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Yash Sonawane
Yash Sonawane

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Docker Series: Episode 25 — Docker Troubleshooting & Debugging: Common Issues & Fixes 🛠️

#docker #devops #tutorial

Welcome back! After mastering Docker deployment, networking, and orchestration, it’s essential to know how to identify, troubleshoot, and fix issues. Containers are isolated, but problems can arise anywhere — from images, networks, volumes, or Swarm services.

🔹 Common Docker Issues & Fixes

1. Container Won’t Start

Possible causes:

  • Incorrect command or entrypoint
  • Missing environment variables
  • Port conflicts

Fix:

docker logs <container_name>
docker inspect <container_name>
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  • Check logs for errors.
  • Verify environment variables and ports.

2. Image Pull Failures

Possible causes:

  • Network issues
  • Wrong image name/tag
  • Docker Hub limits

Fix:

docker pull nginx:latest
docker login
docker system prune -f
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  • Ensure network access and correct image name.

3. Volume & Data Issues

Possible causes:

  • Permission errors
  • Wrong mount paths

Fix:

docker volume ls
docker volume inspect <volume_name>
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  • Correct ownership and paths.
  • Use chown if needed.

4. Networking Problems

Possible causes:

  • Port conflicts
  • Containers can’t communicate
  • Overlay network misconfiguration

Fix:

docker network ls
docker network inspect <network_name>
docker exec -it <container_name> ping <other_container>
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  • Verify networks and connectivity.

5. Swarm & Stack Issues

Possible causes:

  • Service not running on nodes
  • Secrets/configs not applied
  • Rolling updates fail

Fix:

docker service ls
docker service ps <service_name>
docker stack ps <stack_name>
docker service logs <service_name>
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  • Check node status, service tasks, and logs.

🔹 Debugging Tips

  • Use docker inspect to understand container configuration.
  • Check logs with docker logs -f.
  • Prune unused resources: docker system prune -f.
  • Use docker stats to monitor real-time resource usage.

🔹 Hands-On Challenge

  1. Run a container with a wrong command and fix it using logs.
  2. Simulate a network conflict and resolve using docker network commands.
  3. Break a volume mount and fix permissions.
  4. Deploy a Swarm stack and troubleshoot service failures.

✅ Next Episode: Episode 26 — Docker Image Optimization & Best Practices — make your images faster, smaller, and more secure for production.

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