I have 6 devices that i rsync to a central location to back them up. Ive been using ssh as the -e option. Problem is i use public key with passphrases, meaning to backup all six i need to go to each device and run the backup script. Since i typically backup /etc, /home, and /root this means entering sudo and the ssh passphrase 3x for each device.
I would much prefer a script that runs on back storage device that can pull the data from each device without having to use ssh (encryption is not necessary since all traffic is either local or going through a vpn connection).
I could then put this script in root’s crontab or make it a systemd service running as root.
But i dont know how i can remote sync without ssh
You can run rsyncd as a service on host you wish to back up and connect to that from your central point directly without ssh. Traffic is unencrypted and I wouldn’t trust on that over public network, but you can bind rsyncd to localhost and open a single ssh tunnel for each host (or even write a small script to keep tunnels open automatically) and then just run rsync over that. That’s how I backup my things, just with backuppc in the mix (I’ve got scripts to open/close ssh tunnels at backuppc configuration). VPN tunnels are also an option to encrypt traffic, but depending on your use case that might be a bit overkill.
Or if you’re not tied to rsync you could use something like BorgBackup or other tools which manage the whole jazz for you out of the box.