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.\" 3. 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: src/sbin/reboot/boot_i386.8,v 1.23.2.11 2002/04/24 17:47:58 rnordier Exp $ 38.\" 39.Dd July 23, 2015 40.Dt BOOT 8 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). Some BIOSes allow 55you to change this default sequence, and may also include a CD-ROM 56drive as a boot device. 57.Pp 58By default, a three-stage bootstrap is employed, and control is 59automatically passed from the boot blocks (bootstrap stages one and 60two) to a separate third-stage bootstrap program, 61.Xr loader 8 . 62This third stage provides more sophisticated control over the booting 63process than it is possible to achieve in the boot blocks, which are 64constrained by occupying limited fixed space on a given disk or slice. 65.Pp 66However, it is possible to dispense with the third stage altogether, 67either by specifying a kernel name in the boot block parameter 68file, 69.Pa /boot.config , 70or, unless option 71.Fl n 72is set, by hitting a key during a brief pause (while one of the characters 73.Sy - , 74.Sy \e , 75.Sy \&| , 76or 77.Sy / 78is displayed) before 79.Xr loader 8 80is invoked. Booting will also be attempted at stage two, if the 81third stage cannot be loaded. 82.Pp 83The remainder of this subsection deals only with the boot blocks. The 84.Xr loader 8 85program is documented separately. 86.Pp 87After the boot blocks have been loaded, 88you should see a prompt similar to the following: 89.Bd -literal 90DragonFly boot 910:ad(0,a)/boot/loader: 92.Ed 93.Pp 94The automatic boot will attempt to load 95.Pa /boot/loader 96and if that fails 97.Pa /loader 98from partition 99.Ql a 100of either the floppy or the hard disk. 101This boot may be aborted by typing any character on the keyboard 102at the 103.Ql boot: 104prompt. At this time, the following input will be accepted: 105.Bl -tag -width indent 106.It Ic \&? 107Give a short listing of the files in the root directory of the default 108boot device, as a hint about available boot files. (A 109.Ic ?\& 110may also be specified as the last segment of a path, in which case 111the listing will be of the relevant subdirectory.) 112.It Xo 113.Ar bios_drive : Ns Ar interface Ns Po 114.Ar unit , Ns Ar part Pc 115.Ar filename 116.Op Fl aCcDdghmnPprsVv 117.Xc 118Specify boot file and flags. 119.Bl -tag -width indent 120.It Ar bios_drive 121The drive number as recognized by the BIOS. 1220 for the first drive, 1 for the second drive, etc. 123.It Ar interface 124The type of controller to boot from. Note that the controller is required 125to have BIOS support since the BIOS services are used to load the 126boot file image. 127.Pp 128The supported interfaces are: 129.Pp 130.Bl -tag -width "adXX" -compact 131.It ad 132ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike 133controller 134.It fd 1355 \(14" or 3 \(12" High density floppies 136.It da 137SCSI disk on any supported SCSI controller 138.\".It cd 139.\"boot from CDROM 140.El 141.It Ar unit 142The unit number of the drive on the interface being used. 1430 for the first drive, 1 for the second drive, etc. 144.It Ar part 145The partition letter inside the 146.Bx 147portion of the disk. See 148.Xr disklabel 8 . 149By convention, only partition 150.Ql a 151contains a bootable image. If sliced disks are used 152.Pq Dq fdisk partitions , 153any slice can be booted from, with the default being the active slice 154or, otherwise, the first 155.Dx 156slice. 157.It Ar filename 158The pathname of the file to boot (relative to the root directory 159on the specified partition). Defaults to 160.Pa /boot/kernel . 161Symbolic links are not supported (hard links are). 162.It Fl aCcDdghmnPprsVv 163Boot flags: 164.Pp 165.Bl -tag -width "-CXX" -compact 166.It Fl a 167during kernel initialization, 168ask for the device to mount as the root file system. 