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 alloc_snapshot [FTRACE]
324 Allocate the ftrace snapshot buffer on boot up when the
325 main buffer is allocated. This is handy if debugging
326 and you need to use tracing_snapshot() on boot up, and
327 do not want to use tracing_snapshot_alloc() as it needs
328 to be done where GFP_KERNEL allocations are allowed.
330 amd_iommu= [HW,X86-64]
331 Pass parameters to the AMD IOMMU driver in the system.
333 fullflush - enable flushing of IO/TLB entries when
334 they are unmapped. Otherwise they are
335 flushed before they will be reused, which
337 off - do not initialize any AMD IOMMU found in
339 force_isolation - Force device isolation for all
340 devices. The IOMMU driver is not
341 allowed anymore to lift isolation
342 requirements as needed. This option
343 does not override iommu=pt
345 amd_iommu_dump= [HW,X86-64]
346 Enable AMD IOMMU driver option to dump the ACPI table
347 for AMD IOMMU. With this option enabled, AMD IOMMU
348 driver will print ACPI tables for AMD IOMMU during
349 IOMMU initialization.
351 amijoy.map= [HW,JOY] Amiga joystick support
352 Map of devices attached to JOY0DAT and JOY1DAT
354 See also Documentation/input/joystick.txt
356 analog.map= [HW,JOY] Analog joystick and gamepad support
357 Specifies type or capabilities of an analog joystick
358 connected to one of 16 gameports
359 Format: <type1>,<type2>,..<type16>
362 Power management functions (SPARCstation-4/5 + deriv.)
364 Disable APC CPU standby support. SPARCstation-Fox does
365 not play well with APC CPU idle - disable it if you have
366 APC and your system crashes randomly.
368 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
369 Change the output verbosity whilst booting
370 Format: { quiet (default) | verbose | debug }
371 Change the amount of debugging information output
372 when initialising the APIC and IO-APIC components.
375 See Documentation/networking/ipv6.txt.
377 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
378 Limit apic dumping. The parameter defines the maximal
379 number of local apics being dumped. Also it is possible
380 to set it to "all" by meaning -- no limit here.
381 Format: { 1 (default) | 2 | ... | all }.
382 The parameter valid if only apic=debug or
383 apic=verbose is specified.
384 Example: apic=debug show_lapic=all
386 apm= [APM] Advanced Power Management
387 See header of arch/x86/kernel/apm_32.c.
389 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
390 Format: <io>,<irq>,<nodeID>
394 atarimouse= [HW,MOUSE] Atari Mouse
396 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
397 EzKey and similar keyboards
399 atkbd.reset= [HW] Reset keyboard during initialization
401 atkbd.set= [HW] Select keyboard code set
402 Format: <int> (2 = AT (default), 3 = PS/2)
404 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
407 atkbd.softraw= [HW] Choose between synthetic and real raw mode
408 Format: <bool> (0 = real, 1 = synthetic (default))
410 atkbd.softrepeat= [HW]
411 Use software keyboard repeat
413 baycom_epp= [HW,AX25]
416 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
418 See header of drivers/net/hamradio/baycom_par.c.
420 baycom_ser_fdx= [HW,AX25]
421 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
422 Format: <io>,<irq>,<mode>[,<baud>]
423 See header of drivers/net/hamradio/baycom_ser_fdx.c.
425 baycom_ser_hdx= [HW,AX25]
426 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
427 Format: <io>,<irq>,<mode>
428 See header of drivers/net/hamradio/baycom_ser_hdx.c.
430 boot_delay= Milliseconds to delay each printk during boot.
431 Values larger than 10 seconds (10000) are changed to
435 bootmem_debug [KNL] Enable bootmem allocator debug messages.
437 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
438 bttv.radio= Most important insmod options are available as
440 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
443 bulk_remove=off [PPC] This parameter disables the use of the pSeries
444 firmware feature for flushing multiple hpte entries
447 c101= [NET] Moxa C101 synchronous serial card
449 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
450 Sometimes CPU hardware bugs make them report the cache
451 size incorrectly. The kernel will attempt work arounds
452 to fix known problems, but for some CPUs it is not
453 possible to determine what the correct size should be.
454 This option provides an override for these situations.
456 ccw_timeout_log [S390]
457 See Documentation/s390/CommonIO for details.
459 cgroup_disable= [KNL] Disable a particular controller
460 Format: {name of the controller(s) to disable}
461 {Currently supported controllers - "memory"}
463 checkreqprot [SELINUX] Set initial checkreqprot flag value.
464 Format: { "0" | "1" }
465 See security/selinux/Kconfig help text.
466 0 -- check protection applied by kernel (includes
467 any implied execute protection).
468 1 -- check protection requested by application.
469 Default value is set via a kernel config option.
470 Value can be changed at runtime via
471 /selinux/checkreqprot.
474 See Documentation/s390/CommonIO for details.
476 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
478 Forces specified clocksource (if available) to be used
479 when calculating gettimeofday(). If specified
480 clocksource is not available, it defaults to PIT.
481 Format: { pit | tsc | cyclone | pmtmr }
483 clocksource= Override the default clocksource
485 Override the default clocksource and use the clocksource
486 with the name specified.
487 Some clocksource names to choose from, depending on
489 [all] jiffies (this is the base, fallback clocksource)
491 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
492 pxa_timer,timer3,32k_counter,timer0_1
494 [X86-32] pit,hpet,tsc;
495 scx200_hrt on Geode; cyclone on IBM x440
503 clearcpuid=BITNUM [X86]
504 Disable CPUID feature X for the kernel. See
505 arch/x86/include/asm/cpufeature.h for the valid bit
506 numbers. Note the Linux specific bits are not necessarily
507 stable over kernel options, but the vendor specific
509 Also note that user programs calling CPUID directly
510 or using the feature without checking anything
511 will still see it. This just prevents it from
512 being used by the kernel or shown in /proc/cpuinfo.
513 Also note the kernel might malfunction if you disable
517 Sets the size of kernel global memory area for contiguous
518 memory allocations. For more information, see
519 include/linux/dma-contiguous.h
521 cmo_free_hint= [PPC] Format: { yes | no }
522 Specify whether pages are marked as being inactive
523 when they are freed. This is used in CMO environments
524 to determine OS memory pressure for page stealing by
528 coherent_pool=nn[KMG] [ARM,KNL]
529 Sets the size of memory pool for coherent, atomic dma
530 allocations, by default set to 256K.
532 code_bytes [X86] How many bytes of object code to print
537 com20020= [HW,NET] ARCnet - COM20020 chipset
539 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
541 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
545 ARCnet - COM90xx chipset (memory-mapped buffers)
546 Format: <io>[,<irq>[,<memstart>]]
548 condev= [HW,S390] console device
551 console= [KNL] Output console device and options.
553 tty<n> Use the virtual console device <n>.
557 Use the specified serial port. The options are of
558 the form "bbbbpnf", where "bbbb" is the baud rate,
559 "p" is parity ("n", "o", or "e"), "n" is number of
560 bits, and "f" is flow control ("r" for RTS or
561 omit it). Default is "9600n8".
563 See Documentation/serial-console.txt for more
565 Documentation/networking/netconsole.txt for an
568 uart[8250],io,<addr>[,options]
569 uart[8250],mmio,<addr>[,options]
570 Start an early, polled-mode console on the 8250/16550
571 UART at the specified I/O port or MMIO address,
572 switching to the matching ttyS device later. The
573 options are the same as for ttyS, above.
575 If the device connected to the port is not a TTY but a braille
576 device, prepend "brl," before the device type, for instance
578 For now, only VisioBraille is supported.
580 consoleblank= [KNL] The console blank (screen saver) timeout in
581 seconds. Defaults to 10*60 = 10mins. A value of 0
582 disables the blank timer.
585 [KNL] Change the default value for
586 /proc/<pid>/coredump_filter.
587 See also Documentation/filesystems/proc.txt.
589 cpuidle.off=1 [CPU_IDLE]
590 disable the cpuidle sub-system
592 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
594 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
596 crashkernel=size[KMG][@offset[KMG]]
597 [KNL] Using kexec, Linux can switch to a 'crash kernel'
598 upon panic. This parameter reserves the physical
599 memory region [offset, offset + size] for that kernel
600 image. If '@offset' is omitted, then a suitable offset
601 is selected automatically. Check
602 Documentation/kdump/kdump.txt for further details.
604 crashkernel=range1:size1[,range2:size2,...][@offset]
605 [KNL] Same as above, but depends on the memory
606 in the running system. The syntax of range is
607 start-[end] where start and end are both
608 a memory unit (amount[KMG]). See also
609 Documentation/kdump/kdump.txt for an example.
614 cs89x0_media= [HW,NET]
615 Format: { rj45 | aui | bnc }
618 See header of drivers/s390/block/dasd_devmap.c.
620 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
621 (one device per port)
622 Format: <port#>,<type>
623 See also Documentation/input/joystick-parport.txt
625 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
626 time. See Documentation/dynamic-debug-howto.txt for
627 details. Deprecated, see dyndbg.
629 debug [KNL] Enable kernel debugging (events log level).
632 [KNL] verbose self-tests
634 Print debugging info while doing the locking API
636 We default to 0 (no extra messages), setting it to
637 1 will print _a lot_ more information - normally
638 only useful to kernel developers.
640 debug_objects [KNL] Enable object debugging
643 [KNL] Disable object debugging
645 debug_guardpage_minorder=
646 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
647 parameter allows control of the order of pages that will
648 be intentionally kept free (and hence protected) by the
649 buddy allocator. Bigger value increase the probability
650 of catching random memory corruption, but reduce the
651 amount of memory for normal system use. The maximum
652 possible value is MAX_ORDER/2. Setting this parameter
653 to 1 or 2 should be enough to identify most random
654 memory corruption problems caused by bugs in kernel or
655 driver code when a CPU writes to (or reads from) a
656 random memory location. Note that there exists a class
657 of memory corruptions problems caused by buggy H/W or
658 F/W or by drivers badly programing DMA (basically when
659 memory is written at bus level and the CPU MMU is
660 bypassed) which are not detectable by
661 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
662 tracking down these problems.
664 debugpat [X86] Enable PAT debugging
666 decnet.addr= [HW,NET]
667 Format: <area>[,<node>]
668 See also Documentation/networking/decnet.txt.
671 [same as hugepagesz=] The size of the default
672 HugeTLB page size. This is the size represented by
673 the legacy /proc/ hugepages APIs, used for SHM, and
674 default size when mounting hugetlbfs filesystems.
675 Defaults to the default architecture's huge page size
679 Set number of hash buckets for dentry cache.
682 IO parameters + enable/disable command.
684 digiepca= [HW,SERIAL]
685 See drivers/char/README.epca and
686 Documentation/serial/digiepca.txt.
689 See Documentation/networking/ipv6.txt.
691 disable_ddw [PPC/PSERIES]
692 Disable Dynamic DMA Window support. Use this if
693 to workaround buggy firmware.
696 See Documentation/networking/ipv6.txt.
698 disable_mtrr_cleanup [X86]
699 The kernel tries to adjust MTRR layout from continuous
700 to discrete, to make X server driver able to add WB
701 entry later. This parameter disables that.
