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 # runner
 
-This repo is a small “appliance” (a handful of Bash scripts + systemd unit files) that runs a single
-GitHub Actions self-hosted runner on a Linux machine.
-
 If you’re new to self-hosted runners: it’s GitHub’s runner program, but running on your own machine
 instead of GitHub’s hosted runners.
 
-Linux notes:
-
-- This works on general Linux (Raspberry Pi is supported, but it’s not a requirement).
-- systemd is used to start/stop things reliably at boot.
+This is useful when you want to test code against a Linux host but you don’t want every workflow run to permanently
+mutate the machine. The core idea is to keep the runner operationally predictable (systemd-managed, reliable at boot),
+while running container-style job steps inside an ephemeral `systemd-nspawn` guest so filesystem changes made during a
+job are discarded when the guest is torn down. Writing to real devices (USB/ACM/TTY) is not reverted on teardown.
 
 What it aims to do: