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Add Circle CI questions
In addition to a couple of k8s questions.
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‎README.md

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<td align="center"><a href="topics/perl/README.md"><img src="images/perl.png" width="75px;" height="75px;" alt="perl"/><br /><b>Perl</b></a></td>
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</tr>
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<tr>
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<td align="center"><a href="topics/kafka/README.md"><img src="images/logos/kafka.png" width="70px;" height="80px;" alt="Kafka"/><br /><b>Kafka</b></a></td>
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<td align="center"><a href="topics/circleci/README.md"><img src="images/logos/circleci.png" width="70px;" height="70px;" alt="Circle CI"/><br /><b>Circle CI</b></a></td>
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<td align="center"><a href="topics/argo/README.md"><img src="images/logos/argo.png" width="80px;" height="80px;" alt="Argo"/><br /><b>Argo</b></a></td>
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<td align="center"><a href="topics/kafka/README.md"><img src="images/logos/kafka.png" width="70px;" height="80px;" alt="Kafka"/><br /><b>Kafka</b></a></td>
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</tr>
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</table>
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</center>

‎images/logos/circleci.png

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‎topics/circleci/README.md

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# Circle CI
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## Circle CI Questions
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### Circle CI 101
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<details>
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<summary>What is Circle CI?</summary><br><b>
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[Circle CI](https://circleci.com): "CircleCI is a continuous integration and continuous delivery platform that can be used to implement DevOps practices."
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</b></details>
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<details>
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<summary>What are some benefits of Circle CI?</summary><br><b>
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[Circle CI Docs](https://circleci.com/docs/about-circleci): "SSH into any job to debug your build issues.
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Set up parallelism in your .circleci/config.yml file to run jobs faster.
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Configure caching with two simple keys to reuse data from previous jobs in your workflow.
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Configure self-hosted runners for unique platform support.
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Access Arm resources for the machine executor.
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Use orbs, reusable packages of configuration, to integrate with third parties.
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Use pre-built Docker images in a variety of languages.
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Use the API
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to retrieve information about jobs and workflows.
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Use the CLI to access advanced tools locally.
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Get flaky test detection with test insights."
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</b></details>
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<details>
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<summary>What is an Orb?</summary><br><b>
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[Circle CI Docs](https://circleci.com/developer/orbs): "Orbs are shareable packages of CircleCI configuration you can use to simplify your builds"
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They can come from the public registry or defined privately as part of an organization.
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</b></details>
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### Circle CI Hands-On 101
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<details>
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<summary>Where (in what location in the project) Circle CI pipelines are defined?</summary><br><b>
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`.circleci/config.yml`
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</b></details>

