I have a Ubuntu image file (.iso) and I'd like to burn the image file into a DVD, is there any software for this purpose on Ubuntu?
Let me see if I got it right, you have an Ubuntu image file and you want to burn it into a DVD. Right?
If so, just open your Dash menu click on Applications (the icon with an "A" in the bottom) and in "Filter" look for "Media" an application called Brasero Disk Burner will show up, just click it and burn you image.
Doubts? Follow this tutorial (click in the image for a fullsize version).
You could install k3b too :
sudo apt-get install k3b
( when you create boot-cd in k3b simply drag-and-drop iso-image from above file-window into below window of to-burn-CD/DVD. )
Or use command wodim in terminal to burn boot-CD/DVD like:
( if necessary : sudo apt-get install wodim )
wodim -v -eject name-of-file.iso