no such disk error occured. I tried to format and reinstall 12.04, the problem remained. I also repaired with boot-repair, the problem remained. http://paste.ubuntu.com/1224005/ is url of the details. server is dell R710, the bios is set to uefi and disk is raid0 gpt. I typed commands in grub rescue: ls (hd0, gpt2), `no such partition' is shown set, `prefix=((null),gpt2)/grub' is shown I don't know why /efi/ubuntu/grubx64.efi doesn't recognize disk. another strange thing is that there is only 1 file in /efi/ubuntu