dockerize application running on rhel6

Question

I have been asked to containerize a COTS product. I found that there's no deployment/configuration steps/procedures for this app. This uses rhel6 and previous application team originally copied the app into EBS volume when they first moved to AWS from on premise. After that, they keep taking snapshot of this volume and attach to a new instance whenever there's a new ami available w/ security patches.

So, essentially I don't know how to create a Dockerfile for this since I have only running app, but no one knows how it was created.

Any thoughts on how to Dockerize this application?

Answer 1

I suggest using a centos:6 base image, and copying the entire EBS volume as an image layer.

Answer 2

The only way I can think of to do this is to copy the contents of the installed application as a tar file, and then build a Dockerfile around that.

FROM centos:6
ADD opt-application.tar.gz /opt
CMD ["/opt/application/bin/start.sh"]

It's worth checking if the application is really compatible with the Docker model. If there are tight dependencies with the rest of the RHEL ecosystem, the "start the application" wants to start multiple daemons, and there's an assumption that things like cron are running, your existing AMI setup might be better.