Recommendations on cloning a bootable main disk

[Dan Jenkins]

On some of the BIOSes, unless you have the USB drive connected, before 
you go into the BIOS, it will not appear as a boot option.

Also, depending on the USB flash drive model, it may appear:
1) as a removable device (aka a floppy drive),
2) a hard drive (appearing as second choice under hard disk drives;
    you would need to change the 1st drive to USB and the 2nd drive to 
your current boot drive), or
3) as a CDROM drive.

Also, if you have a UEFI BIOS, you may need to switch it to Legacy, 
instead of UEFI.

Lastly, if you have a UEFI BIOS, you need a UEFI compatible boot device. 
In the case of Clonezilla, you need to download an AMD664 alternative 
version (Ubuntu-based), rather than the default Debian-based. (We have 
both the UEFI and Legacy versions of Clonezilla to try when we run into 
such issues.)

And, rarely, I encounter computers that simply cannot boot USB flash 
drives, but those tend to be much older ones.