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.
568 If the device connected to the port is not a TTY but a braille
569 device, prepend "brl," before the device type, for instance
571 For now, only VisioBraille is supported.
573 consoleblank= [KNL] The console blank (screen saver) timeout in
574 seconds. Defaults to 10*60 = 10mins. A value of 0
575 disables the blank timer.
578 [KNL] Change the default value for
579 /proc/<pid>/coredump_filter.
580 See also Documentation/filesystems/proc.txt.
582 cpuidle.off=1 [CPU_IDLE]
583 disable the cpuidle sub-system
585 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
587 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
589 crashkernel=size[KMG][@offset[KMG]]
590 [KNL] Using kexec, Linux can switch to a 'crash kernel'
591 upon panic. This parameter reserves the physical
592 memory region [offset, offset + size] for that kernel
593 image. If '@offset' is omitted, then a suitable offset
594 is selected automatically. Check
595 Documentation/kdump/kdump.txt for further details.
597 crashkernel=range1:size1[,range2:size2,...][@offset]
598 [KNL] Same as above, but depends on the memory
599 in the running system. The syntax of range is
600 start-[end] where start and end are both
601 a memory unit (amount[KMG]). See also
602 Documentation/kdump/kdump.txt for an example.
607 cs89x0_media= [HW,NET]
608 Format: { rj45 | aui | bnc }
611 See header of drivers/s390/block/dasd_devmap.c.
613 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
614 (one device per port)
615 Format: <port#>,<type>
616 See also Documentation/input/joystick-parport.txt
618 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
619 time. See Documentation/dynamic-debug-howto.txt for
620 details. Deprecated, see dyndbg.
622 debug [KNL] Enable kernel debugging (events log level).
625 [KNL] verbose self-tests
627 Print debugging info while doing the locking API
629 We default to 0 (no extra messages), setting it to
630 1 will print _a lot_ more information - normally
631 only useful to kernel developers.
633 debug_objects [KNL] Enable object debugging
636 [KNL] Disable object debugging
638 debug_guardpage_minorder=
639 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
640 parameter allows control of the order of pages that will
641 be intentionally kept free (and hence protected) by the
642 buddy allocator. Bigger value increase the probability
643 of catching random memory corruption, but reduce the
644 amount of memory for normal system use. The maximum
645 possible value is MAX_ORDER/2. Setting this parameter
646 to 1 or 2 should be enough to identify most random
647 memory corruption problems caused by bugs in kernel or
648 driver code when a CPU writes to (or reads from) a
649 random memory location. Note that there exists a class
650 of memory corruptions problems caused by buggy H/W or
651 F/W or by drivers badly programing DMA (basically when
652 memory is written at bus level and the CPU MMU is
653 bypassed) which are not detectable by
654 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
655 tracking down these problems.
657 debugpat [X86] Enable PAT debugging
659 decnet.addr= [HW,NET]
660 Format: <area>[,<node>]
661 See also Documentation/networking/decnet.txt.
664 [same as hugepagesz=] The size of the default
665 HugeTLB page size. This is the size represented by
666 the legacy /proc/ hugepages APIs, used for SHM, and
667 default size when mounting hugetlbfs filesystems.
668 Defaults to the default architecture's huge page size
672 Set number of hash buckets for dentry cache.
675 IO parameters + enable/disable command.
677 digiepca= [HW,SERIAL]
678 See drivers/char/README.epca and
679 Documentation/serial/digiepca.txt.
682 See Documentation/networking/ipv6.txt.
684 disable_ddw [PPC/PSERIES]
685 Disable Dynamic DMA Window support. Use this if
686 to workaround buggy firmware.
689 See Documentation/networking/ipv6.txt.
691 disable_mtrr_cleanup [X86]
692 The kernel tries to adjust MTRR layout from continuous
693 to discrete, to make X server driver able to add WB
694 entry later. This parameter disables that.
696 disable_mtrr_trim [X86, Intel and AMD only]
697 By default the kernel will trim any uncacheable
698 memory out of your available memory pool based on
699 MTRR settings. This parameter disables that behavior,
700 possibly causing your machine to run very slowly.
702 disable_timer_pin_1 [X86]
703 Disable PIN 1 of APIC timer
704 Can be useful to work around chipset bugs.
706 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
707 this option disables the debugging code at boot.
709 dma_debug_entries=<number>
710 This option allows to tune the number of preallocated
711 entries for DMA-API debugging code. One entry is
712 required per DMA-API allocation. Use this if the
713 DMA-API debugging code disables itself because the
714 architectural default is too low.
716 dma_debug_driver=<driver_name>
717 With this option the DMA-API debugging driver
718 filter feature can be enabled at boot time. Just
719 pass the driver to filter for as the parameter.
720 The filter can be disabled or changed to another
721 driver later using sysfs.
723 drm_kms_helper.edid_firmware=[<connector>:]<file>
724 Broken monitors, graphic adapters and KVMs may
725 send no or incorrect EDID data sets. This parameter
726 allows to specify an EDID data set in the
727 /lib/firmware directory that is used instead.
728 Generic built-in EDID data sets are used, if one of
729 edid/1024x768.bin, edid/1280x1024.bin,
730 edid/1680x1050.bin, or edid/1920x1080.bin is given
731 and no file with the same name exists. Details and
732 instructions how to build your own EDID data are
733 available in Documentation/EDID/HOWTO.txt. An EDID
734 data set will only be used for a particular connector,
735 if its name and a colon are prepended to the EDID
740 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
741 module.dyndbg[="val"]
742 Enable debug messages at boot time. See
743 Documentation/dynamic-debug-howto.txt for details.
745 earlycon= [KNL] Output early console device and options.
746 uart[8250],io,<addr>[,options]
747 uart[8250],mmio,<addr>[,options]
748 uart[8250],mmio32,<addr>[,options]
749 Start an early, polled-mode console on the 8250/16550
750 UART at the specified I/O port or MMIO address.
751 MMIO inter-register address stride is either 8-bit
752 (mmio) or 32-bit (mmio32).
753 The options are the same as for ttyS, above.
755 earlyprintk= [X86,SH,BLACKFIN]
757 earlyprintk=serial[,ttySn[,baudrate]]
758 earlyprintk=ttySn[,baudrate]
759 earlyprintk=dbgp[debugController#]
761 Append ",keep" to not disable it when the real console
764 Only vga or serial or usb debug port at a time.
766 Currently only ttyS0 and ttyS1 are supported.
768 Interaction with the standard serial driver is not
771 The VGA output is eventually overwritten by the real
774 ekgdboc= [X86,KGDB] Allow early kernel console debugging
777 This is designed to be used in conjunction with
778 the boot argument: earlyprintk=vga
781 Format: {"off" | "on" | "skip[mbr]"}
783 eisa_irq_edge= [PARISC,HW]
784 See header of drivers/parisc/eisa.c.
787 See comment before function elanfreq_setup() in
788 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
791 Format: {"cfq" | "deadline" | "noop"}
792 See Documentation/block/cfq-iosched.txt and
793 Documentation/block/deadline-iosched.txt for details.
795 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
796 Specifies physical address of start of kernel core
797 image elf header and optionally the size. Generally
798 kexec loader will pass this option to capture kernel.
799 See Documentation/kdump/kdump.txt for details.
801 enable_mtrr_cleanup [X86]
802 The kernel tries to adjust MTRR layout from continuous
803 to discrete, to make X server driver able to add WB
804 entry later. This parameter enables that.
806 enable_timer_pin_1 [X86]
807 Enable PIN 1 of APIC timer
808 Can be useful to work around chipset bugs
809 (in particular on some ATI chipsets).
810 The kernel tries to set a reasonable default.
812 enforcing [SELINUX] Set initial enforcing status.
814 See security/selinux/Kconfig help text.
815 0 -- permissive (log only, no denials).
816 1 -- enforcing (deny and log).
818 Value can be changed at runtime via /selinux/enforce.
821 Disable Error Record Serialization Table (ERST)
824 ether= [HW,NET] Ethernet cards parameters
825 This option is obsoleted by the "netdev=" option, which
826 has equivalent usage. See its documentation for details.
830 Permit 'security.evm' to be updated regardless of
831 current integrity status.
835 fail_make_request=[KNL]
836 General fault injection mechanism.
837 Format: <interval>,<probability>,<space>,<times>
838 See also Documentation/fault-injection/.
841 See Documentation/blockdev/floppy.txt.
843 force_pal_cache_flush
844 [IA-64] Avoid check_sal_cache_flush which may hang on
845 buggy SAL_CACHE_FLUSH implementations. Using this
846 parameter will force ia64_sal_cache_flush to call
847 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
850 [FTRACE] will set and start the specified tracer
851 as early as possible in order to facilitate early
854 ftrace_dump_on_oops[=orig_cpu]
855 [FTRACE] will dump the trace buffers on oops.
856 If no parameter is passed, ftrace will dump
857 buffers of all CPUs, but if you pass orig_cpu, it will
858 dump only the buffer of the CPU that triggered the
861 ftrace_filter=[function-list]
862 [FTRACE] Limit the functions traced by the function
863 tracer at boot up. function-list is a comma separated
864 list of functions. This list can be changed at run
865 time by the set_ftrace_filter file in the debugfs
868 ftrace_notrace=[function-list]
869 [FTRACE] Do not trace the functions specified in
870 function-list. This list can be changed at run time
871 by the set_ftrace_notrace file in the debugfs
874 ftrace_graph_filter=[function-list]
875 [FTRACE] Limit the top level callers functions traced
876 by the function graph tracer at boot up.
877 function-list is a comma separated list of functions
878 that can be changed at run time by the
879 set_graph_function file in the debugfs tracing directory.
882 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
883 support via parallel port (up to 5 devices per port)
884 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
885 See also Documentation/input/joystick-parport.txt
889 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
893 gcov_persist= [GCOV] When non-zero (default), profiling data for
894 kernel modules is saved and remains accessible via
895 debugfs, even when the module is unloaded/reloaded.
896 When zero, profiling data is discarded and associated
897 debugfs files are removed at module unload time.
899 gpt [EFI] Forces disk with valid GPT signature but
900 invalid Protective MBR to be treated as GPT.
902 grcan.enable0= [HW] Configuration of physical interface 0. Determines
903 the "Enable 0" bit of the configuration register.
906 grcan.enable1= [HW] Configuration of physical interface 1. Determines
907 the "Enable 0" bit of the configuration register.
