]> code.delx.au - refind/blob - docs/refind/linux.html
Version 0.7.7 full release
[refind] / docs / refind / linux.html
1 <?xml version="1.0" encoding="utf-8" standalone="no"?>
2 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
3 "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
4
5 <html xmlns="http://www.w3.org/1999/xhtml">
6 <head>
7 <title>The rEFInd Boot Manager: Methods of Booting Linux</title>
8 <link href="../Styles/styles.css" rel="stylesheet" type="text/css" />
9 </head>
10
11 <body>
12 <h1>The rEFInd Boot Manager:<br />Methods of Booting Linux</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: 3/19/2012; last Web page update:
18 1/3/2014, referencing rEFInd 0.7.7</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>
22
23 <table border="1">
24 <tr>
25 <td>Donate $1.00</td>
26 <td>Donate $2.50</td>
27 <td>Donate $5.00</td>
28 <td>Donate $10.00</td>
29 <td>Donate $20.00</td>
30 <td>Donate another value</td>
31 </tr>
32 <tr>
33
34 <td>
35 <form action="https://www.paypal.com/cgi-bin/webscr" method="post">
36 <input type="hidden" name="cmd" value="_donations">
37 <input type="hidden" name="business" value="rodsmith@rodsbooks.com">
38 <input type="hidden" name="lc" value="US">
39 <input type="hidden" name="no_note" value="0">
40 <input type="hidden" name="currency_code" value="USD">
41 <input type="hidden" name="amount" value="1.00">
42 <input type="hidden" name="item_name" value="rEFInd Boot Manager">
43 <input type="hidden" name="bn" value="PP-DonationsBF:btn_donate_LG.gif:NonHostedGuest">
44 <input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_donate_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
45 <img alt="Donate with PayPal" border="0" src="https://www.paypalobjects.com/en_US/i/scr/pixel.gif" width="1" height="1">
46 </form>
47 </td>
48
49 <td>
50 <form action="https://www.paypal.com/cgi-bin/webscr" method="post">
51 <input type="hidden" name="cmd" value="_donations">
52 <input type="hidden" name="business" value="rodsmith@rodsbooks.com">
53 <input type="hidden" name="lc" value="US">
54 <input type="hidden" name="no_note" value="0">
55 <input type="hidden" name="currency_code" value="USD">
56 <input type="hidden" name="amount" value="2.50">
57 <input type="hidden" name="item_name" value="rEFInd Boot Manager">
58 <input type="hidden" name="bn" value="PP-DonationsBF:btn_donate_LG.gif:NonHostedGuest">
59 <input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_donate_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
60 <img alt="Donate with PayPal" border="0" src="https://www.paypalobjects.com/en_US/i/scr/pixel.gif" width="1" height="1">
61 </form>
62 </td>
63
64
65 <td>
66 <form action="https://www.paypal.com/cgi-bin/webscr" method="post">
67 <input type="hidden" name="cmd" value="_donations">
68 <input type="hidden" name="business" value="rodsmith@rodsbooks.com">
69 <input type="hidden" name="lc" value="US">
70 <input type="hidden" name="no_note" value="0">
71 <input type="hidden" name="currency_code" value="USD">
72 <input type="hidden" name="amount" value="5.00">
73 <input type="hidden" name="item_name" value="rEFInd Boot Manager">
74 <input type="hidden" name="bn" value="PP-DonationsBF:btn_donate_LG.gif:NonHostedGuest">
75 <input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_donate_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
76 <img alt="Donate with PayPal" border="0" src="https://www.paypalobjects.com/en_US/i/scr/pixel.gif" width="1" height="1">
77 </form>
78 </td>
79
80 <td>
81 <form action="https://www.paypal.com/cgi-bin/webscr" method="post">
82 <input type="hidden" name="cmd" value="_donations">
83 <input type="hidden" name="business" value="rodsmith@rodsbooks.com">
84 <input type="hidden" name="lc" value="US">
85 <input type="hidden" name="no_note" value="0">
86 <input type="hidden" name="currency_code" value="USD">
87 <input type="hidden" name="amount" value="10.00">
88 <input type="hidden" name="item_name" value="rEFInd Boot Manager">
89 <input type="hidden" name="bn" value="PP-DonationsBF:btn_donate_LG.gif:NonHostedGuest">
90 <input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_donate_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
91 <img alt="Donate with PayPal" border="0" src="https://www.paypalobjects.com/en_US/i/scr/pixel.gif" width="1" height="1">
92 </form>
93 </td>
94
95 <td>
96 <form action="https://www.paypal.com/cgi-bin/webscr" method="post">
97 <input type="hidden" name="cmd" value="_donations">
98 <input type="hidden" name="business" value="rodsmith@rodsbooks.com">
99 <input type="hidden" name="lc" value="US">
