openarena-server +set fs_game baseoa +set dedicated 1 +set net_port 27960
Something like this should work:
openarena-server +set fs_game baseoa +set dedicated 1 +set net_port 27960 +map aggressor
In most cases even should be enough to get started:
openarena-server +map aggressor
the "map" command is the only mandatory one to start a server (although it may be located in a exec command instead)