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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
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3
4The 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
7case insensitive manner), and with descriptions where known.
8
9Module parameters for loadable modules are specified only as the
10parameter name with optional '=' and value as appropriate, such as:
11
12 modprobe usbcore blinkenlights=1
13
14Module parameters for modules that are built into the kernel image
15are specified on the kernel command line with the module name plus
16'.' plus parameter name, with '=' and value if appropriate, such as:
17
18 usbcore.blinkenlights=1
19
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20This document may not be entirely up to date and comprehensive. The command
21"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22module. Loadable modules, after being loaded into the running kernel, also
23reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24parameters may be changed at runtime by the command
25"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
26
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27The parameters listed below are only valid if certain kernel build options were
28enabled and if respective hardware is present. The text in square brackets at
29the beginning of each description states the restrictions within which a
30parameter is applicable:
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31
32 ACPI ACPI support is enabled.
c99c108a 33 AGP AGP (Accelerated Graphics Port) is enabled.
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34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
e7ba176b 37 AVR32 AVR32 architecture is enabled.
1da177e4 38 AX25 Appropriate AX.25 support is enabled.
0ae53640 39 BLACKFIN Blackfin architecture is enabled.
a9913044 40 DRM Direct Rendering Management support is enabled.
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41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
42 EFI EFI Partitioning (GPT) is enabled
43 EIDE EIDE/ATAPI support is enabled.
44 FB The frame buffer device is enabled.
45 HW Appropriate hardware is enabled.
1da177e4 46 IA-64 IA-64 architecture is enabled.
6146f0d5 47 IMA Integrity measurement architecture is enabled.
1da177e4 48 IOSCHED More than one I/O scheduler is enabled.
41e2e8be 49 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
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50 ISAPNP ISA PnP code is enabled.
51 ISDN Appropriate ISDN support is enabled.
52 JOY Appropriate joystick support is enabled.
11ef697b 53 LIBATA Libata driver is enabled
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54 LP Printer support is enabled.
55 LOOP Loopback device support is enabled.
56 M68k M68k architecture is enabled.
57 These options have more detailed description inside of
58 Documentation/m68k/kernel-options.txt.
59 MCA MCA bus support is enabled.
60 MDA MDA console support is enabled.
61 MOUSE Appropriate mouse support is enabled.
309e57df 62 MSI Message Signaled Interrupts (PCI).
c8facbb6 63 MTD MTD (Memory Technology Device) support is enabled.
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64 NET Appropriate network support is enabled.
65 NUMA NUMA support is enabled.
734efb46 66 GENERIC_TIME The generic timeofday code is enabled.
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67 NFS Appropriate NFS support is enabled.
68 OSS OSS sound support is enabled.
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69 PV_OPS A paravirtualized kernel is enabled.
70 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
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71 PARISC The PA-RISC architecture is enabled.
72 PCI PCI bus support is enabled.
7f785763 73 PCIE PCI Express support is enabled.
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74 PCMCIA The PCMCIA subsystem is enabled.
75 PNP Plug & Play support is enabled.
76 PPC PowerPC architecture is enabled.
77 PPT Parallel port support is enabled.
78 PS2 Appropriate PS/2 support is enabled.
79 RAM RAM disk support is enabled.
20510f2f 80 ROOTPLUG The example Root Plug LSM is enabled.
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81 S390 S390 architecture is enabled.
82 SCSI Appropriate SCSI support is enabled.
83 A lot of drivers has their options described inside of
84 Documentation/scsi/.
20510f2f 85 SECURITY Different security models are enabled.
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86 SELINUX SELinux support is enabled.
87 SERIAL Serial support is enabled.
e523d93c 88 SH SuperH architecture is enabled.
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89 SMP The kernel is an SMP kernel.
90 SPARC Sparc architecture is enabled.
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91 SWSUSP Software suspend (hibernation) is enabled.
92 SUSPEND System suspend states are enabled.
f38f1d2a 93 FTRACE Function tracing enabled.
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94 TS Appropriate touchscreen support is enabled.
95 USB USB support is enabled.
96 USBHID USB Human Interface Device support is enabled.
97 V4L Video For Linux support is enabled.
98 VGA The VGA console has been enabled.
99 VT Virtual terminal support is enabled.
100 WDT Watchdog support is enabled.
101 XT IBM PC/XT MFM hard disk support is enabled.
cd4f0ef7 102 X86-32 X86-32, aka i386 architecture is enabled.
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103 X86-64 X86-64 architecture is enabled.
104 More X86-64 boot options can be found in
71cced6e 105 Documentation/x86/x86_64/boot-options.txt .
c0115606 106 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
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107
108In addition, the following text indicates that the option:
109
110 BUGS= Relates to possible processor bugs on the said processor.
111 KNL Is a kernel start-up parameter.
112 BOOT Is a boot loader parameter.
113
114Parameters denoted with BOOT are actually interpreted by the boot
115loader, and have no meaning to the kernel directly.
116Do not modify the syntax of boot loader parameters without extreme
71cced6e 117need or coordination with <Documentation/x86/i386/boot.txt>.
1da177e4 118
5558870b 119There are also arch-specific kernel-parameters not documented here.
71cced6e 120See for example <Documentation/x86/x86_64/boot-options.txt>.
5558870b 121
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122Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
123a trailing = on the name of any parameter states that that parameter will
124be entered as an environment variable, whereas its absence indicates that
125it will appear as a kernel argument readable via /proc/cmdline by programs
126running once the system is up.
127
9c4751fd 128The number of kernel parameters is not limited, but the length of the
129complete command line (parameters including spaces etc.) is limited to
130a fixed number of characters. This limit depends on the architecture
131and is between 256 and 4096 characters. It is defined in the file
132./include/asm/setup.h as COMMAND_LINE_SIZE.
133
134
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135 acpi= [HW,ACPI,X86-64,i386]
136 Advanced Configuration and Power Interface
a9913044 137 Format: { force | off | ht | strict | noirq }
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138 force -- enable ACPI if default was off
139 off -- disable ACPI if default was on
140 noirq -- do not use ACPI for IRQ routing
141 ht -- run only enough ACPI to enable Hyper Threading
a9913044 142 strict -- Be less tolerant of platforms that are not
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143 strictly ACPI specification compliant.
144
53471121 145 See also Documentation/power/pm.txt, pci=noacpi
1da177e4 146
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147 acpi_apic_instance= [ACPI, IOAPIC]
148 Format: <int>
149 2: use 2nd APIC table, if available
150 1,0: use 1st APIC table
4e381a4f 151 default: 0
a1fdcc0d 152
1da177e4 153 acpi_sleep= [HW,ACPI] Sleep options
bdfe6b7c 154 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, old_ordering }
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155 See Documentation/power/video.txt for s3_bios and s3_mode.
156 s3_beep is for debugging; it makes the PC's speaker beep
157 as soon as the kernel's real-mode entry point is called.
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158 s4_nohwsig prevents ACPI hardware signature from being
159 used during resume from hibernation.
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160 old_ordering causes the ACPI 1.0 ordering of the _PTS
161 control method, wrt putting devices into low power
162 states, to be enforced (the ACPI 2.0 ordering of _PTS is
163 used by default).
a9913044 164
1da177e4 165 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
a9913044 166 Format: { level | edge | high | low }
1da177e4 167
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168 acpi_irq_balance [HW,ACPI]
169 ACPI will balance active IRQs
170 default in APIC mode
1da177e4 171
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172 acpi_irq_nobalance [HW,ACPI]
173 ACPI will not move active IRQs (default)
174 default in PIC mode
1da177e4 175
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176 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
177 use by PCI
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178 Format: <irq>,<irq>...
179
a9913044 180 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
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181 Format: <irq>,<irq>...
182
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183 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
184
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185 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
186 Format: To spoof as Windows 98: ="Microsoft Windows"
187
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188 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
189 acpi_osi="string1" # add string1 -- only one string
190 acpi_osi="!string2" # remove built-in string2
191 acpi_osi= # disable all strings
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192
193 acpi_serialize [HW,ACPI] force serialization of AML methods
194
195 acpi_skip_timer_override [HW,ACPI]
196 Recognize and ignore IRQ0/pin2 Interrupt Override.
197 For broken nForce2 BIOS resulting in XT-PIC timer.
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198 acpi_use_timer_override [HW,ACPI}
199 Use timer override. For some broken Nvidia NF5 boards
200 that require a timer override, but don't have
201 HPET
1da177e4 202
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203 acpi_backlight= [HW,ACPI]
204 acpi_backlight=vendor
205 acpi_backlight=video
206 If set to vendor, prefer vendor specific driver
207 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
208 of the ACPI video.ko driver.
209
210 acpi_display_output= [HW,ACPI]
211 acpi_display_output=vendor
212 acpi_display_output=video
213 See above.
214
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215 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
216 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
1da177e4 217 Format: <int>
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218 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
219 debug output. Bits in debug_layer correspond to a
220 _COMPONENT in an ACPI source file, e.g.,
221 #define _COMPONENT ACPI_PCI_COMPONENT
222 Bits in debug_level correspond to a level in
223 ACPI_DEBUG_PRINT statements, e.g.,
224 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
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225 The debug_level mask defaults to "info". See
226 Documentation/acpi/debug.txt for more information about
227 debug layers and levels.
a0d84a92 228
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229 Enable processor driver info messages:
230 acpi.debug_layer=0x20000000
231 Enable PCI/PCI interrupt routing info messages:
232 acpi.debug_layer=0x400000
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233 Enable AML "Debug" output, i.e., stores to the Debug
234 object while interpreting AML:
235 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
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236 Enable all messages related to ACPI hardware:
237 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
238
239 Some values produce so much output that the system is
240 unusable. The "log_buf_len" parameter may be useful
241 if you need to capture more output.
f989106c 242
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243 acpi.power_nocheck= [HW,ACPI]
244 Format: 1/0 enable/disable the check of power state.
245 On some bogus BIOS the _PSC object/_STA object of
246 power resource can't return the correct device power
247 state. In such case it is unneccessary to check its
248 power state again in power transition.
249 1 : disable the power state check
250
cd4f0ef7 251 acpi_pm_good [X86-32,X86-64]
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252 Override the pmtimer bug detection: force the kernel
253 to assume that this machine's pmtimer latches its value
254 and always returns good values.
255
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256 agp= [AGP]
257 { off | try_unsupported }
258 off: disable AGP support
259 try_unsupported: try to drive unsupported chipsets
260 (may crash computer or cause data corruption)
261
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262 enable_timer_pin_1 [i386,x86-64]
263 Enable PIN 1 of APIC timer
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264 Can be useful to work around chipset bugs
265 (in particular on some ATI chipsets).
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266 The kernel tries to set a reasonable default.