703 disable_mtrr_trim [X86, Intel and AMD only]
704 By default the kernel will trim any uncacheable
705 memory out of your available memory pool based on
706 MTRR settings. This parameter disables that behavior,
707 possibly causing your machine to run very slowly.
709 disable_timer_pin_1 [X86]
710 Disable PIN 1 of APIC timer
711 Can be useful to work around chipset bugs.
713 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
714 this option disables the debugging code at boot.
716 dma_debug_entries=<number>
717 This option allows to tune the number of preallocated
718 entries for DMA-API debugging code. One entry is
719 required per DMA-API allocation. Use this if the
720 DMA-API debugging code disables itself because the
721 architectural default is too low.
723 dma_debug_driver=<driver_name>
724 With this option the DMA-API debugging driver
725 filter feature can be enabled at boot time. Just
726 pass the driver to filter for as the parameter.
727 The filter can be disabled or changed to another
728 driver later using sysfs.
730 drm_kms_helper.edid_firmware=[<connector>:]<file>
731 Broken monitors, graphic adapters and KVMs may
732 send no or incorrect EDID data sets. This parameter
733 allows to specify an EDID data set in the
734 /lib/firmware directory that is used instead.
735 Generic built-in EDID data sets are used, if one of
736 edid/1024x768.bin, edid/1280x1024.bin,
737 edid/1680x1050.bin, or edid/1920x1080.bin is given
738 and no file with the same name exists. Details and
739 instructions how to build your own EDID data are
740 available in Documentation/EDID/HOWTO.txt. An EDID
741 data set will only be used for a particular connector,
742 if its name and a colon are prepended to the EDID
747 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
748 module.dyndbg[="val"]
749 Enable debug messages at boot time. See
750 Documentation/dynamic-debug-howto.txt for details.
752 earlycon= [KNL] Output early console device and options.
753 uart[8250],io,<addr>[,options]
754 uart[8250],mmio,<addr>[,options]
755 uart[8250],mmio32,<addr>[,options]
756 Start an early, polled-mode console on the 8250/16550
757 UART at the specified I/O port or MMIO address.
758 MMIO inter-register address stride is either 8-bit
759 (mmio) or 32-bit (mmio32).
760 The options are the same as for ttyS, above.
762 earlyprintk= [X86,SH,BLACKFIN]
764 earlyprintk=serial[,ttySn[,baudrate]]
765 earlyprintk=ttySn[,baudrate]
766 earlyprintk=dbgp[debugController#]
768 Append ",keep" to not disable it when the real console
771 Only vga or serial or usb debug port at a time.
773 Currently only ttyS0 and ttyS1 are supported.
775 Interaction with the standard serial driver is not
778 The VGA output is eventually overwritten by the real
781 ekgdboc= [X86,KGDB] Allow early kernel console debugging
784 This is designed to be used in conjunction with
785 the boot argument: earlyprintk=vga
788 Format: {"off" | "on" | "skip[mbr]"}
790 eisa_irq_edge= [PARISC,HW]
791 See header of drivers/parisc/eisa.c.
794 See comment before function elanfreq_setup() in
795 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
798 Format: {"cfq" | "deadline" | "noop"}
799 See Documentation/block/cfq-iosched.txt and
800 Documentation/block/deadline-iosched.txt for details.
802 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
803 Specifies physical address of start of kernel core
804 image elf header and optionally the size. Generally
805 kexec loader will pass this option to capture kernel.
806 See Documentation/kdump/kdump.txt for details.
808 enable_mtrr_cleanup [X86]
809 The kernel tries to adjust MTRR layout from continuous
810 to discrete, to make X server driver able to add WB
811 entry later. This parameter enables that.
813 enable_timer_pin_1 [X86]
814 Enable PIN 1 of APIC timer
815 Can be useful to work around chipset bugs
816 (in particular on some ATI chipsets).
817 The kernel tries to set a reasonable default.
819 enforcing [SELINUX] Set initial enforcing status.
821 See security/selinux/Kconfig help text.
822 0 -- permissive (log only, no denials).
823 1 -- enforcing (deny and log).
825 Value can be changed at runtime via /selinux/enforce.
828 Disable Error Record Serialization Table (ERST)
831 ether= [HW,NET] Ethernet cards parameters
832 This option is obsoleted by the "netdev=" option, which
833 has equivalent usage. See its documentation for details.
837 Permit 'security.evm' to be updated regardless of
838 current integrity status.
842 fail_make_request=[KNL]
843 General fault injection mechanism.
844 Format: <interval>,<probability>,<space>,<times>
845 See also Documentation/fault-injection/.
848 See Documentation/blockdev/floppy.txt.
850 force_pal_cache_flush
851 [IA-64] Avoid check_sal_cache_flush which may hang on
852 buggy SAL_CACHE_FLUSH implementations. Using this
853 parameter will force ia64_sal_cache_flush to call
854 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
857 [FTRACE] will set and start the specified tracer
858 as early as possible in order to facilitate early
861 ftrace_dump_on_oops[=orig_cpu]
862 [FTRACE] will dump the trace buffers on oops.
863 If no parameter is passed, ftrace will dump
864 buffers of all CPUs, but if you pass orig_cpu, it will
865 dump only the buffer of the CPU that triggered the
868 ftrace_filter=[function-list]
869 [FTRACE] Limit the functions traced by the function
870 tracer at boot up. function-list is a comma separated
871 list of functions. This list can be changed at run
872 time by the set_ftrace_filter file in the debugfs
875 ftrace_notrace=[function-list]
876 [FTRACE] Do not trace the functions specified in
877 function-list. This list can be changed at run time
878 by the set_ftrace_notrace file in the debugfs
881 ftrace_graph_filter=[function-list]
882 [FTRACE] Limit the top level callers functions traced
883 by the function graph tracer at boot up.
884 function-list is a comma separated list of functions
885 that can be changed at run time by the
886 set_graph_function file in the debugfs tracing directory.
889 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
890 support via parallel port (up to 5 devices per port)
891 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
892 See also Documentation/input/joystick-parport.txt
896 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
900 gcov_persist= [GCOV] When non-zero (default), profiling data for
901 kernel modules is saved and remains accessible via
902 debugfs, even when the module is unloaded/reloaded.
903 When zero, profiling data is discarded and associated
904 debugfs files are removed at module unload time.
906 gpt [EFI] Forces disk with valid GPT signature but
907 invalid Protective MBR to be treated as GPT.
909 grcan.enable0= [HW] Configuration of physical interface 0. Determines
910 the "Enable 0" bit of the configuration register.
913 grcan.enable1= [HW] Configuration of physical interface 1. Determines
914 the "Enable 0" bit of the configuration register.
917 grcan.select= [HW] Select which physical interface to use.
920 grcan.txsize= [HW] Sets the size of the tx buffer.
921 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
923 grcan.rxsize= [HW] Sets the size of the rx buffer.
924 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
927 hashdist= [KNL,NUMA] Large hashes allocated during boot
928 are distributed across NUMA nodes. Defaults on
929 for 64-bit NUMA, off otherwise.
930 Format: 0 | 1 (for off | on)
932 hcl= [IA-64] SGI's Hardware Graph compatibility layer
934 hd= [EIDE] (E)IDE hard drive subsystem geometry
935 Format: <cyl>,<head>,<sect>
938 Disable Hardware Error Source Table (HEST) support;
939 corresponding firmware-first mode error processing
940 logic will be disabled.
942 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
943 size of <nn>. This works even on boxes that have no
944 highmem otherwise. This also works to reduce highmem
945 size on bigger boxes.
947 highres= [KNL] Enable/disable high resolution timer mode.
948 Valid parameters: "on", "off"
952 See Documentation/isdn/README.HiSax.
956 hpet= [X86-32,HPET] option to control HPET usage
957 Format: { enable (default) | disable | force |
959 disable: disable HPET and use PIT instead
960 force: allow force enabled of undocumented chips (ICH4,
962 verbose: show contents of HPET registers during setup
964 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
965 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
966 On x86-64 and powerpc, this option can be specified
967 multiple times interleaved with hugepages= to reserve
968 huge pages of different sizes. Valid pages sizes on
969 x86-64 are 2M (when the CPU supports "pse") and 1G
970 (when the CPU supports the "pdpe1gb" cpuinfo flag)
971 Note that 1GB pages can only be allocated at boot time
972 using hugepages= and not freed afterwards.
974 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
975 terminal devices. Valid values: 0..8
976 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
977 If specified, z/VM IUCV HVC accepts connections
978 from listed z/VM user IDs only.
981 Do not unregister boot console at start. This is only
982 useful for debugging when something happens in the window
983 between unregistering the boot console and initializing
986 i2c_bus= [HW] Override the default board specific I2C bus speed
987 or register an additional I2C bus that is not
988 registered from board initialization code.
992 i8042.debug [HW] Toggle i8042 debug mode
993 i8042.direct [HW] Put keyboard port into non-translated mode
994 i8042.dumbkbd [HW] Pretend that controller can only read data from
995 keyboard and cannot control its state
996 (Don't attempt to blink the leds)
997 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
998 i8042.nokbd [HW] Don't check/create keyboard port
999 i8042.noloop [HW] Disable the AUX Loopback command while probing
1001 i8042.nomux [HW] Don't check presence of an active multiplexing
1003 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1005 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1006 i8042.reset [HW] Reset the controller during init and cleanup
1007 i8042.unlock [HW] Unlock (ignore) the keylock
1011 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1012 indicates that the driver is running on unsupported
1014 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1015 does not match list of supported models.
1017 [HW] Report power status in /proc/i8k
1018 (disabled by default)
1019 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1022 i915.invert_brightness=
1023 [DRM] Invert the sense of the variable that is used to
1024 set the brightness of the panel backlight. Normally a
1025 brightness value of 0 indicates backlight switched off,
1026 and the maximum of the brightness value sets the backlight
1027 to maximum brightness. If this parameter is set to 0
1028 (default) and the machine requires it, or this parameter
1029 is set to 1, a brightness value of 0 sets the backlight
1030 to maximum brightness, and the maximum of the brightness
1031 value switches the backlight off.
1032 -1 -- never invert brightness
1033 0 -- machine default
1034 1 -- force brightness inversion
1037 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1039 ide-core.nodma= [HW] (E)IDE subsystem
1040 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1041 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1042 .cdrom .chs .ignore_cable are additional options
1043 See Documentation/ide/ide.txt.
1045 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1046 Claim all unknown PCI IDE storage controllers.
1049 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1050 Poll forces a polling idle loop that can slightly
1051 improve the performance of waking up a idle CPU, but
1052 will use a lot of power and make the system run hot.
1054 idle=mwait: On systems which support MONITOR/MWAIT but
1055 the kernel chose to not use it because it doesn't save
1056 as much power as a normal idle loop, use the
1057 MONITOR/MWAIT idle loop anyways. Performance should be
1058 the same as idle=poll.
1059 idle=halt: Halt is forced to be used for CPU idle.
1060 In such case C2/C3 won't be used again.
1061 idle=nomwait: Disable mwait for CPU C-states
1063 ignore_loglevel [KNL]
1064 Ignore loglevel setting - this will print /all/
1065 kernel messages to the console. Useful for debugging.
1066 We also add it as printk module parameter, so users
1067 could change it dynamically, usually by
1068 /sys/module/printk/parameters/ignore_loglevel.
