I have a dual-boot system, with the first partition as 100gb NTFS for Windows 7, then a 200mb partition for /boot, then the rest of the partitions for Fedora 12.

It was all installed and working fine, but for reasons I don't know, grub.conf suddenly was a blank file, and when I booted the system, I just got the grub prompt, and I can boot Windows by manually typing root (hd0,0) and chainloader +1.

Booting into Fedora is a bigger pain because I don't know the full kernel string and all that.

Doing find grub.conf returns (hd0,1), which is right. So I do root (hd0,1), then setup (hd0), it says it worked, but if I reboot, still get the grub prompt.

If I boot using the Fedora 12 CD to "rescue" an installed system, i cat /boot/grub/grub.conf and it's still blank. I try to run the setup in the recovery shell as well (after chrooting to the local install), and grub.conf remains blank.

Any ideas? Or is my best bet to try and rebuild the file from hand? But that begs the question why did the file blank in the first place and why won't grub fix it?

p.s. This acutally happened once before shortly after I had installed F12, but I don't remember how I fixed it... it just suddenly seemed to start working again hah

boot in rescue mode with install dvd/cd and then chroot to your fedora system and then
#grub-install /dev/sda

Well, the grub-install command completes successfully, but doesn't make a grub.conf file either.

An interesting note, if I run grub from the recovery console (after chrooting to the local disk) and then do root (hd0,1) and then setup (hd0) it says it worked.

However, if I manually enter the command
install /grub/stage1 (hd0) (hd0,1)1+26 p (hd0,1)/grub/stage2 grub/grub.conf
I get "Error 1: Invalid device requested"
I tried toying around with the command a little bit to see if I could figure it out, but I dunno what device it's looking for and where it's looking for it in that string....

Hmm... I think I'm gunna give a crack at just remaking the grub.conf file myself and see if I can get into fedora and have that make the conf file the way it wants it....

Fedora 12 still uses the 0.9... version of grub.

grub.conf should be in /boot/grub

File a bug report at redhat bugzilla