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

[Pavel Goran]

Hello Erik,

Post by 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
# 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

[Erik Hjelmås]

Post by Pavel Goran

Post by 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
# 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

Post by Pavel Goran
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