910 grcan.select= [HW] Select which physical interface to use.
913 grcan.txsize= [HW] Sets the size of the tx buffer.
914 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
916 grcan.rxsize= [HW] Sets the size of the rx buffer.
917 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
920 hashdist= [KNL,NUMA] Large hashes allocated during boot
921 are distributed across NUMA nodes. Defaults on
922 for 64-bit NUMA, off otherwise.
923 Format: 0 | 1 (for off | on)
925 hcl= [IA-64] SGI's Hardware Graph compatibility layer
927 hd= [EIDE] (E)IDE hard drive subsystem geometry
928 Format: <cyl>,<head>,<sect>
931 Disable Hardware Error Source Table (HEST) support;
932 corresponding firmware-first mode error processing
933 logic will be disabled.
935 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
936 size of <nn>. This works even on boxes that have no
937 highmem otherwise. This also works to reduce highmem
938 size on bigger boxes.
940 highres= [KNL] Enable/disable high resolution timer mode.
941 Valid parameters: "on", "off"
945 See Documentation/isdn/README.HiSax.
949 hpet= [X86-32,HPET] option to control HPET usage
950 Format: { enable (default) | disable | force |
952 disable: disable HPET and use PIT instead
953 force: allow force enabled of undocumented chips (ICH4,
955 verbose: show contents of HPET registers during setup
957 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
958 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
959 On x86-64 and powerpc, this option can be specified
960 multiple times interleaved with hugepages= to reserve
961 huge pages of different sizes. Valid pages sizes on
962 x86-64 are 2M (when the CPU supports "pse") and 1G
963 (when the CPU supports the "pdpe1gb" cpuinfo flag)
964 Note that 1GB pages can only be allocated at boot time
965 using hugepages= and not freed afterwards.
967 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
968 terminal devices. Valid values: 0..8
969 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
970 If specified, z/VM IUCV HVC accepts connections
971 from listed z/VM user IDs only.
973 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
974 hardware thread id mappings.
975 Format: <cpu>:<hwthread>
978 Do not unregister boot console at start. This is only
979 useful for debugging when something happens in the window
980 between unregistering the boot console and initializing
983 i2c_bus= [HW] Override the default board specific I2C bus speed
984 or register an additional I2C bus that is not
985 registered from board initialization code.
989 i8042.debug [HW] Toggle i8042 debug mode
990 i8042.direct [HW] Put keyboard port into non-translated mode
991 i8042.dumbkbd [HW] Pretend that controller can only read data from
992 keyboard and cannot control its state
993 (Don't attempt to blink the leds)
994 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
995 i8042.nokbd [HW] Don't check/create keyboard port
996 i8042.noloop [HW] Disable the AUX Loopback command while probing
998 i8042.nomux [HW] Don't check presence of an active multiplexing
1000 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1002 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1003 i8042.reset [HW] Reset the controller during init and cleanup
1004 i8042.unlock [HW] Unlock (ignore) the keylock
1008 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
1009 indicates that the driver is running on unsupported
1011 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
1012 does not match list of supported models.
1014 [HW] Report power status in /proc/i8k
1015 (disabled by default)
1016 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
1019 i915.invert_brightness=
1020 [DRM] Invert the sense of the variable that is used to
1021 set the brightness of the panel backlight. Normally a
1022 brightness value of 0 indicates backlight switched off,
1023 and the maximum of the brightness value sets the backlight
1024 to maximum brightness. If this parameter is set to 0
1025 (default) and the machine requires it, or this parameter
1026 is set to 1, a brightness value of 0 sets the backlight
1027 to maximum brightness, and the maximum of the brightness
1028 value switches the backlight off.
1029 -1 -- never invert brightness
1030 0 -- machine default
1031 1 -- force brightness inversion
1034 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1036 ide-core.nodma= [HW] (E)IDE subsystem
1037 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1038 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1039 .cdrom .chs .ignore_cable are additional options
1040 See Documentation/ide/ide.txt.
1042 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1043 Claim all unknown PCI IDE storage controllers.
1046 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1047 Poll forces a polling idle loop that can slightly
1048 improve the performance of waking up a idle CPU, but
1049 will use a lot of power and make the system run hot.
1051 idle=mwait: On systems which support MONITOR/MWAIT but
1052 the kernel chose to not use it because it doesn't save
1053 as much power as a normal idle loop, use the
1054 MONITOR/MWAIT idle loop anyways. Performance should be
1055 the same as idle=poll.
1056 idle=halt: Halt is forced to be used for CPU idle.
1057 In such case C2/C3 won't be used again.
1058 idle=nomwait: Disable mwait for CPU C-states
1060 ignore_loglevel [KNL]
1061 Ignore loglevel setting - this will print /all/
1062 kernel messages to the console. Useful for debugging.
1063 We also add it as printk module parameter, so users
1064 could change it dynamically, usually by
1065 /sys/module/printk/parameters/ignore_loglevel.
1067 ihash_entries= [KNL]
1068 Set number of hash buckets for inode cache.
1070 ima_appraise= [IMA] appraise integrity measurements
1071 Format: { "off" | "enforce" | "fix" }
1074 ima_appraise_tcb [IMA]
1075 The builtin appraise policy appraises all files
1079 Format: { "0" | "1" }
1080 0 -- integrity auditing messages. (Default)
1081 1 -- enable informational integrity auditing messages.
1084 Format: { "sha1" | "md5" }
1088 Load a policy which meets the needs of the Trusted
1089 Computing Base. This means IMA will measure all
1090 programs exec'd, files mmap'd for exec, and all files
1091 opened for read by uid=0.
1095 Run specified binary instead of /sbin/init as init
1098 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1099 for working out where the kernel is dying during
1102 initrd= [BOOT] Specify the location of the initial ramdisk
1104 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1107 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1109 Enable intel iommu driver.
1111 Disable intel iommu driver.
1112 igfx_off [Default Off]
1113 By default, gfx is mapped as normal device. If a gfx
1114 device has a dedicated DMAR unit, the DMAR unit is
1115 bypassed by not enabling DMAR with this option. In
1116 this case, gfx device will use physical address for
1119 With this option iommu will not optimize to look
1120 for io virtual address below 32-bit forcing dual
1121 address cycle on pci bus for cards supporting greater
1122 than 32-bit addressing. The default is to look
1123 for translation below 32-bit and if not available
1124 then look in the higher range.
1125 strict [Default Off]
1126 With this option on every unmap_single operation will
1127 result in a hardware IOTLB flush operation as opposed
1128 to batching them for performance.
1129 sp_off [Default Off]
1130 By default, super page will be supported if Intel IOMMU
1131 has the capability. With this option, super page will
1134 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
1135 0 disables intel_idle and fall back on acpi_idle.
1136 1 to 6 specify maximum depth of C-state.
1138 intremap= [X86-64, Intel-IOMMU]
1139 on enable Interrupt Remapping (default)
1140 off disable Interrupt Remapping
1141 nosid disable Source ID checking
1143 BIOS x2APIC opt-out request will be ignored
1145 iomem= Disable strict checking of access to MMIO memory
1146 strict regions from userspace.
1163 io7= [HW] IO7 for Marvel based alpha systems
1164 See comment before marvel_specify_io7 in
1165 arch/alpha/kernel/core_marvel.c.
1167 io_delay= [X86] I/O delay method
1169 Standard port 0x80 based delay
1171 Alternate port 0xed based delay (needed on some systems)
1173 Simple two microseconds delay
1178 See Documentation/filesystems/nfs/nfsroot.txt.
1180 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1181 See comment before ip2_setup() in
1182 drivers/char/ip2/ip2base.c.
1185 When an interrupt is not handled search all handlers
1186 for it. Intended to get systems with badly broken
1190 When an interrupt is not handled search all handlers
1191 for it. Also check all handlers each timer
1192 interrupt. Intended to get systems with badly broken
1196 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1198 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1200 <cpu number>,...,<cpu number>
1202 <cpu number>-<cpu number>
1203 (must be a positive range in ascending order)
1205 <cpu number>,...,<cpu number>-<cpu number>
1207 This option can be used to specify one or more CPUs
1208 to isolate from the general SMP balancing and scheduling
1209 algorithms. You can move a process onto or off an
1210 "isolated" CPU via the CPU affinity syscalls or cpuset.
1211 <cpu number> begins at 0 and the maximum value is
1212 "number of CPUs in system - 1".
1214 This option is the preferred way to isolate CPUs. The
1215 alternative -- manually setting the CPU mask of all
1216 tasks in the system -- can cause problems and
1217 suboptimal load balancer performance.
1221 js= [HW,JOY] Analog joystick
1222 See Documentation/input/joystick.txt.
1226 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1227 specifies the amount of memory usable by the kernel
1228 for non-movable allocations. The requested amount is
1229 spread evenly throughout all nodes in the system. The
1230 remaining memory in each node is used for Movable
1231 pages. In the event, a node is too small to have both
1232 kernelcore and Movable pages, kernelcore pages will
1233 take priority and other nodes will have a larger number
1234 of kernelcore pages. The Movable zone is used for the
1235 allocation of pages that may be reclaimed or moved
1236 by the page migration subsystem. This means that
1237 HugeTLB pages may not be allocated from this zone.
1238 Note that allocations like PTEs-from-HighMem still
1239 use the HighMem zone if it exists, and the Normal
1240 zone if it does not.
1242 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1243 Format: <Controller#>[,poll interval]
1244 The controller # is the number of the ehci usb debug
1245 port as it is probed via PCI. The poll interval is
1246 optional and is the number seconds in between
1247 each poll cycle to the debug port in case you need
1248 the functionality for interrupting the kernel with
1249 gdb or control-c on the dbgp connection. When
1250 not using this parameter you use sysrq-g to break into
1251 the kernel debugger.
1253 kgdboc= [KGDB,HW] kgdb over consoles.
1254 Requires a tty driver that supports console polling,
1255 or a supported polling keyboard driver (non-usb).
1256 Serial only format: <serial_device>[,baud]
1257 keyboard only format: kbd
1258 keyboard and serial format: kbd,<serial_device>[,baud]
1259 Optional Kernel mode setting:
1260 kms, kbd format: kms,kbd
1261 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1263 kgdbwait [KGDB] Stop kernel execution and enter the
1264 kernel debugger at the earliest opportunity.
1266 kmac= [MIPS] korina ethernet MAC address.
