apt-get install mod_ssl ERROR

[zustudios]

I tried to do the tutorial but it said: http://docs.sentora.org/?node=103
root@panel:~#  service apache2 stop
* Stopping web server apache2                                                   *
root@panel:~# ./letsencrypt-auto certonly --standalone -d example.com -d www.example.com
-bash: ./letsencrypt-auto: No such file or directory
root@panel:~# -bash: ./letsencrypt-auto: No such file or directory
-bash:: command not found
root@panel:~# service apache2 start
* Starting web server apache2                                                   *
root@panel:~# apt-get install mod_ssl -y
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package mod_ssl
root@panel:~# E: Unable to locate package mod_ssl
E:: command not found
root@panel:~#