Help! Computer won't boot

[Sureshot324]

I was trying to update my installation of Fedora core 2 to kernel 2.6.7, and after a reboot i got the error message "Error loading operating system". Now i cannot boot into windows xp or linux. My main hard drive is a 120gb and had Win XP and Fedora Linux on it. My second hard drive is a 60gb which is dynamic disk.

The last thing i did before the reboot was edit the grub configuration file so that the 2.6.7 kernel would use a ramdisk, since it wasn't working before. Also a while earlier I executed the following statement trying to resolve a problem i had:

dd if=/dev/zero of=/dev/hda bs=1022k count=1000

This is the site that got that statement from. Apparently it changes something in the master boot record, and in retrospect executing this statement was probably a stupid idea.

I assumed that the problem was that my mbr got messed up somehow, so i put in my windows xp cd and executed fixmbr. It gave me a warning that the computer appears to have a non-standard or invalid master boot record and that continuing could damage my partition table. I ran it anyway but my computer still wouldn't boot. I went back into the winxp recovery console and ran partdisk and was shocked to see that hard disk 0 (the 120gb) is all unpartitioned space!

Is there any way to fix my boot sector so that my windows xp and linux partitions work again? Or at least get the data of the windows xp partition?

[mugstar]

This is a known bug. Explanation and solution here: http://lwn.net/Articles/86835/

I'm not sure if what you've already done will have smoked it or not - you can but try. Good luck.

[variant]

The link mugstar posted does not aply to this situation whatsoever.

[Sureshot324]

Yeah i don't think it's the same thing because a can't even get to the bootloader and my partition table seems to be messed up.

[Dolda2000]

Wow! You wrote a GB of zeroes over the start of your hard drive?! Why would you do such a thing? No wonder it doesn't boot!

That way, you didn't just toast your MBR and partition table - you also toasted the better part of the beginning of your first partition: at the very least the superblock and allocation bitmaps.

I'm sorry to tell you, but if you don't have your previous partition layout written down somewhere, there's nothing to do anymore (OK, that's saying too much, but any possible solutions would be really hardcore). Unless you had valuable data on any partition, just give up and reinstall.

[Dolda2000]

I just read the text on that link, and I found that it didn't apply to your situation to begin with. However, the author of that text should be shot for not having a large warning sign when giving such a dangerous command.

[Sureshot324]

Ok, i repartioned and formatted and managed to save almost all my data with a data recovery program, so it didn't turn out too badly. The reason this happened is when i tried to make a ramdisk for the new kernel, i was getting a an error message that said "/usr/2.6.7 is not a directory" or something (it was actually 2.6.75, d'oh!). That site seemed to have a solution for this exact problem and i thought whatever it did the the mbr could be fixed with fixmbr.

However, the author of that text should be shot for not having a large warning sign when giving such a dangerous command.

So should the person who made that command which can easily zero out your entire hard drive without so much as a confirmation message!

[Dolda2000]

Well, dd isn't really something you use by accident, after all, especially not with the kind of redirection. ;-)

dd is just a data streamer - it copies a given amount of data from one file to another (it's kind of like cat, except you can make it stop after a fixed amount of data, and you can apply certain data transformation rules to the data it streams). /dev/zero is a magic file that generates zero bytes when a program reads it, and as you should know, /dev/hda is a magic file that corresponds to your hard drive. That's why /dev/hda only is available to root. ;-)