Understanding how the BSD filesystem manages disk space is critical to successfully managing a BSD server or workstation. However, this topic is generally overlooked since it is rarely used outside of installation and upgrades. It is also a very simple topic and most people assume you understand how it all works.
This article gives a quick synopsis on filesystem layout and tries to briefly explain how to understand /etc/fstab. The fstab(5) man pages, while good, do little to teach the basics to new sysadmins.
The first thing to realize when dealing with the Unix filesystem is that everything can be addressed as a file. Even system hardware has a file representation that is used to access it. Those special files live in /dev.
The second thing to understand is the starting location for all these files is / and pronounced "root". Those are the two points of Unix doctrine that everyone expects you to already understand before even thinking about trying BSD.
But what does that mean to me? First, if you have used a Microsoft operating system, you will notice there is no "C:" drive or any other drive letters. Unix has no concept of the drive letter mentality. With Unix all things exist in one directory structure. This may seem very unusual at first given the way you may be used to dealing with removable media. Instead of assigning a drive letter to removable media, you must find a place in the existing file structure to attach it.
Think of it like docking a module on to a very large space station. You find an empty docking station, connect the module. While the module is connected, the entire contents of the module are accessible for storage or removal by authorized personnel.
