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Date:      Fri, 23 Mar 2018 11:42:37 -0600 (MDT)
From:      Warren Block <wblock@wonkity.com>
To:        Victor Sudakov <vas@mpeks.tomsk.su>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: Solved. Re: Dualboot and ZFS
Message-ID:  <alpine.BSF.2.21.1803231141450.86278@wonkity.com>
In-Reply-To: <20180323023202.GA55860@admin.sibptus.transneft.ru>
References:  <VI1PR02MB120018D174817F8FFB2981D5F6EB0@VI1PR02MB1200.eurprd02.prod.outlook.com> <20180115151526.GA66342@admin.sibptus.transneft.ru> <a7920f859b666cff48f4f73ee1b2f954@dweimer.net> <20180116034929.GB89443@admin.sibptus.transneft.ru> <20180131082738.GA46395@admin.sibptus.transneft.ru> <547e65d16ef16667f61d88463ca73079@roundcube.fjl.org.uk> <20180319025914.GA57490@admin.sibptus.transneft.ru> <alpine.BSF.2.21.1803210626040.85475@wonkity.com> <20180322012621.GA15678@admin.sibptus.transneft.ru> <alpine.BSF.2.21.1803220726210.5586@wonkity.com> <20180323023202.GA55860@admin.sibptus.transneft.ru>

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On Fri, 23 Mar 2018, Victor Sudakov wrote:

> Warren Block wrote:
>>>> On Mon, 19 Mar 2018, Victor Sudakov wrote:
>>>>>
>>>>> sysctl kern.geom.debugflags=0x10
>>>>
>>>> Please reconsider doing this without it being required.  It means "allow
>>>> destroying mounted partitions" and is usually not necessary.
>>>
>>> It is recommended, or even required ("must") by the zfsboot(8) man page:
>>
>> The vagueness here is from the "If the drive is currently in use".  It
>> could easily be replaced with "If the user wants to destroy data from a
>> drive that is currently being used".
>
> In my script, the ${DISK} is supposed to be a new disk onto which a
> system is installed (cloned actually), so any data thereon would be
> destroyed anyway.
>
>> I would argue that we should
>> remove or rewrite that, as it is misleading.  Overwriting a drive that
>> is "in use" is generally exactly the opposite of what people want.
>
> I'm afraid your concern is a bit misdirected. If you can suggest a way
> to install zfsboot without dd, and document it in zfsboot(8) then of course
> kern.geom.debugflags=0x10 is better avoided.

That's the thing, dd should work without the debugflags setting.  If it 
does not, it means you are trying to overwrite something in use.



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