更改Ubuntu源

今天在云服务器上安装软件特别卡，有的时候还失败。上网查了一下，有网友说更新一下源再安装就好了。现在记录一下更新的过程。

1、在修改之前记得先备份一份
cp /etc/apt/sources.list /etc/apt/sources.list.backup

2、修改源列表为中国科技大学的源
删除source.list文件中的源，将下面的直接复制过去。

# USTC (University of Science and Technology of Thina)
# xenial is ubuntu 16.04 version #根据系统版本修改
deb http://mirrors.ustc.edu.cn/ubuntu/ xenial main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ xenial-security main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ xenial-proposed main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ xenial main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ xenial-security main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ xenial-proposed main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse

3、查看源地址：http://mirrors.ustc.edu.cn/ubuntu/dists/

4、Ubuntu各版本与代号对照表

4、查看自己的系统版本

5、修改源为对应的版本
# USTC (University of Science and Technology of Thina)
# bionic is ubuntu 18.04 version
deb http://mirrors.ustc.edu.cn/ubuntu/ bionic main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ bionic-security main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse
deb http://mirrors.ustc.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ bionic main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ bionic-security main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse
deb-src http://mirrors.ustc.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse

6、好了，我的三丰云服务器源修改完成