UNIX Administratosphere

My post on the importance and methods of wheel groups remains popular. I though I would go into various UNIX variants and detail specifically how to activate wheel groups.

Today, the discussion is around Red Hat Linux (speaking generally). The test system was running Fedora Core 5; however, this area of Red Hat has not changed in quite some time, so it is likely to be the same in Fedora 7 and so forth.

First, make sure there is a wheel group in the /etc/group file. On Fedora Core 5, there is:

wheel:x:10:root

If this line does not exist, add it.

Of course, you must put users that you want to be admins into the wheel group. To do this, add the user to the end of the wheel group line. This will make the wheel group a secondary group; I don’t know if that will make a difference today, but it might somewhere.

Second, change into the /etc/pam.d directory, and edit the file su. This file controls the access to the program su and modifies its behaviors during the authentication process. The change will modify the access so that only those in the wheel group have access to the program su.

Find these lines in /etc/pam.d/su:

# Uncomment the following line to require a user to be in the “wheel” group.
#auth required pam_wheel.so use_uid

And change them (as suggested) to this:

# Uncomment the following line to require a user to be in the “wheel” group.
auth required pam_wheel.so use_uid

This access change is not necessarily limited to the su command, but no other command has normally been included in the past. If there are other commands that only those in the wheel group should be able to access, then this line could be put into their PAM configuration (in the right place).

Note that editing PAM files could very easily lock you out of your machine completely; thus do not take editing PAM files (in /etc/pam.d) lightly. The Red Hat authored wheel group modification is simple and easy; other changes you make may not be.

Then, expand the permissions in sudo to account for those with wheel permissions. Edit the configuration file with visudo and change these lines:

# Uncomment to allow people in group wheel to run all commands
# %wheel ALL=(ALL) ALL

To this (as recommended):

# Uncomment to allow people in group wheel to run all commands
%wheel ALL=(ALL) ALL

This will allow anyone in the wheel group to execute commands using sudo (rather than having to add each person one by one). It would also allow anyone this sort of access on any machine that they have wheel group membership.