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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How Do You Troubleshoot the Message “jq: error…Cannot iterate over null”?

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Problem scenario
You are running a jq command (e.g., piping output to jq). You receive message “jq: error…Cannot iterate over null.” What should you do?

Solution
Change the word “Parameters” to “Parameter”. By omitting an “s” from “Parameters”, the error may go away.

Verify there is output. Try running the command without the “jq” utility if possible. This error can happen if there is no output to parse.

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How Do You Get an Ansible Playbook to Not Skip a Section?

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Problem scenario
You are running a playbook. A section is being skipped. When you use “-vvvv” to enhance the verbosity of the output messages, you see “Condition result was false”. How do you get the playbook section that is being skipped to execute?

Solution
The most likely cause is that you have a “when” statement that governs the clause of the playbook that is being skipped.

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How Do You Troubleshoot the AWS CLI Error “Invalid Document Name”?

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Problem scenario
You run an AWS SSM command. You receive “An error occurred (ValidationException) when calling the CreateDocument operation: Invalid document Amazon…” What do you do to get the command to work?

Solution
Document names cannot begin with three strings (regardless of capitalization): “aws”, “amazon”, or “amzn”.

Change the document name to not have a string such as one of the above.

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Using Python How Do You Run Bash Commands That Include More Than One Word?

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Problem scenario
You are trying to have Python run Bash commands. As soon as the command includes a flag or a second argument, there is no value being assigned in Python. Two or more words in the Bash command cause no value to be assigned. What can you do?

Solution
This only works if you have complete control of the Bash command arguments.

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How Do You Troubleshoot the Error “DNS: A new record cannot be created. Refused.”?

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Problem scenario
Using Windows Server and Active Directory, you try to add a PTR record to a Reverse Lookup Zone. You get “DNS: A new record cannot be created. Refused.” What do you do?

Possible Solution #1
Click “Ok” to the pop up. Continue where you were interrupted. The error message should be ignorable (other than the fact that you have to click “Ok” to the pop-up itself and the window to create a New Resource Record).

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