Date: Tue, 11 Jan 2022 15:04:33 +0100 From: Tomasz CEDRO <tomek@cedro.info> To: Roderick <hruodr@gmail.com> Cc: FreeBSD Questions List <questions@freebsd.org> Subject: Re: dd and mbr Message-ID: <CAM8r67By518wp_1p9%2BJ5p7CE6Zj1M97Rm%2BaA-CSA-qtSVgyidw@mail.gmail.com> In-Reply-To: <4af920fc-eff1-a92e-d36e-1ba97079864c@gmail.com> References: <4af920fc-eff1-a92e-d36e-1ba97079864c@gmail.com>
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On Tue, Jan 11, 2022 at 11:05 AM Roderick wrote: > The command: > dd if=/dev/zero of=/dev/da0 > does not delete the mbr, I still see the partition table with > fdisk. My questions: > (1) What does this command do? > (2) How to delete the mbr with dd? How to address the whole disk with dd? > In OpenBSD is simply > dd if=/dev/zero of=/dev/rsd0c > with perhaps a count argument. > Rod. There seems to be a tricky sysctl introduced some time ago that prevents some operations on mbr.. I got into that issuse some time ago but don't remember details sorry.. I also do not like that FreeBSD system hides something from me like Linux then requires searching for a magic solution.. I would prefer to stay OpenBSD way you presented :-( Check for mbr related warnings in dmesg. Try: sysctl kern.geom.debugflags=16 sysctl kern.geom.part.check_integrity=0 Hope that helps / hints the direction :-) -- CeDeROM, SQ7MHZ, http://www.tomek.cedro.info
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