ERROR: NMO not setuid-root (Unix-only)

Thus error came up while I was specifying a host credentials on EM 12c.

 After some research I found that I had not run root.sh on the agent home.

Solution:

# cd $AGENT_HOME
# ./root.sh
Finished product-specific root actions.
/etc exist
Finished product-specific root actions.
#

This solved my problem!