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 -- only one string
239 acpi_osi="!string2" # remove built-in string2
240 acpi_osi= # disable all strings
243 Override the pmtimer bug detection: force the kernel
244 to assume that this machine's pmtimer latches its value
245 and always returns good values.
247 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
248 Format: { level | edge | high | low }
250 acpi_serialize [HW,ACPI] force serialization of AML methods
252 acpi_skip_timer_override [HW,ACPI]
253 Recognize and ignore IRQ0/pin2 Interrupt Override.
254 For broken nForce2 BIOS resulting in XT-PIC timer.
256 acpi_sleep= [HW,ACPI] Sleep options
257 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
258 old_ordering, nonvs, sci_force_enable }
259 See Documentation/power/video.txt for information on
261 s3_beep is for debugging; it makes the PC's speaker beep
262 as soon as the kernel's real-mode entry point is called.
263 s4_nohwsig prevents ACPI hardware signature from being
264 used during resume from hibernation.
265 old_ordering causes the ACPI 1.0 ordering of the _PTS
266 control method, with respect to putting devices into
267 low power states, to be enforced (the ACPI 2.0 ordering
268 of _PTS is used by default).
269 nonvs prevents the kernel from saving/restoring the
270 ACPI NVS memory during suspend/hibernation and resume.
271 sci_force_enable causes the kernel to set SCI_EN directly
272 on resume from S1/S3 (which is against the ACPI spec,
273 but some broken systems don't work without it).
275 acpi_use_timer_override [HW,ACPI]
276 Use timer override. For some broken Nvidia NF5 boards
277 that require a timer override, but don't have HPET
279 acpi_enforce_resources= [ACPI]
280 { strict | lax | no }
281 Check for resource conflicts between native drivers
282 and ACPI OperationRegions (SystemIO and SystemMemory
283 only). IO ports and memory declared in ACPI might be
284 used by the ACPI subsystem in arbitrary AML code and
285 can interfere with legacy drivers.
286 strict (default): access to resources claimed by ACPI
287 is denied; legacy drivers trying to access reserved
288 resources will fail to bind to device using them.
289 lax: access to resources claimed by ACPI is allowed;
290 legacy drivers trying to access reserved resources
291 will bind successfully but a warning message is logged.
292 no: ACPI OperationRegions are not marked as reserved,
293 no further checks are performed.
295 add_efi_memmap [EFI; X86] Include EFI memory map in
296 kernel's map of available physical RAM.
299 { off | try_unsupported }
300 off: disable AGP support
301 try_unsupported: try to drive unsupported chipsets
302 (may crash computer or cause data corruption)
305 See Documentation/sound/alsa/alsa-parameters.txt
308 Allow the default userspace alignment fault handler
309 behaviour to be specified. Bit 0 enables warnings,
310 bit 1 enables fixups, and bit 2 sends a segfault.
312 align_va_addr= [X86-64]
313 Align virtual addresses by clearing slice [14:12] when
314 allocating a VMA at process creation time. This option
315 gives you up to 3% performance improvement on AMD F15h
316 machines (where it is enabled by default) for a
317 CPU-intensive style benchmark, and it can vary highly in
318 a microbenchmark depending on workload and compiler.
320 32: only for 32-bit processes
321 64: only for 64-bit processes
322 on: enable for both 32- and 64-bit processes
323 off: disable for both 32- and 64-bit processes
325 alloc_snapshot [FTRACE]
326 Allocate the ftrace snapshot buffer on boot up when the
327 main buffer is allocated. This is handy if debugging
328 and you need to use tracing_snapshot() on boot up, and
329 do not want to use tracing_snapshot_alloc() as it needs
330 to be done where GFP_KERNEL allocations are allowed.
332 amd_iommu= [HW,X86-64]
333 Pass parameters to the AMD IOMMU driver in the system.
335 fullflush - enable flushing of IO/TLB entries when
336 they are unmapped. Otherwise they are
337 flushed before they will be reused, which
339 off - do not initialize any AMD IOMMU found in
341 force_isolation - Force device isolation for all
342 devices. The IOMMU driver is not
343 allowed anymore to lift isolation
344 requirements as needed. This option
345 does not override iommu=pt
347 amd_iommu_dump= [HW,X86-64]
348 Enable AMD IOMMU driver option to dump the ACPI table
349 for AMD IOMMU. With this option enabled, AMD IOMMU
350 driver will print ACPI tables for AMD IOMMU during
351 IOMMU initialization.
353 amijoy.map= [HW,JOY] Amiga joystick support
354 Map of devices attached to JOY0DAT and JOY1DAT
356 See also Documentation/input/joystick.txt
358 analog.map= [HW,JOY] Analog joystick and gamepad support
359 Specifies type or capabilities of an analog joystick
360 connected to one of 16 gameports
361 Format: <type1>,<type2>,..<type16>
364 Power management functions (SPARCstation-4/5 + deriv.)
366 Disable APC CPU standby support. SPARCstation-Fox does
367 not play well with APC CPU idle - disable it if you have
368 APC and your system crashes randomly.
370 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
371 Change the output verbosity whilst booting
372 Format: { quiet (default) | verbose | debug }
373 Change the amount of debugging information output
374 when initialising the APIC and IO-APIC components.
377 See Documentation/networking/ipv6.txt.
379 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
380 Limit apic dumping. The parameter defines the maximal
381 number of local apics being dumped. Also it is possible
382 to set it to "all" by meaning -- no limit here.
383 Format: { 1 (default) | 2 | ... | all }.
384 The parameter valid if only apic=debug or
385 apic=verbose is specified.
386 Example: apic=debug show_lapic=all
388 apm= [APM] Advanced Power Management
389 See header of arch/x86/kernel/apm_32.c.
391 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
392 Format: <io>,<irq>,<nodeID>
396 atarimouse= [HW,MOUSE] Atari Mouse
398 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
399 EzKey and similar keyboards
401 atkbd.reset= [HW] Reset keyboard during initialization
403 atkbd.set= [HW] Select keyboard code set
404 Format: <int> (2 = AT (default), 3 = PS/2)
406 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
409 atkbd.softraw= [HW] Choose between synthetic and real raw mode
410 Format: <bool> (0 = real, 1 = synthetic (default))
412 atkbd.softrepeat= [HW]
413 Use software keyboard repeat
415 baycom_epp= [HW,AX25]
418 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
420 See header of drivers/net/hamradio/baycom_par.c.
422 baycom_ser_fdx= [HW,AX25]
423 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
424 Format: <io>,<irq>,<mode>[,<baud>]
425 See header of drivers/net/hamradio/baycom_ser_fdx.c.
427 baycom_ser_hdx= [HW,AX25]
428 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
429 Format: <io>,<irq>,<mode>
430 See header of drivers/net/hamradio/baycom_ser_hdx.c.
432 boot_delay= Milliseconds to delay each printk during boot.
433 Values larger than 10 seconds (10000) are changed to
437 bootmem_debug [KNL] Enable bootmem allocator debug messages.
439 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
440 bttv.radio= Most important insmod options are available as
442 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
445 bulk_remove=off [PPC] This parameter disables the use of the pSeries
446 firmware feature for flushing multiple hpte entries
449 c101= [NET] Moxa C101 synchronous serial card
451 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
452 Sometimes CPU hardware bugs make them report the cache
453 size incorrectly. The kernel will attempt work arounds
454 to fix known problems, but for some CPUs it is not
455 possible to determine what the correct size should be.
456 This option provides an override for these situations.
458 ccw_timeout_log [S390]
459 See Documentation/s390/CommonIO for details.
461 cgroup_disable= [KNL] Disable a particular controller
462 Format: {name of the controller(s) to disable}
463 {Currently supported controllers - "memory"}
465 checkreqprot [SELINUX] Set initial checkreqprot flag value.
466 Format: { "0" | "1" }
467 See security/selinux/Kconfig help text.
468 0 -- check protection applied by kernel (includes
469 any implied execute protection).
470 1 -- check protection requested by application.
471 Default value is set via a kernel config option.
472 Value can be changed at runtime via
473 /selinux/checkreqprot.
476 See Documentation/s390/CommonIO for details.
479 Keep all clocks already enabled by bootloader on,
480 even if no driver has claimed them. This is useful
481 for debug and development, but should not be
482 needed on a platform with proper driver support.
483 For more information, see Documentation/clk.txt.
485 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
487 Forces specified clocksource (if available) to be used
488 when calculating gettimeofday(). If specified
489 clocksource is not available, it defaults to PIT.
490 Format: { pit | tsc | cyclone | pmtmr }
492 clocksource= Override the default clocksource
494 Override the default clocksource and use the clocksource
495 with the name specified.
496 Some clocksource names to choose from, depending on
498 [all] jiffies (this is the base, fallback clocksource)
500 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
501 pxa_timer,timer3,32k_counter,timer0_1
503 [X86-32] pit,hpet,tsc;
504 scx200_hrt on Geode; cyclone on IBM x440
512 clearcpuid=BITNUM [X86]
513 Disable CPUID feature X for the kernel. See
514 arch/x86/include/asm/cpufeature.h for the valid bit
515 numbers. Note the Linux specific bits are not necessarily
516 stable over kernel options, but the vendor specific
518 Also note that user programs calling CPUID directly
519 or using the feature without checking anything
520 will still see it. This just prevents it from
521 being used by the kernel or shown in /proc/cpuinfo.
522 Also note the kernel might malfunction if you disable
526 Sets the size of kernel global memory area for contiguous
527 memory allocations. For more information, see
528 include/linux/dma-contiguous.h
530 cmo_free_hint= [PPC] Format: { yes | no }
531 Specify whether pages are marked as being inactive
532 when they are freed. This is used in CMO environments
533 to determine OS memory pressure for page stealing by
537 coherent_pool=nn[KMG] [ARM,KNL]
538 Sets the size of memory pool for coherent, atomic dma
539 allocations, by default set to 256K.
541 code_bytes [X86] How many bytes of object code to print
546 com20020= [HW,NET] ARCnet - COM20020 chipset
548 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
550 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
554 ARCnet - COM90xx chipset (memory-mapped buffers)
555 Format: <io>[,<irq>[,<memstart>]]
557 condev= [HW,S390] console device
560 console= [KNL] Output console device and options.
562 tty<n> Use the virtual console device <n>.
566 Use the specified serial port. The options are of
567 the form "bbbbpnf", where "bbbb" is the baud rate,
568 "p" is parity ("n", "o", or "e"), "n" is number of
569 bits, and "f" is flow control ("r" for RTS or
570 omit it). Default is "9600n8".
572 See Documentation/serial-console.txt for more
574 Documentation/networking/netconsole.txt for an
577 uart[8250],io,<addr>[,options]
578 uart[8250],mmio,<addr>[,options]
579 Start an early, polled-mode console on the 8250/16550
580 UART at the specified I/O port or MMIO address,
581 switching to the matching ttyS device later. The
582 options are the same as for ttyS, above.
583 hvc<n> Use the hypervisor console device <n>. This is for
584 both Xen and PowerPC hypervisors.
586 If the device connected to the port is not a TTY but a braille
587 device, prepend "brl," before the device type, for instance
589 For now, only VisioBraille is supported.
591 consoleblank= [KNL] The console blank (screen saver) timeout in
592 seconds. Defaults to 10*60 = 10mins. A value of 0
593 disables the blank timer.
596 [KNL] Change the default value for
597 /proc/<pid>/coredump_filter.
598 See also Documentation/filesystems/proc.txt.
600 cpuidle.off=1 [CPU_IDLE]
601 disable the cpuidle sub-system
603 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
605 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
607 crashkernel=size[KMG][@offset[KMG]]
608 [KNL] Using kexec, Linux can switch to a 'crash kernel'
609 upon panic. This parameter reserves the physical
610 memory region [offset, offset + size] for that kernel
611 image. If '@offset' is omitted, then a suitable offset
612 is selected automatically. Check
613 Documentation/kdump/kdump.txt for further details.
615 crashkernel=range1:size1[,range2:size2,...][@offset]
616 [KNL] Same as above, but depends on the memory
617 in the running system. The syntax of range is
618 start-[end] where start and end are both
619 a memory unit (amount[KMG]). See also
620 Documentation/kdump/kdump.txt for an example.
622 crashkernel=size[KMG],high
623 [KNL, x86_64] range could be above 4G. Allow kernel
624 to allocate physical memory region from top, so could
625 be above 4G if system have more than 4G ram installed.
