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Chapter 3.2 - Directory Structure

Learning Objectives​

By the end of this chapter, you will be able to:

  • Understand the detailed structure of Linux directories
  • Identify the role of each main directory
  • Navigate the system effectively
  • Find configuration files and data

Main Directories​

/ (Root)​

Starting point of the entire hierarchy. All other directories are under /.

/bin - Essential Binaries​

Essential commands for all users:

  • ls, cp, mv, rm
  • cat, grep, find
  • bash, sh

Characteristics:

  • Accessible to all
  • Necessary for booting
  • Basic commands

/sbin - System Binaries​

Commands for system administration:

  • fdisk, mkfs
  • ifconfig, iptables
  • systemctl, init

Characteristics:

  • Generally requires root
  • System administration
  • Maintenance

/etc - Configuration​

System configuration files:

  • /etc/passwd: Users
  • /etc/group: Groups
  • /etc/hosts: Local name resolution
  • /etc/fstab: Mounted file systems
  • /etc/ssh/: SSH configuration

Characteristics:

  • Editable text configuration
  • Modifications often require root
  • Backup before modification

/home - Users​

Personal directories for users:

  • /home/user1/
  • /home/user2/
  • Each user has their own directory

Characteristics:

  • Personal space
  • User permissions
  • Personal files

/usr - User Programs​

Programs and libraries:

  • /usr/bin: User binaries
  • /usr/lib: Libraries
  • /usr/share: Shared data
  • /usr/local: Local programs

Characteristics:

  • Non-essential programs
  • Can be mounted read-only
  • Large portion of software

/var - Variable Data​

Data that changes during operation:

  • /var/log: System logs
  • /var/cache: Cache
  • /var/spool: Queues
  • /var/tmp: Persistent temporary

Characteristics:

  • Changing data
  • Can grow quickly
  • Monitor disk space

/tmp - Temporary​

Temporary files:

  • Accessible to all
  • Generally cleared on reboot
  • Broad permissions

/dev - Devices​

Representations of devices:

  • /dev/sda, /dev/sdb: Disks
  • /dev/tty: Terminals
  • /dev/null: Bottomless pit
  • /dev/random: Random

Characteristics:

  • Interface to hardware
  • Created dynamically
  • Special (not normal files)

/proc - Kernel Interface​

Information about processes and the system:

  • /proc/cpuinfo: CPU info
  • /proc/meminfo: Memory info
  • /proc/pid/: Process details

Characteristics:

  • Virtual file system
  • Real-time data
  • Read-only (generally)

/sys - System Interface​

System and hardware information:

  • /sys/class/: Device classes
  • /sys/devices/: Devices
  • Interface to the kernel

Characteristics:

  • Virtual file system
  • Hardware information
  • Hardware configuration

Practical Navigation​

Finding Files​

# Search for a file
find / -name "file.txt" 2>/dev/null
find /home -name "*.txt"

# Search by type
find / -type f -name "*.conf"
find / -type d -name "config"

# Search recently modified
find /var/log -mtime -1  # Last 24h

Viewing Size​

# Directory sizes
du -sh /home/*
du -h --max-depth=1 /

# Disk space
df -h
df -h /home

Summary​

In this chapter, you learned:

Main directories: /, /bin, /etc, /home, /usr, /var, /tmp
Configuration: /etc contains config files
Users: /home for personal directories
Programs: /usr for software
Variables: /var for changing data
Devices: /dev for hardware access
Kernel: /proc and /sys for system info

Next Steps​

Chapter 3.3: Navigation and Basic Commands
Chapter 3.4: File Management

Chapter created on: December 2024