1070 ihash_entries= [KNL]
1071 Set number of hash buckets for inode cache.
1073 ima_appraise= [IMA] appraise integrity measurements
1074 Format: { "off" | "enforce" | "fix" }
1077 ima_appraise_tcb [IMA]
1078 The builtin appraise policy appraises all files
1082 Format: { "0" | "1" }
1083 0 -- integrity auditing messages. (Default)
1084 1 -- enable informational integrity auditing messages.
1087 Format: { "sha1" | "md5" }
1091 Load a policy which meets the needs of the Trusted
1092 Computing Base. This means IMA will measure all
1093 programs exec'd, files mmap'd for exec, and all files
1094 opened for read by uid=0.
1098 Run specified binary instead of /sbin/init as init
1101 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1102 for working out where the kernel is dying during
1105 initrd= [BOOT] Specify the location of the initial ramdisk
1107 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1110 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1112 Enable intel iommu driver.
1114 Disable intel iommu driver.
1115 igfx_off [Default Off]
1116 By default, gfx is mapped as normal device. If a gfx
1117 device has a dedicated DMAR unit, the DMAR unit is
1118 bypassed by not enabling DMAR with this option. In
1119 this case, gfx device will use physical address for
1122 With this option iommu will not optimize to look
1123 for io virtual address below 32-bit forcing dual
1124 address cycle on pci bus for cards supporting greater
1125 than 32-bit addressing. The default is to look
1126 for translation below 32-bit and if not available
1127 then look in the higher range.
1128 strict [Default Off]
1129 With this option on every unmap_single operation will
1130 result in a hardware IOTLB flush operation as opposed
1131 to batching them for performance.
1132 sp_off [Default Off]
1133 By default, super page will be supported if Intel IOMMU
1134 has the capability. With this option, super page will
1137 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1138 0 disables intel_idle and fall back on acpi_idle.
1139 1 to 6 specify maximum depth of C-state.
1141 intremap= [X86-64, Intel-IOMMU]
1142 on enable Interrupt Remapping (default)
1143 off disable Interrupt Remapping
1144 nosid disable Source ID checking
1146 BIOS x2APIC opt-out request will be ignored
1148 iomem= Disable strict checking of access to MMIO memory
1149 strict regions from userspace.
1166 io7= [HW] IO7 for Marvel based alpha systems
1167 See comment before marvel_specify_io7 in
1168 arch/alpha/kernel/core_marvel.c.
1170 io_delay= [X86] I/O delay method
1172 Standard port 0x80 based delay
1174 Alternate port 0xed based delay (needed on some systems)
1176 Simple two microseconds delay
1181 See Documentation/filesystems/nfs/nfsroot.txt.
1183 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1184 See comment before ip2_setup() in
1185 drivers/char/ip2/ip2base.c.
1188 When an interrupt is not handled search all handlers
1189 for it. Intended to get systems with badly broken
1193 When an interrupt is not handled search all handlers
1194 for it. Also check all handlers each timer
1195 interrupt. Intended to get systems with badly broken
1199 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1201 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1203 <cpu number>,...,<cpu number>
1205 <cpu number>-<cpu number>
1206 (must be a positive range in ascending order)
1208 <cpu number>,...,<cpu number>-<cpu number>
1210 This option can be used to specify one or more CPUs
1211 to isolate from the general SMP balancing and scheduling
1212 algorithms. You can move a process onto or off an
1213 "isolated" CPU via the CPU affinity syscalls or cpuset.
1214 <cpu number> begins at 0 and the maximum value is
1215 "number of CPUs in system - 1".
1217 This option is the preferred way to isolate CPUs. The
1218 alternative -- manually setting the CPU mask of all
1219 tasks in the system -- can cause problems and
1220 suboptimal load balancer performance.
1224 js= [HW,JOY] Analog joystick
1225 See Documentation/input/joystick.txt.
1229 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1230 specifies the amount of memory usable by the kernel
1231 for non-movable allocations. The requested amount is
1232 spread evenly throughout all nodes in the system. The
1233 remaining memory in each node is used for Movable
1234 pages. In the event, a node is too small to have both
1235 kernelcore and Movable pages, kernelcore pages will
1236 take priority and other nodes will have a larger number
1237 of kernelcore pages. The Movable zone is used for the
1238 allocation of pages that may be reclaimed or moved
1239 by the page migration subsystem. This means that
1240 HugeTLB pages may not be allocated from this zone.
1241 Note that allocations like PTEs-from-HighMem still
1242 use the HighMem zone if it exists, and the Normal
1243 zone if it does not.
1245 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1246 Format: <Controller#>[,poll interval]
1247 The controller # is the number of the ehci usb debug
1248 port as it is probed via PCI. The poll interval is
1249 optional and is the number seconds in between
1250 each poll cycle to the debug port in case you need
1251 the functionality for interrupting the kernel with
1252 gdb or control-c on the dbgp connection. When
1253 not using this parameter you use sysrq-g to break into
1254 the kernel debugger.
1256 kgdboc= [KGDB,HW] kgdb over consoles.
1257 Requires a tty driver that supports console polling,
1258 or a supported polling keyboard driver (non-usb).
1259 Serial only format: <serial_device>[,baud]
1260 keyboard only format: kbd
1261 keyboard and serial format: kbd,<serial_device>[,baud]
1262 Optional Kernel mode setting:
1263 kms, kbd format: kms,kbd
1264 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1266 kgdbwait [KGDB] Stop kernel execution and enter the
1267 kernel debugger at the earliest opportunity.
1269 kmac= [MIPS] korina ethernet MAC address.
1270 Configure the RouterBoard 532 series on-chip
1271 Ethernet adapter MAC address.
1273 kmemleak= [KNL] Boot-time kmemleak enable/disable
1274 Valid arguments: on, off
1277 kstack=N [X86] Print N words from the kernel stack
1280 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1281 Default is 0 (don't ignore, but inject #GP)
1283 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1287 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1288 Default is 1 (enabled)
1290 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1292 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1294 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1295 (virtualized MMU) support on capable Intel chips.
1296 Default is 1 (enabled)
1298 kvm-intel.emulate_invalid_guest_state=
1299 [KVM,Intel] Enable emulation of invalid guest states
1300 Default is 0 (disabled)
1302 kvm-intel.flexpriority=
1303 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1304 Default is 1 (enabled)
1307 [KVM,Intel] Enable VMX nesting (nVMX).
1308 Default is 0 (disabled)
1310 kvm-intel.unrestricted_guest=
1311 [KVM,Intel] Disable unrestricted guest feature
1312 (virtualized real and unpaged mode) on capable
1313 Intel chips. Default is 1 (enabled)
1315 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1316 feature (tagged TLBs) on capable Intel chips.
1317 Default is 1 (enabled)
1323 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1326 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1327 value for LAPIC timer one-shot implementation. Default
1328 back to the programmable timer unit in the LAPIC.
1330 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1333 libata.dma= [LIBATA] DMA control
1334 libata.dma=0 Disable all PATA and SATA DMA
1335 libata.dma=1 PATA and SATA Disk DMA only
1336 libata.dma=2 ATAPI (CDROM) DMA only
1337 libata.dma=4 Compact Flash DMA only
1338 Combinations also work, so libata.dma=3 enables DMA
1339 for disks and CDROMs, but not CFs.
1341 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1342 libata.ignore_hpa=0 keep BIOS limits (default)
1343 libata.ignore_hpa=1 ignore limits, using full disk
1345 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1349 libata.force= [LIBATA] Force configurations. The format is comma
1350 separated list of "[ID:]VAL" where ID is
1351 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1352 matching port, link or device. Basically, it matches
1353 the ATA ID string printed on console by libata. If
1354 the whole ID part is omitted, the last PORT and DEVICE
1355 values are used. If ID hasn't been specified yet, the
1356 configuration applies to all ports, links and devices.
1358 If only DEVICE is omitted, the parameter applies to
1359 the port and all links and devices behind it. DEVICE
1360 number of 0 either selects the first device or the
1361 first fan-out link behind PMP device. It does not
1362 select the host link. DEVICE number of 15 selects the
1363 host link and device attached to it.
1365 The VAL specifies the configuration to force. As long
1366 as there's no ambiguity shortcut notation is allowed.
1367 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1368 The following configurations can be forced.
1370 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1371 Any ID with matching PORT is used.
1373 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1375 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1376 udma[/][16,25,33,44,66,100,133] notation is also
1379 * [no]ncq: Turn on or off NCQ.
1381 * nohrst, nosrst, norst: suppress hard, soft
1384 * rstonce: only attempt one reset during
1385 hot-unplug link recovery
1387 * dump_id: dump IDENTIFY data.
1389 If there are multiple matching configurations changing
1390 the same attribute, the last one is used.
1392 memblock=debug [KNL] Enable memblock debug messages.
1394 load_ramdisk= [RAM] List of ramdisks to load from floppy
1395 See Documentation/blockdev/ramdisk.txt.
1397 lockd.nlm_grace_period=P [NFS] Assign grace period.
1400 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1403 lockd.nlm_timeout=T [NFS] Assign timeout value.
1406 lockd.nlm_udpport=M [NFS] Assign UDP port.
1409 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1412 loglevel= All Kernel Messages with a loglevel smaller than the
1413 console loglevel will be printed to the console. It can
1414 also be changed with klogd or other programs. The
1415 loglevels are defined as follows:
1417 0 (KERN_EMERG) system is unusable
1418 1 (KERN_ALERT) action must be taken immediately
1419 2 (KERN_CRIT) critical conditions
1420 3 (KERN_ERR) error conditions
1421 4 (KERN_WARNING) warning conditions
1422 5 (KERN_NOTICE) normal but significant condition
1423 6 (KERN_INFO) informational
1424 7 (KERN_DEBUG) debug-level messages
1426 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1427 in bytes. n must be a power of two. The default
1428 size is set in the kernel config file.
1430 logo.nologo [FB] Disables display of the built-in Linux logo.
1431 This may be used to provide more screen space for
1432 kernel log messages and is useful when debugging
1433 kernel boot problems.
1435 lp=0 [LP] Specify parallel ports to use, e.g,
1436 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1437 lp=reset first parallel port). 'lp=0' disables the
1438 lp=auto printer driver. 'lp=reset' (which can be
1439 specified in addition to the ports) causes
1440 attached printers to be reset. Using
1441 lp=port1,port2,... specifies the parallel ports
1442 to associate lp devices with, starting with
1443 lp0. A port specification may be 'none' to skip
1444 that lp device, or a parport name such as
1445 'parport0'. Specifying 'lp=auto' instead of a
1446 port specification list means that device IDs
1447 from each port should be examined, to see if
1448 an IEEE 1284-compliant printer is attached; if
1449 so, the driver will manage that printer.
1450 See also header of drivers/char/lp.c.
1453 Sets loops_per_jiffy to given constant, thus avoiding
1454 time-consuming boot-time autodetection (up to 250 ms per
1455 CPU). 0 enables autodetection (default). To determine
1456 the correct value for your kernel, boot with normal
1457 autodetection and see what value is printed. Note that
1458 on SMP systems the preset will be applied to all CPUs,
1459 which is likely to cause problems if your CPUs need
1460 significantly divergent settings. An incorrect value
1461 will cause delays in the kernel to be wrong, leading to
1462 unpredictable I/O errors and other breakage. Although
1463 unlikely, in the extreme case this might damage your
1467 Format: <io>,<irq>,<dma>
1469 machvec= [IA-64] Force the use of a particular machine-vector
1470 (machvec) in a generic kernel.
