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* [linux-lvm] brainfart: lilo'd a PV
@ 2009-12-17 23:41 Brian J. Murrell
  2009-12-18  0:48 ` Takahiro Yasui
  0 siblings, 1 reply; 7+ messages in thread
From: Brian J. Murrell @ 2009-12-17 23:41 UTC (permalink / raw)
  To: linux-lvm

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I managed to write a lilo block (lilo) to the start of a PV which I have
on /dev/sda (note, /dev/sda is a whole disk PV, unpartitioned).

However, looking at a number of different PVs here, it appears that the
LVM data starts at 0x200 with: "LABELONE".  i.e.:

# hexdump -C /dev/sdc3
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000200  4c 41 42 45 4c 4f 4e 45  01 00 00 00 00 00 00 00  |LABELONE........|
...
# hexdump -C /dev/sdb
00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000001b0  00 00 00 00 00 00 00 00  dc 59 0f 10 cf c9 00 00  |.........Y......|
000001c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000200  4c 41 42 45 4c 4f 4e 45  01 00 00 00 00 00 00 00  |LABELONE........|
...
# hexdump -C /dev/sda 
00000000  fa eb 31 12 00 00 4c 49  4c 4f 16 08 10 00 01 00  |..1...LILO......|
...
00000180  30 e4 cd 13 eb 91 e8 93  fe 44 69 73 6b 20 72 65  |0........Disk re|
00000190  61 64 20 65 72 72 6f 72  0d 0a 00 00 00 00 00 00  |ad error........|
000001a0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001b0  00 00 00 00 00 00 00 00  c6 08 1a 45 cf c9 00 00  |...........E....|
000001c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000001f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 55 aa  |..............U.|
00000200  4c 41 42 45 4c 4f 4e 45  01 00 00 00 00 00 00 00  |LABELONE........|

Is that correct?

Is there anything I should do to repair this or is my brainfart benign
to this PV?

Thanx!

b.


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^ permalink raw reply	[flat|nested] 7+ messages in thread
* Re: [linux-lvm] brainfart: lilo'd a PV
  2009-12-17 23:41 [linux-lvm] brainfart: lilo'd a PV Brian J. Murrell
@ 2009-12-18  0:48 ` Takahiro Yasui
  2009-12-18  2:03   ` [linux-lvm] " Brian J. Murrell
  2009-12-18 12:09   ` [linux-lvm] " Bryn M. Reeves
  0 siblings, 2 replies; 7+ messages in thread
From: Takahiro Yasui @ 2009-12-18  0:48 UTC (permalink / raw)
  To: linux-lvm

On 12/17/09 18:41, Brian J. Murrell wrote:
> I managed to write a lilo block (lilo) to the start of a PV which I have
> on /dev/sda (note, /dev/sda is a whole disk PV, unpartitioned).
> 
> However, looking at a number of different PVs here, it appears that the
> LVM data starts at 0x200 with: "LABELONE".  i.e.:
> 
> # hexdump -C /dev/sdc3
> 00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
> *
> 00000200  4c 41 42 45 4c 4f 4e 45  01 00 00 00 00 00 00 00  |LABELONE........|
> ...
> # hexdump -C /dev/sdb
> 00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
> *
> 000001b0  00 00 00 00 00 00 00 00  dc 59 0f 10 cf c9 00 00  |.........Y......|
> 000001c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
> *
> 00000200  4c 41 42 45 4c 4f 4e 45  01 00 00 00 00 00 00 00  |LABELONE........|
> ...
> # hexdump -C /dev/sda 
> 00000000  fa eb 31 12 00 00 4c 49  4c 4f 16 08 10 00 01 00  |..1...LILO......|
> ...
> 00000180  30 e4 cd 13 eb 91 e8 93  fe 44 69 73 6b 20 72 65  |0........Disk re|
> 00000190  61 64 20 65 72 72 6f 72  0d 0a 00 00 00 00 00 00  |ad error........|
> 000001a0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
> 000001b0  00 00 00 00 00 00 00 00  c6 08 1a 45 cf c9 00 00  |...........E....|
> 000001c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
> *
> 000001f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 55 aa  |..............U.|
> 00000200  4c 41 42 45 4c 4f 4e 45  01 00 00 00 00 00 00 00  |LABELONE........|
> 
> Is that correct?

