Troubleshooting Git Clone Authentication Failures Inside Docker

Symptoms

Git clone fails due to authentication errors when executed inside a Docker container.

Environment

Docker container running a Linux distribution with Git installed.

Most Likely Causes

Incorrect Git credentials or SSH keys not configured properly within the Docker container.

What to Check First

1. Verify if the correct Git repository URL is being used.
2. Check if the Docker container has access to the necessary SSH keys or credentials.

Insight Cluster

Parent question: How do we isolate container failures by naming the broken branch first: image, runtime, service-networking, or ingress?

• Planning Container Runtime, Registry, and Service-Networking Failures Systematically (parent Insight)
• Comparing Container Validation Paths for Runtime, Registry, Network, and Ingress (supporting Insight)
• Container Evidence-First Comparison Between Good and Broken Service Paths (supporting Insight)
• Troubleshooting DNS Issues in Docker: Unable to Get Image Due to Lookup Failure (tactical leaf)
• Troubleshooting Docker Container Communication Issues: Ping vs HTTP Requests (tactical leaf)
• Troubleshooting Docker Container Exit Code 0 and Dependency Failures (tactical leaf)
• Troubleshooting 'Error Reading File Content' in Helm Template on Kubernetes (tactical leaf)
• Troubleshooting Kubernetes Webhook Timeout: No Endpoints Available for AWS LB Controller and External Secrets during ArgoCD Sync (tactical leaf)
• Troubleshooting NuGet Source Addition in Dockerfile for .NET Applications (tactical leaf)

• This parent cluster is meant to stop container leaves from being treated as disconnected Docker or Kubernetes incidents.
• The supporting pages frame branch selection and good-vs-broken comparison before the reader drops into exact runtime, registry, network, or ingress failures.

Fix Steps

1. Check the Git repository URL for correctness.

   Ensure the URL format is correct (e.g., https:// or git@).

   Example pattern only. Adjust for your environment before running.

   echo 'Repository URL: <your-repo-url>'

2. Verify if SSH keys are present in the Docker container.

   Check for the presence of SSH keys in the default location.

   Safe to run: read-only

   ls -la ~/.ssh

3. Add SSH keys to the Docker container if missing.

   Copy the SSH keys from the host to the container.

   Safe to run: read-only

   docker cp ~/.ssh/id_rsa <container_id>:/root/.ssh/id_rsa
   docker cp ~/.ssh/id_rsa.pub <container_id>:/root/.ssh/id_rsa.pub

4. Set the correct permissions for the SSH keys.

   Ensure that the SSH private key has the correct permissions.

   Changes system state: review before running

   docker exec <container_id> chmod 600 /root/.ssh/id_rsa

5. Test SSH connection to the Git server.

   Verify that the SSH connection works without issues.

   Safe to run: read-only

   docker exec <container_id> ssh -T git@<git-server>

6. Attempt to clone the repository again.

   Retry the git clone command after resolving authentication issues.

   Safe to run: read-only

   docker exec <container_id> git clone <your-repo-url>

Validation

• Confirm that the repository has been cloned successfully.
• Check for the presence of the cloned directory.

Logs to Check

• /var/log/syslog
• /var/log/auth.log

Rollback and Escalation

Escalate When

• If the issue persists after following all steps, escalate to the DevOps team for further investigation.

Edge Cases

• Using a different user than root inside the container may require additional permissions.
• If using HTTPS, ensure that the correct username and password/token are used.

Notes from the Field

• Always ensure that the Docker container has network access to the Git server.
• Consider using Docker secrets for managing sensitive information like SSH keys.