How Do You Invoke the main Section of a Groovy Program?

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Problem scenario
Your Groovy code has a section like this:

class Example {
static void main(String[] args) {
…

But this section above is not executing when you run your Groovy program. There are no errors however. How do you get it to execute?

Possible Solution #1
Remove lines of code (or statements) that are outside the “class Example {…”

Possible Solution #2
See this posting: How Do You Invoke a Class in a Groovy Program?

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How Do You Use the aws update-kubeconfig Command?

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Problem scenario
You want to manage your Amazon Kubernetes (i.e., EKS) cluster. You have installed the AWS CLI version on a Linux server, and you want to use the update-config or update-kubeconfig command.

But when you try you see messages like “error argument command: Invalid choice…” or “update-config: command not found”. You could not readily find an example. What should you do?

Solution
Background
The command is update-kubeconfig,

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How Do You Interpret the dstat Utility’s Results on a Linux Server in AWS?

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Problem scenario
You want to monitor network traffic on an EC-2 server’s NICs. You are not sure what to look for or what a baseline should look like. What do you do?

Solution
1. Install dstat. With a CentOS/RHEL/Fedora server, run this: sudo yum -y install dstat
2. Run this command: dstat -nt
3. With no network activity beyond the PuTTy session to the EC-2 server,

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How Do You Terminate Pods in Kubernetes?

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Problem scenario
You have some Pods in Kubernetes that you want deleted. What should you do?

Solution
1. Find the names. You can run this to find out: kubectl get pods

2. Run this command, but replace “foobar” with the name of the pod you want deleted: kubectl delete pods foobar

3. That should be it. Run kubectl get pods to verify deletion was successful.

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How Do You Troubleshoot the Java Program Message “java.sql.SQLException: No database selected”

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Problem scenario
Your Java program returns this message: “java.sql.SQLException: No database selected”
What should you do?

Possible Solution #1
Your SQL statement was appropriate for a database but not for the circumstance of connecting to a SQL instance. Try show databases; instead of the SQL you were running.

Possible Solution #2
Did you connect to the SQL instance you thought you connected to?

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How Do You Get a List of Mail Queue IDs and Nothing Else?

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Problem scenario
You use the mailq command. You see several emails have timed out. These emails are essentially in an “outbox” and a future delivery attempt is in the near future. How do you produce a list of the mail queue IDs by themselves?

Solution
If you want a list of the mail queue IDs in the queue, run this:
mailq | awk ‘{print $1}’ | grep -v ‘[[:punct:]]’ | sort | uniq

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How Do You Troubleshoot the Error “sed: -e expression #1, char 1: unknown command: `””?

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Problem scenario
You have a sed command in a script, but you get an error like one of the following:

sed: -e expression #1, char 1: unknown command: ” sed: -e expression #1, char 1: unknown command:”‘

How do you troubleshoot this?

Solution
You may need to assign variables like this:

var1=” foo””‘”” bar” # Place quotes around any unusual characters (e.g.,

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