deb http://mirrors.163.com/ubuntu/ focal main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ focal-security main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ focal-updates main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ focal-proposed main restricted universe multiverse deb http://mirrors.163.com/ubuntu/ focal-backports main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ focal main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ focal-security main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ focal-updates main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ focal-proposed main restricted universe multiverse deb-src http://mirrors.163.com/ubuntu/ focal-backports main restricted universe multiverse