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1 Kernel Parameters 2 ~~~~~~~~~~~~~~~~~ 3 4The following is a consolidated list of the kernel parameters as implemented 5(mostly) by the __setup() macro and sorted into English Dictionary order 6(defined as ignoring all punctuation and sorting digits before letters in a 7case insensitive manner), and with descriptions where known. 8 9Module parameters for loadable modules are specified only as the 10parameter name with optional '=' and value as appropriate, such as: 11 12 modprobe usbcore blinkenlights=1 13 14Module parameters for modules that are built into the kernel image 15are specified on the kernel command line with the module name plus 16'.' plus parameter name, with '=' and value if appropriate, such as: 17 18 usbcore.blinkenlights=1 19 20This document may not be entirely up to date and comprehensive. The command 21"modinfo -p ${modulename}" shows a current list of all parameters of a loadable 22module. Loadable modules, after being loaded into the running kernel, also 23reveal their parameters in /sys/module/${modulename}/parameters/. Some of these 24parameters may be changed at runtime by the command 25"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}". 26 27The parameters listed below are only valid if certain kernel build options were 28enabled and if respective hardware is present. The text in square brackets at 29the beginning of each description states the restrictions within which a 30parameter is applicable: 31 32 ACPI ACPI support is enabled. 33 AGP AGP (Accelerated Graphics Port) is enabled. 34 ALSA ALSA sound support is enabled. 35 APIC APIC support is enabled. 36 APM Advanced Power Management support is enabled. 37 AVR32 AVR32 architecture is enabled. 38 AX25 Appropriate AX.25 support is enabled. 39 BLACKFIN Blackfin architecture is enabled. 40 DRM Direct Rendering Management support is enabled. 41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled 42 EFI EFI Partitioning (GPT) is enabled 43 EIDE EIDE/ATAPI support is enabled. 44 FB The frame buffer device is enabled. 45 HW Appropriate hardware is enabled. 46 IA-64 IA-64 architecture is enabled. 47 IOSCHED More than one I/O scheduler is enabled. 48 IP_PNP IP DHCP, BOOTP, or RARP is enabled. 49 ISAPNP ISA PnP code is enabled. 50 ISDN Appropriate ISDN support is enabled. 51 JOY Appropriate joystick support is enabled. 52 LIBATA Libata driver is enabled 53 LP Printer support is enabled. 54 LOOP Loopback device support is enabled. 55 M68k M68k architecture is enabled. 56 These options have more detailed description inside of 57 Documentation/m68k/kernel-options.txt. 58 MCA MCA bus support is enabled. 59 MDA MDA console support is enabled. 60 MOUSE Appropriate mouse support is enabled. 61 MSI Message Signaled Interrupts (PCI). 62 MTD MTD (Memory Technology Device) support is enabled. 63 NET Appropriate network support is enabled. 64 NUMA NUMA support is enabled. 65 GENERIC_TIME The generic timeofday code is enabled. 66 NFS Appropriate NFS support is enabled. 67 OSS OSS sound support is enabled. 68 PV_OPS A paravirtualized kernel is enabled. 69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled. 70 PARISC The PA-RISC architecture is enabled. 71 PCI PCI bus support is enabled. 72 PCIE PCI Express support is enabled. 73 PCMCIA The PCMCIA subsystem is enabled. 74 PNP Plug & Play support is enabled. 75 PPC PowerPC architecture is enabled. 76 PPT Parallel port support is enabled. 77 PS2 Appropriate PS/2 support is enabled. 78 RAM RAM disk support is enabled. 79 ROOTPLUG The example Root Plug LSM is enabled. 80 S390 S390 architecture is enabled. 81 SCSI Appropriate SCSI support is enabled. 82 A lot of drivers has their options described inside of 83 Documentation/scsi/. 84 SECURITY Different security models are enabled. 85 SELINUX SELinux support is enabled. 86 SERIAL Serial support is enabled. 87 SH SuperH architecture is enabled. 88 SMP The kernel is an SMP kernel. 89 SPARC Sparc architecture is enabled. 90 SWSUSP Software suspend (hibernation) is enabled. 91 SUSPEND System suspend states are enabled. 92 TS Appropriate touchscreen support is enabled. 93 USB USB support is enabled. 94 USBHID USB Human Interface Device support is enabled. 95 V4L Video For Linux support is enabled. 96 VGA The VGA console has been enabled. 97 VT Virtual terminal support is enabled. 98 WDT Watchdog support is enabled. 99 XT IBM PC/XT MFM hard disk support is enabled. 100 X86-32 X86-32, aka i386 architecture is enabled. 101 X86-64 X86-64 architecture is enabled. 102 More X86-64 boot options can be found in 103 Documentation/x86_64/boot-options.txt . 104 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64) 105 106In addition, the following text indicates that the option: 107 108 BUGS= Relates to possible processor bugs on the said processor. 109 KNL Is a kernel start-up parameter. 110 BOOT Is a boot loader parameter. 111 112Parameters denoted with BOOT are actually interpreted by the boot 113loader, and have no meaning to the kernel directly. 114Do not modify the syntax of boot loader parameters without extreme 115need or coordination with <Documentation/i386/boot.txt>. 116 117There are also arch-specific kernel-parameters not documented here. 118See for example <Documentation/x86_64/boot-options.txt>. 119 120Note that ALL kernel parameters listed below are CASE SENSITIVE, and that 121a trailing = on the name of any parameter states that that parameter will 122be entered as an environment variable, whereas its absence indicates that 123it will appear as a kernel argument readable via /proc/cmdline by programs 124running once the system is up. 125 126The number of kernel parameters is not limited, but the length of the 127complete command line (parameters including spaces etc.) is limited to 128a fixed number of characters. This limit depends on the architecture 129and is between 256 and 4096 characters. It is defined in the file 130./include/asm/setup.h as COMMAND_LINE_SIZE. 131 132 133 acpi= [HW,ACPI,X86-64,i386] 134 Advanced Configuration and Power Interface 135 Format: { force | off | ht | strict | noirq } 136 force -- enable ACPI if default was off 137 off -- disable ACPI if default was on 138 noirq -- do not use ACPI for IRQ routing 139 ht -- run only enough ACPI to enable Hyper Threading 140 strict -- Be less tolerant of platforms that are not 141 strictly ACPI specification compliant. 142 143 See also Documentation/power/pm.txt, pci=noacpi 144 145 acpi_apic_instance= [ACPI, IOAPIC] 146 Format: <int> 147 2: use 2nd APIC table, if available 148 1,0: use 1st APIC table 149 default: 0 150 151 acpi_sleep= [HW,ACPI] Sleep options 152 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, old_ordering } 153 See Documentation/power/video.txt for s3_bios and s3_mode. 154 s3_beep is for debugging; it makes the PC's speaker beep 155 as soon as the kernel's real-mode entry point is called. 156 s4_nohwsig prevents ACPI hardware signature from being 157 used during resume from hibernation. 158 old_ordering causes the ACPI 1.0 ordering of the _PTS 159 control method, wrt putting devices into low power 160 states, to be enforced (the ACPI 2.0 ordering of _PTS is 161 used by default). 162 163 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode 164 Format: { level | edge | high | low } 165 166 acpi_irq_balance [HW,ACPI] 167 ACPI will balance active IRQs 168 default in APIC mode 169 170 acpi_irq_nobalance [HW,ACPI] 171 ACPI will not move active IRQs (default) 172 default in PIC mode 173 174 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for 175 use by PCI 176 Format: <irq>,<irq>... 177 178 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA 179 Format: <irq>,<irq>... 180 181 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT 182 183 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS 184 Format: To spoof as Windows 98: ="Microsoft Windows" 185 186 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings 187 acpi_osi="string1" # add string1 -- only one string 188 acpi_osi="!string2" # remove built-in string2 189 acpi_osi= # disable all strings 190 191 acpi_serialize [HW,ACPI] force serialization of AML methods 192 193 acpi_skip_timer_override [HW,ACPI] 194 Recognize and ignore IRQ0/pin2 Interrupt Override. 195 For broken nForce2 BIOS resulting in XT-PIC timer. 196 acpi_use_timer_override [HW,ACPI} 197 Use timer override. For some broken Nvidia NF5 boards 198 that require a timer override, but don't have 199 HPET 200 201 acpi.debug_layer= [HW,ACPI] 202 Format: <int> 203 Each bit of the <int> indicates an ACPI debug layer, 204 1: enable, 0: disable. It is useful for boot time 205 debugging. After system has booted up, it can be set 206 via /sys/module/acpi/parameters/debug_layer. 207 CONFIG_ACPI_DEBUG must be enabled for this to produce any output. 208 Available bits (add the numbers together) to enable debug output 209 for specific parts of the ACPI subsystem: 210 0x01 utilities 0x02 hardware 0x04 events 0x08 tables 211 0x10 namespace 0x20 parser 0x40 dispatcher 212 0x80 executer 0x100 resources 0x200 acpica debugger 213 0x400 os services 0x800 acpica disassembler. 214 The number can be in decimal or prefixed with 0x in hex. 215 Warning: Many of these options can produce a lot of 216 output and make your system unusable. Be very careful. 217 218 acpi.debug_level= [HW,ACPI] 219 Format: <int> 220 Each bit of the <int> indicates an ACPI debug level, 221 which corresponds to the level in an ACPI_DEBUG_PRINT 222 statement. After system has booted up, this mask 223 can be set via /sys/module/acpi/parameters/debug_level. 224 225 CONFIG_ACPI_DEBUG must be enabled for this to produce 226 any output. The number can be in decimal or prefixed 227 with 0x in hex. Some of these options produce so much 228 output that the system is unusable. 229 230 The following global components are defined by the 231 ACPI CA: 232 0x01 error 233 0x02 warn 234 0x04 init 235 0x08 debug object 236 0x10 info 237 0x20 init names 238 0x40 parse 239 0x80 load 240 0x100 dispatch 241 0x200 execute 242 0x400 names 243 0x800 operation region 244 0x1000 bfield 245 0x2000 tables 246 0x4000 values 247 0x8000 objects 248 0x10000 resources 249 0x20000 user requests 250 0x40000 package 251 The number can be in decimal or prefixed with 0x in hex. 252 Warning: Many of these options can produce a lot of 253 output and make your system unusable. Be very careful. 