Page 219 - DCAP602_NETWORK_OPERATING_SYSTEMS_I

Unit 11: User Accounts

sudo notes

The program sudo allows normal users to execute certain root-only commands. Which users
are authorized to run which commands is specified in the /etc/sudoers file. This should only be
edited with the command visudo.
For example, suppose I wanted to add a group of users who are allowed to shut down the
machine. So I first want to add a group called “shutdown” (run these commands while root)

groupadd shutdown
Then I need to edit the /etc/group file to add users to the “shutdown” group. I just tack the
usernames at the end of the shutdown line, separated by commas, e.g.

shutdown:x:407:user1,user2,...
Whatever users I put there will be able to shut down the computer (so choose wisely). Now
I need to configure sudo to allow members of the “shutdown” group to actually invoke the
assorted shutdown commands provided in linux. Run visudo and add the following lines

%shutdown ALL=(root) NOPASSWD: /sbin/reboot
%shutdown ALL=(root) NOPASSWD: /sbin/halt
%shutdown ALL=(root) NOPASSWD: /sbin/shutdown
This allows the “shutdown” group to run /sbin/reboot, /sbin/halt, and /sbin/shutdown AS IF
THEY WERE ROOT. The only caveat is that the users must run the commands with the command
sudo in front, e.g.
sudo /sbin/halt
This is always a bit of a pain (and users never remember), so I can create the following script
called “/usr/bin/reboot” (and similar scripts for halt and shutdown)

#! /bin/sh
sudo /sbin/reboot $*
Remember to make these scripts executable! To make this slightly more secure, I might want to
change the ownership of these scripts to the “shutdown” group

chgrp shutdown /usr/bin/reboot /usr/bin/halt /usr/bin/shutdown
and then make them executable only for the group “shutdown”
chmod g+x /usr/bin/reboot /usr/bin/halt /usr/bin/shutdown
KDE shutdown

If you are running kdm (the kde display manager - e.g. graphical login) then the shutdown
behavior can be modified in “Control Panel” (in “Administrator Mode” of course). If you are
starting KDE manually (using startx or startkde) then you will have to resort to the previous
“sudo” solution (and probably add a shortcut on the desktop to one of those scripts).

XFCE4 shutdown

If you are using xfce4 then you will need to configure a few items in order to use the built-in
“Reboot computer”/”Turn off computer” options available when you are logging out.

LoveLy professionaL university 213