Linux Format Newsletter -- #43, November 2008

M-Saunders — Tue Feb 17, 2009 3:50 pm

Author: M-Saunders

Posted: Tue Feb 17, 2009 3:50 pm

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LINUX FORMAT WEBSITE NEWSLETTER -- #43, NOVEMBER 2008

www.linuxformat.co.uk

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CONTENTS

1. Welcome!

2. LXF 113 on sale

3. In the news...

4. This month on the forum

5. Special Newsletter feature

6. Coming up next issue

7. Receiving this Newsletter

8. Contact details

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1. Welcome!
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It's been a busy couple of months here at LXF Towers, but alongside
the regular magazine we've also produced a special edition: You Can
Code! This is a follow-up to Code It, and is chock full of hands-on
programming tutorials. We don't spend ages waffling on about drab
theory and algorithms: instead, we show you how to make cool
projects from start to finish, such as news reader, IRC bot,
flashcard game and music synth library. We even touch on the black
magic of assembly language! Click here for more info:

http://www.linuxformat.co.uk/blog/?p=434

Meanwhile, enjoy this month's Newsletter. We have a look at LXF
issue 113, roundups of the most notable news stories and forum
threads, and a special feature on unraveling the mysteries of
executable files...

Mike Saunders
Newsletter Editor
Mike.Saunders@futurenet.com

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2. LXF 113 on sale
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If you're based in the UK, you should find the latest issue of Linux
Format waiting eagerly on newsstands -- or if you're a subscriber,
you'll already have it! This month we've turned our attention to the
wild and wonderful world of distro building. Surely only ubergeeks
can make their own distro, right? Not so: with the right tips and
tricks, anyone with a bit of time can craft a flavour of Linux with
personalised software selections, themes and more.

We also look at Ulteo, the ongoing effort to revolutionise Linux
from Mandrake founder Gael Duval. Ulteo hopes to free your desktop
from the shackles of a single machine -- you'll be able to access it
wherever you have an internet connection, much like webmail.

Meanwhile, Neil Bothwick shows you how to get your Linux laptop
running with mobile broadband, and on our 4GB DVD we have the brand
new Mandriva One 2009, a super-friendly distro that runs in Live
mode (it's also installable). Editor Paul has taken the HotPicks
helm this month, and one of his choices is this bizarrely named RPG
construction kit...

# OHRRPGCE 2008-10-03 -- http://hamsterrepublic.com

Are you feeling creative? Good, because you're about to delve into
a program that gives you complete control over the role-playing
game of your dreams. Yes, that means you can draw your own
graphics, create complex, multi-area maps, design mighty heroes
and enemies, forge powerful magic items and create gigantic
fictional worlds for them all to live in.

What's impressive about OHRRPGCE isn't its name, which apparently
stands for Official Hamster Republic Role Playing Game
Construction Engine. Instead, what we like is that the engine lets
you create everything for your world - you can draw tiles, heroes
and items in its pixel graphics editor, then you can go straight
to the map editor and use those tiles to create your worlds. From
there, you can go on and create all the other artwork you want,
using boxes, lines, fills, air brushes and even a basic clone
stamping tool. If you'd rather use Gimp, just create your graphics
there and import them when you're done.

With your artwork in place, the real work begins: you can assign
every hero and enemy statistics - how hard are their attacks? How
well can they evade? How powerful is their magic? This is done
quite neatly - you set values for level 0 and for level 99,
leaving OHRRPGCE to calculate the values in between for you. You
can then specify strengths and weaknesses for them all. Again, you
don't have to get into the maths here: simply tell the engine what
you want, and it figures it out for you.

The last step of creation is the most fun: arranging the fight
sequences. Again, this is all done graphically - you get a live
preview of how the fight will look as you choose your background,
add your bad guys, then position them as you please. After your
work, you get a single RPG file that you can distribute to friends
and the internet at large. Then you can sit back and wait for the
global adoration and multu-million dollar publishing contracts to
arrive...

See the LXF website (http://www.linuxformat.co.uk) and click on the
right-hand issue pic for a full lowdown on 113's contents.

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3. In the news
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Mandriva and Ubuntu get a wee bit faster...

# Xfce-fronted Mandriva respin pops up
http://www.linuxformat.co.uk/modules.php?op=modload&name=News&file=article&sid=765

Love Mandriva? Fancy a version with a snappier GUI? XFCELive is a
community-based effort to bring the distro and desktop environment
closer together, and the 2009.0 release is now available (albeit
with a few rough edges -- see the 'Known Issues' bit).

# The LXF Test: OpenOffice.org 3.0
http://www.linuxformat.co.uk/modules.php?op=modload&name=News&file=article&sid=763

Debian 5.0, aka Lenny, inches closer with the first release
candidate of the installer. Details are up of the most recent
improvements and gotchas, and the team is looking for more testers
to ensure Debian's famous stability is maintained.

# Making Ubuntu faster
http://www.linuxformat.co.uk/modules.php?op=modload&name=News&file=article&sid=761

The end of October saw the much anticipated release of Ubuntu 8.10 -
affectionately called the Intrepid Ibex. It's a release that sees
Ubuntu going from strength to strength. And with its popularity
reaching stratospheric proportions, TechRadar thought that now was
the perfect time to pool together its favourite tips into one place.

