1# install
 2apt install openssh-server
 3
 4# config
 5cp /etc/ssh/sshd_config /etc/ssh/sshd_config-bak
 6echo "PermitRootLogin yes" > /etc/ssh/sshd_config
 7
 8# start
 9sudo service ssh start
10# OR
11# sudo /etc/init.d/ssh start
12# OR for systemd based Ubuntu Linux 16.04 LTS or above server:
13# sudo systemctl start ssh