1471 Example: machvec=hpzx1_swiotlb
1473 machtype= [Loongson] Share the same kernel image file between different
1475 Example: machtype=lemote-yeeloong-2f-7inch
1477 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1478 than or equal to this physical address is ignored.
1480 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1481 should make use of. maxcpus=n : n >= 0 limits the
1482 kernel to using 'n' processors. n=0 is a special case,
1483 it is equivalent to "nosmp", which also disables
1486 max_loop= [LOOP] The number of loop block devices that get
1487 (loop.max_loop) unconditionally pre-created at init time. The default
1488 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1489 of statically allocating a predefined number, loop
1490 devices can be requested on-demand with the
1491 /dev/loop-control interface.
1493 mce [X86-32] Machine Check Exception
1495 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1497 md= [HW] RAID subsystems devices and level
1498 See Documentation/md.txt.
1501 Format: <first>,<last>
1502 Specifies range of consoles to be captured by the MDA.
1504 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1505 Amount of memory to be used when the kernel is not able
1506 to see the whole system memory or for test.
1507 [X86] Work as limiting max address. Use together
1508 with memmap= to avoid physical address space collisions.
1509 Without memmap= PCI devices could be placed at addresses
1510 belonging to unused RAM.
1512 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1516 [KNL,SH] Allow user to override the default size for
1517 per-device physically contiguous DMA buffers.
1519 memmap=exactmap [KNL,X86] Enable setting of an exact
1520 E820 memory map, as specified by the user.
1521 Such memmap=exactmap lines can be constructed based on
1522 BIOS output or other requirements. See the memmap=nn@ss
1525 memmap=nn[KMG]@ss[KMG]
1526 [KNL] Force usage of a specific region of memory
1527 Region of memory to be used, from ss to ss+nn.
1529 memmap=nn[KMG]#ss[KMG]
1530 [KNL,ACPI] Mark specific memory as ACPI data.
1531 Region of memory to be used, from ss to ss+nn.
1533 memmap=nn[KMG]$ss[KMG]
1534 [KNL,ACPI] Mark specific memory as reserved.
1535 Region of memory to be used, from ss to ss+nn.
1536 Example: Exclude memory from 0x18690000-0x1869ffff
1537 memmap=64K$0x18690000
1539 memmap=0x10000$0x18690000
1541 memory_corruption_check=0/1 [X86]
1542 Some BIOSes seem to corrupt the first 64k of
1543 memory when doing things like suspend/resume.
1544 Setting this option will scan the memory
1545 looking for corruption. Enabling this will
1546 both detect corruption and prevent the kernel
1547 from using the memory being corrupted.
1548 However, its intended as a diagnostic tool; if
1549 repeatable BIOS-originated corruption always
1550 affects the same memory, you can use memmap=
1551 to prevent the kernel from using that memory.
1553 memory_corruption_check_size=size [X86]
1554 By default it checks for corruption in the low
1555 64k, making this memory unavailable for normal
1556 use. Use this parameter to scan for
1557 corruption in more or less memory.
1559 memory_corruption_check_period=seconds [X86]
1560 By default it checks for corruption every 60
1561 seconds. Use this parameter to check at some
1562 other rate. 0 disables periodic checking.
1564 memtest= [KNL,X86] Enable memtest
1566 default : 0 <disable>
1567 Specifies the number of memtest passes to be
1568 performed. Each pass selects another test
1569 pattern from a given set of patterns. Memtest
1570 fills the memory with this pattern, validates
1571 memory contents and reserves bad memory
1572 regions that are detected.
1574 meye.*= [HW] Set MotionEye Camera parameters
1575 See Documentation/video4linux/meye.txt.
1577 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1578 Multi-Function General Purpose Timers on AMD Geode
1581 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1582 the BIOS has incorrectly applied a workaround. TinyBIOS
1583 version 0.98 is known to be affected, 0.99 fixes the
1584 problem by letting the user disable the workaround.
1588 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1589 physical address is ignored.
1591 mini2440= [ARM,HW,KNL]
1592 Format:[0..2][b][c][t]
1594 MINI2440 configuration specification:
1595 0 - The attached screen is the 3.5" TFT
1596 1 - The attached screen is the 7" TFT
1597 2 - The VGA Shield is attached (1024x768)
1598 Leaving out the screen size parameter will not load
1599 the TFT driver, and the framebuffer will be left
1601 b - Enable backlight. The TFT backlight pin will be
1602 linked to the kernel VESA blanking code and a GPIO
1603 LED. This parameter is not necessary when using the
1605 c - Enable the s3c camera interface.
1606 t - Reserved for enabling touchscreen support. The
1607 touchscreen support is not enabled in the mainstream
1608 kernel as of 2.6.30, a preliminary port can be found
1609 in the "bleeding edge" mini2440 support kernel at
1610 http://repo.or.cz/w/linux-2.6/mini2440.git
1613 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1614 parameter allows control of the logging verbosity for
1615 the additional memory initialisation checks. A value
1616 of 0 disables mminit logging and a level of 4 will
1617 log everything. Information is printed at KERN_DEBUG
1618 so loglevel=8 may also need to be specified.
1621 [KNL] When CONFIG_MODULE_SIG is set, this means that
1622 modules without (valid) signatures will fail to load.
1623 Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
1624 is always true, so this option does nothing.
1627 [MOUSE] Maximum time between finger touching and
1628 leaving touchpad surface for touch to be considered
1629 a tap and be reported as a left button click (for
1630 touchpads working in absolute mode only).
1632 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1633 reporting absolute coordinates, such as tablets
1634 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1635 reporting absolute coordinates, such as tablets
1637 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1638 is similar to kernelcore except it specifies the
1639 amount of memory used for migratable allocations.
1640 If both kernelcore and movablecore is specified,
1641 then kernelcore will be at *least* the specified
1642 value but may be more. If movablecore on its own
1643 is specified, the administrator must be careful
1644 that the amount of memory usable for all allocations
1647 MTD_Partition= [MTD]
1648 Format: <name>,<region-number>,<size>,<offset>
1650 MTD_Region= [MTD] Format:
1651 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1654 See drivers/mtd/cmdlinepart.c.
1656 multitce=off [PPC] This parameter disables the use of the pSeries
1657 firmware feature for updating multiple TCE entries
1660 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1662 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1664 boundary - index of last SLC block on Flex-OneNAND.
1665 The remaining blocks are configured as MLC blocks.
1666 lock - Configure if Flex-OneNAND boundary should be locked.
1667 Once locked, the boundary cannot be changed.
1668 1 indicates lock status, 0 indicates unlock status.
1671 ARM/S3C2412 JIVE boot control
1673 See arch/arm/mach-s3c2412/mach-jive.c
1675 mtouchusb.raw_coordinates=
1676 [HW] Make the MicroTouch USB driver use raw coordinates
1677 ('y', default) or cooked coordinates ('n')
1679 mtrr_chunk_size=nn[KMG] [X86]
1680 used for mtrr cleanup. It is largest continuous chunk
1681 that could hold holes aka. UC entries.
1683 mtrr_gran_size=nn[KMG] [X86]
1684 Used for mtrr cleanup. It is granularity of mtrr block.
1686 Large value could prevent small alignment from
1689 mtrr_spare_reg_nr=n [X86]
1691 Range: 0,7 : spare reg number
1693 Used for mtrr cleanup. It is spare mtrr entries number.
1694 Set to 2 or more if your graphical card needs more.
1696 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1698 netdev= [NET] Network devices parameters
1699 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1700 Note that mem_start is often overloaded to mean
1701 something different and driver-specific.
1702 This usage is only documented in each driver source
1706 [NETFILTER] Enable connection tracking flow accounting
1707 0 to disable accounting
1708 1 to enable accounting
1711 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1712 See Documentation/filesystems/nfs/nfsroot.txt.
1714 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1715 See Documentation/filesystems/nfs/nfsroot.txt.
1717 nfsrootdebug [NFS] enable nfsroot debugging messages.
1718 See Documentation/filesystems/nfs/nfsroot.txt.
1720 nfs.callback_tcpport=
1721 [NFS] set the TCP port on which the NFSv4 callback
1722 channel should listen.
1725 [NFS] sets the pathname to the program which is used
1726 to update the NFS client cache entries.
1728 nfs.cache_getent_timeout=
1729 [NFS] sets the timeout after which an attempt to
1730 update a cache entry is deemed to have failed.
1732 nfs.idmap_cache_timeout=
1733 [NFS] set the maximum lifetime for idmapper cache
1737 [NFS] enable 64-bit inode numbers.
1738 If zero, the NFS client will fake up a 32-bit inode
1739 number for the readdir() and stat() syscalls instead
1740 of returning the full 64-bit number.
1741 The default is to return 64-bit inode numbers.
1743 nfs.max_session_slots=
1744 [NFSv4.1] Sets the maximum number of session slots
1745 the client will attempt to negotiate with the server.
1746 This limits the number of simultaneous RPC requests
1747 that the client can send to the NFSv4.1 server.
1748 Note that there is little point in setting this
1749 value higher than the max_tcp_slot_table_limit.
1751 nfs.nfs4_disable_idmapping=
1752 [NFSv4] When set to the default of '1', this option
1753 ensures that both the RPC level authentication
1754 scheme and the NFS level operations agree to use
1755 numeric uids/gids if the mount is using the
1756 'sec=sys' security flavour. In effect it is
1757 disabling idmapping, which can make migration from
1758 legacy NFSv2/v3 systems to NFSv4 easier.
1759 Servers that do not support this mode of operation
1760 will be autodetected by the client, and it will fall
1761 back to using the idmapper.
1762 To turn off this behaviour, set the value to '0'.
1764 [NFS4] Specify an additional fixed unique ident-
1765 ification string that NFSv4 clients can insert into
1766 their nfs_client_id4 string. This is typically a
1767 UUID that is generated at system install time.
1769 nfs.send_implementation_id =
1770 [NFSv4.1] Send client implementation identification
1771 information in exchange_id requests.
1772 If zero, no implementation identification information
1774 The default is to send the implementation identification
1777 nfsd.nfs4_disable_idmapping=
1778 [NFSv4] When set to the default of '1', the NFSv4
1779 server will return only numeric uids and gids to
1780 clients using auth_sys, and will accept numeric uids
1781 and gids from such clients. This is intended to ease
1782 migration from NFSv2/v3.
1784 objlayoutdriver.osd_login_prog=
1785 [NFS] [OBJLAYOUT] sets the pathname to the program which
1786 is used to automatically discover and login into new
1787 osd-targets. Please see:
1788 Documentation/filesystems/pnfs.txt for more explanations
1790 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1791 when a NMI is triggered.
1792 Format: [state][,regs][,debounce][,die]
1794 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1795 Format: [panic,][nopanic,][num]
1797 0 - turn nmi_watchdog off
1798 When panic is specified, panic when an NMI watchdog
1799 timeout occurs (or 'nopanic' to override the opposite
1801 This is useful when you use a panic=... timeout and
1802 need the box quickly up again.
