The trick is that to have a real chance of administering a k8s cluster you need Linux kernel knowledge (namespaces to understand docker, a bit of iptables, VXLA

The trick is that to have a real chance of administering a k8s cluster you need Linux kernel knowledge (namespaces to understand docker, a bit of iptables, VXLAN or something similar to understand CNI/overlay network, how the container network namespace is connected via veth pipe, chroot/bind mounts, a very little bit of SElinux/apparmor/seccomp), systemd to see how it all starts, etcd to know about the consistency/consensus layer.. so far this is almost identical for all container orchestrator/scheduler platforms (nomad, docker swarm). Then there are the specific k8s concepts: pod (containers that share a network and PID namespace), service (a name, a TCP and/or UDP port number, and the name/selector of the target pod), ingress (HTTP routing, basically haproxy/nginx/envoy or other layer 7 stuff), LoadBalancer (the magic API that connects your cluster to the outside world, allocates IP addresses for Services/Ingresses). Then there are the background parts that take the YAML and convert it into actual running stuff: apiserver (this is the central info hub, kubectl and kubelets and controllers all talk to this basically), kubelet is the actual agent on each node, controllers have control loops and those actually calculate the necessary actions/operations to achieve what the YAML declared. Then there are the subsystems: storage (persistent volume claims and PVs), settings (secrets - see vault too - and configmaps, and various special/custom resources like a TLS certificate, these are stored in etcd, through the apiserver of course), CNI networking flavors and knobs, an endless list of kubelet and apiserver command line arguments, PCI passthrough for GPUs or HSMs or whatever. And of course there's RBAC, security, admission webhooks, see how nowadays Authz and Authn is done through a "lookaside" OpenId Connect service (some Ingress Controllers support these out of the box).