Access to shared folders in Virtual Box
By default Virtual Box shared folders are created with read/write permission for the guest. This can be done from the command line with:
VBoxManage sharedfolder add "VM name" --name "sharename" --hostpath "C:\test"
By adding the option
--readonly we can restrict these for read only access. Use the
--transient option if you only want the shares to appear in the present session but not persistent for follwing sessions. There are some limitations for shared folders (see this question for details). If prerequisites are met we may mount these shared folders manually by running the following commands in the guest:
sudo mount -t vboxsf -o uid=1000,gid=1000 share /home/<user>/vboxshare
Of course we can also use different mount options to mount as read/only or mount with read access only to root.
Auto-Mount through Virtual Box Manager
In case we enabled auto-mounting on creating a shared folder from the Virtual Box Manager those shared folders will automatically be mounted in the guest with mount point
/media/sf_<name_of_folder>. To have access to these folders users in the guest need to be a member of the group
Source and further reading: Virtual Box User Manual