今天在ESC上安装mariaDB，发现centOS 7默认的yum源上的mariaDB版本过低，然后又镜像到网易上，发现网易源上没有mariaDB，几经折腾才发现阿里镜像上mariaDB版本较新。更改镜像源之前先备份原来的镜像源文件，执行如下命令：
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/ContOS-Base.repo_backup
在centos 7系统下：
vi /etc/yum.repos.d/CentOS-Base.repo
全新插入如下内容并保存，即可成为阿里云镜像源：
# 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-$releasever - Base - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/os/$basearch/
http://mirrors.aliyuncs.com/centos/$releasever/os/$basearch/
http://mirrors.cloud.aliyuncs.com/centos/$releasever/os/$basearch/
gpgcheck=
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7 #released updates
[updates]
name=CentOS-$releasever - Updates - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/updates/$basearch/
http://mirrors.aliyuncs.com/centos/$releasever/updates/$basearch/
http://mirrors.cloud.aliyuncs.com/centos/$releasever/updates/$basearch/
gpgcheck=
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7 #additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/extras/$basearch/
http://mirrors.aliyuncs.com/centos/$releasever/extras/$basearch/
http://mirrors.cloud.aliyuncs.com/centos/$releasever/extras/$basearch/
gpgcheck=
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7 #additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/centosplus/$basearch/
http://mirrors.aliyuncs.com/centos/$releasever/centosplus/$basearch/
http://mirrors.cloud.aliyuncs.com/centos/$releasever/centosplus/$basearch/
gpgcheck=
enabled=
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7 #contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/contrib/$basearch/
http://mirrors.aliyuncs.com/centos/$releasever/contrib/$basearch/
http://mirrors.cloud.aliyuncs.com/centos/$releasever/contrib/$basearch/
gpgcheck=
enabled=
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7