Date: Sun, 07 Aug 2011 11:00:59 +0400 From: Test Rat <ttsestt@gmail.com> To: freebsd-fs@freebsd.org Subject: Re: kern.geom.debugflags=16 does NOT allow me to write to device Message-ID: <867h6pemdw.fsf@gmail.com> References: <y2z5a1151761004221355l391c05f4qc6c0f760321b56f5@mail.gmail.com> <g2rb269bc571004221414m828ac15ahdde1abaf43b6ee8c@mail.gmail.com> <h2w5a1151761004221429y43d71d7ga13febd1c518c0d1@mail.gmail.com>
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Peter Schuller <peter.schuller@infidyne.com> writes: [...] > In addition, geom(4) still has: > > 0x10 (allow foot shooting) > Allow writing to Rank 1 providers. This would, for example, > allow the super=E2=80=90user to overwrite the MBR on the roo= t disk or > write random sectors elsewhere to a mounted disk. The impli= ca=E2=80=90 > tions are obvious. > > In addition, geom/geom_subr.c has: > > /* If foot-shooting is enabled, any open on rank#1 is OK */ > if ((g_debugflags & 16) && pp->geom->rank =3D=3D 1) > ; > > I wonder if the problem is that it's not of rank 1 because I'm writing > to the slice's first second rather than the MBR... That's now feeling > pretty likely and can perhaps explain lots of confusion that seems to > exist based on Googling. [...] The issue still seems unanswered. For example, this guide http://wiki.freebsd.org/RootOnZFS/ZFSBootPartition silently avoids explaining why zroot on MBR & BSD should be exported. If gpart is ever fixed I still think shooting the foot on rank > 1 is useful for things like testing FS for corruption without accidentally destroying partition table if operating on rank =3D=3D 1.
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