1July 2000		  Kernel Parameters			v2.4.0
2			  ~~~~~~~~~~~~~~~~~
3
4The following is a consolidated list of the kernel parameters as implemented
5by the __setup() macro and sorted into English Dictionary order (defined
6as ignoring all punctuation and sorting digits before letters in a case
7insensitive manner), and with descriptions where known.
8
9The text in square brackets at the beginning of the description state the
10restrictions on the kernel for the said kernel parameter to be valid. The
11restrictions referred to are that the relevant option is valid if:
12
13	ACPI    ACPI support is enabled.
14	APIC	APIC support is enabled.
15	APM 	Advanced Power Management support is enabled.
16	AX25	Appropriate AX.25 support is enabled.
17	CD	Appropriate CD support is enabled.
18	DEVFS   devfs support is enabled.
19	DRM	Direct Rendering Management support is enabled.
20	EFI	EFI Partitioning (GPT) is enabled
21	EIDE	EIDE/ATAPI support is enabled.
22	FB	The frame buffer device is enabled.
23	HW	Appropriate hardware is enabled.
24	IA-32	IA-32 aka i386 architecture is enabled.
25	IA-64	IA-64 architecture is enabled.
26	IP_PNP	IP DCHP, BOOTP, or RARP is enabled.
27	ISAPNP  ISA PnP code is enabled.
28	ISDN	Appropriate ISDN support is enabled.
29	JOY 	Appropriate joystick support is enabled.
30	LP	Printer support is enabled.
31	LOOP	Loopback device support is enabled.
32	M68k	M68k architecture is enabled.
33	MCA 	MCA bus support is enabled.
34	MDA 	MDA console support is enabled.
35	MOUSE	Appropriate mouse support is enabled.
36	NET 	Appropriate network support is enabled.
37	NFS 	Appropriate NFS support is enabled.
38	PARIDE	The ParIDE subsystem is enabled.
39	PCI 	PCI bus support is enabled.
40	PCMCIA	The PCMCIA subsystem is enabled.
41	PNP 	Plug & Play support is enabled.
42	PPT	Parallel port support is enabled.
43	PS2 	Appropriate PS/2 support is enabled.
44	RAM 	RAM disk support is enabled.
45	SCSI	Appropriate SCSI support is enabled.
46	SERIAL	Serial support is enabled.
47	SMP 	The kernel is an SMP kernel.
48	SOUND	Appropriate sound system support is enabled.
49	V4L	Video For Linux support is enabled.
50	VGA 	The VGA console has been enabled.
51	VT	Virtual terminal support is enabled.
52	XT	IBM PC/XT MFM hard disk support is enabled.
53
54In addition, the following text indicates that the option:
55
56	BUGS=	Relates to possible processor bugs on the said processor.
57	KNL 	Is a kernel start-up parameter.
58	BOOT	Is a boot loader parameter.
59
60Parameters denoted with BOOT are actually interpreted by the boot
61loader, and have no meaning to the kernel directly.
62
63Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
64a trailing = on the name of any parameter states that that parameter will
65be entered as an environment variable, whereas its absence indicates that
66it will appear as a kernel argument readable via /proc/cmdline by programs
67running once the system is up.
68
69	53c7xx=		[HW,SCSI] Amiga SCSI controllers.
70
71	acpi=		[HW,ACPI] Advanced Configuration and Power Interface
72		force	Enable ACPI if default was off
73		off	Disable ACPI if default was on
74		noirq	Do not use ACPI for IRQ routing (see pci=noacpi)
75		ht	Limit ACPI to boot-time LAPIC enumeration for HT,
76			disabling the run-time AML interpreter.
77		strict	Be less tolerant of platforms that are not
78			strictly ACPI specification compliant.
79
80	acpi_sci=	[HW,ACPI] ACPI System Control Interrupt trigger mode
81			Format: { level | edge |  high | low }
82
83	acpi_irq_balance	ACPI will balance active IRQs
84	acpi_irq_nobalance	ACPI will not move active IRQs
85	acpi_irq_pci=	If irq_balance, Clear listed IRQs for use by PCI
86	acpi_irq_isa=	If irq_balance, Mark listed IRQs used by ISA
87
88	acpi_osi=	[HW,ACPI] empty param disables _OSI
89
90	acpi_serialize	[HW,ACPI] force serialization of AML methods
91
92	ad1816=		[HW,SOUND]
93
94	ad1848=		[HW,SOUND]
95
96	adb_buttons=	[HW,MOUSE]
97
98	adlib=		[HW,SOUND]
99
100	advansys=	[HW,SCSI]
101
102	aedsp16=	[HW,SOUND]
103
104	aha152x=	[HW,SCSI]
105
106	aha1542=	[HW,SCSI]
107
108	aic7xxx=	[HW,SCSI]
109
110	AM53C974=	[HW,SCSI]
111
112	amijoy=		[HW,JOY] Amiga joystick support
113
114	apm=		[APM] Advanced Power Management.
115
116	applicom=	[HW]
117
118	arcrimi=	[HW,NET]
119
120	ataflop=	[HW,M68k]
121
122	atarimouse=	[HW,MOUSE] Atari Mouse.
123
124	atascsi=	[HW,SCSI] Atari SCSI.
125
126	awe=            [HW,SOUND]
127
128	aztcd=		[HW,CD] Aztec CD driver.
129
130	baycom_epp=	[HW,AX25]
131
132	baycom_par= 	[HW,AX25] BayCom Parallel Port AX.25 Modem.
133
134	baycom_ser_fdx=	[HW,AX25] BayCom Serial Port AX.25 Modem in Full
135			Duplex Mode.
136
137	baycom_ser_hdx=	[HW,AX25] BayCom Serial Port AX.25 Modem in Half
138			Duplex Mode.
139
140	bmouse=		[HW,MOUSE,PS2] Bus mouse.
141
142	bttv.card=	[HW,V4L] bttv (bt848 + bt878 based grabber cards), most
143	bttv.radio=	important insmod options are available as kernel args too.
144	bttv.pll=	see Documentation/video4linux/bttv/Insmod-options
145	bttv.tuner=	and Documentation/video4linux/bttv/CARDLIST
146
147	BusLogic=	[HW,SCSI]
148
149	cdu31a=		[HW,CD]
150
151	chandev=	[HW,NET]
152
153	cm206=		[HW,CD]
154
155	com20020=	[HW,NET]
156
157	com90io=	[HW,NET]
158
159	com90xx=	[HW,NET]
160
161	condev=		[HW]
162
163	console=	[KNL] output console + comm spec (speed, control,
164			parity).
165
166	cpia_pp=	[HW,PPT]
167
168	cs4232=		[HW,SOUND]
169
170	cs89x0_dma=	[HW,NET]
171
172	ctc=		[HW,NET]
173
174	cyclades=	[HW,SERIAL] Cyclades multi-serial port adapter.
175
176	dasd=		[HW,NET]
177
178	db9=		[HW,JOY]
179
180	db9_2=		[HW,JOY]
181
182	db9_3=		[HW,JOY]
183
184	debug		[KNL] Enable kernel debugging (events log level).
185
186	decnet=		[HW,NET]
187
188	devfs=          [DEVFS]
189
190	digi=		[HW,SERIAL] io parameters + enable/disable command.
191
192	digiepca=	[HW,SERIAL]
193
194	dmascc=		[HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
195			support available.
196
197	dmasound=	[HW,SOUND] (sound subsystem buffers).
