topic Re: Bad Magic number in Operating System - HP-UX

Bad Magic number

kiran bachu — Fri, 27 Sep 2002 22:36:14 GMT

With online JFS, increased the size of the filesystem from 120GB to 141GB. Then tried to take the backup of the filesystem with new size 141GB.

Our software complains - Bad magic number.

My code looks like this -
/*
* Get super block
*/
if (lseek(fd, VX_SUPERBOFF, SEEK_SET) != VX_SUPERBOFF) {
Error("Can't seek to super block: %s\n", strerror(errno));
return 1;
}
if (read(fd, (char *) psb, sizeof(*psb)) != sizeof(*psb)) {
Error("Can't read super block: %s\n", strerror(errno));
return 1;
}
/*
* Validate super block
*/

/*
* Check magic number
*/
if (psb->fs_c.fsc_magic != VX_MAGIC) {
Error("Bad super block (bad magic number)\n");
return 1;
}

Please let me know if anbody has any idea on this.

thanks
kiran

Re: Bad Magic number

James Murtagh — Sat, 28 Sep 2002 00:40:46 GMT

Hi Kiran,

First thing to check is the version of hpux and vxfs filesystem :

# uname -r
B.11.11

# fstyp -v /dev/vg00/rlvol9|grep -i version
version: 4

(lvol 9 as an example)

You need to be on at least hpux 11.00 and have vxfs version 3 or above for JFS 3.1 or 3.3 to have a filesystem over 128GB.

Next I would create a new program to print the magic numbers of the filesystem and cross check it with fsdb.

To get the fsdb output :

# echo "8b;p S" | fsdb -F vxfs /dev/vg00/rlvol9
super-block at 00000008.0000
magic a501fcf5 version 4
ctime 1030658989 334384 (Thu Aug 29 23:09:49 2002 BST)
log_version 9 logstart 0 logend 0
bsize 1024 size 36864 dsize 36864 ninode 0 nau 0
defiextsize 0 oilbsize 0 immedlen 96 ndaddr 10
aufirst 0 emap 0 imap 0 iextop 0 istart 0
bstart 0 femap 0 fimap 0 fiextop 0 fistart 0 fbstart 0
nindir 2048 aulen 32768 auimlen 0 auemlen 8
auilen 0 aupad 0 aublocks 32768 maxtier 15
inopb 4 inopau 0 ndiripau 0 iaddrlen 8 bshift 10
inoshift 2 bmask fffffc00 boffmask 3ff checksum e277df6e
free 33463 ifree 0
efree 1 3 2 1 0 3 1 2 1 2 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
flags 0 mod 0 clean 3c
time 1033171147 70001 (Sat Sep 28 00:59:07 2002 BST)
oltext[0] 33 oltext[1] 1282 oltsize 1
iauimlen 1 iausize 4 dinosize 256
checksum2 62b
checksum3 0

So you can see the magic number is a501fcf5.

You should then be able to see what variable is wrong in the code.

Regards,

James.

Re: Bad Magic number

Jeff Schussele — Sat, 28 Sep 2002 00:53:57 GMT

Hi Kiran,

James has it.
You must be >=11.0 AND >=JFS 3+ to go beyond 128Gb.

If you meet these requirements then you can go to 1Tb & up to 2Tb at best.

Check your versions as the 1st thing.

Rgds,
Jeff