bookmark_borderAllocate memory to work as swap space on VMs

When physical RAM is already in use, VM instances use swap space as a short-term replacement for physical RAM.

Contents of RAM that aren’t in active use or that aren’t needed as urgently as other data or instructions can be temporarily paged to a swap file. This frees up RAM for more immediate use.

Resolution

Calculate the swap space size

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

Amount of physical RAMRecommended swap space
2 GB of RAM or less2x the amount of RAM but never less than 32 MB
More than 2 GB of RAM but less than 32 GB4 GB + (RAM – 2 GB)
32 GB of RAM or more1x the amount of RAM
Note: Swap space should never be less than 32 MB.

In this example dd command, the swap file is 4 GB (128 MB x 32):  

$ sudo dd if=/dev/zero of=/swapfile bs=128M count=32

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:

$ sudo swapon -s

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

Open the file in the editor:

$ sudo nano /etc/fstab

Add the following new line at the end of the file, save the file, and then exit:

/swapfile swap swap defaults 0 0

Done )

run $ htop and check swp [ ] section.