most appropriate distro or setup to ensure root filesystem is never changed

Question

I have a project I'm doing where I just want the computer to start up, run an application, and shut down. I don't want any data (log files, etc) to be saved and I want the drive to be clean (and hopefully I can verify this) upon reboot. I was looking into remastering Ubuntu mini, and plop the files from the ISO onto the HD, since RAM drives in LiveCD installs are built to work this way, however the remaster is getting out of hand and hard to maintain. Is the best approach using a distro that works in RAM or could I get away with a very strict user setup? I know I will have to at least remaster the CD to add my startup script and set up users or additional files, but I'd rather be working from a CD that has more than just the minimal setup to make things less complicated.

Answer 1

In principle, it is possible to run a unix system from disk with the root partition mounted read-only. Starting with a typical distribution, you'll have to mount a tmpfs filesystem, and make a number of files and directories symbolic links into tmpfs, and tweak the init scripts to populate the tmpfs at the right time. I don't have a list of files to offer you, but it should be reasonably easy to examine a running system and find what has been modified since boot.

I think customizing a live CD will be easier in the short term (of course, you don't make an iso until you're satisfied with your setup). I suppose you've already read the Ubuntu community pages on Live CD customization and live CD from scratch? An alternative distribution that is designed specifically for live CDs is Knoppix; see the Knoppix remastering howto.

Answer 2

The one tip I can give you is to boot slax from the ISO in qemu and modify the setup from in there. Then you can burn the changes onto the disc. I'm not sure if this'll work however.