yum mirrorlist

vi /etc/yum.repos.d/CentOS-Base.repo

[base]
name=CentOS-$releasever - Base
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
#baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/
baseurl=http://mirrors.163.com/centos/$releasever/os/$basearch/

http://mirrors.ta139.com/centos/$releasever/os/$basearch/

http://centos.ustc.edu.cn/centos/$releasever/os/$basearch/

http://mirror.neu.edu.cn/centos/$releasever/os/$basearch/

gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6

#released updates
[updates]
name=CentOS-$releasever - Updates
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates
#baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/
baseurl=http://mirrors.163.com/centos/$releasever/updates/$basearch/

http://mirrors.ta139.com/centos/$releasever/updates/$basearch/

http://centos.ustc.edu.cn/centos/$releasever/updates/$basearch/

http://mirror.neu.edu.cn/centos/$releasever/updates/$basearch/

gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6

#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras
#baseurl=http://mirror.centos.org/centos/$releasever/extras/$basearch/
baseurl=http://mirrors.163.com/centos/$releasever/extras/$basearch/

http://mirrors.ta139.com/centos/$releasever/extras/$basearch/

http://centos.ustc.edu.cn/centos/$releasever/extras/$basearch/

http://mirror.neu.edu.cn/centos/$releasever/extras/$basearch/

gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6

#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus
#baseurl=http://mirror.centos.org/centos/$releasever/centosplus/$basearch/
baseurl=http://mirrors.163.com/centos/$releasever/centosplus/$basearch/

http://mirrors.ta139.com/centos/$releasever/centosplus/$basearch/

http://centos.ustc.edu.cn/centos/$releasever/centosplus/$basearch/

http://mirror.neu.edu.cn/centos/$releasever/centosplus/$basearch/

gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6

#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib
mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=contrib
#baseurl=http://mirror.centos.org/centos/$releasever/contrib/$basearch/
baseurl=http://mirrors.163.com/centos/$releasever/contrib/$basearch/

http://mirrors.ta139.com/centos/$releasever/contrib/$basearch/

http://centos.ustc.edu.cn/centos/$releasever/contrib/$basearch/

http://mirror.neu.edu.cn/centos/$releasever/contrib/$basearch/

gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6

rpm –import /etc/pki/rpm-gpg-key*

yum upgrade