SSH is used during installation to configure cluster member nodes, and SSH is used after installation by configuration assistants, Oracle Enterprise Manager, Opatch, and other features.

• About Passwordless SSH Configuration
  Passwordless SSH configuration is a mandatory installation requirement for Oracle Grid Infrastructure installation to configure cluster member nodes.
• Checking Existing SSH Configuration on the System
  Use this procedure to check if SSH is already configured and running on your server.
• Configuring SSH on Cluster Nodes
  You must configure SSH separately for each Oracle software installation owner that you intend to use for installation.
• Enabling SSH User Equivalency on Cluster Nodes
  After you have copied the authorized_keys file that contains all keys to each node in the cluster, complete the following procedure.