Ebuild repository

An ebuild repository, colloquially known as an overlay, is Article description::a structure of directories and files used to add and extend software packages for a Gentoo-based system. Ebuild repositories contain ebuilds, eclasses, and other types of descriptive metadata files. These files inform the package manager of software available for installation. An ebuild repository should conform to one or more Ebuild APIs as detailed in Gentoo's Package Manager Specification.

The primary repository on a Gentoo system is called the Gentoo ebuild repository. This term is sometimes contextually abbreviated as Gentoo repo, ::gentoo, gentoo.git, or occasionally just "repo". It was historically known within the Gentoo community as the Portage tree, rsync tree, or sometimes just "the tree". The Gentoo ebuild repository contains ebuilds that are maintained by official Gentoo developers and members of the community (through the Proxy Maintainers project).

Administrator of Gentoo systems can add additional ebuild repositories by using various utilities and methods described below.

Repositories
Ebuild repositories are nothing more (or less) than a set of files (ebuilds, metadata files, ...). These can be pulled in from public repositories (git, CVS, SVN, ...) or downloaded as tarballs and extracted manually onto the system.

The now default approach for handling repositories is through which, like many other Portage configuration locations, can be a file or a directory of files.

Repository definitions inside also inform Portage if and how the repository can be updated. With it, calling will automatically update the enabled repositories as well.

A deprecated, yet still supported method is to use the PORTDIR_OVERLAY variable inside. This variable can point to one or more additional locations on the file system where additional repositories are available. The use of the directory is highly preferred.

For more information, see /etc/portage/repos.conf and the Portage/Sync article.

Priorities
Each ebuild repository has a unique priority to the package manager. This ensures that in the case of a specific version being found in several ebuild repositories, the resolution is unambiguous. Ebuilds from repositories with higher priority numbers (for example ) will take precedence over ebuilds from repositories with lower priorities (such as  ).

The list of ebuild repositories with their priorities can be obtained through the output of the following commands (look for the "Repositories" string):

The Gentoo ebuild repository will have a priority of  which means that all other repositories generally take precedence if they are assigned a higher priority. This is the default behaviour, because ebuild repositories are designed to "lay over" or "on top" of the Gentoo repository.

Available software
A number of tools support or integrate with ebuild repositories.

Layman
The application makes it easier to manage and update multiple additional ebuild repositories. It is a command-line application through which publicly available ebuild repositories can be listed, subscribed to and unsubscribed from, as well as update those repositories.

It supports both the as well as  method.
 * When using the method,  manages a dedicated configuration file which should be sourced in by
 * When using, manages the  file directly

For more information, see Layman and Project:Portage/Sync.

emaint
See the Sync (Portage project) article and.

eix
is a wrapper starting (which in turn starts ) followed by. For further details see the Eix article and.

eselect-repository
maintains entries for Portage to access and synchronize. See Eselect/Repository article for details.

Emerging a duplicate package
When working with ebuild repositories it is possible to encounter a situation where multiple versions of the same package are available from different ebuild repositories. Instruct Portage to install a specific package from a specific ebuild repository with the  version specifier:

The same notation can be used for different emerge instructions, including uninstalling a package through.

Cache generation
When large ebuild repositories are installed, Portage may take a long time to perform operations like dependency resolution. This is because ebuild repositories do not usually contain a metadata cache.

Generate a local metadata cache by running after syncing the ebuild repositories:

Be careful, because takes a lot of time and it's not recommended for rsync users as rsync updates the cache using server-side caches (most of users of portage are rsync users). Rsync users should simply run (or ) to regenerate the cache. It's probably only users of very large ebuild repositories should try.

Masking installed but unsafe ebuild repositories
When using large ebuild repositories or those with unknown/low quality code, it is best practice to hard mask the whole ebuild repository and only accept specific ebuilds on a case-by-case basis. For example, for an overlay named "repository-foobar":

Then add the specific package(s) from the repository-foobar overlay so that they will be available visible to Portage for installation:

After the above unmask the package named "foo-category/bar" should be available and none of the other packages from the repository-foobar overlay will be available, which is by design.

External resources

 * https://repos.gentoo.org
 * https://github.com/gentoo/
 * https://gpo.zugaina.org/Overlays