Acho que eu entendo isso. verificando os logs de ssh para o script automatizado revelado
Feb 22 23:46:02 PiScanner scan.sh: debug1: Connecting to 192.168.1.20 [192.168.1.20] port 22.#015
Feb 22 23:46:02 PiScanner scan.sh: debug1: Connection established.#015
Feb 22 23:46:02 PiScanner scan.sh: debug1: permanently_set_uid: 0/0#015
Feb 22 23:46:02 PiScanner scan.sh: debug1: identity file /root/.ssh/id_rsa type 1#015
Feb 22 23:46:02 PiScanner scan.sh: debug1: Checking blacklist file /usr/share/ssh/blacklist.RSA-2048#015
Feb 22 23:46:02 PiScanner scan.sh: debug1: Checking blacklist file /etc/ssh/blacklist.RSA-2048#015
Feb 22 23:46:02 PiScanner scan.sh: debug1: **identity file /root/.ssh/id_rsa-cert type -1#015**
Feb 22 23:46:02 PiScanner scan.sh: debug1: identity file /root/.ssh/id_dsa type -1#015
Feb 22 23:46:02 PiScanner scan.sh: debug1: identity file /root/.ssh/id_dsa-cert type -1#015
Feb 22 23:46:02 PiScanner scan.sh: debug1: identity file /root/.ssh/id_ecdsa type -1#015
Feb 22 23:46:02 PiScanner scan.sh: debug1: identity file /root/.ssh/id_ecdsa-cert type -1#015
Feb 22 23:46:02 PiScanner scan.sh: debug1: Remote protocol version 2.0, remote software version OpenSSH_6.6.1p1 Ubuntu-2ubuntu2#015
Feb 22 23:46:02 PiScanner scan.sh: debug1: match: OpenSSH_6.6.1p1 Ubuntu-2ubuntu2 pat OpenSSH*#015
O log do usuário que eu gerou as chaves tinha
debug1: Checking blacklist file /usr/share/ssh/blacklist.RSA-2048
debug1: Checking blacklist file /etc/ssh/blacklist.RSA-2048
debug1: identity file /home/pi/.ssh/id_rsa-cert type -1
debug1: identity file /home/pi/.ssh/id_dsa type -1
debug1: identity file /home/pi/.ssh/id_dsa-cert type -1
debug1: identity file /home/pi/.ssh/id_ecdsa type -1
debug1: identity file /home/pi/.ssh/id_ecdsa-cert type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.6.1p1 Ubuntu-2ubuntu2
Eu tinha copiado as chaves geradas pelo usuário raiz. diretório ~ / .ssh depois de um sudo -i
PermitRootLogin yes no arquivo ssh_config não funcionou comigo e gerou outros erros.