267
268 disable_timer_pin_1 [i386,x86-64]
269 Disable PIN 1 of APIC timer
270 Can be useful to work around chipset bugs.
271
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272 ad1848= [HW,OSS]
273 Format: <io>,<irq>,<dma>,<dma2>,<type>
274
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275 advansys= [HW,SCSI]
276 See header of drivers/scsi/advansys.c.
277
278 advwdt= [HW,WDT] Advantech WDT
279 Format: <iostart>,<iostop>
280
281 aedsp16= [HW,OSS] Audio Excel DSP 16
282 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
283 See also header of sound/oss/aedsp16.c.
a9913044 284
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285 aha152x= [HW,SCSI]
286 See Documentation/scsi/aha152x.txt.
287
288 aha1542= [HW,SCSI]
289 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
290
291 aic7xxx= [HW,SCSI]
292 See Documentation/scsi/aic7xxx.txt.
293
294 aic79xx= [HW,SCSI]
295 See Documentation/scsi/aic79xx.txt.
296
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297 amd_iommu= [HW,X86-84]
298 Pass parameters to the AMD IOMMU driver in the system.
299 Possible values are:
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300 isolate - enable device isolation (each device, as far
301 as possible, will get its own protection
3ce1f93c 302 domain) [default]
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303 share - put every device behind one IOMMU into the
304 same protection domain
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305 fullflush - enable flushing of IO/TLB entries when
306 they are unmapped. Otherwise they are
307 flushed before they will be reused, which
308 is a lot of faster
309
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310 amd_iommu_size= [HW,X86-64]
311 Define the size of the aperture for the AMD IOMMU
312 driver. Possible values are:
313 '32M', '64M' (default), '128M', '256M', '512M', '1G'
314
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315 amijoy.map= [HW,JOY] Amiga joystick support
316 Map of devices attached to JOY0DAT and JOY1DAT
317 Format: <a>,<b>
318 See also Documentation/kernel/input/joystick.txt
319
320 analog.map= [HW,JOY] Analog joystick and gamepad support
321 Specifies type or capabilities of an analog joystick
322 connected to one of 16 gameports
323 Format: <type1>,<type2>,..<type16>
324
a9913044
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325 apc= [HW,SPARC]
326 Power management functions (SPARCstation-4/5 + deriv.)
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327 Format: noidle
328 Disable APC CPU standby support. SPARCstation-Fox does
329 not play well with APC CPU idle - disable it if you have
330 APC and your system crashes randomly.
331
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332 apic= [APIC,i386] Advanced Programmable Interrupt Controller
333 Change the output verbosity whilst booting
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334 Format: { quiet (default) | verbose | debug }
335 Change the amount of debugging information output
336 when initialising the APIC and IO-APIC components.
a9913044 337
1da177e4 338 apm= [APM] Advanced Power Management
71f77055 339 See header of arch/x86/kernel/apm_32.c.
1da177e4 340
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LT
341 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
342 Format: <io>,<irq>,<nodeID>
343
344 ataflop= [HW,M68k]
345
346 atarimouse= [HW,MOUSE] Atari Mouse
347
348 atascsi= [HW,SCSI] Atari SCSI
349
350 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
351 EzKey and similar keyboards
352
353 atkbd.reset= [HW] Reset keyboard during initialization
354
a9913044
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355 atkbd.set= [HW] Select keyboard code set
356 Format: <int> (2 = AT (default), 3 = PS/2)
1da177e4
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357
358 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
359 keyboards
360
361 atkbd.softraw= [HW] Choose between synthetic and real raw mode
362 Format: <bool> (0 = real, 1 = synthetic (default))
a9913044
RD
363
364 atkbd.softrepeat= [HW]
365 Use software keyboard repeat
1da177e4
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366
367 autotest [IA64]
368
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369 baycom_epp= [HW,AX25]
370 Format: <io>,<mode>
a9913044 371
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372 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
373 Format: <io>,<mode>
374 See header of drivers/net/hamradio/baycom_par.c.
375
a9913044
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376 baycom_ser_fdx= [HW,AX25]
377 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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378 Format: <io>,<irq>,<mode>[,<baud>]
379 See header of drivers/net/hamradio/baycom_ser_fdx.c.
380
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381 baycom_ser_hdx= [HW,AX25]
382 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
1da177e4
LT
383 Format: <io>,<irq>,<mode>
384 See header of drivers/net/hamradio/baycom_ser_hdx.c.
385
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RD
386 boot_delay= Milliseconds to delay each printk during boot.
387 Values larger than 10 seconds (10000) are changed to
388 no delay (0).
389 Format: integer
390
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AH
391 bootmem_debug [KNL] Enable bootmem allocator debug messages.
392
1da177e4 393 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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394 bttv.radio= Most important insmod options are available as
395 kernel args too.
1da177e4
LT
396 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
397 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
398
399 BusLogic= [HW,SCSI]
400 See drivers/scsi/BusLogic.c, comment before function
401 BusLogic_ParseDriverOptions().
402
403 c101= [NET] Moxa C101 synchronous serial card
404
cd4f0ef7 405 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
1da177e4
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406 Sometimes CPU hardware bugs make them report the cache
407 size incorrectly. The kernel will attempt work arounds
408 to fix known problems, but for some CPUs it is not
409 possible to determine what the correct size should be.
410 This option provides an override for these situations.
411
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AD
412 security= [SECURITY] Choose a security module to enable at boot.
413 If this boot parameter is not specified, only the first
414 security module asking for security registration will be
415 loaded. An invalid security module name will be treated
416 as if no module has been chosen.
417
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JM
418 capability.disable=
419 [SECURITY] Disable capabilities. This would normally
420 be used only if an alternative security model is to be
421 configured. Potentially dangerous and should only be
422 used if you are entirely sure of the consequences.
423
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SO
424 ccw_timeout_log [S390]
425 See Documentation/s390/CommonIO for details.
1da177e4 426
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PM
427 cgroup_disable= [KNL] Disable a particular controller
428 Format: {name of the controller(s) to disable}
429 {Currently supported controllers - "memory"}
430
1da177e4
LT
431 checkreqprot [SELINUX] Set initial checkreqprot flag value.
432 Format: { "0" | "1" }
433 See security/selinux/Kconfig help text.
a9913044
RD
434 0 -- check protection applied by kernel (includes
435 any implied execute protection).
1da177e4
LT
436 1 -- check protection requested by application.
437 Default value is set via a kernel config option.
a9913044
RD
438 Value can be changed at runtime via
439 /selinux/checkreqprot.
440
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SO
441 cio_ignore= [S390]
442 See Documentation/s390/CommonIO for details.
443
cd4f0ef7 444 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 445 [Deprecated]
3f6dee9b 446 Forces specified clocksource (if available) to be used
734efb46 447 when calculating gettimeofday(). If specified
3f6dee9b 448 clocksource is not available, it defaults to PIT.
1da177e4
LT
449 Format: { pit | tsc | cyclone | pmtmr }
450
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RD
451 clocksource= [GENERIC_TIME] Override the default clocksource
452 Format: <string>
453 Override the default clocksource and use the clocksource
454 with the name specified.
455 Some clocksource names to choose from, depending on
456 the platform:
457 [all] jiffies (this is the base, fallback clocksource)
458 [ACPI] acpi_pm
459 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
460 pxa_timer,timer3,32k_counter,timer0_1
461 [AVR32] avr32
cd4f0ef7 462 [X86-32] pit,hpet,tsc,vmi-timer;
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RD
463 scx200_hrt on Geode; cyclone on IBM x440
464 [MIPS] MIPS
465 [PARISC] cr16
466 [S390] tod
467 [SH] SuperH
468 [SPARC64] tick
469 [X86-64] hpet,tsc
470
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471 clearcpuid=BITNUM [X86]
472 Disable CPUID feature X for the kernel. See
473 include/asm-x86/cpufeature.h for the valid bit numbers.
474 Note the Linux specific bits are not necessarily
475 stable over kernel options, but the vendor specific
476 ones should be.
477 Also note that user programs calling CPUID directly
478 or using the feature without checking anything
479 will still see it. This just prevents it from
480 being used by the kernel or shown in /proc/cpuinfo.
481 Also note the kernel might malfunction if you disable
482 some critical bits.
483
a25bd949
AV
484 code_bytes [IA32/X86_64] How many bytes of object code to print
485 in an oops report.
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CE
486 Range: 0 - 8192
487 Default: 64
488
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TG
489 hpet= [X86-32,HPET] option to control HPET usage
490 Format: { enable (default) | disable | force }
491 disable: disable HPET and use PIT instead
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CC
492 force: allow force enabled of undocumented chips (ICH4,
493 VIA, nVidia)
1da177e4 494
1da177e4 495 com20020= [HW,NET] ARCnet - COM20020 chipset
a9913044
RD
496 Format:
497 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
1da177e4
LT
498
499 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
500 Format: <io>[,<irq>]
501
a9913044
RD
502 com90xx= [HW,NET]
503 ARCnet - COM90xx chipset (memory-mapped buffers)
1da177e4
LT
504 Format: <io>[,<irq>[,<memstart>]]
505
506 condev= [HW,S390] console device
507 conmode=
a9913044 508
1da177e4
LT
509 console= [KNL] Output console device and options.
510
511 tty<n> Use the virtual console device <n>.
512
513 ttyS<n>[,options]
f1a1c2dc 514 ttyUSB0[,options]
1da177e4 515 Use the specified serial port. The options are of
f1a1c2dc
RD
516 the form "bbbbpnf", where "bbbb" is the baud rate,
517 "p" is parity ("n", "o", or "e"), "n" is number of
518 bits, and "f" is flow control ("r" for RTS or
519 omit it). Default is "9600n8".
520
521 See Documentation/serial-console.txt for more
522 information. See
523 Documentation/networking/netconsole.txt for an
524 alternative.
1da177e4 525
18a8bd94
YL
526 uart[8250],io,<addr>[,options]
527 uart[8250],mmio,<addr>[,options]
1da177e4
LT
528 Start an early, polled-mode console on the 8250/16550
529 UART at the specified I/O port or MMIO address,
530 switching to the matching ttyS device later. The
531 options are the same as for ttyS, above.
532
f7511d5f
ST
533 If the device connected to the port is not a TTY but a braille
534 device, prepend "brl," before the device type, for instance
535 console=brl,ttyS0
536 For now, only VisioBraille is supported.
537
18a8bd94
YL
538 earlycon= [KNL] Output early console device and options.
539 uart[8250],io,<addr>[,options]
540 uart[8250],mmio,<addr>[,options]
541 Start an early, polled-mode console on the 8250/16550
542 UART at the specified I/O port or MMIO address.
543 The options are the same as for ttyS, above.
544
8f4ce8c3
AS
545 no_console_suspend
546 [HW] Never suspend the console
547 Disable suspending of consoles during suspend and
548 hibernate operations. Once disabled, debugging
549 messages can reach various consoles while the rest
550 of the system is being put to sleep (ie, while
551 debugging driver suspend/resume hooks). This may
552 not work reliably with all consoles, but is known
553 to work with serial and VGA consoles.
554
1da177e4 555 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
a9913044
RD
556 Format:
557 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 558
dc009d92
EB
559 crashkernel=nn[KMG]@ss[KMG]
560 [KNL] Reserve a chunk of physical memory to
561 hold a kernel to switch to with kexec on panic.
562
fb391599
BW
563 crashkernel=range1:size1[,range2:size2,...][@offset]
564 [KNL] Same as above, but depends on the memory
565 in the running system. The syntax of range is
566 start-[end] where start and end are both
567 a memory unit (amount[KMG]). See also
568 Documentation/kdump/kdump.txt for a example.
569
1da177e4
LT
570 cs4232= [HW,OSS]
571 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
572
573 cs89x0_dma= [HW,NET]
574 Format: <dma>
575
576 cs89x0_media= [HW,NET]
577 Format: { rj45 | aui | bnc }
a9913044 578
a9913044 579 dasd= [HW,NET]
1da177e4
LT
580 See header of drivers/s390/block/dasd_devmap.c.
581
582 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
583 (one device per port)
584 Format: <port#>,<type>
585 See also Documentation/input/joystick-parport.txt
586
587 debug [KNL] Enable kernel debugging (events log level).
588
cae2ed9a
IM
589 debug_locks_verbose=
590 [KNL] verbose self-tests
591 Format=<0|1>
592 Print debugging info while doing the locking API
593 self-tests.
594 We default to 0 (no extra messages), setting it to
595 1 will print _a lot_ more information - normally
596 only useful to kernel developers.
