Getting console output from a Docker container

Question

I build an image with Python installed and a Python application too. My Python application is a Hello, World! application, just printing "Hello, World!" on the screen. Dockerfile:

FROM python:2-onbuild
CMD ["python", "./helloworld.py"]

In the console I execute:

docker run xxx/zzz

I can see the Hello, World! output. Now I am trying to execute the same application, using the task from ECS. I already pulled it to Docker Hub.

How can I see the output Hello, World!? Is there a way to see that my container runs correctly?

Solution 1

docker logs <container id> will show you all the output of the container run. If you're running it on ECS, you'll probably need to set DOCKER_HOST=tcp://ip:port for the host that ran the container.

Solution 2

To view the logs of a Docker container in real time, use the following command:

docker logs -f <CONTAINER>

The -f or --follow option will show live log output. Also if the container is stopped it will fetch its logs.

Solution 3

Maybe beside of tracing logs is better idea to enter into container with:

docker exec -it CONTAINER_ID /bin/sh

and investigate your process from inside.

Comments

[p.magalhaes]

The container is not running. It already stopped so I can't connect to the container. I just want to get the messages that were printed in the console. I don't know if it is possible.

[p.magalhaes]

My container is already stopped. Using the cmd line doing, docker run -d image, it returns me the container id. Then i can make docker logs id. But running using the ECS, i cant get this log. I really cant get the container id.

[grayaii]

it doesn't matter if the container is stopped or running, "docker logs <container id>" will get you the output. in ECS you have to log in to each instance and do a "sudo docker ps -a" to find what you are looking for.