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1. Create a DOS VM

 
 

Howard Burpee, Professor, Computer Technology, 207.741.5527, howardburpee@ctech.smccme.edu

 

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1. Create a DOS VM
2. Create a VFD
3. Managing a VM
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Student How-tos

 

 

 

How to create a DOS virtual machine in Virtual Box

Why?

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?

When you want to start with something simple to learn and master the basics of the command line interface (CLI).

System requirements

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.

Software requirements

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 physical FD.

To complete the process described here, you will also need the CDBurnerXP 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 Virtual Box:

  1. Download and install Virtual Box on your system.  Basic instructions on how to install Virtual Box can be seen here.
     
  2. When you first start Virtual Box you will see the basic interface (Fig. 1).


    Fig. 1


     
  3. Select the New button to start the new virtual machine wizard (Fig. 2).


    Fig. 2


     
  4. The wizard will now start, select the Next button (Fig. 3)


    Fig. 3


     
  5. 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 (Fig. 4).


    Fig. 4


     
  6. 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.


    Fig. 5


     
  7. 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 it.

    Make your choice and select next.


    Fig. 6


     
  8. 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


     

  9. At this screen select next to continue (Fig. 8).


    Fig. 8


     
  10. 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 drive.
    • 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 size.

    Make your choice based upon your need for speed, or the total available space on your physical hard drive, and select next.


    Fig. 9


     

  11. 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.


    Fig. 10


     

  12. Select finish on the summary screen to complete the new virtual machine wizard (Fig. 11).


    Fig. 11


     
  13. You will now be returned to the Virtual Box Manager screen where you will see the DOS VM you just created (Fig. 11).


    Fig. 11

     

Part 2, Create a virtual floppy disk file using CDBurnerXP

Part 3, Manage the DOS virtual machine settings to make it boot from a virtual floppy disk


Other Resources

Virtual Box online manuals: Chapter 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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