Commit | Line | Data |
---|---|---|
e53dd083 MCC |
1 | Kernel Parameters |
2 | ~~~~~~~~~~~~~~~~~ | |
1da177e4 LT |
3 | |
4 | The following is a consolidated list of the kernel parameters as implemented | |
5 | (mostly) by the __setup() macro and sorted into English Dictionary order | |
6 | (defined as ignoring all punctuation and sorting digits before letters in a | |
7 | case insensitive manner), and with descriptions where known. | |
8 | ||
9 | Module parameters for loadable modules are specified only as the | |
10 | parameter name with optional '=' and value as appropriate, such as: | |
11 | ||
12 | modprobe usbcore blinkenlights=1 | |
13 | ||
14 | Module parameters for modules that are built into the kernel image | |
15 | are specified on the kernel command line with the module name plus | |
16 | '.' plus parameter name, with '=' and value if appropriate, such as: | |
17 | ||
18 | usbcore.blinkenlights=1 | |
19 | ||
ca1eda2d RD |
20 | Hyphens (dashes) and underscores are equivalent in parameter names, so |
21 | log_buf_len=1M print-fatal-signals=1 | |
22 | can also be entered as | |
23 | log-buf-len=1M print_fatal_signals=1 | |
24 | ||
25 | ||
a901ebb9 SR |
26 | This document may not be entirely up to date and comprehensive. The command |
27 | "modinfo -p ${modulename}" shows a current list of all parameters of a loadable | |
28 | module. Loadable modules, after being loaded into the running kernel, also | |
29 | reveal their parameters in /sys/module/${modulename}/parameters/. Some of these | |
30 | parameters may be changed at runtime by the command | |
31 | "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}". | |
32 | ||
6585fa8a SR |
33 | The parameters listed below are only valid if certain kernel build options were |
34 | enabled and if respective hardware is present. The text in square brackets at | |
35 | the beginning of each description states the restrictions within which a | |
36 | parameter is applicable: | |
1da177e4 LT |
37 | |
38 | ACPI ACPI support is enabled. | |
c99c108a | 39 | AGP AGP (Accelerated Graphics Port) is enabled. |
1da177e4 LT |
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. |
9cfe268e AC |
46 | DRM Direct Rendering Management support is enabled. |
47 | DYNAMIC_DEBUG Build in debug messages and enable them at runtime | |
1da177e4 LT |
48 | EDD BIOS Enhanced Disk Drive Services (EDD) is enabled |
49 | EFI EFI Partitioning (GPT) is enabled | |
50 | EIDE EIDE/ATAPI support is enabled. | |
51 | FB The frame buffer device is enabled. | |
2521f2c2 | 52 | GCOV GCOV profiling is enabled. |
1da177e4 | 53 | HW Appropriate hardware is enabled. |
1da177e4 | 54 | IA-64 IA-64 architecture is enabled. |
6146f0d5 | 55 | IMA Integrity measurement architecture is enabled. |
1da177e4 | 56 | IOSCHED More than one I/O scheduler is enabled. |
41e2e8be | 57 | IP_PNP IP DHCP, BOOTP, or RARP is enabled. |
b0f83b28 | 58 | IPV6 IPv6 support is enabled. |
1da177e4 LT |
59 | ISAPNP ISA PnP code is enabled. |
60 | ISDN Appropriate ISDN support is enabled. | |
61 | JOY Appropriate joystick support is enabled. | |
84c08fd6 | 62 | KGDB Kernel debugger support is enabled. |
fef07aae | 63 | KVM Kernel Virtual Machine support is enabled. |
11ef697b | 64 | LIBATA Libata driver is enabled |
1da177e4 LT |
65 | LP Printer support is enabled. |
66 | LOOP Loopback device support is enabled. | |
67 | M68k M68k architecture is enabled. | |
68 | These options have more detailed description inside of | |
69 | Documentation/m68k/kernel-options.txt. | |
70 | MCA MCA bus support is enabled. | |
71 | MDA MDA console support is enabled. | |
72 | MOUSE Appropriate mouse support is enabled. | |
309e57df | 73 | MSI Message Signaled Interrupts (PCI). |
c8facbb6 | 74 | MTD MTD (Memory Technology Device) support is enabled. |
1da177e4 LT |
75 | NET Appropriate network support is enabled. |
76 | NUMA NUMA support is enabled. | |
77 | NFS Appropriate NFS support is enabled. | |
78 | OSS OSS sound support is enabled. | |
c8facbb6 RD |
79 | PV_OPS A paravirtualized kernel is enabled. |
80 | PARIDE The ParIDE (parallel port IDE) subsystem is enabled. | |
1da177e4 LT |
81 | PARISC The PA-RISC architecture is enabled. |
82 | PCI PCI bus support is enabled. | |
7f785763 | 83 | PCIE PCI Express support is enabled. |
1da177e4 LT |
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. | |
163475fb RD |
92 | A lot of drivers have their options described inside |
93 | the Documentation/scsi/ sub-directory. | |
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. |
1da177e4 LT |
99 | SMP The kernel is an SMP kernel. |
100 | SPARC Sparc architecture is enabled. | |
77437fd4 DB |
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. |
1da177e4 LT |
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. |
1da177e4 LT |
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 |
1da177e4 LT |
120 | |
121 | In 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 | ||
127 | Parameters denoted with BOOT are actually interpreted by the boot | |
128 | loader, and have no meaning to the kernel directly. | |
129 | Do not modify the syntax of boot loader parameters without extreme | |
954a8b81 | 130 | need or coordination with <Documentation/x86/boot.txt>. |
1da177e4 | 131 | |
5558870b | 132 | There are also arch-specific kernel-parameters not documented here. |
71cced6e | 133 | See for example <Documentation/x86/x86_64/boot-options.txt>. |
5558870b | 134 | |
1da177e4 LT |
135 | Note that ALL kernel parameters listed below are CASE SENSITIVE, and that |
136 | a trailing = on the name of any parameter states that that parameter will | |
137 | be entered as an environment variable, whereas its absence indicates that | |
138 | it will appear as a kernel argument readable via /proc/cmdline by programs | |
139 | running once the system is up. | |
140 | ||
9c4751fd | 141 | The number of kernel parameters is not limited, but the length of the |
142 | complete command line (parameters including spaces etc.) is limited to | |
143 | a fixed number of characters. This limit depends on the architecture | |
144 | and is between 256 and 4096 characters. It is defined in the file | |
145 | ./include/asm/setup.h as COMMAND_LINE_SIZE. | |
146 | ||
7a19a237 AD |
147 | Finally, the [KMG] suffix is commonly described after a number of kernel |
148 | parameter values. These 'K', 'M', and 'G' letters represent the _binary_ | |
149 | multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30 | |
150 | bytes respectively. Such letter suffixes can also be entirely omitted. | |
151 | ||
9c4751fd | 152 | |
6cececfc | 153 | acpi= [HW,ACPI,X86] |
03d926f8 | 154 | Advanced Configuration and Power Interface |
68ca4069 | 155 | Format: { force | off | strict | noirq | rsdt } |
1da177e4 LT |
156 | force -- enable ACPI if default was off |
157 | off -- disable ACPI if default was on | |
158 | noirq -- do not use ACPI for IRQ routing | |
a9913044 | 159 | strict -- Be less tolerant of platforms that are not |
1da177e4 | 160 | strictly ACPI specification compliant. |
237889bf | 161 | rsdt -- prefer RSDT over (default) XSDT |
aa2110cb | 162 | copy_dsdt -- copy DSDT to memory |
1da177e4 | 163 | |
53471121 | 164 | See also Documentation/power/pm.txt, pci=noacpi |
1da177e4 | 165 | |
a1fdcc0d LB |
166 | acpi_apic_instance= [ACPI, IOAPIC] |
167 | Format: <int> | |
168 | 2: use 2nd APIC table, if available | |
169 | 1,0: use 1st APIC table | |
4e381a4f | 170 | default: 0 |
a1fdcc0d | 171 | |
c3d6de69 TR |
172 | acpi_backlight= [HW,ACPI] |
173 | acpi_backlight=vendor | |
174 | acpi_backlight=video | |
175 | If set to vendor, prefer vendor specific driver | |
176 | (e.g. thinkpad_acpi, sony_acpi, etc.) instead | |
177 | of the ACPI video.ko driver. | |
178 | ||
a0d84a92 BH |
179 | acpi.debug_layer= [HW,ACPI,ACPI_DEBUG] |
180 | acpi.debug_level= [HW,ACPI,ACPI_DEBUG] | |
1da177e4 | 181 | Format: <int> |
a0d84a92 BH |
182 | CONFIG_ACPI_DEBUG must be enabled to produce any ACPI |
183 | debug output. Bits in debug_layer correspond to a | |
184 | _COMPONENT in an ACPI source file, e.g., | |
185 | #define _COMPONENT ACPI_PCI_COMPONENT | |
186 | Bits in debug_level correspond to a level in | |
187 | ACPI_DEBUG_PRINT statements, e.g., | |
188 | ACPI_DEBUG_PRINT((ACPI_DB_INFO, ... | |
e76f4276 BH |
189 | The debug_level mask defaults to "info". See |
190 | Documentation/acpi/debug.txt for more information about | |
191 | debug layers and levels. | |
a0d84a92 | 192 | |
e76f4276 BH |
193 | Enable processor driver info messages: |
194 | acpi.debug_layer=0x20000000 | |
195 | Enable PCI/PCI interrupt routing info messages: | |
196 | acpi.debug_layer=0x400000 | |
a0d84a92 BH |
197 | Enable AML "Debug" output, i.e., stores to the Debug |
198 | object while interpreting AML: | |
199 | acpi.debug_layer=0xffffffff acpi.debug_level=0x2 | |
a0d84a92 BH |
200 | Enable all messages related to ACPI hardware: |
201 | acpi.debug_layer=0x2 acpi.debug_level=0xffffffff | |
202 | ||
203 | Some values produce so much output that the system is | |
204 | unusable. The "log_buf_len" parameter may be useful | |
205 | if you need to capture more output. | |
f989106c | 206 | |
0cb55ad2 RD |
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] |
0cb55ad2 RD |
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 | ||
4af94f39 RD |
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 } |
4af94f39 RD |
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). | |
72ad5d77 RW |
259 | nonvs prevents the kernel from saving/restoring the |
260 | ACPI NVS memory during suspend/hibernation and resume. | |
d7f0eea9 ZR |
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). | |
4af94f39 RD |
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 | ||
7e90560c LT |
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 | ||
4af94f39 RD |
285 | add_efi_memmap [EFI; X86] Include EFI memory map in |
286 | kernel's map of available physical RAM. | |
287 | ||
0cb55ad2 RD |
288 | agp= [AGP] |
289 | { off | try_unsupported } | |
290 | off: disable AGP support | |
291 | try_unsupported: try to drive unsupported chipsets | |
292 | (may crash computer or cause data corruption) | |
293 | ||
bcfde334 RD |
294 | ALSA [HW,ALSA] |
295 | See Documentation/sound/alsa/alsa-parameters.txt | |
296 | ||
d944d549 RK |
297 | alignment= [KNL,ARM] |
298 | Allow the default userspace alignment fault handler | |
299 | behaviour to be specified. Bit 0 enables warnings, | |
300 | bit 1 enables fixups, and bit 2 sends a segfault. | |
301 | ||
54b4cbd2 JR |
302 | amd_iommu= [HW,X86-84] |
303 | Pass parameters to the AMD IOMMU driver in the system. | |
304 | Possible values are: | |
afa9fdc2 FT |
305 | fullflush - enable flushing of IO/TLB entries when |
306 | they are unmapped. Otherwise they are | |
307 | flushed before they will be reused, which | |
308 | is a lot of faster | |
a5235725 JR |
309 | off - do not initialize any AMD IOMMU found in |
310 | the system | |
afa9fdc2 | 311 | |
1da177e4 LT |
312 | amijoy.map= [HW,JOY] Amiga joystick support |
313 | Map of devices attached to JOY0DAT and JOY1DAT | |
314 | Format: <a>,<b> | |
315 | See also Documentation/kernel/input/joystick.txt | |
316 | ||
317 | analog.map= [HW,JOY] Analog joystick and gamepad support | |
318 | Specifies type or capabilities of an analog joystick | |
319 | connected to one of 16 gameports | |
320 | Format: <type1>,<type2>,..<type16> | |
321 | ||
a9913044 RD |
322 | apc= [HW,SPARC] |
323 | Power management functions (SPARCstation-4/5 + deriv.) | |
1da177e4 LT |
324 | Format: noidle |
325 | Disable APC CPU standby support. SPARCstation-Fox does | |
326 | not play well with APC CPU idle - disable it if you have | |
327 | APC and your system crashes randomly. | |
328 | ||
ca1eda2d | 329 | apic= [APIC,X86-32] Advanced Programmable Interrupt Controller |
c8facbb6 | 330 | Change the output verbosity whilst booting |
1da177e4 LT |
331 | Format: { quiet (default) | verbose | debug } |
332 | Change the amount of debugging information output | |
333 | when initialising the APIC and IO-APIC components. | |
a9913044 | 334 | |
b0f83b28 BH |
335 | autoconf= [IPV6] |
336 | See Documentation/networking/ipv6.txt. | |
337 | ||
9636bc05 CG |
338 | show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller |
339 | Limit apic dumping. The parameter defines the maximal | |
340 | number of local apics being dumped. Also it is possible | |
341 | to set it to "all" by meaning -- no limit here. | |
342 | Format: { 1 (default) | 2 | ... | all }. | |
343 | The parameter valid if only apic=debug or | |
344 | apic=verbose is specified. | |
345 | Example: apic=debug show_lapic=all | |
346 | ||
1da177e4 | 347 | apm= [APM] Advanced Power Management |
71f77055 | 348 | See header of arch/x86/kernel/apm_32.c. |
1da177e4 | 349 | |
1da177e4 LT |
350 | arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards |
351 | Format: <io>,<irq>,<nodeID> | |
352 | ||
353 | ataflop= [HW,M68k] | |
354 | ||
355 | atarimouse= [HW,MOUSE] Atari Mouse | |
356 | ||
1da177e4 LT |
357 | atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, |
358 | EzKey and similar keyboards | |
359 | ||
360 | atkbd.reset= [HW] Reset keyboard during initialization | |
361 | ||
a9913044 RD |
362 | atkbd.set= [HW] Select keyboard code set |
363 | Format: <int> (2 = AT (default), 3 = PS/2) | |
1da177e4 LT |
364 | |
365 | atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar | |
366 | keyboards | |
367 | ||
368 | atkbd.softraw= [HW] Choose between synthetic and real raw mode | |
369 | Format: <bool> (0 = real, 1 = synthetic (default)) | |
a9913044 RD |
370 | |
371 | atkbd.softrepeat= [HW] | |
372 | Use software keyboard repeat | |
1da177e4 LT |
373 | |
374 | autotest [IA64] | |
375 | ||
1da177e4 LT |
376 | baycom_epp= [HW,AX25] |
377 | Format: <io>,<mode> | |
a9913044 | 378 | |
1da177e4 LT |
379 | baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem |
380 | Format: <io>,<mode> | |
381 | See header of drivers/net/hamradio/baycom_par.c. | |
382 | ||
a9913044 RD |
383 | baycom_ser_fdx= [HW,AX25] |
384 | BayCom Serial Port AX.25 Modem (Full Duplex Mode) | |
1da177e4 LT |
385 | Format: <io>,<irq>,<mode>[,<baud>] |
386 | See header of drivers/net/hamradio/baycom_ser_fdx.c. | |
387 | ||
a9913044 RD |
388 | baycom_ser_hdx= [HW,AX25] |
389 | BayCom Serial Port AX.25 Modem (Half Duplex Mode) | |
1da177e4 LT |
390 | Format: <io>,<irq>,<mode> |
391 | See header of drivers/net/hamradio/baycom_ser_hdx.c. | |
392 | ||
bfe8df3d RD |
393 | boot_delay= Milliseconds to delay each printk during boot. |
394 | Values larger than 10 seconds (10000) are changed to | |
395 | no delay (0). | |
396 | Format: integer | |
397 | ||
35fc908d AH |
398 | bootmem_debug [KNL] Enable bootmem allocator debug messages. |
399 | ||
1da177e4 | 400 | bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) |
a9913044 RD |
401 | bttv.radio= Most important insmod options are available as |
402 | kernel args too. | |
1da177e4 LT |
403 | bttv.pll= See Documentation/video4linux/bttv/Insmod-options |
404 | bttv.tuner= and Documentation/video4linux/bttv/CARDLIST | |
