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In-Reply-To: <4E8F5D47.9070904@yandex.ru>
References: <81477.1318015137@critter.freebsd.dk>
	<4E8F55CC.3060302@FreeBSD.org> <4E8F5D47.9070904@yandex.ru>
Date: Sun, 23 Oct 2011 17:54:28 -0400
Message-ID: <CACqU3MXr-JoAd=q+obUiSOkQG03Kq4jEs6g+vkJ5V99i23713g@mail.gmail.com>
From: Arnaud Lacombe <lacombar@gmail.com>
To: "Andrey V. Elsukov" <bu7cher@yandex.ru>
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Cc: Warren Block <wblock@wonkity.com>, Garrett Cooper <yanegomi@gmail.com>,
	Glen Barber <gjb@freebsd.org>, Poul-Henning Kamp <phk@phk.freebsd.dk>,
	freebsd-current@freebsd.org, Benjamin Kaduk <kaduk@mit.edu>
Subject: Re: aliasing (or renaming) kern.geom.debugflags
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Hi,

2011/10/7 Andrey V. Elsukov <bu7cher@yandex.ru>:
> On 07.10.2011 23:41, Glen Barber wrote:
>> In my experience, without kern.geom.debugflags=16, the MBR will not be
>> written to the memstick, leaving you with what would effectively be a
>> coaster in the not-so-distant past.
>
> The problem is that this bad suggestion is everywhere in the Internet.
> And users use it always even when it not needed. I think it is bad idea
> add it in the our official documentation.
FWIW, boot0cfg(8) also mentions it:

NOTE
 Protection mechanisms in the geom(4) subsystem might prevent boot0cfg
 from being able to update the MBR on a mounted disk.  Instructions for
 temporarily disabling these protection mechanisms can be found in the
 geom(4) manpage. Specifically, do a

       sysctl kern.geom.debugflags=0x10

 to allow writing to the MBR, and restore it to 0 afterwards.

 - Arnaud

> When you doing all in the right way using debugflags=16 is not needed.
> And it is really dangerous when you doing something what you do not know
> exactly.
>
> --
> WBR, Andrey V. Elsukov
>
>