I’ve had a couple of times now that on one of my computers df keeps reporting 100% disk usage. Until now I have resolved this issue by rebooting. But today this happened on one of our servers. And I was reluctant to boot and I had to solve it fast because mysql was down.
After some searching I found that it was because of a process keeping a hold of some deleted files. So after shuttding down some processes I found the right one and df reported a dropping disk usage %. After starting mysql again we were back up again.