc }
704 See header of drivers/s390/block/dasd_devmap.c.
706 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
707 (one device per port)
708 Format: <port#>,<type>
709 See also Documentation/input/joystick-parport.txt
711 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
712 time. See Documentation/dynamic-debug-howto.txt for
713 details. Deprecated, see dyndbg.
715 debug [KNL] Enable kernel debugging (events log level).
718 [KNL] verbose self-tests
720 Print debugging info while doing the locking API
722 We default to 0 (no extra messages), setting it to
723 1 will print _a lot_ more information - normally
724 only useful to kernel developers.
726 debug_objects [KNL] Enable object debugging
729 [KNL] Disable object debugging
731 debug_guardpage_minorder=
732 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
733 parameter allows control of the order of pages that will
734 be intentionally kept free (and hence protected) by the
735 buddy allocator. Bigger value increase the probability
736 of catching random memory corruption, but reduce the
737 amount of memory for normal system use. The maximum
738 possible value is MAX_ORDER/2. Setting this parameter
739 to 1 or 2 should be enough to identify most random
740 memory corruption problems caused by bugs in kernel or
741 driver code when a CPU writes to (or reads from) a
742 random memory location. Note that there exists a class
743 of memory corruptions problems caused by buggy H/W or
744 F/W or by drivers badly programing DMA (basically when
745 memory is written at bus level and the CPU MMU is
746 bypassed) which are not detectable by
747 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
748 tracking down these problems.
750 debugpat [X86] Enable PAT debugging
752 decnet.addr= [HW,NET]
753 Format: <area>[,<node>]
754 See also Documentation/networking/decnet.txt.
757 [same as hugepagesz=] The size of the default
758 HugeTLB page size. This is the size represented by
759 the legacy /proc/ hugepages APIs, used for SHM, and
760 default size when mounting hugetlbfs filesystems.
761 Defaults to the default architecture's huge page size
765 Set number of hash buckets for dentry cache.
768 IO parameters + enable/disable command.
770 digiepca= [HW,SERIAL]
771 See drivers/char/README.epca and
772 Documentation/serial/digiepca.txt.
775 See Documentation/networking/ipv6.txt.
777 disable_cpu_apicid= [X86,APIC,SMP]
779 The number of initial APIC ID for the
780 corresponding CPU to be disabled at boot,
781 mostly used for the kdump 2nd kernel to
782 disable BSP to wake up multiple CPUs without
783 causing system reset or hang due to sending
786 disable_ddw [PPC/PSERIES]
787 Disable Dynamic DMA Window support. Use this if
788 to workaround buggy firmware.
791 See Documentation/networking/ipv6.txt.
793 disable_mtrr_cleanup [X86]
794 The kernel tries to adjust MTRR layout from continuous
795 to discrete, to make X server driver able to add WB
796 entry later. This parameter disables that.
798 disable_mtrr_trim [X86, Intel and AMD only]
799 By default the kernel will trim any uncacheable
800 memory out of your available memory pool based on
801 MTRR settings. This parameter disables that behavior,
802 possibly causing your machine to run very slowly.
804 disable_timer_pin_1 [X86]
805 Disable PIN 1 of APIC timer
806 Can be useful to work around chipset bugs.
808 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
809 this option disables the debugging code at boot.
811 dma_debug_entries=<number>
812 This option allows to tune the number of preallocated
813 entries for DMA-API debugging code. One entry is
814 required per DMA-API allocation. Use this if the
815 DMA-API debugging code disables itself because the
816 architectural default is too low.
818 dma_debug_driver=<driver_name>
819 With this option the DMA-API debugging driver
820 filter feature can be enabled at boot time. Just
821 pass the driver to filter for as the parameter.
822 The filter can be disabled or changed to another
823 driver later using sysfs.
825 drm_kms_helper.edid_firmware=[<connector>:]<file>
826 Broken monitors, graphic adapters and KVMs may
827 send no or incorrect EDID data sets. This parameter
828 allows to specify an EDID data set in the
829 /lib/firmware directory that is used instead.
830 Generic built-in EDID data sets are used, if one of
831 edid/1024x768.bin, edid/1280x1024.bin,
832 edid/1680x1050.bin, or edid/1920x1080.bin is given
833 and no file with the same name exists. Details and
834 instructions how to build your own EDID data are
835 available in Documentation/EDID/HOWTO.txt. An EDID
836 data set will only be used for a particular connector,
837 if its name and a colon are prepended to the EDID
842 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
843 module.dyndbg[="val"]
844 Enable debug messages at boot time. See
845 Documentation/dynamic-debug-howto.txt for details.
847 earlycon= [KNL] Output early console device and options.
848 uart[8250],io,<addr>[,options]
849 uart[8250],mmio,<addr>[,options]
850 uart[8250],mmio32,<addr>[,options]
851 Start an early, polled-mode console on the 8250/16550
852 UART at the specified I/O port or MMIO address.
853 MMIO inter-register address stride is either 8-bit
854 (mmio) or 32-bit (mmio32).
855 The options are the same as for ttyS, above.
857 earlyprintk= [X86,SH,BLACKFIN,ARM]
861 earlyprintk=serial[,ttySn[,baudrate]]
862 earlyprintk=serial[,0x...[,baudrate]]
863 earlyprintk=ttySn[,baudrate]
864 earlyprintk=dbgp[debugController#]
866 earlyprintk is useful when the kernel crashes before
867 the normal console is initialized. It is not enabled by
868 default because it has some cosmetic problems.
870 Append ",keep" to not disable it when the real console
873 Only one of vga, efi, serial, or usb debug port can
876 Currently only ttyS0 and ttyS1 may be specified by
877 name. Other I/O ports may be explicitly specified
878 on some architectures (x86 and arm at least) by
879 replacing ttySn with an I/O port address, like this:
880 earlyprintk=serial,0x1008,115200
881 You can find the port for a given device in
882 /proc/tty/driver/serial:
883 2: uart:ST16650V2 port:00001008 irq:18 ...
885 Interaction with the standard serial driver is not
888 The VGA and EFI output is eventually overwritten by
891 The xen output can only be used by Xen PV guests.
893 ekgdboc= [X86,KGDB] Allow early kernel console debugging
896 This is designed to be used in conjunction with
897 the boot argument: earlyprintk=vga
900 Format: {"off" | "on" | "skip[mbr]"}
903 Format: { "old_map" }
904 old_map [X86-64]: switch to the old ioremap-based EFI
905 runtime services mapping. 32-bit still uses this one by
908 efi_no_storage_paranoia [EFI; X86]
909 Using this parameter you can use more than 50% of
910 your efi variable storage. Use this parameter only if
911 you are really sure that your UEFI does sane gc and
912 fulfills the spec otherwise your board may brick.
914 eisa_irq_edge= [PARISC,HW]
915 See header of drivers/parisc/eisa.c.
918 See comment before function elanfreq_setup() in
919 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
922 Format: {"cfq" | "deadline" | "noop"}
923 See Documentation/block/cfq-iosched.txt and
924 Documentation/block/deadline-iosched.txt for details.
926 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
927 Specifies physical address of start of kernel core
928 image elf header and optionally the size. Generally
929 kexec loader will pass this option to capture kernel.
930 See Documentation/kdump/kdump.txt for details.
932 enable_mtrr_cleanup [X86]
933 The kernel tries to adjust MTRR layout from continuous
934 to discrete, to make X server driver able to add WB
935 entry later. This parameter enables that.
937 enable_timer_pin_1 [X86]
938 Enable PIN 1 of APIC timer
939 Can be useful to work around chipset bugs
940 (in particular on some ATI chipsets).
941 The kernel tries to set a reasonable default.
943 enforcing [SELINUX] Set initial enforcing status.
945 See security/selinux/Kconfig help text.
946 0 -- permissive (log only, no denials).
947 1 -- enforcing (deny and log).
949 Value can be changed at runtime via /selinux/enforce.
952 Disable Error Record Serialization Table (ERST)
955 ether= [HW,NET] Ethernet cards parameters
956 This option is obsoleted by the "netdev=" option, which
957 has equivalent usage. See its documentation for details.
961 Permit 'security.evm' to be updated regardless of
962 current integrity status.
966 fail_make_request=[KNL]
967 General fault injection mechanism.
968 Format: <interval>,<probability>,<space>,<times>
969 See also Documentation/fault-injection/.
972 See Documentation/blockdev/floppy.txt.
974 force_pal_cache_flush
975 [IA-64] Avoid check_sal_cache_flush which may hang on
976 buggy SAL_CACHE_FLUSH implementations. Using this
977 parameter will force ia64_sal_cache_flush to call
978 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
981 [FTRACE] will set and start the specified tracer
982 as early as possible in order to facilitate early
985 ftrace_dump_on_oops[=orig_cpu]
986 [FTRACE] will dump the trace buffers on oops.
987 If no parameter is passed, ftrace will dump
988 buffers of all CPUs, but if you pass orig_cpu, it will
989 dump only the buffer of the CPU that triggered the
992 ftrace_filter=[function-list]
993 [FTRACE] Limit the functions traced by the function
994 tracer at boot up. function-list is a comma separated
995 list of functions. This list can be changed at run
996 time by the set_ftrace_filter file in the debugfs
999 ftrace_notrace=[function-list]
1000 [FTRACE] Do not trace the functions specified in
1001 function-list. This list can be changed at run time
1002 by the set_ftrace_notrace file in the debugfs
1005 ftrace_graph_filter=[function-list]
1006 [FTRACE] Limit the top level callers functions traced
1007 by the function graph tracer at boot up.
1008 function-list is a comma separated list of functions
1009 that can be changed at run time by the
1010 set_graph_function file in the debugfs tracing directory.
1013 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1014 support via parallel port (up to 5 devices per port)
1015 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1016 See also Documentation/input/joystick-parport.txt
1020 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1024 gcov_persist= [GCOV] When non-zero (default), profiling data for
1025 kernel modules is saved and remains accessible via
1026 debugfs, even when the module is unloaded/reloaded.
1027 When zero, profiling data is discarded and associated
1028 debugfs files are removed at module unload time.
1030 gpt [EFI] Forces disk with valid GPT signature but
1031 invalid Protective MBR to be treated as GPT.
1033 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1034 the "Enable 0" bit of the configuration register.
1037 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1038 the "Enable 0" bit of the configuration register.
1041 grcan.select= [HW] Select which physical interface to use.
1044 grcan.txsize= [HW] Sets the size of the tx buffer.
1045 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1047 grcan.rxsize= [HW] Sets the size of the rx buffer.
1048 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1051 hashdist= [KNL,NUMA] Large hashes allocated during boot
1052 are distributed across NUMA nodes. Defaults on
1053 for 64-bit NUMA, off otherwise.
1054 Format: 0 | 1 (for off | on)
1056 hcl= [IA-64] SGI's Hardware Graph compatibility layer
1058 hd= [EIDE] (E)IDE hard drive subsystem geometry
1059 Format: <cyl>,<head>,<sect>
1062 Disable Hardware Error Source Table (HEST) support;
1063 corresponding firmware-first mode error processing
1064 logic will be disabled.
1066 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1067 size of <nn>. This works even on boxes that have no
1068 highmem otherwise. This also works to reduce highmem
1069 size on bigger boxes.
