One more interesting and useful topic for the software developers.

---

 

PostgreSQL

PostgreSQL, also known as postgres, is a popular database management system that is used to handle the data of many websites and applications.

sudo apt-get update
sudo apt-get install postgresql postgresql-contrib

The installation procedure created a user account called postgres that is associated with the default Postgres role. In order to use Postgres, we'll need to log into that account.

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 by typing:

createuser --interactive

Note this :

So if I have a user called test1, that role will attempt to connect to a database called test1 by default.

You can create the appropriate database by simply calling this command as the postgres user:

createdb test1

If you want your user to connect to a different database, you can do so by specifying the database like this:

psql -d postgres

Variations of changing password in Postgresql

---

Change a user’s password:

ALTER USER davide WITH PASSWORD 'hu8jmn3';

Change the expiration date of the user’s password:

ALTER USER manuel VALID UNTIL 'Jan 31 2030';

Change a password expiration date, specifying that the password should expire at midday on 4th May 2005 using the time zone which is one hour ahead of UTC:

ALTER USER chris VALID UNTIL 'May 4 12:00:00 2005 +1';

Make a password valid forever:

ALTER USER fred VALID UNTIL 'infinity';

Give a user the ability to create other users and new databases:

ALTER USER miriam CREATEUSER CREATEDB;

List the current roles and their attributes by typing:

---

 

\du

---

---

 Refer more links: 
https://www.digitalocean.com/community/tutorials/how-to-secure-postgresql-on-an-ubuntu-vps
https://www.digitalocean.com/community/tutorials/how-to-install-and-use-postgresql-on-ubuntu-14-04