Linux & DevOPS: Kubernetes

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Kubernetes Interview Questions and Answers 2019 2020

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<a href="https://1.bp.blogspot.com/-F5d5mpedD4s/XbvwpQONkEI/AAAAAAAADeE/poZDU8a2HHAofH0fofukZ1jNLkQbnblUwCEwYBhgL/s1600/Kubernetes.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img alt="Interview Kubernetes engine" border="0" data-original-height="164" data-original-width="308" height="106" src="https://1.bp.blogspot.com/-F5d5mpedD4s/XbvwpQONkEI/AAAAAAAADeE/poZDU8a2HHAofH0fofukZ1jNLkQbnblUwCEwYBhgL/s200/Kubernetes.png" title="Interview Kubernetes engine" width="200" /></a></h4>
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Kubernetes Interview Questions and Answers </h2>
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<span style="color: blue;">Interview Kubernetes engine</span></h4>
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Top 25 Kubernetes Interview Questions You Must Prepare In 2019 &  2020 </h3>
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<span style="color: blue;"><b>Q1 :-  What is Kubernetes?</b></span><br />
Kubernetes is an open-source container management tool which holds the responsibilities of container deployment, scaling & descaling of containers & load balancing. Being the Google’s brainchild, it offers excellent community and works brilliantly with all the cloud providers. So, we can say that Kubernetes is not a containerization platform, but it is a multi-container management solution.<br />
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<span style="color: blue;"><b>Q2. What is the relation between Docker and Kubernetes?</b></span><br />
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Answer: This is one of the most common questions asked in a Kubernetes interview. You can find this question commonly in all the lists of Kubernetes interview questions. The candidate should answer this question as Docker is a platform used for lifecycle management of containers with a Docker image, responsible for building runtime containers. However, Kubernetes is the solution for communication between the individual containers. Therefore, Kubernetes helps in manual linking and orchestration of containers running on multiple hosts created using Docker. Let us move towards the next entry in Kubernetes interview questions<br />
<span style="color: blue;"><br /><b>Q3. What is the difference between Kubernetes and Docker Swarm?</b></span><br />
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Answer: The third entry is also one of the top Kubernetes interview questions. The answer to this Kubernetes interview question would be a little detailed with a focus on different points. The difference points include installation and cluster configuration, GUI, auto-scaling, data volume, scalability, load balancing, logging and monitoring, and rolling updates and rollbacks. Here are the main points of difference between Kubernetes and Docker Swarm.<br />
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<ul style="text-align: left;">
<li>Kubernetes has a complicated setup with the assurance of a robust cluster while Docker Swarm is easier to set up but without a robust cluster.</li>
<li>The scalability of Docker Swarm is five times faster than Kubernetes. Kubernetes provides a dashboard as GUI while Docker Swarm does not have any GUI.</li>
<li>Kubernetes is capable of auto-scaling while Docker Swarm cannot. However, Kubernetes needs manual intervention for load balancing of traffic as compared to the automatic load balancing in Docker Swarm.</li>
<li>Kubernetes has integrated tools for logging and monitoring, unlike Docker Swarm, which needs third party tools for the same.</li>
<li>Kubernetes is limited in term of data volumes as it can share storage with other containers in the same pod while Docker swarm could share storage volumes with other containers easily.</li>
<li>The final point is the ability of Kubernetes to deploy rolling updates and automatic rollbacks. On the other hand, Docker Swarm could deploy rolling updates but does not have the ability for automatic rollbacks.</li>
</ul>
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<span style="color: blue;"><b>Q4. How is Kubernetes related to Docker?</b></span><br />
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It’s a known fact that Docker provides the lifecycle management of containers and a Docker image builds the runtime containers. But, since these individual containers have to communicate, Kubernetes is used.  So, Docker builds the containers and these containers communicate with each other via Kubernetes. So, containers running on multiple hosts can be manually linked and orchestrated using Kubernetes. <br />
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<span style="color: blue;"><b>Q5. What is Container Orchestration?</b></span><br />
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Consider a scenario where you have 5-6 microservices for an application. Now, these microservices are put in individual containers, but won’t be able to communicate without container orchestration. So, as orchestration means the amalgamation of all instruments playing together in harmony in music, similarly container orchestration means all the services in individual containers working together to fulfill the needs of a single server.<br />
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<span style="color: blue;"><b>Q6. How does Kubernetes simplify containerized Deployment?</b></span><br />
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As a typical application would have a cluster of containers running across multiple hosts, all these containers would need to talk to each other. So, to do this you need something big that would load balance, scale & monitor the containers. Since Kubernetes is cloud-agnostic and can run on any public/private providers it must be your choice simplify containerized deployment.<br />
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<span style="color: blue;"><b>Q7. What is Google Container Engine?</b></span><br />
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Google Container Engine (GKE) is an open source management platform for Docker containers and the clusters. This Kubernetes based engine supports only those clusters which run within the Google’s public cloud services.<br />
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<span style="color: blue;"><b>Q8.  What is Heapster?</b></span><br />
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Heapster is a cluster-wide aggregator of data provided by Kubelet running on each node. This container management tool is supported natively on Kubernetes cluster and runs as a pod, just like any other pod in the cluster. So, it basically discovers all nodes in the cluster and queries usage information from the Kubernetes nodes in the cluster, via on-machine Kubernetes agent.<br />
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<span style="color: blue;"><b>Q9.  What is Minikube?</b></span><br />
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Minikube is a tool that makes it easy to run Kubernetes locally. This runs a single-node Kubernetes cluster inside a virtual machine.<br />
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<span style="color: blue;"><b>Q10.  What is Kubectl?</b></span><br />
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Kubectl is the platform using which you can pass commands to the cluster. So, it basically provides the CLI to run commands against the Kubernetes cluster with various ways to create and manage the Kubernetes component.<br />
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<span style="color: blue;"><b>Q11.  What is Kubelet?</b></span><br />
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This is an agent service which runs on each node and enables the slave to communicate with the master. So, Kubelet works on the description of containers provided to it in the PodSpec and makes sure that the containers described in the PodSpec are healthy and running.<br />
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<span style="color: blue;"><b>Q12. What do you understand by Kube-proxy?</b></span><br />
