BOOT.CONFIG(5)            FreeBSD File Formats Manual           BOOT.CONFIG(5)

NAME

     boot.config - Configuration file for the legacy boot blocks

DESCRIPTION

     The boot.config file contains options for the FreeBSD boot block code.

     When the first- and second-stage FreeBSD boot loaders run, they search
     the "a" slice of the boot partition for a boot.config file (as a result,
     slices which are missing an "a" partition require user intervention
     during the boot process).  If the boot.config file is found, its contents
     are used as the default configuration options for the boot block code and
     are echoed to the system console.

     A valid format of this file is to put BIOS drive number, a controller
     type, a unit number, a partition, a kernel file name, and any other valid
     boot(8) option on a single line, as it is done at the "boot:" prompt.

     The options related to the boot image selection described below and all
     the other options available for boot.config are documented in detail in
     the boot(8) manual page.

FILES

     /boot.config  parameters for the boot blocks (optional)
     /boot/config  alternate location for boot config information

EXAMPLES

     The command:

           # echo "-P" > /boot.config

     will activate the serial console of FreeBSD if no keyboard is present,
     otherwise video console will be used.

     The command:

           # echo "1:ad(1,a)/boot/loader" > /boot.config

     will instruct the second stage of boot(8) on the first disk to boot with
     the third boot(8) stage from the second disk.

     The command:

           # echo "1:ad(1,a)/boot/loader -P" > /boot.config

     will do both of the above.

SEE ALSO

     boot(8), loader(8)

AUTHORS

     This manual page was written by Daniel Gerzo <danger@FreeBSD.org>.

FreeBSD 15.1-STABLE-HBSD       November 14, 2025                BOOT.CONFIG(5)