How Do You Install Spring Framework with Docker?

Problem scenario
You want to deploy the Spring framework with Docker. How do you do this?

Solution
Warning: The last step in this is not a security “recommended practice.” Only follow these directions (with sudo docker run…), if the server is not that important or you are in a very secure network. One published book says you can use “sudo docker …” as long as the server is not in production (page 43 of Docker Up and Running).

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How Do You Troubleshoot the HDFS Error “failed on connection exception: java.net.ConnectException: Connection refused;”?

Problem scenario
You have a multi-node Hadoop cluster running Hadoop version 3. You run this command: hdfs dfsadmin -report

You receive an error that includes this message: “failed on connection exception: java.net.ConnectException: Connection refused; “

What should you do?

Potential Solution
Run these three commands:

bash /usr/local/hadoop/sbin/stop-dfs.sh
hdfs namenode -format
bash /usr/local/hadoop/sbin/start-dfs.sh

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What is a Secret in Kubernetes?

Question
What is a Secret in Kubernetes?

Answer
It is a ConfigMap with sensitive data that is encoded in Base64 text. What is a ConfigMap? It is a .yaml with a special format. There is always a “data:” section that is part of the YAML definition of a ConfigMap. The key-value pairs in the “data” section will have keys that appear in regular text;

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How Do You Troubleshoot the AWS Error “could not get token: NoCredentialProviders: no valid providers in chain. Deprecated.”

Problem scenario
You run this command: kubectl get svc

You receive this:
” could not get token: NoCredentialProviders: no valid providers in chain. Deprecated.
For verbose messaging see aws.Config.CredentialsChainVerboseErrors”

What should you do?

Solution
Install and configure the AWS CLI. If you need assistance with this, see this posting.

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What is a Service, a Deployment, an HPA, a Pod, an Ingress, a Secret, and a Node in Kubernetes?

Question
In Kubernetes you have heard of these things: service, deployment, HPA, pod, ingress, secret, configmap, and node. What are they?

Answer
Click on the relevant question for its answer:
What is a Secret in Kubernetes?
What is a ConfigMap in Kubernetes?
What is a Deployment in Kubernetes?
What is an Ingress Resource in Kubernetes?

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How Do You Deploy AKS (Azure’s Kubernetes) Using the GUI?

Problem scenario
You want to use Azure’s Kubernetes PaaS offering using the GUI. What do you do?

Solution

1. Sign into the Azure portal.
2. Click on “Services” on the left.
3. Click on “Containers”.
4. Click on “Kubernetes services”.
5. Click “Add”.
6. Fill out the required fields.
7. Click the “Review + create” button.

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What Are the Recommended Practices of Monitoring?

Question
AWS’s Five Pillars of Well-Architected Framework recommend monitoring as a component of three of the pillars (operational excellence, reliability and performance efficiency).

There is no question that monitoring is important inside or outside of a public cloud. What patterns or traits might a good centralized monitoring system have?

Answer
Here are 12 characteristics of good monitoring.

1.

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How Do You Make a Web UI Service Accessible to Outside Web Browser Traffic?

Problem scenario
Sometimes you have a web service listening on the loop back IP address on a non-standard port.

When you run nmap -Pn localhost, you see a service is listening on a given port (e.g., 9200). When you run nmap -Pn on an internal or external IP address, you do not see a service listening on that given port. You want to direct traffic to this listening service (e.g.,

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What Is The Immutable Bit vs. The Sticky Bit?

Problem scenario
You have heard of the immutable bit and want to know how it is different from the sticky bit. What is the immutable bit versus the sticky bit? What are the differences between the two?

Solution
We like the term “immutable flag” as opposed to “immutable bit” to help distinguish the two. We have three parts to explain this.

Part 1: What is the immutable flag?

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What is a ConfigMap in Kubernetes?

Question
What is a ConfigMap in Kubernetes?

Answer
A ConfigMap is a mapping of configuration in YAML format. A .yaml file will define the version of the Kubernetes API (e.g., version 1), data, and the “kind:” key will be set to “ConfigMap”.

The content of the ConfigMap is consumed by an application in Kubernetes. The values in the ConfigMap are “passed to containers as either environment variables or as files in a volume” (page 198 Kubernetes in Action by Luksa).

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