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 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 ALSA ALSA sound support is enabled.
34 APIC APIC support is enabled.
35 APM Advanced Power Management support is enabled.
36 AX25 Appropriate AX.25 support is enabled.
37 CD Appropriate CD support is enabled.
38 DRM Direct Rendering Management support is enabled.
39 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
40 EFI EFI Partitioning (GPT) is enabled
41 EIDE EIDE/ATAPI support is enabled.
42 FB The frame buffer device is enabled.
43 HW Appropriate hardware is enabled.
44 IA-32 IA-32 aka i386 architecture is enabled.
45 IA-64 IA-64 architecture is enabled.
46 IOSCHED More than one I/O scheduler is enabled.
47 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
48 ISAPNP ISA PnP code is enabled.
49 ISDN Appropriate ISDN support is enabled.
50 JOY Appropriate joystick support is enabled.
51 LIBATA Libata driver is enabled
52 LP Printer support is enabled.
53 LOOP Loopback device support is enabled.
54 M68k M68k architecture is enabled.
55 These options have more detailed description inside of
56 Documentation/m68k/kernel-options.txt.
57 MCA MCA bus support is enabled.
58 MDA MDA console support is enabled.
59 MOUSE Appropriate mouse support is enabled.
60 MSI Message Signaled Interrupts (PCI).
61 MTD MTD support is enabled.
62 NET Appropriate network support is enabled.
63 NUMA NUMA support is enabled.
64 GENERIC_TIME The generic timeofday code is enabled.
65 NFS Appropriate NFS support is enabled.
66 OSS OSS sound support is enabled.
67 PV_OPS A paravirtualized kernel
68 PARIDE The ParIDE subsystem is enabled.
69 PARISC The PA-RISC architecture is enabled.
70 PCI PCI bus support is enabled.
71 PCMCIA The PCMCIA subsystem is enabled.
72 PNP Plug & Play support is enabled.
73 PPC PowerPC architecture is enabled.
74 PPT Parallel port support is enabled.
75 PS2 Appropriate PS/2 support is enabled.
76 RAM RAM disk support is enabled.
77 S390 S390 architecture is enabled.
78 SCSI Appropriate SCSI support is enabled.
79 A lot of drivers has their options described inside of
81 SELINUX SELinux support is enabled.
82 SERIAL Serial support is enabled.
83 SH SuperH architecture is enabled.
84 SMP The kernel is an SMP kernel.
85 SPARC Sparc architecture is enabled.
86 SWSUSP Software suspend is enabled.
87 TS Appropriate touchscreen support is enabled.
88 USB USB support is enabled.
89 USBHID USB Human Interface Device support is enabled.
90 V4L Video For Linux support is enabled.
91 VGA The VGA console has been enabled.
92 VT Virtual terminal support is enabled.
93 WDT Watchdog support is enabled.
94 XT IBM PC/XT MFM hard disk support is enabled.
95 X86-64 X86-64 architecture is enabled.
96 More X86-64 boot options can be found in
97 Documentation/x86_64/boot-options.txt .
99 In addition, the following text indicates that the option:
101 BUGS= Relates to possible processor bugs on the said processor.
102 KNL Is a kernel start-up parameter.
103 BOOT Is a boot loader parameter.
105 Parameters denoted with BOOT are actually interpreted by the boot
106 loader, and have no meaning to the kernel directly.
107 Do not modify the syntax of boot loader parameters without extreme
108 need or coordination with <Documentation/i386/boot.txt>.
110 There are also arch-specific kernel-parameters not documented here.
111 See for example <Documentation/x86_64/boot-options.txt>.
113 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
114 a trailing = on the name of any parameter states that that parameter will
115 be entered as an environment variable, whereas its absence indicates that
116 it will appear as a kernel argument readable via /proc/cmdline by programs
117 running once the system is up.
119 The number of kernel parameters is not limited, but the length of the
120 complete command line (parameters including spaces etc.) is limited to
121 a fixed number of characters. This limit depends on the architecture
122 and is between 256 and 4096 characters. It is defined in the file
123 ./include/asm/setup.h as COMMAND_LINE_SIZE.
126 53c7xx= [HW,SCSI] Amiga SCSI controllers
127 See header of drivers/scsi/53c7xx.c.
128 See also Documentation/scsi/ncr53c7xx.txt.
130 acpi= [HW,ACPI,X86-64,i386]
131 Advanced Configuration and Power Interface
132 Format: { force | off | ht | strict | noirq }
133 force -- enable ACPI if default was off
134 off -- disable ACPI if default was on
135 noirq -- do not use ACPI for IRQ routing
136 ht -- run only enough ACPI to enable Hyper Threading
137 strict -- Be less tolerant of platforms that are not
138 strictly ACPI specification compliant.
140 See also Documentation/pm.txt, pci=noacpi
142 acpi_apic_instance= [ACPI, IOAPIC]
144 2: use 2nd APIC table, if available
145 1,0: use 1st APIC table
148 acpi_sleep= [HW,ACPI] Sleep options
149 Format: { s3_bios, s3_mode }
150 See Documentation/power/video.txt
152 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
153 Format: { level | edge | high | low }
155 acpi_irq_balance [HW,ACPI]
156 ACPI will balance active IRQs
159 acpi_irq_nobalance [HW,ACPI]
160 ACPI will not move active IRQs (default)
163 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
165 Format: <irq>,<irq>...
167 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
168 Format: <irq>,<irq>...
170 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
171 Format: To spoof as Windows 98: ="Microsoft Windows"
173 acpi_osi= [HW,ACPI] empty param disables _OSI
175 acpi_serialize [HW,ACPI] force serialization of AML methods
177 acpi_skip_timer_override [HW,ACPI]
178 Recognize and ignore IRQ0/pin2 Interrupt Override.
179 For broken nForce2 BIOS resulting in XT-PIC timer.
180 acpi_use_timer_override [HW,ACPI}
181 Use timer override. For some broken Nvidia NF5 boards
182 that require a timer override, but don't have
185 acpi.debug_layer= [HW,ACPI]
187 Each bit of the <int> indicates an ACPI debug layer,
188 1: enable, 0: disable. It is useful for boot time
189 debugging. After system has booted up, it can be set
190 via /sys/module/acpi/parameters/debug_layer.
191 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
192 Available bits (add the numbers together) to enable debug output
193 for specific parts of the ACPI subsystem:
194 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
195 0x10 namespace 0x20 parser 0x40 dispatcher
196 0x80 executer 0x100 resources 0x200 acpica debugger
197 0x400 os services 0x800 acpica disassembler.
198 The number can be in decimal or prefixed with 0x in hex.
199 Warning: Many of these options can produce a lot of
200 output and make your system unusable. Be very careful.
202 acpi.debug_level= [HW,ACPI]
204 Each bit of the <int> indicates an ACPI debug level,
205 1: enable, 0: disable. It is useful for boot time
206 debugging. After system has booted up, it can be set
207 via /sys/module/acpi/parameters/debug_level.
