NEXTBOOT(8)             FreeBSD System Manager's Manual            NEXTBOOT(8)

NAME

     nextboot - specify an alternate kernel and boot flags for the next reboot

SYNOPSIS

     nextboot [-aDf] [-e variable=value] [-k kernel] [-o options]
     nextboot -D

DESCRIPTION

     The nextboot utility allows specifying some combination of an alternate
     kernel, boot flags, and kernel environment for the next time the machine
     is booted.  Once the loader(8) loads in the new kernel information from
     the /boot/nextboot.conf file, it is disabled so in case the new kernel
     hangs the machine, once it is rebooted, the machine will automatically
     revert to its previous configuration.

     The options are as follows:

     -a            This option causes nextboot to append to an existing
                   configuration in /boot/nextboot.conf.  By default any
                   existing configuration is overwritten.

     -D            Invoking nextboot with this option removes an existing
                   nextboot configuration.

     -e variable=value
                   This option adds the provided variable and value to the
                   kernel environment.  The value is quoted when written to
                   the nextboot configuration.

     -f            This option disables the sanity checking which checks if
                   the kernel really exists before writing the nextboot
                   configuration.

     -k kernel     This option specifies a kernel directory relative to /boot
                   to load the kernel and any modules from.

     -o options    This option allows the passing of kernel flags for the next
                   boot.

FILES

     /boot/nextboot.conf  The configuration file that the nextboot
                          configuration is written into.

EXAMPLES

     To boot the GENERIC kernel with the nextboot command:

           nextboot -k GENERIC

     To enable into single user mode with the normal kernel:

           nextboot -o "-s" -k kernel

     To remove an existing nextboot configuration:

           nextboot -D

SEE ALSO

     boot(8), freebsd-update(8), loader(8)

HISTORY

     The original nextboot manual page first appeared in FreeBSD 2.2.  It used
     a very different interface to achieve similar results.

     The current incarnation of nextboot appeared in FreeBSD 5.0.

AUTHORS

     This manual page was written by Gordon Tetlow <gordon@FreeBSD.org>.

BUGS

     The nextboot code is implemented in the loader(8).  It is not the most
     thoroughly tested code.  It is also my first attempt to write in Forth.

     Finally, it does some evil things like writing to the file system before
     it has been checked.  If it scrambles your file system, do not blame me.

FreeBSD 15.1-STABLE-HBSD       December 8, 2025                    NEXTBOOT(8)