I have four VM's running on a Windows Server 2008 R2 box - not 'core.' What is the best way to install Windows Updates on that server? Do I need to shut the VM's down first in case it wants a reboot? Is there a way to configure Windows Updates to do the shutdown itself?
WIndows saves the VM's then restarts. If saving takes too long some vm's just fail and restart from cold boot.
Server 8 can - in a cluster - empty the machine by moving the VM's over first, but that is not in standard 2008 R2, sadly.
We do save / shutdown before upating the virtual servers. But we only have three.
Assuming that you are working in a Hyper-V cluster you'll want to manually move all the guests from the host to another host then patch the host.
If you are in a standalone config you'll want to down the guests then patch the server.