Date: Wed, 25 May 2005 12:54:19 -0500 From: Dan Nelson <dnelson@allantgroup.com> To: David Andersen <dga+@cs.cmu.edu> Cc: freebsd-hackers@freebsd.org Subject: Re: Opening raw disk while mounted in 5.x? Message-ID: <20050525175419.GA87847@dan.emsphone.com> In-Reply-To: <f7355c61ebfc40d096adb2c862cacf3b@cs.cmu.edu> References: <f7355c61ebfc40d096adb2c862cacf3b@cs.cmu.edu>
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In the last episode (May 25), David Andersen said: > Hoping someone knows the quick answer to this - in 4.x, it was > possible to open /dev/ad0 while a filesystem one one of its slices > was mounted. This no longer appears possible under 5.x. Could > someone point me to the spot in the code where I'd need to disable a > permissions check (or a sysctl, or anything) to permit this behavior > again? > > (The context: mounting slice 2 of a disk and using it to store a > compressed filesystem image. Then opening the primary disk device to > directly write the filesystem image onto slice 1. The kernel seems > to muck with the write calls if we try to do the write onto slice 1 > instead of the raw disk). This is using the very cool > imagezip/imageunzip utilities from the Utah Emulab project. Try setting the kern.geom.debugflags sysctl to 16. The kerenl shouldn't have stopped you from writing to slice 1 though. -- Dan Nelson dnelson@allantgroup.com
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