PostgreSQL or Postgres is an open-source general-purpose object-relational database management system with many advanced features that allows you to build fault-tolerant environments or complex applications.

In this guide, we will explain how to install the PostgreSQL database server on Ubuntu 20.04, and explore the basics of PostgreSQL database administration.

Prerequisites #

To be able to install packages, you need to be logged in as root or user with sudo privileges.

Install PostgreSQL on Ubuntu #

At the time of writing this article, the latest version of PostgreSQL available from the official Ubuntu repositories is PostgreSQL version 10.4.

Run the following commands to install PostgreSQL server on Ubuntu:

sudo apt updatesudo apt install postgresql postgresql-contrib

We’re also installing the PostgreSQL contrib package that provides several additional features for the PostgreSQL database system.

Once the installation is completed, the PostgreSQL service will start automatically. Use the psql tool to verify the installation by connecting to the PostgreSQL database server and printing its version:

sudo -u postgres psql -c "SELECT version();"

PostgreSQL 12.2 (Ubuntu 12.2-4) on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 9.3.0-8ubuntu1) 9.3.0, 64-bit

That’s it. PostgreSQL has been installed, and you can start using it.

PostgreSQL Roles and Authentication Methods #

Database access permissions within PostgreSQL are handled with the concept of roles. A role can represent a database user or a group of database users.

PostgreSQL supports multiple authentication methods. The most commonly-used methods are:

• Trust – A role can connect without a password, as long as the conditions defined in the pg_hba.conf are met.
• Password – A role can connect by providing a password. The passwords can be stored as scram-sha-256, md5, and password (clear-text).
• Ident – Only supported on TCP/IP connections. It works by obtaining the client’s operating system user name, with an optional user name mapping.
• Peer – Same as Ident, but it is supported on local connections only.

PostgreSQL client authentication is defined in the configuration file named pg_hba.conf. By default, PostgreSQL is using the peer authentication method for local connections.

The postgres user is automatically created when you install PostgreSQL. This user is the superuser for the PostgreSQL instance, and it is equivalent to the MySQL root user.

To log in to the PostgreSQL server as the postgres user, first switch to the user and then access the PostgreSQL prompt using the psql utility:

sudo su - postgrespsql

From here, you can interact with your PostgreSQL instance. To exit out of the PostgreSQL shell type:

\q

Another way to access the PostgreSQL prompt without switching users, is to use the sudo command:

sudo -u postgres psql

Generally, you should log in to the database server as postgres only from the localhost.

Creating PostgreSQL Role and Database #

Only superusers and roles with CREATEROLE privilege can create new roles.

The following example shows how to create a new role named john a database named johndb and grant privileges on the database:

1. Create a new PostgreSQL role:

   sudo su - postgres -c "createuser john"

2. Create a new PostgreSQL Database:

   sudo su - postgres -c "createdb johndb"

To grant permissions to the user on the database, connect to the PostgreSQL shell:

sudo -u postgres psql

and run the following query:

grant all privileges on database johndb to john;

Enable Remote Access to PostgreSQL server #

By default, the PostgreSQL server listens only on the local interface (127.0.0.1).

To enable remote access to your PostgreSQL server open the configuration file postgresql.conf and add listen_addresses = '*' in the CONNECTIONS AND AUTHENTICATION section.

sudo nano /etc/postgresql/12/main/postgresql.conf

#------------------------------------------------------------------------------
# CONNECTIONS AND AUTHENTICATION
#------------------------------------------------------------------------------

# - Connection Settings -

listen_addresses = '*'     # what IP address(es) to listen on;

Save the file and restart the PostgreSQL service:

sudo service postgresql restart

Verify the changes with the ss utility:

ss -nlt | grep 5432

The output shows that the PostgreSQL server is listening on all interfaces (0.0.0.0):

LISTEN  0        244              0.0.0.0:5432           0.0.0.0:*              
LISTEN  0        244                 [::]:5432              [::]:* 

The next step is to configure the server to accept remote connections by editing the pg_hba.conf file.

Below are some examples showing different use cases:

# TYPE  DATABASE        USER            ADDRESS                 METHOD

# The user jane can access all databases from all locations using md5 password
host    all             jane            0.0.0.0/0                md5

# The user jane can access only the janedb from all locations using md5 password
host    janedb          jane            0.0.0.0/0                md5

# The user jane can access all databases from a trusted location (192.168.1.134) without a password
host    all             jane            192.168.1.134            trust

The last step is to open the port 5432 in your firewall.

Assuming you are using UFW to manage your firewall, and you want to allow access from the 192.168.1.0/24 subnet, you would run the following command:

sudo ufw allow proto tcp from 192.168.1.0/24 to any port 5432

Make sure your firewall is configured to accept connections only from trusted IP ranges.

Conclusion #

We’ve shown you how to install and configure PostgreSQL on Ubuntu 20.04 server. Consult the PostgreSQL 12 Documentation for more information on this topic.

If you have any questions, please leave a comment below.