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Practical field notes for teams diagnosing email deliverability, DNS authentication, sender reputation, Linux, MTA, cloud, monitoring, and DevOps failures.

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Technical notes

Articles on email deliverability, DNS, Linux, MTA operations, DevOps, monitoring, and incident recovery.

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Short, practical guidance for teams that need to diagnose, repair, and run production email systems.

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Linux, MTA & Security · Sep 29, 2022 · 16 min read

Configure Your Own Squid Proxy Server: Secure Step-by-Step Guide

Install and secure an explicit Squid forward proxy with source ACLs, user authentication, safe ports, firewall rules, client configuration, logging, troubleshooting, and rollback.

Platform engineer operating a secure container workflow with isolated applications, image delivery, private networking, persistent storage, and observability

Linux, MTA & Security · Sep 1, 2022 · 21 min read

Docker Container

Learn what every Docker command and option does, then install Docker, run containers, use images, volumes, Dockerfiles, Compose, and add a node.

Infrastructure engineer supervising a controlled Chef policy pipeline through validation, staged promotion, Linux and Windows node convergence, and verification

Linux, MTA & Security · Aug 26, 2022 · 35 min read

Chef For Automation

Install Chef Workstation, build and test a cookbook, lock a Policyfile, add Linux and Windows nodes, promote safely, troubleshoot runs, and roll back.

Systems operator connecting through a verified SSH host-key checkpoint and bastion to terminal, file-transfer, network-device, and mobile access paths

Linux, MTA & Security · Aug 25, 2022 · 22 min read

Best SSH Clients

Compare current SSH clients for Windows, macOS, Linux, mobile, file transfer, automation, and teams, then secure host keys, credentials, bastions, and tunnels.

Linux administrator validating an APF ruleset while preserving an administrative access path and blocking untrusted traffic

Linux, MTA & Security · Jul 19, 2022 · 24 min read

Advanced Policy Firewall (APF)

A current guide to Advanced Policy Firewall for Linux, including dynamic DNS trust refresh, remote block lists, global policy, safe testing, IPv6, containers, and upgrades.

Two private office networks connected through plain VPN gateways by one monitored encrypted site-to-site tunnel

Linux, MTA & Security · May 21, 2022 · 13 min read

StrongSwan Site-to-Site VPN: Step-by-Step Guide

Build a StrongSwan IKEv2 site-to-site VPN with swanctl, secure proposals, routing, firewall and NAT controls, testing, troubleshooting, and rollback.

Administrator monitoring a protected request path through internet edge, Apache server, isolated PHP workers, and a private database

Linux, MTA & Security · Mar 16, 2022 · 27 min read

Secure Your LAMP Stack: Step-by-Step Hardening Guide

Harden Linux, Apache, PHP-FPM, MariaDB, TLS, headers, files, application secrets, logs, and backups with safe commands, verification, and rollback.

Two parallel web server configuration paths apply file protection, routing, caching, compression, response security, verification, and protected rollback

Linux, MTA & Security · Sep 4, 2021 · 22 min read

Secure and Speed Up Apache and Nginx: Configuration Guide

Protect files, control caching, enable compression, add security headers, and test safe redirects with current Apache .htaccess and equivalent Nginx configurations.

Two Linux server networking designs compare an active link with a standby failover path and a pair of active links grouped through an LACP switch

Linux, MTA & Security · Aug 22, 2021 · 18 min read

Linux Ethernet Bonding: Active-Backup and LACP with NetworkManager

Build and test Linux Ethernet bonding with NetworkManager or Netplan, including active-backup, 802.3ad LACP, monitoring, troubleshooting, and rollback.