I am more of a linux applications developer than an admin. Over time, I've built servers and maintained them, sometimes to offer services, mostly just to develop the applications I work on.
Way back when I would create a file in my account to keep notes on what I did on each machine, so that I could replicate that when I migrated to other machines.
Nowadays, I install something a private trac installation, install it's blog plugin, and then use that to make notes of everything I install, and most commands that I run, as well as the output. This provides me a combination wiki and blog that I find very useful as a "captain's log". I do this mostly so that when I migrate to a new clean machine, I have a much easier time in bringing it up.
And yet, I am always amazed when I see others just install this, delete that, run this, setup this config, ... without seeming to use any way to actually note what they are doing.
What do YOU do, and what tools are available?
I am especially interested in the transition between maintaining a few machines for a few people and maintaining several to dozens of machines providing a real service.
What are the best practices, and where can I find good resources?