1、 yum install yum-priorities
2、 确认/etc/yum/pluginconf.d/priorities.conf 中enabled=1
3、 修改/etc/yum.repos.d/centos_base.repo
[base], [addons], [updates], [extras]节点添加 priority=1
[centosplus],[contrib]节点添加 priority=2
4、 wget wget http://apt.sw.be/redhat/el5/en/i386/rpmforge/RPMS/rpmforge-release-0.5.2-2.el5.rf.i386.rpm
5、 rpm –import http://apt.sw.be/RPM-GPG-KEY.dag.txt
6、 rpm -K rpmforge-release-0.5.2-2.el5.rf.i386.rpm
7、 rpm -i rpmforge-release-0.5.2-2.el5.rf.i386.rpm
8、 yum install mercurial