Originally written: 3/14/2012; last Web page update: -12/11/2012, referencing rEFInd 0.5.1
+8/25/2013, referencing rEFInd 0.7.4I'm a technical writer and consultant specializing in Linux technologies. This Web page is provided free of charge and with no annoying outside ads; however, I did take time to prepare it, and Web hosting does cost money. If you find this Web page useful, please consider making a small donation to help keep this site up and running. Thanks!
@@ -26,49 +26,87 @@ href="mailto:rodsmith@rodsbooks.com">rodsmith@rodsbooks.comBefore you invest time in downloading and trying to install rEFInd, you may want to verify that you can actually use the program at all. rEFInd is useful only on EFI-based computers, not older BIOS-based computers. In fact, most EFI-based x86-64 computers provide a Compatibility Support Module (CSM), which is essentially a BIOS emulation mode. Some EFI implementations are in fact built atop a conventional BIOS, and retain BIOS's boot abilities via this underlying code. Thus, it's possible that you're currently booting a modern EFI-capable computer in BIOS mode.
+Unfortunately, determining which mode you're using can be tricky; the clues are subtle or hidden in ways that require specialized knowledge to extract. This page will help you figure it out. I first present general information on identifying your hardware's capabilities. I then describe ways to identify your current boot mode in both Linux and Windows.
+Let's get the easy case out of the way: If you have a Macintosh with an Intel CPU, it's got EFI capabilities, and you'll be able to use rEFInd. Earlier Macs with PowerPC CPUs use OpenFirmware, and rEFInd can't be used with them.
@@ -108,13 +168,15 @@ href="mailto:rodsmith@rodsbooks.com">rodsmith@rodsbooks.comA casual reader might easily overlook this option, or misinterpret it to mean that the feature is much less important than it is. In fact, this particular motherboard offers very poor control over its EFI vs. BIOS booting features. (See my Web page on this EFI implementation for details.)
-Some manuals omit even mention of EFI, and instead refer to "legacy boot" or some similar term, referring to BIOS-style booting. Such references may imply that the firmware supports EFI booting if the "legacy boot" mode is disabled or restricted in some way.
+Some manuals omit even mention of EFI, and instead refer to "legacy boot" or some similar term, referring to BIOS-style booting. The firmware for my ASUS P8H77-I motherboard uses the technical term CSM, which of course will be baffling to the uninitiated. (I referred to it earlier. It's the Compatibility Support Module—in other words, the BIOS support code.) Such references may imply that the firmware supports EFI booting if the "legacy boot" mode is disabled or restricted in some way.
Understated EFI features often indicate a slapdash approach to EFI. Such systems sometimes implement EFI as a layer atop a conventional BIOS. More modern EFIs, though, completely replace the BIOS. Some manufacturers, such as ASUS and its sibling ASRock, are now actively promoting their more advanced EFI implementations. Such products often come with flashy new GUIs in their firmware.
Positive identification of EFI support in your firmware does not guarantee that your current OSes are booting in EFI mode. (Mac OS X booting on a Mac is an exception to this rule, though.) For that, you'll need to run some tests in your running OSes.
+Identifying your boot mode in Linux is relatively straightforward. The simplest way is to check for the presence of a /sys/firmware/efi directory. The mere existence of this directory indicates that the computer has booted in EFI mode. Its absence suggests a BIOS-mode boot—but see below for an important caveat.
@@ -147,9 +209,13 @@ href="mailto:rodsmith@rodsbooks.com">rodsmith@rodsbooks.comI've actually cut quite a few lines from this output; there are a total of 60 EFI: mem## lines on this computer. (Another of my computers has 148 such lines!) A BIOS-based computer will lack most or all of these lines, and certainly the EFI: mem## lines. I've heard of some BIOS-based computers that produce the final EFI Variables Facility line, though.
-One caveat exists to these tests: It's possible to boot Linux in EFI mode but disable the EFI features that create the /sys/firmware/efi directory and the copious EFI output in dmesg. This can happen because your kernel was compiled without EFI support or because you've added the noefi line to your existing BIOS boot loader configuration. To the best of my knowledge, no major Linux distribution ships with EFI support disabled in either of these ways, so chances are your tests won't mislead you to thinking you're using BIOS mode unless you've recompiled your kernel or deliberately added a noefi parameter to your boot loader configuration.
+One caveat exists to these tests: It's possible to boot Linux in EFI mode but disable the EFI features that create the /sys/firmware/efi directory and the copious EFI output in dmesg. This can happen because your kernel was compiled without EFI support or because you've added the noefi line to your existing BIOS boot loader configuration. Some of these features will also be absent if the efivars driver is not built into the kernel and is not loaded as a module. Typing modprobe efivars should load this module, so you might try that before concluding you've booted in BIOS mode. To the best of my knowledge, no major Linux distribution ships with EFI support disabled in any of these ways, so chances are your tests won't mislead you to thinking you're using BIOS mode unless you've recompiled your kernel or deliberately added a noefi parameter to your boot loader configuration.
+Another way to identify your boot mode is to examine your partitions. Microsoft has tied use of the GUID Partition Table (GPT) to EFI booting. If you've booted from a GPT disk, then you must be using EFI, and if you've booted from a Master Boot Record (MBR) disk, you must have booted in BIOS mode. Therefore, you can check your partition table type as a proxy for your boot mode. To do this in Windows 7, follow these steps:
+The most reliable way I know of to identify your boot mode is to examine your partitions. Microsoft has tied use of the GUID Partition Table (GPT) to EFI booting. If you've booted from a GPT disk, then you must be using EFI, and if you've booted from a Master Boot Record (MBR) disk, you must have booted in BIOS mode. Therefore, you can check your partition table type as a proxy for your boot mode. To do this in Windows 7, follow these steps:
copyright © 2012 by Roderick W. Smith
+copyright © 2012–2013 by Roderick W. Smith
This document is licensed under the terms of the GNU Free Documentation License (FDL), version 1.3.