Originally written: 4/19/2012; last Web page update: -6/23/2012, referencing rEFInd 0.4.4
+7/28/2014, referencing rEFInd 0.8.3 -I'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!
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Beginning with version 0.2.7, rEFInd has been able to load EFI drivers, and as of version 0.4.0, it has shipped with some EFI filesystem drivers. Although EFI implementations should be able to load drivers prior to rEFInd's launch, in my experience, most EFI implementations offer such poor control over EFI driver loading that they can't be counted on to do this. Thus, if you want to use EFI drivers, rEFInd's ability to do so can be useful. This page tells you why you might want to use drivers, how you can install and use rEFInd's own drivers, where you can go to find other drivers, and provides tips on a few specific drivers.
+EFI supports drivers, which can activate hardware or filesystems in the pre-boot environment. At the moment, EFI drivers are few and far between; but you can or might want to use them for various reasons:
Note that most of these uses are theoretical, at least to me; I don't know of any specific examples of EFI drivers (available as separate files) for disk controller hardware, network cards, or video cards. Such drivers are often embedded in the firmware of the devices themselves, and should be loaded automatically by the EFI. Chances are good that a few such drivers are available, unknown to me, and more may become available in the future. If you happen to have a device and need support for it under EFI, searching for drivers is certainly worth doing.
-To the best of my knowledge, the best reason to want EFI driver support in rEFInd is to provide access to filesystems. Although EFI filesystem driver choices are currently limited, those that are available can help to improve your installation and configuration options, particularly if you've found yourself "boxed in" by awkward installation or bugs, such as the dinky ESP that Ubuntu creates by default or the bug that prevents a Linux kernel with EFI stub loader support from booting from the ESP of at least some Macs.
+To the best of my knowledge, the best reason to want EFI driver support in rEFInd is to provide access to filesystems. Although EFI filesystem driver choices are currently somewhat limited, those that are available can help to improve your installation and configuration options, particularly if you've found yourself "boxed in" by awkward installation or bugs, such as the dinky ESP that Ubuntu creates by default or the bug that prevents a Linux kernel with EFI stub loader support from booting from the ESP of at least some Macs.
As a side note, using an ISO-9660 driver can theoretically help you keep the size of a custom Linux boot CD/DVD down to a reasonable value. This is because EFI systems normally boot from optical discs by reading a FAT image file in El Torito format and treating that file as an ESP. If you need to store the kernel both in that file and directly in the ISO-9660 filesystem (to maintain bootability on BIOS systems), that can represent an unwanted extra space requirement. Placing rEFInd and an ISO-9660 driver in the FAT image file should enable you to store the kernel on the disc only once. Unfortunately, this doesn't work in practice. When the ISO-9660 driver is loaded from the El Torito image, the driver discovers that the optical disc is in use and refuses to access it. It's possible to use EFI shell commands to give the ISO-9660 driver access to the shell device, but this causes the El Torito access to go away, which means that anything loaded from the El Torito image (such as rEFInd) is likely to malfunction. Also, some EFI implementations include ISO-9660 drivers, so you might not need a separate ISO-9660 driver if you're building a disc for a particular computer.
+All of these drivers rely on filesystem wrapper code written by rEFIt's author, Christoph Phisterer. They all suffer from speed problems on some systems, as described later in "Notes on Specific Drivers;" however, these problems are very minor on most systems.
+All of these drivers rely on filesystem wrapper code written by rEFIt's author, Christoph Phisterer.
- + -If you want to use one or more of these drivers, you can install them from the rEFInd binary package from the refind/drivers_arch directory, where arch is a CPU architecture code—x64 or ia32. The files are named after the filesystems they handle, such as ext2_x64.efi for the 64-bit ext2fs driver. You should copy the files for the filesystems you want to use to the drivers or drivers_arch subdirectory of the main rEFInd installation directory. (You may need to create this subdirectory.) Be careful to install drivers only for your own architecture. Attempting to load drivers for the wrong CPU type will cause a small delay at best, or may cause the computer to crash at worst. I've placed rEFInd's drivers in directories that are named to minimize this risk, but you should exercise care when copying driver files.
