Ubuntu – Different value for free space in GUI and df -kh

du reports free space by scanning reachable inodes and calculating their size.

If a file is created, opened, and later deleted while it is still open, the program that opened it will continue to have access to the file, and writes and reads can be performed to that memory location on disk. du does not account for such open files whereas df does.

A simple restart should flush /tmp and solve your problem.

An alternative would be to scan open files and restart or kill the process that did not release the deleted files.

This is quite interesting but it is that xfs keeps metadata about the files in the xfs filesystem internally but this does not seem to be picked up by du that much but is by df. However xfs has its own xfs_estimate command. df properly shows the free space used on the xfs partition. I have found that running sudo du -h -x --max-depth=0 /path ; sudo xfs_estimate /path sudo can be nesecary in case there are files your normal user cannot see like kvm/qemu virtual machines by defualt which are one thing in / that do take up a lot of space. For example when I run sudo du -h -x --max-depth=0 /path ; sudo xfs_estimate /path on /etc with etc having lots of small configuration files This shows /etc as taking up 13 MB of space but xfs estimate shows it will need a 20 MB partition which would seem like you are using 65 % on your du command but in reality the metadata is using the rest. So in the end xfs_estimate can tell you a lot.