Created question in FIWARE Q/A platform on 30-11-2014 at 11:11
Please, ANSWER this question AT http://stackoverflow.com/questions/27212465/rex-and-identity-files

Question:
Rex and identity files

Description:
I'm trying to configure a fi-ware cloud instance using Rex. What these instances (and probably other OpenStack-based systems) prove is a "identity file", a single private key that you can use to connect to them. I have been using variations of this:

user "root";
private_key "/home/jmerelo/.ssh/jj-iv.pem";
public_key "/home/one/public/key.dsa";
key_auth;

group fiware => "130.206.x.y";

desc "Install git";
task "git", group => "fiware", sub {
install "git";
};

where the private key is the one provided by fi-ware, and the public key is, well, whatever I thought of, or nothing.
If no public key is provided, error is

[2014-11-30 11:45:45] WARN - Error running task/batch: No public_key file defined. at /home/jmerelo/perl5/perlbrew/perls/perl-5.20.0/lib/site_perl/5.20.0/Rex/Task.pm line 621.
at /home/jmerelo/perl5/perlbrew/perls/perl-5.20.0/lib/site_perl/5.20.0/Rex/TaskList/Base.pm line 273.

which is quite obviously true. But if I try other public keys, error is:

[2014-11-30 11:48:37] WARN - Error running task/batch: Wrong username/password or wrong key on 130.206.127.211. Or root is not permitted to login over SSH. at /home/jmerelo/perl5/perlbrew/perls/perl-5.20.0/lib/site_perl/5.20.0/Rex/TaskList/Base.pm line 273.

Using

ssh -i ~/.ssh/jj-iv.pem root@130.206.x.y

connects correctly to the instance. So maybe the question is "Can Rex use a single private key to connect to a host?"