Passing a script while starting an instance in Ama

Question

Is it possible to pass a script while I'm starting an instance? So that the instance will execute that script once its initialized?

public static void startInstance(final String instanceId) {
    StartInstancesRequest startRequest = new StartInstancesRequest().withInstanceIds(instanceId);
    logger.info(String.format("Starting instance '%s':...", instanceId));
    ec2.startInstances(startRequest);       
}

Any idea? Script will be kind of startup script which I need to execute as soon as the instance is ready. Thanks in advance.

Answer 1

You can use the Userdata to pass a script to a new EC2 Instance although I dont know if you can start a pre existing instance and pass it data.

I have a pre configured AMI that has a script saved on the root drive, this script is used to configure the server and download the latest source.

So your request could look like the following:

var runInstance = new RunInstancesRequest();

        runInstance.WithImageId("{ami-id}")
            .WithInstanceType("{size}")
            .WithMaxCount(1)
            .WithMinCount(1)
            .WithSecurityGroup("{the security group}")
            .WithKeyName("{your key}")
            .WithUserData(Convert.ToBase64String(Encoding.ASCII.GetBytes(userData)));

        ec2.RunInstances(runInstance);

The user data can contain either a reference to a script or the script itself.

Answer 2

I introduced the concept of user-data scripts in the community Ubuntu AMIs in 2009 (simplified version of some ideas from RightScale):

http://alestic.com/2009/06/ec2-user-data-scripts

It boils down to:

If the instance user-data starts with the two characters #! then the instance runs it as the root user on the first boot.

This feature was later included in the official Ubuntu AMIs in the CloudInit package:

https://help.ubuntu.com/community/CloudInit

Amazon now includes the CloudInit package in their own Amazon Linux AMIs:

http://docs.amazonwebservices.com/AWSEC2/latest/UserGuide/AmazonLinuxAMIBasics.html

Other distros are welcome to (and may already) include this feature in their AMIs.