1267 Configure the RouterBoard 532 series on-chip
1268 Ethernet adapter MAC address.
1270 kmemleak= [KNL] Boot-time kmemleak enable/disable
1271 Valid arguments: on, off
1274 kstack=N [X86] Print N words from the kernel stack
1277 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1278 Default is 0 (don't ignore, but inject #GP)
1280 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1284 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1285 Default is 1 (enabled)
1287 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1289 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1291 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1292 (virtualized MMU) support on capable Intel chips.
1293 Default is 1 (enabled)
1295 kvm-intel.emulate_invalid_guest_state=
1296 [KVM,Intel] Enable emulation of invalid guest states
1297 Default is 0 (disabled)
1299 kvm-intel.flexpriority=
1300 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1301 Default is 1 (enabled)
1304 [KVM,Intel] Enable VMX nesting (nVMX).
1305 Default is 0 (disabled)
1307 kvm-intel.unrestricted_guest=
1308 [KVM,Intel] Disable unrestricted guest feature
1309 (virtualized real and unpaged mode) on capable
1310 Intel chips. Default is 1 (enabled)
1312 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1313 feature (tagged TLBs) on capable Intel chips.
1314 Default is 1 (enabled)
1320 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1323 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
1324 value for LAPIC timer one-shot implementation. Default
1325 back to the programmable timer unit in the LAPIC.
1327 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1330 libata.dma= [LIBATA] DMA control
1331 libata.dma=0 Disable all PATA and SATA DMA
1332 libata.dma=1 PATA and SATA Disk DMA only
1333 libata.dma=2 ATAPI (CDROM) DMA only
1334 libata.dma=4 Compact Flash DMA only
1335 Combinations also work, so libata.dma=3 enables DMA
1336 for disks and CDROMs, but not CFs.
1338 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1339 libata.ignore_hpa=0 keep BIOS limits (default)
1340 libata.ignore_hpa=1 ignore limits, using full disk
1342 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1346 libata.force= [LIBATA] Force configurations. The format is comma
1347 separated list of "[ID:]VAL" where ID is
1348 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1349 matching port, link or device. Basically, it matches
1350 the ATA ID string printed on console by libata. If
1351 the whole ID part is omitted, the last PORT and DEVICE
1352 values are used. If ID hasn't been specified yet, the
1353 configuration applies to all ports, links and devices.
1355 If only DEVICE is omitted, the parameter applies to
1356 the port and all links and devices behind it. DEVICE
1357 number of 0 either selects the first device or the
1358 first fan-out link behind PMP device. It does not
1359 select the host link. DEVICE number of 15 selects the
1360 host link and device attached to it.
1362 The VAL specifies the configuration to force. As long
1363 as there's no ambiguity shortcut notation is allowed.
1364 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1365 The following configurations can be forced.
1367 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1368 Any ID with matching PORT is used.
1370 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1372 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1373 udma[/][16,25,33,44,66,100,133] notation is also
1376 * [no]ncq: Turn on or off NCQ.
1378 * nohrst, nosrst, norst: suppress hard, soft
1381 * rstonce: only attempt one reset during
1382 hot-unplug link recovery
1384 * dump_id: dump IDENTIFY data.
1386 If there are multiple matching configurations changing
1387 the same attribute, the last one is used.
1389 memblock=debug [KNL] Enable memblock debug messages.
1391 load_ramdisk= [RAM] List of ramdisks to load from floppy
1392 See Documentation/blockdev/ramdisk.txt.
1394 lockd.nlm_grace_period=P [NFS] Assign grace period.
1397 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1400 lockd.nlm_timeout=T [NFS] Assign timeout value.
1403 lockd.nlm_udpport=M [NFS] Assign UDP port.
1406 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1409 loglevel= All Kernel Messages with a loglevel smaller than the
1410 console loglevel will be printed to the console. It can
1411 also be changed with klogd or other programs. The
1412 loglevels are defined as follows:
1414 0 (KERN_EMERG) system is unusable
1415 1 (KERN_ALERT) action must be taken immediately
1416 2 (KERN_CRIT) critical conditions
1417 3 (KERN_ERR) error conditions
1418 4 (KERN_WARNING) warning conditions
1419 5 (KERN_NOTICE) normal but significant condition
1420 6 (KERN_INFO) informational
1421 7 (KERN_DEBUG) debug-level messages
1423 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1424 in bytes. n must be a power of two. The default
1425 size is set in the kernel config file.
1427 logo.nologo [FB] Disables display of the built-in Linux logo.
1428 This may be used to provide more screen space for
1429 kernel log messages and is useful when debugging
1430 kernel boot problems.
1432 lp=0 [LP] Specify parallel ports to use, e.g,
1433 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1434 lp=reset first parallel port). 'lp=0' disables the
1435 lp=auto printer driver. 'lp=reset' (which can be
1436 specified in addition to the ports) causes
1437 attached printers to be reset. Using
1438 lp=port1,port2,... specifies the parallel ports
1439 to associate lp devices with, starting with
1440 lp0. A port specification may be 'none' to skip
1441 that lp device, or a parport name such as
1442 'parport0'. Specifying 'lp=auto' instead of a
1443 port specification list means that device IDs
1444 from each port should be examined, to see if
1445 an IEEE 1284-compliant printer is attached; if
1446 so, the driver will manage that printer.
1447 See also header of drivers/char/lp.c.
1450 Sets loops_per_jiffy to given constant, thus avoiding
1451 time-consuming boot-time autodetection (up to 250 ms per
1452 CPU). 0 enables autodetection (default). To determine
1453 the correct value for your kernel, boot with normal
1454 autodetection and see what value is printed. Note that
1455 on SMP systems the preset will be applied to all CPUs,
1456 which is likely to cause problems if your CPUs need
1457 significantly divergent settings. An incorrect value
1458 will cause delays in the kernel to be wrong, leading to
1459 unpredictable I/O errors and other breakage. Although
1460 unlikely, in the extreme case this might damage your
1464 Format: <io>,<irq>,<dma>
1466 machvec= [IA-64] Force the use of a particular machine-vector
1467 (machvec) in a generic kernel.
1468 Example: machvec=hpzx1_swiotlb
1470 machtype= [Loongson] Share the same kernel image file between different
1472 Example: machtype=lemote-yeeloong-2f-7inch
1474 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1475 than or equal to this physical address is ignored.
1477 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1478 should make use of. maxcpus=n : n >= 0 limits the
1479 kernel to using 'n' processors. n=0 is a special case,
1480 it is equivalent to "nosmp", which also disables
1483 max_loop= [LOOP] The number of loop block devices that get
1484 (loop.max_loop) unconditionally pre-created at init time. The default
1485 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1486 of statically allocating a predefined number, loop
1487 devices can be requested on-demand with the
1488 /dev/loop-control interface.
1490 mce [X86-32] Machine Check Exception
1492 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1494 md= [HW] RAID subsystems devices and level
1495 See Documentation/md.txt.
1498 Format: <first>,<last>
1499 Specifies range of consoles to be captured by the MDA.
1501 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1502 Amount of memory to be used when the kernel is not able
1503 to see the whole system memory or for test.
1504 [X86] Work as limiting max address. Use together
1505 with memmap= to avoid physical address space collisions.
1506 Without memmap= PCI devices could be placed at addresses
1507 belonging to unused RAM.
1509 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1513 [KNL,SH] Allow user to override the default size for
1514 per-device physically contiguous DMA buffers.
1516 memmap=exactmap [KNL,X86] Enable setting of an exact
1517 E820 memory map, as specified by the user.
1518 Such memmap=exactmap lines can be constructed based on
1519 BIOS output or other requirements. See the memmap=nn@ss
1522 memmap=nn[KMG]@ss[KMG]
1523 [KNL] Force usage of a specific region of memory
1524 Region of memory to be used, from ss to ss+nn.
1526 memmap=nn[KMG]#ss[KMG]
1527 [KNL,ACPI] Mark specific memory as ACPI data.
1528 Region of memory to be used, from ss to ss+nn.
1530 memmap=nn[KMG]$ss[KMG]
1531 [KNL,ACPI] Mark specific memory as reserved.
1532 Region of memory to be used, from ss to ss+nn.
1533 Example: Exclude memory from 0x18690000-0x1869ffff
1534 memmap=64K$0x18690000
1536 memmap=0x10000$0x18690000
1538 memory_corruption_check=0/1 [X86]
1539 Some BIOSes seem to corrupt the first 64k of
1540 memory when doing things like suspend/resume.
1541 Setting this option will scan the memory
1542 looking for corruption. Enabling this will
1543 both detect corruption and prevent the kernel
1544 from using the memory being corrupted.
1545 However, its intended as a diagnostic tool; if
1546 repeatable BIOS-originated corruption always
1547 affects the same memory, you can use memmap=
1548 to prevent the kernel from using that memory.
1550 memory_corruption_check_size=size [X86]
1551 By default it checks for corruption in the low
1552 64k, making this memory unavailable for normal
1553 use. Use this parameter to scan for
1554 corruption in more or less memory.
1556 memory_corruption_check_period=seconds [X86]
1557 By default it checks for corruption every 60
1558 seconds. Use this parameter to check at some
1559 other rate. 0 disables periodic checking.
1561 memtest= [KNL,X86] Enable memtest
1563 default : 0 <disable>
1564 Specifies the number of memtest passes to be
1565 performed. Each pass selects another test
1566 pattern from a given set of patterns. Memtest
1567 fills the memory with this pattern, validates
1568 memory contents and reserves bad memory
1569 regions that are detected.
1571 meye.*= [HW] Set MotionEye Camera parameters
1572 See Documentation/video4linux/meye.txt.
1574 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1575 Multi-Function General Purpose Timers on AMD Geode
1578 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1579 the BIOS has incorrectly applied a workaround. TinyBIOS
1580 version 0.98 is known to be affected, 0.99 fixes the
1581 problem by letting the user disable the workaround.
1585 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1586 physical address is ignored.
1588 mini2440= [ARM,HW,KNL]
1589 Format:[0..2][b][c][t]
1591 MINI2440 configuration specification:
1592 0 - The attached screen is the 3.5" TFT
1593 1 - The attached screen is the 7" TFT
1594 2 - The VGA Shield is attached (1024x768)
1595 Leaving out the screen size parameter will not load
1596 the TFT driver, and the framebuffer will be left
1598 b - Enable backlight. The TFT backlight pin will be
1599 linked to the kernel VESA blanking code and a GPIO
1600 LED. This parameter is not necessary when using the
1602 c - Enable the s3c camera interface.
