# Sysadmin Diagnose

> Diagnose a failing service or system issue on a Debian/Ubuntu Linux machine with a hypothesis-driven loop that gathers evidence from journalctl and systemctl, finds patterns, tests a hypothesis, fixes, and verifies. Use when something is broken and you need root cause, not a guess.

- Skill: `hermeticormus/sysadmin-diagnose` (Agent Skill)
- Install (CLI): `npx skillmds@latest add hermeticormus/sysadmin-diagnose`
- Raw SKILL.md: https://api.skillmd.com/api/skills/hermeticormus/sysadmin-diagnose/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- License: MIT
- Author: hermeticormus (https://skillmd.com/u/hermeticormus)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/hermeticormus/sysadmin-diagnose

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# System diagnosis

A system issue is happening. Diagnose and fix it on a Debian/Ubuntu Linux machine using a systematic, hypothesis-driven loop. Gather evidence before changing anything; confirm before applying a fix.

## Diagnostic steps

1. Describe the problem: what is happening, and when did it start?
2. Gather information:
   - System logs: `journalctl -xe`
   - Specific service logs: `systemctl status <service>` and `journalctl -u <service> -xe`
   - Resource usage: `top`, `htop`, `df -h`
   - Network: `ip addr`, `ping`, `ss -tlnp`
3. Identify patterns: is it consistent or intermittent?
4. Check recent changes: what changed before the issue appeared?
5. Research: look for known issues.
6. Test hypotheses: verify the likely cause before acting.
7. Implement the fix: apply the solution.
8. Verify: confirm the issue is resolved (`systemctl is-active <service>`, reproduce the original symptom).

Be systematic and thorough. Form a hypothesis from the evidence rather than guessing, and document findings for future reference.

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See full content at https://github.com/HermeticOrmus/linux-sysadmin-skills.