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BOOT.CFG(5) File Formats Manual BOOT.CFG(5)
NAME
boot.cfg - configuration file for /boot
DESCRIPTION
The file /boot.cfg is used to alter the behaviour of the standard boot
loader described in boot(8). Configuration changes include setting the
timeout, choosing a console device, altering the banner text and
displaying a menu allowing boot commands to be easily chosen. If a
boot.cfg file is not present, the system will boot as normal.
FILE FORMAT
The format of the file is a series of lines containing keyword/value
pairs separated by an equals sign (`='). There should be no whitespace
surrounding the equals sign. Lines beginning with a hash (`#') are
comments and will be ignored.
The "banner", "load", "menu", and "userconf" keywords can be present
multiple times in the file to define additional items. See the
description for each keyword for guidance and limitations on using
multiple entries.
banner The text from banner lines is displayed instead of the standard
welcome text by the boot loader. Up to 12 lines can be defined.
No special character sequences are recognised, so to specify a
blank line, a banner line with no value should be given.
clear If nonzero, clear the screen before printing the banner. If
zero, do not clear the screen (the default).
consdev Changes the console device to that specified in the value.
Valid values are any of those that could be specified at the
normal boot prompt with the consdev command.
default Used to specify the default menu item which will be chosen in
the case of Return being pressed or the timeout timer reaching
zero. The value is the number of the menu item as displayed.
As described above, the menu items are counted from 1 in the
order listed in boot.cfg. If not specified, the default value
will be option 1, i.e. the first item.
format Changes how the menu options are displayed. Should be set to
one of `a' for automatic, `l' for letters and `n' for numbers.
If set to automatic (the default), menu options will be
displayed numerically unless there are more than 9 options and
the timeout is greater than zero. If there are more than 9
options with a timeout greater than zero and the format is set
to number, only the first 9 options will be available.
load Used to load kernel modules, which will be passed on to the
kernel for initialization during early boot. The argument is
either the complete path and file name of the module to be
loaded, or a symbolic module name. When the argument is not an
absolute path, the boot loader will first attempt to load
/stand/<machine>/<kernel_version>/modules/<name>/<name>.kmod.
If that file does not exist, it will then attempt to load
/<name>. May be used as many times as needed.
menu Used to define a menu item to be displayed to the end-user at
boot time which allows a series of boot commands to be run
without further typing. The value consists of the required menu
text, followed by a colon (`:') and then the desired command(s).
Multiple commands can be specified separated by a semi-colon.
If the specified menu text is empty (the colon appears
immediately after the equals sign), then the displayed menu text
is the same as the command. For example:
menu=Boot normally:boot
menu=Boot single-user:boot -s
menu=Boot with module foo:load /foo.kmod;boot
menu=Boot with serial console:consdev com0;boot
menu=:boot hd1a:netbsd -as
Each menu item will be prefixed by an ascending number when
displayed, i.e. the order in the boot.cfg file is important.
Each command is executed just as though the user had typed it in
and so can be any valid command that would be accepted at the
normal boot prompt. In addition, "prompt" can be used to drop
to the normal boot prompt.
rndseed Takes the path to a random-seed file as written by the -S flag
to rndctl(8) as an argument. This file is used to seed the
kernel entropy pool rnd(9) very early in kernel startup, so that
high quality randomness is available to all kernel modules.
This argument should be supplied before any "load" commands that
may load executable modules.
timeout If the value is greater than zero, this specifies the time in
seconds that the boot loader will wait for the end-user to
choose a menu item. During the countdown period, they may press
Return to choose the default option or press a number key
corresponding to a menu option. If any other key is pressed,
the countdown will stop and the user will be prompted to choose
a menu option with no further time limit. If the timeout value
is set to zero, the default option will be booted immediately.
If the timeout value is negative or is not a number, there will
be no time limit for the user to choose an option.
userconf
Passes a userconf(4) command to the kernel at boot time. May be
used as many times as needed.
EXAMPLES
Here is an example boot.cfg file:
banner=Welcome to NetBSD
banner==================
banner=
banner=Please choose an option from the following menu:
menu=Boot normally:boot
menu=Boot single-user:boot -s
menu=Boot from second disk:boot hd1a:
menu=Boot with module foo:load /foo.kmod;boot
menu=Boot with modules foo and bar:load /foo.kmod;load /bar.kmod;boot
menu=Boot Xen with 256MB for dom0:load /netbsd-XEN3_DOM0 console=pc;multiboot /usr/pkg/xen3-kernel/xen.gz dom0_mem=256M
menu=Boot Xen with 256MB for dom0 (serial):load /netbsd-XEN3_DOM0 console=com0;multiboot /usr/pkg/xen3-kernel/xen.gz dom0_mem=256M console=com1 com1=115200,8n1
menu=Boot Xen with dom0 in single-user mode:load /netbsd-XEN3_DOM0 -s;multiboot /usr/pkg/xen3-kernel/xen.gz dom0_mem=256M
menu=Go to command line (advanced users only):prompt
clear=1
timeout=-1
default=1
# Disable Direct Rendering Manager (DRM) drivers
userconf=disable i915drmkms*
userconf=disable nouveau*
userconf=disable radeon*
# Always load ramdisk module
load=/miniroot.kmod
N.B. Xen counts serial ports from com1 upwards, but NetBSD counts from
com0, so the appropriate device name must be used. Please see the Xen
with serial console example above.
This will clear the screen and display:
Welcome to NetBSD
=================
Please choose an option from the following menu:
1. Boot normally
2. Boot single-user
3. Boot from second disk
4. Boot with module foo
5. Boot with modules foo and bar
6. Boot Xen with 256 MB for dom0
7. Boot Xen with 256 MB for dom0 (serial)
8. Boot Xen with dom0 in single-user mode
9. Go to command line (advanced users only)
Option [1]:
It will then wait for the user to type 1, 2, 3, 4, 5, 6, 7, 8 or 9
followed by Return. Pressing Return by itself will run option 1. There
will be no timeout.
SEE ALSO
boot(8), boothowto(9)
HISTORY
The boot.cfg file appeared in NetBSD 5.0.
AUTHORS
The boot.cfg extensions to boot(8) were written by Stephen Borrill
<sborrill@NetBSD.org>.
BUGS
Support for boot.cfg is currently for NetBSD/i386 and NetBSD/amd64 only.
It is hoped that its use will be extended to other appropriate ports that
use the boot(8) interface.
NetBSD 10.99 November 24, 2020 NetBSD 10.99