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 DRM Direct Rendering Management support is enabled.
48 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
49 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50 EFI EFI Partitioning (GPT) is enabled
51 EIDE EIDE/ATAPI support is enabled.
52 EVM Extended Verification Module
53 FB The frame buffer device is enabled.
54 FTRACE Function tracing enabled.
55 GCOV GCOV profiling is enabled.
56 HW Appropriate hardware is enabled.
57 IA-64 IA-64 architecture is enabled.
58 IMA Integrity measurement architecture is enabled.
59 IOSCHED More than one I/O scheduler is enabled.
60 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
61 IPV6 IPv6 support is enabled.
62 ISAPNP ISA PnP code is enabled.
63 ISDN Appropriate ISDN support is enabled.
64 JOY Appropriate joystick support is enabled.
65 KGDB Kernel debugger support is enabled.
66 KVM Kernel Virtual Machine support is enabled.
67 LIBATA Libata driver is enabled
68 LP Printer support is enabled.
69 LOOP Loopback device support is enabled.
70 M68k M68k architecture is enabled.
71 These options have more detailed description inside of
72 Documentation/m68k/kernel-options.txt.
73 MDA MDA console support is enabled.
74 MIPS MIPS architecture is enabled.
75 MOUSE Appropriate mouse support is enabled.
76 MSI Message Signaled Interrupts (PCI).
77 MTD MTD (Memory Technology Device) support is enabled.
78 NET Appropriate network support is enabled.
79 NUMA NUMA support is enabled.
80 NFS Appropriate NFS support is enabled.
81 OSS OSS sound support is enabled.
82 PV_OPS A paravirtualized kernel is enabled.
83 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
84 PARISC The PA-RISC architecture is enabled.
85 PCI PCI bus support is enabled.
86 PCIE PCI Express support is enabled.
87 PCMCIA The PCMCIA subsystem is enabled.
88 PNP Plug & Play support is enabled.
89 PPC PowerPC architecture is enabled.
90 PPT Parallel port support is enabled.
91 PS2 Appropriate PS/2 support is enabled.
92 RAM RAM disk support is enabled.
93 S390 S390 architecture is enabled.
94 SCSI Appropriate SCSI support is enabled.
95 A lot of drivers have their options described inside
96 the Documentation/scsi/ sub-directory.
97 SECURITY Different security models are enabled.
98 SELINUX SELinux support is enabled.
99 APPARMOR AppArmor support is enabled.
100 SERIAL Serial support is enabled.
101 SH SuperH architecture is enabled.
102 SMP The kernel is an SMP kernel.
103 SPARC Sparc architecture is enabled.
104 SWSUSP Software suspend (hibernation) is enabled.
105 SUSPEND System suspend states are enabled.
106 TPM TPM drivers are enabled.
107 TS Appropriate touchscreen support is enabled.
108 UMS USB Mass Storage support is enabled.
109 USB USB support is enabled.
110 USBHID USB Human Interface Device support is enabled.
111 V4L Video For Linux support is enabled.
112 VMMIO Driver for memory mapped virtio devices is enabled.
113 VGA The VGA console has been enabled.
114 VT Virtual terminal support is enabled.
115 WDT Watchdog support is enabled.
116 XT IBM PC/XT MFM hard disk support is enabled.
117 X86-32 X86-32, aka i386 architecture is enabled.
118 X86-64 X86-64 architecture is enabled.
119 More X86-64 boot options can be found in
120 Documentation/x86/x86_64/boot-options.txt .
121 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
122 XEN Xen support is enabled
124 In addition, the following text indicates that the option:
126 BUGS= Relates to possible processor bugs on the said processor.
127 KNL Is a kernel start-up parameter.
128 BOOT Is a boot loader parameter.
130 Parameters denoted with BOOT are actually interpreted by the boot
131 loader, and have no meaning to the kernel directly.
132 Do not modify the syntax of boot loader parameters without extreme
133 need or coordination with <Documentation/x86/boot.txt>.
135 There are also arch-specific kernel-parameters not documented here.
136 See for example <Documentation/x86/x86_64/boot-options.txt>.
138 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
139 a trailing = on the name of any parameter states that that parameter will
140 be entered as an environment variable, whereas its absence indicates that
141 it will appear as a kernel argument readable via /proc/cmdline by programs
142 running once the system is up.
144 The number of kernel parameters is not limited, but the length of the
145 complete command line (parameters including spaces etc.) is limited to
146 a fixed number of characters. This limit depends on the architecture
147 and is between 256 and 4096 characters. It is defined in the file
148 ./include/asm/setup.h as COMMAND_LINE_SIZE.
150 Finally, the [KMG] suffix is commonly described after a number of kernel
151 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
152 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
153 bytes respectively. Such letter suffixes can also be entirely omitted.
157 Advanced Configuration and Power Interface
158 Format: { force | off | strict | noirq | rsdt }
159 force -- enable ACPI if default was off
160 off -- disable ACPI if default was on
161 noirq -- do not use ACPI for IRQ routing
162 strict -- Be less tolerant of platforms that are not
163 strictly ACPI specification compliant.
164 rsdt -- prefer RSDT over (default) XSDT
165 copy_dsdt -- copy DSDT to memory
167 See also Documentation/power/runtime_pm.txt, pci=noacpi
169 acpi_rsdp= [ACPI,EFI,KEXEC]
170 Pass the RSDP address to the kernel, mostly used
171 on machines running EFI runtime service to boot the
172 second kernel for kdump.
174 acpi_apic_instance= [ACPI, IOAPIC]
176 2: use 2nd APIC table, if available
177 1,0: use 1st APIC table
180 acpi_backlight= [HW,ACPI]
181 acpi_backlight=vendor
183 If set to vendor, prefer vendor specific driver
184 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
185 of the ACPI video.ko driver.
187 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
188 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
190 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
191 debug output. Bits in debug_layer correspond to a
192 _COMPONENT in an ACPI source file, e.g.,
193 #define _COMPONENT ACPI_PCI_COMPONENT
194 Bits in debug_level correspond to a level in
195 ACPI_DEBUG_PRINT statements, e.g.,
196 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
197 The debug_level mask defaults to "info". See
198 Documentation/acpi/debug.txt for more information about
199 debug layers and levels.
201 Enable processor driver info messages:
202 acpi.debug_layer=0x20000000
203 Enable PCI/PCI interrupt routing info messages:
204 acpi.debug_layer=0x400000
205 Enable AML "Debug" output, i.e., stores to the Debug
206 object while interpreting AML:
207 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
208 Enable all messages related to ACPI hardware:
209 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
211 Some values produce so much output that the system is
212 unusable. The "log_buf_len" parameter may be useful
213 if you need to capture more output.
215 acpi_irq_balance [HW,ACPI]
216 ACPI will balance active IRQs
219 acpi_irq_nobalance [HW,ACPI]
220 ACPI will not move active IRQs (default)
223 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
224 Format: <irq>,<irq>...
226 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
228 Format: <irq>,<irq>...
230 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
232 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
233 Format: To spoof as Windows 98: ="Microsoft Windows"
235 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
236 acpi_osi="string1" # add string1 -- only one string
237 acpi_osi="!string2" # remove built-in string2
238 acpi_osi= # disable all strings
241 Override the pmtimer bug detection: force the kernel
242 to assume that this machine's pmtimer latches its value
243 and always returns good values.
245 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
246 Format: { level | edge | high | low }
248 acpi_serialize [HW,ACPI] force serialization of AML methods
250 acpi_skip_timer_override [HW,ACPI]
251 Recognize and ignore IRQ0/pin2 Interrupt Override.
252 For broken nForce2 BIOS resulting in XT-PIC timer.
254 acpi_sleep= [HW,ACPI] Sleep options
255 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
256 old_ordering, nonvs, sci_force_enable }
257 See Documentation/power/video.txt for information on
259 s3_beep is for debugging; it makes the PC's speaker beep
260 as soon as the kernel's real-mode entry point is called.
261 s4_nohwsig prevents ACPI hardware signature from being
262 used during resume from hibernation.
263 old_ordering causes the ACPI 1.0 ordering of the _PTS
264 control method, with respect to putting devices into
265 low power states, to be enforced (the ACPI 2.0 ordering
266 of _PTS is used by default).
267 nonvs prevents the kernel from saving/restoring the
268 ACPI NVS memory during suspend/hibernation and resume.
269 sci_force_enable causes the kernel to set SCI_EN directly
270 on resume from S1/S3 (which is against the ACPI spec,
271 but some broken systems don't work without it).
273 acpi_use_timer_override [HW,ACPI]
274 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer override, but don't have HPET
277 acpi_enforce_resources= [ACPI]
278 { strict | lax | no }
279 Check for resource conflicts between native drivers
280 and ACPI OperationRegions (SystemIO and SystemMemory
281 only). IO ports and memory declared in ACPI might be
282 used by the ACPI subsystem in arbitrary AML code and
283 can interfere with legacy drivers.
284 strict (default): access to resources claimed by ACPI
285 is denied; legacy drivers trying to access reserved
286 resources will fail to bind to device using them.
287 lax: access to resources claimed by ACPI is allowed;
288 legacy drivers trying to access reserved resources
289 will bind successfully but a warning message is logged.
290 no: ACPI OperationRegions are not marked as reserved,
291 no further checks are performed.
293 add_efi_memmap [EFI; X86] Include EFI memory map in
294 kernel's map of available physical RAM.
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
303 See Documentation/sound/alsa/alsa-parameters.txt
306 Allow the default userspace alignment fault handler
307 behaviour to be specified. Bit 0 enables warnings,
308 bit 1 enables fixups, and bit 2 sends a segfault.
310 align_va_addr= [X86-64]
311 Align virtual addresses by clearing slice [14:12] when
312 allocating a VMA at process creation time. This option
313 gives you up to 3% performance improvement on AMD F15h
314 machines (where it is enabled by default) for a
315 CPU-intensive style benchmark, and it can vary highly in
316 a microbenchmark depending on workload and compiler.
318 32: only for 32-bit processes
319 64: only for 64-bit processes
320 on: enable for both 32- and 64-bit processes
321 off: disable for both 32- and 64-bit processes
323 amd_iommu= [HW,X86-64]
324 Pass parameters to the AMD IOMMU driver in the system.
326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
330 off - do not initialize any AMD IOMMU found in
332 force_isolation - Force device isolation for all
333 devices. The IOMMU driver is not
334 allowed anymore to lift isolation
335 requirements as needed. This option
336 does not override iommu=pt
338 amd_iommu_dump= [HW,X86-64]
339 Enable AMD IOMMU driver option to dump the ACPI table
340 for AMD IOMMU. With this option enabled, AMD IOMMU
341 driver will print ACPI tables for AMD IOMMU during
342 IOMMU initialization.
344 amijoy.map= [HW,JOY] Amiga joystick support
345 Map of devices attached to JOY0DAT and JOY1DAT
347 See also Documentation/input/joystick.txt
349 analog.map= [HW,JOY] Analog joystick and gamepad support
350 Specifies type or capabilities of an analog joystick
351 connected to one of 16 gameports
352 Format: <type1>,<type2>,..<type16>
355 Power management functions (SPARCstation-4/5 + deriv.)
357 Disable APC CPU standby support. SPARCstation-Fox does
358 not play well with APC CPU idle - disable it if you have
359 APC and your system crashes randomly.
361 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
362 Change the output verbosity whilst booting
363 Format: { quiet (default) | verbose | debug }
364 Change the amount of debugging information output
365 when initialising the APIC and IO-APIC components.
368 See Documentation/networking/ipv6.txt.
370 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
371 Limit apic dumping. The parameter defines the maximal
372 number of local apics being dumped. Also it is possible
373 to set it to "all" by meaning -- no limit here.
374 Format: { 1 (default) | 2 | ... | all }.
375 The parameter valid if only apic=debug or
376 apic=verbose is specified.
377 Example: apic=debug show_lapic=all
379 apm= [APM] Advanced Power Management
380 See header of arch/x86/kernel/apm_32.c.
382 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
383 Format: <io>,<irq>,<nodeID>
387 atarimouse= [HW,MOUSE] Atari Mouse
389 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
390 EzKey and similar keyboards
392 atkbd.reset= [HW] Reset keyboard during initialization
394 atkbd.set= [HW] Select keyboard code set
395 Format: <int> (2 = AT (default), 3 = PS/2)
397 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
400 atkbd.softraw= [HW] Choose between synthetic and real raw mode
401 Format: <bool> (0 = real, 1 = synthetic (default))
403 atkbd.softrepeat= [HW]
404 Use software keyboard repeat
406 baycom_epp= [HW,AX25]
409 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
411 See header of drivers/net/hamradio/baycom_par.c.
413 baycom_ser_fdx= [HW,AX25]
414 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
415 Format: <io>,<irq>,<mode>[,<baud>]
416 See header of drivers/net/hamradio/baycom_ser_fdx.c.
418 baycom_ser_hdx= [HW,AX25]
419 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
420 Format: <io>,<irq>,<mode>
421 See header of drivers/net/hamradio/baycom_ser_hdx.c.
423 boot_delay= Milliseconds to delay each printk during boot.
424 Values larger than 10 seconds (10000) are changed to
428 bootmem_debug [KNL] Enable bootmem allocator debug messages.
430 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
431 bttv.radio= Most important insmod options are available as
433 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
436 bulk_remove=off [PPC] This parameter disables the use of the pSeries
437 firmware feature for flushing multiple hpte entries
440 c101= [NET] Moxa C101 synchronous serial card
442 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
443 Sometimes CPU hardware bugs make them report the cache
444 size incorrectly. The kernel will attempt work arounds
445 to fix known problems, but for some CPUs it is not
446 possible to determine what the correct size should be.
447 This option provides an override for these situations.
449 ccw_timeout_log [S390]
450 See Documentation/s390/CommonIO for details.
452 cgroup_disable= [KNL] Disable a particular controller
453 Format: {name of the controller(s) to disable}
454 {Currently supported controllers - "memory"}
456 checkreqprot [SELINUX] Set initial checkreqprot flag value.
457 Format: { "0" | "1" }
458 See security/selinux/Kconfig help text.
459 0 -- check protection applied by kernel (includes
460 any implied execute protection).
461 1 -- check protection requested by application.
462 Default value is set via a kernel config option.
463 Value can be changed at runtime via
464 /selinux/checkreqprot.
467 See Documentation/s390/CommonIO for details.
469 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
471 Forces specified clocksource (if available) to be used
472 when calculating gettimeofday(). If specified
473 clocksource is not available, it defaults to PIT.
474 Format: { pit | tsc | cyclone | pmtmr }
476 clocksource= Override the default clocksource
478 Override the default clocksource and use the clocksource
479 with the name specified.
480 Some clocksource names to choose from, depending on
482 [all] jiffies (this is the base, fallback clocksource)
484 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
485 pxa_timer,timer3,32k_counter,timer0_1
487 [X86-32] pit,hpet,tsc;
488 scx200_hrt on Geode; cyclone on IBM x440
496 clearcpuid=BITNUM [X86]
497 Disable CPUID feature X for the kernel. See
498 arch/x86/include/asm/cpufeature.h for the valid bit
499 numbers. Note the Linux specific bits are not necessarily
500 stable over kernel options, but the vendor specific
502 Also note that user programs calling CPUID directly
503 or using the feature without checking anything
504 will still see it. This just prevents it from
505 being used by the kernel or shown in /proc/cpuinfo.
506 Also note the kernel might malfunction if you disable
510 Sets the size of kernel global memory area for contiguous
511 memory allocations. For more information, see
512 include/linux/dma-contiguous.h
514 cmo_free_hint= [PPC] Format: { yes | no }
515 Specify whether pages are marked as being inactive
516 when they are freed. This is used in CMO environments
517 to determine OS memory pressure for page stealing by
521 coherent_pool=nn[KMG] [ARM,KNL]
522 Sets the size of memory pool for coherent, atomic dma
523 allocations, by default set to 256K.
525 code_bytes [X86] How many bytes of object code to print
530 com20020= [HW,NET] ARCnet - COM20020 chipset
532 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
534 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
538 ARCnet - COM90xx chipset (memory-mapped buffers)
539 Format: <io>[,<irq>[,<memstart>]]
541 condev= [HW,S390] console device
544 console= [KNL] Output console device and options.
546 tty<n> Use the virtual console device <n>.
550 Use the specified serial port. The options are of
551 the form "bbbbpnf", where "bbbb" is the baud rate,
552 "p" is parity ("n", "o", or "e"), "n" is number of
553 bits, and "f" is flow control ("r" for RTS or
554 omit it). Default is "9600n8".
556 See Documentation/serial-console.txt for more
558 Documentation/networking/netconsole.txt for an
561 uart[8250],io,<addr>[,options]
562 uart[8250],mmio,<addr>[,options]
563 Start an early, polled-mode console on the 8250/16550
564 UART at the specified I/O port or MMIO address,
565 switching to the matching ttyS device later. The
566 options are the same as for ttyS, above.
567 hvc<n> Use the hypervisor console device <n>. This is for
568 both Xen and PowerPC hypervisors.
570 If the device connected to the port is not a TTY but a braille
571 device, prepend "brl," before the device type, for instance
573 For now, only VisioBraille is supported.
575 consoleblank= [KNL] The console blank (screen saver) timeout in
576 seconds. Defaults to 10*60 = 10mins. A value of 0
577 disables the blank timer.
580 [KNL] Change the default value for
581 /proc/<pid>/coredump_filter.
582 See also Documentation/filesystems/proc.txt.
584 cpuidle.off=1 [CPU_IDLE]
585 disable the cpuidle sub-system
587 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
589 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
591 crashkernel=size[KMG][@offset[KMG]]
592 [KNL] Using kexec, Linux can switch to a 'crash kernel'
593 upon panic. This parameter reserves the physical
594 memory region [offset, offset + size] for that kernel
595 image. If '@offset' is omitted, then a suitable offset
596 is selected automatically. Check
597 Documentation/kdump/kdump.txt for further details.
599 crashkernel_low=size[KMG]
600 [KNL, x86] parts under 4G.
602 crashkernel=range1:size1[,range2:size2,...][@offset]
603 [KNL] Same as above, but depends on the memory
604 in the running system. The syntax of range is
605 start-[end] where start and end are both
606 a memory unit (amount[KMG]). See also
607 Documentation/kdump/kdump.txt for an example.
612 cs89x0_media= [HW,NET]
613 Format: { rj45 | aui | bnc }
616 See header of drivers/s390/block/dasd_devmap.c.
618 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
619 (one device per port)
620 Format: <port#>,<type>
621 See also Documentation/input/joystick-parport.txt
623 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
624 time. See Documentation/dynamic-debug-howto.txt for
625 details. Deprecated, see dyndbg.
627 debug [KNL] Enable kernel debugging (events log level).
630 [KNL] verbose self-tests
632 Print debugging info while doing the locking API
634 We default to 0 (no extra messages), setting it to
635 1 will print _a lot_ more information - normally
636 only useful to kernel developers.
638 debug_objects [KNL] Enable object debugging
641 [KNL] Disable object debugging
643 debug_guardpage_minorder=
644 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
645 parameter allows control of the order of pages that will
646 be intentionally kept free (and hence protected) by the
647 buddy allocator. Bigger value increase the probability
648 of catching random memory corruption, but reduce the
649 amount of memory for normal system use. The maximum
650 possible value is MAX_ORDER/2. Setting this parameter
651 to 1 or 2 should be enough to identify most random
652 memory corruption problems caused by bugs in kernel or
653 driver code when a CPU writes to (or reads from) a
654 random memory location. Note that there exists a class
655 of memory corruptions problems caused by buggy H/W or
656 F/W or by drivers badly programing DMA (basically when
657 memory is written at bus level and the CPU MMU is
658 bypassed) which are not detectable by
659 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
660 tracking down these problems.
662 debugpat [X86] Enable PAT debugging
664 decnet.addr= [HW,NET]
665 Format: <area>[,<node>]
666 See also Documentation/networking/decnet.txt.
669 [same as hugepagesz=] The size of the default
670 HugeTLB page size. This is the size represented by
671 the legacy /proc/ hugepages APIs, used for SHM, and
672 default size when mounting hugetlbfs filesystems.
673 Defaults to the default architecture's huge page size
677 Set number of hash buckets for dentry cache.
680 IO parameters + enable/disable command.
682 digiepca= [HW,SERIAL]
683 See drivers/char/README.epca and
684 Documentation/serial/digiepca.txt.
687 See Documentation/networking/ipv6.txt.
689 disable_ddw [PPC/PSERIES]
690 Disable Dynamic DMA Window support. Use this if
691 to workaround buggy firmware.
694 See Documentation/networking/ipv6.txt.
696 disable_mtrr_cleanup [X86]
697 The kernel tries to adjust MTRR layout from continuous
698 to discrete, to make X server driver able to add WB
699 entry later. This parameter disables that.
701 disable_mtrr_trim [X86, Intel and AMD only]
702 By default the kernel will trim any uncacheable
703 memory out of your available memory pool based on
704 MTRR settings. This parameter disables that behavior,
705 possibly causing your machine to run very slowly.
707 disable_timer_pin_1 [X86]
708 Disable PIN 1 of APIC timer
709 Can be useful to work around chipset bugs.
711 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
712 this option disables the debugging code at boot.
714 dma_debug_entries=<number>
715 This option allows to tune the number of preallocated
716 entries for DMA-API debugging code. One entry is
717 required per DMA-API allocation. Use this if the
718 DMA-API debugging code disables itself because the
719 architectural default is too low.
721 dma_debug_driver=<driver_name>
722 With this option the DMA-API debugging driver
723 filter feature can be enabled at boot time. Just
724 pass the driver to filter for as the parameter.
725 The filter can be disabled or changed to another
726 driver later using sysfs.
728 drm_kms_helper.edid_firmware=[<connector>:]<file>
729 Broken monitors, graphic adapters and KVMs may
730 send no or incorrect EDID data sets. This parameter
731 allows to specify an EDID data set in the
732 /lib/firmware directory that is used instead.
733 Generic built-in EDID data sets are used, if one of
734 edid/1024x768.bin, edid/1280x1024.bin,
735 edid/1680x1050.bin, or edid/1920x1080.bin is given
736 and no file with the same name exists. Details and
737 instructions how to build your own EDID data are
738 available in Documentation/EDID/HOWTO.txt. An EDID
739 data set will only be used for a particular connector,
740 if its name and a colon are prepended to the EDID
745 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
746 module.dyndbg[="val"]
747 Enable debug messages at boot time. See
748 Documentation/dynamic-debug-howto.txt for details.
750 earlycon= [KNL] Output early console device and options.
751 uart[8250],io,<addr>[,options]
752 uart[8250],mmio,<addr>[,options]
753 uart[8250],mmio32,<addr>[,options]
754 Start an early, polled-mode console on the 8250/16550
755 UART at the specified I/O port or MMIO address.
756 MMIO inter-register address stride is either 8-bit
757 (mmio) or 32-bit (mmio32).
758 The options are the same as for ttyS, above.
760 earlyprintk= [X86,SH,BLACKFIN]
763 earlyprintk=serial[,ttySn[,baudrate]]
764 earlyprintk=ttySn[,baudrate]
765 earlyprintk=dbgp[debugController#]
767 Append ",keep" to not disable it when the real console
770 Only vga or serial or usb debug port at a time.
772 Currently only ttyS0 and ttyS1 are supported.
774 Interaction with the standard serial driver is not
777 The VGA output is eventually overwritten by the real
780 The xen output can only be used by Xen PV guests.
782 ekgdboc= [X86,KGDB] Allow early kernel console debugging
785 This is designed to be used in conjunction with
786 the boot argument: earlyprintk=vga
789 Format: {"off" | "on" | "skip[mbr]"}
791 efi_no_storage_paranoia [EFI; X86]
792 Using this parameter you can use more than 50% of
793 your efi variable storage. Use this parameter only if
794 you are really sure that your UEFI does sane gc and
795 fulfills the spec otherwise your board may brick.
797 eisa_irq_edge= [PARISC,HW]
798 See header of drivers/parisc/eisa.c.
801 See comment before function elanfreq_setup() in
802 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
805 Format: {"cfq" | "deadline" | "noop"}
806 See Documentation/block/cfq-iosched.txt and
807 Documentation/block/deadline-iosched.txt for details.
809 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
810 Specifies physical address of start of kernel core
811 image elf header and optionally the size. Generally
812 kexec loader will pass this option to capture kernel.
813 See Documentation/kdump/kdump.txt for details.
815 enable_mtrr_cleanup [X86]
816 The kernel tries to adjust MTRR layout from continuous
817 to discrete, to make X server driver able to add WB
818 entry later. This parameter enables that.
820 enable_timer_pin_1 [X86]
821 Enable PIN 1 of APIC timer
822 Can be useful to work around chipset bugs
823 (in particular on some ATI chipsets).
824 The kernel tries to set a reasonable default.
826 enforcing [SELINUX] Set initial enforcing status.
828 See security/selinux/Kconfig help text.
829 0 -- permissive (log only, no denials).
830 1 -- enforcing (deny and log).
832 Value can be changed at runtime via /selinux/enforce.
835 Disable Error Record Serialization Table (ERST)
838 ether= [HW,NET] Ethernet cards parameters
839 This option is obsoleted by the "netdev=" option, which
840 has equivalent usage. See its documentation for details.
844 Permit 'security.evm' to be updated regardless of
845 current integrity status.
849 fail_make_request=[KNL]
850 General fault injection mechanism.
851 Format: <interval>,<probability>,<space>,<times>
852 See also Documentation/fault-injection/.
855 See Documentation/blockdev/floppy.txt.
857 force_pal_cache_flush
858 [IA-64] Avoid check_sal_cache_flush which may hang on
859 buggy SAL_CACHE_FLUSH implementations. Using this
860 parameter will force ia64_sal_cache_flush to call
861 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
864 [FTRACE] will set and start the specified tracer
865 as early as possible in order to facilitate early
868 ftrace_dump_on_oops[=orig_cpu]
869 [FTRACE] will dump the trace buffers on oops.
870 If no parameter is passed, ftrace will dump
871 buffers of all CPUs, but if you pass orig_cpu, it will
872 dump only the buffer of the CPU that triggered the
875 ftrace_filter=[function-list]
876 [FTRACE] Limit the functions traced by the function
877 tracer at boot up. function-list is a comma separated
878 list of functions. This list can be changed at run
879 time by the set_ftrace_filter file in the debugfs
882 ftrace_notrace=[function-list]
883 [FTRACE] Do not trace the functions specified in
884 function-list. This list can be changed at run time
885 by the set_ftrace_notrace file in the debugfs
888 ftrace_graph_filter=[function-list]
889 [FTRACE] Limit the top level callers functions traced
890 by the function graph tracer at boot up.
891 function-list is a comma separated list of functions
892 that can be changed at run time by the
893 set_graph_function file in the debugfs tracing directory.
896 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
897 support via parallel port (up to 5 devices per port)
898 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
899 See also Documentation/input/joystick-parport.txt
903 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
907 gcov_persist= [GCOV] When non-zero (default), profiling data for
908 kernel modules is saved and remains accessible via
909 debugfs, even when the module is unloaded/reloaded.
910 When zero, profiling data is discarded and associated
911 debugfs files are removed at module unload time.
913 gpt [EFI] Forces disk with valid GPT signature but
914 invalid Protective MBR to be treated as GPT.
916 grcan.enable0= [HW] Configuration of physical interface 0. Determines
917 the "Enable 0" bit of the configuration register.
920 grcan.enable1= [HW] Configuration of physical interface 1. Determines
921 the "Enable 0" bit of the configuration register.
924 grcan.select= [HW] Select which physical interface to use.
927 grcan.txsize= [HW] Sets the size of the tx buffer.
928 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
930 grcan.rxsize= [HW] Sets the size of the rx buffer.
931 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
934 hashdist= [KNL,NUMA] Large hashes allocated during boot
935 are distributed across NUMA nodes. Defaults on
936 for 64-bit NUMA, off otherwise.
937 Format: 0 | 1 (for off | on)
939 hcl= [IA-64] SGI's Hardware Graph compatibility layer
941 hd= [EIDE] (E)IDE hard drive subsystem geometry
942 Format: <cyl>,<head>,<sect>
945 Disable Hardware Error Source Table (HEST) support;
946 corresponding firmware-first mode error processing
947 logic will be disabled.
949 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
950 size of <nn>. This works even on boxes that have no
951 highmem otherwise. This also works to reduce highmem
952 size on bigger boxes.
954 highres= [KNL] Enable/disable high resolution timer mode.
955 Valid parameters: "on", "off"
959 See Documentation/isdn/README.HiSax.
963 hpet= [X86-32,HPET] option to control HPET usage
964 Format: { enable (default) | disable | force |
966 disable: disable HPET and use PIT instead
967 force: allow force enabled of undocumented chips (ICH4,
969 verbose: show contents of HPET registers during setup
971 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
972 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
973 On x86-64 and powerpc, this option can be specified
974 multiple times interleaved with hugepages= to reserve
975 huge pages of different sizes. Valid pages sizes on
976 x86-64 are 2M (when the CPU supports "pse") and 1G
977 (when the CPU supports the "pdpe1gb" cpuinfo flag)
978 Note that 1GB pages can only be allocated at boot time
979 using hugepages= and not freed afterwards.
981 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
982 terminal devices. Valid values: 0..8
983 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
984 If specified, z/VM IUCV HVC accepts connections
985 from listed z/VM user IDs only.
987 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
988 hardware thread id mappings.
989 Format: <cpu>:<hwthread>
992 Do not unregister boot console at start. This is only
993 useful for debugging when something happens in the window
994 between unregistering the boot console and initializing
997 i2c_bus= [HW] Override the default board specific I2C bus speed
998 or register an additional I2C bus that is not
999 registered from board initialization code.
1003 i8042.debug [HW] Toggle i8042 debug mode
1004 i8042.direct [HW] Put keyboard port into non-translated mode
1005 i8042.dumbkbd [HW] Pretend that controller can only read data from
1006 keyboard and cannot control its state
1007 (Don't attempt to blink the leds)
1008 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1009 i8042.nokbd [HW] Don't check/create keyboard port
1010 i8042.noloop [HW] Disable the AUX Loopback command while probing
1012 i8042.nomux [HW] Don't check presence of an active multiplexing
1014 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1016 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1017 i8042.reset [HW] Reset the controller during init and cleanup
1018 i8042.unlock [HW] Unlock (ignore) the keylock
1022 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1023 indicates that the driver is running on unsupported
1025 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1026 does not match list of supported models.
1028 [HW] Report power status in /proc/i8k
1029 (disabled by default)
1030 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1033 i915.invert_brightness=
1034 [DRM] Invert the sense of the variable that is used to
1035 set the brightness of the panel backlight. Normally a
1036 brightness value of 0 indicates backlight switched off,
1037 and the maximum of the brightness value sets the backlight
1038 to maximum brightness. If this parameter is set to 0
1039 (default) and the machine requires it, or this parameter
1040 is set to 1, a brightness value of 0 sets the backlight
1041 to maximum brightness, and the maximum of the brightness
1042 value switches the backlight off.
1043 -1 -- never invert brightness
1044 0 -- machine default
1045 1 -- force brightness inversion
1048 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1050 ide-core.nodma= [HW] (E)IDE subsystem
1051 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1052 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1053 .cdrom .chs .ignore_cable are additional options
1054 See Documentation/ide/ide.txt.
1056 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1057 Claim all unknown PCI IDE storage controllers.
1060 Format: idle=poll, idle=halt, idle=nomwait
1061 Poll forces a polling idle loop that can slightly
1062 improve the performance of waking up a idle CPU, but
1063 will use a lot of power and make the system run hot.
1065 idle=halt: Halt is forced to be used for CPU idle.
1066 In such case C2/C3 won't be used again.
1067 idle=nomwait: Disable mwait for CPU C-states
1069 ignore_loglevel [KNL]
1070 Ignore loglevel setting - this will print /all/
1071 kernel messages to the console. Useful for debugging.
1072 We also add it as printk module parameter, so users
1073 could change it dynamically, usually by
1074 /sys/module/printk/parameters/ignore_loglevel.
1076 ihash_entries= [KNL]
1077 Set number of hash buckets for inode cache.
1079 ima_appraise= [IMA] appraise integrity measurements
1080 Format: { "off" | "enforce" | "fix" }
1083 ima_appraise_tcb [IMA]
1084 The builtin appraise policy appraises all files
1088 Format: { "0" | "1" }
1089 0 -- integrity auditing messages. (Default)
1090 1 -- enable informational integrity auditing messages.
1093 Format: { "sha1" | "md5" }
1097 Load a policy which meets the needs of the Trusted
1098 Computing Base. This means IMA will measure all
1099 programs exec'd, files mmap'd for exec, and all files
1100 opened for read by uid=0.
1104 Run specified binary instead of /sbin/init as init
1107 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1108 for working out where the kernel is dying during
1111 initrd= [BOOT] Specify the location of the initial ramdisk
1113 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1116 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1118 Enable intel iommu driver.
1120 Disable intel iommu driver.
1121 igfx_off [Default Off]
1122 By default, gfx is mapped as normal device. If a gfx
1123 device has a dedicated DMAR unit, the DMAR unit is
1124 bypassed by not enabling DMAR with this option. In
1125 this case, gfx device will use physical address for
1128 With this option iommu will not optimize to look
1129 for io virtual address below 32-bit forcing dual
1130 address cycle on pci bus for cards supporting greater
1131 than 32-bit addressing. The default is to look
1132 for translation below 32-bit and if not available
1133 then look in the higher range.
1134 strict [Default Off]
1135 With this option on every unmap_single operation will
1136 result in a hardware IOTLB flush operation as opposed
1137 to batching them for performance.
1138 sp_off [Default Off]
1139 By default, super page will be supported if Intel IOMMU
1140 has the capability. With this option, super page will
1143 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1144 0 disables intel_idle and fall back on acpi_idle.
1145 1 to 6 specify maximum depth of C-state.
1149 Do not enable intel_pstate as the default
1150 scaling driver for the supported processors
1152 intremap= [X86-64, Intel-IOMMU]
1153 on enable Interrupt Remapping (default)
1154 off disable Interrupt Remapping
1155 nosid disable Source ID checking
1157 BIOS x2APIC opt-out request will be ignored
1159 iomem= Disable strict checking of access to MMIO memory
1160 strict regions from userspace.
1177 io7= [HW] IO7 for Marvel based alpha systems
1178 See comment before marvel_specify_io7 in
1179 arch/alpha/kernel/core_marvel.c.
1181 io_delay= [X86] I/O delay method
1183 Standard port 0x80 based delay
1185 Alternate port 0xed based delay (needed on some systems)
1187 Simple two microseconds delay
1192 See Documentation/filesystems/nfs/nfsroot.txt.
1194 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1195 See comment before ip2_setup() in
1196 drivers/char/ip2/ip2base.c.
1199 When an interrupt is not handled search all handlers
1200 for it. Intended to get systems with badly broken
1204 When an interrupt is not handled search all handlers
1205 for it. Also check all handlers each timer
1206 interrupt. Intended to get systems with badly broken
1210 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1212 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1214 <cpu number>,...,<cpu number>
1216 <cpu number>-<cpu number>
1217 (must be a positive range in ascending order)
1219 <cpu number>,...,<cpu number>-<cpu number>
1221 This option can be used to specify one or more CPUs
1222 to isolate from the general SMP balancing and scheduling
1223 algorithms. You can move a process onto or off an
1224 "isolated" CPU via the CPU affinity syscalls or cpuset.
1225 <cpu number> begins at 0 and the maximum value is
1226 "number of CPUs in system - 1".
1228 This option is the preferred way to isolate CPUs. The
1229 alternative -- manually setting the CPU mask of all
1230 tasks in the system -- can cause problems and
1231 suboptimal load balancer performance.
1235 js= [HW,JOY] Analog joystick
1236 See Documentation/input/joystick.txt.
1240 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1241 specifies the amount of memory usable by the kernel
1242 for non-movable allocations. The requested amount is
1243 spread evenly throughout all nodes in the system. The
1244 remaining memory in each node is used for Movable
1245 pages. In the event, a node is too small to have both
1246 kernelcore and Movable pages, kernelcore pages will
1247 take priority and other nodes will have a larger number
1248 of kernelcore pages. The Movable zone is used for the
1249 allocation of pages that may be reclaimed or moved
1250 by the page migration subsystem. This means that
1251 HugeTLB pages may not be allocated from this zone.
1252 Note that allocations like PTEs-from-HighMem still
1253 use the HighMem zone if it exists, and the Normal
1254 zone if it does not.
1256 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1257 Format: <Controller#>[,poll interval]
1258 The controller # is the number of the ehci usb debug
1259 port as it is probed via PCI. The poll interval is
1260 optional and is the number seconds in between
1261 each poll cycle to the debug port in case you need
1262 the functionality for interrupting the kernel with
1263 gdb or control-c on the dbgp connection. When
1264 not using this parameter you use sysrq-g to break into
1265 the kernel debugger.
1267 kgdboc= [KGDB,HW] kgdb over consoles.
1268 Requires a tty driver that supports console polling,
1269 or a supported polling keyboard driver (non-usb).
1270 Serial only format: <serial_device>[,baud]
1271 keyboard only format: kbd
1272 keyboard and serial format: kbd,<serial_device>[,baud]
1273 Optional Kernel mode setting:
1274 kms, kbd format: kms,kbd
1275 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1277 kgdbwait [KGDB] Stop kernel execution and enter the
1278 kernel debugger at the earliest opportunity.
1280 kmac= [MIPS] korina ethernet MAC address.
1281 Configure the RouterBoard 532 series on-chip
1282 Ethernet adapter MAC address.
1284 kmemleak= [KNL] Boot-time kmemleak enable/disable
1285 Valid arguments: on, off
1288 kstack=N [X86] Print N words from the kernel stack
1291 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1292 Default is 0 (don't ignore, but inject #GP)
1294 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1298 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1299 Default is 1 (enabled)
1301 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1303 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1305 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1306 (virtualized MMU) support on capable Intel chips.
1307 Default is 1 (enabled)
1309 kvm-intel.emulate_invalid_guest_state=
1310 [KVM,Intel] Enable emulation of invalid guest states
1311 Default is 0 (disabled)
1313 kvm-intel.flexpriority=
1314 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1315 Default is 1 (enabled)
1318 [KVM,Intel] Enable VMX nesting (nVMX).
1319 Default is 0 (disabled)
1321 kvm-intel.unrestricted_guest=
1322 [KVM,Intel] Disable unrestricted guest feature
1323 (virtualized real and unpaged mode) on capable
1324 Intel chips. Default is 1 (enabled)
1326 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1327 feature (tagged TLBs) on capable Intel chips.
1328 Default is 1 (enabled)
1334 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1337 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1338 value for LAPIC timer one-shot implementation. Default
1339 back to the programmable timer unit in the LAPIC.
1341 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1344 libata.dma= [LIBATA] DMA control
1345 libata.dma=0 Disable all PATA and SATA DMA
1346 libata.dma=1 PATA and SATA Disk DMA only
1347 libata.dma=2 ATAPI (CDROM) DMA only
1348 libata.dma=4 Compact Flash DMA only
1349 Combinations also work, so libata.dma=3 enables DMA
1350 for disks and CDROMs, but not CFs.
1352 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1353 libata.ignore_hpa=0 keep BIOS limits (default)
1354 libata.ignore_hpa=1 ignore limits, using full disk
1356 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1360 libata.force= [LIBATA] Force configurations. The format is comma
1361 separated list of "[ID:]VAL" where ID is
1362 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1363 matching port, link or device. Basically, it matches
1364 the ATA ID string printed on console by libata. If
1365 the whole ID part is omitted, the last PORT and DEVICE
1366 values are used. If ID hasn't been specified yet, the
1367 configuration applies to all ports, links and devices.
1369 If only DEVICE is omitted, the parameter applies to
1370 the port and all links and devices behind it. DEVICE
1371 number of 0 either selects the first device or the
1372 first fan-out link behind PMP device. It does not
1373 select the host link. DEVICE number of 15 selects the
1374 host link and device attached to it.
1376 The VAL specifies the configuration to force. As long
1377 as there's no ambiguity shortcut notation is allowed.
1378 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1379 The following configurations can be forced.
1381 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1382 Any ID with matching PORT is used.
1384 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1386 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1387 udma[/][16,25,33,44,66,100,133] notation is also
1390 * [no]ncq: Turn on or off NCQ.
1392 * nohrst, nosrst, norst: suppress hard, soft
1395 * rstonce: only attempt one reset during
1396 hot-unplug link recovery
1398 * dump_id: dump IDENTIFY data.
1400 If there are multiple matching configurations changing
1401 the same attribute, the last one is used.
1403 memblock=debug [KNL] Enable memblock debug messages.
1405 load_ramdisk= [RAM] List of ramdisks to load from floppy
1406 See Documentation/blockdev/ramdisk.txt.
1408 lockd.nlm_grace_period=P [NFS] Assign grace period.
1411 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1414 lockd.nlm_timeout=T [NFS] Assign timeout value.
1417 lockd.nlm_udpport=M [NFS] Assign UDP port.
1420 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1423 loglevel= All Kernel Messages with a loglevel smaller than the
1424 console loglevel will be printed to the console. It can
1425 also be changed with klogd or other programs. The
1426 loglevels are defined as follows:
1428 0 (KERN_EMERG) system is unusable
1429 1 (KERN_ALERT) action must be taken immediately
1430 2 (KERN_CRIT) critical conditions
1431 3 (KERN_ERR) error conditions
1432 4 (KERN_WARNING) warning conditions
1433 5 (KERN_NOTICE) normal but significant condition
1434 6 (KERN_INFO) informational
1435 7 (KERN_DEBUG) debug-level messages
1437 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1438 in bytes. n must be a power of two. The default
1439 size is set in the kernel config file.
1441 logo.nologo [FB] Disables display of the built-in Linux logo.
1442 This may be used to provide more screen space for
1443 kernel log messages and is useful when debugging
1444 kernel boot problems.
1446 lp=0 [LP] Specify parallel ports to use, e.g,
1447 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1448 lp=reset first parallel port). 'lp=0' disables the
1449 lp=auto printer driver. 'lp=reset' (which can be
1450 specified in addition to the ports) causes
1451 attached printers to be reset. Using
1452 lp=port1,port2,... specifies the parallel ports
1453 to associate lp devices with, starting with
1454 lp0. A port specification may be 'none' to skip
1455 that lp device, or a parport name such as
1456 'parport0'. Specifying 'lp=auto' instead of a
1457 port specification list means that device IDs
1458 from each port should be examined, to see if
1459 an IEEE 1284-compliant printer is attached; if
1460 so, the driver will manage that printer.
1461 See also header of drivers/char/lp.c.
1464 Sets loops_per_jiffy to given constant, thus avoiding
1465 time-consuming boot-time autodetection (up to 250 ms per
1466 CPU). 0 enables autodetection (default). To determine
1467 the correct value for your kernel, boot with normal
1468 autodetection and see what value is printed. Note that
1469 on SMP systems the preset will be applied to all CPUs,
1470 which is likely to cause problems if your CPUs need
1471 significantly divergent settings. An incorrect value
1472 will cause delays in the kernel to be wrong, leading to
1473 unpredictable I/O errors and other breakage. Although
1474 unlikely, in the extreme case this might damage your
1478 Format: <io>,<irq>,<dma>
1480 machvec= [IA-64] Force the use of a particular machine-vector
1481 (machvec) in a generic kernel.
1482 Example: machvec=hpzx1_swiotlb
1484 machtype= [Loongson] Share the same kernel image file between different
1486 Example: machtype=lemote-yeeloong-2f-7inch
1488 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1489 than or equal to this physical address is ignored.
1491 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1492 should make use of. maxcpus=n : n >= 0 limits the
1493 kernel to using 'n' processors. n=0 is a special case,
1494 it is equivalent to "nosmp", which also disables
1497 max_loop= [LOOP] The number of loop block devices that get
1498 (loop.max_loop) unconditionally pre-created at init time. The default
1499 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1500 of statically allocating a predefined number, loop
1501 devices can be requested on-demand with the
1502 /dev/loop-control interface.
1504 mce [X86-32] Machine Check Exception
1506 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1508 md= [HW] RAID subsystems devices and level
1509 See Documentation/md.txt.
1512 Format: <first>,<last>
1513 Specifies range of consoles to be captured by the MDA.
1515 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1516 Amount of memory to be used when the kernel is not able
1517 to see the whole system memory or for test.
1518 [X86] Work as limiting max address. Use together
1519 with memmap= to avoid physical address space collisions.
1520 Without memmap= PCI devices could be placed at addresses
1521 belonging to unused RAM.
1523 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1527 [KNL,SH] Allow user to override the default size for
1528 per-device physically contiguous DMA buffers.
1530 memmap=exactmap [KNL,X86] Enable setting of an exact
1531 E820 memory map, as specified by the user.
1532 Such memmap=exactmap lines can be constructed based on
1533 BIOS output or other requirements. See the memmap=nn@ss
1536 memmap=nn[KMG]@ss[KMG]
1537 [KNL] Force usage of a specific region of memory
1538 Region of memory to be used, from ss to ss+nn.
1540 memmap=nn[KMG]#ss[KMG]
1541 [KNL,ACPI] Mark specific memory as ACPI data.
1542 Region of memory to be used, from ss to ss+nn.
1544 memmap=nn[KMG]$ss[KMG]
1545 [KNL,ACPI] Mark specific memory as reserved.
1546 Region of memory to be used, from ss to ss+nn.
1547 Example: Exclude memory from 0x18690000-0x1869ffff
1548 memmap=64K$0x18690000
1550 memmap=0x10000$0x18690000
1552 memory_corruption_check=0/1 [X86]
1553 Some BIOSes seem to corrupt the first 64k of
1554 memory when doing things like suspend/resume.
1555 Setting this option will scan the memory
1556 looking for corruption. Enabling this will
1557 both detect corruption and prevent the kernel
1558 from using the memory being corrupted.
1559 However, its intended as a diagnostic tool; if
1560 repeatable BIOS-originated corruption always
1561 affects the same memory, you can use memmap=
1562 to prevent the kernel from using that memory.
1564 memory_corruption_check_size=size [X86]
1565 By default it checks for corruption in the low
1566 64k, making this memory unavailable for normal
1567 use. Use this parameter to scan for
1568 corruption in more or less memory.
1570 memory_corruption_check_period=seconds [X86]
1571 By default it checks for corruption every 60
1572 seconds. Use this parameter to check at some
1573 other rate. 0 disables periodic checking.
1575 memtest= [KNL,X86] Enable memtest
1577 default : 0 <disable>
1578 Specifies the number of memtest passes to be
1579 performed. Each pass selects another test
1580 pattern from a given set of patterns. Memtest
1581 fills the memory with this pattern, validates
1582 memory contents and reserves bad memory
1583 regions that are detected.
1585 meye.*= [HW] Set MotionEye Camera parameters
1586 See Documentation/video4linux/meye.txt.
1588 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1589 Multi-Function General Purpose Timers on AMD Geode
1592 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1593 the BIOS has incorrectly applied a workaround. TinyBIOS
1594 version 0.98 is known to be affected, 0.99 fixes the
1595 problem by letting the user disable the workaround.
1599 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1600 physical address is ignored.
1602 mini2440= [ARM,HW,KNL]
1603 Format:[0..2][b][c][t]
1605 MINI2440 configuration specification:
1606 0 - The attached screen is the 3.5" TFT
1607 1 - The attached screen is the 7" TFT
1608 2 - The VGA Shield is attached (1024x768)
1609 Leaving out the screen size parameter will not load
1610 the TFT driver, and the framebuffer will be left
1612 b - Enable backlight. The TFT backlight pin will be
1613 linked to the kernel VESA blanking code and a GPIO
1614 LED. This parameter is not necessary when using the
1616 c - Enable the s3c camera interface.
1617 t - Reserved for enabling touchscreen support. The
1618 touchscreen support is not enabled in the mainstream
1619 kernel as of 2.6.30, a preliminary port can be found
1620 in the "bleeding edge" mini2440 support kernel at
1621 http://repo.or.cz/w/linux-2.6/mini2440.git
1624 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1625 parameter allows control of the logging verbosity for
1626 the additional memory initialisation checks. A value
1627 of 0 disables mminit logging and a level of 4 will
1628 log everything. Information is printed at KERN_DEBUG
1629 so loglevel=8 may also need to be specified.
1632 [KNL] When CONFIG_MODULE_SIG is set, this means that
1633 modules without (valid) signatures will fail to load.
1634 Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
1635 is always true, so this option does nothing.
1638 [MOUSE] Maximum time between finger touching and
1639 leaving touchpad surface for touch to be considered
1640 a tap and be reported as a left button click (for
1641 touchpads working in absolute mode only).
1643 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1644 reporting absolute coordinates, such as tablets
1645 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1646 reporting absolute coordinates, such as tablets
1648 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1649 is similar to kernelcore except it specifies the
1650 amount of memory used for migratable allocations.
1651 If both kernelcore and movablecore is specified,
1652 then kernelcore will be at *least* the specified
1653 value but may be more. If movablecore on its own
1654 is specified, the administrator must be careful
1655 that the amount of memory usable for all allocations
1658 MTD_Partition= [MTD]
1659 Format: <name>,<region-number>,<size>,<offset>
1661 MTD_Region= [MTD] Format:
1662 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1665 See drivers/mtd/cmdlinepart.c.
1667 multitce=off [PPC] This parameter disables the use of the pSeries
1668 firmware feature for updating multiple TCE entries
1671 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1673 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1675 boundary - index of last SLC block on Flex-OneNAND.
1676 The remaining blocks are configured as MLC blocks.
1677 lock - Configure if Flex-OneNAND boundary should be locked.
1678 Once locked, the boundary cannot be changed.
1679 1 indicates lock status, 0 indicates unlock status.
1682 ARM/S3C2412 JIVE boot control
1684 See arch/arm/mach-s3c2412/mach-jive.c
1686 mtouchusb.raw_coordinates=
1687 [HW] Make the MicroTouch USB driver use raw coordinates
1688 ('y', default) or cooked coordinates ('n')
1690 mtrr_chunk_size=nn[KMG] [X86]
1691 used for mtrr cleanup. It is largest continuous chunk
1692 that could hold holes aka. UC entries.
1694 mtrr_gran_size=nn[KMG] [X86]
1695 Used for mtrr cleanup. It is granularity of mtrr block.
1697 Large value could prevent small alignment from
1700 mtrr_spare_reg_nr=n [X86]
1702 Range: 0,7 : spare reg number
1704 Used for mtrr cleanup. It is spare mtrr entries number.
1705 Set to 2 or more if your graphical card needs more.
1707 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1709 netdev= [NET] Network devices parameters
1710 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1711 Note that mem_start is often overloaded to mean
1712 something different and driver-specific.
1713 This usage is only documented in each driver source
1717 [NETFILTER] Enable connection tracking flow accounting
1718 0 to disable accounting
1719 1 to enable accounting
1722 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1723 See Documentation/filesystems/nfs/nfsroot.txt.
1725 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1726 See Documentation/filesystems/nfs/nfsroot.txt.
1728 nfsrootdebug [NFS] enable nfsroot debugging messages.
1729 See Documentation/filesystems/nfs/nfsroot.txt.
1731 nfs.callback_tcpport=
1732 [NFS] set the TCP port on which the NFSv4 callback
1733 channel should listen.
1736 [NFS] sets the pathname to the program which is used
1737 to update the NFS client cache entries.
1739 nfs.cache_getent_timeout=
1740 [NFS] sets the timeout after which an attempt to
1741 update a cache entry is deemed to have failed.
1743 nfs.idmap_cache_timeout=
1744 [NFS] set the maximum lifetime for idmapper cache
1748 [NFS] enable 64-bit inode numbers.
1749 If zero, the NFS client will fake up a 32-bit inode
1750 number for the readdir() and stat() syscalls instead
1751 of returning the full 64-bit number.
1752 The default is to return 64-bit inode numbers.
1754 nfs.max_session_slots=
1755 [NFSv4.1] Sets the maximum number of session slots
1756 the client will attempt to negotiate with the server.
1757 This limits the number of simultaneous RPC requests
1758 that the client can send to the NFSv4.1 server.
1759 Note that there is little point in setting this
1760 value higher than the max_tcp_slot_table_limit.
1762 nfs.nfs4_disable_idmapping=
1763 [NFSv4] When set to the default of '1', this option
1764 ensures that both the RPC level authentication
1765 scheme and the NFS level operations agree to use
1766 numeric uids/gids if the mount is using the
1767 'sec=sys' security flavour. In effect it is
1768 disabling idmapping, which can make migration from
1769 legacy NFSv2/v3 systems to NFSv4 easier.
1770 Servers that do not support this mode of operation
1771 will be autodetected by the client, and it will fall
1772 back to using the idmapper.
1773 To turn off this behaviour, set the value to '0'.
1775 [NFS4] Specify an additional fixed unique ident-
1776 ification string that NFSv4 clients can insert into
1777 their nfs_client_id4 string. This is typically a
1778 UUID that is generated at system install time.
1780 nfs.send_implementation_id =
1781 [NFSv4.1] Send client implementation identification
1782 information in exchange_id requests.
1783 If zero, no implementation identification information
1785 The default is to send the implementation identification
1788 nfsd.nfs4_disable_idmapping=
1789 [NFSv4] When set to the default of '1', the NFSv4
1790 server will return only numeric uids and gids to
1791 clients using auth_sys, and will accept numeric uids
1792 and gids from such clients. This is intended to ease
1793 migration from NFSv2/v3.
1795 objlayoutdriver.osd_login_prog=
1796 [NFS] [OBJLAYOUT] sets the pathname to the program which
1797 is used to automatically discover and login into new
1798 osd-targets. Please see:
1799 Documentation/filesystems/pnfs.txt for more explanations
1801 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1802 when a NMI is triggered.
1803 Format: [state][,regs][,debounce][,die]
1805 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1806 Format: [panic,][nopanic,][num]
1808 0 - turn nmi_watchdog off
1809 When panic is specified, panic when an NMI watchdog
1810 timeout occurs (or 'nopanic' to override the opposite
1812 This is useful when you use a panic=... timeout and
1813 need the box quickly up again.
1815 netpoll.carrier_timeout=
1816 [NET] Specifies amount of time (in seconds) that
1817 netpoll should wait for a carrier. By default netpoll
1820 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1821 emulation library even if a 387 maths coprocessor
1825 [HW] Never suspend the console
1826 Disable suspending of consoles during suspend and
1827 hibernate operations. Once disabled, debugging
1828 messages can reach various consoles while the rest
1829 of the system is being put to sleep (ie, while
1830 debugging driver suspend/resume hooks). This may
1831 not work reliably with all consoles, but is known
1832 to work with serial and VGA consoles.
1833 To facilitate more flexible debugging, we also add
1834 console_suspend, a printk module parameter to control
1835 it. Users could use console_suspend (usually
1836 /sys/module/printk/parameters/console_suspend) to
1837 turn on/off it dynamically.
1839 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1840 caches in the slab allocator. Saves per-node memory,
1841 but will impact performance.
1845 noapic [SMP,APIC] Tells the kernel to not make use of any
1846 IOAPICs that may be present in the system.
1848 noautogroup Disable scheduler automatic task group creation.
1850 nobats [PPC] Do not use BATs for mapping kernel lowmem
1851 on "Classic" PPC cores.
1855 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1857 nodelayacct [KNL] Disable per-task delay accounting
1859 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1861 nodsp [SH] Disable hardware DSP at boot time.
1863 noefi [X86] Disable EFI runtime services support.
1868 On X86-32 available only on PAE configured kernels.
1869 noexec=on: enable non-executable mappings (default)
1870 noexec=off: disable non-executable mappings
1873 Disable SMAP (Supervisor Mode Access Prevention)
1874 even if it is supported by processor.
1877 Disable SMEP (Supervisor Mode Execution Prevention)
1878 even if it is supported by processor.
1881 This affects only 32-bit executables.
1882 noexec32=on: enable non-executable mappings (default)
1883 read doesn't imply executable mappings
1884 noexec32=off: disable non-executable mappings
1885 read implies executable mappings
1887 nofpu [SH] Disable hardware FPU at boot time.
1889 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1890 register save and restore. The kernel will only save
1891 legacy floating-point registers on task switch.
1893 noxsave [BUGS=X86] Disables x86 extended register state save
1894 and restore using xsave. The kernel will fallback to
1895 enabling legacy floating-point and sse state.
1898 on enable eager fpu restore
1899 off disable eager fpu restore
1900 auto selects the default scheme, which automatically
1901 enables eagerfpu restore for xsaveopt.
1903 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1904 wfi(ARM) instruction doesn't work correctly and not to
1905 use it. This is also useful when using JTAG debugger.
1907 no_file_caps Tells the kernel not to honor file capabilities. The
1908 only way then for a file to be executed with privilege
1909 is to be setuid root or executed by root.
1911 nohalt [IA-64] Tells the kernel not to use the power saving
1912 function PAL_HALT_LIGHT when idle. This increases
1913 power-consumption. On the positive side, it reduces
1914 interrupt wake-up latency, which may improve performance
1915 in certain environments such as networked servers or
1918 nohz= [KNL] Boottime enable/disable dynamic ticks
1919 Valid arguments: on, off
1922 noiotrap [SH] Disables trapped I/O port accesses.
1924 noirqdebug [X86-32] Disables the code which attempts to detect and
1925 disable unhandled interrupt sources.
1927 no_timer_check [X86,APIC] Disables the code which tests for
1928 broken timer IRQ sources.
1930 noisapnp [ISAPNP] Disables ISA PnP code.
1932 noinitrd [RAM] Tells the kernel not to load any configured
1935 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1937 [Deprecated - use intremap=off]
1941 nojitter [IA-64] Disables jitter checking for ITC timers.
1943 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1945 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1948 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1949 steal time is computed, but won't influence scheduler
1952 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1954 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1956 noltlbs [PPC] Do not use large page/tlb entries for kernel
1957 lowmem mapping on PPC40x.
1959 nomca [IA-64] Disable machine check abort handling
1961 nomce [X86-32] Machine Check Exception
1963 nomfgpt [X86-32] Disable Multi-Function General Purpose
1964 Timer usage (for AMD Geode machines).
1966 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1967 shutdown the other cpus. Instead use the REBOOT_VECTOR
1970 nomodule Disable module load
1972 nopat [X86] Disable PAT (page attribute table extension of
1973 pagetables) support.
1975 norandmaps Don't use address space randomization. Equivalent to
1976 echo 0 > /proc/sys/kernel/randomize_va_space
1978 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1980 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1981 with UP alternatives
1983 noresidual [PPC] Don't use residual data on PReP machines.
1985 nordrand [X86] Disable the direct use of the RDRAND
1986 instruction even if it is supported by the
1987 processor. RDRAND is still available to user
1990 noresume [SWSUSP] Disables resume and restores original swap
1993 no-scroll [VGA] Disables scrollback.
1994 This is required for the Braillex ib80-piezo Braille
1995 reader made by F.H. Papenmeier (Germany).
1999 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2001 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2002 and disable the IO APIC. legacy for "maxcpus=0".
2004 nosoftlockup [KNL] Disable the soft-lockup detector.
2006 nosync [HW,M68K] Disables sync negotiation for all devices.
2008 notsc [BUGS=X86-32] Disable Time Stamp Counter
2010 nousb [USB] Disable the USB subsystem
2012 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2016 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2018 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2019 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2020 Some features depend on CPU0. Known dependencies are:
2021 1. Resume from suspend/hibernate depends on CPU0.
2022 Suspend/hibernate will fail if CPU0 is offline and you
2023 need to online CPU0 before suspend/hibernate.
2024 2. PIC interrupts also depend on CPU0. CPU0 can't be
2025 removed if a PIC interrupt is detected.
2026 It's said poweroff/reboot may depend on CPU0 on some
2027 machines although I haven't seen such issues so far
2028 after CPU0 is offline on a few tested machines.
2029 If the dependencies are under your control, you can
2030 turn on cpu0_hotplug.
2032 nptcg= [IA-64] Override max number of concurrent global TLB
2033 purges which is reported from either PAL_VM_SUMMARY or
2036 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2037 could support. nr_cpus=n : n >= 1 limits the kernel to
2038 supporting 'n' processors. Later in runtime you can not
2039 use hotplug cpu feature to put more cpu back to online.
2040 just like you compile the kernel NR_CPUS=n
2042 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2044 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2045 Allowed values are enable and disable
2047 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2048 one of ['zone', 'node', 'default'] can be specified
2049 This can be set from sysctl after boot.
2050 See Documentation/sysctl/vm.txt for details.
2052 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2053 See Documentation/debugging-via-ohci1394.txt for more
2056 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2057 Rather than timing out after 20 ms if an EC
2058 command is not properly ACKed, override the length
2059 of the timeout. We have interrupts disabled while
2060 waiting for the ACK, so if this is set too high
2061 interrupts *may* be lost!
2063 omap_mux= [OMAP] Override bootloader pin multiplexing.
2064 Format: <mux_mode0.mode_name=value>...
2065 For example, to override I2C bus2:
2066 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2068 oprofile.timer= [HW]
2069 Use timer interrupt instead of performance counters
2071 oprofile.cpu_type= Force an oprofile cpu type
2072 This might be useful if you have an older oprofile
2073 userland or if you want common events.
2074 Format: { arch_perfmon }
2075 arch_perfmon: [X86] Force use of architectural
2076 perfmon on Intel CPUs instead of the
2077 CPU specific event set.
2078 timer: [X86] Force use of architectural NMI
2079 timer mode (see also oprofile.timer
2080 for generic hr timer mode)
2081 [s390] Force legacy basic mode sampling
2082 (report cpu_type "timer")
2084 oops=panic Always panic on oopses. Default is to just kill the
2085 process, but there is a small probability of
2086 deadlocking the machine.
2087 This will also cause panics on machine check exceptions.
2088 Useful together with panic=30 to trigger a reboot.
2091 See Documentation/sound/oss/oss-parameters.txt
2093 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2094 timeout > 0: seconds before rebooting
2095 timeout = 0: wait forever
2096 timeout < 0: reboot immediately
2099 parkbd.port= [HW] Parallel port number the keyboard adapter is
2100 connected to, default is 0.
2102 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2103 0 for XT, 1 for AT (default is AT).
2106 parport= [HW,PPT] Specify parallel ports. 0 disables.
2107 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2108 Use 'auto' to force the driver to use any
2109 IRQ/DMA settings detected (the default is to
2110 ignore detected IRQ/DMA settings because of
2111 possible conflicts). You can specify the base
2112 address, IRQ, and DMA settings; IRQ and DMA
2113 should be numbers, or 'auto' (for using detected
2114 settings on that particular port), or 'nofifo'
2115 (to avoid using a FIFO even if it is detected).
2116 Parallel ports are assigned in the order they
2117 are specified on the command line, starting
2120 parport_init_mode= [HW,PPT]
2121 Configure VIA parallel port to operate in
2122 a specific mode. This is necessary on Pegasos
2123 computer where firmware has no options for setting
2124 up parallel port mode and sets it to spp.
2125 Currently this function knows 686a and 8231 chips.
2126 Format: [spp|ps2|epp|ecp|ecpepp]
2129 Halt all CPUs after the first oops has been printed for
2130 the specified number of seconds. This is to be used if
2131 your oopses keep scrolling off the screen.
2136 See header of drivers/block/paride/pcd.c.
2137 See also Documentation/blockdev/paride.txt.
2139 pci=option[,option...] [PCI] various PCI subsystem options:
2140 earlydump [X86] dump PCI config space before the kernel
2142 off [X86] don't probe for the PCI bus
2143 bios [X86-32] force use of PCI BIOS, don't access
2144 the hardware directly. Use this if your machine
2145 has a non-standard PCI host bridge.
2146 nobios [X86-32] disallow use of PCI BIOS, only direct
2147 hardware access methods are allowed. Use this
2148 if you experience crashes upon bootup and you
2149 suspect they are caused by the BIOS.
2150 conf1 [X86] Force use of PCI Configuration
2152 conf2 [X86] Force use of PCI Configuration
2154 noaer [PCIE] If the PCIEAER kernel config parameter is
2155 enabled, this kernel boot option can be used to
2156 disable the use of PCIE advanced error reporting.
2157 nodomains [PCI] Disable support for multiple PCI
2158 root domains (aka PCI segments, in ACPI-speak).
2159 nommconf [X86] Disable use of MMCONFIG for PCI
2161 check_enable_amd_mmconf [X86] check for and enable
2162 properly configured MMIO access to PCI
2163 config space on AMD family 10h CPU
2164 nomsi [MSI] If the PCI_MSI kernel config parameter is
2165 enabled, this kernel boot option can be used to
2166 disable the use of MSI interrupts system-wide.
2167 noioapicquirk [APIC] Disable all boot interrupt quirks.
2168 Safety option to keep boot IRQs enabled. This
2169 should never be necessary.
2170 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2171 primary IO-APIC for bridges that cannot disable
2172 boot IRQs. This fixes a source of spurious IRQs
2173 when the system masks IRQs.
2174 noioapicreroute [APIC] Disable workaround that uses the
2175 boot IRQ equivalent of an IRQ that connects to
2176 a chipset where boot IRQs cannot be disabled.
2177 The opposite of ioapicreroute.
2178 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2179 routing table. These calls are known to be buggy
2180 on several machines and they hang the machine
2181 when used, but on other computers it's the only
2182 way to get the interrupt routing table. Try
2183 this option if the kernel is unable to allocate
2184 IRQs or discover secondary PCI buses on your
2186 rom [X86] Assign address space to expansion ROMs.
2187 Use with caution as certain devices share
2188 address decoders between ROMs and other
2190 norom [X86] Do not assign address space to
2191 expansion ROMs that do not already have
2192 BIOS assigned address ranges.
2193 nobar [X86] Do not assign address space to the
2194 BARs that weren't assigned by the BIOS.
2195 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2196 assigned automatically to PCI devices. You can
2197 make the kernel exclude IRQs of your ISA cards
2199 pirqaddr=0xAAAAA [X86] Specify the physical address
2200 of the PIRQ table (normally generated
2201 by the BIOS) if it is outside the
2202 F0000h-100000h range.
2203 lastbus=N [X86] Scan all buses thru bus #N. Can be
2204 useful if the kernel is unable to find your
2205 secondary buses and you want to tell it
2206 explicitly which ones they are.
2207 assign-busses [X86] Always assign all PCI bus
2208 numbers ourselves, overriding
2209 whatever the firmware may have done.
2210 usepirqmask [X86] Honor the possible IRQ mask stored
2211 in the BIOS $PIR table. This is needed on
2212 some systems with broken BIOSes, notably
2213 some HP Pavilion N5400 and Omnibook XE3
2214 notebooks. This will have no effect if ACPI
2215 IRQ routing is enabled.
2216 noacpi [X86] Do not use ACPI for IRQ routing
2217 or for PCI scanning.
2218 use_crs [X86] Use PCI host bridge window information
2219 from ACPI. On BIOSes from 2008 or later, this
2220 is enabled by default. If you need to use this,
2221 please report a bug.
2222 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2223 If you need to use this, please report a bug.
2224 routeirq Do IRQ routing for all PCI devices.
2225 This is normally done in pci_enable_device(),
2226 so this option is a temporary workaround
2227 for broken drivers that don't call it.
2228 skip_isa_align [X86] do not align io start addr, so can
2229 handle more pci cards
2230 firmware [ARM] Do not re-enumerate the bus but instead
2231 just use the configuration from the
2232 bootloader. This is currently used on
2233 IXP2000 systems where the bus has to be
2234 configured a certain way for adjunct CPUs.
2235 noearly [X86] Don't do any early type 1 scanning.
2236 This might help on some broken boards which
2237 machine check when some devices' config space
2238 is read. But various workarounds are disabled
2239 and some IOMMU drivers will not work.
2240 bfsort Sort PCI devices into breadth-first order.
2241 This sorting is done to get a device
2242 order compatible with older (<= 2.4) kernels.
2243 nobfsort Don't sort PCI devices into breadth-first order.
2244 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2245 tuning and use the BIOS-configured MPS defaults.
2246 pcie_bus_safe Set every device's MPS to the largest value
2247 supported by all devices below the root complex.
2248 pcie_bus_perf Set device MPS to the largest allowable MPS
2249 based on its parent bus. Also set MRRS (Max
2250 Read Request Size) to the largest supported
2251 value (no larger than the MPS that the device
2252 or bus can support) for best performance.
2253 pcie_bus_peer2peer Set every device's MPS to 128B, which
2254 every device is guaranteed to support. This
2255 configuration allows peer-to-peer DMA between
2256 any pair of devices, possibly at the cost of
2257 reduced performance. This also guarantees
2258 that hot-added devices will work.
2259 cbiosize=nn[KMG] The fixed amount of bus space which is
2260 reserved for the CardBus bridge's IO window.
2261 The default value is 256 bytes.
2262 cbmemsize=nn[KMG] The fixed amount of bus space which is
2263 reserved for the CardBus bridge's memory
2264 window. The default value is 64 megabytes.
2267 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2268 Specifies alignment and device to reassign
2269 aligned memory resources.
2270 If <order of align> is not specified,
2271 PAGE_SIZE is used as alignment.
2272 PCI-PCI bridge can be specified, if resource
2273 windows need to be expanded.
2274 ecrc= Enable/disable PCIe ECRC (transaction layer
2275 end-to-end CRC checking).
2276 bios: Use BIOS/firmware settings. This is the
2280 hpiosize=nn[KMG] The fixed amount of bus space which is
2281 reserved for hotplug bridge's IO window.
2282 Default size is 256 bytes.
2283 hpmemsize=nn[KMG] The fixed amount of bus space which is
2284 reserved for hotplug bridge's memory window.
2285 Default size is 2 megabytes.
2286 realloc= Enable/disable reallocating PCI bridge resources
2287 if allocations done by BIOS are too small to
2288 accommodate resources required by all child
2290 off: Turn realloc off
2292 realloc same as realloc=on
2293 noari do not use PCIe ARI.
2294 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2295 only look for one device below a PCIe downstream
2298 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2301 force Enable ASPM even on devices that claim not to support it.
2302 WARNING: Forcing ASPM on may cause system lockups.
2304 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2305 nomsi Do not use MSI for PCI Express Native Hotplug (this
2306 makes all PCIe ports use INTx for hotplug services).
2308 pcie_ports= [PCIE] PCIe ports handling:
2309 auto Ask the BIOS whether or not to use native PCIe services
2310 associated with PCIe ports (PME, hot-plug, AER). Use
2311 them only if that is allowed by the BIOS.
2312 native Use native PCIe services associated with PCIe ports
2314 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2317 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2318 nomsi Do not use MSI for native PCIe PME signaling (this makes
2319 all PCIe root ports use INTx for all services).
2321 pcmv= [HW,PCMCIA] BadgePAD 4
2324 See Documentation/blockdev/paride.txt.
2326 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2329 See arch/parisc/kernel/pdc_chassis.c
2331 percpu_alloc= Select which percpu first chunk allocator to use.
2332 Currently supported values are "embed" and "page".
2333 Archs may support subset or none of the selections.
2334 See comments in mm/percpu.c for details on each
2335 allocator. This parameter is primarily for debugging
2336 and performance comparison.
2339 See Documentation/blockdev/paride.txt.
2342 See Documentation/blockdev/paride.txt.
2344 pirq= [SMP,APIC] Manual mp-table setup
2345 See Documentation/x86/i386/IO-APIC.txt.
2347 plip= [PPT,NET] Parallel port network link
2348 Format: { parport<nr> | timid | 0 }
2349 See also Documentation/parport.txt.
2351 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2352 Override pmtimer IOPort with a hex value.
2356 Enable PNP debug messages (depends on the
2357 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2358 via /sys/module/pnp/parameters/debug. We always show
2359 current resource usage; turning this on also shows
2360 possible settings and some assignment information.
2366 { on | off | curr | res | no-curr | no-res }
2369 [ISAPNP] Exclude IRQs for the autoconfiguration
2372 [ISAPNP] Exclude DMAs for the autoconfiguration
2374 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2375 Ranges are in pairs (I/O port base and size).
2378 [ISAPNP] Exclude memory regions for the
2380 Ranges are in pairs (memory base and size).
2382 ports= [IP_VS_FTP] IPVS ftp helper module
2384 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2386 Format: <port>,<port>....
2388 print-fatal-signals=
2389 [KNL] debug: print fatal signals
2391 If enabled, warn about various signal handling
2392 related application anomalies: too many signals,
2393 too many POSIX.1 timers, fatal signals causing a
2396 If you hit the warning due to signal overflow,
2397 you might want to try "ulimit -i unlimited".
2401 printk.always_kmsg_dump=
2402 Trigger kmsg_dump for cases other than kernel oops or
2404 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2407 printk.time= Show timing data prefixed to each printk message line
2408 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2410 processor.max_cstate= [HW,ACPI]
2411 Limit processor to maximum C-state
2412 max_cstate=9 overrides any DMI blacklist limit.
2414 processor.nocst [HW,ACPI]
2415 Ignore the _CST method to determine C-states,
2416 instead using the legacy FADT method
2418 profile= [KNL] Enable kernel profiling via /proc/profile
2419 Format: [schedule,]<number>
2420 Param: "schedule" - profile schedule points.
2421 Param: <number> - step/bucket size as a power of 2 for
2422 statistical time based profiling.
2423 Param: "sleep" - profile D-state sleeping (millisecs).
2424 Requires CONFIG_SCHEDSTATS
2425 Param: "kvm" - profile VM exits.
2427 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2429 See Documentation/blockdev/ramdisk.txt.
2431 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2432 probe for; one of (bare|imps|exps|lifebook|any).
2433 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2435 psmouse.resetafter= [HW,MOUSE]
2436 Try to reset the device after so many bad packets
2439 [HW,MOUSE] Set desired mouse resolution, in dpi.
2440 psmouse.smartscroll=
2441 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2442 0 = disabled, 1 = enabled (default).
2444 pstore.backend= Specify the name of the pstore backend to use
2447 See Documentation/blockdev/paride.txt.
2450 [KNL] Number of legacy pty's. Overwrites compiled-in
2453 quiet [KNL] Disable most log messages
2458 See Documentation/md.txt.
2460 ramdisk_blocksize= [RAM]
2461 See Documentation/blockdev/ramdisk.txt.
2463 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2464 See Documentation/blockdev/ramdisk.txt.
2466 rcu_nocbs= [KNL,BOOT]
2467 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2468 the specified list of CPUs to be no-callback CPUs.
2469 Invocation of these CPUs' RCU callbacks will
2470 be offloaded to "rcuoN" kthreads created for
2471 that purpose. This reduces OS jitter on the
2472 offloaded CPUs, which can be useful for HPC and
2473 real-time workloads. It can also improve energy
2474 efficiency for asymmetric multiprocessors.
2476 rcu_nocb_poll [KNL,BOOT]
2477 Rather than requiring that offloaded CPUs
2478 (specified by rcu_nocbs= above) explicitly
2479 awaken the corresponding "rcuoN" kthreads,
2480 make these kthreads poll for callbacks.
2481 This improves the real-time response for the
2482 offloaded CPUs by relieving them of the need to
2483 wake up the corresponding kthread, but degrades
2484 energy efficiency by requiring that the kthreads
2485 periodically wake up to do the polling.
2487 rcutree.blimit= [KNL,BOOT]
2488 Set maximum number of finished RCU callbacks to process
2491 rcutree.fanout_leaf= [KNL,BOOT]
2492 Increase the number of CPUs assigned to each
2493 leaf rcu_node structure. Useful for very large
2496 rcutree.qhimark= [KNL,BOOT]
2497 Set threshold of queued
2498 RCU callbacks over which batch limiting is disabled.
2500 rcutree.qlowmark= [KNL,BOOT]
2501 Set threshold of queued RCU callbacks below which
2502 batch limiting is re-enabled.
2504 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2505 Suppress RCU CPU stall warning messages.
2507 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2508 Set timeout for RCU CPU stall warning messages.
2510 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2511 Set delay from grace-period initialization to
2512 first attempt to force quiescent states.
2513 Units are jiffies, minimum value is zero,
2514 and maximum value is HZ.
2516 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2517 Set delay between subsequent attempts to force
2518 quiescent states. Units are jiffies, minimum
2519 value is one, and maximum value is HZ.
2521 rcutorture.fqs_duration= [KNL,BOOT]
2522 Set duration of force_quiescent_state bursts.
2524 rcutorture.fqs_holdoff= [KNL,BOOT]
2525 Set holdoff time within force_quiescent_state bursts.
2527 rcutorture.fqs_stutter= [KNL,BOOT]
2528 Set wait time between force_quiescent_state bursts.
2530 rcutorture.irqreader= [KNL,BOOT]
2531 Test RCU readers from irq handlers.
2533 rcutorture.n_barrier_cbs= [KNL,BOOT]
2534 Set callbacks/threads for rcu_barrier() testing.
2536 rcutorture.nfakewriters= [KNL,BOOT]
2537 Set number of concurrent RCU writers. These just
2538 stress RCU, they don't participate in the actual
2539 test, hence the "fake".
2541 rcutorture.nreaders= [KNL,BOOT]
2542 Set number of RCU readers.
2544 rcutorture.onoff_holdoff= [KNL,BOOT]
2545 Set time (s) after boot for CPU-hotplug testing.
2547 rcutorture.onoff_interval= [KNL,BOOT]
2548 Set time (s) between CPU-hotplug operations, or
2549 zero to disable CPU-hotplug testing.
2551 rcutorture.shuffle_interval= [KNL,BOOT]
2552 Set task-shuffle interval (s). Shuffling tasks
2553 allows some CPUs to go into dyntick-idle mode
2554 during the rcutorture test.
2556 rcutorture.shutdown_secs= [KNL,BOOT]
2557 Set time (s) after boot system shutdown. This
2558 is useful for hands-off automated testing.
2560 rcutorture.stall_cpu= [KNL,BOOT]
2561 Duration of CPU stall (s) to test RCU CPU stall
2562 warnings, zero to disable.
2564 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2565 Time to wait (s) after boot before inducing stall.
2567 rcutorture.stat_interval= [KNL,BOOT]
2568 Time (s) between statistics printk()s.
2570 rcutorture.stutter= [KNL,BOOT]
2571 Time (s) to stutter testing, for example, specifying
2572 five seconds causes the test to run for five seconds,
2573 wait for five seconds, and so on. This tests RCU's
2574 ability to transition abruptly to and from idle.
2576 rcutorture.test_boost= [KNL,BOOT]
2577 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2578 "Maybe" means test if the RCU implementation
2579 under test support RCU priority boosting.
2581 rcutorture.test_boost_duration= [KNL,BOOT]
2582 Duration (s) of each individual boost test.
2584 rcutorture.test_boost_interval= [KNL,BOOT]
2585 Interval (s) between each boost test.
2587 rcutorture.test_no_idle_hz= [KNL,BOOT]
2588 Test RCU's dyntick-idle handling. See also the
2589 rcutorture.shuffle_interval parameter.
2591 rcutorture.torture_type= [KNL,BOOT]
2592 Specify the RCU implementation to test.
2594 rcutorture.verbose= [KNL,BOOT]
2595 Enable additional printk() statements.
2599 Run specified binary instead of /init from the ramdisk,
2600 used for early userspace startup. See initrd.
2602 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2603 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2604 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2607 [KNL, SMP] Set scheduler's default relax_domain_level.
2608 See Documentation/cgroups/cpusets.txt.
2610 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2612 reservetop= [X86-32]
2614 Reserves a hole at the top of the kernel virtual
2619 Set the amount of memory to reserve for BIOS at
2620 the bottom of the address space.
2622 reset_devices [KNL] Force drivers to reset the underlying device
2623 during initialization.
2626 Specify the partition device for software suspend
2628 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2630 resume_offset= [SWSUSP]
2631 Specify the offset from the beginning of the partition
2632 given by "resume=" at which the swap header is located,
2633 in <PAGE_SIZE> units (needed only for swap files).
2634 See Documentation/power/swsusp-and-swap-files.txt
2636 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2637 read the resume files
2639 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2640 Useful for devices that are detected asynchronously
2641 (e.g. USB and MMC devices).
2643 hibernate= [HIBERNATION]
2644 noresume Don't check if there's a hibernation image
2645 present during boot.
2646 nocompress Don't compress/decompress hibernation images.
2648 retain_initrd [RAM] Keep initrd memory after extraction
2650 rhash_entries= [KNL,NET]
2651 Set number of hash buckets for route cache
2653 riscom8= [HW,SERIAL]
2654 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2656 ro [KNL] Mount root device read-only on boot
2658 root= [KNL] Root filesystem
2659 See name_to_dev_t comment in init/do_mounts.c.
2661 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2662 mount the root filesystem
2664 rootflags= [KNL] Set root filesystem mount option string
2666 rootfstype= [KNL] Set root filesystem type
2668 rootwait [KNL] Wait (indefinitely) for root device to show up.
2669 Useful for devices that are detected asynchronously
2670 (e.g. USB and MMC devices).
2672 rw [KNL] Mount root device read-write on boot
2674 S [KNL] Run init in single mode
2677 See drivers/net/irda/sa1100_ir.c.
2679 sbni= [NET] Granch SBNI12 leased line adapter
2681 sched_debug [KNL] Enables verbose scheduler debug messages.
2683 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2684 xtime_lock contention on larger systems, and/or RCU lock
2685 contention on all systems with CONFIG_MAXSMP set.
2686 Format: { "0" | "1" }
2687 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2689 Note: increases power consumption, thus should only be
2690 enabled if running jitter sensitive (HPC/RT) workloads.
2692 security= [SECURITY] Choose a security module to enable at boot.
2693 If this boot parameter is not specified, only the first
2694 security module asking for security registration will be
2695 loaded. An invalid security module name will be treated
2696 as if no module has been chosen.
2698 selinux= [SELINUX] Disable or enable SELinux at boot time.
2699 Format: { "0" | "1" }
2700 See security/selinux/Kconfig help text.
2703 Default value is set via kernel config option.
2704 If enabled at boot time, /selinux/disable can be used
2705 later to disable prior to initial policy load.
2707 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2708 Format: { "0" | "1" }
2709 See security/apparmor/Kconfig help text
2712 Default value is set via kernel config option.
2714 serialnumber [BUGS=X86-32]
2717 Maximal number of shapers.
2719 show_msr= [x86] show boot-time MSR settings
2720 Format: { <integer> }
2721 Show boot-time (BIOS-initialized) MSR settings.
2722 The parameter means the number of CPUs to show,
2723 for example 1 means boot CPU only.
2730 slab_max_order= [MM, SLAB]
2731 Determines the maximum allowed order for slabs.
2732 A high setting may cause OOMs due to memory
2733 fragmentation. Defaults to 1 for systems with
2734 more than 32MB of RAM, 0 otherwise.
2736 slub_debug[=options[,slabs]] [MM, SLUB]
2737 Enabling slub_debug allows one to determine the
2738 culprit if slab objects become corrupted. Enabling
2739 slub_debug can create guard zones around objects and
2740 may poison objects when not in use. Also tracks the
2741 last alloc / free. For more information see
2742 Documentation/vm/slub.txt.
2744 slub_max_order= [MM, SLUB]
2745 Determines the maximum allowed order for slabs.
2746 A high setting may cause OOMs due to memory
2747 fragmentation. For more information see
2748 Documentation/vm/slub.txt.
2750 slub_min_objects= [MM, SLUB]
2751 The minimum number of objects per slab. SLUB will
2752 increase the slab order up to slub_max_order to
2753 generate a sufficiently large slab able to contain
2754 the number of objects indicated. The higher the number
2755 of objects the smaller the overhead of tracking slabs
2756 and the less frequently locks need to be acquired.
2757 For more information see Documentation/vm/slub.txt.
2759 slub_min_order= [MM, SLUB]
2760 Determines the minimum page order for slabs. Must be
2761 lower than slub_max_order.
2762 For more information see Documentation/vm/slub.txt.
2764 slub_nomerge [MM, SLUB]
2765 Disable merging of slabs with similar size. May be
2766 necessary if there is some reason to distinguish
2767 allocs to different slabs. Debug options disable
2768 merging on their own.
2769 For more information see Documentation/vm/slub.txt.
2772 Format: <io1>[,<io2>[,...,<io8>]]
2774 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2775 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2776 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2777 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2778 smsc-ircc2.ircc_irq= [HW] IRQ line
2779 smsc-ircc2.ircc_dma= [HW] DMA channel
2780 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2781 0: Toshiba Satellite 1800 (GP data pin select)
2782 1: Fast pin select (default)
2786 [KNL] Should the soft-lockup detector generate panics.
2789 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2790 See Documentation/laptops/sonypi.txt
2792 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2793 See Documentation/serial/specialix.txt.
2795 spia_io_base= [HW,MTD]
2801 Enabled the stack tracer on boot up.
2803 stacktrace_filter=[function-list]
2804 [FTRACE] Limit the functions that the stack tracer
2805 will trace at boot up. function-list is a comma separated
2806 list of functions. This list can be changed at run
2807 time by the stack_trace_filter file in the debugfs
2808 tracing directory. Note, this enables stack tracing
2809 and the stacktrace above is not needed.
2813 Set the STI (builtin display/keyboard on the HP-PARISC
2814 machines) console (graphic card) which should be used
2815 as the initial boot-console.
2816 See also comment in drivers/video/console/sticore.c.
2819 See comment in drivers/video/console/sticore.c.
2822 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2824 sunrpc.min_resvport=
2825 sunrpc.max_resvport=
2827 SunRPC servers often require that client requests
2828 originate from a privileged port (i.e. a port in the
2829 range 0 < portnr < 1024).
2830 An administrator who wishes to reserve some of these
2831 ports for other uses may adjust the range that the
2832 kernel's sunrpc client considers to be privileged
2833 using these two parameters to set the minimum and
2834 maximum port values.
2838 Control how the NFS server code allocates CPUs to
2839 service thread pools. Depending on how many NICs
2840 you have and where their interrupts are bound, this
2841 option will affect which CPUs will do NFS serving.
2842 Note: this parameter cannot be changed while the
2843 NFS server is running.
2845 auto the server chooses an appropriate mode
2846 automatically using heuristics
2847 global a single global pool contains all CPUs
2848 percpu one pool for each CPU
2849 pernode one pool for each NUMA node (equivalent
2850 to global on non-NUMA machines)
2852 sunrpc.tcp_slot_table_entries=
2853 sunrpc.udp_slot_table_entries=
2855 Sets the upper limit on the number of simultaneous
2856 RPC calls that can be sent from the client to a
2857 server. Increasing these values may allow you to
2858 improve throughput, but will also increase the
2859 amount of memory reserved for use by the client.
2862 [KNL] Enable accounting of swap in memory resource
2863 controller if no parameter or 1 is given or disable
2864 it if 0 is given (See Documentation/cgroups/memory.txt)
2866 swiotlb= [IA-64] Number of I/O TLB slabs
2870 sysfs.deprecated=0|1 [KNL]
2871 Enable/disable old style sysfs layout for old udev
2872 on older distributions. When this option is enabled
2873 very new udev will not work anymore. When this option
2874 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2875 in older udev will not work anymore.
2876 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2877 the kernel configuration.
2879 sysrq_always_enabled
2881 Ignore sysrq setting - this boot parameter will
2882 neutralize any effect of /proc/sys/kernel/sysrq.
2883 Useful for debugging.
2887 test_suspend= [SUSPEND]
2888 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2889 standby suspend) as the system sleep state to briefly
2890 enter during system startup. The system is woken from
2891 this state using a wakeup-capable RTC alarm.
2893 thash_entries= [KNL,NET]
2894 Set number of hash buckets for TCP connection
2896 thermal.act= [HW,ACPI]
2897 -1: disable all active trip points in all thermal zones
2898 <degrees C>: override all lowest active trip points
2900 thermal.crt= [HW,ACPI]
2901 -1: disable all critical trip points in all thermal zones
2902 <degrees C>: override all critical trip points
2904 thermal.nocrt= [HW,ACPI]
2905 Set to disable actions on ACPI thermal zone
2906 critical and hot trip points.
2908 thermal.off= [HW,ACPI]
2909 1: disable ACPI thermal control
2911 thermal.psv= [HW,ACPI]
2912 -1: disable all passive trip points
2913 <degrees C>: override all passive trip points to this
2916 thermal.tzp= [HW,ACPI]
2917 Specify global default ACPI thermal zone polling rate
2918 <deci-seconds>: poll all this frequency
2919 0: no polling (default)
2922 Force threading of all interrupt handlers except those
2923 marked explicitly IRQF_NO_THREAD.
2927 Specify if the kernel should make use of the cpu
2928 topology information if the hardware supports this.
2929 The scheduler will make use of this information and
2930 e.g. base its process migration decisions on it.
2935 tpm_suspend_pcr=[HW,TPM]
2936 Format: integer pcr id
2937 Specify that at suspend time, the tpm driver
2938 should extend the specified pcr with zeros,
2939 as a workaround for some chips which fail to
2940 flush the last written pcr on TPM_SaveState.
2941 This will guarantee that all the other pcrs
2944 trace_buf_size=nn[KMG]
2945 [FTRACE] will set tracing buffer size.
2947 trace_event=[event-list]
2948 [FTRACE] Set and start specified trace events in order
2949 to facilitate early boot debugging.
2950 See also Documentation/trace/events.txt
2952 trace_options=[option-list]
2953 [FTRACE] Enable or disable tracer options at boot.
2954 The option-list is a comma delimited list of options
2955 that can be enabled or disabled just as if you were
2956 to echo the option name into
2958 /sys/kernel/debug/tracing/trace_options
2960 For example, to enable stacktrace option (to dump the
2961 stack trace of each event), add to the command line:
2963 trace_options=stacktrace
2965 See also Documentation/trace/ftrace.txt "trace options"
2968 transparent_hugepage=
2970 Format: [always|madvise|never]
2971 Can be used to control the default behavior of the system
2972 with respect to transparent hugepages.
2973 See Documentation/vm/transhuge.txt for more details.
2975 tsc= Disable clocksource stability checks for TSC.
2977 [x86] reliable: mark tsc clocksource as reliable, this
2978 disables clocksource verification at runtime, as well
2979 as the stability checks done at bootup. Used to enable
2980 high-resolution timer mode on older hardware, and in
2981 virtualized environment.
2982 [x86] noirqtime: Do not use TSC to do irq accounting.
2983 Used to run time disable IRQ_TIME_ACCOUNTING on any
2984 platforms where RDTSC is slow and this accounting
2987 turbografx.map[2|3]= [HW,JOY]
2988 TurboGraFX parallel port interface
2990 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2991 See also Documentation/input/joystick-parport.txt
2993 udbg-immortal [PPC] When debugging early kernel crashes that
2994 happen after console_init() and before a proper
2995 console driver takes over, this boot options might
2996 help "seeing" what's going on.
2998 uhash_entries= [KNL,NET]
2999 Set number of hash buckets for UDP/UDP-Lite connections
3002 [USB] Ignore overcurrent events (default N).
3003 Some badly-designed motherboards generate lots of
3004 bogus events, for ports that aren't wired to
3005 anything. Set this parameter to avoid log spamming.
3006 Note that genuine overcurrent events won't be
3010 [X86] Cause panic on unknown NMI.
3012 usbcore.authorized_default=
3013 [USB] Default USB device authorization:
3014 (default -1 = authorized except for wireless USB,
3015 0 = not authorized, 1 = authorized)
3017 usbcore.autosuspend=
3018 [USB] The autosuspend time delay (in seconds) used
3019 for newly-detected USB devices (default 2). This
3020 is the time required before an idle device will be
3021 autosuspended. Devices for which the delay is set
3022 to a negative value won't be autosuspended at all.
3024 usbcore.usbfs_snoop=
3025 [USB] Set to log all usbfs traffic (default 0 = off).
3027 usbcore.blinkenlights=
3028 [USB] Set to cycle leds on hubs (default 0 = off).
3030 usbcore.old_scheme_first=
3031 [USB] Start with the old device initialization
3032 scheme (default 0 = off).
3034 usbcore.usbfs_memory_mb=
3035 [USB] Memory limit (in MB) for buffers allocated by
3036 usbfs (default = 16, 0 = max = 2047).
3038 usbcore.use_both_schemes=
3039 [USB] Try the other device initialization scheme
3040 if the first one fails (default 1 = enabled).
3042 usbcore.initial_descriptor_timeout=
3043 [USB] Specifies timeout for the initial 64-byte
3044 USB_REQ_GET_DESCRIPTOR request in milliseconds
3045 (default 5000 = 5.0 seconds).
3048 [USBHID] The interval which mice are to be polled at.
3050 usb-storage.delay_use=
3051 [UMS] The delay in seconds before a new device is
3052 scanned for Logical Units (default 5).
3055 [UMS] A list of quirks entries to supplement or
3056 override the built-in unusual_devs list. List
3057 entries are separated by commas. Each entry has
3058 the form VID:PID:Flags where VID and PID are Vendor
3059 and Product ID values (4-digit hex numbers) and
3060 Flags is a set of characters, each corresponding
3061 to a common usb-storage quirk flag as follows:
3062 a = SANE_SENSE (collect more than 18 bytes
3064 b = BAD_SENSE (don't collect more than 18
3065 bytes of sense data);
3066 c = FIX_CAPACITY (decrease the reported
3067 device capacity by one sector);
3068 d = NO_READ_DISC_INFO (don't use
3069 READ_DISC_INFO command);
3070 e = NO_READ_CAPACITY_16 (don't use
3071 READ_CAPACITY_16 command);
3072 h = CAPACITY_HEURISTICS (decrease the
3073 reported device capacity by one
3074 sector if the number is odd);
3075 i = IGNORE_DEVICE (don't bind to this
3077 l = NOT_LOCKABLE (don't try to lock and
3078 unlock ejectable media);
3079 m = MAX_SECTORS_64 (don't transfer more
3080 than 64 sectors = 32 KB at a time);
3081 n = INITIAL_READ10 (force a retry of the
3082 initial READ(10) command);
3083 o = CAPACITY_OK (accept the capacity
3084 reported by the device);
3085 p = WRITE_CACHE (the device cache is ON
3087 r = IGNORE_RESIDUE (the device reports
3088 bogus residue values);
3089 s = SINGLE_LUN (the device has only one
3091 w = NO_WP_DETECT (don't test whether the
3092 medium is write-protected).
3093 Example: quirks=0419:aaf5:rl,0421:0433:rc
3095 user_debug= [KNL,ARM]
3097 See arch/arm/Kconfig.debug help text.
3098 1 - undefined instruction events
3100 4 - invalid data aborts
3103 Example: user_debug=31
3106 [X86] Flags controlling user PTE allocations.
3108 nohigh = do not allocate PTE pages in
3109 HIGHMEM regardless of setting
3113 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3114 vdso=1: enable VDSO (default)
3115 vdso=0: disable VDSO mapping
3118 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3119 vdso32=1: enable 32-bit VDSO (default)
3120 vdso32=0: disable 32-bit VDSO mapping
3123 vector=percpu: enable percpu vector domain
3125 video= [FB] Frame buffer configuration
3126 See Documentation/fb/modedb.txt.
3129 [VMMIO] Memory mapped virtio (platform) device.
3131 <size>@<baseaddr>:<irq>[:<id>]
3133 <size> := size (can use standard suffixes
3135 <baseaddr> := physical base address
3136 <irq> := interrupt number (as passed to
3138 <id> := (optional) platform device id
3140 virtio_mmio.device=1K@0x100b0000:48:7
3142 Can be used multiple times for multiple devices.
3144 vga= [BOOT,X86-32] Select a particular video mode
3145 See Documentation/x86/boot.txt and
3146 Documentation/svga.txt.
3147 Use vga=ask for menu.
3148 This is actually a boot loader parameter; the value is
3149 passed to the kernel using a special protocol.
3151 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3152 size of <nn>. This can be used to increase the
3153 minimum size (128MB on x86). It can also be used to
3154 decrease the size and leave more room for directly
3157 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3160 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3163 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3167 Controls the behavior of vsyscalls (i.e. calls to
3168 fixed addresses of 0xffffffffff600x00 from legacy
3169 code). Most statically-linked binaries and older
3170 versions of glibc use these calls. Because these
3171 functions are at fixed addresses, they make nice
3172 targets for exploits that can control RIP.
3174 emulate [default] Vsyscalls turn into traps and are
3175 emulated reasonably safely.
3177 native Vsyscalls are native syscall instructions.
3178 This is a little bit faster than trapping
3179 and makes a few dynamic recompilers work
3180 better than they would in emulation mode.
3181 It also makes exploits much easier to write.
3183 none Vsyscalls don't work at all. This makes
3184 them quite hard to use for exploits but
3185 might break your system.
3187 vt.cur_default= [VT] Default cursor shape.
3188 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3189 the parameters of the <Esc>[?A;B;Cc escape sequence;
3190 see VGA-softcursor.txt. Default: 2 = underline.
3192 vt.default_blu= [VT]
3193 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3194 Change the default blue palette of the console.
3195 This is a 16-member array composed of values
3198 vt.default_grn= [VT]
3199 Format: <green0>,<green1>,<green2>,...,<green15>
3200 Change the default green palette of the console.
3201 This is a 16-member array composed of values
3204 vt.default_red= [VT]
3205 Format: <red0>,<red1>,<red2>,...,<red15>
3206 Change the default red palette of the console.
3207 This is a 16-member array composed of values
3213 Set system-wide default UTF-8 mode for all tty's.
3214 Default is 1, i.e. UTF-8 mode is enabled for all
3215 newly opened terminals.
3217 vt.global_cursor_default=
3220 Set system-wide default for whether a cursor
3221 is shown on new VTs. Default is -1,
3222 i.e. cursors will be created by default unless
3223 overridden by individual drivers. 0 will hide
3224 cursors, 1 will display them.
3226 watchdog timers [HW,WDT] For information on watchdog timers,
3227 see Documentation/watchdog/watchdog-parameters.txt
3228 or other driver-specific files in the
3229 Documentation/watchdog/ directory.
3231 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3232 default x2apic cluster mode on platforms
3235 x86_mrst_timer= [X86-32,APBT]
3236 Choose timer option for x86 Moorestown MID platform.
3237 Two valid options are apbt timer only and lapic timer
3238 plus one apbt timer for broadcast timer.
3239 x86_mrst_timer=apbt_only | lapic_and_apbt
3241 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3242 xd_geo= See header of drivers/block/xd.c.
3244 xen_emul_unplug= [HW,X86,XEN]
3245 Unplug Xen emulated devices
3246 Format: [unplug0,][unplug1]
3247 ide-disks -- unplug primary master IDE devices
3248 aux-ide-disks -- unplug non-primary-master IDE devices
3249 nics -- unplug network devices
3250 all -- unplug all emulated devices (NICs and IDE disks)
3251 unnecessary -- unplugging emulated devices is
3252 unnecessary even if the host did not respond to
3254 never -- do not unplug even if version check succeeds
3256 xirc2ps_cs= [NET,PCMCIA]
3258 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3260 ______________________________________________________________________
3264 Add more DRM drivers.
projects / platform / adaptation / renesas_rcar / renesas_kernel.git / blob