626 Otherwise memory region will be allocated below 4G, if
628 It will be ignored if crashkernel=X is specified.
629 crashkernel=size[KMG],low
630 [KNL, x86_64] range under 4G. When crashkernel=X,high
631 is passed, kernel could allocate physical memory region
632 above 4G, that cause second kernel crash on system
633 that require some amount of low memory, e.g. swiotlb
634 requires at least 64M+32K low memory. Kernel would
635 try to allocate 72M below 4G automatically.
636 This one let user to specify own low range under 4G
637 for second kernel instead.
638 0: to disable low allocation.
639 It will be ignored when crashkernel=X,high is not used
640 or memory reserved is below 4G.
645 cs89x0_media= [HW,NET]
646 Format: { rj45 | aui | bnc }
649 See header of drivers/s390/block/dasd_devmap.c.
651 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
652 (one device per port)
653 Format: <port#>,<type>
654 See also Documentation/input/joystick-parport.txt
656 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
657 time. See Documentation/dynamic-debug-howto.txt for
658 details. Deprecated, see dyndbg.
660 debug [KNL] Enable kernel debugging (events log level).
663 [KNL] verbose self-tests
665 Print debugging info while doing the locking API
667 We default to 0 (no extra messages), setting it to
668 1 will print _a lot_ more information - normally
669 only useful to kernel developers.
671 debug_objects [KNL] Enable object debugging
674 [KNL] Disable object debugging
676 debug_guardpage_minorder=
677 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
678 parameter allows control of the order of pages that will
679 be intentionally kept free (and hence protected) by the
680 buddy allocator. Bigger value increase the probability
681 of catching random memory corruption, but reduce the
682 amount of memory for normal system use. The maximum
683 possible value is MAX_ORDER/2. Setting this parameter
684 to 1 or 2 should be enough to identify most random
685 memory corruption problems caused by bugs in kernel or
686 driver code when a CPU writes to (or reads from) a
687 random memory location. Note that there exists a class
688 of memory corruptions problems caused by buggy H/W or
689 F/W or by drivers badly programing DMA (basically when
690 memory is written at bus level and the CPU MMU is
691 bypassed) which are not detectable by
692 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
693 tracking down these problems.
695 debugpat [X86] Enable PAT debugging
697 decnet.addr= [HW,NET]
698 Format: <area>[,<node>]
699 See also Documentation/networking/decnet.txt.
702 [same as hugepagesz=] The size of the default
703 HugeTLB page size. This is the size represented by
704 the legacy /proc/ hugepages APIs, used for SHM, and
705 default size when mounting hugetlbfs filesystems.
706 Defaults to the default architecture's huge page size
710 Set number of hash buckets for dentry cache.
713 IO parameters + enable/disable command.
715 digiepca= [HW,SERIAL]
716 See drivers/char/README.epca and
717 Documentation/serial/digiepca.txt.
720 See Documentation/networking/ipv6.txt.
722 disable_ddw [PPC/PSERIES]
723 Disable Dynamic DMA Window support. Use this if
724 to workaround buggy firmware.
727 See Documentation/networking/ipv6.txt.
729 disable_mtrr_cleanup [X86]
730 The kernel tries to adjust MTRR layout from continuous
731 to discrete, to make X server driver able to add WB
732 entry later. This parameter disables that.
734 disable_mtrr_trim [X86, Intel and AMD only]
735 By default the kernel will trim any uncacheable
736 memory out of your available memory pool based on
737 MTRR settings. This parameter disables that behavior,
738 possibly causing your machine to run very slowly.
740 disable_timer_pin_1 [X86]
741 Disable PIN 1 of APIC timer
742 Can be useful to work around chipset bugs.
744 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
745 this option disables the debugging code at boot.
747 dma_debug_entries=<number>
748 This option allows to tune the number of preallocated
749 entries for DMA-API debugging code. One entry is
750 required per DMA-API allocation. Use this if the
751 DMA-API debugging code disables itself because the
752 architectural default is too low.
754 dma_debug_driver=<driver_name>
755 With this option the DMA-API debugging driver
756 filter feature can be enabled at boot time. Just
757 pass the driver to filter for as the parameter.
758 The filter can be disabled or changed to another
759 driver later using sysfs.
761 drm_kms_helper.edid_firmware=[<connector>:]<file>
762 Broken monitors, graphic adapters and KVMs may
763 send no or incorrect EDID data sets. This parameter
764 allows to specify an EDID data set in the
765 /lib/firmware directory that is used instead.
766 Generic built-in EDID data sets are used, if one of
767 edid/1024x768.bin, edid/1280x1024.bin,
768 edid/1680x1050.bin, or edid/1920x1080.bin is given
769 and no file with the same name exists. Details and
770 instructions how to build your own EDID data are
771 available in Documentation/EDID/HOWTO.txt. An EDID
772 data set will only be used for a particular connector,
773 if its name and a colon are prepended to the EDID
778 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
779 module.dyndbg[="val"]
780 Enable debug messages at boot time. See
781 Documentation/dynamic-debug-howto.txt for details.
783 earlycon= [KNL] Output early console device and options.
784 uart[8250],io,<addr>[,options]
785 uart[8250],mmio,<addr>[,options]
786 uart[8250],mmio32,<addr>[,options]
787 Start an early, polled-mode console on the 8250/16550
788 UART at the specified I/O port or MMIO address.
789 MMIO inter-register address stride is either 8-bit
790 (mmio) or 32-bit (mmio32).
791 The options are the same as for ttyS, above.
793 earlyprintk= [X86,SH,BLACKFIN,ARM]
796 earlyprintk=serial[,ttySn[,baudrate]]
797 earlyprintk=serial[,0x...[,baudrate]]
798 earlyprintk=ttySn[,baudrate]
799 earlyprintk=dbgp[debugController#]
801 earlyprintk is useful when the kernel crashes before
802 the normal console is initialized. It is not enabled by
803 default because it has some cosmetic problems.
805 Append ",keep" to not disable it when the real console
808 Only vga or serial or usb debug port at a time.
810 Currently only ttyS0 and ttyS1 may be specified by
811 name. Other I/O ports may be explicitly specified
812 on some architectures (x86 and arm at least) by
813 replacing ttySn with an I/O port address, like this:
814 earlyprintk=serial,0x1008,115200
815 You can find the port for a given device in
816 /proc/tty/driver/serial:
817 2: uart:ST16650V2 port:00001008 irq:18 ...
819 Interaction with the standard serial driver is not
822 The VGA output is eventually overwritten by the real
825 The xen output can only be used by Xen PV guests.
827 ekgdboc= [X86,KGDB] Allow early kernel console debugging
830 This is designed to be used in conjunction with
831 the boot argument: earlyprintk=vga
834 Format: {"off" | "on" | "skip[mbr]"}
836 efi_no_storage_paranoia [EFI; X86]
837 Using this parameter you can use more than 50% of
838 your efi variable storage. Use this parameter only if
839 you are really sure that your UEFI does sane gc and
840 fulfills the spec otherwise your board may brick.
842 eisa_irq_edge= [PARISC,HW]
843 See header of drivers/parisc/eisa.c.
846 See comment before function elanfreq_setup() in
847 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
850 Format: {"cfq" | "deadline" | "noop"}
851 See Documentation/block/cfq-iosched.txt and
852 Documentation/block/deadline-iosched.txt for details.
854 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
855 Specifies physical address of start of kernel core
856 image elf header and optionally the size. Generally
857 kexec loader will pass this option to capture kernel.
858 See Documentation/kdump/kdump.txt for details.
860 enable_mtrr_cleanup [X86]
861 The kernel tries to adjust MTRR layout from continuous
862 to discrete, to make X server driver able to add WB
863 entry later. This parameter enables that.
865 enable_timer_pin_1 [X86]
866 Enable PIN 1 of APIC timer
867 Can be useful to work around chipset bugs
868 (in particular on some ATI chipsets).
869 The kernel tries to set a reasonable default.
871 enforcing [SELINUX] Set initial enforcing status.
873 See security/selinux/Kconfig help text.
874 0 -- permissive (log only, no denials).
875 1 -- enforcing (deny and log).
877 Value can be changed at runtime via /selinux/enforce.
880 Disable Error Record Serialization Table (ERST)
883 ether= [HW,NET] Ethernet cards parameters
884 This option is obsoleted by the "netdev=" option, which
885 has equivalent usage. See its documentation for details.
889 Permit 'security.evm' to be updated regardless of
890 current integrity status.
894 fail_make_request=[KNL]
895 General fault injection mechanism.
896 Format: <interval>,<probability>,<space>,<times>
897 See also Documentation/fault-injection/.
900 [ARM] Commands, delimited by semicolon, that will be
901 executed on FIQ debugger popup
904 See Documentation/blockdev/floppy.txt.
906 force_pal_cache_flush
907 [IA-64] Avoid check_sal_cache_flush which may hang on
908 buggy SAL_CACHE_FLUSH implementations. Using this
909 parameter will force ia64_sal_cache_flush to call
910 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
913 [FTRACE] will set and start the specified tracer
914 as early as possible in order to facilitate early
917 ftrace_dump_on_oops[=orig_cpu]
918 [FTRACE] will dump the trace buffers on oops.
919 If no parameter is passed, ftrace will dump
920 buffers of all CPUs, but if you pass orig_cpu, it will
921 dump only the buffer of the CPU that triggered the
924 ftrace_filter=[function-list]
925 [FTRACE] Limit the functions traced by the function
926 tracer at boot up. function-list is a comma separated
927 list of functions. This list can be changed at run
928 time by the set_ftrace_filter file in the debugfs
931 ftrace_notrace=[function-list]
932 [FTRACE] Do not trace the functions specified in
933 function-list. This list can be changed at run time
934 by the set_ftrace_notrace file in the debugfs
937 ftrace_graph_filter=[function-list]
938 [FTRACE] Limit the top level callers functions traced
939 by the function graph tracer at boot up.
940 function-list is a comma separated list of functions
941 that can be changed at run time by the
942 set_graph_function file in the debugfs tracing directory.
945 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
946 support via parallel port (up to 5 devices per port)
947 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
948 See also Documentation/input/joystick-parport.txt
952 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
956 gcov_persist= [GCOV] When non-zero (default), profiling data for
957 kernel modules is saved and remains accessible via
958 debugfs, even when the module is unloaded/reloaded.
959 When zero, profiling data is discarded and associated
960 debugfs files are removed at module unload time.
962 gpt [EFI] Forces disk with valid GPT signature but
963 invalid Protective MBR to be treated as GPT.
965 grcan.enable0= [HW] Configuration of physical interface 0. Determines
966 the "Enable 0" bit of the configuration register.
969 grcan.enable1= [HW] Configuration of physical interface 1. Determines
970 the "Enable 0" bit of the configuration register.
973 grcan.select= [HW] Select which physical interface to use.
976 grcan.txsize= [HW] Sets the size of the tx buffer.
977 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
979 grcan.rxsize= [HW] Sets the size of the rx buffer.
980 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
983 hashdist= [KNL,NUMA] Large hashes allocated during boot
984 are distributed across NUMA nodes. Defaults on
985 for 64-bit NUMA, off otherwise.
986 Format: 0 | 1 (for off | on)
988 hcl= [IA-64] SGI's Hardware Graph compatibility layer
990 hd= [EIDE] (E)IDE hard drive subsystem geometry
991 Format: <cyl>,<head>,<sect>
994 Disable Hardware Error Source Table (HEST) support;
995 corresponding firmware-first mode error processing
996 logic will be disabled.
998 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
999 size of <nn>. This works even on boxes that have no
1000 highmem otherwise. This also works to reduce highmem
1001 size on bigger boxes.
1003 highres= [KNL] Enable/disable high resolution timer mode.
1004 Valid parameters: "on", "off"
1008 See Documentation/isdn/README.HiSax.
1012 hpet= [X86-32,HPET] option to control HPET usage
1013 Format: { enable (default) | disable | force |
1015 disable: disable HPET and use PIT instead
1016 force: allow force enabled of undocumented chips (ICH4,
1018 verbose: show contents of HPET registers during setup
1020 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1021 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1022 On x86-64 and powerpc, this option can be specified
1023 multiple times interleaved with hugepages= to reserve
1024 huge pages of different sizes. Valid pages sizes on
1025 x86-64 are 2M (when the CPU supports "pse") and 1G
1026 (when the CPU supports the "pdpe1gb" cpuinfo flag)
1027 Note that 1GB pages can only be allocated at boot time
1028 using hugepages= and not freed afterwards.