‎topics/kubernetes/CKA.md

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- [Deployments](#deployments)
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- [Troubleshooting Deployments](#troubleshooting-deployments)
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- [Scheduler](#scheduler)
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- [Node Affinity](#node-affinity)
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- [Labels and Selectors](#labels-and-selectors)
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- [Node Selector](#node-selector)
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- [Taints](#taints)
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## Setup
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Note: if you don't have a node1 in your cluster the Pod will be stuck on "Pending" state.
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</b></details>
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### Node Affinity
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<details>
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<summary>Using node affinity, set a Pod to schedule on a node where the key is "region" and value is either "asia" or "emea"</summary><br><b>
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`vi pod.yaml`
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```yaml
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affinity:
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nodeAffinity:
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requiredDuringSchedlingIgnoredDuringExecution:
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nodeSelectorTerms:
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- matchExpressions:
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- key: region
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operator: In
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values:
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- asia
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- emea
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```
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</b></details>
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<details>
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<summary>Using node affinity, set a Pod to never schedule on a node where the key is "region" and value is "neverland"</summary><br><b>
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`vi pod.yaml`
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```yaml
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affinity:
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nodeAffinity:
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requiredDuringSchedlingIgnoredDuringExecution:
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nodeSelectorTerms:
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- matchExpressions:
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- key: region
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operator: NotIn
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values:
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- neverland
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```
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</b></details>
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## Labels and Selectors
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<details>
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`k get deploy -l env=prod,type=web`
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</b></details>
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### Node Selector
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<details>
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<summary>Apply the label "hw=max" on one of the nodes in your cluster</summary><br><b>
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`kubectl label nodes some-node hw=max`
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</b></details>
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<details>
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<summary>reate and run a Pod called `some-pod` with the image `redis` and configure it to use the selector `hw=max`</summary><br><b>
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```
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kubectl run some-pod --image=redis --dry-run=client -o yaml > pod.yaml
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vi pod.yaml
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spec:
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nodeSelector:
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hw: max
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kubectl apply -f pod.yaml
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```
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</b></details>
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<details>
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<summary>Explain why node selectors might be limited</summary><br><b>
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Assume you would like to run your Pod on all the nodes with with either `hw` set to max or to min, instead of just max. This is not possible with nodeSelectors which are quite simplified and this is where you might want to consider `node affinity`.
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</b></details>
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## Taints
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</b></details>
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<details>
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<summary>Create a taint on one of the nodes in your cluster with key of "app" and value of "web" and effect of "NoSchedule"</summary><br><b>
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<summary>Create a taint on one of the nodes in your cluster with key of "app" and value of "web" and effect of "NoSchedule". Verify it was applied</summary><br><b>
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`k taint node minikube app=web:NoSchedule`
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`k describe no minikube | grep -i taints`
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</b></details>
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<details>
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<summary>You applied a taint with <code>k taint node minikube app=web:NoSchedule</code> on the only node in your cluster and then executed <code>kubectl run some-pod --image=redis</code>. What will happen?</summary><br><b>
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The Pod will remain in "Pending" status due to the only node in the cluster having a taint of "app=web".
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</b></details>
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<details>
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<summary>You applied a taint with <code>k taint node minikube app=web:NoSchedule</code> on the only node in your cluster and then executed <code>kubectl run some-pod --image=redis</code> but the Pod is in pending state. How to fix it?</summary><br><b>
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`kubectl edit po some-pod` and add the following
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```
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- effect: NoSchedule
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key: app
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operator: Equal
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value: web
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```
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Exit and save. The pod should be in Running state now.
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</b></details>
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<details>
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<summary>Remove an existing taint from one of the nodes in your cluster</summary><br><b>
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`k taint node minikube app=web:NoSchedule-`
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</b></details>

