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: <id>,<membase>,<irq>
443 eisa_irq_edge= [PARISC,HW]
444 See header of drivers/parisc/eisa.c.
447 See comment before function elanfreq_setup() in
448 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
451 Format: {"as"|"cfq"|"deadline"|"noop"}
452 See Documentation/block/as-iosched.txt
453 and Documentation/block/deadline-iosched.txt for details.
455 enforcing [SELINUX] Set initial enforcing status.
457 See security/selinux/Kconfig help text.
458 0 -- permissive (log only, no denials).
459 1 -- enforcing (deny and log).
461 Value can be changed at runtime via /selinux/enforce.
464 Format: <lineout>[,<micbias>]
465 See also header of sound/oss/es1370.c.
468 Format: <spdif>,[<nomix>,[<amplifier>]]
469 See also header of sound/oss/es1371.c.
471 ether= [HW,NET] Ethernet cards parameters
472 This option is obsoleted by the "netdev=" option, which
473 has equivalent usage. See its documentation for details.
475 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
479 See header of drivers/scsi/fd_mcs.c.
482 See header of drivers/scsi/fdomain.c.
485 See Documentation/floppy.txt.
487 ftape= [HW] Floppy Tape subsystem debugging options.
488 See Documentation/ftape.txt.
491 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
492 support via parallel port (up to 5 devices per port)
493 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
494 See also Documentation/input/joystick-parport.txt
499 See header of drivers/scsi/gdth.c.
501 gpt [EFI] Forces disk with valid GPT signature but
502 invalid Protective MBR to be treated as GPT.
507 gt96100eth= [NET] MIPS GT96100 Advanced Communication Controller
510 Format: <io>,<irq>,<dma>,<dma16>
514 hashdist= [KNL,NUMA] Large hashes allocated during boot
515 are distributed across NUMA nodes. Defaults on
516 for IA-64, off otherwise.
518 hcl= [IA-64] SGI's Hardware Graph compatibility layer
520 hd= [EIDE] (E)IDE hard drive subsystem geometry
521 Format: <cyl>,<head>,<sect>
523 hd?= [HW] (E)IDE subsystem
524 hd?lun= See Documentation/ide.txt.
526 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
527 size of <nn>. This works even on boxes that have no
528 highmem otherwise. This also works to reduce highmem
529 size on bigger boxes.
532 See Documentation/isdn/README.HiSax.
534 hugepages= [HW,IA-32,IA-64] Maximal number of HugeTLB pages.
536 noirqbalance [IA-32,SMP,KNL] Disable kernel irq balancing
538 i8042.direct [HW] Put keyboard port into non-translated mode
539 i8042.dumbkbd [HW] Pretend that controlled can only read data from
540 keyboard and can not control its state
541 (Don't attempt to blink the leds)
542 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
543 i8042.nomux [HW] Don't check presence of an active multiplexing
545 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
548 [HW] Frequency with which keyboard LEDs should blink
549 when kernel panics (default is 0.5 sec)
550 i8042.reset [HW] Reset the controller during init and cleanup
551 i8042.unlock [HW] Unlock (ignore) the keylock
555 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
556 indicates that the driver is running on unsupported
558 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
559 does not match list of supported models.
561 [HW] Report power status in /proc/i8k
562 (disabled by default)
563 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
566 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
567 See Documentation/mca.txt.
570 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
572 ide= [HW] (E)IDE subsystem
573 Format: ide=nodma or ide=doubler or ide=reverse
574 See Documentation/ide.txt.
576 ide?= [HW] (E)IDE subsystem
577 Format: ide?=noprobe or chipset specific parameters.
578 See Documentation/ide.txt.
580 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
581 See Documentation/ide.txt.
584 Format: idle=poll or idle=halt
587 Set number of hash buckets for inode cache.
590 See header of drivers/scsi/in2000.c.
594 Run specified binary instead of /sbin/init as init
597 initcall_debug [KNL] Trace initcalls as they are executed. Useful
598 for working out where the kernel is dying during
601 initrd= [BOOT] Specify the location of the initial ramdisk
603 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
608 io7= [HW] IO7 for Marvel based alpha systems
609 See comment before marvel_specify_io7 in
610 arch/alpha/kernel/core_marvel.c.
