We face with this error while We are making 2 node RAC installation

Db version :
Os : AIX 7.1

We run root.sh on node 1 without any issue. While we run root.sh node 2 we face this message:

Adding Clusterware entries to inittab
CRS-4402: The CSS daemon was started in exclusive mode but found an active CSS daemon on node Node1, number 1, and is terminating
An active cluster was found during exclusive start-up, restarting to join the cluster
Configure Oracle Grid Infrastructure for a Cluster … succeeded

So we check crs healthy and also run cluvfy to be sure our system is healthy

# crsctl check crs
CRS-4638: Oracle High Availability Services is online
CRS-4537: Cluster Ready Services is online
CRS-4529: Cluster Synchronization Services is online
CRS-4533: Event Manager is online

# cluvfy stage post -h crsinst -n node1,node2 -verbose
#cluvfy comp crs -n node-1,node-2 -verbose

All passed and seems everything is okey. We found some hints at MOS Troubleshooting 11.2 Grid Infrastructure root.sh Issues (Doc ID 1053970.1).

The note mention, If the root.sh is successful but there are subsequent startup problems, see Note: 1050908.1 for more troubleshooting information. So we try to reebot servet to can see there is problem during startup.. End of the startup there is no any error on our CRS.

So what is this Error message? Here is the answer:

Error CRS-4402 is expected on second node because the CSS is already running on first node and so the css should be started in cluster mode on second node.

Please ignore this error. As per the root.sh output the clusterware install is completed successfully on both the nodes.

Also similar explanations avaliable at:
Oracle® Database Appliance Getting Started Guide


Error “CRS-4402: The CSS daemon was started in exclusive mode but found an
active CSS daemon on node oda2-1, number 1, and is terminating”

Cause: This error occurs when the Oracle Grid Infrastructure CSS daemon attempts to start the node as a standalone cluster node, but during start-up discovers that the other cluster node is running, and changes to cluster mode to join the cluster.
Action: Ignore this error

So, If you hit this error message just Ignore the error