Services or capabilities described in Amazon Web Services documentation might vary by Region. To see the differences applicable to the China Regions, see Getting Started with Amazon Web Services in China (PDF).

Working with parameter versions

Each time you edit the value of a parameter, Parameter Store, a capability of Amazon Systems Manager creates a new version of the parameter and retains the previous versions. When you initially create a parameter, Parameter Store assigns version 1 to that parameter. When you change the value of the parameter, Parameter Store automatically increments the version number by one. You can view the details, including the values, of all versions in a parameter's history.

You can also specify the version of a parameter to use in API commands and SSM documents; for example: ssm:MyParameter:3. You can specify a parameter name and a specific version number in API calls and SSM documents. If you don't specify a version number, the system automatically uses the latest version. If you specify the number for a version that doesn't exist, the system returns an error rather than falling back to the latest or default version of the parameter.

You can use parameter versions to see the number of times a parameter changed over a period of time. Parameter versions also provide a layer of protection if a parameter value is accidentally changed.

You can create and maintain up to 100 versions of a parameter. After you have created 100 versions of a parameter, each time you create a new version, the oldest version of the parameter is removed from history to make room for the new version.

An exception to this is when there are already 100 parameter versions in history, and a parameter label is assigned to the oldest version of a parameter. In this case, that version isn't removed from history, and the request to create a new parameter version fails. This safeguard is to prevent parameter versions with mission critical labels assigned to them from being deleted. To continue creating new parameters, first move the label from the oldest version of the parameter to a newer one for use in your operations. For information about moving parameter labels, see Move a parameter label (console) and Move a parameter label (Amazon CLI).

The following procedures show you how to edit a parameter and then verify that you created a new version. You can use the get-parameter and get-parameters commands to view parameter versions. For examples on using these commands, see GetParameter and GetParameters in the Amazon Systems Manager API Reference

Create a new version of a parameter (console)

You can use the Systems Manager console to create a new version of a parameter and view the version history of a parameter.

Reference a parameter version

You can reference specific parameter versions in commands, API calls, and SSM documents by using the following format: ssm:parameter-name:version-number.

In the following example, the Amazon Elastic Compute Cloud (Amazon EC2) run-instances command uses version 3 of the parameter golden-ami.

Linux & macOS

aws ec2 run-instances \
    --image-id resolve:ssm:/golden-ami:3 \
    --count 1 \
    --instance-type t2.micro \
    --key-name my-key-pair \
    --security-groups my-security-group

Windows

aws ec2 run-instances ^
    --image-id resolve:ssm:/golden-ami:3 ^
    --count 1 ^
    --instance-type t2.micro ^
    --key-name my-key-pair ^
    --security-groups my-security-group

Here is an example for specifying version 2 of a parameter named MyRunCommandParameter in an SSM document.

YAML

---
schemaVersion: '2.2'
description: Run a shell script or specify the commands to run.
parameters:
  commands:
    type: String
    description: "(Required) Specify a shell script or a command to run."
    displayType: textarea
    default: "{{ssm:MyRunCommandParameter:2}}"
mainSteps:
- action: aws:runShellScript
  name: RunScript
  inputs:
    runCommand:
    - "{{commands}}"

JSON

{
    "schemaVersion": "2.2",
    "description": "Run a shell script or specify the commands to run.",
    "parameters": {
        "commands": {
            "type": "String",
            "description": "(Required) Specify a shell script or a command to run.",
            "displayType": "textarea",
            "default": "{{ssm:MyRunCommandParameter:2}}"
        }
    },
    "mainSteps": [
        {
            "action": "aws:runShellScript",
            "name": "RunScript",
            "inputs": {
                "runCommand": [
                    "{{commands}}"
                ]
            }
        }
    ]
}