The Linux directory structure follows the Filesystem Hierarchy Standard (FHS), which defines a consistent layout across all distributions. Understanding this structure is essential for system administration, troubleshooting, and working efficiently with Linux.
The Root Directory (/)
Everything in Linux starts from the root directory /. Unlike Windows with drive letters (C:, D:), Linux has a single unified tree structure.
Essential Directories
/bin - Essential User Binaries
Contains fundamental commands needed for single-user mode and system recovery: ls, cp, mv, cat, bash. These commands are available to all users.
/sbin - System Binaries
Contains system administration commands typically requiring root: fdisk, iptables, reboot, ifconfig.
/etc - Configuration Files
The central location for system-wide configuration files:
/etc/passwd- User account information/etc/fstab- Filesystem mount table/etc/hosts- Static hostname resolution/etc/nginx/- Nginx web server configuration/etc/ssh/- SSH server and client configuration/etc/cron.d/- System cron jobs
/home - User Home Directories
Each user has a personal directory: /home/username. Contains personal files, settings, and user-specific configurations in dotfiles (.bashrc, .ssh/).
/root - Root User Home
The home directory for the root (superuser) account. Kept separate from /home for security and recovery purposes.
/var - Variable Data
Contains data that changes frequently during system operation:
/var/log/- System and application logs/var/www/- Web server document root/var/lib/- Application state data (databases, package managers)/var/mail/- User mailboxes/var/tmp/- Temporary files preserved between reboots
/tmp - Temporary Files
Temporary files created by programs. Contents may be deleted on reboot. World-writable with sticky bit.
/usr - User Programs
Contains the majority of user applications and utilities:
/usr/bin/- User commands (non-essential)/usr/sbin/- System commands (non-essential)/usr/lib/- Libraries for /usr/bin and /usr/sbin/usr/local/- Locally installed software (compiled from source)/usr/share/- Architecture-independent data (docs, icons)
/opt - Optional Software
Third-party applications that do not follow the standard hierarchy. Examples: /opt/google/chrome, /opt/lampp.
/proc and /sys - Virtual Filesystems
Not real files on disk ā they provide kernel and hardware information:
cat /proc/cpuinfo # CPU information
cat /proc/meminfo # Memory information
cat /proc/version # Kernel version
ls /sys/class/net/ # Network interfaces/dev - Device Files
Represents hardware devices as files:
/dev/sda- First hard drive/dev/null- Discards all data written to it/dev/zero- Provides null bytes/dev/random- Random number generator
/boot - Boot Files
Contains the Linux kernel, initial RAM disk, and bootloader configuration (GRUB).
/mnt and /media - Mount Points
/mnt/- Temporary mount points for manual mounting/media/- Automatically mounted removable media (USB drives, CDs)
Quick Reference Commands
# Show directory tree
tree -L 1 /
# Find where a command lives
which nginx
type ls
# Check disk usage per directory
du -sh /*
# Find files across the filesystem
find / -name "nginx.conf" 2>/dev/nullOnce you understand the Linux directory structure, navigating and managing a Linux system becomes intuitive. Every file has a logical place, and knowing where to look is half of solving any administration challenge.