1804 netpoll.carrier_timeout=
1805 [NET] Specifies amount of time (in seconds) that
1806 netpoll should wait for a carrier. By default netpoll
1809 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1810 emulation library even if a 387 maths coprocessor
1814 [HW] Never suspend the console
1815 Disable suspending of consoles during suspend and
1816 hibernate operations. Once disabled, debugging
1817 messages can reach various consoles while the rest
1818 of the system is being put to sleep (ie, while
1819 debugging driver suspend/resume hooks). This may
1820 not work reliably with all consoles, but is known
1821 to work with serial and VGA consoles.
1822 To facilitate more flexible debugging, we also add
1823 console_suspend, a printk module parameter to control
1824 it. Users could use console_suspend (usually
1825 /sys/module/printk/parameters/console_suspend) to
1826 turn on/off it dynamically.
1828 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1829 caches in the slab allocator. Saves per-node memory,
1830 but will impact performance.
1834 noapic [SMP,APIC] Tells the kernel to not make use of any
1835 IOAPICs that may be present in the system.
1837 noautogroup Disable scheduler automatic task group creation.
1839 nobats [PPC] Do not use BATs for mapping kernel lowmem
1840 on "Classic" PPC cores.
1844 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1846 nodelayacct [KNL] Disable per-task delay accounting
1848 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1850 nodsp [SH] Disable hardware DSP at boot time.
1852 noefi [X86] Disable EFI runtime services support.
1857 On X86-32 available only on PAE configured kernels.
1858 noexec=on: enable non-executable mappings (default)
1859 noexec=off: disable non-executable mappings
1862 Disable SMAP (Supervisor Mode Access Prevention)
1863 even if it is supported by processor.
1866 Disable SMEP (Supervisor Mode Execution Prevention)
1867 even if it is supported by processor.
1870 This affects only 32-bit executables.
1871 noexec32=on: enable non-executable mappings (default)
1872 read doesn't imply executable mappings
1873 noexec32=off: disable non-executable mappings
1874 read implies executable mappings
1876 nofpu [SH] Disable hardware FPU at boot time.
1878 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1879 register save and restore. The kernel will only save
1880 legacy floating-point registers on task switch.
1882 noxsave [BUGS=X86] Disables x86 extended register state save
1883 and restore using xsave. The kernel will fallback to
1884 enabling legacy floating-point and sse state.
1887 on enable eager fpu restore
1888 off disable eager fpu restore
1889 auto selects the default scheme, which automatically
1890 enables eagerfpu restore for xsaveopt.
1892 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1893 wfi(ARM) instruction doesn't work correctly and not to
1894 use it. This is also useful when using JTAG debugger.
1896 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1897 instruction doesn't work correctly and not to
1900 no_file_caps Tells the kernel not to honor file capabilities. The
1901 only way then for a file to be executed with privilege
1902 is to be setuid root or executed by root.
1904 nohalt [IA-64] Tells the kernel not to use the power saving
1905 function PAL_HALT_LIGHT when idle. This increases
1906 power-consumption. On the positive side, it reduces
1907 interrupt wake-up latency, which may improve performance
1908 in certain environments such as networked servers or
1911 nohz= [KNL] Boottime enable/disable dynamic ticks
1912 Valid arguments: on, off
1915 noiotrap [SH] Disables trapped I/O port accesses.
1917 noirqdebug [X86-32] Disables the code which attempts to detect and
1918 disable unhandled interrupt sources.
1920 no_timer_check [X86,APIC] Disables the code which tests for
1921 broken timer IRQ sources.
1923 noisapnp [ISAPNP] Disables ISA PnP code.
1925 noinitrd [RAM] Tells the kernel not to load any configured
1928 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1930 [Deprecated - use intremap=off]
1934 nojitter [IA-64] Disables jitter checking for ITC timers.
1936 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1938 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1941 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1942 steal time is computed, but won't influence scheduler
1945 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1947 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1949 noltlbs [PPC] Do not use large page/tlb entries for kernel
1950 lowmem mapping on PPC40x.
1952 nomca [IA-64] Disable machine check abort handling
1954 nomce [X86-32] Machine Check Exception
1956 nomfgpt [X86-32] Disable Multi-Function General Purpose
1957 Timer usage (for AMD Geode machines).
1959 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1960 shutdown the other cpus. Instead use the REBOOT_VECTOR
1963 nomodule Disable module load
1965 nopat [X86] Disable PAT (page attribute table extension of
1966 pagetables) support.
1968 norandmaps Don't use address space randomization. Equivalent to
1969 echo 0 > /proc/sys/kernel/randomize_va_space
1971 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1973 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1974 with UP alternatives
1976 noresidual [PPC] Don't use residual data on PReP machines.
1978 nordrand [X86] Disable the direct use of the RDRAND
1979 instruction even if it is supported by the
1980 processor. RDRAND is still available to user
1983 noresume [SWSUSP] Disables resume and restores original swap
1986 no-scroll [VGA] Disables scrollback.
1987 This is required for the Braillex ib80-piezo Braille
1988 reader made by F.H. Papenmeier (Germany).
1992 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1994 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1995 and disable the IO APIC. legacy for "maxcpus=0".
1997 nosoftlockup [KNL] Disable the soft-lockup detector.
1999 nosync [HW,M68K] Disables sync negotiation for all devices.
2001 notsc [BUGS=X86-32] Disable Time Stamp Counter
2003 nousb [USB] Disable the USB subsystem
2005 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2009 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2011 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2012 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2013 Some features depend on CPU0. Known dependencies are:
2014 1. Resume from suspend/hibernate depends on CPU0.
2015 Suspend/hibernate will fail if CPU0 is offline and you
2016 need to online CPU0 before suspend/hibernate.
2017 2. PIC interrupts also depend on CPU0. CPU0 can't be
2018 removed if a PIC interrupt is detected.
2019 It's said poweroff/reboot may depend on CPU0 on some
2020 machines although I haven't seen such issues so far
2021 after CPU0 is offline on a few tested machines.
2022 If the dependencies are under your control, you can
2023 turn on cpu0_hotplug.
2025 nptcg= [IA-64] Override max number of concurrent global TLB
2026 purges which is reported from either PAL_VM_SUMMARY or
2029 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2030 could support. nr_cpus=n : n >= 1 limits the kernel to
2031 supporting 'n' processors. Later in runtime you can not
2032 use hotplug cpu feature to put more cpu back to online.
2033 just like you compile the kernel NR_CPUS=n
2035 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2037 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2038 Allowed values are enable and disable
2040 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2041 one of ['zone', 'node', 'default'] can be specified
2042 This can be set from sysctl after boot.
2043 See Documentation/sysctl/vm.txt for details.
2045 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2046 See Documentation/debugging-via-ohci1394.txt for more
2049 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2050 Rather than timing out after 20 ms if an EC
2051 command is not properly ACKed, override the length
2052 of the timeout. We have interrupts disabled while
2053 waiting for the ACK, so if this is set too high
2054 interrupts *may* be lost!
2056 omap_mux= [OMAP] Override bootloader pin multiplexing.
2057 Format: <mux_mode0.mode_name=value>...
2058 For example, to override I2C bus2:
2059 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2061 oprofile.timer= [HW]
2062 Use timer interrupt instead of performance counters
2064 oprofile.cpu_type= Force an oprofile cpu type
2065 This might be useful if you have an older oprofile
2066 userland or if you want common events.
2067 Format: { arch_perfmon }
2068 arch_perfmon: [X86] Force use of architectural
2069 perfmon on Intel CPUs instead of the
2070 CPU specific event set.
2071 timer: [X86] Force use of architectural NMI
2072 timer mode (see also oprofile.timer
2073 for generic hr timer mode)
2074 [s390] Force legacy basic mode sampling
2075 (report cpu_type "timer")
2077 oops=panic Always panic on oopses. Default is to just kill the
2078 process, but there is a small probability of
2079 deadlocking the machine.
2080 This will also cause panics on machine check exceptions.
2081 Useful together with panic=30 to trigger a reboot.
2084 See Documentation/sound/oss/oss-parameters.txt
2086 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2087 timeout > 0: seconds before rebooting
2088 timeout = 0: wait forever
2089 timeout < 0: reboot immediately
2092 parkbd.port= [HW] Parallel port number the keyboard adapter is
2093 connected to, default is 0.
2095 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2096 0 for XT, 1 for AT (default is AT).
2099 parport= [HW,PPT] Specify parallel ports. 0 disables.
2100 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2101 Use 'auto' to force the driver to use any
2102 IRQ/DMA settings detected (the default is to
2103 ignore detected IRQ/DMA settings because of
2104 possible conflicts). You can specify the base
2105 address, IRQ, and DMA settings; IRQ and DMA
2106 should be numbers, or 'auto' (for using detected
2107 settings on that particular port), or 'nofifo'
2108 (to avoid using a FIFO even if it is detected).
2109 Parallel ports are assigned in the order they
2110 are specified on the command line, starting
2113 parport_init_mode= [HW,PPT]
2114 Configure VIA parallel port to operate in
2115 a specific mode. This is necessary on Pegasos
2116 computer where firmware has no options for setting
2117 up parallel port mode and sets it to spp.
2118 Currently this function knows 686a and 8231 chips.
2119 Format: [spp|ps2|epp|ecp|ecpepp]
2122 Halt all CPUs after the first oops has been printed for
2123 the specified number of seconds. This is to be used if
2124 your oopses keep scrolling off the screen.
2129 See header of drivers/block/paride/pcd.c.
2130 See also Documentation/blockdev/paride.txt.
2132 pci=option[,option...] [PCI] various PCI subsystem options:
2133 earlydump [X86] dump PCI config space before the kernel
2135 off [X86] don't probe for the PCI bus
2136 bios [X86-32] force use of PCI BIOS, don't access
2137 the hardware directly. Use this if your machine
2138 has a non-standard PCI host bridge.
2139 nobios [X86-32] disallow use of PCI BIOS, only direct
2140 hardware access methods are allowed. Use this
2141 if you experience crashes upon bootup and you
2142 suspect they are caused by the BIOS.
2143 conf1 [X86] Force use of PCI Configuration
2145 conf2 [X86] Force use of PCI Configuration
2147 noaer [PCIE] If the PCIEAER kernel config parameter is
2148 enabled, this kernel boot option can be used to
2149 disable the use of PCIE advanced error reporting.
2150 nodomains [PCI] Disable support for multiple PCI
2151 root domains (aka PCI segments, in ACPI-speak).
2152 nommconf [X86] Disable use of MMCONFIG for PCI
2154 check_enable_amd_mmconf [X86] check for and enable
2155 properly configured MMIO access to PCI
2156 config space on AMD family 10h CPU
2157 nomsi [MSI] If the PCI_MSI kernel config parameter is
2158 enabled, this kernel boot option can be used to
2159 disable the use of MSI interrupts system-wide.
2160 noioapicquirk [APIC] Disable all boot interrupt quirks.
2161 Safety option to keep boot IRQs enabled. This
2162 should never be necessary.
2163 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2164 primary IO-APIC for bridges that cannot disable
2165 boot IRQs. This fixes a source of spurious IRQs
2166 when the system masks IRQs.
