Docker containers in Oh-My-Vagrant


The Oh-My-Vagrant (omv) project is an easy way to bootstrap a development environment. It is particularly useful for spinning up an arbitrary number of virtual machines in Vagrant without writing ruby code. For multi-machine container development, omv can be used to help this happen more naturally.

Oh-My-Vagrant can be very useful as a docker application development environment. I’ve made a quick (<9min) screencast demoing this topic. Please have a look:

https://dl.fedoraproject.org/pub/alt/purpleidea/screencasts/oh-my-vagrant-docker-screencast.ogv

If you watched the screencast, you should have a good overview of what’s possible. Let’s discuss some of these features in more detail.

Pull an arbitrary list of docker images:

If you use an image that was baked with vagrant-builder, you can make sure that an arbitrary list of docker images will be pre-cached into the base image so that you don’t have to wait for the slow docker registry every time you boot up a development vm.

This is easily seen in the CentOS-7.1 image definition file seen here. Here’s an excerpt:

VERSION='centos-7.1'
POSTFIX='docker'
SIZE='40'
DOCKER='centos fedora'		# list of docker images to include

The GlusterFS community gracefully hosts a copy of this image here.

If you’d like to add images to a vm you can add a list of things to pull in the docker omv.yaml variable:

---
:domain: example.com
:network: 192.168.123.0/24
:image: centos-7.1-docker
:docker:
- ubuntu
- busybox
:count: 1
: vms: []

This key is also available in the vms array.

Automatic docker builds:

If you have a Dockerfile in a vagrant/docker/*/ folder, then it will get automatically added to the running vagrant vm, and built every time you run a vagrant up. If the machine is already running, and you’d like to rebuild it from your local working directory, you can run: vagrant rsync && vagrant provision.

Automatic docker environments:

Building and defining docker applications can be a tricky process, particularly because the techniques are still quite new to developers. With Oh-My-Vagrant, this process is simplified for container developers because you can build an enhanced omv.yaml file which defines your app for you:

---
:domain: example.com
:network: 192.168.123.0/24
:image: centos-7.0-docker
:extern:
- type: git
  system: docker
  repository: https://github.com/purpleidea/docker-simple1
  directory: simple-app1
:docker: []
:vms: []
:count: 3

By listing multiple git repos in your omv.yaml file, they will be automatically pulled down and built for you. An example of the above running would look similar to this:

$ time vup omv1
Cloning into 'simple-app1'...
remote: Counting objects: 6, done.
remote: Total 6 (delta 0), reused 0 (delta 0), pack-reused 6
Unpacking objects: 100% (6/6), done.
Checking connectivity... done.

Bringing machine 'omv1' up with 'libvirt' provider...
==> omv1: Creating image (snapshot of base box volume).
==> omv1: Creating domain with the following settings...
==> omv1:  -- Name:              omv_omv1
==> omv1:  -- Domain type:       kvm
==> omv1:  -- Cpus:              1
==> omv1:  -- Memory:            512M
==> omv1:  -- Base box:          centos-7.0-docker
==> omv1:  -- Storage pool:      default
==> omv1:  -- Image:             /var/lib/libvirt/images/omv_omv1.img
==> omv1:  -- Volume Cache:      default
==> omv1:  -- Kernel:            
==> omv1:  -- Initrd:            
==> omv1:  -- Graphics Type:     vnc
==> omv1:  -- Graphics Port:     5900
==> omv1:  -- Graphics IP:       127.0.0.1
==> omv1:  -- Graphics Password: Not defined
==> omv1:  -- Video Type:        cirrus
==> omv1:  -- Video VRAM:        9216
==> omv1:  -- Command line : 
==> omv1: Starting domain.
==> omv1: Waiting for domain to get an IP address...
==> omv1: Waiting for SSH to become available...
==> omv1: Starting domain.
==> omv1: Waiting for domain to get an IP address...
==> omv1: Waiting for SSH to become available...
==> omv1: Creating shared folders metadata...
==> omv1: Setting hostname...
==> omv1: Rsyncing folder: /home/james/code/oh-my-vagrant/vagrant/ => /vagrant
==> omv1: Configuring and enabling network interfaces...
==> omv1: Running provisioner: shell...
    omv1: Running: inline script
==> omv1: Running provisioner: docker...
    omv1: Configuring Docker to autostart containers...
==> omv1: Running provisioner: docker...
    omv1: Configuring Docker to autostart containers...
==> omv1: Building Docker images...
==> omv1: -- Path: /vagrant/docker/simple-app1
==> omv1: Sending build context to Docker daemon 54.27 kB
==> omv1: Sending build context to Docker daemon 
==> omv1: Step 0 : FROM fedora
==> omv1:  ---> 834629358fe2
==> omv1: Step 1 : MAINTAINER James Shubin <[email protected]>
==> omv1:  ---> Running in 2afded16eec7
==> omv1:  ---> a7baf4784f57
==> omv1: Removing intermediate container 2afded16eec7
==> omv1: Step 2 : RUN echo Hello and welcome to the Technical Blog of James > README
==> omv1:  ---> Running in 709b9dc66e9b
==> omv1:  ---> b955154474f4
==> omv1: Removing intermediate container 709b9dc66e9b
==> omv1: Step 3 : ENTRYPOINT python -m SimpleHTTPServer
==> omv1:  ---> Running in 76840da9e963
==> omv1:  ---> b333c179dd56
==> omv1: Removing intermediate container 76840da9e963
==> omv1: Step 4 : EXPOSE 8000
==> omv1:  ---> Running in ebf83f08328e
==> omv1:  ---> f13049706668
==> omv1: Removing intermediate container ebf83f08328e
==> omv1: Successfully built f13049706668

real	1m12.221s
user	0m5.923s
sys	0m0.932s

All that happened in about a minute!

Conclusion:

I hope these tools help, if you’re following my git commits, you’ll notice that there are some new features I haven’t blogged about yet. Kubernetes integration exists, so please have a look, and hopefully I’ll have some screencasts and blog posts about this shortly.

Happy hacking,

James


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