Automated Screen resizing is one of the great features available with Oracle VM VirtualBox; this is related to the option to get the Virtual Machine display resolution and sizing
To Configure a VM to use VirtualBox 6.1 3D acceleration:
Then simply start-up your Oracle Linux 8 guest (same is valid for Red Hat Enterprise Linux 8 and CentOS 8).
Install VirtualBox Guest Additions (same release of VirtualBox is the best choice):
# dnf install kernel-uek-devel -y
On Red Hat Enterprise Linux 8 / CentOS 8:
# dnf install kernel-devel -y
# dnf install glx-utils -y
and click on "Run" to proceed to install VirtualBox Guest Additions.
[root@ol8u1-uek6 ~]# cat /etc/gdm/custom.conf
# GDM configuration storage [daemon]
# Uncoment the line below to force the login screen to use Xorg