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RidgeRun Yocto Developer Guide/Yocto Main Concepts: Difference between revisions
RidgeRun Yocto Developer Guide/Yocto Main Concepts (view source)
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== Yocto Environment == | == Yocto Environment == | ||
As mentioned before, Yocto Project is a conjunction of diferent components. The main idea of those components is to provide the user a set of tools and | As mentioned before, Yocto Project is a conjunction of diferent components. The main idea of those components is to provide the user with a set of tools and metadata that enables the creation of a customized Linux based system. The main parts are described in the diagram below: | ||
[[File:Yocto diagram.png|450px|thumb|center|Yocto | [[File:Yocto diagram.png|450px|thumb|center|Yocto components diagram|alt=Yocto layers diagram]] | ||
== Concepts == | == Concepts == | ||
To create a Yocto project there are several concepts the user must understand first before start developing on | To create a Yocto project there are several concepts the user must understand first before they start developing on their platforms. | ||
=== What is OpenEmbedded? === | === What is OpenEmbedded? === | ||
OpenEmbedded is a build system based on "Poky" which works as a task executor for the system. OpenEmbedded essentially | OpenEmbedded is a build system based on "Poky" which works as a task executor for the system. OpenEmbedded essentially has two components: | ||
==== BitBake ==== | ==== BitBake ==== | ||
BitBake is a task execution engine that works through | BitBake is a task execution engine that works through recipes, interpreting the metadata to decide, run and execute the tasks. BitBake is one of the most important components of the Yocto Project, so it requires external maintenance from the Yocto Project. There is a comprehensive user manual about BitBake available here: [https://docs.yoctoproject.org/bitbake/2.8/bitbake-user-manual/bitbake-user-manual-intro.html#introduction BitBake User Manual] | ||
==== OpenEmbedded-Core ==== | ==== OpenEmbedded-Core ==== | ||
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=== What is Metadata? === | === What is Metadata? === | ||
Metadata is the most basic data able to provide information about other data. The metadata is formed by instructions, definitions of values and modifications building files such as: configuration files, recipes, classes, etc. Here you can see a simple example of metadata describing a dummy Linux Kernel on the system: | Metadata is the most basic data able to provide information about other data. The metadata is formed by instructions, definitions of values and modifications to building files such as: configuration files, recipes, classes, etc. Here you can see a simple example of metadata describing a dummy Linux Kernel on the system: | ||
<syntaxhighlight line lang=bash> | <syntaxhighlight line lang=bash> | ||
SUMMARY = "Dummy Linux kernel" | SUMMARY = "Dummy Linux kernel" | ||
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=== What is a recipe? === | === What is a recipe? === | ||
Recipes one of the most important parts of BitBake, | Recipes are one of the most important parts of BitBake, they are files with the .bb extension. A recipe represents the most basic metadata providing: descriptive information, dependencies, fetching rules, patches, configuration and compilation instructions. | ||
Here you can see an example: | Here you can see an example: | ||
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=== What is a Meta Layer? === | === What is a Meta Layer? === | ||
A Meta-Layer is a group of recipes, which are usually organized by categories depending on | A Meta-Layer is a group of recipes, which are usually organized by categories depending on their functionality. The meta-layers follow the syntax '''meta-<layername>'''. In Poky, you can find the following meta-layers: | ||
<syntaxhighlight line lang=bash> | <syntaxhighlight line lang=bash> | ||
tree ~/yocto-test/poky/ -L 1 | grep meta | tree ~/yocto-test/poky/ -L 1 | grep meta | ||