libguestfs is a very handy library for manipulating image files. guestfis is a utility that uses libguestfs that allows you to mount an image file and make changes inside the image. One of the coolest features of libguestfs is that it does not require root prevelages to run or access an image file. The below example shows how to use guest fish to mount an make a change to a machine image.
1) install guestfish# yum install guestfish
2) connect to the imageguestfish –rw -a ~/Downloads/rhel-server-x86_64-kvm-6.4_20130130.0-4.qcow2
3) edit image><fs> run
><fs> mount /dev/vda1 /
><fs> vi /etc/fstab make any changes you need to ><fs> umount /
Download machine images: