LINUX NEWS
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Thursday, June 13, 2002TABLE OF CONTENTS
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 choice.
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 ~/.Xclients)
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 GNOME.
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:
PREFERRED=kde or PREFERRED=fvwm
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:
GNOME KDE checks ~/.wm_style to see if you want to run Window Maker, FVWM 95, or mwm FVWM95 FVWM TWM
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,
Sean mailto:swalberg@cramsession.com
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…
http://newsforge.com/newsforge/02/06/07/0121241.shtml?tid#
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!)
http://www.redhat.com/about/presscenter/2002/press_oracle1.html
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?
http://www.ooodocs.org/modules.php?name=News&file=article&sid
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.”
http://biz.yahoo.com/bw/020319/192155_1.html
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.
http://infocenter.cramsession.com/techlibrary/gethtml.asp?ID11
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 chuckles.
http://www.redhat.com/advice/ask_shadowman.html
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!
http://www.linuxgazette.com/issue79/fraile.html
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.
http://bhami.com/rosetta.html
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.
http://www.sun.com/solutions/blueprints/0502/816-4816-10.pdf
4) App o’ the Week
Mozilla released 1.0 last week. Congratulations to the development team!
http://www.mozilla.org
(C) 2002 BrainBuzz.com, Inc. All Rights Reserved.
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