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Re: [linux-lvm] brainfart: lilo'd a PV



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


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