The traditional way for creating a linux swapfile would be using dd to create an empty file e.g.
dd if=/dev/zero of=/swapfile1 bs=1M count=2048
A faster way is to use “fallocate” e.g. (( http://www.cyberciti.biz/faq/ubuntu-linux-create-add-swap-file/ ))
fallocate -l 2G /swapfile1
Don’t forget the usually procedure for swapfiles:
chmod 0600 /swapfile1 chown root:root /swapfile1 mkswap /swapfile1 swapon /swapfile1 # edit /etc/fstab to add the swapfile during boot