There are two ways to do this, one easy and one harder. This can be used before the upgrade/downgrade process or if you want to have same setting on another ATV.
The easy way is to copy the userdata folder via SFTP (winscp, et al) from the iOS device to another computer:
For all of your XBMC data, add-ons, skins, etc,
For just the settings files themselves (which takes up less space, but means you would have to re-download add-ons, etc).
SFTP the directory back to its original location, then SSH (putty, et al) to the ATV2 and run the following command to reset ownership/permissions:
chown -R mobile:mobile /private/var/mobile/Library/Preferences/XBMC/
Install XBMC backup onto device
Here's a video on it
Once you get the back up to run you may want to put the files onto DROPBOX... this is how to set it up:
1. You will need to sign-up for you own developer app key and secret by visiting dropbox.com/developers/apps
2. Choose the API one
3. Name your app whatevery you want, and make it an "App Folder" type
application. Your app can run in developer mode and you should never
need to apply for production status. This is to get around Dropbox's
rule not allow distribution of production key/secret pairs.
4. Once you have your app key and secret add them to the XBMC Backup settings.*
5. XBMC Backup now needs to have permission to access your Dropbox
account. When you see the prompt regarding the Dropbox URL Authorization
DO NOT click OK.
4. On you computer use your favorite SCP program, I use WinSCP.
5. Once connected to your ATV go to
/private/var/mobile/Library/Preferences and open xbmc.log. Check your
XBMC log file for a line from "script.xbmcbackup" (should be at bottom
of file) containing the authorization URL.
6. Cut/paste this into a browser and click Allow.
7. Once this is done you can click "OK" in XBMC and proceed as normal.
NOTE: In XBMC backup you may want to mark the run in background
option so you can keep using your ATV. Back up takes a long time.
* you may want to be ready to read your log file ASAP because
dropbox will time out the link if you take too long. If it does just try
your backup again to get another link.