> For the complete documentation index, see [llms.txt](https://greymatter.gitbook.io/grey-matter-documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://greymatter.gitbook.io/grey-matter-documentation/usage/fabric/discovery/ec2.md).

# ec2

Deployments into bare metal AWS EC2 instances can take advantage of [Instance Tagging](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/Using_Tags.html) to perform service announcement and service discovery. `gm-control` uses the AWS SDKs to parse out this information and populate the mesh.

## Tagging

Instances must be tagged with both the service name and the port that should be exposed to the mesh. The form of this tag will default to `gm:cluster:<service-name>:<port>`. There are many ways to tag instances, but an example with the AWS CLI is shown below.

```bash
aws ec2 create-tags \
  --resources <your instance id> \
  --tags Key=gm:cluster:service-a:8080,Value=
```

If multiple services are exposed on a single EC2 instance, then multiple tags can be used:

```bash
aws ec2 create-tags \
  --resources <your instance id> \
  --tags \
      Key=gm:cluster:service-a:8080,Value=
      Key=gm:cluster:service-b:443,Value=
```

> **NOTE** The default tag can be changed by the CLI flag `--cluster-tag-namespace` or environment variable `GM_CONTROL_AWS_CLUSTER_TAG_NAMESPACE` when running `gm-control`. This changes the `gm:cluster` prefix, but the : section must remain in the same form.

### Configuration and AWS Credentials

`gm-control` does require access to AWS credentials to run and perform service discovery against the deployed EC2 clusters. The server will need access to:

* `GM_CONTROL_AWS_AWS_ACCESS_KEY_ID`
* `GM_CONTROL_AWS_AWS_SECRET_ACCESS_KEY`
* `GM_CONTROL_AWS_AWS_REGION`

To enable ec2 discovery, the following two environment variables almost must be set:

* `GM_CONTROL_CMD=aws`
* `GM_CONTROL_AWS_VPC_ID={instance(s)-vpc-id}`

If not provided directly, `gm-control` will fall back to the keys available on it's running instance. See `gm-control aws --help` or the [EC2 Usage](https://github.com/DecipherNow/gm-gitbook-sync/tree/e291b7c6efe71715000ac2f5742a714439ecf33d/usage/fabric/usage/gm-control-aws.md) page for details and more information.