Here's my process:
- Move all VM's onto 2nd ESX Host
- PUT ESX Host into Maintenance mode
- Reboot ESX Host with Image CD in it (Ghost)
- Get a Image of the system
- Reboot ESX Host with upgrade / install CD in it
- Go through the upgrade using the default options (if doing upgrade the defaults are what you set when you did the inital install)
- Reboot ESX Host
- I then check a couple files to make sure my custom changes didn't get overwritten. 2 of my changes are: take out the hda= link int he grub.conf to fix my CD/DVD Drive and I enable ssh for my management system.
- Via Virtual Center bring the newly upgraded ESX host out of maintenence mode.
- start up a test VM on the new ESX Host and run some tests / network tests on it.
- migrate a second running test VM from the production ESX Host to the newly upgraded ESX Host... again perform tests / network tests to verify it's running ok.
- slowly migrate production VM's over.
Another really cool part to this is the ability to upgrade your ESX Hosts directly from Virtual Center and apply patches.
Way to go VMWare.