597
3ac7fe5a
TG
598 debug_objects [KNL] Enable object debugging
599
d3af01f1
TG
600 debugpat [X86] Enable PAT debugging
601
2d27a966 602 decnet.addr= [HW,NET]
1da177e4
LT
603 Format: <area>[,<node>]
604 See also Documentation/networking/decnet.txt.
605
ecb77fa9 606 vt.default_blu= [VT]
55ff9780
AD
607 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
608 Change the default blue palette of the console.
609 This is a 16-member array composed of values
610 ranging from 0-255.
611
ecb77fa9 612 vt.default_grn= [VT]
55ff9780
AD
613 Format: <green0>,<green1>,<green2>,...,<green15>
614 Change the default green palette of the console.
615 This is a 16-member array composed of values
616 ranging from 0-255.
617
ecb77fa9 618 vt.default_red= [VT]
55ff9780
AD
619 Format: <red0>,<red1>,<red2>,...,<red15>
620 Change the default red palette of the console.
621 This is a 16-member array composed of values
622 ranging from 0-255.
623
ecb77fa9
ST
624 vt.default_utf8=
625 [VT]
55ff9780
AD
626 Format=<0|1>
627 Set system-wide default UTF-8 mode for all tty's.
ecb77fa9
ST
628 Default is 1, i.e. UTF-8 mode is enabled for all
629 newly opened terminals.
55ff9780 630
1da177e4
LT
631 dhash_entries= [KNL]
632 Set number of hash buckets for dentry cache.
a9913044 633
1da177e4
LT
634 digi= [HW,SERIAL]
635 IO parameters + enable/disable command.
636
637 digiepca= [HW,SERIAL]
638 See drivers/char/README.epca and
31c00fc1 639 Documentation/serial/digiepca.txt.
1da177e4 640
95ffa243
YL
641 disable_mtrr_cleanup [X86]
642 enable_mtrr_cleanup [X86]
643 The kernel tries to adjust MTRR layout from continuous
644 to discrete, to make X server driver able to add WB
645 entry later. This parameter enables/disables that.
646
647 mtrr_chunk_size=nn[KMG] [X86]
648 used for mtrr cleanup. It is largest continous chunk
649 that could hold holes aka. UC entries.
650
651 mtrr_gran_size=nn[KMG] [X86]
12031a62
YL
652 Used for mtrr cleanup. It is granularity of mtrr block.
653 Default is 1.
654 Large value could prevent small alignment from
655 using up MTRRs.
656
657 mtrr_spare_reg_nr=n [X86]
658 Format: <integer>
659 Range: 0,7 : spare reg number
660 Default : 1
661 Used for mtrr cleanup. It is spare mtrr entries number.
662 Set to 2 or more if your graphical card needs more.
95ffa243 663
093af8d7 664 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
665 By default the kernel will trim any uncacheable
666 memory out of your available memory pool based on
667 MTRR settings. This parameter disables that behavior,
668 possibly causing your machine to run very slowly.
669
1da177e4
LT
670 dmasound= [HW,OSS] Sound subsystem buffers
671
672 dscc4.setup= [NET]
673
674 dtc3181e= [HW,SCSI]
675
0ae53640 676 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
1da177e4
LT
677 earlyprintk=vga
678 earlyprintk=serial[,ttySn[,baudrate]]
5c05917e 679 earlyprintk=dbgp
1da177e4 680
a9913044 681 Append ",keep" to not disable it when the real console
1da177e4
LT
682 takes over.
683
5c05917e 684 Only vga or serial or usb debug port at a time.
1da177e4
LT
685
686 Currently only ttyS0 and ttyS1 are supported.
687
688 Interaction with the standard serial driver is not
689 very good.
690
691 The VGA output is eventually overwritten by the real
692 console.
693
694 eata= [HW,SCSI]
695
1da177e4 696 edd= [EDD]
8c4dd606 697 Format: {"off" | "on" | "skip[mbr]"}
1da177e4 698
1da177e4
LT
699 eisa_irq_edge= [PARISC,HW]
700 See header of drivers/parisc/eisa.c.
701
cd4f0ef7 702 elanfreq= [X86-32]
1da177e4 703 See comment before function elanfreq_setup() in
71f77055 704 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1da177e4
LT
705
706 elevator= [IOSCHED]
16ab3adf 707 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
708 See Documentation/block/as-iosched.txt and
709 Documentation/block/deadline-iosched.txt for details.
710
e515a0d6 711 elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
a9913044 712 Specifies physical address of start of kernel core
aac04b32
VG
713 image elf header. Generally kexec loader will
714 pass this option to capture kernel.
715 See Documentation/kdump/kdump.txt for details.
1da177e4
LT
716
717 enforcing [SELINUX] Set initial enforcing status.
718 Format: {"0" | "1"}
719 See security/selinux/Kconfig help text.
720 0 -- permissive (log only, no denials).
721 1 -- enforcing (deny and log).
722 Default value is 0.
723 Value can be changed at runtime via /selinux/enforce.
724
1da177e4
LT
725 es1371= [HW,OSS]
726 Format: <spdif>,[<nomix>,[<amplifier>]]
727 See also header of sound/oss/es1371.c.
a9913044 728
1da177e4
LT
729 ether= [HW,NET] Ethernet cards parameters
730 This option is obsoleted by the "netdev=" option, which
731 has equivalent usage. See its documentation for details.
732
733 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
734 Format: <io>[,<irq>]
735
de1ba09b
AM
736 failslab=
737 fail_page_alloc=
738 fail_make_request=[KNL]
739 General fault injection mechanism.
740 Format: <interval>,<probability>,<space>,<times>
741 See also /Documentation/fault-injection/.
742
1da177e4
LT
743 fd_mcs= [HW,SCSI]
744 See header of drivers/scsi/fd_mcs.c.
745
746 fdomain= [HW,SCSI]
747 See header of drivers/scsi/fdomain.c.
748
749 floppy= [HW]
31c00fc1 750 See Documentation/blockdev/floppy.txt.
1da177e4 751
f13ae30e
AC
752 force_pal_cache_flush
753 [IA-64] Avoid check_sal_cache_flush which may hang on
754 buggy SAL_CACHE_FLUSH implementations. Using this
755 parameter will force ia64_sal_cache_flush to call
756 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
757
d9e54076
PZ
758 ftrace=[tracer]
759 [ftrace] will set and start the specified tracer
760 as early as possible in order to facilitate early
761 boot debugging.
762
763 ftrace_dump_on_oops
764 [ftrace] will dump the trace buffers on oops.
765
1da177e4
LT
766 gamecon.map[2|3]=
767 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
768 support via parallel port (up to 5 devices per port)
769 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
770 See also Documentation/input/joystick-parport.txt
771
772 gamma= [HW,DRM]
773
aaf23042
YL
774 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
775 Format: off | on
776 default: on
777
1da177e4
LT
778 gdth= [HW,SCSI]
779 See header of drivers/scsi/gdth.c.
780
781 gpt [EFI] Forces disk with valid GPT signature but
782 invalid Protective MBR to be treated as GPT.
783
1da177e4
LT
784 gvp11= [HW,SCSI]
785
786 hashdist= [KNL,NUMA] Large hashes allocated during boot
787 are distributed across NUMA nodes. Defaults on
788 for IA-64, off otherwise.
a9913044 789 Format: 0 | 1 (for off | on)
1da177e4
LT
790
791 hcl= [IA-64] SGI's Hardware Graph compatibility layer
792
793 hd= [EIDE] (E)IDE hard drive subsystem geometry
794 Format: <cyl>,<head>,<sect>
795
1da177e4
LT
796 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
797 size of <nn>. This works even on boxes that have no
798 highmem otherwise. This also works to reduce highmem
799 size on bigger boxes.
800
54cdfdb4
TG
801 highres= [KNL] Enable/disable high resolution timer mode.
802 Valid parameters: "on", "off"
803 Default: "on"
804
1da177e4
LT
805 hisax= [HW,ISDN]
806 See Documentation/isdn/README.HiSax.
807
b4718e62
AK
808 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
809 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
0d9ea754
JT
810 On x86-64 and powerpc, this option can be specified
811 multiple times interleaved with hugepages= to reserve
812 huge pages of different sizes. Valid pages sizes on
813 x86-64 are 2M (when the CPU supports "pse") and 1G
814 (when the CPU supports the "pdpe1gb" cpuinfo flag)
b4718e62
AK
815 Note that 1GB pages can only be allocated at boot time
816 using hugepages= and not freed afterwards.
e11bfbfc
NP
817 default_hugepagesz=
818 [same as hugepagesz=] The size of the default
819 HugeTLB page size. This is the size represented by
820 the legacy /proc/ hugepages APIs, used for SHM, and
821 default size when mounting hugetlbfs filesystems.
822 Defaults to the default architecture's huge page size
823 if not specified.
1da177e4 824
6902aa84
PM
825 hlt [BUGS=ARM,SH]
826
cef7125d
HB
827 hvc_iucv= [S390] Number of z/VM IUCV Hypervisor console (HVC)
828 back-ends. Valid parameters: 0..8
829
36d95739 830 i8042.debug [HW] Toggle i8042 debug mode
1da177e4 831 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
832 i8042.dumbkbd [HW] Pretend that controller can only read data from
833 keyboard and cannot control its state
1da177e4
LT
834 (Don't attempt to blink the leds)
835 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 836 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
837 i8042.noloop [HW] Disable the AUX Loopback command while probing
838 for the AUX port
1da177e4
LT
839 i8042.nomux [HW] Don't check presence of an active multiplexing
840 controller
841 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
842 controllers
843 i8042.panicblink=
844 [HW] Frequency with which keyboard LEDs should blink
845 when kernel panics (default is 0.5 sec)
846 i8042.reset [HW] Reset the controller during init and cleanup
847 i8042.unlock [HW] Unlock (ignore) the keylock
848
849 i810= [HW,DRM]
850
e70c9d5e
DT
851 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
852 indicates that the driver is running on unsupported
853 hardware.
1da177e4
LT
854 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
855 does not match list of supported models.
856 i8k.power_status
857 [HW] Report power status in /proc/i8k
858 (disabled by default)
859 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
860 capability is set.
861
862 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
863 See Documentation/mca.txt.
864
865 icn= [HW,ISDN]
866 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
867
868 ide= [HW] (E)IDE subsystem
a594eeb1 869 Format: ide=nodma or ide=doubler
1c10e938 870 See Documentation/ide/ide.txt.
1da177e4 871
1da177e4 872 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
1c10e938 873 See Documentation/ide/ide.txt.
1da177e4 874
f039b754 875 idle= [X86]
da5e09a1 876 Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
f039b754
AK
877 Poll forces a polling idle loop that can slightly improves the performance
878 of waking up a idle CPU, but will use a lot of power and make the system
879 run hot. Not recommended.
880 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
881 to not use it because it doesn't save as much power as a normal idle
882 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
883 as idle=poll.
c1e3b377
ZY
884 idle=halt. Halt is forced to be used for CPU idle.
885 In such case C2/C3 won't be used again.
da5e09a1 886 idle=nomwait. Disable mwait for CPU C-states
a9913044 887
594765a7
DC
888 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
889 Claim all unknown PCI IDE storage controllers.
890
79290822
IM
891 ignore_loglevel [KNL]
892 Ignore loglevel setting - this will print /all/
893 kernel messages to the console. Useful for debugging.
894
1da177e4
LT
895 ihash_entries= [KNL]
896 Set number of hash buckets for inode cache.
897
898 in2000= [HW,SCSI]
899 See header of drivers/scsi/in2000.c.
900
901 init= [KNL]
902 Format: <full_path>
903 Run specified binary instead of /sbin/init as init
904 process.
905
906 initcall_debug [KNL] Trace initcalls as they are executed. Useful
907 for working out where the kernel is dying during
908 startup.
909
910 initrd= [BOOT] Specify the location of the initial ramdisk
911
912 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
913 Format: <irq>
914
915 inttest= [IA64]
916
b552da87
PM
917 iommu= [x86]
918 off
919 force
920 noforce
921 biomerge
922 panic
923 nopanic
924 merge
925 nomerge
926 forcesac
927 soft
928
929
ba395927
KA
930 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
931 off
932 Disable intel iommu driver.
933 igfx_off [Default Off]
934 By default, gfx is mapped as normal device. If a gfx
935 device has a dedicated DMAR unit, the DMAR unit is
936 bypassed by not enabling DMAR with this option. In
937 this case, gfx device will use physical address for
938 DMA.
7d3b03ce
KA
939 forcedac [x86_64]
940 With this option iommu will not optimize to look
941 for io virtual address below 32 bit forcing dual
942 address cycle on pci bus for cards supporting greater
943 than 32 bit addressing. The default is to look
944 for translation below 32 bit and if not available
945 then look in the higher range.
5e0d2a6f 946 strict [Default Off]
947 With this option on every unmap_single operation will
948 result in a hardware IOTLB flush operation as opposed
949 to batching them for performance.
ba395927 950
b02aae9c 951 io_delay= [X86-32,X86-64] I/O delay method
6e7c4025
IM
952 0x80
953 Standard port 0x80 based delay
954 0xed
955 Alternate port 0xed based delay (needed on some systems)
b02aae9c 956 udelay
6e7c4025
IM
957 Simple two microseconds delay
958 none
959 No delay
b02aae9c 960
1da177e4
LT
961 io7= [HW] IO7 for Marvel based alpha systems
962 See comment before marvel_specify_io7 in
963 arch/alpha/kernel/core_marvel.c.
964
965 ip= [IP_PNP]
6ded55da 966 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
967
968 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
969 See comment before ip2_setup() in
970 drivers/char/ip2/ip2base.c.
1da177e4
LT
971
972 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
973 See header of drivers/scsi/ips.c.
974
72c4a13a
SH
975 ports= [IP_VS_FTP] IPVS ftp helper module
976 Default is 21.
977 Up to 8 (IP_VS_APP_MAX_PORTS) ports
978 may be specified.
979 Format: <port>,<port>....
980
200803df
AC
981 irqfixup [HW]
982 When an interrupt is not handled search all handlers
983 for it. Intended to get systems with badly broken
984 firmware running.
985
986 irqpoll [HW]
987 When an interrupt is not handled search all handlers
988 for it. Also check all handlers each timer
989 interrupt. Intended to get systems with badly broken
990 firmware running.
991
1da177e4 992 isapnp= [ISAPNP]
a9913044 993 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
994
995 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
996 Format:
997 <cpu number>,...,<cpu number>
998 or
b225d44e
LZ
999 <cpu number>-<cpu number>
1000 (must be a positive range in ascending order)
22f2e280
DF
1001 or a mixture
1002 <cpu number>,...,<cpu number>-<cpu number>
b225d44e 1003
1da177e4
LT
1004 This option can be used to specify one or more CPUs
1005 to isolate from the general SMP balancing and scheduling
b225d44e
LZ
1006 algorithms. You can move a process onto or off an
1007 "isolated" CPU via the CPU affinity syscalls or cpuset.
1da177e4
LT
1008 <cpu number> begins at 0 and the maximum value is
1009 "number of CPUs in system - 1".
1010
1011 This option is the preferred way to isolate CPUs. The
a9913044
RD
1012 alternative -- manually setting the CPU mask of all
1013 tasks in the system -- can cause problems and
1014 suboptimal load balancer performance.
1da177e4 1015
a9913044 1016 iucv= [HW,NET]
1da177e4
LT
1017
1018 js= [HW,JOY] Analog joystick
1019 See Documentation/input/joystick.txt.
1020
cd4f0ef7 1021 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
ed7ed365
MG
1022 specifies the amount of memory usable by the kernel
1023 for non-movable allocations. The requested amount is
1024 spread evenly throughout all nodes in the system. The
1025 remaining memory in each node is used for Movable
1026 pages. In the event, a node is too small to have both
1027 kernelcore and Movable pages, kernelcore pages will
1028 take priority and other nodes will have a larger number
1029 of kernelcore pages. The Movable zone is used for the
1030 allocation of pages that may be reclaimed or moved
1031 by the page migration subsystem. This means that
1032 HugeTLB pages may not be allocated from this zone.
1033 Note that allocations like PTEs-from-HighMem still
1034 use the HighMem zone if it exists, and the Normal
1035 zone if it does not.
1036
cd4f0ef7 1037 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
7e63efef
MG
1038 is similar to kernelcore except it specifies the
1039 amount of memory used for migratable allocations.
1040 If both kernelcore and movablecore is specified,
1041 then kernelcore will be at *least* the specified
1042 value but may be more. If movablecore on its own
1043 is specified, the administrator must be careful
1044 that the amount of memory usable for all allocations
1045 is not too small.
1046
1da177e4
LT
1047 keepinitrd [HW,ARM]
1048
cd4f0ef7 1049 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1da177e4
LT
1050 in oops dumps.
1051
6cdf6e06
JW
1052 kgdboc= [HW] kgdb over consoles.
1053 Requires a tty driver that supports console polling.
1054 (only serial suported for now)
1055 Format: <serial_device>[,baud]
1056
9bed90c6
FF
1057 kmac= [MIPS] korina ethernet MAC address.
1058 Configure the RouterBoard 532 series on-chip
1059 Ethernet adapter MAC address.
1060
1da177e4
LT
1061 l2cr= [PPC]
1062
a78bfbfc
RB
1063 l3cr= [PPC]
1064
cd4f0ef7 1065 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 1066 disabled it.
1da177e4 1067
cd4f0ef7 1068 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
e585bef8
TG
1069 C2 power state.
1070
fcb71f6f
FC
1071 libata.dma= [LIBATA] DMA control
1072 libata.dma=0 Disable all PATA and SATA DMA
1073 libata.dma=1 PATA and SATA Disk DMA only
1074 libata.dma=2 ATAPI (CDROM) DMA only
1075 libata.dma=4 Compact Flash DMA only
1076 Combinations also work, so libata.dma=3 enables DMA
1077 for disks and CDROMs, but not CFs.
1078
78e70c23
DJ
1079 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1080 when set.
1081 Format: <int>
1082
33267325
TH
1083 libata.force= [LIBATA] Force configurations. The format is comma
1084 separated list of "[ID:]VAL" where ID is
1085 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1086 matching port, link or device. Basically, it matches
1087 the ATA ID string printed on console by libata. If
1088 the whole ID part is omitted, the last PORT and DEVICE
1089 values are used. If ID hasn't been specified yet, the
1090 configuration applies to all ports, links and devices.
1091
1092 If only DEVICE is omitted, the parameter applies to
1093 the port and all links and devices behind it. DEVICE
1094 number of 0 either selects the first device or the
1095 first fan-out link behind PMP device. It does not
1096 select the host link. DEVICE number of 15 selects the
1097 host link and device attached to it.
1098
1099 The VAL specifies the configuration to force. As long
1100 as there's no ambiguity shortcut notation is allowed.
1101 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1102 The following configurations can be forced.
1103
1104 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1105 Any ID with matching PORT is used.
1106
1107 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1108
1109 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1110 udma[/][16,25,33,44,66,100,133] notation is also
1111 allowed.
1112
1113 * [no]ncq: Turn on or off NCQ.
1114
05944bdf
TH
1115 * nohrst, nosrst, norst: suppress hard, soft
1116 and both resets.
1117
33267325
TH
1118 If there are multiple matching configurations changing
1119 the same attribute, the last one is used.
1120
1da177e4 1121 load_ramdisk= [RAM] List of ramdisks to load from floppy
31c00fc1 1122 See Documentation/blockdev/ramdisk.txt.
1da177e4 1123
a6b25b67
RD
1124 lockd.nlm_grace_period=P [NFS] Assign grace period.
1125 Format: <integer>
1da177e4 1126
a6b25b67
RD
1127 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1128 Format: <integer>
1129
1130 lockd.nlm_timeout=T [NFS] Assign timeout value.
1131 Format: <integer>
1132
1133 lockd.nlm_udpport=M [NFS] Assign UDP port.
1134 Format: <integer>
1da177e4
LT
1135
1136 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1137 Format: <irq>
1138
1139 loglevel= All Kernel Messages with a loglevel smaller than the
1140 console loglevel will be printed to the console. It can
1141 also be changed with klogd or other programs. The
1142 loglevels are defined as follows:
1143
1144 0 (KERN_EMERG) system is unusable
1145 1 (KERN_ALERT) action must be taken immediately
1146 2 (KERN_CRIT) critical conditions
1147 3 (KERN_ERR) error conditions
1148 4 (KERN_WARNING) warning conditions
1149 5 (KERN_NOTICE) normal but significant condition
1150 6 (KERN_INFO) informational
1151 7 (KERN_DEBUG) debug-level messages
1152
1153 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1154 Format: { n | nk | nM }
1155 n must be a power of two. The default size
1156 is set in the kernel config file.
1da177e4 1157
accaa24c
RD
1158 logo.nologo [FB] Disables display of the built-in Linux logo.
1159 This may be used to provide more screen space for
1160 kernel log messages and is useful when debugging
1161 kernel boot problems.
1162
1da177e4
LT
1163 lp=0 [LP] Specify parallel ports to use, e.g,
1164 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1165 lp=reset first parallel port). 'lp=0' disables the
1166 lp=auto printer driver. 'lp=reset' (which can be
1167 specified in addition to the ports) causes
1168 attached printers to be reset. Using
1169 lp=port1,port2,... specifies the parallel ports
1170 to associate lp devices with, starting with
1171 lp0. A port specification may be 'none' to skip
1172 that lp device, or a parport name such as
1173 'parport0'. Specifying 'lp=auto' instead of a
1174 port specification list means that device IDs
1175 from each port should be examined, to see if
1176 an IEEE 1284-compliant printer is attached; if
1177 so, the driver will manage that printer.
1178 See also header of drivers/char/lp.c.
1179
1180 lpj=n [KNL]
1181 Sets loops_per_jiffy to given constant, thus avoiding
1182 time-consuming boot-time autodetection (up to 250 ms per
1183 CPU). 0 enables autodetection (default). To determine
1184 the correct value for your kernel, boot with normal
1185 autodetection and see what value is printed. Note that
1186 on SMP systems the preset will be applied to all CPUs,
1187 which is likely to cause problems if your CPUs need
1188 significantly divergent settings. An incorrect value
1189 will cause delays in the kernel to be wrong, leading to
1190 unpredictable I/O errors and other breakage. Although
1191 unlikely, in the extreme case this might damage your
1192 hardware.
1193
1194 ltpc= [NET]
1195 Format: <io>,<irq>,<dma>
1196
a9913044
RD
1197 mac5380= [HW,SCSI] Format:
1198 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1199
a9913044
RD
1200 machvec= [IA64] Force the use of a particular machine-vector
1201 (machvec) in a generic kernel.
1202 Example: machvec=hpzx1_swiotlb
1da177e4 1203
a9913044 1204 max_loop= [LOOP] Maximum number of loopback devices that can
1da177e4
LT
1205 be mounted
1206 Format: <1-256>
1207
1208 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1209 should make use of. maxcpus=n : n >= 0 limits the
1210 kernel to using 'n' processors. n=0 is a special case,
1211 it is equivalent to "nosmp", which also disables
1212 the IO APIC.
1da177e4 1213
1c207f95
RD
1214 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater than
1215 or equal to this physical address is ignored.
2b2c3750 1216
a9913044 1217 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1218 Should be between 1 and 2^32-1.
1219
1220 max_report_luns=
a9913044 1221 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1222 Should be between 1 and 16384.
