Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/Documentation/kernel-parameters.txt
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1 July 2000 Kernel Parameters v2.4.0 2 ~~~~~~~~~~~~~~~~~ 3 4 The following is a consolidated list of the kernel parameters as implemented 5 by the __setup() macro and sorted into English Dictionary order (defined 6 as ignoring all punctuation and sorting digits before letters in a case 7 insensitive manner), and with descriptions where known. 8 9 The text in square brackets at the beginning of the description state the 10 restrictions on the kernel for the said kernel parameter to be valid. The 11 restrictions referred to are that the relevant option is valid if: 12 13 ACPI ACPI support is enabled. 14 APIC APIC support is enabled. 15 APM Advanced Power Management support is enabled. 16 AX25 Appropriate AX.25 support is enabled. 17 CD Appropriate CD support is enabled. 18 DEVFS devfs support is enabled. 19 DRM Direct Rendering Management support is enabled. 20 EFI EFI Partitioning (GPT) is enabled 21 EIDE EIDE/ATAPI support is enabled. 22 FB The frame buffer device is enabled. 23 HW Appropriate hardware is enabled. 24 IA-32 IA-32 aka i386 architecture is enabled. 25 IA-64 IA-64 architecture is enabled. 26 IP_PNP IP DCHP, BOOTP, or RARP is enabled. 27 ISAPNP ISA PnP code is enabled. 28 ISDN Appropriate ISDN support is enabled. 29 JOY Appropriate joystick support is enabled. 30 LP Printer support is enabled. 31 LOOP Loopback device support is enabled. 32 M68k M68k architecture is enabled. 33 MCA MCA bus support is enabled. 34 MDA MDA console support is enabled. 35 MOUSE Appropriate mouse support is enabled. 36 NET Appropriate network support is enabled. 37 NFS Appropriate NFS support is enabled. 38 PARIDE The ParIDE subsystem is enabled. 39 PCI PCI bus support is enabled. 40 PCMCIA The PCMCIA subsystem is enabled. 41 PNP Plug & Play support is enabled. 42 PPT Parallel port support is enabled. 43 PS2 Appropriate PS/2 support is enabled. 44 RAM RAM disk support is enabled. 45 SCSI Appropriate SCSI support is enabled. 46 SERIAL Serial support is enabled. 47 SMP The kernel is an SMP kernel. 48 SOUND Appropriate sound system support is enabled. 49 V4L Video For Linux support is enabled. 50 VGA The VGA console has been enabled. 51 VT Virtual terminal support is enabled. 52 XT IBM PC/XT MFM hard disk support is enabled. 53 54 In addition, the following text indicates that the option: 55 56 BUGS= Relates to possible processor bugs on the said processor. 57 KNL Is a kernel start-up parameter. 58 BOOT Is a boot loader parameter. 59 60 Parameters denoted with BOOT are actually interpreted by the boot 61 loader, and have no meaning to the kernel directly. 62 63 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that 64 a trailing = on the name of any parameter states that that parameter will 65 be entered as an environment variable, whereas its absence indicates that 66 it will appear as a kernel argument readable via /proc/cmdline by programs 67 running once the system is up. 68 69 53c7xx= [HW,SCSI] Amiga SCSI controllers. 70 71 acpi= [HW,ACPI] Advanced Configuration and Power Interface 72 force Force ACPI on, even if blacklisted platform 73 off Disable ACPI 74 ht Limit ACPI to boot-time LAPIC enumeration for HT, 75 disabling the run-time AML interpreter. 