405 | ||
4e89a2d8 WS |
406 | bulk_remove=off [PPC] This parameter disables the use of the pSeries |
407 | firmware feature for flushing multiple hpte entries | |
408 | at a time. | |
409 | ||
1da177e4 LT |
410 | c101= [NET] Moxa C101 synchronous serial card |
411 | ||
cd4f0ef7 | 412 | cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. |
1da177e4 LT |
413 | Sometimes CPU hardware bugs make them report the cache |
414 | size incorrectly. The kernel will attempt work arounds | |
415 | to fix known problems, but for some CPUs it is not | |
416 | possible to determine what the correct size should be. | |
417 | This option provides an override for these situations. | |
418 | ||
20510f2f JM |
419 | capability.disable= |
420 | [SECURITY] Disable capabilities. This would normally | |
421 | be used only if an alternative security model is to be | |
422 | configured. Potentially dangerous and should only be | |
423 | used if you are entirely sure of the consequences. | |
424 | ||
14ff56bb SO |
425 | ccw_timeout_log [S390] |
426 | See Documentation/s390/CommonIO for details. | |
1da177e4 | 427 | |
8bab8dde PM |
428 | cgroup_disable= [KNL] Disable a particular controller |
429 | Format: {name of the controller(s) to disable} | |
430 | {Currently supported controllers - "memory"} | |
431 | ||
1da177e4 LT |
432 | checkreqprot [SELINUX] Set initial checkreqprot flag value. |
433 | Format: { "0" | "1" } | |
434 | See security/selinux/Kconfig help text. | |
a9913044 RD |
435 | 0 -- check protection applied by kernel (includes |
436 | any implied execute protection). | |
1da177e4 LT |
437 | 1 -- check protection requested by application. |
438 | Default value is set via a kernel config option. | |
a9913044 RD |
439 | Value can be changed at runtime via |
440 | /selinux/checkreqprot. | |
441 | ||
661ca0da SO |
442 | cio_ignore= [S390] |
443 | See Documentation/s390/CommonIO for details. | |
444 | ||
cd4f0ef7 | 445 | clock= [BUGS=X86-32, HW] gettimeofday clocksource override. |
734efb46 | 446 | [Deprecated] |
3f6dee9b | 447 | Forces specified clocksource (if available) to be used |
734efb46 | 448 | when calculating gettimeofday(). If specified |
3f6dee9b | 449 | clocksource is not available, it defaults to PIT. |
1da177e4 LT |
450 | Format: { pit | tsc | cyclone | pmtmr } |
451 | ||
592913ec | 452 | clocksource= Override the default clocksource |
3d6ac984 RD |
453 | Format: <string> |
454 | Override the default clocksource and use the clocksource | |
455 | with the name specified. | |
456 | Some clocksource names to choose from, depending on | |
457 | the platform: | |
458 | [all] jiffies (this is the base, fallback clocksource) | |
459 | [ACPI] acpi_pm | |
460 | [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, | |
461 | pxa_timer,timer3,32k_counter,timer0_1 | |
462 | [AVR32] avr32 | |
9863c90f | 463 | [X86-32] pit,hpet,tsc; |
3d6ac984 RD |
464 | scx200_hrt on Geode; cyclone on IBM x440 |
465 | [MIPS] MIPS | |
466 | [PARISC] cr16 | |
467 | [S390] tod | |
468 | [SH] SuperH | |
469 | [SPARC64] tick | |
470 | [X86-64] hpet,tsc | |
471 | ||
ac72e788 AK |
472 | clearcpuid=BITNUM [X86] |
473 | Disable CPUID feature X for the kernel. See | |
07983f0e RD |
474 | arch/x86/include/asm/cpufeature.h for the valid bit |
475 | numbers. Note the Linux specific bits are not necessarily | |
ac72e788 AK |
476 | stable over kernel options, but the vendor specific |
477 | ones should be. | |
478 | Also note that user programs calling CPUID directly | |
479 | or using the feature without checking anything | |
480 | will still see it. This just prevents it from | |
481 | being used by the kernel or shown in /proc/cpuinfo. | |
482 | Also note the kernel might malfunction if you disable | |
483 | some critical bits. | |
484 | ||
14f966e7 RJ |
485 | cmo_free_hint= [PPC] Format: { yes | no } |
486 | Specify whether pages are marked as being inactive | |
487 | when they are freed. This is used in CMO environments | |
488 | to determine OS memory pressure for page stealing by | |
489 | a hypervisor. | |
490 | Default: yes | |
491 | ||
6cececfc | 492 | code_bytes [X86] How many bytes of object code to print |
a25bd949 | 493 | in an oops report. |
86c41837 CE |
494 | Range: 0 - 8192 |
495 | Default: 64 | |
496 | ||
1da177e4 | 497 | com20020= [HW,NET] ARCnet - COM20020 chipset |
a9913044 RD |
498 | Format: |
499 | <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] | |
1da177e4 LT |
500 | |
501 | com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) | |
502 | Format: <io>[,<irq>] | |
503 | ||
a9913044 RD |
504 | com90xx= [HW,NET] |
505 | ARCnet - COM90xx chipset (memory-mapped buffers) | |
1da177e4 LT |
506 | Format: <io>[,<irq>[,<memstart>]] |
507 | ||
508 | condev= [HW,S390] console device | |
509 | conmode= | |
a9913044 | 510 | |
1da177e4 LT |
511 | console= [KNL] Output console device and options. |
512 | ||
513 | tty<n> Use the virtual console device <n>. | |
514 | ||
515 | ttyS<n>[,options] | |
f1a1c2dc | 516 | ttyUSB0[,options] |
1da177e4 | 517 | Use the specified serial port. The options are of |
f1a1c2dc RD |
518 | the form "bbbbpnf", where "bbbb" is the baud rate, |
519 | "p" is parity ("n", "o", or "e"), "n" is number of | |
520 | bits, and "f" is flow control ("r" for RTS or | |
521 | omit it). Default is "9600n8". | |
522 | ||
523 | See Documentation/serial-console.txt for more | |
524 | information. See | |
525 | Documentation/networking/netconsole.txt for an | |
526 | alternative. | |
1da177e4 | 527 | |
18a8bd94 YL |
528 | uart[8250],io,<addr>[,options] |
529 | uart[8250],mmio,<addr>[,options] | |
1da177e4 LT |
530 | Start an early, polled-mode console on the 8250/16550 |
531 | UART at the specified I/O port or MMIO address, | |
532 | switching to the matching ttyS device later. The | |
533 | options are the same as for ttyS, above. | |
534 | ||
f7511d5f ST |
535 | If the device connected to the port is not a TTY but a braille |
536 | device, prepend "brl," before the device type, for instance | |
537 | console=brl,ttyS0 | |
538 | For now, only VisioBraille is supported. | |
539 | ||
f324edc8 DM |
540 | consoleblank= [KNL] The console blank (screen saver) timeout in |
541 | seconds. Defaults to 10*60 = 10mins. A value of 0 | |
542 | disables the blank timer. | |
543 | ||
4cb0e11b HK |
544 | coredump_filter= |
545 | [KNL] Change the default value for | |
546 | /proc/<pid>/coredump_filter. | |
547 | See also Documentation/filesystems/proc.txt. | |
548 | ||
1da177e4 | 549 | cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver |
a9913044 RD |
550 | Format: |
551 | <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] | |
1da177e4 | 552 | |
6f21e646 AD |
553 | crashkernel=size[KMG][@offset[KMG]] |
554 | [KNL] Using kexec, Linux can switch to a 'crash kernel' | |
555 | upon panic. This parameter reserves the physical | |
556 | memory region [offset, offset + size] for that kernel | |
557 | image. If '@offset' is omitted, then a suitable offset | |
558 | is selected automatically. Check | |
559 | Documentation/kdump/kdump.txt for further details. | |
dc009d92 | 560 | |
fb391599 BW |
561 | crashkernel=range1:size1[,range2:size2,...][@offset] |
562 | [KNL] Same as above, but depends on the memory | |
563 | in the running system. The syntax of range is | |
564 | start-[end] where start and end are both | |
565 | a memory unit (amount[KMG]). See also | |
6f21e646 | 566 | Documentation/kdump/kdump.txt for an example. |
fb391599 | 567 | |
1da177e4 LT |
568 | cs89x0_dma= [HW,NET] |
569 | Format: <dma> | |
570 | ||
571 | cs89x0_media= [HW,NET] | |
572 | Format: { rj45 | aui | bnc } | |
a9913044 | 573 | |
a9913044 | 574 | dasd= [HW,NET] |
1da177e4 LT |
575 | See header of drivers/s390/block/dasd_devmap.c. |
576 | ||
577 | db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port | |
578 | (one device per port) | |
579 | Format: <port#>,<type> | |
580 | See also Documentation/input/joystick-parport.txt | |
581 | ||
a648ec05 TR |
582 | ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot |
583 | time. See Documentation/dynamic-debug-howto.txt for | |
584 | details. | |
585 | ||
1da177e4 LT |
586 | debug [KNL] Enable kernel debugging (events log level). |
587 | ||
cae2ed9a IM |
588 | debug_locks_verbose= |
589 | [KNL] verbose self-tests | |
590 | Format=<0|1> | |
591 | Print debugging info while doing the locking API | |
592 | self-tests. | |
593 | We default to 0 (no extra messages), setting it to | |
594 | 1 will print _a lot_ more information - normally | |
595 | only useful to kernel developers. | |
596 | ||
3ac7fe5a TG |
597 | debug_objects [KNL] Enable object debugging |
598 | ||
3e8ebb5c KM |
599 | no_debug_objects |
600 | [KNL] Disable object debugging | |
601 | ||
d3af01f1 TG |
602 | debugpat [X86] Enable PAT debugging |
603 | ||
2d27a966 | 604 | decnet.addr= [HW,NET] |
1da177e4 LT |
605 | Format: <area>[,<node>] |
606 | See also Documentation/networking/decnet.txt. | |
607 | ||
0cb55ad2 RD |
608 | default_hugepagesz= |
609 | [same as hugepagesz=] The size of the default | |
610 | HugeTLB page size. This is the size represented by | |
611 | the legacy /proc/ hugepages APIs, used for SHM, and | |
612 | default size when mounting hugetlbfs filesystems. | |
613 | Defaults to the default architecture's huge page size | |
614 | if not specified. | |
55ff9780 | 615 | |
1da177e4 LT |
616 | dhash_entries= [KNL] |
617 | Set number of hash buckets for dentry cache. | |
a9913044 | 618 | |
1da177e4 LT |
619 | digi= [HW,SERIAL] |
620 | IO parameters + enable/disable command. | |
621 | ||
622 | digiepca= [HW,SERIAL] | |
623 | See drivers/char/README.epca and | |
31c00fc1 | 624 | Documentation/serial/digiepca.txt. |
1da177e4 | 625 | |
b0f83b28 BH |
626 | disable= [IPV6] |
627 | See Documentation/networking/ipv6.txt. | |
628 | ||
4e8b0cf4 NA |
629 | disable_ddw [PPC/PSERIES] |
630 | Disable Dynamic DMA Window support. Use this if | |
631 | to workaround buggy firmware. | |
632 | ||
b0f83b28 BH |
633 | disable_ipv6= [IPV6] |
634 | See Documentation/networking/ipv6.txt. | |
635 | ||
95ffa243 | 636 | disable_mtrr_cleanup [X86] |
95ffa243 YL |
637 | The kernel tries to adjust MTRR layout from continuous |
638 | to discrete, to make X server driver able to add WB | |
0cb55ad2 | 639 | entry later. This parameter disables that. |
95ffa243 | 640 | |
093af8d7 | 641 | disable_mtrr_trim [X86, Intel and AMD only] |
99fc8d42 JB |
642 | By default the kernel will trim any uncacheable |
643 | memory out of your available memory pool based on | |
644 | MTRR settings. This parameter disables that behavior, | |
645 | possibly causing your machine to run very slowly. | |
646 | ||
6cececfc | 647 | disable_timer_pin_1 [X86] |
0cb55ad2 RD |
648 | Disable PIN 1 of APIC timer |
649 | Can be useful to work around chipset bugs. | |
650 | ||
0cb55ad2 RD |
651 | dma_debug=off If the kernel is compiled with DMA_API_DEBUG support, |
652 | this option disables the debugging code at boot. | |
653 | ||
654 | dma_debug_entries=<number> | |
655 | This option allows to tune the number of preallocated | |
656 | entries for DMA-API debugging code. One entry is | |
657 | required per DMA-API allocation. Use this if the | |
658 | DMA-API debugging code disables itself because the | |
659 | architectural default is too low. | |
660 | ||
1745de5e JR |
661 | dma_debug_driver=<driver_name> |
662 | With this option the DMA-API debugging driver | |
663 | filter feature can be enabled at boot time. Just | |
664 | pass the driver to filter for as the parameter. | |
665 | The filter can be disabled or changed to another | |
666 | driver later using sysfs. | |
667 | ||
1da177e4 LT |
668 | dscc4.setup= [NET] |
669 | ||
0cb55ad2 RD |
670 | earlycon= [KNL] Output early console device and options. |
671 | uart[8250],io,<addr>[,options] | |
672 | uart[8250],mmio,<addr>[,options] | |
1917ac76 | 673 | uart[8250],mmio32,<addr>[,options] |
0cb55ad2 RD |
674 | Start an early, polled-mode console on the 8250/16550 |
675 | UART at the specified I/O port or MMIO address. | |
1917ac76 SG |
676 | MMIO inter-register address stride is either 8bit (mmio) |
677 | or 32bit (mmio32). | |
0cb55ad2 RD |
678 | The options are the same as for ttyS, above. |
679 | ||
6cececfc | 680 | earlyprintk= [X86,SH,BLACKFIN] |
1da177e4 LT |
681 | earlyprintk=vga |
682 | earlyprintk=serial[,ttySn[,baudrate]] | |
ea3acb19 | 683 | earlyprintk=ttySn[,baudrate] |
9780bc41 | 684 | earlyprintk=dbgp[debugController#] |
1da177e4 | 685 | |
a9913044 | 686 | Append ",keep" to not disable it when the real console |
1da177e4 LT |
687 | takes over. |
688 | ||
5c05917e | 689 | Only vga or serial or usb debug port at a time. |
1da177e4 LT |
690 | |
691 | Currently only ttyS0 and ttyS1 are supported. | |
692 | ||
693 | Interaction with the standard serial driver is not | |
694 | very good. | |
695 | ||
696 | The VGA output is eventually overwritten by the real | |
697 | console. | |
698 | ||
9731191f JW |
699 | ekgdboc= [X86,KGDB] Allow early kernel console debugging |
700 | ekgdboc=kbd | |
701 | ||
25985edc | 702 | This is designed to be used in conjunction with |
9731191f JW |
703 | the boot argument: earlyprintk=vga |
704 | ||
1da177e4 | 705 | edd= [EDD] |
8c4dd606 | 706 | Format: {"off" | "on" | "skip[mbr]"} |
1da177e4 | 707 | |
1da177e4 LT |
708 | eisa_irq_edge= [PARISC,HW] |
709 | See header of drivers/parisc/eisa.c. | |
710 | ||
cd4f0ef7 | 711 | elanfreq= [X86-32] |
1da177e4 | 712 | See comment before function elanfreq_setup() in |
71f77055 | 713 | arch/x86/kernel/cpu/cpufreq/elanfreq.c. |
1da177e4 LT |
714 | |
715 | elevator= [IOSCHED] | |
17a9e7bb | 716 | Format: {"cfq" | "deadline" | "noop"} |
a9913044 RD |
717 | See Documentation/block/as-iosched.txt and |
718 | Documentation/block/deadline-iosched.txt for details. | |
719 | ||
6cececfc | 720 | elfcorehdr= [IA64,PPC,SH,X86] |
a9913044 | 721 | Specifies physical address of start of kernel core |
aac04b32 VG |
722 | image elf header. Generally kexec loader will |
723 | pass this option to capture kernel. | |
724 | See Documentation/kdump/kdump.txt for details. | |
1da177e4 | 725 | |
0cb55ad2 RD |
726 | enable_mtrr_cleanup [X86] |
727 | The kernel tries to adjust MTRR layout from continuous | |
728 | to discrete, to make X server driver able to add WB | |
729 | entry later. This parameter enables that. | |
730 | ||
ca1eda2d | 731 | enable_timer_pin_1 [X86] |
0cb55ad2 RD |
732 | Enable PIN 1 of APIC timer |
733 | Can be useful to work around chipset bugs | |
734 | (in particular on some ATI chipsets). | |
735 | The kernel tries to set a reasonable default. | |
736 | ||
1da177e4 LT |
737 | enforcing [SELINUX] Set initial enforcing status. |
738 | Format: {"0" | "1"} | |
739 | See security/selinux/Kconfig help text. | |
740 | 0 -- permissive (log only, no denials). | |
741 | 1 -- enforcing (deny and log). | |
742 | Default value is 0. | |
743 | Value can be changed at runtime via /selinux/enforce. | |
744 | ||
a08f82d0 HY |
745 | erst_disable [ACPI] |
746 | Disable Error Record Serialization Table (ERST) | |
747 | support. | |
748 | ||
1da177e4 LT |
