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Linux File System Hierarchy

Understanding the Linux file system hierarchy is essential for DevOps engineers managing cloud, container, and multi-user environments. This guide provides a practical overview, real-world examples, and best practices for navigating and using the Linux directory structure.

Key Directories and Their Purpose

Directory Purpose & Examples
/ Root of the file system. All other directories branch from here. Only root can write here.
/root Home directory for the root user.
/etc System-wide configuration files. E.g., /etc/resolv.conf, /etc/logrotate.conf.
/home User home directories. E.g., /home/alice, /home/bob.
/var Variable data: logs, spools, cache. E.g., /var/log/syslog.
/opt Optional/add-on application software. E.g., /opt/google/chrome.
/lib, /lib64 Essential shared libraries for binaries in /bin and /sbin. 64-bit libraries in /lib64.
/tmp Temporary files, cleared on reboot.
/mnt Temporary mount point for filesystems.
/srv Site-specific data served by the system (web, FTP, VCS).
/usr User programs, libraries, docs. E.g., /usr/bin, /usr/local, /usr/src.
/dev Device files (disks, terminals, USB). E.g., /dev/sda, /dev/null.
/proc Virtual filesystem for process and kernel info. E.g., /proc/cpuinfo.
/bin Essential user binaries (e.g., ls, cp).
/sbin System binaries for admin tasks (e.g., reboot, fdisk).
/media Mount points for removable media (CD-ROM, USB).
/boot Boot loader files (kernel, initrd, grub).

Real-World DevOps Examples

1. Mounting Cloud Storage (AWS, Azure, GCP)

# Mount an EBS volume to /mnt/data (AWS EC2)
sudo mkfs.ext4 /dev/xvdf
sudo mkdir -p /mnt/data
sudo mount /dev/xvdf /mnt/data

2. Managing Logs in /var

# View system logs
sudo tail -f /var/log/syslog
# Rotate logs manually
sudo logrotate /etc/logrotate.conf

3. Using /etc for Configuration Management

# Use Ansible to manage /etc/ssh/sshd_config
- name: Ensure SSH root login is disabled
  ansible.builtin.lineinfile:
    path: /etc/ssh/sshd_config
    regexp: '^PermitRootLogin'
    line: 'PermitRootLogin no'

4. Container Volumes

# Kubernetes pod mounting /data from host
volumes:
  - name: data-volume
    hostPath:
      path: /mnt/data
      type: Directory

Best Practices

  • Never store application data in /tmp or /var/tmp for production workloads.
  • Use /opt or /usr/local for custom or third-party software.
  • Automate configuration management for /etc using tools like Ansible or Terraform.
  • Regularly monitor /var for log growth to avoid disk space issues.
  • Use /mnt and /media for temporary and removable storage only.

References

Tip: In cloud and container environments, always use persistent storage for important data and automate mount/configuration steps in your deployment pipeline.

Linux File System Hierarchy Diagram