Debian Stable to Windows 10 v2004 (NTFS, DOS names disabled) dattobd file backups failing with "Writing directory metada ... failed" error

I’m trying to backup a Debian Stable PC to an NTFS directory on a Windows 10 v2004 server (detailed hardware configs at both links.)

The Debian PC has dattobd installed and the datto snapshot method selected for the urbackup client. The backup source directory was set using urbackupclientctl add-backupdir -d / -n root in the Debian terminal. Excluded files are */var/cache*; */mnt/*; */media/*; */dev/*; */snap/*; */proc/*; */sys/* in the server web UI.

The Windows PC has DOS names disabled as described here.

Both incremental and full file backups fail with the same error message in the Logs tab of the server web interface:

Errors 07/26/20 01:08 Writing directory metadata to "E:\UrBackup\DellOptiPlex390-1\200726-0102\.hashes\root\home\judah\.kde\cache-DellOptiPlex390-1" failed.
Errors 07/26/20 01:09 Backup failed

The tail of the server-side live log is:

07/26/20 01:30  	DEBUG  	Saved metadata of 40759 files and directories. 95% done...
07/26/20 01:30  	INFO  	Waiting for file hashing and copying threads...
07/26/20 01:30  	INFO  	Writing new file list...
07/26/20 01:30  	INFO  	All metadata was present
07/26/20 01:30  	DEBUG  	Syncing file system...
07/26/20 01:31  	INFO  	Transferred 3.70542 GB - Average speed: 75.0027 MBit/s
07/26/20 01:31  	DEBUG  	Script does not exist urbackup\post_full_filebackup.bat
07/26/20 01:31  	INFO  	Time taken for backing up client DellOptiPlex390-1: 7m 53s
07/26/20 01:31  	ERROR  	Backup failed
07/26/20 01:31  	WARNING  	Exponential backoff: Waiting at least 3 days 13h 20m before next file backup

I’ve emailed the client and server debug logs.

Any idea what the problem may be?

Could you have a look at this file to see what kind of file it is (e.g. output of stat). Thanks!

$ stat .kde/cache-DellOptiPlex390-1
  File: .kde/cache-DellOptiPlex390-1 -> /var/tmp/kdecache-judah
  Size: 23              Blocks: 0          IO Block: 4096   symbolic link
Device: fd00h/64768d    Inode: 2629460     Links: 1
Access: (0777/lrwxrwxrwx)  Uid: ( 1000/   judah)   Gid: ( 1000/   judah)
Access: 2020-07-26 07:00:04.057874573 -0500
Modify: 2019-09-09 05:01:25.743254025 -0500
Change: 2019-09-09 05:01:25.743254025 -0500
 Birth: -

Any update? Is this a fixable issue? This is my 2nd time trying to use urbackup and the 2nd time it’s failed. Previous attempt was with a Debian server and a FreeBSD client. In both cases, it seems the client just chokes … and that’s if you can even get it to start.

I’m not able to reproduce the problem. I created the link on a Ubuntu machine (snapshotting with dattodb) backing up to a Windows server.