misc/findsuper.c

   1 /*
   2  * findsuper --- quick hacked up program to find ext2 superblocks.
   3  *
   4  * This is a hack, and really shouldn't be installed anywhere.  If you
   5  * need a program which does this sort of functionality, please try
   6  * using gpart program.
   7  *
   8  * Portions Copyright 1998-2000, Theodore Ts'o.
   9  *
  10  * This program may be used under the provisions of the GNU Public
  11  * License, *EXCEPT* that a binary copy of the executable may not be
  12  * packaged as a part of binary package which is distributed as part
  13  * of a Linux distribution.  (Yes, this violates the Debian Free
  14  * Software Guidelines in terms of restricting its field of use.
  15  * That's the point.  I don't want this program being distributed in
  16  * Debian, because I don't care to support it, and the maintainer,
  17  * Yann Dirson, doesn't seem to pay attention to my wishes on this
  18  * matter.  So I'm delibiately adding this clause so it violates the
  19  * Debian Free Software Guidelines to force him to take it out.  If
  20  * this doesn't work, I'll have to remove it from the upstream source
  21  * distribution at the next release.  End of Rant.  :-)
  22  *
  23  *
  24  * Well, here's my linux version of findsuper.
  25  * I'm sure you coulda done it faster.  :)
  26  * IMHO there isn't as much interesting data to print in the
  27  * linux superblock as there is in the SunOS superblock--disk geometry is
  28  * not there...and linux seems to update the dates in all the superblocks.
  29  * SunOS doesn't ever touch the backup superblocks after the fs is created,
  30  * as far as I can tell, so the date is more interesting IMHO and certainly
  31  * marks which superblocks are backup ones.
  32  *
  33  * This still doesn't handle disks >2G.
  34  *
  35  * I wanted to add msdos support, but I couldn't make heads or tails
  36  * of the kernel include files to find anything I could look for in msdos.
  37  *
  38  * Reading every block of a Sun partition is fairly quick.  Doing the
  39  * same under linux (slower hardware I suppose) just isn't the same.
  40  * It might be more useful to default to reading the first (second?) block
  41  * on each cyl; however, if the disk geometry is wrong, this is useless.
  42  * But ya could still get the cyl size to print the numbers as cyls instead
  43  * of blocks...
  44  *
  45  * run this as (for example)
  46  *   findsuper /dev/hda
  47  *   findsuper /dev/hda 437760 1024   (my disk has cyls of 855*512)
  48  *
  49  * I suppose the next step is to figgure out a way to determine if
  50  * the block found is the first superblock somehow, and if so, build
  51  * a partition table from the superblocks found... but this is still
  52  * useful as is.
  53  *
  54  *              Steve
  55  * ssd@nevets.oau.org
  56  * ssd@mae.engr.ucf.edu
  57  *
  58  */
  59
  60 /*
  61  * Documentation addendum added by Andreas dwguest@win.tue.nl/aeb@cwi.nl
  62  *
  63  * The program findsuper is a utility that scans a disk and finds
  64  * copies of ext2 superblocks (by checking for the ext2 signature; it
  65  * will occasionally find other blocks that by coincidence have this
  66  * signature - often these can be recognised by their ridiculous
  67  * dates).
  68  *
  69  * For each superblock found, it prints the offset in bytes, the
  70  * offset in 1024-byte blocks, the size of ext2 partition in 1024-byte
  71  * blocks, the filesystem blocksize (given as log(blocksize)-10, so
  72  * that 0 means 1024), the block group number (0 for older ext2
  73  * systems), and a timestamp (s_mtime).
  74  *
  75  * This program can be used to retrieve partitions that have been
  76  * lost.  The superblock for block group 0 is found 1 block (2
  77  * sectors) after the partition start.
  78  *
  79  * For new systems that have a block group number in the superblock it
  80  * is immediately clear which superblock is the first of a partition.
  81  * For old systems where no group numbers are given, the first
  82  * superblock can be recognised by the timestamp: all superblock
  83  * copies have the creation time in s_mtime, except the first, which
  84  * has the last time e2fsck or tune2fs wrote to the filesystem.
  85  *
  86  */
  87
  88
  89 #include <stdio.h>
  90 #include <stdlib.h>
  91 #include <time.h>
  92
  93 #include "ext2fs/ext2_fs.h"
  94 #include "nls-enable.h"
  95
  96
  97 main(int argc, char *argv[])
  98 {
  99         int i;
 100         int skiprate=512;               /* one sector */
 101         long sk=0;                      /* limited to 2G filesystems!! */
 102         FILE *f;
 103         char *s;
 104         time_t tm;
 105
 106         struct ext2_super_block ext2;
 107         /* interesting fields: EXT2_SUPER_MAGIC
 108          *      s_blocks_count s_log_block_size s_mtime s_magic s_lastcheck */
 109
 110 #ifdef ENABLE_NLS
 111         setlocale(LC_MESSAGES, "");
 112         bindtextdomain(NLS_CAT_NAME, LOCALEDIR);
 113         textdomain(NLS_CAT_NAME);
 114 #endif
 115         if (argc<2) {
 116                 fprintf(stderr,
 117                         _("Usage:  findsuper device [skiprate [start]]\n"));
 118                 exit(1);
 119         }
 120         if (argc>2)
 121                 skiprate=atoi(argv[2]);
 122         if (skiprate<512) {
 123                 fprintf(stderr,
 124                         _("Do you really want to skip less than a sector??\n"));
 125                 exit(2);
 126         }
 127         if (argc>3)
 128                 sk=atol(argv[3]);
 129         if (sk<0) {
 130                 fprintf(stderr,_("Have to start at 0 or greater,not %ld\n"),sk);
 131                 exit(1);
 132         }
 133         f=fopen(argv[1],"r");
 134         if (!f) {
 135                 perror(argv[1]);
 136                 exit(1);
 137         }
 138
 139         /* Now, go looking for the superblock ! */
 140         printf("  thisoff     block fs_blk_sz  blksz grp last_mount\n");
 141         for (;!feof(f) &&  (i=fseek(f,sk,SEEK_SET))!= -1; sk+=skiprate){
 142                 if (i=fread(&ext2,sizeof(ext2),1, f)!=1) {
 143                         perror(_("read failed"));
 144                 }
 145                 if (ext2.s_magic != EXT2_SUPER_MAGIC)
 146                         continue;
 147
 148                 tm = ext2.s_mtime;
 149                 s=ctime(&tm);
 150                 s[24]=0;
 151                 printf("%9ld %9ld %9ld %5ld %4d %s\n", sk,
 152                        sk/1024, ext2.s_blocks_count,
 153                        ext2.s_log_block_size,
 154                        ext2.s_block_group_nr, s);
 155         }
 156         printf(_("Failed on %d at %ld\n"), i, sk);
 157         fclose(f);
 158 }