Type the following command with count being equal to the desired block size:
dd if=/dev/zero of=/extraswap bs=1M count=4024
Setup the swap file with the command:
mkswap /extraswap
To enable the swap file immediately but not automatically at boot time:
swapon /extraswap
To enable it at the boot time, add the following entry into /etc/fstab:
/extraswap swap swap defaults 0 0