1030 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1031 terminal devices. Valid values: 0..8
1032 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1033 If specified, z/VM IUCV HVC accepts connections
1034 from listed z/VM user IDs only.
1036 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1037 hardware thread id mappings.
1038 Format: <cpu>:<hwthread>
1041 Do not unregister boot console at start. This is only
1042 useful for debugging when something happens in the window
1043 between unregistering the boot console and initializing
1046 i2c_bus= [HW] Override the default board specific I2C bus speed
1047 or register an additional I2C bus that is not
1048 registered from board initialization code.
1052 i8042.debug [HW] Toggle i8042 debug mode
1053 i8042.direct [HW] Put keyboard port into non-translated mode
1054 i8042.dumbkbd [HW] Pretend that controller can only read data from
1055 keyboard and cannot control its state
1056 (Don't attempt to blink the leds)
1057 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1058 i8042.nokbd [HW] Don't check/create keyboard port
1059 i8042.noloop [HW] Disable the AUX Loopback command while probing
1061 i8042.nomux [HW] Don't check presence of an active multiplexing
1063 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1065 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1066 i8042.reset [HW] Reset the controller during init and cleanup
1067 i8042.unlock [HW] Unlock (ignore) the keylock
1068 i8042.kbdreset [HW] Reset device connected to KBD port
1072 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1073 indicates that the driver is running on unsupported
1075 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1076 does not match list of supported models.
1078 [HW] Report power status in /proc/i8k
1079 (disabled by default)
1080 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1083 i915.invert_brightness=
1084 [DRM] Invert the sense of the variable that is used to
1085 set the brightness of the panel backlight. Normally a
1086 brightness value of 0 indicates backlight switched off,
1087 and the maximum of the brightness value sets the backlight
1088 to maximum brightness. If this parameter is set to 0
1089 (default) and the machine requires it, or this parameter
1090 is set to 1, a brightness value of 0 sets the backlight
1091 to maximum brightness, and the maximum of the brightness
1092 value switches the backlight off.
1093 -1 -- never invert brightness
1094 0 -- machine default
1095 1 -- force brightness inversion
1098 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1100 ide-core.nodma= [HW] (E)IDE subsystem
1101 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1102 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1103 .cdrom .chs .ignore_cable are additional options
1104 See Documentation/ide/ide.txt.
1106 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1107 Claim all unknown PCI IDE storage controllers.
1110 Format: idle=poll, idle=halt, idle=nomwait
1111 Poll forces a polling idle loop that can slightly
1112 improve the performance of waking up a idle CPU, but
1113 will use a lot of power and make the system run hot.
1115 idle=halt: Halt is forced to be used for CPU idle.
1116 In such case C2/C3 won't be used again.
1117 idle=nomwait: Disable mwait for CPU C-states
1119 ignore_loglevel [KNL]
1120 Ignore loglevel setting - this will print /all/
1121 kernel messages to the console. Useful for debugging.
1122 We also add it as printk module parameter, so users
1123 could change it dynamically, usually by
1124 /sys/module/printk/parameters/ignore_loglevel.
1126 ihash_entries= [KNL]
1127 Set number of hash buckets for inode cache.
1129 ima_appraise= [IMA] appraise integrity measurements
1130 Format: { "off" | "enforce" | "fix" }
1133 ima_appraise_tcb [IMA]
1134 The builtin appraise policy appraises all files
1138 Format: { "0" | "1" }
1139 0 -- integrity auditing messages. (Default)
1140 1 -- enable informational integrity auditing messages.
1143 Format: { "sha1" | "md5" }
1147 Load a policy which meets the needs of the Trusted
1148 Computing Base. This means IMA will measure all
1149 programs exec'd, files mmap'd for exec, and all files
1150 opened for read by uid=0.
1154 Run specified binary instead of /sbin/init as init
1157 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1158 for working out where the kernel is dying during
1161 initrd= [BOOT] Specify the location of the initial ramdisk
1163 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1166 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1168 Enable intel iommu driver.
1170 Disable intel iommu driver.
1171 igfx_off [Default Off]
1172 By default, gfx is mapped as normal device. If a gfx
1173 device has a dedicated DMAR unit, the DMAR unit is
1174 bypassed by not enabling DMAR with this option. In
1175 this case, gfx device will use physical address for
1178 With this option iommu will not optimize to look
1179 for io virtual address below 32-bit forcing dual
1180 address cycle on pci bus for cards supporting greater
1181 than 32-bit addressing. The default is to look
1182 for translation below 32-bit and if not available
1183 then look in the higher range.
1184 strict [Default Off]
1185 With this option on every unmap_single operation will
1186 result in a hardware IOTLB flush operation as opposed
1187 to batching them for performance.
1188 sp_off [Default Off]
1189 By default, super page will be supported if Intel IOMMU
1190 has the capability. With this option, super page will
1193 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1194 0 disables intel_idle and fall back on acpi_idle.
1195 1 to 6 specify maximum depth of C-state.
1199 Do not enable intel_pstate as the default
1200 scaling driver for the supported processors
1202 intremap= [X86-64, Intel-IOMMU]
1203 on enable Interrupt Remapping (default)
1204 off disable Interrupt Remapping
1205 nosid disable Source ID checking
1207 BIOS x2APIC opt-out request will be ignored
1209 iomem= Disable strict checking of access to MMIO memory
1210 strict regions from userspace.
1227 io7= [HW] IO7 for Marvel based alpha systems
1228 See comment before marvel_specify_io7 in
1229 arch/alpha/kernel/core_marvel.c.
1231 io_delay= [X86] I/O delay method
1233 Standard port 0x80 based delay
1235 Alternate port 0xed based delay (needed on some systems)
1237 Simple two microseconds delay
1242 See Documentation/filesystems/nfs/nfsroot.txt.
1244 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1245 See comment before ip2_setup() in
1246 drivers/char/ip2/ip2base.c.
1249 When an interrupt is not handled search all handlers
1250 for it. Intended to get systems with badly broken
1254 When an interrupt is not handled search all handlers
1255 for it. Also check all handlers each timer
1256 interrupt. Intended to get systems with badly broken
1260 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1262 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1264 <cpu number>,...,<cpu number>
1266 <cpu number>-<cpu number>
1267 (must be a positive range in ascending order)
1269 <cpu number>,...,<cpu number>-<cpu number>
1271 This option can be used to specify one or more CPUs
1272 to isolate from the general SMP balancing and scheduling
1273 algorithms. You can move a process onto or off an
1274 "isolated" CPU via the CPU affinity syscalls or cpuset.
1275 <cpu number> begins at 0 and the maximum value is
1276 "number of CPUs in system - 1".
1278 This option is the preferred way to isolate CPUs. The
1279 alternative -- manually setting the CPU mask of all
1280 tasks in the system -- can cause problems and
1281 suboptimal load balancer performance.
1285 ivrs_ioapic [HW,X86_64]
1286 Provide an override to the IOAPIC-ID<->DEVICE-ID
1287 mapping provided in the IVRS ACPI table. For
1288 example, to map IOAPIC-ID decimal 10 to
1289 PCI device 00:14.0 write the parameter as:
1290 ivrs_ioapic[10]=00:14.0
1292 ivrs_hpet [HW,X86_64]
1293 Provide an override to the HPET-ID<->DEVICE-ID
1294 mapping provided in the IVRS ACPI table. For
1295 example, to map HPET-ID decimal 0 to
1296 PCI device 00:14.0 write the parameter as:
1297 ivrs_hpet[0]=00:14.0
1299 js= [HW,JOY] Analog joystick
1300 See Documentation/input/joystick.txt.
1304 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1305 specifies the amount of memory usable by the kernel
1306 for non-movable allocations. The requested amount is
1307 spread evenly throughout all nodes in the system. The
1308 remaining memory in each node is used for Movable
1309 pages. In the event, a node is too small to have both
1310 kernelcore and Movable pages, kernelcore pages will
1311 take priority and other nodes will have a larger number
1312 of kernelcore pages. The Movable zone is used for the
1313 allocation of pages that may be reclaimed or moved
1314 by the page migration subsystem. This means that
1315 HugeTLB pages may not be allocated from this zone.
1316 Note that allocations like PTEs-from-HighMem still
1317 use the HighMem zone if it exists, and the Normal
1318 zone if it does not.
1320 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1321 Format: <Controller#>[,poll interval]
1322 The controller # is the number of the ehci usb debug
1323 port as it is probed via PCI. The poll interval is
1324 optional and is the number seconds in between
1325 each poll cycle to the debug port in case you need
1326 the functionality for interrupting the kernel with
1327 gdb or control-c on the dbgp connection. When
1328 not using this parameter you use sysrq-g to break into
1329 the kernel debugger.
1331 kgdboc= [KGDB,HW] kgdb over consoles.
1332 Requires a tty driver that supports console polling,
1333 or a supported polling keyboard driver (non-usb).
1334 Serial only format: <serial_device>[,baud]
1335 keyboard only format: kbd
1336 keyboard and serial format: kbd,<serial_device>[,baud]
1337 Optional Kernel mode setting:
1338 kms, kbd format: kms,kbd
1339 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1341 kgdbwait [KGDB] Stop kernel execution and enter the
1342 kernel debugger at the earliest opportunity.
1344 kmac= [MIPS] korina ethernet MAC address.
1345 Configure the RouterBoard 532 series on-chip
1346 Ethernet adapter MAC address.
1348 kmemleak= [KNL] Boot-time kmemleak enable/disable
1349 Valid arguments: on, off
1352 kstack=N [X86] Print N words from the kernel stack
1355 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1356 Default is 0 (don't ignore, but inject #GP)
1358 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1362 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1363 Default is 1 (enabled)
1365 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1367 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1369 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1370 (virtualized MMU) support on capable Intel chips.
1371 Default is 1 (enabled)
1373 kvm-intel.emulate_invalid_guest_state=
1374 [KVM,Intel] Enable emulation of invalid guest states
1375 Default is 0 (disabled)
1377 kvm-intel.flexpriority=
1378 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1379 Default is 1 (enabled)
1382 [KVM,Intel] Enable VMX nesting (nVMX).
1383 Default is 0 (disabled)
1385 kvm-intel.unrestricted_guest=
1386 [KVM,Intel] Disable unrestricted guest feature
1387 (virtualized real and unpaged mode) on capable
1388 Intel chips. Default is 1 (enabled)
1390 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1391 feature (tagged TLBs) on capable Intel chips.
1392 Default is 1 (enabled)
1398 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1401 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1402 value for LAPIC timer one-shot implementation. Default
1403 back to the programmable timer unit in the LAPIC.
1405 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1408 libata.dma= [LIBATA] DMA control
1409 libata.dma=0 Disable all PATA and SATA DMA
1410 libata.dma=1 PATA and SATA Disk DMA only
1411 libata.dma=2 ATAPI (CDROM) DMA only
1412 libata.dma=4 Compact Flash DMA only
1413 Combinations also work, so libata.dma=3 enables DMA
1414 for disks and CDROMs, but not CFs.
1416 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1417 libata.ignore_hpa=0 keep BIOS limits (default)
1418 libata.ignore_hpa=1 ignore limits, using full disk
1420 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1424 libata.force= [LIBATA] Force configurations. The format is comma
1425 separated list of "[ID:]VAL" where ID is
1426 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1427 matching port, link or device. Basically, it matches
1428 the ATA ID string printed on console by libata. If
1429 the whole ID part is omitted, the last PORT and DEVICE
1430 values are used. If ID hasn't been specified yet, the
1431 configuration applies to all ports, links and devices.
1433 If only DEVICE is omitted, the parameter applies to
1434 the port and all links and devices behind it. DEVICE
1435 number of 0 either selects the first device or the
1436 first fan-out link behind PMP device. It does not
1437 select the host link. DEVICE number of 15 selects the
1438 host link and device attached to it.
1440 The VAL specifies the configuration to force. As long
1441 as there's no ambiguity shortcut notation is allowed.
1442 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1443 The following configurations can be forced.
1445 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1446 Any ID with matching PORT is used.
1448 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1450 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1451 udma[/][16,25,33,44,66,100,133] notation is also
1454 * [no]ncq: Turn on or off NCQ.
1456 * nohrst, nosrst, norst: suppress hard, soft
1459 * rstonce: only attempt one reset during
1460 hot-unplug link recovery
1462 * dump_id: dump IDENTIFY data.
