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📂 Main folders in / (the root directory)

🔹 bin

  • Contains basic programs (binaries = compiled commands) needed by all users.
  • Examples: ls, cp, mv, cat.
  • Think of it as your toolbox of everyday commands.

🔹 boot

  • Contains files needed to start (boot) the system, like the Linux kernel.
  • Think of it like the ignition key of your computer.

🔹 dev

  • Contains device files (not real files, but ways to talk to hardware).
  • Example: /dev/sda = your hard disk, /dev/tty = your terminal.
  • Think of it like remote controls for your hardware.

🔹 etc

  • Contains configuration files for the system and applications.
  • Example: /etc/passwd (user info), /etc/ssh/sshd_config (SSH config).
  • Think of it as the settings folder.

🔹 home

  • Each user gets their own folder inside here.
  • Example: /home/alice, /home/bob.
  • It’s like your Documents folder in Windows — personal space.

🔹 lib & lib64

  • Contains shared libraries (like .dll files in Windows).
  • Programs need these to run.
  • Think of them as ingredients that programs need to cook their recipes.

🔹 lost+found

  • A special place where recovered files are stored after a crash.
  • Usually empty.
  • Think of it as the lost & found box at school.

🔹 media

  • Temporary mount point for external drives (USB, CD/DVD).
  • If you plug in a USB stick, it might show up here.
  • Think of it as the USB ports drawer.

🔹 mnt

  • Another place where filesystems can be temporarily mounted.
  • Often used by system admins.
  • Think of it as a spare storage shelf.

🔹 opt

  • Optional software installed here (not part of the base system).
  • Example: some third-party apps may go into /opt.
  • Think of it as a miscellaneous apps folder.

🔹 proc

  • A virtual folder that shows information about running processes and the system.
  • Example: /proc/cpuinfo shows CPU details.
  • Think of it as the system’s self-reporting dashboard.

🔹 root

  • The home folder of the root user (administrator).
  • Different from / (the root directory).
  • Think of it as the admin’s private room.

🔹 run

  • Stores temporary runtime data (like process IDs, sockets).
  • Gets cleared after reboot.
  • Think of it as the scratchpad for running programs.

🔹 sbin

  • Like /bin, but contains system administration commands.
  • Example: reboot, fdisk, ifconfig.
  • Think of it as the toolbox for mechanics (admins).

🔹 srv

  • Contains data served by the system (like websites or FTP).
  • Rarely used on desktops.
  • Think of it as the storefront for services.

🔹 sys

  • A virtual filesystem showing devices and drivers.
  • Works with /proc.
  • Think of it as the control panel for hardware.

🔹 tmp

  • Temporary files go here.
  • Cleared on reboot.
  • Think of it as the scratch paper bin.

🔹 usr

  • Contains user programs and libraries.
  • Inside, you’ll see /usr/bin, /usr/lib, etc.
  • Think of it as the app store shelf — where most software lives.

🔹 var

  • Stores variable data: logs, mail, cache, databases.
  • Example: /var/log/syslog (system logs).
  • Think of it as the diary/journal of the system.

🔹 Special merged folders:

  • bin.usr-is-merged, sbin.usr-is-merged, lib.usr-is-merged

    • These are Ubuntu’s way of merging /bin with /usr/bin, /sbin with /usr/sbin, etc.
    • They’re basically links for backward compatibility. You don’t usually need to worry about them.

✅ Summary for beginners

  • /bin & /sbin → commands (user vs admin)
  • /etc → settings
  • /home → personal files
  • /var → logs & changing data
  • /tmp → temporary junk
  • /boot → startup stuff
  • /dev & /proc & /sys → system internals
  • /root → admin’s home
  • /usr → most installed software