🐧 Understanding the Linux System Directory Structure

“The root directory of the Linux system is like the root of a large tree, from which all files and folders grow.”

🌲 1. Starting with <span><span>ls /</span></span> command

After logging into the Linux system, enter the command:

ls /
你会看到一串看似复杂的目录，如同一棵树的分枝。这就是 Linux 的 
根目录结构。

📂 2. Detailed Explanation of Common Linux Directories

Below is an explanation of the functions of each directory👇

🔧 /bin

Binaries is an abbreviation for binary files, which store the most commonly used commands in the system, such as <span>ls</span>, <span>cp</span>, <span>mv</span>, etc.👉 It is equivalent to a “toolbox” that the system cannot run without.

🚀 /boot

Contains essential files for system booting, such as the kernel image and bootloader (<span>grub</span>).⚠️ Do not modify it casually, as it may prevent the system from booting.

💽 /dev

Device is an abbreviation for device files, which store all external device files in the system.👉 In Linux, devices are also files; for example, <span>/dev/sda</span> represents the hard disk.

⚙️ /etc

Etcetera is an abbreviation for various configuration files of the system.Common examples include:

• <span>/etc/passwd</span>: User information

• <span>/etc/fstab</span>: Disk mount information⚠️ Please back up before modifying, as it may prevent the system from booting!

🏠 /home

The home directory for users. Each user has an independent home directory, such as <span>/home/alice</span>.👉 All personal files, downloads, and desktop files are stored here.

📚 /lib

Library is an abbreviation for the basic dynamic link libraries of the system (similar to Windows DLL files).👉 Almost all programs need it to run.

🧩 /lost+found

When the system shuts down abnormally or crashes, recovered fragment files will temporarily reside in this directory.Generally, it is empty.

💾 /media

Auto-mount directory. When a USB drive or external hard drive is inserted, the system will automatically mount it under <span>/media</span>.

🧱 /mnt

A directory provided by the system for temporary mounting of file systems.For example, you can mount a CD drive to <span>/mnt</span> and then access the contents of the CD.

📦 /opt

Optional is an abbreviation for storing additional installed software packages.For example, when installing software like Oracle or Chrome, it may be placed here.

🔍 /proc

Processes is an abbreviation for a virtual file system that stores content in memory rather than on disk.👉 It records system running status, process information, etc.For example:

echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all

This can temporarily suppress the system’s ping response.

👑 /root

The home directory of the superuser (root).⚠️ It has very high permissions, and ordinary users generally do not have access.

🧰 /sbin

Superuser Binaries stores management commands used by system administrators, such as <span>reboot</span>, <span>ifconfig</span>, etc.

🔒 /selinux

A directory specific to RedHat/CentOS.It stores files related to SELinux (Security-Enhanced Linux) for access control and security management.

🛰️ /srv

Stores data provided by services after they start, such as data directories for Web and FTP services.

⚡ /sys

A directory added after the Linux 2.6 kernel, which mounts the sysfs file system to display the system device tree.👉 It can be understood as:the mapping view of system hardware in the kernel.

🧹 /tmp

Temporary file directory used to store various temporary data.It is usually cleared after a system reboot.

🧑💻 /usr

Unix System Resources is an abbreviation for storing user applications, system commands, and documentation, and is one of the largest directories.It is similar to Windows’ <span>Program Files</span>.

/usr/bin

Directory where executable programs for ordinary users are located.

/usr/sbin

Advanced commands used by system administrators.

/usr/src

Default directory for kernel source code and development files.

📈 /var

Variable is an abbreviation for storing frequently changing data, such as logs, caches, emails, databases, etc.Common subdirectories include:

• <span>/var/log</span>: System log files

• <span>/var/mail</span>: Mail storage directory

👉 If system logs accumulate too much, it may also lead to insufficient disk space.

🔄 /run

Temporary runtime information storage after the system starts.After a system reboot, the contents of this directory will be cleared.In some systems, <span>/var/run</span> will be a symbolic link to <span>/run</span>.

🚫 3. Directories to be Particularly Cautious With

⚙️ <span>/etc</span>

The core configuration directory of the system.📌 Stores all configuration files for the system and services, such as network settings, user information, startup items, etc.⚠️ Be sure to back up before modifying, as incorrect configurations may cause the system to fail to boot directly.

🧰 <span>/bin</span>, <span>/sbin</span>, <span>/usr/bin</span>, <span>/usr/sbin</span>

Storage locations for executable commands in the system.For example, the most commonly used command <span>ls</span> is located at <span>/bin/ls</span>.

📌 In simple terms, their differences lie in the different users:

• <span>/bin</span> and <span>/usr/bin</span>: Regular commands for ordinary system users, such as <span>ls</span>, <span>cp</span>, <span>cat</span>, etc.;

• <span>/sbin</span> and <span>/usr/sbin</span>: Management commands for system administrators (root), such as <span>reboot</span>, <span>ifconfig</span>, <span>mount</span>, etc.

💡 You can understand it as:

<span>/bin</span> series is the “toolbox for everyone”,<span>/sbin</span> series is the “control panel for administrators”.

⚠️ Never delete or move these commands, as it may cause system functionality to fail.

🧾 <span>/var</span>

The system’s “record warehouse”.📌 Stores log files, caches, emails, databases, and other dynamic data.⚠️ Be particularly careful when cleaning logs or caches, and do not accidentally delete critical system log directories (such as <span>/var/log</span>).

🧭 4. Conclusion

The directory structure of Linux is like an orderly world: each directory has its own mission for the system to operate stably.

🔹 <span>/</span> is the root🔹 <span>/bin /sbin</span> is the command repository🔹 <span>/etc</span> is the brain🔹 <span>/usr</span> is the resource center🔹 <span>/var</span> is the recorder

Understanding the directory structure is to understand the soul of Linux.

💡 Final Note

If you are new to Linux, it is advisable to start by familiarizing yourself with these directories.Every time you type <span>ls /</span>, you are greeting the “tree of life” of the operating system.🌳