go-docker-melt is a simple tool to merge layers of Docker images. It takes a tar file produced by docker save as input and produces a tar file that can be imported with docker load.

When the input tar file to go-docker-melt only contains a single Docker image go-docker-melt will melt all layers into a single layer. If the input tar file contains multiple Docker images go-docker-melt will minimize the number of layers. It will melt sequences of shared layers between images and sequences of unique layers but will not melt unique layers into shared layers.

Note that go-docker-melt is only intended to work with images relying on the manifest.json file. As does the Docker daemon in newer versions, go-docker-melt ignores per layer configuration files.

Usage is pretty simple:

go-docker-melt -i input.tar -o output.tar -t tmpdir

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

docker load -i output.tar