How could I have dropped out of sudoers?

Question

I started to receive a message

dims is not in the sudoers file.  This incident will be reported.

about myself.

How could this happen?

The suspicious command I made was creating group "advanced" and adding myself to it.

addgroup advanced
usermod -G advanced dims

Could this break my sudo rights?

Post groups command output, this will print dims groups. — Lety, Oct 19 '14 at 18:40
@VolkerSiegel While I think the questions are related, I'm not so sure this is a dupe. IMO Dims is asking how or why this happened, not how to fix it. The answer here wouldn't fit on the other question either, which is a strong suggestion they are not duplicates. — Seth, Oct 20 '14 at 03:36
@Seth I see - I was noticing that other question has an answer also mentioning the other groups - but it's more a related, and not strictly relevant to the "how comes" question (but very relevant to the "how to fix" question) — Volker Siegel, Oct 20 '14 at 03:49
You might have dropped out of other groups too, see: http://askubuntu.com/a/59367/260447 — Volker Siegel, Oct 20 '14 at 03:50
This is why it's best to avoid usermod and use adduser: adduser <username> <groupname>. — muru, Oct 21 '14 at 12:34

score 22 · Accepted Answer · answered Oct 19 '14 at 18:46

After

usermod -G advanced dims

the user dims is only a member of the group advanced but not of any other group. So as he isn't a member of the group admin or sudo he is no longer allowed to use sudo.

To just add a user to another group you need to use the -a switch to usermod, like

usermod -a -G advanced dims

How could I have dropped out of sudoers?

1 Answers1