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.\" 4. 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.\" $FreeBSD$ 38.\" 39.Dd April 19, 1994 40.Dt BOOT 8 i386 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). 55Some BIOSes allow 56you to change this default sequence, and may 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. 82Booting will also be attempted at stage two, if the 83third stage cannot be loaded. 84.Pp 85The remainder of this subsection deals only with the boot blocks. 86The 87.Xr loader 8 88program is documented separately. 89.Pp 90After the boot blocks have been loaded, 91you should see a prompt similar to the following: 92.Bd -literal 93>> FreeBSD/i386 BOOT 94Default: 0:ad(0,a)/kernel 95boot: 96.Ed 97.Pp 98The automatic boot will attempt to load 99.Pa /kernel 100from partition 101.Ql a 102of either the floppy or the hard disk. 103This boot may be aborted by typing any character on the keyboard 104at the 105.Ql boot: 106prompt. 107At 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. 112(A 113.Ic ?\& 114may also be specified as the last segment of a path, in which case 115the listing will be of the relevant subdirectory.) 116.Pp 117.It Xo 118.Sm off 119.Ar bios_drive : interface ( unit , Oo Ar slice , Oc Ar part ) 120.Sm on 121.Ar filename 122.Op Fl aCcDdghmnPprsv 123.Xc 124Specify boot file and flags. 125.Bl -tag -width indent 126.It Ar bios_drive 127The drive number as recognized by the BIOS. 1280 for the first drive, 1 for the second drive, etc. 129.It Ar interface 130The type of controller to boot from. 131Note that the controller is required 132to have BIOS support since the BIOS services are used to load the 133boot file image. 134.Pp 135The supported interfaces are: 136.Pp 137.Bl -tag -width "adXX" -compact 138.It ad 139ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike 140controller 141.It fd 1425 1/4" or 3 1/2" High density floppies 143.It da 144SCSI disk on any supported SCSI controller 145.\".It cd 146.\"boot from CDROM 147.El 148.It Ar unit 149The unit number of the drive on the interface being used. 1500 for the first drive, 1 for the second drive, etc. 151.It Oo Ar slice , Oc Ns Ar part 152The partition letter inside the 153.Bx 154portion of the disk. 155See 156.Xr disklabel 8 . 157By convention, only partition 158.Ql a 159contains a bootable image. 160If sliced disks are used 161.Pq Dq fdisk partitions , 162any 163.Ar slice 164(1 for the first slice, 2 for the second slice, etc.\&) 165can be booted from, with the default (if not specified) being the active slice 166or, otherwise, the first 167.Fx 168slice. 169If 170.Ar slice 171is specified as 0, the first 172.Fx 173slice (also known as 174.Dq compatibility 175slice) is booted from. 176.It Ar filename 177The pathname of the file to boot (relative to the root directory 178on the specified partition). 179Defaults to 180.Pa /kernel . 181Symbolic links are not supported (hard links are). 182.It Fl aCcDdghmnPprsv 183Boot flags: 184.Pp 185.Bl -tag -width "-CXX" -compact 186.It Fl a 187during kernel initialization, 188ask for the device to mount as the root file system. 189.It Fl C 190boot from CDROM. 191.It Fl c 192run UserConfig to modify hardware parameters for the loaded 193kernel. 194If the kernel was built with one of 195.Dv USERCONFIG , INTRO_USERCONFIG , VISUAL_USERCONFIG 196options, 197remain in UserConfig regardless of any 198.Ic quit 199commands present in the script. 200.It Fl D 201toggle single and dual console configurations. 202In the single 203configuration the console will be either the internal display 204or the serial port, depending on the state of the 205.Fl h 206option below. 207In the dual console configuration, 208both the internal display and the serial port will become the console 209at the same time, regardless of the state of the 210.Fl h 211option. 212However, the dual console configuration takes effect only during 213the boot prompt. 214Once the kernel is loaded, the console specified 215by the 216.Fl h 217option becomes the only console. 