安装了第三方yum源后，就可以轻松安装某些预订的软件包了，比如网速监控的ifstat

首先查看你的centos 版本

cat /etc/redhat-release

一般都用64位的系统，不论521M的VPS，还是16G的独立服务器

CentOS-6

rpm -ivh http://apt.sw.be/redhat/el6/en/x86_64/rpmforge/RPMS/rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm

CentOS-7

wget http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.3-1.el7.rf.x86_64.rpm
rpm -Uvh rpmforge-release-0.5.3-1.el7.rf.x86_64.rpm
wget http://dag.wieers.com/rpm/packages/RPM-GPG-KEY.dag.txt
rpm –import RPM-GPG-KEY.dag.txt

wget http://ftp.tu-chemnitz.de/pub/linux/dag/redhat/el7/en/x86_64/rpmforge/RPMS/rpmforge-release-0.5.3-1.el7.rf.x86_64.rpm
rpm -Uvh rpmforge-release-0.5.3-1.el7.rf.x86_64.rpm

安装错了版本，怎样卸载？

rpm -e rpmforge-release