Fresh potatoes are dried then ground or flaked. Most commonly the product is sold for making "instant mashed potatoes" by just adding liquid. The product can also be used as a coating for meats and for quick versions of gnocci.
This is a common grocery store item with a long shelf life so it qualifies as a good "emergency food" for your pantry.
Potatoes can also be purchased dehydrated and diced or sliced or grated for hash browns. These potatoes can be used to make soups or casseroles or even a frittata.