1603 t - Reserved for enabling touchscreen support. The
1604 touchscreen support is not enabled in the mainstream
1605 kernel as of 2.6.30, a preliminary port can be found
1606 in the "bleeding edge" mini2440 support kernel at
1607 http://repo.or.cz/w/linux-2.6/mini2440.git
1610 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1611 parameter allows control of the logging verbosity for
1612 the additional memory initialisation checks. A value
1613 of 0 disables mminit logging and a level of 4 will
1614 log everything. Information is printed at KERN_DEBUG
1615 so loglevel=8 may also need to be specified.
1618 [KNL] When CONFIG_MODULE_SIG is set, this means that
1619 modules without (valid) signatures will fail to load.
1620 Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
1621 is always true, so this option does nothing.
1624 [MOUSE] Maximum time between finger touching and
1625 leaving touchpad surface for touch to be considered
1626 a tap and be reported as a left button click (for
1627 touchpads working in absolute mode only).
1629 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1630 reporting absolute coordinates, such as tablets
1631 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1632 reporting absolute coordinates, such as tablets
1634 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1635 is similar to kernelcore except it specifies the
1636 amount of memory used for migratable allocations.
1637 If both kernelcore and movablecore is specified,
1638 then kernelcore will be at *least* the specified
1639 value but may be more. If movablecore on its own
1640 is specified, the administrator must be careful
1641 that the amount of memory usable for all allocations
1644 MTD_Partition= [MTD]
1645 Format: <name>,<region-number>,<size>,<offset>
1647 MTD_Region= [MTD] Format:
1648 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1651 See drivers/mtd/cmdlinepart.c.
1653 multitce=off [PPC] This parameter disables the use of the pSeries
1654 firmware feature for updating multiple TCE entries
1657 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1659 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1661 boundary - index of last SLC block on Flex-OneNAND.
1662 The remaining blocks are configured as MLC blocks.
1663 lock - Configure if Flex-OneNAND boundary should be locked.
1664 Once locked, the boundary cannot be changed.
1665 1 indicates lock status, 0 indicates unlock status.
1668 ARM/S3C2412 JIVE boot control
1670 See arch/arm/mach-s3c2412/mach-jive.c
1672 mtouchusb.raw_coordinates=
1673 [HW] Make the MicroTouch USB driver use raw coordinates
1674 ('y', default) or cooked coordinates ('n')
1676 mtrr_chunk_size=nn[KMG] [X86]
1677 used for mtrr cleanup. It is largest continuous chunk
1678 that could hold holes aka. UC entries.
1680 mtrr_gran_size=nn[KMG] [X86]
1681 Used for mtrr cleanup. It is granularity of mtrr block.
1683 Large value could prevent small alignment from
1686 mtrr_spare_reg_nr=n [X86]
1688 Range: 0,7 : spare reg number
1690 Used for mtrr cleanup. It is spare mtrr entries number.
1691 Set to 2 or more if your graphical card needs more.
1693 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1695 netdev= [NET] Network devices parameters
1696 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1697 Note that mem_start is often overloaded to mean
1698 something different and driver-specific.
1699 This usage is only documented in each driver source
1703 [NETFILTER] Enable connection tracking flow accounting
1704 0 to disable accounting
1705 1 to enable accounting
1708 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1709 See Documentation/filesystems/nfs/nfsroot.txt.
1711 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1712 See Documentation/filesystems/nfs/nfsroot.txt.
1714 nfsrootdebug [NFS] enable nfsroot debugging messages.
1715 See Documentation/filesystems/nfs/nfsroot.txt.
1717 nfs.callback_tcpport=
1718 [NFS] set the TCP port on which the NFSv4 callback
1719 channel should listen.
1722 [NFS] sets the pathname to the program which is used
1723 to update the NFS client cache entries.
1725 nfs.cache_getent_timeout=
1726 [NFS] sets the timeout after which an attempt to
1727 update a cache entry is deemed to have failed.
1729 nfs.idmap_cache_timeout=
1730 [NFS] set the maximum lifetime for idmapper cache
1734 [NFS] enable 64-bit inode numbers.
1735 If zero, the NFS client will fake up a 32-bit inode
1736 number for the readdir() and stat() syscalls instead
1737 of returning the full 64-bit number.
1738 The default is to return 64-bit inode numbers.
1740 nfs.max_session_slots=
1741 [NFSv4.1] Sets the maximum number of session slots
1742 the client will attempt to negotiate with the server.
1743 This limits the number of simultaneous RPC requests
1744 that the client can send to the NFSv4.1 server.
1745 Note that there is little point in setting this
1746 value higher than the max_tcp_slot_table_limit.
1748 nfs.nfs4_disable_idmapping=
1749 [NFSv4] When set to the default of '1', this option
1750 ensures that both the RPC level authentication
1751 scheme and the NFS level operations agree to use
1752 numeric uids/gids if the mount is using the
1753 'sec=sys' security flavour. In effect it is
1754 disabling idmapping, which can make migration from
1755 legacy NFSv2/v3 systems to NFSv4 easier.
1756 Servers that do not support this mode of operation
1757 will be autodetected by the client, and it will fall
1758 back to using the idmapper.
1759 To turn off this behaviour, set the value to '0'.
1761 [NFS4] Specify an additional fixed unique ident-
1762 ification string that NFSv4 clients can insert into
1763 their nfs_client_id4 string. This is typically a
1764 UUID that is generated at system install time.
1766 nfs.send_implementation_id =
1767 [NFSv4.1] Send client implementation identification
1768 information in exchange_id requests.
1769 If zero, no implementation identification information
1771 The default is to send the implementation identification
1774 nfsd.nfs4_disable_idmapping=
1775 [NFSv4] When set to the default of '1', the NFSv4
1776 server will return only numeric uids and gids to
1777 clients using auth_sys, and will accept numeric uids
1778 and gids from such clients. This is intended to ease
1779 migration from NFSv2/v3.
1781 objlayoutdriver.osd_login_prog=
1782 [NFS] [OBJLAYOUT] sets the pathname to the program which
1783 is used to automatically discover and login into new
1784 osd-targets. Please see:
1785 Documentation/filesystems/pnfs.txt for more explanations
1787 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1788 when a NMI is triggered.
1789 Format: [state][,regs][,debounce][,die]
1791 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1792 Format: [panic,][nopanic,][num]
1794 0 - turn nmi_watchdog off
1795 When panic is specified, panic when an NMI watchdog
1796 timeout occurs (or 'nopanic' to override the opposite
1798 This is useful when you use a panic=... timeout and
1799 need the box quickly up again.
1801 netpoll.carrier_timeout=
1802 [NET] Specifies amount of time (in seconds) that
1803 netpoll should wait for a carrier. By default netpoll
1806 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1807 emulation library even if a 387 maths coprocessor
1811 [HW] Never suspend the console
1812 Disable suspending of consoles during suspend and
1813 hibernate operations. Once disabled, debugging
1814 messages can reach various consoles while the rest
1815 of the system is being put to sleep (ie, while
1816 debugging driver suspend/resume hooks). This may
1817 not work reliably with all consoles, but is known
1818 to work with serial and VGA consoles.
1819 To facilitate more flexible debugging, we also add
1820 console_suspend, a printk module parameter to control
1821 it. Users could use console_suspend (usually
1822 /sys/module/printk/parameters/console_suspend) to
1823 turn on/off it dynamically.
1825 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1826 caches in the slab allocator. Saves per-node memory,
1827 but will impact performance.
1831 noapic [SMP,APIC] Tells the kernel to not make use of any
1832 IOAPICs that may be present in the system.
1834 noautogroup Disable scheduler automatic task group creation.
1836 nobats [PPC] Do not use BATs for mapping kernel lowmem
1837 on "Classic" PPC cores.
1841 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1843 nodelayacct [KNL] Disable per-task delay accounting
1845 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1847 nodsp [SH] Disable hardware DSP at boot time.
1849 noefi [X86] Disable EFI runtime services support.
1854 On X86-32 available only on PAE configured kernels.
1855 noexec=on: enable non-executable mappings (default)
1856 noexec=off: disable non-executable mappings
1859 Disable SMAP (Supervisor Mode Access Prevention)
1860 even if it is supported by processor.
1863 Disable SMEP (Supervisor Mode Execution Prevention)
1864 even if it is supported by processor.
1867 This affects only 32-bit executables.
1868 noexec32=on: enable non-executable mappings (default)
1869 read doesn't imply executable mappings
1870 noexec32=off: disable non-executable mappings
1871 read implies executable mappings
1873 nofpu [SH] Disable hardware FPU at boot time.
1875 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1876 register save and restore. The kernel will only save
1877 legacy floating-point registers on task switch.
1879 noxsave [BUGS=X86] Disables x86 extended register state save
1880 and restore using xsave. The kernel will fallback to
1881 enabling legacy floating-point and sse state.
1884 on enable eager fpu restore
1885 off disable eager fpu restore
1886 auto selects the default scheme, which automatically
1887 enables eagerfpu restore for xsaveopt.
1889 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1890 wfi(ARM) instruction doesn't work correctly and not to
1891 use it. This is also useful when using JTAG debugger.
1893 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1894 instruction doesn't work correctly and not to
1897 no_file_caps Tells the kernel not to honor file capabilities. The
1898 only way then for a file to be executed with privilege
1899 is to be setuid root or executed by root.
1901 nohalt [IA-64] Tells the kernel not to use the power saving
1902 function PAL_HALT_LIGHT when idle. This increases
1903 power-consumption. On the positive side, it reduces
1904 interrupt wake-up latency, which may improve performance
1905 in certain environments such as networked servers or
1908 nohz= [KNL] Boottime enable/disable dynamic ticks
1909 Valid arguments: on, off
1912 noiotrap [SH] Disables trapped I/O port accesses.
1914 noirqdebug [X86-32] Disables the code which attempts to detect and
1915 disable unhandled interrupt sources.
1917 no_timer_check [X86,APIC] Disables the code which tests for
1918 broken timer IRQ sources.
1920 noisapnp [ISAPNP] Disables ISA PnP code.
1922 noinitrd [RAM] Tells the kernel not to load any configured
1925 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1927 [Deprecated - use intremap=off]
1931 nojitter [IA-64] Disables jitter checking for ITC timers.
1933 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1935 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1938 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1939 steal time is computed, but won't influence scheduler
1942 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1944 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1946 noltlbs [PPC] Do not use large page/tlb entries for kernel
1947 lowmem mapping on PPC40x.
