Launches the specified number of instances using an AMI for which you have permissions.

When you launch an instance, it enters the pending state. After the instance is ready for you, it enters the running state. To check the state of your instance, call DescribeInstances.

To ensure faster instance launches, break up large requests into smaller batches. For example, create five separate launch requests for 100 instances each instead of one launch request for 500 instances.

To tag your instance, ensure that it is running as CreateTags requires a resource ID. For more information about tagging, see Tagging Your Amazon EC2 Resources (

If you don't specify a security group when launching an instance, Amazon EC2 uses the default security group. For more information, see Security Groups ( in the Amazon Elastic Compute Cloud User Guide.

[EC2-VPC only accounts] If you don't specify a subnet in the request, we choose a default subnet from your default VPC for you.

[EC2-Classic accounts] If you're launching into EC2-Classic and you don't specify an Availability Zone, we choose one for you.

Linux instances have access to the public key of the key pair at boot. You can use this key to provide secure access to the instance. Amazon EC2 public images use this feature to provide secure access without passwords. For more information, see Key Pairs ( in the Amazon Elastic Compute Cloud User Guide.

You can provide optional user data when launching an instance. For more information, see Instance Metadata ( in the Amazon Elastic Compute Cloud User Guide.

If any of the AMIs have a product code attached for which the user has not subscribed, RunInstances fails.

Some instance types can only be launched into a VPC. If you do not have a default VPC, or if you do not specify a subnet ID in the request, RunInstances fails. For more information, see Instance Types Available Only in a VPC (

For more information about troubleshooting, see What To Do If An Instance Immediately Terminates (, and Troubleshooting Connecting to Your Instance ( in the Amazon Elastic Compute Cloud User Guide.