[Mxsmanic]

Floyd L. Davidson writes:

Most Linux distributions provide a "live DVD" which can
be used to demonstrate the OS, also as a installation
disk, and then also as a rescue disk.

Demonstrating and productively using are two different things. An operating
system being used for productive work is always writing to disk.

Any OS that cannot do that is abjectly insecure.

There's no correlation between being able to boot and run from read-only media
and security.