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-ge         


        

Answer 1

Each RUN instruction creates a new container and you can inspect what a container changed by using docker diff .

So after building your dockerfile, run docker ps -a to get a list of the containers the buildfile created. It should look something like:

CONTAINER ID  IMAGE        COMMAND               CREATED        STATUS ...
53d7dadafee7  f71e394eb0fc /bin/sh -c apt-get i  7 minutes ago  Exit 0 ...
...

Now you can do do docker diff 53d7dadafee7 to see what was changed.