1 /* Well, here's my linux version of findsuper.
2 * I'm sure you coulda done it faster. :)
3 * IMHO there isn't as much interesting data to print in the
4 * linux superblock as there is in the SunOS superblock--disk geometry is
5 * not there...and linux seems to update the dates in all the superblocks.
6 * SunOS doesn't ever touch the backup superblocks after the fs is created,
7 * as far as I can tell, so the date is more interesting IMHO and certainly
8 * marks which superblocks are backup ones.
10 * This still doesn't handle disks >2G.
12 * I wanted to add msdos support, but I couldn't make heads or tails
13 * of the kernel include files to find anything I could look for in msdos.
15 * Reading every block of a Sun partition is fairly quick. Doing the
16 * same under linux (slower hardware I suppose) just isn't the same.
17 * It might be more useful to default to reading the first (second?) block
18 * on each cyl; however, if the disk geometry is wrong, this is useless.
19 * But ya could still get the cyl size to print the numbers as cyls instead
22 * run this as (for example)
24 * findsuper /dev/hda 437760 1024 (my disk has cyls of 855*512)
26 * I suppose the next step is to figgure out a way to determine if
27 * the block found is the first superblock somehow, and if so, build
28 * a partition table from the superblocks found... but this is still
33 * ssd@mae.engr.ucf.edu
38 * Documentation addendum added by Andreas dwguest@win.tue.nl/aeb@cwi.nl
40 * The program findsuper is a utility that scans a disk and finds
41 * copies of ext2 superblocks (by checking for the ext2 signature; it
42 * will occasionally find other blocks that by coincidence have this
43 * signature - often these can be recognised by their ridiculous
46 * For each superblock found, it prints the offset in bytes, the
47 * offset in 1024-byte blocks, the size of ext2 partition in 1024-byte
48 * blocks, the filesystem blocksize (given as log(blocksize)-10, so
49 * that 0 means 1024), the block group number (0 for older ext2
50 * systems), and a timestamp (s_mtime).
52 * This program can be used to retrieve partitions that have been
53 * lost. The superblock for block group 0 is found 1 block (2
54 * sectors) after the partition start.
56 * For new systems that have a block group number in the superblock it
57 * is immediately clear which superblock is the first of a partition.
58 * For old systems where no group numbers are given, the first
59 * superblock can be recognised by the timestamp: all superblock
60 * copies have the creation time in s_mtime, except the first, which
61 * has the last time e2fsck or tune2fs wrote to the filesystem.
70 #include <linux/ext2_fs.h>
73 main(int argc, char *argv[])
76 int skiprate=512; /* one sector */
77 long sk=0; /* limited to 2G filesystems!! */
82 struct ext2_super_block ext2;
83 /* interesting fields: EXT2_SUPER_MAGIC
84 * s_blocks_count s_log_block_size s_mtime s_magic s_lastcheck */
88 "Usage: findsuper device [skiprate [start]]\n");
92 skiprate=atoi(argv[2]);
95 "Do you really want to skip less than a sector??\n");
101 fprintf(stderr,"Have to start at 0 or greater,not %ld\n",sk);
104 f=fopen(argv[1],"r");
110 /* Now, go looking for the superblock ! */
111 printf(" thisoff block fs_blk_sz blksz grp last_mount\n");
112 for (;!feof(f) && (i=fseek(f,sk,SEEK_SET))!= -1; sk+=skiprate){
113 if (i=fread(&ext2,sizeof(ext2),1, f)!=1) {
114 perror("read failed");
116 if (ext2.s_magic != EXT2_SUPER_MAGIC)
122 printf("%9ld %9ld %9ld %5ld %4d %s\n", sk,
123 sk/1024, ext2.s_blocks_count,
124 ext2.s_log_block_size,
125 ext2.s_block_group_nr, s);
127 printf("Failed on %d at %ld\n", i, sk);