In my openvpn.conf:
...
askpass /etc/openvpn/jdoe.pass <<< new line here
ca /etc/openvpn/jdoe_ca.crt
cert /etc/openvpn/jdoe.crt
key /etc/openvpn/jdoe.key
...
The file /etc/openvpn/jdoe.pass just contains the password.
You can chmod this file to 600.
This method save my life… 😉
Ubuntu 12.04.4 LTS
OpenVPN 2.2.1 x86_64-linux-gnu [SSL] [LZO2] [EPOLL] [PKCS11] [eurephia] [MH] [PF_INET6] [IPv6 payload 20110424-2 (2.2RC2)] built on Mar 13 2014