For Lightsail system there is a limitation of 1Gb of Memory space on Free tier. To gain the most out of the system we need to increase the memory capability of the system by adding the swap storage.
Here's how its done.

Creating a Swap File

In this example, we will create 2 GB swap file. If you want to add more swap, replace 2G with the size of the swap space you need.

Complete the steps below to add swap space on Ubuntu 20.04:

1. First, create a file that will be used as swap:

    sudo fallocate -l 2G /swapfile
   

   If the fallocate utility is not present on your system, or you get an error message saying fallocate failed: Operation not supported, use the following command to create the swap file:

    sudo dd if=/dev/zero of=/swapfile bs=1024 count=2097152
   

2. Set the file permissions to 600 to prevent regular users to write and read the file:

    sudo chmod 600 /swapfile
   

3. Create a Linux swap area on the file:

    sudo mkswap /swapfile
   

    Setting up swapspace version 1, size = 2 GiB (2147479552 bytes)
    no label, UUID=fde7d2c8-06ea-400a-9027-fd731d8ab4c8
   

4. Activate the swap file by running the following command:

    sudo swapon /swapfile
   

   To make the change permanent open the /etc/fstab file:

    sudo nano /etc/fstab
   

   and paste the following line:

   /etc/fstab

    /swapfile swap swap defaults 0 0
   

5. Verify that the swap is active by using either the swapon or the free command, as shown below:

    sudo swapon --show
   

    NAME      TYPE      SIZE  USED PRIO
    /swapfile file        2G    0B   -1
   

    sudo free -h
   

                  total        used        free      shared  buff/cache   available
    Mem:          981Mi        97Mi        68Mi       0.0Ki       814Mi       735Mi
    Swap:         2.0Gi        10Mi       1.9Gi
   

Adjusting the Swappiness Value

Swappiness is a Linux kernel property that defines how often the system will use the swap space. It can have a value between 0 and 100. A low value will make the kernel to try to avoid swapping whenever possible, while a higher value will make the kernel to use the swap space more aggressively.

On Ubuntu, the default swappiness value is set to 60. You can check the current value by typing the following command:

cat /proc/sys/vm/swappiness

60

While the swappiness value of 60 is OK for most Linux systems, for production servers, you may need to set a lower value.

For example, to set the swappiness value to 10, run:

sudo sysctl vm.swappiness=10

To make this parameter persistent across reboots, append the following line to the /etc/sysctl.conf file:

/etc/sysctl.conf

vm.swappiness=10

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The optimal swappiness value depends on your system workload and how the memory is being used. You should adjust this parameter in small increments to find an optimal value.

Removing a Swap File

To deactivate and delete the swap file, follow these steps:

1. First, deactivate the swap space:

    sudo swapoff -v /swapfile
   

2. Next, remove the swap file entry /swapfile swap swap defaults 0 0 from the /etc/fstab file.

3. Finally, remove the actual swapfile file using the rm command:

    sudo rm /swapfile