PodSpec

PodSpec is the specification that describes the desired state of a Pod in Kubernetes. It is a core part of the Pod API object and defines the runtime requirements that Kubernetes should deliver when creating and running a pod. The PodSpec focuses on what containers and volumes the pod should contain, how they should be configured, and various scheduling and networking settings that affect the pod’s execution.

At the heart of a PodSpec are containers. The containers array specifies one or more container definitions, each typically including a name and an image. Additional container-level settings control how the container runs, such as command and arguments, environment variables, resource requests and limits, ports, and volumeMounts that attach volumes to the container. Containers may also define lifecycle hooks, probes for health and readiness, and features like stdin or TTY support. A PodSpec can also include initContainers, which run before the main containers start.

Volumes defined in the PodSpec provide persistent or ephemeral storage to the containers. Each volume is given a name and a volume type (for example, emptyDir, hostPath, persistentVolumeClaim, configMap, secret, or downwardAPI). The containers reference these volumes via volumeMounts.

Beyond containers and volumes, the PodSpec includes scheduling and networking-related settings. These include restartPolicy, dnsPolicy, serviceAccountName, imagePullSecrets, automountServiceAccountToken, nodeSelector, affinity, tolerations, securityContext, runtimeClassName, hostNetwork, hostPID, and hostIPC. Other fields cover timing and lifecycle controls, such as terminationGracePeriodSeconds and activeDeadlineSeconds, as well as DNS configuration and priority classes.

PodSpec is used by Pods directly and by higher-level controllers through PodTemplateSpec to describe the desired state of pods created by those controllers.