VirtualBox shared folders
Install virtualbox-guest-additions and virtualbox-guest-modules-virthardened at first:
apk add virtualbox-guest-additions virtualbox-guest-modules-virthardened
The following error may occur:
ERROR: unsatisfiable constraints: virtualbox-guest-additions (missing): required by: world[virtualbox-guest-additions] virtualbox-guest-modules-virthardened (missing): required by: world[virtualbox-guest-modules-virthardened]
If the error occurs, make sure your alpine version is greater than v3.6 and alpine community repo is enabled:
echo "http://dl-cdn.alpinelinux.org/alpine/edge/community" >> /etc/apk/repositories
Update respository indexes from all remote repositories, then install guest modules and reboot:
apk update apk add virtualbox-guest-additions virtualbox-guest-modules-virthardened reboot
Goto Device > Shared Folders > Shared Folder Settings ... add a directory mapping like this:
Mount it to alpine:
mkdir /mnt/outside mount -t vboxsf vbox_shared /mnt/outside
which vbox_shared is your folder name and /mnt/outside is the mounting point.
After this step the following error may occur:
mount: mounting vbox_shared on /mnt/outside failed: No such device
If the error occurs, run command below:
modprobe -a vboxsf mount -t vboxsf vbox_shared /mnt/outside
And you will see /tmp/vbox_shared and /mnt/outside are connected.
P.S. Alpine will raise error "Invalid argument" if virtualbox-guest-additions is not installed when mounting drive.
VirtualBox will raise error "Guest Additions unavailable" if virtualbox-guest-modules-virthardened is not installed when adding shared path.