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 20Hyphens (dashes) and underscores are equivalent in parameter names, so 21 log_buf_len=1M print-fatal-signals=1 22can also be entered as 23 log-buf-len=1M print_fatal_signals=1 24 25 26This document may not be entirely up to date and comprehensive. The command 27"modinfo -p ${modulename}" shows a current list of all parameters of a loadable 28module. Loadable modules, after being loaded into the running kernel, also 29reveal their parameters in /sys/module/${modulename}/parameters/. Some of these 30parameters may be changed at runtime by the command 31"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}". 32 33The parameters listed below are only valid if certain kernel build options were 34enabled and if respective hardware is present. The text in square brackets at 35the beginning of each description states the restrictions within which a 36parameter is applicable: 37 38 ACPI ACPI support is enabled. 39 AGP AGP (Accelerated Graphics Port) is enabled. 40 ALSA ALSA sound support is enabled. 41 APIC APIC support is enabled. 42 APM Advanced Power Management support is enabled. 43 AVR32 AVR32 architecture is enabled. 44 AX25 Appropriate AX.25 support is enabled. 45 BLACKFIN Blackfin architecture is enabled. 46 DRM Direct Rendering Management support is enabled. 47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled 48 EFI EFI Partitioning (GPT) is enabled 49 EIDE EIDE/ATAPI support is enabled. 50 FB The frame buffer device is enabled. 51 GCOV GCOV profiling is enabled. 52 HW Appropriate hardware is enabled. 53 IA-64 IA-64 architecture is enabled. 54 IMA Integrity measurement architecture is enabled. 55 IOSCHED More than one I/O scheduler is enabled. 56 IP_PNP IP DHCP, BOOTP, or RARP is enabled. 57 IPV6 IPv6 support is enabled. 58 ISAPNP ISA PnP code is enabled. 59 ISDN Appropriate ISDN support is enabled. 60 JOY Appropriate joystick support is enabled. 61 KGDB Kernel debugger support is enabled. 62 KVM Kernel Virtual Machine support is enabled. 63 LIBATA Libata driver is enabled 64 LP Printer support is enabled. 65 LOOP Loopback device support is enabled. 66 M68k M68k architecture is enabled. 67 These options have more detailed description inside of 68 Documentation/m68k/kernel-options.txt. 69 MCA MCA bus support is enabled. 70 MDA MDA console support is enabled. 71 MOUSE Appropriate mouse support is enabled. 72 MSI Message Signaled Interrupts (PCI). 73 MTD MTD (Memory Technology Device) support is enabled. 74 NET Appropriate network support is enabled. 75 NUMA NUMA support is enabled. 76 NFS Appropriate NFS support is enabled. 77 OSS OSS sound support is enabled. 78 PV_OPS A paravirtualized kernel is enabled. 79 PARIDE The ParIDE (parallel port IDE) subsystem is enabled. 80 PARISC The PA-RISC architecture is enabled. 81 PCI PCI bus support is enabled. 82 PCIE PCI Express support is enabled. 83 PCMCIA The PCMCIA subsystem is enabled. 84 PNP Plug & Play support is enabled. 85 PPC PowerPC architecture is enabled. 86 PPT Parallel port support is enabled. 87 PS2 Appropriate PS/2 support is enabled. 88 RAM RAM disk support is enabled. 89 S390 S390 architecture is enabled. 90 SCSI Appropriate SCSI support is enabled. 91 A lot of drivers have their options described inside 92 the Documentation/scsi/ sub-directory. 93 SECURITY Different security models are enabled. 94 SELINUX SELinux support is enabled. 95 APPARMOR AppArmor support is enabled. 96 SERIAL Serial support is enabled. 97 SH SuperH architecture is enabled. 98 SMP The kernel is an SMP kernel. 99 SPARC Sparc architecture is enabled. 100 SWSUSP Software suspend (hibernation) is enabled. 101 SUSPEND System suspend states are enabled. 102 FTRACE Function tracing enabled. 103 TPM TPM drivers are enabled. 104 TS Appropriate touchscreen support is enabled. 105 UMS USB Mass Storage support is enabled. 106 USB USB support is enabled. 107 USBHID USB Human Interface Device support is enabled. 108 V4L Video For Linux support is enabled. 109 VGA The VGA console has been enabled. 110 VT Virtual terminal support is enabled. 111 WDT Watchdog support is enabled. 112 XT IBM PC/XT MFM hard disk support is enabled. 113 X86-32 X86-32, aka i386 architecture is enabled. 114 X86-64 X86-64 architecture is enabled. 115 More X86-64 boot options can be found in 116 Documentation/x86/x86_64/boot-options.txt . 117 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64) 118 XEN Xen support is enabled 119 120In addition, the following text indicates that the option: 121 122 BUGS= Relates to possible processor bugs on the said processor. 123 KNL Is a kernel start-up parameter. 124 BOOT Is a boot loader parameter. 125 126Parameters denoted with BOOT are actually interpreted by the boot 127loader, and have no meaning to the kernel directly. 128Do not modify the syntax of boot loader parameters without extreme 129need or coordination with <Documentation/x86/boot.txt>. 130 131There are also arch-specific kernel-parameters not documented here. 132See for example <Documentation/x86/x86_64/boot-options.txt>. 133 134Note that ALL kernel parameters listed below are CASE SENSITIVE, and that 135a trailing = on the name of any parameter states that that parameter will 136be entered as an environment variable, whereas its absence indicates that 137it will appear as a kernel argument readable via /proc/cmdline by programs 138running once the system is up. 139 140The number of kernel parameters is not limited, but the length of the 141complete command line (parameters including spaces etc.) is limited to 142a fixed number of characters. This limit depends on the architecture 143and is between 256 and 4096 characters. It is defined in the file 144./include/asm/setup.h as COMMAND_LINE_SIZE. 145 146 147 acpi= [HW,ACPI,X86] 148 Advanced Configuration and Power Interface 149 Format: { force | off | strict | noirq | rsdt } 150 force -- enable ACPI if default was off 151 off -- disable ACPI if default was on 152 noirq -- do not use ACPI for IRQ routing 153 strict -- Be less tolerant of platforms that are not 154 strictly ACPI specification compliant. 155 rsdt -- prefer RSDT over (default) XSDT 156 copy_dsdt -- copy DSDT to memory 157 158 See also Documentation/power/pm.txt, pci=noacpi 159 160 acpi_apic_instance= [ACPI, IOAPIC] 161 Format: <int> 162 2: use 2nd APIC table, if available 163 1,0: use 1st APIC table 164 default: 0 165 166 acpi_backlight= [HW,ACPI] 167 acpi_backlight=vendor 168 acpi_backlight=video 169 If set to vendor, prefer vendor specific driver 170 (e.g. thinkpad_acpi, sony_acpi, etc.) instead 171 of the ACPI video.ko driver. 172 173 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG] 174 acpi.debug_level= [HW,ACPI,ACPI_DEBUG] 175 Format: <int> 176 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI 177 debug output. Bits in debug_layer correspond to a 178 _COMPONENT in an ACPI source file, e.g., 179 #define _COMPONENT ACPI_PCI_COMPONENT 180 Bits in debug_level correspond to a level in 181 ACPI_DEBUG_PRINT statements, e.g., 182 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ... 183 The debug_level mask defaults to "info". See 184 Documentation/acpi/debug.txt for more information about 185 debug layers and levels. 186 187 Enable processor driver info messages: 188 acpi.debug_layer=0x20000000 189 Enable PCI/PCI interrupt routing info messages: 190 acpi.debug_layer=0x400000 191 Enable AML "Debug" output, i.e., stores to the Debug 192 object while interpreting AML: 193 acpi.debug_layer=0xffffffff acpi.debug_level=0x2 194 Enable all messages related to ACPI hardware: 195 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff 196 197 Some values produce so much output that the system is 198 unusable. The "log_buf_len" parameter may be useful 199 if you need to capture more output. 200 201 acpi_display_output= [HW,ACPI] 202 acpi_display_output=vendor 203 acpi_display_output=video 204 See above. 205 206 acpi_irq_balance [HW,ACPI] 207 ACPI will balance active IRQs 208 default in APIC mode 209 210 acpi_irq_nobalance [HW,ACPI] 211 ACPI will not move active IRQs (default) 212 default in PIC mode 213 214 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA 215 Format: <irq>,<irq>... 216 217 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for 218 use by PCI 219 Format: <irq>,<irq>... 220 221 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT 222 223 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS 224 Format: To spoof as Windows 98: ="Microsoft Windows" 225 226 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings 227 acpi_osi="string1" # add string1 -- only one string 228 acpi_osi="!string2" # remove built-in string2 229 acpi_osi= # disable all strings 230 231 acpi_pm_good [X86] 232 Override the pmtimer bug detection: force the kernel 233 to assume that this machine's pmtimer latches its value 234 and always returns good values. 235 236 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode 237 Format: { level | edge | high | low } 238 239 acpi_serialize [HW,ACPI] force serialization of AML methods 240 241 acpi_skip_timer_override [HW,ACPI] 242 Recognize and ignore IRQ0/pin2 Interrupt Override. 243 For broken nForce2 BIOS resulting in XT-PIC timer. 244 245 acpi_sleep= [HW,ACPI] Sleep options 246 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, 247 old_ordering, s4_nonvs, sci_force_enable } 248 See Documentation/power/video.txt for information on 249 s3_bios and s3_mode. 250 s3_beep is for debugging; it makes the PC's speaker beep 251 as soon as the kernel's real-mode entry point is called. 252 s4_nohwsig prevents ACPI hardware signature from being 253 used during resume from hibernation. 254 old_ordering causes the ACPI 1.0 ordering of the _PTS 255 control method, with respect to putting devices into 256 low power states, to be enforced (the ACPI 2.0 ordering 257 of _PTS is used by default). 258 nonvs prevents the kernel from saving/restoring the 259 ACPI NVS memory during suspend/hibernation and resume. 260 sci_force_enable causes the kernel to set SCI_EN directly 261 on resume from S1/S3 (which is against the ACPI spec, 262 but some broken systems don't work without it). 263 264 acpi_use_timer_override [HW,ACPI] 265 Use timer override. For some broken Nvidia NF5 boards 266 that require a timer override, but don't have HPET 267 268 acpi_enforce_resources= [ACPI] 269 { strict | lax | no } 270 Check for resource conflicts between native drivers 271 and ACPI OperationRegions (SystemIO and SystemMemory 272 only). IO ports and memory declared in ACPI might be 273 used by the ACPI subsystem in arbitrary AML code and 274 can interfere with legacy drivers. 275 strict (default): access to resources claimed by ACPI 276 is denied; legacy drivers trying to access reserved 277 resources will fail to bind to device using them. 278 lax: access to resources claimed by ACPI is allowed; 279 legacy drivers trying to access reserved resources 280 will bind successfully but a warning message is logged. 281 no: ACPI OperationRegions are not marked as reserved, 282 no further checks are performed. 283 284 add_efi_memmap [EFI; X86] Include EFI memory map in 285 kernel's map of available physical RAM. 286 287 agp= [AGP] 288 { off | try_unsupported } 289 off: disable AGP support 290 try_unsupported: try to drive unsupported chipsets 291 (may crash computer or cause data corruption) 292 293 ALSA [HW,ALSA] 294 See Documentation/sound/alsa/alsa-parameters.txt 295 296 alignment= [KNL,ARM] 297 Allow the default userspace alignment fault handler 298 behaviour to be specified. Bit 0 enables warnings, 299 bit 1 enables fixups, and bit 2 sends a segfault. 300 301 amd_iommu= [HW,X86-84] 302 Pass parameters to the AMD IOMMU driver in the system. 