[18.04] systemd-resolve does not update DNS servers

[Peter Jose De Sousa]

Hi,

A number of my nodes were in a broken state resolving DNS on an unattended-upgrades enabled nodes, running dhclient and checking systemd-resolve --status shows the following:

Link 2 (eth0)
      Current Scopes: none
       LLMNR setting: yes
MulticastDNS setting: no
      DNSSEC setting: no
    DNSSEC supported: no

Compared to a working node:

Link 2 (eth0)
      Current Scopes: DNS
       LLMNR setting: yes
MulticastDNS setting: no
      DNSSEC setting: no
    DNSSEC supported: no
         DNS Servers: 145.218.226.65
                      145.218.238.29
          DNS Domain: reddog.microsoft.com

[Workaround]

Reboot the node, DNS should return back to normal.

sos report and additional information: https://private-fileshare.canonical.com/~pjds/dsv/dns-issue/

Thanks,

Peter

[Lutz Willek (willek)]

Exact the same as described above happened today morning after an unattended update on Ubuntu 18.04 and 20.04 machines. Another similarity is that the affected instances are running as virtual instance in Azure. (could be a correlation - I am not sure about that)

`grep 'configure systemd:amd64 237-3ubuntu10.54' /var/log/dpkg.log`

EDIT: see https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1988119