Update: Using the following settings on the Synology DSM does allow me to rsync from the My Cloud (first gen single bay) to a Synlology NAS.
Access the Synology DSM (I’m running DSM 6.2.3-25426 Update 2) and navigate to Control Panel > File Services > rsync. Select Enable rsync service.
I went an extra step and made sure to use a Synology user (name) who has administrator group privileges and who has read/write access to the Share on the Synology that I copy/rsync the files to. This may or may not be needed.
Next, accessed the My Cloud using Putty from a Windows PC and issued the following Linux terminal command. Note: one will have to adjust the command to suit their use. This includes My Cloud location the files are to be copied from, the IP address of the Synology NAS, the Synology user, and the destination on the Synology NAS. My example:
rsync -avz /DataVolume/shares/Public/Shared\ Pictures/ john@192.168.1.100:/volume1/Pictures/
Generally the very first connection one makes from the My Cloud to the Synology NAS they may be asked to accept the SSH/Certificate from the Synology NAS. If this is the case, type in: yes. Subsequent connections one typically isn’t asked to accept the certificate as it is already stored by the My Cloud.
When the rsync connection is made one typically will have to manually enter the Synology user’s password. There are probably ways to automate this process but for my use I just manually typed in the password. Note: I also got a warning error from the Synology NAS: Could not chdir to home directory /var/services/homes/john: No such file or directory. The rsync program ignores this message, and proceeds to rsync the files/directories.
I found the following Synology document that helped figure out the quick and dirty process to rsync from a first gen single bay My Cloud to a Synology NAS.
How to back up Linux computer to Synology NAS
