Welcome to Stack Simplify

Author: Kalyan Reddy Daida

02-Docker-Fundamentals/README.md

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+# Docker Fundamentals
+- For Docker Fundamentals github repository, please click on below link
+- https://github.com/stacksimplify/docker-fundamentals

03-Kubernetes-Fundamentals-with-kubectl/03-01-PODs-with-kubectl/README.md

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+# Kubernetes  - PODs
+
+## Step-01: PODs Introduction
+- What is a POD ?
+- What is a Multi-Container POD?
+
+## Step-02: PODs Demo
+### Get Worker Nodes Status
+- Verify if kubernetes worker nodes are ready. 
+```
+# Get Worker Node Status
+kubectl get nodes
+
+# Get Worker Node Status with wide option
+kubectl get nodes -o wide
+```
+
+### Create a Pod
+- Create a Pod
+```
+# Template
+kubectl run <desired-pod-name> --image <Container-Image> 
+
+# Replace Pod Name, Container Image
+kubectl run my-first-pod --image stacksimplify/kubenginx:1.0.0
+```  
+
+### List Pods
+- Get the list of pods
+```
+# List Pods
+kubectl get pods
+
+# Alias name for pods is po
+kubectl get po
+```
+
+### List Pods with wide option
+- List pods with wide option which also provide Node information on which Pod is running
+```
+kubectl get pods -o wide
+```
+
+### What happened in the backgroup when above command is run?
+1. Kubernetes created a pod
+2. Pulled the docker image from docker hub
+3. Created the container in the pod
+4. Started the container present in the pod
+
+
+### Describe Pod
+- Describe the POD, primarily required during troubleshooting. 
+- Events shown will be of a great help during troubleshooting. 
+```
+# To get list of pod names
+kubectl get pods
+
+# Describe the Pod
+kubectl describe pod <Pod-Name>
+kubectl describe pod my-first-pod 
+```
+
+### Access Application
+- Currently we can access this application only inside worker nodes. 
+- To access it externally, we need to create a **NodePort or Load Balancer Service**. 
+- **Services** is one very very important concept in Kubernetes. 
+
+### Delete Pod
+```
+# To get list of pod names
+kubectl get pods
+
+# Delete Pod
+kubectl delete pod <Pod-Name>
+kubectl delete pod my-first-pod
+```
+
+## Step-03: Load Balancer Service Introduction
+- What are Services in k8s?
+- What is a Load Balancer Service?
+- How it works?
+
+## Step-04: Demo - Expose Pod with a Service
+- Expose pod with a service (Load Balancer Service) to access the application externally (from internet)
+- **Ports**
+  - **port:** Port on which node port service listens in Kubernetes cluster internally
+  - **targetPort:** We define container port here on which our application is running.
+```
+# Create  a Pod
+kubectl run <desired-pod-name> --image <Container-Image> 
+kubectl run my-first-pod --image stacksimplify/kubenginx:1.0.0 
+
+# Expose Pod as a Service
+kubectl expose pod <Pod-Name>  --type=LoadBalancer --port=80 --name=<Service-Name>
+kubectl expose pod my-first-pod  --type=LoadBalancer --port=80 --name=my-first-service
+
+# Get Service Info
+kubectl get service
+kubectl get svc
+
+# Access Application
+http://<External-IP-from-get-service-output>
+```
+
+- **Important Note about: target-port**
+  -  If target-port is not defined, by default and for convenience, the **targetPort** is set to the same value as the **port** field.
+
+## Step-05: Interact with a Pod
+
+### Verify Pod Logs
+```
+# Get Pod Name
+kubectl get po
+
+# Dump Pod logs
+kubectl logs <pod-name>
+kubectl logs my-first-pod
+
+# Stream pod logs with -f option and access application to see logs
+kubectl logs <pod-name>
+kubectl logs -f my-first-pod
+```
+- **Important Notes**
+  - Refer below link and search for **Interacting with running Pods** for additional log options
+  - Troubleshooting skills are very important. So please go through all logging options available and master them.
+  - **Reference:** https://kubernetes.io/docs/reference/kubectl/cheatsheet/
+
+### Connect to Container in a POD
+- **Connect to a Container in POD and execute commands**
+```
+# Connect to Nginx Container in a POD
+kubectl exec -it <pod-name> -- /bin/bash
+kubectl exec -it my-first-pod -- /bin/bash
+
+# Execute some commands in Nginx container
+ls
+cd /usr/share/nginx/html
+cat index.html
+exit
+```
+
+- **Running individual commands in a Container**
+```
+kubectl exec -it <pod-name> env
+
+# Sample Commands
+kubectl exec -it my-first-pod env
+kubectl exec -it my-first-pod ls
+kubectl exec -it my-first-pod cat /usr/share/nginx/html/index.html
+```
+## Step-06: Get YAML Output of Pod & Service
+### Get YAML Output
+```
+# Get pod definition YAML output
+kubectl get pod my-first-pod -o yaml   
+
+# Get service definition YAML output
+kubectl get service my-first-service -o yaml   
+```
+
+## Step-07: Clean-Up
+```
+# Get all Objects in default namespace
+kubectl get all
+
+# Delete Services
+kubectl delete svc my-first-service
+kubectl delete svc my-first-service2
+kubectl delete svc my-first-service3
+
+# Delete Pod
+kubectl delete pod my-first-pod
+
+# Get all Objects in default namespace
+kubectl get all
+```

