sample cap deployment , deploy.rb

set :application, "My supper app"
set :repository,  "svn://yoursvnhost/svn/yourproject/"

set :scm, :subversion
# Or: `accurev`, `bzr`, `cvs`, `darcs`, `git`, `mercurial`, `perforce`, `subversion` or `none`

role :web, "http://mywebserver.com"                          # Your HTTP server, Apache/etc
role :app, "http://myappserver.com"                          # This may be the same as your `Web` server
role :db,  "http://mymaindbserver.com", :primary => true # This is where Rails migrations will run
role :db,  "http://myslaveserver.com"

set :deploy_to, '/www/your_deployment_path' # the deployment path in your server deployment 

#set :port, 609  # specify your ssh port , your may change the default port(22) due to security issue

set :user, "root" # which user would be used to run the deployment process 
set :scm_username, "xxxx" #your svn username
set :scm_password, "1111" #your svn password
set :use_sudo, false

# If you are using Passenger mod_rails uncomment this:
# if you're still using the script/reapear helper you will need
# these http://github.com/rails/irs_process_scripts

namespace :deploy do
  task :start do ; end
  task :stop do ; end
  task :restart, :roles => :app, :except => { :no_release => true } do
    run "#{try_sudo} touch #{File.join(current_path,'tmp','restart.txt')}"
    # restart your app server after the deployment process
  end
end

namespace :custom do
  
  desc "custom task need to run after deployment"
  task :my_task, :roles => [:web, :app] do
    run <<-CMD
       ln -nfs  #{shared_path}/config/database.yml #{current_path}/config/database.yml
    CMD

  end

end

after "custom:my_task"