Ubuntu APT 国内镜像

• 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 TUNA 的软件源镜像。
• https://mirror.tuna.tsinghua.edu.cn/help/ubuntu/

选择你的ubuntu版本: 20.04 LTS

# 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 http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal main restricted universe multiverse 
# deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal main restricted universe multiverse 
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted universe multiverse 
# deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-updates main restricted universe multiverse 
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-backports main restricted universe multiverse 
# deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-backports main restricted universe multiverse 
deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security main restricted universe multiverse 
# deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-security main restricted universe multiverse 
# 预发布软件源，不建议启用 
# deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-proposed main restricted universe multiverse 
# deb-src http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ focal-proposed main restricted universe multiverse