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:B~ Overview of tools
1~overview-of-tools Overview of tools
This chapter contains an overview of the three main tools used in building live systems: live-build, live-boot and live-config.
2~live-build The live-build package
live-build is a collection of scripts to build 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 used to build Debian packages with /{debhelper}/:
_* The scripts have a central location for configuring their operation. In /{debhelper}/, this is the #{debian/}# subdirectory of a package tree. For example, dh_install will look, among others, for a file called #{debian/install}# to determine which files should exist in a particular binary package. In much the same way, live-build stores its configuration entirely under a #{config/}# subdirectory.
_* The scripts are independent - that is to say, it is always safe to run each command.
Unlike /{debhelper}/, live-build provides the tools to generate a skeleton configuration directory. This could be considered to be similar to tools such as /{dh-make}/. For more information about these tools, read on, since the remainder of this section discuses the four most important commands. Note that the preceding #{lb}# is a generic wrapper for live-build commands.
_* *{lb config}*: Responsible for initializing a Live system configuration directory. See {The lb config command}#lb-config for more information.
_* *{lb build}*: Responsible for starting a Live system build. See {The lb build command}#lb-build for more information.
_* *{lb clean}*: Responsible for removing parts of a Live system build. See {The lb clean command}#lb-clean for more information.
3~lb-config The #{lb config}# command
As discussed in {live-build}#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 the initial skeleton configuration tree.
Issuing #{lb config}# without any arguments creates the #{config/}# subdirectory which is populated with some default settings in configuration files, and two skeleton trees named #{auto/}# and #{local/}#.
code{
$ lb config
[2015-01-06 19:25:58] lb config
P: Creating config tree for a debian/stretch/i386 system
P: Symlinking hooks...
}code
Using #{lb config}# without any arguments would be suitable for users who need a very basic image, or who intend to provide a more complete configuration via #{auto/config}# later (see {Managing a configuration}#managing-a-configuration for details).
Normally, you will want to specify some options. For example, to specify which package manager to use while building the image:
code{
$ lb config --apt aptitude
}code
It is possible to specify many options, such as:
code{
$ lb config --binary-images netboot --bootappend-live "boot=live components hostname=live-host username=live-user" ...
}code
A full list of options is available in the #{lb_config}# man page.
3~lb-build The #{lb build}# command
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.
3~lb-clean The #{lb clean}# command
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. If your changes invalidate the bootstrap and/or package caches, e.g. changes to #{--mode}#, #{--architecture}#, or #{--bootstrap}#, you must use #{lb clean --purge}#. See the #{lb_clean}# man page for a full list of options.
2~live-boot The live-boot package
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 live system 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.
2~live-config The live-config package
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.
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