Systemd-resolved DNS configuration for VPN

VPN GUI

When using ubuntu GUI VPN connection, the DNS might not be updated correctly. Following command can be used to update search domain and DNS server.

sudo systemd-resolve --interface tun0 --set-dns <dns_server> --set-domain <domain>

Note: The latest test in VPN GUI, the DNS setting is working as expected.

VPN CLI

For openvpn command line,

openvpn --config client.ovpn --script-security 2 --up ./manual-config

The manual-config script can be as follow

#!/bin/sh
set -e
resolvectl dns $dev 192.0.2.53 192.0.2.54
resolvectl domain $dev "~foo.example.com" "~bar.example.com"
resolvectl dnssec $dev off

or

#!/bin/sh
systemd-resolve -i $dev \
  --set-dns=192.0.2.53 --set-dns=192.0.2.54 \
  --set-domain=foo.example.com --set-domain=bar.example.com \
  --set-dnssec=off  # <- Not super nice, but might be needed.

Another method is to use /etc/openvpn/update-systemd-resolved script, which is in openvpn-systemd-resolved package,

openvpn \
  --config client.ovpn \
  --up /etc/openvpn/update-systemd-resolved \
  --down /etc/openvpn/update-systemd-resolved \
  --down-pre \

NetworkManager Integration

To allow DNS and other options applied to new interface, a dispatcher file can be created, for example, /etc/NetworkManager/dispatcher.d/10-openvpn-tun0-up. The content can be as follows

#!/usr/bin/env bash

interface=$1
event=$2

if [[ $interface != "tun0" ]] || [[ $event != "up" ]]
then
  return 0
fi

# place your commands bellow this line

resolvectl dns tun0 192.168.1.1 192.168.1.2
resolvectl domain tun0 "~new.com"

References

Systemd-resolved DNS configuration for VPN
Network Manager script when interface up?