What is PostgreSQL?
PostgreSQL is a powerful open source object-oriented database system. It originated from the POSTGRES project of the University of California, Berkeley in 1986. This project has more than 30 years of development history.
When PostgreSQL is installed, a direct connection will prompt FATAL：no pg_hba.conf entry for host "192.168.0.2"，user "postgres"，database "postgres"，SSL off, which means: serious error, pg_hba.conf has no host entry, the user is postgres, the database is postgres, and SSL is not enabled.
The location of the pg_hba.conf file depends on the platform, and is usually in the data directory.
host all all 0.0.0.0/0 trust
Effective after restarting the service
systemctl restart postgresql