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#159 Remote Disk support

Robert Banhegyi

It would be cool if i could boot from a remote disk in rEFIt, since the superdrive of my macbook pro is broken, and USB booting won't work because of that unfixable firmware problem.


    • priority: 5 --> 9
    • priority: 9 --> 5
  • Norbert

    I have a JMB630 based esata controlelr and an attached ssd.

    I cannot boot off the drive although it is visible in refit.

    This issue is known and the refit troubleshooting says

    "It may be possible to properly support booting from the second disk in rEFIt, but the author currently lacks a suitable test system. If you can help investigate this and are willing to test patched rEFIt builds, please get in touch."

    So I am willing to test patched rEFIt builds.

    The question is if the author could find the time. I could even help to provide a suitable test system.

    Thanks for the cool work

    PS By the way :
    I am trying for day and now I used a linux install on the first drive to boot into grub where I have a menuentry to boot of the ssd. This is also not working and I cannot understand why. After selecting the grub entry from the first drive it reports that a drive with given uuid does not exist also I am sure it does. After booting the linux from the first drive the ssd is visible and accessable with correct uuid.

    Thanks for your cool work so far

  • Joe van Tunen
    Joe van Tunen

    The support for booting from multiple disks has already been added to the source code but does not exist in the 0.14 version. You have to build it yourself. However, the code only works on disks that the Mac's firmware can boot. i.e. If you can't boot the disk using the Mac's boot menu (hold option when you startup), then you can't boot the disk using rEFIt (I'm referring to Mac OS X and legacy OS's - rEFIt adds support for other OS's that use EFI loaders which the Mac's boot menu may not support).

    Note that the multiple disk support is only needed if you have a Mac with multiple disks that contain legacy OS's (Windows, Linux). You do not need the support if all your legacy OS's are on the same disk.

    The rEFIt troubleshooting note only mentions internal disks. This is an oversimplification but is generally true. For example, my Mac Pro (2008) has 4 built in disks that I can boot from. The Mac Pro has 2 other extra SATA ports that it can't boot a legacy OS from but can boot OS's that have an EFI loader like Mac OS X. It also can't boot legacy OS's from USB or FireWire. Later Mac's may have better boot support for legacy OS's. It depends on the BIOS included in their EFI firmware.

    rEFIt can see the external SSD on the eSATA controller because rEFIt uses EFI. When you boot a legacy OS, it switches to BIOS.

    When you run Linux, the GRUB setup can see the external SSD because it is using Linux drivers. However, the GRUB menu on your internal disk can't boot your external SSD because GRUB uses BIOS (used for booting legacy OSs) at this point and the BIOS does not know how to use the eSATA controller.

    I don't know of the Apple BIOS is smart enough to use option ROM's on expansion cards (http://en.wikipedia.org/wiki/Option_ROM). Is it possible to boot PC's using the JMB630 controller? If so, then it would seem that the Apple BIOS is not smart enough.

    To boot unsupported devices using BIOS, you need to boot from a supported device which has a BIOS extender (http://grub4dos.sourceforge.net/wiki/index.php/BIOS_extender) that will boot from the unsupported device.

    I wonder if it would be possible to create an EFI loader which loads it's own BIOS compatibility mode. Then we wouldn't be dependant on Apple's crappy BIOS. It seems that writing an entire BIOS on top of EFI would be a big task though. http://www.coreboot.org/SeaBIOS