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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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20Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22can also be entered as
23 log-buf-len=1M print_fatal_signals=1
24
25
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26This document may not be entirely up to date and comprehensive. The command
27"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28module. Loadable modules, after being loaded into the running kernel, also
29reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30parameters may be changed at runtime by the command
31"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
32
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33The parameters listed below are only valid if certain kernel build options were
34enabled and if respective hardware is present. The text in square brackets at
35the beginning of each description states the restrictions within which a
36parameter is applicable:
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37
38 ACPI ACPI support is enabled.
c99c108a 39 AGP AGP (Accelerated Graphics Port) is enabled.
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40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
e7ba176b 43 AVR32 AVR32 architecture is enabled.
1da177e4 44 AX25 Appropriate AX.25 support is enabled.
0ae53640 45 BLACKFIN Blackfin architecture is enabled.
a9913044 46 DRM Direct Rendering Management support is enabled.
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47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
2521f2c2 51 GCOV GCOV profiling is enabled.
1da177e4 52 HW Appropriate hardware is enabled.
1da177e4 53 IA-64 IA-64 architecture is enabled.
6146f0d5 54 IMA Integrity measurement architecture is enabled.
1da177e4 55 IOSCHED More than one I/O scheduler is enabled.
41e2e8be 56 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
b0f83b28 57 IPV6 IPv6 support is enabled.
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58 ISAPNP ISA PnP code is enabled.
59 ISDN Appropriate ISDN support is enabled.
60 JOY Appropriate joystick support is enabled.
84c08fd6 61 KGDB Kernel debugger support is enabled.
fef07aae 62 KVM Kernel Virtual Machine support is enabled.
11ef697b 63 LIBATA Libata driver is enabled
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64 LP Printer support is enabled.
65 LOOP Loopback device support is enabled.
66 M68k M68k architecture is enabled.
67 These options have more detailed description inside of
68 Documentation/m68k/kernel-options.txt.
69 MCA MCA bus support is enabled.
70 MDA MDA console support is enabled.
71 MOUSE Appropriate mouse support is enabled.
309e57df 72 MSI Message Signaled Interrupts (PCI).
c8facbb6 73 MTD MTD (Memory Technology Device) support is enabled.
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74 NET Appropriate network support is enabled.
75 NUMA NUMA support is enabled.
734efb46 76 GENERIC_TIME The generic timeofday code is enabled.
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77 NFS Appropriate NFS support is enabled.
78 OSS OSS sound support is enabled.
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79 PV_OPS A paravirtualized kernel is enabled.
80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
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81 PARISC The PA-RISC architecture is enabled.
82 PCI PCI bus support is enabled.
7f785763 83 PCIE PCI Express support is enabled.
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84 PCMCIA The PCMCIA subsystem is enabled.
85 PNP Plug & Play support is enabled.
86 PPC PowerPC architecture is enabled.
87 PPT Parallel port support is enabled.
88 PS2 Appropriate PS/2 support is enabled.
89 RAM RAM disk support is enabled.
90 S390 S390 architecture is enabled.
91 SCSI Appropriate SCSI support is enabled.
92 A lot of drivers has their options described inside of
93 Documentation/scsi/.
20510f2f 94 SECURITY Different security models are enabled.
1da177e4 95 SELINUX SELinux support is enabled.
c1c124e9 96 APPARMOR AppArmor support is enabled.
1da177e4 97 SERIAL Serial support is enabled.
e523d93c 98 SH SuperH architecture is enabled.
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99 SMP The kernel is an SMP kernel.
100 SPARC Sparc architecture is enabled.
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101 SWSUSP Software suspend (hibernation) is enabled.
102 SUSPEND System suspend states are enabled.
f38f1d2a 103 FTRACE Function tracing enabled.
225a9be2 104 TPM TPM drivers are enabled.
1da177e4 105 TS Appropriate touchscreen support is enabled.
d4f373e5 106 UMS USB Mass Storage support is enabled.
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107 USB USB support is enabled.
108 USBHID USB Human Interface Device support is enabled.
109 V4L Video For Linux support is enabled.
110 VGA The VGA console has been enabled.
111 VT Virtual terminal support is enabled.
112 WDT Watchdog support is enabled.
113 XT IBM PC/XT MFM hard disk support is enabled.
cd4f0ef7 114 X86-32 X86-32, aka i386 architecture is enabled.
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115 X86-64 X86-64 architecture is enabled.
116 More X86-64 boot options can be found in
71cced6e 117 Documentation/x86/x86_64/boot-options.txt .
c0115606 118 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
c1c5413a 119 XEN Xen support is enabled
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120
121In addition, the following text indicates that the option:
122
123 BUGS= Relates to possible processor bugs on the said processor.
124 KNL Is a kernel start-up parameter.
125 BOOT Is a boot loader parameter.
126
127Parameters denoted with BOOT are actually interpreted by the boot
128loader, and have no meaning to the kernel directly.
129Do not modify the syntax of boot loader parameters without extreme
954a8b81 130need or coordination with <Documentation/x86/boot.txt>.
1da177e4 131
5558870b 132There are also arch-specific kernel-parameters not documented here.
71cced6e 133See for example <Documentation/x86/x86_64/boot-options.txt>.
5558870b 134
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135Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
136a trailing = on the name of any parameter states that that parameter will
137be entered as an environment variable, whereas its absence indicates that
138it will appear as a kernel argument readable via /proc/cmdline by programs
139running once the system is up.
140
9c4751fd 141The number of kernel parameters is not limited, but the length of the
142complete command line (parameters including spaces etc.) is limited to
143a fixed number of characters. This limit depends on the architecture
144and is between 256 and 4096 characters. It is defined in the file
145./include/asm/setup.h as COMMAND_LINE_SIZE.
146
147
6cececfc 148 acpi= [HW,ACPI,X86]
03d926f8 149 Advanced Configuration and Power Interface
68ca4069 150 Format: { force | off | strict | noirq | rsdt }
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151 force -- enable ACPI if default was off
152 off -- disable ACPI if default was on
153 noirq -- do not use ACPI for IRQ routing
a9913044 154 strict -- Be less tolerant of platforms that are not
1da177e4 155 strictly ACPI specification compliant.
237889bf 156 rsdt -- prefer RSDT over (default) XSDT
aa2110cb 157 copy_dsdt -- copy DSDT to memory
1da177e4 158
53471121 159 See also Documentation/power/pm.txt, pci=noacpi
1da177e4 160
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161 acpi_apic_instance= [ACPI, IOAPIC]
162 Format: <int>
163 2: use 2nd APIC table, if available
164 1,0: use 1st APIC table
4e381a4f 165 default: 0
a1fdcc0d 166
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167 acpi_backlight= [HW,ACPI]
168 acpi_backlight=vendor
169 acpi_backlight=video
170 If set to vendor, prefer vendor specific driver
171 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
172 of the ACPI video.ko driver.
173
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174 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
175 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
1da177e4 176 Format: <int>
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177 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
178 debug output. Bits in debug_layer correspond to a
179 _COMPONENT in an ACPI source file, e.g.,
180 #define _COMPONENT ACPI_PCI_COMPONENT
181 Bits in debug_level correspond to a level in
182 ACPI_DEBUG_PRINT statements, e.g.,
183 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
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184 The debug_level mask defaults to "info". See
185 Documentation/acpi/debug.txt for more information about
186 debug layers and levels.
a0d84a92 187
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188 Enable processor driver info messages:
189 acpi.debug_layer=0x20000000
190 Enable PCI/PCI interrupt routing info messages:
191 acpi.debug_layer=0x400000
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192 Enable AML "Debug" output, i.e., stores to the Debug
193 object while interpreting AML:
194 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
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195 Enable all messages related to ACPI hardware:
196 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
197
198 Some values produce so much output that the system is
199 unusable. The "log_buf_len" parameter may be useful
200 if you need to capture more output.
f989106c 201
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202 acpi_display_output= [HW,ACPI]
203 acpi_display_output=vendor
204 acpi_display_output=video
205 See above.
206
207 acpi_irq_balance [HW,ACPI]
208 ACPI will balance active IRQs
209 default in APIC mode
210
211 acpi_irq_nobalance [HW,ACPI]
212 ACPI will not move active IRQs (default)
213 default in PIC mode
214
215 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
216 Format: <irq>,<irq>...
217
218 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
219 use by PCI
220 Format: <irq>,<irq>...
221
222 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
223
224 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
225 Format: To spoof as Windows 98: ="Microsoft Windows"
226
227 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
228 acpi_osi="string1" # add string1 -- only one string
229 acpi_osi="!string2" # remove built-in string2
230 acpi_osi= # disable all strings
231
6cececfc 232 acpi_pm_good [X86]
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233 Override the pmtimer bug detection: force the kernel
234 to assume that this machine's pmtimer latches its value
235 and always returns good values.
236
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237 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
238 Format: { level | edge | high | low }
239
240 acpi_serialize [HW,ACPI] force serialization of AML methods
241
242 acpi_skip_timer_override [HW,ACPI]
243 Recognize and ignore IRQ0/pin2 Interrupt Override.
244 For broken nForce2 BIOS resulting in XT-PIC timer.
245
246 acpi_sleep= [HW,ACPI] Sleep options
247 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
d7f0eea9 248 old_ordering, s4_nonvs, sci_force_enable }
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249 See Documentation/power/video.txt for information on
250 s3_bios and s3_mode.
251 s3_beep is for debugging; it makes the PC's speaker beep
252 as soon as the kernel's real-mode entry point is called.
253 s4_nohwsig prevents ACPI hardware signature from being
254 used during resume from hibernation.
255 old_ordering causes the ACPI 1.0 ordering of the _PTS
256 control method, with respect to putting devices into
257 low power states, to be enforced (the ACPI 2.0 ordering
258 of _PTS is used by default).
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259 nonvs prevents the kernel from saving/restoring the
260 ACPI NVS memory during suspend/hibernation and resume.
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261 sci_force_enable causes the kernel to set SCI_EN directly
262 on resume from S1/S3 (which is against the ACPI spec,
263 but some broken systems don't work without it).
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264
265 acpi_use_timer_override [HW,ACPI]
266 Use timer override. For some broken Nvidia NF5 boards
267 that require a timer override, but don't have HPET
268
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269 acpi_enforce_resources= [ACPI]
270 { strict | lax | no }
271 Check for resource conflicts between native drivers
272 and ACPI OperationRegions (SystemIO and SystemMemory
273 only). IO ports and memory declared in ACPI might be
274 used by the ACPI subsystem in arbitrary AML code and
275 can interfere with legacy drivers.
276 strict (default): access to resources claimed by ACPI
277 is denied; legacy drivers trying to access reserved
278 resources will fail to bind to device using them.
279 lax: access to resources claimed by ACPI is allowed;
280 legacy drivers trying to access reserved resources
281 will bind successfully but a warning message is logged.
282 no: ACPI OperationRegions are not marked as reserved,
283 no further checks are performed.
284
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285 ad1848= [HW,OSS]
286 Format: <io>,<irq>,<dma>,<dma2>,<type>
287
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288 add_efi_memmap [EFI; X86] Include EFI memory map in
289 kernel's map of available physical RAM.
290
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291 advansys= [HW,SCSI]
292 See header of drivers/scsi/advansys.c.
293
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294 aedsp16= [HW,OSS] Audio Excel DSP 16
295 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
296 See also header of sound/oss/aedsp16.c.
a9913044 297
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298 agp= [AGP]
299 { off | try_unsupported }
300 off: disable AGP support
301 try_unsupported: try to drive unsupported chipsets
302 (may crash computer or cause data corruption)
303
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304 aha152x= [HW,SCSI]
305 See Documentation/scsi/aha152x.txt.
306
307 aha1542= [HW,SCSI]
308 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
309
310 aic7xxx= [HW,SCSI]
311 See Documentation/scsi/aic7xxx.txt.
312
313 aic79xx= [HW,SCSI]
314 See Documentation/scsi/aic79xx.txt.
315
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316 alignment= [KNL,ARM]
317 Allow the default userspace alignment fault handler
318 behaviour to be specified. Bit 0 enables warnings,
319 bit 1 enables fixups, and bit 2 sends a segfault.
320
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321 amd_iommu= [HW,X86-84]
322 Pass parameters to the AMD IOMMU driver in the system.
323 Possible values are:
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324 fullflush - enable flushing of IO/TLB entries when
325 they are unmapped. Otherwise they are
326 flushed before they will be reused, which
327 is a lot of faster
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328 off - do not initialize any AMD IOMMU found in
329 the system
afa9fdc2 330
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331 amijoy.map= [HW,JOY] Amiga joystick support
332 Map of devices attached to JOY0DAT and JOY1DAT
333 Format: <a>,<b>
334 See also Documentation/kernel/input/joystick.txt
335
336 analog.map= [HW,JOY] Analog joystick and gamepad support
337 Specifies type or capabilities of an analog joystick
338 connected to one of 16 gameports
339 Format: <type1>,<type2>,..<type16>
340
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341 apc= [HW,SPARC]
342 Power management functions (SPARCstation-4/5 + deriv.)
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343 Format: noidle
344 Disable APC CPU standby support. SPARCstation-Fox does
345 not play well with APC CPU idle - disable it if you have
346 APC and your system crashes randomly.
347
ca1eda2d 348 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
c8facbb6 349 Change the output verbosity whilst booting
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350 Format: { quiet (default) | verbose | debug }
351 Change the amount of debugging information output
352 when initialising the APIC and IO-APIC components.
a9913044 353
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354 autoconf= [IPV6]
355 See Documentation/networking/ipv6.txt.
356
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357 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
358 Limit apic dumping. The parameter defines the maximal
359 number of local apics being dumped. Also it is possible
360 to set it to "all" by meaning -- no limit here.
361 Format: { 1 (default) | 2 | ... | all }.
362 The parameter valid if only apic=debug or
363 apic=verbose is specified.
364 Example: apic=debug show_lapic=all
365
1da177e4 366 apm= [APM] Advanced Power Management
71f77055 367 See header of arch/x86/kernel/apm_32.c.
