4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 ARM ARM architecture is enabled.
44 AVR32 AVR32 architecture is enabled.
45 AX25 Appropriate AX.25 support is enabled.
46 BLACKFIN Blackfin architecture is enabled.
47 DRM Direct Rendering Management support is enabled.
48 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
49 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
50 EFI EFI Partitioning (GPT) is enabled
51 EIDE EIDE/ATAPI support is enabled.
52 EVM Extended Verification Module
53 FB The frame buffer device is enabled.
54 FTRACE Function tracing enabled.
55 GCOV GCOV profiling is enabled.
56 HW Appropriate hardware is enabled.
57 IA-64 IA-64 architecture is enabled.
58 IMA Integrity measurement architecture is enabled.
59 IOSCHED More than one I/O scheduler is enabled.
60 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
61 IPV6 IPv6 support is enabled.
62 ISAPNP ISA PnP code is enabled.
63 ISDN Appropriate ISDN support is enabled.
64 JOY Appropriate joystick support is enabled.
65 KGDB Kernel debugger support is enabled.
66 KVM Kernel Virtual Machine support is enabled.
67 LIBATA Libata driver is enabled
68 LP Printer support is enabled.
69 LOOP Loopback device support is enabled.
70 M68k M68k architecture is enabled.
71 These options have more detailed description inside of
72 Documentation/m68k/kernel-options.txt.
73 MDA MDA console support is enabled.
74 MIPS MIPS architecture is enabled.
75 MOUSE Appropriate mouse support is enabled.
76 MSI Message Signaled Interrupts (PCI).
77 MTD MTD (Memory Technology Device) support is enabled.
78 NET Appropriate network support is enabled.
79 NUMA NUMA support is enabled.
80 NFS Appropriate NFS support is enabled.
81 OSS OSS sound support is enabled.
82 PV_OPS A paravirtualized kernel is enabled.
83 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
84 PARISC The PA-RISC architecture is enabled.
85 PCI PCI bus support is enabled.
86 PCIE PCI Express support is enabled.
87 PCMCIA The PCMCIA subsystem is enabled.
88 PNP Plug & Play support is enabled.
89 PPC PowerPC architecture is enabled.
90 PPT Parallel port support is enabled.
91 PS2 Appropriate PS/2 support is enabled.
92 RAM RAM disk support is enabled.
93 S390 S390 architecture is enabled.
94 SCSI Appropriate SCSI support is enabled.
95 A lot of drivers have their options described inside
96 the Documentation/scsi/ sub-directory.
97 SECURITY Different security models are enabled.
98 SELINUX SELinux support is enabled.
99 APPARMOR AppArmor support is enabled.
100 SERIAL Serial support is enabled.
101 SH SuperH architecture is enabled.
102 SMP The kernel is an SMP kernel.
103 SPARC Sparc architecture is enabled.
104 SWSUSP Software suspend (hibernation) is enabled.
105 SUSPEND System suspend states are enabled.
106 TPM TPM drivers are enabled.
107 TS Appropriate touchscreen support is enabled.
108 UMS USB Mass Storage support is enabled.
109 USB USB support is enabled.
110 USBHID USB Human Interface Device support is enabled.
111 V4L Video For Linux support is enabled.
112 VMMIO Driver for memory mapped virtio devices is enabled.
113 VGA The VGA console has been enabled.
114 VT Virtual terminal support is enabled.
115 WDT Watchdog support is enabled.
116 XT IBM PC/XT MFM hard disk support is enabled.
117 X86-32 X86-32, aka i386 architecture is enabled.
118 X86-64 X86-64 architecture is enabled.
119 More X86-64 boot options can be found in
120 Documentation/x86/x86_64/boot-options.txt .
121 X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
122 XEN Xen support is enabled
124 In addition, the following text indicates that the option:
126 BUGS= Relates to possible processor bugs on the said processor.
127 KNL Is a kernel start-up parameter.
128 BOOT Is a boot loader parameter.
130 Parameters denoted with BOOT are actually interpreted by the boot
131 loader, and have no meaning to the kernel directly.
132 Do not modify the syntax of boot loader parameters without extreme
133 need or coordination with <Documentation/x86/boot.txt>.
135 There are also arch-specific kernel-parameters not documented here.
136 See for example <Documentation/x86/x86_64/boot-options.txt>.
138 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
139 a trailing = on the name of any parameter states that that parameter will
140 be entered as an environment variable, whereas its absence indicates that
141 it will appear as a kernel argument readable via /proc/cmdline by programs
142 running once the system is up.
144 The number of kernel parameters is not limited, but the length of the
145 complete command line (parameters including spaces etc.) is limited to
146 a fixed number of characters. This limit depends on the architecture
147 and is between 256 and 4096 characters. It is defined in the file
148 ./include/asm/setup.h as COMMAND_LINE_SIZE.
150 Finally, the [KMG] suffix is commonly described after a number of kernel
151 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
152 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
153 bytes respectively. Such letter suffixes can also be entirely omitted.
157 Advanced Configuration and Power Interface
158 Format: { force | off | strict | noirq | rsdt }
159 force -- enable ACPI if default was off
160 off -- disable ACPI if default was on
161 noirq -- do not use ACPI for IRQ routing
162 strict -- Be less tolerant of platforms that are not
163 strictly ACPI specification compliant.
164 rsdt -- prefer RSDT over (default) XSDT
165 copy_dsdt -- copy DSDT to memory
167 See also Documentation/power/runtime_pm.txt, pci=noacpi
169 acpi_rsdp= [ACPI,EFI,KEXEC]
170 Pass the RSDP address to the kernel, mostly used
171 on machines running EFI runtime service to boot the
172 second kernel for kdump.
174 acpi_apic_instance= [ACPI, IOAPIC]
176 2: use 2nd APIC table, if available
177 1,0: use 1st APIC table
180 acpi_backlight= [HW,ACPI]
181 acpi_backlight=vendor
183 If set to vendor, prefer vendor specific driver
184 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
185 of the ACPI video.ko driver.
187 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
188 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
190 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
191 debug output. Bits in debug_layer correspond to a
192 _COMPONENT in an ACPI source file, e.g.,
193 #define _COMPONENT ACPI_PCI_COMPONENT
194 Bits in debug_level correspond to a level in
195 ACPI_DEBUG_PRINT statements, e.g.,
196 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
197 The debug_level mask defaults to "info". See
198 Documentation/acpi/debug.txt for more information about
199 debug layers and levels.
201 Enable processor driver info messages:
202 acpi.debug_layer=0x20000000
203 Enable PCI/PCI interrupt routing info messages:
204 acpi.debug_layer=0x400000
205 Enable AML "Debug" output, i.e., stores to the Debug
206 object while interpreting AML:
207 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
208 Enable all messages related to ACPI hardware:
209 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
211 Some values produce so much output that the system is
212 unusable. The "log_buf_len" parameter may be useful
213 if you need to capture more output.
215 acpi_irq_balance [HW,ACPI]
216 ACPI will balance active IRQs
219 acpi_irq_nobalance [HW,ACPI]
220 ACPI will not move active IRQs (default)
223 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
224 Format: <irq>,<irq>...
226 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
228 Format: <irq>,<irq>...
230 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
232 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
233 Format: To spoof as Windows 98: ="Microsoft Windows"
235 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
236 acpi_osi="string1" # add string1 -- only one string
237 acpi_osi="!string2" # remove built-in string2
238 acpi_osi= # disable all strings
241 Override the pmtimer bug detection: force the kernel
242 to assume that this machine's pmtimer latches its value
243 and always returns good values.
245 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
246 Format: { level | edge | high | low }
248 acpi_serialize [HW,ACPI] force serialization of AML methods
250 acpi_skip_timer_override [HW,ACPI]
251 Recognize and ignore IRQ0/pin2 Interrupt Override.
252 For broken nForce2 BIOS resulting in XT-PIC timer.
254 acpi_sleep= [HW,ACPI] Sleep options
255 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
256 old_ordering, nonvs, sci_force_enable }
257 See Documentation/power/video.txt for information on
259 s3_beep is for debugging; it makes the PC's speaker beep
260 as soon as the kernel's real-mode entry point is called.
261 s4_nohwsig prevents ACPI hardware signature from being
262 used during resume from hibernation.
263 old_ordering causes the ACPI 1.0 ordering of the _PTS
264 control method, with respect to putting devices into
265 low power states, to be enforced (the ACPI 2.0 ordering
266 of _PTS is used by default).
267 nonvs prevents the kernel from saving/restoring the
268 ACPI NVS memory during suspend/hibernation and resume.
269 sci_force_enable causes the kernel to set SCI_EN directly
270 on resume from S1/S3 (which is against the ACPI spec,
271 but some broken systems don't work without it).
273 acpi_use_timer_override [HW,ACPI]
274 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer override, but don't have HPET
277 acpi_enforce_resources= [ACPI]
278 { strict | lax | no }
279 Check for resource conflicts between native drivers
280 and ACPI OperationRegions (SystemIO and SystemMemory
281 only). IO ports and memory declared in ACPI might be
282 used by the ACPI subsystem in arbitrary AML code and
283 can interfere with legacy drivers.
284 strict (default): access to resources claimed by ACPI
285 is denied; legacy drivers trying to access reserved
286 resources will fail to bind to device using them.
287 lax: access to resources claimed by ACPI is allowed;
288 legacy drivers trying to access reserved resources
289 will bind successfully but a warning message is logged.
290 no: ACPI OperationRegions are not marked as reserved,
291 no further checks are performed.
293 add_efi_memmap [EFI; X86] Include EFI memory map in
294 kernel's map of available physical RAM.
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
303 See Documentation/sound/alsa/alsa-parameters.txt
306 Allow the default userspace alignment fault handler
307 behaviour to be specified. Bit 0 enables warnings,
308 bit 1 enables fixups, and bit 2 sends a segfault.
310 align_va_addr= [X86-64]
311 Align virtual addresses by clearing slice [14:12] when
312 allocating a VMA at process creation time. This option
313 gives you up to 3% performance improvement on AMD F15h
314 machines (where it is enabled by default) for a
315 CPU-intensive style benchmark, and it can vary highly in
316 a microbenchmark depending on workload and compiler.
318 32: only for 32-bit processes
319 64: only for 64-bit processes
320 on: enable for both 32- and 64-bit processes
321 off: disable for both 32- and 64-bit processes
323 amd_iommu= [HW,X86-64]
324 Pass parameters to the AMD IOMMU driver in the system.
326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
330 off - do not initialize any AMD IOMMU found in
332 force_isolation - Force device isolation for all
333 devices. The IOMMU driver is not
334 allowed anymore to lift isolation
335 requirements as needed. This option
336 does not override iommu=pt
338 amd_iommu_dump= [HW,X86-64]
339 Enable AMD IOMMU driver option to dump the ACPI table
340 for AMD IOMMU. With this option enabled, AMD IOMMU
341 driver will print ACPI tables for AMD IOMMU during
342 IOMMU initialization.
344 amijoy.map= [HW,JOY] Amiga joystick support
345 Map of devices attached to JOY0DAT and JOY1DAT
347 See also Documentation/input/joystick.txt
349 analog.map= [HW,JOY] Analog joystick and gamepad support
350 Specifies type or capabilities of an analog joystick
351 connected to one of 16 gameports
352 Format: <type1>,<type2>,..<type16>
355 Power management functions (SPARCstation-4/5 + deriv.)
357 Disable APC CPU standby support. SPARCstation-Fox does
358 not play well with APC CPU idle - disable it if you have
359 APC and your system crashes randomly.
361 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
362 Change the output verbosity whilst booting
363 Format: { quiet (default) | verbose | debug }
364 Change the amount of debugging information output
365 when initialising the APIC and IO-APIC components.
368 See Documentation/networking/ipv6.txt.
370 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
371 Limit apic dumping. The parameter defines the maximal
372 number of local apics being dumped. Also it is possible
373 to set it to "all" by meaning -- no limit here.
374 Format: { 1 (default) | 2 | ... | all }.
375 The parameter valid if only apic=debug or
376 apic=verbose is specified.
