Date: Sun, 25 Mar 2018 11:33:51 +0700 From: Victor Sudakov <vas@mpeks.tomsk.su> To: Warren Block <wblock@wonkity.com> Cc: freebsd-questions@freebsd.org Subject: Re: Solved. Re: Dualboot and ZFS Message-ID: <20180325043351.GA95361@admin.sibptus.transneft.ru> In-Reply-To: <alpine.BSF.2.21.1803231141450.86278@wonkity.com> References: <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> <alpine.BSF.2.21.1803231141450.86278@wonkity.com>
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Warren Block wrote:
> On Fri, 23 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.
To my surprise, my script works just fine without sysctl kern.geom.debugflags=0x10.
This may mean that this requirement in man zfsboot is superfluous.
Thanks for pointing this out, I've updated my bug report
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=226714
Still I'm surprised that geom permits my overwriting of a VBR with dd.
--
Victor Sudakov, VAS4-RIPE, VAS47-RIPN
AS43859
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