I have little actual experience with Debian in particular, although i'm pretty knowledgeable with Linux in general (using it for 8+ years, been a Slackware user long time ago, created my own two distributions from scratch back when Linux-on-a-floppy things were not so popular, recently been using RedHat/Fedora massively and playing with Gentoo).

I read that after installing on a hard-drive, Knoppix becomes essentially Debian unstable. My question is: how close is it to Debian?
What if i install a "pure" Debian, selecting the same packages as on the Knoppix CD? Will the system be the same?

I am asking the question because i want to build a small embedded Linux system, and Knoppix seems an excellent candidate for the distribution to build upon (no point in starting from scratch these days). I envision the system like a combination between a pure hard-disk install, and a Knoppix CD running in RAM:
- the OS will be stored in a Flash, and the Flash mounted read-only (like the Knoppix CD)
- those few directories that must be read-write will be in a RAM-disk
- however, the Flash is essentially a hard-drive, it is "seen" by the kernel just like any IDE hard-drive

I want to start out with Knoppix, because my model is pretty close to Knoppix's: a massive read-only media that has the OS, plus a few tiny read-write things residing in RAM.
But if Knoppix-on-harddrive is very close to Debian, perhaps i should begin customising Debian instead.

Keeping the OS in a compressed ISO or using any kind of compression on the main storage device is out of question. I have enough space for my needs (Flash devices are getting pretty big nowadays) and i have to avoid the decompression overhead (i need all the CPU cycles i can get). So the Flash will contain essentially a typical "boring" hard-drive install (except the details mentioned above).

Any hint will be appreciated. Thanks.

Florin Andrei