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Re: Minidisk support (was: Installation Question)

On 2009-12-24, Frans Pop wrote:
> Here's one of the reason why I cannot do anything about this: I only have 
> access to Hercules running Linux, so I cannot create CMS formatted disks.

Well, there are copies of very old releases of VM out there, such as VM/370
Release 6.  VM/370 Release 6 has passed into the public domain now.  But it
is useless for this purpose.  VM/370 Release 6 does not support the modern
EDF disk format, with blocksizes of 512, 1024, 2048, and 4096.  It only
supports the original CDF format, with a blocksize of 800.  That format is
now obsolete, and Linux does not support it.

It is technologically possible to run modern releases of z/VM under Hercules.
I have heard that some people have done a Disaster Recovery Test of a modern
z/VM system under Hercules.  The problem is licensing.  z/VM is not free
software: you have to license it from IBM.  And IBM normally won't license
z/VM to run under Hercules, except maybe by special bid.  And if they do
license it to you by special bid, they'll probably charge you enough that it
will be cheaper to buy a real mainframe and run it there!

But I think IBM has, or used to have, some mainframes that have been set up
for Linux developers to use, and they give away time and space on the
machines for those who qualify.  You might check into that.

It would be nice if someone were to write a program that runs under Linux
that can format a DASD device in the CMS format.  That would help.  As far
as I know, there's no such program today.

On 2009-12-24, Frans Pop wrote:
> Why? It has the eckd kernel driver which supports all four formats if I 
> understand you correctly. The fact that you cannot do a low-level CMS 
> format is IMO not relevant as the first thing should be to support 
> pre-formatted disks anyway.

Yes, that's true.  I'm not asking for support for doing a low-level format
in CMS format while the Debian installer is running.  That would be wonderful,
but even Suse doesn't give me that.  All I'm asking for right now is the
capability to use pre-formatted CMS disks.

On 2009-12-24, Frans Pop wrote:
> So what exactly is missing there? At what point does it go wrong: is it in 
> s390-dasd, or is it in partman? I still don't get it...

I'm going from memory here.  I haven't done an install in quite a while.
But if I recall correctly, there is an initial screen in
which the dasd devices that it finds are listed, and you can pick which ones
you want to use.  That works fine.  Then there is a second screen after that
on which you can do things like create partitions and assign mount points.
I think that's partman.  The problem is that a disk in CMS FORMAT, reserved
or non-reserved, is treated like an unformatted disk.  Partman does not
recognize that the disk already has a "partition" on it.  Therefore, I cannot
assign a mount point to it or designate it as swap space.  It will not let me
do anything with the disk unless it runs dasdfmt and fdasd on it first.
Then, and only then, does it recognize a "partition" on the disk, which I
can assign a mount point to or designate as swap space.  But that destroys
the pre-existing CMS format which I need to keep.  If I were to boil the
problem definition down to one sentence it would be:

"Partman does not recognize the pre-existing "partition" on disks which are
pre-formatted in the CMS non-reserved format or the CMS reserved format."

> It also still seems to me that anybody who 
> *does* have access to such devices should be able to implement basic 
> support, even without much coding skills.

Well, I'm working on it, but I'm not there yet.  I am currently teaching
myself bash scripting by reading online tutorials and man pages.  After
that, I'll probably tackle awk, perl, and sed.  And then eventually, C.
I'm heading in the right direction.  Maybe someday I'll be useful to you.
But Rome wasn't built in a day.  I'm sorry if the problem description wasn't
clear to you.  It was clear to me.  But understanding a problem is one thing.
Being able to explain it to someone else who comes from a different background
and a different perspective is another thing.  That takes work.  And apparently
I'm not as good at that as I thought I was.

What I have is a real mainframe, a legitimate z/VM license, and a willingness
to help.  What I lack but am working on is Linux programming skills.  I think I will
eventually have them, but I'm not there yet.  What I don't have, and likely
never will, is FBA DASD.  Someone else will need to test that support.
You might be able to create emulated FBA dasd devices under Hercules.  But
formatting them in CMS format (EDF CMS format) is another story.

In the meantime, if there's anything I *can* do for you, let me know.

Merry Christmas!

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