Determine the size of the new swap file in megabytes and multiply by 1024 to determine the number of blocks. For example, the block size of a 64 MB swap file is 65536.

At a shell prompt as root, type the following command with count being equal to the desired block size:

dd if=/dev/zero of=/swapfile bs=1024 count=65536

Setup the swap file with the command:

mkswap /swapfile

To enable the swap file immediately but not automatically at boot time:

swapon /swapfile

To enable it at boot time, edit /etc/fstab to include the following entry:

/swapfile swap swap defaults 0 0

The next time the system boots, it enables the new swap file.