The following the my approved process for patching VM’s:
- Wait at least one week after “Patch Tuesday”; this gives Microsoft time to have others beta test the patches and for Microsoft to pull / adjust problem patches
- Shut Down (VM equivalent of Power Off) any running Virtual Machines
- Copy the VHD’s to an external disk (or some other disk you trust)
- Power Up your VM’s and patch them
- Reboot the VM’s as required
- Shut Down the VM’s
- Patch the Host
- Reboot the Host as required
- Start Up the VM’s
Many other qualified tech’s also:
- Set the VM’s to start automatically when the Host starts
- Set the VM’s to have a delayed start so they do not cause resource contention on boot.
There are many good discussion threads on this topic including THIS one.