1 February 2003 Kernel Parameters v2.5.59
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 The text in square brackets at the beginning of the description state the
21 restrictions on the kernel for the said kernel parameter to be valid. The
22 restrictions referred to are that the relevant option is valid if:
24 ACPI ACPI support is enabled.
25 ALSA ALSA sound support is enabled.
26 APIC APIC support is enabled.
27 APM Advanced Power Management support is enabled.
28 AX25 Appropriate AX.25 support is enabled.
29 CD Appropriate CD support is enabled.
30 DEVFS devfs support is enabled.
31 DRM Direct Rendering Management support is enabled.
32 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
33 EFI EFI Partitioning (GPT) is enabled
34 EIDE EIDE/ATAPI support is enabled.
35 FB The frame buffer device is enabled.
36 HW Appropriate hardware is enabled.
37 IA-32 IA-32 aka i386 architecture is enabled.
38 IA-64 IA-64 architecture is enabled.
39 IOSCHED More than one I/O scheduler is enabled.
40 IP_PNP IP DCHP, BOOTP, or RARP is enabled.
41 ISAPNP ISA PnP code is enabled.
42 ISDN Appropriate ISDN support is enabled.
43 JOY Appropriate joystick support is enabled.
44 LP Printer support is enabled.
45 LOOP Loopback device support is enabled.
46 M68k M68k architecture is enabled.
47 These options have more detailed description inside of
48 Documentation/m68k/kernel-options.txt.
49 MCA MCA bus support is enabled.
50 MDA MDA console support is enabled.
51 MOUSE Appropriate mouse support is enabled.
52 MTD MTD support is enabled.
53 NET Appropriate network support is enabled.
54 NUMA NUMA support is enabled.
55 NFS Appropriate NFS support is enabled.
56 OSS OSS sound support is enabled.
57 PARIDE The ParIDE subsystem is enabled.
58 PARISC The PA-RISC architecture is enabled.
59 PCI PCI bus support is enabled.
60 PCMCIA The PCMCIA subsystem is enabled.
61 PNP Plug & Play support is enabled.
62 PPC PowerPC architecture is enabled.
63 PPT Parallel port support is enabled.
64 PS2 Appropriate PS/2 support is enabled.
65 RAM RAM disk support is enabled.
66 S390 S390 architecture is enabled.
67 SCSI Appropriate SCSI support is enabled.
68 A lot of drivers has their options described inside of
70 SELINUX SELinux support is enabled.
71 SERIAL Serial support is enabled.
72 SMP The kernel is an SMP kernel.
73 SPARC Sparc architecture is enabled.
74 SWSUSP Software suspension is enabled.
75 TS Appropriate touchscreen support is enabled.
76 USB USB support is enabled.
77 USBHID USB Human Interface Device support is enabled.
78 V4L Video For Linux support is enabled.
79 VGA The VGA console has been enabled.
80 VT Virtual terminal support is enabled.
81 WDT Watchdog support is enabled.
82 XT IBM PC/XT MFM hard disk support is enabled.
83 X86-64 X86-64 architecture is enabled.
84 More X86-64 boot options can be found in
85 Documentation/x86_64/boot-options.txt .
87 In addition, the following text indicates that the option:
89 BUGS= Relates to possible processor bugs on the said processor.
90 KNL Is a kernel start-up parameter.
91 BOOT Is a boot loader parameter.
93 Parameters denoted with BOOT are actually interpreted by the boot
94 loader, and have no meaning to the kernel directly.
95 Do not modify the syntax of boot loader parameters without extreme
96 need or coordination with <Documentation/i386/boot.txt>.
98 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
99 a trailing = on the name of any parameter states that that parameter will
100 be entered as an environment variable, whereas its absence indicates that
101 it will appear as a kernel argument readable via /proc/cmdline by programs
102 running once the system is up.
104 53c7xx= [HW,SCSI] Amiga SCSI controllers
105 See header of drivers/scsi/53c7xx.c.
106 See also Documentation/scsi/ncr53c7xx.txt.
108 acpi= [HW,ACPI] Advanced Configuration and Power Interface
109 Format: { force | off | ht | strict }
110 force -- enable ACPI if default was off
111 off -- disable ACPI if default was on
112 noirq -- do not use ACPI for IRQ routing
113 ht -- run only enough ACPI to enable Hyper Threading
114 strict -- Be less tolerant of platforms that are not
115 strictly ACPI specification compliant.
117 See also Documentation/pm.txt, pci=noacpi
119 acpi_sleep= [HW,ACPI] Sleep options
120 Format: { s3_bios, s3_mode }
121 See Documentation/power/video.txt
123 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
124 Format: { level | edge | high | low }
126 acpi_irq_balance [HW,ACPI] ACPI will balance active IRQs
129 acpi_irq_nobalance [HW,ACPI] ACPI will not move active IRQs (default)
132 acpi_irq_pci= [HW,ACPI] If irq_balance, Clear listed IRQs for use by PCI
133 Format: <irq>,<irq>...
135 acpi_irq_isa= [HW,ACPI] If irq_balance, Mark listed IRQs used by ISA
136 Format: <irq>,<irq>...
138 acpi_osi= [HW,ACPI] empty param disables _OSI
140 acpi_serialize [HW,ACPI] force serialization of AML methods
142 acpi_skip_timer_override [HW,ACPI]
143 Recognize and ignore IRQ0/pin2 Interrupt Override.
144 For broken nForce2 BIOS resulting in XT-PIC timer.
146 acpi_dbg_layer= [HW,ACPI]
148 Each bit of the <int> indicates an acpi debug layer,
149 1: enable, 0: disable. It is useful for boot time
150 debugging. After system has booted up, it can be set
151 via /proc/acpi/debug_layer.