1071 highres= [KNL] Enable/disable high resolution timer mode.
1072 Valid parameters: "on", "off"
1076 See Documentation/isdn/README.HiSax.
1080 hpet= [X86-32,HPET] option to control HPET usage
1081 Format: { enable (default) | disable | force |
1083 disable: disable HPET and use PIT instead
1084 force: allow force enabled of undocumented chips (ICH4,
1086 verbose: show contents of HPET registers during setup
1088 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1089 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1091 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1092 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1093 On x86-64 and powerpc, this option can be specified
1094 multiple times interleaved with hugepages= to reserve
1095 huge pages of different sizes. Valid pages sizes on
1096 x86-64 are 2M (when the CPU supports "pse") and 1G
1097 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1098 Note that 1GB pages can only be allocated at boot time
1099 using hugepages= and not freed afterwards.
1101 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1102 terminal devices. Valid values: 0..8
1103 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1104 If specified, z/VM IUCV HVC accepts connections
1105 from listed z/VM user IDs only.
1107 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1108 hardware thread id mappings.
1109 Format: <cpu>:<hwthread>
1112 Do not unregister boot console at start. This is only
1113 useful for debugging when something happens in the window
1114 between unregistering the boot console and initializing
1117 i2c_bus= [HW] Override the default board specific I2C bus speed
1118 or register an additional I2C bus that is not
1119 registered from board initialization code.
1123 i8042.debug [HW] Toggle i8042 debug mode
1124 i8042.direct [HW] Put keyboard port into non-translated mode
1125 i8042.dumbkbd [HW] Pretend that controller can only read data from
1126 keyboard and cannot control its state
1127 (Don't attempt to blink the leds)
1128 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1129 i8042.nokbd [HW] Don't check/create keyboard port
1130 i8042.noloop [HW] Disable the AUX Loopback command while probing
1132 i8042.nomux [HW] Don't check presence of an active multiplexing
1134 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1136 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1137 i8042.reset [HW] Reset the controller during init and cleanup
1138 i8042.unlock [HW] Unlock (ignore) the keylock
1142 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1143 indicates that the driver is running on unsupported
1145 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1146 does not match list of supported models.
1148 [HW] Report power status in /proc/i8k
1149 (disabled by default)
1150 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1153 i915.invert_brightness=
1154 [DRM] Invert the sense of the variable that is used to
1155 set the brightness of the panel backlight. Normally a
1156 brightness value of 0 indicates backlight switched off,
1157 and the maximum of the brightness value sets the backlight
1158 to maximum brightness. If this parameter is set to 0
1159 (default) and the machine requires it, or this parameter
1160 is set to 1, a brightness value of 0 sets the backlight
1161 to maximum brightness, and the maximum of the brightness
1162 value switches the backlight off.
1163 -1 -- never invert brightness
1164 0 -- machine default
1165 1 -- force brightness inversion
1168 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1170 ide-core.nodma= [HW] (E)IDE subsystem
1171 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1172 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1173 .cdrom .chs .ignore_cable are additional options
1174 See Documentation/ide/ide.txt.
1176 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1177 Claim all unknown PCI IDE storage controllers.
1180 Format: idle=poll, idle=halt, idle=nomwait
1181 Poll forces a polling idle loop that can slightly
1182 improve the performance of waking up a idle CPU, but
1183 will use a lot of power and make the system run hot.
1185 idle=halt: Halt is forced to be used for CPU idle.
1186 In such case C2/C3 won't be used again.
1187 idle=nomwait: Disable mwait for CPU C-states
1189 ignore_loglevel [KNL]
1190 Ignore loglevel setting - this will print /all/
1191 kernel messages to the console. Useful for debugging.
1192 We also add it as printk module parameter, so users
1193 could change it dynamically, usually by
1194 /sys/module/printk/parameters/ignore_loglevel.
1196 ihash_entries= [KNL]
1197 Set number of hash buckets for inode cache.
1199 ima_appraise= [IMA] appraise integrity measurements
1200 Format: { "off" | "enforce" | "fix" }
1203 ima_appraise_tcb [IMA]
1204 The builtin appraise policy appraises all files
1208 Format: { md5 | sha1 | rmd160 | sha256 | sha384
1212 The list of supported hash algorithms is defined
1213 in crypto/hash_info.h.
1216 Load a policy which meets the needs of the Trusted
1217 Computing Base. This means IMA will measure all
1218 programs exec'd, files mmap'd for exec, and all files
1219 opened for read by uid=0.
1222 Select one of defined IMA measurements template formats.
1223 Formats: { "ima" | "ima-ng" }
1228 Run specified binary instead of /sbin/init as init
1231 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1232 for working out where the kernel is dying during
1235 initrd= [BOOT] Specify the location of the initial ramdisk
1237 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1240 int_pln_enable [x86] Enable power limit notification interrupt
1242 integrity_audit=[IMA]
1243 Format: { "0" | "1" }
1244 0 -- basic integrity auditing messages. (Default)
1245 1 -- additional integrity auditing messages.
1247 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1249 Enable intel iommu driver.
1251 Disable intel iommu driver.
1252 igfx_off [Default Off]
1253 By default, gfx is mapped as normal device. If a gfx
1254 device has a dedicated DMAR unit, the DMAR unit is
1255 bypassed by not enabling DMAR with this option. In
1256 this case, gfx device will use physical address for
1259 With this option iommu will not optimize to look
1260 for io virtual address below 32-bit forcing dual
1261 address cycle on pci bus for cards supporting greater
1262 than 32-bit addressing. The default is to look
1263 for translation below 32-bit and if not available
1264 then look in the higher range.
1265 strict [Default Off]
1266 With this option on every unmap_single operation will
1267 result in a hardware IOTLB flush operation as opposed
1268 to batching them for performance.
1269 sp_off [Default Off]
1270 By default, super page will be supported if Intel IOMMU
1271 has the capability. With this option, super page will
1274 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1275 0 disables intel_idle and fall back on acpi_idle.
1276 1 to 6 specify maximum depth of C-state.
1280 Do not enable intel_pstate as the default
1281 scaling driver for the supported processors
1283 intremap= [X86-64, Intel-IOMMU]
1284 on enable Interrupt Remapping (default)
1285 off disable Interrupt Remapping
1286 nosid disable Source ID checking
1288 BIOS x2APIC opt-out request will be ignored
1290 iomem= Disable strict checking of access to MMIO memory
1291 strict regions from userspace.
1308 io7= [HW] IO7 for Marvel based alpha systems
1309 See comment before marvel_specify_io7 in
1310 arch/alpha/kernel/core_marvel.c.
1312 io_delay= [X86] I/O delay method
1314 Standard port 0x80 based delay
1316 Alternate port 0xed based delay (needed on some systems)
1318 Simple two microseconds delay
1323 See Documentation/filesystems/nfs/nfsroot.txt.
1325 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1326 See comment before ip2_setup() in
1327 drivers/char/ip2/ip2base.c.
1330 When an interrupt is not handled search all handlers
1331 for it. Intended to get systems with badly broken
1335 When an interrupt is not handled search all handlers
1336 for it. Also check all handlers each timer
1337 interrupt. Intended to get systems with badly broken
1341 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1343 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1345 <cpu number>,...,<cpu number>
1347 <cpu number>-<cpu number>
1348 (must be a positive range in ascending order)
1350 <cpu number>,...,<cpu number>-<cpu number>
1352 This option can be used to specify one or more CPUs
1353 to isolate from the general SMP balancing and scheduling
1354 algorithms. You can move a process onto or off an
1355 "isolated" CPU via the CPU affinity syscalls or cpuset.
1356 <cpu number> begins at 0 and the maximum value is
1357 "number of CPUs in system - 1".
1359 This option is the preferred way to isolate CPUs. The
1360 alternative -- manually setting the CPU mask of all
1361 tasks in the system -- can cause problems and
1362 suboptimal load balancer performance.
1366 ivrs_ioapic [HW,X86_64]
1367 Provide an override to the IOAPIC-ID<->DEVICE-ID
1368 mapping provided in the IVRS ACPI table. For
1369 example, to map IOAPIC-ID decimal 10 to
1370 PCI device 00:14.0 write the parameter as:
1371 ivrs_ioapic[10]=00:14.0
1373 ivrs_hpet [HW,X86_64]
1374 Provide an override to the HPET-ID<->DEVICE-ID
1375 mapping provided in the IVRS ACPI table. For
1376 example, to map HPET-ID decimal 0 to
1377 PCI device 00:14.0 write the parameter as:
1378 ivrs_hpet[0]=00:14.0
1380 js= [HW,JOY] Analog joystick
1381 See Documentation/input/joystick.txt.
1385 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1386 specifies the amount of memory usable by the kernel
1387 for non-movable allocations. The requested amount is
1388 spread evenly throughout all nodes in the system. The
1389 remaining memory in each node is used for Movable
1390 pages. In the event, a node is too small to have both
1391 kernelcore and Movable pages, kernelcore pages will
1392 take priority and other nodes will have a larger number
1393 of Movable pages. The Movable zone is used for the
1394 allocation of pages that may be reclaimed or moved
1395 by the page migration subsystem. This means that
1396 HugeTLB pages may not be allocated from this zone.
1397 Note that allocations like PTEs-from-HighMem still
1398 use the HighMem zone if it exists, and the Normal
1399 zone if it does not.
1401 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1402 Format: <Controller#>[,poll interval]
1403 The controller # is the number of the ehci usb debug
1404 port as it is probed via PCI. The poll interval is
1405 optional and is the number seconds in between
1406 each poll cycle to the debug port in case you need
1407 the functionality for interrupting the kernel with
1408 gdb or control-c on the dbgp connection. When
1409 not using this parameter you use sysrq-g to break into
1410 the kernel debugger.
1412 kgdboc= [KGDB,HW] kgdb over consoles.
1413 Requires a tty driver that supports console polling,
1414 or a supported polling keyboard driver (non-usb).
1415 Serial only format: <serial_device>[,baud]
1416 keyboard only format: kbd
1417 keyboard and serial format: kbd,<serial_device>[,baud]
1418 Optional Kernel mode setting:
1419 kms, kbd format: kms,kbd
1420 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1422 kgdbwait [KGDB] Stop kernel execution and enter the
1423 kernel debugger at the earliest opportunity.
1425 kmac= [MIPS] korina ethernet MAC address.
1426 Configure the RouterBoard 532 series on-chip
1427 Ethernet adapter MAC address.
1429 kmemleak= [KNL] Boot-time kmemleak enable/disable
1430 Valid arguments: on, off
1433 kstack=N [X86] Print N words from the kernel stack
1436 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1437 Default is 0 (don't ignore, but inject #GP)
1439 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1443 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1444 Default is 1 (enabled)
1446 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1448 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1450 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1451 (virtualized MMU) support on capable Intel chips.
1452 Default is 1 (enabled)
1454 kvm-intel.emulate_invalid_guest_state=
1455 [KVM,Intel] Enable emulation of invalid guest states
1456 Default is 0 (disabled)
1458 kvm-intel.flexpriority=
1459 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1460 Default is 1 (enabled)
1463 [KVM,Intel] Enable VMX nesting (nVMX).