76 77 ad1816= [HW,SOUND] 78 79 ad1848= [HW,SOUND] 80 81 adb_buttons= [HW,MOUSE] 82 83 adlib= [HW,SOUND] 84 85 advansys= [HW,SCSI] 86 87 aedsp16= [HW,SOUND] 88 89 aha152x= [HW,SCSI] 90 91 aha1542= [HW,SCSI] 92 93 aic7xxx= [HW,SCSI] 94 95 AM53C974= [HW,SCSI] 96 97 amijoy= [HW,JOY] Amiga joystick support 98 99 apm= [APM] Advanced Power Management. 100 101 applicom= [HW] 102 103 arcrimi= [HW,NET] 104 105 ataflop= [HW,M68k] 106 107 atarimouse= [HW,MOUSE] Atari Mouse. 108 109 atascsi= [HW,SCSI] Atari SCSI. 110 111 awe= [HW,SOUND] 112 113 aztcd= [HW,CD] Aztec CD driver. 114 115 baycom_epp= [HW,AX25] 116 117 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem. 118 119 baycom_ser_fdx= [HW,AX25] BayCom Serial Port AX.25 Modem in Full 120 Duplex Mode. 121 122 baycom_ser_hdx= [HW,AX25] BayCom Serial Port AX.25 Modem in Half 123 Duplex Mode. 124 125 bmouse= [HW,MOUSE,PS2] Bus mouse. 126 127 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards), most 128 bttv.radio= important insmod options are available as kernel args too. 129 bttv.pll= see Documentation/video4linux/bttv/Insmod-options 130 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST 131 132 BusLogic= [HW,SCSI] 133 134 cdu31a= [HW,CD] 135 136 chandev= [HW,NET] 137 138 cm206= [HW,CD] 139 140 com20020= [HW,NET] 141 142 com90io= [HW,NET] 143 144 com90xx= [HW,NET] 145 146 condev= [HW] 147 148 console= [KNL] output console + comm spec (speed, control, 149 parity). 150 151 cpia_pp= [HW,PPT] 152 153 cs4232= [HW,SOUND] 154 155 cs89x0_dma= [HW,NET] 156 157 ctc= [HW,NET] 158 159 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter. 160 161 dasd= [HW,NET] 162 163 db9= [HW,JOY] 164 165 db9_2= [HW,JOY] 166 167 db9_3= [HW,JOY] 168 169 debug [KNL] Enable kernel debugging (events log level). 170 171 decnet= [HW,NET] 172 173 devfs= [DEVFS] 174 175 digi= [HW,SERIAL] io parameters + enable/disable command. 176 177 digiepca= [HW,SERIAL] 178 179 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA 180 support available. 181 182 dmasound= [HW,SOUND] (sound subsystem buffers). 183 184 dtc3181e= [HW,SCSI] 185 186 eata= [HW,SCSI] 187 188 eda= [HW,PS2] 189 190 edb= [HW,PS2] 191 192 eicon= [HW,ISDN] 193 194 es1370= [HW,SOUND] 195 196 es1371= [HW,SOUND] 197 198 ether= [HW,NET] Ethernet cards parameters (irq, 199 base_io_addr, mem_start, mem_end, name. 200 (mem_start is often overloaded to mean something 201 different and driver-specific). 202 203 fd_mcs= [HW,SCSI] 204 205 fdomain= [HW,SCSI] 206 207 floppy= [HW] 208 209 ftape= [HW] Floppy Tape subsystem debugging options. 210 211 gamma= [HW,DRM] 212 213 gc= [HW,JOY] 214 215 gc_2= [HW,JOY] 216 217 gc_3= [HW,JOY] 218 219 gdth= [HW,SCSI] 220 221 gpt [EFI] Forces disk with valid GPT signature but 222 invalid Protective MBR to be treated as GPT. 223 224 gscd= [HW,CD] 225 226 gus= [HW,SOUND] 227 228 gvp11= [HW,SCSI] 229 230 hd= [EIDE] (E)IDE hard drive subsystem geometry 231 (Cyl/heads/sectors) or tune parameters. 232 233 hfmodem= [HW,AX25] 234 235 hisax= [HW,ISDN] 236 237 i810= [HW,DRM] 238 239 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter. 240 241 icn= [HW,ISDN] 242 243 ide?= [HW] (E)IDE subsystem : config (iomem/irq), tuning or 244 debugging (serialize,reset,no{dma,tune,probe}) or 245 chipset specific parameters. 246 247 idebus= [HW] (E)IDE subsystem : VLB/PCI bus speed. 248 249 idle= [HW] 250 251 in2000= [HW,SCSI] 252 253 init= [KNL] 254 255 initrd= [BOOT] Specify the location of the initial ramdisk. 