If you’re stepping into the world of Linux, understanding its file system hierarchy is crucial. Think of it like learning your way around a city—once you know where everything is, using it becomes second nature. This guide will take you from the basics to expert-level knowledge about Linux directories, their roles, important files, and even symbolic links (shortcuts).

🔍 What Is the Linux File System?

The Linux file system is the structure where data is stored, organized, and accessed. Unlike Windows (which uses drive letters like C:, D:), Linux uses a tree-like structure starting at a single root directory: / .

🧾 Basic Terms to Know:

• Directory: A folder used to group files.

• File: A data container (text, binary, config, etc.)

• Root (/ ): The topmost directory in the hierarchy.

• Symlink (Symbolic Link): A shortcut or reference to another file/directory.

🌲 The File System Tree Overview

Everything starts from / (root). All files and folders branch out from here.

/
├── bin
├── boot
├── dev
├── etc
├── home
├── lib -> usr/lib
├── lib64 -> usr/lib64
├── media
├── mnt
├── opt
├── proc
├── root
├── run
├── sbin -> usr/sbin
├── srv
├── sys
├── tmp
├── usr
└── var

🔁 Notice: Some directories like /lib , /sbin , and /bin are now symlinks pointing to /usr/lib , /usr/sbin , and /usr/bin on modern Linux systems.

🧰 In-Depth Directory Breakdown

Let’s explore each directory in detail with examples, real-world use, and shortcut (symlink) info.

📦 /bin – Essential User Commands

• Purpose: Contains basic executable programs and command-line tools required by all users.

• Examples: ls , cp , mv , rm , cat

• Access: Available to all users.

• Important: Needed during system recovery.

🔁 On newer distros, /bin is a symlink to /usr/bin .

⚙️ /sbin – System Binaries

• Purpose: Holds system-level utilities mainly used by the root (admin) user.

• Examples: fsck , reboot , shutdown , ifconfig

• Access: Restricted to root for system maintenance.

🔁 Typically symlinked to /usr/sbin .

🧠 /boot – Boot Loader Files

• Purpose: Contains all files required to boot the system.

• Includes: Kernel files (vmlinuz), initrd, grub config files.

• Caution: Messing with this can break your system!

📝 Example files:

/boot/grub/grub.cfg
/boot/vmlinuz-5.15.0

🧪 /dev – Device Files

• Purpose: Represents system devices as files.

• Type: Virtual, dynamically managed by the kernel (udev).

• Examples:

  • /dev/sda → Hard disk

  • /dev/tty → Terminals

  • /dev/null → “Black hole” file

• 🧠 Why? Because in Linux, everything is a file—including hardware.

🔐 /etc – Configuration Files

• Purpose: Houses all system-wide configuration files and directories.

• DO NOT store personal data here.

• Examples:

  • /etc/passwd : List of system users

  • /etc/ssh/sshd_config : SSH settings

  • /etc/fstab : Filesystem mount table

🧠 Most services (like networking, cron jobs, etc.) read their settings from /etc .

🏠 /home – User Home Directories

• Purpose: Personal directories for every user (non-root).

• Layout: /home/username/

• What’s Inside: Documents, Pictures, Downloads, personal app settings

💡 Each user can modify files in their own home but not in others’ or system directories.

👑 /root – Root User’s Home

• Purpose: Home directory of the superuser.

• Not to be confused with / (root of the file system).

• Path: /root/ (not under /home!)

🛑 Only accessible by the root user.

🧬 /lib and /lib64 – Shared Libraries

• Purpose: Contains essential shared libraries needed by binaries in /bin and /sbin.

• 64-bit Systems: Use/lib64 for 64-bit libraries.

🔁 These are often symbolic links to /usr/lib and /usr/lib64 .

📂 /media and /mnt – Mount Points

• /media : Auto-mounted external devices (USBs, DVDs)

• /mnt : Temporary mount point for system admin (manual)

🧠 Mounting means linking a device to the file system so it becomes accessible.

💼 /opt – Optional Software Packages

• Purpose: For third-party software that doesn’t fit into standard paths.

• Example: Google Chrome or proprietary software installations.

🗂️ Often used for large software suites.

🧾 /proc – Process Info (Virtual Filesystem)

• Purpose: Dynamic, virtual files showing system and process info.

• Managed by: Kernel

• Examples:

  • /proc/cpuinfo : CPU details

  • /proc/meminfo : Memory usage

  • /proc/[PID]/ : Info about a specific process

• 🧠 These files don’t exist on disk—they’re created in real time!

🔁 /run – Runtime Data

• Purpose: Stores volatile runtime info (like PID files) needed between boot and services.

• Cleared at: Every reboot.

• Used by: systemd, network services, login sessions

🗃️ /srv – Service Data

• Purpose: Contains data for services like FTP, HTTP, etc.

• Examples:

  • /srv/ftp/

  • /srv/www/

• 👨‍💻 Useful for servers hosting public services.

⚠️ /tmp – Temporary Files

• Purpose: Temp files created by applications.

• Auto-cleared: On reboot or scheduled cleanup.

• Examples:

  • Download caches

  • Unzipped install files

🧼 Never store important data here!

🌐 /usr – User System Resources (Not “Home” Users)

• Purpose: Contains application binaries, libraries, docs not critical to boot.

• Structure:

  • /usr/bin : User-level commands

  • /usr/lib : Libraries

  • /usr/share : Shared documentation, icons

💡 On modern distros, this is the core of most Linux software.

📊 /var – Variable Files

• Purpose: Data that changes frequently.

• Includes:

  • Logs (/var/log )

  • Mail spools

  • Print queues

  • Databases

📉 If your system runs out of space, /var is often the culprit.

🧩 Which Directories Are Symlinks?

Here are the most common symlinked directories:

These symlinks ensure backward compatibility and maintain a cleaner structure under /usr.

📌 Key System Files to Know

🧭 Why Learning the Linux File System Matters

Mastering the file system allows you to:

✅ Troubleshoot faster

✅ Understand where apps store data

✅ Secure your system better

✅ Automate tasks using the terminal

✅ Feel confident working with Linux 💪