Now that we have an internal SSH certificate authority, instead of
explicitly listing all M×N keys for each user and client machine, we can
list only the CA certificate in the SSH authorized keys file for the
*core* user. This will allow any user who presents a valid, signed SSH
certificate for the *core* principal to log in.
The first host running Fedora CoreOS (FCOS) is
*k8s-aarch64-n0.pyrocufflink.blue*. This is a Raspberry Pi 4 that is a
specialized member of the Kubernetes cluster. It hosts the Zigbee2MQTT
and ZWaveJS2MQTT containers, and has the Zigbee and ZWave controller USB
devices attached.