This question already has an answer here: How do I add myself back as a sudo user? 3 answers I have lost sudo privileges in Ubuntu 13.04 these are the responses I get user@user-desktop:~$ sudo sudo: effective uid is not 0, is sudo installed setuid root? user@user-desktop:~$ groups user user : user adm cdrom sudo dip plugdev lpadmin sambashare user@user-desktop:~$ su user Password: su: Authentication failure user@user-desktop:~$ who am i user pts/0 2013-10-24 08:54 (:0.0) user@user-desktop:~$ why can't I invoke sudo if one of my groups is sudo? also I have noticed that /etc/sudoers needs sudo privileges. sudoers.so doesn't exist in /usr/lib but does in /usr/lib/sudo is this correct in 13.04? Please note that the user is already a member of both sudo and adm groups.