1464 * atapi_dmadir: Enable ATAPI DMADIR bridge support
1466 * disable: Disable this device.
1468 If there are multiple matching configurations changing
1469 the same attribute, the last one is used.
1471 memblock=debug [KNL] Enable memblock debug messages.
1473 load_ramdisk= [RAM] List of ramdisks to load from floppy
1474 See Documentation/blockdev/ramdisk.txt.
1476 lockd.nlm_grace_period=P [NFS] Assign grace period.
1479 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1482 lockd.nlm_timeout=T [NFS] Assign timeout value.
1485 lockd.nlm_udpport=M [NFS] Assign UDP port.
1488 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1491 loglevel= All Kernel Messages with a loglevel smaller than the
1492 console loglevel will be printed to the console. It can
1493 also be changed with klogd or other programs. The
1494 loglevels are defined as follows:
1496 0 (KERN_EMERG) system is unusable
1497 1 (KERN_ALERT) action must be taken immediately
1498 2 (KERN_CRIT) critical conditions
1499 3 (KERN_ERR) error conditions
1500 4 (KERN_WARNING) warning conditions
1501 5 (KERN_NOTICE) normal but significant condition
1502 6 (KERN_INFO) informational
1503 7 (KERN_DEBUG) debug-level messages
1505 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1506 in bytes. n must be a power of two. The default
1507 size is set in the kernel config file.
1509 logo.nologo [FB] Disables display of the built-in Linux logo.
1510 This may be used to provide more screen space for
1511 kernel log messages and is useful when debugging
1512 kernel boot problems.
1514 lp=0 [LP] Specify parallel ports to use, e.g,
1515 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1516 lp=reset first parallel port). 'lp=0' disables the
1517 lp=auto printer driver. 'lp=reset' (which can be
1518 specified in addition to the ports) causes
1519 attached printers to be reset. Using
1520 lp=port1,port2,... specifies the parallel ports
1521 to associate lp devices with, starting with
1522 lp0. A port specification may be 'none' to skip
1523 that lp device, or a parport name such as
1524 'parport0'. Specifying 'lp=auto' instead of a
1525 port specification list means that device IDs
1526 from each port should be examined, to see if
1527 an IEEE 1284-compliant printer is attached; if
1528 so, the driver will manage that printer.
1529 See also header of drivers/char/lp.c.
1532 Sets loops_per_jiffy to given constant, thus avoiding
1533 time-consuming boot-time autodetection (up to 250 ms per
1534 CPU). 0 enables autodetection (default). To determine
1535 the correct value for your kernel, boot with normal
1536 autodetection and see what value is printed. Note that
1537 on SMP systems the preset will be applied to all CPUs,
1538 which is likely to cause problems if your CPUs need
1539 significantly divergent settings. An incorrect value
1540 will cause delays in the kernel to be wrong, leading to
1541 unpredictable I/O errors and other breakage. Although
1542 unlikely, in the extreme case this might damage your
1546 Format: <io>,<irq>,<dma>
1548 machvec= [IA-64] Force the use of a particular machine-vector
1549 (machvec) in a generic kernel.
1550 Example: machvec=hpzx1_swiotlb
1552 machtype= [Loongson] Share the same kernel image file between different
1554 Example: machtype=lemote-yeeloong-2f-7inch
1556 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1557 than or equal to this physical address is ignored.
1559 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1560 should make use of. maxcpus=n : n >= 0 limits the
1561 kernel to using 'n' processors. n=0 is a special case,
1562 it is equivalent to "nosmp", which also disables
1565 max_loop= [LOOP] The number of loop block devices that get
1566 (loop.max_loop) unconditionally pre-created at init time. The default
1567 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1568 of statically allocating a predefined number, loop
1569 devices can be requested on-demand with the
1570 /dev/loop-control interface.
1572 mce [X86-32] Machine Check Exception
1574 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1576 md= [HW] RAID subsystems devices and level
1577 See Documentation/md.txt.
1580 Format: <first>,<last>
1581 Specifies range of consoles to be captured by the MDA.
1583 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1584 Amount of memory to be used when the kernel is not able
1585 to see the whole system memory or for test.
1586 [X86] Work as limiting max address. Use together
1587 with memmap= to avoid physical address space collisions.
1588 Without memmap= PCI devices could be placed at addresses
1589 belonging to unused RAM.
1591 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1595 [KNL,SH] Allow user to override the default size for
1596 per-device physically contiguous DMA buffers.
1598 memmap=exactmap [KNL,X86] Enable setting of an exact
1599 E820 memory map, as specified by the user.
1600 Such memmap=exactmap lines can be constructed based on
1601 BIOS output or other requirements. See the memmap=nn@ss
1604 memmap=nn[KMG]@ss[KMG]
1605 [KNL] Force usage of a specific region of memory
1606 Region of memory to be used, from ss to ss+nn.
1608 memmap=nn[KMG]#ss[KMG]
1609 [KNL,ACPI] Mark specific memory as ACPI data.
1610 Region of memory to be used, from ss to ss+nn.
1612 memmap=nn[KMG]$ss[KMG]
1613 [KNL,ACPI] Mark specific memory as reserved.
1614 Region of memory to be used, from ss to ss+nn.
1615 Example: Exclude memory from 0x18690000-0x1869ffff
1616 memmap=64K$0x18690000
1618 memmap=0x10000$0x18690000
1620 memory_corruption_check=0/1 [X86]
1621 Some BIOSes seem to corrupt the first 64k of
1622 memory when doing things like suspend/resume.
1623 Setting this option will scan the memory
1624 looking for corruption. Enabling this will
1625 both detect corruption and prevent the kernel
1626 from using the memory being corrupted.
1627 However, its intended as a diagnostic tool; if
1628 repeatable BIOS-originated corruption always
1629 affects the same memory, you can use memmap=
1630 to prevent the kernel from using that memory.
1632 memory_corruption_check_size=size [X86]
1633 By default it checks for corruption in the low
1634 64k, making this memory unavailable for normal
1635 use. Use this parameter to scan for
1636 corruption in more or less memory.
1638 memory_corruption_check_period=seconds [X86]
1639 By default it checks for corruption every 60
1640 seconds. Use this parameter to check at some
1641 other rate. 0 disables periodic checking.
1643 memtest= [KNL,X86] Enable memtest
1645 default : 0 <disable>
1646 Specifies the number of memtest passes to be
1647 performed. Each pass selects another test
1648 pattern from a given set of patterns. Memtest
1649 fills the memory with this pattern, validates
1650 memory contents and reserves bad memory
1651 regions that are detected.
1653 meye.*= [HW] Set MotionEye Camera parameters
1654 See Documentation/video4linux/meye.txt.
1656 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1657 Multi-Function General Purpose Timers on AMD Geode
1660 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1661 the BIOS has incorrectly applied a workaround. TinyBIOS
1662 version 0.98 is known to be affected, 0.99 fixes the
1663 problem by letting the user disable the workaround.
1667 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1668 physical address is ignored.
1670 mini2440= [ARM,HW,KNL]
1671 Format:[0..2][b][c][t]
1673 MINI2440 configuration specification:
1674 0 - The attached screen is the 3.5" TFT
1675 1 - The attached screen is the 7" TFT
1676 2 - The VGA Shield is attached (1024x768)
1677 Leaving out the screen size parameter will not load
1678 the TFT driver, and the framebuffer will be left
1680 b - Enable backlight. The TFT backlight pin will be
1681 linked to the kernel VESA blanking code and a GPIO
1682 LED. This parameter is not necessary when using the
1684 c - Enable the s3c camera interface.
1685 t - Reserved for enabling touchscreen support. The
1686 touchscreen support is not enabled in the mainstream
1687 kernel as of 2.6.30, a preliminary port can be found
1688 in the "bleeding edge" mini2440 support kernel at
1689 http://repo.or.cz/w/linux-2.6/mini2440.git
1692 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1693 parameter allows control of the logging verbosity for
1694 the additional memory initialisation checks. A value
1695 of 0 disables mminit logging and a level of 4 will
1696 log everything. Information is printed at KERN_DEBUG
1697 so loglevel=8 may also need to be specified.
1700 [KNL] When CONFIG_MODULE_SIG is set, this means that
1701 modules without (valid) signatures will fail to load.
1702 Note that if CONFIG_MODULE_SIG_FORCE is set, that
1703 is always true, so this option does nothing.
1706 [MOUSE] Maximum time between finger touching and
1707 leaving touchpad surface for touch to be considered
1708 a tap and be reported as a left button click (for
1709 touchpads working in absolute mode only).
1711 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1712 reporting absolute coordinates, such as tablets
1713 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1714 reporting absolute coordinates, such as tablets
1716 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1717 is similar to kernelcore except it specifies the
1718 amount of memory used for migratable allocations.
1719 If both kernelcore and movablecore is specified,
1720 then kernelcore will be at *least* the specified
1721 value but may be more. If movablecore on its own
1722 is specified, the administrator must be careful
1723 that the amount of memory usable for all allocations
1726 MTD_Partition= [MTD]
1727 Format: <name>,<region-number>,<size>,<offset>
1729 MTD_Region= [MTD] Format:
1730 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1733 See drivers/mtd/cmdlinepart.c.
1735 multitce=off [PPC] This parameter disables the use of the pSeries
1736 firmware feature for updating multiple TCE entries
1739 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1741 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1743 boundary - index of last SLC block on Flex-OneNAND.
1744 The remaining blocks are configured as MLC blocks.
1745 lock - Configure if Flex-OneNAND boundary should be locked.
1746 Once locked, the boundary cannot be changed.
1747 1 indicates lock status, 0 indicates unlock status.
1750 ARM/S3C2412 JIVE boot control
1752 See arch/arm/mach-s3c2412/mach-jive.c
1754 mtouchusb.raw_coordinates=
1755 [HW] Make the MicroTouch USB driver use raw coordinates
1756 ('y', default) or cooked coordinates ('n')
1758 mtrr_chunk_size=nn[KMG] [X86]
1759 used for mtrr cleanup. It is largest continuous chunk
1760 that could hold holes aka. UC entries.
1762 mtrr_gran_size=nn[KMG] [X86]
1763 Used for mtrr cleanup. It is granularity of mtrr block.
1765 Large value could prevent small alignment from
1768 mtrr_spare_reg_nr=n [X86]
1770 Range: 0,7 : spare reg number
1772 Used for mtrr cleanup. It is spare mtrr entries number.
1773 Set to 2 or more if your graphical card needs more.
1775 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1777 netdev= [NET] Network devices parameters
1778 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1779 Note that mem_start is often overloaded to mean
1780 something different and driver-specific.
1781 This usage is only documented in each driver source
1785 [NETFILTER] Enable connection tracking flow accounting
1786 0 to disable accounting
1787 1 to enable accounting
1790 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1791 See Documentation/filesystems/nfs/nfsroot.txt.
1793 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1794 See Documentation/filesystems/nfs/nfsroot.txt.
1796 nfsrootdebug [NFS] enable nfsroot debugging messages.
1797 See Documentation/filesystems/nfs/nfsroot.txt.
1799 nfs.callback_tcpport=
1800 [NFS] set the TCP port on which the NFSv4 callback
1801 channel should listen.
1804 [NFS] sets the pathname to the program which is used
1805 to update the NFS client cache entries.
1807 nfs.cache_getent_timeout=
1808 [NFS] sets the timeout after which an attempt to
1809 update a cache entry is deemed to have failed.
1811 nfs.idmap_cache_timeout=
1812 [NFS] set the maximum lifetime for idmapper cache
1816 [NFS] enable 64-bit inode numbers.
1817 If zero, the NFS client will fake up a 32-bit inode
1818 number for the readdir() and stat() syscalls instead
1819 of returning the full 64-bit number.
1820 The default is to return 64-bit inode numbers.
1822 nfs.max_session_slots=
1823 [NFSv4.1] Sets the maximum number of session slots
1824 the client will attempt to negotiate with the server.
1825 This limits the number of simultaneous RPC requests
1826 that the client can send to the NFSv4.1 server.
1827 Note that there is little point in setting this
1828 value higher than the max_tcp_slot_table_limit.
1830 nfs.nfs4_disable_idmapping=
1831 [NFSv4] When set to the default of '1', this option
1832 ensures that both the RPC level authentication
1833 scheme and the NFS level operations agree to use
1834 numeric uids/gids if the mount is using the
1835 'sec=sys' security flavour. In effect it is
1836 disabling idmapping, which can make migration from
1837 legacy NFSv2/v3 systems to NFSv4 easier.
