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Old 06-19-2007, 04:09 AM   #1
ahpin
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How to Remove MBR from /dev/cciss/ filesystem


Can anyone tell me how can i remove the MBR from /dev/cciss filesystem in SUSE built? The purpose is to do it remotely so that when we reboot the server, it can automatically boot up from PXE instead of local drive.

Thanks
 
Old 06-19-2007, 07:19 AM   #2
pixellany
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Am I correct that cciss has to do with a RAID setup?

With a regular drive, you would not "remove the MBR". The MBR is defined as the first sector of the disk and normally contains boot code (which can be removed using "dd if=/dev/zero of=dev/xxx bs=446 count=1") I don't know if this is applicable to a RAID setup.

To see what is in the first sector of /dev/cciss, do "dd if=/dev/cciss bs=512 count=1 | hexdump -C | more" If you don't recognize this as boot code, post the first few lines here.
 
Old 06-19-2007, 08:28 PM   #3
ahpin
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it is running on RAID 0. It is still no go.

#dd if=/dev/cciss/c0d0p1 bs=512 count=1 | hexdump -C | more
1+0 records in
1+0 records out
00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
*
00000200

or

# dd if=/dev/cciss/c0d0 bs=512 count=1 | hexdump -C | more
1+0 records in
1+0 records out
00000000 eb 48 90 10 8e d0 bc 00 b0 b8 00 00 8e d8 8e c0 |.H..............|
00000010 fb be 00 7c bf 00 06 b9 00 02 f3 a4 ea 21 06 00 |...|.........!..|
00000020 00 be be 07 38 04 75 0b 83 c6 10 81 fe fe 07 75 |....8.u........u|
00000030 f3 eb 16 b4 02 b0 01 bb 00 7c b2 80 8a 74 03 02 |.........|...t..|
00000040 ff 00 00 80 80 ec 04 00 00 08 fa 80 ca 80 ea 53 |...............S|
00000050 7c 00 00 31 c0 8e d8 8e d0 bc 00 20 fb a0 40 7c ||..1....... ..@||
 
Old 06-19-2007, 10:39 PM   #4
pixellany
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Well, the 2nd 1 is not grub--hard to say what...

BUT--I asked for this to be run on /dev/cciss (without the partition part) If in fact this device behaves as a drive, then the MBR is the 1st sector of the device--not the partitions.
 
Old 06-20-2007, 04:53 AM   #5
ahpin
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# dd if=/dev/cciss bs=512 count=1 | hexdump -C | more
dd: reading `/dev/cciss': Is a directory
0+0 records in
0+0 records out

it will not recognised at all...
 
Old 06-23-2007, 08:54 PM   #6
pixellany
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OK---so I am in over my head... What IS /dev/cciss???
 
Old 06-23-2007, 10:53 PM   #7
jschiwal
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Can you select boot from network or PXE as the boot device in the bios?

The grub info manual has a section on booting from the network (section 6).
 
Old 06-23-2007, 11:08 PM   #8
Quakeboy02
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/dev/cciss/c0d0 is the drive
/dev/cciss/c0d0p1 is the first partition on the drive

If you really really truly and honestly want to clear the MBR, then you want to use

dd of=/dev/cciss/c0d0 if=/dev/null bs=446 count=1

I Strongly recommend that you give up on this idea. It is dangerous to the health of your array, and possibly your system if you type it wrong or if this isn't really the device you want to mess up, err change. I can't see ANY positive to it. But, there's the command if you absolutely insist.
 
  


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