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4. This month on the forum
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Is KDE 4 going to be the next Vista? That was the question posed by
Haakin, who'd had less than positive experiences with the new
desktop. Even the most ardent KDE fan agrees that 4.0 wasn't the
most mind-blowingly exciting release, but many believe that 4.1 has
filled in the gaps and is ready for regular usage, a sentiment
echoed by some of the forum regulars. What have been your
experiences of 4.1? Join in the thread! [1]

Full-time Linux users naturally save quite a bit of money by not
buying commercial products. But what about the other aspects: eg not
having to pay for support calls (due to improved reliability)? Some
users noted that more important than cash-saving is time-saving, and
Free Software works very well there when you've got more freedom and
flexibility. [2]

[1] http://www.linuxformat.co.uk/index.php?name=PNphpBB2&file=viewtopic&t=8849

[2] http://www.linuxformat.co.uk/index.php?name=PNphpBB2&file=viewtopic&t=8847

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5. Special Newsletter feature
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UNRAVEL THE MYSTERIES OF EXECUTABLE FILES

A program: it's just a bit of code run by the CPU right? Well,
that's partially correct, but an executable binary file on a Linux
system actually does a lot more. Firstly, most binaries use dynamic
linking to run code that's in separate libraries, hence why
dependencies play a major part in Linux distros.

You can find out which libraries a program needs via the 'ldd'
command:

mike@mikehost:~$ ldd /bin/ls
linux-gate.so.1 => (0xb7f0a000)
librt.so.1 => /lib/tls/i686/cmov/librt.so.1 (0xb7eea000)
libselinux.so.1 => /lib/libselinux.so.1 (0xb7ed1000)
libacl.so.1 => /lib/libacl.so.1 (0xb7ec9000)
libc.so.6 => /lib/tls/i686/cmov/libc.so.6 (0xb7d7a000)
libpthread.so.0 => /lib/tls/i686/cmov/libpthread.so.0 (0xb7d62000)
/lib/ld-linux.so.2 (0xb7f0b000)
libdl.so.2 => /lib/tls/i686/cmov/libdl.so.2 (0xb7d5e000)
libattr.so.1 => /lib/libattr.so.1 (0xb7d5a000)

Here we see that the 'ls' binary depends on several libraries, and
it shows where it's finding those libraries. Just about every
program on your system, apart from those statically compiled (ie
having all the libraries rolled in) depends on the C library,
called libc.so.6 here.

Linux systems primarily use a binary format called ELF (Executable
and Linkable Format). These files are composed of sections to
separate code and data, and one of the benefits of this is
stability. You don't want to start accidentally executing plain text
or image data, for instance!

To find out which sections are in a binary, use the 'readelf'
command: 'readelf -S gedit'. The most important sections are:

.bss -- Uninitialised data for use by the program
.data -- Pre-initialised data (eg text strings)
.text -- Executable machine code

The use of sections makes it easy to disassemble the machine code in
a program -- that is, convert the binary into human-readable
assembly language. (Contrast this with simple binary formats which
mix together code and data; when you disassemble a program, you
don't always know if you're looking at real code!)

For instance, save this C program as foo.c and compile it:

#include <stdio.h>

int main()
{
return(999);
}

eg using 'gcc foo.c'. Then run 'objdump -d a.out > foo.txt' to
disassemble the machine code parts of the resulting binary. 999 in
decimal is 3e7 in hexadecimal, so search through foo.txt for 3e7.
Ta-da: it's in the 'main' section:

8048352: b8 e7 03 00 00 mov $0x3e7,%eax
8048357: 59 pop %ecx
8048358: 5d pop %ebp
8048359: 8d 61 fc lea -0x4(%ecx),%esp
804835c: c3 ret

You don't need to understand assembly language for this, but you can
see the number 0x3e7 in the first line of this code chunk. Then
there's a bit of clearing up, before the 'ret' exits from our main()
routine. The disassembly contains a lot of other code generated by
GCC for housekeeping and initialisation, but with objdump you can
find out exactly where your code lies in the binary using the above
method.

This subject can get very complicated, but now you know the
fundamentals of how a Linux executable fits together. For more, see
this IBM DeveloperWorks article:

http://www.ibm.com/developerworks/aix/library/au-unixtools.html

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6. Coming up next issue
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Linux Format 114, on sale Thursday 11 December...

# Linux in your pocket! Store your OS, programs and documents
in a tiny, cheap USB stick

# Banish daemons: prevent memory-hogging apps from running
when your distro starts

# Host your own web server and become a .com millionaire

# Keep tabs on your personal finances with Free Software

(Exact contents of future issues are subject to change. Only
Mystic Meg knows for certain.)

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7. Receiving this Newsletter
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If you've been forwarded this Newsletter from someone else, and want
to sign up for future issues, just follow the steps below. Each
month you'll receive a sparkling new LXF Newsletter straight in your
Inbox, and the 30-second sign-up process is even easier than Green
Hill Zone 1:

1. Go to the website forums and log in (or sign up first):
http://www.linuxformat.co.uk/forums/
2. At the top of the main forum page, click on 'Usergroups'
3. Join the 'Newsletter' group, and you're done!

If for some reason you no longer wish to receive this newsletter
(which'll make the internet scream) you can opt-out like this:

1. Log into the LXF site and go to the forums
2. Click Usergroups at the top of the page
3. Select Newsletter and then View information
4. Click Unsubscribe next to 'You are a member...'

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8. Contact details
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If you have any questions or suggestions, please send them to the
Newsletter Editor at the address below:

Newsletter Editor: Mike Saunders -- Mike.Saunders@futurenet.com

Letters for the magazine: lxf.letters@futurenet.com

LXF website: http://www.linuxformat.co.uk

Subscriptions: 0870 837 4722 (overseas +44 1858 438794)
Website subscription page: http://www.linuxformat.co.uk/subscribe/

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(C) 2008 Future Publishing Limited

Linux Format forums

Linux Format Newsletter -- #43, November 2008