Master Linux File System: What Every Directory Means and How to Use Them

/bin and /sbin

bin

(Binary) stores executable files and shortcuts such as cp, chmod, and cat. These are regular user commands. sbin (System Binary) holds utilities that affect system configuration and typically require sudo or root privileges, like ifconfig and iptables.

/boot

This directory contains files needed for system boot, including the grub bootloader. Modifying files here is generally discouraged.

/dev

dev

(device) holds device files that represent hardware components as files, e.g., sda and sdb for hard‑disk partitions. All hardware appears as files under this directory.

/etc

Configuration files for the system and installed packages reside here. For example, /etc/apt stores APT repository lists, and most program‑specific settings are found under sub‑directories of /etc.

/lib, /lib32, /lib64

lib

contains shared libraries required by binaries in /bin and /sbin. Architecture‑specific variants ( lib32, lib64) hold libraries for 32‑bit or 64‑bit binaries.

/media and /mnt

/media

automatically mounts removable devices (USB drives, external disks) under a sub‑folder named after the user (e.g., /media/fdl). /mnt is intended for manual mounts, though modern systems often handle mounting automatically.

/opt

Optional third‑party software is placed here. Users often install manually downloaded applications (e.g., Chrome, music players, IDEs) in /opt.

/proc

proc

(process) provides a virtual filesystem exposing runtime information about processes. Each sub‑directory named with a PID contains files describing that process, and the directory also offers system details such as CPU status and kernel version.

/root

The superuser’s home directory. Access requires root privileges.

/run and /sys

These directories store runtime data and kernel‑exposed system information. Files here reside in memory and disappear after a reboot; they should not be used for persistent storage.

sudo vim /sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight/brightness

/srv

Intended for service data. Empty on desktop installations but used on servers to hold web or FTP service files.

/tmp

Temporary files created by applications. Contents are cleared on reboot, though occasional manual cleanup may be needed.

/usr and /usr/local

usr

(Universal System Resource) holds user‑installed applications and libraries. Sub‑directories /usr/bin and /usr/sbin contain executables, while /usr/local mirrors this hierarchy for locally compiled software.

/var

Historically “variable”, now primarily stores log files (e.g., /var/log) and other mutable data. Logs accumulate over time and may need periodic cleanup.

/home

User home directories contain personal files, downloads, and hidden configuration folders (e.g., .config, .cache, .local). Hidden folders beginning with a dot store per‑application settings and user‑specific binaries such as ~/.local/bin.

Final Summary

To modify system configuration, edit files under /etc. User‑specific settings reside in hidden files within the home directory. Executable commands are typically found in /bin, /sbin, /usr/bin, /usr/sbin, and their /local equivalents. Logs are under /var/log, temporary files under /tmp, and device files under /dev (auto‑mounted to /media).

/bin
/sbin
/usr/bin
/usr/sbin
/usr/local/bin
/usr/local/sbin
/home/USER/.local/bin
/home/USER/.local/sbin

If you write a script and want it globally accessible, place it in one of the directories above.