修改/etc/yum.repos.d/CentOS-Base.repo，将镜象站点地址改为在中国的镜象站点地址。不然我们通过yum安装软件速度会比较慢。
以下的URL地址我都验证过了在当前完全可以下载，而且速度挺快。
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.bak
vi /etc/yum.repos.d/CentOS-Base.repo
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# CentOS-Base.repo
#
# This file uses a new mirrorlist system developed by Lance Davis for CentOS.
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client. You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the
# remarked out baseurl= line instead.
#
#
[base]
name=CentOS-$releasever - Base
baseurl=http://mirror.be10.com/centos/$releasever/os/$basearch/
$releasever/os/$basearch/
$releasever/os/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos4
#released updates
[update]
name=CentOS-$releasever - Updates
baseurl=http://mirror.be10.com/centos/$releasever/os/$basearch/
$releasever/os/$basearch/
$releasever/os/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos4
#packages used/produced in the build but not released
[addons]
name=CentOS-$releasever - Addons
baseurl=http://mirror.be10.com/centos/$releasever/os/$basearch/
$releasever/os/$basearch/
$releasever/os/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos4
#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
baseurl=http://mirror.be10.com/centos/$releasever/os/$basearch/
$releasever/os/$basearch/
$releasever/os/$basearch/
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos4
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
baseurl=http://mirror.centos.org/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos4
#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib
baseurl=http://mirror.centos.org/centos/$releasever/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos4