Today, a friend's server space is full. After inspection, it is found that the server apache log occupies 3.6G of space. After cleaning the log, it is found that df -h still displays / occupies 100% of the space.
Why is this? Because some linux files controlled by the running program will not make space immediately after deletion, and he deletes just the log file of the running apache
Use the following command to see which files are still being occupied by which process
ls -ld /proc/*/fd/* 2>&1 | fgrep '(deleted)'