Just installed fresh system on Hyper-V VM. OS /dev/sda (XFS), /dev/sdb => /mnt/sdb/backup (BTRFS). I can see these in logs. There are no backups, was before I have added Windows client.
2025-11-17 10:35:13: WARNING: Creating file entry index. This might take a while...
# This error legacy from old versions, still occurs. 2025-11-17 10:35:13: ERROR: No permission to access
"/mnt/data/backup/urbackup_tmp_files"
2025-11-17 16:01:37: WARNING: Shutting down (Signal 15)
# I have disabled IPv6 via systemd, and this error disappears
2025-11-17 20:34:33: ERROR: Binding UDP socket failed for interface eth0 errno=99 interface ipv6 fe80::5a8a:b75d:1db9:3e88 2025-11-17 20:34:34: ERROR: Sending broadcast failed! (ipv6)
# This is legacy issue too.
2025-11-17 20:34:34: ERROR: Error downloading dataplan database: Could not resolve hostname(ec=6), Could not resolve host: update.urbackup.org
# Here I have added windows client and started backup into uncompressed simple VHD
2025-11-17 20:58:29: WARNING: Error retrieving last image backup. Doing full image backup instead.
2025-11-17 21:00:05: ERROR: Error sending client access key
Finally, it looks like everything working good. Will test in production soon.