[BUG] DNS issue where deprovisioning sets the hostname to localhost.localdomain

[edwardsp]

Describe the bug: A clear and concise description of what the bug is.

Deprovisioning sets the hostname to localhost.localdomain but it also sets the hostname for dhclient to localhost.localdomain. This can result in nslookup localhost on the network resolving to another Virtual Machine in the starting state between the time where dhclient is initially run and when the hostname is setup by walinuxagent.

Distro and WALinuxAgent details (please complete the following information):

• Distro and Version: [e.g. Ubuntu 16.04]
• WALinuxAgent version [e.g. 2.2.40, you can copy the output of waagent --version, more info here ]

CentOS 7.9 and Ubuntu. Although this will effect all distros if dhclient is run before the actual hostname is set.

Additional context

This breaks scripting that would rely on localhost being correct.

You can reproduce this with the following steps:

• Create a new image after running waagent -deprovision.
• On another VM on the VNET, run the command watch nslookup localhost (or run in a loop and pipe to a file)
• Start a new VM on the VNET with the image that was created
• For a short period while the new VM starts up you will see nslookup localhost being resolved to the new VMs private IP address

Log file attached

Any /var/log/messages will show the hostname being set to localhost.localdomain when the VM initially starts if it has been created after using waagent deprovision.

[maddieford]

Assigning to provisioning, during deprovisioning we set dhcp hostname to localhost.localdomain. The bug described in this issue occurs after creating a new VM with the image and before provisioning updates the hostname.