fdisk writes MBR to wrong location

[Dave A <temp131 at ymail dot com>]

Attempting to use cygwin's fdisk to?create or modify the partition table (MBR) on a USB flash device, I find it isn't working right.? There's an "Error closing file" reported after a write attempt, and the program then exits.? Rerunning it,?the partition table doesn't seem changed.? Looking around on the device, I find that it appears a copy of the changed MBR did get written - 120 blocks (61440 bytes) in on the device, rather than at the beginning.? This apparently clobbers a bit of the FAT area, causing chkdsk some grief?(thanks be that at least the write seems to be?to the correct disk!).

_> /usr/sbin/fdisk /dev/sdb
Command (m for help): p
Disk /dev/sdb: 2040 MB, 2040528896 bytes
128 heads, 32 sectors/track, 973 cylinders
Units = cylinders of 4096 * 512 = 2097152 bytes
Disk identifier: 0x00035818
?? Device Boot????? Start???????? End????? Blocks?? Id? System
/dev/sdb1?? *?????????? 1???????? 973???? 1992688??? 6? FAT16
Command (m for help): d
Selected partition 1
Command (m for help): p
Disk /dev/sdb: 2040 MB, 2040528896 bytes
128 heads, 32 sectors/track, 973 cylinders
Units = cylinders of 4096 * 512 = 2097152 bytes
Disk identifier: 0x00035818
?? Device Boot????? Start???????? End????? Blocks?? Id? System
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Error closing file
__
__ 1 12:25am.? 3 172
_> dd if=/dev/sdb of=x4.mbr count=1
1+0 records in
1+0 records out
512 bytes (512 B) copied, 0.075 s, 6.8 kB/s
__
__ 0 12:35am.? 3 174
_> od -x < x4.mbr
0000000 b8fa 1000 d08e 00bc b8b0 0000 d88e c08e
0000020 befb 7c00 00bf b906 0200 a4f3 21ea 0006
0000040 be00 07be 0438 0b75 c683 8110 fefe 7507
0000060 ebf3 b416 b002 bb01 7c00 80b2 748a 8b01
0000100 024c 13cd 00ea 007c eb00 00fe 0000 0000
0000120 0000 0000 0000 0000 0000 0000 0000 0000
*
0000660 0000 0000 0000 0000 5818 0003 0000 0180
0000700 0001 7f06 cce0 0020 0000 cfe0 003c 0000
0000720 0000 0000 0000 0000 0000 0000 0000 0000
*
0000760 0000 0000 0000 0000 0000 0000 0000 aa55
0001000
__
__ 0 12:35am.? 3 175
_> dd if=/dev/sdb of=x4.mbr count=1 skip=120
1+0 records in
1+0 records out
512 bytes (512 B) copied, 0.109 s, 4.7 kB/s
__
__ 0 12:36am.? 3 176
_> od -x < x4.mbr
0000000 b8fa 1000 d08e 00bc b8b0 0000 d88e c08e
0000020 befb 7c00 00bf b906 0200 a4f3 21ea 0006
0000040 be00 07be 0438 0b75 c683 8110 fefe 7507
0000060 ebf3 b416 b002 bb01 7c00 80b2 748a 8b01
0000100 024c 13cd 00ea 007c eb00 00fe 0000 0000
0000120 0000 0000 0000 0000 0000 0000 0000 0000
*
0000660 0000 0000 0000 0000 5818 0003 0000 01000
0000700 0000 0000 0000 0000 0000 0000 0000 0000
*
0000760 0000 0000 0000 0000 0000 0000 0000 aa55
0001000
__
__ 0 12:36am.? 3 177
_> 

- Dave

Attachment: cygcheck.out
Description: Text document

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