To recognize kernel executable format, the -b flag specifies BFD name of kernel.
If the -s flags is given, mdsetimage will write back the actual disk image size back into kernel.
If the -v flag is given, mdsetimage will print out status information as it is copying the image.
If the -x flag is given, mdsetimage will extract the disk image from kernel into the file image. This is the opposite of the default behavior.