Ubuntu更改下载源

## 1.备份原始源文件 sources.list

桌面打开终端，执行命令：sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak

## 2.修改源文件sources.list

（1）终端执行命令：sudo chmod 777 /etc/apt/sources.list更改文件权限使其可编辑；

（2）执行命令：sudo gedit /etc/apt/sources.list打开文件进行编辑；

（3）删除原来的文件内容，复制下面的任意一个到其中并保存（常用的是阿里源和清华源，推荐阿里源，内容可以去博客复制）；

阿里源：

`deb http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse

deb 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 main restricted universe multiverse

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

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

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

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