Kubernetes Container API

// A single application container that you want to run within a pod.
type Container struct {
	// Name of the container specified as a DNS_LABEL.
	Name string `json:"name"`

	// Docker image name.
	// More info: https://kubernetes.io/docs/concepts/containers/images
	Image string `json:"image,omitempty"`

	// Entrypoint array.
	// More info: https://kubernetes.io/docs/tasks/inject-data-application/define-command-argument-container/#running-a-command-in-a-shell
	Command []string `json:"command,omitempty"`

	// Arguments to the entrypoint.
	// More info: https://kubernetes.io/docs/tasks/inject-data-application/define-command-argument-container/#running-a-command-in-a-shell
	Args []string `json:"args,omitempty"`

	// Periodic probe of container liveness. Container will be restarted if the probe fails.
	// More info: https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes
	LivenessProbe *Probe `json:"livenessProbe,omitempty"`

	// Periodic probe of container service readiness. Container will be removed from service endpoints if the probe fails.
	// More info: https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle#container-probes
	ReadinessProbe *Probe `json:"readinessProbe,omitempty"`

	// List of ports to expose from the container. Exposing a port here gives
	// the system additional information about the network connections a
	// container uses, but is primarily informational.
	Ports []ContainerPort `json:"ports,omitempty"`

	// List of sources to populate environment variables in the container.
	EnvFrom []EnvFromSource `json:"envFrom,omitempty"`

	// List of environment variables to set in the container.
	Env []EnvVar `json:"env,omitempty"`

	// Compute Resources required by this container.
	// More info: https://kubernetes.io/docs/concepts/configuration/manage-compute-resources-container/
	Resources ResourceRequirements `json:"resources,omitempty"`

	// Pod volumes to mount into the container's filesystem. Cannot be updated.
	VolumeMounts []VolumeMount `json:"volumeMounts,omitempty"`

	// Image pull policy. One of Always, Never, IfNotPresent.
	// More info: https://kubernetes.io/docs/concepts/containers/images#updating-images
	ImagePullPolicy PullPolicy `json:"imagePullPolicy,omitempty"`

	// Security options the pod should run with.
	// More info: https://kubernetes.io/docs/concepts/policy/security-context/
	// More info: https://kubernetes.io/docs/tasks/configure-pod-container/security-context/
	SecurityContext *SecurityContext `json:"securityContext,omitempty"`
}

// shouldPullImage returns whether we should pull an image according to
// the presence and pull policy of the image.
func shouldPullImage(container *v1.Container, imagePresent bool) bool {
	if container.ImagePullPolicy == v1.PullNever {
		return false
	}

	if container.ImagePullPolicy == v1.PullAlways ||
		(container.ImagePullPolicy == v1.PullIfNotPresent && (!imagePresent)) {
		return true
	}

	return false
}

readinessProbe:
  exec:
    command:
      - cat
      - /tmp/health
  initialDelaySeconds: 5
  periodSeconds: 5

  ports:
  - name: liveness-port
    containerPort: 8080
    hostPort: 8080

  livenessProbe:
    httpGet:
      path: /healthz
      port: liveness-port
    failureThreshold: 1
    periodSeconds: 10

apiVersion: v1
kind: Pod
metadata:
  name: dapi-test-pod
spec:
  containers:
    - name: test-container
      image: k8s.gcr.io/busybox
      command: [ "/bin/sh", "-c", "env" ]
      envFrom:
      - configMapRef:
          name: special-config
  restartPolicy: Never
kubectl logs pod

$ kubectl create configmap special-config --from-literal=var=value
$ kubectl create -f pod.yaml
$ kubectl logs dapi-test-pod
KUBERNETES_PORT=tcp://10.96.0.1:443
KUBERNETES_SERVICE_PORT=443
HOSTNAME=dapi-test-pod
SHLVL=1
HOME=/root
var=value

apiVersion: v1
kind: Pod
metadata:
  name: cpu-demo
  namespace: cpu-example
spec:
  containers:
  - name: cpu-demo-ctr
    image: vish/stress
    resources:
      limits:
        cpu: "1"
      requests:
        cpu: "0.5"
    args:
    - -cpus
    - "2"

$ kubectl describe node
Non-terminated Pods:         (10 in total)
  Namespace                  Name                                          CPU Requests  CPU Limits  Memory Requests  Memory Limits  AGE
  ---------                  ----                                          ------------  ----------  ---------------  -------------  ---
  default                    busybox                                       0 (0%)        0 (0%)      0 (0%)           0 (0%)         30m
  default                    cpu-demo                                      500m (12%)    1 (25%)     0 (0%)           0 (0%)         45s