613 See Documentation/nfsroot.txt.
615 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
616 See comment before ip2_setup() in drivers/char/ip2.c.
618 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
619 See header of drivers/scsi/ips.c.
622 Format: <RDP>, <reset>, <pci_scan>, <verbosity>
624 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
625 Format: <cpu number>,...,<cpu number>
626 This option can be used to specify one or more CPUs
627 to isolate from the general SMP balancing and scheduling
628 algorithms. The only way to move a process onto or off
629 an "isolated" CPU is via the CPU affinity syscalls.
630 <cpu number> begins at 0 and the maximum value is
631 "number of CPUs in system - 1".
633 This option is the preferred way to isolate CPUs. The
634 alternative - manually setting the CPU mask of all tasks
635 in the system can cause problems and suboptimal load
636 balancer performance.
639 Format: <io>,<irq>,<dma>,<setup>
643 js= [HW,JOY] Analog joystick
644 See Documentation/input/joystick.txt.
648 kstack=N [IA-32, X86-64] Print N words from the kernel stack
653 lapic [IA-32,APIC] Enable the local APIC even if BIOS disabled it.
655 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
656 Format: addr:<io>,irq:<irq>
659 See function print_params() in arch/ia64/sn/kernel/llsc4.c.
661 load_ramdisk= [RAM] List of ramdisks to load from floppy
662 See Documentation/ramdisk.txt.
668 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
671 loglevel= All Kernel Messages with a loglevel smaller than the
672 console loglevel will be printed to the console. It can
673 also be changed with klogd or other programs. The
674 loglevels are defined as follows:
676 0 (KERN_EMERG) system is unusable
677 1 (KERN_ALERT) action must be taken immediately
678 2 (KERN_CRIT) critical conditions
679 3 (KERN_ERR) error conditions
680 4 (KERN_WARNING) warning conditions
681 5 (KERN_NOTICE) normal but significant condition
682 6 (KERN_INFO) informational
683 7 (KERN_DEBUG) debug-level messages
685 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
686 Format is n, nk, nM. n must be a power of two. The
687 default is set in kernel config.
689 lp=0 [LP] Specify parallel ports to use, e.g,
690 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
691 lp=reset first parallel port). 'lp=0' disables the
692 lp=auto printer driver. 'lp=reset' (which can be
693 specified in addition to the ports) causes
694 attached printers to be reset. Using
695 lp=port1,port2,... specifies the parallel ports
696 to associate lp devices with, starting with
697 lp0. A port specification may be 'none' to skip
698 that lp device, or a parport name such as
699 'parport0'. Specifying 'lp=auto' instead of a
700 port specification list means that device IDs
701 from each port should be examined, to see if
702 an IEEE 1284-compliant printer is attached; if
703 so, the driver will manage that printer.
704 See also header of drivers/char/lp.c.
707 Sets loops_per_jiffy to given constant, thus avoiding
708 time-consuming boot-time autodetection (up to 250 ms per
709 CPU). 0 enables autodetection (default). To determine
710 the correct value for your kernel, boot with normal
711 autodetection and see what value is printed. Note that
712 on SMP systems the preset will be applied to all CPUs,
713 which is likely to cause problems if your CPUs need
714 significantly divergent settings. An incorrect value
715 will cause delays in the kernel to be wrong, leading to
716 unpredictable I/O errors and other breakage. Although
717 unlikely, in the extreme case this might damage your
721 Format: <io>,<irq>,<dma>
724 Format: <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
727 Format: <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
730 Force the use of a particular machine-vector (machvec) in a generic
731 kernel. Example: machvec=hpzx1_swiotlb
734 Format: <io>,<irq>,<dma>,<dma16>,<mpu_io>,<mpu_irq>,<joystick>
739 max_loop= [LOOP] Maximum number of loopback devices that can
743 maxcpus= [SMP] Maximum number of processors that an SMP kernel
746 max_luns= [SCSI] Maximum number of LUNs to probe
747 Should be between 1 and 2^32-1.
750 [SCSI] Maximum number of LUNs received
751 Should be between 1 and 16384.
753 mca-pentium [BUGS=IA-32]
758 Format: <port>,<irq>,<mitsumi_bug_93_wait>
762 mce [IA-32] Machine Check Exception
764 md= [HW] RAID subsystems devices and level
765 See Documentation/md.txt.
768 Format: <first>,<last>
769 Specifies range of consoles to be captured by the MDA.
771 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
772 Amount of memory to be used when the kernel is not able
773 to see the whole system memory or for test.
774 [IA-32] Use together with memmap= to avoid physical
775 address space collisions. Without memmap= PCI devices
776 could be placed at addresses belonging to unused RAM.
778 mem=nopentium [BUGS=IA-32] Disable usage of 4MB pages for kernel
781 memmap=exactmap [KNL,IA-32] Enable setting of an exact
782 E820 memory map, as specified by the user.
783 Such memmap=exactmap lines can be constructed based on
784 BIOS output or other requirements. See the memmap=nn@ss
787 memmap=nn[KMG]@ss[KMG]
788 [KNL] Force usage of a specific region of memory
789 Region of memory to be used, from ss to ss+nn.
791 memmap=nn[KMG]#ss[KMG]
792 [KNL,ACPI] Mark specific memory as ACPI data.
793 Region of memory to be used, from ss to ss+nn.
795 memmap=nn[KMG]$ss[KMG]
796 [KNL,ACPI] Mark specific memory as reserved.
797 Region of memory to be used, from ss to ss+nn.
799 meye.*= [HW] Set MotionEye Camera parameters
800 See Documentation/video4linux/meye.txt.
805 [MOUSE] Maximum time between finger touching and
806 leaving touchpad surface for touch to be considered
807 a tap and be reported as a left button click (for
808 touchpads working in absolute mode only).
810 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
811 reporting absolute coordinates, such as tablets
812 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
813 reporting absolute coordinates, such as tablets
819 Format: <name>,<region-number>,<size>,<offset>
822 Format: <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
825 See drivers/mtd/cmdline.c.
827 mtouchusb.raw_coordinates=
828 [HW] Make the MicroTouch USB driver use raw coordinates ('y', default)
829 or cooked coordinates ('n')
831 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
834 See header of drivers/scsi/NCR_D700.c.
840 ncr53c400a= [HW,SCSI]
842 ncr53c406a= [HW,SCSI]
846 netdev= [NET] Network devices parameters
847 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
848 Note that mem_start is often overloaded to mean
849 something different and driver-specific.
852 See Documentation/nfsroot.txt.
854 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
855 See Documentation/nfsroot.txt.
857 nmi_watchdog= [KNL,BUGS=IA-32] Debugging features for SMP kernels
859 no387 [BUGS=IA-32] Tells the kernel to use the 387 maths
860 emulation library even if a 387 maths coprocessor
865 noapic [SMP,APIC] Tells the kernel to not make use of any
866 IOAPICs that may be present in the system.
868 noasync [HW,M68K] Disables async and sync negotiation for
871 nobats [PPC] Do not use BATs for mapping kernel lowmem
872 on "Classic" PPC cores.
876 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
880 noexec [IA-32, X86-64]
881 noexec=on: enable non-executable mappings (default)
882 noexec=off: disable nn-executable mappings
888 no-hlt [BUGS=IA-32] Tells the kernel that the hlt
889 instruction doesn't work correctly and not to
892 nohalt [IA-64] Tells the kernel not to use the power saving
893 function PAL_HALT_LIGHT when idle. This increases
894 power-consumption. On the positive side, it reduces
895 interrupt wake-up latency, which may improve performance
896 in certain environments such as networked servers or
899 noirqdebug [IA-32] Disables the code which attempts to detect and
900 disable unhandled interrupt sources.
