Author: Voxfor Lifetime.

Security

Audit a systemd Service With systemd-analyze security

An OK result from systemd-analyze security is not proof that a daemon is safe, and an EXPOSED result is not proof that…

Aug 11, 202612 min read

AI & Machine Learning

Measure RAG Retrieval Quality With Recall@K and MRR

A fluent answer cannot prove that Retrieval-Augmented Generation found the right evidence. The generator may write confidently from incomplete context, while a…

Aug 11, 202614 min read

DevOps

Design Prometheus Histogram Buckets Around Your SLO

A Prometheus p95 alert can cross a 300 ms service-level objective even when the exact 95th observation is 290 ms. The alert…

Aug 11, 202615 min read

Dedicated Server

How a 95th Percentile Bandwidth Commit Becomes a Bill

Start with the billing window: a 95th-percentile bandwidth bill is built from sampled rates, not from total transferred bytes and not from…

Aug 11, 202615 min read

DevOps

Test Ansible Idempotency With a Fail-Closed Second Run

Run the same Ansible playbook twice against unchanged state. The first normal run may make every necessary change; the second should finish…

Aug 11, 202614 min read

Linux

What QCOW2 File Size Tells You Before Reclaiming Space

A QCOW2 image has more than one meaningful size. Virtual size is the capacity visible to the guest, apparent file size is…

Aug 11, 202614 min read

Web Hosting

Calculate a Hosting Uptime SLA Before You Buy

A hosting uptime SLA becomes useful only after the percentage has a time window, a definition of good service, a measurement owner,…

Aug 11, 202614 min read

DevOps

n8n Queue Mode: Prove Every Execution Reaches a Worker

An n8n queue-mode deployment is ready for production only when a real trigger returns an execution ID that can be joined to…

Aug 11, 202619 min read

Database

PostgreSQL HOT Updates: Measure the Fillfactor Tradeoff

Lowering PostgreSQL table fillfactor can create more heap-only tuple (HOT) updates, but a copied value such as 70 or 80 is not…

Aug 11, 202614 min read

DevOps

Kubernetes Service Has No Endpoints: Trace the Missing Backend

A Kubernetes Service can exist, resolve in cluster DNS, and still have no usable backend. The shortest diagnosis is not to restart…

Aug 10, 202614 min read

Security

When DKIM Body Hash Fails, Trace the Post-Signing Change

dkim=fail (body hash did not verify) is not a generic instruction to replace a DNS record. It means the receiver canonicalized the…

Aug 10, 202616 min read

Linux

DNS Negative Caching: Why a New Record Still Fails

You add a DNS record, confirm that the authoritative server returns it, and still see NXDOMAIN from the resolver used by your…

Aug 10, 202615 min read

Linux

A Restic Restore Is Not Finished Until the Data Matches

Restic can restore bytes correctly and still return the wrong recovery point. latest is a selector, not a business decision: a shared…

Aug 10, 202615 min read

Security

Rotate SOPS age Recipients Without Losing Decryption

Changing an age recipient in SOPS is an access migration, not a one-command key swap. A safe rotation keeps the existing identity…

Aug 10, 202614 min read

DevOps

Test an HAProxy Graceful Reload Under Live Traffic

A successful HAProxy reload message is only one half of a safe change. The new worker must accept the intended traffic, while…

Aug 10, 202619 min read

Security

Rotate WordPress Security Salts: Prove What Gets Invalidated

Rotating WordPress security salts has one precise security effect: cookies and nonces created with the old secrets stop validating. That can end…

Aug 10, 202618 min read

Linux

Logrotate Not Rotating? Diagnose State and Permissions

The Logrotate job ran, yet the log file stayed put. That result does not prove Logrotate is broken. It may have loaded…

Aug 9, 202614 min read

DevOps

Prometheus Blackbox Exporter: Prove HTTP, DNS, and TLS

A green probe can still prove the wrong thing. An HTTP request may return 200 while serving an error page, a DNS…

Aug 9, 202615 min read

VPS Hosting

Test VPS Network Speed Across Route, Direction, and Time

A VPS speed test becomes useful only when you can answer which endpoint, route, direction, stream count, protocol, duration, and time window…

Aug 9, 202617 min read

DevOps

Forgejo Backups: Prove a Restore Before You Need It

A Forgejo backup can contain every Git object and still fail the team if issues, users, permissions, configuration or application secrets are…

Aug 9, 202614 min read

DevOps

Terraform to OpenTofu: Test State Before Switching

Replacing the terraform executable with tofu is easy. Proving that the new engine can read the same configuration, providers and state without…

Aug 9, 202611 min read