How can I use metadata variables from ec2 datasource

[boshido]

RancherOS Version: (ros os version)
ros -v = ros version v0.5.0

Where are you running RancherOS? (docker-machine, AWS, GCE, baremetal, etc.)
AWS

Here is my cloud-config

#cloud-config
rancher:
  cloud_init:
    datasources:
      - ec2
  services:
    register:
      image: rancher/agent:v1.0.2
      privileged: true
      volumes:
        - /var/run/docker.sock:/var/run/docker.sock
        - /var/lib/rancher:/var/lib/rancher
      environment:
        CATTLE_HOST_LABELS: "access_mode=private"
        CATTLE_AGENT_IP: $private_ipv4
      command:
        - http://blablabla:blablabla

As you see I used $private_ipv4 to assign value to CATTLE_AGENT_IP and It was not work.

The problem is I found this technical from https://forums.rancher.com/t/ec2-metadata-and-cloud-init/2975 that was CoreOS technical long time ago and I'm not sure where are the others technical to use on RancherOS.

I read rancher cloud-config document "http://docs.rancher.com/os/cloud-config/" and It just said that I can set the ec2 as datasource but it does not said about what the benefit of it (How to use the mapped metadata).

I read cloud-init config document "http://cloudinit.readthedocs.io/en/latest/topics/datasources.html" but it didn't help me at all

Is my understanding correct that when I map the ec2 datasource to cloud-init, I could use the data from mapped metadata from environment variable or function or any technicals that give me the data ?

[boshido]

Any updates on this issue ?
After faced this problem I had to move to coreOS that was not what I really wanted.

[ibuildthecloud]

This really should work.... After boot, what is in /var/lib/rancher/conf/metadata and what is the output of sudo ros config export