This can work fine if Linux is your only OS, but it complicates the boot process if you're dual-booting with Windows in EFI mode. In particular, it's far too easy to accidentally boot your Linux installation medium in BIOS/CSM/legacy mode, which will result in a BIOS/CSM/legacy-mode installation of Linux. when it boots in BIOS (aka CSM or legacy) mode. This can be a great convenience because it provides backwards compatibility but it also creates complications because there's no standardization in the rules and user interfaces for controlling when a computer boots in EFI mode vs. The USB flash drive or CD-R image of rEFInd is a good choice for this test.īefore proceeding further, you should understand that most EFIs on x86 and x86-64 computers include a component known as the Compatibility Support Module (CSM), which enables the EFI to boot OSes using the older BIOS-style boot mechanisms. You can also try booting a medium that contains only an EFI-mode boot loader. (Searching a PDF of your user manual can be a quick way to do this.) If you find no such references, your computer probably uses an old-style ('legacy') BIOS but if you find references to these terms, it almost certainly uses EFI. If you're uncertain about your computer's EFI support status, you should check your firmware setup utility and your user manual for references to EFI, UEFI, or legacy booting. A few PCs sold prior to 2011 also support EFI, although most such computers boot in BIOS mode by default. Beginning in late 2012, most computers that ship with Windows 8 or later boot using UEFI by default, and in fact most PCs released since mid-2011 use UEFI, although they may not boot in EFI mode by default. This task is best handled from OS X by using the Mac's bless utility, which I don't describe here.ĮFI has been used on Intel-based Macs since they were first introduced in 2006. Although much of this page applies to Macs, some details differ, particularly when it comes to setting up EFI boot loaders. Note: The EFI that Apple uses on Macs is unusual in many respects. I consider this usage confusing, so I avoid it in my view, EFIs and BIOSes are two different types of firmware. Note that most manufacturers use the term 'BIOS' to refer to their EFIs. (A partial exception to this rule is described shortly.) This difference can greatly complicate the design of OS installation media, but it has little effect on the day-to-day operation of the computer, once everything is set up and running.

Most importantly, the firmware controls the computer's boot process, which in turn means that EFI-based computers boot differently than do BIOS-based computers. Oops: Converting a Legacy-Mode Install to Boot in EFI ModeĮFI is a type of firmware, meaning that it's software built into the computer to handle low-level tasks.

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