CentOS virt - Mar 2013 - Need to unmount an LV from host system

Greetings -

Ok, I made a mistake that I need to fix.  Fortunately it is not a
destructive mistake, but I need some advice on how to correct the problem.

CentOS 6.3 host system named Earth

I was creating some new logical volumes within my exiting volume group for
a new virtual machine using the LVM GUI.  When I created the LV that I
plan to use for root partition of the new VM (Bacteria) I mistakenly
clicked on the box to mount the LV, and specified the mount point as /.

[root at earth ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_mei-lv_earthroot
                      5.0G  3.9G  880M  82% /
tmpfs                 5.9G  276K  5.9G   1% /dev/shm
/dev/sda1             485M  116M  344M  26% /boot
/dev/mapper/vg_mei-lv_earthvar
                      3.0G  748M  2.1G  27% /var
/dev/mapper/vg_mei-lv_bacteriaroot
                      5.0G  3.9G  880M  82% /

I tried to unmount the device, but as shown below, it is busy.

[root at earth ~]# umount /dev/mapper/vg_mei-lv_bacteriaroot
umount: /: device is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))

I tried to force unmount the device, but that failed also.

[root at earth ~]# umount -f /dev/mapper/vg_mei-lv_bacteriaroot
umount2: Device or resource busy
umount: /: device is busy.
        (In some cases useful info about processes that use
         the device is found by lsof(8) or fuser(1))
umount2: Device or resource busy


What other options are there.  Is there are way to get this unmounted
without having to shutdown my host system and boot into rescue mode.  I
don't really want to shutdown my active VM's while other staff are
working
on them right now.

Please cc me directly as I only receive the daily digest.  Thanks.

Jeff
Meridian Environmental

On Tue, Mar 5, 2013 at 3:24 PM, <jboyce at meridianenv.com> wrote:
> Greetings -
>
> Ok, I made a mistake that I need to fix.  Fortunately it is not a
> destructive mistake, but I need some advice on how to correct the problem.
>
> CentOS 6.3 host system named Earth
>
> I was creating some new logical volumes within my exiting volume group for
> a new virtual machine using the LVM GUI.  When I created the LV that I
> plan to use for root partition of the new VM (Bacteria) I mistakenly
> clicked on the box to mount the LV, and specified the mount point as /.
>
>
So you mounted that new LV as / (or over the existing root) on your host
node?

You may end up needing to boot to a rescue CD, mount, and rsync files from
Bacteria's root to Earth's [real] root.  ( I wonder if anything is being
written to Bacteria's root since it's mounted over the real root. )

> [root at earth ~]# df -h
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/mapper/vg_mei-lv_earthroot
>                       5.0G  3.9G  880M  82% /
> tmpfs                 5.9G  276K  5.9G   1% /dev/shm
> /dev/sda1             485M  116M  344M  26% /boot
> /dev/mapper/vg_mei-lv_earthvar
>                       3.0G  748M  2.1G  27% /var
> /dev/mapper/vg_mei-lv_bacteriaroot
>                       5.0G  3.9G  880M  82% /
>
> I tried to unmount the device, but as shown below, it is busy.
>
> [root at earth ~]# umount /dev/mapper/vg_mei-lv_bacteriaroot
> umount: /: device is busy.
>         (In some cases useful info about processes that use
>          the device is found by lsof(8) or fuser(1))
>
>
I would have expected you could unmount it given that you're umounting by
the device name.  Having it mounted on or over root likely makes this a bit
finicky.

> I tried to force unmount the device, but that failed also.
>
> [root at earth ~]# umount -f /dev/mapper/vg_mei-lv_bacteriaroot
> umount2: Device or resource busy
> umount: /: device is busy.
>         (In some cases useful info about processes that use
>          the device is found by lsof(8) or fuser(1))
> umount2: Device or resource busy
>
>
> What other options are there.  Is there are way to get this unmounted
> without having to shutdown my host system and boot into rescue mode.  I
> don't really want to shutdown my active VM's while other staff are
working
> on them right now.
>
Take the advice of the output you pasted ... check the output from lsof and
see if you can't narrow down the problem.

After you accidentally mounted that LV on root did you change your
directory?  Something is hanging on to that device.

>
> Please cc me directly as I only receive the daily digest.  Thanks.
>
> Jeff
> Meridian Environmental
>
>
> _______________________________________________
> CentOS-virt mailing list
> CentOS-virt at centos.org
> http://lists.centos.org/mailman/listinfo/centos-virt
>

-- 
---~~.~~---
Mike
//  SilverTip257  //
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Il 05/03/2013 21:24, jboyce at meridianenv.com ha
scritto:
> Greetings -
>
> Ok, I made a mistake that I need to fix.  Fortunately it is not a
> destructive mistake, but I need some advice on how to correct the problem.
>
> CentOS 6.3 host system named Earth
>
> I was creating some new logical volumes within my exiting volume group for
> a new virtual machine using the LVM GUI.  When I created the LV that I
> plan to use for root partition of the new VM (Bacteria) I mistakenly
> clicked on the box to mount the LV, and specified the mount point as /.
>
> [root at earth ~]# df -h
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/mapper/vg_mei-lv_earthroot
>                        5.0G  3.9G  880M  82% /
> tmpfs                 5.9G  276K  5.9G   1% /dev/shm
> /dev/sda1             485M  116M  344M  26% /boot
> /dev/mapper/vg_mei-lv_earthvar
>                        3.0G  748M  2.1G  27% /var
> /dev/mapper/vg_mei-lv_bacteriaroot
>                        5.0G  3.9G  880M  82% /
>
> I tried to unmount the device, but as shown below, it is busy.
>
> [root at earth ~]# umount /dev/mapper/vg_mei-lv_bacteriaroot
> umount: /: device is busy.
>          (In some cases useful info about processes that use
>           the device is found by lsof(8) or fuser(1))
>
> I tried to force unmount the device, but that failed also.
>
> [root at earth ~]# umount -f /dev/mapper/vg_mei-lv_bacteriaroot
> umount2: Device or resource busy
> umount: /: device is busy.
>          (In some cases useful info about processes that use
>           the device is found by lsof(8) or fuser(1))
> umount2: Device or resource busy
>
>
> What other options are there.  Is there are way to get this unmounted
> without having to shutdown my host system and boot into rescue mode.  I
> don't really want to shutdown my active VM's while other staff are
working
> on them right now.
>
> Please cc me directly as I only receive the daily digest.  Thanks.
>
> Jeff
> Meridian Environmental
>
>
> _______________________________________________
> CentOS-virt mailing list
> CentOS-virt at centos.org
> http://lists.centos.org/mailman/listinfo/centos-virt
I don't know if this is usefull to you but you can try one of these:
mount --bind olddir newdir
or
mount -o remount olddir newdir
or
mount --move olddir newdir

Hope this can help you.

Sincerely,
Gabriele Matteelli