mkdir /dev/net
mknod /dev/net/tun c 10 200

Follow tutorial at https://openvpn.net/index.php/open-source/documentation/howto.html#pki

apt-get install openvpn

In server.conf plugin path for user/pass authentication:

plugin /usr/lib/openvpn/openvpn-auth-pam.so system-auth

For Jessie (Debian 8):

plugin /usr/lib/openvpn/openvpn-plugin-auth-pam.so system-auth

In case of error:

Mon Dec 18 14:48:14 2017 srv02/xxx.xxx.x.x:39658 Authenticate/Decrypt packet error: cipher final failed

make sure the ciphers are same in server.conf and client.conf.

For unprivileged container inside Proxmox for mknod to work add this to /etc/pve/lxc/lxc.conf:

lxc.mount.entry = /dev/net dev/net none bind,create=dir

Also check owner of files on host vs container.

• https://wiki.archlinux.org/index.php/OpenVPN_(server)_in_Linux_containers
• https://robert.penz.name/1498/tips-solutions-for-settings-up-openvpn-on-debian-9-within-proxmox-lcx-containers/