303 Possible values are: 304 fullflush - enable flushing of IO/TLB entries when 305 they are unmapped. Otherwise they are 306 flushed before they will be reused, which 307 is a lot of faster 308 off - do not initialize any AMD IOMMU found in 309 the system 310 311 amijoy.map= [HW,JOY] Amiga joystick support 312 Map of devices attached to JOY0DAT and JOY1DAT 313 Format: <a>,<b> 314 See also Documentation/kernel/input/joystick.txt 315 316 analog.map= [HW,JOY] Analog joystick and gamepad support 317 Specifies type or capabilities of an analog joystick 318 connected to one of 16 gameports 319 Format: <type1>,<type2>,..<type16> 320 321 apc= [HW,SPARC] 322 Power management functions (SPARCstation-4/5 + deriv.) 323 Format: noidle 324 Disable APC CPU standby support. SPARCstation-Fox does 325 not play well with APC CPU idle - disable it if you have 326 APC and your system crashes randomly. 327 328 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller 329 Change the output verbosity whilst booting 330 Format: { quiet (default) | verbose | debug } 331 Change the amount of debugging information output 332 when initialising the APIC and IO-APIC components. 333 334 autoconf= [IPV6] 335 See Documentation/networking/ipv6.txt. 336 337 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller 338 Limit apic dumping. The parameter defines the maximal 339 number of local apics being dumped. Also it is possible 340 to set it to "all" by meaning -- no limit here. 341 Format: { 1 (default) | 2 | ... | all }. 342 The parameter valid if only apic=debug or 343 apic=verbose is specified. 344 Example: apic=debug show_lapic=all 345 346 apm= [APM] Advanced Power Management 347 See header of arch/x86/kernel/apm_32.c. 348 349 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards 350 Format: <io>,<irq>,<nodeID> 351 352 ataflop= [HW,M68k] 353 354 atarimouse= [HW,MOUSE] Atari Mouse 355 356 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, 357 EzKey and similar keyboards 358 359 atkbd.reset= [HW] Reset keyboard during initialization 360 361 atkbd.set= [HW] Select keyboard code set 362 Format: <int> (2 = AT (default), 3 = PS/2) 363 364 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar 365 keyboards 366 367 atkbd.softraw= [HW] Choose between synthetic and real raw mode 368 Format: <bool> (0 = real, 1 = synthetic (default)) 369 370 atkbd.softrepeat= [HW] 371 Use software keyboard repeat 372 373 autotest [IA64] 374 375 baycom_epp= [HW,AX25] 376 Format: <io>,<mode> 377 378 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem 379 Format: <io>,<mode> 380 See header of drivers/net/hamradio/baycom_par.c. 381 382 baycom_ser_fdx= [HW,AX25] 383 BayCom Serial Port AX.25 Modem (Full Duplex Mode) 384 Format: <io>,<irq>,<mode>[,<baud>] 385 See header of drivers/net/hamradio/baycom_ser_fdx.c. 386 387 baycom_ser_hdx= [HW,AX25] 388 BayCom Serial Port AX.25 Modem (Half Duplex Mode) 389 Format: <io>,<irq>,<mode> 390 See header of drivers/net/hamradio/baycom_ser_hdx.c. 391 392 boot_delay= Milliseconds to delay each printk during boot. 393 Values larger than 10 seconds (10000) are changed to 394 no delay (0). 395 Format: integer 396 397 bootmem_debug [KNL] Enable bootmem allocator debug messages. 398 399 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards) 400 bttv.radio= Most important insmod options are available as 401 kernel args too. 402 bttv.pll= See Documentation/video4linux/bttv/Insmod-options 403 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST 404 405 c101= [NET] Moxa C101 synchronous serial card 406 407 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection. 408 Sometimes CPU hardware bugs make them report the cache 409 size incorrectly. The kernel will attempt work arounds 410 to fix known problems, but for some CPUs it is not 411 possible to determine what the correct size should be. 412 This option provides an override for these situations. 413 414 capability.disable= 415 [SECURITY] Disable capabilities. This would normally 416 be used only if an alternative security model is to be 417 configured. Potentially dangerous and should only be 418 used if you are entirely sure of the consequences. 419 420 ccw_timeout_log [S390] 421 See Documentation/s390/CommonIO for details. 422 423 cgroup_disable= [KNL] Disable a particular controller 424 Format: {name of the controller(s) to disable} 425 {Currently supported controllers - "memory"} 426 427 checkreqprot [SELINUX] Set initial checkreqprot flag value. 428 Format: { "0" | "1" } 429 See security/selinux/Kconfig help text. 430 0 -- check protection applied by kernel (includes 431 any implied execute protection). 432 1 -- check protection requested by application. 433 Default value is set via a kernel config option. 434 Value can be changed at runtime via 435 /selinux/checkreqprot. 436 437 cio_ignore= [S390] 438 See Documentation/s390/CommonIO for details. 439 440 clock= [BUGS=X86-32, HW] gettimeofday clocksource override. 441 [Deprecated] 442 Forces specified clocksource (if available) to be used 443 when calculating gettimeofday(). If specified 444 clocksource is not available, it defaults to PIT. 445 Format: { pit | tsc | cyclone | pmtmr } 446 447 clocksource= Override the default clocksource 448 Format: <string> 449 Override the default clocksource and use the clocksource 450 with the name specified. 451 Some clocksource names to choose from, depending on 452 the platform: 453 [all] jiffies (this is the base, fallback clocksource) 454 [ACPI] acpi_pm 455 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2, 456 pxa_timer,timer3,32k_counter,timer0_1 457 [AVR32] avr32 458 [X86-32] pit,hpet,tsc,vmi-timer; 459 scx200_hrt on Geode; cyclone on IBM x440 460 [MIPS] MIPS 461 [PARISC] cr16 462 [S390] tod 463 [SH] SuperH 464 [SPARC64] tick 465 [X86-64] hpet,tsc 466 467 clearcpuid=BITNUM [X86] 468 Disable CPUID feature X for the kernel. See 469 arch/x86/include/asm/cpufeature.h for the valid bit 470 numbers. Note the Linux specific bits are not necessarily 471 stable over kernel options, but the vendor specific 472 ones should be. 473 Also note that user programs calling CPUID directly 474 or using the feature without checking anything 475 will still see it. This just prevents it from 476 being used by the kernel or shown in /proc/cpuinfo. 477 Also note the kernel might malfunction if you disable 478 some critical bits. 479 480 cmo_free_hint= [PPC] Format: { yes | no } 481 Specify whether pages are marked as being inactive 482 when they are freed. This is used in CMO environments 483 to determine OS memory pressure for page stealing by 484 a hypervisor. 485 Default: yes 486 487 code_bytes [X86] How many bytes of object code to print 488 in an oops report. 489 Range: 0 - 8192 490 Default: 64 491 492 com20020= [HW,NET] ARCnet - COM20020 chipset 493 Format: 494 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]] 495 496 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers) 497 Format: <io>[,<irq>] 498 499 com90xx= [HW,NET] 500 ARCnet - COM90xx chipset (memory-mapped buffers) 501 Format: <io>[,<irq>[,<memstart>]] 502 503 condev= [HW,S390] console device 504 conmode= 505 506 console= [KNL] Output console device and options. 507 508 tty<n> Use the virtual console device <n>. 509 510 ttyS<n>[,options] 511 ttyUSB0[,options] 512 Use the specified serial port. The options are of 513 the form "bbbbpnf", where "bbbb" is the baud rate, 514 "p" is parity ("n", "o", or "e"), "n" is number of 515 bits, and "f" is flow control ("r" for RTS or 516 omit it). Default is "9600n8". 517 518 See Documentation/serial-console.txt for more 519 information. See 520 Documentation/networking/netconsole.txt for an 521 alternative. 522 523 uart[8250],io,<addr>[,options] 524 uart[8250],mmio,<addr>[,options] 525 Start an early, polled-mode console on the 8250/16550 526 UART at the specified I/O port or MMIO address, 527 switching to the matching ttyS device later. The 528 options are the same as for ttyS, above. 529 530 If the device connected to the port is not a TTY but a braille 531 device, prepend "brl," before the device type, for instance 532 console=brl,ttyS0 533 For now, only VisioBraille is supported. 534 535 consoleblank= [KNL] The console blank (screen saver) timeout in 536 seconds. Defaults to 10*60 = 10mins. A value of 0 537 disables the blank timer. 538 539 coredump_filter= 540 [KNL] Change the default value for 541 /proc/<pid>/coredump_filter. 542 See also Documentation/filesystems/proc.txt. 543 544 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver 545 Format: 546 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>] 547 548 crashkernel=nn[KMG]@ss[KMG] 549 [KNL] Reserve a chunk of physical memory to 550 hold a kernel to switch to with kexec on panic. 551 552 crashkernel=range1:size1[,range2:size2,...][@offset] 553 [KNL] Same as above, but depends on the memory 554 in the running system. The syntax of range is 555 start-[end] where start and end are both 556 a memory unit (amount[KMG]). See also 557 Documentation/kdump/kdump.txt for a example. 558 559 cs89x0_dma= [HW,NET] 560 Format: <dma> 561 562 cs89x0_media= [HW,NET] 563 Format: { rj45 | aui | bnc } 564 565 dasd= [HW,NET] 566 See header of drivers/s390/block/dasd_devmap.c. 567 568 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port 569 (one device per port) 570 Format: <port#>,<type> 571 See also Documentation/input/joystick-parport.txt 572 573 debug [KNL] Enable kernel debugging (events log level). 574 575 debug_locks_verbose= 576 [KNL] verbose self-tests 577 Format=<0|1> 578 Print debugging info while doing the locking API 579 self-tests. 580 We default to 0 (no extra messages), setting it to 581 1 will print _a lot_ more information - normally 582 only useful to kernel developers. 583 584 debug_objects [KNL] Enable object debugging 585 586 no_debug_objects 587 [KNL] Disable object debugging 588 589 debugpat [X86] Enable PAT debugging 590 591 decnet.addr= [HW,NET] 592 Format: <area>[,<node>] 593 See also Documentation/networking/decnet.txt. 594 595 default_hugepagesz= 596 [same as hugepagesz=] The size of the default 597 HugeTLB page size. This is the size represented by 598 the legacy /proc/ hugepages APIs, used for SHM, and 599 default size when mounting hugetlbfs filesystems. 600 Defaults to the default architecture's huge page size 601 if not specified. 602 603 dhash_entries= [KNL] 604 Set number of hash buckets for dentry cache. 605 606 digi= [HW,SERIAL] 607 IO parameters + enable/disable command. 608 609 digiepca= [HW,SERIAL] 610 See drivers/char/README.epca and 611 Documentation/serial/digiepca.txt. 612 613 disable= [IPV6] 614 See Documentation/networking/ipv6.txt. 615 616 disable_ipv6= [IPV6] 617 See Documentation/networking/ipv6.txt. 618 619 disable_mtrr_cleanup [X86] 620 The kernel tries to adjust MTRR layout from continuous 621 to discrete, to make X server driver able to add WB 622 entry later. This parameter disables that. 623 624 disable_mtrr_trim [X86, Intel and AMD only] 625 By default the kernel will trim any uncacheable 626 memory out of your available memory pool based on 627 MTRR settings. This parameter disables that behavior, 628 possibly causing your machine to run very slowly. 629 630 disable_timer_pin_1 [X86] 631 Disable PIN 1 of APIC timer 632 Can be useful to work around chipset bugs. 633 634 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support, 635 this option disables the debugging code at boot. 636 637 dma_debug_entries=<number> 638 This option allows to tune the number of preallocated 639 entries for DMA-API debugging code. One entry is 640 required per DMA-API allocation. Use this if the 641 DMA-API debugging code disables itself because the 642 architectural default is too low. 643 644 dma_debug_driver=<driver_name> 645 With this option the DMA-API debugging driver 646 filter feature can be enabled at boot time. Just 647 pass the driver to filter for as the parameter. 648 The filter can be disabled or changed to another 649 driver later using sysfs. 650 651 dscc4.setup= [NET] 652 653 dynamic_printk Enables pr_debug()/dev_dbg() calls if 654 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. 655 These can also be switched on/off via 656 <debugfs>/dynamic_printk/modules 657 658 earlycon= [KNL] Output early console device and options. 