The Yocto Project is a Linux Foundation workgroup and is defined as follows:

The Yocto Project is an open source collaboration project that helps developers create custom Linux-based systems that are designed for embedded products regardless of the product’s hardware architecture. Yocto Project provides a flexible toolset and a development environment that allows embedded device developers across the world to collaborate through shared technologies, software stacks, configurations, and best practices used to create these tailored Linux images.

Thousands of developers worldwide have discovered that Yocto Project provides advantages in both systems and applications development, archival and management benefits, and customizations used for speed, footprint, and memory utilization. The project is a standard when it comes to delivering embedded software stacks. The project allows software customizations and build interchange for multiple hardware...

To ease our understanding of the duties and outcomes of the Yocto Project, we can use the analogy of a computing machine. The input is a set of data that describes what we want, that is, our specification. As an output, we have the desired Linux-based embedded product.

The output is composed of the pieces of the operating system. It encompasses the Linux kernel, bootloader, and the root filesystem (rootfs) bundled and organized to work together.

The Yocto Project’s tools are present in all intermediary steps to produce the resultant rootfs bundle and other deliverables. The previously built software components are reused across builds – applications, libraries, or any software component.

When reuse is not possible, the software components are built in the correct order and with the desired configuration, including fetching the required source code from their respective repositories, such as The Linux Kernel Archives (www.kernel.org...

The OpenEmbedded project was created around January 2003 when some core developers from the OpenZaurus project started to work with the new build system. Since its beginning, the OpenEmbedded build system has been a task scheduler inspired and based on the Gentoo Portage package system named BitBake. As a result, the project quickly grew its software collection and the supported machine list.

Due to chaotic and uncoordinated development, it was challenging to use OpenEmbedded in products that demand a more stable and polished code base, which is how Poky distribution was born. Poky started as a subset of the OpenEmbedded build system, and had a more polished and stable code base across a limited set of architectures. Additionally, its reduced size allowed Poky to develop highlighting technologies, such as IDE plugins and Quick Emulator (QEMU) integration, which are still in use.

The Yocto Project and OpenEmbedded...

Poky is the default Yocto Project reference distribution, which uses OpenEmbedded build system technology. It is composed of a collection of tools, configuration files, and recipe data (known as metadata). It is platform-independent and performs cross-compiling using the BitBake tool, OpenEmbedded Core, and a default set of metadata, as shown in the following figure. In addition, it provides the mechanism to build and combine thousands of distributed open source projects to form a fully customizable, complete, and coherent Linux software stack.

Poky’s main objective is to provide all the features an embedded developer needs.

Figure 1.1 – Poky main components

BitBake

BitBake is a task scheduler and execution system that parses Python and Shell Script code. The code that is parsed generates and runs tasks, which are a set of steps ordered per the code’s dependencies.

BitBake evaluates all available metadata...

The Yocto Project has a release every six months, in April and October. This release cycle ensures continuous development flow while providing points of increased testing and focus on stability. A release becomes a Stable or a Long-Term Support (LTS) release whenever a release is ready.

The support period differs significantly between the stable and LTS releases. The support for the stable release is for 7 months, offering 1 month of overlapped support for every stable release. The LTS release has a minimal support period of 2 years, optionally extended. After the official support period ends, it moves to Community support and finally reaches End Of Life (EOL).

When the official release support period ends, a release can be Community support if a community member steps in to become the community maintainer. Finally, a release turns EOL when there is no change in the source code by 2 months, or the community maintainer is no longer an active member.

This chapter provided an overview of how the OpenEmbedded project is related to the Yocto Project, the components that form Poky, and how the project began. The next chapter will introduce the Poky workflow with steps to download, configure, and prepare the Poky build environment and how to have the first image built and running using QEMU.