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<h1><span><em>live Arch Linux</em> builder</span></h1>
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<h2 id="pagetitle" level="1">Introduction</h2>
<blockquote>
<h3>Warning</h3>
<p><em>Before we get started I should point out that most of the
<em>larch</em> scripts must be run as root in order to do their work,
and that much of this work consists of deleting and overwriting files
and even complete directories. If just one of these is wrong it might make
quite a mess of your system. That is quite normal for an installer,
but you will be using it on a system that
is already configured and this is somewhat risky - if you set up your
configuration wrong (or if you or I made some other mistake ...), you
might find you have destroyed some important data and/or your system
doesn't work any more. But that's life - <strong>Share and
Enjoy!</strong></em>
</p>
</blockquote>
<p>Below is the general introductory blurb, but for those who want to jump
straight in and try it out I would suggest the following pages as possible
starting points:
<ul>
<li><a href="larch_quick.html" >Quick Start with the GUI</a>
</li>
<li><a href="larch_quick-console.html" >Quick Start on the command line</a>
</li>
</ul>
</p>
<h3><a name="live_system"></a>What is a <em>live</em> system?</h3>
<p><em>larch</em> is a collection of scripts designed around the creation and
use of custom <em>live</em> media (USB-stick/CD/DVD) of <em>Arch Linux</em>.
A <em>live</em> operating system is one which can reside on a removable medium
and boot on (ideally) any computer (of compatible architecture) into which
it is inserted. This can be useful in quite a variety of situations, for
example for testing purposes, for rescue purposes on machines whose
installed operating system is broken, or as an installation medium (many
linux distributions use <em>live</em> systems as installers). But there
are also situations where a permanently installed <em>live</em> system
can offer advantages over a normal installation, perhaps because of the
compression or because a <em>live</em> system is quite robust - it is
in essence read-only (though there are ways of supporting data persistence),
and can be quite insensitive to hardware changes.
</p>
<p>The main features of the <em>larch</em> system are listed on the
<a href="larch_features.html">Features</a> page, among the most
significant might be the use of <a href="profiles.html">'profiles'</a>
to define the characteristics of the system to be built, the ability
to install the <em>live</em> system to various media and simple support
of data persistence. In addition it tries to remain as close
to standard Arch Linux as possible, using (by default) the standard
kernel, the same initscripts, <em>mkinitcpio</em> for building the
<em>initramfs</em>, etc.
</p>
<h3><a name="requirements"></a>Build system requirements</h3>
<p><em>larch</em> has been designed to work without extensive demands on
the build system. Although it has been developed under <em>Arch Linux</em>,
<em>larch</em> should run on other <em>GNU/Linux</em> systems. By means
of a sort of bootstrapping, the required software has been kept to a
minimum - many of the build functions are carried out on the newly
installed <em>Arch</em> system using <em>chroot</em>.
For example, you do not need support for <em>squashfs</em> or <em>aufs</em>
on the build system. But basic utilities which are normally available on any
<em>GNU/Linux</em> system, such as <em>bash</em>, <em>file</em>,
<em>find</em>, <em>blkid</em>, <em>mkisofs</em> - and
of course <em>chroot</em> - are assumed to be present (on <em>Arch</em>
that is packages 'bash', 'e2fsprogs', 'util-linux-ng',
'coreutils', 'findutils', 'file', 'cdrkit').
</p>
<p> The <em>larch</em> scripts are written mainly in python, but snippets
of bash crop up here and there.
In addition to python you must also have the pexpect module available
(in <em>Arch</em> the 'python-pexpect' package). The (optional) GUI
requires pyqt. I'm not sure what the oldest supported versions are,
development was done using python-2.6 and pyqt-4.7.
I think python-2.5 should be alright, and I have heard that
pyqt-4.4 probably doesn't work.
</p>
<h3><a name="cli_gui"></a>Command line vs. GUI</h3>
<p>
The basic functionality of <em>larch</em> is provided by command-line scripts,
but a graphical user interface is available, to make it easier to see what
options are available and to avoid the need to remember and not mistype
obscure command line parameters. In addition to providing a front-end to the
main scripts the GUI also provides help with organising the configuration
files.
</p>
<h3><a name="overview"></a>Overview</h3>
<p>One design aim was easy customisation, so that even relatively inexperienced
users could build personalised <em>live</em> systems on USB-stick or CD/DVD,
containing whatever
packages they wanted and with their own personal configurations. The resulting
medium should also be usable for installation purposes, so that one has a
customised <em>Arch Linux</em> installation/rescue medium. As the content can
be chosen freely, a comfortable working environment is possible - in contrast
to the rather Spartan standard <em>Arch</em> installation CD. However, note
that it is also possible, using the officially supported <em>archiso</em>, to
produce a customised <em>Arch Linux</em> installation/rescue medium (see the
corresponding <em>Arch wiki</em> page). The approach taken by the two projects
is somewhat different so do have a look at both. Note that at the latest since
version 7, <em>larch</em> makes no pretence of a 'KISS' approach. The code is,
I'm afraid, rather complicated. The resulting <em>live</em> system should,
however, be very close to a normal non-<em>live Arch Linux</em> system (as
far as the <em>squashfs + aufs</em> basis allows).
</p>
<p><em>larch</em> offers a flexible approach to building your
<em>live</em> media. You can use 'profiles' to determine what gets installed,
and how it is configured. The advantage of this method is that all your
specifications are kept together in a folder which can be used to rebuild the
same or a similar system at a later date. Alternatively you can do a normal
<em>Arch Linux</em> installation (if there is such a thing!) and then make a
<em>live</em> medium from this (e.g. by running <em>larch</em> on it from a
<em>live</em> medium).