1da177e4 368
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369 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
370 Format: <io>,<irq>,<nodeID>
371
372 ataflop= [HW,M68k]
373
374 atarimouse= [HW,MOUSE] Atari Mouse
375
376 atascsi= [HW,SCSI] Atari SCSI
377
378 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
379 EzKey and similar keyboards
380
381 atkbd.reset= [HW] Reset keyboard during initialization
382
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383 atkbd.set= [HW] Select keyboard code set
384 Format: <int> (2 = AT (default), 3 = PS/2)
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385
386 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
387 keyboards
388
389 atkbd.softraw= [HW] Choose between synthetic and real raw mode
390 Format: <bool> (0 = real, 1 = synthetic (default))
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391
392 atkbd.softrepeat= [HW]
393 Use software keyboard repeat
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394
395 autotest [IA64]
396
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397 baycom_epp= [HW,AX25]
398 Format: <io>,<mode>
a9913044 399
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400 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
401 Format: <io>,<mode>
402 See header of drivers/net/hamradio/baycom_par.c.
403
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404 baycom_ser_fdx= [HW,AX25]
405 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
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406 Format: <io>,<irq>,<mode>[,<baud>]
407 See header of drivers/net/hamradio/baycom_ser_fdx.c.
408
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409 baycom_ser_hdx= [HW,AX25]
410 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
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411 Format: <io>,<irq>,<mode>
412 See header of drivers/net/hamradio/baycom_ser_hdx.c.
413
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414 boot_delay= Milliseconds to delay each printk during boot.
415 Values larger than 10 seconds (10000) are changed to
416 no delay (0).
417 Format: integer
418
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419 bootmem_debug [KNL] Enable bootmem allocator debug messages.
420
1da177e4 421 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
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422 bttv.radio= Most important insmod options are available as
423 kernel args too.
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424 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
425 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
426
427 BusLogic= [HW,SCSI]
428 See drivers/scsi/BusLogic.c, comment before function
429 BusLogic_ParseDriverOptions().
430
431 c101= [NET] Moxa C101 synchronous serial card
432
cd4f0ef7 433 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
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434 Sometimes CPU hardware bugs make them report the cache
435 size incorrectly. The kernel will attempt work arounds
436 to fix known problems, but for some CPUs it is not
437 possible to determine what the correct size should be.
438 This option provides an override for these situations.
439
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440 capability.disable=
441 [SECURITY] Disable capabilities. This would normally
442 be used only if an alternative security model is to be
443 configured. Potentially dangerous and should only be
444 used if you are entirely sure of the consequences.
445
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446 ccw_timeout_log [S390]
447 See Documentation/s390/CommonIO for details.
1da177e4 448
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449 cgroup_disable= [KNL] Disable a particular controller
450 Format: {name of the controller(s) to disable}
451 {Currently supported controllers - "memory"}
452
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453 checkreqprot [SELINUX] Set initial checkreqprot flag value.
454 Format: { "0" | "1" }
455 See security/selinux/Kconfig help text.
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456 0 -- check protection applied by kernel (includes
457 any implied execute protection).
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458 1 -- check protection requested by application.
459 Default value is set via a kernel config option.
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460 Value can be changed at runtime via
461 /selinux/checkreqprot.
462
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SO
463 cio_ignore= [S390]
464 See Documentation/s390/CommonIO for details.
465
cd4f0ef7 466 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
734efb46 467 [Deprecated]
3f6dee9b 468 Forces specified clocksource (if available) to be used
734efb46 469 when calculating gettimeofday(). If specified
3f6dee9b 470 clocksource is not available, it defaults to PIT.
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471 Format: { pit | tsc | cyclone | pmtmr }
472
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473 clocksource= [GENERIC_TIME] Override the default clocksource
474 Format: <string>
475 Override the default clocksource and use the clocksource
476 with the name specified.
477 Some clocksource names to choose from, depending on
478 the platform:
479 [all] jiffies (this is the base, fallback clocksource)
480 [ACPI] acpi_pm
481 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
482 pxa_timer,timer3,32k_counter,timer0_1
483 [AVR32] avr32
cd4f0ef7 484 [X86-32] pit,hpet,tsc,vmi-timer;
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485 scx200_hrt on Geode; cyclone on IBM x440
486 [MIPS] MIPS
487 [PARISC] cr16
488 [S390] tod
489 [SH] SuperH
490 [SPARC64] tick
491 [X86-64] hpet,tsc
492
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493 clearcpuid=BITNUM [X86]
494 Disable CPUID feature X for the kernel. See
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495 arch/x86/include/asm/cpufeature.h for the valid bit
496 numbers. Note the Linux specific bits are not necessarily
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497 stable over kernel options, but the vendor specific
498 ones should be.
499 Also note that user programs calling CPUID directly
500 or using the feature without checking anything
501 will still see it. This just prevents it from
502 being used by the kernel or shown in /proc/cpuinfo.
503 Also note the kernel might malfunction if you disable
504 some critical bits.
505
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506 cmo_free_hint= [PPC] Format: { yes | no }
507 Specify whether pages are marked as being inactive
508 when they are freed. This is used in CMO environments
509 to determine OS memory pressure for page stealing by
510 a hypervisor.
511 Default: yes
512
6cececfc 513 code_bytes [X86] How many bytes of object code to print
a25bd949 514 in an oops report.
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515 Range: 0 - 8192
516 Default: 64
517
1da177e4 518 com20020= [HW,NET] ARCnet - COM20020 chipset
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519 Format:
520 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
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521
522 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
523 Format: <io>[,<irq>]
524
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525 com90xx= [HW,NET]
526 ARCnet - COM90xx chipset (memory-mapped buffers)
1da177e4
LT
527 Format: <io>[,<irq>[,<memstart>]]
528
529 condev= [HW,S390] console device
530 conmode=
a9913044 531
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LT
532 console= [KNL] Output console device and options.
533
534 tty<n> Use the virtual console device <n>.
535
536 ttyS<n>[,options]
f1a1c2dc 537 ttyUSB0[,options]
1da177e4 538 Use the specified serial port. The options are of
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RD
539 the form "bbbbpnf", where "bbbb" is the baud rate,
540 "p" is parity ("n", "o", or "e"), "n" is number of
541 bits, and "f" is flow control ("r" for RTS or
542 omit it). Default is "9600n8".
543
544 See Documentation/serial-console.txt for more
545 information. See
546 Documentation/networking/netconsole.txt for an
547 alternative.
1da177e4 548
18a8bd94
YL
549 uart[8250],io,<addr>[,options]
550 uart[8250],mmio,<addr>[,options]
1da177e4
LT
551 Start an early, polled-mode console on the 8250/16550
552 UART at the specified I/O port or MMIO address,
553 switching to the matching ttyS device later. The
554 options are the same as for ttyS, above.
555
f7511d5f
ST
556 If the device connected to the port is not a TTY but a braille
557 device, prepend "brl," before the device type, for instance
558 console=brl,ttyS0
559 For now, only VisioBraille is supported.
560
f324edc8
DM
561 consoleblank= [KNL] The console blank (screen saver) timeout in
562 seconds. Defaults to 10*60 = 10mins. A value of 0
563 disables the blank timer.
564
4cb0e11b
HK
565 coredump_filter=
566 [KNL] Change the default value for
567 /proc/<pid>/coredump_filter.
568 See also Documentation/filesystems/proc.txt.
569
1da177e4 570 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
a9913044
RD
571 Format:
572 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
1da177e4 573
dc009d92
EB
574 crashkernel=nn[KMG]@ss[KMG]
575 [KNL] Reserve a chunk of physical memory to
576 hold a kernel to switch to with kexec on panic.
577
fb391599
BW
578 crashkernel=range1:size1[,range2:size2,...][@offset]
579 [KNL] Same as above, but depends on the memory
580 in the running system. The syntax of range is
581 start-[end] where start and end are both
582 a memory unit (amount[KMG]). See also
583 Documentation/kdump/kdump.txt for a example.
584
1da177e4
LT
585 cs89x0_dma= [HW,NET]
586 Format: <dma>
587
588 cs89x0_media= [HW,NET]
589 Format: { rj45 | aui | bnc }
a9913044 590
a9913044 591 dasd= [HW,NET]
1da177e4
LT
592 See header of drivers/s390/block/dasd_devmap.c.
593
594 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
595 (one device per port)
596 Format: <port#>,<type>
597 See also Documentation/input/joystick-parport.txt
598
599 debug [KNL] Enable kernel debugging (events log level).
600
cae2ed9a
IM
601 debug_locks_verbose=
602 [KNL] verbose self-tests
603 Format=<0|1>
604 Print debugging info while doing the locking API
605 self-tests.
606 We default to 0 (no extra messages), setting it to
607 1 will print _a lot_ more information - normally
608 only useful to kernel developers.
609
3ac7fe5a
TG
610 debug_objects [KNL] Enable object debugging
611
3e8ebb5c
KM
612 no_debug_objects
613 [KNL] Disable object debugging
614
d3af01f1
TG
615 debugpat [X86] Enable PAT debugging
616
2d27a966 617 decnet.addr= [HW,NET]
1da177e4
LT
618 Format: <area>[,<node>]
619 See also Documentation/networking/decnet.txt.
620
0cb55ad2
RD
621 default_hugepagesz=
622 [same as hugepagesz=] The size of the default
623 HugeTLB page size. This is the size represented by
624 the legacy /proc/ hugepages APIs, used for SHM, and
625 default size when mounting hugetlbfs filesystems.
626 Defaults to the default architecture's huge page size
627 if not specified.
55ff9780 628
1da177e4
LT
629 dhash_entries= [KNL]
630 Set number of hash buckets for dentry cache.
a9913044 631
1da177e4
LT
632 digi= [HW,SERIAL]
633 IO parameters + enable/disable command.
634
635 digiepca= [HW,SERIAL]
636 See drivers/char/README.epca and
31c00fc1 637 Documentation/serial/digiepca.txt.
1da177e4 638
b0f83b28
BH
639 disable= [IPV6]
640 See Documentation/networking/ipv6.txt.
641
642 disable_ipv6= [IPV6]
643 See Documentation/networking/ipv6.txt.
644
95ffa243 645 disable_mtrr_cleanup [X86]
95ffa243
YL
646 The kernel tries to adjust MTRR layout from continuous
647 to discrete, to make X server driver able to add WB
0cb55ad2 648 entry later. This parameter disables that.
95ffa243 649
093af8d7 650 disable_mtrr_trim [X86, Intel and AMD only]
99fc8d42
JB
651 By default the kernel will trim any uncacheable
652 memory out of your available memory pool based on
653 MTRR settings. This parameter disables that behavior,
654 possibly causing your machine to run very slowly.
655
6cececfc 656 disable_timer_pin_1 [X86]
0cb55ad2
RD
657 Disable PIN 1 of APIC timer
658 Can be useful to work around chipset bugs.
659
1da177e4
LT
660 dmasound= [HW,OSS] Sound subsystem buffers
661
0cb55ad2
RD
662 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
663 this option disables the debugging code at boot.
664
665 dma_debug_entries=<number>
666 This option allows to tune the number of preallocated
667 entries for DMA-API debugging code. One entry is
668 required per DMA-API allocation. Use this if the
669 DMA-API debugging code disables itself because the
670 architectural default is too low.
671
1745de5e
JR
672 dma_debug_driver=<driver_name>
673 With this option the DMA-API debugging driver
674 filter feature can be enabled at boot time. Just
675 pass the driver to filter for as the parameter.
676 The filter can be disabled or changed to another
677 driver later using sysfs.
678
1da177e4
LT
679 dscc4.setup= [NET]
680
681 dtc3181e= [HW,SCSI]
682
0cb55ad2
RD
683 dynamic_printk Enables pr_debug()/dev_dbg() calls if
684 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
685 These can also be switched on/off via
686 <debugfs>/dynamic_printk/modules
687
688 earlycon= [KNL] Output early console device and options.
689 uart[8250],io,<addr>[,options]
690 uart[8250],mmio,<addr>[,options]
691 Start an early, polled-mode console on the 8250/16550
692 UART at the specified I/O port or MMIO address.
693 The options are the same as for ttyS, above.
694
6cececfc 695 earlyprintk= [X86,SH,BLACKFIN]
1da177e4
LT
696 earlyprintk=vga
697 earlyprintk=serial[,ttySn[,baudrate]]
ea3acb19 698 earlyprintk=ttySn[,baudrate]
9780bc41 699 earlyprintk=dbgp[debugController#]
1da177e4 700
a9913044 701 Append ",keep" to not disable it when the real console
1da177e4
LT
702 takes over.
703
5c05917e 704 Only vga or serial or usb debug port at a time.
1da177e4
LT
705
706 Currently only ttyS0 and ttyS1 are supported.
707
708 Interaction with the standard serial driver is not
709 very good.
710
711 The VGA output is eventually overwritten by the real
712 console.
713
9731191f
JW
714 ekgdboc= [X86,KGDB] Allow early kernel console debugging
715 ekgdboc=kbd
716
717 This is desgined to be used in conjunction with
718 the boot argument: earlyprintk=vga
719
1da177e4
LT
720 eata= [HW,SCSI]
721
1da177e4 722 edd= [EDD]
8c4dd606 723 Format: {"off" | "on" | "skip[mbr]"}
1da177e4 724
1da177e4
LT
725 eisa_irq_edge= [PARISC,HW]
726 See header of drivers/parisc/eisa.c.
727
cd4f0ef7 728 elanfreq= [X86-32]
1da177e4 729 See comment before function elanfreq_setup() in
71f77055 730 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1da177e4
LT
731
732 elevator= [IOSCHED]
16ab3adf 733 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
a9913044
RD
734 See Documentation/block/as-iosched.txt and
735 Documentation/block/deadline-iosched.txt for details.
736
6cececfc 737 elfcorehdr= [IA64,PPC,SH,X86]
a9913044 738 Specifies physical address of start of kernel core
aac04b32
VG
739 image elf header. Generally kexec loader will
740 pass this option to capture kernel.
741 See Documentation/kdump/kdump.txt for details.
1da177e4 742
0cb55ad2
RD
743 enable_mtrr_cleanup [X86]
744 The kernel tries to adjust MTRR layout from continuous
745 to discrete, to make X server driver able to add WB
746 entry later. This parameter enables that.
747
ca1eda2d 748 enable_timer_pin_1 [X86]
0cb55ad2
RD
749 Enable PIN 1 of APIC timer
750 Can be useful to work around chipset bugs
751 (in particular on some ATI chipsets).
752 The kernel tries to set a reasonable default.
753
1da177e4
LT
754 enforcing [SELINUX] Set initial enforcing status.
755 Format: {"0" | "1"}
756 See security/selinux/Kconfig help text.
757 0 -- permissive (log only, no denials).
758 1 -- enforcing (deny and log).
