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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 1/16/2013, referencing rEFInd 0.6.5</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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  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 <div style="float:right; width:55%">
  94
  95 <p>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.</p>
  96
  97 </div>
  98
  99 <div class="navbar">
 100
 101 <h4 class="tight">Contents</h4>
 102
 103 <ul>
 104
 105 <li class="tight"><a href="#why">Why Should You Use Drivers?</li>
 106
 107 <li class="tight"><a href="#using">Using rEFInd's EFI Drivers</a></li>
 108
 109 <li class="tight"><a href="#finding">Finding Additional Drivers</a></li>
 110
 111 <li class="tight"><a href="#notes">Notes on Specific Drivers</a></li>
 112
 113 </ul>
 114
 115 </div>
 116
 117 <br/>
 118 <a name="why">
 119 <h2>Why Should You Use EFI Drivers?</h2>
 120 </a>
 121
 122 <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>
 123
 124 <ul>
 125
 126 <!-- <p class="sidebar"><b>Tip:</b> Some Linux installation media come as <i>hybrid ISO</i> files, which can be written to either optical discs or USB flash drives for installation. Some of these media, though, are useless for installing to EFI systems from USB flash drives&mdash;unless your computer supports ISO-9660 on non-optical media. rEFInd's ISO-9660 driver provides this support. To use such a hybrid image from USB flash drive, you must boot using rEFInd on another disk that has the ISO-9660 driver installed. rEFInd should then provide an option to boot from the USB flash drive. I cannot guarantee that the installer will boot at this point, but it might.</p> -->
 127
 128 <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>
 129
 130 <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>
 131
 132 <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>
 133
 134 <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>
 135
 136 </ul>
 137
 138 <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>
 139
 140 <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="http://www.rodsbooks.com/efi-bootloaders/efistub.html">EFI stub loader support</a> from booting from the ESP of at least some Macs.</p>
 141
 142 <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, 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.</p>
 143
 144 <a name="using">
 145 <h2>Using rEFInd's EFI Drivers</h2>
 146 </a>
 147
 148 <p class="sidebar"><b>Note:</b> If you want to use the drivers with a Mac, be sure to use at least version 0.4.3. Earlier versions were incompatible with the Mac's EFI 1.x firmware. Alternatively, you can use the drivers that came with <a href="http://refit.sourceforge.net">rEFIt,</a> which work on Macs.</p>
 149
 150 <p>Since version 0.4.0, rEFInd has shipped with a small collection of read-only EFI filesystem drivers. These are:</p>
 151
 152 <ul>
 153
 154 <li><b>ReiserFS</b>&mdash;This driver originated with rEFIt. It's useful
 155     for reading Linux kernels from a separate <tt>/boot</tt> partition, or
 156     even from a root (<tt>/</tt>) filesystem, if you use ReiserFS on it.
 157     <b>Caution:</b> If you use this driver, you should use the
 158     <tt>notail</tt> option in Linux's <tt>/etc/fstab</tt> file for the
 159     partition(s) you want the EFI to read. This is because the driver
 160     doesn't properly handle ReiserFS's "tail-packing" feature, so files can
 161     seem to be corrupted in EFI if you use this feature, which is disabled
 162     by <tt>notail</tt>.</li>
 163
 164 <li><b>Ext2fs</b>&mdash;This driver also originated with rEFIt. It can be
 165     used in the same way as the ReiserFS driver. Although it's called an
 166     "ext2fs" driver, it also works with ext3fs.</li>
 167
 168 <li><b>Ext4fs</b>&mdash;Stefan Agner <a
 169     href="https://github.com/falstaff84/rEFInd">modified the rEFIt/rEFInd
 170     ext2fs driver</a> so that it could handle ext4fs. I'm including this as
 171     a separate driver from the ext2fs driver, although the ext4fs version
 172     can handle ext2fs and ext3fs, too. (I may eventually retire the
 173     original ext2fs driver, but I want to be conservative about this in
 174     case there's an undiscovered problem with the new driver.) This driver
 175     has some limitations. Most notably, for various reasons it maxes out at
 176     16TiB and won't mount any ext4 filesystem that's larger than this. As
 177     of version 0.6.1, this driver supports the <tt>meta_bg</tt> feature,
 178     which can also be used on ext2fs and ext3fs. Thus, it can handle some
 179     ext2fs and ext3fs partitions that the ext2fs driver can't handle. You
 180     can learn about your ext2/3/4 filesystem features by typing <tt
 181     class="userinput">dumpe2fs <i>/dev/sda2</i> | grep features</tt>,
 182     changing <tt class="userinput"><i>/dev/sda2</i></tt> to your
 183     filesystem's device.</li>
 184
 185 <li><b>ISO-9660</b>&mdash;This driver originated with rEFIt's author, but
 186     he never released a final version. Its code was improved by Oracle for
 187     use in its VirtualBox product, and then further modified by the authors
 188     of the <a
 189     href="https://sourceforge.net/projects/cloverefiboot/">Clover</a> boot
 190     loader. If your firmware doesn't provide its own ISO-9660 driver, this
 191     one can be helpful; however, you may need to install it on your hard
 192     disk before you can read an optical disc.</li>
 193
 194 <li><b>HFS+</b>&mdash;Oracle seems to have written this driver, apparently
 195     with some code taken from open source Apple examples. It was then
 196     further modified by the Clover authors. I expect this driver to have
 197     limited appeal to most rEFInd users. Macs don't need it, since Apple's EFI
 198     implementation provides its own HFS+ driver, and HFS+ isn't normally
 199     used on UEFI-based PCs. Some CDs are mastered with both ISO-9660 and
 200     HFS+, or even with HFS+ alone, and it's conceivable that an HFS+ driver
 201     would be useful when accessing such discs. I'm providing the driver
 202     mainly because it compiled cleanly with no extra work, aside from
 203     providing a Makefile entry for it.</li>
 204
 205 </ul>
 206
 207 <p>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 <a href="#notes">"Notes on Specific Drivers;"</a> however, these problems are very minor on most systems.</p>
