Using yum works fine for installing software that is provided as part of CentOS, but what about if you want to install a software package that isn't provided by CentOS? This is where 3rd party repositories come in. A vast amount of software has been packaged and is maintained by the packagers and placed into 3rd party software repositories such that it can be installed using YUM. Please read the Wiki page on repositories here:
RPMForge and ATrpms are two of the larger 3rd party repositories that provide software packages for CentOS. However, before we can use any additional repositories, we must first configure them. There is a Wiki page on how to configure RPMForge here:
The default RPMforge repository does not replace any CentOS base packages. In the past it used to, but those packages are now in a separate repository (rpmforge-extras) which is disabled by default.
You can find a complete listing of the RPMforge package packages at http://packages.sw.be/
Download the rpmforge-release package. Choose one of the two links below, selecting to match your host's architecture. If you are unsure of which one to use you can check your architecture with the command uname -i
The preferred rpmforge-release package to retrieve and to install in order to enable that repository is one of the two listed above.
Install DAG's GPG key
rpm --import http://apt.sw.be/RPM-GPG-KEY.dag.txt
If you get an error message like the following the key has already been imported:
error: http://apt.sw.be/RPM-GPG-KEY.dag.txt: key 1 import failed.
Verify the package you have downloaded
rpm -K rpmforge-release-0.5.2-2.el6.rf.*.rpm
Security warning: The rpmforge-release package imports GPG keys into your RPM database. As long as you have verified the md5sum of the key injection package, and trust Dag, et al., then it should be as safe as your trust of them extends.
Install the package
rpm -i rpmforge-release-0.5.2-2.el6.rf.*.rpm
This will add a yum repository config file and import the appropriate GPG keys.
Then try to install something like this
yum install htop