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 states 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 DHCP, 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 suspend 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 | noirq }
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]
127 ACPI will balance active IRQs
130 acpi_irq_nobalance [HW,ACPI]
131 ACPI will not move active IRQs (default)
134 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
136 Format: <irq>,<irq>...
138 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
139 Format: <irq>,<irq>...
141 acpi_osi= [HW,ACPI] empty param disables _OSI
143 acpi_serialize [HW,ACPI] force serialization of AML methods
145 acpi_skip_timer_override [HW,ACPI]
146 Recognize and ignore IRQ0/pin2 Interrupt Override.
147 For broken nForce2 BIOS resulting in XT-PIC timer.
149 acpi_dbg_layer= [HW,ACPI]
151 Each bit of the <int> indicates an ACPI debug layer,
152 1: enable, 0: disable. It is useful for boot time
153 debugging. After system has booted up, it can be set
154 via /proc/acpi/debug_layer.
156 acpi_dbg_level= [HW,ACPI]
158 Each bit of the <int> indicates an ACPI debug level,
159 1: enable, 0: disable. It is useful for boot time
160 debugging. After system has booted up, it can be set
161 via /proc/acpi/debug_level.
163 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
165 acpi_generic_hotkey [HW,ACPI]
166 Allow consolidated generic hotkey driver to
167 override platform specific driver.
168 See also Documentation/acpi-hotkey.txt.
170 enable_timer_pin_1 [i386,x86-64]
171 Enable PIN 1 of APIC timer
172 Can be useful to work around chipset bugs
173 (in particular on some ATI chipsets).
174 The kernel tries to set a reasonable default.
176 disable_timer_pin_1 [i386,x86-64]
177 Disable PIN 1 of APIC timer
178 Can be useful to work around chipset bugs.
181 Format: <io>,<irq>,<dma>,<dma2>
182 See also Documentation/sound/oss/AD1816.
185 Format: <io>,<irq>,<dma>,<dma2>,<type>
191 See header of drivers/scsi/advansys.c.
193 advwdt= [HW,WDT] Advantech WDT
194 Format: <iostart>,<iostop>
196 aedsp16= [HW,OSS] Audio Excel DSP 16
197 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
198 See also header of sound/oss/aedsp16.c.
201 See Documentation/scsi/aha152x.txt.
204 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
207 See Documentation/scsi/aic7xxx.txt.
210 See Documentation/scsi/aic79xx.txt.
212 amijoy.map= [HW,JOY] Amiga joystick support
213 Map of devices attached to JOY0DAT and JOY1DAT
215 See also Documentation/kernel/input/joystick.txt
217 analog.map= [HW,JOY] Analog joystick and gamepad support
218 Specifies type or capabilities of an analog joystick
219 connected to one of 16 gameports
220 Format: <type1>,<type2>,..<type16>
223 Power management functions (SPARCstation-4/5 + deriv.)
225 Disable APC CPU standby support. SPARCstation-Fox does
226 not play well with APC CPU idle - disable it if you have
227 APC and your system crashes randomly.
229 apic= [APIC,i386] Change the output verbosity whilst booting
230 Format: { quiet (default) | verbose | debug }
231 Change the amount of debugging information output
232 when initialising the APIC and IO-APIC components.
234 apm= [APM] Advanced Power Management
235 See header of arch/i386/kernel/apm.c.
240 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
241 Format: <io>,<irq>,<nodeID>
245 atarimouse= [HW,MOUSE] Atari Mouse
247 atascsi= [HW,SCSI] Atari SCSI
249 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
250 EzKey and similar keyboards
252 atkbd.reset= [HW] Reset keyboard during initialization
254 atkbd.set= [HW] Select keyboard code set
255 Format: <int> (2 = AT (default), 3 = PS/2)
257 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
260 atkbd.softraw= [HW] Choose between synthetic and real raw mode
261 Format: <bool> (0 = real, 1 = synthetic (default))
263 atkbd.softrepeat= [HW]
264 Use software keyboard repeat
268 awe= [HW,OSS] AWE32/SB32/AWE64 wave table synth
269 Format: <io>,<memsize>,<isapnp>
271 aztcd= [HW,CD] Aztech CD268 CDROM driver
272 Format: <io>,0x79 (?)
274 baycom_epp= [HW,AX25]
277 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
279 See header of drivers/net/hamradio/baycom_par.c.
281 baycom_ser_fdx= [HW,AX25]
282 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
283 Format: <io>,<irq>,<mode>[,<baud>]
284 See header of drivers/net/hamradio/baycom_ser_fdx.c.
286 baycom_ser_hdx= [HW,AX25]
287 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
288 Format: <io>,<irq>,<mode>
289 See header of drivers/net/hamradio/baycom_ser_hdx.c.
291 blkmtd_device= [HW,MTD]
297 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
298 bttv.radio= Most important insmod options are available as
300 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
301 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
304 See drivers/scsi/BusLogic.c, comment before function
305 BusLogic_ParseDriverOptions().
307 c101= [NET] Moxa C101 synchronous serial card
309 cachesize= [BUGS=IA-32] Override level 2 CPU cache size detection.
