Net::SSH::AuthenticationFailed: deployer

If you are getting an inexplicable error along the lines of

 connection failed for: xxx.xxx.xxx.xxx (Net::SSH::AuthenticationFailed: deployer)

despite checking all the usuals (key files, usernames, etc) it could be the Net:SSH implementation.

Try:

gem uninstall net-ssh
gem install net-ssh -v 2.0.24

add the following line to your deploy.rb file:

#require 'logger'
#ssh_options[:verbose] = Logger::DEBUG
ssh_options[:auth_methods] = %{publickey}    # it *should* check this anyway but seems not to

The Logger stuff could be used to help get some more info.