Date: Tue, 6 Jan 2004 15:17:29 -0500 (EST) From: Jerry McAllister <jerrymc@clunix.cl.msu.edu> To: scott@sremick.net Cc: FreeBSD <freebsd-questions@freebsd.org> Subject: Re: "Cannot find file system superblock" error - how to recover? Message-ID: <200401062017.i06KHUM08886@clunix.cl.msu.edu> In-Reply-To: <20040106195408.31698.qmail@web41112.mail.yahoo.com> from "Scott I. Remick" at Jan 06, 2004 11:54:08 AM
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> > --- Jerry McAllister <jerrymc@clunix.cl.msu.edu> wrote: > > > (is disklabel/bsdlabel only meant to be run on slices and not > > > bsd-partitions?). > > > > You have it backwards in this question. Disklabel is meant to run > > only on bsd partitions and not slices. Slices (1-4) are the major > > divisions of the disk and partitions (a-h) are divisions within slices. > > Fdisk is what creates slices. First, as I look at what I wrote, I said this wrong in two ways - because I didn't read carefully and had just come off a bad headache, probably caused by breathing spray paint fumes - always use in well ventilated area. The biggie!! disklabel DOES work on slices and CREATES partitions. It does not work on partitions - it creates them which is where my sleepy [Groggy has already been claimed by a famous contributer] got lost. So, trying to run disklabel on ad0s1c would definitely cause an error. The other thing is, I should have left out the word 'only' (after writing the rest of it correctly, of course) because disklabel can, but usually shouldn't, be run on the whole disk ad0 (as apposed to just a slice ad0s1) which will create a "dangerously dedicated" disk. There is no real danger as long as you only use FreeBSD on it and don't want to multi-boot it or anything. Since you only lose the tiny bit by slicing it (63 sectors), you should just always first slice it (with fdisk) - even if that means making it all one big slice. That will make sure things are happy should you get weird creative ideas later on. > Ok, well the reason I thought it might be the other way is because if you > run disklabel (bsdlabel) on a slice (such as /dev/ad4s1 on my machine, which > is working, or /dev/ad0s1 on another machine I have access to) it works fine > (and reports an offset of 0), but if you run it on the partition > (/dev/ad0s1c) you get an offset of 63 and errors like: Yes, the offset in disklabel is from the beginning of the slice. I am not sure what it is trying to do if you try to further partition a partition. Anyway, the 'c' partition is a special one that refers to the whole slice regardless of the partitions it has been carved in to. I would have to go wading through code to figure out how it is handled differently. Just for fun, try doing a disklabel on ad0s1a or something like that and see what it does - on a disk you can afford to trash. Anyway, sorry for the first round of mis-statement. ////jerry > > partition c: partition extends past end of unit > bsdlabel: partition c doesn't start at 0! > bsdlabel: An incorrect partition c may cause problems for standard system > utilities > partition f: partition extends past end of unit > > So why does disklabel/bsdlabel produce errors when run on the partition even > when the disk is fine, if it is meant to be run on partitions and not > slices? > > Trying to learn... thanks! > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org" >
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