using knoppix tohd=/dev/sda1 boot option when sda1 is an external USB HD

[Blacksimon]

Are you sure you mean tohd and not fromhd option ?

[carolus]

Are you sure you mean tohd and not fromhd option ?

Yes. I first tried these options on another computer in a virtual machine to see how they work. They work as advertised on a virtual hard drive. In contrast, on my target machine, with only an external USB hard drive, tohd fails to copy the knoppix files to the external hard drive. Apart from ignoring the boot option, it boots normally, with no relevant messages.

Since the hard disk is probably installed earlier in the boot process than USB devices, it seems possible that tohd might not work with USB devices.

[Werner P. Schulz]

In contrast, on my target machine, with only an external USB hard drive, ..

This machine has no internal hard disk, only an external USB drive?

You didn't tell us the output of "blkid" and "fdisk -l" and you didn't tell us the error messages while trying to boot with the cheatcode "tohd=/dev/sda1"