> ## Documentation Index > Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt > Use this file to discover all available pages before exploring further. # Demo Buildpack Layers > This guide demonstrates separating the Node.js runtime and Node modules into dedicated layers to improve build performance and caching. In this guide, we demonstrate how to separate the Node.js runtime and Node modules installation into dedicated layers. Separating these components not only clarifies the build process but also leverages caching and boosts launch performance. Below is a comprehensive step-by-step walkthrough with clearly structured code blocks. *** ## Creating the Node.js Runtime Layer In this section, we create a dedicated layer for the Node.js runtime. Here, we download and extract Node.js into a specified directory. The runtime layer’s metadata is configured in a TOML file to ensure it is available at launch. ```bash theme={null} #!/usr/bin/env bash set -euo pipefail echo "Building image using my-js-buildpack buildpack" # Create the Node.js runtime layer directory node_js_layer="${CNB_LAYERS_DIR}/node-js" mkdir -p "${node_js_layer}" default_node_js_version="18.18.0" # Retrieve the user's desired Node.js version from the plan or use the default node_js_version=$(jq -r '.entries[] | select(.name == "node-js") | .metadata.version' < "$CNB_BP_PLAN_PATH" || echo "${default_node_js_version}") echo "nodejs version: ${node_js_version}" echo "--> Downloading and extracting NodeJS" node_js_url="https://nodejs.org/dist/v${node_js_version}/node-v${node_js_version}-linux-x64.tar.xz" wget -q -O - "${node_js_url}" | tar -xJf - --strip-components=1 -C "${node_js_layer}" # Create the TOML file for Node.js layer metadata cat > "${CNB_LAYERS_DIR}/node-js.toml" << EOL [types] build = false launch = true cache = false EOL ``` After executing these steps, the Node.js runtime is installed into the custom layer defined by the `node_js_layer` variable. To ensure that this runtime is available for subsequent build steps and the final image, update the PATH to include the Node.js binary directory: ```bash theme={null} export PATH="${node_js_layer}/bin:$PATH" ``` You can verify the installation with the following commands: ```bash theme={null} pwd ls -la ``` *** ## Installing Application Dependencies in a Separate Node Modules Layer Next, we focus on installing your application’s dependencies in a distinct layer. This separation allows you to cache Node modules separately, improving build times and resource utilization. Since dependency installation normally occurs in the current directory, we copy the package files into a new directory, install the dependencies there with `npm ci`, and then create a symbolic link back to the workspace. First, capture the current working directory to reference later: ```bash theme={null} workdir=$(pwd) ``` Now, create the layer for your Node modules, install dependencies, and configure the launch process: ```bash theme={null} # Create layer for the node modules node_modules_layer="${CNB_LAYERS_DIR}/node-dependencies" mkdir -p "${node_modules_layer}" echo "---> Installing Application Dependencies" # Copy package files to the node_modules layer and install dependencies there cp package*.json "${node_modules_layer}" cd "${node_modules_layer}" npm ci cd "$workdir" # Create launch configuration for the final runtime image cat > "${CNB_LAYERS_DIR}/launch.toml" << EOL [[processes]] type = "web" command = ["node", "index.js"] default = true EOL # Symlink the installed node_modules back into the workspace to satisfy the application structure ln -s "${node_modules_layer}/node_modules" "/workspace/node_modules" ``` This setup ensures that your dependencies reside in their own layer while keeping your application code in the workspace. The symbolic link enables Node.js to locate the `node_modules` folder during runtime. *** ## Resolving the Node.js Executable Path During preliminary testing, you might encounter an error similar to: ```plaintext theme={null} npm: command not found ``` This error occurs because Node.js is installed in a separate layer, and the PATH variable has not been updated to include the binary location. To resolve this issue: 1. First, add the Node.js runtime layer (and its `bin` folder) to your PATH: ```bash theme={null} export PATH="${node_js_layer}/bin:$PATH" ``` 2. Ensure the launch process is correctly configured. In the final launch TOML, reference the proper command as shown below: ```bash theme={null} cat > "${CNB_LAYERS_DIR}/launch.toml" << EOL [[processes]] type = "web" command = ["node", "index.js"] default = true EOL ``` The runtime image builder automatically includes the Node.js layer in the PATH so that both `node` and `npm` are recognized. *** ## Final Build and Verification After configuring both layers, you are ready to build the image. During the export stage, you should see that both the Node.js runtime layer and the node modules layer have been added: ```plaintext theme={null} [exporter] Adding layer 'my-js-buildpack:node-dependencies' [exporter] Adding layer 'my-js-buildpack:node-js' [exporter] Saving myapp... ``` To build the image with the appropriate buildpacks, use the following command: ```bash theme={null} pack build myapp --path nodejs-app --builder cnbs/sample-builder:jammy --buildpack js-buildpack/ ``` Once the image is successfully built, run a container and verify that the application functions as expected. For example, you can use a command like the one below to check for a “Hello World” response: ```bash theme={null} curl localhost:8000 ``` *** By following these steps, you have successfully separated the Node.js runtime and Node modules into individual layers. This modular approach optimizes caching and ensures that your final runtime image includes only the necessary components, enhancing both build performance and deployability.