153 acpi_dbg_level= [HW,ACPI]
155 Each bit of the <int> indicates an acpi debug level,
156 1: enable, 0: disable. It is useful for boot time
157 debugging. After system has booted up, it can be set
158 via /proc/acpi/debug_level.
160 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
163 Format: <io>,<irq>,<dma>,<dma2>
164 See also Documentation/sound/oss/AD1816.
167 Format: <io>,<irq>,<dma>,<dma2>,<type>
173 See header of drivers/scsi/advansys.c.
175 advwdt= [HW,WDT] Advantech WDT
176 Format: <iostart>,<iostop>
178 aedsp16= [HW,OSS] Audio Excel DSP 16
179 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
180 See also header of sound/oss/aedsp16.c.
183 See Documentation/scsi/aha152x.txt.
186 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
189 See Documentation/scsi/aic7xxx.txt.
192 See Documentation/scsi/aic79xx.txt.
195 Format: <host-scsi-id>,<target-scsi-id>,<max-rate>,<max-offset>
196 See also header of drivers/scsi/AM53C974.c.
198 amijoy.map= [HW,JOY] Amiga joystick support
199 Map of devices attached to JOY0DAT and JOY1DAT
201 See also Documentation/kernel/input/joystick.txt
203 analog.map= [HW,JOY] Analog joystick and gamepad support
204 Specifies type or capabilities of an analog joystick
205 connected to one of 16 gameports
206 Format: <type1>,<type2>,..<type16>
208 apc= [HW,SPARC] Power management functions (SPARCstation-4/5 + deriv.)
210 Disable APC CPU standby support. SPARCstation-Fox does
211 not play well with APC CPU idle - disable it if you have
212 APC and your system crashes randomly.
214 apic= [APIC,i386] Change the output verbosity whilst booting
215 Format: { quiet (default) | verbose | debug }
216 Change the amount of debugging information output
217 when initialising the APIC and IO-APIC components.
219 apm= [APM] Advanced Power Management
220 See header of arch/i386/kernel/apm.c.
225 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
226 Format: <io>,<irq>,<nodeID>
230 atarimouse= [HW,MOUSE] Atari Mouse
232 atascsi= [HW,SCSI] Atari SCSI
234 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
235 EzKey and similar keyboards
237 atkbd.reset= [HW] Reset keyboard during initialization
239 atkbd.set= [HW] Select keyboard code set
240 Format: <int> (2 = AT (default) 3 = PS/2)
242 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
245 atkbd.softraw= [HW] Choose between synthetic and real raw mode
246 Format: <bool> (0 = real, 1 = synthetic (default))
249 [HW] Use software keyboard repeat
253 awe= [HW,OSS] AWE32/SB32/AWE64 wave table synth
254 Format: <io>,<memsize>,<isapnp>
256 aztcd= [HW,CD] Aztech CD268 CDROM driver
257 Format: <io>,0x79 (?)
259 baycom_epp= [HW,AX25]
262 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
264 See header of drivers/net/hamradio/baycom_par.c.
266 baycom_ser_fdx= [HW,AX25] BayCom Serial Port AX.25 Modem (Full Duplex Mode)
267 Format: <io>,<irq>,<mode>[,<baud>]
268 See header of drivers/net/hamradio/baycom_ser_fdx.c.
270 baycom_ser_hdx= [HW,AX25] BayCom Serial Port AX.25 Modem (Half Duplex Mode)
271 Format: <io>,<irq>,<mode>
272 See header of drivers/net/hamradio/baycom_ser_hdx.c.
274 blkmtd_device= [HW,MTD]
280 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
281 bttv.radio= Most important insmod options are available as kernel args too.
282 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
283 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
286 See drivers/scsi/BusLogic.c, comment before function
287 BusLogic_ParseDriverOptions().
289 c101= [NET] Moxa C101 synchronous serial card
291 cachesize= [BUGS=IA-32] Override level 2 CPU cache size detection.
292 Sometimes CPU hardware bugs make them report the cache
293 size incorrectly. The kernel will attempt work arounds
294 to fix known problems, but for some CPUs it is not
295 possible to determine what the correct size should be.
296 This option provides an override for these situations.
299 Format: <io>,<irq>[,PAS]
300 See header of drivers/cdrom/cdu31a.c.
302 chandev= [HW,NET] Generic channel device initialisation
304 checkreqprot [SELINUX] Set initial checkreqprot flag value.
305 Format: { "0" | "1" }
306 See security/selinux/Kconfig help text.
307 0 -- check protection applied by kernel (includes any implied execute protection).
308 1 -- check protection requested by application.
309 Default value is set via a kernel config option.
310 Value can be changed at runtime via /selinux/checkreqprot.
312 clock= [BUGS=IA-32, HW] gettimeofday timesource override.