1838 Servers that do not support this mode of operation
1839 will be autodetected by the client, and it will fall
1840 back to using the idmapper.
1841 To turn off this behaviour, set the value to '0'.
1843 [NFS4] Specify an additional fixed unique ident-
1844 ification string that NFSv4 clients can insert into
1845 their nfs_client_id4 string. This is typically a
1846 UUID that is generated at system install time.
1848 nfs.send_implementation_id =
1849 [NFSv4.1] Send client implementation identification
1850 information in exchange_id requests.
1851 If zero, no implementation identification information
1853 The default is to send the implementation identification
1856 nfsd.nfs4_disable_idmapping=
1857 [NFSv4] When set to the default of '1', the NFSv4
1858 server will return only numeric uids and gids to
1859 clients using auth_sys, and will accept numeric uids
1860 and gids from such clients. This is intended to ease
1861 migration from NFSv2/v3.
1863 objlayoutdriver.osd_login_prog=
1864 [NFS] [OBJLAYOUT] sets the pathname to the program which
1865 is used to automatically discover and login into new
1866 osd-targets. Please see:
1867 Documentation/filesystems/pnfs.txt for more explanations
1869 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1870 when a NMI is triggered.
1871 Format: [state][,regs][,debounce][,die]
1873 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1874 Format: [panic,][nopanic,][num]
1876 0 - turn nmi_watchdog off
1877 When panic is specified, panic when an NMI watchdog
1878 timeout occurs (or 'nopanic' to override the opposite
1880 This is useful when you use a panic=... timeout and
1881 need the box quickly up again.
1883 netpoll.carrier_timeout=
1884 [NET] Specifies amount of time (in seconds) that
1885 netpoll should wait for a carrier. By default netpoll
1888 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1889 emulation library even if a 387 maths coprocessor
1893 [HW] Never suspend the console
1894 Disable suspending of consoles during suspend and
1895 hibernate operations. Once disabled, debugging
1896 messages can reach various consoles while the rest
1897 of the system is being put to sleep (ie, while
1898 debugging driver suspend/resume hooks). This may
1899 not work reliably with all consoles, but is known
1900 to work with serial and VGA consoles.
1901 To facilitate more flexible debugging, we also add
1902 console_suspend, a printk module parameter to control
1903 it. Users could use console_suspend (usually
1904 /sys/module/printk/parameters/console_suspend) to
1905 turn on/off it dynamically.
1907 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1908 caches in the slab allocator. Saves per-node memory,
1909 but will impact performance.
1913 noapic [SMP,APIC] Tells the kernel to not make use of any
1914 IOAPICs that may be present in the system.
1916 noautogroup Disable scheduler automatic task group creation.
1918 nobats [PPC] Do not use BATs for mapping kernel lowmem
1919 on "Classic" PPC cores.
1923 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1925 nodelayacct [KNL] Disable per-task delay accounting
1927 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1929 nodsp [SH] Disable hardware DSP at boot time.
1931 noefi [X86] Disable EFI runtime services support.
1936 On X86-32 available only on PAE configured kernels.
1937 noexec=on: enable non-executable mappings (default)
1938 noexec=off: disable non-executable mappings
1941 Disable SMAP (Supervisor Mode Access Prevention)
1942 even if it is supported by processor.
1945 Disable SMEP (Supervisor Mode Execution Prevention)
1946 even if it is supported by processor.
1949 This affects only 32-bit executables.
1950 noexec32=on: enable non-executable mappings (default)
1951 read doesn't imply executable mappings
1952 noexec32=off: disable non-executable mappings
1953 read implies executable mappings
1955 nofpu [SH] Disable hardware FPU at boot time.
1957 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1958 register save and restore. The kernel will only save
1959 legacy floating-point registers on task switch.
1961 noxsave [BUGS=X86] Disables x86 extended register state save
1962 and restore using xsave. The kernel will fallback to
1963 enabling legacy floating-point and sse state.
1966 on enable eager fpu restore
1967 off disable eager fpu restore
1968 auto selects the default scheme, which automatically
1969 enables eagerfpu restore for xsaveopt.
1971 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1972 wfi(ARM) instruction doesn't work correctly and not to
1973 use it. This is also useful when using JTAG debugger.
1975 no_file_caps Tells the kernel not to honor file capabilities. The
1976 only way then for a file to be executed with privilege
1977 is to be setuid root or executed by root.
1979 nohalt [IA-64] Tells the kernel not to use the power saving
1980 function PAL_HALT_LIGHT when idle. This increases
1981 power-consumption. On the positive side, it reduces
1982 interrupt wake-up latency, which may improve performance
1983 in certain environments such as networked servers or
1986 nohz= [KNL] Boottime enable/disable dynamic ticks
1987 Valid arguments: on, off
1990 nohz_full= [KNL,BOOT]
1991 In kernels built with CONFIG_NO_HZ_FULL=y, set
1992 the specified list of CPUs whose tick will be stopped
1993 whenever possible. The boot CPU will be forced outside
1994 the range to maintain the timekeeping.
1995 The CPUs in this range must also be included in the
1998 noiotrap [SH] Disables trapped I/O port accesses.
2000 noirqdebug [X86-32] Disables the code which attempts to detect and
2001 disable unhandled interrupt sources.
2003 no_timer_check [X86,APIC] Disables the code which tests for
2004 broken timer IRQ sources.
2006 noisapnp [ISAPNP] Disables ISA PnP code.
2008 noinitrd [RAM] Tells the kernel not to load any configured
2011 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
2013 [Deprecated - use intremap=off]
2017 nojitter [IA-64] Disables jitter checking for ITC timers.
2019 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
2021 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
2024 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
2025 steal time is computed, but won't influence scheduler
2028 nolapic [X86-32,APIC] Do not enable or use the local APIC.
2030 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
2032 noltlbs [PPC] Do not use large page/tlb entries for kernel
2033 lowmem mapping on PPC40x.
2035 nomca [IA-64] Disable machine check abort handling
2037 nomce [X86-32] Machine Check Exception
2039 nomfgpt [X86-32] Disable Multi-Function General Purpose
2040 Timer usage (for AMD Geode machines).
2042 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
2043 shutdown the other cpus. Instead use the REBOOT_VECTOR
2046 nomodule Disable module load
2048 nopat [X86] Disable PAT (page attribute table extension of
2049 pagetables) support.
2051 norandmaps Don't use address space randomization. Equivalent to
2052 echo 0 > /proc/sys/kernel/randomize_va_space
2054 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
2056 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
2057 with UP alternatives
2059 nordrand [X86] Disable the direct use of the RDRAND
2060 instruction even if it is supported by the
2061 processor. RDRAND is still available to user
2064 noresume [SWSUSP] Disables resume and restores original swap
2067 no-scroll [VGA] Disables scrollback.
2068 This is required for the Braillex ib80-piezo Braille
2069 reader made by F.H. Papenmeier (Germany).
2073 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2075 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2076 and disable the IO APIC. legacy for "maxcpus=0".
2078 nosoftlockup [KNL] Disable the soft-lockup detector.
2080 nosync [HW,M68K] Disables sync negotiation for all devices.
2082 notsc [BUGS=X86-32] Disable Time Stamp Counter
2084 nousb [USB] Disable the USB subsystem
2086 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2090 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2092 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2093 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2094 Some features depend on CPU0. Known dependencies are:
2095 1. Resume from suspend/hibernate depends on CPU0.
2096 Suspend/hibernate will fail if CPU0 is offline and you
2097 need to online CPU0 before suspend/hibernate.
2098 2. PIC interrupts also depend on CPU0. CPU0 can't be
2099 removed if a PIC interrupt is detected.
2100 It's said poweroff/reboot may depend on CPU0 on some
2101 machines although I haven't seen such issues so far
2102 after CPU0 is offline on a few tested machines.
2103 If the dependencies are under your control, you can
2104 turn on cpu0_hotplug.
2106 nptcg= [IA-64] Override max number of concurrent global TLB
2107 purges which is reported from either PAL_VM_SUMMARY or
2110 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2111 could support. nr_cpus=n : n >= 1 limits the kernel to
2112 supporting 'n' processors. Later in runtime you can not
2113 use hotplug cpu feature to put more cpu back to online.
2114 just like you compile the kernel NR_CPUS=n
2116 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2118 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2119 Allowed values are enable and disable
2121 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2122 one of ['zone', 'node', 'default'] can be specified
2123 This can be set from sysctl after boot.
2124 See Documentation/sysctl/vm.txt for details.
2126 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2127 See Documentation/debugging-via-ohci1394.txt for more
2130 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2131 Rather than timing out after 20 ms if an EC
2132 command is not properly ACKed, override the length
2133 of the timeout. We have interrupts disabled while
2134 waiting for the ACK, so if this is set too high
2135 interrupts *may* be lost!
2137 omap_mux= [OMAP] Override bootloader pin multiplexing.
2138 Format: <mux_mode0.mode_name=value>...
2139 For example, to override I2C bus2:
2140 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2142 oprofile.timer= [HW]
2143 Use timer interrupt instead of performance counters
2145 oprofile.cpu_type= Force an oprofile cpu type
2146 This might be useful if you have an older oprofile
2147 userland or if you want common events.
2148 Format: { arch_perfmon }
2149 arch_perfmon: [X86] Force use of architectural
2150 perfmon on Intel CPUs instead of the
2151 CPU specific event set.
2152 timer: [X86] Force use of architectural NMI
2153 timer mode (see also oprofile.timer
2154 for generic hr timer mode)
2155 [s390] Force legacy basic mode sampling
2156 (report cpu_type "timer")
2158 oops=panic Always panic on oopses. Default is to just kill the
2159 process, but there is a small probability of
2160 deadlocking the machine.
2161 This will also cause panics on machine check exceptions.
2162 Useful together with panic=30 to trigger a reboot.
2165 See Documentation/sound/oss/oss-parameters.txt
2167 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2168 timeout > 0: seconds before rebooting
2169 timeout = 0: wait forever
2170 timeout < 0: reboot immediately
2173 parkbd.port= [HW] Parallel port number the keyboard adapter is
2174 connected to, default is 0.
2176 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2177 0 for XT, 1 for AT (default is AT).
2180 parport= [HW,PPT] Specify parallel ports. 0 disables.
2181 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2182 Use 'auto' to force the driver to use any
2183 IRQ/DMA settings detected (the default is to
2184 ignore detected IRQ/DMA settings because of
2185 possible conflicts). You can specify the base
2186 address, IRQ, and DMA settings; IRQ and DMA
2187 should be numbers, or 'auto' (for using detected
2188 settings on that particular port), or 'nofifo'
2189 (to avoid using a FIFO even if it is detected).
2190 Parallel ports are assigned in the order they
2191 are specified on the command line, starting
2194 parport_init_mode= [HW,PPT]
2195 Configure VIA parallel port to operate in
2196 a specific mode. This is necessary on Pegasos
2197 computer where firmware has no options for setting
2198 up parallel port mode and sets it to spp.
2199 Currently this function knows 686a and 8231 chips.
2200 Format: [spp|ps2|epp|ecp|ecpepp]
2203 Halt all CPUs after the first oops has been printed for
2204 the specified number of seconds. This is to be used if
2205 your oopses keep scrolling off the screen.
2210 See header of drivers/block/paride/pcd.c.
2211 See also Documentation/blockdev/paride.txt.
2213 pci=option[,option...] [PCI] various PCI subsystem options:
2214 earlydump [X86] dump PCI config space before the kernel
2216 off [X86] don't probe for the PCI bus
2217 bios [X86-32] force use of PCI BIOS, don't access
2218 the hardware directly. Use this if your machine
2219 has a non-standard PCI host bridge.
2220 nobios [X86-32] disallow use of PCI BIOS, only direct
2221 hardware access methods are allowed. Use this
2222 if you experience crashes upon bootup and you
2223 suspect they are caused by the BIOS.
2224 conf1 [X86] Force use of PCI Configuration
2226 conf2 [X86] Force use of PCI Configuration
2228 noaer [PCIE] If the PCIEAER kernel config parameter is
2229 enabled, this kernel boot option can be used to
2230 disable the use of PCIE advanced error reporting.
2231 nodomains [PCI] Disable support for multiple PCI
2232 root domains (aka PCI segments, in ACPI-speak).
