Want to troubleshoot your boot scripts for EC2?

Tee the output like so.

#!/usr/bin/env bash
exec > >(tee /var/log/user-data.log|logger -t user-data -s 2>/dev/console) 2>&1

  sudo su
  yum update -y
  # bla blah bloing
  # ...

When your instance is launching, ssh into it and tail the logs.

tail -f /var/log/user-data.log

Hot pajamas!