Since my developing work is moved to Docker platform for Mac, it makes the machine setup quicker and easier.

Now they have stable version of Docker for Mac for use which is great However, the easiness comes with a price of file size inflation on the development machine.

On Mac, its not uncommon to find that we are running out of diskspace.

After Docker for Mac is in place for a couple of months, theres a surprise over the size of their qcow2 file: ls -l LibraryContainerscom.docker.dockerDatacom.docker.driver.amd64-linux.

I remember I have regularly remove unused images and containers.

In theory, Docker.qcow2 file keeps those layers and containers in use for Docker Engine.

But the fact is that Docker doesnt come with a cleanup mechanism for all these.

This is why we see a huge file sitting on the harddrive as time goes by.

You may try deleting Docker.qcow2 file but you are going to destroy everything youve built inside the containers.

After a restart of Docker engine, this file may still grow up to the previous size based on Dockers registry information for all those used or unused layers and containers.

Through using qemu utilities, we can shrink the size of.qcow2 file effectively.

The etc directory is also mapped so that it can read any exclude files that we have created.

Once we git clone the source of docker-gc, we can start modifying to our needs.

Heres the modified version of my Dockerfile FROM gliderlabsalpine:3.2.

Docker For Mac Qcow2