How do I access Greengrass Core environment variables in AWS System Manager Run Command

Question

I have AWS systems manager managed node setup for a greengrass core device and want to run command to execute shell script. The shell script needs to access greengrass core environment variables $AWS_IOT_THING_NAME to process. However, I do not see any value returned by $AWS_IOT_THING_NAME. 
1. Is there a different mechanism to access the greengrass env variables by the AWS SSM run command? 
2. I can see that the SourceId of the node is same as the AWS_IOT_THING_NAME. Can I access it inside a shell script as environmental variable?

I need to execute a script to run on multiple devices which uploads images to the s3 bucket with folder name {AWS_IOT_THING_NAME}/images. I know this can be done using custom greengrass component, but I want to try it using the AWS SSM fleet manager.

Answer

Hi,

SSM Agent is not able to access Greengrass variables since it is not executed as a child process of Greengrass, but as an independent process executed by `systemd`, even when you deploy it via `aws.greengrass.SystemManagerAgent` component.

What you can do is to write a component that export that variable so that it is available to the script run by the SSM Agent. One example would be to write that ThingName in a file inside `/var/` or `/etc/` folders, and then read it from your script before executing it. Alternatively the custom component could add an `export` to the `.bashrc` file of the SSM Agent user and execute your script in bash.

Cheers,

Massimiliano

How do I access Greengrass Core environment variables in AWS System Manager Run Command

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