How To Use Capistrano to Automate Deployments: Getting Started

1. Ruby Programming Language
2. Capistrano Recipes
3. System/Server Administration
4. Application Deployment

1. Preparing The System
2. Installing Ruby
3. Installing Capistrano

1. Capistrano Basics
2. Initiating Capistrano Inside A Project
3. Creating Users For Deploying With Capistrano

Ruby is a general-purpose (i.e. not created to solve a specific problem), dynamic programming language that has gained a significant popularity with the release of Ruby-on-Rails web-application development framework.

The concise and ordered way one can use Ruby to write scripts (thanks to the way the language is designed) helped the language gain huge momentum. Coupled with the goals and mentality of RoR framework, and features it provided as an Object Oriented Programming (OOP) language (compared to competitors available at the time), Ruby became one of the most widely preferred languages in the last decade.

Capistrano, being a Ruby based tool, offers its users the possibility to take advantage of Ruby’s clean and clear syntax when compiling its recipes for deployments.

Recipes in Capistrano lingo translate to files which contain operative directions for deploying (or managing) applications and servers. These recipes can be modified to support a great variety of language specific deployments that are not Ruby (or Rails) related. You can think of them as a script which Capistrano uses to perform its actions.

If you are wondering in what situations Capistrano might come on in handy, below you can find a few examples.

System and server administration jobs (usually) include pretty much everything that relates to:

• Building a server

• Installing applications

• Maintenance of systems running these applications

• And monitoring

When you begin working with your very own VPS (which is a fully-fledged virtualised server with full control / access), things that appear as a mystery will quickly start to become familiar to you.

As your application starts to gain some popularity and things begin to grow, the need of managing multiple droplets and repeating everything over and over again ceases to become fun. When you deploy your applications and deal with their maintenance, it is only natural to expect that you will be running into some issues - especially overheads and time-wasters.

Capistrano can help them with most, if not all of them - beginning with application deployment.

Deploying an application (regardless of it being a web site, an API, or a server) usually means setting up a system from scratch (or from a snapshot taken in time), preparing it by updating everything, downloading dependencies, setting up the file structure and permissions followed by finally uploading your codebase - or downloading it using a source control manager (SCM) such as Git.

During the development process, chances are you will have commands that need to be routinely executed during each step (e.g. right before entering a deployment cycle).

Being able to script these tasks (both local and remote), in a logically organized and – most importantly – programmable manner proves to be invaluable shortly after you realise how much time is being wasted repeating the same steps constantly, rendering everything error-prone during the process.

In order to install Ruby (and Capistrano), we need to prepare our minimally shipped CentOS droplet, equipping it with development tools made for purposes of installing other applications and tools (e.g. a compiler to install Ruby from source).

Let’s begin with updating our system.

Run the following to update the default tools of you CentOS based droplet:

yum -y update

Install the bundle containing development tools by executing the following command:

yum groupinstall -y 'development tools'

We are going to be using Ruby Version Manager, RVM, to download and install “rubies” (a Ruby interpreter, as referred by the RVM).

Run the following two commands to install RVM and create a system environment for Ruby:

curl -L get.rvm.io | bash -s stable
source /etc/profile.d/rvm.sh

Finally, to finish getting Ruby on our system, let’s get RVM to download and install Ruby version 2.1.0:

rvm reload
rvm install 2.1.0

In order to verify that Ruby is indeed installed and set up, run the following:

ruby --version 
# ruby 2.1.0p0 (2013-12-25 revision 44422) [i686-linux]

Once we have our system ready, getting Capistrano’s latest version thanks to RubyGems is a breeze.

You can simply use the following to get Capistrano version 3:

gem install capistrano

If you would like to work with the absolutely latest version, you can link to the Github repository:

git clone https://github.com/capistrano/capistrano.git
cd capistrano
gem build *.gemspec
gem install *.gem

You can verify your Capistrano installation in a similar way to Ruby’s:

cap --version
# Capistrano Version: 3.1.0 (Rake Version: 10.1.0)

The key to get working with Capistrano is committing your project to an external Git repository where it can be downloaded during deployment.

You can choose any provider such as Github to do so.

Alternatively, you can see DigitalOcean’s community articles on Git by visiting here to learn about hosting a private Git repository on a VPS or to learn about how to work with Git.

Note: As recommended by Capistrano, you should not contain any sensitive information (e.g. secure credentials for database connections) inside your repository.

Initiating Capistrano version 3 slightly differs from version 2 and consists of the following command:

# Usage:
# Enter the project directory: cd [project-name]
# Initiate Capistrano:         cap install
cd  myapp
cap install

When using Capistrano for deployment, the good way of executing the recipes is by using a user other than default root. To begin with, we will create a deployers group, and give them the permission to proceed.

To add a new group to your droplet, run the following:

groupadd deployers

Now we can continue with adding users to our deployers group with privileged access.

Let’s add deployer as a deployer:

# Usage: sudo usermod -a -G deployers [name]
sudo usermod -a -G deployers deployer

Finally, to give the deployers group the permissions, run the following and edit the /etc/sudoers file:

nano /etc/sudoers

Add the following line to after the groups:

..
## Allows people in group wheel to run all commands
%deployers      ALL=(ALL) ALL

..

Note: To learn more about SSH and sudo, check out DigitalOcean community articles on Linux Basics.

And that’s it! We are now ready to use Capistrano for deployments. Move on with our next Capistrano articles to see how to use this tool in various deployment scenarios.

<div class=“author”>Submitted by: <a href=“https://twitter.com/ostezer”>O.S. Tezer</a></div>