Very Computer

by **Huang Zhong-Yu** » Tue, 21 Jan 1997 04:00:00

Does anyone know how to rescure (or mount) a corrupted filesystem with
the following message:

unable to read superblock.

I believe the hdisk is still working properly.

Thanks in advance...

Tiong Guan

by **Thijs_Po** » Wed, 22 Jan 1997 04:00:00

Quote:Zhong-Yuan) writes:
> Does anyone know how to rescure (or mount) a corrupted filesystem with
> the following message:

> unable to read superblock.

> I believe the hdisk is still working properly.

> Thanks in advance...

Find out which raw device contains the filesystem. (/dev/rhd... see
/etc/filesystems).
Block 1 is the superblock, and block 31 contains a copy of it.
You could extract block 31 with dd or a little C program, and copy it
over block 1, also with dd (I do not remember the exact options, it is
some time ago I did this) or with the following C program.
You can then run fsck over it and the filesystem may mount again.

In any case, BE VERY CAREFUL !!
Good luck, Thijs.

/***************************************************

putblock.c
puts a block of data into a file

usage: putblock blocknr file < blockfile

Thijs Post, 07-Nov-1994

***************************************************/

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>

#define BLOCKSIZE 4096

void MyUsage(void);

char block[BLOCKSIZE];

int main( int argc, char *argv[] ) {

int blocknr;
char *file;
int fd;
int bytesread, byteswritten;

/* check arguments */
if( argc != 3 ) { MyUsage(); }
sscanf(argv[1],"%d",&blocknr);
file = argv[2];

/* read data from stdin */
bytesread = fread( block, 1, BLOCKSIZE, stdin );
if( bytesread != BLOCKSIZE ) {
fprintf(stderr,"fread returned %d, should be BLOCKSIZE\n",bytesread);
exit(2);
}

/* open file */
if( (fd = open(file,O_WRONLY,0)) <= 0 ) {
fprintf(stderr,"Could not open %s\n",file);
exit(2);
}

/* seek the block */
if( lseek(fd,blocknr*BLOCKSIZE,SEEK_SET) < 0 ) {
fprintf(stderr,"Lseek failed\n");
exit(2);
}

/* write it */
byteswritten = write(fd,block,BLOCKSIZE);
fprintf(stdout,"bytes written: %d\n",byteswritten);

/* close the file */
close(fd);

Quote:}

void MyUsage(void) { /* writes Usage message to stderr and exits */
fprintf(stderr,"Usage: putblock blocknr file < blockfile\n");
exit(1);

Quote:}

--

Systems group fax: +31 20 525 5788
Faculty of Mathematics, Computer Science, Physics and Astronomy
Univ. of Amsterdam, Valckenierstraat 65, NL-1018 XE Amsterdam, The Netherlands

by **Schwitter Rued** » Wed, 22 Jan 1997 04:00:00

> Does anyone know how to rescure (or mount) a corrupted filesystem with
> the following message:

> unable to read superblock.

> I believe the hdisk is still working properly.

> Thanks in advance...

> Tiong Guan

try the fsck (FileSystemCheck). Normaly, when there is a SuperBlock
wrong, you can fix ist with the -b Option. See the man-pages

--
Regards Ruedi

----------------------------------------------------------------

Haselstrasse Fax: ++41 56 205 54 66
CH-5400 Baden
---------------------------------------------------------------

by **Huang Zhong-Yu** » Thu, 23 Jan 1997 04:00:00

Thank you for those who had replied to me.
Any way the IBM engineer said the hard disk was corrupted.
Nonething can be done to save the data.
He evantually changed a new hard disk for me.
Luckily (!?) it is still under warrenty (just 3 months old).

Anybody have any recommendation for IBM compatible SCSI HDD
(internal or external). IBM original just too ex.

Regards,
Tiong Guan