+If you want to use one or more of these drivers, you can install them from the rEFInd binary package from the refind/drivers_arch directory, where arch is a CPU architecture code—x64 or ia32. The files are named after the filesystems they handle, such as ext4_x64.efi for the 64-bit ext4fs driver. You should copy the files for the filesystems you want to use to the drivers or drivers_arch subdirectory of the main rEFInd installation directory. (You may need to create this subdirectory.) Be careful to install drivers only for your own architecture. Attempting to load drivers for the wrong CPU type will cause a small delay at best, or may cause the computer to crash at worst. I've placed rEFInd's drivers in directories that are named to minimize this risk, but you should exercise care when copying driver files.
@@ -168,25 +275,31 @@ fs0: load reiserfs_x64.efi fs0: map -r -If you build rEFInd from source, you should be aware that the drivers rely on TianoCore's development kit, whereas rEFInd itself uses GNU-EFI. Thus, to compile both, you'll need to install both development kits. Unfortunately, the TianoCore kit is a bit unusual from a Linux developer's perspective, and you'll probably have to build it from source code. Consult the BUILDING.txt file in the source package for more information. None of this is important if you use a binary build of rEFInd, unless you've obtained it from a third party who hasn't built the drivers. If that's the case, you'll have to download rEFInd from Sourceforge (see the Getting rEFInd page for details) or use drivers from another source.
- +As already noted, I know of no EFI drivers for EFI hardware, aside from those that are built into motherboards' EFI implementations. I do, however, know of a few EFI filesystem drivers, in addition to those provided with rEFInd:
Most of these cross-project drivers appear to be related, and most of them have fed into rEFInd's drivers. I used the Clover package, which in turn was based on the VirtualBox drivers, as a starting point. Everybody else has dropped rEFIt's original ReiserFS driver, but I added that back. Of these drivers, only the Clover EFI Tools NTFS driver is missing from rEFInd. Specific versions can have their own quirks, though. For instance, the Clover (and I suspect VirtualBox) drivers don't return volume labels, which causes rEFInd to display loaders on those volumes as being on a disk called Unknown. (I fixed that bug for rEFInd's version, and it wasn't present in the original rEFIt drivers.)
+Most of these cross-project drivers appear to be related, and most of them have fed into rEFInd's drivers. I used the Clover package, which in turn was based on the VirtualBox drivers, as a starting point. Everybody else has dropped rEFIt's original ReiserFS driver, but I added that back. Of these drivers, only the Clover EFI Tools NTFS driver is missing from rEFInd. Specific versions can have their own quirks, though. For instance, the Clover (and I suspect VirtualBox) drivers don't return volume labels, which causes rEFInd to display loaders on those volumes as being on a disk called Unknown. (I fixed that bug for rEFInd's version, and it wasn't present in the original rEFIt drivers.) Most of these drivers also suffer from speed problems on some computers. This is worst with the ext2fs drivers under VirtualBox; on my main computer, that combination takes 3 minutes to load a Linux kernel and initial RAM disk file! Most real computers don't suffer nearly so badly, but some can take an extra five seconds or so to boot a kernel. I've fixed the speed problems in rEFInd's drivers as of version 0.7.0.
Driver availability could increase in the future. Source code to a wide variety of filesystems is available in GRUB Legacy, GRUB 2, Linux, various BSD kernels, and in other projects. Sooner or later somebody's likely to begin porting those drivers to EFI. If you do so, or if you know of additional EFI drivers, please tell me about it, so I can share the information here. Likewise if you know of a source for other EFI drivers—say, for a video card or disk controller card.
@@ -196,19 +309,17 @@ fs0: map -rI've tested several of the drivers described on this page on a handful of systems. The ext2fs driver (from any source) works on both ext2fs and ext3fs, but not on ext4fs—at least, not in my one test. (There may be options you can use when creating an ext4 filesystem that would enable the ext2fs driver to handle it, but if so I don't know what they are.) The ReiserFS driver is obviously useful only on ReiserFS partitions. (Reiser4 is not supported, as far as I know.) Given that these filesystems are getting a bit on in age by Linux standards, you might do well to use them on a separate Linux /boot partition; however, if you're willing to use ext3fs or ReiserFS on your root (/) filesystem, you can use the EFI drivers to read your kernel from it. Note that this assumes you use conventional partitions; to the best of my knowledge, there's no EFI driver for Linux's Logical Volume Manager (LVM) or Redundant Array of Independent Disks (RAID) configurations, so the EFI can't access filesystems stored in these ways.