759 Default value is 0.
760 Value can be changed at runtime via /selinux/enforce.
761
a08f82d0
HY
762 erst_disable [ACPI]
763 Disable Error Record Serialization Table (ERST)
764 support.
765
1da177e4
LT
766 ether= [HW,NET] Ethernet cards parameters
767 This option is obsoleted by the "netdev=" option, which
768 has equivalent usage. See its documentation for details.
769
de1ba09b
AM
770 failslab=
771 fail_page_alloc=
772 fail_make_request=[KNL]
773 General fault injection mechanism.
774 Format: <interval>,<probability>,<space>,<times>
775 See also /Documentation/fault-injection/.
776
1da177e4
LT
777 fd_mcs= [HW,SCSI]
778 See header of drivers/scsi/fd_mcs.c.
779
780 fdomain= [HW,SCSI]
781 See header of drivers/scsi/fdomain.c.
782
783 floppy= [HW]
31c00fc1 784 See Documentation/blockdev/floppy.txt.
1da177e4 785
f13ae30e
AC
786 force_pal_cache_flush
787 [IA-64] Avoid check_sal_cache_flush which may hang on
788 buggy SAL_CACHE_FLUSH implementations. Using this
789 parameter will force ia64_sal_cache_flush to call
790 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
791
d9e54076 792 ftrace=[tracer]
2af15d6a 793 [FTRACE] will set and start the specified tracer
d9e54076
PZ
794 as early as possible in order to facilitate early
795 boot debugging.
796
cecbca96 797 ftrace_dump_on_oops[=orig_cpu]
2af15d6a 798 [FTRACE] will dump the trace buffers on oops.
cecbca96
FW
799 If no parameter is passed, ftrace will dump
800 buffers of all CPUs, but if you pass orig_cpu, it will
801 dump only the buffer of the CPU that triggered the
802 oops.
2af15d6a
SR
803
804 ftrace_filter=[function-list]
805 [FTRACE] Limit the functions traced by the function
806 tracer at boot up. function-list is a comma separated
807 list of functions. This list can be changed at run
808 time by the set_ftrace_filter file in the debugfs
809 tracing directory.
810
811 ftrace_notrace=[function-list]
812 [FTRACE] Do not trace the functions specified in
813 function-list. This list can be changed at run time
814 by the set_ftrace_notrace file in the debugfs
815 tracing directory.
d9e54076 816
369bc18f
SA
817 ftrace_graph_filter=[function-list]
818 [FTRACE] Limit the top level callers functions traced
819 by the function graph tracer at boot up.
820 function-list is a comma separated list of functions
821 that can be changed at run time by the
822 set_graph_function file in the debugfs tracing directory.
823
1da177e4
LT
824 gamecon.map[2|3]=
825 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
826 support via parallel port (up to 5 devices per port)
827 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
828 See also Documentation/input/joystick-parport.txt
829
830 gamma= [HW,DRM]
831
aaf23042
YL
832 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
833 Format: off | on
834 default: on
835
2521f2c2
PO
836 gcov_persist= [GCOV] When non-zero (default), profiling data for
837 kernel modules is saved and remains accessible via
838 debugfs, even when the module is unloaded/reloaded.
839 When zero, profiling data is discarded and associated
840 debugfs files are removed at module unload time.
841
1da177e4
LT
842 gdth= [HW,SCSI]
843 See header of drivers/scsi/gdth.c.
844
845 gpt [EFI] Forces disk with valid GPT signature but
846 invalid Protective MBR to be treated as GPT.
847
1da177e4
LT
848 gvp11= [HW,SCSI]
849
850 hashdist= [KNL,NUMA] Large hashes allocated during boot
851 are distributed across NUMA nodes. Defaults on
429aa0fc 852 for 64bit NUMA, off otherwise.
a9913044 853 Format: 0 | 1 (for off | on)
1da177e4
LT
854
855 hcl= [IA-64] SGI's Hardware Graph compatibility layer
856
857 hd= [EIDE] (E)IDE hard drive subsystem geometry
858 Format: <cyl>,<head>,<sect>
859
ea8c071c
HY
860 hest_disable [ACPI]
861 Disable Hardware Error Source Table (HEST) support;
862 corresponding firmware-first mode error processing
863 logic will be disabled.
864
1da177e4
LT
865 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
866 size of <nn>. This works even on boxes that have no
867 highmem otherwise. This also works to reduce highmem
868 size on bigger boxes.
869
54cdfdb4
TG
870 highres= [KNL] Enable/disable high resolution timer mode.
871 Valid parameters: "on", "off"
872 Default: "on"
873
1da177e4
LT
874 hisax= [HW,ISDN]
875 See Documentation/isdn/README.HiSax.
876
0cb55ad2
RD
877 hlt [BUGS=ARM,SH]
878
879 hpet= [X86-32,HPET] option to control HPET usage
880 Format: { enable (default) | disable | force |
881 verbose }
882 disable: disable HPET and use PIT instead
883 force: allow force enabled of undocumented chips (ICH4,
884 VIA, nVidia)
885 verbose: show contents of HPET registers during setup
886
b4718e62
AK
887 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
888 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
0d9ea754
JT
889 On x86-64 and powerpc, this option can be specified
890 multiple times interleaved with hugepages= to reserve
891 huge pages of different sizes. Valid pages sizes on
892 x86-64 are 2M (when the CPU supports "pse") and 1G
893 (when the CPU supports the "pdpe1gb" cpuinfo flag)
b4718e62
AK
894 Note that 1GB pages can only be allocated at boot time
895 using hugepages= and not freed afterwards.
6902aa84 896
555d61d6
HB
897 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
898 terminal devices. Valid values: 0..8
431429ff
HB
899 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
900 If specified, z/VM IUCV HVC accepts connections
901 from listed z/VM user IDs only.
cef7125d 902
3a853fb9 903 i2c_bus= [HW] Override the default board specific I2C bus speed
7954763b
JN
904 or register an additional I2C bus that is not
905 registered from board initialization code.
3a853fb9
JN
906 Format:
907 <bus_id>,<clkrate>
908
36d95739 909 i8042.debug [HW] Toggle i8042 debug mode
1da177e4 910 i8042.direct [HW] Put keyboard port into non-translated mode
84eb8d06
ML
911 i8042.dumbkbd [HW] Pretend that controller can only read data from
912 keyboard and cannot control its state
1da177e4
LT
913 (Don't attempt to blink the leds)
914 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
945ef0d4 915 i8042.nokbd [HW] Don't check/create keyboard port
75d08c78
JK
916 i8042.noloop [HW] Disable the AUX Loopback command while probing
917 for the AUX port
1da177e4
LT
918 i8042.nomux [HW] Don't check presence of an active multiplexing
919 controller
920 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
921 controllers
922 i8042.panicblink=
923 [HW] Frequency with which keyboard LEDs should blink
924 when kernel panics (default is 0.5 sec)
925 i8042.reset [HW] Reset the controller during init and cleanup
926 i8042.unlock [HW] Unlock (ignore) the keylock
927
928 i810= [HW,DRM]
929
e70c9d5e
DT
930 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
931 indicates that the driver is running on unsupported
932 hardware.
1da177e4
LT
933 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
934 does not match list of supported models.
935 i8k.power_status
936 [HW] Report power status in /proc/i8k
937 (disabled by default)
938 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
939 capability is set.
940
941 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
942 See Documentation/mca.txt.
943
944 icn= [HW,ISDN]
945 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
946
0af80c04
DF
947 ide-core.nodma= [HW] (E)IDE subsystem
948 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
075affcb
BZ
949 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
950 .cdrom .chs .ignore_cable are additional options
1c10e938 951 See Documentation/ide/ide.txt.
1da177e4 952
0cb55ad2
RD
953 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
954 Claim all unknown PCI IDE storage controllers.
955
f039b754 956 idle= [X86]
ada9cfdd
RD
957 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
958 Poll forces a polling idle loop that can slightly
959 improve the performance of waking up a idle CPU, but
960 will use a lot of power and make the system run hot.
961 Not recommended.
962 idle=mwait: On systems which support MONITOR/MWAIT but
963 the kernel chose to not use it because it doesn't save
964 as much power as a normal idle loop, use the
965 MONITOR/MWAIT idle loop anyways. Performance should be
966 the same as idle=poll.
967 idle=halt: Halt is forced to be used for CPU idle.
c1e3b377 968 In such case C2/C3 won't be used again.
ada9cfdd 969 idle=nomwait: Disable mwait for CPU C-states
a9913044 970
79290822
IM
971 ignore_loglevel [KNL]
972 Ignore loglevel setting - this will print /all/
973 kernel messages to the console. Useful for debugging.
974
1da177e4
LT
975 ihash_entries= [KNL]
976 Set number of hash buckets for inode cache.
977
3323eec9
MZ
978 ima_audit= [IMA]
979 Format: { "0" | "1" }
980 0 -- integrity auditing messages. (Default)
981 1 -- enable informational integrity auditing messages.
982
983 ima_hash= [IMA]
a9ed83a5 984 Format: { "sha1" | "md5" }
3323eec9
MZ
985 default: "sha1"
986
5789ba3b
EP
987 ima_tcb [IMA]
988 Load a policy which meets the needs of the Trusted
989 Computing Base. This means IMA will measure all
990 programs exec'd, files mmap'd for exec, and all files
991 opened for read by uid=0.
992
1da177e4
LT
993 in2000= [HW,SCSI]
994 See header of drivers/scsi/in2000.c.
995
996 init= [KNL]
997 Format: <full_path>
998 Run specified binary instead of /sbin/init as init
999 process.
1000
1001 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1002 for working out where the kernel is dying during
1003 startup.
1004
1005 initrd= [BOOT] Specify the location of the initial ramdisk
1006
1007 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1008 Format: <irq>
1009
ba395927 1010 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
0cd5c3c8
KM
1011 on
1012 Enable intel iommu driver.
ba395927
KA
1013 off
1014 Disable intel iommu driver.
1015 igfx_off [Default Off]
1016 By default, gfx is mapped as normal device. If a gfx
1017 device has a dedicated DMAR unit, the DMAR unit is
1018 bypassed by not enabling DMAR with this option. In
1019 this case, gfx device will use physical address for
1020 DMA.
7d3b03ce
KA
1021 forcedac [x86_64]
1022 With this option iommu will not optimize to look
1023 for io virtual address below 32 bit forcing dual
1024 address cycle on pci bus for cards supporting greater
1025 than 32 bit addressing. The default is to look
1026 for translation below 32 bit and if not available
1027 then look in the higher range.
5e0d2a6f 1028 strict [Default Off]
1029 With this option on every unmap_single operation will
1030 result in a hardware IOTLB flush operation as opposed
1031 to batching them for performance.
ba395927 1032
0cb55ad2
RD
1033 inttest= [IA64]
1034
1035 iomem= Disable strict checking of access to MMIO memory
1036 strict regions from userspace.
1037 relaxed
1038
1039 iommu= [x86]
1040 off
1041 force
1042 noforce
1043 biomerge
1044 panic
1045 nopanic
1046 merge
1047 nomerge
1048 forcesac
1049 soft
4ed0d3e6 1050 pt [x86, IA64]
0cb55ad2
RD
1051
1052 io7= [HW] IO7 for Marvel based alpha systems
1053 See comment before marvel_specify_io7 in
1054 arch/alpha/kernel/core_marvel.c.
1055
6cececfc 1056 io_delay= [X86] I/O delay method
6e7c4025
IM
1057 0x80
1058 Standard port 0x80 based delay
1059 0xed
1060 Alternate port 0xed based delay (needed on some systems)
b02aae9c 1061 udelay
6e7c4025
IM
1062 Simple two microseconds delay
1063 none
1064 No delay
b02aae9c 1065
1da177e4 1066 ip= [IP_PNP]
dc7a0816 1067 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4
LT
1068
1069 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
c8facbb6
RD
1070 See comment before ip2_setup() in
1071 drivers/char/ip2/ip2base.c.
1da177e4
LT
1072
1073 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1074 See header of drivers/scsi/ips.c.
1075
200803df
AC
1076 irqfixup [HW]
1077 When an interrupt is not handled search all handlers
1078 for it. Intended to get systems with badly broken
1079 firmware running.
1080
1081 irqpoll [HW]
1082 When an interrupt is not handled search all handlers
1083 for it. Also check all handlers each timer
1084 interrupt. Intended to get systems with badly broken
1085 firmware running.
1086
1da177e4 1087 isapnp= [ISAPNP]
a9913044 1088 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1da177e4
LT
1089
1090 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
22f2e280
DF
1091 Format:
1092 <cpu number>,...,<cpu number>
1093 or
b225d44e
LZ
1094 <cpu number>-<cpu number>
1095 (must be a positive range in ascending order)
22f2e280
DF
1096 or a mixture
1097 <cpu number>,...,<cpu number>-<cpu number>
b225d44e 1098
1da177e4
LT
1099 This option can be used to specify one or more CPUs
1100 to isolate from the general SMP balancing and scheduling
b225d44e
LZ
1101 algorithms. You can move a process onto or off an
1102 "isolated" CPU via the CPU affinity syscalls or cpuset.
1da177e4
LT
1103 <cpu number> begins at 0 and the maximum value is
1104 "number of CPUs in system - 1".
1105
1106 This option is the preferred way to isolate CPUs. The
a9913044
RD
1107 alternative -- manually setting the CPU mask of all
1108 tasks in the system -- can cause problems and
1109 suboptimal load balancer performance.
1da177e4 1110
a9913044 1111 iucv= [HW,NET]
1da177e4
LT
1112
1113 js= [HW,JOY] Analog joystick
1114 See Documentation/input/joystick.txt.
1115
0cb55ad2
RD
1116 keepinitrd [HW,ARM]
1117
6cececfc 1118 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
ed7ed365
MG
1119 specifies the amount of memory usable by the kernel
1120 for non-movable allocations. The requested amount is
1121 spread evenly throughout all nodes in the system. The
1122 remaining memory in each node is used for Movable
1123 pages. In the event, a node is too small to have both
1124 kernelcore and Movable pages, kernelcore pages will
1125 take priority and other nodes will have a larger number
1126 of kernelcore pages. The Movable zone is used for the
1127 allocation of pages that may be reclaimed or moved
1128 by the page migration subsystem. This means that
1129 HugeTLB pages may not be allocated from this zone.
1130 Note that allocations like PTEs-from-HighMem still
1131 use the HighMem zone if it exists, and the Normal
1132 zone if it does not.