310 Sometimes CPU hardware bugs make them report the cache
311 size incorrectly. The kernel will attempt work arounds
312 to fix known problems, but for some CPUs it is not
313 possible to determine what the correct size should be.
314 This option provides an override for these situations.
317 Format: <io>,<irq>[,PAS]
318 See header of drivers/cdrom/cdu31a.c.
320 chandev= [HW,NET] Generic channel device initialisation
322 checkreqprot [SELINUX] Set initial checkreqprot flag value.
323 Format: { "0" | "1" }
324 See security/selinux/Kconfig help text.
325 0 -- check protection applied by kernel (includes
326 any implied execute protection).
327 1 -- check protection requested by application.
328 Default value is set via a kernel config option.
329 Value can be changed at runtime via
330 /selinux/checkreqprot.
332 clock= [BUGS=IA-32,HW] gettimeofday timesource override.
333 Forces specified timesource (if avaliable) to be used
334 when calculating gettimeofday(). If specicified
335 timesource is not avalible, it defaults to PIT.
336 Format: { pit | tsc | cyclone | pmtmr }
338 hpet= [IA-32,HPET] option to disable HPET and use PIT.
342 Format: { auto | [<io>,][<irq>] }
344 com20020= [HW,NET] ARCnet - COM20020 chipset
346 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
348 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
352 ARCnet - COM90xx chipset (memory-mapped buffers)
353 Format: <io>[,<irq>[,<memstart>]]
355 condev= [HW,S390] console device
358 console= [KNL] Output console device and options.
360 tty<n> Use the virtual console device <n>.
363 Use the specified serial port. The options are of
364 the form "bbbbpn", where "bbbb" is the baud rate,
365 "p" is parity ("n", "o", or "e"), and "n" is bits.
368 See also Documentation/serial-console.txt.
370 uart,io,<addr>[,options]
371 uart,mmio,<addr>[,options]
372 Start an early, polled-mode console on the 8250/16550
373 UART at the specified I/O port or MMIO address,
374 switching to the matching ttyS device later. The
375 options are the same as for ttyS, above.
377 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
379 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
382 Format: { parport<nr> | auto | none }
384 crashkernel=nn[KMG]@ss[KMG]
385 [KNL] Reserve a chunk of physical memory to
386 hold a kernel to switch to with kexec on panic.
389 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
394 cs89x0_media= [HW,NET]
395 Format: { rj45 | aui | bnc }
397 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
400 See header of drivers/s390/block/dasd_devmap.c.
402 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
403 (one device per port)
404 Format: <port#>,<type>
405 See also Documentation/input/joystick-parport.txt
407 debug [KNL] Enable kernel debugging (events log level).
410 Format: <area>[,<node>]
411 See also Documentation/networking/decnet.txt.
414 See Documentation/filesystems/devfs/boot-options.
417 Set number of hash buckets for dentry cache.
420 IO parameters + enable/disable command.
422 digiepca= [HW,SERIAL]
423 See drivers/char/README.epca and
424 Documentation/digiepca.txt.
426 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
428 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
430 dmasound= [HW,OSS] Sound subsystem buffers
436 earlyprintk= [IA-32,X86-64]
438 earlyprintk=serial[,ttySn[,baudrate]]
440 Append ",keep" to not disable it when the real console
443 Only vga or serial at a time, not both.
445 Currently only ttyS0 and ttyS1 are supported.
447 Interaction with the standard serial driver is not
450 The VGA output is eventually overwritten by the real
455 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
458 non-0: interrupt mode (default)
465 Format: {"of[f]" | "sk[ipmbr]"}
466 See comment in arch/i386/boot/edd.S
469 Format: <id>,<membase>,<irq>
471 eisa_irq_edge= [PARISC,HW]
472 See header of drivers/parisc/eisa.c.
475 See comment before function elanfreq_setup() in
476 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
479 Format: {"as" | "cfq" | "deadline" | "noop"}
480 See Documentation/block/as-iosched.txt and
481 Documentation/block/deadline-iosched.txt for details.
484 Specifies physical address of start of kernel core
486 See Documentation/kdump.txt for details.
488 enforcing [SELINUX] Set initial enforcing status.
490 See security/selinux/Kconfig help text.
491 0 -- permissive (log only, no denials).
492 1 -- enforcing (deny and log).