1949 nomca [IA-64] Disable machine check abort handling
1951 nomce [X86-32] Machine Check Exception
1953 nomfgpt [X86-32] Disable Multi-Function General Purpose
1954 Timer usage (for AMD Geode machines).
1956 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
1957 shutdown the other cpus. Instead use the REBOOT_VECTOR
1960 nomodule Disable module load
1962 nopat [X86] Disable PAT (page attribute table extension of
1963 pagetables) support.
1965 norandmaps Don't use address space randomization. Equivalent to
1966 echo 0 > /proc/sys/kernel/randomize_va_space
1968 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1970 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1971 with UP alternatives
1973 noresidual [PPC] Don't use residual data on PReP machines.
1975 nordrand [X86] Disable the direct use of the RDRAND
1976 instruction even if it is supported by the
1977 processor. RDRAND is still available to user
1980 noresume [SWSUSP] Disables resume and restores original swap
1983 no-scroll [VGA] Disables scrollback.
1984 This is required for the Braillex ib80-piezo Braille
1985 reader made by F.H. Papenmeier (Germany).
1989 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1991 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1992 and disable the IO APIC. legacy for "maxcpus=0".
1994 nosoftlockup [KNL] Disable the soft-lockup detector.
1996 nosync [HW,M68K] Disables sync negotiation for all devices.
1998 notsc [BUGS=X86-32] Disable Time Stamp Counter
2000 nousb [USB] Disable the USB subsystem
2002 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
2006 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
2008 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
2009 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2010 Some features depend on CPU0. Known dependencies are:
2011 1. Resume from suspend/hibernate depends on CPU0.
2012 Suspend/hibernate will fail if CPU0 is offline and you
2013 need to online CPU0 before suspend/hibernate.
2014 2. PIC interrupts also depend on CPU0. CPU0 can't be
2015 removed if a PIC interrupt is detected.
2016 It's said poweroff/reboot may depend on CPU0 on some
2017 machines although I haven't seen such issues so far
2018 after CPU0 is offline on a few tested machines.
2019 If the dependencies are under your control, you can
2020 turn on cpu0_hotplug.
2022 nptcg= [IA-64] Override max number of concurrent global TLB
2023 purges which is reported from either PAL_VM_SUMMARY or
2026 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
2027 could support. nr_cpus=n : n >= 1 limits the kernel to
2028 supporting 'n' processors. Later in runtime you can not
2029 use hotplug cpu feature to put more cpu back to online.
2030 just like you compile the kernel NR_CPUS=n
2032 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
2034 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
2035 Allowed values are enable and disable
2037 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2038 one of ['zone', 'node', 'default'] can be specified
2039 This can be set from sysctl after boot.
2040 See Documentation/sysctl/vm.txt for details.
2042 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
2043 See Documentation/debugging-via-ohci1394.txt for more
2046 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2047 Rather than timing out after 20 ms if an EC
2048 command is not properly ACKed, override the length
2049 of the timeout. We have interrupts disabled while
2050 waiting for the ACK, so if this is set too high
2051 interrupts *may* be lost!
2053 omap_mux= [OMAP] Override bootloader pin multiplexing.
2054 Format: <mux_mode0.mode_name=value>...
2055 For example, to override I2C bus2:
2056 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2058 oprofile.timer= [HW]
2059 Use timer interrupt instead of performance counters
2061 oprofile.cpu_type= Force an oprofile cpu type
2062 This might be useful if you have an older oprofile
2063 userland or if you want common events.
2064 Format: { arch_perfmon }
2065 arch_perfmon: [X86] Force use of architectural
2066 perfmon on Intel CPUs instead of the
2067 CPU specific event set.
2068 timer: [X86] Force use of architectural NMI
2069 timer mode (see also oprofile.timer
2070 for generic hr timer mode)
2071 [s390] Force legacy basic mode sampling
2072 (report cpu_type "timer")
2074 oops=panic Always panic on oopses. Default is to just kill the
2075 process, but there is a small probability of
2076 deadlocking the machine.
2077 This will also cause panics on machine check exceptions.
2078 Useful together with panic=30 to trigger a reboot.
2081 See Documentation/sound/oss/oss-parameters.txt
2083 panic= [KNL] Kernel behaviour on panic: delay <timeout>
2084 timeout > 0: seconds before rebooting
2085 timeout = 0: wait forever
2086 timeout < 0: reboot immediately
2089 parkbd.port= [HW] Parallel port number the keyboard adapter is
2090 connected to, default is 0.
2092 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
2093 0 for XT, 1 for AT (default is AT).
2096 parport= [HW,PPT] Specify parallel ports. 0 disables.
2097 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2098 Use 'auto' to force the driver to use any
2099 IRQ/DMA settings detected (the default is to
2100 ignore detected IRQ/DMA settings because of
2101 possible conflicts). You can specify the base
2102 address, IRQ, and DMA settings; IRQ and DMA
2103 should be numbers, or 'auto' (for using detected
2104 settings on that particular port), or 'nofifo'
2105 (to avoid using a FIFO even if it is detected).
2106 Parallel ports are assigned in the order they
2107 are specified on the command line, starting
2110 parport_init_mode= [HW,PPT]
2111 Configure VIA parallel port to operate in
2112 a specific mode. This is necessary on Pegasos
2113 computer where firmware has no options for setting
2114 up parallel port mode and sets it to spp.
2115 Currently this function knows 686a and 8231 chips.
2116 Format: [spp|ps2|epp|ecp|ecpepp]
2119 Halt all CPUs after the first oops has been printed for
2120 the specified number of seconds. This is to be used if
2121 your oopses keep scrolling off the screen.
2126 See header of drivers/block/paride/pcd.c.
2127 See also Documentation/blockdev/paride.txt.
2129 pci=option[,option...] [PCI] various PCI subsystem options:
2130 earlydump [X86] dump PCI config space before the kernel
2132 off [X86] don't probe for the PCI bus
2133 bios [X86-32] force use of PCI BIOS, don't access
2134 the hardware directly. Use this if your machine
2135 has a non-standard PCI host bridge.
2136 nobios [X86-32] disallow use of PCI BIOS, only direct
2137 hardware access methods are allowed. Use this
2138 if you experience crashes upon bootup and you
2139 suspect they are caused by the BIOS.
2140 conf1 [X86] Force use of PCI Configuration
2142 conf2 [X86] Force use of PCI Configuration
2144 noaer [PCIE] If the PCIEAER kernel config parameter is
2145 enabled, this kernel boot option can be used to
2146 disable the use of PCIE advanced error reporting.
2147 nodomains [PCI] Disable support for multiple PCI
2148 root domains (aka PCI segments, in ACPI-speak).
2149 nommconf [X86] Disable use of MMCONFIG for PCI
2151 check_enable_amd_mmconf [X86] check for and enable
2152 properly configured MMIO access to PCI
2153 config space on AMD family 10h CPU
2154 nomsi [MSI] If the PCI_MSI kernel config parameter is
2155 enabled, this kernel boot option can be used to
2156 disable the use of MSI interrupts system-wide.
2157 noioapicquirk [APIC] Disable all boot interrupt quirks.
2158 Safety option to keep boot IRQs enabled. This
2159 should never be necessary.
2160 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
2161 primary IO-APIC for bridges that cannot disable
2162 boot IRQs. This fixes a source of spurious IRQs
2163 when the system masks IRQs.
2164 noioapicreroute [APIC] Disable workaround that uses the
2165 boot IRQ equivalent of an IRQ that connects to
2166 a chipset where boot IRQs cannot be disabled.
2167 The opposite of ioapicreroute.
2168 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
2169 routing table. These calls are known to be buggy
2170 on several machines and they hang the machine
2171 when used, but on other computers it's the only
2172 way to get the interrupt routing table. Try
2173 this option if the kernel is unable to allocate
2174 IRQs or discover secondary PCI buses on your
2176 rom [X86] Assign address space to expansion ROMs.
2177 Use with caution as certain devices share
2178 address decoders between ROMs and other
2180 norom [X86] Do not assign address space to
2181 expansion ROMs that do not already have
2182 BIOS assigned address ranges.
2183 nobar [X86] Do not assign address space to the
2184 BARs that weren't assigned by the BIOS.
2185 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
2186 assigned automatically to PCI devices. You can
2187 make the kernel exclude IRQs of your ISA cards
2189 pirqaddr=0xAAAAA [X86] Specify the physical address
2190 of the PIRQ table (normally generated
2191 by the BIOS) if it is outside the
2192 F0000h-100000h range.
2193 lastbus=N [X86] Scan all buses thru bus #N. Can be
2194 useful if the kernel is unable to find your
2195 secondary buses and you want to tell it
2196 explicitly which ones they are.
2197 assign-busses [X86] Always assign all PCI bus
2198 numbers ourselves, overriding
2199 whatever the firmware may have done.
2200 usepirqmask [X86] Honor the possible IRQ mask stored
2201 in the BIOS $PIR table. This is needed on
2202 some systems with broken BIOSes, notably
2203 some HP Pavilion N5400 and Omnibook XE3
2204 notebooks. This will have no effect if ACPI
2205 IRQ routing is enabled.
2206 noacpi [X86] Do not use ACPI for IRQ routing
2207 or for PCI scanning.
2208 use_crs [X86] Use PCI host bridge window information
2209 from ACPI. On BIOSes from 2008 or later, this
2210 is enabled by default. If you need to use this,
2211 please report a bug.
2212 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2213 If you need to use this, please report a bug.
2214 routeirq Do IRQ routing for all PCI devices.
2215 This is normally done in pci_enable_device(),
2216 so this option is a temporary workaround
2217 for broken drivers that don't call it.
2218 skip_isa_align [X86] do not align io start addr, so can
2219 handle more pci cards
2220 firmware [ARM] Do not re-enumerate the bus but instead
2221 just use the configuration from the
2222 bootloader. This is currently used on
2223 IXP2000 systems where the bus has to be
2224 configured a certain way for adjunct CPUs.
2225 noearly [X86] Don't do any early type 1 scanning.
2226 This might help on some broken boards which
2227 machine check when some devices' config space
2228 is read. But various workarounds are disabled
2229 and some IOMMU drivers will not work.
2230 bfsort Sort PCI devices into breadth-first order.
2231 This sorting is done to get a device
2232 order compatible with older (<= 2.4) kernels.
