How to Work on Pre-Packed images (.img) ?

mkdir temp-mnt

losetup /dev/loop5 root.img


mount /dev/loop5 temp-mnt
  
where temp-mnt is the Mount  Point

mount -o bind /proc temp-mnt/proc
mount -o bind /sys temp-mnt/sys
mount -o bind /dev temp-mnt/dev 

To wok on the Mounted File System,

chroot temp-mnt 

Once all the works have been completed,

umount /dev/loop5
losetup -d /dev/loop5



Reference : http://open.eucalyptus.com/participate/wiki/modifying-prepackaged-image