Re: Bug#486549: The single partition present on a CMS minidisk is not supported (s390/s390x only) - Debian

This is a discussion on Re: Bug#486549: The single partition present on a CMS minidisk is not supported (s390/s390x only) - Debian ; On Wednesday 18 June 2008, Stephen Powell wrote: > I currently have a Debian GNU/Linux system running in a virtual machine > under z/VM that uses CMS minidisks. But I had to install to cdl disks > and then use ...

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Thread: Re: Bug#486549: The single partition present on a CMS minidisk is not supported (s390/s390x only)

  1. Re: Bug#486549: The single partition present on a CMS minidisk is not supported (s390/s390x only)

    On Wednesday 18 June 2008, Stephen Powell wrote:
    > I currently have a Debian GNU/Linux system running in a virtual machine
    > under z/VM that uses CMS minidisks. But I had to install to cdl disks
    > and then use the installer as a "rescue floppy" to copy the data to CMS
    > minidisks. Another problem is that the dasd_mod driver does not
    > automatically bring CMS minidisks on-line. I had to create a file
    > called dasd in /etc/modprobe.d to supply options to dasd_mod to bring
    > these minidisks online at IPL time. (And then I had to run
    > update-initramfs and zipl.) It worked. But figuring out what to do
    > and how to do it was not trivial. And of course, there is nothing in
    > the install manual about this. I would hardly call this a
    > user-friendly install.
    >
    > Further complicating matters was my desire to use the dasd_diag_mod
    > module to do the I/O, which did not exist in the stock kernel for etch.
    > I had to download the kernel source package and create a custom kernel
    > in order to use dasd_diag_mod. (And then I had to update
    > /etc/modprobe.d/dasd again to tell dasd_mod to use dasd_diag_mod for
    > all the CMS minidisks, and then I had to run update-initramfs and zipl
    > again.) Fortunately, it appears that the 2.6.24 stock kernel for lenny
    > now includes this module. :-)
    >
    > It is possible to get it working. But when it comes to CMS minidisks,
    > Debian for s390 is definitely a hacker's distro only.


    All the above is complete Greek too me because I don't have any context.

    And it sounds like you already did the hard part: you managed to get it
    working. That means you are the expert now. Tell us *in detail* what is
    missing and what manual steps were required to get it supported. Then
    *maybe* someone will step up and do the actual integration.

    But even better: run the installer at medium priority, figure out exactly
    what needs to happen in which phase, add that in manually and see if it
    works. Send us the resulting patches.

    More than 90% of the installer is shell script! Which means it has an
    extremely low barrier of entry. If you run into a step that is performed
    by something that is not shell, fine: tell us what should be happening at
    that point. But even then it should often be possible to create a
    temporary solution by using some shell code around or next to the C
    program.

    Here is some solid basic info that can help you get started with the
    installer: http://d-i.alioth.debian.org/doc/internals/

    > And even if you elect to go with an unsupported distro, the software
    > packages that they provide are in rpm format only.


    Which means that we need people packaging this stuff in .deb format. Do
    you think that for other platforms we actually wait for vendors to
    package their stuff for us? We don't, really!

    > It appears that source packages are available. But the source packages
    > are also in rpm format only.


    There is 'alien' of course (aptitude show alien), but I don't have any
    personal experience with it and probably isn't really a solution for
    stuff that's related to hardware as it won't configure things properly.

    > Somehow, you've got to persuade IBM to support Debian. And if they
    > think it will increase their sales enough to make it worth their while,
    > they will.


    No. That is definitely not how it works! The _community_ has to make it
    worth for IBM to take an interest. Debian does not go begging. It goes
    completely against the principles behind the Debian project; Debian does
    not have some marketing or PR or whatever "department" that does this.

    Other vendors have taken an interest because there was a demand from their
    market, not because Debian came begging at their doorstep!

    I'm sorry, but I skipped the rest of the mail. It's just a repeat of the
    same flawed starting point.

    You're still trying to tell us that we or IBM need to do the work here.
    That's wrong. The community needs to do the work. That's how free
    software works, and that's how projects get started. There really is no
    chicken and egg problem here. You want something done: get doing it!

    Alternatively: offer a bounty (at industry pay scale, not at bargain
    rates).

    Cheers,
    FJP

    P.S. Apologies if I'm being too direct here.

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  2. Bug#486549: The single partition present on a CMS minidisk is not supported (s390/s390x only)

    I need to correct an error in my previous e-mail. In my previous e-mail,
    I said that the dasd_diag_mod driver could only be used with CMS
    minidisks. As it turns out, that is not true. The dasd_diag_mod driver
    can also be used with minidisks formatted with the Linux disk layout
    (ldl). Such a format is created by using the "-d ldl" switch of
    dasdfmt. And such a disk can also be used as the /boot partition. By
    switching my 201 disk to an ldl-format disk, I was able to use the
    dasd_diag_mod driver for ALL the minidisks. Thus, /etc/modprobe.d/dasd
    now looks like this:

    options dasd_mod dasd=0.0.0200-0.0.0203(diag)

    Like CMS minidisks, ldl disks contain one implicit partition and do
    not need to be partitioned separately with the fdasd utility.

    Just for grins I tried using a CMS minidisk as the /boot partition.
    When I ran zipl to write out the boot loader code,
    it gave me an "unsupported disk type" error message,
    as I expected.

    In summary:

    1. The DASD driver for Linux for System z supports three disk
    formats: CMS, ldl, and cdl.

    2. The CMS format has two sub-formats: non-reserved and reserved.

    3. The /boot partition cannot be CMS format. (If the /boot directory is
    included in the / partition, then the / partition cannot be CMS format.)

    4. The ECKD driver supports all three formats: CMS, ldl, and cdl.

    5. The DIAG driver supports two formats: CMS and ldl.

    6. The FBA driver supports only CMS format.

    7. CMS-format disks can only be created by the CMS operating system
    running as a guest under z/VM. Linux can USE CMS-format disks, but it
    cannot CREATE them.

    8. The DIAG driver can only be used if Linux is running as a guest
    under z/VM.

    9. The Debian installer supports only the cdl format. Therein lies
    the problem.

    An interesting question is how to IPL the boot loader if all one has is
    FBA DASD. Perhaps zipl can be IPLed from a CMS minidisk if the CMS
    minidisk is on FBA DASD, but not if it is on ECKD DASD. I suspect that
    that is the case, but I don't have any FBA DASD with which to test my
    theory.

    Anyway, I wanted to correct the factual error in my prior e-mail.
    If there's anything else you want to know, or if there's anything I can
    do to help, please ask.








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