Comment 2 for bug 414997

> The decision here is a tough call as we're trying to meet a couple major
> use cases:
>
> 1. User runs a base AMI; installs some software; rebundles to create
> another AMI which is them migrated to multiple regions. User wants (or
> wouldn't mind) instances of the new AMI to automatically detect the
> region and update local and sources.

This is, the one I was thinking of. It feels to me like this would be
more common. I think we should be striving for a OS that "just works",
and the user doesn't really even think about changing the OS behavior, but
rather adding their apps on top.

> 2. User runs a base AMI; sets the locale and/or tweaks the
> apt/sources.list to her preferences; rebundles to create another AMI.
> User does *not* want the local and apt sources changes overwritten in
> instances of the new AMI.

If ec2-set-defaults runs 'once-per-ami', the user can force their changes
by changing the template files in /etc/ec2-init/templates/. Ie, if they
want to add sources to the sources.list, or set the locale, they can
modify /etc/ec2-init/templates/sources.list.tmpl or locale.tmpl
respectively.

I realize this isn't well documented, but as it is right now thats how
that *could* work. This way, the user is more explicitly overriding "just
work" behavior.