377 Example: apic=debug show_lapic=all
379 apm= [APM] Advanced Power Management
380 See header of arch/x86/kernel/apm_32.c.
382 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
383 Format: <io>,<irq>,<nodeID>
387 atarimouse= [HW,MOUSE] Atari Mouse
389 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
390 EzKey and similar keyboards
392 atkbd.reset= [HW] Reset keyboard during initialization
394 atkbd.set= [HW] Select keyboard code set
395 Format: <int> (2 = AT (default), 3 = PS/2)
397 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
400 atkbd.softraw= [HW] Choose between synthetic and real raw mode
401 Format: <bool> (0 = real, 1 = synthetic (default))
403 atkbd.softrepeat= [HW]
404 Use software keyboard repeat
406 baycom_epp= [HW,AX25]
409 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
411 See header of drivers/net/hamradio/baycom_par.c.
413 baycom_ser_fdx= [HW,AX25]
414 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
415 Format: <io>,<irq>,<mode>[,<baud>]
416 See header of drivers/net/hamradio/baycom_ser_fdx.c.
418 baycom_ser_hdx= [HW,AX25]
419 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
420 Format: <io>,<irq>,<mode>
421 See header of drivers/net/hamradio/baycom_ser_hdx.c.
423 boot_delay= Milliseconds to delay each printk during boot.
424 Values larger than 10 seconds (10000) are changed to
428 bootmem_debug [KNL] Enable bootmem allocator debug messages.
430 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
431 bttv.radio= Most important insmod options are available as
433 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
436 bulk_remove=off [PPC] This parameter disables the use of the pSeries
437 firmware feature for flushing multiple hpte entries
440 c101= [NET] Moxa C101 synchronous serial card
442 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
443 Sometimes CPU hardware bugs make them report the cache
444 size incorrectly. The kernel will attempt work arounds
445 to fix known problems, but for some CPUs it is not
446 possible to determine what the correct size should be.
447 This option provides an override for these situations.
449 ccw_timeout_log [S390]
450 See Documentation/s390/CommonIO for details.
452 cgroup_disable= [KNL] Disable a particular controller
453 Format: {name of the controller(s) to disable}
454 {Currently supported controllers - "memory"}
456 checkreqprot [SELINUX] Set initial checkreqprot flag value.
457 Format: { "0" | "1" }
458 See security/selinux/Kconfig help text.
459 0 -- check protection applied by kernel (includes
460 any implied execute protection).
461 1 -- check protection requested by application.
462 Default value is set via a kernel config option.
463 Value can be changed at runtime via
464 /selinux/checkreqprot.
467 See Documentation/s390/CommonIO for details.
469 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
471 Forces specified clocksource (if available) to be used
472 when calculating gettimeofday(). If specified
473 clocksource is not available, it defaults to PIT.
474 Format: { pit | tsc | cyclone | pmtmr }
476 clocksource= Override the default clocksource
478 Override the default clocksource and use the clocksource
479 with the name specified.
480 Some clocksource names to choose from, depending on
482 [all] jiffies (this is the base, fallback clocksource)
484 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
485 pxa_timer,timer3,32k_counter,timer0_1
487 [X86-32] pit,hpet,tsc;
488 scx200_hrt on Geode; cyclone on IBM x440
496 clearcpuid=BITNUM [X86]
497 Disable CPUID feature X for the kernel. See
498 arch/x86/include/asm/cpufeature.h for the valid bit
499 numbers. Note the Linux specific bits are not necessarily
500 stable over kernel options, but the vendor specific
502 Also note that user programs calling CPUID directly
503 or using the feature without checking anything
504 will still see it. This just prevents it from
505 being used by the kernel or shown in /proc/cpuinfo.
506 Also note the kernel might malfunction if you disable
510 Sets the size of kernel global memory area for contiguous
511 memory allocations. For more information, see
512 include/linux/dma-contiguous.h
514 cmo_free_hint= [PPC] Format: { yes | no }
515 Specify whether pages are marked as being inactive
516 when they are freed. This is used in CMO environments
517 to determine OS memory pressure for page stealing by
521 coherent_pool=nn[KMG] [ARM,KNL]
522 Sets the size of memory pool for coherent, atomic dma
523 allocations, by default set to 256K.
525 code_bytes [X86] How many bytes of object code to print
530 com20020= [HW,NET] ARCnet - COM20020 chipset
532 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
534 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
538 ARCnet - COM90xx chipset (memory-mapped buffers)
539 Format: <io>[,<irq>[,<memstart>]]
541 condev= [HW,S390] console device
544 console= [KNL] Output console device and options.
546 tty<n> Use the virtual console device <n>.
550 Use the specified serial port. The options are of
551 the form "bbbbpnf", where "bbbb" is the baud rate,
552 "p" is parity ("n", "o", or "e"), "n" is number of
553 bits, and "f" is flow control ("r" for RTS or
554 omit it). Default is "9600n8".
556 See Documentation/serial-console.txt for more
558 Documentation/networking/netconsole.txt for an
561 uart[8250],io,<addr>[,options]
562 uart[8250],mmio,<addr>[,options]
563 Start an early, polled-mode console on the 8250/16550
564 UART at the specified I/O port or MMIO address,
565 switching to the matching ttyS device later. The
566 options are the same as for ttyS, above.
567 hvc<n> Use the hypervisor console device <n>. This is for
568 both Xen and PowerPC hypervisors.
570 If the device connected to the port is not a TTY but a braille
571 device, prepend "brl," before the device type, for instance
573 For now, only VisioBraille is supported.
575 consoleblank= [KNL] The console blank (screen saver) timeout in
576 seconds. Defaults to 10*60 = 10mins. A value of 0
577 disables the blank timer.
580 [KNL] Change the default value for
581 /proc/<pid>/coredump_filter.
582 See also Documentation/filesystems/proc.txt.
584 cpuidle.off=1 [CPU_IDLE]
585 disable the cpuidle sub-system
587 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
589 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
591 crashkernel=size[KMG][@offset[KMG]]
592 [KNL] Using kexec, Linux can switch to a 'crash kernel'
593 upon panic. This parameter reserves the physical
594 memory region [offset, offset + size] for that kernel
595 image. If '@offset' is omitted, then a suitable offset
596 is selected automatically. Check
597 Documentation/kdump/kdump.txt for further details.
599 crashkernel=range1:size1[,range2:size2,...][@offset]
600 [KNL] Same as above, but depends on the memory
601 in the running system. The syntax of range is
602 start-[end] where start and end are both
603 a memory unit (amount[KMG]). See also
604 Documentation/kdump/kdump.txt for an example.
606 crashkernel_low=size[KMG]
607 [KNL, x86_64] range under 4G. When crashkernel= is
608 passed, kernel allocate physical memory region
609 above 4G, that cause second kernel crash on system
610 that require some amount of low memory, e.g. swiotlb
611 requires at least 64M+32K low memory. Kernel would
612 try to allocate 72M below 4G automatically.
613 This one let user to specify own low range under 4G
614 for second kernel instead.
615 0: to disable low allocation.
620 cs89x0_media= [HW,NET]
621 Format: { rj45 | aui | bnc }
624 See header of drivers/s390/block/dasd_devmap.c.
626 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
627 (one device per port)
628 Format: <port#>,<type>
629 See also Documentation/input/joystick-parport.txt
631 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
632 time. See Documentation/dynamic-debug-howto.txt for
633 details. Deprecated, see dyndbg.
635 debug [KNL] Enable kernel debugging (events log level).
638 [KNL] verbose self-tests
640 Print debugging info while doing the locking API
642 We default to 0 (no extra messages), setting it to
643 1 will print _a lot_ more information - normally
644 only useful to kernel developers.
646 debug_objects [KNL] Enable object debugging
649 [KNL] Disable object debugging
651 debug_guardpage_minorder=
652 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
653 parameter allows control of the order of pages that will
654 be intentionally kept free (and hence protected) by the
655 buddy allocator. Bigger value increase the probability
656 of catching random memory corruption, but reduce the
657 amount of memory for normal system use. The maximum
658 possible value is MAX_ORDER/2. Setting this parameter
659 to 1 or 2 should be enough to identify most random
660 memory corruption problems caused by bugs in kernel or
661 driver code when a CPU writes to (or reads from) a
662 random memory location. Note that there exists a class
663 of memory corruptions problems caused by buggy H/W or
664 F/W or by drivers badly programing DMA (basically when
665 memory is written at bus level and the CPU MMU is
666 bypassed) which are not detectable by
667 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
668 tracking down these problems.
670 debugpat [X86] Enable PAT debugging
672 decnet.addr= [HW,NET]
673 Format: <area>[,<node>]
674 See also Documentation/networking/decnet.txt.
677 [same as hugepagesz=] The size of the default
678 HugeTLB page size. This is the size represented by
679 the legacy /proc/ hugepages APIs, used for SHM, and
680 default size when mounting hugetlbfs filesystems.
681 Defaults to the default architecture's huge page size
685 Set number of hash buckets for dentry cache.
688 IO parameters + enable/disable command.
690 digiepca= [HW,SERIAL]
691 See drivers/char/README.epca and
692 Documentation/serial/digiepca.txt.
695 See Documentation/networking/ipv6.txt.
697 disable_ddw [PPC/PSERIES]
698 Disable Dynamic DMA Window support. Use this if
699 to workaround buggy firmware.
702 See Documentation/networking/ipv6.txt.
704 disable_mtrr_cleanup [X86]
705 The kernel tries to adjust MTRR layout from continuous
706 to discrete, to make X server driver able to add WB
707 entry later. This parameter disables that.
709 disable_mtrr_trim [X86, Intel and AMD only]
710 By default the kernel will trim any uncacheable
711 memory out of your available memory pool based on
712 MTRR settings. This parameter disables that behavior,
713 possibly causing your machine to run very slowly.
715 disable_timer_pin_1 [X86]
716 Disable PIN 1 of APIC timer
717 Can be useful to work around chipset bugs.
719 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
720 this option disables the debugging code at boot.
722 dma_debug_entries=<number>
723 This option allows to tune the number of preallocated
724 entries for DMA-API debugging code. One entry is
725 required per DMA-API allocation. Use this if the
726 DMA-API debugging code disables itself because the
727 architectural default is too low.
729 dma_debug_driver=<driver_name>
730 With this option the DMA-API debugging driver
731 filter feature can be enabled at boot time. Just
732 pass the driver to filter for as the parameter.
733 The filter can be disabled or changed to another
734 driver later using sysfs.
736 drm_kms_helper.edid_firmware=[<connector>:]<file>
737 Broken monitors, graphic adapters and KVMs may
738 send no or incorrect EDID data sets. This parameter
739 allows to specify an EDID data set in the
740 /lib/firmware directory that is used instead.
741 Generic built-in EDID data sets are used, if one of
742 edid/1024x768.bin, edid/1280x1024.bin,
743 edid/1680x1050.bin, or edid/1920x1080.bin is given
744 and no file with the same name exists. Details and
745 instructions how to build your own EDID data are
746 available in Documentation/EDID/HOWTO.txt. An EDID
747 data set will only be used for a particular connector,
748 if its name and a colon are prepended to the EDID
753 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
754 module.dyndbg[="val"]
755 Enable debug messages at boot time. See
756 Documentation/dynamic-debug-howto.txt for details.
758 earlycon= [KNL] Output early console device and options.
759 uart[8250],io,<addr>[,options]
760 uart[8250],mmio,<addr>[,options]
761 uart[8250],mmio32,<addr>[,options]
762 Start an early, polled-mode console on the 8250/16550
763 UART at the specified I/O port or MMIO address.
764 MMIO inter-register address stride is either 8-bit
765 (mmio) or 32-bit (mmio32).
766 The options are the same as for ttyS, above.
768 earlyprintk= [X86,SH,BLACKFIN]
771 earlyprintk=serial[,ttySn[,baudrate]]
772 earlyprintk=ttySn[,baudrate]
773 earlyprintk=dbgp[debugController#]
775 Append ",keep" to not disable it when the real console
778 Only vga or serial or usb debug port at a time.
780 Currently only ttyS0 and ttyS1 are supported.
782 Interaction with the standard serial driver is not
785 The VGA output is eventually overwritten by the real
788 The xen output can only be used by Xen PV guests.
790 ekgdboc= [X86,KGDB] Allow early kernel console debugging
793 This is designed to be used in conjunction with
794 the boot argument: earlyprintk=vga
797 Format: {"off" | "on" | "skip[mbr]"}
799 eisa_irq_edge= [PARISC,HW]
800 See header of drivers/parisc/eisa.c.
803 See comment before function elanfreq_setup() in
804 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
807 Format: {"cfq" | "deadline" | "noop"}
808 See Documentation/block/cfq-iosched.txt and
809 Documentation/block/deadline-iosched.txt for details.
811 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
812 Specifies physical address of start of kernel core
813 image elf header and optionally the size. Generally
814 kexec loader will pass this option to capture kernel.
815 See Documentation/kdump/kdump.txt for details.
817 enable_mtrr_cleanup [X86]
818 The kernel tries to adjust MTRR layout from continuous
819 to discrete, to make X server driver able to add WB
820 entry later. This parameter enables that.
822 enable_timer_pin_1 [X86]
823 Enable PIN 1 of APIC timer
824 Can be useful to work around chipset bugs
825 (in particular on some ATI chipsets).
