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getting-started, dev-manual: Created Layer Model section
This involved removing the general information about layers from the dev-manual and incorporating it into the new section of the getting-started manual. (From yocto-docs rev: 26438b03751948661f48fb0c023e393101b80e19) Signed-off-by: Scott Rifenbark <srifenbark@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
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Scott Rifenbark
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Richard Purdie
Richard Purdie
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@@ -22,78 +22,12 @@
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multiple layers.
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multiple layers.
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Layers allow you to isolate different types of customizations from
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Layers allow you to isolate different types of customizations from
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each other.
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each other.
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You might find it tempting to keep everything in one layer when
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For introductory information on the Yocto Project Layer Model,
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working on a single project.
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see the
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However, the more modular your Metadata, the easier
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"<ulink url='&YOCTO_DOCS_GS_URL;#the-yocto-project-layer-model'>The Yocto Project Layer Model</ulink>"
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it is to cope with future changes.
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section in the Getting Started With Yocto Project Manual.
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</para>
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</para>
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<para>
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To illustrate how layers are used to keep things modular, consider
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machine customizations.
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These types of customizations typically reside in a special layer,
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rather than a general layer, called a Board Support Package (BSP)
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Layer.
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Furthermore, the machine customizations should be isolated from
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recipes and Metadata that support a new GUI environment,
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for example.
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This situation gives you a couple of layers: one for the machine
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configurations, and one for the GUI environment.
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It is important to understand, however, that the BSP layer can
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still make machine-specific additions to recipes within the GUI
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environment layer without polluting the GUI layer itself
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with those machine-specific changes.
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You can accomplish this through a recipe that is a BitBake append
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(<filename>.bbappend</filename>) file, which is described later
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in this section.
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<note>
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For general information on BSP layer structure, see the
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<ulink url='&YOCTO_DOCS_BSP_URL;#bsp'>Board Support Packages (BSP) - Developer's Guide</ulink>.
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</note>
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</para>
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<para>
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</para>
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<section id='yocto-project-layers'>
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<title>Layers</title>
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<para>
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The <ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
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contains both general layers and BSP
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layers right out of the box.
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You can easily identify layers that ship with a
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Yocto Project release in the Source Directory by their
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folder names.
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Folders that represent layers typically have names that begin with
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the string <filename>meta-</filename>.
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<note>
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It is not a requirement that a layer name begin with the
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prefix <filename>meta-</filename>, but it is a commonly
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accepted standard in the Yocto Project community.
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</note>
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For example, when you set up the Source Directory structure,
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you will see several layers:
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<filename>meta</filename>,
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<filename>meta-skeleton</filename>,
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<filename>meta-selftest</filename>,
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<filename>meta-poky</filename>, and
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<filename>meta-yocto-bsp</filename>.
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Each of these folders represents a distinct layer.
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</para>
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<para>
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As another example, if you set up a local copy of the
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<filename>meta-intel</filename> Git repository
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and then explore the folder of that general layer,
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you will discover many Intel-specific BSP layers inside.
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For more information on BSP layers, see the
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"<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-layers'>BSP Layers</ulink>"
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section in the Yocto Project Board Support Package (BSP)
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Developer's Guide.
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</para>
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</section>
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<section id='creating-your-own-layer'>
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<section id='creating-your-own-layer'>
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<title>Creating Your Own Layer</title>
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<title>Creating Your Own Layer</title>
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@@ -265,9 +265,123 @@
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</section>
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</section>
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</section>
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</section>
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<section id='what-are-layers'>
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<section id='the-yocto-project-layer-model'>
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<title>What are Layers?</title>
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<title>The Yocto Project Layer Model</title>
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<para>
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The Yocto Project's "Layer Model" is a development model for
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embedded and IoT Linux creation that distinguishes the
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Yocto Project from other simple build systems.
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The Layer Model simultaneously supports collaboration and
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customization.
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Layers are repositories that contain related sets of instructions
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that tell the OpenEmbedded build system what to do.
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You can collaborate, share, and reuse layers.
