User data is a script you provide when launching an EC2 instance that runs automatically on first boot — used to install software, apply configuration, or bootstrap the instance without manual steps.
The tell
When a scenario needs instances to self-configure at launch (install a web server, pull config, join a cluster) automatically — especially with Auto Scaling launching new instances — that’s user data in the launch template. It runs once at first boot by default.
Test yourself
Auto Scaling launches new EC2 instances that must automatically install and configure a web server on startup, with no manual steps. What achieves this?
- Manually SSH into each new instance
- An EC2 user-data bootstrap script in the launch template
- A larger instance type
- An Elastic IP
👉 Click to reveal the answer & explanation
Correct answer: B. User data runs a bootstrap script automatically on first boot, so new instances self-configure — essential with Auto Scaling. Manual SSH (A) doesn’t scale; instance size (C) and Elastic IPs (D) don’t configure software.
Related topics
Amazon EC2 · Auto Scaling · EC2 Instance Types
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