Tuesday, March 30, 2010

Advance your career with a degree in medical coding

On Jan 07, 2009 22:42 +0100, Christian Ohm wrote: Can you upload someplace the output of dumpe2fs /dev/XXX dumpe2fs -o superblock=32768 /dev/XXX dumpe2fs -o superblock=98304 /dev/XXX That would be helpful to see what had happened. I'll do that soon; I got another harddisk to copy the partition, but both disks aren't connected right now. You could also and compile and run the e2fsprogs "findsuper" tool (I've attached it here, it isn't built by default). This will scan the specified device and look for ext2/3/4 superblock signatures. 2. Is this corruption a fault of ext4? I guess this is difficult to answer, but I had ext3 survive any lockups without much problems. So far ext4 seems not quite that robust, but perhaps another file system would have blown up as well in this situation. Is there any information I can give you to help make ext4 more robust? I'm not sure what the hard system hang did, but it looks like it splattered a lot of random crap all over the harddrive. I doubt ext4 did this, and I doubt ext3 would have done any better.... we need to know a lot more about exactly what sort damage was done to the filesytem to say for certain, though. I did one copy of the partition already (took three hours, so not something to do often...), and ran fsck -y on that. The result was an endless fsck loop like that described in http://www.linuxquestions.org/questions/linux-hardware-18/corrupt-ext3-partition-need-to-recover-376366/ . Oh, and I have to try if dumpe2fs actually works, either that or debugfs failed when I tried to run it on the original disk (I also ran dumpe2fs on the copy while fsck was doing its looping, and depending on the time it did or did not find a file system on the device). Anyway, I hope I can experiment some more tomorrow. Oh, and is there a human understandable description of the on-disk data format to compare with a hexdump? A (admittedly very short) search didn't turn up anything. Best regards, Christian Ohm -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majo ... @vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc. /* * findsuper --- quick hacked up program to find ext2 superblocks. * * This is a hack, and really shouldn't be installed anywhere. If you * need a program which does this sort of functionality, please try * using gpart program. * * Portions Copyright 1998-2000, Theodore Ts'o. * * Well, here's my linux version of findsuper. * I'm sure you coulda done it faster. :) * IMHO there isn't as much interesting data to print in the * linux superblock as there is in the SunOS superblock--disk geometry is * not there...and linux seems to update the dates in all the superblocks. * SunOS doesn't ever touch the backup superblocks after the fs is created, * as far as I can tell, so the date is more interesting IMHO and certainly * marks which superblocks are backup ones. * * I wanted to add msdos support, but I couldn't make heads or tails * of the kernel include files to find anything I could look for in msdos. * * Reading every block of a Sun partition is fairly quick. Doing the * same under linux (slower hardware I suppose) just isn't the same. * It might be more useful to default to reading the first (second?) block * on each cyl; however, if the disk geometry is wrong, this is useless. * But ya could still get the cyl size to print the numbers as cyls instead * of blocks... * * run this as (for example) * findsuper /dev/hda * findsuper /dev/hda 437760 1024 (my disk has cyls of 855*512) * * I suppose the next step is to figgure out a way to determine if * the block found is the first superblock somehow, and if so, build * a partition table from the superblocks found... but this is still * useful as is. * * Steve * ss ... @nevets.oau.org * ss ... @mae.engr.ucf.edu * * Additional notes by Andreas Dilger < adil ... @turbolinux.com >: * - fixed to support > 2G devices by using lseek64 * - add reliability checking for the superblock to avoid random garbage * - add adaptive progress meter * * It _should_ also handle signals and tell you the ending block, so * that you can resume at a later time, but it doesn't yet... * * Note that gpart does not appear to find all superblocks that aren't aligned * with the start of a possible partition, so it is not useful in systems * with LVM or similar setups which don't use fat partition alignment. * * %Begin-Header% * This file may be redistributed under the terms of the GNU Public * License. * %End-Header% */ /* * Documentation addendum added by Andreas dwgu ... @win.tue.nl /ae ... @cwi.nl * * The program findsuper is a utility that scans a disk and finds * copies of ext2 superblocks (by checking for the ext2 signature). * * For each superblock found, it prints the offset in bytes, the * offset in 1024-byte blocks, the size of the ext2 partition in fs * blocks, the filesystem blocksize (in bytes), the block group number * (always 0 for older ext2 systems), and a timestamp (s_mtime). * * This program can be used to retrieve partitions that have been * lost. The superblock for block group 0 is found 1 block (2 * sectors) after the partition start. * * For new systems that have a block group number in the superblock it * is immediately clear which superblock is the first of a partition. * For old systems where no group numbers are given, the first * superblock can be recognised by the timestamp: all superblock * copies have the creation time in s_mtime, except the first, which * has the last time e2fsck or tune2fs wrote to the filesystem. * */ #define _FILE_OFFSET_BITS 64 #include #include #include #include #include #include #include #include "ext2fs/ext2_fs.h" #include "nls-enable.h" #undef DEBUG #ifdef DEBUG #define WHY(fmt, arg...) { printf("\r%Ld: " fmt, sk, ##arg) ; continue; } #else #define WHY(fmt, arg...) { continue; }
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