This week when I was working with Linux monitoring from a resource pool in Operations Manager 2012 I got this alert
SSL Certificate Error
Description: The SSL Certificate used by the Agent has a configuration error.
The server certificate on the destination computer (SERVERNAME:1270) has the following errors: The SSL certificate could not be checked for revocation. The server used to check for revocation might be unreachable. The SSL certificate is signed by an unknown certificate authority.
During discovery of Linux/UNIX machines Operations Manager when the discovery wizard deploys an agent, it retrieves the certificate from the agent, signs the certificate, deploys the certificate back to the agent, and then restarts the agent. Operations Manager uses certificates to authenticate access to the agent computer. During this process the certificate is signed by the management server that is doing the discovery. So even if you configure monitoring to be executed by a resource pool, one of those management servers will do the discovery. After discovery any of management server in the resource pool can do the job, for example run a task against the machine.
You get this alert when another management server in the resource pool is trying to communicate with the Linux/UNIX machine. The root cause is that the another management server is not trusting the first management server as certificate authority, the one that sign the certificate. Therefor when the Linux/UNIX machine is trying to communicate the management server is saying it is using a untrusted certificate. The resolution is to copy the certificate from the management server that sign the agent certificate (Linux/UNIX machine in this case) to all other management server in the resource pool.
More info how to copy the certificate between management servers is here.