Good day to you!
Repositories – are structured storages of software packages for Linux operating systems. By default, in CentOS standard repositories are installed, which contain not all the necessary programs.
Besides the standard ones, there are lots of other repositories, some of which contain program collections, others are specialized ones.
If you don’t know which programs you may need, you should install one of (or all) the most popular repositories - EPEL, RPMFORGE or REMI; further, I will tell you about each of them.
Specialized repositories are meant for installing and updating specific software. For example, MariaDB and Nginx have their own repositories (please, turn to the articles for details: Installing and configuring NGINX + PHP (php-fpm) on a Linux server, How to install MariaDB on Linux server - a guide).
Installation of CentOS additional repositories
EPEL repository
The repository’s full name - Extra Packages for Enterprise Linux; it has been created by developers specially for Fedora operating system and supports CentOS, RHEL and Oracle Linux.
The packages of this repository don’t conflict with official CentOS packages and don’t erase them. Therefore, it is the first repository recommended for installing.
To install EPEL in CentOS, type in the command:
yum -y install epel-release

After this simple action, yum program will see all the packages of this great repository.
Rpmforge repository
Another extremely popular repository. CentOS developers don’t recommend to use it, as it is not updated anymore and can erase official CentOS packages. But if you need some kind of rare software, you can use it with great care.
To install rpmforge repository, follow this simple instruction:
- Proceed to the project site and copy the link to the architecture you need to exchange buffer.
- Execute the following commands:
rpm --import http://apt.sw.be/RPM-GPG-KEY.dag.txt
yum -y install [the copied link]
REMI repository
This repository’s packages erase the official ones; therefore you should use it very carefully. But if, due to some reasons, you need the latest PHP and MySQL assembles – this is the repository for you.
Installation:
wget http://rpms.remirepo.net/enterprise/remi-release-7.rpm
rpm -Uvh remi-release-7*.rpm
If you have any questions or need more details - please, ask a question or leave a comment.