dotcloud/docker — pull request #5578 by msulima (2014-05-03 10:23:32+00:00)
Title: hello_world.md - $container_id variable case sensitivity

If you run the tutorial step-by-step, following error occurs:

```
$ sudo docker logs $container_id
Usage: docker logs CONTAINER
Fetch the logs of a container
-f, --follow=false: Follow log output
```

This is obviously because bash variables are case-sensitive, so it mustn't be `CONTAINER_ID` above.