mnt-system read-only?

[utu]

Greetings, moritz.b.

The purpose of Knoppix using a LiveUSB is usually to allow writing data
to a persistence file somewhere on it.

/mnt-system is usually on a fat32 partition with all your cloop-compacted
overlays. Using a separate reiserfs partition for persistence makes it
unnecessary to write anything to the fat32 system, unless you want to modify
some /boot, /efi or reference material there.

If you actually never want to record ANY changes, then a LiveCD or LiveDVD
would seem a better and cheaper answer than restricting a LiveUSB to read-only.