安装Ubuntu20.04系统后，下载安装软件包使用默认的国外源太慢了，因此我们可以把源修改为国内源这个样会快很多。

1、首先以root用户登录主机。

2、进入源文件目录。
root@lanan:~# cd /etc/apt

root@lanan:/etc/apt#

3、保险起见先备份一下原来的源文件，避免更换出问题可以还原回去哈哈哈。
root@lanan:/etc/apt# cp sources.list sources.list.bak

4、修改源。
root@lanan:/etc/apt# vi sources.list
国外源：

然后把国外源删除或用#注释后更换成我们想要的国内源，这里我修改为阿里源。
阿里源：

5、最后更新下源和软件。（第一次更新有点慢耐心等待！更新完我们下载安装软件包就会快很多了）

root@lanan:/etc/apt# apt update
root@lanan:/etc/apt# apt upgrade
6、附：常用源。
阿里源：
deb http://www.landui.com/ubuntu/ bionic main restricted universe multiverse

deb-src http://www.landui.com/ubuntu/ bionic main restricted universe multiverse

deb http://www.landui.com/ubuntu/ bionic-security main restricted universe multiverse

deb-src http://www.landui.com/ubuntu/ bionic-security main restricted universe multiverse

deb http://www.landui.com/ubuntu/ bionic-updates main restricted universe multiverse

deb-src http://www.landui.com/ubuntu/ bionic-updates main restricted universe multiverse

deb http://www.landui.com/ubuntu/ bionic-proposed main restricted universe multiverse

deb-src http://www.landui.com/ubuntu/ bionic-proposed main restricted universe multiverse

deb http://www.landui.com/ubuntu/ bionic-backports main restricted universe multiverse

deb-src http://www.landui.com/ubuntu/ bionic-backports main restricted universe multiverse

中科大源：
deb https://www.landui.com/ubuntu/ bionic main restricted universe multiverse

deb-src https://www.landui.com/ubuntu/ bionic main restricted universe multiverse

deb https://www.landui.com/ubuntu/ bionic-updates main restricted universe multiverse

deb-src https://www.landui.com/ubuntu/ bionic-updates main restricted universe multiverse

deb https://www.landui.com/ubuntu/ bionic-backports main restricted universe multiverse

deb-src https://www.landui.com/ubuntu/ bionic-backports main restricted universe multiverse

deb https://www.landui.com/ubuntu/ bionic-security main restricted universe multiverse

deb-src https://www.landui.com/ubuntu/ bionic-security main restricted universe multiverse

deb https://www.landui.com/ubuntu/ bionic-proposed main restricted universe multiverse

deb-src https://www.landui.com/ubuntu/ bionic-proposed main restricted universe multiverse

清华源：
deb https://www.landui.com/ubuntu/ bionic main restricted universe multiverse

deb-src https://www.landui.com/ubuntu/ bionic main restricted universe multiverse

deb https://www.landui.com/ubuntu/ bionic-updates main restricted universe multiverse

deb-src https://www.landui.com/ubuntu/ bionic-updates main restricted universe multiverse

deb https://www.landui.com/ubuntu/ bionic-backports main restricted universe multiverse

deb-src https://www.landui.com/ubuntu/ bionic-backports main restricted universe multiverse

deb https://www.landui.com/ubuntu/ bionic-security main restricted universe multiverse

deb-src https://www.landui.com/ubuntu/ bionic-security main restricted universe multiverse

deb https://www.landui.com/ubuntu/ bionic-proposed main restricted universe multiverse

deb-src https://www.landui.com/ubuntu/ bionic-proposed main restricted universe multiverse

163源：
deb http://www.landui.com/ubuntu/ bionic main restricted universe multiverse

deb http://www.landui.com/ubuntu/ bionic-security main restricted universe multiverse

deb http://www.landui.com/ubuntu/ bionic-updates main restricted universe multiverse

deb http://www.landui.com/ubuntu/ bionic-proposed main restricted universe multiverse

deb http://www.landui.com/ubuntu/ bionic-backports main restricted universe multiverse

deb-src http://www.landui.com/ubuntu/ bionic main restricted universe multiverse

deb-src http://www.landui.com/ubuntu/ bionic-security main restricted universe multiverse

deb-src http://www.landui.com/ubuntu/ bionic-updates main restricted universe multiverse

deb-src http://www.landui.com/ubuntu/ bionic-proposed main restricted universe multiverse

deb-src http://www.landui.com/ubuntu/ bionic-backports main restricted universe multiverse