254 255 acpi.power_nocheck= [HW,ACPI] 256 Format: 1/0 enable/disable the check of power state. 257 On some bogus BIOS the _PSC object/_STA object of 258 power resource can't return the correct device power 259 state. In such case it is unneccessary to check its 260 power state again in power transition. 261 1 : disable the power state check 262 263 acpi_pm_good [X86-32,X86-64] 264 Override the pmtimer bug detection: force the kernel 265 to assume that this machine's pmtimer latches its value 266 and always returns good values. 267 268 agp= [AGP] 269 { off | try_unsupported } 270 off: disable AGP support 271 try_unsupported: try to drive unsupported chipsets 272 (may crash computer or cause data corruption) 273 274 enable_timer_pin_1 [i386,x86-64] 275 Enable PIN 1 of APIC timer 276 Can be useful to work around chipset bugs 277 (in particular on some ATI chipsets). 278 The kernel tries to set a reasonable default. 279 280 disable_timer_pin_1 [i386,x86-64] 281 Disable PIN 1 of APIC timer 282 Can be useful to work around chipset bugs. 283 284 ad1848= [HW,OSS] 285 Format: <io>,<irq>,<dma>,<dma2>,<type> 286 287 advansys= [HW,SCSI] 288 See header of drivers/scsi/advansys.c. 289 290 advwdt= [HW,WDT] Advantech WDT 291 Format: <iostart>,<iostop> 292 293 aedsp16= [HW,OSS] Audio Excel DSP 16 294 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq> 295 See also header of sound/oss/aedsp16.c. 296 297 aha152x= [HW,SCSI] 298 See Documentation/scsi/aha152x.txt. 299 300 aha1542= [HW,SCSI] 301 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]] 302 303 aic7xxx= [HW,SCSI] 304 See Documentation/scsi/aic7xxx.txt. 305 306 aic79xx= [HW,SCSI] 307 See Documentation/scsi/aic79xx.txt. 308 309 amd_iommu= [HW,X86-84] 310 Pass parameters to the AMD IOMMU driver in the system. 311 Possible values are: 312 isolate - enable device isolation (each device, as far 313 as possible, will get its own protection 314 domain) 315 fullflush - enable flushing of IO/TLB entries when 316 they are unmapped. Otherwise they are 317 flushed before they will be reused, which 318 is a lot of faster 319 320 amd_iommu_size= [HW,X86-64] 321 Define the size of the aperture for the AMD IOMMU 322 driver. Possible values are: 323 '32M', '64M' (default), '128M', '256M', '512M', '1G' 324 325 amijoy.map= [HW,JOY] Amiga joystick support 326 Map of devices attached to JOY0DAT and JOY1DAT 327 Format: <a>,<b> 328 See also Documentation/kernel/input/joystick.txt 329 330 analog.map= [HW,JOY] Analog joystick and gamepad support 331 Specifies type or capabilities of an analog joystick 332 connected to one of 16 gameports 333 Format: <type1>,<type2>,..<type16> 334 335 apc= [HW,SPARC] 336 Power management functions (SPARCstation-4/5 + deriv.) 337 Format: noidle 338 Disable APC CPU standby support. SPARCstation-Fox does 339 not play well with APC CPU idle - disable it if you have 340 APC and your system crashes randomly. 341 342 apic= [APIC,i386] Advanced Programmable Interrupt Controller 343 Change the output verbosity whilst booting 344 Format: { quiet (default) | verbose | debug } 345 Change the amount of debugging information output 346 when initialising the APIC and IO-APIC components. 347 348 apm= [APM] Advanced Power Management 349 See header of arch/x86/kernel/apm_32.c. 350 351 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards 352 Format: <io>,<irq>,<nodeID> 353 354 ataflop= [HW,M68k] 355 356 atarimouse= [HW,MOUSE] Atari Mouse 357 358 atascsi= [HW,SCSI] Atari SCSI 359 360 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, 361 EzKey and similar keyboards 362 363 atkbd.reset= [HW] Reset keyboard during initialization 364 365 atkbd.set= [HW] Select keyboard code set 366 Format: <int> (2 = AT (default), 3 = PS/2) 367 368 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar 369 keyboards 370 371 atkbd.softraw= [HW] Choose between synthetic and real raw mode 372 Format: <bool> (0 = real, 1 = synthetic (default)) 373 374 atkbd.softrepeat= [HW] 375 Use software keyboard repeat 376 377 autotest [IA64] 378 379 baycom_epp= [HW,AX25] 380 Format: <io>,<mode> 381 382 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem 383 Format: <io>,<mode> 384 See header of drivers/net/hamradio/baycom_par.c. 385 386 baycom_ser_fdx= [HW,AX25] 387 BayCom Serial Port AX.25 Modem (Full Duplex Mode) 388 Format: <io>,<irq>,<mode>[,<baud>] 389 See header of drivers/net/hamradio/baycom_ser_fdx.c. 390 391 baycom_ser_hdx= [HW,AX25] 392 BayCom Serial Port AX.25 Modem (Half Duplex Mode) 393 Format: <io>,<irq>,<mode> 394 See header of drivers/net/hamradio/baycom_ser_hdx.c. 395 396 boot_delay= Milliseconds to delay each printk during boot. 397 Values larger than 10 seconds (10000) are changed to 398 no delay (0). 399 Format: integer 400 401 bootmem_debug [KNL] Enable bootmem allocator debug messages. 402 403 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) 404 bttv.radio= Most important insmod options are available as 405 kernel args too. 406 bttv.pll= See Documentation/video4linux/bttv/Insmod-options 407 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST 408 409 BusLogic= [HW,SCSI] 410 See drivers/scsi/BusLogic.c, comment before function 411 BusLogic_ParseDriverOptions(). 412 413 c101= [NET] Moxa C101 synchronous serial card 414 415 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. 416 Sometimes CPU hardware bugs make them report the cache 417 size incorrectly. The kernel will attempt work arounds 418 to fix known problems, but for some CPUs it is not 419 possible to determine what the correct size should be. 420 This option provides an override for these situations. 421 422 security= [SECURITY] Choose a security module to enable at boot. 423 If this boot parameter is not specified, only the first 424 security module asking for security registration will be 425 loaded. An invalid security module name will be treated 426 as if no module has been chosen. 427 428 capability.disable= 429 [SECURITY] Disable capabilities. This would normally 430 be used only if an alternative security model is to be 431 configured. Potentially dangerous and should only be 432 used if you are entirely sure of the consequences. 433 434 ccw_timeout_log [S390] 435 See Documentation/s390/CommonIO for details. 436 437 cgroup_disable= [KNL] Disable a particular controller 438 Format: {name of the controller(s) to disable} 439 {Currently supported controllers - "memory"} 440 441 checkreqprot [SELINUX] Set initial checkreqprot flag value. 442 Format: { "0" | "1" } 443 See security/selinux/Kconfig help text. 444 0 -- check protection applied by kernel (includes 445 any implied execute protection). 446 1 -- check protection requested by application. 447 Default value is set via a kernel config option. 448 Value can be changed at runtime via 449 /selinux/checkreqprot. 450 451 cio_ignore= [S390] 452 See Documentation/s390/CommonIO for details. 453 454 clock= [BUGS=X86-32, HW] gettimeofday clocksource override. 455 [Deprecated] 456 Forces specified clocksource (if available) to be used 457 when calculating gettimeofday(). If specified 458 clocksource is not available, it defaults to PIT. 459 Format: { pit | tsc | cyclone | pmtmr } 460 461 clocksource= [GENERIC_TIME] Override the default clocksource 462 Format: <string> 463 Override the default clocksource and use the clocksource 464 with the name specified. 465 Some clocksource names to choose from, depending on 466 the platform: 467 [all] jiffies (this is the base, fallback clocksource) 468 [ACPI] acpi_pm 469 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, 470 pxa_timer,timer3,32k_counter,timer0_1 471 [AVR32] avr32 472 [X86-32] pit,hpet,tsc,vmi-timer; 473 scx200_hrt on Geode; cyclone on IBM x440 474 [MIPS] MIPS 475 [PARISC] cr16 476 [S390] tod 477 [SH] SuperH 478 [SPARC64] tick 479 [X86-64] hpet,tsc 480 481 clearcpuid=BITNUM [X86] 482 Disable CPUID feature X for the kernel. See 483 include/asm-x86/cpufeature.h for the valid bit numbers. 484 Note the Linux specific bits are not necessarily 485 stable over kernel options, but the vendor specific 486 ones should be. 487 Also note that user programs calling CPUID directly 488 or using the feature without checking anything 489 will still see it. This just prevents it from 490 being used by the kernel or shown in /proc/cpuinfo. 491 Also note the kernel might malfunction if you disable 492 some critical bits. 493 494 code_bytes [IA32/X86_64] How many bytes of object code to print 495 in an oops report. 496 Range: 0 - 8192 497 Default: 64 498 499 hpet= [X86-32,HPET] option to control HPET usage 500 Format: { enable (default) | disable | force } 501 disable: disable HPET and use PIT instead 502 force: allow force enabled of undocumented chips (ICH4, 503 VIA, nVidia) 504 505 com20020= [HW,NET] ARCnet - COM20020 chipset 506 Format: 507 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] 508 509 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) 510 Format: <io>[,<irq>] 511 512 com90xx= [HW,NET] 513 ARCnet - COM90xx chipset (memory-mapped buffers) 514 Format: <io>[,<irq>[,<memstart>]] 515 516 condev= [HW,S390] console device 517 conmode= 518 519 console= [KNL] Output console device and options. 520 521 tty<n> Use the virtual console device <n>. 522 523 ttyS<n>[,options] 524 ttyUSB0[,options] 525 Use the specified serial port. The options are of 526 the form "bbbbpnf", where "bbbb" is the baud rate, 527 "p" is parity ("n", "o", or "e"), "n" is number of 528 bits, and "f" is flow control ("r" for RTS or 529 omit it). Default is "9600n8". 530 531 See Documentation/serial-console.txt for more 532 information. See 533 Documentation/networking/netconsole.txt for an 534 alternative. 535 536 uart[8250],io,<addr>[,options] 537 uart[8250],mmio,<addr>[,options] 538 Start an early, polled-mode console on the 8250/16550 539 UART at the specified I/O port or MMIO address, 540 switching to the matching ttyS device later. The 541 options are the same as for ttyS, above. 542 543 If the device connected to the port is not a TTY but a braille 544 device, prepend "brl," before the device type, for instance 545 console=brl,ttyS0 546 For now, only VisioBraille is supported. 547 548 earlycon= [KNL] Output early console device and options. 549 uart[8250],io,<addr>[,options] 550 uart[8250],mmio,<addr>[,options] 551 Start an early, polled-mode console on the 8250/16550 552 UART at the specified I/O port or MMIO address. 553 The options are the same as for ttyS, above. 554 555 no_console_suspend 556 [HW] Never suspend the console 557 Disable suspending of consoles during suspend and 558 hibernate operations. Once disabled, debugging 559 messages can reach various consoles while the rest 560 of the system is being put to sleep (ie, while 561 debugging driver suspend/resume hooks). This may 562 not work reliably with all consoles, but is known 563 to work with serial and VGA consoles. 564 565 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver 566 Format: 567 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] 568 569 crashkernel=nn[KMG]@ss[KMG] 570 [KNL] Reserve a chunk of physical memory to 571 hold a kernel to switch to with kexec on panic. 572 573 crashkernel=range1:size1[,range2:size2,...][@offset] 574 [KNL] Same as above, but depends on the memory 575 in the running system. The syntax of range is 576 start-[end] where start and end are both 577 a memory unit (amount[KMG]). See also 578 Documentation/kdump/kdump.txt for a example. 579 580 cs4232= [HW,OSS] 581 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq> 582 583 cs89x0_dma= [HW,NET] 584 Format: <dma> 585 586 cs89x0_media= [HW,NET] 587 Format: { rj45 | aui | bnc } 588 589 dasd= [HW,NET] 590 See header of drivers/s390/block/dasd_devmap.c. 591 592 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port 593 (one device per port) 594 Format: <port#>,<type> 595 See also Documentation/input/joystick-parport.txt 596 597 debug [KNL] Enable kernel debugging (events log level). 598 599 debug_locks_verbose= 600 [KNL] verbose self-tests 601 Format=<0|1> 602 Print debugging info while doing the locking API 603 self-tests. 604 We default to 0 (no extra messages), setting it to 605 1 will print _a lot_ more information - normally 606 only useful to kernel developers. 607 608 debug_objects [KNL] Enable object debugging 609 610 debugpat [X86] Enable PAT debugging 611 612 decnet.addr= [HW,NET] 613 Format: <area>[,<node>] 614 See also Documentation/networking/decnet.txt. 615 616 vt.default_blu= [VT] 617 Format: <blue0>,<blue1>,<blue2>,...,<blue15> 618 Change the default blue palette of the console. 619 This is a 16-member array composed of values 620 ranging from 0-255. 621 622 vt.default_grn= [VT] 623 Format: <green0>,<green1>,<green2>,...,<green15> 624 Change the default green palette of the console. 625 This is a 16-member array composed of values 626 ranging from 0-255. 627 628 vt.default_red= [VT] 629 Format: <red0>,<red1>,<red2>,...,<red15> 630 Change the default red palette of the console. 631 This is a 16-member array composed of values 632 ranging from 0-255. 633 634 vt.default_utf8= 635 [VT] 636 Format=<0|1> 637 Set system-wide default UTF-8 mode for all tty's. 638 Default is 1, i.e. UTF-8 mode is enabled for all 639 newly opened terminals. 640 641 dhash_entries= [KNL] 642 Set number of hash buckets for dentry cache. 643 644 digi= [HW,SERIAL] 645 IO parameters + enable/disable command. 646 647 digiepca= [HW,SERIAL] 648 See drivers/char/README.epca and 649 Documentation/digiepca.txt. 650 651 disable_mtrr_cleanup [X86] 652 enable_mtrr_cleanup [X86] 653 The kernel tries to adjust MTRR layout from continuous 654 to discrete, to make X server driver able to add WB 655 entry later. This parameter enables/disables that. 656 657 mtrr_chunk_size=nn[KMG] [X86] 658 used for mtrr cleanup. It is largest continous chunk 659 that could hold holes aka. UC entries. 660 661 mtrr_gran_size=nn[KMG] [X86] 662 Used for mtrr cleanup. It is granularity of mtrr block. 663 Default is 1. 664 Large value could prevent small alignment from 665 using up MTRRs. 666 667 mtrr_spare_reg_nr=n [X86] 668 Format: <integer> 669 Range: 0,7 : spare reg number 670 Default : 1 671 Used for mtrr cleanup. It is spare mtrr entries number. 672 Set to 2 or more if your graphical card needs more. 673 674 disable_mtrr_trim [X86, Intel and AMD only] 675 By default the kernel will trim any uncacheable 676 memory out of your available memory pool based on 677 MTRR settings. This parameter disables that behavior, 678 possibly causing your machine to run very slowly. 679 680 dmasound= [HW,OSS] Sound subsystem buffers 681 682 dscc4.setup= [NET] 683 684 dtc3181e= [HW,SCSI] 685 686 earlyprintk= [X86-32,X86-64,SH,BLACKFIN] 687 earlyprintk=vga 688 earlyprintk=serial[,ttySn[,baudrate]] 689 earlyprintk=dbgp 690 691 Append ",keep" to not disable it when the real console 692 takes over. 693 694 Only vga or serial or usb debug port at a time. 695 696 Currently only ttyS0 and ttyS1 are supported. 697 698 Interaction with the standard serial driver is not 699 very good. 700 701 The VGA output is eventually overwritten by the real 702 console. 703 704 eata= [HW,SCSI] 705 706 edd= [EDD] 707 Format: {"off" | "on" | "skip[mbr]"} 708 709 eisa_irq_edge= [PARISC,HW] 710 See header of drivers/parisc/eisa.c. 711 712 elanfreq= [X86-32] 713 See comment before function elanfreq_setup() in 714 arch/x86/kernel/cpu/cpufreq/elanfreq.c. 715 716 elevator= [IOSCHED] 717 Format: {"anticipatory" | "cfq" | "deadline" | "noop"} 718 See Documentation/block/as-iosched.txt and 719 Documentation/block/deadline-iosched.txt for details. 720 721 elfcorehdr= [IA64,PPC,SH,X86-32,X86_64] 722 Specifies physical address of start of kernel core 723 image elf header. Generally kexec loader will 724 pass this option to capture kernel. 725 See Documentation/kdump/kdump.txt for details. 726 727 enforcing [SELINUX] Set initial enforcing status. 728 Format: {"0" | "1"} 729 See security/selinux/Kconfig help text. 730 0 -- permissive (log only, no denials). 731 1 -- enforcing (deny and log). 732 Default value is 0. 733 Value can be changed at runtime via /selinux/enforce. 734 735 es1371= [HW,OSS] 736 Format: <spdif>,[<nomix>,[<amplifier>]] 737 See also header of sound/oss/es1371.c. 738 739 ether= [HW,NET] Ethernet cards parameters 740 This option is obsoleted by the "netdev=" option, which 741 has equivalent usage. See its documentation for details. 742 743 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog. 744 Format: <io>[,<irq>] 745 746 failslab= 747 fail_page_alloc= 748 fail_make_request=[KNL] 749 General fault injection mechanism. 750 Format: <interval>,<probability>,<space>,<times> 751 See also /Documentation/fault-injection/. 752 753 fd_mcs= [HW,SCSI] 754 See header of drivers/scsi/fd_mcs.c. 755 756 fdomain= [HW,SCSI] 757 See header of drivers/scsi/fdomain.c. 758 759 floppy= [HW] 760 See Documentation/floppy.txt. 761 762 force_pal_cache_flush 763 [IA-64] Avoid check_sal_cache_flush which may hang on 764 buggy SAL_CACHE_FLUSH implementations. Using this 765 parameter will force ia64_sal_cache_flush to call 766 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. 767 768 gamecon.map[2|3]= 769 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad 770 support via parallel port (up to 5 devices per port) 771 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> 772 See also Documentation/input/joystick-parport.txt 773 774 gamma= [HW,DRM] 775 776 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART 777 Format: off | on 778 default: on 779 780 gdth= [HW,SCSI] 781 See header of drivers/scsi/gdth.c. 782 783 gpt [EFI] Forces disk with valid GPT signature but 784 invalid Protective MBR to be treated as GPT. 785 786 gvp11= [HW,SCSI] 787 788 hashdist= [KNL,NUMA] Large hashes allocated during boot 789 are distributed across NUMA nodes. Defaults on 790 for IA-64, off otherwise. 791 Format: 0 | 1 (for off | on) 792 793 hcl= [IA-64] SGI's Hardware Graph compatibility layer 794 795 hd= [EIDE] (E)IDE hard drive subsystem geometry 796 Format: <cyl>,<head>,<sect> 797 798 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact 799 size of <nn>. This works even on boxes that have no 800 highmem otherwise. This also works to reduce highmem 801 size on bigger boxes. 802 803 highres= [KNL] Enable/disable high resolution timer mode. 804 Valid parameters: "on", "off" 805 Default: "on" 806 807 hisax= [HW,ISDN] 808 See Documentation/isdn/README.HiSax. 809 810 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot. 811 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages. 812 On x86-64 and powerpc, this option can be specified 813 multiple times interleaved with hugepages= to reserve 814 huge pages of different sizes. Valid pages sizes on 815 x86-64 are 2M (when the CPU supports "pse") and 1G 816 (when the CPU supports the "pdpe1gb" cpuinfo flag) 817 Note that 1GB pages can only be allocated at boot time 818 using hugepages= and not freed afterwards. 819 default_hugepagesz= 820 [same as hugepagesz=] The size of the default 821 HugeTLB page size. This is the size represented by 822 the legacy /proc/ hugepages APIs, used for SHM, and 823 default size when mounting hugetlbfs filesystems. 824 Defaults to the default architecture's huge page size 825 if not specified. 826 827 hlt [BUGS=ARM,SH] 828 829 i8042.debug [HW] Toggle i8042 debug mode 830 i8042.direct [HW] Put keyboard port into non-translated mode 831 i8042.dumbkbd [HW] Pretend that controller can only read data from 832 keyboard and cannot control its state 833 (Don't attempt to blink the leds) 834 i8042.noaux [HW] Don't check for auxiliary (== mouse) port 835 i8042.nokbd [HW] Don't check/create keyboard port 836 i8042.noloop [HW] Disable the AUX Loopback command while probing 837 for the AUX port 838 i8042.nomux [HW] Don't check presence of an active multiplexing 839 controller 840 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX 841 controllers 842 i8042.panicblink= 843 [HW] Frequency with which keyboard LEDs should blink 844 when kernel panics (default is 0.5 sec) 845 i8042.reset [HW] Reset the controller during init and cleanup 846 i8042.unlock [HW] Unlock (ignore) the keylock 847 848 i810= [HW,DRM] 849 850 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data 851 indicates that the driver is running on unsupported 852 hardware. 853 i8k.force [HW] Activate i8k driver even if SMM BIOS signature 854 does not match list of supported models. 855 i8k.power_status 856 [HW] Report power status in /proc/i8k 857 (disabled by default) 858 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN 859 capability is set. 860 861 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter 862 See Documentation/mca.txt. 863 864 icn= [HW,ISDN] 865 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] 866 867 ide= [HW] (E)IDE subsystem 868 Format: ide=nodma or ide=doubler 869 See Documentation/ide/ide.txt. 870 871 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed 872 See Documentation/ide/ide.txt. 873 874 idle= [X86] 875 Format: idle=poll or idle=mwait, idle=halt, idle=nomwait 876 Poll forces a polling idle loop that can slightly improves the performance 877 of waking up a idle CPU, but will use a lot of power and make the system 878 run hot. Not recommended. 879 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose 880 to not use it because it doesn't save as much power as a normal idle 881 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same 882 as idle=poll. 883 idle=halt. Halt is forced to be used for CPU idle. 884 In such case C2/C3 won't be used again. 885 idle=nomwait. Disable mwait for CPU C-states 886 887 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem 888 Claim all unknown PCI IDE storage controllers. 889 890 ignore_loglevel [KNL] 891 Ignore loglevel setting - this will print /all/ 892 kernel messages to the console. Useful for debugging. 893 894 ihash_entries= [KNL] 895 Set number of hash buckets for inode cache. 896 897 in2000= [HW,SCSI] 898 See header of drivers/scsi/in2000.c. 899 900 init= [KNL] 901 Format: <full_path> 902 Run specified binary instead of /sbin/init as init 903 process. 904 905 initcall_debug [KNL] Trace initcalls as they are executed. Useful 906 for working out where the kernel is dying during 907 startup. 908 909 initrd= [BOOT] Specify the location of the initial ramdisk 910 911 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver 912 Format: <irq> 913 914 inttest= [IA64] 915 916 iommu= [x86] 917 off 918 force 919 noforce 920 biomerge 921 panic 922 nopanic 923 merge 924 nomerge 925 forcesac 926 soft 927 928 929 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option 930 off 931 Disable intel iommu driver. 932 igfx_off [Default Off] 933 By default, gfx is mapped as normal device. If a gfx 934 device has a dedicated DMAR unit, the DMAR unit is 935 bypassed by not enabling DMAR with this option. In 936 this case, gfx device will use physical address for 937 DMA. 938 forcedac [x86_64] 939 With this option iommu will not optimize to look 940 for io virtual address below 32 bit forcing dual 941 address cycle on pci bus for cards supporting greater 942 than 32 bit addressing. The default is to look 943 for translation below 32 bit and if not available 944 then look in the higher range. 945 strict [Default Off] 946 With this option on every unmap_single operation will 947 result in a hardware IOTLB flush operation as opposed 948 to batching them for performance. 949 950 io_delay= [X86-32,X86-64] I/O delay method 951 0x80 952 Standard port 0x80 based delay 953 0xed 954 Alternate port 0xed based delay (needed on some systems) 955 udelay 956 Simple two microseconds delay 957 none 958 No delay 959 960 io7= [HW] IO7 for Marvel based alpha systems 961 See comment before marvel_specify_io7 in 962 arch/alpha/kernel/core_marvel.c. 963 964 ip= [IP_PNP] 965 See Documentation/filesystems/nfsroot.txt. 966 967 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards 968 See comment before ip2_setup() in 969 drivers/char/ip2/ip2base.c. 970 971 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller 972 See header of drivers/scsi/ips.c. 973 974 ports= [IP_VS_FTP] IPVS ftp helper module 975 Default is 21. 976 Up to 8 (IP_VS_APP_MAX_PORTS) ports 977 may be specified. 978 Format: <port>,<port>.... 979 980 irqfixup [HW] 981 When an interrupt is not handled search all handlers 982 for it. Intended to get systems with badly broken 983 firmware running. 984 985 irqpoll [HW] 986 When an interrupt is not handled search all handlers 987 for it. Also check all handlers each timer 988 interrupt. Intended to get systems with badly broken 989 firmware running. 990 991 isapnp= [ISAPNP] 992 Format: <RDP>,<reset>,<pci_scan>,<verbosity> 993 994 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler. 995 Format: 996 <cpu number>,...,<cpu number> 997 or 998 <cpu number>-<cpu number> (must be a positive range in ascending order) 999 or a mixture 1000 <cpu number>,...,<cpu number>-<cpu number> 1001 This option can be used to specify one or more CPUs 1002 to isolate from the general SMP balancing and scheduling 1003 algorithms. The only way to move a process onto or off 1004 an "isolated" CPU is via the CPU affinity syscalls. 1005 <cpu number> begins at 0 and the maximum value is 1006 "number of CPUs in system - 1". 1007 1008 This option is the preferred way to isolate CPUs. The 1009 alternative -- manually setting the CPU mask of all 1010 tasks in the system -- can cause problems and 1011 suboptimal load balancer performance. 1012 1013 iucv= [HW,NET] 1014 1015 js= [HW,JOY] Analog joystick 1016 See Documentation/input/joystick.txt. 1017 1018 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter 1019 specifies the amount of memory usable by the kernel 1020 for non-movable allocations. The requested amount is 1021 spread evenly throughout all nodes in the system. The 1022 remaining memory in each node is used for Movable 1023 pages. In the event, a node is too small to have both 1024 kernelcore and Movable pages, kernelcore pages will 1025 take priority and other nodes will have a larger number 1026 of kernelcore pages. The Movable zone is used for the 1027 allocation of pages that may be reclaimed or moved 1028 by the page migration subsystem. This means that 1029 HugeTLB pages may not be allocated from this zone. 1030 Note that allocations like PTEs-from-HighMem still 1031 use the HighMem zone if it exists, and the Normal 1032 zone if it does not. 1033 1034 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter 1035 is similar to kernelcore except it specifies the 1036 amount of memory used for migratable allocations. 1037 If both kernelcore and movablecore is specified, 1038 then kernelcore will be at *least* the specified 1039 value but may be more. If movablecore on its own 1040 is specified, the administrator must be careful 1041 that the amount of memory usable for all allocations 1042 is not too small. 1043 1044 keepinitrd [HW,ARM] 1045 1046 kstack=N [X86-32,X86-64] Print N words from the kernel stack 1047 in oops dumps. 1048 1049 kgdboc= [HW] kgdb over consoles. 1050 Requires a tty driver that supports console polling. 1051 (only serial suported for now) 1052 Format: <serial_device>[,baud] 1053 1054 kmac= [MIPS] korina ethernet MAC address. 1055 Configure the RouterBoard 532 series on-chip 1056 Ethernet adapter MAC address. 1057 1058 l2cr= [PPC] 1059 1060 l3cr= [PPC] 1061 1062 lapic [X86-32,APIC] Enable the local APIC even if BIOS 1063 disabled it. 1064 1065 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in 1066 C2 power state. 1067 1068 libata.dma= [LIBATA] DMA control 1069 libata.dma=0 Disable all PATA and SATA DMA 1070 libata.dma=1 PATA and SATA Disk DMA only 1071 libata.dma=2 ATAPI (CDROM) DMA only 1072 libata.dma=4 Compact Flash DMA only 1073 Combinations also work, so libata.dma=3 enables DMA 1074 for disks and CDROMs, but not CFs. 1075 1076 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume 1077 when set. 1078 Format: <int> 1079 1080 libata.force= [LIBATA] Force configurations. The format is comma 1081 separated list of "[ID:]VAL" where ID is 1082 PORT[:DEVICE]. PORT and DEVICE are decimal numbers 1083 matching port, link or device. Basically, it matches 1084 the ATA ID string printed on console by libata. If 1085 the whole ID part is omitted, the last PORT and DEVICE 1086 values are used. If ID hasn't been specified yet, the 1087 configuration applies to all ports, links and devices. 1088 1089 If only DEVICE is omitted, the parameter applies to 1090 the port and all links and devices behind it. DEVICE 1091 number of 0 either selects the first device or the 1092 first fan-out link behind PMP device. It does not 1093 select the host link. DEVICE number of 15 selects the 1094 host link and device attached to it. 1095 1096 The VAL specifies the configuration to force. As long 1097 as there's no ambiguity shortcut notation is allowed. 1098 For example, both 1.5 and 1.5G would work for 1.5Gbps. 1099 The following configurations can be forced. 1100 1101 * Cable type: 40c, 80c, short40c, unk, ign or sata. 1102 Any ID with matching PORT is used. 1103 1104 * SATA link speed limit: 1.5Gbps or 3.0Gbps. 1105 1106 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. 1107 udma[/][16,25,33,44,66,100,133] notation is also 1108 allowed. 1109 1110 * [no]ncq: Turn on or off NCQ. 1111 1112 * nohrst, nosrst, norst: suppress hard, soft 1113 and both resets. 1114 1115 If there are multiple matching configurations changing 1116 the same attribute, the last one is used. 1117 1118 load_ramdisk= [RAM] List of ramdisks to load from floppy 1119 See Documentation/ramdisk.txt. 1120 1121 lockd.nlm_grace_period=P [NFS] Assign grace period. 1122 Format: <integer> 1123 1124 lockd.nlm_tcpport=N [NFS] Assign TCP port. 1125 Format: <integer> 1126 1127 lockd.nlm_timeout=T [NFS] Assign timeout value. 1128 Format: <integer> 1129 1130 lockd.nlm_udpport=M [NFS] Assign UDP port. 1131 Format: <integer> 1132 1133 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver 1134 Format: <irq> 1135 1136 loglevel= All Kernel Messages with a loglevel smaller than the 1137 console loglevel will be printed to the console. It can 1138 also be changed with klogd or other programs. The 1139 loglevels are defined as follows: 1140 1141 0 (KERN_EMERG) system is unusable 1142 1 (KERN_ALERT) action must be taken immediately 1143 2 (KERN_CRIT) critical conditions 1144 3 (KERN_ERR) error conditions 1145 4 (KERN_WARNING) warning conditions 1146 5 (KERN_NOTICE) normal but significant condition 1147 6 (KERN_INFO) informational 1148 7 (KERN_DEBUG) debug-level messages 1149 1150 log_buf_len=n Sets the size of the printk ring buffer, in bytes. 