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.Op Fl S Ns Ar speed 133.Xc 134Specify boot file and flags. 135.Bl -tag -width indent 136.It Ar bios_drive 137The drive number as recognized by the BIOS. 1380 for the first drive, 1 for the second drive, etc. 139.It Ar interface 140The type of controller to boot from. 141Note that the controller is required 142to have BIOS support since the BIOS services are used to load the 143boot file image. 144.Pp 145The supported interfaces are: 146.Pp 147.Bl -tag -width "adXX" -compact 148.It ad 149ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike 150controller 151.It fd 1525 1/4" or 3 1/2" High density floppies 153.It da 154SCSI disk on any supported SCSI controller 155.\".It cd 156.\"boot from CDROM 157.El 158.It Ar unit 159The unit number of the drive on the interface being used. 1600 for the first drive, 1 for the second drive, etc. 161.It Oo Ar slice , Oc Ns Ar part 162The partition letter inside the 163.Bx 164portion of the disk. 165See 166.Xr bsdlabel 8 . 167By convention, only partition 168.Ql a 169contains a bootable image. 170If sliced disks are used 171.Pq Dq fdisk partitions , 172any 173.Ar slice 174(1 for the first slice, 2 for the second slice, etc.\&) 175can be booted from, with the default (if not specified) being the active slice 176or, otherwise, the first 177.Fx 178slice. 179If 180.Ar slice 181is specified as 0, the first 182.Fx 183slice (also known as 184.Dq compatibility 185slice) is booted from. 186.It Ar filename 187The pathname of the file to boot (relative to the root directory 188on the specified partition). 189Defaults to 190.Pa /boot/kernel/kernel . 191Symbolic links are not supported (hard links are). 192.It Xo Op Fl aCcDdghmnPprsv 193.Op Fl S Ns Ar speed 194.Xc 195Boot flags: 196.Pp 197.Bl -tag -width "-CXX" -compact 198.It Fl a 199during kernel initialization, 200ask for the device to mount as the root file system. 201.It Fl C 202try to mount root file system from a CD-ROM. 203.It Fl c 204this flag is currently a no-op. 205.It Fl D 206boot with the dual console configuration. 207In the single 208configuration, the console will be either the internal display 209or the serial port, depending on the state of the 210.Fl h 211option below. 212In the dual console configuration, 213both the internal display and the serial port will become the console 214at the same time, regardless of the state of the 215.Fl h 216option. 217.It Fl d 218enter the DDB kernel debugger 219(see 220.Xr ddb 4 ) 221as early as possible in kernel initialization. 222.It Fl g 223use the GDB remote debugging protocol. 224.It Fl h 225force the serial console. 226For instance, if you boot from the internal console, 227you can use the 228.Fl h 229option to force the kernel to use the serial port as its 230console device. 231The serial port driver 232.Xr sio 4 233has a flag (0x20) to override this option. 234If that flag is set, the serial port will always be used as the console, 235regardless of the 236.Fl h 237option described here. 238See the man page for 239.Xr sio 4 240for more details. 241.It Fl m 242mute the console. 243.It Fl n 244ignore key press to interrupt boot before 245.Xr loader 8 246is invoked. 247.It Fl P 248probe the keyboard. 249If no keyboard is found, the 250.Fl D 251and 252.Fl h 253options are automatically set. 254.It Fl p 255pause after each attached device during the device probing phase. 256.It Fl r 257use the statically configured default for the device containing the 258root file system 259(see 260.Xr config 8 ) . 261Normally, the root file system is on the device 262that the kernel was loaded from. 263.It Fl s 264boot into single-user mode; if the console is marked as 265.Dq insecure 266(see 267.Xr ttys 5 ) , 268the root password must be entered. 269.It Fl S Ns Ar speed 270set the speed of the serial console to 271.Ar speed . 272The default is 9600 unless it has been overridden by setting 273.Va BOOT_COMCONSOLE_SPEED 274in 275.Xr make.conf 5 276and recompiling the boot blocks. 277.It Fl v 278be verbose during device probing (and later). 279.El 280.El 281.El 282.Pp 283You may put a BIOS drive number, a controller type, a unit number, 284a partition, a kernel file name, and any valid option in 285.Pa /boot.config 286to set defaults. 287Enter them in one line just as you type at the 288.Ql boot: 289prompt. 290.Sh FILES 291.Bl -tag -width /boot/loader -compact 292.It Pa /boot.config 293parameters for the boot blocks (optional) 294.It Pa /boot/boot1 295first stage bootstrap file 296.It Pa /boot/boot2 297second stage bootstrap file 298.It Pa /boot/loader 299third stage bootstrap 300.It Pa /boot/kernel/kernel 301default kernel 302.It Pa /boot/kernel.old/kernel 303typical non-default kernel (optional) 304.El 305.Sh DIAGNOSTICS 306When disk-related errors occur, these are reported by the second-stage 307bootstrap using the same error codes returned by the BIOS, for example 308.Dq Disk error 0x1 (lba=0x12345678) . 309Here is a partial list of these error codes: 310.Pp 311.Bl -tag -width "0x80" -compact 312.It 0x1 313Invalid argument 314.It 0x2 315Address mark not found 316.It 0x4 317Sector not found 318.It 0x8 319DMA overrun 320.It 0x9 321DMA attempt across 64K boundary 322.It 0xc 323Invalid media 324.It 0x10 325Uncorrectable CRC/ECC error 326.It 0x20 327Controller failure 328.It 0x40 329Seek failed 330.It 0x80 331Timeout 332.El 333.Pp 334.Sy "NOTE" : 335On older machines, or otherwise where EDD support (disk packet 336interface support) is not available, all boot-related files and 337structures (including the kernel) that need to be accessed during the 338boot phase must reside on the disk at or below cylinder 1023 (as the 339BIOS understands the geometry). 340When a 341.Dq Disk error 0x1 342is reported by the second-stage bootstrap, it generally means that this 343requirement has not been adhered to. 344.Sh SEE ALSO 345.Xr ddb 4 , 346.Xr make.conf 5 , 347.Xr ttys 5 , 348.Xr boot0cfg 8 , 349.Xr bsdlabel 8 , 350.Xr btxld 8 , 351.Xr config 8 , 352.Xr halt 8 , 353.Xr loader 8 , 354.Xr reboot 8 , 355.Xr shutdown 8 356.Sh BUGS 357The 358.Xr bsdlabel 5 359format used by this version of 360.Bx 361is quite 362different from that of other architectures. 363.Pp 364Due to space constraints, the keyboard probe initiated by the 365.Fl P 366option is simply a test that the BIOS has detected an 367.Dq extended 368keyboard. 369If an 370.Dq XT/AT 371keyboard (with no F11 and F12 keys, etc.) is attached, the probe will 372fail. 373