2002 06 13

                    LINUX NEWS
      Resources & Links From www.CramSession.com
             Thursday, June 13, 2002


1) Sean’s Notes

2) Linux News

I Wish We Had Viruses...
Red Hat, Oracle, and Dell
Microsoft Shills on the Attack, Again
SELinux to be Certified?

3) Linux Resources

Apache for WebHeads
Ask Shadowman
Linux Fax Server
Sysadmin's Universal Translator
How do Hackers do it?

4) App o’ the Week

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1) Sean's Notes

A common question is "How do I change my window manager?"
The answer is both simple and complex, depending on how
deep you want to go.

I'll start off with the simple answer, at least for Red Hat
and compatible users.  Just run "switchdesk", and make your

Taking a look at the harder way will show us what switchdesk
really does, and also give some insight into how X runs.

X is often started via "startx", a shell script that does
some small housekeeping before starting the X server.  One
of the more important things it does is find out what is
supposed to happen right after the X server is started,
such as starting up a window manager or desktop environment.

These instructions take the form of a shell script.  Usually
one shell script calls another shell script, which leads to
a chain of events needed to start up X.  As we'll see, there
are lots of opportunities for the user to take over the
process and customize it to his own needs.

One of the first things that startx does is tries to find out
if you're going to provide your own startup instructions, or
if the global ones are to be used.  This is handled by
xinitrc (which might be called Xinitrc depending on your OS).
In the event that you've got a file called ".xinitrc" in your
home directory (note the leading dot), it will be used instead.
xinitrc does lots of important things such as loading in
resources (sort of environment variables for X) and performing
keyboard remappings.  The final thing that xinitrc (assuming
you haven't overridden it) does is tries to find out what X
clients to run (from its perspective, your window manager is
just another X client, like a terminal window).

The list of clients to run is another shell script.  The
global version is called "Xclients", but it can be overridden
if you have a ".Xclients" file in your home directory (using
the tilde to represent your home directory, it'll be called

This .Xclients is what switchdesk changes.  It basically copies
some of the templates from /usr/share/apps/switchdesk/Xclients.\*
into ~/.Xclients.  For example, the one to start up GNOME is
pretty simple:

exec gnome-session

gnome-session will then start up everything needed to work in

If you don't have a ~/.Xclients, then the global Xclients
file has to decide what to run for you.  First, it checks for
the existence of /etc/sysconfig/desktop.  If that file sets
a variable called "PREFERRED", then that is used to set the
default window manager.

If PREFERRED is either "gnome" or "kde" (case insensitive),
then the appropriate one is loaded.  If PREFERRED is the name
of an executable, ie "twm", then that is executed:


Note that this step is specific to Red Hat and compatible
distributions.  One of the things that makes me really like
Red Hat is that the behaviour of many scripts can be changed
in simple configuration files rather than digging into the
shell scripts.

If you don't have a "desktop" file, or didn't set PREFERRED,
then the global Xclients tries the following, in order:

checks ~/.wm_style to see if you want to run Window Maker, FVWM 95,
or mwm

Since a lightweight WM like TWM is installed on pretty much
every X-Window capable device,

Each Window Manager or Desktop Environment is then free to
load up whatever it thinks appropriate.  For example, gnome-
session will restore your windows, load up gmc or nautilus,
and start the panel.  FVWM will read the ~/.fvwmrc file to
see what to do.

For those logging in through the graphical interface (called
the Display Manager), the procedure is mostly the same.  If
you selected a specific environment when you logged in, the
appropriate program will be loaded.  If you left it on "default",
then ~/.xsession is consulted, failing that, your ~/.xclients
is used, and failing that, the global Xclients is run.

Phew!  That's a lot of files, and we haven't even looked at
the ones that the individual Window Managers are going to
touch!  For my own sanity, I'll stop here.

Lots of files come together to bring up the complex
environment known as X.  The default scripts are very good at
trying to figure out what you want, but like everything Unix,
the user knows best and can override almost anything.

Long live the Penguin,


2) Linux News

I Wish We Had Viruses...
"One of the great defects in Linux compared to Windows is that
it is not infected by cool viruses. Viruses are obviously fun,
as is made obvious by the refusal of so many Internet-connected
Windows users to switch to Linux as the easiest way to make
themselves virus-free. For a few days there, we hoped the new
cross-platform Simile.D virus would let us Linux users in on
the fun, but it turned out to be a false alarm."

It only gets better from there...


Red Hat, Oracle, and Dell
In a series of announcements, these three companies have
indicated they are going to work on bringing highly available,
scalable database clusters to Linux, using inexpensive Intel
hardware. I wish the best for all three, they all have to
notch products, and I'm looking forward to seeing them play
on each other's strengths. (and they can send one of those
babies over for a review any time!)


Microsoft Shills on the Attack, Again
Here are more allegations that Microsoft is paying for
supposedly unbiased reviews. Gartner group is a longstanding
proponent of Microsoft, though they have spoken against them
in the past (recommending IIS not be used at one point). Who
can you trust these days?


SELinux to be Certified?
"Project EGOVOS (TM) (Project E-Government Operating System)
will apply for certification of the National Security Agency's
Security-Enhanced Linux (SELinux) under the NIAP Common
Criteria Evaluation and Validation Scheme for IT Security.
SELinux is an ideal and secure operating system for the global
critical IT infrastructure."


3) Linux Resources

Apache for WebHeads
A good introduction to the Apache web server, this article
covers the installation and basic configuration of Apache.
Setting up a web server is a great way to becoming accustomed
to the Unix operating system, as it pulls in concepts like
networking, file permissions, and editing files into a
package that most people are already familiar with.


Ask Shadowman
RedHat has answered some common security related questions
through its "Ask Shadowman" webpage. The answers are solid
and down to earth, and well worth a read.  It's also a good
laugh, as the style is quite informal and brings on a few


Linux Fax Server
Tired of a fax modem at every computer that needs to fax?
Sick of the high cost of network fax software? Samba and
HylaFax to the rescue!


Sysadmin's Universal Translator
Someone has taken a list of common Unix flavours and common
tasks, and thrown them into a large table. It's helpful if
you know how to do something on one variant, but are stuck
having to do it on a different one.


How do Hackers do it?
A pretty good PDF article on how crackers find and exploit
vulnerabilities in Solaris. Most of what is in here applies
to all variants of Unix.


4) App o' the Week
Mozilla released 1.0 last week.  Congratulations to the
development team!


(C) 2002 BrainBuzz.com, Inc. All Rights Reserved.

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