Date: Wed, 21 Apr 1999 11:13:55 -0700 (PDT) From: Doug White <dwhite@resnet.uoregon.edu> To: cjclark@home.com Cc: Dale Anderson <danderso@crystalsugar.com>, freebsd-questions@FreeBSD.ORG Subject: Re: Using Raw wd Message-ID: <Pine.BSF.4.03.9904211110460.27954-100000@resnet.uoregon.edu> In-Reply-To: <199904202007.QAA10390@cc942873-a.ewndsr1.nj.home.com>
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On Tue, 20 Apr 1999, Crist J. Clark wrote: > Dale Anderson wrote, > > I can't imagine how you would be able to write to a raw > > unformatted disk partition. The only way would be to write your own > > disk access utilities, which would mean that you would create a > > proprietary disk format of your own, that only your access routines > > could get to. > > Sounds a bit scarry, in my opinion. > > I don't understand why that would be true (althoug it may be). I can > write to a raw tape just fine with tar. I can do the same thing and > tar directly to a floppy, no filesystem or special utilities needed > (not that tar is not very special to me). Why can't I do the > same with a hard drive? Plus, I've seen more than one mention of > people using 'dd' to clone disks (not _that_ scares _me_). I've never seen it; the only time someone tried got a 'Read-only filesystem' error. I suggested tar|tar or dump|restore. > If it is true that it does not work for a hard drive, what is the > fundamental difference between writing a tar archive to a raw tape, > a raw floppy disk, or a raw hard disk? A tape is a sequential-access device. One bit goes before the other, always. The sa tape driver does the fixups for you. A floppy has a fixed geometry based on size. The fd driver lets you get away with raw file dumps since it takes care of the fixups. A hard disk has variable geometry and partition information in the disklabel that is specific to the disk & slice. You'd have to regenerate the disklabel as you were writing the chunk. The ?d driver does not do the fixups necessary for this access mode to work correctly. In sum: don't do that :) Doug White Internet: dwhite@resnet.uoregon.edu | FreeBSD: The Power to Serve http://gladstone.uoregon.edu/~dwhite | www.freebsd.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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