494 Value can be changed at runtime via /selinux/enforce.
497 Format: <lineout>[,<micbias>]
498 See also header of sound/oss/es1370.c.
501 Format: <spdif>,[<nomix>,[<amplifier>]]
502 See also header of sound/oss/es1371.c.
504 ether= [HW,NET] Ethernet cards parameters
505 This option is obsoleted by the "netdev=" option, which
506 has equivalent usage. See its documentation for details.
508 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
512 See header of drivers/scsi/fd_mcs.c.
515 See header of drivers/scsi/fdomain.c.
518 See Documentation/floppy.txt.
520 ftape= [HW] Floppy Tape subsystem debugging options.
521 See Documentation/ftape.txt.
524 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
525 support via parallel port (up to 5 devices per port)
526 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
527 See also Documentation/input/joystick-parport.txt
532 See header of drivers/scsi/gdth.c.
534 gpt [EFI] Forces disk with valid GPT signature but
535 invalid Protective MBR to be treated as GPT.
540 gt96100eth= [NET] MIPS GT96100 Advanced Communication Controller
543 Format: <io>,<irq>,<dma>,<dma16>
547 hashdist= [KNL,NUMA] Large hashes allocated during boot
548 are distributed across NUMA nodes. Defaults on
549 for IA-64, off otherwise.
550 Format: 0 | 1 (for off | on)
552 hcl= [IA-64] SGI's Hardware Graph compatibility layer
554 hd= [EIDE] (E)IDE hard drive subsystem geometry
555 Format: <cyl>,<head>,<sect>
557 hd?= [HW] (E)IDE subsystem
558 hd?lun= See Documentation/ide.txt.
560 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
561 size of <nn>. This works even on boxes that have no
562 highmem otherwise. This also works to reduce highmem
563 size on bigger boxes.
566 See Documentation/isdn/README.HiSax.
568 hugepages= [HW,IA-32,IA-64] Maximal number of HugeTLB pages.
570 noirqbalance [IA-32,SMP,KNL] Disable kernel irq balancing
572 i8042.direct [HW] Put keyboard port into non-translated mode
573 i8042.dumbkbd [HW] Pretend that controlled can only read data from
574 keyboard and can not control its state
575 (Don't attempt to blink the leds)
576 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
577 i8042.nokbd [HW] Don't check/create keyboard port
578 i8042.nomux [HW] Don't check presence of an active multiplexing
580 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
583 [HW] Frequency with which keyboard LEDs should blink
584 when kernel panics (default is 0.5 sec)
585 i8042.reset [HW] Reset the controller during init and cleanup
586 i8042.unlock [HW] Unlock (ignore) the keylock
590 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
591 indicates that the driver is running on unsupported
593 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
594 does not match list of supported models.
596 [HW] Report power status in /proc/i8k
597 (disabled by default)
598 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
601 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
602 See Documentation/mca.txt.
605 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
607 ide= [HW] (E)IDE subsystem
608 Format: ide=nodma or ide=doubler or ide=reverse
609 See Documentation/ide.txt.
611 ide?= [HW] (E)IDE subsystem
612 Format: ide?=noprobe or chipset specific parameters.
613 See Documentation/ide.txt.
615 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
616 See Documentation/ide.txt.
619 Format: idle=poll or idle=halt
622 Set number of hash buckets for inode cache.
625 See header of drivers/scsi/in2000.c.
629 Run specified binary instead of /sbin/init as init
632 initcall_debug [KNL] Trace initcalls as they are executed. Useful
633 for working out where the kernel is dying during
636 initrd= [BOOT] Specify the location of the initial ramdisk
638 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
643 io7= [HW] IO7 for Marvel based alpha systems
644 See comment before marvel_specify_io7 in
645 arch/alpha/kernel/core_marvel.c.
648 See Documentation/nfsroot.txt.
650 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
651 See comment before ip2_setup() in drivers/char/ip2.c.
653 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
654 See header of drivers/scsi/ips.c.
657 When an interrupt is not handled search all handlers
658 for it. Intended to get systems with badly broken
662 When an interrupt is not handled search all handlers
663 for it. Also check all handlers each timer
664 interrupt. Intended to get systems with badly broken
668 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
670 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
671 Format: <cpu number>,...,<cpu number>
672 This option can be used to specify one or more CPUs
673 to isolate from the general SMP balancing and scheduling
674 algorithms. The only way to move a process onto or off
675 an "isolated" CPU is via the CPU affinity syscalls.
676 <cpu number> begins at 0 and the maximum value is
677 "number of CPUs in system - 1".
679 This option is the preferred way to isolate CPUs. The
680 alternative -- manually setting the CPU mask of all
681 tasks in the system -- can cause problems and
682 suboptimal load balancer performance.
