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.
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35 .\" @(#)boot_i386.8 8.2 (Berkeley) 4/19/94
44 .Nd system bootstrapping procedures
46 .Sy Power fail and crash recovery .
47 Normally, the system will reboot itself at power-up or after crashes.
48 An automatic consistency check of the file systems will be performed,
49 and unless this fails, the system will resume multi-user operations.
52 Most i386 PCs attempt to boot first from floppy disk drive 0 (sometimes
53 known as drive A:) and, failing that, from hard disk drive 0 (sometimes
54 known as drive C:, or as drive 0x80 to the BIOS).
56 you to change this default sequence, and may also include a CD-ROM
57 drive as a boot device.
59 By default, a three-stage bootstrap is employed, and control is
60 automatically passed from the boot blocks (bootstrap stages one and
61 two) to a separate third-stage bootstrap program,
63 This third stage provides more sophisticated control over the booting
64 process than it is possible to achieve in the boot blocks, which are
65 constrained by occupying limited fixed space on a given disk or slice.
67 However, it is possible to dispense with the third stage altogether,
68 either by specifying a kernel name in the boot block parameter
73 is set, by hitting a key during a brief pause (while one of the characters
82 Booting will also be attempted at stage two, if the
83 third stage cannot be loaded.
85 Make note of the fact that
90 As a result, slices which are missing an
92 partition require user intervention during the boot process.
94 The remainder of this subsection deals only with the boot blocks.
97 program is documented separately.
99 After the boot blocks have been loaded,
100 you should see a prompt similar to the following:
103 Default: 0:ad(0,a)/boot/loader
107 The automatic boot will attempt to load
111 of either the floppy or the hard disk.
112 This boot may be aborted by typing any character on the keyboard
116 At this time, the following input will be accepted:
117 .Bl -tag -width indent
119 Give a short listing of the files in the root directory of the default
120 boot device, as a hint about available boot files.
123 may also be specified as the last segment of a path, in which case
124 the listing will be of the relevant subdirectory.)
128 .Ar bios_drive : interface ( unit , Oo Ar slice , Oc Ar part )
131 .Op Fl aCcDdghmnPprsv
136 Specify boot file and flags.
137 .Bl -tag -width indent
139 The drive number as recognized by the BIOS.
140 0 for the first drive, 1 for the second drive, etc.
142 The type of controller to boot from.
143 Note that the controller is required
144 to have BIOS support since the BIOS services are used to load the
147 The supported interfaces are:
149 .Bl -tag -width "adXX" -compact
151 ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike
154 5 1/4" or 3 1/2" High density floppies
156 SCSI disk on any supported SCSI controller
161 The unit number of the drive on the interface being used.
162 0 for the first drive, 1 for the second drive, etc.
163 .It Oo Ar slice , Oc Ns Ar part
164 The partition letter inside the
169 By convention, only partition
171 contains a bootable image.
172 If sliced disks are used
173 .Pq Dq fdisk partitions ,
176 (1 for the first slice, 2 for the second slice, etc.\&)
177 can be booted from, with the default (if not specified) being the active slice
178 or, otherwise, the first
183 is specified as 0, the first
187 slice) is booted from.
189 The pathname of the file to boot (relative to the root directory
190 on the specified partition).
192 .Pa /boot/kernel/kernel .
193 Symbolic links are not supported (hard links are).
194 .It Xo Op Fl aCcDdghmnPprsv
201 .Bl -tag -width "-CXX" -compact
203 during kernel initialization,
204 ask for the device to mount as the root file system.
206 try to mount root file system from a CD-ROM.
208 this flag is currently a no-op.
210 boot with the dual console configuration.
212 configuration, the console will be either the internal display
213 or the serial port, depending on the state of the
216 In the dual console configuration,
217 both the internal display and the serial port will become the console
218 at the same time, regardless of the state of the
222 enter the DDB kernel debugger
225 as early as possible in kernel initialization.
227 use the GDB remote debugging protocol.
229 force the serial console.
230 For instance, if you boot from the internal console,
233 option to force the kernel to use the serial port as its
235 The serial port driver
237 has a flag (0x20) to override this option.
238 If that flag is set, the serial port will always be used as the console,
241 option described here.
248 ignore key press to interrupt boot before
253 If no keyboard is found, the
257 options are automatically set.
259 pause after each attached device during the device probing phase.
261 use the statically configured default for the device containing the
265 Normally, the root file system is on the device
266 that the kernel was loaded from.
268 boot into single-user mode; if the console is marked as
272 the root password must be entered.
277 set the speed of the serial console to
279 The default is 9600 unless it has been overridden by setting
280 .Va BOOT_COMCONSOLE_SPEED
283 and recompiling the boot blocks.
285 be verbose during device probing (and later).
290 You may put a BIOS drive number, a controller type, a unit number,
291 a partition, a kernel file name, and any valid option in
294 Enter them in one line just as you type at the
298 .Bl -tag -width /boot/loader -compact
300 parameters for the boot blocks (optional)
302 first stage bootstrap file
304 second stage bootstrap file
306 third stage bootstrap
307 .It Pa /boot/kernel/kernel
309 .It Pa /boot/kernel.old/kernel
310 typical non-default kernel (optional)
313 When disk-related errors occur, these are reported by the second-stage
314 bootstrap using the same error codes returned by the BIOS, for example
315 .Dq Disk error 0x1 (lba=0x12345678) .
316 Here is a partial list of these error codes:
318 .Bl -tag -width "0x80" -compact
322 Address mark not found
328 DMA attempt across 64K boundary
332 Uncorrectable CRC/ECC error
342 On older machines, or otherwise where EDD support (disk packet
343 interface support) is not available, all boot-related files and
344 structures (including the kernel) that need to be accessed during the
345 boot phase must reside on the disk at or below cylinder 1023 (as the
346 BIOS understands the geometry).
349 is reported by the second-stage bootstrap, it generally means that this
350 requirement has not been adhered to.
365 format used by this version of
368 different from that of other architectures.
370 Due to space constraints, the keyboard probe initiated by the
372 option is simply a test that the BIOS has detected an
377 keyboard (with no F11 and F12 keys, etc.) is attached, the probe will