208 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
209 Available bits (add the numbers together) to enable different
210 debug output levels of the ACPI subsystem:
211 0x01 error 0x02 warn 0x04 init 0x08 debug object
212 0x10 info 0x20 init names 0x40 parse 0x80 load
213 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
214 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
215 0x10000 resources 0x20000 user requests 0x40000 package.
216 The number can be in decimal or prefixed with 0x in hex.
217 Warning: Many of these options can produce a lot of
218 output and make your system unusable. Be very careful.
221 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
223 acpi_generic_hotkey [HW,ACPI]
224 Allow consolidated generic hotkey driver to
225 override platform specific driver.
226 See also Documentation/acpi-hotkey.txt.
228 acpi_pm_good [IA-32,X86-64]
229 Override the pmtimer bug detection: force the kernel
230 to assume that this machine's pmtimer latches its value
231 and always returns good values.
233 enable_timer_pin_1 [i386,x86-64]
234 Enable PIN 1 of APIC timer
235 Can be useful to work around chipset bugs
236 (in particular on some ATI chipsets).
237 The kernel tries to set a reasonable default.
239 disable_timer_pin_1 [i386,x86-64]
240 Disable PIN 1 of APIC timer
241 Can be useful to work around chipset bugs.
244 Format: <io>,<irq>,<dma>,<dma2>
245 See also Documentation/sound/oss/AD1816.
248 Format: <io>,<irq>,<dma>,<dma2>,<type>
254 See header of drivers/scsi/advansys.c.
256 advwdt= [HW,WDT] Advantech WDT
257 Format: <iostart>,<iostop>
259 aedsp16= [HW,OSS] Audio Excel DSP 16
260 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
261 See also header of sound/oss/aedsp16.c.
264 See Documentation/scsi/aha152x.txt.
267 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
270 See Documentation/scsi/aic7xxx.txt.
273 See Documentation/scsi/aic79xx.txt.
275 amijoy.map= [HW,JOY] Amiga joystick support
276 Map of devices attached to JOY0DAT and JOY1DAT
278 See also Documentation/kernel/input/joystick.txt
280 analog.map= [HW,JOY] Analog joystick and gamepad support
281 Specifies type or capabilities of an analog joystick
282 connected to one of 16 gameports
283 Format: <type1>,<type2>,..<type16>
286 Power management functions (SPARCstation-4/5 + deriv.)
288 Disable APC CPU standby support. SPARCstation-Fox does
289 not play well with APC CPU idle - disable it if you have
290 APC and your system crashes randomly.
292 apic= [APIC,i386] Change the output verbosity whilst booting
293 Format: { quiet (default) | verbose | debug }
294 Change the amount of debugging information output
295 when initialising the APIC and IO-APIC components.
297 apm= [APM] Advanced Power Management
298 See header of arch/i386/kernel/apm.c.
303 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
304 Format: <io>,<irq>,<nodeID>
308 atarimouse= [HW,MOUSE] Atari Mouse
310 atascsi= [HW,SCSI] Atari SCSI
312 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
313 EzKey and similar keyboards
315 atkbd.reset= [HW] Reset keyboard during initialization
317 atkbd.set= [HW] Select keyboard code set
318 Format: <int> (2 = AT (default), 3 = PS/2)
320 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
323 atkbd.softraw= [HW] Choose between synthetic and real raw mode
324 Format: <bool> (0 = real, 1 = synthetic (default))
326 atkbd.softrepeat= [HW]
327 Use software keyboard repeat
331 aztcd= [HW,CD] Aztech CD268 CDROM driver
332 Format: <io>,0x79 (?)
334 baycom_epp= [HW,AX25]
337 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
339 See header of drivers/net/hamradio/baycom_par.c.
341 baycom_ser_fdx= [HW,AX25]
342 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
343 Format: <io>,<irq>,<mode>[,<baud>]
344 See header of drivers/net/hamradio/baycom_ser_fdx.c.
346 baycom_ser_hdx= [HW,AX25]
347 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
348 Format: <io>,<irq>,<mode>
349 See header of drivers/net/hamradio/baycom_ser_hdx.c.
351 blkmtd_device= [HW,MTD]
357 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
358 bttv.radio= Most important insmod options are available as
360 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
361 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
364 See drivers/scsi/BusLogic.c, comment before function
365 BusLogic_ParseDriverOptions().
367 c101= [NET] Moxa C101 synchronous serial card
369 cachesize= [BUGS=IA-32] Override level 2 CPU cache size detection.
370 Sometimes CPU hardware bugs make them report the cache
371 size incorrectly. The kernel will attempt work arounds
372 to fix known problems, but for some CPUs it is not
373 possible to determine what the correct size should be.
374 This option provides an override for these situations.
377 Format: <io>,<irq>[,PAS]
378 See header of drivers/cdrom/cdu31a.c.
380 chandev= [HW,NET] Generic channel device initialisation
382 checkreqprot [SELINUX] Set initial checkreqprot flag value.
383 Format: { "0" | "1" }
384 See security/selinux/Kconfig help text.
385 0 -- check protection applied by kernel (includes
386 any implied execute protection).
387 1 -- check protection requested by application.
388 Default value is set via a kernel config option.
389 Value can be changed at runtime via
390 /selinux/checkreqprot.
392 clock= [BUGS=IA-32, HW] gettimeofday clocksource override.
394 Forces specified clocksource (if available) to be used
395 when calculating gettimeofday(). If specified
396 clocksource is not available, it defaults to PIT.
397 Format: { pit | tsc | cyclone | pmtmr }
399 clocksource= [GENERIC_TIME] Override the default clocksource
401 Override the default clocksource and use the clocksource
402 with the name specified.
403 Some clocksource names to choose from, depending on
405 [all] jiffies (this is the base, fallback clocksource)
407 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
408 pxa_timer,timer3,32k_counter,timer0_1
410 [IA-32] pit,hpet,tsc,vmi-timer;
411 scx200_hrt on Geode; cyclone on IBM x440
419 code_bytes [IA32] How many bytes of object code to print in an
426 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
427 over the 8254 in addition to over the IO-APIC. The
428 kernel tries to set a sensible default.
430 hpet= [IA-32,HPET] option to disable HPET and use PIT.
434 Format: { auto | [<io>,][<irq>] }
436 com20020= [HW,NET] ARCnet - COM20020 chipset
438 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
440 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
444 ARCnet - COM90xx chipset (memory-mapped buffers)
445 Format: <io>[,<irq>[,<memstart>]]
447 condev= [HW,S390] console device
450 console= [KNL] Output console device and options.
452 tty<n> Use the virtual console device <n>.
456 Use the specified serial port. The options are of
457 the form "bbbbpnf", where "bbbb" is the baud rate,
458 "p" is parity ("n", "o", or "e"), "n" is number of
459 bits, and "f" is flow control ("r" for RTS or
460 omit it). Default is "9600n8".
462 See Documentation/serial-console.txt for more
464 Documentation/networking/netconsole.txt for an
467 uart,io,<addr>[,options]
468 uart,mmio,<addr>[,options]
469 Start an early, polled-mode console on the 8250/16550
470 UART at the specified I/O port or MMIO address,
471 switching to the matching ttyS device later. The
472 options are the same as for ttyS, above.
474 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
476 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
479 Format: { parport<nr> | auto | none }
481 crashkernel=nn[KMG]@ss[KMG]
482 [KNL] Reserve a chunk of physical memory to
483 hold a kernel to switch to with kexec on panic.
486 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
491 cs89x0_media= [HW,NET]
492 Format: { rj45 | aui | bnc }
494 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
497 See header of drivers/s390/block/dasd_devmap.c.
499 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
500 (one device per port)
501 Format: <port#>,<type>
502 See also Documentation/input/joystick-parport.txt
504 debug [KNL] Enable kernel debugging (events log level).
507 [KNL] verbose self-tests
509 Print debugging info while doing the locking API
511 We default to 0 (no extra messages), setting it to
512 1 will print _a lot_ more information - normally
513 only useful to kernel developers.
516 Format: <area>[,<node>]
517 See also Documentation/networking/decnet.txt.
520 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
521 Change the default blue palette of the console.
522 This is a 16-member array composed of values
526 Format: <green0>,<green1>,<green2>,...,<green15>
527 Change the default green palette of the console.
528 This is a 16-member array composed of values
532 Format: <red0>,<red1>,<red2>,...,<red15>
533 Change the default red palette of the console.
534 This is a 16-member array composed of values
539 Set system-wide default UTF-8 mode for all tty's.
540 Default is 0 and by setting to 1, it enables UTF-8
541 mode for all newly opened or allocated terminals.
544 Set number of hash buckets for dentry cache.
547 IO parameters + enable/disable command.
549 digiepca= [HW,SERIAL]
550 See drivers/char/README.epca and
551 Documentation/digiepca.txt.
553 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
555 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
557 dmasound= [HW,OSS] Sound subsystem buffers
563 earlyprintk= [IA-32,X86-64,SH]
565 earlyprintk=serial[,ttySn[,baudrate]]
567 Append ",keep" to not disable it when the real console
570 Only vga or serial at a time, not both.
572 Currently only ttyS0 and ttyS1 are supported.
574 Interaction with the standard serial driver is not
577 The VGA output is eventually overwritten by the real
582 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
585 non-0: interrupt mode (default)
592 Format: {"of[f]" | "sk[ipmbr]"}
593 See comment in arch/i386/boot/edd.S
596 Format: <id>,<membase>,<irq>
598 eisa_irq_edge= [PARISC,HW]
599 See header of drivers/parisc/eisa.c.
602 See comment before function elanfreq_setup() in
603 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
606 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
607 See Documentation/block/as-iosched.txt and
608 Documentation/block/deadline-iosched.txt for details.
610 elfcorehdr= [IA-32, X86_64]
611 Specifies physical address of start of kernel core
612 image elf header. Generally kexec loader will
613 pass this option to capture kernel.
614 See Documentation/kdump/kdump.txt for details.
616 enforcing [SELINUX] Set initial enforcing status.
618 See security/selinux/Kconfig help text.
619 0 -- permissive (log only, no denials).
620 1 -- enforcing (deny and log).
622 Value can be changed at runtime via /selinux/enforce.
625 Format: <spdif>,[<nomix>,[<amplifier>]]
626 See also header of sound/oss/es1371.c.
628 ether= [HW,NET] Ethernet cards parameters
629 This option is obsoleted by the "netdev=" option, which
630 has equivalent usage. See its documentation for details.
632 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
637 fail_make_request=[KNL]
638 General fault injection mechanism.
639 Format: <interval>,<probability>,<space>,<times>
640 See also /Documentation/fault-injection/.
643 See header of drivers/scsi/fd_mcs.c.
646 See header of drivers/scsi/fdomain.c.
649 See Documentation/floppy.txt.
652 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
653 support via parallel port (up to 5 devices per port)
654 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
655 See also Documentation/input/joystick-parport.txt
660 See header of drivers/scsi/gdth.c.
662 gpt [EFI] Forces disk with valid GPT signature but
663 invalid Protective MBR to be treated as GPT.
670 hashdist= [KNL,NUMA] Large hashes allocated during boot
671 are distributed across NUMA nodes. Defaults on
672 for IA-64, off otherwise.
673 Format: 0 | 1 (for off | on)
675 hcl= [IA-64] SGI's Hardware Graph compatibility layer
677 hd= [EIDE] (E)IDE hard drive subsystem geometry
678 Format: <cyl>,<head>,<sect>
680 hd?= [HW] (E)IDE subsystem
681 hd?lun= See Documentation/ide.txt.
683 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
684 size of <nn>. This works even on boxes that have no
685 highmem otherwise. This also works to reduce highmem
686 size on bigger boxes.
688 highres= [KNL] Enable/disable high resolution timer mode.
689 Valid parameters: "on", "off"
693 See Documentation/isdn/README.HiSax.
695 hugepages= [HW,IA-32,IA-64] Maximal number of HugeTLB pages.
697 i8042.direct [HW] Put keyboard port into non-translated mode
698 i8042.dumbkbd [HW] Pretend that controller can only read data from
699 keyboard and cannot control its state
700 (Don't attempt to blink the leds)
701 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
702 i8042.nokbd [HW] Don't check/create keyboard port
703 i8042.nomux [HW] Don't check presence of an active multiplexing
705 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
708 [HW] Frequency with which keyboard LEDs should blink
709 when kernel panics (default is 0.5 sec)
710 i8042.reset [HW] Reset the controller during init and cleanup
711 i8042.unlock [HW] Unlock (ignore) the keylock
715 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
716 indicates that the driver is running on unsupported
718 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
719 does not match list of supported models.
721 [HW] Report power status in /proc/i8k
722 (disabled by default)
723 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
726 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
727 See Documentation/mca.txt.
730 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
732 ide= [HW] (E)IDE subsystem
733 Format: ide=nodma or ide=doubler or ide=reverse
734 See Documentation/ide.txt.
736 ide?= [HW] (E)IDE subsystem
737 Format: ide?=noprobe or chipset specific parameters.
738 See Documentation/ide.txt.
740 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
741 See Documentation/ide.txt.
744 Format: idle=poll or idle=mwait
745 Poll forces a polling idle loop that can slightly improves the performance
746 of waking up a idle CPU, but will use a lot of power and make the system
747 run hot. Not recommended.
748 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
749 to not use it because it doesn't save as much power as a normal idle
750 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
753 ignore_loglevel [KNL]
754 Ignore loglevel setting - this will print /all/
755 kernel messages to the console. Useful for debugging.
