Kubernetes Basic Tutorial-1
What is Kubernetes?
An Introduction to Kubernetes (also known as k8s or kube) is an open-source container-orchestration system for automating computer application deployment, scaling, and management. It was originally designed by Google and is now maintained by the Cloud Native Computing Foundation. (Wikipedia, kubernetes.io)
Why you need Kubernetes and what it can do
Containers are a good way to bundle and run your applications. In a production environment, you need to manage the containers that run the applications and ensure that there is no downtime. For example, if a container goes down, another container needs to start.
That’s how Kubernetes comes to the rescue! Kubernetes provides you with a framework to run distributed systems resiliently. It takes care of scaling and failover for your application, provides deployment patterns, and more. For example, Kubernetes can easily manage a canary deployment for your system.
Kubernetes provides you with:
- Service discovery and load balancing
- Storage orchestration
- Automated rollouts and rollbacks
- Automatic bin packing
- Self-healing
- Secret and configuration management
Cluster: If our a node fails, our app will be down. So a cluster is a set of nodes grouped together. Even if one node fails, your application will still be accessible from the other nodes. In addition, having multiple nodes helps in sharing the computational load as well. A Kubernetes cluster should be:
- Secure.
- Easy to use.
- Extendable.
Nodes: A node is a machine either physical or virtual machine on which Kubernetes is installed. A node is a worker machine and this is where containers inside the pods will be launched by Kubernetes.
Kubernetes Components:
Master Node Components
API Server: The API server is a component of the Kubernetes control plane that exposes the Kubernetes API. The API server is the front end for the Kubernetes control plane.
Controller Manager: Control Plane component that runs controller processes.
- Logically, each controller is a separate process, but to reduce complexity, they are all compiled into a single binary and run in a single process.
- These controllers include:
- Node controller: Responsible for noticing and responding when nodes go down.
- Replication controller: Responsible for maintaining the correct number of pods for every replication controller object in the system.
- Endpoints controller: Populates the Endpoints object (that is, joins Services & Pods).
- Service Account & Token controllers: Create default accounts and API access tokens for new namespaces.
ETCD: Consistent and highly-available key-value store used as Kubernetes’ backing store for all cluster data.
Scheduler: It is a service in master responsible for distributing the workload or containers across multiple nodes.
Worker Node Components:
Pod: A pod is the smallest deployable unit that can be managed by Kubernetes. A pod is a logical group of one or more containers that share the same IP address and port space. The main purpose of a pod is to support co-located processes, such as an application server and its local cache.
Kubelet: Creating and managing containers. When the control plane needs something to happen in a node, the kubelet executes the action.
Kube-proxy: Manages network connectivity and maintains network rules across nodes.
