you can't mount the external usb drive, because the permission on /dev/vboxdrv

To check usb's devices, and u can check if the external stroage are available or not.

$ VBoxManage list usbhost

Manufacturer: JMicron
Product: Storage

Current State: Unavailable

This mean, the VirtualBox doesnt have permssion.

 

To resolv this issue:

you need manipulating the permission on /dev/vboxdrv, so open the terminal

1) sudo su –

2)  unload the kernel extension:

kextunload -b com.apple.iokit.IOUSBMassStorageClass

3) change the group and set permission

after:

# ls -lah /dev/vboxdrv
crw——- 1 root wheel 36, 0 Jan 25 19:22 /dev/vboxdrv

 chgrp vboxusers /dev/vboxdrv
 chmod g+rw /dev/vboxdrv

before:

# ls -lah /dev/vboxdrv
crw-rw—- 1 root admin 36, 0 Jan 25 19:22 /dev/vboxdrv

4) load the kernel extension:

kextload com.apple.iokit.IOUSBMassStorageClass

 

After the procedure, u can mount the external storage on virtual machine.