2233 nommconf [X86] Disable use of MMCONFIG for PCI
2235 check_enable_amd_mmconf [X86] check for and enable
2236 properly configured MMIO access to PCI
2237 config space on AMD family 10h CPU
2238 nomsi [MSI] If the PCI_MSI kernel config parameter is
2239 enabled, this kernel boot option can be used to
2240 disable the use of MSI interrupts system-wide.
2241 noioapicquirk [APIC] Disable all boot interrupt quirks.
2242 Safety option to keep boot IRQs enabled. This
2243 should never be necessary.
2244 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2245 primary IO-APIC for bridges that cannot disable
2246 boot IRQs. This fixes a source of spurious IRQs
2247 when the system masks IRQs.
2248 noioapicreroute [APIC] Disable workaround that uses the
2249 boot IRQ equivalent of an IRQ that connects to
2250 a chipset where boot IRQs cannot be disabled.
2251 The opposite of ioapicreroute.
2252 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2253 routing table. These calls are known to be buggy
2254 on several machines and they hang the machine
2255 when used, but on other computers it's the only
2256 way to get the interrupt routing table. Try
2257 this option if the kernel is unable to allocate
2258 IRQs or discover secondary PCI buses on your
2260 rom [X86] Assign address space to expansion ROMs.
2261 Use with caution as certain devices share
2262 address decoders between ROMs and other
2264 norom [X86] Do not assign address space to
2265 expansion ROMs that do not already have
2266 BIOS assigned address ranges.
2267 nobar [X86] Do not assign address space to the
2268 BARs that weren't assigned by the BIOS.
2269 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2270 assigned automatically to PCI devices. You can
2271 make the kernel exclude IRQs of your ISA cards
2273 pirqaddr=0xAAAAA [X86] Specify the physical address
2274 of the PIRQ table (normally generated
2275 by the BIOS) if it is outside the
2276 F0000h-100000h range.
2277 lastbus=N [X86] Scan all buses thru bus #N. Can be
2278 useful if the kernel is unable to find your
2279 secondary buses and you want to tell it
2280 explicitly which ones they are.
2281 assign-busses [X86] Always assign all PCI bus
2282 numbers ourselves, overriding
2283 whatever the firmware may have done.
2284 usepirqmask [X86] Honor the possible IRQ mask stored
2285 in the BIOS $PIR table. This is needed on
2286 some systems with broken BIOSes, notably
2287 some HP Pavilion N5400 and Omnibook XE3
2288 notebooks. This will have no effect if ACPI
2289 IRQ routing is enabled.
2290 noacpi [X86] Do not use ACPI for IRQ routing
2291 or for PCI scanning.
2292 use_crs [X86] Use PCI host bridge window information
2293 from ACPI. On BIOSes from 2008 or later, this
2294 is enabled by default. If you need to use this,
2295 please report a bug.
2296 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2297 If you need to use this, please report a bug.
2298 routeirq Do IRQ routing for all PCI devices.
2299 This is normally done in pci_enable_device(),
2300 so this option is a temporary workaround
2301 for broken drivers that don't call it.
2302 skip_isa_align [X86] do not align io start addr, so can
2303 handle more pci cards
2304 firmware [ARM] Do not re-enumerate the bus but instead
2305 just use the configuration from the
2306 bootloader. This is currently used on
2307 IXP2000 systems where the bus has to be
2308 configured a certain way for adjunct CPUs.
2309 noearly [X86] Don't do any early type 1 scanning.
2310 This might help on some broken boards which
2311 machine check when some devices' config space
2312 is read. But various workarounds are disabled
2313 and some IOMMU drivers will not work.
2314 bfsort Sort PCI devices into breadth-first order.
2315 This sorting is done to get a device
2316 order compatible with older (<= 2.4) kernels.
2317 nobfsort Don't sort PCI devices into breadth-first order.
2318 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2319 tuning and use the BIOS-configured MPS defaults.
2320 pcie_bus_safe Set every device's MPS to the largest value
2321 supported by all devices below the root complex.
2322 pcie_bus_perf Set device MPS to the largest allowable MPS
2323 based on its parent bus. Also set MRRS (Max
2324 Read Request Size) to the largest supported
2325 value (no larger than the MPS that the device
2326 or bus can support) for best performance.
2327 pcie_bus_peer2peer Set every device's MPS to 128B, which
2328 every device is guaranteed to support. This
2329 configuration allows peer-to-peer DMA between
2330 any pair of devices, possibly at the cost of
2331 reduced performance. This also guarantees
2332 that hot-added devices will work.
2333 cbiosize=nn[KMG] The fixed amount of bus space which is
2334 reserved for the CardBus bridge's IO window.
2335 The default value is 256 bytes.
2336 cbmemsize=nn[KMG] The fixed amount of bus space which is
2337 reserved for the CardBus bridge's memory
2338 window. The default value is 64 megabytes.
2341 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2342 Specifies alignment and device to reassign
2343 aligned memory resources.
2344 If <order of align> is not specified,
2345 PAGE_SIZE is used as alignment.
2346 PCI-PCI bridge can be specified, if resource
2347 windows need to be expanded.
2348 ecrc= Enable/disable PCIe ECRC (transaction layer
2349 end-to-end CRC checking).
2350 bios: Use BIOS/firmware settings. This is the
2354 hpiosize=nn[KMG] The fixed amount of bus space which is
2355 reserved for hotplug bridge's IO window.
2356 Default size is 256 bytes.
2357 hpmemsize=nn[KMG] The fixed amount of bus space which is
2358 reserved for hotplug bridge's memory window.
2359 Default size is 2 megabytes.
2360 realloc= Enable/disable reallocating PCI bridge resources
2361 if allocations done by BIOS are too small to
2362 accommodate resources required by all child
2364 off: Turn realloc off
2366 realloc same as realloc=on
2367 noari do not use PCIe ARI.
2368 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2369 only look for one device below a PCIe downstream
2372 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2375 force Enable ASPM even on devices that claim not to support it.
2376 WARNING: Forcing ASPM on may cause system lockups.
2378 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2379 nomsi Do not use MSI for PCI Express Native Hotplug (this
2380 makes all PCIe ports use INTx for hotplug services).
2382 pcie_ports= [PCIE] PCIe ports handling:
2383 auto Ask the BIOS whether or not to use native PCIe services
2384 associated with PCIe ports (PME, hot-plug, AER). Use
2385 them only if that is allowed by the BIOS.
2386 native Use native PCIe services associated with PCIe ports
2388 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2391 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2392 nomsi Do not use MSI for native PCIe PME signaling (this makes
2393 all PCIe root ports use INTx for all services).
2395 pcmv= [HW,PCMCIA] BadgePAD 4
2398 See Documentation/blockdev/paride.txt.
2400 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2403 See arch/parisc/kernel/pdc_chassis.c
2405 percpu_alloc= Select which percpu first chunk allocator to use.
2406 Currently supported values are "embed" and "page".
2407 Archs may support subset or none of the selections.
2408 See comments in mm/percpu.c for details on each
2409 allocator. This parameter is primarily for debugging
2410 and performance comparison.
2413 See Documentation/blockdev/paride.txt.
2416 See Documentation/blockdev/paride.txt.
2418 pirq= [SMP,APIC] Manual mp-table setup
2419 See Documentation/x86/i386/IO-APIC.txt.
2421 plip= [PPT,NET] Parallel port network link
2422 Format: { parport<nr> | timid | 0 }
2423 See also Documentation/parport.txt.
2425 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2426 Override pmtimer IOPort with a hex value.
2430 Enable PNP debug messages (depends on the
2431 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2432 via /sys/module/pnp/parameters/debug. We always show
2433 current resource usage; turning this on also shows
2434 possible settings and some assignment information.
2440 { on | off | curr | res | no-curr | no-res }
2443 [ISAPNP] Exclude IRQs for the autoconfiguration
2446 [ISAPNP] Exclude DMAs for the autoconfiguration
2448 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2449 Ranges are in pairs (I/O port base and size).
2452 [ISAPNP] Exclude memory regions for the
2454 Ranges are in pairs (memory base and size).
2456 ports= [IP_VS_FTP] IPVS ftp helper module
2458 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2460 Format: <port>,<port>....
2462 print-fatal-signals=
2463 [KNL] debug: print fatal signals
2465 If enabled, warn about various signal handling
2466 related application anomalies: too many signals,
2467 too many POSIX.1 timers, fatal signals causing a
2470 If you hit the warning due to signal overflow,
2471 you might want to try "ulimit -i unlimited".
2475 printk.always_kmsg_dump=
2476 Trigger kmsg_dump for cases other than kernel oops or
2478 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2481 printk.time= Show timing data prefixed to each printk message line
2482 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2484 processor.max_cstate= [HW,ACPI]
2485 Limit processor to maximum C-state
2486 max_cstate=9 overrides any DMI blacklist limit.
2488 processor.nocst [HW,ACPI]
2489 Ignore the _CST method to determine C-states,
2490 instead using the legacy FADT method
2492 profile= [KNL] Enable kernel profiling via /proc/profile
2493 Format: [schedule,]<number>
2494 Param: "schedule" - profile schedule points.
2495 Param: <number> - step/bucket size as a power of 2 for
2496 statistical time based profiling.
2497 Param: "sleep" - profile D-state sleeping (millisecs).
2498 Requires CONFIG_SCHEDSTATS
2499 Param: "kvm" - profile VM exits.
2501 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2503 See Documentation/blockdev/ramdisk.txt.
2505 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2506 probe for; one of (bare|imps|exps|lifebook|any).
2507 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2509 psmouse.resetafter= [HW,MOUSE]
2510 Try to reset the device after so many bad packets
2513 [HW,MOUSE] Set desired mouse resolution, in dpi.
2514 psmouse.smartscroll=
2515 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2516 0 = disabled, 1 = enabled (default).
2518 pstore.backend= Specify the name of the pstore backend to use
2521 See Documentation/blockdev/paride.txt.
2524 [KNL] Number of legacy pty's. Overwrites compiled-in
2527 quiet [KNL] Disable most log messages
2532 See Documentation/md.txt.
2534 ramdisk_blocksize= [RAM]
2535 See Documentation/blockdev/ramdisk.txt.
2537 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2538 See Documentation/blockdev/ramdisk.txt.
2540 rcu_nocbs= [KNL,BOOT]
2541 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2542 the specified list of CPUs to be no-callback CPUs.
2543 Invocation of these CPUs' RCU callbacks will
2544 be offloaded to "rcuox/N" kthreads created for
2545 that purpose, where "x" is "b" for RCU-bh, "p"
2546 for RCU-preempt, and "s" for RCU-sched, and "N"
2547 is the CPU number. This reduces OS jitter on the
2548 offloaded CPUs, which can be useful for HPC and
2550 real-time workloads. It can also improve energy
2551 efficiency for asymmetric multiprocessors.
2553 rcu_nocb_poll [KNL,BOOT]
2554 Rather than requiring that offloaded CPUs
2555 (specified by rcu_nocbs= above) explicitly
2556 awaken the corresponding "rcuoN" kthreads,
2557 make these kthreads poll for callbacks.
2558 This improves the real-time response for the
2559 offloaded CPUs by relieving them of the need to
2560 wake up the corresponding kthread, but degrades
2561 energy efficiency by requiring that the kthreads
2562 periodically wake up to do the polling.
2564 rcutree.blimit= [KNL,BOOT]
2565 Set maximum number of finished RCU callbacks to process
2568 rcutree.fanout_leaf= [KNL,BOOT]
2569 Increase the number of CPUs assigned to each
2570 leaf rcu_node structure. Useful for very large
2573 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2574 Set delay from grace-period initialization to
2575 first attempt to force quiescent states.
2576 Units are jiffies, minimum value is zero,
2577 and maximum value is HZ.
2579 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2580 Set delay between subsequent attempts to force
2581 quiescent states. Units are jiffies, minimum
2582 value is one, and maximum value is HZ.
2584 rcutree.qhimark= [KNL,BOOT]
2585 Set threshold of queued
2586 RCU callbacks over which batch limiting is disabled.
2588 rcutree.qlowmark= [KNL,BOOT]
2589 Set threshold of queued RCU callbacks below which
2590 batch limiting is re-enabled.
2592 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2593 Suppress RCU CPU stall warning messages.
2595 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2596 Set timeout for RCU CPU stall warning messages.
2598 rcutree.rcu_idle_gp_delay= [KNL,BOOT]
2599 Set wakeup interval for idle CPUs that have
2600 RCU callbacks (RCU_FAST_NO_HZ=y).
2602 rcutree.rcu_idle_lazy_gp_delay= [KNL,BOOT]
2603 Set wakeup interval for idle CPUs that have
2604 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2605 Lazy RCU callbacks are those which RCU can
2606 prove do nothing more than free memory.
