Getting it running on Fedora 34

[waltertamboer]

Hi, unfortunately I don't have the time to create a PR but in case anyone wants to get this running on Fedora, here's a how to guide.

1. The installer doesn't work since it expects apt to exist so we have to install manually.
2. Run GATEWAY=$(ip -4 addr show docker0 | grep -oP '(?<=inet\s)\d+(\.\d+){3}')
3. Run echo ${GATEWAY} to make sure the gateway address is found.
4. Run the container:

docker run -d --name dns-gen \
  --restart always \
  --net host \
  -e GATEWAY=$GATEWAY \
  --log-opt "max-size=10m" \
  --volume /:/host \
  --volume /var/run/docker.sock:/var/run/docker.sock \
  jderusse/dns-gen:2

5. Run sudo mkdir /etc/systemd/resolved.conf.d since in my installation the folder did not exist.
6. Run sudo vi /etc/systemd/resolved.conf.d/docker-dns.conf
7. Within vim add the Gateway address (obviously the 3 dots should be replaced with the IP address):

[Resolve]
DNS=...

8. Restart resolv: sudo systemctl restart systemd-resolved.service
9. Verify the config is found: systemd-analyze cat-config systemd/resolved.conf

It should now work, you can start a nginx container:

1. docker run -d --rm --name test nginx:alpine
2. dig test.docker @${GATEWAY}
3. dig test.docker

Everything should work now.