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</para>
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<para>
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Layers can contain changes to previous instructions or settings
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at any time.
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This powerful override capability is what allows you to customize
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previously supplied collaborative or community layers to suit your
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product requirements.
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</para>
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<para>
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You use different layers to logically separate information in your
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build.
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As an example, you could have BSP, GUI, distro configuration,
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middleware, or application layers.
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Putting your entire build into one layer limits and complicates
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future customization and reuse.
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Isolating information into layers, on the other hand, helps
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simplify future customizations and reuse.
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You might find it tempting to keep everything in one layer when
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working on a single project.
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However, the more modular your Metadata, the easier
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it is to cope with future changes.
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<note><title>Notes</title>
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<itemizedlist>
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<listitem><para>
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Use Board Support Package (BSP) layers from silicon
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vendors when possible.
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</para></listitem>
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<listitem><para>
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Familiarize yourself with the
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<ulink url='https://caffelli-staging.yoctoproject.org/software-overview/layers/'>Yocto Project curated layer index</ulink>
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or the
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<ulink url='http://layers.openembedded.org/layerindex/branch/master/layers/'>OpenEmbedded layer index</ulink>.
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The latter contains more layers but they are less
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universally validated.
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</para></listitem>
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<listitem><para>
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Layers support the inclusion of technologies, hardware
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components, and software components.
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The Yocto Project Compatible designation provides a
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minimum level of standardization that contributes to a
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strong ecosystem.
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"YP Compatible" is applied to appropriate products and
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software components such as BSPs, other OE-compatible
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layers, and related open-source projects, allowing the
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producer to use Yocto Project badges and branding
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assets.
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</para></listitem>
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</itemizedlist>
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</note>
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</para>
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<para>
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To illustrate how layers are used to keep things modular, consider
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machine customizations.
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These types of customizations typically reside in a special layer,
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rather than a general layer, called a BSP Layer.
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Furthermore, the machine customizations should be isolated from
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recipes and Metadata that support a new GUI environment,
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for example.
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This situation gives you a couple of layers: one for the machine
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configurations, and one for the GUI environment.
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It is important to understand, however, that the BSP layer can
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still make machine-specific additions to recipes within the GUI
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|
environment layer without polluting the GUI layer itself
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with those machine-specific changes.
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You can accomplish this through a recipe that is a BitBake append
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(<filename>.bbappend</filename>) file, which is described later
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in this section.
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<note>
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For general information on BSP layer structure, see the
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<ulink url='&YOCTO_DOCS_BSP_URL;#bsp'>Board Support Packages (BSP) - Developer's Guide</ulink>.
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</note>
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</para>
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<para>
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The
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<ulink url='&YOCTO_DOCS_REF_URL;#source-directory'>Source Directory</ulink>
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contains both general layers and BSP layers right out of the box.
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You can easily identify layers that ship with a Yocto Project
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release in the Source Directory by their names.
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Layers typically have names that begin with the string
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<filename>meta-</filename>.
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<note>
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It is not a requirement that a layer name begin with the
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prefix <filename>meta-</filename>, but it is a commonly
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accepted standard in the Yocto Project community.
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</note>
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For example, if you were to examine the
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<ulink url='https://git.yoctoproject.org/cgit/cgit.cgi/poky/tree/'>tree view</ulink>
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of the <filename>poky</filename> repository, you will see several
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layers: <filename>meta</filename>,
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<filename>meta-skeleton</filename>,
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<filename>meta-selftest</filename>,
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<filename>meta-poky</filename>, and
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<filename>meta-yocto-bsp</filename>.
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Each of these repositories represents a distinct layer.
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</para>
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<para>
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For procedures on how to create layers, see the
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"<ulink url='&YOCTO_DOCS_DEV_URL;#understanding-and-creating-layers'>Understanding and Creating Layers</ulink>"
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section in the Yocto Project Development Tasks Manual.
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</para>
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</section>
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</section>
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<section id='components-and-tools'>
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<section id='components-and-tools'>
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Reference in New Issue
Block a user