826 The kernel tries to set a reasonable default.
828 enforcing [SELINUX] Set initial enforcing status.
830 See security/selinux/Kconfig help text.
831 0 -- permissive (log only, no denials).
832 1 -- enforcing (deny and log).
834 Value can be changed at runtime via /selinux/enforce.
837 Disable Error Record Serialization Table (ERST)
840 ether= [HW,NET] Ethernet cards parameters
841 This option is obsoleted by the "netdev=" option, which
842 has equivalent usage. See its documentation for details.
846 Permit 'security.evm' to be updated regardless of
847 current integrity status.
851 fail_make_request=[KNL]
852 General fault injection mechanism.
853 Format: <interval>,<probability>,<space>,<times>
854 See also Documentation/fault-injection/.
857 See Documentation/blockdev/floppy.txt.
859 force_pal_cache_flush
860 [IA-64] Avoid check_sal_cache_flush which may hang on
861 buggy SAL_CACHE_FLUSH implementations. Using this
862 parameter will force ia64_sal_cache_flush to call
863 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
866 [FTRACE] will set and start the specified tracer
867 as early as possible in order to facilitate early
870 ftrace_dump_on_oops[=orig_cpu]
871 [FTRACE] will dump the trace buffers on oops.
872 If no parameter is passed, ftrace will dump
873 buffers of all CPUs, but if you pass orig_cpu, it will
874 dump only the buffer of the CPU that triggered the
877 ftrace_filter=[function-list]
878 [FTRACE] Limit the functions traced by the function
879 tracer at boot up. function-list is a comma separated
880 list of functions. This list can be changed at run
881 time by the set_ftrace_filter file in the debugfs
884 ftrace_notrace=[function-list]
885 [FTRACE] Do not trace the functions specified in
886 function-list. This list can be changed at run time
887 by the set_ftrace_notrace file in the debugfs
890 ftrace_graph_filter=[function-list]
891 [FTRACE] Limit the top level callers functions traced
892 by the function graph tracer at boot up.
893 function-list is a comma separated list of functions
894 that can be changed at run time by the
895 set_graph_function file in the debugfs tracing directory.
898 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
899 support via parallel port (up to 5 devices per port)
900 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
901 See also Documentation/input/joystick-parport.txt
905 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
909 gcov_persist= [GCOV] When non-zero (default), profiling data for
910 kernel modules is saved and remains accessible via
911 debugfs, even when the module is unloaded/reloaded.
912 When zero, profiling data is discarded and associated
913 debugfs files are removed at module unload time.
915 gpt [EFI] Forces disk with valid GPT signature but
916 invalid Protective MBR to be treated as GPT.
918 grcan.enable0= [HW] Configuration of physical interface 0. Determines
919 the "Enable 0" bit of the configuration register.
922 grcan.enable1= [HW] Configuration of physical interface 1. Determines
923 the "Enable 0" bit of the configuration register.
926 grcan.select= [HW] Select which physical interface to use.
929 grcan.txsize= [HW] Sets the size of the tx buffer.
930 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
932 grcan.rxsize= [HW] Sets the size of the rx buffer.
933 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
936 hashdist= [KNL,NUMA] Large hashes allocated during boot
937 are distributed across NUMA nodes. Defaults on
938 for 64-bit NUMA, off otherwise.
939 Format: 0 | 1 (for off | on)
941 hcl= [IA-64] SGI's Hardware Graph compatibility layer
943 hd= [EIDE] (E)IDE hard drive subsystem geometry
944 Format: <cyl>,<head>,<sect>
947 Disable Hardware Error Source Table (HEST) support;
948 corresponding firmware-first mode error processing
949 logic will be disabled.
951 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
952 size of <nn>. This works even on boxes that have no
953 highmem otherwise. This also works to reduce highmem
954 size on bigger boxes.
956 highres= [KNL] Enable/disable high resolution timer mode.
957 Valid parameters: "on", "off"
961 See Documentation/isdn/README.HiSax.
965 hpet= [X86-32,HPET] option to control HPET usage
966 Format: { enable (default) | disable | force |
968 disable: disable HPET and use PIT instead
969 force: allow force enabled of undocumented chips (ICH4,
971 verbose: show contents of HPET registers during setup
973 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
974 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
975 On x86-64 and powerpc, this option can be specified
976 multiple times interleaved with hugepages= to reserve
977 huge pages of different sizes. Valid pages sizes on
978 x86-64 are 2M (when the CPU supports "pse") and 1G
979 (when the CPU supports the "pdpe1gb" cpuinfo flag)
980 Note that 1GB pages can only be allocated at boot time
981 using hugepages= and not freed afterwards.
983 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
984 terminal devices. Valid values: 0..8
985 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
986 If specified, z/VM IUCV HVC accepts connections
987 from listed z/VM user IDs only.
989 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
990 hardware thread id mappings.
991 Format: <cpu>:<hwthread>
994 Do not unregister boot console at start. This is only
995 useful for debugging when something happens in the window
996 between unregistering the boot console and initializing
999 i2c_bus= [HW] Override the default board specific I2C bus speed
1000 or register an additional I2C bus that is not
1001 registered from board initialization code.
1005 i8042.debug [HW] Toggle i8042 debug mode
1006 i8042.direct [HW] Put keyboard port into non-translated mode
1007 i8042.dumbkbd [HW] Pretend that controller can only read data from
1008 keyboard and cannot control its state
1009 (Don't attempt to blink the leds)
1010 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1011 i8042.nokbd [HW] Don't check/create keyboard port
1012 i8042.noloop [HW] Disable the AUX Loopback command while probing
1014 i8042.nomux [HW] Don't check presence of an active multiplexing
1016 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1018 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1019 i8042.reset [HW] Reset the controller during init and cleanup
1020 i8042.unlock [HW] Unlock (ignore) the keylock
1024 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1025 indicates that the driver is running on unsupported
1027 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1028 does not match list of supported models.
1030 [HW] Report power status in /proc/i8k
1031 (disabled by default)
1032 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1035 i915.invert_brightness=
1036 [DRM] Invert the sense of the variable that is used to
1037 set the brightness of the panel backlight. Normally a
1038 brightness value of 0 indicates backlight switched off,
1039 and the maximum of the brightness value sets the backlight
1040 to maximum brightness. If this parameter is set to 0
1041 (default) and the machine requires it, or this parameter
1042 is set to 1, a brightness value of 0 sets the backlight
1043 to maximum brightness, and the maximum of the brightness
1044 value switches the backlight off.
1045 -1 -- never invert brightness
1046 0 -- machine default
1047 1 -- force brightness inversion
1050 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1052 ide-core.nodma= [HW] (E)IDE subsystem
1053 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1054 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1055 .cdrom .chs .ignore_cable are additional options
1056 See Documentation/ide/ide.txt.
1058 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1059 Claim all unknown PCI IDE storage controllers.
1062 Format: idle=poll, idle=halt, idle=nomwait
1063 Poll forces a polling idle loop that can slightly
1064 improve the performance of waking up a idle CPU, but
1065 will use a lot of power and make the system run hot.
1067 idle=halt: Halt is forced to be used for CPU idle.
1068 In such case C2/C3 won't be used again.
1069 idle=nomwait: Disable mwait for CPU C-states
1071 ignore_loglevel [KNL]
1072 Ignore loglevel setting - this will print /all/
1073 kernel messages to the console. Useful for debugging.
1074 We also add it as printk module parameter, so users
1075 could change it dynamically, usually by
1076 /sys/module/printk/parameters/ignore_loglevel.
1078 ihash_entries= [KNL]
1079 Set number of hash buckets for inode cache.
1081 ima_appraise= [IMA] appraise integrity measurements
1082 Format: { "off" | "enforce" | "fix" }
1085 ima_appraise_tcb [IMA]
1086 The builtin appraise policy appraises all files
1090 Format: { "0" | "1" }
1091 0 -- integrity auditing messages. (Default)
1092 1 -- enable informational integrity auditing messages.
1095 Format: { "sha1" | "md5" }
1099 Load a policy which meets the needs of the Trusted
1100 Computing Base. This means IMA will measure all
1101 programs exec'd, files mmap'd for exec, and all files
1102 opened for read by uid=0.
1106 Run specified binary instead of /sbin/init as init
1109 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1110 for working out where the kernel is dying during
1113 initrd= [BOOT] Specify the location of the initial ramdisk
1115 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1118 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1120 Enable intel iommu driver.
1122 Disable intel iommu driver.
1123 igfx_off [Default Off]
1124 By default, gfx is mapped as normal device. If a gfx
1125 device has a dedicated DMAR unit, the DMAR unit is
1126 bypassed by not enabling DMAR with this option. In
1127 this case, gfx device will use physical address for
1130 With this option iommu will not optimize to look
1131 for io virtual address below 32-bit forcing dual
1132 address cycle on pci bus for cards supporting greater
1133 than 32-bit addressing. The default is to look
1134 for translation below 32-bit and if not available
1135 then look in the higher range.
1136 strict [Default Off]
1137 With this option on every unmap_single operation will
1138 result in a hardware IOTLB flush operation as opposed
1139 to batching them for performance.
1140 sp_off [Default Off]
1141 By default, super page will be supported if Intel IOMMU
1142 has the capability. With this option, super page will
1145 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1146 0 disables intel_idle and fall back on acpi_idle.
1147 1 to 6 specify maximum depth of C-state.
1151 Do not enable intel_pstate as the default
1152 scaling driver for the supported processors
1154 intremap= [X86-64, Intel-IOMMU]
1155 on enable Interrupt Remapping (default)
1156 off disable Interrupt Remapping
1157 nosid disable Source ID checking
1159 BIOS x2APIC opt-out request will be ignored
1161 iomem= Disable strict checking of access to MMIO memory
1162 strict regions from userspace.
1179 io7= [HW] IO7 for Marvel based alpha systems
1180 See comment before marvel_specify_io7 in
1181 arch/alpha/kernel/core_marvel.c.
1183 io_delay= [X86] I/O delay method
1185 Standard port 0x80 based delay
1187 Alternate port 0xed based delay (needed on some systems)
1189 Simple two microseconds delay
1194 See Documentation/filesystems/nfs/nfsroot.txt.
1196 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1197 See comment before ip2_setup() in
1198 drivers/char/ip2/ip2base.c.
1201 When an interrupt is not handled search all handlers
1202 for it. Intended to get systems with badly broken
1206 When an interrupt is not handled search all handlers
1207 for it. Also check all handlers each timer
1208 interrupt. Intended to get systems with badly broken
1212 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1214 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1216 <cpu number>,...,<cpu number>
1218 <cpu number>-<cpu number>
1219 (must be a positive range in ascending order)
1221 <cpu number>,...,<cpu number>-<cpu number>
1223 This option can be used to specify one or more CPUs
1224 to isolate from the general SMP balancing and scheduling
1225 algorithms. You can move a process onto or off an
1226 "isolated" CPU via the CPU affinity syscalls or cpuset.
1227 <cpu number> begins at 0 and the maximum value is
1228 "number of CPUs in system - 1".
1230 This option is the preferred way to isolate CPUs. The
1231 alternative -- manually setting the CPU mask of all
1232 tasks in the system -- can cause problems and
1233 suboptimal load balancer performance.
1237 js= [HW,JOY] Analog joystick
1238 See Documentation/input/joystick.txt.
1242 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1243 specifies the amount of memory usable by the kernel
1244 for non-movable allocations. The requested amount is
1245 spread evenly throughout all nodes in the system. The
1246 remaining memory in each node is used for Movable
1247 pages. In the event, a node is too small to have both
1248 kernelcore and Movable pages, kernelcore pages will
1249 take priority and other nodes will have a larger number
1250 of kernelcore pages. The Movable zone is used for the
1251 allocation of pages that may be reclaimed or moved
1252 by the page migration subsystem. This means that
1253 HugeTLB pages may not be allocated from this zone.
1254 Note that allocations like PTEs-from-HighMem still
1255 use the HighMem zone if it exists, and the Normal
1256 zone if it does not.
1258 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1259 Format: <Controller#>[,poll interval]
1260 The controller # is the number of the ehci usb debug
1261 port as it is probed via PCI. The poll interval is
1262 optional and is the number seconds in between
1263 each poll cycle to the debug port in case you need
1264 the functionality for interrupting the kernel with
1265 gdb or control-c on the dbgp connection. When
1266 not using this parameter you use sysrq-g to break into
1267 the kernel debugger.
1269 kgdboc= [KGDB,HW] kgdb over consoles.
1270 Requires a tty driver that supports console polling,
1271 or a supported polling keyboard driver (non-usb).
