[TUHS] DEC RL01/RL02 RX01/RX02 Disk Image Creator

Clem Cole clemc at ccc.com
Tue Jun 2 23:31:28 AEST 2020

Frankly, using a common tape format, and then a raw disk as the 'tape'
tends to be easy.  For instance,  if it's an older system like v6, there is
a binary for v6tar kicking around that was created as part of the v7
conversion utilities (or you can build it yourself with a little work - the
issue a few changes in some headers).   Put that binary on your v6 system.
 Then create a tar image on your modern system.   Tar uses a threaded ASCII
header and actually had a bug in it, that is exploited as an extension
mechanism and became a feature (I'll explain off line if need be).  So
modern tar's will produce a checksum that the original's will correctly
accept.  Note the modern tar can create >>file types<< that the old tar
will not understand, but it will just skip them.

Going the back works too, but is limited by the original's handling of
things like directories.  It is generally not a problem.

So, the result is that you can attach that 'tarball' as a raw disk on simh
and then read it with v6tar.

Another possible way to go it to try to get stp(1) to compile on the more
modern system [it's on the Harvard tape IIRC -- it was the first version of
tp in C -- earlier versions were in PDP-11 assembler).  But ...  since that
was written with the a pre-Typesetter C compiler, and has a PDP-11 binary
format knowledge in it and I think used Lesk's portable I/O package, so it
might be a little more difficult to get running on a more modern C.

On Mon, Jun 1, 2020 at 6:45 PM Paul Riley <paul at rileyriot.com> wrote:

> Clem,
> Thanks for your help. You’ve correctly interpreted my question.
> Is the disk image independent from the disk hardware? I’d assume that
> different disks may have different block sizes etc, so the disk type may be
> important.
> The target system is LSX, a cut-down version of V6 designed to run on the
> LSI-11. There are very few system utilities in the standard build (no mount
> for example). The second floppy is permanently mounted at boot time. I’m
> interested in making source file floppies on my modern system to use on the
> LSX, so I want to be able to create an image file from a source folder tree.
> Paul
> On Mon, 1 Jun 2020 at 9:05 pm, Clem Cole <clemc at ccc.com> wrote:
>> On Mon, Jun 1, 2020 at 6:19 AM Paul Riley <paul at rileyriot.com> wrote:
>>> Is there a Windows or Linux utility to create a disk image in any of the
>>> above formats, from a local folder tree?
>> What I think you are asking, is there a utility for a modern OS that will
>> walk a local folder tree on my OS and create a new file whose structure is
>> that of the file system for OS <insert yours here>.
>> The issue is not the device as much as the OS and disk file layout.    As
>> far as UNIX (or simh at the OS level) is concerned, the disk is just a
>> linear array of bytes, addressed by blocks.  The physical format is not
>> seen by UNIX.
>> There are numerious utilities, as well as 'foreign file systems' that are
>> available.   For instance, many Unix's can write RT-11 and MS-DOS format
>> with standard utilities.   It really depends the OS.  That said,
>> if the target OS is modern enough to support NFS or Samba, the easiest
>> way might be export the file system from local system, and then running a
>> simulated OS, 'mount' the file system.
> --
> *Paul Riley*
> Mo: +86 186 8227 8332
> Email: paul at rileyriot.com
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