Boot2Docker is a lightweight Linux distribution made specifically to run Docker containers. It runs completely from RAM, is a ~45MB download and boots quickly.
What this means concretely is new Docker releases, kernel updates, etc, but concerted attempts to keep new features/functionality to an absolute minimum to ensure continued maintainability for the few folks who can't yet transition to the better-suited Docker for Windows / Docker for Mac products (Windows 7 users who can't Docker for Windows at all, Windows 10 Home users who thus can't Hyper-V, VirtualBox users who thus can't Hyper-V, etc etc).
See docker/machine#4537 for some useful discussion around Docker Machine also being in a similar state.
- Recent Linux Kernel, Docker pre-installed and ready-to-use
- VM guest additions (VirtualBox, Parallels, VMware, XenServer)
- Container persistence via disk automount on
- SSH keys persistence via disk automount
Note: Boot2Docker uses port 2376, the registered IANA Docker TLS port
Boot2Docker is designed and tuned for development. Using it for any kind of production workloads is highly discouraged.
How to use
Boot2Docker is used via Docker Machine
(installed as part of Docker Toolbox) which leverages VirtualBox's
initialise, start, stop and delete the VM right from the command line.
See Frequently asked questions for more details.
Boot script log
The bootup script output is logged to
/boot.log, so you can see (and
potentially debug) what happens. Note that this is not persistent between boots
because we're logging from before the persistence partition is mounted (and it
may not exist at all).
Docker daemon options
If you need to customize the options used to start the Docker daemon, you can
do so by adding entries to the
/var/lib/boot2docker/profile file on the
persistent partition inside the Boot2Docker virtual machine. Then restart the
The following example will enable core dumps inside containers, but you can specify any other options you may need.
docker-machine ssh default -t sudo vi /var/lib/boot2docker/profile # Add something like: # EXTRA_ARGS="--default-ulimit core=-1" docker-machine restart default
Installing secure Registry certificates
As discussed in the Docker Engine documentation
certificates should be placed at
hostname is your Registry server's hostname.
docker-machine scp certfile default:ca.crt docker-machine ssh default sudo mv ~/ca.crt /etc/docker/certs.d/hostname/ca.crt exit docker-machine restart
Alternatively the older Boot2Docker method can be used and you can add your
Registry server's public certificate (in
.crt format) into
/var/lib/boot2docker/certs/ directory, and Boot2Docker will automatically
load it from the persistence partition at boot.
You may need to add several certificates (as separate
.crt files) to this
directory, depending on the CA signing chain used for your certificate.
As of Docker version 1.3.1, if your registry doesn't support HTTPS, you must add it as an insecure registry.
$ docker-machine ssh default "echo $'EXTRA_ARGS=\"--insecure-registry <YOUR INSECURE HOST>\"' | sudo tee -a /var/lib/boot2docker/profile && sudo /etc/init.d/docker restart"
then you should be able to do a docker push/pull.
Running behind a VPN (Cisco AnyConnect, etc)
So sometimes if you are behind a VPN, you'll get an
i/o timeout error.
The current work around is to forward the port in the boot2docker-vm.
If you get an error like the following:
Sending build context to Docker daemon 2014/11/19 13:53:33 Post https://192.168.59.103:2376/v1.15/build?rm=1&t=your-tag: dial tcp 192.168.59.103:2376: i/o timeout
That means you have to forward port
2376, which can be done like so:
- Open VirtualBox
- Open Settings > Network for your 'default' VM
- Select the adapter that is 'Attached To': 'NAT' and click 'Port Forwarding'.
- Add a new rule:
- Protocol: TCP
- Host IP: 127.0.0.1
- Host Port: 5555
- Guest Port: 2376
SSH into VM
$ docker-machine ssh default
Docker Machine auto logs in using the generated SSH key, but if you want to SSH into the machine manually (or you're not using a Docker Machine managed VM), the credentials are:
user: docker pass: tcuser
Boot2docker uses Tiny Core Linux, which runs from RAM and so does not persist filesystem changes by default.
When you run
docker-machine, the tool auto-creates a disk that
will be automounted and used to persist your docker data in
/var/lib/boot2docker. This virtual disk will be removed when you run
docker-machine delete default. It will also persist the SSH keys of the machine.
Changes outside of these directories will be lost after powering down or
restarting the VM.
If you are not using the Docker Machine management tool, you can create an
formatted partition with the label
mkfs.ext4 -L boot2docker-data /dev/sdX5) to your VM or host, and Boot2Docker will automount
/mnt/sdX and then softlink