Luca Casagrande: luca.casagrande@gmail.com; http://ominiverdi.org

Introducition

What is a Livecd

As Wikipedia report, liveCd is a "is a generic term for an operating system distribution that is executed upon boot, without installation on a hard drive. Typically, it is stored on bootable media such as a CD-ROM (Live CD), DVD (Live DVD), USB flash drive (Live USB), among others". using this kind of application user can get a "taste" of a full Linux box without fighting with any setup or installation. Once the liveCd has been booted, everything it's loaded in the RAM keeping safe the hard disk. Of course, as soon as the machine it's shuted down, every change it's lost.

Tasks

There are many application that can be satisfied by a livecd:

Using your favorite application everywhere you can find a pc
Teaching purpose: people can have machine with the needed software in a boot time
Using old machine: livecd can be run on smooth machine and also without HD.
Showing project: it's a very cool way of spread your work aroun. You deliver your work ( for example data ) and all application needed to appreciate it !

Limitation of a Livecd

When building a livecd, it contains both the kernel, the drivers, the WM and all the applications. Of course is pretty impossible to put all the driver that are used for all the machine, so can happen that, during the boot the cd stops or something else goes wrong (missine lan detection for example). During the years, have been created very good tool that detect the hardware during the boot, but, like every software application, there can be still bug. So you must see a failing boot, as a crash..that will be fixed soon.

The other thing that should be clear, it's that no information it's saved while working in the livecd enveiroment. This is good from a side ( for example for keeping safe your data) but can be thedius for another way. The solution for this is use a Storage Device (like an USB HD for example) to store all your output.This approach could also be used to save configuration file, so that you can have the same setting at every boot.

Livecd and open source geospatial software

Choice

While planning the first relase, we decided those points

Ominiverdi Livecd

Objective

Our livecd will try to offer to user always this thing:

Keep all software up to date with every single official release
Include Guide, Documents and Tutorial
Grant a good hardware compatibilty

Tecnical development

We decided to use the same tool that Gentoo Release Engineering use: Catalyst. The building of a livecd using this tool, it's split in 2 phasis:

Livecd-stage1:During this phase all selected packages are built inside a chroot env. Packages that need kernel source, are skipped.
Livecd-stage2:In this phase are built the kernel and all packages that need its source.After this a bash script fsscript.sh it's runned in the chroot env and then the root-overlay it's copied in.

In each phasis configuration settings are read from text file (called spec file). Let's go more in deep:

Spec file

subarch: i686
version_stamp:sample
target: livecd-stage1
rel_type: default
profile: default-linux/x86/2006.1
snapshot: 20061227

livecd/use:

Generic

       grass
       geos
       proj
       gdal
       png
       jpeg
       szip

livecd/packages:
       x11-libs/libXft
       x11-libs/pango
       app-admin/ide-smart
       [..]

Spec file contain

Catalyst it's a tool that read a text file (spec file in gergo) that contains all the info about the cd that will be built.

This is an excerpt of a spec file:

For building the livecd, we decided to use Catalyst, the tool used by Gentoo Release Team. this choices come from 2 points:

Catalyst allow full customization
Upgrading the softwares

This tool allows the creation of "highly customized liveCd" about architecture and softwares. Catalyst uses a text file that contains information about how creating the liveCd:

Architecture to use
Software to add

Each application can be built with a custom configuration, adding or removing item from the default configuration:

[..]
sci-libs/gdal -png gif
[..]

This mean that gdal will be built using default configuration with gif support, but not with

png support.

Once the application list is read the softwares are installed using the configuration information described inside a file called packages.use

Future Development and task

Our goal is to keep the cd updated, creating new version at regular times, or at least as soon as major update or included softwares will come out.

Right now we are working on two tasks:

An Installer for the livecd
A server edition with mapserver and some webgis application

LiveCD installer

The installer will be accessible trough an icon on the desktop. The installation process will guide the user to the set up of the linux distribution in his computer. Installing on the hard disk will allow better performances and the possibility to update all packages thanks to Gentoo systems.

Server Edition

The server edition will target a server machine with minimum graphical support but full featured set of application to offer OCG Web Services and UMN Mapserver front ends (ka-Map, Open Layers, p.Mapper, ecc.).

Newsletter Volume 1 Livecd

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