1.4.1 • Public • Published

Serverless Env Generator Plugin

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This plugin automatically creates a .env file during deployment by merging environment variables from one or more YAML files. During runtime these variables can then be loaded into process.env using dotenv.

For a brief introduction, read our blogpost about introducing serverless-env-generator.

Key features:

  • Support for multi-stage configurations and custom profiles
  • Value of environment variables can be encrypted with AWS KMS, allowing teams to manage sensitive information in git.
  • By using KMS, access to secrets can be controlled with IAM. We recommend to create one KMS key per serverless-profile, so you can limit access to credentials to deployment privileges.
  • During deployment a temporary .env file is created and uploaded to Lambda by merging and decrypting values of your environment YAML files.
  • Environment variables can be loaded with dotenv at startup in Lambda without delays from KMS.
  • Supports serverless-local-dev-server and serverless offline for local development.


Please note that the uploaded .env file contains secrets in cleartext. Therefore we recommend to use Serverless Crypt for critical secrets. This tool aims to strike a balance between storing secrets in plaintext in Lambda environment variables and having to decrypt them at runtime using KMS.

Furthermore the tool does not support environment variables generated by Serverless. We recommend to set these variables directly in each functions configuration in serverless.yml.

When used with serverless-local-dev-server your environment variables are directly loaded into process.env. No .env file is created to make sure that your local development and deployment tasks do not interfere :-)

This package requires node >= 8.0. Due to the reliance on KMS, encryption is only supported for AWS.

The .env.local file in the project root is here only for the tests.

Table of Contents


Getting Started

1. Install the plugin and dotenv

npm install dotenv --save
npm install serverless-env-generator --save-dev

2. Create a key on KMS


Please make sure to create the KMS key in the same region as your deployment.

For aliases we recommend to use the service name, for administration privileges no user (your AWS account has full permissions by default) and for usage privileges "serverless-admin" to link access permissions to deployment permissions.

3. Add the plugin to your serverless configuration file

serverless.yml configuration example:

  name: aws
  runtime: nodejs8.10
    handler: handler.hello
# Add serverless-env-generator to your plugins: 
  - serverless-env-generator
# Plugin config goes into custom: 
  envFiles: #YAML files used to create .env file 
    - environment.yml
  envEncryptionKeyId: #KMS Key used for encrypting values 
    dev: ${env:AWS_KMS_KEYID} #Key used for development-stage 

4. Add the .env file to your .gitignore

As the generated .env file contains the secrets in cleartext, make sure that it will never be checked into git!

.gitignore code example:


5. Add variables to your environment YAML file

Command example:

serverless env --attribute name --value "This is not a secret"
serverless env --attribute secret_name --value "This is a secret" --encrypt

6. Write your function

Note that the .env file is automatically created when you deploy your function, so you can just load those variables with dotenv 🎉

Code example:

require('dotenv').config() // Load variables from .env file
module.exports.hello = (event, context, callback) => {
  const response = {
    statusCode: 200,
    body: JSON.stringify({
      message: process.env.secret_name,
      input: event
  callback(null, response)

7. Deploy & test your function

Command example:

serverless deploy
serverless invoke -f $FUNCTION_NAME

Result example:

    "body": "{\"input\": {}, \"message\": \"This is a secret\"}",
    "statusCode": 200


You can use these commands to modify your YAML environment files.

If no stage is specified the default one as specified in serverless.yml is used.

Viewing environment variables

Use the following commands to read and decrypt variables from your YAML environment files:

List variables

serverless env
serverless env --stage $STAGE

View one variable

serverless env --attribute $NAME
serverless env --attribute $NAME --stage $STAGE
sls env -a $NAME
sls env -a $NAME -s $STAGE

Decrypt variables

serverless env --decrypt
serverless env --attribute $NAME --decrypt
serverless env --attribute $NAME --stage $STAGE --decrypt
sls env -a $NAME --decrypt
sls env -a $NAME -s $STAGE -d

Setting environment variables

Use the following commands to store and encrypt variables in your YAML environment files:

Note that variables are stored to the first file listed in envFiles.

Set a variable

serverless env --attribute $NAME --value $PLAINTEXT
serverless env --attribute $NAME --value $PLAINTEXT --stage $STAGE
sls env -a $NAME -v $PLAINTEXT
sls env --a $NAME -v $PLAINTEXT --s $STAGE

Set and encrypt a variable

serverless env --attribute $NAME --value $PLAINTEXT --encrypt
serverless env --attribute $NAME --value $PLAINTEXT --stage $STAGE --encrypt
sls env -a $NAME -v $PLAINTEXT -e
sls env -a $NAME -v $PLAINTEXT -s $STAGE -e

YAML File Structure

Environment variables are stored in stage-agnostic YAML files, which are then merged into a .env file on deployment.

File example:

dev: #stage 
    foo: bar #cleartext variable 
    bla: crypted:bc89hwnch8hncoaiwjnd... #encrypted variable 
    foo: baz
    bla: crypted:ncibinv0iwokncoiao3d...

You can create additional YAML environment files, for example to include variables that are dynamically generated. Just add them to the envFiles in your serverless.yml.

Usage with the serverless-plugin-webpack

In case you are also using the serverless-plugin-webpack there are some caveats:

1. Plugin order in `serverless.yml'

You have to place serverless-env-generator before the serverless-plugin-webpack in the serverless.yml

# serverless.yml 
  - serverless-env-generator
  - serverless-plugin-webpack

2. Additional dotenv-webpack

You need to have the dotenv-webpack plugin installed:

npm install dotenv-webpack --save-dev

and configured:

// webpack.config.js
const Dotenv = require('dotenv-webpack')
module.exports = {
  // ...
  plugins: [
    // ...
    new Dotenv()


Anyone is more than welcome to contribute to the serverless-env-generator plugin. Here just a few things to consider when doing so:

  • this project uses yarn as a package manager
  • make sure to pass all tests (run yarn test)
  • you can add your local serverless-env-generator version to other projects: yarn add --dev file:/../serverless-env-generator

License & Credits

Licensed under the MIT license.

Created and maintained by DieProduktMacher.

Inspired by Serverless Crypt.

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