yum源更换为阿里源及制作yum本地源

一.更换yum源为阿里源

1.由于centos自带的yum源在国内使用时有时候速度会很慢，导致yum在线安装速度缓慢。这时候就需要yum源为国内的一些镜像站点。

2.首先访问阿里云镜像站点：http://mirrors.aliyun.com

3.选择对应的linux发行版（此次使用CentOS Linux release 7.4.1708进行测试）

4.进入7.6.1810版本，此次准备创建4个repo
1）os/：即发行版光盘上附带的所有基础rpm包
2）updates/ ：所有更新的rpm包
3）extras/ ：附带的一些额外包
4）centosplus/ ：额外增添的一些包

5.找到repodata所在目录并记录其路径：

6.repo的配置文件在/etc/yum.repos.d/*repo，制作名称为CentOS-Base.repo；并将之前的CentOS-Base.repo更改为CentOS-Base.repo.apk
1）开始编辑CentOS-Base.repo文件

[aliyun]      仓库ID
name=this is os repo  仓库介绍
baseurl=https://mirrors.aliyun.com/centos/$releasever/os/$basearch/       repo链接，$releasever为版本号，$basearch为基础架构
enabled=1     开启仓库
gpgcheck=1    检查其rpm包的合法性及完整性
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7      秘钥地址

7.依据上面步骤添加剩余三个仓库，并且将网易镜像链接也添加进来做防范措施.。

[aliyun]
name=this is os repo
failovermethod=priority    出错防范措施，为顺序执行
baseurl=https://mirrors.aliyun.com/centos/$releasever/os/$basearch/https://mirrors.163.com/centos/$releasever/os/$basearch
enabled=1
gpgcheck=1
gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
#https://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-7[updates]
name=this is updates repo
failovermethod=priority
baseurl=https://mirrors.aliyun.com/centos/$releasever/updates/$basearch/https://mirrors.163.com/centos/$releasever/updates/$basearch
enabled=1
gpgcheck=1
gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
#https://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-7[centosplus]
name=this is centosplus repo
failovermethod=priority
baseurl=https://mirrors.aliyun.com/centos/$releasever/centosplus/$basearch/https://mirrors.163.com/centos/$releasever/centosplus/$basearch
enabled=1
gpgcheck=1
gpgkey=https://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
#https://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-7[extras]
name=this is extras repo
failovermethod=priority
baseurl=https://mirrors.aliyun.com/centos/$releasever/extras/$basearch/https://mirrors.163.com/centos/$releasever/extras/$basearch
enabled=1
gpgcheck&