Understand the composition of the Linux file system in one picture

Today let’s talk about the Linux file system.

In the past, the Linux file system used to be like a disorderly town, allowing people to build their own houses as they pleased. However, the introduction of the Filesystem Hierarchy Standard (FHS) in 1994 brought order to Linux file systems. This standard provides a set of specifications for Linux systems, defining the organizational structure of files and directories, ensuring that file placement and management become more orderly. By following the FHS, users and developers of Linux systems can more easily understand the layout of the file system, making the installation, configuration, and management of software packages more consistent and reliable. This orderliness provides better stability, security and maintainability of the Linux system

By adopting a standard like FHS, software can ensure a consistent layout across various Linux distributions. However, not all Linux distributions strictly adhere to this standard. They often add unique elements or tweak to meet specific needs.

To master this standard, you can achieve it through exploration. You can start by using commands such as "cd" to navigate, and the "ls" command to list the directory contents. Think of the file system as a tree, starting at the root (/) and exploring it.

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• / (root directory): The root directory is the top-level directory in the Linux file system. All other directories are subdirectories of the root directory, making it the parent directory of the entire file system.
• /bin: Contains the basic binary executable files needed to start the system and perform basic operations. These are available to all users.
• /boot: Saves the files needed to boot the system, including the Linux kernel, the initial RAM disk image (for drivers required at boot), and boot loader configuration files (such as GRUB).
• /dev: Contains device files that represent hardware components or other system devices. For example, /dev/sda represents the first SATA drive and /dev/tty represents the terminal.
• /etc: Storage system and application configuration files. These files are typically text files that can be edited to change the behavior of a system or application.
• /home: Contains the personal directories of all users with accounts on the system, except the root user. User-specific settings and files are stored here.
• /lib: Includes basic shared libraries and kernel modules required for system and application running.
• /media and /mnt: Directories for mounting removable media (such as USB drives) and temporarily mounted file systems.
• /opt: used to install additional application packages. It is where third-party applications are installed, keeping them separate from the system default applications in /usr.
• /proc: A virtual file system that provides a mechanism for the kernel to send information to the process. It does not contain real files, but runtime system information (e.g., system memory, mounted devices, hardware configuration, etc.).
• /sbin: Contains basic system binaries, similar to /bin, but used for system administration tasks and generally not accessible to unprivileged users.
• /tmp: A temporary directory where applications can store temporary files. It is usually cleared after a reboot or interval.
• /usr: Hosts user applications and a large amount of system content. It contains subdirectories for programs, libraries, documentation, etc. that are not required to start or repair the system.
• /var: Contains variable data files. This directory contains files to which the system writes data during operation, such as logs (/var/log), mail (/var/mail), and print queues (/var/spool).

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