$ curl cheat.sh/

# mkswap
# Sets up a Linux swap area on a device or in a file.
# More information: <https://manned.org/mkswap>.

# Setup a given partition as swap area:
sudo mkswap /dev/sdb7

# Use a given file as swap area:
sudo mkswap path/to/file

# Check a partition for bad blocks before creating the swap area:
sudo mkswap -c /dev/sdb7

# Specify a label for the file (to allow `swapon` to use the label):
sudo mkswap -L swap1 path/to/file

$

Follow @igor_chubin cheat.sh tldr