1464 Default is 0 (disabled)
1466 kvm-intel.unrestricted_guest=
1467 [KVM,Intel] Disable unrestricted guest feature
1468 (virtualized real and unpaged mode) on capable
1469 Intel chips. Default is 1 (enabled)
1471 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1472 feature (tagged TLBs) on capable Intel chips.
1473 Default is 1 (enabled)
1479 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1482 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1483 value for LAPIC timer one-shot implementation. Default
1484 back to the programmable timer unit in the LAPIC.
1486 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1489 libata.dma= [LIBATA] DMA control
1490 libata.dma=0 Disable all PATA and SATA DMA
1491 libata.dma=1 PATA and SATA Disk DMA only
1492 libata.dma=2 ATAPI (CDROM) DMA only
1493 libata.dma=4 Compact Flash DMA only
1494 Combinations also work, so libata.dma=3 enables DMA
1495 for disks and CDROMs, but not CFs.
1497 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1498 libata.ignore_hpa=0 keep BIOS limits (default)
1499 libata.ignore_hpa=1 ignore limits, using full disk
1501 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1505 libata.force= [LIBATA] Force configurations. The format is comma
1506 separated list of "[ID:]VAL" where ID is
1507 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1508 matching port, link or device. Basically, it matches
1509 the ATA ID string printed on console by libata. If
1510 the whole ID part is omitted, the last PORT and DEVICE
1511 values are used. If ID hasn't been specified yet, the
1512 configuration applies to all ports, links and devices.
1514 If only DEVICE is omitted, the parameter applies to
1515 the port and all links and devices behind it. DEVICE
1516 number of 0 either selects the first device or the
1517 first fan-out link behind PMP device. It does not
1518 select the host link. DEVICE number of 15 selects the
1519 host link and device attached to it.
1521 The VAL specifies the configuration to force. As long
1522 as there's no ambiguity shortcut notation is allowed.
1523 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1524 The following configurations can be forced.
1526 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1527 Any ID with matching PORT is used.
1529 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1531 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1532 udma[/][16,25,33,44,66,100,133] notation is also
1535 * [no]ncq: Turn on or off NCQ.
1537 * nohrst, nosrst, norst: suppress hard, soft
1540 * rstonce: only attempt one reset during
1541 hot-unplug link recovery
1543 * dump_id: dump IDENTIFY data.
1545 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1547 * disable: Disable this device.
1549 If there are multiple matching configurations changing
1550 the same attribute, the last one is used.
1552 memblock=debug [KNL] Enable memblock debug messages.
1554 load_ramdisk= [RAM] List of ramdisks to load from floppy
1555 See Documentation/blockdev/ramdisk.txt.
1557 lockd.nlm_grace_period=P [NFS] Assign grace period.
1560 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1563 lockd.nlm_timeout=T [NFS] Assign timeout value.
1566 lockd.nlm_udpport=M [NFS] Assign UDP port.
1569 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1572 loglevel= All Kernel Messages with a loglevel smaller than the
1573 console loglevel will be printed to the console. It can
1574 also be changed with klogd or other programs. The
1575 loglevels are defined as follows:
1577 0 (KERN_EMERG) system is unusable
1578 1 (KERN_ALERT) action must be taken immediately
1579 2 (KERN_CRIT) critical conditions
1580 3 (KERN_ERR) error conditions
1581 4 (KERN_WARNING) warning conditions
1582 5 (KERN_NOTICE) normal but significant condition
1583 6 (KERN_INFO) informational
1584 7 (KERN_DEBUG) debug-level messages
1586 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1587 in bytes. n must be a power of two. The default
1588 size is set in the kernel config file.
1590 logo.nologo [FB] Disables display of the built-in Linux logo.
1591 This may be used to provide more screen space for
1592 kernel log messages and is useful when debugging
1593 kernel boot problems.
1595 lp=0 [LP] Specify parallel ports to use, e.g,
1596 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1597 lp=reset first parallel port). 'lp=0' disables the
1598 lp=auto printer driver. 'lp=reset' (which can be
1599 specified in addition to the ports) causes
1600 attached printers to be reset. Using
1601 lp=port1,port2,... specifies the parallel ports
1602 to associate lp devices with, starting with
1603 lp0. A port specification may be 'none' to skip
1604 that lp device, or a parport name such as
1605 'parport0'. Specifying 'lp=auto' instead of a
1606 port specification list means that device IDs
1607 from each port should be examined, to see if
1608 an IEEE 1284-compliant printer is attached; if
1609 so, the driver will manage that printer.
1610 See also header of drivers/char/lp.c.
1613 Sets loops_per_jiffy to given constant, thus avoiding
1614 time-consuming boot-time autodetection (up to 250 ms per
1615 CPU). 0 enables autodetection (default). To determine
1616 the correct value for your kernel, boot with normal
1617 autodetection and see what value is printed. Note that
1618 on SMP systems the preset will be applied to all CPUs,
1619 which is likely to cause problems if your CPUs need
1620 significantly divergent settings. An incorrect value
1621 will cause delays in the kernel to be wrong, leading to
1622 unpredictable I/O errors and other breakage. Although
1623 unlikely, in the extreme case this might damage your
1627 Format: <io>,<irq>,<dma>
1629 machvec= [IA-64] Force the use of a particular machine-vector
1630 (machvec) in a generic kernel.
1631 Example: machvec=hpzx1_swiotlb
1633 machtype= [Loongson] Share the same kernel image file between different
1635 Example: machtype=lemote-yeeloong-2f-7inch
1637 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1638 than or equal to this physical address is ignored.
1640 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1641 should make use of. maxcpus=n : n >= 0 limits the
1642 kernel to using 'n' processors. n=0 is a special case,
1643 it is equivalent to "nosmp", which also disables
1646 max_loop= [LOOP] The number of loop block devices that get
1647 (loop.max_loop) unconditionally pre-created at init time. The default
1648 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1649 of statically allocating a predefined number, loop
1650 devices can be requested on-demand with the
1651 /dev/loop-control interface.
1653 mce [X86-32] Machine Check Exception
1655 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1657 md= [HW] RAID subsystems devices and level
1658 See Documentation/md.txt.
1661 Format: <first>,<last>
1662 Specifies range of consoles to be captured by the MDA.
1664 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1665 Amount of memory to be used when the kernel is not able
1666 to see the whole system memory or for test.
1667 [X86] Work as limiting max address. Use together
1668 with memmap= to avoid physical address space collisions.
1669 Without memmap= PCI devices could be placed at addresses
1670 belonging to unused RAM.
1672 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1676 [KNL,SH] Allow user to override the default size for
1677 per-device physically contiguous DMA buffers.
1679 memmap=exactmap [KNL,X86] Enable setting of an exact
1680 E820 memory map, as specified by the user.
1681 Such memmap=exactmap lines can be constructed based on
1682 BIOS output or other requirements. See the memmap=nn@ss
1685 memmap=nn[KMG]@ss[KMG]
1686 [KNL] Force usage of a specific region of memory
1687 Region of memory to be used, from ss to ss+nn.
1689 memmap=nn[KMG]#ss[KMG]
1690 [KNL,ACPI] Mark specific memory as ACPI data.
1691 Region of memory to be used, from ss to ss+nn.
1693 memmap=nn[KMG]$ss[KMG]
1694 [KNL,ACPI] Mark specific memory as reserved.
1695 Region of memory to be used, from ss to ss+nn.
1696 Example: Exclude memory from 0x18690000-0x1869ffff
1697 memmap=64K$0x18690000
1699 memmap=0x10000$0x18690000
1701 memory_corruption_check=0/1 [X86]
1702 Some BIOSes seem to corrupt the first 64k of
1703 memory when doing things like suspend/resume.
1704 Setting this option will scan the memory
1705 looking for corruption. Enabling this will
1706 both detect corruption and prevent the kernel
1707 from using the memory being corrupted.
1708 However, its intended as a diagnostic tool; if
1709 repeatable BIOS-originated corruption always
1710 affects the same memory, you can use memmap=
1711 to prevent the kernel from using that memory.
1713 memory_corruption_check_size=size [X86]
1714 By default it checks for corruption in the low
1715 64k, making this memory unavailable for normal
1716 use. Use this parameter to scan for
1717 corruption in more or less memory.
1719 memory_corruption_check_period=seconds [X86]
1720 By default it checks for corruption every 60
1721 seconds. Use this parameter to check at some
1722 other rate. 0 disables periodic checking.
1724 memtest= [KNL,X86] Enable memtest
1726 default : 0 <disable>
1727 Specifies the number of memtest passes to be
1728 performed. Each pass selects another test
1729 pattern from a given set of patterns. Memtest
1730 fills the memory with this pattern, validates
1731 memory contents and reserves bad memory
1732 regions that are detected.
1734 meye.*= [HW] Set MotionEye Camera parameters
1735 See Documentation/video4linux/meye.txt.
1737 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1738 Multi-Function General Purpose Timers on AMD Geode
1741 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1742 the BIOS has incorrectly applied a workaround. TinyBIOS
1743 version 0.98 is known to be affected, 0.99 fixes the
1744 problem by letting the user disable the workaround.
1748 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1749 physical address is ignored.
1751 mini2440= [ARM,HW,KNL]
1752 Format:[0..2][b][c][t]
1754 MINI2440 configuration specification:
1755 0 - The attached screen is the 3.5" TFT
1756 1 - The attached screen is the 7" TFT
1757 2 - The VGA Shield is attached (1024x768)
1758 Leaving out the screen size parameter will not load
1759 the TFT driver, and the framebuffer will be left
1761 b - Enable backlight. The TFT backlight pin will be
1762 linked to the kernel VESA blanking code and a GPIO
1763 LED. This parameter is not necessary when using the
1765 c - Enable the s3c camera interface.
1766 t - Reserved for enabling touchscreen support. The
1767 touchscreen support is not enabled in the mainstream
1768 kernel as of 2.6.30, a preliminary port can be found
1769 in the "bleeding edge" mini2440 support kernel at
1770 http://repo.or.cz/w/linux-2.6/mini2440.git
1773 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1774 parameter allows control of the logging verbosity for
1775 the additional memory initialisation checks. A value
1776 of 0 disables mminit logging and a level of 4 will
1777 log everything. Information is printed at KERN_DEBUG
1778 so loglevel=8 may also need to be specified.
1781 [KNL] When CONFIG_MODULE_SIG is set, this means that
1782 modules without (valid) signatures will fail to load.
1783 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1784 is always true, so this option does nothing.
1787 [MOUSE] Maximum time between finger touching and
1788 leaving touchpad surface for touch to be considered
1789 a tap and be reported as a left button click (for
1790 touchpads working in absolute mode only).
1792 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1793 reporting absolute coordinates, such as tablets
1794 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1795 reporting absolute coordinates, such as tablets
1797 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1798 is similar to kernelcore except it specifies the
1799 amount of memory used for migratable allocations.
1800 If both kernelcore and movablecore is specified,
1801 then kernelcore will be at *least* the specified
1802 value but may be more. If movablecore on its own
1803 is specified, the administrator must be careful
1804 that the amount of memory usable for all allocations
1807 movable_node [KNL,X86] Boot-time switch to enable the effects
1808 of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1810 MTD_Partition= [MTD]
1811 Format: <name>,<region-number>,<size>,<offset>
1813 MTD_Region= [MTD] Format:
1814 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1817 See drivers/mtd/cmdlinepart.c.
