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
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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
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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
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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”
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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
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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
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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
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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
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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
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18. OpenZaurus III
• Buildroot supported the creation of ipk
packages, feeds and images and had support
for more than one machine
But => impossible to use different patches,
les for different architectures, machines orfi
distributions
(ipk: lightweight package management system
designed specifically for use in Linux devices with
limited storage)
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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
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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
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21. Objectives
• Be self-contained
• Be able to use external toolchains or build
them
• Easily cross-compile software, build
packages or create root-filesystems
• Easily add new features, machines,
architectures,…
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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
BitBake
Recipes
Binary
Packages
Task Graph
Flash Image
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()
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
