dd if=/dev/zero of=/swapfile bs=1k count=2048000
2048000+0 records in
2048000+0 records out
2097152000 bytes (2.1 GB) copied, 34.6782 s, 60.5 MB/s

mkswap /swapfile
Setting up swapspace version 1, size = 2047996 KiB
no label, UUID=56026239-26e6-40d9-b080-b95acd9db058

swapon /swapfile
swapon: /swapfile: insecure permissions 0644, 0600 suggested.

chmod 600 /swapfile