Launch from Template#

The point of creating our launch template was so we could treat servers like cattle, not pets. Let’s do that.

We’ll terminate our patientping-web instance, and launch a brand new one from the patientping-web-launcher template to get the site back up. Because the AMI already has the app baked in, we’ll basically just need to SSH back in and start the app.

Assignment#

Terminate the current PatientPing instance and launch a replacement from your launch template.

Cost check: You’re replacing one t3.micro with another. No change in cost.

1. Terminate the old instance:
   • In the AWS Console, go to “EC2” → “Instances.”
   • Select the patientping-web instance.
   • Click “Instance state” → “Terminate (delete) instance” and confirm.
   • Wait until the instance shows Terminated (may take a minute or two).
2. Launch a new instance from the template:
   • Go to “EC2” → “Launch Templates.”
   • Select the patientping-web-launcher template.
   • Click “Actions” → “Launch instance from template.”
   • On the launch page, everything should be pre-filled from the template. The only change: under Resource tags, add a Name tag with the value patientping-web-v2.
   • Click “Launch instance.”
3. Re-associate your Elastic IP:
   • Go to “EC2” → “Elastic IPs.”
   • Select your existing EIP (it should be unassociated after the old instance was terminated).
   • Click “Actions” → “Associate Elastic IP address.”
   • Select the new patientping-web-v2 instance and click “Associate.”
4. Update your SSH config to remove the old host key (the new instance has a different host key even though the IP is the same):

ssh-keygen -R YOUR_ELASTIC_IP

5. SSH into the new instance:

ssh patientping

6. Start the application. The app code is already on the server (baked into the AMI), so you just need to start it:

cd ~/patientping-web
uv run patientping.py

7. Verify again that the site loads at http://<your-elastic-ip>:8080 in a browser on your local machine.

Notice how much faster this was than the first time. No installing git, no cloning, no installing uv. The AMI had it all. That’s the power of baking your app into a custom image.

Tip#

If you want to use the CLI instead:

# Terminate the old instance
aws ec2 terminate-instances --instance-ids OLD-INSTANCE-ID

# Launch from template
aws ec2 run-instances --launch-template LaunchTemplateName=patientping-web-launcher --tag-specifications 'ResourceType=instance,Tags=[{Key=Name,Value=patientping-web-v2}]'

# Re-associate the Elastic IP
aws ec2 associate-address --instance-id NEW-INSTANCE-ID --allocation-id EIP-ALLOCATION-ID