Sometimes it occurs that a device runs full with memory. Simply deleting the files on the device doesn’t help. Ubuntu stills shows that the device is 100% full, even if there are no files on it anymore. This command usually helps to give free the memory.
sudo tune2fs -m 0 /dev/sda5
If it doesn’t help you need to execute this command as well. It quits all processes which are using the device.
sudo fuser -km /mnt/share
Robert Reiz 
I hadn’t thought of using containers but that’s a great idea. Thanks so much for sharing!