How to check whether my user data passing to EC2 instance is working

You can verify using the following steps:

1. SSH on launch EC2 instance.
2. Check the log of your user data script in:
   • /var/log/cloud-init.log and
   • /var/log/cloud-init-output.log

You can see all logs of your user data script, and it will also create the /etc/cloud folder.

Source: https://stackoverflow.com/questions/15904095/how-to-check-whether-my-user-data-passing-to-ec2-instance-is-working