复制源

mv /etc/apt/sources.list /etc/apt/sources.list.bak

配置国内镜像

cat <<EOF >/etc/apt/sources.list
deb http://mirrors.ustc.edu.cn/debian stable main contrib non-free
deb http://mirrors.ustc.edu.cn/debian stable-updates main contrib non-free
EOF

更新源

apt update

恢复回来

mv /etc/apt/sources.list.bak /etc/apt/sources.list