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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 6/8/2014, referencing rEFInd 0.8.2</p>
  19
  20
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 124
 125 <hr />
 126
 127 <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>
 128
 129 <hr />
 130
 131 <div style="float:right; width:55%">
 132
 133 <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>
 134
 135 </div>
 136
 137 <div class="navbar">
 138
 139 <h4 class="tight">Contents</h4>
 140
 141 <ul>
 142
 143 <li class="tight"><a href="#why">Why Should You Use Drivers?</li>
 144
 145 <li class="tight"><a href="#using">Using rEFInd's EFI Drivers</a></li>
 146
 147 <li class="tight"><a href="#finding">Finding Additional Drivers</a></li>
 148
 149 <li class="tight"><a href="#notes">Notes on Specific Drivers</a></li>
 150
 151 </ul>
 152
 153 </div>
 154
 155 <br/>
 156 <a name="why">
 157 <h2>Why Should You Use EFI Drivers?</h2>
 158 </a>
 159
 160 <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>
 161
 162 <ul>
 163
 164 <!-- <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> -->
 165
 166 <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>
 167
 168 <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>
 169
 170 <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>
 171
 172 <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>
 173
 174 </ul>
 175
 176 <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>
 177
 178 <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 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 <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>
 179
 180 <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>
 181
 182 <a name="using">
 183 <h2>Using rEFInd's EFI Drivers</h2>
 184 </a>
 185
 186 <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>
 187
 188 <p>Since version 0.4.0, rEFInd has shipped with a small collection of read-only EFI filesystem drivers. These are:</p>
 189
 190 <ul>
 191
 192 <li><b>ReiserFS</b>&mdash;This driver originated with rEFIt. It's useful
 193     for reading Linux kernels from a separate <tt>/boot</tt> partition, or
 194     even from a root (<tt>/</tt>) filesystem, if you use ReiserFS on it.
 195     <b>Caution:</b> If you use this driver, you should use the
 196     <tt>notail</tt> option in Linux's <tt>/etc/fstab</tt> file for the
 197     partition(s) you want the EFI to read. This is because the driver
 198     doesn't properly handle ReiserFS's "tail-packing" feature, so files can
 199     seem to be corrupted in EFI if you use this feature, which is disabled
 200     by <tt>notail</tt>.</li>
 201
 202 <li><b>Ext2fs</b>&mdash;This driver also originated with rEFIt. It can be
 203     used in the same way as the ReiserFS driver. Although it's called an
 204     "ext2fs" driver, it also works with ext3fs.</li>
 205
 206 <li><b>Ext4fs</b>&mdash;Stefan Agner <a
 207     href="https://github.com/falstaff84/rEFInd">modified the rEFIt/rEFInd
 208     ext2fs driver</a> so that it could handle ext4fs. I'm including this as
 209     a separate driver from the ext2fs driver, although the ext4fs version
 210     can handle ext2fs and ext3fs, too. Providing both drivers enables
 211     easy filesystem separation&mdash;for instance, you can use ext2fs on a
 212     <tt>/boot</tt> partition and ext4fs on your root (<tt>/</tt>)
 213     partition, to have the EFI scan only the former. This driver has some
 214     limitations. Most notably, for various reasons it maxes out at 16TiB
 215     and won't mount any ext4 filesystem that's larger than this. As of
 216     version 0.6.1, this driver supports the <tt>meta_bg</tt> feature, which
 217     can also be used on ext2fs and ext3fs. Thus, it can handle some ext2fs
 218     and ext3fs partitions that the ext2fs driver can't handle. You can
 219     learn about your ext2/3/4 filesystem features by typing <tt
 220     class="userinput">dumpe2fs <i>/dev/sda2</i> | grep features</tt>,
 221     changing <tt class="userinput"><i>/dev/sda2</i></tt> to your
 222     filesystem's device.</li>
 223
 224 <li><b>Btrfs</b>&mdash;</b>Samuel Liao contributed this driver, which is
 225     based on the rEFIt/rEFInd driver framework and algorithms from the GRUB
 226     2.0 Btrfs driver. I've tested this driver with a simple one-partition
 227     filesystem and with a filesystem that spans two physical devices
 228     (although I've made no attempt to ensure that the driver can actually
 229     read files written to both devices). Lamuel Liao has used the driver
 230     with a compressed Btrfs volume. The driver will handle subvolumes, but
 231     you may need to add kernel options if you're booting a Linux kernel
 232     directly from a filesystem that uses subvolumes. For instance, on a
 233     test installation of Ubuntu 14.04 alpha on such a system, I needed to
 234     set <tt>also_scan_dirs + @/boot</tt> in <tt>refind.conf</tt> and add
 235     <tt>rootflags=subvol=@</tt> to the kernel options in my
 236     <tt>refind_linux.conf</tt> file. Without the first of these options,
 237     rEFInd could not locate my kernel; and without the second, the boot
 238     failed with a message to the effect that the initial RAM disk could not