902 noisapnp [ISAPNP] Disables ISA PnP code.
904 noinitrd [RAM] Tells the kernel not to load any configured
909 nolapic [IA-32,APIC] Do not enable or use the local APIC.
911 noltlbs [PPC] Do not use large page/tlb entries for kernel
912 lowmem mapping on PPC40x.
914 nomce [IA-32] Machine Check Exception
916 noresidual [PPC] Don't use residual data on PReP machines.
918 noresume [SWSUSP] Disables resume and restore original swap space.
920 no-scroll [VGA] Disables scrollback.
921 This is required for the Braillex ib80-piezo Braille
922 reader made by F.H. Papenmeier (Germany).
926 nosmp [SMP] Tells an SMP kernel to act as a UP kernel.
928 nosync [HW,M68K] Disables sync negotiation for all devices.
930 notsc [BUGS=IA-32] Disable Time Stamp Counter
932 nousb [USB] Disable the USB subsystem
940 Format: <io>,<irq>,<dma>,<dma2>,<mpu_io>,<mpu_irq>
943 Format: <io>,<irq>,<dma>,<dma2>,<mss_io>,<mpu_io>,<ymode>,<loopback>[,<isapnp>,<multiple]
946 Use timer interrupt instead of performance counters
951 osst= [HW,SCSI] SCSI Tape Driver
952 Format: <buffer_size>,<write_threshold>
953 See also Documentation/scsi/st.txt.
955 panic= [KNL] Kernel behaviour on panic
958 parkbd.port= [HW] Parallel port number the keyboard adapter is
959 connected to, default is 0.
961 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
962 0 for XT, 1 for AT (default is AT).
965 parport=0 [HW,PPT] Specify parallel ports. 0 disables.
966 parport=auto Use 'auto' to force the driver to use
967 parport=0xBBB[,IRQ[,DMA]] any IRQ/DMA settings detected (the
968 default is to ignore detected IRQ/DMA
969 settings because of possible
970 conflicts). You can specify the base
971 address, IRQ, and DMA settings; IRQ and
972 DMA should be numbers, or 'auto' (for
973 using detected settings on that
974 particular port), or 'nofifo' (to avoid
975 using a FIFO even if it is detected).
976 Parallel ports are assigned in the
977 order they are specified on the command
978 line, starting with parport0.
981 [HW,PPT] Configure VIA parallel port to
982 operate in specific mode. This is
983 necessary on Pegasos computer where
984 firmware has no options for setting up
985 parallel port mode and sets it to
986 spp. Currently this function knows
988 Format: [spp|ps2|epp|ecp|ecpepp]
991 Format: <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
994 See header of drivers/scsi/pas16.c.
999 See header of drivers/block/paride/pcd.c.
1000 See also Documentation/paride.txt.
1002 pci=option[,option...] [PCI] various PCI subsystem options:
1003 off [IA-32] don't probe for the PCI bus
1004 bios [IA-32] force use of PCI BIOS, don't access
1005 the hardware directly. Use this if your machine
1006 has a non-standard PCI host bridge.
1007 nobios [IA-32] disallow use of PCI BIOS, only direct
1008 hardware access methods are allowed. Use this
1009 if you experience crashes upon bootup and you
1010 suspect they are caused by the BIOS.
1011 conf1 [IA-32] Force use of PCI Configuration Mechanism 1.
1012 conf2 [IA-32] Force use of PCI Configuration Mechanism 2.
1013 nosort [IA-32] Don't sort PCI devices according to
1014 order given by the PCI BIOS. This sorting is done
1015 to get a device order compatible with older kernels.
1016 biosirq [IA-32] Use PCI BIOS calls to get the interrupt
1017 routing table. These calls are known to be buggy
1018 on several machines and they hang the machine when used,
1019 but on other computers it's the only way to get the
1020 interrupt routing table. Try this option if the kernel
1021 is unable to allocate IRQs or discover secondary PCI
1022 buses on your motherboard.
1023 rom [IA-32] Assign address space to expansion ROMs.
1024 Use with caution as certain devices share address
1025 decoders between ROMs and other resources.
1026 irqmask=0xMMMM [IA-32] Set a bit mask of IRQs allowed to be assigned
1027 automatically to PCI devices. You can make the kernel
1028 exclude IRQs of your ISA cards this way.
1029 lastbus=N [IA-32] Scan all buses till bus #N. Can be useful
1030 if the kernel is unable to find your secondary buses
1031 and you want to tell it explicitly which ones they are.
1032 assign-busses [IA-32] Always assign all PCI bus
1033 numbers ourselves, overriding
1034 whatever the firmware may have
1036 usepirqmask [IA-32] Honor the possible IRQ mask
1037 stored in the BIOS $PIR table. This is
1038 needed on some systems with broken
1039 BIOSes, notably some HP Pavilion N5400
1040 and Omnibook XE3 notebooks. This will
1041 have no effect if ACPI IRQ routing is
1043 noacpi [IA-32] Do not use ACPI for IRQ routing
1044 or for PCI scanning.
1045 routeirq Do IRQ routing for all PCI devices.
1046 This is normally done in pci_enable_device(),
1047 so this option is a temporary workaround
1048 for broken drivers that don't call it.
1050 firmware [ARM] Do not re-enumerate the bus but
1051 instead just use the configuration
1052 from the bootloader. This is currently
1053 used on IXP2000 systems where the
1054 bus has to be configured a certain way
1057 pcmv= [HW,PCMCIA] BadgePAD 4
1060 See Documentation/paride.txt.
1062 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1065 See arch/parisc/kernel/pdc_chassis.c
1068 See Documentation/paride.txt.
1071 See Documentation/paride.txt.
1073 pirq= [SMP,APIC] Manual mp-table setup
1074 See Documentation/i386/IO-APIC.txt.
1076 plip= [PPT,NET] Parallel port network link
1077 Format: { parport<nr> | timid | 0 }
1078 See also Documentation/parport.txt.
1084 { on | off | curr | res | no-curr | no-res }
1087 [ISAPNP] Exclude IRQs for the autoconfiguration
1090 [ISAPNP] Exclude DMAs for the autoconfiguration
1092 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1093 Ranges are in pairs (I/O port base and size).
1096 [ISAPNP] Exclude memory regions for the autoconfiguration
1097 Ranges are in pairs (memory base and size).
1099 profile= [KNL] Enable kernel profiling via /proc/profile
1100 { schedule | <number> }
1101 (param: schedule - profile schedule points}
1102 (param: profile step/bucket size as a power of 2 for
1103 statistical time based profiling)
1105 processor.max_cstate= [HW, ACPI]
1106 Limit processor to maximum C-state
1107 max_cstate=9 overrides any DMI blacklist limit.
1109 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1111 See Documentation/ramdisk.txt.
1113 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1114 probe for (bare|imps|exps).
1115 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1118 [HW,MOUSE] Try to reset the device after so many bad packets
1121 [HW,MOUSE] Set desired mouse resolution, in dpi.
1122 psmouse.smartscroll=
1123 [HW,MOUSE] Controls Logitech smartscroll autorepeat,
1124 0 = disabled, 1 = enabled (default).
1126 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1127 Format: <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1130 See Documentation/paride.txt.
1132 quiet= [KNL] Disable log messages
1137 See Documentation/md.txt.
1139 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1140 See Documentation/ramdisk.txt.
1144 See Documentation/ramdisk.txt.
1146 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1147 New name for the ramdisk parameter.
1148 See Documentation/ramdisk.txt.
1150 reboot= [BUGS=IA-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1151 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1152 See arch/*/kernel/reboot.c.
