Rootless docker, systemd-resolved and DNS inside containers

Help
1

Setup:

  • host uses systemd-resolved
  • rootless docker is set up

The issue:
inside containers DNS does not resolve internet addresses.
as i see in containers /etc/resolve.conf is set to 10.0.2.3
if manually changed to nameserver 1.1.1.1 - dns works fine

don’t see any drops in host’s iptables

I don’t have much experience with docker, but this issue seem to be related to nixos setup, not sure, need guidance
also found this, but not sure what does it mean

2

Have you got a docker-compose.yaml or the command used to build the containers?

It’s possibly missing some network configuration within docker and / or containers.
e.g

  • capabilities (--cap-add=NET_ADMIN or others)
  • host network to containers bridged correctly
  • etc

You can also declare DNS in your docker-compose.yaml or add to the command --dns=1.1.1.1.
See Networking overview | Docker Docs .

3

Thank you
I’ve added dns setting to docker.daemon.settings option.
After all, I did not want docker daemon to take my resolve.conf into an image anyway (though it’s said to be the default behaviour, even for systemd-resolved on host)

1 Like
4

I figured it out!

  1. Make sure your are using virtualisation.docker.rootless.daemon.settings instead of virtualisation.docker.daemon.settings.
  2. Restart docker manually after you rebuild! systemctl --user restart docker.service

More info: virtualisation.docker.rootless.daemon.settings is not working · Issue #258141 · NixOS/nixpkgs · GitHub