# freebsd-update upgrade -r 9.1-RELEASE
Looking up update.FreeBSD.org mirrors... 3 mirrors found.
Fetching metadata signature for 9.0-RELEASE from update5.FreeBSD.org... done.
Fetching metadata index... done.
Inspecting system... done.
The following components of FreeBSD seem to be installed:
kernel/generic world/base
The following components of FreeBSD do not seem to be installed:
src/src world/doc world/games world/lib32
Does this look reasonable (y/n)? y
Fetching metadata signature for 9.1-RELEASE from update5.FreeBSD.org... done.
Fetching metadata index... done.
Fetching 1 metadata patches. done.
Applying metadata patches... done.
Fetching 1 metadata files... done.
Inspecting system... done.
Fetching files from 9.0-RELEASE for merging... done.
Preparing to download files... done.
Fetching 9409 patches.....10....20....30....40....50... ....9400.... done.
Applying patches...
...reboot...
[root@samba4] ~# freebsd-update install
Installing updates... done.
[root@samba4] ~# uname -a
FreeBSD samba4.lab.mundounix.com.br 9.1-RELEASE FreeBSD 9.1-RELEASE #0 r243825: Tue Dec 4 09:23:10 UTC 2012 root@farrell.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC amd64