Are you asking about an operating system backup? Normally when I do an image of my system disk, it is much too large to fit onto a DVD, either single or double layer. In fact, my backups are too large for a single layer Blu-ray.
Best to check the size of your operating system disk first.
If you have sufficient room in your target, I'd suggest using the free version of Acronis True Image that is available from either Western Digital or Seagate. I believe the version from Seagate is called Seatools. You'll need a hard drive in your computer from one of these two companies as a general rule, in order to use these programs.
If not, then I'd suggest Clonezilla or Macrium Reflect Free Edition.