Date: Sat, 26 Mar 2011 15:27:09 +0100 From: Anders Andersson <pipatron@gmail.com> To: freebsd-fs@freebsd.org Subject: Re: Recover a ufs2 filesystem from a reformat with another ufs2 filesystem Message-ID: <AANLkTimBjjCjvtwh08NOEHBEppO0QP8nHbMBLzKE_Hap@mail.gmail.com> In-Reply-To: <ij9td4$8dh$1@dough.gmane.org> References: <AANLkTikSTgcsVnjRuF2Un4oBXfYaYy0r_o%2BgKzcRmkrX@mail.gmail.com> <ij9td4$8dh$1@dough.gmane.org>
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Dear list! I realized that I never replied with a follow-up to this problem I had, and even though a long time have passed I want to explain what I did so that others in a similar situation can read about it. On Mon, Feb 14, 2011 at 1:35 AM, Ivan Voras <ivoras@freebsd.org> wrote: > On 13/02/2011 21:39, Anders Andersson wrote: > >> 1) If an old file system is overwritten by a new file system with the >> same size, are there any traces of the old file system meta data left? >> I'm thinking randomized backup headers scattered throughout the file >> system, which would have a different location after each new format. > > No, not randomized at all, unfortunately for your purpose - there are copies > of superblocks, but all important data is on precisely deterministic > positions for somewhat the same reasons - to help recovery in case parts of > it are missing. Perhaps it would be beneficial if some of this information was spread out at random for recover purpose, although I don't know what bad side effects this would create. >> 4) If everything else fails, can you recommend a good overview about >> UFS2, how and where the bits and pieces are stored on disk? > > That would be a very complicated but also very interesting way to learn in > extreme details about a file system :) The more you learn, the better. :) I never went to this length though. I ended up just using photorec/magicrescue on the block device to find at least some photos and documents. > In any case, as others said, DO NOT WORK ON THE "LIVE" HARD DRIVE. Make a > copy image of it. Naturally. Though I had to do some extra trickery here since I didn't have 2TB spare to take a full backup. What I did was to use the device mapper subsystem in linux to create writable snapshots over the read-only master. Having multiple writable snapshots is handy when comparing things.
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