1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
|
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<chapter id="user-manual-intro">
<title>BitBake User Manual</title>
<section id="intro">
<title>Introduction</title>
<para>
BitBake is a tool for executing tasks commonly performed by software
developers when building embedded Linux systems on a daily basis.
BitBake can build systems consisting of numerous individual pieces
of software, or can be used to build a single application.
Example tasks that BitBake can execute are fetching source code,
applying patches to source code, configuring, compiling, and
packaging applications into a complete system, and managing metadata.
Metadata is stored in recipe (<filename>.bb</filename>),
configuration (<filename>.conf</filename>), and class
(<filename>.bbclass</filename>) files and provide to BitBake the
instructions for which sources to build and how to build them.
BitBake abstracts the information for completing individual tasks
into files known as recipes.
Recipes contain all of the relevant information required by BitBake
to complete a given task including dependencies, source file
locations, etc.
BitBake is similar to
<ulink url='http://www.gnu.org/software/make/'>GNU Make</ulink>
and other build tools.
</para>
</section>
<section id="history-and-goals">
<title>History and Goals</title>
<para>
BitBake was originally a part of the OpenEmbedded project.
It was inspired by the Portage package management system
used by the Gentoo Linux distribution.
On December 7, 2004, OpenEmbedded project team member,
Chris Larson split the project into two distinct pieces:
<itemizedlist>
<listitem><para>BitBake, a generic task executor</para></listitem>
<listitem><para>OpenEmbedded, a metadata set utilized by
BitBake.</para></listitem>
</itemizedlist>
Today, BitBake is the primary basis of the
<ulink url="http://www.openembedded.org/">OpenEmbedded</ulink>
project, which is being used to build and maintain a
number of projects and embedded Linux distributions
such as the Angstrom Distribution and the Yocto
Project.
</para>
<para>
Prior to BitBake, no other build tool adequately met the needs of
an aspiring embedded Linux distribution.
All of the build systems used by traditional desktop Linux
distributions lacked important functionality, and none of the
ad-hoc <emphasis>buildroot</emphasis> systems, prevalent in the
embedded space, were scalable or maintainable.
</para>
<para>
Some important original goals for BitBake were:
<itemizedlist>
<listitem><para>Handle cross-compilation.</para></listitem>
<listitem><para>Handle inter-package dependencies (build
time on target architecture, build time
on native architecture, and runtime).</para></listitem>
<listitem><para>Support running any number of tasks
within a given package, including, but
not limited to, fetching upstream
sources, unpacking them, patching them,
configuring them, etc.</para></listitem>
<listitem><para>Must be Linux distribution agnostic (both
build and target).</para></listitem>
<listitem><para>Must be architecture agnostic</para></listitem>
<listitem><para>Must support multiple build and target
operating systems (including Cygwin, the BSDs, etc).
</para></listitem>
<listitem><para>Must be able to be self contained, rather
than tightly integrated into the build
machine's root filesystem.</para></listitem>
<listitem><para>There must be a way to handle conditional
metadata (on target architecture,
operating system, distribution, machine).</para>
</listitem>
<listitem><para>It must be easy for the person using the
tools to supply their own local
metadata and packages to operate against.</para>
</listitem>
<listitem><para>Must make it easy to collaborate between
multiple projects using BitBake for
their builds.</para></listitem>
<listitem><para>Should provide an inheritance mechanism
to share common metadata between many
packages.</para></listitem>
</itemizedlist>
</para>
<para>
Over time it has become apparent that some further requirements
were necessary:
<itemizedlist>
<listitem><para>Handle variants of a base recipe (native,
sdk, multilib).</para></listitem>
<listitem><para>Able to split metadata into layers and
allow layers to override each other.</para></listitem>
<listitem><para>Allow representation of a given set of
input variables to a task as a checksum.
Based on that checksum, allow acceleration of builds with
prebuilt components.</para></listitem>
</itemizedlist>
</para>
<para>
BitBake satisfies all the original requirements and many more
with extensions being made to the basic functionality to
reflect the additional requirements.
Flexibility and power have always been the priorities.
It is highly extensible, supporting embedded Python code and
execution of any arbitrary tasks.
</para>
</section>
<section id="Concepts">
<title>Concepts</title>
<para>
Concepts Here.
</para>
</section>
</chapter>
|
