Installing web servers on EC2 instances is a process full with pitfalls and potential problems.

Usually you would pick a distro you are comfortable with, install LAMP and other packages,
configure, create external drive copy more stuff in there, then perform reboot. If you encounter
problem during reboot and instance is not coming up, you're screwed.

One solution is to build your own custom bundle and upload it to amazon. You will nede to be
careful and not to bundle files you're not supposed to. However you can't re-create a bundle
after changing anything inside /etc/

Another solution is to keep list of files which was changed since the last bundle creation
on the external archive. 

This set of tools encorporates utilties for both approaches and in both cases makes
process fully automated. It's optimized for Gentoo, but can be used with other distros.
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1. Installation

mkdir /etc/private
chmod 700 /etc/private

vim /etc/private/pk.pem

[ paste PRIVATE key, for image generation ]