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Kube-proxy can run on each and every node and can do simple TCP/UDP packet forwarding across backend network service. So basically, it is a network proxy which reflects the services as configured in Kubernetes API on each node. So, the Docker-linkable compatible environment variables provide the cluster IPs and ports which are opened by proxy.<br />
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<span style="color: blue;"><b>Q13.  What is the role of kube-apiserver and kube-scheduler?</b></span><br />
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The kube – apiserver follows the scale-out architecture and, is the front-end of the master node control panel. This exposes all the APIs of the Kubernetes Master node components and is responsible for establishing communication between Kubernetes Node and the Kubernetes master components.<br />
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The kube-scheduler is responsible for distribution and management of workload on the worker nodes. So, it selects the most suitable node to run the unscheduled pod based on resource requirement and keeps a track of resource utilization. It makes sure that the workload is not scheduled on nodes which are already full.<br />
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<span style="color: blue;"><b><br />Q14.  What is ETCD?</b></span><br />
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Etcd is written in Go programming language and is a distributed key-value store used for coordinating between distributed work. So, Etcd stores the configuration data of the Kubernetes cluster, representing the state of the cluster at any given point in time.<br />
<span style="color: blue;"><b><br />Q15. What do you understand by load balancer in Kubernetes?</b></span><br />
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A load balancer is one of the most common and standard ways of exposing service. There are two types of load balancer used based on the working environment i.e. either the Internal Load Balancer or the External Load Balancer. The Internal Load Balancer automatically balances load and allocates the pods with the required configuration whereas the External Load Balancer directs the traffic from the external load to the backend pods.<br />
<span style="color: blue;"><b><br />Q16. What is the difference between a replica set and replication controller?</b></span><br />
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Replica Set and Replication Controller do almost the same thing. Both of them ensure that a specified number of pod replicas are running at any given time. The difference comes with the usage of selectors to replicate pods. Replica Set use Set-Based selectors while replication controllers use Equity-Based selectors.<br />
<b><br />Equity-Based Selectors</b>: This type of selector allows filtering by label key and values. So, in layman terms, the equity-based selector will only look for the pods which will have the exact same phrase as that of the label.<br />
Example: Suppose your label key says app=nginx, then, with this selector, you can only look for those pods with label app equal to nginx.<br />
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<b>Selector-Based Selectors</b>: This type of selector allows filtering keys according to a set of values. So, in other words, the selector based selector will look for pods whose label has been mentioned in the set.<br />
Example: Say your label key says app in (nginx, NPS, Apache). Then, with this selector, if your app is equal to any of nginx, NPS, or Apache, then the selector will take it as a true result.<br />
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    <span style="color: blue;"><b><br />Q17. How does the master node work in Kubernetes?</b></span><br />
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Answer: The answer to the question would be that the master node controls the nodes having the containers. The containers are placed inside pods, and each pod may have different containers. The pods can be deployed through the command line interface or user interface. Following that, the pods are scheduled on the nodes, and then pods are allocated to the nodes based on resource requirements.<br />
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<span style="color: blue;"><b>Q18. What is the Kubernetes controller manager?</b></span><br />
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Answer: Another latest Kubernetes interview question is on the Kubernetes controller manager. The controller manager works as a daemon that is used for embedding controllers and garbage collection as well as namespace creation. It helps in running multiple controller processes on the master node albeit compiled together for running as a single process.<br />
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<span style="color: blue;"><b>Q19. What are different types of controller manager?</b></span><br />
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Answer: You can find Kubernetes architecture interview questions such as “What are different types of controller manager?” The notable controller managers that can run on the master node are node controller, service account and token controller, endpoints controller, and replication controll<br />
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<b><span style="color: blue;">Q20. What is a load balancer in Kubernetes?</span></b><br />
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Answer: It is also an important interview question commonly asked in a Kubernetes interview. You can state that load balancer is a method for exposing service, and two types of load balancers can be used in Kubernetes. The two-load balancer includes external load balancer and internal load balancer. <br />
<span style="color: blue;"><b><br />Q21. What is a headless service?</b></span><br />
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Answer: A can also come across a different question in your Kubernetes interview such as “What is a headless service?”. Headless service can be described as any other normal service, albeit without any cluster IP.<br />
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<b><span style="color: blue;">Q22. What is a Swarm in Docker?</span></b><br />
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The docker Swarm is a clustering and scheduling tool for the Docker containers. When it comes to Swarm, the IT administrators and developers would establish and manage a cluster of Docker nodes as part of the single virtual system.<br />
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<span style="color: blue;"><b>Q23. What is OpenShift?</b></span><br />
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OpenShift online is Red Hat’s public cloud application development and hosting platform which provides automation for management, provision and the scaling of application so it is possible to focus on writing the code for the business or big idea. <br />
<span style="color: blue;"><b><br />Q24. Can you please tell me what some of the main advantages of Kubernetes is?</b></span><br />
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With container orchestration tool Kubernetes, it has become easy for one to handle the containers. You may respond to different customer demands through deploying the applications in a faster manner and in a way, which is predictable. So there is:<br />
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• Automated rollback<br />
• Automated scheduling<br />
• Horizontal scaling<br />
• Auto healing capabilities<br />
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<span style="color: blue;"><b>Q25. What are K8s?</b></span><br />
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This is another term for Kubernetes, whereby (K-eight characters-S), would be the open source orchestration framework for the containerized applications. It just another name for what we call Kubernetes.<br />
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Can you tell me how you get a static IP for a Kubernetes load balancer?<br />
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The Kubernetes Master is allowed to assign a new IP static address. It is possible to get a static IP for Kubernetes load balancer through changing the DNS records.</div>
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Kubernetes Interview Questions and Answers 2019 2020

Kubernetes Interview Questions and Answers Interview Kubernetes engine Top 25 Kubernetes Interview Questions You Must Prepare In 201...