256 257 ip= [IP_PNP] 258 259 isapnp= [ISAPNP] Specify RDP, reset, pci_scan and verbosity. 260 261 isapnp_reserve_irq= [ISAPNP] Exclude IRQs for the autoconfiguration. 262 263 isapnp_reserve_dma= [ISAPNP] Exclude DMAs for the autoconfiguration. 264 265 isapnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration. 266 Ranges are in pairs (I/O port base and size). 267 268 isapnp_reserve_mem= [ISAPNP] Exclude memory regions for the autoconfiguration. 269 Ranges are in pairs (memory base and size). 270 271 isp16= [HW,CD] 272 273 iucv= [HW,NET] 274 275 js= [HW,JOY] Analog joystick 276 277 kbd-reset [VT] 278 279 keepinitrd [HW, ARM] 280 281 load_ramdisk= [RAM] List of ramdisks to load from floppy. 282 283 lockd.udpport= [NFS] 284 285 lockd.tcpport= [NFS] 286 287 logi_busmouse= [HW, MOUSE] 288 289 lp=0 [LP] Specify parallel ports to use, e.g, 290 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses 291 lp=reset first parallel port). 'lp=0' disables the 292 lp=auto printer driver. 'lp=reset' (which can be 293 specified in addition to the ports) causes 294 attached printers to be reset. Using 295 lp=port1,port2,... specifies the parallel ports 296 to associate lp devices with, starting with 297 lp0. A port specification may be 'none' to skip 298 that lp device, or a parport name such as 299 'parport0'. Specifying 'lp=auto' instead of a 300 port specification list means that device IDs 301 from each port should be examined, to see if 302 an IEEE 1284-compliant printer is attached; if 303 so, the driver will manage that printer. 304 305 ltpc= [HW] 306 307 mac5380= [HW,SCSI] 308 309 mac53c9x= [HW,SCSI] 310 311 mad16= [HW,SOUND] 312 313 maui= [HW,SOUND] 314 315 max_loop=[0-255] [LOOP] Set the maximum number of loopback devices 316 that can be mounted. 317 318 maxcpus= [SMP] States the maximum number of processors that 319 an SMP kernel should make use of. 320 321 max_scsi_luns= [SCSI] 322 323 mca-pentium [BUGS=IA-32] 324 325 mcd= [HW,CD] 326 327 mcdx= [HW,CD] 328 329 md= [HW] RAID subsystems devices and level. 330 331 mdisk= [HW] 332 333 mdacon= [MDA] 334 335 megaraid= [HW,SCSI] 336 337 mem=exactmap [KNL,BOOT,IA-32] enable setting of an exact 338 e820 memory map, as specified by the user. 339 Such mem=exactmap lines can be constructed 340 based on BIOS output or other requirements. 341 342 mem=nn[KMG] [KNL,BOOT] force use of a specific amount of 343 memory; to be used when the kernel is not able 344 to see the whole system memory or for test. 345 346 mem=nn[KMG]@ss[KMG] 347 [KNL,BOOT] Force usage of a specific region of memory 348 Region of memory to be used, from ss to ss+nn. 349 350 mem=nn[KMG]#ss[KMG] 351 [KNL,BOOT,ACPI] Mark specific memory as ACPI data. 352 Region of memory to be used, from ss to ss+nn. 353 354 mem=nn[KMG]$ss[KMG] 355 [KNL,BOOT,ACPI] Mark specific memory as reserved. 356 Region of memory to be used, from ss to ss+nn. 357 358 memfrac= [KNL] 359 360 mga= [HW,DRM] 361 362 mpu401= [HW,SOUND] 363 364 msmouse= [HW,MOUSE] Microsoft Mouse. 365 366 ncr5380= [HW,SCSI] 367 368 ncr53c400= [HW,SCSI] 369 370 ncr53c400a= [HW,SCSI] 371 372 ncr53c406a= [HW,SCSI] 373 374 ncr53c8xx= [HW,SCSI] 375 376 netdev= [NET] Ethernet cards parameters (irq, 377 base_io_addr, mem_start, mem_end, name. 378 (mem_start is often overloaded to mean something 379 different and driver-specific). 