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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