Capistrano

Capistrano is a utility and framework for executing commands in parallel on multiple remote machines, via SSH. It uses a simple DSL (borrowed in part from Rake, rake.rubyforge.org/) that allows you to define tasks, which may be applied to machines in certain roles. It also supports tunneling connections via some gateway machine to allow operations to be performed behind VPN’s and firewalls.

Capistrano was originally designed to simplify and automate deployment of web applications to distributed environments, and originally came bundled with a set of tasks designed for deploying Rails applications. The deployment tasks are now (as of Capistrano 2.0) opt-in and require clients to explicitly put “load ‘deploy’” in their recipes.

Dependencies

• Net::SSH v2 (net-ssh.rubyforge.org)

• Net::SFTP v2 (net-ssh.rubyforge.org)

• Net::SCP v1 (net-ssh.rubyforge.org)

• Net::SSH::Gateway v1 (net-ssh.rubyforge.org)

• HighLine (highline.rubyforge.org)

If you want to run the tests, you’ll also need to have the following dependencies installed:

• Mocha (mocha.rubyforge.org)

Assumptions

Capistrano is “opinionated software”, which means it has very firm ideas about how things ought to be done, and tries to force those ideas on you. Some of the assumptions behind these opinions are:

• You are using SSH to access the remote servers.

• You either have the same password to all target machines, or you have public keys in place to allow passwordless access to them.

Do not expect these assumptions to change.

Usage

In general, you’ll use Capistrano as follows:

• Create a recipe file (“capfile” or “Capfile”).

• Use the cap script to execute your recipe.

Use the cap script as follows:

cap sometask

By default, the script will look for a file called one of capfile or Capfile. The someaction text indicates which task to execute. You can do “cap -h” to see all the available options and “cap -T” to see all the available tasks.