AWS IoT Greengrass Version 1 entered the extended life phase on June 30, 2023. For more information, see the AWS IoT Greengrass V1 maintenance policy. After this date, AWS IoT Greengrass V1 won't release updates that provide features, enhancements, bug fixes, or security patches. Devices that run on AWS IoT Greengrass V1 won't be disrupted and will continue to operate and to connect to the cloud. We strongly recommend that you migrate to AWS IoT Greengrass Version 2, which adds significant new features and support for additional platforms.

OTA updates of AWS IoT Greengrass Core software

The AWS IoT Greengrass Core software package includes an update agent that can perform over-the-air (OTA) updates of AWS IoT Greengrass software. You can use OTA updates to install the latest version of the AWS IoT Greengrass Core software or OTA update agent software on one or more cores. With OTA updates, your core devices don't have to be physically present.

We recommend that you use OTA updates when possible. They provide a mechanism you can use to track update status and update history. If a failed update occurs, the OTA update agent rolls back to the previous software version.

OTA updates make it more efficient to:

This feature integrates with AWS IoT jobs.

Requirements

The following requirements apply for OTA updates of AWS IoT Greengrass software.

IAM permissions for OTA updates

When AWS IoT Greengrass releases a new version of the AWS IoT Greengrass Core software, AWS IoT Greengrass updates the software artifacts stored in Amazon S3 that are used for the OTA update.

Your AWS account must include an Amazon S3 URL signer role that can be used to access these artifacts. The role must have a permissions policy that allows the s3:GetObject action on the buckets in target AWS Regions. The role must also have a trust policy that allows iot.amazonaws.com to assume the role as a trusted entity.

In addition, the user who initiates an OTA update must have permissions to use greengrass:CreateSoftwareUpdateJob and iot:CreateJob, and to use iam:PassRole to pass the permissions of the signer role. Here's an example IAM policy:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "greengrass:CreateSoftwareUpdateJob"
            ],
            "Effect": "Allow",
            "Resource": "*"
        },
        {
            "Effect": "Allow",
            "Action": [
                "iot:CreateJob"
            ],
            "Resource": "*"
        },
        {
            "Effect": "Allow",
            "Action": [
                "iam:PassRole"
            ],
            "Resource": "arn-of-s3-url-signer-role"
        }
    ]
}

Considerations

Before you launch an OTA update of Greengrass Core software, be aware of the impact on the devices in your Greengrass group, both on the core device and on client devices connected locally to that core:

The following state information is preserved during an OTA update:

Greengrass OTA update agent

The Greengrass OTA update agent is the software component on the device that handles update jobs created and deployed in the cloud. The OTA update agent is distributed in the same software package as the AWS IoT Greengrass Core software. The agent is located in /greengrass-root/ota/ota_agent/ggc-ota. It writes logs to /var/log/greengrass/ota/ggc_ota.txt.

You can start the OTA update agent by executing the binary manually or by integrating it as part of an init script, such as a systemd service file. If you execute the binary manually, it should be run as root. When it starts, the OTA update agent listens for AWS IoT Greengrass software update jobs from AWS IoT Core and executes them sequentially. The OTA update agent ignores all other AWS IoT job types.

The following excerpt shows an example of a systemd service file to start, stop, and restart the OTA update agent:

[Unit]
Description=Greengrass OTA Daemon

[Service]
Type=forking
Restart=on-failure
ExecStart=/greengrass/ota/ota_agent/ggc-ota

[Install]
WantedBy=multi-user.target

A core that is the target of an update must not run two instances of the OTA update agent. Doing so causes the two agents to process the same jobs, which creates conflicts.

Integration with init systems

During an OTA update, the OTA update agent restarts binaries on the core device. If the binaries are running, this might cause conflicts when an init system is monitoring the state of the AWS IoT Greengrass Core software or the agent during the update. To help integrate the OTA update mechanism with your init monitoring strategies, you can write shell scripts that run before and after an update. For example, you can use the ggc_pre_update.sh script to back up data or stop processes before the device shuts down.

To tell the OTA update agent to run these scripts, you must include the "managedRespawn" : true flag in the config.json file. This setting is shown in the following excerpt:

{
   "coreThing": {                                                     
       …
   },
   "runtime": {                                                       
       …
   },
   "managedRespawn": true
       …
}

Managed respawn with OTA updates

The following requirements apply to OTA updates with managedRespawn set to true:

The OTA update agent runs the scripts from the /greengrass-root/usr/scripts. The directory tree should look like the following:

<greengrass_root>
|-- certs
|-- config
|   |-- config.json
|-- ggc
|-- usr/scripts
|   |-- ggc_pre_update.sh
|   |-- ggc_post_update.sh
|   |-- ota_pre_update.sh
|   |-- ota_post_update.sh
|-- ota

When managedRespawn is set to true, the OTA update agent checks the /greengrass-root/usr/scripts directory for these scripts before and after the software update. If the scripts don't exist, the update fails. AWS IoT Greengrass does not validate the contents of these scripts. As a best practice, verify that your scripts function correctly and issue appropriate exit codes for errors.

Create an OTA update

Follow these steps to perform an OTA update of AWS IoT Greengrass software on one or more cores:

CreateSoftwareUpdateJob API

You can use the CreateSoftwareUpdateJob API to update the AWS IoT Greengrass Core software or OTA update agent software on your core devices. This API creates an AWS IoT snapshot job that notifies devices when an update is available. After you call CreateSoftwareUpdateJob, you can use other AWS IoT job commands to track the software update. For more information, see Jobs in the AWS IoT Developer Guide.

The following example shows how to use the AWS CLI to create a job that updates the AWS IoT Greengrass Core software on a core device:

aws greengrass create-software-update-job \
--update-targets-architecture x86_64 \
--update-targets [\"arn:aws:iot:region:123456789012:thing/myCoreDevice\"] \
--update-targets-operating-system ubuntu \
--software-to-update core \
--s3-url-signer-role arn:aws:iam::123456789012:role/myS3UrlSignerRole \
--update-agent-log-level WARN \
--amzn-client-token myClientToken1

The create-software-update-job command returns a JSON response that contains the job ID, job ARN, and software version that was installed by the update:

{
    "IotJobId": "GreengrassUpdateJob_c3bd7f36-ee80-4d42-8321-a1da0EXAMPLE",
    "IotJobArn": "arn:aws:iot:region:123456789012:job/GreengrassUpdateJob_c3bd7f36-ee80-4d42-8321-a1da0EXAMPLE",
    "PlatformSoftwareVersion": "1.9.2"
}

For steps that show you how to use create-software-update-job to update a core device, see Create an OTA update.

The create-software-update-job command has the following parameters: