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Lockheed

Member

Registered: 2010-03-16

Posts: 1,521

Unable to wipe ZFS partition table from the disk

I used an SD card as part of a zfs zpool made of three SD cards, without partition table. ZFS was managing the entire devices, not just partitions.
I subsequently retired this zpool but did not run “zpool destroy”. This worked for two of the cards, but it seems as if one of the SD cards just can’t shake the zfs_member marker, no matter what I do.

So far I tried multiple times, on several different machines (including two without ZOL installed, so zfs cache file is not an issue here):

1. dd the entire device with zeros. Four times.

2. zpool labelclear -f /dev/sdc

3. create new msdos partition table in gparted and fdisk

4.

$ mkfs.btrfs -f /dev/sdc
$ mount /dev/sdc /mnt/usb
mount: unknown filesystem type 'zfs_member'
Unable to wipe ZFS partition table from the disk

5. Windows format and Partition Minitools windows equivalent of gparted.

As you can see, none of those methods wrote over the zfs data. It remains intact and invulnerable to anything I tried.
I am out of ideas. It looks like google is out of ideas, too.

slytux

Member

From: New York

Registered: 2010-09-25

Posts: 129

Re: Unable to wipe ZFS partition table from the disk

Install gptfdisk

gdisk /dev/sdx  # where x is your SD card

x
z
w
q

Lockheed

Member

Registered: 2010-03-16

Posts: 1,521

Re: Unable to wipe ZFS partition table from the disk

Thanks, but no dice. Operation completed, but no change occurred:

As an example, this is a message from fdisk

/dev/sdc: device contains a valid 'zfs_member' signature; it is strongly recommended to wipe the device with wipefs(8) if this is unexpected, in order to avoid possible collisions

t0m5k1

Member

From: overthere

Registered: 2012-02-10

Posts: 324

Re: Unable to wipe ZFS partition table from the disk

The clue was in the error:

it is strongly recommended to wipe the device with wipefs(8)

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Lockheed

Member

Registered: 2010-03-16

Posts: 1,521

Re: Unable to wipe ZFS partition table from the disk

Yeah, somehow while writing the first post I missed that wipefs also does absolutely nothing.

# wipefs /dev/sdc
offset               type
----------------------------------------------------------------
0x23000              zfs_member   [raid]
                     LABEL: SD
                     UUID:  9662645799256520897

# wipefs /dev/sdc -o 0x23000
/dev/sdc: 8 bytes were erased at offset 0x00023000 (zfs_member): 0c b1 ba 00 00 00 00 00
# wipefs /dev/sdc
offset               type
----------------------------------------------------------------
0x23000              zfs_member   [raid]
                     LABEL: SD
                     UUID:  9662645799256520897