Vihostupdate
From Peter Pap's Technowiki
The vihostupdate command, as the name suggests, is used for performing updates/patching on existing systems.
Usage
In order to find out the command line arguments you can use with this command, do:
vihostupdate --help
Query the ESXi server
This command will allow you to see what patches, if any, have been deployed on your server at the present time:
vihostupdate --username adminuser --password adminpassword --server hostname/IP --query
If you omit the username and pasword, you will be prompted for them when you run the command.