Hardware Testing Script Metadata

Hardware testing scripts are used to evaluate system hardware, and you can run your own from both the web UI and from the command line.

This page explains the various metadata fields used within these scripts, along with how parameters are passed to scripts and how any results are returned.

Metadata fields

Metadata fields tell MAAS when the script should be used, how it should be run, and what information a script is gathering. A script can have the following fields:

  • name: Corresponds to the script's filename.
  • title: Human-friendly descriptive version of name, used within the web UI.
  • description: Brief outline of what the script does.
  • tags: List of tags associated with the script.
  • type: Either commissioning or testing.
  • timeout: Length of time before MAAS automatically fails and kills execution of the script.
  • destructive: True or False, depending on whether the script will overwrite system data.
  • comment: Describes changes made in this revision of the script.
  • hardware_type: Defines the type of hardware the script configures or tests. If the script returns results, hardware type dictates what hardware the results are associated with. The following types are valid:
    • node: Not associated with any hardware type. This is the default.
    • cpu: Configures or tests the CPUs on the node.
    • memory: Configures or tests memory on the node.
    • storage: Configures or test storage on the node. Each storage result may be associated with a block device on the system.
  • parallel: Enables scripts to be run in parallel and can be one of the following:
    • disabled: The script will run serially on its own.
    • instance: Runs in parallel only with other instances of the same script.
    • any: Runs in parallel alongside any other scripts with parallel set to any.
  • packages: List of packages to be installed or extracted before running the script. Packages may be specified as a JSON string, a list of strings, or as a dictionary. For example, packages: {apt: stress-ng}, would ask apt to install stress-ng. Package sources can be any of the following:
    • apt: Used by default if the source is omitted.
    • snap: Installs packages using snap. May also be a list of dictionaries. The dictionary must define the name of the package to be installed, and optionally, the channel, mode and revision.
    • url: The archive will be downloaded and, if possible, extracted. URL_DIR will be exported to the script as an environment variable.

Environment variables

The following environment variables are available when a script is run within the MAAS environment:

  • OUTPUT_STDOUT_PATH: The path to the log of STDOUT from the script.
  • OUTPUT_STDERR_PATH: The path to the log of STDERR from the script.
  • OUTPUT_COMBINED_PATH: The path to the log of the combined STDOUT and STDERR from the script.
  • RESULT_PATH: Path for the script to write a result YAML to.


Scripts can accept values defined within the parameters field. Parameter values can then be set by users before commissioning or before testing. The default values are used if they are run as a group action, or automatically by MAAS.

Parameters may only be defined within the embedded YAML of the script, and they take the form of a dictionary of dictionaries.

The key of the dictionary must be a string and it's this string that's used by the UI and API when users are setting parameter values during commissioning or testing.

The value is a dictionary with the following fields:

  • type: Every parameter must contain a type field. This describes what the parameter may accept and its default values. It may be one of the following:
    • storage: Allows the selection of a strong device on the node being run.
    • runtime: The amount of time the script should run for. This will be passed to the script in seconds.
  • min: The minimum numeric value an input is allowed to have. Only applicable to runtime and defaults to 0.
  • max: The maximum numeric value an input is allowed to have. Only applicable to runtime. The default is unlimited.
  • title: The title of the parameter field when displayed in the UI. The following types have the following default values:
    • storage: Storage device.
    • runtime: Runtime.
  • argument-format: Specifies how the argument should be passed to the script. Input is described as {input}. The storage type may also use {name}, {path}, {model} or {serial}. MAAS will lookup the values of path, model, and serial based on user selection. For storage, {input} is synonymous with {path}. The following types have the following default values:
    • storage: --storage={path}
    • runtime: --runtime={input}
  • default: The default value of the parameter. The following types have the following default values. Setting these to '' or None will override these values:
    • storage: all.
    • runtime: If set, the runtime value of the script.
  • required: Whether or not user input is required. If set to false, no default is set and no user input will mean the parameter is not passed to the script. Defaults to true.
  • results: What results the script will return on completion. This may only be defined within the embedded YAML of the script. Results may be a list of strings or a dictionary of dictionaries.


A script can output its results to a YAML file and those results will be associated with the hardware type defined within the script.

If the hardware type is storage, for example, and the script accepts a storage type parameter, the result will be associated with a specific storage device.

The YAML file must represent a dictionary with the following fields:

  • result: The completion status of the script. This can be either passed, failed or degraded. If no status is defined, an exit code of 0 indicates a pass while a non-zero value indicates a failure.
  • results: A dictionary of results. The key may map to a results key defined as embedded YAML within the script. The value of each result must be a string or a list of strings.

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