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 August 18, 2005 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. 90As a result, slices which are missing an 91.Ql a 92partition require user intervention during the boot process. 93.Pp 94The remainder of this subsection deals only with the boot blocks. 95The 96.Xr loader 8 97program is documented separately. 98.Pp 99After the boot blocks have been loaded, 100you should see a prompt similar to the following: 101.Bd -literal 102>> FreeBSD/i386 BOOT 103Default: 0:ad(0,a)/boot/loader 104boot: 105.Ed 106.Pp 107The automatic boot will attempt to load 108.Pa /boot/loader 109from partition 110.Ql a 111of either the floppy or the hard disk. 112This boot may be aborted by typing any character on the keyboard 113at the 114.Ql boot: 115prompt. 116At this time, the following input will be accepted: 117.Bl -tag -width indent 118.It Ic \&? 119Give a short listing of the files in the root directory of the default 120boot device, as a hint about available boot files. 121(A 122.Ic ?\& 123may also be specified as the last segment of a path, in which case 124the listing will be of the relevant subdirectory.) 125.Pp 126.It Xo 127.Sm off 128.Ar bios_drive : interface ( unit , Oo Ar slice , Oc Ar part ) 129.Ar filename 130.Sm on 131.Op Fl aCcDdghmnPprsv 132.Sm off 133.Op Fl S Ar speed 134.Sm on 135.Xc 136Specify boot file and flags. 137.Bl -tag -width indent 138.It Ar bios_drive 139The drive number as recognized by the BIOS. 1400 for the first drive, 1 for the second drive, etc. 141.It Ar interface 142The type of controller to boot from. 143Note that the controller is required 144to have BIOS support since the BIOS services are used to load the 145boot file image. 146.Pp 147The supported interfaces are: 148.Pp 149.Bl -tag -width "adXX" -compact 150.It ad 151ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike 152controller 153.It fd 1545 1/4" or 3 1/2" High density floppies 155.It da 156SCSI disk on any supported SCSI controller 157.\".It cd 158.\"boot from CDROM 159.El 160.It Ar unit 161The unit number of the drive on the interface being used. 1620 for the first drive, 1 for the second drive, etc. 163.It Oo Ar slice , Oc Ns Ar part 164The partition letter inside the 165.Bx 166portion of the disk. 167See 168.Xr bsdlabel 8 . 169By convention, only partition 170.Ql a 171contains a bootable image. 172If sliced disks are used 173.Pq Dq fdisk partitions , 174any 175.Ar slice 176(1 for the first slice, 2 for the second slice, etc.\&) 177can be booted from, with the default (if not specified) being the active slice 178or, otherwise, the first 179.Fx 180slice. 181If 182.Ar slice 183is specified as 0, the first 184.Fx 185slice (also known as 186.Dq compatibility 187slice) is booted from. 188.It Ar filename 189The pathname of the file to boot (relative to the root directory 190on the specified partition). 191Defaults to 192.Pa /boot/kernel/kernel . 193Symbolic links are not supported (hard links are). 194.It Xo Op Fl aCcDdghmnPprsv 195.Sm off 196.Op Fl S Ar speed 197.Sm on 198.Xc 199Boot flags: 200.Pp 201.Bl -tag -width "-CXX" -compact 202.It Fl a 203during kernel initialization, 204ask for the device to mount as the root file system. 205.It Fl C 206try to mount root file system from a CD-ROM. 207.It Fl c 208this flag is currently a no-op. 209.It Fl D 210boot with the dual console configuration. 211In the single 212configuration, the console will be either the internal display 213or the serial port, depending on the state of the 214.Fl h 215option below. 216In the dual console configuration, 217both the internal display and the serial port will become the console 218at the same time, regardless of the state of the 219.Fl h 220option. 221.It Fl d 222enter the DDB kernel debugger 223(see 224.Xr ddb 4 ) 225as early as possible in kernel initialization. 226.It Fl g 227use the GDB remote debugging protocol. 