218.It Fl d 219enter the DDB kernel debugger 220(see 221.Xr ddb 4 ) 222as early as possible in kernel initialization. 223.It Fl g 224use the GDB remote debugging protocol. 225.It Fl h 226toggle internal and serial consoles. 227You can use this to switch 228console devices. 229For instance, if you boot from the internal console, 230you can use the 231.Fl h 232option to force the kernel to use the serial port as its 233console device. 234Alternatively, if you boot from the serial port, 235you can use this option to force the kernel to use the internal display 236as the console instead. 237The serial port driver 238.Xr sio 4 239has a flag to override this option. 240If that flag is set, the serial port will always be used as the console, 241regardless of the 242.Fl h 243option described here. 244See the man page for 245.Xr sio 4 246for more details. 247.It Fl m 248mute the console. 249.It Fl n 250ignore key press to interrupt boot before 251.Xr loader 8 252is invoked. 253.It Fl P 254probe the keyboard. 255If no keyboard is found, the 256.Fl D 257and 258.Fl h 259options are automatically set. 260.It Fl p 261pause after each attached device during the device probing phase. 262.It Fl r 263use the statically configured default for the device containing the 264root file system 265(see 266.Xr config 8 ) . 267Normally, the root file system is on the device 268that the kernel was loaded from. 269.It Fl s 270boot into single-user mode; if the console is marked as 271.Dq insecure 272(see 273.Xr ttys 5 ) , 274the root password must be entered. 275.It Fl v 276be verbose during device probing (and later). 277.El 278.El 279.El 280.Pp 281You may put a BIOS drive number, a controller type, a unit number, 282a partition, a kernel file name, and any valid option in 283.Pa /boot.config 284to set defaults. 285Enter them in one line just as you type at the 286.Ql boot: 287prompt. 288.Sh FILES 289.Bl -tag -width /boot/loader -compact 290.It Pa /boot.config 291parameters for the boot blocks (optional) 292.It Pa /boot/boot1 293first stage bootstrap file 294.It Pa /boot/boot2 295second stage bootstrap file 296.It Pa /boot/loader 297third stage bootstrap 298.It Pa /boot/kernel/kernel 299default kernel 300.It Pa /boot/kernel.old/kernel 301typical non-default kernel (optional) 302.El 303.Sh SEE ALSO 304.Xr ddb 4 , 305.Xr ttys 5 , 306.Xr boot0cfg 8 , 307.Xr btxld 8 , 308.Xr config 8 , 309.Xr disklabel 8 , 310.Xr halt 8 , 311.Xr loader 8 , 312.Xr reboot 8 , 313.Xr shutdown 8 314.Sh DIAGNOSTICS 315When disk-related errors occur, these are reported by the second-stage 316bootstrap using the same error codes returned by the BIOS, for example 317.Dq Disk error 0x1 (lba=0x12345678) . 318Here is a partial list of these error codes: 319.Pp 320.Bl -tag -width "0x80" -compact 321.It 0x1 322Invalid argument 323.It 0x2 324Address mark not found 325.It 0x4 326Sector not found 327.It 0x8 328DMA overrun 329.It 0x9 330DMA attempt across 64K boundary 331.It 0xc 332Invalid media 333.It 0x10 334Uncorrectable CRC/ECC error 335.It 0x20 336Controller failure 337.It 0x40 338Seek failed 339.It 0x80 340Timeout 341.El 342.Pp 343.Sy "NOTE" : 344On older machines, or otherwise where EDD support (disk packet 345interface support) is not available, all boot-related files and 346structures (including the kernel) that need to be accessed during the 347boot phase must reside on the disk at or below cylinder 1023 (as the 348BIOS understands the geometry). 349When a 350.Dq Disk error 0x1 351is reported by the second-stage bootstrap, it generally means that this 352requirement has not been adhered to. 353.Sh BUGS 354The 355.Xr disklabel 5 356format used by this version of 357.Bx 358is quite 359different from that of other architectures. 360.Pp 361Due to space constraints, the keyboard probe initiated by the 362.Fl P 363option is simply a test that the BIOS has detected an 364.Dq extended 365keyboard. 366If an 367.Dq XT/AT 368keyboard (with no F11 and F12 keys, etc.) is attached, the probe will 369fail. 370