LINUX NEWS
RESOURCES & LINKS FROM BRAINBUZZ.COM
Thursday, February 22, 2001TABLE OF CONTENTS
1) Sean’s Notes
2) Linux News
Planning GNOME 2.0
Linux and POS systems
Bastille Linux Update
Real World Linux Security Book Review3) Linux Resources
Tired of FSCKing?
GNOME 1.4 Beta 1 Released
Fun With Netfilter
Linuxsecurity.com on Netfilter
KDE 2.1 Released4) App o’ the week
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1) Sean's Notes
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The way that Linux knows what processes to start up, and the
order in which it does this, tends to be a source of
confusion for many. This week, I hope that I'll be able to
clarify this for you.
The first thing to do is to define a runlevel. UNIX uses
runlevels as a way to keep track of what state the system is
in. There are 7 default runlevels, numbered 0-6. Each one
is associated with a particular state. 0 and 6 are halt and
reboot respectively. So, another way of saying "reboot that
machine" is to say "switch to runlevel 6!". Runlevel 1 is
called "single user mode". In this state we're either
bringing up the system or are in maintenance mode. No users
can log in remotely, and there is limited functionality. The
idea is to get the system at a state where it is stable so
file system checks and others can be run.
Runlevels 2 and 4 aren't really used anymore, which leaves
us with 3 and 5. 3 is called "multiuser". If anyone
remembers the way Slackware used to boot up, it would say
"going multiuser..." at which point it would switch into RL3.
This is the normal operation for a server, as all the normal
services are running. 5 is the same as 3, except that you
add your X window system. Most of us will be in runlevel 5.
Another thing to note is that to get to runlevel 5, you
don't have to hit 0-4. You can jump between them all you
want. To actually change runlevels, use
/sbin/init newrunlevel
That's all well and good, but how does one define what
services are started in what run level? Glad you asked.
The answer is in the SysV init system. Take a peek in
/etc/rc.d:
\[sean ~]$ ls /etc/rc.d
init.d rc rc.sysinit rc1.d rc3.d rc5.d
rc.local rc0.d rc2.d rc4.d rc6.d
The important ones to note are init.d, and the rc?.d
directories. First take a peek in init.d. You'll see a
bunch of files, one for each service, in that directory.
Each one is responsible for starting and stopping a
service. If you have a file called httpd, which starts
and stops the web server, you can run
httpd start # start the web server
httpd stop # stop the web server
httpd status # is the web server running?
The next piece in the puzzle is the rc?.d directories. You
probably guessed it, but the number has something to do with
the runlevel. Looking in the directory, you'll see that the
files are links to the respective file in ../init.d, and
that the names are funny. S80sendmail? What's that mean?
A good question!
Upon entering runlevel N, the system does the following:
1. Iterate through all the files in /etc/rc.d/rcN.d that
start with K, processing them in order of the number,
ie. K10abc before K20def. For each file, run it with the
"stop" parameter
2. Do the same thing for all the "S" files, but with the
"start" parameter
So, if you want a service to start in runlevel 3, say,
between cron (40) and inetd (50), give it a start priority
of 45. (Note that the priorities aren't necessarily
essential, but it allows you to ensure that networking is up
before you start your web server and the like). You'll also
want to make sure that all the other runlevels have a
corresponding Kill script, since it's entirely possible that
you switched from a runlevel where it was running into one
where it shouldn't.
Managing those symlinks is a big task. Fear not, Red Hat-
based distributions include "chkconfig" to help manage, and
Debian-based ones use "update-rc.d" (thanks to faithful
reader and Debian aficionado Guitarlynn for finding that
one!) Alas, the use of those commands will have to wait for
another newsletter, but the man pages are pretty good!
Don't forget about the Linux Newsletter board, where you can
talk to myself and other subscribers:
http://boards.brainbuzz.com/boards/vbt.asp?b2
Long Live the Penguin.
Sean
swalberg@brainbuzz.com
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2) Linux News
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------------------
Planning GNOME 2.0
------------------
Miguel de Icaza, guru of all GNOME, shares his vision of
what's going in to GNOME 2.0, and even closer, 1.4. There
are lots of things in there, like GNOME-VFS (a shared
filesystem), and better interoperability between
applications.
http://primates.ximian.com/~miguel/gnome-2.0/
---------------------
Linux and POS Systems
---------------------
"Red Hat and Wincor Nixdorf to Deliver a Linux and JavaPOS
Solution Platform for Retail POS Systems". Linux is easily
deployable, and runs on a variety of different hardware,
making it an ideal candidate to run a Point of Sale (POS)
system. Home Depot uses it, so have a look!
http://www.redhat.com/about/presscenter/2001/press_wincor.html
---------------------
Bastille Linux Update
---------------------
Bastille Linux is a set of scripts that really harden a
Linux box. They've gone through some rapid development
lately after some cash infusion, so now is a good time to
look at this. It's great for people just getting started in
Linux, because all the options are well explained.
http://bastille-linux.sourceforge.net/
-------------------------------------
Real World Linux Security Book Review
-------------------------------------
If you're looking to start taking security into your own
hands, this cookbook style manual is a good one. Real World
Linux Security walks you through the ways to lock down
Linux, to monitor for weaknesses, and how to minimize the
damage if you do get broken.
http://itresources.brainbuzz.com/tutorials/tutorial.asp?t=S1TU1171
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3) Linux Resources
-------------------------
-----------------
Tired of FSCKing?
-----------------
Journalling file systems allow quick recovery after an
unclean shutdown. Did you know that they can also make your
file system faster and make more efficient use of space?
This article investigates some of the various journalling
file systems out there, with an eye on how they improve
performance.
http://freshmeat.net/articles/view/212/
-------------------------
GNOME 1.4 Beta 1 Released
-------------------------
With features like a newer panel, better help, better
applications, and the usual bug fixes (and fresh bugs, of
course), a Beta of GNOME has been released. I wonder if
this has anything to do with the upcoming KDE 2.1 release?
http://slashdot.org/articles/01/02/18/1343236.shtml
------------------
Fun With Netfilter
------------------
This tuneup article from Linux.com takes you through some
basic and advanced iptables commands. iptables has some
really fancy modules, so you can trigger a rule based on
traffic volumes and the like.
http://linux.com/tuneup/database.phtml/Networking/2192.html
------------------------------
Linuxsecurity.com on Netfilter
------------------------------
Linuxsecurity.com is a pretty good place to pick up tips
and tricks about securing your Linux system. Dave Wreski,
security guru and all around nice guy, has put together an
informative article on what netfilter is all about.
http://www.linuxsecurity.com/feature_stories/kernel-netfilter.html
----------------
KDE 2.1 Released
----------------
According to the KDE home page, 2.1 was supposed to be
released by the time you get this. At any rate, 2.1beta was
released a couple of weeks ago in anticipation of the 2.1
release. KDE is a great WM that doesn't seem to have
received the breaks that GNOME has.
http://www.kde.org
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4) App o' the week
-------------------------
Need a system to run your helpdesk, track trouble tickets,
or software issues? Look no further than Request Tracker!
Featuring powerful tracking, multiple users and queues, and
a great web interface, this software is sure to help you out.
http://www.fsck.com/projects/rt/
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