Component manifests

CML files are JSON5{: .external} files that end with a .cml extension. Below is an example CML manifest file for a simple component running an ELF binary that prints a “Hello, World” message to the system log:

    // Information about the program to run.
    program: {
        // Use the built-in ELF runner.
        runner: "elf",
        // The binary to run for this component.
        binary: "bin/hello",
        // Program arguments
        args: [

    // Capabilities used by this component.
    use: [
        { protocol: "fuchsia.logger.LogSink" },

This file declares two main sections of information about the component:

Note: For more details on component manifests, see component manifests.

  • program: Describes the executable information such as the binary file, program arguments, and the associated runtime. In this example, a binary is compiled as an ELF executable and uses the built-in ELF runner.
  • use: Declares the capabilities this component requires to run. In this example, the fuchsia.logger.LogSink protocol enables the component to write messages to the system log (syslog).