Installing additional repositories is not necessarily considered to be a troubleshooter's task, but it does serve to alleviate many issues regarding package dependencies and attempts to keep your system relevant within a Dev/Ops environment.
In the following text, I have included instructions for some of the most popular repositories. However, you should realize that the locations of these repositories will be different for alternative versions of CentOS, and that these links will be updated over time. Additional information can be found at the end of this chapter for future reference.
The Extra Packages for Enterprise Linux (EPEL) repository provides useful software packages that are not included in the official CentOS Linux repositories, some of which will be covered in the following chapters of this book. It is also a requirement for many other third-party repositories.
For CentOS 7, you should follow this procedure to install the EPEL repository...