1819 multitce=off [PPC] This parameter disables the use of the pSeries
1820 firmware feature for updating multiple TCE entries
1823 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1825 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1827 boundary - index of last SLC block on Flex-OneNAND.
1828 The remaining blocks are configured as MLC blocks.
1829 lock - Configure if Flex-OneNAND boundary should be locked.
1830 Once locked, the boundary cannot be changed.
1831 1 indicates lock status, 0 indicates unlock status.
1834 ARM/S3C2412 JIVE boot control
1836 See arch/arm/mach-s3c2412/mach-jive.c
1838 mtouchusb.raw_coordinates=
1839 [HW] Make the MicroTouch USB driver use raw coordinates
1840 ('y', default) or cooked coordinates ('n')
1842 mtrr_chunk_size=nn[KMG] [X86]
1843 used for mtrr cleanup. It is largest continuous chunk
1844 that could hold holes aka. UC entries.
1846 mtrr_gran_size=nn[KMG] [X86]
1847 Used for mtrr cleanup. It is granularity of mtrr block.
1849 Large value could prevent small alignment from
1852 mtrr_spare_reg_nr=n [X86]
1854 Range: 0,7 : spare reg number
1856 Used for mtrr cleanup. It is spare mtrr entries number.
1857 Set to 2 or more if your graphical card needs more.
1859 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1861 netdev= [NET] Network devices parameters
1862 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1863 Note that mem_start is often overloaded to mean
1864 something different and driver-specific.
1865 This usage is only documented in each driver source
1869 [NETFILTER] Enable connection tracking flow accounting
1870 0 to disable accounting
1871 1 to enable accounting
1874 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1875 See Documentation/filesystems/nfs/nfsroot.txt.
1877 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1878 See Documentation/filesystems/nfs/nfsroot.txt.
1880 nfsrootdebug [NFS] enable nfsroot debugging messages.
1881 See Documentation/filesystems/nfs/nfsroot.txt.
1883 nfs.callback_tcpport=
1884 [NFS] set the TCP port on which the NFSv4 callback
1885 channel should listen.
1888 [NFS] sets the pathname to the program which is used
1889 to update the NFS client cache entries.
1891 nfs.cache_getent_timeout=
1892 [NFS] sets the timeout after which an attempt to
1893 update a cache entry is deemed to have failed.
1895 nfs.idmap_cache_timeout=
1896 [NFS] set the maximum lifetime for idmapper cache
1900 [NFS] enable 64-bit inode numbers.
1901 If zero, the NFS client will fake up a 32-bit inode
1902 number for the readdir() and stat() syscalls instead
1903 of returning the full 64-bit number.
1904 The default is to return 64-bit inode numbers.
1906 nfs.max_session_slots=
1907 [NFSv4.1] Sets the maximum number of session slots
1908 the client will attempt to negotiate with the server.
1909 This limits the number of simultaneous RPC requests
1910 that the client can send to the NFSv4.1 server.
1911 Note that there is little point in setting this
1912 value higher than the max_tcp_slot_table_limit.
1914 nfs.nfs4_disable_idmapping=
1915 [NFSv4] When set to the default of '1', this option
1916 ensures that both the RPC level authentication
1917 scheme and the NFS level operations agree to use
1918 numeric uids/gids if the mount is using the
1919 'sec=sys' security flavour. In effect it is
1920 disabling idmapping, which can make migration from
1921 legacy NFSv2/v3 systems to NFSv4 easier.
1922 Servers that do not support this mode of operation
1923 will be autodetected by the client, and it will fall
1924 back to using the idmapper.
1925 To turn off this behaviour, set the value to '0'.
1927 [NFS4] Specify an additional fixed unique ident-
1928 ification string that NFSv4 clients can insert into
1929 their nfs_client_id4 string. This is typically a
1930 UUID that is generated at system install time.
1932 nfs.send_implementation_id =
1933 [NFSv4.1] Send client implementation identification
1934 information in exchange_id requests.
1935 If zero, no implementation identification information
1937 The default is to send the implementation identification
1940 nfs.recover_lost_locks =
1941 [NFSv4] Attempt to recover locks that were lost due
1942 to a lease timeout on the server. Please note that
1943 doing this risks data corruption, since there are
1944 no guarantees that the file will remain unchanged
1945 after the locks are lost.
1946 If you want to enable the kernel legacy behaviour of
1947 attempting to recover these locks, then set this
1949 The default parameter value of '0' causes the kernel
1950 not to attempt recovery of lost locks.
1952 nfsd.nfs4_disable_idmapping=
1953 [NFSv4] When set to the default of '1', the NFSv4
1954 server will return only numeric uids and gids to
1955 clients using auth_sys, and will accept numeric uids
1956 and gids from such clients. This is intended to ease
1957 migration from NFSv2/v3.
1959 objlayoutdriver.osd_login_prog=
1960 [NFS] [OBJLAYOUT] sets the pathname to the program which
1961 is used to automatically discover and login into new
1962 osd-targets. Please see:
1963 Documentation/filesystems/pnfs.txt for more explanations
1965 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1966 when a NMI is triggered.
1967 Format: [state][,regs][,debounce][,die]
1969 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1970 Format: [panic,][nopanic,][num]
1972 0 - turn nmi_watchdog off
1973 When panic is specified, panic when an NMI watchdog
1974 timeout occurs (or 'nopanic' to override the opposite
1976 This is useful when you use a panic=... timeout and
1977 need the box quickly up again.
1979 netpoll.carrier_timeout=
1980 [NET] Specifies amount of time (in seconds) that
1981 netpoll should wait for a carrier. By default netpoll
1984 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1985 emulation library even if a 387 maths coprocessor
1989 [HW] Never suspend the console
1990 Disable suspending of consoles during suspend and
1991 hibernate operations. Once disabled, debugging
1992 messages can reach various consoles while the rest
1993 of the system is being put to sleep (ie, while
1994 debugging driver suspend/resume hooks). This may
1995 not work reliably with all consoles, but is known
1996 to work with serial and VGA consoles.
1997 To facilitate more flexible debugging, we also add
1998 console_suspend, a printk module parameter to control
1999 it. Users could use console_suspend (usually
2000 /sys/module/printk/parameters/console_suspend) to
2001 turn on/off it dynamically.
2003 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
2004 caches in the slab allocator. Saves per-node memory,
2005 but will impact performance.
2009 noapic [SMP,APIC] Tells the kernel to not make use of any
2010 IOAPICs that may be present in the system.
2012 noautogroup Disable scheduler automatic task group creation.
2014 nobats [PPC] Do not use BATs for mapping kernel lowmem
2015 on "Classic" PPC cores.
2019 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
2021 nodelayacct [KNL] Disable per-task delay accounting
2023 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
2025 nodsp [SH] Disable hardware DSP at boot time.
2027 noefi [X86] Disable EFI runtime services support.
2032 On X86-32 available only on PAE configured kernels.
2033 noexec=on: enable non-executable mappings (default)
2034 noexec=off: disable non-executable mappings
2037 Disable SMAP (Supervisor Mode Access Prevention)
2038 even if it is supported by processor.
2041 Disable SMEP (Supervisor Mode Execution Prevention)
2042 even if it is supported by processor.
2045 This affects only 32-bit executables.
2046 noexec32=on: enable non-executable mappings (default)
2047 read doesn't imply executable mappings
2048 noexec32=off: disable non-executable mappings
2049 read implies executable mappings
2051 nofpu [SH] Disable hardware FPU at boot time.
2053 nofxsr [BUGS=X86-32] Disables x86 floating point extended
2054 register save and restore. The kernel will only save
2055 legacy floating-point registers on task switch.
2057 noxsave [BUGS=X86] Disables x86 extended register state save
2058 and restore using xsave. The kernel will fallback to
2059 enabling legacy floating-point and sse state.
2062 on enable eager fpu restore
2063 off disable eager fpu restore
2064 auto selects the default scheme, which automatically
2065 enables eagerfpu restore for xsaveopt.
2067 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2068 wfi(ARM) instruction doesn't work correctly and not to
2069 use it. This is also useful when using JTAG debugger.
2071 no_file_caps Tells the kernel not to honor file capabilities. The
2072 only way then for a file to be executed with privilege
2073 is to be setuid root or executed by root.
2075 nohalt [IA-64] Tells the kernel not to use the power saving
2076 function PAL_HALT_LIGHT when idle. This increases
2077 power-consumption. On the positive side, it reduces
2078 interrupt wake-up latency, which may improve performance
2079 in certain environments such as networked servers or
2082 nohz= [KNL] Boottime enable/disable dynamic ticks
2083 Valid arguments: on, off
2086 nohz_full= [KNL,BOOT]
2087 In kernels built with CONFIG_NO_HZ_FULL=y, set
2088 the specified list of CPUs whose tick will be stopped
2089 whenever possible. The boot CPU will be forced outside
2090 the range to maintain the timekeeping.
2091 The CPUs in this range must also be included in the
2094 noiotrap [SH] Disables trapped I/O port accesses.
2096 noirqdebug [X86-32] Disables the code which attempts to detect and
2097 disable unhandled interrupt sources.
2099 no_timer_check [X86,APIC] Disables the code which tests for
2100 broken timer IRQ sources.
2102 noisapnp [ISAPNP] Disables ISA PnP code.
2104 noinitrd [RAM] Tells the kernel not to load any configured
2107 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2109 [Deprecated - use intremap=off]
2113 nojitter [IA-64] Disables jitter checking for ITC timers.
2115 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2117 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2120 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2121 steal time is computed, but won't influence scheduler
2124 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2126 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2128 noltlbs [PPC] Do not use large page/tlb entries for kernel
2129 lowmem mapping on PPC40x.
2131 nomca [IA-64] Disable machine check abort handling
2133 nomce [X86-32] Machine Check Exception
2135 nomfgpt [X86-32] Disable Multi-Function General Purpose
2136 Timer usage (for AMD Geode machines).
2138 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2139 shutdown the other cpus. Instead use the REBOOT_VECTOR
2142 nomodule Disable module load
2144 nopat [X86] Disable PAT (page attribute table extension of
2145 pagetables) support.
2147 norandmaps Don't use address space randomization. Equivalent to
2148 echo 0 > /proc/sys/kernel/randomize_va_space
2150 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2152 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2153 with UP alternatives
2155 nordrand [X86] Disable the direct use of the RDRAND
2156 instruction even if it is supported by the
2157 processor. RDRAND is still available to user
2160 noresume [SWSUSP] Disables resume and restores original swap
2163 no-scroll [VGA] Disables scrollback.
2164 This is required for the Braillex ib80-piezo Braille
2165 reader made by F.H. Papenmeier (Germany).
2169 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2171 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2172 and disable the IO APIC. legacy for "maxcpus=0".
2174 nosoftlockup [KNL] Disable the soft-lockup detector.
2176 nosync [HW,M68K] Disables sync negotiation for all devices.
2178 notsc [BUGS=X86-32] Disable Time Stamp Counter
2180 nousb [USB] Disable the USB subsystem
2182 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2186 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2188 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2189 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2190 Some features depend on CPU0. Known dependencies are:
2191 1. Resume from suspend/hibernate depends on CPU0.
