nikola
47 lines
1.9 KiB
Markdown
47 lines
1.9 KiB
Markdown
---
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name: sysadmin
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description: Linux system administration, networking diagnostics, and production hardening workflows. Use when handling SSH/connectivity incidents, DNS/routing/firewall issues, host health checks, systemd/service failures, disk or memory pressure, log triage, baseline security checks, or when the user asks for repeatable Linux ops runbooks.
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---
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# Sysadmin
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## Overview
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Execute Linux and network operations with a diagnose-first approach.
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Prefer minimal-risk commands, capture evidence before changes, and verify outcome after every fix.
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## Workflow
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1. Confirm scope and blast radius.
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2. Capture current state with `scripts/sysdiag.sh` when possible.
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3. Isolate layer: host, service, network path, DNS, or policy.
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4. Apply the smallest reversible fix.
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5. Re-check service health and user-facing behavior.
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6. Summarize root cause, change made, and follow-up hardening actions.
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## Triage Decision Map
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- Connection refused or timeout:
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Check `ss -tulpn`, service status, local firewall (`nft list ruleset` or `iptables -S`), and routing (`ip route`).
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- Name resolves incorrectly:
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Check `/etc/resolv.conf`, `resolvectl status`, `dig`, and local cache behavior.
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- Service flapping:
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Check `systemctl status`, `journalctl -u <service> --since "-30m"`, restart policy, and resource pressure.
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- Packet loss or latency spikes:
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Check `ping`, `mtr` (if present), interface errors via `ip -s link`, and host saturation.
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- Host unhealthy:
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Check CPU, memory, disk inode usage, and top failing units from `systemctl --failed`.
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## Command Guardrails
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- Prefer read-only diagnostics first.
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- Ask before destructive actions (mass deletes, firewall flush, forced reboot).
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- For privileged reads, run with `sudo` only when required.
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- Before config edits, back up file: `cp <file> <file>.bak.<timestamp>`.
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- After change, validate with targeted checks and logs.
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## Resources
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- Incident runbook and command matrix: `references/runbook.md`
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- Snapshot collector: `scripts/sysdiag.sh`
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