4:09 PM

Kubernetes kubectl commands cheatsheet

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Collection of useful <span style="color: blue;">kubectl </span>commands</h2>
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Here is list of important kubectl commands cheatsheet of Kubernetes. </div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Impersonate a user and group</span></b></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get pods
--as-group="somecompany:somecompany-teamname" --as="test"<br style="mso-special-character: line-break;" />
</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Explain a resource<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl explain hpa<br />
kubectl explain svc</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Get nodes region and zone<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get nodes <br />
--label-columns
failure-domain.beta.kubernetes.io/region,failure-domain.beta.kubernetes.io/zone</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Get Arch, OS, Instance type and node type if kops<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get nodes -o wide -L beta.kubernetes.io/arch -L
beta.kubernetes.io/os -L beta.kubernetes.io/instance-type -L<span style="mso-spacerun: yes;">  </span>kops.k8s.io/instancegroupkubectl get nodes -L
beta.kubernetes.io/arch -L beta.kubernetes.io/os -L
beta.kubernetes.io/instance-type -L<span style="mso-spacerun: yes;"> 
</span>kops.k8s.io/instancegroup</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Get node version and name only<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get nodes -o custom-columns=NAME:.metadata.name,VER:.status.nodeInfo.kubeletVersion</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Get scheduleable nodes<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get nodes --output 'jsonpath={range
$.items[*]}{.metadata.name} {.spec.taints[*].effect}{"\n"}{end}' |
awk '!/NoSchedule/{print $1}'</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Get all deployments nameonly<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get deployment -o=jsonpath={.items[*].metadata.name}</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Get one deployment only (first one)<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get deployment
-o=jsonpath={.items[0].metadata.name}</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Get all pods statuses only<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get pods -o=jsonpath=‘{.items[*].status.phase}’
--all-namespaces</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Get pods qos<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get pods --all-namespaces -o
custom-columns=NAME:.metadata.name,NAMESPACE:.metadata.namespace,QOS-CLASS:.status.qosClass</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Get images running<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get pod
-o=jsonpath='{.spec.containers[*].image}' --all-namespaces<br />
<span style="mso-spacerun: yes;">    </span>kubectl get pod
-o=custom-columns=NAME:.metadata.name,IMAGE:.spec.containers[*].image
--all-namespaces</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Where is my pod running<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get pods -n sock-shop -l name=carts -o wide</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Check node/pod usage memory and cpu<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl top nodes<br />
kubectl top pods</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Check health of etcd<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get --raw=/healthz/etcd</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Check status of node autoscaler<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl describe configmap cluster-autoscaler-status -n
kube-system</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Get where pods are running from nodenames<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get pod
-o=custom-columns=NAME:.metadata.name,STATUS:.status.phase,NODE:.spec.nodeName
--all-namespaceskubectl get pod
-o=custom-columns=NODE:.spec.nodeName,NAME:.metadata.name --all-namespaces</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<span style="font-family: "georgia" , serif; letter-spacing: -0.05pt;">E<b>xample
sorting pods by nodeName:</b><span style="font-size: 16pt;"><o:p></o:p></span></span></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get pods -o wide
--sort-by="{.spec.nodeName}"</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<span style="font-family: "georgia" , serif; letter-spacing: -0.05pt;"><b>Example
of getting pods on nodes using label filter:</b><span style="font-size: 16pt;"><o:p></o:p></span></span></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">for n in $(kubectl get nodes -l
your_label_key=your_label_value --no-headers | cut -d " " -f1); do <br />
<span style="mso-spacerun: yes;">        </span>kubectl get pods
--all-namespaces<span style="mso-spacerun: yes;">  </span>--no-headers
--field-selector spec.nodeName=${n} <br />
<span style="mso-spacerun: yes;">  </span>done</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<span style="font-family: "georgia" , "serif"; font-size: 16.0pt; letter-spacing: -0.05pt;"><b>or
by number of restarts</b><o:p></o:p></span></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get pods
--sort-by="{.status.containerStatuses[:1].restartCount}"</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<span style="font-family: "georgia" , "serif"; font-size: 16.0pt; letter-spacing: -0.05pt;"><b>Example
filtering by nodeName using — template flag:</b><o:p></o:p></span></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">$ kubectl get nodes<span style="mso-spacerun: yes;"> 
</span>NAME<span style="mso-spacerun: yes;">                        
</span>STATUS<span style="mso-spacerun: yes;">                 </span><span style="mso-spacerun: yes;">    </span>AGE<br />
<span style="mso-spacerun: yes;">  </span>ip-254-0-90-30.ec2.internal<span style="mso-spacerun: yes;">   </span>Ready<span style="mso-spacerun: yes;">                      </span>2d<br />
<span style="mso-spacerun: yes;">  </span>ip-254-0-90-35.ec2.internal<span style="mso-spacerun: yes;">   </span>Ready<span style="mso-spacerun: yes;">                      </span>2d<br />
<span style="mso-spacerun: yes;">  </span>ip-254-0-90-50.ec2.internal<span style="mso-spacerun: yes;">   </span>Ready,SchedulingDisabled<span style="mso-spacerun: yes;">   </span>2d<br />
<span style="mso-spacerun: yes;">  </span>ip-254-0-91-60.ec2.internal<span style="mso-spacerun: yes;">   </span>Ready<span style="mso-spacerun: yes;">                      </span>2d<br />
<span style="mso-spacerun: yes;">  </span>ip-254-0-91-65.ec2.internal<span style="mso-spacerun: yes;">   </span>Ready<span style="mso-spacerun: yes;">                      </span>2d<br />
<span style="mso-spacerun: yes;">  </span>$ kubectl get pods --template '{{range
.items}}{{if eq .spec.nodeName
"ip-254-0-90-30.ec2.internal"}}{{.metadata.name}}{{"\n"}}{{end}}}{{end}}'<span style="mso-spacerun: yes;">  </span>filebeat-000<br />
<span style="mso-spacerun: yes;">  </span>app-0000<br />
<span style="mso-spacerun: yes;">  </span>node-exporter-0000<br />
<span style="mso-spacerun: yes;">  </span>prometheus-000<br />
<span style="mso-spacerun: yes;"> </span></span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Check pods which are not Runnning<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get pods --field-selector=status.phase!=Running
--all-namespaces</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Sort Nodes by Role, Age and kubelet version<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
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<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get nodes
--sort-by={.metadata.labels."kubernetes\.io\/role"}<br />
<span style="mso-spacerun: yes;">   </span>kubectl get node
--sort-by={.status.nodeInfo.kubeletVersion}<br />
<span style="mso-spacerun: yes;">   </span>watch kubectl get node
--sort-by={.status.nodeInfo.kubeletVersion}<br />
<span style="mso-spacerun: yes;">   </span>watch "kubectl get nodes