758 Set number of hash buckets for inode cache.
761 See header of drivers/scsi/in2000.c.
765 Run specified binary instead of /sbin/init as init
768 initcall_debug [KNL] Trace initcalls as they are executed. Useful
769 for working out where the kernel is dying during
772 initrd= [BOOT] Specify the location of the initial ramdisk
774 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
779 io7= [HW] IO7 for Marvel based alpha systems
780 See comment before marvel_specify_io7 in
781 arch/alpha/kernel/core_marvel.c.
784 See Documentation/nfsroot.txt.
786 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
787 See comment before ip2_setup() in drivers/char/ip2.c.
789 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
790 See header of drivers/scsi/ips.c.
792 ports= [IP_VS_FTP] IPVS ftp helper module
794 Up to 8 (IP_VS_APP_MAX_PORTS) ports
796 Format: <port>,<port>....
799 When an interrupt is not handled search all handlers
800 for it. Intended to get systems with badly broken
804 When an interrupt is not handled search all handlers
805 for it. Also check all handlers each timer
806 interrupt. Intended to get systems with badly broken
810 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
812 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
814 <cpu number>,...,<cpu number>
816 <cpu number>-<cpu number> (must be a positive range in ascending order)
818 <cpu number>,...,<cpu number>-<cpu number>
819 This option can be used to specify one or more CPUs
820 to isolate from the general SMP balancing and scheduling
821 algorithms. The only way to move a process onto or off
822 an "isolated" CPU is via the CPU affinity syscalls.
823 <cpu number> begins at 0 and the maximum value is
824 "number of CPUs in system - 1".
826 This option is the preferred way to isolate CPUs. The
827 alternative -- manually setting the CPU mask of all
828 tasks in the system -- can cause problems and
829 suboptimal load balancer performance.
832 Format: <io>,<irq>,<dma>,<setup>
836 js= [HW,JOY] Analog joystick
837 See Documentation/input/joystick.txt.
841 kstack=N [IA-32,X86-64] Print N words from the kernel stack
846 lapic [IA-32,APIC] Enable the local APIC even if BIOS
849 lapic_timer_c2_ok [IA-32,x86-64,APIC] trust the local apic timer in
852 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
853 Format: addr:<io>,irq:<irq>
855 legacy_serial.force [HW,IA-32,X86-64]
856 Probe for COM ports at legacy addresses even
857 if PNPBIOS or ACPI should describe them. This
858 is for working around firmware defects.
860 llsc*= [IA64] See function print_params() in
861 arch/ia64/sn/kernel/llsc4.c.
863 load_ramdisk= [RAM] List of ramdisks to load from floppy
864 See Documentation/ramdisk.txt.
866 lockd.nlm_grace_period=P [NFS] Assign grace period.
869 lockd.nlm_tcpport=N [NFS] Assign TCP port.
872 lockd.nlm_timeout=T [NFS] Assign timeout value.
875 lockd.nlm_udpport=M [NFS] Assign UDP port.
878 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
881 loglevel= All Kernel Messages with a loglevel smaller than the
882 console loglevel will be printed to the console. It can
883 also be changed with klogd or other programs. The
884 loglevels are defined as follows:
886 0 (KERN_EMERG) system is unusable
887 1 (KERN_ALERT) action must be taken immediately
888 2 (KERN_CRIT) critical conditions
889 3 (KERN_ERR) error conditions
890 4 (KERN_WARNING) warning conditions
891 5 (KERN_NOTICE) normal but significant condition
892 6 (KERN_INFO) informational
893 7 (KERN_DEBUG) debug-level messages
895 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
896 Format: { n | nk | nM }
897 n must be a power of two. The default size
898 is set in the kernel config file.
900 lp=0 [LP] Specify parallel ports to use, e.g,
901 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
902 lp=reset first parallel port). 'lp=0' disables the
903 lp=auto printer driver. 'lp=reset' (which can be
904 specified in addition to the ports) causes
905 attached printers to be reset. Using
906 lp=port1,port2,... specifies the parallel ports
907 to associate lp devices with, starting with
908 lp0. A port specification may be 'none' to skip
909 that lp device, or a parport name such as
910 'parport0'. Specifying 'lp=auto' instead of a
911 port specification list means that device IDs
912 from each port should be examined, to see if
913 an IEEE 1284-compliant printer is attached; if
914 so, the driver will manage that printer.
915 See also header of drivers/char/lp.c.
918 Sets loops_per_jiffy to given constant, thus avoiding
919 time-consuming boot-time autodetection (up to 250 ms per
920 CPU). 0 enables autodetection (default). To determine
921 the correct value for your kernel, boot with normal
922 autodetection and see what value is printed. Note that
923 on SMP systems the preset will be applied to all CPUs,
924 which is likely to cause problems if your CPUs need
925 significantly divergent settings. An incorrect value
926 will cause delays in the kernel to be wrong, leading to
927 unpredictable I/O errors and other breakage. Although
928 unlikely, in the extreme case this might damage your
932 Format: <io>,<irq>,<dma>
934 mac5380= [HW,SCSI] Format:
935 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
937 mac53c9x= [HW,SCSI] Format:
938 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
940 machvec= [IA64] Force the use of a particular machine-vector
941 (machvec) in a generic kernel.
942 Example: machvec=hpzx1_swiotlb
944 max_loop= [LOOP] Maximum number of loopback devices that can
948 maxcpus= [SMP] Maximum number of processors that an SMP kernel
950 Using "nosmp" or "maxcpus=0" will disable SMP
951 entirely (the MPS table probe still happens, though).
952 A command-line option of "maxcpus=<NUM>", where <NUM>
953 is an integer greater than 0, limits the maximum number
954 of CPUs activated in SMP mode to <NUM>.
955 Using "maxcpus=1" on an SMP kernel is the trivial
956 case of an SMP kernel with only one CPU.
958 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
959 equal to this physical address is ignored.
961 max_luns= [SCSI] Maximum number of LUNs to probe.
962 Should be between 1 and 2^32-1.
965 [SCSI] Maximum number of LUNs received.
966 Should be between 1 and 16384.
968 mca-pentium [BUGS=IA-32]
973 Format: <port>,<irq>,<mitsumi_bug_93_wait>
977 mce [IA-32] Machine Check Exception
979 md= [HW] RAID subsystems devices and level
980 See Documentation/md.txt.
983 Format: <first>,<last>
984 Specifies range of consoles to be captured by the MDA.
986 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
987 Amount of memory to be used when the kernel is not able
988 to see the whole system memory or for test.
989 [IA-32] Use together with memmap= to avoid physical
990 address space collisions. Without memmap= PCI devices
991 could be placed at addresses belonging to unused RAM.
993 mem=nopentium [BUGS=IA-32] Disable usage of 4MB pages for kernel
996 memmap=exactmap [KNL,IA-32,X86_64] Enable setting of an exact
997 E820 memory map, as specified by the user.
998 Such memmap=exactmap lines can be constructed based on
999 BIOS output or other requirements. See the memmap=nn@ss
1002 memmap=nn[KMG]@ss[KMG]
1003 [KNL] Force usage of a specific region of memory
1004 Region of memory to be used, from ss to ss+nn.
1006 memmap=nn[KMG]#ss[KMG]
1007 [KNL,ACPI] Mark specific memory as ACPI data.
1008 Region of memory to be used, from ss to ss+nn.
1010 memmap=nn[KMG]$ss[KMG]
1011 [KNL,ACPI] Mark specific memory as reserved.
1012 Region of memory to be used, from ss to ss+nn.
1014 meye.*= [HW] Set MotionEye Camera parameters
1015 See Documentation/video4linux/meye.txt.
1020 [KNL,SMP] debug: override scheduler migration costs
1021 Format: <level-1-usecs>,<level-2-usecs>,...
1022 This debugging option can be used to override the
1023 default scheduler migration cost matrix. The numbers
1024 are indexed by 'CPU domain distance'.
1025 E.g. migration_cost=1000,2000,3000 on an SMT NUMA
1026 box will set up an intra-core migration cost of
1027 1 msec, an inter-core migration cost of 2 msecs,
1028 and an inter-node migration cost of 3 msecs.
1030 WARNING: using the wrong values here can break
1031 scheduler performance, so it's only for scheduler
1032 development purposes, not production environments.
1035 [KNL,SMP] migration cost auto-detect verbosity
1037 If a system's migration matrix reported at bootup
1038 seems erroneous then this option can be used to
1039 increase verbosity of the detection process.
1040 We default to 0 (no extra messages), 1 will print
1041 some more information, and 2 will be really
1042 verbose (probably only useful if you also have a
1043 serial console attached to the system).
1046 [KNL,SMP] multiply/divide migration costs by a factor
1048 This debug option can be used to proportionally
1049 increase or decrease the auto-detected migration
1050 costs for all entries of the migration matrix.
1051 E.g. migration_factor=150 will increase migration
1052 costs by 50%. (and thus the scheduler will be less
1053 eager migrating cache-hot tasks)
1054 migration_factor=80 will decrease migration costs
1055 by 20%. (thus the scheduler will be more eager to
1058 WARNING: using the wrong values here can break
1059 scheduler performance, so it's only for scheduler
1060 development purposes, not production environments.
1063 [MOUSE] Maximum time between finger touching and
1064 leaving touchpad surface for touch to be considered
1065 a tap and be reported as a left button click (for
1066 touchpads working in absolute mode only).
1068 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1069 reporting absolute coordinates, such as tablets
1070 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1071 reporting absolute coordinates, such as tablets
1076 MTD_Partition= [MTD]
1077 Format: <name>,<region-number>,<size>,<offset>
1079 MTD_Region= [MTD] Format:
1080 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1083 See drivers/mtd/cmdline.c.
1085 mtouchusb.raw_coordinates=
1086 [HW] Make the MicroTouch USB driver use raw coordinates
1087 ('y', default) or cooked coordinates ('n')
1089 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1092 See header of drivers/scsi/NCR_D700.c.
1096 ncr53c400= [HW,SCSI]
1098 ncr53c400a= [HW,SCSI]
1100 ncr53c406a= [HW,SCSI]
1102 ncr53c8xx= [HW,SCSI]
1104 netdev= [NET] Network devices parameters
1105 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1106 Note that mem_start is often overloaded to mean
1107 something different and driver-specific.
1108 This usage is only documented in each driver source
1112 See Documentation/nfsroot.txt.
1114 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1115 See Documentation/nfsroot.txt.
1117 nfs.callback_tcpport=
1118 [NFS] set the TCP port on which the NFSv4 callback
1119 channel should listen.
1121 nfs.idmap_cache_timeout=
1122 [NFS] set the maximum lifetime for idmapper cache
1125 nmi_watchdog= [KNL,BUGS=IA-32] Debugging features for SMP kernels
1127 no387 [BUGS=IA-32] Tells the kernel to use the 387 maths
1128 emulation library even if a 387 maths coprocessor
1131 noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1135 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1136 caches in the slab allocator. Saves per-node memory,
1137 but will impact performance.
1141 noapic [SMP,APIC] Tells the kernel to not make use of any
1142 IOAPICs that may be present in the system.
1144 noasync [HW,M68K] Disables async and sync negotiation for
1147 nobats [PPC] Do not use BATs for mapping kernel lowmem
1148 on "Classic" PPC cores.
1152 nodelayacct [KNL] Disable per-task delay accounting
1154 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1158 noexec [IA-32,X86-64]
1159 noexec=on: enable non-executable mappings (default)
1160 noexec=off: disable nn-executable mappings
1162 nofxsr [BUGS=IA-32] Disables x86 floating point extended
1163 register save and restore. The kernel will only save
1164 legacy floating-point registers on task switch.
1168 no-hlt [BUGS=IA-32] Tells the kernel that the hlt
1169 instruction doesn't work correctly and not to
1172 nohalt [IA-64] Tells the kernel not to use the power saving
1173 function PAL_HALT_LIGHT when idle. This increases
1174 power-consumption. On the positive side, it reduces
1175 interrupt wake-up latency, which may improve performance
1176 in certain environments such as networked servers or
1179 nohz= [KNL] Boottime enable/disable dynamic ticks
1180 Valid arguments: on, off
1183 noirqbalance [IA-32,SMP,KNL] Disable kernel irq balancing
1185 noirqdebug [IA-32] Disables the code which attempts to detect and
1186 disable unhandled interrupt sources.
1188 no_timer_check [IA-32,X86_64,APIC] Disables the code which tests for
1189 broken timer IRQ sources.
1191 noisapnp [ISAPNP] Disables ISA PnP code.
1193 noinitrd [RAM] Tells the kernel not to load any configured
1198 nolapic [IA-32,APIC] Do not enable or use the local APIC.
1200 nolapic_timer [IA-32,APIC] Do not use the local APIC timer.
1202 noltlbs [PPC] Do not use large page/tlb entries for kernel
1203 lowmem mapping on PPC40x.
1205 nomca [IA-64] Disable machine check abort handling
1207 nomce [IA-32] Machine Check Exception
1209 noreplace-paravirt [IA-32,PV_OPS] Don't patch paravirt_ops
1211 noreplace-smp [IA-32,SMP] Don't replace SMP instructions
1212 with UP alternatives
1214 noresidual [PPC] Don't use residual data on PReP machines.
1216 noresume [SWSUSP] Disables resume and restores original swap
1219 no-scroll [VGA] Disables scrollback.
1220 This is required for the Braillex ib80-piezo Braille
1221 reader made by F.H. Papenmeier (Germany).