380 (cf: ether=) 381 382 nfsaddrs= [NFS] 383 384 nfsroot= [NFS] nfs root filesystem for disk-less boxes. 385 386 nmi_watchdog= [KNL,BUGS=IA-32] debugging features for SMP kernels. 387 388 no387 [BUGS=IA-32] Tells the kernel to use the 387 maths 389 emulation library even if a 387 maths coprocessor 390 is present. 391 392 noalign [KNL,ARM] 393 394 noapic [SMP,APIC] Tells the kernel not to make use of any 395 APIC that may be present on the system. 396 397 noasync [HW, M68K] Disables async and sync negotiation for 398 all devices. 399 400 nocache [ARM] 401 402 nodisconnect [HW,SCSI, M68K] Disables SCSI disconnects. 403 404 nohlt [BUGS=ARM] 405 406 no-hlt [BUGS=IA-32] Tells the kernel that the hlt 407 instruction doesn't work correctly and not to 408 use it. 409 410 noisapnp [ISAPNP] Disables ISA PnP code. 411 412 noinitrd [RAM] Tells the kernel not to load any configured 413 initial RAM disk. 414 415 nointroute [IA-64] 416 417 no-scroll [VGA] 418 419 nosmp [SMP] Tells an SMP kernel to act as a UP kernel. 420 421 nosync [HW, M68K] Disables sync negotiation for all devices. 422 423 notsc [BUGS=IA-32] Disable Time Stamp Counter 424 425 nowb [ARM] 426 427 opl3= [HW,SOUND] 428 429 opl3sa= [HW,SOUND] 430 431 opl3sa2= [HW,SOUND] 432 433 optcd= [HW,CD] 434 435 panic= [KNL] kernel behaviour on panic. 436 437 parport=0 [HW,PPT] Specify parallel ports. 0 disables. 438 parport=auto Use 'auto' to force the driver to use 439 parport=0xBBB[,IRQ[,DMA]] any IRQ/DMA settings detected (the 440 default is to ignore detected IRQ/DMA 441 settings because of possible 442 conflicts). You can specify the base 443 address, IRQ, and DMA settings; IRQ and 444 DMA should be numbers, or 'auto' (for 445 using detected settings on that 446 particular port), or 'nofifo' (to avoid 447 using a FIFO even if it is detected). 448 Parallel ports are assigned in the 449 order they are specified on the command 450 line, starting with parport0. 451 452 pas2= [HW,SOUND] 453 454 pas16= [HW,SCSI] 455 456 pcbit= [HW,ISDN] 457 458 pcd. [PARIDE] 459 460 pci=option[,option...] [PCI] various PCI subsystem options: 461 off [IA-32] don't probe for the PCI bus 462 bios [IA-32] force use of PCI BIOS, don't access 463 the hardware directly. Use this if your machine 464 has a non-standard PCI host bridge. 465 nobios [IA-32] disallow use of PCI BIOS, only direct 466 hardware access methods are allowed. Use this 467 if you experience crashes upon bootup and you 468 suspect they are caused by the BIOS. 469 conf1 [IA-32] Force use of PCI Configuration Mechanism 1. 470 conf2 [IA-32] Force use of PCI Configuration Mechanism 2. 471 nosort [IA-32] Don't sort PCI devices according to 472 order given by the PCI BIOS. This sorting is done 473 to get a device order compatible with older kernels. 474 biosirq [IA-32] Use PCI BIOS calls to get the interrupt 475 routing table. These calls are known to be buggy 476 on several machines and they hang the machine when used, 477 but on other computers it's the only way to get the 478 interrupt routing table. Try this option if the kernel 479 is unable to allocate IRQs or discover secondary PCI 480 buses on your motherboard. 481 rom [IA-32] Assign address space to expansion ROMs. 482 Use with caution as certain devices share address 483 decoders between ROMs and other resources. 