All Linux OS Types

There are many Linux distributions available today, and they all have commands that are specific to them, however there are a lot of Linux commands that are generic and work across most, if not all of the Linux flavours. This section then is dedicated to those commands that span the cosmos of Linux distros.
Check Disk Space
Delete Raspbian User
Using Aliases in Raspbian
Make a file Executable
Linux Permissions Introduction
Adding and Removing Linux Permissions
Adding and Removing Permissions Shorthand
Permissions for Directories