685 Format: <io>,<irq>,<dma>,<setup>
689 js= [HW,JOY] Analog joystick
690 See Documentation/input/joystick.txt.
694 kstack=N [IA-32,X86-64] Print N words from the kernel stack
699 lapic [IA-32,APIC] Enable the local APIC even if BIOS
702 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
703 Format: addr:<io>,irq:<irq>
705 llsc*= [IA64] See function print_params() in
706 arch/ia64/sn/kernel/llsc4.c.
708 load_ramdisk= [RAM] List of ramdisks to load from floppy
709 See Documentation/ramdisk.txt.
715 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
718 loglevel= All Kernel Messages with a loglevel smaller than the
719 console loglevel will be printed to the console. It can
720 also be changed with klogd or other programs. The
721 loglevels are defined as follows:
723 0 (KERN_EMERG) system is unusable
724 1 (KERN_ALERT) action must be taken immediately
725 2 (KERN_CRIT) critical conditions
726 3 (KERN_ERR) error conditions
727 4 (KERN_WARNING) warning conditions
728 5 (KERN_NOTICE) normal but significant condition
729 6 (KERN_INFO) informational
730 7 (KERN_DEBUG) debug-level messages
732 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
733 Format: { n | nk | nM }
734 n must be a power of two. The default size
735 is set in the kernel config file.
737 lp=0 [LP] Specify parallel ports to use, e.g,
738 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
739 lp=reset first parallel port). 'lp=0' disables the
740 lp=auto printer driver. 'lp=reset' (which can be
741 specified in addition to the ports) causes
742 attached printers to be reset. Using
743 lp=port1,port2,... specifies the parallel ports
744 to associate lp devices with, starting with
745 lp0. A port specification may be 'none' to skip
746 that lp device, or a parport name such as
747 'parport0'. Specifying 'lp=auto' instead of a
748 port specification list means that device IDs
749 from each port should be examined, to see if
750 an IEEE 1284-compliant printer is attached; if
751 so, the driver will manage that printer.
752 See also header of drivers/char/lp.c.
755 Sets loops_per_jiffy to given constant, thus avoiding
756 time-consuming boot-time autodetection (up to 250 ms per
757 CPU). 0 enables autodetection (default). To determine
758 the correct value for your kernel, boot with normal
759 autodetection and see what value is printed. Note that
760 on SMP systems the preset will be applied to all CPUs,
761 which is likely to cause problems if your CPUs need
762 significantly divergent settings. An incorrect value
763 will cause delays in the kernel to be wrong, leading to
764 unpredictable I/O errors and other breakage. Although
765 unlikely, in the extreme case this might damage your
769 Format: <io>,<irq>,<dma>
771 mac5380= [HW,SCSI] Format:
772 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
774 mac53c9x= [HW,SCSI] Format:
775 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
777 machvec= [IA64] Force the use of a particular machine-vector
778 (machvec) in a generic kernel.
779 Example: machvec=hpzx1_swiotlb
781 mad16= [HW,OSS] Format:
782 <io>,<irq>,<dma>,<dma16>,<mpu_io>,<mpu_irq>,<joystick>
787 max_loop= [LOOP] Maximum number of loopback devices that can
791 maxcpus= [SMP] Maximum number of processors that an SMP kernel
794 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
795 equal to this physical address is ignored.
797 max_luns= [SCSI] Maximum number of LUNs to probe.
798 Should be between 1 and 2^32-1.
801 [SCSI] Maximum number of LUNs received.
802 Should be between 1 and 16384.
804 mca-pentium [BUGS=IA-32]
809 Format: <port>,<irq>,<mitsumi_bug_93_wait>
813 mce [IA-32] Machine Check Exception
815 md= [HW] RAID subsystems devices and level
816 See Documentation/md.txt.
819 Format: <first>,<last>
820 Specifies range of consoles to be captured by the MDA.
822 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
823 Amount of memory to be used when the kernel is not able
824 to see the whole system memory or for test.
825 [IA-32] Use together with memmap= to avoid physical
826 address space collisions. Without memmap= PCI devices
827 could be placed at addresses belonging to unused RAM.
829 mem=nopentium [BUGS=IA-32] Disable usage of 4MB pages for kernel
832 memmap=exactmap [KNL,IA-32] Enable setting of an exact
833 E820 memory map, as specified by the user.
834 Such memmap=exactmap lines can be constructed based on
835 BIOS output or other requirements. See the memmap=nn@ss
838 memmap=nn[KMG]@ss[KMG]
839 [KNL] Force usage of a specific region of memory
840 Region of memory to be used, from ss to ss+nn.
842 memmap=nn[KMG]#ss[KMG]
843 [KNL,ACPI] Mark specific memory as ACPI data.
844 Region of memory to be used, from ss to ss+nn.
846 memmap=nn[KMG]$ss[KMG]
847 [KNL,ACPI] Mark specific memory as reserved.
848 Region of memory to be used, from ss to ss+nn.
850 meye.*= [HW] Set MotionEye Camera parameters
851 See Documentation/video4linux/meye.txt.
856 [MOUSE] Maximum time between finger touching and
857 leaving touchpad surface for touch to be considered
858 a tap and be reported as a left button click (for
859 touchpads working in absolute mode only).
861 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
862 reporting absolute coordinates, such as tablets
863 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
864 reporting absolute coordinates, such as tablets
870 Format: <name>,<region-number>,<size>,<offset>
872 MTD_Region= [MTD] Format:
873 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
876 See drivers/mtd/cmdline.c.
878 mtouchusb.raw_coordinates=
879 [HW] Make the MicroTouch USB driver use raw coordinates
880 ('y', default) or cooked coordinates ('n')
882 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
885 See header of drivers/scsi/NCR_D700.c.
891 ncr53c400a= [HW,SCSI]
893 ncr53c406a= [HW,SCSI]
897 netdev= [NET] Network devices parameters
898 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
899 Note that mem_start is often overloaded to mean
900 something different and driver-specific.
901 This usage is only documented in each driver source
905 See Documentation/nfsroot.txt.
907 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
908 See Documentation/nfsroot.txt.
910 nmi_watchdog= [KNL,BUGS=IA-32] Debugging features for SMP kernels
912 no387 [BUGS=IA-32] Tells the kernel to use the 387 maths
913 emulation library even if a 387 maths coprocessor
918 noapic [SMP,APIC] Tells the kernel to not make use of any
919 IOAPICs that may be present in the system.
921 noasync [HW,M68K] Disables async and sync negotiation for
924 nobats [PPC] Do not use BATs for mapping kernel lowmem
925 on "Classic" PPC cores.
929 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
933 noexec [IA-32,X86-64]
934 noexec=on: enable non-executable mappings (default)
935 noexec=off: disable nn-executable mappings
941 no-hlt [BUGS=IA-32] Tells the kernel that the hlt
942 instruction doesn't work correctly and not to
945 nohalt [IA-64] Tells the kernel not to use the power saving
946 function PAL_HALT_LIGHT when idle. This increases
947 power-consumption. On the positive side, it reduces
948 interrupt wake-up latency, which may improve performance
949 in certain environments such as networked servers or
952 noirqdebug [IA-32] Disables the code which attempts to detect and
953 disable unhandled interrupt sources.
955 noisapnp [ISAPNP] Disables ISA PnP code.
957 noinitrd [RAM] Tells the kernel not to load any configured
962 nolapic [IA-32,APIC] Do not enable or use the local APIC.
964 noltlbs [PPC] Do not use large page/tlb entries for kernel
965 lowmem mapping on PPC40x.
967 nomce [IA-32] Machine Check Exception
969 noresidual [PPC] Don't use residual data on PReP machines.
971 noresume [SWSUSP] Disables resume and restores original swap
974 no-scroll [VGA] Disables scrollback.
975 This is required for the Braillex ib80-piezo Braille
976 reader made by F.H. Papenmeier (Germany).
980 nosmp [SMP] Tells an SMP kernel to act as a UP kernel.
982 nosync [HW,M68K] Disables sync negotiation for all devices.
984 notsc [BUGS=IA-32] Disable Time Stamp Counter
986 nousb [USB] Disable the USB subsystem
994 Format: <io>,<irq>,<dma>,<dma2>,<mpu_io>,<mpu_irq>
996 opl3sa2= [HW,OSS] Format:
997 <io>,<irq>,<dma>,<dma2>,<mss_io>,<mpu_io>,<ymode>,<loopback>[,<isapnp>,<multiple]
1000 Use timer interrupt instead of performance counters
1005 osst= [HW,SCSI] SCSI Tape Driver
1006 Format: <buffer_size>,<write_threshold>
1007 See also Documentation/scsi/st.txt.
1009 panic= [KNL] Kernel behaviour on panic
1012 parkbd.port= [HW] Parallel port number the keyboard adapter is
1013 connected to, default is 0.
1015 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1016 0 for XT, 1 for AT (default is AT).
1019 parport= [HW,PPT] Specify parallel ports. 0 disables.
1020 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1021 Use 'auto' to force the driver to use any
1022 IRQ/DMA settings detected (the default is to
1023 ignore detected IRQ/DMA settings because of
1024 possible conflicts). You can specify the base
1025 address, IRQ, and DMA settings; IRQ and DMA
1026 should be numbers, or 'auto' (for using detected
1027 settings on that particular port), or 'nofifo'
1028 (to avoid using a FIFO even if it is detected).
