Enable Swap memory using swapfile in Ubuntu EC2 instance

Calculate the swap space size

As a general rule, calculate swap space according to the following: 

Amount of physical RAM	Recommended swap space
2 GB of RAM or less	2x the amount of RAM but never less than 32 MB
More than 2 GB of RAM but less than 32 GB	4 GB + (RAM – 2 GB)
32 GB of RAM or more	1x the amount of RAM

Note: Swap space should never be less than 32 MB.

Create a swap file

1.    Use the dd command to create a swap file on the root file system, where "bs" is the block size and "count" is the number of blocks. In this example the swap file is 4 GB:

$ sudo dd if=/dev/zero of=/swapfile bs=1G count=4

2.    Update the read and write permissions for the swap file: 

$ sudo chmod 600 /swapfile

3.    Set up a Linux swap area: 

$ sudo mkswap /swapfile

4.    Make the swap file available for immediate use by adding the swap file to swap space: 

$ sudo swapon /swapfile

5.    Verify that the procedure was successful: 

$ swapon -s

6.    Enable the swap file at boot time by editing the /etc/fstab file:

$ sudo vi /etc/fstab
$ /swapfile swap swap defaults 0 0