How to disable systemd-resolved in Ubuntu

README.md

How to disable systemd-resolved in Ubuntu

Stages

• Disable and stop the systemd-resolved service:

    sudo systemctl disable systemd-resolved.service
    sudo systemctl stop systemd-resolved
  

• Then put the following line in the [main] section of your /etc/NetworkManager/NetworkManager.conf:

    dns=default
  

• Delete the symlink /etc/resolv.conf

    rm /etc/resolv.conf
  

• Restart network-manager

    sudo service network-manager restart
    or
    sudo systemctl restart NetworkManager.service
  

Sources

• https://askubuntu.com/questions/907246/how-to-disable-systemd-resolved-in-ubuntu

Thanks, this resolved VPN-issued DNS servers not being used in Docker containers for me on Pop_OS! 21.10.

If anyone wants to do it extra quick I wrote a little playbook:

# apt/yum install ansible, then:
curl -L https://bit.ly/3MqjHO0 > disable-systemd-resolved.yaml
ansible-galaxy collection install community.general
ansible-playbook -v disable-systemd-resolved.yaml

@thekoma: I'd advise everyone to no to use URL shorteners when it comes to blind code execution on user's machines. The content that hides behind that URL could change at any moment in time and could become malicious.

It's not blind. I'm not piping into bash. I've just shortened the gist url which is marked in the first statement.
But if you prefer: https://gist.githubusercontent.com/thekoma/b0d28f96b0384d9c630c244e216a6e03/raw/b9a2be01d6d0a7521c2102a7ea2c0bb74c0365c1/disable-systemd-resolved.yaml

We did not have NetworkManager service installed (fresh ubuntu 20.04). We kept the systemd-resolved service running and changed the /etc/resolv.conf symlink to use another resolv.conf file.

Default symlink was this:

/etc/resolv.conf  ->  ../run/systemd/resolve/stub-resolv.conf

We changed it to:

/etc/resolv.conf  ->  ../run/systemd/resolve/resolv.conf

This means we don't use a 127.0.0.53 cached resolver, but we keep using the generated resolv.conf file from the systemd-resolved service. Which is overwritten/managed by netplan.

Original issue

We are running applications in docker which could not connect to any internally hosted applications on their local DNS name. Docker documentation about DNS:

By default, a container inherits the DNS settings of the host, as defined in the /etc/resolv.conf configuration file [..] If the container cannot reach any of the IP addresses you specify, Google’s public DNS server 8.8.8.8 is added, so that your container can resolve internet domains.

We discovered using journalctl -xeu docker that docker was using google's DNS, so we figured that docker was not able to reach the configured DNS service. Which is correct. The /etc/resolv.conf file which was using nameserver 127.0.0.53 also for docker, resolves to the docker container and not the guest host.

Following these steps on a fresh Ubuntu 22.10 install completely breaks dns

Local dns servers are perfectly functional, Ubuntu sees them and they show in network config, but it refuses to use them, what gives?

Don't forget to add back the resolv.conf:

echo 'search example.com' > /etc/resolv.conf
echo 'nameserver 1.1.1.1' >> /etc/resolv.conf
echo 'nameserver 1.0.0.1' >> /etc/resolv.conf

systemd-resolvwhatever broke after upgrading ubuntu, and it was easier to just switch back to the Thing That Always Worked than to try to figure it out.

Following these steps on a fresh Ubuntu 22.10 install completely breaks dns

Local dns servers are perfectly functional, Ubuntu sees them and they show in network config, but it refuses to use them, what gives?

How do you solve the DNS issue for 22.10 please?

root@www::> systemctl disable systemd-resolved
root@www::> systemctl stop systemd-resolved
root@www::> rm -f /etc/resolv.conf
root@www::> cat < /etc/resolv.conf
nameserver 9.9.9.9
nameserver 8.8.8.8
nameserver 1.1.1.1
EOF
root@www:~:> reboot

Why not just rename instead of remove?

mv /etc/resolv.conf /etc/resolv.conf.del