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. All advertising materials mentioning features or use of this software 20.\" must display the following acknowledgement: 21.\" This product includes software developed by the University of 22.\" California, Berkeley and its contributors. 23.\" 4. Neither the name of the University nor the names of its contributors 24.\" may be used to endorse or promote products derived from this software 25.\" without specific prior written permission. 26.\" 27.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 28.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 29.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 30.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 31.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 32.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 33.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 34.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 35.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 36.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 37.\" SUCH DAMAGE. 38.\" 39.\" @(#)boot_i386.8 8.2 (Berkeley) 4/19/94 40.\" 41.\" $FreeBSD$ 42.\" 43.Dd April 19, 1994 44.Dt BOOT 8 i386 45.Os 46.Sh NAME 47.Nm boot 48.Nd system bootstrapping procedures 49.Sh DESCRIPTION 50.Sy Power fail and crash recovery . 51Normally, the system will reboot itself at power-up or after crashes. 52An automatic consistency check of the file systems will be performed, 53and unless this fails, the system will resume multi-user operations. 54.Pp 55.Sy Cold starts . 56Most i386 PCs attempt to boot first from floppy disk drive 0 (sometimes 57known as drive A:) and, failing that, from hard disk drive 0 (sometimes 58known as drive C:, or as drive 0x80 to the BIOS). Some BIOSes allow 59you to change this default sequence, and may also include a CD-ROM 60drive as a boot device. 61.Pp 62By default, a three-stage bootstrap is employed, and control is 63automatically passed from the boot blocks (bootstrap stages one and 64two) to a separate third-stage bootstrap program, 65.Xr loader 8 . 66This third stage provides more sophisticated control over the booting 67process than it is possible to achieve in the boot blocks, which are 68constrained by occupying limited fixed space on a given disk or slice. 69.Pp 70However, it is possible to dispense with the third stage altogether, 71either by specifying a kernel name in the boot block parameter 72file, 73.Pa /boot.config , 74or, unless option 75.Fl n 76is set, by hitting a key during a brief pause (while one of the characters 77.Sy - , 78.Sy \e , 79.Sy \&| , 80or 81.Sy / 82is displayed) before 83.Xr loader 8 84is invoked. Booting will also be attempted at stage two, if the 85third stage cannot be loaded. 86.Pp 87The remainder of this subsection deals only with the boot blocks. The 88.Xr loader 8 89program is documented separately. 90.Pp 91After the boot blocks have been loaded, 92you should see a prompt similar to the following: 93.Bd -literal 94>> FreeBSD/i386 BOOT 95Default: 0:ad(0,a)/kernel 96boot: 97.Ed 98.Pp 99The automatic boot will attempt to load 100.Pa /kernel 101from partition 102.Ql a 103of either the floppy or the hard disk. 104This boot may be aborted by typing any character on the keyboard 105at the 106.Ql boot: 107prompt. At this time, the following input will be accepted: 108.Bl -tag -width indent 109.It Ic \&? 110Give a short listing of the files in the root directory of the default 111boot device, as a hint about available boot files. (A 112.Ic ?\& 113may also be specified as the last segment of a path, in which case 114the listing will be of the relevant subdirectory.) 115.Pp 116.It Xo 117.Sm off 118.Ar bios_drive : interface ( unit , Oo Ar slice , Oc Ar part ) 119.Sm on 120.Ar filename 121.Op Fl aCcDdghmnPprsv 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 1/4" or 3 1/2" 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 Oo Ar slice , Oc Ns 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 159.Ar slice 160(1 for the first slice, 2 for the second slice, etc.\&) 161can be booted from, with the default (if not specified) being the active slice 162or, otherwise, the first 163.Fx 164slice. 165If 166.Ar slice 167is specified as 0, the first 168.Fx 169slice (also known as 170.Dq compatibility 171slice) is booted from. 172.It Ar filename 173The pathname of the file to boot (relative to the root directory 174on the specified partition). Defaults to 175.Pa /kernel . 176Symbolic links are not supported (hard links are). 177.It Fl aCcDdghmnPprsv 178Boot flags: 179.Pp 180.Bl -tag -width "-CXX" -compact 181.It Fl a 182during kernel initialization, 183ask for the device to mount as the root file system. 184.It Fl C 185boot from CDROM. 