Update Manager scan fails with error: "An error occurred while scanning , check event logs for more details"

Products

• VMware vCenter Server

Issue/Introduction

Symptoms:

• Update manger scan/stage fails with error: "An error occurred while scanning, check event logs for more details on all hosts"

The vmware-vum-server-log4cpp.log show the following messages:

[2020-01-28 12:47:19:384 'HostUpdateDepotManager' 140049206277888 ERROR]  [scanHost20, 371] result for host: <HOST FQDN> (entity: host-20) shows error :
-----Result Begin (<HOST FQDN>)-----
<esxupdate-response>
<version>1.50</version>
<error errorClass="MetadataDownloadError">
  <errorCode>4</errorCode>
  <errorDesc>Failed to download metadata.</errorDesc>
  <url>http://<HOST FQDN>:9084/vum/repository/hostupdate/Unknown/metadata-175.zip</url>
  <localfile>None</localfile>
  <msg>('http://<HOST FQDN>:9084/vum/repository/hostupdate/Unknown/metadata-175.zip', '/tmp/tmpvapusf93', '&lt;urlopen error [Errno -2] Name or service not known&gt;')</msg>
</error>
</esxupdate-response>

-----Result End (<HOST FQDN>)-----

Environment

VMware vCenter Server Appliance 6.7.x

Cause

The host is able to connect to the vCenter using the IP, but update manager is attempting to connect to the vCenter using the FQDN and unable to resolve.

Resolution

To resolve this issue:

1. Login in to a SSH session to the vCenter and navigate to less /etc/hostname
2. The file contains the short name of the vCenter. Change it to fully qualified name.
3. Open SSH session to each host and edit the /etc/hosts file
4. In this file add the following line:

<vCenter IP> <FQDN of vCenter> <vCenter short name>

-- this does not seem valid 

host file reads 

127.0.0.1 <FQDN> short name localhost