2192 Suspend/hibernate will fail if CPU0 is offline and you
2193 need to online CPU0 before suspend/hibernate.
2194 2. PIC interrupts also depend on CPU0. CPU0 can't be
2195 removed if a PIC interrupt is detected.
2196 It's said poweroff/reboot may depend on CPU0 on some
2197 machines although I haven't seen such issues so far
2198 after CPU0 is offline on a few tested machines.
2199 If the dependencies are under your control, you can
2200 turn on cpu0_hotplug.
2202 nptcg= [IA-64] Override max number of concurrent global TLB
2203 purges which is reported from either PAL_VM_SUMMARY or
2206 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2207 could support. nr_cpus=n : n >= 1 limits the kernel to
2208 supporting 'n' processors. Later in runtime you can not
2209 use hotplug cpu feature to put more cpu back to online.
2210 just like you compile the kernel NR_CPUS=n
2212 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2214 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2215 Allowed values are enable and disable
2217 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2218 one of ['zone', 'node', 'default'] can be specified
2219 This can be set from sysctl after boot.
2220 See Documentation/sysctl/vm.txt for details.
2222 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2223 See Documentation/debugging-via-ohci1394.txt for more
2226 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2227 Rather than timing out after 20 ms if an EC
2228 command is not properly ACKed, override the length
2229 of the timeout. We have interrupts disabled while
2230 waiting for the ACK, so if this is set too high
2231 interrupts *may* be lost!
2233 omap_mux= [OMAP] Override bootloader pin multiplexing.
2234 Format: <mux_mode0.mode_name=value>...
2235 For example, to override I2C bus2:
2236 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2238 oprofile.timer= [HW]
2239 Use timer interrupt instead of performance counters
2241 oprofile.cpu_type= Force an oprofile cpu type
2242 This might be useful if you have an older oprofile
2243 userland or if you want common events.
2244 Format: { arch_perfmon }
2245 arch_perfmon: [X86] Force use of architectural
2246 perfmon on Intel CPUs instead of the
2247 CPU specific event set.
2248 timer: [X86] Force use of architectural NMI
2249 timer mode (see also oprofile.timer
2250 for generic hr timer mode)
2251 [s390] Force legacy basic mode sampling
2252 (report cpu_type "timer")
2254 oops=panic Always panic on oopses. Default is to just kill the
2255 process, but there is a small probability of
2256 deadlocking the machine.
2257 This will also cause panics on machine check exceptions.
2258 Useful together with panic=30 to trigger a reboot.
2261 See Documentation/sound/oss/oss-parameters.txt
2263 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2264 timeout > 0: seconds before rebooting
2265 timeout = 0: wait forever
2266 timeout < 0: reboot immediately
2269 parkbd.port= [HW] Parallel port number the keyboard adapter is
2270 connected to, default is 0.
2272 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2273 0 for XT, 1 for AT (default is AT).
2276 parport= [HW,PPT] Specify parallel ports. 0 disables.
2277 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2278 Use 'auto' to force the driver to use any
2279 IRQ/DMA settings detected (the default is to
2280 ignore detected IRQ/DMA settings because of
2281 possible conflicts). You can specify the base
2282 address, IRQ, and DMA settings; IRQ and DMA
2283 should be numbers, or 'auto' (for using detected
2284 settings on that particular port), or 'nofifo'
2285 (to avoid using a FIFO even if it is detected).
2286 Parallel ports are assigned in the order they
2287 are specified on the command line, starting
2290 parport_init_mode= [HW,PPT]
2291 Configure VIA parallel port to operate in
2292 a specific mode. This is necessary on Pegasos
2293 computer where firmware has no options for setting
2294 up parallel port mode and sets it to spp.
2295 Currently this function knows 686a and 8231 chips.
2296 Format: [spp|ps2|epp|ecp|ecpepp]
2299 Halt all CPUs after the first oops has been printed for
2300 the specified number of seconds. This is to be used if
2301 your oopses keep scrolling off the screen.
2306 See header of drivers/block/paride/pcd.c.
2307 See also Documentation/blockdev/paride.txt.
2309 pci=option[,option...] [PCI] various PCI subsystem options:
2310 earlydump [X86] dump PCI config space before the kernel
2312 off [X86] don't probe for the PCI bus
2313 bios [X86-32] force use of PCI BIOS, don't access
2314 the hardware directly. Use this if your machine
2315 has a non-standard PCI host bridge.
2316 nobios [X86-32] disallow use of PCI BIOS, only direct
2317 hardware access methods are allowed. Use this
2318 if you experience crashes upon bootup and you
2319 suspect they are caused by the BIOS.
2320 conf1 [X86] Force use of PCI Configuration
2322 conf2 [X86] Force use of PCI Configuration
2324 noaer [PCIE] If the PCIEAER kernel config parameter is
2325 enabled, this kernel boot option can be used to
2326 disable the use of PCIE advanced error reporting.
2327 nodomains [PCI] Disable support for multiple PCI
2328 root domains (aka PCI segments, in ACPI-speak).
2329 nommconf [X86] Disable use of MMCONFIG for PCI
2331 check_enable_amd_mmconf [X86] check for and enable
2332 properly configured MMIO access to PCI
2333 config space on AMD family 10h CPU
2334 nomsi [MSI] If the PCI_MSI kernel config parameter is
2335 enabled, this kernel boot option can be used to
2336 disable the use of MSI interrupts system-wide.
2337 noioapicquirk [APIC] Disable all boot interrupt quirks.
2338 Safety option to keep boot IRQs enabled. This
2339 should never be necessary.
2340 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2341 primary IO-APIC for bridges that cannot disable
2342 boot IRQs. This fixes a source of spurious IRQs
2343 when the system masks IRQs.
2344 noioapicreroute [APIC] Disable workaround that uses the
2345 boot IRQ equivalent of an IRQ that connects to
2346 a chipset where boot IRQs cannot be disabled.
2347 The opposite of ioapicreroute.
2348 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2349 routing table. These calls are known to be buggy
2350 on several machines and they hang the machine
2351 when used, but on other computers it's the only
2352 way to get the interrupt routing table. Try
2353 this option if the kernel is unable to allocate
2354 IRQs or discover secondary PCI buses on your
2356 rom [X86] Assign address space to expansion ROMs.
2357 Use with caution as certain devices share
2358 address decoders between ROMs and other
2360 norom [X86] Do not assign address space to
2361 expansion ROMs that do not already have
2362 BIOS assigned address ranges.
2363 nobar [X86] Do not assign address space to the
2364 BARs that weren't assigned by the BIOS.
2365 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2366 assigned automatically to PCI devices. You can
2367 make the kernel exclude IRQs of your ISA cards
2369 pirqaddr=0xAAAAA [X86] Specify the physical address
2370 of the PIRQ table (normally generated
2371 by the BIOS) if it is outside the
2372 F0000h-100000h range.
2373 lastbus=N [X86] Scan all buses thru bus #N. Can be
2374 useful if the kernel is unable to find your
2375 secondary buses and you want to tell it
2376 explicitly which ones they are.
2377 assign-busses [X86] Always assign all PCI bus
2378 numbers ourselves, overriding
2379 whatever the firmware may have done.
2380 usepirqmask [X86] Honor the possible IRQ mask stored
2381 in the BIOS $PIR table. This is needed on
2382 some systems with broken BIOSes, notably
2383 some HP Pavilion N5400 and Omnibook XE3
2384 notebooks. This will have no effect if ACPI
2385 IRQ routing is enabled.
2386 noacpi [X86] Do not use ACPI for IRQ routing
2387 or for PCI scanning.
2388 use_crs [X86] Use PCI host bridge window information
2389 from ACPI. On BIOSes from 2008 or later, this
2390 is enabled by default. If you need to use this,
2391 please report a bug.
2392 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2393 If you need to use this, please report a bug.
2394 routeirq Do IRQ routing for all PCI devices.
2395 This is normally done in pci_enable_device(),
2396 so this option is a temporary workaround
2397 for broken drivers that don't call it.
2398 skip_isa_align [X86] do not align io start addr, so can
2399 handle more pci cards
2400 firmware [ARM] Do not re-enumerate the bus but instead
2401 just use the configuration from the
2402 bootloader. This is currently used on
2403 IXP2000 systems where the bus has to be
2404 configured a certain way for adjunct CPUs.
2405 noearly [X86] Don't do any early type 1 scanning.
2406 This might help on some broken boards which
2407 machine check when some devices' config space
2408 is read. But various workarounds are disabled
2409 and some IOMMU drivers will not work.
2410 bfsort Sort PCI devices into breadth-first order.
2411 This sorting is done to get a device
2412 order compatible with older (<= 2.4) kernels.
2413 nobfsort Don't sort PCI devices into breadth-first order.
2414 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2415 tuning and use the BIOS-configured MPS defaults.
2416 pcie_bus_safe Set every device's MPS to the largest value
2417 supported by all devices below the root complex.
2418 pcie_bus_perf Set device MPS to the largest allowable MPS
2419 based on its parent bus. Also set MRRS (Max
2420 Read Request Size) to the largest supported
2421 value (no larger than the MPS that the device
2422 or bus can support) for best performance.
2423 pcie_bus_peer2peer Set every device's MPS to 128B, which
2424 every device is guaranteed to support. This
2425 configuration allows peer-to-peer DMA between
2426 any pair of devices, possibly at the cost of
2427 reduced performance. This also guarantees
2428 that hot-added devices will work.
2429 cbiosize=nn[KMG] The fixed amount of bus space which is
2430 reserved for the CardBus bridge's IO window.
2431 The default value is 256 bytes.
2432 cbmemsize=nn[KMG] The fixed amount of bus space which is
2433 reserved for the CardBus bridge's memory
2434 window. The default value is 64 megabytes.
2437 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2438 Specifies alignment and device to reassign
2439 aligned memory resources.
2440 If <order of align> is not specified,
2441 PAGE_SIZE is used as alignment.
2442 PCI-PCI bridge can be specified, if resource
2443 windows need to be expanded.
2444 ecrc= Enable/disable PCIe ECRC (transaction layer
2445 end-to-end CRC checking).
2446 bios: Use BIOS/firmware settings. This is the
2450 hpiosize=nn[KMG] The fixed amount of bus space which is
2451 reserved for hotplug bridge's IO window.
2452 Default size is 256 bytes.
2453 hpmemsize=nn[KMG] The fixed amount of bus space which is
2454 reserved for hotplug bridge's memory window.
2455 Default size is 2 megabytes.
2456 realloc= Enable/disable reallocating PCI bridge resources
2457 if allocations done by BIOS are too small to
2458 accommodate resources required by all child
2460 off: Turn realloc off
2462 realloc same as realloc=on
2463 noari do not use PCIe ARI.
2464 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2465 only look for one device below a PCIe downstream
2468 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2471 force Enable ASPM even on devices that claim not to support it.
2472 WARNING: Forcing ASPM on may cause system lockups.
2474 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2475 nomsi Do not use MSI for PCI Express Native Hotplug (this
2476 makes all PCIe ports use INTx for hotplug services).
2478 pcie_ports= [PCIE] PCIe ports handling:
2479 auto Ask the BIOS whether or not to use native PCIe services
2480 associated with PCIe ports (PME, hot-plug, AER). Use
2481 them only if that is allowed by the BIOS.
