# The Jailed Engineer Hardened systems from silicon to security: Deep dives into FreeBSD, custom routers, and ZFS. Page: Feed: --- ## [From Electronics Engineer to FreeBSD 15.1: An MSR Offset Bug on AMD Zen 3](https://jailedengineer.substack.com/p/from-electronics-engineer-to-freebsd) _2026-06-28 · Paulo Fragoso_ The Discovery: A Bug Hidden in Plain Sight ## [Resurrecting a University Physics Cluster: Moving from Rocks to OpenHPC 3 on Rocky Linux 9](https://jailedengineer.substack.com/p/resurrecting-a-university-physics) _2026-06-28 · Paulo Fragoso_ How a 2013 Dell cluster at UFPE was saved from a 5-year dormancy and modernized using Rocky Linux 9.7, Warewulf 4, and Slurm 25.11. ## [The Boot Glitch: Registering an External UART on Linux 2.6.36 for ARMv5](https://jailedengineer.substack.com/p/the-boot-glitch-registering-an-external) _2026-04-07 · Paulo Fragoso_ How wrong interrupt pin configuration and a missing flag brought a TL16C2550 dual-UART to life on the AT91SAM9G45 — 15 years before the code went public. ## [The Embedded Frontier: From i386 PCs to Jailed Multi-Core Routers](https://jailedengineer.substack.com/p/the-embedded-frontier-from-i386-pcs) _2026-01-01 · Paulo Fragoso_ How we scaled a wireless broadband empire in Recife and evolved into High-Availability Managed Security using FreeBSD Jails. ## [The Multi-Headed Daemon: Building a 24/7 Data Center Video Wall on FreeBSD](https://jailedengineer.substack.com/p/the-multi-headed-daemon-building) _2025-12-26 · Paulo Fragoso_ How I used a NVIDIA NVS 810, Xinerama, and shell scripting to create a resilient, 8-monitor NOC display that survives any power loss. ## [The 16x Leap: How I Saved a 15-Year-Old Mail Server](https://jailedengineer.substack.com/p/the-16x-leap-how-i-saved-a-15-year) _2025-12-25 · Paulo Fragoso_ From PERC 6/i bottlenecks to ZFS mastery: Scaling a Dell T410 to 21 million inodes on FreeBSD.