OpenEmbedded

1
OpenEmbedded BitBake

• Open Source Software
• Carlos Ramirez Martinez-Eiroa
• Professor Corby Schmitz

2
Index

• Build Tools
• Make
• Ant
• Maven
• OpenZaurus
• OpenEmbedded
• BitBake

3
Evolution

• Make Ant Maven
• BuiltRoot BitBake

4
Build Tools

• The process of building a computer program is
  usually managed by a build tool
• Build Tool program that coordinates and
  controls other programs
• The build utility needs to compile and link the
  various files, in the correct order

5
Make

• Initial release 1977
• Already seen in class

6
Ant I

• Similar to make, but
• Implemented using the Java language
• Requires the Java platform
• Is best suited to building Java projects
• Ant uses XML to describe the build process and
  its dependencies - Make has its Makefile format

7
Ant II

• Conceived by James Duncan Davidson while turning
  Apache Tomcat (from Sun) into open source
• A proprietary version of Make was used to build
  it on the Solaris Operating Environment

8
Ant III

• In the open source world there was no way of
  controlling which platform was used to build
  Tomcat
• Ant was created as a simple, platform-independent
  tool to build Tomcat from directives in an XML
  "build file

9
Ant IV

• In a Makefile the actions required to create a
  target are specified as shell commands which are
  specific to the current platform (usually Unix)
• Ant provides a large amount of built-in
  functionality which can guarantee will behave
  (nearly) identically on all platforms

10
Ant V

• January 2000, Ant was moved to a separate CVS
  module and was promoted to a project of its own,
  independent of Tomcat, and became Apache Ant

11

• Maven uses a construct known as a Project Object
  Model (POM) to describe
• The software project being built
• Its dependencies on other external modules and
  components
• The build order
• A key feature of Maven is that it is
  network-ready - The core engine can dynamically
  download plug-ins from a repository

12
Towards OpenEmbedded
13
A Bit of History I

• 2001 Sharp introducestheSL-5000 PDA running
  Linux
• 2002 Chris Larson finds out that the SharpROM
  sucks and starts hacking on a build system for a
  customized Linux distribution called "OpenZaurus
• 2002-2003 The OpenZaurus build system is getting
  stretched (beyond belief) by adding support for
  many more packages and target devices
• January 2003 Brainstorming towards a new
  distribution and device independent build system

14
A Bit of History II

• February 2003 Holger Schurig creates the
  OpenEmbedded repository and starts hacking on the
  first version
• May 2003 Chris Larson adds major functionality
  to the OpenEmbedded core and starts converting
  packages from the OpenZaurus build system
• December 2003 Michael Lauer releases
  OpenZaurus3.3.5, abandons the OpenZaurus build
  system, and converts100s of packages to
  OpenEmbedded
• December 2004 OpenEmbedded is split up into the
  BitBake build system and the OpenEmbedded metadata

15
OpenZaurus

• OpenEmbedded is the successor to the great
  OpenZaurus project
• The OpenZaurus project was created as an
  alternative ROM image for the Sharp Zaurus
  Personal Mobile Tool

16
(ROM image)

• (ROM image computer file which contains a copy
  of the data from a read-only memory chip
• Software which is being developed for embedded
  computers is often written to ROM files for
  testing on a standard computer before it is
  written to a ROM chip for use in the embedded
  system)

17
OpenZaurus II

• The project had pushed buildroot to its limits
• Buildroot set of Makefiles and patches that
  makes it easy generate a cross-compilation
  toolchain and root filesystem for a target Linux
  system using the uClibc C library

18
OpenZaurus III

• Buildroot supported the creation of ipk packages,
  feeds and images and had support for more than
  one machine
• But gt impossible to use different patches, ?les
  for different architectures, machines or
  distributions
• (ipk lightweight package management system
  designed specifically for use in Linux devices
  with limited storage)

19
OpenEmbedded

• OpenEmbedded was created to overcome this
  shortcoming
• On 7 December 2004 Chris Larson split the project
  into two parts BitBake, a generic task executor
  and OpenEmbedded, the metadata for BitBake

20
OpenEmbedded II

• Software framework to create Linux distributions
  for embedded systems
• This may include bootloader, Linux, and
  applications
• Is a set of metadata used to cross-compile,
  package and install software packages
• License GPL

21
Objectives

• Be self-contained
• Be able to use external toolchains or build them
• Easily cross-compile software, build packages or
  create root-?lesystems
• Easily add new features, machines, architectures,

22
BitBake I

• OpenEmbedded built tool
• Controls how to build things and the build
  dependencies
• Collects and manages an open set of largely
  independent build descriptions (package recipes)
  and builds them in proper order

23
BitBake II

• Used to compile different Linux kernels for a
  variety of PDAs
• Easier to use (in theory) than manually using
  tools like patch and make
• Programming language Python
• License GNU General Public License (GPL), MIT/X
  Consortium License

24
Process of Making Images
Binary Packages
BitBake Recipes
Flash Image
Task Graph
25
BitBake File and Data Types

• Three different file types
• .conf configuration data
• .bbclass (build) classes
• .bb (.inc) package recipes
• BitBake parses the build classes, config files,
  and recipes
• For every task BitBake creates a shell script
  on-the-fly and executes it

26
Main Tasks
TASK DESCRIPTION FUNCTION
Fetch Downloads data from upstream do_fetch()
Unpack Unpacks data do_unpack()
Patch Applies patches do_patch()
Configure Configures the source tree do_configure()
Compile Compiles the source tree do_compile()
Stage Installs to the staging area do_stage()
Install Installs into the packaging are do_install()
Package Creates packages do_package()
27
BitBake Recipe

• DESCRIPTION "Hello world program
• PR "r0
• SRC_URI "file//myhelloworld.c \
  file//README.txt
• do_compile()
• CC CFLAGS LDFLAGS WORKDIR/myhelloworl
  d.c -o myhelloworld
• do_install()
• install -m 0755 -d Dbindir
  Ddocdir/myhelloworld
• install -m 0644 S/myhelloworld Dbindir
  
• install -m 0644 WORKDIR/README.txt
  Ddocdir/myhelloworld

28
Summary I

• OpenEmbedded A metadata repository containing
• Build classes
• Machine configurations
• Distribution policies
• Recipes
• To create complete embedded Linux distributions
  from scratch

29
Summary II

• BitBake A simple tool to execute tasks on
  metadata
• Parser to handle metadata
• Package graph to handle package interdependencies
  
• Task graph to handle task interdependencies
• On-the-fly shell script generator

30
Why all this?

• SlugOS/BE is a replacement firmware image for the
  Linksys NSLU2
• It is produced using OpenEmbedded

31

• Questions?