[ale] Examining pre-existing LVM

[Jeff Hubbs]

Well, here's how things are looking now:

# ls /dev/mapper
control  vg0-aux
# pvs
  PV         VG   Fmt  Attr PSize  PFree
  /dev/sdb1  vg0  lvm2 a-   68.50G     0
  /dev/sdc1  vg0  lvm2 a-    8.47G     0
  /dev/sdd1  vg0  lvm2 a-   16.95G     0
  /dev/sde1  vge  lvm2 a-   16.95G 16.95G
  /dev/sdf1  vgf  lvm2 a-   16.95G 16.95G
# vgs
  VG   #PV #LV #SN Attr   VSize  VFree
  vg0    3   1   0 wz--n- 93.91G     0
  vge    1   0   0 wz--n- 16.95G 16.95G
  vgf    1   0   0 wz--n- 16.95G 16.95G
# lvs
  LV   VG   Attr   LSize  Origin Snap%  Move Log Copy%
  aux  vg0  -wi-ao 93.91G

Anything here referring to "vg0" is a pre-existing LVM arrrangement 
involving a mixture of real drives, as you can see in the pvs output.  
The "problem children" I've created are sde1 and sdf1, the two external 
SCSI drives.  Note that they are in an "all space free" state.  As I see 
my current dilemma, I don't have LVs to go any further with.

Daniel Kahn Gillmor wrote:
> On Thu 2008-03-20 19:32:52 -0400, Jeff Hubbs wrote:
>
>   
>> Yeah, I'm thinking now I shouldn't have run vgcreate; the
>> information in the dd'ed files made as described in the article now
>> reflects my vge and vgf volume groups.  Where I'm stuck now is that
>> I don't have any devices /dev/vge and /dev/vgf
>>     
>
> aiui, you should never have device nodes for the VGs themselves, since
> they aren't block devices.  you'll have device nodes for the PVs (they
> must be device nodes before they're PVs, actually), and device nodes
> for any active LVs (which are auto-created in
> /dev/mapper/$VGNAME-$LVNAME, in my experience, and then linked from
> /dev/$VGNAME/$LVNAME as a convenience).
>
>   
>> and vgscan --mknodes prints out those volume groups but makes no new
>> nodes.  One other possibility is that the two disks were put in a vg
>> together and I suppose I could re-do vgcreate to accomplish that,
>> but I'm still concerned that I won't be able to generate a /dev/vgef
>> or whatever.
>>     
>
> Have you looked at the output of lvs?  before i touch anything to do
> with LVM, i always try to get my bearings with the basic reports: 
>
>  pvs && vgs && lvs
>
> and if i need more information, i use one of the more detailed variants:
>
>  pvdisplay
>  vgdisplay
>  lvdisplay
>
> I know it's a little late, but you should do this kind of exploration
> *before* any potentially destructive operations like vgcreate.
>
> hth,
>
>         --dkg
>   
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