EFI-Booting Ubuntu on a Mac
Originally written: 1/2011; Last Web page update: 6/17/2013 (last major update: 5/4/2012)
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Note: This page is written using a rather elderly 32-bit Mac Mini as a reference, and using Ubuntu 12.04 as a reference. Developments in the last year have rendered certain of the procedures on this page sub-optimal. I've tried to point these out, but I haven't fully researched better replacements, and I lack the modern hardware on which to test some of the better methods on more recent 64-bit Macs. Thus, you may need to deviate from these instructions on modern computers.
When installing Ubuntu Linux on an Intel-based Macintosh, most people
follow any of several guides available on the Internet, such as this
Ubuntu document. Most of these guides, however, rely on features of the
Macintosh that are intended to enable it to boot Windows. In particular,
these guides typically end up creating a configuration that boots Linux
using its Compatibility Support Module (CSM), which provides BIOS
emulation on the Mac. In this mode, the Mac sets up a Basic Input Output
System (BIOS) layer that the OS can use, rather than rely on the Extensible
Firmware Interface (EFI) that OS X uses to run on the computer. BIOS
emulation is expedient, and it's the only way that most versions of Windows
can boot directly on a Mac, but it's got several drawbacks:
- Longer boot times—BIOS emulation is widely regarded as
slowing the boot process. I've not tested this effect myself, so I'm
not sure how significant it is.
- Reduced graphics card flexibility—On some models with
multiple graphics chipsets, you can't select which chipset to use in
BIOS mode, but you can in EFI mode. My own Mac isn't one of the
affected models, so I can't comment further on this issue.
- Use of a hybrid MBR—Intel-based Macs use the GUID Partition
Table (GPT) rather than the more common Master Boot
Record (MBR) partitioning system. Windows, however, can't boot from
GPT disks on BIOS-based computers (which it thinks a Mac is thanks to
Apple's BIOS emulation). Therefore, Apple uses an ugly and dangerous
hack known as a hybrid MBR, in
which a GPT data structure known as the protective MBR is
altered to make the disk look like an MBR disk to Windows. The trouble
is that hybrid MBRs frequently cause problems. In fact, even the Ubuntu
installer often gets it wrong; it tries to be helpful by creating a
hybrid MBR, but depending on your partition layout, it can create a
partition table that the popular libparted-based partitioning tools
As far as I can tell, BIOS emulation mode only works when a hybrid MBR
is present on the hard disk or when a BIOS-bootable optical disk is
inserted in the optical drive. Thus, you can't use BIOS emulation mode with
a conventional GPT disk unless you plan to use a bootable optical disc to
Ubuntu can use the BIOS emulation and hybrid MBR that enable Windows to
boot on Macs, but it doesn't need to! If you don't use these
features, you won't see their problems. Hybrid MBRs, in particular, are a
Bad Idea (with a capital B and a capital I). I've seen numerous problems
reported at the Ubuntu Forums related
to Ubuntu installations on Macs with hybrid MBRs, and more problems with
similar configurations elsewhere. See my hybrid MBR Web page
for a technical description of what they are and what can go wrong with
them. In short, they can get out of sync, cause confusion about which
partition is which, and become damaged in frustrating ways. Whenever I
think I've heard of every possible problem with hybrid MBRs, I stumble
across a new one. You're better off without one, if that's
possible—and it is, if you dual-boot OS X and Linux but not
The trouble is that Ubuntu doesn't support installing to a Mac in EFI
mode, at least not as of version 12.04. (Some sources claim that this now
works on some later versions, but I haven't tested this claim—indeed,
I lack the hardware to do so!) The normal 64-bit discs can boot on PCs in
either BIOS mode or (if the PC supports it) UEFI mode (UEFI being,
essentially, EFI 2.x). These discs reportedly do not boot on Macs
(although I suspect they might with the help of rEFIt or rEFInd). The 32-bit Ubuntu
installation discs lack EFI support. Ubuntu has also released 64-bit disc
images for Macs. Ironically, these boot only in BIOS mode! Therefore, to
rid your computer of the dangerous hybrid MBR, you'll need to jump through
some hoops. An alternative to all of this is to run Ubuntu in a virtual
environment, such as VirtualBox.
This can be a good solution in some cases, but it doesn't give Linux direct
access to the hardware and you'll lose some speed.
Although my opinion is that Intel-based Macs are best booted using EFI
and a GPT with a protective MBR rather than a hybrid MBR, there are
drawbacks to doing it this way. These include:
- No Windows—As noted earlier, Windows relies heavily on
BIOS emulation to boot on a Mac; therefore, if you want to triple-boot
OS X, Linux, and Windows, you'll need a hybrid MBR to boot Windows.
(You might, however, consider dual-booting OS X and Linux and run
Windows in a virtual machine such as VirtualBox. This will eliminate
the need for BIOS emulation and hybrid MBRs.) In theory, you could
triple-boot with a hybrid MBR but still use EFI mode to boot Linux.
I've not tested this, and the benefits are greatly reduced since you've
still got the hybrid MBR on your hard disk.
- Limited nVidia driver support—The biggest caveat to
booting Linux in EFI mode on Macs is that some Linux video drivers,
particularly for nVidia chipsets, don't work well when you boot in EFI
mode. Thus, if you've got a Mac with an nVidia video chipset, you'll
need to use the less capable fbdev drivers rather than the faster
nVidia drivers. My own first-generation Intel Mac Mini uses an Intel
video chipset and is not affected by this problem, so it doesn't bother
me, but it could be a deal-breaker for you. I've seen some suggestions
that these problems are less serious now (in April of 2012) than they
were a year or two ago. The UEFIBooting
page has some notes on specific Mac models' video support when
booted in EFI mode; see the table under "Tested Configurations" about
2/3 of the way down the page.
- Missing hardware features—I've seen reports that Linux
features such as screen brightness control and suspend/resume may not
work correctly when booting using EFI. I don't use such features, so I
can't comment personally.
- Virtual terminals—I've seen reports that text-mode virtual
terminals don't work from an EFI boot; however, this limitation doesn't
apply to my computer. Perhaps it interacts with the video chipset,
framebuffer driver use, kernel version, or some other variable.
- OS architecture limitations—Older Intel-based Macs, such
as my Mac Mini, use 32-bit CPUs and EFIs. Newer models come with 64-bit
CPUs and EFIs. If you try to run a 32-bit distribution on a 64-bit EFI,
you may not have access to EFI Runtime Services. This can reportedly
limit some features, but I'm a bit unclear about the details. In my
opinion, it's best to stick with 64-bit distributions on 64-bit
hardware even on BIOS-based computers, so I don't see this as a big
If you're running Fedora, CentOS, Mandriva, OpenSUSE, Gentoo, Debian, or
most other Linux distributions, the procedure I'm about to describe will
probably work; however, some details may differ. In fact, at one time or
another, I've installed Ubuntu, CentOS, and OpenSUSE on my Mac Mini, all
using EFI-mode boots. It's possible that your preferred distribution
already supports direct EFI installation, in which case the problem of
installing to a Mac in EFI mode may not exist. Check your distribution's
documentation to be sure.
I've tested this procedure only on my first-generation Intel-based Mac
Mini. This computer uses a 32-bit CPU and 32-bit EFI, so I've tested only
the 32-bit version of Ubuntu. It's possible that the 64-bit version has
different requirements, or you may need to do things differently on newer
64-bit Macs. You can check which type of EFI you've got with the following
command, typed in an OS X Terminal:
$ ioreg -l -p IODeviceTree | grep firmware-abi
The result should include the string EFI32 or EFI64;
the meaning of each should be obvious.
Before proceeding, you'll need to download a few items:
- Ubuntu Linux—You can obtain Ubuntu from its main Web site. The Web site
describes the 32-bit version as "recommended," but lacks such a
description for the 64-bit version. Don't worry, though; the 64-bit
version works fine for almost everything. Remember that you'll probably
need the Mac-specific version to boot on a Mac if you've got a 64-bit
system. This version can be harder to track down; I used this
torrent list. I recommend using the 64-bit version if you've got a
64-bit EFI, as described earlier. (Note that the string AMD64
appears in many places in reference to the 64-bit version of Ubuntu,
but this version works fine on Intel's x86-64 CPUs; the
AMD64 string is used simply because AMD invented the
architecture.) I used a desktop version of Ubuntu 12.04 as a reference
for this Web page, but the basic procedures should be similar for the
server or alternate installer, as well as for Ubuntu variants such as
Kubuntu and Edubuntu. I strongly recommend installing Ubuntu 12.04.2 or
a more recent version rather than the original 12.04, since more recent
versions come with kernels that include an EFI stub loader, which can
simplify certain configuration procedures. Burn the disc and check that
it includes directories called boot, install,
isolinux, and so on. If you prefer to use a USB flash drive or
similar device, you can do so. See Ubuntu's Installing
Ubuntu Desktop page for instructions on creating bootable USB flash
drives under various OSes.
- GPT fdisk (gdisk)—Go to the GPT fdisk Sourceforge
download page and download the Mac
(gdisk-version.pkg) package. Install this package in OS
X. Once you have Linux installed, you may want to install the Linux
version from the Ubuntu repositories (it's in a package called
- Super GRUB 2 Disk—Download this handy CD image from its home page. Be sure to get
Super GRUB 2 Disk, not Super GRUB Disk. Burn the disc image like
you burned the Ubuntu install disc image, or copy it to a second USB
- rEFInd—This is a fork of the earlier rEFIt Mac boot
manager. It's part of the boot process as described on this Web page.
Download either the ISO image or the binary .zip file from its Web page.
If you're already using rEFIt, you can continue to use it rather than
install rEFInd; however, rEFIt appears to have been abandoned, and
rEFInd adds many improvements, so you may want to upgrade sooner or
With these items in hand, you can proceed with installing Ubuntu, and
then fix it up so that it doesn't use a hybrid MBR.
If you've already got a working dual-boot configuration with OS X and
Ubuntu, you can skip this section and jump ahead to "Fixing the Installation." You may be able to skip some
of the steps in that section, too, such as rEFInd installation.
To install Ubuntu Linux 12.04 on an Intel-based Mac, follow these
- If necessary, install Mac OS X.
- Boot into Mac OS X.
- If necessary, using OS X's Disk Utility, adjust the sizes of your
partitions, making room for Linux. Note that resizing partitions is
inherently dangerous, so back up your data before beginning! You may
also want to create a FAT or unjournaled HFS+ ("Mac OS
Extended") shared-data partition. The result might look like the below
(the Linux partition in this screen shot could as easily be blank
space; I've created it here mainly to show you where Linux will
- If you haven't done so already, install the OS X version of GPT fdisk
- Open a Terminal program.
- In the Terminal program, type sudo gdisk /dev/disk0
(change /dev/disk0 to /dev/disk1 or above if your
computer has multiple hard disks and the one on which you want to
install Ubuntu isn't /dev/disk0).
- In gdisk, type p to display your partition
table. Verify that it's the same one shown by Disk Utility. (Note that
Disk Utility hides the EFI System Partition (ESP), which is normally
the first partition on the disk.)
- If you created a Linux partition, type d in
gdisk to delete it. Enter its number when prompted. (If you
created multiple partitions for Linux with the intention of using them
as you created them, you can skip this step.)
- In gdisk, type n to create a new partition.
Give it a number of 99, hit the Enter key to use the default starting
sector (the program may tell you it's changed the sector value, but you
can ignore this message), +128M as the ending sector,
and a hex code of ef02. This creates a BIOS Boot
Partition of 128 MiB at the start of the largest block of free space on
the disk. This partition will be used by the initial Ubuntu GRUB
installation, but you can delete it once you've got native EFI booting
working. 128 MiB is actually much bigger than is required for this
purpose, but OS X likes to see gaps between partitions when it installs
or upgrades the OS, so when you eventually delete this partition, it
will leave the type of gap that OS X likes to see. (If you created all
your Linux partitions in OS X's Disk Utility, you can put the BIOS Boot
Partition in one of the gaps that Disk Utility leaves, but you may need
to accept a default value or use +1M rather than enter
+128M as the end value.) Type p again
to see the results; they should look something like this (although I've
got two OS X partitions):
- In gdisk, type w to save your changes. When
asked, type y to confirm this choice.
- Insert your Ubuntu installation CD or DVD in the computer's drive, or
plug in the USB flash drive that holds the Ubuntu installer.
