备份一下Ubuntu 原来的源地址列表文件
sudo cp /etc/apt/sources.list /etc/apt/sources.list.old
在终端 cd /etc/apt 修改文件sources.list
sudo vim sources.list
把文件的源替换成阿里源
deb http://mirrors.aliyun.com/ubuntu/ xenial main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse
![sudo apt-get update 出错 Updating from such a repository can‘t be done securely, and is therefore[图]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)