Lost parbreastion table

Bruce

Try changing your master boot record (MBR) by hand First, as root dd if=-dev-hdc of=cmbr bs=512 count=1 this places a copy of your MBR into "cmbr" Then use this command to see the parbreastion table part of the MBR: od -v -A x -t x1 -N 512dev-hdc Here is a sample output of the lines containing the parbreastion table.

0001b0 01 00 00 00 01 00 00 00 02 00 00 00 b0 4b 00 01 0001c0 01 00 83 fe ff ff 3f 00 00 00 4f a6 bd 0d 00 fe 0001d0 ff ff 82 fe ff ff 8e a6 bd 0d 33 91 3b 00 00 00 0001e0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 aa

See the 55 aa, that's a magic number that marks the end of the MBR. just in front of that are 4 sets of parbreastion table entries. Each entry is 16 bytes. So the above parbreastion table breaks down to this:

End of MBR code - ignore 0001b0 01 00 00 00 01 00 00 00 02 00 00 00 b0 4b Parbreaston 1 00 01 0001c0 01 00 83 fe ff ff 3f 00 00 00 4f a6 bd 0d Parbreastion 2 00 fe 0001d0 ff ff 82 fe ff ff 8e a6 bd 0d 33 91 3b 00 Parbreastion 3 00 00 0001e0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Parbreastion 4 00 00 0001f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Magic number - ignore 55 aa

A parbreastion table entry has the following form: Number of Bytes Description 1 Active flag 3 CHS begin 1 Type 3 CHS end 4 LBA start 4 length

What you want to do is: 1) put '00' in the active flag byte, you probably don't want this as a boot parbreastion. 2) put 'ffffff' in the 3 bytes for CHS start and CHS end, this tells linux to ignore them (DOS uses these but not newer OS's). 3) put '83' in the type byte, this sets the parbreastion type to ext2-3. 4) reverse the order of bytes for start and length. Thus my parbreastion 1 starts at sector 0x0000003f (63) and it has a length of 0x0dbda64f (230532687), each sector is 512 bytes, so this works out to about 110GB (118 billion bytes). If your damaged parbreastion is hdc1, put 0x3f in your start field, reversing the byte order. Calculate the length by subtracting the start value for the next parbreastion from this start value. This is your length. Put it in the length field, reversing the byte order. If your damaged parbreastion is hdc2, hdc3 or hdc4, add the previous parbreastion's start and length values. Enter this in your start field, reversing the byte order. If a parbreastion follows this one, use the same method as above to find the length value. If ther is no following parbreastion you'll have to guess the length. 120GB, has 251658240 (0x0f00000) sectors.

That's as far as I can take you. Someone else may be able to help you guess your parbreastion length from the location of backup superblocks.

Good luck, I hate to see data lost.

Duane Evenson

PS In case you're wondering, the second parbreastion is a little 2GB swap parbreastion.