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Creates a new LoopBack4 application using REST API.

lb4 [app] [options] [<name>]


--applicationName : Application class name.

--description : Description of the application.

--outdir : Project root directory for the application.

--eslint : Add ESLint to LoopBack4 application project.

--prettier : Add Prettier to LoopBack4 application project.

--mocha : Add Mocha to LoopBack4 application project.

--loopbackBuild : Add @loopback/build module’s script set to LoopBack4 application project.

--vscode: Add VSCode config files to LoopBack4 application project

--docker: Generate Dockerfile and add npm scripts to build/run the project in a docker container. See also Dockerfile considerations below.

Standard options

-h, --help
Print the generator’s options and usage.
Do not remember prompt answers. Default is false.
Do not automatically install dependencies. Default is false.
-c, --config
JSON file name or value to configure options
Format generated code using npm run lint:fix

For example,

lb4 app --config config.json
lb4 app --config '{"name":"my-app"}'
cat config.json | lb4 app --config stdin
lb4 app --config stdin < config.json
lb4 app --config stdin << EOF
> {"name":"my-app"}
-y, --yes
Skip all confirmation prompts with default or provided value


<name> - Optional name of the application given as an argument to the command.  If provided, the tool will use that as the default when prompting for the name.

Interactive Prompts

The tool will prompt you for:

  • Name of the application as will be shown in package.json. If the name had been supplied from the command-line, the prompt is skipped and the application is built with the name from the command-line argument. Must follow npm naming conventions.

  • Description of the application as will be shown in package.json.

  • Name of the directory in which to create your application. Defaults to the name of the application previously entered.

  • Name of the Application class in application.ts. Defaults to nameApplication.

  • Optional modules to add to the application. These modules are helpful tools to help format, test, and build a LoopBack4 application. Defaults to true for all of the modules. The prompted modules are:


The core scaffold of a LoopBack4 application generated by the CLI consists of the following files and directories:

├── src/
|   ├── __tests__/
|   ├── controllers/
|   |   └── ping.controller.ts
|   ├── datasources/
|   ├── models/
|   ├── repositories/
|   ├── application.ts
|   ├── index.ts
|   ├── migrate.ts
|   └── sequence.ts
└── package.json

ping.controller.ts is a file used to provide the application with a responsive endpoint. It contains logic to respond with a greeting message when the application receives a GET request from endpoint /ping.

cd to the application’s newly created directory and run npm start to see the application running at localhost:3000. Go to localhost:3000/ping to be greeted with a message.

Once the application has been created, additional generators such as controller generator can be run from the application’s root directory to further scaffold the application.

Dockerfile Considerations

The Dockerfile that is generated by the --docker option is based on a slim version of a node Docker image.

Here are the first two lines of the Dockerfile:

# Check out to select a new base image

As the comment suggests, the Docker image name is only a default, and you are encouraged to select an appropriate base image for your application.

If your application has a dependency on a node module that requires and invokes build tools during docker build (for example : loopback-connector-db2 ), an error may occur due to missing libraries.

Using the Docker image node:10, however, will allow the docker build step to complete successfully.

If you intend to use a node:alpine Docker image, please see node-gyp-alpine for an example of how you would install dependencies for packages that require node-gyp support.

Example compilation error when build tools/libraries are not in place:

Downloading and extraction of DB2 ODBC CLI Driver completed successfully ...

{ Error: Command failed: node-gyp configure build  --IS_DOWNLOADED=true --IBM_DB_HOME="$IBM_DB_HOME"
gyp ERR! configure error
gyp ERR! stack Error: Can't find Python executable "python", you can set the PYTHON env variable.
gyp ERR! stack     at PythonFinder.failNoPython (/usr/local/lib/node_modules/npm/node_modules/node-gyp/lib/configure.js:484:19)
gyp ERR! stack     at PythonFinder.<anonymous> (/usr/local/lib/node_modules/npm/node_modules/node-gyp/lib/configure.js:406:16)
gyp ERR! stack     at F (/usr/local/lib/node_modules/npm/node_modules/which/which.js:68:16)
gyp ERR! stack     at E (/usr/local/lib/node_modules/npm/node_modules/which/which.js:80:29)
gyp ERR! stack     at /usr/local/lib/node_modules/npm/node_modules/which/which.js:89:16
gyp ERR! stack     at /usr/local/lib/node_modules/npm/node_modules/isexe/index.js:42:5
gyp ERR! stack     at /usr/local/lib/node_modules/npm/node_modules/isexe/mode.js:8:5
gyp ERR! stack     at FSReqWrap.oncomplete (fs.js:152:21)
gyp ERR! System Linux 4.9.184-linuxkit
gyp ERR! command "/usr/local/bin/node" "/usr/local/lib/node_modules/npm/node_modules/node-gyp/bin/node-gyp.js" "configure" "build" "--IS_DOWNLOADED=true" "--IBM_DB_HOME=/home/node/app/node_modules/ibm_db/installer/clidriver"
gyp ERR! cwd /home/node/app/node_modules/ibm_db
gyp ERR! node -v v8.16.1
gyp ERR! node-gyp -v v3.8.0
gyp ERR! not ok

    at ChildProcess.exithandler (child_process.js:281:12)