This is a long-form response to this question, and describes how to get the nova-docker driver up running with devstack under Ubuntu 14.04 (Trusty). I wrote a similar post for Fedora 21, although that one was using the RDO Juno packages, while this one is using devstack and the upstream sources.

Getting started⌗

We’ll be using the Ubuntu 14.04 cloud image (because my test environment runs on OpenStack).

First, let’s install a few prerequisites:

$ sudo apt-get update
$ sudo apt-get -y install git git-review python-pip python-dev

And generally make sure things are up-to-date:

$ sudo apt-get -y upgrade

Installing Docker⌗

We need to install Docker if we’re going to use nova-docker.

Ubuntu 14.04 includes a fairly dated version of Docker, so I followed the instructions on the Docker website for installing the current version of Docker on Ubuntu; this ultimately got me:

$ sudo apt-get -y install lxc-docker
$ sudo docker version
Client version: 1.5.0
Client API version: 1.17
Go version (client): go1.4.1
Git commit (client): a8a31ef
OS/Arch (client): linux/amd64
Server version: 1.5.0
Server API version: 1.17
Go version (server): go1.4.1
Git commit (server): a8a31ef

Docker by default creates its socket (/var/run/docker.socket) with root:root ownership. We’re going to be running devstack as the ubuntu user, so let’s change that by editing /etc/default/docker and setting:

DOCKER_OPTS='-G ubuntu'

And restart docker:

$ sudo restart docker

And verify that we can access Docker as the ubuntu user:

$ docker version
Client version: 1.5.0
Client API version: 1.17
[...]

Installing nova-docker⌗

As the ubuntu user, let’s get the nova-docker source code:

$ git clone http://github.com/stackforge/nova-docker.git
$ cd nova-docker

As of this writing (HEAD is “984900a Give some time for docker.stop to work”), you need to apply a patch to nova-docker to get it to work with the current Nova master branch:

$ git fetch https://review.openstack.org/stackforge/nova-docker \
  refs/changes/50/154750/3 \
  && git checkout FETCH_HEAD

Once that change has merged (update, 2015-02-12: the patch has merged), this step should no longer be necessary. With the patch we applied, we can install the nova-docker driver:

$ sudo pip install .

Configuring devstack⌗

Now we’re ready to get devstack up and running. Start by cloning the repository:

$ git clone https://git.openstack.org/openstack-dev/devstack
$ cd devstack

Then create a local.conf file with the following content:

[[local|localrc]]
ADMIN_PASSWORD=secret
DATABASE_PASSWORD=$ADMIN_PASSWORD
RABBIT_PASSWORD=$ADMIN_PASSWORD
SERVICE_PASSWORD=$ADMIN_PASSWORD
SERVICE_TOKEN=super-secret-admin-token
VIRT_DRIVER=novadocker.virt.docker.DockerDriver

DEST=$HOME/stack
SERVICE_DIR=$DEST/status
DATA_DIR=$DEST/data
LOGFILE=$DEST/logs/stack.sh.log
LOGDIR=$DEST/logs

# The default fixed range (10.0.0.0/24) conflicted with an address
# range I was using locally.
FIXED_RANGE=10.254.1.0/24
NETWORK_GATEWAY=10.254.1.1

# This enables Neutron, because that's how I roll.
disable_service n-net
enable_service q-svc
enable_service q-agt
enable_service q-dhcp
enable_service q-l3
enable_service q-meta

# I am disabling horizon (because I rarely use the web ui)
# and tempest in order to make the installer complete a 
# little faster.
disable_service horizon
disable_service tempest

# Introduce glance to docker images
[[post-config|$GLANCE_API_CONF]]
[DEFAULT]
container_formats=ami,ari,aki,bare,ovf,ova,docker

# Configure nova to use the nova-docker driver
[[post-config|$NOVA_CONF]]
[DEFAULT]
compute_driver=novadocker.virt.docker.DockerDriver

This will result in things getting installed in subdirectories of $HOME/stack. We enable Neutron and leave pretty much everything else set to default values.

Start the installation⌗

So, now we’re all ready to roll!

$ ./stack.sh
[Call Trace]
./stack.sh:151:source
/home/ubuntu/devstack/stackrc:665:die
[ERROR] /home/ubuntu/devstack/stackrc:665 Could not determine host ip address. See local.conf for suggestions on setting HOST_IP.
/home/ubuntu/devstack/functions-common: line 322: /home/ubuntu/stack/logs/error.log: No such file or directory

…or not. This error happens if devstack is unable to turn your hostname into an IP address. We can set HOST_IP in our environment:

$ HOST_IP=10.0.0.232 ./stack.sh

And then go grab a cup of coffee or something.

Install nova-docker rootwrap filters⌗

Once stack.sh is finished running, we need to install a rootwrap configuration file for nova-docker:

$ sudo cp nova-docker/etc/nova/rootwrap.d/docker.filters \
  /etc/nova/rootwrap.d/

Starting a Docker container⌗

Now that our environment is up and running, we should be able to start a container. We’ll start by grabbing some admin credentials for our OpenStack environment:

$ . openrc admin

Next, we need an appropriate image; my larsks/thttpd image is small (so it’s quick to download) and does not require any interactive terminal (so it’s appropriate for nova-docker), so let’s start with that:

$ docker pull larsks/thttpd
$ docker save larsks/thttpd |
  glance image-create --name larsks/thttpd \
    --is-public true --container-format docker \
    --disk-format raw

And now we’ll boot it up. I like to do this as a non-admin user:

$ . openrc demo
$ nova boot --image larsks/thttpd --flavor m1.small test0

After a bit, we should see:

$ nova list
+----...+-------+--------+...+-------------+--------------------+
| ID ...| Name  | Status |...| Power State | Networks           |
+----...+-------+--------+...+-------------+--------------------+
| 0c3...| test0 | ACTIVE |...| Running     | private=10.254.1.4 |
+----...+-------+--------+...+-------------+--------------------+

Let’s create a floating ip address:

$ nova floating-ip-create
+------------+-----------+----------+--------+
| Ip         | Server Id | Fixed Ip | Pool   |
+------------+-----------+----------+--------+
| 172.24.4.3 | -         | -        | public |
+------------+-----------+----------+--------+

And assign it to our container:

$ nova floating-ip-associate test0 172.24.4.3

And now access our service:

$ curl http://172.24.4.3
<!DOCTYPE html>
<html>
        <head>            
                <title>Your web server is working</title>
[...]