Increasing the disk size

on Ubuntu operating system under VirtualBox

1) Before starting the Ubuntu system in the VirtualBox software choose this menu:
File -> Tools -> Virtual Media Manager (or push ctrl+D)

2) On the right, double click the virtual disk of the Ubuntu (DEIK Ubuntu 22.04 LTS.vdi).

3) At the bottom of the screen change the Size to the maximum.

4) Start the virtual Linux system, and log in.

5) Execute the following 3 commands in a terminal (take care about the space characters):
sudo apt install cloud-guest-utils
sudo growpart /dev/sda 3
sudo resize2fs /dev/sda3