To begin with, lets take a look at the deepOfix directory structure.

The base directory of the deepOfix development trunk contains the following content:

 bin
 install_cd
 LICENSE
 scripts
 packages
 packages-dev
 var

* The bin directory contains scripts that are used to perform maintenance tasks on the deepOfix install CD source code.

* The install_cd directory is the one that is contained on the install CD image. This directory contains all that is required on the install CD to install deepOfix.

* The LICENSE file outlines the licensing terms of the deepOfix install cd source code.

* The packages and packages-dev directory contains the source code, build scripts etc. for the various binary packages that are custom-built for the deepOfix operating system.

* var contains rootfs folders and files.

Further sections discuss each of these directories in greater detail.

Currently the bin directory contains three important scripts:

* The mkcd script which can be used to create a new deepOfix install CD ISO image from the source code. You could then write this new image to a CD and install it. This script simply takes the contents of the install_cd directory along with the requisite boot options to generate the new CD image. To include new content to the install CD, you must add the content to the install_cd directory.

* The update-packages script generates a new PACKAGES file. This PACKAGES file is required to make a valid Debian package repository on the install CD. * The build_rootfs.sh which builds the initramfs, a basic system that is used by the kernel as init

These scripts were designed to automate and simplify manual and repetitive tasks related to the developing, extending and testing the deepOfix install CD.

This is one of the most important directories of the source code repository. It contains the layout of the on-disk filesystem found on the deepOfix install CD.

Here is a tree of the important files and directories in this directory:

install_cd/
|`- bin/
|   |`- eject
|   |`- mdadm
|    `- sfdisk
|
|`- COPYING
|
|`- deepofix/
|    |`- deepofix-packages/
|    |`- dists/
|    |`- installer/
|    |    |`- deepofix-installer-first-stage
|    |    |`- deepofix-installer-second-stage
|    |    |`- first-stage/
|    |    |`- second-stage/
|    |     `- zoneinfo
|    |
|    |`- kernel/
|     `- packages/
|
|`- isolinux/
|
|`- LICENSE
|
 `- tools/

This directory is meant to contain simple tools that will be used from the install CD during the process of installing deepOfix. All tools that exist in this directory are compiled statically to ensure that they have no runtime dependencies on shared object (.so) libraries.

This directory is meant to contain the bulk of deepOfix specific install CD source code.

* install_cd/deepofix/deepofix-packages/ contains the compiled binary version of deepOfix specific packages in the Debian .deb format.

* install_cd/deepofix/dists/: This directory is the base of the deepOfix Debian packaged distribution. It contains a directory layout (and corresponding config and data files) that can be used by the Debian apt-get package management system to install packages and their automatically computed dependencies.

* install_cd/deepofix/installer/ contains the complete source code of the deepOfix installer - both the first and second stage. First stage installer code: install_cd/deepofix/installer/first-stage/ Second stage installer code: install_cd/deepofix/installer/second-stage/

The deepOfix installer is written in simple Bash shell syntax. On the deepOfix install CD, however, the ash shell is used; this is a simpler shell with a syntax similar to that of Bash.

* The install_cd/deepofix/kernel/ directory contains different versions of the Linux kernel compiled for different platforms and CPU architectures.

* The install_cd/deepofix/packages/ directory contains all the standard, unmodified Debian packages that are installed as a part of the deepOfix operating system.

This directory contains all data required to boot the deepOfix installation CD. It includes the following important files:

* The Linux kernel - install_cd/isolinux/bzImage

* An initrd (initial ram disk) with a minimal root file system to start the deepOfix installer - install_cd/isolinux/initrd

* The main ISOLINUX configuration file - install_cd/isolinux/isolinux.cfg

* The pre-boot image that is displayed just after the CD has booted up - install_cd/isolinux/splash.lss

This directory contains the source code all deepOfix specific .deb packages. All these packages are generated using the [http://easysw.com/epm/ Easy Package Manager (epm)] tool.

* altermime - The deepofix-altermime package that plugs into the email scanning system to optionally attach disclaimers to all outgoing email messages.

* deepofix-mta - This is a virtual Debian package that provides the mail-transfer-agent package to the deepOfix system. This eliminates the need to have any other MTA such as exim or postfix installed on deepOfix.

* djbdns - This is the source for the deepofix-djbdns package used to compile and install dnscache, a caching, forward-only DNS server and tinydns, a DNS server, along with other DNS related utilities.