1133
4fe1da4e
JW
1134 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1135 Format: <Controller#>[,poll interval]
1136 The controller # is the number of the ehci usb debug
1137 port as it is probed via PCI. The poll interval is
1138 optional and is the number seconds in between
1139 each poll cycle to the debug port in case you need
1140 the functionality for interrupting the kernel with
1141 gdb or control-c on the dbgp connection. When
1142 not using this parameter you use sysrq-g to break into
1143 the kernel debugger.
1144
84c08fd6 1145 kgdboc= [KGDB,HW] kgdb over consoles.
ada64e4c
JW
1146 Requires a tty driver that supports console polling,
1147 or a supported polling keyboard driver (non-usb).
1148 Serial only format: <serial_device>[,baud]
1149 keyboard only format: kbd
1150 keyboard and serial format: kbd,<serial_device>[,baud]
6cdf6e06 1151
84c08fd6
JW
1152 kgdbwait [KGDB] Stop kernel execution and enter the
1153 kernel debugger at the earliest opportunity.
1154
9bed90c6
FF
1155 kmac= [MIPS] korina ethernet MAC address.
1156 Configure the RouterBoard 532 series on-chip
1157 Ethernet adapter MAC address.
1158
04f70336
CM
1159 kmemleak= [KNL] Boot-time kmemleak enable/disable
1160 Valid arguments: on, off
1161 Default: on
1162
6cececfc 1163 kstack=N [X86] Print N words from the kernel stack
0cb55ad2
RD
1164 in oops dumps.
1165
fef07aae
AP
1166 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1167 Default is 0 (don't ignore, but inject #GP)
1168
1169 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1170 Default is 1 (enabled)
1171
1172 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1173 Default is 0 (off)
1174
1175 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1176 for all guests.
1177 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1178
1179 kvm-intel.bypass_guest_pf=
1180 [KVM,Intel] Disables bypassing of guest page faults
1181 on Intel chips. Default is 1 (enabled)
1182
1183 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1184 (virtualized MMU) support on capable Intel chips.
1185 Default is 1 (enabled)
1186
1187 kvm-intel.emulate_invalid_guest_state=
1188 [KVM,Intel] Enable emulation of invalid guest states
1189 Default is 0 (disabled)
1190
1191 kvm-intel.flexpriority=
1192 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1193 Default is 1 (enabled)
1194
1195 kvm-intel.unrestricted_guest=
1196 [KVM,Intel] Disable unrestricted guest feature
1197 (virtualized real and unpaged mode) on capable
1198 Intel chips. Default is 1 (enabled)
1199
1200 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1201 feature (tagged TLBs) on capable Intel chips.
1202 Default is 1 (enabled)
1203
1da177e4
LT
1204 l2cr= [PPC]
1205
a78bfbfc
RB
1206 l3cr= [PPC]
1207
cd4f0ef7 1208 lapic [X86-32,APIC] Enable the local APIC even if BIOS
a9913044 1209 disabled it.
1da177e4 1210
6cececfc 1211 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
ada9cfdd 1212 in C2 power state.
e585bef8 1213
fcb71f6f
FC
1214 libata.dma= [LIBATA] DMA control
1215 libata.dma=0 Disable all PATA and SATA DMA
1216 libata.dma=1 PATA and SATA Disk DMA only
1217 libata.dma=2 ATAPI (CDROM) DMA only
1218 libata.dma=4 Compact Flash DMA only
1219 Combinations also work, so libata.dma=3 enables DMA
1220 for disks and CDROMs, but not CFs.
20308871
MP
1221
1222 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1223 libata.ignore_hpa=0 keep BIOS limits (default)
1224 libata.ignore_hpa=1 ignore limits, using full disk
fcb71f6f 1225
78e70c23
DJ
1226 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1227 when set.
1228 Format: <int>
1229
33267325
TH
1230 libata.force= [LIBATA] Force configurations. The format is comma
1231 separated list of "[ID:]VAL" where ID is
4c44f309 1232 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
33267325
TH
1233 matching port, link or device. Basically, it matches
1234 the ATA ID string printed on console by libata. If
1235 the whole ID part is omitted, the last PORT and DEVICE
1236 values are used. If ID hasn't been specified yet, the
1237 configuration applies to all ports, links and devices.
1238
1239 If only DEVICE is omitted, the parameter applies to
1240 the port and all links and devices behind it. DEVICE
1241 number of 0 either selects the first device or the
1242 first fan-out link behind PMP device. It does not
1243 select the host link. DEVICE number of 15 selects the
1244 host link and device attached to it.
1245
1246 The VAL specifies the configuration to force. As long
1247 as there's no ambiguity shortcut notation is allowed.
1248 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1249 The following configurations can be forced.
1250
1251 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1252 Any ID with matching PORT is used.
1253
1254 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1255
1256 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1257 udma[/][16,25,33,44,66,100,133] notation is also
1258 allowed.
1259
1260 * [no]ncq: Turn on or off NCQ.
1261
05944bdf
TH
1262 * nohrst, nosrst, norst: suppress hard, soft
1263 and both resets.
1264
43c9c591
TH
1265 * dump_id: dump IDENTIFY data.
1266
33267325
TH
1267 If there are multiple matching configurations changing
1268 the same attribute, the last one is used.
1269
95f72d1e 1270 memblock=debug [KNL] Enable memblock debug messages.
7c4be253 1271
1da177e4 1272 load_ramdisk= [RAM] List of ramdisks to load from floppy
31c00fc1 1273 See Documentation/blockdev/ramdisk.txt.
1da177e4 1274
a6b25b67
RD
1275 lockd.nlm_grace_period=P [NFS] Assign grace period.
1276 Format: <integer>
1da177e4 1277
a6b25b67
RD
1278 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1279 Format: <integer>
1280
1281 lockd.nlm_timeout=T [NFS] Assign timeout value.
1282 Format: <integer>
1283
1284 lockd.nlm_udpport=M [NFS] Assign UDP port.
1285 Format: <integer>
1da177e4
LT
1286
1287 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1288 Format: <irq>
1289
1290 loglevel= All Kernel Messages with a loglevel smaller than the
1291 console loglevel will be printed to the console. It can
1292 also be changed with klogd or other programs. The
1293 loglevels are defined as follows:
1294
1295 0 (KERN_EMERG) system is unusable
1296 1 (KERN_ALERT) action must be taken immediately
1297 2 (KERN_CRIT) critical conditions
1298 3 (KERN_ERR) error conditions
1299 4 (KERN_WARNING) warning conditions
1300 5 (KERN_NOTICE) normal but significant condition
1301 6 (KERN_INFO) informational
1302 7 (KERN_DEBUG) debug-level messages
1303
1304 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
a9913044
RD
1305 Format: { n | nk | nM }
1306 n must be a power of two. The default size
1307 is set in the kernel config file.
1da177e4 1308
accaa24c
RD
1309 logo.nologo [FB] Disables display of the built-in Linux logo.
1310 This may be used to provide more screen space for
1311 kernel log messages and is useful when debugging
1312 kernel boot problems.
1313
1da177e4
LT
1314 lp=0 [LP] Specify parallel ports to use, e.g,
1315 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1316 lp=reset first parallel port). 'lp=0' disables the
1317 lp=auto printer driver. 'lp=reset' (which can be
1318 specified in addition to the ports) causes
1319 attached printers to be reset. Using
1320 lp=port1,port2,... specifies the parallel ports
1321 to associate lp devices with, starting with
1322 lp0. A port specification may be 'none' to skip
1323 that lp device, or a parport name such as
1324 'parport0'. Specifying 'lp=auto' instead of a
1325 port specification list means that device IDs
1326 from each port should be examined, to see if
1327 an IEEE 1284-compliant printer is attached; if
1328 so, the driver will manage that printer.
1329 See also header of drivers/char/lp.c.
1330
1331 lpj=n [KNL]
1332 Sets loops_per_jiffy to given constant, thus avoiding
1333 time-consuming boot-time autodetection (up to 250 ms per
1334 CPU). 0 enables autodetection (default). To determine
1335 the correct value for your kernel, boot with normal
1336 autodetection and see what value is printed. Note that
1337 on SMP systems the preset will be applied to all CPUs,
1338 which is likely to cause problems if your CPUs need
1339 significantly divergent settings. An incorrect value
1340 will cause delays in the kernel to be wrong, leading to
1341 unpredictable I/O errors and other breakage. Although
1342 unlikely, in the extreme case this might damage your
1343 hardware.
1344
1345 ltpc= [NET]
1346 Format: <io>,<irq>,<dma>
1347
a9913044
RD
1348 mac5380= [HW,SCSI] Format:
1349 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1da177e4 1350
a9913044
RD
1351 machvec= [IA64] Force the use of a particular machine-vector
1352 (machvec) in a generic kernel.
1353 Example: machvec=hpzx1_swiotlb
1da177e4 1354
3209e70e
WZ
1355 machtype= [Loongson] Share the same kernel image file between different
1356 yeeloong laptop.
1357 Example: machtype=lemote-yeeloong-2f-7inch
1358
0cb55ad2
RD
1359 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1360 than or equal to this physical address is ignored.
1da177e4
LT
1361
1362 maxcpus= [SMP] Maximum number of processors that an SMP kernel
61ec7567
LB
1363 should make use of. maxcpus=n : n >= 0 limits the
1364 kernel to using 'n' processors. n=0 is a special case,
1365 it is equivalent to "nosmp", which also disables
1366 the IO APIC.
1da177e4 1367
0cb55ad2
RD
1368 max_loop= [LOOP] Maximum number of loopback devices that can
1369 be mounted
1370 Format: <1-256>
2b2c3750 1371
a9913044 1372 max_luns= [SCSI] Maximum number of LUNs to probe.
1da177e4
LT
1373 Should be between 1 and 2^32-1.
1374
1375 max_report_luns=
a9913044 1376 [SCSI] Maximum number of LUNs received.
1da177e4
LT
1377 Should be between 1 and 16384.
1378
1da177e4
LT
1379 mcatest= [IA-64]
1380
cd4f0ef7 1381 mce [X86-32] Machine Check Exception
1da177e4 1382
71cced6e 1383 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
909dd324 1384
1da177e4
LT
1385 md= [HW] RAID subsystems devices and level
1386 See Documentation/md.txt.
a9913044 1387
1da177e4
LT
1388 mdacon= [MDA]
1389 Format: <first>,<last>
1390 Specifies range of consoles to be captured by the MDA.
a9913044 1391
1da177e4
LT
1392 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1393 Amount of memory to be used when the kernel is not able
1394 to see the whole system memory or for test.
cd4f0ef7 1395 [X86-32] Use together with memmap= to avoid physical
1da177e4
LT
1396 address space collisions. Without memmap= PCI devices
1397 could be placed at addresses belonging to unused RAM.
1398
cd4f0ef7 1399 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1da177e4
LT
1400 memory.
1401
6902aa84
PM
1402 memchunk=nn[KMG]
1403 [KNL,SH] Allow user to override the default size for
1404 per-device physically contiguous DMA buffers.
1405
6cececfc 1406 memmap=exactmap [KNL,X86] Enable setting of an exact
1da177e4
LT
1407 E820 memory map, as specified by the user.
1408 Such memmap=exactmap lines can be constructed based on
1409 BIOS output or other requirements. See the memmap=nn@ss
1410 option description.
1411
1412 memmap=nn[KMG]@ss[KMG]
1413 [KNL] Force usage of a specific region of memory
1414 Region of memory to be used, from ss to ss+nn.
1415
1416 memmap=nn[KMG]#ss[KMG]
1417 [KNL,ACPI] Mark specific memory as ACPI data.
1418 Region of memory to be used, from ss to ss+nn.
1419
1420 memmap=nn[KMG]$ss[KMG]
1421 [KNL,ACPI] Mark specific memory as reserved.
1422 Region of memory to be used, from ss to ss+nn.
1312848e
PM
1423 Example: Exclude memory from 0x18690000-0x1869ffff
1424 memmap=64K$0x18690000
1425 or
1426 memmap=0x10000$0x18690000
1da177e4 1427
9f077871
JF
1428 memory_corruption_check=0/1 [X86]
1429 Some BIOSes seem to corrupt the first 64k of
1430 memory when doing things like suspend/resume.
1431 Setting this option will scan the memory
1432 looking for corruption. Enabling this will
1433 both detect corruption and prevent the kernel
1434 from using the memory being corrupted.
1435 However, its intended as a diagnostic tool; if
1436 repeatable BIOS-originated corruption always
1437 affects the same memory, you can use memmap=
1438 to prevent the kernel from using that memory.
1439
1440 memory_corruption_check_size=size [X86]
1441 By default it checks for corruption in the low
1442 64k, making this memory unavailable for normal
1443 use. Use this parameter to scan for
1444 corruption in more or less memory.
1445
1446 memory_corruption_check_period=seconds [X86]
1447 By default it checks for corruption every 60
1448 seconds. Use this parameter to check at some
1449 other rate. 0 disables periodic checking.
1450
caadbdce 1451 memtest= [KNL,X86] Enable memtest
c64df707 1452 Format: <integer>
c64df707 1453 default : 0 <disable>
9e5f6cf5
AH
1454 Specifies the number of memtest passes to be
1455 performed. Each pass selects another test
1456 pattern from a given set of patterns. Memtest
1457 fills the memory with this pattern, validates
1458 memory contents and reserves bad memory
1459 regions that are detected.
c64df707 1460
1da177e4
LT
1461 meye.*= [HW] Set MotionEye Camera parameters
1462 See Documentation/video4linux/meye.txt.
1463
8f36881b
AS
1464 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1465 Multi-Function General Purpose Timers on AMD Geode
1466 platforms.
1467
e6c4dc6c
WT
1468 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1469 the BIOS has incorrectly applied a workaround. TinyBIOS
1470 version 0.98 is known to be affected, 0.99 fixes the
1471 problem by letting the user disable the workaround.
1472
1da177e4
LT
1473 mga= [HW,DRM]
1474
1c207f95
RD
1475 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1476 physical address is ignored.
1477
39f45d7b
MP
1478 mini2440= [ARM,HW,KNL]
1479 Format:[0..2][b][c][t]
1480 Default: "0tb"
1481 MINI2440 configuration specification:
1482 0 - The attached screen is the 3.5" TFT
1483 1 - The attached screen is the 7" TFT
1484 2 - The VGA Shield is attached (1024x768)
1485 Leaving out the screen size parameter will not load
1486 the TFT driver, and the framebuffer will be left
1487 unconfigured.
