I have been upgrading a few servers (Ubuntu 12.04.1 LTS) today and it turned out something broke openvpn.
tun0 interface has disappeared each time.
Since security upgrades are down unattended, it must come from a regular upgrade.
- How can I restore the interface so that OpenVPN works again?
apt-get remove openvpn; apt-get install openvpn but it did not bring back