100 <input type="hidden" name="no_note" value="0">
101 <input type="hidden" name="currency_code" value="USD">
102 <input type="hidden" name="amount" value="20.00">
103 <input type="hidden" name="item_name" value="rEFInd Boot Manager">
104 <input type="hidden" name="bn" value="PP-DonationsBF:btn_donate_LG.gif:NonHostedGuest">
105 <input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_donate_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
106 <img alt="Donate with PayPal" border="0" src="https://www.paypalobjects.com/en_US/i/scr/pixel.gif" width="1" height="1">
107 </form>
108 </td>
109
110 <td>
111 <form action="https://www.paypal.com/cgi-bin/webscr" method="post">
112 <input type="hidden" name="cmd" value="_donations">
113 <input type="hidden" name="business" value="rodsmith@rodsbooks.com">
114 <input type="hidden" name="lc" value="US">
115 <input type="hidden" name="no_note" value="0">
116 <input type="hidden" name="currency_code" value="USD">
117 <input type="hidden" name="item_name" value="rEFInd Boot Manager">
118 <input type="hidden" name="bn" value="PP-DonationsBF:btn_donate_LG.gif:NonHostedGuest">
119 <input type="image" src="https://www.paypalobjects.com/en_US/i/btn/btn_donate_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
120 <img alt="Donate with PayPal" border="0" src="https://www.paypalobjects.com/en_US/i/scr/pixel.gif" width="1" height="1">
121 </form>
122 </td></tr>
123 </table>
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>Windows and Mac OS X both provide relatively simple EFI boot loader programs. Launch them, and if they're launched from the correct locations and have the correct files in place, they'll boot their respective OSes. This makes rEFInd's job easy; it just locates the boot loader program files and runs them.</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="#traditional">Using a Traditional Linux Boot Loader</li>
144
145 <li class="tight"><a href="#quickstart">Using the EFI Stub Loader: Three Configuration Options</a>
146
147 <ul>
148
149 <li class="tight"><a href="#easiest">For Those With Foresight or Luck: The Easiest Method</a></li>
150
151 <li class="tight"><a href="#testing">Preparing a Test Configuration</a></li>
152
153 <li class="tight"><a href="#reconfigure">If You Need to Reconfigure Your Partitions....</a></li>
154
155 </ul></li>
156
157 <li class="tight"><a href="#efistub">EFI Stub Loader Support Technical Details</a></li>
158
159 </ul>
160
161 </div>
162
163 <p>Under Linux, by contrast, things can get complicated. As detailed on my <a href="http://www.rodsbooks.com/efi-bootloaders/index.html">Managing EFI Boot Loaders for Linux</a> page, several different EFI boot loaders for Linux exist, and all of them require configuration. If you're lucky, your distribution will have set up a Linux boot loader in a sensible way, in which case rEFInd should detect it and it will work as easily as a Windows or Mac OS X boot loader. If you're not lucky, though, you may need to configure it further. rEFInd offers options to help out with this task. Naturally, rEFInd supports <a href="#traditional">traditional Linux boot loaders.</a> It works even better with the Linux EFI stub loader, so I provide <a href="#quickstart">instructions on starting with it.</a> For those interested in manual configuration, I also provide <a href="#efistub">detailed instructions</a> on how the EFI stub support works and how to configure it.</p>
164
165 <a name="traditional">
166 <h2>Using a Traditional Linux Boot Loader</h2>
167 </a>
168
169 <p>I consider <a href="http://www.rodsbooks.com/efi-bootloaders/elilo.html">ELILO,</a> <a href="http://www.rodsbooks.com/efi-bootloaders/grub_legacy.html">GRUB Legacy,</a> and <a href="http://www.rodsbooks.com/efi-bootloaders/grub2.html">GRUB 2</a> to be traditional Linux boot loaders. These programs all exist independent of the Linux kernel, but they can load a kernel and hand off control to it. All three programs have their own configuration files that reside in the same directory as the boot loader itself (or optionally elsewhere, in the case of GRUB 2).</p>
170
171 <p>Ordinarily, rEFInd will detect these traditional boot loaders and provide main menu entries for them. If the boot loader exists in a directory with a name that matches a Linux distribution's icon filename, you'll automatically get a distribution-specific icon to refer to the boot loader.</p>
172
173 <p>If you prefer, you can disable automatic scanning and create an entry in <tt>refind.conf</tt> for your distribution, as described on the <a href="configfile.html">Configuring the Boot Manager</a> page. This method is harder to set up but can be preferable if you want to customize your options.</p>
