From Ubuntu 18.04 onwards, a swapfile rather than a dedicated swap partition is used (except when LVM is used). The swap file is named "swapfile". To change the size of this swap file:

Disable the swap file and delete it (not really needed as you will overwrite it)

sudo swapoff /swapfile
sudo rm  /swapfile

Create a new swap file of the desired size. With thanks to user Hackinet, you can create a 4 GB swap file with the command

sudo fallocate -l 4G /swapfile

In this command, adjust 4G to the size you want.

Alternatively, you can use dd but feeding the correct parameters requires some calculations. If you want to make a 4 GB swap file, you will need to write 4 * 1024 blocks of 10242 bytes (= 1 MiB). That will make your count equal to 4 * 1024 = 4096. Create the file of this size with the command

sudo dd if=/dev/zero of=/swapfile bs=1M count=4096

Assign it read/write permissions for root only (not strictly needed, but it tightens security)

sudo chmod 600 /swapfile

sudo mkswap /swapfile

The file will be activated on the next reboot. If you want to activate it for the current session:

sudo swapon /swapfile

You can check the swap that is available with the command swapon -s (no root permissions needed).

swapon -s

https://askubuntu.com/questions/1075505/how-do-i-increase-swapfile-in-ubuntu-18-04