Can you host a Linux OS on a Cisco routers unused memory? If so how do you do this?

Trying to figure out if you can host a Linux OS on a Cisco Router. Cisco config's usually doesn't take up that much space in memory and I'm trying to find out if anyone has tried to place a small version on the Linux Operation System on a Cisco Router. If so, were you successful? How can this be done? Thanks so much