--sort-by={.metadata.labels.\"kubernetes\.io\/role\"}"<br />
<span style="mso-spacerun: yes;">   </span>kubectl get nodes
--sort-by=".status.conditions[?(@.reason == 'KubeletReady'
)].lastTransitionTime"</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
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<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Query apiservers<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
<div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; tab-stops: 45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt;">
<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get --raw=/apis<br />
kubectl get --raw=/logs/kube-apiserver.log</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 0in; margin-right: 0in; margin-top: 23.4pt; mso-outline-level: 1;">
<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Setup a deployment with limits and requests<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 10.3pt; mso-list: l0 level1 lfo1; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: "symbol"; font-size: 10.0pt; letter-spacing: -0.05pt;"><span style="mso-list: Ignore;">·<span style="font: 7.0pt "Times New Roman";">        
</span></span></span><span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.05pt;">kubectl run
ken-test --image=docker/docker-curl -i --tty
--limits='cpu=50m,memory=128Mi' --requests='cpu=50m,memory=128Mi'</span><span style="font-family: "georgia" , "serif"; font-size: 16.0pt; letter-spacing: -0.05pt;"><o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l0 level1 lfo1; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: "symbol"; font-size: 10.0pt; letter-spacing: -0.05pt;"><span style="mso-list: Ignore;">·<span style="font: 7.0pt "Times New Roman";">        
</span></span></span><span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.05pt;">kubectl delete
deployment docker-test</span><span style="font-family: "georgia" , "serif"; font-size: 16.0pt; letter-spacing: -0.05pt;"><o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 0in; margin-right: 0in; margin-top: 23.4pt; mso-outline-level: 1;">
<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Get events for an individual resource<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
<div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; tab-stops: 45.8pt 91.6pt 137.4pt 183.2pt 229.0pt 274.8pt 320.6pt 366.4pt 412.2pt 458.0pt 503.8pt 549.6pt 595.4pt 641.2pt 687.0pt 732.8pt;">
<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.25pt;">kubectl get event --field-selector=involvedObject.name
=foo -w</span><span style="font-family: "courier new"; font-size: 10.0pt;"><o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 0in; margin-right: 0in; margin-top: 23.4pt; mso-outline-level: 1;">
<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Get apiresources<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 10.3pt; mso-list: l1 level1 lfo2; tab-stops: list .5in; text-indent: -.25in;">
<b><span style="font-family: "symbol"; letter-spacing: -0.05pt;"><span style="font-family: "times new roman"; font-stretch: normal; font-style: normal; font-variant: normal; line-height: normal;"> </span></span></b><span style="font-family: "georgia" , serif; letter-spacing: -0.05pt;"><b>Check for an api resources available, this should show
your crd api endpoints as well</b><span style="font-size: 16pt;"><o:p></o:p></span></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l1 level1 lfo2; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: "symbol"; font-size: 10.0pt; letter-spacing: -0.05pt;"><span style="mso-list: Ignore;">·<span style="font: 7.0pt "Times New Roman";">        
</span></span></span><span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.05pt;">kubectl
api-resources</span><span style="font-family: "georgia" , "serif"; font-size: 16.0pt; letter-spacing: -0.05pt;"><o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l1 level1 lfo2; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: "symbol"; font-size: 10.0pt; letter-spacing: -0.05pt;"><span style="mso-list: Ignore;">·<span style="font: 7.0pt "Times New Roman";">        
</span></span></span><span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.05pt;">kubectl
api-versions</span><span style="font-family: "georgia" , "serif"; font-size: 16.0pt; letter-spacing: -0.05pt;"><o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l1 level1 lfo2; tab-stops: list .5in; text-indent: -.25in;">
<b><span style="font-family: "symbol"; letter-spacing: -0.05pt;"><span style="font-family: "times new roman"; font-stretch: normal; font-style: normal; font-variant: normal; line-height: normal;">  </span></span></b><span style="font-family: "georgia" , serif; letter-spacing: -0.05pt;"><b>Check apiservices added (registered)</b><span style="font-size: 16pt;"><o:p></o:p></span></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l1 level1 lfo2; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: "symbol"; font-size: 10.0pt; letter-spacing: -0.05pt;"><span style="mso-list: Ignore;">·<span style="font: 7.0pt "Times New Roman";">        
</span></span></span><span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.05pt;">kubectl get
apiservices.apiregistration.k8s.io</span><span style="font-family: "georgia" , "serif"; font-size: 16.0pt; letter-spacing: -0.05pt;"><o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l1 level1 lfo2; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: "symbol"; font-size: 10.0pt; letter-spacing: -0.05pt;"><span style="mso-list: Ignore;">·<span style="font: 7.0pt "Times New Roman";">        
</span></span></span><span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.05pt;">kubectl get
apiservices.apiregistration.k8s.io v1beta1.metrics.k8s.io -o yaml</span><span style="font-family: "georgia" , "serif"; font-size: 16.0pt; letter-spacing: -0.05pt;"><o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l1 level1 lfo2; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: "georgia" , serif; letter-spacing: -0.05pt;"><b>Check hpa (maybe because you have custom metrics enabled
in prometheus)?</b><span style="font-size: 16pt;"><o:p></o:p></span></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l1 level1 lfo2; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: "symbol"; font-size: 10.0pt; letter-spacing: -0.05pt;"><span style="mso-list: Ignore;">·<span style="font: 7.0pt "Times New Roman";">        
</span></span></span><span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.05pt;">kubectl get
hpa</span><span style="font-family: "georgia" , "serif"; font-size: 16.0pt; letter-spacing: -0.05pt;"><o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l1 level1 lfo2; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: "symbol"; font-size: 10.0pt; letter-spacing: -0.05pt;"><span style="mso-list: Ignore;">·<span style="font: 7.0pt "Times New Roman";">        
</span></span></span><span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.05pt;">kubectl get
hpa --all-namespaces</span><br />
<span style="letter-spacing: -0.05pt;"><span style="font-family: "courier new" , "courier" , monospace;">   kubectl get --raw /apis/metrics.k8s.io</span><span style="font-family: "georgia" , serif; font-size: 16pt;"><o:p></o:p></span></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 0in; margin-right: 0in; margin-top: 23.4pt; mso-outline-level: 1;">
<b><span style="font-family: "lucida sans unicode" , sans-serif; letter-spacing: -0.25pt;">Kube Diff<span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 10.3pt; mso-list: l2 level1 lfo3; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: "symbol"; font-size: 10.0pt; letter-spacing: -0.05pt;"><span style="mso-list: Ignore;">·<span style="font: 7.0pt "Times New Roman";">        
</span></span></span><span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.05pt;">kubectl alpha
diff -h</span><span style="font-family: "georgia" , "serif"; font-size: 16.0pt; letter-spacing: -0.05pt;"><o:p></o:p></span><br />
<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.05pt;"><br /></span>
<span style="font-family: "courier new"; font-size: 12.0pt; letter-spacing: -0.05pt;"><br /></span></div>
</div>
</div>

