Docker Container Not Starting — How to Fix

A Docker container that won't start is one of the most frustrating issues in containerized development. This guide covers every common cause and its fix.

What You'll Learn

You'll learn how to diagnose why a Docker container fails to start and apply the correct fix in under two minutes.

Why It Matters

A non-starting container blocks your entire development or deployment pipeline, wasting time and delaying releases.

Real-World Use

A staging server goes down after a deploy because the container exits immediately — you need to identify and fix the root cause fast.

Step 1 — Check Container Logs

Always start with logs:

docker logs <container-name>

Expected output: Error messages showing exactly why the container stopped.

If the container is not running, use:

docker logs --tail 50 <container-name>

Step 2 — Check Container Status

docker ps -a | grep <container-name>

Expected output: Shows the container with status like Exited (1) 2 minutes ago. The exit code tells you what happened.

Step 3 — Common Fixes

Container Exits Immediately (Exit 0)

Your app starts and finishes without staying alive. Add a foreground process:

CMD ["tail", "-f", "/dev/null"]

Or run interactively:

docker run -it <image> /bin/bash

Expected behavior: Container stays running with an active shell.

Port Already in Use (Exit 125)

Error response from daemon: driver failed programming external connectivity

Find and stop the conflicting container:

docker ps | grep <port>
docker stop <conflicting-container>

Or use a different host port:

docker run -p 8081:80 <image>

OOM Killed (Exit 137)

The container ran out of memory. Increase the limit:

docker run -m 512m <image>

Or check for memory leaks in your application.

Volume Mount Issues

docker run -v /host/path:/container/path <image>

Verify the host path exists:

ls /host/path

Expected behavior: If the path doesn't exist, Docker creates an empty directory owned by root, which may cause permission errors inside the container.

Entrypoint or CMD Error

Override the entrypoint to debug:

docker run --entrypoint /bin/bash <image>

Then manually start your application to see the exact error.

Prevention Tips

• Always run docker build --no-cache after changing Dockerfiles
• Pin base image versions, never use latest
• Add health checks to your Dockerfile
• Use <a href="/devops/docker-compose/">docker compose</a> up for multi-container debugging

Quick Reference

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