1.\" Copyright (c) 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software written and contributed 5.\" to Berkeley by William Jolitz. 6.\" 7.\" Almost completely rewritten for FreeBSD 2.1 by Joerg Wunsch. 8.\" 9.\" Substantially revised for FreeBSD 3.1 by Robert Nordier. 10.\" 11.\" Redistribution and use in source and binary forms, with or without 12.\" modification, are permitted provided that the following conditions 13.\" are met: 14.\" 1. Redistributions of source code must retain the above copyright 15.\" notice, this list of conditions and the following disclaimer. 16.\" 2. Redistributions in binary form must reproduce the above copyright 17.\" notice, this list of conditions and the following disclaimer in the 18.\" documentation and/or other materials provided with the distribution. 19.\" 4. Neither the name of the University nor the names of its contributors 20.\" may be used to endorse or promote products derived from this software 21.\" without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.\" @(#)boot_i386.8 8.2 (Berkeley) 4/19/94 36.\" 37.\" $FreeBSD$ 38.\" 39.Dd September 30, 2004 40.Dt BOOT 8 i386 41.Os 42.Sh NAME 43.Nm boot 44.Nd system bootstrapping procedures 45.Sh DESCRIPTION 46.Sy Power fail and crash recovery . 47Normally, the system will reboot itself at power-up or after crashes. 48An automatic consistency check of the file systems will be performed, 49and unless this fails, the system will resume multi-user operations. 50.Pp 51.Sy Cold starts . 52Most i386 PCs attempt to boot first from floppy disk drive 0 (sometimes 53known as drive A:) and, failing that, from hard disk drive 0 (sometimes 54known as drive C:, or as drive 0x80 to the BIOS). 55Some BIOSes allow 56you to change this default sequence, and may also include a CD-ROM 57drive as a boot device. 58.Pp 59By default, a three-stage bootstrap is employed, and control is 60automatically passed from the boot blocks (bootstrap stages one and 61two) to a separate third-stage bootstrap program, 62.Xr loader 8 . 63This third stage provides more sophisticated control over the booting 64process than it is possible to achieve in the boot blocks, which are 65constrained by occupying limited fixed space on a given disk or slice. 66.Pp 67However, it is possible to dispense with the third stage altogether, 68either by specifying a kernel name in the boot block parameter 69file, 70.Pa /boot.config , 71or, unless option 72.Fl n 73is set, by hitting a key during a brief pause (while one of the characters 74.Sy - , 75.Sy \e , 76.Sy \&| , 77or 78.Sy / 79is displayed) before 80.Xr loader 8 81is invoked. 82Booting will also be attempted at stage two, if the 83third stage cannot be loaded. 84.Pp 85Make note of the fact that 86.Pa /boot.config 87is read only from the 88.Ql a 89partition. 90As a result, slices which are missing an 91.Ql a 92parition require user intervention during the boot process. 93.Pp 94The remainder of this subsection deals only with the boot blocks. 95The 96.Xr loader 8 97program is documented separately. 98.Pp 99After the boot blocks have been loaded, 100you should see a prompt similar to the following: 101.Bd -literal 102>> FreeBSD/i386 BOOT 103Default: 0:ad(0,a)/boot/loader 104boot: 105.Ed 106.Pp 107The automatic boot will attempt to load 108.Pa /boot/loader 109from partition 110.Ql a 111of either the floppy or the hard disk. 112This boot may be aborted by typing any character on the keyboard 113at the 114.Ql boot: 115prompt. 116At this time, the following input will be accepted: 117.Bl -tag -width indent 118.It Ic \&? 119Give a short listing of the files in the root directory of the default 120boot device, as a hint about available boot files. 121(A 122.Ic ?\& 123may also be specified as the last segment of a path, in which case 124the listing will be of the relevant subdirectory.) 125.Pp 126.It Xo 127.Sm off 128.Ar bios_drive : interface ( unit , Oo Ar slice , Oc Ar part ) 129.Sm on 130.Ar filename 131.Op Fl aCcDdghmnPprsv 132.Xc 133Specify boot file and flags. 134.Bl -tag -width indent 135.It Ar bios_drive 136The drive number as recognized by the BIOS. 1370 for the first drive, 1 for the second drive, etc. 138.It Ar interface 139The type of controller to boot from. 140Note that the controller is required 141to have BIOS support since the BIOS services are used to load the 142boot file image. 143.Pp 144The supported interfaces are: 145.Pp 146.Bl -tag -width "adXX" -compact 147.It ad 148ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike 149controller 150.It fd 1515 1/4" or 3 1/2" High density floppies 152.It da 153SCSI disk on any supported SCSI controller 154.\".It cd 155.\"boot from CDROM 156.El 157.It Ar unit 158The unit number of the drive on the interface being used. 1590 for the first drive, 1 for the second drive, etc. 160.It Oo Ar slice , Oc Ns Ar part 161The partition letter inside the 162.Bx 163portion of the disk. 164See 165.Xr bsdlabel 8 . 166By convention, only partition 167.Ql a 168contains a bootable image. 