Alright, let me see if I can break this down in easy steps.
First, you have to make sure that both devices have the same version of rsync, or at least compatible versions. The DroboFS has 3.0.7.
Then you have to prepare the FS for rsync. This means installing the DroboApp from the DRI page, and editing the rsyncd.conf file to look like this:
uid = root
gid = root
pid file = /mnt/DroboFS/Shares/DroboApps/rsync/rsyncd.pid
path = /mnt/DroboFS/Shares
comment = DroboFS Shares
read only = no
WARNING: this configuration exposes all the precious data of your FS without any protection! If you want to enforce user account on you FS, then this config file will bypass all of that. The reason this configuration is ok is because the FS is protected by your firewall (a.k.a. router). The only connections to the outside will come from the SSH server, which we’ll address next.
Now you have to make sure that you can access your FS from outside your home network using SSH. First, install OpenSSH (Dropbear is not enough, and you have to remove it from the FS). Now, you have to permanently change the root password to something more complicated than ‘root’ (the default). If you have dropbear installed, use the root_passwd script that ships with it.
Next, configure your router to port forward SSH connections to your FS (see www.portforward.com to figure this step out for your specific brand of router). You have to make sure that you can SSH to your FS from outside your network (for instance, using a smartphone), otherwise the rest won’t work. This step can’t be done automatically for you (well, it can for certain brands of routers, but it is just easier to do it by hand).
Next step is to give your router some easy to remember DNS name. What you are looking for is Dynamic DNS (aka DDNS). Again, this is router specific and can’t be automatically done for you. Check your router’s manual. For the rest of this post, let’s assume your DDNS name is “myhome.ddns.com”.
Now, go to the other device, make sure it has rsync and ssh installed, and try this command:
rsync -aviP -e ssh --rsync-path=/mnt/DroboFS/Shares/DroboApps/rsync/rsync --dry-run email@example.com:/mnt/DroboFS/Shares/Public
You’ll be asked for the root password on your Drobo.
This should output a lot of stuff, because if everything worked ok, then what you see is a simulation of what would actually happen (i.e., which files being copied where).
If not, then something is missing on the setup. Let’s summarize:
Install rsync DroboApp on your DroboFS, change the content of rsyncd.conf to the model above, restart FS.
Change the root password on the FS, using the dropbear root_passwd script.
If necessary, remove Dropbear, and install OpenSSH.
Change router config to enable port forward of port 22 to your FS - check www.portforward.com for more help
Change router config to enable dynamic DNS - check your router manual
Test that you can actually ssh to your FS from some device outside your home network
[*]Go to the other device and run the test command above.
Once you have all of that working, automating it so it runs on a schedule is piece of cake. In fact, the hardest part is to configure your router, since we can’t really help you there.