wanting to add a line of code in text editor

Modifying Default Settings

The first set of basic critical changes requires you to modify three insecure default system settings:

    * Reconfiguring shared memory
      Load your favorite text editor, open the file "/etc/fstab" and add the following line of code:

      tmpfs /dev/shm tmpfs defaults,ro 0 0
    * Disabling SSH root login
      Load your favorite text editor, open the file "/etc/ssh/sshd_config" and add change the following line of code:

      PermitRootLogin yes

      to

      PermitRootLogin no
    * Limiting access to the "su" program
      Open the terminal by clicking "Applications" selecting "Accessories" and choosing "Terminal." From there enter the commands:

      sudo chown root:admin /bin/su sudo
      chmod 04750 /bin/su