Good Afternoon. I have a working freeradius 2.1.1 server installed in Debian 5.0 and IO would like to migrate it to a fereradius 3.0.11 installed on Ubuntu Server 14.04 LTS. My question would be , Does it work simply migrating the config files ?.
No, although the basic structure of the configuration files are the same, the places the modules look for data within the files have changed.
In most instances you cannot simply copy the configuration files from one version to another.
See 2.2.x->v3.0.x upgrade guide for more details about specific modules.