2482 native Use native PCIe services associated with PCIe ports
2484 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2487 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2488 nomsi Do not use MSI for native PCIe PME signaling (this makes
2489 all PCIe root ports use INTx for all services).
2491 pcmv= [HW,PCMCIA] BadgePAD 4
2494 See Documentation/blockdev/paride.txt.
2496 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2499 See arch/parisc/kernel/pdc_chassis.c
2501 percpu_alloc= Select which percpu first chunk allocator to use.
2502 Currently supported values are "embed" and "page".
2503 Archs may support subset or none of the selections.
2504 See comments in mm/percpu.c for details on each
2505 allocator. This parameter is primarily for debugging
2506 and performance comparison.
2509 See Documentation/blockdev/paride.txt.
2512 See Documentation/blockdev/paride.txt.
2514 pirq= [SMP,APIC] Manual mp-table setup
2515 See Documentation/x86/i386/IO-APIC.txt.
2517 plip= [PPT,NET] Parallel port network link
2518 Format: { parport<nr> | timid | 0 }
2519 See also Documentation/parport.txt.
2521 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2522 Override pmtimer IOPort with a hex value.
2526 Enable PNP debug messages (depends on the
2527 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2528 via /sys/module/pnp/parameters/debug. We always show
2529 current resource usage; turning this on also shows
2530 possible settings and some assignment information.
2536 { on | off | curr | res | no-curr | no-res }
2539 [ISAPNP] Exclude IRQs for the autoconfiguration
2542 [ISAPNP] Exclude DMAs for the autoconfiguration
2544 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2545 Ranges are in pairs (I/O port base and size).
2548 [ISAPNP] Exclude memory regions for the
2550 Ranges are in pairs (memory base and size).
2552 ports= [IP_VS_FTP] IPVS ftp helper module
2554 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2556 Format: <port>,<port>....
2558 print-fatal-signals=
2559 [KNL] debug: print fatal signals
2561 If enabled, warn about various signal handling
2562 related application anomalies: too many signals,
2563 too many POSIX.1 timers, fatal signals causing a
2566 If you hit the warning due to signal overflow,
2567 you might want to try "ulimit -i unlimited".
2571 printk.always_kmsg_dump=
2572 Trigger kmsg_dump for cases other than kernel oops or
2574 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2577 printk.time= Show timing data prefixed to each printk message line
2578 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2580 processor.max_cstate= [HW,ACPI]
2581 Limit processor to maximum C-state
2582 max_cstate=9 overrides any DMI blacklist limit.
2584 processor.nocst [HW,ACPI]
2585 Ignore the _CST method to determine C-states,
2586 instead using the legacy FADT method
2588 profile= [KNL] Enable kernel profiling via /proc/profile
2589 Format: [schedule,]<number>
2590 Param: "schedule" - profile schedule points.
2591 Param: <number> - step/bucket size as a power of 2 for
2592 statistical time based profiling.
2593 Param: "sleep" - profile D-state sleeping (millisecs).
2594 Requires CONFIG_SCHEDSTATS
2595 Param: "kvm" - profile VM exits.
2597 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2599 See Documentation/blockdev/ramdisk.txt.
2601 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2602 probe for; one of (bare|imps|exps|lifebook|any).
2603 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2605 psmouse.resetafter= [HW,MOUSE]
2606 Try to reset the device after so many bad packets
2609 [HW,MOUSE] Set desired mouse resolution, in dpi.
2610 psmouse.smartscroll=
2611 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2612 0 = disabled, 1 = enabled (default).
2614 pstore.backend= Specify the name of the pstore backend to use
2617 See Documentation/blockdev/paride.txt.
2620 [KNL] Number of legacy pty's. Overwrites compiled-in
2623 quiet [KNL] Disable most log messages
2628 See Documentation/md.txt.
2630 ramdisk_blocksize= [RAM]
2631 See Documentation/blockdev/ramdisk.txt.
2633 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2634 See Documentation/blockdev/ramdisk.txt.
2637 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2638 the specified list of CPUs to be no-callback CPUs.
2639 Invocation of these CPUs' RCU callbacks will
2640 be offloaded to "rcuox/N" kthreads created for
2641 that purpose, where "x" is "b" for RCU-bh, "p"
2642 for RCU-preempt, and "s" for RCU-sched, and "N"
2643 is the CPU number. This reduces OS jitter on the
2644 offloaded CPUs, which can be useful for HPC and
2645 real-time workloads. It can also improve energy
2646 efficiency for asymmetric multiprocessors.
2649 Rather than requiring that offloaded CPUs
2650 (specified by rcu_nocbs= above) explicitly
2651 awaken the corresponding "rcuoN" kthreads,
2652 make these kthreads poll for callbacks.
2653 This improves the real-time response for the
2654 offloaded CPUs by relieving them of the need to
2655 wake up the corresponding kthread, but degrades
2656 energy efficiency by requiring that the kthreads
2657 periodically wake up to do the polling.
2659 rcutree.blimit= [KNL]
2660 Set maximum number of finished RCU callbacks to
2661 process in one batch.
2663 rcutree.rcu_fanout_leaf= [KNL]
2664 Increase the number of CPUs assigned to each
2665 leaf rcu_node structure. Useful for very large
2668 rcutree.jiffies_till_first_fqs= [KNL]
2669 Set delay from grace-period initialization to
2670 first attempt to force quiescent states.
2671 Units are jiffies, minimum value is zero,
2672 and maximum value is HZ.
2674 rcutree.jiffies_till_next_fqs= [KNL]
2675 Set delay between subsequent attempts to force
2676 quiescent states. Units are jiffies, minimum
2677 value is one, and maximum value is HZ.
2679 rcutree.qhimark= [KNL]
2680 Set threshold of queued RCU callbacks beyond which
2681 batch limiting is disabled.
2683 rcutree.qlowmark= [KNL]
2684 Set threshold of queued RCU callbacks below which
2685 batch limiting is re-enabled.
2687 rcutree.rcu_idle_gp_delay= [KNL]
2688 Set wakeup interval for idle CPUs that have
2689 RCU callbacks (RCU_FAST_NO_HZ=y).
2691 rcutree.rcu_idle_lazy_gp_delay= [KNL]
2692 Set wakeup interval for idle CPUs that have
2693 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2694 Lazy RCU callbacks are those which RCU can
2695 prove do nothing more than free memory.
2697 rcutorture.fqs_duration= [KNL]
2698 Set duration of force_quiescent_state bursts.
2700 rcutorture.fqs_holdoff= [KNL]
2701 Set holdoff time within force_quiescent_state bursts.
2703 rcutorture.fqs_stutter= [KNL]
2704 Set wait time between force_quiescent_state bursts.
2706 rcutorture.gp_exp= [KNL]
2707 Use expedited update-side primitives.
2709 rcutorture.gp_normal= [KNL]
2710 Use normal (non-expedited) update-side primitives.
2711 If both gp_exp and gp_normal are set, do both.
2712 If neither gp_exp nor gp_normal are set, still
2715 rcutorture.n_barrier_cbs= [KNL]
2716 Set callbacks/threads for rcu_barrier() testing.
2718 rcutorture.nfakewriters= [KNL]
2719 Set number of concurrent RCU writers. These just
2720 stress RCU, they don't participate in the actual
2721 test, hence the "fake".
2723 rcutorture.nreaders= [KNL]
2724 Set number of RCU readers.
2726 rcutorture.object_debug= [KNL]
2727 Enable debug-object double-call_rcu() testing.
2729 rcutorture.onoff_holdoff= [KNL]
2730 Set time (s) after boot for CPU-hotplug testing.
2732 rcutorture.onoff_interval= [KNL]
2733 Set time (s) between CPU-hotplug operations, or
2734 zero to disable CPU-hotplug testing.
2736 rcutorture.rcutorture_runnable= [BOOT]
2737 Start rcutorture running at boot time.
2739 rcutorture.shuffle_interval= [KNL]
2740 Set task-shuffle interval (s). Shuffling tasks
2741 allows some CPUs to go into dyntick-idle mode
2742 during the rcutorture test.
2744 rcutorture.shutdown_secs= [KNL]
2745 Set time (s) after boot system shutdown. This
2746 is useful for hands-off automated testing.
2748 rcutorture.stall_cpu= [KNL]
2749 Duration of CPU stall (s) to test RCU CPU stall
2750 warnings, zero to disable.
2752 rcutorture.stall_cpu_holdoff= [KNL]
2753 Time to wait (s) after boot before inducing stall.
2755 rcutorture.stat_interval= [KNL]
2756 Time (s) between statistics printk()s.
2758 rcutorture.stutter= [KNL]
2759 Time (s) to stutter testing, for example, specifying
2760 five seconds causes the test to run for five seconds,
2761 wait for five seconds, and so on. This tests RCU's
2762 ability to transition abruptly to and from idle.
2764 rcutorture.test_boost= [KNL]
2765 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2766 "Maybe" means test if the RCU implementation
2767 under test support RCU priority boosting.
2769 rcutorture.test_boost_duration= [KNL]
2770 Duration (s) of each individual boost test.
2772 rcutorture.test_boost_interval= [KNL]
2773 Interval (s) between each boost test.
2775 rcutorture.test_no_idle_hz= [KNL]
2776 Test RCU's dyntick-idle handling. See also the
2777 rcutorture.shuffle_interval parameter.
2779 rcutorture.torture_type= [KNL]
2780 Specify the RCU implementation to test.
2782 rcutorture.verbose= [KNL]
2783 Enable additional printk() statements.
2785 rcupdate.rcu_expedited= [KNL]
2786 Use expedited grace-period primitives, for
2787 example, synchronize_rcu_expedited() instead
2788 of synchronize_rcu(). This reduces latency,
2789 but can increase CPU utilization, degrade
2790 real-time latency, and degrade energy efficiency.
2792 rcupdate.rcu_cpu_stall_suppress= [KNL]
2793 Suppress RCU CPU stall warning messages.
2795 rcupdate.rcu_cpu_stall_timeout= [KNL]
2796 Set timeout for RCU CPU stall warning messages.
2800 Run specified binary instead of /init from the ramdisk,
2801 used for early userspace startup. See initrd.
2804 Format (x86 or x86_64):
2805 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2807 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2809 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2810 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2811 reboot_force is either force or not specified,
2812 reboot_cpu is s[mp]#### with #### being the processor
2813 to be used for rebooting.
2816 [KNL, SMP] Set scheduler's default relax_domain_level.
2817 See Documentation/cgroups/cpusets.txt.
2819 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2821 reservetop= [X86-32]
2823 Reserves a hole at the top of the kernel virtual
2828 Set the amount of memory to reserve for BIOS at
2829 the bottom of the address space.
2831 reset_devices [KNL] Force drivers to reset the underlying device
2832 during initialization.
2835 Specify the partition device for software suspend
2837 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2839 resume_offset= [SWSUSP]
2840 Specify the offset from the beginning of the partition
2841 given by "resume=" at which the swap header is located,
2842 in <PAGE_SIZE> units (needed only for swap files).
2843 See Documentation/power/swsusp-and-swap-files.txt
2845 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2846 read the resume files
2848 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2849 Useful for devices that are detected asynchronously
2850 (e.g. USB and MMC devices).
