DNS is broken on Focal staging server.

[kushaldas]

Description

/etc/resolv.conf contains;

nameserver 127.0.0.53

Steps to Reproduce

• apt install nmap

Expected Behavior

• apt should be able to reach to the servers

Actual Behavior

• it is stuck as it can not do any name resolution.

Comments

Suggestions to fix, any other relevant information.

[emkll]

I can reproduce this locally, looks like the default DNS resolver is different in 20.04.

Looking at /etc/resolv.conf there is a comment in that file:

# 127.0.0.53 is the systemd-resolved stub resolver

The DNS name servers should be configured in /etc/systemd/resolved.conf, if the target OS is based on Ubuntu Focal. We should add some conditional logic to handle

We should also add a testinfra test here to ensure we have test coverage.

[kushaldas]

Okay, the whole trouble is most probably coming from systemd-resolve package on Ubuntu Focal.

#  ss -pln sport = 53
RTNETLINK answers: Invalid argument
Netid            State              Recv-Q             Send-Q                         Local Address:Port                         Peer Address:Port            Process                                               
udp              UNCONN             0                  0                              127.0.0.53%lo:53                                0.0.0.0:*                users:(("systemd-resolve",pid=582,fd=12))            
tcp              LISTEN             0                  4096                           127.0.0.53%lo:53                                0.0.0.0:*                users:(("systemd-resolve",pid=582,fd=13))

[emkll]

closed via #5638