Enable or disable service on OS start

$ systemctl disable httpd
rm '/etc/systemd/system/multi-user.target.wants/httpd.service'

$ systemctl status httpd
httpd.service - The Apache HTTP Server
   Loaded: loaded (/usr/lib/systemd/system/httpd.service; **disabled**)

$ systemctl enable httpd
ln -s '/usr/lib/systemd/system/httpd.service' '/etc/systemd/system/multi-user.target.wants/httpd.service'

$ systemctl status httpd
httpd.service - The Apache HTTP Server
   Loaded: loaded (/usr/lib/systemd/system/httpd.service; **enabled**)