findsuper.c, ChangeLog:
findsuper.c: Added documentation from aeb@cwi.nl; some minor code
cleanups.
diff --git a/misc/findsuper.c b/misc/findsuper.c
index 2a059f8..3a1ef3b 100644
--- a/misc/findsuper.c
+++ b/misc/findsuper.c
@@ -31,8 +31,38 @@
* Steve
* ssd@nevets.oau.org
* ssd@mae.engr.ucf.edu
+ *
*/
+/*
+ * Documentation addendum added by Andreas dwguest@win.tue.nl/aeb@cwi.nl
+ *
+ * The program findsuper is a utility that scans a disk and finds
+ * copies of ext2 superblocks (by checking for the ext2 signature; it
+ * will occasionally find other blocks that by coincidence have this
+ * signature - often these can be recognised by their ridiculous
+ * dates).
+ *
+ * For each superblock found, it prints the offset in bytes, the
+ * offset in 1024-byte blocks, the size of ext2 partition in 1024-byte
+ * blocks, the filesystem blocksize (given as log(blocksize)-10, so
+ * that 0 means 1024), the block group number (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.
+ *
+ */
+
+
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
@@ -82,15 +112,17 @@
for (;!feof(f) && (i=fseek(f,sk,SEEK_SET))!= -1; sk+=skiprate){
if (i=fread(&ext2,sizeof(ext2),1, f)!=1) {
perror("read failed");
- } else if (ext2.s_magic == EXT2_SUPER_MAGIC){
- tm = ext2.s_mtime;
- s=ctime(&tm);
- s[24]=0;
- printf("%9ld %9ld %9ld %5ld %4d %s\n", sk,
- sk/1024, ext2.s_blocks_count,
- ext2.s_log_block_size,
- ext2.s_block_group_nr, s);
}
+ if (ext2.s_magic != EXT2_SUPER_MAGIC)
+ continue;
+
+ tm = ext2.s_mtime;
+ s=ctime(&tm);
+ s[24]=0;
+ printf("%9ld %9ld %9ld %5ld %4d %s\n", sk,
+ sk/1024, ext2.s_blocks_count,
+ ext2.s_log_block_size,
+ ext2.s_block_group_nr, s);
}
printf("Failed on %d at %ld\n", i, sk);
fclose(f);