可以联网：yum 好用：

方法1 好用：

(2)添加软件源进行加速
curl  -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
​
(3)安装epel软件源
curl  -o /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-7.repo
​

# 方法2：修改yum源

1) 安装wget & 安装epel第三方源
yum install -y wget
yum install epel-release

2) 备份/etc/yum.repos.d/CentOS-Base.repo文件
cd /etc/yum.repos.d/
mv CentOS-Base.repo CentOS-Base.repo.back

3) 下载阿里云的Centos-6.repo文件
# 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


4) 重新加载yum
yum clean all
yum makecache fast

二、 yum 失效 wget 不能使用

cd /etc/yum.repos.d/

 mv CentOS-Base.repo CentOS-Base.repo.back

将etc/yum.repos.d/CentOS-Base.repo 内容替换为以下内容：

替换为：

[base]
name=CentOS-$releasever - Base - mirrors.aliyun.com
baseurl=http://mirrors.aliyun.com/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7

[updates]
name=CentOS-$releasever - Updates - mirrors.aliyun.com
baseurl=http://mirrors.aliyun.com/centos/$releasever/updates/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7

[extras]
name=CentOS-$releasever - Extras - mirrors.aliyun.com
baseurl=http://mirrors.aliyun.com/centos/$releasever/extras/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7

[centosplus]
name=CentOS-$releasever - Plus - mirrors.aliyun.com
baseurl=http://mirrors.aliyun.com/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7

清理缓存：

sudo yum clean all
sudo yum makecache
sudo yum update