run openvpn in client mode automatically after linux boot

Context: Remote raspberry pi model b rev1, all setup with raspberry os / raspbian.

the hardware specs are nothing much, but the machine is reliable, even when apparently half the ram chips are dead.

1. Install openvpn from the distro’s repository
2. Take the config file from the server you want to connect to - in my case an ovpn file generated by pivpn - and put it into the config folder /etc/openvpn/.
3. if your vpn profile is password protected, add a textfile with the cleartext pass and reference it in your vpn profile file like so:

   askpass /etc/openvpn/passwordfilename
   

4. make sure openvpn.service is started and enabled.

   systemctl enable openvpn && systemctl restart openvpn
   

ip a should show you the tunnel interface already.

NB: for the routing, make sure that your that your router has a static entry that sends all the traffic to the vpn subnet to the vpn server, but that is something that depends really on your own net topology.