Repositories
A repository is a storage location with a collection of Alpine Linux packages. In addition to the three official repositories, technically, any directory with a collection of *.apk files with a special index file, named APKINDEX.tar.gz can be considered a repository, albeit a personal repository. Alpine Package Keeper(apk) loads repository definitions from /etc/apk/repositories, has sub-commands to query repositories and maintain the desired system state as per world.
Official repositories
There are three official package repositories available in Alpine Linux i.e main, community and testing. These repositories directly correspond to three directories of aports.
Main
Packages in main repository are the software that have direct support and updates from the Alpine core team. Alpine Linux tries to limit the amount of packages in main to only include base system packages, i.e packages which are needed by other packages or are needed to setup a basic system.
Community
Packages in community repository are those made by users in team with the official developers and close to the Alpine package process. They are supported by those user(s) contributions and could end if the user(s) stops; they may also be removed in a future release due to lack of support by upstream authors.
If packages from community repository are used, one needs to upgrade to the latest stable release branch to continue to have support.
Testing
The testing repository is only available on edge branch i.e development branch and this is where new packages go. These are made by any contributor to Alpine Linux. Packages from testing that are accepted go to the community repository or (rarely) to the main repository. Packages in testing have no support (staging only) and are built only for edge branch.
Release Branches
Each stable release branch of Alpine Linux has its own main and community repositories. Releases page has information on all the release branches along with support status. Support entails security patches for the given feature versions.
The current stable release branch of Alpine Linux is 3.22.
Edge
edge is the name given to the current development tree of Alpine Linux. edge branch includes all three official repositories and contains the latest build of all available Alpine Linux packages. Those packages are updated on a regular basis. Since edge is a development branch, many changes are not heavily tested (or tested at all) and packages can and sometimes do break without warning. edge can be considered as rolling release version of Alpine Linux.
Upgrading to Edge branch and/or installing packages from testing repository and submitting bug reports is one of the best ways to contribute to Alpine Linux. This is a very valuable activity which helps Alpine Linux development, as it ensures that the quality of stable releases is high.
The current installed edge version i.e the build date that is attached to the edge release may be checked with command:
$ cat /etc/alpine-release
Managing repositories
The package repositories that apk uses to retrieve package files for installation are specified in file /etc/apk/repositories. Each line of /etc/apk/repositories specifies the location of a package repository, one repository per line and optionally a tag. Lines that start with a hash character (#) are ignored.
The location may be an http:// or https:// URL, or the path to a directory on the local filesystem. If you booted from a USB stick (/media/sda1) or CD-ROM (/media/cdrom), your repository file probably looks something like this:
Contents of /etc/apk/repositories
Enabling the community repository
setup-apkrepos script can be used to enable community repository as follows:
# setup-apkrepos -c
With the above change, the /etc/apk/repositories file will look something like:
Contents of /etc/apk/repositories
Tagged repository
A tagged repository is prefixed with the @tag specifier, followed by a space and the repository location in the /etc/apk/repositories file as follows.
Contents of /etc/apk/repositories
The optional @tag, when used as shown above indicates that the tagged repository should not be used by default.
apk will by default only use the untagged repositories, but adding a package with a @tag will make apk prefer the tagged repository for the named package, even if a later version of the package is available in another repository. It allows pulling in dependencies for the tagged package from the tagged repository (though it prefers to use untagged repositories to satisfy dependencies if possible).
For eg: apk add busybox@personal enables selection of busybox from a tagged repository @personal. The above command allows installation of busybox and it's dependencies from the tagged repository @personal. Since tagged repositories are not prioritized, if a version of busybox's dependency from an untagged repository is a better fit, it will be used.
Upgrading to edge
Follow the instructions for Upgrading to Edge.
When using edge branch, testing repository can be added as a tagged repository. Remember that, packages in testing repository have no support.
Using testing repository
Unlike edge branch, installing packages from testing repository in a stable release branch is not recommended and not guaranteed to work. However, if you need a package which is available only in the testing repository, add testing repository as a tagged repository by editing the /etc/apk/repositories file as follows:
Contents of /etc/apk/repositories
Before installing a package from testing repository, check for dependencies. Installing a package from testing repository that depends on libraries in main or community often won't work due to potential version mismatch. Alpine does not officially support mixing branches this way, as mixing packages from stable and edge repositories can break your system.
In the example command # apk add wireguard-go@testing, the tag @testing allows apk to pull the necessary package(s) from testing repository without potentially messing up your installation (too badly).