749 | ether= [HW,NET] Ethernet cards parameters |
750 | This option is obsoleted by the "netdev=" option, which | |
751 | has equivalent usage. See its documentation for details. | |
752 | ||
de1ba09b AM |
753 | failslab= |
754 | fail_page_alloc= | |
755 | fail_make_request=[KNL] | |
756 | General fault injection mechanism. | |
757 | Format: <interval>,<probability>,<space>,<times> | |
758 | See also /Documentation/fault-injection/. | |
759 | ||
1da177e4 | 760 | floppy= [HW] |
31c00fc1 | 761 | See Documentation/blockdev/floppy.txt. |
1da177e4 | 762 | |
f13ae30e AC |
763 | force_pal_cache_flush |
764 | [IA-64] Avoid check_sal_cache_flush which may hang on | |
765 | buggy SAL_CACHE_FLUSH implementations. Using this | |
766 | parameter will force ia64_sal_cache_flush to call | |
767 | ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. | |
768 | ||
d9e54076 | 769 | ftrace=[tracer] |
2af15d6a | 770 | [FTRACE] will set and start the specified tracer |
d9e54076 PZ |
771 | as early as possible in order to facilitate early |
772 | boot debugging. | |
773 | ||
cecbca96 | 774 | ftrace_dump_on_oops[=orig_cpu] |
2af15d6a | 775 | [FTRACE] will dump the trace buffers on oops. |
cecbca96 FW |
776 | If no parameter is passed, ftrace will dump |
777 | buffers of all CPUs, but if you pass orig_cpu, it will | |
778 | dump only the buffer of the CPU that triggered the | |
779 | oops. | |
2af15d6a SR |
780 | |
781 | ftrace_filter=[function-list] | |
782 | [FTRACE] Limit the functions traced by the function | |
783 | tracer at boot up. function-list is a comma separated | |
784 | list of functions. This list can be changed at run | |
785 | time by the set_ftrace_filter file in the debugfs | |
786 | tracing directory. | |
787 | ||
788 | ftrace_notrace=[function-list] | |
789 | [FTRACE] Do not trace the functions specified in | |
790 | function-list. This list can be changed at run time | |
791 | by the set_ftrace_notrace file in the debugfs | |
792 | tracing directory. | |
d9e54076 | 793 | |
369bc18f SA |
794 | ftrace_graph_filter=[function-list] |
795 | [FTRACE] Limit the top level callers functions traced | |
796 | by the function graph tracer at boot up. | |
797 | function-list is a comma separated list of functions | |
798 | that can be changed at run time by the | |
799 | set_graph_function file in the debugfs tracing directory. | |
800 | ||
1da177e4 LT |
801 | gamecon.map[2|3]= |
802 | [HW,JOY] Multisystem joystick and NES/SNES/PSX pad | |
803 | support via parallel port (up to 5 devices per port) | |
804 | Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> | |
805 | See also Documentation/input/joystick-parport.txt | |
806 | ||
807 | gamma= [HW,DRM] | |
808 | ||
aaf23042 YL |
809 | gart_fix_e820= [X86_64] disable the fix e820 for K8 GART |
810 | Format: off | on | |
811 | default: on | |
812 | ||
2521f2c2 PO |
813 | gcov_persist= [GCOV] When non-zero (default), profiling data for |
814 | kernel modules is saved and remains accessible via | |
815 | debugfs, even when the module is unloaded/reloaded. | |
816 | When zero, profiling data is discarded and associated | |
817 | debugfs files are removed at module unload time. | |
818 | ||
1da177e4 LT |
819 | gpt [EFI] Forces disk with valid GPT signature but |
820 | invalid Protective MBR to be treated as GPT. | |
821 | ||
1da177e4 LT |
822 | hashdist= [KNL,NUMA] Large hashes allocated during boot |
823 | are distributed across NUMA nodes. Defaults on | |
429aa0fc | 824 | for 64bit NUMA, off otherwise. |
a9913044 | 825 | Format: 0 | 1 (for off | on) |
1da177e4 LT |
826 | |
827 | hcl= [IA-64] SGI's Hardware Graph compatibility layer | |
828 | ||
829 | hd= [EIDE] (E)IDE hard drive subsystem geometry | |
830 | Format: <cyl>,<head>,<sect> | |
831 | ||
ea8c071c HY |
832 | hest_disable [ACPI] |
833 | Disable Hardware Error Source Table (HEST) support; | |
834 | corresponding firmware-first mode error processing | |
835 | logic will be disabled. | |
836 | ||
1da177e4 LT |
837 | highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact |
838 | size of <nn>. This works even on boxes that have no | |
839 | highmem otherwise. This also works to reduce highmem | |
840 | size on bigger boxes. | |
841 | ||
54cdfdb4 TG |
842 | highres= [KNL] Enable/disable high resolution timer mode. |
843 | Valid parameters: "on", "off" | |
844 | Default: "on" | |
845 | ||
1da177e4 LT |
846 | hisax= [HW,ISDN] |
847 | See Documentation/isdn/README.HiSax. | |
848 | ||
0cb55ad2 RD |
849 | hlt [BUGS=ARM,SH] |
850 | ||
851 | hpet= [X86-32,HPET] option to control HPET usage | |
852 | Format: { enable (default) | disable | force | | |
853 | verbose } | |
854 | disable: disable HPET and use PIT instead | |
855 | force: allow force enabled of undocumented chips (ICH4, | |
856 | VIA, nVidia) | |
857 | verbose: show contents of HPET registers during setup | |
858 | ||
b4718e62 AK |
859 | hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot. |
860 | hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages. | |
0d9ea754 JT |
861 | On x86-64 and powerpc, this option can be specified |
862 | multiple times interleaved with hugepages= to reserve | |
863 | huge pages of different sizes. Valid pages sizes on | |
864 | x86-64 are 2M (when the CPU supports "pse") and 1G | |
865 | (when the CPU supports the "pdpe1gb" cpuinfo flag) | |
b4718e62 AK |
866 | Note that 1GB pages can only be allocated at boot time |
867 | using hugepages= and not freed afterwards. | |
6902aa84 | 868 | |
555d61d6 HB |
869 | hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) |
870 | terminal devices. Valid values: 0..8 | |
431429ff HB |
871 | hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. |
872 | If specified, z/VM IUCV HVC accepts connections | |
873 | from listed z/VM user IDs only. | |
cef7125d | 874 | |
7bf69395 FDN |
875 | keep_bootcon [KNL] |
876 | Do not unregister boot console at start. This is only | |
877 | useful for debugging when something happens in the window | |
878 | between unregistering the boot console and initializing | |
879 | the real console. | |
880 | ||
3a853fb9 | 881 | i2c_bus= [HW] Override the default board specific I2C bus speed |
7954763b JN |
882 | or register an additional I2C bus that is not |
883 | registered from board initialization code. | |
3a853fb9 JN |
884 | Format: |
885 | <bus_id>,<clkrate> | |
886 | ||
36d95739 | 887 | i8042.debug [HW] Toggle i8042 debug mode |
1da177e4 | 888 | i8042.direct [HW] Put keyboard port into non-translated mode |
84eb8d06 ML |
889 | i8042.dumbkbd [HW] Pretend that controller can only read data from |
890 | keyboard and cannot control its state | |
1da177e4 LT |
891 | (Don't attempt to blink the leds) |
892 | i8042.noaux [HW] Don't check for auxiliary (== mouse) port | |
945ef0d4 | 893 | i8042.nokbd [HW] Don't check/create keyboard port |
75d08c78 JK |
894 | i8042.noloop [HW] Disable the AUX Loopback command while probing |
895 | for the AUX port | |
1da177e4 LT |
896 | i8042.nomux [HW] Don't check presence of an active multiplexing |
897 | controller | |
898 | i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX | |
899 | controllers | |
f8313ef1 | 900 | i8042.notimeout [HW] Ignore timeout condition signalled by conroller |
1da177e4 LT |
901 | i8042.reset [HW] Reset the controller during init and cleanup |
902 | i8042.unlock [HW] Unlock (ignore) the keylock | |
903 | ||
904 | i810= [HW,DRM] | |
905 | ||
e70c9d5e DT |
906 | i8k.ignore_dmi [HW] Continue probing hardware even if DMI data |
907 | indicates that the driver is running on unsupported | |
908 | hardware. | |
1da177e4 LT |
909 | i8k.force [HW] Activate i8k driver even if SMM BIOS signature |
910 | does not match list of supported models. | |
911 | i8k.power_status | |
912 | [HW] Report power status in /proc/i8k | |
913 | (disabled by default) | |
914 | i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN | |
915 | capability is set. | |
916 | ||
1da177e4 LT |
917 | icn= [HW,ISDN] |
918 | Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] | |
919 | ||
0af80c04 DF |
920 | ide-core.nodma= [HW] (E)IDE subsystem |
921 | Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc | |
075affcb BZ |
922 | .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr |
923 | .cdrom .chs .ignore_cable are additional options | |
1c10e938 | 924 | See Documentation/ide/ide.txt. |
1da177e4 | 925 | |
0cb55ad2 RD |
926 | ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem |
927 | Claim all unknown PCI IDE storage controllers. | |
928 | ||
f039b754 | 929 | idle= [X86] |
ada9cfdd RD |
930 | Format: idle=poll, idle=mwait, idle=halt, idle=nomwait |
931 | Poll forces a polling idle loop that can slightly | |
932 | improve the performance of waking up a idle CPU, but | |
933 | will use a lot of power and make the system run hot. | |
934 | Not recommended. | |
935 | idle=mwait: On systems which support MONITOR/MWAIT but | |
936 | the kernel chose to not use it because it doesn't save | |
937 | as much power as a normal idle loop, use the | |
938 | MONITOR/MWAIT idle loop anyways. Performance should be | |
939 | the same as idle=poll. | |
940 | idle=halt: Halt is forced to be used for CPU idle. | |
c1e3b377 | 941 | In such case C2/C3 won't be used again. |
ada9cfdd | 942 | idle=nomwait: Disable mwait for CPU C-states |
a9913044 | 943 | |
79290822 IM |
944 | ignore_loglevel [KNL] |
945 | Ignore loglevel setting - this will print /all/ | |
946 | kernel messages to the console. Useful for debugging. | |
947 | ||
1da177e4 LT |
948 | ihash_entries= [KNL] |
949 | Set number of hash buckets for inode cache. | |
950 | ||
3323eec9 MZ |
951 | ima_audit= [IMA] |
952 | Format: { "0" | "1" } | |
953 | 0 -- integrity auditing messages. (Default) | |
954 | 1 -- enable informational integrity auditing messages. | |
955 | ||
956 | ima_hash= [IMA] | |
a9ed83a5 | 957 | Format: { "sha1" | "md5" } |
3323eec9 MZ |
958 | default: "sha1" |
959 | ||
5789ba3b EP |
960 | ima_tcb [IMA] |
961 | Load a policy which meets the needs of the Trusted | |
962 | Computing Base. This means IMA will measure all | |
963 | programs exec'd, files mmap'd for exec, and all files | |
964 | opened for read by uid=0. | |
965 | ||
1da177e4 LT |
966 | init= [KNL] |
967 | Format: <full_path> | |
968 | Run specified binary instead of /sbin/init as init | |
969 | process. | |
970 | ||
971 | initcall_debug [KNL] Trace initcalls as they are executed. Useful | |
972 | for working out where the kernel is dying during | |
973 | startup. | |
974 | ||
975 | initrd= [BOOT] Specify the location of the initial ramdisk | |
976 | ||
977 | inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver | |
978 | Format: <irq> | |
979 | ||
ba395927 | 980 | intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option |
0cd5c3c8 KM |
981 | on |
982 | Enable intel iommu driver. | |
ba395927 KA |
983 | off |
984 | Disable intel iommu driver. | |
985 | igfx_off [Default Off] | |
986 | By default, gfx is mapped as normal device. If a gfx | |
987 | device has a dedicated DMAR unit, the DMAR unit is | |
988 | bypassed by not enabling DMAR with this option. In | |
989 | this case, gfx device will use physical address for | |
990 | DMA. | |
7d3b03ce KA |
991 | forcedac [x86_64] |
992 | With this option iommu will not optimize to look | |
993 | for io virtual address below 32 bit forcing dual | |
994 | address cycle on pci bus for cards supporting greater | |
995 | than 32 bit addressing. The default is to look | |
996 | for translation below 32 bit and if not available | |
997 | then look in the higher range. | |
5e0d2a6f | 998 | strict [Default Off] |
999 | With this option on every unmap_single operation will | |
1000 | result in a hardware IOTLB flush operation as opposed | |
1001 | to batching them for performance. | |
ba395927 | 1002 | |
d1423d56 CW |
1003 | intremap= [X86-64, Intel-IOMMU] |
1004 | Format: { on (default) | off | nosid } | |
1005 | on enable Interrupt Remapping (default) | |
1006 | off disable Interrupt Remapping | |
1007 | nosid disable Source ID checking | |
1008 | ||
0cb55ad2 RD |
1009 | inttest= [IA64] |
1010 | ||
1011 | iomem= Disable strict checking of access to MMIO memory | |
1012 | strict regions from userspace. | |
1013 | relaxed | |
1014 | ||
1015 | iommu= [x86] | |
1016 | off | |
1017 | force | |
1018 | noforce | |
1019 | biomerge | |
1020 | panic | |
1021 | nopanic | |
1022 | merge | |
1023 | nomerge | |
1024 | forcesac | |
1025 | soft | |
4ed0d3e6 | 1026 | pt [x86, IA64] |
0cb55ad2 RD |
1027 | |
1028 | io7= [HW] IO7 for Marvel based alpha systems | |
1029 | See comment before marvel_specify_io7 in | |
1030 | arch/alpha/kernel/core_marvel.c. | |
1031 | ||
6cececfc | 1032 | io_delay= [X86] I/O delay method |
6e7c4025 IM |
1033 | 0x80 |
1034 | Standard port 0x80 based delay | |
1035 | 0xed | |
1036 | Alternate port 0xed based delay (needed on some systems) | |
b02aae9c | 1037 | udelay |
6e7c4025 IM |
1038 | Simple two microseconds delay |
1039 | none | |
1040 | No delay | |
b02aae9c | 1041 | |
1da177e4 | 1042 | ip= [IP_PNP] |
dc7a0816 | 1043 | See Documentation/filesystems/nfs/nfsroot.txt. |
1da177e4 LT |
1044 | |
1045 | ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards | |
c8facbb6 RD |
1046 | See comment before ip2_setup() in |
1047 | drivers/char/ip2/ip2base.c. | |
1da177e4 | 1048 | |
200803df AC |
1049 | irqfixup [HW] |
1050 | When an interrupt is not handled search all handlers | |
1051 | for it. Intended to get systems with badly broken | |
1052 | firmware running. | |
1053 | ||
1054 | irqpoll [HW] | |
1055 | When an interrupt is not handled search all handlers | |
1056 | for it. Also check all handlers each timer | |
1057 | interrupt. Intended to get systems with badly broken | |
1058 | firmware running. | |
1059 | ||
1da177e4 | 1060 | isapnp= [ISAPNP] |
a9913044 | 1061 | Format: <RDP>,<reset>,<pci_scan>,<verbosity> |
1da177e4 LT |
1062 | |
1063 | isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler. | |
22f2e280 DF |
1064 | Format: |
1065 | <cpu number>,...,<cpu number> | |
1066 | or | |
b225d44e LZ |
1067 | <cpu number>-<cpu number> |
1068 | (must be a positive range in ascending order) | |
22f2e280 DF |
1069 | or a mixture |
1070 | <cpu number>,...,<cpu number>-<cpu number> | |
b225d44e | 1071 | |
1da177e4 LT |
1072 | This option can be used to specify one or more CPUs |
1073 | to isolate from the general SMP balancing and scheduling | |
b225d44e LZ |
1074 | algorithms. You can move a process onto or off an |
1075 | "isolated" CPU via the CPU affinity syscalls or cpuset. | |
1da177e4 LT |
1076 | <cpu number> begins at 0 and the maximum value is |
1077 | "number of CPUs in system - 1". | |
1078 | ||
1079 | This option is the preferred way to isolate CPUs. The | |
a9913044 RD |
1080 | alternative -- manually setting the CPU mask of all |
1081 | tasks in the system -- can cause problems and | |
1082 | suboptimal load balancer performance. | |
1da177e4 | 1083 | |
a9913044 | 1084 | iucv= [HW,NET] |
1da177e4 LT |
1085 | |
1086 | js= [HW,JOY] Analog joystick | |
1087 | See Documentation/input/joystick.txt. | |
1088 | ||
