freebsd/sbin/reboot/boot_i386.8

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.\" Almost completely rewritten for FreeBSD 2.1 by Joerg Wunsch.
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.\"     @(#)boot_i386.8	8.2 (Berkeley) 4/19/94
.\"
.\" $Id: boot_i386.8,v 1.3 1995/10/07 12:05:00 joerg Exp $
.\"
.Dd April 19, 1994
.Dt BOOT 8 i386
.Os
.Sh NAME
.Nm boot
.Nd
system bootstrapping procedures
.Sh DESCRIPTION
.Sy Power fail and crash recovery.
Normally, the system will reboot itself at power-up or after crashes.
An automatic consistency check of the file systems will be performed,
and unless this fails, the system will resume multi-user operations.
.Pp
.Sy Cold starts.
Most 386
.Tn "PC AT"
clones attempt to boot the floppy disk drive 0 (otherwise known as
drive A:) first, and failing that, attempt to boot the hard disk
controller 1, drive 0 (otherwise known as drive C:, or drive 0x80 in
the BIOS).  The automatic boot will attempt to load
.Pa /kernel
from partition
.Ql a
of either the floppy or the hard disk.
This boot may be aborted by typing any character on the keyboard
at the
.Ql Boot:
prompt.  At this time, the following input will be accepted:
.Bl -tag -offset indent -width 10x
.It \&?
Give a short listing of the files in the root directory of the default
boot device, as a hint about available boot files.
.It Op ctrlr(unit,part) Op /filename Op Fl abcCdhrsv
Specify boot file and flags.
.Bl -tag -offset indent -width 10x -compact
.It ctrlr
The controller to boot from.  Note that the controller is required
to have BIOS support since the BIOS services are used to load the
boot file image.
.Pp
Common controller names are:
.Bl -tag -offset indent -width "wdXX" -compact
.It wd
ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike
controller
.It fd
5 1/4" or 3 1/2" High density floppies
.It sd
SCSI disk on any supported SCSI controller
.It cd
boot from CDROM
.It hd
Pseudo-controller, must be used to specify that unit number
1 (known to the BIOS as drive 0x81) is on a different controller
than unit number 0.  This can happen for the wd vs. sd case.
.El
.It unit
The unit number of the drive on the controller being used.  Either 0
or 1 for the wd and fd and most sd controllers, between 0 and 6 for
some newer sd controllers.
.It part
The partition letter inside the BSD portion of the disk.  See
.Xr disklabel 8  .
By convention, only partition
.Ql a
contains a bootable image.  If sliced disks are used
.Pq Dq fdisk partitions ,
only the first BSD slice can be used to boot from.  The partition
letter does always refer to this slice then.
.It /filename
The pathname of the file to boot; must be inside the root directory
of the specified partition.  Defaults to
.Pa /kernel .
Symbolic links are not supported (hard links are).
.It Fl abcCdhrsv
Boot flags:
.Bl -tag -offset indent -width "-CXX" -compact
.It Fl a
ask for the device to install as root file system during kernel
initialization
.It Fl b
do not automatically reboot after shutdown or crash
.It Fl c
run UserConfig to modify hardware parameters for the loaded
kernel
.It Fl C
boot from CDROM
.It Fl d
enter the DDB kernel debugger
.Pq see Xr ddb 4
before configuring any device (except the system's console)
.It Fl h
toggle serial/graphics console
.It Fl r
do not establish the root directory of the file system
hierarchy on the device where the boot file is being loaded
from
.It Fl s
boot into single-user mode; if the console is marked as
.Dq insecure
.Pq see Xr ttys 5 ,
the root password must be entered
.It Fl v
be verbose during device probing
.El
.El
.El
.Sh FILES
.Bl -tag -width /kernelxx -compact
.It Pa /kernel
system code
.\" .It Pa /boot
.\" system bootstrap
.El
.Sh SEE ALSO
.Xr ddb 4 ,
.Xr ttys 5 ,
.Xr halt 8 ,
.Xr reboot 8 ,
.Xr shutdown 8 ,
.Xr disklabel 8 .
.Sh BUGS
The disklabel format used by this version of
.Bx
is quite
different from that of other architectures.
.Pp
The boot flags are not very self-explanatory, and the alphabet has
too few characters to implement every potentially useful boot option.