+.B bootsize
+is not recommended when using
+.B extlinux
+\- use grub instead.
+Versions of grub2 in wheezy
+can fail to install in the VM, at which point vmdebootstrap will fall back to
+extlinux. It may still be possible to complete the installation of grub2 after
+booting the VM as the problem may be related to the need to use loopback
+devices during the grub-install operation. Details of the error will appear in the
+vmdebootstrap log file, if enabled with the \-\-log option. Note that
+.B grub-legacy
+is not supported.
+.SH INSTALLATION IMAGES AND VIRTUAL MACHINES
+.B vmdebootstrap
+is aimed principally at creating virtual machines, not installers or prebuilt
+installation images. It is possible to create prebuilt installation images
+for some devices but this depends on the specific device. (A 'prebuilt
+installation image' is a single image file which can be written to physical
+media in a single operation and which allows the device to boot directly
+into a fully installed system \- in a similar way to how a virtual machine
+would behave.)
+.PP
+.B vmdebootstrap
+assumes that all operations take place on a local image file, not a
+physical block device / removable media.
+.PP
+.B vmdebootstrap
+is intended to be used with tools like qemu on the command line to launch
+a new virtual machine. Not all devices have virtualisation support in hardware.
+.PP
+This has implications for
+.B u-boot
+support in some cases. If the device can support reading the bootloader
+from a known partition, like the beaglebone-black, then
+.B vmdebootstrap
+can provide space for the bootloader and the image will work as a prebuilt
+installation image. If the device expects that the bootloader exists at a
+specific offset and therefore requires that the bootloader is written as
+an image not as a binary which can be copied into an existing partition,
+.B vmdebootstrap
+is unable to include that bootloader image into the virtual machine image.
+.PP
+The beagleboneblack.sh script in the examples/ directory provides a worked
+example to create a prebuilt installation image. However, the beagleboneblack
+itself does not support virtualisation in hardware, so is unable to launch
+a virtual machine. Other devices, like the Cubietruck or Wandboard need
+.B u-boot
+at a predefined offset but can launch a virtual machine using qemu, so
+the cubietruck and wandboard6q scripts in the examples/ directory relate
+to building images for virtual machines once the device is already
+installed and booted into a suitable kernel.
+.PP
+It is possible to wrap
+.B vmdebootstrap
+in such a way as to prepare a
+.B physical block device
+with a bootloader image and then deploy the bootstrap on top. However,
+this does require physical media to be inserted and removed each time
+the wrapper is executed. To do this, use the \-\-tarball option instead
+of the \-\-image option. Then setup the physical media and bootloader
+image manually, as required for the device, redefine the partitions to
+make space for the rootfs, create a filesystem on the physical media and
+unpack the
+.B vmdebootstrap
+tarball onto that filesystem. Once you have working media, an image can be
+created using dd to read back from the media to an image file, allowing
+other media to be written with a single image file.