659 uart[8250],io,<addr>[,options] 660 uart[8250],mmio,<addr>[,options] 661 uart[8250],mmio32,<addr>[,options] 662 Start an early, polled-mode console on the 8250/16550 663 UART at the specified I/O port or MMIO address. 664 MMIO inter-register address stride is either 8bit (mmio) 665 or 32bit (mmio32). 666 The options are the same as for ttyS, above. 667 668 earlyprintk= [X86,SH,BLACKFIN] 669 earlyprintk=vga 670 earlyprintk=serial[,ttySn[,baudrate]] 671 earlyprintk=ttySn[,baudrate] 672 earlyprintk=dbgp[debugController#] 673 674 Append ",keep" to not disable it when the real console 675 takes over. 676 677 Only vga or serial or usb debug port at a time. 678 679 Currently only ttyS0 and ttyS1 are supported. 680 681 Interaction with the standard serial driver is not 682 very good. 683 684 The VGA output is eventually overwritten by the real 685 console. 686 687 ekgdboc= [X86,KGDB] Allow early kernel console debugging 688 ekgdboc=kbd 689 690 This is desgined to be used in conjunction with 691 the boot argument: earlyprintk=vga 692 693 edd= [EDD] 694 Format: {"off" | "on" | "skip[mbr]"} 695 696 eisa_irq_edge= [PARISC,HW] 697 See header of drivers/parisc/eisa.c. 698 699 elanfreq= [X86-32] 700 See comment before function elanfreq_setup() in 701 arch/x86/kernel/cpu/cpufreq/elanfreq.c. 702 703 elevator= [IOSCHED] 704 Format: {"anticipatory" | "cfq" | "deadline" | "noop"} 705 See Documentation/block/as-iosched.txt and 706 Documentation/block/deadline-iosched.txt for details. 707 708 elfcorehdr= [IA64,PPC,SH,X86] 709 Specifies physical address of start of kernel core 710 image elf header. Generally kexec loader will 711 pass this option to capture kernel. 712 See Documentation/kdump/kdump.txt for details. 713 714 enable_mtrr_cleanup [X86] 715 The kernel tries to adjust MTRR layout from continuous 716 to discrete, to make X server driver able to add WB 717 entry later. This parameter enables that. 718 719 enable_timer_pin_1 [X86] 720 Enable PIN 1 of APIC timer 721 Can be useful to work around chipset bugs 722 (in particular on some ATI chipsets). 723 The kernel tries to set a reasonable default. 724 725 enforcing [SELINUX] Set initial enforcing status. 726 Format: {"0" | "1"} 727 See security/selinux/Kconfig help text. 728 0 -- permissive (log only, no denials). 729 1 -- enforcing (deny and log). 730 Default value is 0. 731 Value can be changed at runtime via /selinux/enforce. 732 733 erst_disable [ACPI] 734 Disable Error Record Serialization Table (ERST) 735 support. 736 737 ether= [HW,NET] Ethernet cards parameters 738 This option is obsoleted by the "netdev=" option, which 739 has equivalent usage. See its documentation for details. 740 741 failslab= 742 fail_page_alloc= 743 fail_make_request=[KNL] 744 General fault injection mechanism. 745 Format: <interval>,<probability>,<space>,<times> 746 See also /Documentation/fault-injection/. 747 748 floppy= [HW] 749 See Documentation/blockdev/floppy.txt. 750 751 force_pal_cache_flush 752 [IA-64] Avoid check_sal_cache_flush which may hang on 753 buggy SAL_CACHE_FLUSH implementations. Using this 754 parameter will force ia64_sal_cache_flush to call 755 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. 756 757 ftrace=[tracer] 758 [FTRACE] will set and start the specified tracer 759 as early as possible in order to facilitate early 760 boot debugging. 761 762 ftrace_dump_on_oops[=orig_cpu] 763 [FTRACE] will dump the trace buffers on oops. 764 If no parameter is passed, ftrace will dump 765 buffers of all CPUs, but if you pass orig_cpu, it will 766 dump only the buffer of the CPU that triggered the 767 oops. 768 769 ftrace_filter=[function-list] 770 [FTRACE] Limit the functions traced by the function 771 tracer at boot up. function-list is a comma separated 772 list of functions. This list can be changed at run 773 time by the set_ftrace_filter file in the debugfs 774 tracing directory. 775 776 ftrace_notrace=[function-list] 777 [FTRACE] Do not trace the functions specified in 778 function-list. This list can be changed at run time 779 by the set_ftrace_notrace file in the debugfs 780 tracing directory. 781 782 ftrace_graph_filter=[function-list] 783 [FTRACE] Limit the top level callers functions traced 784 by the function graph tracer at boot up. 785 function-list is a comma separated list of functions 786 that can be changed at run time by the 787 set_graph_function file in the debugfs tracing directory. 788 789 gamecon.map[2|3]= 790 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad 791 support via parallel port (up to 5 devices per port) 792 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5> 793 See also Documentation/input/joystick-parport.txt 794 795 gamma= [HW,DRM] 796 797 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART 798 Format: off | on 799 default: on 800 801 gcov_persist= [GCOV] When non-zero (default), profiling data for 802 kernel modules is saved and remains accessible via 803 debugfs, even when the module is unloaded/reloaded. 804 When zero, profiling data is discarded and associated 805 debugfs files are removed at module unload time. 806 807 gpt [EFI] Forces disk with valid GPT signature but 808 invalid Protective MBR to be treated as GPT. 809 810 hashdist= [KNL,NUMA] Large hashes allocated during boot 811 are distributed across NUMA nodes. Defaults on 812 for 64bit NUMA, off otherwise. 813 Format: 0 | 1 (for off | on) 814 815 hcl= [IA-64] SGI's Hardware Graph compatibility layer 816 817 hd= [EIDE] (E)IDE hard drive subsystem geometry 818 Format: <cyl>,<head>,<sect> 819 820 hest_disable [ACPI] 821 Disable Hardware Error Source Table (HEST) support; 822 corresponding firmware-first mode error processing 823 logic will be disabled. 824 825 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact 826 size of <nn>. This works even on boxes that have no 827 highmem otherwise. This also works to reduce highmem 828 size on bigger boxes. 829 830 highres= [KNL] Enable/disable high resolution timer mode. 831 Valid parameters: "on", "off" 832 Default: "on" 833 834 hisax= [HW,ISDN] 835 See Documentation/isdn/README.HiSax. 836 837 hlt [BUGS=ARM,SH] 838 839 hpet= [X86-32,HPET] option to control HPET usage 840 Format: { enable (default) | disable | force | 841 verbose } 842 disable: disable HPET and use PIT instead 843 force: allow force enabled of undocumented chips (ICH4, 844 VIA, nVidia) 845 verbose: show contents of HPET registers during setup 846 847 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot. 848 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages. 849 On x86-64 and powerpc, this option can be specified 850 multiple times interleaved with hugepages= to reserve 851 huge pages of different sizes. Valid pages sizes on 852 x86-64 are 2M (when the CPU supports "pse") and 1G 853 (when the CPU supports the "pdpe1gb" cpuinfo flag) 854 Note that 1GB pages can only be allocated at boot time 855 using hugepages= and not freed afterwards. 856 857 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC) 858 terminal devices. Valid values: 0..8 859 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. 860 If specified, z/VM IUCV HVC accepts connections 861 from listed z/VM user IDs only. 862 863 i2c_bus= [HW] Override the default board specific I2C bus speed 864 or register an additional I2C bus that is not 865 registered from board initialization code. 866 Format: 867 <bus_id>,<clkrate> 868 869 i8042.debug [HW] Toggle i8042 debug mode 870 i8042.direct [HW] Put keyboard port into non-translated mode 871 i8042.dumbkbd [HW] Pretend that controller can only read data from 872 keyboard and cannot control its state 873 (Don't attempt to blink the leds) 874 i8042.noaux [HW] Don't check for auxiliary (== mouse) port 875 i8042.nokbd [HW] Don't check/create keyboard port 876 i8042.noloop [HW] Disable the AUX Loopback command while probing 877 for the AUX port 878 i8042.nomux [HW] Don't check presence of an active multiplexing 879 controller 880 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX 881 controllers 882 i8042.notimeout [HW] Ignore timeout condition signalled by conroller 883 i8042.reset [HW] Reset the controller during init and cleanup 884 i8042.unlock [HW] Unlock (ignore) the keylock 885 886 i810= [HW,DRM] 887 888 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data 889 indicates that the driver is running on unsupported 890 hardware. 891 i8k.force [HW] Activate i8k driver even if SMM BIOS signature 892 does not match list of supported models. 893 i8k.power_status 894 [HW] Report power status in /proc/i8k 895 (disabled by default) 896 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN 897 capability is set. 898 899 icn= [HW,ISDN] 900 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]] 901 902 ide-core.nodma= [HW] (E)IDE subsystem 903 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc 904 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr 905 .cdrom .chs .ignore_cable are additional options 906 See Documentation/ide/ide.txt. 907 908 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem 909 Claim all unknown PCI IDE storage controllers. 910 911 idle= [X86] 912 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait 913 Poll forces a polling idle loop that can slightly 914 improve the performance of waking up a idle CPU, but 915 will use a lot of power and make the system run hot. 916 Not recommended. 917 idle=mwait: On systems which support MONITOR/MWAIT but 918 the kernel chose to not use it because it doesn't save 919 as much power as a normal idle loop, use the 920 MONITOR/MWAIT idle loop anyways. Performance should be 921 the same as idle=poll. 922 idle=halt: Halt is forced to be used for CPU idle. 923 In such case C2/C3 won't be used again. 924 idle=nomwait: Disable mwait for CPU C-states 925 926 ignore_loglevel [KNL] 927 Ignore loglevel setting - this will print /all/ 928 kernel messages to the console. Useful for debugging. 929 930 ihash_entries= [KNL] 931 Set number of hash buckets for inode cache. 932 933 ima_audit= [IMA] 934 Format: { "0" | "1" } 935 0 -- integrity auditing messages. (Default) 936 1 -- enable informational integrity auditing messages. 937 938 ima_hash= [IMA] 939 Format: { "sha1" | "md5" } 940 default: "sha1" 941 942 ima_tcb [IMA] 943 Load a policy which meets the needs of the Trusted 944 Computing Base. This means IMA will measure all 945 programs exec'd, files mmap'd for exec, and all files 946 opened for read by uid=0. 947 948 init= [KNL] 949 Format: <full_path> 950 Run specified binary instead of /sbin/init as init 951 process. 952 953 initcall_debug [KNL] Trace initcalls as they are executed. Useful 954 for working out where the kernel is dying during 955 startup. 956 957 initrd= [BOOT] Specify the location of the initial ramdisk 958 959 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver 960 Format: <irq> 961 962 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option 963 on 964 Enable intel iommu driver. 965 off 966 Disable intel iommu driver. 967 igfx_off [Default Off] 968 By default, gfx is mapped as normal device. If a gfx 969 device has a dedicated DMAR unit, the DMAR unit is 970 bypassed by not enabling DMAR with this option. In 971 this case, gfx device will use physical address for 972 DMA. 973 forcedac [x86_64] 974 With this option iommu will not optimize to look 975 for io virtual address below 32 bit forcing dual 976 address cycle on pci bus for cards supporting greater 977 than 32 bit addressing. The default is to look 978 for translation below 32 bit and if not available 979 then look in the higher range. 980 strict [Default Off] 981 With this option on every unmap_single operation will 982 result in a hardware IOTLB flush operation as opposed 983 to batching them for performance. 984 985 intremap= [X86-64, Intel-IOMMU] 986 Format: { on (default) | off | nosid } 987 on enable Interrupt Remapping (default) 988 off disable Interrupt Remapping 989 nosid disable Source ID checking 990 991 inttest= [IA64] 992 993 iomem= Disable strict checking of access to MMIO memory 994 strict regions from userspace. 