Kubernetes kubectl commands cheatsheet

Collection of useful kubectl commands Here is list of important kubectl commands cheatsheet of Kubernetes. Impersonate a user and ...

12:13 PM

Introduction to Kubernetes Networking

<div dir="ltr" style="text-align: left;" trbidi="on">
<h3 style="text-align: left;">
<a href="https://1.bp.blogspot.com/-F5d5mpedD4s/XbvwpQONkEI/AAAAAAAADeI/NRTqdehanE8OFCkyPj1c74Rg3RI5NOWSgCPcBGAYYCw/s1600/Kubernetes.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img alt="Kubernetes networking" border="0" data-original-height="164" data-original-width="308" height="106" src="https://1.bp.blogspot.com/-F5d5mpedD4s/XbvwpQONkEI/AAAAAAAADeI/NRTqdehanE8OFCkyPj1c74Rg3RI5NOWSgCPcBGAYYCw/s200/Kubernetes.png" title="Kubernetes networking" width="200" /></a><span style="color: blue;">Here we are introducing Kubernetes networking. </span></h3>
This is meant to be an <b>introduction into Kubernetes networking</b> and I assume you have a basic understanding of <b>Kubernetes pods and Kubernetes service </b>and their use cases.<br />
<br />
Before we can understand <b>Kubernetes networking</b> we must first understand what we are trying to solve. There are 3 issues we need to solve in a Kubernetes cluster:<br />
<br />
<br />
<ol style="text-align: left;">
<li>Container to Container communication</li>
<li>pod to pod communication</li>
<li>pod to service communication</li>
</ol>
<h4 style="text-align: left;">
<span style="color: blue;">Solving for Kubernetes Network Issues</span></h4>
Let us go over each one of the bullet points we mentioned above and how Kubernetes attempts to solves it.<br />
<h4 style="text-align: left;">
<span style="color: blue;">Container to Container Communication</span></h4>
This is solved with the concept of Pods. In Linux, a network namespace contains its own network resources, i.e interfaces, routing tables, etc. This same concept applies to Pods. When a pod is created, it gets a network namespace that the containers in the pod will share resources therefore allowing all containers in a pod to communicate through localhost.<br />
<h4 style="text-align: left;">
<span style="color: blue;">Pod to Service Communication</span></h4>
A service is an abstraction that routes traffic to a set of pods. A service gets its own <b>Cluster IP</b>, the pods also get their own IP’s and when requests need to reach the pods, it is sent to the service Cluster IP and then forwarded to the actual IP of the pods. This way pods(mortals) can come and go without worrying about updating IP’s since by default the service will automatically update its endpoint with the IP of the pod that it targets as those pod changes IP. The way the service knows what pod to target is through LabelSelector. This is an important concept to be aware of since LabelSelector is the only way the service knows what pod to target and keep track of their IP’s.<br />
<h4 style="text-align: left;">
<span style="color: blue;">Pod to Pod Communication</span></h4>
For communication between pods, Kubernetes imposes the following fundamental requirements on any networking implementation:<br />
<br />
<ul style="text-align: left;">
<li><span style="color: blue;"><b>all Pods can communicate with all other Pods without using network address translation (NAT)</b></span></li>
<li><span style="color: blue;"><b>all Nodes can communicate with all Pods without NAT.</b></span></li>
<li><span style="color: blue;"><b>the IP that a Pod sees itself as is the same IP that others see it as.</b></span></li>
</ul>
There are plenty of tools we can add to Kubernetes to help us meet these requirements like <b>Cilium </b>which is open source software for providing and transparently securing network connectivity between application containers, <b>Flannel </b>which is a very simple overlay network that simply satisfies the Kubernetes requirements, Kube-router which is a purpose-built networking solution for Kubernetes that aims to provide high performance and operational simplicity. There are plenty of other solids projects we can use outside of the 3 mentioned.<br />
<br />
The idea is that when a pod is created, Linux Virtual Ethernet Device or veth pair can be used to connect Pod network namespaces to the root network namespace. Pods on the same node can talk through a bridge.<br />
<br />
A Linux Ethernet bridge is a virtual Layer 2 networking device used to unite two or more network segments, working transparently to connect the two networks together. For Pods on separate nodes, assuming connectivity between the nodes, request will go from root namespace of one node to the root namespace of other node. The node should then know how to route traffic to the correct pod.</div>

