Hello world! I'm a new member here, and this is the fist time I post a question on a forum, I would really appreciate your help, I've been digging the internet for an answer for couple months now.
my problem is that I cant use su while on X, it always returns "Authentication failure" so every time I need superuser privileges I have to logout to the boot terminal or do all the work there! any thoughts on what might be the cause of this issue? its been like this since day 1.

and just to clarify, root has its password, my user is a member of wheel group, my keyboard is working fine,I enter root password, and the password is correct, please help.

thanks!

All I can say it that this is truly unusual. In every Slackware install I've had, I've been able ot open a terminal in desktop environment or window manager and use su to assume root privileges.

When you try to use su in a terminal in the GUI, what error messages, if any, do you get?

@frankbell thank you very much for your quick feed-back!
when I enter the correct password for root I get "su: Authentication failure" that occurs only when I'm on the GUI terminal.

And this same password works from the command line when X is not running?

If that's the case, I admit that I am baffled.

There are many Slackware users here who are much more knowledgeable than I; one hopes that one of them will join in this thread.

@frankbell Yes it works fine from the command line!
hopefully someone with the answer will show up, Thank you very much for your input I really appreciate it.

In MSEC in Mageia (which uses KDE) there is an option "allow superuser login on terminal", if this is not hooked it causes the behaviour that the threadstarter is talking about. Sadly I don't know MSEC very well, but it is a GUI (probably scripts) that adjust various security settings in the GNU/Mageia environment itself.

It could be that this setting is a generic GNU/Linux option in some setting file in /etc or in some xorg config file or something like that, or some parameter added to some setting file. Unfortunately I do not know more than this. I just know that su works in tty, but not on a GUI terminal (emulator).

edit
Ok, so Mageia uses PAM ofcourse, and this behaviour I am talking about is highly likely to be PAM related. So, you can pretty much disregard my post, but keep it in the back of your mind, if there is perhaps a similar function in Slackware through Xorg, or KDE or something similar, or if I am wrong, and this function is not provided by PAM in Mageia.

I suspect that the issue is related to the keyboard mapping on my system, when I installed Slackware I chose an "AZERTY" keyboard map because that's what I have, but when GUI loaded it was "QWERTY" so I had to change it, and even now there is still some discrepancies between the mapping on the command line and the GUI, however the password I enter is in fact correct even with the different mapping but still its not accepted, and I just discovered today that I can only log in using the command line if I lock screen and try to log back it gives me the authentication failure error!

This is a long shot, but, when in the GUI, try opening a text editor and typing your root password into it. I'm guessing that, if it's keyboard mapping error in the GUI, the password won't display properly when typed in the clear--but that's just a guess and as I said a very long shot.

1 members found this post helpful.

To me it just sounds like a mapping error. Frank's idea is what I was going to suggest. Also try different terminals.

Also read:

https://docs.slackware.com/howtos:wi...eyboard_layout
https://docs.slackware.com/slackware:localization

I tried that before, the password display correctly! that's what puzzling me.



I did try different terminals but same problem occurs, I will check out the links thanks!

a tty "terminal" and a terminal emulator is not the same thing. Different security settings or access rights can affect the right of the terminal emulator to invoke super user privileges.

I know this is a case in Mageia, but I am not yet familiar enough with various configurations and mechanisms in Slackware to point to where this could be the case in Slackware as well. I don't know Xorg very well, but it can definitely be the case that such a parameter is set in Xorg somewhere, such that any Xorg process cannot invoke super user.

Edit. As far as I remember from discussions, Slackware 14.2 and prior versions do not use PAM. But do they use Polkit through KDE? I don't know yet, I haven't explored that much..

If yes, could the issue be a polkit issue?

Thank you all very much for your support especially @frankbell your guess about the issue being keyboard mapping error was accurate, the problem was that some special chars in my password was different than what I thought they were! so basically the way I type my password will depend on weather I'm in terminal or tty as if I have two passwords for every account!