I had a problem adding a ESX 3.0.1 host to a Virtual Center 2.0.1. When connecting the message “Failed to install virtualcenter agent service” appeared.

To solve this try manually install the agent:

- Copy the vpx-upgrade-esx-6-linux-32042 from the upgrade folder in the VC folder to /tmp on the ESX server

- run the command sh vpx-upgrade-esx-6-linux-32042

(By default the script is located in C:\program files\vmware\vmware virtualcenter\upgrade )

Next restart management services:
service mgmt-vmware restart

After completing the above steps, try to reconnect to the esx.