添加DNS，yum源并更新

echo "nameserver 8.8.8.8">>/etc/resolv.conf
mkdir -p /tmp/bak/
mv -f /etc/yum.repos.d/* /tmp/bak/
cat >/etc/yum.repos.d/CentOS6.repo <<EOF
# CentOS-Base.repo
#
# 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-6 - Base - 163.com
baseurl=http://mirrors.163.com/centos/6/os/\$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6&arch=$basearch&repo=os
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6

#released updates 
[updates]
name=CentOS-6 - Updates - 163.com
baseurl=http://mirrors.163.com/centos/6/updates/\$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6&arch=$basearch&repo=updates
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6

#additional packages that may be useful
[extras]
name=CentOS-6 - Extras - 163.com
baseurl=http://mirrors.163.com/centos/6/extras/\$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6&arch=$basearch&repo=extras
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6

#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-6 - Plus - 163.com
baseurl=http://mirrors.163.com/centos/6/centosplus/\$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6&arch=$basearch&repo=centosplus
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6

#contrib - packages by Centos Users
[contrib]
name=CentOS-6 - Contrib - 163.com
baseurl=http://mirrors.163.com/centos/6/contrib/\$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=6&arch=$basearch&repo=contrib
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
EOF

cd /etc/yum.repos.d
wget http://mirrors.163.com/.help/CentOS6-Base-163.repo
mv CentOS6-Base-163.repo CentOS-Base.repo
yum clean all
yum makecache