- Restart your Mac and hold down the Option key (Alt if you're using a PC
keyboard) as it restarts to get the Mac's OS selection screen.
- Pick the Ubuntu install disc from the options. (It may be mis-labelled
as "Windows.") The Ubuntu installer will start up. If you're using a CD
and the installer doesn't boot, try using a USB flash drive instead.
- When the appropriate screen comes up, select Install Ubuntu
and proceed with a normal Ubuntu installation, except as noted in the
next few steps....
- When the Installation Type dialog box appears, select "Something Else."
- You will initially see a partitioning screen with your original OS X
partitions, a biosgrub partition (what Ubuntu's partitioner
calls the BIOS Boot Partition), and free space at the end of the disk.
Select the free space and click Add to begin adding partitions....
- Create partitions for your Ubuntu installation in the free space near
the end of the disk. (If you did this in OS X's Disk Utility, you
should modify each partition by selecting it and clicking Change,
then clicking the Format option and setting an appropriate filesystem
and mount point.) I recommend creating the following partitions:
When you're done, you'll
see your new partitions displayed....
- /boot—500 MiB, ReiserFS or ext2fs. This
partition is optional. It can simplify some types of boot loader
configurations, particularly if you want to use XFS, JFS, or Btrfs
on your root (/) partition.
- / (root)—5–25 GiB, ext4fs or your
preferred Linux filesystem. This partition is absolutely vital. If
you choose not to create a separate /home partition, make
the root partition suitably larger. Take note of the number of this
partition (7 in the below screen shot).
- swap—1–2 times your system's RAM size.
- /home—The rest of your available disk space,
in ext4fs or your preferred Linux filesystem. You can merge this
with the root (/) partition if you're short on space or
plan to store little in the way of Ubuntu-specific files. Having a
separate /home partition simplifies OS re-installations
and some types of upgrades, though.
- Be sure that the "Device for boot loader installation" option is set to
/dev/sda (it will include a complete name for your hard
disk—I used VirtualBox to collect the last few screen shots, but
yours will show a real disk model number).
- Click Install Now. The installation will proceed as on a PC. You can
find generic installation guides online, such as this one
at the Ubuntu site.
When the installation finishes, the computer will reboot—straight
into Mac OS X! (See the below note if it doesn't boot, though.) You must
now proceed with fixing it up in various ways....
Fixing the Installation
If you've followed the directions, your computer should now be booted
into OS X, looking very much like it did before. Ubuntu is
installed, however, and your disk has a hybrid MBR. You must now take steps
to return the hybrid MBR to a safer protective MBR, as the GPT standard
requires, and to set up a boot loader that enables you to select which OS
to boot when the computer powers up. To do so, follow these steps:
- In OS X, launch a Terminal.
- Type sudo gdisk /dev/disk0 (changing the disk
identifier as necessary). If at any point in the next few steps
something seems wrong, type q to exit without saving
- In gdisk, type x. The command prompt will
change to read Expert command (? for help):.
- In gdisk, type o. This command displays the
contents of the hybrid MBR, which will probably consist of four
partitions, one of which is of type 0xEE. The Ubuntu installer created
a hybrid MBR (if one wasn't already present) in an attempt to be
- In gdisk, type n. The program won't seem to
do anything; it will just show you another command prompt.
- In gdisk, type o again. The MBR contents
should be different from before; there should just be one partition, of
type 0xEE. This is a standards-compliant protective MBR.
- In gdisk, type w to save your changes.
- Unpack the rEFInd zip file you downloaded earlier. If you downloaded
the CD image, mount it.
- In the Terminal, change into the directory created by unpacking the
rEFInd zip file, or to the CD image's mount point.
- Type ./install.sh. This runs a script that
installs rEFInd to your OS X boot partition and "blesses" the program
so that the Mac will use it when you next boot. If you're using
whole-disk encryption on your OS X partition or if you want to install
rEFInd to the ESP rather than to the OS X boot partition, type ./install.sh esp rather than ./install.sh.
