:B~ Managing a configuration

1~managing-a-configuration Managing a configuration

This chapter explains how to manage a live configuration from initial
creation, through successive revisions and successive releases of both the
live-build software and the live image itself.

2~ Dealing with configuration changes

Live configurations rarely are perfect on the first try. It may be fine to
pass #{lb config}# options from the command-line to perform a single build,
but it is more typical to revise those options and build again until you are
satisfied. To support these changes, you will need auto scripts which ensure
your configuration is kept in a consistent state.

3~ Why use auto scripts? What do they do?

The #{lb config}# command stores the options you pass to it in #{config/*}#
files along with many other options set to default values. If you run #{lb
config}# again, it will not reset any option that was defaulted based on
your initial options. So, for example, if you run #{lb config}# again with a
new value for #{--binary-images}#, any dependent options that were defaulted
for the old image type may no longer work with the new ones. Nor are these
files intended to be read or edited. They store values for over a hundred
options, so nobody, let alone yourself, will be able to see in these which
options you actually specified. And finally, if you run #{lb config}#, then
upgrade live-build and it happens to rename an option, #{config/*}# would
still contain variables named after the old option that are no longer valid.

For all these reasons, #{auto/*}# scripts will make your life easier. They
are simple wrappers to the #{lb config}#, #{lb build}# and #{lb clean}#
commands that are designed to help you manage your configuration. The
#{auto/config}# script stores your #{lb config}# command with all desired
options, the #{auto/clean}# script removes the files containing
configuration variable values, and the #{auto/build}# script keeps a
#{build.log}# of each build. Each of these scripts is run automatically
every time you run the corresponding #{lb}# command. By using these scripts,
your configuration is easier to read and is kept internally consistent from
one revision to the next. Also, it will be much easier for you identify and
fix options which need to change when you upgrade live-build after reading
the updated documentation.

3~ Use example auto scripts

For your convenience, live-build comes with example auto shell scripts to
copy and edit. Start a new, default configuration, then copy the examples
into it:

code{

 $ mkdir mylive && cd mylive && lb config
 $ mkdir auto
 $ cp /usr/share/doc/live-build/examples/auto/* auto/

}code

Edit #{auto/config}#, adding any options as you see fit. For instance:

code{

 #!/bin/sh
 lb config noauto \
     --architectures i386 \
     --linux-flavours 686-pae \
     --binary-images hdd \
     --mirror-bootstrap http://ftp.ch.debian.org/debian/ \
     --mirror-binary http://ftp.ch.debian.org/debian/ \
     "${@}"

}code

Now, each time you use #{lb config}#, #{auto/config}# will reset the
configuration based on these options. When you want to make changes to them,
edit the options in this file instead of passing them to #{lb config}#. When
you use #{lb clean}#, #{auto/clean}# will clean up the #{config/*}# files
along with any other build products. And finally, when you use #{lb build}#,
a log of the build will be written by #{auto/build}# in #{build.log}#.

*{Note:}* A special #{noauto}# parameter is used here to suppress another call to #{auto/config}#, thereby preventing infinite recursion. Make sure you don't accidentally remove it when making edits. Also, take care to ensure when you split the #{lb config}# command across multiple lines for readability, as shown in the example above, that you don't forget the backslash (\) at the end of each line that continues to the next.

2~clone-configuration-via-git Clone a configuration published via Git

Use the #{lb config --config}# option to clone a Git repository that
contains a live system configuration. If you would like to base your
configuration on one maintained by the ${project}, look at
http://http://anonscm.debian.org/cgit/debian-live/ for the repository named #{live-images}# in
the category #{Packages}#. This repository contains the configurations for
the live systems {prebuilt images}#downloading-prebuilt-images.

For example, to build a standard image, use the #{live-images}# repository
as follows:

code{

 $ mkdir live-images && cd live-images
 $ lb config --config git://http://anonscm.debian.org/git/debian-live/live-images.git
 $ cd images/standard

}code

Edit #{auto/config}# and any other things you need in the #{config}# tree to
suit your needs. For example, the unofficial non-free prebuilt images are
made by simply adding #{--archive-areas "main contrib non-free"}#.

You may optionally define a shortcut in your Git configuration by adding the
following to your #{${HOME}/.gitconfig}#:

code{

 [url "git://http://anonscm.debian.org/git/debian-live/"]
         insteadOf = lso:

}code

This enables you to use #{lso:}# anywhere you need to specify the address of
a #{debian-live.alioth.debian.org}# git repository. If you also drop the optional
#{.git}# suffix, starting a new image using this configuration is as easy
as:

code{

 $ lb config --config lso:live-images

}code

Cloning the entire #{live-images}# repository pulls the configurations used
for several images. If you feel like building a different image after you
have finished with the first one, change to another directory and again and
optionally, make any changes to suit your needs.

In any case, remember that every time you will have to build the image as
superuser: #{lb build}#
