topic Re: Remove LVM info in Operating System - HP-UX

Remove LVM info

SAM_24 — Tue, 02 Jul 2002 23:44:10 GMT

Hi,

When I reinstall the OS still system remembers the old disk groups. How to remove the old info? Just running pvremove is enough?

Thanks

Re: Remove LVM info

Scott Van Kalken — Tue, 02 Jul 2002 23:46:41 GMT

It depends.

I'd be tempted to do the lot.

if mirrored reduce logical volumes

remove logical volumes
remove volume groups
remove disks (if required).

Then again, the idea of an ignite is to rebuild a system that has crashed or to clone identical systems.

Scott.

Re: Remove LVM info

Michael Tully — Wed, 03 Jul 2002 00:16:41 GMT

The LVM information will remain on the disk headers of volume groups other than vg00.

You can just re-use the disks into new volume groups if you don't require the old information.

To re-use the new disks use 'pvcreate -f /dev/rdsk/cxtydz

Re: Remove LVM info

Mike Hassell — Wed, 03 Jul 2002 01:17:31 GMT

Raj,

As Michael has already stataed, the LVM info will remain on the disks even after you remove it from LVM.

The easiest way is to just reuse the disk with a pvcreate -f /dev/rdsk/cXtXdX, although if you really want to ensure that all data has been fully removed from the disk you can use dd:

dd if=/dev/zero of=/dev/dsk/cXtYdZ count=

I don't think /dev/zero is installed by default, but the major number is the same as /dev/null and the minor is 3, but I would check on that before creating the device if it is not already present.

The bottom line is that I wouldn't go to all the trouble of wiping the disks clean with dd, unless I had a reason to, otherwise a simple pvcreate will suffice.

Hope that helps.

-Mike

Re: Remove LVM info

Sean McConkey_2 — Wed, 03 Jul 2002 12:19:18 GMT

If you do a pvcreate -f and the disk is already in lvmtab, you may get an error message;

pvcreate: The physical volume "/dev/dsk/c0t5d0" is already recorded in the "/etc
/lvmtab" file.

You will need to "vgexport" the associated volume group, as well as removing the logical volumes etc. as already suggested.

I also delete and re-create the /dev/vg?? special files for all non-root volume groups.

eg rm -r /dev/vg01

mkdir /dev/vg01
mknod /dev/vg01/group c 64 0x010000

However I question why you are doing this if you are using Ignite on the same box, it was created on? Normally only required on a DR box where device names are similar.

HTH

Sean

Re: Remove LVM info

PIYUSH D. PATEL — Wed, 03 Jul 2002 12:27:20 GMT

Hi,

pvcreate -f /dev/rdsk/c1t2d0

vgexport does not remove any information from the disks, it removes the info about the vg from the OS.

Piyush

Re: Remove LVM info

Sean McConkey_2 — Wed, 03 Jul 2002 12:38:32 GMT

Piyush,

It is necessary to remove the the information using vgexport from /etc/lvmtab before you can destroy the data on the disk with pvcreate.

This applies as already suggested if the physical volume already matches that stored in /etc/lvmtab. If it doesn't then pvcreate will work.

Disaster recovery is my game and I have to do this regularly when testing client systems.

Re: Remove LVM info

Craig Rants — Wed, 03 Jul 2002 12:55:53 GMT

One way to tell if you have an LVM record on a disk is:

echo "0x2000?4S" | adb /dev/dsk/cXtXdX

you should see something like

2000: LVMREC01adjfakdjfa;

If you you have a record on that disk.

HTH,
C

Re: Remove LVM info

Robert Sipe — Thu, 04 Jul 2002 01:37:54 GMT

pvcreate -f

Re: Remove LVM info

Frank Slootweg — Thu, 04 Jul 2002 08:01:14 GMT

Because you say "remembers the old disk groups" (note "groups"), I assume that it still shows the old *volume* groups (i.e. "vgdisplay vg??"). If so, then it is best to vgexport the unwanted groups.

The others have already given solutions for the other scenarios.

BTW, "pvremove" does not exist.

Re: Remove LVM info

SAM_24 — Thu, 04 Jul 2002 15:33:40 GMT

Thank you for all of your responses.
Now I know what to do.