Mount the Mount shared folder in the VirtualBox ubuntu/linux virtual machine

REFEREMCE:
https://www.smarthomebeginner.com/mount-virtualbox-shared-folder-on-ubuntu-linux/

1) VirtualBox Manager, setting, share folder, add share folder, select "Auto-mount" "Make permanent"

2) Open the VirtualBox virtual machine, the shared folder sf_xxxx should already be mounted under the/media folder

3) The user of the shared folder is vboxsf, which can be ls -l viewed by viewing the folder status. By default, VBOXSF does not have read and write permissions.
Use instructions to increase read and write permissions for vboxsf users
$ sudo usermod-a-G vboxsf USER

4) Reboot, restart the computer

Mount the Mount shared folder in the VirtualBox ubuntu/linux virtual machine