Date: Thu, 10 Aug 2000 16:16:18 -0700 From: "Kevin Oberman" <oberman@es.net> To: Wilko Bulte <wkb@freebie.demon.nl> Cc: Ben Weaver <bweaver@tranquility.net>, Alan Clegg <abc@bsdi.com>, freebsd-questions@FreeBSD.ORG Subject: Re: An sblock magic number is... Message-ID: <200008102316.e7ANGIU01939@ptavv.es.net> In-Reply-To: Your message of "Wed, 09 Aug 2000 21:47:03 %2B0200." <20000809214703.A10364@freebie.demon.nl>
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The solution to the problem has already been given, I think, but nobody has explained what this message REALLY means. The superblock is sort of the prime node of the UFS file system. It is a block which allows the rest of the file structure to be accessed and is replicated, often many times, so that a good copy can almost always be found. If it and all copies are lost, the file system is lost. The superblock is identified by the presence of a "magic number", a 32 bit value that is always written into the same location near the end of the superblock. It is used as a quick check that a block is really a superblock and has not been overwritten, or, in the case of dump, to make sure that you are dumping a valid file system. Did I miss anything? I learned about this when I had a similar dump problem, although in may case the problem was with the /etc/fstab file. R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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