2167 noioapicreroute [APIC] Disable workaround that uses the
2168 boot IRQ equivalent of an IRQ that connects to
2169 a chipset where boot IRQs cannot be disabled.
2170 The opposite of ioapicreroute.
2171 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2172 routing table. These calls are known to be buggy
2173 on several machines and they hang the machine
2174 when used, but on other computers it's the only
2175 way to get the interrupt routing table. Try
2176 this option if the kernel is unable to allocate
2177 IRQs or discover secondary PCI buses on your
2179 rom [X86] Assign address space to expansion ROMs.
2180 Use with caution as certain devices share
2181 address decoders between ROMs and other
2183 norom [X86] Do not assign address space to
2184 expansion ROMs that do not already have
2185 BIOS assigned address ranges.
2186 nobar [X86] Do not assign address space to the
2187 BARs that weren't assigned by the BIOS.
2188 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2189 assigned automatically to PCI devices. You can
2190 make the kernel exclude IRQs of your ISA cards
2192 pirqaddr=0xAAAAA [X86] Specify the physical address
2193 of the PIRQ table (normally generated
2194 by the BIOS) if it is outside the
2195 F0000h-100000h range.
2196 lastbus=N [X86] Scan all buses thru bus #N. Can be
2197 useful if the kernel is unable to find your
2198 secondary buses and you want to tell it
2199 explicitly which ones they are.
2200 assign-busses [X86] Always assign all PCI bus
2201 numbers ourselves, overriding
2202 whatever the firmware may have done.
2203 usepirqmask [X86] Honor the possible IRQ mask stored
2204 in the BIOS $PIR table. This is needed on
2205 some systems with broken BIOSes, notably
2206 some HP Pavilion N5400 and Omnibook XE3
2207 notebooks. This will have no effect if ACPI
2208 IRQ routing is enabled.
2209 noacpi [X86] Do not use ACPI for IRQ routing
2210 or for PCI scanning.
2211 use_crs [X86] Use PCI host bridge window information
2212 from ACPI. On BIOSes from 2008 or later, this
2213 is enabled by default. If you need to use this,
2214 please report a bug.
2215 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2216 If you need to use this, please report a bug.
2217 routeirq Do IRQ routing for all PCI devices.
2218 This is normally done in pci_enable_device(),
2219 so this option is a temporary workaround
2220 for broken drivers that don't call it.
2221 skip_isa_align [X86] do not align io start addr, so can
2222 handle more pci cards
2223 firmware [ARM] Do not re-enumerate the bus but instead
2224 just use the configuration from the
2225 bootloader. This is currently used on
2226 IXP2000 systems where the bus has to be
2227 configured a certain way for adjunct CPUs.
2228 noearly [X86] Don't do any early type 1 scanning.
2229 This might help on some broken boards which
2230 machine check when some devices' config space
2231 is read. But various workarounds are disabled
2232 and some IOMMU drivers will not work.
2233 bfsort Sort PCI devices into breadth-first order.
2234 This sorting is done to get a device
2235 order compatible with older (<= 2.4) kernels.
2236 nobfsort Don't sort PCI devices into breadth-first order.
2237 cbiosize=nn[KMG] The fixed amount of bus space which is
2238 reserved for the CardBus bridge's IO window.
2239 The default value is 256 bytes.
2240 cbmemsize=nn[KMG] The fixed amount of bus space which is
2241 reserved for the CardBus bridge's memory
2242 window. The default value is 64 megabytes.
2245 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2246 Specifies alignment and device to reassign
2247 aligned memory resources.
2248 If <order of align> is not specified,
2249 PAGE_SIZE is used as alignment.
2250 PCI-PCI bridge can be specified, if resource
2251 windows need to be expanded.
2252 ecrc= Enable/disable PCIe ECRC (transaction layer
2253 end-to-end CRC checking).
2254 bios: Use BIOS/firmware settings. This is the
2258 realloc= Enable/disable reallocating PCI bridge resources
2259 if allocations done by BIOS are too small to
2260 accommodate resources required by all child
2262 off: Turn realloc off
2264 realloc same as realloc=on
2265 noari do not use PCIe ARI.
2266 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2267 only look for one device below a PCIe downstream
2270 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2273 force Enable ASPM even on devices that claim not to support it.
2274 WARNING: Forcing ASPM on may cause system lockups.
2276 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2277 nomsi Do not use MSI for PCI Express Native Hotplug (this
2278 makes all PCIe ports use INTx for hotplug services).
2280 pcie_ports= [PCIE] PCIe ports handling:
2281 auto Ask the BIOS whether or not to use native PCIe services
2282 associated with PCIe ports (PME, hot-plug, AER). Use
2283 them only if that is allowed by the BIOS.
2284 native Use native PCIe services associated with PCIe ports
2286 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2289 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2290 nomsi Do not use MSI for native PCIe PME signaling (this makes
2291 all PCIe root ports use INTx for all services).
2293 pcmv= [HW,PCMCIA] BadgePAD 4
2296 See Documentation/blockdev/paride.txt.
2298 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2301 See arch/parisc/kernel/pdc_chassis.c
2303 percpu_alloc= Select which percpu first chunk allocator to use.
2304 Currently supported values are "embed" and "page".
2305 Archs may support subset or none of the selections.
2306 See comments in mm/percpu.c for details on each
2307 allocator. This parameter is primarily for debugging
2308 and performance comparison.
2311 See Documentation/blockdev/paride.txt.
2314 See Documentation/blockdev/paride.txt.
2316 pirq= [SMP,APIC] Manual mp-table setup
2317 See Documentation/x86/i386/IO-APIC.txt.
2319 plip= [PPT,NET] Parallel port network link
2320 Format: { parport<nr> | timid | 0 }
2321 See also Documentation/parport.txt.
2323 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2324 Override pmtimer IOPort with a hex value.
2328 Enable PNP debug messages (depends on the
2329 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2330 via /sys/module/pnp/parameters/debug. We always show
2331 current resource usage; turning this on also shows
2332 possible settings and some assignment information.
2338 { on | off | curr | res | no-curr | no-res }
2341 [ISAPNP] Exclude IRQs for the autoconfiguration
2344 [ISAPNP] Exclude DMAs for the autoconfiguration
2346 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2347 Ranges are in pairs (I/O port base and size).
2350 [ISAPNP] Exclude memory regions for the
2352 Ranges are in pairs (memory base and size).
2354 ports= [IP_VS_FTP] IPVS ftp helper module
2356 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2358 Format: <port>,<port>....
2360 print-fatal-signals=
2361 [KNL] debug: print fatal signals
2363 If enabled, warn about various signal handling
2364 related application anomalies: too many signals,
2365 too many POSIX.1 timers, fatal signals causing a
2368 If you hit the warning due to signal overflow,
2369 you might want to try "ulimit -i unlimited".
2373 printk.always_kmsg_dump=
2374 Trigger kmsg_dump for cases other than kernel oops or
2376 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2379 printk.time= Show timing data prefixed to each printk message line
2380 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2382 processor.max_cstate= [HW,ACPI]
2383 Limit processor to maximum C-state
2384 max_cstate=9 overrides any DMI blacklist limit.
2386 processor.nocst [HW,ACPI]
2387 Ignore the _CST method to determine C-states,
2388 instead using the legacy FADT method
2390 profile= [KNL] Enable kernel profiling via /proc/profile
2391 Format: [schedule,]<number>
2392 Param: "schedule" - profile schedule points.
2393 Param: <number> - step/bucket size as a power of 2 for
2394 statistical time based profiling.
2395 Param: "sleep" - profile D-state sleeping (millisecs).
2396 Requires CONFIG_SCHEDSTATS
2397 Param: "kvm" - profile VM exits.
2399 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2401 See Documentation/blockdev/ramdisk.txt.
2403 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2404 probe for; one of (bare|imps|exps|lifebook|any).
2405 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2407 psmouse.resetafter= [HW,MOUSE]
2408 Try to reset the device after so many bad packets
2411 [HW,MOUSE] Set desired mouse resolution, in dpi.
2412 psmouse.smartscroll=
2413 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2414 0 = disabled, 1 = enabled (default).
2416 pstore.backend= Specify the name of the pstore backend to use
2419 See Documentation/blockdev/paride.txt.
2422 [KNL] Number of legacy pty's. Overwrites compiled-in
2425 quiet [KNL] Disable most log messages
2430 See Documentation/md.txt.
2432 ramdisk_blocksize= [RAM]
2433 See Documentation/blockdev/ramdisk.txt.
2435 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2436 See Documentation/blockdev/ramdisk.txt.
2438 rcu_nocbs= [KNL,BOOT]
2439 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2440 the specified list of CPUs to be no-callback CPUs.
2441 Invocation of these CPUs' RCU callbacks will
2442 be offloaded to "rcuoN" kthreads created for
2443 that purpose. This reduces OS jitter on the
2444 offloaded CPUs, which can be useful for HPC and
2445 real-time workloads. It can also improve energy
2446 efficiency for asymmetric multiprocessors.
2448 rcu_nocb_poll [KNL,BOOT]
2449 Rather than requiring that offloaded CPUs
2450 (specified by rcu_nocbs= above) explicitly
2451 awaken the corresponding "rcuoN" kthreads,
2452 make these kthreads poll for callbacks.
2453 This improves the real-time response for the
2454 offloaded CPUs by relieving them of the need to
2455 wake up the corresponding kthread, but degrades
2456 energy efficiency by requiring that the kthreads
2457 periodically wake up to do the polling.
2459 rcutree.blimit= [KNL,BOOT]
2460 Set maximum number of finished RCU callbacks to process
2463 rcutree.fanout_leaf= [KNL,BOOT]
2464 Increase the number of CPUs assigned to each
2465 leaf rcu_node structure. Useful for very large
2468 rcutree.qhimark= [KNL,BOOT]
2469 Set threshold of queued
2470 RCU callbacks over which batch limiting is disabled.
2472 rcutree.qlowmark= [KNL,BOOT]
2473 Set threshold of queued RCU callbacks below which
2474 batch limiting is re-enabled.
2476 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2477 Suppress RCU CPU stall warning messages.
2479 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2480 Set timeout for RCU CPU stall warning messages.
2482 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2483 Set delay from grace-period initialization to
2484 first attempt to force quiescent states.
2485 Units are jiffies, minimum value is zero,
2486 and maximum value is HZ.
2488 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2489 Set delay between subsequent attempts to force
2490 quiescent states. Units are jiffies, minimum
2491 value is one, and maximum value is HZ.
2493 rcutorture.fqs_duration= [KNL,BOOT]
2494 Set duration of force_quiescent_state bursts.
2496 rcutorture.fqs_holdoff= [KNL,BOOT]
2497 Set holdoff time within force_quiescent_state bursts.
2499 rcutorture.fqs_stutter= [KNL,BOOT]
2500 Set wait time between force_quiescent_state bursts.
2502 rcutorture.irqreader= [KNL,BOOT]
2503 Test RCU readers from irq handlers.
2505 rcutorture.n_barrier_cbs= [KNL,BOOT]
2506 Set callbacks/threads for rcu_barrier() testing.
2508 rcutorture.nfakewriters= [KNL,BOOT]
2509 Set number of concurrent RCU writers. These just
2510 stress RCU, they don't participate in the actual
2511 test, hence the "fake".
