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

     reboot, halt, fastboot, fasthalt - stopping and restarting the system

     halt [-lNnpq] [-k kernel]
     reboot [-dlNnpqr] [-k kernel]
     fasthalt [-lNnpq] [-k kernel]
     fastboot [-dlNnpq] [-k kernel]

     The halt and reboot utilities flush the file system cache to disk, send
     all running processes a SIGTERM (and subsequently a SIGKILL) and,
     respectively, halt or restart the system.  The action is logged,
     including entering a shutdown record into the user accounting database.

     The options are as follows:

     -d      The system is requested to create a crash dump.  This option is
             supported only when rebooting, and it has no effect unless a dump
             device has previously been specified with dumpon(8).

     -k kernel
             Boot the specified kernel on the next system boot.  If the kernel
             boots successfully, the default kernel will be booted on
             successive boots, this is a one-shot option.  If the boot fails,
             the system will continue attempting to boot kernel until the boot
             process is interrupted and a valid kernel booted.  This may
             change in the future.

     -l      The halt or reboot is not logged to the system log.  This option
             is intended for applications such as shutdown(8), that call
             reboot or halt and log this themselves.

     -N      The file system cache is not flushed during the initial process
             clean-up, however the kernel level reboot(2) is still processed
             with a sync.  This option can be useful for performing a
             ``best-effort'' reboot when devices might be unavailable.  This
             can happen when devices have been disconnected, such as with

     -n      The file system cache is not flushed.  This option should
             probably not be used.

     -p      The system will turn off the power if it can.  If the power down
             action fails, the system will halt or reboot normally, depending
             on whether halt or reboot was called.

     -q      The system is halted or restarted quickly and ungracefully, and
             only the flushing of the file system cache is performed (if the
             -n option is not specified).  This option should probably not be

     -r      The system kills all processes, unmounts all filesystems, mounts
             the new root filesystem, and begins the usual startup sequence.
             After changing vfs.root.mountfrom with kenv(1), reboot -r can be
             used to change the root filesystem while preserving kernel state.

     The fasthalt and fastboot utilities are nothing more than aliases for the
     halt and reboot utilities.

     Normally, the shutdown(8) utility is used when the system needs to be
     halted or restarted, giving users advance warning of their impending doom
     and cleanly terminating specific programs.

     Replace current root filesystem with UFS mounted from /dev/ada0s1a:

           kenv vfs.root.mountfrom=ufs:/dev/ada0s1a
           reboot -r

     This mechanism can also be used with NFS, with a caveat that it only
     works with NFSv4, and requires a numeric IPv4 address:

           kenv vfs.root.mountfrom=nfs:
           reboot -r

     kenv(1), getutxent(3), boot(8), dumpon(8), nextboot(8), savecore(8),
     shutdown(8), sync(8)

     A reboot utility appeared in Version 6 AT&T UNIX.

FreeBSD 11.1-RELEASE-p4         March 19, 2017         FreeBSD 11.1-RELEASE-p4
Command Section