On Sat, 13 Aug 2011, Ivan Shmakov wrote: > A couple of weeks ago I've started working on a tool > (tentantively named “Ext2 disassembler”) to walk through an > Ext2+ filesystem (or an image of) and produce the mapping of > files' (inodes') relative block numbers to the image's (or > “physical”) block numbers. Hi Ivan, I have not seen your code, but that sounds like something that debugfs (part of e2fsprogs) is already doing very well (and a lot more). This is exactly the "extN disassembler" you're talking about and with a little bit of scripting around it you should be able dig any information you desire from the file system so I do not think that new application is needed. But I might be wrong, just take a look at it. Thanks! -Lukas > > The version-that-works (apparently) is almost done, pending > upload to a publicly-accessible Git repository. > > However, there's a considerable amount of work to be done so > that the tool will become really usable. Therefore, I'd > appreciate any help with it. > > TIA. > > Why I'm interested in that? > > Recently, there was a discussion in debian-devel@ on whether the > Debian project should provide images for easy deployment within > “virtual” environments (such as KVM, Xen, etc.) > > Such images (which, I assume, will use a filesystem supported by > e2fsprogs) are going to be quite large: hundreds MiB to a few > GiB's (depending on the intended usage) per architecture per > version. > > Earlier, to reduce the burden of mirroring of the ISO 9660 (CD, > DVD, etc.) images, the Jigdo (for Jigsaw Download) tool was > introduced. The tool uses SHA-1 to associate pieces of a > filesystem image with the contents of the files of a specified > set. As the result, the tool produces the association map, > which has the parts of the image for which no matching files are > known embedded. (A helper file, which contains the URI's the > files may be downloaded from, is also generated.) > > Given such an association map, and the files, the tool is > capable of restoring the image. > > The tool is filesystem-agnostic. Unfortunately, it relies on > the fact that the files on the ISO 9660 filesystem are never > fragmented. Which doesn't hold for Ext2+. > > However, given the knowledge of the filesystem, it's possible to > solve the task of describing the parts of a given image as being > parts of the files specified. > > Done > > The tool iterates over the inodes, and records the > logical-to-physical blocks correspondence. All the “chunks” > belonging to the same inode are marked as such. > > The mapping is written to a SQLite database. > > To do > > Message digests are to be computed and recorded just as well. > > Non-payload blocks are to be annotated as well. > > A tool to reassemble the image. > > Command line interface. (Preferably compliant to the GNU Coding > Standards.) > > --
