Kubernetes
Kubernetes is an open-source system that runs containerised applications across a group of machines, keeping the running state matched to a declared one.
What is kubernetes?
Kubernetes is an open-source system that runs containerised applications across a group of machines, keeping the running state matched to a declared one.
Plain and technical
You tell Kubernetes what you want (three copies of this application, reachable at this address, with this much memory), and it works out which machines to run them on and keeps them running. If a machine fails, it moves the work elsewhere without anyone intervening.
Kubernetes is a set of control loops. The control plane (API server, etcd, scheduler and controller manager) stores desired state and continuously reconciles actual state towards it. Each node runs a kubelet that realises the pods assigned to it, a container runtime, and kube-proxy for service networking. Changes are eventually consistent: a successful apply means the desired state was recorded, not that it has taken effect.
What it looks like in practice
Nearby vocabulary
Containerization
Containerization packages an application together with its dependencies into an image that runs identically on any machine with a compatible container runtime.
GitOps
GitOps is an operating model in which a system desired state is declared in Git and an automated process continuously reconciles the running system to it.
How DevOpsArk handles kubernetes
Articles on this subject
Kubernetes architecture explained: the parts that matter operationally
What each Kubernetes component actually does, which ones you will meet during an incident, and the mental model that makes cluster behaviour predictable.
Kubernetes monitoring: what to measure and why
A practical guide to Kubernetes monitoring: the cluster, node and workload signals that predict failure, the ones that only look useful, and how to alert on them without drowning.
More definitions
See these concepts in a running system
A 30-minute walkthrough against your own infrastructure rather than a slide about the theory.