因为 Linux 服务器源都是在国外的，以至于我们有时候更新很慢，甚至无法访问。要解决这个问题，我们可以把默认源改为阿里云、腾讯等国内 Yum 源，会极大的改善更新缓慢或者失败的问题。
CentOS 7 yum源配置
rm -rf /etc/yum.repos.d/*.repo #删除repo文件，或者自己备份
curl -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
curl -o /etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-7.repo
yum makecache #更新缓存
CentOS 6 yum源
rm -rf /etc/yum.repos.d/*.repo #删除repo文件，或者自己备份
curl -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo
curl -o/etc/yum.repos.d/epel.repo http://mirrors.aliyun.com/repo/epel-6.repo
yum makecache #更新缓存
Ubuntu 18 apt源
mv /etc/apt/sources.list{,bak} #备份sources.list
cat > /etc/apt/sources.list << EOF
deb http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse
EOF
apt update
Ubuntu 16 apt源
mv /etc/apt/sources.list{,bak} #备份sources.list
cat > /etc/apt/sources.list << EOF
deb http://mirrors.aliyun.com/ubuntu/ xenial main
deb-src http://mirrors.aliyun.com/ubuntu/ xenial main
deb http://mirrors.aliyun.com/ubuntu/ xenial-updates main
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-updates main
deb http://mirrors.aliyun.com/ubuntu/ xenial universe
deb-src http://mirrors.aliyun.com/ubuntu/ xenial universe
deb http://mirrors.aliyun.com/ubuntu/ xenial-updates universe
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-updates universe
deb http://mirrors.aliyun.com/ubuntu/ xenial-security main
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-security main
deb http://mirrors.aliyun.com/ubuntu/ xenial-security universe
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-security universe
EOF
apt update
Debian 9 apt源
mv /etc/apt/sources.list{,bak} #备份sources.list
cat > /etc/apt/sources.list << EOF
deb http://mirrors.aliyun.com/debian/ stretch main non-free contrib
deb-src http://mirrors.aliyun.com/debian/ stretch main non-free contrib
deb http://mirrors.aliyun.com/debian-security stretch/updates main
deb-src http://mirrors.aliyun.com/debian-security stretch/updates main
deb http://mirrors.aliyun.com/debian/ stretch-updates main non-free contrib
deb-src http://mirrors.aliyun.com/debian/ stretch-updates main non-free contrib
deb http://mirrors.aliyun.com/debian/ stretch-backports main non-free contrib
deb-src http://mirrors.aliyun.com/debian/ stretch-backports main non-free contrib
EOF
apt update
Debian 8 apt源
mv /etc/apt/sources.list{,bak} #备份sources.list
cat > /etc/apt/sources.list << EOF
deb http://mirrors.aliyun.com/debian/ jessie main non-free contrib
deb http://mirrors.aliyun.com/debian/ jessie-proposed-updates main non-free contrib
deb-src http://mirrors.aliyun.com/debian/ jessie main non-free contrib
deb-src http://mirrors.aliyun.com/debian/ jessie-proposed-updates main non-free contrib
EOF
apt update
再推荐几个国内yum源网站：
不用试了，不能用。ec2的源都自定义了。
你确定你这么配置上能用？？？
不确定！转载留用的，还没试过。