PostgreSQL is a free and open-source database management system focusing on extensibility and SQL compliance. PostgreSQL is an advanced and enterprise-class RDBMS (Relational Database Management System) supports both SQL (relational) and JSON (non-relational) querying.
It’s a highly stable database management system backed by more than 20 years of development by the open-source community and has a strong reputation among developers and system admins for its reliability, flexibility, feature robustness, and performance.
PostgreSQL is used as a primary database for web applications, mobile applications, and analytic applications. Some notable PostgreSQL users around the globe are Reddit, Skype, Instagram, Disqus, The Guardian, Yandex, Bloomberg, Nokia, BMW, etc.
In this guide, you will learn how to install the PostgreSQL database on Rocky Linux, securing the PostgreSQL database deployment, and basic usage of PostgreSQL queries for managing users and databases.
Prerequisites
- An Rocky Linux system.
- A user with root or sudo privileges. This user will be used for installing new packages and make changes system-wide.
Adding PostgreSQL Repository
For this guide, you will be installing the latest stable version of PostgreSQL v13.4.This version is available on the official PostgreSQL repository, so you need to add the PostgreSQL repository to your Rocky Linux system.
1. Add the official PostgreSQL repository for the Rocky Linux system by running the following command.
sudo dnf install -y https://download.postgresql.org/pub/repos/yum/reporpms/EL-8-x86_64/pgdg-redhat-repo-latest.noarch.rpm
2. Next, execute the following command below to verify the PostgreSQL repository are available on your system.
sudo dnf -qy repolist
If the PostgreSQL repository is available on your system, you will see multiple versions of PostgreSQL repositories as the screenshot below.
Installing PostgreSQL 13 on Rocky Linux
To be able to install PostgreSQL from the official PostgreSQL repository (not from the Rocky Linux repository), you need to disable the built-in PostgreSQL repository module.
1. Execute the following command below to disable the built-in PostgreSQL module repository.
sudo dnf module -qy disable postgresql
The command will run the DNF command on quiet mode and accept all gpg keys (-qy option) for PostgreSQL repositories.
2. After that, install the latest version of PostgreSQL 13.4 from the PostgreSQL repository using the dnf command below.
sudo dnf install postgresql13-server
Type ‘y‘ and press ‘Enter‘ to install the PostgreSQL 13.x.
Then wait for the PostgreSQL installation.
PostgreSQL Database Initialization
Next, after the PostgreSQL installation is complete, you must initialize the PostgreSQL configuration and then start and enable the PostgreSQL service.
1. Execute the following command to initialize the PostgreSQL database configuration.
sudo /usr/pgsql-13/bin/postgresql-13-setup initdb
2. After that, start and enable the PostgreSQL service using the command below.
sudo systemctl enable postgresql-13
sudo systemctl start postgresql-13
Now the PostgreSQL service is active and running, and it will run automatically on every boot.
3. Now execute the command below to verify the PostgreSQL service.
sudo systemctl status postgresql-13
If your PostgreSQL service is running, you will see the green output such as “active(running)” as below. Otherwise, you will see the red output such as “failed” following by the error message logs.
Securing PostgreSQL Deployment
During the installation, PostgreSQL will create a new system user and database user name as “postgres“. And for this stage, you will be setting up a new password for the “postgres” user, both for the system user and database user.
1. Change the password for default system user “postgres” using the following command.
passwd postgres
Now type the new password for the system user “postgres“.
2. Next, to change the password for the “postgres” database user, you must log in to the PostgreSQL shell.
First, log in as a system user “postgres” using the following command.
su - postgres
Now login to the PostgreSQL shell using the psql command below.
psql
Execute the following query to create a new password for the default “postgres” database user.
ALTER USER postgres WITH PASSWORD 'strongpostgrespassword';
Now type exit and press “Ctrl d” to exit and log out from the ‘postgres‘ user shell.
Change Authentication Method
By default, local PostgreSQL users will connect to the PostgreSQL shell using the ‘peer’ method. The peer authentication method will work only for local connections. In the development environment, you can use this type of authentication, but for production, consider using the password-based authentication method.
For this stage, you will learn how to change the default peer authentication method to password authentication using ‘scram-sha-256‘.Advertisement
1. First, log in to the PostgreSQL shell using the following command.
sudo -u postgres psql
Now execute the following query to check the location of the PostgreSQL configuration ‘pg_hba.conf‘.
SHOW hba_file;
SHOW password_encryption;
You will see the output as below.
You will notice the PostgreSQL configuration “pg_hba.conf” are located at the ‘/var/lib/pgsql/13/data‘ directory, and the default password encryption for PostgreSQL on RHEL based operating system is ‘scram-sha-256‘.
