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.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. All advertising materials mentioning features or use of this software 18.\" must display the following acknowledgement: 19.\" This product includes software developed by the University of 20.\" California, Berkeley and its contributors. 21.\" 4. Neither the name of the University nor the names of its contributors 22.\" may be used to endorse or promote products derived from this software 23.\" without specific prior written permission. 24.\" 25.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 26.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 27.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 28.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 29.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 30.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 31.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 32.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 33.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 34.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 35.\" SUCH DAMAGE. 36.\" 37.\" @(#)boot_i386.8 8.2 (Berkeley) 4/19/94 38.\" 39.\" $Id: boot_i386.8,v 1.14 1998/09/23 06:54:14 yokota Exp $ 40.\" 41.Dd April 19, 1994 42.Dt BOOT 8 i386 43.Os 44.Sh NAME 45.Nm boot 46.Nd 47system bootstrapping procedures 48.Sh DESCRIPTION 49.Sy Power fail and crash recovery. 50Normally, the system will reboot itself at power-up or after crashes. 51An automatic consistency check of the file systems will be performed, 52and unless this fails, the system will resume multi-user operations. 53.Pp 54.Sy Cold starts. 55Most 386 56.Tn "PC AT" 57clones attempt to boot the floppy disk drive 0 (otherwise known as 58drive A:) first, and failing that, attempt to boot the hard disk 59drive 0 (otherwise known as drive C:, 60or (confusingly) hard disk drive 1, or drive 0x80 in the BIOS). 61Some BIOSes let you change this default sequence or may include a CD-ROM 62drive as a boot device. 63.Pp 64By default, a three-stage bootstrap is employed, and control is 65automatically passed from the boot blocks (bootstrap stages one and 66two) to a separate third-stage bootstrap program, 67.Pa /boot/loader . 68This third stage provides considerably more sophisticated control 69over the booting process than it is possible to achieve in the boot 70blocks, which are constrained by occupying limited fixed space on a 71given disk or slice. 72.Pp 73However, it is possible to dispense with the third stage altogether, 74either by specifying a kernel name in the boot block parameter 75file, 76.Pa /boot.config , 77or by hitting a key during a brief pause (while one of the characters 78.Dv - , 79.Dv \e , 80.Dv \&| , 81or 82.Dv / 83is displayed) before 84.Pa /boot/loader 85is invoked. Booting will also be attempted at stage two, if the 86third stage cannot be loaded. 87.Pp 88The remainder of this subsection deals only with the boot blocks. 89At present, documentation of the third stage is chiefly 90available though online help in the 91.Pa /boot/loader 92program itself. 93.Pp 94After the boot blocks have been loaded, 95you should see a prompt similar to the following: 96.Bd -literal 97>> FreeBSD/i386 BOOT 98Default: 0:wd(0,a)/kernel 99 100boot: 101.Ed 102.Pp 103(You may see some tips printed on the screen too.) 104.Pp 105The automatic boot will attempt to load 106.Pa /kernel 107from partition 108.Ql a 109of either the floppy or the hard disk. 110This boot may be aborted by typing any character on the keyboard 111at the 112.Ql boot: 113prompt. At this time, the following input will be accepted: 114.Bl -tag -width 10x 115.It \&? 116Give a short listing of the files in the root directory of the default 117boot device, as a hint about available boot files. (A 118.Dv \&? 119may also be specified as the last segment of a path, in which case 120the listing will be of the relevant subdirectory.) 121.It Op bios_drive:interface(unit,part) Op filename Op Fl aCcDdghPrsv 122Specify boot file and flags. 123.Bl -tag -width 10x -compact 124.It bios_drive 125The drive number as recognized by the BIOS. 1260 for the first drive, 1 for the second drive, etc. 127.It interface 128The type of controller to boot from. Note that the controller is required 129to have BIOS support since the BIOS services are used to load the 130boot file image. 