Kubernetes Cluster

• A group or pool of nodes form a powerful machine, which is a cluster
• When you deploy programs in cluster, it intelligently distributes the work to available nodes

# cluster details
kubectl cluster-info



# troubleshoot cluster
kubectl cluster-info dump

Kubernetes Config

• Modify cluster config and switch between context of a cluster
• You can have different config for a single cluster; every single config is called context

# view current kubectl context/config
kubectl view config

# switch context/config of a cluster
kubectl config set current-context config-name
(i.e., kubectl config set current-context minikube)

# list all the available context/config
kubectl config get-contexts

Kubernetes Node

• A node can be a physical machine or virtual machine

LIST NODES
# list all nodes in a cluster
kubectl get nodes



# list all nodes in a cluster with details [Internal/External IP, etc.,] 
kubectl get nodes -o wide

# get External IP of a node in a cluster
kubectl get nodes -o jsonpath='{.items[*].status.addresses[?(@.type=="InternalIP")].address}'
[get Internal IP of a node in a cluster]
kubectl get nodes -o jsonpath='{.items[*].status.addresses[?(@.type=="ExternalIP")].address}'

DELETE NODES
# remove a node from the service
kubectl drain 
kubectl drain --ignore-daemonsets --force
(e.g., kubectl drain minikube --ignore-daemonsets --force)

# uncordon the drained node
kubectl uncordon
(e.g., kubectl uncordon minikube)

MANIPULATE NODES
# troubleshoot node
kubectl describe node node_name
(i.e., kubectl describe node minikube)

Kubernetes Namespace

• Namespace is intended for in use of environments

CREATE NAMESPACE
# create namespace
kubectl create namespace namespace_name
(i.e., kubectl create namespace zalenium)

LIST NAMESPACE
# list all the namespaces
kubectl get namespaces

# list all the namespaces with labels
kubectl get namespaces --show-labels

# list specific namespace with labels
kubectl get namespace namespace_name --show-labels
(i.e., kubectl get namespace zalenium --show-labels)



# list all namespaces with namespace counts
kubectl get pods --all-namespaces -o jsonpath="{..namespace}" |tr -s '[[:space:]]' '\n' |sort |uniq -c

DELETE NAMESPACE
# delete all namespaces
kubectl delete --all namespaces

# delete specific namespace
kubectl delete namespace namespace_name
(i.e.,
kubectl delete --all pods --namespace=zalenium
kubectl delete namespace zalenium
)

Kubernetes Service

• A service is a grouping of Pods running on a cluster; you can have many services in a cluster; moreover, it helps you as a load balancer, and provide zero-downtime application deployments

LIST SERVICES
# list all the services in default namespace
kubectl get service
kubectl get services


# list all the services in another namespace
kubectl get services --namespace namespace_name
(i.e., kubectl get services --namespace zalenium)

# list all the services with details [selector]
kubectl get services --namespace namespace_name -o wide
(i.e., kubectl get services --namespace zalenium -o wide)

# list all the services with selector filter
kubectl get services --all-namespaces --selector=selector_name
(i.e., kubectl get services --all-namespaces --selector=app.kubernetes.io/name=zalenium -o wide)

# list all the services from entire namespace
kubectl get services --all-namespaces

DELETE SERVICES 
# delete kubernetes service
kubectl delete service service_name --namespace namespace_name
(i.e., kubectl delete service zalenium --namespace zalenium)

Kubernetes Deployment

• When you create a deployment, it creates a pod with containers in it

CREATE DEPLOYMENTS 
# create deployment that deploy pods with dynamic image name 
kubectl create deployment deployment_name --image=image_name 
(i.e., kubectl create deployment ngnix --image=nginx)

LIST DEPLOYMENTS 
# list all the deployments in the default namespace 
kubectl get deployment kubectl get deployments

# list all the deployments in another namespace
kubectl get deployments --namespace namespace_name
(i.e., kubectl get deployments --namespace zalenium)

# list all the deployments with details [container name, image, selector]
kubectl get deployments --namespace namespace_name -o wide
(i.e., kubectl get deployments --namespace zalenium -o wide)

# list all the deployments with selector filter
kubectl get deployments --all-namespaces --selector=selector_name
(i.e., kubectl get deployments --all-namespaces --selector=app.kubernetes.io/name=zalenium -o wide)

# list all the deployments from entire namespace
kubectl get deployments --all-namespaces

DELETE DEPLOYMENTS
# delete deployment
kubectl delete deployment deployment_name --namespace namespace_name
(i.e., kubectl delete deployment zalenium --namespace zalenium)

MANIPULATE DEPLOYMENTS
# expose deployment - NodePort [this will create a service from the deployment/pod]
kubectl expose deployment pod_name --type=NodePort

SCALE DEPLOYMENTS
[make sure the deployment is in running state whenever you scale them]
# scale the existing deployment
kubectl scale deployment --all --replicas=4

# scale a specific deployment
kubectl scale deployment/deployment_name --all --replicas=4
(i.e., kubectl scale deployment/nginx-deployment --all --replicas=4)

# scale multiple controllers
kubectl scale deployment/deployment_name1 deployment/deployment_name2 --all --replicas=4

# scale a specific deployment locating the yaml file
kubectl scale --replicas=4 -f yaml-path
(i.e., kubectl scale --replicas=4 -f deployment.yaml)

# rule while scaling deployment
kubectl scale --current-replicas=3 --replicas=3 -f yaml-path

Kubernetes Pods

• Pod is a group of containers
• Each Pod has a unique IP
• The containers inside a pod talk to each other and share volumes

LIST PODS
# list all the pods in the default namespace
kubectl get pods
kubectl get pods --namespace default

# list all the pods in another namespace
kubectl get pods --namespace namespace_name
(i.e., kubectl get pods --namespace zalenium)

# list all the pods with details [ip addresss, concerned node]
kubectl get pods --namespace namespace_name -o wide
(i.e., kubectl get pods --namespace zalenium -o wide)

# list all the pods with selector filter
kubectl get pods --all-namespaces --selector=selector_name
(i.e., kubectl get pods --all-namespaces --selector=app.kubernetes.io/name=zalenium -o wide)

# list all the pods with status filter [Running, Pending, etc.,]
kubectl get pods --all-namespaces --field-selector=status.phase=Running

# list all the pods from entire namespace
kubectl get pods --all-namespaces

# list pods without column headers
kubectl get pods -n namespace_name --no-headers

# list pod labels
kubectl get pods -n namespace_name --no-headers -o custom-columns=:metadata.labels.app

# list pod names
kubectl get pods -n namespace_name --no-headers -o custom-columns=:metadata.name
kubectl get pods -o=name -n namespace_name | sed "s/^.\{4\}//"
kubectl get pods -n namespace_name --template '{{range .items}}{{.metadata.name}}{{"\n"}}{{end}}'

# list pod's release names
kubectl get pods -n namespace_name --no-headers -o custom-columns=:metadata.labels.release

MANIPULATE PODS
# debug/enter into a pod
kubectl exec -it pod_name bash --namespace namespace_name
(i.e., kubectl exec -it zalenium-40000-4zbtm bash --namespace zalenium)

# copy data into a pod 
kubectl cp local_path namespace_name/pod_name:pod_path
(i.e., kubectl cp ./ zalenium/zalenium-40000-4zbtm bash --namespace zalenium)

# get logs of the pod
kubectl logs pod_name -n namespace_name
watch kubectl logs pod_name -n namespace_name

# troubleshoot pod
[list the pods and check for running status]
kubectl describe pod pod_name --namespace namespace_name
(i.e., kubectl describe pod zalenium-40000-4zbtm --namespace zalenium)

LIST & CHECK STATUS
# list all the details (services, deployments, pods, replicas) related to all namespaces
kubectl get all --all-namespaces

# list all the details (services, deployments, pods, replicas) specific to a namespace
kubectl get all -n namespace_name

# live status
watch kubectl get all -n namespace_name 

# list all the deleted pod names too
kubectl get event --all-namespaces -o custom-columns=NAME:.metadata.name | cut -d "." -f1

# check all supported api versions
kubectl api-versions

# get details about a specific api-version
kubectl get --raw api-version
(i.e., kubectl get --raw /apis/autoscaling/v2beta2)

# default cmd to create services/deployments/pods/volumes from yaml file 
kubectl create -f yaml-path
(i.e., kubectl create -f .)