my properties file is ...
As you can see the above message, whirr is trying to startup a host whose ip address is '10.245.106.99'. But, whirr hangs and doesn't startup the hadoop service. So, I tried to login to the host '10.245.106.99' via ssh.
I expected that whirr hangs when the file '$HOME/.ssh/known_hosts' includes the obsolete entry. Although such case may occur rarely, someone who employs many instances in EC2 would meet such case. whirr needs to prevent hanging caused by obsolete identifiers of ssh.