‎topics/kubernetes/README.md

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- [Istio](#istio)
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- [Controllers](#controllers)
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- [Scheduler](#scheduler-1)
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- [Node Affinity](#node-affinity)
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- [Taints](#taints)
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- [Scenarios](#scenarios)
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|Name|Topic|Objective & Instructions|Solution|Comments|
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|--------|--------|------|----|----|
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| Labels and Selectors 101 | Labels, Selectors | [Exercise](exercises/labels_and_selectors/exercise.md) | [Solution](exercises/labels_and_selectors/solution.md)
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| Node Selectors | Labels, Selectors | [Exercise](exercises/node_selectors/exercise.md) | [Solution](exercises/node_selectors/solution.md)
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### Scheduler
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Note: if you don't have a node1 in your cluster the Pod will be stuck on "Pending" state.
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</b></details>
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#### Node Affinity
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<details>
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<summary>Using node affinity, set a Pod to schedule on a node where the key is "region" and value is either "asia" or "emea"</summary><br><b>
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`vi pod.yaml`
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```yaml
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affinity:
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nodeAffinity:
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requiredDuringSchedlingIgnoredDuringExecution:
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nodeSelectorTerms:
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- matchExpressions:
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- key: region
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operator: In
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values:
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- asia
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- emea
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```
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</b></details>
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<details>
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<summary>Using node affinity, set a Pod to never schedule on a node where the key is "region" and value is "neverland"</summary><br><b>
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`vi pod.yaml`
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```yaml
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affinity:
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nodeAffinity:
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requiredDuringSchedlingIgnoredDuringExecution:
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nodeSelectorTerms:
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- matchExpressions:
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- key: region
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operator: NotIn
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values:
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- neverland
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```
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</b></details>
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<details>
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<summary>True of False? Using the node affinity type "requiredDuringSchedlingIgnoredDuringExecution" means the scheduler can't schedule unless the rule is met</summary><br><b>
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True
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</b></details>
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<details>
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<summary>True of False? Using the node affinity type "preferredDuringSchedlingIgnoredDuringExecution" means the scheduler can't schedule unless the rule is met</summary><br><b>
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False. The scheduler tries to find a node that meets the requirements/rules and if it doesn't it will schedule the Pod anyway.
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</b></details>
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## Taints
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</b></details>
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<details>
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<summary>Create a taint on one of the nodes in your cluster with key of "app" and value of "web" and effect of "NoSchedule"</summary><br><b>
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<summary>Create a taint on one of the nodes in your cluster with key of "app" and value of "web" and effect of "NoSchedule". Verify it was applied</summary><br><b>
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`k taint node minikube app=web:NoSchedule`
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`k describe no minikube | grep -i taints`
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</b></details>
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<details>
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<summary>You applied a taint with <code>k taint node minikube app=web:NoSchedule</code> on the only node in your cluster and then executed <code>kubectl run some-pod --image=redis</code>. What will happen?</summary><br><b>
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The Pod will remain in "Pending" status due to the only node in the cluster having a taint of "app=web".
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</b></details>
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<details>
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<summary>You applied a taint with <code>k taint node minikube app=web:NoSchedule</code> on the only node in your cluster and then executed <code>kubectl run some-pod --image=redis</code> but the Pod is in pending state. How to fix it?</summary><br><b>
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`kubectl edit po some-pod` and add the following
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```
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- effect: NoSchedule
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key: app
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operator: Equal
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value: web
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```
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Exit and save. The pod should be in Running state now.
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</b></details>
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<details>
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<summary>Remove an existing taint from one of the nodes in your cluster</summary><br><b>
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`k taint node minikube app=web:NoSchedule-`
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<details>

‎topics/kubernetes/exercises/node_selectors/exercise.md

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# Node Selectors
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## Objectives
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1. Apply the label "hw=max" on one of the nodes in your cluster
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2. Create and run a Pod called `some-pod` with the image `redis` and configure it to use the selector `hw=max`
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3. Explain why node selectors might be limited
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## Solution
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Click [here](solution.md) to view the solution

‎topics/kubernetes/exercises/node_selectors/solution.md

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# Node Selectors
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## Objectives
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1. Apply the label "hw=max" on one of the nodes in your cluster
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2. Create and run a Pod called `some-pod` with the image `redis` and configure it to use the selector `hw=max`
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3. Explain why node selectors might be limited
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## Solution
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Click [here](solution.md) to view the solution
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1. `kubectl label nodes some-node hw=max`
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2.
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```
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kubectl run some-pod --image=redis --dry-run=client -o yaml > pod.yaml
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vi pod.yaml
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spec:
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nodeSelector:
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hw: max
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kubectl apply -f pod.yaml
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```
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3. Assume you would like to run your Pod on all the nodes with with either `hw` set to max or to min, instead of just max. This is not possible with nodeSelectors which are quite simplified and this is where you might want to consider `node affinity`.

‎topics/kubernetes/exercises/taints_101/exercise.md

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2. Create a taint on one of the nodes in your cluster with key of "app" and value of "web" and effect of "NoSchedule"
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1. Explain what it does exactly
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2. Verify it was applied
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3. Run a Pod that will be able to run on the node on which you applied the taint
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## Solution
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Click [here](solution.md) to view the solution.
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1. `kubectl describe no minikube | grep -i taints`
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2. `kubectl taint node minikube app=web:NoSchedule`
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1. Any resource with "app=web" key value will not be scheduled on node `minikube`
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2. `kubectl describe no minikube | grep -i taints`
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Click [here](solution.md) to view the solution.

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