Скачать или смотреть Troubleshooting Your GitLab Dedicated Runner - Docker Image Pull Issues

Learn how to resolve issues with your GitLab dedicated runner not being able to pull Docker images. Common causes and solutions are discussed in this guide.
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Troubleshooting Your GitLab Dedicated Runner - Docker Image Pull Issues

If you're a developer or a DevOps engineer using GitLab, you might encounter a frustrating issue with your dedicated runner. Specifically, you may find that your runner is failing to pull the Docker image you've specified in your CI/CD pipeline, such as amazonlinux:latest. In this guide, we'll break down the problem and discuss how to effectively resolve it.

The Problem: Unable to Pull Docker Image

A common scenario that leads to this issue involves the runner getting stuck when trying to prepare the Docker executor. You might see logs similar to:

[[See Video to Reveal this Text or Code Snippet]]

In these cases, the runner is unable to proceed because it cannot pull the Docker image required for the build process. This can halt your CI/CD pipeline and cause delays in development.

Possible Causes

Understanding the possible causes of this issue can help you troubleshoot effectively. Here are a few common problems that you might encounter:

Network Configuration: The runner might be facing network issues that prevent it from reaching Docker Hub or another registry for pulling images.

Subnets and Security Groups: If your runner is configured in a cloud environment (like AWS), it may be blocked by security groups or subnet configurations that restrict outbound traffic.

Access Permissions: Ensure that your runner has the necessary permissions to pull the images, especially if your images are stored in a private registry.

The Solution: Fixing the Subnet Issue

In one real-world case, the issue was traced back to a subnet configuration problem. Here is a step-by-step approach to resolving similar issues:

Diagnose the Network Setup:

Check the configuration of your runner's EC2 instance (if on AWS). Look into the subnet settings and associated route tables to ensure they allow outbound traffic.

Review Security Groups:

Inspect the security groups attached to your EC2 instance. Make sure that they allow outbound requests to the internet or the specific Docker registry you are trying to access.

Verify IAM Roles (if applicable):

If you're using IAM roles for granting permissions, ensure that the role associated with your EC2 instance has the correct permissions to pull images from the specified registry.

Test Connectivity:

Run a diagnostic command from the EC2 instance to confirm connectivity to Docker Hub, such as:

[[See Video to Reveal this Text or Code Snippet]]

Retry the CI/CD Pipeline:

Once you’ve confirmed that the network configuration is correct, go ahead and retry your pipeline to see if the runner can now successfully pull the Docker image.

Conclusion

Encountering issues with your GitLab dedicated runner can indeed be frustrating, but with proper troubleshooting steps, you can quickly identify and resolve the root cause. In many cases, such as the one we explored, addressing network and subnet configurations can make all the difference. If you find yourself stuck, don’t hesitate to reach out to the GitLab community or consult with your team. Happy coding!