1151 Format: { n | nk | nM } 1152 n must be a power of two. The default size 1153 is set in the kernel config file. 1154 1155 logo.nologo [FB] Disables display of the built-in Linux logo. 1156 This may be used to provide more screen space for 1157 kernel log messages and is useful when debugging 1158 kernel boot problems. 1159 1160 lp=0 [LP] Specify parallel ports to use, e.g, 1161 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses 1162 lp=reset first parallel port). 'lp=0' disables the 1163 lp=auto printer driver. 'lp=reset' (which can be 1164 specified in addition to the ports) causes 1165 attached printers to be reset. Using 1166 lp=port1,port2,... specifies the parallel ports 1167 to associate lp devices with, starting with 1168 lp0. A port specification may be 'none' to skip 1169 that lp device, or a parport name such as 1170 'parport0'. Specifying 'lp=auto' instead of a 1171 port specification list means that device IDs 1172 from each port should be examined, to see if 1173 an IEEE 1284-compliant printer is attached; if 1174 so, the driver will manage that printer. 1175 See also header of drivers/char/lp.c. 1176 1177 lpj=n [KNL] 1178 Sets loops_per_jiffy to given constant, thus avoiding 1179 time-consuming boot-time autodetection (up to 250 ms per 1180 CPU). 0 enables autodetection (default). To determine 1181 the correct value for your kernel, boot with normal 1182 autodetection and see what value is printed. Note that 1183 on SMP systems the preset will be applied to all CPUs, 1184 which is likely to cause problems if your CPUs need 1185 significantly divergent settings. An incorrect value 1186 will cause delays in the kernel to be wrong, leading to 1187 unpredictable I/O errors and other breakage. Although 1188 unlikely, in the extreme case this might damage your 1189 hardware. 1190 1191 ltpc= [NET] 1192 Format: <io>,<irq>,<dma> 1193 1194 mac5380= [HW,SCSI] Format: 1195 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags> 1196 1197 machvec= [IA64] Force the use of a particular machine-vector 1198 (machvec) in a generic kernel. 1199 Example: machvec=hpzx1_swiotlb 1200 1201 max_loop= [LOOP] Maximum number of loopback devices that can 1202 be mounted 1203 Format: <1-256> 1204 1205 maxcpus= [SMP] Maximum number of processors that an SMP kernel 1206 should make use of. maxcpus=n : n >= 0 limits the 1207 kernel to using 'n' processors. n=0 is a special case, 1208 it is equivalent to "nosmp", which also disables 1209 the IO APIC. 1210 1211 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or 1212 equal to this physical address is ignored. 1213 1214 max_luns= [SCSI] Maximum number of LUNs to probe. 1215 Should be between 1 and 2^32-1. 1216 1217 max_report_luns= 1218 [SCSI] Maximum number of LUNs received. 1219 Should be between 1 and 16384. 1220 1221 mcatest= [IA-64] 1222 1223 mce [X86-32] Machine Check Exception 1224 1225 mce=option [X86-64] See Documentation/x86_64/boot-options.txt 1226 1227 md= [HW] RAID subsystems devices and level 1228 See Documentation/md.txt. 1229 1230 mdacon= [MDA] 1231 Format: <first>,<last> 1232 Specifies range of consoles to be captured by the MDA. 1233 1234 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory 1235 Amount of memory to be used when the kernel is not able 1236 to see the whole system memory or for test. 1237 [X86-32] Use together with memmap= to avoid physical 1238 address space collisions. Without memmap= PCI devices 1239 could be placed at addresses belonging to unused RAM. 1240 1241 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel 1242 memory. 1243 1244 memchunk=nn[KMG] 1245 [KNL,SH] Allow user to override the default size for 1246 per-device physically contiguous DMA buffers. 1247 1248 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact 1249 E820 memory map, as specified by the user. 1250 Such memmap=exactmap lines can be constructed based on 1251 BIOS output or other requirements. See the memmap=nn@ss 1252 option description. 1253 1254 memmap=nn[KMG]@ss[KMG] 1255 [KNL] Force usage of a specific region of memory 1256 Region of memory to be used, from ss to ss+nn. 1257 1258 memmap=nn[KMG]#ss[KMG] 1259 [KNL,ACPI] Mark specific memory as ACPI data. 1260 Region of memory to be used, from ss to ss+nn. 1261 1262 memmap=nn[KMG]$ss[KMG] 1263 [KNL,ACPI] Mark specific memory as reserved. 1264 Region of memory to be used, from ss to ss+nn. 1265 Example: Exclude memory from 0x18690000-0x1869ffff 1266 memmap=64K$0x18690000 1267 or 1268 memmap=0x10000$0x18690000 1269 1270 memory_corruption_check=0/1 [X86] 1271 Some BIOSes seem to corrupt the first 64k of 1272 memory when doing things like suspend/resume. 1273 Setting this option will scan the memory 1274 looking for corruption. Enabling this will 1275 both detect corruption and prevent the kernel 1276 from using the memory being corrupted. 1277 However, its intended as a diagnostic tool; if 1278 repeatable BIOS-originated corruption always 1279 affects the same memory, you can use memmap= 1280 to prevent the kernel from using that memory. 1281 1282 memory_corruption_check_size=size [X86] 1283 By default it checks for corruption in the low 1284 64k, making this memory unavailable for normal 1285 use. Use this parameter to scan for 1286 corruption in more or less memory. 1287 1288 memory_corruption_check_period=seconds [X86] 1289 By default it checks for corruption every 60 1290 seconds. Use this parameter to check at some 1291 other rate. 0 disables periodic checking. 1292 1293 memtest= [KNL,X86] Enable memtest 1294 Format: <integer> 1295 range: 0,4 : pattern number 1296 default : 0 <disable> 1297 1298 meye.*= [HW] Set MotionEye Camera parameters 1299 See Documentation/video4linux/meye.txt. 1300 1301 mfgpt_irq= [IA-32] Specify the IRQ to use for the 1302 Multi-Function General Purpose Timers on AMD Geode 1303 platforms. 1304 1305 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when 1306 the BIOS has incorrectly applied a workaround. TinyBIOS 1307 version 0.98 is known to be affected, 0.99 fixes the 1308 problem by letting the user disable the workaround. 1309 1310 mga= [HW,DRM] 1311 1312 mminit_loglevel= 1313 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this 1314 parameter allows control of the logging verbosity for 1315 the additional memory initialisation checks. A value 1316 of 0 disables mminit logging and a level of 4 will 1317 log everything. Information is printed at KERN_DEBUG 1318 so loglevel=8 may also need to be specified. 1319 1320 mousedev.tap_time= 1321 [MOUSE] Maximum time between finger touching and 1322 leaving touchpad surface for touch to be considered 1323 a tap and be reported as a left button click (for 1324 touchpads working in absolute mode only). 1325 Format: <msecs> 1326 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices 1327 reporting absolute coordinates, such as tablets 1328 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices 1329 reporting absolute coordinates, such as tablets 1330 1331 mpu401= [HW,OSS] 1332 Format: <io>,<irq> 1333 1334 MTD_Partition= [MTD] 1335 Format: <name>,<region-number>,<size>,<offset> 1336 1337 MTD_Region= [MTD] Format: 1338 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] 1339 1340 mtdparts= [MTD] 1341 See drivers/mtd/cmdlinepart.c. 1342 1343 mtdset= [ARM] 1344 ARM/S3C2412 JIVE boot control 1345 1346 See arch/arm/mach-s3c2412/mach-jive.c 1347 1348 mtouchusb.raw_coordinates= 1349 [HW] Make the MicroTouch USB driver use raw coordinates 1350 ('y', default) or cooked coordinates ('n') 1351 1352 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card 1353 1354 NCR_D700= [HW,SCSI] 1355 See header of drivers/scsi/NCR_D700.c. 1356 1357 ncr5380= [HW,SCSI] 1358 1359 ncr53c400= [HW,SCSI] 1360 1361 ncr53c400a= [HW,SCSI] 1362 1363 ncr53c406a= [HW,SCSI] 1364 1365 ncr53c8xx= [HW,SCSI] 1366 1367 netdev= [NET] Network devices parameters 1368 Format: <irq>,<io>,<mem_start>,<mem_end>,<name> 1369 Note that mem_start is often overloaded to mean 1370 something different and driver-specific. 1371 This usage is only documented in each driver source 1372 file if at all. 1373 1374 nf_conntrack.acct= 1375 [NETFILTER] Enable connection tracking flow accounting 1376 0 to disable accounting 1377 1 to enable accounting 1378 Default value depends on CONFIG_NF_CT_ACCT that is 1379 going to be removed in 2.6.29. 1380 1381 nfsaddrs= [NFS] 1382 See Documentation/filesystems/nfsroot.txt. 1383 1384 nfsroot= [NFS] nfs root filesystem for disk-less boxes. 1385 See Documentation/filesystems/nfsroot.txt. 1386 1387 nfs.callback_tcpport= 1388 [NFS] set the TCP port on which the NFSv4 callback 1389 channel should listen. 1390 1391 nfs.idmap_cache_timeout= 1392 [NFS] set the maximum lifetime for idmapper cache 1393 entries. 1394 1395 nfs.enable_ino64= 1396 [NFS] enable 64-bit inode numbers. 1397 If zero, the NFS client will fake up a 32-bit inode 1398 number for the readdir() and stat() syscalls instead 1399 of returning the full 64-bit number. 1400 The default is to return 64-bit inode numbers. 1401 1402 nmi_debug= [KNL,AVR32] Specify one or more actions to take 1403 when a NMI is triggered. 1404 Format: [state][,regs][,debounce][,die] 1405 1406 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels 1407 1408 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths 1409 emulation library even if a 387 maths coprocessor 1410 is present. 1411 1412 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien 1413 caches in the slab allocator. Saves per-node memory, 1414 but will impact performance. 1415 1416 noalign [KNL,ARM] 1417 1418 noapic [SMP,APIC] Tells the kernel to not make use of any 1419 IOAPICs that may be present in the system. 1420 1421 nobats [PPC] Do not use BATs for mapping kernel lowmem 1422 on "Classic" PPC cores. 1423 1424 nocache [ARM] 1425 1426 nodelayacct [KNL] Disable per-task delay accounting 1427 1428 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects. 1429 1430 nodsp [SH] Disable hardware DSP at boot time. 1431 1432 noefi [X86-32,X86-64] Disable EFI runtime services support. 