===========================================================
                        LINUX NEWS
            RESOURCES & LINKS FROM BRAINBUZZ.COM
                 Thursday, April 26, 2001
           Read By 5,000 Linux Enthusiasts Weekly!
===========================================================

-----------------
TABLE OF CONTENTS
-----------------

1) Sean's Notes

2) Linux News

 	Ximian GNOME 1.4 is Out!
	Perl: The Complete Reference (2ed)
	IBM Takes to the Street
	Linux as a Radio Station

3) Linux Resources

	Application Directories
	Using Stunnel to Secure IMAP Connections
	More Honeynets
	Building A Better Gaming Machine
	Dynamic IPTables Firewalls


4) App o' the week


~~~~~~~~~~~~~~~~~~~~~~ ADVERTISEMENT ~~~~~~~~~~~~~~~~~~~~~~~
                        CBT NUGGETS

Get your hands on the best training resources available for
Win2K certifications. Unmatched quality at an incredibly
low price gets you $10,000 worth of training for only $299.
Click below to view a sample clip...

http://ad.brainbuzz.com/?RC06&AI$59

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

For information on how to advertise in this newsletter
please contact mailto:adsales@BrainBuzz.com or visit
http://cramsession.brainbuzz.com/marketing/default.asp

===========================================================
1) Sean's Notes
===========================================================
I was browsing around the web the other day, and came across
a helpful hint that should make your X-Windows session more
responsive.

renice -10 -p PIDOF_X

where PIDOF_X is the processid of your X-Windows server.
Recall from the March 8th issue of this newsletter, each task
in the system is given a processid:

http://www.ertw.com/~sean/newsletter/March+8%2C+2001

Each processid also has a "nice level" attached to it, a
value of -20 to +20 (or +19, depending on who you ask), with
-20 being the highest priority.  So, a process is considered
"nice" if it doesn't want too much of the CPU.  What we're
doing in the above command is giving the X process a higher
priority. Note that you probably don't want to do this on a
server!

UNIX is a pre-emptive multitasking operating system.
"Pre-emptive" means that processes don't have to be aware
they're running alongside others -- the operating system will
dole out (and take away) their use of the CPU as it sees fit.
Contrast this with a non pre-emptive system like Windows 3.1,
where the application had to relinquish control of the CPU
when it was done.

So, the Linux scheduler (part of the kernel) works hard at
giving CPU time to processes, timing them, and then moving on.
But how does it choose which process to put on the burner?
Enter priorities.

In a nutshell, each process gets a priority based on the nice
level and some other factors, such as how long it's been
sitting idle.  This is all mashed into a number between 0-99,
and is considered to be the process's priority.  The kernel
looks in the top priority bin to see if any processes are in
there.  If so, they get the CPU for a time slice.  When it's
done with it's slice, the process goes to the end of the queue
(within the same priority).  So, as long as a process with a
higher priority is ready for the CPU, lower ones won't execute.

As I said above, the priority depends on other factors.  The
kernel is tuned so that a process can't hog the CPU -- if it
stays on the burner too long, its priority is slowly
decremented until the system is normal again.

The next thing to remember is that the computer is super fast
compared to the IO system (including the users!).  A process
may need to access the disk or other input device.  While
it's waiting for the data, the kernel marks it as waiting for
IO and puts it to sleep.  While in this state, it doesn't get
the CPU.  Once the data arrives, this process will pre-empt a
lower priority process that is on the CPU, if applicable.  On
most systems, this is enough to keep the system usable.  Put a
few CPU bound processes in, and that's when the administrator
is going to have to step in with the renice command.

renice isn't just for administrators, users can use it too,
subject to some restrictions.  A normal user can only assign
priorities between 0 and 20 -- negative numbers aren't allowed.
Furthermore, you can only increase the nice level, you can't
decrease it. You can also start the process at a nice level of
10 (most processes by default are 9 or less) with the nice
command:

nice mycommand

(check out the man pages for "nice" and "renice" for more
 usage)

That's the process scheduling system in a nutshell.  Those
interested in the dirty details can check out

http://www.oreilly.com/catalog/linuxkernel/chapter/ch10.html

sched_setscheduler manpage, and the pages in the see also
section /usr/src/linux/kernel/sched.c  (it is well commented).

Don't forget about the Brainbuzz Linux News Board, where you
can post your comments about the newsletter and talk with
other readers:

http://boards.brainbuzz.com/boards/vbt.asp?b–2

Long live the Penguin,

Sean
mailto:swalberg@brainbuzz.com

