In my spare time, I help administer a hosted Debian Linux server that serves a variety of websites and hosts email for a few people. It doesn't see huge volumes of traffic, but of course we want to do things properly. However, when we first got this server, someone rolled a custom kernel for us which allowed us to do various things that we wanted to do (like LVM, RAID etc). That's now a few years ago and of course there's various security bugs been fixed etc and we'd rather just be operating from a stock kernel that is kept up-to-date.
The problem is that we don't have a list of the features we enabled when we rolled the custom kernel and a couple of attempts to use a new one have resulted in a kernal that won't boot. So the question is - how do we go about using the stock Debian kernels whilst still being able to have all the functionality we depend on? What information do I need to gather first, and then what are the steps to make it happen?