On hosts which have upgraded from 13.0 to 13.1, the virtualbox driver gives the following error:
VBoxHeadless: Error -1908 in suplibOsInit!
VBoxHeadless: Kernel driver not installed
VBoxHeadless: Tip! Make sure the kernel module is loaded. It may also help to reinstall VirtualBox.
With the September quarterlies, and Virtualbox version 6.1.36, you will need to remove the driver and uninstall Virtualbox, then reboot.
kldunload vboxdrv
pkg delete -f virtualbox-ose virtualbox-ose-kmod
Now reboot, and log back in as root.
pkg install -y virtualbox-ose virtualbox-ose-kmod
kldload vboxdrv
mkdir -p /etc/vbox
mkdir -p /usr/local/etc/vbox
echo "* 0.0.0.0/0" > /usr/local/etc/vbox/networks.conf
ln -s /usr/local/etc/vbox/networks.conf /etc/vbox/networks.conf
service vboxnet restart
The packbox and startvms commands should work fine now.
The plugin vagrant-disksize may start to give errors about "Conflicting dependency chains" on a host which upgraded.
Attempts to fix by upgrading gems only make the problem worse.
The solution is to install a fresh FreeBSD-13.1 system with quarterlies packages and run through detailed install again. The plugin install works correctly then.
However, you can also try the following, which works to update everything without dependency errors:
VAGRANT_DISABLE_STRICT_DEPENDENCY_ENFORCEMENT=1 VAGRANT_ALLOW_PRERELEASE=1 vagrant upgrade
While most virtualbox installations make use of /etc/vbox, including older FreeBSD versions 12.x, 13.0, from FreeBSD 13.1 /usr/local/etc/vbox/ is used and /etc/box/ shouldn't exist.
However if /etc/vbox doesn't exist there is an error. You can create the directory and symlink across /usr/local/etc/vbox/networks.conf, and you'll still get an error as follows. You can safely ignore it.
packer-builder-virtualbox-iso plugin: stderr: WARNING: Directory /etc/vbox found, but ignored. VirtualBox
configuration files are stored in /usr/local/etc/vbox/.