Hi everyone! New to Duplicati due to late Crashplan migration, hoping to help with reporting and improving 
I am backing up via SFTP to an Ubuntu server in a secret location (the other side of the room). The “Test connection” button appears to not only test the connection, but also add the RSA key of the server as trusted. This popup appears:
No certificate was specified previously, please verify with the server administrator that the key is correct: ssh-rsa 2048 the:rsa:key:of:my:server Do you want to approve the reported host key?
If I do not press Test connection when doing a Direct restore, the next screen will hang at “Listing backup dates …” and then say:
Failed to connect: Please add --ssh-fingerprint=“ssh-rsa 2048 the:rsa:key:of:my:server” to trust this host. Optionally you can use --ssh-accept-any-fingerprints (NOT SECURE) for testing!
This also happens if I add a completely new backup and do not press “Test connection”, but the error appears later when I try to run the backup for the first time.
The error is easy to avoid by pressing Test connection, but the UX gives you the impression that testing the connection is optional. My suggestion is that the same RSA popup should appear on the next screen (or when running the first backup) and ask the user if the key should be added at that stage instead.
Technically, the testing is optional, but you would then have to type in the RSA fingerprint manually (fairly nerdy thing to do).
I understand what you want, but it is a bit difficult, as it is possible for the user to skip steps by pressing the numbers on top, thus bypassing the check.
We could capture it during the “Save” process, and say something like “You have not tested, would you like to test?” Or maybe more specifically “You have not set an SSH fingerprint, which you need”
We cannot show popup during the run, because it is not given that there is a UI attached during the backup (i.e. schedule it and close the browser), or run from the commandline.
2 Likes
You’re right, it’s probably tricky to move the dialog too far away. Maybe one way is to simply make the check mandatory, unless there are specific cases when you definitely want to skip it?
The check could then be even more extensive and save some troubleshooting - when the check passed the first time I thought everything was fine, but got permission errors when initiating the backup since I missed some chown and chmod business 
Those are details though, I guess most people will run a test backup the first thing they do.
The test process can take a long time (in some cases anyway), so personally I would be annoyed if I had to wait, knowing that I set it up correctly (maybe I tested at some other time).
Sorry if this has been covered and I just forgot, but does “Test connection” also test write/read/delete capabilities at the destination as well?
Those are details though, I guess most people will run a test backup the first thing they do.