How to run a script on a newly created EC2 instance via AWS SDK?

user_24098 0
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I'm currently using AWS's Javascript SDK to launch custom EC2 instances and so far so good.

But now, I need these instances to be able to run some tasks when they are created, for example, clone a repo from Github, install a software stack and configure some services.

This is meant to emulate a similar behaviour I have for local virtual machine deployment. In this case, I run some provisioning scripts with Ansible that get the job done.

For my use case, which would be the best option amongst AWS's different services to achieve this using AWS's Javascript SDK?

Is there anyway I could maybe have a template script to which I passed along some runtime obtained variables to execute some tasks in the instance I just created? I read about user-data but I can't figure out how that wraps with AWS's SDK. Also, it doesn't seem to be customisable.

At the end of the day, I think I need a way to use the SDK to do this:

"On the newly created instance, run this script that is stored in such place, replacing these placeholder values in the script with these I'm giving you now"

Any hints?

amazon-web-services amazon-ec2 javascript
2 Answers

As Mark B. stated, UserData is the way to go for executing commands on instance launch. As you tagged the question with javascript here's an example on passing this in the ec2.runInstances command:

let AWS = require('aws-sdk')
let ec2 = new AWS.EC2({region: 'YOUR_REGION'})
// Example commands to create a folder, a file and delete it
let commands = [
    '#!/usr/bin/env bash',
    'mkdir /home/ubuntu/test',
    'touch /home/ubuntu/test/examplefile',
    'rm -rf /home/ubuntu/test'
];
let params = {
    ...YOUR PARAMS HERE...
    UserData: new Buffer(commands.join("\n")).toString('base64')
}
// You need to encode it with Base64 for it to be executed by the userdata interpreter
ec2.runInstances(params).promise().then(res => { console.log(res); })
user_42788700

When you launch the new instances you can provide the user-data at that time, in the same AWS SDK/API call. That's the best place to put any server initialization code.

The only other way to kick off a script on the instance via the SDK is via the SSM service's Run Command feature. But that requires the instance to already have the AWS SSM agent installed. This is great for remote server administration, but user-data is more appropriate for initializing an instance on first boot.

user_130700
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