Re: PANIC : srmountfun - Error 22

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Date: Sun, 19 Sep 2004 05:13:20 GMT

Hari wrote:
>
> I am running SCO Open Server 5.0.5 on HP Net Server E800. This morning
> i have following message on console
>
> NOTICE: Sdisk: Unrecoverable error reading SCCI disk 0 dev 1/42 (hd=0
> bus=0 id=0 lun=0) block=0
>
> Medium Error
>
> "PANIC : srmountfun - Error 22 mounting rootdev hd(1/42)

1/42 is the root file system.

> Cannot dump 32654 pages to dumpdev hd (1/41) Space for only 0 pages."
>
> Dump not completed
>
> ** Safe to Power Off **
> -or-
> ** Press Any Key to Reboot **
>
> I have searched both SCO TA's and archive of the news groups but no
> help. Could any one help me?
>
> Thanks
> Hari.

The last time I saw that message was on a client's SCO Xenix 2.3.4 system.
The message then meant that the superblock on the root file system was
corrupted. All SCO tech articles indicated that the only fix was to
boot the emergency boot floppy, divvy and create a new (empty) root
file system, and restore the root file system backup. Since my client
did not have a good root file system backup, I had to develop the
the following information and fix the problem. Once fsck was happy,
I booted the emergency boot floppy, mounted the recovered root
file system (hd0root) read-only and used cpio to back up the file system
to tape. I then used divvy to create a clean root file system and restored
the tape.

With the Xenix file system, there were only 4 important settings and
once they were fixed with the filesystem debugger (fsdb), fsck would then
rebuild the rest of the superblock. I don't know it that remains the same
for SCO 5.0.5 HTFS file system. Executing 1024p0e will display the Xenix
superblock after typing fsdb /dev/hd0root.

2000: The ISIZE of the file system
2002D: The low byte value of the FSIZE
3770D: The magic number for the file system
3774: 2 (file system type for lK file systems)

For Xenix 2.3.4 these values are determined as follows:

Boot the Xenix emergency boot floppy and execute fsdb /dev/hd0root.
To get the value for ISIZE you need only type 2i to display
the root i-node. The value labeled A0: is the starting block
of the root directory. This block is the same or one number higher
than the number of blocks for ISIZE. Enter this value in 2000
by typing 1024=1562 (Use the correct number for your system.)

The file size is determined by using the divvy command to display
the division table of the file system. The file system size to use
is the starting block number of the first division starting after
the root division. Convert this number to the high and low components
of the 32-bit integer value to be stored at 2002D. As an example: The
starting block of the next file system is 99841, subtract 65536 from
99841 and enter the result in 2002 as 34305. The number you enter
in 2004 is the whole number of times that 99841 is divided by 65536.
So the hi-byte value entered in 2004 is 1.

The "magic number" is used to identify the superblock. The
value of the magic number is arbitrary (up until it has been chosen
by the system designer) and its occurrence at address 3770D in any
other block is reported to be one chance in 4.3 billion. To find what
magic number to use is simple, just use fsdb to look at the superblock
on your emergency boot floppy. (Remember this was developed on
Xenix 2.3.4 and the magic number for SCO 5.0.5 systems may be different.)

On my client's Xenix system I found the magic number by typing 2038
and then pressing return until the display was: 003770: 052504 (21828)
and then pressing return again resulted in 003772: 000053 (43). This
representation of the magic number is more useful because you can
transfer the values inside of the parentheses directly to the hard
disk when you are ready. Pressing return again displays 03774: 000002 (2),
the indicator for the Xenix System V 1K type file system.

Credits: Before I tried this I had read the section
on fsdb in UNIX ADMINISTRATION GUIDE FOR SYSTEM V by Rebecca
Thomas and Rik Farrow.

End Xenix discussion. If you have another SCO 5.0.5 system you have the option
to install a disk and configure it to match the disk layout of the failed
system. you can then use dd if=/dev/root of=root.superblock bs=1k count=1
to copy the superblock of a good file system. Then place the root.supreblock
file on a UNIX file system floppy and use your emergency boot floppy and
boot it in the failed system. Copy the root.superblock to the failed
root file system by executing dd if=root.superblock of=/dev/hd0root bs=1k.

Use caution. A good idea is to use dd to copy the bad superblock to a file
on the unix file system floppy before you write the copied root.superblock:
dd if=/dev/hd0root of=bad.root.superblock bs=1k count=1.

I just checked 5.0.6 HTFS and found fsdb displays the superblock with
512p0e and the table becomes

1000: The ISIZE of the file system
1002D: The low byte value of the FSIZE
1770D: The magic number for the file system
1774: 2 (file system type for lK file systems)

On 5.0.6 /dev/root /dev/u and /dev/app1 the magic
number and file system type is as follows:

001770: 044452 (18730)
001772: 120140 (41056)
001774: 000002 (2

Type 1016=18730 [Enter]
     1018=41056 [Enter]
     1020=2 [Enter]

--
                                      Steve Fabac
                                       S.M. Fabac & Associates
                                        816/765-1670

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