**Example 1: To start an instance refresh with command line parameters** The following ``start-instance-refresh`` example starts an instance refresh using command line arguments. The optional ``preferences`` parameter specifies an ``InstanceWarmup`` of ``400`` seconds and a ``MinHealthyPercentage`` of ``50`` percent. :: aws autoscaling start-instance-refresh \ --auto-scaling-group-name my-asg \ --preferences '{"InstanceWarmup": 400, "MinHealthyPercentage": 50}' Output:: { "InstanceRefreshId": "08b91cf7-8fa6-48af-b6a6-d227f40f1b9b" } For more information, see `Replacing Auto Scaling instances based on an instance refresh `__ in the *Amazon EC2 Auto Scaling User Guide*. **Example 2: To start an instance refresh using a JSON file** The following ``start-instance-refresh`` example starts an instance refresh using a JSON file. You can specify the Auto Scaling group and define your preferences in a JSON file, as shown in the following example. :: aws autoscaling start-instance-refresh \ --cli-input-json file://config.json Contents of ``config.json``:: { "AutoScalingGroupName": "my-asg", "Preferences": { "InstanceWarmup": 400, "MinHealthyPercentage": 50 } } Output:: { "InstanceRefreshId": "08b91cf7-8fa6-48af-b6a6-d227f40f1b9b" } For more information, see `Replacing Auto Scaling instances based on an instance refresh `__ in the *Amazon EC2 Auto Scaling User Guide*.