If you’re using GitLab CI to build your software, you might also want to use it to build Docker images of your application.This can be a little tricky, because by default GitLab CI runs jobs inside Docker containers.

The standard technique for getting around this problem is using Docker-in-Docker, but you can also use a simpler technique by using Podman, the reimplemented version of Docker.Let’s see why and how.

Option #1: Docker-in-Docker

When you run the docker command-line tool, it is actually not doing much work itself.Instead, it talks to dockerd, a daemon or server typically running on the same machine where you’re running the CLI.The actual work of running a container or building an image is done by dockerd.

When GitLab Runner is started as a system service (for example, with Systemd), the logs are in most cases logged through Syslog or other system logging mechanism. With GitLab Runner started as a Docker based service, since the gitlab-runner. Command is the main process of the container, the logs can be read using the docker logs command.

• If the GitLab Runner is run as service on Linux/macOS the daemon logs to syslog. If GitLab Runner is running as a service on Windows, it creates system event logs. To view them, open the Event Viewer (from the Run menu, type eventvwr.msc or search for “Event Viewer”). Then go to Windows Logs Application. The Source for Runner logs is gitlab-runner.
• Python development guidelines SCSS style guide Shell scripting standards and style guidelines Sidekiq debugging Sidekiq style guide. GitLab Runner officially supported binaries are available for the following architectures: x86, AMD64, ARM64, ARM, s390x, ppc64le.
• Clone with HTTPS. Open in your IDE. Visual Studio Code (SSH) Visual Studio Code (HTTPS) Copy HTTPS clone URL. Copy SSH clone URL git@gitlab.com:ayufan/python-getting-started.git. Copy HTTPS clone URL.
• GitLab Runner is an application that works with GitLab CI/CD to run jobs in a pipeline. You can choose to install the GitLab Runner application on infrastructure that you own or manage. If you do, you should install GitLab Runner on a machine that’s separate from the one that hosts the GitLab instance for security and performance reasons.

When you want to run docker inside GitLab CI, you face the issue that GitLab CI jobs typically run as Docker containers.So you can’t just rely on a normal dockerd being available as you would, for example, in a virtual machine.

To help with this scenario, there’s a Docker image that runs dockerd for you: docker:dind.Once that is running, you can point docker at that running daemon and issue commands like docker build.

In the context of GitLab CI, your jobs can run services, which are also Docker containers.So we can configure .gitlab-ci.yml to run docker:dind as a service in a job:

In this case, the service is given the hostname alias dockerdaemon.You also need to tell the docker CLI how to find the server, which you can do via an environment variable DOCKER_HOST, as well as set a couple of other variables that make it work, and work faster:

A full configuration that builds an image and pushes it to the GitLab image registry corresponding to the GitLab CI repository looks like this:

For more details see the relevant GitLab CI documentation.

A working example

I’ve set up an example repository that contains this configuration.Here’s what the Dockerfile looks like:

Like most GitLab repositories, it has a corresponding Docker image registry, and you can run the image built by the above configuration like so:

Note: Outside the very specific topic under discussion, the Dockerfiles in this article are not examples of best practices, since the added complexity would obscure the main point of the article.

To ensure you’re following all the best practices you need to have a secure, correct, fast Dockerfiles, check out the Python on Docker Production Handbook.

Gitlab Api Python

Option #2: Podman

Podman is a reimplemented version of Docker from RedHat.It supports the same command-line options, but has a fundamentally different architecture: unlike Docker, there is no daemon by default.The CLI does all the work itself.

Gitlab Runner Python Online

That means we can do a much simpler GitLab CI config, without the service running the daemon:

Notice all we had to do was change the docker command-line to do podman instead; they basically accept the same options.

A working example

The same example repository is also configured to use Podman.Again, you can run the resulting image:

Docker-in-Docker (DinD) vs Podman

Gitlab Runner Python Script

Which of these two should you choose?DinD gives you access to BuildKit, which has some useful features and performance improvements; Podman does not support all of them yet, though it does support build secrets.

On the other hand, running the DinD daemon adds some overhead, since another image has to be downloaded; the DinD build adds another 20 seconds of fixed overhead in my test.For less trivial builds this overhead probably will be overwhelmed by other factors.

Gitlab Runner Python Virtualenv

If you don’t care about BuildKit’s additional features, using Podman is just a little bit simpler while offering the same user experience.Finally, you could look into Buildah, which is how podman build is implemented: it’s a tool specifically focused only on building images.