You may see following error when you scanning ESXi hosts by vCenter Update Manager. Host cannot download files from VMware vSphere Update Manager patch store. Check the network connectivity and firewall setup, and check esxupdate logs for details. You also see similar logs in /var/log/esxupdate.log. [Errno -2] Name or service not known The root cause could be following: ESXi host cannot resolve DNS name of vCenter Update Manager Server. One of the DNS servers incorrect if you set multiple DNS servers on ESXi host.