1223
1da177e4
LT
1224 mcatest= [IA-64]
1225
cd4f0ef7 1226 mce [X86-32] Machine Check Exception
1da177e4 1227
71cced6e 1228 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
909dd324 1229
1da177e4
LT
1230 md= [HW] RAID subsystems devices and level
1231 See Documentation/md.txt.
a9913044 1232
1da177e4
LT
1233 mdacon= [MDA]
1234 Format: <first>,<last>
1235 Specifies range of consoles to be captured by the MDA.
a9913044 1236
1da177e4
LT
1237 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1238 Amount of memory to be used when the kernel is not able
1239 to see the whole system memory or for test.
cd4f0ef7 1240 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1241 address space collisions. Without memmap= PCI devices
1242 could be placed at addresses belonging to unused RAM.
1243
cd4f0ef7 1244 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1245 memory.
1246
6902aa84
PM
1247 memchunk=nn[KMG]
1248 [KNL,SH] Allow user to override the default size for
1249 per-device physically contiguous DMA buffers.
1250
cd4f0ef7 1251 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1da177e4
LT
1252 E820 memory map, as specified by the user.
1253 Such memmap=exactmap lines can be constructed based on
1254 BIOS output or other requirements. See the memmap=nn@ss
1255 option description.
1256
1257 memmap=nn[KMG]@ss[KMG]
1258 [KNL] Force usage of a specific region of memory
1259 Region of memory to be used, from ss to ss+nn.
1260
1261 memmap=nn[KMG]#ss[KMG]
1262 [KNL,ACPI] Mark specific memory as ACPI data.
1263 Region of memory to be used, from ss to ss+nn.
1264
1265 memmap=nn[KMG]$ss[KMG]
1266 [KNL,ACPI] Mark specific memory as reserved.
1267 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1268 Example: Exclude memory from 0x18690000-0x1869ffff
1269 memmap=64K$0x18690000
1270 or
1271 memmap=0x10000$0x18690000
1da177e4 1272
9f077871
JF
1273 memory_corruption_check=0/1 [X86]
1274 Some BIOSes seem to corrupt the first 64k of
1275 memory when doing things like suspend/resume.
1276 Setting this option will scan the memory
1277 looking for corruption. Enabling this will
1278 both detect corruption and prevent the kernel
1279 from using the memory being corrupted.
1280 However, its intended as a diagnostic tool; if
1281 repeatable BIOS-originated corruption always
1282 affects the same memory, you can use memmap=
1283 to prevent the kernel from using that memory.
1284
1285 memory_corruption_check_size=size [X86]
1286 By default it checks for corruption in the low
1287 64k, making this memory unavailable for normal
1288 use. Use this parameter to scan for
1289 corruption in more or less memory.
1290
1291 memory_corruption_check_period=seconds [X86]
1292 By default it checks for corruption every 60
1293 seconds. Use this parameter to check at some
1294 other rate. 0 disables periodic checking.
1295
caadbdce 1296 memtest= [KNL,X86] Enable memtest
c64df707
YL
1297 Format: <integer>
1298 range: 0,4 : pattern number
1299 default : 0 <disable>
1300
1da177e4
LT
1301 meye.*= [HW] Set MotionEye Camera parameters
1302 See Documentation/video4linux/meye.txt.
1303
8f36881b
AS
1304 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1305 Multi-Function General Purpose Timers on AMD Geode
1306 platforms.
1307
e6c4dc6c
WT
1308 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1309 the BIOS has incorrectly applied a workaround. TinyBIOS
1310 version 0.98 is known to be affected, 0.99 fixes the
1311 problem by letting the user disable the workaround.
1312
1da177e4
LT
1313 mga= [HW,DRM]
1314
1c207f95
RD
1315 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1316 physical address is ignored.
1317
6b74ab97
MG
1318 mminit_loglevel=
1319 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1320 parameter allows control of the logging verbosity for
1321 the additional memory initialisation checks. A value
1322 of 0 disables mminit logging and a level of 4 will
1323 log everything. Information is printed at KERN_DEBUG
1324 so loglevel=8 may also need to be specified.
1325
1da177e4
LT
1326 mousedev.tap_time=
1327 [MOUSE] Maximum time between finger touching and
1328 leaving touchpad surface for touch to be considered
1329 a tap and be reported as a left button click (for
1330 touchpads working in absolute mode only).
1331 Format: <msecs>
1332 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1333 reporting absolute coordinates, such as tablets
1334 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1335 reporting absolute coordinates, such as tablets
1336
1337 mpu401= [HW,OSS]
1338 Format: <io>,<irq>
1339
1340 MTD_Partition= [MTD]
1341 Format: <name>,<region-number>,<size>,<offset>
1342
a9913044
RD
1343 MTD_Region= [MTD] Format:
1344 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1345
1346 mtdparts= [MTD]
c8facbb6 1347 See drivers/mtd/cmdlinepart.c.
1da177e4 1348
9db829f4
BD
1349 mtdset= [ARM]
1350 ARM/S3C2412 JIVE boot control
1351
1352 See arch/arm/mach-s3c2412/mach-jive.c
1353
1da177e4 1354 mtouchusb.raw_coordinates=
a9913044
RD
1355 [HW] Make the MicroTouch USB driver use raw coordinates
1356 ('y', default) or cooked coordinates ('n')
1da177e4
LT
1357
1358 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1359
1360 NCR_D700= [HW,SCSI]
1361 See header of drivers/scsi/NCR_D700.c.
1362
1363 ncr5380= [HW,SCSI]
1364
1365 ncr53c400= [HW,SCSI]
1366
1367 ncr53c400a= [HW,SCSI]
1368
1369 ncr53c406a= [HW,SCSI]
1370
1371 ncr53c8xx= [HW,SCSI]
1372
1373 netdev= [NET] Network devices parameters
1374 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1375 Note that mem_start is often overloaded to mean
1376 something different and driver-specific.
a9913044
RD
1377 This usage is only documented in each driver source
1378 file if at all.
1379
58401572
KPO
1380 nf_conntrack.acct=
1381 [NETFILTER] Enable connection tracking flow accounting
1382 0 to disable accounting
1383 1 to enable accounting
1384 Default value depends on CONFIG_NF_CT_ACCT that is
1385 going to be removed in 2.6.29.
1386
1da177e4 1387 nfsaddrs= [NFS]
6ded55da 1388 See Documentation/filesystems/nfsroot.txt.
1da177e4
LT
1389
1390 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
6ded55da 1391 See Documentation/filesystems/nfsroot.txt.
1da177e4 1392
a72b4422
TM
1393 nfs.callback_tcpport=
1394 [NFS] set the TCP port on which the NFSv4 callback
1395 channel should listen.
1396
58df095b
TM
1397 nfs.idmap_cache_timeout=
1398 [NFS] set the maximum lifetime for idmapper cache
1399 entries.
1400
f43bf0be
TM
1401 nfs.enable_ino64=
1402 [NFS] enable 64-bit inode numbers.
1403 If zero, the NFS client will fake up a 32-bit inode
1404 number for the readdir() and stat() syscalls instead
1405 of returning the full 64-bit number.
1406 The default is to return 64-bit inode numbers.
1407
e7ba176b
HS
1408 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1409 when a NMI is triggered.
1410 Format: [state][,regs][,debounce][,die]
1411
5b9a0e14
CG
1412 nmi_watchdog= [KNL,BUGS=X86-32,X86-64] Debugging features for SMP kernels
1413 Format: [panic,][num]
1414 Valid num: 0,1,2
1415 0 - turn nmi_watchdog off
1416 1 - use the IO-APIC timer for the NMI watchdog
1417 2 - use the local APIC for the NMI watchdog using
1418 a performance counter. Note: This will use one performance
1419 counter and the local APIC's performance vector.
1420 When panic is specified panic when an NMI watchdog timeout occurs.
1421 This is useful when you use a panic=... timeout and need the box
1422 quickly up again.
1423 Instead of 1 and 2 it is possible to use the following
1424 symbolic names: lapic and ioapic
1425 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1da177e4 1426
cd4f0ef7 1427 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1428 emulation library even if a 387 maths coprocessor
1429 is present.
1430
c1aee215
CL
1431 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1432 caches in the slab allocator. Saves per-node memory,
1433 but will impact performance.
3395ee05 1434
a9913044
RD
1435 noalign [KNL,ARM]
1436
1da177e4
LT
1437 noapic [SMP,APIC] Tells the kernel to not make use of any
1438 IOAPICs that may be present in the system.
1439
1da177e4
LT
1440 nobats [PPC] Do not use BATs for mapping kernel lowmem
1441 on "Classic" PPC cores.
1442
1443 nocache [ARM]
a9913044 1444
163ecdff
SN
1445 nodelayacct [KNL] Disable per-task delay accounting
1446
1da177e4
LT
1447 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1448
6902aa84
PM
1449 nodsp [SH] Disable hardware DSP at boot time.
1450
8b2cb7a8
HY
1451 noefi [X86-32,X86-64] Disable EFI runtime services support.
1452
1da177e4
LT
1453 noexec [IA-64]
1454
cd4f0ef7 1455 noexec [X86-32,X86-64]
f5a1b191 1456 On X86-32 available only on PAE configured kernels.
1da177e4 1457 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
1458 noexec=off: disable non-executable mappings
1459
1460 noexec32 [X86-64]
1461 This affects only 32-bit executables.
1462 noexec32=on: enable non-executable mappings (default)
1463 read doesn't imply executable mappings
1464 noexec32=off: disable non-executable mappings
1465 read implies executable mappings
1da177e4 1466
6902aa84
PM
1467 nofpu [SH] Disable hardware FPU at boot time.
1468
cd4f0ef7 1469 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1470 register save and restore. The kernel will only save
1471 legacy floating-point registers on task switch.
1da177e4 1472
191679fd
AK
1473 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1474
6902aa84 1475 nohlt [BUGS=ARM,SH]
a9913044 1476
cd4f0ef7 1477 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1478 instruction doesn't work correctly and not to
1479 use it.
1480
1f29fae2
SH
1481 no_file_caps Tells the kernel not to honor file capabilities. The
1482 only way then for a file to be executed with privilege
1483 is to be setuid root or executed by root.
1484
1da177e4
LT
1485 nohalt [IA-64] Tells the kernel not to use the power saving
1486 function PAL_HALT_LIGHT when idle. This increases
1487 power-consumption. On the positive side, it reduces
1488 interrupt wake-up latency, which may improve performance
1489 in certain environments such as networked servers or
1490 real-time systems.
1491
79bf2bb3
TG
1492 nohz= [KNL] Boottime enable/disable dynamic ticks
1493 Valid arguments: on, off
1494 Default: on
1495
cd4f0ef7 1496 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1497 disable unhandled interrupt sources.
1498
cd4f0ef7 1499 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
8542b200
ZA
1500 broken timer IRQ sources.
1501
1da177e4
LT
1502 noisapnp [ISAPNP] Disables ISA PnP code.
1503
1504 noinitrd [RAM] Tells the kernel not to load any configured
1505 initial RAM disk.
1506
1507 nointroute [IA-64]
1508
0aa366f3
TL
1509 nojitter [IA64] Disables jitter checking for ITC timers.
1510
cd4f0ef7 1511 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1512
cd4f0ef7 1513 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1514
6e1cb38a
SS
1515 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1516
af9d1388
SS
1517 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
1518 default x2apic cluster mode on platforms
1519 supporting x2apic.
1520
1da177e4
LT
1521 noltlbs [PPC] Do not use large page/tlb entries for kernel
1522 lowmem mapping on PPC40x.
1523
312f1f01
H
1524 nomca [IA-64] Disable machine check abort handling
1525
cd4f0ef7 1526 nomce [X86-32] Machine Check Exception
abe37e5a 1527
83d7384f
AS
1528 nomfgpt [X86-32] Disable Multi-Function General Purpose
1529 Timer usage (for AMD Geode machines).
1530
cd4f0ef7 1531 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1532
cd4f0ef7 1533 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1534 with UP alternatives
1535
1da177e4
LT
1536 noresidual [PPC] Don't use residual data on PReP machines.
1537
a9913044
RD
1538 noresume [SWSUSP] Disables resume and restores original swap
1539 space.
1540
1da177e4
LT
1541 no-scroll [VGA] Disables scrollback.
1542 This is required for the Braillex ib80-piezo Braille
1543 reader made by F.H. Papenmeier (Germany).
1544
1545 nosbagart [IA-64]
1546
cd4f0ef7 1547 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1548
61ec7567
LB
1549 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1550 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1551
97842216
DJ
1552 nosoftlockup [KNL] Disable the soft-lockup detector.
1553
1da177e4
LT
1554 nosync [HW,M68K] Disables sync negotiation for all devices.
1555
cd4f0ef7 1556 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1557
1558 nousb [USB] Disable the USB subsystem
1559
1560 nowb [ARM]
a9913044 1561
a6c75b86
FY
1562 nptcg= [IA64] Override max number of concurrent global TLB
1563 purges which is reported from either PAL_VM_SUMMARY or
1564 SAL PALO.
1565
f0c0b2b8
KH
1566 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1567 one of ['zone', 'node', 'default'] can be specified
1568 This can be set from sysctl after boot.
1569 See Documentation/sysctl/vm.txt for details.
1570
a61c2d78
DJ
1571 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1572
3ef0e1f8
AS
1573 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1574 Rather than timing out after 20 ms if an EC
1575 command is not properly ACKed, override the length
1576 of the timeout. We have interrupts disabled while
1577 waiting for the ACK, so if this is set too high
1578 interrupts *may* be lost!
1579
1da177e4
LT
1580 opl3= [HW,OSS]
1581 Format: <io>
1582
1da177e4
LT
1583 oprofile.timer= [HW]
1584 Use timer interrupt instead of performance counters
1585
1da177e4
LT
1586 osst= [HW,SCSI] SCSI Tape Driver
1587 Format: <buffer_size>,<write_threshold>
1588 See also Documentation/scsi/st.txt.
1589
1590 panic= [KNL] Kernel behaviour on panic
1591 Format: <timeout>
1592
1593 parkbd.port= [HW] Parallel port number the keyboard adapter is
1594 connected to, default is 0.
1595 Format: <parport#>
1596 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1597 0 for XT, 1 for AT (default is AT).
a9913044
RD
1598 Format: <mode>
1599
1600 parport= [HW,PPT] Specify parallel ports. 0 disables.
1601 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1602 Use 'auto' to force the driver to use any
1603 IRQ/DMA settings detected (the default is to
1604 ignore detected IRQ/DMA settings because of
1605 possible conflicts). You can specify the base
1606 address, IRQ, and DMA settings; IRQ and DMA
1607 should be numbers, or 'auto' (for using detected
1608 settings on that particular port), or 'nofifo'
1609 (to avoid using a FIFO even if it is detected).
1610 Parallel ports are assigned in the order they
1611 are specified on the command line, starting
1612 with parport0.
1613
1614 parport_init_mode= [HW,PPT]
1615 Configure VIA parallel port to operate in
1616 a specific mode. This is necessary on Pegasos
1617 computer where firmware has no options for setting
1618 up parallel port mode and sets it to spp.
1619 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1620 Format: [spp|ps2|epp|ecp|ecpepp]
1621
a9913044
RD
1622 pas2= [HW,OSS] Format:
1623 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1624
1da177e4
LT
1625 pas16= [HW,SCSI]
1626 See header of drivers/scsi/pas16.c.
1627
dd287796
AM
1628 pause_on_oops=
1629 Halt all CPUs after the first oops has been printed for
1630 the specified number of seconds. This is to be used if
1631 your oopses keep scrolling off the screen.
1632
1da177e4
LT
1633 pcbit= [HW,ISDN]
1634
1635 pcd. [PARIDE]
1636 See header of drivers/block/paride/pcd.c.
31c00fc1 1637 See also Documentation/blockdev/paride.txt.
1da177e4 1638
a9913044 1639 pci=option[,option...] [PCI] various PCI subsystem options:
c0115606 1640 off [X86] don't probe for the PCI bus
cd4f0ef7 1641 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1642 the hardware directly. Use this if your machine
1643 has a non-standard PCI host bridge.
cd4f0ef7 1644 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1645 hardware access methods are allowed. Use this
1646 if you experience crashes upon bootup and you
1647 suspect they are caused by the BIOS.
c0115606 1648 conf1 [X86] Force use of PCI Configuration
a9913044 1649 Mechanism 1.
c0115606 1650 conf2 [X86] Force use of PCI Configuration
a9913044 1651 Mechanism 2.
7f785763
RD
1652 noaer [PCIE] If the PCIEAER kernel config parameter is
1653 enabled, this kernel boot option can be used to
1654 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1655 nodomains [PCI] Disable support for multiple PCI
1656 root domains (aka PCI segments, in ACPI-speak).
cd4f0ef7 1657 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
61be6d66 1658 Configuration
309e57df
MW
1659 nomsi [MSI] If the PCI_MSI kernel config parameter is
1660 enabled, this kernel boot option can be used to
1661 disable the use of MSI interrupts system-wide.
a9322f64
SA
1662 noioapicquirk [APIC] Disable all boot interrupt quirks.
1663 Safety option to keep boot IRQs enabled. This
1664 should never be necessary.
9197979b
SA
1665 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1666 primary IO-APIC for bridges that cannot disable
1667 boot IRQs. This fixes a source of spurious IRQs
1668 when the system masks IRQs.
41b9eb26
SA
1669 noioapicreroute [APIC] Disable workaround that uses the
1670 boot IRQ equivalent of an IRQ that connects to
1671 a chipset where boot IRQs cannot be disabled.
1672 The opposite of ioapicreroute.
cd4f0ef7 1673 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1674 routing table. These calls are known to be buggy
1675 on several machines and they hang the machine
1676 when used, but on other computers it's the only
1677 way to get the interrupt routing table. Try
1678 this option if the kernel is unable to allocate
1679 IRQs or discover secondary PCI buses on your
1680 motherboard.
c0115606 1681 rom [X86] Assign address space to expansion ROMs.
a9913044
RD
1682 Use with caution as certain devices share
1683 address decoders between ROMs and other
1684 resources.
c0115606 1685 norom [X86] Do not assign address space to
bb71ad88
GH
1686 expansion ROMs that do not already have
1687 BIOS assigned address ranges.
c0115606 1688 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
a9913044
RD
1689 assigned automatically to PCI devices. You can
1690 make the kernel exclude IRQs of your ISA cards
1691 this way.
c0115606 1692 pirqaddr=0xAAAAA [X86] Specify the physical address
a9913044
RD
1693 of the PIRQ table (normally generated
1694 by the BIOS) if it is outside the
1695 F0000h-100000h range.
c0115606 1696 lastbus=N [X86] Scan all buses thru bus #N. Can be
a9913044
RD
1697 useful if the kernel is unable to find your
1698 secondary buses and you want to tell it
1699 explicitly which ones they are.
c0115606 1700 assign-busses [X86] Always assign all PCI bus
a9913044
RD
1701 numbers ourselves, overriding
1702 whatever the firmware may have done.
c0115606 1703 usepirqmask [X86] Honor the possible IRQ mask stored
a9913044
RD
1704 in the BIOS $PIR table. This is needed on
1705 some systems with broken BIOSes, notably
1706 some HP Pavilion N5400 and Omnibook XE3
1707 notebooks. This will have no effect if ACPI
1708 IRQ routing is enabled.
c0115606 1709 noacpi [X86] Do not use ACPI for IRQ routing
a9913044 1710 or for PCI scanning.
c0115606 1711 use_crs [X86] Use _CRS for PCI resource
62f420f8 1712 allocation.
a9913044
RD
1713 routeirq Do IRQ routing for all PCI devices.
1714 This is normally done in pci_enable_device(),
1715 so this option is a temporary workaround
1716 for broken drivers that don't call it.
13a6ddb0
YL
1717 skip_isa_align [X86] do not align io start addr, so can
1718 handle more pci cards
a9913044
RD
1719 firmware [ARM] Do not re-enumerate the bus but instead
1720 just use the configuration from the
1721 bootloader. This is currently used on
1722 IXP2000 systems where the bus has to be
1723 configured a certain way for adjunct CPUs.
0637a70a
AK
1724 noearly [X86] Don't do any early type 1 scanning.
1725 This might help on some broken boards which
1726 machine check when some devices' config space
1727 is read. But various workarounds are disabled
1728 and some IOMMU drivers will not work.
6b4b78fe
MD
1729 bfsort Sort PCI devices into breadth-first order.
1730 This sorting is done to get a device
1731 order compatible with older (<= 2.4) kernels.
1732 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
1733 cbiosize=nn[KMG] The fixed amount of bus space which is
1734 reserved for the CardBus bridge's IO window.
1735 The default value is 256 bytes.
1736 cbmemsize=nn[KMG] The fixed amount of bus space which is
1737 reserved for the CardBus bridge's memory
1738 window. The default value is 64 megabytes.
6b4b78fe 1739
e5665a45
CE
1740 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1741 Management.
1742 off Disable ASPM.
1743 force Enable ASPM even on devices that claim not to support it.
1744 WARNING: Forcing ASPM on may cause system lockups.
1745
1da177e4
LT
1746 pcmv= [HW,PCMCIA] BadgePAD 4
1747
1748 pd. [PARIDE]
31c00fc1 1749 See Documentation/blockdev/paride.txt.
1da177e4
LT
1750
1751 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1752 boot time.
1753 Format: { 0 | 1 }
1754 See arch/parisc/kernel/pdc_chassis.c
1755
1756 pf. [PARIDE]
31c00fc1 1757 See Documentation/blockdev/paride.txt.
1da177e4
LT
1758
1759 pg. [PARIDE]
31c00fc1 1760 See Documentation/blockdev/paride.txt.
1da177e4
LT
1761
1762 pirq= [SMP,APIC] Manual mp-table setup
71cced6e 1763 See Documentation/x86/i386/IO-APIC.txt.
1da177e4
LT
1764
1765 plip= [PPT,NET] Parallel port network link
1766 Format: { parport<nr> | timid | 0 }
1767 See also Documentation/parport.txt.
1768
de32a243
TG
1769 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1770 Override pmtimer IOPort with a hex value.
1771 e.g. pmtmr=0x508
1772
97ef062b
BH
1773 pnp.debug [PNP]
1774 Enable PNP debug messages. This depends on the
1775 CONFIG_PNP_DEBUG_MESSAGES option.
1776
1da177e4
LT
1777 pnpacpi= [ACPI]
1778 { off }
1779
1780 pnpbios= [ISAPNP]
1781 { on | off | curr | res | no-curr | no-res }
1782
1783 pnp_reserve_irq=
1784 [ISAPNP] Exclude IRQs for the autoconfiguration
1785
1786 pnp_reserve_dma=
1787 [ISAPNP] Exclude DMAs for the autoconfiguration
1788
1789 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 1790 Ranges are in pairs (I/O port base and size).
1da177e4
LT
1791
1792 pnp_reserve_mem=
a9913044
RD
1793 [ISAPNP] Exclude memory regions for the
1794 autoconfiguration.
1da177e4
LT
1795 Ranges are in pairs (memory base and size).
1796
346e15be
JB
1797 dynamic_printk
1798 Enables pr_debug()/dev_dbg() calls if
1799 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. These can also
1800 be switched on/off via <debugfs>/dynamic_printk/modules
1801
45807a1d
IM
1802 print-fatal-signals=
1803 [KNL] debug: print fatal signals
1804 print-fatal-signals=1: print segfault info to
1805 the kernel console.
1806 default: off.
1807
e84845c4
RD
1808 printk.time= Show timing data prefixed to each printk message line
1809 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1810
1da177e4 1811 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
1812 Format: [schedule,]<number>
1813 Param: "schedule" - profile schedule points.
1814 Param: <number> - step/bucket size as a power of 2 for
1815 statistical time based profiling.
b3da2a73
MG
1816 Param: "sleep" - profile D-state sleeping (millisecs).
1817 Requires CONFIG_SCHEDSTATS
c0fe2e69 1818 Param: "kvm" - profile VM exits.
1da177e4 1819
a9913044 1820 processor.max_cstate= [HW,ACPI]
1da177e4
LT
1821 Limit processor to maximum C-state
1822 max_cstate=9 overrides any DMI blacklist limit.
1823
41c0d868
LB
1824 processor.nocst [HW,ACPI]
1825 Ignore the _CST method to determine C-states,
1826 instead using the legacy FADT method
1827
1da177e4
LT
1828 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1829 before loading.
31c00fc1 1830 See Documentation/blockdev/ramdisk.txt.
1da177e4 1831
a9913044
RD
1832 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1833 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
1834 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1835 per second.
a9913044
RD
1836 psmouse.resetafter= [HW,MOUSE]
1837 Try to reset the device after so many bad packets
1da177e4
LT
1838 (0 = never).
1839 psmouse.resolution=
1840 [HW,MOUSE] Set desired mouse resolution, in dpi.
1841 psmouse.smartscroll=
a9913044 1842 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
1843 0 = disabled, 1 = enabled (default).
1844
1845 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
1846 Format:
1847 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
1848
1849 pt. [PARIDE]
31c00fc1 1850 See Documentation/blockdev/paride.txt.
1da177e4 1851
dc8c8587
KS
1852 pty.legacy_count=
1853 [KNL] Number of legacy pty's. Overwrites compiled-in
1854 default number.
1855
7d2c502f 1856 quiet [KNL] Disable most log messages
a9913044 1857
1da177e4
LT
1858 r128= [HW,DRM]
1859
1860 raid= [HW,RAID]
1861 See Documentation/md.txt.
1862
a9913044 1863 ramdisk_blocksize= [RAM]
31c00fc1 1864 See Documentation/blockdev/ramdisk.txt.
a9913044 1865
1da177e4 1866 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
31c00fc1 1867 See Documentation/blockdev/ramdisk.txt.
1da177e4 1868
24aaef8d
RD
1869 rcupdate.blimit= [KNL,BOOT]
1870 Set maximum number of finished RCU callbacks to process
1871 in one batch.
21a1ea9e 1872
24aaef8d
RD
1873 rcupdate.qhimark= [KNL,BOOT]
1874 Set threshold of queued
21a1ea9e
DS
1875 RCU callbacks over which batch limiting is disabled.
1876
24aaef8d
RD
1877 rcupdate.qlowmark= [KNL,BOOT]
1878 Set threshold of queued RCU callbacks below which
1879 batch limiting is re-enabled.
21a1ea9e 1880
ffdfc409
OJ
1881 rdinit= [KNL]
1882 Format: <full_path>
1883 Run specified binary instead of /init from the ramdisk,
1884 used for early userspace startup. See initrd.
1885
cd4f0ef7 1886 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 1887 Format: <reboot_mode>[,<reboot_mode2>[,...]]
e53dd083 1888 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4 1889
46b6d94e
PJ
1890 relax_domain_level=
1891 [KNL, SMP] Set scheduler's default relax_domain_level.
1892 See Documentation/cpusets.txt.
1893
1da177e4
LT
1894 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1895
cd4f0ef7 1896 reservetop= [X86-32]
461a9aff
ZA
1897 Format: nn[KMG]
1898 Reserves a hole at the top of the kernel virtual
1899 address space.
1900
7e96287d
VG
1901 reset_devices [KNL] Force drivers to reset the underlying device
1902 during initialization.
1903
a9913044
RD
1904 resume= [SWSUSP]
1905 Specify the partition device for software suspend
1da177e4 1906
ecbd0da1
RW
1907 resume_offset= [SWSUSP]
1908 Specify the offset from the beginning of the partition
1909 given by "resume=" at which the swap header is located,
1910 in <PAGE_SIZE> units (needed only for swap files).
1911 See Documentation/power/swsusp-and-swap-files.txt
1912
0a7b35cb
MN
1913 retain_initrd [RAM] Keep initrd memory after extraction
1914
1da177e4
LT
1915 rhash_entries= [KNL,NET]
1916 Set number of hash buckets for route cache
1917
1918 riscom8= [HW,SERIAL]
1919 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1920
1921 ro [KNL] Mount root device read-only on boot
1922
1923 root= [KNL] Root filesystem
1924
1925 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1926 mount the root filesystem
1927
1928 rootflags= [KNL] Set root filesystem mount option string
1929
1930 rootfstype= [KNL] Set root filesystem type
1931
cc1ed754
PO
1932 rootwait [KNL] Wait (indefinitely) for root device to show up.
1933 Useful for devices that are detected asynchronously
1934 (e.g. USB and MMC devices).
1935
20510f2f
JM
1936 root_plug.vendor_id=
1937 [ROOTPLUG] Override the default vendor ID
1938
1939 root_plug.product_id=
1940 [ROOTPLUG] Override the default product ID
1941
1942 root_plug.debug=
1943 [ROOTPLUG] Enable debugging output
1944
1da177e4
LT
1945 rw [KNL] Mount root device read-write on boot
1946
1947 S [KNL] Run init in single mode
1948
1949 sa1100ir [NET]
1950 See drivers/net/irda/sa1100_ir.c.
1951
1da177e4 1952 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 1953
1da177e4
LT
1954 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1955 Format: <io>[,<timeout>[,<isapnp>]]
1956
1957 scsi_debug_*= [SCSI]
1958 See drivers/scsi/scsi_debug.c.
1959
1960 scsi_default_dev_flags=
1961 [SCSI] SCSI default device flags
1962 Format: <integer>
1963
1964 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1965 Format: <vendor>:<model>:<flags>
1966 (flags are integer value)
1967
6af6632a
RD
1968 scsi_logging_level= [SCSI] a bit mask of logging levels
1969 See drivers/scsi/scsi_logging.h for bits. Also
1970 settable via sysctl at dev.scsi.logging_level
1971 (/proc/sys/dev/scsi/logging_level).
1972 There is also a nice 'scsi_logging_level' script in the
1973 S390-tools package, available for download at
1974 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 1975
3e082a91
MW
1976 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1977 discovered. async scans them in kernel threads,
1978 allowing boot to proceed. none ignores them, expecting
1979 user space to do the scan.
1980
1da177e4
LT
1981 selinux [SELINUX] Disable or enable SELinux at boot time.
1982 Format: { "0" | "1" }
1983 See security/selinux/Kconfig help text.
1984 0 -- disable.
1985 1 -- enable.
1986 Default value is set via kernel config option.
1987 If enabled at boot time, /selinux/disable can be used
1988 later to disable prior to initial policy load.
1989
4e5ab4cb
JM
1990 selinux_compat_net =
1991 [SELINUX] Set initial selinux_compat_net flag value.
e53dd083
MCC
1992 Format: { "0" | "1" }
1993 0 -- use new secmark-based packet controls
1994 1 -- use legacy packet controls
1995 Default value is 0 (preferred).
1996 Value can be changed at runtime via
1997 /selinux/compat_net.
4e5ab4cb 1998
cd4f0ef7 1999 serialnumber [BUGS=X86-32]
1da177e4 2000
1da177e4
LT
2001 shapers= [NET]
2002 Maximal number of shapers.
a9913044 2003
b05f78f5
YL
2004 show_msr= [x86] show boot-time MSR settings
2005 Format: { <integer> }
2006 Show boot-time (BIOS-initialized) MSR settings.
2007 The parameter means the number of CPUs to show,
2008 for example 1 means boot CPU only.
2009
1da177e4
LT
2010 sim710= [SCSI,HW]
2011 See header of drivers/scsi/sim710.c.
2012
2013 simeth= [IA-64]
2014 simscsi=
a9913044 2015
1da177e4
LT
2016 slram= [HW,MTD]
2017
f0630fff
CL
2018 slub_debug[=options[,slabs]] [MM, SLUB]
2019 Enabling slub_debug allows one to determine the
2020 culprit if slab objects become corrupted. Enabling
2021 slub_debug can create guard zones around objects and
2022 may poison objects when not in use. Also tracks the
2023 last alloc / free. For more information see
2024 Documentation/vm/slub.txt.
c1aee215
CL
2025
2026 slub_max_order= [MM, SLUB]
f0630fff
CL
2027 Determines the maximum allowed order for slabs.
2028 A high setting may cause OOMs due to memory
2029 fragmentation. For more information see
2030 Documentation/vm/slub.txt.
c1aee215
CL
2031
2032 slub_min_objects= [MM, SLUB]
f0630fff
CL
2033 The minimum number of objects per slab. SLUB will
2034 increase the slab order up to slub_max_order to
2035 generate a sufficiently large slab able to contain
2036 the number of objects indicated. The higher the number
2037 of objects the smaller the overhead of tracking slabs
2038 and the less frequently locks need to be acquired.
c1aee215
CL
2039 For more information see Documentation/vm/slub.txt.
2040
2041 slub_min_order= [MM, SLUB]
2042 Determines the mininum page order for slabs. Must be
f0630fff 2043 lower than slub_max_order.
c1aee215
CL
2044 For more information see Documentation/vm/slub.txt.
2045
2046 slub_nomerge [MM, SLUB]
f0630fff 2047 Disable merging of slabs with similar size. May be
c1aee215 2048 necessary if there is some reason to distinguish
f0630fff
CL
2049 allocs to different slabs. Debug options disable
2050 merging on their own.
c1aee215
CL
2051 For more information see Documentation/vm/slub.txt.
2052
1da177e4
LT
2053 smart2= [HW]
2054 Format: <io1>[,<io2>[,...,<io8>]]
2055
cd4f0ef7 2056 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
2057 attempt to substitute SMP alternatives once at boot.