0cb55ad2 RD |
1089 | keepinitrd [HW,ARM] |
1090 | ||
6cececfc | 1091 | kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter |
ed7ed365 MG |
1092 | specifies the amount of memory usable by the kernel |
1093 | for non-movable allocations. The requested amount is | |
1094 | spread evenly throughout all nodes in the system. The | |
1095 | remaining memory in each node is used for Movable | |
1096 | pages. In the event, a node is too small to have both | |
1097 | kernelcore and Movable pages, kernelcore pages will | |
1098 | take priority and other nodes will have a larger number | |
1099 | of kernelcore pages. The Movable zone is used for the | |
1100 | allocation of pages that may be reclaimed or moved | |
1101 | by the page migration subsystem. This means that | |
1102 | HugeTLB pages may not be allocated from this zone. | |
1103 | Note that allocations like PTEs-from-HighMem still | |
1104 | use the HighMem zone if it exists, and the Normal | |
1105 | zone if it does not. | |
1106 | ||
4fe1da4e JW |
1107 | kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port. |
1108 | Format: <Controller#>[,poll interval] | |
1109 | The controller # is the number of the ehci usb debug | |
1110 | port as it is probed via PCI. The poll interval is | |
1111 | optional and is the number seconds in between | |
1112 | each poll cycle to the debug port in case you need | |
1113 | the functionality for interrupting the kernel with | |
1114 | gdb or control-c on the dbgp connection. When | |
1115 | not using this parameter you use sysrq-g to break into | |
1116 | the kernel debugger. | |
1117 | ||
84c08fd6 | 1118 | kgdboc= [KGDB,HW] kgdb over consoles. |
ada64e4c JW |
1119 | Requires a tty driver that supports console polling, |
1120 | or a supported polling keyboard driver (non-usb). | |
65b5ac14 JW |
1121 | Serial only format: <serial_device>[,baud] |
1122 | keyboard only format: kbd | |
1123 | keyboard and serial format: kbd,<serial_device>[,baud] | |
1124 | Optional Kernel mode setting: | |
1125 | kms, kbd format: kms,kbd | |
1126 | kms, kbd and serial format: kms,kbd,<ser_dev>[,baud] | |
6cdf6e06 | 1127 | |
84c08fd6 JW |
1128 | kgdbwait [KGDB] Stop kernel execution and enter the |
1129 | kernel debugger at the earliest opportunity. | |
1130 | ||
9bed90c6 FF |
1131 | kmac= [MIPS] korina ethernet MAC address. |
1132 | Configure the RouterBoard 532 series on-chip | |
1133 | Ethernet adapter MAC address. | |
1134 | ||
04f70336 CM |
1135 | kmemleak= [KNL] Boot-time kmemleak enable/disable |
1136 | Valid arguments: on, off | |
1137 | Default: on | |
1138 | ||
6cececfc | 1139 | kstack=N [X86] Print N words from the kernel stack |
0cb55ad2 RD |
1140 | in oops dumps. |
1141 | ||
fef07aae AP |
1142 | kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. |
1143 | Default is 0 (don't ignore, but inject #GP) | |
1144 | ||
1145 | kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging. | |
1146 | Default is 1 (enabled) | |
1147 | ||
a182d873 XG |
1148 | kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit |
1149 | KVM MMU at runtime. | |
fef07aae AP |
1150 | Default is 0 (off) |
1151 | ||
fef07aae | 1152 | kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. |
8475f94a | 1153 | Default is 1 (enabled) |
fef07aae AP |
1154 | |
1155 | kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU) | |
1156 | for all guests. | |
1157 | Default is 1 (enabled) if in 64bit or 32bit-PAE mode | |
1158 | ||
1159 | kvm-intel.bypass_guest_pf= | |
1160 | [KVM,Intel] Disables bypassing of guest page faults | |
1161 | on Intel chips. Default is 1 (enabled) | |
1162 | ||
1163 | kvm-intel.ept= [KVM,Intel] Disable extended page tables | |
1164 | (virtualized MMU) support on capable Intel chips. | |
1165 | Default is 1 (enabled) | |
1166 | ||
1167 | kvm-intel.emulate_invalid_guest_state= | |
1168 | [KVM,Intel] Enable emulation of invalid guest states | |
1169 | Default is 0 (disabled) | |
1170 | ||
1171 | kvm-intel.flexpriority= | |
1172 | [KVM,Intel] Disable FlexPriority feature (TPR shadow). | |
1173 | Default is 1 (enabled) | |
1174 | ||
1175 | kvm-intel.unrestricted_guest= | |
1176 | [KVM,Intel] Disable unrestricted guest feature | |
1177 | (virtualized real and unpaged mode) on capable | |
1178 | Intel chips. Default is 1 (enabled) | |
1179 | ||
1180 | kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification | |
1181 | feature (tagged TLBs) on capable Intel chips. | |
1182 | Default is 1 (enabled) | |
1183 | ||
1da177e4 LT |
1184 | l2cr= [PPC] |
1185 | ||
a78bfbfc RB |
1186 | l3cr= [PPC] |
1187 | ||
cd4f0ef7 | 1188 | lapic [X86-32,APIC] Enable the local APIC even if BIOS |
a9913044 | 1189 | disabled it. |
1da177e4 | 1190 | |
6cececfc | 1191 | lapic_timer_c2_ok [X86,APIC] trust the local apic timer |
ada9cfdd | 1192 | in C2 power state. |
e585bef8 | 1193 | |
fcb71f6f FC |
1194 | libata.dma= [LIBATA] DMA control |
1195 | libata.dma=0 Disable all PATA and SATA DMA | |
1196 | libata.dma=1 PATA and SATA Disk DMA only | |
1197 | libata.dma=2 ATAPI (CDROM) DMA only | |
1198 | libata.dma=4 Compact Flash DMA only | |
1199 | Combinations also work, so libata.dma=3 enables DMA | |
1200 | for disks and CDROMs, but not CFs. | |
20308871 MP |
1201 | |
1202 | libata.ignore_hpa= [LIBATA] Ignore HPA limit | |
1203 | libata.ignore_hpa=0 keep BIOS limits (default) | |
1204 | libata.ignore_hpa=1 ignore limits, using full disk | |
fcb71f6f | 1205 | |
78e70c23 DJ |
1206 | libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume |
1207 | when set. | |
1208 | Format: <int> | |
1209 | ||
33267325 TH |
1210 | libata.force= [LIBATA] Force configurations. The format is comma |
1211 | separated list of "[ID:]VAL" where ID is | |
4c44f309 | 1212 | PORT[.DEVICE]. PORT and DEVICE are decimal numbers |
33267325 TH |
1213 | matching port, link or device. Basically, it matches |
1214 | the ATA ID string printed on console by libata. If | |
1215 | the whole ID part is omitted, the last PORT and DEVICE | |
1216 | values are used. If ID hasn't been specified yet, the | |
1217 | configuration applies to all ports, links and devices. | |
1218 | ||
1219 | If only DEVICE is omitted, the parameter applies to | |
1220 | the port and all links and devices behind it. DEVICE | |
1221 | number of 0 either selects the first device or the | |
1222 | first fan-out link behind PMP device. It does not | |
1223 | select the host link. DEVICE number of 15 selects the | |
1224 | host link and device attached to it. | |
1225 | ||
1226 | The VAL specifies the configuration to force. As long | |
1227 | as there's no ambiguity shortcut notation is allowed. | |
1228 | For example, both 1.5 and 1.5G would work for 1.5Gbps. | |
1229 | The following configurations can be forced. | |
1230 | ||
1231 | * Cable type: 40c, 80c, short40c, unk, ign or sata. | |
1232 | Any ID with matching PORT is used. | |
1233 | ||
1234 | * SATA link speed limit: 1.5Gbps or 3.0Gbps. | |
1235 | ||
1236 | * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. | |
1237 | udma[/][16,25,33,44,66,100,133] notation is also | |
1238 | allowed. | |
1239 | ||
1240 | * [no]ncq: Turn on or off NCQ. | |
1241 | ||
05944bdf TH |
1242 | * nohrst, nosrst, norst: suppress hard, soft |
1243 | and both resets. | |
1244 | ||
43c9c591 TH |
1245 | * dump_id: dump IDENTIFY data. |
1246 | ||
33267325 TH |
1247 | If there are multiple matching configurations changing |
1248 | the same attribute, the last one is used. | |
1249 | ||
95f72d1e | 1250 | memblock=debug [KNL] Enable memblock debug messages. |
7c4be253 | 1251 | |
1da177e4 | 1252 | load_ramdisk= [RAM] List of ramdisks to load from floppy |
31c00fc1 | 1253 | See Documentation/blockdev/ramdisk.txt. |
1da177e4 | 1254 | |
a6b25b67 RD |
1255 | lockd.nlm_grace_period=P [NFS] Assign grace period. |
1256 | Format: <integer> | |
1da177e4 | 1257 | |
a6b25b67 RD |
1258 | lockd.nlm_tcpport=N [NFS] Assign TCP port. |
1259 | Format: <integer> | |
1260 | ||
1261 | lockd.nlm_timeout=T [NFS] Assign timeout value. | |
1262 | Format: <integer> | |
1263 | ||
1264 | lockd.nlm_udpport=M [NFS] Assign UDP port. | |
1265 | Format: <integer> | |
1da177e4 LT |
1266 | |
1267 | logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver | |
1268 | Format: <irq> | |
1269 | ||
1270 | loglevel= All Kernel Messages with a loglevel smaller than the | |
1271 | console loglevel will be printed to the console. It can | |
1272 | also be changed with klogd or other programs. The | |
1273 | loglevels are defined as follows: | |
1274 | ||
1275 | 0 (KERN_EMERG) system is unusable | |
1276 | 1 (KERN_ALERT) action must be taken immediately | |
1277 | 2 (KERN_CRIT) critical conditions | |
1278 | 3 (KERN_ERR) error conditions | |
1279 | 4 (KERN_WARNING) warning conditions | |
1280 | 5 (KERN_NOTICE) normal but significant condition | |
1281 | 6 (KERN_INFO) informational | |
1282 | 7 (KERN_DEBUG) debug-level messages | |
1283 | ||
c756d08a RD |
1284 | log_buf_len=n[KMG] Sets the size of the printk ring buffer, |
1285 | in bytes. n must be a power of two. The default | |
1286 | size is set in the kernel config file. | |
1da177e4 | 1287 | |
accaa24c RD |
1288 | logo.nologo [FB] Disables display of the built-in Linux logo. |
1289 | This may be used to provide more screen space for | |
1290 | kernel log messages and is useful when debugging | |
1291 | kernel boot problems. | |
1292 | ||
1da177e4 LT |
1293 | lp=0 [LP] Specify parallel ports to use, e.g, |
1294 | lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses | |
1295 | lp=reset first parallel port). 'lp=0' disables the | |
1296 | lp=auto printer driver. 'lp=reset' (which can be | |
1297 | specified in addition to the ports) causes | |
1298 | attached printers to be reset. Using | |
1299 | lp=port1,port2,... specifies the parallel ports | |
1300 | to associate lp devices with, starting with | |
1301 | lp0. A port specification may be 'none' to skip | |
1302 | that lp device, or a parport name such as | |
1303 | 'parport0'. Specifying 'lp=auto' instead of a | |
1304 | port specification list means that device IDs | |
1305 | from each port should be examined, to see if | |
1306 | an IEEE 1284-compliant printer is attached; if | |
1307 | so, the driver will manage that printer. | |
1308 | See also header of drivers/char/lp.c. | |
1309 | ||
1310 | lpj=n [KNL] | |
1311 | Sets loops_per_jiffy to given constant, thus avoiding | |
1312 | time-consuming boot-time autodetection (up to 250 ms per | |
1313 | CPU). 0 enables autodetection (default). To determine | |
1314 | the correct value for your kernel, boot with normal | |
1315 | autodetection and see what value is printed. Note that | |
1316 | on SMP systems the preset will be applied to all CPUs, | |
1317 | which is likely to cause problems if your CPUs need | |
1318 | significantly divergent settings. An incorrect value | |
1319 | will cause delays in the kernel to be wrong, leading to | |
1320 | unpredictable I/O errors and other breakage. Although | |
1321 | unlikely, in the extreme case this might damage your | |
1322 | hardware. | |
1323 | ||
1324 | ltpc= [NET] | |
1325 | Format: <io>,<irq>,<dma> | |
1326 | ||
a9913044 RD |
1327 | machvec= [IA64] Force the use of a particular machine-vector |
1328 | (machvec) in a generic kernel. | |
1329 | Example: machvec=hpzx1_swiotlb | |
1da177e4 | 1330 | |
3209e70e WZ |
1331 | machtype= [Loongson] Share the same kernel image file between different |
1332 | yeeloong laptop. | |
1333 | Example: machtype=lemote-yeeloong-2f-7inch | |
1334 | ||
0cb55ad2 RD |
1335 | max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater |
1336 | than or equal to this physical address is ignored. | |
1da177e4 LT |
1337 | |
1338 | maxcpus= [SMP] Maximum number of processors that an SMP kernel | |
61ec7567 LB |
1339 | should make use of. maxcpus=n : n >= 0 limits the |
1340 | kernel to using 'n' processors. n=0 is a special case, | |
1341 | it is equivalent to "nosmp", which also disables | |
1342 | the IO APIC. | |
1da177e4 | 1343 | |
0cb55ad2 RD |
1344 | max_loop= [LOOP] Maximum number of loopback devices that can |
1345 | be mounted | |
1346 | Format: <1-256> | |
2b2c3750 | 1347 | |
1da177e4 LT |
1348 | mcatest= [IA-64] |
1349 | ||
cd4f0ef7 | 1350 | mce [X86-32] Machine Check Exception |
1da177e4 | 1351 | |
71cced6e | 1352 | mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt |
909dd324 | 1353 | |
1da177e4 LT |
1354 | md= [HW] RAID subsystems devices and level |
1355 | See Documentation/md.txt. | |
a9913044 | 1356 | |
1da177e4 LT |
1357 | mdacon= [MDA] |
1358 | Format: <first>,<last> | |
1359 | Specifies range of consoles to be captured by the MDA. | |
a9913044 | 1360 | |
1da177e4 LT |
1361 | mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory |
1362 | Amount of memory to be used when the kernel is not able | |
1363 | to see the whole system memory or for test. | |
cd4f0ef7 | 1364 | [X86-32] Use together with memmap= to avoid physical |
1da177e4 LT |
1365 | address space collisions. Without memmap= PCI devices |
1366 | could be placed at addresses belonging to unused RAM. | |
1367 | ||
cd4f0ef7 | 1368 | mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel |
1da177e4 LT |
1369 | memory. |
1370 | ||
6902aa84 PM |
1371 | memchunk=nn[KMG] |
1372 | [KNL,SH] Allow user to override the default size for | |
1373 | per-device physically contiguous DMA buffers. | |
1374 | ||
6cececfc | 1375 | memmap=exactmap [KNL,X86] Enable setting of an exact |
1da177e4 LT |
1376 | E820 memory map, as specified by the user. |
1377 | Such memmap=exactmap lines can be constructed based on | |
1378 | BIOS output or other requirements. See the memmap=nn@ss | |
1379 | option description. | |
1380 | ||
1381 | memmap=nn[KMG]@ss[KMG] | |
1382 | [KNL] Force usage of a specific region of memory | |
1383 | Region of memory to be used, from ss to ss+nn. | |
1384 | ||
1385 | memmap=nn[KMG]#ss[KMG] | |
1386 | [KNL,ACPI] Mark specific memory as ACPI data. | |
1387 | Region of memory to be used, from ss to ss+nn. | |
1388 | ||
1389 | memmap=nn[KMG]$ss[KMG] | |
1390 | [KNL,ACPI] Mark specific memory as reserved. | |
1391 | Region of memory to be used, from ss to ss+nn. | |
1312848e PM |
1392 | Example: Exclude memory from 0x18690000-0x1869ffff |
1393 | memmap=64K$0x18690000 | |
1394 | or | |
1395 | memmap=0x10000$0x18690000 | |
1da177e4 | 1396 | |
9f077871 JF |
1397 | memory_corruption_check=0/1 [X86] |
1398 | Some BIOSes seem to corrupt the first 64k of | |
1399 | memory when doing things like suspend/resume. | |
1400 | Setting this option will scan the memory | |
1401 | looking for corruption. Enabling this will | |
1402 | both detect corruption and prevent the kernel | |
1403 | from using the memory being corrupted. | |
1404 | However, its intended as a diagnostic tool; if | |
1405 | repeatable BIOS-originated corruption always | |
1406 | affects the same memory, you can use memmap= | |
1407 | to prevent the kernel from using that memory. | |
1408 | ||
1409 | memory_corruption_check_size=size [X86] | |
1410 | By default it checks for corruption in the low | |
1411 | 64k, making this memory unavailable for normal | |
