Backup Fail - Installed as Service

Hello, looking for some help.

Have been using Cobian for years and feel it’s time to replace with something that will be further developed to work with changing technologies. After research I decided to go with Duplicati. Installed it yesterday as a service using a reddit post as a guide on a Windows Server 2016 system.

I configured the settings after installation and setup a scheduled backup job.

This morning I went to check the results and after logging into the server I could not bring up the Duplicati GUI. I checked that the service was running and was finally able to get to the GUI via localhost:8200.

Looking at the logs the backup had failed, but honestly, I can’t understand why. I was hoping to get some help from this forum so that I can get this working properly.

Here is a snippet of the log file:

Mar 19, 2019 12:56 AM: Failed while executing “Backup” with id: 1
System.AggregateException: One or more errors occurred. —> System.AggregateException: Object reference not set to an instance of an object. —> System.NullReferenceException: Object reference not set to an instance of an object.

at Duplicati.Library.Main.Volumes.BlockVolumeWriter.AddBlock(String hash, Byte data, Int32 offset, Int32 size, CompressionHint hint)

at Duplicati.Library.Main.Operation.Backup.SpillCollectorProcess.<>c__DisplayClass0_0.<b__0>d.MoveNext()

— End of stack trace from previous location where exception was thrown —

at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

at CoCoL.AutomationExtensions.d__10`1.MoveNext()

— End of stack trace from previous location where exception was thrown —

at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

at Duplicati.Library.Main.Operation.BackupHandler.d__12.MoveNext()

— End of stack trace from previous location where exception was thrown —

at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

at Duplicati.Library.Main.Operation.BackupHandler.d__19.MoveNext()

— End of inner exception stack trace —

Any help will be appreciated. Thank you.

Actually I’m pretty sure I know what the issue is. The backup job is set to upload to an FTP server. That FTP server is configured for passive transfers over ports 12000-12099.

Testing the connection in Duplicati passes because that connection is over port 21. Duplicati only tests the connection, not data transmission.

How can I set the data ports used for FTP?

Hello @Sabyre and welcome to the forum!

I’m not sure if that’s the right question. Server picks its data port (and returns info) when client says PASV. Maybe the question is how to get the FTP client to get passive mode. There are two FTP clients available:

FTP which I think is the .NET built-in.
FTP (Alternative) which is FluentFTP, and which (unlike most) uses a test file a file for Test connection.

What I don’t quite understand is how the FTP LIST command that the .NET FTP client ran was able to get its listing back over the data connection (it’s not returned on the control connection) without passive mode, however to pursue your passive mode theory I suggest --ftp-passive on .NET FTP, or try FTP (Alternative).

Thank you it worked using Alternative FTP.