make buildworld && make buildkernel

http://d.hatena.ne.jp/taizooo/searchdiary?word=buildworld

http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/makeworld.html

To update your system, you should check /usr/src/UPDATING for any pre-buildworld steps necessary for your version of the sources and then use the following procedure:

# make buildworld
# make buildkernel
# make installkernel
# reboot

Note: There are a few rare cases when an extra run of mergemaster -p is needed before the buildworld step. These are described in UPDATING. In general, though, you can safely omit this step if you are not updating across one or more major FreeBSD versions.

After installkernel finishes successfully, you should boot in single user mode (i.e. using boot -s from the loader prompt). Then run:

# mergemaster -p
# make installworld
# mergemaster
# reboot

Read Further Explanations: The sequence described above is only a short resume to help you getting started. You should however read the following sections to clearly understand each step, especially if you want to use a custom kernel configuration.