deb http://ftp.de.debian.org/debian/ testing main
deb-src http://ftp.de.debian.org/debian/ testing main
 
deb http://security.debian.org/debian-security testing/updates main contrib
deb-src http://security.debian.org/debian-security testing/updates main contr$
 
deb http://http.kali.org/kali kali-rolling main contrib non-free

nano /etc/apt/preferences.d/debiankali
Package: *
Pin: release a=testing
Pin-Priority: 1000
 
Package: *
Pin: release n=kali-rolling
Pin-Priority: 800

wget -q -O - https://archive.kali.org/archive-key.asc | apt-key add
apt-get update

deb http://repo.vivaldi.com/stable/deb/ stable main
wget -O - http://repo.vivaldi.com/stable/linux_signing_key.pub | apt-key add

wget -qO - https://download.sublimetext.com/sublimehq-pub.gpg | sudo apt-key add -
Ensure apt is set up to work with https sources:

sudo apt-get install apt-transport-https
Select the channel to use:

Stable
echo "deb https://download.sublimetext.com/ apt/stable/" | sudo tee /etc/apt/sources.list.d/sublime-text.list

adduser <user> vboxsf

apt-get install apt-transport-https ca-certificates curl gnupg2 software-properties-common
wget -qO - https://download.docker.com/linux/debian/gpg | apt-key add -
add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/debian $(lsb_release -cs) stable"
apt-get install docker-ce