1272 Serial only format: <serial_device>[,baud]
1273 keyboard only format: kbd
1274 keyboard and serial format: kbd,<serial_device>[,baud]
1275 Optional Kernel mode setting:
1276 kms, kbd format: kms,kbd
1277 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1279 kgdbwait [KGDB] Stop kernel execution and enter the
1280 kernel debugger at the earliest opportunity.
1282 kmac= [MIPS] korina ethernet MAC address.
1283 Configure the RouterBoard 532 series on-chip
1284 Ethernet adapter MAC address.
1286 kmemleak= [KNL] Boot-time kmemleak enable/disable
1287 Valid arguments: on, off
1290 kstack=N [X86] Print N words from the kernel stack
1293 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1294 Default is 0 (don't ignore, but inject #GP)
1296 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1300 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1301 Default is 1 (enabled)
1303 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1305 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1307 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1308 (virtualized MMU) support on capable Intel chips.
1309 Default is 1 (enabled)
1311 kvm-intel.emulate_invalid_guest_state=
1312 [KVM,Intel] Enable emulation of invalid guest states
1313 Default is 0 (disabled)
1315 kvm-intel.flexpriority=
1316 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1317 Default is 1 (enabled)
1320 [KVM,Intel] Enable VMX nesting (nVMX).
1321 Default is 0 (disabled)
1323 kvm-intel.unrestricted_guest=
1324 [KVM,Intel] Disable unrestricted guest feature
1325 (virtualized real and unpaged mode) on capable
1326 Intel chips. Default is 1 (enabled)
1328 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1329 feature (tagged TLBs) on capable Intel chips.
1330 Default is 1 (enabled)
1336 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1339 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1340 value for LAPIC timer one-shot implementation. Default
1341 back to the programmable timer unit in the LAPIC.
1343 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1346 libata.dma= [LIBATA] DMA control
1347 libata.dma=0 Disable all PATA and SATA DMA
1348 libata.dma=1 PATA and SATA Disk DMA only
1349 libata.dma=2 ATAPI (CDROM) DMA only
1350 libata.dma=4 Compact Flash DMA only
1351 Combinations also work, so libata.dma=3 enables DMA
1352 for disks and CDROMs, but not CFs.
1354 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1355 libata.ignore_hpa=0 keep BIOS limits (default)
1356 libata.ignore_hpa=1 ignore limits, using full disk
1358 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1362 libata.force= [LIBATA] Force configurations. The format is comma
1363 separated list of "[ID:]VAL" where ID is
1364 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1365 matching port, link or device. Basically, it matches
1366 the ATA ID string printed on console by libata. If
1367 the whole ID part is omitted, the last PORT and DEVICE
1368 values are used. If ID hasn't been specified yet, the
1369 configuration applies to all ports, links and devices.
1371 If only DEVICE is omitted, the parameter applies to
1372 the port and all links and devices behind it. DEVICE
1373 number of 0 either selects the first device or the
1374 first fan-out link behind PMP device. It does not
1375 select the host link. DEVICE number of 15 selects the
1376 host link and device attached to it.
1378 The VAL specifies the configuration to force. As long
1379 as there's no ambiguity shortcut notation is allowed.
1380 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1381 The following configurations can be forced.
1383 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1384 Any ID with matching PORT is used.
1386 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1388 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1389 udma[/][16,25,33,44,66,100,133] notation is also
1392 * [no]ncq: Turn on or off NCQ.
1394 * nohrst, nosrst, norst: suppress hard, soft
1397 * rstonce: only attempt one reset during
1398 hot-unplug link recovery
1400 * dump_id: dump IDENTIFY data.
1402 If there are multiple matching configurations changing
1403 the same attribute, the last one is used.
1405 memblock=debug [KNL] Enable memblock debug messages.
1407 load_ramdisk= [RAM] List of ramdisks to load from floppy
1408 See Documentation/blockdev/ramdisk.txt.
1410 lockd.nlm_grace_period=P [NFS] Assign grace period.
1413 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1416 lockd.nlm_timeout=T [NFS] Assign timeout value.
1419 lockd.nlm_udpport=M [NFS] Assign UDP port.
1422 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1425 loglevel= All Kernel Messages with a loglevel smaller than the
1426 console loglevel will be printed to the console. It can
1427 also be changed with klogd or other programs. The
1428 loglevels are defined as follows:
1430 0 (KERN_EMERG) system is unusable
1431 1 (KERN_ALERT) action must be taken immediately
1432 2 (KERN_CRIT) critical conditions
1433 3 (KERN_ERR) error conditions
1434 4 (KERN_WARNING) warning conditions
1435 5 (KERN_NOTICE) normal but significant condition
1436 6 (KERN_INFO) informational
1437 7 (KERN_DEBUG) debug-level messages
1439 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1440 in bytes. n must be a power of two. The default
1441 size is set in the kernel config file.
1443 logo.nologo [FB] Disables display of the built-in Linux logo.
1444 This may be used to provide more screen space for
1445 kernel log messages and is useful when debugging
1446 kernel boot problems.
1448 lp=0 [LP] Specify parallel ports to use, e.g,
1449 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1450 lp=reset first parallel port). 'lp=0' disables the
1451 lp=auto printer driver. 'lp=reset' (which can be
1452 specified in addition to the ports) causes
1453 attached printers to be reset. Using
1454 lp=port1,port2,... specifies the parallel ports
1455 to associate lp devices with, starting with
1456 lp0. A port specification may be 'none' to skip
1457 that lp device, or a parport name such as
1458 'parport0'. Specifying 'lp=auto' instead of a
1459 port specification list means that device IDs
1460 from each port should be examined, to see if
1461 an IEEE 1284-compliant printer is attached; if
1462 so, the driver will manage that printer.
1463 See also header of drivers/char/lp.c.
1466 Sets loops_per_jiffy to given constant, thus avoiding
1467 time-consuming boot-time autodetection (up to 250 ms per
1468 CPU). 0 enables autodetection (default). To determine
1469 the correct value for your kernel, boot with normal
1470 autodetection and see what value is printed. Note that
1471 on SMP systems the preset will be applied to all CPUs,
1472 which is likely to cause problems if your CPUs need
1473 significantly divergent settings. An incorrect value
1474 will cause delays in the kernel to be wrong, leading to
1475 unpredictable I/O errors and other breakage. Although
1476 unlikely, in the extreme case this might damage your
1480 Format: <io>,<irq>,<dma>
1482 machvec= [IA-64] Force the use of a particular machine-vector
1483 (machvec) in a generic kernel.
1484 Example: machvec=hpzx1_swiotlb
1486 machtype= [Loongson] Share the same kernel image file between different
1488 Example: machtype=lemote-yeeloong-2f-7inch
1490 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1491 than or equal to this physical address is ignored.
1493 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1494 should make use of. maxcpus=n : n >= 0 limits the
1495 kernel to using 'n' processors. n=0 is a special case,
1496 it is equivalent to "nosmp", which also disables
1499 max_loop= [LOOP] The number of loop block devices that get
1500 (loop.max_loop) unconditionally pre-created at init time. The default
1501 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1502 of statically allocating a predefined number, loop
1503 devices can be requested on-demand with the
1504 /dev/loop-control interface.
1506 mce [X86-32] Machine Check Exception
1508 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1510 md= [HW] RAID subsystems devices and level
1511 See Documentation/md.txt.
1514 Format: <first>,<last>
1515 Specifies range of consoles to be captured by the MDA.
1517 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1518 Amount of memory to be used when the kernel is not able
1519 to see the whole system memory or for test.
1520 [X86] Work as limiting max address. Use together
1521 with memmap= to avoid physical address space collisions.
1522 Without memmap= PCI devices could be placed at addresses
1523 belonging to unused RAM.
1525 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1529 [KNL,SH] Allow user to override the default size for
1530 per-device physically contiguous DMA buffers.
1532 memmap=exactmap [KNL,X86] Enable setting of an exact
1533 E820 memory map, as specified by the user.
1534 Such memmap=exactmap lines can be constructed based on
1535 BIOS output or other requirements. See the memmap=nn@ss
1538 memmap=nn[KMG]@ss[KMG]
1539 [KNL] Force usage of a specific region of memory
1540 Region of memory to be used, from ss to ss+nn.
1542 memmap=nn[KMG]#ss[KMG]
1543 [KNL,ACPI] Mark specific memory as ACPI data.
1544 Region of memory to be used, from ss to ss+nn.
1546 memmap=nn[KMG]$ss[KMG]
1547 [KNL,ACPI] Mark specific memory as reserved.
1548 Region of memory to be used, from ss to ss+nn.
1549 Example: Exclude memory from 0x18690000-0x1869ffff
1550 memmap=64K$0x18690000
1552 memmap=0x10000$0x18690000
1554 memory_corruption_check=0/1 [X86]
1555 Some BIOSes seem to corrupt the first 64k of
1556 memory when doing things like suspend/resume.
1557 Setting this option will scan the memory
1558 looking for corruption. Enabling this will
1559 both detect corruption and prevent the kernel
1560 from using the memory being corrupted.
1561 However, its intended as a diagnostic tool; if
1562 repeatable BIOS-originated corruption always
1563 affects the same memory, you can use memmap=
1564 to prevent the kernel from using that memory.
1566 memory_corruption_check_size=size [X86]
1567 By default it checks for corruption in the low
1568 64k, making this memory unavailable for normal
1569 use. Use this parameter to scan for
1570 corruption in more or less memory.
1572 memory_corruption_check_period=seconds [X86]
1573 By default it checks for corruption every 60
1574 seconds. Use this parameter to check at some
1575 other rate. 0 disables periodic checking.
1577 memtest= [KNL,X86] Enable memtest
1579 default : 0 <disable>
1580 Specifies the number of memtest passes to be
1581 performed. Each pass selects another test
1582 pattern from a given set of patterns. Memtest
1583 fills the memory with this pattern, validates
1584 memory contents and reserves bad memory
1585 regions that are detected.
1587 meye.*= [HW] Set MotionEye Camera parameters
1588 See Documentation/video4linux/meye.txt.
1590 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1591 Multi-Function General Purpose Timers on AMD Geode
1594 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1595 the BIOS has incorrectly applied a workaround. TinyBIOS
1596 version 0.98 is known to be affected, 0.99 fixes the
1597 problem by letting the user disable the workaround.
1601 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1602 physical address is ignored.
1604 mini2440= [ARM,HW,KNL]
1605 Format:[0..2][b][c][t]
1607 MINI2440 configuration specification:
1608 0 - The attached screen is the 3.5" TFT
1609 1 - The attached screen is the 7" TFT
1610 2 - The VGA Shield is attached (1024x768)
1611 Leaving out the screen size parameter will not load
1612 the TFT driver, and the framebuffer will be left
1614 b - Enable backlight. The TFT backlight pin will be
1615 linked to the kernel VESA blanking code and a GPIO
1616 LED. This parameter is not necessary when using the
1618 c - Enable the s3c camera interface.
1619 t - Reserved for enabling touchscreen support. The
1620 touchscreen support is not enabled in the mainstream
1621 kernel as of 2.6.30, a preliminary port can be found
1622 in the "bleeding edge" mini2440 support kernel at
1623 http://repo.or.cz/w/linux-2.6/mini2440.git
1626 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1627 parameter allows control of the logging verbosity for
1628 the additional memory initialisation checks. A value
1629 of 0 disables mminit logging and a level of 4 will
1630 log everything. Information is printed at KERN_DEBUG
1631 so loglevel=8 may also need to be specified.
1634 [KNL] When CONFIG_MODULE_SIG is set, this means that
1635 modules without (valid) signatures will fail to load.
1636 Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
1637 is always true, so this option does nothing.
1640 [MOUSE] Maximum time between finger touching and
1641 leaving touchpad surface for touch to be considered
1642 a tap and be reported as a left button click (for
1643 touchpads working in absolute mode only).
1645 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1646 reporting absolute coordinates, such as tablets
1647 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1648 reporting absolute coordinates, such as tablets
1650 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1651 is similar to kernelcore except it specifies the
1652 amount of memory used for migratable allocations.
1653 If both kernelcore and movablecore is specified,
1654 then kernelcore will be at *least* the specified
1655 value but may be more. If movablecore on its own
1656 is specified, the administrator must be careful
1657 that the amount of memory usable for all allocations
1660 MTD_Partition= [MTD]
1661 Format: <name>,<region-number>,<size>,<offset>
1663 MTD_Region= [MTD] Format:
1664 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1667 See drivers/mtd/cmdlinepart.c.
1669 multitce=off [PPC] This parameter disables the use of the pSeries
1670 firmware feature for updating multiple TCE entries
1673 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1675 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1677 boundary - index of last SLC block on Flex-OneNAND.