- -The ext2fs and ReiserFS drivers work, but they are a bit sluggish—particularly the ext2fs driver. The extent of the problem depends on the computer. In my tests so far, VirtualBox has fared the worst. On it, loading a Linux kernel with EFI stub loader from a FAT partition takes 2 seconds, from the moment of selecting the OS in rEFInd to the moment the kernel messages begin to appear. The equivalent time using ReiserFS or HFS+ is 20 seconds, and with ext2fs it's 200 seconds (that is, 3 minutes and 20 seconds). On a 32-bit Mac Mini, though, the speed problem is much less pronounced—my kernel loads in just 3 seconds from a ReiserFS partition and in 13 seconds from an ext2 filesystem. Times with ext2fs on a UEFI PC with an Intel motherboard are in the 2–4 second range. Nonetheless, if you try the ext2fs driver and it seems to hang, be patient; it may finally boot up. If so, and if the delay is too great for you to accept, you might consider using ReiserFS instead of ext2fs or ext3fs, at least if a change is practical. (For a /boot partition, it almost certainly is practical; you can back it up quite easily, create a fresh filesystem on it, and restore it. You may need to adjust your /etc/fstab entry for a new UUID value, though.) You can even use HFS+ on a Linux /boot partition, although this makes the most sense on a Mac, which has its own EFI HFS+ driver.
+I've tested several of the drivers described on this page on a handful of systems. The Pfisterer ext2fs driver (from any source) works on both ext2fs and ext3fs, but not on ext4fs—but Agner's derivative ext4fs driver handles ext4fs, so that's not a problem. The ReiserFS driver is obviously useful only on ReiserFS partitions. (Reiser4 is not supported, as far as I know.) The Btrfs driver is the newest of the lot, and so I've tested it the least, but it's worked for me on two test systems. Given that ext2fs, ext3fs, and ReiserFS are getting a bit on in age by Linux standards, you might do well to use them on a separate Linux /boot partition; however, if you're willing to use ext3fs, ext4fs, Btrfs, or ReiserFS on your root (/) filesystem, you can use the EFI drivers to read your kernel from it. Note that this assumes you use conventional partitions; to the best of my knowledge, there's no EFI driver for Linux's Logical Volume Manager (LVM) or Redundant Array of Independent Disks (RAID) configurations, so the EFI can't access filesystems stored in these ways.
-Since the ext2fs and ReiserFS drivers share a common origin, it should come as no surprise that they perform in much the same way no matter which version (rEFIt, Clover, or rEFInd) you use. One exception is that the Clover EFI Tools drivers don't deliver filesystem labels, which makes them less desirable than the rEFIt or rEFInd drivers. The NTFS driver from the Clover Tools package is nice and speedy, though, so if for some reason you need to place a boot loader on an NTFS volume, this driver might be worth tracking down.
+As noted earlier, rEFInd's drivers prior to version 0.7.0, as well as related drivers from rEFIt, Clover, and VirtualBox, suffer from speed problems. These problems are mostly minor, adding a second or two to boot times; but on some computers, the speed problems can be dramatic, boosting kernel-load times up to as much as three minutes (under VirtualBox). If you run into excessive boot times with such a driver, try switching to the latest rEFInd driver instead.
-Although both ext2fs and ReiserFS are case-sensitive, these drivers treat them in a case-insensitive way. Symbolic links work, which opens up possibilities for configuration, such as using a single kernel binary for multiple Linux distributions, with a link in one subdirectory pointing to a file in another directory. (If you try this, though, be sure to use relative links, as in ../otherdist/bzImage.efi, at least if the partition is not Linux's root filesystem.)
+Although ext2fs, ext3fs, ext4fs, and ReiserFS are all case-sensitive, these drivers treat them in a case-insensitive way. Symbolic links work; however, rEFInd 0.6.11 and later ignore symbolic links, since many distributions use them in a way that creates redundant or non-functional entries in the rEFInd menu. You should be able to use hard links if you want to use a single kernel file in multiple ways (say for two distributions).
copyright © 2012 by Roderick W. Smith
+copyright © 2012–2014 by Roderick W. Smith
This document is licensed under the terms of the GNU Free Documentation License (FDL), version 1.3.