.\"	$OpenBSD: boot.8,v 1.2 2023/03/14 06:55:31 jmc Exp $
.\"
.\" Copyright (c) 1997-2001 Michael Shalayeff
.\" All rights reserved.
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.\" modification, are permitted provided that the following conditions
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE AUTHOR OR HIS RELATIVES BE LIABLE FOR ANY DIRECT,
.\" INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
.\" SERVICES; LOSS OF MIND, USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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.\" IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
.\" THE POSSIBILITY OF SUCH DAMAGE.
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.Dd $Mdocdate: March 14 2023 $
.Dt BOOT 8 alpha
.Os
.Sh NAME
.Nm boot ,
.Nm boot.conf
.Nd alpha-specific bootstrap
.Sh DESCRIPTION
The main purpose of this program is to load the system kernel.
.Pp
As described in
.Xr boot_alpha 8 ,
this program is loaded by the SRM firmware
and provides a convenient way to load the kernel.
This program acts as an enhanced boot monitor for alpha systems, providing
a common interface for the kernel to start from.
.Pp
Basic operations include:
.Pp
.Bl -bullet -compact
.It
Loading kernels from hard disk.
.It
Loading kernels compressed by
.Xr gzip 1 .
.It
Providing an interactive command line.
.El
.Pp
The sequence of its operation is as follows: initialization,
parsing the configuration file, then an interactive command line.
While at the command line you have 5 seconds to type any commands, if needed.
If time expires, the kernel will be loaded according to
the current variable settings (see the
.Ic set
command).
Each time a kernel load fails, the timeout is increased by one second.
The sequence of
.Nm
operations is as follows:
.Bl -enum
.It
If the file
.Pa /etc/boot.conf
exists on the filesystem in slice
.Sq a
on the disk
.Nm
was loaded from, open and parse it.
Lines beginning with the
.Sq #
character,
as well as whitespace at the beginning of lines,
are ignored.
The file may contain any commands
.Nm
accepts at the interactive prompt.
Though default settings usually suffice, they can be changed here.
.It
The header line
.Pp
.Dl >> OpenBSD/alpha BOOT [x.xx]
.Pp
is displayed to the active console, where
.Ar x.xx
is the version number of the
.Nm
program, followed by the
.Pp
.Dl boot>
.Pp
prompt, which means you are in interactive mode and may enter commands.
If you do not,
.Nm
will proceed to load the kernel with the current parameters after the
timeout period has expired.
.El
.Pp
By default,
.Nm
attempts to load the kernel executable specified in the SRM environment
variable
.Em boot_file ,
defaulting to
.Pa /bsd
if not set.
If it fails to find the kernel and no alternative kernel image has
been specified, the system will be unable to boot.
.Sh COMMANDS
The following commands are accepted at the
.Nm
prompt:
.Bl -tag -width shorten
.It Ic boot Oo Ns Ar image Oc Op Fl cdns
Boots the specified kernel image with any options given.
If
.Ar image
is omitted, values from the
.Nm
variables will be used.
.Bl -tag -width _a_
.\" XXX Consider documenting -a as silently doing nothing, accepted for
.\" XXX compatibility purpose (since multiuser boot is the default).
.It Fl c
Causes the kernel to go into
.Xr boot_config 8
before performing
.Xr autoconf 4
procedures.
.It Fl d
Causes the kernel to drop into
.Xr ddb 4
at the earliest convenient point.
.It Fl n
Causes the kernel to ask for the
.Nm root
device to use.
.It Fl s
Causes the kernel to boot single-user.
.El
.It Ic echo Op Ar args
Displays
.Ar args
on the console device.
.It Ic help
Prints a list of available commands.
.It Ic hexdump Ar addr size
Show
.Ar size
bytes of memory at address
.Ar addr .
.It Ic ls Op Ar directory
Prints contents of the specified
.Ar directory
in long format including: attributes and file type, owner, group,
size, filename.
.It Ic reboot
Reboots the machine by initiating a warm boot procedure.
.It Ic set Op Ar varname Op Ar value
If invoked without arguments, prints a list of variables and their values.
If only
.Ar varname
is specified, displays contents of that variable.
If
.Ar varname
and
.Ar value
are both specified, sets that variable to the given value.
Variables include:
.Pp
.Bl -tag -compact -width boothow
.It Ic debug
Debug flag if
.Nm
was compiled with DEBUG defined.
.It Ic image
File name containing the kernel image.
.It Ic timeout
Number of seconds boot will wait for human intervention before
booting the default kernel image.
.\" .It Ic time
.\" Displays system time and date.
.El
.El
.Sh FILES
.Bl -tag -width /etc/boot.conf -compact
.It Pa /usr/mdec/boot
system bootstrap
.It Pa /etc/boot.conf
system bootstrap's startup file
.It Pa /bsd
kernel image
.It Pa /bsd.rd
kernel image for installation/recovery
.El
.Sh EXAMPLES
Boot the default kernel:
.Pp
.Dl boot> boot
.Pp
Remove the 5 second pause at boot-time permanently, causing
.Nm
to load the kernel immediately without prompting:
.Pp
.Dl # echo \&"boot\&" > /etc/boot.conf
.Pp
Boot the kernel named
.Pa /obsd
in
.Dq User Kernel Configuration
mode (see
.Xr boot_config 8 ) .
This mechanism allows for the explicit enabling and disabling of devices
during the current boot sequence, as well as the modification
of device parameters.
Once booted, such changes can be made permanent by using
.Xr config 8 Ns 's
.Fl e
option.
.Pp
.Dl boot> boot /obsd -c
.Sh SEE ALSO
.Xr gzip 1 ,
.Xr autoconf 4 ,
.Xr ddb 4 ,
.Xr boot_alpha 8 ,
.Xr boot_config 8 ,
.Xr fdisk 8 ,
.Xr reboot 8
.Sh HISTORY
This program was written by Michael Shalayeff for
.Ox 2.1
on the i386 platform, and was later ported to the alpha platform.