Install Postgresql 13 on RHEL 8. Configure scram-sha-256 password authentication.

1. Steps Summary
   a. install postgresql-server
   b. initialize database
   c. set password for postgres os user
   d. enable and run postgresql service
   e. modify postgresql.conf file ( listen_address and password_encryption)
   f. login to postgresql database using peer authentication and modify postgres db user password
   g. modify pg_hba.conf file to set authnetication to scram-sha-256
   h. restart postgresql service.
2. Install postgresql 13

# dnf module list | grep postgres
# dnf module install postgresql:13

2. Initialize database

# which postgresql-setup
# postgresql-setup --initdb

3. Change password for os user postgres auto created after installing postgresql

# passwd postgres

4. Enable and start postgresql service

# systemctl enable postgresql
# systemctl start postgresql
# systemctl status postgresql

5. Modify postgresql.conf file

#vim /var/lib/pgsql/data/postgresql.conf
listen_addresses = '*'
password_encryption = scram-sha-256

6. login to postgres database using peer authentication.

# su - postgres
# psql
postgres=# \conninfo

7. Change postgres database user password and password encryption method

postgres=# \password
postgres=# set password_encryption TO 'scram-sha-256';

8. Change authentication type to scram-sha-256 in pg_hba.conf file

# cd /var/lib/pgsql/data
# vim pg_hba.conf
# TYPE  DATABASE        USER            ADDRESS                 METHOD
# "local" is for Unix domain socket connections only
local   all   all                              scram-sha-256
# IPv4 local connections:
host    all   all     127.0.0.1/32             scram-sha-256
# IPv6 local connections:
host    all   all      ::1/128                 scram-sha-256
# Allow replication connections from localhost, by a user with the
# replication privilege.
local   replication     all                     scram-sha-256
host    replication     all    127.0.0.1/32     scram-sha-256
host    replication     all    ::1/128          scram-sha-256

9. Restart postgresql service and login using password authentication

# systemctl restart postgresql
$ psql -U postgres -d postgres