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Exploring the AlmaLinux Build System

Package Packer

Article from ADMIN 79/2024
The AlmaLinux Build System lets you build, test, sign, and release packages from a single interface.

When IBM announced that it was restricting access to Red Hat Enterprise (RHEL) source code and moving CentOS upstream, the distros that depended on RHEL and CentOS source code were sent scrambling. It is still a little unclear whether IBM's moves are legal and consistent with the GNU Public License (GPL), but the litigation to sort it out could take years, and in the meantime, the derivatives need a solution.

One enterprise distribution that weathered the storm quite smoothly was AlmaLinux [1] (see the box entitled "Where Do They Get Their Code?"). If you ask the AlmaLinux developers, they will say that one reason for their success in navigating the transition to the post-RHEL era is the AlmaLinux Build System [2].

Where Do They Get Their Code?

AlmaLinux was envisioned as a free alternative to RHEL, which comes with a subscription fee and other corporate licensing arrangements. AlmaLinux and other RHEL derivatives used source code from Red Hat repositories as the basis for building an independent distro. It is important to note that Red Hat does not own the source code in the sense that the term own is used with proprietary software. Because Linux and most of the code included with it are open source and licensed under the GNU Public License (GPL), the code is available for others to use and modify.

IBM currently restricts access to some, but not all, RHEL source code. Some source code is available through the Red Hat Universal Base Image (UBI) [3]. AlmaLinux uses as much of the Red Hat UBI code as it can, but a majority of the code comes from the CentOS Stream project [4]. IBM did not eliminate all access to CentOS; they just moved it upstream, so the code does not include some of the final bug fixes and updates that go into the final version of RHEL. AlmaLinux uses some code from the CentOS Stream project and performs its own fixes and updates. They also pull code from other upstream sources when necessary.

The AlmaLinux Build System evolved from an earlier system used by CloudLinux. (CloudLinux is a contributor to the AlmaLinux project.) The developers refer to their build system as "a project designed to automate processes of building distribution and packages, testing packages, signing packages, and releasing them to public repositories." In other words, the goal is to assist with every phase of the package development process, relying on automation to reduce human error and minimize manpower requirements.

The AlmaLinux Build System is a free software project that is available on GitHub. Other Linux distributions are welcome to use the AlmaLinux Build System as a tool for building and managing packages. You can also point the build system at other, third-party Git repositories, which makes it suitable for many in-house DevOps development settings.

How Does It Work?

The AlmaLinux Build System automates the process of building, supporting, and managing packages. The vision is for something that is more than a build tool, with support for testing, signing, and releasing software packages.

If the AlmaLinux project needed a build system to interact with source code originating from a Red Hat environment, you might be wondering why they didn't just use Koji [5], the freely available build tool associated with Red Hat's Fedora project. The answer given by the developers is that, although Koji is an effective tool, the AlmaLinux project had a much broader vision. For one thing, they wanted to integrate additional package formats (Koji is limited to RPMs). They also wanted to provide a complete, integrated pipeline to manage a package from the build phase, to testing, to signing the package, and finally to release. The AlmaLinux Build System includes controls that allow the user to specify where to release packages, and it is one of the first build systems to support modularity. A module is a collection of packages that occur together, such as the packages in a single application or an operating system component. Support for modularity lets you treat the packages together, thus saving steps and streamlining the configuration.

Like other build platforms, the AlmaLinux Build System is not a monolithic application but a combination of back-end tools behind a single, unified interface. Some of the tools incorporated into the AlmaLinux Build System include:

  • Mock – a tool for building RPM packages
  • Pulp – a content repository for organizing and distributing software packages
  • NGINX – a web server that serves as an interface for managing access to the build system
  • Terraform – an infrastructure-as-code tool used to build simulated environments for package testing
  • PGP – an encryption utility that provides signing services for package verification
  • Git – a source code repository system

Git isn't actually part of the build system itself, but it is an integral part of the ecosystem, providing source code for building packages and communicating with the build system through an API.

Figure 1 shows the complete system at a glance. Users interact through either a graphical user interface or text-based commands. Support for command-line processing creates the possibility for scripting and other custom automation scenarios.

Figure 1: The AlmaLinux Build System at a glance.

At the center of the system is the Build System Master Service. The Master Service receives commands from the user and sets the process in motion, creating, restarting, and deleting builds and communicating with the rest of the system via API calls. Responsibilities of the master service include requesting and receiving source code from the Git server and assigning tasks to the build nodes.

Another important component of the build system is Pulp [6], which provides artifact storage for newly-built packages and other products of the build process. According to AlmaLinux Community Manager Jack Aboutboul, "the master service is the brain, and Pulp is the heart" of the build system. As you can see in Figure 1, Pulp is essential to the later stages of the process, providing packages for signing and testing, and forwarding finished packages for release. Much of the power of the AlmaLinux Build System is in its ability to oversee the testing, signing, and release phases of the development process.

Getting the Code

The AlmaLinux Build System uses the Gitea software development service [7] to communicate with the Git server. Gitea is described as an all-in-one service for managing a Git environment, including "code review, team collaboration, package registry and CI/CD." The AlmaLinux team has developed a gitea-listener tool for interfacing with Gitea and the Git repository. The AlmaLinux Build System also supports Fedora Community Repository Platform format (COPR), which makes it easy to add alternative repositories to the system.

First Look

When you log in to the AlmaLinux Build System, a view of configured builds appears in the main screen (Figure 2). A menu on the left offers options for creating a new build, new release, or new distribution.

Figure 2: Your first view shows the builds configured for the system.

Click on the Details link for a configured build to view the build settings. You can choose an architecture (Figure 3) or view the artifacts associated with the build (Figure 4).

Figure 3: The AlmaLinux Build Systems supports several hardware architectures.
Figure 4: Viewing the artifacts associated with the build.

To create a new build, choose New build in the main view. In subsequent menus, you can select a platform and choose architecture(s), set options for the Mock build tool, and specify whether to build for a Secure Boot system.

Once you have configured the build settings, select the project (the packages) you would like to build (Figure 5) and click on Create Build .

Figure 5: Adding a project to the build.

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