How to use 'poweroff' without being root?

servnov · 08-21-2005, 08:47 PM

I have multiple users on a desktop system and want them to be able to shutdown the machine. I can't get sudo working, and even that would be overkill; i just want users to be able to shutdown the machine.

Can I somehow change the permissions on /sbin/poweroff to something everyone can use? It's already chmod 777...

Thanks.

Bruce Hill · 08-21-2005, 09:01 PM

I'll take a gander...what if you add these users to the bin group?
As root issue "vigr" and add whichever users to bin, because of:

Code:

mingdao@james:~$ ls -al /sbin/poweroff        
lrwxrwxrwx  1 root root 4 2005-07-21 21:28 /sbin/poweroff -> halt*
mingdao@james:~$ ls -al /sbin/halt     
-rwxr-xr-x  1 root bin 8844 2005-07-18 07:48 /sbin/halt*

/sbin/poweroff being a symlink to /sbin/halt.

imitheos · 08-22-2005, 04:35 AM

Quote:

Originally posted by servnov

I have multiple users on a desktop system and want them to be able to shutdown the machine. I can't get sudo working, and even that would be overkill; i just want users to be able to shutdown the machine.

Can I somehow change the permissions on /sbin/poweroff to something everyone can use? It's already chmod 777...

poweroff is a symlink to halt that is why you see 777. the real permissions are the ones of halt

Quote:

Originally posted by Chinaman
I'll take a gander...what if you add these users to the bin group?
As root issue "vigr" and add whichever users to bin, because of:

Code:

mingdao@james:~$ ls -al /sbin/poweroff lrwxrwxrwx 1 root root 4 2005-07-21 21:28 /sbin/poweroff -> halt* mingdao@james:~$ ls -al /sbin/halt -rwxr-xr-x 1 root bin 8844 2005-07-18 07:48 /sbin/halt*

/sbin/poweroff being a symlink to /sbin/halt.

As you can see from the permissions "others" have "r-x" permissions, so everyone can execute it.
Adding the users to the "bin" group would do good if the permissions were "-rwxr-x---", so it will do no good.

If you run KDM/GDM (graphical login) you can easily setup the login manager so that any local user can reboot/shutdown the pc.
If you run console logins and then startx, then i guess sudo would be a way.

if you read the manpage of "halt" you will see that it runs "shutdown".
in the "shutdown" manpage it is mentioned that it was not written so that it would be run setuid so that every user can run it.

So, i guess the quickest way is sudo, unless i forget something.

oneandoneis2 · 08-22-2005, 05:27 AM

I cheated and put a "Shutdown" button on my XDM login screen. Since all apps on the login screen are run as root, this works perfectly without any need for sudo-ing, passwords, chmod-ing or anything else. . .

Here's a Wish script (requires TCL & TK) that I use:

Code:

#!/usr/bin/wish


proc restartf {} {
exec /sbin/shutdown -r now
}

proc shutdownf {} {
exec /sbin/shutdown -h now
}

proc syncf {} {
exec /usr/bin/emerge --sync
}

button .restart -text "Reboot" \
-background white \
-activebackground orange \
-relief groove \
-command restartf

button .shutdown -text "Shutdown" \
-background white \
-activebackground red \
-relief groove \
-command shutdownf

button .sync -text "Sync" \
-background white \
-activebackground cyan \
-relief groove \
-command syncf

pack .shutdown .restart .sync -fill x -side bottom

Bruce Hill · 08-22-2005, 05:31 AM

I don't personally run KDE, but am building a box for someone today with it.
I installed Slackware -current and using KDE with runlevel 4 gives 3 choices:
End Current Session
Turn Off Computer
Restart Computer
They all work fine for all users. You might need to enable either APM or ACPI
in the kernel to get the box to actually shut down, rather than hanging at
Power off. I don't know with KDE, because it changes many things "behind
the scenes." I know you do with Fluxbox, the window manager I use on my
workstation. But I compiled a new kernel already for the box, so can't say
how that behavior will work with KDE and a default kernel.

chandru.in · 08-22-2005, 07:10 AM

Hey,

I did this to get it working, as root type what is below,

cd /sbin
chmod 4777 halt
chmod 4777 shutdown

imitheos · 08-22-2005, 09:16 AM

Quote:

Originally posted by chandru.in
Hey,

I did this to get it working, as root type what is below,

cd /sbin
chmod 4777 halt
chmod 4777 shutdown

yes. and a user does "cat /bin/bash > /sbin/shutdown"

Instant suid shell (i know that the suid bit is supposed to be turned off but it doesn't happen all the time)

Even if this scheme was a good solution the right command would be
"chmod 4755"

But, let me say again.

"Shutdown wasn't designed to be run setuid."
(From the shutdown manpage)
It doesn't mean that it won't work. It will work ok, but the author mentions that shutdown has not been written with the thought
that it would be run setuid, so they didn't take the measures that are needed from security point of view.
If you don't care about security or you have few/trusted users or whatever then do it.

"cd /sbin
chmod 4755 halt shutdown"

But, I (and the author whose opinion has more weight than mine) don't recommend it.

servnov · 08-23-2005, 07:12 AM

The chmod 4777 or chmod 4755 worked! Thanks guys.