backport的解释：Backports are packages taken from the next Debian release (called “testing”)
参考：
如何使用 Debian backports 更新源 https://cloud.tencent.com/developer/article/1374722
列出所有已经安装的backports
dpkg-query -W | grep ~bpo
原文：https://www.cnblogs.com/weihua2020/p/13747583.html