2513 rcutorture.nreaders= [KNL,BOOT]
2514 Set number of RCU readers.
2516 rcutorture.onoff_holdoff= [KNL,BOOT]
2517 Set time (s) after boot for CPU-hotplug testing.
2519 rcutorture.onoff_interval= [KNL,BOOT]
2520 Set time (s) between CPU-hotplug operations, or
2521 zero to disable CPU-hotplug testing.
2523 rcutorture.shuffle_interval= [KNL,BOOT]
2524 Set task-shuffle interval (s). Shuffling tasks
2525 allows some CPUs to go into dyntick-idle mode
2526 during the rcutorture test.
2528 rcutorture.shutdown_secs= [KNL,BOOT]
2529 Set time (s) after boot system shutdown. This
2530 is useful for hands-off automated testing.
2532 rcutorture.stall_cpu= [KNL,BOOT]
2533 Duration of CPU stall (s) to test RCU CPU stall
2534 warnings, zero to disable.
2536 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2537 Time to wait (s) after boot before inducing stall.
2539 rcutorture.stat_interval= [KNL,BOOT]
2540 Time (s) between statistics printk()s.
2542 rcutorture.stutter= [KNL,BOOT]
2543 Time (s) to stutter testing, for example, specifying
2544 five seconds causes the test to run for five seconds,
2545 wait for five seconds, and so on. This tests RCU's
2546 ability to transition abruptly to and from idle.
2548 rcutorture.test_boost= [KNL,BOOT]
2549 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2550 "Maybe" means test if the RCU implementation
2551 under test support RCU priority boosting.
2553 rcutorture.test_boost_duration= [KNL,BOOT]
2554 Duration (s) of each individual boost test.
2556 rcutorture.test_boost_interval= [KNL,BOOT]
2557 Interval (s) between each boost test.
2559 rcutorture.test_no_idle_hz= [KNL,BOOT]
2560 Test RCU's dyntick-idle handling. See also the
2561 rcutorture.shuffle_interval parameter.
2563 rcutorture.torture_type= [KNL,BOOT]
2564 Specify the RCU implementation to test.
2566 rcutorture.verbose= [KNL,BOOT]
2567 Enable additional printk() statements.
2571 Run specified binary instead of /init from the ramdisk,
2572 used for early userspace startup. See initrd.
2574 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2575 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2576 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2579 [KNL, SMP] Set scheduler's default relax_domain_level.
2580 See Documentation/cgroups/cpusets.txt.
2582 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2584 reservetop= [X86-32]
2586 Reserves a hole at the top of the kernel virtual
2591 Set the amount of memory to reserve for BIOS at
2592 the bottom of the address space.
2594 reset_devices [KNL] Force drivers to reset the underlying device
2595 during initialization.
2598 Specify the partition device for software suspend
2600 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2602 resume_offset= [SWSUSP]
2603 Specify the offset from the beginning of the partition
2604 given by "resume=" at which the swap header is located,
2605 in <PAGE_SIZE> units (needed only for swap files).
2606 See Documentation/power/swsusp-and-swap-files.txt
2608 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2609 read the resume files
2611 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2612 Useful for devices that are detected asynchronously
2613 (e.g. USB and MMC devices).
2615 hibernate= [HIBERNATION]
2616 noresume Don't check if there's a hibernation image
2617 present during boot.
2618 nocompress Don't compress/decompress hibernation images.
2620 retain_initrd [RAM] Keep initrd memory after extraction
2622 rhash_entries= [KNL,NET]
2623 Set number of hash buckets for route cache
2625 riscom8= [HW,SERIAL]
2626 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2628 ro [KNL] Mount root device read-only on boot
2630 root= [KNL] Root filesystem
2631 See name_to_dev_t comment in init/do_mounts.c.
2633 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2634 mount the root filesystem
2636 rootflags= [KNL] Set root filesystem mount option string
2638 rootfstype= [KNL] Set root filesystem type
2640 rootwait [KNL] Wait (indefinitely) for root device to show up.
2641 Useful for devices that are detected asynchronously
2642 (e.g. USB and MMC devices).
2644 rw [KNL] Mount root device read-write on boot
2646 S [KNL] Run init in single mode
2649 See drivers/net/irda/sa1100_ir.c.
2651 sbni= [NET] Granch SBNI12 leased line adapter
2653 sched_debug [KNL] Enables verbose scheduler debug messages.
2655 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2656 xtime_lock contention on larger systems, and/or RCU lock
2657 contention on all systems with CONFIG_MAXSMP set.
2658 Format: { "0" | "1" }
2659 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2661 Note: increases power consumption, thus should only be
2662 enabled if running jitter sensitive (HPC/RT) workloads.
2664 security= [SECURITY] Choose a security module to enable at boot.
2665 If this boot parameter is not specified, only the first
2666 security module asking for security registration will be
2667 loaded. An invalid security module name will be treated
2668 as if no module has been chosen.
2670 selinux= [SELINUX] Disable or enable SELinux at boot time.
2671 Format: { "0" | "1" }
2672 See security/selinux/Kconfig help text.
2675 Default value is set via kernel config option.
2676 If enabled at boot time, /selinux/disable can be used
2677 later to disable prior to initial policy load.
2679 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2680 Format: { "0" | "1" }
2681 See security/apparmor/Kconfig help text
2684 Default value is set via kernel config option.
2686 serialnumber [BUGS=X86-32]
2689 Maximal number of shapers.
2691 show_msr= [x86] show boot-time MSR settings
2692 Format: { <integer> }
2693 Show boot-time (BIOS-initialized) MSR settings.
2694 The parameter means the number of CPUs to show,
2695 for example 1 means boot CPU only.
2702 slab_max_order= [MM, SLAB]
2703 Determines the maximum allowed order for slabs.
2704 A high setting may cause OOMs due to memory
2705 fragmentation. Defaults to 1 for systems with
2706 more than 32MB of RAM, 0 otherwise.
2708 slub_debug[=options[,slabs]] [MM, SLUB]
2709 Enabling slub_debug allows one to determine the
2710 culprit if slab objects become corrupted. Enabling
2711 slub_debug can create guard zones around objects and
2712 may poison objects when not in use. Also tracks the
2713 last alloc / free. For more information see
2714 Documentation/vm/slub.txt.
2716 slub_max_order= [MM, SLUB]
2717 Determines the maximum allowed order for slabs.
2718 A high setting may cause OOMs due to memory
2719 fragmentation. For more information see
2720 Documentation/vm/slub.txt.
2722 slub_min_objects= [MM, SLUB]
2723 The minimum number of objects per slab. SLUB will
2724 increase the slab order up to slub_max_order to
2725 generate a sufficiently large slab able to contain
2726 the number of objects indicated. The higher the number
2727 of objects the smaller the overhead of tracking slabs
2728 and the less frequently locks need to be acquired.
2729 For more information see Documentation/vm/slub.txt.
2731 slub_min_order= [MM, SLUB]
2732 Determines the minimum page order for slabs. Must be
2733 lower than slub_max_order.
2734 For more information see Documentation/vm/slub.txt.
2736 slub_nomerge [MM, SLUB]
2737 Disable merging of slabs with similar size. May be
2738 necessary if there is some reason to distinguish
2739 allocs to different slabs. Debug options disable
2740 merging on their own.
2741 For more information see Documentation/vm/slub.txt.
2744 Format: <io1>[,<io2>[,...,<io8>]]
2746 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2747 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2748 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2749 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2750 smsc-ircc2.ircc_irq= [HW] IRQ line
2751 smsc-ircc2.ircc_dma= [HW] DMA channel
2752 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2753 0: Toshiba Satellite 1800 (GP data pin select)
2754 1: Fast pin select (default)
2758 [KNL] Should the soft-lockup detector generate panics.
2761 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2762 See Documentation/laptops/sonypi.txt
2764 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2765 See Documentation/serial/specialix.txt.
2767 spia_io_base= [HW,MTD]
2773 Enabled the stack tracer on boot up.
2775 stacktrace_filter=[function-list]
2776 [FTRACE] Limit the functions that the stack tracer
2777 will trace at boot up. function-list is a comma separated
2778 list of functions. This list can be changed at run
2779 time by the stack_trace_filter file in the debugfs
2780 tracing directory. Note, this enables stack tracing
2781 and the stacktrace above is not needed.
2785 Set the STI (builtin display/keyboard on the HP-PARISC
2786 machines) console (graphic card) which should be used
2787 as the initial boot-console.
2788 See also comment in drivers/video/console/sticore.c.
2791 See comment in drivers/video/console/sticore.c.
2794 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2796 sunrpc.min_resvport=
2797 sunrpc.max_resvport=
2799 SunRPC servers often require that client requests
2800 originate from a privileged port (i.e. a port in the
2801 range 0 < portnr < 1024).
2802 An administrator who wishes to reserve some of these
2803 ports for other uses may adjust the range that the
2804 kernel's sunrpc client considers to be privileged
2805 using these two parameters to set the minimum and
2806 maximum port values.
2810 Control how the NFS server code allocates CPUs to
2811 service thread pools. Depending on how many NICs
2812 you have and where their interrupts are bound, this
2813 option will affect which CPUs will do NFS serving.
2814 Note: this parameter cannot be changed while the
2815 NFS server is running.
2817 auto the server chooses an appropriate mode
2818 automatically using heuristics
2819 global a single global pool contains all CPUs
2820 percpu one pool for each CPU
2821 pernode one pool for each NUMA node (equivalent
2822 to global on non-NUMA machines)
2824 sunrpc.tcp_slot_table_entries=
2825 sunrpc.udp_slot_table_entries=
2827 Sets the upper limit on the number of simultaneous
2828 RPC calls that can be sent from the client to a
2829 server. Increasing these values may allow you to
2830 improve throughput, but will also increase the
2831 amount of memory reserved for use by the client.
2834 [KNL] Enable accounting of swap in memory resource
2835 controller if no parameter or 1 is given or disable
2836 it if 0 is given (See Documentation/cgroups/memory.txt)
2838 swiotlb= [IA-64] Number of I/O TLB slabs
2842 sysfs.deprecated=0|1 [KNL]
2843 Enable/disable old style sysfs layout for old udev
2844 on older distributions. When this option is enabled
2845 very new udev will not work anymore. When this option
2846 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2847 in older udev will not work anymore.
2848 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2849 the kernel configuration.
2851 sysrq_always_enabled
2853 Ignore sysrq setting - this boot parameter will
2854 neutralize any effect of /proc/sys/kernel/sysrq.
2855 Useful for debugging.
2859 test_suspend= [SUSPEND]
2860 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2861 standby suspend) as the system sleep state to briefly
2862 enter during system startup. The system is woken from
2863 this state using a wakeup-capable RTC alarm.
2865 thash_entries= [KNL,NET]
2866 Set number of hash buckets for TCP connection
2868 thermal.act= [HW,ACPI]
2869 -1: disable all active trip points in all thermal zones
2870 <degrees C>: override all lowest active trip points
2872 thermal.crt= [HW,ACPI]
2873 -1: disable all critical trip points in all thermal zones
2874 <degrees C>: override all critical trip points
2876 thermal.nocrt= [HW,ACPI]
2877 Set to disable actions on ACPI thermal zone
2878 critical and hot trip points.
