You need to add public key (most likely .ssh/id_rsa.pub) to authorized keys in Karaf. You can edit ${OPENHAB_HOME}/userdata/etc/keys.properties. This is flat property file where key is username and value is public key used for authentication. Public key must be without perfix (ssh-rsa) and comment at the end, just one long string. After comma you need to assign group, so whole line looks like this openhab=sshkey,_g_:admingroup.