1225 nosep [BUGS=IA-32] Disables x86 SYSENTER/SYSEXIT support.
1227 nosmp [SMP] Tells an SMP kernel to act as a UP kernel.
1229 nosync [HW,M68K] Disables sync negotiation for all devices.
1231 notsc [BUGS=IA-32] Disable Time Stamp Counter
1233 nousb [USB] Disable the USB subsystem
1237 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1242 opl3sa2= [HW,OSS] Format:
1243 <io>,<irq>,<dma>,<dma2>,<mss_io>,<mpu_io>,<ymode>,<loopback>[,<isapnp>,<multiple]
1245 oprofile.timer= [HW]
1246 Use timer interrupt instead of performance counters
1251 osst= [HW,SCSI] SCSI Tape Driver
1252 Format: <buffer_size>,<write_threshold>
1253 See also Documentation/scsi/st.txt.
1255 panic= [KNL] Kernel behaviour on panic
1258 parkbd.port= [HW] Parallel port number the keyboard adapter is
1259 connected to, default is 0.
1261 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1262 0 for XT, 1 for AT (default is AT).
1265 parport= [HW,PPT] Specify parallel ports. 0 disables.
1266 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1267 Use 'auto' to force the driver to use any
1268 IRQ/DMA settings detected (the default is to
1269 ignore detected IRQ/DMA settings because of
1270 possible conflicts). You can specify the base
1271 address, IRQ, and DMA settings; IRQ and DMA
1272 should be numbers, or 'auto' (for using detected
1273 settings on that particular port), or 'nofifo'
1274 (to avoid using a FIFO even if it is detected).
1275 Parallel ports are assigned in the order they
1276 are specified on the command line, starting
1279 parport_init_mode= [HW,PPT]
1280 Configure VIA parallel port to operate in
1281 a specific mode. This is necessary on Pegasos
1282 computer where firmware has no options for setting
1283 up parallel port mode and sets it to spp.
1284 Currently this function knows 686a and 8231 chips.
1285 Format: [spp|ps2|epp|ecp|ecpepp]
1287 pas2= [HW,OSS] Format:
1288 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1291 See header of drivers/scsi/pas16.c.
1294 Halt all CPUs after the first oops has been printed for
1295 the specified number of seconds. This is to be used if
1296 your oopses keep scrolling off the screen.
1301 See header of drivers/block/paride/pcd.c.
1302 See also Documentation/paride.txt.
1304 pci=option[,option...] [PCI] various PCI subsystem options:
1305 off [IA-32] don't probe for the PCI bus
1306 bios [IA-32] force use of PCI BIOS, don't access
1307 the hardware directly. Use this if your machine
1308 has a non-standard PCI host bridge.
1309 nobios [IA-32] disallow use of PCI BIOS, only direct
1310 hardware access methods are allowed. Use this
1311 if you experience crashes upon bootup and you
1312 suspect they are caused by the BIOS.
1313 conf1 [IA-32] Force use of PCI Configuration
1315 conf2 [IA-32] Force use of PCI Configuration
1317 nommconf [IA-32,X86_64] Disable use of MMCONFIG for PCI
1319 nomsi [MSI] If the PCI_MSI kernel config parameter is
1320 enabled, this kernel boot option can be used to
1321 disable the use of MSI interrupts system-wide.
1322 nosort [IA-32] Don't sort PCI devices according to
1323 order given by the PCI BIOS. This sorting is
1324 done to get a device order compatible with
1326 biosirq [IA-32] Use PCI BIOS calls to get the interrupt
1327 routing table. These calls are known to be buggy
1328 on several machines and they hang the machine
1329 when used, but on other computers it's the only
1330 way to get the interrupt routing table. Try
1331 this option if the kernel is unable to allocate
1332 IRQs or discover secondary PCI buses on your
1334 rom [IA-32] Assign address space to expansion ROMs.
1335 Use with caution as certain devices share
1336 address decoders between ROMs and other
1338 irqmask=0xMMMM [IA-32] Set a bit mask of IRQs allowed to be
1339 assigned automatically to PCI devices. You can
1340 make the kernel exclude IRQs of your ISA cards
1342 pirqaddr=0xAAAAA [IA-32] Specify the physical address
1343 of the PIRQ table (normally generated
1344 by the BIOS) if it is outside the
1345 F0000h-100000h range.
1346 lastbus=N [IA-32] Scan all buses thru bus #N. Can be
1347 useful if the kernel is unable to find your
1348 secondary buses and you want to tell it
1349 explicitly which ones they are.
1350 assign-busses [IA-32] Always assign all PCI bus
1351 numbers ourselves, overriding
1352 whatever the firmware may have done.
1353 usepirqmask [IA-32] Honor the possible IRQ mask stored
1354 in the BIOS $PIR table. This is needed on
1355 some systems with broken BIOSes, notably
1356 some HP Pavilion N5400 and Omnibook XE3
1357 notebooks. This will have no effect if ACPI
1358 IRQ routing is enabled.
1359 noacpi [IA-32] Do not use ACPI for IRQ routing
1360 or for PCI scanning.
1361 routeirq Do IRQ routing for all PCI devices.
1362 This is normally done in pci_enable_device(),
1363 so this option is a temporary workaround
1364 for broken drivers that don't call it.
1365 firmware [ARM] Do not re-enumerate the bus but instead
1366 just use the configuration from the
1367 bootloader. This is currently used on
1368 IXP2000 systems where the bus has to be
1369 configured a certain way for adjunct CPUs.
1370 noearly [X86] Don't do any early type 1 scanning.
1371 This might help on some broken boards which
1372 machine check when some devices' config space
1373 is read. But various workarounds are disabled
1374 and some IOMMU drivers will not work.
1375 bfsort Sort PCI devices into breadth-first order.
1376 This sorting is done to get a device
1377 order compatible with older (<= 2.4) kernels.
1378 nobfsort Don't sort PCI devices into breadth-first order.
1379 cbiosize=nn[KMG] The fixed amount of bus space which is
1380 reserved for the CardBus bridge's IO window.
1381 The default value is 256 bytes.
1382 cbmemsize=nn[KMG] The fixed amount of bus space which is
1383 reserved for the CardBus bridge's memory
1384 window. The default value is 64 megabytes.
1386 pcmv= [HW,PCMCIA] BadgePAD 4
1389 See Documentation/paride.txt.
1391 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1394 See arch/parisc/kernel/pdc_chassis.c
1397 See Documentation/paride.txt.
1400 See Documentation/paride.txt.
1402 pirq= [SMP,APIC] Manual mp-table setup
1403 See Documentation/i386/IO-APIC.txt.
1405 plip= [PPT,NET] Parallel port network link
1406 Format: { parport<nr> | timid | 0 }
1407 See also Documentation/parport.txt.
1413 { on | off | curr | res | no-curr | no-res }
1416 [ISAPNP] Exclude IRQs for the autoconfiguration
1419 [ISAPNP] Exclude DMAs for the autoconfiguration
1421 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1422 Ranges are in pairs (I/O port base and size).
