Software Containerisation

Table of Contents

Kubernetes architecture

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Kubernetes architecture

Control plane

1-3+ master nodes: do not run user workloads directly, but manage the cluster
kube-apiserver: exposes Kubernetes API
etcd: storage of key-value pairs for Kubernetes config
kube-scheduler: selects node on which to run new pods
kube-controller-manager: runs controller processes (Node, Replication, Endpoints, Service Account & Token controllers)
cloud controller manager: connects cluster to cloud provider’s API

Worker nodes

node/worker/minion: executes user workloads
kubelet: ensures that pods are running in node as declared by their specs
kube-proxy: network proxy, maintains network rules on nodes
pods: groups of containers that share storage/net resources

You interact with Kubernetes using kubectl. Kubectl config is in ~/.kube/config.

Nodes:

runs kubelet agent, kube-prxy pod, and network pod
- allows cluster manage pods that run on node
network pod: not by default via kubeadm, but Calico in microk8s

Namespaces:

used to create virtual clusters (avoid name conflicts, restrict resource usage, establish quotas, add policies)
K8s creates objects in default namespace
K8s components run in separate namespace – kube-system
new namespaces can be created with kubectl create namespace <name>
cannot be nested. persistent volumes and nodes are not in a namespace.