[ubuntu] uefi does not show anything

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http://ubuntuforums.org – I have a dell inspiron 15r.Installed on Ubuntu 13.04 64 bit.I was trying to repair my ubuntu via harddisc boot(iso file)(added a menu item to grub2).Ubuntu booted from iso file.I chose "erase ubuntu and reinstall".Then it said something like this:device ... is mounted.unmount the device.Then i tried to umount but it said:device is busy.Then i forced to unmount with Code: umount -f -a / .Then when i restarted th pc, there is nothing in uefi booting menu.before that there was an ubuntu choice in uefi booting menu.So i can not drop into a terminal or linux console.i can not do any (Hardware)