131.Pp 132The supported interfaces are: 133.Bl -tag -width "wdXX" -compact 134.It wd 135ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike 136controller 137.It fd 1385 1/4" or 3 1/2" High density floppies 139.It da 140SCSI disk on any supported SCSI controller 141.\".It cd 142.\"boot from CDROM 143.El 144.It unit 145The unit number of the drive on the interface being used. 1460 for the first drive, 1 for the second drive, etc. 147.It part 148The partition letter inside the BSD portion of the disk. See 149.Xr disklabel 8 . 150By convention, only partition 151.Ql a 152contains a bootable image. If sliced disks are used 153.Pq Dq fdisk partitions , 154any slice can be booted from, with the default being the active slice 155or, otherwise, the first slice. 156.It filename 157The pathname of the file to boot (relative to the root directory 158on the specified partition). Defaults to 159.Pa /kernel . 160Symbolic links are not supported (hard links are). 161.It Fl acCdDghPrsv 162Boot flags: 163.Bl -tag -width "-CXX" -compact 164.It Fl a 165during kernel initialization, 166ask for the device to mount as as the root file system. 167.It Fl C 168boot from CDROM. 169.It Fl c 170run UserConfig to modify hardware parameters for the loaded 171kernel. If the kernel was built with the USERCONFIG_BOOT option, 172remain in UserConfig regardless of any 173.Ic quit 174commands present in the script. 175.It Fl D 176toggle single and dual console configurations. In the single 177configuration the console will be either the internal display 178or the serial port, depending on the state of the 179.Fl h 180option below. In the dual console configuration, 181both the internal display and the serial port will become the console 182at the same time, regardless of the state of the 183.Fl h 184option. However, the dual console configuration takes effect only during 185the boot prompt. Once the kernel is loaded, the console specified 186by the 187.Fl h 188option becomes the only console. 189.It Fl d 190enter the DDB kernel debugger 191.Pq see Xr ddb 4 192as early as possible in kernel initialization. 193.It Fl g 194use the GDB remote debugging protocol. 195.It Fl h 196toggle internal and serial consoles. You can use this to switch 197console devices. For instance, if you boot from the internal console, 198you can use the 199.Fl h 200option to force the kernel to use the serial port as its 201console device. Alternatively, if you boot from the serial port, 202you can use this option to force the kernel to use the internal display 203as the console instead. This option has no effect if the kernel was 204compiled with 205.Em options COMCONSOLE . 206.It Fl P 207probe the keyboard. If no keyboard is found, the 208.Fl D 209and 210.Fl h 211options are automatically set. 212.It Fl r 213use the statically configured default for the device containing the 214root file system 215.Pq see Xr config 8 . 216Normally, the root file system is on the device 217that the kernel was loaded from. 218.It Fl s 219boot into single-user mode; if the console is marked as 220.Dq insecure 221.Pq see Xr ttys 5 , 222the root password must be entered. 223.It Fl v 224be verbose during device probing (and later). 225.El 226.El 227.El 228.Pp 229You may put a BIOS drive number, a controller type, a unit number, 230a partition, a kernel file name and the 231.Fl D, 232.Fl h 233or 234.Fl P 235options in 236.Pa /boot.config 237to set defaults. Write them in one line just as you type at the 238.Ql boot: 239prompt. 240.Sh FILES 241.Bl -tag -width /kernel.old.config -compact 242.It Pa /boot.config 243parameters for the boot blocks (optional) 244.It Pa /boot.help 245help messages (optional) 246.It Pa /boot/loader 247third-stage bootstrap 248.It Pa /kernel 249default kernel 250.It Pa /kernel.old 251typical non-default kernel (optional) 252.El 253.Sh SEE ALSO 254.Xr ddb 4 , 255.Xr ttys 5 , 256.Xr config 8 , 257.Xr disklabel 8 , 258.Xr halt 8 , 259.Xr reboot 8 , 260.Xr shutdown 8 261.Sh BUGS 262The disklabel format used by this version of 263.Bx 264is quite 265different from that of other architectures. 266.Pp 267Some features are, as yet, undocumented. 268