Re: mdadm: Cannot get exclusive access to /dev/md127

[Rich Emberson]

Tried:

# wipefs -a /dev/md127

which did not word, so I next tried:

# wipefs -f -a  /dev/md127
/dev/md127: 6 bytes were erased at offset 0x00000000 (crypto_LUKS): 4c 55
4b 53 ba be

and then

# mdadm  -S /dev/md127
mdadm: Cannot get exclusive access to /dev/md127:Perhaps a running process,
mounted filesystem or active volume group?

but the filesystem is still mounted.

curious, that creating an encrypted raid system on fedora seems to be an
irreversible action.

Now, with part of the raid file system "wipefs"-ed, above, I fear rebooting
and hanging when it does not come up.

Richard

mdadm: Cannot get exclusive access to /dev/md127

[Rick Stevens]

On 02/02/2015 06:32 PM, Rich Emberson wrote:
> Tried:
>
> # wipefs -a /dev/md127
>
> which did not word, so I next tried:
>
> # wipefs -f -a  /dev/md127
> /dev/md127: 6 bytes were erased at offset 0x00000000 (crypto_LUKS): 4c
> 55 4b 53 ba be
>
> and then
>
> # mdadm  -S /dev/md127
> mdadm: Cannot get exclusive access to /dev/md127:Perhaps a running
> process, mounted filesystem or active volume group?
>
> but the filesystem is still mounted.

Wiping a filesystem (and certainly using a force option) is a bad idea
if the filesystem is mounted. You should have unmounted it before you
did the wipefs, but I'm sure you knew that.

"lsof +d /mountpoint" or "lsof +D /mountpoint" should show you what is
using the filesystem if a "umount" doesn't work. In dire straits, you
could try "umount -f" to force an unmount, but again if something is
using the filesystem, that could be bad.

Also, just in case you're using LVM, make sure you disable/delete any
logical volumes in the volume group ("lvchange" and "lvremove") and
disable/delete the volume group as well ("vgchange" and "vgremove").
I'd also recommend destroying the PVs associated with the deleted VGs
before you try to delete the RAID.
> curious, that creating an encrypted raid system on fedora seems to be an
> irreversible action.

IIRC, it's a one-way encryption of the data. If that's the case, of
course it's irreversible. If you're talking about not being able to get
rid of an encrypted filesystem, you're just not doing it correctly. All
filesystems can be deleted unless there's something specific in the
hardware that prevents it (protected partitions of FLASH drives, for
example).
> Now, with part of the raid file system "wipefs"-ed, above, I fear
> rebooting and hanging when it does not come up.

Make sure the filesystem is not in your /etc/fstab file (or has the
mount option "noauto") so the system doesn't try to mount it on the
reboot.
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