That would depend on whether the authors of these "Knoppix variants" kept and/or modified the scripts that allow the use of the "bootfrom" cheatcode.

Quantian allows "bootfrom". Its author explains how to use the "bootfrom" cheatcode here. (It's sort of convoluted, in that you have to download clusterKnoppix and burn it to CD in order to have something to boot from...if you don't have a DVD burner.)

Damn Small Linux has its own modified set of cheatcodes, but includes "bootfrom".