Modifying an Existing Docker Image

2018-05-06

docker

To install a custom package or modify an existing docker image we need to

1 run a docker a container from the image we wish to modify
2 modify the docker container
3 commit the changes to the container as a docker image
4 test changes made to image

Running a docker container from an image

The command to do this is,

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docker run -it yhat/scienceops-python:0.0.2 /bin/bash
  • The -i tells docker to attach stdin to the container
  • The -t tells docker to give us a pseudo-terminal
  • /bin/bash will run a terminal process in your container

Modify the docker container

Once we are in our container we can install package(s), and set environment variables

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$ sudo apt-get install vim
$ export AWS_SECRET_KEY=mysecretkey123
$ export AWS_ACCESS_KEY=fooKey

When you are done modifying your container you must exit by running the exit command. Once we exit the container, we need to find the container ID by running

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docker ps -a

Commit the changes to the container as a new image

Copy the container ID for the container you just modified, and then run the docker commit command to commit changes to your container as an image.

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docker commit [options] [container ID] [repository:tag]

An example docker commit command is the following.

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docker commit e8f0671518a2 yhat/scienceops-python:0.0.2

Note here! You must commit the changes with the same tags as the scienceops image on your system. To see your new image run.

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docker images

Test changes made to image

To test your changes when adding an environment variable run the test command

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$ docker run -it yhat/scienceops-python:0.0.2 echo $AWS_SECRET_KEY