995 relaxed 996 997 iommu= [x86] 998 off 999 force 1000 noforce 1001 biomerge 1002 panic 1003 nopanic 1004 merge 1005 nomerge 1006 forcesac 1007 soft 1008 pt [x86, IA64] 1009 1010 io7= [HW] IO7 for Marvel based alpha systems 1011 See comment before marvel_specify_io7 in 1012 arch/alpha/kernel/core_marvel.c. 1013 1014 io_delay= [X86] I/O delay method 1015 0x80 1016 Standard port 0x80 based delay 1017 0xed 1018 Alternate port 0xed based delay (needed on some systems) 1019 udelay 1020 Simple two microseconds delay 1021 none 1022 No delay 1023 1024 ip= [IP_PNP] 1025 See Documentation/filesystems/nfs/nfsroot.txt. 1026 1027 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards 1028 See comment before ip2_setup() in 1029 drivers/char/ip2/ip2base.c. 1030 1031 irqfixup [HW] 1032 When an interrupt is not handled search all handlers 1033 for it. Intended to get systems with badly broken 1034 firmware running. 1035 1036 irqpoll [HW] 1037 When an interrupt is not handled search all handlers 1038 for it. Also check all handlers each timer 1039 interrupt. Intended to get systems with badly broken 1040 firmware running. 1041 1042 isapnp= [ISAPNP] 1043 Format: <RDP>,<reset>,<pci_scan>,<verbosity> 1044 1045 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler. 1046 Format: 1047 <cpu number>,...,<cpu number> 1048 or 1049 <cpu number>-<cpu number> 1050 (must be a positive range in ascending order) 1051 or a mixture 1052 <cpu number>,...,<cpu number>-<cpu number> 1053 1054 This option can be used to specify one or more CPUs 1055 to isolate from the general SMP balancing and scheduling 1056 algorithms. You can move a process onto or off an 1057 "isolated" CPU via the CPU affinity syscalls or cpuset. 1058 <cpu number> begins at 0 and the maximum value is 1059 "number of CPUs in system - 1". 1060 1061 This option is the preferred way to isolate CPUs. The 1062 alternative -- manually setting the CPU mask of all 1063 tasks in the system -- can cause problems and 1064 suboptimal load balancer performance. 1065 1066 iucv= [HW,NET] 1067 1068 js= [HW,JOY] Analog joystick 1069 See Documentation/input/joystick.txt. 1070 1071 keepinitrd [HW,ARM] 1072 1073 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter 1074 specifies the amount of memory usable by the kernel 1075 for non-movable allocations. The requested amount is 1076 spread evenly throughout all nodes in the system. The 1077 remaining memory in each node is used for Movable 1078 pages. In the event, a node is too small to have both 1079 kernelcore and Movable pages, kernelcore pages will 1080 take priority and other nodes will have a larger number 1081 of kernelcore pages. The Movable zone is used for the 1082 allocation of pages that may be reclaimed or moved 1083 by the page migration subsystem. This means that 1084 HugeTLB pages may not be allocated from this zone. 1085 Note that allocations like PTEs-from-HighMem still 1086 use the HighMem zone if it exists, and the Normal 1087 zone if it does not. 1088 1089 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port. 1090 Format: <Controller#>[,poll interval] 1091 The controller # is the number of the ehci usb debug 1092 port as it is probed via PCI. The poll interval is 1093 optional and is the number seconds in between 1094 each poll cycle to the debug port in case you need 1095 the functionality for interrupting the kernel with 1096 gdb or control-c on the dbgp connection. When 1097 not using this parameter you use sysrq-g to break into 1098 the kernel debugger. 1099 1100 kgdboc= [KGDB,HW] kgdb over consoles. 1101 Requires a tty driver that supports console polling, 1102 or a supported polling keyboard driver (non-usb). 1103 Serial only format: <serial_device>[,baud] 1104 keyboard only format: kbd 1105 keyboard and serial format: kbd,<serial_device>[,baud] 1106 Optional Kernel mode setting: 1107 kms, kbd format: kms,kbd 1108 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud] 1109 1110 kgdbwait [KGDB] Stop kernel execution and enter the 1111 kernel debugger at the earliest opportunity. 1112 1113 kmac= [MIPS] korina ethernet MAC address. 1114 Configure the RouterBoard 532 series on-chip 1115 Ethernet adapter MAC address. 1116 1117 kmemleak= [KNL] Boot-time kmemleak enable/disable 1118 Valid arguments: on, off 1119 Default: on 1120 1121 kstack=N [X86] Print N words from the kernel stack 1122 in oops dumps. 1123 1124 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs. 1125 Default is 0 (don't ignore, but inject #GP) 1126 1127 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging. 1128 Default is 1 (enabled) 1129 1130 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM. 1131 Default is 0 (off) 1132 1133 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU) 1134 for all guests. 1135 Default is 1 (enabled) if in 64bit or 32bit-PAE mode 1136 1137 kvm-intel.bypass_guest_pf= 1138 [KVM,Intel] Disables bypassing of guest page faults 1139 on Intel chips. Default is 1 (enabled) 1140 1141 kvm-intel.ept= [KVM,Intel] Disable extended page tables 1142 (virtualized MMU) support on capable Intel chips. 1143 Default is 1 (enabled) 1144 1145 kvm-intel.emulate_invalid_guest_state= 1146 [KVM,Intel] Enable emulation of invalid guest states 1147 Default is 0 (disabled) 1148 1149 kvm-intel.flexpriority= 1150 [KVM,Intel] Disable FlexPriority feature (TPR shadow). 1151 Default is 1 (enabled) 1152 1153 kvm-intel.unrestricted_guest= 1154 [KVM,Intel] Disable unrestricted guest feature 1155 (virtualized real and unpaged mode) on capable 1156 Intel chips. Default is 1 (enabled) 1157 1158 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification 1159 feature (tagged TLBs) on capable Intel chips. 1160 Default is 1 (enabled) 1161 1162 l2cr= [PPC] 1163 1164 l3cr= [PPC] 1165 1166 lapic [X86-32,APIC] Enable the local APIC even if BIOS 1167 disabled it. 1168 1169 lapic_timer_c2_ok [X86,APIC] trust the local apic timer 1170 in C2 power state. 1171 1172 libata.dma= [LIBATA] DMA control 1173 libata.dma=0 Disable all PATA and SATA DMA 1174 libata.dma=1 PATA and SATA Disk DMA only 1175 libata.dma=2 ATAPI (CDROM) DMA only 1176 libata.dma=4 Compact Flash DMA only 1177 Combinations also work, so libata.dma=3 enables DMA 1178 for disks and CDROMs, but not CFs. 1179 1180 libata.ignore_hpa= [LIBATA] Ignore HPA limit 1181 libata.ignore_hpa=0 keep BIOS limits (default) 1182 libata.ignore_hpa=1 ignore limits, using full disk 1183 1184 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume 1185 when set. 1186 Format: <int> 1187 1188 libata.force= [LIBATA] Force configurations. The format is comma 1189 separated list of "[ID:]VAL" where ID is 1190 PORT[.DEVICE]. PORT and DEVICE are decimal numbers 1191 matching port, link or device. Basically, it matches 1192 the ATA ID string printed on console by libata. If 1193 the whole ID part is omitted, the last PORT and DEVICE 1194 values are used. If ID hasn't been specified yet, the 1195 configuration applies to all ports, links and devices. 1196 1197 If only DEVICE is omitted, the parameter applies to 1198 the port and all links and devices behind it. DEVICE 1199 number of 0 either selects the first device or the 1200 first fan-out link behind PMP device. It does not 1201 select the host link. DEVICE number of 15 selects the 1202 host link and device attached to it. 1203 1204 The VAL specifies the configuration to force. As long 1205 as there's no ambiguity shortcut notation is allowed. 1206 For example, both 1.5 and 1.5G would work for 1.5Gbps. 1207 The following configurations can be forced. 1208 1209 * Cable type: 40c, 80c, short40c, unk, ign or sata. 1210 Any ID with matching PORT is used. 1211 1212 * SATA link speed limit: 1.5Gbps or 3.0Gbps. 1213 1214 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. 1215 udma[/][16,25,33,44,66,100,133] notation is also 1216 allowed. 1217 1218 * [no]ncq: Turn on or off NCQ. 1219 1220 * nohrst, nosrst, norst: suppress hard, soft 1221 and both resets. 1222 1223 * dump_id: dump IDENTIFY data. 1224 1225 If there are multiple matching configurations changing 1226 the same attribute, the last one is used. 1227 1228 memblock=debug [KNL] Enable memblock debug messages. 1229 1230 load_ramdisk= [RAM] List of ramdisks to load from floppy 1231 See Documentation/blockdev/ramdisk.txt. 1232 1233 lockd.nlm_grace_period=P [NFS] Assign grace period. 1234 Format: <integer> 1235 1236 lockd.nlm_tcpport=N [NFS] Assign TCP port. 1237 Format: <integer> 1238 1239 lockd.nlm_timeout=T [NFS] Assign timeout value. 1240 Format: <integer> 1241 1242 lockd.nlm_udpport=M [NFS] Assign UDP port. 1243 Format: <integer> 1244 1245 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver 1246 Format: <irq> 1247 1248 loglevel= All Kernel Messages with a loglevel smaller than the 1249 console loglevel will be printed to the console. It can 1250 also be changed with klogd or other programs. The 1251 loglevels are defined as follows: 1252 1253 0 (KERN_EMERG) system is unusable 1254 1 (KERN_ALERT) action must be taken immediately 1255 2 (KERN_CRIT) critical conditions 1256 3 (KERN_ERR) error conditions 1257 4 (KERN_WARNING) warning conditions 1258 5 (KERN_NOTICE) normal but significant condition 1259 6 (KERN_INFO) informational 1260 7 (KERN_DEBUG) debug-level messages 1261 1262 log_buf_len=n Sets the size of the printk ring buffer, in bytes. 1263 Format: { n | nk | nM } 1264 n must be a power of two. The default size 1265 is set in the kernel config file. 1266 1267 logo.nologo [FB] Disables display of the built-in Linux logo. 1268 This may be used to provide more screen space for 1269 kernel log messages and is useful when debugging 1270 kernel boot problems. 1271 1272 lp=0 [LP] Specify parallel ports to use, e.g, 1273 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses 1274 lp=reset first parallel port). 'lp=0' disables the 1275 lp=auto printer driver. 'lp=reset' (which can be 1276 specified in addition to the ports) causes 1277 attached printers to be reset. Using 1278 lp=port1,port2,... specifies the parallel ports 1279 to associate lp devices with, starting with 1280 lp0. A port specification may be 'none' to skip 1281 that lp device, or a parport name such as 1282 'parport0'. Specifying 'lp=auto' instead of a 1283 port specification list means that device IDs 1284 from each port should be examined, to see if 1285 an IEEE 1284-compliant printer is attached; if 1286 so, the driver will manage that printer. 1287 See also header of drivers/char/lp.c. 1288 1289 lpj=n [KNL] 1290 Sets loops_per_jiffy to given constant, thus avoiding 1291 time-consuming boot-time autodetection (up to 250 ms per 1292 CPU). 0 enables autodetection (default). To determine 1293 the correct value for your kernel, boot with normal 1294 autodetection and see what value is printed. Note that 1295 on SMP systems the preset will be applied to all CPUs, 1296 which is likely to cause problems if your CPUs need 1297 significantly divergent settings. An incorrect value 1298 will cause delays in the kernel to be wrong, leading to 1299 unpredictable I/O errors and other breakage. Although 1300 unlikely, in the extreme case this might damage your 1301 hardware. 1302 1303 ltpc= [NET] 1304 Format: <io>,<irq>,<dma> 1305 1306 machvec= [IA64] Force the use of a particular machine-vector 1307 (machvec) in a generic kernel. 1308 Example: machvec=hpzx1_swiotlb 1309 1310 machtype= [Loongson] Share the same kernel image file between different 1311 yeeloong laptop. 1312 Example: machtype=lemote-yeeloong-2f-7inch 1313 1314 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater 1315 than or equal to this physical address is ignored. 