Bootable system from the hard drive, good bootable floppy w/kernel, win95 boot disk w/ fdisk, bootnet.img installation diskette(RH6.2), clean MBR, LILO installed on /boot (primary partition marked active).
fdisk -l /dev/sda
Disk /dev/sda: 64 heads, 32 sectors, 1001 cylinders
Units = cylinders of 2048 * 512 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 33 63 31744 83 Linux
/dev/sda2 64 1001 960512 5 Extended
/dev/sda3 1 32 32752 12 Compaq diagnostics
/dev/sda5 64 264 205808 82 Linux swap
/dev/sda6 265 1001 754672 83 Linux
Boot Sector on active partition is corrupt, clean MBR:
I then zero'd out the MBR and got the following message:
Non-System disk or disk error
replace and strike any key when ready
_
I then booted to my Linux boot diskette. After it loaded the SCSI driver from the diskette, I received:
SCSI device sda: hdwr sector= 512 bytes. Sectors= 2051000 [1001 MB] [1.0GB]
sda: unknown partition table
autodetecting RAID arrays
autorun ...
... autorun DONE.
VFS: Cannon open root device 08:06
Kernel panic: VFS: Unable to mount root fs on 08:06
I then booted to my Linux network installation diskette (bootnet.img). Found the NIC, found the SCSI driver, went through custom. Custom showed the following message:
Bad Partition Table
The partition table on device sda is
corrupted. To create new partitions
it must be initialized, causing the
loss of ALL DATA on this drive.
"INITIALIZE" "SKIP DRIVE"
I switched over to the BASH screen (Alt+F2) and ran fdisk:
fdisk /tmp/sda
Device contains neither a valid DOS partition table, nor Sun or SGI disklabel
Building a new DOS disklabel. Changes will remain in memory only,
until you decide to write them. After that, of course, the previous
content won't be recoverable.
Command (m for help): _
Printing the partition gives the following result:
Disk /tmp/sda: 33 heads, 61 sectors, 1018 cylinders
Units = cylinders of 2013 * 512 bytes
Device Boot Start End Blocks Id System
I created the partitions exactly as they existed before (I printed out a listing of the partitions before I zero'd the MBR.); however, the drive geometry is different.
Here is the new printout from fdisk:
Disk /tmp/sda: 33 heads, 61 sectors, 1018 cylinders
Units = cylinders of 2013 * 512 bytes
Device Boot Start End Blocks Id System
/tmp/sda1 * 33 63 31744 83 Linux
/tmp/sda2 64 1001 960512 5 Extended
/tmp/sda3 1 32 32752 12 Compaq diagnostics
/tmp/sda5 64 264 205808 82 Linux swap
/tmp/sda6 265 1001 754672 83 Linux
I wrote this out and rebooted. The geometry of the two do not match; however, I want to see if it will come up. I received the blinking cursor in the upper left corner on the next boot up.
_
After reading the man page on fdisk for Linux, I realized that it will assume its own geometry if fdisk for Linux is the first utility to partition the disk. In my example, where I have no partitions, fdisk for Linux created its own geometry assignments.
I then zero'd out the MBR (ran through network install up to the point where the SCSI driver was loaded, I inserted an ext2 floppy containing dd, mounted it [mknod /tmp/fd0 b 2 0; mkdir /adir; mount /tmp/fd0 /adir], and then zero'd the MBR).
After zeroing the MBR, I ran win95 fdisk /mbr.
After running Win95's fdisk /mbr, I then recreated the fdisk partitions using Linux (again, using the RedHat 6.2 installation CD to do this). Here's a listing of partitions under Linux after zeroing the MBR, and running Win95's fdisk /mbr:
Command (m for help): p
Disk /tmp/sda: 64 heads, 32 sectors, 1001 cylinders
Units = cylinders of 2048 * 512 bytes
Device Boot Start End Blocks Id System
/tmp/sda1 * 1 1001 1025008 e Win95 FAT16 (LBA)
Command (m for help): _
After deleting this partition and recreating the partitions exactly as before, here's a printout again of the correct partitions on my hard drive (and the correct geometry):
Command (m for help): p
Disk /tmp/sda: 64 heads, 32 sectors, 1001 cylinders
Units = cylinders of 2048 * 512 bytes
Device Boot Start End Blocks Id System
/tmp/sda1 * 33 63 31744 83 Linux
/tmp/sda2 64 1001 960512 5 Extended
/tmp/sda3 1 32 32752 12 Compaq diagnostics
/tmp/sda5 64 264 205808 82 Linux swap
/tmp/sda6 265 1001 754672 83 Linux
I wrote this table out and rebooted. The system came up just fine once again off of the hard drive.
********Currently working on this section********
so in desaster recovery, you need to know the drive geometry, a partition printout with starting and ending cylinder values and partition types, a copy of your /etc/fstab, /etc/lilo.conf.
********Currently working on this section********
I then booted to a Win95 boot disk and ran "fdisk /mbr" and got the following message:
Starting MS-DOS
I then booted back to Linux and reran "/sbin/lilo" and got the following message:
The following error was generated by having a zero'd out MBR:
Non-System disk or disk error
replace and strike any key when ready
_
Also /sbin/lilo complained with the following message:
To remedy this, use fdisk to mark the /boot partition active.
After correcting this
Starting MS-DOS...
Oops, I guess the MBR contains the partition table as well...
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P R E C A U T I O N A R Y S T E P S T O T A K E B E F O R E
A L T E R I N G T H E M B R
Preparation steps to take before altering the MBR:
This section below is under construction. I don't have time to finish it up now, but the information above is pretty valuable, so I decided to go ahead and push what I have to the web.
********Currently working on this section********
so in desaster recovery, you need to know the drive geometry, a partition printout with starting and ending cylinder values and partition types, a copy of your /etc/fstab, /etc/lilo.conf.
********Currently working on this section********
I then booted to a Win95 boot disk and ran "fdisk /mbr" and got the following message:
Starting MS-DOS
I then booted back to Linux and reran "/sbin/lilo" and got the following message:
The following error was generated by having a zero'd out MBR:
Non-System disk or disk error
replace and strike any key when ready
_
Also /sbin/lilo complained with the following message:
To remedy this, use fdisk to mark the /boot partition active.
After correcting this
Starting MS-DOS...
Oops, I guess the MBR contains the partition table as well...
