Kali Linux is a distribution of Linux that is used for penetration testing. While normally distributed in a typical ISO file for install on hardware, it has also been wrapped into a Docker image to run it on basically any OS with Docker installed.
On DigitalOcean, you can’t install an ISO file. This is where the Docker image comes into play. On DigitalOcean you can set up a container distribution to use Kali. I like to use CoreOS.
Once you’ve set up your container distribution, go ahead and login with your SSH key, using the ‘core’ user. That was one thing that was not immediately obvious, because I would typically SSH into virtual machines with ‘root’.
As the Kali Docker documentation explains, you can pull the OS like so:
docker pull kalilinux/kali-linux-docker docker run -t -i kalilinux/kali-linux-docker /bin/bash
It’s important to note, you can’t install the GUI version of Kali Linux through a Docker container like this. If you really want a GUI, you will need to install another OS and setup RDP or VNC - and then add and install the Kali Linux repo and packages. I will detail this in a later post.
And that’s it! You can install and update the tools you’ll need as you would normally.
Installing the tools
If you don’t know what tools you want - maybe you’re just exploring - you can install them as bundles called ‘metapackages’. The metapackages are listed here, but I’ll list some that you might actually be interested in below:
kali-linux-top10: the most popular security tools on Kali (3.5GB)
kali-linux-pwtools: password cracking utilities (6GB)
kali-linux-web: web application assessments / penetration testing (4.9GB)
Note that RFID and wireless tools are almost definitely useless on a virtual machine in the cloud.