Of course, nothing ever stopped people from building a Linux system capable of using a CD disk as its root file system. In fact, one of the early Linux systems, Yggdrasil, did exactly that for the installer CD. So, how Knoppix was different from Yggdrasil or DemoLinux?
The secret sauce was in a special kernel module implementing CD-ROM friendly compressed block device. Without it, the Live CD experience was subpar, and the amount of software that was shipped on the LiveCD was minuscule. Compare 1999's DemoLinux 1.1 shipping Mandrake 6 with basically just Netscape and Gimp, and Knoppix 3.2 that comes with hundreds of tools, _two_ full office suites, and even WINE - all on one CD.
( screenshots 🧵 cont)