2608 rcutorture.fqs_duration= [KNL,BOOT]
2609 Set duration of force_quiescent_state bursts.
2611 rcutorture.fqs_holdoff= [KNL,BOOT]
2612 Set holdoff time within force_quiescent_state bursts.
2614 rcutorture.fqs_stutter= [KNL,BOOT]
2615 Set wait time between force_quiescent_state bursts.
2617 rcutorture.irqreader= [KNL,BOOT]
2618 Test RCU readers from irq handlers.
2620 rcutorture.n_barrier_cbs= [KNL,BOOT]
2621 Set callbacks/threads for rcu_barrier() testing.
2623 rcutorture.nfakewriters= [KNL,BOOT]
2624 Set number of concurrent RCU writers. These just
2625 stress RCU, they don't participate in the actual
2626 test, hence the "fake".
2628 rcutorture.nreaders= [KNL,BOOT]
2629 Set number of RCU readers.
2631 rcutorture.onoff_holdoff= [KNL,BOOT]
2632 Set time (s) after boot for CPU-hotplug testing.
2634 rcutorture.onoff_interval= [KNL,BOOT]
2635 Set time (s) between CPU-hotplug operations, or
2636 zero to disable CPU-hotplug testing.
2638 rcutorture.shuffle_interval= [KNL,BOOT]
2639 Set task-shuffle interval (s). Shuffling tasks
2640 allows some CPUs to go into dyntick-idle mode
2641 during the rcutorture test.
2643 rcutorture.shutdown_secs= [KNL,BOOT]
2644 Set time (s) after boot system shutdown. This
2645 is useful for hands-off automated testing.
2647 rcutorture.stall_cpu= [KNL,BOOT]
2648 Duration of CPU stall (s) to test RCU CPU stall
2649 warnings, zero to disable.
2651 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2652 Time to wait (s) after boot before inducing stall.
2654 rcutorture.stat_interval= [KNL,BOOT]
2655 Time (s) between statistics printk()s.
2657 rcutorture.stutter= [KNL,BOOT]
2658 Time (s) to stutter testing, for example, specifying
2659 five seconds causes the test to run for five seconds,
2660 wait for five seconds, and so on. This tests RCU's
2661 ability to transition abruptly to and from idle.
2663 rcutorture.test_boost= [KNL,BOOT]
2664 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2665 "Maybe" means test if the RCU implementation
2666 under test support RCU priority boosting.
2668 rcutorture.test_boost_duration= [KNL,BOOT]
2669 Duration (s) of each individual boost test.
2671 rcutorture.test_boost_interval= [KNL,BOOT]
2672 Interval (s) between each boost test.
2674 rcutorture.test_no_idle_hz= [KNL,BOOT]
2675 Test RCU's dyntick-idle handling. See also the
2676 rcutorture.shuffle_interval parameter.
2678 rcutorture.torture_type= [KNL,BOOT]
2679 Specify the RCU implementation to test.
2681 rcutorture.verbose= [KNL,BOOT]
2682 Enable additional printk() statements.
2686 Run specified binary instead of /init from the ramdisk,
2687 used for early userspace startup. See initrd.
2690 Format (x86 or x86_64):
2691 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2693 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2695 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2696 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2697 reboot_force is either force or not specified,
2698 reboot_cpu is s[mp]#### with #### being the processor
2699 to be used for rebooting.
2702 [KNL, SMP] Set scheduler's default relax_domain_level.
2703 See Documentation/cgroups/cpusets.txt.
2705 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2707 reservetop= [X86-32]
2709 Reserves a hole at the top of the kernel virtual
2714 Set the amount of memory to reserve for BIOS at
2715 the bottom of the address space.
2717 reset_devices [KNL] Force drivers to reset the underlying device
2718 during initialization.
2721 Specify the partition device for software suspend
2723 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2725 resume_offset= [SWSUSP]
2726 Specify the offset from the beginning of the partition
2727 given by "resume=" at which the swap header is located,
2728 in <PAGE_SIZE> units (needed only for swap files).
2729 See Documentation/power/swsusp-and-swap-files.txt
2731 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2732 read the resume files
2734 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2735 Useful for devices that are detected asynchronously
2736 (e.g. USB and MMC devices).
2738 hibernate= [HIBERNATION]
2739 noresume Don't check if there's a hibernation image
2740 present during boot.
2741 nocompress Don't compress/decompress hibernation images.
2743 retain_initrd [RAM] Keep initrd memory after extraction
2745 rhash_entries= [KNL,NET]
2746 Set number of hash buckets for route cache
2748 riscom8= [HW,SERIAL]
2749 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2751 ro [KNL] Mount root device read-only on boot
2753 root= [KNL] Root filesystem
2754 See name_to_dev_t comment in init/do_mounts.c.
2756 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2757 mount the root filesystem
2759 rootflags= [KNL] Set root filesystem mount option string
2761 rootfstype= [KNL] Set root filesystem type
2763 rootwait [KNL] Wait (indefinitely) for root device to show up.
2764 Useful for devices that are detected asynchronously
2765 (e.g. USB and MMC devices).
2767 rproc_mem=nn[KMG][@address]
2768 [KNL,ARM,CMA] Remoteproc physical memory block.
2769 Memory area to be used by remote processor image,
2772 rw [KNL] Mount root device read-write on boot
2774 S [KNL] Run init in single mode
2777 See drivers/net/irda/sa1100_ir.c.
2779 sbni= [NET] Granch SBNI12 leased line adapter
2781 sched_debug [KNL] Enables verbose scheduler debug messages.
2783 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2784 xtime_lock contention on larger systems, and/or RCU lock
2785 contention on all systems with CONFIG_MAXSMP set.
2786 Format: { "0" | "1" }
2787 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2789 Note: increases power consumption, thus should only be
2790 enabled if running jitter sensitive (HPC/RT) workloads.
2792 security= [SECURITY] Choose a security module to enable at boot.
2793 If this boot parameter is not specified, only the first
2794 security module asking for security registration will be
2795 loaded. An invalid security module name will be treated
2796 as if no module has been chosen.
2798 selinux= [SELINUX] Disable or enable SELinux at boot time.
2799 Format: { "0" | "1" }
2800 See security/selinux/Kconfig help text.
2803 Default value is set via kernel config option.
2804 If enabled at boot time, /selinux/disable can be used
2805 later to disable prior to initial policy load.
2807 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2808 Format: { "0" | "1" }
2809 See security/apparmor/Kconfig help text
2812 Default value is set via kernel config option.
2814 serialnumber [BUGS=X86-32]
2817 Maximal number of shapers.
2819 show_msr= [x86] show boot-time MSR settings
2820 Format: { <integer> }
2821 Show boot-time (BIOS-initialized) MSR settings.
2822 The parameter means the number of CPUs to show,
2823 for example 1 means boot CPU only.
2830 slab_max_order= [MM, SLAB]
2831 Determines the maximum allowed order for slabs.
2832 A high setting may cause OOMs due to memory
2833 fragmentation. Defaults to 1 for systems with
2834 more than 32MB of RAM, 0 otherwise.
2836 slub_debug[=options[,slabs]] [MM, SLUB]
2837 Enabling slub_debug allows one to determine the
2838 culprit if slab objects become corrupted. Enabling
2839 slub_debug can create guard zones around objects and
2840 may poison objects when not in use. Also tracks the
2841 last alloc / free. For more information see
2842 Documentation/vm/slub.txt.
2844 slub_max_order= [MM, SLUB]
2845 Determines the maximum allowed order for slabs.
2846 A high setting may cause OOMs due to memory
2847 fragmentation. For more information see
2848 Documentation/vm/slub.txt.
2850 slub_min_objects= [MM, SLUB]
2851 The minimum number of objects per slab. SLUB will
2852 increase the slab order up to slub_max_order to
2853 generate a sufficiently large slab able to contain
2854 the number of objects indicated. The higher the number
2855 of objects the smaller the overhead of tracking slabs
2856 and the less frequently locks need to be acquired.
2857 For more information see Documentation/vm/slub.txt.
2859 slub_min_order= [MM, SLUB]
2860 Determines the minimum page order for slabs. Must be
2861 lower than slub_max_order.
2862 For more information see Documentation/vm/slub.txt.
2864 slub_nomerge [MM, SLUB]
2865 Disable merging of slabs with similar size. May be
2866 necessary if there is some reason to distinguish
2867 allocs to different slabs. Debug options disable
2868 merging on their own.
2869 For more information see Documentation/vm/slub.txt.
2872 Format: <io1>[,<io2>[,...,<io8>]]
2874 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2875 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2876 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2877 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2878 smsc-ircc2.ircc_irq= [HW] IRQ line
2879 smsc-ircc2.ircc_dma= [HW] DMA channel
2880 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2881 0: Toshiba Satellite 1800 (GP data pin select)
2882 1: Fast pin select (default)
2886 [KNL] Should the soft-lockup detector generate panics.
2889 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2890 See Documentation/laptops/sonypi.txt
2892 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2893 See Documentation/serial/specialix.txt.
2895 spia_io_base= [HW,MTD]
2901 Enabled the stack tracer on boot up.
2903 stacktrace_filter=[function-list]
2904 [FTRACE] Limit the functions that the stack tracer
2905 will trace at boot up. function-list is a comma separated
2906 list of functions. This list can be changed at run
2907 time by the stack_trace_filter file in the debugfs
2908 tracing directory. Note, this enables stack tracing
2909 and the stacktrace above is not needed.
2913 Set the STI (builtin display/keyboard on the HP-PARISC
2914 machines) console (graphic card) which should be used
2915 as the initial boot-console.
2916 See also comment in drivers/video/console/sticore.c.
2919 See comment in drivers/video/console/sticore.c.
2922 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2924 sunrpc.min_resvport=
2925 sunrpc.max_resvport=
2927 SunRPC servers often require that client requests
2928 originate from a privileged port (i.e. a port in the
2929 range 0 < portnr < 1024).
2930 An administrator who wishes to reserve some of these
2931 ports for other uses may adjust the range that the
2932 kernel's sunrpc client considers to be privileged
2933 using these two parameters to set the minimum and
2934 maximum port values.
2938 Control how the NFS server code allocates CPUs to
2939 service thread pools. Depending on how many NICs
2940 you have and where their interrupts are bound, this
2941 option will affect which CPUs will do NFS serving.
2942 Note: this parameter cannot be changed while the
2943 NFS server is running.
2945 auto the server chooses an appropriate mode
2946 automatically using heuristics
2947 global a single global pool contains all CPUs
2948 percpu one pool for each CPU
2949 pernode one pool for each NUMA node (equivalent
2950 to global on non-NUMA machines)
2952 sunrpc.tcp_slot_table_entries=
2953 sunrpc.udp_slot_table_entries=
2955 Sets the upper limit on the number of simultaneous
2956 RPC calls that can be sent from the client to a
2957 server. Increasing these values may allow you to
2958 improve throughput, but will also increase the
2959 amount of memory reserved for use by the client.
2962 [KNL] Enable accounting of swap in memory resource
2963 controller if no parameter or 1 is given or disable
2964 it if 0 is given (See Documentation/cgroups/memory.txt)
2966 swiotlb= [IA-64] Number of I/O TLB slabs
2970 sysfs.deprecated=0|1 [KNL]
2971 Enable/disable old style sysfs layout for old udev
2972 on older distributions. When this option is enabled
2973 very new udev will not work anymore. When this option
2974 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2975 in older udev will not work anymore.
2976 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2977 the kernel configuration.
2979 sysrq_always_enabled
2981 Ignore sysrq setting - this boot parameter will
2982 neutralize any effect of /proc/sys/kernel/sysrq.
2983 Useful for debugging.
2987 test_suspend= [SUSPEND]
2988 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2989 standby suspend) as the system sleep state to briefly
2990 enter during system startup. The system is woken from
2991 this state using a wakeup-capable RTC alarm.
2993 thash_entries= [KNL,NET]
2994 Set number of hash buckets for TCP connection
2996 thermal.act= [HW,ACPI]
2997 -1: disable all active trip points in all thermal zones
2998 <degrees C>: override all lowest active trip points
3000 thermal.crt= [HW,ACPI]
3001 -1: disable all critical trip points in all thermal zones
3002 <degrees C>: override all critical trip points
3004 thermal.nocrt= [HW,ACPI]
3005 Set to disable actions on ACPI thermal zone
3006 critical and hot trip points.
