All Kuberneters - Components

 

Kubernetes Core Resources Explained

1. Pods

What It Is

A Pod is the smallest deployable unit in Kubernetes.
It contains one or more containers that share:

  • Network
  • Storage
  • Lifecycle

Used For

  • Running application containers
  • Grouping tightly coupled containers together

Example

A web application container running inside a pod.


2. Deployments

What It Is

A Deployment manages Pods and ReplicaSets.

Used For

  • Rolling updates
  • Application version upgrades
  • Scaling applications
  • Self-healing applications

Example

Deploying 3 replicas of an NGINX application.


3. ReplicaSets

What It Is

A ReplicaSet ensures a specified number of pod replicas are always running.

Used For

  • High availability
  • Maintaining desired pod count

Example

Keeping 5 backend pods running at all times.


4. DaemonSets

What It Is

A DaemonSet ensures one pod runs on every node (or selected nodes).

Used For

  • Monitoring agents
  • Log collectors
  • Security agents

Example

Running Fluentd or Prometheus Node Exporter on all nodes.


5. StatefulSets

What It Is

A StatefulSet manages stateful applications.

Features

  • Stable pod names
  • Persistent storage
  • Ordered deployment/startup

Used For

  • Databases
  • Kafka
  • Elasticsearch

Example

Running MySQL with persistent volumes.


6. Services

What It Is

A Service exposes pods internally or externally.

Types

  • ClusterIP
  • NodePort
  • LoadBalancer
  • ExternalName

Used For

  • Stable networking
  • Load balancing
  • Service discovery

Example

Exposing frontend pods to users.


7. Ingress

What It Is

Ingress manages external HTTP/HTTPS access to services.

Used For

  • URL routing
  • SSL termination
  • Reverse proxy

Example

Routing:

  • app.example.com → frontend service
  • api.example.com → backend service

8. Jobs

What It Is

A Job runs a task until completion.

Used For

  • Batch processing
  • One-time tasks
  • Database migrations

Example

Running a backup script once.


9. CronJobs

What It Is

A CronJob schedules Jobs periodically.

Used For

  • Automated backups
  • Scheduled reports
  • Cleanup tasks

Example

Running a backup every midnight.


10. ConfigMaps

What It Is

ConfigMaps store non-sensitive configuration data.

Used For

  • Environment variables
  • Application configuration files

Example

Storing application settings.


11. Secrets

What It Is

Secrets store sensitive information securely.

Used For

  • Passwords
  • API keys
  • Tokens
  • Certificates

Example

Database password storage.


12. Nodes

What It Is

A Node is a worker machine in Kubernetes.

Types

  • Master/Control Plane Node
  • Worker Node

Used For

  • Running pods and workloads

Components

  • Kubelet
  • Container runtime
  • Kube-proxy

13. PersistentVolumes (PV)

What It Is

A PersistentVolume is cluster storage provisioned for applications.

Used For

  • Persistent data storage

Example

Disk storage for databases.


14. PersistentVolumeClaims (PVC)

What It Is

A PVC requests storage from a PersistentVolume.

Used For

  • Dynamically allocating storage to pods

Example

A pod requesting 10GB storage.


15. ServiceAccounts

What It Is

A ServiceAccount provides identity for pods.

Used For

  • API authentication
  • Access control within cluster

Example

A pod accessing Kubernetes API securely.


16. Roles

What It Is

A Role defines permissions within a namespace.

Used For

  • RBAC authorization

Example

Allowing read access to pods in a namespace.


17. RoleBindings

What It Is

A RoleBinding assigns a Role to users, groups, or ServiceAccounts.

Used For

  • Granting namespace-level permissions

Example

Binding pod-reader role to a developer.


8. ClusterRoles

What It Is

A ClusterRole defines cluster-wide permissions.

Used For

  • Access across namespaces
  • Cluster-level resources

Example

Allowing node read access cluster-wide.


19. ClusterRoleBindings

What It Is

A ClusterRoleBinding assigns ClusterRoles to users or ServiceAccounts.

Used For

  • Granting cluster-wide access

Example

Giving admin privileges to DevOps team


Quick Summary Table

ResourcePurpose
PodsRun containers
DeploymentsManage stateless applications
ReplicaSetsMaintain pod count
DaemonSetsRun pod on every node
StatefulSetsManage stateful applications
ServicesExpose applications
IngressHTTP/HTTPS routing
JobsRun one-time tasks
CronJobsSchedule recurring tasks
ConfigMapsStore configuration
SecretsStore sensitive data
NodesWorker machines
PersistentVolumesProvide storage
PersistentVolumeClaimsRequest storage
ServiceAccountsPod identity
RolesNamespace permissions
RoleBindingsAssign namespace permissions
ClusterRolesCluster-wide permissions
ClusterRoleBindingsAssign cluster-wide permissions


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