A Technical I.T./DevOps Blog
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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Continue reading “How Do You Make a Web UI Service Accessible to Outside Web Browser Traffic?”
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.
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Continue reading “What Is The Immutable Bit vs. The Sticky Bit?”
Question
What is a ConfigMap in Kubernetes?
Answer
A ConfigMap is a mapping of configuration originally in YAML format that resides in etcd (partially taken from this external posting). 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.
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Problem scenario
You want to create a Jenksinfile for a pipeline. Where can you find a complete list of the reserved words for Declarative pipeline syntax?
Answer
This external page has something close. It does not go into into how “sh” works. Using “sh” you can run Linux commands. There are “bat” and “powershell” options too. Here is an example (taken from Jenkins’ website) :
pipeline {
agent any
stages {
stage(‘Build’) {
steps {
sh ‘echo “Hello World”‘
sh ”’
echo “Multiline shell steps works too”
ls -lah
”’
}
}
}
} …
Question
What is an HPA in Kubernetes?
Answer
HPA stands for HorizontalPodAutoscaler. It is a concept and resource that allows clusters to scale out upon a certain condition being met. HPA can support a pod to scale based on certain amounts of CPU utilization. It natively supports granular CPU requests down to a single millicore. A .yaml file in Kubernetes has the key “kind”;
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Problem scenario
You want to use the Docker Pipline (with the Jenkins ID of “docker-workflow”). What do you do?
Solution
Prerequisites
Jenkins needs to be installed. If you need assistance, see this posting if you are using a CentOS/RHEL/Fedora server; if you want to install Jenkins on a Debian/Ubuntu server, see this posting.
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Continue reading “How Do You Use the Docker Pipeline Plugin with Jenkins?”
Question
How would a DevOps engineer define operational readiness or what is operational readiness in I.T.?
Answer
“All things are ready, if our mind be so.” –William Shakespeare
While some people would say it is more of a state*, others may say it is more of a journey**. Operational readiness is having sufficient staff and automation to maintain the minimum level of service that the business requires for a given product or service.
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Question
What is an Ingress resource in Kubernetes?
Answer
It is a Kubernetes technique of exposing services via an individual IP address (page 135 of Kubernetes in Action by Luksa). In TCP/IP networking, the Ingress port allows inbound traffic to route somewhere. Kubernetes supports other IP address to service mapping methods (e.g., NodePort or LoadBalancer). NodePort operates on layer 4 of the OSI seven-layer model (according to this posting).
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Continue reading “What is an Ingress Resource in Kubernetes?”
Problem scenario
You want to run Splunk from a Docker container. What do you do?
Solution
Prerequisites
Install Docker. If you need assistance, see this posting.
Procedures
1. Run this command: docker pull splunk/splunk:latest
2. Run this command, but replace “simpleword” with the password that you want the administrator account for the web UI to have:
docker run -d -p 8000:8000 -e ‘SPLUNK_START_ARGS=–accept-license’ -e ‘SPLUNK_PASSWORD=simpleword’ splunk/splunk:latest
3.
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Continue reading “How Do You Install Splunk in a Docker Container?”
Problem scenario
You want to know how dictionaries perform as iterables in Python. In Python for printing the values of every key-value pair in a dictionary, is it faster or slower than printing every item in a list? How does it compare to a tuple?
Solution
For this example we use integer keys in the dictionary. Keys can be strings or other objects.
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