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,

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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.

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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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