Issues with El Capitan on Macbook 5,1

[Nick Smithies]

Thank you so much for the great software and apolagies if the following is written in the terms of a novice.

rEFInd has been working without problem on my MacBook 5,1 under 10.6.8 then Yosemite (with Ubuntu 14.04 dual booted).
After upgrade to El Capitan I followed steps to disable 'System Integrity Protection' (SIP) and had rEFInd working without problem under El Capitan also.
After setting this up I decided to re-enable SIP.
I have been working between OSX and Ubuntu via rEFInd without problem (last Ubuntu boot about a week ago) untill trying to boot Ubuntu today.

Trying to boot Ubuntu from whole disc (black Penguin) now fails with error "No bootable device — insert boot disk and press any key"
Trying to boot from other Ubuntu option (orange symbol) loads the system but the system invariably freezes after a few minutes.
I have taken the steps to disable SIP again and checked my partitions still exist using Diskutil in OSX Terminal.

I am hoping you cant assist me in repairing this set up or if this is the wrong place to post this question then point me to a forum better suited to answering it.

Thanks again for your time in creating this software and running this forum.

All the best

nsmithies

ps. Please do not hesitate to probe me for more information as I will happy to provide any logs / test results - though you may have to indicate what tests to run or tell me what specific information you need.

[Roderick W. Smith]

My suspicion is that the black penguin icon was booting in BIOS/CSM/legacy mode, but this may have broken because of a change to your partition table. Such a change might easily wipe out the hybrid MBR, which on Macs is required for BIOS-mode booting. The fix is to regenerate a new hybrid MBR, either using gdisk or via the gptsync utility that comes with rEFInd. (If you installed rEFInd from OS X, gptsync is probably installed but disabled; you must edit the showtools option in refind.conf to access it.) Once enabled, gptsync will be easier to use; but gdisk is more flexible. Read the hybrid MBR page to which I just linked to learn about this subject.

Note, however, that hybrid MBRs are flaky and dangerous. It might therefore be better to get a direct EFI-mode boot working. I suspect this is the "orange symbol" option you note. If highlighting that symbol produces descriptive text that includes the string vmlinuz, then it's booting the Linux kernel directly. Ordinarily, this works fine -- but obviously, if the system is freezing that's not what anybody would call "fine." You might try this:

1. Boot to Ubuntu, despite the fact that it will likely freeze. (You may need to re-boot to re-start this procedure if that happens.)
2. Run the mkrlconf script that comes with rEFInd. This will generate a file called /boot/refind_linux.conf
3. Check the /boot/grub/grub.cfg file for lines that begin with linux. (There are likely to be many such lines.) These include Linux boot options, which is what you're after.
4. Edit at least the first line in /boot/refind_linux.conf to duplicate the boot options you find in grub.cfg.

For instance, suppose you see this in grub.cfg:

linux   /boot/vmlinuz-4.3.0-7-generic.efi.signed root=UUID=f8b548e2-4984-47d4-896e-0f47bb753373 ro  quiet splash $vt_handoff

You'd then edit /boot/refind_linux.conf to look like this:

"Boot with standard options"        "ro root=UUID=f8b548e2-4984-47d4-896e-0f47bb753373  quiet splash "
"Boot to single-user mode"          "ro root=UUID=f8b548e2-4984-47d4-896e-0f47bb753373  quiet splash single"
"Boot with minimal options"         "ro root=UUID=f8b548e2-4984-47d4-896e-0f47bb753373"

This example shows nothing particularly unusual. The root=UUID={blahblah} part identifies the root (/) filesystem, ro says to mount the filesystem read-only (the startup script later changes this to read/write), and the quiet and splash options tell the kernel to display the Ubuntu logo during startup rather than a scrolling set of kernel status lines. The $vt_handoff part of the grub.cfg line can be ignored; it's a GRUB variable that has no exact counterpart in rEFInd. The point of this exercise is that your GRUB configuration might have something that's not duplicated in the rEFInd setup, in which case you'd want to copy it over, in the hopes that it will fix the freezing problem.

If this doesn't help, then either the EFI stub loader (which rEFInd uses to boot kernels directly) just isn't quite working on your system or there's something about a BIOS-mode boot that's necessary on your system. In the first case, another EFI boot loader might help, but testing something else opens a new can of worms that might not be worth tackling, so fixing the BIOS-mode boot may be the best option. In the latter case, you'll need to get the BIOS-mode GRUB working by creating a new hybrid MBR, despite the reservations I stated earlier. (You might also prefer to do that rather than muck with the configuration files as I've just described. Although hybrid MBRs are nasty things, they do work, and as long as you're aware of their dangers, those dangers are manageable.)