1316 1317 maxcpus= [SMP] Maximum number of processors that an SMP kernel 1318 should make use of. maxcpus=n : n >= 0 limits the 1319 kernel to using 'n' processors. n=0 is a special case, 1320 it is equivalent to "nosmp", which also disables 1321 the IO APIC. 1322 1323 max_loop= [LOOP] Maximum number of loopback devices that can 1324 be mounted 1325 Format: <1-256> 1326 1327 mcatest= [IA-64] 1328 1329 mce [X86-32] Machine Check Exception 1330 1331 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt 1332 1333 md= [HW] RAID subsystems devices and level 1334 See Documentation/md.txt. 1335 1336 mdacon= [MDA] 1337 Format: <first>,<last> 1338 Specifies range of consoles to be captured by the MDA. 1339 1340 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory 1341 Amount of memory to be used when the kernel is not able 1342 to see the whole system memory or for test. 1343 [X86-32] Use together with memmap= to avoid physical 1344 address space collisions. Without memmap= PCI devices 1345 could be placed at addresses belonging to unused RAM. 1346 1347 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel 1348 memory. 1349 1350 memchunk=nn[KMG] 1351 [KNL,SH] Allow user to override the default size for 1352 per-device physically contiguous DMA buffers. 1353 1354 memmap=exactmap [KNL,X86] Enable setting of an exact 1355 E820 memory map, as specified by the user. 1356 Such memmap=exactmap lines can be constructed based on 1357 BIOS output or other requirements. See the memmap=nn@ss 1358 option description. 1359 1360 memmap=nn[KMG]@ss[KMG] 1361 [KNL] Force usage of a specific region of memory 1362 Region of memory to be used, from ss to ss+nn. 1363 1364 memmap=nn[KMG]#ss[KMG] 1365 [KNL,ACPI] Mark specific memory as ACPI data. 1366 Region of memory to be used, from ss to ss+nn. 1367 1368 memmap=nn[KMG]$ss[KMG] 1369 [KNL,ACPI] Mark specific memory as reserved. 1370 Region of memory to be used, from ss to ss+nn. 1371 Example: Exclude memory from 0x18690000-0x1869ffff 1372 memmap=64K$0x18690000 1373 or 1374 memmap=0x10000$0x18690000 1375 1376 memory_corruption_check=0/1 [X86] 1377 Some BIOSes seem to corrupt the first 64k of 1378 memory when doing things like suspend/resume. 1379 Setting this option will scan the memory 1380 looking for corruption. Enabling this will 1381 both detect corruption and prevent the kernel 1382 from using the memory being corrupted. 1383 However, its intended as a diagnostic tool; if 1384 repeatable BIOS-originated corruption always 1385 affects the same memory, you can use memmap= 1386 to prevent the kernel from using that memory. 1387 1388 memory_corruption_check_size=size [X86] 1389 By default it checks for corruption in the low 1390 64k, making this memory unavailable for normal 1391 use. Use this parameter to scan for 1392 corruption in more or less memory. 1393 1394 memory_corruption_check_period=seconds [X86] 1395 By default it checks for corruption every 60 1396 seconds. Use this parameter to check at some 1397 other rate. 0 disables periodic checking. 1398 1399 memtest= [KNL,X86] Enable memtest 1400 Format: <integer> 1401 default : 0 <disable> 1402 Specifies the number of memtest passes to be 1403 performed. Each pass selects another test 1404 pattern from a given set of patterns. Memtest 1405 fills the memory with this pattern, validates 1406 memory contents and reserves bad memory 1407 regions that are detected. 1408 1409 meye.*= [HW] Set MotionEye Camera parameters 1410 See Documentation/video4linux/meye.txt. 1411 1412 mfgpt_irq= [IA-32] Specify the IRQ to use for the 1413 Multi-Function General Purpose Timers on AMD Geode 1414 platforms. 1415 1416 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when 1417 the BIOS has incorrectly applied a workaround. TinyBIOS 1418 version 0.98 is known to be affected, 0.99 fixes the 1419 problem by letting the user disable the workaround. 1420 1421 mga= [HW,DRM] 1422 1423 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this 1424 physical address is ignored. 1425 1426 mini2440= [ARM,HW,KNL] 1427 Format:[0..2][b][c][t] 1428 Default: "0tb" 1429 MINI2440 configuration specification: 1430 0 - The attached screen is the 3.5" TFT 1431 1 - The attached screen is the 7" TFT 1432 2 - The VGA Shield is attached (1024x768) 1433 Leaving out the screen size parameter will not load 1434 the TFT driver, and the framebuffer will be left 1435 unconfigured. 1436 b - Enable backlight. The TFT backlight pin will be 1437 linked to the kernel VESA blanking code and a GPIO 1438 LED. This parameter is not necessary when using the 1439 VGA shield. 1440 c - Enable the s3c camera interface. 1441 t - Reserved for enabling touchscreen support. The 1442 touchscreen support is not enabled in the mainstream 1443 kernel as of 2.6.30, a preliminary port can be found 1444 in the "bleeding edge" mini2440 support kernel at 1445 http://repo.or.cz/w/linux-2.6/mini2440.git 1446 1447 mminit_loglevel= 1448 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this 1449 parameter allows control of the logging verbosity for 1450 the additional memory initialisation checks. A value 1451 of 0 disables mminit logging and a level of 4 will 1452 log everything. Information is printed at KERN_DEBUG 1453 so loglevel=8 may also need to be specified. 1454 1455 mousedev.tap_time= 1456 [MOUSE] Maximum time between finger touching and 1457 leaving touchpad surface for touch to be considered 1458 a tap and be reported as a left button click (for 1459 touchpads working in absolute mode only). 1460 Format: <msecs> 1461 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices 1462 reporting absolute coordinates, such as tablets 1463 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices 1464 reporting absolute coordinates, such as tablets 1465 1466 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter 1467 is similar to kernelcore except it specifies the 1468 amount of memory used for migratable allocations. 1469 If both kernelcore and movablecore is specified, 1470 then kernelcore will be at *least* the specified 1471 value but may be more. If movablecore on its own 1472 is specified, the administrator must be careful 1473 that the amount of memory usable for all allocations 1474 is not too small. 1475 1476 MTD_Partition= [MTD] 1477 Format: <name>,<region-number>,<size>,<offset> 1478 1479 MTD_Region= [MTD] Format: 1480 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>] 1481 1482 mtdparts= [MTD] 1483 See drivers/mtd/cmdlinepart.c. 1484 1485 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration 1486 1487 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock] 1488 1489 boundary - index of last SLC block on Flex-OneNAND. 1490 The remaining blocks are configured as MLC blocks. 1491 lock - Configure if Flex-OneNAND boundary should be locked. 1492 Once locked, the boundary cannot be changed. 1493 1 indicates lock status, 0 indicates unlock status. 1494 1495 mtdset= [ARM] 1496 ARM/S3C2412 JIVE boot control 1497 1498 See arch/arm/mach-s3c2412/mach-jive.c 1499 1500 mtouchusb.raw_coordinates= 1501 [HW] Make the MicroTouch USB driver use raw coordinates 1502 ('y', default) or cooked coordinates ('n') 1503 1504 mtrr_chunk_size=nn[KMG] [X86] 1505 used for mtrr cleanup. It is largest continuous chunk 1506 that could hold holes aka. UC entries. 1507 1508 mtrr_gran_size=nn[KMG] [X86] 1509 Used for mtrr cleanup. It is granularity of mtrr block. 1510 Default is 1. 1511 Large value could prevent small alignment from 1512 using up MTRRs. 1513 1514 mtrr_spare_reg_nr=n [X86] 1515 Format: <integer> 1516 Range: 0,7 : spare reg number 1517 Default : 1 1518 Used for mtrr cleanup. It is spare mtrr entries number. 1519 Set to 2 or more if your graphical card needs more. 1520 1521 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card 1522 1523 netdev= [NET] Network devices parameters 1524 Format: <irq>,<io>,<mem_start>,<mem_end>,<name> 1525 Note that mem_start is often overloaded to mean 1526 something different and driver-specific. 1527 This usage is only documented in each driver source 1528 file if at all. 1529 1530 nf_conntrack.acct= 1531 [NETFILTER] Enable connection tracking flow accounting 1532 0 to disable accounting 1533 1 to enable accounting 1534 Default value is 0. 1535 1536 nfsaddrs= [NFS] 1537 See Documentation/filesystems/nfs/nfsroot.txt. 1538 1539 nfsroot= [NFS] nfs root filesystem for disk-less boxes. 1540 See Documentation/filesystems/nfs/nfsroot.txt. 1541 1542 nfs.callback_tcpport= 1543 [NFS] set the TCP port on which the NFSv4 callback 1544 channel should listen. 1545 1546 nfs.cache_getent= 1547 [NFS] sets the pathname to the program which is used 1548 to update the NFS client cache entries. 1549 1550 nfs.cache_getent_timeout= 1551 [NFS] sets the timeout after which an attempt to 1552 update a cache entry is deemed to have failed. 1553 1554 nfs.idmap_cache_timeout= 1555 [NFS] set the maximum lifetime for idmapper cache 1556 entries. 1557 1558 nfs.enable_ino64= 1559 [NFS] enable 64-bit inode numbers. 1560 If zero, the NFS client will fake up a 32-bit inode 1561 number for the readdir() and stat() syscalls instead 1562 of returning the full 64-bit number. 1563 The default is to return 64-bit inode numbers. 1564 1565 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take 1566 when a NMI is triggered. 1567 Format: [state][,regs][,debounce][,die] 1568 1569 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels 1570 Format: [panic,][num] 1571 Valid num: 0,1,2 1572 0 - turn nmi_watchdog off 1573 1 - use the IO-APIC timer for the NMI watchdog 1574 2 - use the local APIC for the NMI watchdog using 1575 a performance counter. Note: This will use one 1576 performance counter and the local APIC's performance 1577 vector. 1578 When panic is specified, panic when an NMI watchdog 1579 timeout occurs. 1580 This is useful when you use a panic=... timeout and 1581 need the box quickly up again. 1582 Instead of 1 and 2 it is possible to use the following 1583 symbolic names: lapic and ioapic 1584 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic 1585 1586 netpoll.carrier_timeout= 1587 [NET] Specifies amount of time (in seconds) that 1588 netpoll should wait for a carrier. By default netpoll 1589 waits 4 seconds. 1590 1591 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths 1592 emulation library even if a 387 maths coprocessor 1593 is present. 1594 1595 no_console_suspend 1596 [HW] Never suspend the console 1597 Disable suspending of consoles during suspend and 1598 hibernate operations. Once disabled, debugging 1599 messages can reach various consoles while the rest 1600 of the system is being put to sleep (ie, while 1601 debugging driver suspend/resume hooks). This may 1602 not work reliably with all consoles, but is known 1603 to work with serial and VGA consoles. 1604 1605 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien 1606 caches in the slab allocator. Saves per-node memory, 1607 but will impact performance. 1608 1609 noalign [KNL,ARM] 1610 1611 noapic [SMP,APIC] Tells the kernel to not make use of any 1612 IOAPICs that may be present in the system. 1613 1614 nobats [PPC] Do not use BATs for mapping kernel lowmem 1615 on "Classic" PPC cores. 1616 1617 nocache [ARM] 1618 1619 noclflush [BUGS=X86] Don't use the CLFLUSH instruction 1620 1621 nodelayacct [KNL] Disable per-task delay accounting 1622 1623 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects. 1624 1625 nodsp [SH] Disable hardware DSP at boot time. 1626 1627 noefi [X86] Disable EFI runtime services support. 1628 1629 noexec [IA-64] 1630 1631 noexec [X86] 1632 On X86-32 available only on PAE configured kernels. 1633 noexec=on: enable non-executable mappings (default) 1634 noexec=off: disable non-executable mappings 1635 1636 noexec32 [X86-64] 1637 This affects only 32-bit executables. 1638 noexec32=on: enable non-executable mappings (default) 1639 read doesn't imply executable mappings 1640 noexec32=off: disable non-executable mappings 1641 read implies executable mappings 1642 1643 nofpu [SH] Disable hardware FPU at boot time. 1644 1645 nofxsr [BUGS=X86-32] Disables x86 floating point extended 1646 register save and restore. The kernel will only save 1647 legacy floating-point registers on task switch. 1648 1649 noxsave [BUGS=X86] Disables x86 extended register state save 1650 and restore using xsave. The kernel will fallback to 1651 enabling legacy floating-point and sse state. 