I’ve previously discussed using Chef as a great way to manage servers, the key part of the process being writing “cookbooks” to describe what software you want installed, how it should be configured, and what services should be running. But a question that I’ve been asked by a few people is how do I test my cookbooks as I are writing them?
Of course, a simple way to test them is run them on my laptop – which would be great, except that I would end up with all kinds of things installed that I don’t need, and there’s things that I don’t want to repeatedly uninstall just to check my cookbooks install it properly. The second approach is to keep run and re-run them on a server as I go along, but that involves uploading a half-written cookbook to my chef server, running chef-client on the server, seeing if it worked, rinsing and repeating. And I’d have to be brave or foolhardy to do this when the server is in production!
Step forward Vagrant. Vagrant bills itself as a way to:
“Create and configure lightweight, reproducible, and portable development environments.”
but ignore the slogan, that’s not what I use it for. Instead, I treat Vagrant as:
“A command-line interface to test chef cookbooks using virtual machines”
After a few weeks of using chef, I’d started testing cookbooks using VirtualBox to avoid trashing my laptop. But clicking around in the GUI, installing VMs by hand, and running Chef was getting a bit tedious, never mind soaking up disk-space with lots of virtual machine images that I was loathe to delete. With Vagrant, however, things become much more straightforward.
Vagrant creates virtual machines using a simple config file, and lets you specify a local path to your cookbooks, and which recipes you want to run. An example config file looks like:
Vagrant.configure("2") do |config|
config.vm.box = "precise64"
config.vm.provision :chef_solo do |chef|
chef.cookbooks_path = "/home/andy/src/toolkit-chef/cookbooks"
config.vm.network :forwarded_port, guest: 80, host: 11180
You then run `vagrant up` and it will create the virtual machine from the “precise64″ base box, set up networking, shared folders and any other customisations, and run your cookbooks. If, inevitably, your in-development cookbook has a mistake, you can fix it and run `vagrant provision` to re-run Chef. No need to upload cookbooks anywhere or copy them around, and it keeps your development safely separated from your production machines. Other useful commands are `vagrant ssh` to log into the virtual machine (if you need to poke around to figure out if the recipes are doing what you want), `vagrant halt` to shut down the VM when you’re done for the day, and finally `vagrant destroy` to remove the virtual machine entirely. I do this fairly regularly – I’ve got half a dozen Vagrant instances configured for different projects and so often need to free up the disk space – but given I keep the config files then recreating the virtual machine a few months later is no more complex than `vagrant up` and a few minutes wait.
Going back to the original purpose of Vagrant, it’s based around redistributing “boxes” i.e. virtual machines configured in a particular way. I’ve never needed to redistibute a box, but once or twice found myself needing a particular base box that’s not available on vagrantbox.es – for example, testing cookbooks on old versions of Ubuntu. Given my dislike of creating virtual machines manually, I found the Veewee project useful. It takes a config file and installs the OS for you (effectively pressing the keyboard on your behalf during the install) and creates a reusable Vagrant base box. The final piece of the jigsaw is then writing the Veewee config files – step forward Bento, which is a pre-written collection of them. Using all these, you can start with a standard Ubuntu .iso file, convert that into a base box with Veewee, and use that base box in as many Vagrant projects as you like.
Finally, I’ve also used Vagrant purely as a command line for VirtualBox – if I’m messing around with a weekend project and don’t want to mess up my laptop installing random depenedencies, I instead create a minimal Vagrantfile using vagrant init, vagrant up, vagrant ssh, and mess around in the virtual machine – it’s much quicker than installing a fresh VM by hand, and useful even if you aren’t using Chef.
Do you have your own way of testing Chef cookbooks? Or any other tricks or useful projects? If so, let me know!