Simple article to help you create a .img file that you can use to do some testing of different technologies or add to a virtual machine your hosting for more storage space or anything else you might need a .img file for.
dd if=/dev/zero of=/home/brad/Desktop/test.img bs=1M
Now you can use the file like a normal block device, for example.
mkfs.ext4 /home/brad/Desktop/test.img