169.It Fl C 170boot from CDROM. 171.It Fl D 172Use all available consoles as the system console. Input will be accepted 173on any console and output will be routed to all of them. This is the 174default. 175.It Fl h 176Use the serial console as the system console. 177.It Fl V 178Use the video console as the system console. 179.It Fl m 180Mute the system console. None of the console devices will be used for the 181system console. 182.It Fl d 183enter the DDB kernel debugger 184(see 185.Xr ddb 4 ) 186as early as possible in kernel initialization. 187.It Fl g 188use the GDB remote debugging protocol. 189.It Fl n 190ignore key press to interrupt boot before 191.Xr loader 8 192is invoked. 193.It Fl P 194probe the keyboard. If no keyboard is found, the 195.Fl D 196and 197.Fl h 198options are automatically set. 199.It Fl p 200pause after each attached device during the device probing phase. 201.It Fl r 202use the statically configured default for the device containing the 203root file system 204(see 205.Xr config 8 ) . 206Normally, the root file system is on the device 207that the kernel was loaded from. 208.It Fl s 209boot into single-user mode; if the console is marked as 210.Dq insecure 211(see 212.Xr ttys 5 ) , 213the root password must be entered. 214.It Fl v 215be verbose during device probing (and later). 216.El 217.El 218.El 219.Pp 220You may put a BIOS drive number, a controller type, a unit number, 221a partition, a kernel file name, and any valid option in 222.Pa /boot.config 223to set defaults. Enter them in one line just as you type at the 224.Ql boot: 225prompt. 226.Sh FILES 227.Bl -tag -width /boot/loader -compact 228.It Pa /boot.config 229parameters for the boot blocks (optional) 230.It Pa /boot/boot1 231first stage bootstrap file 232.It Pa /boot/boot2 233second stage bootstrap file 234.It Pa /boot/loader 235third stage bootstrap 236.It Pa /boot/kernel 237default kernel 238.It Pa /boot/kernel.old 239typical non-default kernel (optional) 240.El 241.Sh DIAGNOSTICS 242When disk-related errors occur, these are reported by the second-stage 243bootstrap using the same error codes returned by the BIOS, for example 244.Dq Disk error 0x1 (lba=0x12345678) . 245Here is a partial list of these error codes: 246.Pp 247.Bl -tag -width "0x80" -compact 248.It 0x1 249Invalid argument 250.It 0x2 251Address mark not found 252.It 0x4 253Sector not found 254.It 0x8 255DMA overrun 256.It 0x9 257DMA attempt across 64K boundary 258.It 0xc 259Invalid media 260.It 0x10 261Uncorrectable CRC/ECC error 262.It 0x20 263Controller failure 264.It 0x40 265Seek failed 266.It 0x80 267Timeout 268.El 269.Pp 270.Sy "NOTE" : 271On older machines, or otherwise where EDD support (disk packet 272interface support) is not available, all boot-related files and 273structures (including the kernel) that need to be accessed during the 274boot phase must reside on the disk at or below cylinder 1023 (as the 275BIOS understands the geometry). When a 276.Dq Disk error 0x1 277is reported by the second-stage bootstrap, it generally means that this 278requirement has not been adhered to. 279.Sh SEE ALSO 280.Xr ddb 4 , 281.Xr ttys 5 , 282.Xr boot0cfg 8 , 283.Xr btxld 8 , 284.Xr config 8 , 285.Xr disklabel 8 , 286.Xr halt 8 , 287.Xr loader 8 , 288.Xr reboot 8 , 289.Xr shutdown 8 290.Sh BUGS 291The 292.Xr disklabel 5 293format used by this version of 294.Bx 295is quite 296different from that of other architectures. 297.Pp 298Due to space constraints, the keyboard probe initiated by the 299.Fl P 300option is simply a test that the BIOS has detected an 301.Dq extended 302keyboard. If an 303.Dq XT/AT 304keyboard (with no F11 and F12 keys, etc.) is attached, the probe will 305fail. 306.Pp 307Some features are not yet documented. 308