cookies[:remember_token] = { :value => user.id, :expires => 20.years.from_now.utc }
A “remember token” cookie is created, you can also do the 20 years part as:
cookies.permanent[:remember_token] = user.remember_token
cookies.permanent.signed[:remember_token] = [user.id, user.salt]
Obscures the real user.id with the salt, for security purposes
Retrieving stuff from cookies:
User.find_by_remember_token(cookies[:remember_token]) // This will query for a user with remember_token