VMware: ESXi upgrade 4.0 to 4.1 (USB)

Upgrade a single ESX1i 4.x host to a higher version by executing the following steps:

1. On your laptop/pc install vSphere CLI
2. Download an upgrade package like ESXi4.0-to-4.1.0-0.0.260247-release.zip
3. Put the ESX host in maintenance mode.
4. Open a MSDOS console on you laptop and goto C:\Program Files\VMware\VMware vSphere CLI\bin
5. vihostupdate.pl –server 192.168.0.1 -i -b F:\upgrade-from-ESXi4.0-to-4.1.0-0.0.260247-release.zip
   Enter username: root
   Enter password:
   Please wait patch installation is in progress …
   The update completed successfully, but the system needs to be rebooted for the changes to be effective.
6. Update your VI Client and login to the ESX server.

That' s it. I upgraded my free ESX version like this. You can also use vCenters host update utility.