The Life of a Block Device: Seven Names for One Disk, and Not One of Them Is Both Stable and Unique
Every name a Linux disk has is either a value stored inside it, and so copied by anything that copies the disk, or a description of the slot it is…
The Life of a Scheduled Job: Eight Stages, and the Failure You Should Fear Exits Zero
A scheduled job is the only routine thing on a Linux machine that destroys the evidence it ran by succeeding. Eight stages between the line you wrote and the person…
The Life of an Outbound Email: Four Addresses, and the One You Set Is the One Nobody Checks
The nine stages between an application calling sendmail and a person deciding they wanted it — and why every mechanism that judges the message authenticates an address somebody else chose.
The Life of a Log Line: Every Field Has an Author, and the Record Does Not Say Who
The standard way to answer “who logged in as root” is one of three commands: journalctl -t sshd, journalctl _COMM=sshd, or journalctl -u ssh. They are taught interchangeably. Here is…
Restoring a Linux Server: What the Backup Kept and the Restore Threw Away
The seven stages between a backup and a working machine, and the six decisions the restore makes that the backup did not. Why diff exits 0 on a tree that…
How Time Works on a Linux Machine: When the Clock Moves, Nothing Writes It Down
Stage 1: The clock nobody is keeping Run the hinge here, and then run the tool that is supposed to read what it finds: Three device paths, tried in order,…
Building a Container Image: What a Green Build Log Does Not Prove
Stage 1: Solved, not run Everyone learns the Dockerfile as a shell script: a list of commands, executed top to bottom, one after another. That model was correct, and both…
What Ships in Your Container Image, and What Happens to It After You Push
Stage 1: The build context, and what got in that you did not put there The build starts by sending a directory to the builder. Not the files your Dockerfile…
The Life of a DNS Zone: What Your Parent Publishes About You
Stage 1: What the parent publishes about you A registry holds almost nothing about your domain. Three things, and you can write none of them directly: What the registry actually…
The Half of Patching That Happens After the Patch is Installed
One of this site’s own pages carries a sentence that is true and stops exactly one clause short. It is in Hardening a Public-Facing Service, in the step about updates:…