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
134 Specify boot file and flags.
135 .Bl -tag -width indent
137 The drive number as recognized by the BIOS.
138 0 for the first drive, 1 for the second drive, etc.
140 The type of controller to boot from.
141 Note that the controller is required
142 to have BIOS support since the BIOS services are used to load the
145 The supported interfaces are:
147 .Bl -tag -width "adXX" -compact
149 ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike
152 5 1/4" or 3 1/2" High density floppies
154 SCSI disk on any supported SCSI controller
159 The unit number of the drive on the interface being used.
160 0 for the first drive, 1 for the second drive, etc.
161 .It Oo Ar slice , Oc Ns Ar part
162 The partition letter inside the
167 By convention, only partition
169 contains a bootable image.
170 If sliced disks are used
171 .Pq Dq fdisk partitions ,
174 (1 for the first slice, 2 for the second slice, etc.\&)
175 can be booted from, with the default (if not specified) being the active slice
176 or, otherwise, the first
181 is specified as 0, the first
185 slice) is booted from.
187 The pathname of the file to boot (relative to the root directory
188 on the specified partition).
190 .Pa /boot/kernel/kernel .
191 Symbolic links are not supported (hard links are).
192 .It Xo Op Fl aCcDdghmnPpqrsv
197 .Bl -tag -width "-CXX" -compact
199 during kernel initialization,
200 ask for the device to mount as the root file system.
202 try to mount root file system from a CD-ROM.
204 this flag is currently a no-op.
206 boot with the dual console configuration.
208 configuration, the console will be either the internal display
209 or the serial port, depending on the state of the
212 In the dual console configuration,
213 both the internal display and the serial port will become the console
214 at the same time, regardless of the state of the
218 enter the DDB kernel debugger
221 as early as possible in kernel initialization.
223 use the GDB remote debugging protocol.
225 force the serial console.
226 For instance, if you boot from the internal console,
229 option to force the kernel to use the serial port as its
231 The serial port driver
233 has a flag (0x20) to override this option.
234 If that flag is set, the serial port will always be used as the console,
237 option described here.
242 mute the console to suppress all console input and output during the
245 ignore key press to interrupt boot before
250 If no keyboard is found, the
254 options are automatically set.
256 pause after each attached device during the device probing phase.
259 do not write anything to the console unless automatic boot fails or
261 This option only affects second-stage bootstrap,
262 to prevent next stages from writing to the console use in
267 use the statically configured default for the device containing the
271 Normally, the root file system is on the device
272 that the kernel was loaded from.
274 boot into single-user mode; if the console is marked as
278 the root password must be entered.
280 set the speed of the serial console to
282 The default is 9600 unless it has been overridden by setting
283 .Va BOOT_COMCONSOLE_SPEED
286 and recompiling and reinstalling the boot blocks.
288 be verbose during device probing (and later).
293 You may put a BIOS drive number, a controller type, a unit number,
294 a partition, a kernel file name, and any valid option in
297 Enter them in one line just as you type at the
301 .Bl -tag -width /boot/loader -compact
303 parameters for the boot blocks (optional)
305 first stage bootstrap file
307 second stage bootstrap file
309 third stage bootstrap
310 .It Pa /boot/kernel/kernel
312 .It Pa /boot/kernel.old/kernel
313 typical non-default kernel (optional)
316 When disk-related errors occur, these are reported by the second-stage
317 bootstrap using the same error codes returned by the BIOS, for example
318 .Dq Disk error 0x1 (lba=0x12345678) .
319 Here is a partial list of these error codes:
321 .Bl -tag -width "0x80" -compact
325 Address mark not found
331 DMA attempt across 64K boundary
335 Uncorrectable CRC/ECC error
345 On older machines, or otherwise where EDD support (disk packet
346 interface support) is not available, all boot-related files and
347 structures (including the kernel) that need to be accessed during the
348 boot phase must reside on the disk at or below cylinder 1023 (as the
349 BIOS understands the geometry).
352 is reported by the second-stage bootstrap, it generally means that this
353 requirement has not been adhered to.
370 format used by this version of
373 different from that of other architectures.
375 Due to space constraints, the keyboard probe initiated by the
377 option is simply a test that the BIOS has detected an
382 keyboard (with no F11 and F12 keys, etc.) is attached, the probe will