Oracle Linux 7.6 black screen while boot from virtualbox

I am trying to boot my oracle linux 7.6 which is running under virtual box but black screen appear long time

Causes :

Network manager & network manager wait online service have a problem

Solution :

Boot as rescue mode like below

Edit mode (e)

end of line linux16, add below command

systemd.unit=target.rescue

control + x  –> enter

Maintenance mode will appear

Enter root password maintenance

Execute below command

systemctl mask systemd-NetworkManager-wait-online.service

reboot the machine

The network manager may have a problem after restarted the machine, so start the network manager like below

systemctl enable NetworkManager

systemctl unmask NetworkManager.service

systemctl start NetworkManager.service

In case selinux may also making issue for black screen appeared while booting. Please disable and reboot the machine.