This is an adaptation of the mkmmc-android.sh script and the instructions found at http://maniacbug.wordpress.com/2012/08/03/pandayocto/ that will load an SD card with your custom Yocto build.. Some modifications had to be made to make the image components work with the beaglebone. The default images assumes you are building "core-image-basic". …

mkmmc-beaglebone.sh

#!/bin/bash

##  Arguement Validation

EXPECTED_ARGS=1
if [ $# == $EXPECTED_ARGS ]
then
	echo "Assuming Default Locations for Prebuilt Images"
	$0 $1 $PWD/tmp/deploy/images/MLO $PWD/tmp/deploy/images/u-boot.img $PWD/tmp/deploy/images/uImage $PWD/tmp/deploy/images/uImage-am335x-bone.dtb $PWD/tmp/deploy/images/core-image-basic-beaglebone.tar.gz
	exit
fi

if [[ -z $1 || -z $2 || -z $3 || -z $4 ]]
then
	echo "mkmmc-android Usage:"
	echo "	mkmmc-beaglebone.sh <device> <MLO> <u-boot.img> <uImage> <uImage-am335x-bone.dtb> <rootfs tar.gz >"
	echo "	Example: mkmmc-beaglebone.sh /dev/sdc MLO u-boot.img uImage uImage-am335x-bone.dtb rootfs.tar.gz"
	exit
fi

if ! [[ -e $2 ]]
then
	echo "Incorrect MLO location!"
	exit
fi

if ! [[ -e $3 ]]
then
	echo "Incorrect u-boot.bin location!"
	exit
fi

if ! [[ -e $4 ]]
then
	echo "Incorrect uImage location!"
	exit
fi

if ! [[ -e $5 ]]
then
	echo "Incorrect boot.scr location!"
	exit
fi

if ! [[ -e $6 ]]
then
	echo "Incorrect rootfs location! "
	exit
fi

echo "All data on "$1" now will be destroyed! Continue? [y/n]"
read ans
if ! [ $ans == 'y' ]
then
	exit
fi

## Unmounting all partitioins

echo "[Unmounting all existing partitions on the device ]"
umount $1*

## Writing new partition table using sfdisk
 
echo "[Partitioning $1...]"
DRIVE=$1

dd if=/dev/zero of=$DRIVE bs=1024 count=1024
	 
SIZE=`fdisk -l $DRIVE | grep Disk | awk '{print $5}'`
	 
echo DISK SIZE - $SIZE bytes
 
CYLINDERS=`echo $SIZE/255/63/512 | bc`
 
echo CYLINDERS - $CYLINDERS
{ echo ,9,0x0C,*; echo ,,,-; } | sudo sfdisk -D -H 255 -S 63 -C $CYLINDERS $1 &> /dev/null



## Making New file systems

echo "[Making filesystems...]"

mkfs.vfat -F 32 -n boot "$1"1 &> /dev/null
mkfs.ext3 -L rootfs "$1"2 &> /dev/null


## Copying Contents

echo "[Copying files...]"

mount "$1"1 /mnt
cp $2 /mnt/MLO
cp $3 /mnt/u-boot.img

sync
umount "$1"1

mount -t ext3 "$1"2 /mnt

export PATH_TO_TMPFS_DIR=$PWD/tmp_fs
export PATH_TO_SDROOTFS=/mnt
echo "[Copying File System to rootfs partition]"

tar -x -f $6 --numeric-owner -C $PATH_TO_SDROOTFS &> /dev/null

cp $4 /mnt/boot/uImage
cp $5 /mnt/boot/am335x-bone.dtb

sync
umount "$1"2


echo "[Done]"