NanoBSD/FreeBSD: GPT bootable image: howto create sparse VMDK for ESXi?

[O. Hartmann]

Hello out there.

First please CC me as I do not subscribe this list.

I successfully use the NanoBSD framework with some modifications for creation
of GPT/UEFI bootable images with recent CURRENT. The appliance boots off microSD
cards, ISO 9660 images (with some modifications made to the nanoBSD framework)
and USB flash drives.

I need this image of a FreeBSD appliance on an ESXi 5.5 and 6.0 system. I
already tried to apply the vmdktool taken from ports (sysutils/vmdktool), but
neither the ESXi 5.5 nor 6.0 recognizes the resulting vmdk file as a valid
disk. The manpage of vmdktool states it suits disk format VMDisk Format 1.1,
ESXi 5.5 or 6.0 has version 5.0, if not higher (as far as I know). Converting
any tested and booting image is not recognized by the ESXi. Several manually
applied manipulations did not go well - the vmdk file is seen then, but the
ESXi complains about unknown disk type 7 in some cases. 

I tried then FreeBSD's mkimg(1) tool. Without success. The resulting vmdk file
is well recognized by the ESXi, it also boots, but then the loader stops at
the point where we have to issue "?" to get the recognized GEOM drives.
Consider nano.img to be a raw image conatining a GPT partitioning layout and
the EFIFAT UEFI partition and two (or three, depending on whether nanoBSD is
configured using a second, ALTROOT partition, or not)
partitions, named/labeled "/dev/ufs/nanos1a" and "/dev/ufs/nanos3" (the labels
actually are s1a and s3). Put onot a SD or USB flash, booting off on a UEFI
capable/configured box (using a Fujitsu Server as well as a ZOTAC nano box and
Intel NUC) works well! Now I apply

mkimg -s gpt -p freebsd:=nano.img -f vmdk -o nano.vmdk

The resulting vmdk disk image boots - but then fails at the loader prompt
calling for a boot partition. The labeling is wrong, when hitting "?" and
showing the list of recognizes partitions. 

It seems, mkimg "envelopes" the whole image again instead of simply emitting a
vmdk file suitable as ESXi disk with the partitioning layout represented by
the RAW image.

At the end, I'm floating dead in the water! Either I can convert a raw image
to an ESXi vmdk file, but it isn't recognized, or I have a bootable vmdk, but
it stops working because of a wrong partition layout and non-recognized
labeling.

Is there a way to convert RAW images of a working/booting disk into a vmdk
file that is working with both ESXi 5.5 and 6.0? 

Thank yo very much in advance,

oliver