0.首先附上本地centos7.0yun源基础地址及epel源地址：
[base-local]
name=CentOS-$releasever – Base
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os&infra=$infra
baseurl=http://172.16.1.254/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
priority=1
#released updates
[updates-local]
name=CentOS-$releasever – Updates
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates&infra=$infra
baseurl=http://172.16.1.254/centos/$releasever/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
priority=1
#additional packages that may be useful
[extras-local]
name=CentOS-$releasever – Extras
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras&infra=$infra
baseurl=http://172.16.1.254/centos/$releasever/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
priority=1
#additional packages that extend functionality of existing packages
[centosplus-local]
name=CentOS-$releasever – Plus
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus&infra=$infra
baseurl=http://172.16.1.254/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
priority=1
1.安装源的优先级支持：
# yum install yum-plugin-priorities
2.修改/etc/yum.repos.d目录中的CentOS-Base.repo、CentOS-local.repo的优先级
//直接加上priority=N即可
3.验证
yum clean all #清除缓存
yum makecache #生成缓存
