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  • Iteration #4: Docker 1.9 upgrade, Swarm, and Secret Data

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For step 5, storing sensitive information:


1 – Information about all the successive layers from a Docker image can be obtained using dfimage (3rd party tool) or by analyzing the images in Docker hub.

2 – In order to protect sensitive information we can use docker-compose:

[root@docker-web1 ~]# docker-compose -v

docker-compose version 1.5.2, build 7240ff3

3 – Docker-compose uses docker-compose.yml as its configuration file.

Information that can be added to docker-compose.yml is shown below:


Add environment variables. You can use either an array or a dictionary.

Environment variables with only a key are resolved to their values on the machine Compose is running on, which can be helpful for secret or host-specific values.


  RACK_ENV: development



Add environment variables from a file. Can be a single value or a list.

Environment variables specified in environment override these values.


  - .env

RACK_ENV: development

4 – Following the creation of docker-compose.yml, we run:

Docker-compose build

5 – We then run:

Docker-compose up


Potential Next Steps