Lambda layer contents not showing up in /opt

Hello.

I added a layer to my AWS account using the steps in the document below and confirmed that files were created under "/opt".
https://docs.aws.amazon.com/lambda/latest/dg/nodejs-layers.html

I added the layer by running the following AWS CLI command:

mkdir nodejs
cd nodejs
mkdir certs
cd certs/
openssl genrsa -out whatever.pem 2048
cd ../../
zip -r layer.zip nodejs
aws lambda publish-layer-version --layer-name cert --zip-file fileb://layer.zip --compatible-runtimes nodejs22.x --region your-region
aws lambda update-function-configuration --function-name nodetest --cli-binary-format raw-in-base64-out --layers "arn:aws:lambda:your-region:your-aws-account-id:layer:cert:1"

I used the following code to check the files in "/opt".

import fs from 'fs';
import path from 'path';

export const handler = async (event) => {
  const targetDir = '/opt';
  
  try {
    const listFiles = (dir) => {
      const entries = fs.readdirSync(dir, { withFileTypes: true });
      const results = [];

      for (const entry of entries) {
        const fullPath = path.join(dir, entry.name);
        if (entry.isDirectory()) {
          results.push(...listFiles(fullPath));
        } else {
          results.push(fullPath);
        }
      }
      return results;
    };

    const files = listFiles(targetDir);

    console.log("===== /opt file list =====");
    console.log(files);

    return {
      statusCode: 200,
      body: JSON.stringify({
        message: `/opt contains ${files.length} file(s).`,
        files,
      }),
    };
  } catch (err) {
    console.error("Error reading /opt:", err);
    return {
      statusCode: 500,
      body: JSON.stringify({ error: err.message }),
    };
  }
};

As a result of execution, you can confirm that the following files have been created:

{
  "statusCode": 200,
  "body": "{\"message\":\"/opt contains 1 file(s).\",\"files\":[\"/opt/nodejs/certs/whatever.pem\"]}"
}