Ubuntu docker running docker

Question

I have the following docker-compose file:

version: '2'
services:
  ubuntu:
    image: 'ubuntu:16.04'
    ports:
      - '22:22'

When start this, the container seems to crash, the following are the logs that I see:

Attaching to playground_ubuntu_1
ubuntu_1  | Error grabbing logs: EOF

playground_ubuntu_1 exited with code 0

My host OS is Ubuntu 16.04 with Docker version 17.12.0-ce, build c97c6d6.

All of my other containers seem to start normally, but this one just flat out fails on boot.

Answer 1

This is normal. When you start a container it will run as long as the main process started inside the container is still running.

This process is specified using the CMD command inside a Dockerfile. The ubuntu image does not have a CMD as it is intended to be used as a building block for other docker images. Thus when you run this image without specifying a command, it exits successful as can be seen from the 0 exit code.

If you want this image to stay alive just for testing, you can specify a command that will keep it living.

version: '2'
services:
  ubuntu:
    image: 'ubuntu:16.04'
    ports:
      - '22:22'
    command: "tail -f /dev/null"

Answer 2

Exit status in log playground_ubuntu_1 exited with code 0 shows that its expected. In order to make a container up & running for long, you need to give/define a foreground process for your container. I have momentarily edited your compose file -

version: '2'
services:
  ubuntu:
    image: 'ubuntu:16.04'
    ports:
      - '22:22'
    command: "tail -f /dev/null"

Now you run it -

$ docker-compose up -d && docker ps

Your container is up & running now.