single stack IPv6 fails with 18.04 ubuntu image

[aramase]

Describe the bug
With 18.04 ubuntu image, the systemd-resolved uses the port :53 on the host and is being used by default for dns. This causes the coredns pods to crash for single stack IPv6 with bind address already in use as coredns pods are run on hostNetwork to leverage the host routes for dns resolution.

Steps for resolution -

• Update /etc/systemd/resolv.conf and set DNSStubListener=no
• sudo mv /etc/resolv.conf /etc/resolv.conf.OLD && sudo ln -s /run/systemd/resolve/resolv.conf /etc/resolv.conf
• systemctl restart systemd-resolved

This frees up :53 on the host and the coredns pods start running without errors.

Steps To Reproduce

Expected behavior

AKS Engine version

Kubernetes version

Additional context

[jackfrancis]

Is there a definitive api model configuration that should engage the resolution steps provided?

[aramase]

I've added a sample api model as part of this PR - https://github.com/Azure/aks-engine/pull/3777/files. I've set the distro: ubuntu in the api model so users can try it out with Ubuntu 16.04. We can remove that after the fix is merged to aks-engine.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[bridgetkromhout]

Per @aramase with CAPZ this is supported (kubernetes-sigs/cluster-api-provider-azure#646) and given that AKS Engine is being deprecated, we don't need to add this to AKS Engine.