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Ephemeral Containers: Advanced Debugging

Key Takeaways for AI & Readers
  • Debugging Distroless Images: Ephemeral containers provide a solution for debugging minimalist "distroless" images that lack common troubleshooting tools like shell or ls.
  • Temporary Injection: They allow you to "inject" a temporary container with debugging utilities into a running Pod without restarting or modifying the original application container.
  • kubectl debug Utility: The kubectl debug command facilitates the creation of ephemeral containers, enabling access to shared process namespaces for deep inspection.
  • Beyond kubectl exec: Ephemeral containers overcome the limitations of kubectl exec by providing their own shell and tools, essential when the target container is highly optimized for production.

Modern production pods often run Distroless images—minimal images that contain ONLY your application binary and its dependencies. They have no shell (sh), no ls, and no curl. This is excellent for security, but a nightmare for debugging.

Ephemeral Containers solve this by letting you "inject" a temporary container into a running pod.

1. Injecting a Debugger​

Instead of restarting the pod or changing its image, you attach a new container to it.

Running Pod
🚀
Main Application
distroless (No shell)
🛠️
Ephemeral Debugger
/bin/sh, curl, gdb
Ephemeral Containers allow you to inject a temporary container into an already running pod. Perfect for debugging production "Distroless" images.

2. Usage via kubectl​

You use the kubectl debug command to create an ephemeral container:

kubectl debug -it <pod-name> --image=busybox --target=<app-container-name>
  • --image: The image containing your tools (e.g., busybox, nmap, python).
  • --target: This allows the debug container to share the process namespace of the application container. You can run ps and see your app's processes!

3. Why not just use kubectl exec?​

kubectl exec requires a shell (like /bin/sh) to be present inside the container image. If the image is minimal/distroless, exec will fail. Ephemeral containers bring their own shell.