198
199	dtc3181e=	[HW,SCSI]
200
201	eata=		[HW,SCSI]
202
203	eda=		[HW,PS2]
204
205	edb=		[HW,PS2]
206
207	eicon=		[HW,ISDN]
208
209	es1370=		[HW,SOUND]
210
211	es1371=		[HW,SOUND]
212
213	ether=		[HW,NET] Ethernet cards parameters (irq,
214			base_io_addr, mem_start, mem_end, name.
215			(mem_start is often overloaded to mean something
216			different and driver-specific).
217
218	fd_mcs=		[HW,SCSI]
219
220	fdomain=	[HW,SCSI]
221
222	floppy=		[HW]
223
224	ftape=		[HW] Floppy Tape subsystem debugging options.
225
226	gamma=		[HW,DRM]
227
228	gc=		[HW,JOY]
229
230	gc_2=		[HW,JOY]
231
232	gc_3=		[HW,JOY]
233
234	gdth=		[HW,SCSI]
235
236	gpt             [EFI] Forces disk with valid GPT signature but
237			invalid Protective MBR to be treated as GPT.
238
239	gscd=		[HW,CD]
240
241	gus=		[HW,SOUND]
242
243	gvp11=		[HW,SCSI]
244
245	hd= 		[EIDE] (E)IDE hard drive subsystem geometry
246			(Cyl/heads/sectors) or tune parameters.
247
248	hfmodem=	[HW,AX25]
249
250	hisax=		[HW,ISDN]
251
252	i810=		[HW,DRM]
253
254	ibmmcascsi=	[HW,MCA,SCSI] IBM MicroChannel SCSI adapter.
255
256	icn=		[HW,ISDN]
257
258	ide?=		[HW] (E)IDE subsystem : config (iomem/irq), tuning or
259			debugging (serialize,reset,no{dma,tune,probe}) or
260			chipset specific parameters.
261
262	idebus=		[HW] (E)IDE subsystem : VLB/PCI bus speed.
263
264	idle=		[HW]
265
266	in2000=		[HW,SCSI]
267
268	init=		[KNL]
269
270	initrd=		[BOOT] Specify the location of the initial ramdisk.
271
272	ip=		[IP_PNP]
273
274	isapnp=		[ISAPNP] Specify RDP, reset, pci_scan and verbosity.
275
276	isapnp_reserve_irq= [ISAPNP] Exclude IRQs for the autoconfiguration.
277
278	isapnp_reserve_dma= [ISAPNP] Exclude DMAs for the autoconfiguration.
279
280	isapnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration.
281				    Ranges are in pairs (I/O port base and size).
282
283	isapnp_reserve_mem= [ISAPNP] Exclude memory regions for the autoconfiguration.
284				     Ranges are in pairs (memory base and size).
285
286	isp16=		[HW,CD]
287
288	iucv=		[HW,NET]
289
290	js=		[HW,JOY] Analog joystick
291
292	kbd-reset	[VT]
293
294	keepinitrd	[HW, ARM]
295
296	lapic		[IA-32,APIC] Enable the local APIC even if BIOS disabled it.
297
298	load_ramdisk=	[RAM] List of ramdisks to load from floppy.
299
300	lockd.udpport=	[NFS]
301
302	lockd.tcpport=	[NFS]
303
304	logi_busmouse=	[HW, MOUSE]
305
306	lp=0		[LP]	Specify parallel ports to use, e.g,
307	lp=port[,port...]	lp=none,parport0 (lp0 not configured, lp1 uses
308	lp=reset		first parallel port). 'lp=0' disables the
309	lp=auto			printer driver. 'lp=reset' (which can be
310				specified in addition to the ports) causes
311				attached printers to be reset. Using
312				lp=port1,port2,... specifies the parallel ports
313				to associate lp devices with, starting with
314				lp0. A port specification may be 'none' to skip
315				that lp device, or a parport name such as
316				'parport0'. Specifying 'lp=auto' instead of a
317				port specification list means that device IDs
318				from each port should be examined, to see if
319				an IEEE 1284-compliant printer is attached; if
320				so, the driver will manage that printer.
321
322	ltpc=		[HW]
323
324	mac5380=	[HW,SCSI]
325
326	mac53c9x= 	[HW,SCSI]
327
328	mad16=		[HW,SOUND]
329
330	maui=		[HW,SOUND]
331
332	max_loop=[0-255] [LOOP] Set the maximum number of loopback devices
333				that can be mounted.
334
335	maxcpus=	[SMP] States the maximum number of processors that
336			an SMP kernel should make use of.
337
338	max_scsi_luns=	[SCSI]
339
340	mca-pentium	[BUGS=IA-32]
341
342	mcd=		[HW,CD]
343
344	mcdx=		[HW,CD]
345
346	md=		[HW] RAID subsystems devices and level.
347
348	mdisk=		[HW]
349
350	mdacon=		[MDA]
351
352	megaraid=	[HW,SCSI]
353
354	mem=exactmap	[KNL,BOOT,IA-32] enable setting of an exact
355			e820 memory map, as specified by the user.
356			Such mem=exactmap lines can be constructed
357			based on BIOS output or other requirements.
358
359	mem=nn[KMG]	[KNL,BOOT] force use of a specific amount of
360			memory; to be used when the kernel is not able
361			to see the whole system memory or for test.
362
363	mem=nn[KMG]@ss[KMG]
364			[KNL,BOOT] Force usage of a specific region of memory
365			Region of memory to be used, from ss to ss+nn.
366
367	mem=nn[KMG]#ss[KMG]
368			[KNL,BOOT,ACPI] Mark specific memory as ACPI data.
369			Region of memory to be used, from ss to ss+nn.
370
371	mem=nn[KMG]$ss[KMG]
372			[KNL,BOOT,ACPI] Mark specific memory as reserved.
373			Region of memory to be used, from ss to ss+nn.
374
375	memfrac=	[KNL]
376
377	mga=		[HW,DRM]
378
379	mpu401=		[HW,SOUND]
380
381	msmouse=	[HW,MOUSE] Microsoft Mouse.
382
383	ncr5380=	[HW,SCSI]
384
385	ncr53c400=	[HW,SCSI]
386
387	ncr53c400a=	[HW,SCSI]
388
389	ncr53c406a=	[HW,SCSI]
390
391	ncr53c8xx=	[HW,SCSI]
392
393	netdev=		[NET] Ethernet cards parameters (irq,
394			base_io_addr, mem_start, mem_end, name.
395			(mem_start is often overloaded to mean something
396			different and driver-specific).
397			(cf: ether=)
398
399	nfsaddrs=	[NFS]
400
401	nfsroot=	[NFS] nfs root filesystem for disk-less boxes.
402
403	nmi_watchdog=	[KNL,BUGS=IA-32] debugging features for SMP kernels.
404
405	no387		[BUGS=IA-32] Tells the kernel to use the 387 maths
406			emulation library even if a 387 maths coprocessor
407			is present.
408
409	noalign		[KNL,ARM]
410
411	noapic		[SMP,APIC] Tells the kernel not to make use of any
412			APIC that may be present on the system.
413
414	noasync		[HW, M68K] Disables async and sync negotiation for
415			all devices.
416
417	nocache		[ARM]
418
419	nodisconnect	[HW,SCSI, M68K] Disables SCSI disconnects.
420
421	nohlt		[BUGS=ARM]
422
423	no-hlt		[BUGS=IA-32] Tells the kernel that the hlt
424			instruction doesn't work correctly and not to
425			use it.
426
427	noisapnp	[ISAPNP] Disables ISA PnP code.
428
429	noinitrd	[RAM] Tells the kernel not to load any configured
430			initial RAM disk.
431
432	nointroute	[IA-64]
433
434	nokeyb		[HW] Skip console keyboard initialization for systems
435			without a console keyboard, removable keyboard, or
436			bladecenters with a USB console keyboard switch, etc.