Yes. The area begin with "LABELONE" is PV label, which is recorded in
the first sector by default. This is the description from the pvcreate
man page.

       --labelsector sector
              By default the PV is labelled with an  LVM2  identifier  in  its
              second  sector (sector 1).  This lets you use a different sector
              near the start of the disk (between 0  and  3  inclusive  -  see
              LABEL_SCAN_SECTORS in the source).  Use with care.

> Is there anything I should do to repair this or is my brainfart benign
> to this PV?

You don't have any problem on the PV, do you?
I don't think you need something to repair the PV.

Thanks,
Taka

^ permalink raw reply	[flat|nested] 7+ messages in thread
* [linux-lvm] Re: brainfart: lilo'd a PV
  2009-12-18  0:48 ` Takahiro Yasui
@ 2009-12-18  2:03   ` Brian J. Murrell
  2009-12-18  2:16     ` malahal
  2009-12-18  3:31     ` Ray Morris
  2009-12-18 12:09   ` [linux-lvm] " Bryn M. Reeves
  1 sibling, 2 replies; 7+ messages in thread
From: Brian J. Murrell @ 2009-12-18  2:03 UTC (permalink / raw)
  To: linux-lvm

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On Thu, 2009-12-17 at 19:48 -0500, Takahiro Yasui wrote: 
> 
> Yes. The area begin with "LABELONE" is PV label,

Looks like the LVM developers foresaw my brainfart and left the first
sector of the disk for me to bugger up without buggering up LVM.  :-)

> which is recorded in
> the first sector by default.

Hrm.  Do you really mean "first" there or second, which is sector 1 if
you start counting with 0?

> This is the description from the pvcreate
> man page.
> 
>        --labelsector sector
>               By default the PV is labelled with an  LVM2  identifier  in  its
>               second  sector (sector 1).

Yes, this looks so.

>   This lets you use a different sector
>               near the start of the disk (between 0  and  3  inclusive  -  see
>               LABEL_SCAN_SECTORS in the source).  Use with care.

> You don't have any problem on the PV, do you?

I don't think I do:

# pvdisplay /dev/sda
  --- Physical volume ---
  PV Name               /dev/sda
  VG Name               datavol
  PV Size               931.51 GB / not usable 1.71 MB
  Allocatable           yes 
  PE Size (KByte)       4096
  Total PE              238467
  Free PE               85356
  Allocated PE          153111
  PV UUID               C22uVB-4m26-5cvl-I11V-NXCm-mVNo-UTAXUH

But of course, I just want to get the opinion of the experts.

> I don't think you need something to repair the PV.

I don't think so either, but of course, do want to confirm my suspicion.

Thanx much for your insight.

b.


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^ permalink raw reply	[flat|nested] 7+ messages in thread
* Re: [linux-lvm] Re: brainfart: lilo'd a PV
  2009-12-18  2:03   ` [linux-lvm] " Brian J. Murrell
@ 2009-12-18  2:16     ` malahal
  2009-12-18  3:12       ` Takahiro Yasui
  2009-12-18  3:31     ` Ray Morris
  1 sibling, 1 reply; 7+ messages in thread
From: malahal @ 2009-12-18  2:16 UTC (permalink / raw)
  To: linux-lvm

Brian J. Murrell [brian@interlinx.bc.ca] wrote:
> On Thu, 2009-12-17 at 19:48 -0500, Takahiro Yasui wrote: 
> > 
> > Yes. The area begin with "LABELONE" is PV label,
> 
> Looks like the LVM developers foresaw my brainfart and left the first
> sector of the disk for me to bugger up without buggering up LVM.  :-)

Partition table uses the first sector (0th sector), so pretty much every
other software that uses labels avoid the first sector.

