newly uploaded files show up alright, but file size says "empty" (permissions seem to be ok). How can I fix that?
32 bit system and a file larger than 2GB?
Sh...! You are right. It's a 32 bit system and occurs, if files are larger than 2 GB! BTW: Is there a easy way to swap to 64bit (system ist Debian Stretch on a Pi2)?
Easy, I don't think so, as it would probably require an OS reinstall. And that is only if the CPU is actually 64 bit, as many Pi2 aren't: https://www.raspberrypi.org/forums/viewtopic.php?t=202487
Customer support service by UserEcho