1 .\" Copyright (c) 1991, 1993
2 .\" The Regents of the University of California. All rights reserved.
4 .\" This code is derived from software written and contributed
5 .\" to Berkeley by William Jolitz.
7 .\" Almost completely rewritten for FreeBSD 2.1 by Joerg Wunsch.
9 .\" Substantially revised for FreeBSD 3.1 by Robert Nordier.
11 .\" Redistribution and use in source and binary forms, with or without
12 .\" modification, are permitted provided that the following conditions
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19 .\" 3. All advertising materials mentioning features or use of this software
20 .\" must display the following acknowledgement:
21 .\" This product includes software developed by the University of
22 .\" California, Berkeley and its contributors.
23 .\" 4. Neither the name of the University nor the names of its contributors
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27 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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29 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
30 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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33 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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39 .\" @(#)boot_i386.8 8.2 (Berkeley) 4/19/94
48 .Nd system bootstrapping procedures
50 .Sy Power fail and crash recovery .
51 Normally, the system will reboot itself at power-up or after crashes.
52 An automatic consistency check of the file systems will be performed,
53 and unless this fails, the system will resume multi-user operations.
56 Most i386 PCs attempt to boot first from floppy disk drive 0 (sometimes
57 known as drive A:) and, failing that, from hard disk drive 0 (sometimes
58 known as drive C:, or as drive 0x80 to the BIOS). Some BIOSes allow
59 you to change this default sequence, and may also include a CD-ROM
60 drive as a boot device.
62 By default, a three-stage bootstrap is employed, and control is
63 automatically passed from the boot blocks (bootstrap stages one and
64 two) to a separate third-stage bootstrap program,
66 This third stage provides more sophisticated control over the booting
67 process than it is possible to achieve in the boot blocks, which are
68 constrained by occupying limited fixed space on a given disk or slice.
70 However, it is possible to dispense with the third stage altogether,
71 either by specifying a kernel name in the boot block parameter
76 is set, by hitting a key during a brief pause (while one of the characters
84 is invoked. Booting will also be attempted at stage two, if the
85 third stage cannot be loaded.
87 The remainder of this subsection deals only with the boot blocks. The
89 program is documented separately.
91 After the boot blocks have been loaded,
92 you should see a prompt similar to the following:
95 Default: 0:ad(0,a)/kernel
99 The automatic boot will attempt to load
103 of either the floppy or the hard disk.
104 This boot may be aborted by typing any character on the keyboard
107 prompt. At this time, the following input will be accepted:
108 .Bl -tag -width indent
110 Give a short listing of the files in the root directory of the default
111 boot device, as a hint about available boot files. (A
113 may also be specified as the last segment of a path, in which case
114 the listing will be of the relevant subdirectory.)
118 .Ar bios_drive : interface ( unit , Oo Ar slice , Oc Ar part )
121 .Op Fl aCcDdghmnPprsv
123 Specify boot file and flags.
124 .Bl -tag -width indent
126 The drive number as recognized by the BIOS.
127 0 for the first drive, 1 for the second drive, etc.
129 The type of controller to boot from. Note that the controller is required
130 to have BIOS support since the BIOS services are used to load the
133 The supported interfaces are:
135 .Bl -tag -width "adXX" -compact
137 ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike
140 5 1/4" or 3 1/2" High density floppies
142 SCSI disk on any supported SCSI controller
147 The unit number of the drive on the interface being used.
148 0 for the first drive, 1 for the second drive, etc.
149 .It Oo Ar slice , Oc Ns Ar part
150 The partition letter inside the
152 portion of the disk. See
154 By convention, only partition
156 contains a bootable image. If sliced disks are used
157 .Pq Dq fdisk partitions ,
160 (1 for the first slice, 2 for the second slice, etc.\&)
161 can be booted from, with the default (if not specified) being the active slice
162 or, otherwise, the first
167 is specified as 0, the first
171 slice) is booted from.
173 The pathname of the file to boot (relative to the root directory
174 on the specified partition). Defaults to
176 Symbolic links are not supported (hard links are).
177 .It Fl aCcDdghmnPprsv
180 .Bl -tag -width "-CXX" -compact
182 during kernel initialization,
183 ask for the device to mount as the root file system.
187 run UserConfig to modify hardware parameters for the loaded
188 kernel. If the kernel was built with one of
189 .Dv USERCONFIG , INTRO_USERCONFIG , VISUAL_USERCONFIG
191 remain in UserConfig regardless of any
193 commands present in the script.
195 toggle single and dual console configurations. In the single
196 configuration the console will be either the internal display
197 or the serial port, depending on the state of the
199 option below. In the dual console configuration,
200 both the internal display and the serial port will become the console
201 at the same time, regardless of the state of the
203 option. However, the dual console configuration takes effect only during
204 the boot prompt. Once the kernel is loaded, the console specified
207 option becomes the only console.
209 enter the DDB kernel debugger
212 as early as possible in kernel initialization.
214 use the GDB remote debugging protocol.
216 toggle internal and serial consoles. You can use this to switch
217 console devices. For instance, if you boot from the internal console,
220 option to force the kernel to use the serial port as its
221 console device. Alternatively, if you boot from the serial port,
222 you can use this option to force the kernel to use the internal display
223 as the console instead.
224 The serial port driver
226 has a flag to override this option.
227 If that flag is set, the serial port will always be used as the console,
230 option described here. See the man page for
236 ignore key press to interrupt boot before
240 probe the keyboard. If no keyboard is found, the
244 options are automatically set.
246 pause after each attached device during the device probing phase.
248 use the statically configured default for the device containing the
252 Normally, the root file system is on the device
253 that the kernel was loaded from.
255 boot into single-user mode; if the console is marked as
259 the root password must be entered.
261 be verbose during device probing (and later).
266 You may put a BIOS drive number, a controller type, a unit number,
267 a partition, a kernel file name, and any valid option in
269 to set defaults. Enter them in one line just as you type at the
273 .Bl -tag -width /boot/loader -compact
275 parameters for the boot blocks (optional)
277 first stage bootstrap file
279 second stage bootstrap file
281 third stage bootstrap
285 typical non-default kernel (optional)
299 When disk-related errors occur, these are reported by the second-stage
300 bootstrap using the same error codes returned by the BIOS, for example
301 .Dq Disk error 0x1 (lba=0x12345678) .
302 Here is a partial list of these error codes:
304 .Bl -tag -width "0x80" -compact
308 Address mark not found
314 DMA attempt across 64K boundary
318 Uncorrectable CRC/ECC error
328 On older machines, or otherwise where EDD support (disk packet
329 interface support) is not available, all boot-related files and
330 structures (including the kernel) that need to be accessed during the
331 boot phase must reside on the disk at or below cylinder 1023 (as the
332 BIOS understands the geometry). When a
334 is reported by the second-stage bootstrap, it generally means that this
335 requirement has not been adhered to.
339 format used by this version of
342 different from that of other architectures.
344 Due to space constraints, the keyboard probe initiated by the
346 option is simply a test that the BIOS has detected an
350 keyboard (with no F11 and F12 keys, etc.) is attached, the probe will