hexcowboy / docker-vm

A proof of concept for creating persistent virtual machines in Docker

Docker VM

Docker has the capabilities to create virtual machines, however the majority of it's use case right now is to host ephemeral containers, meaning they live short and aren't persistent. To make a Docker container behave more like a VM, it needs to have the following qualities:

1. User Interface. For a lot of users, a default bash shell is not enough and a TUI or GUI is needed.
2. Persistence. When you shut down and restart the VM, it should remember your file system structure.

User Interface

A simple solution to this problem is to install an X server.

macOS

1. Install the latest version of XQuartz
   • Or use brew: brew install --cask xquartz
2. Launch XQuartz and in the menu, choose XQuartz -> Preferences -> Security
3. Check the box for Allow connections from network clients and restart XQuartz
4. In your macOS terminal, type xhost + 127.0.0.1

Windows

1. Install the latest version of VcXsrv
   • Or use choco: choco install vcxsrv
2. Launch VcXsrv to start the setup
3. Use all default settings, checking ✅ Disable access control

Linux

(wip)

This Dockerfile will run xterm which is a simple GUI terminal.

FROM ubuntu:latest
RUN apt-get update && apt-get install -y xterm
CMD xterm

And now we can run our container, setting the DISPLAY environment variable to host.docker.internal:0.

$ docker build -t vm .
$ docker run -e DISPLAY=host.docker.internal:0 vm

Persistence

Since there is no way to mount the entire / filesystem to volume in Docker, we have to hand-select our persistent directories. Using the manpage for file-heirarchy we can get a good idea of what needs to happen in our docker-compose.yml:

version: "3.8"

services:
  virtualmachine:
    build: .
    environment:
      - "DISPLAY=host.docker.internal:0"
    volumes:
      - "./bin:/bin"
      - "./etc:/etc"
      - "./home:/home"
      - "./lib:/lib"
      - "./opt:/opt"
      - "./usr:/usr"
      - "./var:/var"