High Linux load: what evidence should you collect first?
Use load, CPU, memory and I/O together to distinguish compute contention from blocked work.
2026.10.043 min readload averageCPUI/O
All notes.
Start with a specific problem. Find an investigation you can verify.
The notebook / FIELD NOTES
10 notesA backup is accepted when a restore succeeds
Use PostgreSQL logical backups to connect integrity checks, restore drills and RPO / RTO.
2026.10.043 min readPostgreSQLBackupsRestore drills
DNS troubleshooting: separate authoritative records from caches
Check NS, A/AAAA, CNAME and TTL to distinguish incorrect records, cache differences and connection failures.
2026.10.043 min readDNSdigTLS
What belongs in an actionable incident record?
Organize investigation around impact, a timeline and tested hypotheses, then make improvements trackable.
2026.10.043 min readIncident responseRunbooksPostmortems
CrashLoopBackOff: start with the previous exit
Connect termination reasons, previous logs, events and probes before restarting hides the evidence.
2026.10.043 min readPodContainer logsProbes
Nginx 502 and 504: trace the request through each layer
Use error logs to distinguish connection and response failures, then check upstream health, connections and timeouts.
2026.10.043 min readNginx502504
Install and configure OpenVPN: UDP and TCP in practice
Set up OpenVPN on Ubuntu with complete UDP and TCP server and client configurations, covering certificates, forwarding, DNS, full-tunnel egress and certificate revocation.
2026.10.0414 min readOpenVPNUDPTCPVPN
Prometheus latency: aggregate buckets before calculating quantiles
Calculate P95 correctly for classic histograms and investigate traffic, errors and latency together.
2026.10.043 min readPromQLP95Histogram
Kubernetes releases: define rollback conditions before deployment
Prepare version history, an observation window and rollback actions for a release you can verify.
2026.10.043 min readDeploymentReleasesRollback
Build a strongSwan IKEv2 VPN: certificates, routing and DNS validation
Build a password-authenticated remote-access VPN with swanctl, covering certificates, address pools, firewall rules, split routing and DNS, with lessons from maintaining older installations.
2026.10.0412 min readstrongSwanIKEv2VPNDNS
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