313 Forces specified timesource (if avaliable) to be used
314 when calculating gettimeofday(). If specicified timesource
315 is not avalible, it defaults to PIT.
316 Format: { pit | tsc | cyclone | pmtmr }
318 hpet= [IA-32,HPET] option to disable HPET and use PIT.
322 Format: { auto | [<io>,][<irq>] }
324 com20020= [HW,NET] ARCnet - COM20020 chipset
325 Format: <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
327 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
330 com90xx= [HW,NET] ARCnet - COM90xx chipset (memory-mapped buffers)
331 Format: <io>[,<irq>[,<memstart>]]
333 condev= [HW,S390] console device
336 console= [KNL] Output console device and options.
338 tty<n> Use the virtual console device <n>.
341 Use the specified serial port. The options are of
342 the form "bbbbpn", where "bbbb" is the baud rate,
343 "p" is parity ("n", "o", or "e"), and "n" is bits.
346 See also Documentation/serial-console.txt.
348 uart,io,<addr>[,options]
349 uart,mmio,<addr>[,options]
350 Start an early, polled-mode console on the 8250/16550
351 UART at the specified I/O port or MMIO address,
352 switching to the matching ttyS device later. The
353 options are the same as for ttyS, above.
355 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
356 Format: <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
359 Format: { parport<nr> | auto | none }
361 crashkernel=nn[KMG]@ss[KMG]
362 [KNL] Reserve a chunk of physical memory to
363 hold a kernel to switch to with kexec on panic.
366 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
371 cs89x0_media= [HW,NET]
372 Format: { rj45 | aui | bnc }
374 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
377 See header of drivers/s390/block/dasd_devmap.c.
379 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
380 (one device per port)
381 Format: <port#>,<type>
382 See also Documentation/input/joystick-parport.txt
384 debug [KNL] Enable kernel debugging (events log level).
387 Format: <area>[,<node>]
388 See also Documentation/networking/decnet.txt.
391 See Documentation/filesystems/devfs/boot-options.
394 Set number of hash buckets for dentry cache.
397 IO parameters + enable/disable command.
399 digiepca= [HW,SERIAL]
400 See drivers/char/README.epca and
401 Documentation/digiepca.txt.
403 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
405 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
407 dmasound= [HW,OSS] Sound subsystem buffers
413 earlyprintk= [IA-32, X86-64]
415 earlyprintk=serial[,ttySn[,baudrate]]
417 Append ,keep to not disable it when the real console
420 Only vga or serial at a time, not both.
422 Currently only ttyS0 and ttyS1 are supported.
424 Interaction with the standard serial driver is not
427 The VGA output is eventually overwritten by the real
437 Format: {"of[f]" | "sk[ipmbr]"}
438 See comment in arch/i386/boot/edd.S
441 Format: {"of[f]" | "sk[ipmbr]"}
442 See comment in arch/i386/boot/edd.S
445 Format: <id>,<membase>,<irq>
447 eisa_irq_edge= [PARISC,HW]
448 See header of drivers/parisc/eisa.c.
451 See comment before function elanfreq_setup() in
452 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
455 Format: {"as"|"cfq"|"deadline"|"noop"}
456 See Documentation/block/as-iosched.txt
457 and Documentation/block/deadline-iosched.txt for details.
459 Specifies physical address of start of kernel core image
461 See Documentation/kdump.txt for details.
463 enforcing [SELINUX] Set initial enforcing status.
465 See security/selinux/Kconfig help text.
466 0 -- permissive (log only, no denials).
467 1 -- enforcing (deny and log).
469 Value can be changed at runtime via /selinux/enforce.
472 Format: <lineout>[,<micbias>]
473 See also header of sound/oss/es1370.c.
476 Format: <spdif>,[<nomix>,[<amplifier>]]
477 See also header of sound/oss/es1371.c.
479 ether= [HW,NET] Ethernet cards parameters
480 This option is obsoleted by the "netdev=" option, which
481 has equivalent usage. See its documentation for details.
483 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
487 See header of drivers/scsi/fd_mcs.c.
490 See header of drivers/scsi/fdomain.c.
493 See Documentation/floppy.txt.
495 ftape= [HW] Floppy Tape subsystem debugging options.
496 See Documentation/ftape.txt.
499 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
500 support via parallel port (up to 5 devices per port)
501 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
502 See also Documentation/input/joystick-parport.txt
507 See header of drivers/scsi/gdth.c.
509 gpt [EFI] Forces disk with valid GPT signature but
510 invalid Protective MBR to be treated as GPT.
515 gt96100eth= [NET] MIPS GT96100 Advanced Communication Controller
518 Format: <io>,<irq>,<dma>,<dma16>
522 hashdist= [KNL,NUMA] Large hashes allocated during boot
523 are distributed across NUMA nodes. Defaults on
524 for IA-64, off otherwise.
526 hcl= [IA-64] SGI's Hardware Graph compatibility layer
528 hd= [EIDE] (E)IDE hard drive subsystem geometry
529 Format: <cyl>,<head>,<sect>
531 hd?= [HW] (E)IDE subsystem
532 hd?lun= See Documentation/ide.txt.
534 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
535 size of <nn>. This works even on boxes that have no
536 highmem otherwise. This also works to reduce highmem
537 size on bigger boxes.
