Automate EC2 Instance Setup with user-data Scripts - Alestic.com: "Debugging
Since you are passing code to the new EC2 instance, there is a very small chance that you may have made a mistake in writing the software. Well maybe not you, but somebody else out there might not be perfect, so I have to write this for them.
The stdout and stderr of your user-data script is output in /var/log/syslog and you can review this for any success and failure messages. It will contain both things you echo directly in the script as well as output from programs you run.
Tip: If you add set -x at the top of a bash script, then it will output every command executed. If you add set -e to the script, then the user-data script will exit on the first command which does not succeed. These help you quickly identify where problems might have started."
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