1488 b - Enable backlight. The TFT backlight pin will be
1489 linked to the kernel VESA blanking code and a GPIO
1490 LED. This parameter is not necessary when using the
1491 VGA shield.
1492 c - Enable the s3c camera interface.
1493 t - Reserved for enabling touchscreen support. The
1494 touchscreen support is not enabled in the mainstream
1495 kernel as of 2.6.30, a preliminary port can be found
1496 in the "bleeding edge" mini2440 support kernel at
1497 http://repo.or.cz/w/linux-2.6/mini2440.git
1498
6b74ab97
MG
1499 mminit_loglevel=
1500 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1501 parameter allows control of the logging verbosity for
1502 the additional memory initialisation checks. A value
1503 of 0 disables mminit logging and a level of 4 will
1504 log everything. Information is printed at KERN_DEBUG
1505 so loglevel=8 may also need to be specified.
1506
1da177e4
LT
1507 mousedev.tap_time=
1508 [MOUSE] Maximum time between finger touching and
1509 leaving touchpad surface for touch to be considered
1510 a tap and be reported as a left button click (for
1511 touchpads working in absolute mode only).
1512 Format: <msecs>
1513 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1514 reporting absolute coordinates, such as tablets
1515 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1516 reporting absolute coordinates, such as tablets
1517
6cececfc 1518 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
0cb55ad2
RD
1519 is similar to kernelcore except it specifies the
1520 amount of memory used for migratable allocations.
1521 If both kernelcore and movablecore is specified,
1522 then kernelcore will be at *least* the specified
1523 value but may be more. If movablecore on its own
1524 is specified, the administrator must be careful
1525 that the amount of memory usable for all allocations
1526 is not too small.
1527
1da177e4
LT
1528 mpu401= [HW,OSS]
1529 Format: <io>,<irq>
1530
1531 MTD_Partition= [MTD]
1532 Format: <name>,<region-number>,<size>,<offset>
1533
a9913044
RD
1534 MTD_Region= [MTD] Format:
1535 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1da177e4
LT
1536
1537 mtdparts= [MTD]
c8facbb6 1538 See drivers/mtd/cmdlinepart.c.
1da177e4 1539
5988af23
RH
1540 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1541
1542 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1543
1544 boundary - index of last SLC block on Flex-OneNAND.
1545 The remaining blocks are configured as MLC blocks.
1546 lock - Configure if Flex-OneNAND boundary should be locked.
1547 Once locked, the boundary cannot be changed.
1548 1 indicates lock status, 0 indicates unlock status.
1549
9db829f4
BD
1550 mtdset= [ARM]
1551 ARM/S3C2412 JIVE boot control
1552
1553 See arch/arm/mach-s3c2412/mach-jive.c
1554
1da177e4 1555 mtouchusb.raw_coordinates=
a9913044
RD
1556 [HW] Make the MicroTouch USB driver use raw coordinates
1557 ('y', default) or cooked coordinates ('n')
1da177e4 1558
0cb55ad2 1559 mtrr_chunk_size=nn[KMG] [X86]
19f59460 1560 used for mtrr cleanup. It is largest continuous chunk
0cb55ad2
RD
1561 that could hold holes aka. UC entries.
1562
1563 mtrr_gran_size=nn[KMG] [X86]
1564 Used for mtrr cleanup. It is granularity of mtrr block.
1565 Default is 1.
1566 Large value could prevent small alignment from
1567 using up MTRRs.
1568
1569 mtrr_spare_reg_nr=n [X86]
1570 Format: <integer>
1571 Range: 0,7 : spare reg number
1572 Default : 1
1573 Used for mtrr cleanup. It is spare mtrr entries number.
1574 Set to 2 or more if your graphical card needs more.
1575
1da177e4
LT
1576 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1577
1578 NCR_D700= [HW,SCSI]
1579 See header of drivers/scsi/NCR_D700.c.
1580
1581 ncr5380= [HW,SCSI]
1582
1583 ncr53c400= [HW,SCSI]
1584
1585 ncr53c400a= [HW,SCSI]
1586
1587 ncr53c406a= [HW,SCSI]
1588
1589 ncr53c8xx= [HW,SCSI]
1590
1591 netdev= [NET] Network devices parameters
1592 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1593 Note that mem_start is often overloaded to mean
1594 something different and driver-specific.
a9913044
RD
1595 This usage is only documented in each driver source
1596 file if at all.
1597
58401572
KPO
1598 nf_conntrack.acct=
1599 [NETFILTER] Enable connection tracking flow accounting
1600 0 to disable accounting
1601 1 to enable accounting
d70a011d 1602 Default value is 0.
58401572 1603
1da177e4 1604 nfsaddrs= [NFS]
dc7a0816 1605 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4
LT
1606
1607 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
dc7a0816 1608 See Documentation/filesystems/nfs/nfsroot.txt.
1da177e4 1609
a72b4422
TM
1610 nfs.callback_tcpport=
1611 [NFS] set the TCP port on which the NFSv4 callback
1612 channel should listen.
1613
e571cbf1
TM
1614 nfs.cache_getent=
1615 [NFS] sets the pathname to the program which is used
1616 to update the NFS client cache entries.
1617
1618 nfs.cache_getent_timeout=
1619 [NFS] sets the timeout after which an attempt to
1620 update a cache entry is deemed to have failed.
1621
58df095b
TM
1622 nfs.idmap_cache_timeout=
1623 [NFS] set the maximum lifetime for idmapper cache
1624 entries.
1625
f43bf0be
TM
1626 nfs.enable_ino64=
1627 [NFS] enable 64-bit inode numbers.
1628 If zero, the NFS client will fake up a 32-bit inode
1629 number for the readdir() and stat() syscalls instead
1630 of returning the full 64-bit number.
1631 The default is to return 64-bit inode numbers.
1632
1e1030dc 1633 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
e7ba176b
HS
1634 when a NMI is triggered.
1635 Format: [state][,regs][,debounce][,die]
1636
6cececfc 1637 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
5b9a0e14
CG
1638 Format: [panic,][num]
1639 Valid num: 0,1,2
1640 0 - turn nmi_watchdog off
1641 1 - use the IO-APIC timer for the NMI watchdog
1642 2 - use the local APIC for the NMI watchdog using
0cb55ad2
RD
1643 a performance counter. Note: This will use one
1644 performance counter and the local APIC's performance
1645 vector.
1646 When panic is specified, panic when an NMI watchdog
1647 timeout occurs.
1648 This is useful when you use a panic=... timeout and
1649 need the box quickly up again.
5b9a0e14
CG
1650 Instead of 1 and 2 it is possible to use the following
1651 symbolic names: lapic and ioapic
1652 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1da177e4 1653
bff38771
AV
1654 netpoll.carrier_timeout=
1655 [NET] Specifies amount of time (in seconds) that
1656 netpoll should wait for a carrier. By default netpoll
1657 waits 4 seconds.
1658
cd4f0ef7 1659 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1da177e4
LT
1660 emulation library even if a 387 maths coprocessor
1661 is present.
1662
0cb55ad2
RD
1663 no_console_suspend
1664 [HW] Never suspend the console
1665 Disable suspending of consoles during suspend and
1666 hibernate operations. Once disabled, debugging
1667 messages can reach various consoles while the rest
1668 of the system is being put to sleep (ie, while
1669 debugging driver suspend/resume hooks). This may
1670 not work reliably with all consoles, but is known
1671 to work with serial and VGA consoles.
1672
c1aee215
CL
1673 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1674 caches in the slab allocator. Saves per-node memory,
1675 but will impact performance.
3395ee05 1676
a9913044
RD
1677 noalign [KNL,ARM]
1678
1da177e4
LT
1679 noapic [SMP,APIC] Tells the kernel to not make use of any
1680 IOAPICs that may be present in the system.
1681
1da177e4
LT
1682 nobats [PPC] Do not use BATs for mapping kernel lowmem
1683 on "Classic" PPC cores.
1684
1685 nocache [ARM]
a9913044 1686
0cb55ad2
RD
1687 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1688
163ecdff
SN
1689 nodelayacct [KNL] Disable per-task delay accounting
1690
1da177e4
LT
1691 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1692
6902aa84
PM
1693 nodsp [SH] Disable hardware DSP at boot time.
1694
6cececfc 1695 noefi [X86] Disable EFI runtime services support.
8b2cb7a8 1696
1da177e4
LT
1697 noexec [IA-64]
1698
6cececfc 1699 noexec [X86]
f5a1b191 1700 On X86-32 available only on PAE configured kernels.
1da177e4 1701 noexec=on: enable non-executable mappings (default)
f5a1b191
JS
1702 noexec=off: disable non-executable mappings
1703
1704 noexec32 [X86-64]
1705 This affects only 32-bit executables.
1706 noexec32=on: enable non-executable mappings (default)
1707 read doesn't imply executable mappings
1708 noexec32=off: disable non-executable mappings
1709 read implies executable mappings
1da177e4 1710
6902aa84
PM
1711 nofpu [SH] Disable hardware FPU at boot time.
1712
cd4f0ef7 1713 nofxsr [BUGS=X86-32] Disables x86 floating point extended
4f886511
CE
1714 register save and restore. The kernel will only save
1715 legacy floating-point registers on task switch.
1da177e4 1716
0c752a93
SS
1717 noxsave [BUGS=X86] Disables x86 extended register state save
1718 and restore using xsave. The kernel will fallback to
1719 enabling legacy floating-point and sse state.
1720
01a24d2b
PZ
1721 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1722 wfi(ARM) instruction doesn't work correctly and not to
1723 use it. This is also useful when using JTAG debugger.
a9913044 1724
cd4f0ef7 1725 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1da177e4
LT
1726 instruction doesn't work correctly and not to
1727 use it.
1728
1f29fae2
SH
1729 no_file_caps Tells the kernel not to honor file capabilities. The
1730 only way then for a file to be executed with privilege
1731 is to be setuid root or executed by root.
1732
1da177e4
LT
1733 nohalt [IA-64] Tells the kernel not to use the power saving
1734 function PAL_HALT_LIGHT when idle. This increases
1735 power-consumption. On the positive side, it reduces
1736 interrupt wake-up latency, which may improve performance
1737 in certain environments such as networked servers or
1738 real-time systems.
1739
79bf2bb3
TG
1740 nohz= [KNL] Boottime enable/disable dynamic ticks
1741 Valid arguments: on, off
1742 Default: on
1743
eeee7853
PM
1744 noiotrap [SH] Disables trapped I/O port accesses.
1745
cd4f0ef7 1746 noirqdebug [X86-32] Disables the code which attempts to detect and
1da177e4
LT
1747 disable unhandled interrupt sources.
1748
6cececfc 1749 no_timer_check [X86,APIC] Disables the code which tests for
8542b200
ZA
1750 broken timer IRQ sources.
1751
1da177e4
LT
1752 noisapnp [ISAPNP] Disables ISA PnP code.
1753
1754 noinitrd [RAM] Tells the kernel not to load any configured
1755 initial RAM disk.
1756
03ea8155
WH
1757 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1758 remapping.
1759
1da177e4
LT
1760 nointroute [IA-64]
1761
0aa366f3
TL
1762 nojitter [IA64] Disables jitter checking for ITC timers.
1763
cd4f0ef7 1764 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1da177e4 1765
cd4f0ef7 1766 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
ad62ca2b 1767
1da177e4
LT
1768 noltlbs [PPC] Do not use large page/tlb entries for kernel
1769 lowmem mapping on PPC40x.
1770
312f1f01
H
1771 nomca [IA-64] Disable machine check abort handling
1772
cd4f0ef7 1773 nomce [X86-32] Machine Check Exception
abe37e5a 1774
83d7384f
AS
1775 nomfgpt [X86-32] Disable Multi-Function General Purpose
1776 Timer usage (for AMD Geode machines).
1777
016ddd9b
JK
1778 nopat [X86] Disable PAT (page attribute table extension of
1779 pagetables) support.
1780
0cb55ad2
RD
1781 norandmaps Don't use address space randomization. Equivalent to
1782 echo 0 > /proc/sys/kernel/randomize_va_space
1783
cd4f0ef7 1784 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
959b4fdf 1785
cd4f0ef7 1786 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
b7fb4af0
JF
1787 with UP alternatives
1788
1da177e4
LT
1789 noresidual [PPC] Don't use residual data on PReP machines.
1790
a9913044
RD
1791 noresume [SWSUSP] Disables resume and restores original swap
1792 space.
1793
1da177e4
LT
1794 no-scroll [VGA] Disables scrollback.
1795 This is required for the Braillex ib80-piezo Braille
1796 reader made by F.H. Papenmeier (Germany).
1797
1798 nosbagart [IA-64]
1799
cd4f0ef7 1800 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4f886511 1801
61ec7567
LB
1802 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1803 and disable the IO APIC. legacy for "maxcpus=0".
1da177e4 1804
97842216
DJ
1805 nosoftlockup [KNL] Disable the soft-lockup detector.
1806
c077719b 1807 noswapaccount [KNL] Disable accounting of swap in memory resource
21acb9ca 1808 controller. (See Documentation/cgroups/memory.txt)
c077719b 1809
1da177e4
LT
1810 nosync [HW,M68K] Disables sync negotiation for all devices.
1811
cd4f0ef7 1812 notsc [BUGS=X86-32] Disable Time Stamp Counter
1da177e4
LT
1813
1814 nousb [USB] Disable the USB subsystem
1815
1816 nowb [ARM]
a9913044 1817
2b2fd87a
WH
1818 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1819
a6c75b86
FY
1820 nptcg= [IA64] Override max number of concurrent global TLB
1821 purges which is reported from either PAL_VM_SUMMARY or
1822 SAL PALO.
1823
2b633e3f
YL
1824 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1825 could support. nr_cpus=n : n >= 1 limits the kernel to
1826 supporting 'n' processors. Later in runtime you can not
1827 use hotplug cpu feature to put more cpu back to online.
1828 just like you compile the kernel NR_CPUS=n
1829
0cb55ad2
RD
1830 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1831
f0c0b2b8
KH
1832 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1833 one of ['zone', 'node', 'default'] can be specified
1834 This can be set from sysctl after boot.
1835 See Documentation/sysctl/vm.txt for details.
1836
7c4be253
RD
1837 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1838 See Documentation/debugging-via-ohci1394.txt for more
1839 info.
1840
3ef0e1f8
AS
1841 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1842 Rather than timing out after 20 ms if an EC
1843 command is not properly ACKed, override the length
1844 of the timeout. We have interrupts disabled while
1845 waiting for the ACK, so if this is set too high
1846 interrupts *may* be lost!
