源：架构：版本：

  deb http://mirrors.aliyun.com/ubuntu/ focal main restricted universe
  multiverse

  deb http://mirrors.aliyun.com/ubuntu/ focal-security main restricted universe
  multiverse

  deb http://mirrors.aliyun.com/ubuntu/ focal-updates main restricted universe
  multiverse

  deb http://mirrors.aliyun.com/ubuntu/ focal-proposed main restricted universe
  multiverse

  deb http://mirrors.aliyun.com/ubuntu/ focal-backports main restricted universe
  multiverse

  deb-src http://mirrors.aliyun.com/ubuntu/ focal main restricted universe
  multiverse

  deb-src http://mirrors.aliyun.com/ubuntu/ focal-security main restricted universe
  multiverse

  deb-src http://mirrors.aliyun.com/ubuntu/ focal-updates main restricted universe
  multiverse

  deb-src http://mirrors.aliyun.com/ubuntu/ focal-proposed main restricted universe
  multiverse

  deb-src http://mirrors.aliyun.com/ubuntu/ focal-backports main restricted
  universe multiverse