1652 1653 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or 1654 wfi(ARM) instruction doesn't work correctly and not to 1655 use it. This is also useful when using JTAG debugger. 1656 1657 no-hlt [BUGS=X86-32] Tells the kernel that the hlt 1658 instruction doesn't work correctly and not to 1659 use it. 1660 1661 no_file_caps Tells the kernel not to honor file capabilities. The 1662 only way then for a file to be executed with privilege 1663 is to be setuid root or executed by root. 1664 1665 nohalt [IA-64] Tells the kernel not to use the power saving 1666 function PAL_HALT_LIGHT when idle. This increases 1667 power-consumption. On the positive side, it reduces 1668 interrupt wake-up latency, which may improve performance 1669 in certain environments such as networked servers or 1670 real-time systems. 1671 1672 nohz= [KNL] Boottime enable/disable dynamic ticks 1673 Valid arguments: on, off 1674 Default: on 1675 1676 noiotrap [SH] Disables trapped I/O port accesses. 1677 1678 noirqdebug [X86-32] Disables the code which attempts to detect and 1679 disable unhandled interrupt sources. 1680 1681 no_timer_check [X86,APIC] Disables the code which tests for 1682 broken timer IRQ sources. 1683 1684 noisapnp [ISAPNP] Disables ISA PnP code. 1685 1686 noinitrd [RAM] Tells the kernel not to load any configured 1687 initial RAM disk. 1688 1689 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt 1690 remapping. 1691 [Deprecated - use intremap=off] 1692 1693 nointroute [IA-64] 1694 1695 nojitter [IA64] Disables jitter checking for ITC timers. 1696 1697 nolapic [X86-32,APIC] Do not enable or use the local APIC. 1698 1699 nolapic_timer [X86-32,APIC] Do not use the local APIC timer. 1700 1701 noltlbs [PPC] Do not use large page/tlb entries for kernel 1702 lowmem mapping on PPC40x. 1703 1704 nomca [IA-64] Disable machine check abort handling 1705 1706 nomce [X86-32] Machine Check Exception 1707 1708 nomfgpt [X86-32] Disable Multi-Function General Purpose 1709 Timer usage (for AMD Geode machines). 1710 1711 nopat [X86] Disable PAT (page attribute table extension of 1712 pagetables) support. 1713 1714 norandmaps Don't use address space randomization. Equivalent to 1715 echo 0 > /proc/sys/kernel/randomize_va_space 1716 1717 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops 1718 1719 noreplace-smp [X86-32,SMP] Don't replace SMP instructions 1720 with UP alternatives 1721 1722 noresidual [PPC] Don't use residual data on PReP machines. 1723 1724 noresume [SWSUSP] Disables resume and restores original swap 1725 space. 1726 1727 no-scroll [VGA] Disables scrollback. 1728 This is required for the Braillex ib80-piezo Braille 1729 reader made by F.H. Papenmeier (Germany). 1730 1731 nosbagart [IA-64] 1732 1733 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support. 1734 1735 nosmp [SMP] Tells an SMP kernel to act as a UP kernel, 1736 and disable the IO APIC. legacy for "maxcpus=0". 1737 1738 nosoftlockup [KNL] Disable the soft-lockup detector. 1739 1740 noswapaccount [KNL] Disable accounting of swap in memory resource 1741 controller. (See Documentation/cgroups/memory.txt) 1742 1743 nosync [HW,M68K] Disables sync negotiation for all devices. 1744 1745 notsc [BUGS=X86-32] Disable Time Stamp Counter 1746 1747 nousb [USB] Disable the USB subsystem 1748 1749 nowatchdog [KNL] Disable the lockup detector (NMI watchdog). 1750 1751 nowb [ARM] 1752 1753 nox2apic [X86-64,APIC] Do not enable x2APIC mode. 1754 1755 nptcg= [IA64] Override max number of concurrent global TLB 1756 purges which is reported from either PAL_VM_SUMMARY or 1757 SAL PALO. 1758 1759 nr_cpus= [SMP] Maximum number of processors that an SMP kernel 1760 could support. nr_cpus=n : n >= 1 limits the kernel to 1761 supporting 'n' processors. Later in runtime you can not 1762 use hotplug cpu feature to put more cpu back to online. 1763 just like you compile the kernel NR_CPUS=n 1764 1765 nr_uarts= [SERIAL] maximum number of UARTs to be registered. 1766 1767 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. 1768 one of ['zone', 'node', 'default'] can be specified 1769 This can be set from sysctl after boot. 1770 See Documentation/sysctl/vm.txt for details. 1771 1772 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. 1773 See Documentation/debugging-via-ohci1394.txt for more 1774 info. 1775 1776 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands 1777 Rather than timing out after 20 ms if an EC 1778 command is not properly ACKed, override the length 1779 of the timeout. We have interrupts disabled while 1780 waiting for the ACK, so if this is set too high 1781 interrupts *may* be lost! 1782 1783 omap_mux= [OMAP] Override bootloader pin multiplexing. 1784 Format: <mux_mode0.mode_name=value>... 1785 For example, to override I2C bus2: 1786 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 1787 1788 oprofile.timer= [HW] 1789 Use timer interrupt instead of performance counters 1790 1791 oprofile.cpu_type= Force an oprofile cpu type 1792 This might be useful if you have an older oprofile 1793 userland or if you want common events. 1794 Format: { arch_perfmon } 1795 arch_perfmon: [X86] Force use of architectural 1796 perfmon on Intel CPUs instead of the 1797 CPU specific event set. 1798 1799 OSS [HW,OSS] 1800 See Documentation/sound/oss/oss-parameters.txt 1801 1802 panic= [KNL] Kernel behaviour on panic 1803 Format: <timeout> 1804 1805 parkbd.port= [HW] Parallel port number the keyboard adapter is 1806 connected to, default is 0. 1807 Format: <parport#> 1808 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation, 1809 0 for XT, 1 for AT (default is AT). 1810 Format: <mode> 1811 1812 parport= [HW,PPT] Specify parallel ports. 0 disables. 1813 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] } 1814 Use 'auto' to force the driver to use any 1815 IRQ/DMA settings detected (the default is to 1816 ignore detected IRQ/DMA settings because of 1817 possible conflicts). You can specify the base 1818 address, IRQ, and DMA settings; IRQ and DMA 1819 should be numbers, or 'auto' (for using detected 1820 settings on that particular port), or 'nofifo' 1821 (to avoid using a FIFO even if it is detected). 1822 Parallel ports are assigned in the order they 1823 are specified on the command line, starting 1824 with parport0. 1825 1826 parport_init_mode= [HW,PPT] 1827 Configure VIA parallel port to operate in 1828 a specific mode. This is necessary on Pegasos 1829 computer where firmware has no options for setting 1830 up parallel port mode and sets it to spp. 1831 Currently this function knows 686a and 8231 chips. 1832 Format: [spp|ps2|epp|ecp|ecpepp] 1833 1834 pause_on_oops= 1835 Halt all CPUs after the first oops has been printed for 1836 the specified number of seconds. This is to be used if 1837 your oopses keep scrolling off the screen. 1838 1839 pcbit= [HW,ISDN] 1840 1841 pcd. [PARIDE] 1842 See header of drivers/block/paride/pcd.c. 1843 See also Documentation/blockdev/paride.txt. 1844 1845 pci=option[,option...] [PCI] various PCI subsystem options: 1846 earlydump [X86] dump PCI config space before the kernel 1847 changes anything 1848 off [X86] don't probe for the PCI bus 1849 bios [X86-32] force use of PCI BIOS, don't access 1850 the hardware directly. Use this if your machine 1851 has a non-standard PCI host bridge. 1852 nobios [X86-32] disallow use of PCI BIOS, only direct 1853 hardware access methods are allowed. Use this 1854 if you experience crashes upon bootup and you 1855 suspect they are caused by the BIOS. 1856 conf1 [X86] Force use of PCI Configuration 1857 Mechanism 1. 1858 conf2 [X86] Force use of PCI Configuration 1859 Mechanism 2. 1860 noaer [PCIE] If the PCIEAER kernel config parameter is 1861 enabled, this kernel boot option can be used to 1862 disable the use of PCIE advanced error reporting. 1863 nodomains [PCI] Disable support for multiple PCI 1864 root domains (aka PCI segments, in ACPI-speak). 1865 nommconf [X86] Disable use of MMCONFIG for PCI 1866 Configuration 1867 check_enable_amd_mmconf [X86] check for and enable 1868 properly configured MMIO access to PCI 1869 config space on AMD family 10h CPU 1870 nomsi [MSI] If the PCI_MSI kernel config parameter is 1871 enabled, this kernel boot option can be used to 1872 disable the use of MSI interrupts system-wide. 1873 noioapicquirk [APIC] Disable all boot interrupt quirks. 1874 Safety option to keep boot IRQs enabled. This 1875 should never be necessary. 1876 ioapicreroute [APIC] Enable rerouting of boot IRQs to the 1877 primary IO-APIC for bridges that cannot disable 1878 boot IRQs. This fixes a source of spurious IRQs 1879 when the system masks IRQs. 1880 noioapicreroute [APIC] Disable workaround that uses the 1881 boot IRQ equivalent of an IRQ that connects to 1882 a chipset where boot IRQs cannot be disabled. 1883 The opposite of ioapicreroute. 1884 biosirq [X86-32] Use PCI BIOS calls to get the interrupt 1885 routing table. These calls are known to be buggy 1886 on several machines and they hang the machine 1887 when used, but on other computers it's the only 1888 way to get the interrupt routing table. Try 1889 this option if the kernel is unable to allocate 1890 IRQs or discover secondary PCI buses on your 1891 motherboard. 1892 rom [X86] Assign address space to expansion ROMs. 1893 Use with caution as certain devices share 1894 address decoders between ROMs and other 1895 resources. 1896 norom [X86] Do not assign address space to 1897 expansion ROMs that do not already have 1898 BIOS assigned address ranges. 1899 nobar [X86] Do not assign address space to the 1900 BARs that weren't assigned by the BIOS. 1901 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be 1902 assigned automatically to PCI devices. You can 1903 make the kernel exclude IRQs of your ISA cards 1904 this way. 1905 pirqaddr=0xAAAAA [X86] Specify the physical address 1906 of the PIRQ table (normally generated 1907 by the BIOS) if it is outside the 1908 F0000h-100000h range. 1909 lastbus=N [X86] Scan all buses thru bus #N. Can be 1910 useful if the kernel is unable to find your 1911 secondary buses and you want to tell it 1912 explicitly which ones they are. 1913 assign-busses [X86] Always assign all PCI bus 1914 numbers ourselves, overriding 1915 whatever the firmware may have done. 1916 usepirqmask [X86] Honor the possible IRQ mask stored 1917 in the BIOS $PIR table. This is needed on 1918 some systems with broken BIOSes, notably 1919 some HP Pavilion N5400 and Omnibook XE3 1920 notebooks. This will have no effect if ACPI 1921 IRQ routing is enabled. 1922 noacpi [X86] Do not use ACPI for IRQ routing 1923 or for PCI scanning. 1924 use_crs [X86] Use PCI host bridge window information 1925 from ACPI. On BIOSes from 2008 or later, this 1926 is enabled by default. If you need to use this, 1927 please report a bug. 1928 nocrs [X86] Ignore PCI host bridge windows from ACPI. 1929 If you need to use this, please report a bug. 1930 routeirq Do IRQ routing for all PCI devices. 1931 This is normally done in pci_enable_device(), 1932 so this option is a temporary workaround 1933 for broken drivers that don't call it. 1934 skip_isa_align [X86] do not align io start addr, so can 1935 handle more pci cards 1936 firmware [ARM] Do not re-enumerate the bus but instead 1937 just use the configuration from the 1938 bootloader. This is currently used on 1939 IXP2000 systems where the bus has to be 1940 configured a certain way for adjunct CPUs. 1941 noearly [X86] Don't do any early type 1 scanning. 1942 This might help on some broken boards which 1943 machine check when some devices' config space 1944 is read. But various workarounds are disabled 1945 and some IOMMU drivers will not work. 1946 bfsort Sort PCI devices into breadth-first order. 1947 This sorting is done to get a device 1948 order compatible with older (<= 2.4) kernels. 1949 nobfsort Don't sort PCI devices into breadth-first order. 1950 cbiosize=nn[KMG] The fixed amount of bus space which is 1951 reserved for the CardBus bridge's IO window. 