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   7   <title>The rEFInd Boot Manager: Using EFI Drivers</title>
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  12   <h1>The rEFInd Boot Manager:<br />Using EFI Drivers</h1>
  13
  14   <p class="subhead">by Roderick W. Smith, <a
  15 href="mailto:rodsmith@rodsbooks.com">rodsmith@rodsbooks.com</a></p>
  16
  17 <p>Originally written: 4/19/2012; last Web page update:
  18 5/9/2012, referencing rEFInd 0.3.4</p>
  19
  20
  21 <p>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!</p>
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  86
  87 <hr />
  88
  89 <p>This page is part of the documentation for the rEFInd boot manager. If a Web search has brought you here, you may want to start at the <a href="index.html">main page.</a></p>
  90
  91 <hr />
  92
  93 <p>Beginning with version 0.2.7, rEFInd has been able to load EFI drivers. Although EFI implementations should be able to do this 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, where you can go to find them, and provides tips on a few specific drivers.</p>
  94
  95 <h2>Why Should You Use EFI Drivers?</h2>
  96
  97 <p>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:</p>
  98
  99 <ul>
 100
 101 <li>You can load a filesystem driver to gain access to files on a filesystem other than FAT (or HFS+ on Macs or ISO-9660 on some systems). This is most likely to be useful on a Linux installation, since a filesystem driver can enable you to store a Linux kernel with EFI stub loader or for use by ELILO on a Linux-native filesystem if your ESP is getting crowded.</li>
 102
 103 <li>You can load a driver for a plug-in disk controller to give the EFI access to its disks. Note that this is <i>not</i> required if you place your boot loader (and perhaps your OS kernel) on another disk, or if the plug-in disk controller includes EFI-capable firmware. It could be handy, perhaps in conjunction with a filesystem driver, to enable the EFI to read a boot loader or kernel from a disk on a plug-in controller, though.</li>
 104
 105 <li>You can load a driver for a plug-in network card to enable the computer to boot from the network, or to access the network without booting an OS. Note that rEFInd does not currently support network boots itself, though.</li>
 106
 107 <li>You can load a video card driver to set an appropriate video mode or to support a plug-in card that lacks EFI support in ts own firmware.</li>
 108
 109 </ul>
 110
 111 <p>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.</p>
 112
 113 <p>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 <a href="efistub.html">EFI stub loader support</a> from booting from the ESP of at least some Macs.</p>
 114
 115 <p>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, my attempts to get this to work have failed to date. When the ISO-9660 driver is loaded from the El Torito image, my test systems seem to allow only one of the two filesystems (the El Torito image's FAT filesystem or the optical disc's ISO-9660 filesystem) to be active; load one and the other goes away. 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.</p>
 116
 117 <h2>Finding and Installing EFI Drivers</h2>
 118
 119 <p>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:</p>
 120
 121 <ul>
 122
 123 <li><b><a href="http://refit.sourceforge.net">rEFIt's ext2fs and ReiserFS drivers</a></b>&mdash;You can gain read-only access to ext2fs, ext3fs, and ReiserFS volumes with these drivers. You can use the binaries in the <tt>refit-bin-0.14/efi/tools/drivers</tt> directory of the binary package directly on a Mac. On a UEFI-based PC, though, you'll need to break the Mac-style "fat" binary into its 32- and 64-bit components. You can use my <a href="http://www.rodsbooks.com/thin/index.html"><tt>thin</tt></a> program for this job.</li>
 124
 125 <li><b><a href="https://sourceforge.net/projects/cloverefiboot/">Clover EFI's ISO-9660, ext2fs, and HFS+ drivers</a></b>&mdash;This project is an offshoot of TianoCore, the main UEFI project. It's primarily a Hackintosh boot loader, but it includes drivers for <a href="http://cloverefiboot.svn.sourceforge.net/viewvc/cloverefiboot/VBoxFsDxe/">ISO-9660, ext2fs, and HFS+;</a> however, building them requires a fair amount of expertise. You can find a compile script for the ISO-9660 driver <a href="https://github.com/the-ridikulus-rat/My_Shell_Scripts/blob/master/tianocore_uefi/iso9660_virtualbox_x86_64_udk_linux_compile.sh">here,</a> and a compiled ISO-9660 binary <a href="http://dl.dropbox.com/u/9710721/VBoxIso9600.efi">here.</a> The compiled binary has worked in a brief test; however, it didn't give access to the ISO-9660 filesystem when it was loaded from an El Torito image the ISO-9660 filesystem held.</li>
 126
 127 <li><b><a href="http://www.osx86.net/view/2571-clover_v2_r384__efi_bootloader_pkg_+_gpt_efi_tools.html">Clover's EFI Tools package</a></b>&mdash;This osx86.net thread includes links to a package called <tt>EFI_Tools_Clover_v2_r384_EFI_x32_x64_EN.zip</tt>, which holds an OS X application (a directory with a <tt>.app</tt> extension, as seen from other platforms) with a number of drivers in the <tt>Contents/Resources/EFI/drivers64</tt> directory (and an equivalent for 32-bit binaries). Some of these, such as keyboard drivers, are unlikely to be useful unless your system is badly broken as delivered. Three that caught my eye, however, are <tt>VBoxExt2-64.efi</tt>, <tt>NTFS-64.efi</tt>, and <tt>VBoxIso9600-64.efi</tt>.</li>