1425 [ISAPNP] Exclude memory regions for the
1427 Ranges are in pairs (memory base and size).
1429 profile= [KNL] Enable kernel profiling via /proc/profile
1430 Format: [schedule,]<number>
1431 Param: "schedule" - profile schedule points.
1432 Param: <number> - step/bucket size as a power of 2 for
1433 statistical time based profiling.
1434 Param: "sleep" - profile D-state sleeping (millisecs)
1436 processor.max_cstate= [HW,ACPI]
1437 Limit processor to maximum C-state
1438 max_cstate=9 overrides any DMI blacklist limit.
1440 processor.nocst [HW,ACPI]
1441 Ignore the _CST method to determine C-states,
1442 instead using the legacy FADT method
1444 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1446 See Documentation/ramdisk.txt.
1448 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1449 probe for; one of (bare|imps|exps|lifebook|any).
1450 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1452 psmouse.resetafter= [HW,MOUSE]
1453 Try to reset the device after so many bad packets
1456 [HW,MOUSE] Set desired mouse resolution, in dpi.
1457 psmouse.smartscroll=
1458 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1459 0 = disabled, 1 = enabled (default).
1461 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1463 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1466 See Documentation/paride.txt.
1468 quiet [KNL] Disable most log messages
1473 See Documentation/md.txt.
1475 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1476 See Documentation/ramdisk.txt.
1478 ramdisk_blocksize= [RAM]
1479 See Documentation/ramdisk.txt.
1481 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1482 New name for the ramdisk parameter.
1483 See Documentation/ramdisk.txt.
1485 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1486 RCU callbacks to process in one batch.
1488 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1489 RCU callbacks over which batch limiting is disabled.
1491 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1492 RCU callbacks below which batch limiting is re-enabled.
1496 Run specified binary instead of /init from the ramdisk,
1497 used for early userspace startup. See initrd.
1499 reboot= [BUGS=IA-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1500 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1501 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1503 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1507 Reserves a hole at the top of the kernel virtual
1510 reset_devices [KNL] Force drivers to reset the underlying device
1511 during initialization.
1514 Specify the partition device for software suspend
1516 resume_offset= [SWSUSP]
1517 Specify the offset from the beginning of the partition
1518 given by "resume=" at which the swap header is located,
1519 in <PAGE_SIZE> units (needed only for swap files).
1520 See Documentation/power/swsusp-and-swap-files.txt
1522 retain_initrd [RAM] Keep initrd memory after extraction
1524 rhash_entries= [KNL,NET]
1525 Set number of hash buckets for route cache
1527 riscom8= [HW,SERIAL]
1528 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1530 ro [KNL] Mount root device read-only on boot
1532 root= [KNL] Root filesystem
1534 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1535 mount the root filesystem
1537 rootflags= [KNL] Set root filesystem mount option string
1539 rootfstype= [KNL] Set root filesystem type
1541 rw [KNL] Mount root device read-write on boot
1543 S [KNL] Run init in single mode
1546 See drivers/net/irda/sa1100_ir.c.
1549 Format: <io>,<irq>,<dma>,<dma2>
1551 sbni= [NET] Granch SBNI12 leased line adapter
1553 sbpcd= [HW,CD] Soundblaster CD adapter
1555 See a comment before function sbpcd_setup() in
1556 drivers/cdrom/sbpcd.c.
1558 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1559 Format: <io>[,<timeout>[,<isapnp>]]
1561 scsi_debug_*= [SCSI]
1562 See drivers/scsi/scsi_debug.c.
1564 scsi_default_dev_flags=
1565 [SCSI] SCSI default device flags
1568 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1569 Format: <vendor>:<model>:<flags>
1570 (flags are integer value)
1572 scsi_logging= [SCSI]
1574 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1575 discovered. async scans them in kernel threads,
1576 allowing boot to proceed. none ignores them, expecting
1577 user space to do the scan.
1579 selinux [SELINUX] Disable or enable SELinux at boot time.
1580 Format: { "0" | "1" }
1581 See security/selinux/Kconfig help text.
1584 Default value is set via kernel config option.
1585 If enabled at boot time, /selinux/disable can be used
1586 later to disable prior to initial policy load.
1588 selinux_compat_net =
1589 [SELINUX] Set initial selinux_compat_net flag value.
1590 Format: { "0" | "1" }
1591 0 -- use new secmark-based packet controls
1592 1 -- use legacy packet controls
1593 Default value is 0 (preferred).
1594 Value can be changed at runtime via
1595 /selinux/compat_net.
1597 serialnumber [BUGS=IA-32]
1599 sg_def_reserved_size= [SCSI]
1602 Maximal number of shapers.
1605 See header of drivers/scsi/sim710.c.
1611 Format: <io>,<irq>,<dma>
1612 See header of drivers/cdrom/sjcd.c.
1616 slub_debug [MM, SLUB]
1617 Enabling slub_debug allows one to determine the culprit
1618 if slab objects become corrupted. Enabling slub_debug
1619 creates guard zones around objects and poisons objects
1620 when not in use. Also tracks the last alloc / free.
1621 For more information see Documentation/vm/slub.txt.
1623 slub_max_order= [MM, SLUB]
1624 Determines the maximum allowed order for slabs. Setting
1625 this too high may cause fragmentation.
1626 For more information see Documentation/vm/slub.txt.
1628 slub_min_objects= [MM, SLUB]
1629 The minimum objects per slab. SLUB will increase the
1630 slab order up to slub_max_order to generate a
1631 sufficiently big slab to satisfy the number of objects.
1632 The higher the number of objects the smaller the overhead
1634 For more information see Documentation/vm/slub.txt.
1636 slub_min_order= [MM, SLUB]
1637 Determines the mininum page order for slabs. Must be
1638 lower than slub_max_order
1639 For more information see Documentation/vm/slub.txt.
1641 slub_nomerge [MM, SLUB]
1642 Disable merging of slabs of similar size. May be
1643 necessary if there is some reason to distinguish
1644 allocs to different slabs.
1645 For more information see Documentation/vm/slub.txt.
1648 Format: <io1>[,<io2>[,...,<io8>]]
1650 smp-alt-once [IA-32,SMP] On a hotplug CPU system, only
1651 attempt to substitute SMP alternatives once at boot.