174
175 <a name="quickstart">
176 <h2>Using the EFI Stub Loader: Three Configuration Options</h2>
177 </a>
178
179 <p>The EFI stub loader is basic and reliable, but it requires some setup to use it on some computers. It also requires that you run a kernel with the same bit width as your EFI. In most cases, this means running a 64-bit kernel, since 32-bit EFI-based computers are so rare. I describe three methods of using the EFI stub loader: an <a href="#easiest">easiest method</a> for those with compatible partition and filesystem layouts, a <a href="#testing">quick test configuration</a> for those without such a layout, and <a href="#reconfigure">a long-term setup</a> for those without the ideal setup.</p>
180
181 <a name="easiest">
182 <h3>For Those With Foresight or Luck: The Easiest Method</h3>
183 </a>
184
185 <p>This method requires that your <tt>/boot</tt> directory, whether it's on a separate partition or is a regular directory in your root (<tt>/</tt>) filesystem, be readable by the EFI. At the moment, all EFI implementations can read FAT and Macs can read HFS+. By using <a href="drivers.html">drivers,</a> you can make any EFI read HFS+, ISO-9660, ReiserFS, ext2fs, ext3fs, ext4fs, or Btrfs. Thus, if you use any of these filesystems on a regular partition (not an LVM or RAID configuration) that holds your kernels in <tt>/boot</tt>, you qualify for this easy method. The default partition layouts used by Ubuntu, Fedora, and many other distributions qualify, because they use one of these filesystems (usually ext4fs) in a normal partition or on a separate <tt>/boot</tt> partition. You must also have a 3.3.0 or later Linux kernel with EFI stub support, of course.</p>
186
187 <p>If you installed rEFInd 0.6.0 or later with its <tt>install.sh</tt> script from your regular Linux installation, chances are everything's set up; you should be able to reboot and see your Linux kernels as boot options. If you installed manually, from OS X, or from an emergency system, though, you may need to do a couple of things manually:
188
189 <ul>
190
191 <li>Copy the relevant driver file for your filesystem and architecture to
192 the <tt>drivers</tt> or <tt>drivers_<tt class="variable">arch</tt></tt>
193 subdirectory of the rEFInd installation directory on the ESP. You may
194 need to create this subdirectory, too.</li>
195
196 <li>Create a <tt>refind_linux.conf</tt> file in your <tt>/boot</tt>
197 directory. The <tt>mkrlconf.sh</tt> script that comes with rEFInd
198 should do this job, or you can do it manually as described <a
199 href="#efistub">later.</a> Starting with version 0.6.12, rEFInd can
200 create minimal boot options from <tt>/etc/fstab</tt>, if <tt>/boot</tt>
201 is <i>not</i> a separate partition, so a <tt>refind_linux.conf</tt>
202 file may not be strictly necessary. It remains desirable, though, and
203 is necessary if <tt>/boot</tt> is on a separate partition or if you
204 need unusual kernel options to boot your computer.</li>
205
206 </ul>
207
208 <p>When you reboot, you should see rEFInd options for your Linux kernels. If they work, your job is done, although you might want to apply some of the tweaks described in the <a href="#reconfigure">maintenance-free setup</a> section. If you have problems, you may need to adjust the <tt>refind_linux.conf</tt> file, as described in the <a href="#efistub">detailed configuration section.</a></p>
209
210 <a name="testing">
211 <h3>Preparing a Test Configuration</h3>
212 </a>
213
214 <p>If you're not sure you want to use the EFI stub loader in the long term, you can perform a fairly quick initial test of it. This procedure assumes that you have access to a 3.3.0 or later Linux kernel with EFI stub support compiled into it. (Fedora 17, Ubuntu 12.10, and probably other distributions ship with such kernels.) Creating this configuration poses no risk to your current boot options, provided you don't accidentally delete existing files. The procedure for a quick test is:</p>
215
216 <ol>
217
218 <li>Copy your kernel file (<tt>vmlinuz-*</tt>) and matching initial RAM
219 disk file (<tt>init*</tt>) from <tt>/boot</tt> to a subdirectory of
220 <tt>EFI</tt> on your ESP. Your distribution's directory there should
221 work fine. For instance, typing <tt class="userinput">cp
222 /boot/vmlinuz-3.6.7-4.fc17.x86_64
223 /boot/initramfs-3.6.7-4.fc17.x86_64.img /boot/efi/EFI/redhat</tt> might
224 do the trick on a Fedora system, although you'll probably have to
