How to Fix Docker Container Exits Immediately Error

In this tutorial, you'll learn about How to Fix Docker Container Exits Immediately Error. We cover key concepts, practical examples, and best practices.

You start a container with docker run and it exits instantly — containers only run as long as their main process is alive, so if that process finishes or fails, the container stops.

The Problem

docker run ubuntu

Returns immediately with no output. docker ps -a shows:

CONTAINER ID   IMAGE     COMMAND   CREATED          STATUS
abc123         ubuntu    "bash"    2 seconds ago    Exited (0) 1 second ago

Exit code 0 means success — bash exited because no terminal was attached.

Step-by-Step Fix

Step 1: Run in interactive mode

docker run -it ubuntu bash

This keeps the container alive with an interactive shell.

Step 2: Run a foreground process

For services like nginx, the process stays alive:

docker run -d nginx

docker ps

Expected:

CONTAINER ID   IMAGE   COMMAND                  CREATED          STATUS
abc456         nginx   "/docker-entrypoint.…"   5 seconds ago    Up 5 seconds

Step 3: Debug why the process exits

Check logs:

docker logs <container-id>

Inspect exit code:

docker inspect <container-id> --format '{{.State.ExitCode}}'

Exit code meanings: 0 = success, 1 = application error, 137 = OOM kill, 139 = segfault, 143 = SIGTERM.

Step 4: Test with a sleep command

docker run ubuntu sleep 30

The container stays alive for 30 seconds.

Step 5: Check the Dockerfile CMD and ENTRYPOINT

# WRONG — shell form exits immediately
CMD echo "Hello"

# RIGHT — foreground process
CMD ["nginx", "-g", "daemon off;"]

For Node.js apps:

# WRONG
CMD "npm start"

# RIGHT — exec form
CMD ["node", "server.js"]

Step 6: Use a custom entrypoint that stays alive

For debugging:

docker run -d --entrypoint tail ubuntu -f /dev/null

Then exec into it:

docker exec -it <container> bash

This keeps the container running indefinitely for investigation.

Prevention Tips

• Ensure your container's main process runs in the foreground
• Do not use init systems like systemd inside containers
• Use docker run -d for daemon services
• Set ENTRYPOINT to a script that keeps running
• Check logs immediately with docker logs --tail 50

Common Mistakes with container exit

1. Forgetting deriving (Show, Eq) on custom data types needed for debugging
2. Placing the wildcard pattern first in case expressions, making all subsequent patterns unreachable
3. Using head and tail instead of pattern matching, causing runtime errors on empty lists

These mistakes appear frequently in real-world DOCKER code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