Note that the following commands may be used in both the serial console or the SSH terminal emulator.
One of the main principles of Unix systems is that everything is a file. This means that in a Unix system, (almost) everything can be accessed as a file. So, we can use the same commands to read/write a file for every peripheral connected to the system (for example, disks, terminals, serial ports, and so on).
Since this book's main goal is to show you how to get access to the system's peripherals, it's quite obvious that these commands are very important to know. Moreover, in the next chapters, we are going to use several command-line tools to set up our BeagleBone Black and its attached peripherals, so in this section, I'm going to list some of them.