2852 hibernate= [HIBERNATION]
2853 noresume Don't check if there's a hibernation image
2854 present during boot.
2855 nocompress Don't compress/decompress hibernation images.
2857 retain_initrd [RAM] Keep initrd memory after extraction
2859 rhash_entries= [KNL,NET]
2860 Set number of hash buckets for route cache
2862 riscom8= [HW,SERIAL]
2863 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2865 ro [KNL] Mount root device read-only on boot
2867 root= [KNL] Root filesystem
2868 See name_to_dev_t comment in init/do_mounts.c.
2870 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2871 mount the root filesystem
2873 rootflags= [KNL] Set root filesystem mount option string
2875 rootfstype= [KNL] Set root filesystem type
2877 rootwait [KNL] Wait (indefinitely) for root device to show up.
2878 Useful for devices that are detected asynchronously
2879 (e.g. USB and MMC devices).
2881 rproc_mem=nn[KMG][@address]
2882 [KNL,ARM,CMA] Remoteproc physical memory block.
2883 Memory area to be used by remote processor image,
2886 rw [KNL] Mount root device read-write on boot
2888 S [KNL] Run init in single mode
2891 See drivers/net/irda/sa1100_ir.c.
2893 sbni= [NET] Granch SBNI12 leased line adapter
2895 sched_debug [KNL] Enables verbose scheduler debug messages.
2897 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2898 xtime_lock contention on larger systems, and/or RCU lock
2899 contention on all systems with CONFIG_MAXSMP set.
2900 Format: { "0" | "1" }
2901 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2903 Note: increases power consumption, thus should only be
2904 enabled if running jitter sensitive (HPC/RT) workloads.
2906 security= [SECURITY] Choose a security module to enable at boot.
2907 If this boot parameter is not specified, only the first
2908 security module asking for security registration will be
2909 loaded. An invalid security module name will be treated
2910 as if no module has been chosen.
2912 selinux= [SELINUX] Disable or enable SELinux at boot time.
2913 Format: { "0" | "1" }
2914 See security/selinux/Kconfig help text.
2917 Default value is set via kernel config option.
2918 If enabled at boot time, /selinux/disable can be used
2919 later to disable prior to initial policy load.
2921 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2922 Format: { "0" | "1" }
2923 See security/apparmor/Kconfig help text
2926 Default value is set via kernel config option.
2928 serialnumber [BUGS=X86-32]
2931 Maximal number of shapers.
2933 show_msr= [x86] show boot-time MSR settings
2934 Format: { <integer> }
2935 Show boot-time (BIOS-initialized) MSR settings.
2936 The parameter means the number of CPUs to show,
2937 for example 1 means boot CPU only.
2944 slab_max_order= [MM, SLAB]
2945 Determines the maximum allowed order for slabs.
2946 A high setting may cause OOMs due to memory
2947 fragmentation. Defaults to 1 for systems with
2948 more than 32MB of RAM, 0 otherwise.
2950 slub_debug[=options[,slabs]] [MM, SLUB]
2951 Enabling slub_debug allows one to determine the
2952 culprit if slab objects become corrupted. Enabling
2953 slub_debug can create guard zones around objects and
2954 may poison objects when not in use. Also tracks the
2955 last alloc / free. For more information see
2956 Documentation/vm/slub.txt.
2958 slub_max_order= [MM, SLUB]
2959 Determines the maximum allowed order for slabs.
2960 A high setting may cause OOMs due to memory
2961 fragmentation. For more information see
2962 Documentation/vm/slub.txt.
2964 slub_min_objects= [MM, SLUB]
2965 The minimum number of objects per slab. SLUB will
2966 increase the slab order up to slub_max_order to
2967 generate a sufficiently large slab able to contain
2968 the number of objects indicated. The higher the number
2969 of objects the smaller the overhead of tracking slabs
2970 and the less frequently locks need to be acquired.
2971 For more information see Documentation/vm/slub.txt.
2973 slub_min_order= [MM, SLUB]
2974 Determines the minimum page order for slabs. Must be
2975 lower than slub_max_order.
2976 For more information see Documentation/vm/slub.txt.
2978 slub_nomerge [MM, SLUB]
2979 Disable merging of slabs with similar size. May be
2980 necessary if there is some reason to distinguish
2981 allocs to different slabs. Debug options disable
2982 merging on their own.
2983 For more information see Documentation/vm/slub.txt.
2986 Format: <io1>[,<io2>[,...,<io8>]]
2988 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2989 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2990 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2991 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2992 smsc-ircc2.ircc_irq= [HW] IRQ line
2993 smsc-ircc2.ircc_dma= [HW] DMA channel
2994 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2995 0: Toshiba Satellite 1800 (GP data pin select)
2996 1: Fast pin select (default)
3000 [KNL] Should the soft-lockup detector generate panics.
3003 sonypi.*= [HW] Sony Programmable I/O Control Device driver
3004 See Documentation/laptops/sonypi.txt
3006 specialix= [HW,SERIAL] Specialix multi-serial port adapter
3007 See Documentation/serial/specialix.txt.
3009 spia_io_base= [HW,MTD]
3015 Enabled the stack tracer on boot up.
3017 stacktrace_filter=[function-list]
3018 [FTRACE] Limit the functions that the stack tracer
3019 will trace at boot up. function-list is a comma separated
3020 list of functions. This list can be changed at run
3021 time by the stack_trace_filter file in the debugfs
3022 tracing directory. Note, this enables stack tracing
3023 and the stacktrace above is not needed.
3027 Set the STI (builtin display/keyboard on the HP-PARISC
3028 machines) console (graphic card) which should be used
3029 as the initial boot-console.
3030 See also comment in drivers/video/console/sticore.c.
3033 See comment in drivers/video/console/sticore.c.
3036 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3038 sunrpc.min_resvport=
3039 sunrpc.max_resvport=
3041 SunRPC servers often require that client requests
3042 originate from a privileged port (i.e. a port in the
3043 range 0 < portnr < 1024).
3044 An administrator who wishes to reserve some of these
3045 ports for other uses may adjust the range that the
3046 kernel's sunrpc client considers to be privileged
3047 using these two parameters to set the minimum and
3048 maximum port values.
3052 Control how the NFS server code allocates CPUs to
3053 service thread pools. Depending on how many NICs
3054 you have and where their interrupts are bound, this
3055 option will affect which CPUs will do NFS serving.
3056 Note: this parameter cannot be changed while the
3057 NFS server is running.
3059 auto the server chooses an appropriate mode
3060 automatically using heuristics
3061 global a single global pool contains all CPUs
3062 percpu one pool for each CPU
3063 pernode one pool for each NUMA node (equivalent
3064 to global on non-NUMA machines)
3066 sunrpc.tcp_slot_table_entries=
3067 sunrpc.udp_slot_table_entries=
3069 Sets the upper limit on the number of simultaneous
3070 RPC calls that can be sent from the client to a
3071 server. Increasing these values may allow you to
3072 improve throughput, but will also increase the
3073 amount of memory reserved for use by the client.
3076 [KNL] Enable accounting of swap in memory resource
3077 controller if no parameter or 1 is given or disable
3078 it if 0 is given (See Documentation/cgroups/memory.txt)
3080 swiotlb= [IA-64] Number of I/O TLB slabs
3084 sysfs.deprecated=0|1 [KNL]
3085 Enable/disable old style sysfs layout for old udev
3086 on older distributions. When this option is enabled
3087 very new udev will not work anymore. When this option
3088 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3089 in older udev will not work anymore.
3090 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3091 the kernel configuration.
3093 sysrq_always_enabled
3095 Ignore sysrq setting - this boot parameter will
3096 neutralize any effect of /proc/sys/kernel/sysrq.
3097 Useful for debugging.
3101 test_suspend= [SUSPEND]
3102 Specify "mem" (for Suspend-to-RAM) or "standby" (for
3103 standby suspend) as the system sleep state to briefly
3104 enter during system startup. The system is woken from
3105 this state using a wakeup-capable RTC alarm.
3107 thash_entries= [KNL,NET]
3108 Set number of hash buckets for TCP connection
3110 thermal.act= [HW,ACPI]
3111 -1: disable all active trip points in all thermal zones
3112 <degrees C>: override all lowest active trip points
3114 thermal.crt= [HW,ACPI]
3115 -1: disable all critical trip points in all thermal zones
3116 <degrees C>: override all critical trip points
3118 thermal.nocrt= [HW,ACPI]
3119 Set to disable actions on ACPI thermal zone
3120 critical and hot trip points.
3122 thermal.off= [HW,ACPI]
3123 1: disable ACPI thermal control
3125 thermal.psv= [HW,ACPI]
3126 -1: disable all passive trip points
3127 <degrees C>: override all passive trip points to this
3130 thermal.tzp= [HW,ACPI]
3131 Specify global default ACPI thermal zone polling rate
3132 <deci-seconds>: poll all this frequency
3133 0: no polling (default)
3136 Force threading of all interrupt handlers except those
3137 marked explicitly IRQF_NO_THREAD.
3140 Enable the Transcendent memory driver if built-in.
3142 tmem.cleancache=0|1 [KNL, XEN]
3143 Default is on (1). Disable the usage of the cleancache
3144 API to send anonymous pages to the hypervisor.
3146 tmem.frontswap=0|1 [KNL, XEN]
3147 Default is on (1). Disable the usage of the frontswap
3148 API to send swap pages to the hypervisor. If disabled
3149 the selfballooning and selfshrinking are force disabled.
3151 tmem.selfballooning=0|1 [KNL, XEN]
3152 Default is on (1). Disable the driving of swap pages
3155 tmem.selfshrinking=0|1 [KNL, XEN]
3156 Default is on (1). Partial swapoff that immediately
3157 transfers pages from Xen hypervisor back to the
3158 kernel based on different criteria.
3162 Specify if the kernel should make use of the cpu
3163 topology information if the hardware supports this.
3164 The scheduler will make use of this information and
3165 e.g. base its process migration decisions on it.
3170 tpm_suspend_pcr=[HW,TPM]
3171 Format: integer pcr id
3172 Specify that at suspend time, the tpm driver
3173 should extend the specified pcr with zeros,
3174 as a workaround for some chips which fail to
3175 flush the last written pcr on TPM_SaveState.
3176 This will guarantee that all the other pcrs
3179 trace_buf_size=nn[KMG]
3180 [FTRACE] will set tracing buffer size.
3182 trace_event=[event-list]
3183 [FTRACE] Set and start specified trace events in order
3184 to facilitate early boot debugging.
3185 See also Documentation/trace/events.txt
3187 trace_options=[option-list]
3188 [FTRACE] Enable or disable tracer options at boot.
3189 The option-list is a comma delimited list of options
3190 that can be enabled or disabled just as if you were
3191 to echo the option name into
3193 /sys/kernel/debug/tracing/trace_options
3195 For example, to enable stacktrace option (to dump the
3196 stack trace of each event), add to the command line:
3198 trace_options=stacktrace
3200 See also Documentation/trace/ftrace.txt "trace options"
3204 [FTRACE] enable this option to disable tracing when a
3205 warning is hit. This turns off "tracing_on". Tracing can
3206 be enabled again by echoing '1' into the "tracing_on"
3207 file located in /sys/kernel/debug/tracing/
3209 This option is useful, as it disables the trace before
3210 the WARNING dump is called, which prevents the trace to
3211 be filled with content caused by the warning output.
