Install OpenSSH

Updated on: 5.Dec.2020

SSH allows the server administrator to dial-in to the server and managing the server. If you are using cloud server, SSH service should have already been installed.

To check the SSH status, run the following command,

   sudo systemctl status ssh 

To install SSH, run the following command,

  sudo apt install ssh

To dial in to the remote server,

• With Windows OS, install PuTTy - key in your server IP address and press Enter. Key in your Ubuntu login ID & password.
• With Mac OS, run Terminal and execute “ssh user@myhostname” - then, key in your password.

Reference:
The following URL (step 1 to 3) shows you how to restrict the user from using SFTP (SSH will be disabled). In this case, the user may run FileZilla and upload/download files using SFTP protocol.

http://www.howtoforge.com/restricting-users-to-sftp-plus-setting-up-chrooted-ssh-sftp-debian-squeeze

To configure the SFTP access (without SSH access):

             cd /etc/ssh
             sudo nano sshd_config

    * Replace the “Subsystem” with the following value:

              Subsystem internal-sftp

Then, add the following lines to the bottom of the file where “ftpuser” is the OS user ID and “/home/ftpuser” is the user directory. Repeat the whole section for every user

             Match User ftpuser
                   ChrootDirectory /home/ftpuser
                   AllowTCPForwarding no
                   X11Forwarding no
                   ForceCommand internal-sftp

Make sure that “/home/ftpuser” is own by “root”, update the access right and then create a “doc” directory which is own by ftpuser. Finally, restart the service.

            sudo chmod 700 /home/ftpuser
            sudo chown root:root /home/ftpuser
            sudo mkdir /home/ftpuser/doc
            sudo chown ftpuser:ftpuser /home/ftpuser/doc
            sudo service ssh restart

To restrict the user from access SFTP only (do this after you have added the user):

               sudo nano /etc/passwd

   Then, change the shell for the session:

                /bin/sh

   To

                /usr/lib/openssh/sftp-server 

 You may continue with this article: hardening SSH