1952 The default value is 256 bytes. 1953 cbmemsize=nn[KMG] The fixed amount of bus space which is 1954 reserved for the CardBus bridge's memory 1955 window. The default value is 64 megabytes. 1956 resource_alignment= 1957 Format: 1958 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...] 1959 Specifies alignment and device to reassign 1960 aligned memory resources. 1961 If <order of align> is not specified, 1962 PAGE_SIZE is used as alignment. 1963 PCI-PCI bridge can be specified, if resource 1964 windows need to be expanded. 1965 ecrc= Enable/disable PCIe ECRC (transaction layer 1966 end-to-end CRC checking). 1967 bios: Use BIOS/firmware settings. This is the 1968 the default. 1969 off: Turn ECRC off 1970 on: Turn ECRC on. 1971 1972 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power 1973 Management. 1974 off Disable ASPM. 1975 force Enable ASPM even on devices that claim not to support it. 1976 WARNING: Forcing ASPM on may cause system lockups. 1977 1978 pcie_ports= [PCIE] PCIe ports handling: 1979 auto Ask the BIOS whether or not to use native PCIe services 1980 associated with PCIe ports (PME, hot-plug, AER). Use 1981 them only if that is allowed by the BIOS. 1982 native Use native PCIe services associated with PCIe ports 1983 unconditionally. 1984 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe 1985 ports driver. 1986 1987 pcie_pme= [PCIE,PM] Native PCIe PME signaling options: 1988 nomsi Do not use MSI for native PCIe PME signaling (this makes 1989 all PCIe root ports use INTx for all services). 1990 1991 pcmv= [HW,PCMCIA] BadgePAD 4 1992 1993 pd. [PARIDE] 1994 See Documentation/blockdev/paride.txt. 1995 1996 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at 1997 boot time. 1998 Format: { 0 | 1 } 1999 See arch/parisc/kernel/pdc_chassis.c 2000 2001 percpu_alloc= Select which percpu first chunk allocator to use. 2002 Currently supported values are "embed" and "page". 2003 Archs may support subset or none of the selections. 2004 See comments in mm/percpu.c for details on each 2005 allocator. This parameter is primarily for debugging 2006 and performance comparison. 2007 2008 pf. [PARIDE] 2009 See Documentation/blockdev/paride.txt. 2010 2011 pg. [PARIDE] 2012 See Documentation/blockdev/paride.txt. 2013 2014 pirq= [SMP,APIC] Manual mp-table setup 2015 See Documentation/x86/i386/IO-APIC.txt. 2016 2017 plip= [PPT,NET] Parallel port network link 2018 Format: { parport<nr> | timid | 0 } 2019 See also Documentation/parport.txt. 2020 2021 pmtmr= [X86] Manual setup of pmtmr I/O Port. 2022 Override pmtimer IOPort with a hex value. 2023 e.g. pmtmr=0x508 2024 2025 pnp.debug [PNP] 2026 Enable PNP debug messages. This depends on the 2027 CONFIG_PNP_DEBUG_MESSAGES option. 2028 2029 pnpacpi= [ACPI] 2030 { off } 2031 2032 pnpbios= [ISAPNP] 2033 { on | off | curr | res | no-curr | no-res } 2034 2035 pnp_reserve_irq= 2036 [ISAPNP] Exclude IRQs for the autoconfiguration 2037 2038 pnp_reserve_dma= 2039 [ISAPNP] Exclude DMAs for the autoconfiguration 2040 2041 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration 2042 Ranges are in pairs (I/O port base and size). 2043 2044 pnp_reserve_mem= 2045 [ISAPNP] Exclude memory regions for the 2046 autoconfiguration. 2047 Ranges are in pairs (memory base and size). 2048 2049 ports= [IP_VS_FTP] IPVS ftp helper module 2050 Default is 21. 2051 Up to 8 (IP_VS_APP_MAX_PORTS) ports 2052 may be specified. 2053 Format: <port>,<port>.... 2054 2055 print-fatal-signals= 2056 [KNL] debug: print fatal signals 2057 2058 If enabled, warn about various signal handling 2059 related application anomalies: too many signals, 2060 too many POSIX.1 timers, fatal signals causing a 2061 coredump - etc. 2062 2063 If you hit the warning due to signal overflow, 2064 you might want to try "ulimit -i unlimited". 2065 2066 default: off. 2067 2068 printk.time= Show timing data prefixed to each printk message line 2069 Format: <bool> (1/Y/y=enable, 0/N/n=disable) 2070 2071 processor.max_cstate= [HW,ACPI] 2072 Limit processor to maximum C-state 2073 max_cstate=9 overrides any DMI blacklist limit. 2074 2075 processor.nocst [HW,ACPI] 2076 Ignore the _CST method to determine C-states, 2077 instead using the legacy FADT method 2078 2079 profile= [KNL] Enable kernel profiling via /proc/profile 2080 Format: [schedule,]<number> 2081 Param: "schedule" - profile schedule points. 2082 Param: <number> - step/bucket size as a power of 2 for 2083 statistical time based profiling. 2084 Param: "sleep" - profile D-state sleeping (millisecs). 2085 Requires CONFIG_SCHEDSTATS 2086 Param: "kvm" - profile VM exits. 2087 2088 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk 2089 before loading. 2090 See Documentation/blockdev/ramdisk.txt. 2091 2092 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to 2093 probe for; one of (bare|imps|exps|lifebook|any). 2094 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports 2095 per second. 2096 psmouse.resetafter= [HW,MOUSE] 2097 Try to reset the device after so many bad packets 2098 (0 = never). 2099 psmouse.resolution= 2100 [HW,MOUSE] Set desired mouse resolution, in dpi. 2101 psmouse.smartscroll= 2102 [HW,MOUSE] Controls Logitech smartscroll autorepeat. 2103 0 = disabled, 1 = enabled (default). 2104 2105 pt. [PARIDE] 2106 See Documentation/blockdev/paride.txt. 2107 2108 pty.legacy_count= 2109 [KNL] Number of legacy pty's. Overwrites compiled-in 2110 default number. 2111 2112 quiet [KNL] Disable most log messages 2113 2114 r128= [HW,DRM] 2115 2116 raid= [HW,RAID] 2117 See Documentation/md.txt. 2118 2119 ramdisk_blocksize= [RAM] 2120 See Documentation/blockdev/ramdisk.txt. 2121 2122 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes 2123 See Documentation/blockdev/ramdisk.txt. 2124 2125 rcupdate.blimit= [KNL,BOOT] 2126 Set maximum number of finished RCU callbacks to process 2127 in one batch. 2128 2129 rcupdate.qhimark= [KNL,BOOT] 2130 Set threshold of queued 2131 RCU callbacks over which batch limiting is disabled. 2132 2133 rcupdate.qlowmark= [KNL,BOOT] 2134 Set threshold of queued RCU callbacks below which 2135 batch limiting is re-enabled. 2136 2137 rdinit= [KNL] 2138 Format: <full_path> 2139 Run specified binary instead of /init from the ramdisk, 2140 used for early userspace startup. See initrd. 2141 2142 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode 2143 Format: <reboot_mode>[,<reboot_mode2>[,...]] 2144 See arch/*/kernel/reboot.c or arch/*/kernel/process.c 2145 2146 relax_domain_level= 2147 [KNL, SMP] Set scheduler's default relax_domain_level. 2148 See Documentation/cgroups/cpusets.txt. 2149 2150 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area 2151 2152 reservetop= [X86-32] 2153 Format: nn[KMG] 2154 Reserves a hole at the top of the kernel virtual 2155 address space. 2156 2157 reset_devices [KNL] Force drivers to reset the underlying device 2158 during initialization. 2159 2160 resume= [SWSUSP] 2161 Specify the partition device for software suspend 2162 2163 resume_offset= [SWSUSP] 2164 Specify the offset from the beginning of the partition 2165 given by "resume=" at which the swap header is located, 2166 in <PAGE_SIZE> units (needed only for swap files). 2167 See Documentation/power/swsusp-and-swap-files.txt 2168 2169 retain_initrd [RAM] Keep initrd memory after extraction 2170 2171 rhash_entries= [KNL,NET] 2172 Set number of hash buckets for route cache 2173 2174 riscom8= [HW,SERIAL] 2175 Format: <io_board1>[,<io_board2>[,...<io_boardN>]] 2176 2177 ro [KNL] Mount root device read-only on boot 2178 2179 root= [KNL] Root filesystem 2180 2181 rootdelay= [KNL] Delay (in seconds) to pause before attempting to 2182 mount the root filesystem 2183 2184 rootflags= [KNL] Set root filesystem mount option string 2185 2186 rootfstype= [KNL] Set root filesystem type 2187 2188 rootwait [KNL] Wait (indefinitely) for root device to show up. 2189 Useful for devices that are detected asynchronously 2190 (e.g. USB and MMC devices). 2191 2192 rw [KNL] Mount root device read-write on boot 2193 2194 S [KNL] Run init in single mode 2195 2196 sa1100ir [NET] 2197 See drivers/net/irda/sa1100_ir.c. 2198 2199 sbni= [NET] Granch SBNI12 leased line adapter 2200 2201 sched_debug [KNL] Enables verbose scheduler debug messages. 2202 2203 security= [SECURITY] Choose a security module to enable at boot. 2204 If this boot parameter is not specified, only the first 2205 security module asking for security registration will be 2206 loaded. An invalid security module name will be treated 2207 as if no module has been chosen. 2208 2209 selinux= [SELINUX] Disable or enable SELinux at boot time. 2210 Format: { "0" | "1" } 2211 See security/selinux/Kconfig help text. 2212 0 -- disable. 2213 1 -- enable. 2214 Default value is set via kernel config option. 2215 If enabled at boot time, /selinux/disable can be used 2216 later to disable prior to initial policy load. 2217 2218 apparmor= [APPARMOR] Disable or enable AppArmor at boot time 2219 Format: { "0" | "1" } 2220 See security/apparmor/Kconfig help text 2221 0 -- disable. 2222 1 -- enable. 2223 Default value is set via kernel config option. 2224 2225 serialnumber [BUGS=X86-32] 2226 2227 shapers= [NET] 2228 Maximal number of shapers. 2229 2230 show_msr= [x86] show boot-time MSR settings 2231 Format: { <integer> } 2232 Show boot-time (BIOS-initialized) MSR settings. 2233 The parameter means the number of CPUs to show, 2234 for example 1 means boot CPU only. 2235 2236 simeth= [IA-64] 2237 simscsi= 2238 2239 slram= [HW,MTD] 2240 2241 slub_debug[=options[,slabs]] [MM, SLUB] 2242 Enabling slub_debug allows one to determine the 2243 culprit if slab objects become corrupted. Enabling 2244 slub_debug can create guard zones around objects and 2245 may poison objects when not in use. Also tracks the 2246 last alloc / free. For more information see 2247 Documentation/vm/slub.txt. 2248 2249 slub_max_order= [MM, SLUB] 2250 Determines the maximum allowed order for slabs. 2251 A high setting may cause OOMs due to memory 2252 fragmentation. For more information see 2253 Documentation/vm/slub.txt. 2254 2255 slub_min_objects= [MM, SLUB] 2256 The minimum number of objects per slab. SLUB will 2257 increase the slab order up to slub_max_order to 2258 generate a sufficiently large slab able to contain 2259 the number of objects indicated. The higher the number 2260 of objects the smaller the overhead of tracking slabs 2261 and the less frequently locks need to be acquired. 2262 For more information see Documentation/vm/slub.txt. 2263 2264 slub_min_order= [MM, SLUB] 2265 Determines the mininum page order for slabs. Must be 2266 lower than slub_max_order. 2267 For more information see Documentation/vm/slub.txt. 2268 2269 slub_nomerge [MM, SLUB] 2270 Disable merging of slabs with similar size. May be 2271 necessary if there is some reason to distinguish 2272 allocs to different slabs. Debug options disable 2273 merging on their own. 2274 For more information see Documentation/vm/slub.txt. 2275 2276 smart2= [HW] 2277 Format: <io1>[,<io2>[,...,<io8>]] 2278 2279 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only 2280 attempt to substitute SMP alternatives once at boot. 2281 2282 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices 2283 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port 2284 smsc-ircc2.ircc_sir= [HW] SIR base I/O port 2285 smsc-ircc2.ircc_fir= [HW] FIR base I/O port 2286 smsc-ircc2.ircc_irq= [HW] IRQ line 2287 smsc-ircc2.ircc_dma= [HW] DMA channel 2288 smsc-ircc2.ircc_transceiver= [HW] Transceiver type: 2289 0: Toshiba Satellite 1800 (GP data pin select) 2290 1: Fast pin select (default) 2291 2: ATC IRMode 2292 2293 softlockup_panic= 2294 [KNL] Should the soft-lockup detector generate panics. 2295 2296 sonypi.