How do I setup an encrypted swap file?

Thanks to this guide I set up an encrypted swap file (can't be used for hibernation). On Debian based distributions, you will need the cryptsetup package for these instructions.

1. Firstly create an appropriately sized file (here 4 gigabytes) to store the swap data:

   fallocate -l 4G /cryptswap
   

2. Add the following to /etc/crypttab:

   cryptswap /cryptswap /dev/urandom swap
   

3. Activate the newly created encrypted drive:

   service cryptdisks reload
   

4. Add the following to /etc/fstab:

   /dev/mapper/cryptswap none swap sw 0 0
   

5. Activate the new swap file:

   swapon -a
   

Skip the reboot:

sudo cryptdisks_start cryptswap

where cryptswap is the name in /etc/crypttab