How to create a DOS virtual machine in Virtual Box
So, as you read this, you are thinking... why would you want to use an
operating system, the newest version of which shipped in 1994? Right?
Well, command line skills in the DOS operating system apply to multiple
environments in the 21st century, including: Linux, Windows Server 2008
Core, Windows Hyper-V Server 2008, and Windows PE.
When you want to start with something simple to learn and master the basics
of the command line interface (CLI).
System hardware requirements are specific to the
hypervisor1 software you are
using to create the virtual machine (VM). When using any hypervisor
software, e.g. Virtual Box, Microsoft's Virtual PC, Parallels, VMWare
Workstation or Fusion, etc., physical memory is the most important aspect of the
system running the hypervisor software. VMs share the physical memory with
the host OS. I recommend at least 2 GB of memory on any system to support
VMs, but with a simple DOS VM, 1 GB or less is sufficient.
You will also need a floppy disk drive (FDD), or a virtual floppy disk file (VFD), to complete this process.
This how to is about creating a VM that will use Oracle's Virtual Box hypervisor software, downloadable via this
link. Virtual Box
is available for free and comes in versions that can be installed on Windows,
Mac, and Linux host operating systems.
You will also need a system running one of the host operating systems
supported by Virtual Box, listed above, and a virtual floppy disk (VFD) file that is
bootable to the DOS operating system.
Part 2 of this how to explains the process of creating a VFD from a
To complete the process described here, you will also need the
software, downloadable via this link, to create an image file of a FD.
CDBurnerXP is also free.
Part 1, Creating a DOS virtual machine using
- Download and install Virtual Box on your system. Basic
instructions on how
to install Virtual Box can be seen
- When you first start Virtual Box you will see the basic interface (Fig.
- Select the New button to start the new virtual machine wizard (Fig. 2).
- The wizard will now start, select the Next button (Fig. 3)
- In the VM Name and OS Type window, type in DOS 6.22. The wizard
will automatically change the selection on the Operating System and Version
selection boxes. After confirming the options, select the next button
- The next window (Fig. 5) in the wizard asks you to select the amount of
memory to dedicate to the virtual machine. The amount shown has been
automatically selected by the OS choice you made on the previous screen.
In a DOS virtual machine there is no need to adjust this setting. When
I create a Windows virtual machine I will often adjust this setting higher.
Note the colors on the Base Memory Size slider bar. The green area on
the bar indicates the maximum amount of memory recommended by Virtual Box.
The pink and red areas indicate that changing the memory settings to those
amounts are not recommended.
The maximum memory size of 8192 MB (8 GB) is set by the total amount of
memory (RAM) on the physical system I used to create the VM. Your
total amount of memory available will be specific to the system you are
using as the host.
Confirm the setting by selecting the next button.
- The Virtual Hard Disk screen allows you to select the hard disk drive
(HDD) that your VM will boot from (Fig. 6). You should leave the Boot
Hard Disk box checked and select whether to create a new hard disk or use an
existing hard disk.
For our purposes here, you should leave the default selection of create a
new hard disk.
Occasionally you might choose to use an existing hard disk, if and when you
had already created a virtual hard disk file and were building a new VM from
Make your choice and select next.
- You will now be prompted to select the type of virtual hard disk file
to create (Fig. 7).
You may select from four different file types:
- .VDI is the native file type used by Virtual Box
- .VMDK is native to VMWare hypervisor software
- VMWare Workstation for Windows
- VMWare Fusion for Mac
- And other VMWare products
- .VHD is native to Microsoft hypervisor software
- Virtual PC
- Hyper-v service on Windows Server 2008
- Windows Hyper-v Server 2008
- And other Microsoft products
- Parallels is hypervisor software for the Mac
You should leave it at the default setting of VDI. Although if you were
to change it to VHD, you would then be able to use the virtual hard disk
file when creating a new virtual machine in Virtual PC.
Make your choice and select next to continue.
Fig. 7 Image courtesy of Ryan Cordner
- At this screen select next to continue (Fig. 8).
- On the Hard Disk Storage type screen (Fig. 9), you will choose from a
dynamically expanding storage or fixed-size storage type of virtual hard
- Let's say you were to create a 20 GB virtual hard drive (set on the
next screen). If the virtual hard drive was a fixed-size type, the
.VDI file would be 20 GB in size.
- If you choose dynamically expanding, the .VDI file would be much
smaller and would expand as you added files to the virtual machine.
- A Windows XP VM, with a dynamic 20 GB virtual hard drive, would have
a .VDI file approximately 2 GB in
Make your choice based upon your need for speed, or the total
available space on your physical hard drive, and select next.
- You will now choose where to place / store the virtual hard disk file
and what size disk it will be (Fig. 10).
- The default file name for the virtual hard disk will be DOS 6.22.VDI
(assuming you chose .VDI file type in step #8.
- The default storage location for the file will be in a subdirectory
of your My Documents directory.
- For a DOS VM, 512 MB of hard drive is fine. A full install of
DOS 6.22 takes up about 11 MB of hard drive space. The default
virtual hard disk size for a Windows XP VM is usually 20 GB.
Confirm or change the settings and select next.
- Select finish on the summary screen to complete the new virtual
machine wizard (Fig. 11).
- You will now be returned to the Virtual Box Manager screen where you
will see the DOS VM you just created (Fig. 11).
Virtual Box online manuals:
1 First Steps
1. Hypervisor = A hypervisor, also
called a virtual machine manager, is a program that allows multiple operating
systems to share a single hardware host. Each operating system appears to have
the host's processor, memory, and other resources all to itself. However, the
hypervisor is actually controlling the host processor and resources, allocating
what is needed to each operating system in turn and making sure that the guest
operating systems (called virtual mahines) cannot disrupt each other.
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