[linux-lvm] vgexport usage

[linux-lvm] vgexport usage

[Males, Jess]

From 'man 8 vgexport':
vgexport allows you to make the inactive VolumeGroupName(s) unknown to  the  system.

By 'unknown to the system' I would expect it would not appear in vg listings such as vgs (shown below) or vgdisplay.

[root@icarus lvm]# vgcreate junk /dev/loop1 /dev/loop2 /dev/loop3
  Volume group "junk" successfully created
[root@icarus lvm]# vgs
  VG         #PV #LV #SN Attr   VSize  VFree 
  junk         3   0   0 wz--n- 48.00M 48.00M
[root@icarus lvm]# vgchange junk -a n
  0 logical volume(s) in volume group "junk" now active
[root@icarus lvm]# vgs
  VG         #PV #LV #SN Attr   VSize  VFree 
  junk         3   0   0 wz--n- 48.00M 48.00M
[root@icarus lvm]# vgexport junk
  Volume group "junk" successfully exported
[root@icarus lvm]# vgs
  VG         #PV #LV #SN Attr   VSize  VFree 
  junk         3   0   0 wzx-n- 48.00M 48.00M


However, more disturbing is that if I remove one of the disks, lvm complains about a missing item.

[root@icarus lvm]# losetup -d /dev/loop2
[root@icarus lvm]# vgs
  Couldn't find device with uuid 1gNBDl-dOqI-OQid-TIcq-8Lp2-qUa2-PwdvnB.
  VG         #PV #LV #SN Attr   VSize  VFree 
  junk         3   0   0 wzxpn- 48.00M 48.00M


Am I expecting the wrong things from this command?


Thanks,

-- Jess Males

Re: [linux-lvm] vgexport usage

[Anderson Kaiser]

On 03/17/2011 02:32 PM, Males, Jess wrote:
> > From 'man 8 vgexport':
> vgexport allows you to make the inactive VolumeGroupName(s) unknown to  the  system.
>
> By 'unknown to the system' I would expect it would not appear in vg listings such as vgs (shown below) or vgdisplay.
>
> [root@icarus lvm]# vgcreate junk /dev/loop1 /dev/loop2 /dev/loop3
>    Volume group "junk" successfully created
> [root@icarus lvm]# vgs
>    VG         #PV #LV #SN Attr   VSize  VFree
>    junk         3   0   0 wz--n- 48.00M 48.00M
> [root@icarus lvm]# vgchange junk -a n
>    0 logical volume(s) in volume group "junk" now active
> [root@icarus lvm]# vgs
>    VG         #PV #LV #SN Attr   VSize  VFree
>    junk         3   0   0 wz--n- 48.00M 48.00M
> [root@icarus lvm]# vgexport junk
>    Volume group "junk" successfully exported
> [root@icarus lvm]# vgs
>    VG         #PV #LV #SN Attr   VSize  VFree
>    junk         3   0   0 wzx-n- 48.00M 48.00M
>
>
> However, more disturbing is that if I remove one of the disks, lvm complains about a missing item.
>
> [root@icarus lvm]# losetup -d /dev/loop2
> [root@icarus lvm]# vgs
>    Couldn't find device with uuid 1gNBDl-dOqI-OQid-TIcq-8Lp2-qUa2-PwdvnB.
>    VG         #PV #LV #SN Attr   VSize  VFree
>    junk         3   0   0 wzxpn- 48.00M 48.00M
>
>
> Am I expecting the wrong things from this command?
>
>
> Thanks,
>
> -- Jess Males
>
>
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
  Maybe "unknown" is the wrong word in this case. You will be able to 
see this VG using vgs, vgdisplay and so on. But you can't remove when 
you try a vgremove.

You have to import it back (vgimport VolumeGroup) to change it again.

I think that unknown means more like "unchangeable".

[]'s

-- 
Anderson Kaiser (RHCE, RHCVA)
Red Hat Brasil - Global Support Services
akaiser@redhat.com
+55 11 3529-6000
Direct: +55 11 3529-6093

Re: [linux-lvm] vgexport usage

[Males, Jess]

Maybe "unknown" is the wrong word in this case. You will be able to
see this VG using vgs, vgdisplay and so on. But you can't remove when
you try a vgremove.

You have to import it back (vgimport VolumeGroup) to change it again.

I think that unknown means more like "unchangeable".

[]'s

--
Anderson Kaiser (RHCE, RHCVA)
Red Hat Brasil - Global Support Services
akaiser@redhat.com
+55 11 3529-6000
Direct: +55 11 3529-6093

_______________________________________________
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read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
-----

Thanks for the response, Anderson.

the use case I'm imagining is the export of a set of disks from one machine (VG intact) and the subsequent import into another machine.  The command works perfectly in such a scenario.  I can vgexport, yank the disks from one machine, insert into another, scan the scsi bus, vgscan, vgimport, vgchange, mount the lv, and use all my data.  However, after doing all this and going back to the original system that created the VG, not only do I see the VG in vgdisplay or vgs, but I get errors from the missing disk.

And in typing all this up, it occurrs to me to try a vgscan on the original system. <pause>  voila!
I still got disk complaints, but I unlinked /dev/sdb1 and /dev/sdb and now we're clean; no complaints anywhere about previously used disks or VGs.

Thanks,

-- Jess Males