CentOS系统下用yum upgrade命令只能升级到最新版本，CentOS仓库并不维护历史版本，所以只能使用 vault.centos.org 历史版本快照进行更新。
1、备份旧的版本仓库文件：
mkdir -p /etc/yum.repos.d/backup
mv /etc/yum.repos.d/*.repo /etc/yum.repos.d/backup/
2、创建要升级到版本(7.2.1511)的Vault版本仓库文件：
vim /etc/yum.repos.d/CentOS-Vault.repo
# CentOS Vault contains rpms from older releases in the CentOS-7
# tree.
# C7.2.1511
[C7.2.1511-base]
name=CentOS-7.2.1511 - Base
baseurl=http://vault.centos.org/7.2.1511/os/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=1
[C7.2.1511-updates]
name=CentOS-7.2.1511 - Updates
baseurl=http://vault.centos.org/7.2.1511/updates/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=1
[C7.2.1511-extras]
name=CentOS-7.2.1511 - Extras
baseurl=http://vault.centos.org/7.2.1511/extras/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=1
[C7.2.1511-centosplus]
name=CentOS-7.2.1511 - CentOSPlus
baseurl=http://vault.centos.org/7.2.1511/centosplus/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=1
[C7.2.1511-fasttrack]
name=CentOS-7.2.1511 - Fasttrack
baseurl=http://vault.centos.org/7.2.1511/fasttrack/$basearch/
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
enabled=1
3、查看现在可用仓库列表：
yum repolist
4、查看现在可用仓库版本：
yum list updates | grep "centos-release"
5、清空本地缓存：
yum clean all
rm -rf /var/cache/yum
6、版本升级：
yum -y update
7、备份过渡的Vault仓库文件，启用新版的仓库文件：
mv /etc/yum.repos.d/CentOS-Vault.repo /etc/yum.repos.d/backup/
mv /etc/yum.repos.d/CentOS-Vault.repo.rpmnew /etc/yum.repos.d/CentOS-Vault.repo
8、清空本地缓存，更新版本库文件：
yum clean all
yum makecache
备注 需要哪个版本就把版本号改成需要的版本就行