Add PostgreSQL 12 package repository sudo yum -y install https://download.postgresql.org/pub/repos/yum/reporpms/EL-7-x86_64/pgdg-redhat-repo-latest.noarch.rpm Install PostgreSQL 12 client and server sudo yum -y install postgresql12-server postgresql12 Initialize PostgreSQL database sudo /usr/pgsql-12/bin/postgresql-12-setup initdb Enable PostgreSQL on system boot and start immediately sudo systemctl enable --now postgresql-12 Create an opennms database user and password sudo -i -u postgres createuser -P opennms You must provide a password for the opennms database user. This guide uses YOUR-OPENNMS-PASSWORD as a placeholder. Please set a secure password. Create an empty database and set the owner to the opennms user sudo -i -u postgres createdb -O opennms opennms Set a password for PostgreSQL superuser sudo -i -u postgres psql -c "ALTER USER postgres WITH PASSWORD 'YOUR-POSTGRES-PASSWORD';" Change YOUR-POSTGRES-PASSWORD to a secure one. The superuser is required to initialize and change the database schema for installation and updates. Change the access policy for PostgreSQL sudo vi /var/lib/pgsql/12/data/pg_hba.conf Allow Horizon to access the database over the local network with an MD5 hashed password host all all 127.0.0.1/32 md5(1) host all all ::1/128 md5(1) 1 Change method from ident to md5 for IPv4 and IPv6 on localhost. Apply configuration changes for PostgreSQL sudo systemctl reload postgresql-12