OpenVPN in LXC

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This guide explains the process of setting up an OpenVPN container on an unprivileged Debian container with LXC.

All the commands assume a default PVE installation from the official installer.

If your storage is called differently, please adapt the commands accordingly. (e.g., replace 'local' with the name of your storage for holding the templates)

Creating the Container

Firstly you need to download the Debian container template.

 # pveam update
 # pveam available | grep debian-10-standard
 system          debian-10-standard_10.7-1_amd64.tar.gz
 # pveam download local debian-10-standard_10.7-1_amd64.tar.gz

After the download is finished, create the container:

 #  pct create 123 local:vztmpl/debian-10-standard_10.7-1_amd64.tar.gz --unprivileged 1 -features nesting=1 --net0 name=eth0,bridge=vmbr0,firewall=1,ip=dhcp,type=veth --storage local-lvm

After container is created, you need to edit the configuration file to add the /dev/net/tun device.

 # pct config 123
 arch: amd64
 hostname: CT123
 memory: 512
 net0: name=eth0,bridge=vmbr0,firewall=1,hwaddr=FE:75:64:2A:A3:58,ip=dhcp,type=veth
 ostype: debian
 rootfs: local-lvm:vm-123-disk-0,size=4G
 features: nesting=1
 swap: 512
 unprivileged: 1
 # nano /etc/pve/lxc/123.conf

Add the following lines at the end (if you're using PVE < 7.0, change `cgroup2` with `cgroup`)

 lxc.cgroup2.devices.allow: c 10:200 rwm
 lxc.mount.entry: /dev/net dev/net none bind,create=dir

Press Ctrl-X and answer "Y" for saving and press Enter.

For your unprivileged container to be able to access the /dev/net/tun from your host, you need to set the owner by running:

 # chown 100000:100000 /dev/net/tun

Check the permissions are set correctly:

 # ls -l /dev/net/tun
 crw-rw-rw- 1 100000 100000 10, 200 Dec 22 13:26 /dev/net/tun

Finally start the container:

 # pct start 123

If you did everything correctly then the container should start.

Using OpenVPN

Enter the container:

 # pct enter 123

You should now see the container shell prompt.

 root@CT123:~# ls -l /dev/net/tun
 crw-rw-rw- 1 root root 10, 200 Dec 22 12:26 /dev/net/tun

If you see root:root inside the container and 100000:100000 outside the container, it's correct. (This is because the unprivileged userid 100000 on your host is mapped to 'root' user of the container)

Update packages and install openvpn:

 root@CT123:~# apt update
 root@CT123:~# apt dist-upgrade
 root@CT123:~# apt install openvpn git

You can use this repository for a basic configuration: https://github.com/Nyr/openvpn-install

 root@CT123:~# git clone https://github.com/Nyr/openvpn-install
 root@CT123:~# cd openvpn-install
 root@CT123:~# bash openvpn-install.sh

Answer the setup wizard questions according to your setup. At the end you should receive a message like this:

 Finished!
 The client configuration is available in: /root/client.ovpn
 New clients can be added by running this script again.

If everything worked, then the service should be started and enabled by the setup script.

Verify service is working:

 root@CT123:~# systemctl | grep openvpn
 openvpn-iptables.service             loaded active exited    openvpn-iptables.service                             
 openvpn-server@server.service        loaded active running   OpenVPN service for server                           
 system-openvpn\x2dserver.slice       loaded active active    system-openvpn\x2dserver.slice
 root@CT123:~# ps aux | grep vpn
 nobody     136  0.0  1.3  11780  6844 ?        Ss   14:41   0:00 /usr/sbin/openvpn --status /run/openvpn-server/status-server.log --status-version 2 --suppress-timestamps --config server.conf

Congratulations! You now have an unprivileged Debian container running OpenVPN!

If you want to configure networking to make your container accessible from outside, see Network Configuration