If you, like I today, cannot perform a passwordless login via ssh to a remote Linux server after copying a public key to the server with
ssh-copy-id command, please check if the key is actually presents among other authorized keys on the server. I found that sometimes it is not.
$ cat .ssh/authorized_keys
The agent has no identities.
To fix the problem just add the
-i argument like below:
$ ssh-copy-id -i firstname.lastname@example.org