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 85Make note of the fact that 86.Pa /boot.config 87is read only from the 88.Ql a 89partition. As a result, slices which are missing an 90.Ql a 91parition require user intervention during the boot process. 92.Pp 93The remainder of this subsection deals only with the boot blocks. 94The 95.Xr loader 8 96program is documented separately. 97.Pp 98After the boot blocks have been loaded, 99you should see a prompt similar to the following: 100.Bd -literal 101>> FreeBSD/i386 BOOT 102Default: 0:ad(0,a)/boot/loader 103boot: 104.Ed 105.Pp 106The automatic boot will attempt to load 107.Pa /boot/loader 108from partition 109.Ql a 110of either the floppy or the hard disk. 111This boot may be aborted by typing any character on the keyboard 112at the 113.Ql boot: 114prompt. 115At this time, the following input will be accepted: 116.Bl -tag -width indent 117.It Ic \&? 118Give a short listing of the files in the root directory of the default 119boot device, as a hint about available boot files. 120(A 121.Ic ?\& 122may also be specified as the last segment of a path, in which case 123the listing will be of the relevant subdirectory.) 124.Pp 125.It Xo 126.Sm off 127.Ar bios_drive : interface ( unit , Oo Ar slice , Oc Ar part ) 128.Sm on 129.Ar filename 130.Op Fl aCcDdghmnPprsv 131.Xc 132Specify boot file and flags. 133.Bl -tag -width indent 134.It Ar bios_drive 135The drive number as recognized by the BIOS. 1360 for the first drive, 1 for the second drive, etc. 137.It Ar interface 138The type of controller to boot from. 139Note that the controller is required 140to have BIOS support since the BIOS services are used to load the 141boot file image. 142.Pp 143The supported interfaces are: 144.Pp 145.Bl -tag -width "adXX" -compact 146.It ad 147ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike 148controller 149.It fd 1505 1/4" or 3 1/2" High density floppies 151.It da 152SCSI disk on any supported SCSI controller 153.\".It cd 154.\"boot from CDROM 155.El 156.It Ar unit 157The unit number of the drive on the interface being used. 1580 for the first drive, 1 for the second drive, etc. 159.It Oo Ar slice , Oc Ns Ar part 160The partition letter inside the 161.Bx 162portion of the disk. 163See 164.Xr disklabel 8 . 165By convention, only partition 166.Ql a 167contains a bootable image. 168If sliced disks are used 169.Pq Dq fdisk partitions , 170any 171.Ar slice 172(1 for the first slice, 2 for the second slice, etc.\&) 173can be booted from, with the default (if not specified) being the active slice 174or, otherwise, the first 175.Fx 176slice. 177If 178.Ar slice 179is specified as 0, the first 180.Fx 181slice (also known as 182.Dq compatibility 183slice) is booted from. 184.It Ar filename 185The pathname of the file to boot (relative to the root directory 186on the specified partition). 187Defaults to 188.Pa /kernel . 189Symbolic links are not supported (hard links are). 190.It Fl aCcDdghmnPprsv 191Boot flags: 192.Pp 193.Bl -tag -width "-CXX" -compact 194.It Fl a 195during kernel initialization, 196ask for the device to mount as the root file system. 197.It Fl C 198boot from CDROM. 199.It Fl c 200run UserConfig to modify hardware parameters for the loaded 201kernel. 202If the kernel was built with one of 203.Dv USERCONFIG , INTRO_USERCONFIG , VISUAL_USERCONFIG 204options, 205remain in UserConfig regardless of any 206.Ic quit 207commands present in the script. 208.It Fl D 209toggle single and dual console configurations. 210In the single 211configuration the console will be either the internal display 212or the serial port, depending on the state of the 213.Fl h 214option below. 215In the dual console configuration, 216both the internal display and the serial port will become the console 217at the same time, regardless of the state of the 218.Fl h 219option. 220However, the dual console configuration takes effect only during 221the boot prompt. 222Once the kernel is loaded, the console specified 223by the 224.Fl h 225option becomes the only console. 