RSYNC over SSH stopped working

Hi,

 

I had an unexpected problem with my backups from Ubuntu to my ReadyNAS314 (firmware 6.9.3), which seemed to start since I upgraded Ubuntu from 17.10 to 18.04.

I use duplicity via rsync over ssh, and I was getting :

ssh: Could not resolve hostname nas314-xx-xx-xx: Name or service not known

I couldn't ssh into the NAS either, (as me) until I tried adding a .lan domain suffix in the script. So I modified the backup script, and then I got the errors:

Host key verification failed.
rsync: connection unexpectedly closed (0 bytes received so far) [Receiver]
rsync error: unexplained error (code 255) at io.c(235) [Receiver=3.1.2]

Looking on the SSH configuration on the NAS admin console for the backup user, I noticed the imported key for me had RSYNC Only unchecked, but for root on Ubuntu, it was checked.

So I tried unchecking the RSYNC Only checkbox for root on Ubuntu, and now the backup works again.

 

Does anyone have any ideas why this is. Apparently openssh on Ubuntu went from 7.2 to 7.6?

 

Many thanks.