Volume resourcesFiles or directories on the root file system (except under /sys, /dev, or /var). These include:

  • Folders or files used to read or write information across Greengrass Lambda functions (for example, /usr/lib/python2.x/site-packages/local).
  • Folders or files under the host’s /proc file system (for example, /proc/net or /proc/stat). Supported in v1.6 or later. For additional requirements, see Volume resources under the /proc directory. To configure the /var, /var/run, and /var/lib directories as volume resources, first mount the directory in a different folder and then configure the folder as a volume resource. When you configure volume resources, you specify a source path and a destination path. The source path is the absolute path of the resource on the host. The destination path is the absolute path of the resource inside the Lambda namespace environment. This is the container that a Greengrass Lambda function or connector runs in. Any changes to the destination path are reflected in the source path on the host file system.Files in the destination path are visible in the Lambda namespace only. You can’t see them in a regular Linux namespace.

Device resourcesFiles under /dev. Only character devices or block devices under /dev are allowed for device resources. These include:

  • Serial ports used to communicate with devices connected through serial ports (for example, /dev/ttyS0, /dev/ttyS1).
  • USB used to connect USB peripherals (for example, /dev/ttyUSB0 or /dev/bus/usb).
  • GPIOs used for sensors and actuators through GPIO (for example, /dev/gpiomem).
  • GPUs used to accelerate machine learning using on-board GPUs (for example, /dev/nvidia0).
  • Cameras used to capture images and videos (for example, /dev/video0). /dev/shm is an exception. It can be configured as a volume resource only. Resources under /dev/shm must be granted rw permission.

AWS IoT Greengrass also supports resource types that are used to perform machine learning inference. For more information, see Perform machine learning inference.

Greengrass Discovery RESTful API

All devices that communicate with an AWS IoT Greengrass core must be a member of a Greengrass group. Each group must have a Greengrass core. The Discovery API enables devices to retrieve information required to connect to a Greengrass core that is in the same Greengrass group as the device. When a device first comes online, it can connect to the AWS IoT Greengrass service and use the Discovery API to find:

  • The group to which it belongs. A device can be a member of up to 10 groups.
  • The IP address and port for the Greengrass core in the group.
  • The group CA certificate, which can be used to authenticate the Greengrass core device.

NoteDevices can also use the AWS IoT Device SDKs to discover connectivity information for a Greengrass core. For more information, see AWS IoT Device SDK.

To use this API, send HTTP requests to the Discovery API endpoint. For example: