Linux
under the hood.

Administration, hardening, command-line diagnostics, services and troubleshooting for real-world systems.

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Administration

Users, permissions, processes, storage, networking and services.

🛡

Hardening

Reduce attack surface with secure configuration and least privilege.

⌁

Diagnostics

Use logs, processes, sockets and system state to isolate root causes.

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Automation

Make repeatable administration safer with scripts and controlled workflows.

Diagnostic model

Start with symptoms, establish current system state, inspect the relevant subsystem and validate the smallest change that resolves the issue.

Observe→Reproduce→Inspect→Change→Verify

systemctl --failed
journalctl -p warning..alert -b
ss -tulpn
free -h
df -h