3213 This option can also be set at run time via the sysctl
3214 option: kernel/traceoff_on_warning
3216 transparent_hugepage=
3218 Format: [always|madvise|never]
3219 Can be used to control the default behavior of the system
3220 with respect to transparent hugepages.
3221 See Documentation/vm/transhuge.txt for more details.
3223 tsc= Disable clocksource stability checks for TSC.
3225 [x86] reliable: mark tsc clocksource as reliable, this
3226 disables clocksource verification at runtime, as well
3227 as the stability checks done at bootup. Used to enable
3228 high-resolution timer mode on older hardware, and in
3229 virtualized environment.
3230 [x86] noirqtime: Do not use TSC to do irq accounting.
3231 Used to run time disable IRQ_TIME_ACCOUNTING on any
3232 platforms where RDTSC is slow and this accounting
3235 turbografx.map[2|3]= [HW,JOY]
3236 TurboGraFX parallel port interface
3238 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3239 See also Documentation/input/joystick-parport.txt
3241 udbg-immortal [PPC] When debugging early kernel crashes that
3242 happen after console_init() and before a proper
3243 console driver takes over, this boot options might
3244 help "seeing" what's going on.
3246 uhash_entries= [KNL,NET]
3247 Set number of hash buckets for UDP/UDP-Lite connections
3250 [USB] Ignore overcurrent events (default N).
3251 Some badly-designed motherboards generate lots of
3252 bogus events, for ports that aren't wired to
3253 anything. Set this parameter to avoid log spamming.
3254 Note that genuine overcurrent events won't be
3258 [X86] Cause panic on unknown NMI.
3260 usbcore.authorized_default=
3261 [USB] Default USB device authorization:
3262 (default -1 = authorized except for wireless USB,
3263 0 = not authorized, 1 = authorized)
3265 usbcore.autosuspend=
3266 [USB] The autosuspend time delay (in seconds) used
3267 for newly-detected USB devices (default 2). This
3268 is the time required before an idle device will be
3269 autosuspended. Devices for which the delay is set
3270 to a negative value won't be autosuspended at all.
3272 usbcore.usbfs_snoop=
3273 [USB] Set to log all usbfs traffic (default 0 = off).
3275 usbcore.blinkenlights=
3276 [USB] Set to cycle leds on hubs (default 0 = off).
3278 usbcore.old_scheme_first=
3279 [USB] Start with the old device initialization
3280 scheme (default 0 = off).
3282 usbcore.usbfs_memory_mb=
3283 [USB] Memory limit (in MB) for buffers allocated by
3284 usbfs (default = 16, 0 = max = 2047).
3286 usbcore.use_both_schemes=
3287 [USB] Try the other device initialization scheme
3288 if the first one fails (default 1 = enabled).
3290 usbcore.initial_descriptor_timeout=
3291 [USB] Specifies timeout for the initial 64-byte
3292 USB_REQ_GET_DESCRIPTOR request in milliseconds
3293 (default 5000 = 5.0 seconds).
3296 [USBHID] The interval which mice are to be polled at.
3298 usb-storage.delay_use=
3299 [UMS] The delay in seconds before a new device is
3300 scanned for Logical Units (default 5).
3303 [UMS] A list of quirks entries to supplement or
3304 override the built-in unusual_devs list. List
3305 entries are separated by commas. Each entry has
3306 the form VID:PID:Flags where VID and PID are Vendor
3307 and Product ID values (4-digit hex numbers) and
3308 Flags is a set of characters, each corresponding
3309 to a common usb-storage quirk flag as follows:
3310 a = SANE_SENSE (collect more than 18 bytes
3312 b = BAD_SENSE (don't collect more than 18
3313 bytes of sense data);
3314 c = FIX_CAPACITY (decrease the reported
3315 device capacity by one sector);
3316 d = NO_READ_DISC_INFO (don't use
3317 READ_DISC_INFO command);
3318 e = NO_READ_CAPACITY_16 (don't use
3319 READ_CAPACITY_16 command);
3320 h = CAPACITY_HEURISTICS (decrease the
3321 reported device capacity by one
3322 sector if the number is odd);
3323 i = IGNORE_DEVICE (don't bind to this
3325 l = NOT_LOCKABLE (don't try to lock and
3326 unlock ejectable media);
3327 m = MAX_SECTORS_64 (don't transfer more
3328 than 64 sectors = 32 KB at a time);
3329 n = INITIAL_READ10 (force a retry of the
3330 initial READ(10) command);
3331 o = CAPACITY_OK (accept the capacity
3332 reported by the device);
3333 p = WRITE_CACHE (the device cache is ON
3335 r = IGNORE_RESIDUE (the device reports
3336 bogus residue values);
3337 s = SINGLE_LUN (the device has only one
3339 w = NO_WP_DETECT (don't test whether the
3340 medium is write-protected).
3341 Example: quirks=0419:aaf5:rl,0421:0433:rc
3343 user_debug= [KNL,ARM]
3345 See arch/arm/Kconfig.debug help text.
3346 1 - undefined instruction events
3348 4 - invalid data aborts
3351 Example: user_debug=31
3354 [X86] Flags controlling user PTE allocations.
3356 nohigh = do not allocate PTE pages in
3357 HIGHMEM regardless of setting
3361 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3362 vdso=1: enable VDSO (default)
3363 vdso=0: disable VDSO mapping
3366 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3367 vdso32=1: enable 32-bit VDSO (default)
3368 vdso32=0: disable 32-bit VDSO mapping
3371 vector=percpu: enable percpu vector domain
3373 video= [FB] Frame buffer configuration
3374 See Documentation/fb/modedb.txt.
3376 video.brightness_switch_enabled= [0,1]
3377 If set to 1, on receiving an ACPI notify event
3378 generated by hotkey, video driver will adjust brightness
3379 level and then send out the event to user space through
3380 the allocated input device; If set to 0, video driver
3381 will only send out the event without touching backlight
3386 [VMMIO] Memory mapped virtio (platform) device.
3388 <size>@<baseaddr>:<irq>[:<id>]
3390 <size> := size (can use standard suffixes
3392 <baseaddr> := physical base address
3393 <irq> := interrupt number (as passed to
3395 <id> := (optional) platform device id
3397 virtio_mmio.device=1K@0x100b0000:48:7
3399 Can be used multiple times for multiple devices.
3401 vga= [BOOT,X86-32] Select a particular video mode
3402 See Documentation/x86/boot.txt and
3403 Documentation/svga.txt.
3404 Use vga=ask for menu.
3405 This is actually a boot loader parameter; the value is
3406 passed to the kernel using a special protocol.
3408 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3409 size of <nn>. This can be used to increase the
3410 minimum size (128MB on x86). It can also be used to
3411 decrease the size and leave more room for directly
3414 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3417 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3420 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3424 Controls the behavior of vsyscalls (i.e. calls to
3425 fixed addresses of 0xffffffffff600x00 from legacy
3426 code). Most statically-linked binaries and older
3427 versions of glibc use these calls. Because these
3428 functions are at fixed addresses, they make nice
3429 targets for exploits that can control RIP.
3431 emulate [default] Vsyscalls turn into traps and are
3432 emulated reasonably safely.
3434 native Vsyscalls are native syscall instructions.
3435 This is a little bit faster than trapping
3436 and makes a few dynamic recompilers work
3437 better than they would in emulation mode.
3438 It also makes exploits much easier to write.
3440 none Vsyscalls don't work at all. This makes
3441 them quite hard to use for exploits but
3442 might break your system.
3444 vt.color= [VT] Default text color.
3445 Format: 0xYX, X = foreground, Y = background.
3446 Default: 0x07 = light gray on black.
3448 vt.cur_default= [VT] Default cursor shape.
3449 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3450 the parameters of the <Esc>[?A;B;Cc escape sequence;
3451 see VGA-softcursor.txt. Default: 2 = underline.
3453 vt.default_blu= [VT]
3454 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3455 Change the default blue palette of the console.
3456 This is a 16-member array composed of values
3459 vt.default_grn= [VT]
3460 Format: <green0>,<green1>,<green2>,...,<green15>
3461 Change the default green palette of the console.
3462 This is a 16-member array composed of values
3465 vt.default_red= [VT]
3466 Format: <red0>,<red1>,<red2>,...,<red15>
3467 Change the default red palette of the console.
3468 This is a 16-member array composed of values
3474 Set system-wide default UTF-8 mode for all tty's.
3475 Default is 1, i.e. UTF-8 mode is enabled for all
3476 newly opened terminals.
3478 vt.global_cursor_default=
3481 Set system-wide default for whether a cursor
3482 is shown on new VTs. Default is -1,
3483 i.e. cursors will be created by default unless
3484 overridden by individual drivers. 0 will hide
3485 cursors, 1 will display them.
3487 vt.italic= [VT] Default color for italic text; 0-15.
3490 vt.underline= [VT] Default color for underlined text; 0-15.
3493 watchdog timers [HW,WDT] For information on watchdog timers,
3494 see Documentation/watchdog/watchdog-parameters.txt
3495 or other driver-specific files in the
3496 Documentation/watchdog/ directory.
3498 workqueue.disable_numa
3499 By default, all work items queued to unbound
3500 workqueues are affine to the NUMA nodes they're
3501 issued on, which results in better behavior in
3502 general. If NUMA affinity needs to be disabled for
3503 whatever reason, this option can be used. Note
3504 that this also can be controlled per-workqueue for
3505 workqueues visible under /sys/bus/workqueue/.
3507 workqueue.power_efficient
3508 Per-cpu workqueues are generally preferred because
3509 they show better performance thanks to cache
3510 locality; unfortunately, per-cpu workqueues tend to
3511 be more power hungry than unbound workqueues.
3513 Enabling this makes the per-cpu workqueues which
3514 were observed to contribute significantly to power
3515 consumption unbound, leading to measurably lower
3516 power usage at the cost of small performance
3519 The default value of this parameter is determined by
3520 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3522 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3523 default x2apic cluster mode on platforms
3526 x86_intel_mid_timer= [X86-32,APBT]
3527 Choose timer option for x86 Intel MID platform.
3528 Two valid options are apbt timer only and lapic timer
3529 plus one apbt timer for broadcast timer.
3530 x86_intel_mid_timer=apbt_only | lapic_and_apbt
3532 xen_emul_unplug= [HW,X86,XEN]
3533 Unplug Xen emulated devices
3534 Format: [unplug0,][unplug1]
3535 ide-disks -- unplug primary master IDE devices
3536 aux-ide-disks -- unplug non-primary-master IDE devices
3537 nics -- unplug network devices
3538 all -- unplug all emulated devices (NICs and IDE disks)
3539 unnecessary -- unplugging emulated devices is
3540 unnecessary even if the host did not respond to
3542 never -- do not unplug even if version check succeeds
3544 xen_nopvspin [X86,XEN]
3545 Disables the ticketlock slowpath using Xen PV
3548 xirc2ps_cs= [NET,PCMCIA]
3550 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3552 ______________________________________________________________________
3556 Add more DRM drivers.
projects / linux-2.6-block.git / blob