1678 The remaining blocks are configured as MLC blocks.
1679 lock - Configure if Flex-OneNAND boundary should be locked.
1680 Once locked, the boundary cannot be changed.
1681 1 indicates lock status, 0 indicates unlock status.
1684 ARM/S3C2412 JIVE boot control
1686 See arch/arm/mach-s3c2412/mach-jive.c
1688 mtouchusb.raw_coordinates=
1689 [HW] Make the MicroTouch USB driver use raw coordinates
1690 ('y', default) or cooked coordinates ('n')
1692 mtrr_chunk_size=nn[KMG] [X86]
1693 used for mtrr cleanup. It is largest continuous chunk
1694 that could hold holes aka. UC entries.
1696 mtrr_gran_size=nn[KMG] [X86]
1697 Used for mtrr cleanup. It is granularity of mtrr block.
1699 Large value could prevent small alignment from
1702 mtrr_spare_reg_nr=n [X86]
1704 Range: 0,7 : spare reg number
1706 Used for mtrr cleanup. It is spare mtrr entries number.
1707 Set to 2 or more if your graphical card needs more.
1709 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1711 netdev= [NET] Network devices parameters
1712 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1713 Note that mem_start is often overloaded to mean
1714 something different and driver-specific.
1715 This usage is only documented in each driver source
1719 [NETFILTER] Enable connection tracking flow accounting
1720 0 to disable accounting
1721 1 to enable accounting
1724 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1725 See Documentation/filesystems/nfs/nfsroot.txt.
1727 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1728 See Documentation/filesystems/nfs/nfsroot.txt.
1730 nfsrootdebug [NFS] enable nfsroot debugging messages.
1731 See Documentation/filesystems/nfs/nfsroot.txt.
1733 nfs.callback_tcpport=
1734 [NFS] set the TCP port on which the NFSv4 callback
1735 channel should listen.
1738 [NFS] sets the pathname to the program which is used
1739 to update the NFS client cache entries.
1741 nfs.cache_getent_timeout=
1742 [NFS] sets the timeout after which an attempt to
1743 update a cache entry is deemed to have failed.
1745 nfs.idmap_cache_timeout=
1746 [NFS] set the maximum lifetime for idmapper cache
1750 [NFS] enable 64-bit inode numbers.
1751 If zero, the NFS client will fake up a 32-bit inode
1752 number for the readdir() and stat() syscalls instead
1753 of returning the full 64-bit number.
1754 The default is to return 64-bit inode numbers.
1756 nfs.max_session_slots=
1757 [NFSv4.1] Sets the maximum number of session slots
1758 the client will attempt to negotiate with the server.
1759 This limits the number of simultaneous RPC requests
1760 that the client can send to the NFSv4.1 server.
1761 Note that there is little point in setting this
1762 value higher than the max_tcp_slot_table_limit.
1764 nfs.nfs4_disable_idmapping=
1765 [NFSv4] When set to the default of '1', this option
1766 ensures that both the RPC level authentication
1767 scheme and the NFS level operations agree to use
1768 numeric uids/gids if the mount is using the
1769 'sec=sys' security flavour. In effect it is
1770 disabling idmapping, which can make migration from
1771 legacy NFSv2/v3 systems to NFSv4 easier.
1772 Servers that do not support this mode of operation
1773 will be autodetected by the client, and it will fall
1774 back to using the idmapper.
1775 To turn off this behaviour, set the value to '0'.
1777 [NFS4] Specify an additional fixed unique ident-
1778 ification string that NFSv4 clients can insert into
1779 their nfs_client_id4 string. This is typically a
1780 UUID that is generated at system install time.
1782 nfs.send_implementation_id =
1783 [NFSv4.1] Send client implementation identification
1784 information in exchange_id requests.
1785 If zero, no implementation identification information
1787 The default is to send the implementation identification
1790 nfsd.nfs4_disable_idmapping=
1791 [NFSv4] When set to the default of '1', the NFSv4
1792 server will return only numeric uids and gids to
1793 clients using auth_sys, and will accept numeric uids
1794 and gids from such clients. This is intended to ease
1795 migration from NFSv2/v3.
1797 objlayoutdriver.osd_login_prog=
1798 [NFS] [OBJLAYOUT] sets the pathname to the program which
1799 is used to automatically discover and login into new
1800 osd-targets. Please see:
1801 Documentation/filesystems/pnfs.txt for more explanations
1803 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1804 when a NMI is triggered.
1805 Format: [state][,regs][,debounce][,die]
1807 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1808 Format: [panic,][nopanic,][num]
1810 0 - turn nmi_watchdog off
1811 When panic is specified, panic when an NMI watchdog
1812 timeout occurs (or 'nopanic' to override the opposite
1814 This is useful when you use a panic=... timeout and
1815 need the box quickly up again.
1817 netpoll.carrier_timeout=
1818 [NET] Specifies amount of time (in seconds) that
1819 netpoll should wait for a carrier. By default netpoll
1822 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1823 emulation library even if a 387 maths coprocessor
1827 [HW] Never suspend the console
1828 Disable suspending of consoles during suspend and
1829 hibernate operations. Once disabled, debugging
1830 messages can reach various consoles while the rest
1831 of the system is being put to sleep (ie, while
1832 debugging driver suspend/resume hooks). This may
1833 not work reliably with all consoles, but is known
1834 to work with serial and VGA consoles.
1835 To facilitate more flexible debugging, we also add
1836 console_suspend, a printk module parameter to control
1837 it. Users could use console_suspend (usually
1838 /sys/module/printk/parameters/console_suspend) to
1839 turn on/off it dynamically.
1841 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1842 caches in the slab allocator. Saves per-node memory,
1843 but will impact performance.
1847 noapic [SMP,APIC] Tells the kernel to not make use of any
1848 IOAPICs that may be present in the system.
1850 noautogroup Disable scheduler automatic task group creation.
1852 nobats [PPC] Do not use BATs for mapping kernel lowmem
1853 on "Classic" PPC cores.
1857 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1859 nodelayacct [KNL] Disable per-task delay accounting
1861 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1863 nodsp [SH] Disable hardware DSP at boot time.
1865 noefi [X86] Disable EFI runtime services support.
1870 On X86-32 available only on PAE configured kernels.
1871 noexec=on: enable non-executable mappings (default)
1872 noexec=off: disable non-executable mappings
1875 Disable SMAP (Supervisor Mode Access Prevention)
1876 even if it is supported by processor.
1879 Disable SMEP (Supervisor Mode Execution Prevention)
1880 even if it is supported by processor.
1883 This affects only 32-bit executables.
1884 noexec32=on: enable non-executable mappings (default)
1885 read doesn't imply executable mappings
1886 noexec32=off: disable non-executable mappings
1887 read implies executable mappings
1889 nofpu [SH] Disable hardware FPU at boot time.
1891 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1892 register save and restore. The kernel will only save
1893 legacy floating-point registers on task switch.
1895 noxsave [BUGS=X86] Disables x86 extended register state save
1896 and restore using xsave. The kernel will fallback to
1897 enabling legacy floating-point and sse state.
1900 on enable eager fpu restore
1901 off disable eager fpu restore
1902 auto selects the default scheme, which automatically
1903 enables eagerfpu restore for xsaveopt.
1905 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1906 wfi(ARM) instruction doesn't work correctly and not to
1907 use it. This is also useful when using JTAG debugger.
1909 no_file_caps Tells the kernel not to honor file capabilities. The
1910 only way then for a file to be executed with privilege
1911 is to be setuid root or executed by root.
1913 nohalt [IA-64] Tells the kernel not to use the power saving
1914 function PAL_HALT_LIGHT when idle. This increases
1915 power-consumption. On the positive side, it reduces
1916 interrupt wake-up latency, which may improve performance
1917 in certain environments such as networked servers or
1920 nohz= [KNL] Boottime enable/disable dynamic ticks
1921 Valid arguments: on, off
1924 noiotrap [SH] Disables trapped I/O port accesses.
1926 noirqdebug [X86-32] Disables the code which attempts to detect and
1927 disable unhandled interrupt sources.
1929 no_timer_check [X86,APIC] Disables the code which tests for
1930 broken timer IRQ sources.
1932 noisapnp [ISAPNP] Disables ISA PnP code.
1934 noinitrd [RAM] Tells the kernel not to load any configured
1937 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1939 [Deprecated - use intremap=off]
1943 nojitter [IA-64] Disables jitter checking for ITC timers.
1945 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1947 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1950 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1951 steal time is computed, but won't influence scheduler
1954 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1956 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1958 noltlbs [PPC] Do not use large page/tlb entries for kernel
1959 lowmem mapping on PPC40x.
1961 nomca [IA-64] Disable machine check abort handling
1963 nomce [X86-32] Machine Check Exception
1965 nomfgpt [X86-32] Disable Multi-Function General Purpose
1966 Timer usage (for AMD Geode machines).
1968 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1969 shutdown the other cpus. Instead use the REBOOT_VECTOR
1972 nomodule Disable module load
1974 nopat [X86] Disable PAT (page attribute table extension of
1975 pagetables) support.
1977 norandmaps Don't use address space randomization. Equivalent to
1978 echo 0 > /proc/sys/kernel/randomize_va_space
1980 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1982 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1983 with UP alternatives
1985 noresidual [PPC] Don't use residual data on PReP machines.
1987 nordrand [X86] Disable the direct use of the RDRAND
1988 instruction even if it is supported by the
1989 processor. RDRAND is still available to user
1992 noresume [SWSUSP] Disables resume and restores original swap
1995 no-scroll [VGA] Disables scrollback.
1996 This is required for the Braillex ib80-piezo Braille
1997 reader made by F.H. Papenmeier (Germany).
2001 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2003 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
2004 and disable the IO APIC. legacy for "maxcpus=0".
2006 nosoftlockup [KNL] Disable the soft-lockup detector.
2008 nosync [HW,M68K] Disables sync negotiation for all devices.
2010 notsc [BUGS=X86-32] Disable Time Stamp Counter
2012 nousb [USB] Disable the USB subsystem
2014 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2018 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2020 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2021 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2022 Some features depend on CPU0. Known dependencies are:
2023 1. Resume from suspend/hibernate depends on CPU0.
2024 Suspend/hibernate will fail if CPU0 is offline and you
2025 need to online CPU0 before suspend/hibernate.
2026 2. PIC interrupts also depend on CPU0. CPU0 can't be
2027 removed if a PIC interrupt is detected.
2028 It's said poweroff/reboot may depend on CPU0 on some
2029 machines although I haven't seen such issues so far
2030 after CPU0 is offline on a few tested machines.
2031 If the dependencies are under your control, you can
2032 turn on cpu0_hotplug.
2034 nptcg= [IA-64] Override max number of concurrent global TLB
2035 purges which is reported from either PAL_VM_SUMMARY or
2038 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2039 could support. nr_cpus=n : n >= 1 limits the kernel to
2040 supporting 'n' processors. Later in runtime you can not
2041 use hotplug cpu feature to put more cpu back to online.
2042 just like you compile the kernel NR_CPUS=n
2044 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2046 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2047 Allowed values are enable and disable
2049 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2050 one of ['zone', 'node', 'default'] can be specified
2051 This can be set from sysctl after boot.
2052 See Documentation/sysctl/vm.txt for details.
2054 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2055 See Documentation/debugging-via-ohci1394.txt for more
2058 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2059 Rather than timing out after 20 ms if an EC
2060 command is not properly ACKed, override the length
2061 of the timeout. We have interrupts disabled while
2062 waiting for the ACK, so if this is set too high
2063 interrupts *may* be lost!
2065 omap_mux= [OMAP] Override bootloader pin multiplexing.
2066 Format: <mux_mode0.mode_name=value>...
2067 For example, to override I2C bus2:
2068 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2070 oprofile.timer= [HW]
2071 Use timer interrupt instead of performance counters
2073 oprofile.cpu_type= Force an oprofile cpu type
2074 This might be useful if you have an older oprofile
2075 userland or if you want common events.
2076 Format: { arch_perfmon }
2077 arch_perfmon: [X86] Force use of architectural
2078 perfmon on Intel CPUs instead of the
2079 CPU specific event set.
2080 timer: [X86] Force use of architectural NMI
2081 timer mode (see also oprofile.timer
2082 for generic hr timer mode)
2083 [s390] Force legacy basic mode sampling
2084 (report cpu_type "timer")
2086 oops=panic Always panic on oopses. Default is to just kill the
2087 process, but there is a small probability of
2088 deadlocking the machine.
