How do I list all users with root?
Solution 1:
Don't forget to change the root password. If any user has UID 0 besides root, they shouldn't. Bad idea. To check:
grep 'x:0:' /etc/passwd
Again, you shouldn't do this but to check if the user is a member of the root group:
grep root /etc/group
To see if anyone can execute commands as root, check sudoers:
cat /etc/sudoers
To check for SUID bit, which allows programs to be executed with root privileges:
find / -perm -04000
Solution 2:
To see who is UID 0:
getent passwd 0
To see who is in groups root, wheel adm and admin:
getent group root wheel adm admin
To list all users and the groups they are members of:
getent passwd | cut -d : -f 1 | xargs groups
Solution 3:
Pure root is user id "0".
All the users in the system are in the /etc/passwd file:
less /etc/passwd
Those who are root have "0" as the user id, which is the 3rd column. Those with "0" as the group (4th column) may also have some root privileges.
Next, you'll want to look at the groups, and see who is an additional member of the "root" or "wheel" or "admin" groups:
less /etc/group
Users listed in those groups could have some root privileges, especially via the "sudo" command.
The final thing you will want to check is the "sudo" config and see who is listed as having authorisation to run this command. This file itself is well documented so I won't reproduce it here:
less /etc/sudoers
That covers the main areas of who could have root access.
Solution 4:
To print all users
perl -n -e '@user = split /:/ ; print "@user[0]\n";' < /etc/passwd
To print only those users with UID 0, being as others have said, the users with implicit root privileges:
perl -n -e '@user = split /:/ ; print "@user[0]\n" if @user[2] == "0";' < /etc/passwd
Solution 5:
For a quick list of all users, try hitting tab twice (to auto-complete) after typing the passwd command followed by a space. This works with the su command as well.
Must be done as a root-privileged user.