Attempting to open Perl/Tk window by anacron

kaza · 03-14-2012, 02:42 PM

Hello,

I'm attempting to use "anacron" to start a Perl/Tk script
which I wrote "remind_to_backup". When I'm starting it from
a terminal (as root) - it opens OK. But when I didn't see it open
by "anacron" I looked in "/var/spool/mail/root" and saw the following
message:

Code:

From root@localhost.localdomain  Mon Mar 12 14:31:02 2012
Return-Path: <root@localhost.localdomain>
Received: from localhost.localdomain (localhost.localdomain [127.0.0.1])
	by localhost.localdomain (8.14.4/8.14.4) with ESMTP id q2CCV226005184
	for <root@localhost.localdomain>; Mon, 12 Mar 2012 14:31:02 +0200
Received: (from root@localhost)
	by localhost.localdomain (8.14.4/8.14.4/Submit) id q2CCV1DY005183
	for root; Mon, 12 Mar 2012 14:31:02 +0200
Date: Mon, 12 Mar 2012 14:31:02 +0200
Message-Id: <201203121231.q2CCV1DY005183@localhost.localdomain>
From: Anacron <root@localhost.localdomain>
To: root@localhost.localdomain
Content-Type: text/plain; charset="ANSI_X3.4-1968"
Subject: Anacron job 'remind_to_backup' on localhost.localdomain

No protocol specified
couldn't connect to display ":0" at /usr/lib64/perl5/Tk/MainWindow.pm line 55.
MainWindow->new() at /root/bin/remind_to_backup line 23

After searching the net for this error I understand that the issue
here is lack of permission for "root" to access the X windows
server (If I understand correctly).

What I don't quite understand is why I can open this window
from an ordinary root shell but "anacron" can't open it?

The shell I prefare to use is "tcsh", the appropriate line
in /etc/passwd file is:

root:x:0:0:root:/root:/bin/tcsh

which is different from the original shell (bash) after the
installation (FC14). How can I know, in what shell the "anacron"
runs? What's the difference (from the standpoint of X server
access) between programs called by "anacron" and same programs
called from the command line (by root)?
While searching the net I saw suggestions like:

xhost +root

or

xhost +localdomain

but I have none of such commands in my /root/.tcshrc file
but still, I can open the Perl/Tk window as root from the command line.

TIA for any ideas,
kaza.

Tinkster · 03-14-2012, 04:22 PM

This teaches us a few things.

Firstly: you seem to run your machine as root; bad idea ;}

Secondly: you have bad taste in shells... (sorry, couldn't resist).

Anyway, to solve your problem (I don't think it's shell related) just issue
in the running X-session: xhost +localhost

And in the cron file prepend the bit that starts your Tk script w/ DISPLAY=:0.0

Cheers,
Tink

kaza · 03-15-2012, 12:06 PM

Hi Tinkster,

thanks for the reply.

I don't run as root usually, I login as other user. But to test this
script I first did "su -" since I wanted to test as close as possible to the
real situation when the "anacron" will call it.

I added

xhost +localhost > /dev/null

to the /root/.tcshrc

and changed the line in /etc/anacrontab from:

7 50 remind_to_backup env DISPLAY=:0 nice remind_to_backup

to

7 50 remind_to_backup env DISPLAY=:0.0; nice remind_to_backup

Now I'll wait few days to see what the result will be.

Thanks,

Tinkster · 03-15-2012, 02:17 PM

Wait a sec ... so, which user are you running your X-session as?

kaza · 03-16-2012, 05:14 PM

Hi Tinkster,

During boot at login prompt I log in as a normal user,
when I run "ps" I see that gnome-session is run by my login user.
I checked "ps | grep root" and as far as I can tell I only
saw low level or hardware related processes run by root.

Does it adds more insight as to the original problem cause?

TIA,
kaza.

Tinkster · 03-16-2012, 10:55 PM

Nope. It means that you need to do the xhost +localhost from your normal
user account; as an aside, that most likely won't work from your ~/.profile/
~/.tcshrc because xhost needs to be run from within X.
Find out whether Gnome can run scripts and such during login, and add it
to that.

Cheers,
Tink