Swap memory is used when the amount of physical memory (RAM) is full. If the system needs more memory resources and the RAM is full, inactive pages in memory are moved to the swap space. While swap space can help machines with a small amount of RAM, it should not be considered a replacement for more RAM. Commands :

sudo fallocate -l 1G /swapfile (for 1 GB swap memory)

sudo chmod 600 /swapfile

sudo mkswap /swapfile

sudo swapon /swapfile

free -m