CKAD Part17 – Volumes, PersistentVolumes & PersistentVolumeClaims
Kubernetes Volumes Internal container storage is ephemeral, which means that it exits only for the lifetime of the container. When the container is stopped any data written inside the container is lost. Volumes provide a means of storing data beyond the life of the container. The Pod definition below [...]
CKAD Prep Part 16 – Network Policies
Network Policies By default, a Pod can communicate with any other Pod in the same cluster. NetworkPolicies allow you to limit the network traffic allowed to and from Pods in the cluster. A sample NetworkPolicy is shown below. apiVersion: networking.k8s.io/v1 kind: NetworkPolicy metadata: name: sample-network-policy spec: podSelector: matchLabels: app: [...]
CKAD Prep Part 15 – Services
Kubernetes Services A Kubernetes Service object is an abstraction that provides network access to a dynamic set of Pod replicas. Rather than access Pods directly via their IPs, you can use a Service to proxy requests and deal with service discovery and load balancing. A Service usually uses a [...]
CKAD Prep Part 14 – Jobs & Cronjobs
Jobs & Cronjobs Jobs A Job is a Kubernetes object that executes a workload and then terminates once the workload is complete. When a Job finishes, the containers involved are terminated and the Pod transitions to the Completed state. Jobs and Pods are similar in that they're both used [...]
CKAD Prep Part 13 – Rolling Updates & Rollbacks
Rolling Updates & Rollbacks Rolling updates provide a mechanism for updating containers in a cluster without downtime. This powerful Kubernetes feature allows you to update containers while maintaining high availability. To see this in action we'll create a Deployment consisting of 3 nginx Pods using the definition below. Note [...]
CKAD Prep Part 12 – Deployments
Kubernetes Deployments A Kubernetes Deployment object provides a means of managing a group of Pod instances, known as replicas. The Deployment tells Kubernetes the type of Pod you want to run and the number of Pod instances. This is known as the desired state. Kubernetes will actively monitor the [...]
CKAD Prep Part 11 – Labels, Selectors & Annotations
Kubernetes - Labels, Selectors & Annotations Labels Labels are key/value pairs that are used to add metadata to Kubernetes objects. They can be used to select and group subsets of objects in the cluster. Labels are added to an object in the metadata.labels section of the object descriptor as [...]
CKAD Prep Part 10 – Kubernetes Liveness & Readiness Probes
Kubernetes Liveness & Readiness Probes Liveness Probe A Liveness probe indicates whether or not a container is healthy and is used by Kubernetes to determine when a container should be terminated and restarted. You define your own custom criteria for determining container health. For example, if your container is [...]
CKAD Prep Part 9 – Kubernetes Multi Container Pods
Kubernetes Multi Container Pods There are some use cases where you may want to run multiple containers inside the same Pod. For example, you could have a microservice running in one container that writes logs to a volume. A second container running a log agent could capture and push [...]
CKAD Prep Part 8 – Kubernetes Service Accounts
Kubernetes Service Accounts As a developer or a cluster admin, you interact with the Kubernetes apiserver via kubectl. A ServiceAccount is a Kubernetes object that allows an application running inside a Pod to access the Kubernetes apiserver. This is useful for applications that need to interact directly with the [...]