1029 Parallel ports are assigned in the order they
1030 are specified on the command line, starting
1033 parport_init_mode= [HW,PPT]
1034 Configure VIA parallel port to operate in
1035 a specific mode. This is necessary on Pegasos
1036 computer where firmware has no options for setting
1037 up parallel port mode and sets it to spp.
1038 Currently this function knows 686a and 8231 chips.
1039 Format: [spp|ps2|epp|ecp|ecpepp]
1041 pas2= [HW,OSS] Format:
1042 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1045 See header of drivers/scsi/pas16.c.
1050 See header of drivers/block/paride/pcd.c.
1051 See also Documentation/paride.txt.
1053 pci=option[,option...] [PCI] various PCI subsystem options:
1054 off [IA-32] don't probe for the PCI bus
1055 bios [IA-32] force use of PCI BIOS, don't access
1056 the hardware directly. Use this if your machine
1057 has a non-standard PCI host bridge.
1058 nobios [IA-32] disallow use of PCI BIOS, only direct
1059 hardware access methods are allowed. Use this
1060 if you experience crashes upon bootup and you
1061 suspect they are caused by the BIOS.
1062 conf1 [IA-32] Force use of PCI Configuration
1064 conf2 [IA-32] Force use of PCI Configuration
1066 nosort [IA-32] Don't sort PCI devices according to
1067 order given by the PCI BIOS. This sorting is
1068 done to get a device order compatible with
1070 biosirq [IA-32] Use PCI BIOS calls to get the interrupt
1071 routing table. These calls are known to be buggy
1072 on several machines and they hang the machine
1073 when used, but on other computers it's the only
1074 way to get the interrupt routing table. Try
1075 this option if the kernel is unable to allocate
1076 IRQs or discover secondary PCI buses on your
1078 rom [IA-32] Assign address space to expansion ROMs.
1079 Use with caution as certain devices share
1080 address decoders between ROMs and other
1082 irqmask=0xMMMM [IA-32] Set a bit mask of IRQs allowed to be
1083 assigned automatically to PCI devices. You can
1084 make the kernel exclude IRQs of your ISA cards
1086 pirqaddr=0xAAAAA [IA-32] Specify the physical address
1087 of the PIRQ table (normally generated
1088 by the BIOS) if it is outside the
1089 F0000h-100000h range.
1090 lastbus=N [IA-32] Scan all buses thru bus #N. Can be
1091 useful if the kernel is unable to find your
1092 secondary buses and you want to tell it
1093 explicitly which ones they are.
1094 assign-busses [IA-32] Always assign all PCI bus
1095 numbers ourselves, overriding
1096 whatever the firmware may have done.
1097 usepirqmask [IA-32] Honor the possible IRQ mask stored
1098 in the BIOS $PIR table. This is needed on
1099 some systems with broken BIOSes, notably
1100 some HP Pavilion N5400 and Omnibook XE3
1101 notebooks. This will have no effect if ACPI
1102 IRQ routing is enabled.
1103 noacpi [IA-32] Do not use ACPI for IRQ routing
1104 or for PCI scanning.
1105 routeirq Do IRQ routing for all PCI devices.
1106 This is normally done in pci_enable_device(),
1107 so this option is a temporary workaround
1108 for broken drivers that don't call it.
1109 firmware [ARM] Do not re-enumerate the bus but instead
1110 just use the configuration from the
1111 bootloader. This is currently used on
1112 IXP2000 systems where the bus has to be
1113 configured a certain way for adjunct CPUs.
1115 pcmv= [HW,PCMCIA] BadgePAD 4
1118 See Documentation/paride.txt.
1120 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1123 See arch/parisc/kernel/pdc_chassis.c
1126 See Documentation/paride.txt.
1129 See Documentation/paride.txt.
1131 pirq= [SMP,APIC] Manual mp-table setup
1132 See Documentation/i386/IO-APIC.txt.
1134 plip= [PPT,NET] Parallel port network link
1135 Format: { parport<nr> | timid | 0 }
1136 See also Documentation/parport.txt.
1142 { on | off | curr | res | no-curr | no-res }
1145 [ISAPNP] Exclude IRQs for the autoconfiguration
1148 [ISAPNP] Exclude DMAs for the autoconfiguration
1150 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1151 Ranges are in pairs (I/O port base and size).
1154 [ISAPNP] Exclude memory regions for the
1156 Ranges are in pairs (memory base and size).
1158 profile= [KNL] Enable kernel profiling via /proc/profile
1159 Format: [schedule,]<number>
1160 Param: "schedule" - profile schedule points.
1161 Param: <number> - step/bucket size as a power of 2 for
1162 statistical time based profiling.
