Ubuntu – REFIt – rEFInd – Grub2…what is the “right way” for Ubuntu 14.10 on a Mac:

grub2refindrefituefi

Can someone please help me to understand the “right way” (if there is such a thing) to run Ubuntu on an EFI computer (specifically a 2012 iMac — I have Ubuntu 14.10 installed on this iMac, on partition /sda5).

I initially installed rEFIt. It didn't work perfectly, so I later tried to replace it with rEFInd (though I think my removal of rEFIt was incomplete). And of course I had Grub installed on the Ubuntu partition.

I don't remember the sequence of these installs. I think I installed rEFIt on the Mac side, then installed Ubuntu (with Grub) on the /sda5 partition. . . then later “upgraded” to rEFInd by installing it on the Ubuntu side (but it might have been on the Mac side).

When I booted the Mac, for a long while, it would boot into Grub2 – where I would select my Ubuntu install. Then, not sure what happened, but it started booting into rEFInd. In rEFInd, I would select the Ubuntu icon and it would then boot into Grub2. Essentially, I had two different boot managers that I had to use in sequence.

Anyway, I had this working for a long time until after a major crash. After the crash, every time I booted into rEFInd and selected ANY OS (including LiveUSBs), it would initially load but then the screen would eventually go blank and just stop there. Nothing appeared to happen. So I then removed reFIND and installed reFIt. Now the Mac boots into rEFIt, and I when I select the Ubuntu icon, it goes to Grub2. But the Grub screen is not entirely clear, just a little pixelated.

This caused me to wonder: should I have to use two boot managers?

Is it possible/preferable to either:

1. boot directly into Grub2, with no intermediary; or
2. boot into rEFIt (or rEFInd) and not have to then go to Grub?

Thanks for any erudition on this matter. I just don't get it.

Best Answer

Both your #1 and #2 options are possible; however, if you don't understand the Mac's native EFI-mode booting and how the Mac implements BIOS/legacy booting, you're likely to make a hash of things in setting it up. My suspicion is that you installed Ubuntu in BIOS/legacy mode with a BIOS-mode version of GRUB, which means that GRUB will be unable to launch OS X (or maybe it'll manage, but that path is very flaky in my experience). If I'm right, you'll want to install either an EFI version of GRUB or rEFInd to do as you want. Installing from OS X is preferable, although the Mactel tools to which LiveWireBT can theoretically make this more reliable in Linux. (I have limited experience with these tools myself, though, so I can't comment on them in detail.) My pages on hybrid MBRs and EFI boot loaders for Linux will help bring you up to speed, but be prepared to spend some time on the reading. Sorry, but I know of no good shortcut for this. A brains-off step-by-step guide might work, but is more likely to lead you astray because of assumptions the author makes that don't apply to your system.

The rEFInd documentation is pretty extensive. Be aware there have been significant changes in rEFInd's Mac support recently. In particular, version 0.8.4 and later now install to the EFI System Partition (ESP) by default, which is necessary to work with the way Yosemite is set up by default. This change has caused some confusion among users, though.

Full disclosure: I maintain rEFInd, so I'm not unbiased.

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First, there appears to be an error in your GPT layout: The partition beginning at sector 781660160 is identified on the GPT side as an EFI System Partition (ESP); but on the MBR side, it appears as a Linux partition with an ext4 filesystem. Given the way this identification has been done, I trust the MBR data on this one. Chances are you or the installer mistakenly set the "boot flag" on the partition. Using libparted-based programs, setting the "boot flag" on a GPT partition actually sets the ESP type code, which should never be set on a Linux partition. (The ESP is required to hold a FAT filesystem and should hold EFI boot loaders and related files, not a Linux installation.) This error isn't likely to be causing your problem, but it's conceivable it's a contributing factor. Thus, I recommend booting a Linux emergency system and using GParted, parted, gdisk, or some other tool to adjust the type code appropriately. Using GParted or parted, remove the "boot flag" from the Linux partition; or using gdisk, change the type code from EF00 to 8300. Note that these tools will probably show another ESP, this one with a FAT filesystem. You should leave it configured as an ESP (with its "boot flag" or EF00 type code, depending on the tool you use).

Second, I recommend you switch from a BIOS-mode boot of Linux to an EFI-mode boot. This will obviate the need to use a hybrid MBR, which you're using now. Hybrid MBRs are ugly and dangerous hacks. You can install a suitable EFI-mode boot loader without too much difficulty. The easiest to set up is likely to be my rEFInd, which is a fork of the (now-discontinued) rEFIt; however, the procedure I'm about to describe works only with 3.3.0 and later kernels. Ubuntu 12.10 and later, including Ubuntu 12.04.2 (but not the original 12.04) come with suitable kernels. The procedure is:

Download the rEFInd binary .zip file from its downloads page.
Install rEFInd under OS X. This is easily done by using the install.sh script.
Install the rEFInd driver for ext4fs. You can do this by copying the ext4_x64.efi file from the rEFInd package to the /EFI/refind/drivers_x64/ directory (which you'll have to create). (This assumes you install to the default location; if you install rEFInd to your ESP or install manually elsewhere, you'll need to adjust the path appropriately.)
Reboot. rEFInd should appear.
In rEFInd, use the arrow keys to select one of the Linux penguin icons, which rEFInd should identify as launching a Linux kernel with a filename that begins with vmlinuz.
With one of the Linux kernels selected, hit F2 or Insert twice. A text-mode text editor should appear.
Add ro root=/dev/sda2 to the boot options and press Enter. Linux should launch.
In Linux, run the mkrlconf.sh script that came with rEFInd. This will create a configuration file that should obviate the need to add ro root=/dev/sda2 to your Linux options the next time you boot; instead, Linux should launch directly when you select its option and hit the Enter key.

At this point, your system will be basically functional. You can remove the hybrid MBR by using the gdisk program (specifically, by typing x followed by n followed by w) or by making any minor change to your partitions with parted or GParted. You may also want to tweak the rEFInd configuration by editing the /EFI/refind/refind.conf file under OS X; see the rEFInd documentation for details.

Ubuntu – Cannot boot into rEFIt (to choose Ubuntu) on Mac after Yosemite upgrade

Did you reinstall rEFIt manually?

If you didn't, try running this on the OSX Terminal

cd /efi/refit   
./enable.sh

When prompted for your password, use the one Yosemite asks you for while trying to install new software.

After that, you should see the boot menu after you restart. When you choose to load Ubuntu from the boot menu, you may be greeted by the grub rescue> terminal" instead of a normal boot, let me know.

By the way, you can also press the option key (alt) just after you hit the power button, and there you'll see some options, including rEFIt. This has the drawback that it must be done on every boot, hence the preference for the terminal solution.

Best Answer

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