Create a file that will be used for swap:
sudo fallocate -l 1G /swapfile

If faillocate is not installed or if you get an error message saying fallocate failed: Operation not supported then you can use the following command to create the swap file:
sudo dd if=/dev/zero of=/swapfile bs=1024 count=1048576
Only the root user should be able to write and read the swap file. To set the correct permissions type:
sudo chmod 600 /swapfile

Use the mkswap utility to set up the file as Linux swap area:
sudo mkswap /swapfile

Enable the swap with the following command:
sudo swapon /swapfile

To make the change permanent open the /etc/fstab file and append the following line:
nano /etc/fstab
/swapfile swap swap defaults 0 0
To verify that the swap is active, use either the swapon or the free command as shown below:
sudo swapon --show
output :
NAME TYPE SIZE USED PRIO
/swapfile file 1024M 507.4M -1

sudo free -h

verify usage swap :
# grep -i swap /proc/meminfo