To use “Shared Folders” in VirtualBox, the user should install VirtualBox guest additions:
(1) Select Devices -> Insert Guest Additions CD image. If the VirtualBox prompts:
Unable to insert the virtual optical disk C:\Program Files\Oracle\VirtualBox\VBoxGuestAdditions.iso into the machine CentOS.
Would you like to try to force insertion of this disk?
Count not mount the media/drive 'C:\Program Files\Oracle\VirtualBox\VBoxGuestAdditions.iso' (VERR_PDM_MEDIA_LOCKED).
It means the Devices -> CD/DVD DEvices already has ISO file. Please inject it, and try Insert Guest Additions CD image again.
(2) Mount the ISO file:
mount /dev/cdrom /mnt
(3) Install the VirtualBox guest additions (Take Linux as an example):
cd /mnt
./VBoxLinuxAdditions.run
You may also need to install bzip2, gcc and kernel files to install guest additions successfully. When meeting errors, please refer /var/log/vboxadd-install.log for detail info.