I am running Influx 1.7.3 on a Raspberry Pi 3b+ with RaspbianLinux 9 (stretch).
With all databases in the default location (/var/lib/influxdb) in can backup to an external disk (influxd backup -portable /mnt/Mybckuplocation) without a problem.
I prefer to have the database on an external flash drive and moved the files under (/var/lib/influxdb) to an USB flash drive and adjusted the paths in /etc/influxdb/influxdb.conf. Everything works fine except the backup.
Using the same command (influxd backup -portable /mnt/Mybckuplocation) i am getting errors:
Download shard 151 failed copy backup to file: err=<nil>, n=0. Waiting 2s and retrying (0)... 2019/03/14 09:48:58 Download shard 151 failed copy backup to file: err=<nil>, n=0. Waiting 2s and retrying (1)... etc. etc.
Moving everything back to the SD card and the backup is working again. In all cases owner and group of the involved files are influxdb:influxdb.
Any ideas on how to solve this issue is highly appreciated.