(This bypasses the impossibility of sharing folders from an external drive and completely non-standard way to use /etc/fstab in the NAS Synology)
This tip is not officially supported and if you follow it, you do so at your own risk and responsibility.
Need activated access via ssh as user with administrative privileges (eg root).
1. Using the admin web interface to create a share name that we want to share
2. We test mounting up content:
mount --bind /directory-on-external_disk /volume1/Sharing-name
3. In /usr/local/etc/rc.d or /usr/syno/etc/rc.d insert file S99MountiExternSharing.sh
4. Set the file rights to run
#! / bin / sh
# Connecting external drive to a shared resource
# 1 Create a directory /volume1/Sharing-name
# 2 In this file add the line:
# Mount --bind /directory-on-external_disk /volume1/Sharing-name
mount --bind /volumeUSB2/usbshare/Backups /volume1/Backups