Now type ‘q’ to exit and quit the PostgreSQL shell.
2. Next, change the working directory to ‘/var/lib/pgsql/13/data‘ and edit the configuration ‘pg_hba.conf‘ using nano editor.
cd /var/lib/pgsql/13/data/
nano pg_hba.conf
At the bottom of the line, change the local authentication method to ‘scram-sha-256‘ as below.
# TYPE DATABASE USER ADDRESS METHOD# "local" is for Unix domain socket connections only
local all all scram-sha-256
# IPv4 local connections:
host all all 127.0.0.1/32 scram-sha-256
# IPv6 local connections:
host all all ::1/128 scram-sha-256
Now press ‘Ctrl x‘, type ‘y‘, and press “Enter” to save and exit.
Using this configuration, you will be prompted for the password to log in to the PostgreSQL shell.
3. Next, apply the new configuration by restarting the PostgreSQL service using the following command.
sudo systemctl restart postgresql-13
Now every time you want to access the PostgreSQL shell, you must type the password for authentication.
4. To make sure of the password authentication configuration, log in to the PostgreSQL shell using the following command.
su - postgres
psql
Now you will be asked for a password for the default user ‘postgres‘.
Type the password for the ‘postgres‘ database user and press ‘Enter‘. If your password is correct, you will see the PostgreSQL shell as follows. Otherwise, you will see the ‘FATAL‘ error because the password is incorrect.
Additionally, you can use the one-line command to log in to the PostgreSQL shell as below.
# Log in as default "postgres" user
sudo -u postgres psql# Log in as another user
sudo -u postgres psql -U username
Creating New User and Database for your Application
At this stage, you will learn how to create a new user and database on PostgreSQL.
1. Log in to the PostgreSQL shell by executing the command below.
sudo -u postgres psql
Now type the password for PostgreSQL user ‘postgres‘.
2. Run the PostgreSQL query below to create a new user ‘johndoe’ with the password ‘johndoestrongpassword’ and give the user privileges for creating a new database and role.
CREATE USER johndoe WITH
CREATEDB
CREATEROLE
PASSWORD 'johndoestrongpassword';
After that, verify the new user using the following query.
du
Now you will see the new user ‘johndoe’ with the list of roles ‘Create role‘ and ‘Create DB‘ as below.
3. Next, to create a new user database on PostgreSQL, run the following query.
CREATE DATABASE johndoe OWNER johndoe;
Now verify the new database using the following query.
l
And you will see the new database ‘johndoe’ with the owner ‘johndoe’ as the screenshot below.
Create Table and Insert Data
After creating a new database and user, you will learn how to create a table, input data, and showing data from the database.
1. Now log in to the PostgreSQL shell as user ‘johndoe’ using the following command.
su - postgres
psql -U johndoe
Or you can use the one-line command as below.
sudo -u postgres psql -U johndoe
Now type the password for PostgreSQL user ‘johndoe‘ and press ‘Enter‘ to login.
As you can see on the screenshot, you’re now logged in to the PostgreSQL shell at the database ‘johndoe=>‘.
2. Now execute the following query to create a new table ‘users’ with some columns ‘id, name, age, address, and salary’.
CREATE TABLE users (
id INT PRIMARY KEY NOT NULL,
name TEXT NOT NULL,
age INT NOT NULL,
address CHAR(50),
salary REAL
);
To display available tables on the current database, use the ‘d‘ query as ‘describe‘ as below.
d
To display columns on the table, you can use the same query following by the table name as below.
d users
Below is the similar output you will get.
3. Next, add new data to the table using the ‘insert‘ query as below.
INSERT INTO users (id,name,age,address,salary) VALUES (1, 'Paul', 32, 'California', 20000.00);
INSERT INTO users (id,name,age,address,salary) VALUES (2, 'Jesse', 35, 'Mexico', 30000.00);
INSERT INTO users (id,name,age,address,salary) VALUES (3, 'Linda', 27, 'Canada', 40000.00);
4. After that, you can show all available data using the ‘select‘ query as below.
SELECT * FROM users;
The option ‘*’ will dump all columns inside the table.
To specify the column, you can use the ‘select‘ query as below.
SELECT name,age,salary FROM users;
You will see a similar output as below.
Conclusion
Congratulations! Now you’ve learned how to install PostgreSQL on Rocky Linux. Also, you’ve learned how to deploy PostgreSQL in a secure way (minimal), and the basic usage of PostgreSQL queries for managing users, databases, and tables.
