centos使用 YUM升级

把YUM的升级点改成这个镜像站：
#vi /etc/yum.repos.d/CentOS-Base.repo
把文件里的内容改成以下就可以了
[base]
name=CentOS-$releasever - Base
baseurl=
gpgcheck=1
gpgkey=

#released updates
[update]
name=CentOS-$releasever - Updates
baseurl=
gpgcheck=1
gpgkey=

#packages used/produced in the build but not released
[addons]
name=CentOS-$releasever - Addons
baseurl=
gpgcheck=1
gpgkey=

#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
baseurl=
gpgcheck=1
gpgkey=

#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
baseurl=
gpgcheck=1
enabled=0
gpgkey=

#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib
baseurl=
gpgcheck=1
enabled=0
gpgkey=