A Technical I.T./DevOps Blog
Digital Upgrades to Keep Your Business From Falling Behind
Businesspop.net shares a post today intent on helping small businesses get ahead in the digital age.
As a small business owner, you have a lot on your plate. You have to keep your profits in the black, make sure that your customers are happy, and ensure your employees have the tools they need to be effective.
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Problem scenario
You run “sudo usermod -aG wheel jdoe” but you get “usermod: group ‘wheel’ does not exist.” What should you do?
Possible solution #1
Run this:
sudo usermod -aG admin jdoe
Some Linux distributions such as Ubuntu* use “admin” instead of “wheel”
You may want to read this for further information.
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Continue reading “How Do You Troubleshoot the Error Message “usermod: group ‘wheel’ does not exist””
Problem scenario
You modified the /etc/sudoers file. The changes do not seem to have taken effect. What should you do?
Solution
99% of the time you do not need to log out or log back in. You should not need to open another terminal. For the stanza that you added, did you append it to the bottom? The problem may be that the stanza you added was in the middle of the file.
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Continue reading “How Do You Troubleshoot /etc/sudoers Changes Not Working?”
Problem scenario
You get a “Segmentation fault” or “Segmentation fault (core dumped)” error when you run any “hdfs” command. (This is open source Hadoop and not a proprietary, or vendor’s, version.) 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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Continue reading “How Do You Troubleshoot “Segmentation fault” Errors in Hadoop/HDFS?”
Problem scenario
You found some empty files called aquota.group or quota.group. What is the difference?
Solution
The aquota.user file is for version 2 quota systems (per the man page for edquota). quota.user is for version 1. See also What Is the Difference between Version 1 Quotas and Versions 2 Quotas?
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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.”
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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Continue reading “For Databases Is a B-Tree the Same as an Index?”
Problem scenario
You are trying to install Darling. You get this error: “./include/linux/uio.h:16:31: fatal error: 1/hash.h: No such file or directory
#include RH_KABI_HIDE_INCLUDE()”
What should you do?
Solution
Run this:
sudo uname -r
Is the kernel version 5 or higher? If not, that is the root cause.
The source of this was https://github.com/darlinghq/darling/issues/975
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Continue reading “How Do You Troubleshoot “fatal error: 1/hash.h: No such file or directory”?”
Problem scenario
You know .crt and .key files can pair as ssl_certificates and SSL certificate keys respectively. In Nginx, can .pem files replace .crt files? Can .pem files potentially replace .key files? Can a .pem file be a substitute?
Solution
Yes to some extent, for the nginx.conf file, a .pem file can replace a .crt file and potentially a .key file too.
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Continue reading “With Nginx Can a .pem file replace a .crt and/or a .key File?”
Problem scenario
You want to remove the battery from your Nokia flip phone. There is a hinge, and the phone closes as normal like a clamshell. But you need to restart the phone (e.g., and it will not shut off). How do you remove the battery from a Nokia phone?
Solution
While the phone back cover may seem hard to come off,
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Continue reading “How Do You Remove the Battery Cover of a Nokia Cell Phone?”
Problem scenario
You run “docker-compose build” and you get this:
1 error occurred:
* unable to prepare context: unable to evaluate symlinks in Dockerfile path: lstat /home/jane/dockercompose/webapp/Dockerfile: no such file or directory
What should you do?
Solution
Look at your docker-compose.yml file. Look at the “build” stanza. What directory is it referring to? Is a Dockerfile file in that directory?
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