I know a little about users and groups; in the past I might have had a group like 'DBAS' or 'ADMINS' and I'd add individual users to each group…
But I was surprised to learn I could add users to other users – as if they were groups.
For example if my /etc/group contained the following:
user1:x:12501: user2:x:12502:user1 admin:x:123:user2,jim,bob
Since user2 is a member of the admin group, and user1 is a member of user2 – is user1 effectively an admin? If the admin group is in the sudoers file, can user1 use it as well?
I've tried to simulate this and I haven't been able to do so as user1…but I'm not sure it's impossible.
EDIT: SORRY – updated error in question.