Advanced use of Yocto build system (BELK/BXELK)

Info Box Applies to Bora Applies to BORA Xpress

History

Version	Date	BELK version	Notes
1.0.0	November 2015	3.0.0	First release

Introduction

The build process creates an entire Linux distribution from source. The build process can be summarized as follows:

• Make sure that all the prerequisites are met
• Initialize the build environment, as described in here.
• Optionally ensure the conf/local.conf configuration file, which is found in the Build Directory, is set up how you want it. This file defines many aspects of the build environment including the target machine architecture through the MACHINE variable, the development machine's processor use through the BB_NUMBER_THREADS and PARALLEL_MAKE variables, and a centralized tarball download directory through the DL_DIR variable.
• Build the image using the bitbake command. For more information about BitBake, please refer to the BitBake User Manual.

Prerequisites

The following prerequisites are required. They need to be done once only. Some generic development tools are required on the host Linux machine:

• git
• curl
• build-essential
• diffstat
• texinfo
• gawk
• chrpath
• ia32-libs (if the host machine is running a 64-bit OS)
• python-m2crypto.

These packages can be installed with the following command: sudo apt-get install gawk wget git-core diffstat unzip texinfo gcc-multilib build-essential chrpath socat libsdl1.2-dev xterm. It is also recommended to switch the system shell from Ubuntu's standard dash to more universal bash: :~$ sudo dpkg-reconfigure dash

Initializing the build environment

In the BELK, we have simplified the Yocto initialization phase, relying on the repo tool and on a BORA BSP git repository, so that the initialization can be completed with a few commands as reported below:

:~$ mkdir belk && cd belk
:~/belk$ curl http://commondatastorage.googleapis.com/git-repo-downloads/repo > repo
:~/belk$ chmod a+x repo
:~/belk$ ./repo init -u git@git.dave.eu:dave/bora/bora-bsp.git -b bora
:~/belk$ ./repo sync

Build the Yocto image

Please note that even building the basic root file system requires a few hours to complete the process on a mid-hi range desktop PC (4-6 cores, 8-12 GiB RAM), also depending on the Internet connection speed (all source are fetched from the network). Nearly 20GiB of disk space is required for the build. Once completed the initialization phase, developers can launch the Yocto image build process with the following commands:

:~$ cd ~/belk
:~/belk$ source bora-bsp-init-env.sh build
:~/belk/build$ bitbake base-rootfs-image

.

The resulting files (kernel, devicetree and u-boot binaries, plus .tar.gz root file system) will then be available inside build/tmp/deploy/images/bora.

Build additional packages

To build additional packages the user must first enter the directory where the bora-bsp-init-env.sh is placed and source it:

:~$ cd ~/belk
:~/belk$ source bora-bsp-init-env.sh build

And then he/she can run any of the bitbake commands:

:~/belk/build$ bitbake memtester

The resulting packages (the default format is ipk) can be found inside build/tmp/deploy/ipk.