update source

• ali developer center: https://developer.aliyun.com/mirror/

Get system codename

lsb_release -a

backup the old source list

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

update source list

sudo vim /etc/apt/sources.list

replace TODO as focal。

deb http://mirrors.aliyun.com/ubuntu/ TODO main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ TODO-security main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ TODO-updates main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ TODO-proposed main restricted universe multiverse
deb http://mirrors.aliyun.com/ubuntu/ TODO-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ TODO main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ TODO-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ TODO-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ TODO-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ TODO-backports main restricted universe multiverse