HELP -Bad Magic Number in super block

HELP -Bad Magic Number in super block

Post by Michael Cubste » Wed, 28 Jul 1999 04:00:00



I've been trying off an on in my spare time to load linux R5 onto my mac
7600

But every time I get to the graphical installer  and try to mount and
format the screen comes up blank.

Also I can see the partions I created for UNIX_SRV2 with Pdisk for the
MAC OS, But If I run Pdisk from the linux Install CD, it cant even see
the hard drive, what am I doing wrong??

Thanks
Michael

 
 
 

HELP -Bad Magic Number in super block

Post by Ralph Umar Miranda I » Thu, 29 Jul 1999 04:00:00



> I've been trying off an on in my spare time to load linux R5 onto my mac
> 7600

> But every time I get to the graphical installer  and try to mount and
> format the screen comes up blank.

> Also I can see the partions I created for UNIX_SRV2 with Pdisk for the
> MAC OS, But If I run Pdisk from the linux Install CD, it cant even see
> the hard drive, what am I doing wrong??

> Thanks
> Michael

    I would suggest using fdisk within the installer to take care of the
partitioning. I tried out pdisk, but couldn't firgure it out =) fdisk
worked just fine for me.
    Later.

--
=======================================
Ralph Miranda, a.k.a.: "Umar"
Unreal, Quake 'x', Falcon 4.0... you name it!

 
 
 

HELP -Bad Magic Number in super block

Post by Michael Cubste » Thu, 29 Jul 1999 04:00:00


Thanks I'll give it a try

[This followup was posted to comp.os.linux.powerpc and a copy was sent to
the cited author.]


says...


> > I've been trying off an on in my spare time to load linux R5 onto my mac
> > 7600

> > But every time I get to the graphical installer  and try to mount and
> > format the screen comes up blank.

> > Also I can see the partions I created for UNIX_SRV2 with Pdisk for the
> > MAC OS, But If I run Pdisk from the linux Install CD, it cant even see
> > the hard drive, what am I doing wrong??

> > Thanks
> > Michael

>     I would suggest using fdisk within the installer to take care of the
> partitioning. I tried out pdisk, but couldn't firgure it out =) fdisk
> worked just fine for me.
>     Later.

> --
> =======================================
> Ralph Miranda, a.k.a.: "Umar"
> Unreal, Quake 'x', Falcon 4.0... you name it!

 
 
 

1. Bad magic number in super-block / Group descriptors look bad

Hi,

Ever found yourself in this situation ?
You've had a power-failure or just did something very bad with your
harddisk
and now when trying to mount it fsck screams:

Group descriptors look bad... trung backup blocks....
/sbin/e2fsck: Bad magic number in super-block while trying to open
/dev/hdb1

I've had this problem 2 times before now, and i've had a hell of a
time finding any docs related. I DID eventually find this:
(Note: text below is copy-pasted together from several articles, and
so not
 written by myself...)

----- begin of article pastes ----------------

From MANPAGES of mke2fs:

-S
Write superblock and group descriptors only. This is useful if all of
the superblock and backup superblocks are corrupted,
 and a last-ditch recovery method is desired. It causes mke2fs to
reinitialize the superblock and group descriptors, while not
 touching the inode table and the block and inode bitmaps. The e2fsck
program should be run immediately after this option is used,
 and there is no guarantee that any data will be salvageable.

Ofcourse you're should only try this when you've exhausted all other
options.
Other options are:

fsck -b 32 /dev/hdb1  (use the first backup super-block)

To determine the locations of the backup superblocks:
# newfs -N /dev/r

    Caution: Use the "N" option. If the "n" option is used, the
filesystem
             may be destroyed.

Example using fsck on a backup superblock:

     /dev/rsd1a:   204540 sectors in 974 cylinders of 6 tracks, 35
sectors
     104.7MB in 61 cyl groups (16 c/g, 1.72MB/g, 768 i/g)
     super-block backups (for fsck -b #) at:
     32, 3440, 6848, 10256, 13664, 17072, 20480, 23888, 26912,
     30320, 33728, 37136, 40544, 43952, 47360, 50768, 53792, 57200,
     60608, 64016, 67424, 70832, 74240, 77648, 80672, 84080, 87488,
     90896, 94304, 97712, 101120, 104528, 107552, 110960, 114368,
117776,
     121184, 124592, 128000, 131408, 134432, 137840,141248, 144656,
148064,
     151472, 154880, 158288, 161312, 164720, 168128, 171536, 174944,
178352,
     181760, 185168, 188192, 191600, 195008, 198416, 201824,

         In this example, 201824 is the last backup superblock
location
         198416 is the next to last backup superblock location.

------------- end of article pastes --------------
Also it's interesting to note that it seems the larger the disk
the less backup super-block are stored.. I my case, on a 40 GB Maxtor:

32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632,
2654208, 4096000

where the only backups, (the newfs command mentioned above, was not
installed here, and i could not find it anywhere) i learned this only
after mk2fs told me after it had written the new super-block to my
disk...

Hope this helpes some people !

Best regards,

Jan Wilmans

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