The first thing we do with this recipe is allow the new PostgreSQL server to retrieve data from the primary server. There are a few ways to do this, but for the sake of demonstration, we created a rule for the server at 192.168.56.20 to connect to the replication pseudo-database. This allows tools such as pg_basebackup to copy database files from the primary database when we initialize the replica.
In a related concern, we must ensure that the wal_level setting of the primary server is set to hot_standby and that max_wal_senders is a value greater than 0. Earlier chapters on configuring PostgreSQL have already made this suggestion, but this recipe won't work at all if these parameters are set wrong. We restart PostgreSQL after ...
