LINUX NEWS
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Thursday, December 20, 2001TABLE OF CONTENTS
1) Sean’s Notes
2) Linux News
Mandrake 8.1: An Easy Install?
Just What's Up With Lindows?
Perl is 14 Years Old
Sale On Linux Training3) Linux Resources
Test Your Scripts!
Understanding Rootkits
Dual Booting Linux and Windows 2000 on Large Hard Disks
Document Your Code
\*BSD Installation4) App o’ the Week
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1) Sean’s Notes
One of the selling points of Linux is that you have the source to the complete operating system. That’s great, but unless you’re a kernel hacker, why would you need the source? With a basic knowledge of where stuff sits within the kernel tree, you can easily answer questions like what driver to use, or find out if a device is supported.
The kernel sources usually live in /usr/src/linux, /usr/src/linux-2.4, or something close. On my system, the list of directories is as follows:
arch Documentation drivers fs include init ipc kernel lib mm net scripts
The arch directory contains code specific to your architecture (i.e. processor), such as how to boot, or manage memory. Not very interesting to us now.
“Documentation” is full of good stuff. Pretty much every section of the kernel has at least something in there. “serial-console.txt” is a helpful document on how to set up your console on a serial port, so that you don’t need a monitor or keyboard. The “fs” directory has basic information on every file system supported, such as where to get the userland tools to manage them, and the status of the code. “networking” has information on the protocols supported, network drivers, and how to use them. Ditto “usb” and “sound”.
The next top level directory of interest is “drivers”. Here is where you’ll find most of the support for devices. It’s laid out in a haphazard manner, so it may take some digging. Our first stop in this part of the tour is the “net” directory, which contains all the device drivers for network cards.
Let’s say you’ve got a DE202 network card, and want to figure out the driver. Chances are, it’s part of a generic driver for part of the whole family, so it won’t have a de202.c file sitting around:
[root@bob net]# grep "DE202" *.c
depca.c: DE202 Turbo (TP BNC)
depca.c: The driver has been tested on DE100, DE200 and DE202 cards
depca.c: Digital Equipment corporation, 1991, Pub. #EK-DE202-OM.001
depca.c: 0.31 4-feb-94 Added DE202 recognition.
depca.c: "DE200","DE201","DE202",\
Looks like depca.c is the file that implements the driver for the DE202 network card. If you edit the file, you’ll see instructions on what settings the driver supports, limitations (such as multiple cards), and sometimes some hints on getting the card to go. More often than not, the name of the .c file is the name of the driver. We can verify this by looking for the object file (depca.o) that will be the driver:
[root@bob net]# locate depca.o /lib/modules/2.4.7-10/kernel/drivers/net/depca.o
Yep, there you go. So to get that old DE202 card (and I’ve got a bunch!) working, you’d run:
modprobe depca
or add something like:
alias eth0 depca
to /etc/modules.conf
Under drivers/usb, you’ll find a list of drivers for USB devices. Since Linux is relatively new to the USB arena, you’d be wise to check here for support before buying that expensive device. (A search on google.com would also be a good idea, someone may have written a driver that hasn’t yet made it into the kernel.)
drivers/scsi has all the SCSI card drivers, and a lot of README files with helpful advice.
Back to the top level, I’ll skip all the way down to “net” (most of the stuff in between is the kernel itself). This contains all the network protocols. A question was asked on the Network+ board this week “Where is TCP/IP implemented in Linux?” “net/ipv4” would be the answer to that question. You’ll also find the implementation of Ethernet (not to be confused with the Ethernet drivers we saw earlier), x.25 (wow) ipv6, ipx, decnet (ouch!), 802.1D bridging, bluetooth, ATM, and a lot more.
So, really, the kernel source is nothing to be afraid of. The Documentation directory has a wealth of practical information about how the system operates. “drivers” contains all the hardware drivers the operating system comes with, and “net” has information on all the network protocols.