228.It Fl h 229force the serial console. 230For instance, if you boot from the internal console, 231you can use the 232.Fl h 233option to force the kernel to use the serial port as its 234console device. 235The serial port driver 236.Xr sio 4 237has a flag (0x20) to override this option. 238If that flag is set, the serial port will always be used as the console, 239regardless of the 240.Fl h 241option described here. 242See the man page for 243.Xr sio 4 244for more details. 245.It Fl m 246mute the console. 247.It Fl n 248ignore key press to interrupt boot before 249.Xr loader 8 250is invoked. 251.It Fl P 252probe the keyboard. 253If no keyboard is found, the 254.Fl D 255and 256.Fl h 257options are automatically set. 258.It Fl p 259pause after each attached device during the device probing phase. 260.It Fl r 261use the statically configured default for the device containing the 262root file system 263(see 264.Xr config 8 ) . 265Normally, the root file system is on the device 266that the kernel was loaded from. 267.It Fl s 268boot into single-user mode; if the console is marked as 269.Dq insecure 270(see 271.Xr ttys 5 ) , 272the root password must be entered. 273.It Xo Sm off 274.Fl S Ar speed 275.Sm on 276.Xc 277set the speed of the serial console to 278.Ar speed . 279The default is 9600 unless it has been overridden by setting 280.Va BOOT_COMCONSOLE_SPEED 281in 282.Pa /etc/make.conf 283and recompiling the boot blocks. 284.It Fl v 285be verbose during device probing (and later). 286.El 287.El 288.El 289.Pp 290You may put a BIOS drive number, a controller type, a unit number, 291a partition, a kernel file name, and any valid option in 292.Pa /boot.config 293to set defaults. 294Enter them in one line just as you type at the 295.Ql boot: 296prompt. 297.Sh FILES 298.Bl -tag -width /boot/loader -compact 299.It Pa /boot.config 300parameters for the boot blocks (optional) 301.It Pa /boot/boot1 302first stage bootstrap file 303.It Pa /boot/boot2 304second stage bootstrap file 305.It Pa /boot/loader 306third stage bootstrap 307.It Pa /boot/kernel/kernel 308default kernel 309.It Pa /boot/kernel.old/kernel 310typical non-default kernel (optional) 311.El 312.Sh DIAGNOSTICS 313When disk-related errors occur, these are reported by the second-stage 314bootstrap using the same error codes returned by the BIOS, for example 315.Dq Disk error 0x1 (lba=0x12345678) . 316Here is a partial list of these error codes: 317.Pp 318.Bl -tag -width "0x80" -compact 319.It 0x1 320Invalid argument 321.It 0x2 322Address mark not found 323.It 0x4 324Sector not found 325.It 0x8 326DMA overrun 327.It 0x9 328DMA attempt across 64K boundary 329.It 0xc 330Invalid media 331.It 0x10 332Uncorrectable CRC/ECC error 333.It 0x20 334Controller failure 335.It 0x40 336Seek failed 337.It 0x80 338Timeout 339.El 340.Pp 341.Sy "NOTE" : 342On older machines, or otherwise where EDD support (disk packet 343interface support) is not available, all boot-related files and 344structures (including the kernel) that need to be accessed during the 345boot phase must reside on the disk at or below cylinder 1023 (as the 346BIOS understands the geometry). 347When a 348.Dq Disk error 0x1 349is reported by the second-stage bootstrap, it generally means that this 350requirement has not been adhered to. 351.Sh SEE ALSO 352.Xr ddb 4 , 353.Xr ttys 5 , 354.Xr boot0cfg 8 , 355.Xr bsdlabel 8 , 356.Xr btxld 8 , 357.Xr config 8 , 358.Xr halt 8 , 359.Xr loader 8 , 360.Xr reboot 8 , 361.Xr shutdown 8 362.Sh BUGS 363The 364.Xr bsdlabel 5 365format used by this version of 366.Bx 367is quite 368different from that of other architectures. 369.Pp 370Due to space constraints, the keyboard probe initiated by the 371.Fl P 372option is simply a test that the BIOS has detected an 373.Dq extended 374keyboard. 375If an 376.Dq XT/AT 377keyboard (with no F11 and F12 keys, etc.) is attached, the probe will 378fail. 379