Does not do anything on Ubuntu 20.04

[stam]

What is Happening

Running on Ubuntu 20.04, host cannot lookup hostname of docker containers

What is expected

On the host machine running nslookup nginx.docker should work, but it returns:

Server:		127.0.0.53
Address:	127.0.0.53#53

** server can't find nginx.docker: NXDOMAIN

Steps to Reproduce

First I run: docker run --hostname dns.mageddo --restart=unless-stopped
-v /var/run/docker.sock:/var/run/docker.sock
-v /etc/resolv.conf:/etc/resolv.conf
defreitas/dns-proxy-server

Also I run: docker run --rm --hostname nginx.docker nginx

Afterwards I try the nslookup also on the host machine.

Specs:

• OS: Ubuntu 20.04.1 LTS
• Docker Version: docker-version.txt
• DPS Version: 2.19.0
• Please attach DPS Log file: dps.log

[ketilkn]

@stam There is a hint in /etc/resolv.conf

#  This file is managed by man:systemd-resolved(8). Do not edit.
#
# This is a dynamic resolv.conf file for connecting local clients to the
# internal DNS stub resolver of systemd-resolved. This file lists all
# configured search domains.
#
# Run "resolvectl status" to see details about the uplink DNS servers
# currently in use.
#
# Third party programs must not access this file directly, but only through the
# symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a different way,
# replace this symlink by a static file or a different symlink.
#
# See man:systemd-resolved.service(8) for details about the supported modes of
# operation for /etc/resolv.conf.

Specifically: To manage man:resolv.conf(5) in a different way, replace this symlink by a static file or a different symlink.

So what you can do is delete the symlink in etc and copy the current contents from the original source

rm /etc/resolv.conf
cp /run/systemd/resolve/stub-resolv.conf /etc/resolv.conf

This will slightly mess up your system, so you should probably revert the change by recreating the symlink once you are done

rm /etc/resolv.conf
ln -s /run/systemd/resolve/stub-resolv.conf /etc/resolv.conf`

There may very well be a better way to go about this.

[johncadengo]

I am running into this behavior as well. Any fixes? I'm not too sure about trying something that involves the statement "This will slightly mess up your system."

[johncadengo]

@stam a DNS proxy server seems like a more elegant solution, which is why I was trying to get this to work. However, like you, I ran into issues with it working in Ubuntu 20.

So I found a workaround, using the hosts file. If you're still running into this problem, I got this up and running within minutes: https://github.com/dvddarias/docker-hoster

[mageddo]

@ketilkn

There is a hint in /etc/resolv.conf ....

yeah, since DPS 3.5.2 it will prefer to configure using systemd-resolved when avaible, give it a try

[mageddo]

@stam

Running on Ubuntu 20.04, host cannot lookup hostname of docker containers....

DPS is crashing right on the start, I also had this issue, looks to be fixed at 3.5.2, give it a try

[mageddo]

@johncadengo

I am running into this behavior as well. Any fixes?

Yep, it's fixed for now

[mageddo]

I'm closing this but feel free to reopen if you need