1847
15ac7afe
TL
1848 omap_mux= [OMAP] Override bootloader pin multiplexing.
1849 Format: <mux_mode0.mode_name=value>...
1850 For example, to override I2C bus2:
1851 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1852
1da177e4
LT
1853 opl3= [HW,OSS]
1854 Format: <io>
1855
1da177e4
LT
1856 oprofile.timer= [HW]
1857 Use timer interrupt instead of performance counters
1858
7e4e0bd5
RR
1859 oprofile.cpu_type= Force an oprofile cpu type
1860 This might be useful if you have an older oprofile
1861 userland or if you want common events.
8d7ff4f2
RR
1862 Format: { arch_perfmon }
1863 arch_perfmon: [X86] Force use of architectural
7e4e0bd5
RR
1864 perfmon on Intel CPUs instead of the
1865 CPU specific event set.
1dcdb5a9 1866
1da177e4
LT
1867 osst= [HW,SCSI] SCSI Tape Driver
1868 Format: <buffer_size>,<write_threshold>
1869 See also Documentation/scsi/st.txt.
1870
1871 panic= [KNL] Kernel behaviour on panic
1872 Format: <timeout>
1873
1874 parkbd.port= [HW] Parallel port number the keyboard adapter is
1875 connected to, default is 0.
1876 Format: <parport#>
1877 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1878 0 for XT, 1 for AT (default is AT).
a9913044
RD
1879 Format: <mode>
1880
1881 parport= [HW,PPT] Specify parallel ports. 0 disables.
1882 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1883 Use 'auto' to force the driver to use any
1884 IRQ/DMA settings detected (the default is to
1885 ignore detected IRQ/DMA settings because of
1886 possible conflicts). You can specify the base
1887 address, IRQ, and DMA settings; IRQ and DMA
1888 should be numbers, or 'auto' (for using detected
1889 settings on that particular port), or 'nofifo'
1890 (to avoid using a FIFO even if it is detected).
1891 Parallel ports are assigned in the order they
1892 are specified on the command line, starting
1893 with parport0.
1894
1895 parport_init_mode= [HW,PPT]
1896 Configure VIA parallel port to operate in
1897 a specific mode. This is necessary on Pegasos
1898 computer where firmware has no options for setting
1899 up parallel port mode and sets it to spp.
1900 Currently this function knows 686a and 8231 chips.
1da177e4
LT
1901 Format: [spp|ps2|epp|ecp|ecpepp]
1902
a9913044
RD
1903 pas2= [HW,OSS] Format:
1904 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1905
1da177e4
LT
1906 pas16= [HW,SCSI]
1907 See header of drivers/scsi/pas16.c.
1908
dd287796
AM
1909 pause_on_oops=
1910 Halt all CPUs after the first oops has been printed for
1911 the specified number of seconds. This is to be used if
1912 your oopses keep scrolling off the screen.
1913
1da177e4
LT
1914 pcbit= [HW,ISDN]
1915
1916 pcd. [PARIDE]
1917 See header of drivers/block/paride/pcd.c.
31c00fc1 1918 See also Documentation/blockdev/paride.txt.
1da177e4 1919
a9913044 1920 pci=option[,option...] [PCI] various PCI subsystem options:
1cc0ca26
BH
1921 earlydump [X86] dump PCI config space before the kernel
1922 changes anything
c0115606 1923 off [X86] don't probe for the PCI bus
cd4f0ef7 1924 bios [X86-32] force use of PCI BIOS, don't access
a9913044
RD
1925 the hardware directly. Use this if your machine
1926 has a non-standard PCI host bridge.
cd4f0ef7 1927 nobios [X86-32] disallow use of PCI BIOS, only direct
a9913044
RD
1928 hardware access methods are allowed. Use this
1929 if you experience crashes upon bootup and you
1930 suspect they are caused by the BIOS.
c0115606 1931 conf1 [X86] Force use of PCI Configuration
a9913044 1932 Mechanism 1.
c0115606 1933 conf2 [X86] Force use of PCI Configuration
a9913044 1934 Mechanism 2.
7f785763
RD
1935 noaer [PCIE] If the PCIEAER kernel config parameter is
1936 enabled, this kernel boot option can be used to
1937 disable the use of PCIE advanced error reporting.
32a2eea7
JG
1938 nodomains [PCI] Disable support for multiple PCI
1939 root domains (aka PCI segments, in ACPI-speak).
6cececfc 1940 nommconf [X86] Disable use of MMCONFIG for PCI
61be6d66 1941 Configuration
12983077
AH
1942 check_enable_amd_mmconf [X86] check for and enable
1943 properly configured MMIO access to PCI
1944 config space on AMD family 10h CPU
309e57df
MW
1945 nomsi [MSI] If the PCI_MSI kernel config parameter is
1946 enabled, this kernel boot option can be used to
1947 disable the use of MSI interrupts system-wide.
a9322f64
SA
1948 noioapicquirk [APIC] Disable all boot interrupt quirks.
1949 Safety option to keep boot IRQs enabled. This
1950 should never be necessary.
9197979b
SA
1951 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1952 primary IO-APIC for bridges that cannot disable
1953 boot IRQs. This fixes a source of spurious IRQs
1954 when the system masks IRQs.
41b9eb26
SA
1955 noioapicreroute [APIC] Disable workaround that uses the
1956 boot IRQ equivalent of an IRQ that connects to
1957 a chipset where boot IRQs cannot be disabled.
1958 The opposite of ioapicreroute.
cd4f0ef7 1959 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
a9913044
RD
1960 routing table. These calls are known to be buggy
1961 on several machines and they hang the machine
1962 when used, but on other computers it's the only
1963 way to get the interrupt routing table. Try
1964 this option if the kernel is unable to allocate
1965 IRQs or discover secondary PCI buses on your
1966 motherboard.
c0115606 1967 rom [X86] Assign address space to expansion ROMs.
a9913044
RD
1968 Use with caution as certain devices share
1969 address decoders between ROMs and other
1970 resources.
c0115606 1971 norom [X86] Do not assign address space to
bb71ad88
GH
1972 expansion ROMs that do not already have
1973 BIOS assigned address ranges.
c0115606 1974 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
a9913044
RD
1975 assigned automatically to PCI devices. You can
1976 make the kernel exclude IRQs of your ISA cards
1977 this way.
c0115606 1978 pirqaddr=0xAAAAA [X86] Specify the physical address
a9913044
RD
1979 of the PIRQ table (normally generated
1980 by the BIOS) if it is outside the
1981 F0000h-100000h range.
c0115606 1982 lastbus=N [X86] Scan all buses thru bus #N. Can be
a9913044
RD
1983 useful if the kernel is unable to find your
1984 secondary buses and you want to tell it
1985 explicitly which ones they are.
c0115606 1986 assign-busses [X86] Always assign all PCI bus
a9913044
RD
1987 numbers ourselves, overriding
1988 whatever the firmware may have done.
c0115606 1989 usepirqmask [X86] Honor the possible IRQ mask stored
a9913044
RD
1990 in the BIOS $PIR table. This is needed on
1991 some systems with broken BIOSes, notably
1992 some HP Pavilion N5400 and Omnibook XE3
1993 notebooks. This will have no effect if ACPI
1994 IRQ routing is enabled.
c0115606 1995 noacpi [X86] Do not use ACPI for IRQ routing
a9913044 1996 or for PCI scanning.
7bc5e3f2
BH
1997 use_crs [X86] Use PCI host bridge window information
1998 from ACPI. On BIOSes from 2008 or later, this
1999 is enabled by default. If you need to use this,
2000 please report a bug.
2001 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2002 If you need to use this, please report a bug.
a9913044
RD
2003 routeirq Do IRQ routing for all PCI devices.
2004 This is normally done in pci_enable_device(),
2005 so this option is a temporary workaround
2006 for broken drivers that don't call it.
13a6ddb0
YL
2007 skip_isa_align [X86] do not align io start addr, so can
2008 handle more pci cards
a9913044
RD
2009 firmware [ARM] Do not re-enumerate the bus but instead
2010 just use the configuration from the
2011 bootloader. This is currently used on
2012 IXP2000 systems where the bus has to be
2013 configured a certain way for adjunct CPUs.
0637a70a
AK
2014 noearly [X86] Don't do any early type 1 scanning.
2015 This might help on some broken boards which
2016 machine check when some devices' config space
2017 is read. But various workarounds are disabled
2018 and some IOMMU drivers will not work.
6b4b78fe
MD
2019 bfsort Sort PCI devices into breadth-first order.
2020 This sorting is done to get a device
2021 order compatible with older (<= 2.4) kernels.
2022 nobfsort Don't sort PCI devices into breadth-first order.
4516a618
AN
2023 cbiosize=nn[KMG] The fixed amount of bus space which is
2024 reserved for the CardBus bridge's IO window.
2025 The default value is 256 bytes.
2026 cbmemsize=nn[KMG] The fixed amount of bus space which is
2027 reserved for the CardBus bridge's memory
2028 window. The default value is 64 megabytes.
32a9a682
YS
2029 resource_alignment=
2030 Format:
2031 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2032 Specifies alignment and device to reassign
2033 aligned memory resources.
2034 If <order of align> is not specified,
2035 PAGE_SIZE is used as alignment.
2036 PCI-PCI bridge can be specified, if resource
2037 windows need to be expanded.
43c16408
AP
2038 ecrc= Enable/disable PCIe ECRC (transaction layer
2039 end-to-end CRC checking).
2040 bios: Use BIOS/firmware settings. This is the
2041 the default.
2042 off: Turn ECRC off
2043 on: Turn ECRC on.
6b4b78fe 2044
e5665a45
CE
2045 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2046 Management.
2047 off Disable ASPM.
2048 force Enable ASPM even on devices that claim not to support it.
2049 WARNING: Forcing ASPM on may cause system lockups.
2050
c7f48656 2051 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
b27759f8
RW
2052 Format: {auto|force}[,nomsi]
2053 auto Use native PCIe PME signaling if the BIOS allows the
2054 kernel to control PCIe config registers of root ports.
c7f48656
RW
2055 force Use native PCIe PME signaling even if the BIOS refuses
2056 to allow the kernel to control the relevant PCIe config
2057 registers.
c39fae14
RW
2058 nomsi Do not use MSI for native PCIe PME signaling (this makes
2059 all PCIe root ports use INTx for everything).
c7f48656 2060
1da177e4
LT
2061 pcmv= [HW,PCMCIA] BadgePAD 4
2062
2063 pd. [PARIDE]
31c00fc1 2064 See Documentation/blockdev/paride.txt.
1da177e4
LT
2065
2066 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2067 boot time.
2068 Format: { 0 | 1 }
2069 See arch/parisc/kernel/pdc_chassis.c
2070
f58dc01b 2071 percpu_alloc= Select which percpu first chunk allocator to use.
e933a73f
TH
2072 Currently supported values are "embed" and "page".
2073 Archs may support subset or none of the selections.
2074 See comments in mm/percpu.c for details on each
2075 allocator. This parameter is primarily for debugging
2076 and performance comparison.
fa8a7094 2077
1da177e4 2078 pf. [PARIDE]
31c00fc1 2079 See Documentation/blockdev/paride.txt.
1da177e4
LT
2080
2081 pg. [PARIDE]
31c00fc1 2082 See Documentation/blockdev/paride.txt.
1da177e4
LT
2083
2084 pirq= [SMP,APIC] Manual mp-table setup
71cced6e 2085 See Documentation/x86/i386/IO-APIC.txt.
1da177e4
LT
2086
2087 plip= [PPT,NET] Parallel port network link
2088 Format: { parport<nr> | timid | 0 }
2089 See also Documentation/parport.txt.
2090
de32a243
TG
2091 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2092 Override pmtimer IOPort with a hex value.
2093 e.g. pmtmr=0x508
2094
97ef062b
BH
2095 pnp.debug [PNP]
2096 Enable PNP debug messages. This depends on the
2097 CONFIG_PNP_DEBUG_MESSAGES option.
2098
1da177e4
LT
2099 pnpacpi= [ACPI]
2100 { off }
2101
2102 pnpbios= [ISAPNP]
2103 { on | off | curr | res | no-curr | no-res }
2104
2105 pnp_reserve_irq=
2106 [ISAPNP] Exclude IRQs for the autoconfiguration
2107
2108 pnp_reserve_dma=
2109 [ISAPNP] Exclude DMAs for the autoconfiguration
2110
2111 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
a9913044 2112 Ranges are in pairs (I/O port base and size).
1da177e4
LT
2113
2114 pnp_reserve_mem=
a9913044
RD
2115 [ISAPNP] Exclude memory regions for the
2116 autoconfiguration.
1da177e4
LT
2117 Ranges are in pairs (memory base and size).
2118
4af94f39
RD
2119 ports= [IP_VS_FTP] IPVS ftp helper module
2120 Default is 21.
2121 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2122 may be specified.
2123 Format: <port>,<port>....
2124
45807a1d
IM
2125 print-fatal-signals=
2126 [KNL] debug: print fatal signals
f84d49b2
NO
2127
2128 If enabled, warn about various signal handling
2129 related application anomalies: too many signals,
2130 too many POSIX.1 timers, fatal signals causing a
2131 coredump - etc.
2132
2133 If you hit the warning due to signal overflow,
2134 you might want to try "ulimit -i unlimited".
2135
45807a1d
IM
2136 default: off.
2137
e84845c4
RD
2138 printk.time= Show timing data prefixed to each printk message line
2139 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2140
0cb55ad2
RD
2141 processor.max_cstate= [HW,ACPI]
2142 Limit processor to maximum C-state
2143 max_cstate=9 overrides any DMI blacklist limit.
2144
2145 processor.nocst [HW,ACPI]
2146 Ignore the _CST method to determine C-states,
2147 instead using the legacy FADT method
2148
1da177e4 2149 profile= [KNL] Enable kernel profiling via /proc/profile
a9913044
RD
2150 Format: [schedule,]<number>
2151 Param: "schedule" - profile schedule points.
2152 Param: <number> - step/bucket size as a power of 2 for
2153 statistical time based profiling.
b3da2a73
MG
2154 Param: "sleep" - profile D-state sleeping (millisecs).
2155 Requires CONFIG_SCHEDSTATS
c0fe2e69 2156 Param: "kvm" - profile VM exits.
1da177e4 2157
1da177e4
LT
2158 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2159 before loading.
31c00fc1 2160 See Documentation/blockdev/ramdisk.txt.
