What Are Namespaces?

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Problem scenario
You have heard of namespaces in programming, DNS, AWS, operating systems, and in the context of managing containers. You want to see the disambiguation of of this term insofar as computing is concerned. What are namespaces in I.T.?

Overview
Names can be bound to different spaces (or subsystems), and this binding varies depending on the technology. Namespacing helps facilitate locally unique identification/resolution of names.

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How Do You Merge Three Files (.jpegs and PDFs) into One PDF?

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Problem scenario
You have a non-business project (e.g., a non-commercial, non-professional, non-work-related project). You need to combine individual JPEGs and PDFs into one PDF. How do you do this?

Solution

  1. Print the JPEG(s) to Microsoft Print to PDF. Now the JPEG(s) has (or have) been converted into the PDF format.
  2. Use PDFmate.com to download and install “Free PDF Merger for Windows.”
  3. Open PDFmate Merger.

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How Do You Set an Environment Variable for Every User Upon Rebooting a Linux Server?

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Problem scenario
Without creating a hard or soft link of a file, how do you set an environment variable for every user after every reboot?

Solution

  1. Update the /etc/environment file so it has this stanza (but replace “JAVA_HOME” with the variable of your choice and replace /usr/bin/java with the path or value of the variable as you desire):

JAVA_HOME=/usr/bin/java

  1. Save the changes of the file.

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What Is Second Generation CM?

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Question
What is a second generation configuration management tool?

Answer
Page xiii of The DevOps Handbook refers to John Willis characterizing Luke Kanies’ thoughts on configuration mangaement as “second generation CM.” But according to https://www.cmcrossroads.com/article/cm-generations-and-vision-future there are four generations of CM. This may or may not be compatible with what John Willis hand in mind, but we do not see how Luke Kanies’ vision could be the second oldest of the four generations.

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What Do You Do If CloudWatch Metrics Are Not Showing Up in the Dashboard?

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Problem scenario
You used a .json file and the AWS CLI to configure customized metrics. When you go to the GUI you do not see the graphs. The commands that were run with the .json file completed without errors or problems. How do you get the web console to show the metrics you configured for various AWS components?

Possible Solution #1
CloudWatch metrics are not all necessarily graphed.

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How Do You Troubleshoot “The filter VolumeId” is invalid?

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Problem scenario
You run an aws ec2 command and you get use the –filters flag with Name=VolumeId (consistent with the casing that you see in other AWS CLI contexts). You receive a message about “the filter VolumeId” being invalid. What should you do?

Solution
Use “volume-id” instead of “VolumeId”.

In general we find that the syntax of the name itself, for an AWS CLI –filters flag,

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Why Does a User Not Have Access to a VPC when The Configuration Appears to Allow For Connectivity?

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Problem scenario
A user has no access to a VPC from her workstation. What are three ways a user can be given access to resources in a VPC?

Four Possible, Independent Solutions

  1. Network Access Control lists. These are IP address firewalls for the VPCs themselves. Based on the IP address of the user’s workstation, Network Access Control lists can allow or disallow traffic to the VPC.

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