2089 This will also cause panics on machine check exceptions.
2090 Useful together with panic=30 to trigger a reboot.
2093 See Documentation/sound/oss/oss-parameters.txt
2095 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2096 timeout > 0: seconds before rebooting
2097 timeout = 0: wait forever
2098 timeout < 0: reboot immediately
2101 parkbd.port= [HW] Parallel port number the keyboard adapter is
2102 connected to, default is 0.
2104 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2105 0 for XT, 1 for AT (default is AT).
2108 parport= [HW,PPT] Specify parallel ports. 0 disables.
2109 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2110 Use 'auto' to force the driver to use any
2111 IRQ/DMA settings detected (the default is to
2112 ignore detected IRQ/DMA settings because of
2113 possible conflicts). You can specify the base
2114 address, IRQ, and DMA settings; IRQ and DMA
2115 should be numbers, or 'auto' (for using detected
2116 settings on that particular port), or 'nofifo'
2117 (to avoid using a FIFO even if it is detected).
2118 Parallel ports are assigned in the order they
2119 are specified on the command line, starting
2122 parport_init_mode= [HW,PPT]
2123 Configure VIA parallel port to operate in
2124 a specific mode. This is necessary on Pegasos
2125 computer where firmware has no options for setting
2126 up parallel port mode and sets it to spp.
2127 Currently this function knows 686a and 8231 chips.
2128 Format: [spp|ps2|epp|ecp|ecpepp]
2131 Halt all CPUs after the first oops has been printed for
2132 the specified number of seconds. This is to be used if
2133 your oopses keep scrolling off the screen.
2138 See header of drivers/block/paride/pcd.c.
2139 See also Documentation/blockdev/paride.txt.
2141 pci=option[,option...] [PCI] various PCI subsystem options:
2142 earlydump [X86] dump PCI config space before the kernel
2144 off [X86] don't probe for the PCI bus
2145 bios [X86-32] force use of PCI BIOS, don't access
2146 the hardware directly. Use this if your machine
2147 has a non-standard PCI host bridge.
2148 nobios [X86-32] disallow use of PCI BIOS, only direct
2149 hardware access methods are allowed. Use this
2150 if you experience crashes upon bootup and you
2151 suspect they are caused by the BIOS.
2152 conf1 [X86] Force use of PCI Configuration
2154 conf2 [X86] Force use of PCI Configuration
2156 noaer [PCIE] If the PCIEAER kernel config parameter is
2157 enabled, this kernel boot option can be used to
2158 disable the use of PCIE advanced error reporting.
2159 nodomains [PCI] Disable support for multiple PCI
2160 root domains (aka PCI segments, in ACPI-speak).
2161 nommconf [X86] Disable use of MMCONFIG for PCI
2163 check_enable_amd_mmconf [X86] check for and enable
2164 properly configured MMIO access to PCI
2165 config space on AMD family 10h CPU
2166 nomsi [MSI] If the PCI_MSI kernel config parameter is
2167 enabled, this kernel boot option can be used to
2168 disable the use of MSI interrupts system-wide.
2169 noioapicquirk [APIC] Disable all boot interrupt quirks.
2170 Safety option to keep boot IRQs enabled. This
2171 should never be necessary.
2172 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2173 primary IO-APIC for bridges that cannot disable
2174 boot IRQs. This fixes a source of spurious IRQs
2175 when the system masks IRQs.
2176 noioapicreroute [APIC] Disable workaround that uses the
2177 boot IRQ equivalent of an IRQ that connects to
2178 a chipset where boot IRQs cannot be disabled.
2179 The opposite of ioapicreroute.
2180 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2181 routing table. These calls are known to be buggy
2182 on several machines and they hang the machine
2183 when used, but on other computers it's the only
2184 way to get the interrupt routing table. Try
2185 this option if the kernel is unable to allocate
2186 IRQs or discover secondary PCI buses on your
2188 rom [X86] Assign address space to expansion ROMs.
2189 Use with caution as certain devices share
2190 address decoders between ROMs and other
2192 norom [X86] Do not assign address space to
2193 expansion ROMs that do not already have
2194 BIOS assigned address ranges.
2195 nobar [X86] Do not assign address space to the
2196 BARs that weren't assigned by the BIOS.
2197 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2198 assigned automatically to PCI devices. You can
2199 make the kernel exclude IRQs of your ISA cards
2201 pirqaddr=0xAAAAA [X86] Specify the physical address
2202 of the PIRQ table (normally generated
2203 by the BIOS) if it is outside the
2204 F0000h-100000h range.
2205 lastbus=N [X86] Scan all buses thru bus #N. Can be
2206 useful if the kernel is unable to find your
2207 secondary buses and you want to tell it
2208 explicitly which ones they are.
2209 assign-busses [X86] Always assign all PCI bus
2210 numbers ourselves, overriding
2211 whatever the firmware may have done.
2212 usepirqmask [X86] Honor the possible IRQ mask stored
2213 in the BIOS $PIR table. This is needed on
2214 some systems with broken BIOSes, notably
2215 some HP Pavilion N5400 and Omnibook XE3
2216 notebooks. This will have no effect if ACPI
2217 IRQ routing is enabled.
2218 noacpi [X86] Do not use ACPI for IRQ routing
2219 or for PCI scanning.
2220 use_crs [X86] Use PCI host bridge window information
2221 from ACPI. On BIOSes from 2008 or later, this
2222 is enabled by default. If you need to use this,
2223 please report a bug.
2224 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2225 If you need to use this, please report a bug.
2226 routeirq Do IRQ routing for all PCI devices.
2227 This is normally done in pci_enable_device(),
2228 so this option is a temporary workaround
2229 for broken drivers that don't call it.
2230 skip_isa_align [X86] do not align io start addr, so can
2231 handle more pci cards
2232 firmware [ARM] Do not re-enumerate the bus but instead
2233 just use the configuration from the
2234 bootloader. This is currently used on
2235 IXP2000 systems where the bus has to be
2236 configured a certain way for adjunct CPUs.
2237 noearly [X86] Don't do any early type 1 scanning.
2238 This might help on some broken boards which
2239 machine check when some devices' config space
2240 is read. But various workarounds are disabled
2241 and some IOMMU drivers will not work.
2242 bfsort Sort PCI devices into breadth-first order.
2243 This sorting is done to get a device
2244 order compatible with older (<= 2.4) kernels.
2245 nobfsort Don't sort PCI devices into breadth-first order.
2246 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
2247 tuning and use the BIOS-configured MPS defaults.
2248 pcie_bus_safe Set every device's MPS to the largest value
2249 supported by all devices below the root complex.
2250 pcie_bus_perf Set device MPS to the largest allowable MPS
2251 based on its parent bus. Also set MRRS (Max
2252 Read Request Size) to the largest supported
2253 value (no larger than the MPS that the device
2254 or bus can support) for best performance.
2255 pcie_bus_peer2peer Set every device's MPS to 128B, which
2256 every device is guaranteed to support. This
2257 configuration allows peer-to-peer DMA between
2258 any pair of devices, possibly at the cost of
2259 reduced performance. This also guarantees
2260 that hot-added devices will work.
2261 cbiosize=nn[KMG] The fixed amount of bus space which is
2262 reserved for the CardBus bridge's IO window.
2263 The default value is 256 bytes.
2264 cbmemsize=nn[KMG] The fixed amount of bus space which is
2265 reserved for the CardBus bridge's memory
2266 window. The default value is 64 megabytes.
2269 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2270 Specifies alignment and device to reassign
2271 aligned memory resources.
2272 If <order of align> is not specified,
2273 PAGE_SIZE is used as alignment.
2274 PCI-PCI bridge can be specified, if resource
2275 windows need to be expanded.
2276 ecrc= Enable/disable PCIe ECRC (transaction layer
2277 end-to-end CRC checking).
2278 bios: Use BIOS/firmware settings. This is the
2282 hpiosize=nn[KMG] The fixed amount of bus space which is
2283 reserved for hotplug bridge's IO window.
2284 Default size is 256 bytes.
2285 hpmemsize=nn[KMG] The fixed amount of bus space which is
2286 reserved for hotplug bridge's memory window.
2287 Default size is 2 megabytes.
2288 realloc= Enable/disable reallocating PCI bridge resources
2289 if allocations done by BIOS are too small to
2290 accommodate resources required by all child
2292 off: Turn realloc off
2294 realloc same as realloc=on
2295 noari do not use PCIe ARI.
2296 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2297 only look for one device below a PCIe downstream
2300 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2303 force Enable ASPM even on devices that claim not to support it.
2304 WARNING: Forcing ASPM on may cause system lockups.
2306 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2307 nomsi Do not use MSI for PCI Express Native Hotplug (this
2308 makes all PCIe ports use INTx for hotplug services).
2310 pcie_ports= [PCIE] PCIe ports handling:
2311 auto Ask the BIOS whether or not to use native PCIe services
2312 associated with PCIe ports (PME, hot-plug, AER). Use
2313 them only if that is allowed by the BIOS.
2314 native Use native PCIe services associated with PCIe ports
2316 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2319 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2320 nomsi Do not use MSI for native PCIe PME signaling (this makes
2321 all PCIe root ports use INTx for all services).
2323 pcmv= [HW,PCMCIA] BadgePAD 4
2326 See Documentation/blockdev/paride.txt.
2328 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2331 See arch/parisc/kernel/pdc_chassis.c
2333 percpu_alloc= Select which percpu first chunk allocator to use.
2334 Currently supported values are "embed" and "page".
2335 Archs may support subset or none of the selections.
2336 See comments in mm/percpu.c for details on each
2337 allocator. This parameter is primarily for debugging
2338 and performance comparison.
2341 See Documentation/blockdev/paride.txt.
2344 See Documentation/blockdev/paride.txt.
2346 pirq= [SMP,APIC] Manual mp-table setup
2347 See Documentation/x86/i386/IO-APIC.txt.
2349 plip= [PPT,NET] Parallel port network link
2350 Format: { parport<nr> | timid | 0 }
2351 See also Documentation/parport.txt.
2353 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2354 Override pmtimer IOPort with a hex value.
2358 Enable PNP debug messages (depends on the
2359 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2360 via /sys/module/pnp/parameters/debug. We always show
2361 current resource usage; turning this on also shows
2362 possible settings and some assignment information.
2368 { on | off | curr | res | no-curr | no-res }
2371 [ISAPNP] Exclude IRQs for the autoconfiguration
2374 [ISAPNP] Exclude DMAs for the autoconfiguration
2376 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2377 Ranges are in pairs (I/O port base and size).
2380 [ISAPNP] Exclude memory regions for the
2382 Ranges are in pairs (memory base and size).
2384 ports= [IP_VS_FTP] IPVS ftp helper module
2386 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2388 Format: <port>,<port>....
2390 print-fatal-signals=
2391 [KNL] debug: print fatal signals
2393 If enabled, warn about various signal handling
2394 related application anomalies: too many signals,
2395 too many POSIX.1 timers, fatal signals causing a
2398 If you hit the warning due to signal overflow,
2399 you might want to try "ulimit -i unlimited".
2403 printk.always_kmsg_dump=
2404 Trigger kmsg_dump for cases other than kernel oops or
2406 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2409 printk.time= Show timing data prefixed to each printk message line
2410 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2412 processor.max_cstate= [HW,ACPI]
2413 Limit processor to maximum C-state
2414 max_cstate=9 overrides any DMI blacklist limit.
2416 processor.nocst [HW,ACPI]
2417 Ignore the _CST method to determine C-states,
2418 instead using the legacy FADT method
2420 profile= [KNL] Enable kernel profiling via /proc/profile
2421 Format: [schedule,]<number>
2422 Param: "schedule" - profile schedule points.
2423 Param: <number> - step/bucket size as a power of 2 for
2424 statistical time based profiling.
2425 Param: "sleep" - profile D-state sleeping (millisecs).
2426 Requires CONFIG_SCHEDSTATS
2427 Param: "kvm" - profile VM exits.
2429 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2431 See Documentation/blockdev/ramdisk.txt.
2433 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2434 probe for; one of (bare|imps|exps|lifebook|any).
2435 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2437 psmouse.resetafter= [HW,MOUSE]
2438 Try to reset the device after so many bad packets
2441 [HW,MOUSE] Set desired mouse resolution, in dpi.
2442 psmouse.smartscroll=
2443 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2444 0 = disabled, 1 = enabled (default).
2446 pstore.backend= Specify the name of the pstore backend to use
2449 See Documentation/blockdev/paride.txt.
2452 [KNL] Number of legacy pty's. Overwrites compiled-in
2455 quiet [KNL] Disable most log messages
2460 See Documentation/md.txt.
2462 ramdisk_blocksize= [RAM]
2463 See Documentation/blockdev/ramdisk.txt.
2465 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2466 See Documentation/blockdev/ramdisk.txt.
