How to fix: df shows no file systems processed on Linux

If you run df command and get the following output:

df: no file systems processed

At the same time you have no problem with "du" or "ls" commands.

One possible reason is that your disk run out of space. You need to delete some files to recover. You cannot fix it if it is caused by other reason. But this is the first thing you want to do when it happens.

See also:

Solution to Disk Full in production server

Find and delete Files depends on modify days on Linux