Bootstrapping DOS inside VirtualBox

Bootstrapping DOS inside VirtualBox

The biggest challenge with classic OSs like MS-DOS, DR-DOS and so on is the fact that there is no readily available downloadable ISO-image that you could just virtually insert into the virtual CD-tray of VirtualBox. For anything that is just a little bit younger than DOS, you can probably find the CD image file. Even Windows 95 (while still being available on floppy disk) was already distributed on a CD.

The second 10 minutes exercise

Floppy images - the solution

Fortunately there is the concept of floppy disk images as well. These floppy image files can be inserted into the virtual disk drive of VirtualBox in the same way as CD images. The nice thing about that: it gives you the very original visual impression what it looked like, installing DOS on a brand new computer. What is missing though is the typical sound of these classic disk drives.

So let's try DOS 5. You need 2 floppy images. Right click these links and choose "Save As":
Feel free to use any other set of floppy images. You can find them in some places across the internet. Make sure the download site looks trustworthy and doesn't require any fees, subscriptions, ... and so on.

Installation in VirtualBox

Now the installation is straight forward. Insert the disk 1 image into the virtual floppy drive and restart the virtual machine.

The "Reset" button is under the "Machine" menu:

If everything works, you should now be guided through the MS-DOS setup.


The setup sequence will do all the necessary steps like
  • location / keyboard configuration
  • initializing the virtual hard drive
  • copying the operating system
  • install the initial config.sys and autoexec.bat

Result and next steps

This concludes the actual DOS setup. Using this machine you can already do a little bit of playing around. You have a text mode editor. You can manipulate text files and so on. It is a working DOS environment. 

There are a few missing pieces though. 
  • MS-DOS was not designed as an operating system that runs in a virtualized environment. Therefore it will use all the CPU cycles that the VM will get. This does not mean that your host operating system will get significantly slower but it means that one core runs all the time. That causes a temperature increase of the host CPU and you will notice the fans kicking in to cool down the CPU. We will solve this in the next part of the series.
  • MS-DOS initially did not know about CD-ROMs. Juggling floppy disk images going forward with this virtual machines is inconvenient. We will add CD-ROM support to make future installations much easier. It will allow to insert CD/DVD image files into the virtual drive bay.
  • Currently the machine makes no use of the LAN card that is configured in the VM setup. This is a shame. Of course we want to be able to connect the box to the internet. So networking support will be added as well.
  • Finally there should be some real software running inside the virtual box. This could be word processing, programming, classic games, ...
But I will leave that to the next session.

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