* easypush-webserver - This package contains the source for the [http://www.xitami.com/ Xitami Web Server] package for the EasyPush Server Manager.

* openldap - This is the source for the deepofix-openldap package that installs the [http://www.openldap.org/ OpenLDAP] directory server. OpenLDAP is used for all user and group account management functions as well as for serving public addressbooks.

* qmail-ldap - This is the source for the deepofix-qmail-ldap package which compiles and installs the the qmail-ldap mail server from source.

* qmail-scanner - This is the source for the deepofix-qmail-scanner package which installs the [http://qmail-scanner.sf.net/ Qmail Scanner] mail scanning engine for the qmail MTA.

* qmail-tools is a small collection of qmail-related tools that help in mail server administration.

* serialmail is the source of the deepofix-serialmail package that is used to relay emails to users who don't exist on deepOfix but have accounts on a remote SMTP server.

* services is the source for the deepofix-services package that installs, configures and activates various services that are run in deepOfix using the runit service supervision and management system.

* squirrelmail - This contains the source code for the deepofix-webmail package that installs the [http://www.squirrelmail.org/ Squirrelmail] package to let users access their email from anywhere on the network.

* The system-config directory stores the source code for the deepofix-system-config package. This package is responsible for a variety of system configuration and customisation

* uschedule contains the source for the deepofix-uschedule package which is used for scheduling inside the deepOfix operating system.

Now that we are done with the directory structure, lets look at how to add a particular package to deepOfix. We shall use 'kvm ('virtual machine') 'as the platform for our test installations.

Lets say we want to add a package 'test.deb' to deepOfix. The task of this package will be simply to print 'This is a test package' while installation.

We recommend that you refer to [http://www.debian.org/doc/maint-guide/index.en.html#contents http://www.debian.org/doc/maint-guide/index.en.html#contents] to learn how to build a package. Follow these steps to create the test.deb package.

* Open a terminal. cd to any directory.

* Execute the following command in the terminal: 'mkdir -p test/DEBIAN'

* Execute 'vim test/DEBIAN/control'. Enter the following text in the editor:

Package: deepofix-test

Version: 1
Maintainer: BatMan <batman@gothamcity.com>
Architecture: i386
Description: deepofix-test (for deepOfix Messaging Server)
This package teaches the new born how to breathe in the     
deepOfix world :)

Save the file.

* Execute 'vim test/DEBIAN/control'. Enter the following text in the editor:

#!/bin/sh
echo 'This is a test package'

Save the file.

* Execute 'dpkg-deb test/ test.deb'. You will find test.deb in the current directory. This is the debian file we want.

Now we need to add this package into deepOfix's belly, so that it gets installed. Here are the steps.

* cd to deepofix-trunk directory. Copy test.deb to install_cd/deepofix/deepofix-packages/ .

* Now we need to add a new dependency to the deepofix-x.x.deb package. This step is necessary to ensure that test.deb is installed by apt. Go to packages-dev/deepofix . Edit DEBIAN/control. Add deepofix-test to Depends clause in the control file. Increment the version number and save the file. Execute make_deb script in packages-dev/deepofix . You will find a new deb package with a new version number. Copy this to install_cd/deepofix/deepofix-packages/ .

* Now we need to make sure that the new packages' meta-data and signatures are added to appropriate files. For this we simply execute bin/update_packages.

* Execute bin/mkcd. This gives us the new iso.

* Now that we have the new iso, lets rev it up. You need to have kvm/qemu installed for the rest of the tutorial to work.

* Execute 'qemu-img create -f qcow2 test.qcow2 5G'. This creates a qcow2 image of 5G maximum size that can be used my kvm/qemu.

* Execute 'sudo kvm -hda test.qcow2 -net tap -net nic'. Make sure you read some tutorial on kvm networking and set-up the same properly. The command if successfully executed, will bring up a window of the deepOfix installer. Look out for the message 'This is a test package'. If you missed it, you can boot into the freshly installed system and execute 'dpkg -l | grep test' to see that the package was installed successfully.

* Suppose you have made changes to a few deepofix-* packages and want to re-intall the system for testing. Installing the whole deepOfix system is extremely time consuming since the deepOfix specific packages are installed in the second stage, after the first stage is over. The first stage consists of installation of debian base packages which takes some time. A better way is to use the -loadvm -savevm features of kvm/qemu.