capistrano-daemonize adds a daemonize method to Capistrano's DSL to generate tasks that control arbitrary processes as daemons. It makes use of Debian's /sbin/start-stop-daemon, which is available in every Debian-based Linux distribution like Ubuntu. OpenSuSE and Mandriva do have the binary in both the sysvinit and dpkg packages.

Sample usage in your deploy.rb:

require 'capistrano-daemonize'
daemonize '/usr/bin/env bundle exec rake qc:work', as: 'myworker', callbacks: true, role: :worker

This creates three tasks: myworker:start, myworker:stop and myworker:restart. The namspace is defined by the mandatory option :as.

If :callbacks is set, the tasks are automatically added to the respective deploy tasks. You could do that manually by adding:

after 'deploy:restart', 'myworker:restart'
after 'deploy:start', 'myworker:start'
after 'deploy:stop', 'myworker:stop'

You can use the :pidfile and :logfile options to defined the respective files, which default to "#{shared_path}/pids/myworker.pid" and "#{shared_path}/log/myworker.log".

:chdir may be used to set the working directory for the daemon and :user to switch to another user than logged in.

Other options, like :role in the example above, will be used when defining the tasks.