1412 | use. Use this parameter to scan for | |
1413 | corruption in more or less memory. | |
1414 | ||
1415 | memory_corruption_check_period=seconds [X86] | |
1416 | By default it checks for corruption every 60 | |
1417 | seconds. Use this parameter to check at some | |
1418 | other rate. 0 disables periodic checking. | |
1419 | ||
caadbdce | 1420 | memtest= [KNL,X86] Enable memtest |
c64df707 | 1421 | Format: <integer> |
c64df707 | 1422 | default : 0 <disable> |
9e5f6cf5 AH |
1423 | Specifies the number of memtest passes to be |
1424 | performed. Each pass selects another test | |
1425 | pattern from a given set of patterns. Memtest | |
1426 | fills the memory with this pattern, validates | |
1427 | memory contents and reserves bad memory | |
1428 | regions that are detected. | |
c64df707 | 1429 | |
1da177e4 LT |
1430 | meye.*= [HW] Set MotionEye Camera parameters |
1431 | See Documentation/video4linux/meye.txt. | |
1432 | ||
8f36881b AS |
1433 | mfgpt_irq= [IA-32] Specify the IRQ to use for the |
1434 | Multi-Function General Purpose Timers on AMD Geode | |
1435 | platforms. | |
1436 | ||
e6c4dc6c WT |
1437 | mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when |
1438 | the BIOS has incorrectly applied a workaround. TinyBIOS | |
1439 | version 0.98 is known to be affected, 0.99 fixes the | |
1440 | problem by letting the user disable the workaround. | |
1441 | ||
1da177e4 LT |
1442 | mga= [HW,DRM] |
1443 | ||
1c207f95 RD |
1444 | min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this |
1445 | physical address is ignored. | |
1446 | ||
39f45d7b MP |
1447 | mini2440= [ARM,HW,KNL] |
1448 | Format:[0..2][b][c][t] | |
1449 | Default: "0tb" | |
1450 | MINI2440 configuration specification: | |
1451 | 0 - The attached screen is the 3.5" TFT | |
1452 | 1 - The attached screen is the 7" TFT | |
1453 | 2 - The VGA Shield is attached (1024x768) | |
1454 | Leaving out the screen size parameter will not load | |
1455 | the TFT driver, and the framebuffer will be left | |
1456 | unconfigured. | |
1457 | b - Enable backlight. The TFT backlight pin will be | |
1458 | linked to the kernel VESA blanking code and a GPIO | |
1459 | LED. This parameter is not necessary when using the | |
1460 | VGA shield. | |
1461 | c - Enable the s3c camera interface. | |
1462 | t - Reserved for enabling touchscreen support. The | |
1463 | touchscreen support is not enabled in the mainstream | |
1464 | kernel as of 2.6.30, a preliminary port can be found | |
1465 | in the "bleeding edge" mini2440 support kernel at | |
1466 | http://repo.or.cz/w/linux-2.6/mini2440.git | |
1467 | ||
6b74ab97 MG |
1468 | mminit_loglevel= |
1469 | [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this | |
1470 | parameter allows control of the logging verbosity for | |
1471 | the additional memory initialisation checks. A value | |
1472 | of 0 disables mminit logging and a level of 4 will | |
1473 | log everything. Information is printed at KERN_DEBUG | |
1474 | so loglevel=8 may also need to be specified. | |
1475 | ||
1da177e4 LT |
1476 | mousedev.tap_time= |
1477 | [MOUSE] Maximum time between finger touching and | |
1478 | leaving touchpad surface for touch to be considered | |
1479 | a tap and be reported as a left button click (for | |
1480 | touchpads working in absolute mode only). | |
1481 | Format: <msecs> | |
1482 | mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices | |
1483 | reporting absolute coordinates, such as tablets | |
1484 | mousedev.yres= [MOUSE] Vertical screen resolution, used for devices | |
1485 | reporting absolute coordinates, such as tablets | |
1486 | ||
6cececfc | 1487 | movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter |
0cb55ad2 RD |
1488 | is similar to kernelcore except it specifies the |
1489 | amount of memory used for migratable allocations. | |
1490 | If both kernelcore and movablecore is specified, | |
1491 | then kernelcore will be at *least* the specified | |
1492 | value but may be more. If movablecore on its own | |
1493 | is specified, the administrator must be careful | |
1494 | that the amount of memory usable for all allocations | |
1495 | is not too small. | |
1496 | ||
1da177e4 LT |
1497 | MTD_Partition= [MTD] |
1498 | Format: <name>,<region-number>,<size>,<offset> | |
1499 | ||
a9913044 RD |
1500 | MTD_Region= [MTD] Format: |
1501 | <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] | |
1da177e4 LT |
1502 | |
1503 | mtdparts= [MTD] | |
c8facbb6 | 1504 | See drivers/mtd/cmdlinepart.c. |
1da177e4 | 1505 | |
4e89a2d8 WS |
1506 | multitce=off [PPC] This parameter disables the use of the pSeries |
1507 | firmware feature for updating multiple TCE entries | |
1508 | at a time. | |
1509 | ||
5988af23 RH |
1510 | onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration |
1511 | ||
1512 | Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] | |
1513 | ||
1514 | boundary - index of last SLC block on Flex-OneNAND. | |
1515 | The remaining blocks are configured as MLC blocks. | |
1516 | lock - Configure if Flex-OneNAND boundary should be locked. | |
1517 | Once locked, the boundary cannot be changed. | |
1518 | 1 indicates lock status, 0 indicates unlock status. | |
1519 | ||
9db829f4 BD |
1520 | mtdset= [ARM] |
1521 | ARM/S3C2412 JIVE boot control | |
1522 | ||
1523 | See arch/arm/mach-s3c2412/mach-jive.c | |
1524 | ||
1da177e4 | 1525 | mtouchusb.raw_coordinates= |
a9913044 RD |
1526 | [HW] Make the MicroTouch USB driver use raw coordinates |
1527 | ('y', default) or cooked coordinates ('n') | |
1da177e4 | 1528 | |
0cb55ad2 | 1529 | mtrr_chunk_size=nn[KMG] [X86] |
19f59460 | 1530 | used for mtrr cleanup. It is largest continuous chunk |
0cb55ad2 RD |
1531 | that could hold holes aka. UC entries. |
1532 | ||
1533 | mtrr_gran_size=nn[KMG] [X86] | |
1534 | Used for mtrr cleanup. It is granularity of mtrr block. | |
1535 | Default is 1. | |
1536 | Large value could prevent small alignment from | |
1537 | using up MTRRs. | |
1538 | ||
1539 | mtrr_spare_reg_nr=n [X86] | |
1540 | Format: <integer> | |
1541 | Range: 0,7 : spare reg number | |
1542 | Default : 1 | |
1543 | Used for mtrr cleanup. It is spare mtrr entries number. | |
1544 | Set to 2 or more if your graphical card needs more. | |
1545 | ||
1da177e4 LT |
1546 | n2= [NET] SDL Inc. RISCom/N2 synchronous serial card |
1547 | ||
1da177e4 LT |
1548 | netdev= [NET] Network devices parameters |
1549 | Format: <irq>,<io>,<mem_start>,<mem_end>,<name> | |
1550 | Note that mem_start is often overloaded to mean | |
1551 | something different and driver-specific. | |
a9913044 RD |
1552 | This usage is only documented in each driver source |
1553 | file if at all. | |
1554 | ||
58401572 KPO |
1555 | nf_conntrack.acct= |
1556 | [NETFILTER] Enable connection tracking flow accounting | |
1557 | 0 to disable accounting | |
1558 | 1 to enable accounting | |
d70a011d | 1559 | Default value is 0. |
58401572 | 1560 | |
306a0753 | 1561 | nfsaddrs= [NFS] Deprecated. Use ip= instead. |
dc7a0816 | 1562 | See Documentation/filesystems/nfs/nfsroot.txt. |
1da177e4 LT |
1563 | |
1564 | nfsroot= [NFS] nfs root filesystem for disk-less boxes. | |
dc7a0816 | 1565 | See Documentation/filesystems/nfs/nfsroot.txt. |
1da177e4 | 1566 | |
306a0753 CL |
1567 | nfsrootdebug [NFS] enable nfsroot debugging messages. |
1568 | See Documentation/filesystems/nfs/nfsroot.txt. | |
1569 | ||
a72b4422 TM |
1570 | nfs.callback_tcpport= |
1571 | [NFS] set the TCP port on which the NFSv4 callback | |
1572 | channel should listen. | |
1573 | ||
e571cbf1 TM |
1574 | nfs.cache_getent= |
1575 | [NFS] sets the pathname to the program which is used | |
1576 | to update the NFS client cache entries. | |
1577 | ||
1578 | nfs.cache_getent_timeout= | |
1579 | [NFS] sets the timeout after which an attempt to | |
1580 | update a cache entry is deemed to have failed. | |
1581 | ||
58df095b TM |
1582 | nfs.idmap_cache_timeout= |
1583 | [NFS] set the maximum lifetime for idmapper cache | |
1584 | entries. | |
1585 | ||
f43bf0be TM |
1586 | nfs.enable_ino64= |
1587 | [NFS] enable 64-bit inode numbers. | |
1588 | If zero, the NFS client will fake up a 32-bit inode | |
1589 | number for the readdir() and stat() syscalls instead | |
1590 | of returning the full 64-bit number. | |
1591 | The default is to return 64-bit inode numbers. | |
1592 | ||
b064eca2 TM |
1593 | nfs.nfs4_disable_idmapping= |
1594 | [NFSv4] When set, this option disables the NFSv4 | |
1595 | idmapper on the client, but only if the mount | |
1596 | is using the 'sec=sys' security flavour. This may | |
1597 | make migration from legacy NFSv2/v3 systems easier | |
1598 | provided that the server has the appropriate support. | |
1599 | The default is to always enable NFSv4 idmapping. | |
1600 | ||
1e1030dc | 1601 | nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take |
e7ba176b HS |
1602 | when a NMI is triggered. |
1603 | Format: [state][,regs][,debounce][,die] | |
1604 | ||
6cececfc | 1605 | nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels |
fef2c9bc | 1606 | Format: [panic,][nopanic,][num] |
5dc30558 | 1607 | Valid num: 0 |
5b9a0e14 | 1608 | 0 - turn nmi_watchdog off |
0cb55ad2 | 1609 | When panic is specified, panic when an NMI watchdog |
fef2c9bc DZ |
1610 | timeout occurs (or 'nopanic' to override the opposite |
1611 | default). | |
0cb55ad2 RD |
1612 | This is useful when you use a panic=... timeout and |
1613 | need the box quickly up again. | |
1da177e4 | 1614 | |
bff38771 AV |
1615 | netpoll.carrier_timeout= |
1616 | [NET] Specifies amount of time (in seconds) that | |
1617 | netpoll should wait for a carrier. By default netpoll | |
1618 | waits 4 seconds. | |
1619 | ||
cd4f0ef7 | 1620 | no387 [BUGS=X86-32] Tells the kernel to use the 387 maths |
1da177e4 LT |
1621 | emulation library even if a 387 maths coprocessor |
1622 | is present. | |
1623 | ||
0cb55ad2 RD |
1624 | no_console_suspend |
1625 | [HW] Never suspend the console | |
1626 | Disable suspending of consoles during suspend and | |
1627 | hibernate operations. Once disabled, debugging | |
1628 | messages can reach various consoles while the rest | |
1629 | of the system is being put to sleep (ie, while | |
1630 | debugging driver suspend/resume hooks). This may | |
1631 | not work reliably with all consoles, but is known | |
1632 | to work with serial and VGA consoles. | |
1633 | ||
c1aee215 CL |
1634 | noaliencache [MM, NUMA, SLAB] Disables the allocation of alien |
1635 | caches in the slab allocator. Saves per-node memory, | |
1636 | but will impact performance. | |
3395ee05 | 1637 | |
a9913044 RD |
1638 | noalign [KNL,ARM] |
1639 | ||
1da177e4 LT |
1640 | noapic [SMP,APIC] Tells the kernel to not make use of any |
1641 | IOAPICs that may be present in the system. | |
1642 | ||
5091faa4 MG |
1643 | noautogroup Disable scheduler automatic task group creation. |
1644 | ||
1da177e4 LT |
1645 | nobats [PPC] Do not use BATs for mapping kernel lowmem |
1646 | on "Classic" PPC cores. | |
1647 | ||
1648 | nocache [ARM] | |
a9913044 | 1649 | |
0cb55ad2 RD |
1650 | noclflush [BUGS=X86] Don't use the CLFLUSH instruction |
1651 | ||
163ecdff SN |
1652 | nodelayacct [KNL] Disable per-task delay accounting |
1653 | ||
1da177e4 LT |
1654 | nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects. |
1655 | ||
6902aa84 PM |
1656 | nodsp [SH] Disable hardware DSP at boot time. |
1657 | ||
6cececfc | 1658 | noefi [X86] Disable EFI runtime services support. |
8b2cb7a8 | 1659 | |
1da177e4 LT |
1660 | noexec [IA-64] |
1661 | ||
6cececfc | 1662 | noexec [X86] |
f5a1b191 | 1663 | On X86-32 available only on PAE configured kernels. |
1da177e4 | 1664 | noexec=on: enable non-executable mappings (default) |
f5a1b191 JS |
1665 | noexec=off: disable non-executable mappings |
1666 | ||
1667 | noexec32 [X86-64] | |
1668 | This affects only 32-bit executables. | |
1669 | noexec32=on: enable non-executable mappings (default) | |
1670 | read doesn't imply executable mappings | |
1671 | noexec32=off: disable non-executable mappings | |
1672 | read implies executable mappings | |
1da177e4 | 1673 | |
6902aa84 PM |
1674 | nofpu [SH] Disable hardware FPU at boot time. |
1675 | ||
cd4f0ef7 | 1676 | nofxsr [BUGS=X86-32] Disables x86 floating point extended |
4f886511 CE |
1677 | register save and restore. The kernel will only save |
1678 | legacy floating-point registers on task switch. | |
1da177e4 | 1679 | |
0c752a93 SS |
1680 | noxsave [BUGS=X86] Disables x86 extended register state save |
1681 | and restore using xsave. The kernel will fallback to | |
1682 | enabling legacy floating-point and sse state. | |
1683 | ||
01a24d2b PZ |
1684 | nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or |
1685 | wfi(ARM) instruction doesn't work correctly and not to | |
1686 | use it. This is also useful when using JTAG debugger. | |
a9913044 | 1687 | |
cd4f0ef7 | 1688 | no-hlt [BUGS=X86-32] Tells the kernel that the hlt |
1da177e4 LT |
1689 | instruction doesn't work correctly and not to |
1690 | use it. | |
1691 | ||
1f29fae2 SH |
1692 | no_file_caps Tells the kernel not to honor file capabilities. The |
1693 | only way then for a file to be executed with privilege | |
1694 | is to be setuid root or executed by root. | |
1695 | ||
1da177e4 LT |
1696 | nohalt [IA-64] Tells the kernel not to use the power saving |
1697 | function PAL_HALT_LIGHT when idle. This increases | |
1698 | power-consumption. On the positive side, it reduces | |
1699 | interrupt wake-up latency, which may improve performance | |
1700 | in certain environments such as networked servers or | |
1701 | real-time systems. | |
1702 | ||
79bf2bb3 TG |
1703 | nohz= [KNL] Boottime enable/disable dynamic ticks |
1704 | Valid arguments: on, off | |
1705 | Default: on | |
1706 | ||
eeee7853 PM |
1707 | noiotrap [SH] Disables trapped I/O port accesses. |
1708 | ||
cd4f0ef7 | 1709 | noirqdebug [X86-32] Disables the code which attempts to detect and |
1da177e4 LT |
1710 | disable unhandled interrupt sources. |
1711 | ||
6cececfc | 1712 | no_timer_check [X86,APIC] Disables the code which tests for |
8542b200 ZA |
1713 | broken timer IRQ sources. |
1714 | ||
1da177e4 LT |
1715 | noisapnp [ISAPNP] Disables ISA PnP code. |
1716 | ||
1717 | noinitrd [RAM] Tells the kernel not to load any configured | |
1718 | initial RAM disk. | |
1719 | ||
03ea8155 WH |
1720 | nointremap [X86-64, Intel-IOMMU] Do not enable interrupt |
1721 | remapping. | |
d1423d56 | 1722 | [Deprecated - use intremap=off] |
03ea8155 | 1723 | |
1da177e4 LT |
1724 | nointroute [IA-64] |
1725 | ||
0aa366f3 TL |
1726 | nojitter [IA64] Disables jitter checking for ITC timers. |
1727 | ||
9cf4c4fc JK |
1728 | no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver |
1729 | ||
fd10cde9 GN |
1730 | no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page |
1731 | fault handling. | |
1732 | ||
cd4f0ef7 | 1733 | nolapic [X86-32,APIC] Do not enable or use the local APIC. |
1da177e4 | 1734 | |
cd4f0ef7 | 1735 | nolapic_timer [X86-32,APIC] Do not use the local APIC timer. |
ad62ca2b | 1736 | |
1da177e4 LT |
