docker: how to show the diffs between 2 images

Question

I have a Dockerfile with a sequence of RUN instructions that execute "apt-get install"s; for example, a couple of lines:

RUN apt-get install -y tree RUN apt-get install -y git 

After having executed "docker build", if I then execute "docker images -a", I see the listing of all the base-child-child-.... images that were created during the build.

I'd like to see a list of all of the packages that were installed when the "apt-get install -y git" line was executed (including the dependent packages that may have also been installed, besides the git packages).

Note: I believe that the "docker diff" command shows the diffs between a container and the image from which it was started. Instead I'd like the diffs between 2 images (of the same lineage): the "tree" and "git" image IDs. Is this possible?

Thanks.

Answer 1

Have a look at :

https://github.com/GoogleCloudPlatform/container-diff

This tool can diff local or remote docker images and can do so without requiring docker to be installed. It has file as well as package level "differs" (for example: apt, npm, and pip) so that you can more easily see the differences in packages that have changed between two docker images.

Disclaimer: I am a contributor to this project

Answer 2

This one worked for me:

docker run -it e5cba87ecd29 bash -c 'find /path/to/files -type f | sort  | xargs -I{} sha512sum {}' > /tmp/dockerfiles.e5cba87ecd29.txt docker run -it b1d19fe1a941 bash -c 'find /path/to/files -type f | sort  | xargs -I{} sha512sum {}' > /tmp/dockerfiles.b1d19fe1a941.txt meld /tmp/dockerfiles* 

Where e5cba87ecd29 and b1d19fe1a941 are images I am interested in and /path/to/files is a directory which could be "/". It lists all files, sorts it and add hash to it just in case. And meld highlights all the differences.