2880 thermal.off= [HW,ACPI]
2881 1: disable ACPI thermal control
2883 thermal.psv= [HW,ACPI]
2884 -1: disable all passive trip points
2885 <degrees C>: override all passive trip points to this
2888 thermal.tzp= [HW,ACPI]
2889 Specify global default ACPI thermal zone polling rate
2890 <deci-seconds>: poll all this frequency
2891 0: no polling (default)
2894 Force threading of all interrupt handlers except those
2895 marked explicitly IRQF_NO_THREAD.
2899 Specify if the kernel should make use of the cpu
2900 topology information if the hardware supports this.
2901 The scheduler will make use of this information and
2902 e.g. base its process migration decisions on it.
2907 tpm_suspend_pcr=[HW,TPM]
2908 Format: integer pcr id
2909 Specify that at suspend time, the tpm driver
2910 should extend the specified pcr with zeros,
2911 as a workaround for some chips which fail to
2912 flush the last written pcr on TPM_SaveState.
2913 This will guarantee that all the other pcrs
2916 trace_buf_size=nn[KMG]
2917 [FTRACE] will set tracing buffer size.
2919 trace_event=[event-list]
2920 [FTRACE] Set and start specified trace events in order
2921 to facilitate early boot debugging.
2922 See also Documentation/trace/events.txt
2924 trace_options=[option-list]
2925 [FTRACE] Enable or disable tracer options at boot.
2926 The option-list is a comma delimited list of options
2927 that can be enabled or disabled just as if you were
2928 to echo the option name into
2930 /sys/kernel/debug/tracing/trace_options
2932 For example, to enable stacktrace option (to dump the
2933 stack trace of each event), add to the command line:
2935 trace_options=stacktrace
2937 See also Documentation/trace/ftrace.txt "trace options"
2940 transparent_hugepage=
2942 Format: [always|madvise|never]
2943 Can be used to control the default behavior of the system
2944 with respect to transparent hugepages.
2945 See Documentation/vm/transhuge.txt for more details.
2947 tsc= Disable clocksource stability checks for TSC.
2949 [x86] reliable: mark tsc clocksource as reliable, this
2950 disables clocksource verification at runtime, as well
2951 as the stability checks done at bootup. Used to enable
2952 high-resolution timer mode on older hardware, and in
2953 virtualized environment.
2954 [x86] noirqtime: Do not use TSC to do irq accounting.
2955 Used to run time disable IRQ_TIME_ACCOUNTING on any
2956 platforms where RDTSC is slow and this accounting
2959 turbografx.map[2|3]= [HW,JOY]
2960 TurboGraFX parallel port interface
2962 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2963 See also Documentation/input/joystick-parport.txt
2965 udbg-immortal [PPC] When debugging early kernel crashes that
2966 happen after console_init() and before a proper
2967 console driver takes over, this boot options might
2968 help "seeing" what's going on.
2970 uhash_entries= [KNL,NET]
2971 Set number of hash buckets for UDP/UDP-Lite connections
2974 [USB] Ignore overcurrent events (default N).
2975 Some badly-designed motherboards generate lots of
2976 bogus events, for ports that aren't wired to
2977 anything. Set this parameter to avoid log spamming.
2978 Note that genuine overcurrent events won't be
2982 [X86] Cause panic on unknown NMI.
2984 usbcore.authorized_default=
2985 [USB] Default USB device authorization:
2986 (default -1 = authorized except for wireless USB,
2987 0 = not authorized, 1 = authorized)
2989 usbcore.autosuspend=
2990 [USB] The autosuspend time delay (in seconds) used
2991 for newly-detected USB devices (default 2). This
2992 is the time required before an idle device will be
2993 autosuspended. Devices for which the delay is set
2994 to a negative value won't be autosuspended at all.
2996 usbcore.usbfs_snoop=
2997 [USB] Set to log all usbfs traffic (default 0 = off).
2999 usbcore.blinkenlights=
3000 [USB] Set to cycle leds on hubs (default 0 = off).
3002 usbcore.old_scheme_first=
3003 [USB] Start with the old device initialization
3004 scheme (default 0 = off).
3006 usbcore.usbfs_memory_mb=
3007 [USB] Memory limit (in MB) for buffers allocated by
3008 usbfs (default = 16, 0 = max = 2047).
3010 usbcore.use_both_schemes=
3011 [USB] Try the other device initialization scheme
3012 if the first one fails (default 1 = enabled).
3014 usbcore.initial_descriptor_timeout=
3015 [USB] Specifies timeout for the initial 64-byte
3016 USB_REQ_GET_DESCRIPTOR request in milliseconds
3017 (default 5000 = 5.0 seconds).
3020 [USBHID] The interval which mice are to be polled at.
3022 usb-storage.delay_use=
3023 [UMS] The delay in seconds before a new device is
3024 scanned for Logical Units (default 5).
3027 [UMS] A list of quirks entries to supplement or
3028 override the built-in unusual_devs list. List
3029 entries are separated by commas. Each entry has
3030 the form VID:PID:Flags where VID and PID are Vendor
3031 and Product ID values (4-digit hex numbers) and
3032 Flags is a set of characters, each corresponding
3033 to a common usb-storage quirk flag as follows:
3034 a = SANE_SENSE (collect more than 18 bytes
3036 b = BAD_SENSE (don't collect more than 18
3037 bytes of sense data);
3038 c = FIX_CAPACITY (decrease the reported
3039 device capacity by one sector);
3040 d = NO_READ_DISC_INFO (don't use
3041 READ_DISC_INFO command);
3042 e = NO_READ_CAPACITY_16 (don't use
3043 READ_CAPACITY_16 command);
3044 h = CAPACITY_HEURISTICS (decrease the
3045 reported device capacity by one
3046 sector if the number is odd);
3047 i = IGNORE_DEVICE (don't bind to this
3049 l = NOT_LOCKABLE (don't try to lock and
3050 unlock ejectable media);
3051 m = MAX_SECTORS_64 (don't transfer more
3052 than 64 sectors = 32 KB at a time);
3053 n = INITIAL_READ10 (force a retry of the
3054 initial READ(10) command);
3055 o = CAPACITY_OK (accept the capacity
3056 reported by the device);
3057 p = WRITE_CACHE (the device cache is ON
3059 r = IGNORE_RESIDUE (the device reports
3060 bogus residue values);
3061 s = SINGLE_LUN (the device has only one
3063 w = NO_WP_DETECT (don't test whether the
3064 medium is write-protected).
3065 Example: quirks=0419:aaf5:rl,0421:0433:rc
3067 user_debug= [KNL,ARM]
3069 See arch/arm/Kconfig.debug help text.
3070 1 - undefined instruction events
3072 4 - invalid data aborts
3075 Example: user_debug=31
3078 [X86] Flags controlling user PTE allocations.
3080 nohigh = do not allocate PTE pages in
3081 HIGHMEM regardless of setting
3085 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3086 vdso=1: enable VDSO (default)
3087 vdso=0: disable VDSO mapping
3090 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3091 vdso32=1: enable 32-bit VDSO (default)
3092 vdso32=0: disable 32-bit VDSO mapping
3095 vector=percpu: enable percpu vector domain
3097 video= [FB] Frame buffer configuration
3098 See Documentation/fb/modedb.txt.
3101 [VMMIO] Memory mapped virtio (platform) device.
3103 <size>@<baseaddr>:<irq>[:<id>]
3105 <size> := size (can use standard suffixes
3107 <baseaddr> := physical base address
3108 <irq> := interrupt number (as passed to
3110 <id> := (optional) platform device id
3112 virtio_mmio.device=1K@0x100b0000:48:7
3114 Can be used multiple times for multiple devices.
3116 vga= [BOOT,X86-32] Select a particular video mode
3117 See Documentation/x86/boot.txt and
3118 Documentation/svga.txt.
3119 Use vga=ask for menu.
3120 This is actually a boot loader parameter; the value is
3121 passed to the kernel using a special protocol.
3123 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3124 size of <nn>. This can be used to increase the
3125 minimum size (128MB on x86). It can also be used to
3126 decrease the size and leave more room for directly
3129 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3132 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3135 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3139 Controls the behavior of vsyscalls (i.e. calls to
3140 fixed addresses of 0xffffffffff600x00 from legacy
3141 code). Most statically-linked binaries and older
3142 versions of glibc use these calls. Because these
3143 functions are at fixed addresses, they make nice
3144 targets for exploits that can control RIP.
3146 emulate [default] Vsyscalls turn into traps and are
3147 emulated reasonably safely.
3149 native Vsyscalls are native syscall instructions.
3150 This is a little bit faster than trapping
3151 and makes a few dynamic recompilers work
3152 better than they would in emulation mode.
3153 It also makes exploits much easier to write.
3155 none Vsyscalls don't work at all. This makes
3156 them quite hard to use for exploits but
3157 might break your system.
3159 vt.cur_default= [VT] Default cursor shape.
3160 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3161 the parameters of the <Esc>[?A;B;Cc escape sequence;
3162 see VGA-softcursor.txt. Default: 2 = underline.
3164 vt.default_blu= [VT]
3165 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3166 Change the default blue palette of the console.
3167 This is a 16-member array composed of values
3170 vt.default_grn= [VT]
3171 Format: <green0>,<green1>,<green2>,...,<green15>
3172 Change the default green palette of the console.
3173 This is a 16-member array composed of values
3176 vt.default_red= [VT]
3177 Format: <red0>,<red1>,<red2>,...,<red15>
3178 Change the default red palette of the console.
3179 This is a 16-member array composed of values
3185 Set system-wide default UTF-8 mode for all tty's.
3186 Default is 1, i.e. UTF-8 mode is enabled for all
3187 newly opened terminals.
3189 vt.global_cursor_default=
3192 Set system-wide default for whether a cursor
3193 is shown on new VTs. Default is -1,
3194 i.e. cursors will be created by default unless
3195 overridden by individual drivers. 0 will hide
3196 cursors, 1 will display them.
3198 watchdog timers [HW,WDT] For information on watchdog timers,
3199 see Documentation/watchdog/watchdog-parameters.txt
3200 or other driver-specific files in the
3201 Documentation/watchdog/ directory.
3203 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3204 default x2apic cluster mode on platforms
3207 x86_mrst_timer= [X86-32,APBT]
3208 Choose timer option for x86 Moorestown MID platform.
3209 Two valid options are apbt timer only and lapic timer
3210 plus one apbt timer for broadcast timer.
3211 x86_mrst_timer=apbt_only | lapic_and_apbt
3213 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3214 xd_geo= See header of drivers/block/xd.c.
3216 xen_emul_unplug= [HW,X86,XEN]
3217 Unplug Xen emulated devices
3218 Format: [unplug0,][unplug1]
3219 ide-disks -- unplug primary master IDE devices
3220 aux-ide-disks -- unplug non-primary-master IDE devices
3221 nics -- unplug network devices
3222 all -- unplug all emulated devices (NICs and IDE disks)
3223 unnecessary -- unplugging emulated devices is
3224 unnecessary even if the host did not respond to
3226 never -- do not unplug even if version check succeeds
3228 xirc2ps_cs= [NET,PCMCIA]
3230 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3232 ______________________________________________________________________
3236 Add more DRM drivers.
projects / platform / adaptation / renesas_rcar / renesas_kernel.git / blob