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 July 1, 2013 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)/boot/loader 95boot: 96.Ed 97.Pp 98The automatic boot will attempt to load 99.Pa /boot/loader 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.Ar filename 121.Sm on 122.Op Fl aCcDdghmnPprsv 123.Op Fl S Ns Ar speed 124.Xc 125Specify boot file and flags. 126.Bl -tag -width indent 127.It Ar bios_drive 128The drive number as recognized by the BIOS. 1290 for the first drive, 1 for the second drive, etc. 130.It Ar interface 131The type of controller to boot from. 132Note that the controller is required 133to have BIOS support since the BIOS services are used to load the 134boot file image. 135.Pp 136The supported interfaces are: 137.Pp 138.Bl -tag -width "adXX" -compact 139.It ad 140ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike 141controller 142.It fd 1435 1/4" or 3 1/2" High density floppies 144.It da 145SCSI disk on any supported SCSI controller 146.\".It cd 147.\"boot from CDROM 148.El 149.It Ar unit 150The unit number of the drive on the interface being used. 1510 for the first drive, 1 for the second drive, etc. 152.It Oo Ar slice , Oc Ns Ar part 153The partition letter inside the 154.Bx 155portion of the disk. 156See 157.Xr bsdlabel 8 . 158By convention, only partition 159.Ql a 160contains a bootable image. 161If sliced disks are used 162.Pq Dq fdisk partitions , 163any 164.Ar slice 165(1 for the first slice, 2 for the second slice, etc.\&) 166can be booted from, with the default (if not specified) being the active slice 167or, otherwise, the first 168.Fx 169slice. 170If 171.Ar slice 172is specified as 0, the first 173.Fx 174slice (also known as 175.Dq compatibility 176slice) is booted from. 177.It Ar filename 178The pathname of the file to boot (relative to the root directory 179on the specified partition). 180Defaults to 181.Pa /boot/kernel/kernel . 182Symbolic links are not supported (hard links are). 183.It Xo Op Fl aCcDdghmnPpqrsv 184.Op Fl S Ns Ar speed 185.Xc 186Boot flags: 187.Pp 188.Bl -tag -width "-CXX" -compact 189.It Fl a 190during kernel initialization, 191ask for the device to mount as the root file system. 192.It Fl C 193try to mount root file system from a CD-ROM. 194.It Fl c 195this flag is currently a no-op. 196.It Fl D 197boot with the dual console configuration. 198In the single 199configuration, the console will be either the internal display 200or the serial port, depending on the state of the 201.Fl h 202option below. 203In the dual console configuration, 204both the internal display and the serial port will become the console 205at the same time, regardless of the state of the 206.Fl h 207option. 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 216force the serial console. 217For 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. 222The serial port driver 223.Xr sio 4 224(but not 225.Xr uart 4 ) 226has a flag (0x20) 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. 231.It Fl m 232mute the console to suppress all console input and output during the 233boot. 234.It Fl n 235ignore key press to interrupt boot before 236.Xr loader 8 237is invoked. 238.It Fl P 239probe the keyboard. 240If 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 q 248be quiet, 249do not write anything to the console unless automatic boot fails or 250is disabled. 251This option only affects second-stage bootstrap, 252to prevent next stages from writing to the console use in 253combination with the 254.Fl m 255option. 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 and reinstalling the boot blocks. 277.It Fl v 278be verbose during device probing (and later). 279.El 280.El 281.El 282.Pp 283Use the 284.Pa /boot.config 285file to set the default configuration options for the boot block code. 286See 287.Xr boot.config 5 288for more information about the 289.Pa /boot.config 290file. 291.Sh FILES 292.Bl -tag -width /boot/loader -compact 293.It Pa /boot.config 294parameters for the boot blocks (optional) 295.It Pa /boot/boot1 296first stage bootstrap file 297.It Pa /boot/boot2 298second stage bootstrap file 299.It Pa /boot/loader 300third stage bootstrap 301.It Pa /boot/kernel/kernel 302default kernel 303.It Pa /boot/kernel.old/kernel 304typical non-default kernel (optional) 305.El 306.Sh DIAGNOSTICS 307When disk-related errors occur, these are reported by the second-stage 308bootstrap using the same error codes returned by the BIOS, for example 309.Dq Disk error 0x1 (lba=0x12345678) . 310Here is a partial list of these error codes: 311.Pp 312.Bl -tag -width "0x80" -compact 313.It 0x1 314Invalid argument 315.It 0x2 316Address mark not found 317.It 0x4 318Sector not found 319.It 0x8 320DMA overrun 321.It 0x9 322DMA attempt across 64K boundary 323.It 0xc 324Invalid media 325.It 0x10 326Uncorrectable CRC/ECC error 327.It 0x20 328Controller failure 329.It 0x40 330Seek failed 331.It 0x80 332Timeout 333.El 334.Pp 335.Sy "NOTE" : 336On older machines, or otherwise where EDD support (disk packet 337interface support) is not available, all boot-related files and 338structures (including the kernel) that need to be accessed during the 339boot phase must reside on the disk at or below cylinder 1023 (as the 340BIOS understands the geometry). 341When a 342.Dq Disk error 0x1 343is reported by the second-stage bootstrap, it generally means that this 344requirement has not been adhered to. 345.Sh SEE ALSO 346.Xr ddb 4 , 347.Xr boot.config 5 , 348.Xr make.conf 5 , 349.Xr ttys 5 , 350.Xr boot0cfg 8 , 351.Xr bsdlabel 8 , 352.Xr btxld 8 , 353.Xr config 8 , 354.Xr gptboot 8 , 355.Xr halt 8 , 356.Xr loader 8 , 357.Xr nextboot 8 , 358.Xr reboot 8 , 359.Xr shutdown 8 360.Sh BUGS 361The bsdlabel format used by this version of 362.Bx 363is quite 364different from that of other architectures. 365.Pp 366Due to space constraints, the keyboard probe initiated by the 367.Fl P 368option is simply a test that the BIOS has detected an 369.Dq extended 370keyboard. 371If an 372.Dq XT/AT 373keyboard (with no F11 and F12 keys, etc.) is attached, the probe will 374fail. 375