This is useful if you need to creating partitition for Linux while using OSX. If you're trying to mount a raw disk to VirtualBox on OSX and you're getting
VBOX_E_OBJECT_NOT_FOUND errors (hello Google searchers), try this.
Get the disk number
Assuming you want /dev/disk2 from here in. Unmount the disk
diskutil unmountDisk /dev/disk2
We need full access to everyone to the block device.
sudo chmod 777 /dev/disk2
Create the a VirtualBox vmdk file linkink to the raw disk
VBoxManage internalcommands createrawvmdk -filename sd.vmdk -rawdisk /dev/disk2
In the VirtualBox GUI, make sure your guest machine is powered off. Add the vmdk file from Setting->Storage...
For me this mounted the disk again, so unmount it before you start the machine again.