I am using Linux Mint 18, the same distribution I have been using most of the semester for school. I was tasked with making certain adjustments to the sshd_config file, including chaning the listening port to 444, only allowing protocol 2, only allowing myself to login and not the other user named "otheraccount", not allowing root login, disabling the login of accounts with empty passwords, and creating a welcome banner. After using sudo and saving the sshd_config file, I go ahead and try to restart ssh using the sudo /etc/init.d/ssh restart but I get an error.
The error reads "Restarting ssh (via systemctl): ssh.serviceJob for ssh.service failed because the control process exited with error code. See "systemctl status ssh.service" and "journalctl -xe" for details. Underneath this message it reads "failed!" in red lettering.