When you login to GKE-OP nodes and try to run sudo command you will get the following warning:
sudo: unable to resolve host [nodename]
Your command will still execute but will show this warning. It is related to Ubuntu OS settings. To resolve it add the following line into the
/etc/hosts file on the node:
Hope this will be solved soon as Google has already identified this issue. I guess they will add the record in the provisioning process for the nodes.