Generated by an infinite conga-space of monkeys coerced by: unstattedCommoner
The author writes:
That was close! I discovered that my backup script had "tar xf", not "tar cf". That's right: The backup script was trying to read from the backup disc, not write to it. I had no backups.
Fortunately this problem is now fixed, although I've forgotten why I was checking the backup script in the first place.