默认.repo文件中的源为国外的网址，下载速度较慢，可以更换国内源
步骤：
1 删除原来的.repo文件
2 下载国内源的.repo文件到yum.repos.d目录下
[root@hyc-01-01 ~]# curl -O http://mirrors.163.com/.help/CentOS7-Base-163.repo
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 1572 100 1572 0 0 9860 0 --:--:-- --:--:-- --:--:-- 9886
[root@hyc-01-01 ~]# ls
anaconda-ks.cfg CentOS7-Base-163.repo
[root@hyc-01-01 ~]# cp CentOS7-Base-163.repo /etc/yum.repos.d
[root@hyc-01-01 ~]# cd !$
cd /etc/yum.repos.d
[root@hyc-01-01 yum.repos.d]# ls
CentOS7-Base-163.repo CentOS-fasttrack.repo CentOS-Vault.repo
CentOS-CR.repo CentOS-Media.repo
CentOS-Debuginfo.repo CentOS-Sources.repo
[root@hyc-01-01 yum.repos.d]# mv CentOS7-Base-163.repo CentOS7-Base-163.repo.123
修改.repo文件名导致系统无法识别
[root@hyc-01-01 yum.repos.d]# yum install zsh zsh无法正常安装
已加载插件：fastestmirror
Loading mirror speeds from cached hostfile
There are no enabled repos.
Run "yum repolist all" to see the repos you have.
To enable Red Hat Subscription Management repositories:
subscription-manager repos --enable <repo>
To enable custom repositories:
yum-config-manager --enable <repo>
[root@hyc-01-01 yum.repos.d]# yum repolist all 此时查看仓库发现所有仓库处于禁用状态
[root@hyc-01-01 yum.repos.d]# mv CentOS7-Base-163.repo.123 CentOS7-Base-163.repo 改回原来正确的文件名
[root@hyc-01-01 yum.repos.d]# yum clean all 清理yum缓存
已加载插件：fastestmirror
Repodata is over 2 weeks old. Install yum-cron? Or run: yum makecache fast
正在清理软件源： base extras updates
Cleaning up everything
Maybe you want: rm -rf /var/cache/yum, to also free up space taken by orphaned data from disabled or removed repos
Cleaning up list of fastest mirrors
[root@hyc-01-01 yum.repos.d]# yum install zsh 此时zsh可以正常安装，由于先前清空了缓存，此时会重新生成缓存
[root@hyc-01-01 yum.repos.d]# yum repolist all 此时与163.com有关的源为启用状态
[root@hyc-01-01 yum.repos.d]# yum list 查看发现出现了base仓库中的包
7.7 yum下载rpm包
7.8 源码包安装 上
7.9 源码包安装 下
原文：http://blog.51cto.com/12216458/2133950