225 adjust the version numbers. Note that the filename forms vary from one
226 distribution to another, so don't worry if yours look different from
227 these. Be sure that you match up the correct files by version number,
228 though.</li>
229
230 <li>Copy the <tt>/boot/refind_linux.conf</tt> file to the same directory to
231 which you copied your kernel. If this file doesn't exist, create it by
232 running (as <tt>root</tt>) the <tt>mkrlconf.sh</tt> script that came
233 with rEFInd. This step may not be strictly necessary if <tt>/boot</tt>
234 is an ordinary directory on your root (<tt>/</tt>) partition.</li>
235
236 <li>Reboot. You should now see a new entry for launching the Linux kernel
237 that you copied. Try the option. If it works, great. If not, you may
238 need to adjust your <tt>refind_linux.conf</tt> file. See the <a
239 href="#efistub">detailed configuration section</a> for a description of
240 this file's format. If the kernel begins to boot but complains that it
241 couldn't find its root filesystem, double-check the version numbers on
242 your kernel and initial RAM disk file, and check the <tt>root=</tt>
243 option in <tt>refind_linux.conf</tt>.</li>
244
245 </ol>
246
247 <p>You can continue to boot your computer with this type of configuration; however, the drawback is that you'll need to copy your kernel whenever it's updated. This can be a hassle. A better way is to configure you system so that the EFI, and therefore rEFInd, can read your Linux <tt>/boot</tt> directory, where most Linux distributions place their kernels.</p>
248
249 <a name="reconfigure">
250 <h3>If You Need to Reconfigure Your Partitions....</h3>
251 </a>
252
253 <p>If your <tt>/boot</tt> directory happens to be on an XFS or JFS partition that the EFI can't read, or it's tucked away in an LVM or RAID configuration that the EFI can't read, you won't be able to use the <a href="#easiest">easiest solution.</a> Fortunately, this problem can be overcome with relatively little fuss. Several variant procedures are possible, but I begin by describing one that will almost always work, although it's got some important caveats (described at the end). You should perform the following steps as <tt>root</tt>, or precede each of these commands with <tt>sudo</tt>:</p>
254
255 <ol>
256
257 <li>Begin with your ESP mounted at <tt>/boot/efi</tt>, which is the most
258 common location. If it's not mounted there, type <tt
259 class="userinput">mount /dev/sda1 /boot/efi</tt> to do so (adjusting
260 <tt>/dev/sda1</tt>, if necessary), or mount it elsewhere and adjust the
261 paths in the following procedure as necessary.</li>
262
263 <li>Check the size of the ESP by typing <tt class="userinput">df -h
264 /boot/efi</tt>. The ESP must be large enough to hold several Linux
265 kernels and initial RAM disk files&mdash;100MiB at a bare minimum, and
266 preferably 200&ndash;500MiB.</li>
267
268 <li>Check your <tt>/boot</tt> directory to be sure it contains no links or
269 other files that rely on Unix/Linux-style permissions or ownership. If
270 it does, don't proceed, or at least research these files further to
271 determine if you can work around the need for such permissions and
272 ownership.</li>
273
274 <li>Type <tt class="userinput">cp -r /boot/* /boot/efi</tt>. You'll see an
275 error message about being unable to copy <tt>/boot/efi</tt> into
276 itself. Ignore this.</li>
277
278 <li>Type <tt class="userinput">umount /boot/efi</tt>.</li>
279
280 <li>Edit <tt>/etc/fstab</tt> and change the mount point for
281 <tt>/boot/efi</tt> to <tt>/boot</tt>. If the ESP isn't present in
282 <tt>/etc/fstab</tt>, you must create an entry for it, with a mount
283 point of <tt>/boot</tt>.</li>
284
285 <li>Type <tt class="userinput">mount -a</tt> to re-mount everything,
286 including <tt>/boot</tt>. Check that your normal <tt>/boot</tt> files
287 are all present, along with the new <tt>/boot/EFI</tt> directory, which
288 holds what used to be <tt>/boot/efi/EFI</tt>. If something seems to be
289 missing (other than <tt>/boot/efi</tt> with a lowercase <tt>efi</tt>),
290 then you should try to correct the problem.</li>
291
292 <li>If it doesn't already exist, create a file called
293 <tt>/boot/refind_linux.conf</tt> and populate it with kernel options,
294 as described <a href="#refind_linux">later.</a> If this file doesn't
295 already exist, the easiest way to create it is to run the
296 <tt>mkrlconf.sh</tt> script that comes with rEFInd 0.5.1 and
297 later.</li>
298
299 <li>Check your <tt>refind.conf</tt> file (presumably in
300 <tt>/boot/EFI/refind</tt>) to be sure that the
