I was playing with grub on my computer a bit more. Then I tried to reboot and I can't enter my operating systems (windows and Ubuntu). It looks like I've rewritten something very important because it only shows me grub command line and I don't know how it boot. I've tried to set root and then load vmlinuz, but it tells me that I need to specify some root option correctly. I was doing a lot of things with grub and I don't remember every think. I just remember that I tried something like grub-mkconfig recheck. I was also editing grub.cfg. I have also tried to read grub.cfg by cat and it looks normally.
closed as not a real question by Tom Brossman, Ringtail, hhlp, fossfreedom♦ Dec 16 '12 at 0:31
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Have you tried to boot with a LiveCD, and fix with Boot-Repair?
It is straightforward to use, and worked for me before.
and it allows yo to change kernel options as well: