sudo add-apt-repository universe
sudo add-apt-repository multiverse

apt-get update
apt-get upgrade

apt install build-essential dkms virtualbox-dkms unzip wget
OPTIONAL apt-get install linux-headers-lowlatency
reboot

lsb_release -c
nano /etc/apt/sources.list
FILE ADD LINE:
deb [arch=amd64] http://download.virtualbox.org/virtualbox/debian bionic contrib
FILE END

wget -q https://www.virtualbox.org/download/oracle_vbox_2016.asc -O- | sudo apt-key add -
apt update
apt-get install virtualbox-5.2

adduser YOURUSER
usermod -aG vboxusers YOURUSER
reboot

systemctl status vboxdrv

wget https://download.virtualbox.org/virtualbox/5.2.44/Oracle_VM_VirtualBox_Extension_Pack-5.2.44.vbox-extpack
VBoxManage extpack install Oracle_VM_VirtualBox_Extension_Pack-5.2.44.vbox-extpack
OR to fix errors
VBoxManage extpack uninstall "Oracle VM VirtualBox Extension Pack"

apt-get install php-soap

wget https://github.com/phpvirtualbox/phpvirtualbox/archive/master.zip
mv phpvirtualbox* /var/www/html/phpvirtualbox
chmod 777 /var/www/phpvirtualbox/
cp /var/www/phpvirtualbox/config.php-example /var/www/phpvirtualbox/config.php

OPTIONAL: look into how-2-nginx to see how to set a folder or sub-domain password


nano /var/www/phpvirtualbox/config.php
FILE EDIT:
var $username = 'YOURUSER';
var $password = 'YOUR PW';
FILE END

nano /etc/default/virtualbox
FILE ADD:
VBOXWEB_USER=YOURUSER
FILE END

ufw allow 3390:3395/tcp
ufw allow 3390:3395/udp

systemctl restart vboxweb-service
systemctl restart vboxdrv
systemctl restart nginx

su - YOUR_VBOX_USER

VBoxManage setproperty vrdeauthlibrary "VBoxAuthSimple"
VBoxManage internalcommands passwordhash "YOUR_PW"

VBoxManage registervm "/PATH/TO/YOUR/*.vbox" 

VBoxManage setextradata "/PATH/TO/YOUR/*.vbox" "VBoxAuthSimple/users/YOUR_USER" YOUR_HASH

VBoxManage modifyvm "/PATH/TO/YOUR/*.vbox" --vrde on --vrdeauthtype external --vrdemulticon on --vrdereusecon on --vrdeaddress 0.0.0.0 --vrdeport 3390-3395 --vrdeproperty "Security/Method=RDP"
OPTIONAL: also use
--autostart-enabled on --autostart-delay 300 --nestedpaging on 

VBoxManage setproperty vrdeauthlibrary default
VBoxManage modifyvm "/PATH/TO/YOUR/*.vbox" --vrdeauthtype null


HOW-2-Priority
ls /proc/$PID/task | xargs renice $PRIO
for p in `ls /proc/$PID/task`; do taskset -p -c $CORES $p; done