Re: Adding DASD to a Debian guest
On Sun, 16 Aug 2015 08:28:42 -0400 (EDT), Philipp Kern wrote:
> ...
> However it then turned out that I needed to hack the zipl config to
> make the kernel see the DASD from within the initrd.
>
> [ 0.066844] Kernel command line: root=/dev/sysvg/root dasd_mod.dasd=0.0.0100 BOOT_IMAGE=0
That's because sysconfig-hardware isn't in the initial RAM file system,
and therefore doesn't bring DASD volumes online until the permanent root
file system has been mounted. If the permanent root file system is a
partition on a physical volume, there is exception code in
/usr/share/initramfs-tools/scripts/init-premount/sysconfig_hardware
to bring that specific volume online early, but only if the root device
is specified in zipl via the form
root=/dev/disk/by-path/ccw-0.0.xxxx-partz
where xxxx is the device number and z is the partition number. It must
be in this form so that
/usr/share/initramfs-tools/scripts/init-premount/sysconfig_hardware
knows the device number and can bring it online via
echo 1 >/sys/bus/ccw/devices/0.0.xxxx/online
This is one reason, but not the only reason, why I advised the OP not
to make the root file system a logical volume.
On my systems, I add sysconfig-hardware to the initial RAM file system,
using the method described in
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=621080
but of course this cannot be done until *after* installation.
The main reason that I do it is so that I can specifiy the root
file system in zipl as
root=UUID=...
which will only work if all the DASD volumes have been brought online
already, and therefore udev has found the volumes and their partitions
and has created symbolic links for them in /dev/disk. This makes
the boot process much closer to how it works on all other hardware
platforms that Debian supports.
--
.''`. Stephen Powell <zlinuxman@wowway.com>
: :' :
`. `'`
`-
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