Kubernetes Cheatsheet

Volumes

Use this Kubernetes reference while you build software engineering projects, review code for technical interview prep, or polish examples for a software engineer resume.

Volume Types Quick Reference

Type	Lifecycle	Use case
`emptyDir`	Pod lifetime	Scratch space, cache, inter-container sharing
`hostPath`	Node lifetime	Node-local files, DaemonSets
`configMap` / `secret`	Pod lifetime	Inject config files
`persistentVolumeClaim`	Independent	Durable storage (databases, uploads)
`projected`	Pod lifetime	Combine multiple sources into one mount
`downwardAPI`	Pod lifetime	Expose Pod metadata as files
`nfs`	External	Shared read-write across Pods
`csi`	External	Cloud block/file storage via CSI drivers

emptyDir

Created when Pod is scheduled; deleted when Pod is removed.

spec:
  volumes:
  - name: cache
    emptyDir:
      medium: ""          # "" = disk, "Memory" = tmpfs
      sizeLimit: 500Mi
  containers:
  - name: app
    volumeMounts:
    - name: cache
      mountPath: /tmp/cache

hostPath

Mounts a path from the Node's filesystem. Use sparingly; breaks Pod portability.

spec:
  volumes:
  - name: docker-sock
    hostPath:
      path: /var/run/docker.sock
      type: Socket    # File | Directory | Socket | CharDevice | BlockDevice

Persistent Volume (PV) and Persistent Volume Claim (PVC)

Admin creates PV  ──►  Developer creates PVC  ──►  Pod uses PVC

PersistentVolume (admin-managed)

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-data
spec:
  capacity:
    storage: 20Gi
  accessModes:
  - ReadWriteOnce
  reclaimPolicy: Retain       # Retain | Recycle | Delete
  storageClassName: standard
  hostPath:                   # use cloud-specific driver in production
    path: /mnt/data

PersistentVolumeClaim (developer-facing)

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 10Gi
  storageClassName: standard  # must match PV or StorageClass

Use PVC in a Pod

spec:
  volumes:
  - name: data
    persistentVolumeClaim:
      claimName: my-pvc
  containers:
  - name: db
    image: postgres:16
    volumeMounts:
    - name: data
      mountPath: /var/lib/postgresql/data

Access Modes

Mode	Short	Meaning
`ReadWriteOnce`	RWO	R/W by a single Node
`ReadOnlyMany`	ROX	Read-only by many Nodes
`ReadWriteMany`	RWX	R/W by many Nodes (NFS, EFS, GCS)
`ReadWriteOncePod`	RWOP	R/W by a single Pod (k8s 1.22+)

StorageClass (dynamic provisioning)

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: fast
  annotations:
    storageclass.kubernetes.io/is-default-class: "true"
provisioner: ebs.csi.aws.com
parameters:
  type: gp3
  iops: "3000"
  throughput: "125"
reclaimPolicy: Delete
allowVolumeExpansion: true
volumeBindingMode: WaitForFirstConsumer

When a PVC references a StorageClass, a PV is automatically provisioned.

Expand a PVC

# StorageClass must have allowVolumeExpansion: true
kubectl patch pvc my-pvc -p '{"spec":{"resources":{"requests":{"storage":"20Gi"}}}}'
kubectl get pvc my-pvc   # watch status.capacity

Projected Volume

Combine ConfigMap, Secret, ServiceAccountToken, and DownwardAPI into one mount:

spec:
  volumes:
  - name: combined
    projected:
      sources:
      - configMap:
          name: app-config
      - secret:
          name: db-secret
      - serviceAccountToken:
          path: token
          expirationSeconds: 3600

DownwardAPI

Expose Pod/container metadata as files:

spec:
  volumes:
  - name: podinfo
    downwardAPI:
      items:
      - path: "namespace"
        fieldRef:
          fieldPath: metadata.namespace
      - path: "cpu_limit"
        resourceFieldRef:
          containerName: app
          resource: limits.cpu

kubectl Volume Commands

Command	What it does
`kubectl get pv`	List PersistentVolumes
`kubectl get pvc`	List PersistentVolumeClaims
`kubectl get sc`	List StorageClasses
`kubectl describe pvc my-pvc`	Show binding status, events
`kubectl delete pvc my-pvc`	Delete PVC (PV fate = reclaimPolicy)
`kubectl patch pvc my-pvc ...`	Resize PVC