I discovered that the VPN I use to manage one of my Digital Ocean VPS was down. Upon investigation, I found that the service was down and could not start:
root@server:~# service openvpn status [FAIL] VPN 'server' is not running ... failed! root@server:~# service openvpn start [....] Starting virtual private network daemon: serverSIOCSIFADDR: No such device : ERROR while getting interface flags: No such device SIOCSIFDSTADDR: No such device : ERROR while getting interface flags: No such device SIOCSIFMTU: No such device failed!
After quite some research helped by comments on this blog, I understood that it was due to an outdated kernel. To update the kernel, I had to power off the VPS:
root@server:~# poweroff
After that, using Digital Ocean control panel, I changed the kernel to the latest compatible in the Settings tab of the VPS.
For me it was Debian 7.0 x64 vmlinuz-3.2.0-4-amd64 (3.2.65-1+deb7u2).
Change the kernel to the latest compatible, ignore the default value!
Upon restart, OpenVPN service was running!
root@martin-denizet:~# service openvpn status [ ok ] VPN 'server' is running.