Date: Mon, 14 Feb 2011 01:35:44 +0100 From: Ivan Voras <ivoras@freebsd.org> To: freebsd-fs@freebsd.org Subject: Re: Recover a ufs2 filesystem from a reformat with another ufs2 filesystem Message-ID: <ij9td4$8dh$1@dough.gmane.org> In-Reply-To: <AANLkTikSTgcsVnjRuF2Un4oBXfYaYy0r_o%2BgKzcRmkrX@mail.gmail.com> References: <AANLkTikSTgcsVnjRuF2Un4oBXfYaYy0r_o%2BgKzcRmkrX@mail.gmail.com>
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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. > 2) If there are no traces left of the old file system, would there be > any UFS2-aware recovery programs that could scan the disk and try to > regenerate the necessary meta data from, say, partition size, file > offsets, some other magic...? Yes, there are tools which scan the entire drive / partition and try to identify blocks which look like directories and files, but then you need to recover inodes. Fortunately, not all inodes are pre-initializes in UFS2, some may be salvagable. In any case, I don't predict much success. The process would use some of the same tools like "undeleting" files, see * http://www.google.com/search?q=freebsd+undelete * http://www.google.com/search?q=freebsd+recover+filesystem (it's been a long time I tried something similar, I don't know which tools I used). > 3) Are there any powerful tools availaible for tasks like this in > FreeBSD that are not ported to Linux? In that case, I could easily > install FreeBSD in a virtual machine and salvage the files there. Not likely. > 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 :) I don't know of any online description of UFS2 (note: "UFS" systems are slightly different in all BSDs and very different in Solaris) except the sources but if you can find this book it will probably help you get started quickly: http://www.amazon.com/Design-Implementation-FreeBSD-Operating-System/dp/0201702452 In any case, as others said, DO NOT WORK ON THE "LIVE" HARD DRIVE. Make a copy image of it.
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