lvm re-install strategy

Adam Hough adam at
Fri Feb 1 23:20:25 UTC 2008

Okay so the volume group meta-data is actually stored on the disk and
not just in /etc.  So when the kernel is booting up it will see all
volume groups on the disks in the machine or attached to the machine.
Then udev or something will actually activate all the volume groups.

So if you boot from /dev/sda1 and the root is located
in /dev/ROOT_VG/ROOT_LV, the kernel and/or udev should automagically
active / see the volume groups that reside on the hard drives in the
machine assuming that nothing has corrupted the partition information
and the volume group information.  This means that your /dev is
dynamically created every time the system is booted up. Which is why you
will be able to access the volume groups that or on the other 2 disks.

With volume groups you can actually export the volume group and remove
it from a system an put it into another system an import it into the new
machine.  The other machine is just have to be able to see the disk.  I
highly discourage creating a volume groug / logical volume on an
external disk. If that disk is accidentally just unplugged, LVM  gets
really pissed off and you will be rebooting to fix the issue (or at
least that has been my experience in the past).    

You might find that if you go back and re-read the documentation for LVM
that it will make more sense now then when you first looked at the
documentation.  I know that I had to do it for LVM and iptables a few
times before I understood what was going on when I was running those

On a personal note, I like to put a "vg" in my volume group names and a
"lv" in my logical volume names.  So a volume group name would look like
NAMEvg, vg_NAME, or NAME_vg, and a logical volume name would look
similar.  This helps to make the names more meaningful and descriptive
to me.

On Fri, 2008-02-01 at 17:05 +0100, François Patte wrote:
> Hash: SHA1
> Le 01.02.2008 16:39, Adam Hough a écrit :
> > If I am reading this right you still have unallocated space on /dev/sda?
> > 
> > Option 1:
> > If that is the case then with the DVD install just create a new logical
> > volume (ie /dev/VGNAME/rootf8lv) to install Fedora 8 into that logical
> > volume.  You can tell the install to use /dev/sdb1 as your /boot again
> > and tell the installer to not format that device which will preserve the
> > old Fedora 6 kernel files. (You might have to manually edit the
> > grub.conf to add Fedora 6 as a boot option afterwards.
> Thanks for answering. I think that I will follow option1; but what is
> unclear for me is: how will I access logical volumes from volume group
> sdb2+sdc1?
> My idea is to devote sda to the system, so one vg on sda2 with logical
> volume usr, swap, tmp, opt, var,  and use vg sdb2+sdc1 for data,
> including home.
> Right now, home is on /dev/mapper/fedora-home and mounted from /dev
> which is on sdb1.
> As soon as the new install will be booted, this /dev won't exist no
> more, because is it created if you boot with the "/"  partition on sdb1,
> for the new system, it will be on sda1
> There something there that I do not understand, so I might be unclear
> myself....
> <snip>
> > On Tue, 2008-01-29 at 12:16 +0100, François Patte wrote:
> > Timothy Murphy a écrit :
> > | François Patte wrote:
> > |
> > |> I have an fc6 install with LVM and want install f8.
> > |
> > |> I have 3 hdd: sda, sdb, sdc.
> > |>
> > |> sda has 1 partition: sda1 LVM
> > |>
> > |> sdb has 2 partitions: sdb1 ext3
> > |>                       sdb2 LVM
> > |>
> > |> sdc has 1 partition: sdc1 LVM
> > |>
> > |> sdc1 and sdb2 are in the same volume group.
> > |>
> > |> System in living in sdb and sdc and sda is practically free.
> > |>
> > |> The root partition / is on sdb1 and all other vital partitions (/usr,
> > |> swap, /var, /opt, /tmp and /home) are logical volumes on sdc1.
> > |>
> > |> My idea is to perform the new install on sda: sda1 will be the root
> > |> partition /, and build a volume group sda2 for /usr, swap, /opt /tmp and
> > |> /var; /home will be left where it is.
> > |>
> > |> Here begins my problem: I would like, after install retrieve (almost)
> > |> all files from fc6 install. For /home, there is no problem, I think
> > |> that, at install time, I will be be asked if I want to keep my /home
> > |> volume wherever it is. But for other volumes (/var where my dns config
> > |> is...) or /opt (where my texmf and some other out of standard are) I
> > |> don't know how to get them once the new system will be installed.
> > |>
> > |> How could I access to these partitions for, now, they are mounted on
> > |> /dev/mapper/.... but these devices are created at boot time in the /dev
> > |> which is on sdb1 and, even if I mount /dev/sdb1 from the fresh install,
> > |> I will be unable to access them because the new system is mounted on
> > |> sda.....
> - --
> François Patte
> UFR de mathématiques et informatique
> Université Paris Descartes
> 45, rue des Saints Pères
> F-75270 Paris Cedex 06
> Tél. +33 (0)1 44 55 35 61
> Version: GnuPG v1.4.7 (GNU/Linux)
> Comment: Using GnuPG with Fedora -
> RJHFNaGc7VG50Dvf2TH/3Y4=
> =bAPF
Adam Hough <adam at>

More information about the fedora-list mailing list