Linux - No space left on device, yet plenty of free space

My little server ran into an issue, and started reporting the error: No space left on device No worries, lest figure out which disk has full and clean up… Using the df command with the -h (for human-readable output) it should be easy to find the issue: root@server:~# df -h Filesystem Size Used Avail Use% Mounted on udev 483M 0 483M 0% /dev tmpfs 100M 3.1M 97M 4% /run /dev/vda 20G 9.