Kubernetes Architecture
The smallest unit manageable in Kubernetes is a pod
A pod consists of one or more containers with its storage resources and IP.
A master node provides basic cluster services such as APIs and controllers.
A worker node performs work in a Kubernetes cluster. Application pods are scheduled into worker nodes.
A Controller is a Kubernetes process that watches resources and makes changes based on that state.
Services define a single, persistent IP/port combination that provides access to a pool of pods.
Replication Controllers -> A Kubernetes resource that defines how pods are replicated (horizontally scaled) into different nodes. Replication controllers are a basic Kubernetes service to provide high availability for pods and containers.
Persistent Volumes -> Define storage areas to be used by Kubernetes.
Persistent Volume Claims -> Represent a request for storage by a pod. PVCs links a PV to a pod so its container can make use of it.
ConfigMaps and Secrets -> Contains a set of keys and values that can be used by other resources. Passwords, credentials, etc.
Deployment Config (dc) -> Represents the set of containers included in a pod, and the deployment strategies to be used. A dc also provides a basic but extensible continuous delivery workflow.
Build Config (bc) -> Defines a process to be executed in the OpenShift project. Used by the OpenShift Source-to-image (S2I) feature to build a container image from application source code stored in a Git repository.
Routes -> Represent a DNS host name recognized by the OpenShift router as an ingres point for applications and microservices.
OpenShift 4
OpenShift Container Platform 4 uses Red Hat Enterprise Linux CoreOS, a container-oriented operating system. This OS is specifically designed to run containerized applications from OpenShift and provide simpler installation.
Installation of OCP 4.1 is as simple as running a single command.
Updates are simple and automatic.
Operators are a convenient way to deploy applications.
The oc utility -> primary way of interacting with an RHOCP cluster
Before interacting with the cluster:
$> oc login <clusterUrl>
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