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Update on 20.11.2015 New experimental version is 1.10. The image can be found from here. Major experimental thing is the user namespaces.

Update on 27.8.2015 I ran the build for newest experimental and the image for boot2docker for experimental 1.9 can be found from here. I updated the examples to use 1.9. The post can be found from both URLs.

TL;DR

To use boot2docker.iso which includes the 1.10 experimental Docker (at the moment Docker version 1.10.0-dev, build 0cdc96c, experimental), create the machine with

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docker-machine create -d virtualbox --virtualbox-boot2docker-url=http://sirile.github.io/files/boot2docker-1.10.iso dev

I’ll explain the creation process of the image if you want to do it yourself.

General

As I was following an article about Docker experimental features I started to follow the instructions. Getting the Docker client 1.8 experimental installed on Mac was easy enough following the prerequisites chapter. Then I tried to connect to an existing local Docker Machine instance and ran into problems as it complained that the API versions on the client and server didn’t match. I tried upgrading the Docker Machine instance (boot2docker), but version 1.7 (and API version 1.19) was the newest it would do and Docker 1.8 client requires API version 1.20.

It took me quite a while to figure out that the example uses DigitalOcean and gives a parameter called --engine-install-url="https://experimental.docker.com" as a parameter. That script takes care of installing the experimental version on the server, but it can’t be used on boot2docker. Boot2docker uses a special flavor of Linux where most of it (like /usr/local/bin) is immutable after creation. So even if you manually ssh to the server and modify a file, after the next reboot the changes are gone.

Options

As a first option (after hacking the running boot2docker instance and figuring out that isn’t the way forward) I tried to use Docker Machine with the none driver. I created a host using Vagrant and installed the experimental Docker 1.8 there. Getting the server to play along nicely with Docker Machine was quite tedious as LTS based security is basically a requirement and configuring it was more work than I was willing to do.

The next option was to explore the boot2docker ISO creation and see if I could replace the docker-executable with the experimental version. Thanks to the smart boot2docker build mechanism this was really easy.

Extending the boot2docker image

As I only needed to replace the existing docker executable with a new version, the new Dockerfile is just

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FROM boot2docker/boot2docker
RUN curl -L https://experimental.docker.com/builds/Linux/x86_64/docker-latest > $ROOTFS/usr/local/bin/docker && chmod +x $ROOTFS/usr/local/bin/docker
RUN /make_iso.sh
CMD ["cat", "boot2docker.iso"]

It can also be cloned from GitHub.

After building it on a suitable Docker environment (2 GB memory seems to be required) with

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docker build -t my-boot2docker-img .

the new image can be exported with

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docker run --rm my-boot2docker-img > boot2docker-1.10.iso

The resulting file is the one hosted here.

Next steps

The same script can be used to update the boot2docker.iso to the latest experimental Docker executable release, it’s not tied to 1.10.