2233 nobfsort Don't sort PCI devices into breadth-first order.
2234 cbiosize=nn[KMG] The fixed amount of bus space which is
2235 reserved for the CardBus bridge's IO window.
2236 The default value is 256 bytes.
2237 cbmemsize=nn[KMG] The fixed amount of bus space which is
2238 reserved for the CardBus bridge's memory
2239 window. The default value is 64 megabytes.
2242 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2243 Specifies alignment and device to reassign
2244 aligned memory resources.
2245 If <order of align> is not specified,
2246 PAGE_SIZE is used as alignment.
2247 PCI-PCI bridge can be specified, if resource
2248 windows need to be expanded.
2249 ecrc= Enable/disable PCIe ECRC (transaction layer
2250 end-to-end CRC checking).
2251 bios: Use BIOS/firmware settings. This is the
2255 realloc= Enable/disable reallocating PCI bridge resources
2256 if allocations done by BIOS are too small to
2257 accommodate resources required by all child
2259 off: Turn realloc off
2261 realloc same as realloc=on
2262 noari do not use PCIe ARI.
2263 pcie_scan_all Scan all possible PCIe devices. Otherwise we
2264 only look for one device below a PCIe downstream
2267 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2270 force Enable ASPM even on devices that claim not to support it.
2271 WARNING: Forcing ASPM on may cause system lockups.
2273 pcie_hp= [PCIE] PCI Express Hotplug driver options:
2274 nomsi Do not use MSI for PCI Express Native Hotplug (this
2275 makes all PCIe ports use INTx for hotplug services).
2277 pcie_ports= [PCIE] PCIe ports handling:
2278 auto Ask the BIOS whether or not to use native PCIe services
2279 associated with PCIe ports (PME, hot-plug, AER). Use
2280 them only if that is allowed by the BIOS.
2281 native Use native PCIe services associated with PCIe ports
2283 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2286 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2287 nomsi Do not use MSI for native PCIe PME signaling (this makes
2288 all PCIe root ports use INTx for all services).
2290 pcmv= [HW,PCMCIA] BadgePAD 4
2293 See Documentation/blockdev/paride.txt.
2295 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2298 See arch/parisc/kernel/pdc_chassis.c
2300 percpu_alloc= Select which percpu first chunk allocator to use.
2301 Currently supported values are "embed" and "page".
2302 Archs may support subset or none of the selections.
2303 See comments in mm/percpu.c for details on each
2304 allocator. This parameter is primarily for debugging
2305 and performance comparison.
2308 See Documentation/blockdev/paride.txt.
2311 See Documentation/blockdev/paride.txt.
2313 pirq= [SMP,APIC] Manual mp-table setup
2314 See Documentation/x86/i386/IO-APIC.txt.
2316 plip= [PPT,NET] Parallel port network link
2317 Format: { parport<nr> | timid | 0 }
2318 See also Documentation/parport.txt.
2320 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2321 Override pmtimer IOPort with a hex value.
2325 Enable PNP debug messages (depends on the
2326 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
2327 via /sys/module/pnp/parameters/debug. We always show
2328 current resource usage; turning this on also shows
2329 possible settings and some assignment information.
2335 { on | off | curr | res | no-curr | no-res }
2338 [ISAPNP] Exclude IRQs for the autoconfiguration
2341 [ISAPNP] Exclude DMAs for the autoconfiguration
2343 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2344 Ranges are in pairs (I/O port base and size).
2347 [ISAPNP] Exclude memory regions for the
2349 Ranges are in pairs (memory base and size).
2351 ports= [IP_VS_FTP] IPVS ftp helper module
2353 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2355 Format: <port>,<port>....
2357 print-fatal-signals=
2358 [KNL] debug: print fatal signals
2360 If enabled, warn about various signal handling
2361 related application anomalies: too many signals,
2362 too many POSIX.1 timers, fatal signals causing a
2365 If you hit the warning due to signal overflow,
2366 you might want to try "ulimit -i unlimited".
2370 printk.always_kmsg_dump=
2371 Trigger kmsg_dump for cases other than kernel oops or
2373 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2376 printk.time= Show timing data prefixed to each printk message line
2377 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2379 processor.max_cstate= [HW,ACPI]
2380 Limit processor to maximum C-state
2381 max_cstate=9 overrides any DMI blacklist limit.
2383 processor.nocst [HW,ACPI]
2384 Ignore the _CST method to determine C-states,
2385 instead using the legacy FADT method
2387 profile= [KNL] Enable kernel profiling via /proc/profile
2388 Format: [schedule,]<number>
2389 Param: "schedule" - profile schedule points.
2390 Param: <number> - step/bucket size as a power of 2 for
2391 statistical time based profiling.
2392 Param: "sleep" - profile D-state sleeping (millisecs).
2393 Requires CONFIG_SCHEDSTATS
2394 Param: "kvm" - profile VM exits.
2396 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2398 See Documentation/blockdev/ramdisk.txt.
2400 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2401 probe for; one of (bare|imps|exps|lifebook|any).
2402 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2404 psmouse.resetafter= [HW,MOUSE]
2405 Try to reset the device after so many bad packets
2408 [HW,MOUSE] Set desired mouse resolution, in dpi.
2409 psmouse.smartscroll=
2410 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2411 0 = disabled, 1 = enabled (default).
2413 pstore.backend= Specify the name of the pstore backend to use
2416 See Documentation/blockdev/paride.txt.
2419 [KNL] Number of legacy pty's. Overwrites compiled-in
2422 quiet [KNL] Disable most log messages
2427 See Documentation/md.txt.
2429 ramdisk_blocksize= [RAM]
2430 See Documentation/blockdev/ramdisk.txt.
2432 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2433 See Documentation/blockdev/ramdisk.txt.
2435 rcu_nocbs= [KNL,BOOT]
2436 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2437 the specified list of CPUs to be no-callback CPUs.
2438 Invocation of these CPUs' RCU callbacks will
2439 be offloaded to "rcuoN" kthreads created for
2440 that purpose. This reduces OS jitter on the
2441 offloaded CPUs, which can be useful for HPC and
2442 real-time workloads. It can also improve energy
2443 efficiency for asymmetric multiprocessors.
2445 rcu_nocb_poll [KNL,BOOT]
2446 Rather than requiring that offloaded CPUs
2447 (specified by rcu_nocbs= above) explicitly
2448 awaken the corresponding "rcuoN" kthreads,
2449 make these kthreads poll for callbacks.
2450 This improves the real-time response for the
2451 offloaded CPUs by relieving them of the need to
2452 wake up the corresponding kthread, but degrades
2453 energy efficiency by requiring that the kthreads
2454 periodically wake up to do the polling.
2456 rcutree.blimit= [KNL,BOOT]
2457 Set maximum number of finished RCU callbacks to process
2460 rcutree.fanout_leaf= [KNL,BOOT]
2461 Increase the number of CPUs assigned to each
2462 leaf rcu_node structure. Useful for very large
2465 rcutree.qhimark= [KNL,BOOT]
2466 Set threshold of queued
2467 RCU callbacks over which batch limiting is disabled.
2469 rcutree.qlowmark= [KNL,BOOT]
2470 Set threshold of queued RCU callbacks below which
2471 batch limiting is re-enabled.
2473 rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2474 Suppress RCU CPU stall warning messages.
2476 rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2477 Set timeout for RCU CPU stall warning messages.
2479 rcutree.jiffies_till_first_fqs= [KNL,BOOT]
2480 Set delay from grace-period initialization to
2481 first attempt to force quiescent states.
2482 Units are jiffies, minimum value is zero,
2483 and maximum value is HZ.
2485 rcutree.jiffies_till_next_fqs= [KNL,BOOT]
2486 Set delay between subsequent attempts to force
2487 quiescent states. Units are jiffies, minimum
2488 value is one, and maximum value is HZ.
2490 rcutorture.fqs_duration= [KNL,BOOT]
2491 Set duration of force_quiescent_state bursts.
2493 rcutorture.fqs_holdoff= [KNL,BOOT]
2494 Set holdoff time within force_quiescent_state bursts.
2496 rcutorture.fqs_stutter= [KNL,BOOT]
2497 Set wait time between force_quiescent_state bursts.
2499 rcutorture.irqreader= [KNL,BOOT]
2500 Test RCU readers from irq handlers.
2502 rcutorture.n_barrier_cbs= [KNL,BOOT]
2503 Set callbacks/threads for rcu_barrier() testing.
2505 rcutorture.nfakewriters= [KNL,BOOT]
2506 Set number of concurrent RCU writers. These just
2507 stress RCU, they don't participate in the actual
2508 test, hence the "fake".
2510 rcutorture.nreaders= [KNL,BOOT]
2511 Set number of RCU readers.
2513 rcutorture.onoff_holdoff= [KNL,BOOT]
2514 Set time (s) after boot for CPU-hotplug testing.
2516 rcutorture.onoff_interval= [KNL,BOOT]
2517 Set time (s) between CPU-hotplug operations, or
2518 zero to disable CPU-hotplug testing.
2520 rcutorture.shuffle_interval= [KNL,BOOT]
2521 Set task-shuffle interval (s). Shuffling tasks
2522 allows some CPUs to go into dyntick-idle mode
2523 during the rcutorture test.
2525 rcutorture.shutdown_secs= [KNL,BOOT]
2526 Set time (s) after boot system shutdown. This
2527 is useful for hands-off automated testing.
2529 rcutorture.stall_cpu= [KNL,BOOT]
2530 Duration of CPU stall (s) to test RCU CPU stall
2531 warnings, zero to disable.
2533 rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2534 Time to wait (s) after boot before inducing stall.
2536 rcutorture.stat_interval= [KNL,BOOT]
2537 Time (s) between statistics printk()s.
2539 rcutorture.stutter= [KNL,BOOT]
2540 Time (s) to stutter testing, for example, specifying
2541 five seconds causes the test to run for five seconds,
2542 wait for five seconds, and so on. This tests RCU's
2543 ability to transition abruptly to and from idle.
2545 rcutorture.test_boost= [KNL,BOOT]
2546 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
2547 "Maybe" means test if the RCU implementation
2548 under test support RCU priority boosting.
2550 rcutorture.test_boost_duration= [KNL,BOOT]
2551 Duration (s) of each individual boost test.
2553 rcutorture.test_boost_interval= [KNL,BOOT]
2554 Interval (s) between each boost test.
2556 rcutorture.test_no_idle_hz= [KNL,BOOT]
2557 Test RCU's dyntick-idle handling. See also the
2558 rcutorture.shuffle_interval parameter.
2560 rcutorture.torture_type= [KNL,BOOT]
2561 Specify the RCU implementation to test.
2563 rcutorture.verbose= [KNL,BOOT]
2564 Enable additional printk() statements.
2568 Run specified binary instead of /init from the ramdisk,
2569 used for early userspace startup. See initrd.
2571 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2572 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2573 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2576 [KNL, SMP] Set scheduler's default relax_domain_level.
2577 See Documentation/cgroups/cpusets.txt.
2579 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2581 reservetop= [X86-32]
2583 Reserves a hole at the top of the kernel virtual
2588 Set the amount of memory to reserve for BIOS at
2589 the bottom of the address space.
2591 reset_devices [KNL] Force drivers to reset the underlying device
2592 during initialization.
2595 Specify the partition device for software suspend
2597 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2599 resume_offset= [SWSUSP]
2600 Specify the offset from the beginning of the partition
2601 given by "resume=" at which the swap header is located,
2602 in <PAGE_SIZE> units (needed only for swap files).
2603 See Documentation/power/swsusp-and-swap-files.txt
2605 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
2606 read the resume files
2608 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
2609 Useful for devices that are detected asynchronously
2610 (e.g. USB and MMC devices).
2612 hibernate= [HIBERNATION]
2613 noresume Don't check if there's a hibernation image
2614 present during boot.
2615 nocompress Don't compress/decompress hibernation images.
2617 retain_initrd [RAM] Keep initrd memory after extraction
2619 rhash_entries= [KNL,NET]
2620 Set number of hash buckets for route cache
2622 riscom8= [HW,SERIAL]
2623 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2625 ro [KNL] Mount root device read-only on boot
2627 root= [KNL] Root filesystem
2628 See name_to_dev_t comment in init/do_mounts.c.
2630 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2631 mount the root filesystem
2633 rootflags= [KNL] Set root filesystem mount option string
2635 rootfstype= [KNL] Set root filesystem type
2637 rootwait [KNL] Wait (indefinitely) for root device to show up.
2638 Useful for devices that are detected asynchronously
2639 (e.g. USB and MMC devices).
2641 rw [KNL] Mount root device read-write on boot
2643 S [KNL] Run init in single mode
2646 See drivers/net/irda/sa1100_ir.c.
2648 sbni= [NET] Granch SBNI12 leased line adapter
2650 sched_debug [KNL] Enables verbose scheduler debug messages.
2652 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
2653 xtime_lock contention on larger systems, and/or RCU lock
2654 contention on all systems with CONFIG_MAXSMP set.
2655 Format: { "0" | "1" }
2656 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2658 Note: increases power consumption, thus should only be
2659 enabled if running jitter sensitive (HPC/RT) workloads.
2661 security= [SECURITY] Choose a security module to enable at boot.
2662 If this boot parameter is not specified, only the first
2663 security module asking for security registration will be
2664 loaded. An invalid security module name will be treated
2665 as if no module has been chosen.
2667 selinux= [SELINUX] Disable or enable SELinux at boot time.
2668 Format: { "0" | "1" }
2669 See security/selinux/Kconfig help text.
2672 Default value is set via kernel config option.
2673 If enabled at boot time, /selinux/disable can be used
2674 later to disable prior to initial policy load.
2676 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2677 Format: { "0" | "1" }
2678 See security/apparmor/Kconfig help text
2681 Default value is set via kernel config option.
2683 serialnumber [BUGS=X86-32]
2686 Maximal number of shapers.
2688 show_msr= [x86] show boot-time MSR settings
2689 Format: { <integer> }
2690 Show boot-time (BIOS-initialized) MSR settings.
2691 The parameter means the number of CPUs to show,
2692 for example 1 means boot CPU only.
2699 slab_max_order= [MM, SLAB]
2700 Determines the maximum allowed order for slabs.
2701 A high setting may cause OOMs due to memory
2702 fragmentation. Defaults to 1 for systems with
2703 more than 32MB of RAM, 0 otherwise.
2705 slub_debug[=options[,slabs]] [MM, SLUB]
2706 Enabling slub_debug allows one to determine the
2707 culprit if slab objects become corrupted. Enabling
2708 slub_debug can create guard zones around objects and
2709 may poison objects when not in use. Also tracks the
2710 last alloc / free. For more information see
2711 Documentation/vm/slub.txt.
2713 slub_max_order= [MM, SLUB]
2714 Determines the maximum allowed order for slabs.
2715 A high setting may cause OOMs due to memory
2716 fragmentation. For more information see
2717 Documentation/vm/slub.txt.
2719 slub_min_objects= [MM, SLUB]
2720 The minimum number of objects per slab. SLUB will
2721 increase the slab order up to slub_max_order to
2722 generate a sufficiently large slab able to contain
2723 the number of objects indicated. The higher the number
2724 of objects the smaller the overhead of tracking slabs
2725 and the less frequently locks need to be acquired.
2726 For more information see Documentation/vm/slub.txt.
2728 slub_min_order= [MM, SLUB]
2729 Determines the minimum page order for slabs. Must be
2730 lower than slub_max_order.
2731 For more information see Documentation/vm/slub.txt.
2733 slub_nomerge [MM, SLUB]
2734 Disable merging of slabs with similar size. May be
2735 necessary if there is some reason to distinguish
2736 allocs to different slabs. Debug options disable
2737 merging on their own.
2738 For more information see Documentation/vm/slub.txt.
2741 Format: <io1>[,<io2>[,...,<io8>]]
2743 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2744 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2745 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2746 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2747 smsc-ircc2.ircc_irq= [HW] IRQ line
2748 smsc-ircc2.ircc_dma= [HW] DMA channel
2749 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2750 0: Toshiba Satellite 1800 (GP data pin select)
2751 1: Fast pin select (default)
2755 [KNL] Should the soft-lockup detector generate panics.
2758 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2759 See Documentation/laptops/sonypi.txt
2761 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2762 See Documentation/serial/specialix.txt.
2764 spia_io_base= [HW,MTD]
2770 Enabled the stack tracer on boot up.
2772 stacktrace_filter=[function-list]
2773 [FTRACE] Limit the functions that the stack tracer
2774 will trace at boot up. function-list is a comma separated
2775 list of functions. This list can be changed at run
2776 time by the stack_trace_filter file in the debugfs
2777 tracing directory. Note, this enables stack tracing
2778 and the stacktrace above is not needed.
2782 Set the STI (builtin display/keyboard on the HP-PARISC
2783 machines) console (graphic card) which should be used
2784 as the initial boot-console.
2785 See also comment in drivers/video/console/sticore.c.
2788 See comment in drivers/video/console/sticore.c.
2791 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2793 sunrpc.min_resvport=
2794 sunrpc.max_resvport=
2796 SunRPC servers often require that client requests
2797 originate from a privileged port (i.e. a port in the
2798 range 0 < portnr < 1024).
2799 An administrator who wishes to reserve some of these
2800 ports for other uses may adjust the range that the
2801 kernel's sunrpc client considers to be privileged
2802 using these two parameters to set the minimum and
2803 maximum port values.
2807 Control how the NFS server code allocates CPUs to
2808 service thread pools. Depending on how many NICs
2809 you have and where their interrupts are bound, this
2810 option will affect which CPUs will do NFS serving.
2811 Note: this parameter cannot be changed while the
2812 NFS server is running.
2814 auto the server chooses an appropriate mode
2815 automatically using heuristics
2816 global a single global pool contains all CPUs
2817 percpu one pool for each CPU
2818 pernode one pool for each NUMA node (equivalent
2819 to global on non-NUMA machines)
2821 sunrpc.tcp_slot_table_entries=
2822 sunrpc.udp_slot_table_entries=
2824 Sets the upper limit on the number of simultaneous
2825 RPC calls that can be sent from the client to a
2826 server. Increasing these values may allow you to
2827 improve throughput, but will also increase the
2828 amount of memory reserved for use by the client.
2831 [KNL] Enable accounting of swap in memory resource
2832 controller if no parameter or 1 is given or disable
2833 it if 0 is given (See Documentation/cgroups/memory.txt)
2835 swiotlb= [IA-64] Number of I/O TLB slabs
2839 sysfs.deprecated=0|1 [KNL]
2840 Enable/disable old style sysfs layout for old udev
2841 on older distributions. When this option is enabled
2842 very new udev will not work anymore. When this option
2843 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2844 in older udev will not work anymore.
2845 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2846 the kernel configuration.
2848 sysrq_always_enabled
2850 Ignore sysrq setting - this boot parameter will
2851 neutralize any effect of /proc/sys/kernel/sysrq.
2852 Useful for debugging.
2856 test_suspend= [SUSPEND]
2857 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2858 standby suspend) as the system sleep state to briefly
2859 enter during system startup. The system is woken from
2860 this state using a wakeup-capable RTC alarm.
2862 thash_entries= [KNL,NET]
2863 Set number of hash buckets for TCP connection
2865 thermal.act= [HW,ACPI]
2866 -1: disable all active trip points in all thermal zones
2867 <degrees C>: override all lowest active trip points
2869 thermal.crt= [HW,ACPI]
2870 -1: disable all critical trip points in all thermal zones
2871 <degrees C>: override all critical trip points
2873 thermal.nocrt= [HW,ACPI]
2874 Set to disable actions on ACPI thermal zone
2875 critical and hot trip points.
2877 thermal.off= [HW,ACPI]
2878 1: disable ACPI thermal control
2880 thermal.psv= [HW,ACPI]
2881 -1: disable all passive trip points
2882 <degrees C>: override all passive trip points to this
2885 thermal.tzp= [HW,ACPI]
2886 Specify global default ACPI thermal zone polling rate
2887 <deci-seconds>: poll all this frequency
2888 0: no polling (default)
2891 Force threading of all interrupt handlers except those
2892 marked explicitly IRQF_NO_THREAD.
2896 Specify if the kernel should make use of the cpu
2897 topology information if the hardware supports this.
2898 The scheduler will make use of this information and
2899 e.g. base its process migration decisions on it.
2904 tpm_suspend_pcr=[HW,TPM]
2905 Format: integer pcr id
2906 Specify that at suspend time, the tpm driver
2907 should extend the specified pcr with zeros,
2908 as a workaround for some chips which fail to
2909 flush the last written pcr on TPM_SaveState.
