Problem:
	I am using Xen to create Virtual Machines, but how can I resize the virtual disk image?

Solution: 

This solution is to increase your virtual disk size: 

cd /var/lib/xen/images/vlinux1

#use dd to create a 1 GB file

dd if=/dev/zero of=Tempfile bs=1024 count=1000000

#append this file to virtual image file (in this case is hda)

cat Tmpfile >> hda 

resize2fs -f hda