CentOS更换yum源

# cd /etc/yum.repos.d 

#备份默认yum源

# cp CentOS-Base.repo CentOS-Base.repo_bak

 #下载网易源，阿里源不行，至少现在很垃圾

# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.163.com/.help/CentOS7-Base-163.repo  

 #清除系统所有yum源 

# yum clean all 

 #生成yum缓存

# yum makecache 

#安装epel源

# yum list | grep epel-release.noarch

# yum install epel-release.noarch  

#查看系统可用的yum源 

# yum repolist enabled 

# yum repolist all