A Technical I.T./DevOps Blog
Question
Erasure coding versus negative coding: what is the difference?
Answer
In the verbose output of a Hadoop or mapred job, you may have seen “INFO mapreduce.JobResourceUploader: Disabling Erasure Coding for path:”
Erasure coding is a fault-tolerant storage mechanism. Like replication the usable capacity of the disks participating in such a mechanism is not fully utilized as in a RAID 0 configuration.
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Continue reading “What Is the Difference between Erasure Coding and Negative Coding?”
Question
What is the difference between negative coding and throw-away prototyping?
Answer
“Plan to throw one away…” -Frederick P. Brooks, Jr. (Taken from page 266 of The Mythical Man-Month).
Both negative coding and throw-away prototyping involve eliminating lines of code. But this is the only similarity they have. Negative coding is contrasted from throw-away prototyping in that the former is a good practice for production systems and long-term use whereas the latter is designed to be temporary.
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Problem scenario
You have a .yaml configuration file that works with the kubectl command to create a deployment. You want to change the source image from the hub.docker.com to a Google container source. How do you configure the .yaml file to obtain the image from a Google container registry instead of Docker Hub?
Your .yaml file has these four lines (among other lines):
spec:
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Problem scenario
You have a Docker host that is running Linux (the server with Docker containers). You want to run commands inside a Docker container. How do you get into a Docker container?
Solution
Prerequisite
You need to know the container ID of a running container. To find it run this: docker ps -a
Procedures
Run this command:
docker exec -it <container IDbash
You may want to see this
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Problem scenario
You have a Linux server in AWS and another Linux server in Azure. You want to use scp without a password to transfer files rapidly. How do you configure passwordless SSH authentication between the two servers?
Solution
1. Run this command on each server:
ssh-keygen -t rsa -P “”
# Accept the default prompt by pressing enter.
2.i.
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Problem scenario
You want to know the Docker images of the pods running in your Kubernetes cluster(s). How do you determine this?
Solution
From your Kubernetes server, run this single multi-line command:
kubectl get pods –all-namespaces -o jsonpath=”{..image}” |\
tr -s ‘[[:space:]]’ ‘\n’ |\
sort |\
uniq -c
It was taken from this link.
[Sassy_Social_Share]Problem scenario
You want to deploy your own LAMP stack with the power of Kubernetes. You do not want to rely on official Docker Hub images for the underlying Docker containers. How do you do this?
Solution
1. Deploy Kubernetes to AWS. If you need help to deploy Kubernetes to AWS, see this link. If you need assistance installing kubectl on any type of Linux (CentOS/RHEL/Fedora,
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Continue reading “How Do You Deploy a LAMP Stack Application Powered by Kubernetes?”
Problem scenario
Now that the Docker registry is set up and has been tested, you want the “docker login” command to be able to work from other Docker hosts. How do you configure another server (a Docker host, as a client) to work with a Docker registry server?
Solution
1. Install Docker on the server that will be the client. If you need directions,
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Continue reading “How Do You Configure a Docker Host to Be a Client of a Docker Registry?”
Problem scenario
You want to deploy a Kubernetes cluster to Azure. You have an Ubuntu Linux server (e.g., with a nano flavor in AWS, a server on-premises, or an one vCPU Azure server with one GB of RAM). It has no software packages installed on it (e.g., it does not have Docker or Kubernetes). How do you deploy Kubernetes into Azure (from an instance in AWS)?
Solution
Warning:
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Continue reading “How Do You Deploy a Kubernetes Cluster to Azure?”
Updated on 12/26/18
Problem scenario
I.T. security concerns itself with confidentiality, integrity and availability. These three categories are concepts which help professionals prioritize and crystallize what to secure and how to secure it.
In the context of computer security, the CIA triad (confidentiality, integrity and availability) is commonly used. How could data be available if it did not have integrity? What is the difference between integrity and availability?
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Continue reading “What Is the Difference between Integrity and Availability in the CIA Triad?”