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 March 3, 2020 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 59Newer PCs boot using UEFI firmware, not legacy BIOS. 60That process is described in 61.Xr uefi 8 . 62.Pp 63By default, a three-stage bootstrap is employed, and control is 64automatically passed from the boot blocks (bootstrap stages one and 65two) to a separate third-stage bootstrap program, 66.Xr loader 8 . 67This third stage provides more sophisticated control over the booting 68process than it is possible to achieve in the boot blocks, which are 69constrained by occupying limited fixed space on a given disk or slice. 70.Pp 71However, it is possible to dispense with the third stage altogether, 72either by specifying a kernel name in the boot block parameter 73file, 74.Pa /boot.config , 75or, unless option 76.Fl n 77is set, by hitting a key during a brief pause (while one of the characters 78.Sy - , 79.Sy \e , 80.Sy \&| , 81or 82.Sy / 83is displayed) before 84.Xr loader 8 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. The 89.Xr loader 8 90program is documented separately. 91.Pp 92After the boot blocks have been loaded, 93you should see a prompt similar to the following: 94.Bd -literal 95DragonFly boot 960:ad(0,a)/boot/loader: 97.Ed 98.Pp 99The automatic boot will attempt to load 100.Pa /boot/loader 101and if that fails 102.Pa /loader 103from partition 104.Ql a 105of either the floppy or the hard disk. 106This boot may be aborted by typing any character on the keyboard 107at the 108.Ql boot: 109prompt. At this time, the following input will be accepted: 110.Bl -tag -width indent 111.It Ic \&? 112Give a short listing of the files in the root directory of the default 113boot device, as a hint about available boot files. (A 114.Ic ?\& 115may also be specified as the last segment of a path, in which case 116the listing will be of the relevant subdirectory.) 117.It Xo 118.Ar bios_drive : Ns Ar interface Ns Po 119.Ar unit , Ns Ar part Pc 120.Ar filename 121.Op Fl aCcDdghmnPprsVv 122.Xc 123Specify boot file and flags. 124.Bl -tag -width indent 125.It Ar bios_drive 126The drive number as recognized by the BIOS. 1270 for the first drive, 1 for the second drive, etc. 128.It Ar interface 129The type of controller to boot from. Note that the controller is required 130to have BIOS support since the BIOS services are used to load the 131boot file image. 132.Pp 133The supported interfaces are: 134.Pp 135.Bl -tag -width "adXX" -compact 136.It ad 137ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike 138controller 139.It fd 1405 \(14" or 3 \(12" High density floppies 141.It da 142SCSI disk on any supported SCSI controller 143.\".It cd 144.\"boot from CDROM 145.El 146.It Ar unit 147The unit number of the drive on the interface being used. 1480 for the first drive, 1 for the second drive, etc. 149.It Ar part 150The partition letter inside the 151.Bx 152portion of the disk. See 153.Xr disklabel 8 . 154By convention, only partition 155.Ql a 156contains a bootable image. If sliced disks are used 157.Pq Dq fdisk partitions , 158any slice can be booted from, with the default being the active slice 159or, otherwise, the first 160.Dx 161slice. 162.It Ar filename 163The pathname of the file to boot (relative to the root directory 164on the specified partition). Defaults to 165.Pa /boot/kernel . 166Symbolic links are not supported (hard links are). 167.It Fl aCcDdghmnPprsVv 168Boot flags: 169.Pp 170.Bl -tag -width "-CXX" -compact 171.It Fl a 172during kernel initialization, 173ask for the device to mount as the root file system. 174.It Fl C 175boot from CDROM. 176.It Fl D 177Use all available consoles as the system console. Input will be accepted 178on any console and output will be routed to all of them. This is the 179default. 180.It Fl h 181Use the serial console as the system console. 182.It Fl V 183Use the video console as the system console. 184.It Fl m 185Mute the system console. None of the console devices will be used for the 186system console. 187.It Fl d 188enter the DDB kernel debugger 189(see 190.Xr ddb 4 ) 191as early as possible in kernel initialization. 192.It Fl g 193use the GDB remote debugging protocol. 194.It Fl n 195ignore key press to interrupt boot before 196.Xr loader 8 197is invoked. 198.It Fl P 199probe the keyboard. If no keyboard is found, the 200.Fl D 201and 202.Fl h 203options are automatically set. 204.It Fl p 205pause after each attached device during the device probing phase. 206.It Fl r 207use the statically configured default for the device containing the 208root file system 209(see 210.Sq Cd options ROOTDEVNAME 211in the 212.Pa LINT64 213kernel configuration file). 214Normally, the root file system is on the device 215that the kernel was loaded from. 216.It Fl s 217boot into single-user mode; if the console is marked as 218.Dq insecure 219(see 220.Xr ttys 5 ) , 221the root password must be entered. 222.It Fl v 223be verbose during device probing (and later). 224.El 225.El 226.El 227.Pp 228You may put a BIOS drive number, a controller type, a unit number, 229a partition, a kernel file name, and any valid option in 230.Pa /boot.config 231to set defaults. Enter them in one line just as you type at the 232.Ql boot: 233prompt. 234.Sh FILES 235.Bl -tag -width /boot/loader -compact 236.It Pa /boot.config 237parameters for the boot blocks (optional) 238.It Pa /boot/boot1 239first stage bootstrap file 240.It Pa /boot/boot2 241second stage bootstrap file 242.It Pa /boot/loader 243third stage bootstrap 244.It Pa /boot/kernel 245default kernel 246.It Pa /boot/kernel.old 247typical non-default kernel (optional) 248.El 249.Sh DIAGNOSTICS 250When disk-related errors occur, these are reported by the second-stage 251bootstrap using the same error codes returned by the BIOS, for example 252.Dq Disk error 0x1 (lba=0x12345678) . 253Here is a partial list of these error codes: 254.Pp 255.Bl -tag -width "0x80" -compact 256.It 0x1 257Invalid argument 258.It 0x2 259Address mark not found 260.It 0x4 261Sector not found 262.It 0x8 263DMA overrun 264.It 0x9 265DMA attempt across 64K boundary 266.It 0xc 267Invalid media 268.It 0x10 269Uncorrectable CRC/ECC error 270.It 0x20 271Controller failure 272.It 0x40 273Seek failed 274.It 0x80 275Timeout 276.El 277.Pp 278.Sy "NOTE" : 279On older machines, or otherwise where EDD support (disk packet 280interface support) is not available, all boot-related files and 281structures (including the kernel) that need to be accessed during the 282boot phase must reside on the disk at or below cylinder 1023 (as the 283BIOS understands the geometry). When a 284.Dq Disk error 0x1 285is reported by the second-stage bootstrap, it generally means that this 286requirement has not been adhered to. 287.Sh SEE ALSO 288.Xr ddb 4 , 289.Xr ttys 5 , 290.Xr boot0cfg 8 , 291.Xr disklabel 8 , 292.Xr efibootmgr 8 , 293.Xr halt 8 , 294.Xr loader 8 , 295.Xr reboot 8 , 296.Xr shutdown 8 , 297.Xr uefi 8 298.Sh BUGS 299The 300.Xr disklabel 5 301format used by this version of 302.Bx 303is quite 304different from that of other architectures. 305.Pp 306Due to space constraints, the keyboard probe initiated by the 307.Fl P 308option is simply a test that the BIOS has detected an 309.Dq extended 310keyboard. If an 311.Dq XT/AT 312keyboard (with no F11 and F12 keys, etc.) is attached, the probe will 313fail. 314.Pp 315Some features are not yet documented. 316