/bin Contains basic Linux commands required for system operation and recovery. Example: ls, cp, mv, cat, bash, grep, etc.
/boot:
Stores everything needed to boot Linux. Contains:
- Linux kernel (vmlinuz-*)
- Initial RAM disk (initramfs-*)
- GRUB bootloader files
/dev:
Special files representing hardware and disks.
/dev/nvme0n1 → root EBS volume
/dev/nvme1n1 → extra EBS disk
/dev/null → trash device
/dev/random → random number generator
/dev/tty Terminal device (current session)
/dev/usb USB device interface (usually managed by subdirs)
/dev/input/eventX Keyboard
/dev/input/mice Mouse
- Linux treats everything as a file, including hardware devices.
- The files in /dev are not regular files; they are special device files created and managed by the kernel
/etc:
The /etc directory in Linux contains system-wide configuration files and directories. These files control the behavior of the system, services, and installed applications. For example
* /etc/passwd
* /etc/group
* /etc/systemd/system
* /etc/nginx
/home:
The /home directory is where all regular users’ personal files and settings are stored. Each user gets a subdirectory inside /home, named after their username.
User settings Hidden "dotfiles" like .ssh, .bashrc, .profile, .config/ store per-user settings.
lib:
The /lib directory contains essential shared libraries needed by the core system binaries in /bin and /sbin. These libraries are similar to .dll files in Windows or .dylib in macOS.
For example When you run a basic command like ls, the system:
- Finds /bin/ls
- Loads necessary libraries from /lib
- Executes the binary with support from those libraries
/lib64:
The /lib64 directory contains 64-bit shared libraries that are essential for running 64-bit binaries, especially those located in /bin and /sbin.
On 64-bit Linux systems, libraries are separated by architecture to avoid conflicts:
Directory Purpose /lib Contains 32-bit libraries (on multilib systems) /lib64 Contains 64-bit libraries (default on 64-bit systems)
This separation helps the OS load the correct library version depending on whether a program is 32-bit or 64-bit.
/media:
The /media directory is used to automatically mount external storage devices such as:
- USB drives
- CD/DVDs
- SD cards
- External hard drives
When a user named alice inserts a USB named MyUSB, the system might mount it as:
/media/alice/MyUSB/Inside that directory, you’ll see the contents of the USB. NOTE: This media is mostly for desktop auto mount environments. It is like plug and play as we see in windows.
Flow When You Plug in a USB:
- Linux detects hardware and assigns it a device file like /dev/sdb1
- An auto-mount tool mounts it under /media/username/MyUSB/
- You access your files through /media, not /dev
/mnt:
The /mnt directory is a standard mount point used for temporarily mounting filesystems, such as:
- External hard drives
- USB drives (manually mounted)
- Network filesystems (NFS, SMB)
- ISO images
It’s primarily intended for manual or admin use.
Manual Mounts Used by system administrators to mount filesystems temporarily No Auto-mounting Unlike /media, this is not used by desktop auto-mount tools Testing or recovery Often used during system recovery or file system testing
/opt:
The /opt directory stands for “optional” and is used to install third-party software that is not part of the default Linux distribution.
Feature Description 💾 Third-party apps Used for software not managed by the package manager 🗂️ Self-contained Each application has its own subdirectory, keeping things isolated 📥 Manual installs Ideal for software downloaded directly (e.g., Chrome, MATLAB)
/opt/
├── google/
│ └── chrome/
├── myapp/
│ ├── bin/
│ ├── lib/
│ └── config/When to Use /opt
- Installing commercial software (e.g., Oracle, VMware, Zoom)
- Managing applications outside the OS package manager (apt, yum, dnf)
- Deploying self-contained apps or custom-built binaries
/proc:
The /proc directory is a virtual filesystem (not a real one on disk) that provides a real-time interface to kernel and process information.
Think of it as a window into the running Linux kernel.
| Path | Description |
|---|---|
/proc/cpuinfo |
Info about CPU(s) |
/proc/meminfo |
Memory usage |
/proc/uptime |
System uptime |
/proc/version |
Kernel version |
/proc/[PID]/ |
Info about a running process by PID |
/root:
The /root directory is the home directory for the root user, who is the superuser (administrator) on a Linux system.
Do not confuse /root with the root (/) directory — / is the root of the entire filesystem, while /root is the root user’s home folder.
/run:
The /run directory is a temporary filesystem used to store runtime data for processes and services after boot, such as:
- Process ID (PID) files
- Lock files
- Socket files
| Feature | Description |
|---|---|
| ⚡ Volatile | Stored in RAM (tmpfs) — cleared at every reboot |
| 🧰 Used by services | Systemd, udev, network manager, and other daemons store data here |
| 🕒 Early availability | Available very early in boot, even before /var is mounted |
- /proc//: Shows live process data (real-time, kernel-managed).
- /run/*.pid: Text files created by services to store their own PID for tracking or control.
/sbin:
The /sbin directory contains essential system binaries that are primarily intended for the system administrator (root). These binaries are crucial for system boot, repair, and maintenance.
Example: fsck, iptables, reboot, iptables, init, etc.
/srv:
The /srv directory stands for "service" and is used to store data served by system services such as:
- Web servers (httpd, nginx)
- FTP servers
- File sharing services
Often structured like /srv/ftp, /srv/www, /srv/nfs
Not Always Used
- Optional: Not all Linux distributions or setups use /srv.
- Customizable: Some admins prefer /var/www, /usr/share/nginx/html, /home/ftp, or mount points elsewhere.
/swap:
In Linux, /swap is not a directory, but rather a swap space used as virtual memory to help manage the system's memory resources.
Swap space can be located either in a swap partition (a dedicated disk partition) or a swap file (a file on the filesystem). It allows the system to offload less frequently used memory pages when the physical RAM is full.
/tmp: The /tmp directory is used for temporary file storage. It's a standard location where programs and users can store temporary files that are required only for short-term use.
🗑️ Temporary Storage Used to store temporary files created by programs or users 🛠️ Program usage Programs often create files here that they don’t need permanently 📂 Writable by all It’s a world-writable directory, meaning any user or process can create files
Many systems are configured to clear the contents of /tmp on reboot, or periodically through cron jobs.
/usr:
The /usr directory is one of the core system directories in Linux. It contains user-related programs and data that are not required for the basic system to run, but are essential for most applications.
📂 Common Subdirectories of /usr Directory Description /usr/bin User binaries - contains most executable programs for general users /usr/lib Libraries - stores shared libraries required by programs /usr/include Contains C header files for development /usr/share Contains shared data, such as documentation and icons /usr/local Locally installed software (software manually installed by the admin)
/var:
Variable Data. Holds data that grows and changes. Key subfolders:
/var/log → system & app logs
/var/lib → Docker, MySQL, Jenkins, kubelet
/var/spool → mail, cron
/var/lib/docker → Docker home folder
- Fills up the fastest
- Should be on separate EBS in production
- Needs log rotation