Introduction to Kubernetes Networking

Here we are introducing Kubernetes networking. This is meant to be an introduction into Kubernetes networking and I assume you have a b...

7:57 PM

Basic Concept of Kubernetes

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<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://1.bp.blogspot.com/-F5d5mpedD4s/XbvwpQONkEI/AAAAAAAADeI/NRTqdehanE8OFCkyPj1c74Rg3RI5NOWSgCPcBGAYYCw/s1600/Kubernetes.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" data-original-height="164" data-original-width="308" height="106" src="https://1.bp.blogspot.com/-F5d5mpedD4s/XbvwpQONkEI/AAAAAAAADeI/NRTqdehanE8OFCkyPj1c74Rg3RI5NOWSgCPcBGAYYCw/s200/Kubernetes.png" width="200" /></a></div>
<h2 style="background: white; line-height: 36pt; margin: 0in 0in 0.0001pt; text-align: left;">
Introduction to Basic Concept of Kubernetes</h2>
<div>
<br /></div>
<div>
<b><span style="font-family: "Lucida Sans Unicode", sans-serif; letter-spacing: -0.25pt;"><span style="font-size: large;">What is Kubernetes?</span></span></b></div>
<div>

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<span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";">Kubernetes
is an open-source platform/tool created by Google. It is written in GO-Lang. So
currently Kubernetes is an open-source project under Apache 2.0 license.
Sometimes in the industry, <a href="http://www.java67.com/2019/03/5-free-devops-courses-to-learn-jenkins.html" target="_blank"><span style="color: windowtext; text-decoration-line: none;">Kubernete</span></a>s is also known as “K8s”. With Kubernetes, you can
run any Linux container across private, public, and hybrid cloud environments.
Kubernetes provides some edge functions, such as Loadbalancer, Service
discovery, and Roled Based Access Control(RBAC).<o:p></o:p></span></div>
<h3 style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 0in; margin-right: 0in; margin-top: 23.4pt; mso-outline-level: 1;">
<b><span style="font-family: "Lucida Sans Unicode", sans-serif; letter-spacing: -0.25pt;"><span style="font-size: large;">Why we need Kubernetes?</span></span></b></h3>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 0in; margin-right: 0in; margin-top: 10.3pt;">
<span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";">The
answer is to help us manage containers. When we run our production environments
using a microservice pattern with many containers, we need to make sure many
things. Such as health check, version control, scaling, and rollback mechanism.
It will be very frustrating to make sure all of these things still be ok.
Kubernetes gives you the orchestration and management capabilities required to
deploy containers, at scale. Kubernetes orchestration allows you to build
application services that span multiple containers, schedule those containers
across a cluster, scale those containers, and manage the health of those
containers over time. In nutshell, I can say Kubernetes is more like a manager
that has many subordinates(containers). What manager does is maintain what
subordinates need to do.<o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 0in; margin-right: 0in; margin-top: 24.0pt;">
<span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";">Before
used Kubernetes, you need to prepare your infrastructure to deploy a new
microservice. I believe it cost you a few days or weeks. Without Kubernetes,
large teams would have to manually script the deployment workflows. With
Kubernetes, you don’t need to create your deployment script manually and it
will reduce the amount of time and resources spent on DevOps.<o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 0in; margin-right: 0in; margin-top: 24.0pt;">
<span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";">Key
feature of Kubernetes:<o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 24.0pt; mso-list: l2 level1 lfo1; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: Symbol; font-size: 10.0pt; letter-spacing: -.05pt; mso-bidi-font-family: Symbol; mso-bidi-font-size: 16.0pt; mso-fareast-font-family: Symbol;">·<span style="font-family: "Times New Roman"; font-size: 7pt; font-stretch: normal; font-variant-east-asian: normal; font-variant-numeric: normal; line-height: normal;">        
</span></span><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI"; mso-fareast-font-family: "Times New Roman";"><a href="https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale/" target="_blank"><span style="text-decoration-line: none;">Horizontal
Scaling</span></a><o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l2 level1 lfo1; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: Symbol; font-size: 10.0pt; letter-spacing: -.05pt; mso-bidi-font-family: Symbol; mso-bidi-font-size: 16.0pt; mso-fareast-font-family: Symbol;">·<span style="font-family: "Times New Roman"; font-size: 7pt; font-stretch: normal; font-variant-east-asian: normal; font-variant-numeric: normal; line-height: normal;">        
</span></span><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI"; mso-fareast-font-family: "Times New Roman";"><a href="https://kubernetes.io/blog/2016/07/autoscaling-in-kubernetes/" target="_blank"><span style="text-decoration-line: none;">Auto
Scaling</span></a><o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l2 level1 lfo1; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: Symbol; font-size: 10.0pt; letter-spacing: -.05pt; mso-bidi-font-family: Symbol; mso-bidi-font-size: 16.0pt; mso-fareast-font-family: Symbol;">·<span style="font-family: "Times New Roman"; font-size: 7pt; font-stretch: normal; font-variant-east-asian: normal; font-variant-numeric: normal; line-height: normal;">        
</span></span><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI"; mso-fareast-font-family: "Times New Roman";"><a href="https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/" target="_blank"><span style="text-decoration-line: none;">Health
