After creating a key with no password, I can login with SSH to my remote host:
$ ssh email@example.com Welcome to Ubuntu 14.04.1...
However when I try to use SSH to rsync to the same remote host:
$ sudo rsync -avczr -e ssh /home firstname.lastname@example.org:/destination
it asks for my root password on machine.local.
Why does SSH want to login with password for rsync, but with key if I connect directly? How do I make the rsync connection work with key?
One thing I noticed, which may be related, is that the first "authenticity of host can't be established" message I received mentioned the ECDSA key fingerprint, while the key I use for connecting directly are RSA.