If you want to build a Linux from scratch, check Yocto Project. It allows to configure a mind-numbing number of options, from the package format to libraries us

If you want to build a Linux from scratch, check Yocto Project. It allows to configure a mind-numbing number of options, from the package format to libraries used, to what's in the rootfs, to create read-only rootfs, etc etc. It is targeted at embedded, but it's good for desktop too. Disclaimer: worked on it for a couple of years.