yum配置163的yum源(Centos6.9为例)
yum安装需要访问外网，因此需要查看DNS是否配置好，和防火墙是否关闭。
下载163的repo文件
先进入到放yum源文件的目录，需要root用户
cd /etc/yum.repos.d
下载repo文件
wget http://mirrors.163.com/.help/CentOS6-Base-163.repo
编辑yum源repo文件
把文件里面的$releasever全部替换为版本号: 6.9(先不用替换，如果不行再替换试试)，如果系统变量有$releasever这个变量,那么就不需要替换。
yum中$releasever、 $basearch等变量含义
vim CentOS6-Base-163.repo
name=CentOS-$releasever - Base - 163.com
baseurl=http://mirrors.163.com/centos/6.9/os/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
#released updates
[updates]
name=CentOS-$releasever - Updates - 163.com
baseurl=http://mirrors.163.com/centos/6.9/updates/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras - 163.com
baseurl=http://mirrors.163.com/centos/6.9/extras/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras
gpgcheck=1
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus - 163.com
baseurl=http://mirrors.163.com/centos/6.9/centosplus/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib - 163.com
baseurl=http://mirrors.163.com/centos/6.9/contrib/$basearch/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=contrib
gpgcheck=1
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
清理并重建缓存(很重要)
yum clean all
yum makecache fast
测试yum源是否可用
yum -y install gcc