# Disk overlays, FreeDOS, disk-archiving and Photography
2023-03-09
Last few weeks I've spent more and more time down in my basement
darkroom. I've worked with some printing projects, but mostly I've
been spending time with the old 486 and the OpenBSD workstation I keep
down there. The greaseweazle I got some months ago has been frequently
used to dump old discs. I have started getting some of the floppies I
ordered through the auction-site, and I've started doing disk-dumps in
a more controlled manner. I also got a good deal on some random 5,25"
disks in a local thrift-shop that I munched through quickly. Mostly
PC-stuff, really ancient DOS-boot-disks and the like. Also some local
word processors and spreadsheet software that I think will make a
good addition to archive.org. I also got a large box of Amiga disks
that proved to contain some cover disks from computer magazines. These
have so far proven to be mostly overwritten and re-used unfortunately,
so not very interesting to upload anywhere I guess.
I also got my CF-card reader working on the 486, by using an old
disk overlay. There were several choices, but I ended up using
Ontrack Dynamic Disk Overlay. It worked like a charm, and I was
able to format the 16GB CF-card to FAT32 and install FreeDOS 1.3
on it successfully. The problem with disk overlays is of course
that they tend to confuse systems that will not run the code they
place in MBR, so if you try to insert the card in, for example,
an OpenBSD-machine with an USB-adapter, it will not find the FAT32
partition, only an unknown entry in the partition table. I was able
to find a solution to this, in an old twitter thread of all places!
The user "Foone"/"@Foone" made a thread in 2021, where it is described
that you can use losetup to mount a Ontrack-formatted disk with an
offset, to skip the first part of the disk where the overlay resides,
and make it mountable. It works well after testing, the only problem
I see is that OpenBSD does not have losetup. It instead has vnconfig,
which lacks the possibility to set an offset of the image you are
adding. I'll look further into it, but worst case, I can use Linux
on another system I have in the basement to access the card. Not
that convenient, but at least a lot better than transferring files
through floppy images via the Gotek I have installed. I'll link Phils
Computer Lab (where I found the Ontrack software and disk image)
and the Twitter thread below. I don't use twitter, so I cannot thank
Foone for this great thread though.
This is how I used a disk-image of the CF-card I made to test it out:
```
sudo losetup -o $(( 16#fc00 )) /dev/loop5 CFCARD_FREEDOS_ONTRACK.img
sudo mount /dev/loop5 /media/removeable/image1 -o uid=1000,gid=1000
```
The number "fc00" will probably differ for you. I got to that by
checking with hexdump -C to find where "FRDOS5.1" was occuring.
The example from Foone was using MS-DOS, so in that case, it would
have been "MSDOS5.0" or something instead. This is what my output
looked like:
```
---SNIP---
0000fbf0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa |..............U.|
0000fc00 eb 58 90 46 52 44 4f 53 35 2e 31 00 02 10 20 00 |.X.FRDOS5.1... .|
0000fc10 02 00 00 00 00 f8 00 00 3f 00 ff 00 3f 00 00 00 |........?...?...|
0000fc20 db 06 dd 01 92 3b 00 00 00 00 00 00 02 00 00 00 |.....;..........|
0000fc30 01 00 06 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
0000fc40 80 00 29 11 5f ba 07 44 49 53 4b 31 5f 56 4f 4c |..)._..DISK1_VOL|
0000fc50 31 20 46 41 54 33 32 20 20 20 fc fa 29 c0 8e d8 |1 FAT32 ..)...|
0000fc60 bd 00 7c b8 e0 1f 8e c0 89 ee 89 ef b9 00 01 f3 |..|.............|
0000fc70 a5 ea 7a 7c e0 1f 00 00 60 00 8e d8 8e d0 8d 66 |..z|....`......f|
---SNIP---
```
I've actually also spent some time updating my photo-projects on
158.nu. A new album / project was introduced, that I called "The
perception of doors". It's basically a cliché door-photo-project,
but I kind of like the idea of it. Even if it is pretty cheesy
and over-done these days. Most of this first update contains old
photos from several years ago, but I've also thrown in stuff from my
vacation last summer. The name is of course a nod to Alouds Huxley's
"The doors of perception".
I also have other projects in mind that I will
probably develop during spring/summer. I need to get back to actually
photographing more. My motivation is always low during winter, since
it is pretty cold and snowy up here, but once spring is coming along
it's a lot more fun being outside.
=>
https://www.philscomputerlab.com/ontrack-disk-manager.html Ontrack Disk Manager, on Phils Computerlab.
=>
https://twitter.com/Foone/status/1376282711568965635 Twitter-thread by Foone, with instructions for mounting Ontrack-disks on Linux.
The content for this site is CC-BY-SA-4.0.