186.It Fl c 187run UserConfig to modify hardware parameters for the loaded 188kernel. If the kernel was built with one of 189.Dv USERCONFIG , INTRO_USERCONFIG , VISUAL_USERCONFIG 190options, 191remain in UserConfig regardless of any 192.Ic quit 193commands present in the script. 194.It Fl D 195toggle single and dual console configurations. In the single 196configuration the console will be either the internal display 197or the serial port, depending on the state of the 198.Fl h 199option below. In the dual console configuration, 200both the internal display and the serial port will become the console 201at the same time, regardless of the state of the 202.Fl h 203option. However, the dual console configuration takes effect only during 204the boot prompt. Once the kernel is loaded, the console specified 205by the 206.Fl h 207option becomes the only console. 208.It Fl d 209enter the DDB kernel debugger 210(see 211.Xr ddb 4 ) 212as early as possible in kernel initialization. 213.It Fl g 214use the GDB remote debugging protocol. 215.It Fl h 216toggle internal and serial consoles. You can use this to switch 217console devices. For instance, if you boot from the internal console, 218you can use the 219.Fl h 220option to force the kernel to use the serial port as its 221console device. Alternatively, if you boot from the serial port, 222you can use this option to force the kernel to use the internal display 223as the console instead. 224The serial port driver 225.Xr sio 4 226has a flag to override this option. 227If that flag is set, the serial port will always be used as the console, 228regardless of the 229.Fl h 230option described here. See the man page for 231.Xr sio 4 232for more details. 233.It Fl m 234mute the console. 235.It Fl n 236ignore key press to interrupt boot before 237.Xr loader 8 238is invoked. 239.It Fl P 240probe the keyboard. If no keyboard is found, the 241.Fl D 242and 243.Fl h 244options are automatically set. 245.It Fl p 246pause after each attached device during the device probing phase. 247.It Fl r 248use the statically configured default for the device containing the 249root file system 250(see 251.Xr config 8 ) . 252Normally, the root file system is on the device 253that the kernel was loaded from. 254.It Fl s 255boot into single-user mode; if the console is marked as 256.Dq insecure 257(see 258.Xr ttys 5 ) , 259the root password must be entered. 260.It Fl v 261be verbose during device probing (and later). 262.El 263.El 264.El 265.Pp 266You may put a BIOS drive number, a controller type, a unit number, 267a partition, a kernel file name, and any valid option in 268.Pa /boot.config 269to set defaults. Enter them in one line just as you type at the 270.Ql boot: 271prompt. 272.Sh FILES 273.Bl -tag -width /boot/loader -compact 274.It Pa /boot.config 275parameters for the boot blocks (optional) 276.It Pa /boot/boot1 277first stage bootstrap file 278.It Pa /boot/boot2 279second stage bootstrap file 280.It Pa /boot/loader 281third stage bootstrap 282.It Pa /kernel 283default kernel 284.It Pa /kernel.old 285typical non-default kernel (optional) 286.El 287.Sh SEE ALSO 288.Xr ddb 4 , 289.Xr ttys 5 , 290.Xr boot0cfg 8 , 291.Xr btxld 8 , 292.Xr config 8 , 293.Xr disklabel 8 , 294.Xr halt 8 , 295.Xr loader 8 , 296.Xr reboot 8 , 297.Xr shutdown 8 298.Sh DIAGNOSTICS 299When disk-related errors occur, these are reported by the second-stage 300bootstrap using the same error codes returned by the BIOS, for example 301.Dq Disk error 0x1 (lba=0x12345678) . 302Here is a partial list of these error codes: 303.Pp 304.Bl -tag -width "0x80" -compact 305.It 0x1 306Invalid argument 307.It 0x2 308Address mark not found 309.It 0x4 310Sector not found 311.It 0x8 312DMA overrun 313.It 0x9 314DMA attempt across 64K boundary 315.It 0xc 316Invalid media 317.It 0x10 318Uncorrectable CRC/ECC error 319.It 0x20 320Controller failure 321.It 0x40 322Seek failed 323.It 0x80 324Timeout 325.El 326.Pp 327.Sy "NOTE" : 328On older machines, or otherwise where EDD support (disk packet 329interface support) is not available, all boot-related files and 330structures (including the kernel) that need to be accessed during the 331boot phase must reside on the disk at or below cylinder 1023 (as the 332BIOS understands the geometry). When a 333.Dq Disk error 0x1 334is reported by the second-stage bootstrap, it generally means that this 335requirement has not been adhered to. 336.Sh BUGS 337The 338.Xr disklabel 5 339format used by this version of 340.Bx 341is quite 342different from that of other architectures. 343.Pp 344Due to space constraints, the keyboard probe initiated by the 345.Fl P 346option is simply a test that the BIOS has detected an 347.Dq extended 348keyboard. If an 349.Dq XT/AT 350keyboard (with no F11 and F12 keys, etc.) is attached, the probe will 351fail. 352