check</span></a> & <a href="https://multinode-kubernetes-cluster.readthedocs.io/en/latest/14-k8s-selfhealing.html" target="_blank"><span style="text-decoration-line: none;">Self-healing</span></a><o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l2 level1 lfo1; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: Symbol; font-size: 10.0pt; letter-spacing: -.05pt; mso-bidi-font-family: Symbol; mso-bidi-font-size: 16.0pt; mso-fareast-font-family: Symbol;">·<span style="font-family: "Times New Roman"; font-size: 7pt; font-stretch: normal; font-variant-east-asian: normal; font-variant-numeric: normal; line-height: normal;">        
</span></span><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI"; mso-fareast-font-family: "Times New Roman";"><a href="https://kubernetes.io/docs/tasks/access-application-cluster/create-external-load-balancer/" target="_blank"><span style="text-decoration-line: none;">Load
Balancer</span></a><o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l2 level1 lfo1; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: Symbol; font-size: 10.0pt; letter-spacing: -.05pt; mso-bidi-font-family: Symbol; mso-bidi-font-size: 16.0pt; mso-fareast-font-family: Symbol;">·<span style="font-family: "Times New Roman"; font-size: 7pt; font-stretch: normal; font-variant-east-asian: normal; font-variant-numeric: normal; line-height: normal;">        
</span></span><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI"; mso-fareast-font-family: "Times New Roman";"><a href="https://kubernetes.io/docs/concepts/services-networking/service/" target="_blank"><span style="text-decoration-line: none;">Service
Discovery</span></a><o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l2 level1 lfo1; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: Symbol; font-size: 10.0pt; letter-spacing: -.05pt; mso-bidi-font-family: Symbol; mso-bidi-font-size: 16.0pt; mso-fareast-font-family: Symbol;">·<span style="font-family: "Times New Roman"; font-size: 7pt; font-stretch: normal; font-variant-east-asian: normal; font-variant-numeric: normal; line-height: normal;">        
</span></span><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI"; mso-fareast-font-family: "Times New Roman";">Automated <a href="https://kubernetes.io/docs/concepts/workloads/controllers/deployment/#rolling-back-a-deployment" target="_blank"><span style="text-decoration-line: none;">rollbacks</span></a> & <a href="https://kubernetes.io/docs/concepts/workloads/controllers/deployment/#creating-a-deployment" target="_blank"><span style="text-decoration-line: none;">rollouts</span></a><o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l2 level1 lfo1; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: Symbol; font-size: 10.0pt; letter-spacing: -.05pt; mso-bidi-font-family: Symbol; mso-bidi-font-size: 16.0pt; mso-fareast-font-family: Symbol;">·<span style="font-family: "Times New Roman"; font-size: 7pt; font-stretch: normal; font-variant-east-asian: normal; font-variant-numeric: normal; line-height: normal;">        
</span></span><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI"; mso-fareast-font-family: "Times New Roman";">Canary Deployment<o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 0in; margin-right: 0in; margin-top: 23.4pt; mso-outline-level: 1;">
<b><span style="font-family: "Lucida Sans Unicode", sans-serif; letter-spacing: -0.25pt;"><span style="font-size: large;">How Kubernetes Works?</span><span style="font-size: 25.5pt;"><o:p></o:p></span></span></b></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 0in; margin-right: 0in; margin-top: 10.3pt;">
<span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";">When
you start the Kubernetes by reading the official documentation, you might be
overwhelmed to encounter a lot of terminologies. Sometimes we need the overview
to get a better understanding of the concept. Here I show you the complete
overview diagram of Kubernetes Architecture. I hope this helps.<o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 0in; margin-right: 0in; margin-top: 24.0pt;">
<b><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";"><span style="color: blue;">The
sequence of deployment:</span></span></b><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";"><o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 0in; margin-right: 0in; margin-top: 24.0pt;">
<span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";">DevOps
-> API Server -> Scheduler -> Cluster ->Nodes -> Kubelet ->
Container Engine -> Spawn Container in Pod<o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 0in; margin-right: 0in; margin-top: 24.0pt;">
<b><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";"><span style="color: blue;">The
sequence of App user request:</span></span></b><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";"><o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 0in; margin-right: 0in; margin-top: 24.0pt;">
<span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Times New Roman"; mso-fareast-font-family: "Times New Roman";">App
user -> Kube proxy -> Pod -> Container (Your app is run here)<o:p></o:p></span></div>
<h2 style="background: white; margin-top: 20.65pt;">
<span style="font-family: "Lucida Sans Unicode","sans-serif"; font-size: 19.5pt; letter-spacing: -.25pt; line-height: 115%;"><span style="color: blue;">Master</span><o:p></o:p></span></h2>
<div class="im" data-selectable-paragraph="" id="4596" style="background: white; box-sizing: inherit; color: rgba(0, 0, 0, 0.84); margin: 10.3pt 0in 0.0001pt; word-break: break-word;">
<span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt;">Master is the controlling
element of the cluster. Master has 3 parts:<o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 24.0pt; mso-list: l0 level1 lfo2; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: Symbol; font-size: 10.0pt; letter-spacing: -.05pt; mso-bidi-font-family: Symbol; mso-bidi-font-size: 16.0pt; mso-fareast-font-family: Symbol;">·<span style="font-family: "Times New Roman"; font-size: 7pt; font-stretch: normal; font-variant-east-asian: normal; font-variant-numeric: normal; line-height: normal;">        
</span></span><strong style="box-sizing: inherit;"><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI";">API Server: </span></strong><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI";">The application that serves Kubernetes
