Tomas,
There's another possibility: format the DASD from CMS using the LXFMT program.
That eliminates the need to format again from Linux. LXFMT is available on
Sine Nomine's web site.
Dennis O'Brien
Wanted, Dead and Alive: Schrödinger's Cat
-----Original Message-----
From: Linux on 390 Port [mailto:[email protected]] On Behalf Of Pavelka,
Tomas
Sent: Wednesday, March 13, 2013 01:59
To: [email protected]
Subject: Re: DASD format from Linux only
Thanks for the replies, here are my thoughts on the problem:
I agree that before a minidisk is given to a guest (before the guest is started
for the first time) the minidisk needs to be formatted and any data that was
previously on the disk erased. The question is, when to do it and from which OS.
I have the ability to create both the new guest and the minidisk from Linux
(via SMAPI) but not the ability to safely format the disk from Linux, because I
cannot safely bring the disk online for format. By unsafe I mean that bringing
the disk online can create contention on the real device that can last several
minutes.
There are several possibilities I can think of:
1) Format every newly created disk in CMS before formatting in Linux. Directory
maintenance products can do this. This means every disk would be formatted
twice and every new disk creation would take twice as long (unless you stay
with CMS format and not use CDL at all).
2) Do a security erase on every deleted disk. Again directory managers can do
this, but the setting is optional. If you want to do this, you have to follow
this rigorously on the entire DASD pool on which minidisks are created. One
deletion without security erase can potentially cause trouble.
3) Write nonsense data to the first tracks of the disk so that Linux would not
recognize it as a known format and would not go into loops when the data on the
disk is not right. Similar to 1) but faster.
After this, it is safe to format a disk with CDL from Linux.
As Mark has suggested, I need the ability to format the disk from Linux without
needing to put it online first with Linux examining the contents. Without this,
the CDL format is incomplete as it can only be safely applied to an already
formatted disk.
As for the security question about Linux running on LPAR with disk shared by
z/OS: what makes Linux different from other platforms? If Linux is not used to
format disks, there must be another OS that has the ability to wipe out any of
the shared disks and the person doing the format must know which disk they are
formatting. Also, we are talking about security in the sense of preventing
accidental deletion. A malicious user having access to Linux sharing disks with
zOS can do harm to the shared disks by using raw_track_access unless the shared
disks are protected against access from Linux. (As long as the attacker knows
CKD architecture. As I have recently learned, you cannot just redirect
/dev/zero to the disk in raw track format ;-))
Tomas
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