[U-Boot] Most appropriate and scriptable way of creating partition image files

[Arji Cot]

Hi,
I'm new at this, my problem is that I have the kernel, busybox and u-boot
already build for my target platform, I'm not sure what is the most
appropriate way of creating the final ".img" file out of the files that I
already have .

I need to create 2 partitions, 1 vfat/fat32 for the boot and 1 partition
for the rootfs, the resulting 2 .img files will be burned on an eMMC using
the software provided by the vendor, so burning it's not the issue here .

I would like to have a more "scriptable" alternative to using dd, mounting,
writing and sync and then unmount the partition each time I need to create
an img file .

I'm using a linux 64 bit box .

Thanks.