1164 processor.max_cstate= [HW,ACPI]
1165 Limit processor to maximum C-state
1166 max_cstate=9 overrides any DMI blacklist limit.
1168 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1170 See Documentation/ramdisk.txt.
1172 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1173 probe for; one of (bare|imps|exps|lifebook|any).
1174 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1176 psmouse.resetafter= [HW,MOUSE]
1177 Try to reset the device after so many bad packets
1180 [HW,MOUSE] Set desired mouse resolution, in dpi.
1181 psmouse.smartscroll=
1182 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1183 0 = disabled, 1 = enabled (default).
1185 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1187 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1190 See Documentation/paride.txt.
1192 quiet= [KNL] Disable log messages
1197 See Documentation/md.txt.
1199 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1200 See Documentation/ramdisk.txt.
1202 ramdisk_blocksize= [RAM]
1203 See Documentation/ramdisk.txt.
1205 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1206 New name for the ramdisk parameter.
1207 See Documentation/ramdisk.txt.
1211 Run specified binary instead of /init from the ramdisk,
1212 used for early userspace startup. See initrd.
1214 reboot= [BUGS=IA-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1215 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1216 See arch/*/kernel/reboot.c.
1218 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1221 Specify the partition device for software suspend
1223 rhash_entries= [KNL,NET]
1224 Set number of hash buckets for route cache
1226 riscom8= [HW,SERIAL]
1227 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1229 ro [KNL] Mount root device read-only on boot
1231 root= [KNL] Root filesystem
1233 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1234 mount the root filesystem
1236 rootflags= [KNL] Set root filesystem mount option string
1238 rootfstype= [KNL] Set root filesystem type
1240 rw [KNL] Mount root device read-write on boot
1242 S [KNL] Run init in single mode
1245 See drivers/net/irda/sa1100_ir.c.
1248 Format: <io>,<irq>,<dma>,<dma2>
1250 sbni= [NET] Granch SBNI12 leased line adapter
1252 sbpcd= [HW,CD] Soundblaster CD adapter
1254 See a comment before function sbpcd_setup() in
1255 drivers/cdrom/sbpcd.c.
1257 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1258 Format: <io>[,<timeout>[,<isapnp>]]
1260 scsi_debug_*= [SCSI]
1261 See drivers/scsi/scsi_debug.c.
1263 scsi_default_dev_flags=
1264 [SCSI] SCSI default device flags
1267 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1268 Format: <vendor>:<model>:<flags>
1269 (flags are integer value)
1271 scsi_logging= [SCSI]
1273 selinux [SELINUX] Disable or enable SELinux at boot time.
1274 Format: { "0" | "1" }
1275 See security/selinux/Kconfig help text.
1278 Default value is set via kernel config option.
1279 If enabled at boot time, /selinux/disable can be used
1280 later to disable prior to initial policy load.
1282 serialnumber [BUGS=IA-32]
1284 sg_def_reserved_size= [SCSI]
1287 Format: <io>,<irq>,<dma>,<dma2>,<sgbase>
1290 Maximal number of shapers.
1293 See header of drivers/scsi/sim710.c.
1299 Format: <io>,<irq>,<dma>
1300 See header of drivers/cdrom/sjcd.c.
1305 Format: <io1>[,<io2>[,...,<io8>]]
1307 snd-ad1816a= [HW,ALSA]
1309 snd-ad1848= [HW,ALSA]
1311 snd-ali5451= [HW,ALSA]
1313 snd-als100= [HW,ALSA]
1315 snd-als4000= [HW,ALSA]
1317 snd-azt2320= [HW,ALSA]
1319 snd-cmi8330= [HW,ALSA]
1321 snd-cmipci= [HW,ALSA]
1323 snd-cs4231= [HW,ALSA]
1325 snd-cs4232= [HW,ALSA]
1327 snd-cs4236= [HW,ALSA]
1329 snd-cs4281= [HW,ALSA]
1331 snd-cs46xx= [HW,ALSA]
1333 snd-dt019x= [HW,ALSA]
1335 snd-dummy= [HW,ALSA]
1337 snd-emu10k1= [HW,ALSA]
1339 snd-ens1370= [HW,ALSA]
1341 snd-ens1371= [HW,ALSA]
1343 snd-es968= [HW,ALSA]
1345 snd-es1688= [HW,ALSA]
1347 snd-es18xx= [HW,ALSA]
1349 snd-es1938= [HW,ALSA]
1351 snd-es1968= [HW,ALSA]
1353 snd-fm801= [HW,ALSA]
1355 snd-gusclassic= [HW,ALSA]
1357 snd-gusextreme= [HW,ALSA]
1359 snd-gusmax= [HW,ALSA]
1363 snd-ice1712= [HW,ALSA]
1365 snd-intel8x0= [HW,ALSA]
1367 snd-interwave= [HW,ALSA]
1372 snd-korg1212= [HW,ALSA]
1374 snd-maestro3= [HW,ALSA]
1376 snd-mpu401= [HW,ALSA]
1378 snd-mtpav= [HW,ALSA]
1380 snd-nm256= [HW,ALSA]
1382 snd-opl3sa2= [HW,ALSA]
1390 snd-opti93x= [HW,ALSA]
1394 snd-rme32= [HW,ALSA]
1396 snd-rme96= [HW,ALSA]
1398 snd-rme9652= [HW,ALSA]
1404 snd-sbawe= [HW,ALSA]
1406 snd-serial= [HW,ALSA]
1408 snd-sgalaxy= [HW,ALSA]
1410 snd-sonicvibes= [HW,ALSA]
1415 snd-sun-cs4231= [HW,ALSA]
1417 snd-trident= [HW,ALSA]
1419 snd-usb-audio= [HW,ALSA,USB]
1421 snd-via82xx= [HW,ALSA]
1423 snd-virmidi= [HW,ALSA]
1425 snd-wavefront= [HW,ALSA]
1427 snd-ymfpci= [HW,ALSA]
1429 sonicvibes= [HW,OSS]
1433 Format: <io>[,<irq>]
1435 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1436 See Documentation/sonypi.txt
1438 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1439 See Documentation/specialix.txt.