540 See Documentation/isdn/README.HiSax.
542 hugepages= [HW,IA-32,IA-64] Maximal number of HugeTLB pages.
544 noirqbalance [IA-32,SMP,KNL] Disable kernel irq balancing
546 i8042.direct [HW] Put keyboard port into non-translated mode
547 i8042.dumbkbd [HW] Pretend that controlled can only read data from
548 keyboard and can not control its state
549 (Don't attempt to blink the leds)
550 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
551 i8042.nomux [HW] Don't check presence of an active multiplexing
553 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
556 [HW] Frequency with which keyboard LEDs should blink
557 when kernel panics (default is 0.5 sec)
558 i8042.reset [HW] Reset the controller during init and cleanup
559 i8042.unlock [HW] Unlock (ignore) the keylock
563 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
564 indicates that the driver is running on unsupported
566 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
567 does not match list of supported models.
569 [HW] Report power status in /proc/i8k
570 (disabled by default)
571 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
574 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
575 See Documentation/mca.txt.
578 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
580 ide= [HW] (E)IDE subsystem
581 Format: ide=nodma or ide=doubler or ide=reverse
582 See Documentation/ide.txt.
584 ide?= [HW] (E)IDE subsystem
585 Format: ide?=noprobe or chipset specific parameters.
586 See Documentation/ide.txt.
588 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
589 See Documentation/ide.txt.
592 Format: idle=poll or idle=halt
595 Set number of hash buckets for inode cache.
598 See header of drivers/scsi/in2000.c.
602 Run specified binary instead of /sbin/init as init
605 initcall_debug [KNL] Trace initcalls as they are executed. Useful
606 for working out where the kernel is dying during
609 initrd= [BOOT] Specify the location of the initial ramdisk
611 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
616 io7= [HW] IO7 for Marvel based alpha systems
617 See comment before marvel_specify_io7 in
618 arch/alpha/kernel/core_marvel.c.
621 See Documentation/nfsroot.txt.
623 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
624 See comment before ip2_setup() in drivers/char/ip2.c.
626 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
627 See header of drivers/scsi/ips.c.
630 When an interrupt is not handled search all handlers
631 for it. Intended to get systems with badly broken
635 When an interrupt is not handled search all handlers
636 for it. Also check all handlers each timer
637 interrupt. Intended to get systems with badly broken
641 Format: <RDP>, <reset>, <pci_scan>, <verbosity>
643 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
644 Format: <cpu number>,...,<cpu number>
645 This option can be used to specify one or more CPUs
646 to isolate from the general SMP balancing and scheduling
647 algorithms. The only way to move a process onto or off
648 an "isolated" CPU is via the CPU affinity syscalls.
649 <cpu number> begins at 0 and the maximum value is
650 "number of CPUs in system - 1".
652 This option is the preferred way to isolate CPUs. The
653 alternative - manually setting the CPU mask of all tasks
654 in the system can cause problems and suboptimal load
655 balancer performance.
658 Format: <io>,<irq>,<dma>,<setup>
662 js= [HW,JOY] Analog joystick
663 See Documentation/input/joystick.txt.
667 kstack=N [IA-32, X86-64] Print N words from the kernel stack
672 lapic [IA-32,APIC] Enable the local APIC even if BIOS disabled it.
674 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
675 Format: addr:<io>,irq:<irq>
678 See function print_params() in arch/ia64/sn/kernel/llsc4.c.
680 load_ramdisk= [RAM] List of ramdisks to load from floppy
681 See Documentation/ramdisk.txt.
687 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
690 loglevel= All Kernel Messages with a loglevel smaller than the
691 console loglevel will be printed to the console. It can
692 also be changed with klogd or other programs. The
693 loglevels are defined as follows:
695 0 (KERN_EMERG) system is unusable
696 1 (KERN_ALERT) action must be taken immediately
697 2 (KERN_CRIT) critical conditions
698 3 (KERN_ERR) error conditions
699 4 (KERN_WARNING) warning conditions
700 5 (KERN_NOTICE) normal but significant condition
701 6 (KERN_INFO) informational
702 7 (KERN_DEBUG) debug-level messages
704 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
705 Format is n, nk, nM. n must be a power of two. The
706 default is set in kernel config.
708 lp=0 [LP] Specify parallel ports to use, e.g,
709 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
710 lp=reset first parallel port). 'lp=0' disables the
711 lp=auto printer driver. 'lp=reset' (which can be
712 specified in addition to the ports) causes
713 attached printers to be reset. Using
714 lp=port1,port2,... specifies the parallel ports
715 to associate lp devices with, starting with
716 lp0. A port specification may be 'none' to skip
717 that lp device, or a parport name such as
718 'parport0'. Specifying 'lp=auto' instead of a
719 port specification list means that device IDs
720 from each port should be examined, to see if
721 an IEEE 1284-compliant printer is attached; if
722 so, the driver will manage that printer.