1737 | noltlbs [PPC] Do not use large page/tlb entries for kernel |
1738 | lowmem mapping on PPC40x. | |
1739 | ||
312f1f01 H |
1740 | nomca [IA-64] Disable machine check abort handling |
1741 | ||
cd4f0ef7 | 1742 | nomce [X86-32] Machine Check Exception |
abe37e5a | 1743 | |
83d7384f AS |
1744 | nomfgpt [X86-32] Disable Multi-Function General Purpose |
1745 | Timer usage (for AMD Geode machines). | |
1746 | ||
016ddd9b JK |
1747 | nopat [X86] Disable PAT (page attribute table extension of |
1748 | pagetables) support. | |
1749 | ||
0cb55ad2 RD |
1750 | norandmaps Don't use address space randomization. Equivalent to |
1751 | echo 0 > /proc/sys/kernel/randomize_va_space | |
1752 | ||
bbff2168 | 1753 | noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops |
959b4fdf | 1754 | |
cd4f0ef7 | 1755 | noreplace-smp [X86-32,SMP] Don't replace SMP instructions |
b7fb4af0 JF |
1756 | with UP alternatives |
1757 | ||
1da177e4 LT |
1758 | noresidual [PPC] Don't use residual data on PReP machines. |
1759 | ||
a9913044 RD |
1760 | noresume [SWSUSP] Disables resume and restores original swap |
1761 | space. | |
1762 | ||
1da177e4 LT |
1763 | no-scroll [VGA] Disables scrollback. |
1764 | This is required for the Braillex ib80-piezo Braille | |
1765 | reader made by F.H. Papenmeier (Germany). | |
1766 | ||
1767 | nosbagart [IA-64] | |
1768 | ||
cd4f0ef7 | 1769 | nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support. |
4f886511 | 1770 | |
61ec7567 LB |
1771 | nosmp [SMP] Tells an SMP kernel to act as a UP kernel, |
1772 | and disable the IO APIC. legacy for "maxcpus=0". | |
1da177e4 | 1773 | |
97842216 DJ |
1774 | nosoftlockup [KNL] Disable the soft-lockup detector. |
1775 | ||
c077719b | 1776 | noswapaccount [KNL] Disable accounting of swap in memory resource |
21acb9ca | 1777 | controller. (See Documentation/cgroups/memory.txt) |
c077719b | 1778 | |
1da177e4 LT |
1779 | nosync [HW,M68K] Disables sync negotiation for all devices. |
1780 | ||
cd4f0ef7 | 1781 | notsc [BUGS=X86-32] Disable Time Stamp Counter |
1da177e4 LT |
1782 | |
1783 | nousb [USB] Disable the USB subsystem | |
1784 | ||
55142374 | 1785 | nowatchdog [KNL] Disable the lockup detector (NMI watchdog). |
58687acb | 1786 | |
1da177e4 | 1787 | nowb [ARM] |
a9913044 | 1788 | |
2b2fd87a WH |
1789 | nox2apic [X86-64,APIC] Do not enable x2APIC mode. |
1790 | ||
a6c75b86 FY |
1791 | nptcg= [IA64] Override max number of concurrent global TLB |
1792 | purges which is reported from either PAL_VM_SUMMARY or | |
1793 | SAL PALO. | |
1794 | ||
2b633e3f YL |
1795 | nr_cpus= [SMP] Maximum number of processors that an SMP kernel |
1796 | could support. nr_cpus=n : n >= 1 limits the kernel to | |
1797 | supporting 'n' processors. Later in runtime you can not | |
1798 | use hotplug cpu feature to put more cpu back to online. | |
1799 | just like you compile the kernel NR_CPUS=n | |
1800 | ||
0cb55ad2 RD |
1801 | nr_uarts= [SERIAL] maximum number of UARTs to be registered. |
1802 | ||
f0c0b2b8 KH |
1803 | numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. |
1804 | one of ['zone', 'node', 'default'] can be specified | |
1805 | This can be set from sysctl after boot. | |
1806 | See Documentation/sysctl/vm.txt for details. | |
1807 | ||
7c4be253 RD |
1808 | ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. |
1809 | See Documentation/debugging-via-ohci1394.txt for more | |
1810 | info. | |
1811 | ||
3ef0e1f8 AS |
1812 | olpc_ec_timeout= [OLPC] ms delay when issuing EC commands |
1813 | Rather than timing out after 20 ms if an EC | |
1814 | command is not properly ACKed, override the length | |
1815 | of the timeout. We have interrupts disabled while | |
1816 | waiting for the ACK, so if this is set too high | |
1817 | interrupts *may* be lost! | |
1818 | ||
15ac7afe TL |
1819 | omap_mux= [OMAP] Override bootloader pin multiplexing. |
1820 | Format: <mux_mode0.mode_name=value>... | |
1821 | For example, to override I2C bus2: | |
1822 | omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 | |
1823 | ||
1da177e4 LT |
1824 | oprofile.timer= [HW] |
1825 | Use timer interrupt instead of performance counters | |
1826 | ||
7e4e0bd5 RR |
1827 | oprofile.cpu_type= Force an oprofile cpu type |
1828 | This might be useful if you have an older oprofile | |
1829 | userland or if you want common events. | |
8d7ff4f2 RR |
1830 | Format: { arch_perfmon } |
1831 | arch_perfmon: [X86] Force use of architectural | |
7e4e0bd5 RR |
1832 | perfmon on Intel CPUs instead of the |
1833 | CPU specific event set. | |
1dcdb5a9 | 1834 | |
44a4dcf7 RD |
1835 | oops=panic Always panic on oopses. Default is to just kill the |
1836 | process, but there is a small probability of | |
1837 | deadlocking the machine. | |
d404ab0a OH |
1838 | This will also cause panics on machine check exceptions. |
1839 | Useful together with panic=30 to trigger a reboot. | |
1840 | ||
bcfde334 RD |
1841 | OSS [HW,OSS] |
1842 | See Documentation/sound/oss/oss-parameters.txt | |
1843 | ||
44a4dcf7 RD |
1844 | panic= [KNL] Kernel behaviour on panic: delay <timeout> |
1845 | seconds before rebooting | |
1da177e4 LT |
1846 | Format: <timeout> |
1847 | ||
1848 | parkbd.port= [HW] Parallel port number the keyboard adapter is | |
1849 | connected to, default is 0. | |
1850 | Format: <parport#> | |
1851 | parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, | |
1852 | 0 for XT, 1 for AT (default is AT). | |
a9913044 RD |
1853 | Format: <mode> |
1854 | ||
1855 | parport= [HW,PPT] Specify parallel ports. 0 disables. | |
1856 | Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } | |
1857 | Use 'auto' to force the driver to use any | |
1858 | IRQ/DMA settings detected (the default is to | |
1859 | ignore detected IRQ/DMA settings because of | |
1860 | possible conflicts). You can specify the base | |
1861 | address, IRQ, and DMA settings; IRQ and DMA | |
1862 | should be numbers, or 'auto' (for using detected | |
1863 | settings on that particular port), or 'nofifo' | |
1864 | (to avoid using a FIFO even if it is detected). | |
1865 | Parallel ports are assigned in the order they | |
1866 | are specified on the command line, starting | |
1867 | with parport0. | |
1868 | ||
1869 | parport_init_mode= [HW,PPT] | |
1870 | Configure VIA parallel port to operate in | |
1871 | a specific mode. This is necessary on Pegasos | |
1872 | computer where firmware has no options for setting | |
1873 | up parallel port mode and sets it to spp. | |
1874 | Currently this function knows 686a and 8231 chips. | |
1da177e4 LT |
1875 | Format: [spp|ps2|epp|ecp|ecpepp] |
1876 | ||
dd287796 AM |
1877 | pause_on_oops= |
1878 | Halt all CPUs after the first oops has been printed for | |
1879 | the specified number of seconds. This is to be used if | |
1880 | your oopses keep scrolling off the screen. | |
1881 | ||
1da177e4 LT |
1882 | pcbit= [HW,ISDN] |
1883 | ||
1884 | pcd. [PARIDE] | |
1885 | See header of drivers/block/paride/pcd.c. | |
31c00fc1 | 1886 | See also Documentation/blockdev/paride.txt. |
1da177e4 | 1887 | |
a9913044 | 1888 | pci=option[,option...] [PCI] various PCI subsystem options: |
1cc0ca26 BH |
1889 | earlydump [X86] dump PCI config space before the kernel |
1890 | changes anything | |
c0115606 | 1891 | off [X86] don't probe for the PCI bus |
cd4f0ef7 | 1892 | bios [X86-32] force use of PCI BIOS, don't access |
a9913044 RD |
1893 | the hardware directly. Use this if your machine |
1894 | has a non-standard PCI host bridge. | |
cd4f0ef7 | 1895 | nobios [X86-32] disallow use of PCI BIOS, only direct |
a9913044 RD |
1896 | hardware access methods are allowed. Use this |
1897 | if you experience crashes upon bootup and you | |
1898 | suspect they are caused by the BIOS. | |
c0115606 | 1899 | conf1 [X86] Force use of PCI Configuration |
a9913044 | 1900 | Mechanism 1. |
c0115606 | 1901 | conf2 [X86] Force use of PCI Configuration |
a9913044 | 1902 | Mechanism 2. |
7f785763 RD |
1903 | noaer [PCIE] If the PCIEAER kernel config parameter is |
1904 | enabled, this kernel boot option can be used to | |
1905 | disable the use of PCIE advanced error reporting. | |
32a2eea7 JG |
1906 | nodomains [PCI] Disable support for multiple PCI |
1907 | root domains (aka PCI segments, in ACPI-speak). | |
6cececfc | 1908 | nommconf [X86] Disable use of MMCONFIG for PCI |
61be6d66 | 1909 | Configuration |
12983077 AH |
1910 | check_enable_amd_mmconf [X86] check for and enable |
1911 | properly configured MMIO access to PCI | |
1912 | config space on AMD family 10h CPU | |
309e57df MW |
1913 | nomsi [MSI] If the PCI_MSI kernel config parameter is |
1914 | enabled, this kernel boot option can be used to | |
1915 | disable the use of MSI interrupts system-wide. | |
a9322f64 SA |
1916 | noioapicquirk [APIC] Disable all boot interrupt quirks. |
1917 | Safety option to keep boot IRQs enabled. This | |
1918 | should never be necessary. | |
9197979b SA |
1919 | ioapicreroute [APIC] Enable rerouting of boot IRQs to the |
1920 | primary IO-APIC for bridges that cannot disable | |
1921 | boot IRQs. This fixes a source of spurious IRQs | |
1922 | when the system masks IRQs. | |
41b9eb26 SA |
1923 | noioapicreroute [APIC] Disable workaround that uses the |
1924 | boot IRQ equivalent of an IRQ that connects to | |
1925 | a chipset where boot IRQs cannot be disabled. | |
1926 | The opposite of ioapicreroute. | |
cd4f0ef7 | 1927 | biosirq [X86-32] Use PCI BIOS calls to get the interrupt |
a9913044 RD |
1928 | routing table. These calls are known to be buggy |
1929 | on several machines and they hang the machine | |
1930 | when used, but on other computers it's the only | |
1931 | way to get the interrupt routing table. Try | |
1932 | this option if the kernel is unable to allocate | |
1933 | IRQs or discover secondary PCI buses on your | |
1934 | motherboard. | |
c0115606 | 1935 | rom [X86] Assign address space to expansion ROMs. |
a9913044 RD |
1936 | Use with caution as certain devices share |
1937 | address decoders between ROMs and other | |
1938 | resources. | |
c0115606 | 1939 | norom [X86] Do not assign address space to |
bb71ad88 GH |
1940 | expansion ROMs that do not already have |
1941 | BIOS assigned address ranges. | |
7bd1c365 MH |
1942 | nobar [X86] Do not assign address space to the |
1943 | BARs that weren't assigned by the BIOS. | |
c0115606 | 1944 | irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be |
a9913044 RD |
1945 | assigned automatically to PCI devices. You can |
1946 | make the kernel exclude IRQs of your ISA cards | |
1947 | this way. | |
c0115606 | 1948 | pirqaddr=0xAAAAA [X86] Specify the physical address |
a9913044 RD |
1949 | of the PIRQ table (normally generated |
1950 | by the BIOS) if it is outside the | |
1951 | F0000h-100000h range. | |
c0115606 | 1952 | lastbus=N [X86] Scan all buses thru bus #N. Can be |
a9913044 RD |
1953 | useful if the kernel is unable to find your |
1954 | secondary buses and you want to tell it | |
1955 | explicitly which ones they are. | |
c0115606 | 1956 | assign-busses [X86] Always assign all PCI bus |
a9913044 RD |
1957 | numbers ourselves, overriding |
1958 | whatever the firmware may have done. | |
c0115606 | 1959 | usepirqmask [X86] Honor the possible IRQ mask stored |
a9913044 RD |
1960 | in the BIOS $PIR table. This is needed on |
1961 | some systems with broken BIOSes, notably | |
1962 | some HP Pavilion N5400 and Omnibook XE3 | |
1963 | notebooks. This will have no effect if ACPI | |
1964 | IRQ routing is enabled. | |
c0115606 | 1965 | noacpi [X86] Do not use ACPI for IRQ routing |
a9913044 | 1966 | or for PCI scanning. |
7bc5e3f2 BH |
1967 | use_crs [X86] Use PCI host bridge window information |
1968 | from ACPI. On BIOSes from 2008 or later, this | |
1969 | is enabled by default. If you need to use this, | |
1970 | please report a bug. | |
1971 | nocrs [X86] Ignore PCI host bridge windows from ACPI. | |
1972 | If you need to use this, please report a bug. | |
a9913044 RD |
1973 | routeirq Do IRQ routing for all PCI devices. |
1974 | This is normally done in pci_enable_device(), | |
1975 | so this option is a temporary workaround | |
1976 | for broken drivers that don't call it. | |
13a6ddb0 YL |
1977 | skip_isa_align [X86] do not align io start addr, so can |
1978 | handle more pci cards | |
a9913044 RD |
1979 | firmware [ARM] Do not re-enumerate the bus but instead |
1980 | just use the configuration from the | |
1981 | bootloader. This is currently used on | |
1982 | IXP2000 systems where the bus has to be | |
1983 | configured a certain way for adjunct CPUs. | |
0637a70a AK |
1984 | noearly [X86] Don't do any early type 1 scanning. |
1985 | This might help on some broken boards which | |
1986 | machine check when some devices' config space | |
1987 | is read. But various workarounds are disabled | |
1988 | and some IOMMU drivers will not work. | |
6b4b78fe MD |
1989 | bfsort Sort PCI devices into breadth-first order. |
1990 | This sorting is done to get a device | |
1991 | order compatible with older (<= 2.4) kernels. | |
1992 | nobfsort Don't sort PCI devices into breadth-first order. | |
4516a618 AN |
1993 | cbiosize=nn[KMG] The fixed amount of bus space which is |
1994 | reserved for the CardBus bridge's IO window. | |
1995 | The default value is 256 bytes. | |
1996 | cbmemsize=nn[KMG] The fixed amount of bus space which is | |
1997 | reserved for the CardBus bridge's memory | |
1998 | window. The default value is 64 megabytes. | |
32a9a682 YS |
1999 | resource_alignment= |
2000 | Format: | |
2001 | [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...] | |
2002 | Specifies alignment and device to reassign | |
2003 | aligned memory resources. | |
2004 | If <order of align> is not specified, | |
2005 | PAGE_SIZE is used as alignment. | |
2006 | PCI-PCI bridge can be specified, if resource | |
2007 | windows need to be expanded. | |
43c16408 AP |
2008 | ecrc= Enable/disable PCIe ECRC (transaction layer |
2009 | end-to-end CRC checking). | |
2010 | bios: Use BIOS/firmware settings. This is the | |
2011 | the default. | |
2012 | off: Turn ECRC off | |
2013 | on: Turn ECRC on. | |
6b4b78fe | 2014 | |
e5665a45 CE |
2015 | pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power |
2016 | Management. | |
2017 | off Disable ASPM. | |
2018 | force Enable ASPM even on devices that claim not to support it. | |
2019 | WARNING: Forcing ASPM on may cause system lockups. | |
2020 | ||
79dd9182 | 2021 | pcie_ports= [PCIE] PCIe ports handling: |
28eb5f27 RW |
2022 | auto Ask the BIOS whether or not to use native PCIe services |
2023 | associated with PCIe ports (PME, hot-plug, AER). Use | |
2024 | them only if that is allowed by the BIOS. | |
2025 | native Use native PCIe services associated with PCIe ports | |
2026 | unconditionally. | |
79dd9182 RW |
2027 | compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe |
2028 | ports driver. | |
2029 | ||
c7f48656 | 2030 | pcie_pme= [PCIE,PM] Native PCIe PME signaling options: |
c39fae14 | 2031 | nomsi Do not use MSI for native PCIe PME signaling (this makes |
28eb5f27 | 2032 | all PCIe root ports use INTx for all services). |