1441 spia_io_base= [HW,MTD]
1447 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1449 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1450 See Documentation/scsi/st.txt.
1453 See header of drivers/scsi/seagate.c.
1457 Set the STI (builtin display/keyboard on the HP-PARISC
1458 machines) console (graphic card) which should be used
1459 as the initial boot-console.
1460 See also comment in drivers/video/console/sticore.c.
1463 See comment in drivers/video/console/sticore.c.
1466 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1468 swiotlb= [IA-64] Number of I/O TLB slabs
1472 sym53c416= [HW,SCSI]
1473 See header of drivers/scsi/sym53c416.c.
1476 See header of drivers/scsi/t128.c.
1480 thash_entries= [KNL,NET]
1481 Set number of hash buckets for TCP connection
1483 time Show timing data prefixed to each printk message line
1485 tipar.timeout= [HW,PPT]
1486 Set communications timeout in tenths of a second
1489 tipar.delay= [HW,PPT]
1490 Set inter-bit delay in microseconds (default 10).
1493 See header of drivers/scsi/seagate.c.
1496 See comment before function dc390_setup() in
1497 drivers/scsi/tmscsim.c.
1501 trix= [HW,OSS] MediaTrix AudioTrix Pro
1503 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1505 tsdev.xres= [TS] Horizontal screen resolution.
1506 tsdev.yres= [TS] Vertical screen resolution.
1508 turbografx.map[2|3]= [HW,JOY]
1509 TurboGraFX parallel port interface
1511 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1512 See also Documentation/input/joystick-parport.txt
1514 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1515 See header of drivers/scsi/u14-34f.c.
1524 [USBHID] The interval which mice are to be polled at.
1526 video= [FB] Frame buffer configuration
1527 See Documentation/fb/modedb.txt.
1529 vga= [BOOT,IA-32] Select a particular video mode
1530 See Documentation/i386/boot.txt and
1531 Documentation/svga.txt.
1532 Use vga=ask for menu.
1533 This is actually a boot loader parameter; the value is
1534 passed to the kernel using a special protocol.
1536 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1537 size of <nn>. This can be used to increase the
1538 minimum size (128MB on x86). It can also be used to
1539 decrease the size and leave more room for directly
1546 waveartist= [HW,OSS]
1547 Format: <io>,<irq>,<dma>,<dma2>
1550 See header of drivers/scsi/wd33c93.c.
1553 See header of drivers/scsi/wd7000.c.
1556 See Documentation/watchdog/watchdog.txt.
1558 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1559 xd_geo= See header of drivers/block/xd.c.
1561 xirc2ps_cs= [NET,PCMCIA]
1563 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1566 ______________________________________________________________________
1569 2000-06-?? Mr. Unknown
1570 The last known update (for 2.4.0) - the changelog was not kept before.
1572 2002-11-24 Petr Baudis <pasky@ucw.cz>
1573 Randy Dunlap <randy.dunlap@verizon.net>
1574 Update for 2.5.49, description for most of the options introduced,
1575 references to other documentation (C files, READMEs, ..), added S390,
1576 PPC, SPARC, MTD, ALSA and OSS category. Minor corrections and
1579 2005-10-19 Randy Dunlap <rdunlap@xenotime.net>
1580 Lots of typos, whitespace, some reformatting.
1584 Add documentation for ALSA options.
1585 Add more DRM drivers.