1. install openssh server on the target machine:
    sudo apt-get install openssh-server
  2. check the server is running & firewall status:
    sudo service ssh start
    sudo ufw status
  3. find the ip address of the desktop:
    ip addr | grep inet
  4. ssh: (example)
    ssh -v ypgu@


ref: http://askubuntu.com/questions/413650/how-to-connect-to-another-computer-through-the-internet-using-ssh


1. ufw not active?

sudo ufw enable

2. port problem:

sudo ufw allow 22