1、原文件备份

sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak

2、编辑源列表文件

sudo vim /etc/apt/sources.list

3、将原来的列表删除，添加如下内容（阿里镜像源）

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-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multivers
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

4、运行 sudo apt-get update

5、如果出现以下错误：

	E: 无法获得锁 /var/lib/apt/lists/lock - open (11: 资源暂时不可用)
	E: 无法对目录 /var/lib/apt/lists/ 加锁

是因为上一次更新源的时候非常规中断导致的,解决方法如下:

sudo rm /var/lib/apt/lists/lock