brauner / docker-melt Goto Github PK

docker-melt is a simple tool to merge all layers of a Docker image into a single layer. It tries to do as little as possible to achieve the result while preserving extended attributes, acl-permissions etc. (Given that your version of tar does indeed support the corresponding flags.). Whiteout files are deleted per default. That is a Dockerfile that contains the following instructions:

RUN truncate --size 200M /somefile
RUN unlink /somefile
RUN echo bla > /somefile

would normally cause an image to have an extra unnecessary 200MB. docker-melt will remove the 200MB file /somefile while preserving the /somefile in the last instruction. This will lead to a smaller final image.

Usage is pretty simple:

docker-melt -i input.tar -o output.tar [-t tmpdir]

Note that in order to preserve all permissions etc. docker-melt should be run as root. The resulting image can then be imported via:

cat output.tar | docker import - newimage