VMware Update Manager fails to patch a host
On a few occasions I have found sites where VMware Update Manager fails to patch or update a host. The task can fail with the error “VMware vCenter Update Manager had an unknown failure. Check Task and Events tab and logs for more details” or “Failed to scan host for patches”
I have found the most common issue is the /tmp directory is full, this can be confirmed using the df -hmk command from the console.
If the updates are occurring over a WAN link it’s also possible the failure is occuring due to timeouts.