You might have installed RHEL operating system, but you should have registered to Red Hat Network for using its repository. In such case, you will not be able to use yum and not all packages are easy to install from source (especially if the package has plenty of dependencies !). Thankfully, you can make CentOS repository on RHEL machines and then yum to resolve those dependencies automatically.
First you need to add the CentOS repository, create this file using your favorite text editor:
[root@localhost ~]# vi /etc/yum.repos.d/centos.repo
Adding the following contents, note the ‘5’ has to be hardcoded to either 5 or 6 depending on your RHEL version.
name=CentOS $releasever – $basearch
Once you’ve completed this step, you can now use “yum” to install CentOS packages.