2058
d0d4f69b
BH
2059 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2060 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2061 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2062 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2063 smsc-ircc2.ircc_irq= [HW] IRQ line
2064 smsc-ircc2.ircc_dma= [HW] DMA channel
2065 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2066 0: Toshiba Satellite 1800 (GP data pin select)
2067 1: Fast pin select (default)
2068 2: ATC IRMode
2069
1da177e4
LT
2070 snd-ad1816a= [HW,ALSA]
2071
2072 snd-ad1848= [HW,ALSA]
2073
2074 snd-ali5451= [HW,ALSA]
2075
2076 snd-als100= [HW,ALSA]
2077
2078 snd-als4000= [HW,ALSA]
2079
2080 snd-azt2320= [HW,ALSA]
2081
2082 snd-cmi8330= [HW,ALSA]
2083
2084 snd-cmipci= [HW,ALSA]
2085
2086 snd-cs4231= [HW,ALSA]
2087
2088 snd-cs4232= [HW,ALSA]
2089
2090 snd-cs4236= [HW,ALSA]
2091
2092 snd-cs4281= [HW,ALSA]
2093
2094 snd-cs46xx= [HW,ALSA]
2095
2096 snd-dt019x= [HW,ALSA]
2097
2098 snd-dummy= [HW,ALSA]
2099
2100 snd-emu10k1= [HW,ALSA]
2101
2102 snd-ens1370= [HW,ALSA]
2103
2104 snd-ens1371= [HW,ALSA]
2105
2106 snd-es968= [HW,ALSA]
2107
2108 snd-es1688= [HW,ALSA]
2109
2110 snd-es18xx= [HW,ALSA]
2111
2112 snd-es1938= [HW,ALSA]
2113
2114 snd-es1968= [HW,ALSA]
2115
2116 snd-fm801= [HW,ALSA]
2117
2118 snd-gusclassic= [HW,ALSA]
2119
2120 snd-gusextreme= [HW,ALSA]
2121
2122 snd-gusmax= [HW,ALSA]
2123
2124 snd-hdsp= [HW,ALSA]
2125
2126 snd-ice1712= [HW,ALSA]
2127
2128 snd-intel8x0= [HW,ALSA]
2129
2130 snd-interwave= [HW,ALSA]
2131
2132 snd-interwave-stb=
2133 [HW,ALSA]
2134
2135 snd-korg1212= [HW,ALSA]
2136
2137 snd-maestro3= [HW,ALSA]
2138
2139 snd-mpu401= [HW,ALSA]
2140
2141 snd-mtpav= [HW,ALSA]
2142
2143 snd-nm256= [HW,ALSA]
2144
2145 snd-opl3sa2= [HW,ALSA]
2146
2147 snd-opti92x-ad1848=
2148 [HW,ALSA]
2149
2150 snd-opti92x-cs4231=
2151 [HW,ALSA]
2152
2153 snd-opti93x= [HW,ALSA]
2154
2155 snd-pmac= [HW,ALSA]
2156
2157 snd-rme32= [HW,ALSA]
2158
2159 snd-rme96= [HW,ALSA]
2160
2161 snd-rme9652= [HW,ALSA]
2162
2163 snd-sb8= [HW,ALSA]
2164
2165 snd-sb16= [HW,ALSA]
2166
2167 snd-sbawe= [HW,ALSA]
2168
2169 snd-serial= [HW,ALSA]
2170
2171 snd-sgalaxy= [HW,ALSA]
2172
2173 snd-sonicvibes= [HW,ALSA]
2174
2175 snd-sun-amd7930=
2176 [HW,ALSA]
2177
2178 snd-sun-cs4231= [HW,ALSA]
2179
2180 snd-trident= [HW,ALSA]
2181
2182 snd-usb-audio= [HW,ALSA,USB]
2183
2184 snd-via82xx= [HW,ALSA]
2185
2186 snd-virmidi= [HW,ALSA]
2187
2188 snd-wavefront= [HW,ALSA]
2189
2190 snd-ymfpci= [HW,ALSA]
a9913044 2191
9c44bc03
IM
2192 softlockup_panic=
2193 [KNL] Should the soft-lockup detector generate panics.
2194
1da177e4
LT
2195 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2196 See Documentation/sonypi.txt
2197
2198 specialix= [HW,SERIAL] Specialix multi-serial port adapter
31c00fc1 2199 See Documentation/serial/specialix.txt.
1da177e4
LT
2200
2201 spia_io_base= [HW,MTD]
2202 spia_fio_base=
2203 spia_pedr=
2204 spia_peddr=
2205
2206 sscape= [HW,OSS]
2207 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 2208
1da177e4
LT
2209 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2210 See Documentation/scsi/st.txt.
2211
f38f1d2a
SR
2212 stacktrace [FTRACE]
2213 Enabled the stack tracer on boot up.
2214
1da177e4
LT
2215 sti= [PARISC,HW]
2216 Format: <num>
2217 Set the STI (builtin display/keyboard on the HP-PARISC
2218 machines) console (graphic card) which should be used
2219 as the initial boot-console.
2220 See also comment in drivers/video/console/sticore.c.
2221
2222 sti_font= [HW]
2223 See comment in drivers/video/console/sticore.c.
2224
2225 stifb= [HW]
2226 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2227
42a7fc4a
GB
2228 sunrpc.pool_mode=
2229 [NFS]
2230 Control how the NFS server code allocates CPUs to
2231 service thread pools. Depending on how many NICs
2232 you have and where their interrupts are bound, this
2233 option will affect which CPUs will do NFS serving.
2234 Note: this parameter cannot be changed while the
2235 NFS server is running.
2236
2237 auto the server chooses an appropriate mode
2238 automatically using heuristics
2239 global a single global pool contains all CPUs
2240 percpu one pool for each CPU
2241 pernode one pool for each NUMA node (equivalent
2242 to global on non-NUMA machines)
2243
1da177e4 2244 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2245
1da177e4
LT
2246 switches= [HW,M68k]
2247
2248 sym53c416= [HW,SCSI]
2249 See header of drivers/scsi/sym53c416.c.
2250
5d6f647f
IM
2251 sysrq_always_enabled
2252 [KNL]
2253 Ignore sysrq setting - this boot parameter will
2254 neutralize any effect of /proc/sys/kernel/sysrq.
2255 Useful for debugging.
2256
1da177e4
LT
2257 t128= [HW,SCSI]
2258 See header of drivers/scsi/t128.c.
2259
2260 tdfx= [HW,DRM]
2261
77437fd4
DB
2262 test_suspend= [SUSPEND]
2263 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2264 standby suspend) as the system sleep state to briefly
2265 enter during system startup. The system is woken from
2266 this state using a wakeup-capable RTC alarm.
2267
1da177e4
LT
2268 thash_entries= [KNL,NET]
2269 Set number of hash buckets for TCP connection
2270
f8707ec9
LB
2271 thermal.act= [HW,ACPI]
2272 -1: disable all active trip points in all thermal zones
2273 <degrees C>: override all lowest active trip points
2274
c52a7419
LB
2275 thermal.crt= [HW,ACPI]
2276 -1: disable all critical trip points in all thermal zones
22a94d79 2277 <degrees C>: override all critical trip points
c52a7419 2278
f5487145
LB
2279 thermal.nocrt= [HW,ACPI]
2280 Set to disable actions on ACPI thermal zone
2281 critical and hot trip points.
2282
72b33ef8
LB
2283 thermal.off= [HW,ACPI]
2284 1: disable ACPI thermal control
2285
a70cdc52
LB
2286 thermal.psv= [HW,ACPI]
2287 -1: disable all passive trip points
2288 <degrees C>: override all passive trip points to this value
2289
730ff34d
LB
2290 thermal.tzp= [HW,ACPI]
2291 Specify global default ACPI thermal zone polling rate
2292 <deci-seconds>: poll all this frequency
2293 0: no polling (default)
2294
1da177e4
LT
2295 tmscsim= [HW,SCSI]
2296 See comment before function dc390_setup() in
2297 drivers/scsi/tmscsim.c.
2298
2b1a61f0
HC
2299 topology= [S390]
2300 Format: {off | on}
2301 Specify if the kernel should make use of the cpu
2302 topology informations if the hardware supports these.
2303 The scheduler will make use of these informations and
2304 e.g. base its process migration decisions on it.
2305 Default is off.
2306
1da177e4
LT
2307 tp720= [HW,PS2]
2308
2309 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2310 Format:
2311 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2312
395628ef
AK
2313 tsc= Disable clocksource-must-verify flag for TSC.
2314 Format: <string>
2315 [x86] reliable: mark tsc clocksource as reliable, this
2316 disables clocksource verification at runtime.
2317 Used to enable high-resolution timer mode on older
2318 hardware, and in virtualized environment.
2319
a9913044
RD
2320 turbografx.map[2|3]= [HW,JOY]
2321 TurboGraFX parallel port interface
2322 Format:
2323 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2324 See also Documentation/input/joystick-parport.txt
2325
2326 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2327 See header of drivers/scsi/u14-34f.c.
2328
2329 uart401= [HW,OSS]
2330 Format: <io>,<irq>
2331
2332 uart6850= [HW,OSS]
2333 Format: <io>,<irq>
2334
5f8364b7
AS
2335 uhci-hcd.ignore_oc=
2336 [USB] Ignore overcurrent events (default N).
2337 Some badly-designed motherboards generate lots of
2338 bogus events, for ports that aren't wired to
2339 anything. Set this parameter to avoid log spamming.
2340 Note that genuine overcurrent events won't be
2341 reported either.
2342
e3a61b0a
SA
2343 unknown_nmi_panic
2344 [X86-32,X86-64]
2345 Set unknown_nmi_panic=1 early on boot.
2346
b5e795f8
AS
2347 usbcore.autosuspend=
2348 [USB] The autosuspend time delay (in seconds) used
2349 for newly-detected USB devices (default 2). This
2350 is the time required before an idle device will be
2351 autosuspended. Devices for which the delay is set
eaafbc3a 2352 to a negative value won't be autosuspended at all.
b5e795f8 2353
fd7c519d
JK
2354 usbcore.usbfs_snoop=
2355 [USB] Set to log all usbfs traffic (default 0 = off).
2356
2357 usbcore.blinkenlights=
2358 [USB] Set to cycle leds on hubs (default 0 = off).
2359
2360 usbcore.old_scheme_first=
2361 [USB] Start with the old device initialization
2362 scheme (default 0 = off).
2363
2364 usbcore.use_both_schemes=
2365 [USB] Try the other device initialization scheme
2366 if the first one fails (default 1 = enabled).
2367
2368 usbcore.initial_descriptor_timeout=
2369 [USB] Specifies timeout for the initial 64-byte
2370 USB_REQ_GET_DESCRIPTOR request in milliseconds
2371 (default 5000 = 5.0 seconds).
2372
1da177e4
LT
2373 usbhid.mousepoll=
2374 [USBHID] The interval which mice are to be polled at.
a9913044 2375
200001eb
PJ
2376 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2377 kernel's map of available physical RAM.
2378
cd4f0ef7 2379 vdso= [X86-32,SH,x86-64]
1dbf527c 2380 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2381 vdso=1: enable VDSO (default)
2382 vdso=0: disable VDSO mapping
2383
af65d648
RM
2384 vdso32= [X86-32,X86-64]
2385 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2386 vdso32=1: enable 32-bit VDSO (default)
2387 vdso32=0: disable 32-bit VDSO mapping
2388
d080d397
YI
2389 vector= [IA-64,SMP]
2390 vector=percpu: enable percpu vector domain
2391
1da177e4
LT
2392 video= [FB] Frame buffer configuration
2393 See Documentation/fb/modedb.txt.
2394
cd4f0ef7 2395 vga= [BOOT,X86-32] Select a particular video mode
71cced6e 2396 See Documentation/x86/i386/boot.txt and
a9913044 2397 Documentation/svga.txt.
1da177e4
LT
2398 Use vga=ask for menu.
2399 This is actually a boot loader parameter; the value is
2400 passed to the kernel using a special protocol.
2401
a9913044 2402 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2403 size of <nn>. This can be used to increase the
2404 minimum size (128MB on x86). It can also be used to
2405 decrease the size and leave more room for directly
2406 mapped kernel RAM.
2407
585c3047
PO
2408 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2409 Format: <command>
1da177e4 2410
585c3047
PO
2411 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2412 Format: <command>
2413
2414 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2415 Format: <command>
a9913044 2416
1da177e4
LT
2417 waveartist= [HW,OSS]
2418 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2419
1da177e4
LT
2420 wd33c93= [HW,SCSI]
2421 See header of drivers/scsi/wd33c93.c.
2422
2423 wd7000= [HW,SCSI]
2424 See header of drivers/scsi/wd7000.c.
2425
2426 wdt= [WDT] Watchdog
8dfe9c21 2427 See Documentation/watchdog/wdt.txt.
1da177e4
LT
2428
2429 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2430 xd_geo= See header of drivers/block/xd.c.
2431
2432 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2433 Format:
2434 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2435
a62eaf15
AK
2436 norandmaps Don't use address space randomization
2437 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2438
a9913044 2439______________________________________________________________________
1da177e4
LT
2440
2441TODO:
2442
2443 Add documentation for ALSA options.
2444 Add more DRM drivers.