1433 1434 noexec [IA-64] 1435 1436 noexec [X86-32,X86-64] 1437 On X86-32 available only on PAE configured kernels. 1438 noexec=on: enable non-executable mappings (default) 1439 noexec=off: disable non-executable mappings 1440 1441 noexec32 [X86-64] 1442 This affects only 32-bit executables. 1443 noexec32=on: enable non-executable mappings (default) 1444 read doesn't imply executable mappings 1445 noexec32=off: disable non-executable mappings 1446 read implies executable mappings 1447 1448 nofpu [SH] Disable hardware FPU at boot time. 1449 1450 nofxsr [BUGS=X86-32] Disables x86 floating point extended 1451 register save and restore. The kernel will only save 1452 legacy floating-point registers on task switch. 1453 1454 noclflush [BUGS=X86] Don't use the CLFLUSH instruction 1455 1456 nohlt [BUGS=ARM,SH] 1457 1458 no-hlt [BUGS=X86-32] Tells the kernel that the hlt 1459 instruction doesn't work correctly and not to 1460 use it. 1461 1462 nohalt [IA-64] Tells the kernel not to use the power saving 1463 function PAL_HALT_LIGHT when idle. This increases 1464 power-consumption. On the positive side, it reduces 1465 interrupt wake-up latency, which may improve performance 1466 in certain environments such as networked servers or 1467 real-time systems. 1468 1469 nohz= [KNL] Boottime enable/disable dynamic ticks 1470 Valid arguments: on, off 1471 Default: on 1472 1473 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing 1474 1475 noirqdebug [X86-32] Disables the code which attempts to detect and 1476 disable unhandled interrupt sources. 1477 1478 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for 1479 broken timer IRQ sources. 1480 1481 noisapnp [ISAPNP] Disables ISA PnP code. 1482 1483 noinitrd [RAM] Tells the kernel not to load any configured 1484 initial RAM disk. 1485 1486 nointroute [IA-64] 1487 1488 nojitter [IA64] Disables jitter checking for ITC timers. 1489 1490 nolapic [X86-32,APIC] Do not enable or use the local APIC. 1491 1492 nolapic_timer [X86-32,APIC] Do not use the local APIC timer. 1493 1494 nox2apic [X86-64,APIC] Do not enable x2APIC mode. 1495 1496 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of 1497 default x2apic cluster mode on platforms 1498 supporting x2apic. 1499 1500 noltlbs [PPC] Do not use large page/tlb entries for kernel 1501 lowmem mapping on PPC40x. 1502 1503 nomca [IA-64] Disable machine check abort handling 1504 1505 nomce [X86-32] Machine Check Exception 1506 1507 nomfgpt [X86-32] Disable Multi-Function General Purpose 1508 Timer usage (for AMD Geode machines). 1509 1510 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops 1511 1512 noreplace-smp [X86-32,SMP] Don't replace SMP instructions 1513 with UP alternatives 1514 1515 noresidual [PPC] Don't use residual data on PReP machines. 1516 1517 noresume [SWSUSP] Disables resume and restores original swap 1518 space. 1519 1520 no-scroll [VGA] Disables scrollback. 1521 This is required for the Braillex ib80-piezo Braille 1522 reader made by F.H. Papenmeier (Germany). 1523 1524 nosbagart [IA-64] 1525 1526 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support. 1527 1528 nosmp [SMP] Tells an SMP kernel to act as a UP kernel, 1529 and disable the IO APIC. legacy for "maxcpus=0". 1530 1531 nosoftlockup [KNL] Disable the soft-lockup detector. 1532 1533 nosync [HW,M68K] Disables sync negotiation for all devices. 1534 1535 notsc [BUGS=X86-32] Disable Time Stamp Counter 1536 1537 nousb [USB] Disable the USB subsystem 1538 1539 nowb [ARM] 1540 1541 nptcg= [IA64] Override max number of concurrent global TLB 1542 purges which is reported from either PAL_VM_SUMMARY or 1543 SAL PALO. 1544 1545 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. 1546 one of ['zone', 'node', 'default'] can be specified 1547 This can be set from sysctl after boot. 1548 See Documentation/sysctl/vm.txt for details. 1549 1550 nr_uarts= [SERIAL] maximum number of UARTs to be registered. 1551 1552 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands 1553 Rather than timing out after 20 ms if an EC 1554 command is not properly ACKed, override the length 1555 of the timeout. We have interrupts disabled while 1556 waiting for the ACK, so if this is set too high 1557 interrupts *may* be lost! 1558 1559 opl3= [HW,OSS] 1560 Format: <io> 1561 1562 oprofile.timer= [HW] 1563 Use timer interrupt instead of performance counters 1564 1565 osst= [HW,SCSI] SCSI Tape Driver 1566 Format: <buffer_size>,<write_threshold> 1567 See also Documentation/scsi/st.txt. 1568 1569 panic= [KNL] Kernel behaviour on panic 1570 Format: <timeout> 1571 1572 parkbd.port= [HW] Parallel port number the keyboard adapter is 1573 connected to, default is 0. 1574 Format: <parport#> 1575 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, 1576 0 for XT, 1 for AT (default is AT). 1577 Format: <mode> 1578 1579 parport= [HW,PPT] Specify parallel ports. 0 disables. 1580 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } 1581 Use 'auto' to force the driver to use any 1582 IRQ/DMA settings detected (the default is to 1583 ignore detected IRQ/DMA settings because of 1584 possible conflicts). You can specify the base 1585 address, IRQ, and DMA settings; IRQ and DMA 1586 should be numbers, or 'auto' (for using detected 1587 settings on that particular port), or 'nofifo' 1588 (to avoid using a FIFO even if it is detected). 1589 Parallel ports are assigned in the order they 1590 are specified on the command line, starting 1591 with parport0. 1592 1593 parport_init_mode= [HW,PPT] 1594 Configure VIA parallel port to operate in 1595 a specific mode. This is necessary on Pegasos 1596 computer where firmware has no options for setting 1597 up parallel port mode and sets it to spp. 1598 Currently this function knows 686a and 8231 chips. 1599 Format: [spp|ps2|epp|ecp|ecpepp] 1600 1601 pas2= [HW,OSS] Format: 1602 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16> 1603 1604 pas16= [HW,SCSI] 1605 See header of drivers/scsi/pas16.c. 1606 1607 pause_on_oops= 1608 Halt all CPUs after the first oops has been printed for 1609 the specified number of seconds. This is to be used if 1610 your oopses keep scrolling off the screen. 1611 1612 pcbit= [HW,ISDN] 1613 1614 pcd. [PARIDE] 1615 See header of drivers/block/paride/pcd.c. 1616 See also Documentation/paride.txt. 1617 1618 pci=option[,option...] [PCI] various PCI subsystem options: 1619 off [X86] don't probe for the PCI bus 1620 bios [X86-32] force use of PCI BIOS, don't access 1621 the hardware directly. Use this if your machine 1622 has a non-standard PCI host bridge. 1623 nobios [X86-32] disallow use of PCI BIOS, only direct 1624 hardware access methods are allowed. Use this 1625 if you experience crashes upon bootup and you 1626 suspect they are caused by the BIOS. 1627 conf1 [X86] Force use of PCI Configuration 1628 Mechanism 1. 1629 conf2 [X86] Force use of PCI Configuration 1630 Mechanism 2. 1631 noaer [PCIE] If the PCIEAER kernel config parameter is 1632 enabled, this kernel boot option can be used to 1633 disable the use of PCIE advanced error reporting. 1634 nodomains [PCI] Disable support for multiple PCI 1635 root domains (aka PCI segments, in ACPI-speak). 1636 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI 1637 Configuration 1638 nomsi [MSI] If the PCI_MSI kernel config parameter is 1639 enabled, this kernel boot option can be used to 1640 disable the use of MSI interrupts system-wide. 1641 biosirq [X86-32] Use PCI BIOS calls to get the interrupt 1642 routing table. These calls are known to be buggy 1643 on several machines and they hang the machine 1644 when used, but on other computers it's the only 1645 way to get the interrupt routing table. Try 1646 this option if the kernel is unable to allocate 1647 IRQs or discover secondary PCI buses on your 1648 motherboard. 1649 rom [X86] Assign address space to expansion ROMs. 1650 Use with caution as certain devices share 1651 address decoders between ROMs and other 1652 resources. 1653 norom [X86] Do not assign address space to 1654 expansion ROMs that do not already have 1655 BIOS assigned address ranges. 1656 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be 1657 assigned automatically to PCI devices. You can 1658 make the kernel exclude IRQs of your ISA cards 1659 this way. 1660 pirqaddr=0xAAAAA [X86] Specify the physical address 1661 of the PIRQ table (normally generated 1662 by the BIOS) if it is outside the 1663 F0000h-100000h range. 1664 lastbus=N [X86] Scan all buses thru bus #N. Can be 1665 useful if the kernel is unable to find your 1666 secondary buses and you want to tell it 1667 explicitly which ones they are. 1668 assign-busses [X86] Always assign all PCI bus 1669 numbers ourselves, overriding 1670 whatever the firmware may have done. 1671 usepirqmask [X86] Honor the possible IRQ mask stored 1672 in the BIOS $PIR table. This is needed on 1673 some systems with broken BIOSes, notably 1674 some HP Pavilion N5400 and Omnibook XE3 1675 notebooks. This will have no effect if ACPI 1676 IRQ routing is enabled. 1677 noacpi [X86] Do not use ACPI for IRQ routing 1678 or for PCI scanning. 1679 use_crs [X86] Use _CRS for PCI resource 1680 allocation. 1681 routeirq Do IRQ routing for all PCI devices. 1682 This is normally done in pci_enable_device(), 1683 so this option is a temporary workaround 1684 for broken drivers that don't call it. 1685 skip_isa_align [X86] do not align io start addr, so can 1686 handle more pci cards 1687 firmware [ARM] Do not re-enumerate the bus but instead 1688 just use the configuration from the 1689 bootloader. This is currently used on 1690 IXP2000 systems where the bus has to be 1691 configured a certain way for adjunct CPUs. 1692 noearly [X86] Don't do any early type 1 scanning. 1693 This might help on some broken boards which 1694 machine check when some devices' config space 1695 is read. But various workarounds are disabled 1696 and some IOMMU drivers will not work. 1697 bfsort Sort PCI devices into breadth-first order. 1698 This sorting is done to get a device 1699 order compatible with older (<= 2.4) kernels. 1700 nobfsort Don't sort PCI devices into breadth-first order. 1701 cbiosize=nn[KMG] The fixed amount of bus space which is 1702 reserved for the CardBus bridge's IO window. 1703 The default value is 256 bytes. 