$ ssh-keygen -t rsa -b 4096 -f ~/.ssh/vps-cloud.web-server.key -C 'My web-server key'
ssh-add -L
ssh-add -D
kill $SSH_AGENT_PID
trap 'kill $SSH_AGENT_PID' 0
$ sudo vim /etc/ssh/sshd_config
$ sudo vim +/PermitRootLogin /etc/ssh/sshd_config
# adduser vivek
ssh-keygen -p