Update:If you're using a 3.3.0 or later kernel, you can skip most of the rest of this page, and instead perform a much simpler operation:
- Copy an EFI driver for the filesystem you used on /boot (or
your root filesystem, if you didn't split off /boot) from the
rEFInd package to the drivers subidrectory of the rEFInd
installation directory, which is normally /EFI/refind. Note
that you must copy the driver for your EFI's
architecture—architecture codes appear in the filesystem drivers'
filenames. If you did not use ext2/3/4fs or ReiserFS on /boot,
this variant procedure will not work.
- When you reboot, highlight one of the Linux options that refers to a
file called vmlinuz-version, where version is a version number.
- Press F2 or Insert twice to open a line editor.
- Add ro
root=/dev/sda5 to the kernel options, changing
/dev/sda5 to your root filesystem's identifier.
- Press Enter. This should boot Linux, although the screen might go
completely blank for a few seconds.
- If it doesn't already exist, create a directory called
- Edit /etc/fstab and add an entry to mount your ESP (normally)
/dev/sda1 at /boot/efi. The entry should resemble the
/dev/sda1 /boot/efi vfat ro,fmask=133 0 0
- Type mount -a to mount the ESP at
- Run the mkrlconf.sh script that comes with rEFInd, as in sudo ./mkrlconf.sh, typed from the directory
where the file exists. This action should create a file called
/boot/refind_linux.conf, which is briefly described in the Improving the Boot Method section.
At this point, it should be possible to boot Linux by rebooting the
computer and selecting one of the vmlinuz-version entries
in rEFInd's menu. If this doesn't work, continue with the main procedure
- Load /efi/refind/refind.conf into a text editor and locate the
commented-out scanfor line. (If you installed rEFInd to the
ESP, you'll need to mount the ESP and load the configuration file from
there.) Uncomment the scanfor line by removing the leading
hash mark (#) and then add a new item, cd, to the end
of the line. It should read scanfor
internal,external,optical,cd. (If you're using USB flash drives,
add biosexternal instead of or in addition to cd.)
- Reboot. The rEFInd menu should appear, as shown below. Your menu
options might differ from these, though. (This system has two OS X
installations and a working OpenSUSE installation accessible via two
- Insert the Super GRUB 2 Disk into the computer's DVD drive.
- Restart your Mac by selecting the reboot item (the yellow icon with the
circular arrow on the far right of the row of smaller icons).
- When the rEFInd menu re-appears, you'll see a new Linux icon on the far
right of the display. (Depending on your screen's size and the number
of OS loaders rEFInd discovers, you may need to scroll over to see it.)
- After a while, a GRUB 2 menu should appear. Pick the Detect any
GRUB 2 installation (even if MBR is overwritten) option from the
menu. Note: On my system, if I leave this menu up for more than two or
three seconds, it hangs at this point. If yours is the same, you'll
need to act quickly!
- A new menu should appear listing the GRUB 2 installations it could
locate. On my system, this consisted of a grand total of one
installation, identified as (hd1,gpt6)/grub/core.img, so
there's no ambiguity: Select it! (Of course, your disk device numbers
are likely to differ from mine.)
- At this point, a normal Ubuntu GRUB 2 menu should appear, enabling you
to boot Ubuntu as you would on a PC. (The screen may go completely
black for part of the boot process. Don't worry; this is normal.)
- When the login screen appears, log into your Ubuntu installation.
- Click Dash Home (the icon in the upper-left corner of the screen) and
type term in the search field. A few icons
should appear, including one called Terminal. Click it to launch a
- Type sudo mkdir /boot/efi to create the
standard mount point for the EFI System Partition (ESP).
- Type sudo mount /dev/sda1 /boot/efi to mount
the ESP at /boot/efi. (Change /dev/sda1 if your ESP
has an unusual partition number.) You can use gdisk to check
the ESP's number, if you like.
- Type ls /boot/efi. You should see the
contents of the ESP, which will probably consist of a single directory
called efi. There could be other files and directories, but
probably not many of them. If it appears you've mounted the wrong
partition, review your partition layout and the commands you've typed
to mount the ESP. Proceed only when you're sure you've mounted the ESP
- Type sudo apt-get install grub-efi. This
replaces the BIOS version of GRUB that the Ubuntu installer installed
with an EFI-based version of GRUB. In fact, there are two different
EFI-enabled versions of GRUB: grub-efi-ia32 and
grub-efi-amd64. Installing grub-efi installs the
package that's appropriate for your system, assuming you installed the
optimum architecture. If you're running a 32-bit version of Ubuntu on a
recent 64-bit OS X firmware, you may need to explicitly install
grub-efi-amd64. Installing grub-efi also installs a
number of dependencies, such as efibootmgr
- Type sudo mkdir /boot/efi/efi/ubuntu/.
This command creates a home for GRUB on the ESP. (Note the doubled-up
efi in the path. This is not a typo.)
- Type sudo grub-install. (Recent versions of
GRUB seem to require an option. Pass it your ESP's device filename, as
in sudo grub-install /dev/sda1.) You'll see
a few messages appear on the screen, including a couple of "fatal"
errors about EFI variables. Ignore those messages. They're caused by
the fact that you're booted in BIOS mode, and they're irrelevant
because the task they're intended to perform will be handled by rEFInd.
- Type ls -l /boot/efi/efi/ubuntu. You should
see two files, boot.efi and either grubia32.efi or
grubx64.efi, depending on your platform. They should have the
same file size; in fact, they're identical.
- If both of those files are present, remove one of them; having both
will just clutter your rEFInd menu unnecessarily. If you somehow wound
up with just one file, though, leave it in place. If you don't see
either file, then do some troubleshooting now; you won't be able to
boot into Ubuntu without one of those files (or some other EFI boot
loader for Linux).
At this point, if you did everything exactly correctly, you should be
able to boot Ubuntu in EFI mode. When you reboot, your rEFInd menu should
include a new Ubuntu option, as shown below. Select it and your GRUB menu
should appear; it will resemble the one shown earlier, although it may use
a different font and color scheme.
Once you're satisfied with your ability to boot and use both Linux and
OS X, you can delete the BIOS Boot Partition from your hard disk. It's
no longer needed, but OS X may want free space where it resides in the
future. You can use GParted, parted, gdisk, or any other
partitioning tool to delete this partition.
Although my own system doesn't seem to suffer from its presence, it's
conceivable that some Macs will experience boot-time slowdowns because of
the presence of the BIOS version of GRUB's boot code in the hard disk's
MBR. If you think this is happening, you can type sudo dd if=/dev/zero of=/dev/sda bs=440 count=1 to
eliminate it. Be very careful with that command, though! Be
absolutely positive that you've typed it correctly, and particularly
the bs=440 and count=1 numbers. If you write too much
data in this way, you can damage your partition table!
If you've not used it before, you may want to peruse the rEFInd documentation. Although
the default options work well for most systems, you may want to tweak some
of them or install ancillary programs, such as an EFI shell program.
You may want to add an entry for the ESP to your /etc/fstab
file so that it will be mounted automatically whenever you boot. The
following line will do the trick on most systems:
/dev/sda1 /boot/efi vfat ro,fmask=133 0 0
You can tweak this entry as you see fit. The /dev/sda1
specification works for most people, but you could change it to use a
LABEL or UUID specification, as in
UUID=2B68-9A85. This will make the configuration more robust
should the disk identifier change because you boot with a different disk
configuration or you repartition the disk. If you this change, you'll need
to obtain the label or UUID value for your ESP. Typing blkid /dev/sda1 (changing the device identifier, if
necessary) should do this.
Improving the Boot Method
Although GRUB 2 often works in a configuration like the one I've just
described, it also often misbehaves. For instance, on my brand-new Ubuntu
12.04 installation (less than 24 hours old as I type), GRUB 2 often gives
me a "file not found" error when selecting the Ubuntu entry; then if I
select the same entry, it boots fine. On other installations and
computers, GRUB 2 has resulted in kernels that begin to boot and then fail;
it's begun returning a grub> emergency prompt for no apparent
reason; and it's done a poor job of detecting OSes and kernels. What's
more, on my Mac, Ubuntu's packaging system keeps trying to replace
grub-efi with grub-pc, which would result in an
unbootable installation if allowed to continue! For these reasons, GRUB 2
is the EFI boot loader that I favor least. That said, some people
say it works acceptably for them, and it's Ubuntu's default boot loader, so
Ubuntu's installation scripts usually do a tolerable to good job of
automatically configuring it. These are the reasons I provided instructions
for installing GRUB 2. I personally try to remove it as soon as possible
after an installation, or at least shove it out of the way so that it can't
do any real damage.