1da177e4 2161
a9913044
RD
2162 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2163 probe for; one of (bare|imps|exps|lifebook|any).
1da177e4
LT
2164 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2165 per second.
a9913044
RD
2166 psmouse.resetafter= [HW,MOUSE]
2167 Try to reset the device after so many bad packets
1da177e4
LT
2168 (0 = never).
2169 psmouse.resolution=
2170 [HW,MOUSE] Set desired mouse resolution, in dpi.
2171 psmouse.smartscroll=
a9913044 2172 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1da177e4
LT
2173 0 = disabled, 1 = enabled (default).
2174
2175 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
a9913044
RD
2176 Format:
2177 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1da177e4
LT
2178
2179 pt. [PARIDE]
31c00fc1 2180 See Documentation/blockdev/paride.txt.
1da177e4 2181
dc8c8587
KS
2182 pty.legacy_count=
2183 [KNL] Number of legacy pty's. Overwrites compiled-in
2184 default number.
2185
7d2c502f 2186 quiet [KNL] Disable most log messages
a9913044 2187
1da177e4
LT
2188 r128= [HW,DRM]
2189
2190 raid= [HW,RAID]
2191 See Documentation/md.txt.
2192
a9913044 2193 ramdisk_blocksize= [RAM]
31c00fc1 2194 See Documentation/blockdev/ramdisk.txt.
a9913044 2195
1da177e4 2196 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
31c00fc1 2197 See Documentation/blockdev/ramdisk.txt.
1da177e4 2198
24aaef8d
RD
2199 rcupdate.blimit= [KNL,BOOT]
2200 Set maximum number of finished RCU callbacks to process
2201 in one batch.
21a1ea9e 2202
24aaef8d
RD
2203 rcupdate.qhimark= [KNL,BOOT]
2204 Set threshold of queued
21a1ea9e
DS
2205 RCU callbacks over which batch limiting is disabled.
2206
24aaef8d
RD
2207 rcupdate.qlowmark= [KNL,BOOT]
2208 Set threshold of queued RCU callbacks below which
2209 batch limiting is re-enabled.
21a1ea9e 2210
ffdfc409
OJ
2211 rdinit= [KNL]
2212 Format: <full_path>
2213 Run specified binary instead of /init from the ramdisk,
2214 used for early userspace startup. See initrd.
2215
cd4f0ef7 2216 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1da177e4 2217 Format: <reboot_mode>[,<reboot_mode2>[,...]]
ecb08d81 2218 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1da177e4 2219
46b6d94e
PJ
2220 relax_domain_level=
2221 [KNL, SMP] Set scheduler's default relax_domain_level.
21acb9ca 2222 See Documentation/cgroups/cpusets.txt.
46b6d94e 2223
1da177e4
LT
2224 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2225
cd4f0ef7 2226 reservetop= [X86-32]
461a9aff
ZA
2227 Format: nn[KMG]
2228 Reserves a hole at the top of the kernel virtual
2229 address space.
2230
7e96287d
VG
2231 reset_devices [KNL] Force drivers to reset the underlying device
2232 during initialization.
2233
a9913044
RD
2234 resume= [SWSUSP]
2235 Specify the partition device for software suspend
1da177e4 2236
ecbd0da1
RW
2237 resume_offset= [SWSUSP]
2238 Specify the offset from the beginning of the partition
2239 given by "resume=" at which the swap header is located,
2240 in <PAGE_SIZE> units (needed only for swap files).
2241 See Documentation/power/swsusp-and-swap-files.txt
2242
0a7b35cb
MN
2243 retain_initrd [RAM] Keep initrd memory after extraction
2244
1da177e4
LT
2245 rhash_entries= [KNL,NET]
2246 Set number of hash buckets for route cache
2247
2248 riscom8= [HW,SERIAL]
2249 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2250
2251 ro [KNL] Mount root device read-only on boot
2252
2253 root= [KNL] Root filesystem
2254
2255 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2256 mount the root filesystem
2257
2258 rootflags= [KNL] Set root filesystem mount option string
2259
2260 rootfstype= [KNL] Set root filesystem type
2261
cc1ed754
PO
2262 rootwait [KNL] Wait (indefinitely) for root device to show up.
2263 Useful for devices that are detected asynchronously
2264 (e.g. USB and MMC devices).
2265
1da177e4
LT
2266 rw [KNL] Mount root device read-write on boot
2267
2268 S [KNL] Run init in single mode
2269
2270 sa1100ir [NET]
2271 See drivers/net/irda/sa1100_ir.c.
2272
1da177e4 2273 sbni= [NET] Granch SBNI12 leased line adapter
a9913044 2274
f6630114
MT
2275 sched_debug [KNL] Enables verbose scheduler debug messages.
2276
1da177e4
LT
2277 scsi_debug_*= [SCSI]
2278 See drivers/scsi/scsi_debug.c.
2279
2280 scsi_default_dev_flags=
2281 [SCSI] SCSI default device flags
2282 Format: <integer>
2283
2284 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2285 Format: <vendor>:<model>:<flags>
2286 (flags are integer value)
2287
6af6632a
RD
2288 scsi_logging_level= [SCSI] a bit mask of logging levels
2289 See drivers/scsi/scsi_logging.h for bits. Also
2290 settable via sysctl at dev.scsi.logging_level
2291 (/proc/sys/dev/scsi/logging_level).
2292 There is also a nice 'scsi_logging_level' script in the
2293 S390-tools package, available for download at
2294 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1da177e4 2295
3e082a91
MW
2296 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2297 discovered. async scans them in kernel threads,
2298 allowing boot to proceed. none ignores them, expecting
2299 user space to do the scan.
2300
0cb55ad2
RD
2301 security= [SECURITY] Choose a security module to enable at boot.
2302 If this boot parameter is not specified, only the first
2303 security module asking for security registration will be
2304 loaded. An invalid security module name will be treated
2305 as if no module has been chosen.
2306
2307 selinux= [SELINUX] Disable or enable SELinux at boot time.
1da177e4
LT
2308 Format: { "0" | "1" }
2309 See security/selinux/Kconfig help text.
2310 0 -- disable.
2311 1 -- enable.
2312 Default value is set via kernel config option.
2313 If enabled at boot time, /selinux/disable can be used
2314 later to disable prior to initial policy load.
2315
c1c124e9
JJ
2316 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2317 Format: { "0" | "1" }
2318 See security/apparmor/Kconfig help text
2319 0 -- disable.
2320 1 -- enable.
2321 Default value is set via kernel config option.
2322
cd4f0ef7 2323 serialnumber [BUGS=X86-32]
1da177e4 2324
1da177e4
LT
2325 shapers= [NET]
2326 Maximal number of shapers.
a9913044 2327
b05f78f5
YL
2328 show_msr= [x86] show boot-time MSR settings
2329 Format: { <integer> }
2330 Show boot-time (BIOS-initialized) MSR settings.
2331 The parameter means the number of CPUs to show,
2332 for example 1 means boot CPU only.
2333
1da177e4
LT
2334 sim710= [SCSI,HW]
2335 See header of drivers/scsi/sim710.c.
2336
2337 simeth= [IA-64]
2338 simscsi=
a9913044 2339
1da177e4
LT
2340 slram= [HW,MTD]
2341
f0630fff
CL
2342 slub_debug[=options[,slabs]] [MM, SLUB]
2343 Enabling slub_debug allows one to determine the
2344 culprit if slab objects become corrupted. Enabling
2345 slub_debug can create guard zones around objects and
2346 may poison objects when not in use. Also tracks the
2347 last alloc / free. For more information see
2348 Documentation/vm/slub.txt.
c1aee215
CL
2349
2350 slub_max_order= [MM, SLUB]
f0630fff
CL
2351 Determines the maximum allowed order for slabs.
2352 A high setting may cause OOMs due to memory
2353 fragmentation. For more information see
2354 Documentation/vm/slub.txt.
c1aee215
CL
2355
2356 slub_min_objects= [MM, SLUB]
f0630fff
CL
2357 The minimum number of objects per slab. SLUB will
2358 increase the slab order up to slub_max_order to
2359 generate a sufficiently large slab able to contain
2360 the number of objects indicated. The higher the number
2361 of objects the smaller the overhead of tracking slabs
2362 and the less frequently locks need to be acquired.
c1aee215
CL
2363 For more information see Documentation/vm/slub.txt.
2364
2365 slub_min_order= [MM, SLUB]
2366 Determines the mininum page order for slabs. Must be
f0630fff 2367 lower than slub_max_order.
c1aee215
CL
2368 For more information see Documentation/vm/slub.txt.
2369
2370 slub_nomerge [MM, SLUB]
f0630fff 2371 Disable merging of slabs with similar size. May be
c1aee215 2372 necessary if there is some reason to distinguish
f0630fff
CL
2373 allocs to different slabs. Debug options disable
2374 merging on their own.
c1aee215
CL
2375 For more information see Documentation/vm/slub.txt.
2376
1da177e4
LT
2377 smart2= [HW]
2378 Format: <io1>[,<io2>[,...,<io8>]]
2379
cd4f0ef7 2380 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
b7fb4af0
JF
2381 attempt to substitute SMP alternatives once at boot.
2382
d0d4f69b
BH
2383 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2384 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2385 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2386 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2387 smsc-ircc2.ircc_irq= [HW] IRQ line
2388 smsc-ircc2.ircc_dma= [HW] DMA channel
2389 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2390 0: Toshiba Satellite 1800 (GP data pin select)
2391 1: Fast pin select (default)
2392 2: ATC IRMode
2393
1da177e4
LT
2394 snd-ad1816a= [HW,ALSA]
2395
2396 snd-ad1848= [HW,ALSA]
2397
2398 snd-ali5451= [HW,ALSA]
2399
2400 snd-als100= [HW,ALSA]
2401
2402 snd-als4000= [HW,ALSA]
2403
2404 snd-azt2320= [HW,ALSA]
2405
2406 snd-cmi8330= [HW,ALSA]
2407
2408 snd-cmipci= [HW,ALSA]
2409
2410 snd-cs4231= [HW,ALSA]
2411
2412 snd-cs4232= [HW,ALSA]
2413
2414 snd-cs4236= [HW,ALSA]
2415
2416 snd-cs4281= [HW,ALSA]
2417
2418 snd-cs46xx= [HW,ALSA]
2419
2420 snd-dt019x= [HW,ALSA]
2421
2422 snd-dummy= [HW,ALSA]
2423
2424 snd-emu10k1= [HW,ALSA]
2425
2426 snd-ens1370= [HW,ALSA]
2427
2428 snd-ens1371= [HW,ALSA]
2429
2430 snd-es968= [HW,ALSA]
2431
2432 snd-es1688= [HW,ALSA]
2433
2434 snd-es18xx= [HW,ALSA]
2435
2436 snd-es1938= [HW,ALSA]
2437
2438 snd-es1968= [HW,ALSA]
2439
2440 snd-fm801= [HW,ALSA]
2441
2442 snd-gusclassic= [HW,ALSA]
2443
2444 snd-gusextreme= [HW,ALSA]
2445
2446 snd-gusmax= [HW,ALSA]
2447
2448 snd-hdsp= [HW,ALSA]
2449
2450 snd-ice1712= [HW,ALSA]
2451
2452 snd-intel8x0= [HW,ALSA]
2453
2454 snd-interwave= [HW,ALSA]
2455
2456 snd-interwave-stb=
2457 [HW,ALSA]
2458
2459 snd-korg1212= [HW,ALSA]
2460
2461 snd-maestro3= [HW,ALSA]
2462
2463 snd-mpu401= [HW,ALSA]
2464
2465 snd-mtpav= [HW,ALSA]
2466
2467 snd-nm256= [HW,ALSA]
2468
2469 snd-opl3sa2= [HW,ALSA]
2470
2471 snd-opti92x-ad1848=
2472 [HW,ALSA]
2473
2474 snd-opti92x-cs4231=
2475 [HW,ALSA]
2476
2477 snd-opti93x= [HW,ALSA]
2478
2479 snd-pmac= [HW,ALSA]
2480
2481 snd-rme32= [HW,ALSA]
2482
2483 snd-rme96= [HW,ALSA]
2484
2485 snd-rme9652= [HW,ALSA]
2486
2487 snd-sb8= [HW,ALSA]
2488
2489 snd-sb16= [HW,ALSA]
2490
2491 snd-sbawe= [HW,ALSA]
2492
2493 snd-serial= [HW,ALSA]
2494
2495 snd-sgalaxy= [HW,ALSA]
2496
2497 snd-sonicvibes= [HW,ALSA]
2498
2499 snd-sun-amd7930=
2500 [HW,ALSA]
2501
2502 snd-sun-cs4231= [HW,ALSA]
2503
2504 snd-trident= [HW,ALSA]
2505
2506 snd-usb-audio= [HW,ALSA,USB]
2507
2508 snd-via82xx= [HW,ALSA]
2509
2510 snd-virmidi= [HW,ALSA]
2511
2512 snd-wavefront= [HW,ALSA]
2513
2514 snd-ymfpci= [HW,ALSA]
a9913044 2515
9c44bc03
IM
2516 softlockup_panic=
2517 [KNL] Should the soft-lockup detector generate panics.
2518
1da177e4
LT
2519 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2520 See Documentation/sonypi.txt
2521
2522 specialix= [HW,SERIAL] Specialix multi-serial port adapter
31c00fc1 2523 See Documentation/serial/specialix.txt.
1da177e4
LT
2524
2525 spia_io_base= [HW,MTD]
2526 spia_fio_base=
2527 spia_pedr=
2528 spia_peddr=
2529
2530 sscape= [HW,OSS]
2531 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
a9913044 2532
1da177e4
LT
2533 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2534 See Documentation/scsi/st.txt.
2535
f38f1d2a
SR
2536 stacktrace [FTRACE]
2537 Enabled the stack tracer on boot up.
2538
1da177e4
LT
2539 sti= [PARISC,HW]
2540 Format: <num>
2541 Set the STI (builtin display/keyboard on the HP-PARISC
2542 machines) console (graphic card) which should be used
2543 as the initial boot-console.
2544 See also comment in drivers/video/console/sticore.c.
2545
2546 sti_font= [HW]
2547 See comment in drivers/video/console/sticore.c.
2548
2549 stifb= [HW]
2550 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2551
cbf11071
TM
2552 sunrpc.min_resvport=
2553 sunrpc.max_resvport=
2554 [NFS,SUNRPC]
2555 SunRPC servers often require that client requests
2556 originate from a privileged port (i.e. a port in the
2557 range 0 < portnr < 1024).
