Capistrano 3 has slightly changed its symlink implementation

Copy# <capistrano>/lib/capistrano/recipes/deploy.rb

_cset :shared_children,   %w(public/system log tmp/pids)
# ...
task :finalize_update, :except => { :no_release => true } do
  # ...
  shared_children.map do |d|
    run "ln -s #{shared_path}/#{d.split('/').last} #{latest_release}/#{d}" # <-- symlinks only the last segment here
  end
  # ...
end

Copy# <your project>/config/deploy.rb
set :linked_dirs, %w(log public/system)

# <capistrano>/lib/capistrano/tasks/deploy.rake
desc 'Symlink linked directories'
task :linked_dirs do
  # ...
  fetch(:linked_dirs).each do |dir|
    target = release_path.join(dir) # <-- symlinks the whole path
    source = shared_path.join(dir)
    # ...
    execute :ln, '-s', source, target
  end
end