169If sliced disks are used 170.Pq Dq fdisk partitions , 171any 172.Ar slice 173(1 for the first slice, 2 for the second slice, etc.\&) 174can be booted from, with the default (if not specified) being the active slice 175or, otherwise, the first 176.Fx 177slice. 178If 179.Ar slice 180is specified as 0, the first 181.Fx 182slice (also known as 183.Dq compatibility 184slice) is booted from. 185.It Ar filename 186The pathname of the file to boot (relative to the root directory 187on the specified partition). 188Defaults to 189.Pa /kernel . 190Symbolic links are not supported (hard links are). 191.It Fl aCcDdghmnPprsv 192Boot flags: 193.Pp 194.Bl -tag -width "-CXX" -compact 195.It Fl a 196during kernel initialization, 197ask for the device to mount as the root file system. 198.It Fl C 199try to mount root file system from a CD-ROM. 200.It Fl c 201this flag is currently a no-op. 202.It Fl D 203boot with the dual console configuration. 204In the single 205configuration, the console will be either the internal display 206or the serial port, depending on the state of the 207.Fl h 208option below. 209In the dual console configuration, 210both the internal display and the serial port will become the console 211at the same time, regardless of the state of the 212.Fl h 213option. 214.It Fl d 215enter the DDB kernel debugger 216(see 217.Xr ddb 4 ) 218as early as possible in kernel initialization. 219.It Fl g 220use the GDB remote debugging protocol. 221.It Fl h 222force the serial console. 223For instance, if you boot from the internal console, 224you can use the 225.Fl h 226option to force the kernel to use the serial port as its 227console device. 228The serial port driver 229.Xr sio 4 230has a flag (0x20) to override this option. 231If that flag is set, the serial port will always be used as the console, 232regardless of the 233.Fl h 234option described here. 235See the man page for 236.Xr sio 4 237for more details. 238.It Fl m 239mute the console. 240.It Fl n 241ignore key press to interrupt boot before 242.Xr loader 8 243is invoked. 244.It Fl P 245probe the keyboard. 246If no keyboard is found, the 247.Fl D 248and 249.Fl h 250options are automatically set. 251.It Fl p 252pause after each attached device during the device probing phase. 253.It Fl r 254use the statically configured default for the device containing the 255root file system 256(see 257.Xr config 8 ) . 258Normally, the root file system is on the device 259that the kernel was loaded from. 260.It Fl s 261boot into single-user mode; if the console is marked as 262.Dq insecure 263(see 264.Xr ttys 5 ) , 265the root password must be entered. 266.It Fl v 267be verbose during device probing (and later). 268.El 269.El 270.El 271.Pp 272You may put a BIOS drive number, a controller type, a unit number, 273a partition, a kernel file name, and any valid option in 274.Pa /boot.config 275to set defaults. 276Enter them in one line just as you type at the 277.Ql boot: 278prompt. 279.Sh FILES 280.Bl -tag -width /boot/loader -compact 281.It Pa /boot.config 282parameters for the boot blocks (optional) 283.It Pa /boot/boot1 284first stage bootstrap file 285.It Pa /boot/boot2 286second stage bootstrap file 287.It Pa /boot/loader 288third stage bootstrap 289.It Pa /boot/kernel/kernel 290default kernel 291.It Pa /boot/kernel.old/kernel 292typical non-default kernel (optional) 293.El 294.Sh DIAGNOSTICS 295When disk-related errors occur, these are reported by the second-stage 296bootstrap using the same error codes returned by the BIOS, for example 297.Dq Disk error 0x1 (lba=0x12345678) . 298Here is a partial list of these error codes: 299.Pp 300.Bl -tag -width "0x80" -compact 301.It 0x1 302Invalid argument 303.It 0x2 304Address mark not found 305.It 0x4 306Sector not found 307.It 0x8 308DMA overrun 309.It 0x9 310DMA attempt across 64K boundary 311.It 0xc 312Invalid media 313.It 0x10 314Uncorrectable CRC/ECC error 315.It 0x20 316Controller failure 317.It 0x40 318Seek failed 319.It 0x80 320Timeout 321.El 322.Pp 323.Sy "NOTE" : 324On older machines, or otherwise where EDD support (disk packet 325interface support) is not available, all boot-related files and 326structures (including the kernel) that need to be accessed during the 327boot phase must reside on the disk at or below cylinder 1023 (as the 328BIOS understands the geometry). 329When a 330.Dq Disk error 0x1 331is reported by the second-stage bootstrap, it generally means that this 332requirement has not been adhered to. 333.Sh SEE ALSO 334.Xr ddb 4 , 335.Xr ttys 5 , 336.Xr boot0cfg 8 , 337.Xr bsdlabel 8 , 338.Xr btxld 8 , 339.Xr config 8 , 340.Xr halt 8 , 341.Xr loader 8 , 342.Xr reboot 8 , 343.Xr shutdown 8 344.Sh BUGS 345The 346.Xr bsdlabel 5 347format used by this version of 348.Bx 349is quite 350different from that of other architectures. 351.Pp 352Due to space constraints, the keyboard probe initiated by the 353.Fl P 354option is simply a test that the BIOS has detected an 355.Dq extended 356keyboard. 357If an 358.Dq XT/AT 359keyboard (with no F11 and F12 keys, etc.) is attached, the probe will 360fail. 361