du command give you an overview of your file-directory space usage. It tell you about the space occupied by certain directory/file which may be causing overload on your server resulting in system crash or preventing users from logging-in, so for a system administrator this command is very helpful to monitor disk usage for avoiding system crashes.

You can use du –sh * to know which file/directory is eating up your disk space so as to take precaution;

Simply start with du -sh * look for the biggest directory, cd into it and once again fire the command. Repeat the process until you find the particular file.

You can also use du –sk * | sort –n for getting sorted outputted with biggest files/directory at the bottom.

User having read permission on certain directories can only fire this command for those specific files and directories thus, an ordinary user would generally not be able to use du command to determine disk space consumption for files or directories belonging to other users.