Questions[user-management](ubuntu)

My understanding of UIDs is that is a unique positive integer assigned by a Unix-like operating system to each user. Each user is identified to the system by its UID, and user names are generally used only as an interface for humans.

How can two users have the same UID, isn't this a conflict for my system and packages?

root@kdc:~# id test12
uid=1005(test10) gid=1000(server) groups=1005(test10)
root@kdc:~# id test13
uid=1005(test10) gid=1000(server) groups=1005(test10)
root@kdc:~#

I've added two users with same UID and GID: test12 and test13

The output of /etc/passwd:

client@kdc:~$ cat /etc/passwd | grep test12
test12:x:1005:1000::/home/test12:/bin/sh
client@kdc:~$ cat /etc/passwd | grep test13
test13:x:1005:1000::/home/test13:/bin/sh

I added the users by useradd -ou 1005 -g1000 username.

I got confused what is the purpose of this, and can it affect permissions and user logs etc. So now if a user is added with uid=0 and gid=0 will has privileges like a root account?

How can I see all the members of a group in Linux?

There is only one user on my system. How can I change its user ID from the default of 1000?

If there are additional steps that would be required in order to avoid breaking the login process on a typical desktop installation, those should be included as part of the answer.

After I add a user using adduser, I can't see it via System > Administration > Users and Groups unless I log out and then log in again. Is that normal?

Also, can I set a newly added user as a sudoer or do I have to change that only after adding it? How can I do that via the shell?

Finally, can I delete the original user that was created upon initial installation of Ubuntu, or is this user somehow 'special'?

In /etc/sudoers I see this:

# Allow members of group sudo to execute any command after they have
# provided their password
# (Note that later entries override this, so you might need to move
# it further down)
%sudo ALL=(ALL) ALL

So how do I add a user to that sudo group?