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Date: Thu, 15 Nov 2012 08:15:00 -0700 (MST)
From: Warren Block <wblock@wonkity.com>
To: Thomas Mueller <mueller23@insightbb.com>
Subject: Re: Mounting SD card.
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Cc: Mike Clarke <jmc-freebsd2@milibyte.co.uk>, freebsd-questions@freebsd.org
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On Thu, 15 Nov 2012, Thomas Mueller wrote:

>>> I think that's pretty much standard behaviour. The solution appears to be
>>> to "wake" it up with the following incantation:
>
>>>    dd if=/dev/null of=/dev/da0 count=0
>
>>> That's what works here. See the thread starting with
>>> <http://lists.freebsd.org/pipermail/freebsd-questions/2010-February/212109.html>
>
>> true > /dev/da0
>
>> is a little shorter and safer.  The search keywords for this are "GEOM
>> retaste" or "retasting".
>
> Could you also do a read such as
>
> dd if=/dev/da0 of=/dev/null bs=16k count=1

Unfortunately, no.  Retastes are only done after a device has been 
opened for write.  true(1) is nice for that because it never actually 
writes anything.

This still feels awkward and dangerous to me, and I'd like to see an 
explicit gretaste command.