226.It Fl d 227enter the DDB kernel debugger 228(see 229.Xr ddb 4 ) 230as early as possible in kernel initialization. 231.It Fl g 232use the GDB remote debugging protocol. 233.It Fl h 234toggle internal and serial consoles. 235You can use this to switch 236console devices. 237For instance, if you boot from the internal console, 238you can use the 239.Fl h 240option to force the kernel to use the serial port as its 241console device. 242Alternatively, if you boot from the serial port, 243you can use this option to force the kernel to use the internal display 244as the console instead. 245The serial port driver 246.Xr sio 4 247has a flag to override this option. 248If that flag is set, the serial port will always be used as the console, 249regardless of the 250.Fl h 251option described here. 252See the man page for 253.Xr sio 4 254for more details. 255.It Fl m 256mute the console. 257.It Fl n 258ignore key press to interrupt boot before 259.Xr loader 8 260is invoked. 261.It Fl P 262probe the keyboard. 263If no keyboard is found, the 264.Fl D 265and 266.Fl h 267options are automatically set. 268.It Fl p 269pause after each attached device during the device probing phase. 270.It Fl r 271use the statically configured default for the device containing the 272root file system 273(see 274.Xr config 8 ) . 275Normally, the root file system is on the device 276that the kernel was loaded from. 277.It Fl s 278boot into single-user mode; if the console is marked as 279.Dq insecure 280(see 281.Xr ttys 5 ) , 282the root password must be entered. 283.It Fl v 284be verbose during device probing (and later). 285.El 286.El 287.El 288.Pp 289You may put a BIOS drive number, a controller type, a unit number, 290a partition, a kernel file name, and any valid option in 291.Pa /boot.config 292to set defaults. 293Enter them in one line just as you type at the 294.Ql boot: 295prompt. 296.Sh FILES 297.Bl -tag -width /boot/loader -compact 298.It Pa /boot.config 299parameters for the boot blocks (optional) 300.It Pa /boot/boot1 301first stage bootstrap file 302.It Pa /boot/boot2 303second stage bootstrap file 304.It Pa /boot/loader 305third stage bootstrap 306.It Pa /boot/kernel/kernel 307default kernel 308.It Pa /boot/kernel.old/kernel 309typical non-default kernel (optional) 310.El 311.Sh SEE ALSO 312.Xr ddb 4 , 313.Xr ttys 5 , 314.Xr boot0cfg 8 , 315.Xr btxld 8 , 316.Xr config 8 , 317.Xr disklabel 8 , 318.Xr halt 8 , 319.Xr loader 8 , 320.Xr reboot 8 , 321.Xr shutdown 8 322.Sh DIAGNOSTICS 323When disk-related errors occur, these are reported by the second-stage 324bootstrap using the same error codes returned by the BIOS, for example 325.Dq Disk error 0x1 (lba=0x12345678) . 326Here is a partial list of these error codes: 327.Pp 328.Bl -tag -width "0x80" -compact 329.It 0x1 330Invalid argument 331.It 0x2 332Address mark not found 333.It 0x4 334Sector not found 335.It 0x8 336DMA overrun 337.It 0x9 338DMA attempt across 64K boundary 339.It 0xc 340Invalid media 341.It 0x10 342Uncorrectable CRC/ECC error 343.It 0x20 344Controller failure 345.It 0x40 346Seek failed 347.It 0x80 348Timeout 349.El 350.Pp 351.Sy "NOTE" : 352On older machines, or otherwise where EDD support (disk packet 353interface support) is not available, all boot-related files and 354structures (including the kernel) that need to be accessed during the 355boot phase must reside on the disk at or below cylinder 1023 (as the 356BIOS understands the geometry). 357When a 358.Dq Disk error 0x1 359is reported by the second-stage bootstrap, it generally means that this 360requirement has not been adhered to. 361.Sh BUGS 362The 363.Xr disklabel 5 364format used by this version of 365.Bx 366is quite 367different from that of other architectures. 368.Pp 369Due to space constraints, the keyboard probe initiated by the 370.Fl P 371option is simply a test that the BIOS has detected an 372.Dq extended 373keyboard. 374If an 375.Dq XT/AT 376keyboard (with no F11 and F12 keys, etc.) is attached, the probe will 377fail. 378