1154 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1156 resume= [SWSUSP] Specify the partition device for software suspension
1158 rhash_entries= [KNL,NET]
1159 Set number of hash buckets for route cache
1161 riscom8= [HW,SERIAL]
1162 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1164 ro [KNL] Mount root device read-only on boot
1166 root= [KNL] Root filesystem
1168 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1169 mount the root filesystem
1171 rootflags= [KNL] Set root filesystem mount option string
1173 rootfstype= [KNL] Set root filesystem type
1175 rw [KNL] Mount root device read-write on boot
1177 S [KNL] Run init in single mode
1180 See drivers/net/irda/sa1100_ir.c.
1183 Format: <io>,<irq>,<dma>,<dma2>
1185 sbni= [NET] Granch SBNI12 leased line adapter
1187 sbpcd= [HW,CD] Soundblaster CD adapter
1189 See a comment before function sbpcd_setup() in
1190 drivers/cdrom/sbpcd.c.
1192 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1193 Format: <io>[,<timeout>[,<isapnp>]]
1195 scsi_debug_*= [SCSI]
1196 See drivers/scsi/scsi_debug.c.
1198 scsi_default_dev_flags=
1199 [SCSI] SCSI default device flags
1202 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1203 Format: <vendor>:<model>:<flags>
1204 (flags are integer value)
1206 scsi_logging= [SCSI]
1208 selinux [SELINUX] Disable or enable SELinux at boot time.
1209 Format: { "0" | "1" }
1210 See security/selinux/Kconfig help text.
1213 Default value is set via kernel config option.
1214 If enabled at boot time, /selinux/disable can be used
1215 later to disable prior to initial policy load.
1217 serialnumber [BUGS=IA-32]
1219 sg_def_reserved_size=
1223 Format: <io>,<irq>,<dma>,<dma2>,<sgbase>
1226 Maximal number of shapers.
1229 See header of drivers/scsi/sim710.c.
1235 Format: <io>,<irq>,<dma>
1236 See header of drivers/cdrom/sjcd.c.
1241 Format: <io1>[,<io2>[,...,<io8>]]
1243 snd-ad1816a= [HW,ALSA]
1245 snd-ad1848= [HW,ALSA]
1247 snd-ali5451= [HW,ALSA]
1249 snd-als100= [HW,ALSA]
1251 snd-als4000= [HW,ALSA]
1253 snd-azt2320= [HW,ALSA]
1255 snd-cmi8330= [HW,ALSA]
1257 snd-cmipci= [HW,ALSA]
1259 snd-cs4231= [HW,ALSA]
1261 snd-cs4232= [HW,ALSA]
1263 snd-cs4236= [HW,ALSA]
1265 snd-cs4281= [HW,ALSA]
1267 snd-cs46xx= [HW,ALSA]
1269 snd-dt019x= [HW,ALSA]
1271 snd-dummy= [HW,ALSA]
1273 snd-emu10k1= [HW,ALSA]
1275 snd-ens1370= [HW,ALSA]
1277 snd-ens1371= [HW,ALSA]
1279 snd-es968= [HW,ALSA]
1281 snd-es1688= [HW,ALSA]
1283 snd-es18xx= [HW,ALSA]
1285 snd-es1938= [HW,ALSA]
1287 snd-es1968= [HW,ALSA]
1289 snd-fm801= [HW,ALSA]
1291 snd-gusclassic= [HW,ALSA]
1293 snd-gusextreme= [HW,ALSA]
1295 snd-gusmax= [HW,ALSA]
1299 snd-ice1712= [HW,ALSA]
1301 snd-intel8x0= [HW,ALSA]
1303 snd-interwave= [HW,ALSA]
1308 snd-korg1212= [HW,ALSA]
1310 snd-maestro3= [HW,ALSA]
1312 snd-mpu401= [HW,ALSA]
1314 snd-mtpav= [HW,ALSA]
1316 snd-nm256= [HW,ALSA]
1318 snd-opl3sa2= [HW,ALSA]
1326 snd-opti93x= [HW,ALSA]
1330 snd-rme32= [HW,ALSA]
1332 snd-rme96= [HW,ALSA]
1334 snd-rme9652= [HW,ALSA]
1340 snd-sbawe= [HW,ALSA]
1342 snd-serial= [HW,ALSA]
1344 snd-sgalaxy= [HW,ALSA]
1346 snd-sonicvibes= [HW,ALSA]
1351 snd-sun-cs4231= [HW,ALSA]
1353 snd-trident= [HW,ALSA]
1355 snd-usb-audio= [HW,ALSA,USB]
1357 snd-via82xx= [HW,ALSA]
1359 snd-virmidi= [HW,ALSA]
1361 snd-wavefront= [HW,ALSA]
1363 snd-ymfpci= [HW,ALSA]
1365 sonicvibes= [HW,OSS]
1369 Format: <io>[,<irq>]
1371 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1372 See Documentation/sonypi.txt
1374 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1375 See Documentation/specialix.txt.
