On Wednesday 30 November 2005 09:15 pm, Doug H wrote: > One of my disks has 3 active partitions: FreeBSD 5.4-RC3, NTFS > (not-bootable), and FreeBSD 6.0-RELEASE. > > I developed problems while installing FreeBSD 6.0. Installation > went as well as can be expected using sysinstall (no difficulty > other than pulling packages from the CD), but when I rebooted, > nothing was bootable on that disk. I verified that the boot record > (using boot0) seems okay: slice table is fine (40G, 80G, 40G, and > 40G unused on 200G drive). > > Using bsdlabel, I confirmed that slice 3 (FreeBSD 6) is fine, but > for some reason I'm not concerned with now, is unbootable. > > PROBLEM: bsdlabel showed me that slice 1 (FreeBSD 5.4) is damaged > and only partition c existed and was incorrect. I do not have / > cannot find a written copy of my disklabel for that disk (a good > suggestion to *strongly emphasize* in the installation manual for > newbies!). I did recall that ad1s1a ('/') was 512M, so I was able > to write a label and mount that partition from a "Fixit" shell. > > QUESTIONS: How can I rederive the remaining disklabel for that > disk? Could a copy possibly be stored somewhere on root if I > didn't do it myself when building the system? > > I have not tried to boot from that root partition. Trying several > possible labels has resulted in "incorrect super block" errors for > the partitions after 'a'. Random guessing will be very tedious. > > My research has indicated that I could binary grep the raw ad1s1c > partition to locate the magic numbers for the super blocks and > derive the partitions from that information. I even found a little > 'c' language program Peter Dufault posted 11 years ago on this list > to locate magic numbers. > > My hope is that in 11 years of development, FreeBSD would have > created a clever tool to aid this process! I've found enough > entries in these lists to think that the effort would be justified > and much appreciated. If there is no tool, can someone tell me the > value of FS_UFS2_MAGIC? I presume that's what I should search for > - it's a UFS2 filesystem. Having only a "Fixit" shell is somewhat > limiting. > sysutils/scan_ffs I've always used it from a emergency FreeBSD diagnostic CD (custom Freesbie) and it works great. I've never been stuck with only a fixit shell though.
-- Anish Mistry
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