Real time access to user-data script output
The early implementations of user-data scripts on EC2 automatically sent all output of the script (stdout and stderr) to /var/log/syslog as well as to the EC2 console output, to help monitor the startup progress and to debug when things went wrong.
The recent Ubuntu AMIs still send user-data script to the console output, so you can view it remotely, but it is no longer available in syslog on the instance. The console output is only updated a few minutes after the instance boots, reboots, or terminates, which forces you to wait to see the output of the user-data script as well as not capturing output that might come out after the snapshot.
Here is an example written in bash that demonstrates how to send all user-data script stdout and stderr automatically, transparently, and simultaneously to three locations: