Linux Root Directory Structure Explained

The root directory (/) is the foundation of the Linux filesystem hierarchy. Understanding its structure is essential for system administration, troubleshooting, and cybersecurity. Below is a breakdown of key directories and their purposes:

/ (Root Directory)

• The top-level directory containing all other directories.

/home

• Contains user directories (/home/username).
• Command to list home directories:

  ls /home 
  

/usr

• Stores user-installed programs and libraries.
• Check installed software:

  dpkg -l  Debian/Ubuntu 
  rpm -qa  RHEL/CentOS 
  

/var

• Holds variable data like logs (/var/log), caches, and temporary files.
• View system logs:

  tail -f /var/log/syslog 
  

/tmp

• Temporary files (cleared on reboot).
• Secure /tmp with noexec:

  mount -o remount,noexec /tmp 
  

/etc

• System-wide configuration files.
• List all config files:

  ls -l /etc 
  

/bin & /sbin

• Essential binaries (/bin for users, `/sbin` for admins).
• Check binary paths:

  which ls 
  whereis ls 
  

/lib & /lib64

• Shared libraries for applications.
• Find missing libraries:

  ldd /usr/bin/nginx 
  

/mnt & /media

• Mount points for external storage.
• Mount a USB drive:

  mount /dev/sdb1 /mnt/usb 
  

/opt

• Optional third-party software.
• Check installed apps:

  ls /opt 
  

/proc

• Virtual filesystem for running processes.
• View process info:

  cat /proc/cpuinfo 
  

/sys

• Kernel and hardware information.
• List hardware devices:

  ls /sys/class/net 
  

You Should Know:

• Permissions & Security:

  chmod 700 /home/username  Restrict home dir access 
  

• Log Analysis for Intrusions:

  grep "Failed password" /var/log/auth.log 
  

• Clearing Temp Files Securely:

  shred -u /tmp/sensitive_file 
  

• Finding Suspicious Files:

  find / -type f -perm /4000  Find SUID files 
  

• Backup Critical Configs:

  tar -czvf etc_backup.tar.gz /etc 
  

What Undercode Say:

Mastering Linux directory structure enhances cybersecurity posture. Key takeaways:
– Audit `/etc` for misconfigurations.
– Monitor `/var/log` for breaches.
– Restrict `/tmp` to prevent exploits.
– Use `find` to detect unauthorized files.
– Automate backups of critical directories.

Expected Output:

A well-structured Linux system with secure permissions, logged activities, and minimal attack surface.

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References:

Reported By: Parasmayur Root – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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