> > which is recorded in
> > the first sector by default.
> 
> Hrm.  Do you really mean "first" there or second, which is sector 1 if
> you start counting with 0?

He really meant sector 1!

You are just lucky!

^ permalink raw reply	[flat|nested] 7+ messages in thread
* Re: [linux-lvm] Re: brainfart: lilo'd a PV
  2009-12-18  2:16     ` malahal
@ 2009-12-18  3:12       ` Takahiro Yasui
  0 siblings, 0 replies; 7+ messages in thread
From: Takahiro Yasui @ 2009-12-18  3:12 UTC (permalink / raw)
  To: LVM general discussion and development

malahal@us.ibm.com wrote:
> Brian J. Murrell [brian@interlinx.bc.ca] wrote:
>> On Thu, 2009-12-17 at 19:48 -0500, Takahiro Yasui wrote: 
>>> Yes. The area begin with "LABELONE" is PV label,
>> Looks like the LVM developers foresaw my brainfart and left the first
>> sector of the disk for me to bugger up without buggering up LVM.  :-)
> 
> Partition table uses the first sector (0th sector), so pretty much every
> other software that uses labels avoid the first sector.
> 
>>> which is recorded in
>>> the first sector by default.
>> Hrm.  Do you really mean "first" there or second, which is sector 1 if
>> you start counting with 0?
> 
> He really meant sector 1!

Oops, sorry for confusion. The sector number begins with 0,
so the sector 1 should have been written as the "second" sector.

Thank you for correction, Malahal.

Thanks,
Taka

^ permalink raw reply	[flat|nested] 7+ messages in thread
* Re: [linux-lvm] Re: brainfart: lilo'd a PV
  2009-12-18  2:03   ` [linux-lvm] " Brian J. Murrell
  2009-12-18  2:16     ` malahal
@ 2009-12-18  3:31     ` Ray Morris
  1 sibling, 0 replies; 7+ messages in thread
From: Ray Morris @ 2009-12-18  3:31 UTC (permalink / raw)
  To: LVM general discussion and development

> > Yes. The area begin with "LABELONE" is PV label,
> 
> Looks like the LVM developers foresaw my brainfart and left the first
> sector of the disk for me to bugger up without buggering up LVM.  :-)


    Applause.
--
Ray Morris
support@bettercgi.com

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On 12/17/2009 08:03:08 PM, Brian J. Murrell wrote:
> On Thu, 2009-12-17 at 19:48 -0500, Takahiro Yasui wrote:
> >
> > Yes. The area begin with "LABELONE" is PV label,
> 
> Looks like the LVM developers foresaw my brainfart and left the first
> sector of the disk for me to bugger up without buggering up LVM.  :-)
> 
> > which is recorded in
> > the first sector by default.
> 
> Hrm.  Do you really mean "first" there or second, which is sector 1 if
> you start counting with 0?
> 
> > This is the description from the pvcreate
> > man page.
> >
> >        --labelsector sector
> >               By default the PV is labelled with an  LVM2   
> identifier  in  its
> >               second  sector (sector 1).
> 
> Yes, this looks so.
> 
> >   This lets you use a different sector
> >               near the start of the disk (between 0  and  3   
> inclusive  -  see
> >               LABEL_SCAN_SECTORS in the source).  Use with care.
> 
> > You don't have any problem on the PV, do you?
> 
> I don't think I do:
> 
> # pvdisplay /dev/sda
>   --- Physical volume ---
>   PV Name               /dev/sda
>   VG Name               datavol
>   PV Size               931.51 GB / not usable 1.71 MB
>   Allocatable           yes
>   PE Size (KByte)       4096
>   Total PE              238467
>   Free PE               85356
>   Allocated PE          153111
>   PV UUID               C22uVB-4m26-5cvl-I11V-NXCm-mVNo-UTAXUH
> 
> But of course, I just want to get the opinion of the experts.
> 
> > I don't think you need something to repair the PV.
> 
> I don't think so either, but of course, do want to confirm my  
> suspicion.
> 
> Thanx much for your insight.
> 
> b.
> 
> 

------quoted attachment------
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

