146 lines
5.7 KiB
Markdown
146 lines
5.7 KiB
Markdown
# Runners
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In GitLab CI, Runners run your [yaml](../yaml/README.md).
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A runner is an isolated (virtual) machine that picks up builds
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through the coordinator API of GitLab CI.
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A runner can be specific to a certain project or serve any project
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in GitLab CI. A runner that serves all projects is called a shared runner.
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## Shared vs. Specific Runners
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A runner that is specific only runs for the specified project. A shared runner
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can run jobs for every project that has enabled the option
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`Allow shared runners`.
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**Shared runners** are useful for jobs that have similar requirements,
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between multiple projects. Rather than having multiple runners idling for
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many projects, you can have a single or a small number of runners that handle
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multiple projects. This makes it easier to maintain and update runners.
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**Specific runners** are useful for jobs that have special requirements or for
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projects with a very demand. If a job has certain requirements, you can set
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up the specific runner with this in mind, while not having to do this for all
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runners. For example, if you want to deploy a certain project, you can setup
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a specific runner to have the right credentials for this.
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Projects with high demand of CI activity can also benefit from using specific runners.
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By having dedicated runners you are guaranteed that the runner is not being held
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up by another project's jobs.
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You can set up a specific runner to be used by multiple projects. The difference
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with a shared runner is that you have to enable each project explicitly for
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the runner to be able to run its jobs.
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Specific runners do not get shared with forked projects automatically.
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A fork does copy the CI settings (jobs, allow shared, etc) of the cloned repository.
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# Creating and Registering a Runner
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There are several ways to create a runner. Only after creation, upon
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registration its status as Shared or Specific is determined.
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[See the documentation for](https://gitlab.com/gitlab-org/gitlab-ci-multi-runner/#installation)
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the different methods of installing a Runner instance.
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After installing the runner, you can either register it as `Shared` or as `Specific`.
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You can only register a Shared Runner if you have admin access to the GitLab instance.
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## Registering a Shared Runner
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You can only register a shared runner if you are an admin on the linked
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GitLab instance.
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Grab the shared-runner token on the `admin/runners` page of your GitLab CI
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instance.
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Now simply register the runner as any runner:
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```
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sudo gitlab-runner register
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```
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Shared runners are enabled by default as of GitLab 8.2, but can be disabled with the
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`DISABLE SHARED RUNNERS` button. Previous versions of GitLab defaulted shared runners to
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disabled.
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## Registering a Specific Runner
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Registering a specific can be done in two ways:
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1. Creating a runner with the project registration token
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1. Converting a shared runner into a specific runner (one-way, admin only)
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There are several ways to create a runner instance. The steps below only
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concern registering the runner on GitLab CI.
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### Registering a Specific Runner with a Project Registration token
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To create a specific runner without having admin rights to the GitLab instance,
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visit the project you want to make the runner work for in GitLab CI.
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Click on the runner tab and use the registration token you find there to
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setup a specific runner for this project.
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To register the runner, run the command below and follow instructions:
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```
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sudo gitlab-runner register
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```
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### Making an existing Shared Runner Specific
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If you are an admin on your GitLab instance,
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you can make any shared runner a specific runner, _but you can not
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make a specific runner a shared runner_.
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To make a shared runner specific, go to the runner page (`/admin/runners`)
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and find your runner. Add any projects on the left to make this runner
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run exclusively for these projects, therefore making it a specific runner.
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## Using Shared Runners Effectively
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If you are planning to use shared runners, there are several things you
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should keep in mind.
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### Use Tags
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You must setup a runner to be able to run all the different types of jobs
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that it may encounter on the projects it's shared over. This would be
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problematic for large amounts of projects, if it wasn't for tags.
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By tagging a Runner for the types of jobs it can handle, you can make sure
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shared runners will only run the jobs they are equipped to run.
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For instance, at GitLab we have runners tagged with "rails" if they contain
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the appropriate dependencies to run Rails test suites.
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### Be Careful with Sensitive Information
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If you can run a build on a runner, you can get access to any code it runs
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and get the token of the runner. With shared runners, this means that anyone
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that runs jobs on the runner, can access anyone else's code that runs on the runner.
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In addition, because you can get access to the runner token, it is possible
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to create a clone of a runner and submit false builds, for example.
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The above is easily avoided by restricting the usage of shared runners
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on large public GitLab instances and controlling access to your GitLab instance.
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### Forks
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Whenever a project is forked, it copies the settings of the jobs that relate
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to it. This means that if you have shared runners setup for a project and
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someone forks that project, the shared runners will also serve jobs of this
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project.
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# Attack vectors in runners
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Mentioned briefly earlier, but the following things of runners can be exploited.
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We're always looking for contributions that can mitigate these [Security Considerations](https://gitlab.com/gitlab-org/gitlab-ci-multi-runner/blob/master/docs/security/index.md).
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