both the primary and secondry server need the same postgreSQL version.

in my case :
	-primary serv : 10.184.116.91
	-secondary serv : 10.184.116.237
	

# 1 # on the primary server
Dans postgresql.conf :

    wal_level = replica (ou logical)
    max_wal_senders = X
        1 par client par streaming
        défaut : 10
    wal_sender_timeout = 60s

#create replication user
CREATE USER replicator WITH REPLICATION ENCRYPTED PASSWORD 'replicaPassword';

#inside of the pg_hba.conf file add the following line:
host replication replicator 10.184.116.137/24 scram-sha-256

#reload config
psql -c "select pg_reload_conf();"
#in case of issue, exit from postgres user to go back to root and use:
systemctl restart postgresql
#you can then switch back to postgres user
su -- postgres



# 2 # on the replica server
#verify connection between primary and secondary server
telnet 10.184.116.91 5432

#stop postgresql
systemctl stop postgresql

#backup secondary server existing data
sudo su postgres
cp -R /var/lib/postgresql/17/main/ /var/lib/postgresql/17/main_bak/
rm -rf /var/lib/postgresql/17/main/

#initialize the replica with pg_basebackup
pg_basebackup --host=10.184.116.91 --pgdata=/var/lib/postgresql/17/main/ --username=replicator --progress --verbose --write-recovery-conf --wal-method=stream --create-slot --slot=replicaslot1

#confirm replica creation by checking existence of standby.signal file:
ls -ltrh /var/lib/postgresql/17/main/






# 3 # you can then test the replication
#if there was already a database on the primary server, check on the secondary server if it exist as well
\l+
#you should see the same content when you use the same command on the primary server

#try creating a new database
	# on the primary server, create and fill a db
		create database replica_test;
		\c replica_test
		create table users (id serial primary key, username text);
		insert into users (username) values ('Superman');
		insert into users (username) values ('Batman');	
		insert into users (username) values ('Spiderman');
	# on the replica server check existence of newly created db and check it's content
		\l
		\c replica_test
	        select * from users;