301 <tt>scan_all_linux_kernels</tt> line is uncommented. If it's not,
302 uncomment that line.</li>
303
304 <li>Optionally, type <tt class="userinput">cp
305 /boot/EFI/refind/icons/os_<i>name</i>.icns /boot/.VolumeIcon.icns</tt>
306 to give loaders in <tt>/boot</tt> an icon for your distribution.</li>
307
308 <li>Reboot to test that this configuration works.</li>
309
310 </ol>
311
312 <p>Recall that in step #4, you <i>copied</i> the contents of <tt>/boot</tt> (as a safety measure), but you did not move them. Therefore, you ended up with two copies of your kernels and other <tt>/boot</tt> directory contents, with one copy hiding the other when you mounted the ESP at <tt>/boot</tt>. Once you've booted successfully and are sure all is working well, you can recover some disk space by unmounting <tt>/boot</tt> and deleting the contents of the underlying <tt>/boot</tt> directory on your root (<tt>/</tt>) filesystem. Be sure that the <tt>/boot</tt> partition is unmounted before you do this, though! Also, be sure to leave the <tt>/boot</tt> directory itself in place, even if it has no contents; the directory is needed as a mount point for the <tt>/boot</tt> partition. Note that GRUB 2 may stop working if you delete its files from the root filesystem's <tt>/boot/grub</tt> directory, so if you want to keep GRUB around, you should re-install it with the separate <tt>/boot</tt> partition mounted.</p>
313
314 <p>Once this task is done, updates to your kernel will automatically be stored in the root directory of your ESP, where rEFInd will automatically detect them. Thus, the boot configuration becomes maintenance-free. The procedure as just described has some drawbacks, though. By placing your kernels in the root directory of your ESP, you render them vulnerable to any other OS with which you might be dual-booting. Your ESP must also be large enough to hold all your kernels. If you dual-boot with multiple Linux distributions, they might conceivably overwrite each others' kernels, and distinguishing one from another becomes more difficult.</p>
315
316 <p>For these reasons, a variant of this procedure is desirable on some systems. Most of the steps are similar, but in this variant, you create a separate <tt>/boot</tt> partition that's independent of the ESP. This partition can use FAT, HFS+, ReiserFS, ext2fs, ext3fs, ext4fs, or Btrfs; but if you use any of the last six filesystems (five on Macs), you must install the matching EFI filesystem driver that ships with rEFInd. Creating the filesystem will normally require you to shrink an existing partition by a suitable amount (200&ndash;500MiB). Mount your new <tt>/boot</tt> partition at a temporary location, copy or move the current <tt>/boot</tt> files into it, unmount it, and add it to <tt>/etc/fstab</tt> as <tt>/boot</tt>.</p>
317
318 <p>If your distribution already uses a separate <tt>/boot</tt> partition, but if it uses XFS or some other unsuitable filesystem, you can back it up, create a fresh FAT, HFS+, ReiserFS, Btrfs, ext2, ext3, or ext4 filesystem on it, and restore the original files. You'll probably need to adjust the UUID value in <tt>/etc/fstab</tt> to ensure that the computer mounts the new filesystem when you boot. If you use a separate non-ESP <tt>/boot</tt> partition, you'll probably want to continue mounting the ESP at <tt>/boot/efi</tt>.</p>
319
320 <a name="efistub">
321 <h2>EFI Stub Loader Support Technical Details</h2>
322 </a>
323
324 <p>The Linux <a href="http://www.rodsbooks.com/efi-bootloaders/efistub.html">EFI stub loader</a> is a way to turn a Linux kernel into an EFI application. In a sense, the kernel becomes its own boot loader. This approach to booting Linux is very elegant in some ways, but as described on the page to which I just linked, it has its disadvantages, too. One challenge to booting in this way is that modern Linux installations typically require that the kernel be passed a number of options at boot time. These tell the kernel where the Linux root (<tt>/</tt>) filesystem is, where the initial RAM disk is, and so on. Without these options, Linux won't boot. These options are impossible for a generic boot loader to guess without a little help. It's possible to build a kernel with a default set of options, but this is rather limiting. Thus, rEFInd provides configuration options to help.</p>
325
326 <p>With all versions of rEFInd, you can create manual boot loader stanzas
327 in the <tt>refind.conf</tt> file to identify a Linux kernel and to pass it
328 all the options it needs. This approach is effective and flexible, but it
