Esse erro significa que a chave do host remoto foi alterada ou você está usando StrictHostKeyChecking :
StrictHostKeyChecking If this flag is set to “yes”, ssh(1) will never automatically add host keys to the ~/.ssh/known_hosts file, and refuses to connect to hosts whose host key has changed. This provides maximum protection against trojan horse attacks, though it can be annoying when the /etc/ssh /ssh_known_hosts file is poorly maintained or when connections to new hosts are frequently made. This option forces the user to manually add all new hosts. If this flag is set to “no”, ssh will automatically add new host keys to the user known hosts files. If this flag is set to “ask”, new host keys will be added to the user known host files only after the user has confirmed that is what they really want to do, and ssh will refuse to connect to hosts whose host key has changed. The host keys of known hosts will be verified automatically in all cases. The argument must be “yes”, “no”, or “ask”. The default is “ask”.
Purgue-o usando:
$ ssh-keygen -R $remoteserver
e tente novamente. Desta vez, você deve ser solicitado a confirmar a identidade do servidor remoto por meio de sua impressão digital de chave.
Para transferir diretórios inteiros, o -r é usado:
-r Recursively copy entire directories. Note that scp follows symbolic links encountered in the tree traversal.
Tudo isso está documentado no scp(1) , ssh-keygen(1) e ssh_config(5) manpages.