# Create a Google Axion-based GitLab self-hosted runner

## In this learning path

- [Introduction](https://learn.arm.com/learning-paths/cross-platform/gitlab/)
- [Create a Google Axion-based GitLab self-hosted runner](https://learn.arm.com/learning-paths/cross-platform/gitlab/1-gitlab-runner/)
- [Automate the build and deployment of a multi-arch application with GitLab CI/CD](https://learn.arm.com/learning-paths/cross-platform/gitlab/2-gitlab-cicd/)
- [Next Steps](https://learn.arm.com/learning-paths/cross-platform/gitlab/_next-steps/)

## What is a GitLab runner?
A GitLab Runner works with GitLab CI/CD to run jobs in a pipeline. It acts as an agent and executes the jobs you define in your GitLab CI/CD configuration. Some key points to note about GitLab Runner:
1. GitLab offers multiple types of runners - You can use GitLab-hosted runners, self-managed runners, or a combination of both. GitLab manages GitLab-hosted runners, while you install and manage self-managed runners on your own infrastructure.
2. Each runner is configured as an Executor - When you register a runner, you choose an executor, which determines the environment in which the job runs. Executors can be Docker, Shell, Kubernetes, etc.
3. Multi-architecture support: GitLab runners support multiple architectures including - `x86/amd64` and `arm64`.

## What is Google Axion?
Axion is Google’s first Arm-based server processor, built using the Armv9 Neoverse V2 CPU. The VM instances are part of the `C4A` family of compute instances. To learn more about Google Axion refer to this [page](http://cloud.google.com/products/axion/).

## Install GitLab runner on a Google Axion VM
Create a repository in your GitLab account by clicking the “+” sign on top-left corner. Click on `New project/repository` and select a blank project, provide a name and initiate your project/repository.

![GitLab new repository creation interface](https://learn.arm.com/learning-paths/cross-platform/gitlab/_images/repository.png)
*GitLab new repository creation interface*

After you create the repository, navigate to `Settings->CI/CD` in the left-hand pane. Expand the `Runners` section and under `Project Runners`, select `New Project Runner`.

![GitLab runner configuration with arm64 tag](https://learn.arm.com/learning-paths/cross-platform/gitlab/_images/create-gitlab-runner.webp)
*GitLab runner configuration with arm64 tag*

Use `Tags` to specify the jobs that can be executed on the runner. In the `Tags` field, enter `arm64`. In `Runner description` enter `google-axion-arm64-runner` and click the `Create Runner` button.

Once the runner is created, you need to register this runner. Select Linux as the Operating System.

In Google Cloud, the `C4A` VM instance is based on Google Axion. Create a `C4A` VM by following the [Create Arm-based VM in Google Cloud learning path](https://learn.arm.com/learning-paths/servers-and-cloud-computing/csp/google/).

SSH to this VM and use the following steps to install GitLab Runner binaries.

Download the binaries using the command below:
```bash
sudo curl -L --output /usr/local/bin/gitlab-runner https://gitlab-runner-downloads.s3.amazonaws.com/latest/binaries/gitlab-runner-linux-arm64
```

Provide necessary permissions:
```bash
sudo chmod +x /usr/local/bin/gitlab-runner
```

Create a GitLab runner user:
```bash
sudo useradd --comment 'GitLab Runner' --create-home gitlab-runner --shell /bin/bash
```

Install the runner and run it as a service:
```bash
sudo gitlab-runner install --user=gitlab-runner --working-directory=/home/gitlab-runner
sudo gitlab-runner start
```

In the GitLab console, on the `Register Runner` page, copy the command from `Step 1` and run it on the `C4A` VM. The command should look like this:
```bash
sudo gitlab-runner register  --url https://gitlab.com  --token <your-runner-token>
```

Go back to the SSH session for `C4A` VM. When prompted by the command line, keep the default for `GitLab instance URL` and enter a name for the runner. For the executor, use `shell` as the option.

After answering the prompts, the runner should be registered and you should see a message like the one below:
```
Runner registered successfully. Feel free to start it, but if it's running already the config should be automatically reloaded!
```

You should see the newly registered runner in the Runners section of the GitLab console.

![GitLab console showing registered arm64 and amd64 runners](https://learn.arm.com/learning-paths/cross-platform/gitlab/_images/registered-runner.webp)
*GitLab console showing registered arm64 and amd64 runners*

To create an `amd64` GitLab runner, follow the same steps as above, except for the `Download binaries` section. Change the download url to `https://gitlab-runner-downloads.s3.amazonaws.com/latest/binaries/gitlab-runner-linux-amd64`.

Launch an `amd64` VM instance with the `E2` type in Google Cloud and install the runner binaries. Once done, you should be able to see both the runners as shown in the picture above.