723 See also header of drivers/char/lp.c.
726 Sets loops_per_jiffy to given constant, thus avoiding
727 time-consuming boot-time autodetection (up to 250 ms per
728 CPU). 0 enables autodetection (default). To determine
729 the correct value for your kernel, boot with normal
730 autodetection and see what value is printed. Note that
731 on SMP systems the preset will be applied to all CPUs,
732 which is likely to cause problems if your CPUs need
733 significantly divergent settings. An incorrect value
734 will cause delays in the kernel to be wrong, leading to
735 unpredictable I/O errors and other breakage. Although
736 unlikely, in the extreme case this might damage your
740 Format: <io>,<irq>,<dma>
743 Format: <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
746 Format: <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
749 Force the use of a particular machine-vector (machvec) in a generic
750 kernel. Example: machvec=hpzx1_swiotlb
753 Format: <io>,<irq>,<dma>,<dma16>,<mpu_io>,<mpu_irq>,<joystick>
758 max_loop= [LOOP] Maximum number of loopback devices that can
762 maxcpus= [SMP] Maximum number of processors that an SMP kernel
765 max_luns= [SCSI] Maximum number of LUNs to probe
766 Should be between 1 and 2^32-1.
769 [SCSI] Maximum number of LUNs received
770 Should be between 1 and 16384.
772 mca-pentium [BUGS=IA-32]
777 Format: <port>,<irq>,<mitsumi_bug_93_wait>
781 mce [IA-32] Machine Check Exception
783 md= [HW] RAID subsystems devices and level
784 See Documentation/md.txt.
787 Format: <first>,<last>
788 Specifies range of consoles to be captured by the MDA.
790 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
791 Amount of memory to be used when the kernel is not able
792 to see the whole system memory or for test.
793 [IA-32] Use together with memmap= to avoid physical
794 address space collisions. Without memmap= PCI devices
795 could be placed at addresses belonging to unused RAM.
797 mem=nopentium [BUGS=IA-32] Disable usage of 4MB pages for kernel
800 memmap=exactmap [KNL,IA-32] Enable setting of an exact
801 E820 memory map, as specified by the user.
802 Such memmap=exactmap lines can be constructed based on
803 BIOS output or other requirements. See the memmap=nn@ss
806 memmap=nn[KMG]@ss[KMG]
807 [KNL] Force usage of a specific region of memory
808 Region of memory to be used, from ss to ss+nn.
810 memmap=nn[KMG]#ss[KMG]
811 [KNL,ACPI] Mark specific memory as ACPI data.
812 Region of memory to be used, from ss to ss+nn.
814 memmap=nn[KMG]$ss[KMG]
815 [KNL,ACPI] Mark specific memory as reserved.
816 Region of memory to be used, from ss to ss+nn.
818 meye.*= [HW] Set MotionEye Camera parameters
819 See Documentation/video4linux/meye.txt.
824 [MOUSE] Maximum time between finger touching and
825 leaving touchpad surface for touch to be considered
826 a tap and be reported as a left button click (for
827 touchpads working in absolute mode only).
829 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
830 reporting absolute coordinates, such as tablets
831 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
832 reporting absolute coordinates, such as tablets
838 Format: <name>,<region-number>,<size>,<offset>
841 Format: <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
844 See drivers/mtd/cmdline.c.
846 mtouchusb.raw_coordinates=
847 [HW] Make the MicroTouch USB driver use raw coordinates ('y', default)
848 or cooked coordinates ('n')
850 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
853 See header of drivers/scsi/NCR_D700.c.
859 ncr53c400a= [HW,SCSI]
861 ncr53c406a= [HW,SCSI]
865 netdev= [NET] Network devices parameters
866 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
867 Note that mem_start is often overloaded to mean
868 something different and driver-specific.
871 See Documentation/nfsroot.txt.
873 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
874 See Documentation/nfsroot.txt.
876 nmi_watchdog= [KNL,BUGS=IA-32] Debugging features for SMP kernels
878 no387 [BUGS=IA-32] Tells the kernel to use the 387 maths
879 emulation library even if a 387 maths coprocessor
884 noapic [SMP,APIC] Tells the kernel to not make use of any
885 IOAPICs that may be present in the system.
887 noasync [HW,M68K] Disables async and sync negotiation for
890 nobats [PPC] Do not use BATs for mapping kernel lowmem
891 on "Classic" PPC cores.
895 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
899 noexec [IA-32, X86-64]
900 noexec=on: enable non-executable mappings (default)
901 noexec=off: disable nn-executable mappings
907 no-hlt [BUGS=IA-32] Tells the kernel that the hlt
908 instruction doesn't work correctly and not to
911 nohalt [IA-64] Tells the kernel not to use the power saving
912 function PAL_HALT_LIGHT when idle. This increases
913 power-consumption. On the positive side, it reduces
914 interrupt wake-up latency, which may improve performance
915 in certain environments such as networked servers or
918 noirqdebug [IA-32] Disables the code which attempts to detect and
919 disable unhandled interrupt sources.
921 noisapnp [ISAPNP] Disables ISA PnP code.
923 noinitrd [RAM] Tells the kernel not to load any configured
928 nolapic [IA-32,APIC] Do not enable or use the local APIC.
930 noltlbs [PPC] Do not use large page/tlb entries for kernel
931 lowmem mapping on PPC40x.
933 nomce [IA-32] Machine Check Exception
935 noresidual [PPC] Don't use residual data on PReP machines.
937 noresume [SWSUSP] Disables resume and restore original swap space.
939 no-scroll [VGA] Disables scrollback.
