Create a repmgr.conf file on the standby server. It must contain at least the same parameters as the primary's repmgr.conf, but with the mandatory values node, node_name, conninfo (and possibly data_directory) adjusted accordingly, e.g.:

    node_id=2
    node_name='node2'
    conninfo='host=node2 user=repmgr dbname=repmgr connect_timeout=2'
    data_directory='/var/lib/postgresql/data'

Use the --dry-run option to check the standby can be cloned:

    $ repmgr -h node1 -U repmgr -d repmgr -f /etc/repmgr.conf standby clone --dry-run
    NOTICE: using provided configuration file "/etc/repmgr.conf"
    NOTICE: destination directory "/var/lib/postgresql/data" provided
    INFO: connecting to source node
    NOTICE: checking for available walsenders on source node (2 required)
    INFO: sufficient walsenders available on source node (2 required)
    NOTICE: standby will attach to upstream node 1
    HINT: consider using the -c/--fast-checkpoint option
    INFO: all prerequisites for "standby clone" are met

If no problems are reported, the standby can then be cloned with:

    $ repmgr -h node1 -U repmgr -d repmgr -f /etc/repmgr.conf standby clone

    NOTICE: using configuration file "/etc/repmgr.conf"
    NOTICE: destination directory "/var/lib/postgresql/data" provided
    INFO: connecting to source node
    NOTICE: checking for available walsenders on source node (2 required)
    INFO: sufficient walsenders available on source node (2 required)
    INFO: creating directory "/var/lib/postgresql/data"...
    NOTICE: starting backup (using pg_basebackup)...
    HINT: this may take some time; consider using the -c/--fast-checkpoint option
    INFO: executing:
      pg_basebackup -l "repmgr base backup" -D /var/lib/postgresql/data -h node1 -U repmgr -X stream
    NOTICE: standby clone (using pg_basebackup) complete
    NOTICE: you can now start your PostgreSQL server
    HINT: for example: pg_ctl -D /var/lib/postgresql/data start
  

This has cloned the PostgreSQL data directory files from the primary node1 using PostgreSQL's pg_basebackup utility. Replication configuration containing the correct parameters to start streaming from this primary server will be automatically appended to postgresql.auto.conf. (In PostgreSQL 11 and earlier the file recovery.conf will be created).

Make any adjustments to the standby's PostgreSQL configuration files now, then start the server.

For more details on repmgr standby clone, see the command reference. A more detailed overview of cloning options is available in the administration manual.