Duplicati stopped working with SshException error

I’ve just recently starting using Duplicati on a Windows 10 box, connecting to a Linux server via ssh for backup. Everything was working fine for a few days but now I can no longer backup. I’ve tried repairing the database (fails for the same reason) and testing the connection (works fine). The log shows the following exception:

Failed while executing “Backup” with id: 1
Renci.SshNet.Common.SshException: Failure
at Duplicati.Library.Main.BackendManager.Delete(String remotename, Int64 size, Boolean synchronous)
at Duplicati.Library.Main.Operation.FilelistProcessor.RemoteListAnalysis(BackendManager backend, Options options, LocalDatabase database, IBackendWriter log, String protectedfile)
at Duplicati.Library.Main.Operation.FilelistProcessor.VerifyRemoteList(BackendManager backend, Options options, LocalDatabase database, IBackendWriter log, String protectedfile)
at Duplicati.Library.Main.Operation.BackupHandler.PreBackupVerify(BackendManager backend, String protectedfile)
at Duplicati.Library.Main.Operation.BackupHandler.Run(String[] sources, IFilter filter)
at Duplicati.Library.Main.Controller.<>c__DisplayClass16_0.b__0(BackupResults result)
at Duplicati.Library.Main.Controller.RunAction[T](T result, String[]& paths, IFilter& filter, Action`1 method)
at Duplicati.Library.Main.Controller.Backup(String[] inputsources, IFilter filter)
at Duplicati.Server.Runner.Run(IRunnerData data, Boolean fromQueue)

Restarting the service doesn’t help either.

The backup destination works fine when connecting through command-line ssh (e.g. cygwin).

Any suggestions for how to troubleshoot or get backup working again?

I’ll also note that on the target/destination Linux system, I see a successful ssh key-based login each time Duplicati tries to connect, so the failure point isn’t there.

Are you using a CoW (Copy on Write) format such as ZFS or Btrfs on your Linux destination?

If so, then the reason it worked for a while then stopped working is that you might be running into this issue:

The Linux destination is a volume-encrypted Veracrypt drive. I don’t think that is CoW, but in any event there are 7 TB free.

Your tip lead me to the solution, though. The Veracrypt drive needed to be remounted–something had gone awry. Perhaps Duplicati could provide a more informative error message? It looked like an ssh error but it was actually a target-disk mount issue.

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Good job catching the issue. I flagged your post as the solution.

@kenkendk would likely know better than I but I suspect a generic error is coming out of the SSH protocol so Duplicati likely can’t get any specifics about why it failed.

I don’t think there is anything I can do. The error is from the SSH server that fails, and it does not tell why it fails.
That said, the error message “Failure” could probably be clearer :grimacing: but that is something that should be fixed in the SSH library.

Can’t the library distinguish between a failed ssh connection versus something that fails after an ssh connection is successfully opened?