Universal drive adapter -

[Bryn M. Reeves]

On 12/10/2009 09:18 PM, Bob Goodwin wrote:
> Yes, I posted the question and found the response interesting and
> helpful. I spent a couple of hours reading man pages and
> experimenting with the lvm commands on various drives.
>
> But I have not been able to open a volume and list the directories
> and files, such as /home and /etc! I must be dense ...
>
> This from another drive:
>
> [root at box6 bob]# lvm
> lvm> pvdisplay
> --- Physical volume ---
> PV Name /dev/sdb2
> VG Name VolGroup00
> PV Size 74.43 GB / not usable 22.62 MB
> Allocatable yes
> PE Size (KByte) 32768
> Total PE 2381
> Free PE 1
> Allocated PE 2380
> PV UUID J5Yc28-aO4n-ODWI-1c0W-H9Jr-04jN-ufwyRj
>
> And fdisk shows:
>
> Disk /dev/sdc: 20.0 GB, 20020396032 bytes
> 255 heads, 63 sectors/track, 2434 cylinders
> Units = cylinders of 16065 * 512 = 8225280 bytes
> Disk identifier: 0x000c6487
>
> Device Boot Start End Blocks Id System
> /dev/sdc1 * 1 2434 19551073+ 8e Linux LVM
>
> But I can't mount this one either using " mount /dev/sdc1 -t
> ext3 /mnt/hdtest "
>
> It protests about the file type[?]. Perhaps lvm requires a
> different type?

You cannot directly mount an LVM2 physical volume. The idea of the 
volume manager is that it abstracts storage using a layered model:

Physical volumes - actual disks/storage devices
Volume groups - collections of related disks that are managed together
Logical volumes - virtual "partitions" carved out of the disks in the VG

The PV is a container for the LVs that exist in the volume group.

You need to activate any LVs that it contains using the commands in my 
earlier mail before you can mount them.

LVs then behave a lot like regular partitions but with more flexibility; 
they can be resized on the fly, mirrored, snapshotted, migrated to new 
storage etc all without interruption to services.

When you activate an LV or a VG you will get new entries in the /dev 
directory in a subdirectory named after the volume group. E.g. my VG in 
the examples I gave was named "system" and it contains a half-dozen or 
so LVs:

# ls /dev/system/
home  root  swap0  tmp  usr  var
[root at p380-1 ~]# vgs
   VG     #PV #LV #SN Attr   VSize   VFree
   system   1  11   0 wz--n- 231.66G 88.81G
[root at p380-1 ~]# lvs
   LV      VG     Attr   LSize   Origin Snap%  Move Log Copy%  Convert
   home    system -wi-ao 100.00G
   root    system -wi-ao  21.03G
   swap0   system -wi-ao   8.00G
   tmp     system -wi-a-   1.00G
   usr     system -wi-a-   8.00G
   var     system -wi-ao   4.00G

E.g. to mount the tmp logical volume (assuming it's active and not 
already mounted), I would run:

mount /dev/system/tmp /tmp

Regards,
Bryn.