Setting Preferred Credentials in Enterprise Manager "Error: Connection to {hostname} as user {username} failed"

When setting preferred/default credentials:

"Error 
Connection to {hostname} as user {username} failed."

In the agent home on the host: AGENT_HOME/sysman/log/emagent.trc:

ERROR util.fileops: error: file AGENT_HOME/bin/nmo is not a setuid file
WARN  Authentication: nmo binary in current oraHome doesn't have setuid privileges !!!
ERROR Authentication: altNmo binary doesn't exist ... reverting back to nmo

Check that the root.sh was run when the agent product was installed, if not then UNIX admin need to run root.sh to set the proper permissions for the Oracle binaries. This should be under AGENT_HOME/root.sh Try and set preferred/default credetials again in Grid Control.

 
"Information
Credentials successfully verified for {hostname}."