# deb cdrom:[Official Debian GNU/Linux Live 11.1.0 standard 2021-10-09T10:45]/ bullseye main
#deb cdrom:[Official Debian GNU/Linux Live 11.1.0 standard 2021-10-09T10:45]/ bullseye main
deb http://mirrors.ustc.edu.cn/debian/ bullseye main contrib non-free
deb-src http://mirrors.ustc.edu.cn/debian/ bullseye main contrib non-free
deb http://mirrors.ustc.edu.cn/debiancn/ bullseye main
deb-src http://mirrors.ustc.edu.cn/debiancn/ bullseye main
#deb http://security.debian.org/debian-security bullseye-security main non-free contrib
#deb-src http://security.debian.org/debian-security bullseye-security main non-free contrib
deb http://mirrors.ustc.edu.cn/debian-security bullseye-security main non-free contrib
deb-src http://mirrors.ustc.edu.cn/debian-security bullseye-security main non-free contrib
# bullseye-updates, to get updates before a point release is made;
# see https://www.debian.org/doc/manuals/debian-reference/ch02.en.html#_updates_and_backports
deb http://mirrors.ustc.edu.cn/debian/ bullseye-updates main contrib non-free
deb-src http://mirrors.ustc.edu.cn/debian/ bullseye-updates main contrib non-free
# This system was installed using small removable media
# (e.g. netinst, live or single CD). The matching "deb cdrom"
# entries were disabled at the end of the installation process.
# For information about how to configure apt package sources,
# see the sources.list(5) manual.

我的 /etc/apt/source.list里只有一条：
deb https://mirrors.tuna.tsinghua.edu.cn/debian/ sid main contrib non-free

中科大的自动配置源，直接复制就行。
https://mirrors.ustc.edu.cn/repogen/