2468 rcu_nocbs= [KNL,BOOT]
2469 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2470 the specified list of CPUs to be no-callback CPUs.
2471 Invocation of these CPUs' RCU callbacks will
2472 be offloaded to "rcuoN" kthreads created for
2473 that purpose. This reduces OS jitter on the
2474 offloaded CPUs, which can be useful for HPC and
2475 real-time workloads. It can also improve energy
2476 efficiency for asymmetric multiprocessors.
2478 rcu_nocb_poll [KNL,BOOT]
2479 Rather than requiring that offloaded CPUs
2480 (specified by rcu_nocbs= above) explicitly
2481 awaken the corresponding "rcuoN" kthreads,
2482 make these kthreads poll for callbacks.
2483 This improves the real-time response for the
2484 offloaded CPUs by relieving them of the need to
2485 wake up the corresponding kthread, but degrades
2486 energy efficiency by requiring that the kthreads
2487 periodically wake up to do the polling.
2489 rcutree.blimit= [KNL,BOOT]
2490 Set maximum number of finished RCU callbacks to process
2493 rcutree.fanout_leaf= [KNL,BOOT]
2494 Increase the number of CPUs assigned to each
2495 leaf rcu_node structure. Useful for very large
2498 rcutree.qhimark= [KNL,BOOT]
2499 Set threshold of queued
2500 RCU callbacks over which batch limiting is disabled.
2502 rcutree.qlowmark= [KNL,BOOT]
2503 Set threshold of queued RCU callbacks below which
2504 batch limiting is re-enabled.
2506 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2507 Suppress RCU CPU stall warning messages.
2509 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2510 Set timeout for RCU CPU stall warning messages.
2512 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2513 Set delay from grace-period initialization to
2514 first attempt to force quiescent states.
2515 Units are jiffies, minimum value is zero,
2516 and maximum value is HZ.
2518 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2519 Set delay between subsequent attempts to force
2520 quiescent states. Units are jiffies, minimum
2521 value is one, and maximum value is HZ.
2523 rcutorture.fqs_duration= [KNL,BOOT]
2524 Set duration of force_quiescent_state bursts.
2526 rcutorture.fqs_holdoff= [KNL,BOOT]
2527 Set holdoff time within force_quiescent_state bursts.
2529 rcutorture.fqs_stutter= [KNL,BOOT]
2530 Set wait time between force_quiescent_state bursts.
2532 rcutorture.irqreader= [KNL,BOOT]
2533 Test RCU readers from irq handlers.
2535 rcutorture.n_barrier_cbs= [KNL,BOOT]
2536 Set callbacks/threads for rcu_barrier() testing.
2538 rcutorture.nfakewriters= [KNL,BOOT]
2539 Set number of concurrent RCU writers. These just
2540 stress RCU, they don't participate in the actual
2541 test, hence the "fake".
2543 rcutorture.nreaders= [KNL,BOOT]
2544 Set number of RCU readers.
2546 rcutorture.onoff_holdoff= [KNL,BOOT]
2547 Set time (s) after boot for CPU-hotplug testing.
2549 rcutorture.onoff_interval= [KNL,BOOT]
2550 Set time (s) between CPU-hotplug operations, or
2551 zero to disable CPU-hotplug testing.
2553 rcutorture.shuffle_interval= [KNL,BOOT]
2554 Set task-shuffle interval (s). Shuffling tasks
2555 allows some CPUs to go into dyntick-idle mode
2556 during the rcutorture test.
2558 rcutorture.shutdown_secs= [KNL,BOOT]
2559 Set time (s) after boot system shutdown. This
2560 is useful for hands-off automated testing.
2562 rcutorture.stall_cpu= [KNL,BOOT]
2563 Duration of CPU stall (s) to test RCU CPU stall
2564 warnings, zero to disable.
2566 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2567 Time to wait (s) after boot before inducing stall.
2569 rcutorture.stat_interval= [KNL,BOOT]
2570 Time (s) between statistics printk()s.
2572 rcutorture.stutter= [KNL,BOOT]
2573 Time (s) to stutter testing, for example, specifying
2574 five seconds causes the test to run for five seconds,
2575 wait for five seconds, and so on. This tests RCU's
2576 ability to transition abruptly to and from idle.
2578 rcutorture.test_boost= [KNL,BOOT]
2579 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2580 "Maybe" means test if the RCU implementation
2581 under test support RCU priority boosting.
2583 rcutorture.test_boost_duration= [KNL,BOOT]
2584 Duration (s) of each individual boost test.
2586 rcutorture.test_boost_interval= [KNL,BOOT]
2587 Interval (s) between each boost test.
2589 rcutorture.test_no_idle_hz= [KNL,BOOT]
2590 Test RCU's dyntick-idle handling. See also the
2591 rcutorture.shuffle_interval parameter.
2593 rcutorture.torture_type= [KNL,BOOT]
2594 Specify the RCU implementation to test.
2596 rcutorture.verbose= [KNL,BOOT]
2597 Enable additional printk() statements.
2601 Run specified binary instead of /init from the ramdisk,
2602 used for early userspace startup. See initrd.
2604 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2605 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2606 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2609 [KNL, SMP] Set scheduler's default relax_domain_level.
2610 See Documentation/cgroups/cpusets.txt.
2612 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2614 reservetop= [X86-32]
2616 Reserves a hole at the top of the kernel virtual
2621 Set the amount of memory to reserve for BIOS at
2622 the bottom of the address space.
2624 reset_devices [KNL] Force drivers to reset the underlying device
2625 during initialization.
2628 Specify the partition device for software suspend
2630 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2632 resume_offset= [SWSUSP]
2633 Specify the offset from the beginning of the partition
2634 given by "resume=" at which the swap header is located,
2635 in <PAGE_SIZE> units (needed only for swap files).
2636 See Documentation/power/swsusp-and-swap-files.txt
2638 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2639 read the resume files
2641 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2642 Useful for devices that are detected asynchronously
2643 (e.g. USB and MMC devices).
2645 hibernate= [HIBERNATION]
2646 noresume Don't check if there's a hibernation image
2647 present during boot.
2648 nocompress Don't compress/decompress hibernation images.
2650 retain_initrd [RAM] Keep initrd memory after extraction
2652 rhash_entries= [KNL,NET]
2653 Set number of hash buckets for route cache
2655 riscom8= [HW,SERIAL]
2656 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2658 ro [KNL] Mount root device read-only on boot
2660 root= [KNL] Root filesystem
2661 See name_to_dev_t comment in init/do_mounts.c.
2663 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2664 mount the root filesystem
2666 rootflags= [KNL] Set root filesystem mount option string
2668 rootfstype= [KNL] Set root filesystem type
2670 rootwait [KNL] Wait (indefinitely) for root device to show up.
2671 Useful for devices that are detected asynchronously
2672 (e.g. USB and MMC devices).
2674 rw [KNL] Mount root device read-write on boot
2676 S [KNL] Run init in single mode
2679 See drivers/net/irda/sa1100_ir.c.
2681 sbni= [NET] Granch SBNI12 leased line adapter
2683 sched_debug [KNL] Enables verbose scheduler debug messages.
2685 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2686 xtime_lock contention on larger systems, and/or RCU lock
2687 contention on all systems with CONFIG_MAXSMP set.
2688 Format: { "0" | "1" }
2689 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2691 Note: increases power consumption, thus should only be
2692 enabled if running jitter sensitive (HPC/RT) workloads.
2694 security= [SECURITY] Choose a security module to enable at boot.
2695 If this boot parameter is not specified, only the first
2696 security module asking for security registration will be
2697 loaded. An invalid security module name will be treated
2698 as if no module has been chosen.
2700 selinux= [SELINUX] Disable or enable SELinux at boot time.
2701 Format: { "0" | "1" }
2702 See security/selinux/Kconfig help text.
2705 Default value is set via kernel config option.
2706 If enabled at boot time, /selinux/disable can be used
2707 later to disable prior to initial policy load.
2709 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2710 Format: { "0" | "1" }
2711 See security/apparmor/Kconfig help text
2714 Default value is set via kernel config option.
2716 serialnumber [BUGS=X86-32]
2719 Maximal number of shapers.
2721 show_msr= [x86] show boot-time MSR settings
2722 Format: { <integer> }
2723 Show boot-time (BIOS-initialized) MSR settings.
2724 The parameter means the number of CPUs to show,
2725 for example 1 means boot CPU only.
2732 slab_max_order= [MM, SLAB]
2733 Determines the maximum allowed order for slabs.
2734 A high setting may cause OOMs due to memory
2735 fragmentation. Defaults to 1 for systems with
2736 more than 32MB of RAM, 0 otherwise.
2738 slub_debug[=options[,slabs]] [MM, SLUB]
2739 Enabling slub_debug allows one to determine the
2740 culprit if slab objects become corrupted. Enabling
2741 slub_debug can create guard zones around objects and
2742 may poison objects when not in use. Also tracks the
2743 last alloc / free. For more information see
2744 Documentation/vm/slub.txt.
2746 slub_max_order= [MM, SLUB]
2747 Determines the maximum allowed order for slabs.
2748 A high setting may cause OOMs due to memory
2749 fragmentation. For more information see
2750 Documentation/vm/slub.txt.
2752 slub_min_objects= [MM, SLUB]
2753 The minimum number of objects per slab. SLUB will
2754 increase the slab order up to slub_max_order to
2755 generate a sufficiently large slab able to contain
2756 the number of objects indicated. The higher the number
2757 of objects the smaller the overhead of tracking slabs
2758 and the less frequently locks need to be acquired.
2759 For more information see Documentation/vm/slub.txt.
2761 slub_min_order= [MM, SLUB]
2762 Determines the minimum page order for slabs. Must be
2763 lower than slub_max_order.
2764 For more information see Documentation/vm/slub.txt.
2766 slub_nomerge [MM, SLUB]
2767 Disable merging of slabs with similar size. May be
2768 necessary if there is some reason to distinguish
2769 allocs to different slabs. Debug options disable
2770 merging on their own.
2771 For more information see Documentation/vm/slub.txt.
2774 Format: <io1>[,<io2>[,...,<io8>]]
2776 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2777 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2778 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2779 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2780 smsc-ircc2.ircc_irq= [HW] IRQ line
2781 smsc-ircc2.ircc_dma= [HW] DMA channel
2782 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2783 0: Toshiba Satellite 1800 (GP data pin select)
2784 1: Fast pin select (default)
2788 [KNL] Should the soft-lockup detector generate panics.
2791 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2792 See Documentation/laptops/sonypi.txt
2794 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2795 See Documentation/serial/specialix.txt.
2797 spia_io_base= [HW,MTD]
2803 Enabled the stack tracer on boot up.
2805 stacktrace_filter=[function-list]
2806 [FTRACE] Limit the functions that the stack tracer
2807 will trace at boot up. function-list is a comma separated
2808 list of functions. This list can be changed at run
2809 time by the stack_trace_filter file in the debugfs
2810 tracing directory. Note, this enables stack tracing
2811 and the stacktrace above is not needed.
2815 Set the STI (builtin display/keyboard on the HP-PARISC
2816 machines) console (graphic card) which should be used
2817 as the initial boot-console.
2818 See also comment in drivers/video/console/sticore.c.
2821 See comment in drivers/video/console/sticore.c.
2824 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2826 sunrpc.min_resvport=
2827 sunrpc.max_resvport=
2829 SunRPC servers often require that client requests
2830 originate from a privileged port (i.e. a port in the
2831 range 0 < portnr < 1024).
2832 An administrator who wishes to reserve some of these
2833 ports for other uses may adjust the range that the
2834 kernel's sunrpc client considers to be privileged
2835 using these two parameters to set the minimum and
2836 maximum port values.
2840 Control how the NFS server code allocates CPUs to
2841 service thread pools. Depending on how many NICs
2842 you have and where their interrupts are bound, this
2843 option will affect which CPUs will do NFS serving.
2844 Note: this parameter cannot be changed while the
2845 NFS server is running.
2847 auto the server chooses an appropriate mode
2848 automatically using heuristics
2849 global a single global pool contains all CPUs
2850 percpu one pool for each CPU
2851 pernode one pool for each NUMA node (equivalent
2852 to global on non-NUMA machines)
2854 sunrpc.tcp_slot_table_entries=
2855 sunrpc.udp_slot_table_entries=
2857 Sets the upper limit on the number of simultaneous
2858 RPC calls that can be sent from the client to a
2859 server. Increasing these values may allow you to
2860 improve throughput, but will also increase the
2861 amount of memory reserved for use by the client.