1704 cbmemsize=nn[KMG] The fixed amount of bus space which is 1705 reserved for the CardBus bridge's memory 1706 window. The default value is 64 megabytes. 1707 1708 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power 1709 Management. 1710 off Disable ASPM. 1711 force Enable ASPM even on devices that claim not to support it. 1712 WARNING: Forcing ASPM on may cause system lockups. 1713 1714 pcmv= [HW,PCMCIA] BadgePAD 4 1715 1716 pd. [PARIDE] 1717 See Documentation/paride.txt. 1718 1719 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at 1720 boot time. 1721 Format: { 0 | 1 } 1722 See arch/parisc/kernel/pdc_chassis.c 1723 1724 pf. [PARIDE] 1725 See Documentation/paride.txt. 1726 1727 pg. [PARIDE] 1728 See Documentation/paride.txt. 1729 1730 pirq= [SMP,APIC] Manual mp-table setup 1731 See Documentation/i386/IO-APIC.txt. 1732 1733 plip= [PPT,NET] Parallel port network link 1734 Format: { parport<nr> | timid | 0 } 1735 See also Documentation/parport.txt. 1736 1737 pmtmr= [X86] Manual setup of pmtmr I/O Port. 1738 Override pmtimer IOPort with a hex value. 1739 e.g. pmtmr=0x508 1740 1741 pnp.debug [PNP] 1742 Enable PNP debug messages. This depends on the 1743 CONFIG_PNP_DEBUG_MESSAGES option. 1744 1745 pnpacpi= [ACPI] 1746 { off } 1747 1748 pnpbios= [ISAPNP] 1749 { on | off | curr | res | no-curr | no-res } 1750 1751 pnp_reserve_irq= 1752 [ISAPNP] Exclude IRQs for the autoconfiguration 1753 1754 pnp_reserve_dma= 1755 [ISAPNP] Exclude DMAs for the autoconfiguration 1756 1757 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration 1758 Ranges are in pairs (I/O port base and size). 1759 1760 pnp_reserve_mem= 1761 [ISAPNP] Exclude memory regions for the 1762 autoconfiguration. 1763 Ranges are in pairs (memory base and size). 1764 1765 dynamic_printk 1766 Enables pr_debug()/dev_dbg() calls if 1767 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. These can also 1768 be switched on/off via <debugfs>/dynamic_printk/modules 1769 1770 print-fatal-signals= 1771 [KNL] debug: print fatal signals 1772 print-fatal-signals=1: print segfault info to 1773 the kernel console. 1774 default: off. 1775 1776 printk.time= Show timing data prefixed to each printk message line 1777 Format: <bool> (1/Y/y=enable, 0/N/n=disable) 1778 1779 profile= [KNL] Enable kernel profiling via /proc/profile 1780 Format: [schedule,]<number> 1781 Param: "schedule" - profile schedule points. 1782 Param: <number> - step/bucket size as a power of 2 for 1783 statistical time based profiling. 1784 Param: "sleep" - profile D-state sleeping (millisecs). 1785 Requires CONFIG_SCHEDSTATS 1786 Param: "kvm" - profile VM exits. 1787 1788 processor.max_cstate= [HW,ACPI] 1789 Limit processor to maximum C-state 1790 max_cstate=9 overrides any DMI blacklist limit. 1791 1792 processor.nocst [HW,ACPI] 1793 Ignore the _CST method to determine C-states, 1794 instead using the legacy FADT method 1795 1796 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk 1797 before loading. 1798 See Documentation/ramdisk.txt. 1799 1800 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to 1801 probe for; one of (bare|imps|exps|lifebook|any). 1802 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports 1803 per second. 1804 psmouse.resetafter= [HW,MOUSE] 1805 Try to reset the device after so many bad packets 1806 (0 = never). 1807 psmouse.resolution= 1808 [HW,MOUSE] Set desired mouse resolution, in dpi. 1809 psmouse.smartscroll= 1810 [HW,MOUSE] Controls Logitech smartscroll autorepeat. 1811 0 = disabled, 1 = enabled (default). 1812 1813 pss= [HW,OSS] Personal Sound System (ECHO ESC614) 1814 Format: 1815 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq> 1816 1817 pt. [PARIDE] 1818 See Documentation/paride.txt. 1819 1820 pty.legacy_count= 1821 [KNL] Number of legacy pty's. Overwrites compiled-in 1822 default number. 1823 1824 quiet [KNL] Disable most log messages 1825 1826 r128= [HW,DRM] 1827 1828 raid= [HW,RAID] 1829 See Documentation/md.txt. 1830 1831 ramdisk_blocksize= [RAM] 1832 See Documentation/ramdisk.txt. 1833 1834 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes 1835 See Documentation/ramdisk.txt. 1836 1837 rcupdate.blimit= [KNL,BOOT] 1838 Set maximum number of finished RCU callbacks to process 1839 in one batch. 1840 1841 rcupdate.qhimark= [KNL,BOOT] 1842 Set threshold of queued 1843 RCU callbacks over which batch limiting is disabled. 1844 1845 rcupdate.qlowmark= [KNL,BOOT] 1846 Set threshold of queued RCU callbacks below which 1847 batch limiting is re-enabled. 1848 1849 rdinit= [KNL] 1850 Format: <full_path> 1851 Run specified binary instead of /init from the ramdisk, 1852 used for early userspace startup. See initrd. 1853 1854 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode 1855 Format: <reboot_mode>[,<reboot_mode2>[,...]] 1856 See arch/*/kernel/reboot.c or arch/*/kernel/process.c 1857 1858 relax_domain_level= 1859 [KNL, SMP] Set scheduler's default relax_domain_level. 1860 See Documentation/cpusets.txt. 1861 1862 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area 1863 1864 reservetop= [X86-32] 1865 Format: nn[KMG] 1866 Reserves a hole at the top of the kernel virtual 1867 address space. 1868 1869 reset_devices [KNL] Force drivers to reset the underlying device 1870 during initialization. 1871 1872 resume= [SWSUSP] 1873 Specify the partition device for software suspend 1874 1875 resume_offset= [SWSUSP] 1876 Specify the offset from the beginning of the partition 1877 given by "resume=" at which the swap header is located, 1878 in <PAGE_SIZE> units (needed only for swap files). 1879 See Documentation/power/swsusp-and-swap-files.txt 1880 1881 retain_initrd [RAM] Keep initrd memory after extraction 1882 1883 rhash_entries= [KNL,NET] 1884 Set number of hash buckets for route cache 1885 1886 riscom8= [HW,SERIAL] 1887 Format: <io_board1>[,<io_board2>[,...<io_boardN>]] 1888 1889 ro [KNL] Mount root device read-only on boot 1890 1891 root= [KNL] Root filesystem 1892 1893 rootdelay= [KNL] Delay (in seconds) to pause before attempting to 1894 mount the root filesystem 1895 1896 rootflags= [KNL] Set root filesystem mount option string 1897 1898 rootfstype= [KNL] Set root filesystem type 1899 1900 rootwait [KNL] Wait (indefinitely) for root device to show up. 1901 Useful for devices that are detected asynchronously 1902 (e.g. USB and MMC devices). 1903 1904 root_plug.vendor_id= 1905 [ROOTPLUG] Override the default vendor ID 1906 1907 root_plug.product_id= 1908 [ROOTPLUG] Override the default product ID 1909 1910 root_plug.debug= 1911 [ROOTPLUG] Enable debugging output 1912 1913 rw [KNL] Mount root device read-write on boot 1914 1915 S [KNL] Run init in single mode 1916 1917 sa1100ir [NET] 1918 See drivers/net/irda/sa1100_ir.c. 1919 1920 sbni= [NET] Granch SBNI12 leased line adapter 1921 1922 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver 1923 Format: <io>[,<timeout>[,<isapnp>]] 1924 1925 scsi_debug_*= [SCSI] 1926 See drivers/scsi/scsi_debug.c. 1927 1928 scsi_default_dev_flags= 1929 [SCSI] SCSI default device flags 1930 Format: <integer> 1931 1932 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model 1933 Format: <vendor>:<model>:<flags> 1934 (flags are integer value) 1935 1936 scsi_logging_level= [SCSI] a bit mask of logging levels 1937 See drivers/scsi/scsi_logging.h for bits. Also 1938 settable via sysctl at dev.scsi.logging_level 1939 (/proc/sys/dev/scsi/logging_level). 1940 There is also a nice 'scsi_logging_level' script in the 1941 S390-tools package, available for download at 1942 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html 1943 1944 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are 1945 discovered. async scans them in kernel threads, 1946 allowing boot to proceed. none ignores them, expecting 1947 user space to do the scan. 1948 1949 selinux [SELINUX] Disable or enable SELinux at boot time. 1950 Format: { "0" | "1" } 1951 See security/selinux/Kconfig help text. 1952 0 -- disable. 1953 1 -- enable. 1954 Default value is set via kernel config option. 1955 If enabled at boot time, /selinux/disable can be used 1956 later to disable prior to initial policy load. 1957 1958 selinux_compat_net = 1959 [SELINUX] Set initial selinux_compat_net flag value. 1960 Format: { "0" | "1" } 1961 0 -- use new secmark-based packet controls 1962 1 -- use legacy packet controls 1963 Default value is 0 (preferred). 1964 Value can be changed at runtime via 1965 /selinux/compat_net. 1966 1967 serialnumber [BUGS=X86-32] 1968 1969 shapers= [NET] 1970 Maximal number of shapers. 1971 1972 show_msr= [x86] show boot-time MSR settings 1973 Format: { <integer> } 1974 Show boot-time (BIOS-initialized) MSR settings. 1975 The parameter means the number of CPUs to show, 1976 for example 1 means boot CPU only. 1977 1978 sim710= [SCSI,HW] 1979 See header of drivers/scsi/sim710.c. 1980 1981 simeth= [IA-64] 1982 simscsi= 1983 1984 slram= [HW,MTD] 1985 1986 slub_debug[=options[,slabs]] [MM, SLUB] 1987 Enabling slub_debug allows one to determine the 1988 culprit if slab objects become corrupted. Enabling 1989 slub_debug can create guard zones around objects and 1990 may poison objects when not in use. Also tracks the 1991 last alloc / free. For more information see 1992 Documentation/vm/slub.txt. 1993 1994 slub_max_order= [MM, SLUB] 1995 Determines the maximum allowed order for slabs. 1996 A high setting may cause OOMs due to memory 1997 fragmentation. For more information see 1998 Documentation/vm/slub.txt. 1999 2000 slub_min_objects= [MM, SLUB] 2001 The minimum number of objects per slab. SLUB will 2002 increase the slab order up to slub_max_order to 2003 generate a sufficiently large slab able to contain 2004 the number of objects indicated. The higher the number 2005 of objects the smaller the overhead of tracking slabs 2006 and the less frequently locks need to be acquired. 2007 For more information see Documentation/vm/slub.txt. 2008 2009 slub_min_order= [MM, SLUB] 2010 Determines the mininum page order for slabs. Must be 2011 lower than slub_max_order. 