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Welcome to the Yocto Project Software Development Kit (SDK) Developer's Guide. This manual provides information that lets you use both the standard Yocto Project SDK and an extensible SDK to develop applications and images using the Yocto Project. Additionally, the manual also provides information on how to use the popular Eclipse IDE as part of your application development workflow. Prior to the 2.0 Release of the Yocto Project, application development was primarily accomplished through the use of the Application Development Toolkit (ADT) and the availability of stand-alone cross-development toolchains and other tools. With the 2.1 Release of the Yocto Project, application development has transitioned to within a more traditional SDK and extensible SDK. A standard SDK consists of a cross-development toolchain that contains a compiler, debugger, and various miscellaneous tools; libraries, headers, and symbols to match an image; and environment setup script. You can use this SDK to independently develop and test code that is destined to run on some target machine. An extensible SDK consists of everything that the standard SDK has plus tools that allow you to easily add new applications and libraries to an image, modify the source of an existing component, test changes on the target hardware, and easily integrate an application into the the Yocto Project build system.

Fundamentally, the SDK fits into the development process as follows: The SDK is installed on any machine and can be used to develop applications, images, and kernels. An SDK can even be used by a QA Engineer or Release Engineer. The fundamental concept is that the machine that has the SDK installed does not have to be associated with the machine that has the Yocto Project installed. A developer can independently compile and test an object on their machine and then, when the object is ready for integration into an image, they can simply make it available to the machine that has the the Yocto Project. Once the object is available, the image can be rebuilt using the Yocto Project to produce the modified image. You just need to follow these general steps: Install the SDK for your target hardware: For information on how to install the SDK, see the "Installing the SDK" section. Download the Target Image: The Yocto Project supports several target architectures and has many pre-built kernel images and root filesystem images. If you are going to develop your application on hardware, go to the machines download area and choose a target machine area from which to download the kernel image and root filesystem. This download area could have several files in it that support development using actual hardware. For example, the area might contain .hddimg files that combine the kernel image with the filesystem, boot loaders, and so forth. Be sure to get the files you need for your particular development process. If you are going to develop your application and then run and test it using the QEMU emulator, go to the machines/qemu download area. From this area, go down into the directory for your target architecture (e.g. qemux86_64 for an Intel-based 64-bit architecture). Download kernel, root filesystem, and any other files you need for your process. In order to use the root filesystem in QEMU, you need to extract it. See the "Extracting the Root Filesystem" section for information on how to extract the root filesystem. Develop and Test your Application: At this point, you have the tools to develop your application. If you need to separately install and use the QEMU emulator, you can go to QEMU Home Page to download and learn about the emulator. You can see the "Using the Quick EMUlator (QEMU)" chapter in the Yocto Project Development Manual for information on using QEMU within the Yocto Project. The remainder of this manual describes how to use both the standard SDK and the extensible SDK. Information also exists in appendix form that describes how you can build, install, and modify an SDK.