329 requires editing a single configuration file for all the OSes you want to
330 define in this way. If a computer boots two different Linux distributions,
331 and if both were to support rEFInd, problems might arise as each one tries
332 to modify its own rEFInd configuration; or the one that controls rEFInd
333 might set inappropriate options for another distribution. This is a problem
334 that's been a minor annoyance for years under BIOS, since the same
335 potential for poor configuration applies to LILO, GRUB Legacy, and GRUB 2
336 on BIOS. The most reliable solution under BIOS is to chainload one boot
337 loader to another. The same solution is possible under EFI, but rEFInd
338 offers another possibility.</p>
339
340 <p>rEFInd 0.2.1 and later supports semi-automatic Linux EFI stub loader detection. This feature works as part of the standard boot loader scan operation, but it extends it as follows:</p>
341
342 <ol>
343
344 <li>rEFInd looks for boot loaders whose names include the strings
345 <tt>bzImage</tt> or <tt>vmlinuz</tt> and that end in <tt>.efi</tt>. For
346 instance, <tt>bzImage-3.3.0.efi</tt> or <tt>vmlinuz-3.3.0-fc17.efi</tt>
347 would match, and trigger subsequent steps in this procedure. Beginning
348 with version 0.3.0, if you uncomment the
349 <tt>scan_all_linux_kernels</tt> option in <tt>refind.conf</tt>, rEFInd
350 will also scan for kernels <i>without</i> a <tt>.efi</tt> filename
351 extension. This option is uncommented by default, but if you comment it
352 out, delete it, or change it to read <tt>scan_all_linux_kernels 0</tt>,
353 rEFInd won't scan for kernels that lack <tt>.efi</tt> filename
354 extensions.</li>
355
356 <p class="sidebar">A kernel whose filename lacks a version string matches an initial RAM disk that also lacks a version string in its filename. Note that you can reliably use only <i>one</i> kernel and initial RAM disk per directory that lack version numbers in their filenames.</p>
357
358 <li>rEFInd looks for an initial RAM disk in the same directory as the
359 kernel file. A matching initial RAM disk has a name that begins with
360 <tt>init</tt> and that includes the same version string as the kernel.
361 The version string is defined as the part of the filename from the
362 first digit to the last digit, inclusive. Note that the version string
363 can include non-digits. For instance, the version string for
364 <tt>bzImage-3.3.0.efi</tt> is <tt>3.3.0</tt>, which matches
365 <tt>initramfs-3.3.0.bz</tt>; and <tt>vmlinuz-3.3.0-fc17.efi</tt>'s
366 version string is <tt>3.3.0-fc17</tt>, which matches
367 <tt>initrd-3.3.0-fc17.img</tt>. Many other matches are possible. If an
368 initial RAM disk is identified, rEFInd passes a suitable
369 <tt>initrd=</tt> option to the kernel when it boots.</li>
370
371 <p class="sidebar">rEFInd 0.2.1 and 0.2.2 used a filename of <tt>linux.conf</tt> to hold Linux kernel options; however, the Linux kernel developers plan to use this name themselves, so I've switched to <tt>refind_linux.conf</tt> as of rEFInd 0.2.3. Through version 0.4.2, rEFInd still supported the <tt>linux.conf</tt> filename as a backup to <tt>refind_linux.conf</tt>, but as of version 0.4.3, <tt>linux.conf</tt> no longer works, so you should rename rEFInd's <tt>linux.conf</tt> file to <tt>refind_linux.conf</tt> if you're upgrading.</p>
372
373 <li>rEFInd looks for a file called <tt>refind_linux.conf</tt> in the same
374 directory as the kernel file. This file is a practical requirement for
375 booting from an auto-detected kernel. It consists of a series of lines,
376 each of which consists of a label followed by a series of kernel
377 options. The first line sets default options, and subsequent lines set
378 options that are accessible from the main menu tag's submenu screen. If
379 you installed rEFInd 0.5.1 or later with the <tt>install.sh</tt>
380 script, that script created a sample <tt>refind_linux.conf</tt> file,
381 customized for your computer, in <tt>/boot</tt>. This file will work
382 without changes on many installations, but you may need to tweak it for
383 some.</li>
384
385 <li>If rEFInd can't find a <tt>refind_linux.conf</tt> file in the directory
386 that holds the kernel, the program looks for a file called
387 <tt>/etc/fstab</tt> on the partition that holds the kernel. If this
388 standard Linux file is present, rEFInd uses it to identify the root
389 (<tt>/</tt>) filesystem and creates two sets of Linux kernel boot
390 options: One set launches the kernel normally, but with minimal
391 options, and the other set launches the kernel into single-user mode.
