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 get the container ID using this command:

CONTAINER_ID=$(sudo docker run -d my-image /bin/sh -c "sleep 10")

but I'm having trouble with the second part--committing the changes to the image once the sleep 10 command completes. Is there a way for me to tell when the docker container is about to be killed and run another command before it is?

EDIT: As an alternative, is there a way to trigger ctrl-p-q via a shell script in the container to leave the container running but return to the host?

Answer 1

There are following ways to persist container data:

1. Docker volumes

2. Docker commit

   a) create container from ubuntu image and run a bash terminal.

      $ docker run -i -t ubuntu:14.04 /bin/bash
   

   b) Inside the terminal install curl

      # apt-get update
      # apt-get install curl
   

   c) Exit the container terminal

      # exit
   

   d) Take a note of your container id by executing following command :

      $ docker ps -a
   

   e) save container as new image

      $ docker commit <container_id> new_image_name:tag_name(optional)
   

   f) verify that you can see your new image with curl installed.

      $ docker images           
   
      $ docker run -it new_image_name:tag_name bash
         # which curl
           /usr/bin/curl
   

Answer 2

Run it in the foreground, not as daemon. When it ends the script that launched it takes control and commits/push it

Answer 3

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

Answer 4

Try this if you want an auto commit for all which are running. Put this in a cron or something, if this helps

#!/bin/bash
for i in `docker ps|tail -n +2|awk '{print $1}'`; do docker commit -m "commit new change" $i; done