Your Disk Is Full but `du` Says It's Empty

Your server is slow. You check the disk: $ df -h / Filesystem Size Used Avail Use% Mounted on /dev/sda1 100G 95G 0.5G 99% / Ninety-five gigabytes used. So you go looking for what's eating it: $ du -sh /* 2>/dev/null ... 20G /var 2G /home 1G /usr Add it all up and you get maybe 25 gigabytes. So where