There are many repositories that you can add onto your RHEL/CENTOS/FEDORA OS to install additional software. full list of repos can be found here http://wiki.centos.org/AdditionalResources/Repositories
however is it safe to just add the repos and start installing packages? yes and no. We will configure priorities to setup the repos to keep packages from conflicting. Also you will want to protect the base OS installation so that there is less corruption/conflicts later on.
step 1 – install the plugin if its not installed already
yum install -y yum-plugin-priorities yum-plugin-protectbase
step 2 – setup priorities
for *-Base.repo that came with your OS you want to set all the enabled repo to be
priority=1 for epel.repo and rpmforge you will want to set it priority=10
My repos look like this
[base]
name=CentOS-$releasever - Base
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
protect=1
priority=1
#released updates
[updates]
name=CentOS-$releasever - Updates
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates
#baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
protect=1
priority=1
[epel]
name=Extra Packages for Enterprise Linux 6 - $basearch
#baseurl=http://download.fedoraproject.org/pub/epel/6/$basearch
mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-6&arch=$basearch
failovermethod=priority
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6
protect=0
priority=10
[rpmforge]
name = RHEL $releasever - RPMforge.net - dag
baseurl = http://apt.sw.be/redhat/el6/en/$basearch/rpmforge
mirrorlist = http://mirrorlist.repoforge.org/el6/mirrors-rpmforge
#mirrorlist = file:///etc/yum.repos.d/mirrors-rpmforge
enabled = 1
gpgkey = file:///etc/pki/rpm-gpg/RPM-GPG-KEY-rpmforge-dag
gpgcheck = 1
protect=0
priority=10
of course you can add additional repos and set different priorities to fit your needs but above is what i have configured