2910 This will guarantee that all the other pcrs
2913 trace_buf_size=nn[KMG]
2914 [FTRACE] will set tracing buffer size.
2916 trace_event=[event-list]
2917 [FTRACE] Set and start specified trace events in order
2918 to facilitate early boot debugging.
2919 See also Documentation/trace/events.txt
2921 trace_options=[option-list]
2922 [FTRACE] Enable or disable tracer options at boot.
2923 The option-list is a comma delimited list of options
2924 that can be enabled or disabled just as if you were
2925 to echo the option name into
2927 /sys/kernel/debug/tracing/trace_options
2929 For example, to enable stacktrace option (to dump the
2930 stack trace of each event), add to the command line:
2932 trace_options=stacktrace
2934 See also Documentation/trace/ftrace.txt "trace options"
2937 transparent_hugepage=
2939 Format: [always|madvise|never]
2940 Can be used to control the default behavior of the system
2941 with respect to transparent hugepages.
2942 See Documentation/vm/transhuge.txt for more details.
2944 tsc= Disable clocksource stability checks for TSC.
2946 [x86] reliable: mark tsc clocksource as reliable, this
2947 disables clocksource verification at runtime, as well
2948 as the stability checks done at bootup. Used to enable
2949 high-resolution timer mode on older hardware, and in
2950 virtualized environment.
2951 [x86] noirqtime: Do not use TSC to do irq accounting.
2952 Used to run time disable IRQ_TIME_ACCOUNTING on any
2953 platforms where RDTSC is slow and this accounting
2956 turbografx.map[2|3]= [HW,JOY]
2957 TurboGraFX parallel port interface
2959 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2960 See also Documentation/input/joystick-parport.txt
2962 udbg-immortal [PPC] When debugging early kernel crashes that
2963 happen after console_init() and before a proper
2964 console driver takes over, this boot options might
2965 help "seeing" what's going on.
2967 uhash_entries= [KNL,NET]
2968 Set number of hash buckets for UDP/UDP-Lite connections
2971 [USB] Ignore overcurrent events (default N).
2972 Some badly-designed motherboards generate lots of
2973 bogus events, for ports that aren't wired to
2974 anything. Set this parameter to avoid log spamming.
2975 Note that genuine overcurrent events won't be
2979 [X86] Cause panic on unknown NMI.
2981 usbcore.authorized_default=
2982 [USB] Default USB device authorization:
2983 (default -1 = authorized except for wireless USB,
2984 0 = not authorized, 1 = authorized)
2986 usbcore.autosuspend=
2987 [USB] The autosuspend time delay (in seconds) used
2988 for newly-detected USB devices (default 2). This
2989 is the time required before an idle device will be
2990 autosuspended. Devices for which the delay is set
2991 to a negative value won't be autosuspended at all.
2993 usbcore.usbfs_snoop=
2994 [USB] Set to log all usbfs traffic (default 0 = off).
2996 usbcore.blinkenlights=
2997 [USB] Set to cycle leds on hubs (default 0 = off).
2999 usbcore.old_scheme_first=
3000 [USB] Start with the old device initialization
3001 scheme (default 0 = off).
3003 usbcore.usbfs_memory_mb=
3004 [USB] Memory limit (in MB) for buffers allocated by
3005 usbfs (default = 16, 0 = max = 2047).
3007 usbcore.use_both_schemes=
3008 [USB] Try the other device initialization scheme
3009 if the first one fails (default 1 = enabled).
3011 usbcore.initial_descriptor_timeout=
3012 [USB] Specifies timeout for the initial 64-byte
3013 USB_REQ_GET_DESCRIPTOR request in milliseconds
3014 (default 5000 = 5.0 seconds).
3017 [USBHID] The interval which mice are to be polled at.
3019 usb-storage.delay_use=
3020 [UMS] The delay in seconds before a new device is
3021 scanned for Logical Units (default 5).
3024 [UMS] A list of quirks entries to supplement or
3025 override the built-in unusual_devs list. List
3026 entries are separated by commas. Each entry has
3027 the form VID:PID:Flags where VID and PID are Vendor
3028 and Product ID values (4-digit hex numbers) and
3029 Flags is a set of characters, each corresponding
3030 to a common usb-storage quirk flag as follows:
3031 a = SANE_SENSE (collect more than 18 bytes
3033 b = BAD_SENSE (don't collect more than 18
3034 bytes of sense data);
3035 c = FIX_CAPACITY (decrease the reported
3036 device capacity by one sector);
3037 d = NO_READ_DISC_INFO (don't use
3038 READ_DISC_INFO command);
3039 e = NO_READ_CAPACITY_16 (don't use
3040 READ_CAPACITY_16 command);
3041 h = CAPACITY_HEURISTICS (decrease the
3042 reported device capacity by one
3043 sector if the number is odd);
3044 i = IGNORE_DEVICE (don't bind to this
3046 l = NOT_LOCKABLE (don't try to lock and
3047 unlock ejectable media);
3048 m = MAX_SECTORS_64 (don't transfer more
3049 than 64 sectors = 32 KB at a time);
3050 n = INITIAL_READ10 (force a retry of the
3051 initial READ(10) command);
3052 o = CAPACITY_OK (accept the capacity
3053 reported by the device);
3054 p = WRITE_CACHE (the device cache is ON
3056 r = IGNORE_RESIDUE (the device reports
3057 bogus residue values);
3058 s = SINGLE_LUN (the device has only one
3060 w = NO_WP_DETECT (don't test whether the
3061 medium is write-protected).
3062 Example: quirks=0419:aaf5:rl,0421:0433:rc
3064 user_debug= [KNL,ARM]
3066 See arch/arm/Kconfig.debug help text.
3067 1 - undefined instruction events
3069 4 - invalid data aborts
3072 Example: user_debug=31
3075 [X86] Flags controlling user PTE allocations.
3077 nohigh = do not allocate PTE pages in
3078 HIGHMEM regardless of setting
3082 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3083 vdso=1: enable VDSO (default)
3084 vdso=0: disable VDSO mapping
3087 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3088 vdso32=1: enable 32-bit VDSO (default)
3089 vdso32=0: disable 32-bit VDSO mapping
3092 vector=percpu: enable percpu vector domain
3094 video= [FB] Frame buffer configuration
3095 See Documentation/fb/modedb.txt.
3098 [VMMIO] Memory mapped virtio (platform) device.
3100 <size>@<baseaddr>:<irq>[:<id>]
3102 <size> := size (can use standard suffixes
3104 <baseaddr> := physical base address
3105 <irq> := interrupt number (as passed to
3107 <id> := (optional) platform device id
3109 virtio_mmio.device=1K@0x100b0000:48:7
3111 Can be used multiple times for multiple devices.
3113 vga= [BOOT,X86-32] Select a particular video mode
3114 See Documentation/x86/boot.txt and
3115 Documentation/svga.txt.
3116 Use vga=ask for menu.
3117 This is actually a boot loader parameter; the value is
3118 passed to the kernel using a special protocol.
3120 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3121 size of <nn>. This can be used to increase the
3122 minimum size (128MB on x86). It can also be used to
3123 decrease the size and leave more room for directly
3126 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
3129 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
3132 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
3136 Controls the behavior of vsyscalls (i.e. calls to
3137 fixed addresses of 0xffffffffff600x00 from legacy
3138 code). Most statically-linked binaries and older
3139 versions of glibc use these calls. Because these
3140 functions are at fixed addresses, they make nice
3141 targets for exploits that can control RIP.
3143 emulate [default] Vsyscalls turn into traps and are
3144 emulated reasonably safely.
3146 native Vsyscalls are native syscall instructions.
3147 This is a little bit faster than trapping
3148 and makes a few dynamic recompilers work
3149 better than they would in emulation mode.
3150 It also makes exploits much easier to write.
3152 none Vsyscalls don't work at all. This makes
3153 them quite hard to use for exploits but
3154 might break your system.
3156 vt.cur_default= [VT] Default cursor shape.
3157 Format: 0xCCBBAA, where AA, BB, and CC are the same as
3158 the parameters of the <Esc>[?A;B;Cc escape sequence;
3159 see VGA-softcursor.txt. Default: 2 = underline.
3161 vt.default_blu= [VT]
3162 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3163 Change the default blue palette of the console.
3164 This is a 16-member array composed of values
3167 vt.default_grn= [VT]
3168 Format: <green0>,<green1>,<green2>,...,<green15>
3169 Change the default green palette of the console.
3170 This is a 16-member array composed of values
3173 vt.default_red= [VT]
3174 Format: <red0>,<red1>,<red2>,...,<red15>
3175 Change the default red palette of the console.
3176 This is a 16-member array composed of values
3182 Set system-wide default UTF-8 mode for all tty's.
3183 Default is 1, i.e. UTF-8 mode is enabled for all
3184 newly opened terminals.
3186 vt.global_cursor_default=
3189 Set system-wide default for whether a cursor
3190 is shown on new VTs. Default is -1,
3191 i.e. cursors will be created by default unless
3192 overridden by individual drivers. 0 will hide
3193 cursors, 1 will display them.
3195 watchdog timers [HW,WDT] For information on watchdog timers,
3196 see Documentation/watchdog/watchdog-parameters.txt
3197 or other driver-specific files in the
3198 Documentation/watchdog/ directory.
3200 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
3201 default x2apic cluster mode on platforms
3204 x86_mrst_timer= [X86-32,APBT]
3205 Choose timer option for x86 Moorestown MID platform.
3206 Two valid options are apbt timer only and lapic timer
3207 plus one apbt timer for broadcast timer.
3208 x86_mrst_timer=apbt_only | lapic_and_apbt
3210 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3211 xd_geo= See header of drivers/block/xd.c.
3213 xen_emul_unplug= [HW,X86,XEN]
3214 Unplug Xen emulated devices
3215 Format: [unplug0,][unplug1]
3216 ide-disks -- unplug primary master IDE devices
3217 aux-ide-disks -- unplug non-primary-master IDE devices
3218 nics -- unplug network devices
3219 all -- unplug all emulated devices (NICs and IDE disks)
3220 unnecessary -- unplugging emulated devices is
3221 unnecessary even if the host did not respond to
3223 never -- do not unplug even if version check succeeds
3225 xirc2ps_cs= [NET,PCMCIA]
3227 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3229 ______________________________________________________________________
3233 Add more DRM drivers.
projects / profile / ivi / kernel-x86-ivi.git / blob