392 This step can get a computer to boot without any rEFInd-specific
393 configuration files, aside from <tt>refind.conf</tt> in rEFInd's own
394 directory, but only if <tt>/boot</tt> is not a separate partition. The
395 intent is to facilitate the use of rEFInd as an emergency boot manager
396 or to help users who must install rEFInd from OS X or Windows. Note
397 that rEFInd uses <tt>/etc/fstab</tt> only if <tt>refind_linux.conf</tt>
398 is <i>not</i> found.</li>
399
400 </ol>
401
402 <p>The intent of this system is that distribution maintainers can place their kernels, initial RAM disks, and a <tt>refind_linux.conf</tt> file in their own subdirectories on the ESP, on EFI-accessible <tt>/boot</tt> partitions, or in <tt>/boot</tt> directories on EFI-accessible Linux root (<tt>/</tt>) partitions. rEFInd will detect these kernels and create one main menu entry for each kernel. Each entry will implement as many options as there are lines in the <tt>refind_linux.conf</tt> file. In this way, two or more distributions can each maintain their boot loader entries, without being too concerned about who maintains rEFInd as a whole.</p>
403
404 <p>The <tt>scan_all_linux_kernels</tt> option is intended to help users and distribution maintainers when rEFInd is used in conjunction with a Linux filesystem driver for EFI or when the ESP is mounted as the Linux <tt>/boot</tt> partition. In these cases, if all the kernels in Linux's <tt>/boot</tt> directory include EFI stub loader support, rEFInd will automatically detect and use kernels installed in the usual way, such as via an automatic system update. You won't even need to move or rename your kernels. You will need to set up a <tt>refind_linux.conf</tt> file and you may need to install a driver or set the <tt>also_scan_dirs</tt> option in <tt>refind.conf</tt>; but these are one-time requirements. Set up in this way, ongoing maintenance to handle kernel updates drops to zero!</p>
405
406 <p>As an example, consider the following file configuration:</p>
407
408 <pre class="listing">
409 $ <b>ls -l /boot/efi/EFI/ubuntu/</b>
410 total 17943
411 -rwxr-xr-x 1 root root 4781632 2012-03-18 12:01 bzImage-3.3.0.efi
412 -rwxr-xr-x 1 root root 131072 2011-10-14 04:10 grubx64.EFI
413 -rwxr-xr-x 1 root root 13459936 2012-03-18 12:02 initrd.img-3.3.0
414 -rwxr-xr-x 1 root root 266 2012-03-26 19:39 refind_linux.conf
415 </pre>
416
417 <p>When rEFInd scans this directory, it will find two EFI boot loaders in <tt>EFI/ubuntu</tt>: <tt>grubx64.EFI</tt> and <tt>bzImage-3.3.0.efi</tt>. rEFInd will create two main-menu tags for these two loaders, one of which will launch Ubuntu's standard GRUB and the other of which will launch the 3.3.0 kernel file directly. The <tt>refind_linux.conf</tt> file contains a list of labels and options:</p>
418
419 <a name="refind_linux">
420 <pre class="listing">
421 "Boot with standard options" "root=/dev/sda3 ro quiet splash vt.handoff=7"
422 "Boot to single-user mode" "root=UUID=1cd95082-bce0-494c-a290-d2e642dd82b7 ro single"
423 "Boot with minimal options" "root=UUID=1cd95082-bce0-494c-a290-d2e642dd82b7 ro"
424 # "Boot alternate install" "root=/dev/sdb9 ro quiet splash vt.handoff=7"
425 </pre>
426 </a>
427
428 <p>Ordinarily, both fields in this file must be enclosed in quotes. If you have to pass an option that includes quotes, you can do so by doubling up on them, as in <tt>"root=/dev/sdb9 my_opt=""this is it"""</tt>, which passes <tt>root=/dev/sdb9 my_opt="this is it"</tt> to the shell. You can include as much white space as you like between options. You can also place comments in the file, or remove an option by commenting it out with a leading hash mark (<tt>#</tt>), as in the fourth line in this example.</p>
429
430 <p>In the preceding example, the first line sets the options that rEFInd passes to the kernel by default (along with the name of the <tt>initrd.img-3.3.0</tt> file, since its version string matches that of the kernel). The next two lines set options that you can obtain by pressing Insert, F2, or + on the main menu, as shown here:</p>
431
432 <br /><center><img src="automatic-submenu.png" align="center"
433 width="471" height="189" alt="rEFInd can load Linux boot options from
434 a refind_linux.conf file in the Linux kernel's directory."
