These instructions work for both the full install on Linux and the ZEN virtual appliance.
If you installed PacketFence by following our guides, a simple yum update will not show you newer PacketFence versions as the PacketFence repository is disabled by default.
As always, before you upgrade, read the UPGRADE document. Latest version is available here: https://github.com/inverse-inc/packetfence/blob/stable/UPGRADE.asciidoc
To update the whole OS and PacketFence and its external dependencies on RHEL, do:
yum update --enablerepo=PacketFence
On Ubuntu/Debian, do:
apt-get install packetfence