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 The remainder of this subsection deals only with the boot blocks.
88 program is documented separately.
90 After the boot blocks have been loaded,
91 you should see a prompt similar to the following:
94 Default: 0:ad(0,a)/boot/loader
98 The automatic boot will attempt to load
102 of either the floppy or the hard disk.
103 This boot may be aborted by typing any character on the keyboard
107 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.
114 may also be specified as the last segment of a path, in which case
115 the listing will be of the relevant subdirectory.)
118 .Ar bios_drive : interface ( unit , Oo Ar slice , Oc Ar part )
121 .Op Fl aCcDdghmnPprsv
124 Specify boot file and flags.
125 .Bl -tag -width indent
127 The drive number as recognized by the BIOS.
128 0 for the first drive, 1 for the second drive, etc.
130 The type of controller to boot from.
131 Note that the controller is required
132 to have BIOS support since the BIOS services are used to load the
135 The supported interfaces are:
137 .Bl -tag -width "adXX" -compact
139 ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike
142 5 1/4" or 3 1/2" High density floppies
144 SCSI disk on any supported SCSI controller
149 The unit number of the drive on the interface being used.
150 0 for the first drive, 1 for the second drive, etc.
151 .It Oo Ar slice , Oc Ns Ar part
152 The partition letter inside the
157 By convention, only partition
159 contains a bootable image.
160 If sliced disks are used
161 .Pq Dq fdisk partitions ,
164 (1 for the first slice, 2 for the second slice, etc.\&)
165 can be booted from, with the default (if not specified) being the active slice
166 or, otherwise, the first
171 is specified as 0, the first
175 slice) is booted from.
177 The pathname of the file to boot (relative to the root directory
178 on the specified partition).
180 .Pa /boot/kernel/kernel .
181 Symbolic links are not supported (hard links are).
182 .It Xo Op Fl aCcDdghmnPpqrsv
187 .Bl -tag -width "-CXX" -compact
189 during kernel initialization,
190 ask for the device to mount as the root file system.
192 try to mount root file system from a CD-ROM.
194 this flag is currently a no-op.
196 boot with the dual console configuration.
198 configuration, the console will be either the internal display
199 or the serial port, depending on the state of the
202 In the dual console configuration,
203 both the internal display and the serial port will become the console
204 at the same time, regardless of the state of the
208 enter the DDB kernel debugger
211 as early as possible in kernel initialization.
213 use the GDB remote debugging protocol.
215 force the serial console.
216 For instance, if you boot from the internal console,
219 option to force the kernel to use the serial port as its
221 The serial port driver
225 has a flag (0x20) to override this option.
226 If that flag is set, the serial port will always be used as the console,
229 option described here.
231 mute the console to suppress all console input and output during the
234 ignore key press to interrupt boot before
239 If no keyboard is found, the
243 options are automatically set.
245 pause after each attached device during the device probing phase.
248 do not write anything to the console unless automatic boot fails or
250 This option only affects second-stage bootstrap,
251 to prevent next stages from writing to the console use in
256 use the statically configured default for the device containing the
260 Normally, the root file system is on the device
261 that the kernel was loaded from.
263 boot into single-user mode; if the console is marked as
267 the root password must be entered.
269 set the speed of the serial console to
271 The default is 9600 unless it has been overridden by setting
272 .Va BOOT_COMCONSOLE_SPEED
275 and recompiling and reinstalling the boot blocks.
277 be verbose during device probing (and later).
284 file to set the default configuration options for the boot block code.
287 for more information about the
291 .Bl -tag -width /boot/loader -compact
293 parameters for the boot blocks (optional)
295 first stage bootstrap file
297 second stage bootstrap file
299 third stage bootstrap
300 .It Pa /boot/kernel/kernel
302 .It Pa /boot/kernel.old/kernel
303 typical non-default kernel (optional)
306 When disk-related errors occur, these are reported by the second-stage
307 bootstrap using the same error codes returned by the BIOS, for example
308 .Dq Disk error 0x1 (lba=0x12345678) .
309 Here is a partial list of these error codes:
311 .Bl -tag -width "0x80" -compact
315 Address mark not found
321 DMA attempt across 64K boundary
325 Uncorrectable CRC/ECC error
335 On older machines, or otherwise where EDD support (disk packet
336 interface support) is not available, all boot-related files and
337 structures (including the kernel) that need to be accessed during the
338 boot phase must reside on the disk at or below cylinder 1023 (as the
339 BIOS understands the geometry).
342 is reported by the second-stage bootstrap, it generally means that this
343 requirement has not been adhered to.
360 The bsdlabel format used by this version of
363 different from that of other architectures.
365 Due to space constraints, the keyboard probe initiated by the
367 option is simply a test that the BIOS has detected an
372 keyboard (with no F11 and F12 keys, etc.) is attached, the probe will