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Thread: Starting Ubuntu from external disk on Mac

  1. #1
    Join Date
    Feb 2020
    Beans
    7

    Starting Ubuntu from external disk on Mac

    Hey friends,
    Some weeks ago, I installed Ubuntu on an external disk, including a swap partition (if this is important). This external disk also has an external macOS and one other Linux on it, which I do not want to destroy.
    I installed it while using a MacBook and now, if I boot this one, It automatically shows four operating systems:
    - the built in
    - the three external ones named above

    This is correct.

    Now, I would like to boot the Ubuntu operating system from a different MacPC for some reasons, but it does not show many any of the three other while booting.

    Do I need to configure something here on that external disk?

    I am honestly not sure about this and I am in fear of destroying the other two systems on disk or the starting functionality of the disk on the Pc where it works at the moment.

    Is there anybody who can explain me how this works and tell me how I can boot the disk from that second MacPC?

    Many greetings and thanks

  2. #2
    Join Date
    Mar 2011
    Location
    U.K.
    Beans
    Hidden!
    Distro
    Ubuntu 18.04 Bionic Beaver

    Re: Starting Ubuntu from external disk on Mac

    Since I have no experience on MacBook I did some digging.

    https://www.quora.com/Why-is-there-n...le-Mac-Macbook

    Sure enough the loader I now use (rEFInd) on my Dell is mentioned in that thread.
    The reason your external drive does not boot is probably because the boot info is buried in MacBook1.

    If you create a small partition in your external drive (size about 500 MB with boot flags) and install rEFInd on that external drive, you should be able to boot with either MacBook1 or MacBook2. You can also edit refind.conf (as I did on my Dell) to give priority to external device (SSD).

    But I would wait until you get other responses from MacBook users and meanwhile just read about rEFInd.

  3. #3
    Join Date
    Jun 2009
    Location
    SW Forida
    Beans
    Hidden!
    Distro
    Ubuntu

    Re: Starting Ubuntu from external disk on Mac

    Do not know Mac either.

    But Ubuntu's ubiquity installer only installs grub to internal drive, so you can only boot using internal drive.
    You need to add ESP - efi system partition to external drive.

    And internal drives all boot in UEFI mode from /EFI/boot/bootx64.efi.
    And the full install of grub renamed to bootx64.efi needs to also have /EFI/ubuntu folder.
    You probably can just copy from internal drive's ESP to external drive's ESP. Or reinstall grub to external drive.
    For more info on UEFI boot install & repair - Regularly Updated :
    http://ubuntuforums.org/showthread.php?t=2147295
    Please use Thread Tools above first post to change to [Solved] when/if answered completely.

  4. #4
    Join Date
    Feb 2020
    Beans
    7

    Re: Starting Ubuntu from external disk on Mac

    Hey, Thanks to both of you. It is working now, it really was the missing ESP causing this.
    Thank you!
    Have a wonderful day.

  5. #5
    Join Date
    Nov 2012
    Location
    Halloween Town
    Beans
    Hidden!
    Distro
    Xubuntu Development Release

    Re: Starting Ubuntu from external disk on Mac

    Thread moved to Apple Hardware Users.

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