Date: Fri, 6 Apr 2007 23:15:27 -0400
From: "David A. Harding" <harda@gnuisance.net>
To: "The Cherry Hill Linux User's Group Mailing List" <chlug@jesran.net>
Subject: Some Xtra Bits, was Re: [CHLUG] Friendly Reminder

On Fri, Apr 06, 2007 at 10:17:40AM -0400, Joe Smith wrote:
> The outline & slides look great Dave. You should have no problem filling 
> the 2 hours ;-)

Actually, the trouble was NOT filling the whole two hours. :-)

20 Minutes Over and 4 Commands Short
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I read in a guide to speaking that you should put the least useful parts
of your speech last because speeches are mostly likely to not be said.
I, unwisely, didn't follow that advice for tonight's talk.  The four
commands I skipped from my Official Commands list, and a brief
description of what they do, follow:

#4 xev: this program allows you to determine (among other things) what
keycode keypresses and mouse clicks generate.  Once you know the keycode,
you can configure X to do nifty things when that key is pressed.  For
example, my laptop keyboard has volume control buttons that I use to
(wait for it) control the speaker volume.

#8 xwininfo: displays information about the currently running windows.
The command below this paragraph will textually represent the way
windows are ordered into a tree; if you run the command, I think you'll
be able to better understand the window re-parenting I talked about in
the Basics section of my talk.

	xwininfo -root -tree

#9 xsetroot: changes the behavior of the root window.  The root window
is the only window the X server creates for itself.  This program, or a
similar program, is at the core of every desktop environment, for the
default background and mouse cursors in X11 are fugly.

#10 xdpyinfo: prints information about the capabilities (read:
configuration) of your X server.  We didn't talk about configuring X (on
purpose), but if you ever find yourself in a situation where the
configuration file doesn't seem to match the observed behaviour, use xdpyinfo
for a sanity check.

The complete list can still be found in my notes page:

	http://gnuisance.net/archives/xws/


Detailed Answers
~~~~~~~~~~~~~~~~
For secure shell (ssh) encrypted X Window System protocol forwarding,
you may need to edit the file, /etc/ssh/sshd_config, and enable (set to
yes) the following option on the computer with the program you want to
run:

        X11Forwarding no

If this option was not previous set to yes, then you also need to
restart the secure shell server (sshd) on that same computer with the
following command:

        /etc/init.d/sshd restart

The computer you did all the configuration for above is about to become
your X client. For the purposes of this example, we'll call this
computer, mycomputer, and we'll call your username on this computer, me.

Sit down at your X _server_, which can be the same computer or any other
computer that is currently running X. Start a xterm and type the
following command to see a graphical representation of the system load
on your X client's computer:

        ssh -X me@mycomputer xload

You should see a white box with ``mycomputer'' in the top left corner.
As time passes, a plot of the system load will be drawn. Replace xload
with any other command you wish to run. If it don't work, reply to this
email. If my instructions aren't clear, reply to this email and impugn
upon my character.

Note: if you connect to a computer that has be cracked (hacked) using X
display forwarding, the cracker (hacker) could possibly use the display
forwarding to monitor all keystrokes you type on your X server.  That
includes any typed passwords.  I've never seen this attack in the wild,
but you've been warned.

                                * * *

The list of window managers that corresponds to the slideshow at the end
of my presentation is on Wikipedia at the following URL:

        http://en.wikipedia.org/wiki/X_window_manager


Thanks
~~~~~~
Joe Smith for the idea for the presentation and for many great
suggestions.

Etan Reisner for being the X guru I've turned to for about 4 years.

The Wikipedia contributors to the X Window System articles for all the
great information I've learned for, and tried to pass on with, this
presentation.

Everyone else and their ferret.

-Dave
-- 
+-----------------------------------------------------------------------------+
|   David A. Harding   | No violence, gentlemen -- no violence, I beg of you! |
| http://gnuisance.net |                Consider the furniture!               |
|                      |                  -- Sherlock Holmes                  |
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