*= [HW] Sony Programmable I/O Control Device driver 2297 See Documentation/sonypi.txt 2298 2299 specialix= [HW,SERIAL] Specialix multi-serial port adapter 2300 See Documentation/serial/specialix.txt. 2301 2302 spia_io_base= [HW,MTD] 2303 spia_fio_base= 2304 spia_pedr= 2305 spia_peddr= 2306 2307 stacktrace [FTRACE] 2308 Enabled the stack tracer on boot up. 2309 2310 sti= [PARISC,HW] 2311 Format: <num> 2312 Set the STI (builtin display/keyboard on the HP-PARISC 2313 machines) console (graphic card) which should be used 2314 as the initial boot-console. 2315 See also comment in drivers/video/console/sticore.c. 2316 2317 sti_font= [HW] 2318 See comment in drivers/video/console/sticore.c. 2319 2320 stifb= [HW] 2321 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] 2322 2323 sunrpc.min_resvport= 2324 sunrpc.max_resvport= 2325 [NFS,SUNRPC] 2326 SunRPC servers often require that client requests 2327 originate from a privileged port (i.e. a port in the 2328 range 0 < portnr < 1024). 2329 An administrator who wishes to reserve some of these 2330 ports for other uses may adjust the range that the 2331 kernel's sunrpc client considers to be privileged 2332 using these two parameters to set the minimum and 2333 maximum port values. 2334 2335 sunrpc.pool_mode= 2336 [NFS] 2337 Control how the NFS server code allocates CPUs to 2338 service thread pools. Depending on how many NICs 2339 you have and where their interrupts are bound, this 2340 option will affect which CPUs will do NFS serving. 2341 Note: this parameter cannot be changed while the 2342 NFS server is running. 2343 2344 auto the server chooses an appropriate mode 2345 automatically using heuristics 2346 global a single global pool contains all CPUs 2347 percpu one pool for each CPU 2348 pernode one pool for each NUMA node (equivalent 2349 to global on non-NUMA machines) 2350 2351 sunrpc.tcp_slot_table_entries= 2352 sunrpc.udp_slot_table_entries= 2353 [NFS,SUNRPC] 2354 Sets the upper limit on the number of simultaneous 2355 RPC calls that can be sent from the client to a 2356 server. Increasing these values may allow you to 2357 improve throughput, but will also increase the 2358 amount of memory reserved for use by the client. 2359 2360 swiotlb= [IA-64] Number of I/O TLB slabs 2361 2362 switches= [HW,M68k] 2363 2364 sysrq_always_enabled 2365 [KNL] 2366 Ignore sysrq setting - this boot parameter will 2367 neutralize any effect of /proc/sys/kernel/sysrq. 2368 Useful for debugging. 2369 2370 tdfx= [HW,DRM] 2371 2372 test_suspend= [SUSPEND] 2373 Specify "mem" (for Suspend-to-RAM) or "standby" (for 2374 standby suspend) as the system sleep state to briefly 2375 enter during system startup. The system is woken from 2376 this state using a wakeup-capable RTC alarm. 2377 2378 thash_entries= [KNL,NET] 2379 Set number of hash buckets for TCP connection 2380 2381 thermal.act= [HW,ACPI] 2382 -1: disable all active trip points in all thermal zones 2383 <degrees C>: override all lowest active trip points 2384 2385 thermal.crt= [HW,ACPI] 2386 -1: disable all critical trip points in all thermal zones 2387 <degrees C>: override all critical trip points 2388 2389 thermal.nocrt= [HW,ACPI] 2390 Set to disable actions on ACPI thermal zone 2391 critical and hot trip points. 2392 2393 thermal.off= [HW,ACPI] 2394 1: disable ACPI thermal control 2395 2396 thermal.psv= [HW,ACPI] 2397 -1: disable all passive trip points 2398 <degrees C>: override all passive trip points to this 2399 value 2400 2401 thermal.tzp= [HW,ACPI] 2402 Specify global default ACPI thermal zone polling rate 2403 <deci-seconds>: poll all this frequency 2404 0: no polling (default) 2405 2406 topology= [S390] 2407 Format: {off | on} 2408 Specify if the kernel should make use of the cpu 2409 topology informations if the hardware supports these. 2410 The scheduler will make use of these informations and 2411 e.g. base its process migration decisions on it. 2412 Default is off. 2413 2414 tp720= [HW,PS2] 2415 2416 tpm_suspend_pcr=[HW,TPM] 2417 Format: integer pcr id 2418 Specify that at suspend time, the tpm driver 2419 should extend the specified pcr with zeros, 2420 as a workaround for some chips which fail to 2421 flush the last written pcr on TPM_SaveState. 2422 This will guarantee that all the other pcrs 2423 are saved. 2424 2425 trace_buf_size=nn[KMG] 2426 [FTRACE] will set tracing buffer size. 2427 2428 trace_event=[event-list] 2429 [FTRACE] Set and start specified trace events in order 2430 to facilitate early boot debugging. 2431 See also Documentation/trace/events.txt 2432 2433 tsc= Disable clocksource-must-verify flag for TSC. 2434 Format: <string> 2435 [x86] reliable: mark tsc clocksource as reliable, this 2436 disables clocksource verification at runtime. 2437 Used to enable high-resolution timer mode on older 2438 hardware, and in virtualized environment. 2439 2440 turbografx.map[2|3]= [HW,JOY] 2441 TurboGraFX parallel port interface 2442 Format: 2443 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7> 2444 See also Documentation/input/joystick-parport.txt 2445 2446 uhash_entries= [KNL,NET] 2447 Set number of hash buckets for UDP/UDP-Lite connections 2448 2449 uhci-hcd.ignore_oc= 2450 [USB] Ignore overcurrent events (default N). 2451 Some badly-designed motherboards generate lots of 2452 bogus events, for ports that aren't wired to 2453 anything. Set this parameter to avoid log spamming. 2454 Note that genuine overcurrent events won't be 2455 reported either. 2456 2457 unknown_nmi_panic 2458 [X86] 2459 Set unknown_nmi_panic=1 early on boot. 2460 2461 usbcore.autosuspend= 2462 [USB] The autosuspend time delay (in seconds) used 2463 for newly-detected USB devices (default 2). This 2464 is the time required before an idle device will be 2465 autosuspended. Devices for which the delay is set 2466 to a negative value won't be autosuspended at all. 2467 2468 usbcore.usbfs_snoop= 2469 [USB] Set to log all usbfs traffic (default 0 = off). 2470 2471 usbcore.blinkenlights= 2472 [USB] Set to cycle leds on hubs (default 0 = off). 2473 2474 usbcore.old_scheme_first= 2475 [USB] Start with the old device initialization 2476 scheme (default 0 = off). 2477 2478 usbcore.use_both_schemes= 2479 [USB] Try the other device initialization scheme 2480 if the first one fails (default 1 = enabled). 2481 2482 usbcore.initial_descriptor_timeout= 2483 [USB] Specifies timeout for the initial 64-byte 2484 USB_REQ_GET_DESCRIPTOR request in milliseconds 2485 (default 5000 = 5.0 seconds). 2486 2487 usbhid.mousepoll= 2488 [USBHID] The interval which mice are to be polled at. 2489 2490 usb-storage.delay_use= 2491 [UMS] The delay in seconds before a new device is 2492 scanned for Logical Units (default 5). 2493 2494 usb-storage.quirks= 2495 [UMS] A list of quirks entries to supplement or 2496 override the built-in unusual_devs list. List 2497 entries are separated by commas. Each entry has 2498 the form VID:PID:Flags where VID and PID are Vendor 2499 and Product ID values (4-digit hex numbers) and 2500 Flags is a set of characters, each corresponding 2501 to a common usb-storage quirk flag as follows: 2502 a = SANE_SENSE (collect more than 18 bytes 2503 of sense data); 2504 b = BAD_SENSE (don't collect more than 18 2505 bytes of sense data); 2506 c = FIX_CAPACITY (decrease the reported 2507 device capacity by one sector); 2508 h = CAPACITY_HEURISTICS (decrease the 2509 reported device capacity by one 2510 sector if the number is odd); 2511 i = IGNORE_DEVICE (don't bind to this 2512 device); 2513 l = NOT_LOCKABLE (don't try to lock and 2514 unlock ejectable media); 2515 m = MAX_SECTORS_64 (don't transfer more 2516 than 64 sectors = 32 KB at a time); 2517 o = CAPACITY_OK (accept the capacity 2518 reported by the device); 2519 r = IGNORE_RESIDUE (the device reports 2520 bogus residue values); 2521 s = SINGLE_LUN (the device has only one 2522 Logical Unit); 2523 w = NO_WP_DETECT (don't test whether the 2524 medium is write-protected). 2525 Example: quirks=0419:aaf5:rl,0421:0433:rc 2526 2527 userpte= 2528 [X86] Flags controlling user PTE allocations. 2529 2530 nohigh = do not allocate PTE pages in 2531 HIGHMEM regardless of setting 2532 of CONFIG_HIGHPTE. 2533 2534 vdso= [X86,SH] 2535 vdso=2: enable compat VDSO (default with COMPAT_VDSO) 2536 vdso=1: enable VDSO (default) 2537 vdso=0: disable VDSO mapping 2538 2539 vdso32= [X86] 2540 vdso32=2: enable compat VDSO (default with COMPAT_VDSO) 2541 vdso32=1: enable 32-bit VDSO (default) 2542 vdso32=0: disable 32-bit VDSO mapping 2543 2544 vector= [IA-64,SMP] 2545 vector=percpu: enable percpu vector domain 2546 2547 video= [FB] Frame buffer configuration 2548 See Documentation/fb/modedb.txt. 2549 2550 vga= [BOOT,X86-32] Select a particular video mode 2551 See Documentation/x86/boot.txt and 2552 Documentation/svga.txt. 2553 Use vga=ask for menu. 2554 This is actually a boot loader parameter; the value is 2555 passed to the kernel using a special protocol. 2556 2557 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact 2558 size of <nn>. This can be used to increase the 2559 minimum size (128MB on x86). It can also be used to 2560 decrease the size and leave more room for directly 2561 mapped kernel RAM. 2562 2563 vmhalt= [KNL,S390] Perform z/VM CP command after system halt. 2564 Format: <command> 2565 2566 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic. 2567 Format: <command> 2568 2569 vmpoff= [KNL,S390] Perform z/VM CP command after power off. 2570 Format: <command> 2571 2572 vt.cur_default= [VT] Default cursor shape. 2573 Format: 0xCCBBAA, where AA, BB, and CC are the same as 2574 the parameters of the <Esc>[?A;B;Cc escape sequence; 2575 see VGA-softcursor.txt. Default: 2 = underline. 2576 2577 vt.default_blu= [VT] 2578 Format: <blue0>,<blue1>,<blue2>,...,<blue15> 2579 Change the default blue palette of the console. 2580 This is a 16-member array composed of values 2581 ranging from 0-255. 2582 2583 vt.default_grn= [VT] 2584 Format: <green0>,<green1>,<green2>,...,<green15> 2585 Change the default green palette of the console. 2586 This is a 16-member array composed of values 2587 ranging from 0-255. 2588 2589 vt.default_red= [VT] 2590 Format: <red0>,<red1>,<red2>,...,<red15> 2591 Change the default red palette of the console. 2592 This is a 16-member array composed of values 2593 ranging from 0-255. 2594 2595 vt.default_utf8= 2596 [VT] 2597 Format=<0|1> 2598 Set system-wide default UTF-8 mode for all tty's. 2599 Default is 1, i.e. UTF-8 mode is enabled for all 2600 newly opened terminals. 2601 2602 vt.global_cursor_default= 2603 [VT] 2604 Format=<-1|0|1> 2605 Set system-wide default for whether a cursor 2606 is shown on new VTs. Default is -1, 2607 i.e. cursors will be created by default unless 2608 overridden by individual drivers. 0 will hide 2609 cursors, 1 will display them. 2610 2611 watchdog timers [HW,WDT] For information on watchdog timers, 2612 see Documentation/watchdog/watchdog-parameters.txt 2613 or other driver-specific files in the 2614 Documentation/watchdog/ directory. 2615 2616 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of 2617 default x2apic cluster mode on platforms 2618 supporting x2apic. 2619 2620 x86_mrst_timer= [X86-32,APBT] 2621 Choose timer option for x86 Moorestown MID platform. 2622 Two valid options are apbt timer only and lapic timer 2623 plus one apbt timer for broadcast timer. 2624 x86_mrst_timer=apbt_only | lapic_and_apbt 2625 2626 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks. 2627 xd_geo= See header of drivers/block/xd.c. 2628 2629 xen_emul_unplug= [HW,X86,XEN] 2630 Unplug Xen emulated devices 2631 Format: [unplug0,][unplug1] 2632 ide-disks -- unplug primary master IDE devices 2633 aux-ide-disks -- unplug non-primary-master IDE devices 2634 nics -- unplug network devices 2635 all -- unplug all emulated devices (NICs and IDE disks) 2636 unnecessary -- unplugging emulated devices is 2637 unnecessary even if the host did not respond to 2638 the unplug protocol 2639 never -- do not unplug even if version check succeeds 2640 2641 xirc2ps_cs= [NET,PCMCIA] 2642 Format: 2643 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] 2644 2645______________________________________________________________________ 2646 2647TODO: 2648 2649 Add more DRM drivers. 2650