I have a client running docker (Raspberry Shake). The backup always fails with the following message:
Error getting file metadata. Errorcode: TIMEOUT (2)
Error getting complete file “yQD4WkD8BKzMaujKNY8S|root/var/lib/docker/devicemapper/devicemapper/data” from raspberryshake. Errorcode: TIMEOUT (2)
Backup failed
Is this type of installation supported at all? It is special OS to support seismometer data collection. As it seems, it is based upon Debian.
Thanks a lot for your advice 
Can you ls -l that file on the client?
if it has any relation to the devicemapper as the name suggest , it may be a device file or something odd
This is a sparse file. Earlier Linux kernels had a ext performance problem with sparse files which it could be hitting. Solution would be to use a later kernel or to exclude this file. With docker you only need to backup the persistent data dirs anyway.
Thanks for your answers. I have excluded the file, but it doesn’t help. During backup I can now see on the server Gui that amount of Data to be backed up is increasing until the server has nothing free anymore (in theory). The amount to backup can be at max 8 GB (SD Card), but the interface states TBes to be backed up (in reality it doesn’t allocate that amount on the disk).
Backup finally fails.
Besides of successful backups of Ubuntu & Debian servers, I was able to make full- and incremental backups for app. one week on 4 other Raspberry Pis, and suddenly yesterday they all failed completely. On each machine were a couple of files that the server could not open or get and the clients went offline (not runing anymore) Restarting the client does not help, then the server is complaining about other files than before and the client goes offline again.
It’s very frustrating, don’t understand, what is going on. Why one week everything goes well an the next week the clients die? Why can’t I get Urbackup running stable for all machines?