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Learn how to run a `shell script` inside an interactive `bash pod` on Kubernetes effortlessly. Follow our clear steps to get it done!
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This video is based on the question https://stackoverflow.com/q/72681005/ asked by the user 'Vahid' ( https://stackoverflow.com/u/2659499/ ) and on the answer https://stackoverflow.com/a/72681100/ provided by the user 'larsks' ( https://stackoverflow.com/u/147356/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Execute a Shell Script as Input on an Interactive Bash Pod in Kubernetes

Kubernetes is an excellent platform for managing containerized applications. One common scenario developers face is executing scripts within a pod interactively. If you have a shell script ready and want to run it in a Kubernetes pod, you might be wondering how to bring this to life effectively. Let's break this down step-by-step to make it simple for you.

The Problem

You have a shell script called my-script.sh that infinitely outputs 1. Here's the content of your script:

[[See Video to Reveal this Text or Code Snippet]]

You successfully deployed a bash pod in Kubernetes using the command:

[[See Video to Reveal this Text or Code Snippet]]

However, your goal is to execute your script directly within this pod. How can you achieve this? The typical approach would suggest using input redirection, but let’s look at the correct way to do this with Kubernetes.

The Solution

To run your script correctly, you need to pass it as input to the shell process. Here’s how to do that in detail:

Step 1: Modify Your kubectl Command

Instead of using the -t option (which allocates a terminal), you should use the -i option (which keeps standard input open), because the script will read from standard input, not a terminal. Also, you don't need the -c option from bash since the script is being read as input, not an argument. Therefore, your command should be structured like this:

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Step 2: Execute the Command

Run the command in your terminal. You should see the output without needing a command prompt.

[[See Video to Reveal this Text or Code Snippet]]

Understanding Input Redirection

Input Redirection: The < symbol allows you to redirect the content of my-script.sh as input to the bash shell. This is why -i (interactive) is crucial while -t (for terminal allocation) is not needed in this context.

Continuous Execution: Since your script outputs 1 in a loop, the output will keep coming until you stop it. To stop the execution, press Ctrl+ C in your terminal.

Conclusion

Running scripts in Kubernetes is a common task for many developers. By following the simple steps above, you can easily execute your shell scripts within a bash pod without any hassle. Remember to adjust your kubectl run command to streamline the execution according to your needs. Happy scripting!