Merge pull request #21120 from GlennChia/docs/ssm-association-target-…

…all-instances

Docs/add note for ssm association to target all instances

website/docs/r/ssm_association.html.markdown

@@ -12,6 +12,8 @@ Associates an SSM Document to an instance or EC2 tag.
 
 ## Example Usage
 
+### Create an association for a specific instance
+
 ```terraform
 resource "aws_ssm_association" "example" {
   name = aws_ssm_document.example.name
@@ -23,6 +25,36 @@ resource "aws_ssm_association" "example" {
 }
 ```
 
+### Create an association for all managed instances in an AWS account
+
+To target all managed instances in an AWS account, set the `key` as `"InstanceIds"` with `values` set as `["*"]`. This example also illustrates how to use an Amazon owned SSM document named `AmazonCloudWatch-ManageAgent`.
+
+```terraform
+resource "aws_ssm_association" "example" {
+  name = "AmazonCloudWatch-ManageAgent"
+
+  targets {
+    key    = "InstanceIds"
+    values = ["*"]
+  }
+}
+```
+
+### Create an association for a specific tag
+
+This example shows how to target all managed instances that are assigned a tag key of `Environment` and value of `Development`.
+
+```terraform
+resource "aws_ssm_association" "example" {
+  name = "AmazonCloudWatch-ManageAgent"
+
+  targets {
+    key    = "tag:Environment"
+    values = ["Development"]
+  }
+}
+```
+
 ## Argument Reference
 
 The following arguments are supported: