# Linux Filesystem Hierarchy (FHS)

### Root directory: /

Everything starts here. It’s the top of the tree.

### /bin — Basic Programs

Contains the essential commands you use every day.\
Examples:

* `ls`, `cp`, `mv`, `rm`, `cat`

### /sbin — System Programs

System/administration tools (usually for root).\
Examples:

* `fsck`, `iptables`, `mount`

### /usr — User Programs (Most Software)

This is like “Program Files.”\
Contains most apps, libraries, documentation.\
Inside it:

* `/usr/bin` → most user commands
* `/usr/sbin` → more system tools
* `/usr/lib` → libraries

### /var — Variable Data

Changes often. Log files, databases, package files.\
Examples:

* `/var/log` → system logs
* `/var/cache`
* `/var/spool`

### /etc — Configuration Files

System-wide settings for programs and services.\
Examples:

* `/etc/passwd`
* `/etc/fstab`
* `/etc/ssh/`

### /home — Your Personal Files

Each user gets a folder here.\
Examples:

* `/home/alex/Documents/…`

### /root — Root’s Home Folder

Like `/home`, but only for the superuser.

### /lib and /lib64 — Libraries for Programs

Like DLLs in Windows.\
Programs in `/bin` and `/sbin` use them.

### /tmp — Temporary Files

Temporary storage. Safe to delete.\
Cleared on reboot.

### /opt — Optional Software

Third-party apps you install manually go here.

### /media — External Devices

USB drives, external disks, etc., get mounted here.

### /mnt — Manual Mount Point

You mount drives manually here when needed.

### /dev — Devices as Files

Linux treats hardware like files.\
Examples:

* `/dev/sda` → your disk
* `/dev/tty` → terminal
* `/dev/null` → “black hole”

### /proc — Kernel & Process Info 

Not real files. They show system information.\
Examples:

* `/proc/cpuinfo`
* `/proc/meminfo`
* `/proc/1234/` → info about process 1234

### /sys — System Hardware Info 

Another virtual filesystem showing hardware details.

### Summary Table

| Directory | Purpose                        |
| --------- | ------------------------------ |
| `/`       | Root of all files              |
| `/bin`    | Basic user commands            |
| `/sbin`   | System admin commands          |
| `/usr`    | Installed software & libraries |
| `/var`    | Changing data (logs, caches)   |
| `/etc`    | Config files                   |
| `/home`   | User personal files            |
| `/root`   | Root user’s home               |
| `/tmp`    | Temporary files                |
| `/opt`    | Optional third-party software  |
| `/media`  | Mounted external devices       |
| `/mnt`    | Manual mount directory         |
| `/dev`    | Hardware as files              |
| `/proc`   | System & process info          |
| `/sys`    | Hardware & kernel info         |