03-Kubernetes-Fundamentals-with-kubectl/03-02-ReplicaSets-with-kubectl/README.md

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+# Kubernetes - ReplicaSets
+
+## Step-01: Introduction to ReplicaSets
+- What are ReplicaSets?
+- What is the advantage of using ReplicaSets?
+
+## Step-02: Create ReplicaSet
+
+### Create ReplicaSet
+- Create ReplicaSet
+```
+kubectl create -f replicaset-demo.yml
+```
+- **replicaset-demo.yml**
+```yml
+apiVersion: apps/v1
+kind: ReplicaSet
+metadata:
+  name: my-helloworld-rs
+  labels:
+    app: my-helloworld
+spec:
+  replicas: 3
+  selector:
+    matchLabels:
+      app: my-helloworld
+  template:
+    metadata:
+      labels:
+        app: my-helloworld
+    spec:
+      containers:
+      - name: my-helloworld-app
+        image: stacksimplify/kube-helloworld:1.0.0
+```
+
+### List ReplicaSets
+- Get list of ReplicaSets
+```
+kubectl get replicaset
+kubectl get rs
+```
+
+### Describe ReplicaSet
+- Describe the newly created ReplicaSet
+```
+kubectl describe rs/<replicaset-name>
+
+kubectl describe rs/my-helloworld-rs
+[or]
+kubectl describe rs my-helloworld-rs
+```
+
+### List of Pods
+- Get list of Pods
+```
+#Get list of Pods
+kubectl get pods
+kubectl describe pod <pod-name>
+
+# Get list of Pods with Pod IP and Node in which it is running
+kubectl get pods -o wide
+```
+
+### Verify the Owner of the Pod
+- Verify the owner reference of the pod.
+- Verify under **"name"** tag under **"ownerReferences"**. We will find the replicaset name to which this pod belongs to. 
+```
+kubectl get pods <pod-name> -o yaml
+kubectl get pods my-helloworld-rs-c8rrj -o yaml 
+```
+
+## Step-03: Expose ReplicaSet as a Service
+- Expose ReplicaSet with a service (Load Balancer Service) to access the application externally (from internet)
+```
+# Expose ReplicaSet as a Service
+kubectl expose rs <ReplicaSet-Name>  --type=LoadBalancer --port=80 --target-port=8080 --name=<Service-Name-To-Be-Created>
+kubectl expose rs my-helloworld-rs  --type=LoadBalancer --port=80 --target-port=8080 --name=my-helloworld-rs-service
+
+# Get Service Info
+kubectl get service
+kubectl get svc
+
+```
+- **Access the Application using External or Public IP**
+```
+http://<External-IP-from-get-service-output>/hello
+```
+
+## Step-04: Test Replicaset Reliability or High Availability 
+- Test how the high availability or reliability concept is achieved automatically in Kubernetes
+- Whenever a POD is accidentally terminated due to some application issue, ReplicaSet should auto-create that Pod to maintain desired number of Replicas configured to achive High Availability.
+```
+# To get Pod Name
+kubectl get pods
+
+# Delete the Pod
+kubectl delete pod <Pod-Name>
+
+# Verify the new pod got created automatically
+kubectl get pods   (Verify Age and name of new pod)
+``` 
+
+## Step-05: Test ReplicaSet Scalability feature 
+- Test how scalability is going to seamless & quick
+- Update the **replicas** field in **replicaset-demo.yml** from 3 to 6.
+```
+# Before change
+spec:
+  replicas: 3
+
+# After change
+spec:
+  replicas: 6
+```
+- Update the ReplicaSet
+```
+# Apply latest changes to ReplicaSet
+kubectl replace -f replicaset-demo.yml
+
+# Verify if new pods got created
+kubectl get pods -o wide
+```
+
+## Step-06: Delete ReplicaSet & Service
+### Delete ReplicaSet
+```
+# Delete ReplicaSet
+kubectl delete rs <ReplicaSet-Name>
+
+# Sample Commands
+kubectl delete rs/my-helloworld-rs
+[or]
+kubectl delete rs my-helloworld-rs
+
+# Verify if ReplicaSet got deleted
+kubectl get rs
+```
+
+### Delete Service created for ReplicaSet
+```
+# Delete Service
+kubectl delete svc <service-name>
+
+# Sample Commands
+kubectl delete svc my-helloworld-rs-service
+[or]
+kubectl delete svc/my-helloworld-rs-service
+
+# Verify if Service got deleted
+kubectl get svc
+```

03-Kubernetes-Fundamentals-with-kubectl/03-02-ReplicaSets-with-kubectl/replicaset-demo.yml

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+apiVersion: apps/v1
+kind: ReplicaSet
+metadata:
+  name: my-helloworld-rs
+  labels:
+    app: my-helloworld
+spec:
+  replicas: 6
+  selector:
+    matchLabels:
+      app: my-helloworld
+  template:
+    metadata:
+      labels:
+        app: my-helloworld
+    spec:
+      containers:
+      - name: my-helloworld-app
+        image: stacksimplify/kube-helloworld:1.0.0