A Budget-Friendly Resource Guide to Tech Investments for Solopreneurs

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A Budget-Friendly Resource Guide to Tech Investments for Solopreneurs

If you’re a small business owner or solopreneur, keeping overhead costs low is probably a priority. While it’s understandable to save where you can, one area you shouldn’t skimp on is technology. The right tech investments can help streamline your business operations, saving you time, stress, and money.

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Where Is the core-site.xml File in a Hadoop Installation?

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Problem scenario
You downloaded and installed Hadoop core. But you cannot find the core-site.xml file. What should you do?

Possible Solution #1
Run this: sudo find / -name core-site.xml

Possible Solution #2
Did you download the installation media with a file “-site” in its name?

Try again with a .tar.gz file without “-site” (and without “-src”) in its name:
https://dlcdn.apache.org/hadoop/core/stable/

(This is the for open source version and not a specific vendor’s implementation of Hadoop.)

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How Do You Troubleshoot “Segmentation fault” Errors in Hadoop/HDFS?

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Problem scenario
You get a “Segmentation fault” or “Segmentation fault (core dumped)” error when you run any “hdfs” command. What should you do?

Solution

Root cause
There is probably an infinite loop/recursion problem. (Segmentation faults involve writing to the stack. Eventually the memory gets filled up.) There is some configuration problem with your Hadoop / hdfs installation.

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For Databases Is a B-Tree the Same as an Index?

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Question
In the context of databases, Is a B-tree the same as an index?

Answer
For many intents and purposes they are the same.

“B-Tree is a self-balancing search tree.” Taken from
https://www.geeksforgeeks.org/introduction-of-b-tree-2/.

“B-tree is a data structure that store data in its node in sorted order.” Taken from https://dzone.com/articles/database-btree-indexing-in-sqlite.

This source says that the “B” stands for “balanced” (not “binary”): https://use-the-index-luke.com/sql/anatomy/the-tree

To learn more see this: https://www.geeksforgeeks.org/difference-between-binary-tree-and-b-tree/

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Is It a Recommended/Best Practice to Use Email as a Component in Two Factor Authentication?

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Problem scenario
You want to implement a secure protocol for authentication. You want there to be a password and a second factor of authentication. Can an email (being in possession of an inbox) be a factor in MFA?

Answer
Maybe.

No, according to NIST:
https://pages.nist.gov/800-63-FAQ/

But many companies do use email as a factor in multi-factor authentication.

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How Do You Get Hotel Refrigerators to Not Freeze Your Food?

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Problem scenario
You go to hotels with mini-refrigerators. What appears to be a small fridge is actually a freezer from a pragmatic perspective. Your food (e.g., apples or fruit) get destroyed when they are frozen. You want a fridge, but everything seems to freeze your food. What should you do?

Solution
Turn the temperature down. If you open the fridge and do not see a thermostat,

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How Do You Troubleshoot OOM Errors with Restarting Pods in Kubernetes?

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Problem scenario
You find out-of-memory (aka OOM) errors in Kubernetes. The node seems healthy. The pods keep restarting. What should you do?

Possible Solution #1
Are you using a burstable quality of service (aka QoS) with the pods? There may be a non-pod-specific reason and the burstable Pods are being starved of resources. The node may be getting requests for other pods with a superior quality of service.

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How Do You Troubleshoot “ERROR: Hadoop common not found” when Running Hadoop?

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Problem Scenario
You run an HDFS command, but you get this message: “ERROR: Hadoop common not found”

What should you do?

Solution
As the hduser or user that runs hdfs, log in. Run “echo $HADOOP_HOME”

That directory should have a libexec directory with a file called hadoop-config.sh.

Run this: ls -lh $HADOOP_HOME/libexec

One way to create it is this: 1) find a hadoop-config.sh file (e.g.,

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