Ubuntu is using swap files instead of swap partitions (as of Ubuntu 17.04) , except systems upgrading from 16.04 will retain their swap partitions and reuse them instead of swap files, as discussed in this answer. But, if I am upgrading and decide to use a swap file instead, can I place it in the old swap partition?
I realize this will limit the size of the swap file, but this way I can still make use of that drive space. If I can do this, would I have to format the partition to the same file-system type as Ubuntu? And would I have to keep it permanently mounted?