After successfull passwordless ssh login, unable to do rsync

[Boniforti Flavio]

Hello Hendrik and thanks for your reply.

> "rsync rsync://host" is different from "rsync -e ssh path host:/path"
> 
> using ssh, you want the 2nd form

I have to say that on a similar setup, I'm succeeding with the command I
told you before.

I think I have to go a bit deeper in details: I'm using BackupPC and
this piece of software connects remotely to Synology NAS with ssh and
rsync.
It works as follows:
1) SSH tunnel gets opened by:

/var/lib/backuppc/tunnel.sh -fC root at synology.remote -L
8881:127.0.0.1:873 sleep 60

where tunnes.sh contains:

ssh $@ 1>/dev/null 2>/dev/null && echo "SSH started successfully."

2) rsync starts to transfer files within the SSH tunnel.

Where may I need to look for configuration or permission errors?
The differences between the two Synology NAS, besides the hardware ones,
are their firmware versions. Still, the rsync is the same version:
"3.0.4 protocol version 30".

Any other thing?

Kind regards,
Flavio Boniforti

PIRAMIDE INFORMATICA SAGL
Via Ballerini 21
6600 Locarno
Switzerland
Phone: +41 91 751 68 81
Fax: +41 91 751 69 14
URL: http://www.piramide.ch
E-mail: flavio at piramide.ch