k8s pod ??

A pod is the smallest object model that you can create and run. You can add labels to a pod to identify a subset to run operations on. When you are ready to scale your app, you can use the label to tell Kubernetes which Pod you need to scale. 

A pod typically represents a process in your cluster. Pods contain at least one container that runs the job and additionally might have other containers in it called sidecars for monitoring, logging, and so on. Essentially, a pod is a group of containers.

$ kubectl (create|get|apply|delete) -f Resource.yaml

Kubernetes resource model

• Config maps: holds configuration data for pods to consume
• Daemon sets: ensures that each node in the cluster runs this pod
• Deployments: defines a desired state of a deployment object
• Events: provides life cycle events on pods and other deployment objects
• Endpoints: allows an inbound connections to reach the cluster services
• Ingress: a collection of rules that allows inbound connections to reach the cluster services
• Jobs: creates one or more pods and when they complete successfully, the job is marked as completed
• Node: a worker machine in Kubernetes
• Namespaces: multiple virtual clusters backed by the same physical cluster
• Pods: the smallest deployable units of computing that can be created and managed in Kubernetes
• Persistent volumes: provides an API for users and administrators to abstract details about how storage is provided from how it is consumed
• Replica sets: ensures that a specified number of pod replicas are running at any given time
• Secrets: holds sensitive information, such as passwords, OAuth tokens, and SSH keys
• Service accounts: provides an identity for processes that run in a pod
• Services: an abstraction that defines a logical set of pods and a policy by which to access them, sometimes called a microservice
• Stateful sets: the workload API object that manages stateful applications

Command to leave docker swarm

$ docker swarm leave --force

docker update the state of your service by using the command

docker service update

Update docker service with an updated number of replicas.

docker service update --replicas=5 --detach=true [servicename]

verify docker swarm node cluster

docker node ls

To add a worker to this docker swarm

docker swarm join \
    --token **** \
    10.0.120.3:2377