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Re: Universal drive adapter -

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 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 p380-1 ~]# vgs
  VG     #PV #LV #SN Attr   VSize   VFree
  system   1  11   0 wz--n- 231.66G 88.81G
[root 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


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