Passwordless SSH is needed for Ambari Server to install & register ambari-agents on hosts using Ambari API calls (OR) using ambari UI. This is specially needed so that using Passwordless SSH the ambari server user can install the ambari agents on remote hosts.
Hence in case of Single host, we can simply install the ambari-server and ambari-agent binaries on the same host on our own hence it is not mandatory.
Also in case of Manual ambari agent registration/installation the Passwordless SSH is not needed. It is needed only when we want ambari to install the agents on the desired hosts (local / remote) using Ambari API calls or using Ambari UI.
Passwordless SSH is needed for Ambari Server to install & register ambari-agents on hosts using Ambari API calls (OR) using ambari UI. This is specially needed so that using Passwordless SSH the ambari server user can install the ambari agents on remote hosts.
Hence in case of Single host, we can simply install the ambari-server and ambari-agent binaries on the same host on our own hence it is not mandatory.
Also in case of Manual ambari agent registration/installation the Passwordless SSH is not needed. It is needed only when we want ambari to install the agents on the desired hosts (local / remote) using Ambari API calls or using Ambari UI.