yocto - embedded linux distribution maker

Embedded Linux @ Information Technology Institute 1

Embedded Linux

Yocto

Information Technology Institute

Sherif Mousa


Agenda

● What is Yocto?● Why Yocto?● Yocto Project Overview● Yocto Key Concept (recipe)● Yocto Workflow● Yocto Member Organizations● Working with Yocto


What is Yocto?

It's not an embedded Linux distribution -

It creates a custom one for you.● www.yoctoproject.org● The Yocto Project is an open-source collaboration project. It

provides templates, tools and methods to help you create custom Linux-based systems for embedded products regardless of hardware architecture.

● Yocto Project uses a build system based on the OpenEmbedded (OE) project, which uses the BitBake tool, to construct complete Linux images. The BitBake and OE components are combined together to form Poky, a reference build system.

http://www.yoctoproject.org/


Why Yocto?

● Develop using one common Linux OS for different architectures.

● Re-use your software stack with future devices.● Changing hardware platforms with updating just one line

in a config file and rebuild.● Base your work on a validated collection of software and

libraries.Developers spend lots of time porting or making build systems, leaves

less time and resources to develop value-adding software features.


Yocto Project Overview

● OpenEmbedded (OE) – The overall build architecture used by the Yocto Project.

● BitBake – Task executor and scheduler.● Metadata – Task definitions.● Configuration (*.conf) – global definitions of variables.● Classes (*.bbclass) – encapsulation and inheritance of

build logic, packaging, etc.● Recipes (*.bb) – the logical units of software/images to

build.


Yocto Project Overview (cont'd)

● OpenEmbedded Core (oe-core) – A core set of metadata shared by the OpenEmbedded and the Yocto Project.

● meta-yocto – Reference policy/distro configuration and reference hardware support layer.

● Poky – A pre-prepared combination of the build system components needed; also the name of our reference distro in meta-yocto

Poky = Bitbake + OE-core + meta-yocto + docs


Yocto Key Concept (recipe)

● The Yocto Project provides tools and metadata for creating custom Linux images.

● These images are created from a repository of 'baked' recipes.

● A recipe is a set of instructions for building packages:– Where to obtain the upstream sources and which patches to

apply– Dependencies (on libraries or other recipes)– Configuration/compilation options– Define which files go into what output packages


Yocto Workflow


Yocto Member Organizations


Working with Yocto


Yocto First Shot● Download Yocto source

– All releases: http://downloads.yoctoproject.org/releases/yocto/

– Current final release: poky-dizzy-12.0.1.tar.bz2● Untar the downloaded file

$ tar xvf pokydizzy12.0.1.tar.bz2

● Go inside the project directory: $ cd pokydizzy12.0.1● Source the poky default environment script

$ source oeinitbuildenv

● Configure (if you want) your conf ile: $ vim conf/local.conf● Start the build process (and wait ….)

bitbake coreimageminimal

● Run Qemu emulator with output imagerunqemu qemux86

http://downloads.yoctoproject.org/releases/yocto/

http://downloads.yoctoproject.org/releases/yocto/yocto-1.7.1/poky-dizzy-12.0.1.tar.bz2


Poky Directory Structure

● bitbake: the BitBake utility itself.● documentation: documentation sources.● scripts: various support scripts (e.g, runqemu)● meta/conf: important configuration files,

bitbake.conf, reference distro config, machine configs for QEMU architectures.

● meta/classes: BitBake classes.● meta/recipes-* : recipes for all packages & libs


Recipe Skeleton

● Example of a recipe SUMMARY = “”

DISCRIPTION = “”

HOMEPAGE = “”

LICENSE = “”

SRC_URI = “”

SRC_URI[md5sum] = “”

inherit stuff

don't edit the poky default recipes, but create your own recipes & layers


Yocto Configuration Files

● Build directory files● conf/bblayers.conf

– Contains locations for all layers needed for your build process.BBLAYERS ?= " \

/home/user/yocto/poky/metayocto \ ............

● conf/local.conf– Set your build options, choose target machine, add or remove features

from your build imageBB_NUMBER_THREADS = "threads"

PARALLEL_MAKE = "j threads"

MACHINE ?= "qemuarm"

DL_DIR ?= <downloaddirpath>


Recipe build steps

● Building recipes involves executing the following functions, which can be overridden when needed for customizations.– do_fetch– do_unpack– do_patch– do_configure– do_compile– do_install– do_package


Layers

● The Yocto Project build system is composed of layers.

● A layer is a logical collection of recipes representing the core, a Board Support Package (BSP), or an application stack.

● All layers have a priority and can override policy and config settings of the layers beneath it.


Board Support Package (BSP)

● BSPs are layers to enable support for specific hardware platforms.

● Defines machine configuration for the “board”.● Adds machine-specific recipes and

customizations.– Kernel config– Graphics drivers (e.g, Xorg)– Additional recipes to support hardware features


Yocto Layers Stacking

Developers-Specific Layer

Commercial Layer

UI - Optional Layer

Hardware Specific BSP

Yocto Layer Metadata (meta-yocto)

OpenEmbedded Core Metadata (oe-core)


Useful Links

● Yocto Project quick start guide– yocto-project-qs

● Bitbake user manual– bitbake-user-manual

● Yocto Project development manual– dev-manual

http://www.yoctoproject.org/docs/current/yocto-project-qs/yocto-project-qs.html

http://www.yoctoproject.org/docs/current/bitbake-user-manual/bitbake-user-manual.html

http://www.yoctoproject.org/docs/current/dev-manual/dev-manual.html


[email protected]

http://about.me/shatrix

http://about.me/shatrix

yocto - embedded linux distribution maker

Software

yocto workflowembedded

yoctoembedded linux

embedded linux distribution

custom linux images

shot download yocto

complete linux images

openembedded oe project

output packagesembedded