</p>
<p>The use of <em>squashfs</em> in the resulting system means that the space
occupied will be significantly less than in the 'raw' state, normally about a
third of the original. As a result of this decision, it is not possible to write
directly to the system - which would seem to be quite a drawback, though in
some situations it can even be an advantage. The use of <em>aufs</em> (a
'unification' file-system, originally based on <em>unionfs</em>) allows the
resulting system to use a writeable 'overlay', so that the system behaves in
most respects like a normal installation. Of course if the boot medium is not
writeable (e.g. a CD) it may be difficult to provide a persistent writeable
layer (full persistence, which would include kernel updates, is completely
impossible in such a situation). In that case, or in general if it is
desired that there is no
persistence (e.g. for 'kiosk' type situations), <em>tmpfs</em> (a
memory-based file-system) can be used for the writeable layer.
</p>
<p>If the <em>larch</em> system is used in the same way as a normal
<em>Arch</em> installation, including package updates, the space saving
effect of the <em>squashfs</em> archive can be lost (updates cannot
modify the base archive, so they occupy additional space). At some point
it would then be desirable to rebuild the system. This should be fairly
straightforward, but it is not really the envisioned use of <em>larch</em>
media.
</p>
<p>Hardware detection is provided by the same <em>udev</em> approach as is
used in a standard <em>Arch Linux</em> system.
</p>
<p>The <em>larch</em> project comprises several components. The scripts for
building a <em>larch live</em> medium are in the <em>larch</em> package, which
need not itself be installed in the <em>live</em> system, though it may be
useful (and is indeed installed by default). Scripts and data for the
<em>live</em> environment are provided in the
<em>larch-live</em> package, which must be installed in the <em>live</em>
system. There is also an optional installer (<em>larchin</em>) which can
install the <em>live</em> system to hard disk, providing a convenient way
to install a ready-configured <em>Arch Linux</em> system.
</p>
<p>As with <em>Arch Linux</em> in general <em>larch</em> is not really
designed for beginners - you should know your way around a
<em>GNU/Linux</em> system (preferably <em>Arch</em>!), and be aware of the
dangers of running such programs, such as corrupting your whole system.
In any case, I hope that the
documentation will be clear enough to help anyone who wants to exploit
<em>larch</em> to the full (feedback is welcome!).</p>
<p><b>Space Requirements:</b>
You need quite a lot of space to create a <em>live Arch Linux</em> system.
Bear in mind that a complete <em>Arch Linux</em> system is installed, then,
additionally, a compressed ('squashed') version is made, and then perhaps
even a CD image (<em>iso</em>).
Building for a USB-stick requires slightly less space, as the iso-image is
not built. If building a <em>live</em> version of an existing
<em>Arch Linux</em> system, much less space is required as no new
system must be installed.
</p>
<h3><a name="larch_installation"></a>Installation of the <em>larch</em> build
system</h3>
<p>The recommended way of installing <em>larch</em> is by means of the setup
script, see <a href="larch_quick-console.html">here</a> for details.
This installs all the necessary packages to a working directory, and it
should also work on non-<em>Arch</em> linux systems.
</p>
<p>The <em>larch</em> package may, however, be installed in the normal
<em>Arch Linux</em> way using <em>pacman</em>. This method will only work on
an <em>Arch</em> system, of course. The <em>larch</em> repository is at
<a href="ftp://ftp.berlios.de/pub/larch/larch8/i686/">
<strong>berlios</strong></a>.
</p>
<p>The <em>larch</em> command line scripts need to be started as root, and
each has a usage message (run with the '-h' option). The gui should be
started as a normal user (it uses <em>su</em>, or can be configured to
use <em>sudo</em> instead, to get administrator rights when needed).
</p>
<h3><a name="larch_profiles"></a>Profiles</h3>
<p>A <em>larch</em> 'profile' is a directory containing the information
needed to build a particular 'flavour' of <em>Arch Linux</em> as a
<em>live</em> system - which packages to install, and how it should be
set up. For details see <a href="profiles.html">Profiles</a>.
</p>
<h3><a name="stages"></a>The stages of the build process</h3>
<p>The starting point is an <em>Arch Linux</em> installation. This can
be an already existing one from which you want to make a <em>live</em>
version, or - the recommended approach - you can use the
'Installation' stage of the <em>larch</em> system
(using the <strong>archin.py</strong> script) to prepare this.
<em>archin</em> downloads all the desired packages (if they are not already
in the host's package cache) and installs them to a directory on the host.
See <a href="archin.html">this page</a> for details.
</p>
<p>Once we have the <em>Arch Linux</em> installation this can be
processed to build the basis components for the <em>live</em> medium. The
installation is compressed into a <em>squashfs</em> archive, and an
overlay directory containing the necessary modifications to the base
system is built - a sort of 'patch' directory for the basic installation.
The latter contains a few necessary
adjustments for running as a <em>live</em> system and also the
customisations specified in the <em>profile</em>. The other important
component is the <em>initramfs</em>, which also needs to be adapted
to boot the <em>live</em> system. This processing is performed by the
<strong>larchify.py</strong> script, see
<a href="larchify.html">this page</a> for details.
</p>
<p>When the 'larchification' has been completed, the components can
be packed together onto a boot medium together with a bootloader. The
<strong>live_iso.py</strong> script creates an <em>iso</em> file, which
can then be written to a CD or DVD, the <strong>live_part.py</strong>
script sets up a bootable partition on a disk(-like) device, such as a
USB stick. See <a href="medium.html">this page</a> for details.
</p>
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