尝试安装任何东西时，身份验证弹出窗口会显示错误消息而不是密码框，而尝试将 usr 文件夹切换回 root 会导致终端出现以下错误：
helena@helena-PC:/$ sudo chown -R root:root /usr
sudo: /usr/bin/sudo must be owned by uid 0 and have the setuid bit set
helena@helena-PC:/$
尝试按照以下链接中的说明进行操作： 如何解决此错误“sudo：/usr/local/bin/sudo 必须由 uid 0 拥有并设置 setuid 位”而无需重新安装 ubuntu？
结果是：
helena@helena-PC:/$ ls -l /usr/bin/sudo
-rwxrwxrwx 1 helena root 149080 set 23 11:59 /usr/bin/sudo
helena@helena-PC:/$ pkexec bash
pkexec must be setuid root
helena@helena-PC:/$ sudo pkexec bash
sudo: /usr/bin/sudo must be owned by uid 0 and have the setuid bit set
helena@helena-PC:/$ chown -R root:root /usr/bin/sudo
chown: changing ownership of '/usr/bin/sudo': Operation not permitted
helena@helena-PC:/$ sudo chown -R root:root /usr/bin/sudo
sudo: /usr/bin/sudo must be owned by uid 0 and have the setuid bit set
helena@helena-PC:/$
面对这个愚蠢的错误我该怎么办呢？