begin Friday 16 April 2004 04:27, Donald Teed quote:
When cmp -l was used to compare the compressed image files, they were mostly the same except for about 7 bytes around the beginning - I didn't let it finish but waited for about 15 minutes and there were no new differences reported. So that confirms what I suspected - that the partition table was getting corrupted.
This is very interesting. Now, if we could also have the exact output of cmp -l, it would be great! My theory about what happens is that on first boot, the BIOS changes these for some strange reason. Maybe, for some yet unknown reason, the BIOS thinks that the disk needs "initializing" and resets those bytes which might contain certain settings that it thinks are his. It might be interesting to find out _when_ exactly they change. One method is to run a "hexdump -n 512 /dev/hda" on the disk at various stages of the duplication. This prints out a hexdump of the first 512 bytes. Then just check whether the 7 bytes have their "good" state or the changed state. N.B. You can run this command right after the udp-receive without rebooting by pressing Alt-F2 and pressing return. This gives you a shell where you can run various commands. You can get back to the menu with Alt-F1 You may need to prefix the command with the word "busybox": busybox hexdump -n 512 /dev/hda You can also specify an offset: busybox hexdump -n 256 -s 256 /dev/hda This prints out the bytes 256 til 511 (practical to print out only around the offset where you expect the change, so you don't need to wade through 32 lines of output...). My gut feeling is that right after udp-receive, you find the 7 bytes in their "original" (good) state, but that they are change after first reboot. Or maybe, they only change for certain kinds of reboot (i.e. they remain untouched for network boot, but change when attempting to boot from the disk). I think we can reasonably rule out the following hypothesises: - Network transfer corruption: No, because then lzop compression would fail in a *very* obvious way (and corruption would be randomly spread accross the whole disk, rather than limited to 7 bytes somewhere in the MBR / partition table) - Hard disk read or write corruption: If that was the case, corruption would be spread out evenly accross the whole disk - Different interpretation of hard disk geometry: We would see corruption near the end of the disk, rather than near the beginning. Regards, Alain _______________________________________________ Udpcast mailing list Udpcast@udpcast.linux.lu http://udpcast.linux.lu/mailman/listinfo/udpcast