Recently after installing updates on Ubuntu 12.04 , the “Full Screen” functionality of my VM VirtualBox did not work anymore.
Every time I click on VirtualBox window – Devices – Install Guest Additions, gave me this error – VERR_PDM_MEDIA_LOCKED, which implies that your local drive allocated for your VM is locked out for any changes.
Then I realised that I had to unmount the drive, to make any changes.
So easy steps to achieve the “Full Screen” functionality are as follows –
1. ‘Devices‘ Drill down
2. If you are using VM Virtalbox Version 6.0.0 (Qt5.6.2) or later select Optical Drives (for older versions its called ‘CD/DVD Devices‘) uncheck VBoxGuestAdditions.iso
3. without restart, click on “Devices” again and ‘Install Guest Additions‘
4. The terminal automatically starts , give your password… Might take a few minutes.