1377 spia_io_base= [HW,MTD]
1383 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1385 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1386 See Documentation/scsi/st.txt.
1389 See header of drivers/scsi/seagate.c.
1393 Set the STI (builtin display/keyboard on the HP-PARISC
1394 machines) console (graphic card) which should be used
1395 as the initial boot-console.
1396 See also comment in drivers/video/console/sticore.c.
1399 See comment in drivers/video/console/sticore.c.
1402 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1404 stram_swap= [HW,M68k]
1406 swiotlb= [IA-64] Number of I/O TLB slabs
1410 sym53c416= [HW,SCSI]
1411 See header of drivers/scsi/sym53c416.c.
1414 See header of drivers/scsi/t128.c.
1418 thash_entries= [KNL,NET]
1419 Set number of hash buckets for TCP connection
1421 time Show timing data prefixed to each printk message line
1423 tipar.timeout= [HW,PPT]
1424 Set communications timeout in tenths of a second
1427 tipar.delay= [HW,PPT]
1428 Set inter-bit delay in microseconds (default 10).
1431 See header of drivers/scsi/seagate.c.
1434 See comment before function dc390_setup() in
1435 drivers/scsi/tmscsim.c.
1439 trix= [HW,OSS] MediaTrix AudioTrix Pro
1440 Format: <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1442 tsdev.xres= [TS] Horizontal screen resolution.
1443 tsdev.yres= [TS] Vertical screen resolution.
1445 turbografx.map[2|3]=
1446 [HW,JOY] TurboGraFX parallel port interface
1447 Format: <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1448 See also Documentation/input/joystick-parport.txt
1450 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1451 See header of drivers/scsi/u14-34f.c.
1459 usb-handoff [HW] Enable early USB BIOS -> OS handoff
1462 [USBHID] The interval which mice are to be polled at.
1464 video= [FB] Frame buffer configuration
1465 See Documentation/fb/modedb.txt.
1467 vga= [BOOT,IA-32] Select a particular video mode
1468 See Documentation/i386/boot.txt and Documentation/svga.txt.
1469 Use vga=ask for menu.
1470 This is actually a boot loader parameter; the value is
1471 passed to the kernel using a special protocol.
1473 vmalloc=nn[KMG] [KNL,BOOT] forces the vmalloc area to have an exact
1474 size of <nn>. This can be used to increase the
1475 minimum size (128MB on x86). It can also be used to
1476 decrease the size and leave more room for directly
1483 waveartist= [HW,OSS]
1484 Format: <io>,<irq>,<dma>,<dma2>
1487 See header of drivers/scsi/wd33c93.c.
1490 See header of drivers/scsi/wd7000.c.
1493 See Documentation/watchdog/watchdog.txt.
1495 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1496 xd_geo= See header of drivers/block/xd.c.
1498 xirc2ps_cs= [NET,PCMCIA]
1499 Format: <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1505 The last known update (for 2.4.0) - the changelog was not kept before.
1506 2000-06-?? Mr. Unknown
1508 Update for 2.5.49, description for most of the options introduced,
1509 references to other documentation (C files, READMEs, ..), added S390,
1510 PPC, SPARC, MTD, ALSA and OSS category. Minor corrections and
1512 2002-11-24 Petr Baudis <pasky@ucw.cz>
1513 Randy Dunlap <randy.dunlap@verizon.net>
1517 Add documentation for ALSA options.
1518 Add more DRM drivers.