Ubuntu默认的软件更新源是国外的，在国内使用速度很慢，因此需要更换国内源。本文以阿里源为例进行更换。
Ubuntu16.04更换阿里源
1、备份原始源文件sources.list
sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak
2、更改原始源文件sources.list
#更改文件权限使其可编辑。
sudo chmod 666 /etc/apt/sources.list
#打开文件进行编辑。
sudo gedit /etc/apt/sources.list
#将sources.list文件的原始内容删去，输入以下内容，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-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ xenial main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ xenial-backports main restricted universe multiverse
3、将源更新
sudo apt-get update
Ubuntu18.04更换阿里源
1、备份原始源文件sources.list
sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak
2、更改原始源文件sources.list
#更改文件权限使其可编辑。
sudo chmod 666 /etc/apt/sources.list
#打开文件进行编辑。
sudo gedit /etc/apt/sources.list
#将sources.list文件的原始内容删去，输入以下内容，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
3、将源更新
sudo apt-get update