Ubuntu Full Screen in VirtualBox
Open your Virtual Box window for ubuntu and from the options available in the window select "Devices", from the sub-options select "Insert Guest Additions CD image"
Once we choose the option we can see one storage gets mounted.
Now let's go to the terminal and execute the below commands, these are dependencies required for the Virtual box.
sudo apt-get install build-essential gcc make perl dkms
Now let's find the exact Linux file from the mounted storage, we need to find the exact location for the Linux package that is responsible for fullscreen mode in Virtual Machine.
first, let's use the findmnt command to find the mounted storage location
findmnt | grep VBox_GAs
Now we get a location lets CD into the location
cd /media/USERNAME/VBox_GAs_ver-no
Now from this directory let's find the package responsible for fullscreen mode, since we are working with Linux VM, we can select the Linux-based VBoxLinuxAddition.run
Now we can execute the full path in the terminal to install the package
sudo /media/USERNAME/VBox_GAs_ver-no/VBoxLinuxAddition.run
Once the packages are installed we get something like this as output, when we see this we can restart the VM.
Now we can restart the VM and we will be able make the VM fullscreen ^_^