Field manual
Reference library
Not a command dump — recipes organised by the problem you're actually trying to solve, with what the output means and the traps to avoid.
Linux
Open →Task-first recipes for the things you actually do at 2am.
- ▸Find what is using a port
- ▸Check why a service failed
- ▸Find large files safely
- ▸Inspect logs with journalctl
- ▸Check memory pressure
Windows
Open →PowerShell-first diagnostics for Windows Server and AD.
- ▸Find failed logins
- ▸Check service failures
- ▸Inspect event logs
- ▸Test DNS and AD connectivity
- ▸Check GPO application
Networking
Open →Prove where the path breaks instead of guessing.
- ▸Test DNS resolution
- ▸Check TCP connectivity
- ▸Understand common ports
- ▸Trace the route path
- ▸Interpret packet flow
DNS
Open →The first domino. Diagnose resolution like an engineer.
- ▸Compare resolvers
- ▸Authoritative vs recursive
- ▸Caching & TTL
- ▸Record types
- ▸Resolution order (/etc/hosts vs DNS)
Troubleshooting
Open →Mental models that turn panic into a method.
- ▸Confirm symptom & scope
- ▸Narrow the layer
- ▸Mitigate before root cause
- ▸What changed?
- ▸Blast radius