unable to launch ec2 with ssm

Question

I am trying to launch ec2 instance and run some scripts inside it.
I’m using ssm for this on a t2.micro instance with ubuntu24.04. 
I have the iam role with all necessary permissions and vpc.
When I launch the instance and manually set it up - it works perfectly.
However, I want to have all the installations done during launch. 
I tried:
- installing via user-data
- creating an ami of the existing instance and then launch from there
In both the above cases, the instance takes forever to start

Where am I going wrong? or what is the best way to do this?

SHAJAM · Answer

If your userdata is not working, you can check the userdata script logs in the folder `/var/log/cloud-init.log` and `/var/log/cloud-init-output.log`. Other logs might be available in `/etc/cloud` folder.

You suggested the AMI is taking a long time to start. As a test, can you use larger instance type and confirm if it works.

re:Post Agent · Answer

It sounds like you're encountering issues with launching an EC2 instance and running scripts automatically during the launch process. There are a few potential reasons for this and some solutions you can try:

1. User Data Script: 
If you're using user data to install software and run scripts, make sure the script is optimized and not too complex. Long-running or resource-intensive scripts in user data can significantly delay instance startup. Consider breaking down your installations into smaller, more manageable steps.

2. AMI Creation:
When creating an AMI from an existing instance, ensure that you've properly prepared the instance for imaging. This includes cleaning up unnecessary files and optimizing the system. A large or poorly optimized AMI can lead to longer launch times.

3. Instance Type:
While t2.micro is suitable for many tasks, it may struggle with complex launch scripts or large AMIs. Consider using a more powerful instance type for the initial setup, then scaling down if needed.

4. Network Configuration:
Ensure your VPC and subnet configurations are correct and that the instance has proper internet access to download and install packages.

5. SSM Agent:
Verify that the SSM agent is properly installed and configured on your AMI or in your user data script.

Best practices for your use case:

1. Use a combination of AMI and User Data:
Create a "base" AMI with commonly used software pre-installed. Use user data for instance-specific configurations or for installing frequently updated software.

2. Leverage Launch Templates:
Create an EC2 Launch Template that includes your AMI, instance type, IAM role, and user data script. This allows for consistent and repeatable instance launches.

3. Consider using Systems Manager Automation:
Instead of relying solely on user data, you can create Systems Manager Automation documents to perform post-launch configuration. This gives you more control and better error handling.

4. Use CloudFormation or Terraform:
These infrastructure-as-code tools can help manage the entire process of launching instances with the correct configurations and running necessary scripts.

5. Monitor and Log:
Implement proper logging in your scripts and use CloudWatch Logs to monitor the instance launch process. This will help you identify where delays or failures are occurring.

By implementing these practices, you should be able to launch your EC2 instances more reliably and efficiently with the necessary software and configurations in place.
      
**Sources**  
[Unable to launch EC2 despite shutting down and starting up the instance | AWS re:Post](https://repost.aws/questions/QUUrRezV2uSsO4pGvepYN8_g/unable-to-launch-ec2-despite-shutting-down-and-starting-up-the-instance)  
[How do I create a Launch instance with a set of components that I want to install on a new Instance | AWS re:Post](https://repost.aws/questions/QUmsDczzzRSjaxPW_szx4TdQ/how-do-i-create-a-launch-instance-with-a-set-of-components-that-i-want-to-install-on-a-new-instance)

unable to launch ec2 with ssm

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