sudo apt-get update
sudo apt-get install postgresql postgresql-contrib
sudo -i -u postgres
You can get a Postgres prompt immediately by typing:
psql
Exit out of the PostgreSQL prompt by typing:
\q
We can create a new role (user_test) by typing: createuser --interactive
You can create the appropriate database by simply calling this command as the postgres user:
createdb db_test
sudo -i -u user_test
create role myapp with createdb login password 'password';
you can login as postgres user, which is generally a super user, and he can be logged in if you are sudoer or root user.
sudo -u postgres psql
Changing a password via postgres user
ALTER USER postgres PASSWORD 'newPassword';