PodSpecs

PodSpecs are the specifications that describe the desired state of a pod in Kubernetes. They form the core of a Pod object and define what runs inside the pod, how it is scheduled, and how it interacts with the surrounding environment. PodSpecs are typically embedded in Pod templates used by higher-level controllers to create and manage pods.

A PodSpec specifies the pod’s components and runtime behavior. The containers field defines one or more container specifications, each including the container image, name, ports, environment variables, resource requests and limits, command and arguments, and volume mounts. Init containers can be defined to run before app containers. Volumes describe data storage for the pod and are referenced by containers via volumeMounts. Pod-level settings cover restartPolicy, terminationGracePeriodSeconds, dnsPolicy, hostNetwork, hostPID, and hostIPC. Networking and identity options include serviceAccountName, automountServiceAccountToken, imagePullSecrets, and imagePullPolicy. Scheduling and placement are controlled with nodeSelector, affinity, tolerations, topologySpreadConstraints, schedulerName, and priorityClassName. Additional pod-level controls include securityContext, runtimeClassName, and various probes and lifecycle hooks inside containers.

PodSpecs are used by controllers such as Deployments, StatefulSets, DaemonSets, Jobs, and ReplicaSets. The spec in these controllers’ templates determines the pods that will be created and managed, and changes to the PodSpec can trigger rollouts or restarts as part of the controller’s reconciliation process. Pods created from a PodSpec are instantiated by the API server, typically described in YAML or JSON and applied via kubectl or client libraries.