[Bug 1988119] Re: Update to systemd 237-3ubuntu10.54 broke dns

[Lee Van Steerthem]

Not sure if this is the best place to help people out understanding if nodes are impacted. 
We already saw 2 different types of impact on our Azure AKS clusters.
- Pod not able to Terminate
- New images being pulled from ACR (or any container registry 

Sometimes it was very clear that we saw the nodes where "Not Ready` in
order cases it's very hard to detect.

We have found a way to detect if your nodes are affected.

kubectl logs <pod name> 
When you get the following error you know it's impacted: Error from server (InternalError): Internal error occurred: Authorization error (user=masterclient, verb=get, resource=nodes, subresource=proxy)

So restarting the node will help and especially if your cluster is
sensitive then you can be more granular about the restart.

I hope it helps some visitors from the azure status page

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https://bugs.launchpad.net/bugs/1988119

Title:
  Update to systemd 237-3ubuntu10.54 broke dns

Status in systemd package in Ubuntu:
  Confirmed

Bug description:
  Two servers today that updated systemd to "systemd 237-3ubuntu10.54" 
  https://ubuntu.com/security/notices/USN-5583-1

  could not resolve dns anymore.
  no dns servers, normally set through dhcp.

  Ubuntu 18.04

  Temp fix.
   1. Edit /etc/systemd/resolved.conf
   1. Add/Uncomment # FallbackDNS=168.63.129.16
   1. Restart systemd-resolved sudo systemctl restart systemd-resolved.service
   1. Confirm dns working with systemd-resolve google.com

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