437
438	nolapic		[IA-32,APIC] Do not enable or use the local APIC.
439
440	no-scroll	[VGA]
441
442	nosmp		[SMP] Tells an SMP kernel to act as a UP kernel.
443
444	nosync		[HW, M68K] Disables sync negotiation for all devices.
445
446	notsc           [BUGS=IA-32] Disable Time Stamp Counter
447
448	nowb		[ARM]
449
450	opl3=		[HW,SOUND]
451
452	opl3sa=		[HW,SOUND]
453
454	opl3sa2=	[HW,SOUND]
455
456	optcd=		[HW,CD]
457
458	panic=		[KNL] kernel behaviour on panic.
459
460	parport=0	[HW,PPT]	Specify parallel ports. 0 disables.
461	parport=auto			Use 'auto' to force the driver to use
462	parport=0xBBB[,IRQ[,DMA]]	any IRQ/DMA settings detected (the
463					default is to ignore detected IRQ/DMA
464					settings because of possible
465					conflicts). You can specify the base
466					address, IRQ, and DMA settings; IRQ and
467					DMA should be numbers, or 'auto' (for
468					using detected settings on that
469					particular port), or 'nofifo' (to avoid
470					using a FIFO even if it is detected).
471					Parallel ports are assigned in the
472					order they are specified on the command
473					line, starting with parport0.
474
475	pas2=		[HW,SOUND]
476
477	pas16=		[HW,SCSI]
478
479	pcbit=		[HW,ISDN]
480
481	pcd.		[PARIDE]
482
483	pci=option[,option...]		[PCI] various PCI subsystem options:
484		off			[IA-32] don't probe for the PCI bus
485		bios			[IA-32] force use of PCI BIOS, don't access
486					the hardware directly. Use this if your machine
487					has a non-standard PCI host bridge.
488		nobios			[IA-32] disallow use of PCI BIOS, only direct
489					hardware access methods are allowed. Use this
490					if you experience crashes upon bootup and you
491					suspect they are caused by the BIOS.
492		conf1			[IA-32] Force use of PCI Configuration Mechanism 1.
493		conf2			[IA-32] Force use of PCI Configuration Mechanism 2.
494		nosort			[IA-32] Don't sort PCI devices according to
495					order given by the PCI BIOS. This sorting is done
496					to get a device order compatible with older kernels.
497		biosirq			[IA-32] Use PCI BIOS calls to get the interrupt
498					routing table. These calls are known to be buggy
499					on several machines and they hang the machine when used,
500					but on other computers it's the only way to get the
501					interrupt routing table. Try this option if the kernel
502					is unable to allocate IRQs or discover secondary PCI
503					buses on your motherboard.
504		rom			[IA-32] Assign address space to expansion ROMs.
505					Use with caution as certain devices share address
506					decoders between ROMs and other resources.
507		irqmask=0xMMMM		[IA-32] Set a bit mask of IRQs allowed to be assigned
508					automatically to PCI devices. You can make the kernel
509					exclude IRQs of your ISA cards this way.
510		lastbus=N		[IA-32] Scan all buses till bus #N. Can be useful
511					if the kernel is unable to find your secondary buses
512					and you want to tell it explicitly which ones they are.
513		assign-busses		[IA-32] Always assign all PCI bus
514					numbers ourselves, overriding
515					whatever the firmware may have
516					done.
517
518	pd.		[PARIDE]
519
520	pf.		[PARIDE]
521
522	pg.		[PARIDE]
523
524	pirq=		[SMP,APIC] mp-table.
525
526	plip=		[PPT,NET] Parallel port network link.
527
528	profile=	[KNL] enable kernel profiling via /proc/profile
529			(param: profile step/bucket size as a power of 2)
530
531	prompt_ramdisk=	[RAM] List of RAM disks to prompt for floppy disk
532			before loading.
