sudo apt-get dist-upgrade 删除了 sudo 和其他程序

Question

我关注这升级到 Ubuntu 18.04 的指南，执行后sudo apt-get dist-upgrade，我没有费心检查它是否提示我执行它会删除很多程序。之后dist-upgrade，我注意到我不再有程序了sudo。我尝试通过安装，install但收到如下错误：

E: Could not open lock file /var/lib/dpkg/lock-frontend - open (13: Permission denied)
E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), are you root?

我怎样才能恢复？