Topic

Running the box: Docker, Linux, the JVM

What actually happens between systemd and your fat jar.

2 posts · 12 min total · updated 8 Jul 2026

Where does app.jar find its dependencies? The JVM rule hiding in your Dockerfile

Spring Boot's layered jar extraction splits your dependencies from your code for faster Docker rebuilds. But the mechanism that makes the pieces find each other at runtime isn't Spring at all — it's a JVM rule from 1998.

8 Jul 2026 · 5 min read

#jvm
#classpath
#spring-boot
#docker

Systemctl isn't the thing that runs your services

systemctl doesn't start your services — it's a client that phones PID 1. A mental model of systemd built from the D-Bus call down to the kernel cgroups that make it all reliable.

1 Jul 2026 · 7 min read

#cgroups
#systemd
#devops
#linux

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