:B~ Customizing contents

1~customization-overview Customization overview

This chapter gives an overview of the various ways in which you may
customize a Debian Live system.

2~ Build time vs. boot time configuration

Live system configuration options are divided into build-time options which
are options that are applied at build time and boot-time options which are
applied at boot time. Boot-time options are further divided into those
occurring early in the boot, applied by the live-boot package, and those
that happen later in the boot, applied by live-config. Any boot-time option
may be modified by the user by specifying it at the boot prompt. The image
may also be built with default boot parameters so users can normally just
boot directly to the live system without specifying any options when all of
the defaults are suitable. In particular, the argument to #{lb
--bootappend-live}# consists of any default kernel command line options for
the Live system, such as persistence, keyboard layouts, or timezone. See
{Customizing locale and language}#customizing-locale-and-language, for
example.

Build-time configuration options are described in the #{lb config}# man
page. Boot-time options are described in the man pages for live-boot and
live-config. Although the live-boot and live-config packages are installed
within the live system you are building, it is recommended that you also
install them on your build system for easy reference when you are working on
your configuration. It is safe to do so, as none of the scripts contained
within them are executed unless the system is configured as a live system.

2~stages-of-the-build Stages of the build

The build process is divided into stages, with various customizations
applied in sequence in each. The first stage to run is the *{bootstrap}*
stage. This is the initial phase of populating the chroot directory with
packages to make a barebones Debian system. This is followed by the
*{chroot}* stage, which completes the construction of chroot directory,
populating it with all of the packages listed in the configuration, along
with any other materials. Most customization of content occurs in this
stage. The final stage of preparing the live image is the *{binary}* stage,
which builds a bootable image, using the contents of the chroot directory to
construct the root filesystem for the Live system, and including the
installer and any other additional material on the target medium outside of
the Live system's filesystem. After the live image is built, if enabled, the
source tarball is built in the *{source}* stage.

Within each of these stages, there is a particular sequence in which
commands are applied. These are arranged in such a way as to ensure
customizations can be layered in a reasonable fashion. For example, within
the *{chroot}* stage, preseeds are applied before any packages are
installed, packages are installed before any locally included files are
copied, and hooks are run later, after all of the materials are in place.

2~ Supplement lb config with files

Although #{lb config}# creates a skeletal configuration in the config/
directory, to accomplish your goals, you may need to provide additional
files in subdirectories of config/. Depending on where the files are stored
in the configuration, they may be copied into the live system's filesystem
or into the binary image filesystem, or may provide build-time
configurations of the system that would be cumbersome to pass as
command-line options. You may include things such as custom lists of
packages, custom artwork, or hook scripts to run either at build time or at
boot time, boosting the already considerable flexibility of debian-live with
code of your own.

2~ Customization tasks

The following chapters are organized by the kinds of customization task
users typically perform: {Customizing package
installation}#customizing-package-installation, {Customizing
contents}#customizing-contents and {Customizing locale and
language}#customizing-locale-and-language cover just a few of the things you
might want to do.
