I recently installed Lion (like two days ago) and now I have 8GB unaccounted for. Since my main drive is a 40GB SSD, it makes installing things a pain in the butt for installing large apps like Xcode. Code: ROFISH-Mac-Pro:/ ROFISH$ sudo du -x --max-depth=1 -h Password: 1.6M ./.fseventsd 1.6G ./.Spotlight-V100 0 ./.Trashes 0 ./.vol 4.7G ./Applications 3.8M ./bin 0 ./cores 4.5K ./dev 20M ./Developer 1.0K ./home 3.6G ./Library 1.0K ./net 0 ./Network 596M ./opt 948M ./private 2.3M ./sbin 2.5G ./System 4.6G ./Users 5.5G ./usr 12K ./Volumes 24G . ROFISH-Mac-Pro:/ ROFISH$ df -h Filesystem Size Used Avail Use% Mounted on /dev/disk2s2 37G 32G 5.1G 86% / devfs 115K 115K 0 100% /dev /dev/disk1s2 233G 225G 8.4G 97% /Volumes/Old Fangamer /dev/disk0s2 624G 494G 131G 80% /Volumes/Warp Pipe /dev/disk0s3 308G 159G 149G 52% /Volumes/BOOTCAMP It says 24 gigs used when looking at files, but 32 gigs used from the filesystem. WTF, where'd my space go? To answer my own question, "Verify Disk" found errors that needed to be repaired. After repair, free space was 9GB and a 3.5GB file was put into lost and found, thus finding where the space went.