435 border=2></center><br />
436
437 <p>To assist in initial configuration, rEFInd's <tt>install.sh</tt> script creates a sample <tt>refind_linux.conf</tt> file in <tt>/boot</tt>. This sample file defines three entries, the first two of which use the default GRUB options defined in <tt>/etc/default/grub</tt> and the last of which uses minimal options. The first entry boots normally and the second boots into single-user mode. If you want to create a new file, you can use the <tt>mkrlconf.sh</tt> script that comes with rEFInd. If you pass it the <tt>--force</tt> option, it will overwrite the existing <tt>/boot/refind_linux.conf</tt> file; otherwise it will create the file only if one doesn't already exist.</p>
438
439 <p>From a user's perspective, the submenus defined in this way work just like submenus defined via the <tt>submenuentry</tt> options in <tt>refind.conf</tt>, or like the submenus that rEFInd creates automatically for Mac OS X or ELILO. There are, however, limitations in what you can accomplish with this method:</p>
440
441 <ul>
442
443 <li>Your kernels must be compiled with EFI stub loader support.</li>
444
445 <li>You can't set a submenu option to boot via a different boot loader,
446 such as ELILO or GRUB; all the submenu options apply to a single boot
447 loader&mdash;that is, a single kernel. (rEFInd will still detect other
448 boot loaders and provide separate main-menu tags for them,
449 though.)</li>
450
451 <li>If an installation includes two or more kernel files, each one receives
452 its own main-menu entry; you can't combine them together in one menu
453 item. This is essentially a corollary of the preceding limitation. The
454 result can be an overburdened main menu if your system has many
455 kernels.</li>
456
457 <li>All the kernels in a given directory use the same
458 <tt>refind_linux.conf</tt> file. If you need to set different options
459 for different kernels, you'll need to place those kernels in different
460 directories.</li>
461
462 <li>You must place your kernels in a directory other than the one that
463 holds the main rEFInd <tt>.efi</tt> file. This is because rEFInd does
464 not scan its own directory for boot loaders.</li>
465
466 </ul>
467
468 <p>Ordinarily, a kernel booted in this way must reside on the ESP, or at least on another FAT partition. On a Macintosh, though, you can use HFS+ to house your kernel files. In fact, that may be necessary; my Mac Mini hangs when I try to boot a Linux kernel via an EFI stub loader from the computer's ESP, but it works fine when booting from an HFS+ partition. If you use <a href="drivers.html">EFI drivers,</a> though, you can place your kernel on any filesystem for which an EFI driver exists. This list is currently good (ext2fs/ext3fs, ext4fs, ReiserFS, Btrfs, ISO-9660, and HFS+), so chances are you'll be able to use this method to boot your kernel from your root (<tt>/</tt>) partition or from a <tt>/boot</tt> partition.</p>
469
470 <p>rEFInd sorts boot loader entries <i>within each directory</i> by time stamp, so that the most recent entry comes first. Thus, if you specify a directory name (or a volume label, for loaders stored in a volume's root directory) as the <tt>default_selection</tt>, rEFInd will make the most recent loader in the directory the default. This can obviate the need to adjust this configuration parameter when you add a new kernel; chances are you want the most recently-added kernel to be the default, and rEFInd makes it so when you set the <tt>default_selection</tt> in this way. If you <i>don't</i> want the latest kernel to become the default, you can use <tt>touch</tt> to give the desired kernel (or other boot loader) in the directory a more recent time stamp, or you can set <tt>default_selection</tt> to a value that uniquely identifies your desired default loader. One caveat you should keep in mind is that the EFI and Windows interpret the hardware clock as local time, whereas Mac OS X uses <a href="http://en.wikipedia.org/wiki/Coordinated_Universal_Time">Coordinated Universal Time (UTC)</a>. Linux can work either way. Thus, time stamps for boot loaders can be skewed by several hours depending on the environment in which they were created or last modified.</p>
471
472 <p class="sidebar"><b>Tip for distribution maintainers:</b> If you maintain an <tt>EFI/<tt class="variable">distname</tt></tt> directory for your kernels, you can place your version of rEFInd in a directory called <tt>EFI/<tt class="variable">distname</tt>/refind</tt>. This will avoid collisions with duplicate rEFInd installations from other distributions.</p>
473
474 <p>On the whole, this method of configuration has a lot going for it. For distribution maintainers, if you place your Linux kernel files (with EFI stub support) on the ESP, with suitable filenames, matching initial RAM disk files, and a <tt>refind_linux.conf</tt> file, then any rEFInd 0.2.3 or later installation should detect your files, even if the user installs another distribution with another rEFInd that takes over from yours. (If the user, or this other rEFInd installation, disables auto-detection, this won't work.)</p>
475
476 <p>For end users, this method is simpler than maintaining manual configurations in <tt>refind.conf</tt> (or equivalents for ELILO or GRUB). To install a new kernel, you need only copy it and its initial RAM disk, under suitable names, to a scanned directory on the ESP. There's no need to touch any configuration file, provided you've already set up <tt>refind_linux.conf</tt> in your kernel's directory. You will, however, have to adjust <tt>refind_linux.conf</tt> if you make certain changes, such as if your root directory identifier changes.</p>
477
478 <hr/>
479
480 <p>copyright &copy; 2012&ndash;2014 by Roderick W. Smith</p>
481
482 <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>
483
484 <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>
485
486 <p><a href="index.html">Go to the main rEFInd page</a></p>
487
488 <p><a href="secureboot.html">Learn how to manage Secure Boot</a></p>
489
490 <p><a href="http://www.rodsbooks.com/">Return</a> to my main Web page.</p>
491 </body>
492 </html>