As of CrashPlan 4.3+ there are additional steps necessary to alter the local CrashPlan UI to connect to a headless service. All of the steps are nicely laid out on the following website.
http://chrisnelson.ca/2015/07/02/fixing-crashplan-4-3-0-on-synology/
And the following is the official CrashPlan page for configuring headless services.
https://support.code42.com/CrashPlan/4/Configuring/Using_CrashPlan_On_A_Headless_Computer
The following is the Linux command for looking up the GUID of the remote service on my Synology NAS.
cat /var/lib/crashplan/.ui_info ; echo