533
534	pss=		[HW,SOUND]
535
536	pt.		[PARIDE]
537
538	quiet=		[KNL] Disable log messages.
539
540	r128=		[HW,DRM]
541
542	raid=		[HW,RAID]
543
544	ramdisk=	[RAM] Sizes of RAM disks in kilobytes [deprecated].
545
546	ramdisk_blocksize=
547			[RAM]
548
549	ramdisk_size=	[RAM] New name for the ramdisk parameter.
550
551	ramdisk_start=	[RAM] Starting block of RAM disk image (so you can
552			place it after the kernel image on a boot floppy).
553
554	reboot=		[BUGS=IA-32]
555
556	reserve=	[KNL,BUGS] force the kernel to ignore some iomem area.
557
558	riscom8=	[HW,SERIAL]
559
560	ro		[KNL] Mount root device read-only on boot.
561
562	root=		[KNL] root filesystem.
563
564	rootdelay=	[KNL] Delay (in seconds) to pause before attempting to
565			mount the root filesystem
566
567	rootflags=	[KNL] set root filesystem mount option string
568
569	rootfstype=	[KNL] set root filesystem type
570
571	rw		[KNL] Mount root device read-write on boot.
572
573	S		[KNL] run init in single mode.
574
575	sb=		[HW,SOUND]
576
577	sbpcd=		[HW,CD] Soundblaster CD adapter.
578
579	scsi_logging=	[SCSI]
580
581	scsihosts=	[SCSI]
582
583	sg_def_reserved_size=
584			[SCSI]
585
586	sgalaxy=	[HW,SOUND]
587
588	sim710=		[SCSI,HW]
589
590	sjcd=		[HW,CD]
591
592	smart2=		[HW]
593
594	sonicvibes=	[HW,SOUND]
595
596	sonycd535=	[HW,CD]
597
598	sound=		[SOUND]
599
600	soundmodem=	[HW,AX25,SOUND] Use sound card as packet radio modem.
601
602	specialix=	[HW,SERIAL] Specialix multi-serial port adapter.
603
604	sscape=		[HW,SOUND]
605
606	st=		[HW,SCSI] SCSI tape parameters (buffers, etc.).
607
608	st0x=		[HW,SCSI]
609
610	stram_swap=	[HW]
611
612	swiotlb=        [IA-64] Number of I/O TLB slabs.
613
614	switches=	[HW, M68K]
615
616	sym53c416=	[HW,SCSI]
617
618	sym53c8xx=	[HW,SCSI]
619
620	t128=		[HW,SCSI]
621
622	tdfx=		[HW,DRM]
623
624	tgfx=		[HW,JOY]
625
626	tgfx_2=		[HW,JOY]
627
628	tgfx_3=		[HW,JOY]
629
630	tmc8xx=		[HW,SCSI]
631
632	tmscsim=	[HW,SCSI]
633
634	tp720=		[HW,PS2]
635
636	trix=		[HW,SOUND]
637
638	u14-34f=	[HW,SCSI]
639
640	uart401=	[HW,SOUND]
641
642	uart6850=	[HW,SOUND]
643
644	usbfix		[BUGS=IA-64]
645
646	video=		[FB] frame buffer configuration.
647
648	vga=		[BOOT] on ix386, select a particular video mode
649			(use vga=ask for menu).  This is actually a
650			boot loader parameter; the value is passed to
651			the kernel using a special protocol.  See
652			linux/Documentation/i386/boot.txt for information.
653
654	vmhalt=		[KNL,S390]
655
656	vmpoff=		[KNL,S390]
657
658	waveartist=	[HW,SOUND]
659
660	wd33c93=	[HW,SCSI]
661
662	wd7000=		[HW,SCSI]
663
664	wdt=		[HW]
665
666	xd=		[HW,XT] Original XT pre-IDE (RLL encoded) disks.
667
668	xd_geo=		[HW,XT]
669