Ran into this annoying HA error after upgrading some blades all running ESXi 4.0 Update 2.
All hosts were upgraded using VUM from a vCenter 4.1 server. Upgrade all went well, taking only a few short minutes per host.
Upon trying to renable HA, all hosts failed with the error:
HA agent on esxhostname in cluster clustername in datacentername has an error: Error while running health check script
Disabling HA on the cluster or reconfiguring HA on hosts had no effect. The error persisted.
From previous HA errors I remembered that this knowledge base article from VMware (KB1007234) might do the trick.
After enabling remote tech support mode (SSH) on the ESXi host and then connecting in;
Run the uninstall the Legato Automated Availability Manager script:
Then restart management services on the ESXi host:
Then re-enable HA on your cluster and it should install aam-ha agents from scratch on each ESXi host,
I’ve only run into this issue with ESXi and not ESX classic with COS,