 208
 209 <p class="sidebar"><b>Note:</b> rEFInd's <tt>install.sh</tt> script does not install drivers by default on OS X, but on Linux, it installs the driver required to read the <tt>/boot</tt> directory, if one is available. The script installs all the available drivers if you pass it the <tt>--drivers</tt> option. See the <a href="installing.html">Installing rEFInd</a> page for details.</p>
 210
 211 <p>If you want to use one or more of these drivers, you can install them from the rEFInd binary package from the <tt>refind/drivers_<tt class="variable">arch</tt></tt> directory, where <tt class="variable">arch</tt> is a CPU architecture code&mdash;<tt>x64</tt> or <tt>ia32</tt>. The files are named after the filesystems they handle, such as <tt>ext4_x64.efi</tt> for the 64-bit ext4fs driver. You should copy the files for the filesystems you want to use to the <tt>drivers</tt> or <tt>drivers_<tt class="variable">arch</tt></tt> 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.</p>
 212
 213 <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>
 214
 215 <p>When you reboot after installing drivers, rEFInd should automatically detect and use the drivers you install. There's likely to be an extra delay, typically from one to five seconds, as rEFInd loads the drivers and tells the EFI to detect the filesystems they handle. For this reason, and because of the possibility of drivers harboring bugs, I recommend installing only those drivers that you need. If you like, you can install drivers you don't plan on using to some other directory, such as <tt>/drivers</tt> on the ESP's root. You can then load these drivers manually with the EFI shell's <tt>load</tt> command if the need arises in the future. You can then tell the shell to re-assign drive identifiers with <tt>map -r</tt>:</p>
 216
 217 <pre class="listing">
 218 fs0: <tt class="userinput">load reiserfs_x64.efi</tt>
 219 fs0: <tt class="userinput">map -r</tt>
 220 </pre>
 221
 222 <a name="finding">
 223 <h2>Finding Additional EFI Drivers</h2>
 224 </a>
 225
 226 <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, in addition to those provided with rEFInd:</p>
 227
 228 <ul>
 229
 230 <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, originally written by Christoph Pfisterer. 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>
 231
 232 <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. These drivers served as a starting point for rEFInd's drivers.</li>
 233
 234 <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_r447_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>
 235
 236 <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>
 237
 238 <li><b>Ext2Pkg</b>&mdash;This driver, based on <a href="https://bitbucket.org/alinrus/ext2pkg">bitbucket</a> and with a backup on <a href="https://github.com/the-ridikulus-rat/Tianocore_Ext2Pkg">github,</a> appears to be an ext2fs/ext3fs driver built independently of the driver written by Christoph Pfisterer. The linked-to sites provide access to source code via <tt>git</tt> but do not provide binaries. When I built binaries, they failed to work. Under VirtualBox, the driver loaded but then hung when I tried to access an ext2 filesystem. On a 32-bit Mac Mini, I got error messages when I tried to access an ext2 filesystem. As I write, the code was last updated in March of 2012. If you check the project and it's been updated more recently, it might be worth trying. Otherwise, I can't recommend this driver. I mention it here only in case it improves in the future.</li>
 239
 240 </ul>
 241
 242 <p>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 <tt>Unknown</tt>. (I fixed that bug for rEFInd's version, and it wasn't present in the original rEFIt drivers.)</p>
 243
 244 <p>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 <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>
 245
 246 <p>Once you've obtained an EFI driver, you can install it in rEFInd just as you would install rEFInd's own drivers, as described earlier.</p>
 247
 248 <a name="notes">
 249 <h2>Notes on Specific Drivers</h2>
 250 </a>
 251
 252 <p>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&mdash;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.) 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 <tt>/boot</tt> partition; however, if you're willing to use ext3fs, ext4fs, or ReiserFS on your root (<tt>/</tt>) 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.</p>
 253
 254 <p>The Pfisterer ReiserFS and ext2fs drivers work, but they are a bit sluggish&mdash;particularly the ext2fs driver. The Agner ext4fs driver, when handling an actual ext4 filesystem, is in-between these two drivers in speed. 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, with ext4fs it's 75 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. Speeds were similar with my newest computer, an ASUS P8H77-I board. Times with ext2fs on a UEFI PC with an Intel motherboard are in the 2&ndash;4 second range. 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 ext4fs or 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. As noted earlier, be sure to use <tt>notail</tt> as an option in <tt>/etc/fstab</tt> for ReiserFS if you want to read it from EFI.) You can even use HFS+ on a Linux <tt>/boot</tt> partition, although this makes the most sense on a Mac, which has its own EFI HFS+ driver. Of course, you can also create a FAT <tt>/boot</tt> partition and not deal with drivers at all. Mounting your ESP at <tt>/boot</tt> is a practical solution for many users.</p>
 255
 256 <p>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. The NTFS driver from the Clover Tools package is nice and speedy, so if for some reason you need to place a boot loader on an NTFS volume, this driver might be worth tracking down.</p>
 257
 258 <p>Although ext2fs, ext3fs, ext4fs, and ReiserFS are all 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>
 259
 260 </ul>
 261
 262 <hr />
 263
 264 <p>copyright &copy; 2012&ndash;2013 by Roderick W. Smith</p>
 265
 266 <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>
 267
 268 <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>
 269
 270 <p><a href="index.html">Go to the main rEFInd page</a></p>
 271
 272 <p><a href="linux.html">Learn about how to adjust rEFInd's appearance</a></p>
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