 239     find <tt>/sbin/init</tt>.</li>
 240
 241 <li><b>ISO-9660</b>&mdash;This driver originated with rEFIt's author, but
 242     he never released a final version. Its code was improved by Oracle for
 243     use in its VirtualBox product, and then further modified by the authors
 244     of the <a
 245     href="https://sourceforge.net/projects/cloverefiboot/">Clover</a> boot
 246     loader. If your firmware doesn't provide its own ISO-9660 driver, this
 247     one can be helpful; however, you may need to install it on your hard
 248     disk before you can read an optical disc.</li>
 249
 250 <li><b>HFS+</b>&mdash;Oracle seems to have written this driver, apparently
 251     with some code taken from open source Apple examples. It was then
 252     further modified by the Clover authors. I expect this driver to have
 253     limited appeal to most rEFInd users. Macs don't need it, since Apple's EFI
 254     implementation provides its own HFS+ driver, and HFS+ isn't normally
 255     used on UEFI-based PCs. Some CDs are mastered with both ISO-9660 and
 256     HFS+, or even with HFS+ alone, and it's conceivable that an HFS+ driver
 257     would be useful when accessing such discs. I'm providing the driver
 258     mainly because it compiled cleanly with no extra work, aside from
 259     providing a Makefile entry for it.</li>
 260
 261 </ul>
 262
 263 <p>All of these drivers rely on filesystem wrapper code written by rEFIt's author, Christoph Phisterer.</p>
 264
 265 <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>
 266
 267 <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>
 268
 269 <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>
 270
 271 <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>
 272
 273 <pre class="listing">
 274 fs0: <tt class="userinput">load reiserfs_x64.efi</tt>
 275 fs0: <tt class="userinput">map -r</tt>
 276 </pre>
 277
 278 <a name="finding">
 279 <h2>Finding Additional EFI Drivers</h2>
 280 </a>
 281
 282 <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>
 283
 284 <ul>
 285
 286 <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. As a practical matter, there's no advantage to using these drivers over rEFInd's drivers, since the latter are updated versions of the former.</li>
 287
 288 <li><b><a href="https://sourceforge.net/projects/cloverefiboot/">Clover EFI's ISO-9660, ext2fs, ext4fs, 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, ext4fs, and HFS+;</a> however, building them requires a fair amount of expertise. These drivers served as a starting point for rEFInd's drivers, except for the ext4fs driver, which the Clover developers based on rEFInd's ext4fs driver. Thus, as with the rEFIt drivers, there's likely to be no advantage to using the Clover drivers over the rEFInd drivers.</li>
 289
 290 <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_r1888_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>VBoxIso9600-64.efi</tt>, and <tt>NTFS-64.efi</tt>. The first two of those are presumably variants on rEFInd's drivers, but the NTFS driver is not. I don't know this driver's provenance, so I'm reluctant to recommend its use, but it bears mentioning.</li>
 291
 292 <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. As noted earlier, rEFInd's drivers are closely related to these.</li>
 293
 294 <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>
 295
 296 <li><b>Paragon's UFSD</b>&mdash;According to <a href="http://blog.paragon-software.com/?p=2951">this blog post,</a> Paragon Software has ported its <a href="http://www.paragon-software.com/technologies/ufsd.html">Universal File System Drivers (UFSD)</a> to EFI, providing "transparent access to NTFS, HFS+, ExFAT, and ExtFS" (sic). The entry doesn't provide any download links, and it's unclear if the product is (or will be) available for free or on a pay basis. I haven't tried these drivers, so I can't comment on their quality.</li>
 297
 298 </ul>
 299
 300 <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.) 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.</p>
 301
 302 <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>
 303
 304 <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>
 305
 306 <a name="notes">
 307 <h2>Notes on Specific Drivers</h2>
 308 </a>
 309
 310 <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.) 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 <tt>/boot</tt> partition; however, if you're willing to use ext3fs, ext4fs, Btrfs, 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>
 311
 312 <p>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.</p>
 313
 314 <p>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).</p>
 315
 316 </ul>
 317
 318 <hr />
 319
 320 <p>copyright &copy; 2012&ndash;2014 by Roderick W. Smith</p>
 321
 322 <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>
 323
 324 <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>
 325
 326 <p><a href="index.html">Go to the main rEFInd page</a></p>
 327
 328 <p><a href="linux.html">Learn about how to adjust rEFInd's appearance</a></p>
 329
 330   <p><a href="http://www.rodsbooks.com/">Return</a> to my main Web page.</p>
 331 </body>
 332 </html>