Linux Filesystem Structure and Components

File System Hierarchy

Path	Description
/	The top-level directory is the root filesystem. Contains all of the files required to boot the operating system before other filesystems are mounted as well as the files required to boot the other filesystems. After boot, all of the other filesystems are mounted at standard mount points as subdirectories of the root
/bin	Contains essential command binaries
/boot	Consists of the static bootloader, kernel executable, and files required to boot the Linux OS.
/dev	Contains device files (special files) for every hardware device attached to the system
/etc	Local system configuration files. Also stores config files for applications
/home	Stores the home directories for all users (except root).
/lib	Shared library files that are required for system boot.
/media	External removable media devices such as USB drives are mounted here
/mnt	Temporary mount points for regular filesystems
/opt	Optional files like third-party tools are usually saved here
/root	The home directory for the root user
/sbin	This directory contains executables used for system-administration.
/tmp	The operating system and many programs use this directory to store temporary files. This directory is generally cleared upon system-boot and may be deleted at other times without any warning.
/usr	Contains executables, libraries, man files, etc.
/var	This directory contains variable data files (e.g., log files).

Components

Component	Description
Bootloader	A piece of code that runs to guide the bootleg process to start the operating system. Parrot uses the GRUB bootloader.
OS Kernel	The kernel is the main component of an operating system. It manages the resources for system's I/O devices at the hardware level.
Daemons	Background services are called "daemons" in Linux. Their purpose is to ensure that key functions such as scheduling, printing and multimedia are working correctly. These small programs load after the computer is booted.
OS Shell	The operating system shell (command interpreter).
Graphics Server	This provides a graphical sub-system (server) that allows graphical programs to run locally or remotely on an X-windowing system. E.g., X or X-server.
Window Manager	Also known as a graphical user interface (GUI). E.g., GNOME, KDE, MATE, Unity and Cinnamon.
Utilities	Applications or utilities are programs that perform particular functions for the user or another program.

Linux Architecture

Layer	Description
Hardware	Peripheral devices such as the system's RAM, hard drive, CPU and others
Kernel	The core of the operating system, whose function is to virtualize and control hardware resources like CPU, allocated memory, accessed data, etc. The kernel gives each process its own virtual resources and prevents/mitigates conflicts between different processes
Shell	A command-line interface (CLI), also known as a shell that a user can enter commands into to execute the kernels functions.
System Utility	Makes all of the system's functionality available to the user.