c7f48656 | 2033 | |
1da177e4 LT |
2034 | pcmv= [HW,PCMCIA] BadgePAD 4 |
2035 | ||
2036 | pd. [PARIDE] | |
31c00fc1 | 2037 | See Documentation/blockdev/paride.txt. |
1da177e4 LT |
2038 | |
2039 | pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at | |
2040 | boot time. | |
2041 | Format: { 0 | 1 } | |
2042 | See arch/parisc/kernel/pdc_chassis.c | |
2043 | ||
f58dc01b | 2044 | percpu_alloc= Select which percpu first chunk allocator to use. |
e933a73f TH |
2045 | Currently supported values are "embed" and "page". |
2046 | Archs may support subset or none of the selections. | |
2047 | See comments in mm/percpu.c for details on each | |
2048 | allocator. This parameter is primarily for debugging | |
2049 | and performance comparison. | |
fa8a7094 | 2050 | |
1da177e4 | 2051 | pf. [PARIDE] |
31c00fc1 | 2052 | See Documentation/blockdev/paride.txt. |
1da177e4 LT |
2053 | |
2054 | pg. [PARIDE] | |
31c00fc1 | 2055 | See Documentation/blockdev/paride.txt. |
1da177e4 LT |
2056 | |
2057 | pirq= [SMP,APIC] Manual mp-table setup | |
71cced6e | 2058 | See Documentation/x86/i386/IO-APIC.txt. |
1da177e4 LT |
2059 | |
2060 | plip= [PPT,NET] Parallel port network link | |
2061 | Format: { parport<nr> | timid | 0 } | |
2062 | See also Documentation/parport.txt. | |
2063 | ||
de32a243 TG |
2064 | pmtmr= [X86] Manual setup of pmtmr I/O Port. |
2065 | Override pmtimer IOPort with a hex value. | |
2066 | e.g. pmtmr=0x508 | |
2067 | ||
97ef062b BH |
2068 | pnp.debug [PNP] |
2069 | Enable PNP debug messages. This depends on the | |
2070 | CONFIG_PNP_DEBUG_MESSAGES option. | |
2071 | ||
1da177e4 LT |
2072 | pnpacpi= [ACPI] |
2073 | { off } | |
2074 | ||
2075 | pnpbios= [ISAPNP] | |
2076 | { on | off | curr | res | no-curr | no-res } | |
2077 | ||
2078 | pnp_reserve_irq= | |
2079 | [ISAPNP] Exclude IRQs for the autoconfiguration | |
2080 | ||
2081 | pnp_reserve_dma= | |
2082 | [ISAPNP] Exclude DMAs for the autoconfiguration | |
2083 | ||
2084 | pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration | |
a9913044 | 2085 | Ranges are in pairs (I/O port base and size). |
1da177e4 LT |
2086 | |
2087 | pnp_reserve_mem= | |
a9913044 RD |
2088 | [ISAPNP] Exclude memory regions for the |
2089 | autoconfiguration. | |
1da177e4 LT |
2090 | Ranges are in pairs (memory base and size). |
2091 | ||
4af94f39 RD |
2092 | ports= [IP_VS_FTP] IPVS ftp helper module |
2093 | Default is 21. | |
2094 | Up to 8 (IP_VS_APP_MAX_PORTS) ports | |
2095 | may be specified. | |
2096 | Format: <port>,<port>.... | |
2097 | ||
45807a1d IM |
2098 | print-fatal-signals= |
2099 | [KNL] debug: print fatal signals | |
f84d49b2 NO |
2100 | |
2101 | If enabled, warn about various signal handling | |
2102 | related application anomalies: too many signals, | |
2103 | too many POSIX.1 timers, fatal signals causing a | |
2104 | coredump - etc. | |
2105 | ||
2106 | If you hit the warning due to signal overflow, | |
2107 | you might want to try "ulimit -i unlimited". | |
2108 | ||
45807a1d IM |
2109 | default: off. |
2110 | ||
e84845c4 RD |
2111 | printk.time= Show timing data prefixed to each printk message line |
2112 | Format: <bool> (1/Y/y=enable, 0/N/n=disable) | |
2113 | ||
0cb55ad2 RD |
2114 | processor.max_cstate= [HW,ACPI] |
2115 | Limit processor to maximum C-state | |
2116 | max_cstate=9 overrides any DMI blacklist limit. | |
2117 | ||
2118 | processor.nocst [HW,ACPI] | |
2119 | Ignore the _CST method to determine C-states, | |
2120 | instead using the legacy FADT method | |
2121 | ||
1da177e4 | 2122 | profile= [KNL] Enable kernel profiling via /proc/profile |
a9913044 RD |
2123 | Format: [schedule,]<number> |
2124 | Param: "schedule" - profile schedule points. | |
2125 | Param: <number> - step/bucket size as a power of 2 for | |
2126 | statistical time based profiling. | |
b3da2a73 MG |
2127 | Param: "sleep" - profile D-state sleeping (millisecs). |
2128 | Requires CONFIG_SCHEDSTATS | |
c0fe2e69 | 2129 | Param: "kvm" - profile VM exits. |
1da177e4 | 2130 | |
1da177e4 LT |
2131 | prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk |
2132 | before loading. | |
31c00fc1 | 2133 | See Documentation/blockdev/ramdisk.txt. |
1da177e4 | 2134 | |
a9913044 RD |
2135 | psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to |
2136 | probe for; one of (bare|imps|exps|lifebook|any). | |
1da177e4 LT |
2137 | psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports |
2138 | per second. | |
a9913044 RD |
2139 | psmouse.resetafter= [HW,MOUSE] |
2140 | Try to reset the device after so many bad packets | |
1da177e4 LT |
2141 | (0 = never). |
2142 | psmouse.resolution= | |
2143 | [HW,MOUSE] Set desired mouse resolution, in dpi. | |
2144 | psmouse.smartscroll= | |
a9913044 | 2145 | [HW,MOUSE] Controls Logitech smartscroll autorepeat. |
1da177e4 LT |
2146 | 0 = disabled, 1 = enabled (default). |
2147 | ||
1da177e4 | 2148 | pt. [PARIDE] |
31c00fc1 | 2149 | See Documentation/blockdev/paride.txt. |
1da177e4 | 2150 | |
dc8c8587 KS |
2151 | pty.legacy_count= |
2152 | [KNL] Number of legacy pty's. Overwrites compiled-in | |
2153 | default number. | |
2154 | ||
7d2c502f | 2155 | quiet [KNL] Disable most log messages |
a9913044 | 2156 | |
1da177e4 LT |
2157 | r128= [HW,DRM] |
2158 | ||
2159 | raid= [HW,RAID] | |
2160 | See Documentation/md.txt. | |
2161 | ||
a9913044 | 2162 | ramdisk_blocksize= [RAM] |
31c00fc1 | 2163 | See Documentation/blockdev/ramdisk.txt. |
a9913044 | 2164 | |
1da177e4 | 2165 | ramdisk_size= [RAM] Sizes of RAM disks in kilobytes |
31c00fc1 | 2166 | See Documentation/blockdev/ramdisk.txt. |
1da177e4 | 2167 | |
24aaef8d RD |
2168 | rcupdate.blimit= [KNL,BOOT] |
2169 | Set maximum number of finished RCU callbacks to process | |
2170 | in one batch. | |
21a1ea9e | 2171 | |
24aaef8d RD |
2172 | rcupdate.qhimark= [KNL,BOOT] |
2173 | Set threshold of queued | |
21a1ea9e DS |
2174 | RCU callbacks over which batch limiting is disabled. |
2175 | ||
24aaef8d RD |
2176 | rcupdate.qlowmark= [KNL,BOOT] |
2177 | Set threshold of queued RCU callbacks below which | |
2178 | batch limiting is re-enabled. | |
21a1ea9e | 2179 | |
ffdfc409 OJ |
2180 | rdinit= [KNL] |
2181 | Format: <full_path> | |
2182 | Run specified binary instead of /init from the ramdisk, | |
2183 | used for early userspace startup. See initrd. | |
2184 | ||
cd4f0ef7 | 2185 | reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode |
1da177e4 | 2186 | Format: <reboot_mode>[,<reboot_mode2>[,...]] |
ecb08d81 | 2187 | See arch/*/kernel/reboot.c or arch/*/kernel/process.c |
1da177e4 | 2188 | |
46b6d94e PJ |
2189 | relax_domain_level= |
2190 | [KNL, SMP] Set scheduler's default relax_domain_level. | |
21acb9ca | 2191 | See Documentation/cgroups/cpusets.txt. |
46b6d94e | 2192 | |
1da177e4 LT |
2193 | reserve= [KNL,BUGS] Force the kernel to ignore some iomem area |
2194 | ||
cd4f0ef7 | 2195 | reservetop= [X86-32] |
461a9aff ZA |
2196 | Format: nn[KMG] |
2197 | Reserves a hole at the top of the kernel virtual | |
2198 | address space. | |
2199 | ||
9ea77bdb PA |
2200 | reservelow= [X86] |
2201 | Format: nn[K] | |
2202 | Set the amount of memory to reserve for BIOS at | |
2203 | the bottom of the address space. | |
2204 | ||
7e96287d VG |
2205 | reset_devices [KNL] Force drivers to reset the underlying device |
2206 | during initialization. | |
2207 | ||
a9913044 RD |
2208 | resume= [SWSUSP] |
2209 | Specify the partition device for software suspend | |
1da177e4 | 2210 | |
ecbd0da1 RW |
2211 | resume_offset= [SWSUSP] |
2212 | Specify the offset from the beginning of the partition | |
2213 | given by "resume=" at which the swap header is located, | |
2214 | in <PAGE_SIZE> units (needed only for swap files). | |
2215 | See Documentation/power/swsusp-and-swap-files.txt | |
2216 | ||
f996fc96 BS |
2217 | hibernate= [HIBERNATION] |
2218 | noresume Don't check if there's a hibernation image | |
2219 | present during boot. | |
2220 | nocompress Don't compress/decompress hibernation images. | |
2221 | ||
0a7b35cb MN |
2222 | retain_initrd [RAM] Keep initrd memory after extraction |
2223 | ||
1da177e4 LT |
2224 | rhash_entries= [KNL,NET] |
2225 | Set number of hash buckets for route cache | |
2226 | ||
2227 | riscom8= [HW,SERIAL] | |
2228 | Format: <io_board1>[,<io_board2>[,...<io_boardN>]] | |
2229 | ||
2230 | ro [KNL] Mount root device read-only on boot | |
2231 | ||
2232 | root= [KNL] Root filesystem | |
2233 | ||
2234 | rootdelay= [KNL] Delay (in seconds) to pause before attempting to | |
2235 | mount the root filesystem | |
2236 | ||
2237 | rootflags= [KNL] Set root filesystem mount option string | |
2238 | ||
2239 | rootfstype= [KNL] Set root filesystem type | |
2240 | ||
cc1ed754 PO |
2241 | rootwait [KNL] Wait (indefinitely) for root device to show up. |
2242 | Useful for devices that are detected asynchronously | |
2243 | (e.g. USB and MMC devices). | |
2244 | ||
1da177e4 LT |
2245 | rw [KNL] Mount root device read-write on boot |
2246 | ||
2247 | S [KNL] Run init in single mode | |
2248 | ||
2249 | sa1100ir [NET] | |
2250 | See drivers/net/irda/sa1100_ir.c. | |
2251 | ||
1da177e4 | 2252 | sbni= [NET] Granch SBNI12 leased line adapter |
a9913044 | 2253 | |
f6630114 MT |
2254 | sched_debug [KNL] Enables verbose scheduler debug messages. |
2255 | ||
0cb55ad2 RD |
2256 | security= [SECURITY] Choose a security module to enable at boot. |
2257 | If this boot parameter is not specified, only the first | |
2258 | security module asking for security registration will be | |
2259 | loaded. An invalid security module name will be treated | |
2260 | as if no module has been chosen. | |
2261 | ||
2262 | selinux= [SELINUX] Disable or enable SELinux at boot time. | |
1da177e4 LT |
2263 | Format: { "0" | "1" } |
2264 | See security/selinux/Kconfig help text. | |
2265 | 0 -- disable. | |
2266 | 1 -- enable. | |
2267 | Default value is set via kernel config option. | |
2268 | If enabled at boot time, /selinux/disable can be used | |
2269 | later to disable prior to initial policy load. | |
2270 | ||
c1c124e9 JJ |
2271 | apparmor= [APPARMOR] Disable or enable AppArmor at boot time |
2272 | Format: { "0" | "1" } | |
2273 | See security/apparmor/Kconfig help text | |
2274 | 0 -- disable. | |
2275 | 1 -- enable. | |
2276 | Default value is set via kernel config option. | |
2277 | ||
cd4f0ef7 | 2278 | serialnumber [BUGS=X86-32] |
1da177e4 | 2279 | |
1da177e4 LT |
2280 | shapers= [NET] |
2281 | Maximal number of shapers. | |
a9913044 | 2282 | |
b05f78f5 YL |
2283 | show_msr= [x86] show boot-time MSR settings |
2284 | Format: { <integer> } | |
2285 | Show boot-time (BIOS-initialized) MSR settings. | |
2286 | The parameter means the number of CPUs to show, | |
2287 | for example 1 means boot CPU only. | |
2288 | ||
1da177e4 LT |
2289 | simeth= [IA-64] |
2290 | simscsi= | |
a9913044 | 2291 | |
1da177e4 LT |
2292 | slram= [HW,MTD] |
2293 | ||
f0630fff CL |
2294 | slub_debug[=options[,slabs]] [MM, SLUB] |
2295 | Enabling slub_debug allows one to determine the | |
2296 | culprit if slab objects become corrupted. Enabling | |
2297 | slub_debug can create guard zones around objects and | |
2298 | may poison objects when not in use. Also tracks the | |
2299 | last alloc / free. For more information see | |
2300 | Documentation/vm/slub.txt. | |
c1aee215 CL |
2301 | |
2302 | slub_max_order= [MM, SLUB] | |
f0630fff CL |
2303 | Determines the maximum allowed order for slabs. |
2304 | A high setting may cause OOMs due to memory | |
2305 | fragmentation. For more information see | |
2306 | Documentation/vm/slub.txt. | |
c1aee215 CL |
2307 | |
2308 | slub_min_objects= [MM, SLUB] | |
f0630fff CL |
2309 | The minimum number of objects per slab. SLUB will |
2310 | increase the slab order up to slub_max_order to | |
2311 | generate a sufficiently large slab able to contain | |
2312 | the number of objects indicated. The higher the number | |
2313 | of objects the smaller the overhead of tracking slabs | |
2314 | and the less frequently locks need to be acquired. | |
c1aee215 CL |
2315 | For more information see Documentation/vm/slub.txt. |
2316 | ||
2317 | slub_min_order= [MM, SLUB] | |
2318 | Determines the mininum page order for slabs. Must be | |
f0630fff | 2319 | lower than slub_max_order. |
c1aee215 CL |
2320 | For more information see Documentation/vm/slub.txt. |
2321 | ||
2322 | slub_nomerge [MM, SLUB] | |
f0630fff | 2323 | Disable merging of slabs with similar size. May be |
c1aee215 | 2324 | necessary if there is some reason to distinguish |
f0630fff CL |
2325 | allocs to different slabs. Debug options disable |
2326 | merging on their own. | |
c1aee215 CL |
2327 | For more information see Documentation/vm/slub.txt. |
2328 | ||
1da177e4 LT |
2329 | smart2= [HW] |
2330 | Format: <io1>[,<io2>[,...,<io8>]] | |
2331 | ||
cd4f0ef7 | 2332 | smp-alt-once [X86-32,SMP] On a hotplug CPU system, only |
b7fb4af0 JF |
2333 | attempt to substitute SMP alternatives once at boot. |
2334 | ||
d0d4f69b BH |
2335 | smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices |
2336 | smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port | |
2337 | smsc-ircc2.ircc_sir= [HW] SIR base I/O port | |
2338 | smsc-ircc2.ircc_fir= [HW] FIR base I/O port | |
2339 | smsc-ircc2.ircc_irq= [HW] IRQ line | |
2340 | smsc-ircc2.ircc_dma= [HW] DMA channel | |
2341 | smsc-ircc2.ircc_transceiver= [HW] Transceiver type: | |
2342 | 0: Toshiba Satellite 1800 (GP data pin select) | |
2343 | 1: Fast pin select (default) | |
2344 | 2: ATC IRMode | |
2345 | ||
9c44bc03 IM |
2346 | softlockup_panic= |
2347 | [KNL] Should the soft-lockup detector generate panics. | |
44a4dcf7 | 2348 | Format: <integer> |
9c44bc03 | 2349 | |
1da177e4 LT |
2350 | sonypi.*= [HW] Sony Programmable I/O Control Device driver |
2351 | See Documentation/sonypi.txt | |
2352 | ||
2353 | specialix= [HW,SERIAL] Specialix multi-serial port adapter | |
31c00fc1 | 2354 | See Documentation/serial/specialix.txt. |
1da177e4 LT |
2355 | |
2356 | spia_io_base= [HW,MTD] | |
2357 | spia_fio_base= | |
2358 | spia_pedr= | |
2359 | spia_peddr= | |
2360 | ||
f38f1d2a SR |
2361 | stacktrace [FTRACE] |
2362 | Enabled the stack tracer on boot up. | |
2363 | ||
1da177e4 LT |
2364 | sti= [PARISC,HW] |
2365 | Format: <num> | |
2366 | Set the STI (builtin display/keyboard on the HP-PARISC | |
2367 | machines) console (graphic card) which should be used | |
2368 | as the initial boot-console. | |
2369 | See also comment in drivers/video/console/sticore.c. | |
2370 | ||
2371 | sti_font= [HW] | |
2372 | See comment in drivers/video/console/sticore.c. | |
2373 | ||
2374 | stifb= [HW] | |
2375 | Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] | |
2376 | ||
cbf11071 TM |
2377 | sunrpc.min_resvport= |
2378 | sunrpc.max_resvport= | |
2379 | [NFS,SUNRPC] | |
2380 | SunRPC servers often require that client requests | |
2381 | originate from a privileged port (i.e. a port in the | |
2382 | range 0 < portnr < 1024). | |
2383 | An administrator who wishes to reserve some of these | |
2384 | ports for other uses may adjust the range that the | |
2385 | kernel's sunrpc client considers to be privileged | |