functionality through a RESTful interface and stores the state of the cluster.<o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l0 level1 lfo2; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: Symbol; font-size: 10.0pt; letter-spacing: -.05pt; mso-bidi-font-family: Symbol; mso-bidi-font-size: 16.0pt; mso-fareast-font-family: Symbol;">·<span style="font-family: "Times New Roman"; font-size: 7pt; font-stretch: normal; font-variant-east-asian: normal; font-variant-numeric: normal; line-height: normal;">        
</span></span><strong style="box-sizing: inherit;"><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI";">Scheduler:</span></strong><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI";"> Scheduler watches API server for new
Pod requests. It communicates with Nodes to create new pods and to assign work
to nodes while allocating resources or imposing constraints.<o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l0 level1 lfo2; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: Symbol; font-size: 10.0pt; letter-spacing: -.05pt; mso-bidi-font-family: Symbol; mso-bidi-font-size: 16.0pt; mso-fareast-font-family: Symbol;">·<span style="font-family: "Times New Roman"; font-size: 7pt; font-stretch: normal; font-variant-east-asian: normal; font-variant-numeric: normal; line-height: normal;">        
</span></span><strong style="box-sizing: inherit;"><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI";">Controller Manager: </span></strong><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI";">Component on the master that runs <a href="https://kubernetes.io/docs/concepts/architecture/controller/" style="-webkit-tap-highlight-color: transparent; background-position: calc(1em + 1px) center; background-size: 1px 1px; box-sizing: inherit;" target="_blank">controllers</a>.
Includes Node controller, Endpoint Controller, Namespace Controller, etc.<o:p></o:p></span></div>
<h2 data-selectable-paragraph="" id="aa2c" style="background: white; box-sizing: inherit; margin-top: 20.65pt;">
<span style="font-family: "Lucida Sans Unicode", sans-serif; font-size: 19.5pt; letter-spacing: -0.25pt; line-height: 115%;"><span style="color: blue;">Slave(Nodes) / Worker Node </span><span style="color: rgba(0, 0, 0, 0.83921568627451);"><o:p></o:p></span></span></h2>
<div class="im" data-selectable-paragraph="" id="d9fe" style="background: white; box-sizing: inherit; color: rgba(0, 0, 0, 0.84); margin: 10.3pt 0in 0.0001pt; word-break: break-word;">
<span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt;">These machines perform the
requested, assigned tasks. The Kubernetes master controls them. There 4
component inside Nodes:<o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 24.0pt; mso-list: l1 level1 lfo3; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: Symbol; font-size: 10.0pt; letter-spacing: -.05pt; mso-bidi-font-family: Symbol; mso-bidi-font-size: 16.0pt; mso-fareast-font-family: Symbol;">·<span style="font-family: "Times New Roman"; font-size: 7pt; font-stretch: normal; font-variant-east-asian: normal; font-variant-numeric: normal; line-height: normal;">        
</span></span><strong style="box-sizing: inherit;"><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI";">Pod: </span></strong><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI";">All containers will run in a pod. Pods
abstract the network and storage away from the underlying containers. Your app
will run here.<o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l1 level1 lfo3; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: Symbol; font-size: 10.0pt; letter-spacing: -.05pt; mso-bidi-font-family: Symbol; mso-bidi-font-size: 16.0pt; mso-fareast-font-family: Symbol;">·<span style="font-family: "Times New Roman"; font-size: 7pt; font-stretch: normal; font-variant-east-asian: normal; font-variant-numeric: normal; line-height: normal;">        
</span></span><strong style="box-sizing: inherit;"><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI";">Kubelet: </span></strong><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI";">Kubectl registering the nodes with the
cluster, watches for work assignments from the scheduler, instantiate new Pods,
report back to the master.<o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l1 level1 lfo3; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: Symbol; font-size: 10.0pt; letter-spacing: -.05pt; mso-bidi-font-family: Symbol; mso-bidi-font-size: 16.0pt; mso-fareast-font-family: Symbol;">·<span style="font-family: "Times New Roman"; font-size: 7pt; font-stretch: normal; font-variant-east-asian: normal; font-variant-numeric: normal; line-height: normal;">        
</span></span><strong style="box-sizing: inherit;"><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI";">Container Engine: </span></strong><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI";">Responsible for managing containers, image
pulling, stopping the container, starting the container, destroying the
container, etc.<o:p></o:p></span></div>
<div class="MsoNormal" style="background: white; line-height: normal; margin-bottom: .0001pt; margin-bottom: 0in; margin-left: 22.5pt; margin-right: 0in; margin-top: 12.6pt; mso-list: l1 level1 lfo3; tab-stops: list .5in; text-indent: -.25in;">
<span style="font-family: Symbol; font-size: 10.0pt; letter-spacing: -.05pt; mso-bidi-font-family: Symbol; mso-bidi-font-size: 16.0pt; mso-fareast-font-family: Symbol;">·<span style="font-family: "Times New Roman"; font-size: 7pt; font-stretch: normal; font-variant-east-asian: normal; font-variant-numeric: normal; line-height: normal;">        
</span></span><strong style="box-sizing: inherit;"><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI";">Kube Proxy: </span></strong><span style="font-family: "Georgia","serif"; font-size: 16.0pt; letter-spacing: -.05pt; mso-bidi-font-family: "Segoe UI";">Responsible for forwarding app user requests
to the right pod.<o:p></o:p></span></div>
</div>
</div>

Basic Concept of Kubernetes

Introduction to Basic Concept of Kubernetes What is Kubernetes? Kubernetes is an open-source platform/tool created by Google. I...

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