3008 thermal.off= [HW,ACPI]
3009 1: disable ACPI thermal control
3011 thermal.psv= [HW,ACPI]
3012 -1: disable all passive trip points
3013 <degrees C>: override all passive trip points to this
3016 thermal.tzp= [HW,ACPI]
3017 Specify global default ACPI thermal zone polling rate
3018 <deci-seconds>: poll all this frequency
3019 0: no polling (default)
3022 Force threading of all interrupt handlers except those
3023 marked explicitly IRQF_NO_THREAD.
3026 Enable the Transcendent memory driver if built-in.
3028 tmem.cleancache=0|1 [KNL, XEN]
3029 Default is on (1). Disable the usage of the cleancache
3030 API to send anonymous pages to the hypervisor.
3032 tmem.frontswap=0|1 [KNL, XEN]
3033 Default is on (1). Disable the usage of the frontswap
3034 API to send swap pages to the hypervisor. If disabled
3035 the selfballooning and selfshrinking are force disabled.
3037 tmem.selfballooning=0|1 [KNL, XEN]
3038 Default is on (1). Disable the driving of swap pages
3041 tmem.selfshrinking=0|1 [KNL, XEN]
3042 Default is on (1). Partial swapoff that immediately
3043 transfers pages from Xen hypervisor back to the
3044 kernel based on different criteria.
3048 Specify if the kernel should make use of the cpu
3049 topology information if the hardware supports this.
3050 The scheduler will make use of this information and
3051 e.g. base its process migration decisions on it.
3056 tpm_suspend_pcr=[HW,TPM]
3057 Format: integer pcr id
3058 Specify that at suspend time, the tpm driver
3059 should extend the specified pcr with zeros,
3060 as a workaround for some chips which fail to
3061 flush the last written pcr on TPM_SaveState.
3062 This will guarantee that all the other pcrs
3065 trace_buf_size=nn[KMG]
3066 [FTRACE] will set tracing buffer size.
3068 trace_event=[event-list]
3069 [FTRACE] Set and start specified trace events in order
3070 to facilitate early boot debugging.
3071 See also Documentation/trace/events.txt
3073 trace_options=[option-list]
3074 [FTRACE] Enable or disable tracer options at boot.
3075 The option-list is a comma delimited list of options
3076 that can be enabled or disabled just as if you were
3077 to echo the option name into
3079 /sys/kernel/debug/tracing/trace_options
3081 For example, to enable stacktrace option (to dump the
3082 stack trace of each event), add to the command line:
3084 trace_options=stacktrace
3086 See also Documentation/trace/ftrace.txt "trace options"
3089 transparent_hugepage=
3091 Format: [always|madvise|never]
3092 Can be used to control the default behavior of the system
3093 with respect to transparent hugepages.
3094 See Documentation/vm/transhuge.txt for more details.
3096 tsc= Disable clocksource stability checks for TSC.
3098 [x86] reliable: mark tsc clocksource as reliable, this
3099 disables clocksource verification at runtime, as well
3100 as the stability checks done at bootup. Used to enable
3101 high-resolution timer mode on older hardware, and in
3102 virtualized environment.
3103 [x86] noirqtime: Do not use TSC to do irq accounting.
3104 Used to run time disable IRQ_TIME_ACCOUNTING on any
3105 platforms where RDTSC is slow and this accounting
3108 turbografx.map[2|3]= [HW,JOY]
3109 TurboGraFX parallel port interface
3111 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3112 See also Documentation/input/joystick-parport.txt
3114 udbg-immortal [PPC] When debugging early kernel crashes that
3115 happen after console_init() and before a proper
3116 console driver takes over, this boot options might
3117 help "seeing" what's going on.
3119 uhash_entries= [KNL,NET]
3120 Set number of hash buckets for UDP/UDP-Lite connections
3123 [USB] Ignore overcurrent events (default N).
3124 Some badly-designed motherboards generate lots of
3125 bogus events, for ports that aren't wired to
3126 anything. Set this parameter to avoid log spamming.
3127 Note that genuine overcurrent events won't be
3131 [X86] Cause panic on unknown NMI.
3133 usbcore.authorized_default=
3134 [USB] Default USB device authorization:
3135 (default -1 = authorized except for wireless USB,
3136 0 = not authorized, 1 = authorized)
3138 usbcore.autosuspend=
3139 [USB] The autosuspend time delay (in seconds) used
3140 for newly-detected USB devices (default 2). This
3141 is the time required before an idle device will be
3142 autosuspended. Devices for which the delay is set
3143 to a negative value won't be autosuspended at all.
3145 usbcore.usbfs_snoop=
3146 [USB] Set to log all usbfs traffic (default 0 = off).
3148 usbcore.blinkenlights=
3149 [USB] Set to cycle leds on hubs (default 0 = off).
3151 usbcore.old_scheme_first=
3152 [USB] Start with the old device initialization
3153 scheme (default 0 = off).
3155 usbcore.usbfs_memory_mb=
3156 [USB] Memory limit (in MB) for buffers allocated by
3157 usbfs (default = 16, 0 = max = 2047).
3159 usbcore.use_both_schemes=
3160 [USB] Try the other device initialization scheme
3161 if the first one fails (default 1 = enabled).
3163 usbcore.initial_descriptor_timeout=
3164 [USB] Specifies timeout for the initial 64-byte
3165 USB_REQ_GET_DESCRIPTOR request in milliseconds
3166 (default 5000 = 5.0 seconds).
3169 [USBHID] The interval which mice are to be polled at.
3171 usb-storage.delay_use=
3172 [UMS] The delay in seconds before a new device is
3173 scanned for Logical Units (default 5).
3176 [UMS] A list of quirks entries to supplement or
3177 override the built-in unusual_devs list. List
3178 entries are separated by commas. Each entry has
3179 the form VID:PID:Flags where VID and PID are Vendor
3180 and Product ID values (4-digit hex numbers) and
3181 Flags is a set of characters, each corresponding
3182 to a common usb-storage quirk flag as follows:
3183 a = SANE_SENSE (collect more than 18 bytes
3185 b = BAD_SENSE (don't collect more than 18
3186 bytes of sense data);
3187 c = FIX_CAPACITY (decrease the reported
3188 device capacity by one sector);
3189 d = NO_READ_DISC_INFO (don't use
3190 READ_DISC_INFO command);
3191 e = NO_READ_CAPACITY_16 (don't use
3192 READ_CAPACITY_16 command);
3193 h = CAPACITY_HEURISTICS (decrease the
3194 reported device capacity by one
3195 sector if the number is odd);
3196 i = IGNORE_DEVICE (don't bind to this
3198 l = NOT_LOCKABLE (don't try to lock and
3199 unlock ejectable media);
3200 m = MAX_SECTORS_64 (don't transfer more
3201 than 64 sectors = 32 KB at a time);
3202 n = INITIAL_READ10 (force a retry of the
3203 initial READ(10) command);
3204 o = CAPACITY_OK (accept the capacity
3205 reported by the device);
3206 p = WRITE_CACHE (the device cache is ON
3208 r = IGNORE_RESIDUE (the device reports
3209 bogus residue values);
3210 s = SINGLE_LUN (the device has only one
3212 w = NO_WP_DETECT (don't test whether the
3213 medium is write-protected).
3214 Example: quirks=0419:aaf5:rl,0421:0433:rc
3216 user_debug= [KNL,ARM]
3218 See arch/arm/Kconfig.debug help text.
3219 1 - undefined instruction events
3221 4 - invalid data aborts
3224 Example: user_debug=31
3227 [X86] Flags controlling user PTE allocations.
3229 nohigh = do not allocate PTE pages in
3230 HIGHMEM regardless of setting
3234 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3235 vdso=1: enable VDSO (default)
3236 vdso=0: disable VDSO mapping
3239 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3240 vdso32=1: enable 32-bit VDSO (default)
3241 vdso32=0: disable 32-bit VDSO mapping
3244 vector=percpu: enable percpu vector domain
3246 video= [FB] Frame buffer configuration
3247 See Documentation/fb/modedb.txt.
3250 [VMMIO] Memory mapped virtio (platform) device.
3252 <size>@<baseaddr>:<irq>[:<id>]
3254 <size> := size (can use standard suffixes
3256 <baseaddr> := physical base address
3257 <irq> := interrupt number (as passed to
3259 <id> := (optional) platform device id
3261 virtio_mmio.device=1K@0x100b0000:48:7
3263 Can be used multiple times for multiple devices.
3265 vga= [BOOT,X86-32] Select a particular video mode
3266 See Documentation/x86/boot.txt and
3267 Documentation/svga.txt.
3268 Use vga=ask for menu.
3269 This is actually a boot loader parameter; the value is
3270 passed to the kernel using a special protocol.
3272 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3273 size of <nn>. This can be used to increase the
3274 minimum size (128MB on x86). It can also be used to
3275 decrease the size and leave more room for directly
3278 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3281 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3284 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3288 Controls the behavior of vsyscalls (i.e. calls to
3289 fixed addresses of 0xffffffffff600x00 from legacy
3290 code). Most statically-linked binaries and older
3291 versions of glibc use these calls. Because these
3292 functions are at fixed addresses, they make nice
3293 targets for exploits that can control RIP.
3295 emulate [default] Vsyscalls turn into traps and are
3296 emulated reasonably safely.
3298 native Vsyscalls are native syscall instructions.
3299 This is a little bit faster than trapping
3300 and makes a few dynamic recompilers work
3301 better than they would in emulation mode.
3302 It also makes exploits much easier to write.
3304 none Vsyscalls don't work at all. This makes
3305 them quite hard to use for exploits but
3306 might break your system.
3308 vt.cur_default= [VT] Default cursor shape.
3309 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3310 the parameters of the <Esc>[?A;B;Cc escape sequence;
3311 see VGA-softcursor.txt. Default: 2 = underline.
3313 vt.default_blu= [VT]
3314 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3315 Change the default blue palette of the console.
3316 This is a 16-member array composed of values
3319 vt.default_grn= [VT]
3320 Format: <green0>,<green1>,<green2>,...,<green15>
3321 Change the default green palette of the console.
3322 This is a 16-member array composed of values
3325 vt.default_red= [VT]
3326 Format: <red0>,<red1>,<red2>,...,<red15>
3327 Change the default red palette of the console.
3328 This is a 16-member array composed of values
3334 Set system-wide default UTF-8 mode for all tty's.
3335 Default is 1, i.e. UTF-8 mode is enabled for all
3336 newly opened terminals.
3338 vt.global_cursor_default=
3341 Set system-wide default for whether a cursor
3342 is shown on new VTs. Default is -1,
3343 i.e. cursors will be created by default unless
3344 overridden by individual drivers. 0 will hide
3345 cursors, 1 will display them.
3347 watchdog timers [HW,WDT] For information on watchdog timers,
3348 see Documentation/watchdog/watchdog-parameters.txt
3349 or other driver-specific files in the
3350 Documentation/watchdog/ directory.
3352 workqueue.disable_numa
3353 By default, all work items queued to unbound
3354 workqueues are affine to the NUMA nodes they're
3355 issued on, which results in better behavior in
3356 general. If NUMA affinity needs to be disabled for
3357 whatever reason, this option can be used. Note
3358 that this also can be controlled per-workqueue for
3359 workqueues visible under /sys/bus/workqueue/.
3361 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3362 default x2apic cluster mode on platforms
3365 x86_mrst_timer= [X86-32,APBT]
3366 Choose timer option for x86 Moorestown MID platform.
3367 Two valid options are apbt timer only and lapic timer
3368 plus one apbt timer for broadcast timer.
3369 x86_mrst_timer=apbt_only | lapic_and_apbt
3371 xen_emul_unplug= [HW,X86,XEN]
3372 Unplug Xen emulated devices
3373 Format: [unplug0,][unplug1]
3374 ide-disks -- unplug primary master IDE devices
3375 aux-ide-disks -- unplug non-primary-master IDE devices
3376 nics -- unplug network devices
3377 all -- unplug all emulated devices (NICs and IDE disks)
3378 unnecessary -- unplugging emulated devices is
3379 unnecessary even if the host did not respond to
3381 never -- do not unplug even if version check succeeds
3383 xirc2ps_cs= [NET,PCMCIA]
3385 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3387 ______________________________________________________________________
3391 Add more DRM drivers.
projects / sojka / nv-tegra / linux-3.10.git / blob