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

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

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

     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, it is
     deleted 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

     -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.

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

     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

     boot(8), loader(8)

     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.

     This manual page was written by Gordon Tetlow <[email protected]>.

     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.

     loader(8) is only able to read ZFS, not write to it.  nextboot.conf will
     NOT be reset in case of a kernel boot failure.

FreeBSD 11.1-RELEASE-p4          April 9, 2016         FreeBSD 11.1-RELEASE-p4
Command Section