Ubuntu – Are there any drawbacks to legacy BIOS as opposed to UEFI


Are there any drawbacks to installing Ubuntu 13.10 (and soon 14.04) in Legacy BIOS instead of UEFI? I have installed 13.10 64bit in Legacy by mistake and was just wondering if it would hurt anything to simply leave it there as is?


Everything seems to be running just fine in Legacy and all my drivers work.

Best Answer

The main points are:

  • EFI-mode booting can be faster. The difference can be several seconds, contrary to what K. Darien Freeheart wrote, but the difference also varies from one computer to another; on some computers, the speed benefit can be non-existent. The effect is felt mainly in the firmware initialization, not in the Linux boot process itself.
  • An EFI-mode boot gives the OS access to certain EFI features. Today, the biggest of these is the ability to control the firmware's built-in boot manager, via the Linux efibootmgr utility. The kernel can also log crash data in NVRAM, but that's mainly of interest to developers. In the future, the number of things that can be done with an EFI-mode boot from a booted Linux distribution may increase.
  • The much-maligned Secure Boot can actually provide some security benefits, if you choose to configure it properly. You might never need or notice these benefits, but if, at some point in the future, some pre-boot malware spreads and can infect Linux-based computers, you might be glad to have Secure Boot active.
  • EFI provides new and different boot manager and boot loader options. In addition to GRUB, which is available for both BIOS and EFI, you can use rEFInd or gummiboot to choose the OS, and ELILO or the EFI stub loader to boot the kernel. See my page on EFI boot loaders for Linux for more on this topic.
  • On some computers, booting from a GPT disk in BIOS mode requires jumping through some extra hoops. Thus, booting in EFI mode may save you a bit of effort if you've got an over-2TiB disk or if you just plain like GPT.

Overall, these benefits are unlikely to be compelling for most people. Fortunately, switching boot modes is pretty easy. You can try it on a single-boot basis with most computers by preparing a CD-R or USB flash drive with my rEFInd boot manager. Boot to it and it should detect your Linux kernel(s) and let you boot it/them. (If you use a separate /boot partition, though, you'll need to add a root={whatever} kernel option by hitting F2 or Insert twice once you highlight the kernel.)

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