How can I run a docker container and commit the changes once a script completes?

Question

I want to set up a cron job to run a set of commands inside a docker container and then commit the changes to the docker image. I\'m able to run the container as a daemon and ge

Answer 1

I didn't find any of these answers satisfying, as my goal was to 1) launch a container, 2) run a setup script, and 3) capture/store the state after setup, so I can instantly run various scripts against that state later. And all in a local, automated, continuous integration environment (e.g. scripted and non-interactive).

Here's what I came up with (and I run this in Travis-CI install section) for setting up my test environment:

#!/bin/bash

# Run a docker with the env boot script
docker run ubuntu:14.04 /path/to/env_setup_script.sh

# Get the container ID of the last run docker (above)
export CONTAINER_ID=`docker ps -lq`

# Commit the container state (returns an image_id with sha256: prefix cut off)
# and write the IMAGE_ID to disk at ~/.docker_image_id
(docker commit $CONTAINER_ID | cut -c8-) > ~/.docker_image_id

Note that my base image was ubuntu:14.04 but yours could be any image you want.

With that setup, now I can run any number of scripts (e.g. unit tests) against this snapshot (for Travis, these are in my script section). e.g.:

docker run `cat ~/.docker_image_id` /path/to/unit_test_1.sh
docker run `cat ~/.docker_image_id` /path/to/unit_test_2.sh