DOS 6.22 VM

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DOS 6.22 VM

Postby Joe890 » 15. Jul 2021, 16:10

Hello forum,

would like to setup a DOS 6.22 based VM for a test. Host OS is Linux and luckely I do still own a
MS developer CD with MS DOS 6.22 on it (257 files, 6,2mb) :-)

To my understandig VBox needs *.img in order to be able to install DOS...


Questions:
- Which DOS files (among of the 257) are needed in the first image, which in the second image and so long?
- what tool do you suggest to produce the img-files?


Thank's a lot!

Joe
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Re: DOS 6.22 VM

Postby mpack » 15. Jul 2021, 16:21

Joe890 wrote:To my understandig VBox needs *.img in order to be able to install DOS...

Not quite.

A VM is just a PC, so you would install DOS just like on a physical PC - from floppies. You will need either physical floppies and a physical floppy drive, or else you'll need floppy disk images. The MS developer CD probably has folders called DISK1 and DISK2 etc, so that's what each of the floppy images needs to contain.

By the way, VirtualBox floppy images are raw, so don't be misled into using some crazy tool just because it reuses the ".img" extension. A raw image of a 1.44MB floppy usable in VirtualBox should be exactly 1,474,560 bytes. It must not be compressed nor have a header imposed by some tool.

On the subject of tools, I don't know of one (which doesn't mean it won't exist) that can create floppy images from a group of files, also the first floppy in the set would have to be bootable. If I was you I would look online for a boot floppy of the correct version of DOS. That floppy image can be mounted in any other VM (once you add a floppy drive anyway), then you can copy from a shared folder onto the floppy image.

Or, just boot from the floppy but then run setup from the CD: the boot disk you find online will include CD drivers.
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Re: DOS 6.22 VM

Postby Joe890 » 17. Jul 2021, 14:24

mpack wrote:A VM is just a PC, so you would install DOS just like on a physical PC - from floppies. You will need either physical floppies and a physical floppy drive, or else you'll need floppy disk images. The MS developer CD probably has folders called DISK1 and DISK2 etc, so that's what each of the floppy images needs to contain.
Surprisingly this is the case for the russian DOS version (360 kb- and 720 kb-iamges:), but the others do simply consist on one folder with 257 files.

mpack wrote: By the way, VirtualBox floppy images are raw, so don't be misled into using some crazy tool just because it reuses the ".img" extension. A raw image of a 1.44MB floppy usable in VirtualBox should be exactly 1,474,560 bytes. It must not be compressed nor have a header imposed by some tool.
Do you think a dd/raw image of the DOS6.22 floppy could work?

mpack wrote: If I was you I would look online for a boot floppy of the correct version of DOS.
I even found an old DOS 6.22 floppy at my home :)


Thank's a lot in advance for any additional help!
Joe
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Re: DOS 6.22 VM

Postby mpack » 17. Jul 2021, 15:50

Joe890 wrote:Do you think a dd/raw image of the DOS6.22 floppy could work?

I said above that floppy images must be raw. So if you have a tool that creates raw floppy images then it will work.

Joe890 wrote:
mpack wrote: If I was you I would look online for a boot floppy of the correct version of DOS.
I even found an old DOS 6.22 floppy at my home :)

It can't be some random floppy. Boot disks found online typically contain everything needed to run programs and repair damage. For example it will include CD drivers, which DOS did not support out of the box.
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Re: DOS 6.22 VM

Postby Joe890 » 20. Jul 2021, 16:22

Ok, tried it with a dd of DOS622 (floppy) (renamed to DOS622.iso) and a dd of DOS33 (floppy) (remamed to DOS33.iso), but in both cases the following error is shown during booting DOS:


ata0 master: VBOX HARDDISK ATA-6 Hard-Disk (500 MBytes)
ata1 master: VBOX CD-ROM ATAPI-6 CD-ROM/DVD-ROM
ata2 master: Unknown device
ata2 slave: Unknown device
ata3 master: Unknown device
ata3 slave:

FATAL: NO bootable medium found! System halted.

Question:
Any idea what I am doing wrong?


Thank's a lot!

Joe



PS
- the hash of DOS622.iso and DOS33.iso is veryfied against the device (sda). Hashes do match.
- copied back both dd's to empty 1.4 mb floppies. PC does successfully boot DOS6.22 and DOS33
- renamed the *.dd to *.iso because this is working with the Windows7 installation DVD
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Re: DOS 6.22 VM

Postby Martin » 20. Jul 2021, 18:10

You have images of floppy disks, not CD-ROMs. So ".iso" is just wrong.
Also this will never work in a (virtual) CD-/DVD-Drive.
You need to attach thesse images to the virtual floppy disk drive.
Most image software is using .dsk or .img for floppy disk images.
The image file size must be 1,474,560 bytes for a 1,4 MiB disk.
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Re: DOS 6.22 VM

Postby mpack » 21. Jul 2021, 09:48

Joe890 wrote:Ok, tried it with a dd of DOS622 (floppy) (renamed to DOS622.iso)

As Martin has said, you seem to be under the impression that ISO is a synonym for raw. It isn't. ISO is a reference to the ISO-9660 standard for the filesystem on optical drives, so the ".iso" extension is only correct if you created an image of a data CD/DVD/Blu-ray etc.

By giving a file the .ISO extension you are telling VirtualBox that this disk image uses the ISO-9660 filesystem, i.e. it's a small CD. When VirtualBox tries to mount it as a CD then it fails, because it isn't a CD.

The correct extension for a floppy image would be ".flp" or ".img". You will also need to add a floppy controller and floppy drive to your VM recipe (in 2021 VirtualBox no longer adds floppy drives by default), then mount the floppy image in the floppy drive similarly to how you mounted the CD.
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Re: DOS 6.22 VM

Postby mpack » 21. Jul 2021, 09:58

p.s. I hope you have not messed too much with the VM recipe. You can't add any hardware that didn't exist in the DOS era. E.g. SATA would be out of the question, and 64MB would be an extraordinary amount of RAM.
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Re: DOS 6.22 VM

Postby Joe890 » 23. Jul 2021, 16:12

Hello

Renaming DOS622.iso to DOS622.flp does work :) Thank's a lot for your help!

1.
Nevertheless I am wondering if the initial startup-message in the DOS window (the same as before using the wrong file-extension)
is of importance.....

ata0 master: VBOX HARDDISK ATA-6 Hard-Disk (500 MBytes)
ata1 master: VBOX CD-ROM ATAPI-6 CD-ROM/DVD-ROM
ata2 master: Unknown device
ata2 slave: Unknown device
ata3 master: Unknown device
ata3 slave: Unknown device



2.
I used an image of a very basic DOS622 floppy. Is it possible to make a DOS VM with 3 DOS-floppy-images as well? How?


Thank you!

Joe
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Re: DOS 6.22 VM

Postby mpack » 23. Jul 2021, 16:25

Joe890 wrote:I used an image of a very basic DOS622 floppy. Is it possible to make a DOS VM with 3 DOS-floppy-images as well? How?

Well, if you booted from floppy then it's already a working DOS VM. I assume you might be asking how to get it to boot from hard disk?

It's easy enough provided you didn't make the hard disk too large (my own DOS 6.22 VM has a 512 MB hard drive). You need to boot from a system floppy (i.e. a bootable floppy containing DOS system tools including FDISK.EXE and FORMAT.COM). You first need to create partitions on the virtual C: drive using FDISK, and then format the C: drive using the command "format C: /s" (the /s makes the drive bootable). You can then remove the floppy and reboot, it will boot from the hard drive. Then you create config.sys and autoexec.bat files on the C drive. Google should have all the details you need: FDISK can be finicky.

At some point you will want to install that CD driver that I keep mentioning...

DOS is not a modern OS, it doesn't really need to be installed as such. The steps I just mentioned give you a bootable hard drive. You then create a directory on the C: drive (typically called "DOS"), and then you copy everything (i.e. "copy *.*") from your three floppy disks into the DOS directory.
Last edited by mpack on 28. Jul 2021, 17:37, edited 2 times in total.
Reason: correct typo
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Re: DOS 6.22 VM

Postby ghr » 25. Jul 2021, 11:32

Please read C: drive where mpack says (once) CL drive (adjacent keys...)
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Re: DOS 6.22 VM

Postby mpack » 25. Jul 2021, 11:40

Thanks for that, typo now corrected.
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Re: DOS 6.22 VM

Postby Joe890 » 27. Jul 2021, 17:29

Hello

The thing with fdisk works great:-) Thank's a lot! Hmm I am wondering if there is an easier approach to copy the about 250 DOS files to c:\DOS......

-> starting the DOS622-VM -> Devices -> Optical Drives does show my 2 DVD-drives
with Host Drive G and Host Drive H:
(MS Windows Filemanager of the HostOS does show the same drive letter assignement)


Question:
Does that mean, it should be possible to access the two DVD-drives with those drive letters from within the DOS-VM? In my environment, this is not the case (h: Invalid drive specification).



Thank's for any feedback

Joe


PS
My DOS622.flp image does contain the following files:

CHKDSK.EXE
COMMAND.COM
DRVSPACE.BIN
FDISK.EXE
FORMAT.COM
IO.SYS
MSDOS.SYS
SYS.COM
UNDELETE.EXE
UNFORMAT.COM
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Re: DOS 6.22 VM

Postby scottgus1 » 27. Jul 2021, 17:44

The easy way to transfer files into a DOS VM that has access to a CD drive is to make an ISO of the folder containing the files. Virtualbox has a virtual-ISO 'VISO' feature that can make a "fake" ISO to put in the VM's CD drive without having to make a real ISO file using a 3rd-party ISO maker. Or you can just get a free ISO maker.

Load the ISO or VISO into the VM's CD drive (since you have 2 CD drives, load ISO's in both) then start the VM. If the config in the VB is set up correctly, you should be able to 'dir' the CD drives and see each ISO's contents.

Now, getting files out, well.... A network would be good. Or another hard drive in the VM, with a drive file format on the host that the host can mount (like fixed-size VHD on a Windows host.) The "Other Guests" Tutorials may help with the network, see viewforum.php?f=30
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Re: DOS 6.22 VM

Postby Joe890 » 28. Jul 2021, 16:13

Ok made an ISO of the folder containing the files (with PowerISO and checked it with OSFMount) and burned it on a CD.

Then started the DOS622-VM -> Devices -> Optical Drives -> Choose Disk Image (MSDOS622.iso) -> open


Unfortuately the optical drives are still not accessible with Drirve letters from within the DOS-VM....


Question:
What am I doing wrong?


Thank you very much!

Joe
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