2012 For more information see Documentation/vm/slub.txt. 2013 2014 slub_nomerge [MM, SLUB] 2015 Disable merging of slabs with similar size. May be 2016 necessary if there is some reason to distinguish 2017 allocs to different slabs. Debug options disable 2018 merging on their own. 2019 For more information see Documentation/vm/slub.txt. 2020 2021 smart2= [HW] 2022 Format: <io1>[,<io2>[,...,<io8>]] 2023 2024 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only 2025 attempt to substitute SMP alternatives once at boot. 2026 2027 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices 2028 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port 2029 smsc-ircc2.ircc_sir= [HW] SIR base I/O port 2030 smsc-ircc2.ircc_fir= [HW] FIR base I/O port 2031 smsc-ircc2.ircc_irq= [HW] IRQ line 2032 smsc-ircc2.ircc_dma= [HW] DMA channel 2033 smsc-ircc2.ircc_transceiver= [HW] Transceiver type: 2034 0: Toshiba Satellite 1800 (GP data pin select) 2035 1: Fast pin select (default) 2036 2: ATC IRMode 2037 2038 snd-ad1816a= [HW,ALSA] 2039 2040 snd-ad1848= [HW,ALSA] 2041 2042 snd-ali5451= [HW,ALSA] 2043 2044 snd-als100= [HW,ALSA] 2045 2046 snd-als4000= [HW,ALSA] 2047 2048 snd-azt2320= [HW,ALSA] 2049 2050 snd-cmi8330= [HW,ALSA] 2051 2052 snd-cmipci= [HW,ALSA] 2053 2054 snd-cs4231= [HW,ALSA] 2055 2056 snd-cs4232= [HW,ALSA] 2057 2058 snd-cs4236= [HW,ALSA] 2059 2060 snd-cs4281= [HW,ALSA] 2061 2062 snd-cs46xx= [HW,ALSA] 2063 2064 snd-dt019x= [HW,ALSA] 2065 2066 snd-dummy= [HW,ALSA] 2067 2068 snd-emu10k1= [HW,ALSA] 2069 2070 snd-ens1370= [HW,ALSA] 2071 2072 snd-ens1371= [HW,ALSA] 2073 2074 snd-es968= [HW,ALSA] 2075 2076 snd-es1688= [HW,ALSA] 2077 2078 snd-es18xx= [HW,ALSA] 2079 2080 snd-es1938= [HW,ALSA] 2081 2082 snd-es1968= [HW,ALSA] 2083 2084 snd-fm801= [HW,ALSA] 2085 2086 snd-gusclassic= [HW,ALSA] 2087 2088 snd-gusextreme= [HW,ALSA] 2089 2090 snd-gusmax= [HW,ALSA] 2091 2092 snd-hdsp= [HW,ALSA] 2093 2094 snd-ice1712= [HW,ALSA] 2095 2096 snd-intel8x0= [HW,ALSA] 2097 2098 snd-interwave= [HW,ALSA] 2099 2100 snd-interwave-stb= 2101 [HW,ALSA] 2102 2103 snd-korg1212= [HW,ALSA] 2104 2105 snd-maestro3= [HW,ALSA] 2106 2107 snd-mpu401= [HW,ALSA] 2108 2109 snd-mtpav= [HW,ALSA] 2110 2111 snd-nm256= [HW,ALSA] 2112 2113 snd-opl3sa2= [HW,ALSA] 2114 2115 snd-opti92x-ad1848= 2116 [HW,ALSA] 2117 2118 snd-opti92x-cs4231= 2119 [HW,ALSA] 2120 2121 snd-opti93x= [HW,ALSA] 2122 2123 snd-pmac= [HW,ALSA] 2124 2125 snd-rme32= [HW,ALSA] 2126 2127 snd-rme96= [HW,ALSA] 2128 2129 snd-rme9652= [HW,ALSA] 2130 2131 snd-sb8= [HW,ALSA] 2132 2133 snd-sb16= [HW,ALSA] 2134 2135 snd-sbawe= [HW,ALSA] 2136 2137 snd-serial= [HW,ALSA] 2138 2139 snd-sgalaxy= [HW,ALSA] 2140 2141 snd-sonicvibes= [HW,ALSA] 2142 2143 snd-sun-amd7930= 2144 [HW,ALSA] 2145 2146 snd-sun-cs4231= [HW,ALSA] 2147 2148 snd-trident= [HW,ALSA] 2149 2150 snd-usb-audio= [HW,ALSA,USB] 2151 2152 snd-via82xx= [HW,ALSA] 2153 2154 snd-virmidi= [HW,ALSA] 2155 2156 snd-wavefront= [HW,ALSA] 2157 2158 snd-ymfpci= [HW,ALSA] 2159 2160 softlockup_panic= 2161 [KNL] Should the soft-lockup detector generate panics. 2162 2163 sonypi.*= [HW] Sony Programmable I/O Control Device driver 2164 See Documentation/sonypi.txt 2165 2166 specialix= [HW,SERIAL] Specialix multi-serial port adapter 2167 See Documentation/specialix.txt. 2168 2169 spia_io_base= [HW,MTD] 2170 spia_fio_base= 2171 spia_pedr= 2172 spia_peddr= 2173 2174 sscape= [HW,OSS] 2175 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq> 2176 2177 st= [HW,SCSI] SCSI tape parameters (buffers, etc.) 2178 See Documentation/scsi/st.txt. 2179 2180 sti= [PARISC,HW] 2181 Format: <num> 2182 Set the STI (builtin display/keyboard on the HP-PARISC 2183 machines) console (graphic card) which should be used 2184 as the initial boot-console. 2185 See also comment in drivers/video/console/sticore.c. 2186 2187 sti_font= [HW] 2188 See comment in drivers/video/console/sticore.c. 2189 2190 stifb= [HW] 2191 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] 2192 2193 sunrpc.pool_mode= 2194 [NFS] 2195 Control how the NFS server code allocates CPUs to 2196 service thread pools. Depending on how many NICs 2197 you have and where their interrupts are bound, this 2198 option will affect which CPUs will do NFS serving. 2199 Note: this parameter cannot be changed while the 2200 NFS server is running. 2201 2202 auto the server chooses an appropriate mode 2203 automatically using heuristics 2204 global a single global pool contains all CPUs 2205 percpu one pool for each CPU 2206 pernode one pool for each NUMA node (equivalent 2207 to global on non-NUMA machines) 2208 2209 swiotlb= [IA-64] Number of I/O TLB slabs 2210 2211 switches= [HW,M68k] 2212 2213 sym53c416= [HW,SCSI] 2214 See header of drivers/scsi/sym53c416.c. 2215 2216 sysrq_always_enabled 2217 [KNL] 2218 Ignore sysrq setting - this boot parameter will 2219 neutralize any effect of /proc/sys/kernel/sysrq. 2220 Useful for debugging. 2221 2222 t128= [HW,SCSI] 2223 See header of drivers/scsi/t128.c. 2224 2225 tdfx= [HW,DRM] 2226 2227 test_suspend= [SUSPEND] 2228 Specify "mem" (for Suspend-to-RAM) or "standby" (for 2229 standby suspend) as the system sleep state to briefly 2230 enter during system startup. The system is woken from 2231 this state using a wakeup-capable RTC alarm. 2232 2233 thash_entries= [KNL,NET] 2234 Set number of hash buckets for TCP connection 2235 2236 thermal.act= [HW,ACPI] 2237 -1: disable all active trip points in all thermal zones 2238 <degrees C>: override all lowest active trip points 2239 2240 thermal.crt= [HW,ACPI] 2241 -1: disable all critical trip points in all thermal zones 2242 <degrees C>: override all critical trip points 2243 2244 thermal.nocrt= [HW,ACPI] 2245 Set to disable actions on ACPI thermal zone 2246 critical and hot trip points. 2247 2248 thermal.off= [HW,ACPI] 2249 1: disable ACPI thermal control 2250 2251 thermal.psv= [HW,ACPI] 2252 -1: disable all passive trip points 2253 <degrees C>: override all passive trip points to this value 2254 2255 thermal.tzp= [HW,ACPI] 2256 Specify global default ACPI thermal zone polling rate 2257 <deci-seconds>: poll all this frequency 2258 0: no polling (default) 2259 2260 tmscsim= [HW,SCSI] 2261 See comment before function dc390_setup() in 2262 drivers/scsi/tmscsim.c. 2263 2264 tp720= [HW,PS2] 2265 2266 trix= [HW,OSS] MediaTrix AudioTrix Pro 2267 Format: 2268 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq> 2269 2270 turbografx.map[2|3]= [HW,JOY] 2271 TurboGraFX parallel port interface 2272 Format: 2273 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> 2274 See also Documentation/input/joystick-parport.txt 2275 2276 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter 2277 See header of drivers/scsi/u14-34f.c. 2278 2279 uart401= [HW,OSS] 2280 Format: <io>,<irq> 2281 2282 uart6850= [HW,OSS] 2283 Format: <io>,<irq> 2284 2285 uhci-hcd.ignore_oc= 2286 [USB] Ignore overcurrent events (default N). 2287 Some badly-designed motherboards generate lots of 2288 bogus events, for ports that aren't wired to 2289 anything. Set this parameter to avoid log spamming. 2290 Note that genuine overcurrent events won't be 2291 reported either. 2292 2293 unknown_nmi_panic 2294 [X86-32,X86-64] 2295 Set unknown_nmi_panic=1 early on boot. 2296 2297 usbcore.autosuspend= 2298 [USB] The autosuspend time delay (in seconds) used 2299 for newly-detected USB devices (default 2). This 2300 is the time required before an idle device will be 2301 autosuspended. Devices for which the delay is set 2302 to a negative value won't be autosuspended at all. 2303 2304 usbcore.usbfs_snoop= 2305 [USB] Set to log all usbfs traffic (default 0 = off). 2306 2307 usbcore.blinkenlights= 2308 [USB] Set to cycle leds on hubs (default 0 = off). 2309 2310 usbcore.old_scheme_first= 2311 [USB] Start with the old device initialization 2312 scheme (default 0 = off). 2313 2314 usbcore.use_both_schemes= 2315 [USB] Try the other device initialization scheme 2316 if the first one fails (default 1 = enabled). 2317 2318 usbcore.initial_descriptor_timeout= 2319 [USB] Specifies timeout for the initial 64-byte 2320 USB_REQ_GET_DESCRIPTOR request in milliseconds 2321 (default 5000 = 5.0 seconds). 2322 2323 usbhid.mousepoll= 2324 [USBHID] The interval which mice are to be polled at. 2325 2326 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in 2327 kernel's map of available physical RAM. 2328 2329 vdso= [X86-32,SH,x86-64] 2330 vdso=2: enable compat VDSO (default with COMPAT_VDSO) 2331 vdso=1: enable VDSO (default) 2332 vdso=0: disable VDSO mapping 2333 2334 vdso32= [X86-32,X86-64] 2335 vdso32=2: enable compat VDSO (default with COMPAT_VDSO) 2336 vdso32=1: enable 32-bit VDSO (default) 2337 vdso32=0: disable 32-bit VDSO mapping 2338 2339 vector= [IA-64,SMP] 2340 vector=percpu: enable percpu vector domain 2341 2342 video= [FB] Frame buffer configuration 2343 See Documentation/fb/modedb.txt. 2344 2345 vga= [BOOT,X86-32] Select a particular video mode 2346 See Documentation/i386/boot.txt and 2347 Documentation/svga.txt. 2348 Use vga=ask for menu. 2349 This is actually a boot loader parameter; the value is 2350 passed to the kernel using a special protocol. 2351 2352 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact 2353 size of <nn>. This can be used to increase the 2354 minimum size (128MB on x86). It can also be used to 2355 decrease the size and leave more room for directly 2356 mapped kernel RAM. 2357 2358 vmhalt= [KNL,S390] Perform z/VM CP command after system halt. 2359 Format: <command> 2360 2361 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. 2362 Format: <command> 2363 2364 vmpoff= [KNL,S390] Perform z/VM CP command after power off. 2365 Format: <command> 2366 2367 waveartist= [HW,OSS] 2368 Format: <io>,<irq>,<dma>,<dma2> 2369 2370 wd33c93= [HW,SCSI] 2371 See header of drivers/scsi/wd33c93.c. 2372 2373 wd7000= [HW,SCSI] 2374 See header of drivers/scsi/wd7000.c. 2375 2376 wdt= [WDT] Watchdog 2377 See Documentation/watchdog/wdt.txt. 2378 2379 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks. 2380 xd_geo= See header of drivers/block/xd.c. 2381 2382 xirc2ps_cs= [NET,PCMCIA] 2383 Format: 2384 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] 2385 2386 norandmaps Don't use address space randomization 2387 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space 2388 2389______________________________________________________________________ 2390 2391TODO: 2392 2393 Add documentation for ALSA options. 2394 Add more DRM drivers.