Linux internals · systems · security
Deep systems writing where every claim is shown running — interactive visualizers, scenario flashcards, and labs where you type the command yourself.
Dispatches from the engine room
The name is the bug. Type past the end of the buffer and watch what the hardware will happily let you do.
WRITTEN 8CAPACITY 8OVERRUN 0STATUS OK
The same idea, at rest
Offset, bytes, ASCII — the hex is computed from the letters beside it, so this is a real dump rather than a picture of one. Everything on this site is built to the same rule: if a claim can be shown running, it is.
Interactive sandboxes with state machines, syscall players and live bit calculators.
Step the newgrp syscall player, simulate the DAC flowchart for Alice, Bob, Carol and root, and toggle the 16-bit i_mode calculator.
8 modulesLaunch
Follow an HTTP request as it crosses runtime boundaries, slips past sanitation and reaches execution — with the control that stops each hop.
Flagship #2Scheduled
Trace a packet into a VPC subnet: rule evaluation order, stateful versus stateless return traffic, and where ephemeral ports get dropped.
Flagship #3Scheduled
Scenario flashcards that test whether the mechanics actually landed, plus terminal labs with requirements and a solution you unlock when ready.
Stale credentials, fsuid versus euid, SGID inheritance, the 16-bit i_mode bitmask, and the real order of root’s override. Flip for the kernel answer.
Start practisingA scenario, a task list and hard requirements — background jobs with nohup, SGID collaboration directories, setuid audits. Write the command, then check yourself.
Long-form deep-dives, syndicated across Hashnode, Medium and this reader.
You add a developer to a group with usermod -aG, but their open terminal still gets Permission denied. We trace task_struct credentials, the six-step newgrp syscall sequence, in-memory inodes, and the exact evaluation order inside generic_permission().
Infrastructure systems engineer
I design, implement, troubleshoot and operate the systems that keep modern workplaces connected — then write up the parts that are usually explained wrong.