2386 | using these two parameters to set the minimum and | |
2387 | maximum port values. | |
2388 | ||
42a7fc4a GB |
2389 | sunrpc.pool_mode= |
2390 | [NFS] | |
2391 | Control how the NFS server code allocates CPUs to | |
2392 | service thread pools. Depending on how many NICs | |
2393 | you have and where their interrupts are bound, this | |
2394 | option will affect which CPUs will do NFS serving. | |
2395 | Note: this parameter cannot be changed while the | |
2396 | NFS server is running. | |
2397 | ||
2398 | auto the server chooses an appropriate mode | |
2399 | automatically using heuristics | |
2400 | global a single global pool contains all CPUs | |
2401 | percpu one pool for each CPU | |
2402 | pernode one pool for each NUMA node (equivalent | |
2403 | to global on non-NUMA machines) | |
2404 | ||
cbf11071 TM |
2405 | sunrpc.tcp_slot_table_entries= |
2406 | sunrpc.udp_slot_table_entries= | |
2407 | [NFS,SUNRPC] | |
2408 | Sets the upper limit on the number of simultaneous | |
2409 | RPC calls that can be sent from the client to a | |
2410 | server. Increasing these values may allow you to | |
2411 | improve throughput, but will also increase the | |
2412 | amount of memory reserved for use by the client. | |
2413 | ||
a42c390c MH |
2414 | swapaccount[=0|1] |
2415 | [KNL] Enable accounting of swap in memory resource | |
2416 | controller if no parameter or 1 is given or disable | |
2417 | it if 0 is given (See Documentation/cgroups/memory.txt) | |
2418 | ||
1da177e4 | 2419 | swiotlb= [IA-64] Number of I/O TLB slabs |
a9913044 | 2420 | |
1da177e4 LT |
2421 | switches= [HW,M68k] |
2422 | ||
e52eec13 AK |
2423 | sysfs.deprecated=0|1 [KNL] |
2424 | Enable/disable old style sysfs layout for old udev | |
2425 | on older distributions. When this option is enabled | |
2426 | very new udev will not work anymore. When this option | |
2427 | is disabled (or CONFIG_SYSFS_DEPRECATED not compiled) | |
2428 | in older udev will not work anymore. | |
2429 | Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in | |
2430 | the kernel configuration. | |
2431 | ||
5d6f647f IM |
2432 | sysrq_always_enabled |
2433 | [KNL] | |
2434 | Ignore sysrq setting - this boot parameter will | |
2435 | neutralize any effect of /proc/sys/kernel/sysrq. | |
2436 | Useful for debugging. | |
2437 | ||
1da177e4 LT |
2438 | tdfx= [HW,DRM] |
2439 | ||
77437fd4 DB |
2440 | test_suspend= [SUSPEND] |
2441 | Specify "mem" (for Suspend-to-RAM) or "standby" (for | |
2442 | standby suspend) as the system sleep state to briefly | |
2443 | enter during system startup. The system is woken from | |
2444 | this state using a wakeup-capable RTC alarm. | |
2445 | ||
1da177e4 LT |
2446 | thash_entries= [KNL,NET] |
2447 | Set number of hash buckets for TCP connection | |
2448 | ||
f8707ec9 LB |
2449 | thermal.act= [HW,ACPI] |
2450 | -1: disable all active trip points in all thermal zones | |
2451 | <degrees C>: override all lowest active trip points | |
2452 | ||
c52a7419 LB |
2453 | thermal.crt= [HW,ACPI] |
2454 | -1: disable all critical trip points in all thermal zones | |
22a94d79 | 2455 | <degrees C>: override all critical trip points |
c52a7419 | 2456 | |
f5487145 LB |
2457 | thermal.nocrt= [HW,ACPI] |
2458 | Set to disable actions on ACPI thermal zone | |
2459 | critical and hot trip points. | |
2460 | ||
72b33ef8 LB |
2461 | thermal.off= [HW,ACPI] |
2462 | 1: disable ACPI thermal control | |
2463 | ||
a70cdc52 LB |
2464 | thermal.psv= [HW,ACPI] |
2465 | -1: disable all passive trip points | |
ada9cfdd RD |
2466 | <degrees C>: override all passive trip points to this |
2467 | value | |
a70cdc52 | 2468 | |
730ff34d LB |
2469 | thermal.tzp= [HW,ACPI] |
2470 | Specify global default ACPI thermal zone polling rate | |
2471 | <deci-seconds>: poll all this frequency | |
2472 | 0: no polling (default) | |
2473 | ||
8d32a307 TG |
2474 | threadirqs [KNL] |
2475 | Force threading of all interrupt handlers except those | |
2476 | marked explicitely IRQF_NO_THREAD. | |
2477 | ||
2b1a61f0 HC |
2478 | topology= [S390] |
2479 | Format: {off | on} | |
2480 | Specify if the kernel should make use of the cpu | |
f65e51d7 SL |
2481 | topology information if the hardware supports this. |
2482 | The scheduler will make use of this information and | |
2b1a61f0 | 2483 | e.g. base its process migration decisions on it. |
c9af3fa9 | 2484 | Default is on. |
2b1a61f0 | 2485 | |
1da177e4 LT |
2486 | tp720= [HW,PS2] |
2487 | ||
225a9be2 RA |
2488 | tpm_suspend_pcr=[HW,TPM] |
2489 | Format: integer pcr id | |
2490 | Specify that at suspend time, the tpm driver | |
2491 | should extend the specified pcr with zeros, | |
2492 | as a workaround for some chips which fail to | |
2493 | flush the last written pcr on TPM_SaveState. | |
2494 | This will guarantee that all the other pcrs | |
2495 | are saved. | |
2496 | ||
9d612bef LZ |
2497 | trace_buf_size=nn[KMG] |
2498 | [FTRACE] will set tracing buffer size. | |
631595fb | 2499 | |
020e5f85 LZ |
2500 | trace_event=[event-list] |
2501 | [FTRACE] Set and start specified trace events in order | |
2502 | to facilitate early boot debugging. | |
2503 | See also Documentation/trace/events.txt | |
2504 | ||
d3b8f889 | 2505 | tsc= Disable clocksource stability checks for TSC. |
395628ef AK |
2506 | Format: <string> |
2507 | [x86] reliable: mark tsc clocksource as reliable, this | |
d3b8f889 | 2508 | disables clocksource verification at runtime, as well |
2509 | as the stability checks done at bootup. Used to enable | |
2510 | high-resolution timer mode on older hardware, and in | |
2511 | virtualized environment. | |
e82b8e4e VP |
2512 | [x86] noirqtime: Do not use TSC to do irq accounting. |
2513 | Used to run time disable IRQ_TIME_ACCOUNTING on any | |
2514 | platforms where RDTSC is slow and this accounting | |
2515 | can add overhead. | |
395628ef | 2516 | |
a9913044 RD |
2517 | turbografx.map[2|3]= [HW,JOY] |
2518 | TurboGraFX parallel port interface | |
2519 | Format: | |
2520 | <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> | |
1da177e4 LT |
2521 | See also Documentation/input/joystick-parport.txt |
2522 | ||
f86dcc5a ED |
2523 | uhash_entries= [KNL,NET] |
2524 | Set number of hash buckets for UDP/UDP-Lite connections | |
2525 | ||
5f8364b7 AS |
2526 | uhci-hcd.ignore_oc= |
2527 | [USB] Ignore overcurrent events (default N). | |
2528 | Some badly-designed motherboards generate lots of | |
2529 | bogus events, for ports that aren't wired to | |
2530 | anything. Set this parameter to avoid log spamming. | |
2531 | Note that genuine overcurrent events won't be | |
2532 | reported either. | |
2533 | ||
e3a61b0a | 2534 | unknown_nmi_panic |
44a4dcf7 | 2535 | [X86] Cause panic on unknown NMI. |
e3a61b0a | 2536 | |
b5e795f8 AS |
2537 | usbcore.autosuspend= |
2538 | [USB] The autosuspend time delay (in seconds) used | |
2539 | for newly-detected USB devices (default 2). This | |
2540 | is the time required before an idle device will be | |
2541 | autosuspended. Devices for which the delay is set | |
eaafbc3a | 2542 | to a negative value won't be autosuspended at all. |
b5e795f8 | 2543 | |
fd7c519d JK |
2544 | usbcore.usbfs_snoop= |
2545 | [USB] Set to log all usbfs traffic (default 0 = off). | |
2546 | ||
2547 | usbcore.blinkenlights= | |
2548 | [USB] Set to cycle leds on hubs (default 0 = off). | |
2549 | ||
2550 | usbcore.old_scheme_first= | |
2551 | [USB] Start with the old device initialization | |
2552 | scheme (default 0 = off). | |
2553 | ||
2554 | usbcore.use_both_schemes= | |
2555 | [USB] Try the other device initialization scheme | |
2556 | if the first one fails (default 1 = enabled). | |
2557 | ||
2558 | usbcore.initial_descriptor_timeout= | |
2559 | [USB] Specifies timeout for the initial 64-byte | |
2560 | USB_REQ_GET_DESCRIPTOR request in milliseconds | |
2561 | (default 5000 = 5.0 seconds). | |
2562 | ||
1da177e4 LT |
2563 | usbhid.mousepoll= |
2564 | [USBHID] The interval which mice are to be polled at. | |
a9913044 | 2565 | |
d4f373e5 AS |
2566 | usb-storage.delay_use= |
2567 | [UMS] The delay in seconds before a new device is | |
2568 | scanned for Logical Units (default 5). | |
2569 | ||
2570 | usb-storage.quirks= | |
2571 | [UMS] A list of quirks entries to supplement or | |
2572 | override the built-in unusual_devs list. List | |
2573 | entries are separated by commas. Each entry has | |
2574 | the form VID:PID:Flags where VID and PID are Vendor | |
2575 | and Product ID values (4-digit hex numbers) and | |
2576 | Flags is a set of characters, each corresponding | |
2577 | to a common usb-storage quirk flag as follows: | |
c838ea46 AS |
2578 | a = SANE_SENSE (collect more than 18 bytes |
2579 | of sense data); | |
a0bb1081 AS |
2580 | b = BAD_SENSE (don't collect more than 18 |
2581 | bytes of sense data); | |
d4f373e5 AS |
2582 | c = FIX_CAPACITY (decrease the reported |
2583 | device capacity by one sector); | |
c838ea46 AS |
2584 | h = CAPACITY_HEURISTICS (decrease the |
2585 | reported device capacity by one | |
2586 | sector if the number is odd); | |
d4f373e5 AS |
2587 | i = IGNORE_DEVICE (don't bind to this |
2588 | device); | |
2589 | l = NOT_LOCKABLE (don't try to lock and | |
2590 | unlock ejectable media); | |
2591 | m = MAX_SECTORS_64 (don't transfer more | |
2592 | than 64 sectors = 32 KB at a time); | |
c838ea46 AS |
2593 | o = CAPACITY_OK (accept the capacity |
2594 | reported by the device); | |
d4f373e5 AS |
2595 | r = IGNORE_RESIDUE (the device reports |
2596 | bogus residue values); | |
2597 | s = SINGLE_LUN (the device has only one | |
2598 | Logical Unit); | |
2599 | w = NO_WP_DETECT (don't test whether the | |
2600 | medium is write-protected). | |
2601 | Example: quirks=0419:aaf5:rl,0421:0433:rc | |
2602 | ||
14315592 IC |
2603 | userpte= |
2604 | [X86] Flags controlling user PTE allocations. | |
2605 | ||
2606 | nohigh = do not allocate PTE pages in | |
2607 | HIGHMEM regardless of setting | |
2608 | of CONFIG_HIGHPTE. | |
2609 | ||
6cececfc | 2610 | vdso= [X86,SH] |
1dbf527c | 2611 | vdso=2: enable compat VDSO (default with COMPAT_VDSO) |
e6e5494c IM |
2612 | vdso=1: enable VDSO (default) |
2613 | vdso=0: disable VDSO mapping | |
2614 | ||
6cececfc | 2615 | vdso32= [X86] |
af65d648 RM |
2616 | vdso32=2: enable compat VDSO (default with COMPAT_VDSO) |
2617 | vdso32=1: enable 32-bit VDSO (default) | |
2618 | vdso32=0: disable 32-bit VDSO mapping | |
2619 | ||
d080d397 YI |
2620 | vector= [IA-64,SMP] |
2621 | vector=percpu: enable percpu vector domain | |
2622 | ||
1da177e4 LT |
2623 | video= [FB] Frame buffer configuration |
2624 | See Documentation/fb/modedb.txt. | |
2625 | ||
cd4f0ef7 | 2626 | vga= [BOOT,X86-32] Select a particular video mode |
954a8b81 | 2627 | See Documentation/x86/boot.txt and |
a9913044 | 2628 | Documentation/svga.txt. |
1da177e4 LT |
2629 | Use vga=ask for menu. |
2630 | This is actually a boot loader parameter; the value is | |
2631 | passed to the kernel using a special protocol. | |
2632 | ||
a9913044 | 2633 | vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact |
1da177e4 LT |
2634 | size of <nn>. This can be used to increase the |
2635 | minimum size (128MB on x86). It can also be used to | |
2636 | decrease the size and leave more room for directly | |
2637 | mapped kernel RAM. | |
2638 | ||
585c3047 PO |
2639 | vmhalt= [KNL,S390] Perform z/VM CP command after system halt. |
2640 | Format: <command> | |
1da177e4 | 2641 | |
585c3047 PO |
2642 | vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. |
2643 | Format: <command> | |
2644 | ||
2645 | vmpoff= [KNL,S390] Perform z/VM CP command after power off. | |
2646 | Format: <command> | |
a9913044 | 2647 | |
9ea9a886 CL |
2648 | vt.cur_default= [VT] Default cursor shape. |
2649 | Format: 0xCCBBAA, where AA, BB, and CC are the same as | |
2650 | the parameters of the <Esc>[?A;B;Cc escape sequence; | |
2651 | see VGA-softcursor.txt. Default: 2 = underline. | |
2652 | ||
0cb55ad2 RD |
2653 | vt.default_blu= [VT] |
2654 | Format: <blue0>,<blue1>,<blue2>,...,<blue15> | |
2655 | Change the default blue palette of the console. | |
2656 | This is a 16-member array composed of values | |
2657 | ranging from 0-255. | |
2658 | ||
2659 | vt.default_grn= [VT] | |
2660 | Format: <green0>,<green1>,<green2>,...,<green15> | |
2661 | Change the default green palette of the console. | |
2662 | This is a 16-member array composed of values | |
2663 | ranging from 0-255. | |
2664 | ||
2665 | vt.default_red= [VT] | |
2666 | Format: <red0>,<red1>,<red2>,...,<red15> | |
2667 | Change the default red palette of the console. | |
2668 | This is a 16-member array composed of values | |
2669 | ranging from 0-255. | |
2670 | ||
2671 | vt.default_utf8= | |
2672 | [VT] | |
2673 | Format=<0|1> | |
2674 | Set system-wide default UTF-8 mode for all tty's. | |
2675 | Default is 1, i.e. UTF-8 mode is enabled for all | |
2676 | newly opened terminals. | |
2677 | ||
f6c06b68 MG |
2678 | vt.global_cursor_default= |
2679 | [VT] | |
2680 | Format=<-1|0|1> | |
2681 | Set system-wide default for whether a cursor | |
2682 | is shown on new VTs. Default is -1, | |
2683 | i.e. cursors will be created by default unless | |
2684 | overridden by individual drivers. 0 will hide | |
2685 | cursors, 1 will display them. | |
2686 | ||
4724ba57 RD |
2687 | watchdog timers [HW,WDT] For information on watchdog timers, |
2688 | see Documentation/watchdog/watchdog-parameters.txt | |
2689 | or other driver-specific files in the | |
2690 | Documentation/watchdog/ directory. | |
1da177e4 | 2691 | |
0cb55ad2 RD |
2692 | x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of |
2693 | default x2apic cluster mode on platforms | |
2694 | supporting x2apic. | |
2695 | ||
bb24c471 JP |
2696 | x86_mrst_timer= [X86-32,APBT] |
2697 | Choose timer option for x86 Moorestown MID platform. | |
2698 | Two valid options are apbt timer only and lapic timer | |
2699 | plus one apbt timer for broadcast timer. | |
2700 | x86_mrst_timer=apbt_only | lapic_and_apbt | |
2701 | ||
1da177e4 LT |
2702 | xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks. |
2703 | xd_geo= See header of drivers/block/xd.c. | |
2704 | ||
c1c5413a SS |
2705 | xen_emul_unplug= [HW,X86,XEN] |
2706 | Unplug Xen emulated devices | |
2707 | Format: [unplug0,][unplug1] | |
2708 | ide-disks -- unplug primary master IDE devices | |
2709 | aux-ide-disks -- unplug non-primary-master IDE devices | |
2710 | nics -- unplug network devices | |
2711 | all -- unplug all emulated devices (NICs and IDE disks) | |
1dc7ce99 IC |
2712 | unnecessary -- unplugging emulated devices is |
2713 | unnecessary even if the host did not respond to | |
2714 | the unplug protocol | |
c93a4dfb | 2715 | never -- do not unplug even if version check succeeds |
c1c5413a | 2716 | |
1da177e4 | 2717 | xirc2ps_cs= [NET,PCMCIA] |
a9913044 RD |
2718 | Format: |
2719 | <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] | |
1da177e4 | 2720 | |
a9913044 | 2721 | ______________________________________________________________________ |
1da177e4 LT |
2722 | |
2723 | TODO: | |
2724 | ||
1da177e4 | 2725 | Add more DRM drivers. |