Chapter Two
Workloads and Core Objects
The objects you use every day — Pods, controllers, Services, configuration, and the workload types for batch, per-node, and stateful jobs. The heart of the platform.
This is the heart of Kubernetes. Almost everything you do day to day is creating, connecting, and configuring the objects in this chapter.
It starts with the Pod — the smallest unit that runs — then builds up: the controllers that keep Pods running, the labels that wire objects together, the Services and Ingress that route traffic, and the workload types for one-off jobs, per-node agents, and stateful systems.
Topics in This Chapter
Topic 05
Pods
The smallest deployable unit: one or more containers sharing a network namespace and storage. Why you almost never create one directly.
Topic 06
ReplicaSets and Deployments
The controller you actually use. A Deployment manages ReplicaSets to give you rolling updates, rollback, and a stable replica count.
Topic 07
Labels and Selectors
Key-value tags and the queries over them. The loose-coupling mechanism that lets Services find Pods and controllers own replicas.
Topic 08
Services
A stable virtual IP and DNS name in front of a changing set of Pods. ClusterIP, NodePort, and LoadBalancer, and how kube-proxy makes it work.
Topic 09
Ingress and the Gateway API
HTTP routing into the cluster — host and path rules, TLS — and the Gateway API that is replacing Ingress with a richer, role-oriented model.
Topic 10
ConfigMaps and Secrets
Decoupling configuration and credentials from images. How they mount as env vars or files, and why a Secret is only base64, not encryption.
Topic 11
Namespaces
Virtual clusters for scoping names, quotas, and access. The first unit of multi-tenancy, and what they do and do not isolate.
Topic 12
Jobs and CronJobs
Run-to-completion workloads and their scheduled cousin. Parallelism, retries, and the failure modes of cron in a cluster.
Topic 13
DaemonSets
One Pod per node, for agents that must run everywhere — log shippers, CNI, node exporters. How they track the node set.
Topic 14
StatefulSets
Stable identity and storage for stateful systems — databases, queues, clustered stores. Ordered rollout and per-replica volumes.
Topic 15
Init and Sidecar Containers
Ordered setup before the main container, and helper containers that run alongside it. The native sidecar lifecycle and the patterns it enables.