Linux

Linux is the foundation. From workstations to servers, from containers to bare metal.

Core Competencies

Domain Coverage

System Administration

systemd, users, permissions, package management, logging

Hardening

SSH, firewalls, SELinux/AppArmor, auditd, CIS benchmarks

Terminal Mastery

AWK, sed, grep, find, xargs — power user patterns for security and administration

802.1X / EAP-TLS

Certificate-based network authentication, Cisco ISE integration, enterprise NAC

Networking

ip, NetworkManager, systemd-networkd, DNS, bonding

Storage

LVM, filesystems, LUKS, Btrfs, ZFS

Containers

Docker, Podman, rootless containers, systemd integration

Automation

Bash, systemd timers, Ansible

Distributions

Arch, RHEL/Rocky, Debian/Ubuntu, Fedora

Approach

Every guide follows these principles:

  1. Concepts first — understand the "why" before the "how"

  2. Multi-distro — commands for Arch Linux, RHEL/Rocky/Alma, Debian

  3. Verification — always confirm before and after changes

  4. Security by default — principle of least privilege

Distribution Coverage

This documentation covers multiple distributions with tabbed examples:

Distribution Package Manager Use Case

Arch Linux

pacman

Rolling release, bleeding edge, personal workstations

RHEL/Rocky/Alma

dnf

Enterprise servers, long-term support, compliance

Debian

apt

Stable servers, containers, broad hardware support

Fedora

dnf

Workstations, testing RHEL-bound features

Quick References

Essential Commands

# System information
hostnamectl
uname -a
cat /etc/os-release

# Services
systemctl status <service>
systemctl list-units --type=service --state=running
journalctl -u <service> -f

# Networking
ip addr show
ip route show
ss -tlnp

# Storage
lsblk
df -h
mount | column -t

Important Paths

Path Purpose

/etc

System configuration

/etc/systemd/system

Custom systemd units

/etc/ssl/certs

CA certificates

/var/log

System logs

/etc/ssh

SSH server configuration

Enterprise Experience

This documentation reflects real-world implementation experience:

  • 802.1X / Network Access Control — Production deployments with Cisco ISE, certificate-based authentication for Linux endpoints in enterprise environments

  • PKI Integration — End-to-end certificate lifecycle: enrollment, deployment, renewal, revocation

  • systemd Architecture — Service dependencies, boot ordering, failure handling for authentication services

  • Troubleshooting — Battle-tested solutions from production incident response

The patterns here come from solving real problems, not theoretical exercises.

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