^ permalink raw reply	[flat|nested] 7+ messages in thread
* Re: [linux-lvm] brainfart: lilo'd a PV
  2009-12-18  0:48 ` Takahiro Yasui
  2009-12-18  2:03   ` [linux-lvm] " Brian J. Murrell
@ 2009-12-18 12:09   ` Bryn M. Reeves
  1 sibling, 0 replies; 7+ messages in thread
From: Bryn M. Reeves @ 2009-12-18 12:09 UTC (permalink / raw)
  To: LVM general discussion and development

On Thu, 2009-12-17 at 19:48 -0500, Takahiro Yasui wrote:
> On 12/17/09 18:41, Brian J. Murrell wrote:
> > I managed to write a lilo block (lilo) to the start of a PV which I have
> > on /dev/sda (note, /dev/sda is a whole disk PV, unpartitioned).
> > 
> > However, looking at a number of different PVs here, it appears that the
> > LVM data starts at 0x200 with: "LABELONE".  i.e.:
> > 
> > # hexdump -C /dev/sdc3
> > 00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
> > *
> > 00000200  4c 41 42 45 4c 4f 4e 45  01 00 00 00 00 00 00 00  |LABELONE........|
> > ...
> > # hexdump -C /dev/sdb
> > 00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
> > *
> > 000001b0  00 00 00 00 00 00 00 00  dc 59 0f 10 cf c9 00 00  |.........Y......|
> > 000001c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
> > *
> > 00000200  4c 41 42 45 4c 4f 4e 45  01 00 00 00 00 00 00 00  |LABELONE........|
> > ...
> > # hexdump -C /dev/sda 
> > 00000000  fa eb 31 12 00 00 4c 49  4c 4f 16 08 10 00 01 00  |..1...LILO......|
> > ...
> > 00000180  30 e4 cd 13 eb 91 e8 93  fe 44 69 73 6b 20 72 65  |0........Disk re|
> > 00000190  61 64 20 65 72 72 6f 72  0d 0a 00 00 00 00 00 00  |ad error........|
> > 000001a0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
> > 000001b0  00 00 00 00 00 00 00 00  c6 08 1a 45 cf c9 00 00  |...........E....|
> > 000001c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
> > *
> > 000001f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 55 aa  |..............U.|
> > 00000200  4c 41 42 45 4c 4f 4e 45  01 00 00 00 00 00 00 00  |LABELONE........|
> > 
> > Is that correct?
> 
> Yes. The area begin with "LABELONE" is PV label, which is recorded in
> the first sector by default. This is the description from the pvcreate
> man page.
> 
>        --labelsector sector
>               By default the PV is labelled with an  LVM2  identifier  in  its
>               second  sector (sector 1).  This lets you use a different sector
>               near the start of the disk (between 0  and  3  inclusive  -  see
>               LABEL_SCAN_SECTORS in the source).  Use with care.
> 
> > Is there anything I should do to repair this or is my brainfart benign
> > to this PV?
> 
> You don't have any problem on the PV, do you?
> I don't think you need something to repair the PV.

Yeah, you should be fine here since LVM2 does not use the 1st sector of
the device and the MBR (and hence lilo) does all its work in that 1st
sector. The LVM2 PV label begins in the 2nd sector (as you've noticed)
and has been left intact by these changes.

You could always zero out sector 0 to avoid confusion:

dd if=/dev/zero of=/path/to/pv bs=512 count=1

Regards,
Bryn.

^ permalink raw reply	[flat|nested] 7+ messages in thread
end of thread, other threads:[~2009-12-18 12:09 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2009-12-17 23:41 [linux-lvm] brainfart: lilo'd a PV Brian J. Murrell
2009-12-18  0:48 ` Takahiro Yasui
2009-12-18  2:03   ` [linux-lvm] " Brian J. Murrell
2009-12-18  2:16     ` malahal
2009-12-18  3:12       ` Takahiro Yasui
2009-12-18  3:31     ` Ray Morris
2009-12-18 12:09   ` [linux-lvm] " Bryn M. Reeves

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