This will rebuild all of your devices, including any new ones needed for the new system. You should do this both to save disk space, and to be sure that you have a clean start for your next make world . Update your ports tree Chances are that if you were using 2.2.x your ports collection is out of date because of the many changes to the ports system between branches. This is a good time to update your ports to the new versions. The safest way to do this is to delete your current ports collection and start again from scratch.
Opinions differ on whether another make world is required after doing a make upgrade .
For instance, as of this writing perl is unable to manify its module documentation because one of the libraries it is linked against has not yet been installed at the time this process is run. In addition to the things listed above, there are many other changes from the 2.2.8 branch that you should be aware of. There are of course many other differences. You should take a look at the 3.0-Release notes for more details. Another handy change for DHCP users is the inclusion of dhclient in the base system.