The following directory structure (also called folder structure or directory tree) is usually found on every standard installation of Unix and Linux. This directory structure also resembles the structure of macOS. Except for Multics, which is the predecessor of Unix, Unix is the mother of the operating systems.

Directory Structure

Root Directory

With a slash the highest level of the hierarchical directory structure begins, this is the root directory. The name should not be confused with the root folder of the administrator. The root folder of the administrator is located in the root directory and is assigned to the root account (or superuser account).

Binary Files for All

Contains the binaries of the system commands, these programs can be executed by all users.

Files to Boot Up

The static files needed to boot the system (bootloader). Additionally, some configuration files, such as for the current kernel, are located in this directory.

Hardware Connections

This directory contains the files for the devices to ensure the connections to the hardware.

Et Cetera

The other configuration and information files can be found here.

Working Environment

Every registered user, except the root user, more precisely the system administrator, has his or her personal directory in this home directory. This is the personal working environment where data can be edited and saved. The home directory is usually displayed as a tilde (~/user).

Libraries - Kernel Modules

The dynamic libraries required by the system are located in this directory, kernel modules are also located here.

Mount

Partitions, for example a USB flash drive, can be mounted in this directory.

Optional Programmes

Commercial or optional programs with their own libraries that do not directly belong to the system are stored in this directory.

Pseudo File System

The pseudo file system only exists at runtime, it contains information about running processes and hardware resources. Commands enable the display and management of system and process information.

System Administrator

This is the home directory of the system administrator (root user). For security reasons, this directory is not in the home directory of the usual users, and for the same reasons, the root user should only be used for maintenance work.

Binary Files for Superuser

Binary files for necessary system commands are located in this directory. Commands can only be executed with root privileges or superuser privileges.

Device Information

This pseudo file system is similar to /proc, it stores device information and kernel data related to the hardware.

Temporary Files

Temporary files are stored in this folder, and they are completely deleted when the machine is rebooted.

User System Resources

The directory User System Resources is divided into several subdirectories worth mentioning. Here you will find additional user commands, libraries and system commands. This directory can be used by multiple computers in a network.

User

User commands and application programs are located in this directory.

Header Files

Header files for the compiler are located in this directory.

Library

Additional program libraries are stored here.

Structure like usr

The same structure as the parent directory /usr. Among other things, for installing programs outside the package management.

Optional

Optional system commands and system utilities.

Miscellaneous

Files that are not bound to the architecture.

The Source

Source code of the Linux system kernel, the exact path is /usr/src/kernels/3.10.0-862.11.6.el7.x86_64 (CentOS, Red Hat) The kernel name may be different depending on the version and distribution.

Variable Data

Fluctuating data and directories that are created during the processing of programs.

Cache Memory

The cache for data.

Information Status

Variable status information, these change during runtime.

From /usr/local

Variable data related to installed programs from the directory /usr/local.

Prevent Data Loss

Lock files for devices and resources prevent data loss when used by multiple users.

Important Information

The log files are generally located here.

From /opt

Storage for variable data related to programs from the directory /opt.

Running Processes

Directory for files of running processes like process identifier (PID).

Waiting Queue

The files for queued processes are located in this area, including print jobs and email sending jobs.

Not like /tmp

Temporary files that are not deleted during reboot, as is the case in the parent root directory /tmp.

For Web Servers

This directory is not a standard directory. This directory is the root directory for the common web servers Apache or NGINX.