2864 [KNL] Enable accounting of swap in memory resource
2865 controller if no parameter or 1 is given or disable
2866 it if 0 is given (See Documentation/cgroups/memory.txt)
2868 swiotlb= [IA-64] Number of I/O TLB slabs
2872 sysfs.deprecated=0|1 [KNL]
2873 Enable/disable old style sysfs layout for old udev
2874 on older distributions. When this option is enabled
2875 very new udev will not work anymore. When this option
2876 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2877 in older udev will not work anymore.
2878 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2879 the kernel configuration.
2881 sysrq_always_enabled
2883 Ignore sysrq setting - this boot parameter will
2884 neutralize any effect of /proc/sys/kernel/sysrq.
2885 Useful for debugging.
2889 test_suspend= [SUSPEND]
2890 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2891 standby suspend) as the system sleep state to briefly
2892 enter during system startup. The system is woken from
2893 this state using a wakeup-capable RTC alarm.
2895 thash_entries= [KNL,NET]
2896 Set number of hash buckets for TCP connection
2898 thermal.act= [HW,ACPI]
2899 -1: disable all active trip points in all thermal zones
2900 <degrees C>: override all lowest active trip points
2902 thermal.crt= [HW,ACPI]
2903 -1: disable all critical trip points in all thermal zones
2904 <degrees C>: override all critical trip points
2906 thermal.nocrt= [HW,ACPI]
2907 Set to disable actions on ACPI thermal zone
2908 critical and hot trip points.
2910 thermal.off= [HW,ACPI]
2911 1: disable ACPI thermal control
2913 thermal.psv= [HW,ACPI]
2914 -1: disable all passive trip points
2915 <degrees C>: override all passive trip points to this
2918 thermal.tzp= [HW,ACPI]
2919 Specify global default ACPI thermal zone polling rate
2920 <deci-seconds>: poll all this frequency
2921 0: no polling (default)
2924 Force threading of all interrupt handlers except those
2925 marked explicitly IRQF_NO_THREAD.
2929 Specify if the kernel should make use of the cpu
2930 topology information if the hardware supports this.
2931 The scheduler will make use of this information and
2932 e.g. base its process migration decisions on it.
2937 tpm_suspend_pcr=[HW,TPM]
2938 Format: integer pcr id
2939 Specify that at suspend time, the tpm driver
2940 should extend the specified pcr with zeros,
2941 as a workaround for some chips which fail to
2942 flush the last written pcr on TPM_SaveState.
2943 This will guarantee that all the other pcrs
2946 trace_buf_size=nn[KMG]
2947 [FTRACE] will set tracing buffer size.
2949 trace_event=[event-list]
2950 [FTRACE] Set and start specified trace events in order
2951 to facilitate early boot debugging.
2952 See also Documentation/trace/events.txt
2954 trace_options=[option-list]
2955 [FTRACE] Enable or disable tracer options at boot.
2956 The option-list is a comma delimited list of options
2957 that can be enabled or disabled just as if you were
2958 to echo the option name into
2960 /sys/kernel/debug/tracing/trace_options
2962 For example, to enable stacktrace option (to dump the
2963 stack trace of each event), add to the command line:
2965 trace_options=stacktrace
2967 See also Documentation/trace/ftrace.txt "trace options"
2970 transparent_hugepage=
2972 Format: [always|madvise|never]
2973 Can be used to control the default behavior of the system
2974 with respect to transparent hugepages.
2975 See Documentation/vm/transhuge.txt for more details.
2977 tsc= Disable clocksource stability checks for TSC.
2979 [x86] reliable: mark tsc clocksource as reliable, this
2980 disables clocksource verification at runtime, as well
2981 as the stability checks done at bootup. Used to enable
2982 high-resolution timer mode on older hardware, and in
2983 virtualized environment.
2984 [x86] noirqtime: Do not use TSC to do irq accounting.
2985 Used to run time disable IRQ_TIME_ACCOUNTING on any
2986 platforms where RDTSC is slow and this accounting
2989 turbografx.map[2|3]= [HW,JOY]
2990 TurboGraFX parallel port interface
2992 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2993 See also Documentation/input/joystick-parport.txt
2995 udbg-immortal [PPC] When debugging early kernel crashes that
2996 happen after console_init() and before a proper
2997 console driver takes over, this boot options might
2998 help "seeing" what's going on.
3000 uhash_entries= [KNL,NET]
3001 Set number of hash buckets for UDP/UDP-Lite connections
3004 [USB] Ignore overcurrent events (default N).
3005 Some badly-designed motherboards generate lots of
3006 bogus events, for ports that aren't wired to
3007 anything. Set this parameter to avoid log spamming.
3008 Note that genuine overcurrent events won't be
3012 [X86] Cause panic on unknown NMI.
3014 usbcore.authorized_default=
3015 [USB] Default USB device authorization:
3016 (default -1 = authorized except for wireless USB,
3017 0 = not authorized, 1 = authorized)
3019 usbcore.autosuspend=
3020 [USB] The autosuspend time delay (in seconds) used
3021 for newly-detected USB devices (default 2). This
3022 is the time required before an idle device will be
3023 autosuspended. Devices for which the delay is set
3024 to a negative value won't be autosuspended at all.
3026 usbcore.usbfs_snoop=
3027 [USB] Set to log all usbfs traffic (default 0 = off).
3029 usbcore.blinkenlights=
3030 [USB] Set to cycle leds on hubs (default 0 = off).
3032 usbcore.old_scheme_first=
3033 [USB] Start with the old device initialization
3034 scheme (default 0 = off).
3036 usbcore.usbfs_memory_mb=
3037 [USB] Memory limit (in MB) for buffers allocated by
3038 usbfs (default = 16, 0 = max = 2047).
3040 usbcore.use_both_schemes=
3041 [USB] Try the other device initialization scheme
3042 if the first one fails (default 1 = enabled).
3044 usbcore.initial_descriptor_timeout=
3045 [USB] Specifies timeout for the initial 64-byte
3046 USB_REQ_GET_DESCRIPTOR request in milliseconds
3047 (default 5000 = 5.0 seconds).
3050 [USBHID] The interval which mice are to be polled at.
3052 usb-storage.delay_use=
3053 [UMS] The delay in seconds before a new device is
3054 scanned for Logical Units (default 5).
3057 [UMS] A list of quirks entries to supplement or
3058 override the built-in unusual_devs list. List
3059 entries are separated by commas. Each entry has
3060 the form VID:PID:Flags where VID and PID are Vendor
3061 and Product ID values (4-digit hex numbers) and
3062 Flags is a set of characters, each corresponding
3063 to a common usb-storage quirk flag as follows:
3064 a = SANE_SENSE (collect more than 18 bytes
3066 b = BAD_SENSE (don't collect more than 18
3067 bytes of sense data);
3068 c = FIX_CAPACITY (decrease the reported
3069 device capacity by one sector);
3070 d = NO_READ_DISC_INFO (don't use
3071 READ_DISC_INFO command);
3072 e = NO_READ_CAPACITY_16 (don't use
3073 READ_CAPACITY_16 command);
3074 h = CAPACITY_HEURISTICS (decrease the
3075 reported device capacity by one
3076 sector if the number is odd);
3077 i = IGNORE_DEVICE (don't bind to this
3079 l = NOT_LOCKABLE (don't try to lock and
3080 unlock ejectable media);
3081 m = MAX_SECTORS_64 (don't transfer more
3082 than 64 sectors = 32 KB at a time);
3083 n = INITIAL_READ10 (force a retry of the
3084 initial READ(10) command);
3085 o = CAPACITY_OK (accept the capacity
3086 reported by the device);
3087 p = WRITE_CACHE (the device cache is ON
3089 r = IGNORE_RESIDUE (the device reports
3090 bogus residue values);
3091 s = SINGLE_LUN (the device has only one
3093 w = NO_WP_DETECT (don't test whether the
3094 medium is write-protected).
3095 Example: quirks=0419:aaf5:rl,0421:0433:rc
3097 user_debug= [KNL,ARM]
3099 See arch/arm/Kconfig.debug help text.
3100 1 - undefined instruction events
3102 4 - invalid data aborts
3105 Example: user_debug=31
3108 [X86] Flags controlling user PTE allocations.
3110 nohigh = do not allocate PTE pages in
3111 HIGHMEM regardless of setting
3115 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3116 vdso=1: enable VDSO (default)
3117 vdso=0: disable VDSO mapping
3120 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3121 vdso32=1: enable 32-bit VDSO (default)
3122 vdso32=0: disable 32-bit VDSO mapping
3125 vector=percpu: enable percpu vector domain
3127 video= [FB] Frame buffer configuration
3128 See Documentation/fb/modedb.txt.
3131 [VMMIO] Memory mapped virtio (platform) device.
3133 <size>@<baseaddr>:<irq>[:<id>]
3135 <size> := size (can use standard suffixes
3137 <baseaddr> := physical base address
3138 <irq> := interrupt number (as passed to
3140 <id> := (optional) platform device id
3142 virtio_mmio.device=1K@0x100b0000:48:7
3144 Can be used multiple times for multiple devices.
3146 vga= [BOOT,X86-32] Select a particular video mode
3147 See Documentation/x86/boot.txt and
3148 Documentation/svga.txt.
3149 Use vga=ask for menu.
3150 This is actually a boot loader parameter; the value is
3151 passed to the kernel using a special protocol.
3153 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3154 size of <nn>. This can be used to increase the
3155 minimum size (128MB on x86). It can also be used to
3156 decrease the size and leave more room for directly
3159 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3162 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3165 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3169 Controls the behavior of vsyscalls (i.e. calls to
3170 fixed addresses of 0xffffffffff600x00 from legacy
3171 code). Most statically-linked binaries and older
3172 versions of glibc use these calls. Because these
3173 functions are at fixed addresses, they make nice
3174 targets for exploits that can control RIP.
3176 emulate [default] Vsyscalls turn into traps and are
3177 emulated reasonably safely.
3179 native Vsyscalls are native syscall instructions.
3180 This is a little bit faster than trapping
3181 and makes a few dynamic recompilers work
3182 better than they would in emulation mode.
3183 It also makes exploits much easier to write.
3185 none Vsyscalls don't work at all. This makes
3186 them quite hard to use for exploits but
3187 might break your system.
3189 vt.cur_default= [VT] Default cursor shape.
3190 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3191 the parameters of the <Esc>[?A;B;Cc escape sequence;
3192 see VGA-softcursor.txt. Default: 2 = underline.
3194 vt.default_blu= [VT]
3195 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3196 Change the default blue palette of the console.
3197 This is a 16-member array composed of values
3200 vt.default_grn= [VT]
3201 Format: <green0>,<green1>,<green2>,...,<green15>
3202 Change the default green palette of the console.
3203 This is a 16-member array composed of values
3206 vt.default_red= [VT]
3207 Format: <red0>,<red1>,<red2>,...,<red15>
3208 Change the default red palette of the console.
3209 This is a 16-member array composed of values
3215 Set system-wide default UTF-8 mode for all tty's.
3216 Default is 1, i.e. UTF-8 mode is enabled for all
3217 newly opened terminals.
3219 vt.global_cursor_default=
3222 Set system-wide default for whether a cursor
3223 is shown on new VTs. Default is -1,
3224 i.e. cursors will be created by default unless
3225 overridden by individual drivers. 0 will hide
3226 cursors, 1 will display them.
3228 watchdog timers [HW,WDT] For information on watchdog timers,
3229 see Documentation/watchdog/watchdog-parameters.txt
3230 or other driver-specific files in the
3231 Documentation/watchdog/ directory.
3233 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3234 default x2apic cluster mode on platforms
3237 x86_mrst_timer= [X86-32,APBT]
3238 Choose timer option for x86 Moorestown MID platform.
3239 Two valid options are apbt timer only and lapic timer
3240 plus one apbt timer for broadcast timer.
3241 x86_mrst_timer=apbt_only | lapic_and_apbt
3243 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3244 xd_geo= See header of drivers/block/xd.c.
3246 xen_emul_unplug= [HW,X86,XEN]
3247 Unplug Xen emulated devices
3248 Format: [unplug0,][unplug1]
3249 ide-disks -- unplug primary master IDE devices
3250 aux-ide-disks -- unplug non-primary-master IDE devices
3251 nics -- unplug network devices
3252 all -- unplug all emulated devices (NICs and IDE disks)
3253 unnecessary -- unplugging emulated devices is
3254 unnecessary even if the host did not respond to
3256 never -- do not unplug even if version check succeeds
3258 xirc2ps_cs= [NET,PCMCIA]
3260 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3262 ______________________________________________________________________
3266 Add more DRM drivers.
projects / platform / adaptation / renesas_rcar / renesas_kernel.git / blob