This chapter contains an overview of the three main tools used in building Debian Live systems: live-build, live-boot and live-config.
live-build is a collection of scripts to build Debian Live systems. These scripts are also referred to as "commands".
The idea behind live-build is to be a framework that uses a configuration directory to completely automate and customize all aspects of building a Live image.
Many concepts are similar to those in the debhelper Debian package tools written by Joey Hess:
Unlike debhelper, live-build contains a tool to generate a skeleton configuration directory, lb config. This could be considered to be similar to tools such as dh-make. For more information about lb config, please see The lb config command.
The remainder of this section discusses the three most important commands:
As discussed in live-build, the scripts that make up live-build read their configuration with the source command from a single directory named config/. As constructing this directory by hand would be time-consuming and error-prone, the lb config command can be used to create skeleton configuration folders.
Issuing lb config without any arguments creates a config/ subdirectory which it populates with some default settings:
$ lb config
P: Creating config tree
$ ls -l
total 8
drwxr-xr-x 3 user user 4096 Sep 7 13:02 auto
drwxr-xr-x 22 user user 4096 Sep 7 13:02 config
$ ls -l config/
total 104
-rw-r--r-- 1 user user 4197 Sep 7 13:02 binary
drwxr-xr-x 2 user user 4096 Sep 7 13:02 binary_debian-installer
drwxr-xr-x 2 user user 4096 Sep 7 13:02 binary_debian-installer-includes
drwxr-xr-x 2 user user 4096 Sep 7 13:02 binary_grub
drwxr-xr-x 2 user user 4096 Sep 7 13:02 binary_local-debs
drwxr-xr-x 2 user user 4096 Sep 7 13:02 binary_local-hooks
drwxr-xr-x 2 user user 4096 Sep 7 13:02 binary_local-includes
drwxr-xr-x 2 user user 4096 Sep 7 13:02 binary_local-packageslists
drwxr-xr-x 2 user user 4096 Sep 7 13:02 binary_local-udebs
drwxr-xr-x 2 user user 4096 Sep 7 13:02 binary_rootfs
drwxr-xr-x 2 user user 4096 Sep 7 13:02 binary_syslinux
-rw-r--r-- 1 user user 2051 Sep 7 13:02 bootstrap
-rw-r--r-- 1 user user 1647 Sep 7 13:02 chroot
drwxr-xr-x 2 user user 4096 Sep 7 13:02 chroot_apt
drwxr-xr-x 2 user user 4096 Sep 7 13:02 chroot_local-hooks
drwxr-xr-x 2 user user 4096 Sep 7 13:02 chroot_local-includes
drwxr-xr-x 2 user user 4096 Sep 7 13:02 chroot_local-packages
drwxr-xr-x 2 user user 4096 Sep 7 13:02 chroot_local-packageslists
drwxr-xr-x 2 user user 4096 Sep 7 13:02 chroot_local-patches
drwxr-xr-x 2 user user 4096 Sep 7 13:02 chroot_local-preseed
drwxr-xr-x 2 user user 4096 Sep 7 13:02 chroot_sources
-rw-r--r-- 1 user user 2954 Sep 7 13:02 common
drwxr-xr-x 2 user user 4096 Sep 7 13:02 includes
-rw-r--r-- 1 user user 205 Sep 7 13:02 source
drwxr-xr-x 2 user user 4096 Sep 7 13:02 templates
Using lb config without any arguments would be suitable for users who need a very basic image, or who intend to later provide a more complete configuration via auto/config (see Managing a configuration for details).
Normally, you will want to specify some options. For example, to include the 'gnome' package list in your configuration:
$ lb config -p gnome
It is possible to specify many options, such as:
$ lb config --binary-images net --hostname live-machine --username live-user ...
A full list of options is available in the lb_config man page.
The lb build command reads in your configuration from the config/ directory. It then runs the lower level commands needed to build your Live system.
It is the job of the lb clean command to remove various parts of a build so subsequent builds can start from a clean state. By default, chroot, binary and source stages are cleaned, but the cache is left intact. Also, individual stages can be cleaned. For example, if you have made changes that only affect the binary stage, use lb clean --binary prior to building a new binary. See the lb_clean man page for a full list of options.
live-boot is a collection of scripts providing hooks for the initramfs-tools, used to generate an initramfs capable of booting live systems, such as those created by live-build. This includes the Debian Live ISOs, netboot tarballs, and USB stick images.
At boot time it will look for read-only media containing a "/live" directory where a root filesystem (often a compressed filesystem image like squashfs) is stored. If found, it will create a writable environment, using aufs, for Debian like systems to boot from.
More information on initial ramfs in Debian can be found in the Debian Linux Kernel Handbook at ‹http://kernel-handbook.alioth.debian.org/› in the chapter on initramfs.
live-config consists of the scripts that run at boot time after live-boot to configure the live system automatically. It handles such tasks as setting the hostname, locales and timezone, creating the live user, inhibiting cron jobs and performing autologin of the live user.