general-concepts/overlay/text.xml


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<?xml version="1.0" encoding="UTF-8"?>
<guide self="general-concepts/overlay/">
<chapter>
<title>Overlay</title>

<body>
<p>
Portage can look in multiple places for packages by using an overlay. The
locations of overlays are controlled by the <c>location</c> variable
in one or more repos.conf files.
</p>

<p>
The overlay should contain the same directory structure as the Gentoo
repository (although only the necessary directories need be included).
For example, a simple overlay might have a directory structure like:
</p>

<pre>
overlay
|-- dev-util
    `-- gengetopt
        |-- Manifest
        |-- files
        |   `-- gengetopt-2.13-foobar.patch
        `-- gengetopt-2.13.ebuild
</pre>

<p>
An overlay can be used to 'add' items to the tree (although you must ensure that
<c>/etc/portage/categories</c> is used if any new categories are added) or to
override existing entries.
</p>
</body>

<section>
<title>Overlay and eclasses</title>

<body>
<p>
Be very careful when using eclasses in an overlay. Portage will not do cache
updates when an overlay eclass is changed, nor will it do cache updates when a
main Gentoo repository eclass which is used by an overlay ebuild changes. You may
also encounter bogus 'illegal inherit' notices when working with eclasses in
an overlay (see
<uri link="::appendices/common-problems/#QA Notice: ECLASS foo inherited illegally"/>).
To be safe, manually <c>touch</c> all relevant overlay files after updating overlay
eclasses.
</p>
</body>
</section>

</chapter>
</guide>