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 PCs attempt to boot first from hard disk drive 0 (sometimes 53known as drive C:) and, failing that, from various other mass storage 54devices. 55Usually, BIOSes allow 56you to change this default sequence, and typically 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. Booting will also be attempted at stage two, if the 82third stage cannot be loaded. 83.Pp 84The remainder of this subsection deals only with the boot blocks. The 85.Xr loader 8 86program is documented separately. 87.Pp 88After the boot blocks have been loaded, 89you should see a prompt similar to the following: 90.Bd -literal 91DragonFly boot 920:ad(0,a)/boot/loader: 93.Ed 94.Pp 95The automatic boot will attempt to load 96.Pa /boot/loader 97and if that fails 98.Pa /loader 99from partition 100.Ql a 101of either the floppy or the hard disk. 102This boot may be aborted by typing any character on the keyboard 103at the 104.Ql boot: 105prompt. At this time, the following input will be accepted: 106.Bl -tag -width indent 107.It Ic \&? 108Give a short listing of the files in the root directory of the default 109boot device, as a hint about available boot files. (A 110.Ic ?\& 111may also be specified as the last segment of a path, in which case 112the listing will be of the relevant subdirectory.) 113.It Xo 114.Ar bios_drive : Ns Ar interface Ns Po 115.Ar unit , Ns Ar part Pc 116.Ar filename 117.Op Fl aCcDdghmnPprsVv 118.Xc 119Specify boot file and flags. 120.Bl -tag -width indent 121.It Ar bios_drive 122The drive number as recognized by the BIOS. 1230 for the first drive, 1 for the second drive, etc. 124.It Ar interface 125The type of controller to boot from. Note that the controller is required 126to have BIOS support since the BIOS services are used to load the 127boot file image. 128.Pp 129The supported interfaces are: 130.Pp 131.Bl -tag -width "adXX" -compact 132.It ad 133ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike 134controller 135.It fd 1365 \(14" or 3 \(12" High density floppies 137.It da 138SCSI disk on any supported SCSI controller 139.\".It cd 140.\"boot from CDROM 141.El 142.It Ar unit 143The unit number of the drive on the interface being used. 1440 for the first drive, 1 for the second drive, etc. 145.It Ar part 146The partition letter inside the 147.Bx 148portion 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 156.Dx 157slice. 158.It Ar filename 159The pathname of the file to boot (relative to the root directory 160on the specified partition). Defaults to 161.Pa /boot/kernel . 162Symbolic links are not supported (hard links are). 163.It Fl aCcDdghmnPprsVv 164Boot flags: 165.Pp 166.Bl -tag -width "-CXX" -compact 167.It Fl a 168during kernel initialization, 169ask for the device to mount as the root file system. 170.It Fl C 171boot from CDROM. 172.It Fl D 173Use all available consoles as the system console. Input will be accepted 174on any console and output will be routed to all of them. This is the 175default. 176.It Fl h 177Use the serial console as the system console. 178.It Fl V 179Use the video console as the system console. 180.It Fl m 181Mute the system console. None of the console devices will be used for the 182system console. 183.It Fl d 184enter the DDB kernel debugger 185(see 186.Xr ddb 4 ) 187as early as possible in kernel initialization. 188.It Fl g 189use the GDB remote debugging protocol. 190.It Fl n 191ignore key press to interrupt boot before 192.Xr loader 8 193is invoked. 194.It Fl P 195probe the keyboard. If no keyboard is found, the 196.Fl D 197and 198.Fl h 199options are automatically set. 200.It Fl p 201pause after each attached device during the device probing phase. 202.It Fl r 203use the statically configured default for the device containing the 204root file system 205(see 206.Xr config 8 ) . 207Normally, the root file system is on the device 208that the kernel was loaded from. 209.It Fl s 210boot into single-user mode; if the console is marked as 211.Dq insecure 212(see 213.Xr ttys 5 ) , 214the root password must be entered. 215.It Fl v 216be verbose during device probing (and later). 217.El 218.El 219.El 220.Pp 221You may put a BIOS drive number, a controller type, a unit number, 222a partition, a kernel file name, and any valid option in 223.Pa /boot.config 224to set defaults. Enter them in one line just as you type at the 225.Ql boot: 226prompt. 227.Sh FILES 228.Bl -tag -width /boot/loader -compact 229.It Pa /boot.config 230parameters for the boot blocks (optional) 231.It Pa /boot/boot1 232first stage bootstrap file 233.It Pa /boot/boot2 234second stage bootstrap file 235.It Pa /boot/loader 236third stage bootstrap 237.It Pa /boot/kernel 238default kernel 239.It Pa /boot/kernel.old 240typical non-default kernel (optional) 241.El 242.Sh DIAGNOSTICS 243When disk-related errors occur, these are reported by the second-stage 244bootstrap using the same error codes returned by the BIOS, for example 245.Dq Disk error 0x1 (lba=0x12345678) . 246Here is a partial list of these error codes: 247.Pp 248.Bl -tag -width "0x80" -compact 249.It 0x1 250Invalid argument 251.It 0x2 252Address mark not found 253.It 0x4 254Sector not found 255.It 0x8 256DMA overrun 257.It 0x9 258DMA attempt across 64K boundary 259.It 0xc 260Invalid media 261.It 0x10 262Uncorrectable CRC/ECC error 263.It 0x20 264Controller failure 265.It 0x40 266Seek failed 267.It 0x80 268Timeout 269.El 270.Pp 271.Sy "NOTE" : 272On older machines, or otherwise where EDD support (disk packet 273interface support) is not available, all boot-related files and 274structures (including the kernel) that need to be accessed during the 275boot phase must reside on the disk at or below cylinder 1023 (as the 276BIOS understands the geometry). When a 277.Dq Disk error 0x1 278is reported by the second-stage bootstrap, it generally means that this 279requirement has not been adhered to. 280.Sh SEE ALSO 281.Xr ddb 4 , 282.Xr ttys 5 , 283.Xr boot0cfg 8 , 284.Xr btxld 8 , 285.Xr config 8 , 286.Xr disklabel 8 , 287.Xr halt 8 , 288.Xr loader 8 , 289.Xr reboot 8 , 290.Xr shutdown 8 291.Sh BUGS 292The 293.Xr disklabel 5 294format used by this version of 295.Bx 296is quite 297different from that of other architectures. 298.Pp 299Due to space constraints, the keyboard probe initiated by the 300.Fl P 301option is simply a test that the BIOS has detected an 302.Dq extended 303keyboard. If an 304.Dq XT/AT 305keyboard (with no F11 and F12 keys, etc.) is attached, the probe will 306fail. 307.Pp 308Some features are not yet documented. 309