You don’t have to be a C programmer to make use of it, either. The grep technique above works well, and source code comments can be read by anyone. In particular, ISA cards (do they still exist?) can be configured with multiple IRQs, but only the driver source will tell you which one the driver will be looking for. If you’re seeing strange error messages, grepping around can help you determine the source, and the likely cause.
Source isn’t only for programmers anymore. It can now be a valuable tool for the systems administrator.
Happy holidays to everyone…and of course, long live the Penguin!
Sean mailto:swalberg@cramsession.com
2) Linux News
Mandrake 8.1: An Easy Install?
This article focuses on the installation of Mandrake, SuSE, Red Hat, and Win XP. The author’s system has a couple of extras, so it’s not surprising that some of the packages had some trouble. Mandrake came out on top–a few minor hiccups, but a clear winner.
http://www.newsforge.com/article.pl?sid/12/18/1410254
Just What’s Up With Lindows?
The more I think about Lindows, the more I have to wonder about its viability, or even if it will ever be completed. I’m not the only one; desktoplinux.com has written a very good article on the topic – is Lindows a good thing?
http://desktoplinux.com/articles/AT2152579590.html
Perl is 14 Years Old
Wow. I didn’t have a clue that it’s been around so long. I got my start around five years ago, and thought the language was pretty new. There is a lot of Internet history in this document too, a very interesting read if you’re interested in seeing how the Internet and Perl have evolved together.
http://history.perl.org/PerlTimeline.html
Sale On Linux Training
Judging by the amount of people on the Cramsession boards asking for Linux training locations, this $200 discount on Red Hat courses will go over well. If you’re aware of other training centers doing Linux courses, please let me know and I’ll pass it along to everyone else.
http://www.redhat.com/training/skills_offer.html
3) Linux Resources
Test Your Scripts!
I can’t count the number of times I’ve made a change to one part of a script I wrote, which broke another part. I know I should use automated tests, but until I saw this article, I thought it would be too much trouble.
http://www.perl.com/pub/a/2001/12/04/testing.html
Understanding Rootkits
A rootkit is a package a cracker can leave on your system that ensures an easy way back in. Rootkits will replace some of your system binaries, or even load themselves into the kernel. Luckily, there are tools out there to detect unauthorized changes, and some simple precautions you can follow.
http://linux.oreillynet.com/pub/a/linux/2001/12/14/rootkit.html
Dual-Booting Linux and Windows 2000 on Large Hard Disks
With a dual-boot system, you can have multiple operating systems run off the same hard drive. There are limitations, though, and things you have to keep in mind. This article is a great set of instructions on how to get Linux and Win2k to live together happily.
http://www.enterprisedt.com/publications/dual_boot.html
Document Your Code
One feature of Perl that I have been making use of lately is POD, short for “Plain Old Documentation”. It’s nothing more than specially formatted comments, with the added feature that your source code can be run through some filters to generate the documentation. It’s a lot better than trying to remember how to call a module you wrote a year ago!
http://www.linuxgazette.com/issue73/spiel.html
*BSD Installation
Even though this is a Linux newsletter, there are a lot of other Unix flavors out there that deserve the odd mention. The popular free BSDs (Free, Open, and Net) are compared in this multi-part series, focusing on the installation procedures.
http://bsdfreak.org/article_2001_11_24_4013.html
4) App o’ the week
Users are complaining your web site is too slow, but how can you measure it?
“PasTmon is an Open Source passive network application response time monitor, utilizing packet capture (via libpcap), tracking sessions, maintaining transaction state, and collecting metrics of server/network response times, segment size negotiation, and TCP window size advertisements.
The goal of the PasTmon project is to provide an engine to measure application service levels from the perspective of perceivable user response times.
Mechanisms are provided for data summarization/reduction and import into a PostgreSQL database.
A web PHP4-based front-end to example R statistical graphics is provided.”
http://pastmon.sourceforge.net/
(C) 2001 BrainBuzz.com, Inc. All Rights Reserved.
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