To start off, we need to change the PostgreSQL postgres user password; we will not be able to access the server otherwise. As the “postgres” Linux user, we will execute the psql command.
sudo -u postgres psql postgres
Set a password for the "postgres" database role using the command:
\password postgres
and give your password when prompted. The password text will be hidden from the console for security purposes.
Type Control+D to exit the posgreSQL prompt.
To create the first database, which we will call "mydb", simply type :
sudo -u postgres createdb mydb