No name resolution on new Ubuntu 18 vm

Apologies if this is not the correct place for this issue.

My team is building templates with Packer and deploying VMs with az group create deployment ..., based loosely on these docs: https://docs.microsoft.com/en-us/azure/virtual-machines/linux/build-image-with-packer

I noticed that after the provisioning done by Packer, waagent deletes resolv.conf. This is fine, and works as expected when deploying a 16 vm.

However as we attempt to move onto Ubuntu 18, when the vm is created, /etc/resolv.conf is missing, meaning it is not recreated when the vm is created from the disk image. nslookup microsoft.com times out, and no names are resolved when using eg curl. systemd-resolve however does work.

Is this something waagent is responsible for?

[carlosporter]

To whom it may interest,

The issue described happens when the Ubuntu 18.04 is deployed from an image deprovisioned with waagent.

When a new server is deployed the symlink to /run/systemd/resolve/stub-resolv.conf resolv.conf is not restored and as consequence the server cannot find a DNS server where to send queries.

Restoring the link manually does fix the problem after the customized virtual machine has been deployed. However in order to prevent further deployments with the same problem it’s necessary to deprovision and restore the symlink as the root user on the original virtual machine ( you need root privileges to restore the symlink and sudo won’t work after “waagent -deprovision+user” ).

So you should start the creation of a new Ubuntu 18.04 server image with these commands:

sudo -i

waagent -deprovision+user

cd /etc; ln -s …/run/systemd/resolve/stub-resolv.conf resolv.conf

[hglkrijger]

@paulmey I agree - we should not be touching this file, I merged a fix to master.

@dakale the referenced change in #1164 should address your issue, if you are installing from source. If you have any problems, please reopen this issue.