What steps should be taken if disk space is not freed after deleting files in a Linux system?

If the free space in Linux does not increase after deleting files, it is likely that the files are still held by processes. This happens when a file is deleted from the filesystem, but its descriptors are still open.

What to do:

1. Use the lsof (list open files) command to find processes that hold deleted files:

lsof | grep deleted

2. Find the PID of the process holding the file, and restart or terminate it:

kill -9 <PID>

3. After this, the space will be freed.

Alternatively, you can use fuser to find processes using a specific directory or file.

Also, check that the deletion actually occurred on the correct filesystem and that there are no mounted points hiding files.