If you have problems with it, you can switch to another EFI boot loader.
My EFI Boot Loaders for
Linux Web page describes the options that are available. If you've
followed the directions on this page, my personal favorite is actually
quite close to working: If you can install a Linux kernel with the EFI stub
loader support enabled, rEFInd can launch it directly, without the help
of GRUB. The major hurdle to overcome on this score is that Ubuntu 12.04
installs a 3.2.0 kernel, but the EFI stub loader became available with the
3.3.0 kernel. This is why I recommended installing Ubuntu 12.04.2, 13.04,
or a more recent version of Ubuntu; these versions ship with 3.3.0 or later
kernels. In broad outline, to use the EFI stub loader, you must:
- Obtain a kernel with an EFI stub loader, either by finding a suitable
binary package or by compiling the kernel yourself.
- Optionally install an EFI driver for
the filesystem you used on your Linux /boot partition. This
isn't required, but it can simplify setup by enabling the EFI to load
the kernel from its normal home in /boot. If you omit this
step, you'll need to copy the kernel to a FAT or HFS+ volume. (The
possibility of using this approach to booting is why I recommended
creating a separate ReiserFS or ext2fs /boot partition; those
are the Linux filesystems for which EFI drivers are available.)
- Install the new kernel and initial RAM disk in a place where the
ESP can read it. As just noted, this can be /boot if you've
installed an EFI driver. If not, the ESP can work, at least in theory
(it doesn't on my Mac Mini, but that may be a model-specific problem).
An HFS+ volume is also an option. (Odd as it may sound, converting
/boot to use HFS+ can work quite well on Macs—but not on
- Either rename the Linux kernel file so that it includes a .efi
extension or uncomment the scan_all_linux_kernels option in
rEFInd's refind.conf file. The former method works best if you
have kernels that do not have EFI stub loader support enabled in
directories that rEFInd will scan. The latter method works well if
you're using a distribution that provides suitable kernels and you've
loaded drivers so that the EFI can read /boot.
- Create a file called refind_linux.conf in the directory that
holds your kernels. This file holds kernel option sets, one per line,
"Boot using standard options" "root=UUID=17c62fb9-a67a-4bae-97d7-3b71e5d3c8ce ro quiet splash $vt_handoff"
"Boot using minimal options" "root=UUID=17c62fb9-a67a-4bae-97d7-3b71e5d3c8ce ro"
"Boot using recovery options" "root=UUID=17c62fb9-a67a-4bae-97d7-3b71e5d3c8ce ro recovery nomodeset"
This refind_linux.conf file is taken from a working
installation, but you'll need to adjust the UUID value for your own
computer if you use it as a model. When you boot, rEFInd uses the first
line's options by default, but by pressing F2 or Insert when you select a
kernel in rEFInd, you can choose another option set.
The beauty of this method of booting is that you don't need to change
configuration files when you install a new kernel—just place it, with
a suitable filename, in the kernel directory and rEFInd will detect it and
use the options from refind_linux.conf to boot it. Although GRUB 2
is supposed to be as easy to use, it accomplishes this goal by running a
series of configuration scripts whenever you install a new kernel and
updating its configuration file. This process can go wrong, particularly in
advanced or exotic setups.
If you have problems with GRUB 2, ELILO and GRUB Legacy are the best
options, as described on my EFI boot loaders page.
Each has advantages and disadvantages. On my Mac Mini, ELILO doesn't work,
but that may be a model-specific quirk. Unfortunately, you'll need to
adjust either boot loader's configuration whenever you upgrade your kernel,
so keep an eye on that!
You can consult the UEFIBooting page to
learn about more options for GRUB on a Mac. Some of that page's
instructions didn't work for me, though; presumably they're either specific
to particular Mac models or the page is dated.
I hope you've found this Web page informative. I realize the procedures
outlined here are complex, but in my opinion, it's worth getting rid of the
flaky and dangerous hybrid MBR even if doing so requires investing the
effort described here.
The following sites have additional information that you might find
If you have problems with or comments about this web page, please
e-mail me at
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