centos7更新yum源和遇到的问题

• 首先备份

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

mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup

• 进入yum源配置文件所在文件夹

[root@localhost yum.repos.d]# cd /etc/yum.repos.d/

• 下载163的yum源配置文件，放入/etc/yum.repos.d/(操作前请做好相应备份)

[root@localhost yum.repos.d]# wget http://mirrors.163.com/.help/CentOS6-Base-163.repo

（CentOS 5
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-5.repo

CentOS 6

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo

CentOS 7

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo）

• 运行yum makecache生成缓存

[root@localhost yum.repos.d]# yum makecache

• 更新系统

[root@localhost yum.repos.d]# yum -y update

错误总结：

• Cannot retrieve metalink for repository: epel…错误解决办法
  RHEL6下yum -y install epel-release安装了epel源,但yum makecache出错。

centos下安装完EPEL源然后更新一下yum缓存如果发现这样的错误:
Error: Cannot retrieve metalink for repository: epel. Please verify its path and try again
这就表明你需要更新CA证书了，那么只需要更新CA证书就可以，不过在此同时需要临时禁用epel源并更新就可以了，命令如下：

yum --disablerepo=epel -y update ca-certificates

• [yum安装时出现：Cannot retrieve metalink for repository: epel. Please verify its path and try again]

在CentOS下安装出现了问题：Error: Cannot retrieve metalink for repository: epel. Please verify its path and try again，需要安装epel源。

解决方法： 一句话：把/etc/yum.repos.d/epel.repo，文件第3行注释去掉，把第四行注释掉。具体如下：

打开/etc/yum.repos.d/epel.repo，将

[epel]
name=Extra Packages for Enterprise Linux 6 - $basearch

baseurl=http://download.fedoraproject.org/pub/epel/6/$basearch

mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-6&arch=$basearch
修改为

[epel]
name=Extra Packages for Enterprise Linux 6 - basearch

mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=epel-6&arch=$basearch

再清理源，重新安装

yum clean all
yum install -y 需要的包

如果还是不行，修改DNS,到/etc/resolv.conf下添加一下：

nameserver 8.8.8.8
search localdomain

然后重启network服务：service network restart

参考：（https://www.cnblogs.com/dadong616/p/5062727.html）
（https://www.cnblogs.com/shenlanzhizun/p/7683166.html）