Boot2Docker is a minimal (27MB) Linux image for running Docker. I started using it yesterday whilst investigating Docker on Mac OS X.

It’s designed to work with VirtualBox, and comes with a script to control the lifecycle of the Boot2Docker VM inside of VirtualBox. There’s no reason however why it shouldn’t be used with other types of virtualisation. As I have a Hyper-V server to hand I thought I’d give it a go on that.

Getting started

I downloaded the latest ISO (v0.54 at the time of writing). Created a new VM with 1GB RAM and a legacy network adaptor [1], and attached the boot2docker.iso file as a DVD drive. This booted up fine, and I could do Docker stuff.

Need persistence

There’s not much point to doing Docker stuff unless you can keep it around. So I needed a persistent disk.

I created a new dynamic VHD called b2d_base.vhd and attached it to the VM on the IDE controller. After starting up again I ran through the following commands:

sudo fdisk /dev/sda
n
e
<enter for default start>
<enter for deafult end>
n
l
<enter for default start>
<enter for deafult end>
w
sudo mkfs.ext4 -L boot2docker-data /dev/sda5

I then shut down the VM, removed b2d_base.vhd and created a new differencing VHD b2d1.vhd based on b2d_base.vhd and attached that to the IDE controller (so if I choose to make more VMs like this I don’t need to bother with the partitioning, formatting and labelling again).

Trying it out

I booted up again and ran:

docker run -d -p 1880:1880 cpswan/node-red-0.5.0t

Once that completed I could then browse to the NodeRed IDE on http://vm_ip:1880 :)

A quick look at my b2d1.vhd showed that it had grown to 914MB – so the persistence on a differencing disk was working.

Note

[1] First time around I used a regular network adaptor, but boot2docker doesn’t have the drivers for that. With a lot more effort I could probably build my own boot2docker with a customised kernel and the right module. For the time being I’ll live with slightly worse network performance.