root/morphix/trunk/how_tos/morphingmorphix.html

<h1>Morping Morphix</h1>

<p>In this hack we will take a closer look at how Morphix is built up,
how it can be changed and how you can have the modularity of Morphix
make your life easier. If you want to skip the details and dive into
making your first 'morph', jump down to the next section below.

<h2>Structure of a Morphix Live CD</h2>

<p>As stated in the Morphix overview hack, a Morphix live CD has a
number of directories:

<pre>
/base
/mainmod
/minimod
/exec
/copy
/deb
</pre>

<p>We will look at each of the directories on a Morphix live CD and how
they would allow you to change your live CD. The main difference is
the file types: the first three (/base, /mainmod and /minimod) are
compressed filesystems (modules), the last three are provided for
extra flexibility. Morphix' modules can be compressed using a number
of compression techniques, like cloop, squashfs or zisofs.

<p>/base

<p>This directory contains the normal boot files, similar to the /KNOPPIX
directory. The morphix file is comparable with the KNOPPIX file in
this directory. It is a lot smaller (~30MB) however, and contains only
the bare necessities for getting your live CD up and running. Kernel,
kernel modules and hardware detection reside in the boot.img and
morphix files.

<p>/mainmod

<p>A mainmodule is essentially your filesystem after your live CD has
booted up. It contains everything ranging from your commandline tools
to your windowmanager and graphical applications. Typically, most
software of a Morphix iso is kept in the mainmodule.

<p>Once base has done its work, it attempts to find any files in the
/mainmod directory of your live CD. If there are multiple files, it
will prompt the user to select one of these mainmodules. If there are
none, the user will be dropped to a bash prompt.

<p>The mainmodule that gets selected (automatically or manually) is then
mounted. The base module scripts link the necessary directories and
copies the detected configuration files into the mounted
mainmodule. The system then chroot's into the directory of the mounted
mainmodule. Scripts in the /morphix directory of this mainmodule are
executed too. For example, in a normal Morphix iso you startx,
your favorite window manager pops up and you can do business as usual,
without even noticing the modular structure of Morphix underneath.

An interesting ability of mainmodules is that these don't necessarily
have to be Debian-based. Morphix has Slackware, Fedora and SuSE
derivatives, showing the flexibility mainmodules provide.

<p>/minimod

<p>Minimods is the third type of module we currently offer. Essentially
compressed images with a script inside, minimodules can be as simple
or complex as you would like them to be. They are mounted alongside
the mainmodule at boot time. For demonstration purposes, a few examples:

<ul>
<li>Morphix Game 0.4-1 has an Enemy Territory minimodule. This module
  seemlessly integrates with Morphix Game 0.4-1, and if a morpher
  decides he doesn't want to include Enemy Territory, he simply
  removes this module.

<li>Morphix Gnome and KDE 0.4-1 have a WINE minimodule. Likewise, if a
  morpher doesn't want to include WINE on his live CD, he simply has to
  remove this file from his live CD image.
</ul>

<p>There are minimodules for Console-specific tools, Q3A and UT2k3 demos,
OpenOffice.org, Speedtouch USB modems, PHP4/Nanoweb/MySQL, and a whole
range of others. Morphix offers preliminary scripts to autogenerate
these minimodules from Debian packages, however this is an area still under
quite a lot of discussion and development.

<p>You are able to do more down-to-earth changes using
minimodules. If you want to have different minimodules containing different
home directories for your live CDs, take a look at CD-Persistant, which
even allows you to burn your home directory directly to a running
live CD, using multisession cdroms, or Xbroadcast, which will attempt
to locate remote XDMCP hosts on your local network.

<p>Needless to say, minimodules offer an extreme amount of flexibility, maybe even
too much. For this reason, the following three directories for applying changes
to your live CD during boot time have gotten a place in Morphix over the last
year.  No more do you have to rebuild your compressed images for small changes.

<p>/exec

<p>If you simply want to start a few bash scripts at boot time, this directory
is the place to put them. Knoppix gives you a single filename which is
executed at boot time, Morphix gives you a directory.

<p>/copy

<p>Using translucency, the overlay technique in Morphix, you can place
files anywhere on the filesystem. This is of course handy for
minimodules, but also for more simple purposes. Place a file in
/copy/etc and it is placed in /etc of your live CD. Place a file in
/copy/usr/local and it is placed in /usr/local. Morphers, being a lazy
bunch, enjoy using /copy for quick hacks :-)

<p>/deb

<p>Throw a debian package in here and if your mainmodule supports dpkg (ie. it
is Debian-based) the package is installed at boot time. Since this uses dpkg
directly, you will need to make sure you handle your own dependencies for any
packages you add here. As installing debian packages does cost some
RAM, make sure you don't throw too many packages in here (it also
increases the time your live CD takes to boot!). When wanting to
install large packages, using mini/main modules quickly becomes a
better alternative. But, when you need another quick hack...

<h2>Your first Morph</h2>

<p>Now we know how a Morphix live CD can be structured, lets make us a
new Live CD to illustrate. Even if you only skimmed over the last
section, 'morphing' isn't hard to start with. Lets say you want to do
something simple, like change the default background of your live
CD. There are plenty of scripts available to automate most or all of
the process, but we won't use them here. Please note that you will
need to be root for some of these commands.

<p>We need to change the contents of our CD-ROM iso. First things
first, lets make sure we can access the files on it. Lets make a
directory and mount the iso:

<pre>
mkdir /tmp/morphlight
mount MorphixCombined-LightGUI-0.4-1.iso /tmp/morphlight
</pre>

<p>Alas, we can't directly modify the files on the iso. So, as we 
really want to modify the iso, we need to copy the iso files to a new
directory:

<pre>
mkdir /tmp/mylivecd
cp -a /tmp/morphlight/* /tmp/mylivecd
</pre>

<p>Now, where was that background located? Checking the XFCE4 
settings, you discover it is located at /morphix/background.png. Not
wanting to figure out in which module it is located, you use the
/copy-directory instead to copy your new background (located at
~/mybackground.png) over the other one at boot time:

<pre>
mkdir /tmp/mylivecd/copy/morphix
cp ~/mybackground.png /tmp/mylivecd/copy/morphix/background.png
</pre>

<p>Now, lets make us a new CD-ROM iso from this directory:

<pre>
mkisofs -l -v -J -V "My New LiveCD" -r -b base/boot.img -c \
        base/boot.cat -hide -rr -moved -o /tmp/mylivecd.iso \
        /tmp/mylivecd
</pre>

<p>Well, that was it! You can burn your iso using your favorite CD-R 
burning tool, and you're done. One freshly baked live CD with your own
background, coming right up:

<pre>
cdrecord speed=8 dev=0,0,0 /tmp/mylivecd.iso
</pre>

<p>Of course, this was a pretty simple morph. You can do quite
amazing stuff using Morphix without needing to remaster modules
directly, for lots of step-by-step recipes and more elaborate
documentation take a look at the HowTos on www.morphix.org