Ubuntu 的软件源配置文件是 /etc/apt/sources.list。将系统自带的该文件做个备份，将该文件替换为下面内容，即可使用软件源镜像。
# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb https://mirror.bjtu.edu.cn/ubuntu/ focal main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ focal main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ focal-updates main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ focal-updates main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ focal-backports main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ focal-backports main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ focal-security main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ focal-security main restricted universe multiverse
# 预发布软件源，不建议启用
# deb https://mirror.bjtu.edu.cn/ubuntu/ focal-proposed main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ focal-proposed main restricted universe multiverse
# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb https://mirror.bjtu.edu.cn/ubuntu/ disco main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ disco main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ disco-updates main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ disco-updates main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ disco-backports main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ disco-backports main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ disco-security main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ disco-security main restricted universe multiverse
# 预发布软件源，不建议启用
# deb https://mirror.bjtu.edu.cn/ubuntu/ disco-proposed main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ disco-proposed main restricted universe multiverse
# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb https://mirror.bjtu.edu.cn/ubuntu/ eoan main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ eoan main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ eoan-updates main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ eoan-updates main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ eoan-backports main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ eoan-backports main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ eoan-security main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ eoan-security main restricted universe multiverse
# 预发布软件源，不建议启用
# deb https://mirror.bjtu.edu.cn/ubuntu/ eoan-proposed main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ eoan-proposed main restricted universe multiverse
# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb https://mirror.bjtu.edu.cn/ubuntu/ bionic main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ bionic main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ bionic-security main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ bionic-security main restricted universe multiverse
# 预发布软件源，不建议启用
# deb https://mirror.bjtu.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse
# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb https://mirror.bjtu.edu.cn/ubuntu/ xenial main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ xenial main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ xenial-security main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ xenial-security main restricted universe multiverse
# 预发布软件源，不建议启用
# deb https://mirror.bjtu.edu.cn/ubuntu/ xenial-proposed main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ xenial-proposed main restricted universe multiverse
# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb https://mirror.bjtu.edu.cn/ubuntu/ trusty main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ trusty main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ trusty-updates main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ trusty-updates main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ trusty-backports main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ trusty-backports main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ trusty-security main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ trusty-security main restricted universe multiverse
# 预发布软件源，不建议启用
# deb https://mirror.bjtu.edu.cn/ubuntu/ trusty-proposed main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ trusty-proposed main restricted universe multiverse
# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb https://mirror.bjtu.edu.cn/ubuntu/ precise main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ precise main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ precise-updates main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ precise-updates main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ precise-backports main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ precise-backports main restricted universe multiverse
deb https://mirror.bjtu.edu.cn/ubuntu/ precise-security main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ precise-security main restricted universe multiverse
# 预发布软件源，不建议启用
# deb https://mirror.bjtu.edu.cn/ubuntu/ precise-proposed main restricted universe multiverse
# deb-src https://mirror.bjtu.edu.cn/ubuntu/ precise-proposed main restricted universe multiverse