cannot attach backing device, wipefs does not fix it

cannot attach backing device, wipefs does not fix it

[Erik Hjelmås]

Hi, ubuntu 14.04, and a 5TB RAID (sdc) partitioned into two 2.5TB partitions
(sdc1 and sdc2) with parted to be used as backing devices, 

/dev/sdc2 attaches fine

problem with sdc1:

# make-bcache -B /dev/sdc1
Device /dev/sdc1 already has a non-bcache superblock, remove it using wipefs
and wipefs -a

# wipefs /dev/sdc1
wipefs: WARNING: /dev/sdc1: appears to contain 'dos' partition table

# wipefs -a /dev/sdc1
wipefs: WARNING: /dev/sdc1: appears to contain 'dos' partition table

# make-bcache -B /dev/sdc1
Device /dev/sdc1 already has a non-bcache superblock, remove it using wipefs
and wipefs -a

In other words, Im unable to attach sdc1

any help greatly appreciated!

/Erik

Re: cannot attach backing device, wipefs does not fix it

[Pavel Goran]

Hello Erik,

Wednesday, June 18, 2014, 10:38:55 PM, you wrote:

> Hi, ubuntu 14.04, and a 5TB RAID (sdc) partitioned into two 2.5TB partitions
> (sdc1 and sdc2) with parted to be used as backing devices, 

> /dev/sdc2 attaches fine

> problem with sdc1:

> # make-bcache -B /dev/sdc1
> Device /dev/sdc1 already has a non-bcache superblock, remove it using wipefs
> and wipefs -a

> # wipefs /dev/sdc1
> wipefs: WARNING: /dev/sdc1: appears to contain 'dos' partition table

> # wipefs -a /dev/sdc1
> wipefs: WARNING: /dev/sdc1: appears to contain 'dos' partition table

Did you try wipefs -a -f /dev/sdc1 ?

If that fails, just erase the first few MB of the device with zeroes:

dd if=/dev/zero of=/dev/sdc1 bs=1M count=10

Pavel Goran
  

Re: cannot attach backing device, wipefs does not fix it

[Erik Hjelmås]

> > Hi, ubuntu 14.04, and a 5TB RAID (sdc) partitioned into two 2.5TB partitions
> > (sdc1 and sdc2) with parted to be used as backing devices, 
> 
> > /dev/sdc2 attaches fine
> 
> > problem with sdc1:
> 
> > # make-bcache -B /dev/sdc1
> > Device /dev/sdc1 already has a non-bcache superblock, remove it using wipefs
> > and wipefs -a
> 
> > # wipefs /dev/sdc1
> > wipefs: WARNING: /dev/sdc1: appears to contain 'dos' partition table
> 
> > # wipefs -a /dev/sdc1
> > wipefs: WARNING: /dev/sdc1: appears to contain 'dos' partition table
> 
> Did you try wipefs -a -f /dev/sdc1 ?

my wipefs does not have a -f option
 
> If that fails, just erase the first few MB of the device with zeroes:
> 
> dd if=/dev/zero of=/dev/sdc1 bs=1M count=10

I had tried this, but I see now that I copied from /dev/null instead of
/dev/zero and no data got copied :)

so, yes, your suggestion dd if=/dev/zero of=/dev/sdc1 bs=1M count=10 fixed it

thank you Pavel!

/Erik