A Docker container that exits with code 0 immediately after starting has successfully completed its main process. This typically occurs when the container's entrypoint or command is a short-lived task rather than a long-running service, or when running interactive shells without proper terminal attachment.
Exit code 0 in Docker indicates that the container's main process completed successfully—it's not actually an error. Containers are designed to run a single process, and when that process exits, the container stops. Unlike traditional servers that run continuously, Docker containers have a lifecycle tied to their primary process. When you see "exited with code 0," Docker is telling you that your application ran and finished without errors. This behavior is intentional and by design. However, if you expected the container to stay running (like a web server or database), it means your entrypoint/CMD is either completing too quickly or requires an interactive terminal that wasn't provided. The root cause is that Docker needs a foreground process that keeps running. If the main process exits or runs in the background without any foreground process to attach to, the container will shut down immediately.
First, inspect the Dockerfile or docker-compose.yml to see what CMD or ENTRYPOINT is configured:
# View the Dockerfile
cat Dockerfile
# Or inspect a running/stopped container
docker inspect <container_name> | grep -A 10 "Cmd"If the command is something like bash, mkdir, echo, or a script that exits quickly, that's your issue.
If you're trying to run a shell container, you need to attach an interactive terminal:
# Instead of:
docker run -d ubuntu:latest
# Use:
docker run -it ubuntu:latest
# Or for detached mode with terminal:
docker run -dit ubuntu:latestThe -i (interactive) keeps STDIN open, and -t allocates a pseudo-TTY, which prevents the shell from exiting.
If using Docker Compose, add the tty and stdin_open options:
services:
myapp:
image: ubuntu:latest
tty: true
stdin_open: true
# Or specify a long-running command
command: tail -f /dev/nullThis keeps the container running by maintaining an attached terminal.
Replace short-lived commands with processes that run continuously:
# Instead of:
CMD ["echo", "Hello World"]
# Use a web server:
CMD ["nginx", "-g", "daemon off;"]
# Or keep container alive for debugging:
CMD ["tail", "-f", "/dev/null"]The key is ensuring the process runs in the foreground and doesn't exit. For nginx, daemon off; is critical.
If your main process runs in background (with &), ensure there's a foreground process afterward:
#!/bin/bash
# Bad - container will exit
./my-background-service &
# Good - start background service then keep container alive
./my-background-service &
tail -f /dev/nullOr better yet, run your service in foreground mode if it supports it.
To investigate what's happening, start the container with a shell and run commands manually:
# Override entrypoint to get a shell
docker run -it --entrypoint /bin/bash <image_name>
# Now manually run your original CMD to see what happens
./your-original-command.shThis helps you understand why the process is exiting.
Exit Code 0 vs Other Exit Codes: Remember that exit code 0 specifically means "success." If you see other exit codes (like 1, 137, 143), those indicate errors or signals. Code 0 is unique because it means your application is working correctly—it's just not designed to run continuously.
Production Considerations: Using tail -f /dev/null is fine for debugging but not ideal for production. For production containers, ensure your application itself runs as a foreground process. Most production-ready applications (web servers, databases, message queues) have a foreground or non-daemon mode for exactly this reason.
Docker Compose Dependencies: If you're using depends_on in docker-compose and a dependency container exits with 0, it can cause issues. Consider using health checks instead of depends_on for services that need to stay running.
Batch Jobs vs Services: This behavior is perfectly normal for batch jobs or CI/CD containers that perform a task and exit. Not every container needs to stay running forever. If your use case is a one-time task, exit code 0 is exactly what you want.
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