484 irqmask=0xMMMM [IA-32] Set a bit mask of IRQs allowed to be assigned 485 automatically to PCI devices. You can make the kernel 486 exclude IRQs of your ISA cards this way. 487 lastbus=N [IA-32] Scan all buses till bus #N. Can be useful 488 if the kernel is unable to find your secondary buses 489 and you want to tell it explicitly which ones they are. 490 assign-busses [IA-32] Always assign all PCI bus 491 numbers ourselves, overriding 492 whatever the firmware may have 493 done. 494 495 pd. [PARIDE] 496 497 pf. [PARIDE] 498 499 pg. [PARIDE] 500 501 pirq= [SMP,APIC] mp-table. 502 503 plip= [PPT,NET] Parallel port network link. 504 505 profile= [KNL] enable kernel profiling via /proc/profile 506 (param: profile step/bucket size as a power of 2) 507 508 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk 509 before loading. 510 511 pss= [HW,SOUND] 512 513 pt. [PARIDE] 514 515 quiet= [KNL] Disable log messages. 516 517 r128= [HW,DRM] 518 519 raid= [HW,RAID] 520 521 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]. 522 523 ramdisk_blocksize= 524 [RAM] 525 526 ramdisk_size= [RAM] New name for the ramdisk parameter. 527 528 ramdisk_start= [RAM] Starting block of RAM disk image (so you can 529 place it after the kernel image on a boot floppy). 530 531 reboot= [BUGS=IA-32] 532 533 reserve= [KNL,BUGS] force the kernel to ignore some iomem area. 534 535 riscom8= [HW,SERIAL] 536 537 ro [KNL] Mount root device read-only on boot. 538 539 root= [KNL] root filesystem. 540 541 rootflags= [KNL] set root filesystem mount option string 542 543 rootfstype= [KNL] set root filesystem type 544 545 rw [KNL] Mount root device read-write on boot. 546 547 S [KNL] run init in single mode. 548 549 sb= [HW,SOUND] 550 551 sbpcd= [HW,CD] Soundblaster CD adapter. 552 553 scsi_logging= [SCSI] 554 555 scsihosts= [SCSI] 556 557 sg_def_reserved_size= 558 [SCSI] 559 560 sgalaxy= [HW,SOUND] 561 562 sim710= [SCSI,HW] 563 564 sjcd= [HW,CD] 565 566 smart2= [HW] 567 568 sonicvibes= [HW,SOUND] 569 570 sonycd535= [HW,CD] 571 572 sound= [SOUND] 573 574 soundmodem= [HW,AX25,SOUND] Use sound card as packet radio modem. 575 576 specialix= [HW,SERIAL] Specialix multi-serial port adapter. 577 578 sscape= [HW,SOUND] 579 580 st= [HW,SCSI] SCSI tape parameters (buffers, etc.). 581 582 st0x= [HW,SCSI] 583 584 stram_swap= [HW] 585 586 swiotlb= [IA-64] Number of I/O TLB slabs. 587 588 switches= [HW, M68K] 589 590 sym53c416= [HW,SCSI] 591 592 sym53c8xx= [HW,SCSI] 593 594 t128= [HW,SCSI] 595 596 tdfx= [HW,DRM] 597 598 tgfx= [HW,JOY] 599 600 tgfx_2= [HW,JOY] 601 602 tgfx_3= [HW,JOY] 603 604 tmc8xx= [HW,SCSI] 605 606 tmscsim= [HW,SCSI] 607 608 tp720= [HW,PS2] 609 610 trix= [HW,SOUND] 611 612 u14-34f= [HW,SCSI] 613 614 uart401= [HW,SOUND] 615 616 uart6850= [HW,SOUND] 617 618 usbfix [BUGS=IA-64] 619 620 video= [FB] frame buffer configuration. 621 622 vga= [BOOT] on ix386, select a particular video mode 623 (use vga=ask for menu). This is actually a 624 boot loader parameter; the value is passed to 625 the kernel using a special protocol. See 626 linux/Documentation/i386/boot.txt for information. 627 628 vmhalt= [KNL,S390] 629 630 vmpoff= [KNL,S390] 631 632 waveartist= [HW,SOUND] 633 634 wd33c93= [HW,SCSI] 635 636 wd7000= [HW,SCSI] 637 638 wdt= [HW] 639 640 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks. 641 642 xd_geo= [HW,XT]
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