 128
 129 <li><b><a href="https://www.virtualbox.org/browser/vbox/trunk/src/VBox/Devices/EFI/Firmware2/VBoxPkg/VBoxFsDxe">VirtualBox's HFS+ and ISO-9660 drivers</a></b>&mdash;These drivers are available in source code form, and come with VirtualBox binaries. I've not attempted to compile them myself, but I've seen a report that suggests they may include assumptions that require use of <a href="http://www.mingw.org/">MinGW,</a> a GCC-based compiler for Windows (and cross-compiler to build Windows executables under Linux). I don't know of a source for binaries suitable for use on EFI-based computers; if you want to use them, you'll need to figure out how to compile them yourself.</li>
 130
 131 </ul>
 132
 133 <p>Most of these cross-project drivers appear to be related. For instance, the ISO-9660 drivers are both based on code written by Christoph Phisterer for rEFIt (although he doesn't seem to have finished and released it in binary form himself).</p>
 134
 135 <p>As you can see, pickings are rather slim. Nonetheless, the drivers that exist are useful for certain purposes. The options could increase in the future, too. 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 <a href="mailto:rodsmith@rodsbooks.com">tell me about it,</a> so I can share the information here. Likewise if you know of a source for other EFI drivers&mdash;say, for a video card or disk controller card.</p>
 136
 137 <p class="sidebar"><b>Warning:</b> <i>Do not</i> place EFI program files in your driver directories! Unfortunately, EFI uses the same <tt>.efi</tt> filename extension to identify both EFI program files and EFI drivers. Therefore, rEFInd can't distinguish between the two prior to loading them, and if you place program files in a drivers directory, rEFInd will run the EFI program file when it does its driver scan.</p>
 138
 139 <p>Once you've obtained an EFI driver or two, you can install it in rEFInd by creating a subdirectory of the rEFInd directory called <tt>drivers</tt>&mdash;for instance, <tt>EFI/refind/drivers</tt>, if you've installed rEFInd to <tt>EFI/refind</tt> on the ESP. Alternatively, you can create a directory of any other name and use the <tt>scan_driver_dirs</tt> option in <tt>refind.conf</tt> to tell rEFInd where to look for drivers. Either way, rEFInd attempts to load all the EFI drivers from these directories, so placing your files there and rebooting will do the trick.</p>
 140
 141 <p>rEFInd is likely to take slightly longer to start up when you use drivers, but the effect is likely to be small. On my systems, it's usually just a second or so. This effect could be greater with some drivers or on some systems, though.</p>
 142
 143 <h2>Notes on Specific Drivers</h2>
 144
 145 <p>I've tested the original rEFIt drivers on a handful of systems. First let me re-emphasize one point: To use rEFIt's ext2fs and ReiserFS drivers on a UEFI-based PC, you must separate the x86 and x86-64 binaries from the "fat" binary format that come in the binary package. You can do this with my <a href="http://www.rodsbooks.com/thin/index.html"><tt>thin</tt></a> program.</p>
 146
 147 <p>The rEFIt ext2fs driver works on both ext2fs and ext3fs, but not on ext4fs&mdash;at least, not in my one test. (There may be options you can use when creating an ext4 filesystem that would enable the rEFIt 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 <tt>/boot</tt> partition; however, if you're willing to use ext3fs or ReiserFS on your root (<tt>/</tt>) filesystem, you can use the rEFIt 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.</p>
 148
 149 <p>The ext2fs and ReiserFS drivers work, but they are a bit sluggish&mdash;particularly the ext2fs driver. The extent of the problem depends on the computer. In my tests so far, VirtualBox has fared the worse. 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 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&mdash;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 were also reasonable, although I didn't record precise values. 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 <tt>/boot</tt> 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 <tt>/etc/fstab</tt> entry for a new UUID value, though.)</p>
 150
 151 <p>The Clover EFI Tools ext2fs driver performs much like the rEFIt ext2fs driver, but it doesn't deliver a filesystem label, which makes it less desirable. The NTFS driver from this 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.</p>
 152
 153 <p>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 <i>relative</i> links, as in <tt>../otherdist/bzImage.efi</tt>, at least if the partition is not Linux's root filesystem.)</p>
 154
 155 </ul>
 156
 157 <hr />
 158
 159 <p>copyright &copy; 2012 by Roderick W. Smith</p>
 160
 161 <p>This document is licensed under the terms of the <a href="FDL-1.3.txt">GNU Free Documentation License (FDL), version 1.3.</a></p>
 162
 163 <p>If you have problems with or comments about this Web page, please e-mail me at <a href="mailto:rodsmith@rodsbooks.com">rodsmith@rodsbooks.com.</a> Thanks.</p>
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