2558 An administrator who wishes to reserve some of these
2559 ports for other uses may adjust the range that the
2560 kernel's sunrpc client considers to be privileged
2561 using these two parameters to set the minimum and
2562 maximum port values.
2563
42a7fc4a
GB
2564 sunrpc.pool_mode=
2565 [NFS]
2566 Control how the NFS server code allocates CPUs to
2567 service thread pools. Depending on how many NICs
2568 you have and where their interrupts are bound, this
2569 option will affect which CPUs will do NFS serving.
2570 Note: this parameter cannot be changed while the
2571 NFS server is running.
2572
2573 auto the server chooses an appropriate mode
2574 automatically using heuristics
2575 global a single global pool contains all CPUs
2576 percpu one pool for each CPU
2577 pernode one pool for each NUMA node (equivalent
2578 to global on non-NUMA machines)
2579
cbf11071
TM
2580 sunrpc.tcp_slot_table_entries=
2581 sunrpc.udp_slot_table_entries=
2582 [NFS,SUNRPC]
2583 Sets the upper limit on the number of simultaneous
2584 RPC calls that can be sent from the client to a
2585 server. Increasing these values may allow you to
2586 improve throughput, but will also increase the
2587 amount of memory reserved for use by the client.
2588
1da177e4 2589 swiotlb= [IA-64] Number of I/O TLB slabs
a9913044 2590
1da177e4
LT
2591 switches= [HW,M68k]
2592
2593 sym53c416= [HW,SCSI]
2594 See header of drivers/scsi/sym53c416.c.
2595
5d6f647f
IM
2596 sysrq_always_enabled
2597 [KNL]
2598 Ignore sysrq setting - this boot parameter will
2599 neutralize any effect of /proc/sys/kernel/sysrq.
2600 Useful for debugging.
2601
1da177e4
LT
2602 t128= [HW,SCSI]
2603 See header of drivers/scsi/t128.c.
2604
2605 tdfx= [HW,DRM]
2606
77437fd4
DB
2607 test_suspend= [SUSPEND]
2608 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2609 standby suspend) as the system sleep state to briefly
2610 enter during system startup. The system is woken from
2611 this state using a wakeup-capable RTC alarm.
2612
1da177e4
LT
2613 thash_entries= [KNL,NET]
2614 Set number of hash buckets for TCP connection
2615
f8707ec9
LB
2616 thermal.act= [HW,ACPI]
2617 -1: disable all active trip points in all thermal zones
2618 <degrees C>: override all lowest active trip points
2619
c52a7419
LB
2620 thermal.crt= [HW,ACPI]
2621 -1: disable all critical trip points in all thermal zones
22a94d79 2622 <degrees C>: override all critical trip points
c52a7419 2623
f5487145
LB
2624 thermal.nocrt= [HW,ACPI]
2625 Set to disable actions on ACPI thermal zone
2626 critical and hot trip points.
2627
72b33ef8
LB
2628 thermal.off= [HW,ACPI]
2629 1: disable ACPI thermal control
2630
a70cdc52
LB
2631 thermal.psv= [HW,ACPI]
2632 -1: disable all passive trip points
ada9cfdd
RD
2633 <degrees C>: override all passive trip points to this
2634 value
a70cdc52 2635
730ff34d
LB
2636 thermal.tzp= [HW,ACPI]
2637 Specify global default ACPI thermal zone polling rate
2638 <deci-seconds>: poll all this frequency
2639 0: no polling (default)
2640
1da177e4
LT
2641 tmscsim= [HW,SCSI]
2642 See comment before function dc390_setup() in
2643 drivers/scsi/tmscsim.c.
2644
2b1a61f0
HC
2645 topology= [S390]
2646 Format: {off | on}
2647 Specify if the kernel should make use of the cpu
2648 topology informations if the hardware supports these.
2649 The scheduler will make use of these informations and
2650 e.g. base its process migration decisions on it.
2651 Default is off.
2652
1da177e4
LT
2653 tp720= [HW,PS2]
2654
225a9be2
RA
2655 tpm_suspend_pcr=[HW,TPM]
2656 Format: integer pcr id
2657 Specify that at suspend time, the tpm driver
2658 should extend the specified pcr with zeros,
2659 as a workaround for some chips which fail to
2660 flush the last written pcr on TPM_SaveState.
2661 This will guarantee that all the other pcrs
2662 are saved.
2663
9d612bef
LZ
2664 trace_buf_size=nn[KMG]
2665 [FTRACE] will set tracing buffer size.
631595fb 2666
020e5f85
LZ
2667 trace_event=[event-list]
2668 [FTRACE] Set and start specified trace events in order
2669 to facilitate early boot debugging.
2670 See also Documentation/trace/events.txt
2671
1da177e4 2672 trix= [HW,OSS] MediaTrix AudioTrix Pro
a9913044
RD
2673 Format:
2674 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2675
395628ef
AK
2676 tsc= Disable clocksource-must-verify flag for TSC.
2677 Format: <string>
2678 [x86] reliable: mark tsc clocksource as reliable, this
2679 disables clocksource verification at runtime.
2680 Used to enable high-resolution timer mode on older
2681 hardware, and in virtualized environment.
2682
a9913044
RD
2683 turbografx.map[2|3]= [HW,JOY]
2684 TurboGraFX parallel port interface
2685 Format:
2686 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1da177e4
LT
2687 See also Documentation/input/joystick-parport.txt
2688
2689 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2690 See header of drivers/scsi/u14-34f.c.
2691
2692 uart401= [HW,OSS]
2693 Format: <io>,<irq>
2694
2695 uart6850= [HW,OSS]
2696 Format: <io>,<irq>
2697
f86dcc5a
ED
2698 uhash_entries= [KNL,NET]
2699 Set number of hash buckets for UDP/UDP-Lite connections
2700
5f8364b7
AS
2701 uhci-hcd.ignore_oc=
2702 [USB] Ignore overcurrent events (default N).
2703 Some badly-designed motherboards generate lots of
2704 bogus events, for ports that aren't wired to
2705 anything. Set this parameter to avoid log spamming.
2706 Note that genuine overcurrent events won't be
2707 reported either.
2708
e3a61b0a 2709 unknown_nmi_panic
6cececfc 2710 [X86]
e3a61b0a
SA
2711 Set unknown_nmi_panic=1 early on boot.
2712
b5e795f8
AS
2713 usbcore.autosuspend=
2714 [USB] The autosuspend time delay (in seconds) used
2715 for newly-detected USB devices (default 2). This
2716 is the time required before an idle device will be
2717 autosuspended. Devices for which the delay is set
eaafbc3a 2718 to a negative value won't be autosuspended at all.
b5e795f8 2719
fd7c519d
JK
2720 usbcore.usbfs_snoop=
2721 [USB] Set to log all usbfs traffic (default 0 = off).
2722
2723 usbcore.blinkenlights=
2724 [USB] Set to cycle leds on hubs (default 0 = off).
2725
2726 usbcore.old_scheme_first=
2727 [USB] Start with the old device initialization
2728 scheme (default 0 = off).
2729
2730 usbcore.use_both_schemes=
2731 [USB] Try the other device initialization scheme
2732 if the first one fails (default 1 = enabled).
2733
2734 usbcore.initial_descriptor_timeout=
2735 [USB] Specifies timeout for the initial 64-byte
2736 USB_REQ_GET_DESCRIPTOR request in milliseconds
2737 (default 5000 = 5.0 seconds).
2738
1da177e4
LT
2739 usbhid.mousepoll=
2740 [USBHID] The interval which mice are to be polled at.
a9913044 2741
d4f373e5
AS
2742 usb-storage.delay_use=
2743 [UMS] The delay in seconds before a new device is
2744 scanned for Logical Units (default 5).
2745
2746 usb-storage.quirks=
2747 [UMS] A list of quirks entries to supplement or
2748 override the built-in unusual_devs list. List
2749 entries are separated by commas. Each entry has
2750 the form VID:PID:Flags where VID and PID are Vendor
2751 and Product ID values (4-digit hex numbers) and
2752 Flags is a set of characters, each corresponding
2753 to a common usb-storage quirk flag as follows:
c838ea46
AS
2754 a = SANE_SENSE (collect more than 18 bytes
2755 of sense data);
a0bb1081
AS
2756 b = BAD_SENSE (don't collect more than 18
2757 bytes of sense data);
d4f373e5
AS
2758 c = FIX_CAPACITY (decrease the reported
2759 device capacity by one sector);
c838ea46
AS
2760 h = CAPACITY_HEURISTICS (decrease the
2761 reported device capacity by one
2762 sector if the number is odd);
d4f373e5
AS
2763 i = IGNORE_DEVICE (don't bind to this
2764 device);
2765 l = NOT_LOCKABLE (don't try to lock and
2766 unlock ejectable media);
2767 m = MAX_SECTORS_64 (don't transfer more
2768 than 64 sectors = 32 KB at a time);
c838ea46
AS
2769 o = CAPACITY_OK (accept the capacity
2770 reported by the device);
d4f373e5
AS
2771 r = IGNORE_RESIDUE (the device reports
2772 bogus residue values);
2773 s = SINGLE_LUN (the device has only one
2774 Logical Unit);
2775 w = NO_WP_DETECT (don't test whether the
2776 medium is write-protected).
2777 Example: quirks=0419:aaf5:rl,0421:0433:rc
2778
14315592
IC
2779 userpte=
2780 [X86] Flags controlling user PTE allocations.
2781
2782 nohigh = do not allocate PTE pages in
2783 HIGHMEM regardless of setting
2784 of CONFIG_HIGHPTE.
2785
6cececfc 2786 vdso= [X86,SH]
1dbf527c 2787 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
e6e5494c
IM
2788 vdso=1: enable VDSO (default)
2789 vdso=0: disable VDSO mapping
2790
6cececfc 2791 vdso32= [X86]
af65d648
RM
2792 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2793 vdso32=1: enable 32-bit VDSO (default)
2794 vdso32=0: disable 32-bit VDSO mapping
2795
d080d397
YI
2796 vector= [IA-64,SMP]
2797 vector=percpu: enable percpu vector domain
2798
1da177e4
LT
2799 video= [FB] Frame buffer configuration
2800 See Documentation/fb/modedb.txt.
2801
cd4f0ef7 2802 vga= [BOOT,X86-32] Select a particular video mode
954a8b81 2803 See Documentation/x86/boot.txt and
a9913044 2804 Documentation/svga.txt.
1da177e4
LT
2805 Use vga=ask for menu.
2806 This is actually a boot loader parameter; the value is
2807 passed to the kernel using a special protocol.
2808
a9913044 2809 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1da177e4
LT
2810 size of <nn>. This can be used to increase the
2811 minimum size (128MB on x86). It can also be used to
2812 decrease the size and leave more room for directly
2813 mapped kernel RAM.
2814
585c3047
PO
2815 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2816 Format: <command>
1da177e4 2817
585c3047
PO
2818 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2819 Format: <command>
2820
2821 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2822 Format: <command>
a9913044 2823
9ea9a886
CL
2824 vt.cur_default= [VT] Default cursor shape.
2825 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2826 the parameters of the <Esc>[?A;B;Cc escape sequence;
2827 see VGA-softcursor.txt. Default: 2 = underline.
2828
0cb55ad2
RD
2829 vt.default_blu= [VT]
2830 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2831 Change the default blue palette of the console.
2832 This is a 16-member array composed of values
2833 ranging from 0-255.
2834
2835 vt.default_grn= [VT]
2836 Format: <green0>,<green1>,<green2>,...,<green15>
2837 Change the default green palette of the console.
2838 This is a 16-member array composed of values
2839 ranging from 0-255.
2840
2841 vt.default_red= [VT]
2842 Format: <red0>,<red1>,<red2>,...,<red15>
2843 Change the default red palette of the console.
2844 This is a 16-member array composed of values
2845 ranging from 0-255.
2846
2847 vt.default_utf8=
2848 [VT]
2849 Format=<0|1>
2850 Set system-wide default UTF-8 mode for all tty's.
2851 Default is 1, i.e. UTF-8 mode is enabled for all
2852 newly opened terminals.
2853
f6c06b68
MG
2854 vt.global_cursor_default=
2855 [VT]
2856 Format=<-1|0|1>
2857 Set system-wide default for whether a cursor
2858 is shown on new VTs. Default is -1,
2859 i.e. cursors will be created by default unless
2860 overridden by individual drivers. 0 will hide
2861 cursors, 1 will display them.
2862
1da177e4
LT
2863 waveartist= [HW,OSS]
2864 Format: <io>,<irq>,<dma>,<dma2>
a9913044 2865
1da177e4
LT
2866 wd33c93= [HW,SCSI]
2867 See header of drivers/scsi/wd33c93.c.
2868
2869 wd7000= [HW,SCSI]
2870 See header of drivers/scsi/wd7000.c.
2871
4724ba57
RD
2872 watchdog timers [HW,WDT] For information on watchdog timers,
2873 see Documentation/watchdog/watchdog-parameters.txt
2874 or other driver-specific files in the
2875 Documentation/watchdog/ directory.
1da177e4 2876
0cb55ad2
RD
2877 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2878 default x2apic cluster mode on platforms
2879 supporting x2apic.
2880
bb24c471
JP
2881 x86_mrst_timer= [X86-32,APBT]
2882 Choose timer option for x86 Moorestown MID platform.
2883 Two valid options are apbt timer only and lapic timer
2884 plus one apbt timer for broadcast timer.
2885 x86_mrst_timer=apbt_only | lapic_and_apbt
2886
1da177e4
LT
2887 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2888 xd_geo= See header of drivers/block/xd.c.
2889
c1c5413a
SS
2890 xen_emul_unplug= [HW,X86,XEN]
2891 Unplug Xen emulated devices
2892 Format: [unplug0,][unplug1]
2893 ide-disks -- unplug primary master IDE devices
2894 aux-ide-disks -- unplug non-primary-master IDE devices
2895 nics -- unplug network devices
2896 all -- unplug all emulated devices (NICs and IDE disks)
2897 ignore -- continue loading the Xen platform PCI driver even
2898 if the version check failed
2899
1da177e4 2900 xirc2ps_cs= [NET,PCMCIA]
a9913044
RD
2901 Format:
2902 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1da177e4 2903
a9913044 2904______________________________________________________________________
1da177e4
LT
2905
2906TODO:
2907
2908 Add documentation for ALSA options.
2909 Add more DRM drivers.