From mboxrd@z Thu Jan  1 00:00:00 1970
From: NeilBrown <neilb@suse.com>
Subject: Re: Interesting mdadm quirk ...
Date: Mon, 09 Jan 2017 09:44:37 +1100
Message-ID: <87mvf1jhnu.fsf@notabene.neil.brown.name>
References: <5870EB3F.2060206@youngman.org.uk>
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On Sun, Jan 08 2017, Wols Lists wrote:

> Just been doing some raid testing, and this happened ...
>
> linux-lfqf:/dev # mdadm md/parity
> md/parity: 31.97GiB raid5 3 devices, 0 spares. Use mdadm --detail for
> more detail.
> linux-lfqf:/dev # mdadm --stop md/parity
> mdadm: Cannot open md/parity
> linux-lfqf:/dev # mdadm --stop /dev/md/parity
> mdadm: stopped /dev/md/parity
>
> Weird - why can it successfully stop it when passed an absolute path,
> but not when passed a relative path? When I did the first variant, I
> used tab completion, and then when I edited it I really did edit it, not
> retype it, so I can't see any way the two arguments could refer to
> different objects.

If you give mdadm a name of an array that start with "/", it is assumed
to be a path name (usually in /dev).
If it doesn't start with "/", then it is an array name.  The might mean
different things in different contexts, I'm not 100% sure.
However, for --stop, it a name like you would find is /sys/block or
/proc/mdstat.
So "mdadm --stop md0" or "mdadm --stop md_parity" might do what you
want.
Probably the error message could be more useful here.

NeilBrown


>
> Oh - and
>
> mdadm --version
> mdadm - v3.4 - 28th January 2016
>
> ie stock SuSE leap 42.2
>
> Cheers,
> Wol
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