背景：

用Virtual Box 安装Ubuntu 14:

1. 第一次，无法进入Live CD界面.
2. 第二次，勾选EFI界面后成功进入安装流程，成功安装。但是安装完成之后重启，进入了EFI Shell界面，如下:
   

解决方案:

输入：

fs:0cd EFI/ubuntugrubx64.efi

引自ServerFault:

    If you are getting to the EFI shell you likely already installed Ubuntu in EFI mode. The caveat I have found it that thought the OS installs fine using the grub-efi bootloader, an EFI boot entry for that boot loader is not written into the EFI variables correctly. This means the EFI firmware does not know how to load the boot loader and thus the OS and drops into the shell. See if you can load the boot loader and the OS from the shell:    fs0:    cd EFI/ubuntu    grubx64.efi    If this works that is definitely your issue (and mine). Supposedly the installed efibootmgr and can set this up for you but evidently is it confused in this release as it requires efivars and wants you to load this as a kernel module but in 12.04 kernels this is monolithically compiled in (meaning always in the kernel and not as a module) so it fails with an error message telling you to "modprobe efivars".

参考资料

[1] http://serverfault.com/questions/436923/how-to-install-ubuntu-server-12-04-in-a-virtualbox-vm-with-uefi-boot-enabled