1653 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1654 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1655 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1656 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1657 smsc-ircc2.ircc_irq= [HW] IRQ line
1658 smsc-ircc2.ircc_dma= [HW] DMA channel
1659 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1660 0: Toshiba Satellite 1800 (GP data pin select)
1661 1: Fast pin select (default)
1664 snd-ad1816a= [HW,ALSA]
1666 snd-ad1848= [HW,ALSA]
1668 snd-ali5451= [HW,ALSA]
1670 snd-als100= [HW,ALSA]
1672 snd-als4000= [HW,ALSA]
1674 snd-azt2320= [HW,ALSA]
1676 snd-cmi8330= [HW,ALSA]
1678 snd-cmipci= [HW,ALSA]
1680 snd-cs4231= [HW,ALSA]
1682 snd-cs4232= [HW,ALSA]
1684 snd-cs4236= [HW,ALSA]
1686 snd-cs4281= [HW,ALSA]
1688 snd-cs46xx= [HW,ALSA]
1690 snd-dt019x= [HW,ALSA]
1692 snd-dummy= [HW,ALSA]
1694 snd-emu10k1= [HW,ALSA]
1696 snd-ens1370= [HW,ALSA]
1698 snd-ens1371= [HW,ALSA]
1700 snd-es968= [HW,ALSA]
1702 snd-es1688= [HW,ALSA]
1704 snd-es18xx= [HW,ALSA]
1706 snd-es1938= [HW,ALSA]
1708 snd-es1968= [HW,ALSA]
1710 snd-fm801= [HW,ALSA]
1712 snd-gusclassic= [HW,ALSA]
1714 snd-gusextreme= [HW,ALSA]
1716 snd-gusmax= [HW,ALSA]
1720 snd-ice1712= [HW,ALSA]
1722 snd-intel8x0= [HW,ALSA]
1724 snd-interwave= [HW,ALSA]
1729 snd-korg1212= [HW,ALSA]
1731 snd-maestro3= [HW,ALSA]
1733 snd-mpu401= [HW,ALSA]
1735 snd-mtpav= [HW,ALSA]
1737 snd-nm256= [HW,ALSA]
1739 snd-opl3sa2= [HW,ALSA]
1747 snd-opti93x= [HW,ALSA]
1751 snd-rme32= [HW,ALSA]
1753 snd-rme96= [HW,ALSA]
1755 snd-rme9652= [HW,ALSA]
1761 snd-sbawe= [HW,ALSA]
1763 snd-serial= [HW,ALSA]
1765 snd-sgalaxy= [HW,ALSA]
1767 snd-sonicvibes= [HW,ALSA]
1772 snd-sun-cs4231= [HW,ALSA]
1774 snd-trident= [HW,ALSA]
1776 snd-usb-audio= [HW,ALSA,USB]
1778 snd-via82xx= [HW,ALSA]
1780 snd-virmidi= [HW,ALSA]
1782 snd-wavefront= [HW,ALSA]
1784 snd-ymfpci= [HW,ALSA]
1787 Format: <io>[,<irq>]
1789 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1790 See Documentation/sonypi.txt
1792 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1793 See Documentation/specialix.txt.
1795 spia_io_base= [HW,MTD]
1801 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1803 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1804 See Documentation/scsi/st.txt.
1807 See header of drivers/scsi/seagate.c.
1811 Set the STI (builtin display/keyboard on the HP-PARISC
1812 machines) console (graphic card) which should be used
1813 as the initial boot-console.
1814 See also comment in drivers/video/console/sticore.c.
1817 See comment in drivers/video/console/sticore.c.
1820 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1824 Control how the NFS server code allocates CPUs to
1825 service thread pools. Depending on how many NICs
1826 you have and where their interrupts are bound, this
1827 option will affect which CPUs will do NFS serving.
1828 Note: this parameter cannot be changed while the
1829 NFS server is running.
1831 auto the server chooses an appropriate mode
1832 automatically using heuristics
1833 global a single global pool contains all CPUs
1834 percpu one pool for each CPU
1835 pernode one pool for each NUMA node (equivalent
1836 to global on non-NUMA machines)
1838 swiotlb= [IA-64] Number of I/O TLB slabs
1842 sym53c416= [HW,SCSI]
1843 See header of drivers/scsi/sym53c416.c.
1845 sysrq_always_enabled
1847 Ignore sysrq setting - this boot parameter will
1848 neutralize any effect of /proc/sys/kernel/sysrq.
1849 Useful for debugging.
1852 See header of drivers/scsi/t128.c.
1856 thash_entries= [KNL,NET]
1857 Set number of hash buckets for TCP connection
1859 time Show timing data prefixed to each printk message line
1861 tipar.timeout= [HW,PPT]
1862 Set communications timeout in tenths of a second
1865 tipar.delay= [HW,PPT]
1866 Set inter-bit delay in microseconds (default 10).
1869 See header of drivers/scsi/seagate.c.
1872 See comment before function dc390_setup() in
1873 drivers/scsi/tmscsim.c.
1877 trix= [HW,OSS] MediaTrix AudioTrix Pro
1879 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1881 tsdev.xres= [TS] Horizontal screen resolution.
1882 tsdev.yres= [TS] Vertical screen resolution.
1884 turbografx.map[2|3]= [HW,JOY]
1885 TurboGraFX parallel port interface
1887 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1888 See also Documentation/input/joystick-parport.txt
1890 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1891 See header of drivers/scsi/u14-34f.c.
1900 [USB] Ignore overcurrent events (default N).
1901 Some badly-designed motherboards generate lots of
1902 bogus events, for ports that aren't wired to
1903 anything. Set this parameter to avoid log spamming.
1904 Note that genuine overcurrent events won't be
1907 usbcore.autosuspend=
1908 [USB] The autosuspend time delay (in seconds) used
1909 for newly-detected USB devices (default 2). This
1910 is the time required before an idle device will be
1911 autosuspended. Devices for which the delay is set
1912 to a negative value won't be autosuspended at all.
1915 [USBHID] The interval which mice are to be polled at.
1918 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1919 vdso=1: enable VDSO (default)
1920 vdso=0: disable VDSO mapping
1922 video= [FB] Frame buffer configuration
1923 See Documentation/fb/modedb.txt.
1925 vga= [BOOT,IA-32] Select a particular video mode
1926 See Documentation/i386/boot.txt and
1927 Documentation/svga.txt.
1928 Use vga=ask for menu.
1929 This is actually a boot loader parameter; the value is
1930 passed to the kernel using a special protocol.
1932 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1933 size of <nn>. This can be used to increase the
1934 minimum size (128MB on x86). It can also be used to
1935 decrease the size and leave more room for directly
1938 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1941 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1944 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1947 waveartist= [HW,OSS]
1948 Format: <io>,<irq>,<dma>,<dma2>
1951 See header of drivers/scsi/wd33c93.c.
1954 See header of drivers/scsi/wd7000.c.
1957 See Documentation/watchdog/watchdog.txt.
1959 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1960 xd_geo= See header of drivers/block/xd.c.
1962 xirc2ps_cs= [NET,PCMCIA]
1964 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1966 norandmaps Don't use address space randomization
1967 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1969 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
1970 This is useful to get more information why
1971 you got a "dwarf2 unwinder stuck"
1973 ______________________________________________________________________
1977 Add documentation for ALSA options.
1978 Add more DRM drivers.