The main purpose of this program is to load the system kernel.
As described in 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.
Basic operations include:
- Loading kernels from hard disk.
- Loading kernels compressed by gzip(1).
- Providing an interactive command line.
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
set command). Each time a kernel
load fails, the timeout is increased by one second. The sequence of
boot operations is as follows:
- If the file /etc/boot.conf exists on the
filesystem in slice ‘a’ on the disk
bootwas loaded from, open and parse it. Lines beginning with the ‘#’ character, as well as whitespace at the beginning of lines, are ignored. The file may contain any commands
bootaccepts at the interactive prompt. Though default settings usually suffice, they can be changed here.
- The header line
>> OpenBSD/alpha BOOT [x.xx]
is displayed to the active console, where x.xx is the version number of the
bootprogram, followed by the
prompt, which means you are in interactive mode and may enter commands. If you do not,
bootwill proceed to load the kernel with the current parameters after the timeout period has expired.
to load the kernel executable specified in the SRM environment variable
defaulting to /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.
The following commands are accepted at the
- Boots the specified kernel image with any options given. If
image is omitted, values from the
bootvariables will be used.
- Causes the kernel to go into boot_config(8) before performing autoconf(4) procedures.
- Causes the kernel to drop into ddb(4) at the earliest convenient point.
- Causes the kernel to ask for the
rootdevice to use.
- Causes the kernel to boot single-user.
- Displays args on the console device.
- Prints a list of available commands.
- Show size bytes of memory at address addr.
- Prints contents of the specified directory in long format including: attributes and file type, owner, group, size, filename.
- Reboots the machine by initiating a warm boot procedure.
- If invoked without arguments, prints a list of variables and their values.
If only varname is specified, displays contents of
that variable. If varname and
value are both specified, sets that variable to the
given value. Variables include:
- Debug flag if
bootwas compiled with DEBUG defined.
- File name containing the kernel image.
- Number of seconds boot will wait for human intervention before booting the default kernel image.
- system bootstrap
- system bootstrap's startup file
- kernel image
- kernel image for installation/recovery
Boot the default kernel:
Remove the 5 second pause at boot-time permanently, causing
boot to load the kernel immediately without
# echo "boot" > /etc/boot.conf
Boot the kernel named /obsd in
“User Kernel Configuration” mode (see
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 config(8)'s
boot> boot /obsd -c
gzip(1), autoconf(4), ddb(4), boot_alpha(8), boot_config(8), fdisk(8), reboot(8)
This program was written by Michael Shalayeff for OpenBSD 2.1 on the i386 platform, and was later ported to the alpha platform.