Changing the size isn't an issue for me; I size memory so that we *barely* swap
anyway. I've never has to change the size of a vdisk.
Spelling courtesy of Blackberry
----- Original Message -----
From: Linux on 390 Port <LINUX-390@VM.MARIST.EDU>
To: LINUX-390@VM.MARIST.EDU <LINUX-390@VM.MARIST.EDU>
Sent: Fri Sep 11 13:02:54 2009
Subject: Re: Dasd_diag_mod question
My complaint with SWAPGEN going back to when it was first announced was
that it needs to know the number of blocks to format. This means that
if the size or number of the vdisk(s) changes in the directory, the VM
admin also has to go to the target machine's 191 disk and update the
PROFILE EXEC so the right number of blocks get formatted on the right
devices. Having to change things in multiple places seemed like
something to be avoided.
So I wrote a Linux init script that does the whole thing internally
within the guest. It finds all of the FBA disks, formats them, and runs
mkswap. It also enables them in increasing priority order, so they get
used before the default DASD swap partition, and it handles the diag
module and enabling access via diag. We use this on about 100 guests,
and it works very well. My only complaint with it is that it treats all
FBA disks as swap disks, which might be a problem if we had any real FBA
disks, but since we're entirely on 3390's and the odd FCP device, it's a
non issue. It also generates one bogus error message that I never got
around to suppressing.
This version is for Red Hat (RHEL5), but it shouldn't be hard to
customize for Suse.
#!/bin/bash
# $Id: vdswap,v 1.7 2007/11/06 20:44:38 root Exp $
#
# vdswap This shell script does the following:
# 1) Looks in sysfs for any FBA disks
# 2) If they are not already enabled for swap, it formats
# them, and enables them for swap with a higher
priority
# than the default disk swap space
#
# Should run after filesystems are mounted, before starting required
daemons
# that might need to be configured
#
# chkconfig: 2345 01 99
# Description: Formats and enables vdisk swap spaces
#
prog=`basename $0`
start() {
SYSDEV=/sys/bus/ccw/drivers/dasd-fba
echo "Enabling vdisk swap spaces "
modprobe -q dasd_diag_mod
if ls $SYSDEV | grep -q 0.0 ; then
PRIO=1
for A in $SYSDEV/0.0.*
do
DEVICE=`ls $A/block* | grep dasd | head -n 1`
if lsmod | grep -q dasd_diag_mod ; then
echo 0 > $A/online
echo 1 > $A/use_diag
echo 1 > $A/online
sleep 1
fi
DEVBASE=${DEVICE:0:${#DEVICE}-1}
if ! swapon -s | grep -q $DEVBASE ; then
parted -s /dev/$DEVBASE mkpartfs primary swap 1
mkswap /dev/$DEVICE
swapon -p $PRIO /dev/$DEVICE
let PRIO=$PRIO+1
fi
done
fi
touch /var/lock/subsys/vdswap
}
stop() {
echo -n $"Shutting down $prog: "
rm -f /var/lock/subsys/vdswap
return 0
}
# See how we were called.
case "$1" in
start)
start
;;
stop)
stop
;;
status)
status vdswap
RETVAL=0
;;
restart|reload)
stop
start
RETVAL=$?
;;
condrestart)
RETVAL=0
;;
*)
echo $"Usage: $0 {start|stop|restart|condrestart|status}"
exit 1
esac
exit $RETVAL
-----Original Message-----
From: Linux on 390 Port [mailto:linux-...@vm.marist.edu] On Behalf Of
Adam Thornton
Sent: Friday, September 11, 2009 12:30 PM
To: LINUX-390@VM.MARIST.EDU
Subject: Re: [LINUX-390] Dasd_diag_mod question
On Sep 11, 2009, at 10:36 AM, Larry Uher wrote:
> I guess my question would be why is a complex EXEC needed to do a
> normal system administration task? A second question is why didn't
> Novell provide a straightforward method for doing this and document it
> in a manual (without using a complex 3rd party EXEC) ?
Complex?
After the description and the license and update comment blocks, it's
about 240 lines. Of those, about 120 are the various ways the program
can exit (with descriptive text) and the help message. That leaves
about 120 lines of actual code, and those lines are not dense (e.g.
one line per pipe stage). That handles both the raw FBA and the DIAG
device cases.
It's not a normal system administration task on any other Linux
architecture. It's really quite unusual for your swap device to be
destroyed and recreated every time you power on the machine. In the
normal case the swap signature sits there between power cycles.
That's why Dave and I wrote the thing in the first place--Linux does
not generally consider needing to format the swap device as part of
its normal bootup routine and rather than mess with system startup
scripts and their ordering, we thought it was a lot easier to just
take care of it in CMS before handing control to Linux, so that the
swap device was pre-prepared like it expected.
And that, by the way, is the reason Novell doesn't do it: it's not a
task that's necessary on other architectures, and Novell, not
surprisingly, likes to keep as much the same between platforms as
possible.
Adam
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