I ran into what seemed to be a DNS problem when building a Docker container:

Err http://archive.ubuntu.com jammy Release.gpg
  Could not resolve 'archive.ubuntu.com'

W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/jammy/Release.gpg  Could not resolve 'archive.ubuntu.com'

W: Some index files failed to download. They have been ignored, or old ones used instead.

I found that many solutions talked about setting the default DNS server explicitly in /etc/docker/daemon.json:

    "dns": [""]

but that didn't work for me.

I noticed however that I was having these problems whenever I connected to my VPN. So what did work for me was restarting the docker daemon whenever there is a change in networking (e.g. enabling/disabling VPN) by putting the following in /etc/NetworkManager/dispatcher.d/docker-local:



if [ -z "$1" ]; then
    echo "$0: called with no interface" >> $LOGFILE
    exit 1;

if [ "$1" = lo ]; then
    # Ignoring the loopback interface
    exit 0;

case "$2" in
        echo "$0: restarting docker due to action \`$2' on interface \`$1'" >> $LOGFILE
        /bin/systemctl restart docker.service
        echo "$0: ignoring action \`$2' on interface \`$1'" >> $LOGFILE

and then making that new file executable:

chmod +x /etc/NetworkManager/dispatcher.d/docker-local

You can confirm that it's working as intended by watching the logs:

tail -f /var/log/docker-restarts.log

while enabling/disable your VPN or your network connection. If you don't see any output, then something is wrong and the Docker restart isn't happening.