===========================================================
2) Linux News
===========================================================

------------------------
Ximian GNOME 1.4 is Out!
------------------------
Ximian, formerly Helix Code, are the guys that put together
a great distribution of GNOME related stuff. Their latest
release incorporates GNOME 1.4 and Mozilla. Installation is
super easy, but at the moment is pretty slow due to the huge
load.

http://www.ximian.com/

----------------------------------
Perl: The Complete Reference (2ed)
----------------------------------
If you're looking for a book that will teach you PERL, and
then act as a great reference, this is for you. Starting
off with the basics, it takes you through the language,
with plenty of examples to help you along.

http://itresources.brainbuzz.com/tutorials/tutorial.asp?t=S1TU1248

-----------------------
IBM Takes to the Street
-----------------------
IBM's Peace, Love, and Linux slogan which was slapped on
billboards has graced the pavement of San Francisco. You'd
think geeky stuff like this would go over well, but some
key people weren't impressed. At least they were able to
wash it off!

http://www.zdnet.com/zdnn/stories/news/0,4586,2710728,00.html?chkpt
=zdhpnews
01

------------------------
Linux as a Radio Station
------------------------
In the "fascinating, but completely useless category", Real
Time Linux has been used to turn a Linux box into a radio
transmitter. That's right -- it toggles voltages on the
parallel cable to act as an antenna. This article explains
what RTL is, and how it differs from normal Linux operation.

http://www.linuxdevices.com/articles/AT3239582376.html

===========================================================
3) Linux Resources
===========================================================

-----------------------
Application Directories
-----------------------
This Freshmeat editorial asks why the current filesystem
is laid out the way it is. Windows 3.1 had something going
for it, as most everything was stored in its own directory.
In UNIX, though, all the binaries are crammed into a handful
of directories. When package management doesn't cut it, what
do you do?

http://freshmeat.net/articles/view/247/

----------------------------------------
Using Stunnel to Secure IMAP Connections
----------------------------------------
Stunnel is a utility that allows you to tunnel protocols
over SSL. In this example, IMAP is the target. Various
methods of doing it are explained, depending on what your
client can support.

http://members.home.net/beldridg/imaps.htm

--------------
More Honeynets
--------------
The folks at the Honeynet project have updated their "Know
Your Enemy" series of papers. This time, a detailed analysis
of the implementation of their Honeynets is presented. For
those that were wondering how they prevent crackers from
doing serious damage to other sites after cracking a
honeypot, this question has been answered.

http://project.honeynet.org/papers/honeynet/

--------------------------------
Building A Better Gaming Machine
--------------------------------
Building a better gaming machine is different from building
that perfect web server. There are different bottlenecks to
overcome, and different items to add on. This article walks
through the things you'll want to keep in mind for that next
upgrade.

http://linux.com/newsitem.phtml?sid&&aid810

--------------------------
Dynamic IPTables Firewalls
--------------------------
"Firewalls are good and fun, but what do you do when you
need to make rapid, complex changes to your firewall rules?
Easy. Use Daniel Robbins' dynamic firewall scripts that are
demonstrated in this article. You can use these scripts to
increase your network security and responsiveness, and to
inspire your own creative designs."

http://www-106.ibm.com/developerworks/linux/library/l-fw/index.html
?dwzone=l
inux

===========================================================
4) App o' the week
===========================================================
This week's app isn't for Linux, it's for Windows.  Crazy,
you say? Probably. Foxserv is an installer for the Windows
versions of Apache/PHP/MySQL. If you can't spare a box for
Linux, but need a great web development platform, give this
a shot.

http://sourceforge.net/projects/foxserv/

===========================================================
(C) 2001 BrainBuzz.com. All Rights Reserved.
===========================================================

_______________________________________________________

         This message is from BrainBuzz.com.

You are currently subscribed to the
   Hottest Linux News and Resources
   as: sean@ertw.com

To un-subscribe from this newsletter by e-mail:
   send a blank email message to:
   mailto:leave-linuxnews-3825955Y@list.cramsession.com

-------------------------------------------------------

To Subscribe to this newsletter by e-mail:
   send a blank email message to:
   mailto:join-linuxnews@list.brainbuzz.com
_______________________________________________________