940 This is required for the Braillex ib80-piezo Braille
941 reader made by F.H. Papenmeier (Germany).
945 nosmp [SMP] Tells an SMP kernel to act as a UP kernel.
947 nosync [HW,M68K] Disables sync negotiation for all devices.
949 notsc [BUGS=IA-32] Disable Time Stamp Counter
951 nousb [USB] Disable the USB subsystem
959 Format: <io>,<irq>,<dma>,<dma2>,<mpu_io>,<mpu_irq>
962 Format: <io>,<irq>,<dma>,<dma2>,<mss_io>,<mpu_io>,<ymode>,<loopback>[,<isapnp>,<multiple]
965 Use timer interrupt instead of performance counters
970 osst= [HW,SCSI] SCSI Tape Driver
971 Format: <buffer_size>,<write_threshold>
972 See also Documentation/scsi/st.txt.
974 panic= [KNL] Kernel behaviour on panic
977 parkbd.port= [HW] Parallel port number the keyboard adapter is
978 connected to, default is 0.
980 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
981 0 for XT, 1 for AT (default is AT).
984 parport=0 [HW,PPT] Specify parallel ports. 0 disables.
985 parport=auto Use 'auto' to force the driver to use
986 parport=0xBBB[,IRQ[,DMA]] any IRQ/DMA settings detected (the
987 default is to ignore detected IRQ/DMA
988 settings because of possible
989 conflicts). You can specify the base
990 address, IRQ, and DMA settings; IRQ and
991 DMA should be numbers, or 'auto' (for
992 using detected settings on that
993 particular port), or 'nofifo' (to avoid
994 using a FIFO even if it is detected).
995 Parallel ports are assigned in the
996 order they are specified on the command
997 line, starting with parport0.
1000 [HW,PPT] Configure VIA parallel port to
1001 operate in specific mode. This is
1002 necessary on Pegasos computer where
1003 firmware has no options for setting up
1004 parallel port mode and sets it to
1005 spp. Currently this function knows
1006 686a and 8231 chips.
1007 Format: [spp|ps2|epp|ecp|ecpepp]
1010 Format: <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1013 See header of drivers/scsi/pas16.c.
1018 See header of drivers/block/paride/pcd.c.
1019 See also Documentation/paride.txt.
1021 pci=option[,option...] [PCI] various PCI subsystem options:
1022 off [IA-32] don't probe for the PCI bus
1023 bios [IA-32] force use of PCI BIOS, don't access
1024 the hardware directly. Use this if your machine
1025 has a non-standard PCI host bridge.
1026 nobios [IA-32] disallow use of PCI BIOS, only direct
1027 hardware access methods are allowed. Use this
1028 if you experience crashes upon bootup and you
1029 suspect they are caused by the BIOS.
1030 conf1 [IA-32] Force use of PCI Configuration Mechanism 1.
1031 conf2 [IA-32] Force use of PCI Configuration Mechanism 2.
1032 nosort [IA-32] Don't sort PCI devices according to
1033 order given by the PCI BIOS. This sorting is done
1034 to get a device order compatible with older kernels.
1035 biosirq [IA-32] Use PCI BIOS calls to get the interrupt
1036 routing table. These calls are known to be buggy
1037 on several machines and they hang the machine when used,
1038 but on other computers it's the only way to get the
1039 interrupt routing table. Try this option if the kernel
1040 is unable to allocate IRQs or discover secondary PCI
1041 buses on your motherboard.
1042 rom [IA-32] Assign address space to expansion ROMs.
1043 Use with caution as certain devices share address
1044 decoders between ROMs and other resources.
1045 irqmask=0xMMMM [IA-32] Set a bit mask of IRQs allowed to be assigned
1046 automatically to PCI devices. You can make the kernel
1047 exclude IRQs of your ISA cards this way.
1048 pirqaddr=0xAAAAA [IA-32] Specify the physical address
1049 of the PIRQ table (normally generated
1050 by the BIOS) if it is outside the
1051 F0000h-100000h range.
1052 lastbus=N [IA-32] Scan all buses till bus #N. Can be useful
1053 if the kernel is unable to find your secondary buses
1054 and you want to tell it explicitly which ones they are.
1055 assign-busses [IA-32] Always assign all PCI bus
1056 numbers ourselves, overriding
1057 whatever the firmware may have
1059 usepirqmask [IA-32] Honor the possible IRQ mask
1060 stored in the BIOS $PIR table. This is
1061 needed on some systems with broken
1062 BIOSes, notably some HP Pavilion N5400
1063 and Omnibook XE3 notebooks. This will
1064 have no effect if ACPI IRQ routing is
1066 noacpi [IA-32] Do not use ACPI for IRQ routing
1067 or for PCI scanning.
1068 routeirq Do IRQ routing for all PCI devices.
1069 This is normally done in pci_enable_device(),
1070 so this option is a temporary workaround
1071 for broken drivers that don't call it.
1073 firmware [ARM] Do not re-enumerate the bus but
1074 instead just use the configuration
1075 from the bootloader. This is currently
1076 used on IXP2000 systems where the
1077 bus has to be configured a certain way
1080 pcmv= [HW,PCMCIA] BadgePAD 4
1083 See Documentation/paride.txt.
1085 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1088 See arch/parisc/kernel/pdc_chassis.c
1091 See Documentation/paride.txt.
1094 See Documentation/paride.txt.
1096 pirq= [SMP,APIC] Manual mp-table setup
1097 See Documentation/i386/IO-APIC.txt.
1099 plip= [PPT,NET] Parallel port network link
1100 Format: { parport<nr> | timid | 0 }
1101 See also Documentation/parport.txt.
1107 { on | off | curr | res | no-curr | no-res }
1110 [ISAPNP] Exclude IRQs for the autoconfiguration
1113 [ISAPNP] Exclude DMAs for the autoconfiguration
1115 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1116 Ranges are in pairs (I/O port base and size).
1119 [ISAPNP] Exclude memory regions for the autoconfiguration
1120 Ranges are in pairs (memory base and size).
1122 profile= [KNL] Enable kernel profiling via /proc/profile
1123 { schedule | <number> }
1124 (param: schedule - profile schedule points}
1125 (param: profile step/bucket size as a power of 2 for
1126 statistical time based profiling)
1128 processor.max_cstate= [HW, ACPI]
1129 Limit processor to maximum C-state
1130 max_cstate=9 overrides any DMI blacklist limit.
1132 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1134 See Documentation/ramdisk.txt.
1136 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1137 probe for (bare|imps|exps|lifebook|any).
1138 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1141 [HW,MOUSE] Try to reset the device after so many bad packets
1144 [HW,MOUSE] Set desired mouse resolution, in dpi.
1145 psmouse.smartscroll=
1146 [HW,MOUSE] Controls Logitech smartscroll autorepeat,
1147 0 = disabled, 1 = enabled (default).
1149 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1150 Format: <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1153 See Documentation/paride.txt.
1155 quiet= [KNL] Disable log messages
1160 See Documentation/md.txt.
1162 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1163 See Documentation/ramdisk.txt.
1167 See Documentation/ramdisk.txt.
1169 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1170 New name for the ramdisk parameter.
1171 See Documentation/ramdisk.txt.
1173 reboot= [BUGS=IA-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1174 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1175 See arch/*/kernel/reboot.c.
1177 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1179 resume= [SWSUSP] Specify the partition device for software suspension
1181 rhash_entries= [KNL,NET]
1182 Set number of hash buckets for route cache
1184 riscom8= [HW,SERIAL]
1185 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1187 ro [KNL] Mount root device read-only on boot
1189 root= [KNL] Root filesystem
1191 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1192 mount the root filesystem
1194 rootflags= [KNL] Set root filesystem mount option string
1196 rootfstype= [KNL] Set root filesystem type
1198 rw [KNL] Mount root device read-write on boot
1200 S [KNL] Run init in single mode
1203 See drivers/net/irda/sa1100_ir.c.
1206 Format: <io>,<irq>,<dma>,<dma2>
1208 sbni= [NET] Granch SBNI12 leased line adapter
1210 sbpcd= [HW,CD] Soundblaster CD adapter
1212 See a comment before function sbpcd_setup() in
1213 drivers/cdrom/sbpcd.c.
1215 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1216 Format: <io>[,<timeout>[,<isapnp>]]
1218 scsi_debug_*= [SCSI]
1219 See drivers/scsi/scsi_debug.c.
1221 scsi_default_dev_flags=
1222 [SCSI] SCSI default device flags
1225 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1226 Format: <vendor>:<model>:<flags>
1227 (flags are integer value)
1229 scsi_logging= [SCSI]
1231 selinux [SELINUX] Disable or enable SELinux at boot time.
1232 Format: { "0" | "1" }
1233 See security/selinux/Kconfig help text.
1236 Default value is set via kernel config option.
1237 If enabled at boot time, /selinux/disable can be used
1238 later to disable prior to initial policy load.
1240 serialnumber [BUGS=IA-32]
1242 sg_def_reserved_size=
1246 Format: <io>,<irq>,<dma>,<dma2>,<sgbase>
1249 Maximal number of shapers.
1252 See header of drivers/scsi/sim710.c.
1258 Format: <io>,<irq>,<dma>
1259 See header of drivers/cdrom/sjcd.c.
1264 Format: <io1>[,<io2>[,...,<io8>]]
1266 snd-ad1816a= [HW,ALSA]
1268 snd-ad1848= [HW,ALSA]
1270 snd-ali5451= [HW,ALSA]
1272 snd-als100= [HW,ALSA]
1274 snd-als4000= [HW,ALSA]
1276 snd-azt2320= [HW,ALSA]
1278 snd-cmi8330= [HW,ALSA]
1280 snd-cmipci= [HW,ALSA]
1282 snd-cs4231= [HW,ALSA]
1284 snd-cs4232= [HW,ALSA]
1286 snd-cs4236= [HW,ALSA]
1288 snd-cs4281= [HW,ALSA]
1290 snd-cs46xx= [HW,ALSA]
1292 snd-dt019x= [HW,ALSA]
1294 snd-dummy= [HW,ALSA]
1296 snd-emu10k1= [HW,ALSA]
1298 snd-ens1370= [HW,ALSA]
1300 snd-ens1371= [HW,ALSA]
1302 snd-es968= [HW,ALSA]
1304 snd-es1688= [HW,ALSA]
1306 snd-es18xx= [HW,ALSA]
1308 snd-es1938= [HW,ALSA]
1310 snd-es1968= [HW,ALSA]
1312 snd-fm801= [HW,ALSA]
1314 snd-gusclassic= [HW,ALSA]
1316 snd-gusextreme= [HW,ALSA]
1318 snd-gusmax= [HW,ALSA]
1322 snd-ice1712= [HW,ALSA]
1324 snd-intel8x0= [HW,ALSA]
1326 snd-interwave= [HW,ALSA]
1331 snd-korg1212= [HW,ALSA]
1333 snd-maestro3= [HW,ALSA]
1335 snd-mpu401= [HW,ALSA]
1337 snd-mtpav= [HW,ALSA]
1339 snd-nm256= [HW,ALSA]
1341 snd-opl3sa2= [HW,ALSA]
1349 snd-opti93x= [HW,ALSA]
1353 snd-rme32= [HW,ALSA]
1355 snd-rme96= [HW,ALSA]
1357 snd-rme9652= [HW,ALSA]
1363 snd-sbawe= [HW,ALSA]
1365 snd-serial= [HW,ALSA]
1367 snd-sgalaxy= [HW,ALSA]
1369 snd-sonicvibes= [HW,ALSA]
1374 snd-sun-cs4231= [HW,ALSA]
1376 snd-trident= [HW,ALSA]
1378 snd-usb-audio= [HW,ALSA,USB]
1380 snd-via82xx= [HW,ALSA]
1382 snd-virmidi= [HW,ALSA]
1384 snd-wavefront= [HW,ALSA]
1386 snd-ymfpci= [HW,ALSA]
1388 sonicvibes= [HW,OSS]
1392 Format: <io>[,<irq>]
1394 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1395 See Documentation/sonypi.txt
1397 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1398 See Documentation/specialix.txt.
1400 spia_io_base= [HW,MTD]
1406 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1408 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1409 See Documentation/scsi/st.txt.
1412 See header of drivers/scsi/seagate.c.
1416 Set the STI (builtin display/keyboard on the HP-PARISC
1417 machines) console (graphic card) which should be used
1418 as the initial boot-console.
1419 See also comment in drivers/video/console/sticore.c.
1422 See comment in drivers/video/console/sticore.c.
1425 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1427 stram_swap= [HW,M68k]
1429 swiotlb= [IA-64] Number of I/O TLB slabs
1433 sym53c416= [HW,SCSI]
1434 See header of drivers/scsi/sym53c416.c.
1437 See header of drivers/scsi/t128.c.
1441 thash_entries= [KNL,NET]
1442 Set number of hash buckets for TCP connection
1444 time Show timing data prefixed to each printk message line
1446 tipar.timeout= [HW,PPT]
1447 Set communications timeout in tenths of a second
1450 tipar.delay= [HW,PPT]
1451 Set inter-bit delay in microseconds (default 10).
1454 See header of drivers/scsi/seagate.c.
1457 See comment before function dc390_setup() in
1458 drivers/scsi/tmscsim.c.
1462 trix= [HW,OSS] MediaTrix AudioTrix Pro
1463 Format: <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1465 tsdev.xres= [TS] Horizontal screen resolution.
1466 tsdev.yres= [TS] Vertical screen resolution.
1468 turbografx.map[2|3]=
1469 [HW,JOY] TurboGraFX parallel port interface
1470 Format: <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1471 See also Documentation/input/joystick-parport.txt
1473 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1474 See header of drivers/scsi/u14-34f.c.
1482 usb-handoff [HW] Enable early USB BIOS -> OS handoff
1485 [USBHID] The interval which mice are to be polled at.
1487 video= [FB] Frame buffer configuration
1488 See Documentation/fb/modedb.txt.
1490 vga= [BOOT,IA-32] Select a particular video mode
1491 See Documentation/i386/boot.txt and Documentation/svga.txt.
1492 Use vga=ask for menu.
1493 This is actually a boot loader parameter; the value is
1494 passed to the kernel using a special protocol.
1496 vmalloc=nn[KMG] [KNL,BOOT] forces the vmalloc area to have an exact
1497 size of <nn>. This can be used to increase the
1498 minimum size (128MB on x86). It can also be used to
1499 decrease the size and leave more room for directly
1506 waveartist= [HW,OSS]
1507 Format: <io>,<irq>,<dma>,<dma2>
1510 See header of drivers/scsi/wd33c93.c.
1513 See header of drivers/scsi/wd7000.c.
1516 See Documentation/watchdog/watchdog.txt.
1518 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1519 xd_geo= See header of drivers/block/xd.c.
1521 xirc2ps_cs= [NET,PCMCIA]
1522 Format: <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1528 The last known update (for 2.4.0) - the changelog was not kept before.
1529 2000-06-?? Mr. Unknown
1531 Update for 2.5.49, description for most of the options introduced,
1532 references to other documentation (C files, READMEs, ..), added S390,
1533 PPC, SPARC, MTD, ALSA and OSS category. Minor corrections and
1535 2002-11-24 Petr Baudis <pasky@ucw.cz>
1536 Randy Dunlap <randy.dunlap@verizon.net>
1540 Add documentation for ALSA options.
1541 Add more DRM drivers.