"Special Files" with Synology Hyper Backup

[master-kw]

Hello,

I back up DietPi daily as a cron job (rsync dietpi-backup) to my Synology DiskStation. Both the backup and the restore work perfectly.

In addition, I back up the NAS with Synology HyperBackup to both USB-HD and cloud storage. In both cases, there are lots of (>1k) warnings in the log regarding an incomplete backup (see example screenshot), which indicate so-called “special files”. Just to be clear, I am only backing up the “offline backup directory” not the "active RasPi".

How can I solve the problem? Path length? Or are the warnings negligible because, for example, HyperBackup “can't do anything” with the files?

RasPi 4
DietPi: 9.10.0
Synology DS716+II
DSM 7.2.2-72806 Update 3

[Joulinar]

not sure if this would be a question for Synology forum. At least from our side we have no inside how Hyperbackup is working. Our backup is nothing than a rsync.

[master-kw]

I wasn't sure if it was a “general problem” (Linux/RasPi) or a specific one (Synology).

In the meantime, I took a look at the (database-based, encrypted) Synology backup file. The files transmitted by DietPi (rsync) are complete and identical.

I think the problem lies with Synology. There are files without file extensions in a relevant backup subfolder. The classification probably fails because of these and issues a warning message.

Thanks for sharing your thoughts though. :-)

Regards,
Oliver

[MichaIng]

The missing file extension won't be a problem, as this is very common on Linux/UNIX in general, and thousands of files would be affected then. But the files created by Docker are indeed special at a different level:

root@dietpi:~# ls -l /mnt/dietpi_userdata/docker-data/overlay2/c90d98dbb7d14bd6a91b89b8e13b17e3e2544d64a89c6c2d8e694246b419621b-init/work/work/
total 0
c--------- 1 root root 0, 0 Nov 30  2022 '#1705e5'
root@dietpi:~# ls -l /mnt/dietpi_userdata/docker-data/volumes/backingFsBlockDev
brw------- 1 root root 8, 1 Jan 23 05:25 /mnt/dietpi_userdata/docker-data/volumes/backingFsBlockDev

The first is a characters device, the second a block device. Probably a good idea to check whether those file attributes (the c and the b) remain intact at the Synology.