There is a service you can use it in linux, swap file used for supporting RAM by creating file on Harddisk drive make it work same as RAM function.
I have used it to fix some services issues, like mysql was keeping stop when RAM have no enough space and that made my websites stop working till i restart mysql service.
first you need to make file to use it as swap file, and here we will create it on root named “swap.dat” by using dd function. this function have many usages, but right now we just use it to create file with a specific size have zero content.
right now i will guide you to create a 512MB file,
dd if=/dev/zero of=/swap.dat bs=4k count=131072
bs means Block Size, then the equation here working like this 4KB * 131072 = 524288KB /1024 = 512MB
dd if=/dev/zero of=/swap.dat bs=512M
then to init swap file
to check the memory details including swap file
For keep swap file enable at bootup, you have to type this command to add your swap file line in fstab file
echo '/swap.dat swap swap defaults 0 0' | sudo tee -a /etc/fstab